Science.gov

Sample records for h2o flow temperature

  1. Species and temperature measurement in H2/O2 rocket flow fields by means of Raman scattering diagnostics

    NASA Technical Reports Server (NTRS)

    Degroot, Wim A.; Weiss, Jonathan M.

    1992-01-01

    Validation of Computational Fluid Dynamics (CFD) codes developed for prediction and evaluation of rocket performance is hampered by a lack of experimental data. Non-intrusive laser based diagnostics are needed to provide spatially and temporally resolved gas dynamic and fluid dynamic measurements. This paper reports the first non-intrusive temperature and species measurements in the plume of a 110 N gaseous hydrogen/oxygen thruster at and below ambient pressures, obtained with spontaneous Raman spectroscopy. Measurements at 10 mm downstream of the exit plane are compared with predictions from a numerical solution of the axisymmetric Navier-Stokes and species transport equations with chemical kinetics, which fully model the combustor-nozzle-plume flowfield. The experimentally determined oxygen number density at the centerline at 10 mm downstream of the exit plane is four times that predicted by the model. The experimental number density data fall between those numerically predicted for the exit and 10 mm downstream planes in both magnitude and radial gradient. The predicted temperature levels are within 10 to 15 percent of measured values. Some of the discrepancies between experimental data and predictions result from not modeling the three dimensional core flow injection mixing process, facility back pressure effects, and possible diffuser-thruster interactions.

  2. Green hydrophilic modification of PE hollow fiber membranes in a module scale via long-distance and dynamic low-temperature H2O plasma flow

    NASA Astrophysics Data System (ADS)

    Li, Mei-Sheng; Zhao, Zhi-Ping; Wang, Ming-Xing

    2016-11-01

    A green chemistry process, long-distance and dynamic low-temperature (LDDLT) H2O plasma, was developed to modify PE hollow fiber membranes in a module scale using our modified LDDLT plasma setup. The modification degree of LDDLT-H2O plasma was 2 times greater than that of Ar plasma, but the effective treatment distance achieved by LDDLT-Ar plasma was about two times of that obtained by LDDLT-H2O plasma (22 cm). Under the suitable conditions, the effective treatment distance can reach over 54 cm after LDDLT-H2O plasma treatment from the double inlets, closed to some industrial module sizes. The improvement in surface hydrophilicity was because of the introduction of numerous oxygen-containing groups. High concentrations of OH radicals in H2O plasma played a major role in the membrane surface hydroxylation. This directly resulted in a great enhancement in the pure water flux. It increased from about 6 L m-2 h-1 to 45 L m-2 h-1 after treatment. Also, the H2O plasma-treated membrane module exhibited good hydrophilic stability during 285 days storage.

  3. Species and temperature measurement in H2/O2 rocket flow fields by means of Raman scattering diagnostics

    NASA Technical Reports Server (NTRS)

    De Groot, Wim A.; Weiss, Jonathan M.

    1992-01-01

    Validation of CFD codes developed for prediction and evaluation of rocket performance is hampered by a lack of experimental data. Nonintrusive laser based diagnostics are needed to provide spatially and temporally resolved gas dynamic and fluid dynamic measurements. This paper reports the first nonintrusive temperature and species measurements in the plume of a 110 N gaseous hydrogen/oxygen thruster at and below ambient pressures, obtained with spontaneous Raman spectroscopy. Measurements at 10 mm downstream of the exit plane are compared with predictions from a numerical solution of the axisymmetric Navier-Stokes and species transport equations with chemical kinetics, which fully model the combustor-nozzle-plume flowfield. The experimentally determined oxygen number density at the centerline at 10 mm downstream of the exit plane is four times that predicted by the model. The experimental number density data fall between those numerically predicted for the exit and 10 mm downstream planes in both magnitude and radial gradient. The predicted temperature levels are within 10 to 15 percent of measured values.

  4. (H2O)20 Water Clusters at Finite Temperatures

    NASA Astrophysics Data System (ADS)

    Parkkinen, P.; Riikonen, S.; Halonen, L.

    2013-10-01

    We have performed an exhaustive study of energetics of (H2O)20 clusters. Our goal is to study the role that various free-energy terms play in this popular model system and see their effects on the distribution of the (H2O)20 clusters and in the infrared spectrum at finite temperatures. In more detail, we have studied the electronic ground-state structure energy and its long-range correlation (dispersion) part, vibrational zero-point corrections, vibrational entropy, and proton configurational entropy. Our results indicate a delicate competition between the energy terms; polyhedral water clusters are destabilized by dispersion interaction, while vibrational terms (zero-point and entropic) together with proton disorder entropy favor them against compact structural motifs, such as the pentagonal edge- or face-sharing prisms. Apart from small water clusters, our results can be used to understand the influence of these energy terms in water/ice systems in general. We have also developed energy expressions as a function of both earlier proposed and novel hydrogen-bond connectivity parameters for prismatic water clusters.

  5. Base fluid and temperature effects on the heat transfer characteristics of SiC in ethylene glycol/H2O and H2O nanofluids

    NASA Astrophysics Data System (ADS)

    Timofeeva, Elena V.; Yu, Wenhua; France, David M.; Singh, Dileep; Routbort, Jules L.

    2011-01-01

    Experimental data are presented for the thermal conductivity, viscosity, and turbulent flow heat transfer coefficient of nanofluids with SiC particles suspended in ethylene glycol (EG)/water (H2O) mixture with a 50/50 volume ratio. The results are compared to the analogous suspensions in water for four sizes of SiC particles (16-90 nm). It is demonstrated that the heat transfer efficiency is a function of both the average particle size and the system temperature. The results show that adding SiC nanoparticles to an EG/H2O mixture can significantly improve the cooling efficiency while water-based nanofluids are typically less efficient than the base fluids. This is one of the few times that substantial nanofluid heat transfer enhancement has been reported in the literature based on a realistic comparison basis of constant velocity or pumping power. The trends important for engineering efficient heat transfer nanofluids are summarized.

  6. Formation of low-temperature cirrus from H2SO4/H2O aerosol droplets.

    PubMed

    Bogdan, A; Molina, M J; Sassen, K; Kulmala, M

    2006-11-23

    We present experimental results obtained with a differential scanning calorimeter (DSC) that indicate the small ice particles in low-temperature cirrus clouds are not completely solid but rather coated with an unfrozen H2SO4/H2O overlayer. Our results provide a new look on the formation, development, and microphysical properties of low-temperature cirrus clouds.

  7. A new room-temperature ultraviolet emission material: K2[Ni(C2O4)2(H2O)2]·4H2O

    NASA Astrophysics Data System (ADS)

    Narsimhulu, M.; Raju, B.; Saritha, A.; Narayana Rao, D.; Hussain, K. A.

    2015-09-01

    In this study, we investigated the crystal structure, ultraviolet (UV) luminescence, and magnetic properties of potassium bis oxalate nickel(II) tetrahydrate {K2[Ni(C2O4)2(H2O)2]·4H2O} crystals. This compound crystallizes in the monoclinic system with a P21/c space group and exhibits a one-dimensional (1D) chain structure. The Ni(II) metal center possesses an octahedral environment, with four oxygen atoms from two bidentate oxalate ligands and two oxygen atoms from water molecules. Infrared spectroscopy was used to study the vibrational modes of the compound. Interestingly, the complex exhibits intense UV emission at 364 nm when excited at 323 nm. Furthermore, the luminescence lifetime is approximately 50 μs. The magnetic susceptibility and field dependent magnetization measurements revealed a paramagnetic behavior above 20 K and antiferromagnetic ordering at low temperatures.

  8. H2O2 Synthesis Induced by Irradiation of H2O with Energetic H(+) and Ar(+) Ions at Various Temperatures

    NASA Technical Reports Server (NTRS)

    Baragiola, R. A.; Loeffler, M. J.; Raut, U.; Vidal, R. A.; Carlson, R. W.

    2004-01-01

    The detection of H2O2 on Jupiter's icy satellite Europa by the Galileo NIMS instrument presented a strong evidence for the importance of radiation effects on icy surfaces. A few experiments have investigated whether solar flux of protons incident on Europa ice could cause a significant if any H2O2 production. These published results differ as to whether H2O2 can be formed by ions impacting water at temperatures near 80 K, which are appropriate to Europa. This discrepancy may be a result of the use of different incident ion energies, different vacuum conditions, or different ways of processing the data. The latter possibility comes about from the difficulty of identifying the 3.5 m peroxide OH band on the long wavelength wing of the much stronger water 3.1 m band. The problem is aggravated by using straight line baselines to represent the water OH band with a curvature, in the region of the peroxide band, that increases with temperature. To overcome this problem, we use polynomial baselines that provide good fits to the water band and its derivative.

  9. Unexpected phase assemblages in inclusions with ternary H2O-salt fluids at low temperatures

    NASA Astrophysics Data System (ADS)

    Bakker, Ronald J.; Baumgartner, Miriam

    2012-06-01

    Phase assemblages and temperatures of phase changes provide important information about the bulk properties of fluid inclusions, and are typically obtained by microthermometry. Inclusions are synthesized in natural quartz containing an aqueous fluid with a composition in the ternary systems of H2O-NaCl2-CaCl2, H2O-NaCl-MgCl2, and H2O-CaCl2-MgCl2. This study reveals that these fluid inclusions may behave highly unpredictably at low temperatures due to the formation of metastable phase assemblages. Eutectic temperatures cannot be detected in most of the fluid inclusions containing these ternary systems. Nucleation of a variety of solid ice and salt-hydrate phases in single fluid inclusions is often partly inhibited. Raman spectroscopy at low temperatures provides an important tool for interpreting and understanding microthermometric experiments, and visualizing stable and metastable phase assemblages. Final dissolution temperatures of ice, salt-hydrates, and salt must be treated with care, as they can only be interpreted by purely empirical or thermodynamic models at stable conditions.

  10. Diagnosing shock temperature with NH3 and H2O profiles

    NASA Astrophysics Data System (ADS)

    Gómez-Ruiz, A. I.; Codella, C.; Viti, S.; Jiménez-Serra, I.; Navarra, G.; Bachiller, R.; Caselli, P.; Fuente, A.; Gusdorf, A.; Lefloch, B.; Lorenzani, A.; Nisini, B.

    2016-10-01

    In a previous study of the L1157 B1 shocked cavity, a comparison between NH3(10-00) and H2O(110-101) transitions showed a striking difference in the profiles, with H2O emitting at definitely higher velocities. This behaviour was explained as a result of the high-temperature gas-phase chemistry occurring in the post-shock gas in the B1 cavity of this outflow. If the differences in behaviour between ammonia and water are indeed a consequence of the high gas temperatures reached during the passage of a shock, then one should find such differences to be ubiquitous among chemically rich outflows. In order to determine whether the difference in profiles observed between NH3 and H2O is unique to L1157 or a common characteristic of chemically rich outflows, we have performed Herschel-HIFI observations of the NH3(10-00) line at 572.5 GHz in a sample of eight bright low-mass outflow spots already observed in the H2O(110-101) line within the Water In Star-forming regions with Herschel Key Programme. We detected the ammonia emission at high velocities at most of the outflows positions. In all cases, the water emission reaches higher velocities than NH3, proving that this behaviour is not exclusive of the L1157-B1 position. Comparisons with a gas-grain chemical and shock model confirms, for this larger sample, that the behaviour of ammonia is determined principally by the temperature of the gas.

  11. Water in Basaltic Melts: an Experimental and Thermodynamic Study of the Effect of H2O on Liquidus Temperatures.

    NASA Astrophysics Data System (ADS)

    Medard, E.; Grove, T. L.

    2006-12-01

    We present a thermodynamic model for the influence of H2O on liquidus temperatures of olivine-saturated primitive basaltic and andesitic melts. The thermodynamic model has been fitted to a suite of H2O-saturated liquidus experiments carried out on a primitive high-alumina basalt from Medicine Lake Volcano (82-72f) over a pressure range of 10 to 1000 MPa. The model of Silver and Stolper (S+S, 1985, J.Geol. 93:161) has been applied to the experimental data. This model uses the assumption of simple ideal mixing between water species and the anionic matrix in the melt. Water in the melt dissolves as molecular H2O, or dissociates to hydroxyl groups and an oxygen atomic network. For 82-72f, the liquidus olivine shows little compositional variability (Fo87.4 to Fo88.4) over the broad range of pressures and temperatures investigated that is not correlated with H2O content of the melt. This observation supports our assumption that major effect of H2O is on the anionic species in the melt and not on the cation equilibria (e.g. Mg and Si). The model reproduces the experimental data well. We find that there is a large influence of H2O addition on melting point for small amounts of H2O, resulting in a concave-down curvature when liquidus depression is plotted against the amount of H2O added. For addition of 0.8 and 5 wt% H2O to 82-72f, the liquidus is depressed by 35 K and 130 K, respectively. The best fits are obtained by assuming partial water dissociation to OH and H2O species, using the equilibrium constant measured by Stolper (1982). S+S applied their model to simple systems (diopside/H2O, albite/H2O, silica/H2O), and recovered the melting behavior extremely well. They also suggested that melt structure/composition influences the amount of liquidus depression caused by H2O addition. We have investigated the influence of bulk composition by performing complementary experiments on a high-magnesian andesite from Mount Shasta, and on a K, Na, and P rich alkali basalt from

  12. High pressure-temperature Raman spectroscopy of H2-H2O clathrate.

    NASA Astrophysics Data System (ADS)

    Somayazulu, Maddury; Levedahl, Alexander; Goncharov, Alexander; Mao, Ho-Kwang; Hemley, Russell

    2007-03-01

    The melting curve of the C2 clathrate H2-H2O has been determined by in-situ Raman spectroscopy measurements in an externally heated diamond anvil cell. We have determined the melting curve to a maximum pressure of 27 GPa. These are the first measurements on the melting line in this clathrate. Depending on the stoichiometry of the starting mixture of H2 and H2O, we are able to study either a mixture of C2 and H2O or C2 and H2. In either case, we were able to pinpoint the melting of the clathrate from the measurements of the molecular stretching mode (vibron) in the clathrate. In the case of C2 + Ice VII, we observe the vibron in the clathrate at a frequency higher than in pure H2 at the same pressure. We have cross-calibrated the melting temperatures using the Stokes-anti Stokes ratio of the diamond first order and Raman active TO phonon of cubic Boron Nitride. We find that the clathrate melts well above the H2 melting at all pressures studied indicating that the stabilization of this clathrate at high pressures is indeed due to interactions between the host and guest molecules.

  13. Temperature induced immiscibility in the NaCl-H 2O system at high pressure

    NASA Astrophysics Data System (ADS)

    Frank, Mark R.; Scott, Henry P.; Maglio, Steven J.; Prakapenka, Vitali B.; Shen, Guoyin

    2008-09-01

    High-pressure polymorphs of H 2O are a major component in many outer planets, extra solar bodies, and icy satellites. This study sought to examine the influence of ionic impurities on the phase stability, thermal expansion, and melting curve of ice VII. Powder diffraction patterns of ice VII formed from pure H 2O and 5 wt.% NaCl aqueous solutions were taken at room temperature up to 11.1 ± 0.3 and 26.6 ± 0.4 GPa, respectively. Thermal expansions, α, of all ice VII samples were recorded and modeled up to the melting point of the samples. Ice VII formed from a NaCl-bearing aqueous solution at pressures greater than 2.2 GPa and less than 500 K can be indexed by ice VII only, whereas at temperatures greater than 500 K, diffraction lines indicative of halite (NaCl) are observed and become more intense with increasing temperature and only disappear at the melting point of the high-pressure ice. This phenomenon was observed in all NaCl-bearing ice samples that were heated to greater than 500 K. The melting curves of ice VII formed from pure H 2O and a 5 wt.% NaCl aqueous solution suggest that the presence of Na + and Cl - in the ice VII structure results in a depression of the melting curve by approximately 40 K. The exsolution of halite from the NaCl-doped ice VII and the depression of the ice VII melting curve suggest that the presence of ionic impurities in ice VII may promote the formation of a self-segregating zone deep within ice-rich bodies. This zone could initiate the formation of solute-rich melt pockets that may ascend toward the surface and result in surface manifestations such as solute-bearing aqueous vents, unexplained domes/diapirism, and/or salt-rich regions.

  14. In situ H2O and temperature detection close to burning biomass pellets using calibration-free wavelength modulation spectroscopy

    NASA Astrophysics Data System (ADS)

    Qu, Zhechao; Schmidt, Florian M.

    2015-04-01

    The design and application of an H2O/temperature sensor based on scanned calibration-free wavelength modulation spectroscopy (CF-WMS) and a single tunable diode laser at 1.4 µm is presented. The sensor probes two H2O absorption peaks in a single scan and simultaneously retrieves H2O concentration and temperature by least-squares fitting simulated 1f-normalized 2f-WMS spectra to measured 2f/ 1f-WMS signals, with temperature, concentration and nonlinear modulation amplitude as fitting parameters. Given a minimum detectable absorbance of 1.7 × 10-5 cm-1 Hz-1/2, the system is applicable down to an H2O concentration of 0.1 % at 1,000 K and 20 cm path length (200 ppm·m). The temperature in a water-seeded laboratory-scale reactor (670-1220 K at 4 % H2O) was determined within an accuracy of 1 % by comparison with the reactor thermocouple. The CF-WMS sensor was applied to real time in situ measurements of H2O concentration and temperature time histories (0.25-s time resolution) in the hot gases 2-11 mm above biomass pellets during atmospheric combustion in the reactor. Temperatures between 1,200 and 1,600 K and H2O concentrations up to 40 % were detected above the biofuels.

  15. Photodissociation Spectroscopy of Ca^+-H_2O in the Temperature-Variable Ion Trap

    NASA Astrophysics Data System (ADS)

    Ishikawa, Haruki; Eguchi, Toru; Nakano, Takumi; Fujihara, Akimasa; Fuke, Kiyokazu

    2011-06-01

    In the last two decades, developments of infrared spectroscopy and theoretical calculations on gas-phase molecular clusters have revealed detailed solvation structures of various systems, especially of hydrogen-bonded systems. One of the remained problems in studies on microscopic solvation or hydration is a temperature dependence of solvation structures. Lisy and coworkers succeeded in interpreting the hydration structures of alkali metal ions by taking temperature- or entropic effect. They utilized Ar vaporization to cool down the temperature of clusters. Another method for controlling temperature of cluster ions is a buffer gas cooling in an ion trap. In the present study, we have measured photodissociation spectra of Ca^+-H_2O in our temperature-variable ion trap In the present study, we examined the temperature of the Ca^+-H_2O in the trap by simulating the rotational profile of the 0-0 band of the ^2B_1 - ^2A_1 transition. The observed rotational profile is similar to that reported by Duncan and coworkers. By changing the trap period from 10 ms to 40 ms, it was confirmed that the trap period of 10 ms is sufficient to get temperature equilibrium in our experimental condition. Details of the experimental results will be presented in the paper. D. J. Miller, J. M. Lisy J. Am. Chem. Soc. 130, 15393 (2008). A. Fujihara, et al. J. Phys. Chem. A 112, 1457 (2008) A. Fujihara, et al. J. Phys. Chem. A 113, 8169 (2009). C. T. Scurlock, S. H. Pullins, J. E. Reddic, M. A. Duncan J. Chem. Phys. 104, 4591 (1996).

  16. A variationally calculated room temperature line-list for H2O2

    NASA Astrophysics Data System (ADS)

    Al-Refaie, Ahmed F.; Ovsyannikov, Roman I.; Polyansky, Oleg L.; Yurchenko, Sergei N.; Tennyson, Jonathan

    2015-12-01

    A room temperature line list for hydrogen peroxide is computed using a high level ab initio potential energy surface by Małyszek and Koput (2013) with a small adjustment of the equilibrium geometry and height of the torsional barrier and a new ab initio dipole moment surface (CCSD(T)-f12b/aug-cc-pv(T+d)Z). In order to improve further the ab initio accuracy, the vibrational band centers were shifted to match experimental values when available. The line list covers the wavenumber region up to 8000 cm-1 with the rotational excitations J ⩽ 40 . Room temperatures synthetic spectra of H2O2 are generated and compared to the spectra from the HITRAN and PNNL-IR databases showing good agrement.

  17. Melting Temperature and Partial Melt Chemistry of H2O-Saturated Mantle Peridotite to 11 Gigapascals

    PubMed

    Kawamoto; Holloway

    1997-04-11

    The H2O-saturated solidus of a model mantle composition (Kilborne Hole peridotite nodule, KLB-1) was determined to be just above 1000°C from 5 to 11 gigapascals. Given reasonable H2O abundances in Earth's mantle, an H2O-rich fluid could exist only in a region defined by the wet solidus and thermal stability limits of hydrous minerals, at depths between 90 and 330 kilometers. The experimental partial melts monotonously became more mafic with increasing pressure from andesitic composition at 1 gigapascal to more mafic than the starting peridotite at 10 gigapascals. Because the chemistry of the experimental partial melts is similar to that of kimberlites, it is suggested that kimberlites may be derived by low-temperature melting of an H2O-rich mantle at depths of 150 to 300 kilometers. PMID:9092469

  18. Melting Temperature and Partial Melt Chemistry of H2O-Saturated Mantle Peridotite to 11 Gigapascals

    PubMed

    Kawamoto; Holloway

    1997-04-11

    The H2O-saturated solidus of a model mantle composition (Kilborne Hole peridotite nodule, KLB-1) was determined to be just above 1000°C from 5 to 11 gigapascals. Given reasonable H2O abundances in Earth's mantle, an H2O-rich fluid could exist only in a region defined by the wet solidus and thermal stability limits of hydrous minerals, at depths between 90 and 330 kilometers. The experimental partial melts monotonously became more mafic with increasing pressure from andesitic composition at 1 gigapascal to more mafic than the starting peridotite at 10 gigapascals. Because the chemistry of the experimental partial melts is similar to that of kimberlites, it is suggested that kimberlites may be derived by low-temperature melting of an H2O-rich mantle at depths of 150 to 300 kilometers.

  19. High temperatures and high pressures Brillouin scattering studies of liquid H(2)O+CO(2) mixtures.

    PubMed

    Qin, Junfeng; Li, Min; Li, Jun; Chen, Rongyan; Duan, Zhenhao; Zhou, Qiang; Li, Fangfei; Cui, Qiliang

    2010-10-21

    The Brillouin scattering spectroscopy studies have been conducted in a diamond anvil cell for a liquid mixtures composed of 95 mol % H(2)O and 5 mol % CO(2) under high temperatures and pressures. The sound velocity, refractive index, density, and adiabatic bulk modulus of the H(2)O+CO(2) mixtures were determined under pressures up to the freezing point at 293, 453, and 575 K. It is found from the experiment that sound velocities of the liquid mixture are substantially lower than those of pure water at 575 K, but not at lower temperatures. We presented an empirical relation of the density in terms of pressure and temperature. Our results show that liquid H(2)O+CO(2) mixtures are more compressible than water obtained from an existing equation of state of at 453 and 575 K. PMID:20969409

  20. Direct numerical simulations of exhaust gas recirculation effect on multistage autoignition in the negative temperature combustion regime for stratified HCCI flow conditions by using H2O2 addition

    NASA Astrophysics Data System (ADS)

    El-Asrag, Hossam A.; Ju, Yiguang

    2013-04-01

    Direct numerical simulations (DNSs) of a stratified flow in a homogeneous compression charge ignition (HCCI) engine are performed to investigate the exhaust gas recirculation (EGR) and temperature/mixture stratification effects on the autoignition of synthetic dimethyl ether (DME) in the negative temperature combustion region. Detailed chemistry for a DME/air mixture is employed and solved by a hybrid multi-time scale (HMTS) algorithm to reduce the computational cost. The effect of ? to mimic the EGR effect on autoignition are studied. The results show that adding ? enhances autoignition by rapid OH radical pool formation (34-46% reduction in ignition delay time) and changes the ignition heat release rates at different ignition stages. Sensitivity analysis is performed and the important reactions pathways affecting the autoignition are specified. The DNS results show that the scales introduced by thermal and mixture stratifications have a strong effect after the low temperature chemistry (LTC) ignition especially at the locations of high scalar dissipation rates. Compared to homogenous ignition, stratified ignitions show similar first autoignition delay times, but 18% reduction in the second and third ignition delay times. The results also show that molecular transport plays an important role in stratified low temperature ignition, and that the scalar mixing time scale is strongly affected by local ignition in the stratified flow. Two ignition-kernel propagation modes are observed: a wave-like, low-speed, deflagrative mode and a spontaneous, high-speed, ignition mode. Three criteria are introduced to distinguish these modes by different characteristic time scales and Damkhöler numbers using a progress variable conditioned by an ignition kernel indicator. The low scalar dissipation rate flame front is characterized by high displacement speeds and high mixing Damkhöler number. The proposed criteria are applied successfully at the different ignition stages and

  1. H2O2 assisted room temperature oxidation of Ti2C MXene for Li-ion battery anodes

    NASA Astrophysics Data System (ADS)

    Ahmed, Bilal; Anjum, Dalaver H.; Hedhili, Mohamed N.; Gogotsi, Yury; Alshareef, Husam N.

    2016-03-01

    Herein we demonstrate that a prominent member of the MXene family, Ti2C, undergoes surface oxidation at room temperature when treated with hydrogen peroxide (H2O2). The H2O2 treatment results in opening up of MXene sheets and formation of TiO2 nanocrystals on their surface, which is evidenced by the high surface area of H2O2 treated MXene and X-ray diffraction (XRD) analysis. We show that the reaction time and the amount of hydrogen peroxide used are the limiting factors, which determine the morphology and composition of the final product. Furthermore, it is shown that the performance of H2O2 treated MXene as an anode material in Li ion batteries (LIBs) was significantly improved as compared to as-prepared MXenes. For instance, after 50 charge/discharge cycles, specific discharge capacities of 389 mA h g-1, 337 mA h g-1 and 297 mA h g-1 were obtained for H2O2 treated MXene at current densities of 100 mA g-1, 500 mA g-1 and 1000 mA g-1, respectively. In addition, when tested at a very high current density, such as 5000 mA g-1, the H2O2 treated MXene showed a specific capacity of 150 mA h g-1 and excellent rate capability. These results clearly demonstrate that H2O2 treatment of Ti2C MXene improves MXene properties in energy storage applications, such as Li ion batteries or capacitors.Herein we demonstrate that a prominent member of the MXene family, Ti2C, undergoes surface oxidation at room temperature when treated with hydrogen peroxide (H2O2). The H2O2 treatment results in opening up of MXene sheets and formation of TiO2 nanocrystals on their surface, which is evidenced by the high surface area of H2O2 treated MXene and X-ray diffraction (XRD) analysis. We show that the reaction time and the amount of hydrogen peroxide used are the limiting factors, which determine the morphology and composition of the final product. Furthermore, it is shown that the performance of H2O2 treated MXene as an anode material in Li ion batteries (LIBs) was significantly improved as

  2. H2O2 assisted room temperature oxidation of Ti2C MXene for Li-ion battery anodes.

    PubMed

    Ahmed, Bilal; Anjum, Dalaver H; Hedhili, Mohamed N; Gogotsi, Yury; Alshareef, Husam N

    2016-04-14

    Herein we demonstrate that a prominent member of the MXene family, Ti2C, undergoes surface oxidation at room temperature when treated with hydrogen peroxide (H2O2). The H2O2 treatment results in opening up of MXene sheets and formation of TiO2 nanocrystals on their surface, which is evidenced by the high surface area of H2O2 treated MXene and X-ray diffraction (XRD) analysis. We show that the reaction time and the amount of hydrogen peroxide used are the limiting factors, which determine the morphology and composition of the final product. Furthermore, it is shown that the performance of H2O2 treated MXene as an anode material in Li ion batteries (LIBs) was significantly improved as compared to as-prepared MXenes. For instance, after 50 charge/discharge cycles, specific discharge capacities of 389 mA h g(-1), 337 mA h g(-1) and 297 mA h g(-1) were obtained for H2O2 treated MXene at current densities of 100 mA g(-1), 500 mA g(-1) and 1000 mA g(-1), respectively. In addition, when tested at a very high current density, such as 5000 mA g(-1), the H2O2 treated MXene showed a specific capacity of 150 mA h g(-1) and excellent rate capability. These results clearly demonstrate that H2O2 treatment of Ti2C MXene improves MXene properties in energy storage applications, such as Li ion batteries or capacitors.

  3. H2O2 assisted room temperature oxidation of Ti2C MXene for Li-ion battery anodes.

    PubMed

    Ahmed, Bilal; Anjum, Dalaver H; Hedhili, Mohamed N; Gogotsi, Yury; Alshareef, Husam N

    2016-04-14

    Herein we demonstrate that a prominent member of the MXene family, Ti2C, undergoes surface oxidation at room temperature when treated with hydrogen peroxide (H2O2). The H2O2 treatment results in opening up of MXene sheets and formation of TiO2 nanocrystals on their surface, which is evidenced by the high surface area of H2O2 treated MXene and X-ray diffraction (XRD) analysis. We show that the reaction time and the amount of hydrogen peroxide used are the limiting factors, which determine the morphology and composition of the final product. Furthermore, it is shown that the performance of H2O2 treated MXene as an anode material in Li ion batteries (LIBs) was significantly improved as compared to as-prepared MXenes. For instance, after 50 charge/discharge cycles, specific discharge capacities of 389 mA h g(-1), 337 mA h g(-1) and 297 mA h g(-1) were obtained for H2O2 treated MXene at current densities of 100 mA g(-1), 500 mA g(-1) and 1000 mA g(-1), respectively. In addition, when tested at a very high current density, such as 5000 mA g(-1), the H2O2 treated MXene showed a specific capacity of 150 mA h g(-1) and excellent rate capability. These results clearly demonstrate that H2O2 treatment of Ti2C MXene improves MXene properties in energy storage applications, such as Li ion batteries or capacitors. PMID:26984324

  4. H(2)O Outgassing Properties of Fumed and Precipitated Silica Particles by Temperature-Programmed Desorption.

    PubMed

    Dinh; Balooch; LeMay

    2000-10-15

    Temperature-programmed desorption was performed at temperatures up to 850 K on as-received fumed and precipitated silica particles. Physisorbed water molecules on both types of silica had activation energies in the range of 38-61 kJ/mol. However, the activation energies of desorption for chemisorbed water varied from approximately 80 to >247 kJ/mol for fumed silica, Cab-O-Sil-M-7D, and approximately 96 to 155 kJ/mol for precipitated silica, Hi-Sil-233. Our results suggest that physisorbed water can be effectively pumped away at room temperature (or preferably at 320 K) in a matter of hours. Chemisorbed water with high activation energies of desorption (>126 kJ/mol) will not escape silica surfaces in 100 years even at 320 K, while a significant amount of the chemisorbed water with medium activation energies (80-109 kJ/mol) will leave the silica surfaces in that time span. Most of the chemisorbed water with activation energies <126 kJ/mol can be pumped away in a matter of days in a good vacuum environment at 500 K. We had previously measured about 0.1-0.4 wt% of water in silica-reinforced polysiloxane formulations containing approximately 21% Cab-O-Sil-M-7D and approximately 4% Hi-Sil-233. Comparing present results with these formulations, we conclude that the adsorbed H(2)O and the Si-OH bonds on the silica surfaces are the major contributors to water outgassing from these types of silica-filled polymers. Copyright 2000 Academic Press.

  5. 3D CFD Model of High Temperature H2O/CO2 Co-electrolysis

    SciTech Connect

    Grant Hawkes; James O'Brien; Carl Stoots; Stephen Herring; Joe Hartvigsen

    2007-06-01

    3D CFD Model of High Temperature H2O/CO2 Co-Electrolysis Grant Hawkes1, James O’Brien1, Carl Stoots1, Stephen Herring1 Joe Hartvigsen2 1 Idaho National Laboratory, Idaho Falls, Idaho, grant.hawkes@inl.gov 2 Ceramatec Inc, Salt Lake City, Utah INTRODUCTION A three-dimensional computational fluid dynamics (CFD) model has been created to model high temperature co-electrolysis of steam and carbon dioxide in a planar solid oxide electrolyzer (SOE) using solid oxide fuel cell technology. A research program is under way at the Idaho National Laboratory (INL) to simultaneously address the research and scale-up issues associated with the implementation of planar solid-oxide electrolysis cell technology for syn-gas production from CO2 and steam. Various runs have been performed under different run conditions to help assess the performance of the SOE. This paper presents CFD results of this model compared with experimental results. The Idaho National Laboratory (INL), in conjunction with Ceramatec Inc. (Salt Lake City, USA) has been researching for several years the use of solid-oxide fuel cell technology to electrolyze steam for large-scale nuclear-powered hydrogen production. Now, an experimental research project is underway at the INL to produce syngas by simultaneously electrolyzing at high-temperature steam and carbon dioxide (CO2) using solid oxide fuel cell technology. A strong interest exists in the large-scale production of syn-gas from CO2 and steam to be reformed into a usable transportation fuel. If biomass is used as the carbon source, the overall process is climate neutral. Consequently, there is a high level of interest in production of syn-gas from CO2 and steam electrolysis. With the price of oil currently around $60 / barrel, synthetically-derived hydrocarbon fuels (synfuels) have become economical. Synfuels are typically produced from syngas – hydrogen (H2) and carbon monoxide (CO) -- using the Fischer-Tropsch process, discovered by Germany before World

  6. Measurements of Flow Distortion within the IRGASON Integrated Sonic Anemometer and CO_2/H_2O Gas Analyzer

    NASA Astrophysics Data System (ADS)

    Horst, T. W.; Vogt, R.; Oncley, S. P.

    2016-07-01

    Wind-tunnel and field measurements are analyzed to investigate flow distortion within the IRGASON integrated sonic anemometer and CO_2/H_2O gas analyzer as a function of wind speed, wind direction and attack angle. The wind-tunnel measurements are complimentary to the field measurements, and the dependence of the wind-tunnel mean-wind-component flow-distortion errors on wind direction agrees well with that of the field measurements. The field measurements exhibit significant overestimation of the crosswind variance and underestimation of the momentum flux with respect to an adjacent CSAT3 sonic, as well as a transfer of turbulent kinetic energy from the streamwise wind component to the cross-stream wind components. In contrast, we find attenuation of only a few percent in the vertical velocity variance and the vertical flux of sonic temperature. The attenuation of the fluxes appears to be caused to a large extent by decorrelation between the horizontal and vertical-velocity components and between the vertical velocity and sonic temperature. Additional flow distortion due to transducer shadowing reduces to some extent the overestimation, but also increases the underestimation of the IRGASON turbulence statistics.

  7. Bubble nucleation in H2O-CO2 bearing basaltic melts: results of high temperature decompression experiments

    NASA Astrophysics Data System (ADS)

    Le Gall, N.; Pichavant, M.; Burgisser, A.

    2012-12-01

    Previous experiments have shown that mechanisms of basalt degassing are strongly contrasted when gas bubbles are present or when they are absent. Thus, experimental information on the kinetics of bubble nucleation in basaltic melts is needed, and high temperature decompression experiments have been investigated. All experiments used PST-9 basaltic pumice from Stromboli as starting material. The sample was fused in air at 1400°C for 3h and then cylinders (l up to 10mm, d 2.5 and 5mm) were cored. Synthesis experiments were performed to produce the volatile-bearing melts to be used in the decompression experiments. Glass cores, distilled H2O and Ag2C2O4 were loaded in AuPd capsules. Three different H2O/CO2 were introduced, corresponding to XH2Oin=1 (#1: only H2O dissolved in glass), 0.55 (#2: high dissolved H2O/CO2), 0 (#3: low dissolved H2O/CO2). The synthesis experiments were ran at 1200°C during about 40h in an internally heated vessel pressurized with Ar-H2. The synthesized crystal- and bubble-free glasses were cut in 2 parts: one for the decompression experiments and the other for the analysis. Decompression experiments were conducted at a fast rate of 39kPa/s, exceptionally of 77.8kPa/s, at 1200°C from an initial pressure (Pin) of 200MPa and to final pressures (Pf) of 200, 150, 100 and 50MPa. Experiments to 25MPa are in progress. Each run included 3 capsules, corresponding to the 3 XH2Oin conditions of glass synthesis, allowing results for the 3 H2O/CO2 to be directly compared. Charges were rapid-quenched immediately after attainment of Pf. Textures were analyzed by X-ray microtomography, and volatile concentrations and spatial distributions in pre- and post-decompression glasses were determined by FTIR. Pre-decompression glasses have homogeneous volatile contents and distributions. They divide into 3 compositional groups consistent with their XH2Oin conditions of synthesis: group #1 (average H2O content=4.82wt%, average CO2 content=0ppm), group #2 (2.15wt

  8. Effects of H2O Vapor on Vibrational Relaxation in Expanding and Contracting Flows

    NASA Technical Reports Server (NTRS)

    Meador, Willard E.; Townsend, Lawrence W.; Miner, Gilda A.

    1996-01-01

    As opposed to previous explanations based on the effects of anharmonicity of simple diatomic molecules, traces of water vapor are suggested to be the most likely cause of the anomalously fast vibrational relaxation of such gases observed in supersonic and hypersonic nozzles. The mechanism is the strong V-VR coupling with H2O molecules that dramatically facilitates the collisional transfer of vibrational energy. Slight moisture content is thus a real world aspect of gas dynamics that must be considered in characterizations of shock tubes, reflected shock tunnels, and expansion tubes.

  9. Raman spectroscopic quantitative study of NaCl-CaCl2-H2O system at high temperatures and pressures.

    PubMed

    Li, Jing; Mao, Shi-De; Zheng, Hai-Fei

    2014-07-01

    Raman spectra features of the ternary system NaCl-CaCl2-H2O under high temperatures and high pressures were systematically studied in the present work by using hydrothermal diamond anvil cell (HDAC) and Raman shifts of quartz to determine pressures, and it has been obtained for the quantitative relationship between Raman shifts of the O-H stretching band of water, mass fractions of solutes and pressures was obtained. The mass fractions of salts, where salinity of NaCl equal to that of CaCl2, are 4.0 mass %, 8.0 mass %, and 12.0 mass %, respectively. Experimental results indicate that the standardized Raman frequency shift differences of the O-H stretching vibration (deltav(O0H)) rise with the increasing temperatures when the mass fractions of salts and pressures of the NaCl-CaCl2-H2O system remain constant. deltav(O-H) increases with the increase in mass fractions of salts in the system when the temperatures and pressures are constant. Linear relationship between deltav(O-H) and pressure with similar slopes can be found for the NaCl-CaCl2-H2O system with different salinities. The quantitative relationship between deltav(O-H), temperature (T), pressure (P), and mass fraction of solute (M) is P = -31.892 deltav(O-H) + 10.131T + 222.816M - 3 183.567, where the valid PTM range of the equation is 200 MPa < or = P < or = 1 700 MPa, 273 K < or = T < or = 539 K and M < or = 12 mass %. The equation can be used as a geobarometer in the studies of fluid inclusions of NaCl-CaCl2-H2O system with equal salinities. The method, as a direct geological detecting technique, has a potential application value. PMID:25269273

  10. The sublimation temperature of the cometary nucleus Observational evidence for H2O snows

    NASA Technical Reports Server (NTRS)

    Delsemme, A. H.

    1985-01-01

    It is shown that information on the chemical composition of cometary snows can be inferred from the distance r(0) between sublimating states in the cometary nucleus. Consideration is given to three techniques for measuring r(0): estimation of the dependence on distance of non-gravitational forces (NGF); estimation of the dependence on distance of molecular emissions; and (3), analysis of the cometary light curve. The dependence on distance of the NGFs suggests that the observed sublimations of short-period coments are determined by water snow. Light curves of newly discovered comets appear to confirm this result. The large production rates of H and OH in cometary atmospheres suggest that they are due to dissociation of H2O in the vapor states. Estimates of r(0) for eleven different comets are given in a table.

  11. Freezing temperatures of H2SO4/HNO3/H2O mixtures: Implications for polar stratospheric clouds

    NASA Technical Reports Server (NTRS)

    Song, Naihui

    1994-01-01

    The freezing temperatures of H2SO4/HNO3/H2O mixtures were systematically documented. Nitric acid was found to affect freezing significantly. Measurements show that nitric acid can cause substantial supercooling over a broad composition range. However, some ternary compositions, like to those in polar stratospheric clouds (PSCs), have high freezing temperatures. The freezing of PSC particles could be controlled by the temperature and vapor pressure of both nitric acid and water in a non-linear way. Formation of polar stratospheric clouds may be forecasted on the basic of conditions of temperature and vapor contents of water and nitric acid.

  12. Blackbody infrared radiative dissociation at low temperature: hydration of X2+(H2O)n, for X = Mg, Ca

    NASA Astrophysics Data System (ADS)

    Wong, Richard L.; Paech, Kolja; Williams, Evan R.

    2004-03-01

    A new apparatus for making blackbody infrared radiative dissociation (BIRD) measurements at below ambient temperature is described, and its use for measuring threshold dissociation energies of weakly bound clusters is demonstrated. Hydration energies are determined for alkaline-earth metal water clusters, X2+(H2O)n, X=Mg, Ca and n=8-10. For n=8 and 9, the energies obtained from BIRD measurements are in excellent agreement with values reported previously, but for n=10, the energies are slightly lower than those determined previously using the high-pressure ion source mass spectrometry (HPMS) equilibrium method.

  13. Room temperature synthesis of K2Mo3O10x3H2O nanowires in minutes.

    PubMed

    Gong, Weiwei; Xue, Jiongwei; Zhang, Kai; Wu, Zhan; Wei, Dapeng; Chen, Qing; Pan, Huayong; Xu, Shengyong

    2009-05-27

    Polyoxometalates have been widely used in the fields of catalysis, analytical chemistry, biochemistry, medicine and synthesis of novel organic-inorganic materials. It is difficult to synthesize pure polymolybdate products from a solution because several kinds of molybdenum-based anions may coexist. As a result, varied acidification methods are commonly used for solution synthesis of polymolybdates. In this paper we report an approach for the synthesis of [001]-oriented K(2)Mo(3)O(10)x3H(2)O nanowires from an aqueous solution of (NH(4))(6)Mo(7)O(24)x4H(2)O and KCl at low temperatures. The reaction occurs even at temperatures as low as 0 degrees C, and at 30-90 degrees C the whole procedure needs only a few minutes. Without any additional acidification treatments, the pH value of the solution is maintained in a narrow range of +/- 0.1 between 4.9 and 5.5 during the whole synthesis procedure. The starting pH depends on the reaction temperature. Crystalline structure and purity of the final products have been characterized with x-ray diffraction, electron diffraction and dehydration measurements. This simple and rapid method provides a unique case for studying the growth mechanism of polymolybdate nanostructures, and has a promising potential in the mass production of low-cost, pure-phase polymolybdates for a variety of applications. PMID:19423934

  14. Equations of state for H2, H2O, and H2-H2O fluid mixtures at temperatures above 0.01° C and at high pressures

    NASA Astrophysics Data System (ADS)

    Rimbach, Helmut; Chatterjee, Niranjan D.

    1987-11-01

    Modified Redlich-Kwong (MRK) equations of state have been derived for the pure fluid species H2 and H2O by expressing the parameter a as a function of T and P, and b as as a function of P only. These equations are valid above 0° and 0.01° C, respectively. For H2O, the prediction of volumes is successful not only in the supercritical, but also in the subcritical range. As a result of this, the saturation curve of H2O can be calculated with a maximum deviation of ±1.4 bar in the range 100 350° C. Between 350° C and the critical point (374.15° C), the uncertainty increases somewhat; this is due to a fundamental inadequacy of the Redlich-Kwong equation itself. These equations of state permit extrapolations to pressures of 100 kbar for H2 and at least 200 kbar for H2O and are, therefore, eminently suited for geochemical applications. Formulation of the MRK of the binary H2-H2O mixtures was achieved by assuming the quadratic mixing rule for the parameters a mix and b+mix. To derive the cross coefficients, aH2-H2Oand b H 2-H 2O, adjustable corrective factors ɛ and τ had to be introduced. The T- and P-dependences of ɛ and τ are based on P-V-T-X H 2 data (Seward and Franck 1981) to 440° C and 2500 bar. The resulting equation of state very satisfactorily reproduces the volumes observed experimentally at various sets of T, P, and X H 2. At a total pressure of 2 kbar, positive deviation from ideal mixing behaviour is still perceptible at as high a temperature as 1000° C. At some temperature around 380° C, phase separation sets in, an aqueous solution with dissolved H2 coexisting in equilibrium with an H2-rich fluid with dissolved H2O. The computed P-T-X H 2 surface of this two-phase region agrees well with that observed in Seward and Franck's (1981) experiments. An independent proof of the validity of this equation of state is the accuracy with which H {m/ex}can be predicted. Calorimetric measurements of H {m/ex}(Smith et al. 1983, Wormald and Colling 1985

  15. Water Exchange on [Ln(DO3A)(H2O)2] and [Ln(DTTA-Me)(H2O)2](-) Studied by Variable Temperature, Pressure, and Magnetic Field NMR.

    PubMed

    Karimi, Shima; Helm, Lothar

    2016-05-01

    Water exchange kinetics of [Ln(L)(H2O)2](x) complexes (Ln = Pr, Nd, Dy, Tm, and Yb; L = DO3A and DTTA-Me) were studied by (17)O NMR spectroscopy as a function of temperature, pressure, and frequency and by (1)H nuclear magnetic relaxation dispersion. Water exchange rate constants of both complexes show a maximum at dysprosium. Water exchange on negatively charged complexes of the acyclic DTTA-Me ligand is much faster than on the neutral complexes of the macrocyclic DO3A. Small activation volumes |ΔV(⧧)| < 1 cm(3) mol(-1) measured for water exchange on [Ln(DO3A)(H2O)2] indicate an interchange type of mechanism (I) for the lanthanide complexes studied. In the case of [Ln(DTTA-Me)(H2O)2](-), a change in mechanism is detected from a dissociative mechanism (D, ΔV(⧧) = 7 cm(3) mol(-1)) for complexes with larger ions (Pr to Gd) to an interchange mechanism (Id, I; ΔV(⧧) = +1.8 and +0.4 cm(3) mol(-1)) for complexes with smaller ions (Dy and Tm). PMID:27082861

  16. Temperature-dependent kinetic measurements and quasi-classical trajectory studies for the OH(+) + H2/D2 → H2O(+)/HDO(+) + H/D reactions.

    PubMed

    Martinez, Oscar; Ard, Shaun G; Li, Anyang; Shuman, Nicholas S; Guo, Hua; Viggiano, Albert A

    2015-09-21

    We have measured the temperature-dependent kinetics for the reactions of OH(+) with H2 and D2 using a selected ion flow tube apparatus. Reaction occurs via atom abstraction to result in H2O(+)/HDO(+) + H/D. Room temperature rate coefficients are in agreement with prior measurements and resulting temperature dependences are T(0.11) for the hydrogen and T(0.25) for the deuterated reactions. This work is prompted in part by recent theoretical work that mapped a full-dimensional global potential energy surface of H3O(+) for the OH(+) + H2 → H + H2O(+) reaction [A. Li and H. Guo, J. Phys. Chem. A 118, 11168 (2014)], and reported results of quasi-classical trajectory calculations, which are extended to a wider temperature range and initial rotational state specification here. Our experimental results are in excellent agreement with these calculations which accurately predict the isotope effect in addition to an enhancement of the reaction rate constant due to the molecular rotation of OH(+). The title reaction is of high importance to astrophysical models, and the temperature dependence of the rate coefficients determined here should now allow for better understanding of this reaction at temperatures more relevant to the interstellar medium.

  17. Temperature-dependent kinetic measurements and quasi-classical trajectory studies for the OH+ + H2/D2 → H2O+/HDO+ + H/D reactions

    NASA Astrophysics Data System (ADS)

    Martinez, Oscar; Ard, Shaun G.; Li, Anyang; Shuman, Nicholas S.; Guo, Hua; Viggiano, Albert A.

    2015-09-01

    We have measured the temperature-dependent kinetics for the reactions of OH+ with H2 and D2 using a selected ion flow tube apparatus. Reaction occurs via atom abstraction to result in H2O+/HDO+ + H/D. Room temperature rate coefficients are in agreement with prior measurements and resulting temperature dependences are T0.11 for the hydrogen and T0.25 for the deuterated reactions. This work is prompted in part by recent theoretical work that mapped a full-dimensional global potential energy surface of H3O+ for the OH+ + H2 → H + H2O+ reaction [A. Li and H. Guo, J. Phys. Chem. A 118, 11168 (2014)], and reported results of quasi-classical trajectory calculations, which are extended to a wider temperature range and initial rotational state specification here. Our experimental results are in excellent agreement with these calculations which accurately predict the isotope effect in addition to an enhancement of the reaction rate constant due to the molecular rotation of OH+. The title reaction is of high importance to astrophysical models, and the temperature dependence of the rate coefficients determined here should now allow for better understanding of this reaction at temperatures more relevant to the interstellar medium.

  18. Dependence of the four-atom reaction HBr + OH → Br + H2O on temperatures between 20 and 2000 K.

    PubMed

    Ree, J; Kim, Y H; Shin, H K

    2015-04-01

    A quasiclassical trajectory method is used to study the temperature dependence of HBr + OH → Br + H2O using analytic forms of two-, three-, and four-body and long-range interaction potentials. Below 300 K, the reaction is attraction-driven and occurs through formation of a collision complex BrH···OH, which is sufficiently long-lived to enhance H atom tunneling. Strong negative temperature dependence of the complex-mode rate is found between 20 and 300 K, consistent with experimental data reported by various authors. Above 300 K, the reaction occurs primarily through a direct-reaction mechanism. The sum of the complex- and direct-mode rates is shown to describe the reaction over the wide range 20-2000 K. The primary kinetic isotope effect is nearly constant with the normal H reaction faster by a factor of ∼1.7 over the entire temperature range. The product energy distribution in vibration, rotation, and translation at 300 K is found to be 48, 8, and 44%, respectively. The 1:1 resonance leads to efficient flow of energy between the stretching modes. Less than a quarter of the H2O vibrational energy deposits in the bending mode through intramolecular flow from the two stretching modes.

  19. Dependence of the four-atom reaction HBr + OH → Br + H2O on temperatures between 20 and 2000 K.

    PubMed

    Ree, J; Kim, Y H; Shin, H K

    2015-04-01

    A quasiclassical trajectory method is used to study the temperature dependence of HBr + OH → Br + H2O using analytic forms of two-, three-, and four-body and long-range interaction potentials. Below 300 K, the reaction is attraction-driven and occurs through formation of a collision complex BrH···OH, which is sufficiently long-lived to enhance H atom tunneling. Strong negative temperature dependence of the complex-mode rate is found between 20 and 300 K, consistent with experimental data reported by various authors. Above 300 K, the reaction occurs primarily through a direct-reaction mechanism. The sum of the complex- and direct-mode rates is shown to describe the reaction over the wide range 20-2000 K. The primary kinetic isotope effect is nearly constant with the normal H reaction faster by a factor of ∼1.7 over the entire temperature range. The product energy distribution in vibration, rotation, and translation at 300 K is found to be 48, 8, and 44%, respectively. The 1:1 resonance leads to efficient flow of energy between the stretching modes. Less than a quarter of the H2O vibrational energy deposits in the bending mode through intramolecular flow from the two stretching modes. PMID:25751761

  20. Simplified calculations for accuracy of a lidar dial system to measure atmospheric H2O vapor and temperature.

    PubMed

    Braun, W C

    1985-01-01

    A simple method is given for computing the relative errors in H2O vapor and T (temperature) profiles measured by a ground-based differential lidar system: The analysis is based on a simplified model of the earth's atmosphere, which allows one to write exact mathematical expressions for the lidar return signals which can be evaluated in closed form. Error computations can be made from these expressions with a small pocket calculator to an accuracy of a few percent. Error estimates are given for a lidar system used to measure H2O and T profiles from the ground up to a 5-km altitude. The results are given for an ideal system with no instrument noise and for a system using quantum detectors with detector-amplifier noise and less than unity quantum efficiency. The relative merits of the photomultiplier tube and silicon diode as detectors are also assessed using this technique of error analysis. Regions of useful operation for these detectors are defined in terms of the signal energy of the lidar return and the noise equivalent power of the detector.

  1. Room-temperature synthesis of MnO2.3H2O ultrathin nanostructures and their morphological transformation to well-dispersed nanorods.

    PubMed

    Wang, Jinmin; Khoo, Eugene; Ma, Jan; Lee, Pooi See

    2010-04-14

    MnO(2).3H(2)O ultrathin nanostructures with sizes of approximately 2-3 nm were synthesized at room temperature and transformation to well-dispersed nanorods was achieved after hydrothermal treatments.

  2. Surface temperatures and retention of H2O frost on Ganymede and Callisto

    NASA Technical Reports Server (NTRS)

    Squyres, S. W.

    1980-01-01

    Surface temperatures and ice evaporation rates are calculated for Ganymede and Callisto as functions of latitude, time of day, and albedo, according to a model that uses surface thermal properties determined by eclipse radiometry and albedos determined from photometrically decalibrated Voyager images. The difference in temperature between Ganymede and Callisto is not great enough to account for the lack of bright polar caps on Callisto, which seems instead to reflect a real deficiency in the amount of available water frost relative to Ganymede. The temperature difference between Ganymede's grooved and cratered terrains also cannot account for the high concentration of bright ray craters in the former, suggesting that an internal geologic process has enriched the grooved terrain in ice content relative to the cratered terrain.

  3. H2/O2 three-body rates at high temperatures

    NASA Technical Reports Server (NTRS)

    Marinelli, William J.; Kessler, William J.; Piper, Lawrence G.; Rawlins, W. Terry

    1990-01-01

    The extraction of thrust from air breathing hypersonic propulsion systems is critically dependent on the degree to which chemical equilibrium is reached in the combustion process. In the combustion of H2/Air mixtures, slow three-body chemical reactions involving H-atoms, O-atoms, and the OH radical play an important role in energy extraction. A first-generation high temperature and pressure flash-photolysis/laser-induced fluorescence reactor was designed and constructed to measure these important three-body rates. The system employs a high power excimer laser to produce these radicals via the photolysis of stable precursors. A novel two-photon laser-induced fluorescence technique is employed to detect H-atoms without optical thickness or O2 absorption problems. To demonstrate the feasibility of the technique the apparatus in the program is designed to perform preliminary measurements on the H + O2 + M reaction at temperatures from 300 to 835 K.

  4. H2/O2 three-body rates at high temperatures

    NASA Technical Reports Server (NTRS)

    Marinelli, William J.; Kessler, William J.; Carleton, Karen L.

    1991-01-01

    Hydrogen atoms are produced in the presence of excess O2, and the first-order decay are studied as a function of temperature and pressure in order to obtain the rate coefficient for the three-body reaction between H-atoms and O2. Attention is focused on the kinetic scheme employed as well as the reaction cell and photolysis and probe laser system. A two-photon laser-induced fluorescence technique is employed to detect H-atoms without optical-thickness or O2-absorption problems. Results confirm measurements reported previously for the H + O2 + N2 reaction at 300 K and extend these measurements to higher temperatures. Preliminary data indicate non-Arrehenius-type behavior of this reaction rate coefficient as a function of temperature. Measurements of the rate coefficient for H + O2 + Ar reaction at 300 K give a rate coefficient of 2.1 +/- 0.1 x 10 to the -32nd cm exp 6/molecule sec.

  5. Fabrication of porous silicon nanowires by MACE method in HF/H2O2/AgNO3 system at room temperature.

    PubMed

    Li, Shaoyuan; Ma, Wenhui; Zhou, Yang; Chen, Xiuhua; Xiao, Yongyin; Ma, Mingyu; Zhu, Wenjie; Wei, Feng

    2014-01-01

    In this paper, the moderately and lightly doped porous silicon nanowires (PSiNWs) were fabricated by the 'one-pot procedure' metal-assisted chemical etching (MACE) method in the HF/H2O2/AgNO3 system at room temperature. The effects of H2O2 concentration on the nanostructure of silicon nanowires (SiNWs) were investigated. The experimental results indicate that porous structure can be introduced by the addition of H2O2 and the pore structure could be controlled by adjusting the concentration of H2O2. The H2O2 species replaces Ag(+) as the oxidant and the Ag nanoparticles work as catalyst during the etching. And the concentration of H2O2 influences the nucleation and motility of Ag particles, which leads to formation of different porous structure within the nanowires. A mechanism based on the lateral etching which is catalyzed by Ag particles under the motivation by H2O2 reduction is proposed to explain the PSiNWs formation.

  6. Fabrication of porous silicon nanowires by MACE method in HF/H2O2/AgNO3 system at room temperature

    PubMed Central

    2014-01-01

    In this paper, the moderately and lightly doped porous silicon nanowires (PSiNWs) were fabricated by the ‘one-pot procedure’ metal-assisted chemical etching (MACE) method in the HF/H2O2/AgNO3 system at room temperature. The effects of H2O2 concentration on the nanostructure of silicon nanowires (SiNWs) were investigated. The experimental results indicate that porous structure can be introduced by the addition of H2O2 and the pore structure could be controlled by adjusting the concentration of H2O2. The H2O2 species replaces Ag+ as the oxidant and the Ag nanoparticles work as catalyst during the etching. And the concentration of H2O2 influences the nucleation and motility of Ag particles, which leads to formation of different porous structure within the nanowires. A mechanism based on the lateral etching which is catalyzed by Ag particles under the motivation by H2O2 reduction is proposed to explain the PSiNWs formation. PMID:24910568

  7. Laboratory studies of HNO3/H2O mixtures at low temperatures

    NASA Technical Reports Server (NTRS)

    Hanson, David; Mauersberger, Konrad

    1988-01-01

    The possibility of stratospheric HN3 condensing out of the gas-phase at low temperatures has become important in the chemical explanations of the rapid loss of Antarctic ozone in spring. Consequently, knowledge about the behavior of the vapor pressures of water and HNO3 over HNO3/water mixtures at stratospheric temperatures is needed to determine if HNO3 could condense, and by how much the HNO3 vapor pressure could be depressed. Laboratory investigations of vapor pressures above HNO3/water mixtures are described. Vapor pressures were initially measured over liquid and frozen bulk mixtures contained in a glass still which was attached to a stainless steel vacuum chamber. The total pressure in the chamber was monitored with a precision pressure sensor, and the vapor pressures of HNO3, water and impurities were analyzed with a mass spectrometer beam system. In a second set of experiments, vapor deposits were made to produce ice and the mono- and trihydrate of HNO3. Further data and conclusions are presented.

  8. CKA2 functions in H2O2-induced apoptosis and high-temperature stress tolerance by regulating NO accumulation in yeast.

    PubMed

    Liu, Wen-Cheng; Yuan, Hong-Mei; Li, Yun-Hui; Lu, Ying-Tang

    2015-09-01

    Nitric oxide (NO) plays key roles in yeast responses to various environmental factors, such as H2O2 and high temperature. However, the gene encoding NO synthase (NOS) in yeast has not yet been identified, and the mechanism underlying the regulation of NOS-like activity is poorly understood. Here, we report on the involvement of CKA2 in H2O2-induced yeast apoptosis and yeast high-temperature stress tolerance. Our results showed that although Δcka2 mutant had reduced NO accumulation with decreased apoptosis after H2O2 exposure, treatment with a NO donor, sodium nitroprusside, resulted in similar survival rate of Δcka2 mutant compared to that of wild-type yeast when subjected to H2O2 stress. This finding occurred because H2O2-enhanced NOS-like activity in wild-type yeast was significantly repressed in Δcka2. Our additional experiments indicated that both high-temperature-enhanced NO accumulation and NOS-like activity were also suppressed in Δcka2, leading to the hypersensitivity of the mutant to high temperature in terms of changes in survival rate. Thus, our results showed that CKA2 functioned in H2O2-induced apoptosis and high-temperature stress tolerance by regulating NOS-like-dependent NO accumulation in yeast.

  9. Quantum Tunneling Enhancement of the C + H2O and C + D2O Reactions at Low Temperature.

    PubMed

    Hickson, Kevin M; Loison, Jean-Christophe; Nuñez-Reyes, Dianailys; Méreau, Raphaël

    2016-09-15

    Recent studies of neutral gas-phase reactions characterized by barriers show that certain complex forming processes involving light atoms are enhanced by quantum mechanical tunneling at low temperature. Here, we performed kinetic experiments on the activated C((3)P) + H2O reaction, observing a surprising reactivity increase below 100 K, an effect that is only partially reproduced when water is replaced by its deuterated analogue. Product measurements of H- and D-atom formation allowed us to quantify the contribution of complex stabilization to the total rate while confirming the lower tunneling efficiency of deuterium. This result, which is validated through statistical calculations of the intermediate complexes and transition states has important consequences for simulated interstellar water abundances and suggests that tunneling mechanisms could be ubiquitous in cold dense clouds.

  10. Quantum Tunneling Enhancement of the C + H2O and C + D2O Reactions at Low Temperature.

    PubMed

    Hickson, Kevin M; Loison, Jean-Christophe; Nuñez-Reyes, Dianailys; Méreau, Raphaël

    2016-09-15

    Recent studies of neutral gas-phase reactions characterized by barriers show that certain complex forming processes involving light atoms are enhanced by quantum mechanical tunneling at low temperature. Here, we performed kinetic experiments on the activated C((3)P) + H2O reaction, observing a surprising reactivity increase below 100 K, an effect that is only partially reproduced when water is replaced by its deuterated analogue. Product measurements of H- and D-atom formation allowed us to quantify the contribution of complex stabilization to the total rate while confirming the lower tunneling efficiency of deuterium. This result, which is validated through statistical calculations of the intermediate complexes and transition states has important consequences for simulated interstellar water abundances and suggests that tunneling mechanisms could be ubiquitous in cold dense clouds. PMID:27574866

  11. Crop responses to elevated CO2 and interactions with H2O, N, and temperature.

    PubMed

    Kimball, Bruce A

    2016-06-01

    About twenty-seven years ago, free-air CO2 enrichment (FACE) technology was developed that enabled the air above open-field plots to be enriched with CO2 for entire growing seasons. Since then, FACE experiments have been conducted on cotton, wheat, ryegrass, clover, potato, grape, rice, barley, sugar beet, soybean, cassava, rape, mustard, coffee (C3 crops), and sorghum and maize (C4 crops). Elevated CO2 (550ppm from an ambient concentration of about 353ppm in 1990) decreased evapotranspiration about 10% on average and increased canopy temperatures about 0.7°C. Biomass and yield were increased by FACE in all C3 species, but not in C4 species except when water was limiting. Yields of C3 grain crops were increased on average about 19%. PMID:27043481

  12. H+ homeostasis, osmolality, and body temperature during controlled NaCl and H2O intake.

    PubMed

    Anderson, J W; Jennings, D B

    1988-07-01

    Arterial PCO2, arterial [H+] ([H+]a), electrolytes, and osmolality, as well as rectal temperature (Tre), were monitored in six awake dogs over sequential 12- or 13-day periods in which their NaCl intake was first less than 5 meq/day, then approximately 120 meq/day, and finally less than 5 meq/day. Water intake was maintained constant at 77 ml.kg-1.day-1 throughout. During low-NaCl periods, decreases in body and plasma water, indicated by weight loss did not prevent lower arterial [Na+] ([Na+]a), arterial [Cl-] ([Cl-]a), and osmolality relative to the high-NaCl period. During high dietary NaCl, the arterial strong ion difference [[SID]a = ([Na+]a + [K+]a) - (arterial [lactate-] + [Cl-]a)] was lower. From physicochemistry, this lowered [SID]a results in a higher [H+]a. However, independent of NaCl intake, [H+]a was positively correlated with plasma osmolality; moreover, [H+]a, relative to plasma osmolality, was higher at lower Tre than at higher Tre. We speculate that this spectrum of plasma osmolality and body temperature may contribute to the creation of an appropriate protein pK to match plasma [H+]a. We also found that the difference between plasma [protein] (measured by the biuret test) and [ATOT]a (an estimation of plasma protein as total weak acid from physicochemistry) was related to plasma osmolality, [SID]a, and [Na+]a. These latter relations may reflect the effect of plasma water concentration (osmolality) and strong ions on the pK of plasma proteins.

  13. Influence of hydroxyapatite nanoparticles on the viscosity of dimethyl sulfoxide-H2O-NaCl and glycerol-H2O-NaCl ternary systems at subzero temperatures.

    PubMed

    Yi, Jingru; Tang, Heyu; Zhao, Gang

    2014-10-01

    The viscosity, at subzero temperatures, of ternary solutions commonly used in cryopreservation is tremendously important for understanding ice formation and molecular diffusion in biopreservation. However, this information is scarce in the literature. In addition, to the best of our knowledge, the effect of nanoparticles on the viscosity of these solutions has not previously been reported. The objectives of this study were thus: (i) to systematically measure the subzero viscosity of two such systems, dimethyl sulfoxide (Me2SO)-H2O-NaCl and glycerol-H2O-NaCl; (ii) to explore the effect of hydroxyapatite (HA) nanoparticles on the viscosity; and (iii) to provide models that precisely predict viscosity at multiple concentrations of cryoprotective agent (CPA) in saline solutions at subzero temperatures. Our experiments were performed in two parts. We first measured the viscosity at multiple CPA concentrations [0.3-0.75 (w/w)] in saline solution with and without nanoparticles at subzero temperatures (0 to -30°C). The data exhibited a good fit to the Williams-Landel-Ferry (WLF) equation. We then measured the viscosity of residual unfrozen ternary solutions with and without nanoparticles during equilibrium freezing. HA nanoparticles made the solution more viscous, suggesting applications for these nanoparticles in preventing cell dehydration, ice nucleation, and ice growth during freezing and thawing in cryopreservation.

  14. Influence of hydroxyapatite nanoparticles on the viscosity of dimethyl sulfoxide-H2O-NaCl and glycerol-H2O-NaCl ternary systems at subzero temperatures.

    PubMed

    Yi, Jingru; Tang, Heyu; Zhao, Gang

    2014-10-01

    The viscosity, at subzero temperatures, of ternary solutions commonly used in cryopreservation is tremendously important for understanding ice formation and molecular diffusion in biopreservation. However, this information is scarce in the literature. In addition, to the best of our knowledge, the effect of nanoparticles on the viscosity of these solutions has not previously been reported. The objectives of this study were thus: (i) to systematically measure the subzero viscosity of two such systems, dimethyl sulfoxide (Me2SO)-H2O-NaCl and glycerol-H2O-NaCl; (ii) to explore the effect of hydroxyapatite (HA) nanoparticles on the viscosity; and (iii) to provide models that precisely predict viscosity at multiple concentrations of cryoprotective agent (CPA) in saline solutions at subzero temperatures. Our experiments were performed in two parts. We first measured the viscosity at multiple CPA concentrations [0.3-0.75 (w/w)] in saline solution with and without nanoparticles at subzero temperatures (0 to -30°C). The data exhibited a good fit to the Williams-Landel-Ferry (WLF) equation. We then measured the viscosity of residual unfrozen ternary solutions with and without nanoparticles during equilibrium freezing. HA nanoparticles made the solution more viscous, suggesting applications for these nanoparticles in preventing cell dehydration, ice nucleation, and ice growth during freezing and thawing in cryopreservation. PMID:25127873

  15. The low temperature oxidation of lithium thin films on HOPG by O2 and H2O

    NASA Astrophysics Data System (ADS)

    Wulfsberg, Steven M.; Koel, Bruce E.; Bernasek, Steven L.

    2016-09-01

    Lithiated graphite and lithium thin films have been used in fusion devices. In this environment, lithiated graphite will undergo oxidation by background gases. In order to gain insight into this oxidation process, thin (< 15 monolayer (ML)) lithium films on highly ordered pyrolytic graphite (HOPG) were exposed to O2(g) and H2O(g) in an ultra-high vacuum chamber. High resolution electron energy loss spectroscopy (HREELS) was used to identify the surface species formed during O2(g) and H2O(g) exposure. Auger electron spectroscopy (AES) was used to obtain the relative oxidation rates during O2(g) and H2O(g) exposure. AES showed that as the lithium film thickness decreased from 15 to 5 to 1 ML, the oxidation rate decreased for both O2(g) and H2O(g). HREELS showed that a 15 ML lithium film was fully oxidized after 9.7 L (L) of O2(g) exposure and Li2O was formed. HREELS also showed that during initial exposure (< 0.5 L) H2O(g), lithium hydride and lithium hydroxide were formed on the surface of a 15 ML lithium film. After 0.5 L of H2O(g) exposure, the H2O(g) began to physisorb, and after 15 L of H2O(g) exposure, the 15 ML lithium film was not fully oxidized.

  16. Reprint of "The low temperature oxidation of lithium thin films on HOPG by O2 and H2O"

    NASA Astrophysics Data System (ADS)

    Wulfsberg, Steven M.; Koel, Bruce E.; Bernasek, Steven L.

    2016-10-01

    Lithiated graphite and lithium thin films have been used in fusion devices. In this environment, lithiated graphite will undergo oxidation by background gases. In order to gain insight into this oxidation process, thin (< 15 monolayer (ML)) lithium films on highly ordered pyrolytic graphite (HOPG) were exposed to O2(g) and H2O(g) in an ultra-high vacuum chamber. High resolution electron energy loss spectroscopy (HREELS) was used to identify the surface species formed during O2(g) and H2O(g) exposure. Auger electron spectroscopy (AES) was used to obtain the relative oxidation rates during O2(g) and H2O(g) exposure. AES showed that as the lithium film thickness decreased from 15 to 5 to 1 ML, the oxidation rate decreased for both O2(g) and H2O(g). HREELS showed that a 15 ML lithium film was fully oxidized after 9.7 L (L) of O2(g) exposure and Li2O was formed. HREELS also showed that during initial exposure (< 0.5 L) H2O(g), lithium hydride and lithium hydroxide were formed on the surface of a 15 ML lithium film. After 0.5 L of H2O(g) exposure, the H2O(g) began to physisorb, and after 15 L of H2O(g) exposure, the 15 ML lithium film was not fully oxidized.

  17. Efficient H2O2/CH3COOH oxidative desulfurization/denitrification of liquid fuels in sonochemical flow-reactors.

    PubMed

    Calcio Gaudino, Emanuela; Carnaroglio, Diego; Boffa, Luisa; Cravotto, Giancarlo; Moreira, Elizabeth M; Nunes, Matheus A G; Dressler, Valderi L; Flores, Erico M M

    2014-01-01

    The oxidative desulfurization/denitrification of liquid fuels has been widely investigated as an alternative or complement to common catalytic hydrorefining. In this process, all oxidation reactions occur in the heterogeneous phase (the oil and the polar phase containing the oxidant) and therefore the optimization of mass and heat transfer is of crucial importance to enhancing the oxidation rate. This goal can be achieved by performing the reaction in suitable ultrasound (US) reactors. In fact, flow and loop US reactors stand out above classic batch US reactors thanks to their greater efficiency and flexibility as well as lower energy consumption. This paper describes an efficient sonochemical oxidation with H2O2/CH3COOH at flow rates ranging from 60 to 800 ml/min of both a model compound, dibenzotiophene (DBT), and of a mild hydro-treated diesel feedstock. Four different commercially available US loop reactors (single and multi-probe) were tested, two of which were developed in the authors' laboratory. Full DBT oxidation and efficient diesel feedstock desulfurization/denitrification were observed after the separation of the polar oxidized S/N-containing compounds (S≤5 ppmw, N≤1 ppmw). Our studies confirm that high-throughput US applications benefit greatly from flow-reactors. PMID:23735892

  18. The effects of shrinkage flow and gravity level on the onset of convection during vertical directional dendritic solidification of NH4Cl-H2O

    NASA Technical Reports Server (NTRS)

    Hopkins, J. A.; Mccay, T. D.; Mccay, M. H.

    1993-01-01

    A numerical investigation of the conditions influencing the onset of convection during Bridgman vertical directional solidification of NH4Cl- 72 wt percent H2O has been made using a linear stability model. The effects of shrinkage flow and gravity level on the transition from diffusion-dominated to convection-dominated solidification are shown to be significant. Both shrinkage flow opposite the direction of growth and increased gravity levels tend to decrease the stability limits defining the onset of convection for the solidifying NH4Cl-H2O system.

  19. Real-Time Infrared Overtone Laser Control of Temperature in Picoliter H(2)O Samples: "Nanobathtubs" for Single Molecule Microscopy.

    PubMed

    Holmstrom, Erik D; Nesbitt, David J

    2010-01-01

    An approach for high spatiotemporal control of aqueous sample temperatures in confocal microscopy is reported. This technique exploits near-IR diode-laser illumination to locally heat picoliter volumes of water via first-overtone excitation in the OH-stretch manifold. A thin water cell after the objective resonantly removes any residual IR light from the detection system, allowing for continuous observation of single-molecule fluorescence throughout the heating event. This technique is tested quantitatively by reproducing single-molecule RNA folding results obtained from "bulk" stage heating measurements. Calibration of sample temperatures is obtained from time-correlated single-photon counting studies of Rhodamine B fluorescence decay. We obtain an upper limit to the heating response time (τ(heat) < 20 ms) consistent with even faster estimates (τ(heat) ≈ 0.25 ms) based on laser spot size, H(2)O heat capacit,y and absorption cross section. This combination of fast, noncontact heating of picoliter volumes provides new opportunities for real-time thermodynamic/kinetic studies at the single-molecule level.

  20. Late Holocene hydrous mafic magmatism at the Paint Pot Crater and Callahan flows, Medicine Lake Volcano, N. California and the influence of H2O in the generation of silicic magmas

    USGS Publications Warehouse

    Kinzler, R.J.; Donnelly-Nolan, J. M.; Grove, T.L.

    2000-01-01

    This paper characterizes late Holocene basalts and basaltic andesites at Medicine Lake volcano that contain high pre-eruptive H2O contents inherited from a subduction related hydrous component in the mantle. The basaltic andesite of Paint Pot Crater and the compositionally zoned basaltic to andesitic lavas of the Callahan flow erupted approximately 1000 14C years Before Present (14C years B.P.). Petrologic, geochemical and isotopic evidence indicates that this late Holocene mafic magmatism was characterized by H2O contents of 3 to 6 wt% H2O and elevated abundances of large ion lithophile elements (LILE). These hydrous mafic inputs contrast with the preceding episodes of mafic magmatism (from 10,600 to ~3000 14C years B.P.) that was characterized by the eruption of primitive high alumina olivine tholeiite (HAOT) with low H2O (< 0.2 wt%), lower LILE abundance and different isotopic characteristics. Thus, the mantle-derived inputs into the Medicine Lake system have not always been low H2O, primitive HAOT, but have alternated between HAOT and hydrous subduction related, calc-alkaline basalt. This influx of hydrous mafic magma coincides temporally and spatially with rhyolite eruption at Glass Mountain and Little Glass Mountain. The rhyolites contain quenched magmatic inclusions similar in character to the mafic lavas at Callahan and Paint Pot Crater. The influence of H2O on fractional crystallization of hydrous mafic magma and melting of pre-existing granite crust beneath the volcano combined to produce the rhyolite. Fractionation under hydrous conditions at upper crustal pressures leads to the early crystallization of Fe-Mg silicates and the suppression of plagioclase as an early crystallizing phase. In addition, H2O lowers the saturation temperature of Fe and Mg silicates, and brings the temperature of oxide crystallization closer to the liquidus. These combined effects generate SiO2-enrichment that leads to rhyodacitic differentiated lavas. In contrast, low H2O HAOT

  1. Melting temperatures of H2O up to 72 GPa measured in a diamond anvil cell using CO2 laser heating technique.

    PubMed

    Kimura, T; Kuwayama, Y; Yagi, T

    2014-02-21

    The melting curve of H2O from 49 to 72 GPa was determined by using a laser-heated diamond anvil cell. Double-sided CO2 laser heating technique was employed in order to heat the sample directly. Discontinuous changes of the heating efficiency attributed to the H2O melting were observed between 49 and 72 GPa. The obtained melting temperatures at 49 and 72 GPa are 1200 and 1410 K, respectively. We found that the slope of the melting curve significantly decreases with increasing pressure, only 5 K/GPa at 72 GPa while 44 K/GPa at 49 GPa. Our results suggest that the melting curve does not intersect with the isentropes of Uranus and Neptune, and hence, H2O should remain in the liquid state even at the pressure and temperature conditions found deep within Uranus and Neptune. PMID:24559351

  2. Melting temperatures of H2O up to 72 GPa measured in a diamond anvil cell using CO2 laser heating technique.

    PubMed

    Kimura, T; Kuwayama, Y; Yagi, T

    2014-02-21

    The melting curve of H2O from 49 to 72 GPa was determined by using a laser-heated diamond anvil cell. Double-sided CO2 laser heating technique was employed in order to heat the sample directly. Discontinuous changes of the heating efficiency attributed to the H2O melting were observed between 49 and 72 GPa. The obtained melting temperatures at 49 and 72 GPa are 1200 and 1410 K, respectively. We found that the slope of the melting curve significantly decreases with increasing pressure, only 5 K/GPa at 72 GPa while 44 K/GPa at 49 GPa. Our results suggest that the melting curve does not intersect with the isentropes of Uranus and Neptune, and hence, H2O should remain in the liquid state even at the pressure and temperature conditions found deep within Uranus and Neptune.

  3. Results from Boiling Temperature Measurements for Saturated Solutions in the Systems NaCl + Ca(NO3)2 + H2O, NaNO3 + KNO3 + H2O, and NaCl + KNO3 + H2O, and Dry Out Temperatures for NaCl + NaNO3 + KNO3 + Ca(NO3)2 + H2O

    SciTech Connect

    Rard, J A

    2005-11-29

    Boiling temperature measurements have been made for saturated ternary solutions of NaCl + KNO{sub 3} + H{sub 2}O and NaNO{sub 3} + KNO{sub 3} + H{sub 2}O at three selected salt ratios and for NaCl + Ca(NO{sub 3}){sub 2} + H{sub 2}O over the full composition range. The maximum boiling temperature found for the NaCl + Ca(NO{sub 3}){sub 2} + H{sub 2}O system is 164.7 {+-} 0.6 C, and the composition is estimated to occur at x(Ca(NO{sub 3}){sub 2}) {approx} 0.25. Experiments were also performed for the five component NaCl + NaNO{sub 3} + KNO{sub 3} + Ca(NO{sub 3}){sub 2} + H{sub 2}O mixtures with the molar ratio of NaCl:NaNO{sub 3}:KNO{sub 3} held essentially constant at 1:0.9780:1.1468 as the solute mole fraction of Ca(NO{sub 3}){sub 2}, x(Ca(NO{sub 3}){sub 2}), was varied between 0 and 0.25. The NaCl + NaNO{sub 3} + KNO{sub 3} + Ca(NO{sub 3}){sub 2} + H{sub 2}O system forms low melting mixtures and thus boiling temperatures for saturated were not determined. Instead, the temperatures corresponding to the cessation of boiling (i.e., dry out temperatures) of these liquid mixtures were determined. These dry out temperatures range from {approx} 300 C when x(Ca(NO{sub 3}){sub 2}) = 0 to {ge} 400 C when x(Ca(NO{sub 3}){sub 2}) = 0.20 and 0.25. The investigated mixture compositions correspond to some of the major mineral assemblages that are predicted to control the deliquescence relative humidity of salts formed by leaching dust samples from the proposed nuclear repository at Yucca Mountain, Nevada.

  4. Positional Isotope Exchange in HX·(H2O)n (X = F, I) Clusters at Low Temperatures.

    PubMed

    Litman, Yair E; Videla, Pablo E; Rodriguez, Javier; Laria, Daniel

    2016-09-15

    We present molecular dynamics simulation results describing proton/deuteron exchange equilibria along hydrogen bonds at the vicinity of HX acids (X = F, I) in aqueous clusters at low temperatures. To allow for an adequate description of proton transfer processes, our simulation scheme resorted on the implementation of a multistate empirical valence bond hamiltonian coupled to a path integral scheme to account for effects derived from nuclear quantum fluctuations. We focused attention on clusters comprising a number of water molecules close to the threshold values necessary to stabilize contact-ion-pairs. For X = F, our results reveal a clear propensity of the heavy isotope to lie at the bond bridging the halide to the nearest water molecule. Contrasting, for X = I, the thermodynamic stability is reversed and the former connectivity is preferentially articulated via the light isotope. These trends remain valid for undissociated and ionic descriptions of the stable valence bond states. The preferences are rationalized in terms of differences in the quantum kinetic energies of the isotopes which, in turn, reflect the extent of the local spatial confinements prevailing along the different hydrogen bonds in the clusters. In most cases, these features are also clearly reflected in the characteristics of the corresponding stretching bands of the simulated infrared spectra. This opens interesting possibilities to gauge the extent of the isotopic thermodynamic stabilizations and the strengths of the different hydrogen bonds by following the magnitudes and shifts of the spectral signals in temperature-controlled experiments, performed on mixed clusters combining H2O and HOD. PMID:27533318

  5. Positional Isotope Exchange in HX·(H2O)n (X = F, I) Clusters at Low Temperatures.

    PubMed

    Litman, Yair E; Videla, Pablo E; Rodriguez, Javier; Laria, Daniel

    2016-09-15

    We present molecular dynamics simulation results describing proton/deuteron exchange equilibria along hydrogen bonds at the vicinity of HX acids (X = F, I) in aqueous clusters at low temperatures. To allow for an adequate description of proton transfer processes, our simulation scheme resorted on the implementation of a multistate empirical valence bond hamiltonian coupled to a path integral scheme to account for effects derived from nuclear quantum fluctuations. We focused attention on clusters comprising a number of water molecules close to the threshold values necessary to stabilize contact-ion-pairs. For X = F, our results reveal a clear propensity of the heavy isotope to lie at the bond bridging the halide to the nearest water molecule. Contrasting, for X = I, the thermodynamic stability is reversed and the former connectivity is preferentially articulated via the light isotope. These trends remain valid for undissociated and ionic descriptions of the stable valence bond states. The preferences are rationalized in terms of differences in the quantum kinetic energies of the isotopes which, in turn, reflect the extent of the local spatial confinements prevailing along the different hydrogen bonds in the clusters. In most cases, these features are also clearly reflected in the characteristics of the corresponding stretching bands of the simulated infrared spectra. This opens interesting possibilities to gauge the extent of the isotopic thermodynamic stabilizations and the strengths of the different hydrogen bonds by following the magnitudes and shifts of the spectral signals in temperature-controlled experiments, performed on mixed clusters combining H2O and HOD.

  6. Simultaneous measurement of 2-dimensional H2O concentration and temperature distribution in premixed methane/air flame using TDLAS-based tomography technology

    NASA Astrophysics Data System (ADS)

    Wang, Fei; Wu, Qi; Huang, Qunxing; Zhang, Haidan; Yan, Jianhua; Cen, Kefa

    2015-07-01

    An innovative tomographic method using tunable diode laser absorption spectroscopy (TDLAS) and algebraic reconstruction technique (ART) is presented in this paper for detecting two-dimensional distribution of H2O concentration and temperature in a premixed flame. The collimated laser beam emitted from a low cost diode laser module was delicately split into 24 sub-beams passing through the flame from different angles and the acquired laser absorption signals were used to retrieve flame temperature and H2O concentration simultaneously. The efficiency of the proposed reconstruction system and the effect of measurement noise were numerically evaluated. The temperature and H2O concentration in flat methane/air premixed flames under three different equivalence ratios were experimentally measured and reconstruction results were compared with model calculations. Numerical assessments indicate that the TDLAS tomographic system is capable for temperature and H2O concentration profiles detecting even the noise strength reaches 3% of absorption signal. Experimental results under different combustion conditions are well demonstrated along the vertical direction and the distribution profiles are in good agreement with model calculation. The proposed method exhibits great potential for 2-D or 3-D combustion diagnostics including non-uniform flames.

  7. Thermodynamic modelling of clay dehydration, stability and compositional evolution with temperature, pressure and H 2O activity

    NASA Astrophysics Data System (ADS)

    Vidal, O.; Dubacq, B.

    2009-11-01

    We propose a thermodynamic approach to model the stepwise dehydration with increasing temperature or decreasing H 2O activity of K, Na, Ca and Mg-smectite. The approach relies on the relative stability of the different solid-solutions that describe the hydration of di- or trioctahedral-smectites containing 0, 1, 2 or 3 interlayer water layers. The inclusion of anhydrous mica end-members makes it possible to cover, with the same solid-solution model, the entire range of composition from low-charge smectite to mica, through high-charge smectite and illite. Non-ideal Margules parameters were used to describe the non-ideality of the solid solutions between the hydrated and dehydrated smectite end-members. Standard state properties of all smectite end-members as well as Ca- and Mg-muscovite and -phlogopite were initially estimated by oxide summation. These values were then refined and the other non-ideal interactions were estimated on the basis of different experimental data. The stepwise dehydration of smectite, and its stability and compatibility relations were calculated by Gibbs free energy minimising. Our results account for the progressive evolution of smectite to interlayered illite/smectite and then to mica, as observed in nature and experiments, and our model provides an explanation for the thermodynamic stability of smectite and illite/smectite compared to mica + kaolinite or pyrophyllite assemblages. The results suggest that the enthalpic contribution of interlayer water is a function of the ionic potential of the interlayer cation and the number of interlayer water molecules. This evolution makes possible to estimate the standard-state thermodynamic parameters and hydration-temperature behaviour of smectite of virtually all possible compositions. For the four-interlayer cations considered in the study, our model reproduces the 3 → 2 → 1 water-layer transitions that accompany a reduction of water activity or an increase of temperature at ambient pressure

  8. Quantitative agreement between [(15)O]H2O PET and model free QUASAR MRI-derived cerebral blood flow and arterial blood volume.

    PubMed

    Heijtel, D F R; Petersen, E T; Mutsaerts, H J M M; Bakker, E; Schober, P; Stevens, M F; van Berckel, B N M; Majoie, C B L M; Booij, J; van Osch, M J P; van Bavel, E T; Boellaard, R; Lammertsma, A A; Nederveen, A J

    2016-04-01

    The purpose of this study was to assess whether there was an agreement between quantitative cerebral blood flow (CBF) and arterial cerebral blood volume (CBVA) measurements by [(15)O]H2O positron emission tomography (PET) and model-free QUASAR MRI. Twelve healthy subjects were scanned within a week in separate MRI and PET imaging sessions, after which quantitative and qualitative agreement between both modalities was assessed for gray matter, white matter and whole brain region of interests (ROI). The correlation between CBF measurements obtained with both modalities was moderate to high (r(2): 0.28-0.60, P < 0.05), although QUASAR significantly underestimated CBF by 30% (P < 0.001). CBVA was moderately correlated (r(2): 0.28-0.43, P < 0.05), with QUASAR yielding values that were only 27% of the [(15)O]H2O-derived values (P < 0.001). Group-wise voxel statistics identified minor areas with significant contrast differences between [(15)O]H2O PET and QUASAR MRI, indicating similar qualitative CBVA and CBF information by both modalities. In conclusion, the results of this study demonstrate that QUASAR MRI and [(15)O]H2O PET provide similar CBF and CBVA information, but with systematic quantitative discrepancies.

  9. Electron-temperature dependence of the recombination of H3O+(H2O)n ions with electrons

    NASA Technical Reports Server (NTRS)

    Johnsen, R.

    1993-01-01

    The T(e) dependence of the recombination of H3O+(H2O)n cluster-ions with electrons has been measured in an afterglow experiment in which the electrons were heated by a radio-frequency electric field. The recombination coefficients were found to vary with T(e) as about T(e) exp -1/2 in better agreement with theoretical expectations than earlier results of microwave-afterglow measurements.

  10. Reaction kinetics and isotope effect of water formation by the surface reaction of solid H2O2 with H atoms at low temperatures.

    PubMed

    Oba, Yasuhiro; Osaka, Kazuya; Watanabe, Naoki; Chigai, Takeshi; Kouchi, Akira

    2014-01-01

    We performed laboratory experiments on the formation of water and its isotopologues by surface reactions of hydrogen peroxide (H2O2) with hydrogen (H) atoms and their deuterated counterparts (D2O2, D) at 10-30 K. High-purity H2O2 (> 95%) was prepared in situ by the codeposition of molecular oxygen and H atoms at relatively high temperatures (45-50 K). We determined that the high-purity H2O2 solid reacts with both H and deuterium (D) atoms at 10-30 K despite the large activation barriers (-2000 K). Moreover, the reaction rate for H atoms is approximately 45 times faster than that for D atoms at 15 K. Thus, the observed large isotope effect indicates that these reactions occurred through quantum tunneling. We propose that the observed HDO/H2O ratio in molecular clouds might be a good tool for the estimation of the atomic D/H ratio in those environments.

  11. Photolysis of H2O-H2O2 Mixtures: The Destruction of H2O2

    NASA Technical Reports Server (NTRS)

    Loeffler, M. J.; Fama, M.; Baragiola, R. A.; Carlson, R. W.

    2013-01-01

    We present laboratory results on the loss of H2O2 in solid H2O + H2O2 mixtures at temperatures between 21 and 145 K initiated by UV photolysis (193 nm). Using infrared spectroscopy and microbalance gravimetry, we measured the decrease of the 3.5 micrometer infrared absorption band during UV irradiation and obtained a photodestruction cross section that varies with temperature, being lowest at 70 K. We use our results, along with our previously measured H2O2 production rates via ionizing radiation and ion energy fluxes from the spacecraft to compare H2O2 creation and destruction at icy satellites by ions from their planetary magnetosphere and from solar UV photons. We conclude that, in many cases, H2O2 is not observed on icy satellite surfaces because the H2O2 photodestruction rate is much higher than the production rate via energetic particles, effectively keeping the H2O2 infrared signature at or below the noise level.

  12. Tunable diode laser absorption spectroscopy-based tomography system for on-line monitoring of two-dimensional distributions of temperature and H2O mole fraction

    NASA Astrophysics Data System (ADS)

    Xu, Lijun; Liu, Chang; Jing, Wenyang; Cao, Zhang; Xue, Xin; Lin, Yuzhen

    2016-01-01

    To monitor two-dimensional (2D) distributions of temperature and H2O mole fraction, an on-line tomography system based on tunable diode laser absorption spectroscopy (TDLAS) was developed. To the best of the authors' knowledge, this is the first report on a multi-view TDLAS-based system for simultaneous tomographic visualization of temperature and H2O mole fraction in real time. The system consists of two distributed feedback (DFB) laser diodes, a tomographic sensor, electronic circuits, and a computer. The central frequencies of the two DFB laser diodes are at 7444.36 cm-1 (1343.3 nm) and 7185.6 cm-1 (1391.67 nm), respectively. The tomographic sensor is used to generate fan-beam illumination from five views and to produce 60 ray measurements. The electronic circuits not only provide stable temperature and precise current controlling signals for the laser diodes but also can accurately sample the transmitted laser intensities and extract integrated absorbances in real time. Finally, the integrated absorbances are transferred to the computer, in which the 2D distributions of temperature and H2O mole fraction are reconstructed by using a modified Landweber algorithm. In the experiments, the TDLAS-based tomography system was validated by using asymmetric premixed flames with fixed and time-varying equivalent ratios, respectively. The results demonstrate that the system is able to reconstruct the profiles of the 2D distributions of temperature and H2O mole fraction of the flame and effectively capture the dynamics of the combustion process, which exhibits good potential for flame monitoring and on-line combustion diagnosis.

  13. Investigation of Methanol Formation Mechanisms in H2O+CH4 Ices Subjected to 5 keV Electrons at a 10-100 K Temperature Range

    NASA Astrophysics Data System (ADS)

    Stelmach, K. B.; Cooper, P. D.

    2014-12-01

    Methane (CH4) and water are one of the most common molecules in both planetary bodies and interstellar dust grains. Another common molecule, methanol (CH3OH), is thought to form in CH4+H2O ices. However, the exact formation mechanisms of methanol from cosmic rays are not well known, especially in the temperatures of interest. Experiments were performed using high energy electrons (5 keV) to irradiate mixtures of 1:10, 1:5, and 1:3 CH4+H2O ices under a temperature range of 10-100 Kelvin with Fourier Transform Infrared (FTIR) spectroscopy being used to identify the products. Isotopologues of the two molecules (D2O and CD4) were used to probe for the mechanisms. Other products were formed as well and their potential mechanisms are identified. The implications of the mechanisms for planetary and interstellar chemistry are discussed.

  14. In situ high-temperature X-ray diffraction and spectroscopic study of fibroferrite, FeOH(SO4)·5H2O

    NASA Astrophysics Data System (ADS)

    Ventruti, Gennaro; Ventura, Giancarlo Della; Corriero, Nicola; Malferrari, Daniele; Gualtieri, Alessandro F.; Susta, Umberto; Lacalamita, Maria; Schingaro, Emanuela

    2016-09-01

    The thermal dehydration process of fibroferrite, FeOH(SO4)·5H2O, a secondary iron-bearing hydrous sulfate, was investigated by in situ high-temperature synchrotron X-ray powder diffraction (HT-XRPD), in situ high-temperature Fourier transform infrared spectroscopy (HT-FTIR) and thermal analysis (TGA-DTA) combined with evolved gas mass spectrometry. The data analysis allowed the determination of the stability fields and the reaction paths for this mineral as well as characterization of its high-temperature products. Five main endothermic peaks are observed in the DTA curve collected from room T up to 800 °C. Mass spectrometry of gases evolved during thermogravimetric analysis confirms that the first four mass loss steps are due to water emission, while the fifth is due to a dehydroxylation process; the final step is due to the decomposition of the remaining sulfate ion. The temperature behavior of the different phases occurring during the heating process was analyzed, and the induced structural changes are discussed. In particular, the crystal structure of a new phase, FeOH(SO4)·4H2O, appearing at about 80 °C due to release of one interstitial H2O molecule, was solved by ab initio real-space and reciprocal-space methods. This study contributes to further understanding of the dehydration mechanism and thermal stability of secondary sulfate minerals.

  15. An assessment of the accuracy of isochore location techniques for H 2O-CO 2-NaCl fluids at granulite facies pressure-temperature conditions

    NASA Astrophysics Data System (ADS)

    Johnson, Eric Lee

    1992-01-01

    Synthetic H 2O-CO 2-NaCl fluid inclusions with XCO2 compositions ranging from 0.10-0.51 and relative salinities ( r-s = wtNaCl/( wt NaCl + wt H 2O )) of 6 to 23.9 wt% have been produced in spontaneously nucleated forsterite, diopside, and orthopyroxene hosts. Molar volumes of the fluids at the pressure and temperature of formation have been calculated using microthermometric data from the fluid inclusions. These P- V- T data are used to compare the accuracy of published methods of isochore location for H 2O-CO 2-NaCl fluids at elevated pressures and temperatures. The results of these analyses show that isochores calculated with the MRK equation of BOWERS and HELGESON ( Geochim. Cosmochim. Acta, vol. 47, 1247-1275, 1983) reproduce the trapping pressures and temperatures well for fluids with XCO2 ≤ 0.3 and up to 23.9 wt% NaCl. For a fluid with XCO2 = 0.49 and relative salinity of 15%, however, the agreement is poor. For these fluid compositions, the observed molar volume is larger than that predicted from the MRK equation of Bowers and Helgeson and, if not corrected, will give isochores that are too low in pressure for a given temperature. The ideal geometric mixing model of BROWN and LAMB ( Geochim. Cosmochim. Acta, vol. 53, 1209-1221, 1989) provides less satisfactory results for the fluid compositions studied.

  16. In situ high-temperature X-ray diffraction and spectroscopic study of fibroferrite, FeOH(SO4)·5H2O

    NASA Astrophysics Data System (ADS)

    Ventruti, Gennaro; Ventura, Giancarlo Della; Corriero, Nicola; Malferrari, Daniele; Gualtieri, Alessandro F.; Susta, Umberto; Lacalamita, Maria; Schingaro, Emanuela

    2016-05-01

    The thermal dehydration process of fibroferrite, FeOH(SO4)·5H2O, a secondary iron-bearing hydrous sulfate, was investigated by in situ high-temperature synchrotron X-ray powder diffraction (HT-XRPD), in situ high-temperature Fourier transform infrared spectroscopy (HT-FTIR) and thermal analysis (TGA-DTA) combined with evolved gas mass spectrometry. The data analysis allowed the determination of the stability fields and the reaction paths for this mineral as well as characterization of its high-temperature products. Five main endothermic peaks are observed in the DTA curve collected from room T up to 800 °C. Mass spectrometry of gases evolved during thermogravimetric analysis confirms that the first four mass loss steps are due to water emission, while the fifth is due to a dehydroxylation process; the final step is due to the decomposition of the remaining sulfate ion. The temperature behavior of the different phases occurring during the heating process was analyzed, and the induced structural changes are discussed. In particular, the crystal structure of a new phase, FeOH(SO4)·4H2O, appearing at about 80 °C due to release of one interstitial H2O molecule, was solved by ab initio real-space and reciprocal-space methods. This study contributes to further understanding of the dehydration mechanism and thermal stability of secondary sulfate minerals.

  17. Observation of a remarkable temperature effect in the hydrogen bonding structure and dynamics of the CN-(H2O) cluster

    SciTech Connect

    Wang, Xue B.; Werhahn, Jasper C.; Wang, Lai S.; Kowalski, Karol; Laubereau, Alfred; Xantheas, Sotiris S.

    2009-09-03

    The CN-(H2O) cluster represents a model diatomic monohydrate with multiple solvation sites. We report joint experimental and theoretical studies of its structure and dynamics using temperature-controlled photoelectron spectroscopy (PES) and ab-initio electronic structure calculations. The observed PES spectra of CN-(H2O) display a remarkable temperature effect, namely that the T=12 K spectrum shows an unexpectedly large blue shift of 0.25 eV in the electron binding energy relative to the Room Temperature (RT) spectrum. Extensive theoretical analysis of the potential energy function (PEF) of the cluster at the CCSD(T) level of theory reveal the existence of two nearly isoenergetic isomers corresponding to H2O forming a H-bond with either the C or the N atom, respectively. This results in four topologically distinct minima, i.e., CN-(HaOHb), CN-(HbOHa), NC-(HaOHb) and NC-(HbOHa). There are two main pathways connecting these minima: (i) CN- tumbling relative to water and (ii) water rocking relative to CN-. The relative magnitude of the barriers associated with these two motions reverses between low [pathway (i) is preferred] and high [pathway (ii) is preferred] temperatures. As a result, at T=12 K the cluster adopts a structure that is close to the minimum energy CN-(H2O) configuration, while at RT it can effectively access regions of the PEF close to the transition state for pathway (ii), explaining the surprisingly large spectral shift between the 12 K and RT PES spectra. This work was supported by the Division of Chemical Sciences, Geosciences and Biosciences, Office of Basic Energy Sciences, US Department of Energy. Battelle operates Pacific Northwest National Laboratory for the US Department of Energy.

  18. H2O Adsorption Kinetics on Smectites

    NASA Technical Reports Server (NTRS)

    Zent, Aaron P.; Howard, J.; Quinn, R. C.

    2000-01-01

    The adsorptive equilibration of H2O with montomorillonite has been measured. At low temperatures and pressures equilibration can require many hours, effectively preventing smectites at the martian surface from responding to diurnal pressure and temperature variations.

  19. A laser flash photolysis kinetics study of the reaction OH + H2O2 yields HO2 + H2O

    NASA Technical Reports Server (NTRS)

    Wine, P. H.; Semmes, D. H.; Ravishankara, A. R.

    1981-01-01

    Absolute rate constants for the reaction are reported as a function of temperature over the range 273-410 K. OH radicals are produced by 266 nm laser photolysis of H2O2 and detected by resonance fluorescence. H2O2 concentrations are determined in situ in the slow flow system by UV photometry. The results confirm the findings of two recent discharge flow-resonance fluorescence studies that the title reaction is considerably faster, particularly at temperatures below 300 K, than all earlier studies had indicated. A table giving kinetic data from the reaction is included.

  20. Isotope analysis of diamond-surface passivation effect of high-temperature H2O-grown atomic layer deposition-Al2O3 films

    NASA Astrophysics Data System (ADS)

    Hiraiwa, Atsushi; Saito, Tatsuya; Matsumura, Daisuke; Kawarada, Hiroshi

    2015-06-01

    The Al2O3 film formed using an atomic layer deposition (ALD) method with trimethylaluminum as Al precursor and H2O as oxidant at a high temperature (450 °C) effectively passivates the p-type surface conduction (SC) layer specific to a hydrogen-terminated diamond surface, leading to a successful operation of diamond SC field-effect transistors at 400 °C. In order to investigate this excellent passivation effect, we carried out an isotope analysis using D2O instead of H2O in the ALD and found that the Al2O3 film formed at a conventional temperature (100 °C) incorporates 50 times more CH3 groups than the high-temperature film. This CH3 is supposed to dissociate from the film when heated afterwards at a higher temperature (550 °C) and causes peeling patterns on the H-terminated surface. The high-temperature film is free from this problem and has the largest mass density and dielectric constant among those investigated in this study. The isotope analysis also unveiled a relatively active H-exchange reaction between the diamond H-termination and H2O oxidant during the high-temperature ALD, the SC still being kept intact. This dynamic and yet steady H termination is realized by the suppressed oxidation due to the endothermic reaction with H2O. Additionally, we not only observed the kinetic isotope effect in the form of reduced growth rate of D2O-oxidant ALD but found that the mass density and dielectric constant of D2O-grown Al2O3 films are smaller than those of H2O-grown films. This is a new type of isotope effect, which is not caused by the presence of isotopes in the films unlike the traditional isotope effects that originate from the presence of isotopes itself. Hence, the high-temperature ALD is very effective in forming Al2O3 films as a passivation and/or gate-insulation layer of high-temperature-operation diamond SC devices, and the knowledge of the aforementioned new isotope effect will be a basis for further enhancing ALD technologies in general.

  1. Accelerated formation of strontium silicate by solid-state reaction in NaCl-H2O(v) system at lower temperature

    NASA Astrophysics Data System (ADS)

    Zhang, Junhao; Qiu, Yushi; Huang, Man; Zheng, Hongjuan; Yanagisawa, Kazumichi

    2015-08-01

    An environmentally friendly NaCl-H2O system was developed to prepare SrSiO3 nanostructures from commercially available raw materials, SrCO3 and amorphous SiO2 (α-SiO2), by a one-step solid state reaction at 600 °C for 2 h. The formation of SrSiO3 was accelerated by NaCl-H2O(v) system. The results demonstrate that both NaCl and H2O played vital roles to accelerate the formation of SrSiO3 nanostructures at lower temperature. NaCl was considered to enhance the diffusivity of starting materials and the rate of solid state reactions, and promote the crystallization of products at lower temperature. Additionally, two different phases of SrSiO3 (JPDS 00-032-1257) and SrSiO3 (JPDS 00-006-0415) were abtained without or with the addition of NaCl. Water vapor accelerated the decomposition of SrCO3, and absorbed water on the surface of solid materials dissolved NaCl to form an aqueous ionic liquid composed of Na and Cl ions, which was similar to a hydrothermal process, and further increased the diffusivity of components and reduced the reaction temperature.

  2. Natural convection flow of Cu-H2O nanofluid along a vertical wavy surface with uniform heat flux

    NASA Astrophysics Data System (ADS)

    Habiba, Farjana; Molla, Md. Mamun; Khan, M. A. Hakim

    2016-07-01

    A numerical study on natural convection flow of Cu-Water nanofluid along a vertical wavy surface with uniform heat flux has been carried out. The governing boundary layer equations are transformed into parabolic partial differential equations by applying a suitable set of variables. The resulting nonlinear system of equations are then mapped into a regular rectangular computational domain and solved numerically by using an implicit finite difference method. Numerical results are thoroughly discussed in terms of velocity and temperature distributions, surface temperature distribution, skin friction coefficient and Nusselt number coefficient for selected key parameters such as solid volume fraction of nanofluid (ϕ) and amplitude (α) of surface waviness. In addition, velocity vectors, streamlines and isotherms are plotted to visualize momentum and thermal flow pattern within the boundary layer region.

  3. PVTx properties of H 2 O-H 2 S fluid mixtures at elevated temperature and pressure based on new experimental data

    NASA Astrophysics Data System (ADS)

    Zezin, Denis Yu.; Migdisov, Artashes A.; Williams-Jones, Anthony E.

    2011-10-01

    The volumetric properties of H 2O-H 2S fluid mixtures have been determined experimentally at temperatures of 150 to 400 °C and pressures up to 240 bar. Using these data and existing equations of state, we have developed a thermodynamic model for H 2O-H 2S fluid mixtures. This model is based on an asymmetric description of phases, which includes an activity model and a P-T-dependent Henry's law constant for the liquid, and equations of state with mixing rules for the vapour. The fugacity of the vapour was calculated using the cubic equations of state of Peng and Robinson (1976) and Patel and Teja (1982) with density-dependent and composition-dependent mixing rules. Sets of binary interaction parameters for these equations were fitted to the experimental data obtained in this study supplemented by high-temperature PVTx data for H 2O-H 2S fluid mixtures reported in the literature. The Peng-Robinson equation used in conjunction with density-dependent mixing rules was found to be the most accurate of the available equations in representing the properties of the vapour phase. The errors in the pressure of the homogeneous vapour mixtures estimated using the above equations of state (relative deviation from the experimentally determined pressure) were comparatively low, ˜5% to 8%. However, the errors were significantly higher for the estimated pressure of vapour saturated with liquid, i.e., along the vapour-liquid phase boundary (11-15%), due to the polar nature of H 2O and H 2S and the resulting highly non-ideal behaviour of the fluid mixtures. The results of this study make it possible to reliably estimate the volumetric properties of aqueous fluids containing H 2S at temperatures and pressures up to 400 °C and 240 bar, i.e., for conditions commonly encountered in natural hydrothermal systems.

  4. Salvia fruticosa reduces intrinsic cellular and H2O2-induced DNA oxidation in HEK 293 cells; assessment using flow cytometry

    PubMed Central

    Hani, Saleem Bani; Bayachou, Mekki

    2014-01-01

    Objective To investigate the role of water-soluble extract of Salvia fruticosa (Greek sage) (S. fruticosa) leaves in reducing both intrinsic cellular and H2O2-induced DNA oxidation in cultured human embryonic kidney 293 cells. S. fruticosa, native to the Eastern-Mediterranean basin, is widely used as a medicinal herb for treatment of various diseases. Methods Dried leaves of S. fruticosa were extracted in phosphate buffer saline and purified using both vacuum and high pressure filtrations. Each mL of the preparation contained (7.1±1.0) mg of extract. HEK-293 cells were incubated in one set with S. fruticosa extract in the presence of 0.1 mmol/L H2O2, and in the other set with the addition of the extract alone. The DNA oxidation was measured using fluorescence upon fluorescein isothiocyanate derivatization of 8-oxoguanine moieties. The fluorescence was measured using flow cytometry technique. Results Cells incubated 3 h with 150 µL extract and exposed to 0.1 mmol/L H2O2 showed lower intensity of fluorescence, and thus lower DNA oxidation. Moreover, cells incubated 3 h with 100 µL of the extract showed lower intensity of fluorescence, and thus lower intrinsic cellular DNA oxidation compared to control (without S. fruticosa). Conclusions The results from this study suggest that the water-soluble extract of S. fruticosa leaves protects against both H2O2-induced and intrinsic cellular DNA oxidation in human embryonic kidney 293 cells. PMID:25182726

  5. Exit plane H2O concentration measurements correlated with OH PLIF near-injector mixing measurements for scramjet flows

    NASA Technical Reports Server (NTRS)

    Parker, T. E.; Allen, Mark G.; Foutter, R. R.; Sonnenfroh, D. M.; Rawlins, W. T.

    1992-01-01

    Mixing and combusting high enthalpy flows, similar to those encountered in scramjet engines, were investigated using a shock tunnel to produce the flow in conjunction with non-intrusive optical diagnostics which monitored the performance of two injector configurations. The shock tunnel is configured to produce Mach 3 flow and stagnation enthalpies corresponding to flight equivalent Mach numbers between 7 and 11. A pulsed hydrogen injection capability and interchangeable injector blocks provide a means of examining high speed, high enthalpy reacting flows. Planar laser induced fluorescence (PLIF) of OH molecules in the near injector region produced images which show the combusting and mixing zones for the reacting flow. Line-of-sight exit plane measurement of water concentration and temperature were used to provide a unique method of monitoring exit plane products. These results demonstrated that a velocity matched axial injection system produced a fuel jet that lifted off the floor of the duct. Mixing was observed to increase for this system as a velocity mismatch was introduced. Comparison of exit plane water concentrations for a wall jet injection system and a velocity matched injection system indicated similar mixing performance but an accurate pressure measurement is necessary to further validate the result. In addition, exit plane measurements indicated an approximate steady-state condition was achieved during the 1 to 2 ms test times.

  6. Stable solid and aqueous H2CO3 from CO2 and H2O at high pressure and high temperature

    PubMed Central

    Wang, Hongbo; Zeuschner, Janek; Eremets, Mikhail; Troyan, Ivan; Willams, Jonathan

    2016-01-01

    Carbonic acid (H2CO3) forms in small amounts when CO2 dissolves in H2O, yet decomposes rapidly under ambient conditions of temperature and pressure. Despite its fleeting existence, H2CO3 plays an important role in the global carbon cycle and in biological carbonate-containing systems. The short lifetime in water and presumed low concentration under all terrestrial conditions has stifled study of this fundamental species. Here, we have examined CO2/H2O mixtures under conditions of high pressure and high temperature to explore the potential for reaction to H2CO3 inside celestial bodies. We present a novel method to prepare solid H2CO3 by heating CO2/H2O mixtures at high pressure with a CO2 laser. Furthermore, we found that, contrary to present understanding, neutral H2CO3 is a significant component in aqueous CO2 solutions above 2.4 GPa and 110 °C as identified by IR-absorption and Raman spectroscopy. This is highly significant for speciation of deep C–O–H fluids with potential consequences for fluid-carbonate-bearing rock interactions. As conditions inside subduction zones on Earth appear to be most favorable for production of aqueous H2CO3, a role in subduction related phenomena is inferred. PMID:26813580

  7. Stable solid and aqueous H2CO3 from CO2 and H2O at high pressure and high temperature.

    PubMed

    Wang, Hongbo; Zeuschner, Janek; Eremets, Mikhail; Troyan, Ivan; Willams, Jonathan

    2016-01-01

    Carbonic acid (H2CO3) forms in small amounts when CO2 dissolves in H2O, yet decomposes rapidly under ambient conditions of temperature and pressure. Despite its fleeting existence, H2CO3 plays an important role in the global carbon cycle and in biological carbonate-containing systems. The short lifetime in water and presumed low concentration under all terrestrial conditions has stifled study of this fundamental species. Here, we have examined CO2/H2O mixtures under conditions of high pressure and high temperature to explore the potential for reaction to H2CO3 inside celestial bodies. We present a novel method to prepare solid H2CO3 by heating CO2/H2O mixtures at high pressure with a CO2 laser. Furthermore, we found that, contrary to present understanding, neutral H2CO3 is a significant component in aqueous CO2 solutions above 2.4 GPa and 110 °C as identified by IR-absorption and Raman spectroscopy. This is highly significant for speciation of deep C-O-H fluids with potential consequences for fluid-carbonate-bearing rock interactions. As conditions inside subduction zones on Earth appear to be most favorable for production of aqueous H2CO3, a role in subduction related phenomena is inferred.

  8. Stable solid and aqueous H2CO3 from CO2 and H2O at high pressure and high temperature

    NASA Astrophysics Data System (ADS)

    Wang, Hongbo; Zeuschner, Janek; Eremets, Mikhail; Troyan, Ivan; Willams, Jonathan

    2016-01-01

    Carbonic acid (H2CO3) forms in small amounts when CO2 dissolves in H2O, yet decomposes rapidly under ambient conditions of temperature and pressure. Despite its fleeting existence, H2CO3 plays an important role in the global carbon cycle and in biological carbonate-containing systems. The short lifetime in water and presumed low concentration under all terrestrial conditions has stifled study of this fundamental species. Here, we have examined CO2/H2O mixtures under conditions of high pressure and high temperature to explore the potential for reaction to H2CO3 inside celestial bodies. We present a novel method to prepare solid H2CO3 by heating CO2/H2O mixtures at high pressure with a CO2 laser. Furthermore, we found that, contrary to present understanding, neutral H2CO3 is a significant component in aqueous CO2 solutions above 2.4 GPa and 110 °C as identified by IR-absorption and Raman spectroscopy. This is highly significant for speciation of deep C-O-H fluids with potential consequences for fluid-carbonate-bearing rock interactions. As conditions inside subduction zones on Earth appear to be most favorable for production of aqueous H2CO3, a role in subduction related phenomena is inferred.

  9. Stable solid and aqueous H2CO3 from CO2 and H2O at high pressure and high temperature.

    PubMed

    Wang, Hongbo; Zeuschner, Janek; Eremets, Mikhail; Troyan, Ivan; Willams, Jonathan

    2016-01-01

    Carbonic acid (H2CO3) forms in small amounts when CO2 dissolves in H2O, yet decomposes rapidly under ambient conditions of temperature and pressure. Despite its fleeting existence, H2CO3 plays an important role in the global carbon cycle and in biological carbonate-containing systems. The short lifetime in water and presumed low concentration under all terrestrial conditions has stifled study of this fundamental species. Here, we have examined CO2/H2O mixtures under conditions of high pressure and high temperature to explore the potential for reaction to H2CO3 inside celestial bodies. We present a novel method to prepare solid H2CO3 by heating CO2/H2O mixtures at high pressure with a CO2 laser. Furthermore, we found that, contrary to present understanding, neutral H2CO3 is a significant component in aqueous CO2 solutions above 2.4 GPa and 110 °C as identified by IR-absorption and Raman spectroscopy. This is highly significant for speciation of deep C-O-H fluids with potential consequences for fluid-carbonate-bearing rock interactions. As conditions inside subduction zones on Earth appear to be most favorable for production of aqueous H2CO3, a role in subduction related phenomena is inferred. PMID:26813580

  10. CFD convective flow simulation of the varying properties of CO2-H2O mixtures in geothermal systems.

    PubMed

    Yousefi, S; Atrens, A D; Sauret, E; Dahari, M; Hooman, K

    2015-01-01

    Numerical simulation of a geothermal reservoir, modelled as a bottom-heated square box, filled with water-CO2 mixture is presented in this work. Furthermore, results for two limiting cases of a reservoir filled with either pure water or CO2 are presented. Effects of different parameters including CO2 concentration as well as reservoir pressure and temperature on the overall performance of the system are investigated. It has been noted that, with a fixed reservoir pressure and temperature, any increase in CO2 concentration leads to better performance, that is, stronger convection and higher heat transfer rates. With a fixed CO2 concentration, however, the reservoir pressure and temperature can significantly affect the overall heat transfer and flow rate from the reservoir. Details of such variations are documented and discussed in the present paper.

  11. CFD Convective Flow Simulation of the Varying Properties of CO2-H2O Mixtures in Geothermal Systems

    PubMed Central

    Yousefi, S.; Atrens, A. D.; Sauret, E.; Dahari, M.; Hooman, K.

    2015-01-01

    Numerical simulation of a geothermal reservoir, modelled as a bottom-heated square box, filled with water-CO2 mixture is presented in this work. Furthermore, results for two limiting cases of a reservoir filled with either pure water or CO2 are presented. Effects of different parameters including CO2 concentration as well as reservoir pressure and temperature on the overall performance of the system are investigated. It has been noted that, with a fixed reservoir pressure and temperature, any increase in CO2 concentration leads to better performance, that is, stronger convection and higher heat transfer rates. With a fixed CO2 concentration, however, the reservoir pressure and temperature can significantly affect the overall heat transfer and flow rate from the reservoir. Details of such variations are documented and discussed in the present paper. PMID:25879074

  12. Rapid food decomposition by H2O2-H2SO4 for determination of total mercury by flow injection cold vapor atomic absorption spectrometry.

    PubMed

    Zenebon, Odair; Sakuma, Alice M; Dovidauskas, Sergio; Okada, Isaura A; de, MaioFrancaD; Lichtig, Jaim

    2002-01-01

    A mixture of 50% H2O2-H2SO4 (3 + 1, v/v) was used for decomposition of food in open vessels at 80 degrees C. The treatment allowed rapid total mercury determination by flow injection cold vapor atomic absorption spectrometry. Cabbage, potatoes, peanuts paste, hazelnuts paste, oats, tomatoes and their derivatives, oysters, shrimps, prawns, shellfish, marine algae, and many kinds of fish were analyzed by the proposed methodology with a limit of quantitation of 0.86 +/- 0.08 microg/L mercury in the final solution. Reference materials tested also gave excellent recovery.

  13. Nuclear quantum effects on the structure and the dynamics of [H2O]8 at low temperatures.

    PubMed

    Videla, Pablo E; Rossky, Peter J; Laria, D

    2013-11-01

    We use ring-polymer-molecular-dynamics (RPMD) techniques and the semi-empirical q-TIP4P/F water model to investigate the relationship between hydrogen bond connectivity and the characteristics of nuclear position fluctuations, including explicit incorporation of quantum effects, for the energetically low lying isomers of the prototype cluster [H2O]8 at T = 50 K and at 150 K. Our results reveal that tunneling and zero-point energy effects lead to sensible increments in the magnitudes of the fluctuations of intra and intermolecular distances. The degree of proton spatial delocalization is found to map logically with the hydrogen-bond connectivity pattern of the cluster. Dangling hydrogen bonds exhibit the largest extent of spatial delocalization and participate in shorter intramolecular O-H bonds. Combined effects from quantum and polarization fluctuations on the resulting individual dipole moments are also examined. From the dynamical side, we analyze the characteristics of the infrared absorption spectrum. The incorporation of nuclear quantum fluctuations promotes red shifts and sensible broadening relative to the classical profile, bringing the simulation results in much more satisfactory agreement with direct experimental information in the mid and high frequency range of the stretching band. While RPMD predictions overestimate the peak position of the low frequency shoulder, the overall agreement with that reported using an accurate, parameterized, many-body potential is reasonable, and far superior to that one obtains by implementing a partially adiabatic centroid molecular dynamics approach. Quantum effects on the collective dynamics, as reported by instantaneous normal modes, are also discussed.

  14. Relaxation within the electronic ground state of the ferrous ion in [Fe(H2O)6]K2(SO4)2 single crystals at low temperatures

    NASA Astrophysics Data System (ADS)

    Leupold, O.; Nagy, D. L.; Ritter, G.

    1994-12-01

    Single crystal Mössbauer spectra of [Fe(H2O)6]K2(SO4)2 taken in external magnetic fields up to 5 T at low temperatures show large line broadenings, which are due to intermediate relaxation rates within the electronic orbital ground state. The spectra are fitted using a Blume stochastic relaxation model, the ferrous ion flipping between two electronic states. The results of the fit are discussed in a ligand field model of the hexaaquo-coordinated high-spin ferrous ion.

  15. Highly selective catalytic reduction of NO via SO2/H2O-tolerant spinel catalysts at low temperature.

    PubMed

    Cai, Xuanxuan; Sun, Wei; Xu, Chaochao; Cao, Limei; Yang, Ji

    2016-09-01

    Selective catalytic reduction of NO X by hydrogen (H2-SCR) in the presence of oxygen has been investigated over the NiCo2O4 and Pd-doped NiCo2O4 catalysts under varying conditions. The catalysts were prepared by a sol-gel method in the presence of oxygen within 50-350 °C and were characterized using XRD, BET, EDS, XPS, Raman, H2-TPR, and NH3-TPD analysis. The results demonstrated that the doped Pd could improve the catalyst reducibility and change the surface acidity and redox properties, resulting in a higher catalytic performance. The performance of NiCo1.95Pd0.05O4 was consistently better than that of NiCo2O4 within the 150-350 °C range at a gas hourly space velocity (GHSV) of 4800 mL g(-1) h(-1), with a feed stream containing 1070 ppm NO, 10,700 ppm H2, 2 % O2, and N2 as balance gas. The effects of GHSV, NO/H2 ratios, and O2 feed concentration on the NO conversion over the NiCo2O4 and NiCo1.95Pd0.05O4 catalysts were also investigated. The two samples similarly showed that an increase in GHSV from 4800 to 9600 mL h(-1) g(-1), the NO/H2 ratio from 1:10 to 1:1, and the O2 content from 0 to 6 % would result in a decrease in NO conversion. In addition, 2 %, 5 %, and 8 % H2O into the feed gas had a slightly negative influence on SCR activity over the two catalysts. The effect of SO2 on the SCR activity indicated that the NiCo1.95Pd0.05O4 possesses better SO2 tolerance than NiCo2O4 catalyst does. Graphical abstract The NiCo1.95Pd0.05O4 catalyst achieved over 90 % NO conversion with N2 selectivity of 100 % in the 200∼250 °C range than the maximum 40.5 % NO conversion over NiCo2O4 with N2 selectivity of approximately 80 % in 350 °C.

  16. Highly selective catalytic reduction of NO via SO2/H2O-tolerant spinel catalysts at low temperature.

    PubMed

    Cai, Xuanxuan; Sun, Wei; Xu, Chaochao; Cao, Limei; Yang, Ji

    2016-09-01

    Selective catalytic reduction of NO X by hydrogen (H2-SCR) in the presence of oxygen has been investigated over the NiCo2O4 and Pd-doped NiCo2O4 catalysts under varying conditions. The catalysts were prepared by a sol-gel method in the presence of oxygen within 50-350 °C and were characterized using XRD, BET, EDS, XPS, Raman, H2-TPR, and NH3-TPD analysis. The results demonstrated that the doped Pd could improve the catalyst reducibility and change the surface acidity and redox properties, resulting in a higher catalytic performance. The performance of NiCo1.95Pd0.05O4 was consistently better than that of NiCo2O4 within the 150-350 °C range at a gas hourly space velocity (GHSV) of 4800 mL g(-1) h(-1), with a feed stream containing 1070 ppm NO, 10,700 ppm H2, 2 % O2, and N2 as balance gas. The effects of GHSV, NO/H2 ratios, and O2 feed concentration on the NO conversion over the NiCo2O4 and NiCo1.95Pd0.05O4 catalysts were also investigated. The two samples similarly showed that an increase in GHSV from 4800 to 9600 mL h(-1) g(-1), the NO/H2 ratio from 1:10 to 1:1, and the O2 content from 0 to 6 % would result in a decrease in NO conversion. In addition, 2 %, 5 %, and 8 % H2O into the feed gas had a slightly negative influence on SCR activity over the two catalysts. The effect of SO2 on the SCR activity indicated that the NiCo1.95Pd0.05O4 possesses better SO2 tolerance than NiCo2O4 catalyst does. Graphical abstract The NiCo1.95Pd0.05O4 catalyst achieved over 90 % NO conversion with N2 selectivity of 100 % in the 200∼250 °C range than the maximum 40.5 % NO conversion over NiCo2O4 with N2 selectivity of approximately 80 % in 350 °C. PMID:27301438

  17. Temperature measurements in a rapid compression machine using mid-infrared H2O absorption spectroscopy near 7.6 μm.

    PubMed

    Uddi, Mruthunjaya; Das, Apurba Kumar; Sung, Chih-Jen

    2012-08-01

    A method for measuring the temporal temperature and number density in a rapid compression machine (RCM) using quantum cascade laser absorption spectroscopy near 7.6 μm is developed and presented in this paper. The ratios of H(2)O absorption peaks at 1316.55 cm(-1) and 1316.97 cm(-1) are used for these measurements. In order to isolate the effects of chemical reactions, an inert mixture of argon with 2.87% water vapor is used for the present investigation. The end of compression pressures and temperatures in the RCM measurements are P(C)=10, 15, and 20 bar in the range of T(C)=1000 to 1200 K. The measured temperature history is compared with that calculated based on the adiabatic core assumption and is found to be within ±5 K. The measured temporal number density of H(2)O to an accuracy of 1%, using the absolute absorption of the two rovibrational lines, show that the mixture is highly uniform in temperature. A six-pass, 5.08 cm Herriott cell is used to calibrate the line strengths in air and broadening in an Ar bath gas. PMID:22859037

  18. Temperature measurements in a rapid compression machine using mid-infrared H2O absorption spectroscopy near 7.6 μm.

    PubMed

    Uddi, Mruthunjaya; Das, Apurba Kumar; Sung, Chih-Jen

    2012-08-01

    A method for measuring the temporal temperature and number density in a rapid compression machine (RCM) using quantum cascade laser absorption spectroscopy near 7.6 μm is developed and presented in this paper. The ratios of H(2)O absorption peaks at 1316.55 cm(-1) and 1316.97 cm(-1) are used for these measurements. In order to isolate the effects of chemical reactions, an inert mixture of argon with 2.87% water vapor is used for the present investigation. The end of compression pressures and temperatures in the RCM measurements are P(C)=10, 15, and 20 bar in the range of T(C)=1000 to 1200 K. The measured temperature history is compared with that calculated based on the adiabatic core assumption and is found to be within ±5 K. The measured temporal number density of H(2)O to an accuracy of 1%, using the absolute absorption of the two rovibrational lines, show that the mixture is highly uniform in temperature. A six-pass, 5.08 cm Herriott cell is used to calibrate the line strengths in air and broadening in an Ar bath gas.

  19. Subduction Factory 3: An Excel worksheet and macro for calculating the densities, seismic wave speeds, and H2O contents of minerals and rocks at pressure and temperature

    NASA Astrophysics Data System (ADS)

    Hacker, Bradley R.; Abers, Geoffrey A.

    2004-01-01

    An Excel macro to calculate mineral and rock physical properties at elevated pressure and temperature is presented. The workbook includes an expandable database of physical parameters for 52 rock-forming minerals stable at high pressures and temperatures. For these minerals the elastic moduli, densities, seismic velocities, and H2O contents are calculated at any specified P and T conditions, using basic thermodynamic relationships and third-order finite strain theory. The mineral modes of suites of rocks are also specifiable, so that their predicted aggregate properties can be calculated using standard solid mixing theories. A suite of sample rock modes taken from the literature provides a useful starting point. The results of these calculations can be applied to a wide variety of geophysical questions including estimating the alteration of the oceanic crust and mantle; predicting the seismic velocities of lower-crustal xenoliths; estimating the effects of changes in mineralogy, pressure and temperature on buoyancy; and assessing the H2O content and mineralogy of subducted lithosphere from seismic observations.

  20. Oxidation behaviour of ferritic stainless steel grade Crofer 22 APU at 700 °C in flowing Ar-75%CO2-12%H2O

    NASA Astrophysics Data System (ADS)

    Shariff, Nurul Atikah; Othman, Norinsan Kamil; Jalar, Azman

    2013-11-01

    The oxidation of Ferritic Stainless Steel (FSS) grade Crofer 22 APU has been investigated. FSS alloys were exposed to isothermal conditions in a horizontal tube furnace at a 700 °C in flowing Ar-75%CO2-12%H2O at a pressure of approximately 1 atm. The results showed that the growth of non protective Fe2O3 and spinel was observed after 50 h exposure in the presence of 12% H2O. The weight was increased significantly with time of exposure. The formation of different oxides is presented on the interface of the specimen such as MnCr2O4, Fe3O4 and Fe2O3 were revealed by X-ray diffraction and supported by EDAX analysis. FSS did not form a protective Cr2O3 layer due to water vapour accelerates the kinetics oxidation. Data of microstructure observation is presented and discussed in this paper in term of water vapour effects.

  1. Keep the Ideas Flowing at Your Water Table! Ideas to Help Children Get to Know H-2-O

    ERIC Educational Resources Information Center

    Church, Ellen Booth

    2006-01-01

    This article provides teachers with ten tips for introducing young children to activities involving water. The 10 tips include: (1) Prepare Your Water Play Space; (2) Use Containers Within Containers; (3) Keep Things Interesting; (4) Explore Ice; (5) Survey the Effects of Salt; (6) Go With the Flow; (7) Extend Exploration with Spray Bottles; (8)…

  2. Variable temperature pressure broadening of the 4(1,4)-3(2,1) transition of H2O by O2 and N2

    NASA Technical Reports Server (NTRS)

    Goyette, Thomas M.; Delucia, Frank C.; Dutta, J. M.; Jones, C. R.

    1993-01-01

    The O2 and N2 pressure-broadening parameters of the 4(1,4)-3(2,1) rotational transition in the ground vibrational state of H2O have been measured in the temperature range between 100 and 520 K. Above 250 K the measurements were made in an equilibrium cell. Below 250 K a cell, which uses collisional cooling to circumvent the temperature limits imposed by the vapor pressure of the sample gas, was used. The data were fitted to an exponential temperature-dependence for data above 150 K with resultant n values of 0.81(3) for O2 and 0.70(3) for N2, where the entries in parentheses represent the error in the last significant figure of the parameter. Below 150 K the measured pressure-broadening parameters are smaller than those calculated using these values of n.

  3. Low energy isomers of (H2O)25 from a hierarchical method based on Monte Carlo temperature basin paving and molecular tailoring approaches benchmarked by MP2 calculations.

    PubMed

    Sahu, Nityananda; Gadre, Shridhar R; Rakshit, Avijit; Bandyopadhyay, Pradipta; Miliordos, Evangelos; Xantheas, Sotiris S

    2014-10-28

    We report new global minimum candidate structures for the (H2O)25 cluster that are lower in energy than the ones reported previously and correspond to hydrogen bonded networks with 42 hydrogen bonds and an interior, fully coordinated water molecule. These were obtained as a result of a hierarchical approach based on initial Monte Carlo Temperature Basin Paving sampling of the cluster's Potential Energy Surface with the Effective Fragment Potential, subsequent geometry optimization using the Molecular Tailoring Approach with the fragments treated at the second order Møller-Plesset (MP2) perturbation (MTA-MP2) and final refinement of the entire cluster at the MP2 level of theory. The MTA-MP2 optimized cluster geometries, constructed from the fragments, were found to be within <0.5 kcal/mol from the minimum geometries obtained from the MP2 optimization of the entire (H2O)25 cluster. In addition, the grafting of the MTA-MP2 energies yields electronic energies that are within <0.3 kcal/mol from the MP2 energies of the entire cluster while preserving their energy rank order. Finally, the MTA-MP2 approach was found to reproduce the MP2 harmonic vibrational frequencies, constructed from the fragments, quite accurately when compared to the MP2 ones of the entire cluster in both the HOH bending and the OH stretching regions of the spectra.

  4. Generation and loss of reactive oxygen species in low-temperature atmospheric-pressure RF He + O2 + H2O plasmas

    NASA Astrophysics Data System (ADS)

    McKay, K.; Liu, D. X.; Rong, M. Z.; Iza, F.; Kong, M. G.

    2012-05-01

    This study focuses on the generation and loss of reactive oxygen species (ROS) in low-temperature atmospheric-pressure RF (13.56 MHz) He + O2 + H2O plasmas, which are of interest for many biomedical applications. These plasmas create cocktails of ROS containing ozone, singlet oxygen, atomic oxygen, hydroxyl radicals, hydrogen peroxide and hydroperoxyl radicals, i.e. ROS of great significance as recognized by the free-radical biology community. By means of one-dimensional fluid simulations (61 species, 878 reactions), the key ROS and their generation and loss mechanisms are identified as a function of the oxygen and water content in the feed gas. Identification of the main chemical pathways can guide the optimization of He + O2 + H2O plasmas for the production of particular ROS. It is found that for a given oxygen concentration, the presence of water in the feed gas decreases the net production of oxygen-derived ROS, while for a given water concentration, the presence of oxygen enhances the net production of water-derived ROS. Although most ROS can be generated in a wide range of oxygen and water admixtures, the chemical pathways leading to their generation change significantly as a function of the feed gas composition. Therefore, care must be taken when selecting reduced chemical sets to study these plasmas.

  5. Measurement of regional cerebral blood flow in cat brain using intracarotid 2H2O and 2H NMR imaging

    SciTech Connect

    Detre, J.A.; Subramanian, V.H.; Mitchell, M.D.; Smith, D.S.; Kobayashi, A.; Zaman, A.; Leigh, J.S. Jr. )

    1990-05-01

    Cerebral blood flow (CBF) was measured in cat brain in vivo at 2.7 T using 2H NMR to monitor the washout of deuterated saline injected into both carotid arteries via the lingual arteries. In anesthetized cats, global CBF varied directly with PaCO{sub 2} over a range of 20-50 mm Hg, and the corresponding global CBF values ranged from 25 to 125 ml.100 g-1.min-1. Regional CBF was measured in a 1-cm axial section of cat brain using intracarotid deuterated saline and gradient-echo 2H NMR imaging. Blood flow images with a maximum pixel resolution of 0.3 x 0.3 x 1.0 cm were generated from the deuterium signal washout at each pixel. Image derived values for CBF agreed well with other determinations, and decreased significantly with hypocapnia.

  6. Gibbs free energy of reactions involving SiC, Si3N4, H2, and H2O as a function of temperature and pressure

    NASA Technical Reports Server (NTRS)

    Isham, M. A.

    1992-01-01

    Silicon carbide and silicon nitride are considered for application as structural materials and coating in advanced propulsion systems including nuclear thermal. Three-dimensional Gibbs free energy were constructed for reactions involving these materials in H2 and H2/H2O. Free energy plots are functions of temperature and pressure. Calculations used the definition of Gibbs free energy where the spontaneity of reactions is calculated as a function of temperature and pressure. Silicon carbide decomposes to Si and CH4 in pure H2 and forms a SiO2 scale in a wet atmosphere. Silicon nitride remains stable under all conditions. There was no apparent difference in reaction thermodynamics between ideal and Van der Waals treatment of gaseous species.

  7. Structural Properties of the Superconducting Salt (BEDT-TTF) 3Cl 2·(H 2O) 2 at Low Temperatures

    NASA Astrophysics Data System (ADS)

    Gaultier, Jacques; Hébrard-Bracchetti, Sylvie; Guionneau, Philippe; Kepert, Cameron J.; Chasseau, Daniel; Ducasse, Laurent; Barrans, Yvette; Kurmoo, Mohamedally; Day, Peter

    1999-07-01

    The X-ray crystal structure of (BEDT-TTF)3Cl2·(H2O)2 [BEDT-TTF=bis(ethylenedithio)tetrathiafulvalene] has been determined at 190, 130, and 10 K. The broad metal-insulator transition (100-160 K) observed in the resistivity data at ambient pressure, and the pressure induced superconductivity (Tc=5 K at 1.2 GPa) can be associated with temperature-dependent motion of the molecules within the unit cell and charge redistribution among the three independent BEDT-TTF molecules. The motion can be considered as a dimerization of the BEDT-TTF along the a-axis. The thermal expansion tensor in the range 12 to 295 K is anisotropic and reveals no sharp anomaly. The system remains two dimensional at all temperatures, in agreement with the electrical conductivity measurements.

  8. Low-Temperature Thermal Reactions Between SO2 and H2O2 and Their Relevance to the Jovian Icy Satellites

    NASA Technical Reports Server (NTRS)

    Loeffler, Mark J.; Hudson, Reggie L.

    2013-01-01

    Here we present first results on a non-radiolytic, thermally-driven reaction sequence in solid H2O +SO2 + H2O2 mixtures at 50-130 K, which produces sulfate (SO(-2)/(4)), and has an activation energy of 53 kJ/mole. We suspect that these results may explain some of the observations related to the presence and distribution of H2O2 across Europa's surface as well as the lack of H2O2 on Ganymede and Callisto.

  9. Air-Broadening of H2O as a Function of Temperature: 696 - 2163 cm(exp -1)

    NASA Technical Reports Server (NTRS)

    Toth, R. A.; Brown, L. R.; Smith, M. A. H.; Devi, V. Malathy; Benner, D. Chris; Dulick, M.

    2006-01-01

    The temperature dependence of air-broadened halfwidths are reported for some 500 transitions in the (000)-(000) and (010)-(000) bands of H2(16)O using gas sample temperatures ranging from 241 to 388 K. These observations were obtained from infrared laboratory spectra recorded at 0.006 to 0.011 cm(exp-1) resolution with the McMath-Pierce Fourier transform spectrometer located at Kitt Peak. The experimental values of the temperature dependence exponents, eta, were grouped into eight subsets and fitted to empirical functions in a semi-global procedure. Overall, the values of eta were found to decrease with increasing rotational quantum number J. The number of measurements (over 2200) and transitions (586) involved exceeds by a large margin that of any other comparable reported study.

  10. The RealGas and RealGasH2O options of the TOUGH+ code for the simulation of coupled fluid and heat flow in tight/shale gas systems

    EPA Science Inventory

    We developed two new EOS additions to the TOUGH+ family of codes, the RealGasH2O and RealGas. The RealGasH2O EOS option describes the non-isothermal two-phase flow of water and a real gas mixture in gas reservoirs, with a particular focus in ultra-tight (such as tight-sand and sh...

  11. Probing the formation and evolution of comets via nuclear spin temperatures of C_2H_6, CH_3OH, CH_4, NH_3, and H_2O

    NASA Astrophysics Data System (ADS)

    Villanueva, G.; Mumma, M.; Bonev, B.; DiSanti, M.; Paganini, L.; Magee-Sauer, K.; Gibb, E.

    2014-07-01

    Comets are true remnants of our primordial Solar System, and provide unique clues to its formation and evolution, including the delivery of organics and water to our planet. A key indicator stored in the molecular structure of the nuclear ices is the spin temperature (T_{spin}), derived from spin-isomeric ratios (R_{spin}, e.g., ortho/para). At the time when cometary ices formed, the prevailing temperature defined the relative abundance of the different spin-isomeric species, and herewith R_{spin} and T_{spin} are normally treated as ''remnant thermometers'' probing the formation environments of cometary molecules. Radiative and collisional transitions between the ortho and para states are strongly forbidden and herewith this indicator is preserved over time. Most of our knowledge of this indicator comes from the measurements of the ortho-para ratios in water and NH_2 (a proxy for ammonia), suggesting a common T_{spin} near 30 K. This information is based on a restricted sample of comets, and the measurements are particularly sensitive to the molecular modeling technique and adopted spectral database. Here, we present new methodologies for extracting spin temperatures from ethane (C_2H_6), methane (CH_4), and methanol (CH_3OH), and advanced new models for ortho/para water (H_2O) and ammonia (NH_3). Our H_2O analysis is based on the most complete fluorescence radiative-transfer model to date, which incorporates 1,200 million transitions including those originating from high-energy levels that are activated in comets via a non-resonant cascade. In a similar fashion, we developed non-resonant fluorescence models for NH_3 and HCN, and quantum-band models for the ν_7 band of C_2H_6 and ν_3 band of CH_3OH. All models respect spin-symmetry non-conversion radiative rules, and make use of a realistic solar spectrum for the computation of fluorescence pumps. We applied these new methods to derive spin-isomeric ratios for H_2O, CH_4, C_2H_6, CH_3OH, and NH_3 from three high

  12. Experimental deformation of polycrystalline H2O ice at high pressure and low temperature - Preliminary results. [implications for Ganymede and Callisto

    NASA Technical Reports Server (NTRS)

    Durham, W. B.; Heard, H. C.; Kirby, S. H.

    1983-01-01

    A preliminary study is carried out of involving 70 constant strain deformation tests on pure polycrystalline H2O ice under conditions covering most of the stability field of ice I sub h. Brittle failure of I sub h is found to be promoted by lower P, lower T, and higher strain rates. Ductile flow is found to be promoted by higher P, higher T, and lower strain rates. The brittle failure of ice I sub h is found to be most unusual. The fracture strength is a positive function of P only below 50 MPa. At pressures greater than this, the fracture strength is independent of P, and the fracture plane lies approximately 45 deg from the load axis. It is believed that existing extrapolation based on existing experimental data to Ganymede and Callisto may be badly in error.

  13. A temperature dependence kinetics study of the reactions of Cl/2-P-3/2/ with O3, CH4, and H2O2

    NASA Technical Reports Server (NTRS)

    Watson, R.; Machado, G.; Fischer, S.; Davis, D. D.

    1976-01-01

    The temperature dependence of two chlorine atom reactions of considerable fundamental importance to stratospheric chemistry was studied using the technique of flash photolysis-resonance fluorescence. The reactions of interest were: (1) Cl + O3 yields ClO + O2 studied at 220-350 K, and (2) Cl + CH4 yields CH3 + HCl studied at 218-401 K. In addition, the reaction Cl + H2O2 yields HCl + HO2 was studied at 300 K. The corresponding rate constants are provided for the three reactions. The new rate data implies the need to revise downward by a factor of 2.4-3 the magnitude of the ozone perturbation due to the presence of ClO/x/ species in the stratosphere, predicted by earlier model calculations.

  14. H2O Adsorption Kinetics on Smectites

    NASA Technical Reports Server (NTRS)

    Zent, Aaron P.; Quinn, Richard C.; Howard, Jeanie; DeVincenzi, Donald L. (Technical Monitor)

    2000-01-01

    The adsorptive equilibration of H2O a with montomorillonite, a smectite clay has been measured. At low temperatures and pressures, equilibration can require many hours, effectively preventing smectites at the martian surface from responding rapidly to diurnal pressure and temperature variations.

  15. The adsorption of CO(2)/H(2)O/N(2) on 5A zeolite and silica gel in a packed column in one and two-dimensional flows

    NASA Astrophysics Data System (ADS)

    Mohamadinejad, Habib

    The purpose of this work is to develop a computer model that simulates the dynamic behavior of a Four-Bed Molecular Sieves (4-BMS) system. The system will be installed on the International Space Station for removal of CO 2/H2O/N2 on four beds that consist of 5A zeolite, 13X zeolite, and Silica gel. Due to the complexity of the actual 4-BMS, separately packed columns of 5A and Silica gel were built and tested using the model results to obtain the mass and heat transfer coefficients necessary for the development of the 4-BMS. This work begins by introducing the adsorption/desorption process in a packed column. The formulation of the simplest model of adsorption in a packed bed is developed assuming that Darcy's law. In this model, the mass and heat transport gradients are assumed to vary only in the axial direction, i.e., one-dimensional flow. The results of temperature and mass transfer breakthrough of one-dimensional flow are compared with the test results for adsorption of CO2/N2 and CO2/H2O/N2 on 5A zeolite. In the packed column near the wall boundary, the velocity decreases due to the viscous forces and the porosity increases exponentially. This near-wall region of higher porosity results in the channeling of fluid close to the wall surface. This channeling causes an early solute breakthrough relative to the center of the column. In order to accommodate the effect of porosity variation on the breakthrough, a two-dimensional model of the packed column is developed. The results of two-dimensional flow are compared with the test results for adsorption of CO2/N2 and CO2/H 2O/N2 on 5A zeolite. This work also investigates the dynamics of H2O adsorption on Silica gel material. A one-dimensional flow of a packed column bed is developed with the assumption that Darcy's law governs the momentum transport. The results of both models are compared with the test results for adsorption of H 2O/N2 on Silica gel. Finally, a computer model based on the obtained parameters of

  16. Real-Time Infrared Overtone Laser Control of Temperature in Picoliter H2O Samples: “Nanobathtubs” for Single Molecule Microscopy

    PubMed Central

    Holmstrom, Erik D.; Nesbitt, David J.

    2011-01-01

    An approach for high spatiotemporal control of aqueous sample temperatures in confocal microscopy is reported. This technique exploits near-IR diode-laser illumination to locally heat picoliter volumes of water via first-overtone excitation in the OH-stretch manifold. A thin water cell after the objective resonantly removes any residual IR light from the detection system, allowing for continuous observation of single-molecule fluorescence throughout the heating event. This technique is tested quantitatively by reproducing single-molecule RNA folding results obtained from “bulk” stage heating measurements. Calibration of sample temperatures is obtained from time-correlated single-photon counting studies of Rhodamine B fluorescence decay. We obtain an upper limit to the heating response time (τheat < 20 ms) consistent with even faster estimates (τheat ≈ 0.25 ms) based on laser spot size, H2O heat capacit,y and absorption cross section. This combination of fast, noncontact heating of picoliter volumes provides new opportunities for real-time thermodynamic/kinetic studies at the single-molecule level. PMID:21814589

  17. The stability and Raman spectra of ikaite, CaCO3·6H2O, at high pressure and temperature

    USGS Publications Warehouse

    Shahar, Anat; Bassett, William A.; Mao, Ho-kwang; Chou, I-Ming; Mao, Wendy

    2005-01-01

    Raman analyses of single crystals of ikaite, CaCO3·6H2O, synthesized in a diamond-anvil cell at ambient temperature yield spectra from 0.14 to 4.08 GPa; the most intense peaks are at 228 and 1081 cm−1 corresponding to Eg(external) and A1g (internal) modes of vibrations in CO2− 3 ions, respectively. These are in good agreement with Raman spectra previously published for ikaite in powder form at ambient temperature and pressure. Visual observations of a sample consisting initially of a mixture of calcite + water in a hydrothermal diamond-anvil cell yielded a P-T phase diagram up to 2 GPa and 120 °C; the boundary for the reaction ikaite ↔ aragonite + water has a positive slope and is curved convexly toward the aragonite + water field similar to typical melt curves. This curvature can be explained in terms of the Clapeyron equation for a boundary between a solid phase and a more compressible liquid phase or largely liquid phase assemblage.

  18. The spectral variability of kieserite (MgSO4·H2O) with temperature and grain size and its application to the Martian surface

    NASA Astrophysics Data System (ADS)

    Jamieson, C. S.; Noe Dobrea, E. Z.; Dalton, J. B.; Pitman, K. M.; Abbey, W. J.

    2014-06-01

    We spectrally characterize (λ = 0.35-10 µm) the low-humidity polymorph of kieserite (MgSO4·H2O), which is abundant on Mars and likely present on Europa, at various grain sizes and temperatures (100-300 K) relevant to the surfaces of Mars and Europa. Compositional analysis of these surfaces often relies on remote sensing using imaging spectrometers such as Mars Reconnaissance Orbiter Compact Reconnaissance Imaging Spectrometer for Mars (CRISM), Mars Express Observatoire pour la Minéralogie, l'Eau, les Glaces et l'Activité, and Galileo Near-Infrared Mapping Spectrometer. To estimate surface abundances from these observations, well-characterized laboratory spectra are required for comparison. Several variables, including temperature and grain size, affect the observed spectra and must be quantified in the laboratory to more confidently evaluate the returned data. Certain spectral features of kieserite exhibit predictable variability with changes in temperature and grain size that may be exploited to better understand the nature of kieserite on the surface of Mars. For instance, trends in our spectral analysis suggest that absorption features centered at λ < 3.0 µm were primarily sensitive to temperature changes, while features at λ > 3.0 µm were additionally sensitive to grain size changes. We compare our laboratory spectra with selected CRISM data of suspected Martian kieserite and assess the inherent uncertainty that exists in using band center minima to determine surface composition. Incorporation of these temperature and grain size-specific spectra into linear mixture models of planetary surface spectra will improve the compositional interpretation and contribute to our understanding of surface geochemistry and chemical evolution.

  19. Corrosion of 310 stainless steel in H2-H2O-H2S gas mixtures: Studies at constant temperature and fixed oxygen potential

    NASA Technical Reports Server (NTRS)

    Rao, D. B.; Jacob, K. T.; Nelson, H. G.

    1981-01-01

    Corrosion of SAE 310 stainless steel in H2-H2O-H2S gas mixtures was studied at a constant temperature of 1150 K. Reactive gas mixtures were chosen to yield a constant oxygen potential of approximately 6 x 10 to the minus 13th power/cu Nm and sulfur potentials ranging from 0.19 x 10 to the minus 2nd power/cu Nm to 33 x 10 to the minus 2nd power/cu Nm. The kinetics of corrosion were determined using a thermobalance, and the scales were analyzed using metallography, scanning electron microscopy, and energy dispersive X-ray analysis. Two corrosion regimes, which were dependent on sulfur potential, were identified. At high sulfur potentials (p sub S sub 2 less than or equal to 2.7 x 10 to the minus 2nd power/cu Nm) the corrosion rates were high, the kinetics obeyed a linear rate equation, and the scales consisted mainly of sulfide phases similar to those observed from pure sulfication. At low sulfur potentials (P sub S sub 2 less than or equal to 0.19 x 10 to the minus 2nd power/cu Nm) the corrosion rates were low, the kinetics obeyed a parabolic rate equation, and scales consisted mainly of oxide phases.

  20. Phase relations in the system NaCl-KCl-H2O: V. Thermodynamic-PTX analysis of solid-liquid equilibria at high temperatures and pressures

    USGS Publications Warehouse

    Sterner, S.M.; Chou, I.-Ming; Downs, R.T.; Pitzer, Kenneth S.

    1992-01-01

    The Gibbs energies of mixing for NaCl-KCl binary solids and liquids and solid-saturated NaCl-KCl-H2O ternary liquids were modeled using asymmetric Margules treatments. The coefficients of the expressions were calibrated using an extensive array of binary solvus and solidus data, and both binary and ternary liquidus data. Over the PTX range considered, the system exhibits complete liquid miscibility among all three components and extensive solid solution along the anhydrous binary. Solid-liquid and solid-solid phase equilibria were calculated by using the resulting equations and invoking the equality of chemical potentials of NaCl and KCl between appropriate phases at equilibrium. The equations reproduce the ternary liquidus and predict activity coefficients for NaCl and KCl components in the aqueous liquid under solid-saturation conditions between 673 and 1200 K from vapor saturation up to 5 kbar. In the NaCl-KCl anhydrous binary system, the equations describe phase equilibria and predict activity coefficients of the salt components for all stable compositions of solid and liquid phases between room temperature and 1200 K and from 1 bar to 5 kbar. ?? 1992.

  1. Study of temperature effect on far-infrared spectra of liquid H2O and D2O by analytical theory and molecular dynamic simulations.

    PubMed

    Zasetsky, Alexander Y; Gaiduk, Vladimir I

    2007-06-28

    The results of a combined study of dielectric loss (epsilon"(nu)) and power-absorption coefficient (alpha(nu)) are reported. The epsilon"(nu) and alpha(nu) values are obtained for liquid water (H2O) and heavy water (D2O) using analytical modeling and the molecular dynamics (MD) simulations method. The calculated spectra span the microwave and far-infrared (FIR) region. The temperature range probed is 220-355 K. Appropriate parametrization of the analytical model for liquid water enables the quantitative description of the dielectric spectra over the frequency range of 0-1000 cm-1. An excellent agreement between the calculated spectra and the experimental data demonstrates the accuracy of the applied analytical approximations. The spectra obtained using the MD simulations agree rather qualitatively with the experimental epsilon"(nu) and alpha(nu) dependences. The observed spectra are interpreted in terms of four molecular mechanisms that have been recently described [J. Phys. Chem. A 2006, 110, 9361].

  2. Effect of H2O and CO2 on The Oxidation Behavior and Durability at High Temperature of ODS-FeCrAl

    SciTech Connect

    Dryepondt, Sebastien N; Rouaix-Vande Put, Aurelie; Pint, Bruce A

    2012-01-01

    Cyclic oxidation testing was conducted on alloy MA956 and two different batches of alloy PM2000 at 1100 and 1200 C in different atmospheres rich in O2, H2O and CO2. Compare to 1h cycle in dry O2, exposure in air + 10 vol.% H2O resulted in an increase of the oxidation rate and a decrease of the time to breakaway for both alloys at 1200 C, and a faster consumption of Al in the MA956 alloy. 1h cyclic testing in 50%CO2/50%H2O+0.75% O2 had less of an impact on the oxidation rate but led to an increased formation of voids for alloy MA956, which had an impact on the alloy creep resistance. At 1100 C, exposure in 50%CO2/50%H2O resulted in significant oxide spallation compared with oxidation in air, but it was not the case when 0.75% O2 was added to the CO2/H2O mixture as a buffer. The control of impurities levels drastically improved the PM2000 oxidation resistance.

  3. Effect of H2O and CO2 on The Oxidation Behavior and Durability at High Temperature of ODS-FeCrAl

    SciTech Connect

    Dryepondt, Sebastien N; Pint, Bruce A; Rouaix-Vande Put, Aurelie

    2013-01-01

    Cyclic oxidation testing was conducted on alloy MA956 and two different batches of alloy PM2000 at 1100 and 1200 C in different atmospheres rich in O2, H2O and CO2. Compared to 1h cycles in dry O2, exposure in air+10 vol.% H2O resulted in an increase of the oxidation rate and a decrease of the time to breakaway for all alloys at 1200 C, and a faster consumption of Al in the MA956 alloy. One hour cyclic testing in 49.25%CO2+50%H2O+0.75% O2 had a smaller effect on the oxidation rate but led to increased formation of voids in alloy MA956, which had an impact on the alloy creep resistance. At 1100 C, exposure in 50%CO2+50%H2O resulted in significant oxide spallation compared with oxidation in air, but this was not the case when 0.75% O2 was added to the CO2/H2O mixture as a buffer. The control of impurity levels drastically improved the oxidation resistance of PM2000.

  4. Communication: State-to-state dynamics of the Cl + H2O → HCl + OH reaction: Energy flow into reaction coordinate and transition-state control of product energy disposal.

    PubMed

    Zhao, Bin; Sun, Zhigang; Guo, Hua

    2015-06-28

    Quantum state-to-state dynamics of a prototypical four-atom reaction, namely, Cl + H2O → HCl + OH, is investigated for the first time in full dimensionality using a transition-state wave packet method. The state-to-state reactivity and its dependence on the reactant internal excitations are analyzed and found to share many similarities both energetically and dynamically with the H + H2O → H2 + OH reaction. The strong enhancement of reactivity by the H2O stretching vibrational excitations in both reactions is attributed to the favorable energy flow into the reaction coordinate near the transition state. On the other hand, the insensitivity of the product state distributions with regard to reactant internal excitation stems apparently from the transition-state control of product energy disposal.

  5. Communication: State-to-state dynamics of the Cl + H2O → HCl + OH reaction: Energy flow into reaction coordinate and transition-state control of product energy disposal

    NASA Astrophysics Data System (ADS)

    Zhao, Bin; Sun, Zhigang; Guo, Hua

    2015-06-01

    Quantum state-to-state dynamics of a prototypical four-atom reaction, namely, Cl + H2O → HCl + OH, is investigated for the first time in full dimensionality using a transition-state wave packet method. The state-to-state reactivity and its dependence on the reactant internal excitations are analyzed and found to share many similarities both energetically and dynamically with the H + H2O → H2 + OH reaction. The strong enhancement of reactivity by the H2O stretching vibrational excitations in both reactions is attributed to the favorable energy flow into the reaction coordinate near the transition state. On the other hand, the insensitivity of the product state distributions with regard to reactant internal excitation stems apparently from the transition-state control of product energy disposal.

  6. The system H 2O-NaCl. Part I: Correlation formulae for phase relations in temperature-pressure-composition space from 0 to 1000 °C, 0 to 5000 bar, and 0 to 1 XNaCl

    NASA Astrophysics Data System (ADS)

    Driesner, Thomas; Heinrich, Christoph A.

    2007-10-01

    Realistic simulations of fluid flow in geologic systems have severely been hampered by the lack of a consistent formulation for fluid properties for binary salt-water fluids over the temperature-pressure-composition ranges encountered in the Earth's crust. As the first of two companion studies, a set of correlations describing the phase stability relations in the system H 2O-NaCl is developed. Pure water is described by the IAPS-84 equation of state. New correlations comprise the vapor pressure of halite and molten NaCl, the NaCl melting curve, the composition of halite-saturated liquid and vapor, the pressure of vapor + liquid + halite coexistence, the temperature-pressure and temperature-composition relations for the critical curve, and the compositions of liquid and vapor on the vapor + liquid coexistence surface. The correlations yield accurate values for temperatures from 0 to 1000 °C, pressures from 0 to 5000 bar, and compositions from 0 to 1 XNaCl (mole fraction of NaCl). To facilitate their use in fluid flow simulations, the correlations are entirely formulated as functions of temperature, pressure and composition.

  7. The effects of H2O and SO2 on the behaviour of CuSO4-CeO2/TS for low temperature catalytic reduction of NO with NH3.

    PubMed

    Tong, Hua; Dai, Junhong; He, Yong; Tong, Zhiquan

    2011-01-01

    The catalyst CuSO4-CeO2/TiO2-SiO2 (CuSO4-CeO2/TS), for low temperature catalytic reduction (LT-SCR) of NO with NH was prepared by the impregnation method. The impacts of H2O and SO2 on the catalyst were investigated. Experiments showed that H2O brought down the catalyst's activity at low reaction temperature. However, this negative effect of H2O could be mostly eliminated with a raised temperature of above 220 degrees C. In a 10-hour experiment on the catalyst's resistibility to SO2 poisoning, NO conversion increased slightly by the promoting effect of SO2. The same catalyst underwent continuous examination with both SO2 and H2O in the feed gas; NO conversion of around 90.2% was maintained for 37 hours, showing better performance than CuSO4-CeO2/TiO2. This suggested that SiO2 in the TiO2-SiO2 catalyst supported the supression of the oxidization of SO2 to SO3. Therefore, the formation of ammonium sulphate over the catalyst and the sulphation of CeO2 in the catalyst were greatly alleviated, leading to a better resistibility of the catalyst to SO2 poisioning. After the 37 hours, the catalyst activity began to fall, and an irrecoverable deactivation of the catalyst was observed. PMID:21879564

  8. Application of time-division-multiplexed lasers for measurements of gas temperature and CH4 and H2O concentrations at 30 kHz in a high-pressure combustor.

    PubMed

    Caswell, Andrew W; Kraetschmer, Thilo; Rein, Keith; Sanders, Scott T; Roy, Sukesh; Shouse, Dale T; Gord, James R

    2010-09-10

    Two time-division-multiplexed (TDM) sources based on fiber Bragg gratings were applied to monitor gas temperature, H(2)O mole fraction, and CH(4) mole fraction using line-of-sight absorption spectroscopy in a practical high-pressure gas turbine combustor test article. Collectively, the two sources cycle through 14 wavelengths in the 1329-1667 nm range every 33 μs. Although it is based on absorption spectroscopy, this sensing technology is fundamentally different from typical diode-laser-based absorption sensors and has many advantages. Specifically, the TDM lasers allow efficient, flexible acquisition of discrete-wavelength information over a wide spectral range at very high speeds (typically 30 kHz) and thereby provide a multiplicity of precise data at high speeds. For the present gas turbine application, the TDM source wavelengths were chosen using simulated temperature-difference spectra. This approach is used to select TDM wavelengths that are near the optimum values for precise temperature and species-concentration measurements. The application of TDM lasers for other measurements in high-pressure, turbulent reacting flows and for two-dimensional tomographic reconstruction of the temperature and species-concentration fields is also forecast.

  9. Quantitative Measurements of HO2 and other products of n-butane oxidation (H2O2, H2O, CH2O, and C2H4) at elevated temperatures by direct coupling of a jet-stirred reactor with sampling nozzle and cavity ring-down spectroscopy (cw-CRDS).

    PubMed

    Djehiche, Mokhtar; Le Tan, Ngoc Linh; Jain, Chaithanya D; Dayma, Guillaume; Dagaut, Philippe; Chauveau, Christian; Pillier, Laure; Tomas, Alexandre

    2014-11-26

    For the first time quantitative measurements of the hydroperoxyl radical (HO2) in a jet-stirred reactor were performed thanks to a new experimental setup involving fast sampling and near-infrared cavity ring-down spectroscopy at low pressure. The experiments were performed at atmospheric pressure and over a range of temperatures (550-900 K) with n-butane, the simplest hydrocarbon fuel exhibiting cool flame oxidation chemistry which represents a key process for the auto-ignition in internal combustion engines. The same technique was also used to measure H2O2, H2O, CH2O, and C2H4 under the same conditions. This new setup brings new scientific horizons for characterizing complex reactive systems at elevated temperatures. Measuring HO2 formation from hydrocarbon oxidation is extremely important in determining the propensity of a fuel to follow chain-termination pathways from R + O2 compared to chain branching (leading to OH), helping to constrain and better validate detailed chemical kinetics models. PMID:25381864

  10. The TAED/H2O2/NaHCO3 system as an approach to low-temperature and near-neutral pH bleaching of cotton.

    PubMed

    Long, Xiaoxia; Xu, Changhai; Du, Jinmei; Fu, Shaohai

    2013-06-01

    A low-temperature and near-neutral pH bleaching system was conceived for cotton by incorporating TAED, H2O2 and NaHCO3. The TAED/H2O2/NaHCO3 system was investigated and optimized for bleaching of cotton using a central composite design (CCD) combined with response surface methodology (RSM). CCD experimental data were fitted to create a response surface quadratic model (RSQM) describing the degree of whiteness of bleached cotton fabric. Analysis of variance for the RSQM revealed that temperature was the most significant variable, followed by [TAED] and time, while [NaHCO3] was insignificant. An effective system was conducted by adding 5.75 g L(-1) TAED together with H2O2 and NaHCO3 at a molar ratio of 1:2.4:2.8 and applied to bleaching of cotton at 70 °C for 40 min. Compared to a commercial bleaching method, the TAED/H2O2/NaHCO3 system provided cotton with comparable degree of whiteness, slightly inferior water absorbency and acceptable dyeability, but had competitive advantage in protecting cotton from severe chemical damage in bleaching. PMID:23618246

  11. Solubilities of corundum, wollastonite and quartz in H 2O-NaCl solutions at 800 °C and 10 kbar: Interaction of simple minerals with brines at high pressure and temperature

    NASA Astrophysics Data System (ADS)

    Newton, Robert C.; Manning, Craig E.

    2006-11-01

    Solubilities of corundum (Al 2O 3) and wollastonite (CaSiO 3) were measured in H 2O-NaCl solutions at 800 °C and 10 kbar and NaCl concentrations up to halite saturation by weight-loss methods. Additional data on quartz solubility at a single NaCl concentration were obtained as a supplement to previous work. Single crystals of synthetic corundum, natural wollastonite or natural quartz were equilibrated with H 2O and NaCl at pressure ( P) and temperature ( T) in a piston-cylinder apparatus with NaCl pressure medium and graphite heater sleeves. The three minerals show fundamentally different dissolution behavior. Corundum solubility undergoes large enhancement with NaCl concentration, rising rapidly from Al 2O 3 molality (mO) of 0.0013(1) (1 σ error) in pure H 2O and then leveling off to a maximum of ˜0.015 at halite saturation ( XNaCl ≈ 0.58, where X is mole fraction). Solubility enhancement relative to that in pure H 2O, XO/XAlO°, passes through a maximum at XNaCl ≈ 0.15 and then declines towards halite saturation. Quenched fluids have neutral pH at 25 °C. Wollastonite has low solubility in pure H 2O at this P and T(m=0.0167(6)). It undergoes great enhancement, with a maximum solubility relative to that in H 2O at XNaCl ≈ 0.33, and solubility >0.5 molal at halite saturation. Solute silica is 2.5 times higher than at quartz saturation in the system H 2O-NaCl-SiO 2, and quenched fluids are very basic (pH 11). Quartz shows monotonically decreasing solubility from m=1.248 in pure H 2O to 0.202 at halite saturation. Quenched fluids are pH neutral. A simple ideal-mixing model for quartz-saturated solutions that requires as input only the solubility and speciation of silica in pure H 2O reproduces the data and indicates that hydrogen bonding of molecular H 2O to dissolved silica species is thermodynamically negligible. The maxima in XO/XAlO° for corundum and wollastonite indicate that the solute products include hydrates and Na + and/or Cl - species produced by

  12. Effect of H2O, and combined effects of H2O + F, H2O + CO2, and H2O + F + CO2 on the viscosity of a natural basalt from Fuego volcano, Guatemala

    NASA Astrophysics Data System (ADS)

    Robert, G.; Whittington, A. G.; Knipping, J.; Scherbarth, S.; Stechern, A.; Behrens, H.

    2012-12-01

    We measured the viscosity of 5 series of remelted natural basalt from Fuego volcano, Guatemala. These series include single and multiple volatile species: H2O, F, H2O-F, H2O-CO2, and H2O-CO2-F. The hydrous glasses were synthesized at 3 kbar and 1250°C in Internally Heated Pressure Vessels. The multiple volatile series were synthesized at 5 kbar and 1250°C. CO2 was added as Ag2C2O4, F as AlF3, and H2O as distilled water. The anhydrous, F-bearing series was synthesized at 1 atm by simply remelting the Fuego basalt and adding F as CaF2.The natural, dry, remelted Fuego basalt has an NBO/T of 0.64. The following comparisons are based on parallel-plate viscosity measurements in the range ~108 to 1012 Pa s. The temperature at which the viscosity is 1012 Pa s (T12) is taken to be the viscosimetric glass transition temperature (Tg). The addition of 2 wt.% H2O results in a decrease of T12 of ~150°C for basalt. Fluorine on its own has a measurable, but much smaller effect, than the equivalent amount of water. Indeed, ~2 wt.% F results in a T12 depression of only ~30°C. When H2O and F are both present, their effects are approximately additive. For example, the viscosity of a basalt with 1.44 wt.% H2O is very similar to the viscosity of a basalt with ~1 wt.% H2O and ~1.25 wt.% F, and the viscosities of a basalt with 2.29 wt.% H2O and a basalt with ~1.65 wt.% H2O and ~1.3 wt.% F are also very similar. The effect of CO2 is somewhat ambiguous. The viscosity of a basalt with ~1.7 wt.% H2O, ~1.3 wt.% F and ~0.2 wt.% CO2 is essentially the same as the viscosity of a basalt with 2.29 wt.% H2O, so CO2 seems to have a negligible or even viscosity-increasing effect when F and H2O are also present. However, a basalt with ~0.84 wt.% H2O and ~0.09 wt.% CO2 has about the same viscosity as a basalt with 1.34 wt.% H2O, which could suggest a strong (viscosity-decreasing) effect of very small amounts of CO2. These results suggest that the effects on viscosity of F in basaltic systems are

  13. Enhancement of the Curie temperature by isomerization of diarylethene (DAE) for an organic-inorganic hybrid system: Co4(OH)7(DAE)0.5.3H2O.

    PubMed

    Shimizu, H; Okubo, M; Nakamoto, A; Enomoto, M; Kojima, N

    2006-12-11

    Intercalation of an organic photochromic molecule into layered magnetic systems may provide multifunctional properties such as photomagnetism. To build up a photosensitive multifunctional magnet, an organic-inorganic hybrid system coupled with a photochromic diarylethene anion, 2,2'-dimethyl-3,3'-(perfluorocyclopentene-1,2-diyl)bis(benzo[b]thiophene-6-sulfonate) (DAE), and cobalt LDHs (layered double hydroxides), Co4(OH)7(DAE)0.5.3H2O, was synthesized by the anion exchange reaction between Co2(OH)3(CH3COO).H2O and DAE. In the dark and under UV-irradiated (313 nm) conditions, Co4(OH)7(DAE)0.5.3H2O with open and closed forms of DAE were obtained, respectively. The magnetic susceptibility measurements elucidated ferromagnetic intra- and interlayer interactions and Curie temperatures of TC = 9 and 20 K for cobalt LDHs with the open and closed forms of DAE, respectively. The enhancement of the Curie temperature from 9 to 20 K by substitution of the open form of DAE with the closed form of DAE as an intercalated molecule is attributed to the delocalization of the pi-electrons in the closed form of DAE, which enhances the interlayer magnetic interaction. The enhancement of the interlayer magnetic interaction induced by the delocalization of pi-electrons in intercalated molecules is strongly supported by the fact that the Curie temperature (26.0 K) of cobalt LDHs with (E,E)-2,4-hexadienedioate having a conjugated pi-electron system is enormously higher than that (7.0 K) of the cobalt LDHs with hexanedioate. By UV irradiation at 313 nm, Co4(OH)7(DAE)0.5.3H2O shows the photoisomerization of DAE from the open form to the closed one in the solid state, which leads to the enhancement of Curie temperature.

  14. The interaction of H(2)O(2) with ice surfaces between 203 and 233 K.

    PubMed

    Pouvesle, N; Kippenberger, M; Schuster, G; Crowley, J N

    2010-12-21

    The interaction of H(2)O(2) with ice surfaces at temperatures between 203 and 233 K was investigated using a low pressure, coated-wall flow tube equipped with a chemical ionisation/electron impact mass spectrometer. Equilibrium surface coverages of H(2)O(2) on ice were measured at various concentrations and temperatures to derive Langmuir-type adsorption isotherms. H(2)O(2) was found to be strongly partitioned to the ice surface at low temperatures, with a partition coefficient, K(linC), equal to 2.1 × 10(-5) exp(3800/T) cm. At 228 K, this expression results in values of K(linC) which are orders of magnitude larger than the single previous determination and suggests that H(2)O(2) may be significantly partitioned to the ice phase in cirrus clouds. The partition coefficient for H(2)O(2) was compared to several other trace gases which hydrogen-bond to ice surfaces and a good correlation with the free energy of condensation found. For this class of trace gas a simple parameterisation for calculating K(linC)(T) from thermodynamic properties was established.

  15. Hydrogen bonding system in euchroite, Cu2(AsO4)(OH)(H2O)3: low-temperature crystal-structure refinement and solid-state density functional theory modeling

    NASA Astrophysics Data System (ADS)

    Krivovichev, Sergey V.; Zolotarev, Andrey A.; Pekov, Igor V.

    2016-06-01

    Hydrogen bonding in euchroite has been studied by means of low-temperature single-crystal X-ray diffraction (XRD) and solid-state density functional theory (DFT) calculations. The mineral is orthorhombic, P212121, a = 10.0350(8), b = 10.4794(8), c = 6.1075(5) Å, V = 642.27(9) Å3, and Z = 4. The structure has been refined to R 1 = 0.036 for 2436 unique observed reflections with |F o| ≥ 4σ F . DFT calculations were performed with the CRYSTAL14 software package. The basic features of the crystal structure of euchroite are the same as described by previous authors. There are two symmetrically-independent Cu sites octahedrally coordinated by O atoms. The CuO6 octahedra are strongly distorted containing four short (1.927-2.012 Å) and two long (2.360-2.797 Å) bonds each, in agreement with the expected Jahn-Teller distortion of an octahedrally-coordinated Cu2+ cation. There is one symmetrically-independent As site that is tetrahedrally coordinated by four O atoms to form an arsenate oxyanion, AsO4 3-. The structure is based upon chains of edge-sharing CuO6 octahedra running parallel to [001]. The chains are linked by AsO4 tetrahedra into a three-dimensional framework, which is stabilized by hydrogen bonds formed from OH and H2O groups. The coordinates of H atoms determined by single-crystal X-ray diffraction and those calculated using DFT are very similar. The distance Δ between experimental and theoretical H positions does not exceed 0.250 Å, except for the H72 site, for which Δ = 0.609 Å. The hydrogen bonding scheme in euchroite is rather complex and involves a combination of relatively strong two-center hydrogen bonds as well as few three-center (bifurcated) hydrogen bonds. The largest difference between the XRD and DFT results involves the H72 atom of the H2O7 molecule and can be assigned to the effect of temperature, which favors a strong linear hydrogen bond at 0 K (calculated) and a bifurcated three-center bond at 100 K (measured). The Cu-H2O

  16. Stepwise formation of H3O(+)(H2O)n in an ion drift tube: Empirical effective temperature of association/dissociation reaction equilibrium in an electric field.

    PubMed

    Nakai, Yoichi; Hidaka, Hiroshi; Watanabe, Naoki; Kojima, Takao M

    2016-06-14

    We measured equilibrium constants for H3O(+)(H2O)n-1 + H2O↔H3O(+)(H2O)n (n = 4-9) reactions taking place in an ion drift tube with various applied electric fields at gas temperatures of 238-330 K. The zero-field reaction equilibrium constants were determined by extrapolation of those obtained at non-zero electric fields. From the zero-field reaction equilibrium constants, the standard enthalpy and entropy changes, ΔHn,n-1 (0) and ΔSn,n-1 (0), of stepwise association for n = 4-8 were derived and were in reasonable agreement with those measured in previous studies. We also examined the electric field dependence of the reaction equilibrium constants at non-zero electric fields for n = 4-8. An effective temperature for the reaction equilibrium constants at non-zero electric field was empirically obtained using a parameter describing the electric field dependence of the reaction equilibrium constants. Furthermore, the size dependence of the parameter was thought to reflect the evolution of the hydrogen-bond structure of H3O(+)(H2O)n with the cluster size. The reflection of structural information in the electric field dependence of the reaction equilibria is particularly noteworthy.

  17. Stepwise formation of H3O(+)(H2O)n in an ion drift tube: Empirical effective temperature of association/dissociation reaction equilibrium in an electric field.

    PubMed

    Nakai, Yoichi; Hidaka, Hiroshi; Watanabe, Naoki; Kojima, Takao M

    2016-06-14

    We measured equilibrium constants for H3O(+)(H2O)n-1 + H2O↔H3O(+)(H2O)n (n = 4-9) reactions taking place in an ion drift tube with various applied electric fields at gas temperatures of 238-330 K. The zero-field reaction equilibrium constants were determined by extrapolation of those obtained at non-zero electric fields. From the zero-field reaction equilibrium constants, the standard enthalpy and entropy changes, ΔHn,n-1 (0) and ΔSn,n-1 (0), of stepwise association for n = 4-8 were derived and were in reasonable agreement with those measured in previous studies. We also examined the electric field dependence of the reaction equilibrium constants at non-zero electric fields for n = 4-8. An effective temperature for the reaction equilibrium constants at non-zero electric field was empirically obtained using a parameter describing the electric field dependence of the reaction equilibrium constants. Furthermore, the size dependence of the parameter was thought to reflect the evolution of the hydrogen-bond structure of H3O(+)(H2O)n with the cluster size. The reflection of structural information in the electric field dependence of the reaction equilibria is particularly noteworthy. PMID:27306006

  18. Stepwise formation of H3O+(H2O)n in an ion drift tube: Empirical effective temperature of association/dissociation reaction equilibrium in an electric field

    NASA Astrophysics Data System (ADS)

    Nakai, Yoichi; Hidaka, Hiroshi; Watanabe, Naoki; Kojima, Takao M.

    2016-06-01

    We measured equilibrium constants for H3O+(H2O)n-1 + H2O↔H3O+(H2O)n (n = 4-9) reactions taking place in an ion drift tube with various applied electric fields at gas temperatures of 238-330 K. The zero-field reaction equilibrium constants were determined by extrapolation of those obtained at non-zero electric fields. From the zero-field reaction equilibrium constants, the standard enthalpy and entropy changes, Δ Hn , n - 1 0 and Δ Sn , n - 1 0 , of stepwise association for n = 4-8 were derived and were in reasonable agreement with those measured in previous studies. We also examined the electric field dependence of the reaction equilibrium constants at non-zero electric fields for n = 4-8. An effective temperature for the reaction equilibrium constants at non-zero electric field was empirically obtained using a parameter describing the electric field dependence of the reaction equilibrium constants. Furthermore, the size dependence of the parameter was thought to reflect the evolution of the hydrogen-bond structure of H3O+(H2O)n with the cluster size. The reflection of structural information in the electric field dependence of the reaction equilibria is particularly noteworthy.

  19. Isentropic advection and convective lifting of water vapor in the UT - LS as observed over Brazil (22° S) in February 2004 by in situ high-resolution measurements of H2O, CH4, O3 and temperature

    NASA Astrophysics Data System (ADS)

    Durry, G.; Huret, N.; Hauchecorne, A.; Marecal, V.; Pommereau, J.-P.; Jones, R. L.; Held, G.; Larsen, N.; Renard, J.-B.

    2006-12-01

    The micro-SDLA balloonborne diode laser spectrometer was flown twice from Bauru (22° S, Brazil) in February 2004 during HIBISCUS to yield in situ H2O measurements in the Upper Troposphere (UT) and Lower Stratosphere (LS) and in particular in the Tropical Tropopause Layer (TTL). The overall TTL was found warmer (with a subsaturated cold point near -79°C) and the LS moister compared to former measurements obtained in tropical oceanic conditions. The use of specific balloons with a slow descent, combined with the high-resolution of the laser sensor, allowed us to observe in situ in the UT, the TTL and the LS several thin layers correlated on H2O, CH4, O3, temperature and PV. A component of these layers is associated with the isentropic transport into the UT- LS of extratropical stratospheric air masses. Moreover, the examination of temperature and tracer (CH4, O3) profiles gives insights on the potential contribution of convective transport of H2O in the TTL.

  20. Aerosol chamber study of optical constants and N2O5 uptake on supercooled H2SO4/H2O/HNO3 solution droplets at polar stratospheric cloud temperatures.

    PubMed

    Wagner, Robert; Naumann, Karl-Heinz; Mangold, Alexander; Möhler, Ottmar; Saathoff, Harald; Schurath, Ulrich

    2005-09-15

    The mechanism of the formation of supercooled ternary H(2)SO(4)/H(2)O/HNO(3) solution (STS) droplets in the polar winter stratosphere, i.e., the uptake of nitric acid and water onto background sulfate aerosols at T < 195 K, was successfully mimicked during a simulation experiment at the large coolable aerosol chamber AIDA of Forschungszentrum Karlsruhe. Supercooled sulfuric acid droplets, acting as background aerosol, were added to the cooled AIDA vessel at T = 193.6 K, followed by the addition of ozone and nitrogen dioxide. N(2)O(5), the product of the gas phase reaction between O(3) and NO(2), was then hydrolyzed in the liquid phase with an uptake coefficient gamma(N(2)O(5)). From this experiment, a series of FTIR extinction spectra of STS droplets was obtained, covering a broad range of different STS compositions. This infrared spectra sequence was used for a quantitative test of the accuracy of published infrared optical constants for STS aerosols, needed, for example, as input in remote sensing applications. The present findings indicate that the implementation of a mixing rule approach, i.e., calculating the refractive indices of ternary H(2)SO(4)/H(2)O/HNO(3) solution droplets based on accurate reference data sets for the two binary H(2)SO(4)/H(2)O and HNO(3)/H(2)O systems, is justified. Additional model calculations revealed that the uptake coefficient gamma(N(2)O(5)) on STS aerosols strongly decreases with increasing nitrate concentration in the particles, demonstrating that this so-called nitrate effect, already well-established from uptake experiments conducted at room temperature, is also dominant at stratospheric temperatures.

  1. Aerosol chamber study of optical constants and N2O5 uptake on supercooled H2SO4/H2O/HNO3 solution droplets at polar stratospheric cloud temperatures.

    PubMed

    Wagner, Robert; Naumann, Karl-Heinz; Mangold, Alexander; Möhler, Ottmar; Saathoff, Harald; Schurath, Ulrich

    2005-09-15

    The mechanism of the formation of supercooled ternary H(2)SO(4)/H(2)O/HNO(3) solution (STS) droplets in the polar winter stratosphere, i.e., the uptake of nitric acid and water onto background sulfate aerosols at T < 195 K, was successfully mimicked during a simulation experiment at the large coolable aerosol chamber AIDA of Forschungszentrum Karlsruhe. Supercooled sulfuric acid droplets, acting as background aerosol, were added to the cooled AIDA vessel at T = 193.6 K, followed by the addition of ozone and nitrogen dioxide. N(2)O(5), the product of the gas phase reaction between O(3) and NO(2), was then hydrolyzed in the liquid phase with an uptake coefficient gamma(N(2)O(5)). From this experiment, a series of FTIR extinction spectra of STS droplets was obtained, covering a broad range of different STS compositions. This infrared spectra sequence was used for a quantitative test of the accuracy of published infrared optical constants for STS aerosols, needed, for example, as input in remote sensing applications. The present findings indicate that the implementation of a mixing rule approach, i.e., calculating the refractive indices of ternary H(2)SO(4)/H(2)O/HNO(3) solution droplets based on accurate reference data sets for the two binary H(2)SO(4)/H(2)O and HNO(3)/H(2)O systems, is justified. Additional model calculations revealed that the uptake coefficient gamma(N(2)O(5)) on STS aerosols strongly decreases with increasing nitrate concentration in the particles, demonstrating that this so-called nitrate effect, already well-established from uptake experiments conducted at room temperature, is also dominant at stratospheric temperatures. PMID:16834200

  2. Experimental multi-phase H2O-CO2 brine interactions at elevated temperature and pressure: Implications for CO2 sequestration in deep-saline aquifers

    USGS Publications Warehouse

    Rosenbauer, R.; Koksalan, T.

    2004-01-01

    The burning of fossil fuel and other anthropogenic activities have caused a continuous and dramatic 30% increase of atmospheric CO2 over the past 150 yr. CO2 sequestration is increasingly being viewed as a tool for managing these anthropogenic CO2 emissions to the atmosphere. CO2-saturated brine-rock experiments were carried out to evaluate the effects of multiphase H2O-CO2 fluids on mineral equilibria and the potential for CO2 sequestration in mineral phases within deep-saline aquifers. Experimental results were generally consistent with theoretical thermodynamic calculations. The solubility of CO2 was enhanced in brines in the presence of both limestone and sandstone relative to brines alone. Reactions between CO2 saturated brines and arkosic sandstones were characterized by desiccation of the brine and changes in the chemical composition of the brine suggesting fixation of CO2 in mineral phases. These reactions were occurring on a measurable but kinetically slow time scale at 120??C.

  3. H2O2: A Dynamic Neuromodulator

    PubMed Central

    Rice, Margaret E.

    2012-01-01

    Increasing evidence implicates hydrogen peroxide (H2O2) as an intra- and intercellular signaling molecule that can influence processes from embryonic development to cell death. Most research has focused on relatively slow signaling, on the order of minutes to days, via second messenger cascades. However, H2O2 can also mediate subsecond signaling via ion channel activation. This rapid signaling has been examined most thoroughly in the nigrostriatal dopamine (DA) pathway, which plays a key role in facilitating movement mediated by the basal ganglia. In DA neurons of the substantia nigra, endogenously generated H2O2 activates ATP-sensitive K+ (KATP) channels that inhibit DA neuron firing. In the striatum, H2O2 generated downstream from glutamatergic AMPA receptor activation in medium spiny neurons acts as a diffusible messenger that inhibits axonal DA release, also via KATP channels. The source of dynamically generated H2O2 is mitochondrial respiration; thus, H2O2 provides a novel link between activity and metabolism via KATP channels. Additional targets of H2O2 include transient receptor potential (TRP) channels. In contrast to the inhibitory effect of H2O2 acting via KATP channels, TRP channel activation is excitatory. This review describes emerging roles of H2O2 as a signaling agent in the nigrostriatal pathway and other basal ganglia neurons. PMID:21666063

  4. H2O2: a dynamic neuromodulator.

    PubMed

    Rice, Margaret E

    2011-08-01

    Increasing evidence implicates hydrogen peroxide (H(2)O(2)) as an intracellular and intercellular signaling molecule that can influence processes from embryonic development to cell death. Most research has focused on relatively slow signaling, on the order of minutes to days, via second messenger cascades. However, H(2)O(2) can also mediate subsecond signaling via ion channel activation. This rapid signaling has been examined most thoroughly in the nigrostriatal dopamine (DA) pathway, which plays a key role in facilitating movement mediated by the basal ganglia. In DA neurons of the substantia nigra, endogenously generated H(2)O(2) activates ATP-sensitive K(+) (K-ATP) channels that inhibit DA neuron firing. In the striatum, H(2)O(2) generated downstream from glutamatergic AMPA receptor activation in medium spiny neurons acts as a diffusible messenger that inhibits axonal DA release, also via K-ATP channels. The source of dynamically generated H(2)O(2) is mitochondrial respiration; thus, H(2)O(2) provides a novel link between activity and metabolism via K-ATP channels. Additional targets of H(2)O(2) include transient receptor potential (TRP) channels. In contrast to the inhibitory effect of H(2)O(2) acting via K-ATP channels, TRP channel activation is excitatory. This review describes emerging roles of H(2)O(2) as a signaling agent in the nigrostriatal pathway and basal ganglia neurons.

  5. Reconstructing Final H2O Contents of Hydrated Rhyolitic Glasses: Insights into H2O Degassing and Eruptive Style of Silicic Submarine Volcanoes

    NASA Astrophysics Data System (ADS)

    McIntosh, I. M.; Nichols, A. R.; Tani, K.; Llewellin, E. W.

    2015-12-01

    H2O degassing influences the evolution of magma viscosity and vesicularity during ascent through the crust, and ultimately the eruptive style. Investigating H2O degassing requires data on both initial and final H2O contents. Initial H2O contents are revealed by melt inclusion data, while final H2O contents are found from dissolved H2O contents of volcanic glass. However volcanic glasses, particularly of silicic composition, are susceptible to secondary hydration i.e. the addition of H2O from the surrounding environment at ambient temperature during the time following pyroclast deposition. Obtaining meaningful final H2O data therefore requires distinguishing between the original final dissolved H2O content and the H2O added subsequently during hydration. Since H2O added during hydration is added as molecular H2O (H2Om), and the species interconversion between H2Om and hydroxyl (OH) species is negligible at ambient temperature, the final OH content of the glass remains unaltered during hydration. By using H2O speciation models to find the original H2Om content that would correspond to the measured OH content of the glass, the original total H2O (H2Ot) content of the glass prior to hydration can be reconstructed. These H2O speciation data are obtained using FTIR spectroscopy. In many cases, particularly where vesicular glasses necessitate thin wafers, OH cannot be measured directly and instead is calculated indirectly as OH = H2Ot - H2Om. Here we demonstrate the importance of using a speciation-dependent H2Ot molar absorptivity coefficient to obtain accurate H2Ot and H2O speciation data and outline a methodology for calculating such a coefficient for rhyolite glasses, with application to hydrated silicic pumice from submarine volcanoes in the Japanese Izu-Bonin Arc. Although hydrated pumice from Kurose Nishi and Oomurodashi now contain ~1.0 - 2.5 wt% H2Ot, their pre-hydration final H2O contents were typically ~0.3 - 0.4 wt% H2Ot. Furthermore, we show that pre

  6. The RealGas and RealGasH2O Options of the TOUGH+ Code for the Simulation of Coupled Fluid and Heat Flow in Tight/Shale Gas Systems

    SciTech Connect

    Moridis, George; Freeman, Craig

    2013-09-30

    We developed two new EOS additions to the TOUGH+ family of codes, the RealGasH2O and RealGas . The RealGasH2O EOS option describes the non-isothermal two-phase flow of water and a real gas mixture in gas reservoirs, with a particular focus in ultra-tight (such as tight-sand and shale gas) reservoirs. The gas mixture is treated as either a single-pseudo-component having a fixed composition, or as a multicomponent system composed of up to 9 individual real gases. The RealGas option has the same general capabilities, but does not include water, thus describing a single-phase, dry-gas system. In addition to the standard capabilities of all members of the TOUGH+ family of codes (fully-implicit, compositional simulators using both structured and unstructured grids), the capabilities of the two codes include: coupled flow and thermal effects in porous and/or fractured media, real gas behavior, inertial (Klinkenberg) effects, full micro-flow treatment, Darcy and non-Darcy flow through the matrix and fractures of fractured media, single- and multi-component gas sorption onto the grains of the porous media following several isotherm options, discrete and fracture representation, complex matrix-fracture relationships, and porosity-permeability dependence on pressure changes. The two options allow the study of flow and transport of fluids and heat over a wide range of time frames and spatial scales not only in gas reservoirs, but also in problems of geologic storage of greenhouse gas mixtures, and of geothermal reservoirs with multi-component condensable (H2O and CH4) and non-condensable gas mixtures. The codes are verified against available analytical and semi-analytical solutions. Their capabilities are demonstrated in a series of problems of increasing complexity, ranging from isothermal flow in simpler 1D and 2D conventional gas reservoirs, to non-isothermal gas flow in 3D fractured shale gas reservoirs involving 4 types of fractures, micro-flow, non-Darcy flow and gas

  7. The RealGas and RealGasH2O options of the TOUGH+ code for the simulation of coupled fluid and heat flow in tight/shale gas systems

    NASA Astrophysics Data System (ADS)

    Moridis, George J.; Freeman, Craig M.

    2014-04-01

    We developed two new EOS additions to the TOUGH+ family of codes, the RealGasH2O and RealGas. The RealGasH2O EOS option describes the non-isothermal two-phase flow of water and a real gas mixture in gas reservoirs, with a particular focus in ultra-tight (such as tight-sand and shale gas) reservoirs. The gas mixture is treated as either a single-pseudo-component having a fixed composition, or as a multicomponent system composed of up to 9 individual real gases. The RealGas option has the same general capabilities, but does not include water, thus describing a single-phase, dry-gas system. In addition to the standard capabilities of all members of the TOUGH+ family of codes (fully-implicit, compositional simulators using both structured and unstructured grids), the capabilities of the two codes include coupled flow and thermal effects in porous and/or fractured media, real gas behavior, inertial (Klinkenberg) effects, full micro-flow treatment, Darcy and non-Darcy flow through the matrix and fractures of fractured media, single- and multi-component gas sorption onto the grains of the porous media following several isotherm options, discrete and fracture representation, complex matrix-fracture relationships, and porosity-permeability dependence on pressure changes. The two options allow the study of flow and transport of fluids and heat over a wide range of time frames and spatial scales not only in gas reservoirs, but also in problems of geologic storage of greenhouse gas mixtures, and of geothermal reservoirs with multi-component condensable (H2O and CH4) and non-condensable gas mixtures. The codes are verified against available analytical and semi-analytical solutions. Their capabilities are demonstrated in a series of problems of increasing complexity, ranging from isothermal flow in simpler 1D and 2D conventional gas reservoirs, to non-isothermal gas flow in 3D fractured shale gas reservoirs involving 4 types of fractures, micro-flow, non-Darcy flow and gas

  8. A comparison of ice VII formed in the H2O, NaCl-H2O, and CH3OH-H2O systems: Implications for H2O-rich planets

    NASA Astrophysics Data System (ADS)

    Frank, Mark R.; Aarestad, Elizabeth; Scott, Henry P.; Prakapenka, Vitali B.

    2013-02-01

    High-pressure H2O polymorphs, namely ice VI, ice VII, and ice X, are hypothesized to make up a considerable portion of the interiors of large icy satellites and select extra-solar planets. The incorporation of foreign ions or molecules into these high-pressure phases is possible through ocean-ice interaction, rock-ice interaction at depth, or processes that occurred during accretion. Recent research concerning the effects charged ions have on ice VII has shown that these ions notably affect the structure of ice VII (Frank et al., 2006; Klotz et al., 2009). This study was designed to determine the effects of a molecular impurity on ice VII and compare those effects to both pure H2O ice and ice with an ionic impurity. Ice samples were formed in this study via compression in a diamond anvil cell from either H2O, a 1.60 mol% NaCl aqueous solution, a 1.60 mol% CH3OH aqueous solution, or a 5.00 mol% CH3OH aqueous solution and were compressed up to 71 GPa at room temperature. Ice formed from pure H2O had no impurities whereas ices formed in the NaCl-H2O and CH3OH-H2O systems contained the impurities Na+ and Cl- and CH3OH, respectively. Pressure-volume relations were observed in situ by using synchrotron based X-ray diffraction and were used to determine the equations of state for ices formed in the H2O, NaCl-H2O and CH3OH-H2O systems. The data illustrate that ice VII formed from a NaCl-bearing aqueous solution exhibited a depressed volume when compared to that of H2O-only ice VII at any given pressure, whereas ice VII formed from CH3OH-bearing aqueous solutions showed an opposite trend, with an increase in volume relative to that of pure ice VII. The ices within planetary bodies will most likely have both ionic and molecular impurities and the trends outlined in this study can be used to improve density profiles of H2O-rich planetary bodies.

  9. Heterogeneous interaction of H2O2 with TiO2 surface under dark and UV light irradiation conditions.

    PubMed

    Romanias, Manolis N; El Zein, Atallah; Bedjanian, Yuri

    2012-08-01

    The heterogeneous interaction of H(2)O(2) with TiO(2) surface was investigated under dark conditions and in the presence of UV light using a low pressure flow tube reactor coupled with a quadrupole mass spectrometer. The uptake coefficients were measured as a function of the initial concentration of gaseous H(2)O(2) ([H(2)O(2)](0) = (0.17-120) × 10(12) molecules cm(-3)), irradiance intensity (J(NO(2)) = 0.002-0.012 s(-1)), relative humidity (RH = 0.003-82%), and temperature (T = 275-320 K). Under dark conditions, a deactivation of TiO(2) surface upon exposure to H(2)O(2) was observed, and only initial uptake coefficient of H(2)O(2) was measured, given by the following expression: γ(0)(dark) = 4.1 × 10(-3)/(1 + RH(0.65)) (calculated using BET surface area, estimated conservative uncertainty of 30%) at T = 300 K. The steady-state uptake coefficient measured on UV irradiated TiO(2) surface, γ(ss)(UV), was found to be independent of RH and showed a strong inverse dependence on [H(2)O(2)] and linear dependence on photon flux. In addition, slight negative temperature dependence, γ(ss)(UV) = 7.2 × 10(-4) exp[(460 ± 80)/T], was observed in the temperature range (275-320) K (with [H(2)O(2)] ≈ 5 × 10(11) molecules cm(-3) and J(NO(2)) = 0.012 s(-1)). Experiments with NO addition into the reactive system provided indirect evidence for HO(2) radical formation upon H(2)O(2) uptake, and the possible reaction mechanism is proposed. Finally, the atmospheric lifetime of H(2)O(2) with respect to the heterogeneous loss on mineral dust was estimated (using the uptake data for TiO(2)) to be in the range of hours during daytime, i.e., comparable to H(2)O(2) photolysis lifetime (~1 day), which is the major removal process of hydrogen peroxide in the atmosphere. These data indicate a strong potential impact of H(2)O(2) uptake on mineral aerosol on the HO(x) chemistry in the troposphere.

  10. Low energy spin dynamics of a quantum ferrimagnetic chain, NiCu(pba)(H 2O) 32H 2O

    NASA Astrophysics Data System (ADS)

    Fujiwara, N.; Hagiwara, M.

    2000-01-01

    Nuclear magnetic resonance (NMR) for 1H nuclei was performed in a Heisenberg chain with alternating spins S=1 and 1/2, NiCu(pba)(H 2O) 32H 2O (pba=1,3-propylenebis (oxamato)) from 4.2 to 280 K. The relaxation rate (1/ T1) is proportional to 1/ H ( H is applied field), whereas the temperature dependence is weak and is almost constant at high temperatures. The temperature and field dependences are investigated on the basis of the spin-wave theory.

  11. LiOH - H2O2 - H2O trinary system study for the selection of optimal conditions of lithium peroxide synthesis

    NASA Astrophysics Data System (ADS)

    Nefedov, R. A.; Ferapontov, Yu A.; Kozlova, N. P.

    2016-01-01

    Using solubility method the decay kinetics of peroxide products contained in liquid phase of LiOH - H2O2 - H2O trinary system with 2 to 6% by wt hydrogen peroxide content in liquid phase in 21 to 33 °C temperature range has been studied. Conducted studies have allowed to determine temperature and concentration limits of solid phase existence of Li2O2·H2O content, distinctness of which has been confirmed using chemical and qualitative X- ray phase analysis. Stabilizing effect of solid phase of Li2O2·H2O content on hydrogen peroxide decay contained in liquid phase of LiOH - H2O2 - H2O trinary system under conditions of experiments conducted has been shown.

  12. Diode-laser measurements of linestrength and temperature-dependent lineshape parameters for H2O transitions near 1.4 μm using Voigt, Rautian, Galatry, and speed-dependent Voigt profiles

    NASA Astrophysics Data System (ADS)

    Goldenstein, Christopher S.; Hanson, Ronald K.

    2015-02-01

    Linestrengths and lineshapes for 7 H2O absorption transitions in the ν1 +ν3 combination band near 1.4 μm were measured at high resolution using tunable diode laser absorption. H2O- and N2-perturbed lineshapes were measured at 300-1300 K and 2-760 Torr and Voigt, Galatry, Rautian, and quadratic-speed-dependent-Voigt profiles were least-squares fit to measured spectra using a multi-spectrum fitting routine. Transitions with J ″ of 6-18 were studied to highlight the importance of collisional resonance and illustrate how the best-fit lineshape parameters varied with J ″. The accuracy of the Voigt profile decreased as J ″ increased (especially for J =Kc doublets). For transitions in N2, the collisional-broadening temperature exponents varied from ≈ 0.8 to -0.4 (for the Voigt profile) as J ″ increased and this behavior coincided with increasing speed-dependent collisional-broadening coefficients. The quadratic-speed-dependent Voigt profile was found to offer the best combination of accuracy and robust lineshape parameters; however, Rautian and Galatry profiles provided similar performance.

  13. Thermophysical Properties of Fluid H2O

    NASA Astrophysics Data System (ADS)

    Kestin, J.; Sengers, J. V.; Kamgar-Parsi, B.; Sengers, J. M. H. Levelt

    1984-01-01

    In view of the important role that water substance plays in science and industry, this paper lists the thermophysical properties of fluid H2O which are most needed for engineering applications. The properties are described in a very compact form with the aid of explicit expressions for programing on a computer and for inclusion in data banks. The paper includes a fundamental equation in the form of the Helmholtz free energy expressed as an analytic function of temperature and density. This fundamental equation is a dimensionless version of the Provisional IAPS Formulation 1982 for the Thermodynamic Properties of Ordinary Water Substance for Scientific and General Use, which enables one to calculate all equilibrium thermodynamic properties in a wide range of states, but with the exclusion of a small region near the critical point. In the latter region, the equilibrium properties are described by a scaled fundamental equation in the form of the pressure as a function of chemical potential and temperature. In addition, the paper gives equations for the viscosity, thermal conductivity, and surface tension. All equations in the paper are mutually thermodynamically consistent. The set of equations and their constants listed here represents the most reliable information according to the judgment of the authors.

  14. Synthesis, crystal structure and high temperature phase transition in the new organic-inorganic hybrid [N(C4H9)4]3Zn2Cl7H2O crystals

    NASA Astrophysics Data System (ADS)

    Ben Gzaiel, Malika; Oueslati, Abderrazek; Lhoste, Jérôme; Gargouri, Mohamed; Bulou, Alain

    2015-06-01

    The present paper accounts for the synthesis, crystal structure, differential scanning calorimetry and vibrational spectroscopy of a new compound tri-tetrabutylammonium heptachloro-dizincate (I) grown at room temperature by slow evaporation of aqueous solution. From X-ray diffraction data collected at room temperature, it is concluded that it crystallizes in the monoclinic system (P21/n space group) containing ZnCl42- and ZnCl3H2O1- tetrahedra. The atomic arrangement can be described by an alternation of organic and organic-inorganic layers stacked along the c direction. Differential scanning calorimetry (DSC) in the range 250-450 K disclosed a reversible structural phase transition of order-disorder type at 358 K, prior to the melting at 395 K. The temperature dependence of the Raman spectra of [N(C4H9)4]3Zn2Cl7H2O single crystals was studied in the spectral range 100-3500 cm-1 and for temperatures between 300 and 386 K. The most important changes are observed for the line at 261 cm-1 issued from ν1(ZnCl4). The analysis of the wavenumber, intensity and the line width based on an order-disorder model allowed to obtain information relative to the activation energy and the correlation length. The decrease of the activation energy with increasing temperature has been interpreted in term of a change in the re-orientation motion of the anionic parts. The assumption of cluster fluctuations also allowed the critical exponents to be obtained for the transition δ = 0.011 and the correlation length ξ0 = 598 Å.

  15. Syngas production by thermochemical conversion of CO2 and H2O mixtures using a high-temperature heat pipe based reactor

    NASA Astrophysics Data System (ADS)

    Pearlman, Howard; Chen, Chien-Hua

    2012-10-01

    The design of a new high-temperature, solar-based reactor for thermochemical production of syngas using water and carbon dioxide will be discussed. The reactor incorporates the use of high-temperature heat pipe(s) that efficiently transfer the heat from a solar collector to a porous metal oxide material. Special attention is given to the thermal characteristics of the reactor, which are key factors affecting the overall system efficiency and amount of fuel produced. The thermochemical cycle that is considered is that for ceria based material. Preliminary data acquired from an early stage reactor, operated at temperatures up to 1100oC, is presented and efforts are now underway to increase the operating temperature of the reactor to 1300oC to further increase the efficiency of the thermochemical fuel production process.

  16. Interaction between sulphide and H 2O in silicate melts

    NASA Astrophysics Data System (ADS)

    Stelling, Jan; Behrens, Harald; Wilke, Max; Göttlicher, Jörg; Chalmin-Aljanabi, Emilie

    2011-06-01

    Reaction between dissolved water and sulphide was experimentally investigated in soda-lime-silicate (NCS) and sodium trisilicate (NS3) melts at temperatures from 1000 to 1200 °C and pressures of 100 or 200 MPa in internally heated gas pressure vessels. Diffusion couple experiments were conducted at water-undersaturated conditions with one half of the couple being doped with sulphide (added as FeS or Na 2S; 1500-2000 ppm S by weight) and the other with H 2O (˜3.0 wt.%). Additionally, two experiments were performed using a dry NCS glass cylinder and a free H 2O fluid. Here, the melt was water-saturated at least at the melt/fluid interface. Profiling by electron microprobe (sulphur) and infrared microscopy (H 2O) demonstrate that H 2O diffusion in the melts is faster by 1.5-2.3 orders of magnitude than sulphur diffusion and, hence, H 2O can be considered as a rapidly diffusing oxidant while sulphur is quasi immobile in these experiments. In Raman spectra a band at 2576 cm -1 appears in the sulphide - H 2O transition zone which is attributed to fundamental S-H stretching vibrations. Formation of new IR absorption bands at 5025 cm -1 (on expense of the combination band of molecular H 2O at 5225 cm -1) and at 3400 cm -1 was observed at the front of the in-diffusing water in the sulphide bearing melt. The appearance and intensity of these two IR bands is correlated with systematic changes in S K-edge XANES spectra. A pre-edge excitation at 2466.5 eV grows with increasing H 2O concentration while the sulphide peak at 2474.0 eV decreases in intensity relative to the peak at 2477.0 eV and the feature at 2472.3 eV becomes more pronounced (all energies are relative to the sulphate excitation, calibrated to 2482.5 eV). The observations by Raman, IR and XANES spectroscopy indicate a well coordinated S 2- - H 2O complex which was probably formed in the glasses during cooling at the glass transition. No oxidation of sulphide was observed in any of the diffusion couple

  17. Destruction and Sequestration of H2O on Mars

    NASA Astrophysics Data System (ADS)

    Clark, Benton

    2016-07-01

    The availability of water in biologically useable form on any planet is a quintessential resource, even if the planet is in a zone habitable with temperature regimes required for growth of organisms (above -18 °C). Mars and most other planetary objects in the solar system do not have sufficient liquid water at their surfaces that photosynthesis or chemolithoautotrophic metabolism could occur. Given clear evidence of hydrous mineral alteration and geomorphological constructs requiring abundant supplies of liquid water in the past, the question arises whether this H2O only became trapped physically as ice, or whether there could be other, more or less accessible reservoirs that it has evolved into. Salts containing S or Cl appear to be ubiquitous on Mars, having been measured in soils by all six Mars landed missions, and detected in additional areas by orbital investigations. Volcanoes emit gaseous H2S, S, SO2, HCl and Cl2. A variety of evidence indicates the geochemical fate of these gases is to be transformed into sulfates, chlorides, chlorates and perchlorates. Depending on the gas, the net reaction causes the destruction of between one and up to eight molecules of H2O per atom of S or Cl (although hydrogen atoms are also released, they are lost relatively rapidly to atmospheric escape). Furthermore, the salt minerals formed often incorporate H2O into their crystalline structures, and can result in the sequestration of up to yet another six (sometimes, more) molecules of H2O. In addition, if the salts are microcrystalline or amorphous, they are potent adsorbents for H2O. In certain cases, they are even deliquescent under martian conditions. Finally, the high solubility of the vast majority of these salts (with notable exception of CaSO4) can result in dense brines with low water activity, aH, as well as cations which can be inimical to microbial metabolism, effectively "poisoning the well." The original geologic materials on Mars, igneous rocks, also provide some

  18. Effect of atomic layer deposition temperature on current conduction in Al2O3 films formed using H2O oxidant

    NASA Astrophysics Data System (ADS)

    Hiraiwa, Atsushi; Matsumura, Daisuke; Kawarada, Hiroshi

    2016-08-01

    To develop high-performance, high-reliability gate insulation and surface passivation technologies for wide-bandgap semiconductor devices, the effect of atomic layer deposition (ALD) temperature on current conduction in Al2O3 films is investigated based on the recently proposed space-charge-controlled field emission model. Leakage current measurement shows that Al2O3 metal-insulator-semiconductor capacitors formed on the Si substrates underperform thermally grown SiO2 capacitors at the same average field. However, using equivalent oxide field as a more practical measure, the Al2O3 capacitors are found to outperform the SiO2 capacitors in the cases where the capacitors are negatively biased and the gate material is adequately selected to reduce virtual dipoles at the gate/Al2O3 interface. The Al2O3 electron affinity increases with the increasing ALD temperature, but the gate-side virtual dipoles are not affected. Therefore, the leakage current of negatively biased Al2O3 capacitors is approximately independent of the ALD temperature because of the compensation of the opposite effects of increased electron affinity and permittivity in Al2O3. By contrast, the substrate-side sheet of charge increases with increasing ALD temperature above 210 °C and hence enhances the current of positively biased Al2O3 capacitors more significantly at high temperatures. Additionally, an anomalous oscillatory shift of the current-voltage characteristics with ALD temperature was observed in positively biased capacitors formed by low-temperature (≤210 °C) ALD. This shift is caused by dipoles at the Al2O3/underlying SiO2 interface. Although they have a minimal positive-bias leakage current, the low-temperature-grown Al2O3 films cause the so-called blisters problem when heated above 400 °C. Therefore, because of the absence of blistering, a 450 °C ALD process is presently the most promising technology for growing high-reliability Al2O3 films.

  19. The airborne mass spectrometer AIMS - Part 1: AIMS-H2O for UTLS water vapor measurements

    NASA Astrophysics Data System (ADS)

    Kaufmann, Stefan; Voigt, Christiane; Jurkat, Tina; Thornberry, Troy; Fahey, David W.; Gao, Ru-Shan; Schlage, Romy; Schäuble, Dominik; Zöger, Martin

    2016-03-01

    In the upper troposphere and lower stratosphere (UTLS), the accurate quantification of low water vapor concentrations has presented a significant measurement challenge. The instrumental uncertainties are passed on to estimates of H2O transport, cloud formation and the role of H2O in the UTLS energy budget and resulting effects on surface temperatures. To address the uncertainty in UTLS H2O determination, the airborne mass spectrometer AIMS-H2O, with in-flight calibration, has been developed for fast and accurate airborne water vapor measurements. We present a new setup to measure water vapor by direct ionization of ambient air. Air is sampled via a backward facing inlet that includes a bypass flow to assure short residence times (< 0.2 s) in the inlet line, which allows the instrument to achieve a time resolution of ˜ 4 Hz, limited by the sampling frequency of the mass spectrometer. From the main inlet flow, a smaller flow is extracted into the novel pressure-controlled gas discharge ion source of the mass spectrometer. The air is directed through the gas discharge region where ion-molecule reactions lead to the production of hydronium ion clusters, H3O+(H2O)n (n = 0, 1, 2), in a complex reaction scheme similar to the reactions in the D-region of the ionosphere. These ions are counted to quantify the ambient water vapor mixing ratio. The instrument is calibrated during flight using a new calibration source based on the catalytic reaction of H2 and O2 on a Pt surface to generate a calibration standard with well-defined and stable H2O mixing ratios. In order to increase data quality over a range of mixing ratios, two data evaluation methods are presented for lower and higher H2O mixing ratios respectively, using either only the H3O+(H2O) ions or the ratio of all water vapor dependent ions to the total ion current. Altogether, a range of water vapor mixing ratios from 1 to 500 parts per million by volume (ppmv) can be covered with an accuracy between 7 and 15 %. AIMS-H

  20. The airborne mass spectrometer AIMS - Part 1: AIMS-H2O for UTLS water vapor measurements

    NASA Astrophysics Data System (ADS)

    Kaufmann, S.; Voigt, C.; Jurkat, T.; Thornberry, T.; Fahey, D. W.; Gao, R.-S.; Schlage, R.; Schäuble, D.; Zöger, M.

    2015-12-01

    In the upper troposphere and lower stratosphere (UTLS), the accurate quantification of low water vapor concentrations has presented a significant measurement challenge. The instrumental uncertainties are passed on to estimates of H2O transport, cloud formation and the H2O role in the UTLS energy budget and resulting effects on surface temperatures. To address the uncertainty in UTLS H2O determination, the airborne mass spectrometer AIMS-H2O, with in-flight calibration, has been developed for fast and accurate airborne water vapor measurements. We present the new setup to measure water vapor by direct ionization of ambient air. Air is sampled via a backward facing inlet that includes a bypass flow to assure short residence times (< 0.2 s) in the inlet line, which allows the instrument to achieve a time resolution of ∼ 4 Hz. From the main inlet flow, a smaller flow is extracted into the novel pressure-controlled gas discharge ion source of the mass spectrometer. The air is directed through the gas discharge region where water molecules react to form hydronium ion clusters, H3O+(H2O)n (n= 0, 1, 2), in a complex reaction scheme similar to the reactions in the D-region of the ionosphere. These ions are counted to quantify the ambient water vapor mixing ratio. The instrument is calibrated during flight using a new calibration source based on the catalytic reaction of H2 and O2 on a Pt surface to generate a calibration standard with well defined and stable H2O mixing ratios. In order to increase data quality over a range of mixing ratios, two data evaluation methods are presented for lower and higher H2O mixing ratios respectively, using either only the H3O+(H2O) ions or the ratio of all water vapor dependent ions to the total ion current. Altogether, a range of water vapor mixing ratios from 1 to 500 ppmv (mole ratio, 10-6 mol mol-1) can be covered with an accuracy between 7 and 15 %. AIMS-H2O was deployed on two DLR research aircraft, the Falcon during CONCERT

  1. Conductivity measurements on H2O-bearing CO2-rich fluids

    DOE PAGES

    Capobianco, Ryan M.; Miroslaw S. Gruszkiewicz; Bodnar, Robert J.; Rimstidt, J. Donald

    2014-09-10

    Recent studies report rapid corrosion of metals and carbonation of minerals in contact with carbon dioxide containing trace amounts of dissolved water. One explanation for this behavior is that addition of small amounts of H2O to CO2 leads to significant ionization within the fluid, thus promoting reactions at the fluid-solid interface analogous to corrosion associated with aqueous fluids. The extent of ionization in the bulk CO2 fluid was determined using a flow-through conductivity cell capable of detecting very low conductivities. Experiments were conducted from 298 to 473 K and 7.39 to 20 MPa with H2O concentrations up to ~1600 ppmwmore » (xH2O ≈ 3.9 x 10-3), corresponding to the H2O solubility limit in liquid CO2 at ambient temperature. All solutions showed conductivities <10 nS/cm, indicating that the solutions were essentially ion-free. Furthermore, this observation suggests that the observed corrosion and carbonation reactions are not the result of ionization in CO2-rich bulk phase, but does not preclude ionization in the fluid at the fluid-solid interface.« less

  2. Stability of hydration states and hysteresis of rehydration in montmorillonites as a function of temperature, H2O pressure, and interlayer cations

    NASA Astrophysics Data System (ADS)

    Bassett, W. A.; Wu, T.-C.

    The hydration states of Ca- and Mg-exchanged montmorillonite from Wyoming bentonite have been studied as a function of temperature and pressure in a hydrothermal diamond anvil cell (HDAC) by X ray diffraction at the Cornell High Energy Synchrotron Source (CHESS). Runs were made at constant volume allowing pressure to be calculated from the equation of state of water and the homogenization temperature for each sample studied. Observations were made at pressures from the liquid-vapor coexistence boundary up to approximately 1 GPa. Conversion from the 19 to 15Å hydration state was observed to take place in the range 260-350°C for Ca-montmorillonite and in the range 200-250°C for Mg-montmorillonite, with a slight increase with increasing pressure. The rehydration from the 19 to 15Å state occurred at the same temperature (no hysteresis) at pressures just above the liquid-vapor coexistence boundary but decreased to 75°C below dehydration at 0.6 GPa for Ca-montmorillonite and 75°C below dehydration at 0.25 GPa for Mg-montmorillonite. There is evidence that the dehydration is the equilibrium boundary and that the rehydration hysteresis is caused by kinetics. The dehydration boundary is very nearly parallel to the pressure axis (dT/dP = 0). Thus, according to the Clapeyron equation, the volume change is essentially zero. From this we conclude that the molar volume or density of the water inside and outside of the montmorillonite is the same. If this is true, then it follows that entropy increases during dehydration. We attribute this to the change in the structure of the water inside and outside of the montmorillonite. When the conversion temperatures for Ca- and Mg-montmorillonites are combined with our earlier measurements on Na-montmorillonite, systematic trends can be observed in the effect of pressure and interlayer cation species on the dehydration temperature and rehydration hysteresis.

  3. A theoretical study of water equilibria: the cluster distribution versus temperature and pressure for (H2O)n, n = 1-60, and ice.

    PubMed

    Lenz, Annika; Ojamäe, Lars

    2009-10-01

    The size distribution of water clusters at equilibrium is studied using quantum-chemical calculations in combination with statistical thermodynamics. The necessary energetic data is obtained by quantum-chemical B3LYP computations and through extrapolations from the B3LYP results for the larger clusters. Clusters with up to 60 molecules are included in the equilibrium computations. Populations of different cluster sizes are calculated using both an ideal gas model with noninteracting clusters and a model where a correction for the interaction energy is included analogous to the van der Waals law. In standard vapor the majority of the water molecules are monomers. For the ideal gas model at 1 atm large clusters [56-mer (0-120 K) and 28-mer (100-260 K)] dominate at low temperatures and separate to smaller clusters [21-22-mer (170-280 K) and 4-6-mer (270-320 K) and to monomers (300-350 K)] when the temperature is increased. At lower pressure the transition from clusters to monomers lies at lower temperatures and fewer cluster sizes are formed. The computed size distribution exhibits enhanced peaks for the clusters consisting of 21 and 28 water molecules; these sizes are for protonated water clusters often referred to as magic numbers. If cluster-cluster interactions are included in the model the transition from clusters to monomers is sharper (i.e., occurs over a smaller temperature interval) than when the ideal-gas model is used. Clusters with 20-22 molecules dominate in the liquid region. When a large icelike cluster is included it will dominate for temperatures up to 325 K for the noninteracting clusters model. Thermodynamic properties (C(p), DeltaH) were calculated with in general good agreement with experimental values for the solid and gas phase. A formula for the number of H-bond topologies in a given cluster structure is derived. For the 20-mer it is shown that the number of topologies contributes to making the population of dodecahedron-shaped cluster larger

  4. H2O2 space shuttle APU

    NASA Technical Reports Server (NTRS)

    1975-01-01

    A cryogenic H2-O2 auxiliary power unit (APU) was developed and successfully demonstrated. It has potential application as a minimum weight alternate to the space shuttle baseline APU because of its (1) low specific propellant consumption and (2) heat sink capabilities that reduce the amount of expendable evaporants. A reference system was designed with the necessary heat exchangers, combustor, turbine-gearbox, valves, and electronic controls to provide 400 shp to two aircraft hydraulic pumps. Development testing was carried out first on the combustor and control valves. This was followed by development of the control subsystem including the controller, the hydrogen and oxygen control valves, the combustor, and a turbine simulator. The complete APU system was hot tested for 10 hr with ambient and cryogenic propellants. Demonstrated at 95 percent of design power was 2.25 lb/hp-hr. At 10 percent design power, specific propellant consumption was 4 lb/hp-hr with space simulated exhaust and 5.2 lb/hp-hr with ambient exhaust. A 10 percent specific propellant consumption improvement is possible with some seal modifications. It was demonstrated that APU power levels could be changed by several hundred horsepower in less than 100 msec without exceeding allowable turbine inlet temperatures or turbine speed.

  5. Effect of Process Temperature and Reaction Cycle Number on Atomic Layer Deposition of TiO2 Thin Films Using TiCl4 and H2O Precursors: Correlation Between Material Properties and Process Environment

    NASA Astrophysics Data System (ADS)

    Chiappim, W.; Testoni, G. E.; de Lima, J. S. B.; Medeiros, H. S.; Pessoa, Rodrigo Sávio; Grigorov, K. G.; Vieira, L.; Maciel, H. S.

    2016-02-01

    The effect of process temperature and reaction cycle number on atomic layer-deposited TiO2 thin films onto Si(100) using TiCl4 and H2O precursors was investigated in order to discuss the correlation between the growth per cycle (GPC), film structure (crystallinity), and surface roughness as well as the dependence of some of these properties with gas phase environment such as HCl by-product. In this work, these correlations were studied for two conditions: (i) process temperatures in the range of 100-500 °C during 1000 reaction cycles and (ii) number of cycles in the range of 100-2000 for a fixed temperature of 250 °C. To investigate the material properties, Rutherford backscattering spectrometry (RBS), grazing incidence X-ray diffraction (GIXRD), and atomic force microscopy (AFM) techniques were used. Mass spectrometry technique was used to investigate the time evolution of gas phase species HCl and H2O during ALD process. Results indicate that the GPC does not correlate well with film crystallinity and surface roughness for the evaluated process parameters. Basically, the film crystallinity relies solely on grain growth kinetics of the material. This occurs due to higher HCl by-product content during each purge step. Furthermore, for films deposited at variable cycle number, the evolution of film thickness and elemental composition is altered from an initial amorphous structure to a near stoichiometric TiO2-x and, subsequently, becomes fully stoichiometric TiO2 at 400 cycles or above. At this cycle value, the GIXRD spectrum indicates the formation of (101) anatase orientation.

  6. Flow-injection analysis for the determination of total inorganic carbon and total organic carbon in water using the H2O2-luminol-uranine chemiluminescent reaction.

    PubMed

    Fan, Shun-Li; Qu, Fang; Zhao, Lixia; Lin, Jin-Ming

    2006-12-01

    In the presence of carbonate and uranine, the chemiluminescent intensity from the reaction of luminol with hydrogen peroxide was dramatically enhanced in a basic medium. Based on this fact and coupled with the technique of flow-injection analysis, a highly sensitive method was developed for the determination of carbonate with a wide linear range. The method provided the determination of carbonate with a wide linear range of 1.0 x 10(-10)-5.0 x 10(-6) mol L(-1) and a low detection limit (S/N = 3) of carbonate of 1.2 x 10(-11) mol L(-1). The average relative standard deviation for 1.0 x 10(-9)-9.0 x 10(-7) mol L(-1) of carbonate was 3.7% (n = 11). Combined with the wet oxidation of potassium persulfate, the method was applied to the simultaneous determination of total inorganic carbon (TIC) and total organic carbon (TOC) in water. The linear ranges for TIC and TOC were 1.2 x 10(-6)-6.0 x 10(-2) mg L(-1) and 0.08-30 mg L(-1) carbon, respectively. Recoveries of 97.4-106.4% for TIC and 96.0-98.5% for TOC were obtained by adding 5 or 50 mg L(-1) of carbon to the water samples. The relative standard deviations (RSDs) were 2.6-4.8% for TIC and 4.6-6.6% for TOC (n = 5). The mechanism of the chemiluminescent reaction was also explored and a reasonable explanation about chemical energy transfer from luminol to uranine was proposed.

  7. Galactic H2O maser surveys

    NASA Astrophysics Data System (ADS)

    Felli, Marcello; Palagi, Francesco

    The first part is devoted to give an updated situation of the single dish surveys of galactic H2O masers, with particular emphasis on those associated with star forming regions (SFR). The main input for this comes from the updated Arcetri Atlas of H2O masers obtained with the Medicina 32m radio telescope. Available information on variability of the maser emission is also briefly reviewed. The second part gives a description of the results derived from the comparison of VLA observations of H2O masers in SFR and near IR images. J, H, K images are able to reveal the stellar cluster present in these highly obscured regions. IT is found that a stellar source with strong H-K excess is almost always associated with the maser spots (and not necessarily with an ultracompact HII region) and represents the direct evidence of the Young Stellar Object (YSO) which is required for the maser pumping. There are several indications suggesting that the H2O maser/near IR source may represent one of the earliest manifestation of a recently formed star. Finally, the importance of a coordination between near IR full sky surveys and H2O maser surveys is briefly discussed.

  8. Low-Temperature Polymorphic Phase Transition in a Crystalline Tripeptide l-Ala-l-Pro-Gly·H2O Revealed by Adiabatic Calorimetry

    PubMed Central

    Markin, Alexey V.; Markhasin, Evgeny; Sologubov, Semen S.; Ni, Qing Zhe; Smirnova, Natalia N.; Griffin, Robert G.

    2015-01-01

    We demonstrate application of precise adiabatic vacuun calorimetry to observation of phase transition in the tripeptide l-alanyl-l-prolyl-glycine monohydrate (APG) from 6 to 320 K and report the standard thermodynamic properties of the tripeptide in the entire range. Thus, the heat capacity of APG was measured by adiabatic vacuun calorimetry in the above temperature range. The tripeptide exhibits a reversible first-order solid-to-solid phase transition characterized by strong thermal hysteresis. We report the standard thermodynamic characteristics of this transition and show that differential scanning calorimetry can reliably characterize the observed phase transition with <5 mg of the sample. Additionally, the standard entropy of formation from the elemental substances and the standard entropy of hypothetical reaction of synthesis from the amino acids at 298.15 K were calculated for the studied tripeptide. PMID:25588051

  9. Differential regulation of TRPV1 channels by H2O2: implications for diabetic microvascular dysfunction.

    PubMed

    DelloStritto, Daniel J; Connell, Patrick J; Dick, Gregory M; Fancher, Ibra S; Klarich, Brittany; Fahmy, Joseph N; Kang, Patrick T; Chen, Yeong-Renn; Damron, Derek S; Thodeti, Charles K; Bratz, Ian N

    2016-03-01

    We demonstrated previously that TRPV1-dependent coupling of coronary blood flow (CBF) to metabolism is disrupted in diabetes. A critical amount of H2O2 contributes to CBF regulation; however, excessive H2O2 impairs responses. We sought to determine the extent to which differential regulation of TRPV1 by H2O2 modulates CBF and vascular reactivity in diabetes. We used contrast echocardiography to study TRPV1 knockout (V1KO), db/db diabetic, and wild type C57BKS/J (WT) mice. H2O2 dose-dependently increased CBF in WT mice, a response blocked by the TRPV1 antagonist SB366791. H2O2-induced vasodilation was significantly inhibited in db/db and V1KO mice. H2O2 caused robust SB366791-sensitive dilation in WT coronary microvessels; however, this response was attenuated in vessels from db/db and V1KO mice, suggesting H2O2-induced vasodilation occurs, in part, via TRPV1. Acute H2O2 exposure potentiated capsaicin-induced CBF responses and capsaicin-mediated vasodilation in WT mice, whereas prolonged luminal H2O2 exposure blunted capsaicin-induced vasodilation. Electrophysiology studies re-confirms acute H2O2 exposure activated TRPV1 in HEK293A and bovine aortic endothelial cells while establishing that H2O2 potentiate capsaicin-activated TRPV1 currents, whereas prolonged H2O2 exposure attenuated TRPV1 currents. Verification of H2O2-mediated activation of intrinsic TRPV1 specific currents were found in isolated mouse coronary endothelial cells from WT mice and decreased in endothelial cells from V1KO mice. These data suggest prolonged H2O2 exposure impairs TRPV1-dependent coronary vascular signaling. This may contribute to microvascular dysfunction and tissue perfusion deficits characteristic of diabetes.

  10. Microchannel Reactor System Design & Demonstration For On-Site H2O2 Production by Controlled H2/O2 Reaction

    SciTech Connect

    Adeniyi Lawal

    2008-12-09

    We successfully demonstrated an innovative hydrogen peroxide (H2O2) production concept which involved the development of flame- and explosion-resistant microchannel reactor system for energy efficient, cost-saving, on-site H2O2 production. We designed, fabricated, evaluated, and optimized a laboratory-scale microchannel reactor system for controlled direct combination of H2 and O2 in all proportions including explosive regime, at a low pressure and a low temperature to produce about 1.5 wt% H2O2 as proposed. In the second phase of the program, as a prelude to full-scale commercialization, we demonstrated our H2O2 production approach by ‘numbering up’ the channels in a multi-channel microreactor-based pilot plant to produce 1 kg/h of H2O2 at 1.5 wt% as demanded by end-users of the developed technology. To our knowledge, we are the first group to accomplish this significant milestone. We identified the reaction pathways that comprise the process, and implemented rigorous mechanistic kinetic studies to obtain the kinetics of the three main dominant reactions. We are not aware of any such comprehensive kinetic studies for the direct combination process, either in a microreactor or any other reactor system. We showed that the mass transfer parameter in our microreactor system is several orders of magnitude higher than what obtains in the macroreactor, attesting to the superior performance of microreactor. A one-dimensional reactor model incorporating the kinetics information enabled us to clarify certain important aspects of the chemistry of the direct combination process as detailed in section 5 of this report. Also, through mathematical modeling and simulation using sophisticated and robust commercial software packages, we were able to elucidate the hydrodynamics of the complex multiphase flows that take place in the microchannel. In conjunction with the kinetics information, we were able to validate the experimental data. If fully implemented across the whole

  11. A HIFI view on circumstellar H2O in M-type AGB stars: radiative transfer, velocity profiles, and H2O line cooling

    NASA Astrophysics Data System (ADS)

    Maercker, M.; Danilovich, T.; Olofsson, H.; De Beck, E.; Justtanont, K.; Lombaert, R.; Royer, P.

    2016-06-01

    Aims: We aim to constrain the temperature and velocity structures, and H2O abundances in the winds of a sample of M-type asymptotic giant branch (AGB) stars. We further aim to determine the effect of H2O line cooling on the energy balance in the inner circumstellar envelope. Methods: We use two radiative-transfer codes to model molecular emission lines of CO and H2O towards four M-type AGB stars. We focus on spectrally resolved observations of CO and H2O from HIFI aboard the Herschel Space Observatory. The observations are complemented by ground-based CO observations, and spectrally unresolved CO and H2O observations with PACS aboard Herschel. The observed line profiles constrain the velocity structure throughout the circumstellar envelopes (CSEs), while the CO intensities constrain the temperature structure in the CSEs. The H2O observations constrain the o-H2O and p-H2O abundances relative to H2. Finally, the radiative-transfer modelling allows to solve the energy balance in the CSE, in principle including also H2O line cooling. Results: The fits to the line profiles only set moderate constraints on the velocity profile, indicating shallower acceleration profiles in the winds of M-type AGB stars than predicted by dynamical models, while the CO observations effectively constrain the temperature structure. Including H2O line cooling in the energy balance was only possible for the low-mass-loss-rate objects in the sample, and required an ad hoc adjustment of the dust velocity profile in order to counteract extreme cooling in the inner CSE. H2O line cooling was therefore excluded from the models. The constraints set on the temperature profile by the CO lines nevertheless allowed us to derive H2O abundances. The derived H2O abundances confirm previous estimates and are consistent with chemical models. However, the uncertainties in the derived abundances are relatively large, in particular for p-H2O, and consequently the derived o/p-H2O ratios are not well constrained.

  12. H2O beams for zinc oxide film growth produced by a Pt-catalyzed H2-O2 reaction at various divergent aperture angles of a de Laval nozzle

    NASA Astrophysics Data System (ADS)

    Teraguchi, Yusuke; Ishidzuka, Yuki; Nakamura, Tomoki; Takahashi, Kazumasa; Tamayama, Yasuhiro; Harada, Nobuhiro; Yasui, Kanji

    2016-02-01

    High-energy H2O beams generated by a de Laval nozzle, meant for the growth of zinc oxide thin films through chemical vapor deposition, were assessed based on compressible flow theory at various divergent aperture angles. In this process, high temperature H2O was generated by a catalytic reaction between H2 and O2 on Pt nanoparticles and effused through the nozzle into the reaction zone. The theoretical beam temperature distributions, reduced scaling parameters and mean cluster sizes of the H2O beams generated at angles between 50 and 90° were evaluated. The reduced scaling parameters of the H2O beams for all angles were calculated to be less than 200 and the mean cluster sizes were estimated to be less than one irrespective of the divergent aperture angle of the nozzle, suggesting that clusters are not formed in the H2O beam in our apparatus. The crystallinity and electrical properties of the zinc oxide films grown using various divergent aperture angles were also evaluated.

  13. The condensation and vaporization behavior of H2O:CO ices and implications for interstellar grains and cometary activity

    NASA Technical Reports Server (NTRS)

    Sandford, Scott A.; Allamandola, Louis J.

    1988-01-01

    IR spectroscopy has been used to ascertain several parameters associated with CO, H2O, and H2O:CO ices' physical behavior. Since CO is noted to be capable of condensing into H2O-rich ices at temperatures that are twice as high as those required for condensation in pure CO, CO is able to condense onto H2O-rich ice grains at temperatures of up to 50 K. CO's presence in H2O ice modestly enhances the effective volatility of the H2O. Attention is given to the implications of these results for cometary models generally and the question of cometary formation specifically.

  14. Microwave-assisted wet digestion with H2O2 at high temperature and pressure using single reaction chamber for elemental determination in milk powder by ICP-OES and ICP-MS.

    PubMed

    Muller, Edson I; Souza, Juliana P; Muller, Cristiano C; Muller, Aline L H; Mello, Paola A; Bizzi, Cezar A

    2016-08-15

    In this work a green digestion method which only used H2O2 as an oxidant and high temperature and pressure in the single reaction chamber system (SRC-UltraWave™) was applied for subsequent elemental determination by inductively coupled plasma-based techniques. Milk powder was chosen to demonstrate the feasibility and advantages of the proposed method. Samples masses up to 500mg were efficiently digested, and the determination of Ca, Fe, K, Mg and Na was performed by inductively coupled plasma optical emission spectrometry (ICP-OES), while trace elements (B, Ba, Cd, Cu, Mn, Mo, Pb, Sr and Zn) were determined by inductively coupled plasma mass spectrometry (ICP-MS). Residual carbon (RC) lower than 918mgL(-1) of C was obtained for digests which contributed to minimizing interferences in determination by ICP-OES and ICP-MS. Accuracy was evaluated using certified reference materials NIST 1549 (non-fat milk powder certified reference material) and NIST 8435 (whole milk powder reference material). The results obtained by the proposed method were in agreement with the certified reference values (t-test, 95% confidence level). In addition, no significant difference was observed between results obtained by the proposed method and conventional wet digestion using concentrated HNO3. As digestion was performed without using any kind of acid, the characteristics of final digests were in agreement with green chemistry principles when compared to digests obtained using conventional wet digestion method with concentrated HNO3. Additionally, H2O2 digests were more suitable for subsequent analysis by ICP-based techniques due to of water being the main product of organic matrix oxidation. The proposed method was suitable for quality control of major components and trace elements present in milk powder in consonance with green sample preparation. PMID:27260458

  15. Global Flux Balance in the Terrestrial H2O Cycle: Reconsidering the Post-Arc Subducted H2O Flux

    NASA Astrophysics Data System (ADS)

    Parai, R.; Mukhopadhyay, S.

    2010-12-01

    Quantitative estimates of H2O fluxes between the mantle and the exosphere (i.e., the atmosphere, oceans and crust) are critical to our understanding of the chemistry and dynamics of the solid Earth: the abundance and distribution of water in the mantle has dramatic impacts upon mantle melting, degassing history, structure and style of convection. Water is outgassed from the mantle is association with volcanism at mid-ocean ridges, ocean islands and convergent margins. H2O is removed from the exosphere at subduction zones, and some fraction of the subducted flux may be recycled past the arc into the Earth’s deep interior. Estimates of the post-arc subducted H2O flux are primarily based on the stability of hydrous phases at subduction zone pressures and temperatures (e.g. Schmidt and Poli, 1998; Rüpke et al., 2004; Hacker, 2008). However, the post-arc H2O flux remains poorly quantified, in part due to large uncertainties in the water content of the subducting slab. Here we evaluate estimated post-arc subducted fluxes in the context of mantle-exosphere water cycling, using a Monte Carlo simulation of the global H2O cycle. Literature estimates of primary magmatic H2O abundances and magmatic production rates at different tectonic settings are used with estimates of the total subducted H2O flux to establish the parameter space under consideration. Random sampling of the allowed parameter space affords insight into which input and output fluxes satisfy basic constraints on global flux balance, such as a limit on sea-level change over time. The net flux of H2O between mantle and exosphere is determined by the total mantle output flux (via ridges and ocean islands, with a small contribution from mantle-derived arc output) and the input flux subducted beyond the arc. Arc and back-arc output is derived mainly from the slab, and therefore cancels out a fraction of the trench intake in an H2O subcycle. Limits on sea-level change since the end of the Archaean place

  16. Absolute linestrengths in the H2O2 nu6 band

    NASA Technical Reports Server (NTRS)

    May, Randy D.

    1991-01-01

    Absolute linestrengths at 295 K have been measured for selected lines in the nu6 band of H2O2 using a tunable diode-laser spectrometer. H2O2 concentrations in a flowing gas mixture were determined by ultraviolet (uv) absorption at 254 nm using a collinear infrared (ir) and uv optical arrangement. The measured linestrengths are approx. 60 percent larger than previously reported values when absorption by hot bands in H2O2 is taken into account.

  17. EPA H2O User Manual

    EPA Science Inventory

    EPA H2O is a software tool designed to support research being conducted in the Tampa Bay watershed to provide information, data, and approaches and guidance that communities can use to examine alternatives when making strategic decisions to support a prosperous and environmentall...

  18. EPA H2O Software Tool

    EPA Science Inventory

    EPA H2O allows user to: Understand the significance of EGS in Tampa Bay watershed; visually analyze spatial distribution of the EGS in Tampa Bay watershed; obtain map and summary statistics of EGS values in Tampa Bay watershed; analyze and compare potential impacts of development...

  19. The Successive H2O Binding Energies for Fe(H2O)n(+)

    NASA Technical Reports Server (NTRS)

    Ricca, Alessandra; Bauschlicher, Charles W., Jr.; Langhoff, Stephen R. (Technical Monitor)

    1994-01-01

    The binding energy, computed using density functional theory (DFT), are in good agreement with experiment. The bonding is electrostatic (charge-dipole) in origin for all systems. The structures are therefore determined mostly by metal-ligand and ligand-ligand repulsion. The computed structure for FeH2O(+) is C(2v) where sp hybridization is important in reducing the Fe-H2O repulsion. Fe(H2O)2(+) has D2d symmetry where sdo hybridization is the primary factor leading to the linear O-Fe-O geometry. The bonding in Fe(H2O)3(+) and Fe(H2O)4(+) are very complex because ligand-ligand and metal-ligand repulsion, both for the in-plane and out-of-plane water lone-pair orbitals, are important.

  20. The Formation and Spatiotemporal Progress of the pH Wave Induced by the Temperature Gradient in the Thin-Layer H2O2-Na2S2O3-H2SO4-CuSO4 Dynamical System.

    PubMed

    Jędrusiak, Mikołaj; Orlik, Marek

    2016-03-31

    The H2O2-S2O3(2-)-H(+)-Cu(2+) dynamical system exhibits sustained oscillations under flow conditions but reveals only a single initial peak of the indicator electrode potential and pH variation under batch isothermal conditions. Thus, in the latter case, there is no possibility of the coupling of the oscillations and diffusion which could lead to formation of sustained spatiotemporal patterns in this process. However, in the inhomogeneous temperature field, due to dependence of the local reaction kinetics on temperature, spatial inhomogeneities of pH distribution can develop which, in the presence of an appropriate indicator, thymol blue, manifest themselves as the color front traveling along the quasi-one-dimensional reactor. In this work, we describe the experimental conditions under which the above-mentioned phenomena can be observed and present their numerical model based on thermokinetic coupling and spatial coordinate introduced to earlier isothermal homogeneous kinetic mechanism.

  1. Crystal structures of hydrates of simple inorganic salts. II. Water-rich calcium bromide and iodide hydrates: CaBr2 · 9H2O, CaI2 · 8H2O, CaI2 · 7H2O and CaI2 · 6.5H2O.

    PubMed

    Hennings, Erik; Schmidt, Horst; Voigt, Wolfgang

    2014-09-01

    Single crystals of calcium bromide enneahydrate, CaBr(2) · 9H2O, calcium iodide octahydrate, CaI(2) · 8H2O, calcium iodide heptahydrate, CaI(2) · 7H2O, and calcium iodide 6.5-hydrate, CaI(2) · 6.5H2O, were grown from their aqueous solutions at and below room temperature according to the solid-liquid phase diagram. The crystal structure of CaI(2) · 6.5H2O was redetermined. All four structures are built up from distorted Ca(H2O)8 antiprisms. The antiprisms of the iodide hydrate structures are connected either via trigonal-plane-sharing or edge-sharing, forming dimeric units. The antiprisms in calcium bromide enneahydrate are monomeric. PMID:25186361

  2. 40 CFR 1065.350 - H2O interference verification for CO2 NDIR analyzers.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... through distilled water in a sealed vessel. If the sample is not passed through a dryer during emission testing, control the vessel temperature to generate an H2O level at least as high as the maximum expected... vessel temperature to generate an H2O level at least as high as the level determined in §...

  3. Mesospheric H2O Concentrations Retrieved from SABER/TIMED Measurements

    NASA Technical Reports Server (NTRS)

    Feofilov, A. G.; Marshall, B. T.; Garcia-Comas, M.; Kutepov, A. A.; Lopez-Puertas, M.; Manuilova, R. O.; Yankovsky, V.A.; Goldberg, R. A.; Gordley, L. L.; Petelin, S.; Russell, J. M., III

    2008-01-01

    The SABER instrument on board the TIMED Satellite is a limb scanning infrared radiometer designed to measure temperature and minor constituent vertical profiles and energetics parameters in the mesosphere and lower thermosphere (MLT). The H2O concentrations are retrieved from 6.3 micron band radiances. The populations of H2O(v2) vibrational levels are in non-Local Thermodynamic Equilibrium (non-LTE) above approximately 55 km altitude and the interpretation of 6.3 micron radiance requires utilizing non-LTE H2O model that includes various energy exchange processes in the system of H2O vibrational levels coupled with O2, N2, and CO2 vibrational levels. We incorporated these processes including kinetics of O2/O3 photolysis products to our research non-LTE H2O model and applied it for the development and optimization of SABER operational model. The latter has been validated using simultaneous SCISAT1/ACE occultation measurements. This helped us to estimate CO2(020)-O2(X,v=I), O2(X,v=I)- H2O(010), and O2(X,v=1) O rates at mesopause temperatures that is critical for an adequate interpretation of non-LTE H2O radiances in the MLT. The first distributions of seasonal and meridional H2O concentrations retrieved from SABER 6.3 micron radiances applying an updated non-LTE H2O model are demonstrated and discussed.

  4. Silicate-H2O Systems at High Pressure Conditions

    NASA Astrophysics Data System (ADS)

    Tailby, N.; Mavrogenes, J. A.; Hermann, J.; O'Neill, H. S.

    2008-12-01

    Since the discovery of the second critical endpoint (CP2) in the albite-water system, numerous attempts have been made to determine the pressure and temperature of this CP2 and the mutual solubilities within more complex systems. The P-T position of the CP2 has been estimated for many systems: SiO2 (<10 kb/900 °C, Newton and Manning, 2008); NaAlSi3O8 (15 kb/800 °C, Burnham and Davis, 1974; Shen and Keppler, 1997); Pelite (50 kb/1,000 °C, Schmidt et al., 2004), basalt (50 kb/ 1000 °C, Kessel et al., 2004), Peridotite (38 kb/1000 °C, Mibe et al., 2007). A number of experimental techniques have been used to determine phase relations and H2O solubility in experiments. These include in-situ experimental techniques (e.g., HYDAC; Shen and Keppler, 1997), fluid trap techniques (e.g., diamond traps; Stalder et al., 2000), and single crystal weight-loss techniques (e.g., SiO2-H2O techniques employed by Newton and Manning, 2008). None of these techniques is without difficulties, as H2O rich experiments need to overcome huge retrograde fluid solubilities upon quench in order to determine mutual solubilities at experimental conditions. We have developed a new technique to determine "rock"-H2O relationships at high-P conditions, with particular focus on the shape and locus of solvi in pressure temperature space. In this series of experiments, an oxygen fugacity buffer (Re-ReO2) and a sliding H-fugacity sensor (NiO-Ni-Pd mixture) are combined to monitor H2O activity over the entire range of pressure and temperature. Unlike other techniques, the use of sensor capsules does not require textural interpretation of experiments. H2O activity is related to oxygen and hydrogen fugacity by the reaction: H2O = H2 + ½O2 NiO-Ni-Pd mixtures were placed within a ZrO2 jacket and sealed within a welded 2.3 mm Pt capsule. This 2.3 mm Pt sensor capsule was then encased within a larger, thick walled 6 mm diameter Ag capsule. Pelite-H2O mixtures and oxygen buffers were held within this larger

  5. Crystalline and amorphous H2O on Charon

    NASA Astrophysics Data System (ADS)

    Dalle Ore, Cristina M.; Cruikshank, Dale P.; Grundy, Will M.; Ennico, Kimberly; Olkin, Catherine B.; Stern, S. Alan; Young, Leslie A.; Weaver, Harold A.

    2015-11-01

    Charon, the largest satellite of Pluto, is a gray-colored icy world covered mostly in H2O ice, with spectral evidence for NH3, as previously reported (Cook et al. 2007, Astrophys. J. 663, 1406-1419 Merlin, et al. 2010, Icarus, 210, 930; Cook, et al. 2014, AAS/Division for Planetary Sciences Meeting Abstracts, 46, #401.04). Images from the New Horizons spacecraft reveal a surface with terrains of widely different ages and a moderate degree of localized coloration. The presence of H2O ice in its crystalline form (Brown & Calvin 2000 Science 287, 107-109; Buie & Grundy 2000 Icarus 148, 324-339; Merlin et al, 2010) along with NH3 is consistent with a fresh surface.The phase of H2O ice is a key tracer of variations in temperature and physical conditions on the surface of outer Solar System objects. At Charon’s surface temperature H2O is expected to be amorphous, but ground-based observations (e.g., Merlin et al. 2010) show a clearly crystalline signature. From laboratory experiments it is known that amorphous H2O ice becomes crystalline at temperatures of ~130 K. Other mechanisms that can change the phase of the ice from amorphous to crystalline include micro-meteoritic bombardment (Porter et al. 2010, Icarus, 208, 492) or resurfacing processes such as cryovolcanism.New Horizons observed Charon with the LEISA imaging spectrometer, part of the Ralph instrument (Reuter, D.C., Stern, S.A., Scherrer, J., et al. 2008, Space Science Reviews, 140, 129). Making use of high spatial resolution (better than 10 km/px) and spectral resolving power of 240 in the wavelength range 1.25-2.5 µm, and 560 in the range 2.1-2.25 µm, we report on an analysis of the phase of H2O ice on parts of Charon’s surface with a view to investigate the recent history and evolution of this small but intriguing object.This work was supported by NASA’s New Horizons project.

  6. Effects of H2O and H2O2 on Thermal Desorption of Tritium from Stainless Steel

    SciTech Connect

    Quinlan, M.J.; Shmayda, W.T.; Lim, S.; Salnikov, S.; Chambers, Z.; Pollock, E.; Schroder, W.U.

    2010-03-12

    Tritiated stainless steel was subjected to thermal desorption at various temperatures, different temperature profiles, and in the presence of different helium carrier gas additives. In all cases the identities of the desorbing tritiated species were characterized as either water-soluble or insoluble. The samples were found to contain 1.1 mCi±0.4 mCi. Approximately ninety-five percent of this activity was released in molecular water-soluble form. Additives of H2O or H2O2 to dry helium carrier gas increase the desorption rate and lower the maximum temperature to which the sample must be heated, in order to remove the bulk of the tritium. The measurements validate a method of decontamination of tritiated steel and suggest a technique that can be used to further explore the mechanisms of desorption from tritiated metals.

  7. Near Infrared Spectra of H2O/HCN Mixtures

    NASA Technical Reports Server (NTRS)

    Mastrapa, R. M.; Bernstein, M. P.; Sanford, S. A.

    2006-01-01

    Cassini's VIMS has already returned exciting results interpreting spectra of Saturn's icy satellites. The discovery of unidentified features possibly due to CN compounds inspired the work reported here. We wanted to test HCN as a possibility for explaining these features, and also explore how the features of HCN change when mixed with H2O. We have previously noted that mixing H20 and CO2 produces new spectral features and that those features change with temperature and mixing ratio.

  8. Effects of convective ice lofting on H2O and HDO in the tropical tropopause layer

    NASA Astrophysics Data System (ADS)

    Dessler, A. E.; Hanisco, T. F.; Fueglistaler, S.

    2007-09-01

    We have added convective ice lofting to a Lagrangian trajectory model of tropical tropopause layer (TTL) water vapor (H2O) and its stable isotopologue, HDO. The Lagrangian model has been previously shown to accurately simulate H2O in the TTL and lower stratosphere. We show here that the model does a poor job reproducing the observed HDO depletion (δD) in the TTL. When convective ice lofting to altitudes below the cold point (the point where air experiences its lowest H2O saturation mixing ratio) is added to the model, there is little change in H2O in the lower stratosphere, but a large change in δD throughout the TTL that brings the model into better agreement with measurements. Thus convective ice lofting has the capacity to improve the model's δD simulation while not significantly degrading the agreement between simulated and measured H2O. Convective ice lofting to altitudes above the cold point, on the other hand, has a large effect on lower stratospheric H2O, suggesting that changes in convection reaching these altitudes could drive changes in lower stratospheric H2O. This suggests a mechanism by which lower stratospheric H2O trends may be at least partially decoupled from tropopause temperature trends. Such a disconnection was suggested by previous observations of simultaneously increasing stratospheric H2O and a cooling tropical tropopause.

  9. H2O Adsorption on Smectites: Application to the Diurnal Variation of H2O in the Martian Atmosphere

    NASA Technical Reports Server (NTRS)

    Zent, Aaron P.; Howard, J.; Quinn, R. C.

    2000-01-01

    Observations of the Martian planetary boundary layer lead to interpretations that are baffling and contradictory. In this paper, we specifically address the question of whether or not water vapor finds a substantial diurnal reservoir in the Martian regolith. To address this issue, we have measured H2O adsorption kinetics on SWy-1, a Na-rich montmorillonite from Wyoming. The highest-temperature (273 K) data equilibrates rapidly. Data gathered at realistic H2O partial pressures and temperatures appropriate to early morning show two phenomena that preclude a significant role for smectites in diurnally exchanging a large column abundance. First, the equilibration timescale is longer than a sol. Second, the equilibrium abundances are a small fraction of that predicted by earlier adsorption isotherms. The explanation for this phenomenon is that smectite clay actually increases its surface area as a function of adsorptive coverage. At Mars-like conditions, we show that the interlayer sites of smectites are likely to be unavailable.

  10. H2O diffusion in Mount Changbai peralkaline rhyolitic melt

    NASA Astrophysics Data System (ADS)

    Zhang, Y.; Xu, Z.; Wang, H.; Behrens, H.

    2008-05-01

    For quantitative modeling of bubble growth and volcanic eruption dynamics, it is necessary to know H2O diffusivity in the melt. Mount Changbai Volcano at the border of China and North Korea has produced explosive peralkaline rhyolitic eruptions, including a 30-km3 eruption with an age of 1 ky (Horn and Schmincke, 2000). H2O diffusivity is expected to be greater in a peralkaline rhyolitic melt than a calc-alkaline rhyolitic melt. We have experimentally investigated H2O diffusion in Mount Changbai peralkaline rhyolite. Because phenocryst-free glass is not available from Mount Changbai eruption products, the starting materials (nominally dry and hydrous) are synthesized. The diffusion couple technique, with one half dry and the other half wet, is adopted. Three high- temperature experiments have been carried out at 500 MPa and one at 1500 MPa in a piston-cylinder apparatus. After the experiment, the sample is prepared into a doubly-polished section of about 0.2 mm thickness, which is analyzed by a Perkin-Elmer FTIR microscope. The data are fit following the procedures of Zhang and Behrens (2000) and Ni and Zhang (2008). Preliminary data show that H2O diffusivity in peralkaline rhyolitic melt is greater than that in calc-alkaline rhyolitic melt (Zhang and Behrens, 2000), as expected. The exact difference depends on temperature and pressure, and the ratio of diffusivity in the peralkaline rhyolitic melt to that in the calc-alkaline rhyolitic melt ranges from 1 to 3. More experiments will be conducted on this melt to provide the basic data for specific modeling of bubble growth and volcanic eruption dynamics in past and future Mount Changbai eruptions and other peralkaline rhyolitic eruptions. References: Horn S and Schmincke H U (2000) Bull. Volcanol., 61, 537. Ni H and Zhang Y (2008) Chem. Geol., doi: 10.1016/j.chemgeo.2008.01.011. Zhang Y and Behrens H (2000) Chem. Geol., 169, 243.

  11. Hydrogen Bonding, Hydration of Species, Ion Pairing and Clusterization in H2O-NaCl-CaCl2-CO2-NaHCO3-Na2CO3 Fluids: Molecular Dynamics Simulation of the Effects of Temperature, Pressure and Composition

    NASA Astrophysics Data System (ADS)

    Kalinichev, A. G.; Kirkpatrick, R. J.; Wang, J.

    2004-12-01

    Molecular computer simulation is an especially valuable tool to study the structural and dynamic properties of carbon-bearing aqueous fluids on the fundamental atomic time- and length- scale because these fluids are not readily studied experimentally using conventional X-ray or EXAFS methods. In this case, experimental methods can produce ambiguous results, because the carbon and oxygen atoms of the solute species are not easily distinguishable from the oxygen atoms of solvent water. Systematic molecular dynamics (MD) computer simulation studies of several fluid compositions - H2O-CO2, H2O-CO2-NaCl, H2O-NaHCO3, and H2O-Na2CO3 - were performed to study the effects of temperature, pressure (fluid density) and concentration on the structural, energetic, spectroscopic and dynamic properties of these solutions characterized on the atomic scale via the statistical parameters of individual hydrogen bonds and H-bonding networks, local hydration structures of dissolved species, and ion pair formation. Similar molecular-level characteristics of pure water and H2O-NaCl and H2O-CaCl2 solutions are calculated and used for comparison with the properties of carbon-bearing fluids. H2O-rich and CO2-rich compositions of the ternary H2O-CO2-NaCl system demonstrate strikingly different structural and dynamic behavior at about the same average density. In dense CO2-rich fluids, dissolved H2O molecules exhibit a high degree of hydrogen bonding and form relatively stable H-bonded clusters structurally similar to those observed in supercritical water at a much lower density. In contrast, CO2 molecules dissolved in water-rich fluids occur in clathrate-like cages formed by surrounding H-bonded water molecules. The hydration shells of carbonate and bicarbonate ions both contain approximately 10 water molecules, but the water structure around the carbonate ion is much more pronounced due to the higher anion charge. This also leads to the formation of very stable ion pairs and larger ionic

  12. The effect of H2O and CO2 on planetary mantles

    NASA Technical Reports Server (NTRS)

    Wyllie, P. J.

    1978-01-01

    The peridotite-H2O-CO2 system is discussed, and it is shown that even traces of H2O and CO2, in minerals or vapor, lower mantle solidus temperatures through hundreds of degrees in comparison with the volatile-free solidus. The solidus for peridotite-H2O-CO2 is a divariant surface traversed by univariant lines that locate the intersections of subsolidus divariant surfaces for carbonation or hydration reactions occurring in the presence of H2O-CO2 mixtures. Vapor phase compositions are normally buffered to these lines, and near the buffered curve for the solidus of partly carbonated peridotite there is a temperature maximum on the peridotite-vapor solidus. Characteristics on the CO2 side of the maximum and on the H2O side of the maximum are described.

  13. The H2O2-H2O Hypothesis: Extremophiles Adapted to Conditions on Mars?

    NASA Astrophysics Data System (ADS)

    Houtkooper, Joop M.; Schulze-Makuch, Dirk

    2007-08-01

    The discovery of extremophiles on Earth is a sequence of discoveries of life in environments where it had been deemed impossible a few decades ago. The next frontier may be the Martian surface environment: could life have adapted to this harsh environment? What we learned from terrestrial extremophiles is that life adapts to every available niche where energy, liquid water and organic materials are available so that in principle metabolism and propagation are possible. A feasible adaptation mechanism to the Martian surface environment would be the incorporation of a high concentration of hydrogen peroxide in the intracellular fluid of organisms. The H2O2-H2O hypothesis suggests the existence of Martian organisms that have a mixture of H2O2 and H2O instead of salty water as their intracellular liquid (Houtkooper and Schulze-Makuch, 2007). The advantages are that the freezing point is low (the eutectic freezes at 56.5°C) and that the mixture is hygroscopic. This would enable the organisms to scavenge water from the atmosphere or from the adsorbed layers of water molecules on mineral grains, with H2O2 being also a source of oxygen. Moreover, below its freezing point the H2O2-H2O mixture has the tendency to supercool. Hydrogen peroxide is not unknown to biochemistry on Earth. There are organisms for which H2O2 plays a significant role: the bombardier beetle, Brachinus crepitans, produces a 25% H2O2 solution and, when attacked by a predator, mixes it with a fluid containing hydroquinone and a catalyst, which produces an audible steam explosion and noxious fumes. Another example is Acetobacter peroxidans, which uses H2O2 in its metabolism. H2O2 plays various other roles, such as the mediation of physiological responses such as cell proliferation, differentiation, and migration. Moreover, most eukaryotic cells contain an organelle, the peroxisome, which mediates the reactions involving H2O2. Therefore it is feasible that in the course of evolution, water-based organisms

  14. X-Ray Diffraction of Shock Compressed H2O

    NASA Astrophysics Data System (ADS)

    Gleason, A. E.

    2014-12-01

    H2O, critical for life and ubiquitous in biology, is one of the most abundant molecules in the solar system and is relevant to many fields, including fundamental physics and chemistry. Phase transformation information of H2O is also important to applied areas like planetary science where it is a constituent of giant planets Neptune and Uranus, icy satellites (e.g., Europa, Ganymede), and extrasolar planets (icy "super-Earths"). Using the MEC (Matter in Extreme Conditions) hutch at LCLS, we reach simultaneous high pressure (P) and temperature (T) with laser-driven shock waves and the capability of taking snapshots during a dynamic process with the X-ray Free Electron Laser (xFEL). We report the only shock-driven diffraction data on H2O ever collected to date, and examine time-resolved diffraction from ice Ih to high pressure ice VII. At 2 Mbar we find evidence of ice X - this has significant implications for planetary interiors and providing a bound for the onset of the superionic phase.

  15. The Effect of H2O on Ice Photochemistry

    NASA Astrophysics Data System (ADS)

    Öberg, Karin I.; van Dishoeck, Ewine F.; Linnartz, Harold; Andersson, Stefan

    2010-08-01

    UV irradiation of simple ices is proposed to efficiently produce complex organic species during star formation and planet formation. Through a series of laboratory experiments, we investigate the effects of the H2O concentration, the dominant ice constituent in space, on the photochemistry of more volatile species, especially CH4, in ice mixtures. In the experiments, thin (~40 ML) ice mixtures, kept at 20-60 K, are irradiated under ultra-high vacuum conditions with a broadband UV hydrogen discharge lamp. Photodestruction cross sections of volatile species (CH4 and NH3) and production efficiencies of new species (C2H6, C2H4, CO, H2CO, CH3OH, CH3CHO, and CH3CH2OH) in water-containing ice mixtures are determined using reflection-absorption infrared spectroscopy during irradiation and during a subsequent slow warm-up. The four major effects of increasing the H2O concentration are: (1) an increase of the destruction efficiency of the volatile mixture constituent by up to an order of magnitude due to a reduction of back reactions following photodissociation, (2) a shift to products rich in oxygen, e.g., CH3OH and H2CO, (3) trapping of up to a factor of 5 more of the formed radicals in the ice, and (4) a disproportional increase in the diffusion barrier for the OH radical compared with the CH3 and HCO radicals. The radical diffusion temperature dependencies are consistent with calculated H2O-radical bond strengths. All the listed effects are potentially important for the production of complex organics in H2O-rich icy grain mantles around protostars and should thus be taken into account when modeling ice chemistry.

  16. Transport properties of the H2O@C60-dimer-based junction

    NASA Astrophysics Data System (ADS)

    Zhu, Chengbo; Wang, Xiaolin

    2015-09-01

    Theoretical predictions play an important role in finding potential applications in molecular electronics. Fullerenes have a number of potential applications, and the charge flow from a single C60 molecule to another becomes more versatile and more interesting after doping. Here, we report the conductance of two H2O@C60 molecules in series order and how the number of encapsulated water molecules influences the transport properties of the junction. Encapsulating an H2O molecule into one of the C60 cages increases the conductance of the dimer. Negative differential resistance is found in the dimer systems, and its peak-to-valley current ratio depends on the number of encapsulated H2O molecules. The conductance of the C60 dimer and the H2O@C60 dimer is two orders of magnitude smaller than that of the C60 monomer. Furthermore, we demonstrate that the conductance of the molecular junctions based on the H2O@C60 dimer can be tuned by moving the encapsulated H2O molecules. The conductance is H2O-position dependent. Our findings indicate that H2O@C60 can be used as a building block in C60-based molecular electronic devices and sensors.

  17. Stepwise hydration of the cyanide anion: A temperature-controlled photoelectron spectroscopy and ab initio computational study of CN-(H2O)n(n=2-5)

    SciTech Connect

    Wang, Xue B.; Kowalski, Karol; Wang, Lai S.; Xantheas, Sotiris S.

    2010-03-28

    We report the study of microsolvated CN-(H2O)n (n = 1-5) clusters in the gas phase using a combination of experimental and computational approaches. The hydrated cyanide clusters were produced by electrospray and their structural and energetic properties were probed using temperature-controlled photoelectron spectroscopy (PES) and ab initio electronic structure calculations. Comparison between the low temperature (T = 12 K) and the room-temperature (RT) spectra shows a 0.25 eV spectral blue shift in the binding energy of the n = 1 cluster and a significant spectral sharpening and blue shift for n = 2 and 3. The experimental results are complemented with ab initio electronic structure calculations at the MP2 and CCSD(T) levels of theory that identified several isomers on the ground state potential energy function (PEF) arising from the ability of CN- to form hydrogen bonds with water via both the C and N ends. In all cases the N end seems to be the preferred hydration site. The excellent agreement between the low temperature measured PES spectra and the basis set- and correlation-corrected (at the CCSD(T) level of theory) calculated vertical detachment energies, viz. 3.85 vs. 3.84 eV (n = 0), 4.54 vs. 4.54 eV (n = 1), 5.20 vs. 5.32 eV (n = 2), 5.58 vs. 5.50 eV (n = 3) and 5.89 vs. 5.87 eV (n = 4), allow us to firmly establish the global minimum structures for all the hydrated cyanide clusters. The microsolvation pattern was found to be similar to the halide anions (Cl-, Br- and I-), adopting structures in which CN- resides on the surface of a water network. While at T = 12 K the clusters adopt structures that are close to the minimum energy configurations, at room temperature it is expected that other isomers (lying within ~0.6 kcal/mol above the global minima) are also populated, resulting in the broadening of the PES spectra.

  18. Detection of local H2O exposed at the surface of Ceres

    NASA Astrophysics Data System (ADS)

    Combe, Jean-Philippe; McCord, Thomas B.; Tosi, Federico; Ammannito, Eleonora; Carrozzo, Filippo Giacomo; De Sanctis, Maria Cristina; Raponi, Andrea; Byrne, Shane; Landis, Margaret E.; Hughson, Kynan H. G.; Raymond, Carol A.; Russell, Christopher T.

    2016-09-01

    The surface of dwarf planet Ceres contains hydroxyl-rich materials. Theories predict a water ice-rich mantle, and water vapor emissions have been observed, yet no water (H2O) has been previously identified. The Visible and InfraRed (VIR) mapping spectrometer onboard the Dawn spacecraft has now detected water absorption features within a low-illumination, highly reflective zone in Oxo, a 10-kilometer, geologically fresh crater, on five occasions over a period of 1 month. Candidate materials are H2O ice and mineral hydrates. Exposed H2O ice would become optically undetectable within tens of years under current Ceres temperatures; consequently, only a relatively recent exposure or formation of H2O would explain Dawn’s findings. Some mineral hydrates are stable on geological time scales, but their formation would imply extended contact with ice or liquid H2O.

  19. The discovery of five new H2O megamasers in active galaxies

    NASA Technical Reports Server (NTRS)

    Braatz, J. A.; Wilson, A. S.; Henkel, C.

    1994-01-01

    H2O megamasers with (isotropic) luminosities between 60 and 200 solar luminosity (H(sub 0) = 75 km/s/Mpc) have been detected in the Seyfert 2 galaxies Mrk 1, Mrk 1210, and NGC 5506 and in the LINERs NGC 1052 and NGC 2639. No megamasers have been found in Seyfert 1's. The galaxies have redshifts between 1500 and 4800 km/s and are the most distant H2O sources reported to date. NGC 1052 is also the first elliptical galaxy known to contain an H2O maser. The intensity distribution of an H2O five-point map obtained toward NGC 5506 shows that the H2O emission is pointlike compared to the 40 sec telescope beam. The lack of CO emission in NGC 1052 implies a conservative lower limit to the H2O brightness temperature of 1000 K, thus ruling out a thermal origin for the H2O emission. The success of this survey relative to other recent searches makes it evident that H2O megamasers are preferentially found in galaxies with active nuclei.

  20. High temperature kinetic study of the reactions H + O2 = OH + O and O + H2 = OH + H in H2/O2 system by shock tube-laser absorption spectroscopy

    NASA Technical Reports Server (NTRS)

    Ryu, Si-Ok; Hwang, Soon Muk; Dewitt, Kenneth J.

    1995-01-01

    The reactions: (1) H + O2 = OH + O; and (2) O + H2 = OH + H are the most important elementary reactions in gas phase combustion. They are the main chain-branching reaction in the oxidation of H2 and hydrocarbon fuels. In this study, rate coefficients of the reactions and have been measured over a wide range of composition, pressure, density and temperature behind the reflected shock waves. The experiments were performed using the shock tube - laser absorption spectroscopic technique to monitor OH radicals formed in the shock-heated H2/O2/Ar mixtures. The OH radicals were detected using the P(1)(5) line of (0,0) band of the A(exp 2) Sigma(+) from X(exp 2) Pi transition of OH at 310.023 nm (air). The data were analyzed with the aid of computer modeling. In the experiments great care was exercised to obtain high time resolution, linearity and signal-to-noise. The results are well represented by the Arrhenius expressions. The rate coefficient expression for reaction (1) obtained in this study is k(1) = (7.13 +/- 0.31) x 10(exp 13) exp(-6957+/- 30 K/T) cu cm/mol/s (1050 K less than or equal to T less than or equal to 2500 K) and a consensus expression for k(1) from a critical review of the most recent evaluations of k(1) (including our own) is k(1) = 7.82 x 10(exp 13) exp(-7105 K/T) cu cm/mol/s (960 K less than or equal to T less than or equal to 5300 K). The rate coefficient expression of k(2) is given by k(2) = (1.88 +/- 0.07) x 10(exp 14) exp(-6897 +/- 53 K/T) cu cm/mol/s (1424 K less than or equal to T less than or equal to 2427 K). For k(1), the temperature dependent A-factor and the correlation between the values of k(1) and the inverse reactant densities were not found. In the temperature range of this study, non-Arrhenius expression of k(2) which shows the upward curvature was not supported.

  1. Hydrous albite magmas at lower crustal pressure: new results on liquidus H2O content, solubility, and H2O activity in the system NaAlSi3O8-H2O-NaCl at 1.0 GPa

    NASA Astrophysics Data System (ADS)

    Makhluf, A. R.; Newton, R. C.; Manning, C. E.

    2016-09-01

    The system albite-H2O serves as an important model for the generation of granitic magmas, yet relatively few experimental investigations have focused on phase relations at high pressure. This study reports new experimental results, at 1.0 GPa and 690-1050 °C, on the temperature and liquid composition at vapor-saturated melting, the H2O content of undersaturated silicate liquids in equilibrium with albite, the solubility of albite in H2O-NaCl fluids immediately below the solidus, and the activity of H2O in hydrous NaAlSi3O8 liquids along the liquidus. Albite melts and dissolves congruently at all temperatures and salinities. In the NaCl-absent system, the temperature of vapor-saturated melting of low albite, confirmed by X-ray diffraction, is 695 ± 5 °C and the liquid composition is 18.14 ± 1.35 wt% H2O. The temperature dependence of the fluid-undersaturated liquidus curve in the system NaAlSi3O8-H2O varies with H2O wt% (w_{{{{H}}2 {{O}}}}) according to T = - 2.0331 × 10^{ - 3} w_{{{{H}}2 {{O}}}}3 + 1.6497w_{{{{H}}2 {{O}}}}2 {-} 58.963w_{{{{H}}2 {{O}}}} + 1235.5°C} indicating positive curvature in temperature-composition coordinates and a dry melting temperature of 1235 °C. At 690 °C, immediately below the solidus, albite solubility decreases drastically with NaCl content of the fluid phase, from 8.8 ± 0.6 wt% in the NaCl-free fluid to ˂2 % at NaCl concentration of only 10 mol%. Experiments determining the activity of H2O (a_{{{{H}}2 {{O}}}}) in liquids at vapor-saturated melting exploited low Cl solubility in liquids and low albite solubility in the presence of H2O-NaCl fluids. The maximum Cl content of quenched glasses, only 0.95 wt%, and very low albite solubility together make possible H2O activity measurement in melts equilibrated with NaCl-H2O solutions. When combined with activity data for H2O-NaCl fluids, experimentally determined a_{{{{H}}2 {{O}}}} along the liquidus is described by T = - {469.16a_{{H2 O}}L}^{{1/2}} {-} 93.382a_{{H2 O}}L + 1235.5

  2. Optical Absorption and Photo-Thermal Conversion Properties of CuO/H2O Nanofluids.

    PubMed

    Wang, Liangang; Wu, Mingyan; Wu, Daxiong; Zhang, Canying; Zhu, Qunzhi; Zhu, Haitao

    2015-04-01

    Stable CuO/H2O nanofluids were synthesized in a wet chemical method. Optical absorption property of CuO/H2O nanofluids was investigated with hemispheric transmission spectrum in the wavelength range from 200 nm to 2500 nm. Photo-thermal conversion property of the CuO/H2O nanofluids was studied with an evaluation system equipped with an AUT-FSL semiconductor/solid state laser. The results indicate that CuO/H2O nanofluids have strong absorption in visible light region where water has little absorption. Under the irradiation of laser beam with a wavelength of 635 nm and a power of 0.015 W, the temperature of CuO/H2O nanofluids with 1.0% mass fraction increased by 5.6 °C within 40 seconds. Furthermore, the temperature elevation of CuO/H2O nanofluids was proved to increase with increasing mass fractions. On the contrast, water showed little temperature elevation under the identical conditions. The present work shows that the CuO/H2O nanofluids have high potential in the application as working fluids for solar utilization purpose. PMID:26353558

  3. Two temperature-independent spinomers of the dinuclear Mn(III) compound [{Mn(H(2)O)(phen)}(2)(mu-2-ClC(6)H(4)COO)(2)(mu-O)](ClO(4))(2).

    PubMed

    Gómez, Verónica; Corbella, Montserrat; Aullón, Gabriel

    2010-02-15

    Two spin isomers or spinomers of [{Mn(H(2)O)(phen)}(2)(mu-2-ClC(6)H(4)COO)(2)(mu-O)](ClO(4))(2) have been synthesized, characterized, and theoretically analyzed. The thermodynamically most stable, compound 1, shows a spin ground state S = 4, while the kinetically most favorable, compound 2.H(2)O, shows a spin ground state S = 0. Compound 1 exhibits ferromagnetic behavior, with J = 2.7 cm(-1), |D(Mn)| = 2.06 cm(-1), |E(Mn)| = 0.69 cm(-1), and zJ' = -0.11 cm(-1). Because of the anisotropy of the Mn(III) ions, the ground state S = 4 shows zero-field splitting (ZFS) with |D(4)| = 0.51 cm(-1), appreciably smaller than the D value for the single ion (D(Mn)), due to the relative orientations of the Jahn-Teller axes of both Mn(III) ions, which are quite perpendicular (102 degrees ). Compound 2.H(2)O shows antiferromagnetic coupling, with J = -12.6 cm(-1) (H = -JS(1).S(2) for both compounds). The formation of two spinomers has been explained by density functional theory (DFT) studies, which show that the stability of these compounds and their magnetic interaction are very sensitive to the rotation of the phenyl ring with respect to the carboxylate group of the 2-ClC(6)H(4)COO bridging ligand.

  4. Nanoporous magnets of chiral and racemic [{Mn(HL)}2Mn{Mo(CN)7}2] with switchable ordering temperatures (TC = 85 K <--> 106 K) driven by H2O sorption (L = N,N-dimethylalaninol).

    PubMed

    Milon, Julie; Daniel, Marie-Christine; Kaiba, Abdellah; Guionneau, Philippe; Brandès, Stéphane; Sutter, Jean-Pascal

    2007-11-14

    Molecule-based solids represent a rare opportunity to combine, adjust, and interrelate structural and physical functionalities to develop multifunctional materials. Here we report on a series of porous supramolecular magnets whose magnetic properties are related to their sorption state. A family of magnets of the formula [{Mn(HL)(H2O)}2Mn{Mo(CN)7}2].2H2O have been obtained by assembling the heptacyano-metalate building unit {Mo(CN)7}4- with Mn(II) in the presence of protonated N,N-dimethylalaninol (L) as ligand, the latter being either as a racemic mixture or as a chiral R- or S-enantiomer. The resulting magnets possess an open framework structure and exhibit a TC with a switching behavior (TC = 85 K <--> 106 K) as a function of the hydration state. Moreover, chiral magnets are formed with the optically active ligands. The H2O and gas (N2, CO2, CO) sorption features, the magnetic behavior of both the hydrated and dehydrated magnets, and the crystal structures of the hydrated chiral (S) and racemic magnets are described.

  5. Submillimeter H2O and H2O+emission in lensed ultra- and hyper-luminous infrared galaxies at z 2-4

    NASA Astrophysics Data System (ADS)

    Yang, C.; Omont, A.; Beelen, A.; González-Alfonso, E.; Neri, R.; Gao, Y.; van der Werf, P.; Weiß, A.; Gavazzi, R.; Falstad, N.; Baker, A. J.; Bussmann, R. S.; Cooray, A.; Cox, P.; Dannerbauer, H.; Dye, S.; Guélin, M.; Ivison, R.; Krips, M.; Lehnert, M.; Michałowski, M. J.; Riechers, D. A.; Spaans, M.; Valiante, E.

    2016-11-01

    We report rest-frame submillimeter H2O emission line observations of 11 ultra- or hyper-luminous infrared galaxies (ULIRGs or HyLIRGs) at z 2-4 selected among the brightest lensed galaxies discovered in the Herschel-Astrophysical Terahertz Large Area Survey (H-ATLAS). Using the IRAM NOrthern Extended Millimeter Array (NOEMA), we have detected 14 new H2O emission lines. These include five 321-312ortho-H2O lines (Eup/k = 305 K) and nine J = 2 para-H2O lines, either 202-111(Eup/k = 101 K) or 211-202(Eup/k = 137 K). The apparent luminosities of the H2O emission lines are μLH2O 6-21 × 108 L⊙ (3 <μ< 15, where μ is the lens magnification factor), with velocity-integrated line fluxes ranging from 4-15 Jy km s-1. We have also observed CO emission lines using EMIR on the IRAM 30 m telescope in seven sources (most of those have not yet had their CO emission lines observed). The velocity widths for CO and H2O lines are found to be similar, generally within 1σ errors in the same source. With almost comparable integrated flux densities to those of the high-J CO line (ratios range from 0.4 to 1.1), H2O is found to be among the strongest molecular emitters in high-redshift Hy/ULIRGs. We also confirm our previously found correlation between luminosity of H2O (LH2O) and infrared (LIR) that LH2O LIR1.1-1.2, with ournew detections. This correlation could be explained by a dominant role of far-infrared pumping in the H2O excitation. Modelling reveals that the far-infrared radiation fields have warm dust temperature Twarm 45-75 K, H2O column density per unit velocity interval NH2O /ΔV ≳ 0.3 × 1015 cm-2 km-1 s and 100 μm continuum opacity τ100> 1 (optically thick), indicating that H2O is likely to trace highly obscured warm dense gas. However, further observations of J ≥ 4 H2O lines are needed to better constrain the continuum optical depth and other physical conditions of the molecular gas and dust. We have also detected H2O+ emission in three sources. A tight correlation

  6. New Optical Constants of Amorphous and Crystalline H2O-ice, 3-20_m

    NASA Technical Reports Server (NTRS)

    Mastrapa, Rachel Michelle Elizab

    2008-01-01

    We will present new optical constants forth amorphous and crystalline H2O-ice in the spectral range 3-20 _m. Our new measurements provide high temperature resolution for crystalline H2O-ice, 10 K intervals from 20-150 K, including temperatures relevant to Solar System ices. We have found that the shape of the 3 _m feature in amorphous H2O-ice is strongly dependant on deposition temperature and the high and low density phases of amorphous H2O-ice are not easily distinguishable. We will present methods of measuring the change in band shape with phase and temperature. We acknowledge financial support from the NASA Origins of the Solar System Program and the NASA Planetary Geology and Geophysics Program.

  7. Ion desorption from frozen H 2O irradiated by MeV heavy ions

    NASA Astrophysics Data System (ADS)

    Collado, V. M.; Farenzena, L. S.; Ponciano, C. R.; Silveira, E. F. da; Wien, K.

    2004-10-01

    Nitrogen (0.13-0.85 MeV) and 252Cf fission fragments (˜65 MeV) beams are employed to sputter positive and negative secondary ions from frozen water. Desorption yields are measured for different ice temperatures and projectile energies. Target surface is continuously refreshed by condensed water while the target temperature varies and ice thickness changes. In both projectile energy ranges, the preferentially ejected ions are H +, H2+ and (H 2O) nH +-cluster ions. The yields of the corresponding negative ions H - and (H 2O) nO - or (H 2O) nOH - are 1-2 orders of magnitude lower. The (H 2O) nH + desorption yields decrease exponentially as the cluster size, n, increases. In the low energy range, the desorption of positive ion clusters may occur in a two-step process: first, desorption of preformed H 2O clusters and, then, ionization by H + or H 3O + capture. For 0.81 MeV N + projectile ions, the cluster ion emission contributes with 0.05% to the total H 2O desorbed yield. There are indications that emission of the (H 2O) nH + disappears for an electronic energy loss lower than 20 eV/Å. For the high energy range, desorption of small ion clusters is particularly enhanced, revealing that a fragmentation process also exists.

  8. Competition between H2O and (H2O)2 reactions with CH2OO/CH3CHOO.

    PubMed

    Lin, Liang-Chun; Chang, Hung-Tzu; Chang, Chien-Hsun; Chao, Wen; Smith, Mica C; Chang, Chun-Hung; Jr-Min Lin, Jim; Takahashi, Kaito

    2016-02-14

    In this study, we performed ab initio calculations and obtained the bimolecular rate coefficients for the CH2OO/CH3CHOO reactions with H2O/(H2O)2. The energies were calculated with QCISD(T)/CBS//B3LYP/6-311+G(2d,2p) and the partition functions were estimated with anharmonic vibrational corrections by using the second order perturbation theory. Furthermore, we directly measured the rate of the CH2OO reaction with water vapor at high temperatures (348 and 358 K) to reveal the contribution of the water monomer in the CH2OO decay kinetics. We found that the theoretical rate coefficients reproduce the experimental results of CH2OO for a wide range of temperatures. For anti- (syn-) CH3CHOO, we obtained theoretical rate coefficients of 1.60 × 10(-11) (2.56 × 10(-14)) and 3.40 × 10(-14) (1.98 × 10(-19)) cm(3) s(-1) for water dimer and monomer reactions at room temperature. From the detailed analysis of the quantum chemistry and approximations for the thermochemistry calculations, we conclude that our calculated values would be within a factor of 3 of the correct values. Furthermore, at [H2O] = 1 × 10(17) to 5 × 10(17) cm(-3), we estimate that the effective first-order rate coefficients for CH2OO, anti- and syn-CH3CHOO reactions with water vapor will be ∼10(3), ∼10(4), and ∼10(1) s(-1), respectively. Thereby, for Criegee intermediates with a hydrogen atom on the same side as the terminal oxygen atom, the reaction with water vapor will likely dominate the removal processes of these CIs in the atmosphere. PMID:26797528

  9. H2O Formation in C-rich AGB Winds

    NASA Astrophysics Data System (ADS)

    Lombaert, R.; Decin, L.; Royer, P.; de Koter, A.; Cox, N. L. J.; De Ridder, J.; Khouri, T.; Agúndez, M.; Blommaert, J. A. D. L.; Cernicharo, J.; González-Alfonso, E.; Groenewegen, M. A. T.; Kerschbaum, F.; Neufeld, D.; Vandenbussche, B.; Waelkens, C.

    2015-08-01

    The Herschel detection of warm H2O vapor emission from C-rich winds of AGB stars challenges the current understanding of circumstellar chemistry. Two mechanisms have been invoked to explain warm H2O formation. In the first, penetration of UV interstellar radiation through a clumpy circumstellar medium causes the formation of H2O molecules in the inner envelope. In the second, periodic shocks passing through the medium immediately above the stellar surface lead to H2O formation. We have identified H2O emission trends from distance-independent line-strength ratios in a sample of 18 C-rich AGB sources, by comparing to a theoretical model grid. We detect warm H2O emission close to or inside the acceleration zone of all sample stars. We find an anti-correlation between the H2O/CO line-strength ratios and the mass-loss rate for Mgas>3×10-7 M⊙/yr. This implies that the H2O formation mechanism becomes less efficient with increasing envelope column density. The anti-correlation breaks down for SRb objects, which clump together at an overall lower H2O abundance. Finally, a radial dependence of the H2O abundance within individual sources is unlikely. These findings lend support to shock-induced non-equilibrium chemistry as the primary source of H2O formation in C-rich AGB stars.

  10. Descent Without Modification? The Thermal Chemistry of H2O2 on Europa and Other Icy Worlds

    NASA Technical Reports Server (NTRS)

    Loeffler, Mark Josiah; Hudson, Reggie Lester

    2015-01-01

    The strong oxidant H2O2 is known to exist in solid form on Europa and is suspected to exist on several other Solar System worlds at temperatures below 200 K. However, little is known of the thermal chemistry that H2O2 might induce under these conditions. Here, we report new laboratory results on the reactivity of solid H2O2 with eight different compounds in H2O-rich ices. Using infrared spectroscopy, we monitored compositional changes in ice mixtures during warming. The compounds CH4 (methane), C3H4 (propyne), CH3OH (methanol), and CH3CN (acetonitrile) were unaltered by the presence of H2O2 in ices, showing that exposure to either solid H2O2 or frozen H2O+H2O2 at cryogenic temperatures will not oxidize these organics, much less convert them to CO2. This contrasts strongly with the much greater reactivity of organics with H2O2 at higher temperatures, and particularly in the liquid and gas phases. Of the four inorganic compounds studied, CO, H2S, NH3, and SO2, only the last two reacted in ices containing H2O2, NH3 making NHþ 4 and SO2 making SO2 4 by H+ and e - transfer, respectively. An important astrobiological conclusion is that formation of surface H2O2 on Europa and that molecule's downward movement with H2O-ice do not necessarily mean that all organics encountered in icy subsurface regions will be destroyed by H2O2 oxidation.

  11. Descent without Modification? The Thermal Chemistry of H2O2 on Europa and Other Icy Worlds.

    PubMed

    Loeffler, Mark J; Hudson, Reggie L

    2015-06-01

    The strong oxidant H2O2 is known to exist in solid form on Europa and is suspected to exist on several other Solar System worlds at temperatures below 200 K. However, little is known of the thermal chemistry that H2O2 might induce under these conditions. Here, we report new laboratory results on the reactivity of solid H2O2 with eight different compounds in H2O-rich ices. Using infrared spectroscopy, we monitored compositional changes in ice mixtures during warming. The compounds CH4 (methane), C3H4 (propyne), CH3OH (methanol), and CH3CN (acetonitrile) were unaltered by the presence of H2O2 in ices, showing that exposure to either solid H2O2 or frozen H2O+H2O2 at cryogenic temperatures will not oxidize these organics, much less convert them to CO2. This contrasts strongly with the much greater reactivity of organics with H2O2 at higher temperatures, and particularly in the liquid and gas phases. Of the four inorganic compounds studied, CO, H2S, NH3, and SO2, only the last two reacted in ices containing H2O2, NH3 making NH4+ and SO2 making SO(4)2- by H+ and e- transfer, respectively. An important astrobiological conclusion is that formation of surface H2O2 on Europa and that molecule's downward movement with H2O-ice do not necessarily mean that all organics encountered in icy subsurface regions will be destroyed by H2O2 oxidation.

  12. Descent without Modification? The Thermal Chemistry of H2O2 on Europa and Other Icy Worlds.

    PubMed

    Loeffler, Mark J; Hudson, Reggie L

    2015-06-01

    The strong oxidant H2O2 is known to exist in solid form on Europa and is suspected to exist on several other Solar System worlds at temperatures below 200 K. However, little is known of the thermal chemistry that H2O2 might induce under these conditions. Here, we report new laboratory results on the reactivity of solid H2O2 with eight different compounds in H2O-rich ices. Using infrared spectroscopy, we monitored compositional changes in ice mixtures during warming. The compounds CH4 (methane), C3H4 (propyne), CH3OH (methanol), and CH3CN (acetonitrile) were unaltered by the presence of H2O2 in ices, showing that exposure to either solid H2O2 or frozen H2O+H2O2 at cryogenic temperatures will not oxidize these organics, much less convert them to CO2. This contrasts strongly with the much greater reactivity of organics with H2O2 at higher temperatures, and particularly in the liquid and gas phases. Of the four inorganic compounds studied, CO, H2S, NH3, and SO2, only the last two reacted in ices containing H2O2, NH3 making NH4+ and SO2 making SO(4)2- by H+ and e- transfer, respectively. An important astrobiological conclusion is that formation of surface H2O2 on Europa and that molecule's downward movement with H2O-ice do not necessarily mean that all organics encountered in icy subsurface regions will be destroyed by H2O2 oxidation. PMID:26060983

  13. Lateral variation of H2O contents in Quaternary Magma of central Northeastern Japan arc

    NASA Astrophysics Data System (ADS)

    Miyagi, I.; Matsu'ura, T.; Itoh, J.; Morishita, Y.

    2011-12-01

    Water plays a key role in the genesis and eruptive mechanisms of subduction zone volcanoes. We estimated bulk rock water content of both frontal and back arc volcanoes from Northeastern Japan arc in order to understand the lateral variation of magmatic H2O contents in the island arc magma. Our analytical targets are the Adachi volcano located near the volcanic front and the Hijiori volcano located on back arc side. In this study, the bulk magmatic H2O content is estimated by a simple mass balance calculation of the chemistry of bulk rock and melt inclusions in phenocrysts; the melt H2O contents of melt inclusions analyzed by SIMS or EPMA are corrected according to the difference in K2O content between melt inclusions and bulk rock. The bulk magmatic H2O we obtained is 8 wt. % or even more for Adachi and is 2-3 wt. % for Hijiori. Thus, the frontal volcano has higher H2O than the back arc volcano. Although our data are opposed to the previous estimation on the lateral variation of H2O contents in Quaternary volcanoes of Northeastern Japan arc (e.g., Sakuyama, 1979), thermodynamic computations using MELTS (Ghiorso and Sack, 1995) suggest that the amount of bulk magmatic H2O we estimated is consistent with petrographical observations. Our data imply a regional characteristics in the type of eruption that the H2O rich frontal volcanoes will erupt explosively and those H2O poor back arc ones will be effusive, which implication is consistent with actual geological observations that volcanoes located on back arc side of the Northeastern Japan arc generally comprise lava flow (e.g., Iwaki, Kanpu, Chokai, Gassan), in contrast to the frontal ones that produced voluminous tephra (e.g., Osorezan, Towada, Narugo, Adachi). This research project has been conducted under the research contract with Nuclear and Industrial Safety Agency (NISA).

  14. Decrease of H2O2 plasma membrane permeability during adaptation to H2O2 in Saccharomyces cerevisiae.

    PubMed

    Branco, Miguel R; Marinho, H Susana; Cyrne, Luisa; Antunes, Fernando

    2004-02-20

    Contrary to what is widely believed, recent published results show that H2O2 does not freely diffuse across biomembranes. The fast removal of H2O2 by antioxidant enzymes is able to generate a gradient if H2O2 is produced in a different compartment from that containing the enzymes (Antunes, F., and Cadenas, E. (2000) FEBS Lett. 475, 121-126). In this work, we extended these studies and tested whether an active regulation of biomembranes permeability characteristics is part of the cell response to oxidative stress. Using Saccharomyces cerevisiae as a model, we showed that: (a) H2O2 gradients across the plasma membrane are formed upon exposure to external H2O2; (b) there is a correlation between the magnitude of the gradients and the resistance to H2O2; (c) there is not a correlation between the intracellular capacity to remove H2O2 and the resistance to H2O2; (d) the plasma membrane permeability to H2O2 decreases by a factor of two upon acquisition of resistance to this agent by pre-exposing cells either to nonlethal doses of H2O2 or to cycloheximide, an inhibitor of protein synthesis; and (e) erg3Delta and erg6Delta mutants, which have impaired ergosterol biosynthesis pathways, show higher plasma membrane permeability to H2O2 and are more sensitive to H2O2. Altogether, the regulation of the plasma membrane permeability to H2O2 emerged as a new mechanism by which cells respond and adapt to H2O2. The consequences of the results to cellular redox compartmentalization and to the origin and evolution of the eukaryotic cell are discussed.

  15. Highly efficient extraction and oxidative desulfurization system using Na7H2LaW10O36⋅32 H2O in [bmim]BF4 at room temperature.

    PubMed

    Xu, Junhua; Zhao, Shen; Chen, Wei; Wang, Miao; Song, Yu-Fei

    2012-04-10

    Highly efficient, deep desulfurization of model oil containing dibenzothiophene (DBT), benzothiophene (BT), or 4,6-dimethyldibenzothiophene (4,6-DMDBT) has been achieved under mild conditions by using an extraction and catalytic oxidative desulfurization system (ECODS) in which a lanthanide-containing polyoxometalate Na(7)H(2)LnW(10)O(36)⋅32 H(2)O (LnW(10); Ln = Eu, La) acts as catalyst, [bmim]BF(4) (bmim = 1-butyl-3-methylimidazolium) as extractant, and H(2)O(2) as oxidant. Sulfur removal follows the order DBT>4,6-DMDBT>BT at 30 °C. DBT can be completely oxidized to the corresponding sulfone in 25 min under mild conditions, and the LaW(10)/[bmim]BF(4) system could be recycled for ten times with only slight decrease in activity. Thus, LaW(10) in [bmim]BF(4) is one of the most efficient systems for desulfurization using ionic liquids as extractant reported so far. PMID:22374858

  16. Gas-phase H2O and CO2 towards massive protostars

    NASA Astrophysics Data System (ADS)

    Boonman, A. M. S.; van Dishoeck, E. F.; Lahuis, F.; Wright, C. M.; Doty, S. D.

    2000-11-01

    We present a study of gas-phase H2O and CO2 towards a sample of 14 massive protostars with the ISO-SWS. Modeling of the H2O spectra using a homogeneous model with a constant excitation temperature Tex shows that the H2O abundances increase with temperature, up to a few times 10-5 with respect to H2 for the hottest sources (Tex~ 500 K). This is still a factor of 10 lower than the H2O ice abundances observed towards cold sources in which evaporation is not significant (Keane et al. 2000). Gas-phase CO2 is not abundant in our sources. The abundances are nearly constant for Tex >~ 100 K at a value of a few times 10-7, much lower than the solid-state abundances of ~1-3× 10-6 (Gerakines et al. 1999). Gas/solid ratios have been determined, using the solid-state features of H2O (Keane et al. 2000) and CO2 (Gerakines et al. 1999) as observed with ISO-SWS towards the same objects. For both H2O and CO2 the gas/solid ratio increases with temperature, but the increase is much stronger for H2O than for CO2, suggesting a different type of chemistry. In addition to the homogeneous models, a power law model has been developed for one of our sources, based on the physical structure of this region as determined from submillimeter data by van der Tak et al. (1999). The resulting H2O model spectrum gives a good fit to the data.

  17. [Relationships between H2O2 metabolism and Ca2+ transport in dormancy-breaking process of nectarine floral buds].

    PubMed

    Tan, Yue; Gao, Dong-sheng; Li, Ling; Wei, Hai-rong; Wang, Jia-wei; Liu, Qing-zhong

    2015-02-01

    In order to explore regulatory function of H2O2 in bud dormancy release, main effects of three dormancy-breaking treatments (high temperature, hydrogen cyanamide and TDZ) on H2O2 metabolism were determined, and impacts of H2O2 on Ca2+ transport were tested using non-invasive micro-test technique. The results showed that both high temperature and hydrogen cyanamide induced H2O2 accumulation and CAT inhibition were efficient in breaking dormancy during deep dormancy period. However, TDZ showed little impacts on H2O2 metabolism and was much less effective in breaking dormancy. Dormant floral primordium was absorbing state to exogenous Ca2+ due to active calcium channels. The Ca2+ transport could be changed by exogenous H2O2. H2O2 of low concentration reduced the absorption rate of Ca2+, and at high concentration, it changed the Ca2+ transport direction from absorption to release. The results indicated that H2O2 signals were related with Ca2+ signals in dormant buds. Ca2+ signal regulated by H2O2 accumulation might be important in the dormancy-breaking signal transduction process induced by high temperature and hydrogen cyanamide.

  18. Vibrational and reorientational motions of H2O ligands, phase transition and thermal properties of [Sr(H2O)6]Cl2

    NASA Astrophysics Data System (ADS)

    Hetmańczyk, Joanna; Hetmańczyk, Łukasz; Migdał-Mikuli, Anna; Mikuli, Edward

    2013-11-01

    One phase transition (PT) at TCh = 252.9 K (on heating) and at TCc = 226.5 K (on cooling) was detected by DSC for [Sr(H2O)6]Cl2 in 123-295 K range. Thermal hysteresis of this PT equals to 26.4 K. Entropy change (ΔS) value at this first-order type phase transition equals to ca. 1.5 J mol-1 K-1. The temperature dependences of the full width at half maximum (FWHM) values of the infrared bands associated with ρt(H2O)E and δas(HOH)E modes (at ca. 417 and 1628 cm-1, respectively) suggest that the observed phase transition is associated with a sudden change of a speed of the H2O reorientational motions. The H2O ligands in the high temperature phase reorientate quickly (correlation times 10-11-10-13 s) with the activation energy of ca. 2 kJ mol-1. Below TCc probably a part of the H2O ligands stop their reorientation, while the remainders continue their fast reorientation but with the activation energy of ca. 8 kJ mol-1. Far and middle infrared spectra indicated characteristic changes at the vicinity of PT with decreasing of temperature, which suggested lowering of the crystal structure symmetry. Splitting of the band (at 3601 cm-1) connected with vas(OH) mode near the TCc suggests lowering of the crystal lattice symmetry. All these facts suggest that the discovered PT is connected both with a change of the reorientational dynamics of the H2O ligands and with the change of the crystal structure.

  19. Vibrational and reorientational motions of H2O ligands, phase transition and thermal properties of [Sr(H2O)6]Cl2.

    PubMed

    Hetmańczyk, Joanna; Hetmańczyk, Łukasz; Migdał-Mikuli, Anna; Mikuli, Edward

    2013-11-01

    One phase transition (PT) at TC(h)=252.9K (on heating) and at TC(c)=226.5K (on cooling) was detected by DSC for [Sr(H2O)6]Cl2 in 123-295K range. Thermal hysteresis of this PT equals to 26.4K. Entropy change (ΔS) value at this first-order type phase transition equals to ca. 1.5Jmol(-1)K(-1). The temperature dependences of the full width at half maximum (FWHM) values of the infrared bands associated with ρt(H2O)E and δas(HOH)E modes (at ca. 417 and 1628cm(-1), respectively) suggest that the observed phase transition is associated with a sudden change of a speed of the H2O reorientational motions. The H2O ligands in the high temperature phase reorientate quickly (correlation times 10(-11)-10(-13)s) with the activation energy of ca. 2kJmol(-1). Below TC(c) probably a part of the H2O ligands stop their reorientation, while the remainders continue their fast reorientation but with the activation energy of ca. 8kJmol(-1). Far and middle infrared spectra indicated characteristic changes at the vicinity of PT with decreasing of temperature, which suggested lowering of the crystal structure symmetry. Splitting of the band (at 3601cm(-1)) connected with vas(OH) mode near the TC(c) suggests lowering of the crystal lattice symmetry. All these facts suggest that the discovered PT is connected both with a change of the reorientational dynamics of the H2O ligands and with the change of the crystal structure.

  20. Experimental determination of the H2O-undersaturated peridotite solidus

    NASA Astrophysics Data System (ADS)

    Sarafian, E. K.; Gaetani, G. A.; Hauri, E. H.; Sarafian, A. R.

    2014-12-01

    Knowledge of the H2O-undersaturated lherzolite solidus places important constraints on the process of melt generation and mantle potential temperatures beneath oceanic spreading centers. The small concentration of H2O (~50-200 μg/g) dissolved in the oceanic mantle is thought to exert a strong influence on the peridotite solidus, but this effect has not been directly determined. The utility of existing experimental data is limited by a lack of information on the concentration of H2O dissolved in the peridotite and uncertainties involved with identifying small amounts of partial melt. We have developed an experimental approach for determining the peridotite solidus as a function of H2O content that overcomes these difficulties. Our initial results demonstrate that the solidus temperature for spinel lherzolite containing 150 μg/g H2O is higher than existing estimates for the anhydrous solidus. Our approach to determining the H2O-undersaturated lherzolite solidus is as follows. First, a small proportion (~5 %) of San Carlos olivine spheres, ~300 μm in diameter, are added to a peridotite synthesized from high-purity oxides and carbonates. Melting experiments are then conducted in pre-conditioned Au80Pd20 capsules over a range of temperatures at a single pressure using a piston-cylinder device. Water diffuses rapidly in olivine resulting in thorough equilibration between the olivine spheres and the surrounding fine-grained peridotite, and allowing the spheres to be used as hygrometers. After the experiment, the concentration of H2O dissolved in the olivine spheres is determined by secondary ion mass spectrometry. Melting experiments, spaced 20°C apart, were performed from 1250 to 1430°C at 1.5 GPa. The starting material has the composition of the depleted MORB mantle of Workman and Hart (2005) containing 0.13 wt% Na2O and 150 µg/g H2O. The concentration of H2O in the olivine spheres remains constant up to 1350°C, and then decreases systematically with increasing

  1. Tuning the conductance of H2O@C60 by position of the encapsulated H2O

    PubMed Central

    Zhu, Chengbo; Wang, Xiaolin

    2015-01-01

    The change of conductance of single-molecule junction in response to various external stimuli is the fundamental mechanism for the single-molecule electronic devices with multiple functionalities. We propose the concept that the conductance of molecular systems can be tuned from inside. The conductance is varied in C60 with encapsulated H2O, H2O@C60. The transport properties of the H2O@C60-based nanostructure sandwiched between electrodes are studied using first-principles calculations combined with the non-equilibrium Green’s function formalism. Our results show that the conductance of the H2O@C60 is sensitive to the position of the H2O and its dipole direction inside the cage with changes in conductance up to 20%. Our study paves a way for the H2O@C60 molecule to be a new platform for novel molecule-based electronics and sensors. PMID:26643873

  2. Cross Talk between H2O2 and Interacting Signal Molecules under Plant Stress Response.

    PubMed

    Saxena, Ina; Srikanth, Sandhya; Chen, Zhong

    2016-01-01

    It is well established that oxidative stress is an important cause of cellular damage. During stress conditions, plants have evolved regulatory mechanisms to adapt to various environmental stresses. One of the consequences of stress is an increase in the cellular concentration of reactive oxygen species, which is subsequently converted to H2O2. H2O2 is continuously produced as the byproduct of oxidative plant aerobic metabolism. Organelles with a high oxidizing metabolic activity or with an intense rate of electron flow, such as chloroplasts, mitochondria, or peroxisomes are major sources of H2O2 production. H2O2 acts as a versatile molecule because of its dual role in cells. Under normal conditions, H2O2 immerges as an important factor during many biological processes. It has been established that it acts as a secondary messenger in signal transduction networks. In this review, we discuss potential roles of H2O2 and other signaling molecules during various stress responses.

  3. Cross Talk between H2O2 and Interacting Signal Molecules under Plant Stress Response

    PubMed Central

    Saxena, Ina; Srikanth, Sandhya; Chen, Zhong

    2016-01-01

    It is well established that oxidative stress is an important cause of cellular damage. During stress conditions, plants have evolved regulatory mechanisms to adapt to various environmental stresses. One of the consequences of stress is an increase in the cellular concentration of reactive oxygen species, which is subsequently converted to H2O2. H2O2 is continuously produced as the byproduct of oxidative plant aerobic metabolism. Organelles with a high oxidizing metabolic activity or with an intense rate of electron flow, such as chloroplasts, mitochondria, or peroxisomes are major sources of H2O2 production. H2O2 acts as a versatile molecule because of its dual role in cells. Under normal conditions, H2O2 immerges as an important factor during many biological processes. It has been established that it acts as a secondary messenger in signal transduction networks. In this review, we discuss potential roles of H2O2 and other signaling molecules during various stress responses. PMID:27200043

  4. Cross Talk between H2O2 and Interacting Signal Molecules under Plant Stress Response.

    PubMed

    Saxena, Ina; Srikanth, Sandhya; Chen, Zhong

    2016-01-01

    It is well established that oxidative stress is an important cause of cellular damage. During stress conditions, plants have evolved regulatory mechanisms to adapt to various environmental stresses. One of the consequences of stress is an increase in the cellular concentration of reactive oxygen species, which is subsequently converted to H2O2. H2O2 is continuously produced as the byproduct of oxidative plant aerobic metabolism. Organelles with a high oxidizing metabolic activity or with an intense rate of electron flow, such as chloroplasts, mitochondria, or peroxisomes are major sources of H2O2 production. H2O2 acts as a versatile molecule because of its dual role in cells. Under normal conditions, H2O2 immerges as an important factor during many biological processes. It has been established that it acts as a secondary messenger in signal transduction networks. In this review, we discuss potential roles of H2O2 and other signaling molecules during various stress responses. PMID:27200043

  5. Absolute Infrared Cross Sections of Gas-Phase H2O2 Using Fourier Transform Mid-Infrared Spectroscopy

    SciTech Connect

    Johnson, Timothy J.; Blake, Thomas A.; Sams, Robert L.; Burton, Sarah D.

    2010-01-29

    We report quantitative spectra of pressure-broadened H2O2 vapor. An 83% solution was flowed into a disseminator and diluted with N2 gas; water lines were subtracted. The H2O2 spectrum spans the IR and compares well with HITRAN values for ν6 band.

  6. A comparative study of Mn/CeO2, Mn/ZrO2 and Mn/Ce-ZrO2 for low temperature selective catalytic reduction of NO with NH3 in the presence of SO2 and H2O.

    PubMed

    Shen, Boxiong; Zhang, Xiaopeng; Ma, Hongqing; Yao, Yan; Liu, Ting

    2013-04-01

    Ce-ZrO2 is a widely used three-way catalyst support. Because of the large surface area and excellent redox quality, Ce-ZrO2 may have potential application in selective catalytic reduction (SCR) systems. In the present work, Ce-ZrO2 was introduced into a low-temperature SCR system and CeO2 and ZrO2 supports were also introduced to make a contrastive study. Mn/CeO2, Mn/ZrO2 and Mn/Ce-ZrO2 were prepared by impregnating these supports with Mn(NO3)2 solution, and have been characterized by N2-BET, XRD, TPR, TPD, XPS, FT-IR and TG. The activity and resistance to SO2 and H2O of the catalysts were investigated. Mn/Ce-ZrO2 and Mn/CeO2 were proved to have better low-temperature activities than Mn/ZrO2, and yielded 98.6% and 96.8% NO conversion at 180 degrees C, respectively. This is mainly because Mn/Ce-ZrO2 and Mn/CeO2 had higher dispersion of manganese oxides, better redox properties and more weakly adsorbed oxygen species than Mn/ZrO2. In addition, Mn/Ce-ZrO2 showed a good resistance to SO2 and H2O and presented 87.1% NO conversion, even under SO2 and H2O treatment for 6 hours, and the activity of Mn/Ce-ZrO2 was almost restored to its original level after cutting off the injection of SO2 and H2O. This was due to the weak water absorption and weak sulfation process on the surface of the catalyst.

  7. Drosophila TRPA1 isoforms detect UV light via photochemical production of H2O2.

    PubMed

    Guntur, Ananya R; Gu, Pengyu; Takle, Kendra; Chen, Jingyi; Xiang, Yang; Yang, Chung-Hui

    2015-10-20

    The transient receptor potential A1 (TRPA1) channel is an evolutionarily conserved detector of temperature and irritant chemicals. Here, we show that two specific isoforms of TRPA1 in Drosophila are H2O2 sensitive and that they can detect strong UV light via sensing light-induced production of H2O2. We found that ectopic expression of these H2O2-sensitive Drosophila TRPA1 (dTRPA1) isoforms conferred UV sensitivity to light-insensitive HEK293 cells and Drosophila neurons, whereas expressing the H2O2-insensitive isoform did not. Curiously, when expressed in one specific group of motor neurons in adult flies, the H2O2-sensitive dTRPA1 isoforms were as competent as the blue light-gated channelrhodopsin-2 in triggering motor output in response to light. We found that the corpus cardiacum (CC) cells, a group of neuroendocrine cells that produce the adipokinetic hormone (AKH) in the larval ring gland endogenously express these H2O2-sensitive dTRPA1 isoforms and that they are UV sensitive. Sensitivity of CC cells required dTRPA1 and H2O2 production but not conventional phototransduction molecules. Our results suggest that specific isoforms of dTRPA1 can sense UV light via photochemical production of H2O2. We speculate that UV sensitivity conferred by these isoforms in CC cells may allow young larvae to activate stress response--a function of CC cells--when they encounter strong UV, an aversive stimulus for young larvae.

  8. Drosophila TRPA1 isoforms detect UV light via photochemical production of H2O2

    PubMed Central

    Guntur, Ananya R.; Gu, Pengyu; Takle, Kendra; Chen, Jingyi; Xiang, Yang; Yang, Chung-Hui

    2015-01-01

    The transient receptor potential A1 (TRPA1) channel is an evolutionarily conserved detector of temperature and irritant chemicals. Here, we show that two specific isoforms of TRPA1 in Drosophila are H2O2 sensitive and that they can detect strong UV light via sensing light-induced production of H2O2. We found that ectopic expression of these H2O2-sensitive Drosophila TRPA1 (dTRPA1) isoforms conferred UV sensitivity to light-insensitive HEK293 cells and Drosophila neurons, whereas expressing the H2O2-insensitive isoform did not. Curiously, when expressed in one specific group of motor neurons in adult flies, the H2O2-sensitive dTRPA1 isoforms were as competent as the blue light-gated channelrhodopsin-2 in triggering motor output in response to light. We found that the corpus cardiacum (CC) cells, a group of neuroendocrine cells that produce the adipokinetic hormone (AKH) in the larval ring gland endogenously express these H2O2-sensitive dTRPA1 isoforms and that they are UV sensitive. Sensitivity of CC cells required dTRPA1 and H2O2 production but not conventional phototransduction molecules. Our results suggest that specific isoforms of dTRPA1 can sense UV light via photochemical production of H2O2. We speculate that UV sensitivity conferred by these isoforms in CC cells may allow young larvae to activate stress response—a function of CC cells—when they encounter strong UV, an aversive stimulus for young larvae. PMID:26443856

  9. Optimization of intermolecular potential parameters for the CO2/H2O mixture.

    PubMed

    Orozco, Gustavo A; Economou, Ioannis G; Panagiotopoulos, Athanassios Z

    2014-10-01

    Monte Carlo simulations in the Gibbs ensemble were used to obtain optimized intermolecular potential parameters to describe the phase behavior of the mixture CO2/H2O, over a range of temperatures and pressures relevant for carbon capture and sequestration processes. Commonly used fixed-point-charge force fields that include Lennard-Jones 12-6 (LJ) or exponential-6 (Exp-6) terms were used to describe CO2 and H2O intermolecular interactions. For force fields based on the LJ functional form, changes of the unlike interactions produced higher variations in the H2O-rich phase than in the CO2-rich phase. A major finding of the present study is that for these potentials, no combination of unlike interaction parameters is able to adequately represent properties of both phases. Changes to the partial charges of H2O were found to produce significant variations in both phases and are able to fit experimental data in both phases, at the cost of inaccuracies for the pure H2O properties. By contrast, for the Exp-6 case, optimization of a single parameter, the oxygen-oxygen unlike-pair interaction, was found sufficient to give accurate predictions of the solubilities in both phases while preserving accuracy in the pure component properties. These models are thus recommended for future molecular simulation studies of CO2/H2O mixtures. PMID:25198539

  10. Effects of Convective Ice Lofting on H2O and HDO in the Tropical Tropopause Layer

    NASA Technical Reports Server (NTRS)

    Dessler, A. E.; Hanisco, T. F.; Fueglistaler, S.

    2007-01-01

    We have added convective ice lofting to a Lagrangian trajectory model of near-tropopause water vapor (H2O) and its isotopologue HDO. The ice lofting simulation is based on a parameterization derived from Aura Microwave Limb Sounder (MLS) icewater content measurements. In previous papers, the Lagrangian model has accurately interannual and seasonal H2O abundances; there was no need for convection to be included in the model. We show here that this model does a poor job of simulating near-tropopause HDO, but that the addition of convective ice lofting greatly improves the HDO simulation. Convective ice lofting has a small effect on lower stratospheric H2O. H2O there is set by the minimum temperature encountered at the cold-point tropopause, so H2O added by convection below this level does not make it through this cold point and into the lower stratosphere. Thus, adding convection to the model does not degrade the model's previously demonstrated accurate simulations of H2O. We conclude that the HDO data suggest an important role for convective mass flux into the so-called tropical tropopause layer.

  11. Heterogeneous distribution of H2O in the Martian interior: Implications for the abundance of H2O in depleted and enriched mantle sources

    NASA Astrophysics Data System (ADS)

    McCubbin, Francis M.; Boyce, Jeremy W.; Srinivasan, Poorna; Santos, Alison R.; Elardo, Stephen M.; Filiberto, Justin; Steele, Andrew; Shearer, Charles K.

    2016-04-01

    We conducted a petrologic study of apatite within 12 Martian meteorites, including 11 shergottites and one basaltic regolith breccia. These data were combined with previously published data to gain a better understanding of the abundance and distribution of volatiles in the Martian interior. Apatites in individual Martian meteorites span a wide range of compositions, indicating they did not form by equilibrium crystallization. In fact, the intrasample variation in apatite is best described by either fractional crystallization or crustal contamination with a Cl-rich crustal component. We determined that most Martian meteorites investigated here have been affected by crustal contamination and hence cannot be used to estimate volatile abundances of the Martian mantle. Using the subset of samples that did not exhibit crustal contamination, we determined that the enriched shergottite source has 36-73 ppm H2O and the depleted source has 14-23 ppm H2O. This result is consistent with other observed geochemical differences between enriched and depleted shergottites and supports the idea that there are at least two geochemically distinct reservoirs in the Martian mantle. We also estimated the H2O, Cl, and F content of the Martian crust using known crust-mantle distributions for incompatible lithophile elements. We determined that the bulk Martian crust has ~1410 ppm H2O, 450 ppm Cl, and 106 ppm F, and Cl and H2O are preferentially distributed toward the Martian surface. The estimate of crustal H2O results in a global equivalent surface layer (GEL) of ~229 m, which can account for at least some of the surface features on Mars attributed to flowing water and may be sufficient to support the past presence of a shallow sea on Mars' surface.

  12. Vibrational Predissociation Dynamics of the (H_2O)_2 Dimer

    NASA Astrophysics Data System (ADS)

    Ch'ng, L. C.; Rocher, B. E.; Mollner, A. K.; Reisler, H.

    2011-06-01

    The state-to-state vibrational predissociation dynamics of the (H_2O)_2 dimer were studied by resonance-enhanced multiphoton ionization (REMPI) and velocity-map imaging (VMI) to obtain pair-correlated product energy distributions. The 2+1 REMPI spectra of the H_2O photofragments were recorded via the tilde{C}^1B_1 (000) ← tilde{X}^1A_1 (000 and 010) transition following a vibrational excitation of the dimer's bound-OH stretch fundamental. The fragment' center-of-mass translational energy (c.m. E_T) distributions were determined from VMI of selected rotational states of the detected H_2O photofragments. The c.m. E_T distributions were then converted to pair-correlated H_2O cofragment rotational level distributions. This is the first experiment in which H_2O products with bend (ν_2) excitation were observed by REMPI. The dissociation energy of the dimer was determined from the images with spectroscopic accuracy. The predissociation mechanism of (H_2O)_2 will be discussed and compared with the corresponding hydrogen bonded dimers of an acid (HCl-H_2O) and a base (NH_3-H_2O).

  13. Scavenging of H2O2 by mouse brain mitochondria.

    PubMed

    Starkov, Anatoly A; Andreyev, Alexander Yu; Zhang, Steven F; Starkova, Natalia N; Korneeva, Maria; Syromyatnikov, Mikhail; Popov, Vasily N

    2014-12-01

    Mitochondrial reactive oxygen species (ROS) metabolism is unique in that mitochondria both generate and scavenge ROS. Recent estimates of ROS scavenging capacity of brain mitochondria are surprisingly high, ca. 9-12 nmol H2O2/min/mg, which is ~100 times higher than the rate of ROS generation. This raises a question whether brain mitochondria are a source or a sink of ROS. We studied the interaction between ROS generation and scavenging in mouse brain mitochondria by measuring the rate of removal of H2O2 added at a concentration of 0.4 μM, which is close to the reported physiological H2O2 concentrations in tissues, under conditions of low and high levels of mitochondrial H2O2 generation. With NAD-linked substrates, the rate of H2O2 generation by mitochondria was ~50-70 pmol/min/mg. The H2O2 scavenging dynamics was best approximated by the first order reaction equation. H2O2 scavenging was not affected by the uncoupling of mitochondria, phosphorylation of added ADP, or the genetic ablation of glutathione peroxidase 1, but decreased in the absence of respiratory substrates, in the presence of thioredoxin reductase inhibitor auranofin, or in partially disrupted mitochondria. With succinate, the rate of H2O2 generation was ~2,200-2,900 pmol/min/mg; the scavenging of added H2O2 was masked by a significant accumulation of generated H2O2 in the assay medium. The obtained data were fitted into a simple model that reasonably well described the interaction between H2O2 scavenging and production. It showed that mitochondria are neither a sink nor a source of H2O2, but can function as both at the same time, efficiently stabilizing exogenous H2O2 concentration at a level directly proportional to the ratio of the H2O2 generation rate to the rate constant of the first order scavenging reaction.

  14. Hormetic Effect of H2O2 in Saccharomyces cerevisiae

    PubMed Central

    Valishkevych, Bohdana V.

    2016-01-01

    In this study, we investigated the relationship between target of rapamycin (TOR) and H2O2-induced hormetic response in the budding yeast Saccharomyces cerevisiae grown on glucose or fructose. In general, our data suggest that: (1) hydrogen peroxide (H2O2) induces hormesis in a TOR-dependent manner; (2) the H2O2-induced hormetic dose–response in yeast depends on the type of carbohydrate in growth medium; (3) the concentration-dependent effect of H2O2 on yeast colony growth positively correlates with the activity of glutathione reductase that suggests the enzyme involvement in the H2O2-induced hormetic response; and (4) both TOR1 and TOR2 are involved in the reciprocal regulation of the activity of glucose-6-phosphate dehydrogenase and glyoxalase 1. PMID:27099601

  15. Experimental determination of the solubility constant for magnesium chloride hydroxide hydrate (Mg 3Cl(OH) 5·4H 2O, phase 5) at room temperature, and its importance to nuclear waste isolation in geological repositories in salt formations

    NASA Astrophysics Data System (ADS)

    Xiong, Yongliang; Deng, Haoran; Nemer, Martin; Johnsen, Shelly

    2010-08-01

    In this study, the solubility constant of magnesium chloride hydroxide hydrate, Mg 3Cl(OH) 5·4H 2O, termed as phase 5, is determined from a series of solubility experiments in MgCl 2-NaCl solutions. The solubility constant in logarithmic units at 25 °C for the following reaction, MgCl(OH)·4HO+5H=3Mg+9HO(l)+Cl is calculated as 43.21 ± 0.33 (2 σ) based on the specific interaction theory (SIT) model for extrapolation to infinite dilution. The Gibbs free energy and enthalpy of formation for phase 5 at 25 °C are derived as -3384 ± 2 (2 σ) kJ mol -1 and -3896 ± 6 (2 σ) kJ mol -1, respectively. MgO (bulk, pure MgO corresponding to the mineral periclase) is the only engineered barrier certified by the Environmental Protection Agency (EPA) for emplacement in the Waste Isolation Pilot Plant (WIPP) in the US, and an Mg(OH) 2-based engineered barrier (bulk, pure Mg(OH) 2 corresponding to brucite) is to be employed in the Asse repository in Germany. Phase 5, and its similar phase, phase 3 (Mg 2Cl(OH) 3·4H 2O), could have a significant role in influencing the geochemical conditions in geological repositories for nuclear waste in salt formations where MgO or brucite is employed as engineered barriers. Based on our solubility constant for phase 5 in combination with the literature value for phase 3, we predict that the composition for the invariant point of phase 5 and phase 3 would be mMg = 1.70 and pmH = 8.94 in the Mg-Cl binary system. The recent WIPP Compliance Recertification Application Performance Assessment Baseline Calculations indicate that phase 5, instead of phase 3, is indeed a stable phase when the WIPP Generic Weep Brine (GWB), a Na-Mg-Cl-dominated brine associated with the Salado Formation, equilibrates with actinide-source-term phases, brucite, magnesium carbonates, halite and anhydrite. Therefore, phase 5 is important to the WIPP, and potentially important to other repositories in salt formations.

  16. Fast Switching of CO3(-)(H2O)n and O2(-)(H2O)n reactant ions in dopant-assisted negative photoionization ion mobility spectrometry for explosives detection.

    PubMed

    Cheng, Shasha; Wang, Weiguo; Zhou, Qinghua; Chen, Chuang; Peng, Liying; Hua, Lei; Li, Yang; Hou, Keyong; Li, Haiyang

    2014-03-01

    Ion mobility spectrometry (IMS) has become the most deployed technique for on-site detection of trace explosives, and the reactant ions generated in the ionization source are tightly related to the performances of IMS. Combination of multiform reactant ions would provide more information and is in favor of correct identification of explosives. Fast switchable CO3(-)(H2O)n and O2(-)(H2O)n reactant ions were realized in a dopant-assisted negative photoionization ion mobility spectrometer (DANP-IMS). The switching could be achieved in less than 2 s by simply changing the gas flow direction. Up to 88% of the total reactant ions were CO3(-)(H2O)n in the bidirectional mode, and 89% of that were O2(-)(H2O)n in the unidirectional mode. The characteristics of combination of CO3(-)(H2O)n and O2(-)(H2O)n were demonstrated by the detection of explosives, including 2,4,6-trinitrotoluene (TNT), cyclo-1,3,5-trimethylene-2,4,6-trinitramine (RDX), ammonium nitrate fuel oil (ANFO), and black powder (BP). For TNT, RDX, and BP, product ions with different reduced mobility values (K0) were observed with CO3(-)(H2O)n and O2(-)(H2O)n, respectively, which is a benefit for the accurate identification. For ANFO, the same product ions with K0 of 2.07 cm(2) V(-1) s(-1) were generated, but improved peak-to-peak resolution as well as sensitivity were achieved with CO3(-)(H2O)n. Moreover, an improved peak-to-peak resolution was also obtained for BP with CO3(-)(H2O)n, while the better sensitivity was obtained with O2(-)(H2O)n.

  17. Crystal structures of hydrates of simple inorganic salts. III. Water-rich aluminium halide hydrates: AlCl3 · 15H2O, AlBr3 · 15H2O, AlI3 · 15H2O, AlI3 · 17H2O and AlBr3 · 9H2O.

    PubMed

    Schmidt, Horst; Hennings, Erik; Voigt, Wolfgang

    2014-09-01

    Water-rich aluminium halide hydrate structures are not known in the literature. The highest known water content per Al atom is nine for the perchlorate and fluoride. The nonahydrate of aluminium bromide, stable pentadecahydrates of aluminium chloride, bromide and iodide, and a metastable heptadecahydrate of the iodide have now been crystallized from low-temperature solutions. The structures of these hydrates were determined and are discussed in terms of the development of cation hydration spheres. The pentadecahydrate of the chloride and bromide are isostructural. In AlI(3) · 15H2O, half of the Al(3+) cations are surrounded by two complete hydration spheres, with six H2O in the primary and 12 in the secondary. For the heptadecahydrate of aluminium iodide, this hydration was found for every Al(3+). PMID:25186362

  18. Crystal structures of hydrates of simple inorganic salts. III. Water-rich aluminium halide hydrates: AlCl3 · 15H2O, AlBr3 · 15H2O, AlI3 · 15H2O, AlI3 · 17H2O and AlBr3 · 9H2O.

    PubMed

    Schmidt, Horst; Hennings, Erik; Voigt, Wolfgang

    2014-09-01

    Water-rich aluminium halide hydrate structures are not known in the literature. The highest known water content per Al atom is nine for the perchlorate and fluoride. The nonahydrate of aluminium bromide, stable pentadecahydrates of aluminium chloride, bromide and iodide, and a metastable heptadecahydrate of the iodide have now been crystallized from low-temperature solutions. The structures of these hydrates were determined and are discussed in terms of the development of cation hydration spheres. The pentadecahydrate of the chloride and bromide are isostructural. In AlI(3) · 15H2O, half of the Al(3+) cations are surrounded by two complete hydration spheres, with six H2O in the primary and 12 in the secondary. For the heptadecahydrate of aluminium iodide, this hydration was found for every Al(3+).

  19. Direct N2H4/H2O2 Fuel Cells Powered by Nanoporous Gold Leaves

    PubMed Central

    Yan, Xiuling; Meng, Fanhui; Xie, Yun; Liu, Jianguo; Ding, Yi

    2012-01-01

    Dealloyed nanoporous gold leaves (NPGLs) are found to exhibit high electrocatalytic properties toward both hydrazine (N2H4) oxidation and hydrogen peroxide (H2O2) reduction. This observation allows the implementation of a direct hydrazine-hydrogen peroxide fuel cell (DHHPFC) based on these novel porous membrane catalysts. The effects of fuel and oxidizer flow rate, concentration and cell temperature on the performance of DHHPFC are systematically investigated. With a loading of ~0.1 mg cm−2 Au on each side, an open circuit voltage (OCV) of 1.2 V is obtained at 80°C with a maximum power density 195 mW cm−2, which is 22 times higher than that of commercial Pt/C electrocatalyst at the same noble metal loading. NPGLs thus hold great potential as effective and stable electrocatalysts for DHHPFCs. PMID:23230507

  20. Observations of H2O in Titan's atmosphere with Herschel

    NASA Astrophysics Data System (ADS)

    Moreno, R.; Lellouch, E.; Lara, L. M.; Courtin, R.; Hartogh, P.; Rengel, M.

    2012-04-01

    Disk averaged observations of several H2O far infrared lines in Titan’s atmosphere were performed with the Herschel Space Observatory, as part of the guaranteed time key program "Water and related chemistry in the Solar System" (HssO, see Hartogh et al 2011). Two instruments were used: (i) HIFI, a heterodyne instrument (R~ 106 ) in the sub-millimeter, which measured the H2O(110-101) rotational transition at 557 GHz on June 10 and Dec. 31, 2010 (ii) PACS, a photoconductor spectrometer (R~103) which measured three water lines at 108.1, 75.4 and 66.4 microns on June 22, 2010. Additional PACS measurements at 66.4 microns on Dec. 15 and 22, 2010 and on July 09, 2011, do not show any significant line intensity variation with time, nor between the leading/trailing sides (i.e. longitude). Spectra were analyzed with a line-by-line radiative transfer code accounting for spherical geometry (Moreno et al. 2011). This model considers the H2O molecular opacity from JPL catalog (Pickett et al. 1998) and also includes collision-induced opacities N2-N2, N2-CH4 and CH4-CH4 (Borysow and Frommhold 1986, 1987, Borysow and Tang 1993). Far infrared aerosol opacities derived by CIRS were included, following Anderson and Samuelson (2011) for their vertical distribution and spectral dependencies. Analysis of the 557 GHz narrow line (FWHM ~ 2 MHz) indicates that it originates at altitudes above 300 km, while lines measured with PACS probe mainly deeper levels (80-150 km). The HIFI and PACS observations are fitted simultaneously, considering a vertical distribution of H2O mixing ratio which follows a power law dependency q=q0(P/P0)n, where q0 is the mixing ratio at some reference pressure level P0, taken near the expected condensation level. Model fits will be presented, and compared with previously proposed H2O vertical distributions. We show in particular that both the steep profile proposed by Lara et al. (1996) (and adopted by Coustenis et al. (1998) to model the first detection of H2O

  1. H2O Outgassing from Silicones

    SciTech Connect

    Dinh, L N; Maxwell, R S; Schildbach, M A; Balazs, B; McLean II, W

    2004-11-09

    In this fiscal year, we have tested the H{sub 2}O outgassing model for TR55 against independent core tests performed at different temperatures by our collaborators at Y12. At higher temperature ({approx} 71 C), the model properly predicts moisture outgassing from TR55 over the entire experiment. At lower temperature ({approx} 42.5 C), the model correctly predicts long-term moisture outgassing. However, in short-term limit, a better fit with core tests might be expected when the diffusion effect of H{sub 2}O through the silicone matrix is included into the model in the near future. A lookup table for the moisture content as well as moisture outgassing kinetics for M9787 which have previously been heated to 460K for one day and then exposed to relevant low levels of moisture is also now available as a reference for engineers/technicians in the fields.

  2. Phase Separation Kinetics in Isopycnic Mixtures of H2O/CO2/Ethoxylated Alcohol Surfactants

    NASA Technical Reports Server (NTRS)

    Lesemann, Markus; Paulaitis, Michael E.; Kaler, Eric W.

    1999-01-01

    Ternary mixtures of H2O and CO2 with ethoxylated alcohol (C(sub i)E(sub j)) surfactants form three coexisting liquid phases at conditions where two of the phases have equal densities (isopycnic phases). Isopycnic phase behavior has been observed for mixtures containing C8E5, C10E6, and C12E6 surfactants, but not for those mixtures containing either C4E1 or C8E3 surfactants. Pressure-temperature (PT) projections for this three-phase equilibrium were determined for H2O/CO2/C8E5 and H2O/CO2/C10E6 mixtures at temperatures from approximately 25 to 33 C and pressures between 90 and 350 bar. Measurements of the microstructure in H2O/CO2/C12E6 mixtures as a function of temperature (25-31 C), pressure (63.1-90.7 bar), and CO2 composition (0-3.9 wt%) have also been carried out to show that while micellar structure remains essentially un-changed, critical concentration fluctuations increase as the phase boundary and plait point are approached. In this report, we present our first measurements of the kinetics of isopycnic phase separation for ternary mixtures of H2O/CO2/C8E5.

  3. MicroRNA-214 protects cardiac myocytes against H2O2-induced injury.

    PubMed

    Lv, Guangwei; Shao, Suxia; Dong, Hua; Bian, Xiaohua; Yang, Xingwei; Dong, Shimin

    2014-01-01

    Reactive oxygen species (ROS)-induced cardiac myocyte injury resulting from changes in the expression levels of multiple genes plays a critical role in the pathogenesis of numerous heart diseases. The purpose of this study was to determine the potential roles of microRNA-214 (miR-214) in hydrogen peroxide (H2O2)-mediated gene regulation in cardiac myocytes. In this study, we used quantitative real-time RT-PCR (qRT-PCR) to demonstrate that miR-214 was upregulated in cardiac myocytes after treatment with H2O2. We transfected cells with pre-miR-214 to upregulate miR-214 expression and transfected cells with a miR-214 inhibitor (anti-miR-214) to downregulate miR-214 expression. H2O2-induced cardiac cell apoptosis was detected by flow cytometry. The level of apoptosis was increased by the miR-214 inhibitor and decreased by pre-miR-214. Therefore, we believe that miR-214 plays a positive role in H2O2-induced cardiac cell apoptosis. Phosphatase and tensin homolog deleted on chromosome 10 (PTEN) is constitutively active and is considered to be the primary downregulator of the pro-oncogenic PI3K/Akt pathway. Western blot analysis revealed that the expression of the PTEN protein in cardiac myocytes decreased after H2O2 induction. Anti-miR-214 increased PTEN protein expression level, in contrast, pre-miR-214 decreased the PTEN protein expression level in cultured cardiac myocytes. These results indicate that PTEN is regulated by miR-214 and serves as an important target of miR-214 in cardiac myocytes. In conclusion, miR-214 is sensitive to H2O2 stimulation, and miR-214 protects cardiac myocytes against H2O2-induced injury via one of its targets, PTEN.

  4. Measurement and Prediction of H2O Outgassing Kinetics from Silica-Filled Polydimethylsiloxane TR55 and S5370

    SciTech Connect

    Dinh, L N; Burnham, A K; Schildbach, M A; Smith, R A; Maxwell, R S; Balazs, B; McLean II, W

    2006-08-28

    The isoconversional technique was employed for the measurement and prediction of H2O outgassing kinetics from silica-filled polydimethylsiloxane TR55 and S5370 in a vacuum or dry environment. Isoconversional analysis indicates that the energy barrier for H2O release from TR55 and S5370 is an increasing function of the fractional H2O release. This can be interpreted as the release of H2O from physisorbed water and then chemisorbed water with decreasing OH density from the surfaces of the embedded silica particles. Model independent predictions of H2O outgassing based on the measured kinetics follow the trend of actual isothermal outgassing at elevated temperatures, and suggest gradual outgassing in dry storage over many decades at low temperatures for both TR55 and S5370.

  5. Partitioning of H2O in the mantle transition zone and lower mantle

    NASA Astrophysics Data System (ADS)

    Inoue, T.; Katsuda, M.; Yurimoto, H.

    2008-12-01

    Water is the most abundant volatile component in the Earth, and the presence of H2O into the mantle minerals affects the elastic and rheological properties. It is well known that wadsleyite and ringwoodite, which are the most abundant minerals in the mantle transition zone, can accommodate significant amount (~3 wt%) of H2O in the crystal structures (e.g. Inoue et al., 1995; Kohlstedt et al, 1996). On the other hand, majorite garnet is the second abundant mineral in the mantle transition zone, and the H2O content was reported to be ~0.2 wt% (Katayama et al., 2003). It is important to know the maximum H2O storage capacity in the minerals, and also to know the partitioning of H2O in the mantle minerals to evaluate the water content in the Earth with temperature and pressure dependence. We have conducted high pressure experiment to determine the partitioning of H2O between wadsleyite, ringwoodite, perovskite and garnet. High-pressure experiments were conducted by MA-8 type (Kawai-type) high-pressure apparatus in Ehime University. We used pyrolite composition which was approximated with respect to five major components, CaO, MgO, FeO, Al2O3 and SiO2. Three starting H2O contents, 2.9, 8.3 and 15.6 wt% were selected. The experimental P-T conditions were 14-23 GPa and 1200-1700°C. The recovered samples were polished and then the chemical compositions were determined by EPMA in Ehime University and the water contents of minerals were measured by SIMS in Hokkaido University. The H2O contents of wadsleyite and ringwoodite decreased with increasing temperature, which is consistent with Ohtani et al. (2000). However the H2O content of majorite did not change so much with increasing temperature. As the results, the partition coefficients between wadsleyite and majorite, and between ringwoodite and majorite decreased with increasing temperature. Further details will be presented.

  6. Modeling the H2O submillimeter emission in extragalactic sources

    NASA Astrophysics Data System (ADS)

    González-Alfonso, E.; Fischer, J.; Aalto, S.; Falstad, N.

    2014-07-01

    Recent observational studies have shown that H2O emission at (rest) submillimeter wavelengths is ubiquitous in infrared galaxies, both in the local and in the early Universe, suggestive of far-infrared pumping of H2O by dust in warm regions. In this work, models are presented that show that (i) the highest-lying H2O lines (Eupper > 400 K) are formed in very warm (Tdust ≳ 90 K) regions and require high H2O columns (NH2O ≳ 3 × 1017 cm-2), while lower lying lines can be efficiently excited with Tdust ~ 45-75 K and NH2O ~ (0.5-2) × 1017 cm-2; (ii) significant collisional excitation of the lowest lying (Eupper < 200 K) levels, which enhances the overall LH2O-LIR ratios, is identified in sources where the ground-state para-H2O 111-000 line is detected in emission; (iii) the H2O-to-infrared (8-1000 μm) luminosity ratio is expected to decrease with increasing Tdust for all lines with Eupper ≲ 300 K, as has recently been reported in a sample of LIRGs, but increases with Tdust for the highest lying H2O lines (Eupper > 400 K); (iv) we find theoretical upper limits for LH2O/LIR in warm environments, owing to H2O line saturation; (v) individual models are presented for two very different prototypical galaxies, the Seyfert 2 galaxy NGC 1068 and the nearest ultraluminous infrared galaxy Arp 220, showing that the excited submillimeter H2O emission is dominated by far-infrared pumping in both cases; (vi) the LH2O - LIR correlation previously reported in observational studies indicates depletion or exhaustion time scales, tdep = Σgas/ ΣSFR, of ≲12 Myr for star-forming sources where lines up to Eupper = 300 K are detected, in agreement with the values previously found for (U)LIRGs from HCN millimeter emission. We conclude that the submillimeter H2O line emission other than the para-H2O 111-000 transition is pumped primarily by far-infrared radiation, though some collisional pumping may contribute to the low-lying para-H2O 202-111 line, and that collisional pumping of the

  7. Descent with Modification: Thermal Reactions of Subsurface H2O2 of Relevance to Icy Satellites and Other Small Bodies

    NASA Technical Reports Server (NTRS)

    Hudson, Reggie L.; Loefler, Mark J.

    2012-01-01

    Laboratory experiments have demonstrated that magnetospheric radiation in the Jovian system drives reaction chemistry in ices at temperatures relevant to Europa and other icy satellites. Similarly, cosmic radiation (mainly protons) acting on cometary and interstellar ices can promote extensive chemical change. Among the products that have been identified in irradiated H20-ice is hydrogen peroxide (H202), which has been observed on Europa and is suspected on other worlds. Although the infrared spectra and radiation chemistry of H2O2-containing ices are well documented, the thermally-induced solid-phase chemistry of H2O2 is largely unknown. Therefore, in this presentation we report new laboratory results on reactions at 50 - 130 K in ices containing H2O2 and other molecules, both in the presence and absence of H2O. As an example of our results, we find that warming H2O + H2O2 + SO2 ices promotes SO2 oxidation to SO4(2-). We suspect that such redox chemistry may explain some of the observations related to the presence and distribution of H2O2 across Europa's surface as well as the lack of H2O2 on Ganymede and Callisto. If other molecules prove to be just as reactive with frozen H2O2 then it may explain why H2O2 has been absent from surfaces of many of the small icy bodies that are known to be exposed to ionizing radiation. Our results also have implications for the survival of H2O2 as it descends towards a subsurface ocean on Europa.

  8. FLYING-WATER Renewables-H2-H2O TERRAFORMING: PERMANENT Drought(s)-Elimination FOREVER!!!

    NASA Astrophysics Data System (ADS)

    Ertl, G.; Alefeld, G.; Youdelis, W.; Radd, H.; Oertle, G.; Siegel, Edward

    2011-03-01

    "H2O H2O everywhere; ne'er a drop to drink"[Coleridge(1798)]; now: "H2 H2 everywhere; STILL ne'er a drop to drink": ONLY H2 (or methane CH4) can be FLYING-WATER(F-W) chemical-rain-in-pipelines Hindenberg-effect (H2-UP;H2O-DOWN): {O/H2O}=[16]/[18] 90 % ; O already in air uphill; NO H2O pumping need! In global-warming driven H2O-starved glacial-melting world, rescue is possible ONLY by Siegel [{3rd Intl. Conf. Alt.-Energy }(1980)-vol.5/p.459!!!] Renewables-H2-H2O purposely flexible versatile agile customizable scaleable retrofitable integrated operating-system. Rosenfeld[Science 315,1396(3/9/2007)]-Biello [Sci.Am.(3/9/2007)] crucial geomorph-ology which ONLY maximal-buoyancy H2 can exploit, to again make "Mountains into Fountains", ``upthrust rocks trapping the clouds to precipitate their rain/snow/H2O'': "terraforming"(and ocean-rebasificaton!!!) Siegel proprietary magnetic-hydrogen-valve (MHV) permits H2 flow in already in-ground dense BCC/ferritic-steels pipelines-network (NO new infrastructure) counters Tromp[Science 300,1740(2003)] dire warning of global-pandemics (cancers/ blindness/famine) Hydrogen-economy CATASTROPHIC H2 ozone-layer destruction sobering cavat to dangerous H2-automotion-economy panacea hype!!!

  9. H2O outgassing from silica-filled polysiloxane TR55.

    PubMed

    Dinh, L N; Schildbach, M A; Maxwell, R S; Siekhaus, W J; Balazs, B; McLean, W

    2004-06-01

    Temperature-programmed desorption/decomposition (TPD) was employed to obtain the moisture content and outgassing kinetics of TR55, a silica-filled cross-linked polysiloxane. The total moisture content of TR55 in the as-received state and after 20-30 min of vacuum pumping in the load-lock prior to TPD was measured to be on the order of 0.35 wt%. Physisorbed H(2)O and chemisorbed H(2)O account for about 13.2 and 86.8%, respectively, of the 0.35 wt% measured moisture content. H(2)O outgassing models based on the kinetics measured from TPD experiments suggest that loosely bound chemisorbed water outgasses in a dry environment slowly but continuously over many decades at or a little above room temperature. However, physisorbed water can be easily pumped out in a matter of hours at around 400 K.

  10. Development of TDLAS sensor for diagnostics of CO, H2O and soot concentrations in reactor core of pilot-scale gasifier

    NASA Astrophysics Data System (ADS)

    Sepman, A.; Ögren, Y.; Gullberg, M.; Wiinikka, H.

    2016-02-01

    This paper reports on the development of the tunable diode laser absorption spectroscopy sensor near 4350 cm-1 (2298 nm) for measurements of CO and H2O mole fractions and soot volume fraction under gasification conditions. Due to careful selection of the molecular transitions [CO ( υ″ = 0 → υ' = 2) R34-R36 and H2O at 4349.337 cm-1], a very weak (negligible) sensitivity of the measured species mole fractions to the temperature distribution inside the high-temperature zone (1000 K < T < 1900 K) of the gasification process is achieved. The selected transitions are covered by the tuning range of single diode laser. The CO and H2O concentrations measured in flat flames generally agree better than 10 % with the results of 1-D flame simulations. Calibration-free absorption measurements of studied species in the reactor core of atmospheric pilot-scale entrained-flow gasifier operated at 0.1 MW power are reported. Soot concentration is determined from the measured broadband transmittance. The estimated uncertainties in the reactor core CO and H2O measurements are 15 and 20 %, respectively. The reactor core average path CO mole fractions are in quantitative agreement with the µGC CO concentrations sampled at the gasifier output.

  11. Atmospheric H2O2 measurement: comparison of cold trap method with impinger bubbling method.

    PubMed

    Sakugawa, H; Kaplan, I R

    1987-01-01

    Collection of atmospheric H2O2 was performed by a cold trap method using dry ice-acetone as the refrigerant. The air was drawn by a pump into a glass gas trap immersed in the dry ice-acetone slush in a dewar flask at a flow rate of 2.5 l min-1 for approximately 2 h. Collection efficiency was > 99% and negligible interferences by O3, SO2 or organic matter with the collected H2O2 in the trap were observed. This method was compared with the air impinger bubbling method which has been previously described (Kok et al., 1978a, b, Envir. Sci. Technol. 12, 1072-1080). The measured total peroxide (H2O2 + organic peroxide) values in a series of aim samples collected by the impinger bubbling method (0.06-3.7 ppb) were always higher than those obtained by the cold trap method (0.02-1.2 ppb). Laboratory experiments suggest that the difference in values between the two methods probably results from the aqueous phase generation of H2O2 and organic peroxide in the impinger solution by a reaction of atmospheric O3 with olefinic and aromatic compounds. If these O3-organic compound reactions which occur in the impinger also occur in aqueous droplets in the atmosphere, the process could be very important for aqueous phase generation of H2O2 in clouds and rainwater.

  12. Atmospheric H2O2 measurement: comparison of cold trap method with impinger bubbling method

    NASA Technical Reports Server (NTRS)

    Sakugawa, H.; Kaplan, I. R.

    1987-01-01

    Collection of atmospheric H2O2 was performed by a cold trap method using dry ice-acetone as the refrigerant. The air was drawn by a pump into a glass gas trap immersed in the dry ice-acetone slush in a dewar flask at a flow rate of 2.5 l min-1 for approximately 2 h. Collection efficiency was > 99% and negligible interferences by O3, SO2 or organic matter with the collected H2O2 in the trap were observed. This method was compared with the air impinger bubbling method which has been previously described (Kok et al., 1978a, b, Envir. Sci. Technol. 12, 1072-1080). The measured total peroxide (H2O2 + organic peroxide) values in a series of aim samples collected by the impinger bubbling method (0.06-3.7 ppb) were always higher than those obtained by the cold trap method (0.02-1.2 ppb). Laboratory experiments suggest that the difference in values between the two methods probably results from the aqueous phase generation of H2O2 and organic peroxide in the impinger solution by a reaction of atmospheric O3 with olefinic and aromatic compounds. If these O3-organic compound reactions which occur in the impinger also occur in aqueous droplets in the atmosphere, the process could be very important for aqueous phase generation of H2O2 in clouds and rainwater.

  13. Active sites and mechanisms for H2O2 decomposition over Pd catalysts

    PubMed Central

    Plauck, Anthony; Stangland, Eric E.; Dumesic, James A.; Mavrikakis, Manos

    2016-01-01

    A combination of periodic, self-consistent density functional theory (DFT-GGA-PW91) calculations, reaction kinetics experiments on a SiO2-supported Pd catalyst, and mean-field microkinetic modeling are used to probe key aspects of H2O2 decomposition on Pd in the absence of cofeeding H2. We conclude that both Pd(111) and OH-partially covered Pd(100) surfaces represent the nature of the active site for H2O2 decomposition on the supported Pd catalyst reasonably well. Furthermore, all reaction flux in the closed catalytic cycle is predicted to flow through an O–O bond scission step in either H2O2 or OOH, followed by rapid H-transfer steps to produce the H2O and O2 products. The barrier for O–O bond scission is sensitive to Pd surface structure and is concluded to be the central parameter governing H2O2 decomposition activity. PMID:27006504

  14. Atmospheric H2O2 measurement: comparison of cold trap method with impinger bubbling method.

    PubMed

    Sakugawa, H; Kaplan, I R

    1987-01-01

    Collection of atmospheric H2O2 was performed by a cold trap method using dry ice-acetone as the refrigerant. The air was drawn by a pump into a glass gas trap immersed in the dry ice-acetone slush in a dewar flask at a flow rate of 2.5 l min-1 for approximately 2 h. Collection efficiency was > 99% and negligible interferences by O3, SO2 or organic matter with the collected H2O2 in the trap were observed. This method was compared with the air impinger bubbling method which has been previously described (Kok et al., 1978a, b, Envir. Sci. Technol. 12, 1072-1080). The measured total peroxide (H2O2 + organic peroxide) values in a series of aim samples collected by the impinger bubbling method (0.06-3.7 ppb) were always higher than those obtained by the cold trap method (0.02-1.2 ppb). Laboratory experiments suggest that the difference in values between the two methods probably results from the aqueous phase generation of H2O2 and organic peroxide in the impinger solution by a reaction of atmospheric O3 with olefinic and aromatic compounds. If these O3-organic compound reactions which occur in the impinger also occur in aqueous droplets in the atmosphere, the process could be very important for aqueous phase generation of H2O2 in clouds and rainwater. PMID:11542111

  15. Atmospheric H 2O 2 measurement: Comparison of cold trap method with impinger bubbling method

    NASA Astrophysics Data System (ADS)

    Sakugawa, Hiroshi; Kaplan, Isaac R.

    Collection of atmospheric H 2O 2 was performed by a cold trap method using dry ice-acetone as the refrigerant. The air was drawn by a pump into a glass gas trap immersed in the dry ice-acetone slush in a dewar flask at a flow rate of 2.5ℓ -1 for ~ 2 h. Collection efficiency was > 99% and negligible interferences by O 3, SO 2 or organic matter with the collected H 2O 2 in the trap were observed. This method was compared with the air impinger bubbling method which has been previously described (Kok et al., 1978a, b, Envir, Sci. Technol.12, 1072-1080). The measured total peroxide (H 2O 2 + organic peroxide) values in a series of air samples collected by the impinger bubbling method (0.06-3.7 ppb) were always higher than those obtained by the cold trap method (0.02-1.2 ppb). Laboratory experiments suggest that the difference in values between the two methods probably results from the aqueous phase generation of H 2O 2 and organic peroxide in the impinger solution by a reaction of atmospheric O 3 with olefinic and aromatic compounds. If these O 3-organic compound reactions which occur in the impinger also occur in aqueous droplets in the atmosphere, the process could be very important for aqueous phase generation of H 2O 2 in clouds and rainwater.

  16. Modelling the Effects of H2O Activity and Bulk-Rock H2O Content on the Development of Clinopyroxene-Bearing Garnet Amphibolite Assemblages at Mica Creek, British Columbia

    NASA Astrophysics Data System (ADS)

    Tinkham, D. K.; Ghent, E. D.

    2004-05-01

    The orthopyroxene-free assemblage garnet + clinopyroxene + hornblende + plagioclase + quartz is widespread in metabasaltic rocks in the sillimanite zone at Mica Creek, British Columbia. The lower temperature limit at which this assemblage is stable is on the high grade side of the kyanite-sillimanite transition and occurs within the muscovite-sillimanite-quartz and K-feldspar sillimanite zone. This assemblage was investigated by constructing a series of pseudosections for individual bulk-rock compositions in the chemical system TiO2-Na2O-CaO-FeO-MgO-Al2O3-SiO2-H2O. The effect of reduced H2O activity on the development of this assemblage is illustrated in a series of fluid saturated P-T pseudosections with varying H2O activity. The pseudosections are in agreement with previous studies that indicate the activity of H2O in a fluid phase must be significantly reduced from unity ( < 0.5 ) to develop the observed assemblage at amphibolite facies conditions. If it is assumed that these amphibolites were infiltrated by fluids derived from dehydration reactions in surrounding psammites and pelites, it is unlikely any fluid phase in the amphibolites would have an activity of H2O low enough to develop this assemblage. The effect of H2O on the development of this assemblage can be viewed in an alternative manner. We have constructed isobaric temperature-composition pseudosections by varying the amount of bulk-rock H2O to illustrate the effect of variable H2O content. The pseudosections clearly show that development of this assemblage can occur at the P-T conditions appropriate for Mica Creek at low bulk-rock H2O content (below the H2O-saturation limit), implying the assemblage developed in the absence of an H2O fluid phase. Infiltration of a low H2O activity fluid phase from surrounding psammites and pelites is therefore not required. Amphibolites in the Mica Creek region at lower grade (garnet zone) generally lack stable chlorite. This possibly indicates that these rocks were

  17. Upper limits for the rate constant for the reaction Br + H2O2 yields HB2 + HO2

    NASA Technical Reports Server (NTRS)

    Leu, M.-T.

    1980-01-01

    Upper limits for the rate constant for the reaction Br + H2O2 yields HBr + HO2 have been measured over the temperature range 298 to 417 K in a discharge flow system using a mass spectrometer as a detector. Results are k sub 1 less than 1.5 x 10 to the -15th power cu cm/s at 298 K and k sub 1 less than 3.0 x 10 to the -15th power cu cm/s at 417 K, respectively. The implication to stratospheric chemistry is discussed.

  18. Interaction energy and the shift in OH stretch frequency on hydrogen bonding for the H2O --> H2O, CH3OH --> H2O, and H2O --> CH3OH dimers.

    PubMed

    Campen, Richard Kramer; Kubicki, James D

    2010-04-15

    The ability to use calculated OH frequencies to assign experimentally observed peaks in hydrogen bonded systems hinges on the accuracy of the calculation. Here we test the ability of several commonly employed model chemistries--HF, MP2, and several density functionals paired with the 6-31+G(d) and 6-311++G(d,p) basis sets--to calculate the interaction energy (D(e)) and shift in OH stretch fundamental frequency on dimerization (delta(nu)) for the H(2)O --> H(2)O, CH(3)OH --> H(2)O, and H(2)O --> CH(3)OH dimers (where for X --> Y, X is the hydrogen bond donor and Y the acceptor). We quantify the error in D(e) and delta(nu) by comparison to experiment and high level calculation and, using a simple model, evaluate how error in D(e) propagates to delta(nu). We find that B3LYP and MPWB1K perform best of the density functional methods studied, that their accuracy in calculating delta(nu) is approximately 30-50 cm(-1) and that correcting for error in D(e) does little to heighten agreement between the calculated and experimental delta(nu). Accuracy of calculated delta(nu) is also shown to vary as a function of hydrogen bond donor: while the PBE and TPSS functionals perform best in the calculation of delta(nu) for the CH(3)OH --> H(2)O dimer their performance is relatively poor in describing H(2)O --> H(2)O and H(2)O --> CH(3)OH.

  19. Greywater treatment by UVC/H2O2.

    PubMed

    Chin, W H; Roddick, F A; Harris, J L

    2009-09-01

    Greywater treatment by UVC/H(2)O(2) was investigated with regard to the removal of chemical oxygen demand (COD). A COD reduction from 225 to 30 mgl(-1) (overall removal of 87%) was achieved after settling overnight and subsequent irradiation for 3h with 10mM H(2)O(2). Most of the contaminants were removed by oxidation since only 13% COD was removed by settlement. The removal of COD in the greywater followed a second-order kinetic equation, r=0.0637[COD][H(2)O(2)], up to 10mM H(2)O(2). A slightly enhanced COD removal was observed at the initial pH of 10 compared with pH 3 and 7. This was attributed to the dissociation of H(2)O(2) to O(2)H(-). The treatment was not affected by total concentration of carbonate (c(T)) of at least 3 mM, above which operation between pH 3 and 5 was essential. The initial biodegradability of the settled greywater (as BOD(5):COD) was 0.22. After 2h UVC/H(2)O(2) treatment, a higher proportion of the residual contaminants was biodegradable (BOD(5):COD=0.41) which indicated its potential as a pre-treatment for a biological process. PMID:19656542

  20. Greywater treatment by UVC/H2O2.

    PubMed

    Chin, W H; Roddick, F A; Harris, J L

    2009-09-01

    Greywater treatment by UVC/H(2)O(2) was investigated with regard to the removal of chemical oxygen demand (COD). A COD reduction from 225 to 30 mgl(-1) (overall removal of 87%) was achieved after settling overnight and subsequent irradiation for 3h with 10mM H(2)O(2). Most of the contaminants were removed by oxidation since only 13% COD was removed by settlement. The removal of COD in the greywater followed a second-order kinetic equation, r=0.0637[COD][H(2)O(2)], up to 10mM H(2)O(2). A slightly enhanced COD removal was observed at the initial pH of 10 compared with pH 3 and 7. This was attributed to the dissociation of H(2)O(2) to O(2)H(-). The treatment was not affected by total concentration of carbonate (c(T)) of at least 3 mM, above which operation between pH 3 and 5 was essential. The initial biodegradability of the settled greywater (as BOD(5):COD) was 0.22. After 2h UVC/H(2)O(2) treatment, a higher proportion of the residual contaminants was biodegradable (BOD(5):COD=0.41) which indicated its potential as a pre-treatment for a biological process.

  1. Thermochemical Kinetics of H2O and HNO3 on crystalline Nitric Acid Hydrates (alpha-, beta-NAT, NAD) in the range 175-200 K

    NASA Astrophysics Data System (ADS)

    Rossi, Michel J.; Iannarelli, Riccardo

    2015-04-01

    The growth of NAT (Nitric Acid Trihydrate, HNO3x3H2O) and NAD (Nitric Acid Dihydrate, HNO3x2H2O) on an ice substrate, the evaporative lifetime of NAT and NAD as well as the interconversion of alpha- and beta-NAT competing with evaporation and growth under UT/LS conditions depends on the interfacial kinetics of H2O and HNO3 vapor on the condensed phase. Despite the existence of some literature results we have embarked on a systematic investigation of the kinetics using a multidiagnostic experimental approach enabled by the simultaneous observation of both the gas (residual gas mass spectrometry) as well as the condensed phase (FTIR absorption in transmission). We report on thermochemically consistent mass accommodation coefficients alpha and absolute evaporation rates Rev/molecule s-1cm-3 as a function of temperature which yields the corresponding vapor pressures of both H2O and HNO3 in equilibrium with the crystalline phases, hence the term thermochemical kinetics. These results have been obtained using a stirred flow reactor (SFR) using a macroscopic pure ice film of 1 micron or so thickness as a starting substrate mimicking atmospheric ice particles and are reported in a phase diagram specifically addressing UT (Upper Troposphere)/LS (Lower Stratosphere) conditions as far as temperature and partial pressures are concerned. The experiments have been performed either at steady-state flow conditions or in transient supersaturation using a pulsed solenoid valve in order to generate gas pulses whose decay were subsequently monitored in real time. Special attention has been given to the effect of the stainless-steel vessel walls in that Langmuir adsorption isotherms for H2O and HNO3 have been used to correct for wall-adsorption of both probe gases. Typically, the accommodation coefficients of H2O and HNO3 are similar throughout the temperature range whereas the rates of evaporation Rev of H2O are significantly larger than for HNO3 thus leading to the difference in

  2. Heterogeneous kinetics of H2O, HNO3 and HCl on HNO3 hydrates (α-NAT, β-NAT, NAD) in the range 175-200 K

    NASA Astrophysics Data System (ADS)

    Iannarelli, Riccardo; Rossi, Michel J.

    2016-09-01

    Experiments on the title compounds have been performed using a multidiagnostic stirred-flow reactor (SFR) in which the gas phase as well as the condensed phase has been simultaneously investigated under stratospheric temperatures in the range 175-200 K. Wall interactions of the title compounds have been taken into account using Langmuir adsorption isotherms in order to close the mass balance between deposited and desorbed (recovered) compounds. Thin solid films at 1 µm typical thickness have been used as a proxy for atmospheric ice particles and have been deposited on a Si window of the cryostat, with the optical element being the only cold point in the deposition chamber. Fourier transform infrared (FTIR) absorption spectroscopy in transmission as well as partial and total pressure measurement using residual gas mass spectrometry (MS) and sensitive pressure gauges have been employed in order to monitor growth and evaporation processes as a function of temperature using both pulsed and continuous gas admission and monitoring under SFR conditions. Thin solid H2O ice films were used as the starting point throughout, with the initial spontaneous formation of α-NAT (nitric acid trihydrate) followed by the gradual transformation of α- to β-NAT at T > 185 K. Nitric acid dihydrate (NAD) was spontaneously formed at somewhat larger partial pressures of HNO3 deposited on pure H2O ice. In contrast to published reports, the formation of α-NAT proceeded without prior formation of an amorphous HNO3 / H2O layer and always resulted in β-NAT. For α- and β-NAT, the temperature-dependent accommodation coefficient α(H2O) and α(HNO3), the evaporation flux Jev(H2O) and Jev(HNO3) and the resulting saturation vapor pressure Peq(H2O) and Peq(HNO3) were measured and compared to binary phase diagrams of HNO3 / H2O in order to afford a thermochemical check of the kinetic parameters. The resulting kinetic and thermodynamic parameters of activation energies for evaporation (Eev) and

  3. Interhemispheric Differences in Polar Stratospheric HNO3, H2O, CIO, and O3.

    PubMed

    Santee, M L; Read, W G; Waters, J W; Froidevaux, L; Manney, G L; Flower, D A; Jarnot, R F; Harwood, R S; Peckham, G E

    1995-02-10

    Simultaneous global measurements of nitric acid (HNO(3)), water (H(2)O), chlorine monoxide (CIO), and ozone (O(3)) in the stratosphere have been obtained over complete annual cycles in both hemispheres by the Microwave Limb Sounder on the Upper Atmosphere Research Satellite. A sizeable decrease in gas-phase HNO(3) was evident in the lower stratospheric vortex over Antarctica by early June 1992, followed by a significant reduction in gas-phase H(2)O after mid-July. By mid-August, near the time of peak CIO, abundances of gas-phase HNO(3) and H(2)O were extremely low. The concentrations of HNO(3) and H(2)O over Antarctica remained depressed into November, well after temperatures in the lower stratosphere had risen above the evaporation threshold for polar stratospheric clouds, implying that denitrification and dehydration had occurred. No large decreases in either gas-phase HNO(3) or H(2)O were observed in the 1992-1993 Arctic winter vortex. Although CIO was enhanced over the Arctic as it was over the Antarctic, Arctic O(3) depletion was substantially smaller than that over Antarctica. A major factor currently limiting the formation of an Arctic ozone "hole" is the lack of denitrification in the northern polar vortex, but future cooling of the lower stratosphere could lead to more intense denitrification and consequently larger losses of Arctic ozone.

  4. Interhemispheric differences in polar stratospheric HNO3, H2O, ClO, and O3

    NASA Technical Reports Server (NTRS)

    Santee, M. L.; Read, W. G.; Waters, J. W.; Froidevaux, L.; Manney, G. L.; Flower, D. A.; Jarnot, R. F.; Harwood, R. S.; Peckham, G. E.

    1995-01-01

    Simultaneous global measurements of nitric acid (HNO3), water (H2O), chlorine monoxide (ClO), and ozone (O3) in the stratosphere have been obtained over complete annual cycles in both hemispheres by the Microwave Limb Sounder on the Upper Atmosphere Research Satellite. A sizeable decrease in gas-phase HNO3 was evident in the lower stratospheric vortex over Antarctica by early June 1992, followed by a significant reduction in gas-phase H2O after mid-July. By mid-August, near the time of peak ClO, abundances of gas-phase HNO3 and H2O were extremely low. The concentrations of HNO3 and H2O over Antarctica remained depressed into November, well after temperatures in the lower stratosphere had risen above the evaporation threshold for polar stratospheric clouds, implying that denitrification and dehydration had occurred. No large decreases in either gas-phase HNO3 or H2O were observed in the 1992-1993 Arctic winter vortex. Although ClO was enhanced over the Arctic as it was over the Antarctic, Arctic O3 depletion was substantially smaller than that over Antarctica. A major factor currently limiting the formation of an Arctic ozone 'hole' is the lack of denitrification in the northern polar vortex, but future cooling of the lower stratosphere could lead to more intense denitrification and consequently larger losses of Arctic ozone.

  5. Thermodynamics and Mass Transport in Multicomponent, Multiphase H2O Systems of Planetary Interest

    NASA Astrophysics Data System (ADS)

    Lu, Xinli; Kieffer, Susan W.

    2009-05-01

    Heat and mass transport in low-temperature, low-pressure H2O systems are important processes on Earth, and on a number of planets and moons in the Solar System. In most occurrences, these systems will contain other components, the so-called noncondensible gases, such as CO2, CO, SO2, CH4, and N2. The presence of the noncondensible components can greatly alter the thermodynamic properties of the phases and their flow properties as they move in and on the planets. We review various forms of phase diagrams that give information about pressure-temperature-volume-entropy-enthalpy-composition conditions in these complex systems. Fluid dynamic models must be coupled to the thermodynamics to accurately describe flow in gas-driven liquid and solid systems. The concepts are illustrated in detail by considering flow and flow instabilities such as geysering in modern geothermal systems on Earth, paleofluid systems on Mars, and cryogenic ice-gas systems on Mars and Enceladus. We emphasize that consideration of single-component end-member systems often leads to conclusions that exclude many qualitatively and quantitatively important phenomena.

  6. Effects of a single water molecule on the OH + H2O2 reaction.

    PubMed

    Buszek, Robert J; Torrent-Sucarrat, Miquel; Anglada, Josep M; Francisco, Joseph S

    2012-06-21

    The effect of a single water molecule on the reaction between H(2)O(2) and HO has been investigated by employing MP2 and CCSD(T) theoretical approaches in connection with the aug-cc-PVDZ, aug-cc-PVTZ, and aug-cc-PVQZ basis sets and extrapolation to an ∞ basis set. The reaction without water has two elementary reaction paths that differ from each other in the orientation of the hydrogen atom of the hydroxyl radical moiety. Our computed rate constant, at 298 K, is 1.56 × 10(-12) cm(3) molecule(-1) s(-1), in excellent agreement with the suggested value by the NASA/JPL evaluation. The influence of water vapor has been investigated by considering either that H(2)O(2) first forms a complex with water that reacts with hydroxyl radical or that H(2)O(2) reacts with a previously formed H(2)O·OH complex. With the addition of water, the reaction mechanism becomes much more complex, yielding four different reaction paths. Two pathways do not undergo the oxidation reaction but an exchange reaction where there is an interchange between H(2)O(2)·H(2)O and H(2)O·OH complexes. The other two pathways oxidize H(2)O(2), with a computed total rate constant of 4.09 × 10(-12) cm(3) molecule(-1) s(-1) at 298 K, 2.6 times the value of the rate constant of the unassisted reaction. However, the true effect of water vapor requires taking into account the concentration of the prereactive bimolecular complex, namely, H(2)O(2)·H(2)O. With this consideration, water can actually slow down the oxidation of H(2)O(2) by OH between 1840 and 20.5 times in the 240-425 K temperature range. This is an example that demonstrates how water could be a catalyst in an atmospheric reaction in the laboratory but is slow under atmospheric conditions. PMID:22455374

  7. Effects of a single water molecule on the OH + H2O2 reaction.

    PubMed

    Buszek, Robert J; Torrent-Sucarrat, Miquel; Anglada, Josep M; Francisco, Joseph S

    2012-06-21

    The effect of a single water molecule on the reaction between H(2)O(2) and HO has been investigated by employing MP2 and CCSD(T) theoretical approaches in connection with the aug-cc-PVDZ, aug-cc-PVTZ, and aug-cc-PVQZ basis sets and extrapolation to an ∞ basis set. The reaction without water has two elementary reaction paths that differ from each other in the orientation of the hydrogen atom of the hydroxyl radical moiety. Our computed rate constant, at 298 K, is 1.56 × 10(-12) cm(3) molecule(-1) s(-1), in excellent agreement with the suggested value by the NASA/JPL evaluation. The influence of water vapor has been investigated by considering either that H(2)O(2) first forms a complex with water that reacts with hydroxyl radical or that H(2)O(2) reacts with a previously formed H(2)O·OH complex. With the addition of water, the reaction mechanism becomes much more complex, yielding four different reaction paths. Two pathways do not undergo the oxidation reaction but an exchange reaction where there is an interchange between H(2)O(2)·H(2)O and H(2)O·OH complexes. The other two pathways oxidize H(2)O(2), with a computed total rate constant of 4.09 × 10(-12) cm(3) molecule(-1) s(-1) at 298 K, 2.6 times the value of the rate constant of the unassisted reaction. However, the true effect of water vapor requires taking into account the concentration of the prereactive bimolecular complex, namely, H(2)O(2)·H(2)O. With this consideration, water can actually slow down the oxidation of H(2)O(2) by OH between 1840 and 20.5 times in the 240-425 K temperature range. This is an example that demonstrates how water could be a catalyst in an atmospheric reaction in the laboratory but is slow under atmospheric conditions.

  8. An Investigation of Armenite, BaCa2Al6Si9O302H2O.H2O Molecules and H Bonding in Microporous Silicates

    NASA Astrophysics Data System (ADS)

    Geiger, C. A.; Gatta, G.; Xue, X.; McIntyre, G.

    2012-12-01

    strength of hydrogen bonding of the H2O molecules in microporous silicates does not appear to change greatly with decreasing temperatures from 300 K down to 10 K. The reason for this and also understanding better the ion-dipole interaction and its effect on H-bonding strength in Ca-quasi clusters need further study. The crystal structure of armenite viewed down [001] and [010].

  9. Ortho-para mixing hyperfine interaction in the H2O+ ion and nuclear spin equilibration.

    PubMed

    Tanaka, Keiichi; Harada, Kensuke; Oka, Takeshi

    2013-10-01

    The ortho to para conversion of water ion, H2O(+), due to the interaction between the magnetic moments of the unpaired electron and protons has been theoretically studied to calculate the spontaneous emission lifetime between the ortho- and para-levels. The electron spin-nuclear spin interaction term, Tab(SaΔIb + SbΔIa) mixes ortho (I = 1) and para (I = 0) levels to cause the "forbidden" ortho to para |ΔI| = 1 transition. The mixing term with Tab = 72.0 MHz is 4 orders of magnitude higher for H2O(+) than for its neutral counterpart H2O where the magnetic field interacting with proton spins is by molecular rotation rather than the free electron. The resultant 10(8) increase of ortho to para conversion rate possibly makes the effect of conversion in H2O(+) measurable in laboratories and possibly explains the anomalous ortho to para ratio recently reported by Herschel heterodyne instrument for the far-infrared (HIFI) observation. Results of our calculations show that the ortho ↔ para mixings involving near-degenerate ortho and para levels are high (∼10(-3)), but they tend to occur at high energy levels, ∼300 K. Because of the rapid spontaneous emission, such high levels are not populated in diffuse clouds unless the radiative temperature of the environment is very high. The low-lying 101 (para) and 111 (ortho) levels of H2O(+) are mixed by ∼10(-4) making the spontaneous emission lifetime for the para 101 → ortho 000 transition 520 years and 5200 years depending on the F value of the hyperfine structure. Thus the ortho ↔ para conversion due to the unpaired electron is not likely to seriously affect thermalization of interstellar H2O(+) unless either the radiative temperature is very high or number density of the cloud is very low.

  10. An Accurate Potential Energy Surface for H2O

    NASA Technical Reports Server (NTRS)

    Schwenke, David W.; Partridge, Harry; Langhoff, Stephen R. (Technical Monitor)

    1997-01-01

    We have carried out extensive high quality ab initio electronic structure calculations of the ground state potential energy surface (PES) and dipole moment function (DMF) for H2O. A small adjustment is made to the PES to improve the agreement of line positions from theory and experiment. The theoretical line positions are obtained from variational ro-vibrational calculations using the exact kinetic energy operator. For the lines being fitted, the root-mean-square error was reduced from 6.9 to 0.08 /cm. We were then able to match 30,092 of the 30,117 lines from the HITRAN 96 data base to theoretical lines, and 80% of the line positions differed less than 0.1 /cm. About 3% of the line positions in the experimental data base appear to be incorrect. Theory predicts the existence of many additional weak lines with intensities above the cutoff used in the data base. To obtain results of similar accuracy for HDO, a mass dependent correction to the PH is introduced and is parameterized by simultaneously fitting line positions for HDO and D2O. The mass dependent PH has good predictive value for T2O and HTO. Nonadiabatic effects are not explicitly included. Line strengths for vibrational bands summed over rotational levels usually agree well between theory and experiment, but individual line strengths can differ greatly. A high temperature line list containing about 380 million lines has been generated using the present PES and DMF

  11. An open path H2O/CO2 gas analyzer for eddy correlation systems: theory and design.

    PubMed

    Kidd, Gary

    2002-09-01

    A fast response, open path tunable diode laser absorption spectroscopy H2O/CO2 gas analyzer suitable for eddy correlation concentration measurements in near surface turbulent environments is presented. The turbulent temperature characteristics, analysis theory, analysis methods, design structure and specifications of this dual laser analyzer are described. A fiber connected optical head with folded optical path is used to extend the resolution to ppb levels for H2O at 1.3964 microm and CO2 at 2.014 microm. The Fourier (discrete cosine) transform absorbance ratio analysis methods are outlined along with the modifications for temperature and pressure measurements in turbulent flows. Synthesis of the reference absorbance function using measured temperature, pressure and the Hitran parameters is extended with incorporation of the Hitran parameters n, gamma temperature exponent and E'', lower state energy. Additionally, the mole fraction equation developed for this Hitran model is presented and an absolute calibration technique is outlined along with methods of calibration retention. Simulation results on mole fraction estimations and errors are presented for synthetic temperature and laser noise processes and are used to verify the specifications. PMID:12353686

  12. Mixed protein-templated luminescent metal clusters (Au and Pt) for H2O2 sensing

    PubMed Central

    2013-01-01

    A simple and cost-effective method to synthesize the luminescent noble metal clusters (Au and Pt) in chicken egg white aqueous solution at room temperature is reported. The red-emitting Au cluster is used as fluorescent probe for sensitive detection of H2O2. PMID:23601828

  13. Role of Metabolic H2O2 Generation

    PubMed Central

    Sies, Helmut

    2014-01-01

    Hydrogen peroxide, the nonradical 2-electron reduction product of oxygen, is a normal aerobic metabolite occurring at about 10 nm intracellular concentration. In liver, it is produced at 50 nmol/min/g of tissue, which is about 2% of total oxygen uptake at steady state. Metabolically generated H2O2 emerged from recent research as a central hub in redox signaling and oxidative stress. Upon generation by major sources, the NADPH oxidases or Complex III of the mitochondrial respiratory chain, H2O2 is under sophisticated fine control of peroxiredoxins and glutathione peroxidases with their backup systems as well as by catalase. Of note, H2O2 is a second messenger in insulin signaling and in several growth factor-induced signaling cascades. H2O2 transport across membranes is facilitated by aquaporins, denoted as peroxiporins. Specialized protein cysteines operate as redox switches using H2O2 as thiol oxidant, making this reactive oxygen species essential for poising the set point of the redox proteome. Major processes including proliferation, differentiation, tissue repair, inflammation, circadian rhythm, and aging use this low molecular weight oxygen metabolite as signaling compound. PMID:24515117

  14. Electrochemical, H2O2-Boosted Catalytic Oxidation System

    NASA Technical Reports Server (NTRS)

    Akse, James R.; Thompson, John O.; Schussel, Leonard J.

    2004-01-01

    An improved water-sterilizing aqueous-phase catalytic oxidation system (APCOS) is based partly on the electrochemical generation of hydrogen peroxide (H2O2). This H2O2-boosted system offers significant improvements over prior dissolved-oxygen water-sterilizing systems in the way in which it increases oxidation capabilities, supplies H2O2 when needed, reduces the total organic carbon (TOC) content of treated water to a low level, consumes less energy than prior systems do, reduces the risk of contamination, and costs less to operate. This system was developed as a variant of part of an improved waste-management subsystem of the life-support system of a spacecraft. Going beyond its original intended purpose, it offers the advantage of being able to produce H2O2 on demand for surface sterilization and/or decontamination: this is a major advantage inasmuch as the benign byproducts of this H2O2 system, unlike those of systems that utilize other chemical sterilants, place no additional burden of containment control on other spacecraft air- or water-reclamation systems.

  15. Adsorption, Desorption, and Displacement Kinetics of H2O and CO2 on TiO2(110)

    SciTech Connect

    Smith, R. Scott; Li, Zhenjun; Chen, Long; Dohnalek, Zdenek; Kay, Bruce D.

    2014-07-17

    The adsorption, desorption, and displacement kinetics of H2O and CO2 on TiO2(110) are investigated using temperature programmed desorption (TPD) and molecular beam techniques. The TPD spectra for both H2O and CO2 have well-resolved peaks corresponding to desorption from bridge-bonded oxygen (BBO), Ti, and oxygen vacancies (VO) sites in order of increasing peak temperature. Analysis of the saturated monolayer peak for both species reveals that the corresponding adsorption energies on all sites are greater for H2O and for CO2. Sequential dosing of H2O and CO2 reveals that, independent of the dose order, H2O molecules will displace CO2 in order to occupy the highest energy binding sites available. Isothermal experiments show that the displacement of CO2 by H2O occurs between 75 and 80 K. Further analysis shows that a ratio of 4 H2O to 3 CO2 molecules is needed to displace CO2 from the TiO2(110) surface.

  16. Crystal structures of Sr(ClO4)2·3H2O, Sr(ClO4)2·4H2O and Sr(ClO4)2·9H2O.

    PubMed

    Hennings, Erik; Schmidt, Horst; Voigt, Wolfgang

    2014-12-01

    The title compounds, strontium perchlorate trihydrate {di-μ-aqua-aquadi-μ-perchlorato-strontium, [Sr(ClO4)2(H2O)3] n }, strontium perchlorate tetra-hydrate {di-μ-aqua-bis-(tri-aqua-diperchloratostrontium), [Sr2(ClO4)4(H2O)8]} and strontium perchlorate nona-hydrate {hepta-aqua-diperchloratostrontium dihydrate, [Sr(ClO4)2(H2O)7]·2H2O}, were crystallized at low temperatures according to the solid-liquid phase diagram. The structures of the tri- and tetra-hydrate consist of Sr(2+) cations coordinated by five water mol-ecules and four O atoms of four perchlorate tetra-hedra in a distorted tricapped trigonal-prismatic coordination mode. The asymmetric unit of the trihydrate contains two formula units. Two [SrO9] polyhedra in the trihydrate are connected by sharing water mol-ecules and thus forming chains parallel to [100]. In the tetra-hydrate, dimers of two [SrO9] polyhedra connected by two sharing water mol-ecules are formed. The structure of the nona-hydrate contains one Sr(2+) cation coordinated by seven water mol-ecules and by two O atoms of two perchlorate tetra-hedra (point group symmetry ..m), forming a tricapped trigonal prism (point group symmetry m2m). The structure contains additional non-coordinating water mol-ecules, which are located on twofold rotation axes. O-H⋯O hydrogen bonds between the water mol-ecules as donor and ClO4 tetra-hedra and water mol-ecules as acceptor groups lead to the formation of a three-dimensional network in each of the three structures.

  17. H2O2 Release from Human Granulocytes during Phagocytosis

    PubMed Central

    Root, Richard K.; Metcalf, Julia A.

    1977-01-01

    Normal and cytochalasin B-treated human granulocytes have been studied to determine some of the interrelationships between phagocytosis-induced respiration and superoxide and hydrogen peroxide formation and release into the extracellular medium by intact cells. By using the scopoletin fluorescent assay to continuously monitor extracellular hydrogen peroxide concentrations during contact of cells with opsonized staphylococci, it was demonstrated that the superoxide scavengers ferricytochrome c and nitroblue tetrazolium significantly reduced the amount of H2O2 released with time from normal cells but did not abolish it. This inhibitory effect was reversed by the simultaneous addition of superoxide dismutase (SOD), whereas the addition of SOD alone increased the amount of detectable H2O2 in the medium. The addition of sodium azide markedly inhibited myeloperoxidase-H2O2-dependent protein iodination and more than doubled H2O2 release, including the residual amount remaining after exposure of the cells to ferricytochrome c, suggesting its origin from an intracellular pool shared by several pathways for H2O2 catabolism. When cells were pretreated with cytochalasin B and opsonized bacteria added, reduced oxygen consumption was observed, but this was in parallel to a reduction in specific binding of organisms to the cells when compared to normal. Under the influence of inhibited phagosome formation by cytochalasin B, the cells released an increased amount of superoxide and peroxide into the extracellular medium relative to oxygen consumption, and all detectable peroxide release could be inhibited by the addition of ferricytochrome c. Decreased H2O2 production in the presence of this compound could not be ascribed to diminished bacterial binding, decreased oxidase activity, or increased H2O2 catabolism and was reversed by the simultaneous addition of SOD. Furthermore, SOD and ferricytochrome c had similar effects on another H2O2-dependent reaction, protein iodination, in

  18. High-speed Air Temperature Measurements in a Closed-path Cell and Quality of CO2 and H2O Fluxes from a Short-tube Gas Analyzer.

    NASA Astrophysics Data System (ADS)

    Burba, G. G.; Kathilankal, J. C.; Fratini, G.

    2015-12-01

    Gas analyzers traditionally used for eddy covariance method measure gas density. When fluxes are calculated, corrections are applied to account for the changes in gas density due to changing temperature and pressure (Ideal Gas Law) and changing water vapor density (Dalton's Law). The new generation of gas analyzers with fast air temperature and pressure measurements in the sampling cell enables on-the-fly calculation of fast dry mole fraction. This significantly simplifies the flux processing because the WPL density terms are no longer required, and leads to the reduction in uncertainties associated with latent and sensible heat flux inputs into the density terms. Traditional closed-path instruments with long intake tubes often can effectively dampen the fast temperature fluctuations in the tube before reaching the measurement cell, thus reducing or eliminating the need for temperature correction for density-based fluxes. But in instruments with a short-tube design, most - but not all - of the temperature fluctuations are attenuated, so calculating unbiased fluxes using fast dry mole fraction requires high-speed precise temperature measurements of the air stream inside the cell. Fast pressure and water vapor content of the sampled air should also be measured in the cell and carefully aligned in time with gas density and sample temperature measurements.In this study we examine the impact of fast-response air temperature measurements in the cell on the calculations of carbon dioxide and water vapor fluxes at different time scales from three different ecosystems. The fast cell air temperature data is filtered mathematically to obtain slower response cell temperature time series, which is used in the calculation of fluxes. This exercise is intended to simulate the use of thicker slower response thermocouples instead of fast response fine wire thermocouples for estimating cell temperature. The directly measured block temperature is also utilized to illustrate the

  19. EPR of Cu 2+ and VO 2+ in a cobalt saccharin complex, [Co(sac) 2(H 2O) 4]·2H 2O, single crystals

    NASA Astrophysics Data System (ADS)

    Yerli, Y.; Köksal, F.; Karadag, A.

    2003-09-01

    Cu 2+ and VO 2+ doped single crystals of [Co(sac) 2(H 2O) 4]·2H 2O (Cosacaqua) complex were investigated using EPR technique at ambient temperature. Detailed investigation of the EPR spectra indicated that the Cu 2+ and VO 2+ substitute the Co 2+. Two sites were observed for Cu 2+ and VO 2+. But each site of V 4+ corresponds two different orientations of VO 2+. The principal values of the g and the hyperfine tensors were obtained. The spectra indicate that the ground state for Cu 2+ is mainly 3 dx2- y2. The covalent bonding parameters for Cu 2+ and VO 2+ and Fermi contact terms were obtained.

  20. Experimental measurements of vapor-liquid equilibria of the H2O + CO2 + CH4 ternary system

    USGS Publications Warehouse

    Qin, J.; Rosenbauer, R.J.; Duan, Zhenhao

    2008-01-01

    Reported are the experimental measurements on vapor-liquid equilibria in the H2O + CO2 + CH4 ternary system at temperatures from (324 to 375) K and pressures from (10 to 50) MPa. The results indicate that the CH4 solubility in the ternary mixture is about 10 % to 40 % more than that calculated by interpolation from the Henry's law constants of the binary system, H2O + CH4, and the solubility of CO2 is 6 % to 20 % more than what is calculated by the interpolation from the Henry's law constants of the binary mixture, H 2O + CO2. ?? 2008 American Chemical Society.

  1. Composition-dependent freezing nucleation rates for HNO3/H2O aerosols resembling gravity-wave-perturbed stratospheric particles

    NASA Astrophysics Data System (ADS)

    Prenni, Anthony J.; Onasch, Timothy B.; Tisdale, Robert T.; Siefert, Ronald L.; Tolbert, Margaret A.

    1998-11-01

    Laboratory measurements are presented for the freezing kinetics of H2O/HNO3 aerosols over the temperature range of 188-204 K. For 2:1 H2O:HNO3 aerosols crystallizing to NAD we observed a maximum nucleation rate of J = 9.3×109 cm-3 s-1 at 194 K. This temperature is between the glass point of 161 K [Ji et al., 1993] and the melting point of 235.5 K [Ji et al., 1996]. This can be compared to a previous measurement of J = 6.7×109 cm-3 s-1 at 193 K [Disselkamp et al., 1996] and lower temperature measurements of J ≈ 1010-1012 cm-3 s-1 at 178.8 - 175.8 K [Bertram and Sloan, 1998a]. Measured nucleation rates decrease as the aerosol becomes dilute, but NAD formation is still observable for 2.5:1 H2O:HNO3 at temperatures near 195 K. In contrast, freezing of 3:1 H2O:HNO3 aerosol was not observed for constant temperature experiments throughout this temperature range, yielding an upper limit of J<1.5×109 cm-3 s-1. This is the lowest experimental value determined for 3:1 H2O:HNO3 freezing rates at these temperatures. From the measured freezing rates and knowledge of the free energy of diffusion the average interfacial free energy for NAD in a 2:1 H2O:HNO3 solution was determined to be σ = 25.2 ergs cm-2. A limit for the interfacial free energy was placed on 3:1 H2O:HNO3 particles, for which freezing was not observed. These data imply that if aerosols reach compositions more concentrated than 3:1 H2O:HNO3 in the atmosphere, NAD may play a role in polar stratospheric cloud formation.

  2. NASA Lewis H2-O2 MHD program

    NASA Technical Reports Server (NTRS)

    Smith, M.; Nichols, L. D.; Seikel, G. R.

    1974-01-01

    Performance and power costs of H2-O2 combustion powered steam-MHD central power systems are estimated. Hydrogen gas is assumed to be transmitted by pipe from a remote coal gasifier into the city and converted to electricity in a steam MHD plant having an integral gaseous oxygen plant. These steam MHD systems appear to offer an attractive alternative to both in-city clean fueled conventional steam power plants and to remote coal fired power plants with underground electric transmission into the city. Status and plans are outlined for an experimental evaluation of H2-O2 combustion-driven MHD power generators at NASA Lewis Research Center.

  3. The dynamics of the H + H2O reaction.

    PubMed

    Castillo, Jesús F

    2002-04-15

    This article reviews the history and recent progress in the study of the dynamics of the H + H2O reaction, which has become a benchmark for experimental research in the field of gas-phase reaction dynamics. The dynamics of H + H2O is discussed in terms of the different observable properties: integral cross-sections, rate coefficients, product state distributions, differential cross-sections, and vector correlations. It is shown how experimental measurements and first-principle theoretical calculations have revealed the interesting microscopic aspects of this elementary chemical reaction.

  4. Determination of dipyrone in pharmaceutical preparations based on the chemiluminescent reaction of the quinolinic hydrazide-H2O2-vanadium(IV) system and flow-injection analysis.

    PubMed

    Pradana Pérez, Juan A; Durand Alegría, Jesús S; Hernando, Pilar Fernández; Sierra, Adolfo Narros

    2012-01-01

    A rapid, economic and sensitive chemiluminescent method involving flow-injection analysis was developed for the determination of dipyrone in pharmaceutical preparations. The method is based on the chemiluminescent reaction between quinolinic hydrazide and hydrogen peroxide in a strongly alkaline medium, in which vanadium(IV) acts as a catalyst. Principal chemical and physical variables involved in the flow-injection system were optimized using a modified simplex method. The variations in the quantum yield observed when dipyrone was present in the reaction medium were used to determine the concentration of this compound. The proposed method requires no preconcentration steps and reliably quantifies dipyrone over the linear range 1-50 µg/mL. In addition, a sample throughput of 85 samples/h is possible.

  5. Particle-in-Cell Simulations of Atmospheric Pressure He/2%H2O Discharges

    NASA Astrophysics Data System (ADS)

    Kawamura, E.; Lieberman, M. A.; Lichtenberg, A. J.; Graves, D. B.; Gopalakrishnan, R.

    2015-09-01

    Atmospheric pressure micro-discharges in contact with liquid surfaces are of increasing interest, especially in the bio-medical field. We conduct 1D3v particle-in-cell (PIC) simulations of a voltage-driven 1 mm width atmospheric pressure He/2% H2O plasma discharge in series with an 0.5 mm width liquid H2O layer and a 1mm width quartz dielectric layer. A previously developed two-temperature hybrid global model of atmospheric pressure He/H2O discharges was used to determine the most important species and collisional reactions to use in the PIC simulations. We found that H13O6+, H5O3-, and electrons were the most prominent charged species, while most of the metastable helium He* was quenched via Penning ionization. The ion-induced secondary emission coefficient γi was assumed to be 0.15 at all surfaces. A series of simulations were conducted at 27.12 MHz with Jrf ~ 800-2200 A/m2. The H2O rotational and vibrational excitation losses were so high that electrons reached the walls at thermal temperatures. We also simulated a much lower frequency case of 50 kHz with Vrf = 10 kV. In this case, the discharge ran in a pure time-varying γ-mode. This work was supported by the Department of Energy Office of Fusion Energy Science Contract DE-SC0001939.

  6. [Ribonuclease hydration and its heat stability in solutions of H2O and D2O].

    PubMed

    Mrevlishvili, G M; Lobyshev, V I; Dzhaparidze, G Sh; Sokhadze, V M; Tatishvili, D A

    1980-01-01

    Ribonuclease hydration in wide concentration and temperature range using differential scanning microcalorimetry and NMR technique was studied. The temperature- concentration equilibrium diagram for H2O--ribonuclease system was suggested. Protein hydration in D2O was shown to be higher than in ordinary water. NMR measurements in dilute protein solutions showed that cooperative temperature denaturation was followed by solvation changes. Models of globular protein hydration are discussed. PMID:6245723

  7. Melting phase relations in the system H2O - NH3 at high pressure

    NASA Astrophysics Data System (ADS)

    Sugimura, E.; Hirose, K.; Komabayashi, T.; Ohishi, Y.; Hirao, N.; Dubrovinsky, L. S.

    2012-12-01

    The density models of Uranus and Neptune constrained by their gravitational moments from Voyager mission suggest that mantles of these planets may be predominantly comprised of water (H2O), methane (CH4), and ammonia (NH3). The impurities in pure water would greatly influence the phase relations in the water-rich system expected in the icy mantle, which must be known to construct a plausible planetary model. One of important effects of the impurity is on the liquidus temperature (Tliq), since it decides the actual presence of solid phase within the icy mantle. In order to determine Tliq in H2O-rich region of the H2O - CH4 - NH3 ternary system, the melting phase relations in the H2O - CH4 and H2O - NH3 systems must be accurately known. However, previous melting experiments on each binary system were limited to several gigapascals, thus need to be explored to higher P-T conditions for application in interiors of Uranus and Neptune. We have investigated high-pressure (P) and -temperature (T) melting phase relations in the H2O - NH3 system based on a combination of visual observation and angle-dispersive x-ray diffraction (XRD) measurements at BL10XU, SPring-8. High-P-T conditions were generated in an externally-resistive heated diamond anvil cell (DAC). Starting material was 20wt% NH3 aqueous solution whose composition was checked via Tliq of the solution measured in a DAC at near atmospheric pressure. The aqueous solution was loaded into a gold-lined hole in a preindented rhenium gasket in order to insulate the sample from rhenium. Pressure was determined from the unit-cell volume of gold liner. Melting and freezing of the sample were detected by monitoring disappearance/appearance of diffraction peaks of solid and diffuse scattering of liquids, as well as observing melting/crystallization of crystal grains under microscope. Up to 20 GPa at room temperature, in addition to ice VII, diffraction peaks of bcc-like phase, which is most likely to be the reported phase VI

  8. New Optical Constants for Amorphous and Crystalline H2O-ice and H2O-mixtures.

    NASA Technical Reports Server (NTRS)

    Mastrapa, Rachel; Bernstein, Max; Sandford, Scott

    2006-01-01

    We will present the products of new laboratory measurements of ices relevant to Trans-Neptunian Objects. We have calculated the real and imaginary indices of refraction for amorphous and crystalline H2O-ice and also H2O-rich ices containing other molecular species. We create ice samples by condensing gases onto a cold substrate. We measure the thickness of the sample by reflecting a He-Ne laser off of the sample and counting interference fringes as it grows. We then collect transmission spectra of the samples in the wavelength range from 0.7-22 micrometers. Using the thickness and the transmission spectra of the ice we calculate the imaginary part of the index of refraction. We then use a Kramers-Kronig calculation to calculate the real part of the index of refraction (Berland et al. 1994; Hudgins et al. 1993). These optical constants can then be used to create model spectra for comparison to spectra from Solar System objects, including TNOs. We will summarize the difference between the amorphous and crystalline H2O-ice spectra. These changes include weakening of features and shifting of features to shorter wavelength. One important result is that the 2 pm feature is stronger in amorphous H2O ice than it is in crystalline H2O-ice. We will also discuss the changes seen when H2O is mixed with other components, including CO2, CH4, HCN, and NH3 (Bernstein et al. 2005; Bernstein et al. 2006).

  9. Bacterial Ice Nucleation in Monodisperse D2O and H2O-in-Oil Emulsions.

    PubMed

    Weng, Lindong; Tessier, Shannon N; Smith, Kyle; Edd, Jon F; Stott, Shannon L; Toner, Mehmet

    2016-09-13

    Ice nucleation is of fundamental significance in many areas, including atmospheric science, food technology, and cryobiology. In this study, we investigated the ice-nucleation characteristics of picoliter-sized drops consisting of different D2O and H2O mixtures with and without the ice-nucleating bacteria Pseudomonas syringae. We also studied the effects of commonly used cryoprotectants such as ethylene glycol, propylene glycol, and trehalose on the nucleation characteristics of D2O and H2O mixtures. The results show that the median freezing temperature of the suspension containing 1 mg/mL of a lyophilized preparation of P. syringae is as high as -4.6 °C for 100% D2O, compared to -8.9 °C for 100% H2O. As the D2O concentration increases every 25% (v/v), the profile of the ice-nucleation kinetics of D2O + H2O mixtures containing 1 mg/mL Snomax shifts by about 1 °C, suggesting an ideal mixing behavior of D2O and H2O. Furthermore, all of the cryoprotectants investigated in this study are found to depress the freezing phenomenon. Both the homogeneous and heterogeneous freezing temperatures of these aqueous solutions depend on the water activity and are independent of the nature of the solute. These findings enrich our fundamental knowledge of D2O-related ice nucleation and suggest that the combination of D2O and ice-nucleating agents could be a potential self-ice-nucleating formulation. The implications of self-nucleation include a higher, precisely controlled ice seeding temperature for slow freezing that would significantly improve the viability of many ice-assisted cryopreservation protocols. PMID:27495973

  10. Bacterial Ice Nucleation in Monodisperse D2O and H2O-in-Oil Emulsions.

    PubMed

    Weng, Lindong; Tessier, Shannon N; Smith, Kyle; Edd, Jon F; Stott, Shannon L; Toner, Mehmet

    2016-09-13

    Ice nucleation is of fundamental significance in many areas, including atmospheric science, food technology, and cryobiology. In this study, we investigated the ice-nucleation characteristics of picoliter-sized drops consisting of different D2O and H2O mixtures with and without the ice-nucleating bacteria Pseudomonas syringae. We also studied the effects of commonly used cryoprotectants such as ethylene glycol, propylene glycol, and trehalose on the nucleation characteristics of D2O and H2O mixtures. The results show that the median freezing temperature of the suspension containing 1 mg/mL of a lyophilized preparation of P. syringae is as high as -4.6 °C for 100% D2O, compared to -8.9 °C for 100% H2O. As the D2O concentration increases every 25% (v/v), the profile of the ice-nucleation kinetics of D2O + H2O mixtures containing 1 mg/mL Snomax shifts by about 1 °C, suggesting an ideal mixing behavior of D2O and H2O. Furthermore, all of the cryoprotectants investigated in this study are found to depress the freezing phenomenon. Both the homogeneous and heterogeneous freezing temperatures of these aqueous solutions depend on the water activity and are independent of the nature of the solute. These findings enrich our fundamental knowledge of D2O-related ice nucleation and suggest that the combination of D2O and ice-nucleating agents could be a potential self-ice-nucleating formulation. The implications of self-nucleation include a higher, precisely controlled ice seeding temperature for slow freezing that would significantly improve the viability of many ice-assisted cryopreservation protocols.

  11. H2-O2 auxiliary power unit for Space Shuttle vehicles - A progress report.

    NASA Technical Reports Server (NTRS)

    Joyce, J. P.; Beremand, D. G.; Cameron, H. M.; Jefferies, K. S.

    1973-01-01

    Description of a program to establish technology readiness of hydrogen-oxygen (H2-O2) auxiliary power units for use on board the Space Shuttle orbiter vehicle. Fundamental objectives include experimentally establishing an acceptable propellant flow control method, verification of combustor stability, and adequate thermal management. An initial auxiliary power unit (APU) configuration with recycled hydrogen flow has been studied and revised toward greater simplicity and scaling ease. The selected APU is a recuperated open-cycle, turbine-driven unit. Series flow of cryogenic hydrogen removes internally-generated heat and heat from the hydraulic system. The revised configuration schematic and its calculated performance are reviewed. A weight comparison is made between the shuttle baseline hydrazine and H2-O2 APU systems, showing that hydrogen-oxygen APUs have the potential of increasing the payload of the Space Shuttle.

  12. The effects of convective ice lofting on H2O and HDO in the tropical tropopause layer

    NASA Astrophysics Data System (ADS)

    Dessler, A.; Hanisco, T.; Fueglistaler, S.

    2007-12-01

    We have derived a climatology of TTL-penetrating convective events from measurements of Ice-water content (IWC) from the Microwave Limb Sounder onboard NASA's Aura spacecraft. Using this climatology, we have added convective ice lofting to a Lagrangian trajectory model of TTL water vapor (H2O) and its stable isotopologue, HDO. The Lagrangian model has been previously shown to accurately simulate H2O in the TTL and lower stratosphere. We show here that the model without convective lofting does a poor job reproducing the observed HDO depletion (dD) in the TTL. When convective ice lofting to altitudes below the cold point (the point where air experiences its lowest H2O saturation mixing ratio) is added to the model, there is little change in H2O in the lower stratosphere, but a large change in dD throughout the TTL that brings the model into better agreement with measurements. Thus, convective ice lofting has the capacity to improve the model's dD simulation while not significantly degrading the agreement between simulated and measured H2O. Convective ice lofting to altitudes above the cold point, on the other hand, has a large effect on lower stratospheric H2O, suggesting that changes in convection reaching these altitudes could drive changes in lower stratospheric H2O. This suggests a mechanism by which lower stratospheric H2O trends may be at least partially decoupled from tropopause temperature trends. Such a disconnection was suggested by previous observations of simultaneously increasing stratospheric H2O and a cooling tropical tropopause.

  13. Multidimentional Normal Mode Calculations for the OH Vibrational Spectra of (H_2O)_3^+, (H_2O)_3^+Ar, H^+(H_2O)_3, and H^+(H_2O)_3Ar

    NASA Astrophysics Data System (ADS)

    Li, Ying-Cheng; Chuang, Hsiao-Han; Tan, Jake Acedera; Takahashi, Kaito; Kuo, Jer-Lai

    2014-06-01

    Recent experimental observations of (H_2O)_3^+, (H_2O)_3^+Ar, H^+(H_2O)_3, and H^+(H_2O)_3Ar clusters in the region 1400-3800 wn show that the OH stretching vibration has distinct characteristics. Multidimensional normal mode calculations were carried out for OH stretching vibrations in the 1200-4000 wn photon energy range. The potential energy and dipole surfaces were evaluated by using first-principles methods. By comparing the calculated frequencies and intensities of OH stretching vibration with experimental spectra, we found that the assignment of OH strecthing of H_3O^+ moiety and free OH strectching vibration have resonable agreement with experimental data. Jeffrey M. Headrick, Eric G. Diken, Richard S. Walters, Nathan I. Hammer, Richard A. Christie, Jun Cui, Evgeniy M. Myshakin, Michael A. Duncan, Mark A. Johnson, Kenneth D. Jordan, Science, 2005, 17, 1765. Kenta Mizuse, Jer-Lai Kuo and Asuka Fujii, Chem. Sci., 2011, 2, 868 Kenta Mizuse and Asuka Fujii, J. Phys. Chem. A, 2013, 117, 929.

  14. Photochemical synthesis of H2O2 from the H2O...O(3P) van der Waals complex: experimental observations in solid krypton and theoretical modeling.

    PubMed

    Pehkonen, Susanna; Marushkevich, Kseniya; Khriachtchev, Leonid; Räsänen, Markku; Grigorenko, Bella L; Nemukhin, Alexander V

    2007-11-15

    Productive photochemical synthesis of hydrogen peroxide, H(2)O(2), from the H(2)O...O((3)P) van der Waals complex is studied in solid krypton. Experimentally, we achieve the three-step formation of H(2)O(2) from H(2)O and N(2)O precursors frozen in solid krypton. First, 193 nm photolysis of N(2)O yields oxygen atoms in solid krypton. Upon annealing at approximately 25 K, mobile oxygen atoms react with water forming the H(2)O...O complex, where the oxygen atom is in the triplet ground state. Finally, the H(2)O...O complex is converted to H(2)O(2) by irradiation at 300 nm. According to the complete active space self-consistent field modeling, hydrogen peroxide can be formed through the photoexcited H(2)O+-O- charge-transfer state of the H(2)O...O complex, which agrees with the experimental evidence.

  15. Water Planetary and Cometary Atmospheres: H2O/HDO Transmittance and Fluorescence Models

    NASA Technical Reports Server (NTRS)

    Villanueva, G. L.; Mumma, M. J.; Bonev, B. P.; Novak, R. E.; Barber, R. J.; DiSanti, M. A.

    2012-01-01

    We developed a modern methodology to retrieve water (H2O) and deuterated water (HDO) in planetary and cometary atmospheres, and constructed an accurate spectral database that combines theoretical and empirical results. Based on a greatly expanded set of spectroscopic parameters, we built a full non-resonance cascade fluorescence model and computed fluorescence efficiencies for H2O (500 million lines) and HDO (700 million lines). The new line list was also integrated into an advanced terrestrial radiative transfer code (LBLRTM) and adapted to the CO2 rich atmosphere of Mars, for which we adopted the complex Robert-Bonamy formalism for line shapes. We then retrieved water and D/H in the atmospheres of Mars, comet C/2007 WI, and Earth by applying the new formalism to spectra obtained with the high-resolution spectrograph NIRSPEC/Keck II atop Mauna Kea (Hawaii). The new model accurately describes the complex morphology of the water bands and greatly increases the accuracy of the retrieved abundances (and the D/H ratio in water) with respect to previously available models. The new model provides improved agreement of predicted and measured intensities for many H2O lines already identified in comets, and it identifies several unassigned cometary emission lines as new emission lines of H2O. The improved spectral accuracy permits retrieval of more accurate rotational temperatures and production rates for cometary water.

  16. Atomistic molecular dynamics simulations of H2O diffusivity in liquid and supercritical CO2

    NASA Astrophysics Data System (ADS)

    Moultos, Othonas A.; Orozco, Gustavo A.; Tsimpanogiannis, Ioannis N.; Panagiotopoulos, Athanassios Z.; Economou, Ioannis G.

    2015-09-01

    Molecular dynamics simulations were employed for the calculation of diffusion coefficients of pure CO2 and of H2O in CO2 over a wide range of temperatures (298.15 K < T < 523.15 K) and pressures (5.0 MPa < P < 100.0 MPa), that are of interest to CO2 capture-and-sequestration processes. Various combinations of existing fixed-point-charge force-fields for H2O (TIP4P/2005 and Exponential-6) and CO2 (elementary physical model 2 [EPM2], transferable potentials for phase equilibria [TraPPE], and Exponential-6) were tested. All force-field combinations qualitatively reproduce the trends of the experimental data for infinitely diluted H2O in CO2; however, TIP4P/2005-EPM2, TIP4P/2005-TraPPE and Exponential-6-Exponential-6 were found to be the most consistent. Additionally, for H2O compositions ranging from infinite dilution to ?, the Maxwell-Stefan diffusion coefficient is shown to have a weak non-linear composition dependence.

  17. Boiling Temperature and Reversed Deliquescence Relative Humidity Measurements for Mineral Assemblages in the NaCl + NaNO3 + KNO3 + Ca(NO3)2 + H2O System

    SciTech Connect

    Rard, J A; Staggs, K J; Day, S D; Carroll, S A

    2005-12-01

    Boiling temperature measurements have been made at ambient pressure for saturated ternary solutions of NaCl + KNO{sub 3} + H{sub 2}O, NaNO{sub 3} + KNO{sub 3} + H{sub 2}O, and NaCl + Ca(NO{sub 3}){sub 2} + H{sub 2}O over the full composition range, along with those of the single salt systems. Boiling temperatures were also measured for the four component NaCl + NaNO{sub 3} + KNO{sub 3} + H{sub 2}O and five component NaCl + NaNO{sub 3} + KNO{sub 3} + Ca(NO{sub 3}){sub 2} + H{sub 2}O mixtures, where the solute mole fraction of Ca(NO{sub 3}){sub 2}, x(Ca(NO{sub 3}){sub 2}), was varied between 0 and 0.25. The maximum boiling temperature found for the NaCl + KNO{sub 3} + H{sub 2}O system is {approx} 134.9 C; for the NaNO{sub 3} + KNO{sub 3} + H{sub 2}O system is {approx} 165.1 C at x(NaNO{sub 3}) {approx} 0.46 and x(KNO{sub 3}) {approx} 0.54; and for the NaCl + Ca(NO{sub 3}){sub 2} + H{sub 2}O system is 164.7 {+-} 0.6 C at x(NaCl) {approx} 0.25 and x(Ca(NO{sub 3}){sub 2}) {approx} 0.75. The NaCl + NaNO{sub 3} + KNO{sub 3} + Ca(NO{sub 3}){sub 2} + H{sub 2}O system forms molten salts below their maximum boiling temperatures, and the temperatures corresponding to the cessation of boiling (dry out temperatures) of these liquid mixtures were determined. These dry out temperatures range from {approx} 300 C when x(Ca(NO{sub 3}){sub 2}) = 0 to {ge} 400 C when x(Ca(NO{sub 3}){sub 2}) = 0.20 and 0.25. Mutual deliquescence/efflorescence relative humidity (MDRH/MERH) measurements were also made for the NaNO{sub 3} + KNO{sub 3} and NaCl + NaNO{sub 3} + KNO{sub 3} salt mixture from 120 to 180 C at ambient pressure. The NaNO{sub 3} and NaCl + NaNO{sub 3} + KNO{sub 3} salt mixture has a MDRH of 26.4% at 120 C and 20.0% at 150 C. This salt mixture also absorbs water at 180 C, which is higher than expected from the boiling temperature experiments. The NaCl + NaNO{sub 3} + KNO{sub 3} salt mixture was found to have a MDRH of 25.9% at 120 C and 10.5% at 180 C. The investigated mixture

  18. Quantitative evaluation of the effect of H2O degassing on the oxidation state of magmas

    NASA Astrophysics Data System (ADS)

    Lange, R. A.; Waters, L.

    2014-12-01

    The extent to which degassing of the H2O component affects the oxidation state of hydrous magmas is widely debated. Several researchers have examined how degassing of mixed H-C-O-S-Cl fluids may change the Fe3+/FeT ratio of various magmas, whereas our focus is on the H2O component. There are two ways that degassing of H2O by itself may cause oxidation: (1) the reaction: H2O (melt) + 2FeO (melt) = H2 (fluid) + Fe2O3 (melt), and/or (2) if dissolved water preferentially enhances the activity of ferrous vs. ferric iron in magmatic liquids. In this study, a comparison is made between the pre-eruptive oxidation states of 14 crystal-poor, jet-black obsidian samples (obtained from two Fe-Ti oxides) and their post-eruptive values (analyzed with the Wilson 1960 titration method tested against USGS standards). The obsidians are from Medicine Lake (CA), Long Valley (CA), and the western Mexican arc; all have low FeOT (1.1-2.1 wt%), rendering their Fe2+/Fe3+ ratios highly sensitive to the possible effects of substantial H2O degassing. The Fe-Ti oxide thermometer/oxybarometer of Ghiorso and Evans, (2008) gave temperatures for the 14 samples that range for 720 to 940°C and ∆NNO values of -0.9 to +1.4. With temperature known, the plagioclase-liquid hygrometer was applied and show that ≤ 6.5 wt% H2O was dissolved in the melts prior to eruption. In addition, pre-eruptive Cl and S concentrations were constrained on the basis of apatite analyses (Webster et al., 2009) and sulfur concentrations needed for saturation with pyrrhotite (Clemente et al., 2004), respectively. Maximum pre-eruptive chlorine and sulfur contents are 6000 and 200 ppm, respectively. After eruption, the rhyolites lost nearly all of their volatiles. Our results indicate no detectable change between pre- and post-eruptive Fe2+ concentrations, with an average deviation of ± 0.1 wt % FeO. Although degassing of large concentrations of S and/or Cl may affect the oxidation state of magmas, at the pre-eruptive levels

  19. Experimental studies of the formation of cluster ions formed by corona discharge in an atmosphere containing SO2, NH3, and H2O

    NASA Astrophysics Data System (ADS)

    Pedersen, J. O.; Hvelplund, P.; Støchkel, K.; Enghoff, M. B.; Kurten, T.

    2013-12-01

    We report on studies of ion induced nucleation in a corona discharge taking place in an atmosphere containing SO2, NH3, and H2O at standard temperature and pressure. Positive ions such as H3O+(H2O)n, NH4+(H2O)n, and H+(H2SO4)(H2O)n and negative ions such as HSO5-(H2O)n, SO4-(H2O)n, HSO4-(H2O)n and NO3-(H2O)n have been recorded. Large values of n (> 100) were observed and the experiment indicates the existence of even larger water clusters. In contrast, only clusters with a maximum of 2 sulfuric acid molecules were observed. Fragmentation studies also revealed that the negative ion HSO5-, which has been observed in many studies, in our experiments is contaminated by O2-(HNO3)(H2O) ions, and this may also have been the case in other experiments. Finally an ion with m/z = 232 (where m is the cluster mass in amu and z the charge state), capable of attaching H2O-molecules was observed and studied by fragmentation. Positive ion m/z (mass/charge) spectrum

  20. ATR FT-IR H 2O spectra of acidic aqueous solutions. Insights about proton hydration

    NASA Astrophysics Data System (ADS)

    Śmiechowski, Maciej; Stangret, Janusz

    2008-04-01

    Proton hydration in aqueous solutions has been recently characterised in our laboratory by means of vibrational spectra of HDO isotopically diluted in H 2O [M. Śmiechowski, J. Stangret, J. Chem. Phys. 125 (2006) 204508]. Here, we attempt to study quantitatively H 2O spectra of acidic aqueous solutions. In principle, H 2O spectra provide more information about the structural state of water molecules, resulting from oscillator couplings in the system, but they are much more difficult in interpretation, when compared with HDO spectra. The spectra of aqueous solutions of monoprotic acids (HCl, HClO 4, HPF 6) have been measured by Attenuated Total Reflectance (ATR) FT-IR spectroscopy. Spectral data have been analysed in a way that led to removal of the contribution of bulk water, in order to separate the spectra of solute-affected water only. The analysis has been focused on the infinite dilution limit behaviour of the spectrum. Changes induced in the affected spectra by temperature have been studied for HPF 6 solutions at 25-45 °C. The stretching vibration fundamental has been found to be primarily affected by counter-anion. Proton-affected H 2O spectrum shows the presence of very wide absorption bands in the range, where bulk water shows negligible own absorption, rather than "absorption continua". They could be adequately resolved into analytical components. These bands have been unaffected by temperature and loosely correlated with the stretching fundamental, as indicated by 2D IR correlation spectra. All spectral effects of the studied acids on H 2O in solution have been quantitatively evidenced and discussed. They seem to be in accordance with the main conclusions about proton hydration derived from recent studies of HDO spectra mentioned above.

  1. Promotion of CO oxidation on PdO(101) by adsorbed H2O

    NASA Astrophysics Data System (ADS)

    Choi, Juhee; Pan, Li; Mehar, Vikram; Zhang, Feng; Asthagiri, Aravind; Weaver, Jason F.

    2016-08-01

    We investigated the influence of adsorbed H2O on the oxidation of CO on PdO(101) using temperature programmed reaction spectroscopy (TPRS), reflection absorption infrared spectroscopy (RAIRS) and density functional theory (DFT) calculations. We find that water inhibits CO adsorption on PdO(101) by site blocking, but also provides a more facile pathway for CO oxidation compared with the bare oxide surface. In the presence of adsorbed H2O, the oxidation of CO on PdO(101) produces a CO2 TPRS peak that is centered at a temperature ~ 50 K lower than the main CO2 TPRS peak arising from CO oxidation on clean PdO(101) (~ 330 vs. 380 K). RAIRS shows that CO continues to adsorb on atop-Pd sites of PdO(101) when H2O is co-adsorbed, and provides no evidence of other reactive intermediates. DFT calculations predict that the CO oxidation mechanism follows the same steps for CO adsorbed on PdO(101) with and without co-adsorbed H2O, wherein an atop-CO species recombines with an oxygen atom from the oxide surface lattice. According to DFT, hydrogen bonding interactions with adsorbed H2O species stabilize the carboxyl-like transition structure and intermediate that result from the initial recombination of CO and O on the PdO(101) surface. This stabilization lowers the energy barrier for CO oxidation on PdO(101) by ~ 10 kJ/mol, in good agreement with our experimental estimate.

  2. Degassing of H2O in a phonolitic melt: A closer look at decompression experiments

    NASA Astrophysics Data System (ADS)

    Marxer, Holger; Bellucci, Philipp; Nowak, Marcus

    2015-05-01

    Melt degassing during magma ascent is controlled by the decompression rate and can be simulated in decompression experiments. H2O-bearing phonolitic melts were decompressed at a super-liquidus T of 1323 K in an internally heated argon pressure vessel, applying continuous decompression (CD) as well as to date commonly used step-wise decompression (SD) techniques to investigate the effect of decompression method on melt degassing. The hydrous melts were decompressed from 200 MPa at nominal decompression rates of 0.0028-1.7 MPa·s- 1. At final pressure (Pfinal), the samples were quenched rapidly at isobaric conditions with ~ 150 K·s- 1. The bubbles in the quenched samples are often deformed and dented. Flow textures in the glass indicate melt transport at high viscosity. We suggest that this observation is due to bubble shrinkage during quench. This general problem was mostly overlooked in the interpretation of experimentally degassed samples to date. Bubble shrinkage due to decreasing molar volume (Vm) of the exsolved H2O in the bubbles occurs during isobaric rapid quench until the melt is too viscous too relax. The decrease of Vm(H2O) during cooling at Pfinal of the experiments results in a decrease of the bubble volume by a shrinking factor Bs: At nominal decompression rates > 0.17 MPa·s- 1 and a Pfinal of 75 MPa, the decompression method has only minor influence on melt degassing. SD and CD result in high bubble number densities of 104-105 mm- 3. Fast P drop leads to immediate supersaturation with H2O in the melt. At such high nominal decompression rates, the diffusional transport of H2O is limited and therefore bubble nucleation is the predominant degassing process. The residual H2O contents in the melts decompressed to 75 MPa increase with nominal decompression rate. After homogeneous nucleation is triggered, CD rates ≤ 0.024 MPa·s- 1 facilitate continuous reduction of the supersaturation by H2O diffusion into previously nucleated bubbles. Bubble number

  3. Electronic and chemical structure of the H2O/GaN(0001) interface under ambient conditions

    DOE PAGES

    Zhang, Xueqiang; Ptasinska, Sylwia

    2016-04-25

    We employed ambient pressure X-ray photoelectron spectroscopy to investigate the electronic and chemical properties of the H2O/GaN(0001) interface under elevated pressures and/or temperatures. A pristine GaN(0001) surface exhibited upward band bending, which was partially flattened when exposed to H2O at room temperature. However, the GaN surface work function was slightly reduced due to the adsorption of molecular H2O and its dissociation products. At elevated temperatures, a negative charge generated on the surface by a vigorous H2O/GaN interfacial chemistry induced an increase in both the surface work function and upward band bending. We tracked the dissociative adsorption of H2O onto themore » GaN(0001) surface by recording the core-level photoemission spectra and obtained the electronic and chemical properties at the H2O/GaN interface under operando conditions. In conclusion, our results suggest a strong correlation between the electronic and chemical properties of the material surface, and we expect that their evolutions lead to significantly different properties at the electrolyte/ electrode interface in a photoelectrochemical solar cell.« less

  4. Electronic and chemical structure of the H2O/GaN(0001) interface under ambient conditions.

    PubMed

    Zhang, Xueqiang; Ptasinska, Sylwia

    2016-04-25

    We employed ambient pressure X-ray photoelectron spectroscopy to investigate the electronic and chemical properties of the H2O/GaN(0001) interface under elevated pressures and/or temperatures. A pristine GaN(0001) surface exhibited upward band bending, which was partially flattened when exposed to H2O at room temperature. However, the GaN surface work function was slightly reduced due to the adsorption of molecular H2O and its dissociation products. At elevated temperatures, a negative charge generated on the surface by a vigorous H2O/GaN interfacial chemistry induced an increase in both the surface work function and upward band bending. We tracked the dissociative adsorption of H2O onto the GaN(0001) surface by recording the core-level photoemission spectra and obtained the electronic and chemical properties at the H2O/GaN interface under operando conditions. Our results suggest a strong correlation between the electronic and chemical properties of the material surface, and we expect that their evolutions lead to significantly different properties at the electrolyte/electrode interface in a photoelectrochemical solar cell.

  5. Electronic and chemical structure of the H2O/GaN(0001) interface under ambient conditions

    PubMed Central

    Zhang, Xueqiang; Ptasinska, Sylwia

    2016-01-01

    We employed ambient pressure X-ray photoelectron spectroscopy to investigate the electronic and chemical properties of the H2O/GaN(0001) interface under elevated pressures and/or temperatures. A pristine GaN(0001) surface exhibited upward band bending, which was partially flattened when exposed to H2O at room temperature. However, the GaN surface work function was slightly reduced due to the adsorption of molecular H2O and its dissociation products. At elevated temperatures, a negative charge generated on the surface by a vigorous H2O/GaN interfacial chemistry induced an increase in both the surface work function and upward band bending. We tracked the dissociative adsorption of H2O onto the GaN(0001) surface by recording the core-level photoemission spectra and obtained the electronic and chemical properties at the H2O/GaN interface under operando conditions. Our results suggest a strong correlation between the electronic and chemical properties of the material surface, and we expect that their evolutions lead to significantly different properties at the electrolyte/electrode interface in a photoelectrochemical solar cell. PMID:27108711

  6. Oxidative degradation of endotoxin by advanced oxidation process (O3/H2O2 & UV/H2O2).

    PubMed

    Oh, Byung-Taek; Seo, Young-Suk; Sudhakar, Dega; Choe, Ji-Hyun; Lee, Sang-Myeong; Park, Youn-Jong; Cho, Min

    2014-08-30

    The presence of endotoxin in water environments may pose a serious public health hazard. We investigated the effectiveness of advanced oxidative processes (AOP: O3/H2O2 and UV/H2O2) in the oxidative degradation of endotoxin. In addition, we measured the release of endotoxin from Escherichia coli following typical disinfection methods, such as chlorine, ozone alone and UV, and compared it with the use of AOPs. Finally, we tested the AOP-treated samples in their ability to induce tumor necrosis factor alpha (TNF-α) in mouse peritoneal macrophages. The production of hydroxyl radical in AOPs showed superior ability to degrade endotoxin in buffered solution, as well as water samples from Korean water treatment facilities, with the ozone/H2O2 being more efficient compared to UV/H2O2. In addition, the AOPs proved effective not only in eliminating E. coli in the samples, but also in endotoxin degradation, while the standard disinfection methods lead to the release of endotoxin following the bacteria destruction. Furthermore, in the experiments with macrophages, the AOPs-deactivated endotoxin lead to the smallest induction of TNF-α, which shows the loss of inflammation activity, compared to ozone treatment alone. In conclusion, these results suggest that AOPs offer an effective and mild method for endotoxin degradation in the water systems.

  7. Vibrational investigations of CO2-H2O, CO2-(H2O)2, and (CO2)2-H2O complexes isolated in solid neon

    NASA Astrophysics Data System (ADS)

    Soulard, P.; Tremblay, B.

    2015-12-01

    The van der Waals complex of H2O with CO2 has attracted considerable theoretical interest as a typical example of a weak binding complex with a dissociation energy less than 3 kcal/mol. Up to now, experimental vibrational data are sparse. We have studied by FTIR the complexes involving CO2 and water molecules in solid neon. Many new absorption bands close to the well known monomers fundamentals give evidence for at least three (CO2)n-(H2O)m complexes, noted n:m. Concentration effects combined with a detailed vibrational analysis allow for the identification of sixteen, twelve, and five transitions for the 1:1, 1:2, and 2:1 complexes, respectively. Careful examination of the far infrared spectral region allows the assignment of several 1:1 and 1:2 intermolecular modes, confirmed by the observation of combinations of intra + intermolecular transitions, and anharmonic coupling constants have been derived. Our results demonstrate the high sensibility of the solid neon isolation to investigate the hydrogen-bonded complexes in contrast with the gas phase experiments for which two quanta transitions cannot be easily observed.

  8. Vibrational investigations of CO2-H2O, CO2-(H2O)2, and (CO2)2-H2O complexes isolated in solid neon.

    PubMed

    Soulard, P; Tremblay, B

    2015-12-14

    The van der Waals complex of H2O with CO2 has attracted considerable theoretical interest as a typical example of a weak binding complex with a dissociation energy less than 3 kcal/mol. Up to now, experimental vibrational data are sparse. We have studied by FTIR the complexes involving CO2 and water molecules in solid neon. Many new absorption bands close to the well known monomers fundamentals give evidence for at least three (CO2)n-(H2O)m complexes, noted n:m. Concentration effects combined with a detailed vibrational analysis allow for the identification of sixteen, twelve, and five transitions for the 1:1, 1:2, and 2:1 complexes, respectively. Careful examination of the far infrared spectral region allows the assignment of several 1:1 and 1:2 intermolecular modes, confirmed by the observation of combinations of intra + intermolecular transitions, and anharmonic coupling constants have been derived. Our results demonstrate the high sensibility of the solid neon isolation to investigate the hydrogen-bonded complexes in contrast with the gas phase experiments for which two quanta transitions cannot be easily observed. PMID:26671379

  9. Vibrational investigations of CO2-H2O, CO2-(H2O)2, and (CO2)2-H2O complexes isolated in solid neon.

    PubMed

    Soulard, P; Tremblay, B

    2015-12-14

    The van der Waals complex of H2O with CO2 has attracted considerable theoretical interest as a typical example of a weak binding complex with a dissociation energy less than 3 kcal/mol. Up to now, experimental vibrational data are sparse. We have studied by FTIR the complexes involving CO2 and water molecules in solid neon. Many new absorption bands close to the well known monomers fundamentals give evidence for at least three (CO2)n-(H2O)m complexes, noted n:m. Concentration effects combined with a detailed vibrational analysis allow for the identification of sixteen, twelve, and five transitions for the 1:1, 1:2, and 2:1 complexes, respectively. Careful examination of the far infrared spectral region allows the assignment of several 1:1 and 1:2 intermolecular modes, confirmed by the observation of combinations of intra + intermolecular transitions, and anharmonic coupling constants have been derived. Our results demonstrate the high sensibility of the solid neon isolation to investigate the hydrogen-bonded complexes in contrast with the gas phase experiments for which two quanta transitions cannot be easily observed.

  10. Detection of H2O2 at the nanomolar level by electrode modified with ultrathin AuCu nanowires.

    PubMed

    Wang, Ning; Han, Yu; Xu, Ying; Gao, Caizhen; Cao, Xia

    2015-01-01

    Bimetallic AuCu nanowires (AuCuNWs) are synthesized via a facile water solution method at room temperature. Enhanced electrocatalytic activity is observed toward the oxidation of H2O2, which makes the AuCu nanowire, along with its unique catalytic properties, intriguing bifunctional mechanism, and surface atomic construction, a promising platform for the amplification of interfacing signal. A highly sensitive H2O2 biosensor is thus developed on the base of the as-prepared AuCuNW catalyst. A very low real determination limit (2.0 nM) was reached, and a linear range as wide as 5 orders of magnitude was demonstrated. In addition, a trace amount of H2O2, which was released from Raw 264.7 cells, was selectively detected, hinting at the possible applications for real-time quantitative detection of H2O2 in a biological environment. PMID:25418032

  11. In situ observations of a high-pressure phase of H2O ice

    USGS Publications Warehouse

    Chou, I.-Ming; Blank, J.G.; Goncharov, A.F.; Mao, Ho-kwang; Hemley, R.J.

    1998-01-01

    A previously unknown solid phase of H2O has been identified by its peculiar growth patterns, distinct pressure-temperature melting relations, and vibrational Raman spectra. Morphologies of ice crystals and their pressure-temperature melting relations were directly observed in a hydrothermal diamond-anvil cell for H2O bulk densities between 1203 and 1257 kilograms per cubic meter at temperatures between -10??and 50??C. Under these conditions, four different ice forms were observed to melt: two stable phases, ice V and ice VI, and two metastable phases, ice IV and the new ice phase. The Raman spectra and crystal morphology are consistent with a disordered anisotropic structure with some similarities to ice VI.

  12. Chemistry in glow discharges of H2 / O2 mixtures. Diagnostics and modelling

    PubMed Central

    Jiménez-Redondo, M; Carrasco, E; Herrero, V J; Tanarro, I

    2015-01-01

    The chemistry of low pressure H2 + O2 discharges with different mixture ratios has been studied in a hollow cathode DC reactor. Neutral and positive ion distributions have been measured by mass spectrometry, and Langmuir probes have been used to provide charge densities and electron temperatures. A simple zero order kinetic model including neutral species and positive and negative ions, which takes into account gas-phase and heterogeneous chemistry, has been used to reproduce the global composition of the plasmas over the whole range of mixtures experimentally studied, and allows for the identification of the main physicochemical mechanisms that may explain the experimental results. To our knowledge, no combined experimental and modelling studies of the heavy species kinetics of low pressure H2 + O2 plasmas including ions has been reported before. As expected, apart from the precursors, H2O is detected in considerable amounts. The model also predicts appreciable concentrations of H and O atoms and the OH radical. The relevance of the metastable species O(1D) and O2(a1Δg) is analysed. Concerning the charged species, positive ion distributions are dominated by H3O+ for a wide range of intermediate mixtures, while H3+ and O2+ are the major ions for the higher and lower H2/O2 ratios, respectively. The mixed ions OH+, H2O+ and HO2+ are also observed in small amounts. Negative ions are shown to have a limited relevance in the global chemistry; their main contribution is the reduction of the electron density available for electron impact processes. PMID:26702195

  13. Distillation of H2O from hard-frozen Martian permafrost

    NASA Technical Reports Server (NTRS)

    Zent, A. P.; Gwynne, O.

    1991-01-01

    The authors present a method for distillation of hard-frozen Martian permafrost. A cable-tool is drilled into hard frozem permafrost to a depth of 10 to 20 m. They calculate that a 10 m hole could be drilled in a few days. A 10 m shaft with a diameter equal to the bore is inserted into the hole, and a air tight tent-like structure is erected over the borehole. Photovoltaic cells mounted on the tent supply electrical energy that is dissipated in the shaft. Drilling power can be supplied by other sources. With 1000 watts, the shaft can be heated to near 350 K, producing relatively high temperatures in the vicinity of the borehole. Surrounding H2O is vaporized and diffuses up through the regolith. The authors calculate that a tent of a radius of no more than a few meters would intercept most of the H2O as it diffused to the surface. Calculations suggest that it would require perhaps 30 days to extract H2O from most of the volume drained by this technique. Assuming that the hard frozen regolith is no more than 10 percent ice, the author's calculate that that about 2890 kg of H2O could be extracted in 30 days. Since the nominal requirement for each crew member is about 5 kg/day, one such borehole might be expected to supply enough H2O to maintain a crew of 5 for perhaps 100 days. Additional engineering studies will be done to attempt to improve the capacity or efficiency of this method.

  14. Chemistry in glow discharges of H2/O2 mixtures: diagnostics and modelling

    NASA Astrophysics Data System (ADS)

    Jiménez-Redondo, M.; Carrasco, E.; Herrero, V. J.; Tanarro, I.

    2015-02-01

    The chemistry of low pressure H2+O2 discharges with different mixture ratios has been studied in a hollow cathode dc reactor. Neutral and positive ion distributions have been measured by mass spectrometry, and Langmuir probes have been used to provide charge densities and electron temperatures. A simple zero order kinetic model including neutral species and positive and negative ions, which takes into account gas-phase and heterogeneous chemistry, has been used to reproduce the global composition of the plasmas over the whole range of mixtures experimentally studied, and allows for the identification of the main physico-chemical mechanisms that may explain the experimental results. To our knowledge, no combined experimental and modelling studies of the heavy species kinetics of low pressure H2 + O2 plasmas including ions has been reported before. As expected, apart from the precursors, H2O is detected in considerable amounts. The model also predicts appreciable concentrations of H and O atoms and the OH radical. The relevance of the metastable species O(1D) and O2(a 1Δg) is analysed. Concerning the charged species, positive ion distributions are dominated by H3O+ for a wide range of intermediate mixtures, while H3+ and O2+ are the major ions for the higher and lower H2/O2 ratios, respectively. The mixed ions OH+, H2O+ and HO2+ are also observed in small amounts. Negative ions are shown to have a limited relevance in the global chemistry; their main contribution is the reduction of the electron density available for electron impact processes.

  15. Preliminary results in the NASA Lewis H2-O2 combustion MHD experiment

    NASA Technical Reports Server (NTRS)

    Smith, J. M.

    1979-01-01

    MHD (magnetohydrodynamic) power generation experiments were carried out in the NASA Lewis Research Center cesium-seeded H2-O2 combustion facility. This facility uses a neon-cooled cryomagnet capable of producing magnetic fields in excess of 5 tesla. The effects of power takeoff location, generator loading, B-field strength, and electrode breakdown on generator performance are discussed. The experimental data is compared to a theory based on one-dimensional flow with heat transfer, friction, and voltage drops.

  16. Keggin polyoxoanion supported organic-inorganic trinuclear lutetium cluster, {Na(H2O)3[Lu(pydc)(H2O)3]3}[SiW12O40]·26.5H2O.

    PubMed

    Li, Suzhi; Zhang, Dongdi; Guo, Yuan Yuan; Ma, Pengtao; Qiu, Xiaoyang; Wang, Jingping; Niu, Jingyang

    2012-09-01

    A novel strawberry-like organic-inorganic hybrid, {Na(H(2)O)(3)[Lu(pydc)(H(2)O)(3)](3)}[SiW(12)O(40)]·26.5H(2)O (H(2)pydc = pyridine-2,6-dicarboxylate) containing an intriguing trinuclear lutetium cluster {Na(H(2)O)(3)[Lu(pydc)(H(2)O)(3)](3)}(4+) has been synthesized and its luminescent properties, IR, UV, TG, PXRD analyses and single crystal X-ray diffraction were investigated.

  17. The effect of H2O on partial melting of garnet peridotite at 3.5 GPa

    NASA Astrophysics Data System (ADS)

    Tenner, Travis J.; Hirschmann, Marc M.; Humayun, Munir

    2012-03-01

    We present experimental determinations of the influence of H2O on partial melting of garnet peridotite (+1.5, 2.5, and 5 wt. % added H2O) at 3.5 GPa and 1200-1450°C. Experiments produced complex polyphase regions of quenched melt and equilibrium partial melt compositions were reconstructed by combined EMP and LA-ICP-MS analyses. Mass balance-derived melt fractions (F) range from 0.18 to 0.33 and dissolved water contents range from 4.5 to 23.5 wt. %. One exceptional experiment quenched glass, allowing independent verification of H2O concentration by FTIR. The influence of H2O on melt production is quantified by the temperature difference required to achieve a given F under dry and wet conditions, ΔT, which is controlled by the H2O concentration in partial melts. Melts with 1.5, 5, 10, and 15 wt. % H2O yield ΔT values of 50, 150, 250, and 320°C, respectively, consistent with a cryoscopic parameterization that assumes 3 oxygens per mole of silicate melt. Based on this parameterization, we calculate that beneath oceanic ridges, peridotite H2O storage capacity increases from 0 to 240 ppm from 66 to 110 km depth. For H2O to be solely responsible for melting in the oceanic low velocity zone (LVZ) at least 5.7 wt. % H2O must be dissolved in the melt at 110 km, and considerably more (e.g., 15 wt.% at 220 km) is required for melting throughout the entire observed interval. The addition of H2O results in 3.5 GPa partial melts of garnet peridotite (normalized anhydrous) that are SiO2 and Al2O3 poor (43-50 and 9-11.5 wt. %, respectively), and MgO and CaO rich (18-27 and 7-12 wt. %, respectively) when compared to anhydrous analogues. These effects become highly pronounced deep in the upper mantle, and are opposite to the effect of H2O on melt compositions in the spinel stability field, potentially owing in part to OH-association with network modifying cations in high pressure, depolymerized melts and in part to low-temperature stabilization of garnet, which enhances CaO/Al2O

  18. FLYING-WATER Renewables-H2-H2O TERRAFORMING: PERMANENT ETERNAL Drought(s)-Elimination FOREVER!!!

    NASA Astrophysics Data System (ADS)

    Wignall, J.; Lyons, Marv; Ertl, G.; Alefeld, Georg; Youdelis, W.; Radd, H.; Oertle, G.; Siegel, Edward

    2013-03-01

    ''H2O H2O everywhere; ne'er a drop to drink''[Coleridge(1798)] now: ''H2 H2 everywhere; STILL ne'er a drop to drink'': ONLY H2 (or methane CH4) can be FLYING-WATER(F-W) chemical-rain-in-pipelines Hindenberg-effect (H2-UP;H2O-DOWN): { ∖{}O/H2O{ ∖}} =[16]/[18] ∖sim 90{ ∖%} O already in air uphill; NO H2O pumping need! In global-warming driven H2O-starved glacial-melting world, rescue is possible ONLY by Siegel [ ∖underline {3rd Intl. Conf. Alt.-Energy }(1980)-vol.5/p.459!!!] Renewables-H2-H2O purposely flexible versatile agile customizable scaleable retrofitable integrated operating-system. Rosenfeld[Science 315,1396(3/9/2007)]-Biello [Sci.Am.(3/9 /2007)] crucial geomorphology which ONLY maximal-buoyancy H2 can exploit, to again make ''Mountains into Fountains'', ``upthrust rocks trapping the clouds to precipitate their rain/snow/H2O'': ''terraforming''(and ocean-rebasificaton!!!) ONLY VIA Siegel[APS March MTGS.:1960s-2000ss) DIFFUSIVE-MAGNETORESISTANCE (DMR) proprietary MAGNETIC-HYDROGEN-VALVE(MHV) ALL-IMPORTANT PRECLUDED RADIAL-diffusion, permitting ONLY AXIAL-H2-BALLISTIC-flow (``G.A''.''/DoE''/''Terrapower''/''Intellectual-Ventures''/ ''Gileland''/ ''Myhrvold''/''Gates'' ``ARCHIMEDES'') in ALREADY IN-ground dense BCC/ferritic-steels pipelines-network (NO new infrastructure) counters Tromp[Science 300,1740(2003)] dire warning of global-pandemics (cancers/ blindness/ famine)

  19. Kinetics of the reaction OH + H2O2 yields HO2 + H2O

    NASA Technical Reports Server (NTRS)

    Sridharan, U. C.; Reimann, B.; Kaufman, F.

    1980-01-01

    The paper describes an experimental study of the title reaction that uses the discharge-flow technique, laser-induced-fluorescence detection of OH and simultaneous monitoring of O and H atoms in the 250-459 K range. The reaction is normal and free from surface effect interference in Teflon or halocarbon wax-coated tube, but not in clean Pyrex. OH radicals are generated in three ways and at low concentrations to eliminate side reactions. The rate constants were determined at 298 K and over the 250-459 K range, with a factor of two higher at 298 K and factors of 3 to 5 higher at 10 to 30 km altitude in the terrestrial atmosphere than previous studies have indicated. The effect of the higher rate constant on atmospheric processes and on recent laboratory measurements of other reactions is also discussed.

  20. Antiferromagnetism of UO2⋅2H2O

    USGS Publications Warehouse

    Pankey, T.; Senftle, F.E.; Cuttitta, F.

    1963-01-01

    Magnetic susceptibility measurements have been made on UO2⋅xH2O for x=1.78 to x=2.13, and from 77° to 375°K. As the value of x decreased the susceptibility increased. Both these data and structural arguments imply that the formula of this compound is U(OH)4 rather than the dihydrate form. Based on this concept the data have been corrected for diamagnetism and also small amounts of UO2 and H2O which were present. The molar susceptibility of U4+ in U(OH)4 is nearly an order of magnitude less than in other uranium compounds, and it is suggested that this is probably due to superexchange between adjacent uranium atoms through intervening oxygen atoms.

  1. The Target: H2O on the Moon

    NASA Technical Reports Server (NTRS)

    Green, J.; Wys, J. Negusde; Zuppero, A.

    1992-01-01

    The importance of H2O on the lunar surface has long been identified as a high priority for the existence of a human colony for mining activities and, more recently, for space fuel. Using the Earth as an analog, volcanic activity would suggest the generation of water during lunar history. Evidence of volcanism is found not only in present lunar morphology, but in over 400 locations of lunar transient events cataloged by Middlehurst and Kuiper in the 1960's. These events consisted of sightings since early history of vapor emissions and bright spots or flares. Later infrared scanning by Saari and Shorthill showed 'hot spots', many of which coincided with transient event sites. Many of the locations of Middlehurst and Kuiper were the sites of repeat events, leading to the conclusion that these were possibly volcanic in nature. The detection and use of H2O from the lunar surface is discussed.

  2. Detection Of OH+ And H2O+ Towards Orion KL

    NASA Astrophysics Data System (ADS)

    Gupta, Harshal; Rimmer, P.; Pearson, J. C.; Herbst, E.; Yu, S.; Bergin, E. A.; Key Program, HEXOS

    2011-01-01

    The reactive molecular ions, OH+, H2O+, and H3O+, key probes of the oxygen chemistry of the interstellar gas, have been observed toward Orion KL with the Heterodyne Instrument for Far Infrared on board the Herschel Space Observatory. All three N = 1 - 0 fine-structure transitions of OH+ at 909, 971, and 1033 GHz and both fine-structure components of the doublet ortho-H2O+ 111 - 000 transition at 1115 and 1139 GHz were detected, and an upper limit was obtained for H3O+. OH+ and H2O+ are observed purely in absorption, showing a narrow component at the source velocity of 9 km s-1, and a broad blue shifted absorption similar to that reported recently for HF and para-H218O, and attributed to the low velocity outflow of Orion KL. We estimate column densities of OH+ and H2O+ for the 9 km s-1 component of 9 ± 3 x 1012 cm-2 and 7 ± 2 x 1012 cm-2, and those in the outflow of 1.9 ± 0.7 x 1013 cm-2 and 1.0 ± 0.3 x 1013 cm-2. Upper limits of 2.4 x 1012 cm-2 and 8.7 ± 1012 cm-2 were derived for the column densities of ortho and para-H3O+ from transitions near 985 and 1657 GHz. The column densities of the three ions are up to an order of magnitude lower than those obtained from recent observations of W31C and W49N. A higher gas density, despite the assumption of a large ionization rate, may explain the comparatively low column densities of the ions. A part of this work was performed at the Jet Propulsion Laboratory, California Institute of Technology under contract with the National Aeronautics and Space Administration. Copyright 2010© California Institute of Technology. All rights reserved.

  3. Detection of OH+ and H2O+ towards Orion KL

    NASA Astrophysics Data System (ADS)

    Gupta, H.; Rimmer, P.; Pearson, J. C.; Yu, S.; Herbst, E.; Harada, N.; Bergin, E. A.; Neufeld, D. A.; Melnick, G. J.; Bachiller, R.; Baechtold, W.; Bell, T. A.; Blake, G. A.; Caux, E.; Ceccarelli, C.; Cernicharo, J.; Chattopadhyay, G.; Comito, C.; Cabrit, S.; Crockett, N. R.; Daniel, F.; Falgarone, E.; Diez-Gonzalez, M. C.; Dubernet, M.-L.; Erickson, N.; Emprechtinger, M.; Encrenaz, P.; Gerin, M.; Gill, J. J.; Giesen, T. F.; Goicoechea, J. R.; Goldsmith, P. F.; Joblin, C.; Johnstone, D.; Langer, W. D.; Larsson, B.; Latter, W. B.; Lin, R. H.; Lis, D. C.; Liseau, R.; Lord, S. D.; Maiwald, F. W.; Maret, S.; Martin, P. G.; Martin-Pintado, J.; Menten, K. M.; Morris, P.; Müller, H. S. P.; Murphy, J. A.; Nordh, L. H.; Olberg, M.; Ossenkopf, V.; Pagani, L.; Pérault, M.; Phillips, T. G.; Plume, R.; Qin, S.-L.; Salez, M.; Samoska, L. A.; Schilke, P.; Schlecht, E.; Schlemmer, S.; Szczerba, R.; Stutzki, J.; Trappe, N.; van der Tak, F. F. S.; Vastel, C.; Wang, S.; Yorke, H. W.; Zmuidzinas, J.; Boogert, A.; Güsten, R.; Hartogh, P.; Honingh, N.; Karpov, A.; Kooi, J.; Krieg, J.-M.; Schieder, R.; Zaal, P.

    2010-10-01

    We report observations of the reactive molecular ions OH+, H2O+, and H3O+ towards Orion KL with Herschel/HIFI. All three N = 1-0 fine-structure transitions of OH+ at 909, 971, and 1033 GHz and both fine-structure components of the doublet ortho-H2O+ 111-000 transition at 1115 and 1139 GHz were detected; an upper limit was obtained for H3O+. OH+ and H2O+ are observed purely in absorption, showing a narrow component at the source velocity of 9 km s-1, and a broad blueshifted absorption similar to that reported recently for HF and para-H218O, and attributed to the low velocity outflow of Orion KL. We estimate column densities of OH+ and H2O+ for the 9 km s-1 component of 9 ± 3 × 1012 cm-2 and 7 ± 2 × 1012 cm-2, and those in the outflow of 1.9 ± 0.7 × 1013 cm-2 and 1.0 ± 0.3 × 1013 cm-2. Upper limits of 2.4 × 1012 cm-2 and 8.7 × 1012 cm-2 were derived for the column densities of ortho and para-H3O+ from transitions near 985 and 1657 GHz. The column densities of the three ions are up to an order of magnitude lower than those obtained from recent observations of W31C and W49N. The comparatively low column densities may be explained by a higher gas density despite the assumption of a very high ionization rate.

  4. Absorption by H2O and H2O-N2 mixtures at 153 GHz

    NASA Technical Reports Server (NTRS)

    Bauer, A.; Godon, M.; Carlier, J.; Ma, Q.; Tippings, R. H.

    1993-01-01

    New experimental data on and a theoretical analysis of the absorption coefficient at 153 GHz are presented for pure water vapor and water vapor-nitrogen mixtures. This frequency is 30 GHz lower than the resonant frequency of the nearest strong water line (183 GHz) and complements our previous measurements at 213 GHz. The pressure dependence is observed to be quadratic in the case of pure water vapor, while in the case of mixtures there are both linear and quadratic density components. By fitting our experimental data taken at several temperatures we have obtained the temperature dependence of the absorption. Our experimental data are compared to several theoretical models with and without a continuum contribution, and we find that none of the models is in very good agreement with the data; in the case of pure water vapor, the continuum contribution calculated using the recent theoretical absorption gives the best results. In general, the agreement between the data and the various models is less satisfactory than found previously in the high-frequency wing. The anisotropy in the observed absorption differs from that currently used in atmospheric models.

  5. The structural transformation of monoclinic [(R)-C5H14N2][Cu(SO4)2(H2O)4].2H2O into orthorhombic [(R)-C5H14N2]2[Cu(H2O)6](SO4)3: crystal structures and thermal behavior

    NASA Astrophysics Data System (ADS)

    Saïd, Salem; Mhadhbi, Noureddine; Hajlaoui, Fadhel; Yahyaoui, Samia; Norquist, Alexander J.; Mhiri, Tahar; Bataille, Thierry; Naïli, Houcine

    2014-01-01

    Single crystals of [(R)-C5H14N2][Cu(SO4)2(H2O)4].2H2O (1) were grown through the slow evaporation of a solution containing H2SO4, (R)-C5H12N2 and CuSO4.5H2O. These crystals spontaneously transform to [(R)-C5H14N2]2[Cu(H2O)6](SO4)3 (2) over the course of four days at room temperature. The same single crystal on the same mounting was used for the determination of the structure of (1) and the unit cell determination of (2). A second single crystal of the transformed batch has served for the structural determination of (2). Compound 1 crystallizes in the noncentrosymmetric space group P21 (No. 4) and consists of trimeric [Cu(SO4)2(H2O)4]2- anions, [(R)-C5H14N2]2+ cations and occluded water molecules. Compound 2 crystallizes in P21212 (No. 18) and contains [Cu(H2O)6]2+ cations, [SO4]2- anions and occluded water molecules. The thermal decompositions of compounds 1 and 2 were studied by thermogravimetric analyses and temperature-dependent X-ray diffraction.

  6. Thermodynamic calculations in the system CH4-H2O and methane hydrate phase equilibria

    USGS Publications Warehouse

    Circone, S.; Kirby, S.H.; Stern, L.A.

    2006-01-01

    Using the Gibbs function of reaction, equilibrium pressure, temperature conditions for the formation of methane clathrate hydrate have been calculated from the thermodynamic properties of phases in the system CH4-H 2O. The thermodynamic model accurately reproduces the published phase-equilibria data to within ??2 K of the observed equilibrium boundaries in the range 0.08-117 MPa and 190-307 K. The model also provides an estimate of the third-law entropy of methane hydrate at 273.15 K, 0.1 MPa of 56.2 J mol-1 K-1 for 1/n CH4??H 2O, where n is the hydrate number. Agreement between the calculated and published phase-equilibria data is optimized when the hydrate composition is fixed and independent of the pressure and temperature for the conditions modeled. ?? 2006 American Chemical Society.

  7. Normalized fluctuations, H2O vs n-hexane: Site-correlated percolation

    NASA Astrophysics Data System (ADS)

    Koga, Yoshikata; Westh, Peter; Sawamura, Seiji; Taniguchi, Yoshihiro

    1996-08-01

    Entropy, volume and the cross fluctuations were normalized to the average volume of a coarse grain with a fixed number of molecules, within which the local and instantaneous value of interest is evaluated. Comparisons were made between liquid H2O and n-hexane in the range from -10 °C to 120 °C and from 0.1 MPa to 500 MPa. The difference between H2O and n-hexane in temperature and pressure dependencies of these normalized fluctuations was explained in terms of the site-correlated percolation theory for H2O. In particular, the temperature increase was confirmed to reduce the hydrogen bond probability, while the pressure appeared to have little effect on the hydrogen bond probability. According to the Le Chatelier principle, however, the putative formation of ``ice-like'' patches at low temperatures due to the site-correlated percolation requirement is retarded by pressure increases. Thus, only in the limited region of low pressure (<300 MPa) and temperature (<60 °C), the fluctuating ice-like patches are considered to persist.

  8. Reaction Pathways and Excited States in H2O2+OH → HO2+H2O : A New ab initio Investigation

    SciTech Connect

    Ginovska, Bojana; Camaioni, Donald M.; Dupuis, Michel

    2007-08-28

    The mechanism of the hydrogen abstraction reaction H2O2+OH→ HO2+H2O in gas phase was studied, using DFT (MPW1K) level of theory. We located 2 pathways for the reaction, both going through the same intermediate complex OH-H2O2, but via two distinct transition state structures that differ by the orientation of the hydroxyl hydrogen relative to the incipient hydroperoxy hydrogen. In one case, these hydrogens are on same side of the plane made by the 3 oxygen atoms and in the other these hydrogens are on opposite sides of the plane. The first two excited states were calculated for selected points of both pathways using time-dependent DFT, multiconfigurational quasi-degenerate-perturbation theory (MCQDPT2/ CASSCF) and equation of motion coupled cluster singles, doubles model (EOM-CCSD) EOMCCSD energies and completely renormalized EOM-CCSD(T)(IA) correction. An avoided crossing between the two excited states was found on both reaction pathways, on the product side of the barrier to H-transfer on the ground state surface, near the transition states. Further more, we report on the calculation of the rate of the reaction in the gas phase for temperatures in the range of 250-500 K, and suggest that the strong temperature dependence of the rate at high temperatures is due to reaction on the low-lying excited state surface over a barrier that is much larger than on the ground state surface. This work was supported in part by the Office of Basic Energy Sciences of the Department of Energy (DOE), Chemical Sciences program (BG and MD) and in part by the U.S. Department of Energy’s Office of Biological and Environmental Research, Environmental Management Science Program (BG and DMC). The Pacific Northwest National Laboratory is operated for DOE by Battelle Memorial Institute.

  9. Bactericidal Effect of Photolysis of H2O2 in Combination with Sonolysis of Water via Hydroxyl Radical Generation.

    PubMed

    Sheng, Hong; Nakamura, Keisuke; Kanno, Taro; Sasaki, Keiichi; Niwano, Yoshimi

    2015-01-01

    The bactericidal effect of hydroxyl radical (·OH) generated by combination of photolysis of hydrogen peroxide (H2O2) and sonolysis of water was examined under the condition in which the yield of ·OH increased additively when H2O2 aqueous solution was concomitantly irradiated with laser and ultrasound. The suspension of Staphylococcus aureus mixed with the different concentrations of H2O2 was irradiated simultaneously with a laser light (wavelength: 405 nm, irradiance: 46 and 91 mW/cm2) and ultrasound (power: 30 w, frequency: 1.65 MHz) at 20 ± 1°C of the water bulk temperature for 2 min. The combination of laser and ultrasound irradiation significantly reduced the viable bacterial count in comparison with the laser irradiation of H2O2 alone. By contrast, the ultrasound irradiation alone exerted almost no bactericidal effect. These results suggested that the combination effect of photolysis of H2O2 and sonolysis of water on bactericidal activity was synergistic. A multi-way analysis of variance also revealed that the interaction of H2O2 concentration, laser power and ultrasound irradiation significantly affected the bactericidal activity. Since the result of oxidative DNA damage evaluation demonstrated that the combination of laser and ultrasound irradiation significantly induced oxidative damage of bacterial DNA in comparison with the laser irradiation of H2O2 alone, it was suggested that the combination effect of photolysis of H2O2 and sonolysis of water on bactericidal activity would be exerted via oxidative damage of cellular components such as DNA.

  10. Bactericidal Effect of Photolysis of H2O2 in Combination with Sonolysis of Water via Hydroxyl Radical Generation

    PubMed Central

    Sheng, Hong; Nakamura, Keisuke; Kanno, Taro; Sasaki, Keiichi; Niwano, Yoshimi

    2015-01-01

    The bactericidal effect of hydroxyl radical (·OH) generated by combination of photolysis of hydrogen peroxide (H2O2) and sonolysis of water was examined under the condition in which the yield of ·OH increased additively when H2O2 aqueous solution was concomitantly irradiated with laser and ultrasound. The suspension of Staphylococcus aureus mixed with the different concentrations of H2O2 was irradiated simultaneously with a laser light (wavelength: 405 nm, irradiance: 46 and 91 mW/cm2) and ultrasound (power: 30 w, frequency: 1.65 MHz) at 20 ± 1°C of the water bulk temperature for 2 min. The combination of laser and ultrasound irradiation significantly reduced the viable bacterial count in comparison with the laser irradiation of H2O2 alone. By contrast, the ultrasound irradiation alone exerted almost no bactericidal effect. These results suggested that the combination effect of photolysis of H2O2 and sonolysis of water on bactericidal activity was synergistic. A multi-way analysis of variance also revealed that the interaction of H2O2 concentration, laser power and ultrasound irradiation significantly affected the bactericidal activity. Since the result of oxidative DNA damage evaluation demonstrated that the combination of laser and ultrasound irradiation significantly induced oxidative damage of bacterial DNA in comparison with the laser irradiation of H2O2 alone, it was suggested that the combination effect of photolysis of H2O2 and sonolysis of water on bactericidal activity would be exerted via oxidative damage of cellular components such as DNA. PMID:26148024

  11. 3-µm spectroscopy of Near-Earth Asteroids: Searching for OH/H2O on small planetary bodies

    NASA Astrophysics Data System (ADS)

    Wigton, Nathanael; Emery, Joshua; Thomas, Cristina; Rivkin, Andy

    2015-11-01

    Near-Earth asteroids (NEAs) are not expected to have OH and/or H2O ice on their surfaces because; a) most accreted dry in the inner Solar System and therefore never contained hydrated materials, and b) their relatively high surface temperatures should quickly drive OH/H2O off their surface. However, OH/H2O has been detected on other anhydrous inner solar system objects, including the Moon and Vesta. Possible mechanisms to explain OH/H2O on surfaces in the inner Solar System include production via solar wind interactions, carbonaceous chondrite or cometary impact delivery, or native OH/H2O molecules bound to phyllosilicates. As these processes are active in near-Earth space, we hypothesize that detectable levels of OH/H2O are present on NEAs.The OH/H2O feature can be comprised of an OH absorption feature centered near 2.7 μm and H2O features near 2.9 and 3.1 μm, or a blend of both, producing a relatively wide feature spanning 2.7 - 3.1 μm. Analysis of the shape of the 3-µm feature, coupled with the observed NEA orbital parameters and albedos, can help distinguish between the possible sources of OH/H2O.Here we present results of an ongoing observational program to measure spectra of NEAs in the 3-μm region. We are using the SpeX instrument on NASA’s IRTF to measure spectra from ~2 to 4.2 μm. So far, we have 12 observations of 8 NEAs. Of these objects, three exhibit a 3-μm feature: both of our observations of (443) Eros, three observations of (1036) Ganymed, and (3122) Florence exhibit. The NEAs (54789) 2001 MZ7, (96590) 1998 XB, (285944) 2001 RZ11, (214088) 2004 JN13, (357439) 2004 BL86 do not exhibit a feature. Rivkin et al. (2013; LPSC) has also reported detections of the 3-μm feature on Ganymed and Eros with data taken in the same year as ours (2012). Band shape, albedo, and orbital analysis of the NEAs exhibiting the 3-µm feature indicate that the primary production mechanism of OH/H2O on Eros and Ganymed is solar wind interactions. For Florence, on

  12. Mesospheric H2O and H2O2 densities inferred from in situ positive ion composition measurement

    NASA Technical Reports Server (NTRS)

    Kopp, E.

    1984-01-01

    A model for production and loss of oxonium ions in the high-latitude D-region is developed, based on the observed excess of 34(+) which has been interpreted as H2O2(+). The loss mechanism suggested in the study is the attachment of N2 and/or CO2 in three-body reactions. Furthermore, mesospheric water vapor and H2O2 densities are inferred from measurements of four high-latitude ion compositions, based on the oxonium model. Mixing ratios of hydrogen peroxide of up to two orders of magnitude higher than previous values were obtained. A number of reactions, reaction constants, and a block diagram of the oxonium ion chemistry in the D-region are given.

  13. Mechanism for the Direct Synthesis of H2O2 on Pd Clusters: Heterolytic Reaction Pathways at the Liquid-Solid Interface.

    PubMed

    Wilson, Neil M; Flaherty, David W

    2016-01-20

    Direct synthesis (H2 + O2 → H2O2) is a promising reaction for producing H2O2, which can replace chlorinated oxidants in industrial processes. The mechanism of this reaction and the reasons for the importance of seemingly unrelated factors (e.g., Pd cluster size and solvent pH) remain unclear despite significant research. We propose a mechanism for H2O2 formation on Pd clusters consistent with steady-state H2O2 and H2O formation rates measured as functions of reactant pressures and temperature and the interpretations of proton concentration effects. H2O2 forms by sequential proton-electron transfer to O2 and OOH surface intermediates, whereas H2O forms by O-O bond rupture within OOH surface species. Direct synthesis, therefore, does not proceed by the Langmuir-Hinshelwood mechanism often invoked. Rather, H2O2 forms by heterolytic reaction pathways resembling the two-electron oxygen reduction reaction (ORR); however, the chemical potential of H2 replaces an external electrical potential as the thermodynamic driving force. Activation enthalpies (ΔH(⧧)) for H2O formation increase by 14 kJ mol(-1) when Pd cluster diameters increase from 0.7 to 7 nm because changes in the electronic structure of Pd surface atoms decrease their propensity to cleave O-O bonds. ΔH(⧧) values for H2O2 remain nearly constant because barriers for proton-electron transfer depend weakly on the coordinative saturation of Pd surface atoms. Collectively, these results provide a self-consistent mechanism, which clarifies many studies in which H2O2 rates and selectivities were shown to depend on the concentration of acid/halide additives and Pd cluster size. These findings will guide the rational design of selective catalysts for direct synthesis.

  14. Mechanism for the Direct Synthesis of H2O2 on Pd Clusters: Heterolytic Reaction Pathways at the Liquid-Solid Interface.

    PubMed

    Wilson, Neil M; Flaherty, David W

    2016-01-20

    Direct synthesis (H2 + O2 → H2O2) is a promising reaction for producing H2O2, which can replace chlorinated oxidants in industrial processes. The mechanism of this reaction and the reasons for the importance of seemingly unrelated factors (e.g., Pd cluster size and solvent pH) remain unclear despite significant research. We propose a mechanism for H2O2 formation on Pd clusters consistent with steady-state H2O2 and H2O formation rates measured as functions of reactant pressures and temperature and the interpretations of proton concentration effects. H2O2 forms by sequential proton-electron transfer to O2 and OOH surface intermediates, whereas H2O forms by O-O bond rupture within OOH surface species. Direct synthesis, therefore, does not proceed by the Langmuir-Hinshelwood mechanism often invoked. Rather, H2O2 forms by heterolytic reaction pathways resembling the two-electron oxygen reduction reaction (ORR); however, the chemical potential of H2 replaces an external electrical potential as the thermodynamic driving force. Activation enthalpies (ΔH(⧧)) for H2O formation increase by 14 kJ mol(-1) when Pd cluster diameters increase from 0.7 to 7 nm because changes in the electronic structure of Pd surface atoms decrease their propensity to cleave O-O bonds. ΔH(⧧) values for H2O2 remain nearly constant because barriers for proton-electron transfer depend weakly on the coordinative saturation of Pd surface atoms. Collectively, these results provide a self-consistent mechanism, which clarifies many studies in which H2O2 rates and selectivities were shown to depend on the concentration of acid/halide additives and Pd cluster size. These findings will guide the rational design of selective catalysts for direct synthesis. PMID:26597848

  15. Rotational Quenching of Rotationally Excited H2O in Collisions with He

    NASA Astrophysics Data System (ADS)

    Yang, Benhui; Nagao, M.; Satomi, W.; Kimura, M.; Stancil, P. C.

    2013-03-01

    Theoretical rotational quenching cross sections and rate coefficients of ortho- and para-H2O due to collisions with He atoms are presented. The complete angular momentum close-coupling approach as well as the coupled-states approximation for the angular momentum decoupling was applied to solve the scattering problem for a large range of rotationally excited states of water. Results are obtained for quenching from initial levels 11, 0, 21, 2, 22, 1, 30, 3, 31, 2, 32, 1, 41, 4, 33, 0, and 42, 3 of ortho-H2O and from initial levels 11, 1, 20, 2, 21, 1, 22, 0, 31, 3, 32, 2, 40, 4, 41, 3, and 33, 1 of para-H2O for kinetic energies from 10-5 to 104 cm-1. State-to-state and total deexcitation cross sections and rate coefficients for temperatures between 0.1 and 3000 K are reported. The present state-to-state rate coefficients are found to be in good agreement with previous results obtained by Green and coworkers at high temperatures, but significant discrepancies are obtained at lower temperatures likely due to differences in the adopted potential energy surfaces. Astrophysical applications of the current rate coefficients are briefly discussed.

  16. Isopycnic Phases and Structures in H2O/CO2/Ethoxylated Alcohol Surfactant Mixtures

    NASA Technical Reports Server (NTRS)

    Paulaitis, Michael E.; Zielinski, Richard G.; Kaler, Eric W.

    1996-01-01

    Ternary mixtures of H2O and CO2 with ethoxylated alcohol (C(i)E(j)) surfactants can form three coexisting liquid phases at conditions where two of the phases have the same density (isopycnic phases). Isopycnic phase behavior has been observed for mixtures containing the surfactants C8E5, C10E6, and C12E6, but not for those mixtures containing either C4E1 or CgE3. Pressure-temperature (PT) projections for this isopycnic three-phase equilibrium were determined for H2O/CO2/C8E5 and H2O/CO2/C10E6 mixtures at temperatures from approximately 25 to 33 C and pressures between 90 and 350 bar. As a preliminary to measuring the microstructure in isopycnic three component mixtures, phase behavior and small angle neutron scattering (SANS) experiments were performed on mixtures of D2O/CO2/ n-hexaethyleneglycol monododecyl ether (C12E6) as a function of temperature (25-31 C), pressure (63.1-90.7 bar), and CO2 composition (0-3.9 wt%). Parameters extracted from model fits of the SANS spectra indicate that, while micellar structure remains essentially unchanged, critical concentration fluctuations increase as the phase boundary and plait point are approached.

  17. H2-O2 auxiliary power unit for space shuttle vehicles

    NASA Technical Reports Server (NTRS)

    Joyce, J. P.; Beremand, D. G.; Cameron, H. M.; Jefferies, K. S.

    1973-01-01

    A program to establish technology readiness of hydrogen-oxygen (H2-O2) auxiliary power units for use on board the space shuttle orbiter vehicle is discussed. Fundamental objectives include experimentally establishing an acceptable propellant flow control method, verification of combustor stability, and adequate thermal management. An initial APU configuration with recycled hydrogen flow has been studied and revised towards greater simplicity and scaling ease. The selected APU is a recuperated open-cycle, turbine-driven unit. Series flow of cryogenic hydrogen removes internally-generated heat and from the hydraulic system. Steady-state test of the combustor has been successful.

  18. Increasing extracellular H2O2 produces a bi-phasic response in intracellular H2O2, with peroxiredoxin hyperoxidation only triggered once the cellular H2O2-buffering capacity is overwhelmed.

    PubMed

    Tomalin, Lewis Elwood; Day, Alison Michelle; Underwood, Zoe Elizabeth; Smith, Graham Robert; Dalle Pezze, Piero; Rallis, Charalampos; Patel, Waseema; Dickinson, Bryan Craig; Bähler, Jürg; Brewer, Thomas Francis; Chang, Christopher Joh-Leung; Shanley, Daryl Pierson; Veal, Elizabeth Ann

    2016-06-01

    Reactive oxygen species, such as H2O2, can damage cells but also promote fundamental processes, including growth, differentiation and migration. The mechanisms allowing cells to differentially respond to toxic or signaling H2O2 levels are poorly defined. Here we reveal that increasing external H2O2 produces a bi-phasic response in intracellular H2O2. Peroxiredoxins (Prx) are abundant peroxidases which protect against genome instability, ageing and cancer. We have developed a dynamic model simulating in vivo changes in Prx oxidation. Remarkably, we show that the thioredoxin peroxidase activity of Prx does not provide any significant protection against external rises in H2O2. Instead, our model and experimental data are consistent with low levels of extracellular H2O2 being efficiently buffered by other thioredoxin-dependent activities, including H2O2-reactive cysteines in the thiol-proteome. We show that when extracellular H2O2 levels overwhelm this buffering capacity, the consequent rise in intracellular H2O2 triggers hyperoxidation of Prx to thioredoxin-resistant, peroxidase-inactive form/s. Accordingly, Prx hyperoxidation signals that H2O2 defenses are breached, diverting thioredoxin to repair damage. PMID:26944189

  19. Increasing extracellular H2O2 produces a bi-phasic response in intracellular H2O2, with peroxiredoxin hyperoxidation only triggered once the cellular H2O2-buffering capacity is overwhelmed.

    PubMed

    Tomalin, Lewis Elwood; Day, Alison Michelle; Underwood, Zoe Elizabeth; Smith, Graham Robert; Dalle Pezze, Piero; Rallis, Charalampos; Patel, Waseema; Dickinson, Bryan Craig; Bähler, Jürg; Brewer, Thomas Francis; Chang, Christopher Joh-Leung; Shanley, Daryl Pierson; Veal, Elizabeth Ann

    2016-06-01

    Reactive oxygen species, such as H2O2, can damage cells but also promote fundamental processes, including growth, differentiation and migration. The mechanisms allowing cells to differentially respond to toxic or signaling H2O2 levels are poorly defined. Here we reveal that increasing external H2O2 produces a bi-phasic response in intracellular H2O2. Peroxiredoxins (Prx) are abundant peroxidases which protect against genome instability, ageing and cancer. We have developed a dynamic model simulating in vivo changes in Prx oxidation. Remarkably, we show that the thioredoxin peroxidase activity of Prx does not provide any significant protection against external rises in H2O2. Instead, our model and experimental data are consistent with low levels of extracellular H2O2 being efficiently buffered by other thioredoxin-dependent activities, including H2O2-reactive cysteines in the thiol-proteome. We show that when extracellular H2O2 levels overwhelm this buffering capacity, the consequent rise in intracellular H2O2 triggers hyperoxidation of Prx to thioredoxin-resistant, peroxidase-inactive form/s. Accordingly, Prx hyperoxidation signals that H2O2 defenses are breached, diverting thioredoxin to repair damage.

  20. Kinetic Studies of Iron Deposition in Horse Spleen Ferritin Using H2O2 and O2 as Oxidants

    NASA Technical Reports Server (NTRS)

    Lowery, Thomas J., Jr.; Bunker, Jared; Zhang, Bo; Costen, Robert; Watt, Gerald D.

    2004-01-01

    The reaction of horse spleen ferritin (HoSF) with Fe(2+) at pH 6.5 and 7.5 using O2, H2O2 and 1:1 a mixture of both showed that the iron deposition reaction using H2O2 is approx. 20- to 50-fold faster than the reaction with O2 alone. When H2O2 was added during the iron deposition reaction initiated with O2 as oxidant, Fe(2+) was preferentially oxidized by H2O2, consistent with the above kinetic measurements. Both the O2 and H202 reactions were well defined from 15 to 40 C from which activation parameters were determined. The iron deposition reaction was also studied using O2 as oxidant in the presence and absence of catalase using both stopped-flow and pumped-flow measurements. The presence of catalase decreased the rate of iron deposition by approx. 1.5-fold, and gave slightly smaller absorbance changes than in its absence. From the rate constants for the O2 (0.044 per second) and H2O2 (0.67 per second) iron-deposition reactions at pH 7.5, simulations of steady-state H2O2 concentrations were computed to be 0.45 micromolar. This low value and reported Fe2(+)/O2 values of 2.0-2.5 are consistent with H2O2 rapidly reacting by an alternate but unidentified pathway involving a system component such as the protein shell or the mineral core as previously postulated.

  1. Sensitization of H2O2-induced TRPM2 activation and subsequent interleukin-8 (CXCL8) production by intracellular Fe(2+) in human monocytic U937 cells.

    PubMed

    Shimizu, Shunichi; Yonezawa, Ryo; Negoro, Takaharu; Yamamoto, Shinichiro; Numata, Tomohiro; Ishii, Masakazu; Mori, Yasuo; Toda, Takahiro

    2015-11-01

    Transient receptor potential melastatin 2 (TRPM2) is an oxidative stress-sensitive Ca(2+)-permeable channel. In monocytes/macrophages, H2O2-induced TRPM2 activation causes cell death and/or production of chemokines that aggravate inflammatory diseases. However, relatively high concentrations of H2O2 are required for activation of TRPM2 channels in vitro. Thus, in the present study, factors that sensitize TRPM2 channels to H2O2 were identified and subsequent physiological responses were examined in U937 human monocytes. Temperature increase from 30°C to 37°C enhanced H2O2-induced TRPM2-mediated increase in intracellular free Ca(2+) ([Ca(2+)]i) in TRPM2-expressing HEK 293 cells (TRPM2/HEK cells). The H2O2-induced TRPM2 activation enhanced by the higher temperature was dramatically sensitized by intracellular Fe(2+)-accumulation following pretreatment with FeSO4. Thus intracellular Fe(2+)-accumulation sensitizes H2O2-induced TRPM2 activation at around body temperature. Moreover, intracellular Fe(2+)-accumulation increased poly(ADP-ribose) levels in nuclei by H2O2 treatment, and the sensitization of H2O2-induced TRPM2 activation were almost completely blocked by poly(ADP-ribose) polymerase inhibitors, suggesting that intracellular Fe(2+)-accumulation enhances H2O2-induced TRPM2 activation by increase of ADP-ribose production through poly(ADP-ribose) polymerase pathway. Similarly, pretreatment with FeSO4 stimulated H2O2-induced TRPM2 activation at 37°C in U937 cells and enhanced H2O2-induced ERK phosphorylation and interleukin-8 (CXCL8) production. Although the addition of H2O2 to cells under conditions of intracellular Fe(2+)-accumulation caused cell death, concentration of H2O2 required for CXCL8 production was lower than that resulting in cell death. These results indicate that intracellular Fe(2+)-accumulation sensitizes TRPM2 channels to H2O2 and subsequently produces CXCL8 at around body temperature. It is possible that sensitization of H2O2-induced TRPM2

  2. Sensitization of H2O2-induced TRPM2 activation and subsequent interleukin-8 (CXCL8) production by intracellular Fe(2+) in human monocytic U937 cells.

    PubMed

    Shimizu, Shunichi; Yonezawa, Ryo; Negoro, Takaharu; Yamamoto, Shinichiro; Numata, Tomohiro; Ishii, Masakazu; Mori, Yasuo; Toda, Takahiro

    2015-11-01

    Transient receptor potential melastatin 2 (TRPM2) is an oxidative stress-sensitive Ca(2+)-permeable channel. In monocytes/macrophages, H2O2-induced TRPM2 activation causes cell death and/or production of chemokines that aggravate inflammatory diseases. However, relatively high concentrations of H2O2 are required for activation of TRPM2 channels in vitro. Thus, in the present study, factors that sensitize TRPM2 channels to H2O2 were identified and subsequent physiological responses were examined in U937 human monocytes. Temperature increase from 30°C to 37°C enhanced H2O2-induced TRPM2-mediated increase in intracellular free Ca(2+) ([Ca(2+)]i) in TRPM2-expressing HEK 293 cells (TRPM2/HEK cells). The H2O2-induced TRPM2 activation enhanced by the higher temperature was dramatically sensitized by intracellular Fe(2+)-accumulation following pretreatment with FeSO4. Thus intracellular Fe(2+)-accumulation sensitizes H2O2-induced TRPM2 activation at around body temperature. Moreover, intracellular Fe(2+)-accumulation increased poly(ADP-ribose) levels in nuclei by H2O2 treatment, and the sensitization of H2O2-induced TRPM2 activation were almost completely blocked by poly(ADP-ribose) polymerase inhibitors, suggesting that intracellular Fe(2+)-accumulation enhances H2O2-induced TRPM2 activation by increase of ADP-ribose production through poly(ADP-ribose) polymerase pathway. Similarly, pretreatment with FeSO4 stimulated H2O2-induced TRPM2 activation at 37°C in U937 cells and enhanced H2O2-induced ERK phosphorylation and interleukin-8 (CXCL8) production. Although the addition of H2O2 to cells under conditions of intracellular Fe(2+)-accumulation caused cell death, concentration of H2O2 required for CXCL8 production was lower than that resulting in cell death. These results indicate that intracellular Fe(2+)-accumulation sensitizes TRPM2 channels to H2O2 and subsequently produces CXCL8 at around body temperature. It is possible that sensitization of H2O2-induced TRPM2

  3. Study of the reversible water vapour sorption process of MgSO4.7H2O and MgCl2.6H2O under the conditions of seasonal solar heat storage

    NASA Astrophysics Data System (ADS)

    Ferchaud, C. J.; Zondag, H. A.; Veldhuis, J. B. J.; de Boer, R.

    2012-11-01

    The characterization of the structural, compositional and thermodynamic properties of MgSO4.7H2O and MgCl2.6H2O has been done using in-situ X-ray Diffraction and thermal analyses (TG/DSC) under practical conditions for seasonal heat storage (Tmax=150°C, p(H2O)=13 mbar). This study showed that these two materials release heat after a dehydration/hydration cycle with energy densities of 0.38 GJ/m3 for MgSO4.7H2O and 0.71 GJ/m3 MgCl2.6H2O. The low heat release found for MgSO4.7H2O is mainly attributed to the amorphization of the material during the dehydration performed at 13 mbar which reduces its sorption capacity during the rehydration. MgCl2.6H2O presents a high energy density which makes this material interesting for seasonal heat storage in domestic applications. This material would be able to fulfil the winter heat demand of a passive house estimated at 6 GJ with a packed bed reactor of 8.5 m3. However, a seasonal heat storage system built with this material should be carefully set with a restricted temperature at 40°C for the hydration reaction to avoid the liquefaction of the material at lower temperature which limits its performances for long term storage.

  4. Measurements of H2O-broadening coefficients of O2 A-band lines

    NASA Astrophysics Data System (ADS)

    Delahaye, T.; Landsheere, X.; Pangui, E.; Huet, F.; Hartmann, J.-M.; Tran, H.

    2016-11-01

    We report laboratory measurements of H2O-broadening coefficients of O2 absorption lines in the A-band near 13,000 cm-1. For this, four spectra of oxygen gas mixed with water vapor were recorded with a high resolution Fourier transform spectrometer for total pressures ranging from 125 to 175 Torr at 323 K, and a fifth at 175 Torr and 365 K. Broadening coefficients of 39 transitions (up to J″ = 21) were retrieved from the measured spectra through fits using Galatry line profiles. Values at room temperature (296 K) were then extrapolated and compared with previous determinations in the A-band and millimeter waves region. This enables to resolve some controversial issues related to the inconsistencies between these studies. Finally, comparing our results with the line broadening coefficients by dry air confirms that H2O-broadenings of oxygen lines are, on average, 10% larger than those by dry air.

  5. Carbon dioxide adsorption on H2 O 2 treated single-walled carbon nanohorns

    NASA Astrophysics Data System (ADS)

    Migone, Aldo; Krungleviciute, Vaiva; Banjara, Shree; Yudasaka, Masako; Iijima, Sumio

    2011-03-01

    Carbon nanohorns are closed single-wall structures with a hollow interior. Unlike SWNTs, which assemble into cylindrical bundles, nanohorns form spherical aggregates. In our experiments we used dahlia-like carbon nanohorn aggregates. Our sample underwent treatment with H2 O2 which opened access to the interior spaces of the individual nanohorns. We measured carbon dioxide adsorption at several temperatures between 167 and 195 K. We calculated the isosteric heat as a function of loading, and the binding energy values for CO2 on the nanohorn aggregates from the isotherm data. Results on the H2 O2 -treated nanohorns will be compared with those obtained on other carbon substrates. We have also determined detailed equilibration profiles for CO2 adsorption on the nanohorn aggregates; these results will also be presented. This work was supported by the NSF through grants DMR-1006428 and DMR-0705077.

  6. In situ electrical conductivity measurements of H2O under static pressure up to 28 GPa

    NASA Astrophysics Data System (ADS)

    Liu, Bao; Gao, Yang; Han, Yonghao; Ma, Yanzhang; Gao, Chunxiao

    2016-08-01

    The in situ electrical conductivity measurements on water in both solid state and liquid state were performed under pressure up to 28 GPa and temperature from 77 K to 300 K using a microcircuit fabricated on a diamond anvil cell (DAC). Water chemically ionization mainly contributes to electrical conduction in liquid state, which is in accord with the results obtained under dynamic pressure. Energy band theory of liquid water was used to understand effect of static pressure on electrical conduction of water. The electric conductivity of H2O decreased discontinuously by four orders of magnitude at 0.7-0.96 GPa, indicating water frozen at this P-T condition. Correspondingly, the conduction of H2O in solid state is determined by arrangement and bending of H-bond in ice VI and ice VII. Based on Jaccard theory, we have concluded that the charge carriers of ice are already existing ions and Bjerrum defects.

  7. Synthetic fluid inclusions XX. Critical PTx properties of H2O-FeCl2 fluids

    NASA Astrophysics Data System (ADS)

    Steele-MacInnis, Matthew; Lecumberri-Sanchez, Pilar; Bodnar, Robert J.

    2015-01-01

    Iron chloride is a common and abundant component in hydrothermal fluids in many geologic environments, yet the thermodynamic and PTx properties of FeCl2-bearing aqueous fluids are poorly known. In this study we have used the synthetic fluid inclusion technique to characterize the PTx conditions along the critical curve of the system H2O-FeCl2. For a given temperature or salinity, the critical pressure in the H2O-FeCl2 system is lower than that in the H2O-NaCl system. In contrast, the critical curves of aqueous solutions of other divalent-cation chlorides, such as MgCl2 and CaCl2, are at higher pressure than that of NaCl solutions of equivalent temperature or salinity. The results of this study provide the first quantitative constraints on the PTx extent of liquid-vapor immiscibility for FeCl2-rich fluids. Owing to the low pressure along the critical curve compared to other common aqueous chloride systems, immiscibility of FeCl2-rich fluids appears to be limited to relatively low pressures, or relatively shallow levels in the crust, compared to other saline hydrothermal fluids.

  8. H2O2-responsive antioxidant polymeric nanoparticles as therapeutic agents for peripheral arterial disease.

    PubMed

    Kwon, Byeongsu; Kang, Changsun; Kim, Jinsub; Yoo, Donghyuck; Cho, Byung-Ryul; Kang, Peter M; Lee, Dongwon

    2016-09-25

    Peripheral artery disease (PAD) is a common circulatory disorder in which narrowed arteries limit blood flow to the lower extremity and affect millions of people worldwide. Therapeutic angiogenesis has emerged as a promising strategy to treat PAD patients because surgical intervention has been showing limited success. Leg muscles of PAD patients have significantly high level of ROS (reactive oxygen species) and the increased production of ROS is a key mechanism of initiation and progression of PAD. We have recently developed H2O2-responsive polymer PVAX, which is designed to rapidly scavenge H2O2 and release vanillyl alcohol with antioxidant and anti-inflammatory activity. In this study, we investigated the therapeutic efficacy of PVAX nanoparticles for PAD using a cell culture model and a mouse model of hindlimb ischemia. PVAX nanoparticles significantly enhanced the expression of angiogenic inducers such as vascular endothelial growth factor (VEGF) and platelet endothelial cell adhesion molecule (PECAM)-1 in human umbilical vein endothelial cells (HUVEC). PVAX nanoparticles promoted revascularization and restoration of blood perfusion into ischemic tissues by upregulating angiogenic VEGF and PECAM-1. This work demonstrates that H2O2-responsive PVAX nanoparticles facilitate therapeutic angiogenesis and hold tremendous translational potential as therapeutic systems for ischemic diseases such as PAD. PMID:27521705

  9. VUV photoionization cross sections of HO2, H2O2, and H2CO.

    PubMed

    Dodson, Leah G; Shen, Linhan; Savee, John D; Eddingsaas, Nathan C; Welz, Oliver; Taatjes, Craig A; Osborn, David L; Sander, Stanley P; Okumura, Mitchio

    2015-02-26

    The absolute vacuum ultraviolet (VUV) photoionization spectra of the hydroperoxyl radical (HO2), hydrogen peroxide (H2O2), and formaldehyde (H2CO) have been measured from their first ionization thresholds to 12.008 eV. HO2, H2O2, and H2CO were generated from the oxidation of methanol initiated by pulsed-laser-photolysis of Cl2 in a low-pressure slow flow reactor. Reactants, intermediates, and products were detected by time-resolved multiplexed synchrotron photoionization mass spectrometry. Absolute concentrations were obtained from the time-dependent photoion signals by modeling the kinetics of the methanol oxidation chemistry. Photoionization cross sections were determined at several photon energies relative to the cross section of methanol, which was in turn determined relative to that of propene. These measurements were used to place relative photoionization spectra of HO2, H2O2, and H2CO on an absolute scale, resulting in absolute photoionization spectra. PMID:25621533

  10. H2O2-responsive antioxidant polymeric nanoparticles as therapeutic agents for peripheral arterial disease.

    PubMed

    Kwon, Byeongsu; Kang, Changsun; Kim, Jinsub; Yoo, Donghyuck; Cho, Byung-Ryul; Kang, Peter M; Lee, Dongwon

    2016-09-25

    Peripheral artery disease (PAD) is a common circulatory disorder in which narrowed arteries limit blood flow to the lower extremity and affect millions of people worldwide. Therapeutic angiogenesis has emerged as a promising strategy to treat PAD patients because surgical intervention has been showing limited success. Leg muscles of PAD patients have significantly high level of ROS (reactive oxygen species) and the increased production of ROS is a key mechanism of initiation and progression of PAD. We have recently developed H2O2-responsive polymer PVAX, which is designed to rapidly scavenge H2O2 and release vanillyl alcohol with antioxidant and anti-inflammatory activity. In this study, we investigated the therapeutic efficacy of PVAX nanoparticles for PAD using a cell culture model and a mouse model of hindlimb ischemia. PVAX nanoparticles significantly enhanced the expression of angiogenic inducers such as vascular endothelial growth factor (VEGF) and platelet endothelial cell adhesion molecule (PECAM)-1 in human umbilical vein endothelial cells (HUVEC). PVAX nanoparticles promoted revascularization and restoration of blood perfusion into ischemic tissues by upregulating angiogenic VEGF and PECAM-1. This work demonstrates that H2O2-responsive PVAX nanoparticles facilitate therapeutic angiogenesis and hold tremendous translational potential as therapeutic systems for ischemic diseases such as PAD.

  11. Frank-Condon factors for H2O(+) molecular bands

    NASA Astrophysics Data System (ADS)

    Shefov, N. N.

    1983-11-01

    The Frank-Condon factors q sub (v' v'') are calculated for the spectra of the H2O(+) molecule by the method of Volkenstein et al. (1972). The results are presented in a table for values of v' from 5 to 17 and of v'' from zero to 4, indicating which bands have been observed either in the laboratory or in comets. It is shown that the photon scattering coefficient of Chamberlain (1978) can be calculated using these data for the (8,0) band; values of about 0.060 for the earth and about 0.17 for Halley's comet (at its 1986 perihelion) are determined.

  12. From strong van der Waals complexes to hydrogen bonding: From CO⋯H2O to CS⋯H2O and SiO⋯H2O complexes.

    PubMed

    Zhang, Yan; Hollman, David S; Schaeffer, Henry F

    2012-06-28

    Structures and interaction energies of complexes valence isoelectronic to the important CO⋯H(2)O complex, namely SiO⋯H(2)O and CS⋯H(2)O, have been studied for the first time using high-level ab initio methods. Although CO, SiO, and CS are valence isoelectronic, the structures of their complexes with water differ significantly, owing partially to their widely varied dipole moments. The predicted dissociation energies D(0) are 1.8 (CO⋯H(2)O), 2.7 (CS⋯H(2)O), and 4.9 (SiO⋯H(2)O) kcal∕mol. The implications of these results have been examined in light of the dipole moments of the separate moieties and current concepts of hydrogen bonding. It is hoped that the present results will spark additional interest in these complexes and in the general non-covalent paradigms they represent.

  13. Metformin Selectively Attenuates Mitochondrial H2O2 Emission without Affecting Respiratory Capacity in Skeletal Muscle of Obese Rats

    PubMed Central

    Kane, Daniel A.; Anderson, Ethan J.; Price, Jesse W.; Woodlief, Tracey L.; Lin, Chien-Te; Bikman, Benjamin T.; Cortright, Ronald N.; Neufer, P. Darrell

    2010-01-01

    Metformin is a widely prescribed drug for treatment of type 2 diabetes, although no cellular mechanism of action has been established. To determine whether in vivo metformin treatment alters mitochondrial function in skeletal muscle, respiratory O2 flux and H2O2 emission were measured in saponin-permeabilized myofibers from lean and obese (fa/fa) Zucker rats treated for 4 wks with metformin. Succinate- and palmitoyl-carnitine- supported respiration generated >2-fold higher rates of H2O2 emission in myofibers from untreated obese versus lean rats, indicative of an obesity-associated increased mitochondrial oxidant emitting potential. In conjunction with improved glycemic control, metformin treatment reduced H2O2 emission in muscle from obese rats to rates near or below those observed in lean rats during both succinate- and palmitoyl-carnitine- supported respiration. Surprisingly, metformin treatment did not affect basal or maximal rates of O2 consumption in muscle from obese or lean rats. Ex vivo dose-response experiments revealed that metformin inhibits complex I-linked H2O2 emission at a concentration ∼2 orders of magnitude lower than that required to inhibit respiratory O2 flux. These findings suggest that therapeutic concentrations of metformin normalize mitochondrial H2O2 emission by blocking reverse electron flow without affecting forward electron flow or respiratory O2 flux in skeletal muscle. PMID:20600832

  14. Metformin selectively attenuates mitochondrial H2O2 emission without affecting respiratory capacity in skeletal muscle of obese rats.

    PubMed

    Kane, Daniel A; Anderson, Ethan J; Price, Jesse W; Woodlief, Tracey L; Lin, Chien-Te; Bikman, Benjamin T; Cortright, Ronald N; Neufer, P Darrell

    2010-09-15

    Metformin is a widely prescribed drug for treatment of type 2 diabetes, although no cellular mechanism of action has been established. To determine whether in vivo metformin treatment alters mitochondrial function in skeletal muscle, respiratory O(2) flux and H(2)O(2) emission were measured in saponin-permeabilized myofibers from lean and obese (fa/fa) Zucker rats treated for 4 weeks with metformin. Succinate- and palmitoylcarnitine-supported respiration generated greater than twofold higher rates of H(2)O(2) emission in myofibers from untreated obese versus lean rats, indicative of an obesity-associated increased mitochondrial oxidant emitting potential. In conjunction with improved glycemic control, metformin treatment reduced H(2)O(2) emission in muscle from obese rats to rates near or below those observed in lean rats during both succinate- and palmitoylcarnitine-supported respiration. Surprisingly, metformin treatment did not affect basal or maximal rates of O(2) consumption in muscle from obese or lean rats. Ex vivo dose-response experiments revealed that metformin inhibits complex I-linked H(2)O(2) emission at a concentration approximately 2 orders of magnitude lower than that required to inhibit respiratory O(2) flux. These findings suggest that therapeutic concentrations of metformin normalize mitochondrial H(2)O(2) emission by blocking reverse electron flow without affecting forward electron flow or respiratory O(2) flux in skeletal muscle.

  15. Borate mineral assemblages in the system Na2OCaOMgOB2O3H2O

    USGS Publications Warehouse

    Christ, C.L.; Truesdell, A.H.; Erd, Richard C.

    1967-01-01

    he significant known hydrated borate mineral assemblages (principally of the western United States) in the system Na2OCaOz.sbnd;MgOB2O3H2O are expressible in three ternary composition diagrams. Phase rule interpretation of the diagrams is consistent with observation, if the activity of H2O is generally considered to be determined by the geologic environment. The absence of conflicting tie-lines on a diagram indicates that the several mineral assemblages of the diagram were formed under relatively narrow ranges of temperature and pressure. The known structural as well as empirical formulas for the minerals are listed, and the more recent (since 1960) crystal structure findings are discussed briefly. Schematic Gibbs free energy-composition diagrams based on known solubility-temperature relations in the systems Na2B4O7-H2O and Na2B4O7-NaCl-H2O, are highly useful in the interpretation and prediction of the stability relations in these systems; in particular these diagrams indicate clearly that tincalconite, although geologically important, is everywhere a metastable phase. Crystal-chemical considerations indicate that the same thermodynamic and kinetic behavior observed in the Na2B4O7-H2O system will hold in the Ca2B6O11-H2O system. This conclusion is confirmed by the petrologic evidence. The chemical relations among the mineral assemblages of a ternary diagram are expressed by a schematic "activity-activity" diagram. These activity-activity diagrams permit the tracing-out of the paragenetic sequences as a function of changing cation and H2O activities. ?? 1967.

  16. Thermodynamics of Silicon-Hydroxide Formation in H2O Containing Atmospheres

    NASA Technical Reports Server (NTRS)

    Copland, Evan; Myers, Dwight; Opila, Elizabeth J.; Jacobson, Nathan S.

    2001-01-01

    The formation of volatile silicon-hydroxide species from SiO2 in water containing atmospheres has been identified as a potentially important mode of degradation of Si-based ceramics. Availability of thermodynamic data for these species is a major problem. This study is part of an ongoing effort to obtain reliable, experimentally determined thermodynamic data for these species. The transpiration method was used to measure the pressure of Si-containing vapor in equilibrium with SiO2 (cristobalite) and Ar + H2O(g) with various mole fractions of water vapor, X(sub H2O), at temperatures ranging from 1000 to 1780 K. Enthalpies and entropies for the reaction, SiO2(s) + 2H2O(g) = Si(OH)4(g), were obtained, at X(sub H2O) = 0.15 and 0.37, from the variation of lnK with 1/T according to the 'second law method'. The following data were obtained: delta(H)deg = 52.9 +/- 3.7 kJ/mole and delta(S)deg = -68.6 +/- 2.5 J/mole K at an average temperature of 1550 K, and delta(H)deg = 52.5+/-2.0 kJ/mole and delta(S)deg= -69.7 +/- 1.5 J/moleK at an average temperature of 1384 K, for X(sub H2O)= 0.15 and 0.37, respectively. These data agree with results from the literature obtained at an average temperature of 1600 K, and strongly suggest Si(OH)4(g) is the dominant vapor species. Contradictory results were obtained with the determination of the dependence of Si-containing vapor pressure on the partial pressure of water vapor at 1187 and 1722 K. These results suggested the Si-containing vapor could be a mixture of Si(OH)4 + SiO(OH)2. Further pressure dependent studies are in progress to resolve these issues.

  17. Timescales of magma ascent recorded by H2O zonation in clinopyroxene

    NASA Astrophysics Data System (ADS)

    Lloyd, A. S.; Plank, T. A.; Ruprecht, P.; Hauri, E. H.; Rose, W. I.

    2013-12-01

    Magma ascent prior to explosive eruptions occurs on timescales of minutes to hours, and so requires exceptionally fast chronometers to quantify. One promising approach involves the diffusion of water in clinopyroxene (cpx), given laboratory measurements of diffusivities on the order of 10-9.5 to 10-11.5 at temperatures appropriate for mafic magmas [1]. Previous studies have observed H2O zonation in cpx grains but this was accompanied by major element zonation, leaving open the possibility for crystal growth zonation instead of diffusive loss of water [2]. We report SIMS and EMP analyses for three cpx phenocrysts from ash samples collected in situ during the Oct 17, 1974 sub-plinian eruption of Volcán de Fuego. Concentration profiles were assessed by 5-6 measurements along ~350-450 μm transects measured perpendicular to glassy rims. The maximum H2O measured in the cores of the cpx ranges from 230-320 ppm; whereas, the measurements closest to the rim range from 80-170 ppm. Importantly, we chose grains with limited major element zonation (i.e., Mg# and Al2O3 remain relatively constant or do not co-vary with H2O concentrations). Based on a temperature-dependent parameterization for the partition coefficient of H2O between cpx and melt that accounts for tetrahedrally coordinated Al3+ [3], cores and rims of these cpx are in equilibrium with a melt containing 2.0-2.7 wt% (core) and 0.7-1.6 wt% (rim). The maximum H2O concentration measured in olivine-hosted melt inclusions (~4.2 wt% H2O) erupted on the same day as the cpx phenocrysts [4] suggests that the cpx are not in equilibrium with the melt inclusions. The Mg# of the cpxs (73-77) fall within the range of that for the olivines (72-78) indicating that cpx and olivine were co-crystalizing and that H+ loss by diffusion has potentially occurred. Utilizing the same melt inclusion data to constrain the degassing path for the ascending magma under Fuego, we used forward models to estimate the decompression rate needed to

  18. Solvothermal syntheses, high- and low-temperature crystal structures, and thermochromic behavior of [1,2-diethyl-3,4,5-trimethyl-pyrazolium] 4[Bi 4I 16] and [1,10-phenanthrolinium][BiI 4]·(H 2O)

    NASA Astrophysics Data System (ADS)

    Tershansy, M. A.; Goforth, A. M.; Gardinier, J. R.; Smith, M. D.; Peterson, L.; zur Loye, H.-C.

    2007-05-01

    A new iron(II) scorpionate complex, {Fe[HC(3,4,5-Me 3pz) 3] 2}(I) 2 (pz = pyrazolyl) ( 1), and two novel compounds containing low-dimensional poly(iodobismuthate) anions [1,2-Et 2-3,4,5-Me 3pz] 4[Bi 4I 16] ([1,2-Et 2-3,4,5-Me 3pz] + = [1,2-diethyl-3,4,5-trimethyl-pyrazolium] +) ( 2), and [H(1,10-phen)][BiI 4]·(H 2O) ([H(1,10-phen)] + = [1,10-phenanthrolinium] +) ( 3), have been synthesized and characterized by single crystal X-ray diffraction. Crystals of 2 resulted from the solvothermal reaction of BiI 3 and {Fe[HC(3,4,5-Me 3pz) 3] 2}(I) 2 in an ethanol/water solvent mixture. The anion of this compound is discrete (0-D) and consists of four slightly distorted BiI 6 octahedra joined in an edge-sharing arrangement, and the cation is a decomposition/solvent attack product of the iron scorpionate complex. Crystals of 3 resulted from the solvothermal reaction of BiI 3, 1,10-phenanthroline, and CuI in an ethanol/water solvent mixture. [H(1,10-phen)][BiI 4]·(H 2O) contains 1-D chains of BiI 6 octahedra and a protonated phenanthroline/water molecule complex. Both 2 and 3 are thermochromic compounds as their colors change, respectively, from orange at 296 K to yellow upon cooling to 100 K and from red-orange at 296 K to orange at 100 K. Crystallographic data at both temperatures were recorded for each sample and are reported here. The crystallographic data indicate that interatomic distances (Bi-I and Bi⋯Bi) within the inorganic anions change as a function of temperature, and it is believed that these changes are associated with the observation of thermochromism. {Fe[HC(3,4,5-Me 3pz) 3] 2}(I) 2 ( 1) crystallizes in the monoclinic space group P2 1/ n with the following lattice parameters at 150(1) K: a = 10.8489(5) Å, b = 17.6642(9) Å, c = 15.4131(8) Å, β = 102.4860(10)°. [Et 2Me 3pz] 4[Bi 4I 16] ( 2) and [H(1,10-phen)][BiI 4]·(H 2O) ( 3) both crystallize in the triclinic space group P1¯ with the following lattice parameters for 2 at 296(1) K and 100(1) K

  19. High Speed H2O Concentration Measurements Using Absorption Spectroscopy to Monitor Exhaust Gas

    SciTech Connect

    Kranendonk, Laura; Parks, II, James E; Prikhodko, Vitaly Y; Partridge Jr, William P

    2008-01-01

    This paper demonstrates the potential for fast absorption spectroscopy measurements in diesel-engine exhaust to track H2O concentration transients. Wavelength-agile absorption spectroscopy is an optical technique that measures broadband absorption spectra between 10kHz and 100 MHz. From these measured spectra, gas temperature and absorber concentration can be determined. The Fourier-domain mode-locking (FDML) laser is becoming recognized as one of the most robust and reliable wavelength-agile sources available. H2O concentration measurements during combustion events at crank angle resolved speeds are beneficial for a wide variety of applications, such as product improvements for industry, control and reliability checks for experimental researchers, and measures of fit for numerical simulations. The difficulties associated with measuring diesel exhaust compared to in-cylinder measurements are discussed. A full description of the experimental configuration and data processing is explained. Measurements of engine exhaust H2O transients with 10- s temporal resolution are presented for a range of engine conditions.

  20. Phosphate buffer effects on thermal stability and H2O2-resistance of horseradish peroxidase.

    PubMed

    Asad, Sedigheh; Torabi, Seyed-Fakhreddin; Fathi-Roudsari, Mehrnoosh; Ghaemi, Nasser; Khajeh, Khosro

    2011-05-01

    Horseradish peroxidase (HRP) has attracted intense research interest due to its potential applications in biotechnological fields. However, inadequate stability under prevalent conditions such as elevated temperatures and H(2)O(2) exposure, has limited its industrial application. In this study, stability of HRP was investigated in the presence of different buffer systems (potassium phosphate and Tris-HCl) and additives. It was shown that the concentration of phosphate buffer severely affects enzyme thermostability in a way that in diluted potassium phosphate buffer (10mM) half-life (from 13 to 35 min at 80 °C) and T(m) (from 73 to 77.5 °C) increased significantly. Among additives tested, trehalose had the most thermostabilizing effect. Exploring the role of glycosylation in stabilizing effect of phosphate buffer, non-glycosylated recombinant HRP was also examined for its thermal and H(2)O(2) stability in both diluted and concentrated phosphate buffers. The recombinant enzyme was more thermally stable in diluted buffer in accordance to glycosylated HRP; but interestingly recombinant HRP showed higher H(2)O(2) tolerance in concentrated buffer.

  1. Liquid water on Mars - An energy balance climate model for CO2/H2O atmospheres

    NASA Technical Reports Server (NTRS)

    Hoffert, M. I.; Callegari, A. J.; Hsieh, C. T.; Ziegler, W.

    1981-01-01

    A simple climatic model is developed for a Mars atmosphere containing CO2 and sufficient liquid water to account for the observed hydrologic surface features by the existence of a CO2/H2O greenhouse effect. A latitude-resolved climate model originally devised for terrestrial climate studies is applied to Martian conditions, with the difference between absorbed solar flux and emitted long-wave flux to space per unit area attributed to the divergence of the meridional heat flux and the poleward heat flux assumed to equal the atmospheric eddy heat flux. The global mean energy balance is calculated as a function of atmospheric pressure to assess the CO2/H2O greenhouse liquid water hypothesis, and some latitude-resolved cases are examined in detail in order to clarify the role of atmospheric transport and temperature-albedo feedback. It is shown that the combined CO2/H2O greenhouse at plausible early surface pressures may account for climates hot enough to support a hydrological cycle and running water at present-day insolation and visible albedo levels.

  2. Verification of the H2O Linelists with Theoretically Developed Tools

    NASA Technical Reports Server (NTRS)

    Ma, Qiancheng; Tipping, R.; Lavrentieva, N. N.; Dudaryonok, A. S.

    2013-01-01

    Two basic rules (i.e., the pair identity and the smooth variation rules) resulting from the properties of the energy levels and wave functions of H2O states govern how the spectroscopic parameters vary with the H2O lines within the individually defined groups of lines. With these rules, for those lines involving high j states in the same groups, variations of all their spectroscopic parameters (i.e., the transition frequency, intensity, pressure broadened half-width, pressure-induced shift, and temperature exponent) can be well monitored. Thus, the rules can serve as simple and effective tools to screen the H2O spectroscopic data listed in the HITRAN database and verify the latter's accuracies. By checking violations of the rules occurring among the data within the individual groups, possible errors can be picked up and also possible missing lines in the linelist whose intensities are above the threshold can be identified. We have used these rules to check the accuracies of the spectroscopic parameters and the completeness of the linelists for several important H2O vibrational bands. Based on our results, the accuracy of the line frequencies in HITRAN 2008 is consistent. For the line intensity, we have found that there are a substantial number of lines whose intensity values are questionable. With respect to other parameters, many mistakes have been found. The above claims are consistent with a well known fact that values of these parameters in HITRAN contain larger uncertainties. Furthermore, supplements of the missing line list consisting of line assignments and positions can be developed from the screening results.

  3. Catalase activity is stimulated by H(2)O(2) in rich culture medium and is required for H(2)O(2) resistance and adaptation in yeast.

    PubMed

    Martins, Dorival; English, Ann M

    2014-01-01

    Catalases are efficient scavengers of H2O2 and protect cells against H2O2 stress. Examination of the H2O2 stimulon in Saccharomyces cerevisiae revealed that the cytosolic catalase T (Ctt1) protein level increases 15-fold on H2O2 challenge in synthetic complete media although previous work revealed that deletion of the CCT1 or CTA1 genes (encoding peroxisomal/mitochondrial catalase A) does not increase the H2O2 sensitivity of yeast challenged in phosphate buffer (pH 7.4). This we attributed to our observation that catalase activity is depressed when yeast are challenged with H2O2 in nutrient-poor media. Hence, we performed a systematic comparison of catalase activity and cell viability of wild-type yeast and of the single catalase knockouts, ctt1∆ and cta1∆, following H2O2 challenge in nutrient-rich medium (YPD) and in phosphate buffer (pH 7.4). Ctt1 but not Cta1 activity is strongly induced by H2O2 when cells are challenged in YPD but suppressed when cells are challenged in buffer. Consistent with the activity results, exponentially growing ctt1∆ cells in YPD are more sensitive to H2O2 than wild-type or cta1∆ cells, whereas in buffer all three strains exhibit comparable H2O2 hypersensitivity. Furthermore, catalase activity is increased during adaptation to sublethal H2O2 concentrations in YPD but not in buffer. We conclude that induction of cytosolic Ctt1 activity is vital in protecting yeast against exogenous H2O2 but this activity is inhibited by H2O2 when cells are challenged in nutrient-free media.

  4. Catalase activity is stimulated by H2O2 in rich culture medium and is required for H2O2 resistance and adaptation in yeast☆

    PubMed Central

    Martins, Dorival; English, Ann M.

    2014-01-01

    Catalases are efficient scavengers of H2O2 and protect cells against H2O2 stress. Examination of the H2O2 stimulon in Saccharomyces cerevisiae revealed that the cytosolic catalase T (Ctt1) protein level increases 15-fold on H2O2 challenge in synthetic complete media although previous work revealed that deletion of the CCT1 or CTA1 genes (encoding peroxisomal/mitochondrial catalase A) does not increase the H2O2 sensitivity of yeast challenged in phosphate buffer (pH 7.4). This we attributed to our observation that catalase activity is depressed when yeast are challenged with H2O2 in nutrient-poor media. Hence, we performed a systematic comparison of catalase activity and cell viability of wild-type yeast and of the single catalase knockouts, ctt1∆ and cta1∆, following H2O2 challenge in nutrient-rich medium (YPD) and in phosphate buffer (pH 7.4). Ctt1 but not Cta1 activity is strongly induced by H2O2 when cells are challenged in YPD but suppressed when cells are challenged in buffer. Consistent with the activity results, exponentially growing ctt1∆ cells in YPD are more sensitive to H2O2 than wild-type or cta1∆ cells, whereas in buffer all three strains exhibit comparable H2O2 hypersensitivity. Furthermore, catalase activity is increased during adaptation to sublethal H2O2 concentrations in YPD but not in buffer. We conclude that induction of cytosolic Ctt1 activity is vital in protecting yeast against exogenous H2O2 but this activity is inhibited by H2O2 when cells are challenged in nutrient-free media. PMID:24563848

  5. Catalase activity is stimulated by H(2)O(2) in rich culture medium and is required for H(2)O(2) resistance and adaptation in yeast.

    PubMed

    Martins, Dorival; English, Ann M

    2014-01-01

    Catalases are efficient scavengers of H2O2 and protect cells against H2O2 stress. Examination of the H2O2 stimulon in Saccharomyces cerevisiae revealed that the cytosolic catalase T (Ctt1) protein level increases 15-fold on H2O2 challenge in synthetic complete media although previous work revealed that deletion of the CCT1 or CTA1 genes (encoding peroxisomal/mitochondrial catalase A) does not increase the H2O2 sensitivity of yeast challenged in phosphate buffer (pH 7.4). This we attributed to our observation that catalase activity is depressed when yeast are challenged with H2O2 in nutrient-poor media. Hence, we performed a systematic comparison of catalase activity and cell viability of wild-type yeast and of the single catalase knockouts, ctt1∆ and cta1∆, following H2O2 challenge in nutrient-rich medium (YPD) and in phosphate buffer (pH 7.4). Ctt1 but not Cta1 activity is strongly induced by H2O2 when cells are challenged in YPD but suppressed when cells are challenged in buffer. Consistent with the activity results, exponentially growing ctt1∆ cells in YPD are more sensitive to H2O2 than wild-type or cta1∆ cells, whereas in buffer all three strains exhibit comparable H2O2 hypersensitivity. Furthermore, catalase activity is increased during adaptation to sublethal H2O2 concentrations in YPD but not in buffer. We conclude that induction of cytosolic Ctt1 activity is vital in protecting yeast against exogenous H2O2 but this activity is inhibited by H2O2 when cells are challenged in nutrient-free media. PMID:24563848

  6. UV-H2O2 degradation of methyl orange catalysed by H3PW12O40/activated clay.

    PubMed

    Wei, Guangtao; Zhang, Linye; Wei, Tengyou; Luo, Qiyu; Tong, Zhangfa

    2012-01-01

    A catalyst consisting of phosphotungstic acid (H3PW12O40) combined with activated clay was prepared by the impregnation method, and an experiment was carried out to evaluate the catalytic activity of the H3PW12O40/activated clay for the degradation of methyl orange (MO) in the UV-H2O2 process. The degradation ratio of MO can be affected by H2O2 concentration, reaction time, catalyst dosage, pH and temperature. The reaction temperature should be controlled at less than 70 degrees C, and the catalyst has a wide applicable pH range in the UV-H2O2 process. Hydroxyl radicals were generated in the UV-H2O2 system under the action of H3PW12O40/activated clay, and MO was degraded by hydroxyl radicals. Compared with traditional catalysts used in UV-H2O2 systems, H3PW12O40/activated clay has certain advantages for its practical application.

  7. VOLATILECALC: A silicate melt-H2O-CO2 solution model written in Visual Basic for excel

    USGS Publications Warehouse

    Newman, S.; Lowenstern, J. B.

    2002-01-01

    We present solution models for the rhyolite-H2O-CO2 and basalt-H2O-CO2 systems at magmatic temperatures and pressures below ~ 5000 bar. The models are coded as macros written in Visual Basic for Applications, for use within MicrosoftR Excel (Office'98 and 2000). The series of macros, entitled VOLATILECALC, can calculate the following: (1) Saturation pressures for silicate melt of known dissolved H2O and CO2 concentrations and the corresponding equilibrium vapor composition; (2) open- and closed-system degassing paths (melt and vapor composition) for depressurizing rhyolitic and basaltic melts; (3) isobaric solubility curves for rhyolitic and basaltic melts; (4) isoplethic solubility curves (constant vapor composition) for rhyolitic and basaltic melts; (5) polybaric solubility curves for the two end members and (6) end member fugacities of H2O and CO2 vapors at magmatic temperatures. The basalt-H2O-CO2 macros in VOLATILECALC are capable of calculating melt-vapor solubility over a range of silicate-melt compositions by using the relationships provided by Dixon (American Mineralogist 82 (1997) 368). The output agrees well with the published solution models and experimental data for silicate melt-vapor systems for pressures below 5000 bar. ?? 2002 Elsevier Science Ltd. All rights reserved.

  8. H2O and O(3PJ) photodesorption from amorphous solid water deposited on a lunar mare basalt

    NASA Astrophysics Data System (ADS)

    DeSimone, Alice J.; Orlando, Thomas M.

    2015-07-01

    H2O (ν = 0) and O(3PJ=2,1,0) desorbates were measured with resonance-enhanced multiphoton ionization following 157-nm irradiation of amorphous solid water (ASW) deposited on a lunar mare basalt. Both H2O photodesorption and O(3PJ) photodissociation products of ASW were studied in the attempt to better understand the competition between photodesorption and photodissociation of water in the condensed phase on a lunar surface. The oxygen atom time-of-flight (TOF) spectrum was measured as a function of spin-orbit state, H2O exposure, and 157-nm irradiation time. Maxwell-Boltzmann distributions with translational temperatures of 10,000 K, 1800 K, 400 K, and 89 K fit the four TOF components. For high H2O exposures, diffusion out of pores in the lunar substrate made a large portion of the O(3PJ) signal appear to be sub-thermal. Water depletion cross sections were measured at exposures between 0.1 and 10 Langmuir (1 L = 10-6 Torr s). These cross sections decreased with increasing coverage and matched previously measured cross sections from a lunar impact melt breccia. Additionally, non-resonant ionization was employed to detect vibrationally excited water indirectly through its fragments. The OH+ fragment of H2O (ν*) and the O(3PJ) photodissociation product increased in intensity during prolonged irradiation as hydroxyl groups accumulated on the surface and then recombined. For an initial exposure of 5 L H2O, after reaching maximum signal, the cross sections for H2O (ν*) and O(3P2) depletion were measured to be 1.2 × 10-19 cm2 and 6.7 × 10-20 cm2, respectively.

  9. Enhanced Removal of Hexavalent Chromium in the Presence of H2O2 in Frozen Aqueous Solutions.

    PubMed

    Kim, Kitae; Kim, Jaesung; Bokare, Alok D; Choi, Wonyong; Yoon, Ho-Il; Kim, Jungwon

    2015-09-15

    The reductive transformation of Cr(VI) to Cr(III) by H2O2 in ice was compared with that in water. The reduction of Cr(VI) was significant at -20 °C (ice), whereas the reduction efficiency was very low at 25 °C (water). This enhanced reduction of Cr(VI) in ice was observed over a wide range of H2O2 concentration (20-1000 μM), pH (3-11), and freezing temperature (-10 to -30 °C). The observed molar ratio of consumed [H2O2] to reduced [Cr(VI)] in ice was in close agreement with the theoretical (stoichiometric) molar ratio (1.5) for H2O2-mediated Cr(VI) reduction through proton-coupled electron transfer (PCET). The synergistic increase in Cr(VI) reduction in water by increasing the H2O2 and proton concentrations confirms that the freeze concentration of both H2O2 and protons in the liquid brine is primarily responsible for the enhanced Cr(VI) reduction in ice. In comparison, the one-electron reduction of Cr(VI) to Cr(V) and subsequent reoxidation of Cr(V) to Cr(VI) is the major reaction mechanism in aqueous solution. The reduction efficiency of Cr(VI) by H2O2 in the frozen aqueous electroplating wastewater was similar to that in the frozen aqueous deionized water, which verifies the enhanced reduction of Cr(VI) by freezing in real Cr(VI)-contaminated aquatic systems.

  10. The Frequency Detuning Correction and the Asymmetry of Line Shapes: The Far Wings of H2O-H2O

    NASA Technical Reports Server (NTRS)

    Ma, Q.; Tipping, R. H.; Hansen, James E. (Technical Monitor)

    2002-01-01

    A far-wing line shape theory which satisfies the detailed balance principle is applied to the H2O-H2O system. Within this formalism, two line shapes are introduced, corresponding to band-averages over the positive and negative resonance lines, respectively. Using the coordinate representation, the two line shapes can be obtained by evaluating 11-dimensional integrations whose integrands are a product of two factors. One depends on the interaction between the two molecules and is easy to evaluate. The other contains the density matrix of the system and is expressed as a product of two 3-dimensional distributions associated with the density matrices of the absorber and the perturber molecule, respectively. If most of the populated states are included in the averaging process, to obtain these distributions requires extensive computer CPU time, but only have to be computed once for a given temperature. The 11-dimensional integrations are evaluated using the Monte Carlo method, and in order to reduce the variance, the integration variables are chosen such that the sensitivity of the integrands on them is clearly distinguished.

  11. Crystal structures of Ca(ClO4)2·4H2O and Ca(ClO4)2·6H2O.

    PubMed

    Hennings, Erik; Schmidt, Horst; Voigt, Wolfgang

    2014-12-01

    The title compounds, calcium perchlorate tetra-hydrate and calcium perchlorate hexa-hydrate, were crystallized at low temperatures according to the solid-liquid phase diagram. The structure of the tetra-hydrate consists of one Ca(2+) cation eightfold coordinated in a square-anti-prismatic fashion by four water mol-ecules and four O atoms of four perchlorate tetra-hedra, forming chains parallel to [01-1] by sharing corners of the ClO4 tetra-hedra. The structure of the hexa-hydrate contains two different Ca(2+) cations, each coordinated by six water mol-ecules and two O atoms of two perchlorate tetra-hedra, forming [Ca(H2O)6(ClO4)]2 dimers by sharing two ClO4 tetra-hedra. The dimers are arranged in sheets parallel (001) and alternate with layers of non-coordinating ClO4 tetra-hedra. O-H⋯O hydrogen bonds between the water mol-ecules as donor and ClO4 tetra-hedra and water mol-ecules as acceptor groups lead to the formation of a three-dimensional network in the two structures. Ca(ClO4)2·6H2O was refined as a two-component inversion twin, with an approximate twin component ratio of 1:1 in each of the two structures. PMID:25552974

  12. Slow spin relaxation induced by magnetic field in [NdCo(bpdo)(H2O)4(CN)6]⋅3H2O.

    PubMed

    Vrábel, P; Orendáč, M; Orendáčová, A; Čižmár, E; Tarasenko, R; Zvyagin, S; Wosnitza, J; Prokleška, J; Sechovský, V; Pavlík, V; Gao, S

    2013-05-01

    We report on a comprehensive investigation of the magnetic properties of [NdCo(bpdo)(H2O)4(CN)6]⋅3H2O (bpdo=4, 4'-bipyridine-N,N'-dioxide) by use of electron paramagnetic resonance, magnetization, specific heat and susceptibility measurements. The studied material was identified as a magnet with an effective spin S = 1/2 and a weak exchange interaction J/kB = 25 mK. The ac susceptibility studies conducted at audio frequencies and at temperatures from 1.8 to 9 K revealed that the application of a static magnetic field induces a slow spin relaxation. It is suggested that the relaxation in the magnetic field appears due to an Orbach-like process between the two lowest doublet energy states of the magnetic Nd(3+) ion. The appearance of the slow relaxation in a magnetic field cannot be associated with a resonant phonon trapping. The obtained results suggest that the relaxation is influenced by nuclear spin driven quantum tunnelling which is suppressed by external magnetic field. PMID:23587762

  13. Slow spin relaxation induced by magnetic field in [NdCo(bpdo)(H2O)4(CN)6]⋅3H2O.

    PubMed

    Vrábel, P; Orendáč, M; Orendáčová, A; Čižmár, E; Tarasenko, R; Zvyagin, S; Wosnitza, J; Prokleška, J; Sechovský, V; Pavlík, V; Gao, S

    2013-05-01

    We report on a comprehensive investigation of the magnetic properties of [NdCo(bpdo)(H2O)4(CN)6]⋅3H2O (bpdo=4, 4'-bipyridine-N,N'-dioxide) by use of electron paramagnetic resonance, magnetization, specific heat and susceptibility measurements. The studied material was identified as a magnet with an effective spin S = 1/2 and a weak exchange interaction J/kB = 25 mK. The ac susceptibility studies conducted at audio frequencies and at temperatures from 1.8 to 9 K revealed that the application of a static magnetic field induces a slow spin relaxation. It is suggested that the relaxation in the magnetic field appears due to an Orbach-like process between the two lowest doublet energy states of the magnetic Nd(3+) ion. The appearance of the slow relaxation in a magnetic field cannot be associated with a resonant phonon trapping. The obtained results suggest that the relaxation is influenced by nuclear spin driven quantum tunnelling which is suppressed by external magnetic field.

  14. Thermodynamic and transport properties of frozen and reacting pH2-oH2 mixtures

    NASA Technical Reports Server (NTRS)

    Carter, H. G.; Bullock, R. E.

    1972-01-01

    Application of experimental state data and spectroscopic term values shows that the thermodynamic and transport properties of reacting pH2-oH2 mixtures are considerably different than those of chemically frozen pH2 at temperatures below 300 R. Calculated H-S data also show that radiation-induced pH2-oH2 equilibration at constant enthalpy produces a temperature drop of at least 28 R, corresponding to an ideal shaft work loss of 15% or more for a turbine operating downstream from the point of conversion. Aside from differences in thermodynamic and transport properties, frozen pH2-oH2 mixtures may differ from pure pH2 on a purely hydrodynamical basis.

  15. Putative role of the malate valve enzyme NADP-malate dehydrogenase in H2O2 signalling in Arabidopsis.

    PubMed

    Heyno, Eiri; Innocenti, Gilles; Lemaire, Stéphane D; Issakidis-Bourguet, Emmanuelle; Krieger-Liszkay, Anja

    2014-04-19

    In photosynthetic organisms, sudden changes in light intensity perturb the photosynthetic electron flow and lead to an increased production of reactive oxygen species. At the same time, thioredoxins can sense the redox state of the chloroplast. According to our hypothesis, thioredoxins and related thiol reactive molecules downregulate the activity of H2O2-detoxifying enzymes, and thereby allow a transient oxidative burst that triggers the expression of H2O2 responsive genes. It has been shown recently that upon light stress, catalase activity was reversibly inhibited in Chlamydomonas reinhardtii in correlation with a transient increase in the level of H2O2. Here, it is shown that Arabidopsis thaliana mutants lacking the NADP-malate dehydrogenase have lost the reversible inactivation of catalase activity and the increase in H2O2 levels when exposed to high light. The mutants were slightly affected in growth and accumulated higher levels of NADPH in the chloroplast than the wild-type. We propose that the malate valve plays an essential role in the regulation of catalase activity and the accumulation of a H2O2 signal by transmitting the redox state of the chloroplast to other cell compartments. PMID:24591715

  16. Volatile products in the corrosion of Cr, Mo, Ti and four superalloys exposed to O2 containing H2O and gaseous NaCl

    NASA Technical Reports Server (NTRS)

    Fryburg, G. C.; Miller, R. A.; Kohl, F. J.; Stearns, C. A.

    1977-01-01

    Cooled target collection techniques were used to study the formation of volatile products when samples of Cr, Ti, IN-738, 713C, NASA-TRW VIA and B-1900 were exposed, at elevated temperatures, to oxidizing environments containing H2O(g) and NaCl(g). Samples were heated to 1050 C in one atmosphere of slowly flowing oxygen, saturated with water at 21 C, and containing about 50 ppm NaCl(g). Volatile products were detected for all materials except B-1900 and Ti. High pressure mass spectrometric sampling was used to directly identify volatile products emanating from samples of Cr and IN-738 subject to the above environments.

  17. 40 CFR 1065.355 - H2O and CO2 interference verification for CO NDIR analyzers.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... water content (e.g., dewpoint and pressure) or an estimate based on the vessel pressure and temperature... specifications in § 1065.750 through distilled water in a sealed vessel. If the sample is not passed through a dryer during emission testing, control the vessel temperature to generate an H2O level at least as...

  18. A model-based understanding of solid-oxide electrolysis cells (SOECs) for syngas production by H2O/CO2 co-electrolysis

    NASA Astrophysics Data System (ADS)

    Menon, Vikram; Fu, Qingxi; Janardhanan, Vinod M.; Deutschmann, Olaf

    2015-01-01

    High temperature co-electrolysis of H2O and CO2 offers a promising route for syngas (H2, CO) production via efficient use of heat and electricity. The performance of a SOEC during co-electrolysis is investigated by focusing on the interactions between transport processes and electrochemical parameters. Electrochemistry at the three-phase boundary is modeled by a modified Butler-Volmer approach that considers H2O electrolysis and CO2 electrolysis, individually, as electrochemically active charge transfer pathways. The model is independent of the geometrical structure. A 42-step elementary heterogeneous reaction mechanism for the thermo-catalytic chemistry in the fuel electrode, the dusty gas model (DGM) to account for multi-component diffusion through porous media, and a plug flow model for flow through the channels are used in the model. Two sets of experimental data are reproduced by the simulations, in order to deduce parameters of the electrochemical model. The influence of micro-structural properties, inlet cathode gas velocity, and temperature are discussed. Reaction flow analysis is performed, at OCV, to study methane production characteristics and kinetics during co-electrolysis. Simulations are carried out for configurations ranging from simple one-dimensional electrochemical button cells to quasi-two-dimensional co-flow planar cells, to demonstrate the effectiveness of the computational tool for performance and design optimization.

  19. A new oxovanadium(IV) complex containing an O,N-bidentate Schiff base ligand: Synthesis at ambient temperature, characterization, crystal structure and catalytic performance in selective oxidation of sulfides to sulfones using H2O2 under solvent-free conditions

    NASA Astrophysics Data System (ADS)

    Menati, Saeid; Rudbari, Hadi Amiri; Khorshidifard, Mahsa; Jalilian, Fariba

    2016-01-01

    A new bidentate ON Schiff base ligand, HL, was synthesized by simple condensation reaction of isopropylamine and salicylaldehyde. Then by reaction of HL and VO(acac)2 in the ratio of 2:1 at ambient temperature, a new oxovanadium(IV) Schiff base complex, VOL2, was synthesized. The Schiff base ligand and its oxovanadium(IV) complex were characterized by elemental analyses, FT-IR, 1H NMR, 13C NMR and UV-visible spectroscopies. The crystal structure of oxovanadium(IV) complex, VOL2, was also determined by single crystal X-ray analysis. The vanadium center in this structure is coordinated to two bidentate Schiff base ligands with the two nitrogen and two phenolate oxygen atoms in equatorial positions and one oxo oxygen in the axial position to complete the distorted trigonal bipyramidal N2O3 coordination sphere. Catalytic performance of the VOL2 complex was studied in the selective oxidation of thioanisole with the green oxidant 35% aqueous H2O2 under solvent-free conditions and under organic solvents (EtOH, CHCl3, CH2Cl2, DMF, CH3CN, EtOAc) as a model. Due to better catalytic performance of the VOL2 complex under solvent-free conditions, this complex used for the oxidation of the different sulfides to the corresponding sulfones under solvent-free conditions. The use of hydrogen peroxide as oxidant and the absence of solvent makes these reactions interesting from environmental and economic points of view.

  20. Studies on the mechanism, selectivity, and synthetic utility of lactone reduction using SmI(2) and H(2)O.

    PubMed

    Parmar, Dixit; Duffy, Lorna A; Sadasivam, Dhandapani V; Matsubara, Hiroshi; Bradley, Paul A; Flowers, Robert A; Procter, David J

    2009-10-28

    Although simple aliphatic esters and lactones have long been thought to lie outside the reducing range of SmI(2), activation of the lanthanide reagent by H(2)O allows some of these substrates to be manipulated in an unprecedented fashion. For example, the SmI(2)-H(2)O reducing system shows complete selectivity for the reduction of 6-membered lactones over other classes of lactones and esters. The kinetics of reduction has been studied using stopped-flow spectrophotometry. Experimental and computational studies suggest that the origin of the selectivity lies in the initial electron-transfer to the lactone carbonyl. The radical intermediates formed during lactone reduction with SmI(2)-H(2)O can be exploited in cyclizations to give cyclic ketone (or ketal) products with high diastereoselectivity. The cyclizations constitute the first examples of ester-alkene radical cyclizations in which the ester carbonyl acts as an acyl radical equivalent.

  1. Responsive mechanism of a newly synthesized fluorescent probe for sensing H2O2, NO and H2O2/NO

    NASA Astrophysics Data System (ADS)

    Zhang, Yu-Jin; Wang, Xin; Zhou, Yong; Zhao, Ke; Wang, Chuan-Kui

    2016-10-01

    Optical properties of a newly synthesized fluorescent probe for H2O2, NO and H2O2/NO are investigated by employing time-dependent density functional theory. Three different sets of fluorescence signals are obtained when the probe reacts with H2O2, NO and H2O2/NO. Analysis of molecular orbitals is presented to explore responsive mechanism of the probe for the detected objects, where the fluorescent resonance energy transfer process is for H2O2 (H2O2/NO) and the intramolecular charge transfer process is for NO. Our results provide theoretical explanation of the experimental results, and importantly, suggest possibility of the probe as a two-photon fluorescent sensor.

  2. Microcrystalline phase transformation from ZrF4·HF·2H2O to ZrO2 through the intermediate phases ZrF4·3H2O, ZrF4·H2O, Zr2OF6·H2O and ZrF4

    NASA Astrophysics Data System (ADS)

    Dey, C. C.

    2014-09-01

    The behavior of hydrated zirconium fluoride has been studied by perturbed angular correlation spectroscopy. It is found that the crystalline compound ZrF4·HF·2H2O, formed initially by drying solution of Zr metal in concentrated HF, transforms spontaneously to ZrF4·3H2O. This trihydrated compound dehydrates to ZrF4 through the intermediate monohydrates ZrF4·H2O and Zr2OF6·H2O. The compound ZrF4 finally transforms to ZrO2 at ∼343 K. Different crystalline phases of ZrF4·HF·2H2O, ZrF4·3H2O, ZrF4·H2O, Zr2OF6·H2O, ZrF4 and ZrO2 have been identified and characterized by PAC spectroscopy. From previous PAC measurements, the intermediate ZrF4·H2O and Zr2OF6·H2O were not observed and the dehydration from ZrF4·3H2O to ZrF4 was found to be routed directly. Present measurements by PAC exhibits dissimilar crystal structures for ZrF4·3H2O and ZrF4·H2O unlike the crystal structures found in hafnium analogous compounds.

  3. Significance of the direct relaxation process in the low-energy spin dynamics of a one-dimensional ferrimagnet NiCu(C 7H 6N 2O 6)(H 2O) 3·2H 2O

    NASA Astrophysics Data System (ADS)

    Yamamoto, S.

    2000-11-01

    In response to recent nuclear magnetic resonance measurements on a ferrimagnetic chain compound NiCu(C 7H 6N 2O 6)(H 2O) 3·2H 2O [Solid State Commun. 113 (2000) 433], we calculate the nuclear spin-lattice relaxation rate 1/ T1 in terms of a modified spin-wave theory. Emphasizing that the dominant relaxation mechanism arises from the direct (single-magnon) process rather than the Raman (two-magnon) one, we explain the observed temperature and applied-field dependences of 1/ T1. Ferrimagnetic relaxation phenomena are generally discussed and novel ferrimagnets with extremely slow dynamics are predicted.

  4. Synthesis and crystal structure of the lithium perrhenate monohydrate LiReO 4·H 2O

    NASA Astrophysics Data System (ADS)

    Abakumov, Artem M.; Rozova, Marina G.; Shpanchenko, Roman V.; Mironov, Andrei V.; Antipov, Evgeny V.; Bramnik, Kirill G.

    2001-07-01

    A new monohydrate of lithium perrhenate LiReO 4·H 2O was prepared by dehydration of LiReO 4·1.5H 2O at room temperature. The single crystals of LiReO 4·H 2O were obtained by crystallisation from the isoamyl acetate solution of LiReO 4·1.5H 2O. The structure of monohydrate ( a=5.6674(4), b=10.771(1), c=7.4738(7) Å, β=102.422(7)°, R1=0.0414, space group P2 1/ a, Z=4) is built up from LiO 3(H 2O) 2 trigonal bipyramids and ReO 4 tetrahedra sharing common edges and corners inside the layers. The layers are connected together by hydrogen bonds. The relationships between the structures of sesquihydrate, monohydrate and anhydrous LiReO 4 are discussed.

  5. Theoretical studies of photoexcitation and ionization in H2O

    NASA Technical Reports Server (NTRS)

    Diercksen, G. H. F.; Kraemer, W. P.; Rescigno, T. N.; Bender, C. F.; Mckoy, B. V.; Langhoff, S. R.; Langhoff, P. W.

    1982-01-01

    Theoretical studies using Franck-Condon and static-exchange approximations are reported for the complete dipole excitation and ionization spectrum in H2O, where (1) large Cartesian Gaussian basis sets are used to represent the required discrete and continuum electronic eigenfunctions at the ground state equilibrium geometry, and (2) previously devised moment-theory techniques are employed in constructing the continuum oscillator-strength densities from the calculated spectra. Comparisons are made of the calculated excitation and ionization profiles with recent experimental photoabsorption studies and corresponding spectral assignments, electron impact-excitation cross sections, and dipole and synchrotron-radiation studies of partial-channel photoionization cross sections. The calculated partial-channel cross sections are found to be atomic-like, and dominated by 2p-kd components. It is suggested that the latter transition couples with the underlying 1b(1)-kb(1) channel, accounting for a prominent feature in recent synchrotron-radiation measurements.

  6. Experiments on H2-O2MHD power generation

    NASA Technical Reports Server (NTRS)

    Smith, J. M.

    1980-01-01

    Magnetohydrodynamic power generation experiments utilizing a cesium-seeded H2-O2 working fluid were carried out using a diverging area Hall duct having an entrance Mach number of 2. The experiments were conducted in a high-field strength cryomagnet facility at field strengths up to 5 tesla. The effects of power takeoff location, axial duct location within the magnetic field, generator loading, B-field strength, and electrode breakdown voltage were investigated. For the operating conditions of these experiments, it is found that the power output increases with the square of the B-field and can be limited by choking of the channel or interelectrode voltage breakdown which occurs at Hall fields greater than 50 volts/insulator. Peak power densities of greater than 100 MW/cu M were achieved.

  7. Intermolecular potential for thermal H2O-He collisions

    NASA Technical Reports Server (NTRS)

    Palma, Amedeo; Green, Sheldon; Defrees, D. J.; Mclean, A. D.

    1988-01-01

    Theoretical potentials for rotational excitation of H2O by He were constructed via several methods, all of which start with a large basis set SCF interaction. The semiempirical Hartree-Fock with damped dispersion model adds a damped long-range attraction with parameters adjusted to fit experimental total differential cross sections. Purely ab initio potentials add correlation energies obtained via perturbation theory (MP2 and MP4) or a variational method (ICF1). Scattering calculations were performed on all surfaces to compare wih available beam scattering and pressure broadening data and to assess sensitivity of state-to-state rates to uncertainties in the potential. From comparison with the limited experimental data, the ICF1 surface appears to be marginally better than the MP4 surface. Thermal rates calculated from this surface should be accurate to better than 50 percent, at least for the larger, more important rates.

  8. Ferroelectricity in high-density H2O ice.

    PubMed

    Caracas, Razvan; Hemley, Russell J

    2015-04-01

    The origin of longstanding anomalies in experimental studies of the dense solid phases of H2O ices VII, VIII, and X is examined using a combination of first-principles theoretical methods. We find that a ferroelectric variant of ice VIII is energetically competitive with the established antiferroelectric form under pressure. The existence of domains of the ferroelectric form within anti-ferroelectric ice can explain previously observed splittings in x-ray diffraction data. The ferroelectric form is stabilized by density and is accompanied by the onset of spontaneous polarization. The presence of local electric fields triggers the preferential parallel orientation of the water molecules in the structure, which could be stabilized in bulk using new high-pressure techniques.

  9. Utilization of membranes for H2O recycle system

    NASA Technical Reports Server (NTRS)

    Ohya, H.; Oguchi, M.

    1986-01-01

    Conceptual studies of closed ecological life support systems (CELSS) carried out at NAL in Japan for a water recycle system using membranes are reviewed. The system will treat water from shower room, urine, impure condensation from gas recycle system, and so on. The H2O recycle system is composed of prefilter, ultrafiltration membrane, reverse osmosis membrane, and distillator. Some results are shown for a bullet train of toilet-flushing water recycle equipment with an ultraviltration membrane module. The constant value of the permeation rate with a 4.7 square meters of module is about 70 1/h after 500th of operation. Thermovaporization with porous polytetrafluorocarbon membrane is also proposed to replce the distillator.

  10. First Principle Predictions of Isotopic Shifts in H2O

    NASA Technical Reports Server (NTRS)

    Schwenke, David W.; Kwak, Dochan (Technical Monitor)

    2002-01-01

    We compute isotope independent first and second order corrections to the Born-Oppenheimer approximation for water and use them to predict isotopic shifts. For the diagonal correction, we use icMRCI wavefunctions and derivatives with respect to mass dependent, internal coordinates to generate the mass independent correction functions. For the non-adiabatic correction, we use scaled SCF/CIS wave functions and a generalization of the Handy method to obtain mass independent correction functions. We find that including the non-adiabatic correction gives significantly improved results compared to just including the diagonal correction when the Born-Oppenheimer potential energy surface is optimized for H2O-16. The agreement with experimental results for deuterium and tritium containing isotopes is nearly as good as our best empirical correction, however, the present correction is expected to be more reliable for higher, uncharacterized levels.

  11. Fabry-Perot observations of Comet Halley H2O(+)

    NASA Astrophysics Data System (ADS)

    Scherb, F.; Magee-Sauer, K.; Roesler, F. L.; Harlander, J.

    1990-07-01

    Fabry-Perot scanning spectrometer observations of Comet Halley's H2O(+) emissions have yielded 6158.64 and 6158.85 A spin doublet data at distances in the range of 0 to 2 million km from the comet heat in the antisunward direction. Cometary plasma outflow velocities were ascertained on the basis of the emissions' Doppler shifts, yielding results that were mostly but not exclusively consistent with the plasma's constant antisunward acceleration; the acceleration varied from night to night of observations over a 30-300 cm/sec range. The unusual plasma kinematics of December 14-15, 1985, and January 10, 1986, may be associated with the tail-disconnection activity observed by others.

  12. H2O at the Phoenix landing site.

    PubMed

    Smith, P H; Tamppari, L K; Arvidson, R E; Bass, D; Blaney, D; Boynton, W V; Carswell, A; Catling, D C; Clark, B C; Duck, T; Dejong, E; Fisher, D; Goetz, W; Gunnlaugsson, H P; Hecht, M H; Hipkin, V; Hoffman, J; Hviid, S F; Keller, H U; Kounaves, S P; Lange, C F; Lemmon, M T; Madsen, M B; Markiewicz, W J; Marshall, J; McKay, C P; Mellon, M T; Ming, D W; Morris, R V; Pike, W T; Renno, N; Staufer, U; Stoker, C; Taylor, P; Whiteway, J A; Zent, A P

    2009-07-01

    The Phoenix mission investigated patterned ground and weather in the northern arctic region of Mars for 5 months starting 25 May 2008 (solar longitude between 76.5 degrees and 148 degrees ). A shallow ice table was uncovered by the robotic arm in the center and edge of a nearby polygon at depths of 5 to 18 centimeters. In late summer, snowfall and frost blanketed the surface at night; H(2)O ice and vapor constantly interacted with the soil. The soil was alkaline (pH = 7.7) and contained CaCO(3), aqueous minerals, and salts up to several weight percent in the indurated surface soil. Their formation likely required the presence of water. PMID:19574383

  13. Validation of MIPAS-ENVISAT H2O operational data collected between July 2002 and March 2004

    NASA Astrophysics Data System (ADS)

    Wetzel, G.; Oelhaf, H.; Berthet, G.; Bracher, A.; Cornacchia, C.; Feist, D. G.; Fischer, H.; Fix, A.; Iarlori, M.; Kleinert, A.; Lengel, A.; Milz, M.; Mona, L.; Müller, S. C.; Ovarlez, J.; Pappalardo, G.; Piccolo, C.; Raspollini, P.; Renard, J.-B.; Rizi, V.; Rohs, S.; Schiller, C.; Stiller, G.; Weber, M.; Zhang, G.

    2013-06-01

    . However, in the region around the tropopause retrieved MIPAS H2O profiles are less reliable, suffering from a number of obstacles such as retrieval boundary and cloud effects, sharp vertical discontinuities, and frequent horizontal gradients in both temperature and H2O volume mixing ratio (VMR). Some profiles are characterized by retrieval instabilities.

  14. Glass Composition-Dependent Silicate Absorption Peaks in FTIR Spectroscopy: Implications for Measuring Sample Thickness and Molecular H2O

    NASA Astrophysics Data System (ADS)

    McIntosh, I. M.; Nichols, A. R.; Schipper, C. I.; Stewart, R. B.

    2015-12-01

    Fourier-transform infrared spectroscopy (FTIR) is often used to measure the H2O and CO2 contents of volcanic glasses. A key advantage of FTIR over other analytical techniques is that it can reveal not only total H2O concentration but also H2O speciation, i.e. how much H2O is present as molecular H2O (H2Om) and how much as hydroxyl groups (OH) bound to the silicate network. This H2O speciation data can be used to investigate cooling rate and glass transition temperature of volcanic glasses, and to interpret H2O contents of pyroclasts affected by partial bubble resorption during cooling or secondary hydration after deposition. FTIR in transmitted light requires sample wafers polished on both sides of known thickness. Thickness is commonly measured using a micrometer but this may damage fragile samples and in samples with non-uniform thickness, e.g. vesicular samples, it is difficult to position at the exact location of FTIR analysis. Furthermore, in FTIR images or maps of such samples it is impractical to determine the thickness across the whole of the analysed area, resulting either in only a selection of the collected data being processed quantitatively and the rest being unused, or results being presented in terms of absorbance, which does not account for variations in thickness.It is known that FTIR spectra contain absorption peaks related to the glass aluminosilicate network at wavenumbers of ~2000, ~1830 and ~1600 cm-1 [1]. These have been shown to be proportional to sample thickness at the analysis location for one obsidian composition with up to 0.66 wt% H2O [2]. We test whether this calibration can be applied more widely by analysing a range of synthetic and natural glasses (andesitic to rhyolitic) to examine how the position and relative intensities of the different silicate absorption peaks vary with composition and H2O content. Our data show that even minor differences in composition necessitate a unique calibration. Furthermore, importantly we show how

  15. The low frequency dynamics of supercooled LiBr, 6H2O

    NASA Astrophysics Data System (ADS)

    Bove, L.; Dreyfus, C.; Polian, A.; Bonello, B.; Malfanti, I.; Taschin, A.; Torre, R.; Pick, R. M.

    2011-01-01

    We present results of a series of experiments performed on LiBr, 6H20 from room temperature down to 172 K ≈ 1.2Tg. These ultrasound, Brillouin and depolarized light scattering, and transient grating experiments show that, above 215 K, this solution behaves like supercooled water: its zero frequency sound velocity C0 continuously decreases with decreasing temperature, and the reorientational dynamics of the water molecules can be directly detected at some temperatures of this domain. Conversely, below 215 K, a new regime sets in, where the apparent C0 is practically temperature independent and where a β, Arrenhius like, relaxation process coexists with the usual, Vogel-Fulcher like, α relaxation process of the supercooled liquid. These results are similar to those recently obtained in LiCl, 6H2O. The onset of the new regime is possibly due to an increase of the interaction of the water molecules with a neighboring Li+ ion when lowering the temperature. We also compare our results with published dielectric data on water solutions of glass forming polyalcohols. Some of them present a low temperature splitting of their relaxation time similar to what is found in LiBr, 6H2O.

  16. Vesiculation in rhyolite at low H2O contents: A thermodynamic model

    NASA Astrophysics Data System (ADS)

    Ryan, Amy G.; Russell, James K.; Hess, Kai-Uwe; Phillion, Andre B.; Dingwell, Donald B.

    2015-12-01

    We present experimental data on the thermodynamics and kinetics of bubble nucleation and growth in weakly H2O-oversaturated rhyolitic melts. The high-temperature (900-1100°C) experiments involve heating of rhyolitic obsidian from Hrafntinnuhryggur, Krafla, Iceland to above their glass transition temperature (Tg ˜ 690°C) at 0.1 MPa for times of 0.25-24 h. During experiments, the rhyolite cores increase in volume as H2O vapor-filled bubbles nucleate and expand. The extent of vesiculation, as tracked by porosity, is mapped in temperature-time (T-t) space. At constant temperature and for a characteristic dwell time, the rhyolite cores achieve a maximum volume where the T-t conditions reach thermochemical equilibrium. For each T-t snapshot of vesiculation, we use 3-D analysis of X-ray computed tomographic (XCT) images of the quenched cores to obtain the bubble number density (BND) and bubble-size distribution (BSD). BNDs for the experimental cores are insensitive to T and t, indicating a single nucleation event. All BSDs converge to a common distribution, independent of T, melt viscosity (η), or initial degree of saturation, suggesting a common growth process. We use these data to calibrate an empirical model for predicting the rates and amounts of vesiculation in rhyolitic melts as a function of η and thermochemical affinity (A): two computable parameters that are dependent on T, pressure and H2O content. The model reproduces the experimental data set and data from the literature to within experimental error, and has application to natural volcanic systems where bubble formation and growth are not diffusion limited (e.g., lavas, domes, ignimbrites, conduit infill).

  17. The Characteristics of -OH/H2O in Plagioclase by Solar Wind Implantation Simulate

    NASA Astrophysics Data System (ADS)

    Tang, H.; Li, X. Y.; Wang, S. J.; Yu, W.; Li, S. J.; Li, Y.

    2016-08-01

    FTIR analyses has showed the obvious increased hydroxyl and H2O peak about 3622 cm-1 and about 3356 cm-1after ion implantation respectively, compared with small OH and H2O absorption before ion implantation.

  18. A comparison of ATTREX H2O observations in the TTL with values derived from reanalysis-based back trajectories

    NASA Astrophysics Data System (ADS)

    Thornberry, T. D.; Rollins, A. W.; Bui, T. V.; Pfister, L.; Gao, R. S.

    2015-12-01

    Despite very low mixing ratios relative to the troposphere, water vapor in the lower stratosphere (LS) plays a significant role in Earth's radiative balance and climate system, and is an important constituent in stratospheric chemistry. The low H2O content of air entering the LS is established to first order by dehydration processes controlled by the cold temperatures of the tropical tropopause layer (TTL), especially over the western Pacific. Global climate models rely on parameterizations in order to simulate TTL dehydration processes and calculate the amount of H2O transported into the stratosphere. Here we present an analysis of in situ water vapor measurements in the western Pacific TTL from the NASA ATTREX campaign and compare them to reanalysis-based back trajectory calculations of LS H2O in order to investigate the efficiency of TTL dehydration processes and provide constraints on the representation of TTL dehydration in reanalyses and global models.

  19. Thermal Conductivity Measurements of H2O-Methanol Mixtures at High Pressure Using Time Domain Thermoreflectance

    NASA Astrophysics Data System (ADS)

    Hsieh, W. P.

    2014-12-01

    It has been proposed that the presence of methanol, a possible anti-freeze compound, in the primordial oceans in icy moons may affect the internal thermal evolution and the crystallization of primordial oceans. We have measured the thermal conductivity of H2O alloyed with methanol at high pressure and room temperature using time-domain thermoreflectance (TDTR) combined with diamond anvil cell techniques. The TDTR utilizes ultrafast optical pulses to pump and probe the dynamics of thermal diffusion, enabling precise measurements of thermal conductivity under extreme conditions. We found that the addition of methanol into the H2O suppresses the effective thermal conductivity of H2O-methanol compound. We will discuss geophysical implications of these measurements to the thermal evolution within the icy moons.

  20. Geometry of α-Cr2O3(0001) as a Function of H2O Partial Pressure

    PubMed Central

    2015-01-01

    Surface X-ray diffraction has been employed to elucidate the surface structure of α-Cr2O3(0001) as a function of water partial pressure at room temperature. In ultra high vacuum, following exposure to ∼2000 Langmuir of H2O, the surface is found to be terminated by a partially occupied double layer of chromium atoms. No evidence of adsorbed OH/H2O is found, which is likely due to either adsorption at minority sites, or X-ray induced desorption. At a water partial pressure of ∼30 mbar, a single OH/H2O species is found to be bound atop each surface Cr atom. This adsorption geometry does not agree with that predicted by ab initio calculations, which may be a result of some differences between the experimental conditions and those modeled. PMID:26877825

  1. Regulation of H2O and CO in Tropical Tropopause Layer by the Madden-Julian Oscillation

    NASA Astrophysics Data System (ADS)

    Wong, S.; Dessler, A. E.

    2006-12-01

    Impacts of the Madden-Julian oscillation (MJO) on the water vapor (H2O) and carbon monoxide (CO) in the tropical tropopause layer (TTL) are investigated using Aura Microwave Limb Sounder (MLS) data for November 2004 to May 2005. The eastward propagation of deep convection in the H2O and CO fields in the TTL is evident. Tropical mean water vapor at 370 K is regulated by the MJO through the variation of temperature with a timescale of 30-45 days. Enhancement of deep convection associated with the MJO also injects CO from the lower troposphere to the lower stratosphere. However, tropical mean CO at 370 K responds instantaneously to the large surface emission over the African continent. The regulation of TTL CO by the MJO is through the enhancement of deep convection over the African continent and is less evident than that of H2O.

  2. Infrared and Polarized Raman Spectra of RbAl(SO 4) 2·12H 2O

    NASA Astrophysics Data System (ADS)

    Suresh, G.; Ratheesh, R.; Jayasree, R. S.; Nayar, V. U.; Keresztury, G.

    1996-03-01

    The IR and polarized Raman spectra of a single crystal RbAl(SO4)2·12H2O is recorded and analyzed at room temperature. Bands indicate a stronger S-O bond in RbAl(SO4)2·12H2O than that in a free SO2-4ion. The fraction of reversed sulfate group in the Rb alum is much lower than that in the potassium alum. Broad bands with frequencies considerably shifted from the free state values indicate that water molecules form hydrogen bonds of various strengths. Two crystallographically distinct water molecules are identified in the crystal.

  3. Monitoring dehydration of the organic-inorganic [(C3H7)4N][SnCl5(H2O)]·2H2O compound using simultaneous thermal and Raman studies

    NASA Astrophysics Data System (ADS)

    Hajlaoui, S.; Chaabane, I.; Guidara, K.; Bulou, A.

    2016-07-01

    In this work we report the experimental studies of the structural phase transition in the [(C3H7)4N]SnCl5(H2O)]·2H2O compound by differential scanning calorimetric (DSC) and Raman spectroscopic. The X-ray powder diffraction study of the [(C3H7)4N][SnCl5(H2O)]·2H2O sample at room temperature showed that this compound is monoclinic and has P121/c1 space group. Differential scanning calorimetric disclosed two types of phase transitions in the temperature range 356-376 (T1) K and at 393 K (T2) characterized, by a loss of water molecules and probably a reconstruction of new anionic parts after T2 transition. The Raman scattering spectra recorded at various temperatures in the wavenumber range from 100 to 3800 cm- 1 covering the domains of existence of changes in the vicinity of the two phase transitions detected by DSC measurement. A detailed study of the spectral parameters (wave number, reduced intensity and the full width at half maximum) as a function of temperature of a chosen band, associated with (νs(Snsbnd O) + νs(Snsbnd Cl)), based on an order-disorder model allowed us to obtain information relative to the activation energy and correlation length.

  4. Traces of H2O in Ultrahigh-Pressure Metamorphic Rocks

    NASA Astrophysics Data System (ADS)

    Dobrzhinetskaya, L. F.

    2007-05-01

    Ultrahigh-pressure (UHP) metamorphic rocks accommodate a significant amount of H2O at high pressures and temperatures during their deep subduction. Fluid-driven processes are responsible for mineral reactions; they may trigger phase transformations and provide a decisive weakening effect on the rheological behavior of the rocks during deep subduction, or they may lead to brittle failure and earthquakes. Dehydration reactions, producing fluid (i.e., H2O, CO2) during regional metamorphism at low-to-mid crustal levels (P ~ 0.1 - 1 GPa), are reasonably pressure insensitive. At these levels, the maximum dehydration occurs at the greatest temperatures experienced by buried rocks. In the deep subduction zone (> 120 - 150 km), where both high pressures and temperatures operate, the situation is different. There, on the one hand, the water becomes chemically bonded and incorporated into the structure of both nominally hydrous and anhydrous minerals. On the other hand, the aqueous fluid (a supercritical fluid) dissolves a considerable amount of mineral components at high pressures and temperatures, and a solute concentration increases as pressure is increased. Microstructural observations on ultrahigh-pressure minerals from eclogites and metasediments provide convincing evidence of fluid involvement as deep as the upper mantle and possibly, the mantle transition zone. Diamond is one of the minerals of great importance because it unambiguously records the high pressure (minimum 4 GPa and possibly > 4GPa) at which the host rocks were recrystallized. We present here the results of studies of nano-inclusions associated with dislocations of growth and/or with interstitial defects of carbon in diamond structure obtained with transmission electron microscopy, microRaman, and microInfrared synchrotron assisted spectroscopy. A diverse composition of multicomponent fluid and crystalline inclusions and characteristic of nitrogen aggregations, provide evidence that the diamonds were

  5. Biological dosimetry after H2O2/L-histidine treatment

    NASA Astrophysics Data System (ADS)

    Hausmann, Michael; Lentfer, Heiko; Wolf, Dietmar; Bauer, Eckhard; Aldinger, Klaus; Greulich, Karl O.; Cremer, Christoph

    1997-12-01

    In biological dosimetry after radiation or chemical exposure, it has been well established to estimate exposure doses from the relative rate of aberrant chromosomes, especially dicentric chromosomes in a given number of cells. For this purpose, dose-efficiency curves depending on laboratory parameters (e.g. preparation technique, analysis procedure etc.) have to be measured under standard conditions. For statistical reasons, a high number of chromosomes or cells, respectively, has to be evaluated. For a Chinese hamster cell line (CO60) as a typical model system in mutation research, a dose efficiency relation after H2O2/L-histidine treatment of the cells was determined using the Heidelberg slit-scan flow fluorometer. This technique has the advantage that several thousand chromosomes can be automatically analyzed in a very short time. As expected, for low doses of H2O2/L-histidine exposure, a nearly linear dependence of the relative number of dicentric chromosomes to the concentration of H2O2 was obtained. In order to correlate the relative number of dicentric chromosomes to the relative number of double strand breaks, the cells were analyzed by the technique of the neutral comet assay. The dose dependent `tail moment' obtained from the comet assay also showed a linear behavior. This confirmed the results obtained by slit-scan flow fluorometry. Furthermore, the linear dependence of the dose efficiency curve was well compatible to results obtained by visual counting by means of a fluorescence microscope. In this case chromosome 1 of the Chinese hamster cell line DON was specifically labelled by fluorescence in situ hybridization.

  6. Biological dosimetry after H2O2/L-histidine treatment

    NASA Astrophysics Data System (ADS)

    Hausmann, Michael; Lentfer, Heiko; Wolf, Dietmar; Bauer, Eckhard; Aldinger, Klaus; Greulich, Karl-Otto; Cremer, Christoph G.

    1998-01-01

    In biological dosimetry after radiation or chemical exposure, it has been well established to estimate exposure doses from the relative rate of aberrant chromosomes, especially dicentric chromosomes in a given number of cells. For this purpose, dose-efficiency curves depending on laboratory parameters (e.g. preparation technique, analysis procedure etc.) have to be measured under standard conditions. For statistical reasons, a high number of chromosomes or cells, respectively, has to be evaluated. For a Chinese hamster cell line (CO60) as a typical model system in mutation research, a dose efficiency relation after H2O2/L-histidine treatment of the cells was determined using the Heidelberg slit-scan flow fluorometer. This technique has the advantage that several thousand chromosomes can be automatically analyzed in a very short time. As expected, for low doses of H2O2/L-histidine exposure, a nearly linear dependence of the relative number of dicentric chromosomes to the concentration of H2O2 was obtained. In order to correlate the relative number of dicentric chromosomes to the relative number of double strand breaks, the cells were analyzed by the technique of the neutral comet assay. The dose dependent `tail moment' obtained from the comet assay also showed a linear behavior. This confirmed the results obtained by slit-scan flow fluorometry. Furthermore, the linear dependence of the dose efficiency curve was well compatible to results obtained by visual counting by means of a fluorescence microscope. In this case chromosome 1 of the Chinese hamster cell line DON was specifically labelled by fluorescence in situ hybridization.

  7. CO and H2O vibrational emission toward Orion Peak 1 and Peak 2

    NASA Astrophysics Data System (ADS)

    González-Alfonso, E.; Wright, C. M.; Cernicharo, J.; Rosenthal, D.; Boonman, A. M. S.; van Dishoeck, E. F.

    2002-05-01

    ISO/SWS observations of Orion Peak 1 and Peak 2 show strong emission in the ro-vibrational lines of CO v=1-0 at 4.45-4.95 μm and of H2O ν2=1-0 at 6.3-7.0 μm. Toward Peak 1 the total flux in both bands is, assuming isotropic emission, ≈2.4 and ≈0.53 Lsun, respectively. This corresponds to ≈14 and ≈3% of the total H2 luminosity in the same beam. Two temperature components are found to contribute to the CO emission from Peak 1/2: a warm component, with TK=200-400 K, and a hot component with Tk~3×103 K. At Peak 2 the CO flux from the warm component is similar to that observed at Peak 1, but the hot component is a factor of ≈2 weaker. The H2O band is ≈25% stronger toward Peak 2, and seems to arise only in the warm component. The P-branch emission of both bands from the warm component is significantly stronger than the R-branch, indicating that the line emission is optically thick. Neither thermal collisions with H2 nor with H I seem capable of explaining the strong emission from the warm component. Although the emission arises in the postshock gas, radiation from the most prominent mid-infrared sources in Orion BN/KL is most likely pumping the excited vibrational states of CO and H2O. CO column densities along the line of sight of N{(CO)}=5-10×1018 cm-2 are required to explain the band shape, the flux, and the P-R-asymmetry, and beam-filling is invoked to reconcile this high N(CO) with the upper limit inferred from the H2 emission. CO is more abundant than H2O by a factor of at least 2. The density of the warm component is estimated from the H2O emission to be ~ 2×107 cm-3. The CO emission from the hot component is neither satisfactorily explained in terms of non-thermal (streaming) collisions, nor by resonant scattering. Vibrational excitation through collisions with H2 for densities of ~3×108 cm-3 or, alternatively, with atomic hydrogen, with a density of at least 107 cm-3, are invoked to explain simultaneously the emission from the hot component

  8. Probing active galactic nuclei with H2O megamasers.

    PubMed Central

    Moran, J; Greenhill, L; Herrnstein, J; Diamond, P; Miyoshi, M; Nakai, N; Inque, M

    1995-01-01

    the disk must be <1000 K and the toroidal magnetic field component must be <250 mG. If the molecular mass density in the disk is 10(10) cm-3, then the disk mass is approximately 10(4) M[symbol: see text], and the disk is marginally stable as defined by the Toomre stability parameter Q (Q = 6 at the inner edge and 1 at the outer edge). The inward drift velocity is predicted to be <0.007 km.s-1, for a viscosity parameter of 0.1, and the accretion rate is <7 x 10(-5) M[symbol: see text].yr-1. At this value the accretion would be sufficient to power the nuclear x-ray source of 4 x 10(40) ergs-1 (1 erg = 0.1 microJ). The volume of individual maser components may be as large as 10(46) cm3, based on the velocity gradients, which is sufficient to supply the observed luminosity. The pump power undoubtedly comes from the nucleus, perhaps in the form of x-rays. The warp may allow the pump radiation to penetrate the disk obliquely [Neufeld, D. A. & Maloney, P. R. (1995) Astrophys. J. Lett. 447, L17-L19]. A total of 15 H2O megamasers have been identified out of >250 galaxies searched. Galaxy NGC4258 may be the only case where conditions are optimal to reveal a well-defined nuclear disk. Future measurement of proper motions and accelerations for NGC4258 will yield an accurate distance and a more precise definition of the dynamics of the disk Images Fig. 6 PMID:11607612

  9. I + (H2O)2 → HI + (H2O)OH Forward and Reverse Reactions. CCSD(T) Studies Including Spin-Orbit Coupling.

    PubMed

    Wang, Hui; Li, Guoliang; Li, Qian-Shu; Xie, Yaoming; Schaefer, Henry F

    2016-03-01

    The potential energy profile for the atomic iodine plus water dimer reaction I + (H2O)2 → HI + (H2O)OH has been explored using the "Gold Standard" CCSD(T) method with quadruple-ζ correlation-consistent basis sets. The corresponding information for the reverse reaction HI + (H2O)OH → I + (H2O)2 is also derived. Both zero-point vibrational energies (ZPVEs) and spin-orbit (SO) coupling are considered, and these notably alter the classical energetics. On the basis of the CCSD(T)/cc-pVQZ-PP results, including ZPVE and SO coupling, the forward reaction is found to be endothermic by 47.4 kcal/mol, implying a significant exothermicity for the reverse reaction. The entrance complex I···(H2O)2 is bound by 1.8 kcal/mol, and this dissociation energy is significantly affected by SO coupling. The reaction barrier lies 45.1 kcal/mol higher than the reactants. The exit complex HI···(H2O)OH is bound by 3.0 kcal/mol relative to the asymptotic limit. At every level of theory, the reverse reaction HI + (H2O)OH → I + (H2O)2 proceeds without a barrier. Compared with the analogous water monomer reaction I + H2O → HI + OH, the additional water molecule reduces the relative energies of the entrance stationary point, transition state, and exit complex by 3-5 kcal/mol. The I + (H2O)2 reaction is related to the valence isoelectronic bromine and chlorine reactions but is distinctly different from the F + (H2O)2 system.

  10. I + (H2O)2 → HI + (H2O)OH Forward and Reverse Reactions. CCSD(T) Studies Including Spin-Orbit Coupling.

    PubMed

    Wang, Hui; Li, Guoliang; Li, Qian-Shu; Xie, Yaoming; Schaefer, Henry F

    2016-03-01

    The potential energy profile for the atomic iodine plus water dimer reaction I + (H2O)2 → HI + (H2O)OH has been explored using the "Gold Standard" CCSD(T) method with quadruple-ζ correlation-consistent basis sets. The corresponding information for the reverse reaction HI + (H2O)OH → I + (H2O)2 is also derived. Both zero-point vibrational energies (ZPVEs) and spin-orbit (SO) coupling are considered, and these notably alter the classical energetics. On the basis of the CCSD(T)/cc-pVQZ-PP results, including ZPVE and SO coupling, the forward reaction is found to be endothermic by 47.4 kcal/mol, implying a significant exothermicity for the reverse reaction. The entrance complex I···(H2O)2 is bound by 1.8 kcal/mol, and this dissociation energy is significantly affected by SO coupling. The reaction barrier lies 45.1 kcal/mol higher than the reactants. The exit complex HI···(H2O)OH is bound by 3.0 kcal/mol relative to the asymptotic limit. At every level of theory, the reverse reaction HI + (H2O)OH → I + (H2O)2 proceeds without a barrier. Compared with the analogous water monomer reaction I + H2O → HI + OH, the additional water molecule reduces the relative energies of the entrance stationary point, transition state, and exit complex by 3-5 kcal/mol. The I + (H2O)2 reaction is related to the valence isoelectronic bromine and chlorine reactions but is distinctly different from the F + (H2O)2 system. PMID:26562487

  11. Kinetic Studies of Iron Deposition Catalyzed by Recombinant Human Liver Heavy, and Light Ferritins and Azotobacter Vinelandii Bacterioferritin Using O2 and H2O2 as Oxidants

    NASA Technical Reports Server (NTRS)

    Bunker, Jared; Lowry, Thomas; Davis, Garrett; Zhang, Bo; Brosnahan, David; Lindsay, Stuart; Costen, Robert; Choi, Sang; Arosio, Paolo; Watt, Gerald D.

    2005-01-01

    The discrepancy between predicted and measured H2O2 formation during iron deposition with recombinant heavy human liver ferritin (rHF) was attributed to reaction with the iron protein complex [Biochemistry 40 (2001) 10832-10838]. This proposal was examined by stopped-flow kinetic studies and analysis for H2O2 production using (1) rHF, and Azotobacter vinelandii bacterial ferritin (AvBF), each containing 24 identical subunits with ferroxidase centers; (2) site-altered rHF mutants with functional and dysfunctional ferroxidase centers; and (3) rccombinant human liver light ferritin (rLF), containing 110 ferroxidase center. For rHF, nearly identical pseudo-first-order rate constants of 0.18 per second at pH 7.5 were measured for Fe(2+) oxidation by both O2 and H2O2, but for rLF, the rate with O2 was 200-fold slower than that for H2O2 (k-0.22 per second). A Fe(2+)/O2 stoichiometry near 2.4 was measured for rHF and its site altered forms, suggesting formation of H2O2. Direct measurements revealed no H2O2 free in solution 0.5-10 min after all Fe(2+) was oxidized at pH 6.5 or 7.5. These results are consistent with initial H2O2 formation, which rapidly reacts in a secondary reaction with unidentified solution components. Using measured rate constants for rHF, simulations showed that steady-state H2O2 concentrations peaked at 14 pM at approx. 600 ms and decreased to zero at 10-30 s. rLF did not produce measurable H2O2 but apparently conducted the secondary reaction with H2O2. Fe(2+)/O2 values of 4.0 were measured for AvBF. Stopped-flow measurements with AvBF showed that both H2O2 and O2 react at the same rate (k=0.34 per second), that is faster than the reactions with rHF. Simulations suggest that AvBF reduces O2 directly to H2O without intermediate H2O2 formation.

  12. The cellular steady-state of H2O2: latency concepts and gradients.

    PubMed

    Marinho, H Susana; Cyrne, Luísa; Cadenas, Enrique; Antunes, Fernando

    2013-01-01

    Hydrogen peroxide (H2O2) is able to diffuse across biomembranes but, when cells are exposed to external H2O2, the fast consumption of H2O2 inside the cells due to H2O2-removing enzymes provides the driving force for setting up a H2O2 gradient across the plasma membrane. Knowing this gradient is fundamental to standardize studies with H2O2 as for the same extracellular H2O2 concentration cells with different H2O2 gradients may be exposed to different intracellular H2O2 concentrations. Here, we present the kinetic background behind the establishment of the H2O2 gradient and show how the gradient can be determined experimentally using the principle of enzyme latency. Furthermore, we discuss some of the caveats that may arise when determining the H2O2 gradient. Finally, we describe detailed protocols for the experimental determination of the H2O2 gradient across the plasma membrane in Saccharomyces cerevisiae cells and in mammalian cell lines. PMID:23830623

  13. Carbonate-H2O2 Leaching for Sequestering Uranium from Seawater

    SciTech Connect

    Pan, Horng-Bin; Weisheng, Liao; Wai, Chien; Oyola, Yatsandra; Janke, Christopher James; Tian, Guoxin; Rao, Linfeng

    2014-01-01

    Uranium adsorbed on amidoxime-based polyethylene fiber in simulated seawater can be quantitatively eluted at room temperature using 1M Na2CO3 containing 0.1 M H2O2. This efficient elution process is probably due to formation of an extremely stable uranyl-peroxo-carbonato complex in the carbonate solution. After washing with water, the sorbent can be reused with little loss of uranium loading capacity. Possible existence of this stable uranyl species in ocean water is also discussed.

  14. Atmospheric lidar research applying to H2O, O2 and aerosols

    NASA Technical Reports Server (NTRS)

    Mcilrath, T. J.; Wilkerson, T. D.

    1977-01-01

    Experimental research on a near infrared tunable dye laser was reported, and theoretical simulations were presented for various lidar configurations. The visible and nearinfrared wavelengths considered were suitable for observations of aerosols, water vapor, molecular oxygen pressure and temperature in the troposphere and above. The first phase of development work was described on a ruby pumped, tunable dye laser for the wavelength region 715 to 740 nanometers. Lidar simulations were summarized for measurements of H2O and for two color lidar observations of aerosols in the atmosphere.

  15. The distribution of H2O between silicate melt and nominally anhydrous peridotite and the onset of hydrous melting in the deep upper mantle

    NASA Astrophysics Data System (ADS)

    Novella, Davide; Frost, Daniel J.; Hauri, Erik H.; Bureau, Helene; Raepsaet, Caroline; Roberge, Mathilde

    2014-08-01

    The partitioning of H2O between a mantle peridotite assemblage and low degree hydrous melt has been investigated at 6 GPa (corresponding to ∼180 km depth) at a temperature of 1400 °C. Peridotite mineral phases were analysed from 6 melting experiments performed in a natural chemical system. The experiments contained ∼80 wt% of a low degree hydrous melt that was obtained through a series of experiments where the melt composition was iteratively adjusted until saturation with the appropriate peridotite assemblage was achieved. The melt is fluid-undersaturated at the conditions of the experiment. Ion microprobe measurements of the mineral phases indicate olivine H2O concentrations of 434±61 ppm wt and average clinopyroxene (cpx) concentrations of 1268±173 ppm wt H2O. Orthopyroxene (opx) and garnet contain 700±46 ppm wt and 347±83 ppm wt H2O, respectively. The H2O content of the hydrous melts was determined by mass balance to be 11±0.5 wt% H2O. H2O partition coefficients between minerals and melt (DH2Omin/melt=XH2Omin/XH2Omelt) are 0.0040±0.0006 for olivine, 0.0064±0.0004 for opx, 0.0115±0.0016 for cpx and 0.0032±0.0008 for garnet. Using the determined H2O partition coefficients the onset and extent of melting at conditions equivalent to 180 km below mid-ocean ridges was determined as a function of mantle H2O content. Current estimates for the H2O content of the depleted mantle (50-200 ppm wt H2O) are insufficient to induce mantle melting at this depth, which requires ∼700 ppm wt H2O to produce 0.1% melting and 1600 ppm wt H2O for 1% melting, along an adiabat with a potential temperature of 1327 °C. Melting can occur at these conditions within the mantle source of ocean island basalts, which are estimated to contain up to 900 ppm wt H2O. If adiabatic temperatures are 200 °C higher within such plume related sources, then melt fractions of over 1% can be reached at 180 km depth. In addition, a model for the distribution of H2O between peridotite mineral

  16. Precipitation of ALn(CO3),xH2O and Dy2(CO3),xH2O compounds from aqueous solutions for A=Li,Na,K,Cs,NH4+ and =La,Nd,Eu,Dy

    NASA Astrophysics Data System (ADS)

    Philippini, Violaine; Vercouter, Thomas; Chaussé, Annie; Vitorge, Pierre

    2008-09-01

    Double carbonates of lanthanide ( Ln) and alkaline or ammonium ( A) ions, noted ALn(CO3)2,xH2O, were precipitated from concentrated A2CO3 aqueous solutions at room temperature and atmospheric pressure. Twelve hydrated compounds out of the twenty targeted ones have been obtained: Li(Nd or Eu)(CO3)2, NaLa(CO3)2, KNd(CO3)2,xH2O, Cs(La or Nd)(CO3)2, NH4(Nd, Eu or Dy)(CO3)2, Dy2(CO3)3 from concentrated A2CO3 solutions and Na(Nd, Eu or Dy)(CO3)2 from concentrated AHCO3 solutions. Although the trivalent lanthanide ions are often considered as analogs in solution, differences in their precipitation behaviour was observed, which is believed to have a kinetic origin in relation to the small differences in their ionic radii. The solid compounds were characterised by elemental analyses, thermogravimetry (TG), X-ray diffraction (XRD) and scanning electron microscope-energy dispersive spectroscopy (SEM-EDS). The powder diffraction patterns of nine solids were fitted using the tetragonal P4/mmm Laüe class: LiNd(CO3)2,xH2O: a=(12.16±0.02) A˚, c=(9.21±0.02) A˚, LiEu(CO3)2,3H2O: a=(12.201±0.007) A˚, c=(9.23±0.01) A˚, KNd(CO3)2,xH2O: a=(13.28±0.04) A˚, c=(10.00±0.04) A˚, CsLa(CO3)2,xH2O: a=(10.82±0.02) A˚, c=(8.18±0.02) A˚, CsNd(CO3)2,xH2O: a=(10.81±0.07) A˚, c=(8.16±0.07) A˚ for NaLn(CO3)2,xH2O: a=(11.10+1.75r) A˚ and c=(8.60+1.13r) A˚, where r is the ionic radius of for a coordination number of 8 ( r=1.16 A˚, r=1.12 A˚, r=1.07 A˚ and r=1.03 A˚). It is proposed that all the NaLn(CO3)2,xH2O compounds are of very similar structure, as evidenced by their XRD patterns and by the linear variations of the lattice parameters with r. The small differences in the lattice parameters can induce large modification of the precipitation pathways. Conversely, structural changes were evidenced within the A+ series for ANd(CO3)2,xH2O. Dy2(CO3)3,xH2O was also obtained as a by-product. Its lattice parameters are in good agreement with Eu2(CO3)3,3H2O ones.

  17. Vibrations and reorientations of H2O molecules in [Sr(H2O)6]Cl2 studied by Raman light scattering, incoherent inelastic neutron scattering and proton magnetic resonance.

    PubMed

    Hetmańczyk, Joanna; Hetmańczyk, Lukasz; Migdał-Mikuli, Anna; Mikuli, Edward; Florek-Wojciechowska, Małgorzata; Harańczyk, Hubert

    2014-04-24

    Vibrational-reorientational dynamics of H2O ligands in the high- and low-temperature phases of [Sr(H2O)6]Cl2 was investigated by Raman Spectroscopy (RS), proton magnetic resonance ((1)H NMR), quasielastic and inelastic incoherent Neutron Scattering (QENS and IINS) methods. Neutron powder diffraction (NPD) measurements, performed simultaneously with QENS, did not indicated a change of the crystal structure at the phase transition (detected earlier by differential scanning calorimetry (DSC) at TC(h)=252.9 K (on heating) and at TC(c)=226.5K (on cooling)). Temperature dependence of the full-width at half-maximum (FWHM) of νs(OH) band at ca. 3248 cm(-1) in the RS spectra indicated small discontinuity in the vicinity of phase transition temperature, what suggests that the observed phase transition may be associated with a change of the H2O reorientational dynamics. However, an activation energy value (Ea) for the reorientational motions of H2O ligands in both phases is nearly the same and equals to ca. 8 kJ mol(-1). The QENS peaks, registered for low temperature phase do not show any broadening. However, in the high temperature phase a small QENS broadening is clearly visible, what implies that the reorientational dynamics of H2O ligands undergoes a change at the phase transition. (1)H NMR line is a superposition of two powder Pake doublets, differentiated by a dipolar broadening, suggesting that there are two types of the water molecules in the crystal lattice of [Sr(H2O)6]Cl2 which are structurally not equivalent average distances between the interacting protons are: 1.39 and 1.18 Å. However, their reorientational dynamics is very similar (τc=3.3⋅10(-10) s). Activation energies for the reorientational motion of these both kinds of H2O ligands have nearly the same values in an experimental error limit: and equal to ca. 40 kJ mole(-1). The phase transition is not seen in the (1)H NMR spectra temperature dependencies. Infrared (IR), Raman (RS) and inelastic

  18. Growth of CuSO4 · 5H2O single crystals and study of some of their properties

    NASA Astrophysics Data System (ADS)

    Manomenova, V. L.; Stepnova, M. N.; Grebenev, V. V.; Rudneva, E. B.; Voloshin, A. E.

    2013-05-01

    Large single crystals of copper sulfate pentahydrate CuSO4 · 5H2O of optical quality have been grown; they can be applied as broadband UV optical filters. Their transmission spectra are measured. The crystal thermal stability is investigated and the onset temperature of dehydration is determined to be 46°C.

  19. Density functional investigations on the (H 2O) n·CCH and (H 2O) n·HCC complexes ( n=1-3)

    NASA Astrophysics Data System (ADS)

    Qu, Zheng-wang; Zhu, Hui; Zhang, Xing-kang; Zhang, Qi-yuan

    2003-01-01

    The electronic structures and energies of (H 2O) n·CCH and (H 2O) n·HCC complexes ( n=1-3) between CCH and water have been theoretically investigated at the UB3LYP/6-311++G(2df,p)//UB3LYP/6-311G(d,p) level. The complexes with n=2-3 are cyclic structures with homodromic hydrogen-bond chain. The (H 2O) n·CCH ( n=1-3) complexes show increasing stabilities towards CCH- or H 2O-eliminations of 2.3, 5.8 and 7.6 kcal/mol and are energetically more stable than the corresponding (H 2O) n·HCC complexes by 0.8, 2.7 and 3.4 kcal/mol, respectively, due to the charge-separation-enhanced hydrogen bonds within (H 2O) n·CCH ( n=2,3). Strong interactions between CCH and (H 2O) 2 and (H 2O) 3 clusters suggest special solvent effects of water on the chemical behavior of unsaturated radicals.

  20. Self-sufficing H2O2-responsive nanocarriers through tumor-specific H2O2 production for synergistic oxidation-chemotherapy.

    PubMed

    Li, Junjie; Ke, Wendong; Wang, Lei; Huang, Mingming; Yin, Wei; Zhang, Ping; Chen, Qixian; Ge, Zhishen

    2016-03-10

    One of distinct features in tumor tissues is the elevated concentration of reactive oxygen species (ROS) during tumor immortality, proliferation and metastasis. However, ROS-responsive materials are rarely utilized in the field of in vivo tumoral ROS-responsive applications due to the fact that the intrinsic ROS level in the tumors could not escalate to an adequate level that the developed materials can possibly respond. Herein, palmitoyl ascorbate (PA) as a prooxidant for hydrogen peroxide (H2O2) production in tumor tissue is strategically compiled into a H2O2-responsive camptothecin (CPT) polymer prodrug micelle, which endowed the nanocarriers with self-sufficing H2O2 stimuli in tumor tissues. Molecular oncology manifests the hallmarks of tumoral physiology with deteriorating propensity in eliminating hazardous ROS. H2O2 production was demonstrated to specifically sustain in tumors, which not only induced tumor cell apoptosis by elevated oxidation stress but also served as autochthonous H2O2 resource to trigger CPT release for chemotherapy. Excess H2O2 and released CPT could penetrate into cells efficiently, which showed synergistic cytotoxicity toward cancer cells. Systemic therapeutic trial revealed potent tumor suppression of the proposed formulation via synergistic oxidation-chemotherapy. This report represents a novel nanomedicine platform combining up-regulation of tumoral H2O2 level and self-sufficing H2O2-responsive drug release to achieve novel synergistic oxidation-chemotherapy.

  1. P - ρ - T data for H2O up to 260 GPa under laser-driven shock loading

    NASA Astrophysics Data System (ADS)

    Kimura, T.; Ozaki, N.; Sano, T.; Okuchi, T.; Shimizu, K.; Miyanishi, K.; Terai, T.; Kakeshita, T.; Sakawa, Y.; Kodama, R.

    2014-12-01

    H2O is believed to be one of the most abundant compounds in ice giants including Neptune and Uranus1. Therefore, equation of state (EOS) for H2O is critical for understanding the formation and evolution of these planets. Various EOS models have been suggested for modeling the interior structure of the ice giants2-4. The recent shock experiments reported that their P - ρ data of H2O are in agreement with those of the QMD based EOS model5, indicating that this model is most suitable for modeling H2O in the ice giants. Whether H2O is in the solid or liquid state in the planetary interior has a great importance to understand their internal structures6. While the QMD model predicted that the solid H2O is present in deep interior of their planets above ~100 GPa4, the recent measurements revealed that H2O remains in the liquid state even at the deep interior conditions7. This discrepancy between experimental and theoretical studies suggests that the QMD based EOS model is disputable for modeling the planetary interior. Indeed, the comparison between data obtained from the shock experiments and the QMD based EOS did not cover the temperature5. We have obtained P - ρ - T data for H2O up to 260 GPa by using laser-driven shock compression technique. The diamond cell applied for the laser shock experiments was used as the sample container in order to achieve temperature conditions lower than the principal Hugoniot states. This shock technique combined with the cell can be used for an assessment the EOS models because it is possible to compare the states under the conditions that the contrast between the models clearly appears. Our data covering P - ρ - T on both the principal and the off Hugoniot curves agree with those of the QMD model, indicating this model to be adopted as the standard for modeling the interior structures of Neptune, Uranus, and exoplanets. References 1W. B. Hubbard et al., The interior of Neptune: Neptune and Triton(Univ. Arizona Press, Tucson, 1995) p

  2. Comprehensive copper ion hydration: experimental and theoretical investigation of Cu2+(H2O)n, Cu+(H2O)n, CuOH+(H2O)n

    NASA Astrophysics Data System (ADS)

    Sweeney, Andrew

    Guided ion beam tandem mass spectrometry is used to probe the kinetic energy dependence of both Cu2+(H2O)n, where n = 5--10, and CuOH+(H2O)n, where n = 0--4 colliding with Xe. The resulting cross sections are analyzed using statistical models to yield 0 K bond dissociation energies (BDEs). The primary dissociation pathway for Cu2+(H2O)n consists of water loss followed by the sequential loss of additional waters at higher energies until n = 7, at which point charge separation to form CuOH+(H2O) m + H+(H2O)n-m-2 is energetically favored. The primary dissociation pathway for CuOH+(H 2O)n is also water loss and is followed by the sequential loss of additional waters at higher energies until n = 1, at which point OH loss become competitive. The BDEs for loss of water and OH from CuOH +(H2O) are combined in a thermodynamic cycle with literature values to derive BDEs for the loss of OH from CuOH+(H 2O)n, where n = 0, 2--4. Infrared multiple photon dissociation (IRPD) spectroscopy is performed on CuOH+(H2O)n, where n = 2--9. These spectra are characterized through comparison to theoretical spectra of low energy isomers. It is found that CuOH+(H2O) n prefers a 4-coordinate inner shell, although contributions from 5-coordinate geometries cannot be ruled out in most cases and are clearly present for n = 7. This preference is found in the Cu2+(H2O) n system as well and differs from the Cu+(H2O) n system, which prefers a 2-coordinate inner shell. Electronic structure calculations are further employed to yield BDEs which agree reasonably well with experimental values. A method for modeling kinetic energy release distributions (KERD) on a guided ion beam tandem mass spectrometer is proposed. This method achieves reasonable agreement with dissociations occurring over loose transition states when reactants have little energy in excess of the dissociation threshold. Current limitations and future possibilities of this method are discussed in detail.

  3. H2O2 levels in rainwater collected in south Florida and the Bahama Islands

    NASA Technical Reports Server (NTRS)

    Zika, R.; Saltzman, E.; Chameides, W. L.; Davis, D. D.

    1982-01-01

    Measurements of H2O2 in rainwater collected in Miami, Florida, and the Bahama Islands area indicate the presence of H2O2 concentration levels ranging from 100,000 to 700,000 M. No systematic trends in H2O2 concentration were observed during an individual storm, in marked contrast to the behavior of other anions for example, NO3(-), SO4(-2), and Cl(-). The data suggest that a substantial fraction of the H2O2 found in precipitation is generated by aqueous-phase reactions within the cloudwater rather than via rainout and washout of gaseous H2O2.

  4. Formation of Submicron Magnesite during Reaction of Natural Forsterite in H2O-Saturated Supercritical CO2

    SciTech Connect

    Qafoku, Odeta; Hu, Jian Z.; Hess, Nancy J.; Hu, Mary Y.; Ilton, Eugene S.; Feng, Ju; Arey, Bruce W.; Felmy, Andrew R.

    2014-06-01

    Natural forsterite was reacted in a) liquid water saturated with supercritical CO2 (scCO2) and in b) H2O-saturated scCO2 at 35-80 °C and 90 atm. The solid reaction products were analyzed with nuclear magnetic resonance (NMR), scanning electron microscopy (SEM), and confocal Raman spectroscopy. Two carbonate phases, nesquehonite (MgCO3.3H2O) and magnesite (MgCO3), were identified with the proportions of the two phases depending on experimental conditions. In water saturated with scCO2, nesquehonite was the dominant carbonate phase at 35-80 °C with only a limited number of large, micron size magnesite particles forming at the highest temperature, 80 °C. In contrast, in H2O-saturated scCO2 magnesite formation was identified at all three temperatures: 35 °, 50 °, and 80 °C. Magnesite was the dominant carbonation reaction product at 50 ° and 80 °C; but nesquehonite was dominant at 35 °C. The magnesite particles formed under H2O-saturated scCO2 conditions exhibited an extremely uniform submicron grain-size and nearly identical rhombohedral morphologies at all temperatures. The distribution and form of the particles were not consistent with epitaxial nucleation and growth on the forsterite surface.

  5. T. C. Chamberlin and H2O climate feedbacks: A voice from the past

    NASA Astrophysics Data System (ADS)

    Fleming, James R.

    The interaction of positive and negative climate feedbacks has become a central issue for the global change science community. With many expecting surface air temperatures to rise several degrees due to increases in anthropogenic greenhouse gases, the response of H2O (water vapor, liquid, solid) is critical. Will higher temperatures and increased evaporation lead to an enhanced greenhouse effect, especially over the tropical oceans, or will increased cloudiness effectively cap the increase in temperatures? [see Ramanathan and Collins, 1991, 1992; Stephens and Slingo, 1992].“Greenhouse Warming and Cloud Thermostats” is the name of a talk to be given by V. Ramanathan during the Atmospheric Sciences Section luncheon at the AGU 1992 Fall Meeting on December 8. This topic invites comparison between the current H2O feedback hypotheses and work begun almost a century ago by the celebrated geologist Thomas Chrowder Chamberlin (1843-1928) at the University of Chicago [Gillispie, 1970-1980 Schultz, 1976]. Briefly, here are some of Chamberlin's ideas on the roles of water vapor and clouds.

  6. OH and H2O on Vesta and on the Moon: A comparative analysis

    NASA Astrophysics Data System (ADS)

    Combe, J.; McCord, T. B.; De Sanctis, M.; Ammannito, E.; Hayne, P. O.; Bandfield, J. L.; Pieters, C. M.; Palomba, E.; Longobardo, A.; Prettyman, T. H.; Marchi, S.; Capaccioni, F.; Capria, M.; Mittlefehldt, D. W.; Sunshine, J. M.; Tosi, F.; Turrini, D.; Zambon, F.; Raymond, C. A.; Russell, C. T.

    2012-12-01

    Searching for OH and H2O on Vesta and on the Moon is key [1] because the presence of these molecules at the surface of objects in the inner solar system is fundamental for understanding the formation of water in the early history of the solar system, as well as its implications on the mineralogical, thermodynamical, and geological evolution of the planets [2, 3]. Vesta is mineralogically differentiated, more evolved than most of the asteroids, but not as much as a planet [4, 5]. The surface of Vesta shows very strong pyroxene absorption bands in reflectance spectra [6 - 8], and the howardite, eucrite, diogenite (HED) meteorites that are of Vestan origin are also pyroxene-rich [9 - 13], which strongly suggests that the surface of Vesta is mostly made of basalt. This basaltic-rich surface composition of Vesta is one similarity with the surface of the Moon, where OH and H2O have been detected by imaging spectroscopy in the near-infrared [14 - 16]. On Vesta, the possible origins for OH and H2O are the same as what has been suggested for the Moon [17]: 1) indigenous to the object, 2) in-fall of hydrated exogenous material, and 3) implantation of solar wind protons. The objective of this study is to derive abundance estimates for OH and H2O at the surface of Vesta, and to compare them with abundances found on the Moon. The analysis of OH and H2O at the surface of Vesta is done with the Visible and Infrared mapping spectrometer (VIR) [18] onboard the Dawn orbiter using reflectance spectra between 0.25 and 5.1 μm. We are also analyzing again data from the Moon Mineralogy Mapper (M3) a thermal emission correction based on modeling of brightness temperature as function of the surface roughness [19]. VIR has detected an absorption band at 2.8 μm, attributed to OH [11, 12, 13], in coherent spatial units that have been observed multiple times. Associations with surface morphological features are complex. No correlation with temperature or with illumination suggests that the

  7. H2O-CO2-S fluid triggering the 1991 Mount Pinatubo climactic eruption (Philippines)

    NASA Astrophysics Data System (ADS)

    Borisova, Anastassia Y.; Toutain, Jean-Paul; Dubessy, Jean; Pallister, John; Zwick, Antoine; Salvi, Stefano

    2014-02-01

    The factors that trigger explosive eruptions often remain elusive because of the lack of direct data from representative samples. Here, we report the first micro-Raman spectroscopy measurements of fluid and multiphase inclusions trapped in quartz xenocrysts and microlites from andesitic lavas and basaltic enclaves of the 1991 Mount Pinatubo eruption. Our analyses reveal two-phase H2O-CO2-S inclusions containing a CO2-dominated phase and an aqueous sulfate-bearing liquid phase and, less commonly, anhydrite (CaSO4(solid)). The two fluid phases are low-temperature products of a supercritical H2O-CO2-S fluid which was associated with a hydrous silicate melt prior to eruption. The average density of the CO2 phase is 0.4 ± 0.2 g/cm3 at room temperature, corresponding to a supercritical fluid density of 0.6 ± 0.1 g/cm3 at the conditions of entrapment at 760-1000 °C and up to ˜260 MPa. For the first time, a dense CO2-bearing fluid is reported in Mount Pinatubo volcanic samples. We suggest that this hybrid H2O-CO2-S fluid originated from mixing between sulfur-rich basaltic and hydrous dacitic magmas, as the former was intruded into and interacted with the pre-eruptive Mount Pinatubo dacite magma reservoir, at depths of at least 10 km. Thermodynamic modeling demonstrates that part of the SO2 liberated from the intruded basaltic magma was consumed via interaction with the aqueous fluid-saturated dacitic magma according to the reaction 4SO2 basalt + 4H2Odacite = 3HSO4 - + H2S + 3H+, yielding early Cu-rich sulfides, late abundant anhydrite, and SO4-rich apatites, which are commonly found in the Mount Pinatubo dacites. We suggest that this hybrid H2O-CO2-S fluid played an important role in triggering the 1991 climactic eruption.

  8. Transit of H2O2 across the endoplasmic reticulum membrane is not sluggish.

    PubMed

    Appenzeller-Herzog, Christian; Bánhegyi, Gabor; Bogeski, Ivan; Davies, Kelvin J A; Delaunay-Moisan, Agnès; Forman, Henry Jay; Görlach, Agnes; Kietzmann, Thomas; Laurindo, Francisco; Margittai, Eva; Meyer, Andreas J; Riemer, Jan; Rützler, Michael; Simmen, Thomas; Sitia, Roberto; Toledano, Michel B; Touw, Ivo P

    2016-05-01

    Cellular metabolism provides various sources of hydrogen peroxide (H2O2) in different organelles and compartments. The suitability of H2O2 as an intracellular signaling molecule therefore also depends on its ability to pass cellular membranes. The propensity of the membranous boundary of the endoplasmic reticulum (ER) to let pass H2O2 has been discussed controversially. In this essay, we challenge the recent proposal that the ER membrane constitutes a simple barrier for H2O2 diffusion and support earlier data showing that (i) ample H2O2 permeability of the ER membrane is a prerequisite for signal transduction, (ii) aquaporin channels are crucially involved in the facilitation of H2O2 permeation, and (iii) a proper experimental framework not prone to artifacts is necessary to further unravel the role of H2O2 permeation in signal transduction and organelle biology.

  9. Distance-dependent radiation chemistry: Oxidation versus hydrogenation of CO in electron-irradiated H2O/CO/H2O ices

    SciTech Connect

    Petrik, Nikolay G.; Monckton, Rhiannon J.; Koehler, Sven; Kimmel, Gregory A.

    2014-11-26

    Electron-stimulated oxidation of CO in layered H2O/CO/H2O ices was investigated with infrared reflection-absorption spectroscopy (IRAS) as function of the distance of the CO layer from the water/vacuum interface. The results show that while both oxidation and reduction reactions occur within the irradiated water films, there are distinct regions where either oxidation or reduction reactions are dominant. At depths less than ~ 15 ML, CO oxidation dominates over the sequential hydrogenation of CO to methanol (CH3OH), and CO2 is the major product of CO oxidation, consistent with previous observations. At its highest yield, CO2 accounts for ~45% of all the reacted CO. Another oxidation product is identified as the formate anion (HCO2-). In contrast, for CO buried more than ~ 35 ML below the water/vacuum interface, the CO-to-methanol conversion efficiency is close to 100%. Production of CO2 and formate are not observed for the more deeply buried CO layers, where hydrogenation dominates. Experiments with CO dosed on pre-irradiated ASW samples suggest that OH radicals are primarily responsible for the oxidation reactions. Possible mechanisms of CO oxidation, involving primary and secondary processes of water radiolysis at low temperature, are discussed. The observed distance-dependent radiation chemistry results from the higher mobility of hydrogen atoms that are created by the interaction of the 100 eV electrons with the water films. These hydrogen atoms, which are primarily created at or near the water/vacuum interface, can desorb from or diffuse into the water films, while the less-mobile OH radicals remain in the near-surface zone resulting in preferential oxidation reactions there. The diffusing hydrogen atoms are responsible for the hydrogenation reactions that are dominant for the more deeply buried CO layers.

  10. Atomic imaging of nucleation of trimethylaluminum on clean and H2O functionalized Ge(100) surfaces

    NASA Astrophysics Data System (ADS)

    Lee, Joon Sung; Kaufman-Osborn, Tobin; Melitz, Wilhelm; Lee, Sangyeob; Delabie, Annelies; Sioncke, Sonja; Caymax, Matty; Pourtois, Geoffrey; Kummel, Andrew C.

    2011-08-01

    The direct reaction of trimethylaluminum (TMA) on a Ge(100) surface and the effects of monolayer H2O pre-dosing were investigated using ultrahigh vacuum techniques, such as scanning tunneling microscopy (STM), scanning tunneling spectroscopy (STS), and x-ray photoelectron spectroscopy (XPS), and density functional theory (DFT). At room temperature (RT), a saturation TMA dose produced 0.8 monolayers (ML) of semi-ordered species on a Ge(100) surface due to the dissociative chemisorption of TMA. STS confirmed the chemisorption of TMA passivated the bandgap states due to dangling bonds. By annealing the TMA-dosed Ge surface, the STM observed coverage of TMA sites decreased to 0.4 ML at 250 °C, and to 0.15 ML at 450 °C. XPS analysis showed that only carbon content was reduced during annealing, while the Al coverage was maintained at 0.15 ML, consistent with the desorption of methyl (-CH3) groups from the TMA adsorbates. Conversely, saturation TMA dosing at RT on the monolayer H2O pre-dosed Ge(100) surface followed by annealing at 200 °C formed a layer of Ge-O-Al bonds with an Al coverage a factor of two greater than the TMA only dosed Ge(100), consistent with Ge-OH activation of TMA chemisorption and Ge-H blocking of CH3 chemisorption. The DFT shows that the reaction of TMA has lower activation energy and is more exothermic on Ge-OH than Ge-H sites. It is proposed that the H2O pre-dosing enhances the concentration of adsorbed Al and forms thermally stable Ge-O-Al bonds along the Ge dimer row which could serve as a nearly ideal atomic layer deposition nucleation layer on Ge(100) surface.

  11. Detection and evolution of H2O ice spots on 67P/Churyumov-Gerasimenko's nucleus

    NASA Astrophysics Data System (ADS)

    Barucci, Maria Antonieta; Filacchione, Gianrico; Fornasier, Sonia; Raponi, Andrea; Prasanna Deshapriya, Jasinghege Don; Tosi, Federico; Feller, Clement; Ciarniello, Mauro; Sierks, Holger; Capaccioni, Fabrizio; Pommerol, Antoine; Massironi, Matteo; Oklay Vincent, Nilda; Guilbert-Lepoutre, Aurelie; Fulchignoni, Marcello; Érard, Stéphane; OSIRIS Team, VIRTIS Team

    2016-10-01

    The OSIRIS (Optical, Spectroscopic, and Infrared Remote Imaging System), and VIRTIS (Visible InfraRed Thermal Imaging Spectrometer) instruments on board Rosetta spacecraft acquired a huge quantity of resolved images and spectra of the comet 67P/Churyumov-Gerasimenko, producing the most detailed maps at the highest spatial resolution of a cometary nucleus surface. After almost two years of observations, 67P was revealed as an intriguing body with a surface rich in heterogeneous geological structures, different surface properties (albedo, colors, texture, tensile strength, layers, pits, boulders…).A large quantity of bright spots of different size with high visible albedo and flat visible spectrophotometry have been identified by OSIRIS high resolution images. Comparing the image data with near-infrared spectra and modeling the spectra (using Hapke's radiative transfer model) as a mixture of H2O ice and the ubiquitios « Dark Material » present on the nucleus' surface, we were able to study at the same time the morphological, thermal and compositional properties of these areas.With this complementary study we are able to confirm the presence of H2O ice on many brighter areas distributed on the two lobes of 67P.The detected bright spots are mostly situated on consolidated dust free material surfaces, distributed on the two lobes of 67P in locations which stay longer in shadow, mostly concentrated in near equatorial latitudes. Some spots are stable for several months and others show temporal changes connected to diurnal and seasonal variations. Stability of the spots is corroborated by the temperature retrieved at the surface. The behavior of ice at these locations is in very good agreement with theoretical expectations. The majority of the detected H2O ice spots are located in the same approximate position of previously detected cometary outbursts. A general overview of these icy spots on the surface of comet 67P will be presented and discussed.

  12. Removing polysaccharides-and saccharides-related coloring impurities in alkyl polyglycosides by bleaching with the H2O2/TAED/NaHCO3 system.

    PubMed

    Yanmei, Liu; Jinliang, Tao; Jiao, Sun; Wenyi, Chen

    2014-11-01

    The effect of H2O2/TAED/NaHCO3 system, namely NaHCO3 as alkaline agent with the (tetra acetyl ethylene diamine (TAED)) TAED-activated peroxide system, bleaching of alkyl polyglycosides solution was studied by spectrophotometry. The results showed that the optimal bleaching conditions about H2O2/TAED/NaHCO3 system bleaching of alkyl polyglycosides solution were as follows: molar ratio of TAED to H2O2 was 0.06, addition of H2O2 was 8.6%, addition of NaHCO3 was 3.2%, bleaching temperature of 50-65 °C, addition of MgO was 0.13%, and bleaching time was 8h. If too much amount of NaHCO3 was added to the system and maintained alkaline pH, the bleaching effect would be greatly reduced. Fixing molar ratio of TAED to H2O2 and increasing the amount of H2O2 were beneficial to improve the whiteness of alkyl polyglycosides, but adding too much amount of H2O2 would reduce the transparency. In the TAED-activated peroxide system, NaHCO3 as alkaline agent and buffer agent, could overcome the disadvantage of producing black precipitates when NaOH as alkaline agent. PMID:25129762

  13. A thermodynamical model for the surface tension of silicate melts in contact with H2O gas

    USGS Publications Warehouse

    Colucci, Simone; Battaglia, Maurizio; Trig