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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. Study of temperature variations of NMR spectra in monohydrates FeSO4. 1 H2O and MgSO4. 1 H2O

    NASA Astrophysics Data System (ADS)

    Murín, J.

    1986-06-01

    The paper deals with a study of the proton nuclear magnetic resonance (NMR) of crystallization water in isomorphous monohydrates MgSO4. 1 H2O and FeSO4. 1 H2O in the temperature range 123 313 K. The NMR second moment for diamagnetic MgSO4. 1 H2O shows only a weak dependence on temperature but the one for paramagnetic FeSO4. 1 H2O is rather strong. Results obtained for FeSO4. 1 H2O are in a good agreement with the Kroon's theory of NMR in paramagnetics. The Curie-Weiss constant and the effective magnetic moment of Fe2+ ions in FeSO4. 1 H2O are derived from the temperature dependence of NMR second moment. The motion of molecules of crystallization water in these hydrates is discussed on the basis of temperature dependences of the width and second moment of NMR spectra.

  7. Photosynthetic electron flow affects H2O2 signaling by inactivation of catalase in Chlamydomonas reinhardtii.

    PubMed

    Shao, Ning; Beck, Christoph F; Lemaire, Stéphane D; Krieger-Liszkay, Anja

    2008-11-01

    A specific signaling role for H(2)O(2) in Chlamydomonas reinhardtii was demonstrated by the definition of a promoter that specifically responded to this ROS. Expression of a nuclear-encoded reporter gene driven by this promoter was shown to depend not only on the level of exogenously added H(2)O(2) but also on light. In the dark, the induction of the reporter gene by H(2)O(2) was much lower than in the light. This lower induction was correlated with an accelerated disappearance of H(2)O(2) from the culture medium in the dark. Due to a light-induced reduction in catalase activity, H(2)O(2) levels in the light remained higher. Photosynthetic electron transport mediated the light-controlled down-regulation of the catalase activity since it was prevented by 3-(3'4'-dichlorophenyl)-1,1-dimethylurea (DCMU), an inhibitor of photosystem II. In the presence of light and DCMU, expression of the reporter gene was low while the addition of aminotriazole, a catalase inhibitor, led to a higher induction of the reporter gene by H(2)O(2) in the dark. The role of photosynthetic electron transport and thioredoxin in this regulation was investigated by using mutants deficient in photosynthetic electron flow and by studying the correlation between NADP-malate dehydrogenase and catalase activities. It is proposed that, contrary to expectations, a controlled down-regulation of catalase activity occurs upon a shift of cells from dark to light. This down-regulation apparently is necessary to maintain a certain level of H(2)O(2) required to activate H(2)O(2)-dependent signaling pathways.

  8. 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.

  9. Indonesian low rank coal oxidation: The effect of H2O2 concentration and oxidation temperature

    NASA Astrophysics Data System (ADS)

    Rahayu, S. S.; Findiati, F.; Aprilia, F.

    2016-11-01

    Extraction of Indonesian low rank coals by alkaline solution has been performed to isolate the humic substances. Pretreatments of the coals by oxidation using H2O2 prior to extraction are required to have higher yield of humic substances. In the previous research, only the extraction process was considered. Therefore, the effects of reaction temperature and residence time on coal oxidation and composition of extract residues are also investigated in this research. The oxidation temperatures studied were 40°C, 50°C, and 70°C and the H2O2 concentrations studied were 5%, 15%, 20 %, and 30 %. All the oxidation variables were studied for 90 minutes. The results show that the higher the concentration of H2O2 used, the less oxidized coal produced. The same trend was obtained by using higher oxidation temperature. The effect of H2O2 concentration, oxidation temperature and reaction time to the yield of humic substances extraction have positive trends.

  10. Homogeneous bubble nucleation in H2O- and H2O-CO2-bearing basaltic melts: Results of high temperature decompression experiments

    NASA Astrophysics Data System (ADS)

    Le Gall, Nolwenn; Pichavant, Michel

    2016-11-01

    High pressure and temperature decompression experiments were conducted to provide experimental information on the conditions of homogeneous bubble nucleation in basaltic melts. Experiments were performed on H2O- and H2O-CO2-bearing natural melts from Stromboli. Three starting volatile compositions were investigated: series #1 (4.91 wt% H2O, no CO2), series #2 (2.37-2.45 wt% H2O, 901-1011 ppm CO2) and series #3 (0.80-1.09 wt% H2O, 840-923 ppm CO2). The volatile-bearing glasses were first synthesized at 1200 °C and 200 MPa, and second continuously decompressed in the pressure range 150-25 MPa and rapidly quenched. A fast decompression rate of 78 kPa/s (or 3 m/s) was applied to limit the water loss from the glass cylinder and the formation of a H2O-depleted rim. Post-decompression glasses were characterized texturally by X-ray microtomography. The results demonstrate that homogenous bubble nucleation requires supersaturation pressures (difference between saturation pressure and pressure at which homogeneous bubble nucleation is observed, ∆ PHoN) ≤ 50-100 MPa. ∆ PHoN varies with the dissolved CO2 concentration, from ≪ 50 MPa (no CO2, series #1) to ≤ 50 MPa (872 ± 45 ppm CO2, series #3) to < 100 MPa (973 ± 63 ppm CO2, series #2). In series #1 melts, homogeneous bubble nucleation occurs as two distinct events, the first at high pressure (200 < P < 150 MPa) and the second at low pressure (50 < P < 25 MPa), just below the fragmentation level. In contrast, homogenous nucleation in series #2 and #3 melts is a continuous process. As well, chemical near-equilibrium degassing occurs in the series #1 melts, unlike in the series #2 and #3 melts which retain high CO2 concentrations even for higher vesicularities (up to 23% at 25 MPa). Thus, our experimental observations underline a significant effect of CO2 on the physical mechanisms of bubble vesiculation in basaltic melts. Our experimental decompression textures either reproduce or approach the characteristics of

  11. 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.

  12. 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.

  13. 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

  14. 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.

  15. Chitosan-phosphotungstic acid complex as membranes for low temperature H2-O2 fuel cell

    NASA Astrophysics Data System (ADS)

    Santamaria, M.; Pecoraro, C. M.; Di Quarto, F.; Bocchetta, P.

    2015-02-01

    Free-standing Chitosan/phosphotungstic acid polyelectrolyte membranes were prepared by an easy and fast in-situ ionotropic gelation process performed at room temperature. Scanning electron microscopy was employed to study their morphological features and their thickness as a function of the chitosan concentration. The membrane was tested as proton conductor in low temperature H2-O2 fuel cell allowing to get peak power densities up to 350 mW cm-2. Electrochemical impedance measurements allowed to estimate a polyelectrolyte conductivity of 18 mS cm-1.

  16. Fenton Oxidation of H2O2 under Low Temperature Hydrothermal Conditions: Implications for Organics on Mars

    NASA Astrophysics Data System (ADS)

    Grozeva, N.; Foustoukos, D.

    2009-12-01

    Evaluating the stability of organic compounds in the presence of oxidizing agents is essential to assess the potential habitability of present-day Mars. The residence time of CH4, for instance, may be greatly constrained by oxidants proposed to exist in Martian soil and atmosphere, in particular H2O2. Abiotic oxidation processes could play a key role in the removal of CH4 as recent studies suggest that CH4 sequestration in Martian environments occurs more rapidly than previously thought. Since CH4 evolution can be linked to possible subsurface liquid water, the formation of oxidants needs to be investigated under comparable hydrothermal conditions. To examine the possible formation of highly oxidizing hydroxyl radicals on Mars, a series of flow-through hydrothermal experiments involved decomposition of dissolved H2O2 in the presence of Fe-oxides (FeO, Fe3O4) via the Fenton reaction:

    Fe2+ + H2O2(aq) ↔ Fe3+ + ●OH + OH- ○C, consistent with temperature conditions at which liquid water possibly exists at depth in the Martian crust. Results show that the addition of Fe-oxides does not appreciably change the activation energy, but significantly increases the preexponential factor (A), resulting in enhanced rates of H2O2 decomposition relative to the uncatalyzed H2O2-H2O system. Since A is related to activation entropy, higher values reflect an increase in the entropy of the transition state, which likely involves the metastable formation of hydroxyl radicals at rates closely linked to the surface area of mineral catalysts. To further probe the formation of these strong oxidants, the extent of dissolved formic acid oxidation was also evaluated. Preliminary findings from Fe-bearing experiments are indicative of enhanced HCOOH decomposition due to the presence of metastable ●OH. Considering the strong oxidation effects of radicals on organic compounds, constraints on the kinetics and metastable equilibria of the Fenton reaction under hydrothermal conditions

  17. 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.

  18. 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.

  19. 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.

  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. Spatial structures of CO2, H2O, temperature and vertical wind velocity observed by aircraft

    NASA Astrophysics Data System (ADS)

    Selbach, Christoph; Schween, Jan; Crewell, Susanne; Geiss, Heiner; Neininger, Bruno

    2010-05-01

    During the FLUXPAT campaigns in 2008 and 2009 the MetAir Dimona research aricraft performed several fligths above a patchy, agricultural dominated landscape near Juelich/Germany. The measurements are aimed to capture the variability of water vapor and CO2 and derive turbulent fluxes in the atmospheric boundary layer close to the ground. Flights took place at two main levels around 150 m and 250 m above ground. Agriculture in this region is dominated by two different crops: sugar beet and wheat. Flights were scheduled in April and August as at these times of the year strong contrasts can be found between different fields. In April sugar beet is usually just seeded whereas wheat already forms a closed canopy. In August wheat unlike sugar beat is already harvested. We analyse the correlation lengths (L*) of CO2, H2O, temperature and vertical wind velocity on flight legs. L* is the median of the power spectrum i.e. 50 percent of the variance is in structures larger than L*. For the different quantities L* shows different behaviours during the day and between different flight levels. The structure lengthscales of CO2 have a large dependency on daytime and strongly decrease during noon and afternoon. We will present some approaches to explain this behaviour.

  2. High-bandwidth scanned-wavelength-modulation spectroscopy sensors for temperature and H2O in a rotating detonation engine

    NASA Astrophysics Data System (ADS)

    Goldenstein, Christopher S.; Almodóvar, Christopher A.; Jeffries, Jay B.; Hanson, Ronald K.; Brophy, Christopher M.

    2014-10-01

    The design and use of two-color tunable diode laser (TDL) absorption sensors for measurements of temperature and H2O in a rotating detonation engine (RDE) are presented. Both sensors used first-harmonic-normalized scanned-wavelength-modulation spectroscopy with second-harmonic detection (scanned-WMS-2f/1f) to account for non-absorbing transmission losses and emission encountered in the harsh combustion environment. One sensor used two near-infrared (NIR) TDLs near 1391.7 nm and 1469.3 nm that were modulated at 225 kHz and 285 kHz, respectively, and sinusoidally scanned across the peak of their respective H2O absorption transitions to provide a measurement rate of 50 kHz and a detection limit in the RDE of 0.2% H2O by mole. The other sensor used two mid-infrared (MIR) TDLs near 2551 nm and 2482 nm that were modulated at 90 kHz and 112 kHz, respectively, and sinusoidally scanned across the peak of their respective H2O transitions to provide a measurement rate of 10 kHz and a detection limit in the RDE of 0.02% H2O by mole. Four H2O absorption transitions with different lower-state energies were used to assess the homogeneity of temperature in the measurement plane. Experimentally derived spectroscopic parameters that enable temperature and H2O sensing to within 1.5-3.5% of known values are reported. The sensor design enabling the high-bandwidth scanned-WMS-2f/1f measurements is presented. The two sensors were deployed across two orthogonal and coplanar lines-of-sight (LOS) located in the throat of a converging-diverging nozzle at the RDE combustor exit. Measurements in the non-premixed H2-fueled RDE indicate that the temperature and H2O oscillate at the detonation frequency (≈3.25 kHz) and that production of H2O is a weak function of global equivalence ratio.

  3. 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

  4. Arbuscular mycorrhizae improve low temperature tolerance in cucumber via alterations in H2O2 accumulation and ATPase activity.

    PubMed

    Liu, Airong; Chen, Shuangchen; Chang, Rui; Liu, Dilin; Chen, Haoran; Ahammed, Golam Jalal; Lin, Xiaomin; He, Chaoxing

    2014-11-01

    The combined effects of arbuscular mycorrhizal fungi (AMF) and low temperature (LT) on cucumber plants were investigated with respect to biomass production, H2O2 accumulation, NADPH oxidase, ATPase activity and related gene expression. Mycorrhizal colonization ratio was gradually increased after AMF-inoculation. However, LT significantly decreased mycorrhizal colonization ability and mycorrhizal dependency. Regardless of temperature, the total fresh and dry mass, and root activity of AMF-inoculated plants were significantly higher than that of the non-AMF control. The H2O2 accumulation in AMF-inoculated roots was decreased by 42.44% compared with the control under LT. H2O2 predominantly accumulated on the cell walls of apoplast but was hardly detectable in the cytosol or organelles of roots. Again, NADPH oxidase activity involved in H2O2 production was significantly reduced by AMF inoculation under LT. AMF-inoculation remarkably increased the activities of P-type H(+)-ATPase, P-Ca(2+)-ATPase, V-type H(+)-ATPase, total ATPase activity, ATP concentration and plasma membrane protein content in the roots under LT. Additionally, ATP concentration and expression of plasma membrane ATPase genes were increased by AMF-inoculation. These results indicate that NADPH oxidase and ATPase might play an important role in AMF-mediated tolerance to chilling stress, thereby maintaining a lower H2O2 accumulation in the roots of cucumber.

  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 axisymmetric temperature and H2O concentration distributions on a circular flat flame burner based on tunable diode laser absorption tomography

    NASA Astrophysics Data System (ADS)

    Xia, Huihui; Kan, Ruifeng; Xu, Zhenyu; Liu, Jianguo; He, Yabai; Yang, Chenguang; Chen, Bing; Wei, Min; Yao, Lu; Zhang, Guangle

    2016-10-01

    In this paper, the reconstruction of axisymmetric temperature and H2O concentration distributions in a flat flame burner is realized by tunable diode laser absorption spectroscopy (TDLAS) and filtered back-projection (FBP) algorithm. Two H2O absorption transitions (7154.354/7154.353 cm-1 and 7467.769 cm-1) are selected as line pair for temperature measurement, and time division multiplexing technology is adopted to scan this two H2O absorption transitions simultaneously at 1 kHz repetition rate. In the experiment, FBP algorithm can be used for reconstructing axisymmetric distributions of flow field parameters with only single view parallel-beam TDLAS measurements, and the same data sets from the given parallel beam are used for other virtual projection angles and beams scattered between 0° and 180°. The real-time online measurements of projection data, i.e., integrated absorbance both for pre-selected transitions on CH4/air flat flame burner are realized by Voigt on-line fitting, and the fitting residuals are less than 0.2%. By analyzing the projection data from different views based on FBP algorithm, the distributions of temperature and concentration along radial direction can be known instantly. The results demonstrate that the system and the proposed innovative FBP algorithm are capable for accurate reconstruction of axisymmetric temperature and H2O concentration distribution in combustion systems and facilities.

  7. 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.

  8. HIGH-TEMPERATURE CO-ELECTROLYSIS OF H2O AND CO2 FOR SYNGAS PRODUCTION

    SciTech Connect

    Stoots, C.M.

    2006-11-01

    Worldwide, the demand for light hydrocarbon fuels like gasoline and diesel oil is increasing. To satisfy this demand, oil companies have begun to utilize oil deposits of lower hydrogen content (an example is the Athabasca Oil Sands). Additionally, the higher contents of sulfur and nitrogen of these resources requires processes such as hydrotreating to meet environmental requirements. In the mean time, with the price of oil currently over $50 / 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 War II. South Africa has used synfuels to power a significant number of their buses, trucks, and taxicabs. 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 investigate the feasibility of producing syngas by simultaneously electrolyzing at high-temperature steam and carbon dioxide (CO2) using solid oxide fuel cell technology. The syngas can then be used for synthetic fuel production. This program is a combination of experimental and computational activities. Since the solid oxide electrolyte material is a conductor of oxygen ions, CO can be produced by electrolyzing CO2 sequestered from some greenhouse gas-emitting process. Under certain conditions, however, CO can further electrolyze to produce carbon, which can then deposit on cell surfaces and reduce cell performance. The understanding of the co-electrolysis of steam and CO2 is also complicated by the competing water-gas shift reaction. Results of experiments and calculations to date of CO2 and CO2/H2O electrolysis will be presented and discussed. These will include

  9. Ternary liquid-liquid equilibria of Eugenol + Isobutanol + H2O and β-Caryophyllene + Isobutanol + H2O systems at temperatures 303.15 and 323.15 K

    NASA Astrophysics Data System (ADS)

    Parameswari, Zahrida D.; Kurniawan, Andre M.; Wibawa, Gede; Kuswandi, Kuswandi

    2017-05-01

    The liquid-liquid equilibrium (LLE) data of ternary Eugenol + Isobutanol + H2O and β-Caryophyllene + Isobutanol + H2O systems were measured at temperatures of 303.15 K and 323.15 K. Equilibrium cell with water jacket for keeping the temperature was used. Equilibrium data were obtained by stirring the mixture for 4 hours and settled for 20 hours to allow the system reach the equilibrium state. Samples of organic and aqueous phases were analyzed using Gas Chromatography. All the measured data were correlated using NRTL and UNIQUAC models. The reliability of the models is tested by comparison of calculated equilibrium compositions with experimental data in terms of root mean square deviations (RMSD). The system exhibited type II phase behaviour from immiscible area. It has two pairs miscible components (Eugenol + Isobutanol and β-Caryophyllene + Isobutanol), two pairs partially miscible components (Eugenol + H2O and Isobutanol + H2O) and one pair immiscible components (β-Caryophyllene + H2O). The temperatures on this system have small effect on immiscible zone and slope of tie lines. Based on experiment and calculation results, Eugenol + Isobutanol + H2O system has been successfully represented slightly better using UNIQUAC model with average values of RMSD is 2.0842% meanwhile NRTL model has higher value of RMSD that is 2.1359%, and β-Caryophyllene + Isobutanol + H2O system has been successfully represented better using UNIQUAC model with average values of RMSD is 2.1521% meanwhile NRTL model has higher value of RMSD that is 3.2976%.

  10. Low-Temperature Antiferromagnetic Behavior of α-Rb 2FeF 5 · H 2O and α-Cs 2FeF 5 · H 2O

    NASA Astrophysics Data System (ADS)

    Calage, Y.; Reiff, W. M.

    1994-08-01

    D.C. susceptibility and zero field Mössbauer spectroscopy measurements are used to characterize the low-temperature magnetism of α-Rb2FeF5 · H2O and α-Cs2FeF5 · H2O. The compounds are rigorously isotypic quasi-1D Heisenberg magnets based on hydrogen bonded chains of-{FeF5H2O}2- - pseudo-octahedra with intervening Rb+ and Cs+ cations that enhance the low dimensionality. The 1D antiferromagnetic effects appear comparable, Txmax(1D) ∼5 K, while their 3D ordering temperatures are quite different, TN(Rb+) = 4.0 K, TN (Cs+) = 2.7 K. The internal hyperfine fields extrapolated to T = 0 K are ∼ 51 T suggesting zero point spin reduction (∼15%) consistent with 1D behavior. High field d.c. susceptibility measurements for polycrystalline Cs2FeF5 · H2O suggest spin-flop behavior with HSF < 1 T. A qualitative comparison of the low-temperature magnetic properties of the F- and Cl- analogues for the series M2 FeX5 · H2O (M = NH+4, K+, Rb+, Cs+) is given.

  11. Investigations of different chemiluminescent peaks in H2O2-SCN(-)-Cu(2+)-OH(-)-luminol flow system.

    PubMed

    Zhao, Changchun; Zheng, Juhua; Xie, Jingxuan; Liu, Haimiao; Gao, Qingyu

    2011-01-01

    In the H2O2-SCN(-) -Cu(2+)-OH(-)-luminol oscillatory system of chemiluminescence, the effects of the ingredient concentrations, temperature, flow rate and complexing agent on the oscillatory dynamics were investigated in a continuous-flow stirred tank reactor (CSTR). The dynamical structure of two peaks during a period was discussed in detail. By addition of EDTA to the oscillating system, the peak I height decreased sharply while the peak II height was little affected, and the period kept constant. This may be due to the fast reaction between Cu(II) and EDTA and the highly stable complex Cu(II)-EDTA. From the experimental study and mechanism analysis, the chemiluminescent peak I corresponds to Cu(II) → Cu(I) transformation and the peak II corresponds to the Cu(I) → Cu(II) transformation process. The key species involving in the two-transformation process are inferred to be superoxide radical and hydroxyl radical. Copyright © 2010 John Wiley & Sons, Ltd.

  12. 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

  13. 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.

  14. Microdischarge in Porous Ceramics with Atmospheric Pressure High Temperature H2O/SO2 Gas Mixture and its Application for Hydrogen Production

    NASA Astrophysics Data System (ADS)

    Koo, Il Gyo; Choi, Myeong Yeol; Kim, Jong Hoon; Cho, Jin Hoon; Lee, W. M.

    2008-06-01

    Microdischarges in atmospheric pressure H2O/SO2 gas mixture at high temperature are studied to evaluate their plasma-chemical reactivity to produce hydrogen gas. The microplasma is generated inside a porous ceramic (MIPC) covered with two steel meshes as the gas mixture at atmospheric pressure flows through the medium. Voltage-current characteristics and optical emissions are measured to determine the electrical properties of the DC discharge and the degree of non-equilibrium. The discharge current at a given voltage substantially increases as the gas temperature is increased, thus posing a possibility to reduce the electrical power needed to sustain the discharge. The study also showed the possibility of facilitating the reaction between H2O and SO2 not by electrocatalyst like platinum but by non-thermal electrons.

  15. 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.

  16. 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.

  17. Near-Infrared Spectra of Icy Outer Solar System Surfaces: Remote Determination of H 2O Ice Temperatures

    NASA Astrophysics Data System (ADS)

    Grundy, W. M.; Buie, M. W.; Stansberry, J. A.; Spencer, J. R.; Schmitt, B.

    1999-12-01

    We present new 1.20 to 2.35 μm spectra of satellites of Jupiter, Saturn, and Uranus, and the rings of Saturn, obtained in 1995 and 1998 at Lowell Observatory. For most of the target objects, our data provide considerable improvement in spectral resolution and signal-to-noise over previously published data. Absorption bands with shapes characteristic of low-temperature, hexagonal crystalline H 2O ice dominate the spectra of most of our targets in this wavelength range. We make use of newly published temperature-dependent wavelengths and relative strengths of H 2O absorption bands to infer ice temperatures from our spectra. These ice temperatures are distinct from temperatures determined from thermal emission measurements or simulations of radiative balances. Unlike those methods, which average over all terrains including ice-free regions, our temperature-sensing method is only sensitive to the ice component. Our method offers a new constraint which, combined with other observations, can lead to better understanding of thermal properties and textures of remote, icy surfaces. Ice temperatures are generally lower than thermal emission brightness temperatures, indicative of the effects of thermal inertia and segregation between ice and warmer, darker materials. We also present the results of experiments to investigate possible changes of water ice temperature over time, including observations of Titania at two epochs, and of Ganymede and saturnian ring particles following emergence from the eclipse shadows of their primary planets. Finally, we discuss limitations of our temperature measurement method which can result from the presence of H 2O in phases other than hexagonal ice-I h, such as amorphous ice, hydrated mineral phases, or radiation-damaged crystalline ice. Our spectra of Europa and Enceladus exhibit peculiar spectral features which may result from effects such as these.

  18. Vapour pressures of H2SO4/HNO3/HCI/HBr/H2O solutions to low stratospheric temperatures

    SciTech Connect

    Luo, B.; Carslaw, K.S.; Peter, T.; Clegg, S.L. |

    1995-02-01

    Vapor pressures of H2O, HNO3, HCl and HBr over supercooled aqueous mixtures with sulfuric acid have been calculated using an activity coefficient model, for 185 K less than T less than 235 K, 0 less than wt% (H2SO4) + wt% (HNO3) less than 70, and assuming HCl and HBr to be minor constituents. Predicted vapor pressures agree well with most laboratory data, and give confidence in the validity of the model. The results are parameterized as simple formulae, which reproduce the model results to within 40% and cover the entire stratospherically relevant range of composition and temperature.

  19. MHD flow and heat transfer of a power-law non-Newtonian nanofluid (Cu-H2O) over a vertical stretching sheet

    NASA Astrophysics Data System (ADS)

    Ferdows, M.; Hamad, M. A. A.

    2016-07-01

    A steady-state mixed convection boundary layer flow of an electrically conducting nanofluid (Cu-H2O) obeying a power-law model in the presence of an alternating magnetic field due to a stretching vertical heated sheet is investigated numerically through the use of Wolfram Mathematica. The surface stretching velocity and the surface temperature are assumed to vary as linear functions of the distance from the origin. A similarity solution is presented, which depends on the nanoparticle volume fraction, power-law parameter, magnetic field parameter, buoyancy convection parameter, and modified Prandtl number.

  20. Two-temperature stage biphasic CO2-H2O pretreatment of lignocellulosic biomass at high solid loadings.

    PubMed

    Luterbacher, Jeremy S; Tester, Jefferson W; Walker, Larry P

    2012-06-01

    Most biomass pretreatment processes for monosaccharide production are run at low-solid concentration (<10 wt%) and use significant amounts of chemical catalysts. Biphasic CO(2) -H(2) O mixtures could provide a more sustainable pretreatment medium while using high-solid contents. Using a stirred reactor for high solids (40 wt%, biomass water mixture) biphasic CO(2)-H(2) O pretreatment of lignocellulosic biomass allowed us to explore the effects of particle size and mixing on mixed hardwood and switchgrass pretreatment. Subsequently, a two-temperature stage pretreatment was introduced. After optimization, a short high-temperature stage at 210°C (16 min for hardwood and 1 min for switchgrass) was followed by a long low-temperature stage at 160°C for 60 min. Glucan to glucose conversion yields of 83% for hardwood and 80% for switchgrass were obtained. Total molar sugar yields of 65% and 55% were obtained for wood and switchgrass, respectively, which consisted of a 10% points improvement over those obtained during our previous study despite a 10-fold increase in particle size. These yields are similar to those obtained with other major pretreatment technologies for wood and within 10% of major technologies for switchgrass despite the absence of chemical catalysts, the use of large particles (0.95 cm) and high solid contents (40 wt%).

  1. Microemulsion-enhanced electrochemiluminescence of luminol-H2O2 for sensitive flow injection analysis of antioxidant compounds.

    PubMed

    Xiuhua, Wei; Chao, Liu; Yifeng, Tu

    2012-05-30

    A microemulsion enhanced electrochemiluminescence (ECL) of luminol-H(2)O(2) was studied with the flow-injection (FI) technique. The results revealed that the microemulsion composed with cetyltrimethylammonium bromide (CTAB), n-butanol, n-heptane and water greatly enhanced the ECL especially in acidic medium. The ECL emission increased for 20 to 2 times in this microemulsion medium over the pH range of 5.0-8.0 compared to that in aqueous solution. The mechanism of enhancement of surfactant and microemulsion for luminol-H(2)O(2) ECL was discussed. It is mainly based on the electrostatic interaction between luminol anion and the head group of surfactant, which causes the adsorption and promotes the dissociation of luminol on the surfaces of the microemulsion droplets, favors the oxidation of luminol by the yielded reactive oxygen species (ROSs) during electrolysis. This research is very significant for ECL applications because of the extended practicable pH range which was suitable for environmental and biological systems. As an example, this FI-ECL technique can be applied for determination of oligo proanthocyanidin (OPC) because of its antioxidant property and to evaluate the total antioxidant activity of the grape skin using OPC as an index. Copyright © 2012 Elsevier B.V. All rights reserved.

  2. 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

  3. 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

    2016-05-02

    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).

  4. 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

    2015-04-02

    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.

  5. Effect of mild-temperature H2O2 oxidation on solubilization and anaerobic digestion of waste activated sludge.

    PubMed

    Junga, Heejung; Kim, Jaai; Lee, Seungyong; Lee, Changsoo

    2014-08-01

    Efficient sludge management is among the most challenging issues in wastewater treatment today, and anaerobic digestion is regarded as a viable solution. Mild-temperature H202 oxidation was examined for enhanced solubilization and biogas production of waste activated sludge (WAS). The effects of pretreatment factors (i.e. temperature and H202 concentration) on the degree of WAS disintegration (DD) and biogas yield (BY) were assessed by response surface analysis within the design space of 60-90 degrees C and 0-200mM H202. Significant sludge disintegration (up to 23.0% DD) and visibly enhanced BY (up to 26.9%) were shown in the pretreatment trials. Two response surface models to describe how DD and BY respond to changes in the pretreatment conditions were successfully constructed (R2 > 0.95, p < 0.05). The models showed totally different response surface shapes, indicating the DD and BY were influenced by pretreatment conditions in very different ways. DD was dominantly affected by temperature and showed higher model responses at the high-temperature region, while the BY response peaked in the low-temperature and mid-level H2O2 region. This observation implies that the enhanced solubilization of WAS was not directly translated into an increase in biogas production. Our results showed that WAS can be efficiently disintegrated by H202 oxidation under mild-temperature conditions for enhanced anaerobic digestibility. Within the explored region of pretreatment conditions, the maximum BY was estimated to be 82.1 mL/gCODadded (32.8% greater than the untreated control) at (60.0 degrees C, 74.2 mM H2O2).

  6. Mitochondrial sources of H2O2 generation play a key role in flow-mediated dilation in human coronary resistance arteries.

    PubMed

    Liu, Yanping; Zhao, Hongtao; Li, Hongwei; Kalyanaraman, B; Nicolosi, Alfred C; Gutterman, David D

    2003-09-19

    We previously showed that hydrogen peroxide (H2O2) contributes to flow-induced dilation in human coronary resistance arteries (HCRAs); however, the source of this H2O2 is not known. We hypothesized that the H2O2 is derived from superoxide (O2*-) generated by mitochondrial respiration. HCRAs were dissected from right atrial appendages obtained from patients during cardiac surgery and cannulated with micropipettes. H2O2-derived radicals and O2*- were detected by electron spin resonance (ESR) using BMPO as the spin trap and by histofluorescence using hydroethidine (HE, 5 micromol/L) and dichlorodihydrofluorescein (DCFH, 5 micromol/L). Diameter changes to increases in pressure gradients (20 and 100 cm H2O) were examined in the absence and the presence of rotenone (1 micromol/L), myxothiazol (100 nmol/L), cyanide (1 micromol/L), mitochondrial complex I, III, and IV inhibitors, respectively, and apocynin (3 mmol/L), a NADPH oxidase inhibitor. At a pressure gradient of 100 cm H2O, ubisemiquinone and hydroxyl radicals were detected from effluents of vessels. Including superoxide dismutase and catalase in the perfusate reduced the ESR signals. Relative ethidium and DCFH fluorescence intensities in HCRAs exposed to flow were enhanced (1.45+/-0.15 and 1.57+/-0.12, respectively compared with no-flow) and were inhibited by rotenone (0.87+/-0.17 and 0.95+/-0.07). Videomicroscopic studies showed that rotenone and myxothiazol blocked flow-induced dilation (% max. dilation at 100 cm H2O: rotenone, 74+/-3% versus 3+/-13%; myxothiazol, 67+/-3% versus 28+/-4%; P<0.05). Neither cyanide nor apocynin altered flow-induced dilation. These results suggest that shear stress induced H2O2 formation, and flow-induced dilation is derived from O2*- originating from mitochondrial respiration.

  7. Phase equilibria in the system CO 2-H 2O I: New equilibrium relations at low temperatures

    NASA Astrophysics Data System (ADS)

    Longhi, John

    2005-02-01

    Graphical analysis of free-energy relationships involving binary quadruple points and their associated univariant equilibria in the system CO 2-H 2O suggests the presence of at least 2 previously unrecognized quadruple points and a degenerate binary invariant point involving an azeotrope between CO 2-rich gas and liquid. Thermodynamic data extracted from the equilibrium involving clathrate (hydrate), gas, and ice (H = G+I) are employed along with published data to calculate the P-T range of the 3-ice equilibrium curve, S+I = H, where S is solid CO 2. This equilibrium curve intersects the H = G+I curve approximately where the latter curve intersects the S+H = G curve, thus confirming the existence of one of the inferred quadruple points involving the phases S, G, H, and I. Recognition of some binary equilibria probably have been hampered by extremely low mutual solubilities of CO 2 and H 2O in the fluids phases which, for example, render the S+H = G virtually indistinguishable from the CO 2-sublimation curve. To make the published portion of the L(liquid CO 2)-G-H equilibrium "connect" with the other new quadruple point involving S, L, G, and H, it is necessary to change the sense of the equilibrium from L = G+H at higher pressures to L+H = G at lower pressures by positing a L = G azeotrope at very low concentrations of H 2O. At the low-pressure origin of the azeotrope, which is only a few bars above the CO 2-triple point, the azeotrope curve intersects the 3-phase curve tangentially, creating a degenerate invariant point at which the 3-phase equilibrium changes from L+H = G at lower pressures to L = G+H at higher pressures. The azeotrope curve is offset at slightly lower temperature from the L = G+H curve until the 3-phase equilibrium terminates at the quadruple point involving G, L, H, and W (water). With further increase in pressure the azeotrope curve tracks the L = G+W equilibrium and apparently terminates at a critical end point in close proximity to critical

  8. 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.

  9. 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.

  10. 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.

  11. 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.

  12. 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.

  13. 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%. Copyright © 2016 Elsevier Ltd. All rights reserved.

  14. Magneto-Thermo-Marangoni convective flow of Cu-H2O nanoliquid past an infinite disk with particle shape and exponential space based heat source effects

    NASA Astrophysics Data System (ADS)

    Mahanthesh, B.; Gireesha, B. J.; Prasannakumara, B. C.; Sampath Kumar, P. B.

    The exponential space dependent heat source (ESHS) process is utilized to explore the thermal transport characteristics of Marangoni convective flow in a Cu-H2O nanoliquid due to an infinite disk. Flow is driven by linear temperature. Five distinct nanoparticle shapes such as sphere, tetrahedron, column, hexahedron and lamina are accounted. Impacts of Joule heating, radiation and viscous dissipation are also retained. Hamilton-Crosser's expression is employed to deploy effective thermal conductivity of nanoliquid. Multi degree partial differential equations system is reduced by Kármán transformations and then solved via shooting method. It is figured out that the heat transfer rate is enhanced for stronger Marangoni convection and nanoparticle volume fraction. Also, shape of the nanoparticles significantly affects the flow fields.

  15. 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.

  16. 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

  17. H 2O chemisorption and H 2 oxidation on yttria-stabilized zirconia: Density functional theory and temperature-programmed desorption studies

    NASA Astrophysics Data System (ADS)

    Gorski, Alexandr; Yurkiv, Vitaliy; Starukhin, Dzmitry; Volpp, Hans-Robert

    The mechanism of H 2O dissociation as well as the adsorption and oxidation reaction of H 2 on yttria-stabilized zirconia (YSZ), commonly used as part of solid oxide fuel cell (SOFC) anodes, was investigated employing temperature-programmed desorption (TPD) spectroscopy and density functional theory (DFT). In agreement with theory the experimental results show that interaction of gaseous H 2O with YSZ results in dissociative adsorption leading to strongly bound OH surface species. In the interaction of gaseous H 2 with an oxygen-enriched YSZ surface (YSZ + O) similar OH surface species are formed as reaction intermediates in the H 2 oxidation. Our experiments showed that in both the H 2O/YSZ and the H 2/YSZ + O heterogeneous reaction systems noticeable amounts of H 2O are "dissolved" in the bulk as interstitial hydrogen and hydroxyl species. The experimental H 2O desorption data is used to access the accuracy of the H 2/H 2O/YSZ adsorption/desorption and surface reaction kinetics data, employed in previous modeling studies of the electrochemical H 2 oxidation on Ni-pattern/YSZ model anodes by Vogler et al. [J. Electrochem. Soc., 156 (2009) B663] and Goodwin et al. [J. Electrochem. Soc., 156 (2009) B1004]. Finally a refined experimentally validated H 2/H 2O/YSZ adsorption/desorption and surface reaction kinetics data set is presented.

  18. 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.

  19. 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. Copyright © 2014 Elsevier Inc. All rights reserved.

  20. The low temperature oxidation of lithium thin films on HOPG by O 2 and H 2 O

    DOE PAGES

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

    2016-09-01

    Lithiated graphite and lithium thin films are prevalent in fusion devices. In fusion devices, liathiated graphite will undergo oxidation by background gases. In order to gain insight into this oxidation process, thin (< 15 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 decreasedmore » 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 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 was 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.« less

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

    DOE PAGES

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

    2016-04-16

    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 in this paper 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 asmore » 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. Finally, 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.« less

  2. 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.

  3. Wavelength-modulation spectroscopy near 1.4 µm for measurements of H2O and temperature in high-pressure and -temperature gases

    NASA Astrophysics Data System (ADS)

    Goldenstein, C. S.; Spearrin, R. M.; Schultz, I. A.; Jeffries, J. B.; Hanson, R. K.

    2014-05-01

    The development, validation and demonstration of a two-color tunable diode laser (TDL) absorption sensor for measurements of temperature and H2O in high-pressure and high-temperature gases are presented. This sensor uses first-harmonic-normalized wavelength-modulation spectroscopy with second-harmonic detection (WMS-2f/1f) to account for non-absorbing transmission losses and emission encountered in harsh, high-pressure environments. Two telecommunications-grade TDLs were used to probe H2O absorption transitions near 1391.7 and 1469.3 nm. The lasers were frequency-multiplexed and modulated at 160 and 200 kHz to enable a measurement bandwidth up to 30 kHz along a single line-of-sight. In addition, accurate measurements are enabled at extreme conditions via an experimentally derived spectroscopic database. This sensor was validated under low-absorbance (<0.05) conditions in shock-heated H2O-N2 mixtures at temperatures and pressures from 700 to 2400 K and 2 to 25 atm. There, this sensor recovered the known temperature and H2O mole fraction with a nominal accuracy of 2.8% and 4.7% RMS, respectively. Lastly, this sensor resolved expected transients with high bandwidth and high precision in a reactive shock tube experiment and a pulse detonation combustor.

  4. 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.

  5. Concentration effect of sodium carbonate and sodium aluminate as accelerator and H2O mixing against physical properties: Flow ability, setting time, and strength in low cement castable refractory product (Case study: PT. Indoporlen)

    NASA Astrophysics Data System (ADS)

    Krismahariyanto, Mei; Saing, Bungaran; Widodo, Hernowo

    2017-09-01

    The research was intended to analyze effect of comparison concentration between accelerator and H2O mixing against characterization of flow ability, setting time and strength at low cement castable refractory product (case study at PT. Indoporlen Refractory), Shown the kinds of accelerator sodium aluminate and sodium carbonate have good characterization result against flow ability and setting time while additional H2O mixing conclude to good strength with different kinds of temperature at 110 °C, 900 °C and 1450 °C which revealed the measurement are above to allowed specification and as well the strength test coming from accelerator of sodium aluminate and sodium carbonate in various concentration 0.01% until 0.04% and with various of H2O mixing 5.0 until 6.5% achieves the strength above in allowed specification of PT. Indoporlen.

  6. UV-activated ZnO films on a flexible substrate for room temperature O2 and H2O sensing

    DOE PAGES

    Jacobs, Christopher B.; Maksov, Artem B.; Muckley, Eric S.; ...

    2017-07-20

    Here, we demonstrate that UV-light activation of polycrystalline ZnO films on flexible polyimide (Kapton) substrates can be used to detect and differentiate between environmental changes in oxygen and water vapor. The in-plane resistive and impedance properties of ZnO films, fabricated from bacteria-derived ZnS nanoparticles, exhibit unique resistive and capacitive responses to changes in O2 and H2O. We also propose that the distinctive responses to O2 and H2O adsorption on ZnO could be utilized to statistically discriminate between the two analytes. Molecular dynamic simulations (MD) of O2 and H2O adsorption energy on ZnO surfaces were performed using the large-scale Atomic/Molecular Massivelymore » Parallel Simulator (LAMMPS) with a reactive force-field (ReaxFF). Furthermore, these simulations suggest that the adsorption mechanisms differ for O2 and H2O adsorption on ZnO, and are governed by the surface termination and the extent of surface hydroxylation. Electrical response measurements, using DC resistance, AC impedance spectroscopy, and Kelvin Probe Force Microscopy (KPFM), demonstrate differences in response to O2 and H2O, confirming that different adsorption mechanisms are involved. Statistical and machine learning approaches were applied to demonstrate that by integrating the electrical and kinetic responses the flexible ZnO sensor can be used for detection and discrimination between O2 and H2O at low temperature.« less

  7. Abatement of phenolic mixtures by catalytic wet oxidation enhanced by Fenton's pretreatment: effect of H2O2 dosage and temperature.

    PubMed

    Santos, A; Yustos, P; Rodriguez, S; Simon, E; Garcia-Ochoa, F

    2007-07-31

    Catalytic wet oxidation (CWO) of a phenolic mixture containing phenol, o-cresol and p-cresol (500mg/L on each pollutant) has been carried out using a commercial activated carbon (AC) as catalyst, placed in a continuous three-phase reactor. Total pressure was 16 bar and temperature was 127 degrees C. Pollutant conversion, mineralization, intermediate distribution, and toxicity were measured at the reactor outlet. Under these conditions no detoxification of the inlet effluent was found even at the highest catalyst weight (W) to liquid flow rate (Q(L)) ratio used. On the other hand, some Fenton Runs (FR) have been carried out in a batch way using the same phenolic aqueous mixture previously cited. The concentration of Fe(2+) was set to 10mg/L. The influence of the H(2)O(2) amount (between 10 and 100% of the stoichiometric dose) and temperature (30, 50, and 70 degrees C) on phenols conversion, mineralization, and detoxification have been analyzed. Phenols conversion was near unity at low hydrogen peroxide dosage but mineralization and detoxification achieved an asymptotic value at each temperature conditions. The integration of Fenton reagent as pretreatment of the CWO process remarkably improves the efficiency of the CWO reactor and allows to obtain detoxified effluents at mild temperature conditions and relatively low W/Q(L) values. For a given phenolic mixture a temperature range of 30-50 degrees C in the Fenton pretreatment with a H(2)O(2) dosage between 20 and 40% of the stoichiometric amount required can be proposed.

  8. FORTRAN programs for generating fluid inclusion isochores and fugacity coefficients for the system H 2O-CO 2-NaCl at high pressures and temperatures

    NASA Astrophysics Data System (ADS)

    Bowers, Teresa Suter; Helgeson, Harold C.

    Program DENFIND permits calculation of pressures and temperatures corresponding to isochores for H 2O-CO 2-NaCl fluids which can be used to generate pressure corrections of fluid inclusion homogenization temperatures. Program FUGCO facilitates calculation of fugacity coefficients in the system H 2O-CO 2-NaCl as a function of pressure, temperature and fluid composition. Both programs employ a modified Redlich-Kwong equation of state for the ternary system (Bowers and Helgeson, 1983a), which is applicable to fluids containing up to 35 wt. % NaCl (relative to H 2O + NaCl) at pressures above 500 bars and temperature from 350 to 600°C.

  9. Stratospheric H2O

    NASA Technical Reports Server (NTRS)

    Ellsaesser, H. W.; Harries, J. E.; Kley, D.; Penndorf, R.

    1980-01-01

    The present state of our knowledge and understanding of H2O in the stratosphere is reviewed. This reveals continuing discrepancies between observations and expectations following from the Brewer-Dobson hypothesis of stratospheric circulation. In particular, available observations indicate unexplained upward and poleward directed H2O gradients immediately downstream from the tropical tropopause and variable vertical gradients above 20 km which generally disagree with those expected from oxidation of CH4.

  10. 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

  11. Measured Fluid Flow in an Active H2O-CO2 Geothermal Well as an Analog to Fluid Flow in Fractures on Mars: Preliminary Report

    NASA Technical Reports Server (NTRS)

    Kieffer, Susan W.; Brown, K. L.; Simmons, Stuart F.; Watson, Arnold

    2004-01-01

    Water in the Earth's crust generally contains dissolved gases such as CO2. Models for both 'Blue Mars' (H2O-driven processes) and 'White Mars' (CO2-driven processes) predict liquid H2O with dissolved CO2 at depth. The fate of dissolved CO2 as this mixture rises toward the surface has not been quantitatively explored. Our approach is a variation on NASA's 'Follow the Water' as we 'Follow the Fluid' from depth to the surface in hydrothermal areas on Earth and extrapolate our results to Mars. This is a preliminary report on a field study of fluid flow in a producing geothermal well. For proprietary reasons, the name and location of this well cannot be revealed, so we have named it 'Earth1' for this study.

  12. 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.

  13. Low temperature H2O and NO2 coadsorption on theta-Al2O3/NiAl(100) ultrathin films.

    PubMed

    Ozensoy, Emrah; Peden, Charles H F; Szanyi, János

    2006-04-20

    The coadsorption of H(2)O and NO(2) molecules on a well-ordered, ultrathin theta-Al(2)O(3)/NiAl(100) film surface was studied using temperature programmed desorption (TPD), infrared reflection absorption spectroscopy (IRAS), and X-ray photoelectron spectroscopy (XPS). For H(2)O and NO(2) monolayers adsorbed separately on the theta-Al(2)O(3)/NiAl(100) surface, adsorption energies were estimated to be 44.8 and 36.6 kJ/mol, respectively. Coadsorption systems prepared by sequential deposition of NO(2) and H(2)O revealed the existence of coverage and temperature-dependent adsorption regimes where H(2)O molecules and the surface NO(x) species (NO(2)/N(2)O(4)/NO(2)(-),NO(3)(-)) form segregated and/or mixed domains. Influence of the changes in the crystallinity of solid water (amorphous vs crystalline) on the coadsorption properties of the NO(2)/H(2)O/theta-Al(2)O(3)/NiAl(100) system is also discussed.

  14. Low-temperature chemistry in helium droplets: reactions of aluminum atoms with O2 and H2O.

    PubMed

    Krasnokutski, Serge A; Huisken, Friedrich

    2011-06-30

    The doping of He droplets by Al atoms and their reactions with H(2)O and O(2) at T = 0.37 K was investigated. It was found that at high doping concentrations, the incorporated Al atoms do not aggregate to form clusters. They rather remain as separated atoms inside of the He droplets. Mass spectrometry and the recently developed depletion method have been applied to study the reactions. It was found that single Al atoms react with single O(2) molecules. The dominant product of this reaction occurring inside of the He droplets is AlO(2). The reaction between Al and O(2) clusters has also been detected. The Al clusters react with single H(2)O molecules or clusters. While single Al atoms react with H(2)O clusters, no reaction of single Al atoms with a single water molecule was found.

  15. 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.

  16. Defects in the Expression of Chloroplast Proteins Leads to H2O2 Accumulation and Activation of Cyclic Electron Flow around Photosystem I

    PubMed Central

    Strand, Deserah D.; Livingston, Aaron K.; Satoh-Cruz, Mio; Koepke, Tyson; Enlow, Heather M.; Fisher, Nicholas; Froehlich, John E.; Cruz, Jeffrey A.; Minhas, Deepika; Hixson, Kim K.; Kohzuma, Kaori; Lipton, Mary; Dhingra, Amit; Kramer, David M.

    2017-01-01

    We describe a new member of the class of mutants in Arabidopsis exhibiting high rates of cyclic electron flow around photosystem I (CEF), a light-driven process that produces ATP but not NADPH. High cyclic electron flow 2 (hcef2) shows strongly increased CEF activity through the NADPH dehydrogenase complex (NDH), accompanied by increases in thylakoid proton motive force (pmf), activation of the photoprotective qE response, and the accumulation of H2O2. Surprisingly, hcef2 was mapped to a non-sense mutation in the TADA1 (tRNA adenosine deaminase arginine) locus, coding for a plastid targeted tRNA editing enzyme required for efficient codon recognition. Comparison of protein content from representative thylakoid complexes, the cytochrome bf complex, and the ATP synthase, suggests that inefficient translation of hcef2 leads to compromised complex assembly or stability leading to alterations in stoichiometries of major thylakoid complexes as well as their constituent subunits. Altered subunit stoichiometries for photosystem I, ratios and properties of cytochrome bf hemes, and the decay kinetics of the flash-induced thylakoid electric field suggest that these defect lead to accumulation of H2O2 in hcef2, which we have previously shown leads to activation of NDH-related CEF. We observed similar increases in CEF, as well as increases in H2O2 accumulation, in other translation defective mutants. This suggests that loss of coordination in plastid protein levels lead to imbalances in photosynthetic energy balance that leads to an increase in CEF. These results taken together with a large body of previous observations, support a general model in which processes that lead to imbalances in chloroplast energetics result in the production of H2O2, which in turn activates CEF. This activation could be from either H2O2 acting as a redox signal, or by a secondary effect from H2O2 inducing a deficit in ATP. PMID:28133462

  17. Latent porosity in potassium dodecafluoro-closo-dodecaborate(2-). Structures and rapid room temperature interconversions of crystalline K2B12F12, K2(H2O)2B12F12, and K2(H2O)4B12F12 in the presence of water vapor.

    PubMed

    Peryshkov, Dmitry V; Popov, Alexey A; Strauss, Steven H

    2010-10-06

    times were both particle-size dependent and carrier-gas flow rate dependent and continued to decrease up to the maximum carrier-gas flow rate of the TGA instrument that was used, demonstrating that the hydration and dehydration reactions were limited by the rate at which H(2)O((g)) was delivered to or swept away from the microcrystal surfaces. Therefore, the rates of absorption and desorption of H(2)O from unit cells at the surface of the microcrystals, and the rate of diffusion of H(2)O across the moving K(2)(H(2)O)(2)B(12)F(12 (s))/K(2)B(12)F(12 (s)) phase boundary, are even faster than the fastest rates of change in sample mass due to hydration and dehydration that were measured. The exchange of 21 Torr H(2)O((g)) with either D(2)O or H(2)(18)O in microcrystalline K(2)(D(2)O)(2)B(12)F(12) or K(2)(H(2)(18)O)(2)B(12)F(12) at 25 °C was also facile and required as little as 45 min to go to completion (H(2)O((g)) replaced both types of isotopically labeled water at the same rate for a given starting sample of K(2)B(12)F(12), demonstrating that water molecules were exchanging, not protons. Significant portions of mass (m) vs time (t) plots for the (1,2)H(2)O((g))/K(2)((2,1)H(2)O)(2)B(12)F(12 (s)) exchange reactions fit the equation m ∝ e(-kt), with 10(3)k = 1.9 s(-1) for one particle size distribution and 10(3)k = 0.50 s(-1) for another. Finally, K(2)(H(2)O)(2)B(12)F(12) was not transformed into K(2)(H(2)O)(4)B(12)F(12) after prolonged exposure to 21 Torr H(2)O((g)) at 25 °C, 37 Torr H(2)O((g)) at 35 °C, or 55 Torr H(2)O((g)) at 45 °C.

  18. 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

  19. 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.

  20. 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.

  1. Role of weakly bound complexes in temperature-dependence and relative rates of MxOy- + H2O (M = Mo, W) reactions

    NASA Astrophysics Data System (ADS)

    Kafader, Jared O.; Ray, Manisha; Raghavachari, Krishnan; Jarrold, Caroline Chick

    2016-02-01

    Results of a systematic comparison of the MoxOy- + H2O and WxOy- + H2O reaction rate coefficients are reported and compared to previous experimental and computational studies on these reactions. WxOy- clusters undergo more direct oxidation by water to yield WxOy+1- + H2, while for MoxOy- clusters, production of MoxOyH2- (trapped intermediates in the oxidation reaction) is comparatively more prevalent. However, MoxOy- clusters generally have higher rate coefficients than analogous WxOy- clusters if MoxOy+1H2- formation is included. Results of calculations on the M2Oy- + H2O (M = Mo, W; y = 4, 5) reaction entrance channel are reported. They include charge-dipole complexes formed from long-range interactions, and the requisite conversion to a Lewis acid-base complex that leads to MxOy+1H2- formation. The results predict that the Lewis acid-base complex is more strongly bound for MoxOy- clusters than for WxOy- clusters. The calculated free energies along this portion of the reaction path are also consistent with the modest anti-Arrhenius temperature dependence measured for most MoxOy- + H2O reactions, and the WxOy- + H2O reaction rate coefficients generally being constant over the temperature range sampled in this study. For clusters that exhibit evidence of both water addition and oxidation reactions, increasing the temperature increases the branching ratio toward oxidation for both species. A more direct reaction path to H2 production may therefore become accessible at modest temperatures for certain cluster stoichiometries and structures.

  2. 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. Copyright © 2016 John Wiley & Sons, Ltd.

  3. H2O activity in concentrated NaCl solutions at high pressures and temperatures measured by the brucite-periclase equilibrium

    NASA Astrophysics Data System (ADS)

    Aranovich, L. Y.; Newton, R. C.

    1996-10-01

    H2O activities in concentrated NaCl solutions were measured in the ranges 600° 900° C and 2 15 kbar and at NaCl concentrations up to halite saturation by depression of the brucite (Mg(OH)2) periclase (MgO) dehydration equilibrium. Experiments were made in internally heated Ar pressure apparatus at 2 and 4.2 kbar and in 1.91-cm-diameter piston-cylinder apparatus with NaCl pressure medium at 4.2, 7, 10 and 15 kbar. Fluid compositions in equilibrium with brucite and periclase were reversed to closures of less than 2 mol% by measuring weight changes after drying of punctured Pt capsules. Brucite-periclase equilibrium in the binary system was redetermined using coarsely crystalline synthetic brucite and periclase to inhibit back-reaction in quenching. These data lead to a linear expression for the standard Gibbs free energy of the brucite dehydration reaction in the experimental temperature range: ΔG° (±120J)=73418 134.95 T(K). Using this function as a baseline, the experimental dehydration points in the system MgO-H2O-NaCl lead to a simple systematic relationship of high-temperature H2O activity in NaCl solution. At low pressure and low fluid densities near 2 kbar the H2O activity is closely approximated by its mole fraction. At pressures of 10 kbar and greater, with fluid densities approaching those of condensed H2O, the H2O activity becomes nearly equal to the square of its mole fraction. Isobaric halite saturation points terminating the univariant brucite-periclase curves were determined at each experimental pressure. The five temperature-composition points in the system NaCl-H2O are in close agreement with the halite saturation curves (liquidus curves) given by existing data from differential thermal analysis to 6 kbar. Solubility of MgO in the vapor phase near halite saturation is much less than one mole percent and could not have influenced our determinations. Activity concentration relations in the experimental P-T range may be retrieved for the binary

  4. New Temperature and H2O estimates for Post Caldera Yellowstone Rhyolite Lavas from Feldspar Geothermometry and Rhyolite-MELTS Modeling

    NASA Astrophysics Data System (ADS)

    Shaffer, J. S.; Till, C. B.

    2016-12-01

    Determination of the thermal histories of previously erupted silicic magma bodies at Yellowstone, specifically the effusive eruptions that have characterized the system since ca. 260 ka, is critical to understanding the future behavior of the system. Post-caldera Yellowstone rhyolite flows have been extensively studied using Fe-Ti oxides, QUILF, titaniQ, and zircon saturation geothermometry. In this study, we add two-feldspar and liquid-feldspar thermometry of five rhyolitic Upper Basin Member flows (Scaup Lake, South, North, East, and Middle Biscuit Basin) and one Central Plateau Member (Hayden Valley). The feldspar rims record temperatures between 780 to 880°C using the plagioclase-liquid and sanidine-liquid thermometers of Putirka (2008) and the SOLVCALC two feldspar thermometer. Additionally, rhyolite-MELTS modeling was performed at varying water contents assuming a pressure of 3 kbar, similar to the modern day reservoir. We find the modeling best reproduces the overall phase proportions, feldspar compositions, and feldspar thermometry at ≤1.5 H2O wt. % for all flows. In general, the location of the feldspar solvus predicted by rhyolite-MELTS is in excellent agreement with two feldspar thermometry (e.g., for the Scaup Lake flow, MELTS solvus=826°C vs. two feldspar thermometry=819±20°C), whereas the plagioclase-liquid thermometry records higher temperatures. The rhyolite-MELTS models also suggest that quartz, rather than feldspar, is the first silicic phase to crystallize in all the lava compositions. When compared to the location of vapor saturation as predicted by rhyolite-MELTS ( 730-735°C), the thermometry of the feldspar rims suggests they crystallized at temperatures significantly above vapor saturation. This work sheds light on the calibration and interpretation of rhyolite-MELTS models in conjunction with detailed feldspar thermometry.

  5. 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.

  6. The relaxation of OH (v=1) and OD (v=1) by H2O and D2O at temperatures from 251 to 390 K.

    PubMed

    McCabe, D C; Rajakumar, B; Marshall, P; Smith, I W M; Ravishankara, A R

    2006-10-21

    We report rate coefficients for the relaxation of OH(v=1) and OD(v=1) by H2O and D2O as a function of temperature between 251 and 390 K. All four rate coefficients exhibit a negative dependence on temperature. In Arrhenius form, the rate coefficients for relaxation (in units of 10(-12) cm3 molecule-1 s-1) can be expressed as: for OH(v=1)+H2O between 263 and 390 K: k=(2.4+/-0.9) exp((460+/-115)/T); for OH(v=1)+D2O between 256 and 371 K: k=(0.49+/-0.16) exp((610+/-90)/T); for OD(v=1)+H2O between 251 and 371 K: k=(0.92+/-0.16) exp((485+/-48)/T); for OD(v=1)+D2O between 253 and 366 K: k=(2.57+/-0.09) exp((342+/-10)/T). Rate coefficients at (297+/-1 K) are also reported for the relaxation of OH(v=2) by D2O and the relaxation of OD(v=2) by H2O and D2O. The results are discussed in terms of a mechanism involving the formation of hydrogen-bonded complexes in which intramolecular vibrational energy redistribution can occur at rates competitive with re-dissociation to the initial collision partners in their original vibrational states. New ab initio calculations on the H2O-HO system have been performed which, inter alia, yield vibrational frequencies for all four complexes: H2O-HO, D2O-HO, H2O-DO and D2O-DO. These data are then employed, adapting a formalism due to Troe (J. Troe, J. Chem. Phys., 1977, 66, 4758), in order to estimate the rates of intramolecular energy transfer from the OH (OD) vibration to other modes in the complexes in order to explain the measured relaxation rates-assuming that relaxation proceeds via the hydrogen-bonded complexes.

  7. Velocity measurement in rocket exhaust and general aerodynamic flows by photolysis of H2O and laser induced fluorescence of OH

    NASA Technical Reports Server (NTRS)

    Boedeker, Laurence R.

    1992-01-01

    A 'tagging' approach in which the photolysis of H2O by an excimer laser creates a zone of enhanced OH concentration, while a second, pulsed-UV laser detects tagged-zone convection via time-delayed excitation of OH fluorescence, depends on the photodissociation process and the kinetics of OH decay (relative to velocity). For application to the fuel-rich, high supersonic Mach number exhaust flow of the SSME, the detection of OH is being accomplished with either a pulsed narrowband UV dye laser or a tunable XeCl excimer laser for excitation of an OH 0-0 band transition, while the two-photon photolysis of H2O is conducted by focusing an injection-locked KrF excimer laser into the flow.

  8. 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.

  9. 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.

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

    PubMed

    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.

  11. 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.

  12. Direct growth of high-quality Al2O3 dielectric on graphene layers by low-temperature H2O-based ALD

    NASA Astrophysics Data System (ADS)

    Zhang, Youwei; Qiu, Zhijun; Cheng, Xinhong; Xie, Hong; Wang, Haomin; Xie, Xiaomin; Yu, Yuehui; Liu, Ran

    2014-02-01

    A thin Al2O3 dielectric film was directly grown onto graphene layers without any surface treatment prior to H2O-based atomic layer deposition for the first time. The growth mechanism of Al2O3 dielectric film has been studied by changing the growth temperature and purge time. We found that the film morphology was influenced by the amount and distribution of physically adsorbed precursor molecules on the graphene, especially by physically adsorbed H2O molecules. Within an optimal temperature window, conformal and uniform Al2O3 thin films were obtained as confirmed by atomic force microscopy and transmission electron microscopy results. Raman spectroscopy revealed that no extra defects are generated in the graphene layers. Furthermore, the low leakage current and interface traps in dual-gated graphene field-effect transistors demonstrate the high-quality dielectric/graphene stack.

  13. Novel method for investigation of two-phase flow in liquid feed direct methanol fuel cells using an aqueous H 2O 2 solution

    NASA Astrophysics Data System (ADS)

    Bewer, T.; Beckmann, T.; Dohle, H.; Mergel, J.; Stolten, D.

    One major issue in the development of direct methanol fuel cells (DMFC) is the management of the evolving CO 2 gas bubbles in the flow fields. These bubbles influence the flow distribution and therefore the power density of a cell. In this paper, a novel method for in situ production of bubbles in a test cell made of perspex is presented. The method is based on the decomposition of hydrogen peroxide solution (H 2O 2) to oxygen and water in aqueous media at the presence of a catalyst. By using an appropriate H 2O 2-concentration, the gas evolution rate can be set to same order of magnitude as in real direct methanol fuel cells. This approach allows the simulation of the flow distribution in DMFC by simple low-cost hardware. As no current conducting parts are needed, the whole dummy cell can be made of perspex to ensure a complete visibility of the flow. In a perspex flow cell with an active area of 600 cm 2, the flow homogeneity as a function of gas evolution rate, flow field and manifold design was investigated. Experiments show that splayed manifolds have a superior performance concerning flow uniformity compared to other designs. The use of grid structures as a flow field gives good bubble transport at all investigated current densities.

  14. 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.

  15. Temperature effects on prevalent structures of hydrated Fe+ complexes: Infrared spectroscopy and DFT calculations of Fe+(H2O)n (n = 3-8)

    NASA Astrophysics Data System (ADS)

    Ohashi, Kazuhiko; Sasaki, Jun; Yamamoto, Gun; Judai, Ken; Nishi, Nobuyuki; Sekiya, Hiroshi

    2014-12-01

    Hydrated Fe+ ions are produced in a laser-vaporization cluster source of a triple quadrupole mass spectrometer. The Fe+(H2O)n (n = 3-8) complexes are mass-selected and probed with infrared (IR) photodissociation spectroscopy in the OH-stretch region. Density functional theory (DFT) calculations are also carried out for analyzing the experimental IR spectra and for evaluating thermodynamic quantities of low-lying isomers. Solvation through H-bonding instead of direct coordination to Fe+ is observed already at n = 3, indicating the completion of the first hydration shell with two H2O molecules. Size dependent variations in the spectra for n = 5-7 provide evidence for the second-shell completion at n = 6, where a linearly coordinated Fe+(H2O)2 subunit is solvated with four H2O molecules. Overall spectral features for n = 3-8 agree well with those predicted for 2-coordinated structures. DFT calculations predict that such 2-coordinated structures are lowest in energy for smaller n. However, 4-coordinated isomers are predicted to be more stable for n = 7 and 8; the energy ordering is in conflict with the IR spectroscopic observation. Examination of free energy as a function of temperature suggests that the ordering of the isomers at warmer temperatures can be different from the ordering near 0 K. For n = 7 and 8, the 4-coordinated isomers should be observed at low temperatures because they are lowest in enthalpy. Meanwhile, outer-shell waters in the 2-coordinated structures are bound less rigidly; their contribution to entropy is rather large. The 2-coordinated structures become abundant at warmer temperatures, owing to the entropy effect.

  16. 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.

  17. 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.

  18. 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.

  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. 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.

  1. 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.

  2. 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.

  3. Calcium isotope systematics in the NaCl-H2O system at elevated pressure and temperature

    NASA Astrophysics Data System (ADS)

    Scheuermann, P.; Syverson, D. D.; Higgins, J. A.; Seyfried, W. E., Jr.

    2016-12-01

    Two sets of hydrothermal experiments were performed in order to quantify the rate of Ca isotope exchange between a Ca-bearing NaCl fluid and anhydrite and to determine the amount of fractionation between the vapor and liquid phases in the NaCl-H2O system. A flexible gold cell reactor was used for all experiments. The isotope exchange experiments employed 43Ca spikes and in-situ sampling in order to track isotope exchange as a function of time and total dissolved Ca concentration at 410°C, 500 bar. Experiment 1 lasted 282 hours and had a total dissolved Ca concentration (SCa) of 12 mmol/kg. Mass balance calculations indicate that 18.2% exchange occurred within this period. Experiment 2 contained 23 mmol/kg SCa and after 243 hrs 26.5% exchange occurred between dissolved Ca and anhydrite. The third experiment contained 45 mmol/kg SCa and 20.9% exchange occurred within 72 hours. These data indicate that increasing SCa causes an increase in exchange rate. However, these rates are slower than those calculated from similar spiked experiments below 350°C and may reflect a change in exchange mechanism or be due to the retrograde solubility of anhydrite. Two experiments were also performed at 420 and 450°C to determine the extent of Ca isotope fractionation between the vapor and liquid phases in the NaCl-H2O system. Anhydrite, of natural isotopic composition, buffered Ca concentrations in both phases. Within the pressure ranges investigated (420°C, 33-31 MPa; 450°C, 40.5-37.5 MPa), there is no observed isotope fractionation between vapor and liquid. This result implies that the same aqueous Ca species dominates both phases. All experiments presented here provide data necessary to better understand Ca isotope kinetics and fractionation in hydrothermal environments, particularly mid-ocean ridge vent systems.

  4. 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.

  5. 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

  6. One-step synthesis of lightly doped porous silicon nanowires in HF/AgNO3/H2O2 solution at room temperature

    NASA Astrophysics Data System (ADS)

    Bai, Fan; Li, Meicheng; Song, Dandan; Yu, Hang; Jiang, Bing; Li, Yingfeng

    2012-12-01

    One-step synthesis of lightly doped porous silicon nanowire arrays was achieved by etching the silicon wafer in HF/AgNO3/H2O2 solution at room temperature. The lightly doped porous silicon nanowires (pNWs) have circular nanopores on the sidewall, which can emit strong green fluorescence. The surface morphologies of these nanowires could be controlled by simply adjusting the concentration of H2O2, which influences the distribution of silver nanoparticles (Ag NPs) along the nanowire axis. A mechanism based on Ag NPs-induced lateral etching of nanowires was proposed to explain the formation of pNWs. The controllable and widely applicable synthesis of pNWs will open their potential application to nanoscale photoluminescence devices.

  7. Improvement in surface hydrophilicity and resistance to deformation of natural leather through O2/H2O low-temperature plasma treatment

    NASA Astrophysics Data System (ADS)

    You, Xuewei; Gou, Li; Tong, Xingye

    2016-01-01

    The natural leather was modified through O2/H2O low-temperature plasma treatment. Surface morphology was characterized by scanning electron microscopy (SEM) and the results showed that the pores on the leather surface became deeper and larger with enhanced permeability of water and vapor. XPS and FTIR-ATR was performed to determine the chemical composition of natural leather surface. Oxygen-containing groups were successfully grafted onto the surface of natural leather and oxygen content increased with longer treatment time. After O2/H2O plasma treatment, initial water contact angle was about 21° and water contact angles were not beyond 55° after being stored for 3 days. Furthermore, the tensile test indicated that the resistance to deformation had a prominent transform without sacrificing the tensile strength.

  8. H2O and HCl trace gas kinetics on crystalline HCl hydrates and amorphous HCl / H2O in the range 170 to 205 K: the HCl / H2O phase diagram revisited

    NASA Astrophysics Data System (ADS)

    Iannarelli, R.; Rossi, M. J.

    2014-05-01

    In this laboratory study, H2O ice films of 1 to 2 μm thickness have been used as surrogates for ice particles at atmospherically relevant conditions in a stirred flow reactor (SFR) to measure the kinetics of evaporation and condensation of HCl and H2O on crystalline and amorphous HCl hydrates. A multidiagnostic approach has been employed using Fourier transform infrared spectroscopy (FTIR) absorption in transmission to monitor the condensed phase and residual gas mass spectrometry (MS) for the gas phase. An average stoichiometric ratio of H2O : HCl = 5.8 ± 0.7 has been measured for HCl . 6H2O, and a mass balance ratio between HCl adsorbed onto ice and the quantity of HCl measured using FTIR absorption (Nin - Nesc - Nads) / NFTIR = 1.18 ± 0.12 has been obtained. The rate of evaporation Rev(HCl) for crystalline HCl hexahydrate (HCl . 6H2O) films and amorphous HCl / H2O mixtures has been found to be lower by a factor of 10 to 250 compared to Rev(H2O) in the overlapping temperature range 175 to 190 K. Variations of the accommodation coefficient α(HCl) on pure HCl . 6H2O up to a factor of 10 at nominally identical conditions have been observed. The kinetics (α, Rev) are thermochemically consistent with the corresponding equilibrium vapour pressure. In addition, we propose an extension of the HCl / H2O phase diagram of crystalline HCl . 6H2O based on the analysis of deconvoluted FTIR spectra of samples outside its known existence area. A brief evaluation of the atmospheric importance of both condensed phases - amorphous HCl / H2O and crystalline HCl . 6H2O - is performed in favour of the amorphous phase.

  9. Comparison of global cerebral blood flow measured by phase‐contrast mapping MRI with 15O‐H2O positron emission tomography

    PubMed Central

    Lindberg, Ulrich; Aachmann‐Andersen, Niels Jacob; Lisbjerg, Kristian; Christensen, Søren Just; Rasmussen, Peter; Olsen, Niels Vidiendal; Law, Ian; Larsson, Henrik Bo Wiberg; Henriksen, Otto Mølby

    2016-01-01

    Purpose To compare mean global cerebral blood flow (CBF) measured by phase‐contrast mapping magnetic resonance imaging (PCM MRI) and by 15O‐H2O positron emission tomography (PET) in healthy subjects. PCM MRI is increasingly being used to measure mean global CBF, but has not been validated in vivo against an accepted reference technique. Materials and Methods Same‐day measurements of CBF by 15O‐H2O PET and subsequently by PCM MRI were performed on 22 healthy young male volunteers. Global CBF by PET was determined by applying a one‐tissue compartment model with measurement of the arterial input function. Flow was measured in the internal carotid and vertebral arteries by a noncardiac triggered PCM MRI sequence at 3T. The measured flow was normalized to total brain weight determined from a volume‐segmented 3D T 1‐weighted anatomical MR‐scan. Results Mean CBF was 34.9 ± 3.4 mL/100 g/min measured by 15O‐H2O PET and 57.0 ± 6.8 mL/100 g/min measured by PCM MRI. The measurements were highly correlated (P = 0.0008, R2 = 0.44), although values obtained by PCM MRI were higher compared to 15O‐H2O PET (absolute and relative differences were 22.0 ± 5.2 mL/100 g/min and 63.4 ± 14.8%, respectively). Conclusion This study confirms the use of PCM MRI for quantification of global CBF, but also that PCM MRI systematically yields higher values relative to 15O‐H2O PET, probably related to methodological bias. Level of Evidence: 3 J. Magn. Reson. Imaging 2017;45:692–699. PMID:27619317

  10. 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

  11. 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.

  12. 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

    2016-01-27

    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.

  13. 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

  14. A revised model to calculate the dynamic viscosity of H2O-NaCl fluids at elevated temperatures and pressures (≤1000 °C, ≤500 MPa, 0-100 wt. % NaCl)

    NASA Astrophysics Data System (ADS)

    Klyukin, Y.; Lowell, R. P.; Bodnar, R. J.

    2016-12-01

    In order to develop realistic fluid flow models for crustal fluids, the physical and thermodynamic properties of the fluid, including the viscosity, must be known over the range of temperature, pressure and composition (PTx) conditions of interest. Many crustal fluids are reasonably well approximated by the system H2O-NaCl, and the model that is most often used to estimate viscosities of hydrothermal fluids is that of Palliser and McKibbin 1998 (P&M). Examination of the P&M model shows regions of PTx space in which calculated values are inconsistent with experimental data, and predicts trends in viscosity that are unexpected and inconsistent with known fluid behavior. The P&M model is especially unreliable at pressures greater than those on the liquid-vapor-halite coexistence curve and less than that along the liquid-vapor curve for pure H2O and the pure H2O critical isochore. We developed a model to calculate viscosity of H2O-NaCl fluids that shows good correlation with experimental values and predicts trends that are consistent with known or expected behavior outside of the region where experimental data are available. The revised model determines the viscosity of H2O-NaCl at PTx of interest based on the viscosity of H2O (estimated by IAPWS 2008 Viscosity Formulation) at T* and P, where T* is a polynomial function of x and T. The revised model can be used to estimate the viscosity over the range 0-1000 °C, ≤500 MPa and 0-100 wt. % NaCl. Viscosities predicted by the revised model agree with experimental values mostly within ±10%, whereas differences between experimental values and those predicted by the P&M model extend from -40% to >20%, especially for higher salinity fluids. The revised model shows smooth trends in viscosity versus temperature or salinity without discontinuities, unlike the P&M model. As expected, an increase in temperature at constant Px (decrease in density) results in a decrease in viscosity, while an increase in salinity at constant PT

  15. 9Mg(OH)(2)·MgCl(2)·4H(2)O, a high temperature phase of the magnesia binder system.

    PubMed

    Dinnebier, Robert E; Freyer, Daniela; Bette, Sebastian; Oestreich, Melanie

    2010-11-01

    The metastable phase 9Mg(OH)(2)·MgCl(2)·4H(2)O (9-1-4 phase) was found at the extended metastable isotherm of Mg(OH)(2) in the system MgO-MgCl(2)-H(2)O at 120 °C and occurs as intermediate binder phase during setting of magnesia cement due to temperature development of the setting reaction. The crystal structure of the 9-1-4 phase was solved from high resolution laboratory X-ray powder diffraction data in space group I2/m (C2/m) (a = 22.2832(3) Å, b = 3.13501(4) Å, c = 8.1316(2) Å, β = 97.753(1)°, V = 562.86(2) Å(3), and Z = 1). Structural and characteristical relations of the phases in the system MgO-MgCl(2)-H(2)O can be derived, with which the development of the cement or concrete qualities becomes explainable.

  16. Refractive index of NH(4)Cl-H2O as a function of wavelength: the effect of temperature and concentration.

    PubMed

    McCay, M H; Semak, V V; Hopkins, J A; Blaha, B

    1996-07-01

    The refractive index of NH(4)Cl-H(2)O solutions has been measured over a wavelength range from 496.5 to 690 nm. The NH(4)Cl concentration was varied from 15 to 30 wt. % over a temperature range from 10 to 35 °C. We obtained mathematical equations relating the refractive index to wavelength, temperature, and concentration using the least-squares method. A knowledge of these properties is important for analyzing and modeling the dendritic growth of this system.

  17. Porous microspheres of MgO-patched TiO2 for CO2 photoreduction with H2O vapor: temperature-dependent activity and stability.

    PubMed

    Liu, Lianjun; Zhao, Cunyu; Zhao, Huilei; Pitts, Daniel; Li, Ying

    2013-05-07

    A novel MgO-patched TiO2 microsphere photocatalyst demonstrated 10 times higher activity toward CO production from CO2 photoreduction with H2O vapor, when the reaction temperature increased from 50 to 150 °C. The catalytic performance of hybrid MgO-TiO2 was much more stable than TiO2, particularly at a higher temperature, likely due to easier desorption of reaction intermediates and the enhanced CO2 adsorption by MgO.

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

    PubMed

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

    2013-11-07

    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.

  19. O2(b(1)Σg(+)) Quenching by O2, CO2, H2O, and N2 at Temperatures of 300-800 K.

    PubMed

    Zagidullin, M V; Khvatov, N A; Medvedkov, I A; Tolstov, G I; Mebel, A M; Heaven, M C; Azyazov, V N

    2017-09-26

    Rate constants for the removal of O2(b(1)Σg(+)) by collisions with O2, N2, CO2, and H2O have been determined over the temperature range from 297 to 800 K. O2(b(1)Σg(+)) was excited by pulses from a tunable dye laser, and the deactivation kinetics were followed by observing the temporal behavior of the b(1)Σg(+)-X(3)Σg(-) fluorescence. The removal rate constants for CO2, N2, and H2O were not strongly dependent on temperature and could be represented by the expressions kCO2 = (1.18 ± 0.05) × 10(-17) × T(1.5) × exp[Formula: see text], kN2 = (8 ± 0.3) × 10(-20) × T(1.5) × exp[Formula: see text], and kH2O = (1.27 ± 0.08) × 10(-16) × T(1.5) × exp[Formula: see text] cm(3) molecule(-1) s(-1). Rate constants for O2(b(1)Σg(+)) removal by O2(X), being orders of magnitude lower, demonstrated a sharp increase with temperature, represented by the fitted expression kO2 = (7.4 ± 0.8) × 10(-17) × T(0.5) × exp[Formula: see text] cm(3) molecule(-1) s(-1). All of the rate constants measured at room temperature were found to be in good agreement with previously reported values.

  20. 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.

  1. Effect of calcination temperature on the H2O2 decomposition activity of nano-crystalline Co3O4 prepared by combustion method

    NASA Astrophysics Data System (ADS)

    Makhlouf, M. Th.; Abu-Zied, B. M.; Mansoure, T. H.

    2013-06-01

    Cobalt oxide nano-particles were prepared by combustion method using urea as a combustion fuel. The effects of calcination temperature, 350-1000 °C, on the physicochemical, surface and catalytic properties of the prepared Co3O4 nano-particles were studied. The products were characterized by thermal analyses (TGA & DTA), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) techniques. Textural features of the obtained catalysts were investigated using nitrogen adsorption at -196 °C. X-ray diffraction confirmed that the resulting oxide was pure single-crystalline Co3O4 nano-particles. Transmission electron microscopy indicating that, the crystallite size of Co3O4 nano-crystals was in the range of 8-34 nm. The catalytic activities of prepared nano-crystalline Co3O4 catalysts were tested for H2O2 decomposition at 35-50 °C temperature range. Experimental results revealed that, the catalytic decomposition of H2O2 decreases with increasing the calcination temperature. This was correlated with the observed particle size increase accompanying the calcination temperature rise.

  2. Ice Flow, Isostasy and Gravity Anomaly of the Permanent North Polar H2O Ice Cap of Mars

    NASA Astrophysics Data System (ADS)

    Greve, R.; klemann, V.; Wolf, D.

    2000-08-01

    The flow of the permanent north polar H20 ice cap of Mars and the isostatic depression of the underlying bedrock are investigated with the 3-d dynamic/thermodynamic ice-sheet model SICOPOLIS (1) coupled to a two-layer visco-elastic model for the lithosphere/mantle system [2,31. SICOPOLIS describes the ice as a density-preserving, heat-conducting power-law fluid with thermo-mechanical coupling due to the strong temperature dependence of the ice viscosity, and computes three-dimensionally the temporal evolution of ice extent, thickness, temperature, water content and age as a response to external forcing. The tatter must be specified by (1) the mean annual air temperature above the ice, (2) the surface mass balance (ice accumulation minus melting and evaporation), (3) the global sea level (not relevant for Martian applications) and (4) the geothermal heat flux from below into the ice body. However, owing to the now well-known surface topography on the one hand, but the shortage of information about the surface mass balance on the other, here the inverse strategy of prescribing the topography and computing the surface mass balance required to sustain the topography is pursuited. Following further the approach of, we use a conceptional, paraboloid-like ice cap, growing and shrinking between the present minimum extent within 80.5 deg north and an assumed past maximum extent southward to 75 deg north with a period of 1.3 Myr (first modulation of obliquity cycle), vary the surface temperature with the same period between its measured present distribution and a 30 C warming coinciding with the maximum ice extent, and apply a geothermal heat flux of 35 mW m-2. The lithosphere/mantle model displace comprises an elastic lithosphere of constant thickness, underlain by a Maxwell-viscoelastic half-space mantle. Both layers are treated as incompressible, and we apply terrestrial standard values for the rheological parameters: density of the lithosphere and of the mantle rho1

  3. Concurrent separation of CO2 and H2O from air by a temperature-vacuum swing adsorption/desorption cycle.

    PubMed

    Wurzbacher, Jan Andre; Gebald, Christoph; Piatkowski, Nicolas; Steinfeld, Aldo

    2012-08-21

    A temperature-vacuum swing (TVS) cyclic process is applied to an amine-functionalized nanofibrilated cellulose sorbent to concurrently extract CO(2) and water vapor from ambient air. The promoting effect of the relative humidity on the CO(2) capture capacity and on the amount of coadsorbed water is quantified. The measured specific CO(2) capacities range from 0.32 to 0.65 mmol/g, and the corresponding specific H(2)O capacities range from 0.87 to 4.76 mmol/g for adsorption temperatures varying between 10 and 30 °C and relative humidities varying between 20 and 80%. Desorption of CO(2) is achieved at 95 °C and 50 mbar(abs) without dilution by a purge gas, yielding a purity exceeding 94.4%. Sorbent stability and a closed mass balance for both H(2)O and CO(2) are demonstrated for ten consecutive adsorption-desorption cycles. The specific energy requirements of the TVS process based on the measured H(2)O and CO(2) capacities are estimated to be 12.5 kJ/mol(CO2) of mechanical (pumping) work and between 493 and 640 kJ/mol(CO2) of heat at below 100 °C, depending on the air relative humidity. For a targeted CO(2) capacity of 2 mmol/g, the heat requirement would be reduced to between 272 and 530 kJ/mol(CO2), depending strongly on the amount of coadsorbed water.

  4. 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.

  5. The determination of deep temperatures by means of the CO-CO2-H2-H2O geothermometer: an example using fumaroles in the Campi Flegrei, Italy

    NASA Astrophysics Data System (ADS)

    Tedesco, D.; Sabroux, J. C.

    1987-02-01

    Chromatographic analyses of fumarolic gases, collected in sampling bottles containing an alkaline solution, have been carried out using a thermal conductivity detector and a flame ionization detector, after catalytic conversion of CO and CH4. The latter method enables the concentration of carbon monoxide to be measured with sufficient accuracy for use in a CO-CO2-H2-H2O geothermometer. Application of this geothermometer to fumaroles in the crater of Solfatara in the Campi Flegrei, Italy, indicates that they are fed from a steam reservoir at 250±15 °C and at 10-36±2atm of oxygen. On the other hand, the CH4-CO2-H2-H2O geothermobarometer seems to re-equilibrate at superficial temperatures and cannot be used for infering thermodynamic conditions at depth. Regular sampling of these fumaroles together with a geothermometric interpretation of the gas analyses provides a means of monitoring, with comparative accuracy, the chemical and thermal evolution of the hydrothermal reservoir below the Solfatara crater. Such monitoring would probably detect an increase in temperature at depth and the injection of magmatic gas into the reservoir.

  6. Pilot scale annular plug flow photoreactor by UV/H2O2 for the decolorization of azo dye wastewater.

    PubMed

    Shu, Hung-Yee; Chang, Ming-Chin

    2005-10-17

    A pilot scale annular plug flow photoreactor with thin gap size, which combines with UV irradiation and hydrogen peroxide, was employed to deal with colored dyeing wastewater treatment. In the experiment, a mono-azo dye acid orange 10 was the target compound. The experimental parameters such as flow rate, hydrogen peroxide dosage, UV input power, pH and dye initial concentrations in a pilot scale photoreactor with flow rate of 9.32 m3day(-1) were investigated. Ultimately, the degradation rates were calculated and compared with a 100-l batch reactor. In our plug flow photoreactor design, the degradation rate of acid orange 10 was 233 times higher than that of 100-l annular batch reactor with same UV light source. The residence time needed for 99% decolorizing of 100 l of 20 mgl(-1) acid orange 10 wastewater was 26.9 min for the thin gap plug flow reactor and was far shorter than that of batch reactor needed.

  7. 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)…

  8. 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)…

  9. 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.

  10. 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

    NASA Astrophysics Data System (ADS)

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

    2014-10-01

    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.

  11. Temperature dependence of the intensity of the vibration-rotational absorption band ν2 of H2O trapped in an argon matrix

    NASA Astrophysics Data System (ADS)

    Pitsevich, G.; Doroshenko, I.; Malevich, A..; Shalamberidze, E.; Sapeshko, V.; Pogorelov, V.; Pettersson, L. G. M.

    2017-02-01

    Using two sets of effective rotational constants for the ground (000) and the excited bending (010) vibrational states the calculation of frequencies and intensities of vibration-rotational transitions for J″ = 0 - 2; and J‧ = 0 - 3; was carried out in frame of the model of a rigid asymmetric top for temperatures from 0 to 40 K. The calculation of the intensities of vibration-rotational absorption bands of H2O in an Ar matrix was carried out both for thermodynamic equilibrium and for the case of non-equilibrium population of para- and ortho-states. For the analysis of possible interaction of vibration-rotational and translational motions of a water molecule in an Ar matrix by 3D Schrödinger equation solving using discrete variable representation (DVR) method, calculations of translational frequencies of H2O in a cage formed after one argon atom deleting were carried out. The results of theoretical calculations were compared to experimental data taken from literature.

  12. 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.

  13. Ultraviolet Excimer Laser-Based Ignition of H2/Air and H2/O2 Premixed Flows

    DTIC Science & Technology

    1990-08-01

    minimum occurring for lean mixtures. The ignition is due to efficient formation of microplasmas . Unlike the laser-produced microplasmas that are formed...Air Ignition by the ArF Excimer Lasero... ... .o.2 B. Microplasma Formation Mechanism ....... o...... ..... .o.o....2 C. Atmospheric Absorption...Ratio for H2/02 Premixed Flows Using ArF Laser (193 nm) (Unstable Resonator) ............... 3 2 Excitation Spectra for Microplasma Formation in H2

  14. 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.

  15. Diagnostic system for measuring temperature, pressure, CO2 concentration and H2O concentration in a fluid stream

    DOEpatents

    Partridge, Jr., William P.; Jatana, Gurneesh Singh; Yoo, Ji-Hyung; Parks, II, James E.

    2017-01-10

    A diagnostic system for measuring temperature, pressure, CO.sub.2 concentration and H.sub.2O concentration in a fluid stream is described. The system may include one or more probes that sample the fluid stream spatially, temporally and over ranges of pressure and temperature. Laser light sources are directed down pitch optical cables, through a lens and to a mirror, where the light sources are reflected back, through the lens to catch optical cables. The light travels through the catch optical cables to detectors, which provide electrical signals to a processer. The processer utilizes the signals to calculate CO.sub.2 concentration based on the temperatures derived from H.sub.2O vapor concentration. A probe for sampling CO.sub.2 and H.sub.2O vapor concentrations is also disclosed. Various mechanical features interact together to ensure the pitch and catch optical cables are properly aligned with the lens during assembly and use.

  16. Experimental and theoretical kinetics for the H2O+ + H2/D2 → H3O+/H2DO+ + H/D reactions: observation of the rotational effect in the temperature dependence.

    PubMed

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

    2014-12-11

    Thermal rate coefficients for the title reactions computed using a quasi-classical trajectory method on an accurate global potential energy surface fitted to ∼81,000 high-level ab initio points are compared with experimental values measured between 100 and 600 K using a variable temperature selected ion flow tube instrument. Excellent agreement is found across the entire temperature range, showing a subtle, but unusual temperature dependence of the rate coefficients. For both reactions the temperature dependence has a maximum around 350 K, which is a result of H2O(+) rotations increasing the reactivity, while kinetic energy is decreasing the reactivity. A strong isotope effect is found, although the calculations slightly overestimate the kinetic isotope effect. The good experiment-theory agreement not only validates the accuracy of the potential energy surface but also provides more accurate kinetic data over a large temperature range.

  17. 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.

  18. Rotational state dependence of rate constants for the reaction of ions with asymmetric top molecules at very low temperatures: application to the N+/H2O system

    NASA Astrophysics Data System (ADS)

    Dubernet, M. L.; McCarroll, R.

    1990-12-01

    The adiabatic rotational state method is applied to the study of reactions between ions and polar asymmetric top molecules at very low temperatures. Detailed results of the calculated rate coefficients for the reaction of N+ with H2O are presented. A strong dependence of the rate coefficients on the initial rotational state is observed at low temperatures. In the case of a thermal distribution of rotational states, where the rate constants are summed over a Boltzman distribution, the replacement of the asymmetric top by an average symmetric top, which leads to a considerable simplification of the calculations, appears to be satisfactory. On the other hand, for a non thermal distribution, no such simplifying assumption can be made. In particular, the rate coefficient for a specific initial rotational state is quite sensitive to the orientation of the dipole moment.

  19. 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

  20. 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.

  1. 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.

  2. 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...

  3. 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...

  4. Determining noble gas partitioning within a CO2-H2O system at elevated temperatures and pressures

    NASA Astrophysics Data System (ADS)

    Warr, Oliver; Rochelle, Christopher A.; Masters, Andrew; Ballentine, Christopher J.

    2015-06-01

    Quantifying the distribution of noble gases between phases is essential for using these inert trace gases to track the processes controlling multi-phase subsurface systems. Here we present experimental data that defines noble gas partitioning for two phase CO2-water systems. These are at the pressure and temperature range relevant for engineered systems used for anthropogenic carbon capture and geological storage (CCS) technologies, and CO2-rich natural gas reservoirs (CO2 density range 169-656 kg/m3 at 323-377 K and 89-134 bar). The new partitioning data are compared to predictions of noble gas partitioning determined in low-pressure, pure noble gas-water systems for all noble gases except neon and radon. At low CO2 density there was no difference between measured noble gas partitioning and that predicted in pure noble gas-water systems. At high CO2 density, however, partition coefficients express significant deviation from pure noble gas-water systems. At 656 kg/m3, these deviations are -35%, 74%, 113% and 319% for helium, argon, krypton and xenon, respectively. A second order polynomial fit to the data for each noble gas describes the deviation from the pure noble gas-water system as a function of CO2 density. We argue that the difference between pure noble gas-water systems and the high density CO2-water system is due to an enhanced degree of molecular interactions occurring within the dense CO2 phase due to the combined effect of inductive and dispersive forces acting on the noble gases. As the magnitude of these forces are related to the size and polarisability of each noble gas, xenon followed by krypton and argon become significantly more soluble within dense CO2. In the case of helium repulsive forces dominate and so it becomes less soluble as a function of CO2 density.

  5. 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.

  6. Isotope effects in liquid water by infrared spectroscopy. II. Factor analysis of the temperature effect on H2O and D2O

    NASA Astrophysics Data System (ADS)

    Larouche, Pascal; Max, Jean-Joseph; Chapados, Camille

    2008-08-01

    Some 500 infrared (IR) spectra of light and heavy waters were obtained between 29 and 93 °C in order to identify the species present in liquid water. Factor analysis of these gives two species for each type of water with their IR spectra and abundance curves. Using an orthogonalization procedure, we obtained the temperature factor limits of -22 and +118 °C (+/-5 °C) that we coined cold and hot factors, respectively. Within experimental error, these limits are the same for light and heavy waters. The spectra of the orthogonalized factors presented show a decrease of the OH (OD) stretch band integrated intensities of almost 36% from the cold to the hot factors. No ``free'' OH (OD) group is present or formed in the temperature ramp. This indicates that all water molecules in the bulk are made of an oxygen atom surrounded with four hydrogen atoms, two covalently bonded, and two hydrogen bonded. This is consistent with the previous study of mixtures of H2O and D2O [part I: J.-J. Max and C. Chapados, J. Chem. Phys. 116, 4626 (2002)]. To maintain the ordinary liquid within the limits of 0 and 100 °C at atmospheric pressure, a fraction of the cold and hot factors are necessary. With the spectra of the cold and hot factors and the abundance curves, one can generate the spectrum at any temperature between -22 and +118 °C of light and heavy liquid waters.

  7. Ionic conductivity measurements of H2O ice at high pressure and temperature and superionic ice in the mantle of ice giants

    NASA Astrophysics Data System (ADS)

    Sugimura, E.; Komabayashi, T.; Ohta, K.; Hirose, K.; Sata, N.; Ohishi, Y.; Shimizu, K.; Dubrovinsky, L. S.

    2011-12-01

    The experimental evidence for the superionic conduction in H2O ice at high pressure (P) and temperature (T) has been long-searched since its theoretical prediction. Melting experiments reported a steep rise of the melting curve at P-T range of 35-43 GP and 1000-1600 K, which could be due to a first-order phase transition in the solid phases, namely the presence of the triple point of water, ice VII, and a high-T phase which was assumed superionic. Nonetheless, there has still been no report on direct experimental evidence for superionic conduction (ca. 0.1 S/cm) in ice at high pressure. Here we examined ionic conductivity and isothermal molar volume of ice at high-P-T based on impedance spectroscopy (IS) and x-ray diffraction measurements in an externally-resistive heated diamond anvil cell. In situ IS measurements up to 62 GPa and 920 K demonstrated that ice exhibits superionic conduction (> 0.1 S/cm) above 580-720 K at 20-60 GPa. This suggests that superionic conduction occurs at sufficiently lower P-T than the triple point. Isothermal P-V data collected at P = 33-101 GPa and T = 873 K revealed that an anomalous volume reduction occurs at P = 50-53 GPa. This compression manner corresponds to the previously reported highly compressible regime at P = 40-60 GPa, T = 300 K, which were attributed to hydrogen bond symmetrization. There is no volume discontinuity in the isothermal compression, which contradicts the proposed first order P-T boundary between ice VII and superionic ice. Furthermore, all the conductivity data is expressed by a single Arrhenius equation so that the superionic conduction occurs regardless of the ongoing hydrogen bond symmetrization upon compression. We suggests that the previously reported steep rise of the melting temperature of ice above 35-43 GPa is independent of superionic transition, and is a consequence of the hydrogen bond symmetrization. Combining above results with the existing planetary isentropes, superionic conduction in H2O ice

  8. 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.

  9. Full dimensional potential energy surface and low temperature dynamics of the H2CO + OH → HCO + H2O reaction.

    PubMed

    Zanchet, Alexandre; Del Mazo, Pablo; Aguado, Alfredo; Roncero, Octavio; Jiménez, Elena; Canosa, André; Agúndez, Marcelino; Cernicharo, José

    2017-09-29

    A new method is proposed to analytically represent the potential energy surface of reactions involving polyatomic molecules capable of accurately describing long-range interactions and saddle points, needed to describe low-temperature collisions. It is based on two terms, a reactive force field term and a many-body term. The reactive force field term accurately describes the fragments, long-range interactions among them and the saddle points for reactions. The many-body term increases the desired accuracy everywhere else. This method has been applied to the OH + H2CO → H2O + HCO reaction, giving a barrier of 27.4 meV. The simulated classical rate constants with this potential are in good agreement with recent experimental results [Ocaña et al., Astrophys. J., 2017, submitted], showing an important increase at temperatures below 100 K. The reaction mechanism is analyzed in detail here, and explains the observed behavior at low energy by the formation of long-lived collision complexes, with roaming trajectories, with a capture observed for very long impact parameters, >100 a.u., determined by the long-range dipole-dipole interaction.

  10. 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.

  11. 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.

  12. Remote sensing of high temperature H2O CO2 CO mixture with a correlated k-distribution fictitious gas method and the single-mixture gas assumption

    NASA Astrophysics Data System (ADS)

    Caliot, C.; Le Maoult, Y.; El Hafi, M.; Flamant, G.

    2006-11-01

    Infrared spectra of high temperature H2O CO2 CO mixtures are calculated using narrow band models in order to simulate hot jet signature at long distance. The correlated k-distribution with fictitious gas (CKFG) approach generally gives accurate data in such situations (especially for long atmospheric paths) but results in long computation time in cases involving mixtures of gases. This time may be reduced if the mixture is treated as a single gas (single-mixture gas assumption, SMG). Thus the lines of the single-mixture gas are assigned to the fictitious gases. In this study, the accuracy of two narrow band models is evaluated. The first narrow band model considers one single-mixture gas and no fictitious gas (CK-SMG) whereas the second model accounts for one single-mixture gas and three fictitious gases (CKFG-SMG). Both narrow band models are compared with reference spectra calculated with a line-by-line (LBL) approach. As expected, the narrow band accuracy is improved by the fictitious gas (FG) assumption particularly when long atmospheric paths are involved. Concerning the SMG assumption, it may lead to an underestimation of about 10% depending on the variation of the gas mixture composition ratio. Nevertheless, in most of realistic situations the SMG assumption results in negligible errors and may be used for remote sensing of plume signature.

  13. 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.

  14. 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.

  15. 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.

  16. Thermodynamic description of equilibria in mixed fluids (H 2O-non-polar gas) over a wide range of temperature (25-700°C) and pressure (1-5000 bars)

    NASA Astrophysics Data System (ADS)

    Akinfiev, Nikolai; Zotov, Alexander

    1999-07-01

    A new method for computing complicated equilibria in hydrothermal mixed fluids, H 2O-non-polar gas, is proposed. The computation algorithm is based on the electrostatic approach for the interaction between aqueous species and H 2O. The approach uses the SUPCRT92 database and the HKF format and may be considered as an application of the revised HKF model for mixed H 2O-non-polar gas fluids. Thermodynamic properties of dissolved gases at high temperatures and pressures are calculated using the Redlich-Kwong approach. Dielectric permittivity of the mixed solvent is estimated by the modified Kirkwood equation. The proposed approach is validated using available experimental data on the dissociation constants of H 2O and NaCl and the solubility of both covalent and ion crystals (SiO 2, AgCl, Ag 2SO 4, Ca(OH) 2, CaCO 3) in H 2O-non-polar component (dioxane, Ar, CO 2) mixtures. Predicted and experimental data are in close agreement over a wide range of P- T- xgas conditions (up to 500°C, 4 kbar and 0.25-0.3 mole fraction of non-polar gas). It is also shown how the computation method can be applied to estimate the Born parameters of aqueous species. The proposed approach enables not only examination of isolated reactions, but the study of equilibria of whole systems. Thus, it allows modelling of mixed natural fluids.

  17. A shock tube study of OH + H(2)O(2) --> H(2)O + HO(2) and H(2)O(2) + M --> 2OH + M using laser absorption of H(2)O and OH.

    PubMed

    Hong, Zekai; Cook, Robert D; Davidson, David F; Hanson, Ronald K

    2010-05-13

    The rate constants of the reactions: (1) H2O2+M-->2OH+M, (2) OH+H2O2-->H2O+HO2 were measured in shock-heated H(2)O(2)/Ar mixtures using laser absorption diagnostics for H(2)O and OH. Time-histories of H(2)O were monitored using tunable diode laser absorption at 2550.96 nm, and time-histories of OH were achieved using ring dye laser absorption at 306 nm. Initial H(2)O(2) concentrations were also determined utilizing the H(2)O diagnostic. On the basis of simultaneous time-history measurements of OH and H(2)O, k(2) was found to be 4.6 x 10(13) exp(-2630 K/T) [cm(3) mol(-1) s(-1)] over the temperature range 1020-1460 K at 1.8 atm; additional measurements of k(2) near 1 atm showed no significant pressure dependence. Similarly, k(1) was found to be 9.5 x 10(15) exp(-21 250 K/T) [cm(3) mol(-1) s(-1)] over the same temperature and pressure range.

  18. Determination of local concentration of H2O molecules and gas temperature in the process of hydrogen - oxygen gas mixture heating by means of linear and nonlinear laser spectroscopy

    NASA Astrophysics Data System (ADS)

    Kozlov, D. N.; Kobtsev, V. D.; Stel'makh, O. M.; Smirnov, Valery V.; Stepanov, E. V.

    2013-01-01

    Employing the methods of linear absorption spectroscopy and nonlinear four-wave mixing spectroscopy using laserinduced gratings we have simultaneously measured the local concentrations of H2O molecules and the gas temperature in the process of the H2 - O2 mixture heating. During the measurements of the deactivation rates of pulsed-laser excited singlet oxygen O2 (b 1Σ+g) in collisions with H2 in the range 294 - 850 K, the joint use of the two methods made it possible to determine the degree of hydrogen oxidation at a given temperature. As the mixture is heated, H2O molecules are formed by 'dark' reactions of H2 with O2 in the ground state. The experiments have shown that the measurements of tunable diode laser radiation absorption along an optical path through the inhomogeneously heated gas mixture in a cell allows high-accuracy determination of the local H2O concentration in the O2 laser excitation volume, if the gas temperature in this volume is known. When studying the collisional deactivation of O2 (b 1Σ+g) molecules, the necessary measurements of the local temperature can be implemented using laser-induced gratings, arising due to spatially periodic excitation of O2 (X3Σ-g) molecules to the b 1Σ+g state by radiation of the pump laser of the four-wave mixing spectrometer.

  19. 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.

  20. Influence of Gaseous Media Flow in the Dual Ar-H2-H2O/air Atmosphere Setup on the Scale Growth Kinetics of Crofer 22APU Ferritic Stainless Steel

    NASA Astrophysics Data System (ADS)

    Stygar, Mirosław; Dąbrowa, Juliusz; Dziembaj, Piotr; Brylewski, Tomasz

    2017-02-01

    The problem of gaseous media distribution within the metallic interconnects in solid oxide fuel cells (SOFCs) and its influence on the oxidation resistance of the applied materials is currently of great interest. In the presented work, an influence of gas flow within the dual Ar-H2-H2O/air atmosphere experimental setup on the oxidation behavior of the Crofer 22APU ferritic stainless steel was investigated. Examination of the sample oxidized for 1000 h in temperature of 800 °C revealed the presence of coaxial regions on the scale surface, with the differences in scale's thicknesses in those regions being clearly visible. Additionally, the morphology of the surface changed significantly in a function of the radial distance from the sample's center. To further examine the phenomena of uneven gas distribution, a model of the dual-atmosphere setup was created, using Ansys Workbench software. Obtained results suggest that the correlation between scale morphology and distribution of temperature and pressure on the sample's surface, created by gas flow in the system, can be justified.

  1. Influence of Gaseous Media Flow in the Dual Ar-H2-H2O/air Atmosphere Setup on the Scale Growth Kinetics of Crofer 22APU Ferritic Stainless Steel

    NASA Astrophysics Data System (ADS)

    Stygar, Mirosław; Dąbrowa, Juliusz; Dziembaj, Piotr; Brylewski, Tomasz

    2016-12-01

    The problem of gaseous media distribution within the metallic interconnects in solid oxide fuel cells (SOFCs) and its influence on the oxidation resistance of the applied materials is currently of great interest. In the presented work, an influence of gas flow within the dual Ar-H2-H2O/air atmosphere experimental setup on the oxidation behavior of the Crofer 22APU ferritic stainless steel was investigated. Examination of the sample oxidized for 1000 h in temperature of 800 °C revealed the presence of coaxial regions on the scale surface, with the differences in scale's thicknesses in those regions being clearly visible. Additionally, the morphology of the surface changed significantly in a function of the radial distance from the sample's center. To further examine the phenomena of uneven gas distribution, a model of the dual-atmosphere setup was created, using Ansys Workbench software. Obtained results suggest that the correlation between scale morphology and distribution of temperature and pressure on the sample's surface, created by gas flow in the system, can be justified.

  2. 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.

  3. Compromised Photosynthetic Electron Flow and H2O2 Generation Correlate with Genotype-Specific Stomatal Dysfunctions during Resistance against Powdery Mildew in Oats

    PubMed Central

    Sánchez-Martín, Javier; Montilla-Bascón, Gracia; Mur, Luis A. J.; Rubiales, Diego; Prats, Elena

    2016-01-01

    Stomatal dysfunction known as “locking” has been linked to the elicitation of a hypersensitive response (HR) following attack of fungal pathogens in cereals. We here assess how spatial and temporal patterns of different resistance mechanisms, such as HR and penetration resistance influence stomatal and photosynthetic parameters in oat (Avena sativa) and the possible involvement of hydrogen peroxide (H2O2) in the dysfunctions observed. Four oat cultivars with differential resistance responses (i.e., penetration resistance, early and late HR) to powdery mildew (Blumeria graminis f. sp. avenae, Bga) were used. Results demonstrated that stomatal dysfunctions were genotype but not response-type dependent since genotypes with similar resistance responses when assessed histologically showed very different locking patterns. Maximum quantum yield (Fv/Fm) of photosystem II were compromised in most Bga–oat interactions and photoinhibition increased. However, the extent of the photosynthetic alterations was not directly related to the extent of HR. H2O2 generation is triggered during the execution of resistance responses and can influence stomatal function. Artificially increasing H2O2 by exposing plants to increased light intensity further reduced Fv/Fm ratios and augmented the patterns of stomatal dysfunctions previously observed. The latter results suggest that the observed dysfunctions and hence a cost of resistance may be linked with oxidative stress occurring during defense induced photosynthetic disruption. PMID:27877184

  4. Compromised Photosynthetic Electron Flow and H2O2 Generation Correlate with Genotype-Specific Stomatal Dysfunctions during Resistance against Powdery Mildew in Oats.

    PubMed

    Sánchez-Martín, Javier; Montilla-Bascón, Gracia; Mur, Luis A J; Rubiales, Diego; Prats, Elena

    2016-01-01

    Stomatal dysfunction known as "locking" has been linked to the elicitation of a hypersensitive response (HR) following attack of fungal pathogens in cereals. We here assess how spatial and temporal patterns of different resistance mechanisms, such as HR and penetration resistance influence stomatal and photosynthetic parameters in oat (Avena sativa) and the possible involvement of hydrogen peroxide (H2O2) in the dysfunctions observed. Four oat cultivars with differential resistance responses (i.e., penetration resistance, early and late HR) to powdery mildew (Blumeria graminis f. sp. avenae, Bga) were used. Results demonstrated that stomatal dysfunctions were genotype but not response-type dependent since genotypes with similar resistance responses when assessed histologically showed very different locking patterns. Maximum quantum yield (Fv/Fm) of photosystem II were compromised in most Bga-oat interactions and photoinhibition increased. However, the extent of the photosynthetic alterations was not directly related to the extent of HR. H2O2 generation is triggered during the execution of resistance responses and can influence stomatal function. Artificially increasing H2O2 by exposing plants to increased light intensity further reduced Fv/Fm ratios and augmented the patterns of stomatal dysfunctions previously observed. The latter results suggest that the observed dysfunctions and hence a cost of resistance may be linked with oxidative stress occurring during defense induced photosynthetic disruption.

  5. 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.

  6. 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

  7. The generalized k-moment method for the modeling of cumulative k-distributions of H2O at high temperature

    NASA Astrophysics Data System (ADS)

    André, Frédéric; Solovjov, Vladimir P.; Hou, Longfeng; Vaillon, Rodolphe; Lemonnier, Denis

    2014-08-01

    In the present work, a new formulation, limited to a few number of parameters, of cumulative k-distributions over narrow bands from high resolution spectra is presented. The method is described and assessed through comparisons with reference Line-By-Line (LBL) data for pure H2O, in terms of transmission spectra and cumulative k-distributions. Results demonstrate that the proposed approach is very accurate and therefore is likely to provide reliable approximate models for the cumulative k-distribution and the narrow band transmission functions in uniform media.

  8. Phase diagram of the binary H2O-NaCl and salty ice VII at pressure and temperature conditions of exoplanets and large icy moons

    NASA Astrophysics Data System (ADS)

    Journaux, B.; Daniel, I.

    2011-10-01

    We present here the first experimental data for the phase diagram of the H2O-NaCl system at high. Our results show a significant influence of NaCl on the phase diagram. A lot of NaCl is directly disolved into the dense ice phase. This would increase the depth of the solid phase transition inside large icy moons or super-earth exoplanets. These results may have major implication for astrophysical, geophysical and geodynamical modelisations of this water-rich planetary bodies.

  9. 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

  10. 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.

  11. Further insight into the reaction FeO(+) + H2 → Fe(+) + H2O: temperature dependent kinetics, isotope effects, and statistical modeling.

    PubMed

    Ard, Shaun G; Melko, Joshua J; Martinez, Oscar; Ushakov, Vladimir G; Li, Anyang; Johnson, Ryan S; Shuman, Nicholas S; Guo, Hua; Troe, Jürgen; Viggiano, Albert A

    2014-08-28

    The reactions of FeO(+) with H2, D2, and HD were studied in detail from 170 to 670 K by employing a variable temperature selected ion flow tube apparatus. High level electronic structure calculations were performed and compared to previous theoretical treatments. Statistical modeling of the temperature and isotope dependent rate constants was found to reproduce all data, suggesting the reaction could be well explained by efficient crossing from the sextet to quartet surface, with a rigid near thermoneutral barrier accounting for both the inefficiency and strong negative temperature dependence of the reactions over the measured range of thermal energies. The modeling equally well reproduced earlier guided ion beam results up to translational temperatures of about 4000 K.

  12. 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.

    2016-12-01

    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

  13. H2O and HCl trace gas kinetics on crystalline and amorphous HCl hydrates in the range 170 to 205 K: the HCl/H2O phase diagram revisited

    NASA Astrophysics Data System (ADS)

    Iannarelli, R.; Rossi, M. J.

    2013-11-01

    In this laboratory study, H2O ice films of 1 to 2 μm thickness have been used as surrogates for ice particles at atmospherically relevant conditions in a stirred flow reactor (SFR) to measure the kinetics of evaporation and condensation of HCl and H2O on crystalline and amorphous HCl hydrates. A multidiagnostic approach has been employed using FTIR absorption spectroscopy in transmission to monitor the condensed phase and residual gas mass spectrometry (MS) for the gas phase. An average mass balance ratio between HCl adsorbed onto ice and the quantity of HCl measured using FTIR absorption, (Nn - Nesc - Nads)/NFTIR = 1.182 ± 0.123 has been obtained. The rate of evaporation Rev(HCl) for crystalline HCl hexahydrate (HCl·6H2O) films and amorphous HCl/H2O mixtures has been found to be lower by a factor of 10 to 250 compared to Rev(H2O) in the overlapping temperature range 175 to 190 K. Variations of the accommodation coefficient α (HCl) on pure HCl·6H2O up to a factor of 10 have been observed. The kinetic parameters are thermochemically consistent with the corresponding equilibrium vapour pressure. In addition, we propose an extension of the HCl/H2O phase diagram of crystalline HCl·6H2O based on the analysis of deconvoluted FTIR spectra of samples outside its known existence area. A brief evaluation of the atmospheric importance of both condensed phases, amorphous HCl/H2O and crystalline HCl·6H2O, is performed in favour of the amorphous phase.

  14. 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.

  15. 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.

  16. 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.

  17. Thermal studies on the interaction behavior of ternary nitrate mixtures of UO2(NO3)2ṡ6H2O-NaNO3-Sr(NO3)2 at elevated temperatures

    NASA Astrophysics Data System (ADS)

    Kalekar, Bhupesh; Raje, Naina; Reddy, A. V. R.

    2015-04-01

    Thermal and X-ray diffraction measurements have been used to study the formation of various nitrato-complexes as intermediates and mixed oxides as end products using different mol ratios of the ternary mixtures of UO2(NO3)2ṡ6H2O, NaNO3 and Sr(NO3)2 at high temperatures. These results indicate the interaction of UO2(NO3)2ṡ6H2O and NaNO3 in equimolar ratio to form sodium uranyl nitrate monohydrate (Na[UO2(NO3)3]ṡH2O), dimerized sodium uranyl oxynitrate (Na2[(UO2NO3)2(O)2]) and sodium diuranate (Na2U2O7). The decomposition temperature of Sr(NO3)2 decreased by 60 °C in the presence of in-situ formed Na2U2O7. The uranium of Na2U2O7 intermediate reacts with Sr(NO3)2 to form various strontium uranium mixed oxides depending on Sr to U ratio in the initial mixtures. During the interaction of Sr(NO3)2 with Na2U2O7, sodium separates out as amorphous Na2O in the mixtures, containing Sr to U ratio ⩾1. Na2O phase is not formed in the uranium rich ternary mixture.

  18. 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.

  19. Electromagneto squeezing rotational flow of Carbon (C)-Water (H2O) kerosene oil nanofluid past a Riga plate: A numerical study.

    PubMed

    Hayat, Tasawar; Khan, Mumtaz; Khan, Muhammad Ijaz; Alsaedi, Ahmed; Ayub, Muhammad

    2017-01-01

    This article predicts the electromagneto squeezing rotational flow of carbon-water nanofluid between two stretchable Riga plates. Riga plate is known as electromagnetic actuator which is the combination of permanent magnets and a span wise aligned array of alternating electrodes mounted on a plane surface. Mathematical model is developed for the flow problem with the phenomena of melting heat transfer, viscous dissipation and heat generation/absorption. Water and kerosene oil are utilized as the base fluids whereas single and multi-wall carbon nanotubes as the nanomaterials. Numerical solutions of the dimensionless problems are constructed by using built in shooting method. The correlation expressions for Nusselt number and skin friction coefficient are developed and examined through numerical data. Characteristics of numerous relevant parameters on the dimensionless temperature and velocity are sketched and discussed. Horizontal velocity is found to enhance for higher modified Hartman number.

  20. Electromagneto squeezing rotational flow of Carbon (C)-Water (H2O) kerosene oil nanofluid past a Riga plate: A numerical study

    PubMed Central

    Hayat, Tasawar; Khan, Mumtaz; Alsaedi, Ahmed; Ayub, Muhammad

    2017-01-01

    This article predicts the electromagneto squeezing rotational flow of carbon-water nanofluid between two stretchable Riga plates. Riga plate is known as electromagnetic actuator which is the combination of permanent magnets and a span wise aligned array of alternating electrodes mounted on a plane surface. Mathematical model is developed for the flow problem with the phenomena of melting heat transfer, viscous dissipation and heat generation/absorption. Water and kerosene oil are utilized as the base fluids whereas single and multi-wall carbon nanotubes as the nanomaterials. Numerical solutions of the dimensionless problems are constructed by using built in shooting method. The correlation expressions for Nusselt number and skin friction coefficient are developed and examined through numerical data. Characteristics of numerous relevant parameters on the dimensionless temperature and velocity are sketched and discussed. Horizontal velocity is found to enhance for higher modified Hartman number. PMID:28813427

  1. Thermo- and piezochromic properties of [Fe(hyptrz)]A2·H2O spin crossover 1D coordination polymer: Towards spin crossover based temperature and pressure sensors

    NASA Astrophysics Data System (ADS)

    Jureschi, Catalin-Maricel; Rusu, Ionela; Codjovi, Epiphane; Linares, Jorge; Garcia, Yann; Rotaru, Aurelian

    2014-09-01

    We have used reflectance measurements to investigate the effect of a hydrostatic pressure on the molecular 1D spin crossover coordination polymer [Fe(hyptrz)]A2·H2O (hyptrz=4-(3‧-hydroxypropyl)-1,2,4-triazole and A=4-chloro-benzenesulfonate) Rev. Sci. Instrum. 80 (2009) 123901. Both thermal and pressure hysteresis have been recorded at different pressures and temperatures, respectively, in order to obtain valuable information about the optimal conditions of their use as wireless temperature and pressure sensors. The experimental analysis has been completed with a theoretical study and potential applications in terms of temperature and pressure wireless detection are discussed.

  2. 50-kHz-rate 2D imaging of temperature and H2O concentration at the exhaust plane of a J85 engine using hyperspectral tomography.

    PubMed

    Ma, Lin; Li, Xuesong; Sanders, Scott T; Caswell, Andrew W; Roy, Sukesh; Plemmons, David H; Gord, James R

    2013-01-14

    This paper describes a novel laser diagnostic and its demonstration in a practical aero-propulsion engine (General Electric J85). The diagnostic technique, named hyperspectral tomography (HT), enables simultaneous 2-dimensional (2D) imaging of temperature and water-vapor concentration at 225 spatial grid points with a temporal response up to 50 kHz. To our knowledge, this is the first time that such sensing capabilities have been reported. This paper introduces the principles of the HT techniques, reports its operation and application in a J85 engine, and discusses its perspective for the study of high-speed reactive flows.

  3. Room temperature synthesis of rod-like FeC2O4·2H2O and its transition to maghemite, magnetite and hematite nanorods through controlled thermal decomposition

    NASA Astrophysics Data System (ADS)

    Zhou, Weiwei; Tang, Kaibin; Zeng, Suyuan; Qi, Yunxia

    2008-02-01

    FeC2O4·2H2O nanorods with diameter of about 50 nm and length of up to several micrometers were synthesized at room temperature in a surfactant-assisted system, which was obtained by dissolving bis(2-ethylhexyl)sodium sulfosuccinate (AOT) in a mixed solution composed of water and ethylene glycol (EG). The influence of reaction conditions on the morphology of FeC2O4·2H2O is discussed in detail. Through direct thermal decomposition of FeC2O4·2H2O under different calcination conditions, maghemite (γ-Fe2O3), magnetite (Fe3O4) and hematite (α-Fe2O3) can be selectively obtained, preserving the rod-like morphology. Transmission electron microscope (TEM) and high-resolution transmission electron microscope (HRTEM) characterizations showed that the as-obtained iron oxide nanorods were composed of fine particles with different crystal orientations. The magnetic properties of the as-obtained iron oxide nanorods were systematically investigated.

  4. Phonon-mediated nuclear spin relaxation in H2O

    NASA Astrophysics Data System (ADS)

    Yamakawa, Koichiro; Azami, Shinya; Arakawa, Ichiro

    2017-03-01

    A theoretical model of the phonon-mediated nuclear spin relaxation in H2O trapped by cryomatrices has been established for the first time. In order to test the validity of this model, we measured infrared spectra of H2O trapped in solid Ar, which showed absorption peaks due to rovibrational transitions of ortho- and para-H2O in the spectral region of the bending vibration. We monitored the time evolution of the spectra and analyzed the rotational relaxation associated with the nuclear spin flip to obtain the relaxation rates of H2O at temperatures of 5-15 K. Temperature dependence of the rate is discussed in terms of the devised model.

  5. 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.

  6. Interaction of Peroxynitric Acid with Solid H2O Ice

    NASA Technical Reports Server (NTRS)

    Li, Zhuangjie; Friedl, Randall R.; Moore, Steven B.; Sander, Stanley P.

    1996-01-01

    The uptake of peroxynitric acid (PNA), HO2NO2 or HNO4, on solid H2O ice at 193 K (-80 C) was studied using a fast flow-mass spectrometric technique. An uptake coefficient of 0.15 +/- 0.10 was measured, where the quoted uncertainty denotes 2 standard deviations. The uptake process did not result in the production of gas phase products. The composition of the condensed phase was investigated using programmed heating (3 K/min) of the substrate coupled with mass spectrometric detection of desorbed species. Significant quantities of HNO, and HNO3 desorbed from the substrates at temperatures above 225 K and 246 K, respectively. The desorbed HNO3, which was less than 9% of the desorbed HNO, and remained unchanged upon incubation of the substrate, was likely due to impurities in the HNO4 samples rather than reaction of HNO, on the substrate. The onset temperatures for HNO4 desorption increased with increasing H2O to HNO4 ratios, indicating that HNO4, like HNO3, tends to be hydrated in the presence of water. These observations suggest possible mechanisms for removal of HNO4 or repartitioning of total odd nitrogen species in the Earth's upper troposphere and stratosphere.

  7. [An approach for comparative quantification of myocardial blood flow (O-15-H2O-PET), perfusion (Tc-99m-tetrofosmin-SPECT) and metabolism (F-18-FDG-PET)].

    PubMed

    Schäfer, W M; Nowak, B; Kaiser, H J; Block, S; Koch, K C; vom Dahl, J; Büll, U

    2001-10-01

    In the present study a new approach has been developed for comparative quantification of absolute myocardial blood flow (MBF), myocardial perfusion, and myocardial metabolism in short-axis slices. 42 patients with severe CAD, referred for myocardial viability diagnostics, were studied consecutively with 0-15-H2O PET (H2O-PET) (twice), Tc-99m-Tetrofosmin SPECT (TT-SPECT) and F-18-FDG PET (FDG-PET). All data sets were reconstructed using attenuation correction and reoriented into short axis slices. Each heart was divided into three representative slices (base, midventricular, apex) and 18 ROIs were defined on the FDG PET images and transferred to the corresponding H2O-PET and TT-SPECT slices. TT-SPECT and FDG-PET data were normalized to the ROI showing maximum perfusion. MBF was calculated for all left-ventricular ROIs using a single-compartment-model fitting the dynamic H2O-PET studies. Microsphere equivalent MBF (MBF_micr) was calculated by multiplying MBF and tissue-fraction, a parameter which was obtained by fitting the dynamic H2O-PET studies. To reduce influence of viability only well perfused areas (> 70% TT-SPECT) were used for comparative quantification. First and second mean global MBF values were 0.85 ml x min-1 x g-1 and 0.84 ml x min-1 x g-1, respectively, with a repeatability coefficient of 0.30 ml x min-1 x g-1. After sectorization mean MBF_micr was between 0.58 ml x min-1 x ml-1 and 0.68 ml x min-1 x ml-1 in well perfused areas. Corresponding TT-SPECT values ranged from 83% to 91%, and FDG-PET values from 91% to 103%. All procedures yielded higher values for the lateral than the septal regions. Comparative quantification of MBF, MBF_micr, TT-SPECT perfusion and FDG-PET metabolism can be done with the introduced method in short axis slices. The obtained values agree well with experimentally validated values of MBF and MBF_micr.

  8. 40 CFR 1065.370 - CLD CO2 and H2O quench verification.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ...) Humidify the NO span gas by bubbling it through distilled water in a sealed vessel. If the humidified NO... temperature to generate an H2O level approximately equal to the maximum mole fraction of H2O expected during... verification test, control the vessel temperature to generate an H2O level at least as high as the level...

  9. 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

  10. 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

  11. 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

  12. Thermal decomposition of (UO2)O2(H2O)2·2H2O: Influence on structure, microstructure and hydrofluorination

    NASA Astrophysics Data System (ADS)

    Thomas, R.; Rivenet, M.; Berrier, E.; de Waele, I.; Arab, M.; Amaraggi, D.; Morel, B.; Abraham, F.

    2017-01-01

    The thermal decomposition of uranyl peroxide tetrahydrate, (UO2)O2(H2O)2.2H2O, was studied by combining high temperature powder X-ray diffraction, scanning electron microscopy, thermal analyses and spectroscopic techniques (Raman, IR and 1H NMR). In situ analyses reveal that intermediates and final uranium oxides obtained upon heating are different from that obtained after cooling at room temperature and that the uranyl precursor used to synthesize (UO2)O2(H2O)2·2H2O, sulfate or nitrate, has a strong influence on the peroxide thermal behavior and morphology. The decomposition of (UO2)O2(H2O)2·2H2O ex sulfate is pseudomorphic and leads to needle-like shaped particles of metastudtite, (UO2)O2(H2O)2, and UO3-x(OH)2x·zH2O, an amorphous phase found in air in the following of (UO2)O2(H2O)2 dehydration. (UO2)O2(H2O)2·2H2O and the compounds resulting from its thermal decomposition are very reactive towards hydrofluorination as long as their needle-like morphology is kept.

  13. Uricase-adsorbed carbon-felt reactor coupled with a peroxidase-modified carbon-felt-based H2O2 detector for highly sensitive amperometric flow determination of uric acid.

    PubMed

    Wang, Yue; Hasebe, Yasushi

    2012-01-05

    Uricase (urate oxidase, UOx) was adsorbed onto a porous carbon-felt (CF) surface and the resulting UOx-adsorbed CF (UOx-CF) was successfully used as a column-type enzyme reactor coupled with a peroxidase-adsorbed CF-based bioelectrocatalytic H(2)O(2) flow-detector to fabricate a flow-amperometric biosensor for uric acid. In this flow-biosensor system, H(2)O(2) produced in the UOx-CF reactor was cathodically detected by horseradish peroxidase (HRP) and a thionine (Th)-coadsorbed CF (HRP/Th-CF)-based bioelectrocatalytic flow-detector at -0.05V vs. Ag/AgCl. Various adsorption conditions of the UOx (i.e., pH of the adsorption solution, type and concentration of the buffer used as the adsorption solvent, UOx concentration and adsorption time) and the operational conditions of the UOx-CF and HRP/Th-CF-coupled flow-biosensor (i.e., carrier flow rate and carrier pH) were optimized to obtain highly sensitive, selective and stable peak current responses to uric acid. The analytical performance of the UOx-CF and HRP/Th-CF-coupled flow biosensor for uric acid was as follows: sensitivity, 0.25μA/uM; linear range, 0.3-20μM; lower detection limit, 0.18μM; and sample throughput, ca. 30-90 samples/h. The resulting amperometric flow-biosensor for uric acid allowed the determination of uric acid in highly diluted body fluids (human serum and urine), and the analytical results obtained by the present biosensor were in fairly good agreement with those obtained by conventional enzyme-based spectrophotometry. Copyright © 2011 Elsevier B.V. All rights reserved.

  14. Room temperature reduction and hydrolysis of FeCl3ṡ6H2O on self-sacrifice microscale Cu2O octahedron template: A mild chemical synthesis of pseudocapacitor electrode materials

    NASA Astrophysics Data System (ADS)

    Zhang, Mu; Peng, Xiaoyang; Chen, Xu; Chen, Kunfeng; Sun, Xudong; Xue, Dongfeng

    2015-03-01

    Fe(OH)x (x = 2, 3) colloidal aggregations were synthesized at room temperature via a reduction and hydrolysis of FeCl3ṡ6H2O on microscale Cu2O octahedron, which functions as a self-sacrifice template. We herein proposed the growth of Fe(OH)x colloidal aggregation by redox etching Cu2O octahedron while two critical reactions of both redox and precipitation were well employed in this work. As-synthesized Fe(OH)x samples exhibited high specific capacitance of 242.7 F/g, which was higher than those available data of iron oxides and hydroxides.

  15. 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

  16. On the sequence of three related phases of [Ni(H2O)2(15-crown-5)](HSO4)2 in the temperature range 110-295 K.

    PubMed

    Siegler, Maxime A; Stavitski, Eli

    2010-08-01

    Attempts to prepare the compound [Ni(H(2)O)(2)(15-crown-5)](X)(2) were eventually successful with X = NO(3)(-) provided that a synthetic route aimed at restricting water was followed. Application of this method was extended to make the analogous compound with X = HSO(4)(-), for which three symmetry-related phases were isolated between 295 and 110 K: a room-temperature phase with Z' = (1/2) [phase (I)], an intermediate-temperature phase with Z' = 1 [phase (II)] and a low-temperature phase with Z' = 2 [phase (III)]. The phases are related by two reversible solid-solid phase transitions, and both transitions take place without a significant loss of crystallinity. In the phase sequence (I) <--> (II) <--> (III) (Z': (1/2) <--> 1 <--> 2), the crystal packing remains remarkably similar but the degree of order in the crystal changes significantly; the structure is very disordered at room and intermediate temperatures but is ordered at 110 K. The compound [Ni(H(2)O)(2)(15-crown-5)](HSO(4))(2) has a complicated hydrogen-bonding network, which contains O-H...O bonds between the counterions. Structural changes are largest along some face-diagonal directions in the sequence (I) <--> (II) <--> (III).

  17. 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.

  18. Experimental study of the dehydration reactions gypsum-bassanite and bassanite-anhydrite at high pressure: Indication of anomalous behavior of H2O at high pressure in the temperature range of 50-300 °C

    NASA Astrophysics Data System (ADS)

    Mirwald, Peter W.

    2008-02-01

    The system CaSO4-H2O, characterized by the three dehydration reactions gypsum-anhydrite, gypsum-bassanite, and bassanite-anhydrite, was reexamined by in situ differential pressure analysis in the temperature range of 60-350°C up to 3.5GPa pressure. The investigation revealed a fine structure in the dehydration boundaries of gypsum-bassanite and bassanite-anhydrite, each characterized by three inflections at 0.9-1.0, 1.9-2.0, and 2.6-28GPa. In addition, the phase transition of anhydrite high pressure anhydrite (monazite structure) was established for the first time at high P-T conditions intersecting the bassanite-anhydrite dehydration boundary at 2.15GPa /250°C. Furthermore, the triple point gypsum-bassanite-anhydrite was redetermined with 235MPa/80.5°C. The evaluation of the gypsum-bassanite dehydration boundary with respect to the volume and entropy change of the reaction, ΔVreact and ΔSreact, by means of the Clausius-Clapeyron relation yields for the entropy parameter an unusually large increase over the range of the noted inflections. This is interpreted as anomalous entropy behavior of H2O related presumably to a dramatic increase in fluctuations of the hydrogen network of the liquid leading possibly into a new structural state. The effect is strongly related to the three noted pressure levels of 0.9-1.0, 1.9-2.0, and 2.6-28GPa. In a synopsis of data including also a previous high pressure study in the temperature range between 0 and 80°C, a tentative P-T diagram of H2O is proposed.

  19. Abnormal resting state corticolimbic blood flow in depressed unmedicated patients with major depression: a (15)O-H(2)O PET study.

    PubMed

    Monkul, E Serap; Silva, Leandro A P; Narayana, Shalini; Peluso, Marco A M; Zamarripa, Frank; Nery, Fabiano G; Najt, Pablo; Li, John; Lancaster, Jack L; Fox, Peter T; Lafer, Beny; Soares, Jair C

    2012-02-01

    We investigated the differences in the resting state corticolimbic blood flow between 20 unmedicated depressed patients and 21 healthy comparisons. Resting state cerebral blood flow (CBF) was measured with H(2)(15)O PET. Anatomical MRI scans were performed on an Elscint 1.9 T Prestige system for PET-MRI coregistration. Significant changes in cerebral blood flow indicating neural activity were detected using an ROI-free image subtraction strategy. In addition, the resting blood flow in patients was correlated with the severity of depression as measured by HAM-D scores. Depressed patients showed decreases in blood flow in right anterior cingulate (Brodmann areas 24 and 32) and increased blood flow in left and right posterior cingulate (Brodmann areas 23, 29, 30), left parahippocampal gyrus (Brodmann area 36), and right caudate compared with healthy volunteers. The severity of depression was inversely correlated with the left middle and inferior frontal gyri (Brodmann areas 9 and 47) and right medial frontal gyrus (Brodmann area 10) and right anterior cingulate (Brodmann areas 24, 32) blood flow, and directly correlated with the right thalamus blood flow. These findings support previous reports of abnormalities in the resting state blood flow in the limbic-frontal structures in depressed patients compared to healthy volunteers. Copyright © 2011 Wiley Periodicals, Inc.

  20. The metastable HCl · 6H2O phase - IR spectroscopy, phase transitions and kinetic/thermodynamic properties in the range 170-205 K

    NASA Astrophysics Data System (ADS)

    Chiesa, S.; Rossi, M. J.

    2013-07-01

    In this laboratory study, 1 to 2 μm thick polycrystalline ice films have been grown under stirred flow reactor (SFR) conditions and subsequently doped with metered amounts of HCl under static conditions. A multidiagnostic approach including FTIR absorption spectroscopy in transmission, residual gas mass spectrometry (MS) and total pressure measurement was employed. Depending on the growth protocol controlling both temperature and partial pressure of HCl (PHCl), either amorphous HCl/H2O or crystalline HCl hexahydrate (HCl · 6H2O) have been obtained. After controlled doping with HCl and evaporation of excess H2O from the ice film, transmission FTIR of pure HCl · 6H2O films and use of calibrated residual gas MS enabled the measurement of differential (peak) IR cross sections at several mid-IR frequencies (σ = (6.5 ± 1.9) × 10-19 cm2 molec-1 at 1635 cm-1 as an example). Two types of kinetic experiments on pure HCl · 6H2O have been performed under SFR conditions: (a) evaporation of HCl · 6H2O under H2O-poor conditions over a narrow T range, and (b) observation of the phase transition from crystalline HCl · 6H2O to amorphous HCl/H2O under H2O-rich conditions at increasing T. The temperature dependence of the zero-order evaporation flux of HCl in pure HCl · 6H2O monitored at 3426 cm-1 led to log(Jev) molec cm-2s-1= (36.34 ± 3.20) - (80 810 ± 5800)/2.303RT with R=8.312 JK-1 mol-1. HCl · 6H2O has a significant intrinsic kinetic barrier to HCl evaporation of 15.1 kJ mol-1 in excess of the HCl sublimation enthalpy of 65.8 kJ mol-1 at 200 K but is kinetically unstable (metastable) at typical UT/LS conditions of HCl partial pressure (P(HCl)) and temperature. Water-rich HCl · 6H2O undergoes a facile phase transition from crystalline to the amorphous/ supercooled/disordered state easily observable at T≥ 195 K under both static and SFR conditions. This corresponds to low P(HCl) in the neighborhood of 10-7 Torr that also prevails at the Upper Troposphere

  1. Kinetics of the reaction OH + HNO3 yields H2O + NO3

    NASA Technical Reports Server (NTRS)

    Margitan, J. J.; Kaufman, F.; Anderson, J. G.

    1975-01-01

    The reaction OH + HN3 yields H2O + NO3 was studied over the temperature range 270-470 K in a flow system utilizing UV resonance fluorescence detection of OH. A temperature independent rate constant of (8.9 plus or minus 1.3) x 10 to the -14 cu cm/s was obtained, where the reported uncertainty represents a single standard deviation including estimates of systematic errors.

  2. Quasiclassical Trajectory Calculations of the Rate Constant of the OH + HBr → Br + H2O Reaction Using a Full-Dimensional Ab Initio Potential Energy Surface Over the Temperature Range 5 to 500 K.

    PubMed

    de Oliveira-Filho, Antonio G S; Ornellas, Fernando R; Bowman, Joel M

    2014-02-20

    We report a permutationally invariant, ab initio potential energy surface (PES) for the OH + HBr → Br + H2O reaction. The PES is a fit to roughly 26 000 spin-free UCCSD(T)/cc-pVDZ-F12a energies and has no classical barrier to reaction. It is used in quasiclassical trajectory calculations with a focus on the thermal rate constant, k(T), over the temperature range 5 to 500 K. Comparisons with available experimental data over the temperature range 23 to 416 K are made using three approaches to treat the OH rotational and associated electronic partition function. All display an inverse temperature dependence of k(T) below roughly 160 K and a nearly constant temperature dependence above 160 K, in agreement with experiment. The calculated rate constant with no treatment of spin-orbit coupling is overall in the best agreement with experiment, being (probably fortuitously) within 20% of it.

  3. Dissolution kinetics of calcium carbonate minerals in H 2OCO 2 solutions in turbulent flow: The role of the diffusion boundary layer and the slow reaction H 2O + CO 2 → H + + HCO 3-

    NASA Astrophysics Data System (ADS)

    Liu, Zaihua; Dreybrod, Wolfgang

    1997-07-01

    Dissolution and precipitation of calcium carbonate minerals in aqueous solutions with turbulent flow are controlled by a diffusion boundary layer (DBL) adjacent to the surface of the mineral, across which mass transfer is effected by molecular diffusion. A rotating disk technique was used to investigate the effect of the DBL on the dissolution rates of CaCO 3. This technique allows an exact adjustment of the thickness of the DBL by controlling the rotation speed of a circular sample of CaCO 3. Measurements of the dissolution rates in H 2OCO 2Ca 2+-solutions in equilibrium with various partial pressures of CO 2 from 1·10 -3 up to 1 atm showed a dependence of the rates R on the rotation frequency ω, given by R ∝ ωn. The exponent n varies from 0.25 at low Pco 2 to about 0.01 at a Pco 2 of 1 atm. This reveals that the rates are not controlled by mass transport only, which would require n = 0.5. The experimental data can be explained employing a theoretical model, which also takes into account the slow reaction CO 2 + H 2O → H + + HCO 3- and the chemical reactions at the surface (Dreybrodt and Buhmann, 1991). Interpretation of the experimental data in view of this model reveals that conversion of CO 2 plays an important role in the control of the rates. At high PCO 2 and large DBL thickness (ε > 0.001 cm), conversion of CO 2 occurs mainly in the DBL and, therefore, becomes rate limiting. This is corroborated by the observation that upon addition of the enzyme carbonic anhydrase, which catalyzes CO 2-conversion, the dissolution rates are enhanced by 1 order of magnitude. From our experimental observations we conclude that the theoretical model above enables one to predict dissolution rates with satisfactory precision. Since the precipitation rates from supersaturated solutions are determined by the same mechanisms as dissolution, we infer that this model is also valid to predict precipitation rates. The predicted rates for both dissolution and precipitation

  4. Electron ionization of H2O

    NASA Astrophysics Data System (ADS)

    King, Simon J.; Price, Stephen D.

    2008-11-01

    Relative partial ionization cross-sections and precursor-specific relative partial ionization cross-sections for fragment ions formed by electron ionization of H2O have been measured using time-of-flight mass spectrometry coupled with a 2D ion coincidence technique. We report data for the formation of H+, H2+, O2+, O+ and OH+ relative to the formation of H2O+, as a function of ionizing electron energy from 30 to 200 eV. This data includes, for the first time, measurements on the formation all positive ion pairs and ion triples by dissociative multiple electron ionization of H2O. Through determinations of the kinetic energy release involved in ion pair formation we provide further evidence that indirect processes contribute significantly to the yield of H+ + OH+ ion pairs below the vertical double ionization threshold.

  5. 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.

  6. Near-infrared spectra of H2O under high pressure and high temperature: implications for a transition from proton tunneling to hopping states.

    PubMed

    Noguchi, Naoki; Komatsu, Kazuki; Shinozaki, Ayako; Shinoda, Keiji; Kagi, Hiroyuki

    2014-12-10

    The nature of protons in ice VII up to 368°C and 16GPa was investigated with synchrotron near-infrared spectroscopy. The absorption band of the first OH stretching overtone mode divided into doublet peaks above 5GPa at room temperature, suggesting that proton tunneling occurs at the overtone level. As the temperature increased, the doublet peaks gradually reduced to a singlet. This result implies that thermally activated protons hop between the two potential minima along the oxygen-oxygen axis. A pressure-temperature diagram for the proton state was constructed from the changing band shape of the overtone mode. Copyright © 2014 Elsevier B.V. All rights reserved.

  7. 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.

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

    NASA Astrophysics Data System (ADS)

    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 (Cp, ΔH) 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 than

  9. 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

    2009-10-07

    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

  10. Temperature-dependent framework-template interaction of |Na6(H2O)8|[ZnPO4]6 sodalite

    NASA Astrophysics Data System (ADS)

    Robben, Lars; Gesing, Thorsten M.

    2013-11-01

    The partial dehydration followed by the decomposition of sodium-zincophosphate-hydrosodalite caused by the total water loss was examined by temperature-dependent X-ray powder diffraction, Fourier transform infrared (FTIR) and Raman spectroscopy as well as thermogravimetry combined with difference thermoanalysis. The dehydration causing the decomposition of this sodalite could be described in a two step-process. Initially two water molecules per unit-cell were lost, changing the interaction between the zincophosphate framework and the remaining water molecules as well as sodium cations as non-framework constituents. In this stage a 3+3 coordination of water molecules and sodium cations in the sodalite cage is observed. Using the autocorrelation function (AC) for the evaluation of the temperature-dependent FTIR spectra of sodalites is reported here for the first time. Calculating the changes in the AC broadness, structural features could well be analyzed due to its correlation with respective structural parameters. Temperature dependent Raman data was used to give a band assignment of bands at Raman shifts below 300 cm-1.

  11. Effect of H2O2 dosing strategy on sludge pretreatment by microwave-H2O2 advanced oxidation process.

    PubMed

    Wang, Yawei; Wei, Yuansong; Liu, Junxin

    2009-09-30

    Considering characteristics of breaking down H(2)O(2) into water and molecular oxygen by catalase in waste activated sludge (WAS), the effect of H(2)O(2) dosing strategy on sludge pretreatment by the advanced oxidation process (AOP) of microwave-H(2)O(2) was investigated by batch experiments for optimizing H(2)O(2) dosage. Results showed that the catalase in sludge was active at the low temperature range between 15 degrees C and 45 degrees C, and gradually lost activity from 60 degrees C to 80 degrees C. Therefore, the H(2)O(2) was dosed at 80 degrees C, to which the waste activated sludge was first heated by the microwave (MW), and then the sludge dosed with H(2)O(2) was continuously heated till 100 degrees C by the microwave. Results at different H(2)O(2) dosages showed that the higher the H(2)O(2) dosing ratio was, the more the SCOD and total organic carbon (TOC) were released into the supernatant, and the optimum range of H(2)O(2)/TCOD ratio should be between 0.1 and 1.0. The percentages of consumed H(2)O(2) in the AOP of microwave and H(2)O(2) treating the WAS were 25.38%, 22.53%, 14.82%, 13.61% and 19.63% at different H(2)O(2)/TCOD dosing ratios of 0.1, 0.5, 1, 2, 4, respectively. Along with the increasing H(2)O(2)/TCOD ratio, the contents of TCOD on particles, soluble substances and mineralization increased and the TCOD distribution on solids decreased.

  12. Using the full IASI spectrum for the physical retrieval of temperature, H2O, HDO, O3, minor and trace gases

    NASA Astrophysics Data System (ADS)

    Serio, C.; Blasi, M. G.; Liuzzi, G.; Masiello, G.; Venafra, S.

    2017-02-01

    IASI (Infrared Atmospheric Sounder Interferometer) is flying on the European MetOp series of weather satellites. Besides acquiring temperature and humidity data, IASI also observes the infrared emission of the main minor and trace atmospheric components with high precision. The retrieval of these gases would be highly beneficial to the efforts of scientists monitoring Earths climate. IASI retrieval capability and algorithms have been mostly driven by Numerical Weather Prediction centers, whose limited resources for data transmission and computing is hampering the full exploitation of IASI information content. The quest for real or nearly real time processing has affected the precision of the estimation of minor and trace gases, which are normally retrieved on a very coarse spatial grid. The paper presents the very first retrieval of the complete suite of IASI target parameters by exploiting all its 8461 channels. The analysis has been exemplified for sea surface and the target parameters will include sea surface temperature, temperature profile, water vapour and HDO profiles, ozone profile, total column amount of CO, CO2, CH4, N2O, SO2, HNO3, NH3, OCS and CF4. Concerning CO2, CH4 and N2O, it will be shown that their colum amount can be obtained for each single IASI IFOV (Instantaneous Field of View) with a precision better than 1-2%, which opens the possibility to analyze, e.g., the formation of regional patterns of greenhouse gases. To assess the quality of the retrieval, a case study has been set up which considers two years of IASI soundings over the Hawaii, Manua Loa validation station.

  13. 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.

  14. 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.

  15. Crystallization Experiments in the MgO-CO2-H2O system: Role of Amorphous Magnesium Carbonate Precursors in Magnesium Carbonate Hydrated Phases and Morphologies in Low Temperature Hydrothermal Fluids

    NASA Astrophysics Data System (ADS)

    Giampouras, Manolis; Garcia-Ruiz, Juan Manuel; Garrido, Carlos J.

    2017-04-01

    Numerous forms of hydrated or basic magnesium carbonates occur in the complex MgO-CO2-H2O system. Mineral saturation states from low temperature hydrothermal fluids in Semail Ophiolite (Oman), Prony Bay (New Caledonia) and Lost City hydrothermal field (mid-Atlantic ridge) strongly indicate the presence of magnesium hydroxy-carbonate hydrates (e.g. hydromagnesite) and magnesium hydroxides (brucite). Study of formation mechanisms and morphological features of minerals forming in the MgO-CO2-H2O system could give insights into serpentinization-driven, hydrothermal, alkaline environments, which are related to early Earth conditions. Temperature, hydration degree, pH and fluid composition are crucial factors regarding the formation, coexistence and transformation of such mineral phases. The rate of supersaturation, on the other hand, is a fundamental parameter to understand nucleation and crystal growth processes. All these parameters can be examined in a solution using different crystallization techniques. In the present study, we applied different crystallization techniques to synthesize and monitor the crystallization of Mg-bearing carbonates and hydroxides under abiotic conditions. Various crystallization techniques (counter-diffusion, vapor diffusion and unseeded solution mixing) were used to screen the formation conditions of each phase, transformation processes and structural development. Mineral and textural characterization of the different synthesized phases were carried out by X-ray diffraction (XRD), Raman spectroscopy and scanning electron microscopy coupled to dispersive energy spectroscopy (FE-SEM-EDS). Experimental investigation of the effect of pH level and silica content under variable reactant concentrations revealed the importance of Amorphous Magnesium Carbonate (AMC) in the formation of hydroxy-carbonate phases (hydromagnesite and dypingite). Micro-structural resemblance between AMC precursors and later stage crystalline phases highlights the

  16. Low-temperature polymorphic phase transition in a crystalline tripeptide L-Ala-L-Pro-Gly·H2O revealed by adiabatic calorimetry.

    PubMed

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

    2015-02-05

    We demonstrate application of precise adiabatic vacuum 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 vacuum 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.

  17. 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

  18. 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

  19. 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.

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

    DOE PAGES

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

    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

  1. 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

  2. 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

  3. Preformance Analysis of NH3-H2O Absorption Cycle

    NASA Astrophysics Data System (ADS)

    Tsujimori, Atsushi; Ozaki, Eiichi

    Different from H2O-LiBr absorption cycle, it is necessary to have rectifier between generator and condenser in NH3-H2O absorption cycle, because there mixes some steam in refrigerant vapor in the process of regenerating refrigerant from the ammonia strong aqueous solution. And in some case ex. partial load or heating, the efficiency of rectifier might decrease, if the flow rate of refrigerant vapor and ammonia aqueous solution decrease. As a result, steam flow into condenser with ammonia refrigerant vapor, which reduces cycle COPs of cooling and heating. Accordingly in order to evaluate the effect of ammonia concentration in refrigerant for the performance of NH3-H2O absorption heat pump, the simple design approach of modeling condenser and evaporator is introduced in this paper. In the model, the calculation of heat rate in condenser and evaporator was simplified considering the characteristic of NH3-H2O liquid-vapor equilibrium. Then the simulation for cycle perforance based on GAX absorption cycle was made using the efficiency of rectifier that established the ammonia concentration in refrigerant and it was derived that 3 [%] decrease of ammonia concentration in refrigerant induced 15 [%] decrcase of cooling COP and 7 [%] decrease of heating COP and that there existed the most suitable circulation ratio for each ammonia concentration in refrigerant.

  4. Variable-temperature rate coefficients of proton-transfer equilibrium reaction C2H4 + H3O+ ⇄ C2H5+ + H2O measured with a coaxial molecular beam radio frequency ring electrode ion trap.

    PubMed

    Smith, Mark A; Yuan, Bing; Sanov, Andrei

    2012-11-29

    The rate coefficients for the forward and reverse proton-transfer reactions C(2)H(4) + H(3)O(+) ⇄ C(2)H(5)(+) + H(2)O are studied with respect to independent varied neutral molecule and ion temperatures. The measurements are performed using a coaxial molecular beam radio frequency ring electrode ion trap at trap temperatures down to 23 K and beam temperatures up to 450 K. The temperature-dependent rate coefficients suggest that in this temperature window, the reaction proceeds through a statistically equilibrated complex. In order to explain the observed rate coefficients, a new type of reaction temperature was defined in these studies that considered collisional and internal (rotational and vibrational) degrees of freedom of both H(3)O(+) and C(2)H(4). The enthalpy and entropy of the equilibrium reaction deduced from a Van't Hoff plot are ΔH = (5.1 ± 0.5) kJ·mol(-1) and ΔS = (-15.0 ± 0.9) J·mol(-1)·K(-1), respectively.

  5. 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. Copyright © 2016 Elsevier B.V. All rights reserved.

  6. 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.

  7. 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

  8. 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.

  9. 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

  10. Understanding temperature and magnetic-field actuated magnetization polarity reversal in the Prussian blue analogue Cu0.73Mn0.77[Fe(CN)6].zH2O, using XMCD

    SciTech Connect

    Lahiri, Debdutta; Choi, Yongseong; Kumar, Amit; Ramanan, Nitya; Chattopadhyay, Soma; Sharma, Surinder; Haskel, Daniel; Yusuf, S. M.

    2016-03-01

    We have investigated the microscopic origin of temperature and magnetic-field actuated magnetization reversal in Cu0.73Mn0.77[Fe(CN)(6)]center dot zH(2)O, using XMCD. Our results show a fair deviation from the mean-field-theory in the form of different ordering temperatures of Fe and Mn sublattices. A preferential sign reversal of Mn spin under magnetic field and different spin cant angles for the two sublattices have also been observed. An antiferromagnetic coupling between the Fe and Mn sublattices along with different ordering temperatures (sublattice decoupling) for these sublattices explain the temperature-dependent magnetization reversal. Whereas, Mn spin reversal alone (under external magnetic field) is responsible for the observed field-dependent magnetization reversal. The dissimilar magnetic behavior of Fe and Mn sublattices in this cubic 3d-orbital system has been understood by invoking disparity and competition among inter-sublattice magnetic control parameters, viz. magnetic Zeeman energy, exchange coupling constant and magnetic anisotropy constant. Our results have significant design implications for future magnetic switches, by optimizing the competition among these magnetic control parameters.

  11. Quantum yields for OH production from 193 and 248 nm photolysis of HNO3 and H2O2

    NASA Astrophysics Data System (ADS)

    Schiffman, A.; Nelson, D. D., Jr.; Nesbitt, D. J.

    1993-05-01

    Flash kinetic spectroscopy in a flow tube is used to measure at room temperature the absolute yields for OH production from 193 and 248 nm photolysis of HNO3 and H2O2. The OH radicals are produced by excimer laser photolysis and probed via direct absorption of high resolution tunable IR laser light. The results indicate quantum yields for both precursors at both wavelengths which are less than the maximum possible values of 1 for H2O2. The present measurements are discussed in light of contrasting results suggested from other work.

  12. 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...

  13. 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...

  14. 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...

  15. 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...

  16. 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.

  17. 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.

  18. A review of high temperature co-electrolysis of H2O and CO2 to produce sustainable fuels using solid oxide electrolysis cells (SOECs): advanced materials and technology.

    PubMed

    Zheng, Yun; Wang, Jianchen; Yu, Bo; Zhang, Wenqiang; Chen, Jing; Qiao, Jinli; Zhang, Jiujun

    2017-03-06

    High-temperature solid oxide electrolysis cells (SOECs) are advanced electrochemical energy storage and conversion devices with high conversion/energy efficiencies. They offer attractive high-temperature co-electrolysis routes that reduce extra CO2 emissions, enable large-scale energy storage/conversion and facilitate the integration of renewable energies into the electric grid. Exciting new research has focused on CO2 electrochemical activation/conversion through a co-electrolysis process based on the assumption that difficult C[double bond, length as m-dash]O double bonds can be activated effectively through this electrochemical method. Based on existing investigations, this paper puts forth a comprehensive overview of recent and past developments in co-electrolysis with SOECs for CO2 conversion and utilization. Here, we discuss in detail the approaches of CO2 conversion, the developmental history, the basic principles, the economic feasibility of CO2/H2O co-electrolysis, and the diverse range of fuel electrodes as well as oxygen electrode materials. SOEC performance measurements, characterization and simulations are classified and presented in this paper. SOEC cell and stack designs, fabrications and scale-ups are also summarized and described. In particular, insights into CO2 electrochemical conversions, solid oxide cell material behaviors and degradation mechanisms are highlighted to obtain a better understanding of the high temperature electrolysis process in SOECs. Proposed research directions are also outlined to provide guidelines for future research.

  19. The H2O Content of Granite Embryos

    NASA Astrophysics Data System (ADS)

    Bartoli, O.; Cesare, B.; Remusat, L.; Acosta-Vigil, A.; Poli, S.

    2014-12-01

    Quantification of H2O contents of natural granites has been an on-going challenge owing to the extremely fugitive character of H2O during cooling and ascent of melts and magmas. Here we approach this problem by studying granites in their source region (i.e. the partially melted continental crust) and we present the first NanoSIMS analyses of anatectic melt inclusions (MI) hosted in peritectic phases of migmatites and granulites. These MI which totally crystallized upon slow cooling represent the embryos of the upper-crustal granites. The approach based on the combination of MI and NanoSIMS has been here tested on amphibolite-facies migmatites at Ronda (S Spain) that underwent fluid-present to fluid-absent melting at ~700 °C and ~5 kbar. Small (≤ 5 µm) crystallized MI trapped in garnet have been remelted using a piston-cylinder apparatus and they show leucogranitic compositions. We measure high and variable H2O contents (mean of 6.5±1.4 wt%) in these low-temperature, low-pressure granitic melts. We demonstrate that, when the entire population from the same host is considered, MI reveal the H2O content of melt in the specific volume of rock where the host garnet grew. Mean H2O values for the MI in different host crystals range from 5.4 to 9.1 wt%. This range is in rather good agreement with experimental models for granitic melts at the inferred P-T conditions. Our study documents for the first time the occurrence of H2O heterogeneities in natural granitic melts at the source region. These heterogeneities are interpreted to reflect the birth of granitic melts under conditions of "mosaic" equilibrium, where the distinct fractions of melt experience different buffering assemblages at the micro-scale, with concomitant differences in melt H2O content. These results confirm the need for small-scale geochemical studies on natural samples to improve our quantitative understanding of crustal melting and granite formation. The same approach adopted here can be applied to

  20. The H2O content of granite embryos

    NASA Astrophysics Data System (ADS)

    Bartoli, Omar; Cesare, Bernardo; Remusat, Laurent; Acosta-Vigil, Antonio; Poli, Stefano

    2015-04-01

    Quantification of H2O contents of natural granites has been an on-going challenge owing to the extremely fugitive character of H2O during cooling and ascent of melts and magmas. Here we approach this problem by studying granites in their source region (i.e. the partially melted continental crust) and we present the first NanoSIMS analyses of anatectic melt inclusions (MI) hosted in peritectic phases of migmatites and granulites. These MI which totally crystallized upon slow cooling represent the embryos of the upper-crustal granites [1, 2, 3]. The approach based on the combination of MI and NanoSIMS has been here tested on amphibolite-facies migmatites at Ronda (S Spain) that underwent fluid-present to fluid-absent melting at ~700 °C and ~5 kbar. Small (≤ 5 µm) crystallized MI trapped in garnet have been remelted using a piston-cylinder apparatus and they show leucogranitic compositions. We measure high and variable H2O contents (mean of 6.5±1.4 wt%) in these low-temperature, low-pressure granitic melts. We demonstrate that, when the entire population from the same host is considered, MI reveal the H2O content of melt in the specific volume of rock where the host garnet grew. Mean H2O values for the MI in different host crystals range from 5.4 to 9.1 wt%. This range is in rather good agreement with experimental models for granitic melts at the inferred P-T conditions. Our study documents for the first time the occurrence of H2O heterogeneities in natural granitic melts at the source region [3]. These heterogeneities are interpreted to reflect the birth of granitic melts under conditions of "mosaic" equilibrium, where the distinct fractions of melt experience different buffering assemblages at the micro-scale, with concomitant differences in melt H2O content. These results confirm the need for small-scale geochemical studies on natural samples to improve our quantitative understanding of crustal melting and granite formation. The same approach adopted here can

  1. H2O Paradox and its Implications on H2O in Moon

    NASA Astrophysics Data System (ADS)

    Zhang, Youxue

    2017-04-01

    The concentration of H2O in the mantle of a planetary body plays a significant role in the viscosity and partial melting and hence the convection and evolution of the planetary body. Even though the composition of the primitive terrestrial mantle (PTM) is thought to be well known [1-2], the concentration of H2O in PTM remains paradoxial because different methods of estimation give different results [3]: Using H2O/Ce ratio in MORB and OIB and Ce concentration in PTM, the H2O concentration in PTM would be (300÷×1.5) ppm; using mass balance by adding surface water to the mantle [3-4], H2O concentration in PTM would be (900÷×1.3) ppm [2-3]. The inconsistency based on these two seemingly reliable methods is referred to as the H2O paradox [3]. For Moon, H2O contents in the primitive lunar mantle (PLM) estimated from H2O in plagioclase in lunar anorthosite and that from H2O/Ce ratio in melt inclusions are roughly consistent at ˜110 ppm [5-6] even though there is still debate about the volatile depletion trend [7]. One possible solution to the H2O paradox in PTM is to assume that early Earth experienced whole mantle degassing, which lowered the H2O/Ce ratio in the whole mantle but without depleting Ce in the mantle. The second possible solution is that some deep Earth reservoirs with high H2O/Ce ratios have not been sampled by MORB and OIB. Candidates include the transition zone [8] and the D" layer. The third possible solution is that ocean water only partially originated from mantle degassing, but partially from extraterrestrial sources such as comets [9-10]. At present, there is not enough information to determine which scenario is the answer to the H2O paradox. On the other hand, each scenario would have its own implications to H2O in PLM. If the first scenario applies to Moon, because degassed H2O or H2 would have escaped from the lunar surface, the very early lunar mantle could have much higher H2O [11] than that obtained using the H2O/Ce ratio method. The

  2. Measurements of the Activity of dissolved H2O in an Andesite Melt

    NASA Astrophysics Data System (ADS)

    Moore, G. M.; Touran, J. P.; Pu, X.; Kelley, K. A.; Cottrell, E.; Ghiorso, M. S.

    2016-12-01

    The large effect of dissolved H2O on the physical and chemical nature of silicate melts, and its role in driving volcanism, is well known and underscores the importance of this volatile component. A complete understanding of the chemical behavior of dissolved H2O in silicate melts requires the quantification of its thermodynamic activity as a function of pressure, temperature, and melt composition, particularly at low H2O contents (i.e. at under-saturated conditions). Knowledge of the activity of H2O in silicate melts at H2O-undersaturated conditions will improve our understanding of hydrous phase equilibria, as well as our models of physical melt properties. Measurement of the activity of any silicate melt component, much less that of a volatile component such as H2O, is a difficult experimental task however. By using a modified double capsule design (Matjuschkin et al, 2015) to control oxygen fugacity in piston cylinder experiments, along with high precision X-ray absorption techniques (XANES) to measure iron oxidation state in silicate glasses (Cottrell et al, 2009), we are able to constrain the H2O activity in silicate melts at under-saturated conditions. Preliminary results on an andesite melt with low H2O content (3 wt%) have been shown (Moore et al, 2016) to match predicted H2O activity values calculated using the H2O equation of state of Duan and Zhang (1996) and the H2O solubility model of Ghiorso and Gualda (2015). More recent results on the same andesite melt containing approximately 5 wt% H2O however show a large negative deviation from the predicted values. Reversal experiments involving an oxidized starting material are ongoing, as well as further characterization of the samples to detect the presence of possible contaminants that would induce reduction of the melt beyond that related to the H2O activity (e.g. graphite contamination).

  3. Hydrogen polyoxides H2O3 and H2O4 as components of peroxy radical condensate obtained from electro-dissociated water vapor

    NASA Astrophysics Data System (ADS)

    Levanov, Alexander V.; Isaykina, Oksana Ya.; Antipenko, Ewald E.; Lunin, Valerii V.

    2015-02-01

    The peroxy radical condensate synthesized from electro-dissociated water vapor has been investigated by the methods of Raman spectroscopy and chemical analysis of its decomposition products. It has been found that hydrogen peroxide H2O2 and trioxide H2O3 (besides water H2O) are the main components. Also hydrogen tetroxide H2O4 is present in the PRC, but its amount is small. On heating, hydrogen tetroxide breaks down at the first step of the condensate decomposition in the solid phase; hydrogen trioxide chiefly disappears at higher temperatures during the decomposition in the liquid phase. These results make it possible to estimate the experimental value of hydrogen trioxide enthalpy of formation in the liquid solution, ΔfH°220-250(H2O3, aq.) = -32 ± 4 kcal/mol, from the thermochemical data, obtained in references Reznitskii et al. (1958) and Skorokhodov et al. (1959, 1961).

  4. Role of H2O in Generating Subduction Zone Earthquakes

    NASA Astrophysics Data System (ADS)

    Hasegawa, A.

    2017-03-01

    A dense nationwide seismic network and high seismic activity in Japan have provided a large volume of high-quality data, enabling high-resolution imaging of the seismic structures defining the Japanese subduction zones. Here, the role of H2O in generating earthquakes in subduction zones is discussed based mainly on recent seismic studies in Japan using these high-quality data. Locations of intermediate-depth intraslab earthquakes and seismic velocity and attenuation structures within the subducted slab provide evidence that strongly supports intermediate-depth intraslab earthquakes, although the details leading to the earthquake rupture are still poorly understood. Coseismic rotations of the principal stress axes observed after great megathrust earthquakes demonstrate that the plate interface is very weak, which is probably caused by overpressured fluids. Detailed tomographic imaging of the seismic velocity structure in and around plate boundary zones suggests that interplate coupling is affected by local fluid overpressure. Seismic tomography studies also show the presence of inclined sheet-like seismic low-velocity, high-attenuation zones in the mantle wedge. These may correspond to the upwelling flow portion of subduction-induced secondary convection in the mantle wedge. The upwelling flows reach the arc Moho directly beneath the volcanic areas, suggesting a direct relationship. H2O originally liberated from the subducted slab is transported by this upwelling flow to the arc crust. The H2O that reaches the crust is overpressured above hydrostatic values, weakening the surrounding crustal rocks and decreasing the shear strength of faults, thereby inducing shallow inland earthquakes. These observations suggest that H2O expelled from the subducting slab plays an important role in generating subduction zone earthquakes both within the subduction zone itself and within the magmatic arc occupying its hanging wall.

  5. 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

  6. Low energy isomers of (H2O)25 from a hierarchical method based on Monte Carlo Temperature Basin Paving and Molecular Tailoring Approaches benchmarked by full MP2 calculations

    SciTech Connect

    Sahu, Nityananda; Gadre, Shridhar R.; 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 (MCTBP) sampling of the cluster’s Potential Energy Surface (PES) with the Effective Fragment Potential (EFP), subsequent geometry optimization using the Molecular Tailoring fragmentation Approach (MTA) and final refinement at the second order Møller Plesset perturbation (MP2) level of theory. The MTA geometry optimizations used between 14 and 18 main fragments with maximum sizes between 11 and 14 water molecules and average size of 10 water molecules, whose energies and gradients were computed at the MP2 level. The MTA-MP2 optimized geometries were found to be quite close (within < 0.5 kcal/mol) to the ones obtained from the MP2 optimization of the whole cluster. The grafting of the MTA-MP2 energies yields electronic energies that are within < 5×10-4 a.u. from the MP2 results for the whole cluster while preserving their energy order. The MTA-MP2 method was also found to reproduce the MP2 harmonic vibrational frequencies in both the HOH bending and the OH stretching regions.

  7. 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.

  8. 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.

  9. 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.; hide

    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.

  10. Theoretical Modeling of Water Exchange on [Pd(H(2)O)(4)](2+), [Pt(H(2)O)(4)](2+), and trans-[PtCl(2)(H(2)O)(2)].

    PubMed

    Deeth, Robert J.; Elding, Lars I.

    1996-08-14

    )], respectively. The calculated activation enthalpy for a hypothetical dissociative water exchange at [Pd(H(2)O)(4)](2+) is 199 kJ/mol. A qualitative analysis of the modeling procedure, the relative hydration enthalpies, and the zero-point and finite temperature corrections yields an estimated uncertainty for the theoretical activation enthalpies of about 15 kJ/mol.

  11. 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.

  12. Thermodynamic Properties of LiBr/H2O Solution

    NASA Astrophysics Data System (ADS)

    Murakami, Kazuhiko; Sato, Haruki; Watanabe, Koichi

    Although most of the absorption refrigeration/heat pump systems use LiBr/H2O solution for absorbent/refrigerant pair, there exist only a limited number of reliable sets of data on the bubble-point pressures of LiBr/H2O solution. The objective of the present study is to reveal the concentration and temperature dependence of bubble-point pressures of LiBr/H2O solution over a wide range of parameters so as to provide more precise set of thermodynamic property data for advanced design of the absorption refrigeration/heat pump equipments. A total of 44 bubble-point pressures have been measured along seven concentration isopleths of 20, 30, 40, 45, 50, 58 and 60 wt%LiBr solution which cover the range of temperatures 283-413 K and of pressures up to 300 kPa. The experimental uncertainties of temperature, pressure and concentration measurements were not greater than ±20mK, ±0.1 kPa and ±0.1wt%, respectively.

  13. 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.

  14. A shock origin for interstellar H2O masers

    NASA Technical Reports Server (NTRS)

    Hollenbach, David; Elitzur, Moshe; Mckee, Christopher F.

    1993-01-01

    We present a comprehensive model for the powerful H2O masers observed in starforming regions. In this model the masers occur behind dissociative shocks propagating in dense regions. This paper focuses on high-velocity dissociative shocks in which the heat of H2 reformation on dust grains maintains a large column of 300 - 400 K gas, where the chemistry drives a considerable fraction of the oxygen not in CO to form H2O. The H2O column densities, the hydrogen densities, and the warm temperatures produced by these shocks are sufficiently high to enable powerful maser action, where the maser is excited by thermal collisions with H atoms and H2 molecules. A critical ingredient in determining the shock structure is the magnetic pressure, and the fields required by our models are in agreement with recent observations. The observed brightness temperatures are the result of coherent velocity regions which have dimensions in the shock plane that are five to 50 times the postshock thickness.

  15. A shock origin for interstellar H2O masers

    NASA Technical Reports Server (NTRS)

    Hollenbach, David; Elitzur, Moshe; Mckee, Christopher F.

    1993-01-01

    We present a comprehensive model for the powerful H2O masers observed in starforming regions. In this model the masers occur behind dissociative shocks propagating in dense regions. This paper focuses on high-velocity dissociative shocks in which the heat of H2 reformation on dust grains maintains a large column of 300 - 400 K gas, where the chemistry drives a considerable fraction of the oxygen not in CO to form H2O. The H2O column densities, the hydrogen densities, and the warm temperatures produced by these shocks are sufficiently high to enable powerful maser action, where the maser is excited by thermal collisions with H atoms and H2 molecules. A critical ingredient in determining the shock structure is the magnetic pressure, and the fields required by our models are in agreement with recent observations. The observed brightness temperatures are the result of coherent velocity regions which have dimensions in the shock plane that are five to 50 times the postshock thickness.

  16. 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.

  17. EPR of Mn2+ -doped NiSO4 . 7H2O and MgSO4 . 7H2O: Mn2+ -Ni2+ exchange constant

    NASA Astrophysics Data System (ADS)

    Misra, Sushil K.; Kahrizi, Mojtaba

    1984-11-01

    X-band EPR measurements on Mn2+ -doped isostructural single crystals of paramagnetic NiSO4 . 7H2O and diamagnetic MgSO4 . 7H2O have been made at room, liquid-nitrogen, and liquid-helium temperatures. The spin-Hamiltonian parameters are evaluated from the data using a rigorous least-squares-fitting program suitable for electron-nuclear spin-coupled systems. Using the g shift in the paramagnetic lattice from that in the diamagnetic lattice a value of 4.293 GHz for the Mn2+-Ni2+ exchange constant in NiSO4 . 7H2O is estimated. For NiSO4 . 7H2O host the linewidths exhibit temperature and magnetic field dependence. The temperature dependence of the zero-field splitting parameter b02 for both hosts is found to be linear, thus being explained as mainly due to the thermal expansion of the lattice.

  18. 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.

  19. 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

  20. Solar kerosene from H2O and CO2

    NASA Astrophysics Data System (ADS)

    Furler, P.; Marxer, D.; Scheffe, J.; Reinalda, D.; Geerlings, H.; Falter, C.; Batteiger, V.; Sizmann, A.; Steinfeld, A.

    2017-06-01

    The entire production chain for renewable kerosene obtained directly from sunlight, H2O, and CO2 is experimentally demonstrated. The key component of the production process is a high-temperature solar reactor containing a reticulated porous ceramic (RPC) structure made of ceria, which enables the splitting of H2O and CO2 via a 2-step thermochemical redox cycle. In the 1st reduction step, ceria is endo-thermally reduced using concentrated solar radiation as the energy source of process heat. In the 2nd oxidation step, nonstoichiometric ceria reacts with H2O and CO2 to form H2 and CO - syngas - which is finally converted into kerosene by the Fischer-Tropsch process. The RPC featured dual-scale porosity for enhanced heat and mass transfer: mm-size pores for volumetric radiation absorption during the reduction step and μm-size pores within its struts for fast kinetics during the oxidation step. We report on the engineering design of the solar reactor and the experimental demonstration of over 290 consecutive redox cycles for producing high-quality syngas suitable for the processing of liquid hydrocarbon fuels.

  1. 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.

  2. 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.

  3. 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.

  4. Ice-like H2O in hemimorphite, Zn4Si2O7(OH)2H2O: Cp and entropy behavior of confined H2O in microporous silicates

    NASA Astrophysics Data System (ADS)

    Geiger, C. A.; Dachs, E.

    2009-12-01

    The H2O molecule plays a key role in many planetary processes and, thus, it is necessary to investigate how it interacts with a variety of natural materials. In this regard the role of hydrogen bonding is of central importance, but it has received relatively little study. Certain micro/nanoporous silicates offer the possibility for one to investigate the nature of confined H2O and hydrogen bonding at a relatively simple, yet fundamental level. Hemimorphite, Zn4Si2O7(OH)2.H2O, and its dehydrated analog Zn4Si2O7(OH)2 were studied by low-temperature relaxation microcalorimetry and their heat capacity determined to analyze the behavior of the confined H2O between 5 and 300 K. An analysis of the data, which are corrected for the presence of a phase transition, shows that the Cp of H2O in hemimorphite behaves more similar to the Cp of ice than to liquid water or steam. The H2O molecule, with its four planar hydrogen bonds in hemimorphite, as well as its tetrahedral coordination in ice, is more rigidly hydrogen bonded in both than in liquid water. This is reflected in their respective Cp behavior. The heat capacity and entropy for the dehydration reaction at 298 K are ΔCprxn = -2.1 ± 3.6 J/molK and ΔSrxn = 134.7 ± 4.0 J/molK. Cp behavior at 0 K < T < 300 K and entropy values at 298 K for confined H2O in various microporous silicates were analyzed. The entropy for confined H2O in hemimorphite, and the two zeolites analcime, and mordenite is approximately 54 J/molK at 298 K, while that for cordierite is considerably larger. The strength of the interactions (e.g., H bonding) between a H2O molecule and its surroundings increases approximately from steam > cordierite > analcime > hemimorphite ≥ mordenite > heulandite > natrolite ≈ scolecite > liquid H2O > ice and, in the case of microporous silicates, is inversely proportional to the S of the confined H2O.

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

    PubMed

    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

    2016-09-02

    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.

  6. 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.

  7. 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.

  8. 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.

  9. Experimental Determination of the H2O-undersaturated Peridotite Solidus

    NASA Astrophysics Data System (ADS)

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

    2015-12-01

    Knowledge of the H2O-undersaturated lherzolite solidus places important constraints on the process of melt generation beneath oceanic spreading centers. While it is generally accepted that the small concentration of H2O (~50-200 ug/g) dissolved in the oceanic upper mantle has a strong influence on the peridotite solidus, but this effect has not been directly determined through experiments. This is because (1) precisely controlling low concentrations of H2O in high-pressure melting experiments is thought to be difficult, (2) small amounts of melt are difficult to identify, and (3) the size of mineral grains that grow in near-solidus experiments is too small to be analyzed for H2O by either Fourier transform infrared (FTIR) spectroscopy or secondary ion mass spectrometry (SIMS). We have developed an experimental approach for determining the peridotite solidus as a function of H2O content that overcomes these difficulties. Our approach utilizes large (~300 um diameter) spheres of San Carlos olivine to monitor the concentration and behavior of H2O in our experiments.. The spheres are mixed in 5:95 proportions with a synthetic peridotite that has the composition of the depleted MORB mantle of Workman and Hart (2005). Partial melting experiments are conducted in is a piston cylinder device using pre-conditioned Au80Pd20 capsules. During an experiment, the H2O content of the San Carlos olivine spheres diffusively equilibrates with the peridotite matrix. After each experiment, the concentration of H2O dissolved in the olivine spheres is determined by secondary ion mass spectrometry. By analyzing the H2O content of the San Carlos olivine spheres and performing a simple mass balance, we can then calculate the amount of H2O in the capsule. The spheres also provides a means to determine the solidus temperature due to the strong partitioning of H2O into silicate melt compared to olivine, pyroxene, and spinel. When a small amount of melt is present the H2O partitions into the

  10. 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.

  11. Confinement Effects on the Nuclear Spin Isomer Conversion of H2O.

    PubMed

    Turgeon, Pierre-Alexandre; Vermette, Jonathan; Alexandrowicz, Gil; Peperstraete, Yoann; Philippe, Laurent; Bertin, Mathieu; Fillion, Jean-Hugues; Michaut, Xavier; Ayotte, Patrick

    2017-03-02

    The mechanism for interconversion between the nuclear spin isomers (NSI) of H2O remains shrouded in uncertainties. The temperature dependence displayed by NSI interconversion rates for H2O isolated in an argon matrix provides evidence that confinement effects are responsible for the dramatic increase in their kinetics with respect to the gas phase, providing new pathways for o-H2O↔p-H2O conversion in endohedral compounds. This reveals intramolecular aspects of the interconversion mechanism which may improve methodologies for the separation and storage of NSI en route to applications ranging from magnetic resonance spectroscopy and imaging to interpretations of spin temperatures in the interstellar medium.

  12. Superlow elastic stability of MgSO4-H2O ice

    NASA Astrophysics Data System (ADS)

    Fateev, E. G.

    2012-04-01

    A superlow elastic stability of low-saline MgSO4-H2O ice in a broad range of low temperatures (100-255 K) has been observed under the conditions of strong (0-1 GPa) uniaxial compression. The level of elastic stability of the MgSO4-H2O ice (containing a low mass fraction of MgSO4 within p = 0.0001-0.01) was 15-30 times smaller than in pure freshwater ice and also significantly lower than in NaCl-H2O solid solutions at low temperatures (100-215 K).

  13. 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

  14. Reaction kinetics of waste sulfuric acid using H2O2 catalytic oxidation.

    PubMed

    Wang, Jiade; Hong, Binxun; Tong, Xinyang; Qiu, Shufeng

    2016-12-01

    The process of recovering waste sulfuric acids using H2O2 catalytic oxidation is studied in this paper. Activated carbon was used as catalyst. Main operating parameters, such as temperature, feed rate of H2O2, and catalyst dosage, have effects on the removal of impurities from waste sulfuric acids. The reaction kinetics of H2O2 catalytic oxidation on impurities are discussed. At a temperature of 90°C, H2O2 feeding rate of 50 g (kg waste acid)(-1) per hour, and catalyst dosage of 0.2 wt% (waste acid weight), the removal efficiencies of COD and chrominance were both more than 99%, the recovery ratio of sulfuric acid was more than 95%, and the utilization ratio of H2O2 was 88.57%. Waste sulfuric acid is a big environmental problem in China. The amount of waste sulfuric acid is huge every year. Many small and medium-sized businesses produced lots of waste acids, but they don't have an appropriate method to treat and recover them. H2O2 catalytic oxidation has been used to treat and recover waste sulfuric acid and activated carbon is the catalyst here. Main parameters, such as temperature, feed rate of H2O2, and catalyst dosage, have been investigated. The reaction kinetics are discussed. This method can be economical and feasible for most small and medium-sized businesses.

  15. 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.

  16. H2O and CO coadsorption on Co (0001): The effect of intermolecular hydrogen bond

    NASA Astrophysics Data System (ADS)

    Jiawei, Wu; Chen, Jun; Guo, Qing; Su, Hai-Yan; Dai, Dongxu; Yang, Xueming

    2017-09-01

    The co-adsorption of CO and H2O on a Co(0001) surface at 100 K has been systematically studied using temperature programmed desorption (TPD) and density functional theory (DFT) calculations. While the TPD spectra of CO is almost not affected by the presence of H2O, the stabilization of H2O by co-adsorbed CO is found for the first time in a large coverage range (0.15 ML <θCO < 0.66 ML; 0.01 ML <θH2O < 0.6 ML). When the coverage of predosed CO is lower than 0.27 ML, the formerly single desorption peak of H2O is gradually separated into three peaks at 0.6 ML coverage. Those at lower and higher temperatures may be attributed to the repulsive interaction between H2O molecules and the attractive interaction between H2O and CO molecules, respectively. With increasing the coverage of predosed CO, not only the position of the high temperature peak shifts toward higher temperature (by about 15 K), but the intensity is greatly strengthened until a maximum is achieved when θCO = 0.36 ML. DFT calculations suggest that the attractive interaction between H2O and CO on Co(0001) originates from the formation of intermolecular hydrogen bonds. This work not only provides insights into water gas shift reactions with H2O and CO as reactants, but opens new avenues for a volume of catalytic process of technological importance.

  17. Nuclear Magnetic Resonance as a Probe of Meso-timescale Dynamics: Ion and H2O Behavior at Mineral-H2O Interfaces

    NASA Astrophysics Data System (ADS)

    Bowers, G. M.; Kirkpatrick, R. J.; Singer, J. W.

    2012-12-01

    One of the important meso-scales in geochemistry is the meso-timescale that is characteristic of processes too slow to probe with light spectroscopy but too fast to probe macroscopically. Nuclear magnetic resonance (NMR) spectroscopy is one of the only analytical methods with dynamic sensitivity to motions with correlation times on the 10-9 to 1 s timescales and is thus a uniquely powerful probe of meso-timescale dynamic behavior. Here, we describe the results of several studies exploring the meso-timescale motion of ions and H2O at the mineral-H2O interface of hectorite, a smectite clay mineral.1-3 2H, 23Na, 39K and 43Ca NMR results show that H2O molecules associated with the interface undergo anisotropic reorientation due to proximity to the surface and surface-associated cations. This motion can be described by rotational diffusion of the H2O molecule about its C2 symmetry axis at GHz frequencies combined with hopping of the H2O molecule about the normal to the smectite surface at ~>200 kHz. This model describes well the observed 2H NMR spectra of Na+, K+, and Ca2+ hectorites over a range temperatures between -80°C and 50°C, with the specific range dependent only on the total system H2O content. At temperatures above -20°C, systems with excess H2O with respect to a two-layer hydrate (low-H2O pastes through dilute aqueous suspensions) experience additional dynamic averaging due to H2O exchange between cation hydration shells, surface-sorbed species, and bulk inter-particle water. The extent of 2H averaging due to this exchange mechanism is strongly affected by the total H2O content in the system, the identity of the charge balancing cation, and the temperature. The dynamic averaging mechanisms affecting the cationic NMR resonances in these systems become dominated by diffusional processes at progressively lower temperatures as the hydration energy of the cation increases. These interfacial cation dynamics and binding sites are strongly affected by surface

  18. Influence of monolayer amounts of HNO3 on the evaporation rate of H2O over ice in the range 179 to 208 K: a quartz crystal microbalance study.

    PubMed

    Delval, Christophe; Rossi, Michel J

    2005-08-18

    The evaporation flux J(ev) of H2O from thin H2O ice films containing between 0.5 and 7 monolayers of HNO3 has been measured in the range 179 to 208 K under both molecular and stirred flow conditions in isothermal experiments. FTIR absorption of the HNO3/H2O condensate revealed the formation of metastable alpha-NAT (HNO(3).3H2O) converting to stable beta-NAT at 205 K. After deposition of HNO3 for 16-80 s on a 1 mum thick pure ice film at a deposition rate in the range (6-60) x 10(12) molecules s(-1) the initial evaporative flux J(ev)(H2O) was always that of pure ice. J(ev)(H2O) gradually decreased with the evaporation of H2O and the concomitant increase of the average mole fraction of HNO3, chi(HNO3), indicating the presence of an amorphous mixture of H2O/HNO3 that is called complexed or (c)-ice whose vapor pressure is that of pure ice. The final value of J(ev) was smaller by factors varying from 2.7 to 65 relative to pure ice. Depending on the doping conditions and temperature of the ice film the pure ice thickness d(D) of the ice film for which J(ev) < 0.85J(ev)(pure ice) varied between 130 and 700 nm compared to the 1000 nm thick original ice film at 208 and 191 K, respectively, in what seems to be an inverse temperature dependence. There exist three different types of H2O molecules under the present experimental conditions, namely (a) free H2O corresponding to pure ice, (b) complexed H2O or c-ice, and (c) H2O molecules originating from the breakup of NAT or amorphous H2O/HNO3 mixtures. The significant decrease of J(ev)(H2O) with increasing chi(HNO3) leads to an increase of the evaporative lifetime of atmospheric ice particles in the presence of HNO3 and may help explain the occurrence of persistent and/or large contaminated ice particles at certain atmospheric conditions.

  19. Heterogeneous degradation of precipitated hexamine from wastewater by catalytic function of silicotungstic acid in the presence of H2O2 and H2O2/Fe2+.

    PubMed

    Taghdiri, Mehdi; Saadatjou, Naghi; Zamani, Navid; Farrokhi, Reyhaneh

    2013-02-15

    The industrial wastewater produced by hexamine plants is considered as a major environmental polluting factor due to resistance to biodegradation. So the treatment of such wastewater is required. In this work, the removal of hexamine from wastewater and its degradation have been studied. Hexamine was precipitated through formation of an insoluble and stable compound with silicotungstic acid. The oxidative heterogeneous degradation of precipitated hexamine was carried out with hydrogen peroxide (H(2)O(2)) aqueous solution and H(2)O(2)/Fe(2+) under the catalysis of silicotungstic acid. The operating conditions including amount of precipitate, hydrogen peroxide and ferrous ion dosage, temperature, time and pH were optimized by evaluating the removal of total organic carbon from system. A total organic carbon conversion higher than 70% was achieved in the presence of H(2)O(2)/Fe(2+). The experimental results showed that hexamine can be effectively degraded with H(2)O(2) and H(2)O(2)/Fe(2+) under the catalysis of silicotungstic acid. It was interesting that the solution of dissolved precipitate with H(2)O(2) can re-react with hexamine after the removal of excess hydrogen peroxide. This observation indicates the catalysis role of silicotungstic acid in the degradation of hexamine. A kinetic analysis based on total organic carbon reduction was carried out. The two steps mechanism was proposed for the degradation of hexamine.

  20. 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

  1. Effects of ionizing radiation and temperature on uranyl silicates: soddyite (UO2)2(SiO4)(H2O)2 and Uranophane Ca(UO2)2(SiO3OH)2·5H2O.

    PubMed

    Sureda, R; Casas, I; Giménez, J; de Pablo, J; Quiñones, J; Zhang, J; Ewing, R C

    2011-03-15

    The stability of soddyite under electron irradiation has been studied over the temperature range of 25-300 °C. At room temperature, soddyite undergoes a crystalline-to-amorphous transformation (amorphization) at a total dose of 6.38 × 10(8) Gy. The electron beam irradiation results suggest that the soddyite structure is susceptible to radiation-induced nanocrystallization of UO(2). The temperature dependence of amorphization dose increases linearly up to 300 °C. A thermogravimetric and calorimetric analysis (TGA-DSC) combined with X-ray diffraction (XRD) indicates that soddyite retains its water groups up to 400 °C, followed by the collapse of the structure. Based on thermal analysis of uranophane, the removal of some water groups at relatively low temperatures provokes the collapse of the uranophane structure. This structural change appears to be the reason for the increase of amorphization dose at 140 °C. According to the results obtained, radiation field of a nuclear waste repository, rather than temperature effects, may cause changes in the crystallinity of soddyite and affect its stability during long-term storage.

  2. Peroxiredoxin-2 and STAT3 form a redox relay for H2O2 signaling.

    PubMed

    Sobotta, Mirko C; Liou, Willy; Stöcker, Sarah; Talwar, Deepti; Oehler, Michael; Ruppert, Thomas; Scharf, Annette N D; Dick, Tobias P

    2015-01-01

    Hydrogen peroxide (H(2)O(2)) acts as a signaling messenger by oxidatively modifying distinct cysteinyl thiols in distinct target proteins. However, it remains unclear how redox-regulated proteins, which often have low intrinsic reactivity towards H(2)O(2) (k(app) ∼1-10 M(-1) s(-1)), can be specifically and efficiently oxidized by H(2)O(2). Moreover, cellular thiol peroxidases, which are highly abundant and efficient H(2)O(2) scavengers, should effectively eliminate virtually all of the H(2)O(2) produced in the cell. Here, we show that the thiol peroxidase peroxiredoxin-2 (Prx2), one of the most H(2)O(2)-reactive proteins in the cell (k(app) ∼10(7)-10(8) M(-1) s(-1)), acts as a H(2)O(2) signal receptor and transmitter in transcription factor redox regulation. Prx2 forms a redox relay with the transcription factor STAT3 in which oxidative equivalents flow from Prx2 to STAT3. The redox relay generates disulfide-linked STAT3 oligomers with attenuated transcriptional activity. Cytokine-induced STAT3 signaling is accompanied by Prx2 and STAT3 oxidation and is modulated by Prx2 expression levels.

  3. Experimental and Theoretical Kinetics for the H2O H2/D2 H3O /H2DO H/DReactions: Observation of the Rotational Effect in the Temperature Dependence (Postprint)

    DTIC Science & Technology

    2014-11-14

    the water molecular ion and molecular hydrogen is a key step in the formation of hydroxyl radical and water molecules in the interstellar medium.1−3...L min−1) and temperature. After traveling the length of the flow tube, the core of the flow is sampled through a truncated nosecone with a 2 mm...Cheuk Ng for numerous stimulating discussions. ■ REFERENCES (1) Herbst, E.; Klemperer, W. Formation and Depletion of Molecules in Dense Interstellar

  4. Planar H2O masers in star-forming regions

    NASA Technical Reports Server (NTRS)

    Elitzur, Moshe; Hollenbach, David J.; Mckee, Christopher F.

    1992-01-01

    The paper examines the planar geometry of shocked material, which is the key property in enabling the high brightness temperatures of H2O masers in star-forming regions. The brightness temperature, beaming angle, and the maser spot size are determined for thin, saturated planar masers under the assumption that the velocity change across the maser due to ordered motions is small compared with the thermal or microturbulent line width. For a given set of physical parameters, the brightness temperature is essentially fully determined by the length of the velocity-coherent region in the shocked plane along the line of sight. Effective aspect ratios (about 5-50) are found that are in agreement with values previously inferred from observed brightness temperatures.

  5. Planar H2O masers in star-forming regions

    NASA Technical Reports Server (NTRS)

    Elitzur, Moshe; Hollenbach, David J.; Mckee, Christopher F.

    1992-01-01

    The paper examines the planar geometry of shocked material, which is the key property in enabling the high brightness temperatures of H2O masers in star-forming regions. The brightness temperature, beaming angle, and the maser spot size are determined for thin, saturated planar masers under the assumption that the velocity change across the maser due to ordered motions is small compared with the thermal or microturbulent line width. For a given set of physical parameters, the brightness temperature is essentially fully determined by the length of the velocity-coherent region in the shocked plane along the line of sight. Effective aspect ratios (about 5-50) are found that are in agreement with values previously inferred from observed brightness temperatures.

  6. 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.

    2016-12-01

    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 is 695 ± 5 °C and the liquid composition is18.14±1.35 wt% H2O. The temperature dependence of the fluid-undersaturated liquidus curve in the system NaAlSi3O8-H2O varies with H2O wt% (wH2O) according to T = -2.0331*10-3wH2O3 + 1.6497wH2O2 - 58.963 wH2O+ 1235.5 °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 (aH2O) in liquids at vapor saturated melting exploited low Cl solubility (<0.95 wt%) in liquids and low albite solubility in the presence of H2O-NaCl fluids, which together make possible H2O activity measurement in melts equilibrated with NaCl-H2O solutions. When combined with activity data for H2O-NaCl fluids, experimentally determined aH2O along the liquidus is described by T = -469.16aH2O0.5 - 93.382aH2O + 1235.5 °C At 1 GPa, H2O activities in hydrous albitic melts in H2O-NaCl fluids agree with those in the presence of H2O-CO2 fluids. Our results constrain an asymmetric regular solution model for the mixing of Na1/8Al1/8Si3/8O and H2O, yielding Margules parameters of = 25.56±0.54 and = 10.50±0.74 kJ/mole. The results imply critical mixing of

  7. Infrared absorption of H_2_O toward massive young stars.

    NASA Astrophysics Data System (ADS)

    van Dishoeck, E. F.; Helmich, F. P.

    1996-11-01

    We present ISO-SWS observations of absorption lines of gas-phase water within its bending vibrational mode at 6μm toward four massive young stars, which cover a range in physical parameters. Hot water with an excitation temperature >200K is detected toward GL 2136 and GL 4176, in addition to GL 2591 discussed by Helmich et al. (1996A&A...315L.173H). The abundance of water with respect to H_2_ is high in these regions, ~(2-3)x10^-5^, and comparable to the solid H_2_O abundance. In contrast, no gas-phase water absorption lines are seen toward NGC 7538 IRS9. The amount of gas-phase water is correlated with the column density of warm gas along the line of sight. Infrared observations of a larger variety of sources may provide insight into the relative importance of evaporation of grain mantles vs. high temperature gas-phase chemistry in producing the observed high abundance of H_2_O.

  8. 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.

  9. 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.

  10. 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.

  11. 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).

  12. Dissolution of Quartz, Albite and K-feldspar Into H2O-Saturated Haplogranitic Melt at 800oC and 200 MPa: Diffusive Transport Properties of Granitic Melts at Crustal Anatectic Temperatures

    NASA Astrophysics Data System (ADS)

    Acosta, A.; London, D.; Dewers, T.; Morgan, G.

    2002-12-01

    With the aim of investigating the diffusive transport properties of granitic melts at crustal anatectic conditions and obtaining some constraints on speciation and coordination in the melt, we conducted albite, K-feldspar and quartz dissolution experiments in H2O-saturated metaluminous haplogranitic glass (nominal composition of the 200 MPa H2O-saturated haplogranite eutectic of Tuttle and Bowen, 1958) at 800oC and 200 MPa. Mineral and glass cylinders were juxtaposed against flat polished surfaces inside platinum or gold capsules, then run for durations in the range 120-960 h. Based on the time dependence of interface retreat dissolution is interface reaction-controlled up to 700 h, and becomes diffusion-controlled afterwards. Upon dissolution of albite, Al and Na entering the melt decouple and Na diffuses away from the interface to maintain a constant Al/Na molar ratio throughout the entire melt column. Potassium from the bulk melt diffuses uphill towards the albite-melt interface to maintain a constant Aluminum Saturation Index (ASI=molar Al2O3/Na2O+K2O) of 1.00 throughout the entire melt column. Dissolution of K-feldspar results in migration of K away from the interface and uphill diffusion of Na from the bulk melt towards the interface, again maintaining constant Al/Na and ASI ratios in the bulk melt. Dissolution of quartz produces enrichment in SiO2 versus dilution of the rest of components in the interface melt. These results indicate that in the five-component H2O-saturated metaluminous haplogranite system, uncoupled diffusion takes place along the following four directions in composition space: SiO2; Na2O; K2O; and a combination of Al2O3 and alkalis such that the Al/Na molar ratio is equal to that in the bulk melt, and the Al2O3/Na2O+K2O molar ratio is equal to the equilibrium ASI of the melt. These observations are in accord with results obtained from corundum and andalusite dissolution experiments in the same system and P-T-X conditions (Acosta-Vigil et

  13. 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.

  14. Study of the K2Ni(SO4)2 • 6H2O-K2Co(SO4)2 • 6H2O-H2O diagram and determination of the conditions for growing K2(Ni,Co)(SO4)2 • 6H2O mixed crystals

    NASA Astrophysics Data System (ADS)

    Zhokhov, A. A.; Masalov, V. M.; Zverkova, I. I.; Emelchenko, G. A.; Manomenova, V. L.; Rudneva, E. B.; Vasilieva, N. A.; Voloshin, A. E.

    2016-11-01

    The phase diagram of the K2Ni(SO4)2 · 6H2O-K2Co(SO4)2 · 6H2O-H2O ternary system is investigated in the temperature range of 30-70°C, and a relationship between the compositions of the equilibrium phases of the K2Co x Ni(1- x)(SO4)2 · 6H2O (KCNSH) solid solution and the growth solution is established. It is shown how the salt compositions of the liquid and solid phases change during crystal growth upon slow cooling of solution. A dependence of the lattice parameters of the KCNSH solid solution on the concentration of isomorphic components is experimentally found.

  15. Electron scattering and ionization of H2O; OH, H2O2, HO2 radicals and (H2O)2 dimer

    NASA Astrophysics Data System (ADS)

    Joshipura, Kamalnayan N.; Pandya, Siddharth H.; Mason, Nigel J.

    2017-04-01

    Water, its dimer and their dissociative products (OH, H2O2, HO2) play an important role in several diverse processes including atmospheric chemistry, radiation induced damage within cellular systems and atmospheric plasmas used in industry. The interaction of electrons with these species is therefore an important collision process but since OH, H2O2 and HO2 are difficult to prepare as isolated experimental targets to date, electron scattering cross sections from such species are lacking in the literature. In this paper we report the results of a semi-empirical method to estimate such cross sections, benchmarking these cross sections against our knowledge of electron scattering from the water monomer. Calculations on HO2, H2O2 and (H2O2)2 are performed with improved Additivity Rules.

  16. Space-Borne H2O Observations in the Arctic Stratosphere and Mesosphere in the Spring of 1992

    NASA Technical Reports Server (NTRS)

    Aellig, C. P.; Bacmeister, J.; Bevilacqua, R. M.; Daehler, M.; Kriebel, D.; Pauls, T.; Siskind, D.; Kaempfer, N.; Langen, J.; Hartmann, G.; hide

    1996-01-01

    We report on stratospheric and mesospheric water vapor (H2O) observations obtained by the Millimeter wave Atmospheric Sounder (MAS) in the Arctic spring of 1992. In the lower stratosphere, the observations show enhanced H2O inside the vortex between 450 K and 625 K, in agreement with other H2O observations. In the upper stratosphere and lower mesosphere, at potential temperatures between 1850 K and 2200 K, we find regions of depressed H2O volume mixing ratio coincident with remnants of high potential vorticity. The depressed mesospheric H2O, as well as the enhanced lower stratospheric H2O, are consistent with wintertime descent. It also suggests effective containment of air up into the lower mesosphere.

  17. Space-Borne H2O Observations in the Arctic Stratosphere and Mesosphere in the Spring of 1992

    NASA Technical Reports Server (NTRS)

    Aellig, C. P.; Bacmeister, J.; Bevilacqua, R. M.; Daehler, M.; Kriebel, D.; Pauls, T.; Siskind, D.; Kaempfer, N.; Langen, J.; Hartmann, G.; Berg, A.; Park, J. H.; Russell, J. M., III

    1996-01-01

    We report on stratospheric and mesospheric water vapor (H2O) observations obtained by the Millimeter wave Atmospheric Sounder (MAS) in the Arctic spring of 1992. In the lower stratosphere, the observations show enhanced H2O inside the vortex between 450 K and 625 K, in agreement with other H2O observations. In the upper stratosphere and lower mesosphere, at potential temperatures between 1850 K and 2200 K, we find regions of depressed H2O volume mixing ratio coincident with remnants of high potential vorticity. The depressed mesospheric H2O, as well as the enhanced lower stratospheric H2O, are consistent with wintertime descent. It also suggests effective containment of air up into the lower mesosphere.

  18. 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

  19. 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

  20. 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.

  1. 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

  2. Generation of H2O-ice dielectric barrier discharge for the development of novel cryogenic reaction fields

    NASA Astrophysics Data System (ADS)

    Sakakibara, Noritaka; Terashima, Kazuo

    2017-06-01

    We generated H2O-ice dielectric barrier discharge (DBD), which has H2O ice as a dielectric barrier, at a wide range of cryogenic temperatures down to 6.5 K, and controlled plasma gas temperature as a control parameter. H2O-ice DBD exhibited variations in optical emissions and transition of discharge modes with changing plasma gas temperature. Furthermore, H2O-ice DBD is revealed to be anticipated to have sufficient reactivity as a reaction field on the ice surface in comparison with ultraviolet irradiated chemical reactions such as formation of amino acids. This study is the first report on gas temperature-controlled plasma generation coexistent with H2O ice, focusing on plasma gas temperature as a control parameter.

  3. Studies of proton irradiated H2O + CO2 and H2O + CO ices and analysis of synthesized molecules

    NASA Technical Reports Server (NTRS)

    Moore, M. H.; Khanna, R.; Donn, B.

    1991-01-01

    Infrared spectra of H2O + CO2 and H2O + CO ices before and after proton irradiation showed that a major reaction in both mixtures was the interconversion of CO2 yields CO. Radiation synthesized organic compounds such as carbonic acid were identified in the H2O + CO2 ice. Different chemical pathways dominate in the H2O + CO ice in which formaldehyde, methanol, ethanol, and methane were identified. Sublimed material was also analyzed using a mass spectrometer. Implications of these results are discussed in reference to comets.

  4. 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.

  5. 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

  6. 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.

  7. Quantification of the production of hydrogen peroxide H2O2 during accelerated wine oxidation.

    PubMed

    Héritier, Julien; Bach, Benoît; Schönenberger, Patrik; Gaillard, Vanessa; Ducruet, Julien; Segura, Jean-Manuel

    2016-11-15

    Understanding how wines react towards oxidation is of primary importance. Here, a novel approach was developed based on the quantitative determination of the key intermediate H2O2 produced during accelerated oxidation by ambient oxygen. The assay makes use of the conversion of the non-fluorescent Amplex Red substrate into a fluorescent product in presence of H2O2. The total production of H2O2 during 30min was quantified with low within-day and between-day variabilities. Polymerized pigments, but not total polyphenols, played a major role in the determination of H2O2 levels, which were lower in white wines than red wines. H2O2 amounts also increased with temperature and the addition of metal ions, but did not depend on the concentration of many other wine constituents such as SO2. H2O2 levels did not correlate with anti-oxidant properties. We believe that this novel methodology might be generically used to decipher the oxidation mechanisms in wines and food products. Copyright © 2016 Elsevier Ltd. All rights reserved.

  8. 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.

    2016-11-01

    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.

  9. Scavenging of H2O2 by mouse brain mitochondria

    PubMed Central

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

    2015-01-01

    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. PMID:25248416

  10. 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.

  11. Infrared spectroscopy of V2+(H2O) complexes

    NASA Astrophysics Data System (ADS)

    Bandyopadhyay, B.; Duncan, M. A.

    2012-03-01

    Doubly charged vanadium-water complexes are produced by laser vaporization in a pulsed supersonic expansion. Size-selected ions are studied with infrared photodissociation spectroscopy in the O-H stretch region using argon complex predissociation. Density functional theory calculations provide structures and vibrational spectra of these ions. The O-H stretches of V2+(H2O) appear at lower frequencies than those of the free water molecule or V+(H2O). The symmetric stretch is more intense than the asymmetric stretch in both V+(H2O) and V2+(H2O) complexes. Spectra of V2+(H2O)Arn (n = 2-7) show that the coordination of the V2+ is filled with six ligands, i.e. one water and five argon atoms.

  12. Measurements of H2O2 during WATOX-86

    NASA Astrophysics Data System (ADS)

    Heikes, Brian G.; Walega, James G.; Kok, Gregory L.; Lind, John A.; Lazrus, Allan L.

    1988-03-01

    Measurements of gas phase H2O2 were made on all Western Atlantic Ocean Experiment 1986 (WATOX-86) flights aboard the National Oceanic and Atmospheric Administration (NOAA) WP-3D aircraft. These were some of the first airborne real-time H2O2 measurements made in winter. Operation of the instru- ment was limited to altitude < 3.1 km with a detection limit, determined by interference considerations, of 0.05 parts per billion by volume (ppbv), 10% calibration accuracy and 0.03-ppbv precision. Experimental measurements showed the mean H2O2 to be 0.12 ppbv (standard deviation = 0.07, maximum = 1.2 ppbv). Vertical structure was observed with maximum H2O2 above the cloud-capped marine boundary layer. Boundary layer H2O2 was typically at or below the detection limit.

  13. Quercetin reduces the in vitro production of H2O2 during chilled storage of rabbit spermatozoa.

    PubMed

    Johinke, D; de Graaf, S P; Bathgate, R

    2014-12-30

    Reactive oxygen species, such as hydrogen peroxide, H2O2, can reduce sperm quality during storage. This study evaluated the effect of methionine and quercetin on rabbit sperm quality during liquid storage over 96h. Semen was collected from adult bucks (n=4) and pooled following evaluation. In Experiment 1, pooled ejaculates were diluted with a Tris extender supplemented with methionine (1, 6 or 12mM), quercetin (50 or 200μM) or no antioxidant (control) and then subdivided for storage at 5°C or 15°C. Sperm quality was assessed by CASA (total motility [TM]) and flow cytometry (viability, acrosome integrity and H2O2 production) at 0, 48, 72 and 96h. Experiments were replicated three times. Motility was significantly higher in control samples and lowest following dilution with 200μM quercetin, irrespective of storage temperature. Storage at 15°C improved viability and acrosome integrity compared with 5°C, but produced significantly more H2O2 at 72 and 96h in sperm diluted with methionine or no antioxidant. Quercetin-supplemented spermatozoa exhibited lower levels of H2O2 at both storage temperatures for all incubation times (P<0.05). In Experiment 2, the concentration of quercetin (0, 25, 50, 100 and 200μM) was investigated with additional quality parameters; lipid peroxidation and DNA integrity. All concentrations of quercetin reduced H202 and lipid peroxidation during storage at 15°C, but were not beneficial for TM, viability, acrosome or DNA integrity. Only supplementation with 100 and 200μM quercetin resulted in similar H202 levels at 5°C and 15°C (P>0.05). Overall, quercetin-supplementation to sperm medium provided protection against oxidative stress in 15°C-stored rabbit spermatozoa over 96h.

  14. H2O Inner-Surface Interactions in Micro/Nanoporous Silicates: Thermodynamic Behavior and Low Energy Molecular Vibrations

    NASA Astrophysics Data System (ADS)

    Geiger, C. A.; Paukov, I. E.; Kovalevskaya, Y. A.; Kolesov, B. A.

    2007-12-01

    Macroscopic thermodynamic and molecular-scale behavior related to silicate surface-fluid interactions in nature is complex and poorly understood. The study of confined H2O at inner surfaces in micro/ nanoporous silicates is helpful for understanding outer-surface interactions, because such phases offer simpler physicochemical systems for investigation. We are investigating the nature of H2O in various micro/nanoporous silicates. Low temperature calorimetric heat capacity (Cp) determinations have been made to determine thermodynamic behavior. Powder IR and polarized single-crystal Raman spectroscopy are used to investigate local features such as bonding and dynamics. In this report, Cp behavior and low energy external H2O modes related to van der Waals and/or hydrogen bonding at inner surfaces are emphasized. The first group of microporous silicates that includes cordierite, Mg2Al4Si5O18· xH2O, and beryl, Be2Al3Si6O18· xH2O, where x = 0 to 1, can hold single H2O molecules in small structural microcavities and exchange them with the environment with no change in volume. The Cp behavior of the confined H2O, which is characterized by weak van der Waals forces to the aluminosilicate framework, is roughly similar to that of steam at T > 100 K up to moderate T's. Cp is greater than that for ice at T < 100 K. Raman, IR and inelastic neutron scattering measurements show that the H2O molecule is quasi free in both phases. In cordierite, low energy T(H2O) modes occur at ~80 and ~48 cm-1 (Winkler and Hennion, 1994), and possibly at ~31 cm-1 . For beryl, for an external mode T(H2O) at ~ 10 cm-1 is present. The second type of microporous silicate, namely zeolites (those studied are bikitaite Li2[Al2Si4O12]·2H2O, natrolite - Na16[Al16Si24O80]·16H2O, scolecite - Ca8[Al16Si24O80]·24H2O, gmelinite - (Na2,Ca)[Al2Si4O12]·6H2O) are strongly hydrophilic and their intrachannel H2O molecules are hydrogen bonded. Zeolites show measurable changes in volume with loss or gain of H2O

  15. Basalt Reactivity in the Presence of H2O-Saturated Supercritical CO2 Containing Gaseous Sulfur Compounds

    NASA Astrophysics Data System (ADS)

    Schaef, H. T.; McGrail, P.; Owen, A. T.

    2009-12-01

    Future impacts of climate change may be minimized by capture of emissions, primarily CO2 from fossil-fueled electric generating stations and subsequent sequestration in deep geologic formations. Injection of dry liquid CO2 into porous geologic reservoirs for long term storage is expected to eventually form a buoyant water-saturated bubble of supercritical fluid. Depending on purification processes and underground injection control regulations, the injected CO2 also could contain trace compounds associated with flue gas streams (SO2, N2, and O2). Once injected, the scCO2 will absorb water (1500 to 3000 ppmw) until becoming immobilized by reservoir trapping mechanisms. Reactivity of the water-bearing scCO2 with silicate minerals is relatively unknown and could have impacts on long term reservoir seal integrity and trapping by mineralization. To examine the reactivity of H2O-saturated scCO2, basalt experiments were conducted at pressures and temperatures relevant to geologic sequestration. Reaction products differed considerably depending on the gas mixtures used and type of basalt. In the presence of H2O-saturated CO2, the Newark Basin basalt reacted to produce secondary mineralization with needle-like morphologies and chemistries similar to aragonite. Exposing the same basalt to a CO2-H2S mixture (H2O saturated) produced two types of reaction products: carbonates in the form of small discrete nodules or needles and metallic-like circular areas similar in chemistry to pyrite and marcarsite. Tests conducted in the presence of CO2-SO2 produced the most extensive surface reaction products observed during the experiments. Some basalts were completely coated in white precipitate identified as a mixture of gypsum, sulfate bearing minerals (rozenite and melanterite), and a magnesium sulfate compound (MgSO4 ●5H2O). Hawaiian flow top basalts contained extensive reaction products including magnesium sulfate (MgSO4●6H2O), which formed on the large olivine crystals present

  16. Influence of H2O Rich Fluid Inclusions on Quartz Deformation

    NASA Astrophysics Data System (ADS)

    Thust, Anja; Heilbronner, Renée.; Stünitz, Holger; Tarantola, Alexandre; Behrens, Harald

    2010-05-01

    The effect of H2O on the strength of quartz is well known and has been discussed many times in the literature (e.g. Griggs & Blacic 1965, Kronenberg 1994). In this project we study the H2O interactions between natural dry quartz and H2O rich fluid inclusions during deformation in the solid medium Griggs apparatus. High pressure and temperature experiments were carried out using a quartz single crystal containing a large number of H2O-rich fluid inclusions. Adjacent to the fluid inclusions the crystal is essentially dry (< 100 H/106Si, as determined by FTIR). Two sample orientations where used: (1) ⊥{m} orientation: normal to one of the prism planes, (2) O+ orientation: 45° to and 45° to [c]. Confining pressures were 700 MPa, 1000 MPa and 1500 MPa, with a constant displacement rate of 10-6 s-1 and a constant temperature of 900° C. Additionally, experiments where carried out at lower temperatures (800° C, 700° C) and faster strain rate ( 10-5 s-1). During increasing pressure and temperature we remained close to the fluid inclusion isochore and exceeded the α - β transition as late as possible. The strengths of the majority of the samples are between 150 and 250 MPa (the weakest is 84 MPa, the strongest 414 MPa). Low strength can be explained by dynamic recrystallization and deformation by dislocation creep, higher strength correlates with a lower H2O content and absence of dislocation creep. In the undeformed material, the H2O rich fluid inclusions contain different chlorides like antarticite (CaCl2×6H2O) and hydrohalite (NaCl×2H2O), as measured with micro thermometry. They show a large range in size from 50 μm to 700 μm and their spatial distribution is extremely heterogeneous. After deformation the inclusions are more homogeneously distributed throughout the sample and dramatically reduced in size (< 0.1μm). Regions with a high density of very small fluid inclusions are the regions with the highest concentration of deformation and yield an H2O content

  17. Rheologies of H2O ices Ih, II, and III at high pressures - A progress report

    NASA Astrophysics Data System (ADS)

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

    Ordinary hexagonal ice (ice Ih) represents the stable crystalline form of H2O on the earth's surface. It is known that ice exists elsewhere in the solar system. Thus, several of the moons of Saturn and Jupiter are composed predominately of H2O and their surface temperatures are about 75 and 100 K. The pressures in the interior of some of the larger of the moons may be as high as 3 GPa. The involved pressures and temperatures extend far beyond the conditions over which the rheological laws for ice Ih can be confidently extrapolated. It is, therefore, necessary to obtain information regarding the rheologies of H2O ices in pressure and temperature ranges which had not yet been previously considered. Since 1981, over 100 triaxial compression tests have been conducted over a wide range of temperatures (77 to 258 K) and pressures (0.1 to 350 MPa). The present paper provides a progress report of these experiments.

  18. Spectral and thermal studies of MgI2·8H2O

    NASA Astrophysics Data System (ADS)

    Koleva, Violeta; Stefov, Viktor; Najdoski, Metodija; Ilievski, Zlatko; Cahil, Adnan

    2017-10-01

    In the present contribution special attention is paid to the spectroscopic and thermal characterization of MgI2·8H2O which is the stable hydrated form at room temperature. The infrared spectra of MgI2·8H2O and its deuterated analogues recorded at room and liquid nitrogen temperature are presented and interpreted. In the low-temperature diference infrared spectrum of the slightly deuterated analogue (≈5% D) at least four bands are found out of the expected five (at 2595, 2550, 2538 and 2495 cm-1) as a result of the uncoupled O-D oscillators in the isotopically isolated HOD molecules. Multiple bands are observed in the water bending region and only two bands of the HOH librational modes are found. For more precise and deep description of the processes occurring upon heating of MgI2·8H2O we have applied simultaneous TG/DTA/Mass spectrometry technique identifying the gases evolved during the thermal transformations. We have established that the thermal decomposition of MgI2·8H2O is a complex process that takes place in two main stages. In the first stage (between 120 and 275 °C) the salt undergoes a partial stepwise dehydration to MgI2·2H2O followed by a hydrolytic decomposition with formation of magnesium hydroxyiodide Mg(OH)1.44I0.56 accompanied with simultaneous release of H2O and HI. In the second stage Mg(OH)1.44I0.56 is completely decomposed to MgO with elimination of gaseous H2O, HI, I2 and H2. Infrared spectra of the annealed samples heated between 190 and 270 °C confirmed the formation of magnesium hydroxyiodide.

  19. 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.

  20. Sequential hydration energies of the sulfate ion, from determinations of the equilibrium constants for the gas-phase reactions: SO4(H2O)(n)2- = SO4(H2O)(n-1)2- + H2O.

    PubMed

    Blades, Arthur T; Kebarle, Paul

    2005-09-22

    Sequential hydration energies of SO4(H2O)(n)2- were obtained from determinations of the equilibrium constants of the following reactions: SO4(H2O)(n)2- = SO4(H2O)(n-1)2- + H2O. The SO4(2-) ions were produced by electrospray and the equilibrium constants Kn,n-1 were determined with a reaction chamber attached to a mass spectrometer. Determinations of Kn,n-1 at different temperatures were used to obtain DeltaG0n,n-1, DeltaH0 n,n-1, and DeltaS0n,n-1 for n = 7 to 19. Interference of the charge separation reaction SO4(H2O)(n)2- = HSO4(H2O)(n-k)- + OH(H2O)(k-1)- at higher temperatures prevented determinations for n < 7. The DeltaS0n,n-1 values obtained are unusually low and this indicates very loose, disordered structures for the n > or = 7 hydrates. The DeltaH0n,n-1 values are compared with theoretical values DeltaEn,n-1, obtained by Wang, Nicholas, and Wang. Rate constant determinations of the dissociation reactions n,n - 1, obtained with the BIRD method by Wong and Williams, showed relatively lower rates for n = 6 and 12, which indicate that these hydrates are more stable. No discontinuities of the DeltaG0n,n-1 values indicating an unusually stable n = 12 hydrate were observed in the present work. Rate constants evaluated from the DeltaG0n,n-1 results also fail to indicate a lower rate for n = 12. An analysis of the conditions used in the two types of experiments indicates that the different results reflect the different energy distributions expected at the dissociation threshold. Higher internal energies prevail in the equilibrium measurements and allow the participation of more disordered transition states in the reaction.

  1. 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

  2. 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+).

  3. 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

  4. [Degradation of norfloxacin by nano-Fe3O4/H2O2].

    PubMed

    Zhang, Di; Wang, Yi-Xuan; Niu, Hong-Yun; Meng, Zhao-Fu

    2011-10-01

    The degradation of norfloxacin in aquatic environment was studied in the presence of Fe3O4 nanoparticles and H2O2. The effects of solution pH, temperature, dose of catalysts and concentration of H2O2 on norfloxacin degradation were surveyed. The degradation behaviors of different substrates by nano-Fe3O4/H2O2 were investigated and the reaction mechanism of norfloxacin was discussed. The results showed that the reaction was strongly pH-dependent and favored in acidic solution (pH = 3.5). The removal efficiency of norfloxacin was enhanced with the increase of temperature, catalysts dosage and H2O2 concentration. The degradation efficiency of norfloxacin by nano-Fe3O4/H2O2 was significantly higher than those of sulfathiazole, phenolic and aniline compounds. In the presence of 4.4 mmol x L(-1) of H2O2, 0.80 g x L(-1) of Fe3O4 and T = 303 K, norfloxacin was degraded completely in 5 min. The F element in norfloxacin molecule existed totally as F(-) in solution within 5 min, and the removal efficiency of total organic carbon was 57% in 1 h. In the ESR spectrum of nano-Fe3O4/H2O2 system, the characteristic peaks of BMPO-*OH adduct was detected, however, the intensity of the peaks was reduced to 5% with the addition of tert-butanol, a strong *OH scavenger, and the degradation efficiency of norfloxacin was correspondingly decreased to 10% in 1 h. These results indicated that *OH played an important role on norfloxacin degradation, and the reaction proceeded based on a heterogeneous Fenton-like system.

  5. Photoluminescence Probing of Complex H2O Adsorption on InGaN/GaN Nanowires.

    PubMed

    Maier, Konrad; Helwig, Andreas; Müller, Gerhard; Hille, Pascal; Teubert, Jörg; Eickhoff, Martin

    2017-02-08

    We demonstrate that the complex adsorption behavior of H2O on InGaN/GaN nanowire arrays is directly revealed by their ambient-dependent photoluminescence properties. Under low-humidity, ambient-temperature, and low-excitation-light conditions, H2O adsorbates cause a quenching of the photoluminescence. In contrast, for high humidity levels, elevated temperature, and high excitation intensity, H2O adsorbates act as efficient photoluminescence enhancers. We show that this behavior, which can only be detected due to the low operation temperature of the InGaN/GaN nanowires, can be explained on the basis of single H2O adsorbates forming surface recombination centers and multiple H2O adsorbates forming surface passivation layers. Reversible creation of such passivation layers is induced by the photoelectrochemical splitting of adsorbed water molecules and by the interaction of reactive H3O(+) and OH(-) ions with photoactivated InGaN surfaces. Due to electronic coupling of adsorbing molecules with photoactivated surfaces, InGaN/GaN nanowires act as sensitive nanooptical probes for the analysis of photoelectrochemical surface processes.

  6. 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.

  7. Modification and secondary packaging of Na2SO4·10H2O

    NASA Astrophysics Data System (ADS)

    XIAO, Liguang; ZHAO, Mingyue

    2017-08-01

    Na2SO4·10H2O, commonly known as mirabilite, phase change temperature is 32°C, enthalpy is 254 J/g, with large surpercooling degree and easy to stratify. This paper improved the properties of Na2SO4·10H2O by Na2HPO4·12H2O and CMC, expanded glass beads, silica fume, grinded diatomaceous earth, straw powder was used to parcle and covered it twice respectively. Grinded diatomaceous earth showed best effect, with phase change temperature 22-30°C, enthalpy was 168J/g average, and there was no leakage when the temperature went to 40°C.

  8. Pyruvate protects pathogenic spirochetes from H2O2 killing.

    PubMed

    Troxell, Bryan; Zhang, Jun-Jie; Bourret, Travis J; Zeng, Melody Yue; Blum, Janice; Gherardini, Frank; Hassan, Hosni M; Yang, X Frank

    2014-01-01

    Pathogenic spirochetes cause clinically relevant diseases in humans and animals, such as Lyme disease and leptospirosis. The causative agent of Lyme disease, Borrelia burgdorferi, and the causative agent of leptospirosis, Leptospria interrogans, encounter reactive oxygen species (ROS) during their enzootic cycles. This report demonstrated that physiologically relevant concentrations of pyruvate, a potent H2O2 scavenger, and provided passive protection to B. burgdorferi and L. interrogans against H2O2. When extracellular pyruvate was absent, both spirochetes were sensitive to a low dose of H2O2 (≈0.6 µM per h) generated by glucose oxidase (GOX). Despite encoding a functional catalase, L. interrogans was more sensitive than B. burgdorferi to H2O2 generated by GOX, which may be due to the inherent resistance of B. burgdorferi because of the virtual absence of intracellular iron. In B. burgdorferi, the nucleotide excision repair (NER) and the DNA mismatch repair (MMR) pathways were important for survival during H2O2 challenge since deletion of the uvrB or the mutS genes enhanced its sensitivity to H2O2 killing; however, the presence of pyruvate fully protected ΔuvrB and ΔmutS from H2O2 killing further demonstrating the importance of pyruvate in protection. These findings demonstrated that pyruvate, in addition to its classical role in central carbon metabolism, serves as an important H2O2 scavenger for pathogenic spirochetes. Furthermore, pyruvate reduced ROS generated by human neutrophils in response to the Toll-like receptor 2 (TLR2) agonist zymosan. In addition, pyruvate reduced neutrophil-derived ROS in response to B. burgdorferi, which also activates host expression through TLR2 signaling. Thus, pathogenic spirochetes may exploit the metabolite pyruvate, present in blood and tissues, to survive H2O2 generated by the host antibacterial response generated during infection.

  9. Pyruvate Protects Pathogenic Spirochetes from H2O2 Killing

    PubMed Central

    Troxell, Bryan; Zhang, Jun-Jie; Bourret, Travis J.; Zeng, Melody Yue; Blum, Janice; Gherardini, Frank; Hassan, Hosni M.; Yang, X. Frank

    2014-01-01

    Pathogenic spirochetes cause clinically relevant diseases in humans and animals, such as Lyme disease and leptospirosis. The causative agent of Lyme disease, Borrelia burgdorferi, and the causative agent of leptospirosis, Leptospria interrogans, encounter reactive oxygen species (ROS) during their enzootic cycles. This report demonstrated that physiologically relevant concentrations of pyruvate, a potent H2O2 scavenger, and provided passive protection to B. burgdorferi and L. interrogans against H2O2. When extracellular pyruvate was absent, both spirochetes were sensitive to a low dose of H2O2 (≈0.6 µM per h) generated by glucose oxidase (GOX). Despite encoding a functional catalase, L. interrogans was more sensitive than B. burgdorferi to H2O2 generated by GOX, which may be due to the inherent resistance of B. burgdorferi because of the virtual absence of intracellular iron. In B. burgdorferi, the nucleotide excision repair (NER) and the DNA mismatch repair (MMR) pathways were important for survival during H2O2 challenge since deletion of the uvrB or the mutS genes enhanced its sensitivity to H2O2 killing; however, the presence of pyruvate fully protected ΔuvrB and ΔmutS from H2O2 killing further demonstrating the importance of pyruvate in protection. These findings demonstrated that pyruvate, in addition to its classical role in central carbon metabolism, serves as an important H2O2 scavenger for pathogenic spirochetes. Furthermore, pyruvate reduced ROS generated by human neutrophils in response to the Toll-like receptor 2 (TLR2) agonist zymosan. In addition, pyruvate reduced neutrophil-derived ROS in response to B. burgdorferi, which also activates host expression through TLR2 signaling. Thus, pathogenic spirochetes may exploit the metabolite pyruvate, present in blood and tissues, to survive H2O2 generated by the host antibacterial response generated during infection. PMID:24392147

  10. High pressure experimental study of eclogite with varying H2O contents

    NASA Astrophysics Data System (ADS)

    Rosenthal, A.; Frost, D. J.; Petitgirard, S.; Yaxley, G. M.; Berry, A.; Woodland, A. B.; Pinter, Z.; Vasilyev, P.; Ionov, D. A.; Jacob, D. E.; Pearson, G. D.; Kovacs, I.; Padron-Navarta, A.

    2014-12-01

    Given the strong influence of volatiles on mantle melting processes, it is critical to understand the behaviour of volatiles (such as H2O) in subducted oceanic crustal material (eclogite) during subduction and subsequent recycling and mantle melting processes, and their impacts on volcanism. As natural samples from subduction zones from the deep Earth's interior are largely inaccessible, the only way to determine the H2O content of eclogite is to simulate high pressure (P) and temperature (T) conditions equivalent to conditions of the Earth's interior using high-P experimental facilities. A particular interest is to determine the H2O content of eclogitic nominally anhydrous minerals (NAMs; such as garnet, clinopyroxene) at the conditions where hydrous phases (such as phengite) are breaking down to release H2O that would then leave the slab. As a starting material, we use average oceanic basalt (GA1, representative of recycled oceanic crust [1]) with varying bulk %H2O (≤7 wt.%). We conducted experiments using GA1 at different P's (6-10 GPa), T's (850-1500°C) and bulk %H2O (up to 7 wt.%) using multi anvil apparatuses. The run products at each P, T, and bulk H2O contents show well-equilibrated eclogitic phase assemblages of garnet ± clinopyroxene ± coesite/stishovite ± rutile ± phengite ± melt ± vapour. Runs (>0.5 wt.% H2O) at 6 GPa and up to ~950°C, and at 8-9 GPa and up to ~1050°C are subsolidus, while towards higher T small melt fractions appear. Similar to previous studies [e.g. 2-6], the stability of phengite varies as a function of P, T, buffering mineral paragenesis and bulk H2O concentration. Phengite breaks down >9 GPa. Eclogitic NAMs and phengite also break down at subsolidus conditions in the presence of excess of hydrous fluids. For instance, K2O in phengite and clinopyroxene decrease with increasing bulk H2O content at subsolidus conditions at given P, T, suggesting a leaching role of K2O by a vapour-rich fluid. [1] Yaxley, G. M. & Green, D. H

  11. Simultaneous Observations of H2O and SiO Masers toward OH/IR Stars

    NASA Astrophysics Data System (ADS)

    Cho, Chi-Young; Cho, Se-Hyung; Kim, Sungeun; Kim, Jaeheon; Yoon, Dong-hwan; Hwang, Jihye

    2017-09-01

    We performed simultaneous observations of SiO v = 1, 2, 29SiO v = 0, J = 1–0, and H2O {6}12\\to {5}23 maser lines toward 252 OH/IR stars using the individual 21 m telescopes of the Korean VLBI Network (KVN). The observations for studying SiO and H2O maser properties associated with the different evolutionary stages of OH/IR stars were carried out from 2011 November to 2012 July. Both H2O and SiO masers were detected from 50 sources with a detection rate of 20% in one epoch of observation. One-sided SiO maser emissions without H2O were detected from 108 sources and H2O maser emission was detected from 11 sources, of which the detection rates were 43% and 4%, respectively. The overall detection rate of the SiO maser was 63%, and that of the H2O maser was 24%. There were 65 new detections in the SiO maser lines, 22 new detections in the H2O maser line, and 4 new detections in the 29SiO maser line. For the H2O and/or SiO maser- detected sources, mutual relations between SiO and H2O maser properties (including peak and integrated antenna temperatures, and full widths at zero power, etc.) are investigated based on a statistical analysis. We also investigate these maser properties on an IRAS two-color diagram related to stellar evolutionary sequences. In particular, a large number of SiO v = 2-only detected sources appear among the SiO-only detected sources compared to those of both H2O and SiO maser detected sources and also appear in the later evolutionary stages of asymptotic giant branch AGB stars in the IRAS two-color diagram. These results may be associated with the development of a hot and thick dust envelope at later stages of AGB evolution and the different excitation conditions of SiO v = 1 and v = 2 masers. Our observational results will be useful for statistical studies of circumstellar envelopes of OH/IR stars related to their late evolution and future very long baseline interferometry (VLBI) observations.

  12. 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

  13. 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.

  14. The OH and H2O Megamaser Connection: H2O Emission Toward OH Megamaser Hosts

    NASA Astrophysics Data System (ADS)

    Wiggins, Brandon Kerry

    2016-01-01

    Questions surround the connection of luminous extragalactic masers to galactic processes. The observation that water and hydroxyl megamasers rarely coexist in the same galaxy has given rise to a hypothesis that the two species appear in different phases of nuclear activity. The detection of simultaneous hydroxyl and water megamaser emission toward IC694 has called this hypothesis into question but, because many megamasers have not been surveyed for emission in the other molecule, it remains unclear whether IC694 occupies a narrow phase of galaxy evolution or whether the relationship between megamaser species and galactic processes is more complicated than previously believed. In this paper, we present results of a systematic search for 22 GHz water maser emission among OH megamaser hosts to identify additional objects hosting both megamaser. Our work roughly doubles the number of galaxies searched for emission in both molecules which host at least one confirmed maser. We confirm a definitive (>8σ) detection of water emission toward IIZw96, firmly establishing it as the second object to co-host both water and hydroxyl megamasers after IC694. We find high luminosity, narrow features in the water feature in IIZw96. All dual megamaser candidates appear in merging galaxy systems suggestive that megamaser coexistance may signal a brief phase along the merger sequence. A statistical analysis of the results of our observations provide possible evidence for an exclusion of H2O kilomasers among OH megamaser hosts.

  15. 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.

  16. Elastic incoherent neutron scattering from homologous disaccharides/H2O mixtures

    NASA Astrophysics Data System (ADS)

    Magazú, S.; Migliardo, F.; Mondelli, C.

    2003-12-01

    An analysis in terms of elastic scans of the neutron intensity of homologous disaccharide (trehalose, maltose, sucrose)/H2O mixtures as a function of temperature and exchanged wave vector has been carried out. The experimental findings, showing a crossover in molecular fluctuations between harmonic and anharmonic dynamical regimes, allow us to characterize the system "flexibility." A new operative definition for the "fragility" degree, by using elastic incoherent neutron scattering, is furnished. In this frame the lower flexibility and fragility character of trehalose/H2O mixture with respect to maltose and sucrose/H2O mixtures indicate a better attitude to encapsulate biostructures in more rigid and temperature insensitive structures in approaching the glass transition.

  17. Outbursts of H2O in Comet P/Halley

    NASA Astrophysics Data System (ADS)

    Larson, H. P.; Hu, H.-Y.; Mumma, M. J.; Weaver, H. A.

    1990-07-01

    Comet Halley gas-production monitoring efforts in March 1986 with the NASA Kuiper Airborne Observatory's Fourier transform spectrometer have indicated rapid temporal variations in H2O emissions; a continuous record of an H2O outburst was thus obtained. The event, in which H2O brightness increased by a factor of 2.2 in less than 10 min, is ascribable to an energetic process in the nucleus whose character may have been that of amorphous H2O ice crystallization, chemical explosion, thermal stress, or a compressed gas pocket. The timing and energy of the event appear to require an internal energy source; amorphous ice crystallization is held to be most consistent with compositional and thermal models of cometary nuclei as well as the observations.

  18. 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.

  19. 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.

  20. 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

  1. 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!!!

  2. 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.

  3. 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.

  4. 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.

  5. The role of H2O in the Saturn ionosphere

    NASA Astrophysics Data System (ADS)

    Shemansky, Donald; Liu, Xianming

    2010-05-01

    Stellar occultations in the Cassini Ultraviolet Imaging Spectrograph Experiment observation program have provided measurements of the vertical profiles of H2 and and minor components of the atmosphere. The minor species identified and measured in the extinction spectra to date are CH4, C2H2, and C2H4. Measurements of abundance profiles are reported here, with limits on H2O content. The focus of this paper is on H2O because of the importance of this species to the understanding of upper atmospheric physical chemistry with significant consequences for ionospheric properties and energy budget. Ionospheric theory published in several papers beginning as early as 1984 have a common critical dependence on a sufficiently large H2O mixing ratio to control the lifetime of the assumed dominant ion, H+. The vertical extinction profiles, which extend down to an impact parameter of 300 km above the 1 bar pressure level, show no evidence of H2O in the spectrum at mid and low latitudes, establishing a mixing ratio [H2O]/[H2] ≤ 4 × 10-8, compatible with earlier global average measurements. The upper limit on H2O abundance at mid latitude establishes a mixing ratio more an order of magnitude too low to influence the ionosphere population in competition with calculated H+ + H2 X(v:J) charge capture reaction rates. The analysis of the extinction spectra produces densities and mixing ratios of the observed species and these results are reported and discussed.

  6. A dynamical study of the Si(+) + H(2)O reaction.

    PubMed

    Flores, Jesús R

    2007-11-01

    A dynamical study of the Si(+) + H(2)O reaction has been carried out by means of a quasiclassical trajectory method that decomposes the reaction into a capture step, for which an accurate analytical potential is employed, and an unimolecular step, in which the evolution of the collision complex is studied through a direct dynamics BHandHLYP/6-31G(d,p) method. The capture rate coefficient has been computed for thermal conditions corresponding to temperatures ranging from 50 to 1000 K. It is concluded that the main reason why the reaction rate is about 10 times smaller than the capture rate (at T = 298 K) is the topology of the potential energy surface of the ground state. It is also concluded that the ratio between the rates of product and reactant generation from the collision complex decreases quite steeply with increasing temperature, and therefore, the reaction rate decreases even more sharply. Exciting the stretching normal modes of water substantially increases that ratio, and moderate rotational excitation does not appear to have a relevant effect. The collision complex is always initially SiOH(2)(+), but in some trajectories, it becomes HSiOH(+), which generates the products, although the former species is the main intermediate.

  7. 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.

  8. 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

  9. 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

  10. Suggestion for search of cyclopropenone (c-C3H2O) in a cosmic object

    NASA Astrophysics Data System (ADS)

    Sharma, M. K.; Sharma, M.; Chandra, S.

    2017-03-01

    Following Minimum Energy Principle, out of the three isomers of chemical formula C3H2O, the cyclopropenone (c-C3H2O) is the most stable and therefore may be the most abundant and easily detectable in a cosmic object. The cyclopropenone is detected in Sgr B2(N). Owing to half-spin of each of two hydrogen atoms, the c-C3H2O has two distinct ortho and para species. Using the rotational and centrifugal distortion constants along with the electric dipole moment, we have calculated energies of 100 rotational levels of each of the ortho and para species of c-C3H2O and the Einstein A-coefficients for radiative transitions between the levels. The values of Einstein A-coefficients along with the scaled values for collisional rate coefficients are used for solving a set of statistical equilibrium equations coupled with the equations of radiative transfer. Brightness temperatures of seven rotational transitions of each of the ortho and para species of c-C3H2O are investigated. Out of fourteen transitions, seven are found to show anomalous absorption and rest seven are found to show emission feature. We find that the transitions 110 -111 (1.544 GHz) may play important role in identification of cyclopropenone in a cosmic object.

  11. Subduction factory: 4. Depth-dependent flux of H2O from subducting slabs worldwide

    NASA Astrophysics Data System (ADS)

    van Keken, Peter E.; Hacker, Bradley R.; Syracuse, Ellen M.; Abers, Geoff A.

    2011-01-01

    A recent global compilation of the thermal structure of subduction zones is used to predict the metamorphic facies and H2O content of downgoing slabs. Our calculations indicate that mineralogically bound water can pass efficiently through old and fast subduction zones (e.g., in the western Pacific), whereas hot subduction zones such as Cascadia see nearly complete dehydration of the subducting slab. The top of the slab is sufficiently hot in all subduction zones that the upper crust, including sediments and volcanic rocks, is predicted to dehydrate significantly. The degree and depth of dehydration in the deeper crust and uppermost mantle are highly diverse and depend strongly on composition (gabbro versus peridotite) and local pressure and temperature conditions. The upper mantle dehydrates at intermediate depths in all but the coldest subduction zones. On average, about one third of the bound H2O subducted globally in slabs reaches 240 km depth, carried principally and roughly equally in the gabbro and peridotite sections. The predicted global flux of H2O to the deep mantle is smaller than previous estimates but still amounts to about one ocean mass over the age of the Earth. At this rate, the overall mantle H2O content increases by 0.037 wt % (370 ppm) over the age of the Earth. This is qualitatively consistent with inferred H2O concentrations in the Earth's mantle assuming that secular cooling of the Earth has increased the efficiency of volatile recycling over time.

  12. 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.

  13. [Degradation of simazine by O3/H2O2 system].

    PubMed

    Li, Shao-Feng; Shi, Ye; Zhang, Rong-Quan

    2008-07-01

    The endocrine disrupter simazine was oxidized by O3/H2O2 and the reactive productions was analyzed by chromatography to assess the degradation efficiency of Simazine. The initial content of Simazine 2 mg/L was removed about 87.1% by O3H2O2 system when the O3 was dosed as 10.0 mg/L, the H2O2/O3 molar ratio was 0.70, the temperature was 26 degrees C and pH 7-8, which indicated Simazine could be conveniently removed by O3/H2O2 system in ordinary reactive condition. The simazine removal ratio in tap water was 10% more than it in purified water up to 86.9%. The removal of simazine was decreased when the content of humic acid (HA) was high, whereas it was increased while low content HA in water. Also, the removal efficiency was inhabited by hydrogen carbonate fairly. The deethyl-simazine (DES) was trapped by Gas Chromatography Mass Spectrum(GC-MS) which was also certificated by analyzing the Liquid Chromatography Mass Spectrum (LC-MS) of the products. The Ion Chromatography spectrum showed the existing of de-chloro-procedure and breakage of triazine ring. Which indicated the oxidizability of O3/H2O2 system was fairly strong.

  14. Phase relations of phlogopite and pyroxene with magnesite from 4 to 8 GPa: KCMAS-H2O and KCMAS-H2O-CO2

    NASA Astrophysics Data System (ADS)

    Enggist, Andreas; Luth, Robert W.

    2016-11-01

    To constrain the melting phase relationships of phlogopite and magnesite in the presence of clino- and orthopyroxene, we performed experiments in the K2O-CaO-MgO-Al2O3-SiO2-H2O (KCMAS-H2O) and K2O-CaO-MgO-Al2O3-SiO2-H2O-CO2 (KCMAS-H2O-CO2) systems at pressures of 4-8 GPa and temperatures from 1100 to 1600 °C. We bracketed the carbonate-free solidus between 1250 and 1300 °C at 4 and 5 GPa, and between 1300 and 1350 °C at 6, 7 and 8 GPa. The carbonate-bearing solidus was bracketed between 1150 and 1200 °C at 4, 5 and 6 GPa, and between 1100 and 1150 °C at 7 and 8 GPa. Below the solidus in both systems at 4-6 GPa, phlogopite is in equilibrium with enstatite, diopside, garnet (plus magnesite in the carbonate-bearing system) and a fluid. At 7 GPa, phlogopite coexists with KK-richterite, enstatite, diopside, garnet (plus magnesite in the carbonate-bearing system) and a fluid. KK-richterite is the only stable K-bearing phase at 8 GPa and coexists with enstatite, diopside, garnet (plus magnesite in the carbonate-bearing system) and a fluid. In KCMAS-H2O, phlogopite is present to 100 °C above the solidus. Olivine forms at the solidus and coexists with enstatite, diopside, garnet and melt. At depth in a subcontinental lithospheric mantle keel, phlogopite would be stable with orthopyroxene, clinopyroxene and magnesite to 5 GPa along a 40 mW/m2 geotherm. A hydrous, potassic and CO2-bearing melt that intrudes the subcontinental mantle can react with olivine, enstatite and garnet, crystallizing phlogopite, magnesite and potentially liberating a hydrous fluid.

  15. 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.

  16. 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].

  17. Possible sources of H2 to H2O enrichment at evaporation of parent chondritic material

    NASA Technical Reports Server (NTRS)

    Makalkin, A. B.; Dorofeyeva, V. A.; Vityazev, A. V.

    1993-01-01

    One of the results obtained from thermodynamic simulation of recondensation of the source chondritic material is that at 1500-1800 K it's possible to form iron-rich olivine by reaction between enstatite, metallic iron and water vapor in the case of (H2O)/(H2) approximately equal to 0.1. This could be reached if the gas depletion in hydrogen is 200-300 times relative to solar abundance. To get this range of depletion one needs some source material more rich in hydrogen than the carbonaceous CI material which is the richest in volatiles among chondrites. In the case of recondensation at impact heating and evaporation of colliding planetesimals composed of CI material, we obtain insufficiently high value of (H2)/(H2O) ratio. In the present paper we consider some possible source materials and physical conditions necessary to reach gas composition with (H2)/(H2O) approximately 10 at high temperature.

  18. NaBH4/H2O2 Fuel Cells for Lunar and Mars Exploration

    NASA Astrophysics Data System (ADS)

    Luo, Nie; Miley, George H.; Mather, Joseph; Burton, Rodney; Hawkins, Glenn; Gimlin, Richard; Rusek, John; Valdez, Tom I.; Narayanan, Sekharipuram R.

    2006-01-01

    The properties of direct hydrogen peroxide (H2O2) fuel cells are studied in this research. Different catalysts and diffusion electrodes are tested to optimize the cell performance. Initial results indicate: 1) conversion efficiency over 60% at a practical current density of 250mA/cm2; 2) power density over 0.6 W/cm2, at room temperature and ambient pressure, better than that of any traditional fuel cell. Further, the unique combination of NaBH4 and H2O2, both of which are in an aqueous form, paves the way for a convenient unitized regeneration, which is inherently compact compared to other cells that use gas phase reactants, such as the conventional H2 and O2. These excellent properties make the NaBH4/H2O2 fuel cell a very promising candidate for future space power systems. A conceptual design to power Lunar and Mars missions is discussed.

  19. Na(H2O)[Mn(H2O)2(BP2O8)]: Crystal structure refinement

    NASA Astrophysics Data System (ADS)

    Yakubovich, O. V.; Steele, I.; Dimitrova, O. V.

    2009-01-01

    The crystal structure of synthetic manganese sodium borophosphate hydrate Na(H2O)[Mn(H2O)2(BP2O8)] was refined based on X-ray diffraction data. The compound was prepared by soft hydrothermal synthesis in the MnCl2-Na3PO4-B2O3-H2O system. The unit-cell parameters are a= 9.602(1) Å, c= 16.037(3) Å, sp. gr. P6522, Z= 6, D x = 2.57 g/cm3. The water molecules were found to be statistically distributed in the channels of the mixed anionic paraframework consisting of (BO4) and (PO4) tetrahedra and [MnO4(H2O)2] octahedra. The hydrogen atoms of the water molecules coordinated to the Mn2+ cations were located and their positional and thermal parameters were refined. The crystal-chemical features of borophosphates of the general formula A x M(H2O)2(BP2O8)(H2O) are considered.

  20. 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

  1. 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

  2. Ortho-Para Mixing Hyperfine Interaction in the H2O+ Ion and Nuclear Spin Equilibration

    NASA Astrophysics Data System (ADS)

    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(Sa-Ib + Sb-Ia) mixes ortho (I = 1) and para (I = 0) levels to cause the -forbidden- ortho to para |-I| = 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 108 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.

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

    PubMed

    Tanaka, Keiichi; Harada, Kensuke; Oka, Takeshi

    2013-10-03

    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.

  4. Diel variations of H2O2 in Greenland: A discussion of the cause and effect relationship

    NASA Astrophysics Data System (ADS)

    Bales, Roger C.; McConnell, Joseph R.; Losleben, Mark V.; Conklin, Martha H.; Fuhrer, Katrin; Neftel, Albrecht; Dibb, Jack E.; Kahl, Jonathan D. W.; Stearns, Charles R.

    1995-09-01

    Atmospheric hydrogen peroxide (H2O2) measurements at Summit, Greenland, in May-June, 1993 exhibited a diel variation, with afternoon highs typically 1-2 parts per billion by volume (ppbv) and nighttime lows about 0.5 ppbv lower. This variation closely followed that for temperature; specific humidity exhibited the same general trend. During a 17-day snowfall-free period, surface snow was accumulating H2O2, apparently from nighttime cocondensation of H2O and H2O2. Previous photochemical modeling (Neftel et al., 1995) suggests that daytime H2O2 should be about 1 ppbv, significantly lower than our measured values. Previous equilibrium partitioning measurements between ice and gas phase (Conklin et al., 1993) suggest that air in equilibrium with H2O2 concentrations measured in surface snow (15-18 μM) should have an H2O2 concentration 2-3 times what we measured 0.2-3.5 m above the snow surface. A simple eddy diffusion model, with vertical eddy diffusion coefficients calculated from balloon soundings, suggested that atmospheric H2O2 concentrations should be affected by any H2O2 degassed from surface snow. However, field measurements showed the absence of either high concentrations of H2O2 or a measurable concentration gradient between inlets 0.2 and 3 m above the snow. A surface resistance to degassing, that is, slow release of H2O2 from the ice matrix, is a plausible explanation for the differences between observations and modeled atmospheric profiles. Degassing of H2O2 at a rate below our detection limit would still influence measured atmospheric concentrations and help explain the difference between measurements and photochemical modeling. The cumulative evidence suggests that surface snow adjusts slowly to drops in atmospheric H2O2 concentration, over timescales of at least weeks. The H2O2 losses previously observed in pits sampled over more than 1 year are thought to have occurred later in the summer or fall, after the May-July field season.

  5. Simultaneous Online Measurement of H2O and CO2 in the Humid CO2 Adsorption/Desorption Process.

    PubMed

    Yu, Qingni; Ye, Sha; Zhu, Jingke; Lei, Lecheng; Yang, Bin

    2015-01-01

    A dew point meter (DP) and an infrared (IR) CO2 analyzer were assembled in a humid CO2 adsorption/desorption system in series for simultaneous online measurements of H2O and CO2, respectively. The humidifier, by using surface-flushing on a saturated brine solution was self-made for the generation of humid air flow. It was found that by this method it became relatively easy to obtain a low H2O content in air flow and that its fluctuation could be reduced compared to the bubbling method. Water calibration for the DP-IR detector is necessary to be conducted for minimizing the measurement error of H2O. It demonstrated that the relative error (RA) for simultaneous online measurements H2O and CO2 in the desorption process is lower than 0.1%. The high RA in the adsorption of H2O is attributed to H2O adsorption on the transfer pipe and amplification of the measurement error. The high accuracy of simultaneous online measurements of H2O and CO2 is promising for investigating their co-adsorption/desorption behaviors, especially for direct CO2 capture from ambient air.

  6. 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

  7. Synergetic pretreatment of sewage sludge by microwave irradiation in presence of H2O2 for enhanced anaerobic digestion.

    PubMed

    Eskicioglu, Cigdem; Prorot, Audrey; Marin, Juan; Droste, Ronald L; Kennedy, Kevin J

    2008-11-01

    A microwave-enhanced advanced hydrogen peroxide oxidation process (MW/H(2)O(2)-AOP) was studied in order to investigate the synergetic effects of MW irradiation on H(2)O(2) treated waste activated sludges (WAS) in terms of mineralization (permanent stabilization), sludge disintegration/solubilization, and subsequent anaerobic biodegradation as well as dewaterability after digestion. Thickened WAS sample pretreated with 1gH(2)O(2)/g total solids (TS) lost 11-34% of its TS, total chemical oxygen demand (COD) and total biopolymers (humic acids, proteins and sugars) via advanced oxidation. In a temperature range of 60-120 degrees C, elevated MW temperatures (>80 degrees C) further increased the decomposition of H(2)O(2) into OH* radicals and enhanced both oxidation of COD and solubilization of particulate COD (>0.45 micron) of WAS indicating that a synergetic effect was observed when both H(2)O(2) and MW treatments were combined. However, at all temperatures tested, MW/H(2)O(2) treated samples had lower first-order mesophilic (33+/-2 degrees C) biodegradation rate constants and ultimate (after 32 days of digestion) methane yields (mL per gram sample) compared to control and MW irradiated WAS samples, indicating that synergistically (MW/H(2)O(2)-AOP) generated soluble organics were slower to biodegrade or more refractory than those generated during MW irradiation.

  8. Cordierite-garnet-H2O equilibrium: A geological thermometer, barometer and water fugacity indicator

    NASA Astrophysics Data System (ADS)

    Martignole, Jacques; Sisi, Jean-Charles

    1981-03-01

    area of Mg-cordierite stability allowed by the hydration data forP_{H_2 O} = P_{total} . The present model indicates greater stabilization of cordierite by H2O than the model of Newton and Wood (1979) and the calculated curve for metastable breakdown of hydrous MgCd is consistent with experimental data on cordierite breakdown atP_{H_2 O} = P_{total} . Mg/(Mg+Fe) isopleths have been derived for cordierites of varying nH2O in the SiO2-Al2O3-MgO-FeO-H2O system using the additional assumptions that (Fe, Mg) cordierite and (Fe, Mg) garnet behave as ideal solutions, and that typical values of the distribution coefficient of Fe and Mg between coexisting garnet and cordierite observed in natural parageneses can be applied to the calculations. The calculated stable breakdown curve of Fe-cordierite under conditions ofP_{H_2 O} = P_{total} to almandine, sillimanite, quartz and vapor has a positive slope ( dP/dT) apparently in contrast to the experimental negative slope. This may be explained by hydration kinetics, which could have allowed systematic breakdown of cordierites of metastable hydration states in the experiments. The bivariant Cd-Ga fields calibrated from the present model are, potentially, good petrogenetic indicators, as, given the iron-magnesium ratio of garnet and cordierite and the hydration number of cordierite, the temperature, pressure and water fugacity are uniquely determined. As this geothermobarometer is in part based on the water content of cordierite, it can be used only if there is some assurance that the actual hydration is inherited from high-grade metamorphic conditions. Such conditions could be realised if the slope of unloading-cooling retrograde metamorphism is more or less parallel to a cordierite isohydron.

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

    NASA Astrophysics Data System (ADS)

    Li, Min; Yang, Da-Peng; Wang, Xiansong; Lu, Jianxin; Cui, Daxiang

    2013-04-01

    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.

  10. 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

  11. 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.

  12. Rapid Screening of Immobilized Amine CO2 Sorbents for Steam Stability by Their Direct Contact with Liquid H2 O.

    PubMed

    Wilfong, Walter Christopher; Kail, Brian W; Gray, McMahan L

    2015-06-22

    Rapid testing of hydrophilic and hydrophobic basic immobilized amine sorbents (BIAS) for CO2 capture stability under practical conditions was achieved by direct contact of the sorbents with flowing liquid water. Losses in both CO2 capture capacity and amine content of sorbents after exposure to 0.5 mL min(-1) of H2 O at 25 °C for 40 min followed similar trends as losses observed after exposure to N2 /steam (105 °C, 7 % H2 O) for 10 h. We also found that hydrophobic TMPED helped stabilize sorbents to H2 O, which was confirmed by DRIFTS and combined TGA-DSC.

  13. A photochemical microreactor used to analyze hydrogen peroxide (H2O2) production of T lymphocytes.

    PubMed

    Nindl, Gabi; Hess, Werner; Waite, Lee R; Balcavage, Walter X

    2005-01-01

    In this report we describe a new photochemical reactor and its use in the study of ultraviolet-B light (UVB) dependent H2O2 production by T lymphocytes. In the reactor multiple biological samples rotate around a luminescent tube and thus simultaneously absorb a uniform light-flux. The reactor was developed to expand our earlier studies where we showed that UVB activates T lymphocytes so that 10(7) cells produce about 60 nmol H2O2 per minute. H2O2 has increasingly become recognized as a cell signaling molecule regulating immune reactions mediated by T lymphocytes. Our laboratory is researching the potential of such immune regulators as potential future therapeutic agents. To study photochemical H2O2 production in small samples such as suspensions of T lymphocyte cultures or cell extracts, we designed a reactor in which 12 samples (each 50 - 500 microliters) can be exposed to light under temperature-controlled conditions. The samples are mounted on a rotating platform equidistant from the axis of rotation, where the light source of the photoreactor is located. Rotating the samples helps assure that all samples receive a uniform amount of light energy over time. A cooling fan is integrated in the base of the reactor to help minimize convective heat transfer between the lamp and the samples. We simultaneously operate two identical systems to be able to compare data that are obtained from light exposed samples under control and experimental conditions. Data on the influence of therapeutically relevant electromagnetic fields on H2O2 production of T lymphocytes are presented. H2O2 was quantified using the Amplex Red dye.

  14. Single-component and binary CO2 and H2O adsorption of amine-functionalized cellulose.

    PubMed

    Gebald, Christoph; Wurzbacher, Jan A; Borgschulte, Andreas; Zimmermann, Tanja; Steinfeld, Aldo

    2014-02-18

    A fundamental analysis of single-component and binary CO2 and H2O adsorption of amine-functionalized nanofibrillated cellulose is carried out in the temperature range of 283-353 K and at CO2 partial pressures in the range of 0.02-105 kPa, where the ultralow partial pressure range is relevant for the direct capture of CO2 from atmospheric air. Single-component CO2 and H2O adsorption experimental data are fitted to the Toth and Guggenheim-Anderson-de Boer models, respectively. Corresponding heats of adsorption, derived from explicit solutions of the van't Hoff equation, are -50 kJ/mol CO2 and -48.8 kJ/mol H2O. Binary CO2/H2O adsorption measurements for humid air reveal that the presence of H2O at 2.55 kPa enhances CO2 adsorption, while the presence of CO2 at 0.045 kPa does not influence H2O adsorption. The energy demand of the temperature-vacuum-swing adsorption/desorption cycle for delivering pure CO2 from air increases significantly with H2O adsorption and indicates the need to reduce the hygroscopicity of the adsorbent.

  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. Vibrational predissociation of ArH2O

    NASA Astrophysics Data System (ADS)

    Bissonnette, C.; Clary, D. C.

    1992-12-01

    Accurate close-coupling calculations are used to investigate the vibrational predissociation of ArH2O as a function of the overall rotation J of the van der Waals complex. A full vibrational and rotational basis of H2O states is used in the calculation. The potential energy surface is of a form due to Cohen and Saykally and derived from far-infrared spectra, with an additional term to introduce the dependence on the vibrations of H2O. The linewidths calculated in this work show a maximum at J=6 and it is found that Fermi resonances affect dramatically the magnitude of the calculated linewidths. Good agreement with experimentally measured linewidths of Nesbitt and Lascola is achieved and the calculations provide a simple picture for the J dependence of the linewidths.

  17. A Global PLASIMO Model for H2O Chemistry

    NASA Astrophysics Data System (ADS)

    Tadayon Mousavi, Samaneh; Koelman, Peter; Graef, Wouter; Mihailova, Diana; van Dijk, Jan; EPG/ Applied Physics/ Eindhoven University of Technology Team; Plasma Matters B. V. Team

    2016-09-01

    Global warming is one of the critical contemporary problems for mankind. Transformation of CO2 into fuels, like CH4, that are transportable with the current infrastructure seems a promising idea to solve this threatening issue. The final aim of this research is to produce CH4 by using microwave plasma in CO2 -H2 O mixture and follow-up catalytic processes. In this contribution we present a global model for H2 O chemistry that is based on the PLASIMO plasma modeling toolkit. The time variation of the electron energy and the species' densities are calculated based on the source and loss terms in plasma due to chemical reactions. The short simulation times of such models allow an efficient assessment and chemical reduction of the H2O chemistry, which is required for full spatially resolved simulations.

  18. 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

  19. 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.

  20. Pressure drop and heat transfer of Al2O3-H2O nanofluids through silicon microchannels

    NASA Astrophysics Data System (ADS)

    Wu, Xinyu; Wu, Huiying; Cheng, Ping

    2009-10-01

    Experimental investigations were performed on the single-phase flow and heat transfer characteristics through the silicon-based trapezoidal microchannels with a hydraulic diameter of 194.5 µm using Al2O3-H2O nanofluids with particle volume fractions of 0, 0.15% and 0.26% as the working fluids. The effects of the Reynolds number, Prandtl number and nanoparticle concentration on the pressure drop and convective heat transfer were investigated. Experimental results show that the pressure drop and flow friction of the nanofluids increased slightly when compared with that of the pure water, while the Nusselt number increased considerably. At the same pumping power, using nanofluids instead of pure water caused a reduction in the thermal resistance. It was also found that the Nusselt number increased with the increase in the particle concentration, Reynolds number and Prandtl number. Based on the experimental data, the dimensionless correlations for the flow friction and heat transfer of Al2O3-H2O nanofluids through silicon microchannels were proposed for the first time. The agglomeration and deposition of nanoparticles in the silicon microchannels were also examined in this paper. It was found that the Al2O3 nanoparticles deposited on the inner wall of microchannels more easily with increasing wall temperature, and once boiling commenced, there is a severe deposition and adhesion of nanoparticles to the inner wall, which makes the boiling heat transfer of nanofluids in silicon microchannels questionable.

  1. Abundant gas-phase H2O in absorption toward massive protostars

    NASA Astrophysics Data System (ADS)

    Boonman, A. M. S.; van Dishoeck, E. F.

    2003-06-01

    We present infrared spectra of gas-phase H2O around 6 mu m toward 12 deeply embedded massive protostars obtained with the Short Wavelength Spectrometer on board the Infrared Space Observatory (ISO). The nu2 ro-vibrational band has been detected toward 7 of the sources and the excitation temperatures indicate an origin in the warm gas at Tex>~ 250 K. Typical derived gas-phase H2O abundances are ~ 5*E-6-6*E-5, with the abundances increasing with the temperature of the warm gas. The inferred gas/solid ratios show a similar trend with temperature and suggest that grain-mantle evaporation is important. The increasing gas/solid ratio correlates with other indicators of increased temperatures. If the higher temperatures are due to a larger ratio of source luminosity to envelope mass, this makes gas-phase H2O a good evolutionary tracer. Comparison with chemical models shows that three different chemical processes, ice evaporation, high-T chemistry, and shocks, can reproduce the high inferred gas-phase H2O abundances. In a forthcoming paper each of these processes are investigated in more detail in comparison with data from the Long Wavelength Spectrometer on board ISO and the Submillimeter Wave Astronomy Satellite (SWAS). Comparison with existing SWAS data indicates that a jump in the H2O abundance is present and that the observed nu2 ro-vibrational band traces primarily the warm inner envelope. Based on observations with ISO, an ESA project with instruments funded by ESA Member States (especially the PI countries: France, Germany, the Netherlands and the United Kingdom) and with the participation of ISAS and NASA.

  2. Feasibility of ozone absorption by H2O2 solution in rotating packed beds.

    PubMed

    Lin, Chia-Chang; Chao, Cheng-Yu; Liu, Mei-Yun; Lee, Ya-Ling

    2009-08-15

    This work examined the feasibility of ozone (O(3)) absorption by H(2)O(2) solution in a rotating packed bed (RPB). The O(3) removal efficiency was determined at various operating variables including RPB speed, gas flow rate, and liquid flow rate in three RPBs. For each RPB, the results demonstrated that the RPB speed positively affected the O(3) removal efficiency. Also, the O(3) removal efficiency increased with the liquid flow rate but decreased with the gas flow rate. Moreover, the obtained results indicated that the O(3) removal efficiency increased as the inner radius of the bed was increased and the outer radius of the bed was decreased. Furthermore, the developed method for O(3) absorption using H(2)O(2) solution could provide the removal efficiency of more than 95%. Consequently, the novel method would have a great potential in the removal of O(3) from the exhausted gases.

  3. 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.

  4. 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.

  5. Maps of [HDO]/[H2O] near Mars’ Aphelion

    NASA Astrophysics Data System (ADS)

    Novak, Robert E.; Mumma, M. J.; Villanueva, G. L.

    2013-10-01

    We report maps of HDO and H2O taken at three seasonal points before and near Mars’ aphelion (Ls = 71°). These observations were taken at Ls = 357° (15 January 2006), Ls = 50° (26 March 2008) and Ls = 72° (2/3 April 2010) using CSHELL at the NASA Infrared Telescope Facility. For these three seasonal dates, the entrance slit of the spectrometer was positioned N-S on Mars centered at the sub-Earth point; on 3 April 2010, the slit was positioned E-W. Data were extracted at 0.6 arc-second intervals from the spectral-spatial images. Individual spectral lines were measured near 3.67 μm (HDO) and 3.29 μm (H2O). The column densities were obtained by comparing the observed lines to those of a multi-layered, radiative transfer model. The model includes solar Fraunhofer lines, two-way transmission through Mars’ atmosphere, thermal emission from Mars’ surface and atmosphere, and a one-way transmission through the Earth’s atmosphere. Latitudinal maps of HDO, H2O, and their ratios were then constructed. The [HDO]/[H2O] ratios have been found to be larger than those on Earth and they vary with both latitude and season. For the Ls = 357° and 50° observations, the ratio peaks near the sub-solar latitude ([HDO]/[H2O] ~ 6.9 VSMOW) and decreases towards both the North and South polar-regions. At Ls = 72°, column densities of both HDO and H2O and their ratios increase from the Southern hemisphere to the North polar-region. Observations from 3 April 2013 show diurnal variations of both the column densities and their ratio. Specific points on Mars’ surface were tracked for four hours. It is believed that this variation is caused by the vaporization of ground frost and water ice clouds that are formed during the night and disappear during daytime. Our results for H2O column densities will be compared to TES results. The results for HDO and the [HDO]/[H2O] ratios will be compared to model results.This work was partially funded by grants from NASA's Planetary Astronomy

  6. H2O2_COD_EPA; MEC_acclimation

    EPA Pesticide Factsheets

    H2O2_COD_EPA: Measurements of hydrogen peroxide and COD concentrations for water samples from the MEC reactors.MEC_acclimation: raw data for current and voltage of the anode in the MEC reactor.This dataset is associated with the following publication:Sim, J., J. An, E. Elbeshbishy, R. Hodon, and H. Lee. Characterization and optimization of cathodic conditions for H2O2 synthesis in microbial electrochemical cells. Bioresource Technology. Elsevier Online, New York, NY, USA, 195: 31-36, (2015).

  7. Epigallocatechin gallate (EGCG) prevents H2O2-induced oxidative stress in primary rat retinal pigment epithelial cells.

    PubMed

    Cia, David; Vergnaud-Gauduchon, Juliette; Jacquemot, Nathalie; Doly, Michel

    2014-09-01

    To determine whether the green tea polyphenol epigallocatechin gallate (EGCG) could prevent H(2)O(2)-induced oxidative stress in primary rat retinal pigment epithelial cells. Primary cultures of retinal pigment epithelium (RPE) cells were established from Long-Evans newborn rats. RPE cells were pretreated with various concentrations of EGCG for 24 h before being exposed to hydrogen peroxide (H(2)O(2)) for 2 h to induce oxidative stress. Cell metabolic activity was measured using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. Cell death was quantified by flow cytometry using propidium iodide (PI). Treatment of RPE cells with EGCG alone does not affect the cell viability up to 50 µM. Exposure of RPE cells to 600 µM H(2)O(2) caused a significant decrease in cell viability; whereas pretreatment with 10, 25, and 50 µM EGCG significantly reduced this decrease in a dose-dependent manner. The proportion of PI-positive cells increased significantly in cultures treated with H(2)O(2) alone; whereas pretreatment of RPE cells with 50 µM EGCG significantly reduced H(2)O(2)-induced RPE cell death. Our study shows that EGCG pretreatment can protect primary rat RPE cells from H(2)O(2)-induced death. This suggests potential effect of EGCG in the prevention of retinal diseases associated with H(2)O(2)-induced oxidative stress.

  8. 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.

  9. 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.

  10. High-temperature, high-pressure hydrothermal synthesis, crystal structure, and solid-state NMR spectroscopy of Cs2(UO2)(Si2O6) and variable-temperature powder X-ray diffraction study of the hydrate phase Cs2(UO2)(Si2O6) x 0.5H2O.

    PubMed

    Chen, Chih-Shan; Chiang, Ray-Kuang; Kao, Hsien-Ming; Lii, Kwang-Hwa

    2005-05-30

    A new uranium(VI) silicate, Cs2(UO2)(Si2O6), has been synthesized by a high-temperature, high-pressure hydrothermal method and characterized by single-crystal X-ray diffraction and solid-state NMR spectroscopy. It crystallizes in the orthorhombic space group Ibca (No. 73) with a = 15.137(1) A, b = 15.295(1) A, c = 16.401(1) A, and Z = 16. Its structure consists of corrugated achter single chains of silicate tetrahedra extending along the c axis linked together via corner-sharing by UO6 tetragonal bipyramids to form a 3-D framework which delimits 8- and 6-ring channels. The Cs+ cations are located in the channels or at sites between channels. The 29Si and 133Cs MAS NMR spectra are consistent with the crystal structure as determined from X-ray diffraction, and the resonances in the spectra are assigned. Variable-temperature in situ powder X-ray diffraction study of the hydrate Cs2(UO2)(Si2O6) x 0.5H2O indicates that the framework structure is stable up to 800 degrees C and transforms to the structure of the title compound at 900 degrees C. A comparison of related uranyl silicate structures is made.

  11. 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.

  12. 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

  13. Nitroxides protect horseradish peroxidase from H2O2-induced inactivation and modulate its catalase-like activity.

    PubMed

    Samuni, Amram; Maimon, Eric; Goldstein, Sara

    2017-08-01

    Horseradish peroxidase (HRP) catalyzes H2O2 dismutation while undergoing heme inactivation. The mechanism underlying this process has not been fully elucidated. The effects of nitroxides, which protect metmyoglobin and methemoglobin against H2O2-induced inactivation, have been investigated. HRP reaction with H2O2 was studied by following H2O2 depletion, O2 evolution and heme spectral changes. Nitroxide concentration was followed by EPR spectroscopy, and its reactions with the oxidized heme species were studied using stopped-flow. Nitroxide protects HRP against H2O2-induced inactivation. The rate of H2O2 dismutation in the presence of nitroxide obeys zero-order kinetics and increases as [nitroxide] increases. Nitroxide acts catalytically since its oxidized form is readily reduced to the nitroxide mainly by H2O2. The nitroxide efficacy follows the order 2,2,6,6-tetramethyl-piperidine-N-oxyl (TPO)>4-OH-TPO>3-carbamoyl proxyl>4-oxo-TPO, which correlates with the order of the rate constants of nitroxide reactions with compounds I, II, and III. Nitroxide catalytically protects HRP against inactivation induced by H2O2 while modulating its catalase-like activity. The protective role of nitroxide at μM concentrations is attributed to its efficient oxidation by P940, which is the precursor of the inactivated form P670. Modeling the dismutation kinetics in the presence of nitroxide adequately fits the experimental data. In the absence of nitroxide the simulation fits the observed kinetics only if it does not include the formation of a Michaelis-Menten complex. Nitroxides catalytically protect heme proteins against inactivation induced by H2O2 revealing an additional role played by nitroxide antioxidants in vivo. Copyright © 2017 Elsevier B.V. All rights reserved.

  14. 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).

  15. 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).

  16. Appearance of high-pressure H2O ice on ice-covered terrestrial planets

    NASA Astrophysics Data System (ADS)

    Ueta, S.; Sasaki, T.

    2014-03-01

    A lot of terrestrial exoplanets and free-floating planets have been discovered. Whether terrestrial planets with liquid water exist is an important question to consider, especially in terms of their habitability. Even in a globally ice-covered state, liquid water could exist beneath the surface ice shell because sufficient geothermal heat flow from the planetary interior is likely to melt the interior ice, so that an internal ocean under the surface ice shell could appear (e.g., Hoffman & Schrag 2002). In this study, we argue the conditions that must be satisfied for ice-covered terrestrial planets to have an internal ocean on the timescale of planetary evolution (Ueta & Sasaki 2013). Geothermal heat flow calculated by a parameterized convection model (e.g., McGovern & Schubert 1989) is considered as the heat source at the origin of the internal ocean. By applying and improving the model of Tajika (2008), we also examine how the amount of radiogenic heat and H2O mass affect these conditions. Moreover, we investigate the structures of surface H2O layers of ice-covered planets by considering the effects of ice under high pressure (high-pressure ice). At 1 AU from the central star, as shown in Fig. 1, a 1M.+ planet with 0.6-25 times H2O mass of the Earth could have an internal ocean. When the planet has an H2O mass over 25 times that of the Earth, high-pressure ice layers may appear between the internal ocean and the rock-part of the planet. The results indicate that planetary size and surface H2O mass strongly ristrict the conditions under which an extrasolar terrestrial planet could have an internal ocean without high-pressure ice existing under the internal ocean. The habitability of a planet might be influenced by the existence of such high-pressure ice layers.

  17. Morroniside protects SK-N-SH human neuroblastoma cells against H2O2-induced damage

    PubMed Central

    Zhang, Jing-Xing; Wang, Rui; Xi, Jin; Shen, Lin; Zhu, An-You; Qi, Qi; Wang, Qi-Yi; Zhang, Lun-Jun; Wang, Feng-Chao; Lü, He-Zuo; Hu, Jian-Guo

    2017-01-01

    Oxidative stress-induced cell injury has been linked to the pathogenesis of neurodegenerative disorders such as spinal cord injury, Parkinson's disease, and multiple sclerosis. Morroniside is an antioxidant derived from the Chinese herb Shan-Zhu-Yu. The present study investigated the neuroprotective effect of morroniside against hydrogen peroxide (H2O2)-induced cell death in SK-N-SH human neuroblastoma cells. H2O2 increased cell apoptosis, as determined by flow cytometry and Hoechst 33342 staining. This effect was reversed by pretreatment with morroniside at concentrations of 1–100 µM. The increase in intracellular reactive oxygen species (ROS) generation and lipid peroxidation induced by H2O2 was also abrogated by morroniside. H2O2 induced a reduction in mitochondrial membrane potential, increased caspase-3 activity, and caused downregulation of B cell lymphoma-2 (Bcl-2) and upregulation of Bcl-2-associated X protein (Bax) expression. These effects were blocked by morroniside pretreatment. Thus, morroniside protects human neuroblastoma cells against oxidative damage by inhibiting ROS production while suppressing Bax and stimulating Bcl-2 expression, thereby blocking mitochondrial-mediated apoptosis. These results indicate that morroniside has therapeutic potential for the prevention and treatment of neurodegenerative diseases. PMID:28204825

  18. Mussel oligopeptides protect human fibroblasts from hydrogen peroxide (H2O2)-induced premature senescence.

    PubMed

    Zhou, Yue; Dong, Ying; Xu, Qing-Gang; Zhu, Shu-Yun; Tian, Shi-Lei; Huo, Jing-jing; Hao, Ting-Ting; Zhu, Bei-Wei

    2014-01-01

    Mussel bioactive peptides have been viewed as mediators to maximize the high quality of life. In this study, the anti-aging activities of mussel oligopeptides were evaluated using H2O2-induced prematurely senescent MRC-5 fibroblasts. 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay and flow cytometry displayed that exposure to H2O2 led to the loss of cell viability and cell cycle arrest. In addition, H2O2 caused the elevation of senescence-associated-β-galactosidase (SA-β-gal) activity and formation of senescence-associated heterochromatin foci (SAHF). It was found that pretreatment with mussel oligopeptides could significantly attenuate these properties associated with cellular senescence. Mussel oligopeptides also led to the increase of glutathione (GSH) level and mitochondrial transmembrane potential (Δψm) recovery. In addition, mussel oligopeptides resulted in an improvement in transcriptional activity of peroxiredoxin 1 (Prx1), nicotinamide phosphoribosyltransferase (NAMPT) and sirtuin 1 (SIRT1). This study revealed that mussel oligopeptides could protect against cellular senescence induced by H2O2, and the effects were closely associated with redox cycle modulating and potentiating the SIRT1 pathway. These findings provide new insights into the beneficial role of mussel bioactive peptides on retarding senescence process. Crown Copyright © 2013. Published by Elsevier Ireland Ltd. All rights reserved.

  19. Morroniside protects SK-N-SH human neuroblastoma cells against H2O2-induced damage.

    PubMed

    Zhang, Jing-Xing; Wang, Rui; Xi, Jin; Shen, Lin; Zhu, An-You; Qi, Qi; Wang, Qi-Yi; Zhang, Lun-Jun; Wang, Feng-Chao; Lü, He-Zuo; Hu, Jian-Guo

    2017-03-01

    Oxidative stress-induced cell injury has been linked to the pathogenesis of neurodegenerative disorders such as spinal cord injury, Parkinson's disease, and multiple sclerosis. Morroniside is an antioxidant derived from the Chinese herb Shan-Zhu-Yu. The present study investigated the neuroprotective effect of morroniside against hydrogen peroxide (H2O2)-induced cell death in SK-N-SH human neuroblastoma cells. H2O2 increased cell apoptosis, as determined by flow cytometry and Hoechst 33342 staining. This effect was reversed by pretreatment with morroniside at concentrations of 1-100 µM. The increase in intracellular reactive oxygen species (ROS) generation and lipid peroxidation induced by H2O2 was also abrogated by morroniside. H2O2 induced a reduction in mitochondrial membrane potential, increased caspase-3 activity, and caused downregulation of B cell lymphoma-2 (Bcl-2) and upregulation of Bcl-2-associated X protein (Bax) expression. These effects were blocked by morroniside pretreatment. Thus, morroniside protects human neuroblastoma cells against oxidative damage by inhibiting ROS production while suppressing Bax and stimulating Bcl-2 expression, thereby blocking mitochondrial-mediated apoptosis. These results indicate that morroniside has therapeutic potential for the prevention and treatment of neurodegenerative diseases.

  20. Influence of salicylic acid on H2O2 production, oxidative stress, and H2O2-metabolizing enzymes. Salicylic acid-mediated oxidative damage requires H2O2.

    PubMed Central

    Rao, M V; Paliyath, G; Ormrod, D P; Murr, D P; Watkins, C B

    1997-01-01

    We investigated how salicylic acid (SA) enhances H2O2 and the relative significance of SA-enhanced H2O2 in Arabidopsis thaliana. SA treatments enhanced H2O2 production, lipid peroxidation, and oxidative damage to proteins, and resulted in the formation of chlorophyll and carotene isomers. SA-enhanced H2O2 levels were related to increased activities of Cu,Zn-superoxide dismutase and were independent of changes in catalase and ascorbate peroxidase activities. Prolonging SA treatments inactivated catalase and ascorbate peroxidase and resulted in phytotoxic symptoms, suggesting that inactivation of H2O2-degrading enzymes serves as an indicator of hypersensitive cell death. Treatment of leaves with H2O2 alone failed to invoke SA-mediated events. Although leaves treated with H2O2 accumulated in vivo H2O2 by 2-fold compared with leaves treated with SA, the damage to membranes and proteins was significantly less, indicating that SA can cause greater damage than H2O2. However, pretreatment of leaves with dimethylthiourea, a trap for H2O2, reduced SA-induced lipid peroxidation, indicating that SA requires H2O2 to initiate oxidative damage. The relative significance of the interaction among SA, H2O2, and H2O2-metabolizing enzymes with oxidative damage and cell death is discussed. PMID:9306697

  1. 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.

  2. 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.

  3. H 2O + ions in comets: models and observations

    NASA Astrophysics Data System (ADS)

    Wegmann, R.; Jockers, K.; Bonev, T.

    1999-06-01

    An improved magnetohydrodynamic (MHD) model with chemistry is presented. The analysis of the source and sink terms for H 2O + shows that for small comets up to 11% of water molecules are finally ionized. For large comets (such as Halley) this fraction decreases to less than 3%. From the MHD scaling laws a similarity law for the individual ion densities is deduced which takes into account that the mother molecules are depleted by dissociation. This is applied to H 2O + ions. Radial density profiles from model calculations, observations by Giotto near comet Halley, and ground based observations of three comets confirm this scaling law for H 2O + ions. From the similarity law for the density a scaling law for the column density is derived which is more convenient to apply for ground based observations. From these scaling laws methods are derived which allow the determination of the water production rate from the ground based images of the H 2O + ions. Finally, the two dimensional images of model column densities are compared with observations.

  4. 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.

  5. Iron weathering products in a CO 2 + (H 2O or H 2O 2) atmosphere: Implications for weathering processes on the surface of Mars

    NASA Astrophysics Data System (ADS)

    Chevrier, V.; Mathé, P.-E.; Rochette, P.; Grauby, O.; Bourrié, G.; Trolard, F.

    2006-08-01

    Various iron-bearing primary phases and rocks have been weathered experimentally to simulate possible present and past weathering processes occurring on Mars. We used magnetite, monoclinic and hexagonal pyrrhotites, and metallic iron as it is suggested that meteoritic input to the martian surface may account for an important source of reduced iron. The phases were weathered in two different atmospheres: one composed of CO 2 + H 2O, to model the present and primary martian atmosphere, and a CO 2 + H 2O + H 2O 2 atmosphere to simulate the effect of strong oxidizing agents. Experiments were conducted at room temperature and a pressure of 0.75 atm. Magnetite is the only stable phase in the experiments and is thus likely to be released on the surface of Mars from primary rocks during weathering processes. Siderite, elemental sulfur, ferrous sulfates and ferric (oxy)hydroxides (goethite and lepidocrocite) are the main products in a water-bearing atmosphere, depending on the substrate. In the peroxide atmosphere, weathering products are dominated by ferric sulfates and goethite. A kinetic model was then developed for iron weathering in a water atmosphere, using the shrinking core model (SCM). This model includes competition between chemical reaction and diffusion of reactants through porous layers of secondary products. The results indicate that for short time scales, the mechanism is dominated by a chemical reaction with second order kinetics ( k = 7.75 × 10 -5 g -1/h), whereas for longer time scales, the mechanism is diffusion-controlled (De A = 2.71 × 10 -10 m 2/h). The results indicate that a primary CO 2- and H 2O-rich atmosphere should favour sulfur, ferrous phases such as siderite or Fe 2+-sulfates, associated with ferric (oxy)hydroxides (goethite and lepidocrocite). Further evolution to more oxidizing conditions may have forced these precursors to evolve into ferric sulfates and goethite/hematite.

  6. Detection of OH^+ and H_2O^+ Toward Orion KL

    NASA Astrophysics Data System (ADS)

    Gupta, Harshal; Pearson, John C.; Yu, Shanshan; Rimmer, Paul; Herbst, Eric; Bergin, Edwin A.; Hexos Team

    2011-06-01

    The reactive molecular ions, OH^+, H_2O^+, and H_3O^+, 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-H_2O^+ 111 - 000 transition at 1115 and 1139 GHz were detected, and an upper limit was obtained for H_3O^+. OH^+ and H_2O^+ 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 H_2O^+ 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-H_3O^+ 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 OH^+ and H_2O^+.

  7. 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.

  8. 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.

  9. Partial pressures of H 2O above the diphasic Li 2O(s)-LiOH(s, l) system

    NASA Astrophysics Data System (ADS)

    Tetenbaum, M.; Johnson, C. E.

    1984-09-01

    The temperature dependence of the partial pressure of H 2O(g) above the Li 2O(s)-LiOH(s, l) system was determined for temperatures between 300 and 617°C. The partial pressures were measured by means of a flowing gas technique combined with continuous monitoring of the concentration of water vapor in a helium carrier gas. For the reaction LiOH(s) = Li 2O(s) + H 2O(g) , second law heat and entropy of reaction values of ΔH o = 30.7 ± 0.6 kcal/mol and ΔS o = 29.5 ± 1.0 cal/mol.K were obtained. Above the melting point of LiOH (744 K), these values were ΔH o =19.9 ± 0.6 kcal/mol and ΔS o =14.8 ± 0.8 cal/mol.K . Current measurements yield ΔH mo = 5.4 ± 0.4 kcal/mol for the heat of melting of LiOH, which is in good agreement with the JANAF recommended value of 4.99 kcal/mol. The results of these measurements can be used to partially describe the behavior of a Li 2O solid breeding blanket in anticipated fusion reactor environments.

  10. 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.

  11. 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

  12. Effects of resveratrol on H(2)O(2)-induced apoptosis and expression of SIRTs in H9c2 cells.

    PubMed

    Yu, Wei; Fu, Yu-Cai; Zhou, Xiao-Hui; Chen, Chun-Juan; Wang, Xin; Lin, Rui-Bo; Wang, Wei

    2009-07-01

    Resveratrol, a polyphenol found in fruits, has been demonstrated to activate Sir2. Though many studies have demonstrated that resveratrol can activate SIRT1, whether it has effect on other sirtuins (SIRT2-7) are unknown. The present study shows that exposure of H9c2 cells to 50 microM H(2)O(2) for 6 h caused a significant increase in apoptosis, as evaluated by TUNEL and flow cytometry (FCM), but pretreatment of resveratrol (20 microM) eliminated H(2)O(2)-induced apoptosis. Resveratrol also prevented H(2)O(2)-induced caspase-3 activation. Exposure of cells to resveratrol caused rapid activation of SIRT1,3,4,7. Sirtuin inhibitor, nicotinamide (20 mM) attenuated resveratrol's inhibitory effect on cell apoptosis and caspase-3 activity. These results suggest that resveratrol protects cardiomyocytes from H(2)O(2)-induced apoptosis by activating SIRT1,3,4,7. 2009 Wiley-Liss, Inc.