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Sample records for hydration number water

  1. Some thermodynamical aspects of protein hydration water

    Energy Technology Data Exchange (ETDEWEB)

    Mallamace, Francesco, E-mail: francesco.mallamace@unime.it [Dipartimento di Fisica e Scienze della Terra, Università di Messina and CNISM, I-98168 Messina (Italy); Department of Nuclear Science and Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States); Center for Polymer Studies and Department of Physics, Boston University, Boston, Massachusetts 02215 (United States); Corsaro, Carmelo [Dipartimento di Fisica e Scienze della Terra, Università di Messina and CNISM, I-98168 Messina (Italy); CNR-IPCF, Viale F. Stagno D’Alcontres 37, I-98158 Messina (Italy); Mallamace, Domenico [Dipartimento SASTAS, Università di Messina, I-98166 Messina (Italy); Vasi, Sebastiano [Dipartimento di Fisica e Scienze della Terra, Università di Messina and CNISM, I-98168 Messina (Italy); Vasi, Cirino [CNR-IPCF, Viale F. Stagno D’Alcontres 37, I-98158 Messina (Italy); Stanley, H. Eugene [Center for Polymer Studies and Department of Physics, Boston University, Boston, Massachusetts 02215 (United States); Chen, Sow-Hsin [Department of Nuclear Science and Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States)

    2015-06-07

    We study by means of nuclear magnetic resonance the self-diffusion of protein hydration water at different hydration levels across a large temperature range that includes the deeply supercooled regime. Starting with a single hydration shell (h = 0.3), we consider different hydrations up to h = 0.65. Our experimental evidence indicates that two phenomena play a significant role in the dynamics of protein hydration water: (i) the measured fragile-to-strong dynamic crossover temperature is unaffected by the hydration level and (ii) the first hydration shell remains liquid at all hydrations, even at the lowest temperature.

  2. Separation of water through gas hydrate formation

    DEFF Research Database (Denmark)

    Boch Andersen, Torben; Thomsen, Kaj

    2009-01-01

    Gas hydrate is normally recognized as a troublemaker in the oil and gas industry. However, gas hydrate has some interesting possibilities when used in connection with separation of water. Nordic Sugar has investigated the possibility of using gas hydrates for concentration of sugar juice. The goa...... volumes and the needs for high pressure. The process could be interesting for concentration of heat sensitive, high value products......Gas hydrate is normally recognized as a troublemaker in the oil and gas industry. However, gas hydrate has some interesting possibilities when used in connection with separation of water. Nordic Sugar has investigated the possibility of using gas hydrates for concentration of sugar juice. The goal...... of the project was to formulate an alternative separation concept, which can replace the traditional water evaporation process in the sugar production. Work with the separation concept showed that gas hydrates can be used for water separation. The process is not suitable for sugar production because of large...

  3. Dynamics of Hydration Water in Sugars and Peptides Solutions

    Energy Technology Data Exchange (ETDEWEB)

    Perticaroli, Stefania [ORNL; Nakanishi, Masahiro [ORNL; Pashkovski, Eugene [Unilever R& D Trumbull, Trumbull CT; Sokolov, Alexei P [ORNL

    2013-01-01

    We analyzed solute and solvent dynamics of sugars and peptides aqueous solutions using extended epolarized light scattering (EDLS) and broadband dielectric spectroscopies (BDS). Spectra measured with both techniques reveal the same mechanism of rotational diffusion of peptides molecules. In the case of sugars, this solute reorientational relaxation can be isolated by EDLS measurements, whereas its ontribution to the dielectric spectra is almost negligible. In the presented analysis, we characterize the hydration water in terms of hydration number and retardation ratio between relaxation times of hydration and bulk water. Both techniques provide similar estimates of . The retardation imposed on the hydration water by sugars is 3.3 1.3 and involves only water molecules hydrogen-bonded (HB) to solutes ( 3 water molecules per sugar OH-group). In contrast, polar peptides cause longer range erturbations beyond the first hydration shell, and between 2.8 and 8, increasing with the number of chemical groups engaged in HB formation. We demonstrate that chemical heterogeneity and specific HB interactions play a crucial role in hydration dynamics around polar solutes. The obtained results help to disentangle the role of excluded volume and enthalpic contributions in dynamics of hydration water at the interface with biological molecules.

  4. Determination of membrane hydration numbers of alkali metal ions by insertion in a conducting polymer

    DEFF Research Database (Denmark)

    Skaarup, Steen; Junaid Mohamed Jafeen, Mohamed; Careem, M.A.

    2010-01-01

    , and a secondary (or outer) solvation shell, consisting of all other water molecules whose properties are still influenced significantly by the cation. Knowing the hydration number is important when considering, for instance, the transport of Na+ and K+ in biological cell membranes, since their different behavior...... of the number of M+ ions entering the film, and therefore the inserted M+ mass. The mass of the water molecules can then be calculated as a difference. The values determined this way may be called membrane hydration numbers. The results yield the following membrane hydration numbers: Li+: 5.3-5.5; Na+ 4...... membrane....

  5. Vibrational dynamics of hydration water in amylose

    CERN Document Server

    Cavatorta, F; Albanese, G; Angelini, N

    2002-01-01

    We present a study of the dynamical properties of hydration water associated with amylose helices, based on low-temperature vibrational spectra collected using the TOSCA inelastic spectrometer at ISIS. The structural constraints of the polysaccharidic chains favour the formation of a high-density structure for water, which has been suggested by Imberty and Perez on the basis of conformational analysis. According to this model, hydration water can only enter the pores formed by six adjacent helices and completely fills the pores at a hydration level of about 0.27-g water/g dry amylose. Our measurements show that the dynamical behaviour of hydration water is similar to that observed in high-density amorphous ice. (orig.)

  6. RESEARCH ON COUPLED RELATIONSHIP BETWEEN HYDRATION NUMBER WITH RAMAN SPECTRUM

    Institute of Scientific and Technical Information of China (English)

    LEI Huaiyan; LIU Zhihong; FAN Shuanshi; XU Maoquan; GUAN Baocong

    2003-01-01

    As we know, there are three structures-sⅠ, sⅡ, and sH, with hydrocarbonate gas hydrate.Because of those special structures characteristics and potentail large fossil energy resource, gas hydrate play an important role in natural carbonate cycle system. In this paper, CH4, CO2, C3H8, and CH4 +CO2 system have been experimental performed in order to model hydrate formation and discomposition and to obtain hydrate stability conditions of tempreature and pressure. The results from laboratory using Raman spectra show that Raman spectrascopy is a effective tool to identify hydrate structure. Raman spectra of clathrate hydrate guest molecules are presented for two structure (sⅠ and sⅡ) in the following systems: CH4, CO2, C3 H8. Relatively occupancy of CH4 in the large and small cavities of sⅠ were determined by deconvoluting the v1 symmetric bands, resulting in hydration numbers of 6.04±0.03. The freqyuency of the v1 bands for CH4 in structures Ⅰ and Ⅱ differ statistically. The large cavities were measured to be almost fully occupied by CH4 and CO2, whereas only a small fraction of the small cavities are occupied by CH4. No CO2 was found in the small cavities.

  7. The effect of hydrate saturation on water retention curves in hydrate-bearing sediments

    Science.gov (United States)

    Mahabadi, Nariman; Zheng, Xianglei; Jang, Jaewon

    2016-05-01

    The experimental measurement of water retention curve in hydrate-bearing sediments is critically important to understand the behavior of hydrate dissociation and gas production. In this study, tetrahydrofuran (THF) is selected as hydrate former. The pore habit of THF hydrates is investigated by visual observation in a transparent micromodel. It is confirmed that THF hydrates are not wetting phase on the quartz surface of the micromodel and occupy either an entire pore or part of pore space resulting in change in pore size distribution. And the measurement of water retention curves in THF hydrate-bearing sediments with hydrate saturation ranging from Sh = 0 to Sh = 0.7 is conducted for excess water condition. The experimental results show that the gas entry pressure and the capillary pressure increase with increasing hydrate saturation. Based on the experimental results, fitting parameters for van Genuchten equation are suggested for different hydrate saturation conditions.

  8. Complex admixtures of clathrate hydrates in a water desalination method

    Science.gov (United States)

    Simmons, Blake A.; Bradshaw, Robert W.; Dedrick, Daniel E.; Anderson, David W.

    2009-07-14

    Disclosed is a method that achieves water desalination by utilizing and optimizing clathrate hydrate phenomena. Clathrate hydrates are crystalline compounds of gas and water that desalinate water by excluding salt molecules during crystallization. Contacting a hydrate forming gaseous species with water will spontaneously form hydrates at specific temperatures and pressures through the extraction of water molecules from the bulk phase followed by crystallite nucleation. Subsequent dissociation of pure hydrates yields fresh water and, if operated correctly, allows the hydrate-forming gas to be efficiently recycled into the process stream.

  9. Methane storage in dry water gas hydrates.

    Science.gov (United States)

    Wang, Weixing; Bray, Christopher L; Adams, Dave J; Cooper, Andrew I

    2008-09-03

    Dry water stores 175 v(STP)/v methane at 2.7 MPa and 273.2 K in a hydrate form which is close to the Department of Energy volumetric target for methane storage. Dry water is a silica-stabilized free-flowing powder (95% wt water), and fast methane uptakes were observed (90% saturation uptake in 160 min with no mixing) as a result of the relatively large surface-to-volume ratio of this material.

  10. Waters of Hydration of Cupric Hydrates: A Comparison between Heating and Absorbance Methods

    Science.gov (United States)

    Barlag, Rebecca; Nyasulu, Frazier

    2011-01-01

    The empirical formulas of four cupric hydrates are determined by measuring the absorbance in aqueous solution. The Beer-Lambert Law is verified by constructing a calibration curve of absorbance versus known Cu[superscript 2+](aq) concentration. A solution of the unknown hydrate is prepared by using 0.2-0.3 g of hydrate, and water is added such…

  11. Water retention curve for hydrate-bearing sediments

    Science.gov (United States)

    Dai, Sheng; Santamarina, J. Carlos

    2013-11-01

    water retention curve plays a central role in numerical algorithms that model hydrate dissociation in sediments. The determination of the water retention curve for hydrate-bearing sediments faces experimental difficulties, and most studies assume constant water retention curves regardless of hydrate saturation. This study employs network model simulation to investigate the water retention curve for hydrate-bearing sediments. Results show that (1) hydrate in pores shifts the curve to higher capillary pressures and the air entry pressure increases as a power function of hydrate saturation; (2) the air entry pressure is lower in sediments with patchy rather than distributed hydrate, with higher pore size variation and pore connectivity or with lower specimen slenderness along the flow direction; and (3) smaller specimens render higher variance in computed water retention curves, especially at high water saturation Sw > 0.7. Results are relevant to other sediment pore processes such as bioclogging and mineral precipitation.

  12. Hydration and Nanoconfined Water: Insights from Computer Simulations.

    Science.gov (United States)

    Alarcón, Laureano M; Rodríguez Fris, J A; Morini, Marcela A; Sierra, M Belén; Accordino, S A; Montes de Oca, J M; Pedroni, Viviana I; Appignanesi, Gustavo A

    2015-01-01

    The comprehension of the structure and behavior of water at interfaces and under nanoconfinement represents an issue of major concern in several central research areas like hydration, reaction dynamics and biology. From one side, water is known to play a dominant role in the structuring, the dynamics and the functionality of biological molecules, governing main processes like protein folding, protein binding and biological function. In turn, the same principles that rule biological organization at the molecular level are also operative for materials science processes that take place within a water environment, being responsible for the self-assembly of molecular structures to create synthetic supramolecular nanometrically-sized materials. Thus, the understanding of the principles of water hydration, including the development of a theory of hydrophobicity at the nanoscale, is imperative both from a fundamental and an applied standpoint. In this work we present some molecular dynamics studies of the structure and dynamics of water at different interfaces or confinement conditions, ranging from simple model hydrophobic interfaces with different geometrical constraints (in order to single out curvature effects), to self-assembled monolayers, proteins and phospholipid membranes. The tendency of the water molecules to sacrifice the lowest hydrogen bond (HB) coordination as possible at extended interfaces is revealed. This fact makes the first hydration layers to be highly oriented, in some situations even resembling the structure of hexagonal ice. A similar trend to maximize the number of HBs is shown to hold in cavity filling, with small subnanometric hydrophobic cavities remaining empty while larger cavities display an alternation of filled and dry states with a significant inner HB network. We also study interfaces with complex chemical and geometrical nature in order to determine how different conditions affect the local hydration properties. Thus, we show some

  13. Kinetics of hydrate formation using gas bubble suspended in water

    Institute of Scientific and Technical Information of China (English)

    马昌峰; 陈光进; 郭天民

    2002-01-01

    An innovative experimental technique, which was devised to study the effects of temperature and pressure on the rate of hydrate formation at the surface of a gas bubble suspended in a stagnant water phase, was adapted in this work. Under such conditions, the hydrate-growth process is free from dynamic mass transfer factors. The rate of hydrate formation of methane and carbon dioxide has been systematically studied. The measured hydrate-growth data were correlated by using the molar Gibbs free energy as driving force. In the course of the experiments, some interesting surface phenomena were observed.

  14. Are all polar molecules hydrophilic? Hydration numbers of nitro compounds and nitriles in aqueous solution.

    Science.gov (United States)

    Sagawa, Naoya; Shikata, Toshiyuki

    2014-07-14

    The hydration numbers of typical aprotic polar substances bearing dipole moments larger than 3 D, such as nitro compounds and nitriles, were precisely determined in aqueous solution using high frequency dielectric relaxation techniques up to a frequency of 50 GHz at 25 °C. The hydration number is one of the most quantitative parameters for determining the hydrophilicity or hydrophobicity of a compound. The hydration numbers of various nitriles, such as acetonitrile, propionitrile and n-butyronitrile bearing cyano groups, were determined to be ca. 0, irrespective of the species of molecule. Moreover, the hydration numbers of various nitro compounds, such as nitromethane, nitroethane and 1-nitropropane, were also evaluated to be ca. 0. These findings clearly reveal that neither cyano nor nitro functional groups form strong hydrogen bonds to water molecules. Consequently, neither nitro compounds nor nitriles are hydrophilic, despite their high polarities due to their large dipole moments. Rather, these compounds are "hydroneutral," with hydrophilicities intermediate between those of hydrophilic and hydrophobic molecules. The molecular motions of the examined highly polar molecules in aqueous solution were well described with single Debye-type rotational relaxation modes without strong interactions between the solute and water molecules, but with relatively strong interactions between the polar solute molecules due to the Kirkwood factor being less than unity. This small Kirkwood factor indicated that both nitro and cyano groups have a tendency to align in an anti-parallel intermolecular configuration due to their strong dipole-dipole interactions as a result of their dipole moments greater than 3 D.

  15. Application of various water soluble polymers in gas hydrate inhibition

    DEFF Research Database (Denmark)

    Kamal, Muhammad Shahzad; Hussein, Ibnelwaleed A.; Sultan, Abdullah S.

    2016-01-01

    . This review presents the various types of water soluble polymers used for hydrate inhibition, including conventional and novel polymeric inhibitors along with their limitations. The review covers the relevant properties of vinyl lactam, amide, dendrimeric, fluorinated, and natural biodegradable polymers...

  16. The role of water in gas hydrate dissociation

    Science.gov (United States)

    Circone, S.; Stern, L.A.; Kirby, S.H.

    2004-01-01

    When raised to temperatures above the ice melting point, gas hydrates release their gas in well-defined, reproducible events that occur within self-maintained temperature ranges slightly below the ice point. This behavior is observed for structure I (carbon dioxide, methane) and structure II gas hydrates (methane-ethane, and propane), including those formed with either H2O- or D2O-host frameworks, and dissociated at either ambient or elevated pressure conditions. We hypothesize that at temperatures above the H2O (or D2O) melting point: (1) hydrate dissociation produces water + gas instead of ice + gas, (2) the endothermic dissociation reaction lowers the temperature of the sample, causing the water product to freeze, (3) this phase transition buffers the sample temperatures within a narrow temperature range just below the ice point until dissociation goes to completion, and (4) the temperature depression below the pure ice melting point correlates with the average rate of dissociation and arises from solution of the hydrate-forming gas, released by dissociation, in the water phase at elevated concentrations. In addition, for hydrate that is partially dissociated to ice + gas at lower temperatures and then heated to temperatures above the ice point, all remaining hydrate dissociates to gas + liquid water as existing barriers to dissociation disappear. The enhanced dissociation rates at warmer temperatures are probably associated with faster gas transport pathways arising from the formation of water product.

  17. Water diffusion in fully hydrated porcine stratum corneum

    Energy Technology Data Exchange (ETDEWEB)

    Pieper, J.; Charalambopoulou, G.; Steriotis, Th.; Vasenkov, S.; Desmedt, A.; Lechner, R.E

    2003-08-01

    The microscopic mechanisms of water diffusion in fully hydrated porcine stratum corneum (SC) have been studied by a combination of incoherent quasielastic neutron scattering (QENS) and pulsed field gradient-nuclear magnetic resonance (PFG-NMR) for two sample orientations. The presence of three types of water in fully hydrated SC is inferred on the basis of water sorption isotherm data, i.e., (a) bound and (b) weakly bound hydration water forming layers between adjacent lipid bilayers of SC, as well as (c) bulk water probably located in the corneocytes and in intercellular regions. Water self-diffusion coefficients for motions parallel and perpendicular to the membrane plane of D{sub parallel}=3.30x10{sup -10} m{sup 2}/s and D{sub perpendicular}=1.56x10{sup -10} m{sup 2}/s, respectively, were determined by PFG-NMR and assigned to the translational diffusion of weakly bound water. QENS measurements have been carried out using different samples hydrated with H{sub 2}O and D{sub 2}O, respectively, in order to separate the contribution of SC from that of the water. The QENS data for both sample orientations and two different energy resolutions can be fitted by a model which accounts for the microscopic dynamics of all three aforementioned types of water. This analysis establishes rotational diffusion coefficients for bound and weakly bound hydration water of 0.025 and 0.030 meV, respectively. Furthermore, the QENS data prove the presence of bulk water in fully hydrated SC samples.

  18. Water in volcanic glass: From volcanic degassing to secondary hydration

    Science.gov (United States)

    Seligman, Angela N.; Bindeman, Ilya N.; Watkins, James M.; Ross, Abigail M.

    2016-10-01

    Volcanic glass is deposited with trace amounts (0.1-0.6 wt.%) of undegassed magmatic water dissolved in the glass. After deposition, meteoric water penetrates into the glass structure mostly as molecular H2O. Due to the lower δD (‰) values of non-tropical meteoric waters and the ∼30‰ offset between volcanic glass and environmental water during hydration, secondary water imparts lighter hydrogen isotopic values during secondary hydration up to a saturation concentration of 3-4 wt.% H2O. We analyzed compositionally and globally diverse volcanic glass from 0 to 10 ka for their δD and H2Ot across different climatic zones, and thus different δD of precipitation, on a thermal conversion elemental analyzer (TCEA) furnace attached to a mass spectrometer. We find that tephrachronologically coeval rhyolite glass is hydrated faster than basaltic glass, and in the majority of glasses an increase in age and total water content leads to a decrease in δD (‰), while a few equatorial glasses have little change in δD (‰). We compute a magmatic water correction based on our non-hydrated glasses, and calculate an average 103lnαglass-water for our hydrated felsic glasses of -33‰, which is similar to the 103lnαglass-water determined by Friedman et al. (1993a) of -34‰. We also determine a smaller average 103lnαglass-water for all our mafic glasses of -23‰. We compare the δD values of water extracted from our glasses to local meteoric waters following the inclusion of a -33‰ 103lnαglass-water. We find that, following a correction for residual magmatic water based on an average δD and wt.% H2Ot of recently erupted ashes from our study, the δD value of water extracted from hydrated volcanic glass is, on average, within 4‰ of local meteoric water. To better understand the difference in hydration rates of mafic and felsic glasses, we imaged 6 tephra clasts ranging in age and chemical composition with BSE (by FEI SEM) down to a submicron resolution. Mafic tephra

  19. Heterogeneities in confined water and protein hydration water

    Energy Technology Data Exchange (ETDEWEB)

    Stanley, H E; Kumar, P; Han, S; Mazza, M G; Stokely, K; Buldyrev, S V [Center for Polymer Studies and Department of Physics, Boston University, Boston, MA 02215 (United States); Franzese, G [Departament de Fisica Fonamental, Universitat de Barcelona, Diagonal 647, E-08028 Barcelona (Spain); Mallamace, F [Dipartimento di Fisica, Universita di Messina, Villaggio S Agata, CP 55, I-98166 Messina (Italy); Xu, L, E-mail: hes@bu.ed [World Premier International (WPI) Research Center, Advanced Institute for Materials Research, Tohoku University, Sendai 980-8577 (Japan)

    2009-12-16

    We report recent efforts to understand a broad range of experiments on confined water and protein hydration water, many initiated by a collaboration between workers at the University of Messina and MIT-the editors of this special issue. Preliminary calculations are not inconsistent with one tentative interpretation of these experiments as resulting from the system passing from the high-temperature high-pressure 'HDL' side of the Widom line (where the liquid might display non-Arrhenius behavior) to the low-temperature low-pressure 'LDL' side of the Widom line (where the liquid might display Arrhenius behavior). The Widom line-defined to be the line in the pressure-temperature plane where the correlation length has its maximum-arises if there is a critical point. Hence, interpreting the Messina-MIT experiments in terms of a Widom line is of potential relevance to testing, experimentally, the hypothesis that water displays a liquid-liquid critical point.

  20. Hydration of proteins: excess partial volumes of water and proteins.

    Science.gov (United States)

    Sirotkin, Vladimir A; Komissarov, Igor A; Khadiullina, Aigul V

    2012-04-05

    High precision densitometry was applied to study the hydration of proteins. The hydration process was analyzed by the simultaneous monitoring of the excess partial volumes of water and the proteins in the entire range of water content. Five unrelated proteins (lysozyme, chymotrypsinogen A, ovalbumin, human serum albumin, and β-lactoglobulin) were used as models. The obtained data were compared with the excess partial enthalpies of water and the proteins. It was shown that the excess partial quantities are very sensitive to the changes in the state of water and proteins. At the lowest water weight fractions (w(1)), the changes of the excess functions can mainly be attributed to water addition. A transition from the glassy to the flexible state of the proteins is accompanied by significant changes in the excess partial quantities of water and the proteins. This transition appears at a water weight fraction of 0.06 when charged groups of proteins are covered. Excess partial quantities reach their fully hydrated values at w(1) > 0.5 when coverage of both polar and weakly interacting surface elements is complete. At the highest water contents, water addition has no significant effect on the excess quantities. At w(1) > 0.5, changes in the excess functions can solely be attributed to changes in the state of the proteins.

  1. Correlation Between Chain Architecture and Hydration Water Structure in Polysaccharides.

    Science.gov (United States)

    Grossutti, Michael; Dutcher, John R

    2016-03-14

    The physical properties of confined water can differ dramatically from those of bulk water. Hydration water associated with polysaccharides provides a particularly interesting example of confined water, because differences in polysaccharide structure provide different spatially confined environments for water sorption. We have used attenuated total reflection infrared (ATR-IR) spectroscopy to investigate the structure of hydration water in films of three different polysaccharides under controlled relative humidity (RH) conditions. We compare the results obtained for films of highly branched, dendrimer-like phytoglycogen nanoparticles to those obtained for two unbranched polysaccharides, hyaluronic acid (HA), and chitosan. We find similarities between the water structuring in the two linear polysaccharides and significant differences for phytoglycogen. In particular, the results suggest that the high degree of branching in phytoglycogen leads to a much more well-ordered water structure (low density, high connectivity network water), indicating the strong influence of chain architecture on the structuring of water. These measurements provide unique insight into the relationship between the structure and hydration of polysaccharides, which is important for understanding and exploiting these sustainable nanomaterials in a wide range of applications.

  2. Hydration of proteins: excess partial enthalpies of water and proteins.

    Science.gov (United States)

    Sirotkin, Vladimir A; Khadiullina, Aigul V

    2011-12-22

    Isothermal batch calorimetry was applied to study the hydration of proteins. The hydration process was analyzed by the simultaneous monitoring of the excess partial enthalpies of water and the proteins in the entire range of water content. Four unrelated proteins (lysozyme, chymotrypsinogen A, human serum albumin, and β-lactoglobulin) were used as models. The excess partial quantities are very sensitive to the changes in the state of water and proteins. At the lowest water weight fractions (w(1)), the changes of the excess thermochemical functions can mainly be attributed to water addition. A transition from the glassy to the flexible state of the proteins is accompanied by significant changes in the excess partial quantities of water and the proteins. This transition appears at a water weight fraction of 0.06 when charged groups of proteins are covered. Excess partial quantities reach their fully hydrated values at w(1) > 0.5 when coverage of both polar and weakly interacting surface elements is complete. At the highest water contents, water addition has no significant effect on the excess thermochemical quantities. At w(1) > 0.5, changes in the excess functions can solely be attributed to changes in the state of the proteins.

  3. Dynamics of water and hydrated protons in confinement

    NARCIS (Netherlands)

    Liu, L.

    2015-01-01

    In this thesis the dynamics of water and hydrated protons in confinement has been studied using nonlinear spectroscopy methods, including IR pump-probe spectroscopy and vibrational sum frequency generation spectroscopy (VSFG spectroscopy). Using the IR pump-probe spectroscopy, we first investigated

  4. The Water Retention Curves in THF Hydrate-Bearing Sediments - Experimental Measurement and Pore Scale Simulation

    Science.gov (United States)

    Mahabadi, N.; Zheng, X.; Dai, S.; Seol, Y.; Zapata, C.; Yun, T.; Jang, J.

    2015-12-01

    The water retention curve (WRC) of hydrate-bearing sediments is critically important to understand the behaviour of hydrate dissociation for gas production. Most gas hydrates in marine environment have been formed from an aqueous phase (gas-dissolved water). However, the gas hydrate formation from an aqueous phase in a laboratory requires long period due to low gas solubility in water and is also associated with many experimental difficulties such as hydrate dissolution, difficult hydrate saturation control, and dynamic hydrate dissolution and formation. In this study, tetrahydrofuran (THF) is chosen to form THF hydrate because the formation process is faster than gas hydrate formation and hydrate saturation is easy to control. THF hydrate is formed at water-excess condition. Therefore, there is only water in the pore space after a target THF hydrate saturation is obtained. The pore habit of THF hydrate is investigated by visual observation in a transparent micromodel and X-ray computed tomography images; and the water retention curves are obtained under different THF hydrate saturation conditions. Targeted THF hydrate saturations are Sh=0, 0.2, 0.4, 0.6 and 0.8. Results shown that at a given water saturation the capillary pressure increases as THF hydrate saturation increases. And the gas entry pressure increases with increasing hydrate saturation. The WRC obtained by experiments is also compared with the results of a pore-network model simulation and Lattice Boltzmann Method. The fitting parameters of van Genuchten equation for different hydrate saturation conditions are suggested for the use as input parameters of reservoir simulators.

  5. Molecular properties of aqueous solutions: a focus on the collective dynamics of hydration water.

    Science.gov (United States)

    Comez, L; Paolantoni, M; Sassi, P; Corezzi, S; Morresi, A; Fioretto, D

    2016-07-07

    When a solute is dissolved in water, their mutual interactions determine the molecular properties of the solute on one hand, and the structure and dynamics of the surrounding water particles (the so-called hydration water) on the other. The very existence of soft matter and its peculiar properties are largely due to the wide variety of possible water-solute interactions. In this context, water is not an inert medium but rather an active component, and hydration water plays a crucial role in determining the structure, stability, dynamics, and function of matter. This review focuses on the collective dynamics of hydration water in terms of retardation with respect to the bulk, and of the number of molecules whose dynamics is perturbed. Since water environments are in a dynamic equilibrium, with molecules continuously exchanging from around the solute towards the bulk and vice versa, we examine the ability of different techniques to measure the water dynamics on the basis of the explored time scales and exchange rates. Special emphasis is given to the collective dynamics probed by extended depolarized light scattering and we discuss whether and to what extent the results obtained in aqueous solutions of small molecules can be extrapolated to the case of large biomacromolecules. In fact, recent experiments performed on solutions of increasing complexity clearly indicate that a reductionist approach is not adequate to describe their collective dynamics. We conclude this review by presenting current ideas that are being developed to describe the dynamics of water interacting with macromolecules.

  6. Dynamic morphology of gas hydrate on a methane bubble in water: Observations and new insights for hydrate film models

    National Research Council Canada - National Science Library

    Warzinski, Robert P; Lynn, Ronald; Haljasmaa, Igor; Leifer, Ira; Shaffer, Frank; Anderson, Brian J; Levine, Jonathan S

    2014-01-01

    Predicting the fate of subsea hydrocarbon gases escaping into seawater is complicated by potential formation of hydrate on rising bubbles that can enhance their survival in the water column, allowing...

  7. HYDRATION STRUCTURE AND WATER EXCHANGE DYNAMICS ...

    African Journals Online (AJOL)

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    distribution functions, coordination numbers, and angular distributions. The average .... weighted-histogram-analysis method (WHAM) [36, 40, 41] which is adopted in this study. By ... level using the Gaussian 98 program [42]. The ECP basis ...

  8. Production behaviour of gas hydrate under hot sea water injection : laboratory case study

    Energy Technology Data Exchange (ETDEWEB)

    Nengkoda, A. [Schlumberger, Calgary, AB (Canada); Budhijanto, B.; Supranto, S.; Prasetyo, I.; Purwono, S.; Sutijan, S. [Gadjah Mada Univ., Yogyakarta (Indonesia)

    2010-07-01

    The gas hydrate potential in Indonesia was discussed, with particular reference to offshore production of gas from deep-water gas-hydrates by injection of hot seawater. In 2004, the Indonesian National Agency for Assessment and Application Technology estimated the gas hydrate resource potential to be 850 trillion cubic feet (tcf). To date, the 3 most reliable scenarios for gas hydrate production are thermal stimulation which involves increasing the temperature until the hydrates break into water and gas; depressurization which involves lowering the pressure by pumping out gas at the base of the hydrate to cause dissociation of hydrates into gas; and injection of a chemical inhibitor such as methanol into the hydrated sediments to cause destabilization, thus releasing gas from hydrates. This study investigated the effect of hot seawater injection on the gas hydrate production under laboratory conditions. The temperature profile distribution was examined along with operational parameters and flow characteristics of the dissociated gas and water from hydrates in porous systems under a synthetic hydrate setup. The study showed that gas production increases with time until a maximum is reached, at which time it begins to decrease. The energy ratio of thermal stimulation production was found to be influenced by the injection water temperature and rate as well as the hydrate content in the synthetic sediment. Scale problems were found to be associated with high temperature seawater injection. 8 refs., 3 tabs., 7 figs.

  9. Water dynamics in hyperarid soils of Antarctica including water adsorption and salt hydration

    Science.gov (United States)

    Hagedorn, B.; Sletten, R. S.

    2009-12-01

    Soils in the McMurdo Dry Valleys, Antarctica contain ice and considerable amounts of salt. Ice often occurs at shallow depth throughout the dry valleys and other areas of hyperarid permafrost, notably on Mars. This common occurrence of shallow ice is enigmatic; however, since according to published sublimation models it should disappear relatively quickly (at rates of order 0.1 mm a-1) due to vapor loss to the atmosphere. The disagreement between the occurrence of ice on one hand and process-based vapor transport models on other hand suggests that processes in addition to vapor transport have influence on ice stability. From a number of possible processes, infiltration of snowmelt during summer month and vapor trapping due to overlaying snow cover in winter have been discussed in more detail and both processes are likely to slow down ice sublimation. At this point, however, there are only limited field-observations to confirm the presence of such processes. The present study aims to investigate the effect of water adsorption, salt hydration, and freezing point depression on water transport and ice stability. We hypothesize that hydration of salts and water adsorption on grain surfaces play an important role in the survival of ground ice and as water reservoir in these areas and should be taken into account when modeling vapor transport. Furthermore, there is evidence that salt content in ground ice is high enough to cause formation of brines at subfreezing temperatures that can lead to a growth of ground ice. To support our hypothesis we set up a field experiment by monitoring soil temperature, soil humidity, and soil moisture along with climate data and snow cover. In addition we collected soil samples to measure water potential, salt composition, ice content, and soil texture. Soil samples were extracted with water to measure soluble salt content along dry and ice rich soil profiles. In addition we measured soil moisture retention curves at different vapor

  10. Single-particle dynamics of hydration water in protein

    Energy Technology Data Exchange (ETDEWEB)

    Bellissent-Funel, M.C.; Teixeira, J. (Lab. Leon Brillouin (CEA-CNRS), CEN-Saclay, 91 - Gif-sur-Yvette (France)); Bradley, K.F.; Chen, S.H. (Nuclear Engineering Dept., M.I.T., Cambridge, MA (United States)); Crespi, H.L. (Chemistry Div., Argonne National Lab., IL (United States))

    1992-06-01

    Incoherent quasi-elastic and inelastic neutron scattering studies of in vivo deuterated C-phycocyanin have been made. At full hydration the high-temperature data can be interpreted using a model where each water molecule is diffusing in a confined space of 3 A in radius. The excess elastic intensity at large Q indicates that a relatively low fraction of a water molecules attached to the immediate vicinity of the protein surface is immobile, in agreement with computer simulation. The translational and librational density of states show slight up-shifts from the corresponding bulk cases. (orig.).

  11. Hydration number of alkali metal ions determined by insertion in a conducting polymer

    DEFF Research Database (Denmark)

    Skaarup, Steen

    2008-01-01

    . The solvation of alkali metal ions has been discussed for many years without a clear consensus. This work presents a systematic study of the hydration numbers of the 5 alkali metal ions, using the electrochemical insertion of the ions in a conducting polymer (polypyrrole containing the large immobile anion DBS...

  12. Experimental NIR Study of Water Ice, Hydrated Salts, and mixtures.

    Science.gov (United States)

    Singh, S.; Combe, J. P.; McCord, T. B.

    2016-12-01

    The dwarf planet Ceres is the largest object in the main asteroid belt and is currently being explored by the Dawn spacecraft. Recent discoveries by Dawn such as the presence of water ice (Combe et al., 2015) and the ammoniated phyllosilicates (De Sanctis et al., 2015) have carved new paths for a wide of range of laboratory work to explain the physical processes on Ceres. The albedo of Ceres is rather dark, consistent with the albedo of graphite or asphalt. However, there are bright spots with albedo similar to hydrated salts and water ice due to the presence of widely distributed subsurface water or ice that can modify the surface composition. The presence of hydrated salts and water ice had been predicted by McCord et al., (2005) and Castillo et al., (2010), but there is a lack of physical evidence. Here we investigate the dependence of water absorption bands as a function of temperature and concentration of surrounding global candidates such as serpentine, montmorillonite, and carbon black. Laboratory spectra of minerals with bound water show that the wavelengths of the absorption bands do not shift with the temperatures indicating that the bound water should be detectable when a large amount of ice is present. However, the amount of low reflectance (carbon black) material with water tends to suppress the absorption bands. The dependency of water ice grain size with low reflectance material show that the absorption bands of water ice (grain size >100 µm) will appear even with higher concentrations ( 5%) of low reflectance material. Whereas, the absorption bands of water ice of grain size <50 µm will be suppressed by low concentration of global candidate materials (carbon black). Laboratory spectra analysis suggest that even 1% of low reflectance material can mask the absorption bands of water ice < 50 µm and water-minerals. This implies that the lack of detection of hydrated salts or other minerals on the surface of Ceres can simply be due to the presence of

  13. A hydrated ion model of [UO2] 2 + in water: Structure, dynamics, and spectroscopy from classical molecular dynamics

    Science.gov (United States)

    Pérez-Conesa, Sergio; Torrico, Francisco; Martínez, José M.; Pappalardo, Rafael R.; Sánchez Marcos, Enrique

    2016-12-01

    A new ab initio interaction potential based on the hydrated ion concept has been developed to obtain the structure, energetics, and dynamics of the hydration of uranyl in aqueous solution. It is the first force field that explicitly parameterizes the interaction of the uranyl hydrate with bulk water molecules to accurately define the second-shell behavior. The [UO2(H2O)5 ] 2 + presents a first hydration shell U-O average distance of 2.46 Å and a second hydration shell peak at 4.61 Å corresponding to 22 molecules using a coordination number definition based on a multisite solute cavity. The second shell solvent molecules have longer mean residence times than those corresponding to the divalent monatomic cations. The axial regions are relatively de-populated, lacking direct hydrogen bonding to apical oxygens. Angle-solved radial distribution functions as well as the spatial distribution functions show a strong anisotropy in the ion hydration. The [UO2(H2O)5 ] 2 + solvent structure may be regarded as a combination of a conventional second hydration shell in the equatorial and bridge regions, and a clathrate-like low density region in the axial region. Translational diffusion coefficient, hydration enthalpy, power spectra of the main vibrational modes, and the EXAFS spectrum simulated from molecular dynamics trajectories agree fairly well with the experiment.

  14. Water permeability in hydrate-bearing sediments: A pore-scale study

    Science.gov (United States)

    Dai, Sheng; Seol, Yongkoo

    2014-06-01

    Permeability is a critical parameter governing methane flux and fluid flow in hydrate-bearing sediments; however, limited valid data are available due to experimental challenges. Here we investigate the relationship between apparent water permeability (k') and hydrate saturation (Sh), accounting for hydrate pore-scale growth habit and meso-scale heterogeneity. Results from capillary tube models rely on cross-sectional tube shapes and hydrate pore habits, thus are appropriate only for sediments with uniform hydrate distribution and known hydrate pore character. Given our pore network modeling results showing that accumulating hydrate in sediments decreases sediment porosity and increases hydraulic tortuosity, we propose a modified Kozeny-Carman model to characterize water permeability in hydrate-bearing sediments. This model agrees well with experimental results and can be easily implemented in reservoir simulators with no empirical variables other than Sh. Results are also relevant to flow through other natural sediments that undergo diagenesis, salt precipitation, or bio-clogging.

  15. Dynamics of hydration water and coupled protein sidechains around a polymerase protein surface

    Science.gov (United States)

    Qin, Yangzhong; Yang, Yi; Wang, Lijuan; Zhong, Dongping

    2017-09-01

    Water-protein coupled interactions are essential to the protein structural stability, flexibility and dynamic functions. The ultimate effects of the hydration dynamics on the protein fluctuations remain substantially unexplored. Here, we investigated the dynamics of both hydration water and protein sidechains at 13 different sites around the polymerase β protein surface using a tryptophan scan with femtosecond spectroscopy. Three types of hydration-water relaxations and two types of protein sidechain motions were determined, reflecting a highly dynamic water-protein interactions fluctuating on the picosecond time scales. The hydration-water dynamics dominate the coupled interactions with higher flexibility.

  16. Hydration and hydrogen bond network of water around hydrophobic surface investigated by terahertz spectroscopy.

    Science.gov (United States)

    Shiraga, K; Suzuki, T; Kondo, N; Ogawa, Y

    2014-12-21

    Water conformation around hydrophobic side chains of four amino acids (glycine, L-alanine, L-aminobutyric acid, and L-norvaline) was investigated via changes in complex dielectric constant in the terahertz (THz) region. Each of these amino acids has the same hydrophilic backbone, with successive additions of hydrophobic straight methylene groups (-CH2-) to the side chain. Changes in the degree of hydration (number of dynamically retarded water molecules relative to bulk water) and the structural conformation of the water hydrogen bond (HB) network related to the number of methylene groups were quantitatively measured. Since dielectric responses in the THz region represent water relaxations and water HB vibrations at a sub-picosecond and picosecond timescale, these measurements characterized the water relaxations and HB vibrations perturbed by the methylene apolar groups. We found each successive straight -CH2- group on the side chain restrained approximately two hydrophobic hydration water molecules. Additionally, the number of non-hydrogen-bonded (NHB) water molecules increased slightly around these hydrophobic side chains. The latter result seems to contradict the iceberg model proposed by Frank and Evans, where water molecules are said to be more ordered around apolar surfaces. Furthermore, we compared the water-hydrophilic interactions of the hydrophilic amino acid backbone with those with the water-hydrophobic interactions around the side chains. As the hydrophobicity of the side chain increased, the ordering of the surrounding water HB network was altered from that surrounding the hydrophilic amino acid backbone, thereby diminishing the fraction of NHB water and ordering the surrounding tetrahedral water HB network.

  17. Water anomalous thermodynamics, attraction, repulsion, and hydrophobic hydration

    Science.gov (United States)

    Cerdeiriña, Claudio A.; Debenedetti, Pablo G.

    2016-04-01

    A model composed of van der Waals-like and hydrogen bonding contributions that simulates the low-temperature anomalous thermodynamics of pure water while exhibiting a second, liquid-liquid critical point [P. H. Poole et al., Phys. Rev. Lett. 73, 1632 (1994)] is extended to dilute solutions of nonionic species. Critical lines emanating from such second critical point are calculated. While one infers that the smallness of the water molecule may be a relevant factor for those critical lines to move towards experimentally accessible regions, attention is mainly focused on the picture our model draws for the hydration thermodynamics of purely hydrophobic and amphiphilic non-electrolyte solutes. We first focus on differentiating solvation at constant volume from the corresponding isobaric process. Both processes provide the same viewpoint for the low solubility of hydrophobic solutes: it originates from the combination of weak solute-solvent attractive interactions and the specific excluded-volume effects associated with the small molecular size of water. However, a sharp distinction is found when exploring the temperature dependence of hydration phenomena since, in contrast to the situation for the constant-V process, the properties of pure water play a crucial role at isobaric conditions. Specifically, the solubility minimum as well as enthalpy and entropy convergence phenomena, exclusively ascribed to isobaric solvation, are closely related to water's density maximum. Furthermore, the behavior of the partial molecular volume and the partial molecular isobaric heat capacity highlights the interplay between water anomalies, attraction, and repulsion. The overall picture presented here is supported by experimental observations, simulations, and previous theoretical results.

  18. A cheaper, faster, better way to detect water of hydration on Solar System bodies

    Science.gov (United States)

    Vilas, Faith

    1994-01-01

    The 3.0-micrometers water of hydration absorption feature observed in the IR photometry of many low-albedo and some medium-albedo asteroids strongly correlates with the 0.7-micrometers Fe(+2) to Fe(+3) oxidized iron absorption feature observed in narrowband spectrophotometry of these asteroids. Using this relationship, an empirical algorithm for predicting the presence of water of hydration in the surface material of a Solar System body using photometry obtained through the Eight-Color Asteroid Survey nu (0.550 micrometers), w (0.701 micrometers), and x (0.853 micrometers) filters was developed and applied to the ECAS photometry of asteroids and outer planet satellites. The percentage of objects in low-albedo, outer main-belt asteroid classes that test positively for water of hydration increases from P to B to C to G class and correlates linearly with the increasing mean albedos of those objects testing positively. The medium-albedo M-class asteroids do not test positively in large number using this algorithm. Aqueously altered asteroids dominate the Solar System population between heliocentric distances of 2.6 to 3.5 AU, bracketing the Solar System region where the aqueous alteration mechanism operated most strongly. One jovian satellite, J VI Himalia, and one saturnian satellite. Phoebe, tested positively for water of hydration, supporting the hypothesis that these may be captured C-class asteroids from a postaccretional dispersion. The proposed testing technique could be applied to an Earth-based survey of asteroids or a space-probe study of an asteroid's surface characteristic in order to identify a potential water source.

  19. Hydrophobic hydration and the anomalous partial molar volumes in ethanol-water mixtures

    Science.gov (United States)

    Tan, Ming-Liang; Miller, Benjamin T.; Te, Jerez; Cendagorta, Joseph R.; Brooks, Bernard R.; Ichiye, Toshiko

    2015-02-01

    The anomalous behavior in the partial molar volumes of ethanol-water mixtures at low concentrations of ethanol is studied using molecular dynamics simulations. Previous work indicates that the striking minimum in the partial molar volume of ethanol VE as a function of ethanol mole fraction XE is determined mainly by water-water interactions. These results were based on simulations that used one water model for the solute-water interactions but two different water models for the water-water interactions. This is confirmed here by using two more water models for the water-water interactions. Furthermore, the previous work indicates that the initial decrease is caused by association of the hydration shells of the hydrocarbon tails, and the minimum occurs at the concentration where all of the hydration shells are touching each other. Thus, the characteristics of the hydration of the tail that cause the decrease and the features of the water models that reproduce this type of hydration are also examined here. The results show that a single-site multipole water model with a charge distribution that mimics the large quadrupole and the p-orbital type electron density out of the molecular plane has "brittle" hydration with hydrogen bonds that break as the tails touch, which reproduces the deep minimum. However, water models with more typical site representations with partial charges lead to flexible hydration that tends to stay intact, which produces a shallow minimum. Thus, brittle hydration may play an essential role in hydrophobic association in water.

  20. Dynamic morphology of gas hydrate on a methane bubble in water: Observations and new insights for hydrate film models

    Science.gov (United States)

    Warzinski, Robert P.; Lynn, Ronald; Haljasmaa, Igor; Leifer, Ira; Shaffer, Frank; Anderson, Brian J.; Levine, Jonathan S.

    2014-10-01

    Predicting the fate of subsea hydrocarbon gases escaping into seawater is complicated by potential formation of hydrate on rising bubbles that can enhance their survival in the water column, allowing gas to reach shallower depths and the atmosphere. The precise nature and influence of hydrate coatings on bubble hydrodynamics and dissolution is largely unknown. Here we present high-definition, experimental observations of complex surficial mechanisms governing methane bubble hydrate formation and dissociation during transit of a simulated oceanic water column that reveal a temporal progression of deep-sea controlling mechanisms. Synergistic feedbacks between bubble hydrodynamics, hydrate morphology, and coverage characteristics were discovered. Morphological changes on the bubble surface appear analogous to macroscale, sea ice processes, presenting new mechanistic insights. An inverse linear relationship between hydrate coverage and bubble dissolution rate is indicated. Understanding and incorporating these phenomena into bubble and bubble plume models will be necessary to accurately predict global greenhouse gas budgets for warming ocean scenarios and hydrocarbon transport from anthropogenic or natural deep-sea eruptions.

  1. Lysozyme in water-acetonitrile mixtures: Preferential solvation at the inner edge of excess hydration

    Science.gov (United States)

    Sirotkin, Vladimir A.; Kuchierskaya, Alexandra A.

    2017-06-01

    Preferential solvation/hydration is an effective way for regulating the mechanism of the protein destabilization/stabilization. Organic solvent/water sorption and residual enzyme activity measurements were performed to monitor the preferential solvation/hydration of hen egg-white lysozyme at high and low water content in acetonitrile at 25 °C. The obtained results show that the protein destabilization/stabilization depends essentially on the initial hydration level of lysozyme and the water content in acetonitrile. There are three composition regimes for the dried lysozyme. At high water content, the lysozyme has a higher affinity for water than for acetonitrile. The residual enzyme activity values are close to 100%. At the intermediate water content, the dehydrated lysozyme has a higher affinity for acetonitrile than for water. A minimum on the residual enzyme activity curve was observed in this concentration range. At the lowest water content, the organic solvent molecules are preferentially excluded from the dried lysozyme, resulting in the preferential hydration. The residual catalytic activity is ˜80%, compared with that observed after incubation in pure water. Two distinct schemes are operative for the hydrated lysozyme. At high and intermediate water content, lysozyme is preferentially hydrated. However, in contrast to the dried protein, at the intermediate water content, the initially hydrated lysozyme has the increased preferential hydration parameters. At low water content, the preferential binding of the acetonitrile molecules to the initially hydrated lysozyme was detected. No residual enzyme activity was observed in the water-poor acetonitrile. Our data clearly show that the initial hydration level of the protein macromolecules is one of the key factors that govern the stability of the protein-water-organic solvent systems.

  2. Hydration and translocation of an excess proton in water clusters: An ab initio molecular dynamics study

    Indian Academy of Sciences (India)

    Arindam Bankura; Amalendu Chandra

    2005-10-01

    The hydration structure and translocation of an excess proton in hydrogen bonded water clusters of two different sizes are investigated by means of finite temperature quantum simulations. The simulations are performed by employing the method of Car–Parrinello molecular dynamics where the forces on the nuclei are obtained directly from `on the fly' quantum electronic structure calculations. Since no predefined interaction potentials are used in this scheme, it is ideally suited to study proton translocation processes which proceed through breaking and formation of chemical bonds. The coordination number of the hydrated proton and the index of oxygen to which the excess proton is attached are calculated along the simulation trajectories for both the clusters.

  3. Role of hydration and water coordination in micellization of Pluronic block copolymers.

    Science.gov (United States)

    Šturcová, Adriana; Schmidt, Pavel; Dybal, Jiří

    2010-12-15

    Raman, attenuated total reflectance FTIR, near-infrared spectroscopy, and DFT calculations have been used in a study of aqueous solutions of three tri-block copolymers poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) or PEO-PPO-PEO with commercial names Pluronic PE6200, PE6400 and F68. It is shown that the process of micellization as a response to increased temperature is reflected in the hydroxyl stretching region of infrared and Raman spectra, which contains information both about restructuring of water and changes of polymer chains in polymer/water aggregates. Raman spectra exhibit differences between individual Pluronics even at temperatures below the critical micellization temperature (CMT). According to the attenuated total reflection (ATR) FTIR spectra, the same five water coordination types defined by the number of donated/accepted hydrogen bonds are present in interacting water as in bulk water. It indicates that models considering mixed states of water with different hydrogen bonding environments provide appropriate descriptions of bound water both below and above the CMT. Above the CMT, aggregate hydration increases in the order PE6400 < PE6200 < F68, although that does not fully correspond to the EO/PO ratio, and points to the differences in microstructure of aggregates formed by each copolymer. This study relates nanoscale phenomena (hydrophobic and hydrophilic hydration) with the mesoscale phenomenon of micellization. Copyright © 2010 Elsevier Inc. All rights reserved.

  4. The water retention curve and relative permeability for gas production from hydrate-bearing sediments: pore-network model simulation

    Science.gov (United States)

    Mahabadi, Nariman; Dai, Sheng; Seol, Yongkoo; Sup Yun, Tae; Jang, Jaewon

    2016-08-01

    The water retention curve and relative permeability are critical to predict gas and water production from hydrate-bearing sediments. However, values for key parameters that characterize gas and water flows during hydrate dissociation have not been identified due to experimental challenges. This study utilizes the combined techniques of micro-focus X-ray computed tomography (CT) and pore-network model simulation to identify proper values for those key parameters, such as gas entry pressure, residual water saturation, and curve fitting values. Hydrates with various saturation and morphology are realized in the pore-network that was extracted from micron-resolution CT images of sediments recovered from the hydrate deposit at the Mallik site, and then the processes of gas invasion, hydrate dissociation, gas expansion, and gas and water permeability are simulated. Results show that greater hydrate saturation in sediments lead to higher gas entry pressure, higher residual water saturation, and steeper water retention curve. An increase in hydrate saturation decreases gas permeability but has marginal effects on water permeability in sediments with uniformly distributed hydrate. Hydrate morphology has more significant impacts than hydrate saturation on relative permeability. Sediments with heterogeneously distributed hydrate tend to result in lower residual water saturation and higher gas and water permeability. In this sense, the Brooks-Corey model that uses two fitting parameters individually for gas and water permeability properly capture the effect of hydrate saturation and morphology on gas and water flows in hydrate-bearing sediments.

  5. Simulation of gas production from hydrate reservoir by the combination of warm water flooding and depressurization

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    Gas production from hydrate reservoir by the combination of warm water flooding and depressurization is proposed,which can overcome the deficiency of single production method.Based on the combination production method,the physical and mathematical models are developed to simulate the hydrate dissociation.The mathematical model can be used to analyze the effects of the flow of multiphase fluid,the kinetic process of hydrate dissociation,the endothermic process of hydrate dissociation,ice-water phase equilibrium,the convection and conduction on the hydrate dissociation and gas and water production.The mechanism of gas production by the combination of warm water flooding and depressurization is revealed by the numerical simulation.The evolutions of such physical variables as pressure,temperature,saturations and gas and water rates are analyzed.Numerical results show that under certain conditions the combination method has the advantage of longer stable period of high gas rate than the single producing method.

  6. Submarine Slope Failure Primed and Triggered by Bottom Water Warming in Oceanic Hydrate-Bearing Deposits

    Directory of Open Access Journals (Sweden)

    Tae-Hyuk Kwon

    2012-08-01

    Full Text Available Many submarine slope failures in hydrate-bearing sedimentary deposits might be directly triggered, or at least primed, by gas hydrate dissociation. It has been reported that during the past 55 years (1955–2010 the 0–2000 m layer of oceans worldwide has been warmed by 0.09 °C because of global warming. This raises the following scientific concern: if warming of the bottom water of deep oceans continues, it would dissociate natural gas hydrates and could eventually trigger massive slope failures. The present study explored the submarine slope instability of oceanic gas hydrate-bearing deposits subjected to bottom water warming. One-dimensional coupled thermal-hydraulic-mechanical (T-H-M finite difference analyses were performed to capture the underlying physical processes initiated by bottom water warming, which includes thermal conduction through sediments, thermal dissociation of gas hydrates, excess pore pressure generation, pressure diffusion, and hydrate dissociation against depressurization. The temperature rise at the seafloor due to bottom water warming is found to create an excess pore pressure that is sufficiently large to reduce the stability of a slope in some cases. Parametric study results suggest that a slope becomes more susceptible to failure with increases in thermal diffusivity and hydrate saturation and decreases in pressure diffusivity, gas saturation, and water depth. Bottom water warming can be further explored to gain a better understanding of the past methane hydrate destabilization events on Earth, assuming that more reliable geological data is available.

  7. Hydrate Formation/Dissociation in (Natural Gas + Water + Diesel Oil Emulsion Systems

    Directory of Open Access Journals (Sweden)

    Chang-Yu Sun

    2013-02-01

    Full Text Available Hydrate formation/dissociation of natural gas in (diesel oil + water emulsion systems containing 3 wt% anti-agglomerant were performed for five water cuts: 5, 10, 15, 20, and 25 vol%. The natural gas solubilities in the emulsion systems were also examined. The experimental results showed that the solubility of natural gas in emulsion systems increases almost linearly with the increase of pressure, and decreases with the increase of water cut. There exists an initial slow hydrate formation stage for systems with lower water cut, while rapid hydrate formation takes place and the process of the gas-liquid dissolution equilibrium at higher water cut does not appear in the pressure curve. The gas consumption amount due to hydrate formation at high water cut is significantly higher than that at low water cut. Fractional distillation for natural gas components also exists during the hydrate formation process. The experiments on hydrate dissociation showed that the dissociation rate and the amount of dissociated gas increase with the increase of water cut. The variations of temperature in the process of natural gas hydrate formation and dissociation in emulsion systems were also examined.

  8. Water Density Fluctuations Relevant to Hydrophobic Hydration are Unaltered by Attractions

    CERN Document Server

    Remsing, Richard C

    2014-01-01

    An understanding of density fluctuations in bulk water has made significant contributions to our understanding of the hydration and interactions of idealized, purely repulsive hydrophobic solutes. To similarly inform the hydration of realistic hydrophobic solutes that have dispersive interactions with water, here we characterize water density fluctuations in the presence of attractive fields that correspond to solute-water attractions. We find that when the attractive field acts only in the solute hydration shell, but not in the solute core, it does not significantly alter water density fluctuations in the solute core region. We further find that for a wide range of solute sizes and attraction strengths, the free energetics of turning on the attractive fields in bulk water are accurately captured by linear response theory. Our results also suggest strategies for more efficiently estimating hydration free energies of realistic solutes in bulk water and at interfaces.

  9. Quasi-elastic neutron scattering studies on dynamics of water confined in nanoporous copper rubeanate hydrates.

    Science.gov (United States)

    Yamada, Takeshi; Yonamine, Ryo; Yamada, Teppei; Kitagawa, Hiroshi; Tyagi, Madhusudan; Nagao, Michihiro; Yamamuro, Osamu

    2011-11-24

    We have investigated the mechanism of the first order transition and proton conductivity in copper rubeanate hydrates from microscopic and dynamical points of view. Three different types of neutron spectrometer-time-of-flight, backscattering, and neutron spin echo-were used to cover a wide dynamic range (1 ps to 100 ns). We found that the water molecules adsorbed in the pore are divided into "free water" having diffusion coefficients similar to those of bulk water at room temperature and "condensed water" which is about 10 times slower than bulk water owing to the interaction with the pore wall. The hydrogen atoms in the pore wall exhibited no relaxation within the measured time scales. The free water has, in the framework of the jump-diffusion model, smaller activation energy, longer residence time, and longer jump distance than bulk water. The neutron spin echo measurement revealed that the first order transition is a kind of liquid-liquid transition at which the free water is condensed on the pore surface in the low temperature phase. On cooling the condensed water, the relaxation time starts to deviate from the VFT equation around 200 K as previously observed in the water confined in nanoporous silicates. The free water plays an important role as the proton carrier but the proton conductivity is mainly governed by the number of protons provided into the adsorbed water from the pore wall.

  10. New Insights into the Dynamics of Zwitterionic Micelles and Their Hydration Waters by Gigahertz-to-Terahertz Dielectric Spectroscopy

    CERN Document Server

    George, Deepu K; Hull, Olivia A; Mishra, Archana; Capelluto, Daniel G S; Mitchell-Koch, Katie R; Vinh, Nguyen Q

    2016-01-01

    Gigahertz-to-terahertz spectroscopy of macromolecules in aqueous environments provides an important approach for identifying their global and transient molecular structures, as well as directly assessing hydrogen-bonding. We report dielectric properties of zwitterionic dodecylphosphocholine (DPC) micelles in aqueous solutions over a wide frequency range, from 50 MHz to 1.12 THz. The dielectric relaxation spectra reveal different polarization mechanisms at the molecular level, reflecting the complexity of DPC micelle-water interactions. We have made a deconvolution of the spectra into different components and combined them with the effective-medium approximation to separate delicate processes of micelles in water. Our measurements demonstrate reorientational motion of the DPC surfactant head groups within the micelles, and two levels of hydration water shells, including tightly- and loosely-bound hydration water layers. From the dielectric strength of bulk water in DPC solutions, we found that the number of wa...

  11. Vibrational excitations of proteins and their hydration water in the far-infrared range

    Energy Technology Data Exchange (ETDEWEB)

    Paciaroni, A., E-mail: alessandro.paciaroni@fisica.unipg.it [Dipartimento di Fisica, Universita’ degli Studi di Perugia, Via Pascoli, I-06123 Perugia (Italy); Conti Nibali, V. [Lehrstuhl für Physikalische Chemie II, Ruhr-Universität Bochum, 44780 Bochum (Germany); Orecchini, A. [Dipartimento di Fisica, Universita’ degli Studi di Perugia, Via Pascoli, I-06123 Perugia (Italy); Institut Laue Langevin, 6 rue J. Horowitz, F-38042 Grenoble (France); Petrillo, C. [Dipartimento di Fisica, Universita’ degli Studi di Perugia, Via Pascoli, I-06123 Perugia (Italy); Haertlein, M.; Moulin, M. [Institut Laue Langevin, 6 rue J. Horowitz, F-38042 Grenoble (France); Tarek, M. [UMR Structure et Réactivité des Systèmes Moléculaires Complexes, Nancy-University, CNRS (France); D’Angelo, G. [Dipartimento di Fisica, Universita’ degli Studi di Messina, Viale F. Stagno d’Alcontres 31, I-98166 Messina (Italy); Sacchetti, F. [Dipartimento di Fisica, Universita’ degli Studi di Perugia, Via Pascoli, I-06123 Perugia (Italy)

    2013-10-16

    Highlights: • We characterize the vibrations of proteins and hydration water in far-infrared range. • Isotopic contrast is used to highlight protein or water component. • MD simulations help understanding vibrational bands. • The inelastic behavior of proteins is quite independent on the solvent. • Protein hydration water vibrational behavior is similar to amorphous ice. - Abstract: Incoherent neutron scattering has been used to single out the vibrational contribution from maltose binding protein (MBP) and its hydration water in the energy range 1 meV–80 meV. The vibrational density of states from both protein and hydration water have been investigated by measuring respectively dry and D{sub 2}O-hydrated isotopically natural MBP and dry and H{sub 2}O-hydrated perdeuterated MBP. Molecular dynamics simulations done on the same system allow us to attribute the protein inelastic features. The inelastic behavior of the biomolecule seems to be largely independent on the presence of solvent. Conversely, protein hydration water exhibits remarkable differences with respect to hexagonal ice in the whole spectral range, with clear similarities to amorphous phases of ice.

  12. Kinetics of Methane Hydrate Formation in Pure Water and Inhibitor Containing Systems

    Institute of Scientific and Technical Information of China (English)

    QIUJunhong; GUOTianmin

    2002-01-01

    Kinetic data of methane hydrate formation in the presence of pure water,brines with single salt and mixed salts,and aqueous solutions of ethylene glycol(EG) and salt+EG were measured.A new kinetic model of hydrate formation for the methane+water systems was developed based on a four-step formation mechanism and reaction kinetic approach.The proposed kinetic model predicts the kinetic behavior of methane hydrate formation in pure water with good accuracy.The feasibility of extending the kenetic model of salt(s) and EG containing systems was explored.

  13. Water dynamics in protein hydration shells: the molecular origins of the dynamical perturbation.

    Science.gov (United States)

    Fogarty, Aoife C; Laage, Damien

    2014-07-17

    Protein hydration shell dynamics play an important role in biochemical processes including protein folding, enzyme function, and molecular recognition. We present here a comparison of the reorientation dynamics of individual water molecules within the hydration shell of a series of globular proteins: acetylcholinesterase, subtilisin Carlsberg, lysozyme, and ubiquitin. Molecular dynamics simulations and analytical models are used to access site-resolved information on hydration shell dynamics and to elucidate the molecular origins of the dynamical perturbation of hydration shell water relative to bulk water. We show that all four proteins have very similar hydration shell dynamics, despite their wide range of sizes and functions, and differing secondary structures. We demonstrate that this arises from the similar local surface topology and surface chemical composition of the four proteins, and that such local factors alone are sufficient to rationalize the hydration shell dynamics. We propose that these conclusions can be generalized to a wide range of globular proteins. We also show that protein conformational fluctuations induce a dynamical heterogeneity within the hydration layer. We finally address the effect of confinement on hydration shell dynamics via a site-resolved analysis and connect our results to experiments via the calculation of two-dimensional infrared spectra.

  14. Which properties of a spanning network of hydration water enable biological functions?

    Science.gov (United States)

    Brovchenko, Ivan; Oleinikova, Alla

    2008-12-22

    The central role of water in biological functions is well-recognized, but numerous questions concerning the physical mechanisms behind the importance of water for life remain unanswered. Water in biosystems exists mainly as hydration water. Analysis of the phase diagram of hydration water shows that biological functions are possible only when the surfaces of biomolecules are covered by spanning hydrogen-bonded networks of hydration water. The comparative studies of the various properties of hydrated biosystems in the presence and in the absence of a spanning water network should clarify its specific physical properties, which are crucial for biological functions. Herein, we summarize the recent progress in these studies. The biological activity of the living organisms is maximal in a narrow temperature interval, where the spanning network of hydration water breaks up with heating via a percolation transition. The entropy of the hydration water related to the diversity of cluster size diverges at this percolation threshold. The possible role of this phenomenon in life processes is discussed.

  15. High protein flexibility and reduced hydration water dynamics are key pressure adaptive strategies in prokaryotes

    KAUST Repository

    Martinez, N.

    2016-09-06

    Water and protein dynamics on a nanometer scale were measured by quasi-elastic neutron scattering in the piezophile archaeon Thermococcus barophilus and the closely related pressure-sensitive Thermococcus kodakarensis, at 0.1 and 40 MPa. We show that cells of the pressure sensitive organism exhibit higher intrinsic stability. Both the hydration water dynamics and the fast protein and lipid dynamics are reduced under pressure. In contrast, the proteome of T. barophilus is more pressure sensitive than that of T. kodakarensis. The diffusion coefficient of hydration water is reduced, while the fast protein and lipid dynamics are slightly enhanced with increasing pressure. These findings show that the coupling between hydration water and cellular constituents might not be simply a master-slave relationship. We propose that the high flexibility of the T. barophilus proteome associated with reduced hydration water may be the keys to the molecular adaptation of the cells to high hydrostatic pressure.

  16. High protein flexibility and reduced hydration water dynamics are key pressure adaptive strategies in prokaryotes

    Science.gov (United States)

    Martinez, N.; Michoud, G.; Cario, A.; Ollivier, J.; Franzetti, B.; Jebbar, M.; Oger, P.; Peters, J.

    2016-09-01

    Water and protein dynamics on a nanometer scale were measured by quasi-elastic neutron scattering in the piezophile archaeon Thermococcus barophilus and the closely related pressure-sensitive Thermococcus kodakarensis, at 0.1 and 40 MPa. We show that cells of the pressure sensitive organism exhibit higher intrinsic stability. Both the hydration water dynamics and the fast protein and lipid dynamics are reduced under pressure. In contrast, the proteome of T. barophilus is more pressure sensitive than that of T. kodakarensis. The diffusion coefficient of hydration water is reduced, while the fast protein and lipid dynamics are slightly enhanced with increasing pressure. These findings show that the coupling between hydration water and cellular constituents might not be simply a master-slave relationship. We propose that the high flexibility of the T. barophilus proteome associated with reduced hydration water may be the keys to the molecular adaptation of the cells to high hydrostatic pressure.

  17. Hydrophobic hydration and the anomalous partial molar volumes in ethanol-water mixtures

    Energy Technology Data Exchange (ETDEWEB)

    Tan, Ming-Liang; Te, Jerez; Cendagorta, Joseph R. [Department of Chemistry, Georgetown University, Washington, District of Columbia 20057 (United States); Miller, Benjamin T.; Brooks, Bernard R. [Laboratory of Computational Biology, National Heart, Lung, and Blood Institute, National Institutes of Health, Rockville, Maryland 20892 (United States); Ichiye, Toshiko, E-mail: ti9@georgetown.edu [Department of Chemistry, Georgetown University, Washington, District of Columbia 20057 (United States); Laboratory of Computational Biology, National Heart, Lung, and Blood Institute, National Institutes of Health, Rockville, Maryland 20892 (United States)

    2015-02-14

    The anomalous behavior in the partial molar volumes of ethanol-water mixtures at low concentrations of ethanol is studied using molecular dynamics simulations. Previous work indicates that the striking minimum in the partial molar volume of ethanol V{sub E} as a function of ethanol mole fraction X{sub E} is determined mainly by water-water interactions. These results were based on simulations that used one water model for the solute-water interactions but two different water models for the water-water interactions. This is confirmed here by using two more water models for the water-water interactions. Furthermore, the previous work indicates that the initial decrease is caused by association of the hydration shells of the hydrocarbon tails, and the minimum occurs at the concentration where all of the hydration shells are touching each other. Thus, the characteristics of the hydration of the tail that cause the decrease and the features of the water models that reproduce this type of hydration are also examined here. The results show that a single-site multipole water model with a charge distribution that mimics the large quadrupole and the p-orbital type electron density out of the molecular plane has “brittle” hydration with hydrogen bonds that break as the tails touch, which reproduces the deep minimum. However, water models with more typical site representations with partial charges lead to flexible hydration that tends to stay intact, which produces a shallow minimum. Thus, brittle hydration may play an essential role in hydrophobic association in water.

  18. Molecular dynamics simulations of trehalose as a 'dynamic reducer' for solvent water molecules in the hydration shell.

    Science.gov (United States)

    Choi, Youngjin; Cho, Kum Won; Jeong, Karpjoo; Jung, Seunho

    2006-06-12

    Systematic computational work for a series of 13 disaccharides was performed to provide an atomic-level insight of unique biochemical role of the alpha,alpha-(1-->1)-linked glucopyranoside dimer over the other glycosidically linked sugars. Superior osmotic and cryoprotective abilities of trehalose were explained on the basis of conformational and hydration characteristics of the trehalose molecule. Analyses of the hydration number and radial distribution function of solvent water molecules showed that there was very little hydration adjacent to the glycosidic oxygen of trehalose and that the dynamic conformation of trehalose was less flexible than any of the other sugars due to this anisotropic hydration. The remarkable conformational rigidity that allowed trehalose to act as a sugar template was required for stable interactions with hydrogen-bonded water molecules. Trehalose made an average of 2.8 long-lived hydrogen bonds per each MD step, which was much larger than the average of 2.1 for the other sugars. The stable hydrogen-bond network is derived from the formation of long-lived water bridges at the expense of decreasing the dynamics of the water molecules. Evidence for this dynamic reduction of water by trehalose was also established based on each of the lowest translational diffusion coefficients and the lowest intermolecular coulombic energy of the water molecules around trehalose. Overall results indicate that trehalose functions as a 'dynamic reducer' for solvent water molecules based on its anisotropic hydration and conformational rigidity, suggesting that macroscopic solvent properties could be modulated by changes in the type of glycosidic linkages in sugar molecules.

  19. Annular multiphase flow behavior during deep water drilling and the effect of hydrate phase transition

    Institute of Scientific and Technical Information of China (English)

    Wang Zhiyuan; Sun Baojiang

    2009-01-01

    It is very important to understand the annular multiphase flow behavior and the effect of hydrate phase transition during deep water drilling. The basic hydrodynamic models, including mass, momentum, and energy conservation equations, were established for annular flow with gas hydrate phase transition during gas kick. The behavior of annular multiphase flow with hydrate phase transition was investigated by analyzing the hydrate-forming region, the gas fraction in the fluid flowing in the annulus, pit gain, bottom hole pressure, and shut-in casing pressure. The simulation shows that it is possible to move the hydrate-forming region away from sea floor by increasing the circulation rate. The decrease in gas volume fraction in the annulus due to hydrate formation reduces pit gain, which can delay the detection of well kick and increase the risk of hydrate plugging in lines. Caution is needed when a well is monitored for gas kick at a relatively low gas production rate, because the possibility of hydrate presence is much greater than that at a relatively high production rate. The shut-in casing pressure cannot reflect the gas kick due to hydrate formation, which increases with time.

  20. Prediction of natural gas hydrate formation region in wellbore during deep- water gas well testing

    Institute of Scientific and Technical Information of China (English)

    WANG Zhi-yuan; SUN Bao-jiang; WANG Xue-rui; ZHANG Zhen-nan

    2014-01-01

    Wellbore temperature field equations are established with considerations of the enthalpy changes of the natural gas during the deep-water gas well testing. A prediction method for the natural gas hydrate formation region during the deep-water gas well testing is proposed, which combines the wellbore temperature field equations, the phase equilibrium conditions of the natural gas hydrate formation and the calculation methods for the pressure field. Through the sensitivity analysis of the parameters that affect the hydrate formation region, it can be concluded that during the deep-water gas well testing, with the reduction of the gas production rate and the decrease of the geothermal gradient, along with the increase of the depth of water, the hydrate formation region in the wellbore enlarges, the hydrate formation regions differ with different component contents of natural gases, as compared with the pure methane gas, with the increase of ethane and propane, the hydrate formation region expands, the admixture of inhibitors, the type and the concentrations of which can be optimized through the method proposed in the paper, will reduce the hydrate formation region, the throttling effect will lead to the abrupt changes of temperature and pressure, which results in a variation of the hydrate formation region, if the throttling occurs in the shallow part of the wellbore, the temperature will drop too much, which enlarges the hydrate formation region, otherwise, if the throttling occurs in the deep part of the wellbore, the hydrate formation region will be reduced due to the decrease of the pressure.

  1. Impact of Residual Water on CH4-CO2 Exchange rate in Hydrate bearing Sandstone

    Science.gov (United States)

    Ersland, G.; Birkedal, K.; Graue, A.

    2012-12-01

    It is previously shown that sequestration of CO2 in natural gas hydrate reservoirs may offer stable long term deposition of a greenhouse gas while benefiting from methane production, without adding heat to the process. In this work CH4 hydrate formation and CO2 reformation in sandstone has been quantified in a series of experiments using Magnetic Resonance Imaging. The overall objective was to provide an improved basic understanding of processes involved in formation and production of methane from methane hydrates within porous media, and to provide data for numerical modeling and scaling. CH4 hydrate has been formed repeatedly in Bentheim sandstone rocks to study hydrate growth patterns for various brine salinities and saturations to prepare for subsequent lab-scale methane production tests through carbon dioxide replacement at various residual water saturations. Surface area for CO2 exposure and the role of permeability and diffusion on the CH4-CO2 exchange rate will also be discussed.

  2. Kinetic and Phase Behaviors of Catalytic Cracking Dry Gas Hydrate in Water-in-Oil Emulsion

    Institute of Scientific and Technical Information of China (English)

    MA Qinglan; HUANG Qiang; CHEN Guangjin; WANG Xiulin; SUN Changyu; YANG Lanying

    2013-01-01

    The systematic experimental studies were performed on the hydrate formation kinetics and gas-hydrate equilibrium for a simulated catalytic cracking gas in the water-in-oil emulsion.The effect of temperature,pressure and initial gas-liquid ratio on the hydrate formation was studied,respectively.The data were obtained at pressures ranging from 3.5 to 5 MPa and temperatures from 274.15 to 277.15 K.The results showed that hydrogen and methane can be separated from the C2+ fraction by forming hydrate at around 273.15 K which is much higher temperature than that of the cryogenic separation method,and the hydrate formation rate can be enhanced in the water-in-oil emulsion compared to pure water.The experiments provided the basic data for designing the industrial process,and setting the suitable operational conditions.The measured data of gas-hydrate equilibria were compared with the predictions by using the Chen-Guo hydrate thermodynamic model.

  3. Cyclic formation and dissociation of methane hydrate within partially water saturated sand

    Science.gov (United States)

    Kneafsey, T. J.; Nakagawa, S.

    2010-12-01

    For partially water-saturated sediments, laboratory experiments have shown that methane hydrate forms heterogeneously within a sample at the core scale. The heterogeneous distribution of hydrate in combination with grain-scale hydrate location (eg. grain cementing, load bearing, and pore filling), determines the overall mechanical properties of hydrate-bearing sediments including shear strength and seismic properties. For this reason, understanding the heterogeneity of hydrate-bearing sample is essential when the bulk properties of the sample are examined in the laboratory. We present a series of laboratory methane hydrate formation and dissociation experiments with concurrent x-ray CT imaging and low-frequency (near 1 kHz) seismic measurements. The seismic measurements were conducted using a new acoustic resonant bar technique called the Split Hopkinson Resonant Bar method, which allows using a small sediment core (3.75 cm diameter, 7.5 cm length). The experiment was conducted using a jacketed, pre-compacted, fine-grain silica sand sample with a 40% distilled water saturation. Under isotropic confining stress of 6.9 MPa and a temperature 4 oC, the hydrate was formed in the sample by injecting pure methane gas at 5.6 MPa. Once the hydrate formed, it was dissociated by reducing the pore pressure to 2.8 MPa. This cycle was repeated by three times (dissociation test for the third cycle was not done) to examine the resulting changes in the hydrate distribution and seismic signatures. The repeated formation of hydrate resulted in significant changes in its distribution, which resulted in differences in the overall elastic properties of the sample, determined from the seismic measurements. Interestingly, the time intervals between the dissociation and subsequent formation of hydrate affected the rate of hydrate formation, shorter intervals resulting in faster formation. This memory effect, possibly caused by the presence of residual “seed crystals” in the pore water

  4. Experimental investigation of gas hydrate formation, plugging and transportability in partially dispersed and water continuous systems

    Science.gov (United States)

    Vijayamohan, Prithvi

    As oil/gas subsea fields mature, the amount of water produced increases significantly due to the production methods employed to enhance the recovery of oil. This is true especially in the case of oil reservoirs. This increase in the water hold up increases the risk of hydrate plug formation in the pipelines, thereby resulting in higher inhibition cost strategies. A major industry concern is to reduce the severe safety risks associated with hydrate plug formation, and significantly extending subsea tieback distances by providing a cost effective flow assurance management/safety tool for mature fields. Developing fundamental understanding of the key mechanistic steps towards hydrate plug formation for different multiphase flow conditions is a key challenge to the flow assurance community. Such understanding can ultimately provide new insight and hydrate management guidelines to diminish the safety risks due to hydrate formation and accumulation in deepwater flowlines and facilities. The transportability of hydrates in pipelines is a function of the operating parameters, such as temperature, pressure, fluid mixture velocity, liquid loading, and fluid system characteristics. Specifically, the hydrate formation rate and plugging onset characteristics can be significantly different for water continuous, oil continuous, and partially dispersed systems. The latter is defined as a system containing oil/gas/water, where the water is present both as a free phase and partially dispersed in the oil phase (i.e., entrained water in the oil). Since hydrate formation from oil dispersed in water systems and partially dispersed water systems is an area which is poorly understood, this thesis aims to address some key questions in these systems. Selected experiments have been performed at the University of Tulsa flowloop to study the hydrate formation and plugging characteristics for the partially dispersed water/oil/gas systems as well as systems where the oil is completely dispersed

  5. Hydration Simulations of a Carbon Nanotube, Immersed in Water, according to the 3-Attractor Water Model

    Directory of Open Access Journals (Sweden)

    Francis F. Muguet

    2005-04-01

    Full Text Available MC simulations of a set of zigzag ((9,0-(14,0 and armchair ((6,6-(10,10carbon nanotubes immersed in water have been carried out in an NpT-ensemble (512 watermolecules, p=1 bar, T=298 K. Intermolecular interactions were described by BMWpotential according to which, besides the well-known linear water dimer bifurcated andinverted water dimers are metastable. In all cases, it was found that there are large periodicfluctuations of water occupancy inside the nanotubes. Decrease in the size of the nanotubediameter leads to a significant destruction of the H-bond network, and to a bifucarted dimerpopulation increase. Inverted dimer concentration relationship with the nanotube diameter ismore complicated. Population maximum for inverted dimers occurs for diameters of 10-11 å. Water features different intermolecular structures not only inside carbon nanotubesbut also in the outer first hydration shells. The amount of bifurcated and inverted dimers issignificantly more important in the first hydration shell than in bulk water.

  6. Wide-ranging molecular mobilities of water in active pharmaceutical ingredient (API) hydrates as determined by NMR relaxation times.

    Science.gov (United States)

    Yoshioka, Sumie; Aso, Yukio; Osako, Tsutomu; Kawanishi, Toru

    2008-10-01

    In order to examine the possibility of determining the molecular mobility of hydration water in active pharmaceutical ingredient (API) hydrates by NMR relaxation measurement, spin-spin relaxation and spin-lattice relaxation were measured for the 11 API hydrates listed in the Japanese Pharmacopeia using pulsed (1)H-NMR. For hydration water that has relatively high mobility and shows Lorentzian decay, molecular mobility as determined by spin-spin relaxation time (T(2)) was correlated with ease of evaporation under both nonisothermal and isothermal conditions, as determined by DSC and water vapor sorption isotherm analysis, respectively. Thus, T(2) may be considered a useful parameter which indicates the molecular mobility of hydration water. In contrast, for hydration water that has low mobility and shows Gaussian decay, T(2) was found not to correlate with ease of evaporation under nonisothermal conditions, which suggests that in this case, the molecular mobility of hydration water was too low to be determined by T(2). A wide range of water mobilities was found among API hydrates, from low mobility that could not be evaluated by NMR relaxation time, such as that of the water molecules in pipemidic acid hydrate, to high mobility that could be evaluated by this method, such as that of the water molecules in ceftazidime hydrate. (c) 2008 Wiley-Liss, Inc. and the American Pharmacists Association

  7. Strength Development and Hydration Behavior of Self-Activation of Commercial Ground Granulated Blast-Furnace Slag Mixed with Purified Water

    Directory of Open Access Journals (Sweden)

    Hyeoneun Park

    2016-03-01

    Full Text Available In this study, ground granulated blast-furnace slag (GGBFS samples from Singapore, Korea, and the United Arab Emirates were hydrated with purified water to estimate the cementing capabilities without activators. Raw GGBFS samples and hardened pastes were characterized to provide rational explanations for the strengths and hydration products. The slag characteristics that influenced the best strength of raw GGBFS were identified. Although it is widely recognized that GGBFS alone generally shows little cementing capability when hydrated with water, the GGBFSs examined in this study demonstrated various strength developments and hydration behaviors; one of the GGBFS samples even produced a high strength comparable to that of alkali- or Ca(OH2-activated GGBFS. In particular, as the GGBFS exhibited a greater number of favorable slag characteristics for hydraulic reactivity, it produced more C-S-H and ettringite. The results demonstrated a reasonable potential for commercial GGBFS with calcium sulfates to function as an independent cementitious binder without activators.

  8. Hydrate film growth on the surface of a gas bubble suspended in water.

    Science.gov (United States)

    Peng, B Z; Dandekar, A; Sun, C Y; Luo, H; Ma, Q L; Pang, W X; Chen, G J

    2007-11-01

    The lateral film growth rate of CH4, C2H4, CO2, CH4 + C2H4, and CH4 + C3H8 hydrates in pure water were measured at four fixed temperatures of 273.4, 275.4, 277.4, and 279.4 K by means of suspending a single gas bubble in water. The results showed that the lateral growth rates of mixed-gas CH4 + C2H4 hydrate films were slower than that of pure gas (CH4 or C2H4) for the same driving force and that of mixed-gas CH4 + C3H8 hydrate film growth was the slowest. The dependence of the thickness of hydrate film on the driving force was investigated, and it was demonstrated that the thickness of hydrate film was inversely proportional to the driving force. It was found that the convective heat transfer control model reported in the literature could be used to formulate the lateral film growth rate v(f) with the driving force DeltaT perfectly for all systems after introduction of the assumption that the thickness of hydrate films is inversely proportional to the driving force DeltaT; i.e., v(f) = psiDeltaT(5/2) is correct and independent of the composition of gas and the type of hydrate. The thicknesses of different gas hydrate films were estimated, and it is demonstrated that the thicknesses of mixed-gas hydrate films were thicker than those of pure gases, which was qualitatively consistent with the experimental result.

  9. Water Retention Curve and Relative Permeability for Gas Production from Hydrate-Bearing Sediments

    Science.gov (United States)

    Mahabadi, N.; Dai, S.; Seol, Y.; Jang, J.

    2014-12-01

    Water retention curve (soil water characteristic curve SWCC) and relative permeability equations are important to determine gas and water production for gas hydrate development. However, experimental studies to determine fitting parameters of those equations are not available in the literature. The objective of this research is to obtain reliable parameters for capillary pressure functions and relative permeability equations applicable to hydrate dissociation and gas production. In order to achieve this goal, (1) micro X-ray Computer Tomography (CT) is used to scan the specimen under 10MPa effective stress, (2) a pore network model is extracted from the CT image, (3) hydrate dissociation and gas expansion are simulated in the pore network model, (4) the parameters for the van Genuchten-type soil water characteristic curve and relative permeability equation during gas expansion are suggested. The research outcome will enhance the ability of numerical simulators to predict gas and water production rate.

  10. Coarse-grained model of water diffusion and proton conductivity in hydrated polyelectrolyte membrane

    Science.gov (United States)

    Lee, Ming-Tsung; Vishnyakov, Aleksey; Neimark, Alexander V.

    2016-01-01

    Using dissipative particle dynamics (DPD), we simulate nanoscale segregation, water diffusion, and proton conductivity in hydrated sulfonated polystyrene (sPS). We employ a novel model [Lee et al. J. Chem. Theory Comput. 11(9), 4395-4403 (2015)] that incorporates protonation/deprotonation equilibria into DPD simulations. The polymer and water are modeled by coarse-grained beads interacting via short-range soft repulsion and smeared charge electrostatic potentials. The proton is introduced as a separate charged bead that forms dissociable Morse bonds with the base beads representing water and sulfonate anions. Morse bond formation and breakup artificially mimics the Grotthuss mechanism of proton hopping between the bases. The DPD model is parameterized by matching the proton mobility in bulk water, dissociation constant of benzenesulfonic acid, and liquid-liquid equilibrium of water-ethylbenzene solutions. The DPD simulations semi-quantitatively predict nanoscale segregation in the hydrated sPS into hydrophobic and hydrophilic subphases, water self-diffusion, and proton mobility. As the hydration level increases, the hydrophilic subphase exhibits a percolation transition from isolated water clusters to a 3D network. The analysis of hydrophilic subphase connectivity and water diffusion demonstrates the importance of the dynamic percolation effect of formation and breakup of temporary junctions between water clusters. The proposed DPD model qualitatively predicts the ratio of proton to water self-diffusion and its dependence on the hydration level that is in reasonable agreement with experiments.

  11. Hydration status moderates the effects of drinking water on children's cognitive performance.

    Science.gov (United States)

    Perry, Clinton S; Rapinett, Gertrude; Glaser, Nicole S; Ghetti, Simona

    2015-12-01

    Changes in hydration status throughout the day may affect cognitive performance with implications for learning success in the classroom. Our study tested the hypothesis that the benefit of drinking water on working memory and attention depends upon children's hydration status and renal response to water intake. Fifty-two children aged 9-12 years old were tested under two experimental conditions. The treatment session (Water session) consisted of a standard breakfast with 200 ml water, a baseline test, consumption of 750 ml of water over a period of two hours and subsequently retested. No water was provided after breakfast during the control session. Changes in hydration were assessed via urine samples. Cognitive testing consisted of digit span, pair cancellation, and delayed match to sample tasks. Children who exhibited smaller decreases in urine osmolality following water intake performed significantly better on the water day compared to the control day on a digit-span task and pair-cancellation task. Children who exhibited larger decreases in urine osmolality following water intake performed better on the control day compared to the water day on the digit-span task and pair-cancellation task. These results suggest that focusing on adequate hydration over time may be key for cognitive enhancement.

  12. Coarse-grained model of water diffusion and proton conductivity in hydrated polyelectrolyte membrane

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Ming-Tsung; Vishnyakov, Aleksey; Neimark, Alexander V., E-mail: aneimark@rutgers.edu [Department of Chemical and Biochemical Engineering, Rutgers, The State University of New Jersey, 98 Brett Road, Piscataway, New Jersey 08854-8058 (United States)

    2016-01-07

    Using dissipative particle dynamics (DPD), we simulate nanoscale segregation, water diffusion, and proton conductivity in hydrated sulfonated polystyrene (sPS). We employ a novel model [Lee et al. J. Chem. Theory Comput. 11(9), 4395-4403 (2015)] that incorporates protonation/deprotonation equilibria into DPD simulations. The polymer and water are modeled by coarse-grained beads interacting via short-range soft repulsion and smeared charge electrostatic potentials. The proton is introduced as a separate charged bead that forms dissociable Morse bonds with the base beads representing water and sulfonate anions. Morse bond formation and breakup artificially mimics the Grotthuss mechanism of proton hopping between the bases. The DPD model is parameterized by matching the proton mobility in bulk water, dissociation constant of benzenesulfonic acid, and liquid-liquid equilibrium of water-ethylbenzene solutions. The DPD simulations semi-quantitatively predict nanoscale segregation in the hydrated sPS into hydrophobic and hydrophilic subphases, water self-diffusion, and proton mobility. As the hydration level increases, the hydrophilic subphase exhibits a percolation transition from isolated water clusters to a 3D network. The analysis of hydrophilic subphase connectivity and water diffusion demonstrates the importance of the dynamic percolation effect of formation and breakup of temporary junctions between water clusters. The proposed DPD model qualitatively predicts the ratio of proton to water self-diffusion and its dependence on the hydration level that is in reasonable agreement with experiments.

  13. Coalbed Methane Procduced Water Treatment Using Gas Hydrate Formation at the Wellhead

    Energy Technology Data Exchange (ETDEWEB)

    BC Technologies

    2009-12-30

    Water associated with coalbed methane (CBM) production is a significant and costly process waste stream, and economic treatment and/or disposal of this water is often the key to successful and profitable CBM development. In the past decade, advances have been made in the treatment of CBM produced water. However, produced water generally must be transported in some fashion to a centralized treatment and/or disposal facility. The cost of transporting this water, whether through the development of a water distribution system or by truck, is often greater than the cost of treatment or disposal. To address this economic issue, BC Technologies (BCT), in collaboration with Oak Ridge National Laboratory (ORNL) and International Petroleum Environmental Consortium (IPEC), proposed developing a mechanical unit that could be used to treat CBM produced water by forming gas hydrates at the wellhead. This process involves creating a gas hydrate, washing it and then disassociating hydrate into water and gas molecules. The application of this technology results in three process streams: purified water, brine, and gas. The purified water can be discharged or reused for a variety of beneficial purposes and the smaller brine can be disposed of using conventional strategies. The overall objectives of this research are to develop a new treatment method for produced water where it could be purified directly at the wellhead, to determine the effectiveness of hydrate formation for the treatment of produced water with proof of concept laboratory experiments, to design a prototype-scale injector and test it in the laboratory under realistic wellhead conditions, and to demonstrate the technology under field conditions. By treating the water on-site, producers could substantially reduce their surface handling costs and economically remove impurities to a quality that would support beneficial use. Batch bench-scale experiments of the hydrate formation process and research conducted at ORNL

  14. Total allowable concentrations of monomeric inorganic aluminum and hydrated aluminum silicates in drinking water.

    Science.gov (United States)

    Willhite, Calvin C; Ball, Gwendolyn L; McLellan, Clifton J

    2012-05-01

    Maximum contaminant levels are used to control potential health hazards posed by chemicals in drinking water, but no primary national or international limits for aluminum (Al) have been adopted. Given the differences in toxicological profiles, the present evaluation derives total allowable concentrations for certain water-soluble inorganic Al compounds (including chloride, hydroxide, oxide, phosphate and sulfate) and for the hydrated Al silicates (including attapulgite, bentonite/montmorillonite, illite, kaolinite) in drinking water. The chemistry, toxicology and clinical experience with Al materials are extensive and depend upon the particular physical and chemical form. In general, the water solubility of the monomeric Al materials depends on pH and their water solubility and gastrointestinal bioavailability are much greater than that of the hydrated Al silicates. Other than Al-containing antacids and buffered aspirin, food is the primary source of Al exposure for most healthy people. Systemic uptake of Al after ingestion of the monomeric salts is somewhat greater from drinking water (0.28%) than from food (0.1%). Once absorbed, Al accumulates in bone, brain, liver and kidney, with bone as the major site for Al deposition in humans. Oral Al hydroxide is used routinely to bind phosphate salts in the gut to control hyperphosphatemia in people with compromised renal function. Signs of chronic Al toxicity in the musculoskeletal system include a vitamin D-resistant osteomalacia (deranged membranous bone formation characterized by accumulation of the osteoid matrix and reduced mineralization, reduced numbers of osteoblasts and osteoclasts, decreased lamellar and osteoid bands with elevated Al concentrations) presenting as bone pain and proximal myopathy. Aluminum-induced bone disease can progress to stress fractures of the ribs, femur, vertebrae, humerus and metatarsals. Serum Al ≥100 µg/L has a 75-88% positive predictive value for Al bone disease. Chronic Al

  15. Hydration of methanol in water. A DFT-based molecular dynamics study

    CERN Document Server

    Van Erp, T S; Erp, Titus S. van; Meijer, Evert Jan

    2000-01-01

    We studied the hydration of a single methanol molecule in aqueous solution by first-principle DFT-based molecular dynamics simulation. The calculations show that the local structural and short-time dynamical properties of the water molecules remain almost unchanged by the presence of the methanol, confirming the observation from recent experimental structural data for dilute solutions. We also see, in accordance with this experimental work, a distinct shell of water molecules that consists of about 15 molecules. We found no evidence for a strong tangential ordering of the water molecules in the first hydration shell.

  16. Communication: Protein dynamical transition vs. liquid-liquid phase transition in protein hydration water

    Science.gov (United States)

    Schirò, Giorgio; Fomina, Margarita; Cupane, Antonio

    2013-09-01

    In this work, we compare experimental data on myoglobin hydrated powders from elastic neutron scattering, broadband dielectric spectroscopy, and differential scanning calorimetry. Our aim is to obtain new insights on the connection between the protein dynamical transition, a fundamental phenomenon observed in proteins whose physical origin is highly debated, and the liquid-liquid phase transition (LLPT) possibly occurring in protein hydration water and related to the existence of a low temperature critical point in supercooled water. Our results provide a consistent thermodynamic/dynamic description which gives experimental support to the LLPT hypothesis and further reveals how fundamental properties of water and proteins are tightly related.

  17. Hydration water and peptide dynamics--two sides of a coin. A neutron scattering and adiabatic calorimetry study at low hydration and cryogenic temperatures.

    Science.gov (United States)

    Bastos, Margarida; Alves, Nuno; Maia, Sílvia; Gomes, Paula; Inaba, Akira; Miyazaki, Yuji; Zanotti, Jean-Marc

    2013-10-21

    In the present work we bridge neutron scattering and calorimetry in the study of a low-hydration sample of a 15-residue hybrid peptide from cecropin and mellitin CA(1-7)M(2-9) of proven antimicrobial activity. Quasielastic and low-frequency inelastic neutron spectra were measured at defined hydration levels - a nominally 'dry' sample (specific residual hydration h = 0.060 g/g), a H2O-hydrated (h = 0.49) and a D2O-hydrated one (h = 0.51). Averaged mean square proton mobilities were derived over a large temperature range (50-300 K) and the vibrational density of states (VDOS) were evaluated for the hydrated samples. The heat capacity of the H2O-hydrated CA(1-7)M(2-9) peptide was measured by adiabatic calorimetry in the temperature range 5-300 K, for different hydration levels. The glass transition and water crystallization temperatures were derived in each case. The existence of different types of water was inferred and their amounts calculated. The heat capacities as obtained from direct calorimetric measurements were compared to the values derived from the neutron spectroscopy by way of integrating appropriately normalized VDOS functions. While there is remarkable agreement with respect to both temperature dependence and glass transition temperatures, the results also show that the VDOS derived part represents only a fraction of the total heat capacity obtained from calorimetry. Finally our results indicate that both hydration water and the peptide are involved in the experimentally observed transitions.

  18. Temperature effects in deep-water hydrate foam

    CERN Document Server

    Egorov, Alexander V; Rozhkov, Aleksey N

    2016-01-01

    This study focuses on heat and mass exchange processes in hydrate foam during its formation from methane bubbles in gas hydrate stability zone (GHSZ) of the Lake Baikal and following delivery of it in open container to the lake surface. The foam was formed as a result of methane bubble collection with a trap/container. The trap was inverted glass beaker of diameter of 70 mm and 360 mm long. Open bottom end of the beaker used as enter for bubbles ascended from the lakebed. At a depth of 1400 m all bubbles which fed to the trap were transformed here into solid hydrate foam. The sensitive thermometer was mounted in the middle of the trap and recorded the temperature inside trap. The fate of the bubbles in the trap was recorded by video-camera. During ascend within GHSZ with velocity of about 0.375 m/s we observed the continuous decrease of the temperature in the foam up to a level of negative magnitude in a depth interval of 1400 - 750 meters. Above 750 m temperature decrease was changed by small growth. However...

  19. A study of hydrate formation and dissociation from high water cut emulsions and the impact on emulsion inversion

    Energy Technology Data Exchange (ETDEWEB)

    Greaves, D.P.; Boxall, J.A.; Mulligan, J.; Dendy Sloan, E.; Koh, C.A. [Colorado School of Mines, Golden, CO (United States). Dept. of Chemical Engineering, Center for Hydrate Research

    2008-07-01

    The challenges facing the petroleum industry regarding clathrate hydrate formation were discussed, with particular reference to the costly and dangerous pipeline blocking plugs that form upon hydrate accumulation and agglomeration. Although a variety of inhibitors are used to prevent hydrate plug formation, they are not designed for high water content production. As oil and gas are produced from less profitable or older wells, there is a greater probability of higher water cuts. Therefore, this study focused on methane hydrate formation and dissociation from these high water content (greater than 60 per cent volume) emulsions of water-in-oil (W/O) and oil-in-water (O/W). At high water cuts, the system can quickly agglomerate with hydrate formation, while dissociation can lead to a significant change in the emulsion type. Although inhibition can be costly at high water cuts, it must be considered because of the risk of immediate agglomeration and plug formation with hydrates. In this study, the hydrate formation and dissociation from W/O emulsions destabilized the emulsion, with the final emulsion formulation favouring a water continuous state following re-emulsification. After dissociation, the W/O emulsion formed a multiple o/W/O emulsion or inverted at even higher water cuts, forming an O/W emulsion with 68 per cent water volume. In contrast, hydrate formation and dissociation from O/W emulsions with more than 71 per cent water volume stablized the O/W emulsion. 24 refs., 13 figs.

  20. Calculation of Liquid Water-Hydrate-Methane Vapor Phase Equilibria from Molecular Simulations

    DEFF Research Database (Denmark)

    Jensen, Lars; Thomsen, Kaj; von Solms, Nicolas

    2010-01-01

    Monte Carlo simulation methods for determining fluid- and crystal-phase chemical potentials are used for the first time to calculate liquid water-methane hydrate-methane vapor phase equilibria from knowledge of atomistic interaction potentials alone. The water and methane molecules are modeled...... using the TIP4P/ice potential and a united-atom Lennard-Jones potential. respectively. The equilibrium calculation method for this system has three components, (i) thermodynamic integration from a supercritical ideal gas to obtain the fluid-phase chemical potentials. (ii) calculation of the chemical...... potential of the zero-occupancy hydrate system using thermodynamic integration from an Einstein crystal reference state, and (iii) thermodynamic integration to obtain the water and guest molecules' chemical potentials as a function of the hydrate occupancy. The three-phase equilibrium curve is calculated...

  1. Effect of Hydration Aging and Water Binder Ratio on Microstructure and Mechanical Properties of Sprayed Concrete

    Institute of Scientific and Technical Information of China (English)

    NIU Ditao; WANG Jiabin; WANG Yan

    2015-01-01

    In order to study the durability of sprayed concrete (shotcrete), effects of different hydration aging and water-binder ratio (w/b) on the microstructure of cement paste and basic mechanical properties of test specimens were investigated. The phase composition, mass percentage of ettringite and portland in hydration production and microstructure were characterized by X-ray diffraction (XRD), thermo gravimetry-differential scanning calorimetry (TG-DSC) and scanning electron microscopy (SEM), respectively. The experimental results showed that changes in phase composition was more signiifcant than those of water-binder ratio. With hydration aging and water-binder ratio increased, the mass percentage of ettringite and portland was decreased from 4.42%, 1.49% to 3.31%, 1.35%, respectively and the microstructure of paste was signiifcantly compacted. Likewise, the mechanical properties including cubic compressive strength and splitting tensile strength were rised obviously.

  2. In silico studies of the properties of water hydrating a small protein

    Science.gov (United States)

    Sinha, Sudipta Kumar; Jana, Madhurima; Chakraborty, Kausik; Bandyopadhyay, Sanjoy

    2014-12-01

    Atomistic molecular dynamics simulation of an aqueous solution of the small protein HP-36 has been carried out with explicit solvent at room temperature. Efforts have been made to explore the influence of the protein on the relative packing and ordering of water molecules around its secondary structures, namely, three α-helices. The calculations reveal that the inhomogeneous water ordering and density distributions around the helices are correlated with their relative hydrophobicity. Importantly, we have identified the existence of a narrow relatively dehydrated region containing randomly organized "quasi-free" water molecules beyond the first layer of "bound" waters at the protein surface. These water molecules with relatively weaker binding energies form the transition state separating the "bound" and "free" water molecules at the interface. Further, increased contribution of solid-like caging motions of water molecules around the protein is found to be responsible for reduced fluidity of the hydration layer. Interestingly, we notice that the hydration layer of helix-3 is more fluidic with relatively higher entropy as compared to the hydration layers of the other two helical segments. Such characteristics of helix-3 hydration layer correlate well with the activity of HP-36, as helix-3 contains the active site of the protein.

  3. Diffusion and reaction pathways of water near fully hydrated TiO2 surfaces from ab initio molecular dynamics

    Science.gov (United States)

    Agosta, Lorenzo; Brandt, Erik G.; Lyubartsev, Alexander P.

    2017-07-01

    Ab initio molecular dynamics simulations are reported for water-embedded TiO2 surfaces to determine the diffusive and reactive behavior at full hydration. A three-domain model is developed for six surfaces [rutile (110), (100), and (001), and anatase (101), (100), and (001)] which describes waters as "hard" (irreversibly bound to the surface), "soft" (with reduced mobility but orientation freedom near the surface), or "bulk." The model explains previous experimental data and provides a detailed picture of water diffusion near TiO2 surfaces. Water reactivity is analyzed with a graph-theoretic approach that reveals a number of reaction pathways on TiO2 which occur at full hydration, in addition to direct water splitting. Hydronium (H3O+) is identified to be a key intermediate state, which facilitates water dissociation by proton hopping between intact and dissociated waters near the surfaces. These discoveries significantly improve the understanding of nanoscale water dynamics and reactivity at TiO2 interfaces under ambient conditions.

  4. Hydration evolution of pre-cast concrete with steam and water curing

    Institute of Scientific and Technical Information of China (English)

    巴明芳; 钱春香

    2013-01-01

    The hydration characteristics of pre-cast concrete considering the effects of effective initial steam-curing and water-curing duration were measured and analyzed with XRD, TG, X-ray CT, SEM-BSE and MIP techniques. The results show that the effective initial steam-curing duration for pre-cast concrete with lower water-binder ratio was 10 14 h at 50 °C and the initial water-curing duration was 7 14 d. And the hydration evolution of cement, fly ash and slag in pre-cast concrete was obtained respectively by combining the hydrochlorides and EDTA selecting dissolution methods, based on which the contents of hydrated and anhydrate in concrete were calculated and the corresponding dynamic capillary porosity was also determined. Moreover, the comparison between calculated results and experimental ones indicates that the proposed evolution models of microscopic characteristics corresponding to hydration kinetics of cemented materials could be adopted to predict the developing trend of capillary porosity and hydration-products content in pre-cast concrete with fly ash and slag under certain curing conditions.

  5. Methane hydrate stability in the presence of water-soluble hydroxyalkyl cellulose

    Institute of Scientific and Technical Information of China (English)

    M. Mohammad-Taheri; A. Zarringhalam Moghaddam; K. Nazari; N. Gholipour Zanjani

    2012-01-01

    The effect of low-dosage water-soluble hydroxyethyl cellulose (approximate Mw~90,000 and 250,000) as a member ofhydroxyalkyl cellulosic polymer group on methane hydrate stability was investigated by monitoring hydrate dissociation at pressures greater than atmospheric pressure in a closed vessel.In particular,the influence of molecular weight and mass concentration of hydroxyethyl cellulose (HEC) was studied with respect to hydrate formation and dissociation.Methane hydrate formation was performed at 2 ℃ and at a pressure greater than 100 bar.Afterwards,hydrate dissociation was initiated by step heating from - 10 ℃ at a mild pressure of 13 bar to -3 ℃,0 ℃ and 2 ℃.With respect to the results obtained for methane hydrate formation/dissociation and the amount of gas uptake,we concluded that HEC 90,000 at 5000 ppm is suitable for long-term gas storage and transportation under a mild pressure of 13 bar and at temperatures below the freezing point.

  6. Nitrogen-assisted Three-phase Equilibrium in Hydrate Systems Composed of Water, Methane, Carbon Dioxide, and Nitrogen

    Science.gov (United States)

    Darnell, K.; Flemings, P. B.; DiCarlo, D. A.

    2016-12-01

    Guest molecule exchange is a new and promising methane hydrate production technique in which methane gas is produced by injection of another gas without requiring depressurization or thermal stimulation. The technique is generally associated with injection of carbon dioxide, but injection of nitrogen and carbon dioxide mixtures are the most efficient and economical. However, thermodynamic behavior of injection mixtures is poorly understood, and it is unclear how nitrogen affects the exchange process. Here, we describe thermodynamic stability of hydrate systems that contain water, methane, carbon dioxide, and nitrogen. We present a series of ternary and quaternary phase diagrams and show the impact nitrogen has on hydrate stability. Our results demonstrate that nitrogen can either stabilize hydrate, de-stabilize hydrate, or produce three-phase equilibrium (gas, water, and hydrate) depending on its relative abundance. At low abundance nitrogen forms hydrate and directly contributes to the exchange process. At high abundance nitrogen de-stabilizes hydrate akin to traditional hydrate inhibitors, such as salt, alcohol, or mono-ethylene glycol. We show how the dual properties of nitrogen lead to three-phase equilibrium and how three-phase equilibrium may explain much of the behavior observed in methane production from nitrogen-rich injections. We apply our analysis to laboratory experiments and the methane hydrate field test on the northern Alaskan slope at Ignik Sikumi. These results can be extended to analyze dynamic evolution of mixed hydrate systems.

  7. The inhibition of methane hydrate formation by water alignment underneath surface adsorption of surfactants

    Energy Technology Data Exchange (ETDEWEB)

    Nguyen, Ngoc N.; Nguyen, Anh V.; Dang, Liem X.

    2017-06-01

    Sodium dodecyl sulfate (SDS) has been widely shown to strongly promote the formation of methane hydrate. Here we show that SDS displays an extraordinary inhibition effect on methane hydrate formation when the surfactant is used in sub-millimolar concentration (around 0.3 mM). We have also employed Sum Frequency Generation vibrational spectroscopy (SFG) and molecular dynamics simulation (MDS) to elucidate the molecular mechanism of this inhibition. The SFG and MDS results revealed a strong alignment of water molecules underneath surface adsorption of SDS in its sub-millimolar solution. Interestingly, both the alignment of water and the inhibition effect (in 0.3 mM SDS solution) went vanishing when an oppositely-charged surfactant (tetra-n-butylammonium bromide, TBAB) was suitably added to produce a mixed solution of 0.3 mM SDS and 3.6 mM TBAB. Combining structural and kinetic results, we pointed out that the alignment of water underneath surface adsorption of dodecyl sulfate (DS-) anions gave rise to the unexpected inhibition of methane hydration formation in sub-millimolar solution of SDS. The adoption of TBAB mitigated the SDS-induced electrostatic field at the solution’s surface and, therefore, weakened the alignment of interfacial water which, in turn, erased the inhibition effect. We discussed this finding using the concept of activation energy of the interfacial formation of gas hydrate. The main finding of this work is to reveal the interplay of interfacial water in governing gas hydrate formation which sheds light on a universal molecular-scale understanding of the influence of surfactants on gas hydrate formation. This work was supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, Division of Chemical Sciences, Geosciences, and Biosciences. The calculations were carried out using computer resources provided by the Office of Basic Energy Sciences.

  8. Dual reorientation relaxation routes of water molecules in oxyanion’s hydration shell: A molecular geometry perspective

    Energy Technology Data Exchange (ETDEWEB)

    Xie, Wen Jun; Yang, Yi Isaac; Gao, Yi Qin, E-mail: gaoyq@pku.edu.cn [Institute of Theoretical and Computational Chemistry, College of Chemistry and Molecular Engineering and Biodynamic Optical Imaging Center, Peking University, Beijing 100871 (China)

    2015-12-14

    In this study, we examine how complex ions such as oxyanions influence the dynamic properties of water and whether differences exist between simple halide anions and oxyanions. Nitrate anion is taken as an example to investigate the hydration properties of oxyanions. Reorientation relaxation of its hydration water can occur through two different routes: water can either break its hydrogen bond with the nitrate to form one with another water or switch between two oxygen atoms of the same nitrate. The latter molecular mechanism increases the residence time of oxyanion’s hydration water and thus nitrate anion slows down the translational motion of neighbouring water. But it is also a “structure breaker” in that it accelerates the reorientation relaxation of hydration water. Such a result illustrates that differences do exist between the hydration of oxyanions and simple halide anions as a result of different molecular geometries. Furthermore, the rotation of the nitrate solute is coupled with the hydrogen bond rearrangement of its hydration water. The nitrate anion can either tilt along the axis perpendicularly to the plane or rotate in the plane. We find that the two reorientation relaxation routes of the hydration water lead to different relaxation dynamics in each of the two above movements of the nitrate solute. The current study suggests that molecular geometry could play an important role in solute hydration and dynamics.

  9. A Novel Method for the Determination of Membrane Hydration Numbers of Cations in Conducting Polymers

    DEFF Research Database (Denmark)

    Jafeen, M.J.M.; Careem, M.A.; Skaarup, Steen

    2012-01-01

    . Simultaneous cyclic voltammetry and electrochemical quartz crystal microbalance technique was used to determine the amount of charge inserted and the total mass change during the reduction process in a polypyrrole film. From these values, the number of water molecules accompanying each cation was evaluated...

  10. Types and characteristics of drinking water for hydration in the elderly.

    Science.gov (United States)

    Casado, Ángela; Ramos, Primitivo; Rodríguez, Jaime; Moreno, Norberto; Gil, Pedro

    2015-01-01

    The role of hydration in the maintenance of health is increasingly recognized. Hydration requirements vary for each person, depending on physical activity, environmental conditions, dietary patterns, alcohol intake, health problems, and age. Elderly individuals have higher risk of developing dehydration than adults. Diminution of liquid intake and increase in liquid losses are both involved in causing dehydration in the elderly. The water used for drinking is provided through regular public water supply and the official sanitary controls ensure their quality and hygiene, granting a range of variation for most of its physical and chemical characteristics, being sometimes these differences, though apparently small, responsible for some disorders in sensitive individuals. Hence, the advantages of using bottled water, either natural mineral water or spring water, are required by law to specify their composition, their major components, and other specific parameters. It is essential to take this into account to understand the diversity of indications and favorable effects on health that certain waters can offer.

  11. Selective and reactive hydration of nitriles to amides in water using silver nanoparticles stabilized by organic ligands

    Energy Technology Data Exchange (ETDEWEB)

    Kawai, Koji [Hokkaido University, Division of Materials Science and Engineering, Faculty of Engineering (Japan); Kawakami, Hayato [Miyoshi Oil & Fat Co., Ltd. (Japan); Narushima, Takashi; Yonezawa, Tetsu, E-mail: tetsu@eng.hokudai.ac.jp [Hokkaido University, Division of Materials Science and Engineering, Faculty of Engineering (Japan)

    2015-02-15

    Water-dispersible silver nanoparticles stabilized by silver–carbon covalent bonds were prepared. They exhibited high catalytic activities for the selective hydration of nitriles to amides in water. The activation of a nitrile group by the functional groups of the substrates and the hydrophobic layer on the nanoparticles influenced the catalyzed reaction were confirmed. Alkyl nitriles could also be selectively hydrated.

  12. Elucidating water dynamics in MgCl2 hydrates from molecular dynamics simulation

    Science.gov (United States)

    Huinink, Hendrik Pieter; Zahn, Dirk

    2017-07-01

    The water mobility in single crystals of MgCl2 hydrates has been investigated with molecular dynamics. Standard force fields have been benchmarked for molecular dynamics simulations of MgCl2 hydrates. To provide a reliable molecular mechanics model, force fields are selected on their ability to reproduce the structure of MgCl2·6H2O at 300 K. The selected force fields are then tested on their ability to also reproduce the structures of the different hydrates (n = 12, 8, 6, 4, 2, 1) and available thermodynamic data. For the currently best force-field available, constant-temperature, constant-pressure molecular dynamics simulations are preformed to elucidate the mechanisms of hydrate water mobility in perfect single crystals of the tetra- and hexahydrate. Long range water diffusion was not observed; each water molecule remained in the coordination sphere of its original Mg2+ host. However, collective ring-like motions of four water molecules at once within the coordination shell of a Magnesium ion were observed.

  13. Molecular Dynamics Simulation of a Membrane/Water Interface : The Ordering of Water and Its Relation to the Hydration Force

    NARCIS (Netherlands)

    Marrink, Siewert-Jan; Berkowitz, Max; Berendsen, Herman J.C.

    1993-01-01

    In order to obtain a better understanding of the origin of the hydration force, three molecular dynamic simulations of phospholipid/water multilamellar systems were performed. The simulated systems only differed in the amount of interbilayer water, ranging from the minimum to the maximum amount of

  14. Translational diffusion of hydration water correlates with functional motions in folded and intrinsically disordered proteins.

    Science.gov (United States)

    Schirò, Giorgio; Fichou, Yann; Gallat, Francois-Xavier; Wood, Kathleen; Gabel, Frank; Moulin, Martine; Härtlein, Michael; Heyden, Matthias; Colletier, Jacques-Philippe; Orecchini, Andrea; Paciaroni, Alessandro; Wuttke, Joachim; Tobias, Douglas J; Weik, Martin

    2015-01-01

    Hydration water is the natural matrix of biological macromolecules and is essential for their activity in cells. The coupling between water and protein dynamics has been intensively studied, yet it remains controversial. Here we combine protein perdeuteration, neutron scattering and molecular dynamics simulations to explore the nature of hydration water motions at temperatures between 200 and 300 K, across the so-called protein dynamical transition, in the intrinsically disordered human protein tau and the globular maltose binding protein. Quasi-elastic broadening is fitted with a model of translating, rotating and immobile water molecules. In both experiment and simulation, the translational component markedly increases at the protein dynamical transition (around 240 K), regardless of whether the protein is intrinsically disordered or folded. Thus, we generalize the notion that the translational diffusion of water molecules on a protein surface promotes the large-amplitude motions of proteins that are required for their biological activity.

  15. Relative water and gas permeability for gas production from hydrate-bearing sediments

    Science.gov (United States)

    Mahabadi, Nariman; Jang, Jaewon

    2014-06-01

    water and gas permeability equations are important for estimating gas and water production from hydrate-bearing sediments. However, experimental or numerical study to determine fitting parameters of those equations is not available in the literature. In this study, a pore-network model is developed to simulate gas expansion and calculate relative water and gas permeability. Based on the simulation results, fitting parameters for modified Stone equation are suggested for a distributed hydrate system where initial hydrate saturations range from Sh = 0.1 to 0.6. The suggested fitting parameter for relative water permeability is nw ≈ 2.4 regardless of initial hydrate saturation while the suggested fitting parameter for relative gas permeability is increased from ng = 1.8 for Sh = 0.1 to ng = 3.5 for Sh = 0.6. Results are relevant to other systems that experience gas exsolution such as pockmark formation due to sea level change, CO2 gas formation during geological CO2 sequestration, and gas bubble accumulation near the downstream of dams.

  16. Water distribution and related morphology in human stratum corneum at different hydration levels

    NARCIS (Netherlands)

    Bouwstra, J.A.; Graaff, de A.; Gooris, G.S.; Nijsse, J.; Wiechers, J.W.; Aelst, van A.C.

    2003-01-01

    This study focused on the water distribution in human stratum corneum and on the swelling of the corneocytes. For this purpose stratum corneum was hydrated to various levels and used either for Fourier transform infrared spectroscopy or for cryo-scanning electron microscopy. The images were analyzed

  17. Effect of hydration on plasma volume and endocrine responses to water immersion

    Science.gov (United States)

    Harrison, M. H.; Keil, L. C.; Wade, C. A.; Silver, J. E.; Geelen, G.

    1986-01-01

    The effect of hydration status on early endocrine responses and on osmotic and intravascular volume changes during immersion was determined in humans undergoing successive periods of dehydration, immersion, rehydration, and immersion. Immersion caused an isotonic expansion of plasma volume, as well as suppression of plasma renin activity and aldosterone, which all occurred independently of hydration status. On the other hand, the concentration of plasma vasopressin (PVP) was found to decrease during dehydrated immersion, but not during rehydrated immersion. It is concluded that plasma tonicity is not a factor influencing PVP suppression during water immersion.

  18. X-ray computed-tomography observations of water flow through anisotropic methane hydrate-bearing sand

    Energy Technology Data Exchange (ETDEWEB)

    Seol, Yongkoo; Kneafsey, Timothy J.

    2009-06-01

    We used X-ray computed tomography (CT) to image and quantify the effect of a heterogeneous sand grain-size distribution on the formation and dissociation of methane hydrate, as well as the effect on water flow through the heterogeneous hydrate-bearing sand. A 28 cm long sand column was packed with several segments having vertical and horizontal layers with sands of different grain-size distributions. During the hydrate formation, water redistribution occurred. Observations of water flow through the hydrate-bearing sands showed that water was imbibed more readily into the fine sand, and that higher hydrate saturation increased water imbibition in the coarse sand due to increased capillary strength. Hydrate dissociation induced by depressurization resulted in different flow patterns with the different grain sizes and hydrate saturations, but the relationships between dissociation rates and the grain sizes could not be identified using the CT images. The formation, presence, and dissociation of hydrate in the pore space dramatically impact water saturation and flow in the system.

  19. Gas chromatographic thermodynamics on hydration processes of magnesium chloride with low water

    Institute of Scientific and Technical Information of China (English)

    陈建军; 陈关城; 马培华; 保积庆; 马玉涛; 陈丰秋

    2003-01-01

    The dehydration and hydration processes of magnesium chloride hydrates were studied by means of frontal chromatography analysis, calorimetry, thermogravimetry and chemical analysis. The mathematical imitation for the adsorption isotherms of MgCl2*4H2O and MgCl2*2H2O at different temperatures indicates that Boltzmann Function is the ideal equation to describe those adsorption isotherms. Its adsorption heat is -13.06kJ/mol and -16.11kJ/mol, respectively. The adsorption equilibrium constants are also given. From the data obtained, there is a thermodynamical possibility to use partial dehydrated magnesium chloride hydrates as an absorbance to clean water vapor contained in bischophite dehydration equipment and let the protection gas HCl recycle in the fluid bed reaction system.

  20. Calculation of liquid water-hydrate-methane vapor phase equilibria from molecular simulations.

    Science.gov (United States)

    Jensen, Lars; Thomsen, Kaj; von Solms, Nicolas; Wierzchowski, Scott; Walsh, Matthew R; Koh, Carolyn A; Sloan, E Dendy; Wu, David T; Sum, Amadeu K

    2010-05-06

    Monte Carlo simulation methods for determining fluid- and crystal-phase chemical potentials are used for the first time to calculate liquid water-methane hydrate-methane vapor phase equilibria from knowledge of atomistic interaction potentials alone. The water and methane molecules are modeled using the TIP4P/ice potential and a united-atom Lennard-Jones potential, respectively. The equilibrium calculation method for this system has three components, (i) thermodynamic integration from a supercritical ideal gas to obtain the fluid-phase chemical potentials, (ii) calculation of the chemical potential of the zero-occupancy hydrate system using thermodynamic integration from an Einstein crystal reference state, and (iii) thermodynamic integration to obtain the water and guest molecules' chemical potentials as a function of the hydrate occupancy. The three-phase equilibrium curve is calculated for pressures ranging from 20 to 500 bar and is shown to follow the Clapeyron behavior, in agreement with experiment; coexistence temperatures differ from the latter by 4-16 K in the pressure range studied. The enthalpy of dissociation extracted from the calculated P-T curve is within 2% of the experimental value at corresponding conditions. While computationally intensive, simulations such as these are essential to map the thermodynamically stable conditions for hydrate systems.

  1. Inhibition of methane and natural gas hydrate formation by altering the structure of water with amino acids.

    Science.gov (United States)

    Sa, Jeong-Hoon; Kwak, Gye-Hoon; Han, Kunwoo; Ahn, Docheon; Cho, Seong Jun; Lee, Ju Dong; Lee, Kun-Hong

    2016-08-16

    Natural gas hydrates are solid hydrogen-bonded water crystals containing small molecular gases. The amount of natural gas stored as hydrates in permafrost and ocean sediments is twice that of all other fossil fuels combined. However, hydrate blockages also hinder oil/gas pipeline transportation, and, despite their huge potential as energy sources, our insufficient understanding of hydrates has limited their extraction. Here, we report how the presence of amino acids in water induces changes in its structure and thus interrupts the formation of methane and natural gas hydrates. The perturbation of the structure of water by amino acids and the resulting selective inhibition of hydrate cage formation were observed directly. A strong correlation was found between the inhibition efficiencies of amino acids and their physicochemical properties, which demonstrates the importance of their direct interactions with water and the resulting dissolution environment. The inhibition of methane and natural gas hydrate formation by amino acids has the potential to be highly beneficial in practical applications such as hydrate exploitation, oil/gas transportation, and flow assurance. Further, the interactions between amino acids and water are essential to the equilibria and dynamics of many physical, chemical, biological, and environmental processes.

  2. Inhibition of methane and natural gas hydrate formation by altering the structure of water with amino acids

    Science.gov (United States)

    Sa, Jeong-Hoon; Kwak, Gye-Hoon; Han, Kunwoo; Ahn, Docheon; Cho, Seong Jun; Lee, Ju Dong; Lee, Kun-Hong

    2016-08-01

    Natural gas hydrates are solid hydrogen-bonded water crystals containing small molecular gases. The amount of natural gas stored as hydrates in permafrost and ocean sediments is twice that of all other fossil fuels combined. However, hydrate blockages also hinder oil/gas pipeline transportation, and, despite their huge potential as energy sources, our insufficient understanding of hydrates has limited their extraction. Here, we report how the presence of amino acids in water induces changes in its structure and thus interrupts the formation of methane and natural gas hydrates. The perturbation of the structure of water by amino acids and the resulting selective inhibition of hydrate cage formation were observed directly. A strong correlation was found between the inhibition efficiencies of amino acids and their physicochemical properties, which demonstrates the importance of their direct interactions with water and the resulting dissolution environment. The inhibition of methane and natural gas hydrate formation by amino acids has the potential to be highly beneficial in practical applications such as hydrate exploitation, oil/gas transportation, and flow assurance. Further, the interactions between amino acids and water are essential to the equilibria and dynamics of many physical, chemical, biological, and environmental processes.

  3. Transparent hydrogel with enhanced water retention capacity by introducing highly hydratable salt

    Energy Technology Data Exchange (ETDEWEB)

    Bai, Yuanyuan; Xiang, Feng; Wang, Hong, E-mail: hwang@mail.xjtu.edu.cn, E-mail: suo@seas.harvard.edu [Electronic Materials Research Laboratory, School of Electronics and Information Engineering, Xi' an Jiaotong University, Xi' an 710049 (China); Chen, Baohong; Zhou, Jinxiong [State Key Laboratory for Strength and Vibration of Mechanical Structures, International Center for Applied Mechanics and School of Aerospace, Xi' an Jiaotong University, Xi' an 710049 (China); Suo, Zhigang, E-mail: hwang@mail.xjtu.edu.cn, E-mail: suo@seas.harvard.edu [School of Engineering and Applied Sciences, Kavli Institute of Bionano Science and Technology, Harvard University, Cambridge, Massachusetts 02138 (United States)

    2014-10-13

    Polyacrylamide hydrogels containing salt as electrolyte have been used as highly stretchable transparent electrodes in flexible electronics, but those hydrogels are easy to dry out due to water evaporation. Targeted, we try to enhance water retention capacity of polyacrylamide hydrogel by introducing highly hydratable salts into the hydrogel. These hydrogels show enhanced water retention capacity in different level. Specially, polyacrylamide hydrogel containing high content of lithium chloride can retain over 70% of its initial water even in environment with relative humidity of only 10% RH. The excellent water retention capacities of these hydrogels will make more applications of hydrogels become possible.

  4. Molecular dynamics simulation on influence of guest molecule number on methane hydrate thermal performance%客体分子数对甲烷水合物导热性能影响的分子动力学模拟

    Institute of Scientific and Technical Information of China (English)

    万丽华; 梁德青; 吴能友; 关进安

    2012-01-01

    采用EMD方法Green-Kubo理论计算263.15 K晶穴占有率0~100% sI甲烷水合物的热导率,研究客体分子数对甲烷水合物导热性能的影响.模拟结果显示,甲烷水合物的低导热性能由主体分子构建的笼形结构决定.而在相同温压条件下,随着客体分子甲烷进入晶胞数目增多,晶穴占有率增大后,密度增大,同时客体分子对声子的散射也增强,二者均导致导热性能增强.%Thermal conductivity of methane hydrate is an important physical parameter in processes of methane hydrate exploration, mining, gas hydrate storage and transportation as well as other applications. In this paper, equilibrium molecular dynamics (EMD) simulation and the Green-Kubo method are used for the systems with 0-100% occupancy of sI methane hydrate to evaluate the influence of guest molecule number on the thermal performance of methane hydrate. The EMD simulation for the thermodynamics of equilibrium state of si methane hydrate is performed via the Green-Kubo approach for the thermal conductivity of methane hydrates. The DL-POLY molecular dynamics simulation package is employed. TIP4P/Ice water model is used for water-water interactions and the Lennard-Jones potential for methane-methane and methane-water interactions. The Lorentz-Berthelot combination rule is used to determine the parameters of Lennard-Jones potentials between water and methane molecules. The equations of motion are integrated using the Verlet algorithm and the Ewald method is used to handle long-range electrostatic interactions. Results indicate that the poor thermal conduction of methane hydrate is resultedfrom the framework of cage. The thermal conduction of methane hydrate is improved when the framework of cage has slightly higher thermal conductivity with more guest molecules enclosed in the cage> since higher cage occupancy ratio by guest molecules increases the density and their scattering.

  5. The Structure of Hydrated Electron. Part 1. Magnetic Resonance of Internally Trapping Water Anions: A Density Functional Theory Study

    CERN Document Server

    Shkrob, I A

    2006-01-01

    Density functional theory (DFT) is used to rationalize magnetic parameters of hydrated electron trapped in alkaline glasses as observed using Electron Paramagnetic Resonance (EPR) and Electron Spin Echo Envelope Modulation (ESEEM) spectroscopies. To this end, model water cluster anions (n=4-8 and n=20,24) that localize the electron internally are examined. It is shown that EPR parameters of such water anions (such as hyperfine coupling tensors of H/D nuclei in the water molecules) are defined mainly by the cavity size and the coordination number of the electron; the water molecules in the second solvation shell play a relatively minor role. An idealized model of hydrated electron (that is usually attributed to L. Kevan) in which six hydroxyl groups arranged in an octahedral pattern point towards the common center is shown to provide the closest match to the experimental parameters, such as isotropic and anisotropic hyperfine coupling constants for the protons (estimated from ESEEM), the second moment of the E...

  6. Influence of Hydration Level on Polymer and Water Dynamics in Alkaline Anion Exchange Fuel Cell Membranes

    Science.gov (United States)

    Tarver, Jacob; Kim, Jenny; Tyagi, Madhu; Soles, Christopher; Tsai, Tsung-Han; Coughlin, Bryan

    2015-03-01

    Triblock copolymers based on poly(chloromethylstyrene)-b-poly(ethylene)-b-poly(chloromethylstyrene) can be quaternized to different extents to yield anion exchange membranes for alkaline fuel cells. In the absence of moisture, these membranes demonstrate bilayer lamellar morphology. Upon high levels of hydration, however, in-situ small angle neutron scattering reveals the emergence of higher-order diffraction peaks. This phenomena has previously been observed in analogous diblock copolymer-based membranes and has been attributed to the induction of a multilayer lamellar morphology in which selective striping of water occurs in the center of the ion-rich domain. By conducting humidity-resolved quasielastic neutron scattering (QENS) measurements using deuterated water, we are able to isolate differences in the pico- to nanosecond timescale dynamics of the hydrogenated membrane upon hydration. QENS measurements in the presence of a hydrogenated water source subsequently permit deconvolution and isolation of the translational and rotational dynamics of water as a function of relative humidity, revealing spatial and temporal changes in polymer and water motion at high levels of hydration.

  7. Electronic and vibrational spectroscopy of 1-methylthymine and its water clusters: the dark state survives hydration.

    Science.gov (United States)

    Busker, Matthias; Nispel, Michael; Häber, Thomas; Kleinermanns, Karl; Etinski, Mihajlo; Fleig, Timo

    2008-08-04

    Electronic and vibrational gas phase spectra of 1-methylthymine (1MT) and 1-methyluracil (1MU) and their clusters with water are presented. Mass selective IR/UV double resonance spectra confirm the formation of pyrimidine-water clusters and are compared to calculated vibrational spectra obtained from ab initio calculations. In contrast to Y. He, C. Wu, W. Kong; J. Phys. Chem. A, 2004, 108, 94 we are able to detect 1MT/1MU and their water clusters via resonant two-photon delayed ionization under careful control of the applied water-vapor pressure. The long-living dark electronic state of 1MT and 1MU detected by delayed ionization, survives hydration and the photostability of 1MT/1MU cannot be attributed solely to hydration. Oxygen coexpansions and crossed-beam experiments indicate that the triplet state population is probably small compared to the (1)n pi* and/or hot electronic ground state population. Ab initio theory shows that solvation of 1MT by water does not lead to a substantial modification of the electronic relaxation and quenching of the (1)n pi* state. Relaxation pathways via (1)pi pi*(1)-n pi*(1) and (1)pi pi*-S(0) conical intersections and barriers have been identified, but are not significantly altered by hydration.

  8. ATR-FTIR study of water in Nafion membrane combined with proton conductivity measurements during hydration/dehydration cycle.

    Science.gov (United States)

    Kunimatsu, Keiji; Bae, Byungchan; Miyatake, Kenji; Uchida, Hiroyuki; Watanabe, Masahiro

    2011-04-21

    We have conducted combined time-resolved attenuated total reflection Fourier transform infrared (ATR-FTIR) and proton conductivity measurements of Nafion NRE211 membrane during hydration/dehydration cycles at room temperature. Conductivity change was interpreted in terms of different states of water in the membrane based on its δ(HOH) vibrational spectra. It was found that hydration of a dry membrane leads first to complete dissociation of the sulfonic acid groups to liberate hydrated protons, which are isolated from each other and have δ(HOH) vibrational frequency around 1740 cm(-1). The initial hydration is not accompanied by a significant increase of the proton conductivity. Further hydration gives rise to a rapid increase of the conductivity in proportion to intensity of a new δ(HOH) band around 1630 cm(-1). This was interpreted in terms of formation of channels of weakly hydrogen-bonded water to combine the isolated hydrophilic domains containing hydrated protons and hydrated sulfonate ions produced during the initial stage of hydration. Upon dehydration, proton conductivity drops first very rapidly due to loss of the weakly hydrogen bonded water from the channels to leave hydrophilic domains isolated in the membrane. Dehydration of the protons proceeds very slowly after significant loss of the proton conductivity.

  9. Salt hydrates for in situ water activity control have acid-base effects on enzymes in nonaqueous media.

    Science.gov (United States)

    Fontes, Nuno; Harper, Neil; Halling, Peter J; Barreiros, Susana

    2003-06-30

    Salt hydrates very frequently are utilized as in situ water activity buffers in reaction mixtures of enzymes in nonaqueous media. In addition to buffering water activity, there is evidence that salt hydrates also often affect initial rates in other ways. This has been generally overlooked or thought to be related to water transfer effects. Here we show that salt hydrates can have important acid-base effects on enzymes in nonaqueous media. We performed transesterification reactions in n-hexane and in supercritical ethane catalyzed by cross-linked crystals of subtilisin, differing in the method used to set a(W), and confirmed that the presence of salt hydrate pairs significantly affected the catalytic performance of the enzyme. However, in the presence of a solid-state acid-base buffer, salt hydrates had no effect on enzymatic activity. Direct evidence for the acid-base effects of salt hydrates was obtained by testing their effect on the protonation state of an organo-soluble H(+)/Na(+) indicator. The four salt hydrate pairs tested affected the indicator to very different extents. By promoting the exchange of H(+) for Na(+), salt hydrates will tend to affect the ionization state of acidic residues in the protein and, hence, enzymatic activity. In fact, salt hydrates were able to affect the pH memory of subtilisin lyophilized from different aqueous pHs, bringing about up to 20-fold enhancements and up to 5-fold decreases in catalytic activity. The possibility of such acid-base effects need to be considered in all experiments using salt hydrates to control water activity.

  10. Temperature dependence of the structure of protein hydration water and the liquid-liquid transition.

    Science.gov (United States)

    Accordino, S R; Malaspina, D C; Rodriguez Fris, J A; Alarcón, L M; Appignanesi, G A

    2012-03-01

    We study the temperature dependence of the structure and orientation of the first hydration layers of the protein lysozyme and compare it with the situation for a model homogeneous hydrophobic surface, a graphene sheet. We show that in both cases these layers are significantly better structured than bulk water. The geometrical constraint of the interface makes the water molecules adjacent to the surface lose one water-water hydrogen bond and expel the fourth neighbors away from the surface, lowering local density. We show that a decrease in temperature improves the ordering of the hydration water molecules, preserving such a geometrical effect. For the case of graphene, this favors an ice Ih-like local structuring, similar to the water-air interface but in the opposite way along the c axis of the basal plane (while the vicinal water molecules of the air interface orient a hydrogen atom toward the surface, the oxygens of the water molecules close to the graphene plane orient a lone pair in such a direction). In turn, the case of the first hydration layers of the lysozyme molecule is shown to be more complicated, but still displaying signs of both kinds of behavior, together with a tendency of the proximal water molecules to hydrogen bond to the protein both as donors and as acceptors. Additionally, we make evident the existence of signatures of a liquid-liquid transition (Widom line crossing) in different structural parameters at the temperature corresponding to the dynamic transition incorrectly referred to as "the protein glass transition."

  11. Water proton configurations in structures I, II, and H clathrate hydrate unit cells.

    Science.gov (United States)

    Takeuchi, Fumihito; Hiratsuka, Masaki; Ohmura, Ryo; Alavi, Saman; Sum, Amadeu K; Yasuoka, Kenji

    2013-03-28

    Position and orientation of water protons need to be specified when the molecular simulation studies are performed for clathrate hydrates. Positions of oxygen atoms in water are experimentally determined by X-ray diffraction analysis of clathrate hydrate structures, but positions of water hydrogen atoms in the lattice are disordered. This study reports a determination of the water proton coordinates in unit cell of structure I (sI), II (sII), and H (sH) clathrate hydrates that satisfy the ice rules, have the lowest potential energy configuration for the protons, and give a net zero dipole moment. Possible proton coordinates in the unit cell were chosen by analyzing the symmetry of protons on the hexagonal or pentagonal faces in the hydrate cages and generating all possible proton distributions which satisfy the ice rules. We found that in the sI and sII unit cells, proton distributions with small net dipole moments have fairly narrow potential energy spreads of about 1 kJ∕mol. The total Coulomb potential on a test unit charge placed in the cage center for the minimum energy∕minimum dipole unit cell configurations was calculated. In the sI small cages, the Coulomb potential energy spread in each class of cage is less than 0.1 kJ∕mol, while the potential energy spread increases to values up to 6 kJ∕mol in sH and 15 kJ∕mol in the sII cages. The guest environments inside the cages can therefore be substantially different in the sII case. Cartesian coordinates for oxygen and hydrogen atoms in the sI, sII, and sH unit cells are reported for reference.

  12. Modeling of CO{sub 2}-hydrate formation at the gas-water interface in sand sediment

    Energy Technology Data Exchange (ETDEWEB)

    Takahashi, T.; Sato, T.; Hirabayashi, S.; Brumby, P.E. [University of Tokyo, Department of Ocean Technology, Policy, and Environment, Kashiwa (Japan); Inui, M. [Mitsubishi Heavy Industries America, Inc., Environmental Systems Division, Austin, TX (United States)

    2012-10-15

    Sub-seabed geological storage of CO{sub 2} in the form of gas hydrate is attractive because clathrate hydrate stably exists at low temperature and high pressure, even if a fault occurs by diastrophism like a big earthquake. For the effective design of the storage system it is necessary to model the formation of CO{sub 2}-hydrate. Here, it is assumed that the formation of gas hydrate on the interface between gas and water consists of two stages: gas diffusion through the CO{sub 2}-hydrate film and consequent CO{sub 2}-hydrate formation on the interface, between film and water. Also proposed is the presence of a fresh reaction interface, which is part of the interface between the gas and aqueous phases and not covered with CO{sub 2}-hydrate. Parameters necessary to model the hydrate formation in sand sediment are derived by comparing the results of the present numerical simulations and the measurements in the literature. (Copyright copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  13. Protocol for Measuring the Thermal Properties of a Supercooled Synthetic Sand-water-gas-methane Hydrate Sample.

    Science.gov (United States)

    Muraoka, Michihiro; Susuki, Naoko; Yamaguchi, Hiroko; Tsuji, Tomoya; Yamamoto, Yoshitaka

    2016-03-21

    Methane hydrates (MHs) are present in large amounts in the ocean floor and permafrost regions. Methane and hydrogen hydrates are being studied as future energy resources and energy storage media. To develop a method for gas production from natural MH-bearing sediments and hydrate-based technologies, it is imperative to understand the thermal properties of gas hydrates. The thermal properties' measurements of samples comprising sand, water, methane, and MH are difficult because the melting heat of MH may affect the measurements. To solve this problem, we performed thermal properties' measurements at supercooled conditions during MH formation. The measurement protocol, calculation method of the saturation change, and tips for thermal constants' analysis of the sample using transient plane source techniques are described here. The effect of the formation heat of MH on measurement is very small because the gas hydrate formation rate is very slow. This measurement method can be applied to the thermal properties of the gas hydrate-water-guest gas system, which contains hydrogen, CO2, and ozone hydrates, because the characteristic low formation rate of gas hydrate is not unique to MH. The key point of this method is the low rate of phase transition of the target material. Hence, this method may be applied to other materials having low phase-transition rates.

  14. Coordination variation of hydrated Cu2+/Br1- ions traversing the interfacial water in mesopores

    Science.gov (United States)

    Wang, Q.; Huang, X. F.; Li, C. X.; Pan, L. Q.; Wu, Z. H.; Hu, T. D.; Jiang, Z.; Huang, Y. Y.; Cao, Z. X.; Sun, G.; Lu, K. Q.

    2012-06-01

    Resolution of the atomistic and electronic details about the coordination structure variation of hydrated ions in the interfacial water is still a tough challenge, which is, however, essentially important for the understanding of ion adsorption, permeation and other similar processes in aqueous solutions. Here we report the tracing of coordination structure variation for hydrated Cu2+/Br1- ions traversing the interfacial water in Vycor mesopores (ϕ = 7.6 nm) by employing both X-ray absorption near edge structure and extended X-ray absorption fine structure spectroscopies. By controlled desorption/adsorption of water, the filling fraction of the mesopores, thus the water layer thickness, can be adjusted, which in turn effects the variation of coordination structure of the ions therein. It is found that both Cu2+ and Br1- ions prefer staying exclusively in the core water, and in this circumstance no ion pairs have been detected in the solution of concentrations up to 1.0 M. Following capillary decondensation occurring at a filling fraction of ˜35% which corresponds to a water layer of about three monolayers, Br1- ions begin immediately to reconstruct their first coordination shell, characterized by ionic dehydration, shrinkage of ion-water bond length, and formation of ion pairs. In contrast, Cu2+ ions can retain a bulk-like coordination structure till being driven to bond directly to the pore surface when the filling fraction is below 20%. At the final stage of dehydration via thermal vacuum treatment at 110°C, Cu2+ ions can be completely reduced to the Cu1+ state, and recover at room temperature only when the filling fraction is above 14%. These results may be inspirable for the investigation of similar problems concerning hydrated ions in water solution under different confining conditions.

  15. Coordination variation of hydrated Cu2+/Br1− ions traversing the interfacial water in mesopores

    Directory of Open Access Journals (Sweden)

    Q. Wang

    2012-06-01

    Full Text Available Resolution of the atomistic and electronic details about the coordination structure variation of hydrated ions in the interfacial water is still a tough challenge, which is, however, essentially important for the understanding of ion adsorption, permeation and other similar processes in aqueous solutions. Here we report the tracing of coordination structure variation for hydrated Cu2+/Br1- ions traversing the interfacial water in Vycor mesopores (ϕ = 7.6 nm by employing both X-ray absorption near edge structure and extended X-ray absorption fine structure spectroscopies. By controlled desorption/adsorption of water, the filling fraction of the mesopores, thus the water layer thickness, can be adjusted, which in turn effects the variation of coordination structure of the ions therein. It is found that both Cu2+ and Br1- ions prefer staying exclusively in the core water, and in this circumstance no ion pairs have been detected in the solution of concentrations up to 1.0 M. Following capillary decondensation occurring at a filling fraction of ∼35% which corresponds to a water layer of about three monolayers, Br1- ions begin immediately to reconstruct their first coordination shell, characterized by ionic dehydration, shrinkage of ion-water bond length, and formation of ion pairs. In contrast, Cu2+ ions can retain a bulk-like coordination structure till being driven to bond directly to the pore surface when the filling fraction is below 20%. At the final stage of dehydration via thermal vacuum treatment at 110°C, Cu2+ ions can be completely reduced to the Cu1+ state, and recover at room temperature only when the filling fraction is above 14%. These results may be inspirable for the investigation of similar problems concerning hydrated ions in water solution under different confining conditions.

  16. Analysis of the hydration water around bovine serum albumin using terahertz coherent synchrotron radiation.

    Science.gov (United States)

    Bye, Jordan W; Meliga, Stefano; Ferachou, Denis; Cinque, Gianfelice; Zeitler, J Axel; Falconer, Robert J

    2014-01-09

    Terahertz spectroscopy was used to study the absorption of bovine serum albumin (BSA) in water. The Diamond Light Source operating in a low alpha mode generated coherent synchrotron radiation that covered a useable spectral bandwidth of 0.3-3.3 THz (10-110 cm(-1)). As the BSA concentration was raised, there was a nonlinear change in absorption inconsistent with Beer's law. At low BSA concentrations (0-1 mM), the absorption remained constant or rose slightly. Above a concentration of 1 mM BSA, a steady decrease in absorption was observed, which was followed by a plateau that started at 2.5 mM. Using a overlapping hydration layer model, the hydration layer was estimated to extend 15 Å from the protein. Calculation of the corrected absorption coefficient (αcorr) for the water around BSA by subtracting the excluded volume of the protein provides an alternative approach to studying the hydration layer that provides evidence for complexity in the population of water around BSA.

  17. Membrane dipole potentials, hydration forces, and the ordering of water at membrane surfaces.

    Science.gov (United States)

    Gawrisch, K; Ruston, D; Zimmerberg, J; Parsegian, V A; Rand, R P; Fuller, N

    1992-01-01

    We have compared hydration forces, electrical dipole potentials, and structural parameters of dispersions of dipalmitoylphosphatidylcholine (DPPC) and dihexadecylphosphatidylcholine (DHPC) to evaluate the influence of fatty acid carbonyl groups on phospholipid bilayers. NMR and x-ray investigations performed over a wide range of water concentrations in the samples show, that in the liquid crystalline lamellar phase, the presence of carbonyl groups is not essential for lipid structure and hydration. Within experimental error, the two lipids have identical repulsive hydration forces between their bilayers. The higher transport rate of the negatively charged tetraphenylboron over the positively charged tetraphenylarsonium indicates that the dipole potential is positive inside the membranes of both lipids. However, the lack of fatty acid carbonyl groups in the ether lipid DHPC decreased the potential by (118 +/- 15) mV. By considering the sign of the potential and the orientation of carbonyl groups and headgroups, we conclude that the first layer of water molecules at the lipid water interface makes a major contribution to the dipole potential. PMID:1600081

  18. Direct measurement of the correlated dynamics of the protein-backbone and proximal waters of hydration in mechanically strained elastin

    CERN Document Server

    Sun, Cheng; Huang, Jiaxin; Boutis, Gregory S

    2011-01-01

    We report on the direct measurement of the correlation times of the protein backbone carbons and proximal waters of hydration in mechanically strained elastin by nuclear magnetic resonance methods. The experimental data indicate a decrease in the correlation times of the carbonyl carbons as the strain on the biopolymer is increased. These observations are in good agreement with short 4ns molecular dynamics simulations of (VPGVG)3, a well studied mimetic peptide of elastin. The experimental results also indicate a reduction in the correlation time of proximal waters of hydration with increasing strain applied to the elastomer. A simple model is suggested that correlates the increase in the motion of proximal waters of hydration to the increase in frequency of libration of the protein backbone that develops with increasing strain. Together, the reduction in the protein entropy accompanied with the increase in entropy of the proximal waters of hydration with increasing strain, support the notion that the source ...

  19. Hydration status and water turnover of dogsled drivers during an endurance sled dog even in the Arctic

    OpenAIRE

    2012-01-01

    Objectives. To determine changes in common urinary markers of hydration maintained by the drivers (mushers) during a wilderness endurance event in the arctic and to determine water turnover in this select group of individuals. Study Design. During this descriptive study, data was systematically collected on hydration, water turnover, changes in resting and exercise heart rate, fatigue and rating of perceived exertion during an arduous dogsled race in the arctic. Methods. Sixteen mushers were ...

  20. Role of the hydrophobic and hydrophilic sites in the dynamic crossover of the protein-hydration water

    Science.gov (United States)

    Köhler, Mateus Henrique; Barbosa, Rafael C.; da Silva, Leandro B.; Barbosa, Marcia C.

    2017-02-01

    Molecular dynamics simulations were performed to study the water structure and dynamics in the hydration shell of the globular TS-Kappa protein. The results show that for a wide range of temperatures the diffusion coefficient of water near the protein surface is lower than in bulk. A crossover in the diffusion behavior of hydration water is observed at different temperatures for hydrophilic and hydrophobic vicinities. We have found a correlation between the crossover in the hydrophilic case and the protein dynamical transition. An explanation in terms of the competition between water-water water-protein H-bond formation is provided based on H-bond network analysis.

  1. Verification of simple hydration/dehydration methods to characterize multiple water compartments on tendon type 1 collagen.

    Science.gov (United States)

    Cameron, Ivan L; Short, Nicholas J; Fullerton, Gary D

    2007-06-01

    A molecular model of collagen hydration is used to validate centrifugal dehydration force (CDF) and re-hydration isotherm (RHI) methods to measure and characterize hydration compartments on bovine tendon. The CDF method assesses fluid flow rate from flexor and extensor tendons expressed in (g-water/g-dry mass-minute) and hydration capacity of compartments in (g-water/g-dry mass). Measured water compartment capacities agree with the molecular model of collagen hydration [Fullerton GD, Rahal A. Collagen structure: the molecular source of tendon magic angle effect. J Mag Reson Imag 2007;25:345-361; Fullerton GD, Amurao MR. Evidence that collagen and tendon have monolayer water coverage in the native state. Cell Biol Int 2006;30(1):56-65]. Native tendon hydration has monolayer coverage on collagen h(m)=1.6 g/g which divides into primary hydration on polar surfaces h(pp)=0.8 g/g and secondary hydration h(s)=0.8 g/g bridging over hydrophobic surfaces. Primary hydration is hydrogen bonded to collagen polar side chains h(psc)=0.54 g/g with small free energy or to the protein main chain hydration h(pmc)=0.26 g/g with greater free energy of binding. The CDF method replaces the more time consuming water proton NMR spin-lattice dehydration (NMR titration) method, confirms the presence of three non-bulk water compartments on collagen (h(pmc)=0.26 g/g, h(pp)=0.8 g/g and h(m)=1.6 g/g). This CDF method provides the most reproducible experimental measure of total tissue non-bulk water (TNBW). The re-hydration isotherm method, on the other hand, provides the most accurate measure of the Ramachandran water-bridge capacity h(Ra)=0.0656 g/g. The only equipment needed are: microfilterfuge tubes, a microcentrifuge capable of 14,000 x g or 4MPa, a vacuum drying oven, an accurate balance and curve fitting ability. The newly validated methods should be useful for characterizing multiple water compartments in biological and non-biological materials by allowing direct measurement of water

  2. Unraveling the Sc(3+) Hydration Geometry: The Strange Case of the Far-Coordinated Water Molecule.

    Science.gov (United States)

    Migliorati, Valentina; D'Angelo, Paola

    2016-07-05

    The hydration structure and dynamics of Sc(3+) in aqueous solution have been investigated using a combined approach based on quantum mechanical (QM) calculations, molecular dynamics (MD) simulations, and extended X-ray absorption fine structure (EXAFS) spectroscopy. An effective Sc-water two-body potential has been generated from QM calculations and then used in the MD simulation of Sc(3+) in water, and the reliability of the entire procedure has been assessed by comparing the theoretical structural results with the EXAFS experimental data. The outstanding outcome of this work is that the Sc(3+) ion forms a well-defined capped square antiprism (SAP) complex in aqueous solution, where the eight water molecules closest to the ion are located at the vertexes of a SAP polyhedron, while the ninth water molecule occupying the capping position is unusually found at a very long distance from the ion. This far-coordinated water molecule possesses a degree of structure comparable with the other first shell molecules surrounding the ion at much shorter distances, and its presence gave us the unique opportunity to easily identify the geometry of the Sc(3+) coordination polyhedron. Despite very strong ion-water interactions, the Sc(3+) hydration shell is very labile, as the far-coordinated ligand allows first shell water molecules to easily exchange their positions both inside the solvation shell and with the rest of the solvent molecules.

  3. Effects of polar solvents on the fracture resistance of dentin: Role of water hydration

    Energy Technology Data Exchange (ETDEWEB)

    Ritchie, R O; Nalla, R K; Balooch, M; Ager III, J W; Kruzic, J J; Kinney, J H

    2004-12-10

    Although healthy dentin is invariably hydrated in vivo, from a perspective of examining the mechanisms of fracture in dentin, it is interesting to consider the role of water hydration. Furthermore, it is feasible that exposure to certain polar solvents, e.g., those found in clinical adhesives, can induce dehydration. In the present study, in vitro deformation and fracture experiments, the latter involving a resistance-curve (R-curve) approach (i.e., toughness evolution with crack extension), were conducted in order to assess changes in the constitutive and fracture behavior induced by three common solvents - acetone, ethanol and methanol. In addition, nanoindentation-based experiments to evaluate the deformation behavior at the level of individual collagen fibers and ultraviolet Raman spectroscopy to evaluate changes in bonding were performed. The results indicate a reversible effect of chemical dehydration, with increased fracture resistance, strength, and stiffness associated with lower hydrogen bonding ability of the solvent. These results are analyzed both in terms of intrinsic and extrinsic toughening phenomena to further understand the micromechanisms of fracture in dentin and the specific role of water hydration.

  4. Observation of a Dynamic Crossover in RNA Hydration Water which Triggers the Glass Transition in the Biopolymer

    CERN Document Server

    Chu, X; Chen, S H; Faraone, A; Fratini, E; Baglioni, Piero; Chen, Sow-Hsin; Chu, Xiang-qiang; Faraone, Antonio; Fratini, Emiliano

    2007-01-01

    High-resolution quasi-elastic neutron scattering spectroscopy was used to measure H2O and D2O hydrated RNA samples. The contribution of scattering from RNA was subtracted out by taking the difference of the signals between the two samples. The measurements were made at a series of temperatures from 270 K down to 180 K. The Relaxing-Cage Model was used to analyze the difference quasi-elastic spectra. We observed clear evidence of a fragile-to-strong dynamic crossover (FSC) at TL = 220 K in RNA hydration water. We further show that the mean-square displacement of the hydrogen atoms in both RNA and its hydration water exhibit a sharp change in slope at approximately the same temperature 220 K. This latter fact suggests that the dynamic transition (or the glass transition) in RNA is triggered by the abrupt change of mobility of the hydration water at its FSC temperature TL.

  5. Characterizing Natural Gas Hydrates in the Deep Water Gulf of Mexico: Applications for Safe Exploration and Production Activities

    Energy Technology Data Exchange (ETDEWEB)

    Bent, Jimmy

    2014-05-31

    In 2000 Chevron began a project to learn how to characterize the natural gas hydrate deposits in the deep water portion of the Gulf of Mexico (GOM). Chevron is an active explorer and operator in the Gulf of Mexico and is aware that natural gas hydrates need to be understood to operate safely in deep water. In August 2000 Chevron worked closely with the National Energy Technology Laboratory (NETL) of the United States Department of Energy (DOE) and held a workshop in Houston, Texas to define issues concerning the characterization of natural gas hydrate deposits. Specifically, the workshop was meant to clearly show where research, the development of new technologies, and new information sources would be of benefit to the DOE and to the oil and gas industry in defining issues and solving gas hydrate problems in deep water.

  6. PMR Characterization of the Water Structure in Tibetan Milk Mushroom Zooglea: Influence of Medium Hydration and Hydrophobicity

    Science.gov (United States)

    Krupskaya, T. V.; Prylutskyy, Yu. I.; Evstigneev, M. P.; Tsapko, M. D.; Turov, V. V.

    2015-07-01

    The state of water in Tibetan milk mushroom zooglea with different degrees of hydration (h) was investigated using low-temperature PMR spectroscopy in air and in contact with the hydrophobic media polydimethylsiloxane PDMS-1000 and CHCl3 with added trifl uoroacetic acid (TFA). The maximum hydration of the zooglea amounted to h = 32 g/g (of dry matter). Water existed as polyassociates (clusters or domains) of strongly and weakly associated water. Bound water decomposed into clusters in the presence of TFA. The NMR spectra showed six types of bound water at h = 0.3 g/g.

  7. Relation between soil matrix potential changes and water conversion ratios during methane hydrate formation processes in loess

    Institute of Scientific and Technical Information of China (English)

    Peng Zhang; Qingbai Wu; Guanli Jiang; Yibin Pu

    2011-01-01

    With a new apparatus designed and assembled by ourselves,the matrix potential of non-saturated loess was firstly measured and studied during methane hydrate formation processes.The experimental results showed that during two formation processes,the matrix potential changes of the loess all presented a good linear relationship with water conversion ratios.In addition,although it was well known that the secondary gas hydrate formation was easier than the initial,our experimental results showed that the initial hydrate formation efficiency in non-saturated loess was higher than that of the secondary.

  8. Chemical and isotopic characteristics of gas hydrate- and pore-water samples obtained from gas hydrate-bearing sediment cores retrieved from a mud volcano in the Kukuy Canyon, Lake Baikal

    Energy Technology Data Exchange (ETDEWEB)

    Minami, H.; Hachikubo, A.; Krylov, A.; Sakagami, H.; Ohashi, M.; Bai, J.; Kataoka, S.; Yamashita, S.; Takahashi, N.; Shoji, H. [Kitami Inst. of Technology, Kitami (Japan); Khlystov, O.; Zemskaya, T.; Grachev, M. [Russian Academy of Sciences, Irkutsk (Russian Federation). Limnological Inst.

    2008-07-01

    This paper provided details of a method developed to obtain gas hydrate water samples from a mud volcano in Lake Baikal, Russia. Chemical and isotopic analyses were conducted to examine the hydrate and pore water samples as well as to evaluate the original water involved in shallow gas hydrate accumulations in the region. Lake sediment core samples were retrieved from the bottom of the lake with gravity corers. A squeezer was used to take pore water samples from the sediments. Hydrate samples were taken from a gas hydrate placed on a polyethylene funnel. Dissolved hydrate water was filtered through a membrane into bottles. Both samples were kept under chilled or liquid nitrogen temperatures. Ion chromatography was used to determine concentrations of anions and hydrogen carbonate ions. Sodium and magnesium concentrations were determined using an inductively coupled plasma atomic emission spectrometer. An absorption spectrometer was used to determine potassium and calcium concentrations, and a mass spectrometer was used to analyze stable isotopes of oxygen and hydrogen. Results of the study suggested that the gas dissolved in pore water and adsorbed on the surfaces of sediment particles was not the original gas from the hydrates retrieved at the mud volcano. Original gas hydrate-forming fluids were chemically different from the pore- and lake-water samples. The oxygen isotopic composition of the gas hydrate water samples correlated well with hydrogen values. It was concluded that ascending fluid and water delivered the gas into the gas stability zone, and is the main gas hydrate-forming fluid in the area of study. 12 refs., 1 fig.

  9. Polymer Electrolyte Fuel Cells Membrane Hydration by Direct Liquid Water Contact

    Energy Technology Data Exchange (ETDEWEB)

    Wilson, M.S.; Zawodzinski, C.; Gottesfeld, S.

    1998-11-01

    An effective means of providing direct liquid hydration of the membrane tends to improve performance particularly of cells with thicker membranes or at elevated temperatures. Supplying the water to the membrane from the anode flow-field through the anode backing via wicks would appear to have advantages over delivering the water through the thickness of the membrane with regards to the uniformity and stability of the supply and the use of off-the-shelf membranes or MEAs. In addition to improving cell performance, an important contribution of direct liquid hydration approaches may be that the overall fuel cell system becomes simpler and more effective. The next steps in the evolution of this approach are a demonstration of the effectiveness of this technique with larger active area cells as well as the implementation of an internal flow-field water reservoir (to eliminate the injection method). Scale-up to larger cell sizes and the use of separate water channels within the anode flow-field is described.

  10. Comparison of the effects of hydration with water or isotonic solution on the recovery of cardiac autonomic modulation.

    Science.gov (United States)

    Vanderlei, Franciele Marques; Moreno, Isadora Lessa; Vanderlei, Luiz Carlos; Pastre, Carlos Marcelo; de Abreu, Luiz Carlos; Ferreira, Celso

    2015-04-01

    Despite the importance of hydration during exercise, the impact of ingesting water or isotonic solution during and after exercise on the regulation of autonomic modulation is unclear. The study aimed to compare the effect of ingesting water or isotonic solution (Gatorade®, Brazil) on cardiac autonomic modulation in young people after submaximal aerobic exercise. Thirty-one young men were subjected to a protocol consisting of 4 steps: 1) incremental test, 2) control protocol without hydration, 3) protocol with ingestion of water, and 4) protocol with ingestion of isotonic solution. The protocol consisted of 10 min of rest, 90 min of treadmill exercise at 60% VO2peak, and 60 min of recovery at rest. In the hydration protocols, hydration occurred during and after exercise, every 15 min beginning after the 15th minute of exercise, with the amount ingested proportional to body mass lost in the control protocol. Autonomic modulation was evaluated by heart rate variability. The hydration protocols promoted a more efficient recovery of autonomic modulation, and for the exercise performed, regardless of the hydration administered, the effect on autonomic modulation was similar.

  11. Confined Water in Layered Silicates: The Origin of Anomalous Thermal Expansion Behavior in Calcium-Silicate-Hydrates.

    Science.gov (United States)

    Krishnan, N M Anoop; Wang, Bu; Falzone, Gabriel; Le Pape, Yann; Neithalath, Narayanan; Pilon, Laurent; Bauchy, Mathieu; Sant, Gaurav

    2016-12-28

    Water, under conditions of nanoscale confinement, exhibits anomalous dynamics, and enhanced thermal deformations, which may be further enhanced when such water is in contact with hydrophilic surfaces. Such heightened thermal deformations of water could control the volume stability of hydrated materials containing nanoconfined structural water. Understanding and predicting the thermal deformation coefficient (TDC, often referred to as the CTE, coefficient of thermal expansion), which represents volume changes induced in materials under conditions of changing temperature, is of critical importance for hydrated solids including: hydrogels, biological tissues, and calcium silicate hydrates, as changes in their volume can result in stress development, and cracking. By pioneering atomistic simulations, we examine the physical origin of thermal expansion in calcium-silicate-hydrates (C-S-H), the binding agent in concrete that is formed by the reaction of cement with water. We report that the TDC of C-S-H shows a sudden increase when the CaO/SiO2 (molar ratio; abbreviated as Ca/Si) exceeds 1.5. This anomalous behavior arises from a notable increase in the confinement of water contained in the C-S-H's nanostructure. We identify that confinement is dictated by the topology of the C-S-H's atomic network. Taken together, the results suggest that thermal deformations of hydrated silicates can be altered by inducing compositional changes, which in turn alter the atomic topology and the resultant volume stability of the solids.

  12. Acid-base balance and hydration status following consumption of mineral-based alkaline bottled water

    Directory of Open Access Journals (Sweden)

    Heil Daniel P

    2010-09-01

    Full Text Available Abstract Background The present study sought to determine whether the consumption of a mineral-rich alkalizing (AK bottled water could improve both acid-base balance and hydration status in young healthy adults under free-living conditions. The AK water contains a naturally high mineral content along with Alka-PlexLiquid™, a dissolved supplement that increases the mineral content and gives the water an alkalizing pH of 10.0. Methods Thirty-eight subjects were matched by gender and self-reported physical activity (SRPA, hrs/week and then split into Control (12 women, 7 men; Mean +/- SD: 23 +/- 2 yrs; 7.2 +/- 3.6 hrs/week SRPA and Experimental (13 women, 6 men; 22 +/- 2 yrs; 6.4 +/- 4.0 hrs/week SRPA groups. The Control group consumed non-mineralized placebo bottled water over a 4-week period while the Experimental group consumed the placebo water during the 1st and 4th weeks and the AK water during the middle 2-week treatment period. Fingertip blood and 24-hour urine samples were collected three times each week for subsequent measures of blood and urine osmolality and pH, as well as total urine volume. Dependent variables were analyzed using multivariate repeated measures ANOVA with post-hoc focused on evaluating changes over time within Control and Experimental groups (alpha = 0.05. Results There were no significant changes in any of the dependent variables for the Control group. The Experimental group, however, showed significant increases in both the blood and urine pH (6.23 to 7.07 and 7.52 to 7.69, respectively, a decreased blood and increased urine osmolality, and a decreased urine output (2.51 to 2.05 L/day, all during the second week of the treatment period (P Conclusions Consumption of AK water was associated with improved acid-base balance (i.e., an alkalization of the blood and urine and hydration status when consumed under free-living conditions. In contrast, subjects who consumed the placebo bottled water showed no changes over the

  13. Structural and functional properties of hydration and confined water in membrane interfaces.

    Science.gov (United States)

    Disalvo, E A; Lairion, F; Martini, F; Tymczyszyn, E; Frías, M; Almaleck, H; Gordillo, G J

    2008-12-01

    The scope of the present review focuses on the interfacial properties of cell membranes that may establish a link between the membrane and the cytosolic components. We present evidences that the current view of the membrane as a barrier of permeability that contains an aqueous solution of macromolecules may be replaced by one in which the membrane plays a structural and functional role. Although this idea has been previously suggested, the present is the first systematic work that puts into relevance the relation water-membrane in terms of thermodynamic and structural properties of the interphases that cannot be ignored in the understanding of cell function. To pursue this aim, we introduce a new definition of interphase, in which the water is organized in different levels on the surface with different binding energies. Altogether determines the surface free energy necessary for the structural response to changes in the surrounding media. The physical chemical properties of this region are interpreted in terms of hydration water and confined water, which explain the interaction with proteins and could affect the modulation of enzyme activity. Information provided by several methodologies indicates that the organization of the hydration states is not restricted to the membrane plane albeit to a region extending into the cytoplasm, in which polar head groups play a relevant role. In addition, dynamic properties studied by cyclic voltammetry allow one to deduce the energetics of the conformational changes of the lipid head group in relation to the head-head interactions due to the presence of carbonyls and phosphates at the interphase. These groups are, apparently, surrounded by more than one layer of water molecules: a tightly bound shell, that mostly contributes to the dipole potential, and a second one that may be displaced by proteins and osmotic stress. Hydration water around carbonyl and phosphate groups may change by the presence of polyhydroxylated compounds

  14. Hydration level is an internal variable for computing motivation to obtain water rewards in monkeys.

    Science.gov (United States)

    Minamimoto, Takafumi; Yamada, Hiroshi; Hori, Yukiko; Suhara, Tetsuya

    2012-05-01

    In the process of motivation to engage in a behavior, valuation of the expected outcome is comprised of not only external variables (i.e., incentives) but also internal variables (i.e., drive). However, the exact neural mechanism that integrates these variables for the computation of motivational value remains unclear. Besides, the signal of physiological needs, which serves as the primary internal variable for this computation, remains to be identified. Concerning fluid rewards, the osmolality level, one of the physiological indices for the level of thirst, may be an internal variable for valuation, since an increase in the osmolality level induces drinking behavior. Here, to examine the relationship between osmolality and the motivational value of a water reward, we repeatedly measured the blood osmolality level, while 2 monkeys continuously performed an instrumental task until they spontaneously stopped. We found that, as the total amount of water earned increased, the osmolality level progressively decreased (i.e., the hydration level increased) in an individual-dependent manner. There was a significant negative correlation between the error rate of the task (the proportion of trials with low motivation) and the osmolality level. We also found that the increase in the error rate with reward accumulation can be well explained by a formula describing the changes in the osmolality level. These results provide a biologically supported computational formula for the motivational value of a water reward that depends on the hydration level, enabling us to identify the neural mechanism that integrates internal and external variables.

  15. Effects of Water Provision and Hydration on Cognitive Function among Primary-School Pupils in Zambia: A Randomized Trial.

    Directory of Open Access Journals (Sweden)

    Victoria Trinies

    Full Text Available There is a well-established link between hydration and improved cognitive performance among adults, with evidence of similar findings among children. No trials have investigated the impact of water provision on cognitive performance among schoolchildren in hot and arid low-resource settings. We conducted a randomized-controlled trial in five schools with limited water access in Chipata district in Eastern province, Zambia, to assess the efficacy of water provision on cognition. Pupils in grades 3-6 were randomly assigned to either receive a bottle of drinking water that they could refill throughout the day (water group, n = 149 or only have access to drinking water that was normally available at the school (control group, n = 143. Hydration was assessed in the morning before provision of water and in the afternoon through urine specific gravity (Usg measured with a portable refractometer. In the afternoon we administered six cognitive tests to assess short-term memory, concentration, visual attention, and visual motor skills. Morning prevalence of dehydration, defined as Usg≥1.020, was 42%. Afternoon dehydration increased to 67% among the control arm and dropped to 10% among the intervention arm. We did not find that provision of water or hydration impacted cognitive test scores, although there were suggestive relationships between both water provision and hydration and increased scores on tests measuring visual attention. We identified key improvements to the study design that are warranted to further investigate this relationship.ClinicalTrials.gov NCT01924546.

  16. Dynamical Coupling of Intrinsically Disordered Proteins and Their Hydration Water: Comparison with Folded Soluble and Membrane Proteins

    Science.gov (United States)

    Gallat, F.-X.; Laganowsky, A.; Wood, K.; Gabel, F.; van Eijck, L.; Wuttke, J.; Moulin, M.; Härtlein, M.; Eisenberg, D.; Colletier, J.-P.; Zaccai, G.; Weik, M.

    2012-01-01

    Hydration water is vital for various macromolecular biological activities, such as specific ligand recognition, enzyme activity, response to receptor binding, and energy transduction. Without hydration water, proteins would not fold correctly and would lack the conformational flexibility that animates their three-dimensional structures. Motions in globular, soluble proteins are thought to be governed to a certain extent by hydration-water dynamics, yet it is not known whether this relationship holds true for other protein classes in general and whether, in turn, the structural nature of a protein also influences water motions. Here, we provide insight into the coupling between hydration-water dynamics and atomic motions in intrinsically disordered proteins (IDP), a largely unexplored class of proteins that, in contrast to folded proteins, lack a well-defined three-dimensional structure. We investigated the human IDP tau, which is involved in the pathogenic processes accompanying Alzheimer disease. Combining neutron scattering and protein perdeuteration, we found similar atomic mean-square displacements over a large temperature range for the tau protein and its hydration water, indicating intimate coupling between them. This is in contrast to the behavior of folded proteins of similar molecular weight, such as the globular, soluble maltose-binding protein and the membrane protein bacteriorhodopsin, which display moderate to weak coupling, respectively. The extracted mean square displacements also reveal a greater motional flexibility of IDP compared with globular, folded proteins and more restricted water motions on the IDP surface. The results provide evidence that protein and hydration-water motions mutually affect and shape each other, and that there is a gradient of coupling across different protein classes that may play a functional role in macromolecular activity in a cellular context. PMID:22828339

  17. Structural Interpretation of the Large Slowdown of Water Dynamics at Stacked Phospholipid Membranes for Decreasing Hydration Level: All-Atom Molecular Dynamics

    Directory of Open Access Journals (Sweden)

    Carles Calero

    2016-04-01

    Full Text Available Hydration water determines the stability and function of phospholipid membranes as well as the interaction of membranes with other molecules. Experiments and simulations have shown that water dynamics slows down dramatically as the hydration decreases, suggesting that the interfacial water that dominates the average dynamics at low hydration is slower than water away from the membrane. Here, based on all-atom molecular dynamics simulations, we provide an interpretation of the slowdown of interfacial water in terms of the structure and dynamics of water–water and water–lipid hydrogen bonds (HBs. We calculate the rotational and translational slowdown of the dynamics of water confined in stacked phospholipid membranes at different levels of hydration, from completely hydrated to poorly hydrated membranes. For all hydrations, we analyze the distribution of HBs and find that water–lipids HBs last longer than water–water HBs and that at low hydration most of the water is in the interior of the membrane. We also show that water–water HBs become more persistent as the hydration is lowered. We attribute this effect (i to HBs between water molecules that form, in turn, persistent HBs with lipids; (ii to the hindering of the H-bonding switching between water molecules due to the lower water density at the interface; and (iii to the higher probability of water–lipid HBs as the hydration decreases. Our interpretation of the large dynamic slowdown in water under dehydration is potentially relevant in understanding membrane biophysics at different hydration levels.

  18. Distinguishing dynamical features of water inside protein hydration layer: Distribution reveals what is hidden behind the average

    Science.gov (United States)

    Mukherjee, Saumyak; Mondal, Sayantan; Bagchi, Biman

    2017-07-01

    Since the pioneering works of Pethig, Grant, and Wüthrich on a protein hydration layer, many studies have been devoted to find out if there are any "general and universal" characteristic features that can distinguish water molecules inside the protein hydration layer from bulk. Given that the surface itself varies from protein to protein, and that each surface facing the water is heterogeneous, search for universal features has been elusive. Here, we perform an atomistic molecular dynamics simulation in order to propose and demonstrate that such defining characteristics can emerge if we look not at average properties but the distribution of relaxation times. We present results of calculations of distributions of residence times and rotational relaxation times for four different protein-water systems and compare them with the same quantities in the bulk. The distributions in the hydration layer are unusually broad and log-normal in nature due to the simultaneous presence of peptide backbones that form weak hydrogen bonds, hydrophobic amino acid side chains that form no hydrogen bond, and charged polar groups that form a strong hydrogen bond with the surrounding water molecules. The broad distribution is responsible for the non-exponential dielectric response and also agrees with large specific heat of the hydration water. Our calculations reveal that while the average time constant is just about 2-3 times larger than that of bulk water, it provides a poor representation of the real behaviour. In particular, the average leads to the erroneous conclusion that water in the hydration layer is bulk-like. However, the observed and calculated lower value of static dielectric constant of hydration layer remained difficult to reconcile with the broad distribution observed in dynamical properties. We offer a plausible explanation of these unique properties.

  19. Evaluation of electroosmotic drag coefficient of water in hydrated sodium perfluorosulfonate electrolyte polymer.

    Science.gov (United States)

    Yan, Liuming; Shao, Changle; Ji, Xiaobo

    2009-07-15

    The electroosmotic drag coefficient of water molecules in hydrated sodium perfluorosulfonate electrolyte polymer is evaluated on the basis of the velocity distribution functions of the sodium cations and water molecules with an electric field applied using molecular dynamics simulations. The simulation results indicate that both velocity distribution functions of water molecules and of sodium cations agree well with the classic Maxwellian velocity distribution functions when there is no electric field applied. If an electric field is applied, the distribution functions of velocity component in directions perpendicular to the applied electric field still agree with the Maxwellian velocity distribution functions but with different temperature parameters. In the direction of the applied electric field, the electric drag causes the velocity distribution function to deviate from the Maxwellian velocity distribution function; however, to obey the peak shifted Maxwellian distribution function. The peak shifting velocities coincide with the average transport velocities induced by the electric field, and could be applied to the evaluation of the electroosmotic drag coefficient of water. By evaluation of the transport velocities of water molecules in the first coordination shells of sodium cations, sulfonate anion groups, and in the bulk, it is clearly shown that the water molecules in the first coordination shell of sodium cations are the major contribution to the electroosmotic drag and momentum transfer from water molecules within the first coordination shell to the other water molecules also contributes to the electroosmotic drag.

  20. Effects of commercially formulated water on the hydration status of dehydrated collegiate wrestlers.

    Science.gov (United States)

    Valiente, J Scott; Utter, Alan C; Quindry, John C; Nieman, David C

    2009-11-01

    The objective of this study was to evaluate the effects of three different drinks (commercially formulated water, bottled water, and a carbohydrate-electrolyte beverage) on blood and urinary markers of hydration after acute dehydration in collegiate wrestlers. Twenty-one athletes were recruited to perform a randomized, crossover study comparing the effectiveness of commercially formulated water, carbohydrate-electrolyte (6% or 60 g L(-1)), or regular bottled water (placebo) in promoting rehydration after a 3% reduction in body mass. Urine specific gravity (U(sg)), urine osmolarity (U(osm)), plasma osmolarity (P(osm)), and plasma volume were measured pre- and post-dehydration and at 1 hour after rehydration. Statistical analyses used a 3 (conditions) x 3 (times) repeated measures analysis of variance. Significant (p < 0.01) interactions were found for P(osm), U(osm), and U(sg). P(osm) returned to baseline levels and U(osm) remained in a lower balance after 1 hour of rehydration in the trials of the commercially formulated water and regular bottled water. No significant interactions were found for plasma volume shift. The findings of this study demonstrate that the commercially formulated water was no more effective in promoting rehydration than either a carbohydrate-electrolyte solution or plain water in collegiate wrestlers after a 3% reduction in body mass and a rehydration period of 1 hour when consuming 100% of their body weight loss.

  1. Diffusion and spectroscopy of water and lipids in fully hydrated dimyristoylphosphatidylcholine bilayer membranes

    Energy Technology Data Exchange (ETDEWEB)

    Yang, J.; Martí, J., E-mail: jordi.marti@upc.edu [Department of Physics and Nuclear Engineering, Technical University of Catalonia-Barcelona Tech, B4-B5 Northern Campus, Jordi Girona 1-3, 08034 Barcelona, Catalonia (Spain); Calero, C. [Department of Physics and Nuclear Engineering, Technical University of Catalonia-Barcelona Tech, B4-B5 Northern Campus, Jordi Girona 1-3, 08034 Barcelona, Catalonia (Spain); Center for Polymer Studies, Department of Physics, Boston University, 590 Commonwealth Avenue, Boston, Massachusetts 02215 (United States)

    2014-03-14

    Microscopic structure and dynamics of water and lipids in a fully hydrated dimyristoylphosphatidylcholine phospholipid lipid bilayer membrane in the liquid-crystalline phase have been analyzed with all-atom molecular dynamics simulations based on the recently parameterized CHARMM36 force field. The diffusive dynamics of the membrane lipids and of its hydration water, their reorientational motions as well as their corresponding spectral densities, related to the absorption of radiation, have been considered for the first time using the present force field. In addition, structural properties such as density and pressure profiles, a deuterium-order parameter, surface tension, and the extent of water penetration in the membrane have been analyzed. Molecular self-diffusion, reorientational motions, and spectral densities of atomic species reveal a variety of time scales playing a role in membrane dynamics. The mechanisms of lipid motion strongly depend on the time scale considered, from fast ballistic translation at the scale of picoseconds (effective diffusion coefficients of the order of 10{sup −5} cm{sup 2}/s) to diffusive flow of a few lipids forming nanodomains at the scale of hundreds of nanoseconds (diffusion coefficients of the order of 10{sup −8} cm{sup 2}/s). In the intermediate regime of sub-diffusion, collisions with nearest neighbors prevent the lipids to achieve full diffusion. Lipid reorientations along selected directions agree well with reported nuclear magnetic resonance data and indicate two different time scales, one about 1 ns and a second one in the range of 2–8 ns. We associated the two time scales of reorientational motions with angular distributions of selected vectors. Calculated spectral densities corresponding to lipid and water reveal an overall good qualitative agreement with Fourier transform infrared spectroscopy experiments. Our simulations indicate a blue-shift of the low frequency spectral bands of hydration water as a result of

  2. Sequentially sampled gas hydrate water, coupled with pore water and bottom water isotopic and ionic signatures at the Kukuy mud volcano, Lake Baikal: ambiguous deep-rooted source of hydrate-forming water

    Science.gov (United States)

    Minami, Hirotsugu; Hachikubo, Akihiro; Sakagami, Hirotoshi; Yamashita, Satoshi; Soramoto, Yusuke; Kotake, Tsuyoshi; Takahashi, Nobuo; Shoji, Hitoshi; Pogodaeva, Tatyana; Khlystov, Oleg; Khabuev, Andrey; Naudts, Lieven; De Batist, Marc

    2014-06-01

    The isotopic and ionic composition of pure gas hydrate (GH) water was examined for GHs recovered in three gravity cores (165-193 cm length) from the Kukuy K-9 mud volcano (MV) in Lake Baikal. A massive GH sample from core St6GC4 (143-165 cm core depth interval) was dissociated progressively over 6 h in a closed glass chamber, and 11 sequentially collected fractions of dissociated GH water analyzed. Their hydrogen and oxygen isotopic compositions, and the concentrations of Cl- and HCO3 - remained essentially constant over time, except that the fraction collected during the first 50 minutes deviated partly from this pattern. Fraction #1 had a substantially higher Cl- concentration, similar to that of pore water sampled immediately above (135-142 cm core depth) the main GH-bearing interval in that core. Like the subsequent fractions, however, the HCO3 - concentration was markedly lower than that of pore water. For the GH water fractions #2 to #11, an essentially constant HCO3 -/Cl- ratio of 305 differed markedly from downcore pore water HCO3 -/Cl- ratios of 63-99. Evidently, contamination of the extracted GH water by ambient pore water probably adhered to the massive GH sample was satisfactorily restricted to the initial phase of GH dissociation. The hydrogen and oxygen isotopic composition of hydrate-forming water was estimated using the measured isotopic composition of extracted GH water combined with known isotopic fractionation factors between GH and GH-forming water. Estimated δD of -126 to -133‰ and δ18O of -15.7 to -16.7‰ differed partly from the corresponding signatures of ambient pore water (δD of -123‰, δ18O of -15.6‰) and of lake bottom water (δD of -121‰, δ18O of -15.8‰) at the St6GC4 coring site, suggesting that the GH was not formed from those waters. Observations of breccias in that core point to a possible deep-rooted water source, consistent with published thermal measurements for the neighboring Kukuy K-2 MV. By contrast, the pore

  3. Experimental Investigation of Gas Hydrate Production at Injection of Liquid Nitrogen into Water with Bubbles of Freon 134A

    Directory of Open Access Journals (Sweden)

    Meleshkin Anton V.

    2016-01-01

    Full Text Available The hydrodynamic processes during the injection of the cryogenic liquid into the volume of water with bubbles of gas freon 134a are studding experimentally. A processes during the explosive boiling of liquid nitrogen in the volume of water are registered. Video recording of identified gas hydrate flakes formed during this process is carried out by high speed camera. These results may be useful for the study of the new method of producing gas hydrates, based on the shock-wave method.

  4. A Theoretical Study of the Hydration of Methane, from the Aqueous Solution to the sI Hydrate-Liquid Water-Gas Coexistence

    Directory of Open Access Journals (Sweden)

    Daniel Porfirio Luis

    2016-05-01

    Full Text Available Monte Carlo and molecular dynamics simulations were done with three recent water models TIP4P/2005 (Transferable Intermolecular Potential with 4 Points/2005, TIP4P/Ice (Transferable Intermolecular Potential with 4 Points/ Ice and TIP4Q (Transferable Intermolecular Potential with 4 charges combined with two models for methane: an all-atom one OPLS-AA (Optimal Parametrization for the Liquid State and a united-atom one (UA; a correction for the C–O interaction was applied to the latter and used in a third set of simulations. The models were validated by comparison to experimental values of the free energy of hydration at 280, 300, 330 and 370 K, all under a pressure of 1 bar, and to the experimental radial distribution functions at 277, 283 and 291 K, under a pressure of 145 bar. Regardless of the combination rules used for σC,O, good agreement was found, except when the correction to the UA model was applied. Thus, further simulations of the sI hydrate were performed with the united-atom model to compare the thermal expansivity to the experiment. A final set of simulations was done with the UA methane model and the three water models, to study the sI hydrate-liquid water-gas coexistence at 80, 230 and 400 bar. The melting temperatures were compared to the experimental values. The results show the need to perform simulations with various different models to attain a reliable and robust molecular image of the systems of interest.

  5. A Theoretical Study of the Hydration of Methane, from the Aqueous Solution to the sI Hydrate-Liquid Water-Gas Coexistence

    Science.gov (United States)

    Luis, Daniel Porfirio; García-González, Alcione; Saint-Martin, Humberto

    2016-01-01

    Monte Carlo and molecular dynamics simulations were done with three recent water models TIP4P/2005 (Transferable Intermolecular Potential with 4 Points/2005), TIP4P/Ice (Transferable Intermolecular Potential with 4 Points/ Ice) and TIP4Q (Transferable Intermolecular Potential with 4 charges) combined with two models for methane: an all-atom one OPLS-AA (Optimal Parametrization for the Liquid State) and a united-atom one (UA); a correction for the C–O interaction was applied to the latter and used in a third set of simulations. The models were validated by comparison to experimental values of the free energy of hydration at 280, 300, 330 and 370 K, all under a pressure of 1 bar, and to the experimental radial distribution functions at 277, 283 and 291 K, under a pressure of 145 bar. Regardless of the combination rules used for σC,O, good agreement was found, except when the correction to the UA model was applied. Thus, further simulations of the sI hydrate were performed with the united-atom model to compare the thermal expansivity to the experiment. A final set of simulations was done with the UA methane model and the three water models, to study the sI hydrate-liquid water-gas coexistence at 80, 230 and 400 bar. The melting temperatures were compared to the experimental values. The results show the need to perform simulations with various different models to attain a reliable and robust molecular image of the systems of interest. PMID:27240339

  6. Properties of Hydrated Alkali Metals Aimed at the Ion Channel Selectivity

    Institute of Scientific and Technical Information of China (English)

    AN Hai-Long; LIU Yu-Zhi; ZHANG Su-Hua; ZHAN Yong; ZHANG Hai-Lin

    2008-01-01

    The hydration structure properties of different alkali metal ions with eight water molecules and potassium ions with different numbers of water molecules are studied using the mixed density functional theory, B3LYP, with 6-311G basis set. The hydration structures are obtained from structure optimization and the optimum numbers of water molecules in the innermost hydration shell for the alkali metal ions are found. Some useful information about the ion channel selectivity is presented.

  7. 13C MAS NMR studies of the effects of hydration on the cell walls of potatoes and Chinese water chestnuts.

    Science.gov (United States)

    Tang, H; Belton, P S; Ng, A; Ryden, P

    1999-02-01

    13C NMR with magic angle spinning (MAS) has been employed to investigate the cell walls of potatoes and Chinese water chestnuts over a range of hydration levels. Both single-pulse excitation (SPEMAS) and cross-polarization (CPMAS) experiments were carried out. Hydration led to a substantial increase in signal intensities of galactan and galacturonan in the SPEMAS spectra and a decrease in line width, implying mobilization in the backbone and side chains of pectin. In CPMAS spectra of both samples, noncellulose components showed signal loss as hydration increased. However, the signals of some galacturonan in the 3(1) helix configuration remained in the spectra even when the water content was as high as 110%. Cellulose was unaffected. It is concluded that the pectic polysaccharides experience a distribution of molecular conformations and mobility, whereas cellulose remained as typical rigid solid.

  8. Hydrogen bond network in the hydration layer of the water confined in nanotubes increasing the dielectric constant parallel along the nanotube axis

    Science.gov (United States)

    Qi, Wenpeng; Zhao, Hongwei

    2015-09-01

    The water confined in nanotubes has been extensively studied, because of the potential usages in drug delivery and desalination. The radial distribution of the dielectric constant parallel along the nanotube axis was obtained by molecular dynamics simulations in a carbon nanotube and a nanotube with a very small van der Waals potential. The confined water was divided into two parts, the middle part water and the hydration water. In both cases, the hydrogen bond orientation of the middle water is isotropic, while the hydrogen bonds in hydration layers are apt to parallel along the nanotube axis. Therefore, the hydration water has higher dipole correlations increasing the dielectric constant along the nanotube axis.

  9. Hydrogen bond network in the hydration layer of the water confined in nanotubes increasing the dielectric constant parallel along the nanotube axis.

    Science.gov (United States)

    Qi, Wenpeng; Zhao, Hongwei

    2015-09-21

    The water confined in nanotubes has been extensively studied, because of the potential usages in drug delivery and desalination. The radial distribution of the dielectric constant parallel along the nanotube axis was obtained by molecular dynamics simulations in a carbon nanotube and a nanotube with a very small van der Waals potential. The confined water was divided into two parts, the middle part water and the hydration water. In both cases, the hydrogen bond orientation of the middle water is isotropic, while the hydrogen bonds in hydration layers are apt to parallel along the nanotube axis. Therefore, the hydration water has higher dipole correlations increasing the dielectric constant along the nanotube axis.

  10. Evaluation of Hydrate Inhibition Performance of Water-soluble Polymers using Torque Measurement and Differential Scanning Calorimeter

    Energy Technology Data Exchange (ETDEWEB)

    Shin, Kyuchul; Park, Juwoon; Kim, Jakyung; Kim, Hyunho; Seo, Yutaek [KAIST, Daejeon (Korea, Republic of); Lee, Yohan; Seo, Yongwon [UNIST, Ulsan (Korea, Republic of)

    2014-12-15

    In this work, hydrate inhibition performance of water-soluble polymers including pyrrolidone, caprolactam, acrylamide types were evaluated using torque measurement and high pressure differential scanning calorimeter (HP µ-DSC). The obtained experimental results suggest that the studied polymers represent the kinetic hydrate inhibition (KHI) performance. 0.5 wt% polyvinylcaprolactam (PVCap) solution shows the hydrate onset time of 34.4 min and subcooling temperature of 15.9 K, which is better KHI performance than that of pure water - hydrate onset time of 12.3 min and subcooling temperature of 6.0 K. 0.5 wt% polyvinylpyrrolidone (PVP) solution shows the hydrate onset time of 27.6 min and the subcooling temperature of 13.2 K while polyacrylamide-co-acrylic acid partial sodium salt (PAM-co-AA) solution shows less KHI performance than PVP solution at both 0.5 and 5.0 wt%. However, PAM-co-AA solution shows slow growth rate and low hydrate amount than PVCap. In addition to hydrate onset and growth condition, torque change with time was investigated as one of KHI evaluation methods. 0.5 wt% PVCap solution shows the lowest average torque of 6.4 N cm and 0.5 wt% PAM-co-AA solution shows the average torque of 7.2 N cm. For 0.5 wt% PVP solution, it increases 11.5 N cm and 5.0 wt% PAM-co-AA solution shows the maximum average torque of 13.4 N cm, which is similar to the average torque of pure water, 15.2 N cm. Judging from the experimental results obtained by both an autoclave and a HP µ-DSC, the PVCap solution shows the best performance among the KHIs in terms of delaying hydrate nucleation. From these results, it can be concluded that the torque change with time is useful to identify the flow ability of tested solution, and the further research on the inhibition of hydrate formation can be approached in various aspects using a HP µ-DSC.

  11. Multiple-pressure-tapped core holder combined with X-ray computed tomography scanning for gas-water permeability measurements of methane-hydrate-bearing sediments

    Science.gov (United States)

    Konno, Yoshihiro; Jin, Yusuke; Uchiumi, Takashi; Nagao, Jiro

    2013-06-01

    We present a novel setup for measuring the effective gas-water permeability of methane-hydrate-bearing sediments. We developed a core holder with multiple pressure taps for measuring the pressure gradient of the gas and water phases. The gas-water flooding process was simultaneously detected using an X-ray computed tomography scanner. We successfully measured the effective gas-water permeability of an artificial sandy core with methane hydrate during the gas-water flooding test.

  12. Hydration of gelatin molecules in glycerol-water solvent and phase diagram of gelatin organogels.

    Science.gov (United States)

    Sanwlani, Shilpa; Kumar, Pradip; Bohidar, H B

    2011-06-09

    We present a systematic investigation of hydration and gelation of the polypeptide gelatin in water-glycerol mixed solvent (glycerol solutions). Raman spectroscopy results indicated enhancement in water structure in glycerol solutions and the depletion of glycerol density close to hydration sheath of the protein molecule. Gelation concentration (c(g)) was observed to decrease from 1.92 to 1.15% (w/v) while the gelation temperature (T(g)) was observed to increase from 31.4 to 40.7 °C with increase in glycerol concentration. Data on hand established the formation of organogels having interconnected networks, and the universal gelation mechanism could be described through an anomalous percolation model. The viscosity of sol diverged as η ∼ (1 - c(g)/c)(-k) as c(g) was approached from below (c c(g)). It is important to note that values determined for critical exponents k and t were universal; that is, they did not depend on the microscopic details. The measured values were k = 0.38 ± 0.10 and t = 0.92 ± 0.17 whereas the percolation model predicts k = 0.7-1.3 and t = 1.9. Isothermal frequency sweep studies showed power-law dependence of gel storage modulus (G') and loss modulus (G'') on oscillation frequency ω given as G'(ω) ∼ ω(n') and G''(ω) ∼ ω(n''), and consistent with percolation model prediction it was found that n' ≈ n'' ≈ δ ≈ 0.73 close to gelation concentration. We propose a unique 3D phase diagram for the gelatin organogels. Circular dichroism data revealed that the gelatin molecules retained their biological activity in these solvents. Thus, it is shown that the thermomechanical properties of these organogels could be systematically tuned and customized as per application requirement.

  13. Experimental Study on Hydrate Induction Time of Gas-Saturated Water-in-Oil Emulsion using a High-Pressure Flow Loop

    Directory of Open Access Journals (Sweden)

    Lv X.F.

    2015-11-01

    Full Text Available Hydrate is one of the critical precipitates which have to be controlled for subsea flow assurance. The induction time of hydrate is therefore a significant parameter. However, there have been few studies on the induction time of the natural gas hydrate formation in a flow loop system. Consequently, a series of experiments were firstly performed, including water, natural gas and Diesel oil, on the hydrate induction time under various conditions such as the supercooling and supersaturation degree, water cut, anti-agglomerant dosage, etc. The experiments were conducted in a high-pressure hydrate flow loop newly constructed in the China University of Petroleum (Beijing, and dedicated to flow assurance studies. Then, based on previous research, this study puts forward a method for induction time, which is characterized by clear definition, convenient measurement and good generality. Furthermore, we investigated the influences of the experimental parameters and analyzed the experimental phenomena for the hydrate induction time in a flowing system.

  14. The Effects of Hot Water Treatment, Hydration and Order of Nursery Operations on Cuttings of Vitis vinifera Cultivars

    Directory of Open Access Journals (Sweden)

    H. Waite

    2005-08-01

    Full Text Available Hot water treatment (HWT is an effective control for endogenous pathogens, including Phaeomoniella chlamydospora, in grapevine propagating material. However sporadic unexplained failures of HWT material do occur. In order to determine the most reliable HWT protocols the effects of HWT at 50°C for 30 min., order of HWT and storage (store/HWT and HWT/store, and 3 hydration times (0, 4 and 6 h on root and shoot development and final condition in dormant cuttings of Cabernet Sauvignon and Chardonnay were evaluated. After incubation callus, root and shoot development were assessed. Cuttings were potted into cardboard plant bands, grown to marketable size in a protected environment, and assessed as “A” grade, “B” grade or dead. Callus development in Chardonnay was affected by an interaction between HWT protocols and hydration times. Callus was least developed in cuttings hydrated for 15 h and stored before HWT. Callus development in all other treatments was greater (P<0.05 regardless of HWT or hydration. By contrast, callus development in Cabernet Sauvignon was greater (P<0.05 in HWT than in non-HWT cuttings regardless of the duration of hydration or the order of operations. Root development in Chardonnay was furthest advanced in cuttings hydrated for 15 h. (regardless of HWT and in HWT cuttings not hydrated. HWT was the only factor that affected root development in Cabernet Sauvignon. Root development was greatest in non-HWT cuttings. There were no differences between any of the treatments in either variety at final assessment. On this evidence nurseries could apply any of the above protocols successfully. However the benign conditions of the protected environment may have enabled the cuttings to recover from the stresses imposed by the various treatments. Had the cuttings been grown in a field nursery there might have been differences between treatments at final assessment.

  15. Solid and liquid phase equilibria and solid-hydrate formation in binary mixtures of water with amines

    Institute of Scientific and Technical Information of China (English)

    车冠全; 彭文烈; 黄良恩; 古喜兰; 车飙

    1997-01-01

    Solid and liquid phase diagrams have been constructed for {water+triethylamine,or+N,N-dimethylformamide(DMF) or+N,N-dimethlacetamide (DMA)} Solid-hydrates form with the empirical formulae N(C2H5)3 3H2O,DMF 3H2O,DMF 2H2O,DMA 3H2O and (DMA)2 3H2O.All are congruently melting except the first which melts incongruently.The solid-hydrate formation is attributed to hydrogen bond.The results are compared with the references

  16. Multicomponent seismic methods for characterizing gas hydrate occurrences and systems in deep-water Gulf of Mexico

    Science.gov (United States)

    Haines, Seth S.; Lee, Myung W.; Collett, Timothy S.; Hardage, Bob A.

    2011-01-01

    In-situ characterization and quantification of natural gas hydrate occurrences remain critical research directions, whether for energy resource, drilling hazard, or climate-related studies. Marine multicomponent seismic data provide the full seismic wavefield including partial redundancy, and provide a promising set of approaches for gas hydrate characterization. Numerous authors have demonstrated the possibilities of multicomponent data at study sites around the world. We expand on this work by investigating the utility of very densely spaced (10’s of meters) multicomponent receivers (ocean-bottom cables, OBC, or ocean-bottom seismometers, OBS) for gas hydrate studies in the Gulf of Mexico and elsewhere. Advanced processing techniques provide high-resolution compressional-wave (PP) and converted shearwave (PS) reflection images of shallow stratigraphy, as well as P-wave and S-wave velocity estimates at each receiver position. Reflection impedance estimates can help constrain velocity and density, and thus gas hydrate saturation. Further constraint on velocity can be determined through identification of the critical angle and associated phase reversal in both PP and PS wideangle data. We demonstrate these concepts with examples from OBC data from the northeast Green Canyon area and numerically simulated OBS data that are based on properties of known gas hydrate occurrences in the southeast (deeper water) Green Canyon area. These multicomponent data capabilities can provide a wealth of characterization and quantification information that is difficult to obtain with other geophysical methods.

  17. CHARACTERIZING NATURAL GAS HYDRATES IN THE DEEP WATER GULF OF MEXICO: APPLICATIONS FOR SAFE EXPLORATION AND PRODUCTION ACTIVITIES

    Energy Technology Data Exchange (ETDEWEB)

    Steve Holditch; Emrys Jones

    2003-01-01

    In 2000, Chevron began a project to learn how to characterize the natural gas hydrate deposits in the deepwater portions of the Gulf of Mexico. A Joint Industry Participation (JIP) group was formed in 2001, and a project partially funded by the U.S. Department of Energy (DOE) began in October 2001. The primary objective of this project is to develop technology and data to assist in the characterization of naturally occurring gas hydrates in the deep water Gulf of Mexico (GOM). These naturally occurring gas hydrates can cause problems relating to drilling and production of oil and gas, as well as building and operating pipelines. Other objectives of this project are to better understand how natural gas hydrates can affect seafloor stability, to gather data that can be used to study climate change, and to determine how the results of this project can be used to assess if and how gas hydrates act as a trapping mechanism for shallow oil or gas reservoirs. During the first six months of operation, the primary activities of the JIP were to conduct and plan Workshops, which were as follows: (1) Data Collection Workshop--March 2002 (2) Drilling, Coring and Core Analyses Workshop--May 2002 (3) Modeling, Measurement and Sensors Workshop--May 2002.

  18. CHARACTERIZING NATURAL GAS HYDRATES IN THE DEEP WATER GULF OF MEXICO: APPLICATIONS FOR SAFE EXPLORATION AND PRODUCTION ACTIVITIES

    Energy Technology Data Exchange (ETDEWEB)

    Steve Holditch; Emrys Jones

    2003-01-01

    In 2000, Chevron began a project to learn how to characterize the natural gas hydrate deposits in the deepwater portions of the Gulf of Mexico. A Joint Industry Participation (JIP) group was formed in 2001, and a project partially funded by the U.S. Department of Energy (DOE) began in October 2001. The primary objective of this project is to develop technology and data to assist in the characterization of naturally occurring gas hydrates in the deep water Gulf of Mexico (GOM). These naturally occurring gas hydrates can cause problems relating to drilling and production of oil and gas, as well as building and operating pipelines. Other objectives of this project are to better understand how natural gas hydrates can affect seafloor stability, to gather data that can be used to study climate change, and to determine how the results of this project can be used to assess if and how gas hydrates act as a trapping mechanism for shallow oil or gas reservoirs. During April-September 2002, the JIP concentrated on: Reviewing the tasks and subtasks on the basis of the information generated during the three workshops held in March and May 2002; Writing Requests for Proposals (RFPs) and Cost, Time and Resource (CTRs) estimates to accomplish the tasks and subtasks; Reviewing proposals sent in by prospective contractors; Selecting four contractors; Selecting six sites for detailed review; and Talking to drill ship owners and operators about potential work with the JIP.

  19. HYDRATION AND PHASE SEPARATION OF TEMPERATURE-SENSITIVE WATER-SOLUBLE POLYMERS

    Institute of Scientific and Technical Information of China (English)

    Fumihiko Tanaka; Tsuyoshi Koga; Hiroyuki Kojima; Francoise M. Winnik

    2011-01-01

    Collapse of a poly(N-isopropylacrylamide) (PNIPAM) chain upon heating and phase diagrams of aqueous PNIPAM solutions with very flat LCST phase separation line are theoretically studied on the basis of cooperative dehydration (simultaneous dissociation of bound water molecules in a group of correlated sequence), and compared with the experimental observation of temperature-induced coil-globule transition by light scattering methods. The transition becomes sharper with the cooperativity parameter σ of hydration. Reentrant coil-globule-coil transition in mixed solvent of water and methanol is also studied from the viewpoint of competitive hydrogen bonds between polymer-water and polymer-methanol. The downward shift of the cloud-point curves (LCST cononsolvency) with the mole fraction of methanol due to the competition is calculated and compared with the experimental data. Aqueous solutions of hydophobically-modified PNIPAM carrying short alkyl chains at both chain ends (telechelic PNIPAM) are theoretically and experimentally studied. The LCST of these solutions is found to shift downward along the sol-gel transition curve as a result of end-chain association (association-induced phase separation), and separate from the coil-globule transition line. Associated structures in the solution, such as flower micelles, mesoglobules and higher fractal assembly, are studied by USANS with theoretical modeling of the scattering function.

  20. Hydration or dehydration: competing effects of upper tropospheric cloud radiation on the TTL water vapor

    Directory of Open Access Journals (Sweden)

    L. Wu

    2012-02-01

    Full Text Available A tropical channel version of the Weather Research and Forecasting (WRF model is used to investigate the radiative impacts of upper tropospheric clouds on water vapor in the tropical tropopause layer (TTL. The WRF simulations of cloud radiative effects and water vapor in the upper troposphere and lower stratosphere show reasonable agreement with observations, including approximate reproduction of the water vapor "tape recorder" signal. By turning on and off the upper tropospheric cloud radiative effect (UTCRE above 200 hPa, we find that the UTCRE induces a warming of 0.76 K and a moistening of 9% in the upper troposphere at 215 hPa. However, the UTCRE cools and dehydrates the TTL, with a cooling of 0.82 K and a dehydration of 16% at 100 hPa. The enhanced vertical ascent due to the UTCRE contributes substantially to mass transport and the dehydration in the TTL. The hydration due to the enhanced vertical transport is counteracted by the dehydration from adiabatic cooling associated with the enhanced vertical motion. The UTCRE also substantially changes the horizontal winds in the TTL, resulting in shifts of the strongest dehydration away from the lowest temperature anomalies in the TTL. The UTCRE increases in-situ cloud formation in the TTL. A seasonal variation is shown in the simulated UTCRE, with stronger impact in the moist phase from June to November than in the dry phase from December to May.

  1. Water flow in carbon-based nanoporous membranes impacted by interactions between hydrated ions and aromatic rings

    Science.gov (United States)

    Liu, Jian; Shi, Guosheng; Fang, Haiping

    2017-02-01

    Carbon-based nanoporous membranes, such as carbon nanotubes (CNTs), graphene/graphene oxide and graphyne, have shown great potential in water desalination and purification, gas and ion separation, biosensors, and lithium-based batteries, etc. A deep understanding of the interaction between hydrated ions in an aqueous solution and the graphitic surface in systems composed of water, ions and a graphitic surface is essential for applications with carbon-based nanoporous membrane platforms. In this review, we describe the recent progress of the interaction between hydrated ions and aromatic ring structures on the carbon-based surface and its applications in the water flow in a carbon nanotube. We expect that these works can be extended to the understanding of water flow in other nanoporous membranes, such as nanoporous graphene, graphyne and stacked sheets of graphene oxide.

  2. Ternary phase behaviour and vesicle formation of a sodium N-lauroylsarcosinate hydrate/1-decanol/water system

    Science.gov (United States)

    Akter, Nasima; Radiman, Shahidan; Mohamed, Faizal; Rahman, Irman Abdul; Reza, Mohammad Imam Hasan

    2011-08-01

    The phase behaviour of a system composed of amino acid-based surfactant (sodium N-lauroylsarcosinate hydrate), 1-decanol and deionised water was investigated for vesicle formation. Changing the molar ratio of the amphiphiles, two important aggregate structures were observed in the aqueous corner of the phase diagram. Two different sizes of microemulsions were found at two amphiphile-water boundaries. A stable single vesicle lobe was found for 1∶2 molar ratios in 92 wt% water with vesicles approximately 100 nm in size and with high zeta potential value. Structural variation arises due to the reduction of electrostatic repulsions among the ionic headgroups of the surfactants and the hydration forces due to adsorbed water onto monolayer's. The balance of these two forces determines the aggregate structures. Analysis was followed by the molecular geometrical structure. These findings may have implications for the development of drug delivery systems for cancer treatments, as well as cosmetic and food formulations.

  3. Quantitative nanoscale water mapping in frozen-hydrated skin by low-loss electron energy-loss spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Yakovlev, Sergey [Department of Chemical Engineering and Materials Science, Stevens Institute of Technology, Hoboken, NJ 07030 (United States); Misra, Manoj; Shi, Shanling [Unilever Research and Development, Trumbull, CT 06611 (United States); Firlar, Emre [Department of Chemical Engineering and Materials Science, Stevens Institute of Technology, Hoboken, NJ 07030 (United States); Libera, Matthew, E-mail: mlibera@stevens.edu [Department of Chemical Engineering and Materials Science, Stevens Institute of Technology, Hoboken, NJ 07030 (United States)

    2010-06-15

    Spatially resolved low-loss electron energy-loss spectroscopy (EELS) is a powerful method to quantitatively determine the water distribution in frozen-hydrated biological materials at high spatial resolution. However, hydrated tissue, particularly its hydrophilic protein-rich component, is very sensitive to electron radiation. This sensitivity has traditionally limited the achievable spatial resolution because of the relatively high noise associated with low-dose data acquisition. We show that the damage caused by high-dose data acquisition affects the accuracy of a multiple-least-squares (MLS) compositional analysis because of inaccuracies in the reference spectrum used to represent the protein. Higher spatial resolution combined with more accurate compositional analysis can be achieved if a reference spectrum is used that better represents the electron-beam-damaged protein component under frozen-hydrated conditions rather than one separately collected from dry protein under low-dose conditions. We thus introduce a method to extract the best-fitting protein reference spectrum from an experimental spectrum dataset. This method can be used when the MLS-fitting problem is sufficiently constrained so that the only unknown is the reference spectrum for the protein component. We apply this approach to map the distribution of water in cryo-sections obtained from frozen-hydrated tissue of porcine skin. The raw spectral data were collected at doses up to 10{sup 5} e/nm{sup 2} despite the fact that observable damage begins at doses as low as 10{sup 3} e/nm{sup 2}. The resulting spatial resolution of 10 nm is 5-10 times better than that in previous studies of frozen-hydrated tissue and is sufficient to resolve sub-cellular water fluctuations as well as the inter-cellular lipid-rich regions of skin where water-mediated processes are believed to play a significant role in the phenotype of keratinocytes in the stratum corneum.

  4. Methane hydrate distribution from prolonged and repeated formation in natural and compacted sand samples: X-ray CT observations

    Energy Technology Data Exchange (ETDEWEB)

    Rees, E.V.L.; Kneafsey, T.J.; Seol, Y.

    2010-07-01

    To study physical properties of methane gas hydrate-bearing sediments, it is necessary to synthesize laboratory samples due to the limited availability of cores from natural deposits. X-ray computed tomography (CT) and other observations have shown gas hydrate to occur in a number of morphologies over a variety of sediment types. To aid in understanding formation and growth patterns of hydrate in sediments, methane hydrate was repeatedly formed in laboratory-packed sand samples and in a natural sediment core from the Mount Elbert Stratigraphic Test Well. CT scanning was performed during hydrate formation and decomposition steps, and periodically while the hydrate samples remained under stable conditions for up to 60 days. The investigation revealed the impact of water saturation on location and morphology of hydrate in both laboratory and natural sediments during repeated hydrate formations. Significant redistribution of hydrate and water in the samples was observed over both the short and long term.

  5. Interaction of Simple Ions with Water: Theoretical Models for the Study of Ion Hydration

    Science.gov (United States)

    Gancheff, Jorge S.; Kremer, Carlos; Ventura, Oscar N.

    2009-01-01

    A computational experiment aimed to create and systematically analyze models of simple cation hydrates is presented. The changes in the structure (bond distances and angles) and the electronic density distribution of the solvent and the thermodynamic parameters of the hydration process are calculated and compared with the experimental data. The…

  6. Beaufort Sea deep-water gas hydrate recovery from a seafloor mound in a region of widespread BSR occurrence

    Science.gov (United States)

    Hart, Patrick E.; Pohlman, John W.; Lorenson, T.D.; Edwards, Brian D.

    2011-01-01

    Gas hydrate was recovered from the Alaskan Beaufort Sea slope north of Camden Bay in August 2010 during a U.S. Coast Guard Cutter Healy expedition (USCG cruise ID HLY1002) under the direction of the U.S. Geological Survey (USGS). Interpretation of multichannel seismic (MCS) reflection data collected in 1977 by the USGS across the Beaufort Sea continental margin identified a regional bottom simulating reflection (BSR), indicating that a large segment of the Beaufort Sea slope is underlain by gas hydrate. During HLY1002, gas hydrate was sampled by serendipity with a piston core targeting a steep-sided bathymetric high originally thought to be an outcrop of older, exposed strata. The feature cored is an approximately 1100m diameter, 130 m high conical mound, referred to here as the Canning Seafloor Mound (CSM), which overlies the crest of a buried anticline in a region of sub-parallel compressional folds beneath the eastern Beaufort outer slope. An MCS profile shows a prominent BSR upslope and downslope from the mound. The absence of a BSR beneath the CSM and occurrence of gas hydrate near the summit indicates that free gas has migrated via deep-rooted thrust faults or by structural focusing up the flanks of the anticline to the seafloor. Gas hydrate recovered from near the CSM summit at a subbottom depth of about 5.7 meters in a water depth of 2538 m was of nodular and vein-filling morphology. Although the hydrate was not preserved, residual gas from the core liner contained >95% methane by volume when corrected for atmospheric contamination. The presence of trace C4+hydrocarbons (inflation of the seafloor caused by formation and accumulation of shallow hydrate lenses is also a likely factor in CSM growth. Pore water analysis shows the sulfate-methane transition to be very shallow (0-1 mbsf), also supporting an active high-flux interpretation. Pore water with chloride concentrations as low as 160 mM suggest fluid migration pathways may extend to the mound from buried

  7. Hydration index--a better parameter for explaining small molecule hydration in inhibition of ice recrystallization.

    Science.gov (United States)

    Tam, Roger Y; Ferreira, Sandra S; Czechura, Pawel; Chaytor, Jennifer L; Ben, Robert N

    2008-12-24

    Several simple mono- and disaccharides have been assessed for their ability to inhibit ice recrystallization. Two carbohydrates were found to be effective recrystallization inhibitors. D-galactose (1) was the best monosaccharide and D-melibiose (5) was the most active disaccharide. The ability of each carbohydrate to inhibit ice growth was correlated to its respective hydration number reported in the literature. A hydration number reflects the number of tightly bound water molecules to the carbohydrate and is a function of carbohydrate stereochemistry. It was discovered that using the absolute hydration number of a carbohydrate does not allow one to accurately predict its ability to inhibit ice recrystallization. Consequently, we have defined a hydration index in which the hydration number is divided by the molar volume of the carbohydrate. This new parameter not only takes into account the number of water molecules tightly bound to a carbohydrate but also the size or volume of a particular solute and ultimately the concentration of hydrated water molecules. The hydration index of both mono- and disaccharides correlates well with experimentally measured RI activity. C-Linked derivatives of the monosaccharides appear to have RI activity comparable to that of their O-linked saccharides but a more thorough investigation is required. The relationship between carbohydrate concentration and RI activity was shown to be noncolligative and a 0.022 M solution of D-galactose (1) and C-linked galactose derivative (10) inhibited recrystallization as well as a 3% DMSO solution. The carbohydrates examined in this study did not possess any thermal hysteresis activity (selective depression of freezing point relative to melting point) or dynamic ice shaping. As such, we propose that they are inhibiting recrystallization at the interface between bulk water and the quasi liquid layer (a semiordered interface between ice and bulk water) by disrupting the preordering of water.

  8. Effect of temperature on the low-frequency vibrational spectrum and relative structuring of hydration water around a single-stranded DNA.

    Science.gov (United States)

    Chakraborty, Kaushik; Bandyopadhyay, Sanjoy

    2015-01-07

    Molecular dynamics simulations of the single-stranded DNA oligomer (5'-CGCGAAT TCGCG-3') in aqueous solution have been carried out at different temperatures between 160 K and 300 K. The effects of temperature on the low-frequency vibrational spectrum and local structural arrangements of water molecules hydrating the DNA strand have been explored in detail. The low-frequency density of states distributions reveal that increasingly trapped transverse water motions play a dominant role in controlling the band corresponding to O⋯O⋯O bending or transverse oscillations of hydration water at supercooled temperatures. In addition, presence of a broad band around 260 (±20) cm(-1) under supercooled conditions indicates transformation from high density liquid-like structuring of hydration water at higher temperatures to that of a low density liquid at lower temperatures. It is found that long-range correlations between the supercooled hydration water molecules arise due to such local structural transition around the DNA oligomer.

  9. Theoretical study on the hydrophobic and hydrophilic hydration on large solutes: The case of phthalocyanines in water.

    Science.gov (United States)

    Martín, Elisa I; Martínez, José M; Sánchez Marcos, Enrique

    2015-07-28

    A theoretical study on the hydration phenomena of three representative Phthalocyanines (Pcs): the metal-free, H2Pc, and the metal-containing, Cu-phthalocyanine, CuPc, and its soluble sulphonated derivative, [CuPc(SO3)4](4-), is presented. Structural and dynamic properties of molecular dynamics trajectories of these Pcs in solution were evaluated. The hydration shells of the Pcs were defined by means of spheroids adapted to the solute shape. Structural analysis of the axial region compared to the peripheral region indicates that there are no significant changes among the different macrocycles, but that of [CuPc(SO3)4](4-), where the polyoxoanion presence induces a typically hydrophilic hydration structure. The analyzed water dynamic properties cover mean residence times, translational and orientational diffusion coefficients, and hydrogen bond network. These properties allow a thorough discussion about the simultaneous existence of hydrophobic and hydrophilic hydration in these macrocycles, and indicate the trend of water structure to well define shells in the environment of hydrophobic solutes. The comparison between the structural and dynamical analysis of the hydration of the amphipathic [CuPc(SO3)4](4-) and the non-soluble Cu-Pc shows a very weak coupling among the hydrophilic and hydrophobic fragments of the macrocycle. Quantitative results are employed to revisit the iceberg model proposed by Frank and Evans, leading to conclude that structure and dynamics support a non-strict interpretation of the iceberg view, although the qualitative trends pointed out by the model are supported.

  10. Hydration, phase separation and nonlinear rheology of temperature-sensitive water-soluble polymers.

    Science.gov (United States)

    Tanaka, Fumihiko; Koga, Tsuyoshi; Kaneda, Isamu; Winnik, Françoise M

    2011-07-20

    The collapse of a poly(N-isopropylacrylamide) (PNIPAM) chain upon heating and the phase diagrams of aqueous PNIPAM solutions with a very flat lower critical solution temperature (LCST) phase separation line are theoretically studied on the basis of cooperative dehydration (simultaneous dissociation of bound water molecules in a group of correlated sequence), and compared with the experimental observation of temperature-induced coil-globule transition by light scattering methods. The transition becomes sharper with the cooperativity parameter σ of hydration. The reentrant coil-globule-coil transition and cononsolvency in a mixed solvent of water and methanol are also studied from the viewpoint of competitive hydrogen bonds between polymer-water and polymer-methanol. The downward shift of the cloud-point curves (LCST cononsolvency) with the mol fraction of methanol due to the competition is calculated and compared with the experimental data. Aqueous solutions of hydrophobically modified PNIPAM carrying short alkyl chains at both chain ends (telechelic PNIPAM) are theoretically and experimentally studied. The LCST of these solutions is found to shift downward along the sol-gel transition curve as a result of end-chain association (association-induced phase separation), and separate from the coil-globule transition line. Associated structures in the solution, such as flower micelles, mesoglobules, and higher fractal assembly, are studied by ultra small-angle neutron scattering with theoretical modeling of the scattering function. Dynamic-mechanical modulus, nonlinear stationary viscosity, and stress build-up in start-up shear flows of the associated networks are studied on the basis of the affine and non-affine transient network theory. The molecular conditions for thickening, strain hardening, and stress overshoot are found in terms of the nonlinear amplitude A of the chain tension and the tension-dissociation coupling constant g.

  11. A novel continuous colour mapping approach for visualization of facial skin hydration and transepidermal water loss for four ethnic groups.

    Science.gov (United States)

    Voegeli, R; Rawlings, A V; Seroul, P; Summers, B

    2015-12-01

    The aim of this exploratory study was to develop a novel colour mapping approach to visualize and interpret the complexity of facial skin hydration and barrier properties of four ethnic groups (Caucasians, Indians, Chinese and Black Africans) living in Pretoria, South Africa. We measured transepidermal water loss (TEWL) and skin capacitance on 30 pre-defined sites on the forehead, cheek, jaw and eye areas of sixteen women (four per ethnic group) and took digital images of their faces. Continuous colour maps were generated by interpolating between each measured value and superimposing the values on the digital images. The complexity of facial skin hydration and skin barrier properties is revealed by these measurements and visualized by the continuous colour maps of the digital images. Overall, the Caucasian subjects had the better barrier properties followed by the Black African subjects, Chinese subjects and Indian subjects. Nevertheless, the two more darkly pigmented ethnic groups had superior skin hydration properties. Subtle differences were seen when examining the different facial sites. There exists remarkable skin capacitance and TEWL gradients within short distances on selected areas of the face. These gradients are distinctive in the different ethnic groups. In contrast to other reports, we found that darkly pigmented skin does not always have a superior barrier function and differences in skin hydration values are complex on the different parts of the face among the different ethnic groups. © 2015 Society of Cosmetic Scientists and the Société Française de Cosmétologie.

  12. Hydrate morphology: Physical properties of sands with patchy hydrate saturation

    Science.gov (United States)

    Dai, S.; Santamarina, J.C.; Waite, William F.; Kneafsey, T.J.

    2012-01-01

    The physical properties of gas hydrate-bearing sediments depend on the volume fraction and spatial distribution of the hydrate phase. The host sediment grain size and the state of effective stress determine the hydrate morphology in sediments; this information can be used to significantly constrain estimates of the physical properties of hydrate-bearing sediments, including the coarse-grained sands subjected to high effective stress that are of interest as potential energy resources. Reported data and physical analyses suggest hydrate-bearing sands contain a heterogeneous, patchy hydrate distribution, whereby zones with 100% pore-space hydrate saturation are embedded in hydrate-free sand. Accounting for patchy rather than homogeneous hydrate distribution yields more tightly constrained estimates of physical properties in hydrate-bearing sands and captures observed physical-property dependencies on hydrate saturation. For example, numerical modeling results of sands with patchy saturation agree with experimental observation, showing a transition in stiffness starting near the series bound at low hydrate saturations but moving toward the parallel bound at high hydrate saturations. The hydrate-patch size itself impacts the physical properties of hydrate-bearing sediments; for example, at constant hydrate saturation, we find that conductivity (electrical, hydraulic and thermal) increases as the number of hydrate-saturated patches increases. This increase reflects the larger number of conductive flow paths that exist in specimens with many small hydrate-saturated patches in comparison to specimens in which a few large hydrate saturated patches can block flow over a significant cross-section of the specimen.

  13. Comparison of the water change characteristics between the formation and dissociation of methane hydrate and the freezing and thawing of ice in sand

    Institute of Scientific and Technical Information of China (English)

    Peng Zhang; Qingbai Wu; Yingmei Wang

    2009-01-01

    Hydrate formation and dissociation processes are always accompanied by water migration in porous media, which is similar to the ice. In our study, a novel pF-meter sensor which could detect the changes of water content inside sand was first applied to hydrate formation and dissociation processes. It also can study the water change characteristics in the core scale of a partially saturated silica sand sample and compare the differences of water changes between the processes of formation and dissociation of methane hydrate and freezing and thawing of ice. The experimental results showed that the water changes in the processes of formation and dissociation of methane hydrate were basically similar to that of the freezing and thawing of ice in sand. When methane hydrate or ice was formed, water changes showed the decrease in water content on the whole and the pF values rose following the formation processes. However, there were very obvious differences between the ice thawing and hydrate dissociation.

  14. Toward a microscopic understanding of the calcium–silicate–hydrates/water interface

    Energy Technology Data Exchange (ETDEWEB)

    Ebbert, Christoph [Department of Technical and Macromolecular Chemistry, University of Paderborn, Warburger Str. 100, 33098 Paderborn (Germany); Grundmeier, Guido; Buitkamp, Nadine; Kröger, Alexander [Technical Chemistry and Coating Science, University of Paderborn, Warburger Str. 100, 33098 Paderborn (Germany); Messerschmidt, Florian [Karlsruher Institut für Technologie, Institut für Mikroverfahrenstechnik, Hermann-von-Helmholtz-Platz 1, 76344 Eggenstein-Leopoldshafen (Germany); Thissen, Peter, E-mail: peter.thissen@kit.edu [Karlsruher Institut für Technologie, Institut für Funktionelle Grenzflächen, Hermann-von-Helmholtz-Platz 1, 76344 Eggenstein-Leopoldshafen (Germany)

    2014-01-30

    Calcium–Silicate–Hydrates (C–S–H) are the main binding phases in most concrete which is the primarily used composite construction material in the world. However, a big lack is cleaving between the actual knowledge about C–S–H, compared to what could be reached using state-of-the-art technologies of modern research. In this article, the formation of a C–S–H phase on a native oxide covered silicon wafer is investigated by means of in-situ attenuated total reflection infrared (ATR–IR) and ex-situ surface-enhanced Raman spectroscopy (SERS). The total thickness of the C–S–H phase is determined by X-ray photoelectron spectroscopy (XPS) to be 3 nm. The formation appears to be reversible depending on the environment pH value and can be performed at room temperature. Based on density functional theory (DFT) calculations, it is shown that the C–S–H phase in the presence of water will change its chemical composition in order to reach the thermodynamic ground state of the system. This change is achieved by a metal–proton exchange reaction. The stoichiometry of these metal–proton exchange reactions is nearly independent of the environment pH value. Electrokinetic measurements yield isoelectric points of 2.0 and 2.6 for the native oxide covered silicon wafer (SiO{sub 2}) and the C–S–H phase. This is consistent with a predominance of Si–O sites at the C–S–H/water interface.

  15. Clay hydration/dehydration in dry to water-saturated supercritical CO2: Implications for caprock integrity

    Energy Technology Data Exchange (ETDEWEB)

    Loring, John S.; Schaef, Herbert T.; Thompson, Christopher J.; Turcu, Romulus VF; Miller, Quin R.; Chen, Jeffrey; Hu, Jian Z.; Hoyt, David W.; Martin, Paul F.; Ilton, Eugene S.; Felmy, Andrew R.; Rosso, Kevin M.

    2013-01-01

    Injection of supercritical CO2 (scCO2) for the geologic storage of carbon dioxide will displace formation water, and the pore space adjacent to overlying caprocks could eventually be dominated by dry to water-saturated scCO2. Wet scCO2 is highly reactive and capable of carbonating and hydrating certain minerals, whereas anhydrous scCO2 can dehydrate water-containing minerals. Because these geochemical processes affect solid volume and thus porosity and permeability, they have the potential to affect the long-term integrity of the caprock seal. In this study, we investigate the swelling and shrinkage of an expandable clay found in caprock formations, montmorillonite (Ca-STx-1), when exposed to variable water-content scCO2 at 50 °C and 90 bar using a combination of in situ probes, including X-ray diffraction (XRD), in situ magic angle spinning nuclear magnetic resonance spectroscopy (MAS NMR), and in situ attenuated total reflection infrared spectroscopy (ATR-IR). We show that the extent of montmorillonite clay swelling/shrinkage is dependent not only on water hydration/dehydration, but also on CO2 intercalation reactions. Our results also suggest a competition between water and CO2 for interlayer residency where increasing concentrations of intercalated water lead to decreasing concentrations of intercalated CO2. Overall, this paper demonstrates the types of measurements required to develop fundamental knowledge that will enhance modeling efforts and reduce risks associated with subsurface storage of CO2.

  16. Neutron scattering studies of dynamic crossover phenomena in a coupled system of biopolymer and its hydration water

    Energy Technology Data Exchange (ETDEWEB)

    Chen, S H; Mallamace, F; Chu, X Q; Kim, C; Lagi, M [Department of Nuclear Science and Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139 (United States); Faraone, A [Dipartmento di Fisica and CNISM, Universita di Messina, Vil. S. Agata CP 55, 98166 Messina (Italy); Fratini, E; Baglioni, P, E-mail: sowhsin@mit.ed [Department of Chemistry and CSGI, University of Florence, 50019 (Italy)

    2009-06-01

    We have observed a Fragile-to-Strong Dynamic Crossover (FSC) phenomenon of the alpha-relaxation time and self-diffusion constant in hydration water of three biopolymers: lysozyme, B-DNA and RNA. The mean squared displacement (MSD) of hydrogen atoms is measured by Elastic Neutron Scattering (ENS) experiments. The alpha-relaxation time is measured by Quasi-Elastic Neutron Scattering (QENS) experiments and the self-diffusion constant by Nuclear Magnetic Resonance (NMR) experiments. We discuss the active role of the FSC of the hydration water in initiating the dynamic crossover phenomenon (so-called glass transition) in the biopolymer. The latter transition controls the flexibility of the biopolymer and sets the low temperature limit of its biofunctionality. Finally, we show an MD simulation of a realistic hydrated powder model of lysozyme and demonstrate the agreement of the MD simulation with the experimental data on the FSC phenomenon in the plot of logarithm of the alpha-relaxation time vs. 1/T.

  17. Molecular Dynamics Simulation of Atomic Force Microscopy at the Water-Muscovite Interface: Hydration Layer Structure and Force Analysis.

    Science.gov (United States)

    Kobayashi, Kazuya; Liang, Yunfeng; Amano, Ken-ichi; Murata, Sumihiko; Matsuoka, Toshifumi; Takahashi, Satoru; Nishi, Naoya; Sakka, Tetsuo

    2016-04-19

    With the development of atomic force microscopy (AFM), it is now possible to detect the buried liquid-solid interfacial structure in three dimensions at the atomic scale. One of the model surfaces used for AFM is the muscovite surface because it is atomically flat after cleavage along the basal plane. Although it is considered that force profiles obtained by AFM reflect the interfacial structures (e.g., muscovite surface and water structure), the force profiles are not straightforward because of the lack of a quantitative relationship between the force and the interfacial structure. In the present study, molecular dynamics simulations were performed to investigate the relationship between the muscovite-water interfacial structure and the measured AFM force using a capped carbon nanotube (CNT) AFM tip. We provide divided force profiles, where the force contributions from each water layer at the interface are shown. They reveal that the first hydration layer is dominant in the total force from water even after destruction of the layer. Moreover, the lateral structure of the first hydration layer transcribes the muscovite surface structure. It resembles the experimentally resolved surface structure of muscovite in previous AFM studies. The local density profile of water between the tip and the surface provides further insight into the relationship between the water structure and the detected force structure. The detected force structure reflects the basic features of the atomic structure for the local hydration layers. However, details including the peak-peak distance in the force profile (force-distance curve) differ from those in the density profile (density-distance curve) because of disturbance by the tip.

  18. Cooperative hydration effect causes thermal unfolding of proteins and water activity plays a key role in protein stability in solutions.

    Science.gov (United States)

    Miyawaki, Osato; Dozen, Michiko; Hirota, Kaede

    2016-08-01

    The protein unfolding process observed in a narrow temperature range was clearly explained by evaluating the small difference in the enthalpy of hydrogen-bonding between amino acid residues and the hydration of amino acid residue separately. In aqueous solutions, the effect of cosolute on the protein stability is primarily dependent on water activity, aw, the role of which has been long neglected in the literature. The effect of aw on protein stability works as a power law so that a small change in aw is amplified substantially through the cooperative hydration effect. In the present approach, the role of hydrophobic interaction stands behind. This affects protein stability indirectly through the change in solution structure caused by the existence of cosolute.

  19. [Sorption characteristics of tea waste modified by hydrated ferric oxide toward Pb(II) in water].

    Science.gov (United States)

    Wan, Shun-Li; Xue, Yao; Ma, Zhao-Zhao; Liu, Guo-Bin; Yu, Yan-Xia; Ma, Ming-Hai

    2014-10-01

    Hydrated ferric oxide was successfully impregnated onto tea waste by precipitation to obtain a new sorbent named HFO-TW, the adsorption characteristics of which toward Pb(II) in aqueous solution was investigated by evaluating the effects of pH value, contact time, coexisting ion, temperature, and initial concentration of Pb(II). The Pb(II) sorption onto HFO-TW was pH- dependent, and the higher pH value was more helpful for Pb(II) adsorption onto HFO-TW in the pH range of 2.5-7. Lead sorption speed was quick and could reach equilibrium within 100 min, and the kinetics curve could be fitted well by both pseudo-first and pseudo-second models. The related coefficient was 98.8%. HFO-TW exhibited highly selective lead retention and the adsorption capacity of Pb(II) onto HFO-TW was declined by only 12.1 mg · g(-1) and 8.1 mg · g(-1) in the presence of competing Ca(II), Mg(II) at 50 times of the target ion. In addition, Pb(II) sorption onto HFO-TW could be described satisfactorily by Langmuir model, and the maximal sorption capacity calculated by Langmuir equation was 89.43 mg · g(-1), which was much higher than the unmodified tea waste and other bio-sorbents. All the results validated that HFO-TW was a promising sorbent for removal of lead from waters.

  20. Effect of bound state of water on hydronium ion mobility in hydrated Nafion using molecular dynamics simulations

    Energy Technology Data Exchange (ETDEWEB)

    Mabuchi, Takuya, E-mail: mabuchi@nanoint.ifs.tohoku.ac.jp [Graduate School of Engineering, Tohoku University, Sendai, Miyagi 980-8577 (Japan); Tokumasu, Takashi [Institute of Fluid Science, Tohoku University, Sendai, Miyagi 980-8577 (Japan)

    2014-09-14

    We have performed a detailed analysis of the structural properties of the sulfonate groups in terms of isolated and overlapped solvation shells in the nanostructure of hydrated Nafion membrane using classical molecular dynamics simulations. Our simulations have demonstrated the correlation between the two different areas in bound water region, i.e., the first solvation shell, and the vehicular transport of hydronium ions at different water contents. We have employed a model of the Nafion membrane using the improved force field, which is newly modified and validated by comparing the density and water diffusivity with those obtained experimentally. The first solvation shells were classified into the two types, the isolated area and the overlapped area. The mean residence times of solvent molecules explicitly showed the different behaviors in each of those areas in terms of the vehicular transport of protons: the diffusivity of classical hydronium ions in the overlapped area dominates their total diffusion at lower water contents while that in the isolated area dominates for their diffusion at higher water contents. The results provided insights into the importance role of those areas in the solvation shells for the diffusivity of vehicular transport of hydronium ions in hydrated Nafion membrane.

  1. Hydration of protein–RNA recognition sites

    Science.gov (United States)

    Barik, Amita; Bahadur, Ranjit Prasad

    2014-01-01

    We investigate the role of water molecules in 89 protein–RNA complexes taken from the Protein Data Bank. Those with tRNA and single-stranded RNA are less hydrated than with duplex or ribosomal proteins. Protein–RNA interfaces are hydrated less than protein–DNA interfaces, but more than protein–protein interfaces. Majority of the waters at protein–RNA interfaces makes multiple H-bonds; however, a fraction do not make any. Those making H-bonds have preferences for the polar groups of RNA than its partner protein. The spatial distribution of waters makes interfaces with ribosomal proteins and single-stranded RNA relatively ‘dry’ than interfaces with tRNA and duplex RNA. In contrast to protein–DNA interfaces, mainly due to the presence of the 2′OH, the ribose in protein–RNA interfaces is hydrated more than the phosphate or the bases. The minor groove in protein–RNA interfaces is hydrated more than the major groove, while in protein–DNA interfaces it is reverse. The strands make the highest number of water-mediated H-bonds per unit interface area followed by the helices and the non-regular structures. The preserved waters at protein–RNA interfaces make higher number of H-bonds than the other waters. Preserved waters contribute toward the affinity in protein–RNA recognition and should be carefully treated while engineering protein–RNA interfaces. PMID:25114050

  2. Exploring the role of water in molecular recognition: predicting protein ligandability using a combinatorial search of surface hydration sites

    Science.gov (United States)

    Vukovic, Sinisa; Brennan, Paul E.; Huggins, David J.

    2016-09-01

    The interaction between any two biological molecules must compete with their interaction with water molecules. This makes water the most important molecule in medicine, as it controls the interactions of every therapeutic with its target. A small molecule binding to a protein is able to recognize a unique binding site on a protein by displacing bound water molecules from specific hydration sites. Quantifying the interactions of these water molecules allows us to estimate the potential of the protein to bind a small molecule. This is referred to as ligandability. In the study, we describe a method to predict ligandability by performing a search of all possible combinations of hydration sites on protein surfaces. We predict ligandability as the summed binding free energy for each of the constituent hydration sites, computed using inhomogeneous fluid solvation theory. We compared the predicted ligandability with the maximum observed binding affinity for 20 proteins in the human bromodomain family. Based on this comparison, it was determined that effective inhibitors have been developed for the majority of bromodomains, in the range from 10 to 100 nM. However, we predict that more potent inhibitors can be developed for the bromodomains BPTF and BRD7 with relative ease, but that further efforts to develop inhibitors for ATAD2 will be extremely challenging. We have also made predictions for the 14 bromodomains with no reported small molecule K d values by isothermal titration calorimetry. The calculations predict that PBRM1(1) will be a challenging target, while others such as TAF1L(2), PBRM1(4) and TAF1(2), should be highly ligandable. As an outcome of this work, we assembled a database of experimental maximal K d that can serve as a community resource assisting medicinal chemistry efforts focused on BRDs. Effective prediction of ligandability would be a very useful tool in the drug discovery process.

  3. 油藏流体中H型水合物生成条件的计算%Prediction of Structure-H Gas Hydrate Formation Conditions for Reservoir Fluids

    Institute of Scientific and Technical Information of China (English)

    马庆兰; 陈光进; 郭天民; 张坤; Julian Y.Zuo; Dan Zhang; Heng-Joo Ng

    2005-01-01

    In this work, a thermodynamic model is developed for prediction of structure H hydrate formation. The model combines the Peng-Robinson equation of state for the vapor, liquid and aqueous phases with the extended Ng-Robinson hydrate model for gas hydrate formation of all three structures. The parameters of 14 structureH hydrate formers are determined based on the experimental data of structure-H hydrates in the literature. The expression of fugacity of water in the empty hydrate phase is correlated for calculating structure-H hydrate formation conditions in the absence of free water. The model is tested by predicting hydrate formation conditions of a number of structure-H hydrate forming systems which are in good agreement with the experimental data. The proposed model is also applied to the prediction of hydrate formation conditions for various reservoir fluids such as natural gas and gas condensate.

  4. Methane consumption in waters overlying a hydrate-associated mound in the Santa Monica Basin : a project synopsis

    Energy Technology Data Exchange (ETDEWEB)

    Heintz, M.B.; Mau, S.; Valentine, D.L.; Reed, J.H. [California Univ., Santa Barbara, CA (United States); Hallam, S.J.; Yang, J. [British Columbia Univ., Vancouver, BC (Canada). Dept. of Microbiology and Immunology

    2008-07-01

    Understanding the role of methane hydrates in the global carbon cycle and climate change requires an understanding of methane consumption in hydrate-associated environments. A dual-component microbial biofilter consumes up to 80 per cent of methane produced in the marine environment. Throughout most of the oceans around the world, anaerobic methane oxidation within sediment prevents large quantities of methane from leaving the seafloor. However, in regions of increased methane production, methane is released to the water column. The water column component of the marine biofilter for methane is the largest uncharacterized global sink for methane. This study combined geochemical and molecular biology to develop a quantitative understanding of methane consumption in the marine water column of the Southern California Bight. The paper presented geochemical data demonstrating that the degree of basin enclosure and basin-scale circulation patterns, were first order controls on methane oxidation rates in the Santa Monica Basin (SMB). The paper also presented genetic data showing similarities and differences in methanotrophic communities in distinctive horizons within the SMB water column. It described the study site, sampling, and methods as well as the preliminary findings. A contrast was observed between methane concentration and methane turnover time profiles. It was concluded that although methane concentration is a first-order control on methanotrophic activity, community concentration, dilution and seeding control the broad scale efficacy of methane consumption. 23 refs., 2 figs.

  5. Characteristics of hydration water around hen egg lysozyme as the protein model in aqueous solution. FTIR spectroscopy and molecular dynamics simulation.

    Science.gov (United States)

    Panuszko, Aneta; Wojciechowski, Marek; Bruździak, Piotr; Rakowska, Paulina W; Stangret, Janusz

    2012-12-05

    In this paper, the hydration of a model protein--hen egg white lysozyme in aqueous solution has been presented. The leading method used was FTIR spectroscopy with an application of a technique of semi-heavy water (HDO) isotope dilution. Analysis of spectra of HDO isotopically diluted in water solution of lysozyme allowed us to isolate HDO spectra affected by lysozyme, and thus to characterise the energetic state of water molecules and their arrangement around protein molecules. The number of water molecules and the shape of the affected HDO spectrum were obtained using a classical and a chemometric method. This shape showed that the HDO spectrum affected by lysozyme may be presented as a superposition of two spectra corresponding to HDO affected by N-methylacetamide and the carboxylate anion (of the formic acid). Moreover, based on the difference in intermolecular distances distribution of water molecules (obtained from spectral data), we demonstrated that the lysozyme molecule causes a decrease in population of weak hydrogen bonds, and concurrently increases the probability of an occurrence of short hydrogen bonds in water affected by lysozyme. This conclusion was also confirmed by the molecular dynamics (MD) simulation.

  6. Spatial and Orientational Structure of the Hydration Shell of Benzene in Sub- and Supercritical Water.

    Science.gov (United States)

    Choudhary, Ashu; Chandra, Amalendu

    2015-07-09

    The spatial and orientational structure of the solvation shell of benzene in sub- and supercritical water are investigated by means of molecular dynamics simulations. The present study reveals different local organization of water molecules at different parts of the solute. The π-hydrogen-bonding between benzene and water along the axial direction is found to exist even at supercritical conditions although to a reduced extent. The coordination number of benzene decreases substantially on increase of temperature and decrease of density. While the π-hydrogen-bonded part in the axial region shows a slight expansion, the hydrophobically solvated part in the equatorial plane shows an opposite behavior as the temperature is increased from normal to the supercritical temperature. Two other distribution functions, namely the radial/angular and spatial orientational functions (SOFs) are calculated to explore the spatially resolved angular preferences of water molecules around the benzene solute. Water molecules located axial to the benzene are found to have strong inward orientation toward the solute, however an opposite behavior is found in the equatorial region. Although at supercritical conditions, the orientational distributions of water molecules are broadened, the preferential orientations in the axial and equatorial regions remain similar to that under ambient condition on average.

  7. Unexpected inhibition of CO2 gas hydrate formation in dilute TBAB solutions and the critical role of interfacial water structure

    Energy Technology Data Exchange (ETDEWEB)

    Nguyen, Ngoc N.; Nguyen, Anh V.; Nguyen, Khoi T.; Rintoul, Llew; Dang, Liem X.

    2016-12-01

    Gas hydrates formed under moderated conditions open up novel approaches to tackling issues related to energy supply, gas separation, and CO2 sequestration. Several additives like tetra-n-butylammonium bromide (TBAB) have been empirically developed and used to promote gas hydrate formation. Here we report unexpected experimental results which show that TBAB inhibits CO2 gas hydrate formation when used at minuscule concentration. We also used spectroscopic techniques and molecular dynamics simulation to gain further insights and explain the experimental results. They have revealed the critical role of water alignment at the gas-water interface induced by surface adsorption of tetra-n-butylammonium cation (TBA+) which gives rise to the unexpected inhibition of dilute TBAB solution. The water perturbation by TBA+ in the bulk is attributed to the promotion effect of high TBAB concentration on gas hydrate formation. We explain our finding using the concept of activation energy of gas hydrate formation. Our results provide a step toward to mastering the control of gas hydrate formation.

  8. Distribution of long-lived radioactive iodine isotope (I-129) in pore waters from the gas hydrate fields on the continental margins: Indication for methane source of gas hydrate deposits

    Science.gov (United States)

    Tomaru, H.; Lu, Z.; Fehn, U.

    2011-12-01

    Because iodine has a strong association with organic matters in marine environments, pore waters in high methane potential region, in particular gas hydrate occurrences on the continental margins, are enriched significantly in iodine compared with seawater. Natural iodine system is composed of stable and radioactive species, I-129 (half-life of 15.7 Myr) has been used for estimating the age of source formations both for methane and iodine, because iodine can be liberated into pore water during the degradation of organic matter to methane in deep sediments. Here we present I-129 age data in pore waters collected from variety of gas hydrate occurrences on the continental margins. The I-129 ages in pore waters from these locations are significantly older than those of host sediments, indicating long-term transport and accumulation from deep/old sediments. The I-129 ages in the Japan Sea and Okhotsk Sea along the plate boundary between the North American and Amurian Plates correspond to the ages of initial spreading of these marginal seas, pointing to the massive deposition of organic matter for methane generation in deep sediments within limited periods. On the Pacific side of these areas, organic matter-rich back stop is responsible for methane in deep-seated gas hydrate deposits along the Nankai Trough. Deep coaly sequences responsible for deep conventional natural gas deposits are also responsible for overlying gas hydrate deposits off Shimokita Peninsula, NE Japan. Those in the Gulf of Mexico are correlative to the ages of sediments where the top of salt diapirs intrude. Marine sediments on the Pacific Plate subducting beneath the Australian Plate are likely responsible for the methane and iodine in the Hikurangi Trough, New Zealand. These ages reflect well the regional geological settings responsible for generation, transport, and accumulation of methane, I-129 is a key to understand the geological history of gas hydrate deposition.

  9. Structure and dynamics of interfacial water. Role of hydratation water in the globular proteins dynamics; Structure et dynamique de l`eau interfaciale. Role de l`eau d`hydratation dans la dynamique des proteines globulaires

    Energy Technology Data Exchange (ETDEWEB)

    Zanotti, J.M.

    1997-01-27

    This memoir includes five chapters. In the first chapter, are given the elements of the neutrons scattering theory that is used in this study. the second chapter is devoted to a general presentation of the interaction between biological macro molecule and water. The third part is dedicated to the study of the structure and the dynamics of interfacial water in the neighbouring of model systems, the vycor and the amorphous carbon. The results presented in this part are compared with these one relative to water dynamics at the C-phycocyanin surface. This study makes the object of the fourth chapter. Then, in the fifth and last chapter are discussed the results relative to the role of hydratation on the parv-albumin dynamics for which have been combined the neutron quasi elastic incoherent scattering and the nuclear magnetic resonance of the carbon 13 solid in natural abundance.

  10. Formation of porous gas hydrates

    CERN Document Server

    Salamatin, Andrey N

    2015-01-01

    Gas hydrates grown at gas-ice interfaces are examined by electron microscopy and found to have a submicron porous texture. Permeability of the intervening hydrate layers provides the connection between the two counterparts (gas and water molecules) of the clathration reaction and makes further hydrate formation possible. The study is focused on phenomenological description of principal stages and rate-limiting processes that control the kinetics of the porous gas hydrate crystal growth from ice powders. Although the detailed physical mechanisms involved in the porous hydrate formation still are not fully understood, the initial stage of hydrate film spreading over the ice surface should be distinguished from the subsequent stage which is presumably limited by the clathration reaction at the ice-hydrate interface and develops after the ice grain coating is finished. The model reveals a time dependence of the reaction degree essentially different from that when the rate-limiting step of the hydrate formation at...

  11. Why can water cages adsorb aqueous methane? A potential of mean force calculation on hydrate nucleation mechanisms.

    Science.gov (United States)

    Guo, Guang-Jun; Li, Meng; Zhang, Yi-Gang; Wu, Chang-Hua

    2009-11-28

    By performing constrained molecular dynamics simulations in the methane-water system, we successfully calculated the potential of mean force (PMF) between a dodecahedral water cage (DWC) and dissolved methane for the first time. As a function of the distance between DWC and methane, this is characterized by a deep well at approximately 6.2 A and a shallow well at approximately 10.2 A, separated by a potential barrier at approximately 8.8 A. We investigated how the guest molecule, cage rigidity and the cage orientation affected the PMF. The most important finding is that the DWC itself strongly adsorbs methane and the adsorption interaction is independent of the guests. Moreover, the activation energy of the DWC adsorbing methane is comparable to that of hydrogen bonds, despite differing by a factor of approximately 10% when considering different water-methane interaction potentials. We explain that the cage-methane adsorption interaction is a special case of the hydrophobic interaction between methane molecules. The strong net attraction in the DWC shell with radii between 6.2 and 8.8 A may act as the inherent driving force that controls hydrate formation. A cage adsorption hypothesis for hydrate nucleation is thus proposed and discussed.

  12. Method for calculating the parameters of formation of hydrates from multicomponent gases

    Science.gov (United States)

    Zaporozhets, E. P.; Shostak, N. A.

    2016-09-01

    A model of hydrate formation in multicomponent gas-liquid water or ice systems including the exo- and endothermic processes has been suggested. Based on this model, a method for calculating the molecular and energy parameters such as the hydration number, amount of moles of hydrate, amount of gas and water in it, its density and molar mass, and the energy and rate of hydrate formation was developed. A comparison of the calculated and experimental values of the parameters revealed that the difference between them varied from 0 to 5.46%.

  13. The simulation of gas production from oceanic gas hydrate reservoir by the combination of ocean surface warm water flooding with depressurization

    Institute of Scientific and Technical Information of China (English)

    Hao Yang; Yu-Hu Bai; Qing-Ping Li

    2012-01-01

    A new method is proposed to produce gas from oceanic gas hydrate reservoir by combining the ocean surface warm water flooding with depressurization which can efficiently utilize the synthetic effects of thermal,salt and depressurization on gas hydrate dissociation.The method has the advantage of high efficiency,low cost and enhanced safety.Based on the proposed conceptual method,the physical and mathematical models are established,in which the effects of the flow of multiphase fluid,the kinetic process of hydrate dissociation,the endothermic process of hydrate dissociation,ice-water phase equilibrium,salt inhibition,dispersion,convection and conduction on the hydrate dissociation and gas and water production are considered.The gas and water rates,formation pressure for the combination method are compared with that of the single depressurization,which is referred to the method in which only depressurization is used.The results show that the combination method can remedy the deficiency of individual producing methods.It has the advantage of longer stable period of high gas rate than the single depressurization.It can also reduce the geologic hazard caused by the formation deformation due to the maintaining of the formation pressure by injected ocean warm water.

  14. Quantitative analysis of the hydration of lithium salts in water using multivariate curve resolution of near-infrared spectra

    Energy Technology Data Exchange (ETDEWEB)

    Barba, M. Isabel [Group of Research in Applied Thermal Engineering-CREVER, Mechanical Engineering Dept. (Spain); Larrechi, M. Soledad, E-mail: mariasoledad.larrechi@urv.cat [Analytical and Organic Chemistry Dept., Universitat Rovira i Virgili, Tarragona (Spain); Coronas, Alberto [Group of Research in Applied Thermal Engineering-CREVER, Mechanical Engineering Dept. (Spain)

    2016-05-05

    The hydration process of lithium iodide, lithium bromide, lithium chloride and lithium nitrate in water was analyzed quantitatively by applying multivariate curve resolution alternating least squares (MCR-ALS) to their near infrared spectra recorded between 850 nm and 1100 nm. The experiments were carried out using solutions with a salt mass fraction between 0% and 72% for lithium bromide, between 0% and 67% for lithium nitrate and between 0% and 62% for lithium chloride and lithium iodide at 323.15 K, 333.15 K, 343.15 K and 353.15 K, respectively. Three factors were determined for lithium bromide and lithium iodide and two factors for the lithium chloride and lithium nitrate by singular value decomposition (SVD) of their spectral data matrices. These factors are associated with various chemical environments in which there are aqueous clusters containing the ions of the salts and non-coordinated water molecules. Spectra and concentration profiles of non-coordinated water and cluster aqueous were retrieved by MCR-ALS. The amount of water involved in the process of hydration of the various salts was quantified. The results show that the water absorption capacity increases in the following order LiI < LiBr < LiNO{sub 3} < LiCl. The salt concentration at which there is no free water in the medium was calculated at each one of the temperatures considered. The values ranged between 62.6 and 65.1% for LiBr, 45.5–48.3% for LiCl, 60.4–61.2% for LiI and 60.3–63.7% for LiNO{sub 3}. These values are an initial approach to determining the concentration as from which crystal formation is favored. - Highlights: • Quantitative analysis of the hydration of lithium salts in water. • The absorption capacity of the electrolytes in function of the salt is evaluated. • The lithium salt concentration is estimated when the crystal formation is favored.

  15. Phase diagram of water-methane by first-principles thermodynamics: discovery of MH-IV and MH-V hydrates.

    Science.gov (United States)

    Cao, Xiaoxiao; Huang, Yingying; Jiang, Xue; Su, Yan; Zhao, Jijun

    2017-06-21

    Searching novel gas hydrates is an enduring topic of scientific investigations, owing to its outstanding implications on planetology, the origin of life and the exploitation of energy resources. Taking the methane-water system as a representative, we disclose two new dense methane hydrate phases (MH-IV and MH-V) using the Monte-Carlo packing algorithm and density-functional theory (DFT) optimization. Both of these methane clathrates with (CH4)(H2O)4 stoichiometry can be regarded as filled ices, since their hydrogen bond networks are closely related to that of ice i and ice XI, respectively. In particular, the former ice i network is observed for the first time in all gas hydrates. A new chemical composition phase diagram of methane hydrate is constructed. Our newly identified methane hydrate IV emerges in the transition zone for a water-methane ratio between 2 : 1 and 5.75 : 1. It suggests that our MH-IV phase can be stabilized without external pressure, which is superior to previous reported filled ices to apply to energy storage. These findings attest to the importance of composition effects on the packing mechanism of gas hydrate, and provide new perspectives for understanding the physicochemical and geophysical processes in the giant planets of the solar system.

  16. Quantitative analysis of the hydration of lithium salts in water using multivariate curve resolution of near-infrared spectra.

    Science.gov (United States)

    Barba, M Isabel; Larrechi, M Soledad; Coronas, Alberto

    2016-05-05

    The hydration process of lithium iodide, lithium bromide, lithium chloride and lithium nitrate in water was analyzed quantitatively by applying multivariate curve resolution alternating least squares (MCR-ALS) to their near infrared spectra recorded between 850 nm and 1100 nm. The experiments were carried out using solutions with a salt mass fraction between 0% and 72% for lithium bromide, between 0% and 67% for lithium nitrate and between 0% and 62% for lithium chloride and lithium iodide at 323.15 K, 333.15 K, 343.15 K and 353.15 K, respectively. Three factors were determined for lithium bromide and lithium iodide and two factors for the lithium chloride and lithium nitrate by singular value decomposition (SVD) of their spectral data matrices. These factors are associated with various chemical environments in which there are aqueous clusters containing the ions of the salts and non-coordinated water molecules. Spectra and concentration profiles of non-coordinated water and cluster aqueous were retrieved by MCR-ALS. The amount of water involved in the process of hydration of the various salts was quantified. The results show that the water absorption capacity increases in the following order LiI < LiBr < LiNO3 < LiCl. The salt concentration at which there is no free water in the medium was calculated at each one of the temperatures considered. The values ranged between 62.6 and 65.1% for LiBr, 45.5-48.3% for LiCl, 60.4-61.2% for LiI and 60.3-63.7% for LiNO3. These values are an initial approach to determining the concentration as from which crystal formation is favored. Copyright © 2016 Elsevier B.V. All rights reserved.

  17. Investigation on Gas Storage in Methane Hydrate

    Institute of Scientific and Technical Information of China (English)

    Zhigao Sun; Rongsheng Ma; Shuanshi Fan; Kaihua Guo; Ruzhu Wang

    2004-01-01

    The effect of additives (anionic surfactant sodium dodecyl sulfate (SDS), nonionic surfactant alkyl polysaccharide glycoside (APG), and liquid hydrocarbon cyclopentane (CP)) on hydrate induction time and formation rate, and storage capacity was studied in this work. Micelle surfactant solutions were found to reduce hydrate induction time, increase methane hydrate formation rate and improve methane storage capacity in hydrates. In the presence of surfactant, hydrate could form quickly in a quiescent system and the energy costs of hydrate formation were reduced. The critical micelle concentrations of SDS and APG water solutions were found to be 300× 10-6 and 500× 10-6 for methane hydrate formation system respectively. The effect of anionic surfactant (SDS) on methane storage in hydrates is more pronounced compared to a nonionic surfactant (APG). CP also reduced hydrate induction time and improved hydrate formation rate, but could not improve methane storage in hydrates.

  18. Neutrons describe ectoine effects on water H-bonding and hydration around a soluble protein and a cell membrane

    Science.gov (United States)

    Zaccai, Giuseppe; Bagyan, Irina; Combet, Jérôme; Cuello, Gabriel J.; Demé, Bruno; Fichou, Yann; Gallat, François-Xavier; Galvan Josa, Victor M.; von Gronau, Susanne; Haertlein, Michael; Martel, Anne; Moulin, Martine; Neumann, Markus; Weik, Martin; Oesterhelt, Dieter

    2016-01-01

    Understanding adaptation to extreme environments remains a challenge of high biotechnological potential for fundamental molecular biology. The cytosol of many microorganisms, isolated from saline environments, reversibly accumulates molar concentrations of the osmolyte ectoine to counterbalance fluctuating external salt concentrations. Although they have been studied extensively by thermodynamic and spectroscopic methods, direct experimental structural data have, so far, been lacking on ectoine-water-protein interactions. In this paper, in vivo deuterium labeling, small angle neutron scattering, neutron membrane diffraction and inelastic scattering are combined with neutron liquids diffraction to characterize the extreme ectoine-containing solvent and its effects on purple membrane of H. salinarum and E. coli maltose binding protein. The data reveal that ectoine is excluded from the hydration layer at the membrane surface and does not affect membrane molecular dynamics, and prove a previous hypothesis that ectoine is excluded from a monolayer of dense hydration water around the soluble protein. Neutron liquids diffraction to atomic resolution shows how ectoine enhances the remarkable properties of H-bonds in water—properties that are essential for the proper organization, stabilization and dynamics of biological structures. PMID:27527336

  19. Neutrons describe ectoine effects on water H-bonding and hydration around a soluble protein and a cell membrane

    Science.gov (United States)

    Zaccai, Giuseppe; Bagyan, Irina; Combet, Jérôme; Cuello, Gabriel J.; Demé, Bruno; Fichou, Yann; Gallat, François-Xavier; Galvan Josa, Victor M.; von Gronau, Susanne; Haertlein, Michael; Martel, Anne; Moulin, Martine; Neumann, Markus; Weik, Martin; Oesterhelt, Dieter

    2016-08-01

    Understanding adaptation to extreme environments remains a challenge of high biotechnological potential for fundamental molecular biology. The cytosol of many microorganisms, isolated from saline environments, reversibly accumulates molar concentrations of the osmolyte ectoine to counterbalance fluctuating external salt concentrations. Although they have been studied extensively by thermodynamic and spectroscopic methods, direct experimental structural data have, so far, been lacking on ectoine-water-protein interactions. In this paper, in vivo deuterium labeling, small angle neutron scattering, neutron membrane diffraction and inelastic scattering are combined with neutron liquids diffraction to characterize the extreme ectoine-containing solvent and its effects on purple membrane of H. salinarum and E. coli maltose binding protein. The data reveal that ectoine is excluded from the hydration layer at the membrane surface and does not affect membrane molecular dynamics, and prove a previous hypothesis that ectoine is excluded from a monolayer of dense hydration water around the soluble protein. Neutron liquids diffraction to atomic resolution shows how ectoine enhances the remarkable properties of H-bonds in water—properties that are essential for the proper organization, stabilization and dynamics of biological structures.

  20. Structure and water exchange dynamics of hydrated oxo halo ions in aqueous solution using QMCF MD simulation, large angle X-ray scattering and EXAFS

    Science.gov (United States)

    Eklund, Lars; Hofer, Tomas S.

    2014-01-01

    Theoretical ab initio quantum mechanical charge field molecular dynamics (QMCF MD) has been applied in conjunction with experimental large angle X-ray scattering (LAXS) and EXAFS measurements to study structure and dynamics of the hydrated oxo chloro anions chlorite, ClO2−, chlorate, ClO3−, and perchlorate, ClO4−. In addition, the structures of the hydrated hypochlorite, ClO−, bromate, BrO3−, iodate, IO3− and metaperiodate, IO4−, ions have been determined in aqueous solution by means of LAXS. The structures of the bromate, metaperiodate, and orthoperiodate, H2IO63−, ions have been determined by EXAFS as solid sodium salts and in aqueous solution as well. The results show clearly that the only form of periodate present in aqueous solution is metaperiodate. The Cl-O bond distances in the hydrated oxo chloro anions as determined by LAXS and obtained in the QMCF MD simulations are in excellent agreement, being 0.01–0.02 Å longer than in solid anhydrous salts due to hydration through hydrogen bonding to water molecules. The oxo halo anions, all with unit negative charge, have low charge density making them typical structure breakers, thus the hydrogen bonds formed to the hydrating water molecules are weaker and more short-lived than those between water molecules in pure water. The water exchange mechanism of the oxo chloro anions resembles those of the oxo sulfur anions with a direct exchange at the oxygen atoms for perchlorate and sulfate. The water exchange rate for the perchlorate ion is significantly faster, τ0.5=1.4 ps, compared to the hydrated sulfate ion and pure water, τ0.5=2.6 and 1.7 ps, respectively. The angular radial distribution functions show that the chlorate and sulfite ions have a more complex water exchange mechanism. As the chlorite and chlorate ions are more weakly hydrated than the sulfite ion the spatial occupancy is less well-defined and it is not possible to follow any well-defined migration pattern as it is difficult to

  1. Influence of supplementary cementitious materials on water transport kinetics and mechanical properties of hydrated lime and cement mortars

    Directory of Open Access Journals (Sweden)

    Ince, C.

    2015-06-01

    Full Text Available The purpose of this paper is an investigation of the possible role of supplementary cementitious materials (SCMs on water transport kinetics and mechanical properties of hydrated lime (CL90 and Portland cement (PC mortars. The properties of hydrated lime are significantly different from those of cement and therefore modifying fresh and hardened properties of these mortars are vital for mortar/substrate optimisation in masonry construction. The parameters investigated in this paper often are the main barriers to the use of hydrated lime in construction practice. The results show that transfer sorptivity and time to dewater freshly-mixed hydrated lime mortars can be modified when binder is partially replaced with SCMs. Compressive strength of CL90 mortars is increased systematically with the increased replacement levels of SCMs and the results are supported with the microstructural images. The ability to modify the water transport kinetics and mechanical properties allows compatibility between the mortar and the substrate unit in masonry construction.El objetivo de este artículo es investigar el papel de los materiales cementantes suplementarios (SCMs en la cinética de transporte del agua y en las propiedades mecánicas de los morteros de cal hidratada (CL90 y cemento Portland. Las propiedades de la cal hidratada son significativamente diferentes a las del cemento y por lo tanto el control de las propiedades de los morteros frescos y endurecidos es fundamental en la optimización mortero/substrato en albañilería. Los parámetros estudiados en este trabajo son a menudo las principales barreras para el uso de la cal hidratada en la práctica de la construcción. Los resultados indican que la absortividad y el tiempo necesario para deshidratar morteros de cal hidratada recién mezclados pueden ser controlados cuando el conglomerante es parcialmente remplazado por SCMs. La resistencia a compresión de los morteros CL90 aumenta sistem

  2. Influence of hydration water on CHsub>3sub>NHsub>3sub>PbIsub>3sub> perovskite films prepared through one-step procedure.

    Science.gov (United States)

    Wang, Ziyi; Yuan, Sijian; Li, Dahai; Jin, Feng; Zhang, Rongjun; Zhan, Yiqiang; Lu, Ming; Wang, Songyou; Zheng, Yuxiang; Guo, Junpeng; Fan, Zhiyong; Chen, Liangyao

    2016-10-31

    Organic-inorganic perovskites were fabricated through a one-step procedure with different levels of hydration water in precursor solutions. The optical properties of CHsub>3sub>NHsub>3sub>PbIsub>3sub> films were investigated through spectroscopic ellipsometry and photoluminescence measurements. With the measured optical constants, the efficiency limit of perovskite solar cells is predicted with a detailed balance model. By comparing the optical measurement to that of planar heterojunction solar cells, we conclude that the radiative efficiency and porosity of the perovskite film significantly influence the performance of perovskite solar cells. An optimized hydration-water concentration is obtained for the 3CHsub>3sub>NHsub>3sub>I:1PbAcsub>2sub>•xHsub>2sub>O precursor solution. The results can provide guidance for further optimization of the device performance of perovskite solar cells by utilizing hydration water.

  3. A study on gas hydrate

    Energy Technology Data Exchange (ETDEWEB)

    Yoo, Byoung Jae; Jung, Tae Jin; Sunwoo, Don [Korea Institute of Geology Mining and Materials, Taejon (Korea, Republic of)

    1996-12-01

    Sufficient documents were reviewed to understand solid components of water and gaseous hydrocarbon known as gas hydrates, which represent an important potential energy resource of the future. The review provides us with valuable information on crystal structures, kinetics, origin and distribution of gas hydrates. In addition, the review increased our knowledge of exploration and development methods of gas hydrates. Large amounts of methane, the principal component of natural gas, in the form of solid gas hydrate are found mainly offshore in outer continental margin sediment and, to a lesser extent, in polar regions commonly associated with permafrost. Natural gas hydrates are stable in some environments where the hydrostatic pressure exerted by overlying water column is sufficient for hydrate formation and stability. The required high pressures generally restrict gas hydrate to sediments beneath water of approximately 400 m. Higher sediment temperatures at greater subbottom depths destabilize gas hydrates. Based on the pressure- temperature condition, the outer continental margin of East Sea where water depth is deep enough to form gas hydrate is considered to have high potential of gas hydrate accumulations. (author). 56 refs., tabs., figs.

  4. Investigation of Wyoming Bentonite Hydration in Dry to Water-Saturated Supercritical CO2: Implications for Caprock Integrity

    Science.gov (United States)

    Loring, J. S.; Chen, J.; Thompson, C.; Schaef, T.; Miller, Q. R.; Martin, P. F.; Ilton, E. S.; Qafoku, O.; Felmy, A. R.; Rosso, K. M.

    2012-12-01

    The effectiveness of geologic sequestration as an enterprise for CO2 storage depends partly on the reactivity of supercritical CO2 (scCO2) with caprock minerals. Injection of scCO2 will displace formation water, and the pore space adjacent to overlying caprocks could eventually be dominated by dry to water-saturated scCO2. Caprock formations have high concentrations of clay minerals, including expandable montmorillonites. Water-bearing scCO2 is highly reactive and capable of hydrating or dehydrating clays, possibly leading to porosity and permeability changes that directly impact caprock performance. Dehydration will cause montmorillonite clay minerals in caprocks to contract, thereby decreasing solid volume and possibly increasing caprock permeability and porosity. On the other hand, water intercalation will cause these clays to expand, thereby increasing solid volume and possibly leading to self-sealing of caprock fractures. Pacific Northwest National Laboratory's Carbon Sequestration Initiative is developing capabilities for studying wet scCO2-mineral reactions in situ. Here, we introduce novel in situ infrared (IR) spectroscopic instrumentation that enables quantitative titrations of reactant minerals with water in scCO2. Results are presented for the infrared spectroscopic titrations of Na-, Ca-, and Mg-saturated Wyoming betonites with water over concentrations ranging from zero to scCO2 saturated. These experiments were carried out at 50°C and 90 bar. Transmission IR spectroscopy was used to measure concentrations of water dissolved in the scCO2 or intercalated into the clays. The titration curves evaluated from the transmission-IR data are compared between the three types of clays to assess the effects of the cation on water partitioning. Single-reflection attenuated total reflection (ATR) IR spectroscopy was used to collect the spectrum of the clays as they hydrate at every total water concentration during the titration. Clay hydration is evidenced by

  5. Examination of Hydrate Formation Methods: Trying to Create Representative Samples

    Energy Technology Data Exchange (ETDEWEB)

    Kneafsey, T.J.; Rees, E.V.L.; Nakagawa, S.; Kwon, T.-H.

    2011-04-01

    Forming representative gas hydrate-bearing laboratory samples is important so that the properties of these materials may be measured, while controlling the composition and other variables. Natural samples are rare, and have often experienced pressure and temperature changes that may affect the property to be measured [Waite et al., 2008]. Forming methane hydrate samples in the laboratory has been done a number of ways, each having advantages and disadvantages. The ice-to-hydrate method [Stern et al., 1996], contacts melting ice with methane at the appropriate pressure to form hydrate. The hydrate can then be crushed and mixed with mineral grains under controlled conditions, and then compacted to create laboratory samples of methane hydrate in a mineral medium. The hydrate in these samples will be part of the load-bearing frame of the medium. In the excess gas method [Handa and Stupin, 1992], water is distributed throughout a mineral medium (e.g. packed moist sand, drained sand, moistened silica gel, other porous media) and the mixture is brought to hydrate-stable conditions (chilled and pressurized with gas), allowing hydrate to form. This method typically produces grain-cementing hydrate from pendular water in sand [Waite et al., 2004]. In the dissolved gas method [Tohidi et al., 2002], water with sufficient dissolved guest molecules is brought to hydrate-stable conditions where hydrate forms. In the laboratory, this is can be done by pre-dissolving the gas of interest in water and then introducing it to the sample under the appropriate conditions. With this method, it is easier to form hydrate from more soluble gases such as carbon dioxide. It is thought that this method more closely simulates the way most natural gas hydrate has formed. Laboratory implementation, however, is difficult, and sample formation is prohibitively time consuming [Minagawa et al., 2005; Spangenberg and Kulenkampff, 2005]. In another version of this technique, a specified quantity of gas

  6. Storing natural gas as frozen hydrate

    Energy Technology Data Exchange (ETDEWEB)

    Gudmundsson, J.S.; Khokhar, A.A. (Univ. of Trondheim (Norway)); Parlaktuna, M. (Middle East Technical Univ., Ankara (Turkey))

    1994-02-01

    The formation of natural gas hydrates is a well-known problem in the petroleum and natural gas industries. Hydrates are solid materials that form when liquid water and natural gas are brought in contact under pressure. Hydrate formation need not be a problem. On the contrary, it can be an advantage. The volume of hydrates is much less than that of natural gas. At standard conditions, hydrates occupy 150 to 170 times less volume than the corresponding gas. Typically, natural gas hydrates contain 15% gas and 85% water by mass. It follows that hydrates can be used for large-scale storage of natural gas. Benesh proposed using hydrates to improve the load factor of natural gas supply systems. The author suggested that hydrates could be produced by bringing liquid water into contact with natural gas at the appropriate temperature and high pressure. The hydrate then would be stored at a temperature and pressure where it was stable. When gas was needed for the supply system, the hydrate would be melted at low pressure. The stability of a natural gas hydrate during storage at atmospheric pressure and below-freezing temperatures was studied in the laboratory. The gas hydrate was produced in a stirred vessel at 2- to 6-MPa pressure and temperatures from 0 to 20 C. The hydrate was refrigerated and stored in deep freezers at [minus]5, [minus]10, and [minus]18 C for up to 10 days. The natural gas hydrate remained stable when kept frozen at atmospheric pressure.

  7. Hydration rate of obsidian.

    Science.gov (United States)

    Friedman, I; Long, W

    1976-01-30

    The hydration rates of 12 obsidian samples of different chemical compositions were measured at temperatures from 95 degrees to 245 degrees C. An expression relating hydration rate to temperature was derived for each sample. The SiO(2) content and refractive index are related to the hydration rate, as are the CaO, MgO, and original water contents. With this information it is possible to calculate the hydration rate of a sample from its silica content, refractive index, or chemical index and a knowledge of the effective temperature at which the hydration occurred. The effective hydration temperature can be either measured or approximated from weather records. Rates have been calculated by both methods, and the results show that weather records can give a good approximation to the true EHT, particularly in tropical and subtropical climates. If one determines the EHT by any of the methods suggested, and also measures or knows the rate of hydration of the particular obsidian used, it should be possible to carry out absolute dating to +/- 10 percent of the true age over periods as short as several years and as long as millions of years.

  8. Determination of Nucleic Acid Hydration Using Osmotic Stress

    Science.gov (United States)

    Rozners, Eriks

    2010-01-01

    Understanding the role water plays in biological processes requires detailed knowledge of the phenomena of biopolymer hydration. Crystal structures have identified exact sites occupied by the water molecules in immediate hydration layers. NMR and molecular modeling have provided information on dynamics of water molecules occupying these sites. However, these studies give little information on the thermodynamic contribution of water molecules to conformational equilibria and recognition affinity. This unit describes probing of nucleic acid hydration using osmotic stress, a method that provides thermodynamic information complementary to crystallography, NMR and molecular modeling. Osmotic stress monitors the depression of melting temperature upon decreasing the water activity and calculates the number of thermodynamically unique water molecules associated with the double helix and released from the single strands upon melting. PMID:21154532

  9. MOLECULAR DYNAMICS SIMULATIONS OF FILLED AND EMPTY CAGE-LIKE WATER CLUSTERS IN LIQUID WATER AND THEIR SIGNIFICANCE TO GAS HYDRATE FORMATION MECHANISMS

    Institute of Scientific and Technical Information of China (English)

    GUO Guangjun; ZHANG Yigang; ZHAO Yajuan

    2003-01-01

    Molecular dynamics simulations are performed to observe the evolutions of 512 and 51262 cage-like water clusters filled with or without a methane molecule immersed in bulk liquid water at 250 K and 230 K. The lifetimes of these clusters are calculated according to their Lindemann index δ (t) using the criteria of δ≥0.07. For both the filled and empty clusters, we find the dynamics of bulk water determines the lifetimes of cage-like water clusters, and that the lifetime of 512 62 cage-like cluster is the same as that of 512 cage-like cluster. Although the methane molecule indeed makes the filled cage-like cluster more stable than the empty one, the empty cage-like cluster still has chance to be long-lived compared with the filled clusters. These observations support the labile cluster hypothesis on the formation mechanisms of gas hydrates.

  10. Direct phase coexistence molecular dynamics study of the phase equilibria of the ternary methane-carbon dioxide-water hydrate system.

    Science.gov (United States)

    Michalis, Vasileios K; Tsimpanogiannis, Ioannis N; Stubos, Athanassios K; Economou, Ioannis G

    2016-09-14

    Molecular dynamics simulation is used to predict the phase equilibrium conditions of a ternary hydrate system. In particular, the direct phase coexistence methodology is implemented for the determination of the three-phase coexistence temperature of the methane-carbon dioxide-water hydrate system at elevated pressures. The TIP4P/ice, TraPPE-UA and OPLS-UA forcefields for water, carbon dioxide and methane respectively are used, in line with our previous studies of the phase equilibria of the corresponding binary hydrate systems. The solubility in the aqueous phase of the guest molecules of the respective binary and ternary systems is examined under hydrate-forming conditions, providing insight into the predictive capability of the methodology as well as the combination of these forcefields to accurately describe the phase behavior of the ternary system. The three-phase coexistence temperature is calculated at 400, 1000 and 2000 bar for two compositions of the methane-carbon dioxide mixture. The predicted values are compared with available calculations with satisfactory agreement. An estimation is also provided for the fraction of the guest molecules in the mixed hydrate phase under the conditions examined.

  11. Isotopic composition of gypsum hydration water in deep Core SG-1, western Qaidam basin (NE Tibetan Plateau), implications for paleoclimatic evolution

    Science.gov (United States)

    Li, Jiao; Li, Minghui; Fang, Xiaomin; Zhang, Gengxin; Zhang, Weilin; Liu, Xiaoming

    2017-08-01

    The oxygen and hydrogen isotopic compositions of gypsum hydration water can be useful for determining the isotopic composition of the original brine from which gypsum precipitated. However, relatively few long-term and continuous records of the stable isotope geochemistry of gypsum hydration water in arid regions have been reported. We measured the δ18O and δD of primary gypsum hydration water from a 938.5 m-long deep core (SG-1) in the western Qaidam Basin to study the mechanisms that contributed to gypsum formation and to reconstruct potential paleoclimatic change. The measured δ18O and δD ranged from - 4.21‰ to 8.69‰ and from - 72.77‰ to 49.73‰, respectively. The linear relationship between δ18O and δD indicates that meteoric water was the original source of the gypsum hydration water. The gradient of 5.39 for the δ18O and δD plots is lower than that of global meteoric water, suggesting that paleo-lakewater evaporated and became a CaSO4-rich brine leading to gypsum deposition. The evaporation/precipitation (E/P) ratio played an important role in determining δ18O and δD. The oscillations noted in the δ18O and δD of the gypsum hydration water imply that: (a) there was a long-term and stepwise aridification after 2.2 Ma in the western Qaidam Basin; and (b) there were three increasingly dry phases at 2.2-1.2 Ma, 1.2-0.6 Ma, and 0.6-0.1 Ma, with two cold and dry events at 1 Ma and 0.6 Ma. Global cooling, especially during the Mid Pleistocene Climate Transition event (MPT), may have been the primary cause of the aridification recorded in core SG-1 in the Asian inland.

  12. Rapid gas hydrate formation process

    Science.gov (United States)

    Brown, Thomas D.; Taylor, Charles E.; Unione, Alfred J.

    2013-01-15

    The disclosure provides a method and apparatus for forming gas hydrates from a two-phase mixture of water and a hydrate forming gas. The two-phase mixture is created in a mixing zone which may be wholly included within the body of a spray nozzle. The two-phase mixture is subsequently sprayed into a reaction zone, where the reaction zone is under pressure and temperature conditions suitable for formation of the gas hydrate. The reaction zone pressure is less than the mixing zone pressure so that expansion of the hydrate-forming gas in the mixture provides a degree of cooling by the Joule-Thompson effect and provides more intimate mixing between the water and the hydrate-forming gas. The result of the process is the formation of gas hydrates continuously and with a greatly reduced induction time. An apparatus for conduct of the method is further provided.

  13. Overview: Nucleation of clathrate hydrates

    Science.gov (United States)

    Warrier, Pramod; Khan, M. Naveed; Srivastava, Vishal; Maupin, C. Mark; Koh, Carolyn A.

    2016-12-01

    Molecular level knowledge of nucleation and growth of clathrate hydrates is of importance for advancing fundamental understanding on the nature of water and hydrophobic hydrate formers, and their interactions that result in the formation of ice-like solids at temperatures higher than the ice-point. The stochastic nature and the inability to probe the small length and time scales associated with the nucleation process make it very difficult to experimentally determine the molecular level changes that lead to the nucleation event. Conversely, for this reason, there have been increasing efforts to obtain this information using molecular simulations. Accurate knowledge of how and when hydrate structures nucleate will be tremendously beneficial for the development of sustainable hydrate management strategies in oil and gas flowlines, as well as for their application in energy storage and recovery, gas separation, carbon sequestration, seawater desalination, and refrigeration. This article reviews various aspects of hydrate nucleation. First, properties of supercooled water and ice nucleation are reviewed briefly due to their apparent similarity to hydrates. Hydrate nucleation is then reviewed starting from macroscopic observations as obtained from experiments in laboratories and operations in industries, followed by various hydrate nucleation hypotheses and hydrate nucleation driving force calculations based on the classical nucleation theory. Finally, molecular simulations on hydrate nucleation are discussed in detail followed by potential future research directions.

  14. Occurrence of methane hydrate in saturated and unsaturated solutions of sodium chloride and water in dependence of temperature and pressure

    Energy Technology Data Exchange (ETDEWEB)

    de Roo, J.L.; Diepen, G.A.M.; Lichtenthaler, R.N.; Peters, C.J.

    1983-07-01

    Experimental results of the formation of methane hydrate in dependence of temperature and pressure in unsaturated solutions of NaCl in water will be presented in a temperature range from 261.85 to 285.98 K and pressure up to 11.0 MPa. Furthermore the four-phase equilibrium NaCl X 2H/sub 2/O /SUB s/ -CH/sub 4/ X nH/sub 2/O /SUB s/ -L-G has been calculated from the experimental results. Also the heats of transformation of several other equilibria in the ternary system CH/sub 4/-H/sub 2/O-NaCl are obtained.

  15. Determination of methane concentrations in water in equilibrium with sI methane hydrate in the absence of a vapor phase by in situ Raman spectroscopy

    Science.gov (United States)

    Lu, W.; Chou, I.-Ming; Burruss, R.C.

    2008-01-01

    Most submarine gas hydrates are located within the two-phase equilibrium region of hydrate and interstitial water with pressures (P) ranging from 8 to 60 MPa and temperatures (T) from 275 to 293 K. However, current measurements of solubilities of methane in equilibrium with hydrate in the absence of a vapor phase are limited below 20 MPa and 283.15 K, and the differences among these data are up to 30%. When these data were extrapolated to other P-T conditions, it leads to large and poorly known uncertainties. In this study, in situ Raman spectroscopy was used to measure methane concentrations in pure water in equilibrium with sI (structure one) methane hydrate, in the absence of a vapor phase, at temperatures from 276.6 to 294.6 (??0.3) K and pressures at 10, 20, 30 and 40 (??0.4%) MPa. The relationship among concentration of methane in water in equilibrium with hydrate, in mole fraction [X(CH4)], the temperature in K, and pressure in MPa was derived as: X(CH4) = exp [11.0464 + 0.023267 P - (4886.0 + 8.0158 P)/T]. Both the standard enthalpy and entropy of hydrate dissolution at the studied T-P conditions increase slightly with increasing pressure, ranging from 41.29 to 43.29 kJ/mol and from 0.1272 to 0.1330 kJ/K ?? mol, respectively. When compared with traditional sampling and analytical methods, the advantages of our method include: (1) the use of in situ Raman signals for methane concentration measurements eliminates possible uncertainty caused by sampling and ex situ analysis, (2) it is simple and efficient, and (3) high-pressure data can be obtained safely. ?? 2007 Elsevier Ltd. All rights reserved.

  16. Design of a High-Reynolds Number Recirculating Water Tunnel

    Science.gov (United States)

    Daniel, Libin; Elbing, Brian

    2014-11-01

    An experimental fluid mechanics laboratory focused on turbulent boundary layers, drag reduction techniques, multiphase flows and fluid-structure interactions has recently been established at Oklahoma State University. This laboratory has three primary components; (1) a recirculating water tunnel, (2) a multiphase pipe flow loop, and (3) a multi-scale flow visualization system. The design of the water tunnel is the focus of this talk. The criteria used for the water tunnel design was that it had to produce a momentum-thickness based Reynolds number in excess of 104, negligible flow acceleration due to boundary layer growth, maximize optical access for use of the flow visualization system, and minimize inlet flow non-uniformity. This Reynolds number was targeted to bridge the gap between typical university/commercial water tunnels (103) and the world's largest water tunnel facilities (105) . These objectives were achieved with a 152 mm (6-inch) square test section that is 1 m long and has a maximum flow speed of 10 m/s. The flow non-uniformity was mitigated with the use of a tandem honeycomb configuration, a settling chamber and an 8.5:1 contraction. The design process that produced this final design will be presented along with its current status.

  17. In Situ Characterization of Hydrated Proteins in Water by SALVI and ToF-SIMS

    Energy Technology Data Exchange (ETDEWEB)

    Yu, Jiachao; Zhou, Yufan; Hua, Xin; Zhu, Zihua; Yu, Xiao-Ying

    2016-01-01

    We demonstrate in situ chemical imaging of protein biomolecules in the aqueous solution using System for Analysis at the Liquid Vacuum Interface (SALVI) and time-of-flight secondary ion mass spectrometry (ToF-SIMS). The fibronectin protein film was immobilized on the silicon nitride (SiN) membrane forming the SALVI detection area. During ToF-SIMS analysis, three modes of analysis were conducted including high spatial resolution mass spectra, two-dimensional (2D) imaging, and depth profiling. Mass spectra were acquired in both positive and negative modes. Deionized water was also analyzed as a reference sample. Our results show that fibronectin film in water has more distinct and stronger water cluster peaks compared to water alone. Characteristic peaks of amino acid fragments are also observable in the hydrated protein ToF-SIMS spectra. These results illustrate that protein molecule adsorption on a surface can be studied dynamically using SALVI and ToF-SIMS in the liquid environment.

  18. Distribution of gas hydrate inhibitor monoethylene glycol in condensate and water systems: Experimental measurement and thermodynamic modeling using the cubic-plus-association equation of state

    DEFF Research Database (Denmark)

    Riaz, Muhammad; Yussuf, Mustafe A.; Frost, Michael

    2014-01-01

    hydrate formation in subsea pipelines, monoethylene glycol (MEG) and methanol are injected in large amounts. It is important to know the distribution of these chemicals in oil and water systems for economical operation of a production facility and environmental perspective. In this work, we present new......The deepwater energy sector represents one of the major growth areas of the oil and gas industry today. To meet the challenges of hydrate formation, corrosion, scaling, and foaming, the oil and gas industry uses many chemicals and their use has increased significantly over the years. To inhibit gas...

  19. Distinct role of hydration water in protein misfolding and aggregation revealed by fluctuating thermodynamics analysis.

    Science.gov (United States)

    Chong, Song-Ho; Ham, Sihyun

    2015-04-21

    decrease in solvation free energy, harnessing the monomer solvation free energy earned during the misfolding. The second step, where a compact dimer structure is formed, is driven by direct protein-protein interactions, but again it is accompanied by an increase in solvation free energy. The increased solvation free energy of the dimer will function as the driving force to recruit another Aβ protein in the approach stage of subsequent oligomerizations. The fluctuating thermodynamics analysis of the misfolding and dimerization of the Aβ protein indicates that the interaction of the protein with surrounding water plays a critical role in protein aggregation. Such a water-centric perspective is further corroborated by demonstrating that, for a large number of Aβ mutants and mutants of other protein systems, the change in the experimental aggregation propensity upon mutation has a significant correlation with the protein solvation free energy change. We also find striking discrimination between the positively and negatively charged residues on the protein surface by surrounding water molecules, which is shown to play a crucial role in determining the protein aggregation propensity. We argue that the protein total charge dictates such striking behavior of the surrounding water molecules. Our results provide new insights for understanding and predicting the protein aggregation propensity, thereby offering novel design principles for producing aggregation-resistant proteins for biotherapeutics.

  20. 2H and 13C NMR studies on the temperature-dependent water and protein dynamics in hydrated elastin, myoglobin and collagen.

    Science.gov (United States)

    Lusceac, Sorin A; Vogel, Michael R; Herbers, Claudia R

    2010-01-01

    (2)H NMR spin-lattice relaxation and line-shape analyses are performed to study the temperature-dependent dynamics of water in the hydration shells of myoglobin, elastin, and collagen. The results show that the dynamical behaviors of the hydration waters are similar for these proteins when using comparable hydration levels of h=0.25-0.43. Since water dynamics is characterized by strongly nonexponential correlation functions, we use a Cole-Cole spectral density for spin-lattice relaxation analysis, leading to correlation times, which are in nice agreement with results for the main dielectric relaxation process observed for various proteins in the literature. The temperature dependence can roughly be described by an Arrhenius law, with the possibility of a weak crossover in the vicinity of 220 K. Near ambient temperatures, the results substantially depend on the exact shape of the spectral density so that deviations from an Arrhenius behavior cannot be excluded in the high-temperature regime. However, for the studied proteins, the data give no evidence for the existence of a sharp fragile-to-strong transition reported for lysozyme at about 220 K. Line-shape analysis reveals that the mechanism for the rotational motion of hydration waters changes in the vicinity of 220 K. For myoglobin, we observe an isotropic motion at high temperatures and an anisotropic large-amplitude motion at low temperatures. Both mechanisms coexist in the vicinity of 220 K. (13)C CP MAS spectra show that hydration results in enhanced elastin dynamics at ambient temperatures, where the enhancement varies among different amino acids. Upon cooling, the enhanced mobility decreases. Comparison of (2)H and (13)C NMR data reveals that the observed protein dynamics is slower than the water dynamics.

  1. 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.

    Science.gov (United States)

    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+).

  2. The effects of silica fume and hydrated lime on the strength development and durability characteristics of concrete under hot water curing condition

    Directory of Open Access Journals (Sweden)

    Hamza Ali

    2017-01-01

    Full Text Available Sustainability is considered to be highly important for preserving continued industrial growth and human development. Concrete, being the world’s largest manufacturing material comprises cement as an essential binding component for strength development. However, excessive production of cement due to high degree of construction practices around the world frames cement as a leading pollutant of releasing significant amounts of CO2 in the atmosphere. To overcome this environmental degradation, silica fume and hydrated lime are used as partial replacements to cement. This paper begins with the examination of the partial replacement levels of hydrated lime and silica fume in concrete and their influence on the mechanical properties and durability characteristics of concrete. The effect of hot water curing on concrete incorporated with both silica fume and hydrated lime is also investigated in this paper. The results reported in this paper show that the use of silica fume as a partial replacement material improved both the mechanical properties and durability characteristics of concrete due to the formation of calcium silica hydrate crystals through the pozzolanic reaction. Although the hydrated lime did not significantly contribute in the development of strength, its presence enhanced the durability of concrete especially at long-term. The results also showed that hot water curing enhanced the strength development of concrete incorporated with silica fume due to the accelerated rate of both the hydration and pozzolanic reaction that takes place between silica fume and calcium hydroxide of the cement matrix particularly at early times. The results reported in this paper have significant contribution in the development of sustainable concrete. The paper does not only address the use of alternative binders as a partial replacement material in concrete but also suggest proper curing conditions for the proposed replacement materials. These practices

  3. Naphthenic acids hydrates of gases: influence of the water/oil interface on the dispersing properties of an acidic crude oil; Acides naphteniques hydrates de gaz de l'interface eau/huile sur les proprietes dispersantes d'un brut acide

    Energy Technology Data Exchange (ETDEWEB)

    Arla, D.

    2006-01-15

    Nowadays, the development of offshore oil production under increasing water depths (high pressures and low temperatures) has led oil companies to focus on gas hydrates risks. Hydrates are crystals containing gas and water molecules which can plug offshore pipelines. It has been shown that some asphaltenic crude oils stabilize water-in-oil emulsions (W/O) during several months and exhibit very good anti-agglomerant properties avoiding hydrate plugs formation. In this work, we have studied the 'anti-hydrate' properties of a West African acidic crude oil called crude AH. This oil contains naphthenic acids, RCOOH hydrocarbons which are sensitive to both the pH and the salinity of the water phase.The emulsifying properties of the crude AH have firstly been explored. It has been shown that heavy resins and asphaltenes are the main compounds of the crude AH responsible for the long term stability of the W/O emulsions whereas the napthenates RCOO{sup -} lead to less stable W/O emulsions. Dealing with hydrates, the crude AH exhibits moderate anti-agglomerant properties due to the presence of heavy resins and asphaltenes. However, the naphthenates RCOO{sup -} drastically increase the formation of hydrate plugs. Moreover, it has been pointed out that hydrate particles agglomeration accelerates the kinetics of hydrate formation and enhances the water/oil separation. In order to explain these behaviours, a mechanism of agglomeration by 'sticking' between a hydrate particle and a water droplet has been proposed. Finally, we have developed a model which describes the physico-chemical equilibria of the naphthenic acids in the binary system water/crude AH, in order to transpose the results obtained in the laboratory to the real oil field conditions. (author)

  4. EFFECT OF MAGNETIZATION OF WATER ON INDUCTION TIME AND GROWTH PERIOD OF NATURAL GAS HYDRATE

    Institute of Scientific and Technical Information of China (English)

    KUANG Li; FAN Shuanshi

    2003-01-01

    The effect of diluted solution's magnetization on induction time and growth period of natural gas hydrate (NGH) has been investigated in quiescent reaction system at pressure of 4. 5 MPa and temperature of 274 K with SDS as surfactant, by using volume fixed and pressure falling method. Experimental results show that magnetization will have effect on the induction time of NGH. After magnetization with magnetic field intensity of 0.33 T, the induction time of NGH has been reduced to 47 min (average) from 99 min (average) in which there is no magnetization. On the other hand, the induction time has been prolonged after magnetization of the diluted solution with magnetic field intensity of 0.05 T, 0. 11 T, 0.22 T, 0.44T. Especially with magnetic field intensity of 0.11 T, the induction time had even been prolonged to 431min (average). The effect of magnetization on the growth period of NGH has not been found at the experimental condition.

  5. Clinker mineral hydration at reduced relative humidities

    DEFF Research Database (Denmark)

    Jensen, Ole Mejlhede; Hansen, Per Freiesleben; Lachowski, Eric E.;

    1999-01-01

    Vapour phase hydration of purl cement clinker minerals at reduced relative humidities is described. This is relevant to modern high performance concrete that may self-desiccate during hydration and is also relevant to the quality of the cement during storage. Both the oretical considerations...... and experimental data are presented showing that C(3)A can hydrate at lower humidities than either C3S or C2S. It is suggested that the initiation of hydration during exposure to water vapour is nucleation controlled. When C(3)A hydrates at low humidity, the characteristic hydration product is C(3)AH(6...

  6. Using Gypsum Hydration Water to Quantitatively Estimate the Intensity of the Terminal Classic Drought in the Maya Lowlands

    Science.gov (United States)

    Gázquez, F.; Evans, N. P.; Bauska, T. K.; Hodell, D. A.

    2016-12-01

    Paleoclimate evidence suggests that drought coincided with the collapse of the lowland Classic Maya civilization between 800 and 1000 AD. However, attempts to quantitatively determine the magnitude of hydrologic change have met with mixed results. Several periods of gypsum deposition have been documented in Lake Chichancanab (Yucatan Peninsula, Mexico) sediment cores and interpreted as representing times of drought. Here we analyzed the triple oxygen (17O/16O, 18O/16O) and hydrogen (2H/1H) isotope ratios of the gypsum hydration water to obtain the δ18O, δD, 17O-excess, and d-excess of the lake water during the drought periods. By comparing these results to measurements made on the modern lake, rain and ground waters, we are able to better constrain the hydrological changes that occurred in the lake basin during the Terminal Classic Drought (TCD). During the TCD, the δ18O and δD of the lake water increased compared with modern values, whereas the 17O-excess, and d-excess decreased. The isotopic composition of lake water (δ17O, δ18O and δD, and derived d-excess and 17O-excess) is sensitive to changes in atmospheric relative humidity and temperature. We modeled the isotopic data and found the observed changes can be explained by a 10% reduction in relative humidity compared to modern conditions. This reduction in relative humidity was accompanied by a significant increase in evaporation over precipitation. Furthermore, we show that the driest period occurred during the early phase of the TCD (ca 770-870 AD) when the Classic Maya declined. Previous studies based on stalagmite δ18O records suggested that the greatest drought period occurred in the Postclassic Period (1020 and 1100 AD) and post-dated the collapse. Our findings from Lake Chichancanab suggest that the changes to the hydrological budget during the TCD were greater than those during the early Postclassic Period.

  7. Nanostructural analysis of water distribution in hydrated multicomponent gels using thermal analysis and NMR relaxometry.

    Science.gov (United States)

    Codoni, Doroty; Belton, Peter; Qi, Sheng

    2015-06-01

    Highly complex, multicomponent gels and water-containing soft materials have varied applications in biomedical, pharmaceutical, and food sciences, but the characterization of these nanostructured materials is extremely challenging. The aim of this study was to use stearoyl macrogol-32 glycerides (Gelucire 50/13) gels containing seven different species of glycerides, PEG, and PEG-esters, as model, complex, multicomponent gels, to investigate the effect of water content on the micro- and nanoarchitecture of the gel interior. Thermal analysis and NMR relaxometry were used to probe the thermal and diffusional behavior of water molecules within the gel network. For the highly concentrated gels (low water content), the water activity was significantly lowered due to entrapment in the dense gel network. For the gels with intermediate water content, multiple populations of water molecules with different thermal responses and diffusion behavior were detected, indicating the presence of water in different microenvironments. This correlated with the network architecture of the freeze-dried gels observed using SEM. For the gels with high water content, increased quantities of water with similar diffusion characteristics as free water could be detected, indicating the presence of large water pockets in these gels. The results of this study provide new insights into structure of Gelucire gels, which have not been reported before because of the complexity of the material. They also demonstrate that the combination of thermal analysis and NMR relaxometry offers insights into the structure of soft materials not available by the use of each technique alone. However, we also note that in some instances the results of these measurements are overinterpreted and we suggest limitations of the methods that must be considered when using them.

  8. Modelling membrane hydration and water balance of a pem fuel cell

    DEFF Research Database (Denmark)

    Liso, Vincenzo; Nielsen, Mads Pagh

    2015-01-01

    propose a novel mathematical zero-dimensional model for water mass balance of a polymer electrolyte membrane. Physical and electrochemical processes occurring in the membrane electrolyte are included; water adsorption/desorption phenomena are also considered. The effect of diffusivity, surface roughness...... and water content driving force is considered. We validate the model against experimental data. The water balance calculated by this model shows better fit with experimental data-points compared to other models such as the one by Springer et al.. We conclude that this discrepancy is due a different rate...

  9. Flare-Shaped Acoustic Anomalies in the Water Column Along the Ecuadorian Margin: Relationship with Active Tectonics and Gas Hydrates

    Science.gov (United States)

    Michaud, Francois; Proust, Jean-Noël; Dano, Alexandre; Collot, Jean-Yves; Guiyeligou, Grâce Daniella; Hernández Salazar, María José; Ratzov, Gueorgui; Martillo, Carlos; Pouderoux, Hugo; Schenini, Laure; Lebrun, Jean-Frederic; Loayza, Glenda

    2016-10-01

    With hull-mounted multibeam echosounder data, we report for the first time along the active Ecuadorian margin, acoustic signatures of water column fluid emissions and seep-related structures on the seafloor. In total 17 flare-shaped acoustic anomalies were detected from the upper slope (1250 m) to the shelf break (140 m). Nearly half of the flare-shaped acoustic anomalies rise 200-500 m above the seafloor. The base of the flares is generally associated with high-reflectivity backscatter patches contrasting with the neighboring seafloor. We interpret these flares as caused by fluid escape in the water column, most likely gases. High-resolution seismic profiles show that most flares occur close to the surface expression of active faults, deformed areas, slope instabilities or diapiric structures. In two areas tectonic deformation disrupts a Bottom Simulating Reflector (BSR), suggesting that buried frozen gas hydrates are destabilized, thus supplying free gas emissions and related flares. This discovery is important as it opens the way to determine the nature and origin of the emitted fluids and their potential link with the hydrocarbon system of the forearc basins along the Ecuadorian margin.

  10. Surfactants at Single-Walled Carbon Nanotube-Water Interface: Physics of Surfactants, Counter-Ions, and Hydration Shell

    Science.gov (United States)

    Khare, Ketan S.; Phelan, Frederick R., Jr.

    Specialized applications of single-walled carbon nanotubes (SWCNTs) require an efficient and reliable method to sort these materials into monodisperse fractions with respect to their defining metrics (chirality, length, etc.) while retaining their physical and chemical integrity. A popular method to achieve this goal is to use surfactants that individually disperse SWCNTs in water and then to separate the resulting colloidal mixture into fractions that are enriched in monodisperse SWCNTs. Recently, experiments at NIST have shown that subtle point mutations of chemical groups in bile salt surfactants have a large impact on the hydrodynamic properties of SWCNT-surfactant complexes during ultracentrifugation. These results provide strong motivation for understanding the rich physics underlying the assembly of surfactants around SWCNTs, the structure and dynamics of counter ions around the resulting complex, and propagation of these effects into the first hydration shell. Here, all-atom molecular dynamics simulations are used to investigate the thermodynamics of SWCNT-bile salt surfactant complexes in water with an emphasis on the buoyant characteristics of the SWCNT-surfactant complexes. Simulation results will be presented along with a comparison with experimental data. Official contribution of the National Institute of Standards and Technology; not subject to copyright in the United States.

  11. Structure of the ordered hydration of amino acids in proteins: analysis of crystal structures

    Energy Technology Data Exchange (ETDEWEB)

    Biedermannová, Lada, E-mail: lada.biedermannova@ibt.cas.cz; Schneider, Bohdan [Institute of Biotechnology CAS, Videnska 1083, 142 20 Prague (Czech Republic)

    2015-10-27

    The hydration of protein crystal structures was studied at the level of individual amino acids. The dependence of the number of water molecules and their preferred spatial localization on various parameters, such as solvent accessibility, secondary structure and side-chain conformation, was determined. Crystallography provides unique information about the arrangement of water molecules near protein surfaces. Using a nonredundant set of 2818 protein crystal structures with a resolution of better than 1.8 Å, the extent and structure of the hydration shell of all 20 standard amino-acid residues were analyzed as function of the residue conformation, secondary structure and solvent accessibility. The results show how hydration depends on the amino-acid conformation and the environment in which it occurs. After conformational clustering of individual residues, the density distribution of water molecules was compiled and the preferred hydration sites were determined as maxima in the pseudo-electron-density representation of water distributions. Many hydration sites interact with both main-chain and side-chain amino-acid atoms, and several occurrences of hydration sites with less canonical contacts, such as carbon–donor hydrogen bonds, OH–π interactions and off-plane interactions with aromatic heteroatoms, are also reported. Information about the location and relative importance of the empirically determined preferred hydration sites in proteins has applications in improving the current methods of hydration-site prediction in molecular replacement, ab initio protein structure prediction and the set-up of molecular-dynamics simulations.

  12. Effects of the water level hydrated in NMMO on the physical properties of cellulose fiber in dry jet-wet spinning

    Energy Technology Data Exchange (ETDEWEB)

    Kim, D.B.; Lee, W.S.; Kim, B.C.; Jo, S.M.; Park, J.S. [Korea Institute of Science and Technology, Seoul (Korea, Republic of); Lee, Y.M. [Hanyang University, Seoul (Korea, Republic of)

    1998-03-01

    The effects of the amount of water hydrated in N-methylmorpholine N-oxide (NMMO) in dry jet-wet spinning of cellulose was investigated in terms of rheological properties of the spinning dope and the physical properties of the fiber. At the identical polymer concentration of 12 wt%, the solution of cellulose in 90.4 wt% NMMO gave higher viscosity and higher storage modulus (G`) than that in 86.7 wt% NMMO, which was more noticeable at 110 {sup o} C than at 12 {sup o} C. Decrease in the hydrated water level or increase in the air-gap or spin draw ratio increased such physical properties of the fiber as birefringence, initial modulus and tensile strength. The tensile fractured morphology revealed that the fiber from NMMO containing less water gave more fibrils resulting from higher orientation. Further, it produced thicker and longer fibrils when treated with an ultrasonic generator.

  13. Modelling membrane hydration and water balance of a pem fuel cell

    DEFF Research Database (Denmark)

    Liso, Vincenzo; Nielsen, Mads Pagh

    2015-01-01

    and water content driving force is considered. We validate the model against experimental data. The water balance calculated by this model shows better fit with experimental data-points compared to other models such as the one by Springer et al.. We conclude that this discrepancy is due a different rate...

  14. Water exchange at a hydrated platinum electrode is rare and collective

    CERN Document Server

    Limmer, David T; Madden, Paul A; Chandler, David

    2015-01-01

    We use molecular dynamics simulations to study the exchange kinetics of water molecules at a model metal electrode surface -- exchange between water molecules in the bulk liquid and water molecules bound to the metal. This process is a rare event, with a mean residence time of a bound water of about 40 ns for the model we consider. With analysis borrowed from the techniques of rare-event sampling, we show how this exchange or desorption is controlled by (1) reorganization of the hydrogen bond network within the adlayer of bound water molecules, and by (2) interfacial density fluctuations of the bulk liquid adjacent to the adlayer. We define collective coordinates that describe the desorption mechanism. Spatial and temporal correlations associated with a single event extend over nanometers and tens of picoseconds.

  15. Hydration behaviour of polyhydroxylated fullerenes

    Energy Technology Data Exchange (ETDEWEB)

    Rodriguez-Zavala, J G [Departamento de Ciencias Exactas y Tecnologicas, Centro Universitario de Los Lagos, Universidad de Guadalajara, Enrique Diaz de Leon S/N, 47460 Jalisco (Mexico); Barajas-Barraza, R E [Departamento de Matematicas y Fisica, Instituto Tecnologico y de Estudios Superiores de Occidente, Periferico Sur, Manuel Gomez MorIn No 8585, 45604 Jalisco (Mexico); Padilla-Osuna, I; Guirado-Lopez, R A, E-mail: jgrz@culagos.udg.mx, E-mail: ebarajas@iteso.mx, E-mail: ismael@ifisica.uaslp.mx, E-mail: guirado@ifisica.uaslp.mx [Instituto de Fisica ' Manuel Sandoval Vallarta' , Universidad Autonoma de San Luis Potosi, Alvaro Obregon 64, 78000 San Luis Potosi (Mexico)

    2011-10-28

    We have performed semi-empirical as well as density functional theory calculations in order to analyse the hydration properties of both bare C{sub 60} and highly hydroxylated C{sub 60}(OH){sub 26} fullerenes. In all of our calculations, a total of 42 and 98 water molecules are always surrounding our here-considered carbon nanostructures. We found different wetting properties as a function of the chemical composition and structure of the OH-molecular over-layer covering the fullerene surface. In the case of bare C{sub 60}, water adsorption reveals that the H{sub 2}O species are not uniformly arranged around the carbon network but rather forms water droplets of different sizes, clearly revealing the hydrophobic nature of the C{sub 60} structure. In contrast, in the polyhydroxylated C{sub 60}(OH){sub 26} fullerenes, the degree of wetting is strongly influenced by the precise location of the hydroxyl groups. We found that different adsorbed configurations for the OH-molecular coating can lead to the formation of partially hydrated or completely covered C{sub 60}(OH){sub 26} compounds, a result that could be used to synthesize fullerene materials with different degrees of wettability. By comparing the relative stability of our hydroxylated structures in both bare and hydrated conditions we obtain that the energy ordering of the C{sub 60}(OH){sub 26} isomers can change in the presence of water. The radial distribution function of our hydrated fullerenes reveals that water near these kinds of surfaces is densely packed. In fact, by counting the number of H{sub 2}O molecules which are adsorbed, by means of hydrogen bonds, to the surface of our more stable C{sub 60}(OH){sub 26} isomer, we found that it varies in the range of 5-10, in good agreement with experiments. Finally, by comparing the calculated optical absorption spectra of various C{sub 60}(OH){sub 26} structures in the presence and absence of water molecules, we note that only slight variations in the position and

  16. A new combined nanoSIMS and continuous-flow IRMS approach to measure hydrogen isotopes from water in hydrated rhyolitic glass

    Science.gov (United States)

    Gatti, E.; Kitchen, N.; Newman, S.; Guan, Y.; Westgate, J.; Pearce, N. J. G.; Nikolic, D.; Eiler, J. M.

    2016-12-01

    The hydrogen-isotope value of water of hydration (or secondary water) preserved in rhyolitic glasses may provide significant insights regarding the climate at the time of their deposition and the impact of super-eruptions upon the environment. However, the ability of the glass to retain the environmental D/H isotopic signal after hydration needs to be tested, since modifications to the D/H systematics may result from the continuous exchange of D/H with the atmosphere or condensed water after initial glass hydration. Ideal geological archives to test whether the glass retains its original hydrogen signal are sediments in natural waters and ice cores, which preserve tephra in constrained horizons that can be independently isotopically characterised. However, tephra in marine and fresh water sediments and ice cores are often present in concentrations of the order of 1000 grains/cm3 (3 wt%) or 15 mg of dry ( 0.5 wt%) obsidian chips. The method can be improved by reducing the blank to <1 nmol/min and reducing capillary empty space. The bulk results obtained with the continuous-flow IRMS method will be compared to sub-micron mapping of single-grains using a high-resolution ion microprobe, the CAMECA NanoSIMS 50L, in the Microanalysis Center for Geochemistry and Cosmochemistry at California Institute of Technology, in order to define the reliability of the bulk method and assess natural variability within and among grains.

  17. Communication: Librational dynamics in water, sI and sII clathrate hydrates, and ice Ih: Molecular-dynamics insights.

    Science.gov (United States)

    Burnham, Christian J; English, Niall J

    2016-02-01

    Equilibrium molecular-dynamics simulations have been performed for liquid water, and on metastable sI and sII polymorphs of empty hydrate lattices, in addition to ice Ih, in order to study the dynamical properties of librational motion (rotation oscillation) depicted by protons in water molecules. In particular, hydrate lattices were found to display prominent "bifurcated" features, or peaks, at circa 70 and 80-95 meV (or ∼560 and 640-760 cm(-1), respectively), also displayed by ice, in essentially quantitative agreement with experimental neutron-scattering data. However, observed differences in dispersion between these librational modes between these two structures (both hydrate polymorphs vis-à-vis ice), owing primarily to density effects, have been decomposed into contributions arising from angular-velocity dynamics about axes in the local molecular frame of water molecules, with in-plane "wagging" and "twisting" rationalising one mode at ∼70 meV, and out-of-plane motion for the higher-frequency band. This was confirmed explicitly by a type of de facto normal-mode analysis, in which only immediate layers of water molecules about the one under consideration were allowed to move. In contrast, liquid water displayed no marked preference for such local in- or out-of-plane modes characterising librational motion, owing to the marked absence of rigid, pentamers or hexamers therein.

  18. Communication: Librational dynamics in water, sI and sII clathrate hydrates, and ice Ih: Molecular-dynamics insights

    Science.gov (United States)

    Burnham, Christian J.; English, Niall J.

    2016-02-01

    Equilibrium molecular-dynamics simulations have been performed for liquid water, and on metastable sI and sII polymorphs of empty hydrate lattices, in addition to ice Ih, in order to study the dynamical properties of librational motion (rotation oscillation) depicted by protons in water molecules. In particular, hydrate lattices were found to display prominent "bifurcated" features, or peaks, at circa 70 and 80-95 meV (or ˜560 and 640-760 cm-1, respectively), also displayed by ice, in essentially quantitative agreement with experimental neutron-scattering data. However, observed differences in dispersion between these librational modes between these two structures (both hydrate polymorphs vis-à-vis ice), owing primarily to density effects, have been decomposed into contributions arising from angular-velocity dynamics about axes in the local molecular frame of water molecules, with in-plane "wagging" and "twisting" rationalising one mode at ˜70 meV, and out-of-plane motion for the higher-frequency band. This was confirmed explicitly by a type of de facto normal-mode analysis, in which only immediate layers of water molecules about the one under consideration were allowed to move. In contrast, liquid water displayed no marked preference for such local in- or out-of-plane modes characterising librational motion, owing to the marked absence of rigid, pentamers or hexamers therein.

  19. Effects of rooibos tea, bottled water, and a carbohydrate beverage on blood and urinary measures of hydration after acute dehydration.

    Science.gov (United States)

    Utter, Alan C; Quindry, John C; Emerenziani, Gian Pietro; Valiente, J Scott

    2010-04-01

    Rooibos tea contains polyphenol antioxidants, including flavonoids and phenolic acids that are potent free radical scavengers and has purported benefits for accelerated rehydration. The objective was to evaluate the effects of three different drinks (rooibos tea, bottled water, and a carbohydrate beverage) on blood and urinary markers of hydration after acute dehydration in collegiate wrestlers. Twenty-three athletes were recruited and followed a randomized, cross-over design with three different study arms comparing the effectiveness of rooibos tea, carbohydrate beverage (6% or 60 grams l(-1)), or bottled water (placebo) in promoting rehydration after a 3% reduction in body mass. Urine specific gravity (U(sg)) urine (U(osm)) and plasma osmolarity (P(osm)), and plasma volume were measured pre- and post dehydration and at 1-h after rehydration. Statistical analyses utilized a 3 (conditions) x 3 (times) repeated measures analysis of variance to test main effects. Significant interaction effects were found for P(osm) and U(osm), both of which remained below basleline after 1-h rehydration in the rooibos tea and water trials. No significant interaction effects were found for either urine U(sg) or plasma volume shift. The findings of this study demonstrate that rooibos tea was no more effective in promoting rehydration than plain water, with significant changes being found for P(osm) and U(osm) in the carbohydrate/electrolyte solution, in collegiate wrestlers after a 3% reduction in body mass and a rehydration period of 1-h when consuming 100% of their body weight loss.

  20. Investigating syn- vs. post-eruption hydration mechanisms of the 2012 Havre submarine explosive eruption: Water speciation analysis of pumiceous rhyolitic glass

    Science.gov (United States)

    Mitchell, S. J.; McIntosh, I. M.; Houghton, B. F.; Shea, T.; Carey, R.

    2016-12-01

    Volatiles preserved in volcanic glass can record the quenching, fragmentation and solubility conditions during an explosive eruption. The VEI-5 2012 eruption of Havre volcano, which produced >1.5 km3 of rhyolite, provides exciting new insight into deep-submarine explosive eruptions. With no direct observations of the eruption at the 900 mbsl vent, the analysis and interpretation of volatile concentrations and speciation within pyroclasts is essential to constraining the eruption style and quenching mechanisms in this understudied environment. We present here the first detailed water speciation data for a large submarine explosive eruption. Water concentrations were measured in pyroclasts from known deposit localities across the Havre stratigraphic succession after ROV collection in 2015. Variations in total water concentration (H2OT) within pyroclasts were determined using high spatial resolution (1 - 2 µm) micro-Raman spectroscopy and water speciation (molecular water (H2Om) and OH) concentrations were measured using Fourier-transform infrared spectroscopy. H2OT concentrations are consistent between Raman and FTIR analysis, ranging from 0.1 - 1.5 wt % H2OT over different stratigraphic units. Comparison of water speciation data with speciation models suggests the Havre pyroclasts experienced secondary, non-magmatic hydration. Since OH is unaltered by secondary hydration, OH concentrations aid in the interpretation of quench depths and inferring of eruption mechanisms. The variability of excess H2Om across units suggests a more complex glass-hydration mechanism during the eruption instead of exclusively post-eruption, low-temperature secondary rehydration. The young sample ages are inconsistent with our current understanding of low-temperature H2O-diffusivity timescales, implying faster secondary rehydration in a higher-temperature submarine setting. We here explore potentially novel syn-eruptive, higher-temperature hydration mechanisms for deep-submarine pumice.

  1. Water in the hydration shell of halide ions has significantly reduced Fermi resonance and moderately enhanced Raman cross section in the OH stretch regions.

    Science.gov (United States)

    Ahmed, Mohammed; Singh, Ajay K; Mondal, Jahur A; Sarkar, Sisir K

    2013-08-22

    Water in the presence of electrolytes plays an important role in biological and industrial processes. The properties of water, such as the intermolecular coupling, Fermi resonance (FR), hydrogen-bonding, and Raman cross section were investigated by measuring the Raman spectra in the OD and OH stretch regions in presence of alkali halides (NaX; X = F, Cl, Br, I). It is observed that the changes in spectral characteristics by the addition of NaX in D2O are similar to those obtained by the addition of H2O in D2O. The spectral width decreases significantly by the addition of NaX in D2O (H2O) than that in the isotopically diluted water. Quantitative estimation, on the basis of integrated Raman intensity, revealed that the relative Raman cross section, σ(H)/σ(b) (σ(H) and σ(b) are the average Raman cross section of water in the first hydration shell of X(-) and in bulk, respectively), in D2O and H2O is higher than those in the respective isotopically diluted water. These results suggest that water in the hydration shell has reduced FR and intermolecular coupling compared to those in bulk. In the isotopically diluted water, the relative Raman cross section increases with increase in size of the halide ions (σ(H)/σ(b) = 0.6, 1.1, 1.5, and 1.9 for F(-), Cl(-), Br(-), and I(-), respectively), which is assignable to the enhancement of Raman cross section by charge transfer from halide ions to the hydrating water. Nevertheless, the experimentally determined σ(H)/σ(b) is lower than the calculated values obtained on the basis of the energy of the charge transfer state of water. The weak enhancement of σ(H)/σ(b) signifies that the charge transfer transition in the hydration shell of halide ions causes little change in the OD (OH) bond lengths of hydrating water.

  2. Hydration of AN Acid Anhydride: the Water Complex of Acetic Sulfuric Anhydride

    Science.gov (United States)

    Smith, CJ; Huff, Anna; Mackenzie, Becca; Leopold, Ken

    2017-06-01

    The water complex of acetic sulfuric anhydride (ASA, CH_{3}COOSO_{2}OH) has been observed by pulsed nozzle Fourier transform microwave spectroscopy. ASA is formed in situ in the supersonic jet via the reaction of SO_{3} and acetic acid and subsequently forms a complex with water during the expansion. Spectra of the parent and fully deuterated form, as well as those of the species derived from CH_{3}^{13}COOH, have been observed. The fitted internal rotation barrier of the methyl group is 219.599(21), \\wn indicating the complexation with water lowers the internal rotation barrier of the methyl group by 9% relative to that of free ASA. The observed species is one of several isomers identified theoretically in which the water inserts into the intramolecular hydrogen bond of the ASA. Aspects of the intermolecular potential energy surface are discussed.

  3. Gas hydrates forming and decomposition conditions analysis

    Directory of Open Access Journals (Sweden)

    А. М. Павленко

    2017-07-01

    Full Text Available The concept of gas hydrates has been defined; their brief description has been given; factors that affect the formation and decomposition of the hydrates have been reported; their distribution, structure and thermodynamic conditions determining the gas hydrates formation disposition in gas pipelines have been considered. Advantages and disadvantages of the known methods for removing gas hydrate plugs in the pipeline have been analyzed, the necessity of their further studies has been proved. In addition to the negative impact on the process of gas extraction, the hydrates properties make it possible to outline the following possible fields of their industrial use: obtaining ultrahigh pressures in confined spaces at the hydrate decomposition; separating hydrocarbon mixtures by successive transfer of individual components through the hydrate given the mode; obtaining cold due to heat absorption at the hydrate decomposition; elimination of the open gas fountain by means of hydrate plugs in the bore hole of the gushing gasser; seawater desalination, based on the hydrate ability to only bind water molecules into the solid state; wastewater purification; gas storage in the hydrate state; dispersion of high temperature fog and clouds by means of hydrates; water-hydrates emulsion injection into the productive strata to raise the oil recovery factor; obtaining cold in the gas processing to cool the gas, etc.

  4. [Hydration in clinical practice].

    Science.gov (United States)

    Maristany, Cleofé Pérez-Portabella; Segurola Gurruchaga, Hegoi

    2011-01-01

    Water is an essential foundation for life, having both a regulatory and structural function. The former results from active and passive participation in all metabolic reactions, and its role in conserving and maintaining body temperature. Structurally speaking it is the major contributer to tissue mass, accounting for 60% of the basis of blood plasma, intracellular and intersticial fluid. Water is also part of the primary structures of life such as genetic material or proteins. Therefore, it is necessary that the nurse makes an early assessment of patients water needs to detect if there are signs of electrolyte imbalance. Dehydration can be a very serious problem, especially in children and the elderly. Dehydrations treatment with oral rehydration solution decreases the risk of developing hydration disorders, but even so, it is recommended to follow preventive measures to reduce the incidence and severity of dehydration. The key to having a proper hydration is prevention. Artificial nutrition encompasses the need for precise calculation of water needs in enteral nutrition as parenteral, so the nurse should be part of this process and use the tools for calculating the patient's requirements. All this helps to ensure an optimal nutritional status in patients at risk. Ethical dilemmas are becoming increasingly common in clinical practice. On the subject of artificial nutrition and hydration, there isn't yet any unanimous agreement regarding hydration as a basic care. It is necessary to take decisions in consensus with the health team, always thinking of the best interests of the patient.

  5. Constraints of gas venting activity for the interstitial water geochemistry at the shallow gas hydrate site, eastern margin of the Japan Sea; results from high resolution time-series fluid sampling by OsmoSampler

    Science.gov (United States)

    Owari, S.; Tomaru, H.; Matsumoto, R.

    2016-12-01

    We have conducted ROV researches in the eastern margin of the Japan Sea where active gas venting and outcropping of gas hydrates were observed near the seafloor and have found the strength and location of venting had changed within a few days. These observations indicate the seafloor environments with the shallow gas hydrate system could have changed for short period compared to a geological time scale. We have applied a long-term osmotic fluid sampling system "OsmoSampler" on the active gas hydrate system for one year in order to document how the gas venting and gas hydrate activity have changed the geochemical environments near the seafloor. All the major ion concentrations in the interstitial water show synchronous increase and decrease repeatedly in three to five days, reflecting the incorporation and release of fresh water in gas hydrates in response to the gas concentration change near the sampling site. Dissolved methane concentration increases rapidly and excessively (over several mM) in the first 40 days corresponding to the active gas venting. The increases of methane concentration are often associated with high ion concentration during high water pressure period, indicating excess gas release from shallow gas pockets. Contrarily, enhanced gas hydrate growth may plug the fluid-gas paths in shallow sediment, reducing gas hydrate formation due to the decrease of methane flux. This study was conducted under the commission from AIST as a part of the methane hydrate research project funded by METI (the Ministry of Economy, Trade and Industry, Japan).

  6. Drilling Gas Hydrates on hydrate Ridge, Oregon continental margin

    Science.gov (United States)

    Trehu, A. M.; Bohrmann, G.; Leg 204 Science Party

    2002-12-01

    During Leg 204, we cored and logged 9 sites on the Oregon continental margin to determine the distribution and concentration of gas hydrates in an accretionary ridge and adjacent slope basin, investigate the mechanisms that transport methane and other gases into the gas hydrate stability zone (GHSZ), and obtain constraints on physical properties of hydrates in situ. A 3D seismic survey conducted in 2000 provided images of potential subsurface fluid conduits and indicated the position of the GHSZ throughout the survey region. After coring the first site, we acquired Logging-While-Drilling (LWD) data at all but one site to provide an overview of downhole physical properties. The LWD data confirmed the general position of key seismic stratigraphic horizons and yielded an initial estimate of hydrate concentration through the proxy of in situ electrical resistivity. These records proved to be of great value in planning subsequent coring. The second new hydrate proxy to be tested was infrared thermal imaging of cores on the catwalk as rapidly as possible after retrieval. The thermal images were used to identify hydrate samples and to estimate the distribution and texture of hydrate within the cores. Geochemical analyses of interstitial waters and of headspace and void gases provide additional information on the distribution and concentration of hydrate within the stability zone, the origin and pathway of fluids into and through the GHSZ, and the rates at which gas hydrate is forming. Bio- and lithostratigraphic description of cores, measurement of physical properties, and in situ pressure core sampling and thermal measurements complement the data set, providing ground-truth tests of inferred physical and sedimentological properties. Among the most interesting preliminary results are: 1) that gas hydrates are distributed through a broad depth range within the GHSZ and that different physical and chemical proxies for hydrate distribution and concentration give generally

  7. Hydration in Lipid Monolayers: Correlation of Water Activity and Surface Pressure.

    Science.gov (United States)

    Disalvo, E Anibal; Hollmann, Axel; Martini, M Florencia

    2015-01-01

    In order to give a physical meaning to each region of the membrane we define the interphase as the region in a lipid membrane corresponding to the polar head groups imbibed in water with net different properties than the hydrocarbon region and the water phase. The interphase region is analyzed under the scope of thermodynamics of surface and solutions based on the definition of Defay-Prigogine of an interphase and the derivation that it has in the understanding of membrane processeses in the context of biological response. In the view of this approach, the complete monolayer is considered as the lipid layer one molecule thick plus the bidimensional solution of the polar head groups inherent to it (the interphase region). Surface water activity appears as a common factor for the interaction of several aqueous soluble and surface active proteins with lipid membranes of different composition. Protein perturbation can be measured by changes in the surface pressure of lipid monolayers at different initial water surface activities. As predicted by solution chemistry, the increase of surface pressure is independent of the particle nature that dissolves. Therefore, membranes give a similar response in terms of the determined surface states given by water activity independent of the protein or peptide.

  8. Water reorientation in the hydration shells of hydrophilic and hydrophobic solutes

    Institute of Scientific and Technical Information of China (English)

    LAAGE; Damien; STIRNEMANN; Guillaume; HYNES; James; T.

    2010-01-01

    We discuss some key aspects of our recent theoretical work on water reorientation dynamics,which is important in a wide range of phenomena,including aqueous phase chemical reactions,protein folding,and drug binding to proteins and DNA. It is shown that,contrary to the standard conception that these dynamics are diffusional,the reorientation of a water molecule occurs by sudden,large amplitude angular jumps. The mechanism involves the exchange of one hydrogen bond for another by the reorienting water,and the process can be fruitfully viewed as a chemical reaction. The results for reorientation times,which can be well described analytically,are discussed in the context of the molecular level interpretation of recent ultrafast infrared spectroscopic results,focusing on the concepts of structure making/breaking and solvent ’icebergs’.

  9. Hydrated goethite (alpha-FeOOH) (100) interface structure: Ordered water and surface functional groups.

    Energy Technology Data Exchange (ETDEWEB)

    Ghose, S.K.; Waychunas, G.A.; Trainor, T.P.; Eng, P.J.

    2009-12-15

    Goethite({alpha}-FeOOH), an abundant and highly reactive iron oxyhydroxide mineral, has been the subject of numerous stud-ies of environmental interface reactivity. However, such studies have been hampered by the lack of experimental constraints on aqueous interface structure, and especially of the surface water molecular arrangements. Structural information of this type is crucial because reactivity is dictated by the nature of the surface functional groups and the structure or distribution of water and electrolyte at the solid-solution interface. In this study we have investigated the goethite(100) surface using surface diffraction techniques, and have determined the relaxed surface structure, the surface functional groups, and the three dimensional nature of two distinct sorbed water layers. The crystal truncation rod (CTR) results show that the interface structure consists of a double hydroxyl, double water terminated interface with significant atom relaxations. Further, the double hydroxyl terminated surface dominates with an 89% contribution having a chiral subdomain structure on the(100) cleavage faces. The proposed interface stoichiometry is ((H{sub 2}O)-(H{sub 2}O)-OH{sub 2}-OH-Fe-O-O-Fe-R) with two types of terminal hydroxyls; a bidentate (B-type) hydroxo group and a monodentate (A-type) aquo group. Using the bond-valence approach the protonation states of the terminal hydroxyls are predicted to be OH type (bidentate hydroxyl with oxygen coupled to two Fe{sup 3+} ions) and OH{sub 2} type (monodentate hydroxyl with oxygen tied to only one Fe{sup 3+}). A double layer three dimensional ordered water structure at the interface was determined from refinement of fits to the experimental data. Application of bond-valence constraints to the terminal hydroxyls with appropriate rotation of the water dipole moments allowed a plausible dipole orientation model as predicted. The structural results are discussed in terms of protonation and H-bonding at the interface

  10. Gas hydrates

    Digital Repository Service at National Institute of Oceanography (India)

    Ramprasad, T.

    and the role it plays in the global climate and the future of fuels. Russia, Japan, Nigeria, Peru, Chile, Pakistan, Indonesia, Korea, etc are various countries who are perusing the gas hydrates studies as a future resource for fuel. Indian Initiative..., 1993, Free gas at the base of the gas hydrate zone in the vicinity of the Chile Triple junction: Geology, v. 21, pp. 905-908. Borowski, W.S., C.K. Paull, and U. William, III, 1999, Global and local variations of interstitial sulfate gradients...

  11. 甲烷水合物在纯水和抑制剂体系中的生成动力学%Kinetics of Methane Hydrate Formation in Pure Water and Inhibitor Containing Systems

    Institute of Scientific and Technical Information of China (English)

    裘俊红; 郭天民

    2002-01-01

    Kinetic data of methane hydrate formation in the presence of pure water, brines with single salt and mixed salts, and aqueous solutions of ethylene glycol(EG) and salt+EG were measured. A new kinetic model of hydrate formation for the methane-Fwater systems was developed based on a four-step formation mechanism and reaction kinetics approach. The proposed kinetic model predicts the kinetic behavior of methane hydrate formation in pure water with good accuracy. The feasibility of extending the kinetic model to salt(s) and EG containing systems was explored.

  12. Comparison of coconut water and a carbohydrate-electrolyte sport drink on measures of hydration and physical performance in exercise-trained men

    Directory of Open Access Journals (Sweden)

    Kalman Douglas S

    2012-01-01

    Full Text Available Abstract Background Sport drinks are ubiquitous within the recreational and competitive fitness and sporting world. Most are manufactured and artificially flavored carbohydrate-electrolyte beverages. Recently, attention has been given to coconut water, a natural alternative to manufactured sport drinks, with initial evidence indicating efficacy with regard to maintaining hydration. We compared coconut water and a carbohydrate-electrolyte sport drink on measures of hydration and physical performance in exercise-trained men. Methods Following a 60-minute bout of dehydrating treadmill exercise, 12 exercise-trained men (26.6 ± 5.7 yrs received bottled water (BW, pure coconut water (VitaCoco®: CW, coconut water from concentrate (CWC, or a carbohydrate-electrolyte sport drink (SD [a fluid amount based on body mass loss during the dehydrating exercise] on four occasions (separated by at least 5 days in a random order, single blind (subject and not investigators, cross-over design. Hydration status (body mass, fluid retention, plasma osmolality, urine specific gravity and performance (treadmill time to exhaustion; assessed after rehydration were determined during the recovery period. Subjective measures of thirst, bloatedness, refreshed, stomach upset, and tiredness were also determined using a 5-point visual analog scale. Results Subjects lost approximately 1.7 kg (~2% of body mass during the dehydrating exercise and regained this amount in a relatively similar manner following consumption of all conditions. No differences were noted between coconut water (CW or CWC and SD for any measures of fluid retention (p > 0.05. Regarding exercise performance, no significant difference (p > 0.05 was noted between BW (11.9 ± 5.9 min, CW (12.3 ± 5.8 min, CWC (11.9 ± 6.0 min, and SD (12.8 ± 4.9 min. In general, subjects reported feeling more bloated and experienced greater stomach upset with the CW and CWC conditions. Conclusion All tested beverages are

  13. Mean-Field Approximation to the Hydrophobic Hydration in the Liquid-Vapor Interface of Water.

    Science.gov (United States)

    Abe, Kiharu; Sumi, Tomonari; Koga, Kenichiro

    2016-03-03

    A mean-field approximation to the solvation of nonpolar solutes in the liquid-vapor interface of aqueous solutions is proposed. It is first remarked with a numerical illustration that the solvation of a methane-like solute in bulk liquid water is accurately described by the mean-field theory of liquids, the main idea of which is that the probability (Pcav) of finding a cavity in the solvent that can accommodate the solute molecule and the attractive interaction energy (uatt) that the solute would feel if it is inserted in such a cavity are both functions of the solvent density alone. It is then assumed that the basic idea is still valid in the liquid-vapor interface, but Pcav and uatt are separately functions of different coarse-grained local densities, not functions of a common local density. Validity of the assumptions is confirmed for the solvation of the methane-like particle in the interface of model water at temperatures between 253 and 613 K. With the mean-field approximation extended to the inhomogeneous system the local solubility profiles across the interface at various temperatures are calculated from Pcav and uatt obtained at a single temperature. The predicted profiles are in excellent agreement with those obtained by the direct calculation of the excess chemical potential over an interfacial region where the solvent local density varies most rapidly.

  14. Ductile flow of methane hydrate

    Science.gov (United States)

    Durham, W.B.; Stern, L.A.; Kirby, S.H.

    2003-01-01

    Compressional creep tests (i.e., constant applied stress) conducted on pure, polycrystalline methane hydrate over the temperature range 260-287 K and confining pressures of 50-100 MPa show this material to be extraordinarily strong compared to other icy compounds. The contrast with hexagonal water ice, sometimes used as a proxy for gas hydrate properties, is impressive: over the thermal range where both are solid, methane hydrate is as much as 40 times stronger than ice at a given strain rate. The specific mechanical response of naturally occurring methane hydrate in sediments to environmental changes is expected to be dependent on the distribution of the hydrate phase within the formation - whether arranged structurally between and (or) cementing sediments grains versus passively in pore space within a sediment framework. If hydrate is in the former mode, the very high strength of methane hydrate implies a significantly greater strain-energy release upon decomposition and subsequent failure of hydrate-cemented formations than previously expected.

  15. Free Radical Chemistry of Disinfection Byproducts 1: Kinetics of Hydrated Electron and Hydroxyl Radical Reactions with Halonitromethanes in Water

    Energy Technology Data Exchange (ETDEWEB)

    B. J. Mincher; R. V. Fox; S. P. Mezyk; T. Helgeson; S. K. Cole; W. J. Cooper; P. R. Gardinali

    2006-01-01

    Halonitromethanes are disinfection-byproducts formed during ozonation and chlorine/chloramine treatment of waters that contain bromide ion and natural organic matter. In this study, the chemical kinetics of the free-radical-induced degradations of a series of halonitromethanes were determined. Absolute rate constants for hydroxyl radical, OH, and hydrated electron, eaq-, reaction with both chlorinated and brominated halonitromethanes were measured using the techniques of electron pulse radiolysis and transient absorption spectroscopy. The bimolecular rate constants obtained, k (M-1 s-1), for eaq-/OH, respectively, were the following: chloronitromethane (3.01 ± 0.40) × 1010/(1.94 ± 0.32) × 108; dichloronitromethane (3.21 ± 0.17) × 1010/(5.12 ± 0.77) × 108; bromonitromethane (3.13 ± 0.06) × 1010/(8.36 ± 0.57) × 107; dibromonitromethane (3.07 ± 0.40) × 1010/(4.75 ± 0.98) × 108; tribromonitromethane (2.29 ± 0.39) × 1010/(3.25 ± 0.67) × 108; bromochloronitromethane (2.93 ± 0.47) × 1010/(4.2 ± 1.1) × 108; bromodichloronitromethane (2.68 ± 0.13) × 1010/(1.02 ± 0.15) × 108; and dibromochloronitromethane (2.95 ± 0.43) × 1010 / (1.80 ± 0.31) × 108 at room temperature and pH ~7. Comparison data were also obtained for hydroxyl radical reaction with bromoform (1.50 ± 0.05) × 108, bromodichloromethane (7.11 ± 0.26) × 107, and chlorodibromomethane (8.31 ± 0.25) × 107 M-1 s-1, respectively. These rate constants are compared to recently obtained data for trichloronitromethane and bromonitromethane, as well as to other established literature data for analogous compounds.

  16. Study of Formation Mechanisms of Gas Hydrate

    Science.gov (United States)

    Yang, Jia-Sheng; Wu, Cheng-Yueh; Hsieh, Bieng-Zih

    2015-04-01

    Gas hydrates, which had been found in subsurface geological environments of deep-sea sediments and permafrost regions, are solid crystalline compounds of gas molecules and water. The estimated energy resources of hydrates are at least twice of that of the conventional fossil fuel in the world. Gas hydrates have a great opportunity to become a dominating future energy. In the past years, many laboratory experiments had been conducted to study chemical and thermodynamic characteristics of gas hydrates in order to investigate the formation and dissociation mechanisms of hydrates. However, it is difficult to observe the formation and dissociation of hydrates in a porous media from a physical experiment directly. The purpose of this study was to model the dynamic formation mechanisms of gas hydrate in porous media by reservoir simulation. Two models were designed for this study: 1) a closed-system static model with separated gas and water zones; this model was a hydrate equilibrium model to investigate the behavior of the formation of hydrates near the initial gas-water contact; and 2) an open-system dynamic model with a continuous bottom-up gas flow; this model simulated the behavior of gas migration and studied the formation of hydrates from flowed gas and static formation water in porous media. A phase behavior module was developed in this study for reservoir simulator to model the pressure-volume-temperature (PVT) behavior of hydrates. The thermodynamic equilibriums and chemical reactions were coupled with the phase behavior module to have functions modelling the formation and dissociation of hydrates from/to water and gas. The simulation models used in this study were validated from the code-comparison project proposed by the NETL. According to the modelling results of the closed-system static model, we found that predominated location for the formation of hydrates was below the gas-water contact (or at the top of water zone). The maximum hydrate saturation

  17. Hydration of portland cement, natural zeolite mortar in water and sulphate solution

    Directory of Open Access Journals (Sweden)

    Janotka, I.

    2003-03-01

    Full Text Available The objective of this paper is to characterise sulphate resistance of mortars made from ordinary Portland cement ( PC and Portland-pozzolan cement with 35 wt.% of zeolite addition (zeolite-blended cement-ZBC . Mortars with two different cement types were tested in water and 5% sodium sulphate solution for 720 days. A favourable effect of zeolite on increased sulphate resistance of the cement is caused by decrease in free Ca(OH2 content of the mortar There is not sufficient of Ca(OH2 available for reacting with the sulphate solution to form voluminous reaction products. A decreased C3A, content due to 35 wt.% replacement of PC by zeolite is the next pronounced factor improving resistance of the mortar with such blended cement.

    El objetivo de este trabajo ha sido estudiar la resistencia a los sulfatos de morteros preparados con cemento portland ordinario (PC y cemento portland puzolánico, con un 35% en peso de zeolita (zeolite-blended cement (ZBC. Ambos tipos de morteros fueron conservados en agua y en una disolución de sulfato sódico al 5% durante 720 días. Se observó una mayor resistencia a los sulfatos en el mortero preparado con el cemento que contenía zeolita debido a su menor contenido en Ca(OH2. No hay cantidad suficiente de Ca(OH2 para que se produzca la reacción de los constituyentes de la pasta con la disolución de sulfato sódico y formar así productos de naturaleza expansiva. La disminución en el contenido de C,3A, debida a la sustitución de un 35% en peso de PC por zeolita, es el factor más determinante en el aumento de la resistencia del mortero en los cementos con adición.

  18. Temperature effect on the small-to-large crossover lengthscale of hydrophobic hydration.

    Science.gov (United States)

    Djikaev, Y S; Ruckenstein, E

    2013-11-14

    The thermodynamics of hydration is expected to change gradually from entropic for small solutes to enthalpic for large ones. The small-to-large crossover lengthscale of hydrophobic hydration depends on the thermodynamic conditions of the solvent such as temperature, pressure, presence of additives, etc. We attempt to shed some light on the temperature dependence of the crossover lengthscale by using a probabilistic approach to water hydrogen bonding that allows one to obtain an analytic expression for the number of bonds per water molecule as a function of both its distance to a solute and solute radius. Incorporating that approach into the density functional theory, one can examine the solute size effects on its hydration over the entire small-to-large lengthscale range at a series of different temperatures. Knowing the dependence of the hydration free energy on the temperature and solute size, one can also obtain its enthalpic and entropic contributions as functions of both temperature and solute size. These functions can provide some interesting insight into the temperature dependence of the crossover lengthscale of hydrophobic hydration. The model was applied to the hydration of spherical particles of various radii in water in the temperature range from T = 293.15 K to T = 333.15 K. The model predictions for the temperature dependence of the hydration free energy of small hydrophobes are consistent with the experimental and simulational data on the hydration of simple molecular solutes. Three alternative definitions for the small-to-large crossover length-scale of hydrophobic hydration are proposed, and their temperature dependence is obtained. Depending on the definition and temperature, the small-to-large crossover in the hydration mechanism is predicted to occur for hydrophobes of radii from one to several nanometers. Independent of its definition, the crossover length-scale is predicted to decrease with increasing temperature.

  19. Hydrate prevention during formation test of gas in deep water; Prevencao de formacao de hidratos durante teste de formacao de poco de gas em lamina d'agua profunda

    Energy Technology Data Exchange (ETDEWEB)

    Rodrigues, Renato Cunha [PETROBRAS, Rio de Janeiro, RJ (Brazil)

    2008-07-01

    This work shows a scenery of formation test in deep water, for a well of gas, for which, there were made simulations with objective of identifying possible pairs of points (Pressure x Temperature), favorable to the hydrates formation. Besides, they were made comparisons of the values obtained in the simulation with the values registered during the formation test for the well Alfa of the field Beta. Of ownership of those information, we made an evaluation of the real needs of injection of inhibitors with intention of preventing the hydrates formation in each phase of the test. In an including way, the work has as objective recommends the volumes of hydrates inhibitors to be injected in each phase of a test of formation of well of gas in deep water, in way to assure that the operations are made without there is risk of hydrates formation. (author)

  20. Experimental Investigation of Effect on Hydrate Formation in Spray Reactor

    Directory of Open Access Journals (Sweden)

    Jianzhong Zhao

    2015-01-01

    Full Text Available The effects of reaction condition on hydrate formation were conducted in spray reactor. The temperature, pressure, and gas volume of reaction on hydrate formation were measured in pure water and SDS solutions at different temperature and pressure with a high-pressure experimental rig for hydrate formation. The experimental data and result reveal that additives could improve the hydrate formation rate and gas storage capacity. Temperature and pressure can restrict the hydrate formation. Lower temperature and higher pressure can promote hydrate formation, but they can increase production cost. So these factors should be considered synthetically. The investigation will promote the advance of gas storage technology in hydrates.

  1. Perturbation of second and farther hydration shells of alkali cations and bromide in concentrated aqueous protein as a water-shortage medium.

    Science.gov (United States)

    Ohki, Takumi; Harada, Makoto; Okada, Tetsuo

    2008-09-25

    The Gibbs free energies of transfer of selected ions from water to concentrated aqueous ovalbumin and albumin (DeltaW(W') G degrees j) have been determined by ion-transfer voltammetry. Negative values for the tetrabutylammonium ion suggest its direct binding to ovalbumin. In contrast, for alkali cations and bromide, the DeltaW(W') G degrees j values are positive and increase with increasing ovalbumin concentration. Positive values are confirmed for concentrated aqueous albumin and poly(styrenesulfonate) as well. The largest value (ca. 10 kJ mol(-1)) is found for the transfer of K(+) from water to 30 wt % ovalbumin. To reveal the solvation structure of these ions in ovalbumin solutions, X-ray absorption fine structure (XAFS) measurements have been performed at the K, Rb, and Br K-edges. Interestingly, the spectra obtained in 30 wt % ovalbumin solutions are identical to those for the corresponding hydrated ions. This strongly suggests that the first coordination shell structures of these ions are not affected by a large concentration of ovalbumin. The detected positive free energy of transfer is slightly lower than the hydrogen bonding energy of a water molecule and should thus come from the perturbation of the second and farther hydration shells of the ions under a water-shortage condition caused by a high concentration of ovalbumin.

  2. Mars residual north polar cap - Earth-based spectroscopic confirmation of water ice as a major constituent and evidence for hydrated minerals

    Science.gov (United States)

    Clark, R. N.; Mccord, T. B.

    1982-01-01

    A description is presented of new earth-based reflectance spectra of the Martian north residual polar cap. The spectra indicate that the composition is at least mostly water ice plus another component with a 'gray' reflectance. The other minerals in the ice cap appear to be hydrated. The data were obtained with a cooled circular variable filter spectrometer on February 20, 1978, using the 2.2-m telescope on Mauna Kea, Hawaii. It is pointed out that the identification of water ice in the north polar cap alone does not indicate that water makes up all or even most of the bulk of the cap. Kieffer (1970) has shown that a small amount of water will mask the spectral features of CO2.

  3. Molecular dynamics simulations of methane hydrate pre-nucleation phenomena and the effect of PVCap kinetic inhibitor

    Science.gov (United States)

    Kuznetsova, Tatiana; Kvamme, Bjørn; Parmar, Archana

    2012-12-01

    MD simulations were employed to investigate a number of different systems of relevance for methane hydrate formation, dissociation and inhibition. Regions of stability for methane hydrate have been investigated using a model system consisting of a slab of hydrate embedded in liquid water. Water/methane interface structuring and possible precursors to hydrate formation have been investigated using a model system of water and methane at different densities. In yet another system we have investigated the impact of Dodecamers (twelve-unit molecules) of poly (vinyl caprolactam) or PVCap on structuring of water/methane interfaces. PVCap is well known for its performance as hydrate kinetic inhibitor1. Intermolecular interactions were treated by a combination of Coulomb and Lennard-Jones potentials. Temperature was controlled by a simple velocity scaling. Several of the hydrate-containing systems showed a tendency to melt when in contact with methane-saturated water even at temperatures well below the hydrate stability region. We have attributed this behavior to the fact that hydrate volume available in a MD experiment is small and lacks the stabilizing presence of bulk. Systems containing liquid water and methane showed certain signs of hydrate nucleation. The PVCap behavior was shown to be very dependent on its concentration in water. At low concentrations, PVCap tended to prefer the water-methane interface and not to interact with each other, similarly to another kinetic inhibitor, PVP2. When the liquid PVCap content was high, it evidently modified the interfacial tension of water-methane surface, converting the initially disperesed methane phase into separated bubbles. The PVCap molecules then built a system-wide network that partially covered the surface of methane bubbles.

  4. Well log characterization of natural gas hydrates

    Science.gov (United States)

    Collett, Timothy S.; Lee, Myung W.

    2011-01-01

    In the last 25 years we have seen significant advancements in the use of downhole well logging tools to acquire detailed information on the occurrence of gas hydrate in nature: From an early start of using wireline electrical resistivity and acoustic logs to identify gas hydrate occurrences in wells drilled in Arctic permafrost environments to today where wireline and advanced logging-while-drilling tools are routinely used to examine the petrophysical nature of gas hydrate reservoirs and the distribution and concentration of gas hydrates within various complex reservoir systems. The most established and well known use of downhole log data in gas hydrate research is the use of electrical resistivity and acoustic velocity data (both compressional- and shear-wave data) to make estimates of gas hydrate content (i.e., reservoir saturations) in various sediment types and geologic settings. New downhole logging tools designed to make directionally oriented acoustic and propagation resistivity log measurements have provided the data needed to analyze the acoustic and electrical anisotropic properties of both highly inter-bedded and fracture dominated gas hydrate reservoirs. Advancements in nuclear-magnetic-resonance (NMR) logging and wireline formation testing have also allowed for the characterization of gas hydrate at the pore scale. Integrated NMR and formation testing studies from northern Canada and Alaska have yielded valuable insight into how gas hydrates are physically distributed in sediments and the occurrence and nature of pore fluids (i.e., free-water along with clay and capillary bound water) in gas-hydrate-bearing reservoirs. Information on the distribution of gas hydrate at the pore scale has provided invaluable insight on the mechanisms controlling the formation and occurrence of gas hydrate in nature along with data on gas hydrate reservoir properties (i.e., permeabilities) needed to accurately predict gas production rates for various gas hydrate

  5. Hydration and rotational diffusion of levoglucosan in aqueous solutions

    Science.gov (United States)

    Corezzi, S.; Sassi, P.; Paolantoni, M.; Comez, L.; Morresi, A.; Fioretto, D.

    2014-05-01

    Extended frequency range depolarized light scattering measurements of water-levoglucosan solutions are reported at different concentrations and temperatures to assess the effect of the presence and distribution of hydroxyl groups on the dynamics of hydration water. The anhydro bridge, reducing from five to three the number of hydroxyl groups with respect to glucose, considerably affects the hydration properties of levoglucosan with respect to those of mono and disaccharides. In particular, we find that the average retardation of water dynamics is ≈3-4, that is lower than ≈5-6 previously found in glucose, fructose, trehalose, and sucrose. Conversely, the average number of retarded water molecules around levoglucosan is 24, almost double that found in water-glucose mixtures. These results suggest that the ability of sugar molecules to form H-bonds through hydroxyl groups with surrounding water, while producing a more effective retardation, it drastically reduces the spatial extent of the perturbation on the H-bond network. In addition, the analysis of the concentration dependence of the hydration number reveals the aptitude of levoglucosan to produce large aggregates in solution. The analysis of shear viscosity and rotational diffusion time suggests a very short lifetime for these aggregates, typically faster than ≈20 ps.

  6. The Role of the Primitive Relaxation in the Dynamics of Aqueous Mixtures, Nano-confined Water and Hydrated Proteins

    Science.gov (United States)

    2010-01-01

    S. Ancherbaka, P. A. Rollaa, N. Shinyashikic aDipartimento di Fisica , Università di Pisa and CNR-IPCF, Largo Bruno Pontecorvo 3 ,I-56127, Pisa...Dipartimento di Fisica ,Universita di Pisa and CNR-IPCF,Largo Bruno Pontecorvo 3, I-56127,Pisa, Italy, , 8. PERFORMING ORGANIZATION REPORT NUMBER 9...reduce the water molecular clusters down to sizes smaller than the critical size necessary for homogenous nucleation. Another effect of the confinement

  7. Hydration Gibbs free energies of open and closed shell trivalent lanthanide and actinide cations from polarizable molecular dynamics.

    Science.gov (United States)

    Marjolin, Aude; Gourlaouen, Christophe; Clavaguéra, Carine; Ren, Pengyu Y; Piquemal, Jean-Philip; Dognon, Jean-Pierre

    2014-10-01

    The hydration free energies, structures, and dynamics of open- and closed-shell trivalent lanthanide and actinide metal cations are studied using molecular dynamics simulations (MD) based on a polarizable force field. Parameters for the metal cations are derived from an ab initio bottom-up strategy. MD simulations of six cations solvated in bulk water are subsequently performed with the AMOEBA polarizable force field. The calculated first-and second shell hydration numbers, water residence times, and free energies of hydration are consistent with experimental/theoretical values leading to a predictive modeling of f-elements compounds.

  8. Microstructure and Physical Properties of Sulfate Hydrate/Ice Eutectic Aggregates in the Binary System Sodium-Sulfate/Water at Planetary Conditions

    Science.gov (United States)

    McCarthy, C. M.; Kirby, S.; Durham, W.; Stern, L.

    2004-12-01

    Reflectance spectra data from Mars Odyssey, Galileo and potentially from Cassini suggest the presence of hydrated salts on numerous satellites in environments such as evaporate beds or combined with water ice. Improved mission data on these occurrences indicate that grain structures and properties of such materials merit a closer look using laboratory methods. Here we report the synthesis of a two-phase aggregate of sodium sulfate hydrate and water ice made by eutectic solidification from solution, characterization of its microstructure using cryogenic SEM, and comparison of its physical properties to those of its end-member components. Samples are crystallized from solution using a precision cryobath and seeded growth. The reaction is a "simple" one meaning that there is no solid solution formation in either of the two solid phases. The eutectic composition we studied for the sodium sulfate hydrate is 4wt% Na2SO4, which corresponds to about .06 volume fraction of Na2SO4ṡ10H2O, mirabilite, and .94 ice I. The eutectic microstructure observed with this volume fraction, which is termed "broken lamellar", consists of fairly uniform blade-like mirabilite grains arranged in roughly parallel columns within a water ice matrix. The blades and matrix material form a lamella that alternates with lamellae of pure ice. Energy dispersive spectroscopy of these eutectic mixtures confirms the presence of the two crystalline phases. Also, we find that lamellar spacing decreases with increasing growth rate. Constant-strain-rate tests in compression are carried out in the cryogenic gas deformation apparatus at LLNL in a pressure-temperature range appropriate to the icy satellites. We report the rheology of the two-phase aggregate and compare it to the strength properties of pure water ice and pure mirabilite. With the aid of numerous studies on similar structures in the literature on metals, we analyze the deformation mechanics from the perspective of defect and crack propagation

  9. Magnetically Separable and Recyclable Fe3O4-Supported Ag Nanocatalysts for Reduction of Nitro Compounds and Selective Hydration of Nitriles to Amides in Water

    Directory of Open Access Journals (Sweden)

    Hyunje Woo

    2014-01-01

    Full Text Available As hybrid nanostructures have become more important in many fields of chemistry, Ag nanoparticles (NPs are being increasingly immobilized onto Fe3O4 microspheres in situ. Structural characterization reveals that the Ag NPs are uniformly immobilized in the Fe3O4 microsphere-based supports. Moreover, Ag NPs are more stable in the hybrid structure than in the naked state and show high catalytic activity for the reduction of nitro compounds and hydration of nitriles to amides in water. The Fe3O4 microspheres were recycled several times using an external magnet.

  10. Magnetically separable and recyclable Fe3O4-supported Ag nanocatalysts for reduction of nitro compounds and selective hydration of nitriles to amides in water.

    Science.gov (United States)

    Woo, Hyunje; Lee, Kyoungho; Park, Sungkyun; Park, Kang Hyun

    2014-01-07

    As hybrid nanostructures have become more important in many fields of chemistry, Ag nanoparticles (NPs) are being increasingly immobilized onto Fe3O4 microspheres in situ. Structural characterization reveals that the Ag NPs are uniformly immobilized in the Fe3O4 microsphere-based supports. Moreover, Ag NPs are more stable in the hybrid structure than in the naked state and show high catalytic activity for the reduction of nitro compounds and hydration of nitriles to amides in water. The Fe3O4 microspheres were recycled several times using an external magnet.

  11. Gas Hydrate Growth Kinetics: A Parametric Study

    Directory of Open Access Journals (Sweden)

    Remi-Erempagamo Tariyemienyo Meindinyo

    2016-12-01

    Full Text Available Gas hydrate growth kinetics was studied at a pressure of 90 bars to investigate the effect of temperature, initial water content, stirring rate, and reactor size in stirred semi-batch autoclave reactors. The mixing energy during hydrate growth was estimated by logging the power consumed. The theoretical model by Garcia-Ochoa and Gomez for estimation of the mass transfer parameters in stirred tanks has been used to evaluate the dispersion parameters of the system. The mean bubble size, impeller power input per unit volume, and impeller Reynold’s number/tip velocity were used for analyzing observed trends from the gas hydrate growth data. The growth behavior was analyzed based on the gas consumption and the growth rate per unit initial water content. The results showed that the growth rate strongly depended on the flow pattern in the cell, the gas-liquid mass transfer characteristics, and the mixing efficiency from stirring. Scale-up effects indicate that maintaining the growth rate per unit volume of reactants upon scale-up with geometric similarity does not depend only on gas dispersion in the liquid phase but may rather be a function of the specific thermal conductance, and heat and mass transfer limitations created by the limit to the degree of the liquid phase dispersion is batched and semi-batched stirred tank reactors.

  12. Surfactant process for promoting gas hydrate formation and application of the same

    Science.gov (United States)

    Rogers, Rudy E.; Zhong, Yu

    2002-01-01

    This invention relates to a method of storing gas using gas hydrates comprising forming gas hydrates in the presence of a water-surfactant solution that comprises water and surfactant. The addition of minor amounts of surfactant increases the gas hydrate formation rate, increases packing density of the solid hydrate mass and simplifies the formation-storage-decomposition process of gas hydrates. The minor amounts of surfactant also enhance the potential of gas hydrates for industrial storage applications.

  13. Development of Alaskan gas hydrate resources

    Energy Technology Data Exchange (ETDEWEB)

    Kamath, V.A.; Sharma, G.D.; Patil, S.L.

    1991-06-01

    The research undertaken in this project pertains to study of various techniques for production of natural gas from Alaskan gas hydrates such as, depressurization, injection of hot water, steam, brine, methanol and ethylene glycol solutions through experimental investigation of decomposition characteristics of hydrate cores. An experimental study has been conducted to measure the effective gas permeability changes as hydrates form in the sandpack and the results have been used to determine the reduction in the effective gas permeability of the sandpack as a function of hydrate saturation. A user friendly, interactive, menu-driven, numerical difference simulator has been developed to model the dissociation of natural gas hydrates in porous media with variable thermal properties. A numerical, finite element simulator has been developed to model the dissociation of hydrates during hot water injection process.

  14. Clinker mineral hydration at reduced relative humidities

    DEFF Research Database (Denmark)

    Jensen, Ole Mejlhede

    1998-01-01

    This report deals with gas phase hydration of pure cement clinker minerals at reduced relative humidities. This is an important subject in relation to modern high performance concrete which may self-desiccate during hydration. In addition the subject has relevance to storage stability where...... prehydration may occur. In the report both theoretical considerations and experimental data are presented. It is suggested that the initiation of hydration during water vapour exposure is nucleation controlled....

  15. Thermal conductivity of hydrate-bearing sediments

    Science.gov (United States)

    Cortes, Douglas D.; Martin, Ana I.; Yun, Tae Sup; Francisca, Franco M.; Santamarina, J. Carlos; Ruppel, Carolyn

    2009-11-01

    A thorough understanding of the thermal conductivity of hydrate-bearing sediments is necessary for evaluating phase transformation processes that would accompany energy production from gas hydrate deposits and for estimating regional heat flow based on the observed depth to the base of the gas hydrate stability zone. The coexistence of multiple phases (gas hydrate, liquid and gas pore fill, and solid sediment grains) and their complex spatial arrangement hinder the a priori prediction of the thermal conductivity of hydrate-bearing sediments. Previous studies have been unable to capture the full parameter space covered by variations in grain size, specific surface, degree of saturation, nature of pore filling material, and effective stress for hydrate-bearing samples. Here we report on systematic measurements of the thermal conductivity of air dry, water- and tetrohydrofuran (THF)-saturated, and THF hydrate-saturated sand and clay samples at vertical effective stress of 0.05 to 1 MPa (corresponding to depths as great as 100 m below seafloor). Results reveal that the bulk thermal conductivity of the samples in every case reflects a complex interplay among particle size, effective stress, porosity, and fluid-versus-hydrate filled pore spaces. The thermal conductivity of THF hydrate-bearing soils increases upon hydrate formation although the thermal conductivities of THF solution and THF hydrate are almost the same. Several mechanisms can contribute to this effect including cryogenic suction during hydrate crystal growth and the ensuing porosity reduction in the surrounding sediment, increased mean effective stress due to hydrate formation under zero lateral strain conditions, and decreased interface thermal impedance as grain-liquid interfaces are transformed into grain-hydrate interfaces.

  16. Thermal conductivity of hydrate-bearing sediments

    Science.gov (United States)

    Cortes, D.D.; Martin, A.I.; Yun, T.S.; Francisca, F.M.; Santamarina, J.C.; Ruppel, C.

    2009-01-01

    A thorough understanding of the thermal conductivity of hydrate-bearing sediments is necessary for evaluating phase transformation processes that would accompany energy production from gas hydrate deposits and for estimating regional heat flow based on the observed depth to the base of the gas hydrate stability zone. The coexistence of multiple phases (gas hydrate, liquid and gas pore fill, and solid sediment grains) and their complex spatial arrangement hinder the a priori prediction of the thermal conductivity of hydrate-bearing sediments. Previous studies have been unable to capture the full parameter space covered by variations in grain size, specific surface, degree of saturation, nature of pore filling material, and effective stress for hydrate-bearing samples. Here we report on systematic measurements of the thermal conductivity of air dry, water- and tetrohydrofuran (THF)-saturated, and THF hydrate-saturated sand and clay samples at vertical effective stress of 0.05 to 1 MPa (corresponding to depths as great as 100 m below seafloor). Results reveal that the bulk thermal conductivity of the samples in every case reflects a complex interplay among particle size, effective stress, porosity, and fluid-versus-hydrate filled pore spaces. The thermal conductivity of THF hydrate-bearing soils increases upon hydrate formation although the thermal conductivities of THF solution and THF hydrate are almost the same. Several mechanisms can contribute to this effect including cryogenic suction during hydrate crystal growth and the ensuing porosity reduction in the surrounding sediment, increased mean effective stress due to hydrate formation under zero lateral strain conditions, and decreased interface thermal impedance as grain-liquid interfaces are transformed into grain-hydrate interfaces. Copyright 2009 by the American Geophysical Union.

  17. Molecular dynamics study on the structure I helium hydrate

    Institute of Scientific and Technical Information of China (English)

    CHENG Wei; WU Hucai; YE Xiaoqin; HOU Hongyu

    2004-01-01

    A 368- water molecule structure I gas hydrate, encased by the number of helium (He) molecules ranging from two to twenty-two, are calculated by molecular dynamical simulations. The potential TIP4P (transferable intermolecular potentical with four sites) is used for water interactions and Lennard-Jones for He-He and He-water interactions. He molecules do not affect the water lattice and can stabilize the hydrate when their concentration is small. A trough signature of He encased is found at 80~90 meV in the phonon density of states. He molecules prefer to be more off-center in 51262 cages. Heavier isotope He are energetically favorable to be filled in cages.

  18. Correlating steric hydration forces with water dynamics through surface force and diffusion NMR measurements in a lipid–DMSO–H2O system

    Science.gov (United States)

    Schrader, Alex M.; Donaldson, Stephen H.; Song, Jinsuk; Cheng, Chi-Yuan; Lee, Dong Woog; Han, Songi; Israelachvili, Jacob N.

    2015-01-01

    Dimethyl sulfoxide (DMSO) is a common solvent and biological additive possessing well-known utility in cellular cryoprotection and lipid membrane permeabilization, but the governing mechanisms at membrane interfaces remain poorly understood. Many studies have focused on DMSO–lipid interactions and the subsequent effects on membrane-phase behavior, but explanations often rely on qualitative notions of DMSO-induced dehydration of lipid head groups. In this work, surface forces measurements between gel-phase dipalmitoylphosphatidylcholine membranes in DMSO–water mixtures quantify the hydration- and solvation-length scales with angstrom resolution as a function of DMSO concentration from 0 mol% to 20 mol%. DMSO causes a drastic decrease in the range of the steric hydration repulsion, leading to an increase in adhesion at a much-reduced intermembrane distance. Pulsed field gradient NMR of the phosphatidylcholine (PC) head group analogs, dimethyl phosphate and tetramethylammonium ions, shows that the ion hydrodynamic radius decreases with increasing DMSO concentration up to 10 mol% DMSO. The complementary measurements indicate that, at concentrations below 10 mol%, the primary effect of DMSO is to decrease the solvated volume of the PC head group and that, from 10 mol% to 20 mol%, DMSO acts to gradually collapse head groups down onto the surface and suppress their thermal motion. This work shows a connection between surface forces, head group conformation and dynamics, and surface water diffusion, with important implications for soft matter and colloidal systems. PMID:26261313

  19. INFLUENCE OF THE COMPOSITION OF PHOSPHATE ROCK ON THE AMOUNT OF WATER-INSOLUBLE PHOSPHATE IMPURITIES IN SEMI-HYDRATE PHOSPHOGYPSUM

    Directory of Open Access Journals (Sweden)

    Nora Kybartiene

    2015-03-01

    Full Text Available In this work a chemical and mineral composition of phosphate rock and phosphogypsum was investigated in order to identify which impurities of phosphate rock prevent natural phosphates from decomposing in full during the production of phosphoric acid and increase the amount of water-insoluble phosphate impurities in phosphogypsum. The analysis of X-ray diffraction (XRF, X-ray fluorescence (XRD, scanning electron microscopy with energy dispersive X-Ray spectrometry (SEM-EDS and granulometry was carried out. The results showed that phosphate rocks (Kovdor and Kirovsk apatites and the semi-hydrate phosphogypsums differ by their chemical composition. The apatites and phosphogypsums differ in the amount of the major components, as well as other components (MgO, Al2O3, SrO, BaO, ZrO2, Ln2O3. In phosphate rock, Ln2O3 can be found in the composition of the mineral monazite. The SEM-EDS analysis revealed that the minerals of the apatite group and monazite form aggregate crystals. Monazite dissolves in sulphuric and phosphoric acids very marginal, therefore it prevents the apatites from full decomposition, thus influencing the quantity of insoluble phosphates in semi-hydrate phosphogypsum. The higher is the amount of minerals containing Ln2O3 in phosphate rock, the more water-insoluble phosphates remain in phosphogypsum. It was found that influence of Ln2O3 impurity is significant higher than influence of particles size of apatite.

  20. Permeability of laboratory-formed methane-hydrate-bearing sand: Measurements and observations using x-ray computed tomography

    Energy Technology Data Exchange (ETDEWEB)

    Kneafsey, T. J.; Seol, Y.; Gupta, A.; Tomutsa, L.

    2010-09-15

    Methane hydrate was formed in two moist sands and a sand/silt mixture under a confining stress in an X-ray-transparent pressure vessel. Three initial water saturations were used to form three different methane-hydrate saturations in each medium. X-ray computed tomography (CT) was used to observe location-specific density changes caused by hydrate formation and flowing water. Gas-permeability measurements in each test for the dry, moist, frozen, and hydrate-bearing states are presented. As expected, the effective permeabilities (intrinsic permeability of the medium multiplied by the relative permeability) of the moist sands decreased with increasing moisture content. In a series of tests on a single sample, the effective permeability typically decreased as the pore space became more filled, in the order of dry, moist, frozen, and hydrate-bearing. In each test, water was flowed through the hydrate-bearing medium and we observed the location-specific changes in water saturation using CT scanning. We compared our data to a number of models, and our relative permeability data compare most favorably with models in which hydrate occupies the pore bodies rather than the pore throats. Inverse modeling (using the data collected from the tests) will be performed to extend the relative permeability measurements.

  1. Prediction of Refrigerant Gas Hydrates Formation Conditions

    Institute of Scientific and Technical Information of China (English)

    Deqing Liang; Ruzhu Wang; Kaihua Guo; Shuanshi Fan

    2001-01-01

    A fugacity model was developed for prediction of mixed refrigerant gas hydrates formation conditions based on the molecule congregation and solution theories. In this model, g as hydrates were regarded as non-ideal solid solution composed of water groups and guest molecules, and the expressions of fugacity of guest molecules in hydrate phase was proposed accordingly. It has been shown that the developed model can indicate successfully the effect of guest-guest molecule interaction. The results showed that the model can describe better the characteristics of phase equilibrium of mixed refrigerant gas hydrates and predictions are in good agreement with experimental data.

  2. Desalination utilizing clathrate hydrates (LDRD final report).

    Energy Technology Data Exchange (ETDEWEB)

    Simmons, Blake Alexander; Bradshaw, Robert W.; Dedrick, Daniel E.; Cygan, Randall Timothy (Sandia National Laboratories, Albuquerque, NM); Greathouse, Jeffery A. (Sandia National Laboratories, Albuquerque, NM); Majzoub, Eric H. (University of Missouri, Columbia, MO)

    2008-01-01

    Advances are reported in several aspects of clathrate hydrate desalination fundamentals necessary to develop an economical means to produce municipal quantities of potable water from seawater or brackish feedstock. These aspects include the following, (1) advances in defining the most promising systems design based on new types of hydrate guest molecules, (2) selection of optimal multi-phase reactors and separation arrangements, and, (3) applicability of an inert heat exchange fluid to moderate hydrate growth, control the morphology of the solid hydrate material formed, and facilitate separation of hydrate solids from concentrated brine. The rate of R141b hydrate formation was determined and found to depend only on the degree of supercooling. The rate of R141b hydrate formation in the presence of a heat exchange fluid depended on the degree of supercooling according to the same rate equation as pure R141b with secondary dependence on salinity. Experiments demonstrated that a perfluorocarbon heat exchange fluid assisted separation of R141b hydrates from brine. Preliminary experiments using the guest species, difluoromethane, showed that hydrate formation rates were substantial at temperatures up to at least 12 C and demonstrated partial separation of water from brine. We present a detailed molecular picture of the structure and dynamics of R141b guest molecules within water cages, obtained from ab initio calculations, molecular dynamics simulations, and Raman spectroscopy. Density functional theory calculations were used to provide an energetic and molecular orbital description of R141b stability in both large and small cages in a structure II hydrate. Additionally, the hydrate of an isomer, 1,2-dichloro-1-fluoroethane, does not form at ambient conditions because of extensive overlap of electron density between guest and host. Classical molecular dynamics simulations and laboratory trials support the results for the isomer hydrate. Molecular dynamics simulations

  3. Study of clathrate hydrates via equilibrium molecular-dynamics simulation employing polarisable and non-polarisable, rigid and flexible water models

    Science.gov (United States)

    Burnham, Christian J.; English, Niall J.

    2016-04-01

    Equilibrium molecular-dynamics (MD) simulations have been performed on metastable sI and sII polymorphs of empty hydrate lattices, in addition to liquid water and ice Ih. The non-polarisable TIP4P-2005, simple point charge model (SPC), and polarisable Thole-type models (TTM): TTM2, TTM3, and TTM4 water models were used in order to survey the differences between models and to see what differences can be expected when polarisability is incorporated. Rigid and flexible variants were used of each model to gauge the effects of flexibility. Power spectra are calculated and compared to density-of-states spectra inferred from inelastic neutron scattering (INS) measurements. Thermodynamic properties were also calculated, as well as molecular-dipole distributions. It was concluded that TTM models offer optimal fidelity vis-à-vis INS spectra, together with thermodynamic properties, with the flexible TTM2 model offering optimal placement of vibrational modes.

  4. The Hydration of Subglacial Rhyolite to Form Perlite

    Science.gov (United States)

    Denton, J. S.; Tuffen, H.; Gilbert, J. S.

    2009-12-01

    Subglacial rhyolite deposits at Torfajökull, Iceland encountered glacier meltwater as they cooled, leading to variable amounts of hydration. High-temperature lava-meltwater interactions are key to understanding jökulhlaup hazards, perlite formation, cooling rates and, ultimately, soil formation [Denton et al., 2009]. Perlite is a hydrated glass that contains abundant, intersecting, arcuate and gently curved cracks surrounding cores of intact glass. Knowledge of how perlite forms is required for us to better understand the way in which meltwater and lava interact during and after subglacial eruptions. The mechanism for perlite formation is currently poorly understood, it is not known whether cracking leads to hydration or vice versa. Different textural zones from effusively erupted lava lobes from Torfajökull, Iceland [Tuffen et al., 2001] have been studied using a combination of experimental and quantitative textural measurements to examine the processes of hydration and perlite formation. A differential scanning calorimetry - thermogravimetric analyser coupled to a mass spectrometer (DSC-TGA-MS) has been used to quantify the total volatile contents of a number of samples. A novel petrological technique has been used to quantify the concentration of fractures present in a sample which has then been related to the amount of hydration. Water content using infra-red microspectroscopy (FTIR) has been used to study the micro-scale variations of water content and how they relate to fractures in the rhyolitic glasses. The results indicate that progressive perlitisation at the margins of lava bodies is accompanied by an increase in the water content, from ~0.5 wt. % to ~2 wt. %. The speciation of the inwardly diffusing water changes from hydroxyl to molecular water with increasing total volatile content. The temperature of dehydration of samples during TGA experiments decreases with increasing volatile content, consistent with a change in the dominant H2O species from

  5. Clathrate hydrates in nature.

    Science.gov (United States)

    Hester, Keith C; Brewer, Peter G

    2009-01-01

    Scientific knowledge of natural clathrate hydrates has grown enormously over the past decade, with spectacular new findings of large exposures of complex hydrates on the sea floor, the development of new tools for examining the solid phase in situ, significant progress in modeling natural hydrate systems, and the discovery of exotic hydrates associated with sea floor venting of liquid CO2. Major unresolved questions remain about the role of hydrates in response to climate change today, and correlations between the hydrate reservoir of Earth and the stable isotopic evidence of massive hydrate dissociation in the geologic past. The examination of hydrates as a possible energy resource is proceeding apace for the subpermafrost accumulations in the Arctic, but serious questions remain about the viability of marine hydrates as an economic resource. New and energetic explorations by nations such as India and China are quickly uncovering large hydrate findings on their continental shelves.

  6. Experimental Determination of Refractive Index of Gas Hydrates

    DEFF Research Database (Denmark)

    Bylov, Martin; Rasmussen, Peter

    1997-01-01

    The refractive indexes of methane hydrate and natural gas hydrate have been experimentally determined. The refractive indexes were determined in an indirect manner making use of the fact that two non-absorbing materials will have the same refractive index if they cannot be distinguished visually....... For methane hydrate (structure I) the refractive index was found to be 1.346 and for natural gas hydrate (structure II) it was found to be 1.350. The measurements further suggest that the gas hydrate growth rate increases if the water has formed hydrates before. The induction time, on the other hand, seems...

  7. Hydration properties of lanthanoid(III) carbonate complexes in liquid water determined by polarizable molecular dynamics simulations.

    Science.gov (United States)

    Martelli, Fausto; Jeanvoine, Yannick; Vercouter, Thomas; Beuchat, César; Vuilleumier, Rodolphe; Spezia, Riccardo

    2014-02-28

    In this work we have studied the structure and dynamics of complexes formed by three and four carbonates and a central lanthanoid(III) ion in liquid water by means of polarizable molecular dynamics simulations. With this aim we have developed a force field employing an extrapolation procedure that was previously developed for lanthanoid(III) aqua ions and then we have validated it against DFT-based data. In this way we were able to shed light on properties of the whole series, finding some similarities and differences across the series, and to help in interpreting experiments on those systems. We found that the bi-dentate tri-carbonate complexes are the most stable for all the atoms, but a variation of the number of water molecules in the first ion shell, and the associated exchange dynamics, is observed from lighter to heavier elements. On the other hand, for four-carbonate systems only one water molecule is observed in the first shell, with 10-20% probability, for La(III) and Ce(III), while for the rest of the series it seems impossible for a water molecule to enter the first ion shell in the presence of such an excess of carbonate ligands. Finally, the good performance of our extrapolation procedure, based on ionic radii, makes us confident in extending such approaches to study the structure and dynamics of other systems in solution containing Ln(III) and An(III) ions. This parametrization method results particularly useful since it does not need expensive quantum chemistry calculations for all the atoms in the series.

  8. Eigen-like hydrated protons traveling with a local distortion through the water nanotube in new molecular porous crystals {[M(III)(H2bim)3](TMA)·20H2O}n (M = Co, Rh, Ru).

    Science.gov (United States)

    Matsui, Hiroshi; Tadokoro, Makoto

    2012-10-14

    In molecular porous crystals {[M(III)(H(2)bim)(3)](TMA)·20H(2)O}(n) (M = Co, Rh, Ru), the structural property of confined water network and the dynamics of mobile hydrated protons have been examined by the measurement of infrared spectrum and microwave conductivity. The water network undergoes first order phase transition from the ice nanotube (INT) to the water nanotube (WNT) around 200 K, while the infrared spectral features for these states are almost equivalent. Consequently, the water molecules in WNT dynamically fluctuate in the vicinity of the regulated position in INT with maintaining the O-O distance. The additional band observed around 2200 cm(-1) reveals the emergence of an Eigen-like protonic hydrate, around which the O-O distance locally shrinks to ~2.56 Å. The microwave conductivity exhibiting activation-type behavior, isotope effect and anisotropy indicates that the water nanotube is a quasi one-dimensional high proton conductor. Together with the neutron experimental results, we have clarified that the proton and protonic hole are generated by the self-dissociation in some water molecules just hydrated to the carboxylate oxygen atom of trimesic acid. The Eigen-like hydrated proton and protonic hole contribute to the intrinsic proton conduction accompanying local distortions. The carrier density dominated by the intrinsic ionic equilibrium is not large, whereas the actual mobility, which is higher than 1 × 10(-2) (cm(2)/Vs), yields the present high proton conductivity.

  9. Problems of ecological and technical safety by exploration and production of natural gas hydrates

    Institute of Scientific and Technical Information of China (English)

    V.K. Chistyakov; Youhong SUN; Chen CHEN; Zupei ZHANG

    2006-01-01

    Gas hydrates-the firm crystal connections formed water (water, ice, water vapor) and low-molecular waterproof natural gases (mainly methane) whose crystal structure effectively compresses gas: each cubic meter of hydrate can yield over 160 m3 of methane.In present time exploitation of the Messoyahsk (Russia) and Mallik (Canada) deposits of gas hydrates in is conducted actively. The further perfection of prospecting methods in the field of studying gas hydrates containing sediments in round extent depends on improvement of geophysical and well test research, among which native-state core drilling is one of the major. Sampling native-state core from gas hydrates sediments keeping not only original composition, but structural-textural features of their construction.Despite of appeal of use gas hydrates as the perspective and ecologically pure fuel possessing huge resources, investigation and development of their deposits can lead to a number of the negative consequences connected with arising hazards for maintenance of their technical and ecological safety of carrying out. Scales of arising problems can change from local up to regional and even global.

  10. Growth kinetics and microstructure of methane hydrates formed in porous media

    Science.gov (United States)

    Falenty, A.; Klapproth, A.; Techmer, K.; Murshed, M. M.; Kuhs, W. F.

    2007-12-01

    The occurrence of natural gas hydrates within sediments is known from a large number of locations. They commonly occupy pore spaces cementing sedimentary deposits. Yet, detailed information about the influence of mineral composition on the formation process in porous media is still very limited. Laboratory investigations of the microstructure of gas hydrate in porous media, as a function of p-T conditions, mineral composition and water/gas supersaturation are therefore of considerable interest. Such studies may allow a better understanding of the formation process and even the prediction of accumulation /decomposition rates of some natural gas hydrates in a given geological setting. As a model study, we carried out various reactions with methane gas and water in three types of media: 1) quartz, 2) quartz + kaolinite, 3) quartz + montmorillonite. The progress of the reactions was recorded by gas consumption (pressure drop) at 3°C. Samples recovered at various stages of the formation or decomposition reactions were investigated using field-emission scanning electron microscopes (FE-SEM) equipped with a cryo-stage [1]. In the SEM investigations, methane hydrates appeared between the quartz grains acting as cement. Kaolinite particles were observed as a filigree network on the surface of hydrate cement, while montmorillonite form flakes or crust like features. Each of the minerals may play individual/coupled interaction with water and gas hydrate, and thereby display a characteristic configuration in the SEM images. Dissimilar kinetic features, using different porous media at the investigated conditions, confirm that mineral composition directly influences the progress of gas hydrate formation. Medium 3 shows the fastest hydrate saturation. With increasing water content of the porous media the formation tends to proceed in a multi-stage process with a slower diffusion-limited later stage. Reference: [1] A. Klapproth, K. Techmer, S.A. Klapp, M.M. Murshed and W.F. Kuhs

  11. Gas hydrate, fluid flow and free gas: Formation of the bottom-simulating reflector

    Science.gov (United States)

    Haacke, R. Ross; Westbrook, Graham K.; Hyndman, Roy D.

    2007-09-01

    Gas hydrate in continental margins is commonly indicated by a prominent bottom-simulating seismic reflector (BSR) that occurs a few hundred metres below the seabed. The BSR marks the boundary between sediments containing gas hydrate above and free gas below. Most of the reflection amplitude is caused by the underlying free gas. Gas hydrate can occur without a BSR, however, and the controls on its formation are not well understood. Here we describe two complementary mechanisms for free gas accumulation beneath the gas hydrate stability zone (GHSZ). The first is the well-recognised hydrate recycling mechanism that generates gas from dissociating hydrate when the base of the GHSZ moves upward relative to hydrate-bearing sediment. The second is a recently identified mechanism in which the relationship between the advection and diffusion of dissolved gas with the local solubility curve allows the liquid phase to become saturated in a thick layer beneath the GHSZ when hydrate is present near its base. This mechanism for gas production (called the solubility-curvature mechanism) is possible in systems where the influence of diffusion becomes important relative to the influence of advection and where the gas-water solubility decreases to a minimum several hundred metres below the GHSZ. We investigate a number of areas in which gas hydrate occurs to determine where gas formation is dominated by the solubility-curvature mechanism and where it is dominated by hydrate recycling. We show that the former is dominant in areas with low rates of upward fluid flow (such as old, rifted continental margins), low rates of seafloor uplift, and high geothermal gradient and/or pressure. Conversely, free-gas formation is dominated by hydrate recycling where there are rapid rates of upward fluid flow and seabed uplift (such as in subduction zone accretionary wedges). Using these two mechanisms to investigate the formation of free gas beneath gas hydrate in continental margins, we are able

  12. Selected specific rates of reactions of transients from water in aqueous solution. Hydrated electron, supplemental data. [Reactions with transients from water, with inorganic solutes, and with solutes

    Energy Technology Data Exchange (ETDEWEB)

    Ross, A.B.

    1975-06-01

    A compilation of rates of reactions of hydrated electrons with other transients and with organic and inorganic solutes in aqueous solution appeared in NSRDS-NBS 43, and covered the literature up to early 1971. This supplement includes additional rates which have been published through July 1973.

  13. Dimensionless numbers used to characterize stratification in water tanks for discharging at low flow rates

    Energy Technology Data Exchange (ETDEWEB)

    Castell, A.; Medrano, M.; Sole, C.; Cabeza, L.F. [GREA Innovacio concurrent, Universitat de Lleida, Pere de Cabrera s/n, 25001 Lleida (Spain)

    2010-10-15

    The efficiency of thermal energy storage and solar collector systems is improved if the water tank is stratified. There are many parameters to characterize stratification but no work compares their suitability. This paper identifies the most used dimensionless numbers to characterize stratification in water tanks and studies their suitability. Experiments with different flow rates were done and the dimensionless numbers were determined. Richardson is the best number to define stratification in a water tank, while Mix number presents some problems and a bad behaviour. The other numbers do not clearly characterize stratification but can be useful combined with Richardson. (author)

  14. Investigation of hydrate formation and transportability in multiphase flow systems

    Science.gov (United States)

    Grasso, Giovanny A.

    The oil and gas industry is moving towards offshore developments in more challenging environments, where evaluating hydrate plugging risks to avoid operational/safety hazards becomes more difficult (Sloan, 2005). Even though mechanistic models for hydrate plug formation have been developed, components for a full comprehensive model are still missing. Prior to this work, research efforts were focused on flowing hydrate particles with relatively little research on hydrate accumulation, leaving hydrate deposition in multiphase flow an unexplored subject. The focus of this thesis was to better understand hydrate deposition as a form of accumu- lation in pipelines. To incorporate the multiphase flow effect, hydrate formation experiments were carried out at varying water cut (WC) from 15 to 100 vol.%, liquid loading (LL) from 50 to 85 vol.%, mixture velocity (vmix) from 0.75 to 3 m/s, for three fluids systems (100 % WC, water in Conroe crude oil emulsions and King Ranch condensate + water) on the ExxonMobil flowloop (4 in. nominal size and 314 ft. long) at Friendswood, TX. For the 100 % WC flowloop tests, hydrate particle distribution transitions beyond a critical hydrate volume concentration, observed values were between 8.2 to 29.4 vol.%, causing a sudden increase in pressure drop (DP). A revised correlation of the transition as a function of Reynolds number and liquid loading was developed. For Conroe emulsions, DP starts increasing at higher hydrate concentrations than King Ranch condensate, many times at 10 vol.%. Experiments with King Ranch show higher relative DP (10 to 25) than Conroe (2 to 10) performed at the same vmix and LL. Cohesive force measurements between cyclopentane hydrate particles were reduced from a value of 3.32 mN/m to 1.26 mN/m when 6 wt.% Conroe was used and to 0.41 mN/m when 5 wt.% Caratinga crude oil was used; similar values were obtained when extracted asphaltenes were used. King Ranch condensate (11 wt.%) did not significantly change the

  15. Investigation of water mobility and diffusivity in hydrating micronized low-substituted hydroxypropyl cellulose, hydroxypropylmethyl cellulose, and hydroxypropyl cellulose matrix tablets by magnetic resonance imaging (MRI)

    Energy Technology Data Exchange (ETDEWEB)

    Kojima, Masazumi; Nakagami, Hiroaki [Daiichi Pharmaceutical Co., Tokyo (Japan). Pharmaceutical Technology Research Lab.

    2002-12-01

    The water mobility and diffusivity in the gel-layer of hydrating low-substituted hydroxypropyl cellulose (LH41) tablets with or without a drug were investigated by magnetic resonance imaging (MRI) and compared with those properties in the gel-layer of hydroxypropylmethyl cellulose (HPMC) and hydroxypropyl cellulose (HPC) tablets. For this purpose, a localized image-analysis method was newly developed, and the spin-spin relaxation time (T{sub 2}) and apparent self-diffusion coefficient (ADC) of water in the gel-layer were visualized in one-dimensional maps. Those maps showed that the extent of gel-layer growth in the tablets was in the order of HPC>HPMC>>LH41, and there was a water mobility gradient across the gel-layers of all three tablet formulations. The T{sub 2} and ADC in the outer parts of the gel-layers were close to those of free water. In contrast, these values in the inner parts of the gel-layer decreased progressively; suggesting that the water mobility and diffusivity around the core interface were highly restricted. Furthermore, the correlation between the T{sub 2} of {sup 1}H proton in the gel-layer of the tablets and the drug release rate from the tablets was observed. (author)

  16. Hydration of the cyanide ion: an ab initio quantum mechanical charge field molecular dynamics study.

    Science.gov (United States)

    Moin, Syed Tarique; Hofer, Thomas S

    2014-12-21

    This paper presents an ab initio quantum mechanical charge field molecular dynamics simulation study of the cyanide anion (CN(-)) in aqueous solution where hydrogen bond formation plays a dominant role in the hydration process. Preferential orientation of water hydrogens compared to oxygen atoms was quantified in terms of radial, angular as well as coordination number distributions. All structural results indicate that the water hydrogens are attracted towards CN(-) atoms, thus contributing to the formation of the hydration layer. Moreover, a clear picture of the local arrangement of water molecules around the ellipsoidal CN(-) ion is provided via angular-radial distribution and spatial distribution functions. Apart from the structural analysis, the evaluation of water dynamics in terms of ligand mean residence times and H-bond correlation functions indicates the weak structure making capacity of the CN(-) ion. The similar values of H-bond lifetimes obtained for the NHwat and CHwat bonds indicate an isokinetic behaviour of these H-bonds, since there is a very small difference in the magnitude of the lifetimes. On the other hand, the H-bond lifetimes between water molecules of the hydration shell, and between solute and solvent evidence the slightly stable hydration of the CN(-). Overall, the H-bonding dominates in the hydration process of the cyanide anion enabling it to become soluble in the aqueous environment associated to chemical and biological processes.

  17. Investigation of gas hydrate-bearing sandstone reservoirs at the Mount Elbert stratigraphic test well, Milne Point, Alaska

    Energy Technology Data Exchange (ETDEWEB)

    Boswell, R. [United States Dept. of Energy, Morgantown, WV (United States). National Energy Technology Lab; Hunter, R. [ASRC Energy Services, Anchorage, AK (United States); Collett, T. [United States Geological Survey, Denver, CO (United States); Digert, S.; Weeks, M. [BP Exploration Alaska Inc., Anchorage, AK (United States); Hancock, S. [RPS Energy Canada, Calgary, AB (Canada)

    2008-07-01

    Gas hydrates occur within the shallow sand reservoirs on the Alaska North Slope (ANS). The mean estimate for gas hydrate in-place resources on the ANS is 16.7 trillion cubic metres. In the past, they were viewed primarily as a drilling hazard to be managed during the development of deeper oil resources. In 2002, a cooperative research program was launched to help determine the potential for environmentally-sound and economically-viable production of methane from gas hydrates. Additional objectives were to refine ANS gas hydrate resource potential, improve the geologic and geophysical methods used to locate and asses gas hydrate resources, and develop numerical modeling capabilities that are essential in both planning and evaluating gas hydrate field programs. This paper reviewed the results of the an extensive data collection effort conducted at the Mount Elbert number 1 gas hydrates stratigraphic test well on the ANS. The 22-day field program acquired significant gas hydrate-bearing reservoir data, including a suite of open-hole well logs, over 500 feet of continuous core, and open-hole formation pressure response tests. The logging program confirmed the existence of approximately 30 m of gas hydrate saturated, fine-grained sand reservoir. Gas hydrate saturations were observed to range from 60 to 75 per cent. Continuous wire-line coring operations achieved 85 per cent recovery. The Mount Elbert field program also involved gas and water sample collection. It demonstrated the ability to safely and efficiently conduct a research-level open-hole data acquisition program in shallow, sub-permafrost sediments and increased confidence in gas hydrate resource assessment methodologies for the ANS. 10 refs., 9 figs.

  18. Compound Natural Gas Hydrate: A Natural System for Separation of Hydrate-Forming Gases

    Science.gov (United States)

    Max, M. D.; Osegovic, J. P.

    2007-12-01

    Natural processes that separate materials from a mixture may exert a major influence on the development of the atmospheres and surfaces of planets, moons, and other planetary bodies. Natural distillation and gravity separation, amongst others, are well known means of differentiating materials through liquid-gas partitioning. One of the least known attributes of clathrate (gas) hydrates is their potential effect on the evolution of planetary system oceans and atmospheres. Gas hydrates separate gases from mixtures of gases by concentrating preferred hydrate-forming materials (HFM) guests within the water-molecule cage structure of crystalline hydrate. Different HFMs have very different fields of stability. When multiple hydrate formers are present, a preference series based on their selective uptake exists. Compound hydrate, which is formed from two or more species of HFM, extract preferred HFM from a mixture in very different proportions to their relative percentages of the original mixture. These compound hydrates can have different formation and dissociation conditions depending on the evolution of the environment. That is, the phase boundary of the compound hydrate that is required for dissociation lies along a lower pressure - higher temperature course. Compound hydrates respond to variations in temperature, pressure, and HFM composition. On Earth, the primary naturally occurring hydrate of interest to global climate modeling is methane hydrate. Oceanic hydrate on Earth is the largest store of carbon in the biosphere that is immediately reactive to environmental change, and is capable of releasing large amounts of methane into the atmosphere over a short geological time span. Hydrate formation is essentially metastable and is very sensitive to environmental change and to gas flux. Where natural variations in temperature and pressure varies so that hydrate will form and dissociate in some cyclical manner, such as in oceans where sea level is capable of rising and

  19. Polyethylene oxide hydration in grafted layers

    Science.gov (United States)

    Dormidontova, Elena; Wang, Zilu

    Hydration of water soluble polymers is one of the key-factors defining their conformation and properties, similar to biopolymers. Polyethylene oxide (PEO) is one of the most important biomedical-applications polymers and is known for its reverse temperature solubility due to hydrogen bonding with water. As in many practical applications PEO chains are grafted to surfaces, e.g. of nanoparticles or planar surfaces, it is important to understand PEO hydration in such grafted layers. Using atomistic molecular dynamic simulations we investigate the details of molecular conformation and hydration of PEO end-grafted to gold surfaces. We analyze polymer and water density distribution as a function of distance from the surface for different grafting densities. Based on a detailed analysis of hydrogen bonding between polymer and water in grafted PEO layers, we will discuss the extent of PEO hydration and its implication for polymer conformation, mobility and layer properties. This research is supported by NSF (DMR-1410928).

  20. Salinity-buffered methane hydrate formation and dissociation in gas-rich systems

    Science.gov (United States)

    You, Kehua; Kneafsey, Timothy J.; Flemings, Peter B.; Polito, Peter; Bryant, Steven L.

    2015-02-01

    Methane hydrate formation and dissociation are buffered by salinity in a closed system. During hydrate formation, salt excluded from hydrate increases salinity, drives the system to three-phase (gas, water, and hydrate phases) equilibrium, and limits further hydrate formation and dissociation. We developed a zero-dimensional local thermodynamic equilibrium-based model to explain this concept. We demonstrated this concept by forming and melting methane hydrate from a partially brine-saturated sand sample in a controlled laboratory experiment by holding pressure constant (6.94 MPa) and changing temperature stepwise. The modeled methane gas consumptions and hydrate saturations agreed well with the experimental measurements after hydrate nucleation. Hydrate dissociation occurred synchronously with temperature increase. The exception to this behavior is that substantial subcooling (6.4°C in this study) was observed for hydrate nucleation. X-ray computed tomography scanning images showed that core-scale hydrate distribution was heterogeneous. This implied core-scale water and salt transport induced by hydrate formation. Bulk resistivity increased sharply with initial hydrate formation and then decreased as the hydrate ripened. This study reproduced the salinity-buffered hydrate behavior interpreted for natural gas-rich hydrate systems by allowing methane gas to freely enter/leave the sample in response to volume changes associated with hydrate formation and dissociation. It provides insights into observations made at the core scale and log scale of salinity elevation to three-phase equilibrium in natural hydrate systems.

  1. Hydration of Krypton and Consideration of Clathrate Models of Hydrophobic Effects from the Perspective of Quasi-Chemical Theory

    CERN Document Server

    Ashbaugh, H S; Pratt, L R; Rempe, S B; Ashbaugh, Henry S.; Pratt, Lawrence R.; Rempe, Susan B.

    2002-01-01

    AIMD results on a liquid krypton-water system are compared to recent XAFS results for the radial hydration structure for a Kr atom in liquid water solution. The comparisons with the liquid solution results are satisfactory and significantly different from the radial distributions extracted from the data on the solid clathrate hydrate phase. The calculations also produce the coordination number distribution that can be examined for metastable coordination structures suggesting possibilities for clathrate-like organization; none are seen in these results. Clathrate pictures of hydrophobic hydration are discussed, as is the quasi-chemical theory that should provide a basis for clathrate pictures. Outer shell contributions are discussed and accurately estimated; they are positive and larger than the positive experimental hydration free energy of Kr(aq), implying that inner shell contributions must be negative. Clathrate-like inner shell coordination structures extracted from the simulation of the liquid, and then...

  2. Gas hydrate of Lake Baikal: Discovery and varieties

    Science.gov (United States)

    Khlystov, Oleg; De Batist, Marc; Shoji, Hitoshi; Hachikubo, Akihiro; Nishio, Shinya; Naudts, Lieven; Poort, Jeffrey; Khabuev, Andrey; Belousov, Oleg; Manakov, Andrey; Kalmychkov, Gennаdy

    2013-01-01

    This paper summarizes the results of recent gas-hydrate studies in Lake Baikal, the only fresh-water lake in the world containing gas hydrates in its sedimentary infill. We provide a historical overview of the different investigations and discoveries and highlight some recent breakthroughs in our understanding of the Baikal hydrate system. So far, 21 sites of gas hydrate occurrence have been discovered. Gas hydrates are of structures I and II, which are of thermogenic, microbial, and mixed origin. At the 15 sites, gas hydrates were found in mud volcanoes, and the rest six - near gas discharges. Additionally, depending on type of discharge and gas hydrate structure, they were visually different. Investigations using MIR submersibles allowed finding of gas hydrates at the bottom surface of Lake Baikal at the three sites.

  3. Hydration sites of unpaired RNA bases: a statistical analysis of the PDB structures

    Directory of Open Access Journals (Sweden)

    Carugo Oliviero

    2011-10-01

    Full Text Available Abstract Background Hydration is crucial for RNA structure and function. X-ray crystallography is the most commonly used method to determine RNA structures and hydration and, therefore, statistical surveys are based on crystallographic results, the number of which is quickly increasing. Results A statistical analysis of the water molecule distribution in high-resolution X-ray structures of unpaired RNA nucleotides showed that: different bases have the same penchant to be surrounded by water molecules; clusters of water molecules indicate possible hydration sites, which, in some cases, match those of the major and minor grooves of RNA and DNA double helices; complex hydrogen bond networks characterize the solvation of the nucleotides, resulting in a significant rigidity of the base and its surrounding water molecules. Interestingly, the hydration sites around unpaired RNA bases do not match, in general, the positions that are occupied by the second nucleotide when the base-pair is formed. Conclusions The hydration sites around unpaired RNA bases were found. They do not replicate the atom positions of complementary bases in the Watson-Crick pairs.

  4. Physical activity, hydration and health

    Directory of Open Access Journals (Sweden)

    Ascensión Marcos

    2014-06-01

    Full Text Available Since the beginning of mankind, man has sought ways to promote and preserve health as well as to prevent disease. Hydration, physical activity and exercise are key factors for enhancing human health. However, either a little dose of them or an excess can be harmful for health maintenance at any age. Water is an essential nutrient for human body and a major key to survival has been to prevent dehydration. However, there is still a general controversy regarding the necessary amount to drink water or other beverages to properly get an adequate level of hydration. In addition, up to now the tools used to measure hydration are controversial. To this end, there are several important groups of variables to take into account such as water balance, hydration biomarkers and total body water. A combination of methods will be the most preferred tool to find out any risk or situation of dehydration at any age range. On the other hand, physical activity and exercise are being demonstrated to promote health, avoiding or reducing health problems, vascular and inflammatory diseases and helping weight management. Therefore, physical activity is also being used as a pill within a therapy to promote health and reduce risk diseases, but as in the case of drugs, dose, intensity, frequency, duration and precautions have to be evaluated and taken into account in order to get the maximum effectiveness and success of a treatment. On the other hand, sedentariness is the opposite concept to physical activity that has been recently recognized as an important factor of lifestyle involved in the obesogenic environment and consequently in the risk of the non-communicable diseases. In view of the literature consulted and taking into account the expertise of the authors, in this review a Decalogue of global recommendations is included to achieve an adequate hydration and physical activity status to avoid overweight/obesity consequences.

  5. Methods to determine hydration states of minerals and cement hydrates

    Energy Technology Data Exchange (ETDEWEB)

    Baquerizo, Luis G., E-mail: luis.baquerizoibarra@holcim.com [Innovation, Holcim Technology Ltd., CH-5113 Holderbank (Switzerland); Matschei, Thomas [Innovation, Holcim Technology Ltd., CH-5113 Holderbank (Switzerland); Scrivener, Karen L. [Laboratory of Construction Materials, Ecole Polytechnique Fédérale de Lausanne, CH-1015 Lausanne (Switzerland); Saeidpour, Mahsa; Thorell, Alva; Wadsö, Lars [Building Materials, Lund University, Box 124, 221 000 Lund (Sweden)

    2014-11-15

    This paper describes a novel approach to the quantitative investigation of the impact of varying relative humidity (RH) and temperature on the structure and thermodynamic properties of salts and crystalline cement hydrates in different hydration states (i.e. varying molar water contents). The multi-method approach developed here is capable of deriving physico-chemical boundary conditions and the thermodynamic properties of hydrated phases, many of which are currently missing from or insufficiently reported in the literature. As an example the approach was applied to monosulfoaluminate, a phase typically found in hydrated cement pastes. New data on the dehydration and rehydration of monosulfoaluminate are presented. Some of the methods used were validated with the system Na{sub 2}SO{sub 4}–H{sub 2}O and new data related to the absorption of water by anhydrous sodium sulfate are presented. The methodology and data reported here should permit better modeling of the volume stability of cementitious systems exposed to various different climatic conditions.

  6. Water mediated ligand functional group cooperativity: the contribution of a methyl group to binding affinity is enhanced by a COO(-) group through changes in the structure and thermodynamics of the hydration waters of ligand-thermolysin complexes.

    Science.gov (United States)

    Nasief, Nader N; Tan, Hongwei; Kong, Jing; Hangauer, David

    2012-10-11

    Ligand functional groups can modulate the contributions of one another to the ligand-protein binding thermodynamics, producing either positive or negative cooperativity. Data presented for four thermolysin phosphonamidate inhibitors demonstrate that the differential binding free energy and enthalpy caused by replacement of a H with a Me group, which binds in the well-hydrated S2' pocket, are more favorable in presence of a ligand carboxylate. The differential entropy is however less favorable. Dissection of these differential thermodynamic parameters, X-ray crystallography, and density-functional theory calculations suggest that these cooperativities are caused by variations in the thermodynamics of the complex hydration shell changes accompanying the H→Me replacement. Specifically, the COO(-) reduces both the enthalpic penalty and the entropic advantage of displacing water molecules from the S2' pocket and causes a subsequent acquisition of a more enthalpically, less entropically, favorable water network. This study contributes to understanding the important role water plays in ligand-protein binding.

  7. Hydrate bearing clayey sediments: Formation and gas production concepts

    KAUST Repository

    Jang, Jaewon

    2016-06-20

    Hydro-thermo-chemo and mechanically coupled processes determine hydrate morphology and control gas production from hydrate-bearing sediments. Force balance, together with mass and energy conservation analyses anchored in published data provide robust asymptotic solutions that reflect governing processes in hydrate systems. Results demonstrate that hydrate segregation in clayey sediments results in a two-material system whereby hydrate lenses are surrounded by hydrate-free water-saturated clay. Hydrate saturation can reach ≈2% by concentrating the excess dissolved gas in the pore water and ≈20% from metabolizable carbon. Higher hydrate saturations are often found in natural sediments and imply methane transport by advection or diffusion processes. Hydrate dissociation is a strongly endothermic event; the available latent heat in a reservoir can sustain significant hydrate dissociation without triggering ice formation during depressurization. The volume of hydrate expands 2-to-4 times upon dissociation or CO2single bondCH4 replacement. Volume expansion can be controlled to maintain lenses open and to create new open mode discontinuities that favor gas recovery. Pore size is the most critical sediment parameter for hydrate formation and gas recovery and is controlled by the smallest grains in a sediment. Therefore any characterization must carefully consider the amount of fines and their associated mineralogy.

  8. Application of the Split Hopkinson Resonant Bar Test for Seismic Property Characterization of Hydrate-bearing Sand Undergoing Water Saturation

    Energy Technology Data Exchange (ETDEWEB)

    Nakagawa, S.; Kneafsey, T.J.

    2011-05-03

    Conventional resonant bar tests allow the measurement of seismic properties of rocks and sediments at low frequencies (several kilohertz). However, the tests require a long, slender sample which is often difficult to obtain from the deep subsurface and weak and fractured formations. We present an alternative low-frequency measurement technique to the conventional resonant bar tests. This technique involves a jacketed core sample placed between a pair of long, metal extension rods with attached seismic source and receiver—the same geometry as the split Hopkinson pressure bar test for large-strain, dynamic impact experiments. Because of the added length and mass to the sample, the resonance frequency of the entire system can be lowered significantly, compared to the sample alone. The proposed “Split Hopkinson Resonant Bar (SHRB)” test is applied in two steps. In the first step, extension and torsion-mode resonance frequencies and attenuation of the system are measured. Then, numerical inversions for the compressional and shear wave velocities and attenuation are performed. We initially applied the SHRB test to synthetic materials (plastics) for testing its accuracy, then used it for measuring the seismic velocities and attenuation of a rock core containing supercritical CO{sub 2}, and a sediment core while methane hydrate formed in the pore space.

  9. ConocoPhillips Gas Hydrate Production Test

    Energy Technology Data Exchange (ETDEWEB)

    Schoderbek, David; Farrell, Helen; Howard, James; Raterman, Kevin; Silpngarmlert, Suntichai; Martin, Kenneth; Smith, Bruce; Klein, Perry

    2013-06-30

    Work began on the ConocoPhillips Gas Hydrates Production Test (DOE award number DE-NT0006553) on October 1, 2008. This final report summarizes the entire project from January 1, 2011 to June 30, 2013.

  10. Hydration and physical performance.

    Science.gov (United States)

    Murray, Bob

    2007-10-01

    There is a rich scientific literature regarding hydration status and physical function that began in the late 1800s, although the relationship was likely apparent centuries before that. A decrease in body water from normal levels (often referred to as dehydration or hypohydration) provokes changes in cardiovascular, thermoregulatory, metabolic, and central nervous function that become increasingly greater as dehydration worsens. Similarly, performance impairment often reported with modest dehydration (e.g., -2% body mass) is also exacerbated by greater fluid loss. Dehydration during physical activity in the heat provokes greater performance decrements than similar activity in cooler conditions, a difference thought to be due, at least in part, to greater cardiovascular and thermoregulatory strain associated with heat exposure. There is little doubt that performance during prolonged, continuous exercise in the heat is impaired by levels of dehydration >or= -2% body mass, and there is some evidence that lower levels of dehydration can also impair performance even during relatively short-duration, intermittent exercise. Although additional research is needed to more fully understand low-level dehydration's effects on physical performance, one can generalize that when performance is at stake, it is better to be well-hydrated than dehydrated. This generalization holds true in the occupational, military, and sports settings.

  11. Hydration states of AFm cement phases

    Energy Technology Data Exchange (ETDEWEB)

    Baquerizo, Luis G., E-mail: luis.baquerizoibarra@holcim.com [Innovation, Holcim Technology Ltd., CH-5113 Holderbank (Switzerland); Matschei, Thomas [Innovation, Holcim Technology Ltd., CH-5113 Holderbank (Switzerland); Scrivener, Karen L. [Laboratory of Construction Materials, Ecole Polytechnique Fédérale de Lausanne, CH-1015 Lausanne (Switzerland); Saeidpour, Mahsa; Wadsö, Lars [Building Materials, Lund University, Box 124, 221 000 Lund (Sweden)

    2015-07-15

    The AFm phase, one of the main products formed during the hydration of Portland and calcium aluminate cement based systems, belongs to the layered double hydrate (LDH) family having positively charged layers and water plus charge-balancing anions in the interlayer. It is known that these phases present different hydration states (i.e. varying water content) depending on the relative humidity (RH), temperature and anion type, which might be linked to volume changes (swelling and shrinkage). Unfortunately the stability conditions of these phases are insufficiently reported. This paper presents novel experimental results on the different hydration states of the most important AFm phases: monocarboaluminate, hemicarboaluminate, strätlingite, hydroxy-AFm and monosulfoaluminate, and the thermodynamic properties associated with changes in their water content during absorption/desorption. This data opens the possibility to model the response of cementitious systems during drying and wetting and to engineer systems more resistant to harsh external conditions.

  12. Overview on Hydrate Coring, Handling and Analysis

    Energy Technology Data Exchange (ETDEWEB)

    Jon Burger; Deepak Gupta; Patrick Jacobs; John Shillinglaw

    2003-06-30

    Gas hydrates are crystalline, ice-like compounds of gas and water molecules that are formed under certain thermodynamic conditions. Hydrate deposits occur naturally within ocean sediments just below the sea floor at temperatures and pressures existing below about 500 meters water depth. Gas hydrate is also stable in conjunction with the permafrost in the Arctic. Most marine gas hydrate is formed of microbially generated gas. It binds huge amounts of methane into the sediments. Worldwide, gas hydrate is estimated to hold about 1016 kg of organic carbon in the form of methane (Kvenvolden et al., 1993). Gas hydrate is one of the fossil fuel resources that is yet untapped, but may play a major role in meeting the energy challenge of this century. In June 2002, Westport Technology Center was requested by the Department of Energy (DOE) to prepare a ''Best Practices Manual on Gas Hydrate Coring, Handling and Analysis'' under Award No. DE-FC26-02NT41327. The scope of the task was specifically targeted for coring sediments with hydrates in Alaska, the Gulf of Mexico (GOM) and from the present Ocean Drilling Program (ODP) drillship. The specific subjects under this scope were defined in 3 stages as follows: Stage 1: Collect information on coring sediments with hydrates, core handling, core preservation, sample transportation, analysis of the core, and long term preservation. Stage 2: Provide copies of the first draft to a list of experts and stakeholders designated by DOE. Stage 3: Produce a second draft of the manual with benefit of input from external review for delivery. The manual provides an overview of existing information available in the published literature and reports on coring, analysis, preservation and transport of gas hydrates for laboratory analysis as of June 2003. The manual was delivered as draft version 3 to the DOE Project Manager for distribution in July 2003. This Final Report is provided for records purposes.

  13. Importancia del agua en la hidratación de la población española: documento FESNAD 2010 Importance of water in the hydration of the Spanish population: FESNAD 2010 document

    Directory of Open Access Journals (Sweden)

    C. Iglesias Rosado

    2011-02-01

    documento se presentan todas estas consideraciones en cuanto a la hidratación, y se realizan diferentes recomendaciones al respecto.For any healthy individual, thirst is an appropriate sign to drink water, except for babies, sportsmen, and most of ill and elderly people. In these instances, it is convenient to schedule appropriate times to drink water since great demands and the physiological mechanisms that determine thirst in these situations may condition water unbalances with important consequences for health and the physical and intellectual performance. The human body has a number of mechanisms that allow keeping constant the water content by adjusting intakes and wastes. Water balance is determined by intake (consumed water, beverages, and water contained in foods and wastes (urine, stools, the skin, and expired air from the lungs. Failure of these mechanisms and subsequent impairments in water balance may produce severe disarrangements that may threaten somebody´s life. In the present document, we analyze the evidences regarding the factors conditioning water needs in the different life stages and physiological situations, as well as the consequences of water unbalance under different situations. A proper hydration may be achieved by feeding and the use of water and other liquids. Although water is the beverage by excellence and represents the ideal way of restoring the losses and get hydrated, we should be aware that, from the very beginning, we have sought other liquid sources with hydration properties. In the last decades we have increased the consumption of different beverages, with a proliferation of sugar-containing beverages. Since excessive sugar consumption has been related to obesity and other chronic conditions, it is evident that the use of these caloric beverages should be rationalized, especially in children. In this document all the considerations regarding hydration are presented and different recommendations are exposed.

  14. The investigation of structure and IR spectra for hydrated potassium ion clusters K+(H2O)n=1-16 by density functional theory*

    Science.gov (United States)

    Zhu, Fayan; Zhou, Hongxia; Zhou, Yongquan; Miao, Juntao; Fang, Chunhui; Fang, Yan; Sun, Pengchao; Ge, Haiwen; Liu, Hongyan

    2016-11-01

    The hydration of K+(H2O)n has been widely studied and believe to be important for understanding solvent properties in biological and chemical systems. However, understanding the structure and the spectrum information K+(H2O)n with changing n is limited. Here, we investigated the clusters K+(H2O)n=1-16 and further studied the IR spectrums of the most stable clusters with density functional theory. The configuration, bond length, vibration frequency were given out. It shows that K+(H2O)8(H2O)n, a distorted square antiprism in inner layer, is the main configuration with hydration distance rK - OI 0.296 nm when the hydration number n is bigger than 8. The saturated hydration number is 8 in the first hydration layer and the water molecules of the second hydration sphere have little effect on the inner ones when n> 8. A detailed classification about the hydrated water molecules was made according to the role of acceptor or donor hydrogen bonding in clusters. The vibration frequency of the different kinds of water molecules were also detailly identified. The results are valuable for further determination of the K+(H2O)n clusters in aqueous solutions. Supplementary material in the form of one pdf file available from the Journal web page at http://dx.doi.org/10.1140/epjd/e2016-60529-7

  15. Formation rate of natural gas hydrate

    Energy Technology Data Exchange (ETDEWEB)

    Mork, Marit

    2002-07-01

    The rate of methane hydrate and natural gas hydrate formation was measured in a 9.5 litre stirred tank reactor of standard design. The experiments were performed to better understand the performance and scale-up of a reactor for continuous production of natural gas hydrates. The hydrate formation rate was measured at steady-state conditions at pressures between 70 and 90 bar and temperatures between 7 and 15 deg C. Between 44 and 56 % of the gas continuously supplied to the reactor was converted to hydrate. The experimental results show that the rate of hydrate formation is strongly influenced by gas injection rate and pressure. The effect of stirring rate is less significant and subcooling has no observable effect on the formation rate. Hydrate crystal concentration and gas composition do not influence the hydrate formation rate. Observations of produced hydrate crystals indicate that the crystals are elongated, about 5 micron in diameter and 10 micron long. Analysis of the results shows that the rate of hydrate formation is dominated by gas-liquid mass transfer. A mass transfer model, the bubble-to-crystal model, was developed for the hydrate formation rate in a continuous stirred tank reactor, given in terms of concentration driving force and an overall mass transfer coefficient. The driving force is the difference between the gas concentration at the gas-liquid interface and at the hydrate crystal surface. These concentrations correspond to the solubility of gas in water at experimental temperature and pressure and the solubility of gas at hydrate equilibrium temperature and experimental pressure, respectively. The overall mass transfer coefficient is expressed in terms of superficial gas velocity and impeller power consumption, parameters commonly used in study of stirred tank reactors. Experiments and modeling show that the stirred tank reactor has a considerable potential for increased production capacity. However, at higher hydrate production rates the

  16. Gas hydrate inhibition of drilling fluid additives

    Energy Technology Data Exchange (ETDEWEB)

    Xiaolan, L.; Baojiang, S.; Shaoran, R. [China Univ. of Petroleum, Dongying (China). Inst. of Petroleum Engineering

    2008-07-01

    Gas hydrates that form during offshore well drilling can have adverse impacts on well operational safety. The hydrates typically form in the risers and the annulus between the casing and the drillstring, and can stop the circulation of drilling fluids. In this study, experiments were conducted to measure the effect of drilling fluid additives on hydrate inhibition. Polyalcohols, well-stability control agents, lubricating agents, and polymeric materials were investigated in a stirred tank reactor at temperatures ranging from -10 degree C to 60 degrees C. Pressure, temperature, and torque were used to detect onset points of hydrate formation and dissociation. The inhibitive effect of the additives on hydrate formation was quantified. Phase boundary shifts were measured in terms of temperature difference or sub-cooling gained when chemicals were added to pure water. Results showed that the multiple hydroxyl groups in polyalcohol chemicals significantly inhibited hydrate formation. Polymeric and polyacrylamide materials had only a small impact on hydrate formation, while sulfonated methyl tannins were found to increase hydrate formation. 6 refs., 1 tab., 4 figs.

  17. A new geotechnical gas hydrates research laboratory

    Energy Technology Data Exchange (ETDEWEB)

    Grozic, J.L.H. [Calgary Univ., AB (Canada)

    2003-07-01

    Gas hydrates encapsulate natural gas molecules in a very compact form, as ice-like compounds composed of water molecules. Permafrost environments and offshore areas contain vast quantities of gas hydrates within soil and rock. This paper describes the role played by gas hydrates in submarine slope instability, their potential as a sustainable energy source, and their effects on global climate change. A new state-of-the-art laboratory located at the University of Calgary, which was developed to study the geomechanical behaviour of gas hydrate-sediment mixtures, was also presented. A specialized high pressure low temperature triaxial apparatus capable of performing a suite of tests on gas hydrate-sediment mixtures is housed in this laboratory. Extensive renovations were required in order to enable the use of methane gas to simulate natural hydrate formation conditions. The laboratory is specifically designed to examine the properties and behaviour of reconstituted gas hydrate-sediment mixtures and natural gas hydrate core samples. 26 refs., 9 figs.

  18. Investigations into surfactant/gas hydrate relationship

    Energy Technology Data Exchange (ETDEWEB)

    Rogers, Rudy; Zhang, Guochang; Dearman, Jennifer; Woods, Charles [Swalm School of Chemical Engineering, Mississippi State University, Mississippi State, MS 39762 (United States)

    2007-03-15

    Gas hydrates have unique physical properties portending useful industrial applications of gas storage, gas separation, or water desalination. When gas hydrates were found in the early 1990s to occur naturally and abundantly in seafloors, three other primary interests and concerns emerged: potential new energy source, climate threat from their greenhouse gases, and seafloor instabilities. This paper presents research showing how anionic synthetic surfactants helped develop an industrial gas hydrate storage process for natural gas and how naturally-occurring in-situ anionic biosurfactants influence the formation and placement of gas hydrates in ocean sediments. The catalytic effects, mechanisms, and surface specificities imparted by synthetic surfactants in the gas storage process and imparted by biosurfactants in porous media are discussed. The Bacillus subtilis bacterium that is indigenous to gas hydrate mounds in the Gulf of Mexico was cultured in the laboratory. Its biosurfactant was separated and found to catalyze gas hydrates in porous media. The experiments indicate that seafloor-biosurfactants can be produced rapidly in-situ to achieve threshold concentrations whereby hydrates are promoted. The biosurfactants accumulate and promote hydrate formation on specific mineral surfaces such as sodium montmorillonite. (author)

  19. Combining Multicomponent Seismic Attributes, New Rock Physics Models, and In Situ Data to Estimate Gas-Hydrate Concentrations in Deep-Water, Near-Seafloor Strata of the Gulf of Mexico

    Energy Technology Data Exchange (ETDEWEB)

    Bureau of Economic Geology

    2009-04-30

    The Bureau of Economic Geology was contracted to develop technologies that demonstrate the value of multicomponent seismic technology for evaluating deep-water hydrates across the Green Canyon area of the Gulf of Mexico. This report describes the methodologies that were developed to create compressional (P-P) and converted-shear (P-SV) images of near-seafloor geology from four-component ocean-bottom-cable (4C OBC) seismic data and the procedures used to integrate P-P and P-SV seismic attributes with borehole calibration data to estimate hydrate concentration across two study areas spanning 16 and 25 lease blocks (or 144 and 225 square miles), respectively. Approximately 200 km of two-dimensional 4C OBC profiles were processed and analyzed over the course of the 3-year project. The strategies we developed to image near-seafloor geology with 4C OBC data are unique, and the paper describing our methodology was peer-recognized with a Best Paper Award by the Society of Exploration Geophysicists in the first year of the project (2006). Among the valuable research findings demonstrated in this report, the demonstrated ability to image deep-water near-seafloor geology with sub-meter resolution using a standard-frequency (10-200 Hz) air gun array on the sea surface and 4C sensors on the seafloor has been the accomplishment that has received the most accolades from professional peers. Our study found that hydrate is pervasive across the two study areas that were analyzed but exists at low concentrations. Although our joint inversion technique showed that in some limited areas, and in some geologic units across those small areas, hydrates occupied up to 40-percent of the sediment pore space, we found that when hydrate was present, hydrate concentration tended to occupy only 10-percent to 20-percent of the pore volume. We also found that hydrate concentration tended to be greater near the base of the hydrate stability zone than it was within the central part of the stability

  20. Hydration in drug design. 3. Conserved water molecules at the ligand-binding sites of homologous proteins.

    Science.gov (United States)

    Poornima, C S; Dean, P M

    1995-12-01

    Water molecules are known to play an important rôle in mediating protein-ligand interactions. If water molecules are conserved at the ligand-binding sites of homologous proteins, such a finding may suggest the structural importance of water molecules in ligand binding. Structurally conserved water molecules change the conventional definition of 'binding sites' by changing the shape and complementarity of these sites. Such conserved water molecules can be important for site-directed ligand/drug design. Therefore, five different sets of homologous protein/protein-ligand complexes have been examined to identify the conserved water molecules at the ligand-binding sites. Our analysis reveals that there are as many as 16 conserved water molecules at the FAD binding site of glutathione reductase between the crystal structures obtained from human and E. coli. In the remaining four sets of high-resolution crystal structures, 2-4 water molecules have been found to be conserved at the ligand-binding sites. The majority of these conserved water molecules are either bound in deep grooves at the protein-ligand interface or completely buried in cavities between the protein and the ligand. All these water molecules, conserved between the protein/protein-ligand complexes from different species, have identical or similar apolar and polar interactions in a given set. The site residues interacting with the conserved water molecules at the ligand-binding sites have been found to be highly conserved among proteins from different species; they are more conserved compared to the other site residues interacting with the ligand. These water molecules, in general, make multiple polar contacts with protein-site residues.

  1. modelling for optimal number of line storage reservoirs in a water ...

    African Journals Online (AJOL)

    user

    the reservoir system location be integrated into the ... systems experience (figure 1), storage facilities within the system .... Therefore, a computer programme for designing cost effective water distribution net works called Economic Number of.

  2. Kinetic of formation for single carbon dioxide and mixed carbon dioxide and tetrahydrofuran hydrates in water and sodium chloride aqueous solution

    NARCIS (Netherlands)

    Sabil, K.M.; Duarte, A.R.C.; Zevenbergen, J.F.; Ahmad, M.M.; Yusup, S.; Omar, A.A.; Peters, C.J.

    2010-01-01

    A laboratory-scale reactor system is built and operated to measure the kinetic of formation for single and mixed carbon dioxide-tetrahydrofuran hydrates. The T-cycle method, which is used to collect the kinetic data, is briefly discussed. For single carbon dioxide hydrate, the induction time

  3. Kinetic of formation for single carbon dioxide and mixed carbon dioxide and tetrahydrofuran hydrates in water and sodium chloride aqueous solution

    NARCIS (Netherlands)

    Sabil, K.M.; Duarte, A.R.C.; Zevenbergen, J.F.; Ahmad, M.M.; Yusup, S.; Omar, A.A.; Peters, C.J.

    2010-01-01

    A laboratory-scale reactor system is built and operated to measure the kinetic of formation for single and mixed carbon dioxide-tetrahydrofuran hydrates. The T-cycle method, which is used to collect the kinetic data, is briefly discussed. For single carbon dioxide hydrate, the induction time decreas

  4. China's Research on Non-conventional Energy Resources- Gas Hydrate

    Institute of Scientific and Technical Information of China (English)

    Pu Ming; Ma Jianguo

    2002-01-01

    @@ Methane exists in ice-like formations called gas hydrate. Hydrate traps methane molecules inside a cage of frozen water. The magnitude of this previously unknown global storehouse of methane is truly staggering and has raised serious inquiry into the possibility of using methane hydrate as a substitute source of energy for oil and conventional natural gas. According to the estimation by PGC, gas hydrate deposits amount to 7.6 × 1018m3 and contain more than twice as much organic carbon as all the world's coal, oil and non-hydrate natural gas combined.

  5. Molecular mechanisms of decomposition of hydrated Na+Cl- ion pairs under planar nanopore conditions

    Science.gov (United States)

    Shevkunov, S. V.

    2017-02-01

    The decomposition of Na+Cl- ion pairs under the conditions of a nanoscopic planar pore with structureless walls in a material contact with water vapor at 298 K is simulated by Monte Carlo method. The transition from the state of a contact ion pair (CIP) to the state of solvent-separated ion pair (SSIP) is shown to occur as a result of an increase in the vapor pressure over a pore after exceeding the threshold number of molecules in a hydrate shell. It is found that the planar form of a molecular cluster under the conditions of a narrow pore does not level an abrupt structural transition and the formation of hydrogen bonds in the hydrate shell starts after three molecules are added. The hydrogen bond length under pore conditions is found to be resistant to variations in the hydrate shell size and coincides with that in water under normal conditions.

  6. Theoretical Investigation on the Adsorption of Ag+ and Hydrated Ag+ Cations on Clean Si(111)Surface

    Institute of Scientific and Technical Information of China (English)

    SHENG Yong-Li; LI Meng-Hua; WANG Zhi-Guo; LIU Yong-Jun

    2008-01-01

    In this paper,the adsorption of Ag+ and hydrated Ag+ cations on clean Si(111)surface were investigated by using cluster(Gaussian 03)and periodic(DMol3)ab initio calculations.Si(111)surface was described with cluster models(Si14H17 and Si22H21)and a four-silicon layer slab with periodic boundary conditions.The effect of basis set superposition error(BSSE)was taken into account by applying the counterpoise correction.The calculated results indicated that the binding energies between hydrated Ag+ cations and clean Si(111)surface are large,suggesting a strong interaction between hydrated Ag+ cations and the semiconductor surface.With the increase of number,water molecules form hydrogen bond network with one another and only one water molecule binds directly to the Ag+ cation.The Ag+ cation in aqueous solution will safely attach to the clean Si(111)surface.

  7. Proton percolation on hydrated lysozyme powders

    OpenAIRE

    Careri, G; Giansanti, A; Rupley, John A.

    1986-01-01

    The framework of percolation theory is used to analyze the hydration dependence of the capacitance measured for protein samples of pH 3-10, at frequencies from 10 kHz to 4 MHz. For all samples there is a critical value of the hydration at which the capacitance sharply increases with increase in hydration level. The threshold hc = 0.15 g of water per g of protein is independent of pH below pH 9 and shows no solvent deuterium isotope effect. The fractional coverage of the surface at hc is in cl...

  8. IMPORTANCE OF HYDRATION IN SPORTS

    Directory of Open Access Journals (Sweden)

    Goran Vasić

    2008-08-01

    Full Text Available Importance of hydration is detrmined by importance of functions of water in the human organism: i.e. regulation of body temperature, transport, excretion of waste materials through urine, digestion of food which is facilititated by saliva and gastric juices, maintenance of flexibility of organs and tissues About 60 % body mass of an adult person (males: 61 %, females: 54 % is made up of water. Water content of a newly born baby reaches 77 %, and it is up to 50 % in adults. It is very important for sportsmen to provide adequate hydration during and after the time of bodily activities. A symptom of water shortage is thirst. However, thirst is a late response of an organism and it occurs when dehydration has already taken place. Minimum in take of fluids in humans should range between one-and-half to two liters. It has been known for a long time that there is no success in sport without proper hydration in a sportsman.

  9. Effects of lanthanoid cations on the first electronic transition of liquid water studied using attenuated total reflection far-ultraviolet spectroscopy: ligand field splitting of lanthanoid hydrates in aqueous solutions.

    Science.gov (United States)

    Goto, Takeyoshi; Ikehata, Akifumi; Morisawa, Yusuke; Higashi, Noboru; Ozaki, Yukihiro

    2012-10-15

    The effects of the lanthanoid cations (Ln(3+)) on the first electronic transition (à ← X̃) of liquid water were studied from the attenuated total reflection far-ultraviolet (ATR-FUV) spectra of trivalent Ln(3+) electrolyte solutions (1 M), except Pm(3+). The à ← X̃ transition energies of the Ln(3+) electrolyte solutions show a distinct tetrad in their dependence on the number of 4f electrons of the Ln(3+) cations. For the half occupation period of the 4f electrons, the à ← X̃ transition energies decrease from La(3+) (4f(0), 8.0375 eV) to Nd(3+) (4f(3), 8.0277 eV) and increase from Sm(3+) (4f(5), 8.0279 eV) to Gd(3+) (4f(7), 8.0374 eV). For the complete occupation period, there are two local minima at Dy(3+) (4f(9), 8.0349 eV) and Yb(3+) (4f(13), 8.0355 eV). The à ← X̃ transition energies of the tetrad nodes (La(3+), Gd(3+), Ho(3+) (4f(10)), and Lu(3+) (4f(14))) increase slightly, as the nuclear charge increases in accordance with the hydration energies of the Ln(3+) cations. The energy difference (ΔE) between the à ← X̃ transition energies and the line between La(3+) and Lu(3+) is largest at Nd(3+) (80.5 cm(-1)) for the half occupation period and at Dy(3+) (26.1 cm(-1)) and Yb(3+) (24.5 cm(-1)) for the complete occupation period. The order of magnitude of ΔE is comparable to the ligand field splitting (LFS) of the ground state multiplets of Ln(3+) complexes. The observed tetrad trend of the à ← X̃ transition energies of the Ln(3+) electrolyte solutions across the 4f period reflects the hydration energies of the Ln(3+) cations and the LFS induced by water ligands.

  10. Terahertz sensing of corneal hydration.

    Science.gov (United States)

    Singh, Rahul S; Tewari, Priyamvada; Bourges, Jean Louis; Hubschman, Jean Pierre; Bennett, David B; Taylor, Zachary D; Lee, H; Brown, Elliott R; Grundfest, Warren S; Culjat, Martin O

    2010-01-01

    An indicator of ocular health is the hydrodyanmics of the cornea. Many corneal disorders deteriorate sight as they upset the normal hydrodynamics of the cornea. The mechanisms include the loss of endothelial pump function of corneal dystophies, swelling and immune response of corneal graft rejection, and inflammation and edema, which accompany trauma, burn, and irritation events. Due to high sensitivity to changes of water content in materials, a reflective terahertz (300 GHz and 3 THz) imaging system could be an ideal tool to measure the hydration level of the cornea. This paper presents the application of THz technology to visualize the hydration content across ex vivo porcine corneas. The corneas, with a thickness variation from 470 - 940 µm, were successfully imaged using a reflective pulsed THz imaging system, with a maximum SNR of 50 dB. To our knowledge, no prior studies have reported on the use of THz in measuring hydration in corneal tissues or other ocular tissues. These preliminary findings indicate that THz can be used to accurately sense hydration levels in the cornea using a pulsed, reflective THz imaging system.

  11. Physical properties of gas hydrates

    Energy Technology Data Exchange (ETDEWEB)

    Kliner, J.T.R.; Grozic, J.L.H. [Calgary Univ., AB (Canada)

    2003-07-01

    Gas hydrates are naturally occurring, solid crystalline compounds (clathrates) that encapsulate gas molecules inside the lattices of hydrogen bonded water molecules within a specific temperature-pressure stability zone. Estimates of the total quantity of available methane gas in natural occurring hydrates are based on twice the energy content of known conventional fossil fuels reservoirs. Accurate and reliable in-situ quantification techniques are essential in determining the economic viability of this potential energy yield, which is dependent upon several factors such as sensitivity of the temperature-pressure stability zone, sediment type, porosity, permeability, concentration/abundance of free gas, spatial distribution in pore spaces, specific cage occupancy, and the influence of inhibitors. Various techniques like acoustic P and S waves, time domain reflectometry, and electrical resistance have been used to analyze the quantity and spatial distribution of the gas hydrate samples. These techniques were reviewed and the results obtained in the course of gas hydrate research were presented. 34 refs., 8 figs.

  12. Cloud liquid water, mean droplet radius, and number density measurements using a Raman lidar

    Energy Technology Data Exchange (ETDEWEB)

    Whiteman, David N. [Laser Remote Sensing Branch, NASA Goddard Space Flight Center, Greenbelt, Maryland (United States); Melfi, S. Harvey [Department of Physics, University of Maryland, Baltimore County, Baltimore (United States)

    1999-12-27

    A new technique for measuring cloud liquid water, mean droplet radius, and droplet number density is outlined. The technique is based on simultaneously measuring Raman and Mie scattering from cloud liquid droplets using a Raman lidar. Laboratory experiments on liquid microspheres have shown that the intensity of Raman scattering is proportional to the amount of liquid present in the spheres. This fact is used as a constraint on calculated Mie intensity assuming a gamma function particle size distribution. The resulting retrieval technique is shown to give stable solutions with no false minima. It is tested using Raman lidar data where the liquid water signal was seen as an enhancement to the water vapor signal. The general relationship of retrieved average radius and number density is consistent with traditional cloud physics models. Sensitivity to the assumed maximum cloud liquid water amount and the water vapor mixing ratio calibration are tested. Improvements to the technique are suggested. (c) 1999 American Geophysical Union.

  13. Cloud Liquid Water, Mean Droplet Radius and Number Density Measurements Using a Raman Lidar

    Science.gov (United States)

    Whiteman, David N.; Melfi, S. Harvey

    1999-01-01

    A new technique for measuring cloud liquid water, mean droplet radius and droplet number density is outlined. The technique is based on simultaneously measuring Raman and Mie scattering from cloud liquid droplets using a Raman lidar. Laboratory experiments on liquid micro-spheres have shown that the intensity of Raman scattering is proportional to the amount of liquid present in the spheres. This fact is used as a constraint on calculated Mie intensity assuming a gamma function particle size distribution. The resulting retrieval technique is shown to give stable solutions with no false minima. It is tested using Raman lidar data where the liquid water signal was seen as an enhancement to the water vapor signal. The general relationship of retrieved average radius and number density is consistent with traditional cloud physics models. Sensitivity to the assumed maximum cloud liquid water amount and the water vapor mixing ratio calibration are tested. Improvements to the technique are suggested.

  14. EXPERIMENTAL INVESTIGATION ON GAS HYDRATE FORMATION IN PRESENCE OF ADDITIVE COMPONENTS

    Institute of Scientific and Technical Information of China (English)

    SUN Zhigao; FAN Shuanshi; GUO Kaihua

    2003-01-01

    Additives were used to increase gas hydrate formation rate and storage capacity. Experimental tests of methane hydrate formation were carried out in surfactant water solutions in a high-pressure cell.Sodium dodecyl sulfate (SDS) and alkyl polysaccharide glycoside (APG) were used to increase hydrate formation. The effect of SDS on hydrate formation is more pronounced compared APG. Cyclopentane (CP) also improves hydrate formation rates while it cannot increase methane gas storage capacity.

  15. Dielectric dispersion and protonic conduction in hydrated purple membrane.

    Science.gov (United States)

    Kovács, I; Váró, G

    1988-01-01

    Dielectric dispersion effects were studied in purple membranes of different hydration levels. The capacitance and conductivity were measured over the frequency range of 10(2) Hz to 10(5) Hz. With increase in the hydration level, the conductivity increases sharply above the critical hydration of hc = 0.06 g H2O/g protein. This critical hydration is close to the extent of the first continuous strongly bound water layer and is interpreted as the threshold for percolative proton transfer. The capacitance increases continuously with increasing hydration and a larger increase above the water content of 0.1 g H2O/g protein can be seen only at low frequencies. Maxwell-Wagner relaxation also appears above this hydration, showing the presence of a bulk water phase.

  16. Some theoretical considerations concerning ion hydration in the case of ion transfer between water and 1,2-dichloroethane

    CERN Document Server

    Sánchez, C; Baruzzi, A M; Leiva, E P M

    1997-01-01

    Some aspects of direct ion transfer across the water/1,2-dichloroethane are analyzed using a very simple model based on thermodynamic considerations. It was concluded that ion solvation by water molecules may occur in some particular cases in the organic phase, delivering an important contribution to the Gibbs free energy of ion transfer between the aqueous and the organic phase. In general terms, this particular type of transfer should be favored in the case of highly charged small ions at interfaces with a relatively low surface tension and a large difference between the reciprocal of the corresponding dielectric constants.

  17. Design and installation of a high Reynolds number recirculating water tunnel

    Science.gov (United States)

    Daniel, Libin

    The High-Reynolds Number Fluid Mechanics Laboratory has recently been established at Oklahoma State University (OSU). The three primary components of the laboratory are 1) a recirculating water tunnel, 2) a multiphase pipe flow facility, and 3) a multi-scale flow visualization system. This thesis focuses on the design and fabrication of the water tunnel, which will be used for high-Reynolds number turbulent boundary layer research. Two main design criteria for the water tunnel were to achieve a momentum thickness based Reynolds number in excess of 104 and to have high optical access to the flow surfaces in the test section. This is being achieved with a 1 m. long test section and a maximum flow speed of 10 m/s. This Reynolds number was targeted to bridge the gap between typical university water tunnels (103) and the world's largest water tunnel facilities (105). The water tunnel is powered by a 150 hp motor and a 4500 gpm capacity centrifugal pump. The water tunnel is designed for a maximum operating pressure of 40 psi. This will make the facility a low cost option to perform high-Reynolds number aerodynamic and hydrodynamic tests. Improved flow imaging capability is a major advantage to liquid based fluid facilities because of the increased density for seeding and reduced field-of-view for equivalent Reynolds number. The laboratory's state-of-the-art flow visualization system can be used for time-resolved and phase averaged stereo- particle-image-velocimetry (sPIV), laser-induced-fluorescence, and high-speed imaging. Design provisions are also made to allow a multi-phase loop to share the pump and motor configuration of this water tunnel facility. The major design decisions that went into the design of the water tunnel facility are discussed. The design considerations that were taken into account for the test section, flow conditioning sections and the entire flow loop are discussed in greater detail. The final configuration and the technical drawings of the water

  18. Origins of hydration lubrication.

    Science.gov (United States)

    Ma, Liran; Gaisinskaya-Kipnis, Anastasia; Kampf, Nir; Klein, Jacob

    2015-01-14

    Why is friction in healthy hips and knees so low? Hydration lubrication, according to which hydration shells surrounding charges act as lubricating elements in boundary layers (including those coating cartilage in joints), has been invoked to account for the extremely low sliding friction between surfaces in aqueous media, but not well understood. Here we report the direct determination of energy dissipation within such sheared hydration shells. By trapping hydrated ions in a 0.4-1 nm gap between atomically smooth charged surfaces as they slide past each other, we are able to separate the dissipation modes of the friction and, in particular, identify the viscous losses in the subnanometre hydration shells. Our results shed light on the origins of hydration lubrication, with potential implications both for aqueous boundary lubricants and for biolubrication.

  19. Vibrational echo spectral observables and frequency fluctuations of hydration shell water around a fluoride ion from first principles simulations

    Indian Academy of Sciences (India)

    DEEPAK OJHA; AMALENDU CHANDRA

    2017-07-01

    Aqueous solution of a fluoride ion at 300K is studied using the method of ab initio molecular dynamics simulation. Instantaneous fluctuations in vibrational frequencies of local OD stretch modes of deuterated water are calculated using a time-series analysis of the simulated trajectory. The vibrational spectraldiffusion of OD modes in the first and second solvation shells and also in bulk of the aqueous fluoride ionic solution are studied through calculations of the frequency time correlation function (FTCF), joint probability distributions, slope of three pulse photon echo (S3PE) and two dimensional infrared spectrum (2D-IR). The vibrational spectral dynamics in the first solvation shell shows decay with three components which can be correlated with the dynamics of intact ion-water hydrogen bonds, ion-water hydrogen bond lifetime and the escape dynamics of water molecules from the solvation shell. The vibrational spectral diffusion of OD modes in the second solvation shell and in the bulk show very similar decay behavior. The timescales obtained from FTCF, S3PE and the slope of nodal line (SNL) of 2D-IR are found to be in reasonable agreement with each others.

  20. The effect of water structure and solute hydration on the kinetics of mineral growth and dissolution (Arne Richter Award for Outstanding Young Scientists)

    Science.gov (United States)

    Ruiz-Agudo, E.; Putnis, C. V.; Putnis, A.

    2012-04-01

    Classical crystal growth theory relates growth and dissolution rates to the degree of supersaturation. However, the solution composition may also affect the growth rate of carbonate minerals, via the Ca2+ to CO32- concentration ratio (e.g. Perdikouri et al., 2009; Stack and Grantham, 2010), ionic strength (e.g. Ruiz-Agudo et al. 2010) or the presence of organic matter (Hoch et al., 2000). For this reason, the influence of these parameters on the kinetics of mineral growth and dissolution has generated a considerable amount of research in the last decade. In particular, effects of both inorganic and organic impurities on mineral growth and dissolution have been frequently reported in the literature. Commonly, water in contact with rock forming minerals, contains significant and variable amounts of ions in solution. The effect of such ions on dissolution and growth rates has been traditionally ascribed to changes in solubility. However, experimental studies performed on different minerals have shown that the dependence of growth or dissolution rates on ionic strength is complex, and that the effect of ionic strength is not independent of the ionic species producing it. Here, we report investigations aimed at addressing the basic hypothesis that mineral growth and dissolution is governed by complex interactions between solvent structure, surface hydration and the ion solvation environment induced by the presence of electrolytes. It is proposed that any factor affecting ion solvation should alter growth and dissolution rates. These results have opened the possibility of a new understanding of very diverse phenomena in geochemistry and demonstrate the need for the inclusion of this "hydration effect" in the development of predictive models that describe crystal growth and dissolution in complex systems, such as those found in nature. Furthermore, we can hypothesise that ion-assisted dehydration of trace and minor element ions could occur in biological systems, thus

  1. Use of Moringa oleifera seed extracts to reduce helminth egg numbers and turbidity in irrigation water.

    Science.gov (United States)

    Sengupta, Mita E; Keraita, Bernard; Olsen, Annette; Boateng, Osei K; Thamsborg, Stig M; Pálsdóttir, Guðný R; Dalsgaard, Anders

    2012-07-01

    Water from wastewater-polluted streams and dug-outs is the most commonly used water source for irrigation in urban farming in Ghana, but helminth parasite eggs in the water represent health risks when used for crop production. Conventional water treatment is expensive, requires advanced technology and often breaks down in less developed countries so low cost interventions are needed. Field and laboratory based trials were carried out in order to investigate the effect of the natural coagulant Moringa oleifera (MO) seed extracts in reducing helminh eggs and turbidity in irrigation water, turbid water, wastewater and tap water. In medium to high turbid water MO extracts were effective in reducing the number of helminth eggs by 94-99.5% to 1-2 eggs per litre and the turbidity to 7-11 NTU which is an 85-96% reduction. MO is readily available in many tropical countries and can be used by farmers to treat high turbid water for irrigation, however, additional improvements of water quality, e.g. by sand filtration, is suggested to meet the guideline value of ≤ 1 helminth egg per litre and a turbidity of ≤ 2 NTU as recommended by the World Health Organization and the U.S. Environmental Protection Agency for water intended for irrigation. A positive correlation was established between reduction in turbidity and helminth eggs in irrigation water, turbid water and wastewater treated with MO. This indicates that helminth eggs attach to suspended particles and/or flocs facilitated by MO in the water, and that turbidity and helminth eggs are reduced with the settling flocs. However, more experiments with water samples containing naturally occurring helminth eggs are needed to establish whether turbidity can be used as a proxy for helminth eggs.

  2. Aquaporins are critical for provision of water during lactation and intrauterine progeny hydration to maintain tsetse fly reproductive success.

    Directory of Open Access Journals (Sweden)

    Joshua B Benoit

    2014-04-01

    Full Text Available Tsetse flies undergo drastic fluctuations in their water content throughout their adult life history due to events such as blood feeding, dehydration and lactation, an essential feature of the viviparous reproductive biology of tsetse. Aquaporins (AQPs are transmembrane proteins that allow water and other solutes to permeate through cellular membranes. Here we identify tsetse aquaporin (AQP genes, examine their expression patterns under different physiological conditions (blood feeding, lactation and stress response and perform functional analysis of three specific genes utilizing RNA interference (RNAi gene silencing. Ten putative aquaporins were identified in the Glossina morsitans morsitans (Gmm genome, two more than has been previously documented in any other insect. All organs, tissues, and body parts examined had distinct AQP expression patterns. Two AQP genes, gmmdripa and gmmdripb ( = gmmaqp1a and gmmaqp1b are highly expressed in the milk gland/fat body tissues. The whole-body transcript levels of these two genes vary over the course of pregnancy. A set of three AQPs (gmmaqp5, gmmaqp2a, and gmmaqp4b are expressed highly in the Malpighian tubules. Knockdown of gmmdripa and gmmdripb reduced the efficiency of water loss following a blood meal, increased dehydration tolerance and reduced heat tolerance of adult females. Knockdown of gmmdripa extended pregnancy length, and gmmdripb knockdown resulted in extended pregnancy duration and reduced progeny production. We found that knockdown of AQPs increased tsetse milk osmolality and reduced the water content in developing larva. Combined knockdown of gmmdripa, gmmdripb and gmmaqp5 extended pregnancy by 4-6 d, reduced pupal production by nearly 50%, increased milk osmolality by 20-25% and led to dehydration of feeding larvae. Based on these results, we conclude that gmmDripA and gmmDripB are critical for diuresis, stress tolerance and intrauterine lactation through the regulation of water and

  3. Gas hydrate dissociation structures in submarine slopes

    Energy Technology Data Exchange (ETDEWEB)

    Gidley, I.; Grozic, J.L.H. [Calgary Univ., AB (Canada). Dept. of Civil Engineering

    2008-07-01

    Studies have suggested that gas hydrates may play a role in submarine slope failures. However, the mechanics surrounding such failures are poorly understood. This paper discussed experimental tests conducted on a small-scale physical model of submarine soils with hydrate inclusions. The laboratory tests investigated the effects of slope angle and depth of burial of the hydrate on gas escape structures and slope stability. Laponite was used to model the soils due to its ability to swell and produce a clear, colorless thixotropic gel when dispersed in water. An R-11 refrigerant was used to form hydrate layers and nodules. The aim of the experiment was to investigate the path of the fluid escape structures and the development of a subsequent slip plane caused by the dissociation of the R-11 hydrates. Slope angles of 5, 10, and 15 degrees were examined. Slopes were examined using high-resolution, high-speed imaging techniques. Hydrate placement and slope inclinations were varied in order to obtain stability data. Results of the study showed that slope angle influenced the direction of travel of the escaping gas, and that the depth of burial affected sensitivity to slope angle. Theoretical models developed from the experimental data have accurately mapped deformations and stress states during testing. Further research is being conducted to investigate the influence of the size, shape, and placement of the hydrates. 30 refs., 15 figs.

  4. In-situ gas hydrate hydrate saturation estimated from various well logs at the Mount Elbert Gas Hydrate Stratigraphic Test Well, Alaska North Slope

    Science.gov (United States)

    Lee, M.W.; Collett, T.S.

    2011-01-01

    In 2006, the U.S. Geological Survey (USGS) completed detailed analysis and interpretation of available 2-D and 3-D seismic data and proposed a viable method for identifying sub-permafrost gas hydrate prospects within the gas hydrate stability zone in the Milne Point area of northern Alaska. To validate the predictions of the USGS and to acquire critical reservoir data needed to develop a long-term production testing program, a well was drilled at the Mount Elbert prospect in February, 2007. Numerous well log data and cores were acquired to estimate in-situ gas hydrate saturations and reservoir properties.Gas hydrate saturations were estimated from various well logs such as nuclear magnetic resonance (NMR), P- and S-wave velocity, and electrical resistivity logs along with pore-water salinity. Gas hydrate saturations from the NMR log agree well with those estimated from P- and S-wave velocity data. Because of the low salinity of the connate water and the low formation temperature, the resistivity of connate water is comparable to that of shale. Therefore, the effect of clay should be accounted for to accurately estimate gas hydrate saturations from the resistivity data. Two highly gas hydrate-saturated intervals are identified - an upper ???43 ft zone with an average gas hydrate saturation of 54% and a lower ???53 ft zone with an average gas hydrate saturation of 50%; both zones reach a maximum of about 75% saturation. ?? 2009.

  5. Methane Recovery from Hydrate-bearing Sediments

    Energy Technology Data Exchange (ETDEWEB)

    J. Carlos Santamarina; Costas Tsouris

    2011-04-30

    Gas hydrates are crystalline compounds made of gas and water molecules. Methane hydrates are found in marine sediments and permafrost regions; extensive amounts of methane are trapped in the form of hydrates. Methane hydrate can be an energy resource, contribute to global warming, or cause seafloor instability. This study placed emphasis on gas recovery from hydrate bearing sediments and related phenomena. The unique behavior of hydrate-bearing sediments required the development of special research tools, including new numerical algorithms (tube- and pore-network models) and experimental devices (high pressure chambers and micromodels). Therefore, the research methodology combined experimental studies, particle-scale numerical simulations, and macro-scale analyses of coupled processes. Research conducted as part of this project started with hydrate formation in sediment pores and extended to production methods and emergent phenomena. In particular, the scope of the work addressed: (1) hydrate formation and growth in pores, the assessment of formation rate, tensile/adhesive strength and their impact on sediment-scale properties, including volume change during hydrate formation and dissociation; (2) the effect of physical properties such as gas solubility, salinity, pore size, and mixed gas conditions on hydrate formation and dissociation, and it implications such as oscillatory transient hydrate formation, dissolution within the hydrate stability field, initial hydrate lens formation, and phase boundary changes in real field situations; (3) fluid conductivity in relation to pore size distribution and spatial correlation and the emergence of phenomena such as flow focusing; (4) mixed fluid flow, with special emphasis on differences between invading gas and nucleating gas, implications on relative gas conductivity for reservoir simulations, and gas recovery efficiency; (5) identification of advantages and limitations in different gas production strategies with

  6. Role of hydration on the functionality of a proteolytic enzyme α-chymotrypsin under crowded environment.

    Science.gov (United States)

    Verma, Pramod Kumar; Rakshit, Surajit; Mitra, Rajib Kumar; Pal, Samir Kumar

    2011-09-01

    Enzymes and other bio-macromolecules are not only sensitive to physical parameters such as pH, temperature and solute composition but also to water activity. A universally instructive way to vary water activity is the addition of osmotically active but otherwise inert solvents which also mimic the condition of an intercellular milieu. In the present contribution, the role of hydration on the functionality of a proteolytic enzyme α-chymotrypsin (CHT) is investigated by modulating the water activity with the addition of polyethylene glycols (PEG with an average molecular weight of 400). The addition of PEG increases the affinity of the enzyme to its substrate, however, followed by a decrease in the turnover number (k(cat)). Energetic calculations show that entrance path for the substrate is favoured, whereas the exit channel is restricted with increasing concentration of the crowding agent. This decrease is attributed to the thinning of the hydration shell of the enzyme due to the loss of critical water residues from the hydration surface of the enzyme as evidenced from volumetric and compressibility measurements. The overall secondary and tertiary structures of CHT determined from far-UV and near-UV circular dichroism (CD) measurements show no considerable change in the studied osmotic stress range. From kinetic and equilibrium data, we calculate 115 ± 30 numbers of water molecules to be altered during the enzymatic catalysis of CHT. Spectroscopic observation of water relaxation and rotational dynamics of ANS-CHT complex at various concentrations of the osmoting agent also support the dehydration of the hydration layer. Such dehydration/hydration processes during turnover imply a significant contribution of solvation to the energetics of the conformational changes.

  7. In situ study of mass transfer in aqueous solutions under high pressures via Raman spectroscopy: A new method for the determination of diffusion coefficients of methane in water near hydrate formation conditions

    Science.gov (United States)

    Lu, W.J.; Chou, I.-Ming; Burruss, R.C.; Yang, M.Z.

    2006-01-01

    A new method was developed for in situ study of the diffusive transfer of methane in aqueous solution under high pressures near hydrate formation conditions within an optical capillary cell. Time-dependent Raman spectra of the solution at several different spots along the one-dimensional diffusion path were collected and thus the varying composition profile of the solution was monitored. Diffusion coefficients were estimated by the least squares method based on the variations in methane concentration data in space and time in the cell. The measured diffusion coefficients of methane in water at the liquid (L)-vapor (V) stable region and L-V metastable region are close to previously reported values determined at lower pressure and similar temperature. This in situ monitoring method was demonstrated to be suitable for the study of mass transfer in aqueous solution under high pressure and at various temperature conditions and will be applied to the study of nucleation and dissolution kinetics of methane hydrate in a hydrate-water system where the interaction of methane and water would be more complicated than that presented here for the L-V metastable condition. ?? 2006 Society for Applied Spectroscopy.

  8. Hydrate control for WAG injection in the Ekofisk field

    Energy Technology Data Exchange (ETDEWEB)

    Lekvam, Knut; Surguchev, Leonid M.; Ekrann, Steinar; Svartaas, Thor Martin; Kelland, Malcolm; Nilsson, Svante; Oevsthus, Jorun; Gjoevikli, Nils B.

    1997-12-31

    The report relates to a hydrate formation project for the Ekofisk field on the Norwegian continental shelf. To remove the possible hydrate formation problems during WAG (Water Alternating Gas) treatment, the following project was conducted to estimate roughly the distance from the injection well that hydrate formation can be prevented by whatever treatment is most appropriate. The first aim was to test experimentally whether selected kinetic hydrate inhibitors could be used, and in which concentrations and quantities. In addition evaluations were done to calculate the required volume of the inhibitor solutions that have to be injected to prevent mixing of uninhibited water and gas. 8 figs., 8 tabs.

  9. Hydration structure of Ti(III and Cr(III: Monte Carlo simulation including three-body corrections

    Directory of Open Access Journals (Sweden)

    Ahmed M. Mohammed

    2003-12-01

    Full Text Available Classical Monte Carlo simulations were performed to investigate the solvation structures of Ti(III and Cr(III ions in water with only ion-water pair interaction potential and by including three-body correction terms. The hydration structures were evaluated in terms of radial distribution functions, coordination numbers and angular distributions. The structural parameters obtained by including three-body correction terms are in good agreement with experimental values proving that many-body effects play a crucial role in the description of the hydration structure of highly charged ions.

  10. Prospecting for marine gas hydrate resources

    Science.gov (United States)

    Boswell, Ray; Shipp, Craig; Reichel, Thomas; Shelander, Dianna; Saeki, Tetsuo; Frye, Matthew; Shedd, William; Collett, Timothy S.; McConnell, Daniel R.

    2016-01-01

    As gas hydrate energy assessment matures worldwide, emphasis has evolved away from confirmation of the mere presence of gas hydrate to the more complex issue of prospecting for those specific accumulations that are viable resource targets. Gas hydrate exploration now integrates the unique pressure and temperature preconditions for gas hydrate occurrence with those concepts and practices that are the basis for conventional oil and gas exploration. We have aimed to assimilate the lessons learned to date in global gas hydrate exploration to outline a generalized prospecting approach as follows: (1) use existing well and geophysical data to delineate the gas hydrate stability zone (GHSZ), (2) identify and evaluate potential direct indications of hydrate occurrence through evaluation of interval of elevated acoustic velocity and/or seismic events of prospective amplitude and polarity, (3) mitigate geologic risk via regional seismic and stratigraphic facies analysis as well as seismic mapping of amplitude distribution along prospective horizons, and (4) mitigate further prospect risk through assessment of the evidence of gas presence and migration into the GHSZ. Although a wide range of occurrence types might ultimately become viable energy supply options, this approach, which has been tested in only a small number of locations worldwide, has directed prospect evaluation toward those sand-hosted, high-saturation occurrences that were presently considered to have the greatest future commercial potential.

  11. Origin and character of gaseous hydrocarbons in the hydrate and non-hydrate charged sediments on the Norway - Svalbard margins

    Energy Technology Data Exchange (ETDEWEB)

    Vaular, Espen Nesheim

    2011-05-15

    Gas incubated in clathrate water-structures, stabilizes the hydrogen bonded substance termed gas hydrate. In the marine environment vast amount of carbon is stored as gas hydrates within the temperature and pressure zone these ice-like structures are stable. Natural gas hydrate mapping and characterization is important basic research that brings about critical knowledge concerning various topics. Natural gas hydrates is a vital part of the carbon cycle, it is a potential energy resource (and thereby a potential climate agent) and it is a potential geo-hazard. One of the goals the GANS initiative aimed at exploring, was the hydrate bearing sediment of the Norway -Svalbard margins, to investigate the character and expansion of natural gas hydrates. Part of the investigation was to define how the gas in the hydrated sediment was produced and where it came from. As a result this thesis addresses the matter of light hydrocarbon characterization and origin in two Norwegian hydrate deposits. On cruises to Vestnesa on the Svalbard margin and to Nyegga in the mid-Norwegian margin, samples of hydrate charged and non-hydrate charged sediments were obtained and analyzed. Through compositional and isotopic analyses the origin of the hydrate bound gas in the fluid escape feature G11 at Nyegga was determined. The hydrate incubated methane is microbial produced as well as parts of the hydrate bound ethane. The compositional analysis in both the Nyegga area and at the Vestnesa Ridge points at thermogenic contributions in the sediment interstitials and pore water. The two hydrate bearing margins show large differences in hydrocarbon content and microbial activity in the pockmarks investigated. The gravity cores from the penetrated pockmark at Vestnesa showed low hydrocarbon content and thus suggest ceased or periodic venting. The fluid flow escape features at Nyegga show large variety of flux rates based on ROV monitoring and headspace analysis of the sediment and pore water. The

  12. Indian National Gas Hydrate Program Expedition 01 report

    Science.gov (United States)

    Collett, Timothy S.; Riedel, M.; Boswell, R.; Presley, J.; Kumar, P.; Sathe, A.; Sethi, A.; Lall, M.; ,

    2015-01-01

    Gas hydrate is a naturally occurring “ice-like” combination of natural gas and water that has the potential to serve as an immense resource of natural gas from the world’s oceans and polar regions. However, gas-hydrate recovery is both a scientific and a technical challenge and much remains to be learned about the geologic, engineering, and economic factors controlling the ultimate energy resource potential of gas hydrate. The amount of natural gas contained in the world’s gas-hydrate accumulations is enormous, but these estimates are speculative and range over three orders of magnitude from about 2,800 to 8,000,000 trillion cubic meters of gas. By comparison, conventional natural gas accumulations (reserves and undiscovered, technically recoverable resources) for the world are estimated at approximately 440 trillion cubic meters. Gas recovery from gas hydrate is hindered because the gas is in a solid form and because gas hydrate commonly occurs in remote Arctic and deep marine environments. Proposed methods of gas recovery from gas hydrate generally deal with disassociating or “melting” in situ gas hydrate by heating the reservoir beyond the temperature of gas-hydrate formation, or decreasing the reservoir pressure below hydrate equilibrium. The pace of energy-related gas hydrate assessment projects has accelerated over the past several years.

  13. Solid state interconversion between anhydrous norfloxacin and its hydrates.

    Science.gov (United States)

    Chongcharoen, Wanchai; Byrn, Stephen R; Sutanthavibul, Narueporn

    2008-01-01

    This work is focused on characterizing and evaluating the solid state interconversion of norfloxacin (NF) hydrates. Four stoichiometric NF hydrates, dihydrate, hemipentahydrate, trihydrate, pentahydrate and a disordered NF state, were generated by various methods and characterized by X-ray powder diffractometry (XRPD), thermal analysis and Karl Fisher titrimetry. XRPD patterns of all NF hydrates exhibited crystalline structures. NF hydrate conversion was studied with respect to mild elevated temperature and various degrees of moisture levels. NF hydrates transformed to anhydrous NF Form A after gentle heating at 60 degrees C for 48 h except dihydrate and trihydrate where mixture in XRPD patterns between anhydrous NF Form A and former structures existed. Desiccation of NF hydrates at 0% RH for 7 days resulted in only partial removal of water molecules from the hydrated structures. The hydrated transitional phase and the disordered NF state were obtained from the incomplete dehydration of NF hydrates after thermal treatment and pentahydrate NF after desiccation, respectively. Anhydrous NF Form A and NF hydrates transformed to pentahydrate NF when exposed to high moisture environment except dihydrate. In conclusion, surrounding moisture levels, temperatures and the duration of exposure strongly influenced the interconversion pathways and stoichiometry of anhydrous NF and its hydrates. (c) 2007 Wiley-Liss, Inc.

  14. Glass powder blended cement hydration modelling

    Science.gov (United States)

    Saeed, Huda

    The use of waste materials in construction is among the most attractive options to consume these materials without affecting the environment. Glass is among these types of potential waste materials. In this research, waste glass in powder form, i.e. glass powder (GP) is examined for potential use in enhancing the characteristics of concrete on the basis that it is a pozzolanic material. The experimental and the theoretical components of the work are carried out primarily to prove that glass powder belongs to the "family" of the pozzolanic materials. The chemical and physical properties of the hydrated activated glass powder and the hydrated glass powder cement on the microstructure level have been studied experimentally and theoretically. The work presented in this thesis consists of two main phases. The first phase contains experimental investigations of the reaction of glass powder with calcium hydroxide (CH) and water. In addition, it includes experiments that are aimed at determining the consumption of water and CH with time. The reactivity, degree of hydration, and nature of the pore solution of the glass powder-blended cement pastes and the effect of adding different ratios of glass powder on cement hydration is also investigated. The experiments proved that glass powder has a pozzolanic effect on cement hydration; hence it enhances the chemical and physical properties of cement paste. Based on the experimental test results, it is recommended to use a glass powder-to-cement ratio (GP/C) of 10% as an optimum ratio to achieve the best hydration and best properties of the paste. Two different chemical formulas for the produced GP C-S-H gel due to the pure GP and GP-CH pozzolanic reaction hydration are proposed. For the pure GP hydration, the produced GP C-S-H gel has a calcium-to-silica ratio (C/S) of 0.164, water-to-silica ratio (H/S) of 1.3 and sodium/silica ratio (N/S) of 0.18. However, for the GP-CH hydration, the produced GP C-S-H gel has a C/S ratio of 1

  15. Authigenic gypsum found in gas hydrate-associated sediments from Hydrate Ridge, the eastern North Pacific

    Institute of Scientific and Technical Information of China (English)

    WANG; Jiasheng; Erwin; Suess; Dirk; Rickert

    2004-01-01

    Characteristic gypsum micro-sphere and granular mass were discovered by binocular microscope in the gas hydrate-associated sediments at cores SO143-221 and SO143/TVG40-2A respectively on Hydrate Ridge of Cascadia margin, the eastern North Pacific. XRD patterns and EPA analyses show both micro-sphere and granular mass of the crystals have the typical peaks and the typical main chemical compositions of gypsum, although their weight percents are slightly less than the others in the non-gas hydrate-associated marine regions. SEM pictures show that the gypsum crystals have clear crystal boundaries, planes, edges and cleavages of gypsum in form either of single crystal or of twin crystals. In view of the fact that there are meanwhile gas hydrate-associated authigenic carbonates and SO42(-rich pore water in the same sediment cores, it could be inferred reasonably that the gypsums formed also authigenically in the gas hydrate-associated environment too, most probably at the interface between the downward advecting sulfate-rich seawater and the below gas hydrate, which spilled calcium during its formation on Hydrate Ridge. The two distinct forms of crystal intergrowth, which are the granular mass of series single gypsum crystals at core SO143/TVG40-2A and the microsphere of gypsum crystals accompanied with detrital components at core SO143-221 respectively, indicate that they precipitated most likely in different interstitial water dynamic environments. So, the distinct authigenic gypsums found in gas hydrate-associated sediments on Hydrate Ridge could also be believed as one of the parameters which could be used to indicate the presence of gas hydrate in an unknown marine sediment cores.

  16. Methane hydrate stability and anthropogenic climate change

    Directory of Open Access Journals (Sweden)

    D. Archer

    2007-07-01

    Full Text Available Methane frozen into hydrate makes up a large reservoir of potentially volatile carbon below the sea floor and associated with permafrost soils. This reservoir intuitively seems precarious, because hydrate ice floats in water, and melts at Earth surface conditions. The hydrate reservoir is so large that if 10% of the methane were released to the atmosphere within a few years, it would have an impact on the Earth's radiation budget equivalent to a factor of 10 increase in atmospheric CO2.

    Hydrates are releasing methane to the atmosphere today in response to anthropogenic warming, for example along the Arctic coastline of Siberia. However most of the hydrates are located at depths in soils and ocean sediments where anthropogenic warming and any possible methane release will take place over time scales of millennia. Individual catastrophic releases like landslides and pockmark explosions are too small to reach a sizable fraction of the hydrates. The carbon isotopic excursion at the end of the Paleocene has been interpreted as the release of thousands of Gton C, possibly from hydrates, but the time scale of the release appears to have been thousands of years, chronic rather than catastrophic.

    The potential climate impact in the coming century from hydrate methane release is speculative but could be comparable to climate feedbacks from the terrestrial biosphere and from peat, significant but not catastrophic. On geologic timescales, it is conceivable that hydrates could release as much carbon to the atmosphere/ocean system as we do by fossil fuel combustion.

  17. Methane hydrate stability and anthropogenic climate change

    Directory of Open Access Journals (Sweden)

    D. Archer

    2007-04-01

    Full Text Available Methane frozen into hydrate makes up a large reservoir of potentially volatile carbon below the sea floor and associated with permafrost soils. This reservoir intuitively seems precarious, because hydrate ice floats in water, and melts at Earth surface conditions. The hydrate reservoir is so large that if 10% of the methane were released to the atmosphere within a few years, it would have an impact on the Earth's radiation budget equivalent to a factor of 10 increase in atmospheric CO2.

    Hydrates are releasing methane to the atmosphere today in response to anthropogenic warming, for example along the Arctic coastline of Siberia. However most of the hydrates are located at depths in soils and ocean sediments where anthropogenic warming and any possible methane release will take place over time scales of millennia. Individual catastrophic releases like landslides and pockmark explosions are too small to reach a sizable fraction of the hydrates. The carbon isotopic excursion at the end of the Paleocene has been interpreted as the release of thousands of Gton C, possibly from hydrates, but the time scale of the release appears to have been thousands of years, chronic rather than catastrophic.

    The potential climate impact in the coming century from hydrate methane release is speculative but could be comparable to climate feedbacks from the terrestrial biosphere and from peat, significant but not catastrophic. On geologic timescales, it is conceivable that hydrates could release much carbon to the atmosphere/ocean system as we do by fossil fuel combustion.

  18. Octa-coordination and the hydrated Ba2+(aq) ion

    CERN Document Server

    Chaudhari, Mangesh I; Rempe, Susan B

    2014-01-01

    The hydration structure of Ba^{2+} ion is important for understanding blocking mechanisms in potassium ion channels. Here, we combine statistical mechanical theory, ab initio molecular dynamics simulations, and electronic structure methods to calculate the hydration free energy and local hydration structure of Ba^{2+}(aq). The predicted hydration free energy (-302.9$\\pm$0.7 kcal/mol) matches the experimental value (-302.56 kcal/mol) when the fully occupied and exclusive inner solvation shell is treated. In the local environment defined by the inner and first shell of hydrating waters, Ba^{2+} is directly coordinated by eight (8) waters. Octa-coordination resembles the structure of Ba^{2+} and K^+ bound in potassium ion channels, but differs from the local hydration structure of K^+(aq) determined earlier.

  19. Methane Production and Carbon Capture by Hydrate Swapping

    DEFF Research Database (Denmark)

    Mu, Liang; von Solms, Nicolas

    2016-01-01

    gas molecules in the structural lattice. In this work, we quantitatively investigate the swapping behavior from injection of pure carbon dioxide and the (CO2 + N2) binary gas mixture through artificial hydrate-bearing sandstone samples by use of a core-flooding experimental apparatus. A total of 13...... of pure carbon dioxide in swapping methane from its hydrate phase; the methane recovery efficiency in brine water systems is enhanced relative to pure water systems. The replenishment of a fresh (CO2 + N2) gas mixture into the vapor phase can be considered as an efficient extraction method because 46...... in small hydrate cages, as long as the equilibrium formation pressure of (CO2 + N2) binary gas hydrate is below that of methane hydrate, even though adding nitrogen to carbon dioxide reduces the thermodynamic driving force for the formation of a new hydrate. When other conditions are similar, the methane...

  20. Development of Alaskan gas hydrate resources. Final report

    Energy Technology Data Exchange (ETDEWEB)

    Kamath, V.A.; Sharma, G.D.; Patil, S.L.

    1991-06-01

    The research undertaken in this project pertains to study of various techniques for production of natural gas from Alaskan gas hydrates such as, depressurization, injection of hot water, steam, brine, methanol and ethylene glycol solutions through experimental investigation of decomposition characteristics of hydrate cores. An experimental study has been conducted to measure the effective gas permeability changes as hydrates form in the sandpack and the results have been used to determine the reduction in the effective gas permeability of the sandpack as a function of hydrate saturation. A user friendly, interactive, menu-driven, numerical difference simulator has been developed to model the dissociation of natural gas hydrates in porous media with variable thermal properties. A numerical, finite element simulator has been developed to model the dissociation of hydrates during hot water injection process.

  1. Effect of Gemini-type surfactant on methane hydrate formation

    Energy Technology Data Exchange (ETDEWEB)

    Jeong, K.E.; Park, J.M.; Kim, C.U.; Chae, H.J.; Jeong, S.Y. [Korea Research Inst. of Chemical Technology, Jang-Dong, Yuseong-Gu, Daejeon (Korea, Republic of)

    2008-07-01

    Natural gas hydrates are formed from water and natural gas molecules at particular temperatures and pressures that become ice-like inclusion compounds. Gas hydrates offer several benefits such as energy resource potential and high storage capacity of natural gas in the form of hydrates. However, the application of natural gas hydrates has been deterred by its low formation rate and low conversion ratio of water into hydrate resulting in low actual storage capacity. This paper presented an experimental study to determine the effect of adding a novel Gemini-type surfactant on methane hydrate formation. The experimental study was described with reference to the properties of prepared diols and properties of prepared disulfonates. Gemini surfactant is the family of surfactant molecules possessing more than one hydrophobic tail and hydrophilic head group. They generally have better surface-active properties than conventional surfactants of equal chain length. The paper presented the results of the study in terms of the reactions of diols with propane sultone; storage capacity of hydrate formed with and without surfactant; and methane hydrate formation with and without disulfonate. It was concluded that the methane hydrate formation was accelerated by the addition of novel anionic Gemini-type surfactants and that hydrate formation was influenced by the surfactant concentration and alkyl chain length. For a given concentration, the surfactant with the highest chain length demonstrated the highest formation rate and storage capacity. 5 refs., 3 tabs., 4 figs.

  2. Observations of different core water cluster ions Y-(H2O)n (Y = O2, HOx, NOx, COx) and magic number in atmospheric pressure negative corona discharge mass spectrometry.

    Science.gov (United States)

    Sekimoto, Kanako; Takayama, Mitsuo

    2011-01-01

    Reliable mass spectrometry data from large water clusters Y(-)(H(2)O)(n) with various negative core ions Y(-) such as O(2)(-), HO(-), HO(2)(-), NO(2)(-), NO(3)(-), NO(3)(-)(HNO(3))(2), CO(3)(-) and HCO(4)(-) have been obtained using atmospheric pressure negative corona discharge mass spectrometry. All the core Y(-) ions observed were ionic species that play a central role in tropospheric ion chemistry. These mass spectra exhibited discontinuities in ion peak intensity at certain size clusters Y(-)(H(2)O)(m) indicating specific thermochemical stability. Thus, Y(-)(H(2)O)(m) may correspond to the magic number or first hydrated shell in the cluster series Y(-)(H(2)O)(n). The high intensity discontinuity at HO(-)(H(2)O)(3) observed was the first mass spectrometric evidence for the specific stability of HO(-)(H(2)O)(3) as the first hydrated shell which Eigen postulated in 1964. The negative ion water clusters Y(-)(H(2)O)(n) observed in the mass spectra are most likely to be formed via core ion formation in the ambient discharge area (760 torr) and the growth of water clusters by adiabatic expansion in the vacuum region of the mass spectrometers (≈1 torr). The detailed mechanism of the formation of the different core water cluster ions Y(-)(H(2)O)(n) is described.

  3. Modeling DNA hydration: comparison of calculated and experimental hydration properties of nuclic acid bases.

    Science.gov (United States)

    Poltev, V I; Malenkov, G G; Gonzalez, E J; Teplukhin, A V; Rein, R; Shibata, M; Miller, J H

    1996-02-01

    Hydration properties of individual nucleic acid bases were calculated and compared with the available experimental data. Three sets of classical potential functions (PF) used in simulations of nucleic acid hydration were juxtaposed: (i) the PF developed by Poltev and Malenkov (PM), (ii) the PF of Weiner and Kollman (WK), which together with Jorgensen's TIP3P water model are widely used in the AMBER program, and (iii) OPLS (optimized potentials for liquid simulations) developed by Jorgensen (J). The global minima of interaction energy of single water molecules with all the natural nucleic acid bases correspond to the formation of two water-base hydrogen bonds (water bridging of two hydrophilic atoms of the base). The energy values of these minima calculated via PM potentials are in somewhat better conformity with mass-spectrometric data than the values calculated via WK PF. OPLS gave much weaker water-base interactions for all compounds considered, thus these PF were not used in further computations. Monte Carlo simulations of the hydration of 9-methyladenine, 1-methyluracil and 1-methylthymine were performed in systems with 400 water molecules and periodic boundary conditions. Results of simulations with PM potentials give better agreement with experimental data on hydration energies than WK PF. Computations with PM PF of the hydration energy of keto and enol tautomers of 9-methylguanine can account for the shift in the tautomeric equilibrium of guanine in aqueous media to a dominance of the keto form in spite of nearly equal intrinsic stability of keto and enol tautomers. The results of guanine hydration computations are discussed in relation to mechanisms of base mispairing errors in nucleic acid biosynthesis. The data presented in this paper along with previous results on simulation of hydration shell structures in DNA duplex grooves provide ample evidence for the advantages of PM PF in studies of nucleic-acid hydration.

  4. Crystal structures of highly simplified BPTIs provide insights into hydration-driven increase of unfolding enthalpy.

    Science.gov (United States)

    Islam, Mohammad Monirul; Yohda, Masafumi; Kidokoro, Shun-Ichi; Kuroda, Yutaka

    2017-03-07

    We report a thermodynamic and structural analysis of six extensively simplified bovine pancreatic trypsin inhibitor (BPTI) variants containing 19-24 alanines out of 58 residues. Differential scanning calorimetry indicated a two-state thermal unfolding, typical of a native protein with densely packed interior. Surprisingly, increasing the number of alanines induced enthalpy stabilization, which was however over-compensated by entropy destabilization. X-ray crystallography indicated that the alanine substitutions caused the recruitment of novel water molecules facilitating the formation of protein-water hydrogen bonds and improving the hydration shells around the alanine's methyl groups, both of which presumably contributed to enthalpy stabilization. There was a strong correlation between the number of water molecules and the thermodynamic parameters. Overall, our results demonstrate that, in contrast to our initial expectation, a protein sequence in which over 40% of the residues are alanines can retain a densely packed structure and undergo thermal denaturation with a large enthalpy change, mainly contributed by hydration.

  5. Hydration Assessment of Athletes

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    @@ KEY POINTS · Although there is no scientific consensus for 1 ) howbest to assess the hydration status of athletes, 2)what criteria to use as acceptable outcome measurements, or 3) the best time to apply practical assessment methods, there are methods that can be used toprovide athletes with useful feedback about their hydration status

  6. Ionic hydrates, M(p)X(q).nH(2)O: lattice energy and standard enthalpy of formation estimation.

    Science.gov (United States)

    Jenkins, H Donald Brooke; Glasser, Leslie

    2002-08-26

    This paper is one of a series (see: Inorg. Chem. 1999, 38, 3609; J. Am. Chem. Soc. 2000, 122, 632; Inorg. Chem. 2002, 41, 2364) exploring simple approaches for the estimation of lattice energies of ionic materials, avoiding elaborate computation. Knowledge of lattice energy can lead, via thermochemical cycles, to the evaluation of the underlying thermodynamics involving the preparation and subsequent reactions of inorganic materials. A simple and easy to use equation for the estimation of the lattice energy of hydrate salts, U(POT)(M(p)X(q).nH(2)O) (and therefore for solvated salts, M(p)X(q).nS, in general), using either the density or volume of the hydrate, or of another hydrate, or of the parent anhydrous salt or the volumes of the individual ions, is derived from first principles. The equation effectively determines the hydrate lattice energy, U(POT)(M(p)X(q).nH(2)O), from a knowledge of the (estimated) lattice energy, U(POT)(M(p)X(q)), of the parent salt by the addition of ntheta(U) where theta(U)(H(2)O)/kJ mol(-1) = 54.3 and n is the number of water molecules. The average volume of the water molecule of hydration, V(m)(H(2)O)/nm(3) = 0.0245, has been determined from data on a large series of hydrates by plotting hydrate/parent salt volume differences against n. The enthalpy of incorporation of a gaseous water molecule into the structure of an ionic hydrate, [Delta(f)H degrees (M(p)X(q).nH(2)O,s) - Delta(f)H degrees (M(p)X(q),s) - nDelta(f)H degrees (H(2)O,g)], is shown to be a constant, -56.8 kJ (mol of H(2)O)(-1). The physical implications with regard to incorporation of the water into various types of solid-state structures are considered. Examples are given of the use of the derived hydrate lattice energy equation. Standard enthalpies of formation of a number of hydrates are thereby predicted.

  7. Electrical properties of methane hydrate + sediment mixtures: The σ of CH4 Hydrate + Sediment

    Energy Technology Data Exchange (ETDEWEB)

    Du Frane, Wyatt L. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Stern, Laura A. [U. S. Geological Survey, Menlo Park, CA (United States); Constable, Steven [Scripps Institution of Oceanography, La Jolla, CA (United States); Weitemeyer, Karen A. [Scripps Institution of Oceanography, La Jolla, CA (United States); National Oceanography Centre Southampton (United Kingdom), Univ. of Southampton Waterfront Campus, Southampton (United Kingdom); Smith, Megan M. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Roberts, Jeffery J. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)

    2015-07-30

    Knowledge of the electrical properties of multicomponent systems with gas hydrate, sediments, and pore water is needed to help relate electromagnetic (EM) measurements to specific gas hydrate concentration and distribution patterns in nature. We built a pressure cell capable of measuring in situ electrical properties of multicomponent systems such that the effects of individual components and mixing relations can be assessed. We first established the temperature-dependent electrical conductivity (σ) of pure, single-phase methane hydrate to be ~5 orders of magnitude lower than seawater, a substantial contrast that can help differentiate hydrate deposits from significantly more conductive water-saturated sediments in EM field surveys. We report σ measurements of two-component systems in which methane hydrate is mixed with variable amounts of quartz sand or glass beads. Sand by itself has low σ but is found to increase the overall σ of mixtures with well-connected methane hydrate. Alternatively, the overall σ decreases when sand concentrations are high enough to cause gas hydrate to be poorly connected, indicating that hydrate grains provide the primary conduction path. Our measurements suggest that impurities from sand induce chemical interactions and/or doping effects that result in higher electrical conductivity with lower temperature dependence. Finally, these results can be used in the modeling of massive or two-phase gas-hydrate-bearing systems devoid of conductive pore water. Further experiments that include a free water phase are the necessary next steps toward developing complex models relevant to most natural systems.

  8. A positron annihilation study of hydrated DNA

    DEFF Research Database (Denmark)

    Warman, J. M.; Eldrup, Morten Mostgaard

    1986-01-01

    Positron annihilation measurements are reported for hydrated DNA as a function of water content and as a function of temperature (20 to -180.degree. C) for samples containing 10 and 50% wt of water. The ortho-positronium mean lifetime and its intensity show distinct variations with the degree...

  9. Nuclear Well Log Properties of Natural Gas Hydrate Reservoirs

    Science.gov (United States)

    Burchwell, A.; Cook, A.

    2015-12-01

    Characterizing gas hydrate in a reservoir typically involves a full suite of geophysical well logs. The most common method involves using resistivity measurements to quantify the decrease in electrically conductive water when replaced with gas hydrate. Compressional velocity measurements are also used because the gas hydrate significantly strengthens the moduli of the sediment. At many gas hydrate sites, nuclear well logs, which include the photoelectric effect, formation sigma, carbon/oxygen ratio and neutron porosity, are also collected but often not used. In fact, the nuclear response of a gas hydrate reservoir is not known. In this research we will focus on the nuclear log response in gas hydrate reservoirs at the Mallik Field at the Mackenzie Delta, Northwest Territories, Canada, and the Gas Hydrate Joint Industry Project Leg 2 sites in the northern Gulf of Mexico. Nuclear logs may add increased robustness to the investigation into the properties of gas hydrates and some types of logs may offer an opportunity to distinguish between gas hydrate and permafrost. For example, a true formation sigma log measures the thermal neutron capture cross section of a formation and pore constituents; it is especially sensitive to hydrogen and chlorine in the pore space. Chlorine has a high absorption potential, and is used to determine the amount of saline water within pore spaces. Gas hydrate offers a difference in elemental composition compared to water-saturated intervals. Thus, in permafrost areas, the carbon/oxygen ratio may vary between gas hydrate and permafrost, due to the increase of carbon in gas hydrate accumulations. At the Mallik site, we observe a hydrate-bearing sand (1085-1107 m) above a water-bearing sand (1107-1140 m), which was confirmed through core samples and mud gas analysis. We observe a decrease in the photoelectric absorption of ~0.5 barnes/e-, as well as an increase in the formation sigma readings of ~5 capture units in the water-bearing sand as

  10. Hydrate Control for Gas Storage Operations

    Energy Technology Data Exchange (ETDEWEB)

    Jeffrey Savidge

    2008-10-31

    The overall objective of this project was to identify low cost hydrate control options to help mitigate and solve hydrate problems that occur in moderate and high pressure natural gas storage field operations. The study includes data on a number of flow configurations, fluids and control options that are common in natural gas storage field flow lines. The final phase of this work brings together data and experience from the hydrate flow test facility and multiple field and operator sources. It includes a compilation of basic information on operating conditions as well as candidate field separation options. Lastly the work is integrated with the work with the initial work to provide a comprehensive view of gas storage field hydrate control for field operations and storage field personnel.

  11. Theoretical description of biomolecular hydration - Application to A-DNA

    Energy Technology Data Exchange (ETDEWEB)

    Garcia, A.E.; Hummer, G. [Los Alamos National Laboratory, NM (United States); Soumpasis, D.M. [Max Planck Inst. for Biophysical Chemistry, Goettingen (Germany)

    1994-12-31

    The local density of water molecules around a biomolecule is constructed from calculated two- and three-points correlation functions of polar solvents in water using a Potential-of-Mean-Force (PMF) expansion. As a simple approximation, the hydration of all polar (including charged) groups in a biomolecule is represented by the hydration of water oxygen in bulk water, and the effect of non-polar groups on hydration are neglected, except for excluded volume effects. Pair and triplet correlation functions are calculated by molecular dynamics simulations. We present calculations of the structural hydration for ideal A-DNA molecules with sequences [d(CG){sub 5}]{sub 2} and [d(C{sub 5}G{sub 5})]{sub 2}. We find that this method can accurately reproduce the hydration patterns of A-DNA observed in neutron diffraction experiments on oriented DNA fibers.

  12. Proton hydration in aqueous solution: Fourier transform infrared studies of HDO spectra

    Science.gov (United States)

    Śmiechowski, Maciej; Stangret, Janusz

    2006-11-01

    This paper attempts to elucidate the number and nature of the hydration spheres around the proton in an aqueous solution. This phenomenon was studied in aqueous solutions of selected acids by means of Fourier transform infrared spectroscopy of semiheavy water (HDO), isotopically diluted in H2O. The quantitative version of difference spectrum procedure was applied for the first time to investigate such systems. It allowed removal of bulk water contribution and separation of the spectra of solute-affected HDO. The obtained spectral data were confronted with ab initio calculated structures of small gas-phase and polarizable continuum model (PCM) solvated aqueous clusters, H+(H2O)n, n =2-8, in order to help in establishing the structural and energetic states of the consecutive hydration spheres of the hydrated proton. This was achieved by comparison of the calculated optimal geometries with the interatomic distances derived from HDO band positions. The structure of proton hydration shells outside the first hydration sphere essentially follows the model structure of other hydrated cations, previously revealed by affected HDO spectra. The first hydration sphere complex in diluted aqueous solutions was identified as an asymmetric variant of the regular Zundel cation [The Hydrogen Bond: Recent Developments in Theory and Experiments, edited by P. Schuster, G. Zundel, and C. Sandorfy (North-Holland, Amsterdam, 1976), Vol. II, p. 683], intermediate between the ideal Zundel and Eigen structures [E. Wicke et al., Z. Phys. Chem. Neue Folge 1, 340 (1954)]. Evidence was found for the existence of strong and short hydrogen bonds, with oxygen-oxygen distance derived from the experimental affected spectra equal 2.435Å on average and in the PCM calculations about 2.41-2.44Å. It was also evidenced for the first time that the proton possesses four well-defined hydration spheres, which were characterized in terms of hydrogen bonds' lengths and arrangements. Additionally, an outer

  13. Daytime changes of skin biophysical characteristics: A study of hydration, transepidermal water loss, ph, sebum, elasticity, erythema, and color index on middle eastern skin

    Directory of Open Access Journals (Sweden)

    Alireza Firooz

    2016-01-01

    Full Text Available Background: The exposure of skin to ultraviolet radiation and temperature differs significantly during the day. It is reasonable that biophysical parameters of human skin have periodic daily fluctuation. The objective of this study was to study the fluctuations of various biophysical characteristics of Middle Eastern skin in standardized experimental conditions. Materials and Methods: Seven biophysical parameters of skin including stratum corneum hydration, transepidermal water loss, pH, sebum, elasticity, skin color, and erythema index were measured at three time points (8 a.m., 12 p.m. and 4 p.m. on the forearm of 12 healthy participants (mean age of 28.4 years without any ongoing skin disease using the CK MPA 580 device in standard temperature and humidity conditions. Results: A significant difference was observed between means of skin color index at 8 a.m. (175.42 ± 13.92 and 4 p.m. (164.44 ± 13.72, P = 0.025, between the pH at 8 a.m. (5.72 ± 0.48 and 4 p.m. (5.33 ± 0.55, P = 0.001 and pH at 12 p.m. (5.60 ± 0.48 and 4 p.m. (5.33 ± 0.55, P = 0.001. Other comparisons between the means of these parameters at different time points resulted in nonsignificant P values. Conclusion: There are daytime changes in skin color index and pH. Skin color index might be higher and cutaneous pH more basic in the early morning compared to later of the day.

  14. A STUDY OF THE HEAT OF HYDRATION OF SULFONIC ACID RESINS

    Institute of Scientific and Technical Information of China (English)

    XURongnan; JIJunyan; 等

    1992-01-01

    The heat of hydration of dry sulfonic acid resin in different comcentrations of sulfuric acid has been determined. The heat of hydration of the resin in H2O is 143.4J/g(resin). The greater the concentration of sulfuric acid,the less the heat will be released.The hydrate formed from three sulfonic acid groups and one water molecule is the most stable one of all the hydrates of sulfonic acid resin and water.

  15. Ethylene Separation via Hydrate Formation in W/O Emulsions

    Directory of Open Access Journals (Sweden)

    Yong Pan

    2015-05-01

    Full Text Available An hybrid absorption-hydration method was adopted to recover C2H4 from C2H4/CH4 binary gas mixtures and the hydrate formation conditions of C2H4/CH4 mixtures was studied experimentally in diesel in water (w/o emulsions. Span 20 at a concentration of 1.0 wt% in the aqueous phase was added to form water in diesel emulsions before hydrate formation and then hydrate in diesel slurry was separated after hydrate formation. The influences of initial gas-liquid volume ratio (53–142, pressure (3.4–5.4 MPa, temperature (274.15–278.15 K, water cuts (10–30 vol%, and the mole fraction of C2H4 in feed gas (13.19–80.44 mol% upon the C2H4 separation efficiency were systematically investigated. The experimental results show that ethylene can be enriched in hydrate slurry phase with high separation factor (S and recovery ratio (R. Most hydrate formation finished in 20 min, after that, the hydrate formation rate became very slow. The conclusion is useful for determining the suitable operation conditions when adopting an absorption-hydration method to separate C2H4/CH4.

  16. Pore Water Data From Three Gas Hydrate Sites in the Gulf of Mexico: First Results From the HyFlux Project

    Science.gov (United States)

    Shapiro, R. A.; Naehr, T. H.; MacDonald, I.; Kastner, M.; Robertson, G.; Solomon, E. A.

    2009-12-01

    The DOE/NETL funded HyFlux project combines sea-air, water column, and subsurface observations and measurements to better quantify the amount of methane released from seeps and gas hydrate deposits in the Gulf of Mexico. A recently completed research cruise investigated Gulf of Mexico seeps in 540, 900, and 1200 m water depths. Piston, gravity, and push cores were collected for pore water and sediment analysis. Analyses of major pore water constituents were conducted using an ICP-OES. Preliminary pore water analyses included SO42-, alkalinity, HS-, and Ca2+. Cores taken at Mississippi Canyon site MC 118 showed sulfate concentrations decreasing from 25.2 mM at 1 cmbsf to 1.91 mM at 36.5 cmbsf. HS- measurements show a decrease from 3.02 mM at 1.5 cmbsf to 0 mM at 12 cmbsf, followed by an increase in HS- due to SO42- reduction in 12 cmbsf. Alkalinity concentrations show an increase with depth from 3.63 mM at 1.5 cmbsf to 27.8 mM at 36.5 cmbsf. Calcium concentrations decrease from 10.55 mM at 1.5 cmbsf to 4.87 mM at 36.5 cmbsf due to the precipitation of calcium carbonate. Data from a 10 cm-long push core taken at site MC 118 showed the same trends in SO42- reduction, a decrease in Ca2+ concentrations, along with an alkalinity increase and HS- production. Two piston cores were taken at site GC (Green Canyon) 600. The first core showed SO42- concentrations decreasing from 21.34 mM at 0 cmbsf to 0 mM at 20 cmbsf. HS- concentrations increased to 32.11 mM 20 cmbsf, then decreased to 3.05 mM at 282.5 cmbsf. Alkalinity and Ca2+ concentrations both increased with depth. Alkalinity concentrations were 10.27 mM at 1.5 cmbsf and increased to 35.59 mM at 282.5 cmbsf. Ca2+ also increased from 8.96 mM at 1.5 cmbsf to 12.27 mM at 282.5 cmbsf, which may be the result of carbonate dissolution at depth. The second piston core showed a more typical concentration profile for seep areas. The sulfate concentration at 3 cmbsf decreased from 21.93 mM to 3 mM at 44.5 cmbsf, coupled with the

  17. Temperature influence on lanthanoids (III) hydration from molecular dynamics simulations

    Energy Technology Data Exchange (ETDEWEB)

    Duvail, M.; Vitorge, P.; Spezia, R. [Univ Evry Val Essonne, Lab Analyse and Modelisat Biol and Environm, CNRS, UMR 8587, F-91025 Evry (France); Vitorge, P. [CEA Saclay, Nucl Energy Div, Dept Phys Chem, SECR, LSRM, F-91991 Gif Sur Yvette (France)

    2010-07-01

    We studied temperature dependence of lanthanoid (III) cations hydration by molecular dynamics simulations using explicit polarization. The main effect of the temperature (T) is to increase exchange frequencies between the two main stoichiometries and the proportions of the minor species. Activation energies for self-exchange reaction have a minimum in the middle of the series and the CN values of all Ln{sup 3+} ions tends to a limit 8.5 value at high temperature. Linear variations are found through the series for the Gibbs energies of water exchange reactions being at the origin of the coordination number sigmoidal variation across the series. (authors)

  18. Effects of salinity on methane gas hydrate system

    Institute of Scientific and Technical Information of China (English)

    YANG; DingHui; XU; WenYue

    2007-01-01

    Using an approximately analytical formation,we extend the steady state model of the pure methane hydrate system to include the salinity based on the dynamic model of the methane hydrate system.The top and bottom boundaries of the methane hydrate stability zone (MHSZ) and the actual methane hydrate zone (MHZ),and the top of free gas occurrence are determined by using numerical methods and the new steady state model developed in this paper.Numerical results show that the MHZ thickness becomes thinner with increasing the salinity,and the stability is lowered and the base of the MHSZ is shifted toward the seafloor in the presence of salts.As a result,the thickness of actual hydrate occurrence becomes thinner compared with that of the pure water case.On the other hand,since lower solubility reduces the amount of gas needed to form methane hydrate,the existence of salts in seawater can actually promote methane gas hydrate formation in the hydrate stability zone.Numerical modeling also demonstrates that for the salt-water case the presence of methane within the field of methane hydrate stability is not sufficient to ensure the occurrence of gas hydrate,which can only form when the methane concentration dissolved in solution with salts exceeds the local methane solubility in salt water and if the methane flux exceeds a critical value corresponding to the rate of diffusive methane transport.In order to maintain gas hydrate or to form methane gas hydrate in marine sediments,a persistent supplied methane probably from biogenic or thermogenic processes,is required to overcome losses due to diffusion and advection.

  19. Hydration and hydrolysis of thorium(IV) in aqueous solution and the structures of two crystalline thorium(IV) hydrates.

    Science.gov (United States)

    Torapava, Natallia; Persson, Ingmar; Eriksson, Lars; Lundberg, Daniel

    2009-12-21

    Solid octaaqua(kappa(2)O-perchlorato)thorium(IV) perchlorate hydrate, [Th(H(2)O)(8)(ClO(4))](ClO(4))(3).H(2)O, 1, and aquaoxonium hexaaquatris(kappaO-trifluoromethanesulfonato)thorium(IV) trisaquahexakis(kappaO-trifluoromethanesulfonato)thorinate(IV), H(5)O(2)[Th(H(2)O)(6)(OSO(2)CF(3))(3)][Th(H(2)O)(3)(OSO(2)CF(3))(6)], 2, were crystallized from concentrated perchloric and trifluoromethanesulfonic acid solutions, respectively. 1 adopts a severely distorted tricapped trigonal prismatic configuration with an additional oxygen from the perchlorate ion at a longer distance. 2 consists of individual hexaaquatris(kappaO-trifluoromethanesulfonato)thorium(IV) and trisaquahexakis(kappaO-trifluoromethanesulfonato)thorinate(IV) ions and an aquaoxonium ion bridging these two ions through hydrogen bonding. The hydrated thorium(IV) ion is nine-coordinated in aqueous solution as determined by extended X-ray absorption fine structure (EXAFS) and large angle X-ray scattering (LAXS). The LAXS studies also showed a second hydration sphere of about 18 water molecules, and traces of a 3rd hydration sphere. Structural studies in aqueous solution of the hydrolysis products of thorium(IV) have identified three different types of hydrolysis species: a mu(2)O-hydroxo dimer, [Th(2)(OH)(2)(H(2)O)(12)](6+), a mu(2)O-hydroxo tetramer, [Th(4)(OH)(8)(H(2)O)(16)](8+), and a mu(3)O-oxo hexamer, [Th(6)O(8)(H(2)O)(n)](8+). Detailed structures of these three hydrolysis species are given. A compilation of reported solid state structures of actinoid(IV) compounds with oxygen donor ligands show a strong correlation between the An-O bond distance and the coordination number. The earlier reported U-O bond distance in the hydrated uranium(IV) ion in aqueous solution, confirmed in this study, is related to nine-coordination. The hydrated tri- and tetravalent actinoid ions in aqueous solution all seem to be nine-coordinated. The trivalent ions show a significant difference in bond distance to prismatic and

  20. Equilibrium PT curve of methane hydrates in the presence of AlCl3

    Institute of Scientific and Technical Information of China (English)

    2003-01-01

    Using an experimental transparent sapphire high-pressure cell, three-phase (methane hydrate + AlCl3 solution + methane) equilibrium conditions of methane hydrates in the aqueous solution containing AlCl3 have been investigated under conditions of temperature from 272.15 to 278.15 K and pressure from 4.040 to 8.382 MPa. It could be clearly verified that AlCl3 is of stronger inhibitive effect than that observed for other electrolytes, such as KCl, CaCl2, at the same mole fraction. The induction time of the methane hydrate formation becomes longer when the water activity decreases with the increase of ion charge numbers. Methane hydrates tend to crystallize more easily with higher concentration (AlCl3 concentration of 18%) than lower one (AlCl3 concentration of 10%) in the same electriclyte solution. An empirical exponential equation is presented to calculate the equilibrium temperature and pressure of methane hydrate stable occurrence, and to correlate the measured data for aqueous AlCl3 solution. The results show that there was infinitely small discrepancy between the theoretical computed values and the data oberserved in actual experiments.

  1. First-principles elasticity of monocarboaluminate hydrates

    KAUST Repository

    Moon, J.

    2014-07-01

    The elasticity of monocarboaluminate hydrates, 3CaO·Al2O3·CaCO3·xH2O (x = 11 or 8), has been investigated by first-principles calculations. Previous experimental study revealed that the fully hydrated monocarboaluminate (x = 11) exhibits exceptionally low compressibility compared to other reported calcium aluminate hydrates. This stiff hydration product can contribute to the strength of concrete made with Portland cements containing calcium carbonates. In this study, full elastic tensors and mechanical properties of the crystal structures with different water contents (x = 11 or 8) are computed by first-principles methods based on density functional theory. The results indicate that the compressibility of monocarboaluminate is highly dependent on the water content in the interlayer region. The structure also becomes more isotropic with the addition of water molecules in this region. Since the monocarboaluminate is a key hydration product of limestone added cement, elasticity of the crystal is important to understand its mechanical impact on concrete. Besides, it is put forth that this theoretical calculation will be useful in predicting the elastic properties of other complex cementitous materials and the influence of ion exchange on compressibility.

  2. Component analysis of the protein hydration entropy

    Science.gov (United States)

    Chong, Song-Ho; Ham, Sihyun

    2012-05-01

    We report the development of an atomic decomposition method of the protein solvation entropy in water, which allows us to understand global change in the solvation entropy in terms of local changes in protein conformation as well as in hydration structure. This method can be implemented via a combined approach based on molecular dynamics simulation and integral-equation theory of liquids. An illustrative application is made to 42-residue amyloid-beta protein in water. We demonstrate how this method enables one to elucidate the molecular origin for the hydration entropy change upon conformational transitions of protein.

  3. Hydration process in Portland cement blended with activated coal gangue

    Institute of Scientific and Technical Information of China (English)

    Xian-ping LIU; Pei-ming WANG; Min-ju DING

    2011-01-01

    This paper deals with the hydration of a blend of Portland cement and activated coal gangue in order to determine the relationship between the degree of hydration and compressive strength development.The hydration process was investigated by various means:isothermal calorimetry,thermal analysis,non-cvaporable water measurement,and X-ray diffraction analysis.The results show that the activated coal gangue is a pozzolanic material that contributes to the hydration of the cement blend.The pozzolanic reaction occurs over a period of between 7 and 90 d,consuming portlandite and forming both crystal hydrates and ill-crystallized calcium silicate hydrates.These hydrates are similar to those found in pure Portland cement.The results show that if activated coal gangue is substituted for cement at up to 30% (w/w),it does not significantly affect the final compressive strength of the blend.A long-term compressive strength improvement can in fact be achieved by using activated coal gangue as a supplementary cementing material.The relationship between compressive strength and degree of hydration for both pure Portland cement and blended cement can be described with the same equation.However,the parameters are different since blended cement produces fewer calcium silicate hydrates than pure Portland cement at the same degree of hydration.

  4. Comparative analysis of growth characteristics of hydrate formation on the surface of suspended water droplet and bubble%悬垂水滴与悬浮气泡表面气体水合物形成特性对比

    Institute of Scientific and Technical Information of China (English)

    陆引哲; 刘道平; 杨亮

    2015-01-01

    Based on a set of high-pressure visual experiment device used for the natural gas hydrates crystallization and growth on the surface of suspended water droplet and suspended bubble,the influence of factors such as pressure,temperature,water quality on the crystallization and growth are analyzed and discussed respectively.Comparative analysis of the experimental phenomena about the characteristics of hydrate formation on the surface of suspended water droplet and bubble was discussed.Temperature and pressure are the important factors of hydrate crystallization and growth.The decrease of temperature or the increase of pressure will also improve the growth of hydrate.This paper also provides experimental support for the development of spray and bubbling method to improve the hydrate formation.%基于悬垂水滴和悬浮气泡表面形成气体水合物的可视化耐高压实验装置,分析探讨了反应压力、温度、水质等因素对水滴和气泡表面气体水合物成核和生长规律的影响。对已有的关于研究单个静止悬垂水滴和悬浮气泡表面气体水合物生长特性的实验现象及结果进行了对比分析,得出结论:温度和压力是影响表面水合物结晶与生长的重要因素;温度的降低或压力的升高均使水合反应速度加快。研究为发展喷雾法和鼓泡法这两种强化制备水合物的方式提供了有效的实验支撑。

  5. Experimental Dissociation of Methane Hydrates Through Depressurization

    Science.gov (United States)

    Borgfeldt, T.; Flemings, P. B.; Meyer, D.; You, K.

    2015-12-01

    We dissociated methane hydrates by stepwise depressurization. The initial hydrates were formed by injecting gas into a cylindrical sample of brine-saturated, coarse-grained sand at hydrate-stable conditions with the intention of reaching three-phase equilibrium. The sample was initially at 1°C with a pore pressure of 1775 psi and a salinity of 7 wt. % NaBr. The depressurization setup consisted of one pump filled with tap water attached to the confining fluid port and a second pump attached to the inlet port where the methane was injected. Depressurization was conducted over sixteen hours at a constant temperature of 1°C. The pore pressure was stepwise reduced from 1775 psi to atmospheric pressure by pulling known volumes of gas from the sample. After each extraction, we recorded the instantaneous and equilibrium pore pressure. 0.503 moles of methane were removed from the sample. The pore pressure decreased smoothly and nonlinearly with the cumulative gas withdrawn from the sample. We interpret that hydrate began to dissociate immediately with depressurization, and it continued to dissociate when the pressure decreased below the three-phase pressure for 1°C and 0 wt. % salinity. Two breaks in slope in the pressure vs. mass extracted data are bounded by smooth, nonlinear curves with differing slopes on either side. We attribute the breaks to dissociation of three zones of hydrate concentration. We created a box model to simulate the experimental behavior. For a 10% initial gas saturation (estimated from the hydrate formation experiment and based on mass conservation), an initial hydrate saturation of 55% is required to match the total methane extracted from the sample. Future experiments will be conducted over a longer timespan while monitoring hydrate dissociation with CT imaging throughout the process.

  6. Mechanisms Leading to Co-Existence of Gas Hydrate in Ocean Sediments [Part 2 of 2

    Energy Technology Data Exchange (ETDEWEB)

    Bryant, Steven; Juanes, Ruben

    2011-12-31

    saturations. Large volumes (of order one pore volume) of gaseous and aqueous phases must be transported into the gas hydrate stability zone. The driver for this transport is the pressure sink induced by a reduction in occupied pore volume that accompanies the formation of hydrate from gas and water. Pore-scale imbibition models and bed-scale multiphase flow models indicate that the rate-limiting step in converting gas to hydrate is the supply of water to the hydrate stability zone. Moreover, the water supply rate is controlled by capillarity-driven flux for conditions typical of the Alaska North Slope. A meter-scale laboratory experiment confirms that significant volumes of fluid phases move into the hydrate stability zone and that capillarity is essential for the water flux. The model shows that without capillarity-driven flux, large saturations of hydrate cannot form. The observations of thick zones of large saturation at Mallik and Mt Elbert thus suggest that the primary control on these systems is the rate of transport of gaseous and aqueous phases, driven by the pressure sink at the base of the gas hydrate stability zone. A key finding of our project is the elucidation of ?capillary fracturing? as a dominant gas transport mechanism in low-permeability media. We initially investigate this phenomenon by means of grain-scale simulations in which we extended a discrete element mechanics code (PFC, by Itasca) to incorporate the dynamics of first singlephase and then multiphase flow. A reductionist model on a square lattice allows us to determine some of the fundamental dependencies of the mode of gas invasion (capillary fingering, viscous fingering, and fracturing) on the parameters of the system. We then show that the morphology of the gas-invaded region exerts a fundamental control on the fabric of methane hydrate formation, and on the overpressures caused by methane hydrate dissociation. We demonstrate the existence of the different invasion regimes by means of controlled

  7. Mechanisms Leading to Co-Existence of Gas Hydrate in Ocean Sediments [Part 1 of 2

    Energy Technology Data Exchange (ETDEWEB)

    Bryant, Steven; Juanes, Ruben

    2011-12-31

    saturations. Large volumes (of order one pore volume) of gaseous and aqueous phases must be transported into the gas hydrate stability zone. The driver for this transport is the pressure sink induced by a reduction in occupied pore volume that accompanies the formation of hydrate from gas and water. Pore-scale imbibition models and bed-scale multiphase flow models indicate that the rate-limiting step in converting gas to hydrate is the supply of water to the hydrate stability zone. Moreover, the water supply rate is controlled by capillarity-driven flux for conditions typical of the Alaska North Slope. A meter-scale laboratory experiment confirms that significant volumes of fluid phases move into the hydrate stability zone and that capillarity is essential for the water flux. The model shows that without capillarity-driven flux, large saturations of hydrate cannot form. The observations of thick zones of large saturation at Mallik and Mt Elbert thus suggest that the primary control on these systems is the rate of transport of gaseous and aqueous phases, driven by the pressure sink at the base of the gas hydrate stability zone. A key finding of our project is the elucidation of ?capillary fracturing? as a dominant gas transport mechanism in low-permeability media. We initially investigate this phenomenon by means of grain-scale simulations in which we extended a discrete element mechanics code (PFC, by Itasca) to incorporate the dynamics of first single-phase and then multiphase flow. A reductionist model on a square lattice allows us to determine some of the fundamental dependencies of the mode of gas invasion (capillary fingering, viscous fingering, and fracturing) on the parameters of the system. We then show that the morphology of the gas-invaded region exerts a fundamental control on the fabric of methane hydrate formation, and on the overpressures caused by methane hydrate dissociation. We demonstrate the existence of the different invasion regimes by means of controlled

  8. STUDY FOR NATURAL GAS HYDRATE CONVERSED FROM ICE

    Institute of Scientific and Technical Information of China (English)

    WANG Shengjie; SHEN Jiandong; HAO Miaoli; LIU Furong

    2003-01-01

    Natural gas hydrates are crystalline clathrate compounds composed of water and gases of small molecular diameters that can be used for storage and transport of natural gas as a novel method. In the paper a series of experiments of aspects and kinetics for hydrate formed from natural gas and ice were carried out on the industrial small scale production apparatus. The experimental results show that formation conditions of hydrate conversed from ice are independent of induction time, and bigger degrees of supersaturation and supercooling improved the driving force and advanced the hydrate formation.Superpressure is also favorable for ice particle conversion to hydrate. In addition, it was found there have an optimal reaction time during hydrate formation.

  9. Pore capillary pressure and saturation of methane hydrate bearing sediments

    Institute of Scientific and Technical Information of China (English)

    SUN Shicai; LIU Changling; YE Yuguang; LIU Yufeng

    2014-01-01

    To better understand the relationship between the pore capillary pressure and hydrate saturation in sedi-ments, a new method was proposed. First, the phase equilibria of methane hydrate in fine-grained silica sands were measured. As to the equilibrium data, the pore capillary pressure and saturation of methane hydrate were calculated. The results showed that the phase equilibria of methane hydrates in fine-grained silica sands changed due to the depressed activity of pore water caused by the surface group and negatively charged characteristic of silica particles as well as the capillary pressure in small pores together. The capil-lary pressure increased with the increase of methane hydrate saturation due to the decrease of the available pore space. However, the capillary-saturation relationship could not yet be described quantitatively because of the stochastic habit of hydrate growth.

  10. Effect of localized water uptake on backfill hydration and water movement in a backfilled tunnel: half-scale tests at Aespoe Bentonite Laboratory

    Energy Technology Data Exchange (ETDEWEB)

    Dixon, D. [Atomic Energy of Canada Limited, Chalk River (Canada); Jonsson, E. [Swedish Nuclear Fuel and Waste Management Co., Stockholm (Sweden); Hansen, J. [Posiva Oy, Olkiluoto (Finland); Hedin, M. [Aangpannefoereningen, Stockholm (Sweden); Ramqvist, G. [Eltekno AB, Figeholm (Sweden)

    2011-04-15

    The report describes the outcome of the work within the project 'SU508.20 Impact of water inflow in deposition tunnels'. Project decision SKB doc 1178871 Version 3.0. Two activity plans have been used for the field work: AP TD SU50820-09-019 and AP TD SU 50820-09-071. SKB and Posiva have been examining those processes that may have particularly strong effects on the evolution of a newly backfilled deposition tunnel in a KBS-3V repository. These assessments have involved the conduct of increasingly large and complex laboratory tests and simulations of a backfilled tunnel section. In this series of four tests, the effect of water inflow into a backfilled tunnel section via an intersecting fracture feature was evaluated. The tests included the monitoring of mock-ups where water entered via the simulated fractures as well as evaluation of what the effect of isolated tunnel sections caused by localized water inflow would have on subsequent evolution of these isolated sections. It was found that even a slowly seeping fracture can have a substantial effect on the backfill evolution as it will cause development of a gasket-like feature that effectively cuts of air and water movement from inner to outer regions of the backfilled tunnel. Water entering via these fractures will ultimately move out of the tunnel via a single discrete flow path, in a manner similar to what was observed in previous 1/2-scale and smaller simulations. If the low-rate of water inflow from fracture is the only source of water inflow to the tunnel this will result in hydraulic behaviour similar to that observed for a single inflow point in previous tests. The presence of a fracture feature will however result in a larger proportion of water uptake by the process of suction than might occur in a point inflow situation and hence a more uniform water distribution will be present in the pellet fill. This also results in a greater tendency for water to be absorbed into the adjacent block fill

  11. The effect of stereochemistry on carbohydrate hydration in aqueous solutions

    NARCIS (Netherlands)

    Galema, Saskia Alexandra

    1992-01-01

    Although-carbohydrates are widely used, not much is known about the stereochemical aspects of hydration of carbohydrates. For D-aldohexoses, for example, there are eight different stereoisomers. Just how the hydroxy topology of a carbohydrate molecule influences the hydration behaviour in water is r

  12. The interaction of climate change and methane hydrates

    Science.gov (United States)

    Ruppel, Carolyn D.; Kessler, John D.

    2017-01-01

    Gas hydrate, a frozen, naturally-occurring, and highly-concentrated form of methane, sequesters significant carbon in the global system and is stable only over a range of low-temperature and moderate-pressure conditions. Gas hydrate is widespread in the sediments of marine continental margins and permafrost areas, locations where ocean and atmospheric warming may perturb the hydrate stability field and lead to release of the sequestered methane into the overlying sediments and soils. Methane and methane-derived carbon that escape from sediments and soils and reach the atmosphere could exacerbate greenhouse warming. The synergy between warming climate and gas hydrate dissociation feeds a popular perception that global warming could drive catastrophic methane releases from the contemporary gas hydrate reservoir. Appropriate evaluation of the two sides of the climate-methane hydrate synergy requires assessing direct and indirect observational data related to gas hydrate dissociation phenomena and numerical models that track the interaction of gas hydrates/methane with the ocean and/or atmosphere. Methane hydrate is likely undergoing dissociation now on global upper continental slopes and on continental shelves that ring the Arctic Ocean. Many factors—the depth of the gas hydrates in sediments, strong sediment and water column sinks, and the inability of bubbles emitted at the seafloor to deliver methane to the sea-air interface in most cases—mitigate the impact of gas hydrate dissociation on atmospheric greenhouse gas concentrations though. There is no conclusive proof that hydrate-derived methane is reaching the atmosphere now, but more observational data and improved numerical models will better characterize the climate-hydrate synergy in the future.

  13. Kinetic Hydration Heat Modeling for High-Performance Concrete Containing Limestone Powder

    Directory of Open Access Journals (Sweden)

    Xiao-Yong Wang

    2017-01-01

    Full Text Available Limestone powder is increasingly used in producing high-performance concrete in the modern concrete industry. Limestone powder blended concrete has many advantages, such as increasing the early-age strength, reducing the setting time, improving the workability, and reducing the heat of hydration. This study presents a kinetic model for modeling the hydration heat of limestone blended concrete. First, an improved hydration model is proposed which considers the dilution effect and nucleation effect due to limestone powder addition. A degree of hydration is calculated using this improved hydration model. Second, hydration heat is calculated using the degree of hydration. The effects of water to binder ratio and limestone replacement ratio on hydration heat are clarified. Third, the temperature history and temperature distribution of hardening limestone blended concrete are calculated by combining hydration model with finite element method. The analysis results generally agree with experimental results of high-performance concrete with various mixing proportions.

  14. Hydration study of ordinary portland cement in the presence of zinc ions

    Directory of Open Access Journals (Sweden)

    Monica Adriana Trezza

    2007-12-01

    Full Text Available Hydration products of Portland cement pastes, hydrated in water and in the presence of zinc ions were studied comparatively at different ages. Hydration products were studied by X ray diffractions (XRD and infrared spectroscopy (IR. Although IR is not frequently used in cement chemistry, it evidenced a new phase Ca(Zn(OH32. 2H2O formed during cement hydration in the presence of zinc. The significant retardation of early cement hydration in the presence of zinc is assessed in detail by differential calorimetry as a complement to the study carried out by IR and XRD, providing evidence that permits to evaluate the kinetic of the early hydration.

  15. Hydration in soccer: a review

    Directory of Open Access Journals (Sweden)

    Monteiro Cristiano Ralo

    2003-01-01

    Full Text Available Hydration should be considered before, during and after the exercise. This review intends to approach the main points of hydration process in soccer. The replacement of fluids during exercise is proportional to some factors, such as: exercise intensity; climatic conditions; the athlete's acclimatization; the athlete's physical conditioning; physiologic individual characteristics and the player's biomechanics. Performance is improved when players ingest not only water but also carbohydrate. The rates that carbohydrate and water are absorbed by the organism are limited by the rates of gastric emptying and intestinal absorption. The composition of drinks offered to the players should be influenced by the relative importance of the need of supplying carbohydrates or water; it should be remembered that the depletion of carbohydrate can result in fatigue and decrease of performance, but it is not usually a life-threatening condition. The addition of carbohydrate in these drinks increases the concentrations of blood glucose, increases the use of external fuel through the increase of the glucose oxidation in the muscles and it spares muscle glycogen. So, the ingestion of carbohydrate before and during the exercise can delay the emergence of fatigue and increase the players' performance. Several tactics can be used to avoid dehydration, like hyperhydration before exercise and player's acclimatization. The ideal situation to restore the player's fluid losses is between the sessions of exercises. Since soccer is a sport with quite peculiar characteristics related to hydration, the players should be concerned and educated about the importance of fluid ingestion before, during and after the exercise.

  16. Pore-water chemistry of sediment cores off Mahanadi Basin, Bay of Bengal: Possible link to deep seated methane hydrate deposit

    Digital Repository Service at National Institute of Oceanography (India)

    Mazumdar, A.; Peketi, A.; Joao, H; Dewangan, P.; Ramprasad, T.

    ) induced sulfate consumption. The gas rich layers just below the base of hydrate stability zone (BGHSZ) is the possible source of the enhanced diffusive flux of biogenic methane (dalta13CCH4 ranging from -99.7 to - 106.3 percentage...

  17. Water Resistance, Hydration Product and Microstructure of Glass Fiber Reinforced Magnesium Oxychloride Cement Exterior Wall Cladding%玻镁外墙挂板的抗水性、水化产物和微观结构

    Institute of Scientific and Technical Information of China (English)

    董金美; 余红发; 刘倩倩; 李颖; 林启红

    2011-01-01

    Bending mechanical properties and deformations in natural state and wet state under water of common and high-performance glass fiber reinforced magnesium oxychloride cement ( GRMC ) exterior wall cladding were tested in this study. Hydration product components and microstructure were observed by X-ray diffraction ( XRD ) and scanning electron microscopy ( SEM). The results indicated that, in wet state under water, the main hydration product 5 ·1 ·8 was hydrolysed, microstructure is destroyed and bending strength is decreased for common GRMC exterior wall cladding. For high-performance GRMC exterior wall cladding with a complex water-repellent admixture and mixed minerals, the main hydration product 3 ·1 ·8 is stable existing in cement matrix and microstructure has been changed little. The sample reveals high water resistance. So, hydration product components and microstructure stability of GRMC exterior wall cladding are important prerequisites for high water resistance.%试验测定了普通玻镁外墙挂板、掺加复合抗水外加剂和矿物掺合料的高性能玻镁外墙挂板在自然和浸水状态下的弯曲力学性能和变形性能,并运用X射线衍射仪(XRD)和扫描电镜(SEM)分析了水化产物的组成和微观结构特征.结果表明:在浸水条件下,普通玻镁外墙挂板的主要水化产物5 ·1·8相发生了分解,破坏了微观结构,导致其抗弯强度降低;而掺加复合抗水外加剂和矿物掺合料的高性能玻镁外墙挂板的水化产物5·1·8相保持稳定,微观结构未发生变化,显示出较高的抗水性.因此,玻镁外墙挂板的水化产物组成和微观结构的稳定性是确保其抗水性的重要前提.

  18. Wet hydrate dissolution plant

    OpenAIRE

    Stanković Mirjana S.; Kovačević Branimir T.; Pezo Lato L.

    2003-01-01

    The IGPC Engineering Department designed basic projects for a wet hydrate dissolution plant, using technology developed in the IGPC laboratories. Several projects were completed: technological, machine, electrical, automation. On the basis of these projects, a production plant with capacity of 50,000 t/y was manufactured, at "Zeolite Mira", Mira (VE), Italy, in 1997, for increasing detergent zeolite production from 50,000 to 100,000 t/y. Several goals were realized by designing a wet hydrate ...

  19. Molecular modeling of the dissociation of methane hydrate in contact with a silica surface.

    Science.gov (United States)

    Bagherzadeh, S Alireza; Englezos, Peter; Alavi, Saman; Ripmeester, John A

    2012-03-15

    We use constant energy, constant volume (NVE) molecular dynamics simulations to study the dissociation of the fully occupied structure I methane hydrate in a confined geometry between two hydroxylated silica surfaces between 36 and 41 Å apart, at initial temperatures of 283, 293, and 303 K. Simulations of the two-phase hydrate/water system are performed in the presence of silica, with and without a 3 Å thick buffering water layer between the hydrate phase and silica surfaces. Faster decomposition is observed in the presence of silica, where the hydrate phase is prone to decomposition from four surfaces, as compared to only two sides in the case of the hydrate/water simulations. The existence of the water layer between the hydrate phase and the silica surface stabilizes the hydrate phase relative to the case where the hydrate is in direct contact with silica. Hydrates bound between the silica surfaces dissociate layer-by-layer in a shrinking core manner with a curved decomposition front which extends over a 5-8 Å thickness. Labeling water molecules shows that there is exchange of water molecules between the surrounding liquid and intact cages in the methane hydrate phase. In all cases, decomposition of the methane hydrate phase led to the formation of methane nanobubbles in the liquid water phase.

  20. Controls on Gas Hydrate Formation and Dissociation

    Energy Technology Data Exchange (ETDEWEB)

    Miriam Kastner; Ian MacDonald

    2006-03-03

    The main objectives of the project were to monitor, characterize, and quantify in situ the rates of formation and dissociation of methane hydrates at and near the seafloor in the northern Gulf of Mexico, with a focus on the Bush Hill seafloor hydrate mound; to record the linkages between physical and chemical parameters of the deposits over the course of one year, by emphasizing the response of the hydrate mound to temperature and chemical perturbations; and to document the seafloor and water column environmental impacts of hydrate formation and dissociation. For these, monitoring the dynamics of gas hydrate formation and dissociation was required. The objectives were achieved by an integrated field and laboratory scientific study, particularly by monitoring in situ formation and dissociation of the outcropping gas hydrate mound and of the associated gas-rich sediments. In addition to monitoring with the MOSQUITOs, fluid flow rates and temperature, continuously sampling in situ pore fluids for the chemistry, and imaging the hydrate mound, pore fluids from cores, peepers and gas hydrate samples from the mound were as well sampled and analyzed for chemical and isotopic compositions. In order to determine the impact of gas hydrate dissociation and/or methane venting across the seafloor on the ocean and atmosphere, the overlying seawater was sampled and thoroughly analyzed chemically and for methane C isotope ratios. At Bush hill the pore fluid chemistry varies significantly over short distances as well as within some of the specific sites monitored for 440 days, and gas venting is primarily focused. The pore fluid chemistry in the tub-warm and mussel shell fields clearly documented active gas hydrate and authigenic carbonate formation during the monitoring period. The advecting fluid is depleted in sulfate, Ca Mg, and Sr and is rich in methane; at the main vent sites the fluid is methane supersaturated, thus bubble plumes form. The subsurface hydrology exhibits both

  1. Interfacial phenomena in gas hydrate systems.

    Science.gov (United States)

    Aman, Zachary M; Koh, Carolyn A

    2016-03-21

    Gas hydrates are crystalline inclusion compounds, where molecular cages of water trap lighter species under specific thermodynamic conditions. Hydrates play an essential role in global energy systems, as both a hinderance when formed in traditional fuel production and a substantial resource when formed by nature. In both traditional and unconventional fuel production, hydrates share interfaces with a tremendous diversity of materials, including hydrocarbons, aqueous solutions, and inorganic solids. This article presents a state-of-the-art understanding of hydrate interfacial thermodynamics and growth kinetics, and the physiochemical controls that may be exerted on both. Specific attention is paid to the molecular structure and interactions of water, guest molecules, and hetero-molecules (e.g., surfactants) near the interface. Gas hydrate nucleation and growth mechanics are also presented, based on studies using a combination of molecular modeling, vibrational spectroscopy, and X-ray and neutron diffraction. The fundamental physical and chemical knowledge and methods presented in this review may be of value in probing parallel systems of crystal growth in solid inclusion compounds, crystal growth modifiers, emulsion stabilization, and reactive particle flow in solid slurries.

  2. Mobile lidar system for measurement of water vapor mixing ratio and ozone number density

    Science.gov (United States)

    Whiteman, D.

    1988-01-01

    The Water Vapor Lidar was modified and extended to make differential absorption measurements of ozone. Water vapor measurements make use of a weak molecular scattering process known as Raman scattering. It is characterized by a shift in wavelength of the scattered beam of light relative to the incident one. Some of the energy of the incident photon is converted to vibrational or rotational energy within the molecule leaving the scattered photon shifted to a slightly longer wavelength. When performing water vapor measurements, profiles are acquired of water vapor mixing ratio from near the ground to beyond 7 km every 2 minutes. By forming a color composite image of the individual profiles, the spatial and temporal evolution of water vapor is visible with vertical resolution of 75 to 150m and temporal resolution of 2 minutes. The ozone lidar is intended for use as a cross calibration facility for other stationary ozone lidar systems. The ozone measurement employs the technique known as differential absorption. The backscattered laser radiation from two different wavelengths is measured. Successful measurements of 308 nm returns were made from 80 km with an averaging period of 6 hours. Using these data and a standard atmosphere density curve, an ozone number density profile was made which agrees very well with the standard ozone curve between 20 and 40 km.

  3. Are seafloor pockmarks on the Chatham Rise, New Zealand, linked to CO2 hydrates? Gas hydrate stability considerations.

    Science.gov (United States)

    Pecher, I. A.; Davy, B. W.; Rose, P. S.; Coffin, R. B.

    2015-12-01

    Vast areas of the Chatham Rise east of New Zealand are covered by seafloor pockmarks. Pockmark occurrence appears to be bathymetrically controlled with a band of smaller pockmarks covering areas between 500 and 700 m and large seafloor depressions beneath 800 m water depth. The current depth of the top of methane gas hydrate stability in the ocean is about 500 m and thus, we had proposed that pockmark formation may be linked to methane gas hydrate dissociation during sealevel lowering. However, while seismic profiles show strong indications of fluid flow, geochemical analyses of piston cores do not show any evidence for current or past methane flux. The discovery of Dawsonite, indicative of significant CO2 flux, in a recent petroleum exploration well, together with other circumstantial evidence, has led us to propose that instead of methane hydrate, CO2 hydrate may be linked to pockmark formation. We here present results from CO2 hydrate stability calculations. Assuming water temperature profiles remain unchanged, we predict the upper limit of pockmark occurrence to coincide with the top of CO2 gas hydrate stability during glacial-stage sealevel lowstands. CO2 hydrates may therefore have dissociated during sealevel lowering leading to gas escape and pockmark formation. In contrast to our previous model linking methane hydrate dissociation to pockmark formation, gas hydrates would dissociate beneath a shallow base of CO2 hydrate stability, rather than on the seafloor following upward "grazing" of the top of methane hydrate stability. Intriguingly, at the water depths of the larger seafloor depressions, the base of gas hydrate stability delineates the phase boundary between CO2 hydrates and super-saturated CO2. We caution that because of the high solubility of CO2, dissociation from hydrate to free gas or super-saturated CO2 would imply high concentrations of CO2 and speculate that pockmark formation may be linked to CO2 hydrate dissolution rather than dissociation

  4. Hydration dynamics of the collagen triple helix by NMR.

    Science.gov (United States)

    Melacini, G; Bonvin, A M; Goodman, M; Boelens, R; Kaptein, R

    2000-07-28

    The hydration of the collagen-like Ac-(Gly-Pro-Hyp)(6)-NH(2) triple-helical peptide in solution was investigated using an integrated set of high-resolution NMR hydration experiments, including different recently developed exchange-network editing methods. This approach was designed to explore the hydration dynamics in the proximity of labile groups, such as the hydroxyproline hydroxyl group, and revealed that the first shell of hydration in collagen-like triple helices is kinetically labile with upper limits for water molecule residence times in the nanosecond to sub-nanosecond range. This result is consistent with a "hopping" hydration model in which solvent molecules are exchanged in and out of solvation sites at a rate that is not directly correlated to the degree of site localization. The hopping model thus reconciles the dynamic view of hydration revealed by NMR with the previously suggested partially ordered semi-clathrate-like cylinder of hydration. In addition, the nanosecond to sub-nanosecond upper limits for water molecule residence times imply that hydration-dehydration events are not likely to be the rate-limiting step for triple helix self-recognition, complementing previous investigations on water dynamics in collagen fibers. This study has also revealed labile proton features expected to facilitate the characterization of the structure and folding of triple helices in collagen peptides.

  5. Characterizing Ni(II) hydration in aqueous solution using DFT and EXAFS.

    Science.gov (United States)

    Liu, H Y; Fang, C H; Fang, Y; Zhou, Y Q; Ge, H W; Zhu, F Y; Sun, P C; Miao, J T

    2016-01-01

    In the present work, a detailed investigation of Ni(II) hydration in water solutions was carried out using density functional theory (DFT) and extended X-ray absorption fine structure (EXAFS) spectroscopy. The hydrated characteristics of [Ni(H2O)n](2+) clusters, such as energy parameters, atomic charge distributions, and bond parameters, were explored using DFT with Becke's three-parameter exchange potential and the Lee-Yang-Parr correlation functional (B3LYP). DFT calculations indicated that the preferred structure of the first hydration shell of Ni(II) generally has a coordination number of six and is almost unaffected by the water molecules in the outer solvation shell, whereas the structure of the second solvation shell varies as the hydration proceeds. EXAFS measurements are reported for aqueous NiSO4 and Ni(NO3)2 solutions and the Ni(NO3)2·6H2O crystal. Analysis of the EXAFS spectra of these three systems using a multiparameter fitting procedure showed that, in each case, the first coordination shell consists of six water molecules with a Ni-O coordination distance of 2.04 Å, and that there is no Ni-S or Ni-N coordination in the first shell. There was no evidence of outer-shell SO4(2-) or NO3(-) ions substituting inner-sphere water molecules in NiSO4 and Ni(NO3)2. The characteristics of Ni(II) hydration obtained from DFT calculations agreed well with those obtained experimentally using EXAFS.

  6. Temperature dependence of protein hydration hydrodynamics by molecular dynamics simulations.

    Energy Technology Data Exchange (ETDEWEB)

    Lau, E Y; Krishnan, V V

    2007-07-18

    The dynamics of water molecules near the protein surface are different from those of bulk water and influence the structure and dynamics of the protein itself. To elucidate the temperature dependence hydration dynamics of water molecules, we present results from the molecular dynamic simulation of the water molecules surrounding two proteins (Carboxypeptidase inhibitor and Ovomucoid) at seven different temperatures (T=273 to 303 K, in increments of 5 K). Translational diffusion coefficients of the surface water and bulk water molecules were estimated from 2 ns molecular dynamics simulation trajectories. Temperature dependence of the estimated bulk water diffusion closely reflects the experimental values, while hydration water diffusion is retarded significantly due to the protein. Protein surface induced scaling of translational dynamics of the hydration waters is uniform over the temperature range studied, suggesting the importance protein-water interactions.

  7. Calorimetric Determination of Enthalpy of Formation of Natural Gas Hydrates

    Institute of Scientific and Technical Information of China (English)

    高军; KennethN.Marsh

    2003-01-01

    This paper reports the measurements of enthalpies of natural gas hydrates in typical natural gas mixture containing methane, ethane, propane and iso-butane at pressure in the vicinity of 2000 kPa (300 psi) and 6900 kPa(1000psi). The measurements were made in a multi-cell differential scanning calorimeter using modified high pressure cells. The enthalpy of water and the enthalpy of dissociation of the gas hydrate were determined from the calorimeter response during slow temperature scanning at constant pressure. The amount of gas released from the dissociation of hydrate was determined from the pumped volume of the high pressure pump. The occupation ratio (mole ratio) of the water to gas and the enthalpy of hydrate formation are subject to uncertainty of 1.5%.The results show that the enthalpy of hydrate formation and the occupation ratio are essentially independent of pressure.

  8. Determination of Hydrazine Hydrate in Water with Paradime Thylaminobenzaldehyde Spectrophotometric Method%对二甲氨基苯甲醛分光光度法测定水中水合肼

    Institute of Scientific and Technical Information of China (English)

    黄岭; 李叙柏

    2016-01-01

    在酸性条件下,水合肼与对二甲氨基苯甲醛作用,形成黄色醌式化合物,可用分光光度法对其进行测定。文中主要介绍对二甲氨基苯甲醛分光光度法测定的回收率、相对标准偏差及检出限的复验,并对上海水源水及其出厂水水合肼进行测定。%Hydrazine hydrate can be detected using spectrophotometer,because yellow quinine compound is produced when it reacts with paradime thylaminobenzaldehyde under acidic conditions. In this paper,the recovery rate,relative standard deviation and lowest detection limit of this method were analyzed,and the hydrazine hydrate in the raw water and processed water of three water plants were determined.

  9. Hydration dynamics near a model protein surface

    Energy Technology Data Exchange (ETDEWEB)

    Russo, Daniela; Hura, Greg; Head-Gordon, Teresa

    2003-09-01

    The evolution of water dynamics from dilute to very high concentration solutions of a prototypical hydrophobic amino acid with its polar backbone, N-acetyl-leucine-methylamide (NALMA), is studied by quasi-elastic neutron scattering and molecular dynamics simulation for both the completely deuterated and completely hydrogenated leucine monomer. We observe several unexpected features in the dynamics of these biological solutions under ambient conditions. The NALMA dynamics shows evidence of de Gennes narrowing, an indication of coherent long timescale structural relaxation dynamics. The translational water dynamics are analyzed in a first approximation with a jump diffusion model. At the highest solute concentrations, the hydration water dynamics is significantly suppressed and characterized by a long residential time and a slow diffusion coefficient. The analysis of the more dilute concentration solutions takes into account the results of the 2.0M solution as a model of the first hydration shell. Subtracting the first hydration layer based on the 2.0M spectra, the translational diffusion dynamics is still suppressed, although the rotational relaxation time and residential time are converged to bulk-water values. Molecular dynamics analysis shows spatially heterogeneous dynamics at high concentration that becomes homogeneous at more dilute concentrations. We discuss the hydration dynamics results of this model protein system in the context of glassy systems, protein function, and protein-protein interfaces.

  10. Continuous production of CO2 hydrate slurry added antifreeze proteins

    Energy Technology Data Exchange (ETDEWEB)

    Tokunaga, Y.; Ota, M.; Murakami, K. [Tokyo Metropolitan Univ., Tokyo (Japan). Dept. of Mechanical Engineering; Ferdows, M. [Dhaka Univ., Dhaka (Bangladesh). Dept. of Mathematics; Endou, H. [Technova Co. Ltd., Tokyo (Japan). Dept. of Mechanical Engineering

    2008-07-01

    Ocean storage of carbon dioxide (CO{sub 2}) hydrate is possible in deep seas where low temperature and high pressure conditions exist. However, when hydrates are produced in large quantities, they can plug pipelines. The addition of antifreeze proteins (AFPs) can prevent hydrate crystals from forming. The hydrate may then behave like a slurry which can be transported from a production place to a place of storage with minimal pressure loss. This study developed a production method for a CO{sub 2} hydrate slurry and presented the prospect of the inhibition effect for CO{sub 2} hydrate formation by adding AFPs. It revealed the shift in induction time, the formation rate and the torque of the agitator under conditions of AFPs at 0.01 mg/ml. It was concluded that compared to pure water, the induction time for hydrate production increased 244 per cent, the formation rate decreased 76 per cent and the ratio of the torque decreased 48 per cent by adding AFPs. The AFPs rendered the hydrate particles small and well dispersed. It was concluded that type 3 AFPs can effectively inhibit the production of structure s1 type hydrates. 4 refs., 6 figs.

  11. Parameterization of ammonia and water content of atmospheric droplets with fixed number of sulfuric acid molecules

    Science.gov (United States)

    Napari, I.; Makkonen, R.; Kulmala, M.; Vehkamäki, H.

    2006-12-01

    We present a parameterization for numbers of water and ammonia molecules in an equilibrium droplet with fixed number of sulfuric acid molecules at known relative humidity, ammonia mixing ratio and temperature. The radius of the droplet is also parameterized. The parameterizations are based on macroscopic model of solution droplets and up-to-date thermodynamics. The binary parameterizations are valid for temperatures 190-330 K and relative humidities 1-99%. The ternary parameterization can be used at temperatures 240-300 K, relative humidities 5-95%, and ammonia mixing ratios 10 - 4 -100 ppt. In both cases the parameterizations are valid for droplets containing up to 10 11 sulfuric acid molecules. The droplet composition is always between the limits of pure ammonium bisulfate and pure ammonium sulfate.

  12. Evaluation of Gas Hydrate at Alaminos Canyon 810, Northern Gulf of Mexico Slope

    Science.gov (United States)

    Yang, C.; Cook, A.; Sawyer, D.; Hillman, J. I. T.

    2016-12-01

    We characterize the gas hydrate reservoir in Alaminos Canyon Block 810 (AC810) on the northern Gulf of Mexico slope, approximately 400 km southeast of Houston, Texas, USA. Three-dimensional seismic data shows a bottom-simulating-reflection (BSR), over 30 km2, which suggests that a significant gas hydrate accumulation may occur at AC810. Furthermore, logging while drilling (LWD) data acquired from a Statoil well located that penetrated the BSR near the crest of the regional anticline indicates two possible gas hydrate units (Hydrate Unit A and Hydrate Unit B). LWD data in this interval are limited to gamma ray and resistivity only. Resistivity curve separations are observed in Hydrate Unit A (131 to 253 mbsf) suggesting hydrate-filled fractures in marine mud. A spiky high resistivity response in Hydrate Unit B (308 to 354 mbsf) could either be a marine mud or a sand-prone interval. The abrupt decrease (from 7 to 1 Ωm) in resistivity logs at 357 mbsf generally corresponds with the interpreted base of hydrate stability, as the BSR is observed near 350 mbsf on the seismic data. To further investigate the formation characteristics, we generate synthetic traces using general velocity and density trends for marine sediments to match the seismic trace extracted at the Statoil well. We consider models with 1) free gas and 2) water only below the base of hydrate stability. In our free gas-below models, we find the velocity of Hydrate Unit A and Hydrate Unit B is generally low and does not deviate significantly from the general velocity trends, suggesting that gas hydrate is present in a marine mud. In the water-below model, the compressional velocity of Hydrate Unit B ranges from 2450 m/s to 3150 m/s. This velocity is similar to the velocity of high hydrate saturation in sand; typically greater than 2500 m/s. This may indicate that Hydrate Unit B is sand with high hydrate saturation; however, to achieve a suitable match between the water-below synthetic seismogram and the

  13. The hydrodynamics of swimming at intermediate Reynolds numbers in the water boatman (Corixidae).

    Science.gov (United States)

    Ngo, Victoria; McHenry, Matthew James

    2014-08-01

    The fluid forces that govern propulsion determine the speed and energetic cost of swimming. These hydrodynamics are scale dependent and it is unclear what forces matter to the tremendous diversity of aquatic animals that are between a millimeter and a centimeter in length. Animals at this scale generally operate within the regime of intermediate Reynolds numbers, where both viscous and inertial fluid forces have the potential to play a role in propulsion. The present study aimed to resolve which forces create thrust and drag in the paddling of the water boatman (Corixidae), an animal that spans much of the intermediate regime (10acceleration reaction force. Based on these findings, we developed a forward-dynamic model of propulsion in free swimming that accurately predicted changes in the body's center of mass over time. For both tethered and free swimming, we used non-linear optimization algorithms to determine the force coefficients that best matched our measurements. With this approach, the drag coefficients on the body and paddle were found to be up to three times greater than on static structures in fully developed flow at the same Reynolds numbers. This is likely a partial consequence of unsteady interactions between the paddles or between the paddles and the body. In addition, the maximum values for these coefficients were inversely related to the Reynolds number, which suggests that viscous forces additionally play an important role in the hydrodynamics of small water boatmen. This understanding for the major forces that operate at intermediate Reynolds numbers offers a basis for interpreting the mechanics, energetics and functional morphology of swimming in many small aquatic animals.

  14. Study on gas hydrate as a new energy resource in the twenty first century

    Energy Technology Data Exchange (ETDEWEB)

    Ryu, Byung Jae; Kim, Won Sik; Oh, Jae Ho [Korea Institute of Geology Mining and Materials, Taejon (Korea)] [and others

    1998-12-01

    Methane hydrate, a special type of clathrate hydrates, is a metastable solid compound mainly consisted of methane and water and generally called as gas hydrate. It is stable in the specific low- temperature/high-pressure conditions. Very large amount of methane that is the main component of natural gas, is accumulated in the form of methane hydrate subaquatic areas. Methane hydrate are the major reservoir of methane on the earth. On the other hand, the development and transmission through pipeline of oil and natural gas in the permafrost and deep subaquatic regions are significantly complicated by formation and dissociation of methane hydrate. The dissociation of natural methane hydrates caused by increasing temperature and decreasing pressure could cause the atmospheric pollution and geohazard. The formation, stable existence and dissociation of natural methane hydrates depend on the temperature, pressure, and composition of gas and characteristics of the interstitial waters. For the study on geophysical and geological conditions for the methane hydrate accumulation and to find BSR in the East Sea, Korea, the geophysical surveys using air-gun system, multibeam echo sounder, SBP were implemented in last September. The water temperature data vs. depth were obtained to determine the methane hydrate stability zone in the study area. The experimental equilibrium condition of methane hydrate was also measured in 3 wt.% sodium chloride solution. The relationship between Methane hydrate formation time and overpressure was analyzed through the laboratory work. (author). 49 refs., 6 tabs., 26 figs.

  15. Theoretical Study of Hydrated Cd~(2+) Interactions with Guanine

    Institute of Scientific and Technical Information of China (English)

    王敏; 洒荣建; 吴克琛; 李巧红; 韦永勤

    2012-01-01

    Theoretical study was performed to investigate how the hydration of cadmium ca-tion influences the structure and properties of guanine.The aqueous environment was simulated by both explicit solvent(1-5 water molecules) model and implicit solvent model.For complexes in which Cd2+ attached to the N(7) and O(6) sites of guanine,energy analysis together with the Natural Bonding Orbital(NBO) analysis were performed to elucidate the bonding characteristics in detail.The most stable structures are penta-coordinate complexes without aqua ligand located at the guanine site.Higher number of water ligands corresponds to higher stabilization energies.Average bonding energies of G-Cd increase with the number of water molecules.Bonding energies of water ligands depend on its position in the complexes.The charge distribution of guanine changed with increasing the number of water ligands,which may also influence the base-pairing pattern of guanine.There is positive charge transfer from guanine to aqua ligand as the number of the hydration waters increases.IEFPCM optimization has results comparable to the [CdG(H2O)5]2+ structure 5a.

  16. Apparatus investigates geological aspects of gas hydrates

    Science.gov (United States)

    Booth, J.S.; Winters, W.J.; Dillon, William P.

    1999-01-01

    The US Geological Survey has developed a laboratory research system which allows the study of the creation and dissociation of gas hydrates under deepwater conditions and with different sediment types and pore fluids. The system called GHASTLI (gas hydrate and sediment test laboratory instrument) comprises a pressure chamber which holds a sediment specimen, and which can simulate water depths to 2,500m and different sediment overburden. Seawater and gas flow through a sediment specimen can be precisely controlled and monitored. It can simulate a wide range of geology and processes and help to improve understanding of gas hydrate processes and aid prediction of geohazards, their control and potential use as an energy source. This article describes GHASTLI and how it is able to simulate natural conditions, focusing on fluid volume, acoustic velocity-compressional and shear wave, electric resistance, temperature, pore pressure, shear strength, and permeability.

  17. Seepage from an arctic shallow marine gas hydrate reservoir is insensitive to momentary ocean warming

    Science.gov (United States)

    Hong, Wei-Li; Torres, Marta E.; Carroll, Jolynn; Crémière, Antoine; Panieri, Giuliana; Yao, Haoyi; Serov, Pavel

    2017-06-01

    Arctic gas hydrate reservoirs located in shallow water and proximal to the sediment-water interface are thought to be sensitive to bottom water warming that may trigger gas hydrate dissociation and the release of methane. Here, we evaluate bottom water temperature as a potential driver for hydrate dissociation and methane release from a recently discovered, gas-hydrate-bearing system south of Spitsbergen (Storfjordrenna, ~380 m water depth). Modelling of the non-steady-state porewater profiles and observations of distinct layers of methane-derived authigenic carbonate nodules in the sediments indicate centurial to millennial methane emissions in the region. Results of temperature modelling suggest limited impact of short-term warming on gas hydrates deeper than a few metres in the sediments. We conclude that the ongoing and past methane emission episodes at the investigated sites are likely due to the episodic ventilation of deep reservoirs rather than warming-induced gas hydrate dissociation in this shallow water seep site.

  18. Geo-scientific investigations of gas-hydrates in India

    Digital Repository Service at National Institute of Oceanography (India)

    Sain, K.; Gupta, H.; Mazumdar, A.; Bhaumik, A.K.; Bhowmick, P.K.

    The best solution to meet India's overwhelming energy requirement is to tap the nuclear and solar power to the maximum extent possible. Another feasible major energy resource is gas-hydrates (crystalline substances of methane and water) that have...

  19. Perspective: Structure and ultrafast dynamics of biomolecular hydration shells

    Directory of Open Access Journals (Sweden)

    Damien Laage

    2017-07-01

    Full Text Available The structure and function of biomolecules can be strongly influenced by their hydration shells. A key challenge is thus to determine the extent to which these shells differ from bulk water, since the structural fluctuations and molecular excitations of hydrating water molecules within these shells can cover a broad range in both space and time. Recent progress in theory, molecular dynamics simulations, and ultrafast vibrational spectroscopy has led to new and detailed insight into the fluctuations of water structure, elementary water motions, and electric fields at hydrated biointerfaces. Here, we discuss some central aspects of these advances, focusing on elementary molecular mechanisms and processes of hydration on a femto- to picosecond time scale, with some special attention given to several issues subject to debate.

  20. PART II. HYDRATED CEMENTS

    Directory of Open Access Journals (Sweden)

    Milan Drabik

    2014-09-01

    Full Text Available Essential focus of the study has been to acquire thermoanalytical events, incl. enthalpies of decompositions - ΔH, of technological materials based on two types of Portland cements. The values of thermoanalytical events and also ΔH of probes of technological compositions, if related with the data of a choice of minerals of calcium-silicate-sulfate-aluminate hydrates, served as a valued input for the assessment of phases present and phase changes due to the topical hydraulic processes. The results indicate mainly the effects of "standard humidity" or "wet storage" of the entire hydration/hydraulic treatment, but also the presence of cement residues alongside calcium-silicate-sulfate-aluminate hydrates (during the tested period of treatment. "A diluting" effect of unhydrated cement residues upon the values of decomposition enthalpies in the studied multiphase system is postulated and discussed

  1. Foam drilling in natural gas hydrate

    Directory of Open Access Journals (Sweden)

    Wei Na

    2015-01-01

    Full Text Available The key problem of foam drilling in natural gas hydrate is prediction of characteristic parameters of bottom hole. The simulation shows that when the well depth increases, the foam mass number reduces and the pressure increases. At the same depth, pressure in drill string is always higher than annulus. The research findings provide theoretical basis for safety control.

  2. Structural rearrangements and magic numbers in reactions between pyridine-containing water clusters and ammonia.

    Science.gov (United States)

    Ryding, Mauritz J; Ruusuvuori, Kai; Andersson, Patrik U; Zatula, Alexey S; McGrath, Matthew J; Kurtén, Theo; Ortega, Ismael K; Vehkamäki, Hanna; Uggerud, Einar

    2012-05-24

    Molecular cluster ions H(+)(H(2)O)(n), H(+)(pyridine)(H(2)O)(n), H(+)(pyridine)(2)(H(2)O)(n), and H(+)(NH(3))(pyridine)(H(2)O)(n) (n = 16-27) and their reactions with ammonia have been studied experimentally using a quadrupole-time-of-flight mass spectrometer. Abundance spectra, evaporation spectra, and reaction branching ratios display magic numbers for H(+)(NH(3))(pyridine)(H(2)O)(n) and H(+)(NH(3))(pyridine)(2)(H(2)O)(n) at n = 18, 20, and 27. The reactions between H(+)(pyridine)(m)(H(2)O)(n) and ammonia all seem to involve intracluster proton transfer to ammonia, thus giving clusters of high stability as evident from the loss of several water molecules from the reacting cluster. The pattern of the observed magic numbers suggest that H(+)(NH(3))(pyridine)(H(2)O)(n) have structures consisting of a NH(4)(+)(H(2)O)(n) core with the pyridine molecule hydrogen-bonded to the surface of the core. This is consistent with the results of high-level ab initio calculations of small protonated pyridine/ammonia/water clusters.

  3. The characteristics of gas hydrates recovered from the Mount Elbert Gas Hydrate Stratigraphic Test Well, Alaska North Slope

    Science.gov (United States)

    Lu, H.; Lorenson, T.D.; Moudrakovski, I.L.; Ripmeester, J.A.; Collett, T.S.; Hunter, R.B.; Ratcliffe, C.I.

    2011-01-01

    Systematic analyses have been carried out on two gas hydrate-bearing sediment core samples, HYPV4, which was preserved by CH4 gas pressurization, and HYLN7, which was preserved in liquid-nitrogen, recovered from the BPXA-DOE-USGS Mount Elbert Stratigraphic Test Well. Gas hydrate in the studied core samples was found by observation to have developed in sediment pores, and the distribution of hydrate saturation in the cores imply that gas hydrate had experienced stepwise dissociation before it was stabilized by either liquid nitrogen or pressurizing gas. The gas hydrates were determined to be structure Type I hydrate with hydration numbers of approximately 6.1 by instrumentation methods such as powder X-ray diffraction, Raman spectroscopy and solid state 13C NMR. The hydrate gas composition was predominantly methane, and isotopic analysis showed that the methane was of thermogenic origin (mean ??13C=-48.6??? and ??D=-248??? for sample HYLN7). Isotopic analysis of methane from sample HYPV4 revealed secondary hydrate formation from the pressurizing methane gas during storage. ?? 2010 Elsevier Ltd.

  4. Geomechanical Performance of Hydrate-Bearing Sediment in Offshore Environments

    Energy Technology Data Exchange (ETDEWEB)

    Stephen Holditch; Tad Patzek; Jonny Rutqvist; George Moridis; Richard Plumb

    2008-03-31

    The objective of this multi-year, multi-institutional research project was to develop the knowledge base and quantitative predictive capability for the description of geomechanical performance of hydrate-bearing sediments (hereafter referred to as HBS) in oceanic environments. The focus was on the determination of the envelope of hydrate stability under conditions typical of those related to the construction and operation of offshore platforms. We have developed a robust numerical simulator of hydrate behavior in geologic media by coupling a reservoir model with a commercial geomechanical code. We also investigated the geomechanical behavior of oceanic HBS using pore-scale models (conceptual and mathematical) of fluid flow, stress analysis, and damage propagation. The objective of the UC Berkeley work was to develop a grain-scale model of hydrate-bearing sediments. Hydrate dissociation alters the strength of HBS. In particular, transformation of hydrate clusters into gas and liquid water weakens the skeleton and, simultaneously, reduces the effective stress by increasing the pore pressure. The large-scale objective of the study is evaluation of geomechanical stability of offshore oil and gas production infrastructure. At Lawrence Berkeley National Laboratory (LBNL), we have developed the numerical model TOUGH + Hydrate + FLAC3D to evaluate how the formation and disassociation of hydrates in seafloor sediments affects seafloor stability. Several technical papers were published using results from this model. LBNL also developed laboratory equipment and methods to produce realistic laboratory samples of sediments containing gas hydrates so that mechanical properties could be measured in the laboratory. These properties are required to run TOUGH + Hydrate + FLAC3D to evaluate seafloor stability issues. At Texas A&M University we performed a detailed literature review to determine what gas hydrate formation properties had been measured and reported in the literature. We

  5. Well log characterization of natural gas-hydrates

    Science.gov (United States)

    Collett, Timothy S.; Lee, Myung W.

    2012-01-01

    In the last 25 years there have been significant advancements in the use of well-logging tools to acquire detailed information on the occurrence of gas hydrates in nature: whereas wireline electrical resistivity and acoustic logs were formerly used to identify gas-hydrate occurrences in wells drilled in Arctic permafrost environments, more advanced wireline and logging-while-drilling (LWD) tools are now routinely used to examine the petrophysical nature of gas-hydrate reservoirs and the distribution and concentration of gas hydrates within various complex reservoir systems. Resistivity- and acoustic-logging tools are the most widely used for estimating the gas-hydrate content (i.e., reservoir saturations) in various sediment types and geologic settings. Recent integrated sediment coring and well-log studies have confirmed that electrical-resistivity and acoustic-velocity data can yield accurate gas-hydrate saturations in sediment grain-supported (isotropic) systems such as sand reservoirs, but more advanced log-analysis models are required to characterize gas hydrate in fractured (anisotropic) reservoir systems. New well-logging tools designed to make directionally oriented acoustic and propagation-resistivity log measurements provide the data needed to analyze the acoustic and electrical anisotropic properties of both highly interbedded and fracture-dominated gas-hydrate reservoirs. Advancements in nuclear magnetic resonance (NMR) logging and wireline formation testing (WFT) also allow for the characterization of gas hydrate at the pore scale. Integrated NMR and formation testing studies from northern Canada and Alaska have yielded valuable insight into how gas hydrates are physically distributed in sediments and the occurrence and nature of pore fluids(i.e., free water along with clay- and capillary-bound water) in gas-hydrate-bearing reservoirs. Information on the distribution of gas hydrate at the pore scale has provided invaluable insight on the mechanisms

  6. A statistical mechanical description of biomolecular hydration

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1996-02-01

    We present an efficient and accurate theoretical description of the structural hydration of biological macromolecules. The hydration of molecules of almost arbitrary size (tRNA, antibody-antigen complexes, photosynthetic reaction centre) can be studied in solution and in the crystal environment. The biomolecular structure obtained from x-ray crystallography, NMR, or modeling is required as input information. The structural arrangement of water molecules near a biomolecular surface is represented by the local water density analogous to the corresponding electron density in an x-ray diffraction experiment. The water-density distribution is approximated in terms of two- and three-particle correlation functions of solute atoms with water using a potentials-of-mean-force expansion.

  7. Clathrate Hydrates for Thermal Energy Storage in Buildings: Overview of Proper Hydrate-Forming Compounds

    Directory of Open Access Journals (Sweden)

    Beatrice Castellani

    2014-09-01

    Full Text Available Increasing energy costs are at the origin of the great progress in the field of phase change materials (PCMs. The present work aims at studying the application of clathrate hydrates as PCMs in buildings. Clathrate hydrates are crystalline structures in which guest molecules are enclosed in the crystal lattice of water molecules. Clathrate hydrates can form also at ambient pressure and present a high latent heat, and for this reason, they are good candidates for being used as PCMs. The parameter that makes a PCM suitable to be used in buildings is, first of all, a melting temperature at about 25 °C. The paper provides an overview of groups of clathrate hydrates, whose physical and chemical characteristics could meet the requirements needed for their application in buildings. Simulations with a dynamic building simulation tool are carried out to evaluate the performance of clathrate hydrates in enhancing thermal comfort through the moderation of summer temperature swings and, therefore, in reducing energy consumption. Simulations suggest that clathrate hydrates have a potential in terms of improvement of indoor thermal comfort and a reduction of energy consumption for cooling. Cooling effects of 0.5 °C and reduced overheating hours of up to 1.1% are predicted.

  8. Estimation of gas hydrate saturation with temperature calculated from hydrate threshold at C0002 during IODP NanTroSEIZE Stage 1 expeditions in the Nankai Trough

    Science.gov (United States)

    Miyakawa, A.; Yamada, Y.; Saito, S.; Bourlange, S.; Chang, C.; Conin, M.; Tomaru, H.; Kinoshita, M.; Tobin, H.; 314/315/316Scientists, E.

    2008-12-01

    During the IODP Expedition 314, conducted at Nankai trough accretionary prism, gas hydrate was observed at Site C0002. Gas hydrate beneath seafloor is promising energy source and potentially hazardous material during drilling. The precise estimation of gas hydrate saturation is important, but previous works have not considered the effect" of the in-situ temperature. In this study, we propose an estimation method of gas hydrate saturation with temperature calculated from threshold of gas hydrate. Gas hydrate saturation was determined based on the Logging While Drilling (LWD) Expedition 314 data. The gas hydrate bearing zone was located between 218.1 to 400.4 m below seafloor. Archie's relation was used to estimate gas hydrate saturation. This relation requires the porosity, the sea water resistivity and formation resistivity. We determined porosity to be between ~70 to ~30% based on density log. Since the resistivity of sea water is temperature dependent, temperature profile (calculated temperature model) was determined from the thermal conductivity and the temperature at the base of the gas hydrate. In our calculated temperature model, the saturation increases from ~10% at ~220m to ~30% at 400 m below sea floor. Spikes that have a maximum value at 80% at sand layers were observed. We also estimated the gas hydrate saturation from the constant temperature profile in 12°C (temperature constant model). This resulted in almost constant saturation (~15%) with the high saturation spikes. We compared these saturations with the hydrate occupation ratio within sand layers derived from RAB image. The hydrate occupation ratio shows increasing trend with increasing depth, and this trend is similar to the gas hydrate saturation with the calculated temperature model. This result suggests that the temperature profile should be considered to obtain precise gas hydrate saturation. Since the high sedimentation rate can affect thermal condition, we are planning to estimate the

  9. Hydrophobic hydration from small to large lengthscales: Understanding and manipulating the crossover

    OpenAIRE

    Rajamani, Sowmianarayanan; Truskett, Thomas M.; Garde, Shekhar

    2005-01-01

    Small and large hydrophobic solutes exhibit remarkably different hydration thermodynamics. Small solutes are accommodated in water with minor perturbations to water structure, and their hydration is captured accurately by theories that describe density fluctuations in pure water. In contrast, hydration of large solutes is accompanied by dewetting of their surfaces and requires a macroscopic thermodynamic description. A unified theoretical description of these lengthscale dependencies was pres...

  10. Electrical Measurement to Assess Hydration Process and the Porosity Formation

    Institute of Scientific and Technical Information of China (English)

    WEI Xiaosheng; XIAO Lianzhen; LI Zongjin

    2008-01-01

    The change of electrical resistivity with time at early ages was used to investigate the hydration process and the porosity development. Porosity reduction process of cement-based materials hydration was developed by a proposed method. The porosity reduction is fast at the setting period. The results find that the pore discontinuity occurs faster at lower water/cement ratios than at higher water/cement ratios which is similar to the results of the Percolation method.

  11. Effect of temperature, pressure, and cosolvents on structural and dynamic properties of the hydration shell of SNase: a molecular dynamics computer simulation study.

    Science.gov (United States)

    Smolin, Nikolai; Winter, Roland

    2008-01-24

    It is now generally agreed that the hydration water and solvational properties play a crucial role in determining the dynamics and hence the functionality of proteins. We present molecular dynamics computer simulation studies on staphylococcal nuclease (SNase) at various temperatures and pressures as well as in different cosolvent solutions containing various concentrations of urea and glycerol. The aim is to provide a molecular level understanding of how different types of cosolvents (chaotropic and kosmotropic) as well as temperature and high hydrostatic pressure modify the structure and dynamics of the hydration water. Taken together, these three intrinsic thermodynamic variables, temperature, pressure, and chemical potential (or activity) of the solvent, are able to influence the stability and function of the protein by protein-solvent dynamic coupling in different ways. A detailed analysis of the structural and dynamical properties of the water and cosolvents at the protein surface (density profile, coordination numbers, hydrogen-bond distribution, average H-bond lifetimes (water-protein and water-water), and average residence time of water in the hydration shell) was carried out, and differences in the structural and dynamical properties of the hydration water in the presence of the different cosolvents and at temperatures between 300 and 400 K and pressures up to 5000 bar are discussed. Furthermore, the results obtained help understand various thermodynamic properties measured for the protein.

  12. Hydration and cognitive performance.

    Science.gov (United States)

    Sécher, M; Ritz, P

    2012-04-01

    A clinical link exists between severe dehydration and cognitive performance. Using rapid and severe water loss induced either by intense exercise and/or heat stress, initial studies suggested there were alterations in short-term memory and cognitive function related to vision, but more recent studies have not all confirmed these data. Some studies argue that water loss is not responsible for the observations made, and studies compensating water losses have failed to prevent the symptoms. Studies in children have suggested that drinking extra water helps cognitive performance, but these data rely on a small number of children. In older adults (mean age around 60) the data are not strong enough to support a relationship between mild dehydration and cognitive function. Data on frail elderly and demented people are lacking. Methodological heterogeneity in these studies are such that the relationship between mild dehydration and cognitive performance cannot be supported.

  13. Unfolding of Hydrated Alkyl Diammonium Cations Revealed by Cryogenic Ion Mobility-Mass Spectrometry.

    Science.gov (United States)

    Servage, Kelly A; Fort, Kyle L; Silveira, Joshua A; Shi, Liuqing; Clemmer, David E; Russell, David H

    2015-07-22

    Hydration of the ammonium ion plays a key role in determining the biomolecular structure as well as local structure of water in aqueous environments. Experimental data obtained by cryogenic ion mobility-mass spectrometry (cryo-IM-MS) show that dehydration of alkyl diammonium cations induces a distinct unfolding transition at a critical number of water molecules, n = 21 to 23, n = 24 to 26, and n = 27 to 29, for 1,7-diaminoheptane, 1,8-diaminooctane, and 1,10-diaminodecane, respectively. Results are also presented that reveal compelling evidence for unique structural transitions of hydrated ammonium ions associated with the development of the hydrogen-bond network around individual charged groups. The ability to track the evolution of structure upon stepwise dehydration provides direct insight into the intricate interplay between solvent-molecule interactions that are responsible for defining conformations. Such insights are potentially valuable in understanding how ammonium ion solvation influences conformation(s) of larger biomolecules.

  14. Modeling the Nanophase Structural Dynamics of Phenylated Sulfonated Poly Ether Ether Ketone Ketone (Ph-SPEEKK) Membranes as a Function of Hydration

    Energy Technology Data Exchange (ETDEWEB)

    Lins, Roberto D.; Devanathan, Ramaswami; Dupuis, Michel

    2011-03-03

    Solvated phenylated sulfonated poly ether ether ketone ketone (Ph-SPEEKK) membranes in the presence of hydronium ions were modeled by classical molecular dynamics simulations. The characterization of the nanophase structure and dynamics of such membranes was carried out as a function of the water content lambda, where lambda is the number of water molecules per sulfonate group, for lambda values of 3.5, 6, 11, 25, and 40. Analysis of pair correlation functions supports the experimental observation of membrane swelling upon hydration as well the increase in water and hydronium ion diffusion with increasing lambda. While the average number of hydrogen bonds between hydronium ions and sulfonate groups is dramatically affected by the hydration level, the average lifetime of the hydrogen bonds remains essentially constant. The membrane is found to be relatively rigid and its overall flexibility shows little dependence on water content. Compared to Nafion, water and ion diffusion coefficients are considerably smaller at lower hydration levels and room temperature. However, at higher lambda values of 25 and 40 these coefficients are comparable to those in Nafion at a lambda value of 16. This study also shows that water diffusion in Ph-SPEEKK membranes at low hydration levels can be significantly improved by raising the temperature with important implications for proton conductivity.

  15. P-T stability conditions of methane hydrate in sediment from South China Sea

    Institute of Scientific and Technical Information of China (English)

    Shicai Sun; Yuguang Ye; Changling Liu; Fengkui Xiang; Yah Ma

    2011-01-01

    For reasonable assessment and safe exploitation of marine gas hydrate resource,it is important to determine the stability conditions of gas hydrates in marine sediment.In this paper,the seafloor water sample and sediment sample (saturated with pore water) from Shenhu Area of South China Sea were used to synthesize methane hydrates,and the stability conditions of methane hydrates were investigated by multi-step heating dissociation method.Preliminary experimental results show that the dissociation temperature of methane hydrate both in seafloor water and marine sediment,under any given pressure,is depressed by approximately -1.4 K relative to the pure water system.This phenomenon indicates that hydrate stability in marine sediment is mainly affected by pore water ions.

  16. Formation of natural gas hydrates in marine sediments 1. Conceptual model of gas hydrate growth conditioned by host sediment properties

    Science.gov (United States)

    Clennell, M.B.; Hovland, M.; Booth, J.S.; Henry, P.; Winters, W.J.

    1999-01-01

    The stability of submarine gas hydrates is largely dictated by pressure and temperature, gas composition, and pore water salinity. However, the physical properties and surface chemistry of deep marine sediments may also affect the thermodynamic state, growth kinetics, spatial distributions, and growth forms of clathrates. Our conceptual model presumes that gas hydrate behaves in a way analogous to ice in a freezing soil. Hydrate growth is inhibited within fine-grained sediments by a combination of reduced pore water activity in the vicinity of hydrophilic mineral surfaces, and the excess internal energy of small crystals confined in pores. The excess energy can be thought of as a "capillary pressure" in the hydrate crystal, related to the pore size distribution and the state of stress in the sediment framework. The base of gas hydrate stability in a sequence of fine sediments is predicted by our model to occur at a lower temperature (nearer to the seabed) than would be calculated from bulk thermodynamic equilibrium. Capillary effects or a build up of salt in the system can expand the phase boundary between hydrate and free gas into a divariant field extending over a finite depth range dictated by total methane content and pore-size distribution. Hysteresis between the temperatures of crystallization and dissociation of the clathrate is also predicted. Growth forms commonly observed in hydrate samples recovered from marine sediments (nodules, and lenses in muds; cements in sands) can largely be explained by capillary effects, but kinetics of nucleation and growth are also important. The formation of concentrated gas hydrates in a partially closed system with respect to material transport, or where gas can flush through the system, may lead to water depletion in the host sediment. This "freeze-drying" may be detectable through physical changes to the sediment (low water content and overconsolidation) and/or chemical anomalies in the pore waters and metastable

  17. Fundamental challenges to methane recovery from gas hydrates

    Science.gov (United States)

    Servio, P.; Eaton, M.W.; Mahajan, D.; Winters, W.J.

    2005-01-01

    The fundamental challenges, the location, magnitude, and feasibility of recovery, which must be addressed to recover methane from dispersed hydrate sources, are presented. To induce dissociation of gas hydrate prior to methane recovery, two potential methods are typically considered. Because thermal stimulation requires a large energy input, it is less economically feasible than depressurization. The new data will allow the study of the effect of pressure, temperature, diffusion, porosity, tortuosity, composition of gas and water, and porous media on gas-hydrate production. These data also will allow one to improve existing models related to the stability and dissociation of sea floor hydrates. The reproducible kinetic data from the planned runs together with sediment properties will aid in developing a process to economically recover methane from a potential untapped hydrate source. The availability of plentiful methane will allow economical and large-scale production of methane-derived clean fuels to help avert future energy crises.

  18. The Pore Structure and Hydration Performance of Sulphoaluminate MDF Cement

    Institute of Scientific and Technical Information of China (English)

    HUANG Cong-yun; YUAN Run-zhang; LONG Shi-zong

    2004-01-01

    The hydration and pore structure of sulphoaluminate MDF cement were studied by X-ray diffractometer ( XRD ), scanning electron microscope (SEM) and mercury intrusion porosimeter ( MIP ) etc. The ex-perimental results indicate that hydration products of the materials are entringites ( Aft ), aluminium hydroxide andCSH (Ⅰ) gel etc. Due to its very low water-cement ratio, hydration function is only confined to the surfaces of ce-ment grains, and there is a lot of sulphoaluminate cement in the hardenite which is unhydrated yet. Hydration re-action was rapidly carried under the condition of the heat-pressing. Therefore cement hydrates Aft, CSH (Ⅰ) andaluminium hydroxide gel fill in pores. The expansibility of Aft makes the porosity of MDF cement lower ( less than1 percent ) and the size of pore smaller (80 percent pore was less than 250A), and enhances its strength.

  19. Heat of Hydration of Low Activity Cementitious Waste Forms

    Energy Technology Data Exchange (ETDEWEB)

    Nasol, D. [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL)

    2015-07-23

    During the curing of secondary waste grout, the hydraulic materials in the dry mix react exothermally with the water in the secondary low-activity waste (LAW). The heat released, called the heat of hydration, can be measured using a TAM Air Isothermal Calorimeter. By holding temperature constant in the instrument, the heat of hydration during the curing process can be determined. This will provide information that can be used in the design of a waste solidification facility. At the Savannah River National Laboratory (SRNL), the heat of hydration and other physical properties are being collected on grout prepared using three simulants of liquid secondary waste generated at the Hanford Site. From this study it was found that both the simulant and dry mix each had an effect on the heat of hydration. It was also concluded that the higher the cement content in the dry materials mix, the greater the heat of hydration during the curing of grout.

  20. Density dependence of the yield of hydrated electrons in the low-LET radiolysis of supercritical water at 400 °C: influence of the geminate recombination of subexcitation-energy electrons prior to thermalization.

    Science.gov (United States)

    Meesungnoen, Jintana; Sanguanmith, Sunuchakan; Jay-Gerin, Jean-Paul

    2013-10-21

    Monte Carlo simulations were used to calculate the yield of hydrated electrons (eaq(-)) in the low-linear energy transfer radiolysis of supercritical water at 400 °C as a function of water density over the range of ~0.15 to 0.6 g cm(-3). Very good agreement was found between our calculations and picosecond pulse radiolysis experimental data at ~60 ps and 1 ns at high density (>0.35 g cm(-3)). At densities lower than ~0.35 g cm(-3), our eaq(-) yields were lower than the experimental data, especially at ~60 ps. However, if we incorporated into the simulations a prompt geminate electron-cation (H2O˙(+)) recombination (prior thermalization of the electron) that decreased as the density decreased, our computed eaq(-) yields at ~60 ps and 1 ns compared fairly well with the experimental data for the entire density range studied.

  1. Simulation of gas hydrate dissociation caused by repeated tectonic uplift events

    Science.gov (United States)

    Goto, Shusaku; Matsubayashi, Osamu; Nagakubo, Sadao

    2016-05-01

    Gas hydrate dissociation by tectonic uplift is often used to explain geologic and geophysical phenomena, such as hydrate accumulation probably caused by hydrate recycling and the occurrence of double bottom-simulating reflectors in tectonically active areas. However, little is known of gas hydrate dissociation resulting from tectonic uplift. This study investigates gas hydrate dissociation in marine sediments caused by repeated tectonic uplift events using a numerical model incorporating the latent heat of gas hydrate dissociation. The simulations showed that tectonic uplift causes upward movement of some depth interval of hydrate-bearing sediment immediately above the base of gas hydrate stability (BGHS) to the gas hydrate instability zone because the sediment initially maintains its temperature: in that interval, gas hydrate dissociates while absorbing heat; consequently, the temperature of the interval decreases to that of the hydrate stability boundary at that depth. Until the next uplift event, endothermic gas hydrate dissociation proceeds at the BGHS using heat mainly supplied from the sediment around the BGHS, lowering the temperature of that sediment. The cumulative effects of these two endothermic gas hydrate dissociations caused by repeated uplift events lower the sediment temperature around the BGHS, suggesting that in a marine area in which sediment with a highly concentrated hydrate-bearing layer just above the BGHS has been frequently uplifted, the endothermic gas hydrate dissociation produces a gradual decrease in thermal gradient from the seafloor to the BGHS. Sensitivity analysis for model parameters showed that water depth, amount of uplift, gas hydrate saturation, and basal heat flow strongly influence the gas hydrate dissociation rate and sediment temperature around the BGHS.

  2. Approche osmotique de l'hydratation du stratum corneum.

    Science.gov (United States)

    Forestier, J P

    1987-12-01

    Summary An osmotic approach to a study of hydration of the stratum corneum At first Middleton, in his classic studies, explains the water sorption of stratum corneum by osmotic processes. To follow Middleton, and in order to study water osmosis diffusion, we made an osmotic model of stratum corneum (OMSC). The OMSC was constituted by 0.8 g of sheep wool, which was closed in a dialysis bag. When the OMSC was placed in the water, its weight increased, due to water diffusing through the membrane to bind with the protein. The rate of sorption was slow, but the value was about the same as that which Scheuplein has observed for the stratum corneum. At saturation, the weight of 'bound water'was 13 times greater than the weight of keratine. The components of Natural Moisturizing Factor and glycerol enhance the sorption rate and the weight fraction 'bound water'at saturation. The best component is urea. This observation suggests that humectants increase the number of water-binding sites of keratin. The OMSC could allow preliminary tests of water-soluble skin moisturizers.

  3. Preliminary discussion on gas hydrate reservoir system of Shenhu Area, North Slope of South China Sea

    Energy Technology Data Exchange (ETDEWEB)

    Wu, N.; Yang, S.; Liang, J.; Wang, H.; Fu, S. [Guangzhou Marine Geological Survey, Guangzhou (China); Zhang, H. [China Geological Survey, Beijing (China); Su, X. [China Univ. of Geosciences, Beijing (China)

    2008-07-01

    Gas hydrate is a type of ice-like solid substance formed by the combination of certain low-molecular-weight gases such as methane, ethane, and carbon dioxide with water. Gas hydrate primarily occurs naturally in sediments beneath the permafrost and the sediments of the continental slope with the water depth greater than 300 m. Marine gas hydrate geological systems are important because they may be sufficiently concentrated in certain locations to be an economically viable fossil fuel resource. However, gas hydrates can cause geo-hazards through large-scale slope destabilization and can release methane, a potential greenhouse gas, into the environment. This paper discussed the hydrate drilling results from a geological and geophysical investigation of the gas hydrate reservoir system of the Shenhu Area, located in the north slope of South China Sea. The paper identified the basic formation conditions, and discussed the pore-water geochemical features of shallow sediments and their inflected gas sources, gas hydrate distribution and seismic characteristics. It was concluded that the gas hydrate was heterogeneously distributed in space, and mainly distributed in certain ranges above the bottom of the gas hydrate stability zone. It was also concluded that methane gas that formed hydrate was likely from in-situ micro-biogenic methane. Last, it was found that distributed and in-situ micro-biogenic methane resulted in low methane flux, and formed the distributed pattern of gas hydrate system with the features of differential distribution and saturation. 34 refs., 2 tabs., 3 figs.

  4. Synthesis of New Hydrated Geranylphenols and in Vitro Antifungal Activity against Botrytis cinerea

    Directory of Open Access Journals (Sweden)

    Mauricio Soto

    2016-06-01

    Full Text Available Geranylated hydroquinones and other geranylated compounds isolated from Aplydium species have shown interesting biological activities. This fact has prompted a number of studies where geranylated phenol derivatives have been synthesized in order to assay their bioactivities. In this work, we report the synthesis of a series of new hydrated geranylphenols using two different synthetic approaches and their inhibitory effects on the mycelial growth of Botrytis cinerea. Five new hydrated geranylphenols were obtained by direct coupling reaction between geraniol and phenol in dioxane/water and using BF3·Et2O as the catalyst or by the reaction of a geranylated phenol with BF3·Et2O. Two new geranylated quinones were also obtained. The synthesis and structural elucidation of all new compounds is presented. All hydrated geranylphenols efficiently inhibit the mycelial growth of B. cinerea. Their activity is higher than that observed for non-hydrated compounds. These results indicate that structural modification on the geranyl chain brings about an enhancement of the inhibition effect of geranylated phenol derivatives.

  5. Low-δD hydration rinds in Yellowstone perlites record rapid syneruptive hydration during glacial and interglacial conditions

    Science.gov (United States)

    Bindeman, Ilya N.; Lowenstern, Jacob B.

    2016-01-01

    Hydration of silicic volcanic glass forms perlite, a dusky, porous form of altered glass characterized by abundant “onion-skin” fractures. The timing and temperature of perlite formation are enigmatic and could plausibly occur during eruption, during post-eruptive cooling, or much later at ambient temperatures. To learn more about the origin of natural perlite, and to fingerprint the hydration waters, we investigated perlitic glass from several synglacial and interglacial rhyolitic lavas and tuffs from the Yellowstone volcanic system. Perlitic cores are surrounded by a series of conchoidal cracks that separate 30- to 100-µm-thick slivers, likely formed in response to hydration-induced stress. H2O and D/H profiles confirm that most D/H exchange happens together with rapid H2O addition but some smoother D/H variations may suggest separate minor exchange by deuterium atom interdiffusion following hydration. The hydrated rinds (2–3 wt% H2O) transition rapidly (within 30 µm, or by 1 wt% H2O per 10 µm) to unhydrated glass cores. This is consistent with quenched “hydration fronts” where H2O diffusion coefficients are strongly dependent on H2O concentrations. The chemical, δ18O, and δD systematics of bulk glass records last equilibrium between ~110 and 60 °C without chemical exchange but with some δ18O exchange. Similarly, the δ18O of water extracted from glass by rapid heating suggests that water was added to the glass during cooling at C. Our observations support fast hydration at temperatures as low as 60 °C; prolonged exposure to high temperature of 175°–225° during water addition is less likely as the glass would lose alkalies and should alter to clays within days. A compilation of low-temperature hydration diffusion coefficients suggests ~2 orders of magnitude higher rates of diffusion at 60–110 °C temperatures, compared with values expected from extrapolation of high-temperature (>400 °C) experimental data. The thick hydration

  6. Portland cement hydration in the presence of admixtures: black gram pulse and superplasticizer

    Directory of Open Access Journals (Sweden)

    Viveka Nand Dwivedi

    2008-12-01

    Full Text Available Effect of admixtures such as black gram pulse (BGP and sulfonated naphthalene based superplasticizer (SP on the hydration of Portland cement has been studied. The hydration characteristics of OPC in the presence of BGP and SP were studied with the help of non evaporable water content determinations, calorimetric method, Mössbauer spectroscopic and atomic force microscopic techniques. Results have shown that both BGP and SP get adsorbed at the surface of cement and its hydration products. The hydration of Portland cement is retarded in the presence of both the admixtures and nanosize hydration products are formed.

  7. Experimental and Modeling Studies on the Prediction of Gas Hydrate Formation

    Directory of Open Access Journals (Sweden)

    Jian-Yi Liu

    2015-01-01

    Full Text Available On the base of some kinetics model analysis and kinetic observation of hydrate formation process, a new prediction model of gas hydrate formation is proposed. The analysis of the present model shows that the formation of gas hydrate not only relevant with gas composition and free water content but also relevant with temperature and pressure. Through contrast experiment, the predicted result of the new prediction method of gas hydrate crystallization kinetics is close to measured result, it means that the prediction method can reflect the hydrate crystallization accurately.

  8. Effect of bubble size and density on methane conversion to hydrate

    Energy Technology Data Exchange (ETDEWEB)

    Leske, J.; Taylor, C.E.; Ladner, E.P.

    2007-03-01

    Research is underway at NETL to understand the physical properties of methane hydrates. One area of investigation is the storage of methane as methane hydrates. An economical and efficient means of storing methane in hydrates opens many commercial opportunities such as transport of stranded gas, off-peak storage of line gas, etc.We have observed during our investigations that the ability to convert methane to methane hydrate is enhanced by foaming of the methane–water solution using a surfactant. The density of the foam, along with the bubble size, is important in the conversion of methane to methane hydrate.

  9. The Induction Period of Hydrate Formation in a Flow System%流动体系中的水合物成核诱导期研究

    Institute of Scientific and Technical Information of China (English)

    孙长宇; 陈光进; 岳国良

    2004-01-01

    The appearance of turbidity due to large numbers of critical size hydrate nuclei may significantly affect the outgoing light intensity and the flow resistance in the pipe loop. The induction period of hydrate formation was determined by analyzing the experimental data-either based on the shading ratio data of laser detector or based on the pressure drop data of the flow system. The induction period of CCl2F2 (R12) in pure water and that of CH4in (tetrahydrofuran + water) systems were then measured with the above two methods. Experimental data show that the induction period depends on the driving force exponentially. Flow rate also has a significant influence on the hydrate nucleation. A new induction period model taking the driving force and liquid flow rate into account was proposed. And it is successfully applied to the calculation of the induction period, which is in good agreement with the experimental data obtained in this study.

  10. Controls on gas hydrate stability in methane depleted sediments: Laboratory and field measurements

    Science.gov (United States)

    Lapham, L.; Chanton, J.; Martens, C. S.

    2009-12-01

    Gas hydrate deposits are the Earth’s largest reservoir of the powerful greenhouse gas methane and thus a key future energy resource. However, hydrate stability in sedimentary environments featuring highly variable methane concentrations needs to be understood to allow resource estimation and recovery. Hydrates are at chemical equilibrium and therefore stable where high pressures, low temperatures, and moderate salinities coexist with methane-saturated pore waters. When all of these conditions are not met, hydrates should dissociate or dissolve, releasing methane to the overlying water and possibly the atmosphere. In addition, other natural factors may control the kinetics of their degradation complicating models for hydrate stability and occurrence. Our measurements indicate that the pore-waters surrounding some shallow buried hydrates are not methane-saturated suggesting that dissolution should occur relatively rapidly. Yet, these hydrate deposits are known to persist relatively unchanged for years. We hypothesize that, once formed, hydrate deposits may be stabilized by natural factors inhibiting dissolution, including oil or microbial biofilm coatings. While most studies have focused on pressure and temperature changes where hydrates occur, relatively few have included measurements of in situ methane concentration gradients because of the difficulties inherent to making such measurements. Here we present recent measurements of methane concentration and stable carbon isotope gradients immediately adjacent to undisturbed hydrate surfaces obtained through deployments of novel seafloor instruments. Our results suggest that the hydrates studied are relatively stable when exposed to overlying and pore-waters that are undersaturated with methane. Concurrent laboratory measurements of methane concentration gradients next to artificial hydrate surfaces were utilized to test our protective coating hypothesis. After a stable dissolution rate for