WorldWideScience

Sample records for hydrated water molecules

  1. Fractionation of hydrogen and oxygen isotopes between hydrated and free water molecules in aqueous urea solution

    International Nuclear Information System (INIS)

    Kakiuchi, M.; Matsuo, S.

    1985-01-01

    Ratios of D/H and 18 O/ 16 O in the vapor phase in equilibrium with aqueous urea solution with different urea molalities were measured at 15 and 25 0 C. Under the assumption that urea solutions consist of two species, i.e., the urea-water cluster and free water, the results are interpreted to give the average hydration number, i.e., the number of water molecules per urea molecule in the urea-water cluster. Good agreement was obtained for the hydration number estimated independently from hydrogen and oxygen isotopic fractions. On the basis of hydrogen isotopic data at 25 0 C, the average hydration number of urea in the cluster is 6.3 +/- 0.8 at 2.1 m and 2.75 +/- 0.08 at saturation (20.15 m). The corresponding average hydration numbers based on oxygen isotopic data were calculated to be 6.7 +/- 2.4 at 2.1 m and 2.75 +/- 0.25 at urea saturation. HD 16 O is enriched in the urea-water cluster and H 2 18 O is enriched in free water. Isotopic partitioning between the cluster and free water is markedly different from those between hydration spheres and free water in aqueous electrolyte solutions. 29 references, 6 figures, 5 tables

  2. Relationship between diffusivity of water molecules inside hydrating tablets and their drug release behavior elucidated by magnetic resonance imaging.

    Science.gov (United States)

    Kikuchi, Shingo; Onuki, Yoshinori; Kuribayashi, Hideto; Takayama, Kozo

    2012-01-01

    We reported previously that sustained release matrix tablets showed zero-order drug release without being affected by pH change. To understand drug release mechanisms more fully, we monitored the swelling and erosion of hydrating tablets using magnetic resonance imaging (MRI). Three different types of tablets comprised of polyion complex-forming materials and a hydroxypropyl methylcellulose (HPMC) were used. Proton density- and diffusion-weighted images of the hydrating tablets were acquired at intervals. Furthermore, apparent self-diffusion coefficient maps were generated from diffusion-weighted imaging to evaluate the state of hydrating tablets. Our findings indicated that water penetration into polyion complex tablets was faster than that into HPMC matrix tablets. In polyion complex tablets, water molecules were dispersed homogeneously and their diffusivity was relatively high, whereas in HPMC matrix tablets, water molecule movement was tightly restricted within the gel. An optimal tablet formulation determined in a previous study had water molecule penetration and diffusivity properties that appeared intermediate to those of polyion complex and HPMC matrix tablets; water molecules were capable of penetrating throughout the tablets and relatively high diffusivity was similar to that in the polyion complex tablet, whereas like the HPMC matrix tablet, it was well swollen. This study succeeded in characterizing the tablet hydration process. MRI provides profound insight into the state of water molecules in hydrating tablets; thus, it is a useful tool for understanding drug release mechanisms at a molecular level.

  3. 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.

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

    International Nuclear Information System (INIS)

    Xie, Wen Jun; Yang, Yi Isaac; Gao, Yi Qin

    2015-01-01

    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

  5. Hydration water and microstructure in calcium silicate and aluminate hydrates

    International Nuclear Information System (INIS)

    Fratini, Emiliano; Ridi, Francesca; Chen, Sow-Hsin; Baglioni, Piero

    2006-01-01

    Understanding the state of the hydration water and the microstructure development in a cement paste is likely to be the key for the improvement of its ultimate strength and durability. In order to distinguish and characterize the reacted and unreacted water, the single-particle dynamics of water molecules in hydrated calcium silicates (C 3 S, C 2 S) and aluminates (C 3 A, C 4 AF) were studied by quasi-elastic neutron scattering, QENS. The time evolution of the immobile fraction represents the hydration kinetics and the mobile fraction follows a non-Debye relaxation. Less sophisticated, but more accessible and cheaper techniques, like differential scanning calorimetry, DSC, and near-infrared spectroscopy, NIR, were validated through QENS results and they allow one to easily and quantitatively follow the cement hydration kinetics and can be widely applied on a laboratory scale to understand the effect of additives (i.e., superplasticizers, cellulosic derivatives, etc) on the thermodynamics of the hydration process. DSC provides information on the free water index and on the activation energy involved in the hydration process while the NIR band at 7000 cm -1 monitors, at a molecular level, the increase of the surface-interacting water. We report as an example the effect of two classes of additives widely used in the cement industry: superplasticizers, SPs, and cellulose derivatives. SPs interact at the solid surface, leading to a consistent increment of the activation energy for the processes of nucleation and growth of the hydrated phases. In contrast, the cellulosic additives do not affect the nucleation and growth activation energy, but cause a significant increment in the water availability: in other words the hydration process is more efficient without any modification of the solid/liquid interaction, as also evidenced by the 1 H-NMR. Additional information is obtained by scanning electron microscopy (SEM), ultra small angle neutron scattering (USANS) and wide

  6. Adsorption Mechanism of Inhibitor and Guest Molecules on the Surface of Gas Hydrates.

    Science.gov (United States)

    Yagasaki, Takuma; Matsumoto, Masakazu; Tanaka, Hideki

    2015-09-23

    The adsorption of guest and kinetic inhibitor molecules on the surface of methane hydrate is investigated by using molecular dynamics simulations. We calculate the free energy profile for transferring a solute molecule from bulk water to the hydrate surface for various molecules. Spherical solutes with a diameter of ∼0.5 nm are significantly stabilized at the hydrate surface, whereas smaller and larger solutes exhibit lower adsorption affinity than the solutes of intermediate size. The range of the attractive force is subnanoscale, implying that this force has no effect on the macroscopic mass transfer of guest molecules in crystal growth processes of gas hydrates. We also examine the adsorption mechanism of a kinetic hydrate inhibitor. It is found that a monomer of the kinetic hydrate inhibitor is strongly adsorbed on the hydrate surface. However, the hydrogen bonding between the amide group of the inhibitor and water molecules on the hydrate surface, which was believed to be the driving force for the adsorption, makes no contribution to the adsorption affinity. The preferential adsorption of both the kinetic inhibitor and the spherical molecules to the surface is mainly due to the entropic stabilization arising from the presence of cavities at the hydrate surface. The dependence of surface affinity on the size of adsorbed molecules is also explained by this mechanism.

  7. Tracking all-vapor instant gas-hydrate formation and guest molecule populations: A possible probe for molecules trapped in water nanodroplets

    Czech Academy of Sciences Publication Activity Database

    Uras-Aytemiz, N.; Cwiklik, Lukasz; Devlin, J. P.

    2012-01-01

    Roč. 137, č. 20 (2012), s. 204501 ISSN 0021-9606 Institutional support: RVO:61388955 Keywords : Fourier transform infrared emission spectra * clathrate hydrate * simulations Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 3.164, year: 2012

  8. Water Dynamics in the Hydration Shells of Biomolecules

    Science.gov (United States)

    2017-01-01

    The structure and function of biomolecules are strongly influenced by their hydration shells. Structural fluctuations and molecular excitations of hydrating water molecules cover a broad range in space and time, from individual water molecules to larger pools and from femtosecond to microsecond time scales. Recent progress in theory and molecular dynamics simulations as well as in ultrafast vibrational spectroscopy has led to new and detailed insight into fluctuations of water structure, elementary water motions, electric fields at hydrated biointerfaces, and processes of vibrational relaxation and energy dissipation. Here, we review recent advances in both theory and experiment, focusing on hydrated DNA, proteins, and phospholipids, and compare dynamics in the hydration shells to bulk water. PMID:28248491

  9. UV-visible and resonance Raman spectroscopy of halogen molecules in clathrate hydrates

    Energy Technology Data Exchange (ETDEWEB)

    Janda, K.C.; Kerenskaya, G.; Goldsheleger, I.U.; Apkarian, V.A.; Fleischer, E.B. [California Univ., Irvine, CA (United States). Dept. of Chemistry

    2008-07-01

    Resonance Raman spectroscopy was used to study halogen clathrate hydrate solids. In particular, this paper presented an ultraviolet-visible spectra for a polycrystalline sample of chlorine clathrate hydrate and two single crystal samples of bromine clathrate hydrate. UV-visible spectroscopy was used to study the interactions between the halogen guest molecule and the host water lattice. The spectrum for chlorine hydrate had a strong temperature dependence, while the spectra for bromine clathrate hydrate single crystals had a stable cubic type 2 structure as well as a tetragonal structure. A metastable cubic type 1 structure was also observed. Resonance Raman spectroscopy showed how the molecules fit into the host cages. 25 refs., 2 tabs., 7 figs.

  10. Hydration of ammonia, methylamine, and methanol in amorphous solid water

    Science.gov (United States)

    Souda, Ryutaro

    2016-02-01

    Interactions of polar protic molecules with amorphous solid water (ASW) have been investigated using temperature-programmed desorption and time-of-flight secondary ion mass spectrometry. The ammonia and methylamine are incorporated into the interior of porous ASW films. They are caged by water molecules and are released during water crystallization. In contrast, the methanol-water interaction is not influenced by pores of ASW. The methanol additives tend to survive water crystallization and are released during ASW film evaporation. The hydration of n-hexane in ASW is influenced significantly by methanol additives because n-hexane is accommodated in a methanol-induced hydration shell.

  11. Effect of hydration on the organo-noble gas molecule HKrCCH: role of krypton in the stabilization of hydrated HKrCCH complexes.

    Science.gov (United States)

    Biswas, Biswajit; Singh, Prashant Chandra

    2015-11-11

    The effect of hydration on the fluorine free organo-noble gas compound HKrCCH and the role of krypton in the stabilization of the hydrated HKrCCH complexes have been investigated using the quantum chemical calculations on the HKrCCH-(H2O)n=1-6 clusters. Structure and energetics calculations show that water stabilizes HKrCCH through the π hydrogen bond in which the OH group of water interacts with the C[triple bond, length as m-dash]C group of HKrCCH. A maximum of four water molecules can directly interact with the C[triple bond, length as m-dash]C of HKrCCH and after that only inter-hydrogen bonding takes place between the water molecules indicating that the primary hydration shell contains four water molecules. Atom in molecule analysis depicts that π hydrogen bonded complexes of the hydrated HKrCCH are cyclic structures in which the OKr interaction cooperates in the formation of strong O-HC[triple bond, length as m-dash]C interaction. Structure, energetics and charge analysis clearly established that krypton plays an important role in the stabilization as well as the formation of the primary hydration shell of hydrated HKrCCH complexes.

  12. AGOA: A Hydration Procedure and Its Application to the 1-Phenyl-beta-Carboline Molecule

    OpenAIRE

    Hernandes, Marcelo Z.; Silva, João B. P. da; Longo, Ricardo L.

    2002-01-01

    A new procedure, named AGOA, has been developed and implemented in a computer program written in FORTRAN 77 to explore the hydration structures of polar solutes using its molecular electrostatic potential (MEP). This procedure can be generalized to polar solvents other than water. It has been tested for several small molecules, and applied to complex molecules of pharmacological interest, such as the beta-carbolinic systems derived from indole. This is a stringent, but not general, test of th...

  13. Effects of cyclopentane on CO2 hydrate formation and dissociation as a co-guest molecule for desalination

    International Nuclear Information System (INIS)

    Zheng, Jia-nan; Yang, Ming-jun; Liu, Yu; Wang, Da-yong; Song, Yong-chen

    2017-01-01

    Highlights: • CP decreases CO 2 hydrate phase equilibrium pressure by forming CO 2 -CP hydrates. • The increase of CP can’t decrease hydrates phase equilibrium pressure unlimitedly. • Higher CP concentration lowers CO 2 hydrate gas uptake. • The optimal CP molar ratio is 0.01 based on hydrate phase equilibrium and gas uptake. - Abstract: Cyclopentane (CP) is considered to be a potential co-guest molecule in carbon dioxide (CO 2 ) hydrate-based desalination. The experimental thermodynamic data of CO 2 -CP hydrates were measured for a salt solution, where CP was chosen as a hydrate promoter. Seven experimental cases (62 cycles) were studied with different molar ratios of CP/water (0, 0.0025, 0.005, 0.0075, 0.01, 0.02, and 0.03). Hydrate phase equilibrium data were generated using an isochoric method, and the hydrate saturations were calculated based on gas uptake. The results indicated that the increase in CP concentration significantly decreased the CO 2 hydrate equilibrium pressure to a certain limit; the hydrate saturation also decreased during this process. Also, it was determined that CP encouraged the formation of s-II double CO 2 -CP hydrates, which are different from s-I simple CO 2 hydrate. The CO 2 -CP guest provides a strengthened stability and moderate hydrate phase equilibrium conditions for hydrate-based desalination. The recommended optimal molar ratio of CP is 0.01 when the increase in equilibrium was more than 10 K, and the decrease in hydrate saturation was less than 2%.

  14. 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.)

  15. 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 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...... volumes and the needs for high pressure. The process could be interesting for concentration of heat sensitive, high value products...

  16. Far-Infrared Spectroscopy of Weakly Bound Hydrated Cluster Molecules

    DEFF Research Database (Denmark)

    Andersen, Jonas

    The thermodynamic properties of condensed phases, the functionality of many materials and the molecular organization in biological organisms are all governed by the classes of non-covalent interactions that occur already on the microscopic scale between pairs of molecules. A detailed investigation...... of the intermolecular interactions between prototypical molecular assemblies are valuable for accurate descriptions of larger supramolecular systems such as materials, gas hydrates and biological macromolecules. The aim of this PhD dissertation is to investigate intermolecular interactions fora series of medium...... vibrational bands of the cluster molecules in the challenging far-infrared and terahertz spectral regions.A key parameter in the validation of the performance of theoretical predictions for weak non-covalent intermolecular interactions is the dissociation energy D0 that depends heavily on the class of large...

  17. Desalination of Produced Water via Gas Hydrate Formation and Post Treatment

    OpenAIRE

    Niu, Jing

    2012-01-01

    This study presents a two-step desalination process, in which produced water is cleaned by forming gas hydrate in it and subsequently dewatering the hydrate to remove the residual produced water trapped in between the hydrate crystals. All experiments were performed with pressure in the range of 450 to 800psi and temperature in the range of -1 to 1°C using CO? as guest molecule for the hydrate crystals. The experiments were conducted using artificial produced waters containing different amoun...

  18. Probing the hydration water diffusion of macromolecular surfaces and interfaces

    International Nuclear Information System (INIS)

    Ortony, Julia H; Cheng, Chi-Yuan; Franck, John M; Pavlova, Anna; Hunt, Jasmine; Han, Songi; Kausik, Ravinath

    2011-01-01

    We probe the translational dynamics of the hydration water surrounding the macromolecular surfaces of selected polyelectrolytes, lipid vesicles and intrinsically disordered proteins with site specificity in aqueous solutions. These measurements are made possible by the recent development of a new instrumental and methodological approach based on Overhauser dynamic nuclear polarization (DNP)-enhanced nuclear magnetic resonance (NMR) spectroscopy. This technique selectively amplifies 1 H NMR signals of hydration water around a spin label that is attached to a molecular site of interest. The selective 1 H NMR amplification within molecular length scales of a spin label is achieved by utilizing short-distance range (∼r -3 ) magnetic dipolar interactions between the 1 H spin of water and the electron spin of a nitroxide radical-based label. Key features include the fact that only minute quantities (<10 μl) and dilute (≥100 μM) sample concentrations are needed. There is no size limit on the macromolecule or molecular assembly to be analyzed. Hydration water with translational correlation times between 10 and 800 ps is measured within ∼10 A distance of the spin label, encompassing the typical thickness of a hydration layer with three water molecules across. The hydration water moving within this time scale has significant implications, as this is what is modulated whenever macromolecules or molecular assemblies undergo interactions, binding or conformational changes. We demonstrate, with the examples of polymer complexation, protein aggregation and lipid-polymer interaction, that the measurements of interfacial hydration dynamics can sensitively and site specifically probe macromolecular interactions.

  19. Production of Hydrated Metal Ions by Fast Ion or Atom Beam Sputtering. Collision-Induced Dissociation and Successive Hydration Energies of Gaseous Cu+ with 1-4 Water Molecules

    NARCIS (Netherlands)

    Magnera, Thomas F.; David, Donald E.; Stulik, Dusan; Orth, Robert G.; Jonkman, Harry T.; Michl, Josef

    1989-01-01

    Low-temperature sputtering of frozen aqueous solutions of metal salts, of hydrated crystalline transition-metal salts, of frosted metal surfaces, and of frosted metal salts with kiloelectronvolt energy rare gas atoms or ions produces copious amounts of cluster ions, among which M+(H2O)n and/or

  20. A geometry-based simulation of the hydration of ions and small molecules

    International Nuclear Information System (INIS)

    Plumridge, T.H.

    2001-01-01

    The behaviour of solutes in water is of universal significance, but still not fully understood. This thesis provides details of a new computer simulation technique used to investigate the hydration of ions and small molecules. In contrast to conventional techniques such as molecular dynamics, this is a purely geometric method involving no forcefield or energy terms. Molecules of interest are modelled using crystallographic data to ensure that the structures are accurate. Water molecules are added randomly at any hydrogen bonding site in chains. At each addition the chain is rotated through all available space testing for the possibility of ring formation. The constraints used by the program to decide whether a ring should be conserved, i.e. whether the ring-forming hydrogen bond is viable were derived from a survey of (i) all available ice and clathrate hydrate structures and (ii) the hydrates of small biological molecules from the Cambridge Crystallographic Data Centre. If a ring forms, it is conserved and the process restarted with the addition of another random water. If the chain reaches a certain length and no hydrogen bonding opportunities are detected, the water chain is dissolved, and the process restarted. Using these techniques structure makers such as sulfate will readily allow structured water to form around them leading to large networks, whereas structure breakers such as urea will not allow any water chains to bridge the hydrogen bonding groups. The software has been tested with a set of twenty widely varying solutes and has produced results which generally agree with experimental data for structure makers and breakers, and also agrees well with traditional techniques such as molecular dynamics and Monte Carlo techniques. (author)

  1. Nonlinear fluid dynamics of nanoscale hydration water layer

    Science.gov (United States)

    Jhe, Wonho; Kim, Bongsu; Kim, Qhwan; An, Sangmin

    In nature, the hydration water layer (HWL) ubiquitously exists in ambient conditions or aqueous solutions, where water molecules are tightly bound to ions or hydrophilic surfaces. It plays an important role in various mechanisms such as biological processes, abiotic materials, colloidal interaction, and friction. The HWL, for example, can be easily formed between biomaterials since most biomaterials are covered by hydrophilic molecules such as lipid bilayers, and this HWL is expected to be significant to biological and physiological functions. Here (1) we present the general stress tensor of the hydration water layer. The hydration stress tensor provided the platform form for holistic understanding of the dynamic behaviors of the confined HWL including tapping and shear dynamics which are until now individually studied. And, (2) through fast shear velocity ( 1mm/s) experiments, the elastic turbulence caused by elastic property of the HWL is indirectly observed. Our results may contribute to a deeper study of systems where the HWL plays an important role such as biomolecules, colloidal particles, and the MEMS. This work was supported by the National Research Foundation of Korea(NRF) Grant funded by the Korea government(MSIP) (2016R1A3B1908660).

  2. 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…

  3. Thermodynamic Stability of Structure H Hydrates Based on the Molecular Properties of Large Guest Molecules

    OpenAIRE

    Tezuka, Kyoichi; Taguchi, Tatsuhiko; Alavi, Saman; Sum, Amadeu K.; Ohmura, Ryo

    2012-01-01

    This paper report analyses of thermodynamic stability of structure-H clathrate hydrates formed with methane and large guest molecules in terms of their gas phase molecular sizes and molar masses for the selection of a large guest molecule providing better hydrate stability. We investigated the correlation among the gas phase molecular sizes, the molar masses of large molecule guest substances, and the equilibrium pressures. The results suggest that there exists a molecular-size value for the ...

  4. Methane hydrate dissociation using inverted five-spot water flooding method in cubic hydrate simulator

    International Nuclear Information System (INIS)

    Li, Gang; Li, Xiao-Sen; Li, Bo; Wang, Yi

    2014-01-01

    The combination forms of the hydrate dissociation methods in different well systems are divided into 6 main patterns. Dissociation processes of methane hydrate in porous media using the inverted five-spot water flooding method (Pattern 4) are investigated by the experimental observation and numerical simulation. In situ methane hydrate is synthesized in the Cubic Hydrate Simulator (CHS), a 5.832-L cubic reactor. A center vertical well is used as the hot water injection well, while the four vertical wells at the corner are the gas and water production wells. The gas production begins simultaneously with the hot water injection, while after approximately 20 min of compression, the water begins to be produced. One of the common characteristics of the inverted five-spot water flooding method is that both the gas and water production rates decrease with the reduction of the hydrate dissociation rate. The evaluation of the energy efficiency ratio might indicate the inverted five-spot water flooding as a promising gas producing method from the hydrate reservoir. - Highlights: • A three-dimensional 5.8-L cubic pressure vessel is developed. • Gas production of hydrate using inverted five-spot flooding method is studied. • Water/gas production rate and energy efficiency ratio are evaluated. • Temperature distributions of numerical simulation and experiment agree well. • Hydrate dissociation process is a moving boundary problem in this study

  5. Measurements of gas permeability and non-Darcy flow in gas-water-hydrate systems

    Energy Technology Data Exchange (ETDEWEB)

    Ersland, G.; Husebo, J.; Graue, A.; Kvamme, B. [Bergen Univ., Bergen (Norway). Dept. of Physics and Technology; Baldwin, B. [Green Country Petrophysics LLC, Dewey, OK (United States); Stevens, J.; Howard, J. [ConocoPhillips, OK (United States)

    2008-07-01

    Storage of carbon dioxide (CO{sub 2}) in natural gas hydrate reservoirs may offer stable long-term storage of a greenhouse gas while benefiting from methane production, without requiring heat. By exposing hydrate to a thermodynamically preferred hydrate former, CO{sub 2}, the hydrate may be maintained macroscopically in the solid state and retain the stability of the formation. However, there is concern over the flow capacity in such reservoirs. This depends on several factors, notably thermodynamic destabilization of hydrate in small pores due to capillary effects; the presence of liquid channels separating the hydrate from the mineral surfaces; and, the connectivity of gas or liquid filled pores and channels. This paper described a technique for measuring gas permeability in gas-water-hydrate systems. It reported on several experiments that measured gas permeability during stages of hydrate growth in sandstone core plugs. Interactions between minerals and surrounding molecules were also discussed. The formation of methane hydrate in porous media was monitored and quantified with magnetic resonance imaging (MRI). MRI images of hydrate growth within the porous rock were provided along with measurements of gas permeability and non-Darcy flow effects at various hydrate saturations. Gas permeability was measured at steady state flow of methane through the hydrate-bearing core sample. Significant gas permeability was recorded for porous sandstone even when hydrates occupied up to 60 per cent of the pore space. It was concluded that MRI imaging can be used effectively to map and quantify hydrate saturation in sandstone core plugs. 27 refs., 2 tabs., 10 figs.

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

    Energy Technology Data Exchange (ETDEWEB)

    Sinha, Sudipta Kumar; Chakraborty, Kausik; Bandyopadhyay, Sanjoy, E-mail: sanjoy@chem.iitkgp.ernet.in [Molecular Modeling Laboratory, Department of Chemistry, Indian Institute of Technology, Kharagpur - 721302 (India); Jana, Madhurima [Molecular Simulation Laboratory, Department of Chemistry, National Institute of Technology, Rourkela - 769008 (India)

    2014-12-14

    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.

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

    International Nuclear Information System (INIS)

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

    2014-01-01

    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

  8. The effect of the condensed-phase environment on the vibrational frequency shift of a hydrogen molecule inside clathrate hydrates.

    Science.gov (United States)

    Powers, Anna; Scribano, Yohann; Lauvergnat, David; Mebe, Elsy; Benoit, David M; Bačić, Zlatko

    2018-04-14

    We report a theoretical study of the frequency shift (redshift) of the stretching fundamental transition of an H 2 molecule confined inside the small dodecahedral cage of the structure II clathrate hydrate and its dependence on the condensed-phase environment. In order to determine how much the hydrate water molecules beyond the confining small cage contribute to the vibrational frequency shift, quantum five-dimensional (5D) calculations of the coupled translation-rotation eigenstates are performed for H 2 in the v=0 and v=1 vibrational states inside spherical clathrate hydrate domains of increasing radius and a growing number of water molecules, ranging from 20 for the isolated small cage to over 1900. In these calculations, both H 2 and the water domains are treated as rigid. The 5D intermolecular potential energy surface (PES) of H 2 inside a hydrate domain is assumed to be pairwise additive. The H 2 -H 2 O pair interaction, represented by the 5D (rigid monomer) PES that depends on the vibrational state of H 2 , v=0 or v=1, is derived from the high-quality ab initio full-dimensional (9D) PES of the H 2 -H 2 O complex [P. Valiron et al., J. Chem. Phys. 129, 134306 (2008)]. The H 2 vibrational frequency shift calculated for the largest clathrate domain considered, which mimics the condensed-phase environment, is about 10% larger in magnitude than that obtained by taking into account only the small cage. The calculated splittings of the translational fundamental of H 2 change very little with the domain size, unlike the H 2 j = 1 rotational splittings that decrease significantly as the domain size increases. The changes in both the vibrational frequency shift and the j = 1 rotational splitting due to the condensed-phase effects arise predominantly from the H 2 O molecules in the first three complete hydration shells around H 2 .

  9. The effect of the condensed-phase environment on the vibrational frequency shift of a hydrogen molecule inside clathrate hydrates

    Science.gov (United States)

    Powers, Anna; Scribano, Yohann; Lauvergnat, David; Mebe, Elsy; Benoit, David M.; Bačić, Zlatko

    2018-04-01

    We report a theoretical study of the frequency shift (redshift) of the stretching fundamental transition of an H2 molecule confined inside the small dodecahedral cage of the structure II clathrate hydrate and its dependence on the condensed-phase environment. In order to determine how much the hydrate water molecules beyond the confining small cage contribute to the vibrational frequency shift, quantum five-dimensional (5D) calculations of the coupled translation-rotation eigenstates are performed for H2 in the v =0 and v =1 vibrational states inside spherical clathrate hydrate domains of increasing radius and a growing number of water molecules, ranging from 20 for the isolated small cage to over 1900. In these calculations, both H2 and the water domains are treated as rigid. The 5D intermolecular potential energy surface (PES) of H2 inside a hydrate domain is assumed to be pairwise additive. The H2-H2O pair interaction, represented by the 5D (rigid monomer) PES that depends on the vibrational state of H2, v =0 or v =1 , is derived from the high-quality ab initio full-dimensional (9D) PES of the H2-H2O complex [P. Valiron et al., J. Chem. Phys. 129, 134306 (2008)]. The H2 vibrational frequency shift calculated for the largest clathrate domain considered, which mimics the condensed-phase environment, is about 10% larger in magnitude than that obtained by taking into account only the small cage. The calculated splittings of the translational fundamental of H2 change very little with the domain size, unlike the H2 j = 1 rotational splittings that decrease significantly as the domain size increases. The changes in both the vibrational frequency shift and the j = 1 rotational splitting due to the condensed-phase effects arise predominantly from the H2O molecules in the first three complete hydration shells around H2.

  10. Experimental flowloop study on methane hydrate formation and agglomeration in high water cut emulsion systems

    OpenAIRE

    Pham , Trung-Kien; Cameirao , Ana ,; Herri , Jean-Michel

    2016-01-01

    Thème de cette communication: International Conference on Integrated Petroleum Engineering (IPE); International audience; hydrate risk also increases. Especially in the offshore systems, operating at low temperature and high pressure, conditions are favourable to the formation of gas hydrate, from the combination of liquid water and gas molecules, under the form of a solid phase. It is a serious issue in the flow assurance; it may cause many troubles, up to plugging.This work brings new under...

  11. Water Dynamics in Protein Hydration Shells: The Molecular Origins of the Dynamical Perturbation

    Science.gov (United States)

    2014-01-01

    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. PMID:24479585

  12. α-chymotrypsin in water-acetone and water-dimethyl sulfoxide mixtures: Effect of preferential solvation and hydration.

    Science.gov (United States)

    Sirotkin, Vladimir A; Kuchierskaya, Alexandra A

    2017-10-01

    We investigated water/organic solvent sorption and residual enzyme activity to simultaneously monitor preferential solvation/hydration of protein macromolecules in the entire range of water content at 25°C. We applied this approach to estimate protein destabilization/stabilization due to the preferential interactions of bovine pancreatic α-chymotrypsin with water-acetone (moderate-strength H-bond acceptor) and water-DMSO (strong H-bond acceptor) mixtures. There are three concentration regimes for the dried α-chymotrypsin. α-Chymotrypsin is preferentially hydrated at high water content. The residual enzyme activity values are close to 100%. At intermediate water content, the dehydrated α-chymotrypsin has a higher affinity for acetone/DMSO than for water. Residual enzyme activity is minimal in this concentration range. The acetone/DMSO molecules are preferentially excluded from the protein surface at the lowest water content, resulting in preferential hydration. The residual catalytic activity in the water-poor acetone is ∼80%, compared with that observed after incubation in pure water. This effect is very small for the water-poor DMSO. Two different schemes are operative for the hydrated enzyme. At high and intermediate water content, α-chymotrypsin exhibits preferential hydration. However, at intermediate water content, in contrast to the dried enzyme, the initially hydrated α-chymotrypsin possesses increased preferential hydration parameters. At low water content, no residual enzyme activity was observed. Preferential binding of DMSO/acetone to α-chymotrypsin was detected. Our data clearly demonstrate that the hydrogen bond accepting ability of organic solvents and the protein hydration level constitute key factors in determining the stability of protein-water-organic solvent systems. © 2017 Wiley Periodicals, Inc.

  13. Hydration dynamics in water clusters via quantum molecular dynamics simulations

    Energy Technology Data Exchange (ETDEWEB)

    Turi, László, E-mail: turi@chem.elte.hu [Department of Physical Chemistry, Eötvös Loránd University, Budapest 112, P. O. Box 32, H-1518 (Hungary)

    2014-05-28

    We have investigated the hydration dynamics in size selected water clusters with n = 66, 104, 200, 500, and 1000 water molecules using molecular dynamics simulations. To study the most fundamental aspects of relaxation phenomena in clusters, we choose one of the simplest, still realistic, quantum mechanically treated test solute, an excess electron. The project focuses on the time evolution of the clusters following two processes, electron attachment to neutral equilibrated water clusters and electron detachment from an equilibrated water cluster anion. The relaxation dynamics is significantly different in the two processes, most notably restoring the equilibrium final state is less effective after electron attachment. Nevertheless, in both scenarios only minor cluster size dependence is observed. Significantly different relaxation patterns characterize electron detachment for interior and surface state clusters, interior state clusters relaxing significantly faster. This observation may indicate a potential way to distinguish surface state and interior state water cluster anion isomers experimentally. A comparison of equilibrium and non-equilibrium trajectories suggests that linear response theory breaks down for electron attachment at 200 K, but the results converge to reasonable agreement at higher temperatures. Relaxation following electron detachment clearly belongs to the linear regime. Cluster relaxation was also investigated using two different computational models, one preferring cavity type interior states for the excess electron in bulk water, while the other simulating non-cavity structure. While the cavity model predicts appearance of several different hydrated electron isomers in agreement with experiment, the non-cavity model locates only cluster anions with interior excess electron distribution. The present simulations show that surface isomers computed with the cavity predicting potential show similar dynamical behavior to the interior clusters of

  14. Hydration and nutrition knowledge in adolescent swimmers. Does water intake affect urine hydration markers after swimming?

    Directory of Open Access Journals (Sweden)

    Cesare Altavilla

    2017-12-01

    Full Text Available Little data exists regarding nutritional knowledge and hydration in adolescent swimmers. The aim of this study was to assess the level of nutrition and hydration knowledge and to describe the fluid balance in adolescent swimmers during training. A study was carried out with a cross-sectional descriptive part and a longitudinal part with repeated measurements over five swimming sessions. Eighty-six adolescent swimmers completed a questionnaire to assess their sport nutrition and hydration knowledge. Fluid balance and urine hydration markers were studied during training. Swimmers showed a limited nutrition knowledge (33.26 % ± SD 12.59 and meagre hydration knowledge (28.61 % ± SD 28.59. Females showed lower scores than male swimmers in nutrition and hydration knowledge. Based on urine specific gravity, swimmers started the training close to the euhydrated threshold (1.019 g/mL ± SD 0.008. Although urine specific gravity and urine colour were reduced after the training, there were minimal changes in body mass (-0.12 Kg ± SD 0.31. Sweat loss (2.67 g/min ± SD 3.23 and the net changes in the fluid balance (-0.22 % ± SD 0.59 were low. The poor knowledge in nutrition and hydration encountered in the swimmers can justify the development of a strategy to incorporate nutritional education programmes for this group. Body water deficit from swimming activity seems to be easily replaced with the water intake to maintain hydration. After the training, the urine of swimmers was diluted regardless of their water intake. Dilution of urine did not reflect real hydration state in swimming.

  15. The anomalous halogen bonding interactions between chlorine and bromine with water in clathrate hydrates.

    Science.gov (United States)

    Dureckova, Hana; Woo, Tom K; Udachin, Konstantin A; Ripmeester, John A; Alavi, Saman

    2017-10-13

    Clathrate hydrate phases of Cl 2 and Br 2 guest molecules have been known for about 200 years. The crystal structure of these phases was recently re-determined with high accuracy by single crystal X-ray diffraction. In these structures, the water oxygen-halogen atom distances are determined to be shorter than the sum of the van der Waals radii, which indicates the action of some type of non-covalent interaction between the dihalogens and water molecules. Given that in the hydrate phases both lone pairs of each water oxygen atom are engaged in hydrogen bonding with other water molecules of the lattice, the nature of the oxygen-halogen interactions may not be the standard halogen bonds characterized recently in the solid state materials and enzyme-substrate compounds. The nature of the halogen-water interactions for the Cl 2 and Br 2 molecules in two isolated clathrate hydrate cages has recently been studied with ab initio calculations and Natural Bond Order analysis (Ochoa-Resendiz et al. J. Chem. Phys. 2016, 145, 161104). Here we present the results of ab initio calculations and natural localized molecular orbital analysis for Cl 2 and Br 2 guests in all cage types observed in the cubic structure I and tetragonal structure I clathrate hydrates to characterize the orbital interactions between the dihalogen guests and water. Calculations with isolated cages and cages with one shell of coordinating molecules are considered. The computational analysis is used to understand the nature of the halogen bonding in these materials and to interpret the guest positions in the hydrate cages obtained from the X-ray crystal structures.

  16. Gas hydrate inhibition by perturbation of liquid water structure

    Science.gov (United States)

    Sa, Jeong-Hoon; Kwak, Gye-Hoon; Han, Kunwoo; Ahn, Docheon; Lee, Kun-Hong

    2015-06-01

    Natural gas hydrates are icy crystalline materials that contain hydrocarbons, which are the primary energy source for this civilization. The abundance of naturally occurring gas hydrates leads to a growing interest in exploitation. Despite their potential as energy resources and in industrial applications, there is insufficient understanding of hydrate kinetics, which hinders the utilization of these invaluable resources. Perturbation of liquid water structure by solutes has been proposed to be a key process in hydrate inhibition, but this hypothesis remains unproven. Here, we report the direct observation of the perturbation of the liquid water structure induced by amino acids using polarized Raman spectroscopy, and its influence on gas hydrate nucleation and growth kinetics. Amino acids with hydrophilic and/or electrically charged side chains disrupted the water structure and thus provided effective hydrate inhibition. The strong correlation between the extent of perturbation by amino acids and their inhibition performance constitutes convincing evidence for the perturbation inhibition mechanism. The present findings bring the practical applications of gas hydrates significantly closer, and provide a new perspective on the freezing and melting phenomena of naturally occurring gas hydrates.

  17. Small molecule hydration energy and entropy from 3D-RISM

    Science.gov (United States)

    Johnson, J.; Case, D. A.; Yamazaki, T.; Gusarov, S.; Kovalenko, A.; Luchko, T.

    2016-09-01

    Implicit solvent models offer an attractive way to estimate the effects of a solvent environment on the properties of small or large solutes without the complications of explicit simulations. One common test of accuracy is to compute the free energy of transfer from gas to liquid for a variety of small molecules, since many of these values have been measured. Studies of the temperature dependence of these values (i.e. solvation enthalpies and entropies) can provide additional insights into the performance of implicit solvent models. Here, we show how to compute temperature derivatives of hydration free energies for the 3D-RISM integral equation approach. We have computed hydration free energies of 1123 small drug-like molecules (both neutral and charged). Temperature derivatives were also used to calculate hydration energies and entropies of 74 of these molecules (both neutral and charged) for which experimental data is available. While direct results have rather poor agreement with experiment, we have found that several previously proposed linear hydration free energy correction schemes give good agreement with experiment. These corrections also provide good agreement for hydration energies and entropies though simple extensions are required in some cases.

  18. Small molecule hydration energy and entropy from 3D-RISM

    International Nuclear Information System (INIS)

    Johnson, J; Case, D A; Yamazaki, T; Gusarov, S; Kovalenko, A; Luchko, T

    2016-01-01

    Implicit solvent models offer an attractive way to estimate the effects of a solvent environment on the properties of small or large solutes without the complications of explicit simulations. One common test of accuracy is to compute the free energy of transfer from gas to liquid for a variety of small molecules, since many of these values have been measured. Studies of the temperature dependence of these values (i.e. solvation enthalpies and entropies) can provide additional insights into the performance of implicit solvent models. Here, we show how to compute temperature derivatives of hydration free energies for the 3D-RISM integral equation approach. We have computed hydration free energies of 1123 small drug-like molecules (both neutral and charged). Temperature derivatives were also used to calculate hydration energies and entropies of 74 of these molecules (both neutral and charged) for which experimental data is available. While direct results have rather poor agreement with experiment, we have found that several previously proposed linear hydration free energy correction schemes give good agreement with experiment. These corrections also provide good agreement for hydration energies and entropies though simple extensions are required in some cases. (paper)

  19. Active-Site Hydration and Water Diffusion in Cytochrome P450cam: A Highly Dynamic Process

    Energy Technology Data Exchange (ETDEWEB)

    Miao, Yinglong [ORNL; Baudry, Jerome Y [ORNL

    2011-01-01

    Long-timescale molecular dynamics simulations (300 ns) are performed on both the apo- (i.e., camphor-free) and camphor-bound cytochrome P450cam (CYP101). Water diffusion into and out of the protein active site is observed without biased sampling methods. During the course of the molecular dynamics simulation, an average of 6.4 water molecules is observed in the camphor-binding site of the apo form, compared to zero water molecules in the binding site of the substrate-bound form, in agreement with the number of water molecules observed in crystal structures of the same species. However, as many as 12 water molecules can be present at a given time in the camphor-binding region of the active site in the case of apo-P450cam, revealing a highly dynamic process for hydration of the protein active site, with water molecules exchanging rapidly with the bulk solvent. Water molecules are also found to exchange locations frequently inside the active site, preferentially clustering in regions surrounding the water molecules observed in the crystal structure. Potential-of-mean-force calculations identify thermodynamically favored trans-protein pathways for the diffusion of water molecules between the protein active site and the bulk solvent. Binding of camphor in the active site modifies the free-energy landscape of P450cam channels toward favoring the diffusion of water molecules out of the protein active site.

  20. 1H NMR relaxometry as an indicator of setting and water depletion during cement hydration

    International Nuclear Information System (INIS)

    Wang, Biyun; Faure, Paméla; Thiéry, Mickaël; Baroghel-Bouny, Véronique

    2013-01-01

    Proton nuclear magnetic resonance relaxometry has been used to detect setting and microstructure evolution during cement hydration. NMR measurements were performed since casting, during setting and until hardening (from 0 to 3 days). The mobility of water molecules was assessed by an analysis focused on the diagram of longitudinal relaxation time T 1 generated by an Inversion Recovery sequence. The initial stiffening of the solid network was identified by an analysis of the relaxation rate 1/T 1 . The kinetics of water depletion was investigated by using a simple one-pulse acquisition sequence. In parallel, conventional techniques (Vicat needle and temperature monitoring), as well as numerical simulations of hydration, were used to complement and validate these NMR results. Cement pastes and mortars with different water-to-cement ratios made of grey or white OPCs were tested. Furthermore, the effects of the addition of sand, super-plasticizer and silica fume on the hydration kinetics were investigated

  1. Transport of hydrate slurry at high water cut

    OpenAIRE

    Melchuna , Aline; Cameirão , Ana; Herri , Jean-Michel; Ouabbas , Yamina; Glenat , Philippe

    2014-01-01

    Poster; International audience; Oil transportation in pipelines at the end of field production life implies to flow high quantities of water which represents the dominant phase. The process of crystallization of gas hydrates in this system needs to be studied and compared to the opposite one widely studied in the literature where water is the dispersed phase. The laboratory is equipped with the Archimede flow loop where the hydrate crystallization and transport are monitored. The flow loop is...

  2. Adsorption of water and carbon dioxide on hematite and consequences for possible hydrate formation.

    Science.gov (United States)

    Kvamme, Bjørn; Kuznetsova, Tatiana; Kivelae, Pilvi-Helina

    2012-04-07

    The interest in carbon dioxide for enhanced oil recovery is increasing proportional to the decline in naturally driven oil production and also due to the increasing demand for reduced emission of carbon dioxide into the atmosphere. Transport of carbon dioxide in offshore pipelines involves high pressure and low temperatures, conditions which may lead to formation of hydrates from residual water dissolved in carbon dioxide and carbon dioxide. The critical question is whether the water at certain temperatures and pressures will drop out as liquid droplets first, and then form hydrates, or alternatively, adsorb on the pipeline surfaces, and subsequently form hydrates heterogeneously. In this work, we used several different basis sets of density functional theory in ab initio calculations to estimate the charge distribution of hematite (the dominating component of rust) crystals. These rust particles were embedded in water and chemical potential for adsorbed water molecules was estimated through thermodynamic integration and compared to similar estimates for water clusters of the same size. While the generated charges were not unique, the use of high order approximations and different basis sets provides a range of likely charge distributions. Values obtained for the chemical potential of water in different surroundings indicated that it would be thermodynamically favorable for water to adsorb on hematite, and that evaluation of potential carbon dioxide hydrate formation conditions and kinetics should be based on this formation mechanism. Depending on the basis set and approximations, the estimated gain for water to adsorb on the hematite surface rather than condense as droplets varied between -1.7 kJ mole(-1) and -3.4 kJ mole(-1). The partial charge distribution on the hematite surface is incompatible with the hydrate structure, and thus hydrates will be unable to attach to the surface. The behavior of water outside the immediate vicinity of hematite (beyond 3

  3. 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.

  4. 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.

  5. Dynamic lifetimes of cagelike water clusters immersed in liquid water and their implications for hydrate nucleation studies

    Energy Technology Data Exchange (ETDEWEB)

    Guo, G.J.; Zhang, Y.G.; Li, M.; Wu, C.H. [Chinese Academy of Sciences, Inst. of Geology and Geophysics, Beijing (China). Key Laboratory of the Study of Earth' s Deep Interior

    2008-07-01

    In hydrate research fields, the hydrate nucleation mechanism still remains as an unsolved question. The static lifetimes of cagelike water clusters (CLWC) immersed in bulk liquid water have recently been measured by performing molecular dynamics simulations in the methane-water system, during which the member-water molecules of CLWCs are not allowed to exchange with their surrounding water molecules. This paper presented a study that measured the dynamic lifetimes of CLWCs permitting such water exchanges. The study involved re-analysis of previous simulation data that were used to study the effect of methane adsorption on the static lifetimes of a dodecahedral water cluster (DWC). The dynamic lifetimes of the DWC were calculated. The results of lifetime measurements of DWC in different systems were provided. The implications of this study for hydrate nucleation were also discussed. It was found that the dynamic lifetimes of CLWCs were not less than the static lifetimes previously obtained, and their ratio increased with the lifetime values. The results strengthened that CLWCs are metastable structures in liquid water and the occurrence probability of long-lived CLWCs will increase if one uses the dynamic lifetimes instead of the static lifetimes. 13 refs., 1 tab., 3 figs.

  6. Structure and dynamics of interfacial water. Role of hydratation water in the globular proteins dynamics

    International Nuclear Information System (INIS)

    Zanotti, J.M.

    1997-01-01

    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

  7. Prediction of Water Binding to Protein Hydration Sites with a Discrete, Semiexplicit Solvent Model.

    Science.gov (United States)

    Setny, Piotr

    2015-12-08

    Buried water molecules are ubiquitous in protein structures and are found at the interface of most protein-ligand complexes. Determining their distribution and thermodynamic effect is a challenging yet important task, of great of practical value for the modeling of biomolecular structures and their interactions. In this study, we present a novel method aimed at the prediction of buried water molecules in protein structures and estimation of their binding free energies. It is based on a semiexplicit, discrete solvation model, which we previously introduced in the context of small molecule hydration. The method is applicable to all macromolecular structures described by a standard all-atom force field, and predicts complete solvent distribution within a single run with modest computational cost. We demonstrate that it indicates positions of buried hydration sites, including those filled by more than one water molecule, and accurately differentiates them from sterically accessible to water but void regions. The obtained estimates of water binding free energies are in fair agreement with reference results determined with the double decoupling method.

  8. Hydration of a Large Anionic Charge Distribution - Naphthalene-Water Cluster Anions

    Science.gov (United States)

    Weber, J. Mathias; Adams, Christopher L.

    2010-06-01

    We report the infrared spectra of anionic clusters of naphthalene with up to three water molecules. Comparison of the experimental infrared spectra with theoretically predicted spectra from quantum chemistry calculations allow conclusions regarding the structures of the clusters under study. The first water molecule forms two hydrogen bonds with the π electron system of the naphthalene moiety. Subsequent water ligands interact with both the naphthalene and the other water ligands to form hydrogen bonded networks, similar to other hydrated anion clusters. Naphthalene-water anion clusters illustrate how water interacts with negative charge delocalized over a large π electron system. The clusters are interesting model systems that are discussed in the context of wetting of graphene surfaces and polyaromatic hydrocarbons.

  9. Differential scanning calorimetric study of the binding between native DNA and its primary water of hydration.

    Science.gov (United States)

    Marlowe, R. L.; Lukan, A. M.; Lee, S. A.; Anthony, L.; Rupprecht, A.

    1996-03-01

    Differential scanning calorimetry was used to measure the binding strength between calf-thymus DNA and its primary water of hydration. The specific heat of wet-spun films was found to have a broad endothermic transition near 80 ^oC and a sharp exothermic transition near 250 ^oC. The broad transition is believed to be mainly due to the breaking of the bonds of the strongly bound water of hydration. This transition was found to be reversible, as expected. Kissinger analysis indicates that the activation barrier for breaking the bonds of these water molecules is about 0.6 eV. The sharp transition appeared to be an indication of a thermal decomposition of the DNA. Samples taken above this transition lost mass, showed evidence of having melted, and had turned black in color. This transition is irreversible.

  10. Water Intake and Hydration Indices in Healthy European Adults: The European Hydration Research Study (EHRS).

    Science.gov (United States)

    Malisova, Olga; Athanasatou, Adelais; Pepa, Alex; Husemann, Marlien; Domnik, Kirsten; Braun, Hans; Mora-Rodriguez, Ricardo; Ortega, Juan F; Fernandez-Elias, Valentin E; Kapsokefalou, Maria

    2016-04-06

    Hydration status is linked with health, wellness, and performance. We evaluated hydration status, water intake, and urine output for seven consecutive days in healthy adults. Volunteers living in Spain, Germany, or Greece (n = 573, 39 ± 12 years (51.1% males), 25.0 ± 4.6 kg/m² BMI) participated in an eight-day study protocol. Total water intake was estimated from seven-day food and drink diaries. Hydration status was measured in urine samples collected over 24 h for seven days and in blood samples collected in fasting state on the mornings of days 1 and 8. Total daily water intake was 2.75 ± 1.01 L, water from beverages 2.10 ± 0.91 L, water from foods 0.66 ± 0.29 L. Urine parameters were: 24 h volume 1.65 ± 0.70 L, 24 h osmolality 631 ± 221 mOsmol/kg Η2Ο, 24 h specific gravity 1.017 ± 0.005, 24 h excretion of sodium 166.9 ± 54.7 mEq, 24 h excretion of potassium 72.4 ± 24.6 mEq, color chart 4.2 ± 1.4. Predictors for urine osmolality were age, country, gender, and BMI. Blood indices were: haemoglobin concentration 14.7 ± 1.7 g/dL, hematocrit 43% ± 4% and serum osmolality 294 ± 9 mOsmol/kg Η2Ο. Daily water intake was higher in summer (2.8 ± 1.02 L) than in winter (2.6 ± 0.98 L) (p = 0.019). Water intake was associated negatively with urine specific gravity, urine color, and urine sodium and potassium concentrations (p < 0.01). Applying urine osmolality cut-offs, approximately 60% of participants were euhydrated and 20% hyperhydrated or dehydrated. Most participants were euhydrated, but a substantial number of people (40%) deviated from a normal hydration level.

  11. Hydrate phase equilibrium and structure for (methane + ethane + tetrahydrofuran + water) system

    International Nuclear Information System (INIS)

    Sun Changyu; Chen Guangjin; Zhang Lingwei

    2010-01-01

    The separation of methane and ethane through forming hydrate is a possible choice in natural gas, oil processing, or ethylene producing. The hydrate formation conditions of five groups of (methane + ethane) binary gas mixtures in the presence of 0.06 mole fraction tetrahydrofuran (THF) in water were obtained at temperatures ranging from (277.7 to 288.2) K. In most cases, the presence of THF in water can lower the hydrate formation pressure of (methane + ethane) remarkably. However, when the composition of ethane is as high as 0.832, it is more difficult to form hydrate than without THF system. Phase equilibrium model for hydrates containing THF was developed based on a two-step hydrate formation mechanism. The structure of hydrates formed from (methane + ethane + THF + water) system was also determined by Raman spectroscopy. When THF concentration in initial aqueous solution was only 0.06 mole fraction, the coexistence of structure I hydrate dominated by ethane and structure II hydrate dominated by THF in the hydrate sample was clearly demonstrated by Raman spectroscopic data. On the contrary, only structure II hydrate existed in the hydrate sample formed from (methane + ethane + THF + water) system when THF concentration in initial aqueous solution was increased to 0.10 mole fraction. It indicated that higher THF concentration inhibited the formation of structure I hydrate dominated by ethane and therefore lowered the trapping of ethane in hydrate. It implies a very promising method to increase the separation efficiency of methane and ethane.

  12. The impact of kosmotropes and chaotropes on bulk and hydration shell water dynamics in a model peptide solution

    International Nuclear Information System (INIS)

    Russo, Daniela

    2008-01-01

    Kosmotropic (order-making) and chaotropic (order-breaking) co-solvents influence stability and biochemical equilibrium in aqueous solutions of proteins, acting indirectly through the structure and dynamics of the hydration water that surrounds the protein molecules. We have investigated the influence of kosmotropic and chaotropic co-solvents on the hydrogen bonding network dynamics of both bulk water and hydration water. To this end the evolution of bulk water and hydration water dynamics of a prototypical hydrophobic amino acid with polar backbone, N-acetyl-leucine-methylamide (NALMA), has been studied by quasielastic neutron scattering as a function of solvent composition. The results show that bulk water and hydration water dynamics, apart from a dynamical suppression that depends on the NALMA solute, exhibit the same dependence on addition of co-solvent for all of the co-solvents studied (urea, glycerol, MgSO 4 , and dimethyl sulfoxide). The hydrophobic solute and the high concentration water-structuring additive have the same effect on the water hydrogen bonding network. Water remains the preferential hydration of the hydrophobic side chain and backbone. We also find that the reorganization of the bulk water hydrogen bond network, upon addition of kosmotrope and chaotrope additives, is not dynamically perturbed, and that the hydrogen bond lifetime is maintained at 1 ps as in pure bulk water. On the other hand the addition of NALMA to the water/co-solvent binary system causes reorganization of the hydrogen bonds, resulting in an increased hydrogen bond lifetime. Furthermore, the solute's side chain dynamics is not affected by high concentrations of co-solvent. We shall discuss the hydration dynamics results in the context of protein folding and protein-solvent interactions

  13. Conserved water molecules in bacterial serine hydroxymethyltransferases.

    Science.gov (United States)

    Milano, Teresa; Di Salvo, Martino Luigi; Angelaccio, Sebastiana; Pascarella, Stefano

    2015-10-01

    Water molecules occurring in the interior of protein structures often are endowed with key structural and functional roles. We report the results of a systematic analysis of conserved water molecules in bacterial serine hydroxymethyltransferases (SHMTs). SHMTs are an important group of pyridoxal-5'-phosphate-dependent enzymes that catalyze the reversible conversion of l-serine and tetrahydropteroylglutamate to glycine and 5,10-methylenetetrahydropteroylglutamate. The approach utilized in this study relies on two programs, ProACT2 and WatCH. The first software is able to categorize water molecules in a protein crystallographic structure as buried, positioned in clefts or at the surface. The other program finds, in a set of superposed homologous proteins, water molecules that occur approximately in equivalent position in each of the considered structures. These groups of molecules are referred to as 'clusters' and represent structurally conserved water molecules. Several conserved clusters of buried or cleft water molecules were found in the set of 11 bacterial SHMTs we took into account for this work. The majority of these clusters were not described previously. Possible structural and functional roles for the conserved water molecules are envisaged. This work provides a map of the conserved water molecules helpful for deciphering SHMT mechanism and for rational design of molecular engineering experiments. © The Author 2015. Published by Oxford University Press. All rights reserved. For Permissions, please e-mail: journals.permissions@oup.com.

  14. Dietary water affects human skin hydration and biomechanics

    Directory of Open Access Journals (Sweden)

    Palma L

    2015-08-01

    Full Text Available Lídia Palma,1 Liliana Tavares Marques,1 Julia Bujan,2,3 Luís Monteiro Rodrigues1,4 1CBIOS – Research Center for Health Science and Technologies, Universidade Lusófona, Campo Grande, Lisboa, Portugal; 2Department of Medicine and Medical Specialities, Universidad de Alcalá de Henares, Madrid, Spain; 3CIBER-BBN, Madrid, España, Spain; 4Department of Pharmacological Sciences, School of Pharmacy, Universidade de Lisboa, Lisboa, Portugal Abstract: It is generally assumed that dietary water might be beneficial for the health, especially in dermatological (age preventing terms. The present study was designed to quantify the impact of dietary water on major indicators of skin physiology. A total of 49 healthy females (mean 24.5±4.3 years were selected and characterized in terms of their dietary daily habits, especially focused in water consumption, by a Food Frequency Questionnaire. This allowed two groups to be set – Group 1 consuming less than 3,200 mL/day (n=38, and Group 2 consuming more than 3,200 mL/day (n=11. Approximately 2 L of water were added to the daily diet of Group 2 individuals for 1 month to quantify the impact of this surplus in their skin physiology. Measurements involving epidermal superficial and deep hydration, transepidermal water loss, and several biomechanical descriptors were taken at day 0 (T0, 15 (T1, and 30 (T2 in several anatomical sites (face, upper limb, and leg. This stress test (2 L/day for 30 days significantly modified superficial and deep skin hydration, especially in Group 1. The same impact was registered with the most relevant biomechanical descriptors. Thus, in this study, it is clear that higher water inputs in regular diet might positively impact normal skin physiology, in particular in those individuals with lower daily water consumptions. Keywords: dietary water, water consume, skin hydration, TEWL, skin biomechanics

  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....... The factors affecting the performance of these polymers and the structure-property relationships are reviewed. A comprehensive review of the techniques used to evaluate the performance of the polymeric inhibitors is given. This review also addresses recent developments, current and future challenges...

  16. Purification of arsenic contaminated ground water using hydrated manganese dioxide

    International Nuclear Information System (INIS)

    Raje, N.; Swain, K.K.

    2002-01-01

    An analytical methodology has been developed for the separation of arsenic from ground water using inorganic material in neutral medium. The separation procedure involves the quantitative retention of arsenic on hydrated manganese dioxide, in neutral medium. The validity of the separation procedure has been checked by a standard addition method and radiotracer studies. Neutron activation analysis (NAA), a powerful measurement technique, has been used for the quantitative determination of arsenic. (author)

  17. Study of hydrogen-molecule guests in type II clathrate hydrates using a force-matched potential model parameterised from ab initio molecular dynamics

    Science.gov (United States)

    Burnham, Christian J.; Futera, Zdenek; English, Niall J.

    2018-03-01

    The force-matching method has been applied to parameterise an empirical potential model for water-water and water-hydrogen intermolecular interactions for use in clathrate-hydrate simulations containing hydrogen guest molecules. The underlying reference simulations constituted ab initio molecular dynamics (AIMD) of clathrate hydrates with various occupations of hydrogen-molecule guests. It is shown that the resultant model is able to reproduce AIMD-derived free-energy curves for the movement of a tagged hydrogen molecule between the water cages that make up the clathrate, thus giving us confidence in the model. Furthermore, with the aid of an umbrella-sampling algorithm, we calculate barrier heights for the force-matched model, yielding the free-energy barrier for a tagged molecule to move between cages. The barrier heights are reasonably large, being on the order of 30 kJ/mol, and are consistent with our previous studies with empirical models [C. J. Burnham and N. J. English, J. Phys. Chem. C 120, 16561 (2016) and C. J. Burnham et al., Phys. Chem. Chem. Phys. 19, 717 (2017)]. Our results are in opposition to the literature, which claims that this system may have very low barrier heights. We also compare results to that using the more ad hoc empirical model of Alavi et al. [J. Chem. Phys. 123, 024507 (2005)] and find that this model does very well when judged against the force-matched and ab initio simulation data.

  18. Dietary water affects human skin hydration and biomechanics.

    Science.gov (United States)

    Palma, Lídia; Marques, Liliana Tavares; Bujan, Julia; Rodrigues, Luís Monteiro

    2015-01-01

    It is generally assumed that dietary water might be beneficial for the health, especially in dermatological (age preventing) terms. The present study was designed to quantify the impact of dietary water on major indicators of skin physiology. A total of 49 healthy females (mean 24.5±4.3 years) were selected and characterized in terms of their dietary daily habits, especially focused in water consumption, by a Food Frequency Questionnaire. This allowed two groups to be set - Group 1 consuming less than 3,200 mL/day (n=38), and Group 2 consuming more than 3,200 mL/day (n=11). Approximately 2 L of water were added to the daily diet of Group 2 individuals for 1 month to quantify the impact of this surplus in their skin physiology. Measurements involving epidermal superficial and deep hydration, transepidermal water loss, and several biomechanical descriptors were taken at day 0 (T0), 15 (T1), and 30 (T2) in several anatomical sites (face, upper limb, and leg). This stress test (2 L/day for 30 days) significantly modified superficial and deep skin hydration, especially in Group 1. The same impact was registered with the most relevant biomechanical descriptors. Thus, in this study, it is clear that higher water inputs in regular diet might positively impact normal skin physiology, in particular in those individuals with lower daily water consumptions.

  19. On the intermolecular vibrational coupling, hydrogen bonding, and librational freedom of water in the hydration shell of mono- and bivalent anions.

    Science.gov (United States)

    Ahmed, Mohammed; Namboodiri, V; Singh, Ajay K; Mondal, Jahur A

    2014-10-28

    The hydration energy of an ion largely resides within the first few layers of water molecules in its hydration shell. Hence, it is important to understand the transformation of water properties, such as hydrogen-bonding, intermolecular vibrational coupling, and librational freedom in the hydration shell of ions. We investigated these properties in the hydration shell of mono- (Cl(-) and I(-)) and bivalent (SO4(2-) and CO3(2-)) anions by using Raman multivariate curve resolution (Raman-MCR) spectroscopy in the OH stretch, HOH bend, and [bend+librational] combination bands of water. Raman-MCR of aqueous Na-salt (NaCl, NaI, Na2SO4, and Na2CO3) solutions provides ion-correlated spectra (IC-spectrum) which predominantly bear the vibrational characteristics of water in the hydration shell of respective anions. Comparison of these IC-spectra with the Raman spectrum of bulk water in different spectral regions reveals that the water is vibrationally decoupled with its neighbors in the hydration shell. Hydrogen-bond strength and librational freedom also vary with the nature of anion: hydrogen-bond strength, for example, decreases as CO3(2-) > SO4(2-) > bulk water ≈ Cl(-) > I(-); and the librational freedom increases as CO3(2-) ≈ SO4(2-) water water in the hydration shell of anions.

  20. Neutron emission during lithium deuteride hydration in heavy water

    International Nuclear Information System (INIS)

    Arzhannikov, A.V.; Kezerashvili, G.Ya.; Muratov, V.V.; Sinitskij, S.L.

    1989-01-01

    An experiment on neutron detection during lithium deuteride hydration in heavy water using a system of SNM-17 or SNM-18 gas counters was set up. Signals were simultaneously detected by 6 counters and the data were stored in a computer. At the same time the temperature of the reaction ampule external surface was measured. It was found that the neutron number per 1 gram of lithium deuteride reacted with water in the ampule was equal to several dozens if their initial energy was about 2.5 MeV. 4 refs.; 2 figs

  1. Macroscopic investigation of water volume effects on interfacial dynamic behaviors between clathrate hydrate and water.

    Science.gov (United States)

    Cha, Minjun; Couzis, Alexander; Lee, Jae W

    2013-05-14

    This study investigated the effects of the water volume on the interfacial dynamics between cyclopentane (CP) hydrate and water droplet in a CP/n-decane oil mixture. The adhesion force between CP hydrate and various water droplets was determined using the z-directional microbalance. Through repetition of precise measurements over several cycles from contact to detachment, we observed abnormal wetting behaviors in the capillary bridge during the retraction process when the water drop volume is larger than 100 μL. With the increase in water droplet volumes, the contact force between CP hydrate and water also increases up to 300 μL. However, there is a dramatic reduction of increasing rate in the contact forces over 300 μL of water droplet. With the addition of the surfactants of sodium dodecyl sulfate (SDS) and dodecyltrimethylammonium bromide (DTAB) to the water droplet, the contact force between CP hydrate and solution droplet exhibits a lower value and a transition volume of the contact force comes with a smaller solution volume of 200 μL. The water volume effects on the liquid wetting of the probe and the size of capillary bridges provide important insight into hydrate growth and aggregation/agglomeration in the presence of free water phase inside gas/oil pipelines.

  2. Topological modeling of methane hydrate crystallization from low to high water cut emulsion systems

    OpenAIRE

    Melchuna , Aline; Cameirão , Ana; Herri , Jean-Michel; Glénat , Philippe

    2016-01-01

    International audience; Hydrate formation and remediation in oil flowlines facilities represent a major concern for oil industry in respect of capital and operational costs. It is necessary to have a better understanding on the hydrate formation process to be more efficient in hydrate prevention, especially in respect to additive dosage. This work is a contribution to enhance the knowledge of hydrate formation at high water cuts, by introducing new techniques of analysis in the Archimede flow...

  3. 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.

  4. 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.

  5. Visual observation of gas hydrates nucleation and growth at a water - organic liquid interface

    Science.gov (United States)

    Stoporev, Andrey S.; Semenov, Anton P.; Medvedev, Vladimir I.; Sizikov, Artem A.; Gushchin, Pavel A.; Vinokurov, Vladimir A.; Manakov, Andrey Yu.

    2018-03-01

    Visual observation of nucleation sites of methane and methane-ethane-propane hydrates and their further growth in water - organic liquid - gas systems with/without surfactants was carried out. Sapphire Rocking Cell RCS6 with transparent sapphire cells was used. The experiments were conducted at the supercooling ΔTsub = 20.2 °C. Decane, toluene and crude oils were used as organics. Gas hydrate nucleation occurred on water - metal - gas and water - sapphire - organic liquid three-phase contact lines. At the initial stage of growth hydrate crystals rapidly covered the water - gas or water - organics interfaces (depending on the nucleation site). Further hydrate phase accrete on cell walls (sapphire surface) and into the organics volume. At this stage, growth was accompanied by water «drawing out» from under initial hydrate film formed at water - organic interface. Apparently, it takes place due to water capillary inflow in the reaction zone. It was shown that the hydrate crystal morphology depends on the organic phase composition. In the case of water-in-decane emulsion relay hydrate crystallization was observed in the whole sample, originating most likely due to the hydrate crystal intergrowth through decane. Contacts of such crystals with adjacent water droplets result in rapid hydrate crystallization on this droplet.

  6. Water around fullerene shape amphiphiles: A molecular dynamics simulation study of hydrophobic hydration

    Energy Technology Data Exchange (ETDEWEB)

    Varanasi, S. R., E-mail: s.raovaranasi@uq.edu.au, E-mail: guskova@ipfdd.de; John, A. [Institut Theorie der Polymere, Leibniz-Institut für Polymerforschung Dresden e.V., Hohe Straße 6, Dresden D-01069 (Germany); Guskova, O. A., E-mail: s.raovaranasi@uq.edu.au, E-mail: guskova@ipfdd.de [Institut Theorie der Polymere, Leibniz-Institut für Polymerforschung Dresden e.V., Hohe Straße 6, Dresden D-01069 (Germany); Dresden Center for Computational Materials Science (DCMS), Technische Universität Dresden, Dresden D-01069 (Germany); Sommer, J.-U. [Institut Theorie der Polymere, Leibniz-Institut für Polymerforschung Dresden e.V., Hohe Straße 6, Dresden D-01069 (Germany); Dresden Center for Computational Materials Science (DCMS), Technische Universität Dresden, Dresden D-01069 (Germany); Institut für Theoretische Physik, Technische Universität Dresden, Zellescher Weg 17, Dresden D-01069 (Germany)

    2015-06-14

    Fullerene C{sub 60} sub-colloidal particle with diameter ∼1 nm represents a boundary case between small and large hydrophobic solutes on the length scale of hydrophobic hydration. In the present paper, a molecular dynamics simulation is performed to investigate this complex phenomenon for bare C{sub 60} fullerene and its amphiphilic/charged derivatives, so called shape amphiphiles. Since most of the unique properties of water originate from the pattern of hydrogen bond network and its dynamics, spatial, and orientational aspects of water in solvation shells around the solute surface having hydrophilic and hydrophobic regions are analyzed. Dynamical properties such as translational-rotational mobility, reorientational correlation and occupation time correlation functions of water molecules, and diffusion coefficients are also calculated. Slower dynamics of solvent molecules—water retardation—in the vicinity of the solutes is observed. Both the topological properties of hydrogen bond pattern and the “dangling” –OH groups that represent surface defects in water network are monitored. The fraction of such defect structures is increased near the hydrophobic cap of fullerenes. Some “dry” regions of C{sub 60} are observed which can be considered as signatures of surface dewetting. In an effort to provide molecular level insight into the thermodynamics of hydration, the free energy of solvation is determined for a family of fullerene particles using thermodynamic integration technique.

  7. Water around fullerene shape amphiphiles: A molecular dynamics simulation study of hydrophobic hydration

    International Nuclear Information System (INIS)

    Varanasi, S. R.; John, A.; Guskova, O. A.; Sommer, J.-U.

    2015-01-01

    Fullerene C 60 sub-colloidal particle with diameter ∼1 nm represents a boundary case between small and large hydrophobic solutes on the length scale of hydrophobic hydration. In the present paper, a molecular dynamics simulation is performed to investigate this complex phenomenon for bare C 60 fullerene and its amphiphilic/charged derivatives, so called shape amphiphiles. Since most of the unique properties of water originate from the pattern of hydrogen bond network and its dynamics, spatial, and orientational aspects of water in solvation shells around the solute surface having hydrophilic and hydrophobic regions are analyzed. Dynamical properties such as translational-rotational mobility, reorientational correlation and occupation time correlation functions of water molecules, and diffusion coefficients are also calculated. Slower dynamics of solvent molecules—water retardation—in the vicinity of the solutes is observed. Both the topological properties of hydrogen bond pattern and the “dangling” –OH groups that represent surface defects in water network are monitored. The fraction of such defect structures is increased near the hydrophobic cap of fullerenes. Some “dry” regions of C 60 are observed which can be considered as signatures of surface dewetting. In an effort to provide molecular level insight into the thermodynamics of hydration, the free energy of solvation is determined for a family of fullerene particles using thermodynamic integration technique

  8. Influence of surfactants on gas-hydrate formation' kinetics in water-oil emulsion

    Science.gov (United States)

    Zemenkov, Yu D.; Shirshova, A. V.; Arinstein, E. A.; Shuvaev, A. N.

    2018-05-01

    The kinetics of gas hydrate formation of propane in a water-oil emulsion is experimentally studied when three types of surfactants (SAA (surface acting agent)) - anionic type emulsifiers - are added to the aqueous phase. It is shown that all three types of surfactants decelerate the growth of the gas-hydrate in the emulsion and can be considered as anti-agglutinating and kinetic low-dose inhibitors. The most effective inhibitor of hydrate formation in water-oil emulsion of SV-102 surfactant was revealed. For comparison, experimental studies of gas-hydrate formation under the same conditions for bulk water have been carried out. It is shown that in bulk water, all the surfactants investigated act as promoters (accelerators) of hydrate formation. A qualitative explanation of the action mechanisms of emulsifiers in the process of gas-hydrate formation in water-oil emulsion is given.

  9. Numerical analysis of wellbore instability in gas hydrate formation during deep-water drilling

    Science.gov (United States)

    Zhang, Huaiwen; Cheng, Yuanfang; Li, Qingchao; Yan, Chuanliang; Han, Xiuting

    2018-02-01

    Gas hydrate formation may be encountered during deep-water drilling because of the large amount and wide distribution of gas hydrates under the shallow seabed of the South China Sea. Hydrates are extremely sensitive to temperature and pressure changes, and drilling through gas hydrate formation may cause dissociation of hydrates, accompanied by changes in wellbore temperatures, pore pressures, and stress states, thereby leading to wellbore plastic yield and wellbore instability. Considering the coupling effect of seepage of drilling fluid into gas hydrate formation, heat conduction between drilling fluid and formation, hydrate dissociation, and transformation of the formation framework, this study established a multi-field coupling mathematical model of the wellbore in the hydrate formation. Furthermore, the influences of drilling fluid temperatures, densities, and soaking time on the instability of hydrate formation were calculated and analyzed. Results show that the greater the temperature difference between the drilling fluid and hydrate formation is, the faster the hydrate dissociates, the wider the plastic dissociation range is, and the greater the failure width becomes. When the temperature difference is greater than 7°C, the maximum rate of plastic deformation around the wellbore is more than 10%, which is along the direction of the minimum horizontal in-situ stress and associated with instability and damage on the surrounding rock. The hydrate dissociation is insensitive to the variation of drilling fluid density, thereby implying that the change of the density of drilling fluids has a minimal effect on the hydrate dissociation. Drilling fluids that are absorbed into the hydrate formation result in fast dissociation at the initial stage. As time elapses, the hydrate dissociation slows down, but the risk of wellbore instability is aggravated due to the prolonged submersion in drilling fluids. For the sake of the stability of the wellbore in deep-water

  10. The cellular environment of cancerous human tissue. Interfacial and dangling water as a "hydration fingerprint".

    Science.gov (United States)

    Abramczyk, Halina; Brozek-Pluska, Beata; Krzesniak, Marta; Kopec, Monika; Morawiec-Sztandera, Alina

    2014-08-14

    Despite a large number of publications, the role of water in the cellular environment of biological tissue has not been clarified. Characterizing the biological interface is a key challenge in understanding the interactions of water in the tissue. Although we often assume that the properties of the bulk water can be translated to the crowded biological environment, this approach must be considerably revised when considering the biological interface. To our knowledge, few studies have directly monitored the interactions and accumulation of water in the restricted environments of the biological tissue upon realistic crowding conditions. The present study focuses on a molecular picture of water molecules at the biological interface, or specifically, water molecules adjacent to the hydrophobic and hydrophilic surfaces of normal and cancerous tissues. We recorded and analyzed the IR and Raman spectra of the νs(OH) stretching modes of water at the biological interfaces of the human breast and neck tissues. The results revealed dramatic changes in the water content in the tissue and are potentially relevant to both the fundamental problems of interfacial water modeling and the molecular diagnostics of cancer as a 'hydration fingerprint'. Herein, we will discuss the origin of the vibrational substructures observed for the νs(OH) stretching modes of water, showing that the interfacial water interacting via H-bond with other water molecules and biomolecules at the biological surface and free OH vibration of the dangling water are sensitive indicators of the pathology between the normal (noncancerous) and cancerous tissue and cancer types. Copyright © 2014 Elsevier B.V. All rights reserved.

  11. Hydration of DNA by tritiated water and isotope distribution: a study by 1H, 2H, and 3H NMR spectroscopy

    International Nuclear Information System (INIS)

    Mathur-De Vre, R.; Grimee-Declerck, R.; Lejeune, P.; Bertinchamps, A.J.

    1982-01-01

    The hydration layer of DNA (0.75%) in tritiated water represents 3.5% of solvent 3 HHO. The combined effects of temperature (-6 to -40 0 C) and H 2 O/ 2 H 2 O solvent composition on the spin-lattice relaxation times of water protons and deuterons suggest selective distribution of isotopes in the hydration layer. The ''hydration isotope'' effect and the localization of tritiated water molecules in the hydration layer of DNA have important implications in describing the radiobiological effects of tritiated water because the initial molecular damage caused by 3 HHO (internal radiation source) localizes close to 3 H due to the short range and low energy of 3 H β rays

  12. Collective dynamics of protein hydration water by brillouin neutron spectroscopy.

    Science.gov (United States)

    Orecchini, Andrea; Paciaroni, Alessandro; De Francesco, Alessio; Petrillo, Caterina; Sacchetti, Francesco

    2009-04-08

    By a detailed experimental study of THz dynamics in the ribonuclease protein, we could detect the propagation of coherent collective density fluctuations within the protein hydration shell. The emerging picture indicates the presence of both a dispersing mode, traveling with a speed greater than 3000 m/s, and a nondispersing one, characterized by an almost constant energy of 6-7 meV. In agreement with molecular dynamics simulations [Phys. Rev. Lett. 2002, 89, 275501], the features of the dispersion curves closely resemble those observed in pure liquid water [Phys. Rev. E: Stat. Phys., Plasmas, Fluids, Relat. Interdiscip. Top. 2004, 69, 061203]. On the contrary, the observed damping factors are much larger than in bulk water, with the dispersing mode becoming overdamped at Q = 0.6 A(-1) already. Such novel experimental findings are discussed as a dynamic signature of the disordering effect induced by the protein surface on the local structure of water.

  13. Effect of hydration of sugar groups on adsorption of Quillaja bark saponin at air/water and Si/water interfaces.

    Science.gov (United States)

    Wojciechowski, Kamil; Orczyk, Marta; Marcinkowski, Kuba; Kobiela, Tomasz; Trapp, Marcus; Gutberlet, Thomas; Geue, Thomas

    2014-05-01

    Adsorption of a natural glycoside surfactant Quillaja bark saponin ("QBS", Sigma Aldrich 84510) was studied at the air/water and Si/water interfaces using a combination of surface pressure (SP), surface dilatational rheology, neutron reflectivity (NR), Infra-Red Attenuated Total Reflection Spectroscopy (IR ATR) and Quartz Crystal Microbalance (QCM). The adsorbed layers formed at the air/water interface are predominantly elastic, with the dilatational surface storage modulus reaching the maximum value of E'=184 mN/m. The NR results point to a strong hydration of the adsorbed layers (about 65% hydration, corresponding to about 60 molecules of water per one QBS molecule), most likely related to the presence of multiple sugar groups constituting the glycone part of the QBS molecules. With a layer thickness of 19 Å, the adsorbed amount obtained from NR seems largely underestimated in comparison to the value obtained from the surface tension isotherm. While this high extent of hydration does not prevent formation of dense and highly elastic layers at the air-water surface, QBS adsorption at the Si/water interface is much weaker. The adsorption isotherm of QBS on Si obtained from the QCM study reflects much lower affinity of highly hydrated and negatively charged saponin molecules to the Si/water interface. We postulate that at the air/water interface, QBS adsorbs through the triterpene aglycone moiety. In contrast, weak hydrogen bonding between the glycone part and the surface silanol groups of Si is responsible for QBS adsorption on more polar Si/water interface. Copyright © 2014 Elsevier B.V. All rights reserved.

  14. Application of empirical hydration distribution functions around polar atoms for assessing hydration structures of proteins

    International Nuclear Information System (INIS)

    Matsuoka, Daisuke; Nakasako, Masayoshi

    2013-01-01

    Highlights: ► Empirical distribution functions of water molecules in protein hydration are made. ► The functions measure how hydrogen-bond geometry in hydration deviate from ideal. ► The functions assess experimentally identified hydration structures of protein. - Abstract: To quantitatively characterize hydrogen-bond geometry in local hydration structures of proteins, we constructed a set of empirical hydration distribution functions (EHDFs) around polar protein atoms in the main and side chains of 11 types of hydrophilic amino acids (D. Matsuoka, M. Nakasako, Journal of Physical Chemistry B 113 (2009) 11274). The functions are the ensemble average of possible hydration patterns around the polar atoms, and describe the anisotropic deviations from ideal hydrogen bond geometry. In addition, we defined probability distribution function of hydration water molecules (PDFH) over the hydrophilic surface of a protein as the sum of EHDFs of solvent accessible polar protein atoms. The functions envelop most of hydration sites identified in crystal structures of proteins (D. Matsuoka, M. Nakasako, Journal of Physical Chemistry B 114 (2010) 4652). Here we propose the application of EHDFs and PDFHs for assessing crystallographically identified hydration structures of proteins. First, hydration water molecules are classified with respect to the geometry in hydrogen bonds in referring EHDFs. Difference Fourier electron density map weighted by PDFH of protein is proposed to identify easily density peaks as candidates of hydration water molecules. A computer program implementing those ideas was developed and used for assessing hydration structures of proteins

  15. Solvation numbers and hydration constant for thorium(IV) in ethanol-water medium

    International Nuclear Information System (INIS)

    Sedaira, H.; Idriss, K.A.; Hashem, E.Y.

    1996-01-01

    The solvation number and hydration constant of Th 4+ in ethanol-water medium were determined at 25 degrees C using UV-spectral and electrochemical measurements. A solvate formation equilibrium is demonstrated and characterized. Three molecules of ethanol (S) can bond to the metal cation with strengths comparable to that for H 2 O to form ThS 3 (H 2 O) 3 4+ . Formation of thorium monochelate with lawsone (2-hydroxy-1.4-naphthoquinone) eliminates bonding with alcohol molecules. The dissociation constant of the chelating agent s K a and the formation contant of the monochelated metal ion s K f * that are essentially independent of the solution composition are evaluated. Hydration titrations involving thorium-lawsone monochlate are performed and the data obtained from the changes of pH with solvent composition are analyzed. The solution independent constant, s K f * for thorium-lawsone complex formation in mixed aqueous ethanol is given by log x K f * =vpK a + log s K h - log [LH] - vpH + 3 log v where vpK a is the dissociation constant of the chelating agent LH in the solvent system of v volume fraction of water and s K h is the solution-independent hydration constant of thorium (IV) in the solvent system. Log-values for the constants s K h , s K f * and s K z * are found to be 7.8 ±0.02, 11.38±0.04 and -0.753, respectively

  16. 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.

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

    DEFF Research Database (Denmark)

    Liso, Vincenzo; Nielsen, Mads Pagh

    2015-01-01

    Polymer electrolyte membrane (PEM) fuel cells requires an appropriate hydration in order to ensure high efficiency and long durability. As water is essential for promoting proton conductivity in the membrane, it is important to control membrane water hydration to avoid flooding. In this study we...

  18. Analysis of Decomposition for Structure I Methane Hydrate by Molecular Dynamics Simulation

    Science.gov (United States)

    Wei, Na; Sun, Wan-Tong; Meng, Ying-Feng; Liu, An-Qi; Zhou, Shou-Wei; Guo, Ping; Fu, Qiang; Lv, Xin

    2018-05-01

    Under multi-nodes of temperatures and pressures, microscopic decomposition mechanisms of structure I methane hydrate in contact with bulk water molecules have been studied through LAMMPS software by molecular dynamics simulation. Simulation system consists of 482 methane molecules in hydrate and 3027 randomly distributed bulk water molecules. Through analyses of simulation results, decomposition number of hydrate cages, density of methane molecules, radial distribution function for oxygen atoms, mean square displacement and coefficient of diffusion of methane molecules have been studied. A significant result shows that structure I methane hydrate decomposes from hydrate-bulk water interface to hydrate interior. As temperature rises and pressure drops, the stabilization of hydrate will weaken, decomposition extent will go deep, and mean square displacement and coefficient of diffusion of methane molecules will increase. The studies can provide important meanings for the microscopic decomposition mechanisms analyses of methane hydrate.

  19. Hydration states of clays followed by water and hydroxyls vibrational analyses in the near infrared: application to saponite and bentonite systems

    International Nuclear Information System (INIS)

    Rinnert, E.

    2004-01-01

    The study of the feasibility of a deep geological disposal facility conducted by ANDRA - the French national radioactive waste management agency -, requires the knowledge of water status and water content in clays. Thanks to an original lab-built device coupling vibrational spectroscopies and water adsorption isotherms, adsorbed water and clay's structure are described quantitatively and qualitatively. A multidisciplinary approach allows the description of hydration mechanisms and water molecules network in the inter lamellar space of synthetic saponites. The effects of density and nature of inter-foliar cations and the influence of temperature on hydration are presented. Using mechanisms and important parameters established on saponites, hydration of bentonite MX80 is carried out. In order to describe and quantify simultaneously two different water states, a simple but relevant method of spectra analysis was developed. (author)

  20. Water Transfer Characteristics during Methane Hydrate Formation Processes in Layered Media

    Directory of Open Access Journals (Sweden)

    Yousheng Deng

    2011-08-01

    Full Text Available Gas hydrate formation processes in porous media are always accompanied by water transfer. To study the transfer characteristics comprehensively, two kinds of layered media consisting of coarse sand and loess were used to form methane hydrate in them. An apparatus with three PF-meter sensors detecting water content and temperature changes in media during the formation processes was applied to study the water transfer characteristics. It was experimentally observed that the hydrate formation configurations in different layered media were similar; however, the water transfer characteristics and water conversion ratios were different.

  1. Hydrated proton and hydroxide charge transfer at the liquid/vapor interface of water

    Energy Technology Data Exchange (ETDEWEB)

    Soniat, Marielle; Rick, Steven W., E-mail: srick@uno.edu [Department of Chemistry, University of New Orleans, New Orleans, Louisiana 70148 (United States); Kumar, Revati [Department of Chemistry, Louisiana State University, Baton Rouge, Louisiana 70808 (United States)

    2015-07-28

    The role of the solvated excess proton and hydroxide ions in interfacial properties is an interesting scientific question with applications in a variety of aqueous behaviors. The role that charge transfer (CT) plays in interfacial behavior is also an unsettled question. Quantum calculations are carried out on clusters of water with an excess proton or a missing proton (hydroxide) to determine their CT. The quantum results are applied to analysis of multi-state empirical valence bond trajectories. The polyatomic nature of the solvated excess proton and hydroxide ion results in directionally dependent CT, depending on whether a water molecule is a hydrogen bond donor or acceptor in relation to the ion. With polyatomic molecules, CT also depends on the intramolecular bond distances in addition to intermolecular distances. The hydrated proton and hydroxide affect water’s liquid/vapor interface in a manner similar to monatomic ions, in that they induce a hydrogen-bonding imbalance at the surface, which results in charged surface waters. This hydrogen bond imbalance, and thus the charged waters at the surface, persists until the ion is at least 10 Å away from the interface.

  2. Hydrated proton and hydroxide charge transfer at the liquid/vapor interface of water

    International Nuclear Information System (INIS)

    Soniat, Marielle; Rick, Steven W.; Kumar, Revati

    2015-01-01

    The role of the solvated excess proton and hydroxide ions in interfacial properties is an interesting scientific question with applications in a variety of aqueous behaviors. The role that charge transfer (CT) plays in interfacial behavior is also an unsettled question. Quantum calculations are carried out on clusters of water with an excess proton or a missing proton (hydroxide) to determine their CT. The quantum results are applied to analysis of multi-state empirical valence bond trajectories. The polyatomic nature of the solvated excess proton and hydroxide ion results in directionally dependent CT, depending on whether a water molecule is a hydrogen bond donor or acceptor in relation to the ion. With polyatomic molecules, CT also depends on the intramolecular bond distances in addition to intermolecular distances. The hydrated proton and hydroxide affect water’s liquid/vapor interface in a manner similar to monatomic ions, in that they induce a hydrogen-bonding imbalance at the surface, which results in charged surface waters. This hydrogen bond imbalance, and thus the charged waters at the surface, persists until the ion is at least 10 Å away from the interface

  3. Distribution of binding energies of a water molecule in the water liquid-vapor interface

    Energy Technology Data Exchange (ETDEWEB)

    Chempath, Shaji [Los Alamos National Laboratory; Pratt, Lawrence R [TULANE UNIV

    2008-01-01

    Distributions of binding energies of a water molecule in the water liquid-vapor interface are obtained on the basis of molecular simulation with the SPC/E model of water. These binding energies together with the observed interfacial density profile are used to test a minimally conditioned Gaussian quasi-chemical statistical thermodynamic theory. Binding energy distributions for water molecules in that interfacial region clearly exhibit a composite structure. A minimally conditioned Gaussian quasi-chemical model that is accurate for the free energy of bulk liquid water breaks down for water molecules in the liquid-vapor interfacial region. This breakdown is associated with the fact that this minimally conditioned Gaussian model would be inaccurate for the statistical thermodynamics of a dilute gas. Aggressive conditioning greatly improves the performance of that Gaussian quasi-chemical model. The analogy between the Gaussian quasi-chemical model and dielectric models of hydration free energies suggests that naive dielectric models without the conditioning features of quasi-chemical theory will be unreliable for these interfacial problems. Multi-Gaussian models that address the composite nature of the binding energy distributions observed in the interfacial region might provide a mechanism for correcting dielectric models for practical applications.

  4. Differential Scanning Calorimetric Study and Potential Model of the Binding of the Primary Water of Hydration to K-Hyaluronate

    Science.gov (United States)

    Whitson, K. B.; Marlowe, R. L.; Lukan, A. M.; Lee, S. A.; Anthony, L.; Rupprecht, A.

    1997-11-01

    DSC was performed on samples of K-hyaluronate (KHA) through a temperature range of 25-180^oC. A transition peak was observed which is due to the desorption of the primary water of hydration. The maximum position of the peak was observed to change with different scan rates. The average energy of activation, E_A, and enthalpy for desorption of the primary water of hydration was determined to be 0.62 and 0.17 eV per water molecule, respectively. Analysis of Mossbauer data(G. Albanese et al., Hyperfine Int.,) 95, 97 (1995) allowed us to determine the effective force constant, k_eff, of the water bound to KHA to be approximately 19.4 eV/nm^2. The parameters E_A, ΔH,and k_eff allow us to construct a potential model for the primary water of hydration of KHA. Comparison of these parameters with the same parameters for HA and DNA with different counterions reveal that the energy of activation is similar, as well as the enthalpy change.

  5. Characterization of water in hydrated Bombyx mori silk fibroin fiber and films by 2H NMR relaxation and 13C solid state NMR.

    Science.gov (United States)

    Asakura, Tetsuo; Isobe, Kotaro; Kametani, Shunsuke; Ukpebor, Obehi T; Silverstein, Moshe C; Boutis, Gregory S

    2017-03-01

    The mechanical properties of Bombyx mori silk fibroin (SF), such as elasticity and tensile strength, change remarkably upon hydration. However, the microscopic interaction with water is not currently well understood on a molecular level. In this work, the dynamics of water molecules interacting with SF was studied by 2 H solution NMR relaxation and exchange measurements. Additionally, the conformations of hydrated [3- 13 C]Ala-, [3- 13 C]Ser-, and [3- 13 C]Tyr-SF fibers and films were investigated by 13 C DD/MAS NMR. Using an inverse Laplace transform algorithm, we were able to identify four distinct components in the relaxation times for water in SF fiber. Namely, A: bulk water outside the fiber, B: water molecules trapped weakly on the surface of the fiber, C: bound water molecules located in the inner surface of the fiber, and D: bound water molecules located in the inner part of the fiber were distinguishable. In addition, four components were also observed for water in the SF film immersed in methanol for 30s, while only two components for the film immersed in methanol for 24h. The effects of hydration on the conformation of Ser and Tyr residues in the site-specific crystalline and non-crystalline domains of 13 C selectively labeled SF, respectively, could be determined independently. Our measurements provide new insight relating the characteristics of water and the hydration structure of silk, which are relevant in light of current interest in the design of novel silk-based biomaterials. The mechanical properties of Bombyx mori silk fibroin (SF) change remarkably upon hydration. However, the microscopic interaction between SF and water is not currently well understood on a molecular level. We were able to identify four distinct components in the relaxation times for water in SF fiber by 2 H solution NMR relaxation and exchange measurements. In addition, the effects of hydration on the conformation of Ser and Tyr residues in the site-specific crystalline and

  6. 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.

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

    KAUST Repository

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

    2016-01-01

    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.

  8. Optimization of linear and branched alkane interactions with water to simulate hydrophobic hydration

    Science.gov (United States)

    Ashbaugh, Henry S.; Liu, Lixin; Surampudi, Lalitanand N.

    2011-08-01

    Previous studies of simple gas hydration have demonstrated that the accuracy of molecular simulations at capturing the thermodynamic signatures of hydrophobic hydration is linked both to the fidelity of the water model at replicating the experimental liquid density at ambient pressure and an accounting of polarization interactions between the solute and water. We extend those studies to examine alkane hydration using the transferable potentials for phase equilibria united-atom model for linear and branched alkanes, developed to reproduce alkane phase behavior, and the TIP4P/2005 model for water, which provides one of the best descriptions of liquid water for the available fixed-point charge models. Alkane site/water oxygen Lennard-Jones cross interactions were optimized to reproduce the experimental alkane hydration free energies over a range of temperatures. The optimized model reproduces the hydration free energies of the fitted alkanes with a root mean square difference between simulation and experiment of 0.06 kcal/mol over a wide temperature range, compared to 0.44 kcal/mol for the parent model. The optimized model accurately reproduces the temperature dependence of hydrophobic hydration, as characterized by the hydration enthalpies, entropies, and heat capacities, as well as the pressure response, as characterized by partial molar volumes.

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

    International Nuclear Information System (INIS)

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

    2015-01-01

    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 V E as a function of ethanol mole fraction X 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

  10. The Dependence of Water Permeability in Quartz Sand on Gas Hydrate Saturation in the Pore Space

    Science.gov (United States)

    Kossel, E.; Deusner, C.; Bigalke, N.; Haeckel, M.

    2018-02-01

    Transport of fluids in gas hydrate bearing sediments is largely defined by the reduction of the permeability due to gas hydrate crystals in the pore space. Although the exact knowledge of the permeability behavior as a function of gas hydrate saturation is of crucial importance, state-of-the-art simulation codes for gas production scenarios use theoretically derived permeability equations that are hardly backed by experimental data. The reason for the insufficient validation of the model equations is the difficulty to create gas hydrate bearing sediments that have undergone formation mechanisms equivalent to the natural process and that have well-defined gas hydrate saturations. We formed methane hydrates in quartz sand from a methane-saturated aqueous solution and used magnetic resonance imaging to obtain time-resolved, three-dimensional maps of the gas hydrate saturation distribution. These maps were fed into 3-D finite element method simulations of the water flow. In our simulations, we tested the five most well-known permeability equations. All of the suitable permeability equations include the term (1-SH)n, where SH is the gas hydrate saturation and n is a parameter that needs to be constrained. The most basic equation describing the permeability behavior of water flow through gas hydrate bearing sand is k = k0 (1-SH)n. In our experiments, n was determined to be 11.4 (±0.3). Results from this study can be directly applied to bulk flow analysis under the assumption of homogeneous gas hydrate saturation and can be further used to derive effective permeability models for heterogeneous gas hydrate distributions at different scales.

  11. The binding of the primary water of hydration to nucleosides, CsDNA and potassium hyaluronate

    Science.gov (United States)

    Lukan, A. M.; Cavanaugh, D.; Whitson, K. B.; Marlowe, R. L.; Lee, S. A.; Anthony, L.; Rupprecht, A.; Mohan, V.

    1998-03-01

    Differential scanning calorimetry (DSC) has been used to study the eight nucleosides, CsDNA and KHA hydrated at 59% relative humidity. Thermograms were measured between 25 and 180 ^oC for scan rates of 1, 2, 5, 10 and 20 K/min. A broad endothermic transition (due to the desorption of the water) near 80 ^oC was observed for all runs. The average enthalpy of desorption per water molecule was evaluated from the area under the peak. A Kissinger analysis of these data yielded the net activation energy for desorption. Both parameters were very similar for the two biopolymers. Rayleigh scattering of Mossbauer radiation (RSMR) data(G. Albanese et al. ) Hyperfine Int. 95, 97 (1995) were analyzed via a simple harmonic oscillator model to evaluate the effective force constant of the water bound to the biopolymer. This analysis suggests that the effective force constant of water bound to HA is much larger (about 5 times) than for water bound to DNA.

  12. Antioxidant activity of hydrated carboxylated nanodiamonds and its influence on water γ-radiolysis

    Science.gov (United States)

    Santacruz-Gomez, Karla; Sarabia-Sainz, A.; Acosta-Elias, M.; Sarabia-Sainz, M.; Janetanakit, Woraphong; Khosla, Nathan; Melendrez, R.; Pedroza Montero, Martin; Lal, Ratnesh

    2018-03-01

    Water radiolysis involves chemical decomposition of the water molecule into free radicals after exposure to ionizing radiation. These free radicals have deleterious effects on normal cell physiology. Carboxylated nanodiamonds (cNDs) appear to modulate the deleterious effects of γ-irradiation on the pathophysiology of red blood cells (RBCs). In the present work, the antioxidant activity of hydrated cNDs (h-cNDs) on limiting oxidative damage (the water radiolysis effect) by γ-irradiation was confirmed. Our results show that h-cNDs have remarkable free radical scavenging ability and preserve the enzymatic activity of catalase after γ-irradiation. The underlying mechanism through which nanodiamonds exhibit antioxidant activity appears to depend on their colloidal stability. This property of detonation synthesized nanodiamonds is improved after carboxylation, which in turn influences changes in the hydrogen bond strength in water. The observed stability of h-cNDs in water and their antioxidant activity correlates with their protective effect on RBCs against γ-irradiation.

  13. Theoretical investigation of the ultrafast dissociation of core-ionized water and uracil molecules immersed in liquid water

    Energy Technology Data Exchange (ETDEWEB)

    Stia, C.R.; Fojon, O.A. [Instituto de Fisica Rosario - CONICET-Universidad Nacional de Rosario, Rosario (Argentina); Gaigeot, M.P. [Laboratoire Analyse et Modelisation pour la Biologie et l' Environnement, LAMBE, UMR-CNRS 8587, Universite d' Evry-Val-d' Essonne, 91 - Evry (France); Institut Universitaire de France, 75 - Paris (France); Vuilleumier, R. [Departement de chimie, Ecole Normale Superieure, 75 - Paris (France); Herve du Penhoat, M.A.; Politis, M.F. [Institut de Mineralogie et de Physique des Milieux Condenses, IMPMC, UMR-CNRS 7590, Universite Pierre et Marie Curie, 75 - Paris (France)

    2010-10-15

    We present a series of ab initio density functional based calculations of the fragmentation dynamics of core-ionized biomolecules. The computations are performed for pure liquid water, aqueous and isolated Uracil. Core ionization is described by replacing the 1s{sup 2} pseudopotential of one atom of the target molecule (C, N or O) with a pseudopotential for a 1s{sup 1} core-hole state. Our results predict that the dissociation of core-ionized water molecules may be reached during the lifetime of inner-shell vacancy (less than 10 fs), leading to OH bond breakage as a primary outcome. We also observe a second fragmentation channel in which total Coulomb explosion of the ionized water molecule occurs. Fragmentation pathways are found similar for pure water or when the water molecule is in the primary hydration shell of the uracil molecule. In the latter case, the proton may be transferred towards the uracil oxygen atoms. When the core hole is located on the uracil molecule, ultrafast dissociation is only observed in the aqueous environment and for nitrogen-K vacancies, resulting in proton transfers towards the hydrogen-bonded water molecule. (authors)

  14. Hydration water dynamics in biopolymers from NMR relaxation in the rotating frame.

    Science.gov (United States)

    Blicharska, Barbara; Peemoeller, Hartwig; Witek, Magdalena

    2010-12-01

    Assuming dipole-dipole interaction as the dominant relaxation mechanism of protons of water molecules adsorbed onto macromolecule (biopolymer) surfaces we have been able to model the dependences of relaxation rates on temperature and frequency. For adsorbed water molecules the correlation times are of the order of 10(-5)s, for which the dispersion region of spin-lattice relaxation rates in the rotating frame R(1)(ρ)=1/T(1)(ρ) appears over a range of easily accessible B(1) values. Measurements of T(1)(ρ) at constant temperature and different B(1) values then give the "dispersion profiles" for biopolymers. Fitting a theoretical relaxation model to these profiles allows for the estimation of correlation times. This way of obtaining the correlation time is easier and faster than approaches involving measurements of the temperature dependence of R(1)=1/T(1). The T(1)(ρ) dispersion approach, as a tool for molecular dynamics study, has been demonstrated for several hydrated biopolymer systems including crystalline cellulose, starch of different origins (potato, corn, oat, wheat), paper (modern, old) and lyophilized proteins (albumin, lysozyme). Copyright © 2010 Elsevier Inc. All rights reserved.

  15. 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.

  16. 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.

  17. Hydration kinetics of cement composites with varying water-cement ratio using terahertz spectroscopy

    Science.gov (United States)

    Ray, Shaumik; Dash, Jyotirmayee; Devi, Nirmala; Sasmal, Saptarshi; Pesala, Bala

    2015-03-01

    Cement is mixed with water in an optimum ratio to form concrete with desirable mechanical strength and durability. The ability to track the consumption of major cement constituents, viz., Tri- and Dicalcium Silicates (C3S, C2S) reacting with water along with the formation of key hydration products, viz., Calcium-Silicate-Hydrate (C-S-H) which gives the overall strength to the concrete and Calcium Hydroxide (Ca(OH)2), a hydration product which reduces the strength and durability, using an efficient technique is highly desirable. Optimizing the amount of water to be mixed with cement is one of the main parameters which determine the strength of concrete. In this work, THz spectroscopy has been employed to track the variation in hydration kinetics for concrete samples with different water-cement ratios, viz., 0.3, 0.4, 0.5 and 0.6. Results show that for the sample with water-cement ratio of 0.3, significant amount of the C3S and C2S remain unreacted even after the initial hydration period of 28 days while for the cement with water-cement ratio of 0.6, most of the constituents get consumed during this stage. Analysis of the formation of Ca(OH)2 has been done which shows that the concrete sample with water-cement ratio of 0.6 produces the highest amount of Ca(OH)2 due to higher consumption of C3S/C2S in presence of excess water which is not desirable. Samples with water-cement ratio of 0.4 and 0.5 show more controlled reaction during the hydration which can imply formation of an optimized level of desired hydration products resulting in a more mechanically strong and durable concrete.

  18. Hydrophobic hydration and anomalous excess partial molar volume of tert-butyl alcohol-water mixture studied by quasielastic neutron scattering

    International Nuclear Information System (INIS)

    Nakada, Masaru; Maruyama, Kenji; Misawa, Masakatsu; Yamamuro, Osamu

    2007-01-01

    Quasielastic neutron scattering has been used to investigate the hydration of alcohol clusters in tert-butyl alcohol-water mixture. The measurements were made in a range of alcohol concentration, x TBA , from 0.0 to 0.17 in mole fraction at 25degC. Fraction, α, of water molecules hydrated to fractal-surface of alcohol clusters in tert-butyl alcohol-water mixture was obtained as a function of alcohol concentration. Average hydration number N WS of tert-butyl alcohol molecule was derived from the value of α as a function of alcohol concentration. The value of N WS for an isolated alcohol molecule in water was 19-21. The anomalous excess partial molar volume of tert-butyl alcohol-water mixture was interpreted successfully by applying the same model with the same values of volume parameter as used for 1-propanol-water mixture, δ 1 (=-0.36 cm 3 ·mol -1 ) and δ 2 (=0.60 cm 3 ·mol -1 ). (author)

  19. Hydration of alcohol clusters in 1-propanol-water mixture studied by quasielastic neutron scattering and an interpretation of anomalous excess partial molar volume.

    Science.gov (United States)

    Misawa, M; Inamura, Y; Hosaka, D; Yamamuro, O

    2006-08-21

    Quasielastic neutron scattering measurements have been made for 1-propanol-water mixtures in a range of alcohol concentration from 0.0 to 0.167 in mole fraction at 25 degrees C. Fraction alpha of water molecules hydrated to fractal surface of alcohol clusters in 1-propanol-water mixture was obtained as a function of alcohol concentration. Average hydration number N(ws) of 1-propanol molecule is derived from the value of alpha as a function of alcohol concentration. By extrapolating N(ws) to infinite dilution, we obtain values of 12-13 as hydration number of isolated 1-propanol molecule. A simple interpretation of structural origin of anomalous excess partial molar volume of water is proposed and as a result a simple equation for the excess partial molar volume is deduced in terms of alpha. Calculated values of the excess partial molar volumes of water and 1-propanol and the excess molar volume of the mixture are in good agreement with experimental values.

  20. Modelling a deep water oil/gas spill under conditions of gas hydrate formation and decomposition

    International Nuclear Information System (INIS)

    Zheng, L.; Yapa, P.D.

    2000-01-01

    A model for the behavior of oil and gas spills at deepwater locations was presented. Such spills are subjected to pressures and temperatures that can convert gases to gas hydrates which are lighter than water. Knowing the state of gases as they rise with the plume is important in predicting the fate of an oil or gas plume released in deepwater. The objective of this paper was to develop a comprehensive jet/plume model which includes computational modules that simulate the gas hydrate formation/decomposition of gas bubbles. This newly developed model is based on the kinetics of hydrate formation and decomposition coupled with mass and heat transfer phenomena. The numerical model was successfully tested using results of experimental data from the Gulf of Mexico. Hydrate formation and decomposition are integrated with an earlier model by Yapa and Zheng for underwater oil or gas jets and plumes. The effects of hydrate on the behavior of an oil or gas plume was simulated to demonstrate the models capabilities. The model results indicate that in addition to thermodynamics, the kinetics of hydrate formation/decomposition should be considered when studying the behavior of oil and gas spills. It was shown that plume behavior changes significantly depending on whether or not the local conditions force the gases to form hydrates. 25 refs., 4 tabs., 12 figs

  1. The formation of gas hydrates and the effect of inhibitiors on their ...

    African Journals Online (AJOL)

    Natural gas hydrate is a solid crystalline compound produced by combining water and gas and it is considered as the clathrates. Guest gas molecules are stuck insider the pores of water networks produced by hydrogen bonds between molecules of water. There are different ways to analyze the hydrate formation operating ...

  2. Autodissociation of a water molecule in liquid water

    Energy Technology Data Exchange (ETDEWEB)

    Geissler, Phillip L.; Dellago, Christoph; Chandler, David; Hutter, Jurg; Parrinello, Michele

    2000-04-01

    The dissociation of a water molecule in liquid water is the fundamental event in acid-base chemistry, determining the pH of water.Because the microscopic dynamics of this autodissociation are difficult to probe, both by experiment and by computer simulation, its mechanism has been unknown. Here we report several autodissociation trajectories generated by ab initio molecular dynamics [1]. These trajectories, which were harvested using transition path sampling [2-4], reveal the mechanism for the first time. Rare fluctuations in solvation energies destabilize an oxygen-hydrogen bond. Through the transfer of one or more protons along a hydrogen bond.

  3. Slow neutron scattering by water molecules

    Energy Technology Data Exchange (ETDEWEB)

    Stancic, V [Boris Kidric Institute of Nuclear Sciences Vinca, Beograd (Yugoslavia)

    1970-07-01

    In this work some new, preliminary formulae for slow neutron scattering cross section calculation by heavy and light water molecules have been done. The idea was to find, from the sum which exists in well known Nelkin model, other cross sections in a more simple analytical form, so that next approximations may be possible. In order to sum a series it was starting from Euler-Mclaurin formula. Some new summation formulae have been derived there, and defined in two theorems. Extensive calculations, especially during the evaluation of residues, have been made at the CDC 3600 computer. validation of derived formulae was done by comparison with the BNL-325 results. Good agreement is shown. (author)

  4. Slow neutron scattering by water molecules

    International Nuclear Information System (INIS)

    Stancic, V.

    1970-01-01

    In this work some new, preliminary formulae for slow neutron scattering cross section calculation by heavy and light water molecules have been done. The idea was to find, from the sum which exists in well known Nelkin model, other cross sections in a more simple analytical form, so that next approximations may be possible. In order to sum a series it was starting from Euler-Mclaurin formula. Some new summation formulae have been derived there, and defined in two theorems. Extensive calculations, especially during the evaluation of residues, have been made at the CDC 3600 computer. validation of derived formulae was done by comparison with the BNL-325 results. Good agreement is shown. (author)

  5. Exploring the ab initio/classical free energy perturbation method: The hydration free energy of water

    International Nuclear Information System (INIS)

    Sakane, Shinichi; Yezdimer, Eric M.; Liu, Wenbin; Barriocanal, Jose A.; Doren, Douglas J.; Wood, Robert H.

    2000-01-01

    The ab initio/classical free energy perturbation (ABC-FEP) method proposed previously by Wood et al. [J. Chem. Phys. 110, 1329 (1999)] uses classical simulations to calculate solvation free energies within an empirical potential model, then applies free energy perturbation theory to determine the effect of changing the empirical solute-solvent interactions to corresponding interactions calculated from ab initio methods. This approach allows accurate calculation of solvation free energies using an atomistic description of the solvent and solute, with interactions calculated from first principles. Results can be obtained at a feasible computational cost without making use of approximations such as a continuum solvent or an empirical cavity formation energy. As such, the method can be used far from ambient conditions, where the empirical parameters needed for approximate theories of solvation may not be available. The sources of error in the ABC-FEP method are the approximations in the ab initio method, the finite sample of configurations, and the classical solvent model. This article explores the accuracy of various approximations used in the ABC-FEP method by comparing to the experimentally well-known free energy of hydration of water at two state points (ambient conditions, and 973.15 K and 600 kg/m3). The TIP4P-FQ model [J. Chem. Phys. 101, 6141 (1994)] is found to be a reliable solvent model for use with this method, even at supercritical conditions. Results depend strongly on the ab initio method used: a gradient-corrected density functional theory is not adequate, but a localized MP2 method yields excellent agreement with experiment. Computational costs are reduced by using a cluster approximation, in which ab initio pair interaction energies are calculated between the solute and up to 60 solvent molecules, while multi-body interactions are calculated with only a small cluster (5 to 12 solvent molecules). Sampling errors for the ab initio contribution to

  6. 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.

  7. 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)

  8. Hydration measured by doubly labeled water in ALS and its effects on survival.

    Science.gov (United States)

    Scagnelli, Connor N; Howard, Diantha B; Bromberg, Mark B; Kasarskis, Edward J; Matthews, Dwight E; Mitsumoto, Hiroshi M; Simmons, Zachary; Tandan, Rup

    2018-05-01

    We present a study of hydration in ALS patients and its effects on survival. This was a multicenter study over 48 weeks in 80 ALS patients who underwent 250 individual measurements using doubly labeled water (DLW). Total body water (TBW) and water turnover (a surrogate for water intake) were 3.4% and 8.6% lower, respectively, in patients compared to age- and gender-matched healthy controls, and both significantly decreased over study duration. In 20% of patients, water turnover measured over 10 d was 2 standard deviations below the mean value in healthy controls. In a separate clinic cohort of 208 patients, water intake estimated from a de novo equation created from common clinical endpoints was a prognostic indicator of survival. Regardless of nutritional state assessed by BMI, survival was two-fold longer in the group above the median for estimated water intake, suggesting that hydration may be a more important predictor of survival than malnutrition. Risk factors for poor hydration were identified. Water intake equations recommended by US Centers for Medicare and Medicaid Services in healthy elderly were inaccurate for use in ALS patients. We developed equations to estimate TBW and water intake in ALS patients for use in clinics to accurately estimate hydration and improve clinical care.

  9. Description of gas hydrates equilibria in sediments using experimental data of soil water potential

    Energy Technology Data Exchange (ETDEWEB)

    Istomin, V. [NOVATEK, Moscow (Russian Federation); Chuvilin, E. [Moscow State Univ., Moscow (Russian Federation). Dept. of Geology; Makhonina, N.; Kvon, V. [VNIIGAZ, Moscow (Russian Federation); Safonov, S. [Schlumberger Moscow Research, Moscow (Russian Federation)

    2008-07-01

    Analytical relationships have been developed between hydrate dissociation pressure and vapor pressure above the pore water surface. In addition, experiments have been discussed in numerous publications on the effect of narrow interconnected throats between pores on clathrate dissociation conditions in porous media. This paper presented an approach that improved upon the available thermodynamic methods for calculation of hydrate phase equilibria. The approach took into account the properties of pore water in natural sediments including three-phase equilibrium of gas-pore water-gas hydrate in a similar way as for unfrozen water in geocryology science. The purpose of the paper was to apply and adapt geocryology and soil physics method to the thermodynamic calculation of non-clathrated water content in sediments. It answered the question of how to estimate the non-clathrated water content if pore water potential was known. The paper explained the thermodynamics of water phase in porous media including the thermodynamic properties of supercooled water, the thermodynamic properties of pore water and pore ice in sediments, and the phase equilibria of pore water. The paper also discussed the quantitative techniques that were utilized for determination of unfrozen water content in sediments and its dependence on temperature variation. These included contact-saturation, calorimetric, dielectric, nuclear magnetic resonance, and others. The thermodynamic calculations of pore water phase equilibria were also presented. 30 refs., 5 tabs., 8 figs.

  10. Squirt flow due to interfacial water films in hydrate bearing sediments

    Directory of Open Access Journals (Sweden)

    K. Sell

    2018-05-01

    Full Text Available Sediments containing gas hydrate dispersed in the pore space are known to show a characteristic seismic anomaly which is a high attenuation along with increasing seismic velocities. Currently, this observation cannot be fully explained albeit squirt-flow type mechanisms on the microscale have been speculated to be the cause. Recent major findings from in situ experiments, using the gas in excess and water in excess formation method, and coupled with high-resolution synchrotron-based X-ray micro-tomography, have revealed the systematic presence of thin water films between the quartz grains and the encrusting hydrate. The data obtained from these experiments underwent an image processing procedure to quantify the thicknesses and geometries of the aforementioned interfacial water films. Overall, the water films vary from sub-micrometer to a few micrometers in thickness. In addition, some of the water films interconnect through water bridges. This geometrical analysis is used to propose a new conceptual squirt flow model for hydrate bearing sediments. A series of numerical simulations is performed considering variations of the proposed model to study seismic attenuation caused by such thin water films. Our results support previous speculation that squirt flow can explain high attenuation at seismic frequencies in hydrate bearing sediments, but based on a conceptual squirt flow model which is geometrically different than those previously considered.

  11. Thermodynamic analysis of water molecules at the surface of proteins and applications to binding site prediction and characterization.

    Science.gov (United States)

    Beuming, Thijs; Che, Ye; Abel, Robert; Kim, Byungchan; Shanmugasundaram, Veerabahu; Sherman, Woody

    2012-03-01

    Water plays an essential role in determining the structure and function of all biological systems. Recent methodological advances allow for an accurate and efficient estimation of the thermodynamic properties of water molecules at the surface of proteins. In this work, we characterize these thermodynamic properties and relate them to various structural and functional characteristics of the protein. We find that high-energy hydration sites often exist near protein motifs typically characterized as hydrophilic, such as backbone amide groups. We also find that waters around alpha helices and beta sheets tend to be less stable than waters around loops. Furthermore, we find no significant correlation between the hydration site-free energy and the solvent accessible surface area of the site. In addition, we find that the distribution of high-energy hydration sites on the protein surface can be used to identify the location of binding sites and that binding sites of druggable targets tend to have a greater density of thermodynamically unstable hydration sites. Using this information, we characterize the FKBP12 protein and show good agreement between fragment screening hit rates from NMR spectroscopy and hydration site energetics. Finally, we show that water molecules observed in crystal structures are less stable on average than bulk water as a consequence of the high degree of spatial localization, thereby resulting in a significant loss in entropy. These findings should help to better understand the characteristics of waters at the surface of proteins and are expected to lead to insights that can guide structure-based drug design efforts. Copyright © 2011 Wiley Periodicals, Inc.

  12. Supramolecular Organization of Nonstoichiometric Drug Hydrates: Dapsone

    Science.gov (United States)

    Braun, Doris E.; Griesser, Ulrich J.

    2018-01-01

    The observed moisture- and temperature dependent transformations of the dapsone (4,4′-diaminodiphenyl sulfone, DDS) 0. 33-hydrate were correlated to its structure and the number and strength of the water-DDS intermolecular interactions. A combination of characterization techniques was used, including thermal analysis (hot-stage microscopy, differential scanning calorimetry and thermogravimetric analysis), gravimetric moisture sorption/desorption studies and variable humidity powder X-ray diffraction, along with computational modeling (crystal structure prediction and pair-wise intermolecular energy calculations). Depending on the relative humidity the hydrate contains between 0 and 0.33 molecules of water per molecule DDS. The crystal structure is retained upon dehydration indicating that DDS hydrate shows a non-stoichiometric (de)hydration behavior. Unexpectedly, the water molecules are not located in structural channels but at isolated-sites of the host framework, which is counterintuitively for a hydrate with non-stoichiometric behavior. The water-DDS interactions were estimated to be weaker than water-host interactions that are commonly observed in stoichiometric hydrates and the lattice energies of the isomorphic dehydration product (hydrate structure without water molecules) and (form III) differ only by ~1 kJ mol−1. The computational generation of hypothetical monohydrates confirms that the hydrate with the unusual DDS:water ratio of 3:1 is more stable than a feasible monohydrate structure. Overall, this study highlights that a deeper understanding of the formation of hydrates with non-stoichiometric behavior requires a multidisciplinary approach including suitable experimental and computational methods providing a firm basis for the development and manufacturing of high quality drug products. PMID:29520359

  13. Exploring the conserved water site and hydration of a coiled-coil trimerisation motif: a MD simulation study.

    Science.gov (United States)

    Dolenc, Jozica; Baron, Riccardo; Missimer, John H; Steinmetz, Michel O; van Gunsteren, Wilfred F

    2008-07-21

    The solvent structure and dynamics around ccbeta-p, a 17-residue peptide that forms a parallel three-stranded alpha-helical coiled coil in solution, was analysed through 10 ns explicit solvent molecular dynamics (MD) simulations at 278 and 330 K. Comparison with two corresponding simulations of the monomeric form of ccbeta-p was used to investigate the changes of hydration upon coiled-coil formation. Pronounced peaks in the solvent density distribution between residues Arg8 and Glu13 of neighbouring helices show the presence of water bridges between the helices of the ccbeta-p trimer; this is in agreement with the water sites observed in X-ray crystallography experiments. Interestingly, this water site is structurally conserved in many three-stranded coiled coils and, together with the Arg and Glu residues, forms part of a motif that determines three-stranded coiled-coil formation. Our findings show that little direct correlation exists between the solvent density distribution and the temporal ordering of water around the trimeric coiled coil. The MD-calculated effective residence times of up to 40 ps show rapid exchange of surface water molecules with the bulk phase, and indicate that the solvent distribution around biomolecules requires interpretation in terms of continuous density distributions rather than in terms of discrete molecules of water. Together, our study contributes to understanding the principles of three-stranded coiled-coil formation.

  14. Revealing the influence of water-cement ratio on the pore size distribution in hydrated cement paste by using cyclohexane

    Science.gov (United States)

    Bede, Andrea; Ardelean, Ioan

    2017-12-01

    Varying the amount of water in a concrete mix will influence its final properties considerably due to the changes in the capillary porosity. That is why a non-destructive technique is necessary for revealing the capillary pore distribution inside hydrated cement based materials and linking the capillary porosity with the macroscopic properties of these materials. In the present work, we demonstrate a simple approach for revealing the differences in capillary pore size distributions introduced by the preparation of cement paste with different water-to-cement ratios. The approach relies on monitoring the nuclear magnetic resonance transverse relaxation distribution of cyclohexane molecules confined inside the cement paste pores. The technique reveals the whole spectrum of pores inside the hydrated cement pastes, allowing a qualitative and quantitative analysis of different pore sizes. The cement pastes with higher water-to-cement ratios show an increase in capillary porosity, while for all the samples the intra-C-S-H and inter-C-S-H pores (also known as gel pores) remain unchanged. The technique can be applied to various porous materials with internal mineral surfaces.

  15. Historical methane hydrate project review

    Science.gov (United States)

    Collett, Timothy; Bahk, Jang-Jun; Frye, Matt; Goldberg, Dave; Husebo, Jarle; Koh, Carolyn; Malone, Mitch; Shipp, Craig; Torres, Marta

    2013-01-01

    In 1995, U.S. Geological Survey made the first systematic assessment of the volume of natural gas stored in the hydrate accumulations of the United States. That study, along with numerous other studies, has shown that the amount of gas stored as methane hydrates in the world greatly exceeds the volume of known conventional gas resources. However, gas hydrates represent both a scientific and technical challenge and much remains to be learned about their characteristics and occurrence in nature. Methane hydrate research in recent years has mostly focused on: (1) documenting the geologic parameters that control the occurrence and stability of gas hydrates in nature, (2) assessing the volume of natural gas stored within various gas hydrate accumulations, (3) analyzing the production response and characteristics of methane hydrates, (4) identifying and predicting natural and induced environmental and climate impacts of natural gas hydrates, and (5) analyzing the effects of methane hydrate on drilling safety.Methane hydrates are naturally occurring crystalline substances composed of water and gas, in which a solid water-­‐lattice holds gas molecules in a cage-­‐like structure. The gas and water becomes a solid under specific temperature and pressure conditions within the Earth, called the hydrate stability zone. Other factors that control the presence of methane hydrate in nature include the source of the gas included within the hydrates, the physical and chemical controls on the migration of gas with a sedimentary basin containing methane hydrates, the availability of the water also included in the hydrate structure, and the presence of a suitable host sediment or “reservoir”. The geologic controls on the occurrence of gas hydrates have become collectively known as the “methane hydrate petroleum system”, which has become the focus of numerous hydrate research programs.Recognizing the importance of methane hydrate research and the need for a coordinated

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

    International Nuclear Information System (INIS)

    Kawai, Koji; Kawakami, Hayato; Narushima, Takashi; Yonezawa, Tetsu

    2015-01-01

    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

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

    Energy Technology Data Exchange (ETDEWEB)

    Tanaka, Fumihiko; Koga, Tsuyoshi [Department of Polymer Chemistry, Graduate School of Engineering, Kyoto University, Kyoto 615-8510 (Japan); Kaneda, Isamu [Department of Food Science, Rakuno Gakuen University, Ebetsu, Hokkaido 069-8501 (Japan); Winnik, Francoise M, E-mail: ftanaka@phys.polym.kyoto-u.ac.jp [Department of Chemistry and Faculty of Pharmacy, University of Montreal, Montreal, H3C 3J7 (Canada)

    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 {sigma} 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.

  18. Molecular dynamics study of methane hydrate formation at a water/methane interface.

    Science.gov (United States)

    Zhang, Junfang; Hawtin, R W; Yang, Ye; Nakagava, Edson; Rivero, M; Choi, S K; Rodger, P M

    2008-08-28

    We present molecular dynamics simulation results of a liquid water/methane interface, with and without an oligomer of poly(methylaminoethylmethacrylate), PMAEMA. PMAEMA is an active component of a commercial low dosage hydrate inhibitor (LDHI). Simulations were performed in the constant NPT ensemble at temperatures of 220, 235, 240, 245, and 250 K and a pressure of 300 bar. The simulations show the onset of methane hydrate growth within 30 ns for temperatures below 245 K in the methane/water systems; at 240 K there is an induction period of ca. 20 ns, but at lower temperatures growth commences immediately. The simulations were analyzed to calculate hydrate content, the propensity for hydrogen bond formation, and how these were affected by both temperature and the presence of the LDHI. As expected, both the hydrogen bond number and hydrate content decreased with increasing temperature, though little difference was observed between the lowest two temperatures considered. In the presence of PMAEMA, the temperature below which sustained hydrate growth occurred was observed to decrease. Some of the implications for the role of PMAEMA in LDHIs are discussed.

  19. 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.

  20. 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

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

    OpenAIRE

    Bai, Yuanyuan; Chen, Baohong; Xiang, Feng; Zhou, Jinxiong; Wang, Hong; Suo, Zhigang

    2014-01-01

    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 chlorid...

  2. 2H Solid-State NMR Analysis of the Dynamics and Organization of Water in Hydrated Chitosan

    Directory of Open Access Journals (Sweden)

    Fenfen Wang

    2016-04-01

    Full Text Available Understanding water–biopolymer interactions, which strongly affect the function and properties of biopolymer-based tissue engineering and drug delivery materials, remains a challenge. Chitosan, which is an important biopolymer for the construction of artificial tissue grafts and for drug delivery, has attracted extensive attention in recent decades, where neutralization with an alkali solution can substantially enhance the final properties of chitosan films cast from an acidic solution. In this work, to elucidate the effect of water on the properties of chitosan films, we investigated the dynamics and different states of water in non-neutralized (CTS-A and neutralized (CTS-N hydrated chitosan by mobility selective variable-temperature (VT 2H solid-state NMR spectroscopy. Four distinct types of water exist in all of the samples with regards to dynamic behavior. First, non-freezable, rigid and strongly bound water was found in the crystalline domain at low temperatures. The second component consists of weakly bound water, which is highly mobile and exhibits isotropic motion, even below 260 K. Another type of water undergoes well-defined 180° flips around their bisector axis. Moreover, free water is also present in the films. For the CTS-A sample in particular, another special water species were bounded to acetic acid molecules via strong hydrogen bonding. In the case of CTS-N, the onset of motions of the weakly bound water molecules at 260 K was revealed by 2H-NMR spectroscopy. This water is not crystalline, even below 260 K, which is also the major contribution to the flexibility of chitosan chains and thus toughness of materials. By contrast, such motion was not observed in CTS-A. On the basis of the 2H solid-state NMR results, it is concluded that the unique toughness of CTS-N mainly originates from the weakly bound water as well as the interactions between water and the chitosan chains.

  3. Prediction of hydroxyl concentrations in cement pore water using a numerical cement hydration model

    NARCIS (Netherlands)

    Eijk, van R.J.; Brouwers, H.J.H.

    2000-01-01

    In this paper, a 3D numerical cement hydration model is used for predicting alkali and hydroxyl concentrations in cement pore water. First, this numerical model is calibrated for Dutch cement employing both chemical shrinkage and calorimetric experiments. Secondly, the strength development of some

  4. 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

  5. Effects of Water Molecule on CO Oxidation by OH: Reaction Pathways, Kinetic Barriers, and Rate Constants.

    Science.gov (United States)

    Zhang, Linyao; Yang, Li; Zhao, Yijun; Zhang, Jiaxu; Feng, Dongdong; Sun, Shaozeng

    2017-07-06

    The water dilute oxy-fuel combustion is a clean combustion technology for near-zero emission power; and the presence of water molecule could have both kinetic and dynamic effects on combustion reactions. The reaction OH + CO → CO 2 + H, one of the most important elementary reactions, has been investigated by extensive electronic structure calculations. And the effects of a single water molecule on CO oxidation have been studied by considering the preformed OH(H 2 O) complex reacts with CO. The results show little change in the reaction pathways, but the additional water molecule actually increases the vibrationally adiabatic energy barriers (V a G ). Further thermal rate constant calculations in the temperature range of 200 to 2000 K demonstrate that the total low-pressure limit rate constant for the water assisted OH(H 2 O) + CO → CO 2 + H 2 O + H reaction is 1-2 orders lower than that of the water unassisted one, which is consistent with the change of V a G . Therefore, the hydrated radical OH(H 2 O) would actually slow down the oxidation of CO. Meanwhile, comparisons show that the M06-2X/aug-cc-pVDZ method gives a much better estimation in energy and thus is recommended to be employed for direct dynamics simulations.

  6. Hydration of urea and alkylated urea derivatives

    Science.gov (United States)

    Kaatze, Udo

    2018-01-01

    Compressibility data and broadband dielectric spectra of aqueous solutions of urea and some of its alkylated derivatives have been evaluated to yield their numbers Nh of hydration water molecules per molecule of solute. Nh values in a broad range of solute concentrations are discussed and are compared to hydration numbers of other relevant molecules and organic ions. Consistent with previous results, it is found that urea differs from other solutes in its unusually small hydration number, corresponding to just one third of the estimated number of nearest neighbor molecules. This remarkable hydration behavior is explained by the large density φH of hydrogen bonding abilities offered by the urea molecule. In terms of currently discussed models of reorientational motions and allied dynamics in water and related associating liquids, the large density φH causes a relaxation time close to that of undisturbed water with most parts of water encircling the solute. Therefore only a small part of disturbed ("hydration") water is left around each urea molecule. Adding alkyl groups to the basic molecule leads to Nh values which, within the series of n-alkylurea derivatives, progressively increase with the number of methyl groups per solute. With n-butylurea, Nh from dielectric spectra, in conformity with many other organic solutes, slightly exceeds the number of nearest neighbors. Compared to such Nh values, hydration numbers from compressibility data are substantially smaller, disclosing incorrect assumptions in the formula commonly used to interpret the experimental compressibilities. Similar to other series of organic solutes, effects of isomerization have been found with alkylated urea derivatives, indicating that factors other than the predominating density φH of hydrogen bond abilities contribute also to the hydration properties.

  7. Comparison of skin hydration in combination and single use of common moisturizers (cream, toner, and spray water).

    Science.gov (United States)

    Yuanxi, Li; Wei, Hua; Lidan, Xiiong; Li, Li

    2016-01-01

    This study aims to assess the moisturization in combination or single use (including seven general applications) of three common moisturizers: cream, toner, and spray water. Groups were set as C: cream only; T: toner only; C+T, T+C: cream or toner applied successively within a few minutes; C-T, C-S: cream applied with repeated toner or spray water every 2 h; T-T: toner applied with repeated toner every 2 h; and N: untreated group. Outcomes were the change in skin hydration from baseline at 2, 4, 6, and 8 h after applications. All treated zones displayed a significantly higher degree of hydration compared with the untreated zone ( p skin (hydration value at baseline >35 a.u.), C-T led to greatest hydration change rate compared with others, followed by C+T, T+C, and C. Those three applications exhibited analogous hydration at each test point ( p > 0.05). The hydration rate of C-S differed slightly from T-T, followed by those four mentioned above, with T being the last. For dry skin (hydration value at baseline 0.05), the other results were identical. When cream and toner were applied successively, the application order has little effect on skin hydration. The application of cream only was an effective and brief way to achieve favorable moisturization especially for dry skin. As a complement, repeated application of toner rather than spray water is efficacious for skin hydration.

  8. Diaminoethane adsorption and water substitution on hydrated TiO2: a thermochemical study based on first-principles calculations.

    Science.gov (United States)

    Hémeryck, Anne; Motta, Alessandro; Swiatowska, Jolanta; Pereira-Nabais, Catarina; Marcus, Philippe; Costa, Dominique

    2013-07-14

    Epoxy-amines are used as structural adhesives deposited on Ti. The amine adhesion to a Ti surface depends highly on the surface state (oxidation, hydroxylation). Amines may adsorb above preadsorbed water molecules or substitute them to bind directly to surface Ti(4+) Lewis acid sites. The adsorption of a model amine molecule, diaminoethane (DAE), on a model surface, hydrated TiO2-anatase (101) surface, is investigated using Density Functional Theory including Dispersive forces (DFT-D) calculations. DAE adsorption and water substitution by DAE are exothermic processes and turn nearly isoenergetic at high coverage with adsorption-substitution energies around -0.3 eV (including dispersion forces and ZPE). Complementary ab initio molecular dynamics studies also suggest that the formation of an amine-water interaction induces water desorption from the surface at room temperature, a preliminary step towards the amine-Ti bond formation. An atomistic thermodynamic approach is developed to evaluate the interfacial free energy balance of both processes (adsorption and substitution). The main contributions to the energetic balance are dispersive interactions between molecules and the surface on the exergonic side, translational and rotational entropic contributions on the endergonic one. The substitution process is stabilized by 0.55 eV versus the adsorption one when free solvation, rotational and vibrational energies are considered. The main contribution to this free energy gain is due to water solvation. The calculations suggest that in toluene solvent with a water concentration of 10(-4) M or less, a full DAE layer replaces a preadsorbed water layer for a threshold concentration of DAE ≥ 0.1 M.

  9. Heat of hydration measurements on cemented radioactive wastes. Part 1: cement-water pastes

    International Nuclear Information System (INIS)

    Lee, D.J.

    1983-12-01

    This report describes the hydration of cement pastes in terms of chemical and kinetic models. A calorimetric technique was used to measure the heat of hydration to develop these models. The effects of temperature, water/cement ratio and cement replacements, ground granulated blast furnace slag (BFS) and pulverised fuel ash (PFA) on the hydration of ordinary Portland cement (OPC) is reported. The incorporation of BFS or PFA has a marked effect on the hydration reaction. The effect of temperature is also important but changing the water/cement ratio has little effect. Results from cement pastes containing only water and cement yield total heats of reaction of 400, 200 and 100 kJ/kg for OPC, BFS and PFA respectively. Using the results from the models which have been developed, the effect of major salts present in radioactive waste streams can be assessed. Values of the total heat of reaction, the time to complete 50 percent reaction, and the energy of activation, can be compared for different waste systems. (U.K.)

  10. Changes in Transepidermal Water Loss and Skin Hydration according to Expression of Aquaporin-3 in Psoriasis

    Science.gov (United States)

    Lee, Young; Je, Young-Jin; Lee, Sang-Sin; Li, Zheng Jun; Choi, Dae-Kyoung; Kwon, Yoo-Bin; Sohn, Kyung-Cheol; Im, Myung; Seo, Young Joon

    2012-01-01

    Background Aquaporins (AQPs) are a family of water transporting proteins present in many mammalian epithelial and endothelial cell types. Among the AQPs, AQP3 is known to be a water/glycerol transporter expressed in human skin. Objective The relationship between the expression level of AQP3 and transpidermal water loss (TEWL) in the lesional and peri-lesional skin of psoriasis-affected patients, and skin hydration in the lesional and peri-lesional skin of psoriasis patients, was investigated. Methods The expression of AQP3 in psoriasis-affected and healthy control skin was determined using immunohistochemical and immunofluroscence staining. TEWL and skin hydration were measured using a Tewameter® TM210 (Courage & Khazaka, Cologne, Germany) and a Corneometer® CM 820 (Courage & Khazaka), respectively. Results AQP3 was mainly expressed in the plasma membrane of stratum corneum and the stratum spinosum in normal epidermis. Unlike the normal epidermis, AQP3 showed decreased expression in the lesional and peri-lesional epidermis of psoriasis. TEWL was increased, and skin hydration was decreased, in the lesional and peri-lesional skin of psoriasis patients, compared with the healthy control sample. Conclusion Although various factors contribute to reduced skin hydration in the lesional and peri-lesional skin of psoriasis, AQP3 appears to be a key factor in the skin dehydration of psoriasis-affected skin. PMID:22577267

  11. 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

  12. A role for subducted super-hydrated kaolinite in Earth’s deep water cycle

    Energy Technology Data Exchange (ETDEWEB)

    Hwang, Huijeong; Seoung, Donghoon; Lee, Yongjae; Liu, Zhenxian; Liermann, Hanns-Peter; Cynn, Hyunchae; Vogt, Thomas; Kao, Chi-Chang; Mao, Ho-Kwang

    2017-11-20

    Water is the most abundant volatile component in the Earth. It continuously enters the mantle through subduction zones, where it reduces the melting temperature of rocks to generate magmas. The dehydration process in subduction zones, which determines whether water is released from the slab or transported into the deeper mantle, is an essential component of the deep water cycle. Here we use in situ and time-resolved high-pressure/high-temperature synchrotron X-ray diffraction and infrared spectra to characterize the structural and chemical changes of the clay mineral kaolinite. At conditions corresponding to a depth of about 75 km in a cold subducting slab (2.7 GPa and 200 °C), and in the presence of water, we observe the pressure-induced insertion of water into kaolinite. This super-hydrated phase has a unit cell volume that is about 31% larger, a density that is about 8.4% lower than the original kaolinite and, with 29 wt% H2O, the highest water content of any known aluminosilicate mineral in the Earth. As pressure and temperature approach 19 GPa and about 800 °C, we observe the sequential breakdown of super-hydrated kaolinite. The formation and subsequent breakdown of super-hydrated kaolinite in cold slabs subducted below 200 km leads to the release of water that may affect seismicity and help fuel arc volcanism at the surface.

  13. A role for subducted super-hydrated kaolinite in Earth's deep water cycle

    Science.gov (United States)

    Hwang, Huijeong; Seoung, Donghoon; Lee, Yongjae; Liu, Zhenxian; Liermann, Hanns-Peter; Cynn, Hyunchae; Vogt, Thomas; Kao, Chi-Chang; Mao, Ho-Kwang

    2017-12-01

    Water is the most abundant volatile component in the Earth. It continuously enters the mantle through subduction zones, where it reduces the melting temperature of rocks to generate magmas. The dehydration process in subduction zones, which determines whether water is released from the slab or transported into the deeper mantle, is an essential component of the deep water cycle. Here we use in situ and time-resolved high-pressure/high-temperature synchrotron X-ray diffraction and infrared spectra to characterize the structural and chemical changes of the clay mineral kaolinite. At conditions corresponding to a depth of about 75 km in a cold subducting slab (2.7 GPa and 200 °C), and in the presence of water, we observe the pressure-induced insertion of water into kaolinite. This super-hydrated phase has a unit cell volume that is about 31% larger, a density that is about 8.4% lower than the original kaolinite and, with 29 wt% H2O, the highest water content of any known aluminosilicate mineral in the Earth. As pressure and temperature approach 19 GPa and about 800 °C, we observe the sequential breakdown of super-hydrated kaolinite. The formation and subsequent breakdown of super-hydrated kaolinite in cold slabs subducted below 200 km leads to the release of water that may affect seismicity and help fuel arc volcanism at the surface.

  14. Supramolecular Organization of Nonstoichiometric Drug Hydrates: Dapsone

    Directory of Open Access Journals (Sweden)

    Doris E. Braun

    2018-02-01

    Full Text Available The observed moisture- and temperature dependent transformations of the dapsone (4,4′-diaminodiphenyl sulfone, DDS 0. 33-hydrate were correlated to its structure and the number and strength of the water-DDS intermolecular interactions. A combination of characterization techniques was used, including thermal analysis (hot-stage microscopy, differential scanning calorimetry and thermogravimetric analysis, gravimetric moisture sorption/desorption studies and variable humidity powder X-ray diffraction, along with computational modeling (crystal structure prediction and pair-wise intermolecular energy calculations. Depending on the relative humidity the hydrate contains between 0 and 0.33 molecules of water per molecule DDS. The crystal structure is retained upon dehydration indicating that DDS hydrate shows a non-stoichiometric (dehydration behavior. Unexpectedly, the water molecules are not located in structural channels but at isolated-sites of the host framework, which is counterintuitively for a hydrate with non-stoichiometric behavior. The water-DDS interactions were estimated to be weaker than water-host interactions that are commonly observed in stoichiometric hydrates and the lattice energies of the isomorphic dehydration product (hydrate structure without water molecules and (form III differ only by ~1 kJ mol−1. The computational generation of hypothetical monohydrates confirms that the hydrate with the unusual DDS:water ratio of 3:1 is more stable than a feasible monohydrate structure. Overall, this study highlights that a deeper understanding of the formation of hydrates with non-stoichiometric behavior requires a multidisciplinary approach including suitable experimental and computational methods providing a firm basis for the development and manufacturing of high quality drug products.

  15. 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.

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

    International Nuclear Information System (INIS)

    Bai, Yuanyuan; Xiang, Feng; Wang, Hong; Chen, Baohong; Zhou, Jinxiong; Suo, Zhigang

    2014-01-01

    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.

  17. Studies on the fixation of tritiated water using the cement hydration, 2

    International Nuclear Information System (INIS)

    Nishimaki, Kenzo; Tsutsui, Tenson; Miake, Chiaki.

    1989-01-01

    In the previous paper, we have reported the results of basic experiments to fix tritiated water using the hydration of cement, and found that most tritiated water transfers to surrounding water, even if it is incorporated using the hydration of cement. In this report, we tried to apply a simple compartment model to the tritium transfer curves reported in the previous paper, which represent the phenomena that most water containing tritium is exchanging with a surrounding water, regardless of its forms, i.e., a crystalline water, free water and so on. We divided a solidified cement into three groupes with respect to the exchangeability of water, i.e., a compartment of fixed water, of compositions expect water, and of exchanging water. We developed a simple compartment model under the assumption that the water in the third compartment is exchangeable with the sorrounding water with a certain exchanging volume rate E, not altering by time. The transfer curves calculated with the model contains unknown parameter, E. By the method of least squares, varying the values of E, we could obtain most approximated transfer curves of tritium to those obtained by the previous experiments. In the result, we knew that the simple compartment model is applied to the tritium transfer curves reported in the previous paper. (author)

  18. Methane recovery from coal mine gas using hydrate formation in water-in-oil emulsions

    International Nuclear Information System (INIS)

    Zhong, Dong-Liang; Ding, Kun; Lu, Yi-Yu; Yan, Jin; Zhao, Wei-Long

    2016-01-01

    Highlights: • A water-in-oil emulsion was developed for CH_4 separation from coal mine methane gas. • Stable W/O emulsions were obtained with water cut in the range of (10–70%). • Gas hydrates nucleated faster with the reduction of water–oil volume ratio. • Gas uptake increased with the decrease of water–oil volume ratio. • CH_4 recovery was greatly enhanced by hydrate formation in W/O emulsions. - Abstract: In this work, a water-in-oil (W/O) emulsion was developed using liquid water, mineral oil, Sorbitan monooleate (Span 80), and cyclopentane. It was employed to enhance gas hydrate formation for CH_4 separation from a simulated coal mine methane (CMM) gas (30 mol% CH_4, 60 mol% N_2, and 10 mol% O_2). The stability test at atmospheric pressure and at a high pressure of 3.5 MPa showed that stable W/O emulsions were obtained when the water–oil volume ratio (WOR) was below 80%. The emulsified droplets size was measured with WOR ranging from 10% to 70%. Then kinetic experiments of CH_4 separation by hydrate formation in W/O emulsions were carried out at 273.6 K and (3.5–5.0) MPa in batch operation. The results indicated that water–oil volume ratio is a key factor that affects the kinetics of gas hydrate formation from the CMM gas mixture. Hydrate nucleation was observed to occur faster while WOR was decreased, and gas uptake increased significantly with the decrease of WOR. CH_4 concentration in the recovered gas mixture was increased to 52 mol% as compared to 30 mol% in the original gas mixture through one-stage hydrate formation in the W/O emulsions. It was found that the experimental conditions of 273.6 K, 3.5 MPa and WOR = 30% were favorable for CH_4 recovery from the CMM gas. The CH_4 recovery obtained under these conditions was 43%. It was higher than those obtained at WOR = 10% and 70%, and was greatly increased as compared with those obtained in the same reactor with the presence of TBAB (26%) and CP (33%).

  19. 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.

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

    International Nuclear Information System (INIS)

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

    2016-01-01

    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_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_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.

  1. The dynamics of water in hydrated white bread investigated using quasielastic neutron scattering

    International Nuclear Information System (INIS)

    Sjoestroem, J; Kargl, F; Fernandez-Alonso, F; Swenson, J

    2007-01-01

    The dynamics of water in fresh and in rehydrated white bread is studied using quasielastic neutron scattering (QENS). A diffusion constant for water in fresh bread, without temperature gradients and with the use of a non-destructive technique, is presented here for the first time. The self-diffusion constant for fresh bread is estimated to be D s = 3.8 x 10 -10 m 2 s -1 and the result agrees well with previous findings for similar systems. It is also suggested that water exhibits a faster dynamics than previously reported in the literature using equilibration of a hydration-level gradient monitored by vibrational spectroscopy. The temperature dependence of the dynamics of low hydration bread is also investigated for T = 280-350 K. The average relaxation time at constant momentum transfer (Q) shows an Arrhenius behavior in the temperature range investigated

  2. Application of the independent molecule model to elucidate the dynamics of structure I methane hydrate: a third report.

    Science.gov (United States)

    Yoshioki, Shuzo

    2009-01-01

    Two new model systems of methane hydrate, larger than the previous systems, are constructed. One consists of 63 small and large cages with a small cage at the centre. The other has 65 small and large cages with a large cage at the centre. Three different H-bonding network patterns between water are formed, and three random orientations of methane in each cage are chosen. Using the surface water fixed method, we obtained the energy minimum conformations, fitted to the X-ray crystallographic structure. With normal mode analysis, we calculated frequencies of 2915.1 cm(-1) for a small cage, and 2911.0 cm(-1) for a large cage. These frequencies are a little nearer to the Raman spectra than were previous model systems. Treating three force constants of anharmonic potential energy and the strength of H-bonding between methane and water as four parameters, we obtained frequencies of 2913.6 cm(-1) for a small cage, a little lower than the Raman, and 2906.6 cm(-1) for a large cage, a little higher than the Raman. The calculations thus almost reach the Raman spectra.

  3. The adsorption and dissociation of water molecule on goethite (010) surface: A DFT approach

    Energy Technology Data Exchange (ETDEWEB)

    Zhou, Long, E-mail: shuweixia@ouc.edu.cn [Key Laboratory of Marine Chemistry Theory and Technology, Ministry of Education, Ocean University of China, College of Chemistry and Chemical Engineering (China); Xiu, Fangyuan [Key Laboratory of Marine Chemistry Theory and Technology, Ministry of Education, Ocean University of China, College of Chemistry and Chemical Engineering (China); Qiu, Meng [Qingdao Institute of Bioenergy and Bioprocess Technology (China); Xia, Shuwei; Yu, Liangmin [Key Laboratory of Marine Chemistry Theory and Technology, Ministry of Education, Ocean University of China, College of Chemistry and Chemical Engineering (China)

    2017-01-15

    Graphical abstract: The optimized structure of hydrated goethite (010) surface with medium water coverage (water density about 6.7 H{sub 2}O/nm{sup 2}). - Highlights: • Stable adsorption and dissociation structure of H{sub 2}O on goethite (010) surface was investigated by DFT. • Reasonable path for water dissociation was proposed by transitional state analysis. • The mechanism of water adsorption on goethite and binding nature were revealed by PDOS. - Abstract: Using density functional theory (DFT) calculation, we investigate the configuration, stability and electronic properties of fresh cleaved (010) goethite surface (Pnma) and this surface exposed to water monolayer at low, medium and high coverage. Water is predicted to be chemisorbed to the surface, together with the surface reconstruction. The interaction energy of the most stable configuration of both low and medium coverage per water molecule is almost the same (−1.17 eV), while that of high coverage is much lower (less than 1.03 eV). It indicates that highly hydrated surface is less stable. PDOS analysis reveals the adsorption of H{sub 2}O is due to the formation of Fe−O bond, caused by overlapping of Fe's 3d and O's 2p orbitals. Dissociation processes at low and medium water coverage are non-spontaneous; while at high coverage, it can undertake spontaneously both thermodynamically and dynamically. The dissociation paths of all three water coverage are the similar. The proton from one adsorbed water is likely to dissociate to bind to the vicinal surface μ{sub 3}−O as an intermediate product; the proton belonged to μ{sub 3}−O transferred to the neighbor surface μ{sub 2}−O as the dissociative configuration.

  4. Binding of the water of primary hydration to the sodium and cesium salts of deoxyribonucleic acid and potassium hyaluronate

    Science.gov (United States)

    Whitson, K. B.; Lukan, A. M.; Marlowe, R. L.; Lee, S. A.; Anthony, L.; Rupprecht, A.

    1998-08-01

    Differential scanning calorimetry (DSC) has been used to evaluate the average enthalpy of desorption of the water of primary hydration bound to wet-spun films of potassium hyaluronate (KHA) and CsDNA. The enthalpies were measured to be 0.24+/-0.08 eV/H2O molecule for KHA and 0.32+/-0.10 eV/H2O molecule for CsDNA. A Kissinger analysis was used to extract the net activation energy (0.61+/-0.04 eV) for the desorption of this water from KHA by analyzing DSC data acquired at different heating rates. The average effective force constants at 295 K of this water bound to KHA (63+/-3 μdyn/Å) and NaDNA (17+/-4 μdyn/Å) are determined from Rayleigh scattering of Mossbauer radiation data [G. Albanese, A. Deriu, F. Cavatorta, and A. Rupprecht, Hyperfine Interact. 95, 97 (1995)] via a harmonic approximation.

  5. Hydrazine - hydrate water regime and operation of fuel elements

    International Nuclear Information System (INIS)

    Pashevitch, V.I.; Pashevitch, D.V.; Bogancs, J.; Tilky, P.

    1997-01-01

    Water chemistries currently used in WWER reactors are potassium based water chemistry (KOH) to adjust the pH with ammonia or hydrazine as oxygen scavenger. Based on the measurements of Zr 95 which is a corrosion product of the zirconium cladding, it is shown in this paper that the amount of corrosion products accompanying the reactor shutdown is smaller when hydrazine is used. This is particularly obvious on PAKS 1 and 2 when Zr 95 measurements are performed before and after switching the water chemistry from ammonia to hydrazine. It is concluded that the main advantage of using the hydrazine water chemistry is to decrease the thickness of the corrosion product layer formed on the fuel cladding, therefore the fuel temperature can be kept low. It is estimated that the fuel temperature increase due to the layer of corrosion products is 120 deg. C for KOLA 3 which is operated with ammonia water chemistry. (author). 5 figs

  6. Hydrazine - hydrate water regime and operation of fuel elements

    Energy Technology Data Exchange (ETDEWEB)

    Pashevitch, V I; Pashevitch, D V [Pand Co. (Russian Federation); Bogancs, J; Tilky, P [Paks NPP (Hungary)

    1997-02-01

    Water chemistries currently used in WWER reactors are potassium based water chemistry (KOH) to adjust the pH with ammonia or hydrazine as oxygen scavenger. Based on the measurements of Zr 95 which is a corrosion product of the zirconium cladding, it is shown in this paper that the amount of corrosion products accompanying the reactor shutdown is smaller when hydrazine is used. This is particularly obvious on PAKS 1 and 2 when Zr 95 measurements are performed before and after switching the water chemistry from ammonia to hydrazine. It is concluded that the main advantage of using the hydrazine water chemistry is to decrease the thickness of the corrosion product layer formed on the fuel cladding, therefore the fuel temperature can be kept low. It is estimated that the fuel temperature increase due to the layer of corrosion products is 120 deg. C for KOLA 3 which is operated with ammonia water chemistry. (author). 5 figs.

  7. 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

  8. 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.

  9. Theoretical description of biomolecular hydration - Application to A-DNA

    International Nuclear Information System (INIS)

    Garcia, A.E.; Hummer, G.; Soumpasis, D.M.

    1994-01-01

    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) 5 ] 2 and [d(C 5 G 5 )] 2 . We find that this method can accurately reproduce the hydration patterns of A-DNA observed in neutron diffraction experiments on oriented DNA fibers

  10. Morphology studies on gas hydrates interacting with silica gel

    Energy Technology Data Exchange (ETDEWEB)

    Beltran, J.; Servio, P. [McGill Univ., Montreal, PQ (Canada). Dept. of Chemical Engineering

    2008-07-01

    Clathrate hydrates or gas hydrates are non-stoichiometric, crystalline compounds that form when small molecules come in contact with water at certain temperatures and pressures. Natural gas hydrates are found in the ocean bottom and in permafrost regions. It is thought that the amount of energy stored in natural hydrates is at least twice that of all other fossil fuels combined. In addition, trapping carbon dioxide as a hydrate in the bottom of the ocean has been suggested as an alternative means of reducing atmospheric carbon dioxide levels. Naturally occurring clathrates are found in close interaction with fine grained particles of very small mean pore diameters. Even though an increasing amount of hydrate equilibrium data for small diameter porous media has become available, the morphological behavior of hydrates subject to such conditions is yet to be explored. This paper presented a study that visually examined hydrate formation and decomposition of gas hydrates while interacting with fine grains of silica gel. The study showed still frames from high-resolution video recordings for hydrate formation and decomposition. The paper discussed the experiment including the apparatus as well as the results of hydrate formation and hydrate dissociation. This study enabled for the first time to observe clathrate morphology while hydrates interacted closely with fine grain particles with small mean pore diameters. 9 refs., 8 figs.

  11. Skin hydration: interplay between molecular dynamics, structure and water uptake in the stratum corneum.

    Science.gov (United States)

    Mojumdar, Enamul Haque; Pham, Quoc Dat; Topgaard, Daniel; Sparr, Emma

    2017-11-16

    Hydration is a key aspect of the skin that influences its physical and mechanical properties. Here, we investigate the interplay between molecular and macroscopic properties of the outer skin layer - the stratum corneum (SC) and how this varies with hydration. It is shown that hydration leads to changes in the molecular arrangement of the peptides in the keratin filaments as well as dynamics of C-H bond reorientation of amino acids in the protruding terminals of keratin protein within the SC. The changes in molecular structure and dynamics occur at a threshold hydration corresponding to ca. 85% relative humidity (RH). The abrupt changes in SC molecular properties coincide with changes in SC macroscopic swelling properties as well as mechanical properties in the SC. The flexible terminals at the solid keratin filaments can be compared to flexible polymer brushes in colloidal systems, creating long-range repulsion and extensive swelling in water. We further show that the addition of urea to the SC at reduced RH leads to similar molecular and macroscopic responses as the increase in RH for SC without urea. The findings provide new molecular insights to deepen the understanding of how intermediate filament organization responds to changes in the surrounding environment.

  12. Excitation of chiral molecules and their hydrated by clusters by R2PI studies

    International Nuclear Information System (INIS)

    Satta, M.; Piccirillo, S.; Scuderia, D.; Paladini, A.; Della Vedova, L.; Filippi, A.; Speranza, M.; Giardini, A.

    2002-01-01

    Molecular clusters play a key role in the molecular scale explanation of macroscopic phenomena, being in between the isolated gas phase and the condensed phase. Thus, allowing to obtain information on intermolecular forces simply by studying the physicochemical properties of isolated clusters and to extend them macroscopic systems. A comprehensive study of the short-range forces operating in the molecular complexes between several chiral aromatic alcohols (M) and water (solv), through the application of mass resolved REMPI technique is reported. The experimental setup was composed by a supersonic molecular beam, two Nd-YAG pumped dye lasers and a time of flight mass spectrometer. The photoionization efficiency curves were obtained as follows: a) the first exciting laser (hv 1 ) was tuned on the S 1 0 transition of the species of interest; b) the laser intensity is lowered to about 1 % of the initial fluence to minimize the hv 1 absorption; c)a second laser (hv 2 ) is scanned through the cluster ionization and fragmentation threshold regions. The binding energy of the M-solv adduct was computed from the differences between its dissociative ionization threshold and the ionization threshold of bare M. The mass-resolved one colour R2PI excitation spectra of l-tetralol (THN R ), THN R -H 2 O, l i ndanol (I R ) and I R -H 2 O are given. (nevyjel)

  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. STUDY ON THE FACTORS INFLUENCING HYDRATION AND WATER RETENTION CAPACITY OF MEAT

    OpenAIRE

    DANIELA IANIłCHI; CARMEN NICOLAE; CRISTIANA DIACONESCU; GABRIELA MALOS; I. G. MALOS

    2008-01-01

    Top-quality food produce and high profitability in processing requires high quality in raw materials. Therefore, to achieve these objectives, it is imperative to know the properties of the war materials, and the factors that influence these properties.The properties of the meat directly involved in increasing economic efficiency and final produce quality are the so-called technological properties: hydration capacity and water retention capacity of meat. These properties are determined by some...

  15. Hydration dynamics of hyaluronan and dextran.

    Science.gov (United States)

    Hunger, Johannes; Bernecker, Anja; Bakker, Huib J; Bonn, Mischa; Richter, Ralf P

    2012-07-03

    Hyaluronan is a polysaccharide, which is ubiquitous in vertebrates and has been reported to be strongly hydrated in a biological environment. We study the hydration of hyaluronan in solution using the rotational dynamics of water as a probe. We measure these dynamics with polarization-resolved femtosecond-infrared and terahertz time-domain spectroscopies. Both experiments reveal that a subensemble of water molecules is slowed down in aqueous solutions of hyaluronan amounting to ∼15 water molecules per disaccharide unit. This quantity is consistent with what would be expected for the first hydration shell. Comparison of these results to the water dynamics in aqueous dextran solution, a structurally similar polysaccharide, yields remarkably similar results. This suggests that the observed interaction with water is a common feature for hydrophilic polysaccharides and is not specific to hyaluronan. Copyright © 2012 Biophysical Society. Published by Elsevier Inc. All rights reserved.

  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. LABORATORY STRATEGIES FOR HYDRATE FORMATION IN FINE-GRAINED SEDIMENTS

    KAUST Repository

    Lei, L.; Santamarina, Carlos

    2018-01-01

    Fine‐grained sediments limit hydrate nucleation, shift the phase boundary and hinder gas supply. Laboratory experiments in this study explore different strategies to overcome these challenges, including the use of a more soluble guest molecule rather than methane, grain‐scale gas‐storage within porous diatoms, ice‐to‐hydrate transformation to grow lenses at predefined locations, forced gas injection into water saturated sediments, and long‐term guest molecule transport. Tomographic images, thermal and pressure data provide rich information on hydrate formation and morphology. Results show that hydrate formation is inherently displacive in fine‐grained sediments; lenses are thicker and closer to each other in compressible, high specific surface area sediments subjected to low effective stress. Temperature and pressure trajectories follow a shifted phase boundary that is consistent with capillary effects. Exo‐pore growth results in freshly formed hydrate with a striped and porous structure; this open structure becomes an effective pathway for gas transport to the growing hydrate front. Ice‐to‐hydrate transformation goes through a liquid stage at pre‐melt temperatures; then, capillarity and cryogenic suction compete, and some water becomes imbibed into the sediment faster than hydrate reformation. The geometry of hydrate lenses and the internal hydrate structure continue evolving long after the exothermal response to hydrate formation has completely decayed. Multiple time‐dependent processes occur during hydrate formation, including gas, water and heat transport, sediment compressibility, reaction rate and the stochastic nucleation process. Hydrate formation strategies conceived for this study highlight the inherent difficulties in emulating hydrate formation in fine‐grained sediments within the relatively short time‐scale available for laboratory experiments.

  18. LABORATORY STRATEGIES FOR HYDRATE FORMATION IN FINE-GRAINED SEDIMENTS

    KAUST Repository

    Lei, L.

    2018-04-02

    Fine‐grained sediments limit hydrate nucleation, shift the phase boundary and hinder gas supply. Laboratory experiments in this study explore different strategies to overcome these challenges, including the use of a more soluble guest molecule rather than methane, grain‐scale gas‐storage within porous diatoms, ice‐to‐hydrate transformation to grow lenses at predefined locations, forced gas injection into water saturated sediments, and long‐term guest molecule transport. Tomographic images, thermal and pressure data provide rich information on hydrate formation and morphology. Results show that hydrate formation is inherently displacive in fine‐grained sediments; lenses are thicker and closer to each other in compressible, high specific surface area sediments subjected to low effective stress. Temperature and pressure trajectories follow a shifted phase boundary that is consistent with capillary effects. Exo‐pore growth results in freshly formed hydrate with a striped and porous structure; this open structure becomes an effective pathway for gas transport to the growing hydrate front. Ice‐to‐hydrate transformation goes through a liquid stage at pre‐melt temperatures; then, capillarity and cryogenic suction compete, and some water becomes imbibed into the sediment faster than hydrate reformation. The geometry of hydrate lenses and the internal hydrate structure continue evolving long after the exothermal response to hydrate formation has completely decayed. Multiple time‐dependent processes occur during hydrate formation, including gas, water and heat transport, sediment compressibility, reaction rate and the stochastic nucleation process. Hydrate formation strategies conceived for this study highlight the inherent difficulties in emulating hydrate formation in fine‐grained sediments within the relatively short time‐scale available for laboratory experiments.

  19. 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.

  20. Theoretical study on microhydration of SeO42-: On the number of water molecules necessary to stabilize the dianion

    Science.gov (United States)

    Pathak, Arup Kumar

    2012-01-01

    Microhydration of SeO42-·nH2O (n = 1-5) clusters are reported at B3LYP/Aug-cc-pvtz level of theory. Lower size hydrated clusters are stabilized by only double-hydrogen-bonding arrangements and the most stable conformer for higher size cluster (n > 3) contains a cyclic water ring. It is observed that at least one water molecule is necessary to stabilize the dianion in the gas phase against spontaneous electron loss. The microscopic theory based expression provides a route to predict the instability of bare SeO42- and to obtain the VDE for a wide range of cluster sizes including the bulk from the knowledge of the same for a few stable hydrated clusters.

  1. [Interactions of DNA bases with individual water molecules. Molecular mechanics and quantum mechanics computation results vs. experimental data].

    Science.gov (United States)

    Gonzalez, E; Lino, J; Deriabina, A; Herrera, J N F; Poltev, V I

    2013-01-01

    To elucidate details of the DNA-water interactions we performed the calculations and systemaitic search for minima of interaction energy of the systems consisting of one of DNA bases and one or two water molecules. The results of calculations using two force fields of molecular mechanics (MM) and correlated ab initio method MP2/6-31G(d, p) of quantum mechanics (QM) have been compared with one another and with experimental data. The calculations demonstrated a qualitative agreement between geometry characteristics of the most of local energy minima obtained via different methods. The deepest minima revealed by MM and QM methods correspond to water molecule position between two neighbor hydrophilic centers of the base and to the formation by water molecule of hydrogen bonds with them. Nevertheless, the relative depth of some minima and peculiarities of mutual water-base positions in' these minima depend on the method used. The analysis revealed insignificance of some differences in the results of calculations performed via different methods and the importance of other ones for the description of DNA hydration. The calculations via MM methods enable us to reproduce quantitatively all the experimental data on the enthalpies of complex formation of single water molecule with the set of mono-, di-, and trimethylated bases, as well as on water molecule locations near base hydrophilic atoms in the crystals of DNA duplex fragments, while some of these data cannot be rationalized by QM calculations.

  2. Absolute proton hydration free energy, surface potential of water, and redox potential of the hydrogen electrode from first principles: QM/MM MD free-energy simulations of sodium and potassium hydration

    Science.gov (United States)

    Hofer, Thomas S.; Hünenberger, Philippe H.

    2018-06-01

    The absolute intrinsic hydration free energy GH+,w a t ◦ of the proton, the surface electric potential jump χwa t ◦ upon entering bulk water, and the absolute redox potential VH+,w a t ◦ of the reference hydrogen electrode are cornerstone quantities for formulating single-ion thermodynamics on absolute scales. They can be easily calculated from each other but remain fundamentally elusive, i.e., they cannot be determined experimentally without invoking some extra-thermodynamic assumption (ETA). The Born model provides a natural framework to formulate such an assumption (Born ETA), as it automatically factors out the contribution of crossing the water surface from the hydration free energy. However, this model describes the short-range solvation inaccurately and relies on the choice of arbitrary ion-size parameters. In the present study, both shortcomings are alleviated by performing first-principle calculations of the hydration free energies of the sodium (Na+) and potassium (K+) ions. The calculations rely on thermodynamic integration based on quantum-mechanical molecular-mechanical (QM/MM) molecular dynamics (MD) simulations involving the ion and 2000 water molecules. The ion and its first hydration shell are described using a correlated ab initio method, namely resolution-of-identity second-order Møller-Plesset perturbation (RIMP2). The next hydration shells are described using the extended simple point charge water model (SPC/E). The hydration free energy is first calculated at the MM level and subsequently increased by a quantization term accounting for the transformation to a QM/MM description. It is also corrected for finite-size, approximate-electrostatics, and potential-summation errors, as well as standard-state definition. These computationally intensive simulations provide accurate first-principle estimates for GH+,w a t ◦, χwa t ◦, and VH+,w a t ◦, reported with statistical errors based on a confidence interval of 99%. The values obtained

  3. On the Several Molecules and Nanostructures of Water

    Directory of Open Access Journals (Sweden)

    Cynthia Kolb Whitney

    2012-01-01

    Full Text Available This paper investigates the water molecule from a variety of viewpoints. Water can involve different isotopes of Hydrogen and Oxygen, it can form differently shaped isomer molecules, and, when frozen, it occupies space differently than most other substances do. The tool for conducting the investigation of all this is called ‘Algebraic Chemistry’. This tool is a quantitative model for predicting the energy budget for all sorts of changes between different ionization states of atoms that are involved in chemical reactions and in changes of physical state. The model is based on consistent patterns seen in empirical data about ionization potentials, together with rational scaling laws that can interpolate and extrapolate for situations where no data are available. The results of the investigation of the water molecule include comments, both positive and negative, about technologies involving heavy water, poly water, Brown’s gas, and cold fusion.

  4. Quantum Behavior of Water Molecules Confined to Nanocavities in Gemstones.

    Science.gov (United States)

    Gorshunov, Boris P; Zhukova, Elena S; Torgashev, Victor I; Lebedev, Vladimir V; Shakurov, Gil'man S; Kremer, Reinhard K; Pestrjakov, Efim V; Thomas, Victor G; Fursenko, Dimitry A; Dressel, Martin

    2013-06-20

    When water is confined to nanocavities, its quantum mechanical behavior can be revealed by terahertz spectroscopy. We place H2O molecules in the nanopores of a beryl crystal lattice and observe a rich and highly anisotropic set of absorption lines in the terahertz spectral range. Two bands can be identified, which originate from translational and librational motions of the water molecule isolated within the cage; they correspond to the analogous broad bands in liquid water and ice. In the present case of well-defined and highly symmetric nanocavities, the observed fine structure can be explained by macroscopic tunneling of the H2O molecules within a six-fold potential caused by the interaction of the molecule with the cavity walls.

  5. 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.

  6. 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.

  7. FY1995 molecular control technology for mining of methane-gas-hydrate; 1995 nendo methane hydrate no bunshi seigyo mining

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1997-03-01

    The objectives of the investigation are as follows: 1) developing a method to control formation/dissociation of methane-gas-hydrate, 2) developing a technology to displace methane gas by CO{sub 2} in methane-gas-hydrate deposit, 3) developing a technology to produce methane gas from the deposit efficiently. The final purpose of the project is to create new mining industry that solves both the problems of energy and global environment. 1) Clustering of water molecules is found to play the key role in the methane gas hydrate formation. 2) Equilibrium properties and kinetics of gas hydrates formation and dissociation in bulk-scale gas-hydrate are clarified in the practical environmental conditions. 3) Particle size of hydrate deposit influences the formation and dissociation of bulk-scale gas-hydrate crystal. 4) Mass transfer between gas and liquid phase in turbulent bubbly flow is a function of bubble diameter. The mass transfer depends on interfacial dynamics. (NEDO)

  8. Reconsideration on Hydration of Sodium Ion: From Micro-Hydration to Bulk Hydration

    Science.gov (United States)

    Yongquan, Zhou; Chunhui, Fang; Yan, Fang; Fayan, Zhu; Haiwen, Ge; Hongyan, Liu

    2017-12-01

    Micro hydration structures of the sodium ion, [Na(H2O) n ]+, n = 1-12, were probed by density functional theory (DFT) at B3LYP/aug-cc-pVDZ level in both gaseous and aqueous phase. The predicted equilibrium sodium-oxygen distance of 0.240 nm at the present level of theory. The four-, five- and six-coordinated cluster can transform from each other at the ambient condition. The analysis of the successive water binding energy and natural charge population (NBO) on Na+ clearly shows that the influence of Na+ on the surrounding water molecules goes beyond the first hydration shell with the hydration number of 6. The Car-Parrinello molecular dynamic simulation shows that only the first hydration sphere can be found, and the hydration number of Na+ is 5.2 and the hydration distance ( r Na-O) is 0.235 nm. All our simulations mentioned in the present paper show an excellent agreement with the diffraction result from X-ray scattering study.

  9. Crystal water as the mol-ecular glue for obtaining different co-crystal ratios: the case of gallic acid tris-caffeine hexa-hydrate.

    Science.gov (United States)

    Vella-Zarb, L; Baisch, U

    2018-04-01

    The crystal structure of the hexa-hydrate co-crystal of gallic acid and caffeine, C 7 H 6 O 5 ·3C 8 H 10 N 4 O 2 ·6H 2 O or GAL3CAF·6H 2 O , is a remarkable example of the importance of hydrate water acting as structural glue to facilitate the crystallization of two components of different stoichiometries and thus to compensate an imbalance of hydrogen-bond donors and acceptors. The water mol-ecules provide the additional hydrogen bonds required to form a crystalline solid. Whereas the majority of hydrogen bonds forming the inter-molecular network between gallic acid and caffeine are formed by crystal water, only one direct classical hydrogen bond between two mol-ecules is formed between the carb-oxy-lic oxygen of gallic acid and the carbonyl oxygen of caffeine with d ( D ⋯ A ) = 2.672 (2) Å. All other hydrogen bonds either involve crystal water or utilize protonated carbon atoms as donors.

  10. Modeling dissociation behaviour of methane hydrate in porous soil media

    Energy Technology Data Exchange (ETDEWEB)

    Jayasinghe, A.G.; Grozic, J.L.H. [Calgary Univ., AB (Canada). Dept. of Civil Engineering

    2008-07-01

    Gas hydrates, or clathrates, exist in the form of crystalline solid structures of hydrogen bonded water molecules where the lattice cages are occupied by guest gas molecules. Methane gas hydrates are the most common. As such, hydrate bearing sediments are considered to be a potential future energy resource. Gas hydrates also function as a source or sink for atmospheric methane, which may influence global warming. The authors emphasized that an understanding of the behaviour of soils containing gas hydrates is necessary in order to develop ways of recovering the vast gas resources that exist in the form of hydrates, particularly since hydrates are also suspected to be a potential factor in the initiation and propagation of submarine slope failures. Gas hydrate dissociation occurs when water and gas are released, resulting in an increase in pore fluid pressure, thereby causing significant reductions in effective stress leading to sediment failure. Dissociation may occur as a result of pressure reductions or increases in temperature. This study focused on the strength and deformation behaviour of hydrate bearing soils associated with temperature induced dissociation. Modeling the dissociation behavior of hydrates in porous soil media involves an understanding of the geomechanics of hydrate dissociation. This paper addressed the issue of coupling the hydrate dissociation problem with the soil deformation problem. A mathematical framework was constructed in which the thermally stimulated hydrate dissociation process in porous soil media under undrained conditions was considered with conduction heat transfer. It was concluded that a knowledge of geomechanical response of hydrate bearing sediments will enable better estimates of benefits and risks associated with the recovery process, thereby ensuring safe and economical exploration. 20 refs., 1 fig., 1 appendix.

  11. Towards ligand docking including explicit interface water molecules.

    Directory of Open Access Journals (Sweden)

    Gordon Lemmon

    Full Text Available Small molecule docking predicts the interaction of a small molecule ligand with a protein at atomic-detail accuracy including position and conformation the ligand but also conformational changes of the protein upon ligand binding. While successful in the majority of cases, docking algorithms including RosettaLigand fail in some cases to predict the correct protein/ligand complex structure. In this study we show that simultaneous docking of explicit interface water molecules greatly improves Rosetta's ability to distinguish correct from incorrect ligand poses. This result holds true for both protein-centric water docking wherein waters are located relative to the protein binding site and ligand-centric water docking wherein waters move with the ligand during docking. Protein-centric docking is used to model 99 HIV-1 protease/protease inhibitor structures. We find protease inhibitor placement improving at a ratio of 9:1 when one critical interface water molecule is included in the docking simulation. Ligand-centric docking is applied to 341 structures from the CSAR benchmark of diverse protein/ligand complexes [1]. Across this diverse dataset we see up to 56% recovery of failed docking studies, when waters are included in the docking simulation.

  12. The Structure and Transport of Water and Hydrated Ions Within Hydrophobic, Nanoscale Channels

    International Nuclear Information System (INIS)

    Holt, J.K.; Herberg, J.L.; Wu, Y.; Schwegler, E.; Mehta, A.

    2009-01-01

    The purpose of this project includes an experimental and modeling investigation into water and hydrated ion structure and transport at nanomaterials interfaces. This is a topic relevant to understanding the function of many biological systems such as aquaporins that efficiently shuttle water and ion channels that permit selective transport of specific ions across cell membranes. Carbon nanotubes (CNT) are model nanoscale, hydrophobic channels that can be functionalized, making them artificial analogs for these biological channels. This project investigates the microscopic properties of water such as water density distributions and dynamics within CNTs using Nuclear Magnetic Resonance (NMR) and the structure of hydrated ions at CNT interfaces via X-ray Absorption Spectroscopy (XAS). Another component of this work is molecular simulation, which can predict experimental measurables such as the proton relaxation times, chemical shifts, and can compute the electronic structure of CNTs. Some of the fundamental questions this work is addressing are: (1) what is the length scale below which nanoscale effects such as molecular ordering become important, (2) is there a relationship between molecular ordering and transport?, and (3) how do ions interact with CNT interfaces? These are questions of interest to the scientific community, but they also impact the future generation of sensors, filters, and other devices that operate on the nanometer length scale. To enable some of the proposed applications of CNTs as ion filtration media and electrolytic supercapacitors, a detailed knowledge of water and ion structure at CNT interfaces is critical.

  13. Simulation and Characterization of Methane Hydrate Formation

    Science.gov (United States)

    Dhakal, S.; Gupta, I.

    2017-12-01

    The ever rising global energy demand dictates human endeavor to explore and exploit new and innovative energy sources. As conventional oil and gas reserves deplete, we are constantly looking for newer sources for sustainable energy. Gas hydrates have long been discussed as the next big energy resource to the earth. Its global occurrence and vast quantity of natural gas stored is one of the main reasons for such interest in its study and exploration. Gas hydrates are solid crystalline substances with trapped molecules of gas inside cage-like crystals of water molecules. Gases such as methane, ethane, propane and carbon dioxide can form hydrates but in natural state, methane hydrates are the most common. Subsurface geological conditions with high pressure and low temperature favor the formation and stability of gas hydrates. While the occurrence and potential of gas hydrates as energy source has long been studied, there are still gaps in knowledge, especially in the quantitative research of gas hydrate formation and reservoir characterization. This study is focused on exploring and understanding the geological setting in which gas hydrates are formed and the subsequent changes in rock characteristics as they are deposited. It involves the numerical simulation of methane gas flow through fault to form hydrates. The models are representative of the subsurface geologic setting of Gulf of Mexico with a fault through layers of shale and sandstone. Hydrate formation simulated is of thermogenic origin. The simulations are conducted using TOUGH+HYDRATE, a numerical code developed at the Lawrence Berkley National Laboratory for modeling multiphase flow through porous medium. Simulation results predict that as the gas hydrates form in the pores of the model, the porosity, permeability and other rock properties are altered. Preliminary simulation results have shown that hydrates begin to form in the fault zone and gradually in the sandstone layers. The increase in hydrate

  14. Phase equilibrium condition measurements in nitrogen and air clathrate hydrate forming systems at temperatures below freezing point of water

    International Nuclear Information System (INIS)

    Yasuda, Keita; Oto, Yuya; Shen, Renkai; Uchida, Tsutomu; Ohmura, Ryo

    2013-01-01

    Highlights: • Phase equilibrium conditions in the nitrogen and modelled air hydrate forming systems are measured. • Measurements are conducted at temperatures below the freezing point of water. • Results have relevance to the air hydrate formation in the ice sheets. • Measured data are quantitatively compared with the previously reported values. • Range of the equilibrium measurements was from (242 to 268) K. -- Abstract: Contained in this paper are the three phase equilibrium conditions of the (ice + clathrate hydrate + guest-rich) vapour in the (nitrogen + water) and the modelled (air + water) systems at temperatures below the freezing point of water. The precise determination of the equilibrium conditions in those systems are of importance for the analysis of the past climate change using the cored samples from the ice sheets at Antarctica and Greenland because the air hydrates keep the ancient climate signals. The mole ratio of the modelled air composed of nitrogen and oxygen is 0.790:0.210. The equilibrium conditions were measured by the batch, isochoric procedure. The temperature range of the measurements in the nitrogen hydrate forming system is (244.05 < T < 266.55) K and the corresponding equilibrium pressure range is (7.151 < p < 12.613) MPa. The temperature range of the measurements in the modelled air hydrate forming system is (242.55 < T < 267.85) K, and the corresponding equilibrium pressure range is (6.294 < p < 12.144) MPa. The data obtained quantitatively compared with the previously reported data

  15. Effect of the sulphur atom on geometry and spectra of the biomolecule 2-thiouracil and in the WC base pair 2-thiouridine-adenosine. Influence of water in the first hydration shell.

    Science.gov (United States)

    Alcolea Palafox, M; Rastogi, V K; Singh, S P

    2018-04-01

    The effect of the sulphur atom on 2-thiouracil (2TU) and 2-thiouridine molecules, as compared with uracil and uridine molecules, respectively, was carried out in several environments. The predicted IR spectrum of 2TU in the isolated state was compared with that obtained for uracil molecule and with those reported experimentally in matrix isolation. Its crystal unit cell in the solid state was simulated through a tetramer form using DFT methods for the first time. The calculated Raman spectrum was compared to the experimental ones in the solid state. A linear scaling procedure was used for this task. The first hydration shell was simulated by explicit number of water molecules surrounding 2TU up to 30 and was compared with that obtained in uracil molecule. Water molecules 'distributed' around 2TU was preferred over that 'clustering', because it can better reproduce the hydration and their effects on different parameters of the molecular structure of 2TU and uracil. The total atomic charges and several calculated thermodynamic parameters were discussed. The effect of the sulphur atom on the Watson-Crick (WC) and reverse WC base pair uridine-adenosine was estimated, and the CP corrected interaction energies were calculated. 2-thiouridine has a weaker WC pair than that with uridine, although its slight higher dipole moment (μ) facilitates the interaction with the water molecules. Several helical parameters were determined.

  16. Transport behavior of water molecules through two-dimensional nanopores

    International Nuclear Information System (INIS)

    Zhu, Chongqin; Li, Hui; Meng, Sheng

    2014-01-01

    Water transport through a two-dimensional nanoporous membrane has attracted increasing attention in recent years thanks to great demands in water purification and desalination applications. However, few studies have been reported on the microscopic mechanisms of water transport through structured nanopores, especially at the atomistic scale. Here we investigate the microstructure of water flow through two-dimensional model graphene membrane containing a variety of nanopores of different size by using molecular dynamics simulations. Our results clearly indicate that the continuum flow transits to discrete molecular flow patterns with decreasing pore sizes. While for pores with a diameter ≥15 Å water flux exhibits a linear dependence on the pore area, a nonlinear relationship between water flux and pore area has been identified for smaller pores. We attribute this deviation from linear behavior to the presence of discrete water flow, which is strongly influenced by the water-membrane interaction and hydrogen bonding between water molecules

  17. Structures of water molecules in carbon nanotubes under electric fields

    International Nuclear Information System (INIS)

    Winarto,; Takaiwa, Daisuke; Yamamoto, Eiji; Yasuoka, Kenji

    2015-01-01

    Carbon nanotubes (CNTs) are promising for water transport through membranes and for use as nano-pumps. The development of CNT-based nanofluidic devices, however, requires a better understanding of the properties of water molecules in CNTs because they can be very different from those in the bulk. Using all-atom molecular dynamics simulations, we investigate the effect of axial electric fields on the structure of water molecules in CNTs having diameters ranging from (7,7) to (10,10). The water dipole moments were aligned parallel to the electric field, which increases the density of water inside the CNTs and forms ordered ice-like structures. The electric field induces the transition from liquid to ice nanotubes in a wide range of CNT diameters. Moreover, we found an increase in the lifetime of hydrogen bonds for water structures in the CNTs. Fast librational motion breaks some hydrogen bonds, but the molecular pairs do not separate and the hydrogen bonds reform. Thus, hydrogen bonds maintain the water structure in the CNTs, and the water molecules move collectively, decreasing the axial diffusion coefficient and permeation rate

  18. The role of water molecules in computational drug design.

    Science.gov (United States)

    de Beer, Stephanie B A; Vermeulen, Nico P E; Oostenbrink, Chris

    2010-01-01

    Although water molecules are small and only consist of two different atom types, they play various roles in cellular systems. This review discusses their influence on the binding process between biomacromolecular targets and small molecule ligands and how this influence can be modeled in computational drug design approaches. Both the structure and the thermodynamics of active site waters will be discussed as these influence the binding process significantly. Structurally conserved waters cannot always be determined experimentally and if observed, it is not clear if they will be replaced upon ligand binding, even if sufficient space is available. Methods to predict the presence of water in protein-ligand complexes will be reviewed. Subsequently, we will discuss methods to include water in computational drug research. Either as an additional factor in automated docking experiments, or explicitly in detailed molecular dynamics simulations, the effect of water on the quality of the simulations is significant, but not easily predicted. The most detailed calculations involve estimates of the free energy contribution of water molecules to protein-ligand complexes. These calculations are computationally demanding, but give insight in the versatility and importance of water in ligand binding.

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

    International Nuclear Information System (INIS)

    Krishnan, N. M. Anoop; Wang, Bu; Falzone, Gabriel; Le Pape, Yann; Neithalath, Narayanan

    2016-01-01

    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/SiO_2 (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. Altogether, 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.

  20. 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/SiO 2 (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.

  1. Physicochemical Properties of α-Form Hydrated Crystalline Phase of 3-(10-Carboxydecyl)-1,1,1,3,5,5,5-heptamethyl Trisiloxane/Higher alcohol/Polyoxyethylene (5 mol) Glyceryl monostearate/Water System.

    Science.gov (United States)

    Uyama, Makoto; Araki, Hidefumi; Fukuhara, Tadao; Watanabe, Kei

    2018-06-07

    The α-form hydrated crystalline phase (often called as an α-gel) is one of the hydrated crystalline phases which can be exhibited by surfactants and lipids. In this study, a novel system of an α-form hydrated crystal was developed, composed of 3-(10-carboxydecyl)-1,1,1,3,5,5,5-heptamethyl trisiloxane (CDTS), polyoxyethylene (5 mol) glyceryl monostearate (GMS-5), higher alcohol. This is the first report to indicate that a silicone surfactant can form an α-form hydrated crystal. The physicochemical properties of this system were characterized by small and wide angle X-ray scattering (SWAXS), differential scanning calorimetry (DSC), and diffusion-ordered NMR spectroscopy (DOSY) experiments. SWAXS and DSC measurements revealed that a plurality of crystalline phases coexist in the CDTS/higher alcohol/water ternary system. By adding GMS-5 to the ternary system, however, a wide region of a single α-form hydrated crystalline phase was obtained. The self-diffusion coefficients (D sel ) from the NMR measurements suggested that all of the CDTS, GMS-5, and higher alcohol molecules were incorporated into the same α-form hydrated crystals.

  2. 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

  3. Effect of water molecule distribution on the quantitative XRD analysis in the case of Na-montmorillonite exchanged Cu2+

    International Nuclear Information System (INIS)

    Oueslati, W.; Meftah, M.; Ben Rhaiem, H.; Ben Haj Amara, A.

    2010-01-01

    Document available in extended abstract form only. Several theoretical models are proposed to describe hydration process for Wyoming-montmorillonite clay exchanged Na + or Cu 2+ . They propose some theoretical distribution and disposition for water molecule in the inter-lamellar space in the case of homogeneous and inter-stratified hydration states. For example, Ben Brahim et al. (1983a) studied the interlayer structure (atomic positions of interlayer cations) and associated H 2 O molecules of Na-saturated montmorillonite and beidellite samples. Moore and Hower (1986) studied ordered structures composed of mono-hydrated and collapsed interlayers in montmorillonite, and Cuadros (1996) estimated the H 2 O content of smectite as a function of the interlayer cation. Using similar approach, Ferrage et al (2005b) proposed a discreet distribution of water molecule layer in the same z coordinate of the exchangeable cation with inhomogeneous distribution. This heterogeneity was attributed to the surface charge. The main objective of this study is to characterize the structural changes in the theoretical XRD profile, induced by different water molecule distribution, used to simulate experimental XRD patterns in the case of Na-montmorillonite exchanged Cu 2+ . This problem was achieved by quantitative XRD analysis using an indirect method based on the comparison of the experimental 001 reflections obtained from oriented films patterns with those calculated from structural models. The starting materials were Ca-montmorillonite originated from bentonites of Wyoming (USA). The XRD patterns were obtained by reflection setting with a D8 ADVANCE Bruker installation using Cu-Kα radiation and equipped with solid state detector. Intensities were measured at an interval of 2Θ 0.04 deg. and 40-50 s counting time per step. The diffracted intensity was calculated according to the matrix formalism detailed by Drits and Tchoubar, (1990). The fitting strategies was detailed by Ferrage et

  4. STUDY ON THE FACTORS INFLUENCING HYDRATION AND WATER RETENTION CAPACITY OF MEAT

    Directory of Open Access Journals (Sweden)

    DANIELA IANIłCHI

    2008-10-01

    Full Text Available Top-quality food produce and high profitability in processing requires high quality in raw materials. Therefore, to achieve these objectives, it is imperative to know the properties of the war materials, and the factors that influence these properties.The properties of the meat directly involved in increasing economic efficiency and final produce quality are the so-called technological properties: hydration capacity and water retention capacity of meat. These properties are determined by some factors belonging to the intrinsic quality of meat, animal slaughter methods, technological operations applied to the meat, and the auxiliary materials used.

  5. Heterogeneous Nucleation of Methane Hydrate in a Water-Decane-Methane Emulsion

    Science.gov (United States)

    Shestakov, V. A.; Kosyakov, V. I.; Manakov, A. Yu.; Stoporev, A. S.; Grachev, E. V.

    2018-07-01

    Heterogeneous nucleation in disperse systems with metastable disperse phases plays an important role in the mechanisms of environmental and technological processes. The effect the concentration and activity of particles that initiate the formation of a new phase have on nucleation processes in such systems is considered. An approach is proposed that allows construction of a spectrum of particle activity characterizing the features of nucleation in a sample, based on the fraction of crystallized droplets depending on the level of supercooling and the use of Weibull's distribution. The proposed method is used to describe experimental data on the heterogeneous nucleation of methane hydrate in an emulsion in a water-decane-methane system.

  6. Structure and dynamics of water and lipid molecules in charged anionic DMPG lipid bilayer membranes

    International Nuclear Information System (INIS)

    Rønnest, A. K.; Peters, G. H.; Hansen, F. Y.; Taub, H.; Miskowiec, A.

    2016-01-01

    Molecular dynamics simulations have been used to investigate the influence of the valency of counter-ions on the structure of freestanding bilayer membranes of the anionic 1,2-dimyristoyl-sn-glycero-3-phosphoglycerol (DMPG) lipid at 310 K and 1 atm. At this temperature, the membrane is in the fluid phase with a monovalent counter-ion and in the gel phase with a divalent counter-ion. The diffusion constant of water as a function of its depth in the membrane has been determined from mean-square-displacement calculations. Also, calculated incoherent quasielastic neutron scattering functions have been compared to experimental results and used to determine an average diffusion constant for all water molecules in the system. On extrapolating the diffusion constants inferred experimentally to a temperature of 310 K, reasonable agreement with the simulations is obtained. However, the experiments do not have the sensitivity to confirm the diffusion of a small component of water bound to the lipids as found in the simulations. In addition, the orientation of the dipole moment of the water molecules has been determined as a function of their depth in the membrane. Previous indirect estimates of the electrostatic potential within phospholipid membranes imply an enormous electric field of 10 8 –10 9 V m −1 , which is likely to have great significance in controlling the conformation of translocating membrane proteins and in the transfer of ions and molecules across the membrane. We have calculated the membrane potential for DMPG bilayers and found ∼1 V (∼2 ⋅ 10 8 V m −1 ) when in the fluid phase with a monovalent counter-ion and ∼1.4 V (∼2.8 ⋅ 10 8 V m −1 ) when in the gel phase with a divalent counter-ion. The number of water molecules for a fully hydrated DMPG membrane has been estimated to be 9.7 molecules per lipid in the gel phase and 17.5 molecules in the fluid phase, considerably smaller than inferred experimentally for 1,2-dimyristoyl-sn-glycero-3

  7. Structure and dynamics of water and lipid molecules in charged anionic DMPG lipid bilayer membranes

    Energy Technology Data Exchange (ETDEWEB)

    Rønnest, A. K.; Peters, G. H.; Hansen, F. Y., E-mail: flemming@kemi.dtu.dk [Department of Chemistry, Technical University of Denmark, IK 207 DTU, DK-2800 Lyngby (Denmark); Taub, H.; Miskowiec, A. [Department of Physics and Astronomy and the University of Missouri Research Reactor,University of Missouri, Columbia, Missouri 65211 (United States)

    2016-04-14

    Molecular dynamics simulations have been used to investigate the influence of the valency of counter-ions on the structure of freestanding bilayer membranes of the anionic 1,2-dimyristoyl-sn-glycero-3-phosphoglycerol (DMPG) lipid at 310 K and 1 atm. At this temperature, the membrane is in the fluid phase with a monovalent counter-ion and in the gel phase with a divalent counter-ion. The diffusion constant of water as a function of its depth in the membrane has been determined from mean-square-displacement calculations. Also, calculated incoherent quasielastic neutron scattering functions have been compared to experimental results and used to determine an average diffusion constant for all water molecules in the system. On extrapolating the diffusion constants inferred experimentally to a temperature of 310 K, reasonable agreement with the simulations is obtained. However, the experiments do not have the sensitivity to confirm the diffusion of a small component of water bound to the lipids as found in the simulations. In addition, the orientation of the dipole moment of the water molecules has been determined as a function of their depth in the membrane. Previous indirect estimates of the electrostatic potential within phospholipid membranes imply an enormous electric field of 10{sup 8}–10{sup 9} V m{sup −1}, which is likely to have great significance in controlling the conformation of translocating membrane proteins and in the transfer of ions and molecules across the membrane. We have calculated the membrane potential for DMPG bilayers and found ∼1 V (∼2 ⋅ 10{sup 8} V m{sup −1}) when in the fluid phase with a monovalent counter-ion and ∼1.4 V (∼2.8 ⋅ 10{sup 8} V m{sup −1}) when in the gel phase with a divalent counter-ion. The number of water molecules for a fully hydrated DMPG membrane has been estimated to be 9.7 molecules per lipid in the gel phase and 17.5 molecules in the fluid phase, considerably smaller than inferred experimentally for 1

  8. 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.

  9. 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.

  10. The phase equilibria of multicomponent gas hydrate in methanol/ethylene glycol solution based formation water

    International Nuclear Information System (INIS)

    Xu, Shurui; Fan, Shuanshi; Yao, Haiyuan; Wang, Yanhong; Lang, Xuemei; Lv, Pingping; Fang, Songtian

    2017-01-01

    Highlights: • The equilibrium data in THI solution based formation water is first investigated. • The 0.55 mass fraction concentration of EG 0.55 mass fraction fills the vacancy of this area. • The testing pressure range from 4.22 MPa to 34.72 MPa was rare in published data. - Abstract: In this paper, the three-phase coexistence points are generated for multicomponent gas hydrate in methanol (MeOH) solution for (0.05, 0.10, 0.15, and 0.35) mass fraction and ethylene glycol (EG) solution for (0.05, 0.10, 0.15, 0.35, 0.40 and 0.55) mass fraction. The phase equilibrium curves of different system were obtained by an isochoric pressure-search method on high pressure apparatus. The phase equilibrium regions of multicomponent gas hydrate were measured using the same composition of natural gas distributed in the South China Sea. And the different concentration solutions were prepared based formation water. The experimental data were measured in a wide range temperature from 267.74 to 298.53 K and a wide range pressure from 4.22 MPa to 34.72 MPa. The results showed that the hydrate phase equilibrium curves shifted to the inhibition region in accordance with the increased inhibitor concentration. In addition, the equilibrium temperature would decrease about 2.7 K when the concentration of MeOH increased 0.05 mass fraction. Besides, the suppression temperature was 1.25 K with the 0.05 mass fraction increase of EG concentration in the range of 0.05 mass fraction to 0.15 mass fraction. While in high EG concentration region, the suppression temperature was 3.3 K with the same increase of EG concentration (0.05 mass fraction).

  11. The role of hydrophobic interactions for the formation of gas hydrates

    Energy Technology Data Exchange (ETDEWEB)

    Yoon, R.H.; Wang, J.; Eriksson, J.C. [Virginia Polytech Inst. and State Univ., Blacksburg, VA (United States). Center for Advanced Separation Technologies; Sum, A.K. [Colorado School of Mines, Golden, CO (United States). Dept. of Chemical Engineering

    2008-07-01

    The process of hydrate formation remains largely unexplained due to a lack of evidence for the water molecules around the hydrophobic solute such as methane, and the nucleation process leading to the clustering that induces hydrate growth. However, the water structure is known to play a major role in the mechanism for hydrate nucleation. This paper presented evidence that hydrophobic solutes promote the structuring of water. Water molecules at room temperature tend to form ice structures around the hydrocarbon chains of surfactant molecules dissolved in water. An atomic force microscope (AFM) was used in this study to measure the surface forces between thiolated gold surfaces. The purpose was to better understand the structure of the thin films of water between hydrophobic surfaces. The water molecules tended to reorganize themselves to form ordered structures, which may be related to the nucleation of hydrates. The entropy reduction associated with the ice structure can be considered as the net driving force for self-assembly. Recent studies have revealed that long-range attractive forces exist between hydrophobic surfaces, which are likely to result from structuring of the water molecules in the vicinity of the hydrophobic surfaces. Similarly, the hydrophobic nature of most gas hydrate formers may induce ordering of water molecules in the vicinity of dissolved solutes. It was concluded that the results of this study may be used to develop a new mechanism for the formation of gas hydrates, including methane. 20 refs., 2 figs.

  12. Experimental determination of methane hydrate formation in the presence of ammonia

    Energy Technology Data Exchange (ETDEWEB)

    Dong, T.B.; Wang, L.Y.; Liu, A.X.; Guo, X.Q.; Chen, G.J.; Ma, Q.L.; Li, G.W. [China Univ. of Petroleum, Beijng (China). State Key Laboratory of Heavy Oil Processing

    2008-07-01

    Gas hydrates are non-stoichiometric inclusion compounds that are created by a lattice of water molecules. The host molecule has a strong hydrogen bond and encages low molecular weight gases or volatile liquids. The guest molecules favor hydrate formation. Historically, gas hydrates have been thought to be problematic during natural gas transportation because the formed solid hydrate can block pipelines and cause tubing and casing collapse. However, the discovery of huge deposits of gas hydrates in deep-sea sediments and in permafrost has renewed interest in gas hydrates as a new energy resource. This paper discussed a study that is a part of an ongoing experimental and computational program dealing with the thermodynamics of gas hydrate formation in ammonia-water systems. The purpose of the study was to develop a new method to separate and recycle the vent gas of ammonia synthesis by forming or dissociating hydrate. The hydrate-forming conditions of methane in ammonia and water system were studied and reported in this paper with reference to the experimental apparatus and procedure. The materials and preparation of samples were also explained. The experimental results showed that the ammonia had an inhibitive effect on the hydrate formation. 26 refs., 2 tabs., 3 figs.

  13. Study on molecular controlled mining system of methane hydrate; Methane hydrate no bunshi seigyo mining ni kansuru kenkyu

    Energy Technology Data Exchange (ETDEWEB)

    Kuriyagawa, M; Saito, T; Kobayashi, H; Karasawa, H; Kiyono, F; Nagaoki, R; Yamamoto, Y; Komai, T; Haneda, H; Takahashi, Y [National Institute for Resources and Environment, Tsukuba (Japan); Nada, H [Science and Technology Agency, Tokyo (Japan)

    1997-02-01

    Basic studies are conducted for the collection of methane from the methane hydrate that exists at levels deeper than 500m in the sea. The relationship between the hydrate generation mechanism and water cluster structure is examined by use of mass spectronomy. It is found that, among the stable liquid phase clusters, the (H2O)21H{sup +} cluster is the most stable. Stable hydrate clusters are in presence in quantities, and participate in the formation of hydrate crystal nuclei. For the elucidation of the nucleus formation mechanism, a kinetic simulation is conducted of molecules in the cohesion system consisting of water and methane molecules. Water molecules that array near methane molecules at the normal pressure is disarrayed under a higher pressure for rearray into a hydrate structure. Hydrate formation and breakdown in the three-phase equilibrium state of H2O, CH4, and CO2 at a low temperature and high pressure are tested, which discloses that supercooling is required for formation, that it is possible to extract CH4 first for replacement by guest molecule CO2 since CO2 is stabler than CH4 at a lower pressure or higher temperature, and that formation is easier to take place when the grain diameter is larger at the formation point since larger grain diameters result in a higher formation temperature. 3 figs.

  14. Hydrates on tap: scientists say natural gas hydrates may be tough nut to crack

    Energy Technology Data Exchange (ETDEWEB)

    Mahoney, J.

    2001-12-01

    Gas hydrates are methane molecules trapped in cages of water molecules, yielding a substance with a slushy, sherbet-like consistency. Drilling for hydrates is similar to conventional oil and gas drilling, however, the secret to economic production still remains hidden. Hydrates exist in abundance in such places as deep ocean floor and below ground in some polar regions. The real challenge lies in producing gas from this resource, inasmuch as there is no existing technology for production of gas specifically from methane hydrates. This paper describes an international research program, involving a five-country partnership to spud the first of three wells into the permafrost of the Mackenzie River Delta in the Northwest Territories. The project, worth about $15 million, has brought together public funding and expertise from Japan, Germany, India as well as the Canadian and US Geological Surveys and the US Dept. of Energy in an effort to gain information on the production response of gas hydrates. The operator of the project is Japan Petroleum Exploration Company of Canada, a subsidiary of Japan National Oil Corporation. Since Japan is poor in domestic hydrocarbon resources, but is surrounded by deep water that contains potential for gas hydrates, Japan has a great deal riding on the success of this project. Germany and the United States are also very much interested. Current thinking is that gas is in contact with the hydrates and that it should be possible to develop a free gas reservoir as if it were a conventional deposit. As the free gas is drawn off, the pressure is reduced on the hydrates in contact with it , the hydrates dissociate from the gas and replenish the conventional reservoir. So far this is still only a theory, but it appears to be a sensible approach to hydrate production. 1 photo.

  15. Enzyme hydration, activity and flexibility : A neutron scattering approach

    International Nuclear Information System (INIS)

    Kurkal-Siebert, V.; Finney, J.L.; Daniel, R.M.; Smith, Jeremy C.

    2006-01-01

    Recent measurements have demonstrated enzyme activity at hydrations as low as 3%. The question of whether the hydration-induced enzyme flexibility is important for activity is addressed by performing picosecond dynamic neutron scattering experiments on pig liver esterase powders at various temperatures as well as solutions. At all temperatures and hydrations investigated here, significant quasielastic scattering intensity is found in the protein, indicating the presence of anharmonic, diffusive motion. As the hydration increases a temperature-dependent dynamical transition appears and strengthens involving additional diffusive motion. At low temperature, increasing hydration resulted in lower flexibility of the enzyme. At higher temperatures, systems containing sufficient number of water molecules interacting with the protein exhibit increased flexibility. The implication of these results is that, although the additional hydration-induced diffusive motion and flexibility at high temperatures in the enzyme detected here may be related to increased activity, they are not required for the enzyme to function

  16. Radiolysis of liquid water: an attempt to reconcile Monte-Carlo calculations with new experimental hydrated electron yield data at early times

    International Nuclear Information System (INIS)

    Muroya, Y.; Meesungnoen, J.; Jay-Gerin, J.-P.; Filali-Mouhim, A.; Goulet, T.; Katsumura, Y.; Mankhetkorn, S.

    2002-01-01

    A re-examination of our Monte-Carlo modeling of the radiolysis of liquid water by low linear-energy-transfer (LET ∼ 0.3 keV μm -1 ) radiation is undertaken herein in an attempt to reconcile the results of our simulation code with recently revised experimental hydrated electron (e aq - ) yield data at early times. The thermalization distance of subexcitation electrons, the recombination cross section of the electrons with their water parent cations prior to thermalization, and the branching ratios of the different competing mechanisms in the dissociative decay of vibrationally excited states of water molecules were taken as adjustable parameters in our simulations. Using a global-fit procedure, we have been unable to find a set of values for those parameters to simultaneously reproduce (i) the revised e aq - yield of 4.0 ± 0.2 molecules per 100 eV at 'time zero' (that is, a reduction of ∼20% over the hitherto accepted value of 4.8 molecules per 100 eV), (ii) the newly measured e aq - decay kinetic profile from 100 ps to 10 ns, and (iii) the time-dependent yields of the other radiolytic species H . , . OH, H 2 , and H 2 O 2 (up to ∼1 μs). The lowest possible limiting 'time-zero' yield of e aq - that we could in fact obtain, while ensuring an acceptable agreement between all computed and experimental yields, was ∼4.4 to 4.5 molecules per 100 eV. Under these conditions, the mean values of the electron thermalization distance and of the geminate electron-cation recombination probability, averaged over the subexcitation electron 'entry spectrum,' are found to be equal to ∼139 A and ∼18%, respectively. These values are to be compared with those obtained in our previous simulations of liquid water radiolysis, namely ∼88 A and ∼5.5%, respectively. Our average electron thermalization distance is also to be compared with the typical size (∼64-80 A) of the initial hydrated electron distributions estimated in current deterministic models of 'spur' chemistry

  17. Water-assisted dehalogenation of thionyl chloride in the presence of water molecules.

    Science.gov (United States)

    Yeung, Chi Shun; Ng, Ping Leung; Guan, Xiangguo; Phillips, David Lee

    2010-04-01

    A second-order Møller-Plesset perturbation theory (MP2) and density functional theory (DFT) investigation of the dehalogenation reactions of thionyl chloride is reported, in which water molecules (up to seven) were explicitly involved in the reaction complex. The dehalogenation processes of thionyl chloride were found to be dramatically catalyzed by water molecules. The reaction rate became significantly faster as more water molecules became involved in the reaction complex. The dehalogenation processes can be reasonably simulated by the gas-phase water cluster models, which reveals that water molecules can help to solvate the thionyl chloride molecules and activate the release of the Cl(-) leaving group. The computed activation energies were used to compare the calculations to available experimental data.

  18. WatAA: Atlas of Protein Hydration. Exploring synergies between data mining and ab initio calculations.

    Science.gov (United States)

    Černý, Jiří; Schneider, Bohdan; Biedermannová, Lada

    2017-07-14

    Water molecules represent an integral part of proteins and a key determinant of protein structure, dynamics and function. WatAA is a newly developed, web-based atlas of amino-acid hydration in proteins. The atlas provides information about the ordered first hydration shell of the most populated amino-acid conformers in proteins. The data presented in the atlas are drawn from two sources: experimental data and ab initio quantum-mechanics calculations. The experimental part is based on a data-mining study of a large set of high-resolution protein crystal structures. The crystal-derived data include 3D maps of water distribution around amino-acids and probability of occurrence of each of the identified hydration sites. The quantum mechanics calculations validate and extend this primary description by optimizing the water position for each hydration site, by providing hydrogen atom positions and by quantifying the interaction energy that stabilizes the water molecule at the particular hydration site position. The calculations show that the majority of experimentally derived hydration sites are positioned near local energy minima for water, and the calculated interaction energies help to assess the preference of water for the individual hydration sites. We propose that the atlas can be used to validate water placement in electron density maps in crystallographic refinement, to locate water molecules mediating protein-ligand interactions in drug design, and to prepare and evaluate molecular dynamics simulations. WatAA: Atlas of Protein Hydration is freely available without login at .

  19. Vibrational properties of water molecules adsorbed in different zeolitic frameworks

    International Nuclear Information System (INIS)

    Crupi, V; Longo, F; Majolino, D; Venuti, V

    2006-01-01

    The perturbation of water 'sorbed' in samples of zeolites of different structural type, genesis, and cation composition (K-, Na-, Mg- and Ca-rich zeolites), namely the CHA framework of a synthetic K-chabazite, the LTA framework of synthetic Na-A and Mg50-A zeolites, and the NAT framework of a natural scolecite, has been studied by FTIR-ATR spectroscopy, in the -10 to +80 o C temperature range. The aim was to show how differences in the chemical composition and/or in the topology of the zeolite framework and, in particular, the possibility for the guest water molecules to develop guest-guest and/or host-guest interactions, lead to substantial differences in their vibrational dynamical properties. The spectra, collected in the O-H stretching and H 2 O bending mode regions, are complex, with multiple bands being observed. As far as water in the CHA and LTA frameworks is concerned, whose behaviour is governed by the balance of water-water, water-framework and water-extra-framework cations interactions, the assignment of the resolved components of the O-H stretching band has been discussed by fitting the band shapes into individual components attributed to H 2 O molecules engaged in different degrees of hydrogen bonding. A detailed quantitative picture of the connectivity pattern of water, as a function of temperature and according to the chemical and topological properties of the environment, is furnished. The H 2 O bending vibrational bands give additional information that perfectly agrees with the results obtained from the analysis of the O-H stretching spectral region. In the case of scolecite, a small-pored zeolite where water-water interactions are eliminated, the increased complexity observed in the infrared spectra in the O-H stretching and H 2 O bending regions was explained as due to the hydrogen bonding between the water molecules and the network, and also with the extra-framework cation. Furthermore, these observations have been correlated with the different

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

    International Nuclear Information System (INIS)

    Yang, J.; Martí, J.; Calero, C.

    2014-01-01

    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 −5 cm 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 −8 cm 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 its interaction

  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. DFD-01 Reduces Transepidermal Water Loss and Improves Skin Hydration and Flexibility.

    Science.gov (United States)

    Jackson, J Mark; Grove, Gary L; Allenby, Kent; Houser, Tim

    2017-12-01

    In plaque psoriasis, the benefit of topical steroids is well established. The vehicle formulation of topical steroids may also provide benefit in addition to the effects of the steroid itself. DFD-01 (betamethasone dipropionate spray, 0.05%) is a formulation composed of a topical steroid in an emollient-like vehicle that enhances penetration to the target site of inflammation in the skin. The aim of this study was to assess the effect of DFD-01 and its vehicle on skin hydration and barrier function in compromised skin and to evaluate its effect on flexibility in healthy skin. Eighteen healthy white volunteers were enrolled in each of two studies. In Study 1, dry shaving of volar forearms created a compromised skin barrier, through which transepidermal water loss (TEWL) was measured using an evaporimeter. Capacitance, a measure of epidermal hydration, was also measured at baseline and at 1, 2 and 4 h after application of DFD-01 or its vehicle formulation. In Study 2, intact skin flexibility was tested with a cutometer before and at 1, 2 and 4 h after application of DFD-01 or vehicle. In Study 1, both DFD-01 and its vehicle were effective at reducing TEWL through the compromised stratum corneum. Capacitance measurements confirmed this finding; razor-chafed skin treated with either DFD-01 or vehicle exhibited levels of skin hydration similar to unshaved control skin. Study 2 found softening and greater flexibility of normal skin treated with either DFD-01 or vehicle compared with nontreated control skin samples. These tests suggest that the DFD-01 formulation and its vehicle are each effective at retaining moisture within a damaged skin barrier and for softening and increasing the flexibility of intact skin. Dr. Reddy's Laboratories.

  3. Fiber Optic Raman Spectroscopy for Detection of Methane Hydrates and Related Species

    National Research Council Canada - National Science Library

    Hart, Sean

    2001-01-01

    .... The feasibility of using this system for methane hydrate detection is evaluated through the use of organic surrogate molecules, due to the low solubility of methane in water at atmospheric pressures...

  4. 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

  5. Is Br2 hydration hydrophobic?

    Science.gov (United States)

    Alcaraz-Torres, A; Gamboa-Suárez, A; Bernal-Uruchurtu, M I

    2017-02-28

    The spectroscopic properties of bromine in aqueous systems suggest it can behave as either hydrophilic or hydrophobic solute. In small water clusters, the halogen bond and the hydrogen-halogen interaction are responsible for its specific way of binding. In water hydrates, it is efficiently hosted by two different cages forming the crystal structure and it has been frequently assumed that there is little or no interaction between the guest and the host. Bromine in liquid solution poses a challenging question due to its non-negligible solubility and the large blue shift measured in its absorption spectra. Using a refined semi-empirical force field, PM3-PIF, we performed a Born-Oppenheimer molecular dynamics study of bromine in liquid water. Here we present a detailed study in which we retrieved the most representative hydration structures in terms of the most frequent positions around bromine and the most common water orientations. Albeit being an approximate description of the total hydration phenomenon, it captures the contribution of the leading molecular interactions in form of the recurrent structures. Our findings confirm that the spectroscopic signature is mainly caused by the closest neighbors. The dynamics of the whole first hydration shell strongly suggests that the external molecules in that structure effectively isolate the bulk from the presence of bromine. The solvation structure fluctuates from a hydrophilic to a hydrophobic-like environment along the studied trajectory.

  6. THERMODYNAMIC MODEL OF GAS HYDRATES

    OpenAIRE

    Недоступ, В. И.; Недоступ, О. В.

    2015-01-01

    The interest to gas hydrates grows last years. Therefore working out of reliable settlement-theoretical methods of definition of their properties is necessary. The thermodynamic model of gas hydrates in which the central place occupies a behaviour of guest molecule in cell is described. The equations of interaction of molecule hydrate formative gas with cell are received, and also an enthalpy and energy of output of molecule from a cell are determined. The equation for calculation of thermody...

  7. Replacement of CH4 in the hydrate by use of liquid CO2

    International Nuclear Information System (INIS)

    Ota, Masaki; Morohashi, Kenji; Abe, Yuki; Watanabe, Masaru; Smith, Richard Lee Jr.; Inomata, Hiroshi

    2005-01-01

    The dynamics of CH 4 replacement in the CH 4 hydrate with saturated liquid CO 2 at 273.2 K was measured with a high pressure optical cell. The results showed that CH 4 in the hydrate gradually moved to the liquid CO 2 phase while CO 2 in the liquid phase penetrated into the hydrate from the quantitative analysis. The decomposing process of the CH 4 hydrate during the replacement was analyzed with in situ Raman spectroscopy, which allowed us to distinguish the cage structure of the CH 4 hydrate and discuss the microscopic view of the replacement in the hydrate. It was found that the decomposition of the medium cage (M-cage) in the CH 4 hydrate proceeded faster than that of the small cage (S-cage). The observed rate difference could be related to the stability of the S-cage in the CH 4 hydrate or the re-formation tendency of CH 4 and water molecules in the S-cage after decomposing the hydrate structure, whereas the guest molecule exchange of CH 4 with CO 2 could occur in the M-cage. Based on the experimental data, we developed a kinetic model for calculation of the CH 4 remaining in the hydrate considering the decomposition rate difference between the M-cage and S-cage in the CH 4 hydrate. The results indicate that the driving force could be the fugacity difference between the fluid phase and the hydrate phase for the replacement process

  8. Photoionization of water molecules by high energy photons

    Directory of Open Access Journals (Sweden)

    Lara Martini

    2017-07-01

    Full Text Available We theoretically study the photoionization of water molecules by high energy photon impact. We develop a model in which the final state wavefunction is given by a Coulomb continuum wavefunction with effective charges and the water molecule bound states are represented using the Moccia's monocentric wavefunctions. We obtain analytical expressions for the transition matrix element that enable the computation of cross sections by numerical quadratures. We compare our predictions for photon energies between 20 and 300 eV with more elaborated theoretical results and experiments. We obtain a very good agreement with experiments, in particular, at enough high energies where there is a lack of elaborated results due to their high computational cost. Received: 15 March 2017, Accepted: 25 June 2017; Edited by: S. Kais; DOI: http://dx.doi.org/10.4279/PIP.090006 Cite as: L Martini, D I R Boll, O A Fojón, Papers in Physics 9, 090006 (2017

  9. Animated molecular dynamics simulations of hydrated caesium-smectite interlayers

    Directory of Open Access Journals (Sweden)

    Sposito Garrison

    2002-09-01

    Full Text Available Computer animation of center of mass coordinates obtained from 800 ps molecular dynamics simulations of Cs-smectite hydrates (1/3 and 2/3 water monolayers provided information concerning the structure and dynamics of the interlayer region that could not be obtained through traditional simulation analysis methods. Cs+ formed inner sphere complexes with the mineral surface, and could be seen to jump from one attracting location near a layer charge site to the next, while water molecules were observed to migrate from the hydration shell of one ion to that of another. Neighboring ions maintained a partial hydration shell by sharing water molecules, such that a single water molecule hydrated two ions simultaneously for hundreds of picoseconds. Cs-montmorillonite hydrates featured the largest extent of this sharing interaction, because interlayer ions were able to inhabit positions near surface cavities as well as at their edges, close to oxygen triads. The greater positional freedom of Cs+ within the montmorillonite interlayer, a result of structural hydroxyl orientation and low tetrahedral charge, promoted the optimization of distances between cations and water molecules required for water sharing. Preference of Cs+ for locations near oxygen triads was observed within interlayer beidellite and hectorite. Water molecules also could be seen to interact directly with the mineral surface, entering its surface cavities to approach attracting charge sites and structural hydroxyls. With increasing water content, water molecules exhibited increased frequency and duration of both cavity habitation and water sharing interactions. Competition between Cs+ and water molecules for surface sites was evident. These important cooperative and competitive features of interlayer molecular behavior were uniquely revealed by animation of an otherwise highly complex simulation output.

  10. Animated molecular dynamics simulations of hydrated caesium-smectite interlayers

    Science.gov (United States)

    Sutton, Rebecca; Sposito, Garrison

    2002-01-01

    Computer animation of center of mass coordinates obtained from 800 ps molecular dynamics simulations of Cs-smectite hydrates (1/3 and 2/3 water monolayers) provided information concerning the structure and dynamics of the interlayer region that could not be obtained through traditional simulation analysis methods. Cs+ formed inner sphere complexes with the mineral surface, and could be seen to jump from one attracting location near a layer charge site to the next, while water molecules were observed to migrate from the hydration shell of one ion to that of another. Neighboring ions maintained a partial hydration shell by sharing water molecules, such that a single water molecule hydrated two ions simultaneously for hundreds of picoseconds. Cs-montmorillonite hydrates featured the largest extent of this sharing interaction, because interlayer ions were able to inhabit positions near surface cavities as well as at their edges, close to oxygen triads. The greater positional freedom of Cs+ within the montmorillonite interlayer, a result of structural hydroxyl orientation and low tetrahedral charge, promoted the optimization of distances between cations and water molecules required for water sharing. Preference of Cs+ for locations near oxygen triads was observed within interlayer beidellite and hectorite. Water molecules also could be seen to interact directly with the mineral surface, entering its surface cavities to approach attracting charge sites and structural hydroxyls. With increasing water content, water molecules exhibited increased frequency and duration of both cavity habitation and water sharing interactions. Competition between Cs+ and water molecules for surface sites was evident. These important cooperative and competitive features of interlayer molecular behavior were uniquely revealed by animation of an otherwise highly complex simulation output.

  11. Dynamics of hydration in hen egg white lysozyme.

    Science.gov (United States)

    Sterpone, F; Ceccarelli, M; Marchi, M

    2001-08-10

    We investigate the hydration dynamics of a small globular protein, hen egg-white lysozyme. Extensive simulations (two trajectories of 9 ns each) were carried out to identify the time-scales and mechanism of water attachment to this protein. The location of the surface and integral water molecules in lysozyme was also investigated. Three peculiar temporal scales of the hydration dynamics can be discerned: two among these, with sub-nanosecond mean residence time, tau(w), are characteristic of surface hydration water; the slower time-scale (tau(w) approximately 2/3 ns) is associated with buried water molecules in hydrophilic pores and in superficial clefts. The computed tau(w) values in the two independent runs fall in a similar range and are consistent with each other, thus adding extra weight to our result. The tau(w) of surface water obtained from the two independent trajectories is 20 and 24 ps. In both simulations only three water molecules are bound to lysozyme for the entire length of the trajectories, in agreement with nuclear magnetic relaxation dispersion estimates. Locations other than those identified in the protein crystal are found to be possible for these long-residing water molecules. The dynamics of the hydration water molecules observed in our simulations implies that each water molecule visits a multitude of residues during the lifetime of its bound with the protein. The number of residues seen by a single water molecule increases with the time-scale of its residence time and, on average, is equal to one only for the water molecules with shorter residence time. Thus, tau(w) values obtained from inelastic neutron scattering and based on jump-diffusion models are likely not to account for the contribution of water molecules with longer residence time. Copyright 2001 Academic Press.

  12. Influence of the water molecules near surface of viral protein on virus activation process

    Energy Technology Data Exchange (ETDEWEB)

    O, Shepelenko S; S, Salnikov A; V, Rak S; P, Goncharova E; B, Ryzhikov A, E-mail: shep@vector.nsc.r, E-mail: shep@ngs.r [Federal State Research Institution State Research Center of Virology and Biotechnology VECTOR of the Federal Service for Surveillance in Consumer Rights Protection and Human Well-being (FSRI SRC VB VECTOR) Koltsovo, Novosibirsk Region (Russian Federation)

    2009-06-01

    The infection of a cell with influenza virus comprises the stages of receptor binding to the cell membrane, endocytosis of virus particle, and fusion of the virus envelope and cell endosome membrane, which is determined by the conformational changes in hemagglutinin, a virus envelope protein, caused by pH decrease within the endosome. The pH value that induces conformation rearrangements of hemagglutinin molecule considerably varies for different influenza virus strains, first and foremost, due to the differences in amino acid structure of the corresponding proteins. The main goal of this study was to construct a model making it possible to assess the critical pH value characterizing the fusogenic activity of influenza virus hemagglutinin from the data on hemagglutinin structure and experimental verification of this model. Under this model, we assume that when the electrostatic force between interacting hemagglutinin molecules in the virus envelop exceeds a certain value, the hemagglutinin HA1 subunits are arranged so that they form a cavity sufficient for penetration of water molecules. This event leads to an irreversible hydration of the inner fragments of hemagglutinin molecule in a trimer and to the completion of conformational changes. The geometry of electrostatic field in hemagglutinin trimer was calculated taking into account the polarization effects near the interface of two dielectrics, aqueous medium and protein macromolecule. The critical pH values for the conformational changes in hemagglutinin were measured by the erythrocyte hemolysis induced by influenza virus particles when decreasing pH. The critical pH value conditionally separating the pH range into the regions with and without the conformational changes was calculated for several influenza virus H1N1 and H3N2 strains based on the data on the amino acid structure of the corresponding hemagglutinin molecules. Comparison of the theoretical and experimental values of critical pH values for

  13. CO2 solubility in aqueous solutions containing Na+, Ca2+, Cl−, SO42− and HCO3-: The effects of electrostricted water and ion hydration thermodynamics

    International Nuclear Information System (INIS)

    Gilbert, Kimberly; Bennett, Philip C.; Wolfe, Will; Zhang, Tongwei; Romanak, Katherine D.

    2016-01-01

    Dissolution of CO 2 into deep subsurface brines for carbon sequestration is regarded as one of the few viable means of reducing the amount of CO 2 entering the atmosphere. Ions in solution partially control the amount of CO 2 that dissolves, but the mechanisms of the ion's influence are not clearly understood and thus CO 2 solubility is difficult to predict. In this study, CO 2 solubility was experimentally determined in water, NaCl, CaCl 2 , Na 2 SO 4, and NaHCO 3 solutions and a mixed brine similar to the Bravo Dome natural CO 2 reservoir; ionic strengths ranged up to 3.4 molal, temperatures to 140 °C, and CO 2 pressures to 35.5 MPa. Increasing ionic strength decreased CO 2 solubility for all solutions when the salt type remained unchanged, but ionic strength was a poor predictor of CO 2 solubility in solutions with different salts. A new equation was developed to use ion hydration number to calculate the concentration of electrostricted water molecules in solution. Dissolved CO 2 was strongly correlated (R 2  = 0.96) to electrostricted water concentration. Strong correlations were also identified between CO 2 solubility and hydration enthalpy and hydration entropy. These linear correlation equations predicted CO 2 solubility within 1% of the Bravo Dome brine and within 10% of two mixed brines from literature (a 10 wt % NaCl + KCl + CaCl 2 brine and a natural Na + , Ca 2+ , Cl − type brine with minor amounts of Mg 2+ , K + , Sr 2+ and Br − ). - Highlights: • Measured CO 2 solubility in Na + , Cl − , HCO 3 - , Ca 2+ and SO 4 2− solutions at high PCO 2 . • A new equation calculates electrostricted water (mol/kgw) from hydration number. • CO 2 solubility strongly correlates (R 2  = 0.96) to electrostricted water. • Ion electrostriction of water limits its availability for CO 2 caging and solvation. • Correlations predict CO 2 solubility of several mixed brines to within 1–9%.

  14. Manufacture of Methane Hydrate using Carbon Nano Tubes

    International Nuclear Information System (INIS)

    Park, Sung Seek

    2010-02-01

    Methane hydrate is formed by physical binding between water molecule and gas such as methane, ethane, propane, or carbon dioxide, etc., which is captured in the cavities of water molecule under the specific temperature and pressure. More than 99% of naturally produced methane hydrate consists of methane, and is widely dispersed in the continental slope and continental Shelf of the Pacific and the Atlantic, the Antarctica etc. The reserve of fossil fuel is 500 billion carbon ton and the reserve of methane is 360 million carbon ton. The reserve of gas hydrate is more than 1 trillion carbon ton, which is twice the fossil fuel. Therefore, natural gas hydrate as a kind of gas hydrate is expected to replace fossil fuel as new energy source of 21st century. Also 1 m 3 hydrate of pure methane can be decomposed to the maximum of 216 m 3 methane at standard condition. If these characteristics of hydrate are reversely utilized, natural gas is fixed into water in the form of hydrate solid. Therefore, the hydrate is considered to be a great way to transport and store natural gas in large quantity. Especially the transportation cost is known to be 18∼25% less than the liquefied transportation. However, when natural gas hydrate is artificially formed, its reaction time may be too long and the gas consumption in water becomes relatively low, because the reaction rate between water and gas is low. Therefore, for the practical purpose in the application, the present investigation focuses on the rapid production of hydrates and increases gas consumption by adding MWCNT and NaCl into pure water. The results show that the equilibrium pressure in seawater is more higher than that in pure water, and methane hydrate could be formed rapidly during pressurization if the subcooling is maintained at 9K or above in seawater and 8K or above in pure water, respectively. Also, amount of consumed gas volume in pure water is more higher that in seawater at the same experimental conditions

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

    International Nuclear Information System (INIS)

    Shin, Kyuchul; Park, Juwoon; Kim, Jakyung; Kim, Hyunho; Seo, Yutaek; Lee, Yohan; Seo, Yongwon

    2014-01-01

    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

  16. Scattering of thermal neutron by the water molecule

    International Nuclear Information System (INIS)

    Rosa, L.P.

    The calculation of the differenctial cross section for scattering of thermal neutrons by water, taking into account the translational, rotational and vibrational motions of the water molecule, is presented according to Nelkin' model. Some modifications are presented which have been introduced in the original method to improve the results and an application has been made to reactor physics, by calculating the thermal neutron flux in a homogenous medium containing water and absorver. Thirty thermal energy groups have been used to compute the spectra. Within the limits of error, better agreement has been obtained between theory and experiments by using a modified Nelkin kernel consisting of substituting the asymptotic formulae for the rotational and vibrational motions by more exact expressions, similar to the Buttler model for heavy water

  17. 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.

  18. Competing quantum effects in the free energy profiles and diffusion rates of hydrogen and deuterium molecules through clathrate hydrates.

    Science.gov (United States)

    Cendagorta, Joseph R; Powers, Anna; Hele, Timothy J H; Marsalek, Ondrej; Bačić, Zlatko; Tuckerman, Mark E

    2016-11-30

    Clathrate hydrates hold considerable promise as safe and economical materials for hydrogen storage. Here we present a quantum mechanical study of H 2 and D 2 diffusion through a hexagonal face shared by two large cages of clathrate hydrates over a wide range of temperatures. Path integral molecular dynamics simulations are used to compute the free-energy profiles for the diffusion of H 2 and D 2 as a function of temperature. Ring polymer molecular dynamics rate theory, incorporating both exact quantum statistics and approximate quantum dynamical effects, is utilized in the calculations of the H 2 and D 2 diffusion rates in a broad temperature interval. We find that the shape of the quantum free-energy profiles and their height relative to the classical free energy barriers at a given temperature, as well as the rate of diffusion, are strongly affected by competing quantum effects: above 25 K, zero-point energy (ZPE) perpendicular to the reaction path for diffusion between cavities decreases the quantum rate compared to the classical rate, whereas at lower temperatures tunneling outcompetes the ZPE and as a result the quantum rate is greater than the classical rate.

  19. STICKING OF MOLECULES ON NONPOROUS AMORPHOUS WATER ICE

    Energy Technology Data Exchange (ETDEWEB)

    He, Jiao; Vidali, Gianfranco [Physics Department, Syracuse University, Syracuse, NY 13244 (United States); Acharyya, Kinsuk, E-mail: gvidali@syr.edu [Department of Chemistry, University of Virginia, Charlottesville, VA 22904 (United States)

    2016-05-20

    Accurate modeling of physical and chemical processes in the interstellar medium (ISM) requires detailed knowledge of how atoms and molecules adsorb on dust grains. However, the sticking coefficient, a number between 0 and 1 that measures the first step in the interaction of a particle with a surface, is usually assumed in simulations of ISM environments to be either 0.5 or 1. Here we report on the determination of the sticking coefficient of H{sub 2}, D{sub 2}, N{sub 2}, O{sub 2}, CO, CH{sub 4}, and CO{sub 2} on nonporous amorphous solid water. The sticking coefficient was measured over a wide range of surface temperatures using a highly collimated molecular beam. We showed that the standard way of measuring the sticking coefficient—the King–Wells method—leads to the underestimation of trapping events in which there is incomplete energy accommodation of the molecule on the surface. Surface scattering experiments with the use of a pulsed molecular beam are used instead to measure the sticking coefficient. Based on the values of the measured sticking coefficient, we suggest a useful general formula of the sticking coefficient as a function of grain temperature and molecule-surface binding energy. We use this formula in a simulation of ISM gas–grain chemistry to find the effect of sticking on the abundance of key molecules both on grains and in the gas phase.

  20. The spontaneous synchronized dance of pairs of water molecules

    International Nuclear Information System (INIS)

    Roncaratti, Luiz F.; Cappelletti, David; Pirani, Fernando

    2014-01-01

    Molecular beam scattering experiments have been performed to study the effect of long-range anisotropic forces on the collision dynamics of two small polar molecules. The main focus of this paper is on water, but also ammonia and hydrogen sulphide molecules have been investigated, and some results will be anticipated. The intermolecular distances mainly probed are of the order of 1 nm and therefore much larger than the molecular dimensions. In particular, we have found that the natural electric field gradient, generated by different spatial orientations of the permanent electric dipoles, is able to promote the transformation of free rotations into coupled pendular states, letting the molecular partners involved in the collision complex swinging to and fro around the field direction. This long-ranged concerted motion manifested itself as large increases of the magnitude of the total integral cross section. The experimental findings and the theoretical treatment developed to shed light on the details of the process suggest that the transformation from free rotations to pendular states depends on the rotational level of both molecules, on the impact parameter, on the relative collision velocity, on the dipole moment product and occurs in the time scale of picoseconds. The consequences of this intriguing phenomenon may be important for the interpretation and, in perspective, for the control of elementary chemical and biological processes, given by polar molecules, ions, and free radicals, occurring in several environments under various conditions

  1. The spontaneous synchronized dance of pairs of water molecules

    Energy Technology Data Exchange (ETDEWEB)

    Roncaratti, Luiz F. [Dipartimento di Chimica, Biologia e Biotecnologie, Università degli Studi di Perugia, 06123 Perugia (Italy); Instituto de Física, Universidade de Brasília, 70910-900 Brasília (Brazil); Cappelletti, David, E-mail: david.cappelletti@unipg.it; Pirani, Fernando [Dipartimento di Chimica, Biologia e Biotecnologie, Università degli Studi di Perugia, 06123 Perugia (Italy)

    2014-03-28

    Molecular beam scattering experiments have been performed to study the effect of long-range anisotropic forces on the collision dynamics of two small polar molecules. The main focus of this paper is on water, but also ammonia and hydrogen sulphide molecules have been investigated, and some results will be anticipated. The intermolecular distances mainly probed are of the order of 1 nm and therefore much larger than the molecular dimensions. In particular, we have found that the natural electric field gradient, generated by different spatial orientations of the permanent electric dipoles, is able to promote the transformation of free rotations into coupled pendular states, letting the molecular partners involved in the collision complex swinging to and fro around the field direction. This long-ranged concerted motion manifested itself as large increases of the magnitude of the total integral cross section. The experimental findings and the theoretical treatment developed to shed light on the details of the process suggest that the transformation from free rotations to pendular states depends on the rotational level of both molecules, on the impact parameter, on the relative collision velocity, on the dipole moment product and occurs in the time scale of picoseconds. The consequences of this intriguing phenomenon may be important for the interpretation and, in perspective, for the control of elementary chemical and biological processes, given by polar molecules, ions, and free radicals, occurring in several environments under various conditions.

  2. Structural changes and intermolecular interactions of filled ice Ic structure for hydrogen hydrate under high pressure

    International Nuclear Information System (INIS)

    Machida, S; Hirai, H; Kawamura, T; Yamamoto, Y; Yagi, T

    2010-01-01

    High-pressure experiments of hydrogen hydrate were performed using a diamond anvil cell under conditions of 0.1-44.2 GPa and at room temperature. Also, high pressure Raman studies of solid hydrogen were performed in the pressure range of 0.1-43.7 GPa. X-ray diffractometry (XRD) for hydrogen hydrate revealed that a known high-pressure structure, filled ice Ic structure, of hydrogen hydrate transformed to a new high-pressure structure at approximately 35-40 GPa. A comparison of the Raman spectroscopy of a vibron for hydrogen molecules between hydrogen hydrate and solid hydrogen revealed that the extraction of hydrogen molecules from hydrogen hydrate occurred above 20 GPa. Also, the Raman spectra of a roton revealed that the rotation of hydrogen molecules in hydrogen hydrate was suppressed at around 20 GPa and that the rotation recovered under higher pressure. These results indicated that remarkable intermolecular interactions in hydrogen hydrate between neighboring hydrogen molecules and between guest hydrogen molecules and host water molecules might occur. These intermolecular interactions could produce the stability of hydrogen hydrate.

  3. On the densification and hydration of CaCO3 particles by Q-switched laser pulses in water

    Science.gov (United States)

    Lin, Peng-Wen; Wu, Chao-Hsien; Zheng, Yuyuan; Chen, Shuei-Yuan; Shen, Pouyan

    2013-09-01

    Calcite powders subjected to Q-switched laser pulses in water were characterized by X-ray/electron diffraction and optical spectroscopy to have a significant internal compressive stress (up to ca. 1.5 GPa) with accompanied transformation into defective calcite II and hydrates. The defective calcite II particles were (0 1 0), (0 0 1), (0 1¯ 1), (0 1 3) and (0 1¯ 3) faceted with 2×(0 2 0)II commensurate superstructure and tended to hydrate epitaxially as monohydrocalcite co-existing with ikaite (CaCO3·6H2O) with extensive cleavages and amorphous calcium carbonate with porous structure. The colloidal suspension containing the densified calcite polymorphs and hydrates showed two UV-visible absorptions corresponding to a minimum band gap of ca. 5 and 3 eV, respectively.

  4. Barley seed radiosensitivity following post-hydration in oxygen-, nitrogen- and nitrous oxide-saturated water, 1

    International Nuclear Information System (INIS)

    Singh, S.P.; Kesavan, P.C.

    1990-01-01

    Dry (∼3.5 and 4.0 per cent moisture content) barley seeds were exposed to 350 Gy of 60 Co-γ-rays in vacuo and post-hydrated at 4degC for 8 h in O 2 -, N 2 -, or N 2 O-saturated water. The effect of caffeine and t-butyl alcohol (t-BuOH) dissolved in the post-hydration medium on the magnitude of damage developing under these three different gaseous circumstances was studied. The post-irradiation damage and its modification by caffeine and t-BuOH was assessed in terms of 8-day-old seedling injury, peroxidase activity and total peroxides in the 8-day-old seedlings. Post-irradiation O 2 -saturated hydration caused maximal 8-day-old seedling injury, and increased peroxidase activity with concomitant reduction in total peroxides. Both caffeine and t-BuOH afforded significant radioprotection against post-irradiation O 2 -dependent damage. Post-irradiation N 2 O-saturated hydration was even more significantly radioprotective than the N 2 -saturated post-hydration. Under these circumstances, t-BuOH exerted no effect whatsoever on the N 2 - and N 2 O-mediated post-irradiation damage. Caffeine, on the other hand, significantly potentiated these two components of damage. A brief consideration of the physicochemical events which possibly account for the observed effects is presented. (author)

  5. 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.

  6. 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

    2017-02-24

    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.

  7. Electric dipole moments of nanosolvated acid molecules in water clusters.

    Science.gov (United States)

    Guggemos, Nicholas; Slavíček, Petr; Kresin, Vitaly V

    2015-01-30

    The electric dipole moments of (H2O)nDCl (n=3-9) clusters have been measured by the beam-deflection method. Reflecting the (dynamical) charge distribution within the system, the dipole moment contributes information about the microscopic structure of nanoscale solvation. The addition of a DCl molecule to a water cluster results in a strongly enhanced susceptibility. There is evidence for a noticeable rise in the dipole moment occurring at n≈5-6. This size is consistent with predictions for the onset of ionic dissociation. Additionally, a molecular-dynamics model suggests that even with a nominally bound impurity an enhanced dipole moment can arise due to the thermal and zero-point motion of the proton and the water molecules. The experimental measurements and the calculations draw attention to the importance of fluctuations in defining the polarity of water-based nanoclusters and generally to the essential role played by motional effects in determining the response of fluxional nanoscale systems under realistic conditions.

  8. Thermodynamic insight into spontaneous hydration and rapid water permeation in aquaporins

    Energy Technology Data Exchange (ETDEWEB)

    Barati Farimani, A.; Aluru, N. R. [Department of Mechanical Science and Engineering, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801 (United States); Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801 (United States); Tajkhorshid, Emad [Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801 (United States); Department of Biochemistry and Center for Biophysics and Computational Biology, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801 (United States)

    2014-08-25

    We report here a detailed thermodynamic description of water molecules inside a biological water channel. Taking advantage of high-resolution molecular dynamics trajectories calculated for an aquaporin (AQP) channel, we compute the spatial translational and rotational components of water diffusion and entropy in AQP. Our results reveal that the spontaneous filling and entry of water into the pore in AQPs are driven by an entropic gain. Specifically, water molecules exhibit an elevated degree of rotational motion inside the pore, while their translational motion is slow compared with bulk. The partial charges of the lining asparagine residues at the conserved signature Asn-Pro-Ala motifs play a key role in enhancing rotational diffusion and facilitating dipole flipping of water inside the pore. The frequencies of the translational and rotational motions in the power spectra overlap indicating a strong coupling of these motions in AQPs. A shooting mechanism with diffusive behavior is observed in the extracellular region which might be a key factor in the fast conduction of water in AQPs.

  9. Hydrogen bonding characterization in water and small molecules

    Science.gov (United States)

    Silvestrelli, Pier Luigi

    2017-06-01

    The prototypical hydrogen bond in water dimer and hydrogen bonds in the protonated water dimer, in other small molecules, in water cyclic clusters, and in ice, covering a wide range of bond strengths, are theoretically investigated by first-principles calculations based on density functional theory, considering not only a standard generalized gradient approximation functional but also, for the water dimer, hybrid and van der Waals corrected functionals. We compute structural, energetic, and electrostatic (induced molecular dipole moments) properties. In particular, hydrogen bonds are characterized in terms of differential electron density distributions and profiles, and of the shifts of the centres of maximally localized Wannier functions. The information from the latter quantities can be conveyed to a single geometric bonding parameter that appears to be correlated with the Mayer bond order parameter and can be taken as an estimate of the covalent contribution to the hydrogen bond. By considering the water trimer, the cyclic water hexamer, and the hexagonal phase of ice, we also elucidate the importance of cooperative/anticooperative effects in hydrogen-bonding formation.

  10. Continuum simulations of water flow past fullerene molecules

    DEFF Research Database (Denmark)

    Popadic, A.; Praprotnik, M.; Koumoutsakos, P.

    2015-01-01

    We present continuum simulations of water flow past fullerene molecules. The governing Navier-Stokes equations are complemented with the Navier slip boundary condition with a slip length that is extracted from related molecular dynamics simulations. We find that several quantities of interest...... as computed by the present model are in good agreement with results from atomistic and atomistic-continuum simulations at a fraction of the cost. We simulate the flow past a single fullerene and an array of fullerenes and demonstrate that such nanoscale flows can be computed efficiently by continuum flow...

  11. Selective control of photodissociation in deutereted water molecule HOD

    International Nuclear Information System (INIS)

    Adhikari, S.; Deshpande, Sarin; Sarma, Manabendra; Kurkal, Vandana; Mishra, M.K.

    2006-01-01

    Bond dissociation in the deutereted water molecule HOD has been investigated to explore the possibility of selective control of dissociation of O-H and O-D bonds using simple field profiles and initial states that do not require high overtone excitations. Preliminary results indicate that considerable selectivity in dissociation of O-H and O-D bonds can be achieved using fundamental and first overtone excitations only and use of field optimized initial state (FOIST) based scheme with appropriate choice of field parameters and initial states may enhance both selectivity and yield

  12. 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.

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

    International Nuclear Information System (INIS)

    Yakovlev, Sergey; Misra, Manoj; Shi, Shanling; Firlar, Emre; Libera, Matthew

    2010-01-01

    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 5 e/nm 2 despite the fact that observable damage begins at doses as low as 10 3 e/nm 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.

  14. Cation Hydration Constants by Proton NMR: A Physical Chemistry Experiment.

    Science.gov (United States)

    Smith, Robert L.; And Others

    1988-01-01

    Studies the polarization effect on water by cations and anions. Describes an experiment to illustrate the polarization effect of sodium, lithium, calcium, and strontium ions on the water molecule in the hydration spheres of the ions. Analysis is performed by proton NMR. (MVL)

  15. Methane hydrates. A possible energy source in the twenty-first century

    International Nuclear Information System (INIS)

    Sorassi, S.

    1998-01-01

    The morphological characteristics of particular crystal structures, to be found in nature both in arctic and Antarctic regions and under seas and oceans, and consisting of water and gas molecules, the so-called 'gas hydrates', are dealt with. Technical problems related to gas recovery (methane in particular) from hydrates, above all under sea level, mainly due to their reduced stability, are examined. On the ground of these considerations, various gas recovery methods from hydrate fields are described. An overall evaluation of methane availability as hydrates all over the world, as well as a comparison between extraction costs from hydrate and well as a comparison between extraction costs from hydrate and conventional fields, are made. Finally, short-term programmes on research and development of methane hydrate fields in some areas of the Earth are described [it

  16. Thermodynamic properties of water molecules in the presence of cosolute depend on DNA structure: a study using grid inhomogeneous solvation theory

    Science.gov (United States)

    Nakano, Miki; Tateishi-Karimata, Hisae; Tanaka, Shigenori; Tama, Florence; Miyashita, Osamu; Nakano, Shu-ichi; Sugimoto, Naoki

    2015-01-01

    In conditions that mimic those of the living cell, where various biomolecules and other components are present, DNA strands can adopt many structures in addition to the canonical B-form duplex. Previous studies in the presence of cosolutes that induce molecular crowding showed that thermal stabilities of DNA structures are associated with the properties of the water molecules around the DNAs. To understand how cosolutes, such as ethylene glycol, affect the thermal stability of DNA structures, we investigated the thermodynamic properties of water molecules around a hairpin duplex and a G-quadruplex using grid inhomogeneous solvation theory (GIST) with or without cosolutes. Our analysis indicated that (i) cosolutes increased the free energy of water molecules around DNA by disrupting water–water interactions, (ii) ethylene glycol more effectively disrupted water–water interactions around Watson–Crick base pairs than those around G-quartets or non-paired bases, (iii) due to the negative electrostatic potential there was a thicker hydration shell around G-quartets than around Watson–Crick-paired bases. Our findings suggest that the thermal stability of the hydration shell around DNAs is one factor that affects the thermal stabilities of DNA structures under the crowding conditions. PMID:26538600

  17. Determining the water-cement ratio, cement content, water content and degree of hydration of hardened cement paste: Method development and validation on paste samples

    International Nuclear Information System (INIS)

    Wong, H.S.; Buenfeld, N.R.

    2009-01-01

    We propose a new method to estimate the initial cement content, water content and free water/cement ratio (w/c) of hardened cement-based materials made with Portland cements that have unknown mixture proportions and degree of hydration. This method first quantifies the composition of the hardened cement paste, i.e. the volumetric fractions of capillary pores, hydration products and unreacted cement, using high-resolution field emission scanning electron microscopy (FE-SEM) in the backscattered electron (BSE) mode and image analysis. From the obtained data and the volumetric increase of solids during cement hydration, we compute the initial free water content and cement content, hence the free w/c ratio. The same method can also be used to calculate the degree of hydration. The proposed method has the advantage that it is quantitative and does not require comparison with calibration graphs or reference samples made with the same materials and cured to the same degree of hydration as the tested sample. This paper reports the development, assumptions and limitations of the proposed method, and preliminary results from Portland cement pastes with a range of w/c ratios (0.25-0.50) and curing ages (3-90 days). We also discuss the extension of the technique to mortars and concretes, and samples made with blended cements.

  18. 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.

  19. 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…

  20. Hydration numbers of trivalent lanthanide and actinide ions

    International Nuclear Information System (INIS)

    David, F.; Fourest, B.; Duplessis, J.

    1987-01-01

    Investigations on the structure of actinide aquo ions and determination of hydration numbers have to be studied, essentially, through radiochemical methods. They measured the transport numbers, diffusion coefficient D by the open end capillary method and ionic mobility u by electrophoresis. Both methods show a discontinuity in the transport number corresponding to the crystallographic radius of Eu 3+ or Bk 3+ ion. They deduced the volume of the actinide aquo ions, and the coordination number in the primary sphere. From calculations of the electrostriction phenomenon in the vicinity of central ion, they obtained effective volume of the water molecules and the dynamic hydration number corresponding to the second hydration sphere

  1. Nuclear magnetic resonance study of diffusion and relaxation in hydrating white cement pastes of different water content

    International Nuclear Information System (INIS)

    Nestle, Nikolaus; Galvosas, Petrik; Geier, Oliver; Zimmermann, Christian; Dakkouri, Marwan; Karger, Jorg

    2001-01-01

    While the nuclear spin relaxation time changes in hydrating cement materials have been widely studied by various groups during the last 20 years, data on the self-diffusion behavior of the pore water during hydration of a cement paste are much scarcer. Taking advantage of improved spectrometer hardware for pulsed field gradient diffusometry and a specialized pulse sequence which is designed to compensate the detrimental effects of inner magnetic field gradients in the sample we have studied the water self-diffusion behavior in pastes prepared from white cement at various water/cement ratios. For the same mixtures, studies of the transverse spin relaxation behavior were also conducted. A comparison of the results from both techniques shows that the diffusion coefficient starts to decrease only much later than the relaxation times for all pastes studied. [copyright] 2001 American Institute of Physics

  2. A gas production system from methane hydrate layers by hot water injection and BHP control with radial horizontal wells

    Energy Technology Data Exchange (ETDEWEB)

    Yamakawa, T.; Ono, S.; Iwamoto, A.; Sugai, Y.; Sasaki, K. [Kyushu Univ., Fukuoka, Fukuoka (Japan)

    2010-07-01

    Reservoir characterization of methane hydrate (MH) bearing turbidite channel in the eastern Nankai Trough, in Japan has been performed to develop a gas production strategy. This paper proposed a gas production system from methane hydrate (MH) sediment layers by combining the hot water injection method and bottom hole pressure control at the production well using radial horizontal wells. Numerical simulations of the cylindrical homogeneous MH layer model were performed in order to evaluate gas production characteristics by the depressurization method with bottom hole pressure control. In addition, the effects of numerical block modeling and averaging physical properties of MH layers were presented. According to numerical simulations, combining the existing production system with hot water injection and bottom hole pressure control results in an outward expansion of the hot water chamber from the center of the MH layer with continuous gas production. 10 refs., 15 figs.

  3. [Skin hydration and hydrating products].

    Science.gov (United States)

    Duplan, H; Nocera, T

    2018-05-01

    One of the skin's principal functions is to protect the body against its environment by maintaining an effective epidermal barrier, not only against external factors, but also to prevent water loss from the body. Indeed, water homeostasis is vital for the normal physiological functioning of skin. Hydration levels affect not only visible microscopic parameters such as the suppleness and softness of skin, but also molecular parameters, enzyme activities and cellular signalling within the epidermis. The body is continually losing some of its water, but this phenomenon is limited and the optimal hydration gradient in skin is ensured via a set of sophisticated regulatory processes that rely on the functional and dynamic properties of the uppermost level of the skin consisting of the stratum corneum. The present article brings together data recently acquired in the fields of skin hydration and the characterisation of dehydrated or dry skin, whether through study of the regulatory processes involved or as a result of changes in the techniques used for in situ measurement, and thus in optimisation of management. Copyright © 2018. Published by Elsevier Masson SAS.

  4. Hydrophobic hydration of poly-N-isopropyl acrylamide: a matter of the mean energetic state of water

    Science.gov (United States)

    Bischofberger, I.; Calzolari, D. C. E.; de Los Rios, P.; Jelezarov, I.; Trappe, V.

    2014-03-01

    The enthalpically favoured hydration of hydrophobic entities, termed hydrophobic hydration, impacts the phase behaviour of numerous amphiphiles in water. Here, we show experimental evidence that hydrophobic hydration is strongly determined by the mean energetics of the aqueous medium. We investigate the aggregation and collapse of an amphiphilic polymer, poly-N-isopropyl acrylamide (PNiPAM), in aqueous solutions containing small amounts of alcohol and find that the thermodynamic characteristics defining the phase transitions of PNiPAM evolve relative to the solvent composition at which the excess mixing enthalpy of the water/alcohol mixtures becomes minimal. Such correlation between solvent energetics and solution thermodynamics extends to other mixtures containing neutral organic solutes that are considered as kosmotropes to induce a strengthening of the hydrogen bonded water network. This denotes the energetics of water as a key parameter controlling the phase behaviour of PNiPAM and identifies the excess mixing enthalpy of water/kosmotrope mixtures as a gauge of the kosmotropic effect on hydrophobic assemblies.

  5. Gas hydrate in nature

    Science.gov (United States)

    Ruppel, Carolyn D.

    2018-01-17

    Gas hydrate is a naturally occurring, ice-like substance that forms when water and gas combine under high pressure and at moderate temperatures. Methane is the most common gas present in gas hydrate, although other gases may also be included in hydrate structures, particularly in areas close to conventional oil and gas reservoirs. Gas hydrate is widespread in ocean-bottom sediments at water depths greater than 300–500 meters (m; 984–1,640 feet [ft]) and is also present in areas with permanently frozen ground (permafrost). Several countries are evaluating gas hydrate as a possible energy resource in deepwater or permafrost settings. Gas hydrate is also under investigation to determine how environmental change may affect these deposits.

  6. Multicavity SCRF calculation of ion hydration energies

    International Nuclear Information System (INIS)

    Diercksen, B.H.F.; Karelson, M.; Tamm, T.

    1994-01-01

    The hydration energies of the proton, hydroxyl ion, and several inorganic ions were calculated using the multicavity self-consistent reaction field (MCa SCRF) method developed for the quantum-mechanical modeling of rotationally or flexible systems in dielectric media. The ionic complexes H 3 O + (H2O) 4 , OH - (H2O) 4 , NH + 4 (H2O) 4 , and Hal - (H2O) 4 , where Hal = F, Cl, or Br, have been studied. Each complex was divided between five spheres, corresponding to the central ion and four water molecules in their first coordination sphere, respectively. Each cavity was surrounded by a polarizable medium with the dielectric permittivity of water at room temperature (80). The ionic hydration energies of ions were divided into specific and nonspecific parts. After accounting for the cavity-formation energy using scaled particle theory, good agreement between the total calculated and experimental hydration energies was obtained for all ions studied

  7. 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 (extrusion contributing to the development of the mound. Blister-like 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 m

  8. Sequence Dependencies of DNA Deformability and Hydration in the Minor Groove

    Science.gov (United States)

    Yonetani, Yoshiteru; Kono, Hidetoshi

    2009-01-01

    Abstract DNA deformability and hydration are both sequence-dependent and are essential in specific DNA sequence recognition by proteins. However, the relationship between the two is not well understood. Here, systematic molecular dynamics simulations of 136 DNA sequences that differ from each other in their central tetramer revealed that sequence dependence of hydration is clearly correlated with that of deformability. We show that this correlation can be illustrated by four typical cases. Most rigid basepair steps are highly likely to form an ordered hydration pattern composed of one water molecule forming a bridge between the bases of distinct strands, but a few exceptions favor another ordered hydration composed of two water molecules forming such a bridge. Steps with medium deformability can display both of these hydration patterns with frequent transition. Highly flexible steps do not have any stable hydration pattern. A detailed picture of this correlation demonstrates that motions of hydration water molecules and DNA bases are tightly coupled with each other at the atomic level. These results contribute to our understanding of the entropic contribution from water molecules in protein or drug binding and could be applied for the purpose of predicting binding sites. PMID:19686662

  9. 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.

  10. Molecular dynamics study of water molecule diffusion in oil-paper insulation materials

    International Nuclear Information System (INIS)

    Liao Ruijin; Zhu Mengzhao; Yang Lijun; Zhou Xin; Gong Chunyan

    2011-01-01

    Moisture is an important factor that influences the safe operation of transformers. In this study, molecular dynamics was employed to investigate the diffusion behavior of water molecules in the oil-paper insulation materials of transformers. Two oil-cellulose models were built. In the first model, water molecules were initially distributed in oil, and in the second model, water molecules were distributed in cellulose. The non-bonding energies of interaction between water molecules and oil, and between water molecules and cellulose, were calculated by the Dreiding force field. The interaction energy was found to play a dominant role in influencing the equilibrium distribution of water molecules. The radial direction functions of water molecules toward oil and cellulose indicate that the hydrogen bonds between water molecules and cellulose are sufficiently strong to withstand the operating temperature of the transformer. Mean-square displacement analysis of water molecules diffusion suggests that water molecules initially distributed in oil showed anisotropic diffusion; they tended to diffuse toward cellulose. Water molecules initially distributed in cellulose diffused isotropically. This study provides a theoretical contribution for improvements in online monitoring of water in transformers, and for subsequent research on new insulation materials.

  11. Molecular dynamics study of water molecule diffusion in oil-paper insulation materials

    Energy Technology Data Exchange (ETDEWEB)

    Liao Ruijin [State Key Laboratory of Power Transmission Equipment and System Security and New Technology, Chongqing University, Chongqing 400044 (China); Zhu Mengzhao, E-mail: xiaozhupost@163.co [State Key Laboratory of Power Transmission Equipment and System Security and New Technology, Chongqing University, Chongqing 400044 (China); Yang Lijun; Zhou Xin; Gong Chunyan [State Key Laboratory of Power Transmission Equipment and System Security and New Technology, Chongqing University, Chongqing 400044 (China)

    2011-03-01

    Moisture is an important factor that influences the safe operation of transformers. In this study, molecular dynamics was employed to investigate the diffusion behavior of water molecules in the oil-paper insulation materials of transformers. Two oil-cellulose models were built. In the first model, water molecules were initially distributed in oil, and in the second model, water molecules were distributed in cellulose. The non-bonding energies of interaction between water molecules and oil, and between water molecules and cellulose, were calculated by the Dreiding force field. The interaction energy was found to play a dominant role in influencing the equilibrium distribution of water molecules. The radial direction functions of water molecules toward oil and cellulose indicate that the hydrogen bonds between water molecules and cellulose are sufficiently strong to withstand the operating temperature of the transformer. Mean-square displacement analysis of water molecules diffusion suggests that water molecules initially distributed in oil showed anisotropic diffusion; they tended to diffuse toward cellulose. Water molecules initially distributed in cellulose diffused isotropically. This study provides a theoretical contribution for improvements in online monitoring of water in transformers, and for subsequent research on new insulation materials.

  12. Observation of ice sheet formation on methane and ethane gas hydrates using a scanning confocal microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Nagao, J.; Shimomura, N.; Ebinuma, T.; Narita, H. [National Inst. of Advanced Industrial Science and Technology, Toyohira, Sapporo (Japan). Methane Hydrate Research Lab.

    2008-07-01

    Interest in gas hydrates has increased in recent years due to the discovery of large deposits under the ocean floor and in permafrost regions. Natural gas hydrates, including methane, is expected to become a new energy source and a medium for energy storage and transportation. Gas hydrates consist of an open network of water molecules that are hydrogen-bonded in a similar manner to ice. Gas molecules are interstitially engaged under high pressures and low temperatures. Although the dissociation temperature of methane hydrate under atmospheric pressure is about 193 K, studies have shown that methane hydrate can be stored at atmospheric pressure and 267 K for 2 years. Because of this phenomenon, known as self-preservation, transportation and storage of methane hydrate can occur at temperature conditions milder than those for liquefied methane gas at atmospheric pressure. This study examined the surface changes of methane and ethane hydrates during dissociation using an optical microscope and confocal scanning microscope (CSM). This paper reported on the results when the atmospheric gas pressure was decreased. Ice sheets formed on the surfaces of methane and ethane gas hydrates due to depressurizing dissociation of methane and ethane hydrates when the methane and ethane gas pressures were decreased at designated temperatures. The dissociation of methane gas hydrate below below 237 K resulted in the generation of small ice particles on the hydrate surface. A transparent ice sheet formed on the hydrate surface above 242 K. The thickness of the ice sheet on the methane hydrate surface showed the maximum of ca. 30 {mu}m at 253 K. In the case of ethane hydrates, ice particles and ice sheets formed below 262 and 267 respectively. Since the ice particles and ice sheets were formed by water molecules generated during the gas hydrate dissociation, the mechanism of ice sheet formation depends on the dissociation rate of hydrate, ice particle sintering rate, and water molecule

  13. Critical guest concentration and complete tuning pattern appearing in the binary clathrate hydrates

    Energy Technology Data Exchange (ETDEWEB)

    Cha, J.H.; Lee, H. [Korea Advanced Inst. of Science and Technology, Yuseong-gu, Daejeon (Korea, Republic of). Dept. of Chemical and Biomolecular Engineering; Kim, D.Y. [SK Engineering and Construction, Jongno-gu, Seoul (Korea, Republic of); Park, J. [Hanwha Chemical R and D Center, Yuseong-gu, Daejeon (Korea, Republic of); Lee, J.W. [Kongju National Univ., Cheonan, Chungnam (Korea, Republic of); Ripmeester, J.A. [National Research Council of Canada, Ottawa, ON (Canada). Steacie Inst. for Molecular Sciences

    2008-07-01

    Clathrate hydrates, or gas hydrates, are stabilized by van der Waals interaction between a guest molecule and a host framework. Because of their property, they are a potential resource in the exploitation of natural gas hydrates, as a material for the sequestration of carbon dioxide (CO{sub 2}), as a means of storage and transportation of natural gas, as well as hydrogen storage. Clathrate hydrate research can be divided into two categories that emphasize either macroscopic or microscopic approaches. However, these two approaches need to be closely linked for a better understanding of the structures and processes involving both natural phenomena and hydrates for industrial processes. Details on the molecular scale that concern the less usual properties of clathrate hydrates remain unknown. This paper presented the results of a study that reported on the existence of a critical guest concentration (CGC) and established the complete tuning pattern that occurred in the binary hydrates, including water-soluble hydrate formers (promoters) and water-insoluble guests. The paper presented the experimental procedures, including formation of the methane (CH{sub 4}) and tetrahydrofuran (THF) binary hydrate; a schematic diagram of the experimental apparatus; and formation of the CH{sub 4} and t-BuNH{sub 2} binary hydrate. Nuclear magnetic resonance (NMR) spectroscopic measurements and thermodynamic measurements were also presented. It was concluded that the CGC value appeared to primarily depend on the chemical nature of a liquid guest component participating in the binary hydrate formation. 10 refs., 2 tabs., 9 figs.

  14. A consistent and verifiable macroscopic model for the dissolution of liquid CO2 in water under hydrate forming conditions

    International Nuclear Information System (INIS)

    Radhakrishnan, R.; Demurov, A.; Trout, B.L.; Herzog, H.

    2003-01-01

    Direct injection of liquid CO 2 into the ocean has been proposed as one method to reduce the emission levels of CO 2 into the atmosphere. When liquid CO 2 is injected (normally as droplets) at ocean depths >500 m, a solid interfacial region between the CO 2 and the water is observed to form. This region consists of hydrate clathrates and hinders the rate of dissolution of CO 2 . It is, therefore, expected to have a significant impact on the injection of liquid CO 2 into the ocean. Up until now, no consistent and predictive model for the shrinking of droplets of CO 2 under hydrate forming conditions has been proposed. This is because all models proposed to date have had too many unknowns. By computing rates of the physical and chemical processes in hydrates via molecular dynamics simulations, we have been able to determine independently some of these unknowns. We then propose the most reasonable model and use it to make independent predictions of the rates of mass transfer and thickness of the hydrate region. These predictions are compared to measurements, and implications to the rates of shrinkage of CO 2 droplets under varying flow conditions are discussed. (author)

  15. 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.

  16. The effect of water molecules on the thiol collector interaction on the galena (PbS) and sphalerite (ZnS) surfaces: A DFT study

    Energy Technology Data Exchange (ETDEWEB)

    Long, Xianhao [School of Chemistry and Chemical Engineering, Guangxi University, Nanning 530004 (China); Chen, Ye, E-mail: fby18@126.com [College of Resources and Metallurgy, Guangxi University, Nanning 530004 (China); Chen, Jianhua, E-mail: jhchen@gxu.edu.cn [School of Chemistry and Chemical Engineering, Guangxi University, Nanning 530004 (China); College of Resources and Metallurgy, Guangxi University, Nanning 530004 (China); Xu, Zhenghe; Liu, Qingxia [Department of Chemical and Materials Engineering, University of Alberta, Edmonton, AB T6G 2V4 (Canada); Du, Zheng [National Supercomputing Center in Shenzhen, Shenzhen 518055 (China)

    2016-12-15

    Highlights: • Water adsorption has a greater effect on the electron distribution of ZnS surface than PbS surface. • Water adsorption decreases the reactivity of ZnS surface atoms but improves that of PbS. • Thiol collectors cannot interact with the hydrated ZnS surface. • The hydration has little influence on the interaction of thiol collectors with PbS surface. - Abstracts: In froth flotation the molecular interaction between reagents and mineral surfaces take place at the solid liquid interface. In this paper, the effect of water molecule on the three typical thiol collectors (xanthate, dithiocarbomate and dithiophosphate) interactions at the galena (PbS) and sphalerite (ZnS) surfaces has been studied adopting density functional theory (DFT). The results suggests that the presence of water molecule shows a greater influence on the electron distribution of ZnS surface than PbS surface, and reduce the reactivity of ZnS surface atoms but improves the reactivity of PbS surface atoms during the reaction with xanthate. Water adsorption could also reduce the covalent binding between Zn and S atoms but have little influence on Pb-S bond. In the presence of water, xanthate, dithiocarbomate (DTC) and dithiophosphate (DTP) could not adsorb on the sphalerite surface. And for galena (PbS) surface, the interaction of DTP is the strongest, then the DTC and the interaction of xanthate is the weakest. These results agree well with the flotation practice.

  17. Molecular multipole moments of water molecules in ice Ih

    International Nuclear Information System (INIS)

    Batista, E.R.; Xantheas, S.S.; Jonsson, H.

    1998-01-01

    We have used an induction model including dipole, dipole endash quadrupole, quadrupole endash quadrupole polarizability and first hyperpolarizability as well as fixed octopole and hexadecapole moments to study the electric field in ice. The self-consistent induction calculations gave an average total dipole moment of 3.09 D, a 67% increase over the dipole moment of an isolated water molecule. A previous, more approximate induction model study by Coulson and Eisenberg [Proc. R. Soc. Lond. A 291, 445 (1966)] suggested a significantly smaller average value of 2.6 D. This value has been used extensively in recent years as a reference point in the development of various polarizable interaction potentials for water as well as for assessment of the convergence of water cluster properties to those of bulk. The reason for this difference is not due to approximations made in the computational scheme of Coulson and Eisenberg but rather due to the use of less accurate values for the molecular multipoles in these earlier calculations. copyright 1998 American Institute of Physics

  18. 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.

  19. First-principles elasticity of monocarboaluminate hydrates

    KAUST Repository

    Moon, J.; Yoon, S.; Wentzcovitch, R. M.; Monteiro, P. J. M.

    2014-01-01

    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.

  20. Dynamics of water molecules and sodium ions in solid hydrates of nucleotides

    Czech Academy of Sciences Publication Activity Database

    Dračínský, Martin; Šála, Michal; Hodgkinson, P.

    2014-01-01

    Roč. 16, č. 29 (2014), s. 6756-6764 ISSN 1466-8033 R&D Projects: GA ČR GA13-24880S Grant - others:Seventh Framework Programme of the European Union(XE) FP7-299242 People Institutional support: RVO:61388963 Keywords : molecular dynamics simulations * NMR spectroscopy * DFT calculations Subject RIV: CC - Organic Chemistry Impact factor: 4.034, year: 2014

  1. Time-series measurements of bubble plume variability and water column methane distribution above Southern Hydrate Ridge, Oregon

    Science.gov (United States)

    Philip, Brendan T.; Denny, Alden R.; Solomon, Evan A.; Kelley, Deborah S.

    2016-03-01

    An estimated 500-2500 gigatons of methane carbon is sequestered in gas hydrate at continental margins and some of these deposits are associated with overlying methane seeps. To constrain the impact that seeps have on methane concentrations in overlying ocean waters and to characterize the bubble plumes that transport methane vertically into the ocean, water samples and time-series acoustic images were collected above Southern Hydrate Ridge (SHR), a well-studied hydrate-bearing seep site ˜90 km west of Newport, Oregon. These data were coregistered with robotic vehicle observations to determine the origin of the seeps, the plume rise heights above the seafloor, and the temporal variability in bubble emissions. Results show that the locations of seep activity and bubble release remained unchanged over the 3 year time-series investigation, however, the magnitude of gas release was highly variable on hourly time scales. Bubble plumes were detected to depths of 320-620 m below sea level (mbsl), in several cases exceeding the upper limit of hydrate stability by ˜190 m. For the first time, sustained gas release was imaged at the Pinnacle site and in-between the Pinnacle and the Summit area of venting, indicating that the subseafloor transport of fluid and gas is not restricted to the Summit at SHR, requiring a revision of fluid-flow models. Dissolved methane concentrations above background levels from 100 to 300 mbsl are consistent with long-term seep gas transport into the upper water column, which may lead to the build-up of seep-derived carbon in regional subsurface waters and to increases in associated biological activity.

  2. Binding of Divalent Cations to Polygalacturonate: A Mechanism Driven by the Hydration Water.

    Science.gov (United States)

    Huynh, Uyen T D; Lerbret, Adrien; Neiers, Fabrice; Chambin, Odile; Assifaoui, Ali

    2016-02-11

    We have investigated the interactions between polygalacturonate (polyGal) and four divalent cations (M(2+) = Ba(2+), Ca(2+), Mg(2+), Zn(2+)) that differ in size and affinity for water. Our results evidence that M(2+)-polyGal interactions are intimately linked to the affinity of M(2+) for water. Mg(2+) interacts so strongly with water that it remains weakly bound to polyGal (polycondensation) by sharing water molecules from its first coordination shell with the carboxylate groups of polyGal. In contrast, the other cations form transient ionic pairs with polyGal by releasing preferentially one water molecule (for Zn(2+)) or two (for Ca(2+) and Ba(2+)), which corresponds to monodentate and bidentate binding modes with carboxylates, respectively. The mechanism for the binding of these three divalent cations to polyGal can be described by two steps: (i) monocomplexation and formation of point-like cross-links between polyGal chains (at low M(2+)/Gal molar ratios, R) and (ii) dimerization (at higher R). The threshold molar ratio, R*, between these two steps depends on the nature of divalent cations and is lower for calcium ions (R* 0.3). This difference may be explained by the intermediate affinity of Ca(2+) for water with respect to those of Zn(2+) and Ba(2+), which may induce the formation of cross-links of intermediate flexibility. By comparison, the lower and higher flexibilities of the cross-links formed by Zn(2+) and Ba(2+), respectively, may shift the formation of dimers to higher molar ratios (R*).

  3. Approximative Krieger-Nelkin orientation averaging and anisotropy of water molecules vibrations

    International Nuclear Information System (INIS)

    Markovic, M.I.

    1974-01-01

    Quantum-mechanics approach of water molecules dynamics should be taken into account for precise theoretical calculation of differential scattering cross sections of neutrons. Krieger and Nelkin have proposed an approximate method for averaging orientation of molecules regarding directions of incoming and scattered neutron. This paper shows that this approach can be successfully applied for general shape of water molecule vibration anisotropy

  4. Thermodynamic studies on semi-clathrate hydrates of TBAB + gases containing carbon dioxide

    International Nuclear Information System (INIS)

    Eslamimanesh, Ali

    2012-01-01

    CO 2 capture has become an important area of research mainly due to its drastic greenhouse effects. Gas hydrate formation as a separation technique shows tremendous potential, both from a physical feasibility as well as an envisaged lower energy utilization criterion. Briefly, gas (clathrate) hydrates are non-stoichiometric, ice-like crystalline compounds formed through a combination of water and suitably sized guest molecule(s) under low-temperatures and elevated pressures. As the pressure required for gas hydrate formation is generally high, therefore, aqueous solution of tetra-n-butyl ammonium bromide (TBAB) is added to the system as a gas hydrate promoter. TBAB generally reduces the required hydrate formation pressure and/or increases the formation temperature as well as modifies the selectivity of hydrate cages to capture CO 2 molecules. TBAB also takes part in the hydrogen-bonded cages. Such hydrates are called 'semi-clathrate' hydrates. Evidently, reliable and accurate phase equilibrium data, acceptable thermodynamic models, and other thermodynamic studies should be provided to design efficient separation processes using the aforementioned technology. For this purpose, phase equilibria of clathrate/semi-clathrate hydrates of various gas mixtures containing CO 2 (CO 2 + CH 4 /N 2 /H 2 ) in the presence of pure water and aqueous solutions of TBAB have been measured in this thesis. In the theoretical section of the thesis, a thermodynamic model on the basis of the van der Waals and Platteeuw (vdW-P) solid solution theory along with the modified equations for determination of the Langmuir constants of the hydrate formers has been successfully developed to represent/predict equilibrium conditions of semi-clathrate hydrates of CO 2 , CH 4 , and N 2 . Later, several thermodynamic consistency tests on the basis of Gibbs-Duhem equation as well as a statistical approach have been applied on the phase equilibrium data of the systems of mixed/simple clathrate hydrates

  5. Development and preliminary testing of a standardized method for quantifying excess water in over-hydrated skin using evaporimetry

    International Nuclear Information System (INIS)

    Fader, M; Clark-O'Neill, S R; Cottenden, A M; Wong, W K R; Runeman, B; Farbrot, A

    2011-01-01

    Although evaporimetry (the measurement of water vapour flux density from the skin) has often been used to study the impact on skin hydration of using products such as baby diapers and incontinence pads, it is difficult to interpret results and to compare data from different studies because of the diversity of unvalidated methodologies used. The aim of this work was to develop a robust methodology for measuring the excess water in over-hydrated skin and test it on volar forearm and hip skin which had been occluded with saline soaked patches. Three repeat measurements were made on the volar forearm and the hip of five young (31–44 years) and six older (67–85 years) women and moderately good within-subject repeatability was found for both skin sites for both subject groups. Measurements taken from the hip were significantly higher (P = 0.001) than those from the arm and had larger coefficients of variation (3.5–22.1%) compared to arms (3.0–14.0%). There were no significant differences between young and older skin, implying that women for future studies could be recruited without regard to age. This is the first time that a robust evaporimetric methodology for quantifying excess water in over-hydrated skin has been described and validated, and it will form a solid basis for future work

  6. Studies on the crystal structure and arrangement of water in sitagliptin L-tartrate hydrates

    Czech Academy of Sciences Publication Activity Database

    Tieger, E.; Kiss, V.; Pokol, G.; Finta, Z.; Dušek, Michal; Rohlíček, Jan; Skořepová, E.; Brázda, Petr

    2016-01-01

    Roč. 18, č. 21 (2016), s. 3819-3831 ISSN 1466-8033 R&D Projects: GA MŠk LO1603; GA ČR GA16-10035S EU Projects: European Commission(XE) CZ.2.16/3.1.00/24510 Institutional support: RVO:68378271 Keywords : sitagliptin tartarate * crystal structure * channel hydrates * hydration * dehydration Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 3.474, year: 2016

  7. Gibbs Free Energy of Hydrolytic Water Molecule in Acyl-Enzyme Intermediates of a Serine Protease: A Potential Application for Computer-Aided Discovery of Mechanism-Based Reversible Covalent Inhibitors.

    Science.gov (United States)

    Masuda, Yosuke; Yamaotsu, Noriyuki; Hirono, Shuichi

    2017-01-01

    In order to predict the potencies of mechanism-based reversible covalent inhibitors, the relationships between calculated Gibbs free energy of hydrolytic water molecule in acyl-trypsin intermediates and experimentally measured catalytic rate constants (k cat ) were investigated. After obtaining representative solution structures by molecular dynamics (MD) simulations, hydration thermodynamics analyses using WaterMap™ were conducted. Consequently, we found for the first time that when Gibbs free energy of the hydrolytic water molecule was lower, logarithms of k cat were also lower. The hydrolytic water molecule with favorable Gibbs free energy may hydrolyze acylated serine slowly. Gibbs free energy of hydrolytic water molecule might be a useful descriptor for computer-aided discovery of mechanism-based reversible covalent inhibitors of hydrolytic enzymes.

  8. Role of Aquaporin Water Channels in Airway Fluid Transport, Humidification, and Surface Liquid Hydration

    Science.gov (United States)

    Song, Yuanlin; Jayaraman, Sujatha; Yang, Baoxue; Matthay, Michael A.; Verkman, A.S.

    2001-01-01

    Several aquaporin-type water channels are expressed in mammalian airways and lung: AQP1 in microvascular endothelia, AQP3 in upper airway epithelia, AQP4 in upper and lower airway epithelia, and AQP5 in alveolar epithelia. Novel quantitative methods were developed to compare airway fluid transport–related functions in wild-type mice and knockout mice deficient in these aquaporins. Lower airway humidification, measured from the moisture content of expired air during mechanical ventilation with dry air through a tracheotomy, was 54–56% efficient in wild-type mice, and reduced by only 3–4% in AQP1/AQP5 or AQP3/AQP4 double knockout mice. Upper airway humidification, measured from the moisture gained by dry air passed through the upper airways in mice breathing through a tracheotomy, decreased from 91 to 50% with increasing ventilation from 20 to 220 ml/min, and reduced by 3–5% in AQP3/AQP4 knockout mice. The depth and salt concentration of the airway surface liquid in trachea was measured in vivo using fluorescent probes and confocal and ratio imaging microscopy. Airway surface liquid depth was 45 ± 5 μm and [Na+] was 115 ± 4 mM in wild-type mice, and not significantly different in AQP3/AQP4 knockout mice. Osmotic water permeability in upper airways, measured by an in vivo instillation/sample method, was reduced by ∼40% by AQP3/AQP4 deletion. In doing these measurements, we discovered a novel amiloride-sensitive isosmolar fluid absorption process in upper airways (13% in 5 min) that was not affected by aquaporin deletion. These results establish the fluid transporting properties of mouse airways, and indicate that aquaporins play at most a minor role in airway humidification, ASL hydration, and isosmolar fluid absorption. PMID:11382807

  9. δD values of hydrated volcanic glass : a potential record of ancient meteoric water and climate in New Zealand

    International Nuclear Information System (INIS)

    Shane, P.; Ingraham, N.

    2002-01-01

    Tephra beds that are well drained and have been buried by thin paleosols become hydrated within 2-3000 yr on reaction with meteoric waters. Hence, the absorbed water within silicic volcanic glass shards provides a potential record of δD values of ancient meteoric water. Such isotopic records have previously received little investigation. We demonstrate that 1.5-2 m thick tephra beds in central North Island, New Zealand, display uniform δD values vertically through their profiles and laterally up to 250 m in outcrop. Reproducibility is not influenced by grain size or age of the tephra. We obtained an average δD value of -48 ± 3 permille for water within the 1.8 ka Taupo Tephra. This is similar to the composition of present-day surface waters. δD values of -73 ± 2 and -60 ± 2 permille for the 25 ka Kawakawa and 30 ka Mangaone Tephra beds are significantly lower than present waters, indicating that they have been hydrated under different surficial conditions. This is consistent with other proxy paleoclimatic indicators that suggest a cooler, drier, and windier climate at the time of their eruption. Tephra beds are a potential source of paleoclimatic data in terrestrial environments that otherwise may lack proxy records. (author). 17 refs., 5 figs., 3 tabs

  10. Rapid and accurate prediction and scoring of water molecules in protein binding sites.

    Directory of Open Access Journals (Sweden)

    Gregory A Ross

    Full Text Available Water plays a critical role in ligand-protein interactions. However, it is still challenging to predict accurately not only where water molecules prefer to bind, but also which of those water molecules might be displaceable. The latter is often seen as a route to optimizing affinity of potential drug candidates. Using a protocol we call WaterDock, we show that the freely available AutoDock Vina tool can be used to predict accurately the binding sites of water molecules. WaterDock was validated using data from X-ray crystallography, neutron diffraction and molecular dynamics simulations and correctly predicted 97% of the water molecules in the test set. In addition, we combined data-mining, heuristic and machine learning techniques to develop probabilistic water molecule classifiers. When applied to WaterDock predictions in the Astex Diverse Set of protein ligand complexes, we could identify whether a water molecule was conserved or displaced to an accuracy of 75%. A second model predicted whether water molecules were displaced by polar groups or by non-polar groups to an accuracy of 80%. These results should prove useful for anyone wishing to undertake rational design of new compounds where the displacement of water molecules is being considered as a route to improved affinity.

  11. Different Mechanism Effect between Gas-Solid and Liquid-Solid Interface on the Three-Phase Coexistence Hydrate System Dissociation in Seawater: A Molecular Dynamics Simulation Study

    Directory of Open Access Journals (Sweden)

    Zhixue Sun

    2017-12-01

    Full Text Available Almost 98% of methane hydrate is stored in the seawater environment, the study of microscopic mechanism for methane hydrate dissociation on the sea floor is of great significance to the development of hydrate production, involving a three-phase coexistence system of seawater (3.5% NaCl + hydrate + methane gas. The molecular dynamics method is used to simulate the hydrate dissociation process. The dissociation of hydrate system depends on diffusion of methane molecules from partially open cages and a layer by layer breakdown of the closed cages. The presence of liquid or gas phases adjacent to the hydrate has an effect on the rate of hydrate dissociation. At the beginning of dissociation process, hydrate layers that are in contact with liquid phase dissociated faster than layers adjacent to the gas phase. As the dissociation continues, the thickness of water film near the hydrate-liquid interface became larger than the hydrate-gas interface giving more resistance to the hydrate dissociation. Dissociation rate of hydrate layers adjacent to gas phase gradually exceeds the dissociation rate of layers adjacent to the liquid phase. The difficulty of methane diffusion in the hydrate-liquid side also brings about change in dissociation rate.

  12. Cryogenic-SEM investigation of CO{sub 2} hydrate morphologies

    Energy Technology Data Exchange (ETDEWEB)

    Camps, A.P.; Milodowski, A.; Rochelle, C.; Williams, J.F.; Jackson, P. D. [British Geological Survey, Keyworth, Nottinghamshire (United Kingdom); Camps, A.P; Lovell, M.; Williams, J.F. [Leicester Univ., Leicester (United Kingdom). Dept. of Geology

    2008-07-01

    Gas hydrates occur naturally around the world in the shallow-marine geosphere, and are seen as a drilling hazard in the petroleum industry due to their role in the carbon cycle, and their possible contribution in past and present climate change. Hydrates are ice-like structures composed of cages of water molecules containing one or more guest molecules, such as methane and carbon dioxide (CO{sub 2}). CO{sub 2} hydrates also occur naturally on earth and are being investigated for their potential to store large volumes of CO{sub 2} to reduce atmospheric emissions of greenhouse gases as a climate change mitigation strategy. However, the mineralogy and formation processes of hydrates are relatively poorly understood. Different imaging techniques have been utilized to study gas hydrates, such as nuclear magnetic resonance, magnetic resonance imaging, and x-ray computed tomography. Scanning Electron Microscopy (SEM) at cryogenic temperatures is another technique to study hydrates, and has been used successfully for investigation of methane and CO{sub 2} hydrates. This paper presented a study that investigated CO{sub 2} hydrates formed in laboratories, using a cryogenic-SEM. The paper presented the study methods and observations, including euhedral crystalline carbon dioxide hydrate; acicular carbon dioxide hydrate; granoblastic carbon dioxide hydrate; and gas rich carbon dioxide hydrate. It was concluded that the investigation produced various different hydrate morphologies resulting from different formation conditions. Morphologies ranged from well-defined euhedral crystals to acicular needles, and more complex, intricate forms. 22 refs., 6 figs., 1 appendix.

  13. Preliminary report on the economics of gas production from natural gas hydrates

    International Nuclear Information System (INIS)

    Walsh, M.; Wilson, S.; Patil, S.; Moridis, G.; Boswell, R.; Koh, C.; Sloan, D.

    2008-01-01

    Gas hydrates are solid crystalline compounds in which gas molecules reside inside cages that are formed by hydrogen-bonded water molecules in a crystal lattice. At particularly low temperatures and high pressures, a guest molecule will combine with water to form gas hydrates. Gas hydrates are found in two different settings in which the temperature and pressure conditions are suitable for their existence, notably in Arctic permafrost regions and below the seafloor. Because of the size of this possible future resource, if any of the gas in hydrates can be proven to be economically recoverable, then production from gas hydrates could become an important portion of the world's energy portfolio as demand for natural gas increases along with the technology to compress and distribute natural gas to distant markets. This paper presented a compilation of economic research that was conducted on the resource potential of gas hydrates. The paper reported a preliminary estimate of the price of natural gas that may lead to economically-viable production from North American Arctic region hydrates. The paper also discussed the implications of a recent study on the production of class 3 marine hydrate deposits from the Gulf of Mexico. The state of the art technologies and methods in hydrate reservoir modeling and hydrate reservoir production and petrophysical testing were also discussed. It was concluded that the somewhat optimistic results presented in this report should be interpreted with caution, however, the economically-viable gas production from hydrates was not an unreasonable scenario. 23 refs., 2 tabs., 10 figs

  14. Towards understanding the role of amines in the SO2 hydration and the contribution of the hydrated product to new particle formation in the Earth's atmosphere.

    Science.gov (United States)

    Lv, Guochun; Nadykto, Alexey B; Sun, Xiaomin; Zhang, Chenxi; Xu, Yisheng

    2018-08-01

    By theoretical calculations, the gas-phase SO 2 hydration reaction assisted by methylamine (MA) and dimethylamine (DMA) was investigated, and the potential contribution of the hydrated product to new particle formation (NPF) also was evaluated. The results show that the energy barrier for aliphatic amines (MA and DMA) assisted SO 2 hydration reaction is lower than the corresponding that of water and ammonia assisted SO 2 hydration. In these hydration reactions, nearly barrierless reaction (only a barrier of 0.1 kcal mol -1 ) can be found in the case of SO 2  + 2H 2 O + DMA. These lead us to conclude that the SO 2 hydration reaction assisted by MA and DMA is energetically facile. The temporal evolution for hydrated products (CH 3 NH 3 + -HSO 3 - -H 2 O or (CH 3 ) 2 NH 2 + -HSO 3 - -H 2 O) in molecular dynamics simulations indicates that these complexes can self-aggregate into bigger clusters and can absorb water and amine molecules, which means that these hydrated products formed by the hydration reaction may serve as a condensation nucleus to initiate the NPF. Copyright © 2018 Elsevier Ltd. All rights reserved.

  15. Fast Rotational Diffusion of Water Molecules in a 2D Hydrogen Bond Network at Cryogenic Temperatures

    Science.gov (United States)

    Prisk, T. R.; Hoffmann, C.; Kolesnikov, A. I.; Mamontov, E.; Podlesnyak, A. A.; Wang, X.; Kent, P. R. C.; Anovitz, L. M.

    2018-05-01

    Individual water molecules or small clusters of water molecules contained within microporous minerals present an extreme case of confinement where the local structure of hydrogen bond networks are dramatically altered from bulk water. In the zinc silicate hemimorphite, the water molecules form a two-dimensional hydrogen bond network with hydroxyl groups in the crystal framework. Here, we present a combined experimental and theoretical study of the structure and dynamics of water molecules within this network. The water molecules undergo a continuous phase transition in their orientational configuration analogous to a two-dimensional Ising model. The incoherent dynamic structure factor reveals two thermally activated relaxation processes, one on a subpicosecond timescale and another on a 10-100 ps timescale, between 70 and 130 K. The slow process is an in-plane reorientation of the water molecule involving the breaking of hydrogen bonds with a framework that, despite the low temperatures involved, is analogous to rotational diffusion of water molecules in the bulk liquid. The fast process is a localized motion of the water molecule with no apparent analogs among known bulk or confined phases of water.

  16. PRODUCTION OF HYDRATED ELECTRONS FROM PHOTOIONIZATION OF DISSOLVED ORGANIC MATTER IN NATURAL WATERS

    Science.gov (United States)

    Under UV irradiation, an important primary photochemical reaction of colored dissolved organic matter (CDOM) is electron ejection, producing hydrated electrons (e-aq). The efficiency of this process has been studied in both fresh and seawater samples with both steady-state scave...

  17. 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.

  18. Density, distribution, and orientation of water molecules inside and outside carbon nanotubes.

    Science.gov (United States)

    Thomas, J A; McGaughey, A J H

    2008-02-28

    The behavior of water molecules inside and outside 1.1, 2.8, 6.9, and 10.4 nm diameter armchair carbon nanotubes (CNTs) is predicted using molecular dynamics simulations. The effects of CNT diameter on mass density, molecular distribution, and molecular orientation are identified for both the confined and unconfined fluids. Within 1 nm of the CNT surface, unconfined water molecules assume a spatially varying density profile. The molecules distribute nonuniformly around the carbon surface and have preferred orientations. The behavior of the unconfined water molecules is invariant with CNT diameter. The behavior of the confined water, however, can be correlated to tube diameter. Inside the 10.4 nm CNT, the molecular behavior is indistinguishable from that of the unconfined fluid. Within the smaller CNTs, surface curvature effects reduce the equilibrium water density and force water molecules away from the surface. This effect changes both the molecular distribution and preferred molecular orientations.

  19. 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

  20. Petrophysical Characterization and Reservoir Simulator for Methane Gas Production from Gulf of Mexico Hydrates

    Energy Technology Data Exchange (ETDEWEB)

    Kishore Mohanty; Bill Cook; Mustafa Hakimuddin; Ramanan Pitchumani; Damiola Ogunlana; Jon Burger; John Shillinglaw

    2006-06-30

    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. Estimates of the amounts of methane sequestered in gas hydrates worldwide are speculative and range from about 100,000 to 270,000,000 trillion cubic feet (modified from Kvenvolden, 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 this project novel techniques were developed to form and dissociate methane hydrates in porous media, to measure acoustic properties and CT properties during hydrate dissociation in the presence of a porous medium. Hydrate depressurization experiments in cores were simulated with the use of TOUGHFx/HYDRATE simulator. Input/output software was developed to simulate variable pressure boundary condition and improve the ease of use of the simulator. A series of simulations needed to be run to mimic the variable pressure condition at the production well. The experiments can be matched qualitatively by the hydrate simulator. The temperature of the core falls during hydrate dissociation; the temperature drop is higher if the fluid withdrawal rate is higher. The pressure and temperature gradients are small within the core. The sodium iodide concentration affects the dissociation pressure and rate. This procedure and data will be useful in designing future hydrate studies.

  1. Phase equilibrium measurements and the tuning behavior of new sII clathrate hydrates

    Energy Technology Data Exchange (ETDEWEB)

    Shin, Woongchul; Park, Seongmin; Ro, Hyeyoon; Koh, Dong-Yeun; Seol, Jiwoong [Department of Chemical and Biomolecular Engineering (BK21 Program), KAIST, Daejeon 305-701 (Korea, Republic of); Lee, Huen, E-mail: h_lee@kaist.ac.kr [Department of Chemical and Biomolecular Engineering (BK21 Program), KAIST, Daejeon 305-701 (Korea, Republic of); Graduate School of EEWS, KAIST, Daejeon 305-701 (Korea, Republic of)

    2012-01-15

    Graphical abstract: Pyrrolidine and piperidine act as sII clathrate hydrate formers under methane gas. Highlights: > New sII clathrate hydrate formers were proposed: pyrrolidine and piperidine. > Formation of gas hydrate with methane as help gas was confirmed. > NMR, Raman, and XRD patterns were analyzed to identify the hydrate structures. > We measured (L + H + V) phase equilibrium with proposed hydrate formers. > Tuning phenomena increase gas storage in (pyrrolidine + CH{sub 4}) clathrate hydrates. - Abstract: We suggest two types of new amine-type sII formers: pyrrolidine and piperidine. These guest compounds fail to form clathrate hydrate structures with host water, but instead have to combine with light gaseous guest molecules (methane) for enclathration. First, two binary clathrate hydrates of (pyrrolidine + methane) and (piperidine + methane) were synthesized at various amine concentrations. {sup 13}C NMR and Raman analysis were done to identify the clathrate hydrate structure and guest distribution over sII-S and sII-L cages. XRD was also used to find the exact structure and corresponding cell parameters. At a dilute pyrrolidine concentration of less than 5.56 mol%, the tuning phenomenon is observed such that methane molecules surprisingly occupy sII-L cages. At the critical guest concentration of about 0.1 mol%, the cage occupancy ratio reaches the maximum of approximately 0.5. At very dilute guest concentration below 0.1 mol%, the methane molecules fail to occupy large cages on account of their rarefied distribution in the network. Direct-release experiments were performed to determine the actual guest compositions in the clathrate hydrate phases. Finally, we measured the clathrate hydrate phase equilibria of (pyrrolidine + methane) and (piperidine + methane).

  2. Phase equilibrium measurements and the tuning behavior of new sII clathrate hydrates

    International Nuclear Information System (INIS)

    Shin, Woongchul; Park, Seongmin; Ro, Hyeyoon; Koh, Dong-Yeun; Seol, Jiwoong; Lee, Huen

    2012-01-01

    Graphical abstract: Pyrrolidine and piperidine act as sII clathrate hydrate formers under methane gas. Highlights: → New sII clathrate hydrate formers were proposed: pyrrolidine and piperidine. → Formation of gas hydrate with methane as help gas was confirmed. → NMR, Raman, and XRD patterns were analyzed to identify the hydrate structures. → We measured (L + H + V) phase equilibrium with proposed hydrate formers. → Tuning phenomena increase gas storage in (pyrrolidine + CH 4 ) clathrate hydrates. - Abstract: We suggest two types of new amine-type sII formers: pyrrolidine and piperidine. These guest compounds fail to form clathrate hydrate structures with host water, but instead have to combine with light gaseous guest molecules (methane) for enclathration. First, two binary clathrate hydrates of (pyrrolidine + methane) and (piperidine + methane) were synthesized at various amine concentrations. 13 C NMR and Raman analysis were done to identify the clathrate hydrate structure and guest distribution over sII-S and sII-L cages. XRD was also used to find the exact structure and corresponding cell parameters. At a dilute pyrrolidine concentration of less than 5.56 mol%, the tuning phenomenon is observed such that methane molecules surprisingly occupy sII-L cages. At the critical guest concentration of about 0.1 mol%, the cage occupancy ratio reaches the maximum of approximately 0.5. At very dilute guest concentration below 0.1 mol%, the methane molecules fail to occupy large cages on account of their rarefied distribution in the network. Direct-release experiments were performed to determine the actual guest compositions in the clathrate hydrate phases. Finally, we measured the clathrate hydrate phase equilibria of (pyrrolidine + methane) and (piperidine + methane).

  3. Effects of water activity and low molecular weight humectants on skin permeability and hydration dynamics - a double-blind, randomized and controlled study.

    Science.gov (United States)

    Albèr, C; Buraczewska-Norin, I; Kocherbitov, V; Saleem, S; Lodén, M; Engblom, J

    2014-10-01

    The mammalian skin is a barrier that effectively separates the water-rich interior of the body from the normally dryer exterior. Changes in the external conditions, for example ambient humidity, have been shown to affect the skin barrier properties. The prime objective of this study was to evaluate the effect of water activity of a topical formulation on skin hydration and permeability. A second objective was to gain more understanding on how two commonly used humectants, urea and glycerol, affect skin barrier function in vivo. Simple aqueous formulations were applied under occlusion to the volar forearm of healthy volunteers. Following 4-h exposure, skin water loss (by transepidermal water loss measurements), skin hydration (by Corneometry) and skin permeability (by time to vasodilation due to benzyl nicotinate exposure) were monitored. The results demonstrate that a relatively small change in the water activity of a topical formulation is sufficient to induce considerable effects on stratum corneum hydration and permeability to exogenous substances. Exposing the skin to high water activity leads to increased skin hydration and also increased permeability. Furthermore, urea and glycerol promote skin hydration and permeability even at reduced water activity of the applied formulation. These results highlight the importance of considering the water activity in topically applied formulations and the potential benefit of using humectants. The results may impact formulation optimization in how to facilitate skin hydration and to modify skin permeability by temporarily open and close the skin barrier. © 2014 Society of Cosmetic Scientists and the Société Française de Cosmétologie.

  4. Models for the transport of low energy electrons in water and the yield of hydrated electrons at early times

    International Nuclear Information System (INIS)

    Brenner, D.J.; Miller, J.H.; Ritchie, R.H.; Bichsel, H.

    1985-01-01

    An insulator model with four experimental energy bands was used to fit the optical properties of liquid water and to extend these data to non-zero momentum transfer. Inelastic mean free paths derived from this dielectric response function provided the basic information necessary to degrade high energy electrons to the subexcitation energy domain. Two approaches for the transport of subexcitation electrons were investigated. (i) Gas phase cross sections were used to degrade subexcitation electrons to thermal energy and the thermalization lengths were scaled to unit density. (ii) Thermalization lengths were estimated by age-diffusion theory with a stopping power deduced from the data on liquid water and transport cross sections derived from elastic scattering in water vapor. Theoretical ranges were compared to recent experimental results. A stochastic model was used to calculate the rapid diffusion and reaction of hydrated electrons with other radiolysis products. The sensitivity of the calculated yields to the model assumptions and comparison with experimental data are discussed

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

    DEFF Research Database (Denmark)

    Skaarup, Steen

    2008-01-01

    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 may depend on the details of ion hydration....... 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...... direct calculation of the number of M+ ions entering the film, and therefore the inserted M+ mass. The mass of the water molecules is calculated as a difference. The results yield the following primary hydration numbers: Li+: 5.5-5.6; Na+: 4.0-4.1; K+: 2.0-2.5; Rb+: 0.6-1.2; Cs+: ~0. The most important...

  6. Precise structural analysis of methane hydrate by neutron diffraction

    International Nuclear Information System (INIS)

    Igawa, Naoki; Hoshikawa, Akinori; Ishii, Yoshinobu

    2006-01-01

    Methane hydrate has attracted great interest as an energy resource to replace natural gas since this material is deposited in the seafloor and the deposits are estimated to exceed those of natural gas. Understanding the physical proprieties, such as the temperature dependence of the crystal structure, helps to specify the optimum environmental temperature and pressure during drilling, transport, and storage of methane hydrate. Clathrate hydrates consisted of encaging atomic and/or molecular species as a guest and host water formed by a hydrogen bonding. Although many studies on the clathrate hydrate including methane hydrate were reported, no detailed crystallographic property has yet been cleared. We focused on the motion of methane in the clathrate hydrate by the neutron diffraction. The crystal structure of the methane hydrate was analyzed by the applying the combination of the Rietveld refinement and the maximum entropy method (MEM) to neutron powder diffraction. Temperature dependence of the scattering-length density distribution maps revealed that the motion of methane molecules differs between the shapes of dodecahedron and tetrakaidecahedron. (author)

  7. Thermal properties of methane hydrate by experiment and modeling and impacts upon technology

    Energy Technology Data Exchange (ETDEWEB)

    Warzinski, R.P.; Gamwo, I.K.; Rosenbaum, E.J. [United States Dept. of Energy, Pittsburgh, PA (United States). National Energy Technology Laboratory; Myshakin, E.M. [NETL Support Contractor, South Park, PA (United States); Jiang, H.; Jordan, K.D. [Pittsburgh Univ., Pittsburgh, PA (United States). Dept. of Chemistry; English, N.J. [Dublin University College, Dublin (Ireland). Conway Inst. of Biomolecular and Biomedical Research, Centre for Synthesis and Chemical Biology; Shaw, D.W. [Geneva College, Beaver Falls, PA (United States). Dept. of Engineering

    2008-07-01

    The current hydrate research at the National Energy Technology Laboratory (NETL) involves both experimental and theoretical work on developing models and methods for predicting the behaviour of gas hydrates in their natural environment under production of climate change scenarios. The modeling efforts include both fundamental and reservoir scale simulations and economic modeling. The thermal properties of methane hydrate are important for hydrate production, seafloor stability and climate change scenarios. A new experimental technique and advanced molecular dynamics simulation (MDS) have determined the thermal properties of pure methane hydrate under conditions similar to naturally occurring hydrate-bearing sediments. The thermal conductivity and thermal diffusivity values of low-porosity methane hydrate formed in the laboratory were measured using an innovative single-sided, Transient Plane Source (TPS) technique. The results were in good agreement with results from an equilibrium MDS method using in-plane polarization of the water molecules. MDS was also performed using a non-equilibrium model with a fully polarizable force field for water. The Tough+Hydrate reservoir simulator was also used to evaluate the impact of thermal conductivity on gas production from a hydrate-bearing reservoir. 42 refs., 1 tab., 5 figs.

  8. Chemical reactions of water molecules on Ru(0001) induced by selective excitation of vibrational modes

    Energy Technology Data Exchange (ETDEWEB)

    Mugarza, Aitor; Shimizu, Tomoko K.; Ogletree, D. Frank; Salmeron, Miquel

    2009-05-07

    Tunneling electrons in a scanning tunneling microscope were used to excite specific vibrational quantum states of adsorbed water and hydroxyl molecules on a Ru(0 0 0 1) surface. The excited molecules relaxed by transfer of energy to lower energy modes, resulting in diffusion, dissociation, desorption, and surface-tip transfer processes. Diffusion of H{sub 2}O molecules could be induced by excitation of the O-H stretch vibration mode at 445 meV. Isolated molecules required excitation of one single quantum while molecules bonded to a C atom required at least two quanta. Dissociation of single H{sub 2}O molecules into H and OH required electron energies of 1 eV or higher while dissociation of OH required at least 2 eV electrons. In contrast, water molecules forming part of a cluster could be dissociated with electron energies of 0.5 eV.

  9. Deep-Water Acoustic Anomalies from Methane Hydrate in the Bering Sea

    Science.gov (United States)

    Wood, Warren T.; Barth, Ginger A.; Scholl, David W.; Lebedeva-Ivanova, Nina

    2015-01-01

    A recent expedition to the central Bering Sea, one of the most remote locations in the world, has yielded observations confirming gas and gas hydrates in this deep ocean basin. Significant sound speed anomalies found using inversion of pre-stack seismic data are observed in association with variable seismic amplitude anomalies in the thick sediment column. The anomalously low sound speeds below the inferred base of methane hydrate stability indicate the presence of potentially large quantities of gas-phase methane associated with each velocity-amplitude anomaly (VAMP). The data acquired are of such high quality that quantitative estimates of the concentrations of gas hydrates in the upper few hundred meters of sediment are also possible, and analyses are under way to make these estimates. Several VAMPs were specifically targeted in this survey; others were crossed incidentally. Indications of many dozens or hundreds of these features exist throughout the portion of the Bering Sea relevant to the U.S. extended continental shelf (ECS) consistent with the United Nations Convention on the Law of the Sea. 

  10. Phase equilibria and thermodynamic modeling of ethane and propane hydrates in porous silica gels.

    Science.gov (United States)

    Seo, Yongwon; Lee, Seungmin; Cha, Inuk; Lee, Ju Dong; Lee, Huen

    2009-04-23

    In the present study, we examined the active role of porous silica gels when used as natural gas storage and transportation media. We adopted the dispersed water in silica gel pores to substantially enhance active surface for contacting and encaging gas molecules. We measured the three-phase hydrate (H)-water-rich liquid (L(W))-vapor (V) equilibria of C(2)H(6) and C(3)H(8) hydrates in 6.0, 15.0, 30.0, and 100.0 nm silica gel pores to investigate the effect of geometrical constraints on gas hydrate phase equilibria. At specified temperatures, the hydrate stability region is shifted to a higher pressure region depending on pore size when compared with those of bulk hydrates. Through application of the Gibbs-Thomson relationship to the experimental data, we determined the values for the C(2)H(6) hydrate-water and C(3)H(8) hydrate-water interfacial tensions to be 39 +/- 2 and 45 +/- 1 mJ/m(2), respectively. By using these values, the calculation values were in good agreement with the experimental ones. The overall results given in this study could also be quite useful in various fields, such as exploitation of natural gas hydrate in marine sediments and sequestration of carbon dioxide into the deep ocean.

  11. 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.

  12. Changes Of Hydration Level In Type I Collagen And Glycosaminoglycans Synthesized In The Rat’s Skin Under The Mechanical Stress

    Directory of Open Access Journals (Sweden)

    Alexandr M. Ponomarenko

    2013-01-01

    Full Text Available Changes of Hydratation Level Of Type I Collagen And Glycosaminoglycans That Are Synthesized In The Rat’s Skin Under The Mechanical Stress. The effect of the mechanical stress on the levels of hydratation of type I collagen and glycosaminoglycans that are synthesized in it, has been studied in vitro using the rats’ skin. The measured hydration of isotherms has shown that mechanical stress in the skin increases and decreases the amount of absorbed water in glycosaminoglycans and in collagen, respectively. Сalculated the average amounts of water molecules in collagen tripeptide and glycosaminoglycans disaccharide unit in the inside and outside layers of their hydrate shells

  13. Influence of orientation averaging on the anisotropy of thermal neutrons scattering on water molecules

    International Nuclear Information System (INIS)

    Markovic, M. I.; Radunovic, J. B.

    1976-01-01

    Determination of spatial distribution of neutron flux in water, most frequently used moderator in thermal reactors, demands microscopic scattering kernels dependence on cosine of thermal neutrons scattering angle when solving the Boltzmann equation. Since spatial orientation of water molecules influences this dependence it is necessary to perform orientation averaging or rotation-vibrational intermediate scattering function for water molecules. The calculations described in this paper and the obtained results showed that methods of orientation averaging do not influence the anisotropy of thermal neutrons scattering on water molecules, but do influence the inelastic scattering

  14. Body composition and hydration status changes in male and female open-water swimmers during an ultra-endurance event.

    Science.gov (United States)

    Weitkunat, Tim; Knechtle, Beat; Knechtle, Patrizia; Rüst, Christoph Alexander; Rosemann, Thomas

    2012-01-01

    Body mass changes during ultra-endurance performances have been described for running, cycling and for swimming in a heated pool. The present field study of 20 male and 11 female open-water swimmers investigated the changes in body composition and hydration status during an ultra-endurance event. Body mass, both estimated fat mass and skeletal muscle mass, haematocrit, plasma sodium concentration ([Na+]) and urine specific gravity were determined. Energy intake, energy expenditure and fluid intake were estimated. Males experienced significant reductions in body mass (-0.5 %) and skeletal muscle mass (-1.1 %) (P 0.05). Changes in percent body fat, fat mass, and fat-free mass were heterogeneous and did not reach statistical significance (P > 0.05) between gender groups. Fluid intake relative to plasma volume was higher in females than in males during the ultra-endurance event. Compared to males, females' average increase in haematocrit was 3.3 percentage points (pp) higher, urine specific gravity decrease 0.1 pp smaller, and plasma [Na+] 1.3 pp higher. The observed patterns of fluid intake, changes in plasma volume, urine specific gravity, and plasma [Na+] suggest that, particularly in females, a combination of fluid shift from blood vessels to interstitial tissue, facilitated by skeletal muscle damage, as well as exercise-associated hyponatremia had occurred. To summarise, changes in body composition and hydration status are different in male compared to female open-water ultra-endurance swimmers.

  15. 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

  16. The mechanism of 2-dimensional manipulation of DNA molecules by water and ethanol flows

    International Nuclear Information System (INIS)

    Shen Zigang; Huang Yibo; Li Bin; Zhang Yi

    2007-01-01

    Due to its unique physical and chemical properties, DNA has recently become a promising material for building blocks in nanofabrication. Many researches focus on how to use DNA molecules as a template for nanowires. Molecular Combing technique is one of important methods to manipulate DNA molecules by using a water meniscus and form specific DNA nano-structures on surfaces. In this paper, by employing a modified molecular combing technique, special patterns of DNA molecules was formed, and the interaction between liquid flows or meniscus and DNA molecules was analyzed, and the mechanism of manipulating DNA molecules by liquid was studied. (authors)

  17. Influence of hydration water on CH3NH3PbI3 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 CH3NH3PbI3 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 3CH3NH3I:1PbAc2•xH2O precursor solution. The results can provide guidance for further optimization of the device performance of perovskite solar cells by utilizing hydration water.

  18. Low frequency enzyme dynamics as a function of temperature and hydration: A neutron scattering study

    Energy Technology Data Exchange (ETDEWEB)

    Kurkal, V. [Interdisciplinary Center for Scientific Computing (IWR), University of Heidelberg, Im Neuenheimer Feld 368, D-69120 Heidelberg (Germany); Daniel, R.M. [Department of Biological Sciences, University of Waikato, Private Bag 3105, Hamilton (New Zealand); Finney, John L. [Department of Physics and Astronomy, University college, London, Gower Street, London WC1E 6BT, England (United Kingdom); Tehei, M. [Department of Biological Sciences, University of Waikato, Private Bag 3105, Hamilton (New Zealand); Dunn, R.V. [Department of Biological Sciences, University of Waikato, Private Bag 3105, Hamilton (New Zealand); Smith, Jeremy C. [Interdisciplinary Center for Scientific Computing (IWR), University of Heidelberg, Im Neuenheimer Feld 368, D-69120 Heidelberg (Germany)], E-mail: biocomputing@iwr.uni-heidelberg.de

    2005-10-31

    The effect of hydration and temperature on the low-frequency dynamics of the enzyme Pig liver esterase has been investigated with incoherent neutron scattering experiments. The results suggest that at low temperature, increasing hydration results in lower flexibility of the protein. At higher temperatures, systems containing sufficient number of water molecules interacting with the protein exhibit increased flexibility. The environmental force constants indicate that the environment of the protein is more rigid below than it is above the dynamical transition temperature.

  19. Distribution of B, Cl and Their Isotopes in Pore Waters Separated from Gas Hydrate Potential Areas, Offshore Southwestern Taiwan

    Directory of Open Access Journals (Sweden)

    Hung-Chun Chao Chen-Feng You

    2006-01-01

    Full Text Available Boron (B and chlorine (Cl are widely distributed on the Earth’s surface and show distinctive geochemical behaviors. Cl behaves rather conservatively in oceanic environments while B is an excess-volatile and its distribution is sensitive to sediment absorption and organic matter degradation. The distribution of B, Cl and their isotopes in pore waters provide useful information for distinguishing between shallow circulation and deep origin fluid sources. Thirty-six sediment cores 0 - 5 m in length were sampled from a foreland accretionary prism offshore Southwestern Taiwan where strong bottom simulating reflectors (BSRs and an abundance of mud diapirs were discovered. More than 350 pore water samples were separated and analyzed for B, Cl and other major ions. Four long cores were selected for B and Cl isotopic analysis. We found that the Cl in all cores varied less than 10%, suggesting no major hydrate dissolution or formation involvement at shallow depths in the study area. However, the B concentration changed greatly, ranging between 360 and 650 μM, indicating a possible sedimentary contribution during the early diagenesis stage. The B isotopic compositions were relatively depleted (~25 to 37‰ in these pore waters, implying the addition of sedimentary exchangeable B with low δ11B. The Cl isotopes showed rather large variations, more than 8‰, possibly related to the addition of deep situated fluids. In summary, the chemical and isotopic characteristics of pore waters separated from piston cores off Southwestern Taiwan suggest strong influence from organic matter degradation during diagenesis at shallow depths and the possible addition of deep fluids advecting through mud diapir channels at greater depths, causing a minor degree of hydrate dissolution / formation to occur at shallow depths. Further systematic investigation of pore waters δ18O and δD are needed in a future study.

  20. 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.

  1. Dielectric and gravimetric studies of water binding to lysozyme

    International Nuclear Information System (INIS)

    Bone, S.

    1996-01-01

    Time domain dielectric spectroscopy and hydration isotherm measurements as a function of temperature have been applied to hydrated lysozyme powder. Two dielectric dispersions were identified, the first centred at approximately 8 MHz and a second above 1 GHz. The higher dispersion is considered to be the result of rotational relaxation of water molecules bound to the enzyme. In this case the results indicate the existence of a population of 32 water molecules per lysozyme molecule which are irrotationally bound to the lysozyme structure. A larger population of water molecules is relatively free to respond to the electric field and exhibits a dipole moment close to that of vapour phase water molecules. Multi-temperature hydration isotherm measurements are used to calculate enthalpies and entropies associated with the binding of water to lysozyme. Discontinuities both in dielectric and in thermodynamic characteristics in the range 10-14% hydration are interpreted as a re-ordering of the water structure on the enzyme surface

  2. 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.

  3. Implication of Crystal Water Molecules in Inhibitor Binding at ALR2 Active Site

    Directory of Open Access Journals (Sweden)

    Hymavati

    2012-01-01

    Full Text Available Water molecules play a crucial role in mediating the interaction between a ligand and a macromolecule. The solvent environment around such biomolecule controls their structure and plays important role in protein-ligand interactions. An understanding of the nature and role of these water molecules in the active site of a protein could greatly increase the efficiency of rational drug design approaches. We have performed the comparative crystal structure analysis of aldose reductase to understand the role of crystal water in protein-ligand interaction. Molecular dynamics simulation has shown the versatile nature of water molecules in bridge H bonding during interaction. Occupancy and life time of water molecules depend on the type of cocrystallized ligand present in the structure. The information may be useful in rational approach to customize the ligand, and thereby longer occupancy and life time for bridge H-bonding.

  4. Gas hydrates

    Digital Repository Service at National Institute of Oceanography (India)

    Ramprasad, T.

    , not all of them are white like snow. Some hydrates from the deep Gulf of Mexico are richly colored in shades of yellow, orange, or even red. The ice-like masses are beautiful, and contrast with the dull gray of deep sea muds. Hydrates from the Blake... volcanoes and associated gas hydrates: Marine Geology, v. 167, p. 29-42. Milkov, A.V. and R. Sassen, 2001a, Estimate of gas hydrate resource, northwestern Gulf of Mexico continental slope: Marine Geology, v. 179, pp. 71-83. Milkov, A.V., Sassen, R...

  5. Exploring the possibility to store the mixed oxygen-hydrogen cluster in clathrate hydrate in molar ratio 1:2 (O2+2H2).

    Science.gov (United States)

    Qin, Yan; Du, Qi-Shi; Xie, Neng-Zhong; Li, Jian-Xiu; Huang, Ri-Bo

    2017-05-01

    An interesting possibility is explored: storing the mixture of oxygen and hydrogen in clathrate hydrate in molar ratio 1:2. The interaction energies between oxygen, hydrogen, and clathrate hydrate are calculated using high level quantum chemical methods. The useful conclusion points from this study are summarized as follows. (1) The interaction energies of oxygen-hydrogen mixed cluster are larger than the energies of pure hydrogen molecular cluster. (2) The affinity of oxygen molecules with water molecules is larger than that of the hydrogen molecules with water molecules. (3) The dimension of O 2 -2H 2 interaction structure is smaller than the dimension of CO 2 -2H 2 interaction structure. (4) The escaping energy of oxygen molecules from the hydrate cell is larger than that of the hydrogen molecules. (5) The high affinity of the oxygen molecules with both the water molecules and the hydrogen molecules may promote the stability of oxygen-hydrogen mixture in the clathrate hydrate. Therefore it is possible to store the mixed (O 2 +2H 2 ) cluster in clathrate hydrate. Copyright © 2017 Elsevier Inc. All rights reserved.

  6. Femtosecond spectroscopic study of the solvation of amphiphilic molecules by water

    NARCIS (Netherlands)

    Rezus, Y.L.A.; Bakker, H.J.

    2008-01-01

    We use polarization-resolved mid-infrared pump-probe spectroscopy to study the aqueous solvation of proline and N-methylacetamide. These molecules serve as models to study the solvation of proteins. We monitor the orientational dynamics of partly deuterated water molecules (HDO) that are present at

  7. Overview: Nucleation of clathrate hydrates.

    Science.gov (United States)

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

    2016-12-07

    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.

  8. 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.

  9. Dynamics of water molecules in the active-site cavity of human cytochromes P450

    DEFF Research Database (Denmark)

    Rydberg, Patrik; Rod, Thomas Holm; Olsen, Lars

    2007-01-01

    We have studied the dynamics of water molecules in six crystal structures of four human cytochromes P450, 2A6, 2C8, 2C9, and 3A4, with molecular dynamics simulations. In the crystal structures, only a few water molecules are seen and the reported sizes of the active-site cavity vary a lot....... In the simulations, the cavities are completely filled with water molecules, although with approximately 20% lower density than in bulk water. The 2A6 protein differs from the other three in that it has a very small cavity with only two water molecules and no exchange with the surroundings. The other three proteins...... channels, through which there is a quite frequent exchange of water molecules (one molecule is exchanged every 30-200 ps), except in 2A6. Most of the channels are observed also in the crystal structures, but two to three channels in each protein open only during the simulations. There are no water...

  10. Structural Arrangement of Water Molecules around Highly Charged Nanoparticles: Molecular Dynamics Simulation

    International Nuclear Information System (INIS)

    Kim, Eunae; Yeom, Min Sun

    2014-01-01

    Molecular dynamics simulations were performed to understand the structural arrangement of water molecules around highly charged nanoparticles under aqueous conditions. The effect of two highly charged nanoparticles on the solvation charge asymmetry has been examined. We calculated the radial distribution functions of the components of water molecules around nanoparticles which have four charge types at two different salt concentrations. Even though the distributions of water molecules surrounding a sodium ion and a chloride ion are hardly affected by the charges of nanoparticles and the salt concentrations, those around highly charged nanoparticles are strongly influenced by the charges of nanoparticles, but hardly by the charges of nanoparticles and salt concentrations. We find that the distributions of hydrogen atoms in water molecules around one highly charged nanoparticle are dependent on the magnitude of the nanoparticle charge

  11. Quantum Electric Dipole Lattice - Water Molecules Confined to Nanocavities in Beryl

    Science.gov (United States)

    Dressel, Martin; Zhukova, Elena S.; Thomas, Victor G.; Gorshunov, Boris P.

    2018-02-01

    Water is subject to intense investigations due to its importance in biological matter but keeps many of its secrets. Here, we unveil an even other aspect by confining H2O molecules to nanosize cages. Our THz and infrared spectra of water in the gemstone beryl evidence quantum tunneling of H2O molecules in the crystal lattice. The water molecules are spread out when confined in a nanocage. In combination with low-frequency dielectric measurements, we were also able to show that dipolar coupling among the H2O molecules leads towards a ferroelectric state at low temperatures. Upon cooling, a ferroelectric soft mode shifts through the THz range. Only quantum fluctuations prevent perfect macroscopic order to be fully achieved. Beside the significance to life science and possible application, nanoconfined water may become the prime example of a quantum electric dipolar lattice.

  12. Identification of intrinsic catalytic activity for electrochemical reduction of water molecules to generate hydrogen

    KAUST Repository

    Shinagawa, Tatsuya; Takanabe, Kazuhiro

    2015-01-01

    Insufficient hydronium ion activities at near-neutral pH and under unbuffered conditions induce diffusion-limited currents for hydrogen evolution, followed by a reaction with water molecules to generate hydrogen at elevated potentials. The observed

  13. A dynamic model to explain hydration behaviour along the lanthanide series

    International Nuclear Information System (INIS)

    Duvail, M.; Spezia, R.; Vitorge, P.

    2008-01-01

    An understanding of the hydration structure of heavy atoms, such as transition metals, lanthanides and actinides, in aqueous solution is of fundamental importance in order to address their solvation properties and chemical reactivity. Herein we present a systematic molecular dynamics study of Ln 3+ hydration in bulk water that can be used as reference for experimental and theoretical research in this and related fields. Our study of hydration structure and dynamics along the entire Ln 3+ series provides a dynamic picture of the CN behavioural change from light (CN=9 predominating) to heavy (CN=8 predominating) lanthanides consistent with the exchange mechanism proposed by Helm, Merbach and co-workers. This scenario is summarized in this work. The hydrated light lanthanides are stable TTP structures containing two kinds of water molecules: six molecules forming the trigonal prism and three in the centre triangle. Towards the middle of the series both ionic radii and polarizabilities decrease, such that first-shell water-water repulsion increases and water-cation attraction decreases. This mainly applies for molecules of the centre triangle of the nine-fold structure. Thus, one of these molecules stay in the second hydration sphere of the lanthanide for longer average times, as one progresses along the lanthanide series. The interchange between predominantly CN=9 and CN=8 is found between Tb and Dy. Therefore, we propose a model that determines the properties governing the change in the first-shell coordination number across the series, confirming the basic hypothesis proposed by Helm and Merbach. We show that it is not a sudden change in behaviour, but rather that it results from a statistical predominance of one first hydration shell structure containing nine water molecules over one containing eight. This is observed progressively across the series. (O.M.)

  14. Gas hydrate cool storage system

    Science.gov (United States)

    Ternes, M.P.; Kedl, R.J.

    1984-09-12

    The invention presented relates to the development of a process utilizing a gas hydrate as a cool storage medium for alleviating electric load demands during peak usage periods. Several objectives of the invention are mentioned concerning the formation of the gas hydrate as storage material in a thermal energy storage system within a heat pump cycle system. The gas hydrate was formed using a refrigerant in water and an example with R-12 refrigerant is included. (BCS)

  15. Methane Hydrates: Chapter 8

    Science.gov (United States)

    Boswell, Ray; Yamamoto, Koji; Lee, Sung-Rock; Collett, Timothy S.; Kumar, Pushpendra; Dallimore, Scott

    2008-01-01

    Gas hydrate is a solid, naturally occurring substance consisting predominantly of methane gas and water. Recent scientific drilling programs in Japan, Canada, the United States, Korea and India have demonstrated that gas hydrate occurs broadly and in a variety of forms in shallow sediments of the outer continental shelves and in Arctic regions. Field, laboratory and numerical modelling studies conducted to date indicate that gas can be extracted from gas hydrates with existing production technologies, particularly for those deposits in which the gas hydrate exists as pore-filling grains at high saturation in sand-rich reservoirs. A series of regional resource assessments indicate that substantial volumes of gas hydrate likely exist in sand-rich deposits. Recent field programs in Japan, Canada and in the United States have demonstrated the technical viability of methane extraction from gas-hydrate-bearing sand reservoirs and have investigated a range of potential production scenarios. At present, basic reservoir depressurisation shows the greatest promise and can be conducted using primarily standard industry equipment and procedures. Depressurisation is expected to be the foundation of future production systems; additional processes, such as thermal stimulation, mechanical stimulation and chemical injection, will likely also be integrated as dictated by local geological and other conditions. An innovative carbon dioxide and methane swapping technology is also being studied as a method to produce gas from select gas hydrate deposits. In addition, substantial additional volumes of gas hydrate have been found in dense arrays of grain-displacing veins and nodules in fine-grained, clay-dominated sediments; however, to date, no field tests, and very limited numerical modelling, have been conducted with regard to the production potential of such accumulations. Work remains to further refine: (1) the marine resource volumes within potential accumulations that can be

  16. In-situ X-ray diffraction reveals the degradation of crystalline CH3NH3PbI3 by water-molecule collisions at room temperature

    Science.gov (United States)

    Hada, Masaki; Hasegawa, Yoichi; Nagaoka, Ryota; Miyake, Tomoya; Abdullaev, Ulugbek; Ota, Hiromi; Nishikawa, Takeshi; Yamashita, Yoshifumi; Hayashi, Yasuhiko

    2018-02-01

    We have developed a vacuum-compatible chamber for in-situ X-ray diffraction (XRD) studies and have used it to characterize the changing crystal structure of an inorganic-organic hybrid perovskite material, CH3NH3PbI3 (MAPbI3), during interactions with water vapor at room temperature. In the XRD spectra, we have observed the degradation of MAPbI3 and the creation of MAPbI3 hydrates, which follow simple rate equations. The time constant for the degradation of MAPbI3 during accelerated aging suggests that multiple collisions of water molecules with the MAPbI3 crystal trigger the degradation of the crystal.

  17. The effect of mineral-based alkaline water on hydration status and the metabolic response to short-term anaerobic exercise

    Directory of Open Access Journals (Sweden)

    Jakub Chycki

    2017-04-01

    Full Text Available Previously it was demonstrated that mineralization and alkalization properties of mineral water are important factors influencing acid-base balance and hydration in athletes. The purpose of this study was to investigate the effects of drinking different types of water on urine pH, specific urine gravity, and post-exercise lactate utilization in response to strenuous exercise. Thirty-six male soccer players were divided into three intervention groups, consuming around 4.0 l/day of different types of water for 7 days: HM (n=12; highly mineralized water, LM (n=12; low mineralized water, and CON (n=12; table water. The athletes performed an exercise protocol on two occasions (before and after intervention. The exercise protocol consisted of 5 bouts of intensive 60-s (120% VO2max cycling separated by 60 s of passive rest. Body composition, urinalysis and lactate concentration were evaluated – before (t0, immediately after (t1, 5’ (t2, and 30’ (t3 after exercise. Total body water and its active transport (TBW – total body water / ICW – intracellular water / ECW – extracellular water showed no significant differences in all groups, at both occasions. In the post-hydration state we found a significant decrease of specific urine gravity in HM (1021±4.2 vs 1015±3.8 g/L and LM (1022±3.1 vs 1008±4.2 g/L. We also found a significant increase of pH and lactate utilization rate in LM. In conclusion, the athletes hydrated with alkaline, low mineralized water demonstrated favourable changes in hydration status in response to high-intensity interval exercise with a significant decrease of specific urine gravity, increased urine pH and more efficient utilization of lactate after supramaximal exercise.

  18. Final Scientific/Technical Report: Characterizing the Response of the Cascadia Margin Gas Hydrate Reservoir to Bottom Water Warming Along the Upper Continental Slope

    Energy Technology Data Exchange (ETDEWEB)

    Solomon, Evan A. [Univ. of Washington, Seattle, WA (United States); Johnson, H. Paul [Univ. of Washington, Seattle, WA (United States); Salmi, Marie [Univ. of Washington, Seattle, WA (United States); Whorley, Theresa [Univ. of Washington, Seattle, WA (United States)

    2017-11-10

    The objective of this project is to understand the response of the WA margin gas hydrate system to contemporary warming of bottom water along the upper continental slope. Through pre-cruise analysis and modeling of archive and recent geophysical and oceanographic data, we (1) inventoried bottom simulating reflectors along the WA margin and defined the upper limit of gas hydrate stability, (2) refined margin-wide estimates of heat flow and geothermal gradients, (3) characterized decadal scale temporal variations of bottom water temperatures at the upper continental slope of the Washington margin, and (4) used numerical simulations to provide quantitative estimates of how the shallow boundary of methane hydrate stability responds to modern environmental change. These pre-cruise results provided the context for a systematic geophysical and geochemical survey of methane seepage along the upper continental slope from 48° to 46°N during a 10-day field program on the R/V Thompson from October 10-19, 2014. This systematic inventory of methane emissions along this climate-sensitive margin corridor and comprehensive sediment and water column sampling program provided data and samples for Phase 3 of this project that focused on determining fluid and methane sources (deep-source vs. shallow; microbial, thermogenic, gas hydrate dissociation) within the sediment, and how they relate to contemporary intermediate water warming. During the 2014 research expedition, we sampled nine seep sites between ~470 and 520 m water depth, within the zone of predicted methane hydrate retreat over the past 40 years. We imaged 22 bubble plumes with heights commonly rising to ~300 meters below sea level with one reaching near the sea surface. We collected 22 gravity cores and 20 CTD/hydrocasts from the 9 seeps and at background locations (no acoustic evidence of seepage) within the depth interval of predicted downslope retreat of the methane hydrate stability zone. Approximately 300 pore water

  19. In situ Low-temperature Pair Distribution Function (PDF) Analysis of CH4 and CO2 Hydrates

    Science.gov (United States)

    Cladek, B.; Everett, M.; McDonnell, M.; Tucker, M.; Keffer, D.; Rawn, C.

    2017-12-01

    Gas hydrates occur in ocean floor and sub-surface permafrost deposits and are stable at moderate to high pressures and low temperatures. They are a clathrate structure composed of hydrogen bonded water cages that accommodate a wide variety of guest molecules. CO2 and CH4 hydrates both crystallize as the cubic sI hydrate and can form a solid solution. Natural gas hydrates are interesting as a potential methane source and for CO2 sequestration. Long-range diffraction studies on gas hydrates give valuable structural information but do not provide a detailed understanding of the disordered gas molecule interactions with the host lattice. In-situ low temperature total scattering experiments combined with pair distribution function (PDF) analysis are used to investigate the gas molecule motions and guest-cage interactions. CO2 and methane hydrates exhibit different decomposition behavior, and CO2 hydrate has a smaller lattice parameter despite it being a relatively larger molecule. Total scattering studies characterizing both the short- and long-range order simultaneously help to elucidate the structural source of these phenomena. Low temperature neutron total scattering data were collected using the Nanoscale Ordered MAterials Diffractometer (NOMAD) beamline at the Spallation Neutron Source (SNS) on CO2 and CH4 hydrates synthesized with D2O. Guest molecule motion within cages and interactions between gases and cages are investigated through the hydrate stability and decomposition regions. Data were collected from 2-80 K at a pressure of 55 mbar on CO2 and CH4 hydrates, and from 80-270 K at 25 bar on CH4 hydrate. The hydrate systems were modeled with classical molecular dynamic (MD) simulations to provide an analysis of the total energy into guest-guest, guest-host and host-host contributions. Combined Reitveld and Reverse Monte Carlo (RMC) structure refinement were used to fit models of the data. This combined modeling and simulation characterizes the effects of CO2 and

  20. Properties of cyclodextrins. II. Preparation of a stable β-cyclodextrin hydrate and determination of its water content and enthalpy of solution in water from 15 to 30.deg

    NARCIS (Netherlands)

    Wiedenhof, N.; Lammers, J.N.J.J.

    1968-01-01

    The solubility of ß-cyclodextrin (ß-CD) in water has been measured by a refractive-index method at 15–30°. Evidence was obtained that the same, solid ß-CD hydrate phase is present in this temperature range. The formula of the hydrate was shown to be C42H70O35(12.0 ± 0.5)H20. A method for preparation

  1. Adsorptionof polar organic molecules at oil/water interfaces

    Energy Technology Data Exchange (ETDEWEB)

    Aveyard, R; Chapman, J

    1975-03-15

    A study has been made of the adsorption of several esters of dicarboxylic acids at the alkane/water and the air/water interface. The adsorption of n-butanol and n-heptanol at the air/water surface also has been investigated. The surface pressure (pi) -surface area (A) isotherms are compared for the various films, and standard free energies of adsorption have been determined. Attempts have been made to fit the pi, A isotherms using surface equations of state based on the models, of both a 2-dimensional gas and a 2-dimensional solution. The solution model has proved reasonably successful for fairly dilute films at the air/water surface. At higher coverages, an equation derived by Smith for liquid expanded monolayers gives a moderately good description of films of heptanol on water. A simple application of the solution model on adsorbed monolayers at the liquid; liquid interface met with little success. However, it is found that 2-dimensional gas equations describe such systems surprisingly well for fairly low surface concentrations. (20 refs.)

  2. Gas hydrates: entrance to a methane age or climate threat?

    International Nuclear Information System (INIS)

    Krey, Volker; Nakicenovic, Nebojsa; Grubler, Arnulf; O'Neill, Brian; Riahi, Keywan; Canadell, Josep G; Abe, Yuichi; Andruleit, Harald; Archer, David; Hamilton, Neil T M; Johnson, Arthur; Kostov, Veselin; Lamarque, Jean-Francois; Langhorne, Nicholas; Nisbet, Euan G; Riedel, Michael; Wang Weihua; Yakushev, Vladimir

    2009-01-01

    Methane hydrates, ice-like compounds in which methane is held in crystalline cages formed by water molecules, are widespread in areas of permafrost such as the Arctic and in sediments on the continental margins. They are a potentially vast fossil fuel energy source but, at the same time, could be destabilized by changing pressure-temperature conditions due to climate change, potentially leading to strong positive carbon-climate feedbacks. To enhance our understanding of both the vulnerability of and the opportunity provided by methane hydrates, it is necessary (i) to conduct basic research that improves the highly uncertain estimates of hydrate occurrences and their response to changing environmental conditions, and (ii) to integrate the agendas of energy security and climate change which can provide an opportunity for methane hydrates-in particular if combined with carbon capture and storage-to be used as a 'bridge fuel' between carbon-intensive fossil energies and zero-emission energies. Taken one step further, exploitation of dissociating methane hydrates could even mitigate against escape of methane to the atmosphere. Despite these opportunities, so far, methane hydrates have been largely absent from energy and climate discussions, including global hydrocarbon assessments and the Fourth Assessment Report of the Intergovernmental Panel on Climate Change.

  3. Hydration Control of the Mechanical and Dynamical Properties of Cellulose

    Energy Technology Data Exchange (ETDEWEB)

    Petridis, Loukas; O’Neill, Hugh M.; Johnsen, Mariah [Ripon College, Ripon, Wisconsin 54971, United States; Fan, Bingxin [Department; Schulz, Roland [Department; Mamontov, Eugene; Maranas, Janna [Department; Langan, Paul [Department; Smith, Jeremy C. [Department

    2014-10-13

    The mechanical and dynamical properties of cellulose, the most abundant biomolecule on earth, are essential for its function in plant cell walls and advanced biomaterials. Cellulose is almost always found in a hydrated state, and it is therefore important to understand how hydration influences its dynamics and mechanics. Here, the nanosecond-time scale dynamics of cellulose is characterized using dynamic neutron scattering experiments and molecular dynamics (MD) simulation. The experiments reveal that hydrated samples exhibit a higher average mean-square displacement above ~240 K. The MD simulation reveals that the fluctuations of the surface hydroxymethyl atoms determine the experimental temperature and hydration dependence. The increase in the conformational disorder of the surface hydroxymethyl groups with temperature follows the cellulose persistence length, suggesting a coupling between structural and mechanical properties of the biopolymer. In the MD simulation, 20% hydrated cellulose is more rigid than the dry form, due to more closely packed cellulose chains and water molecules bridging cellulose monomers with hydrogen bonds. This finding may have implications for understanding the origin of strength and rigidity of secondary plant cell walls. The detailed characterization obtained here describes how hydration-dependent increased fluctuations and hydroxymethyl disorder at the cellulose surface lead to enhancement of the rigidity of this important biomolecule.

  4. Roles of water molecules in bacteria and viruses

    Science.gov (United States)

    Cox, C. S.

    1993-02-01

    In addition to water, microbes mainly comprise lipids, carbohydrates, proteins and nucleic acids. Their structure and function singularly and conjointly is affected by water activity. Desiccation leads to dramatic lipid phase changes whereas carbohydrates, proteins and nucleic acids initially suffer spontaneous, reversible low activation energy Maillard reactions forming products that more slowly re-arrange, cross-link etc. to give non-native states. While initial products spontaneously may reverse to native states by raising water activity, later products only do so through energy consumption and enzymatic activity eg. repair. Yet, native states of lipid membranes and associated enzymes are required to generate energy. Consequently, good reserves of high energy compounds (e.g. ATP) and of membrane stabilisers (e.g. trehalose) may be expected to enhance survival following drying and rehydration (e.g. anhydrobiotic organisms).

  5. Predicting hydration energies for multivalent ions

    DEFF Research Database (Denmark)

    Andersson, Martin Peter; Stipp, Susan Louise Svane

    2014-01-01

    We have predicted the free energy of hydration for 40 monovalent and multivalent cations and anions using density functional theory and the implicit solvent model COnductor like Screening MOdel for Real Solvents (COSMO-RS) at the Becke-Perdew (BP)/Triple zeta valence with polarization functions...... (TZVP) level. Agreement with experimental data for monovalent and divalent ions is good and shows no significant systematic errors. Predictions are noticeably better than with standard COSMO. The agreement with experimental data for trivalent and tetravalent ions is slightly worse and shows systematic...... errors. Our results indicate that quantum chemical calculations combined with COSMO-RS solvent treatment is a reliable method for treating multivalent ions in solution, provided one hydration shell of explicit water molecules is included for metal cations. The accuracy is not high enough to allow...

  6. Phosphate vibrations as reporters of DNA hydration

    Science.gov (United States)

    Corcelli, Steven

    The asymmetric phosphate stretch vibrational frequency is extraordinarily sensitive to its local solvent environment. Using density functional theory calculations on the model compound dimethyl phosphate, the asymmetric phosphate stretch vibrational frequency was found to shift linearly with the magnitude of an electric field along the symmetry axis of the PO2 moiety (i.e. the asymmetric phosphate stretch is an excellent linear vibrational Stark effect probe). With this linear relationship established, asymmetric phosphate stretch vibrational frequencies were computed during the course of a molecular dynamics simulation of fully hydrated DNA. Moreover, contributions to shifts in the frequencies from subpopulations of water molecules (e.g. backbone, minor groove, major groove, etc.) were calculated to reveal how phosphate vibrations report the onset of DNA hydration in experiments that vary the relative humidity of non-condensing (dry) DNA samples.

  7. Impacts of Hydrate Distribution on the Hydro-Thermo-Mechanical Properties of Hydrate-Bearing Sediments

    Science.gov (United States)

    Dai, S.; Seol, Y.

    2015-12-01

    In general, hydrate makes the sediments hydraulically less conductive, thermally more conductive, and mechanically stronger; yet the dependency of these physical properties on hydrate saturation varies with hydrate distribution and morphology. Hydrate distribution in sediments may cause the bulk physical properties of their host sediments varying several orders of magnitude even with the same amount of hydrate. In natural sediments, hydrate morphology is inherently governed by the burial depth and the grain size of the host sediments. Compare with patchy hydrate, uniformly distributed hydrate is more destructive to fluid flow, yet leads to higher gas and water permeability during hydrate dissociation due to the easiness of forming percolation paths. Water and hydrate have similar thermal conductivity values; the bulk thermal conductivity of hydrate-bearing sediments depends critically on gas-phase saturation. 60% of gas saturation may result in evident thermal conductivity drop and hinder further gas production. Sediments with patchy hydrate yield lower stiffness than that with cementing hydrate but higher stiffness than that with pore filling and loading bearing hydrate. Besides hydrate distribution, the stress state and loading history also play an important role in the mechanical behavior of hydrate-bearing sediments.

  8. Formation of submarine gas hydrates

    Energy Technology Data Exchange (ETDEWEB)

    Soloviev, V.; Ginsburg, G.D. (Reserch Institute of Geology and Mineral Resources of the Ocean ' ' VNII Okeangeologia' ' , St. Petersburg (Russian Federation))

    1994-03-01

    Submarine gas hydrates have been discoverd in the course of deep-sea drilling (DSDP and ODP) and bottom sampling in many offshore regions. This paper reports on expeditions carried out in the Black, Caspian and Okhotsk Seas. Gas hydrate accumulations were discovered and investigated in all these areas. The data and an analysis of the results of the deep-sea drilling programme suggest that the infiltration of gas-bearing fluids is a necessary condition for gas hydrate accumulation. This is confirmed by geological observations at three scale levels. Firstly, hydrates in cores are usually associated with comparatively coarse-grained, permeable sediments as well as voids and fractures. Secondly, hydrate accumulations are controlled by permeable geological structures, i.e. faults, diapirs, mud volcanos as well as layered sequences. Thirdly, in the worldwide scale, hydrate accumulations are characteristic of continental slopes and rises and intra-continental seas where submarine seepages also are widespread. Both biogenic and catagenic gas may occur, and the gas sources may be located at various distances from the accumulation. Gas hydrates presumably originate from water-dissolved gas. The possibility of a transition from dissolved gas into hydrate is confirmed by experimental data. Shallow gas hydrate accumulations associated with gas-bearing fluid plumes are the most convenient features for the study of submarine hydrate formation in general. These accumulations are known from the Black, Caspian and Okhotsk Seas, the Gulf of Mexico and off northern California. (au) (24 refs.)

  9. Contamination of boreholes water by 76 pesticides molecules in the ...

    African Journals Online (AJOL)

    user2

    to be the cause of the degradation of the quality of sur- face and ground waters ... network and the nature of the soil generally clay lateritic with high permeability. .... 0.006 0.008 0.004 0.004 0.004 0.007 0.008 0.004 0.004 0.004 Malathion.

  10. 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+).

  11. Impact of pore-water freshening on clays and the compressibility of hydrate-bearing reservoirs during production

    Energy Technology Data Exchange (ETDEWEB)

    Jang, Junbong [U.S. Geological Survey, Woods Hole, MA; Cao, Shuang [Louisiana State University, Baton Rouge, LA; Waite, William [U.S. Geological Survey, Woods Hole, MA; Jung, Jongwon [Chungbuk National University, Cheongju-si, Chungbuk, South Korea

    2017-06-25

    Gas production efficiency from natural hydrate-bearing sediments depends in part on geotechnical properties of fine-grained materials, which are ubiquitous even in sandy hydrate-bearing sediments. The responses of fine-grained material to pore fluid chemistry changes due to freshening during hydrate dissociation could alter critical sediment characteristics during gas production activities. We investigate the electrical sensitivity of fine grains to pore fluid freshening and the implications of freshening on sediment compression and recompression parameters.

  12. 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

  13. Clinker mineral hydration at reduced relative humidities

    DEFF Research Database (Denmark)

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

    1999-01-01

    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......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...

  14. Chloral Hydrate

    Science.gov (United States)

    ... if you are allergic to chloral hydrate, aspirin, tartrazine (a yellow dye in some processed foods and ... in, tightly closed, and out of reach of children. Store it at room temperature, away from excess ...

  15. Molecular dynamics study on the structure I clathrate-hydrate of methane + ethane mixture

    International Nuclear Information System (INIS)

    Erfan-Niya, Hamid; Modarress, Hamid; Zaminpayma, Esmaeil

    2011-01-01

    Molecular dynamics (MD) simulations are used to study the structure I stability of methane + ethane clathrate-hydrates at temperatures 273, 275 and 277 K. NVT- and NPT-ensembles are utilized in MD simulation, and each consists of 3 x 3 x 3 replica unit cells containing 46 water molecules which are considered as the host molecules and up to eight methane + ethane molecules considered as the guest molecules. In MD simulations for host-host interactions, the potential model used was a type of simple point charge (SPC) model, and for guest-guest and host-guest interactions the potential used was Lennard-Jones model. In the process of MD simulation, achieving equilibrium of the studied system was recognized by stability in calculated pressure for NVT-ensemble and volume for NPT-ensemble. To understand the characteristic configurations of the structure I hydrate, the radial distribution functions (RDFs) of host-host, host-guest and guest-guest molecules as well as other properties including kinetic energy, potential energy and total energy were calculated. The results show that guest molecules interaction with host molecules cannot decompose the hydrate structure, and these results are consistent with most previous experimental and theoretical investigations that methane + ethane mixtures form structure I hydrates over the entire mixture composition range.

  16. Effect of temperature dependence of the Langmuir constant molecular pair potentials on gas hydrates formation mechanism

    Energy Technology Data Exchange (ETDEWEB)

    Mokhtari, B.; Enayati, M. [Iranian Offshore Oil Co., Tehran (Iran, Islamic Republic of); Heidaryan, E. [Islamic Azad Univ., Tehran (Iran, Islamic Republic of). Masjidosolayman Branch

    2008-07-01

    Theoretical methods show that crystalline hydrates can form from single-phase systems consisting of both vapor water with gaseous hydrate former and liquid water with dissolved hydrate former. Two phase systems consist of both liquid water with gaseous hydrate former and with liquid hydrate former on the surface. This paper presented a Langmuir constant related model for the prediction of equilibrium pressures and cage occupancies of pure component hydrates. Intermolecular potentials were fit to quantum mechanical energies to obtain the Langmuir constants, which differed from the procedure utilized with the vdWP model. The paper described the experimental method and model calculations. This included the Fugacity model and Van der Waals and Platteeuw model. The paper also discussed pair potential of non-spherical molecules, including the multicentre (site-site) potential; Gaussian overlap potential; Lennard-Jones potential; and Kihara generalized pair potential. It was concluded that fraction of occupied cavities is a function of pair potentials between hard core and empty hydrate lattice. These pair potentials could be calculated from some model as Kihara cell potential, Gaussian potential, Lennard-Jones potential and multicentre pair potential. 49 refs., 3 figs.

  17. Phase equilibria of carbon dioxide and methane gas-hydrates predicted with the modified analytical S-L-V equation of state

    Directory of Open Access Journals (Sweden)

    Span Roland

    2012-04-01

    Full Text Available Gas-hydrates (clathrates are non-stoichiometric crystallized solutions of gas molecules in the metastable water lattice. Two or more components are associated without ordinary chemical union but through complete enclosure of gas molecules in a framework of water molecules linked together by hydrogen bonds. The clathrates are important in the following applications: the pipeline blockage in natural gas industry, potential energy source in the form of natural hydrates present in ocean bottom, and the CO2 separation and storage. In this study, we have modified an analytical solid-liquid-vapor equation of state (EoS [A. Yokozeki, Fluid Phase Equil. 222–223 (2004] to improve its ability for modeling the phase equilibria of clathrates. The EoS can predict the formation conditions for CO2- and CH4-hydrates. It will be used as an initial estimate for a more complicated hydrate model based on the fundamental EoSs for fluid phases.

  18. Inter-cage dynamics in structure I, II, and H fluoromethane hydrates as studied by NMR and molecular dynamics simulations

    International Nuclear Information System (INIS)

    Trueba, Alondra Torres; Kroon, Maaike C.; Peters, Cor J.; Moudrakovski, Igor L.; Ratcliffe, Christopher I.; Ripmeester, John A.; Alavi, Saman

    2014-01-01

    Prospective industrial applications of clathrate hydrates as materials for gas separation require further knowledge of cavity distortion, cavity selectivity, and defects induction by guest-host interactions. The results presented in this contribution show that under certain temperature conditions the guest combination of CH 3 F and a large polar molecule induces defects on the clathrate hydrate framework that allow intercage guest dynamics. 13 C NMR chemical shifts of a CH 3 F/CH 4 /TBME sH hydrate and a temperature analysis of the 2 H NMR powder lineshapes of a CD 3 F/THF sII and CD 3 F/TBME sH hydrate, displayed evidence that the populations of CH 4 and CH 3 F in the D and D ′ cages were in a state of rapid exchange. A hydrogen bonding analysis using molecular dynamics simulations on the TBME/CH 3 F and TBME/CH 4 sH hydrates showed that the presence of CH 3 F enhances the hydrogen bonding probability of the TBME molecule with the water molecules of the cavity. Similar results were obtained for THF/CH 3 F and THF/CH 4 sII hydrates. The enhanced hydrogen bond formation leads to the formation of defects in the water hydrogen bonding lattice and this can enhance the migration of CH 3 F molecules between adjacent small cages

  19. Hydroxyl and water molecule orientations in trypsin: Comparison to molecular dynamics structures

    Energy Technology Data Exchange (ETDEWEB)

    McDowell, R.S.; Kossiakoff, A.A. [Genentech, Inc., South San Francisco, CA (United States)

    1994-12-31

    A comparison is presented of experimentally observed hydroxyl and water hydrogens in trypsin determined from neutron density maps with the results of a 140ps molecular dynamics (MD) simulation. Experimental determination of hydrogen and deuterium atom positions in molecules as large as proteins is a unique capability of neutron diffraction. The comparison addresses the degree to which a standard force-field approach can adequately describe the local electrostatic and van der Waals forces that determine the orientations of these hydrogens. Neutron densities, derived from 2.1{Angstrom} D{sub 2}O-H{sub 2}O difference Fourier maps, provide a database of 27 well-ordered hydroxyl hydrogens. Most of the simulated hydroxyl orientations are within a standard deviation of the experimentally-observed positions, including several examples in which both the simulation and the neutron density indicate that a hydroxyl group is shifted from a {open_quote}standard{close_quote} rotamer. For the most highly ordered water molecules, the hydrogen distributions calculated from the trajectory were in good agreement with neutron density; simulated water molecules that displayed multiple hydrogen bonding networks had correspondingly broadened neutron density profiles. This comparison was facilitated by development of a method to construct a pseudo 2{Angstrom} density map based on the hydrogen atom distributions from the simulation. The degree of disorder of internal water molecules is shown to result primarily from the electrostatic environment surrounding that water molecule as opposed to the cavity size available to the molecule. A method is presented for comparing the discrete observations sampled in a dynamics trajectory with the time- averaged data obtained from X-ray or neutron diffraction studies. This method is particularly useful for statically-disordered water molecules, in which the average location assigned from a trajectory may represent a site of relatively low occupancy.

  20. Magnetic resonance study of hydration of Na-β''-alumina. Magnetic impurity effects

    International Nuclear Information System (INIS)

    Gobato, Y.G.; Souto, S.P.A.; Gonzalez, J.P.D.; Souza, D.P.F. de; Dept. de Engenharia de Materiais)

    1989-01-01

    The various factors that can affect the hydration of polycristalline Na-β''-alumina were investigated, using magnetic resonance methods. When absorved, water molecules diffuses very fast into the conduction layers. The activation energy for the diffusion motion was found to be 0.16 eV (15.4 KJ/mol) for a pure sample, with 150 - 250 μm particle diameter, with 18.5% of water in relation to the dry sample. A striking result was that the water absorption in a pure sample was twice than in a iron doped sample (500 ppm) hydrated in identical conditions. (author) [pt

  1. 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.

  2. Towards an understanding of the propensity for crystalline hydrate formation by molecular compounds

    Directory of Open Access Journals (Sweden)

    Alankriti Bajpai

    2016-11-01

    Full Text Available Hydrates are technologically important and ubiquitous yet they remain a poorly understood and understudied class of molecular crystals. In this work, we attempt to rationalize propensity towards hydrate formation through crystallization studies of molecules that lack strong hydrogen-bond donor groups. A Cambridge Structural Database (CSD survey indicates that the statistical occurrence of hydrates in 124 molecules that contain five- and six-membered N-heterocyclic aromatic moieties is 18.5%. However, hydrate screening experiments on a library of 11 N-heterocyclic aromatic compounds with at least two acceptor moieties and no competing hydrogen-bond donors or acceptors reveals that over 70% of this group form hydrates, suggesting that extrapolation from CSD statistics might, at least in some cases, be deceiving. Slurrying in water and exposure to humidity were found to be the most effective discovery methods. Electrostatic potential maps and/or analysis of the crystal packing in anhydrate structures was used to rationalize why certain molecules did not readily form hydrates.

  3. Sensitivity of hydrogen bonds of DNA and RNA to hydration, as gauged by 1JNH measurements in ethanol-water mixtures

    International Nuclear Information System (INIS)

    Manalo, Marlon N.; Kong Xiangming; LiWang, Andy

    2007-01-01

    Hydrogen-bond lengths of nucleic acids are (1) longer in DNA than in RNA, and (2) sequence dependent. The physicochemical basis for these variations in hydrogen-bond lengths is unknown, however. Here, the notion that hydration plays a significant role in nucleic acid hydrogen-bond lengths is tested. Watson-Crick N1...N3 hydrogen-bond lengths of several DNA and RNA duplexes are gauged using imino 1 J NH measurements, and ethanol is used as a cosolvent to lower water activity. We find that 1 J NH values of DNA and RNA become less negative with added ethanol, which suggests that mild dehydration reduces hydrogen-bond lengths even as the overall thermal stabilities of these duplexes decrease. The 1 J NH of DNA are increased in 8 mol% ethanol to those of RNA in water, which suggests that the greater hydration of DNA plays a significant role in its longer hydrogen bonds. The data also suggest that ethanol-induced dehydration is greater for the more hydrated G:C base pairs and thereby results in greater hydrogen-bond shortening than for the less hydrated A:T/U base pairs of DNA and RNA

  4. Physical properties and rock physics models of sediment containing natural and laboratory-formed methane gas hydrate

    Science.gov (United States)

    Winters, W.J.; Pecher, I.A.; Waite, W.F.; Mason, D.H.

    2004-01-01

    This paper presents results of shear strength and acoustic velocity (p-wave) measurements performed on: (1) samples containing natural gas hydrate from the Mallik 2L-38 well, Mackenzie Delta, Northwest Territories; (2) reconstituted Ottawa sand samples containing methane gas hydrate formed in the laboratory; and (3) ice-bearing sands. These measurements show that hydrate increases shear strength and p-wave velocity in natural and reconstituted samples. The proportion of this increase depends on (1) the amount and distribution of hydrate present, (2) differences, in sediment properties, and (3) differences in test conditions. Stress-strain curves from the Mallik samples suggest that natural gas hydrate does not cement sediment grains. However, stress-strain curves from the Ottawa sand (containing laboratory-formed gas hydrate) do imply cementation is present. Acoustically, rock physics modeling shows that gas hydrate does not cement grains of natural Mackenzie Delta sediment. Natural gas hydrates are best modeled as part of the sediment frame. This finding is in contrast with direct observations and results of Ottawa sand containing laboratory-formed hydrate, which was found to cement grains (Waite et al. 2004). It therefore appears that the microscopic distribution of gas hydrates in sediment, and hence the effect of gas hydrate on sediment physical properties, differs between natural deposits and laboratory-formed samples. This difference may possibly be caused by the location of water molecules that are available to form hydrate. Models that use laboratory-derived properties to predict behavior of natural gas hydrate must account for these differences.

  5. Calcium Aluminate Cement Hydration Model

    Directory of Open Access Journals (Sweden)

    Matusinović, T.

    2011-01-01

    Full Text Available Calcium aluminate cement (AC is a very versatile special cement used for specific applications. As the hydration of AC is highly temperature dependent, yielding structurally different hydration products that continuously alter material properties, a good knowledge of thermal properties at early stages of hydration is essential. The kinetics of AC hydration is a complex process and the use of single mechanisms models cannot describe the rate of hydration during the whole stage.This paper examines the influence of temperature (ϑ=5–20 °C and water-to-cement mass ratio (mH /mAC = 0.4; 0.5 and 1.0 on hydration of commercial iron-rich AC ISTRA 40 (producer: Istra Cement, Pula, Croatia, which is a part of CALUCEM group, Figs 1–3. The flow rate of heat generation of cement pastes as a result of the hydration reactions was measured with differential microcalorimeter. Chemically bonded water in the hydrated cement samples was determined by thermo-gravimetry.Far less heat is liberated when cement and water come in contact for the first time, Fig. 1, than in the case for portland cement (PC. Higher water-to-cement ratio increases the heat evolved at later ages (Fig. 3 due to higher quantity of water available for hydration. A significant effect of the water-to-cement ratio on the hydration rate and hydration degree showed the importance of water as being the limiting reactant that slows down the reaction early. A simplified stoichiometric model of early age AC hydration (eq. (8 based on reaction schemes of principal minerals, nominally CA, C12A7 and C4AF (Table 1, was employed. Hydration kinetics after the induction period (ϑ < 20 °C had been successfully described (Fig. 4 and Table 2 by a proposed model (eq. (23 which simultaneously comprised three main mechanisms: nucleation and growth, interaction at phase boundary, and mass transfer. In the proposed kinetic model the nucleation and growth is proportional to the amount of reacted minerals (eq

  6. Water-mediated influence of a crowded environment on internal vibrations of a protein molecule.

    Science.gov (United States)

    Kuffel, Anna; Zielkiewicz, Jan

    2016-02-14

    The influence of crowding on the protein inner dynamics is examined by putting a single protein molecule close to one or two neighboring protein molecules. The presence of additional molecules influences the amplitudes of protein fluctuations. Also, a weak dynamical coupling of collective velocities of surface atoms of proteins separated by a layer of water is detected. The possible mechanisms of these phenomena are described. The cross-correlation function of the collective velocities of surface atoms of two proteins was decomposed into the Fourier series. The amplitude spectrum displays a peak at low frequencies. Also, the results of principal component analysis suggest that the close presence of an additional protein molecule influences the high-amplitude, low-frequency modes in the most prominent way. This part of the spectrum covers biologically important protein motions. The neighbor-induced changes in the inner dynamics of the protein may be connected with the changes in the velocity power spectrum of interfacial water. The additional protein molecule changes the properties of solvation water and in this way it can influence the dynamics of the second protein. It is suggested that this phenomenon may be described, at first approximation, by a damped oscillator driven by an external random force. This model was successfully applied to conformationally rigid Choristoneura fumiferana antifreeze protein molecules.

  7. FORMATION OF ORGANIC MOLECULES AND WATER IN WARM DISK ATMOSPHERES

    Energy Technology Data Exchange (ETDEWEB)

    Najita, Joan R. [National Optical Astronomy Observatory, 950 N. Cherry Avenue, Tucson, AZ 85719 (United States); Adamkovics, Mate; Glassgold, Alfred E. [Astronomy Department, University of California, Berkeley, CA 94720 (United States)

    2011-12-20

    Observations from Spitzer and ground-based infrared spectroscopy reveal significant diversity in the molecular emission from the inner few AU of T Tauri disks. We explore theoretically the possible origin of this diversity by expanding on our earlier thermal-chemical model of disk atmospheres. We consider how variations in grain settling, X-ray irradiation, accretion-related mechanical heating, and the oxygen-to-carbon ratio can affect the thermal and chemical properties of the atmosphere at 0.25-40 AU. We find that these model parameters can account for many properties of the detected molecular emission. The column density of the warm (200-2000 K) molecular atmosphere is sensitive to grain settling and the efficiency of accretion-related heating, which may account, at least in part, for the large range in molecular emission fluxes that have been observed. The dependence of the atmospheric properties on the model parameters may also help to explain trends that have been reported in the literature between molecular emission strength and mid-infrared color, stellar accretion rate, and disk mass. We discuss whether some of the differences between our model results and the observations (e.g., for water) indicate a role for vertical transport and freezeout in the disk midplane. We also discuss how planetesimal formation in the outer disk (beyond the snowline) may imprint a chemical signature on the inner few AU of the disk and speculate on possible observational tracers of this process.

  8. FORMATION OF ORGANIC MOLECULES AND WATER IN WARM DISK ATMOSPHERES

    International Nuclear Information System (INIS)

    Najita, Joan R.; Ádámkovics, Máté; Glassgold, Alfred E.

    2011-01-01

    Observations from Spitzer and ground-based infrared spectroscopy reveal significant diversity in the molecular emission from the inner few AU of T Tauri disks. We explore theoretically the possible origin of this diversity by expanding on our earlier thermal-chemical model of disk atmospheres. We consider how variations in grain settling, X-ray irradiation, accretion-related mechanical heating, and the oxygen-to-carbon ratio can affect the thermal and chemical properties of the atmosphere at 0.25-40 AU. We find that these model parameters can account for many properties of the detected molecular emission. The column density of the warm (200-2000 K) molecular atmosphere is sensitive to grain settling and the efficiency of accretion-related heating, which may account, at least in part, for the large range in molecular emission fluxes that have been observed. The dependence of the atmospheric properties on the model parameters may also help to explain trends that have been reported in the literature between molecular emission strength and mid-infrared color, stellar accretion rate, and disk mass. We discuss whether some of the differences between our model results and the observations (e.g., for water) indicate a role for vertical transport and freezeout in the disk midplane. We also discuss how planetesimal formation in the outer disk (beyond the snowline) may imprint a chemical signature on the inner few AU of the disk and speculate on possible observational tracers of this process.

  9. Thermogravimetric and nuclear magnetic resonance study of hydrated Na-β''-alumina

    International Nuclear Information System (INIS)

    Donoso, P.; Panepucci, H.; Gobato, Y.G.; Oliveira, L.N.; Souza, D.P.F. de

    1990-01-01

    This paper reports thermogravimetric and proton spin-lattice relaxation times measurement of hydrated Na-β''-alumina, which yield information about the identification of the sites where the loosely bound water molecules are located in the polycrystalline sample. It examines also the influence of impurities on the motion of the protons. (autor) [pt

  10. How Sodium Chloride Salt Inhibits the Formation of CO2 Gas Hydrates.

    Science.gov (United States)

    Holzammer, Christine; Finckenstein, Agnes; Will, Stefan; Braeuer, Andreas S

    2016-03-10

    We present an experimental Raman study on how the addition of sodium chloride to CO2-hydrate-forming systems inhibits the hydrate formation thermodynamically. For this purpose, the molar enthalpy of reaction and the molar entropy of reaction for the reaction of weakly hydrogen-bonded water molecules to strongly hydrogen bonded water molecules are determined for different salinities from the Raman spectrum of the water-stretching vibration. Simultaneously, the influence of the salinity on the solubility of CO2 in the liquid water-rich phase right before the start of hydrate formation is analyzed. The results demonstrate that various mechanisms contribute to the inhibition of gas hydrate formation. For the highest salt concentration of 20 wt % investigated, the temperature of gas hydrate formation is lowered by 12 K. For this concentration the molar enthalpy and entropy of reaction become smaller by 50 and 20%, respectively. Concurrently, the solubility of carbon dioxide is reduced by 70%. These results are compared with data in literature for systems of sodium chloride in water (without carbon dioxide).

  11. A Molecular Dynamic Simulation of Hydrated Proton Transfer in Perfluorosulfonate Ionomer Membranes (Nafion 117

    Directory of Open Access Journals (Sweden)

    Hong Sun

    2015-01-01

    Full Text Available A molecular dynamic model based on Lennard-Jones Potential, the interaction force between two particles, molecular diffusion, and radial distribution function (RDF is presented. The diffusion of the hydrated ion, triggered by both Grotthuss and vehicle mechanisms, is used to study the proton transfer in Nafion 117. The hydrated ion transfer mechanisms and the effects of the temperature, the water content in the membrane, and the electric field on the diffusion of the hydrated ion are analyzed. The molecular dynamic simulation results are in good agreement with those reported in the literature. The modeling results show that when the water content in Nafion 117 is low, H3O+ is the main transfer ion among the different hydrated ions. However, at higher water content, the hydrated ion in the form of H+(H2O2 is the main transfer ion. It is also found that the negatively charged sulfonic acid group as the fortified point facilitates the proton transfer in Nafion 117 better than the free water molecule. The diffusion of the hydrated ion can be improved by increasing the cell temperature, the water content in Nafion, and the electric field intensity.

  12. Intermolecular Hydrogen Transfer in Isobutane Hydrate

    Directory of Open Access Journals (Sweden)

    Takeshi Sugahara

    2012-05-01

    Full Text Available Electron spin resonance (ESR spectra of butyl radicals induced with γ-ray irradiation in the simple isobutane (2-methylpropane hydrate (prepared with deuterated water were investigated. Isothermal annealing results of the γ-ray-irradiated isobutane hydrate reveal that the isobutyl radical in a large cage withdraws a hydrogen atom from the isobutane molecule through shared hexagonal-faces of adjacent large cages. During this “hydrogen picking” process, the isobutyl radical is apparently transformed into a tert-butyl radical, while the sum of isobutyl and tert-butyl radicals remains constant. The apparent transformation from isobutyl to tert-butyl radicals is an irreversible first-order reaction and the activation energy was estimated to be 35 ± 3 kJ/mol, which was in agreement with the activation energy (39 ± 5 kJ/mol of hydrogen picking in the γ-ray-irradiated propane hydrate with deuterated water.

  13. Influence of the effective mass of water molecule on thermal neutron scattering

    International Nuclear Information System (INIS)

    Markovic, M.

    1981-01-01

    The influence of the effective water molecule mass on the thermal neutron scattering on the nucleus of the hydrogen atom has been investigated. Besides the actual water molecule mass (M = 18) the investigations have been carried out with its two effective values (M1 = 16 and M2 = 20). The differential and total cross sections have been calculated for the incident thermal neutron energy E o = 1 eV. Investigation results show different prominence of the quantum effects and for M2 the appearance of peaks in the quasielastic scattering. (author)

  14. Clathrate hydrates - the energy of the future an overview and a postulated formation mechanism

    International Nuclear Information System (INIS)

    Pratt, R.M.

    2000-01-01

    Clathrate hydrates are non-stoichiometric compounds that form when water and certain low molecular weight hydrocarbons coexist at high pressures and low temperatures. The majority of the earth hydrocarbons are in the hydrate phase and are primarily located along the ocean bottoms and to a lesser degree in the permafrost regions. In addition, hydrate formation is induced in undersea gas transmission lines and causes costly pipeline plugs and requires expensive inhibition measures to be taken. Therefore, both a stick and a carrot motivate hydrate research. They are a costly and dangerous nuisance to the oil and gas industry and represent a tremendous, untapped energy resource of the future. The formation mechanism of clathrate hydrate formation has always been shrouded in mystery, and an ongoing debate has ensued as to whether their formation is a bulk or surface phenomenon. Molecular dynamics simulation and fractal modeling suggest that this may be an irrelevant issue and that two independent factors contribute to the symmetrical ordered structure of clathrate hydrates: hydrophobic hydration of hydrocarbon molecules in water and formation of linked cavities as these small clusters aggregate. (Author)

  15. Shear-stress-induced structural arrangement of water molecules in nanoscale Couette flow with slipping at wall boundary

    International Nuclear Information System (INIS)

    Lin, Jau-Wen

    2014-01-01

    This study investigated the structuring of water molecules in a nanoscale Couette flow with the upper plate subjected to lateral forces with various magnitudes and water slipping against a metal wall. It was found that when the upper plate is subjected to a force, the water body deforms into a parallelepiped. Water molecules in the channel are then gradually arranged into lattice positions, creating a layered structure. The structural arrangement of water molecules is caused by the water molecules accommodating themselves to the increase in energy under the application of a lateral force on the moving plate. The ordering arrangement of water molecules increases the rotational degree of freedom, allowing the molecules to increase their Coulomb potential energy through polar rotation that accounts for the energy input through the upper plate. With a force continuously applied to the upper plate, the water molecules in contact with the upper plate move forward until slip between the water and upper plate occurs. The relation between the structural arrangement of water molecules, slip at the wall, and the shear force is studied. The relation between the slip and the locking/unlocking of water molecules to metal atoms is also studied

  16. Characterizing heterogeneous dynamics at hydrated electrode surfaces

    Science.gov (United States)

    Willard, Adam P.; Limmer, David T.; Madden, Paul A.; Chandler, David

    2013-05-01

    In models of Pt 111 and Pt 100 surfaces in water, motions of molecules in the first hydration layer are spatially and temporally correlated. To interpret these collective motions, we apply quantitative measures of dynamic heterogeneity that are standard tools for considering glassy systems. Specifically, we carry out an analysis in terms of mobility fields and distributions of persistence times and exchange times. In so doing, we show that dynamics in these systems is facilitated by transient disorder in frustrated two-dimensional hydrogen bonding networks. The frustration is the result of unfavorable geometry imposed by strong metal-water bonding. The geometry depends upon the structure of the underlying metal surface. Dynamic heterogeneity of water on the Pt 111 surface is therefore qualitatively different than that for water on the Pt 100 surface. In both cases, statistics of this ad-layer dynamic heterogeneity responds asymmetrically to applied voltage.

  17. Characterizing heterogeneous dynamics at hydrated electrode surfaces.

    Science.gov (United States)

    Willard, Adam P; Limmer, David T; Madden, Paul A; Chandler, David

    2013-05-14

    In models of Pt 111 and Pt 100 surfaces in water, motions of molecules in the first hydration layer are spatially and temporally correlated. To interpret these collective motions, we apply quantitative measures of dynamic heterogeneity that are standard tools for considering glassy systems. Specifically, we carry out an analysis in terms of mobility fields and distributions of persistence times and exchange times. In so doing, we show that dynamics in these systems is facilitated by transient disorder in frustrated two-dimensional hydrogen bonding networks. The frustration is the result of unfavorable geometry imposed by strong metal-water bonding. The geometry depends upon the structure of the underlying metal surface. Dynamic heterogeneity of water on the Pt 111 surface is therefore qualitatively different than that for water on the Pt 100 surface. In both cases, statistics of this ad-layer dynamic heterogeneity responds asymmetrically to applied voltage.

  18. 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 (IRMS methods require much more material ( 100-500 mg) and therefore cannot be applied. We present here a new integrated nanoSIMS and continuous flow IRMS approach to understand how water is distributed within single glass grains (diffusion profiles), quantify the time of hydration of young (Holocene) and old (Miocene) already well-characterised rhyolitic glasses, and measure the D/H ratio of the hydration water on single grains and bulk material consisting of only approximately 0.1-1 mg. The IRMS method measures the absolute abundance of hydrogen released from the sample by continuous-flow mass spectrometry. Current data indicates that the method can accurately measure a hydrogen signal from a rock sample containing at least 400 nanomoles of H2, corresponding to 70 µg of water, which translates to 1 mg of hydrous glass (>3 wt%) or 15 mg of dry ( 0.5 wt%) obsidian chips. The method can be improved by reducing the blank to 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

  19. The energy of hydration and solvation of indium salts in the acetylacetone-InCl3-water system

    International Nuclear Information System (INIS)

    Kulawik, I.; Baumgartner, T.

    1978-01-01

    On the base of the previous papers concerning the investigations in the extraction systems the experiments were performed for the determination of thermodynamical distribution coefficient of indium salts between two phases in the system: acetylacetone-InCl 3 -water and the energy of hydration and solvation of that system. The results of the surface and interfacial potentials measurements of the system were presented as a function of the InCl 3 concentration in the system before the extraction. The extraction coefficients of indium as a function of concentration of InCl 3 in this system were determined. The method of the visible absorption spectra was used to the determination of concentration of indium in both phases after the extraction. The relation between the percentage of the extraction and the extraction coefficient was determined. The investigations were performed in the system containing 0.1 M HCl and 0.001 M HCl in the aqueous phase. The results of experiments are tabulated and graphically presented in figures. (author)

  20. Effect of Surface Hydration on Antifouling Properties of Mixed Charged Polymers.

    Science.gov (United States)

    Leng, Chuan; Huang, Hao; Zhang, Kexin; Hung, Hsiang-Chieh; Xu, Yao; Li, Yaoxin; Jiang, Shaoyi; Chen, Zhan

    2018-05-07

    Interfacial water structure on a polymer surface in water (or surface hydration) is related to the antifouling activity of the polymer. Zwitterionic polymer materials exhibit excellent antifouling activity due to their strong surface hydration. It was proposed to replace zwitterionic polymers using mixed charged polymers because it is much easier to prepare mixed charged polymer samples with much lower costs. In this study, using sum frequency generation (SFG) vibrational spectroscopy, we investigated interfacial water structures on mixed charged polymer surfaces in water, and how such structures change while exposing to salt solutions and protein solutions. The 1:1 mixed charged polymer exhibits excellent antifouling property while other mixed charged polymers with different ratios of the positive/negative charges do not. It was found that on the 1:1 mixed charged polymer surface, SFG water signal is dominated by the contribution of the strongly hydrogen bonded water molecules, indicating strong hydration of the polymer surface. The responses of the 1:1 mixed charged polymer surface to salt solutions are similar to those of zwitterionic polymers. Interestingly, exposure to high concentrations of salt solutions leads to stronger hydration of the 1:1 mixed charged polymer surface after replacing the salt solution with water. Protein molecules do not substantially perturb the interfacial water structure on the 1:1 mixed charged polymer surface and do not adsorb to the surface, showing that this mixed charged polymer is an excellent antifouling material.

  1. Gas hydrates and clathrates. Flow assurance, environmental and economic perspectives and the Nigerian liquefied natural gas project

    International Nuclear Information System (INIS)

    Gbaruko, B.C.; Igwe, J.C.; Nwokeoma, R.C.; Gbaruko, P.N.

    2007-01-01

    Gas hydrates are nonstoichiometric crystalline compounds that belong to the inclusion group known as clathrates. They occur when water molecules attach themselves together through hydrogen bonding and form cavities which can be occupied by a single gas or volatile liquid molecule. Gas hydrates, asphaltenes and waxes are three major threats to flow assurance that must be well assessed by design team uptime. Gas hydrates are also looked upon as a future energy source and as a potential climate hazard. The purpose of this review is to show the chemistry and mechanism of gas hydrate formation, the problems they pose, especially to flow assurance, their system implications, their environmental and economic perspectives with respect to their prospects as storage and transport alternative to the liquefied natural gas technology. (author)

  2. Gas Hydrates of Coal Layers as a Methane Source in the Atmosphere and Mine Working

    Science.gov (United States)

    Dyrdin, Valery; Shepeleva, Sofya; Kim, Tatiana

    2017-11-01

    Living conditions of gas hydrates of a methane in a coal matrix as one of possible forms of finding of molecules of a methane in coal layers are considered. However, gas hydrates are formed not in all mineral coals even under the thermobaric conditions corresponding to their equilibrium state as the minimum humidity and the corresponding pore width are necessary for each brand of coal for formation of gas hydrate. It is shown that it depends on electric electrical dipole moment of a macromolecule of coal. Coals of brands K, D, Zh were considered. The electric field created by the surface of coal does not allow molecules of water to carry out threedimensional driving, and they keep on an internal surface of a time. By means of theoretical model operation a dipole - dipole interaction of molecules of water with the steam surface of coal values of energy of fiber interaction for various functional groups located in coal "fringe" which size for the first and second layers does not allow molecules of water to participate in formation of gas hydrates are received. For coals of brands K, Zh, D, considering distribution of a time on radiuses, the percent of moisture, which cannot share in education solid coal of gas solutions, is calculated.

  3. Proton affinities in water of maingroup-element Hydrides - Effects of hydration and methyl substitution

    NARCIS (Netherlands)

    Swart, M.; Rosler, E.; Bickelhaupt, F.M.

    2007-01-01

    We have computed the proton affinities in water of archetypal anionic and neutral bases across the periodic table using the generalized gradient approximation (GGA) of density functional theory (DFT) at BP86/QZ4P//BP86/TZ2P. The main purpose of this work is to provide an intrinsically consistent set

  4. Shifting Focus: From Hydration for Performance to Hydration for Health.

    Science.gov (United States)

    Perrier, Erica T

    2017-01-01

    Over the past 10 years, literature on hydration biomarkers has evolved considerably - from (de)hydration assessment towards a more global definition of biomarkers of hydration in daily life. This shift in thinking about hydration markers was largely driven by investigating the differences that existed between otherwise healthy individuals whose habitual, ad-libitum drinking habits differ, and by identifying physiological changes in low-volume drinkers who subsequently increase their water intake. Aside from obvious differences in urinary volume and concentration, a growing body of evidence is emerging that links differences in fluid intake with small, but biologically significant, differences in vasopressin (copeptin), glomerular filtration rate, and markers of metabolic dysfunction or disease. Taken together, these pieces of the puzzle begin to form a picture of how much water intake should be considered adequate for health, and represent a shifting focus from hydration for performance, toward hydration for health outcomes. This narrative review outlines the key areas of research in which the global hydration process - including water intake, urinary hydration markers, and vasopressin - has been associated with health outcomes, focusing on kidney and metabolic endpoints. It will also provide a commentary on how various hydration biomarkers may be used in hydration for health assessment. Finally, if adequate water intake can play a role in maintaining health, how might we tell if we are drinking enough? Urine output is easily measured, and can take into account differences in daily physical activity, climate, dietary solute load, and other factors that influence daily water needs. Today, targets have been proposed for urine osmolality, specific gravity, and color that may be used by researchers, clinicians, and individuals as simple indicators of optimal hydration. However, there remain a large number of incomplete or unanswered research questions regarding the

  5. THCM Coupled Model for Hydrate-Bearing Sediments: Data Analysis and Design of New Field Experiments (Marine and Permafrost Settings)

    Energy Technology Data Exchange (ETDEWEB)

    Sanchez, Marcelo J. [Texas A & M Univ., College Station, TX (United States); Santamarina, J. Carlos [King Abdullah Univ. of Science and Technology (Saudi Arabia)

    2017-02-14

    Gas hydrates are solid compounds made of water molecules clustered around low molecular weight gas molecules such as methane, hydrogen, and carbon dioxide. Methane hydrates form under pressure (P) and temperature (T) conditions that are common in sub-permafrost layers and in deep marine sediments. Stability conditions constrain the occurrence of gas hydrates to submarine sediments and permafrost regions. The amount of technically recoverable methane trapped in gas hydrate may exceed 104tcf. Gas hydrates are a potential energy resource, can contribute to climate change, and can cause large-scale seafloor instabilities. In addition, hydrate formation can be used for CO2 sequestration (also through CO2-CH4 replacement), and efficient geological storage seals. The experimental study of hydrate bearing sediments has been hindered by the very low solubility of methane in water (lab testing), and inherent sampling difficulties associated with depressurization and thermal changes during core extraction. This situation has prompted more decisive developments in numerical modeling in order to advance the current understanding of hydrate bearing sediments, and to investigate/optimize production strategies and implications. The goals of this research has been to addresses the complex thermo-hydro-chemo-mechanical THCM coupled phenomena in hydrate-bearing sediments, using a truly coupled numerical model that incorporates sound and proven constitutive relations, satisfies fundamental conservation principles. Analytical solutions aimed at verifying the proposed code have been proposed as well. These tools will allow to better analyze available data and to further enhance the current understanding of hydrate bearing sediments in view of future field experiments and the development of production technology.

  6. Hydration of Atmospheric Molecular Clusters: Systematic Configurational Sampling.

    Science.gov (United States)

    Kildgaard, Jens; Mikkelsen, Kurt V; Bilde, Merete; Elm, Jonas

    2018-05-09

    We present a new systematic configurational sampling algorithm for investigating the potential energy surface of hydrated atmospheric molecular clusters. The algo- rithm is based on creating a Fibonacci sphere around each atom in the cluster and adding water molecules to each point in 9 different orientations. To allow the sam- pling of water molecules to existing hydrogen bonds, the cluster is displaced along the hydrogen bond and a water molecule is placed in between in three different ori- entations. Generated redundant structures are eliminated based on minimizing the root mean square distance (RMSD) of different conformers. Initially, the clusters are sampled using the semiempirical PM6 method and subsequently using density func- tional theory (M06-2X and ωB97X-D) with the 6-31++G(d,p) basis set. Applying the developed algorithm we study the hydration of sulfuric acid with up to 15 water molecules. We find that the additions of the first four water molecules "saturate" the sulfuric acid molecule and are more thermodynamically favourable than the addition of water molecule 5-15. Using the large generated set of conformers, we assess the performance of approximate methods (ωB97X-D, M06-2X, PW91 and PW6B95-D3) in calculating the binding energies and assigning the global minimum conformation compared to high level CCSD(T)-F12a/VDZ-F12 reference calculations. The tested DFT functionals systematically overestimates the binding energies compared to cou- pled cluster calculations, and we find that this deficiency can be corrected by a simple scaling factor.

  7. Transport of water molecules through noncylindrical pores in multilayer nanoporous graphene.

    Science.gov (United States)

    Shahbabaei, Majid; Kim, Daejoong

    2017-08-09

    In this study, molecular dynamics (MD) simulations are used to examine the water transport properties through asymmetric hourglass-shaped pores in multilayer nanoporous graphene with a constant interlayer separation of 6 Å. The properties of the tested asymmetric hourglass-shaped pores [with the models having long cone (l 1 , -P) and short cone (l 2 , +P) entrances] are compared to a symmetric pore model. The study findings indicate that the water occupancy increases across the asymmetric pore (l 1 , -P) compared to (l 2 , +P), because of the length effect. The asymmetric pore, (l 1 , -P), yields higher flux compared to (l 2 , +P) and even the symmetric model, which can be attributed to the increase in the hydrogen bonds. In addition, the single-file water molecules across the narrowest pore diameter inside the (l 2 , +P) pore exhibit higher viscosity compared to those in the (l 1 , -P) pore because of the increase in the water layering effect. Moreover, it is found that the permeability inside the multilayer hourglass-shaped pore depends on the length of the flow path of the water molecules before approaching the layer with the smallest pore diameter. The probability of dipole orientation exhibits wider distribution inside the (l 1 , -P) system compared to (l 2 , +P), implying an enhanced formation of hydrogen bonding of water molecules. This results in the fast flow of water molecules. The MD trajectory shows that the dipole orientation across the single-layer graphene has frequently flipped compared to the dipole orientation across the pores in multilayer graphene, which is maintained during the whole simulation time (although the dipole orientation has flipped for a few picoseconds at the beginning of the simulation). This can be attributed to the energy barrier induced by the individual layer. The diffusion coefficient of water molecules inside the (l 2 , +P) system increases with pressure difference, however, it decreases inside the (l 1 , -P) system because

  8. An Evaluation of Common Cleaning Methods for the Removal of a Clinical Isolate of Escherichia coli in Personal Hydration System Water Reservoirs.

    Science.gov (United States)

    Helmus, Stephanie; Blythe, Jauchia; Guevara, Peter; Washington, Michael A

    2016-01-01

    Waterborne infection is an important cause of morbidity and mortality throughout the world. Personal hydration packs have been used by military personnel since the Gulf War and are now a common issue item. Since military personnel tend to operate under austere conditions and may use a variety of water sources, preventing the acquisition of waterborne infections is extremely important. Further, since hydration pack water reservoir replacements may not be available during combat operations, the development of a reliable cleaning protocol for use in the field is essential. Several methods for cleaning have been described. In the current study, three common cleaning methodologies-bleach treatment, baking soda treatment, and proprietary CAMELBAK Cleaning Tabs™-were evaluated for the ability to remove Escherichia coli contamination from hydration pack water reservoirs. The study results suggest that the use of bleach and proprietary CAMELBAK tablets should be encouraged since they both operate by releasing bactericidal chlorine compounds into solution, which is more effective at reducing post-treatment bacterial burden. It should be noted that no method was 100% effective at completely eliminating bacteria from the reservoirs and that mechanical cleaning was not attempted. 2016.

  9. Identification of intrinsic catalytic activity for electrochemical reduction of water molecules to generate hydrogen

    KAUST Repository

    Shinagawa, Tatsuya

    2015-01-01

    Insufficient hydronium ion activities at near-neutral pH and under unbuffered conditions induce diffusion-limited currents for hydrogen evolution, followed by a reaction with water molecules to generate hydrogen at elevated potentials. The observed constant current behaviors at near neutral pH reflect the intrinsic electrocatalytic reactivity of the metal electrodes for water reduction. This journal is © the Owner Societies.

  10. STABILIZATION OF THE NEUTRAL PROTEASE OF BACILLUS-STEAROTHERMOPHILUS BY REMOVAL OF A BURIED WATER MOLECULE

    NARCIS (Netherlands)

    VRIEND, G; BERENDSEN, HJC; VANDERZEE, [No Value; VANDENBURG, B; VENEMA, G; EIJSINK, VGH

    1991-01-01

    Using site-directed mutagenesis, Ala166 in the neutral protease of Bacillus stearothermophilus was changed into Ser. Model building and molecular dynamics simulations of the mutant enzyme indicated that the Ser hydroxyl group fits well in a cavity which contains a water molecule in the wild-type

  11. Electrochemical monitoring of the co-extraction of water with hydrated ions into an organic solvent

    Czech Academy of Sciences Publication Activity Database

    Mareček, Vladimír

    2018-01-01

    Roč. 88, MAR 2018 (2018), s. 57-60 ISSN 1388-2481 R&D Projects: GA ČR(CZ) GA17-09980S Institutional support: RVO:61388955 Keywords : Liquid/liquid interface * Water co-extraction dynamics * Emulsification Subject RIV: CG - Electrochemistry OBOR OECD: Electrochemistry (dry cells, batteries, fuel cells, corrosion metals, electrolysis) Impact factor: 4.396, year: 2016

  12. Molecular dynamics simulation of polyacrylamides in potassium montmorillonite clay hydrates

    Energy Technology Data Exchange (ETDEWEB)

    Zhang Junfang [CSIRO Petroleum Resources, Ian Wark Laboratory, Bayview Avenue, Clayton, Victoria 3168 (Australia); Rivero, Mayela [CSIRO Petroleum, PO Box 1130, Bentley, Western Australia, 6102 (Australia); Choi, S K [CSIRO Petroleum Resources, Ian Wark Laboratory, Bayview Avenue, Clayton, Victoria 3168 (Australia)

    2007-02-14

    We present molecular dynamics simulation results for polyacrylamide in potassium montmorillonite clay-aqueous systems. Interlayer molecular structure and dynamics properties are investigated. The number density profile, radial distribution function, root-mean-square deviation (RMSD), mean-square displacement (MSD) and diffusion coefficient are reported. The calculations are conducted in constant NVT ensembles, at T = 300 K and with layer spacing of 40 A. Our simulation results showed that polyacrylamides had little impact on the structure of interlayer water. Density profiles and radial distribution function indicated that hydration shells were formed. In the presence of polyacrylamides more potassium counterions move close to the clay surface while water molecules move away, indicating that potassium counterions are hydrated to a lesser extent than the system in which no polyacrylamides were added. The diffusion coefficients for potassium and water decreased when polyacrylamides were added.

  13. 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...... may depend on the details of ion hydration. Although the solvation of alkali metal ions in aqueous solution has been discussed for many years, there is still no clear consensus. Part of the discrepancy is simply that different methods measure over different time scales, and therefore do...... not necessarily define the same hydration shell. This work presents a systematic study of one special variant 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-). The technique...

  14. Small-Angle Neutron Scattering Investigation of Growth Modifiers on Hydrate Crystal Surfaces

    Science.gov (United States)

    Sun, Thomas; Hutter, Jeffrey L.; Lin, M.; King, H. E., Jr.

    1998-03-01

    Hydrates are crystals consisting of small molecules enclathrated within an ice-like water cage. Suppression of their growth is important in the oil industry. The presence of small quantities of specific polymers during hydrate crystallization can induce a transition from an octahedral to planar growth habit. This symmetry breaking is surprising because of the suppression of two 111 planes relative to the other six crystallographically equivalent faces. To better understand the surface effects leading to this behavior, we have studied the surface adsorption of these growth-modifing polymers onto the hydrate crytals using SANS. The total hydrate surface area, as measured by Porod scattering, increases in the presence of the growth modifier, but, no significant increase in polymer concentration on the crystal surfaces is found. Implications for possible growth mechanisms will be discussed.

  15. Barley seed radiosensitivity following post-hydration in oxygen-, nitrogen- and nitrous oxide-saturated water, 1; Influence of caffeine and t-butyl alcohol

    Energy Technology Data Exchange (ETDEWEB)

    Singh, S.P.; Kesavan, P.C. (Jawaharlal Nehru Univ., New Delhi (India). School of Life Sciences)

    1990-06-01

    Dry ({approx}3.5 and 4.0 per cent moisture content) barley seeds were exposed to 350 Gy of {sup 60}Co-{gamma}-rays in vacuo and post-hydrated at 4degC for 8 h in O{sub 2}-, N{sub 2}-, or N{sub 2}O-saturated water. The effect of caffeine and t-butyl alcohol (t-BuOH) dissolved in the post-hydration medium on the magnitude of damage developing under these three different gaseous circumstances was studied. The post-irradiation damage and its modification by caffeine and t-BuOH was assessed in terms of 8-day-old seedling injury, peroxidase activity and total peroxides in the 8-day-old seedlings. Post-irradiation O{sub 2}-saturated hydration caused maximal 8-day-old seedling injury, and increased peroxidase activity with concomitant reduction in total peroxides. Both caffeine and t-BuOH afforded significant radioprotection against post-irradiation O{sub 2}-dependent damage. Post-irradiation N{sub 2}O-saturated hydration was even more significantly radioprotective than the N{sub 2}-saturated post-hydration. Under these circumstances, t-BuOH exerted no effect whatsoever on the N{sub 2}- and N{sub 2}O-mediated post-irradiation damage. Caffeine, on the other hand, significantly potentiated these two components of damage. A brief consideration of the physicochemical events which possibly account for the observed effects is presented. (author).

  16. Integration or segregation: how do molecules behave at oil/water interfaces?

    Science.gov (United States)

    Moore, F G; Richmond, G L

    2008-06-01

    It has been over 250 years since Benjamin Franklin, fascinated with the wave-stilling effect of oil on water, performed his famous oil-drop experiments; nevertheless, the behavior of water molecules adjacent to hydrophobic surfaces continues to fascinate today. In the 18th century, the calming of the seas seemed the most pertinent application of such knowledge; today, we understand that oil-on-water phenomena underlie a range of important chemical, physical, and biological processes, including micelle and membrane formation, protein folding, chemical separation, oil extraction, nanoparticle formation, and interfacial polymerization. Beyond classical experiments of the oil-water interface, recent interest has focused on deriving a molecular-level picture of this interface or, more generally, of water molecules positioned next to any hydrophobic surface. This Account summarizes more than a decade's work from our laboratories aimed at understanding the nature of the hydrogen bonding occurring between water and a series of organic liquids in contact. Although the common perception is that water molecules and oil molecules positioned at the interface between the immiscible liquids want nothing to do with one another, we have found that weak interactions between these hydrophilic and hydrophobic molecules lead to interesting interfacial behavior, including highly oriented water molecules and layering of the organic medium that extends several molecular layers deep into the bulk organic liquid. For some organic liquids, penetration of oriented water into the organic layer is also apparent, facilitated by molecular interactions established at the molecularly thin region of first contact between the two liquids. The studies involve a combined experimental and computational approach. The primary experimental tool that we have used is vibrational sum frequency spectroscopy (VSFS), a powerful surface-specific vibrational spectroscopic method for measuring the molecular

  17. 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.

  18. Observation of interstitial molecular hydrogen in clathrate hydrates.

    Science.gov (United States)

    Grim, R Gary; Barnes, Brian C; Lafond, Patrick G; Kockelmann, Winfred A; Keen, David A; Soper, Alan K; Hiratsuka, Masaki; Yasuoka, Kenji; Koh, Carolyn A; Sum, Amadeu K

    2014-09-26

    The current knowledge and description of guest molecules within clathrate hydrates only accounts for occupancy within regular polyhedral water cages. Experimental measurements and simulations, examining the tert-butylamine + H2 + H2O hydrate system, now suggest that H2 can also be incorporated within hydrate crystal structures by occupying interstitial sites, that is, locations other than the interior of regular polyhedral water cages. Specifically, H2 is found within the shared heptagonal faces of the large (4(3)5(9)6(2)7(3)) cage and in cavities formed from the disruption of smaller (4(4)5(4)) water cages. The ability of H2 to occupy these interstitial sites and fluctuate position in the crystal lattice demonstrates the dynamic behavior of H2 in solids and reveals new insight into guest-guest and guest-host interactions in clathrate hydrates, with potential implications in increasing overall energy storage properties. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  19. Cage occupancies of natural gas hydrates encaging methane and ethane

    Energy Technology Data Exchange (ETDEWEB)

    Kida, M.; Hachikubo, A.; Sakagami, H.; Minami, H.; Krylov, A.; Yamashita, S.; Takahashi, N.; Shoji, H. [Kitami Inst. of Technology, Kitami (Japan); Kida, M. [National Inst. of Advanced Industrial Science and Technology, Toyohira-ku, Sapporo (Japan); Khlystov, O. [Limnological Inst., Irkutsk (Russian Federation). Siberian Branch of the Russian Academy of Sciences; Poort, J. [Ghent Univ., Ghent (Belgium). Renard Centre of Marine Geology; Narita, H. [National Inst. of Advanced Industrial Science and Technology, Toyohira-ku, Sapporo (Japan)

    2008-07-01

    Natural gas hydrates are crystalline compounds that contain large amounts of natural gas in its structure and are expected to provide natural gas resources in the future. The gas species are trapped in different types of polyhedral cages which consist of hydrogen bonded water molecules. Three main types of crystallographic structures exist, notably structure 1, structure 2 and structure H (sH). The crystallographic structure of natural gas hydrates depends on the encaged gas components. The cage occupancy is the ratio of the number of cages occupied by guest molecules to the number of total cages. It is also important to estimate the amount of natural gas, since it depends on the condition of the hydrate formation such as gas composition. The cages of natural gas hydrates mainly contain methane. However, other heavier hydrocarbons such as ethane (C{sub 2}H{sub 6}), propane (C{sub 3}H{sub 8}), and isobutane (i-C{sub 4}H{sub 1}0) may be encaged together with CH{sub 4}. Little is known about cage occupancies of natural gas hydrates including CH{sub 4} and heavier hydrocarbons. This paper discussed a study that developed cage occupancy estimations of natural gas hydrates encaging heavier hydrocarbons. 13C nuclear magnetic resonance (NMR) measurements were conducted. The assignments of resonance lines were based on 13C chemical shifts obtained by artificial sample measurements. The paper presented the experimental data and discussed the results of the study. The large cages were almost fully occupied with CH{sub 4} and C{sub 2}H{sub 6} molecules, whereas the small cage occupancies of CH{sub 4} were below 0.8. The distribution of CH{sub 4} and C{sub 2}H{sub 6} in each cage were similar to that of synthetic CH{sub 4} + C{sub 2}H{sub 6} hydrate. It was concluded that these results should be useful for optimal estimation of the amount of natural gas in gas hydrates. 18 refs., 1 tab., 3 figs.

  20. Dominant Alcohol-Protein Interaction via Hydration-Enabled Enthalpy-Driven Binding Mechanism

    Science.gov (United States)

    Chong, Yuan; Kleinhammes, Alfred; Tang, Pei; Xu, Yan; Wu, Yue

    2015-01-01

    Water plays an important role in weak associations of small drug molecules with proteins. Intense focus has been on binding-induced structural changes in the water network surrounding protein binding sites, especially their contributions to binding thermodynamics. However, water is also tightly coupled to protein conformations and dynamics, and so far little is known about the influence of water-protein interactions on ligand binding. Alcohols are a type of low-affinity drugs, and it remains unclear how water affects alcohol-protein interactions. Here, we present alcohol adsorption isotherms under controlled protein hydration using in-situ NMR detection. As functions of hydration level, Gibbs free energy, enthalpy, and entropy of binding were determined from the temperature dependence of isotherms. Two types of alcohol binding were found. The dominant type is low-affinity nonspecific binding, which is strongly dependent on temperature and the level of hydration. At low hydration levels, this nonspecific binding only occurs above a threshold of alcohol vapor pressure. An increased hydration level reduces this threshold, with it finally disappearing at a hydration level of h~0.2 (g water/g protein), gradually shifting alcohol binding from an entropy-driven to an enthalpy-driven process. Water at charged and polar groups on the protein surface was found to be particularly important in enabling this binding. Although further increase in hydration has smaller effects on the changes of binding enthalpy and entropy, it results in significant negative change in Gibbs free energy due to unmatched enthalpy-entropy compensation. These results show the crucial role of water-protein interplay in alcohol binding. PMID:25856773

  1. Enclathration of CO2 as a co-guest of structure H hydrates and its implications for CO2 capture and sequestration

    International Nuclear Information System (INIS)

    Lee, Yohan; Lee, Dongyoung; Lee, Jong-Won; Seo, Yongwon

    2016-01-01

    Highlights: • We examine sH hydrates with CO 2 + N 2 + neohexane for CO 2 capture and sequestration. • The structural transition occurs in the CO 2 (40%) + N 2 (60%) + neohexane system. • CO 2 molecules are enclathrated into sH hydrates in the N 2 -rich systems. • CO 2 selectivity in sH hydrates is slightly lower than that in sI hydrates. • ΔH d values provide information on the structural transition of sH to sI hydrates. - Abstract: In this study, the thermodynamic behaviors, cage-specific guest distributions, structural transition, and dissociation enthalpies of sH hydrates with CO 2 + N 2 gas mixtures were investigated for their potential applications to hydrate-based CO 2 capture and sequestration. The stability conditions of the CO 2 + N 2 + water systems and the CO 2 + N 2 + neohexane (2,2-dimethylbutane, NH) + water systems indicated that the gas mixtures in the range of flue gas compositions could form sH hydrates, thereby mitigating the pressure and temperature required for gas hydrate formation. Structure identification using powder X-ray diffraction (PXRD) revealed the coexistence of sI and sH hydrates in the CO 2 (40%) + N 2 (60%) + NH system and the hydrate structure transformed from sH into sI as the CO 2 concentration increased. In addition, the Raman analysis clearly demonstrated that CO 2 molecules were enclathrated into the cages of sH hydrates in the N 2 -rich systems. It was found from direct CO 2 composition measurements that CO 2 selectivity in the sH hydrate phase was slightly lower than that in the corresponding sI hydrate phase. Dissociation enthalpy (ΔH d ) measurements using a high-pressure micro-differential scanning calorimeter (HP μ-DSC) indicated that the ΔH d values could also provide valuable information on the structural transition of sH to sI hydrates with respect to the CO 2 concentration in the feed gas. This study provides a better understanding of the thermodynamic and physicochemical background for CO 2

  2. Hydration Structure of the Quaternary Ammonium Cations

    KAUST Repository

    Babiaczyk, Wojtek Iwo

    2010-11-25

    Two indicators of the hydropathicity of small solutes are introduced and tested by molecular dynamics simulations. These indicators are defined as probabilities of the orientation of water molecules\\' dipoles and hydrogen bond vectors, conditional on a generalized distance from the solute suitable for arbitrarily shaped molecules. Using conditional probabilities, it is possible to distinguish features of the distributions in close proximity of the solute. These regions contain the most significant information on the hydration structure but cannot be adequately represented by using, as is usually done, joint distance-angle probability densities. Our calculations show that using our indicators a relative hydropathicity scale for the interesting test set of the quaternary ammonium cations can be roughly determined. © 2010 American Chemical Society.

  3. Thermoanalytical studies of carbamazepine: hydration/dehydration, thermal decomposition, and solid phase transitions

    Directory of Open Access Journals (Sweden)

    Mônia Aparecida Lemos Pinto

    2014-12-01

    Full Text Available Carbamazepine (CBZ, a widely used anticonvulsant drug, can crystallize and exhibits four polymorphic forms and one dihydrate. Anhydrous CBZ can spontaneously absorb water and convert to the hydrate form whose different crystallinity leads to lower biological activity. The present study was concerned to the possibility of recovering the hydrated form by heating. The thermal behavior of spontaneously hydrated carbamazepine was investigated by TG/DTG-DTA and DSC in dynamic atmospheres of air and nitrogen, which revealed that the spontaneous hydration of this pharmaceutical resulted in a Form III hydrate with 1.5 water molecules. After dehydration, this anhydrous Form III converted to Form I, which melted and decomposed in a single event, releasing isocyanic acid, as shown by evolved gas analysis using TG-FTIR. Differential scanning calorimetry analyses revealed that Form III melted and crystallized as Form I, and that subsequent cooling cycles only generated Form I by crystallization. Solid state decomposition kinetic studies showed that there was no change in the substance after the elimination of water by heating to 120 °C. Activation energies of 98 ± 2 and 93 ± 2 kJ mol-1 were found for the hydrated and dried samples, respectively, and similar profiles of activation energy as a function of conversion factor were observed for these samples.

  4. Structure and dynamics of water and lipid molecules in charged anionic DMPG lipid bilayer membranes

    DEFF Research Database (Denmark)

    Rønnest, A. K.; Peters, Günther H.J.; Hansen, Flemming Yssing

    2016-01-01

    Molecular dynamics simulations have been used to investigate the influence of the valency of counter-ions on the structure of freestanding bilayer membranes of the anionic 1,2-dimyristoyl-sn-glycero-3-phosphoglycerol (DMPG) lipid at 310 K and 1 atm. At this temperature, the membrane is in the fluid...... compared to experimental results and used to determine an average diffusion constant for all water molecules in the system. On extrapolating the diffusion constants inferred experimentally to a temperature of 310 K, reasonable agreement with the simulations is obtained. However, the experiments do not have...... the sensitivity to confirm the diffusion of a small component of water bound to the lipids as found in the simulations. In addition, the orientation of the dipole moment of the water molecules has been determined as a function of their depth in the membrane. Previous indirect estimates of the electrostatic...

  5. Atomistic simulations of cation hydration in sodium and calcium montmorillonite nanopores

    Science.gov (United States)

    Yang, Guomin; Neretnieks, Ivars; Holmboe, Michael

    2017-08-01

    During the last four decades, numerous studies have been directed to the swelling smectite-rich clays in the context of high-level radioactive waste applications and waste-liners for contaminated sites. The swelling properties of clay mineral particles arise due to hydration of the interlayer cations and the diffuse double layers formed near the negatively charged montmorillonite (MMT) surfaces. To accurately study the cation hydration in the interlayer nanopores of MMT, solvent-solute and solvent-clay surface interactions (i.e., the solvation effects and the shape effects) on the atomic level should be taken into account, in contrast to many recent electric double layer based methodologies using continuum models. Therefore, in this research we employed fully atomistic simulations using classical molecular dynamics (MD) simulations, the software package GROMACS along with the CLAYFF forcefield and the SPC/E water model. We present the ion distributions and the deformation of the hydrated coordination structures, i.e., the hydration shells of Na+ and Ca2+ in the interlayer, respectively, for MMT in the first-layer, the second-layer, the third-layer, the fourth-layer, and the fifth-layer (1W, 2W, 3W, 4W, and 5W) hydrate states. Our MD simulations show that Na+ in Na-MMT nanopores have an affinity to the ditrigonal cavities of the clay layers and form transient inner-sphere complexes at about 3.8 Å from clay midplane at water contents less than the 5W hydration state. However, these phenomena are not observed in Ca-MMT regardless of swelling states. For Na-MMT, each Na+ is coordinated to four water molecules and one oxygen atom of the clay basal-plane in the first hydration shell at the 1W hydration state, and with five to six water molecules in the first hydration shell within a radius of 3.1 Å at all higher water contents. In Ca-MMT, however each Ca2+ is coordinated to approximately seven water molecules in the first hydration shell at the 1W hydration state and

  6. Partition Coefficients of Organic Molecules in Squalane and Water/Ethanol Mixtures by Molecular Dynamics Simulations

    DEFF Research Database (Denmark)

    Lundsgaard, Rasmus; Kontogeorgis, Georgios; Economou, Ioannis G.

    2011-01-01

    coefficient can be estimated for both a small hydrophilic and a hydrophobic organic molecules between squalane (used here to mimic low density poly ethylene) and water/ethanol solutes using thermodynamic integration to calculate the free energy of solvation. Molecular dynamics simulations are performed, using...... the GROMACS software, by slowly decoupling of firstly the electrostatic and then the Lennard–Jones interactions between molecules in the simulation box. These calculations depend very much on the choice of force field. Two force fields have been tested in this work, the TraPPE-UA (united-atom) and the OPLS...

  7. Alcohol cosurfactants in hydrate antiagglomeration.

    Science.gov (United States)

    York, J Dalton; Firoozabadi, Abbas

    2008-08-28

    Because of availability, as well as economical and environmental considerations, natural gas is projected to be the premium fuel of the 21st century. Natural gas production involves risk of the shut down of onshore and offshore operations because of blockage from hydrates formed from coproduced water and hydrate-forming species in natural gas. Industry practice has been usage of thermodynamic inhibitors such as alcohols often in significant amounts, which have undesirable environmental and safety impacts. Thermodynamic inhibitors affect bulk-phase properties and inhibit hydrate formation. An alternative is changing surface properties through usage of polymers and surfactants, effective at 0.5 to 3 weight % of coproduced water. One group of low dosage hydrate inhibitors (LDHI) are kinetic inhibitors, which affect nucleation rate and growth. A second group of LDHI are antiagglomerants, which prevent agglomeration of small hydrate crystallites. Despite great potential, work on hydrate antiagglomeration is very limited. This work centers on the effect of small amounts of alcohol cosurfactant in mixtures of two vastly different antiagglomerants. We use a model oil, water, and tetrahydrofuran as a hydrate-forming species. Results show that alcohol cosurfactants may help with antiagglomeration when traditional antiagglomerants alone are ineffective. Specifically, as low as 0.5 wt. % methanol cosurfactant used in this study is shown to be effective in antiagglomeration. Without the cosurfactant there will be agglomeration independent of the AA concentration. To our knowledge, this is the first report of alcohol cosurfactants in hydrate antiagglomerants. It is also shown that a rhamnolipid biosurfactant is effective down to only 0.5 wt. % in such mixtures, yet a quaternary ammonium chloride salt, i. e., quat, results in hydrate slurries down to 0.01 wt. %. However, biochemical surfactants are less toxic and biodegradable, and thus their use may prove beneficial even if at

  8. HYDRATE CORE DRILLING TESTS

    Energy Technology Data Exchange (ETDEWEB)

    John H. Cohen; Thomas E. Williams; Ali G. Kadaster; Bill V. Liddell

    2002-11-01

    The ''Methane Hydrate Production from Alaskan Permafrost'' project is a three-year endeavor being conducted by Maurer Technology Inc. (MTI), Noble, and Anadarko Petroleum, in partnership with the U.S. DOE National Energy Technology Laboratory (NETL). The project's goal is to build on previous and ongoing R&D in the area of onshore hydrate deposition. The project team plans to design and implement a program to safely and economically drill, core and produce gas from arctic hydrates. The current work scope includes drilling and coring one well on Anadarko leases in FY 2003 during the winter drilling season. A specially built on-site core analysis laboratory will be used to determine some of the physical characteristics of the hydrates and surrounding rock. Prior to going to the field, the project team designed and conducted a controlled series of coring tests for simulating coring of hydrate formations. A variety of equipment and procedures were tested and modified to develop a practical solution for this special application. This Topical Report summarizes these coring tests. A special facility was designed and installed at MTI's Drilling Research Center (DRC) in Houston and used to conduct coring tests. Equipment and procedures were tested by cutting cores from frozen mixtures of sand and water supported by casing and designed to simulate hydrate formations. Tests were conducted with chilled drilling fluids. Tests showed that frozen core can be washed out and reduced in size by the action of the drilling fluid. Washing of the core by the drilling fluid caused a reduction in core diameter, making core recovery very difficult (if not impossible). One successful solution was to drill the last 6 inches of core dry (without fluid circulation). These tests demonstrated that it will be difficult to capture core when drilling in permafrost or hydrates without implementing certain safeguards. Among the coring tests was a simulated hydrate

  9. Measurements of water molecule density by tunable diode laser absorption spectroscopy in dielectric barrier discharges with gas-water interface

    Science.gov (United States)

    Tachibana, Kunihide; Nakamura, Toshihiro; Kawasaki, Mitsuo; Morita, Tatsuo; Umekawa, Toyofumi; Kawasaki, Masahiro

    2018-01-01

    We measured water molecule (H2O) density by tunable diode-laser absorption spectroscopy (TDLAS) for applications in dielectric barrier discharges (DBDs) with a gas-water interface. First, the effects of water temperature and presence of gas flow were tested using a Petri dish filled with water and a gas injection nozzle. Second, the TDLAS system was applied to the measurements of H2O density in two types of DBDs; one was a normal (non-inverted) type with a dielectric-covered electrode above a water-filled counter electrode and the other was an inverted type with a water-suspending mesh electrode above a dielectric-covered counter electrode. The H2O density in the normal DBD was close to the density estimated from the saturated vapor pressure, whereas the density in the inverted DBD was about half of that in the former type. The difference is attributed to the upward gas flow in the latter type, that pushes the water molecules up towards the gas-water interface.

  10. Gas Hydrate Occurrence Inferred from Dissolved Cl− Concentrations and δ18O Values of Pore Water and Dissolved Sulfate in the Shallow Sediments of the Pockmark Field in Southwestern Xisha Uplift, Northern South China Sea

    Directory of Open Access Journals (Sweden)

    Min Luo

    2014-06-01

    Full Text Available Deep-water pockmarks are frequently accompanied by the occurrence of massive gas hydrates in shallow sediments. A decline in pore-water Cl− concentration and rise in δ18O value provide compelling evidence for the gas hydrate dissociation. Mega-pockmarks are widely scattered in the southwestern Xisha Uplift, northern South China Sea (SCS. Pore water collected from a gravity-core inside of a mega-pockmark exhibits a downward Cl− concentration decrease concomitant with an increase in δ18O value at the interval of 5.7–6.7 mbsf. Concentrations of Cl−, Na+, and K+ mainly cluster along the seawater freshening line without distinct Na+ enrichment and K+ depletion. Thus, we infer that the pore water anomalies of Cl− concentrations and δ18O values are attributed to gas hydrate dissociation instead of clay mineral dehydration. Moreover, the lower δ18O values of sulfate in the target core (C14 than those in the reference core (C9 may be associated with the equilibrium oxygen fractionation during sulfate reduction between sulfate and the relatively 18O-depleted ambient water resulting from gas hydrate formation. The gas hydrate contents are estimated to be 6%–10% and 7%–15%, respectively, according to the offset of Cl− concentrations and δ18O values from the baselines. This pockmark field in southwestern Xisha Uplift is likely to be a good prospective area for the occurrence of gas hydrate in shallow sediments.

  11. Free radicals from irradiated lyophilized DNA: influence of water of hydration

    International Nuclear Information System (INIS)

    Huettermann, J.; Roehrig, M.; Koehnlein, W.

    1992-01-01

    Lyophilized DNA equilibrated with water vapour at various relative humidities (0-95% H 2 O or D 2 O) was X-irradiated at 77 K and analysed for free radicals by electron paramagnetic resonance (EPR) spectroscopy in the temperature range 77-280 K. Analysis of spectra according to variation in humidity, microwave power and temperature generally yielded a doublet and a triplet spectrum at 77 K. The doublet partially converted into the 5-thymyl radical (TH . ). DNA containing deuterated thymine (dTDNA) revealed that the doublet of ''normal'' DNA should be composed of two similar doublets, one of which should be assigned to the thymine anion, the other possibly the cytosine anion. The triplet signal was more stable and could be related to the guanine cation or its deprotonated successor. Several other patterns were detected among them an allyl radical in highly aquated DNA (95% humidity). Other features occurred either predominantly or exclusively in DNA equilibrated above 66% relative humidity and were ascribed to an influence of the secondary structure. (author)

  12. QSPR Study of the Retention/release Property of Odorant Molecules in Water Using Statistical Methods

    Directory of Open Access Journals (Sweden)

    Assia Belhassan

    2017-10-01

    Full Text Available An integrated approach physicochemistry and structures property relationships has been carried out to study the odorant molecules retention/release phenomenon in the water. This study aimed to identify the molecular properties (molecular descriptors that govern this phenomenon assuming that modifying the structure leads automatically to a change in the retention/release property of odorant molecules. ACD/ChemSketch, MarvinSketch, and ChemOffice programs were used to calculate several molecular descriptors of 51 odorant molecules (15 alcohols, 11 aldehydes, 9 ketones and 16 esters. A total of 37 molecules (2/3 of the data set were placed in the training set to build the QSPR models, whereas the remaining, 14 molecules (1/3 of the data set constitute the test set. The best descriptors were selected to establish the quantitative structure property relationship (QSPR of the retention/release property of odorant molecules in water using multiple linear regression (MLR, multiple non-linear regression (MNLR and an artificial neural network (ANN methods. We propose a quantitative model according to these analyses. The models were used to predict the retention/release property of the test set compounds, and agreement between the experimental and predicted values was verified. The descriptors showed by QSPR study are used for study and designing of new compounds. The statistical results indicate that the predicted values are in good agreement with the experimental results. To validate the predictive power of the resulting models, external validation multiple correlation coefficient was calculated and has both in addition to a performant prediction power, a favorable estimation of stability. DOI: http://dx.doi.org/10.17807/orbital.v9i4.978 

  13. 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.

  14. Molecular Dynamics Study of Water Molecules in Interlayer of 14 ^|^Aring; Tobermorite

    KAUST Repository

    Yoon, Seyoon

    2013-01-01

    The molecular structure and dynamics of interlayer water of 14 Å tobermorite are investigated based on molecular dynamics (MD) simulations. Calculated structural parameters of the interlayer water configuration are in good agreement with current knowledge of the refined structure. The MD simulations provide detailed information on the position and mobility of the hydrogen and oxygen of interlayer water, as well as its self-diffusion coefficient, through the interlayer of 14 Å tobermorite. Comparison of the MD simulation results at 100 and 300 K demonstrates that water molecules in the interlayer maintain their structure but change their mobility. The dominant configuration and self-diffusion coefficient of interlayer water are obtained in this study. Copyright © 2013 Japan Concrete Institute.

  15. The examination of biophysical parameters of skin (transepidermal water loss, skin hydration and pH value) in different body regions of normal cats of both sexes.

    Science.gov (United States)

    Szczepanik, Marcin P; Wilkołek, Piotr M; Adamek, Lukasz R; Pomorski, Zbigniew J H

    2011-04-01

    The purpose of this study was to evaluate transepidermal water loss (TEWL), skin hydration and skin pH in normal cats. Twenty shorthaired European cats of both sexes were examined in the study. Measurements were taken from five different sites: the lumbar region, the axillary fossa, the inguinal region, the ventral abdominal region and the left thoracic region. In each of the regions, TEWL, skin hydration and skin pH were measured. The highest TEWL value was observed in the axillary fossa (18.22g/h/m(2)) and the lowest in the lumbar region (10.53g/h/m(2)). The highest skin hydration was found in the inguinal region (18.29CU) and the lowest in the lumbar region (4.62CU). The highest skin pH was observed in the inguinal region (6.64) and the lowest in the lumbar region (6.39). Statistically significant differences in TEWL were observed between the lumbar region and the left side of the thorax region (P=0.016), the axillary fossa (P=0.0004), the ventral region (P=0.005), and the inguinal region (P=0.009). There were significant differences in skin hydration between the lumbar region and the left thorax (P=0.000003), the axillary fossa (P=0.002), the ventral abdomen (P=0.03), and the inguinal region (P=0.0003) as well as between the thorax and the ventral abdomen (P=0.005). TEWL was higher in females (15g/h/m(2)) than in males (4.57g/h/m(2)). Skin hydration was higher in females (13.89CU) than in males (12.28CU). Significant differences were not found between males and females for TEWL and skin hydration. Skin pH was higher in males (6.94) than in females (6.54), which was significant (P=0.004). Crown Copyright © 2010. Published by Elsevier Ltd. All rights reserved.

  16. Ceramide 1 and ceramide 3 act synergistically on skin hydration and the transepidermal water loss of sodium lauryl sulfate-irritated skin.

    Science.gov (United States)

    Huang, Huey-Chun; Chang, Tsong-Min

    2008-08-01

    Stratum corneum intercellular lipids, such as ceramides, play an important role in the regulation of skin water barrier homeostasis and water-holding capacity. Aim To evaluate the potential water retention capacity of control emulsion and three oil-in-water (o/w) emulsions containing ceramide 1, ceramide 3, or both. Fifteen healthy Asian women (age, 20-30 years) with healthy skin, pretreated with sodium lauryl sulfate (SLS), applied the tested emulsions twice daily over a period of 28 days. Skin hydration and transepidermal water loss (TEWL) values were measured on the indicated days with a Corneometer(R)825 and a TEWAMETER TM210, respectively. The maximum increase in skin humidity was reached after 4 weeks, with values of 21.9 +/- 1.8% and 8.9 +/- 0.9% for emulsion C and control emulsion, respectively. The maximum decrease in TEWL was also reached after 4 weeks, with values of 36.7 +/- 4.7% and 5.1 +/- 0.8% for the same emulsions. It can be concluded that all the tested ceramide-containing emulsions improved skin barrier function when compared with untreated skin. There was some indication that ceramides 1 and 3 contained in emulsion C might exert a beneficial synergistic effect on skin biochemical properties, such as skin hydration and TEWL, and play a key role in the protection mechanism against SLS irritation.

  17. Polarization and charge transfer in the hydration of chloride ions

    International Nuclear Information System (INIS)

    Zhao Zhen; Rogers, David M.; Beck, Thomas L.

    2010-01-01

    A theoretical study of the structural and electronic properties of the chloride ion and water molecules in the first hydration shell is presented. The calculations are performed on an ensemble of configurations obtained from molecular dynamics simulations of a single chloride ion in bulk water. The simulations utilize the polarizable AMOEBA force field for trajectory generation and MP2-level calculations are performed to examine the electronic structure properties of the ions and surrounding waters in the external field of more distant waters. The ChelpG method is employed to explore the effective charges and dipoles on the chloride ions and first-shell waters. The quantum theory of atoms in molecules (QTAIM) is further utilized to examine charge transfer from the anion to surrounding water molecules. The clusters extracted from the AMOEBA simulations exhibit high probabilities of anisotropic solvation for chloride ions in bulk water. From the QTAIM analysis, 0.2 elementary charges are transferred from the ion to the first-shell water molecules. The default AMOEBA model overestimates the average dipole moment magnitude of the ion compared to the quantum mechanical value. The average magnitude of the dipole moment of the water molecules in the first shell treated at the MP2-level, with the more distant waters handled with an AMOEBA effective charge model, is 2.67 D. This value is close to the AMOEBA result for first-shell waters (2.72 D) and is slightly reduced from the bulk AMOEBA value (2.78 D). The magnitude of the dipole moment of the water molecules in the first solvation shell is most strongly affected by the local water-water interactions and hydrogen bonds with the second solvation shell, rather than by interactions with the ion.

  18. Water molecule-enhanced CO2 insertion in lanthanide coordination polymers

    International Nuclear Information System (INIS)

    Luo Liushan; Huang Xiaoyuan; Wang Ning; Wu Hongyan; Chen Wenbin; Feng Zihao; Zhu Huiping; Peng Xiaoling; Li Yongxian; Huang Ling; Yue Shantang; Liu Yingliang

    2009-01-01

    Two new lanthanide coordination polymers H 2 N(CH 3 ) 2 .[Eu III 2 (L 1 ) 3 (L 2 )] (1, L 1 =isophthalic acid dianion, L 2 =formic acid anion) and [La III (2,5-PDC)(L 2 )](2, 2,5-PDC=2,5-pyridinedicarboxylate dianion) were synthesized under solvothermal conditions. It is of interest that the formic ligand (L 2 ) is not contained in the stating materials, but arises from the water molecule-enhanced CO 2 insertion during the solvothermal process. Both of the two compounds exhibit complicated three dimensional sandwich-like frameworks. - Graphical abstract: Two new lanthanide coordination polymers involving water molecule-enhanced CO 2 insertion resulting in the formation of formic anion and dimethylammonium cation were synthesized under solvothermal conditions.

  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. Hydration of amino acids: FTIR spectra and molecular dynamics studies.

    Science.gov (United States)

    Panuszko, Aneta; Adamczak, Beata; Czub, Jacek; Gojło, Emilia; Stangret, Janusz

    2015-11-01

    The hydration of selected amino acids, alanine, glycine, proline, valine, isoleucine and phenylalanine, has been studied in aqueous solutions by means of FTIR spectra of HDO isotopically diluted in H2O. The difference spectra procedure and the chemometric method have been applied to remove the contribution of bulk water and thus to separate the spectra of solute-affected HDO. To support interpretation of obtained spectral results, molecular dynamics simulations of amino acids were performed. The structural-energetic characteristic of these solute-affected water molecules shows that, on average, water affected by amino acids forms stronger and shorter H-bonds than those in pure water. Differences in the influence of amino acids on water structure have been noticed. The effect of the hydrophobic side chain of an amino acid on the solvent interactions seems to be enhanced because of the specific cooperative coupling of water strong H-bond chain, connecting the carboxyl and amino groups, with the clathrate-like H-bond network surrounding the hydrocarbon side chain. The parameter derived from the spectral data, which corresponds to the contributions of the population of weak hydrogen bonds of water molecules which have been substituted by the stronger ones in the hydration sphere of amino acids, correlated well with the amino acid hydrophobicity indexes.

  1. CO2 capture by gas hydrate crystallization: Application on the CO2-N2 mixture

    International Nuclear Information System (INIS)

    Bouchemoua, A.

    2012-01-01

    CO 2 capture and sequestration represent a major industrial and scientific challenge of this century. There are different methods of CO 2 separation and capture, such as solid adsorption, amines adsorption and cryogenic fractionation. Although these processes are well developed at industrial level, they are energy intensive. Hydrate formation method is a less energy intensive and has an interesting potential to separate carbon dioxide. Gas hydrates are Document crystalline compounds that consist of hydrogen bonded network of water molecules trapping a gas molecule. Gas hydrate formation is favored by high pressure and low temperature. This study was conducted as a part of the SECOHYA ANR Project. The objective is to study the thermodynamic and kinetic conditions of the process to capture CO 2 by gas hydrate crystallization. Firstly, we developed an experimental apparatus to carry out experiments to determine the thermodynamic and kinetic formation conditions of CO 2 -N 2 gas hydrate mixture in water as liquid phase. We showed that the operative pressure may be very important and the temperature very low. For the feasibility of the project, we used TBAB (Tetrabutylammonium Bromide) as thermodynamic additive in the liquid phase. The use of TBAB may reduce considerably the operative pressure. In the second part of this study, we presented a thermodynamic model, based on the van der Waals and Platteeuw model. This model allows the estimation of thermodynamic equilibrium conditions. Experimental equilibrium data of CO 2 -CH 4 and CO 2 -N 2 mixtures are presented and compared to theoretical results. (author)

  2. Feasibility Study on a Microwave-Based Sensor for Measuring Hydration Level Using Human Skin Models.

    Science.gov (United States)

    Brendtke, Rico; Wiehl, Michael; Groeber, Florian; Schwarz, Thomas; Walles, Heike; Hansmann, Jan

    2016-01-01

    Tissue dehydration results in three major types of exsiccosis--hyper-, hypo-, or isonatraemia. All three types entail alterations of salt concentrations leading to impaired biochemical processes, and can finally cause severe morbidity. The aim of our study was to demonstrate the feasibility of a microwave-based sensor technology for the non-invasive measurement of the hydration status. Electromagnetic waves at high frequencies interact with molecules, especially water. Hence, if a sample contains free water molecules, this can be detected in a reflected microwave signal. To develop the sensor system, human three-dimensional skin equivalents were instituted as a standardized test platform mimicking reproducible exsiccosis scenarios. Therefore, skin equivalents with a specific hydration and density of matrix components were generated and microwave measurements were performed. Hydration-specific spectra allowed deriving the hydration state of the skin models. A further advantage of the skin equivalents was the characterization of the impact of distinct skin components on the measured signals to investigate mechanisms of signal generation. The results demonstrate the feasibility of a non-invasive microwave-based hydration sensor technology. The sensor bears potential to be integrated in a wearable medical device for personal health monitoring.

  3. Feasibility Study on a Microwave-Based Sensor for Measuring Hydration Level Using Human Skin Models.

    Directory of Open Access Journals (Sweden)

    Rico Brendtke

    Full Text Available Tissue dehydration results in three major types of exsiccosis--hyper-, hypo-, or isonatraemia. All three types entail alterations of salt concentrations leading to impaired biochemical processes, and can finally cause severe morbidity. The aim of our study was to demonstrate the feasibility of a microwave-based sensor technology for the non-invasive measurement of the hydration status. Electromagnetic waves at high frequencies interact with molecules, especially water. Hence, if a sample contains free water molecules, this can be detected in a reflected microwave signal. To develop the sensor system, human three-dimensional skin equivalents were instituted as a standardized test platform mimicking reproducible exsiccosis scenarios. Therefore, skin equivalents with a specific hydration and density of matrix components were generated and microwave measurements were performed. Hydration-specific spectra allowed deriving the hydration state of the skin models. A further advantage of the skin equivalents was the characterization of the impact of distinct skin components on the measured signals to investigate mechanisms of signal generation. The results demonstrate the feasibility of a non-invasive microwave-based hydration sensor technology. The sensor bears potential to be integrated in a wearable medical device for personal health monitoring.

  4. Fibrillar structure and elasticity of hydrating collagen: a quantitative multiscale approach.

    Science.gov (United States)

    Morin, Claire; Hellmich, Christian; Henits, Peter

    2013-01-21

    It is well known that hydration of collagenous tissues leads to their swelling, as well as to softening of their elastic behavior. However, it is much less clear which microstructural and micromechanical "rules" are involved in this process. Here, we develop a theoretical approach cast in analytical mathematical formulations, which is experimentally validated by a wealth of independent tests on collagenous tissues, such as X-ray diffraction, vacuum drying, mass measurements, and Brillouin light scattering. The overall emerging picture is the following: air-drying leaves water only in the gap zones between the triple-helical collagen molecules; upon re-hydration, the extrafibrillar space is established at volumes directly proportional to the hydration-induced swelling of the (micro) fibrils, until the maximum equatorial distance between the long collagen molecules is reached. Thereafter, the volume of the fibrils stays constant, and only the extrafibrillar volume continues to grow. At all these hydration stages, the elastic behavior is governed by the same, hydration-invariant mechanical interaction pattern of only two, interpenetrating mechanical phases: transversely isotropic molecular collagen and isotropic water (or empty pores in the vacuum-dried case). Copyright © 2012 Elsevier Ltd. All rights reserved.

  5. An Examination of the Prediction of Hydrate Formation Conditions in the Presence of Thermodynamic Inhibitors

    Directory of Open Access Journals (Sweden)

    Carollina de M. Molinari O. Antunes

    Full Text Available Abstract Gas hydrates are crystalline compounds, solid structures where water traps small guest molecules, typically light gases, in cages formed by hydrogen bonds. They are notorious for causing problems in oil and gas production, transportation and processing. Gas hydrates may form at pressures and temperatures commonly found in natural gas and oil production pipelines, thus causing partial or complete pipe blockages. In order to inhibit hydrate formation, chemicals such as alcohols (e.g., ethanol, methanol, mono-ethylene glycol and salts (sodium, magnesium or potassium chloride are injected into the produced stream. The purpose of this work is to briefly review the literature on hydrate formation in mixtures containing light gases (hydrocarbons and carbon dioxide and water in the presence of thermodynamic inhibitors. Four calculation methods to predict hydrate formation in those systems were examined and compared. Three commercial packages (Multiflash®, PVTSim® and CSMGem and a hydrate prediction routine in Fortran90 using the van der Waals and Platteeuw theory and the Peng-Robinson equation of state were tested. Predictions given by the four methods were compared to independent experimental data from the literature. In general, the four methods were found to be reasonably accurate. CSMGem and Multiflash® showed the best results.

  6. Methane and carbon dioxide hydrates on Mars: Potential origins, distribution, detection, and implications for future in situ resource utilization

    Science.gov (United States)

    Pellenbarg, Robert E.; Max, Michael D.; Clifford, Stephen M.

    2003-04-01

    There is high probability for the long-term crustal accumulation of methane and carbon dioxide on Mars. These gases can arise from a variety of processes, including deep biosphere activity and abiotic mechanisms, or, like water, they could exist as remnants of planetary formation and by-products of internal differentiation. CH4 and CO2 would tend to rise buoyantly toward the planet's surface, condensing with water under appropriate conditions of temperature and pressure to form gas hydrate. Gas hydrates are a class of materials created when gas molecules are trapped within a crystalline lattice of water-ice. The hydrate stability fields of both CH4 and CO2 encompass a portion of the Martian crust that extends from within the water-ice cryosphere, from a depth as shallow as ~10-20 m to as great as a kilometer or more below the base of the Martian cryosphere. The presence and distribution of methane and carbon dioxide hydrates may be of critical importance in understanding the geomorphic evolution of Mars and the geophysical identification of water and other volatiles stored in the hydrates. Of critical importance, Martian gas hydrates would ensure the availability of key in situ resources for sustaining future robotic and human exploration, and the eventual colonization, of Mars.

  7. Investigation of the Hydantoin Monomer and its Interaction with Water Molecules

    Science.gov (United States)

    Gruet, Sébastien; Perez, Cristobal; Schnell, Melanie

    2017-06-01

    Hydantoin (Imidazolidine-2,4-dione, C_3H_4N_2O_2) is a five-membered heterocyclic compound of astrobiological interest. This molecule has been detected in carbonaceous chondrites [1], and its formation can rise from the presence of glycolic acid and urea, two prebiotic molecules [2]. The hydrolysis of hydantoin under acidic conditions can also produce glycine [3], an amino acid actively searched for in the interstellar medium. Spectroscopic data of hydantoin is very limited and mostly dedicated to the solid phase. The high resolution study in gas phase is restricted to the work recently published by Ozeki et al. reporting the pure rotational spectra of the ground state and two vibrational states of the molecule in the millimeter-wave region (90-370 GHz)[4]. Using chirped-pulse Fourier-transform microwave (CP-FTMW) spectroscopy, we recorded the jet-cooled rotational spectra of hydantoin with water between 2 to 8 GHz. We observed the ground state of hydantoin monomer and several water complexes with one or two water molecules. All the observed species exhibit a hyperfine structure due to the two nitrogen atoms present in the molecule, which were fully resolved and analyzed. Additional experiments with a ^{18}O enriched water sample were realized to determine the oxygen-atom positions of the water monomers. These experiments yielded accurate structural information on the preferred water binding sites. The observed complexes and the interactions that hold them together, mainly strong directional hydrogen bonds, will be presented and discussed. [1] Shimoyama, A. and Ogasawara, R., Orig. Life Evol. Biosph., 32, 165-179, 2002. DOI:10.1023/A:1016015319112. [2] Menor-Salván, C. and Marín-Yaseli, M.R., Chem. Soc. Rev., 41(16), 5404-5415, 2012. DOI:10.1039/c2cs35060b. [3] De Marcellus P., Bertrand M., Nuevo M., Westall F. and Le Sergeant d'Hendecourt L., Astrobiology. 11(9), 847-854, 2011. DOI:10.1089/ast.2011.0677. [4] Ozeki, H., Miyahara R., Ihara H., Todaka S., Kobayashi

  8. Measurement of the exchange rate of waters of hydration in elastin by 2D T{sub 2}-T{sub 2} correlation nuclear magnetic resonance spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Sun Cheng; Boutis, Gregory S, E-mail: gboutis@brooklyn.cuny.edu [Brooklyn College, Department of Physics, 2900 Bedford Avenue, Brooklyn, NY 11210 (United States)

    2011-02-15

    We report on a direct measurement of the exchange rate of waters of hydration in elastin by T{sub 2}-T{sub 2} exchange spectroscopy. The exchange rates in bovine nuchal ligament elastin and aortic elastin at temperatures near, below and at the physiological temperature are reported here. Using an inverse Laplace transform (ILT) algorithm, we are able to identify four components in the relaxation times. While three of the components are in good agreement with previous measurements that used multi-exponential fitting, the ILT algorithm distinguishes a fourth component having relaxation times close to that of free water and is identified as water between fibers. With the aid of scanning electron microscopy, a model is proposed that allows for the application of a two-site exchange analysis between any two components for the determination of exchange rates between reservoirs. The results of the measurements support a model (described by Urry and Parker 2002 J. Muscle Res. Cell Motil. 23 543-59) wherein the net entropy of waters of hydration should increase with increasing temperature in the inverse temperature transition.

  9. Measurement of the exchange rate of waters of hydration in elastin by 2D T2-T2 correlation nuclear magnetic resonance spectroscopy

    International Nuclear Information System (INIS)

    Sun Cheng; Boutis, Gregory S

    2011-01-01

    We report on a direct measurement of the exchange rate of waters of hydration in elastin by T 2 -T 2 exchange spectroscopy. The exchange rates in bovine nuchal ligament elastin and aortic elastin at temperatures near, below and at the physiological temperature are reported here. Using an inverse Laplace transform (ILT) algorithm, we are able to identify four components in the relaxation times. While three of the components are in good agreement with previous measurements that used multi-exponential fitting, the ILT algorithm distinguishes a fourth component having relaxation times close to that of free water and is identified as water between fibers. With the aid of scanning electron microscopy, a model is proposed that allows for the application of a two-site exchange analysis between any two components for the determination of exchange rates between reservoirs. The results of the measurements support a model (described by Urry and Parker 2002 J. Muscle Res. Cell Motil. 23 543-59) wherein the net entropy of waters of hydration should increase with increasing temperature in the inverse temperature transition.

  10. Measurement of the Exchange Rate of Waters of Hydration in Elastin by 2D T(2)-T(2) Correlation Nuclear Magnetic Resonance Spectroscopy.

    Science.gov (United States)

    Sun, Cheng; Boutis, Gregory S

    2011-02-28

    We report on the direct measurement of the exchange rate of waters of hydration in elastin by T(2)-T(2) exchange spectroscopy. The exchange rates in bovine nuchal ligament elastin and aortic elastin at temperatures near, below and at the physiological temperature are reported. Using an Inverse Laplace Transform (ILT) algorithm, we are able to identify four components in the relaxation times. While three of the components are in good agreement with previous measurements that used multi-exponential fitting, the ILT algorithm distinguishes a fourth component having relaxation times close to that of free water and is identified as water between fibers. With the aid of scanning electron microscopy, a model is proposed allowing for the application of a two-site exchange analysis between any two components for the determination of exchange rates between reservoirs. The results of the measurements support a model (described elsewhere [1]) wherein the net entropy of bulk waters of hydration should increase upon increasing temperature in the inverse temperature transition.

  11. Changes in the solid state of anhydrous and hydrated forms of sodium naproxen under different grinding and environmental conditions: Evidence of the formation of new hydrated forms.

    Science.gov (United States)

    Censi, Roberta; Rascioni, Riccardo; Di Martino, Piera

    2015-05-01

    particles by liquid nitrogen and by the grinding forces that created a close contact between water and drug. The simultaneous disruption of the crystals, occurring during grinding, and their close contact with water molecules promoted the conversion in higher hydrates. Under the Method D, it was possible to highlight a certain tendency to hydration probably due to a rearrangement of water already present into the hydrates, but results were substantially different from Method B. Thus, summarizing, the different SN forms behave differently under different grinding and environmental conditions. Copyright © 2015 Elsevier B.V. All rights reserved.

  12. A Raman spectroscopy study on the effects of intermolecular hydrogen bonding on water molecules absorbed by borosilicate glass surface

    Science.gov (United States)

    Li, Fabing; Li, Zhanlong; Wang, Ying; Wang, Shenghan; Wang, Xiaojun; Sun, Chenglin; Men, Zhiwei

    2018-05-01

    The structural forms of water/deuterated water molecules located on the surface of borosilicate capillaries have been first investigated in this study on the basis of the Raman spectral data obtained at different temperatures and under atmospheric pressure for molecules in bulk and also for molecules absorbed by borosilicate glass surface. The strongest two fundamental bands locating at 3063 cm-1 (2438 cm-1) in the recorded Raman spectra are assigned here to the Osbnd H (Osbnd D) bond stretching vibrations and they are compared with the corresponding bands observed at 3124 cm-1 (2325 cm-1) in the Raman spectrum of ice Ih. Our spectroscopic observations have indicated that the structure of water and deuterated water molecules on borosilicate surface is similar to that of ice Ih (hexagonal phase of ice). These observations have also indicated that water molecules locate on the borosilicate surface so as to construct a bilayer structure and that strong and weak intermolecular hydrogen bonds are formed between water/deuterated molecules and silanol groups on borosilicate surface. In accordance with these findings, water and deuterated water molecules at the interface of capillary have a higher melting temperature.

  13. Influence of smectite hydration and swelling on atrazine sorption behavior.

    Science.gov (United States)

    Chappell, Mark A; Laird, David A; Thompson, Michael L; Li, Hui; Teppen, Brian J; Aggarwal, Vaneet; Johnston, Cliff T; Boyd, Stephen A

    2005-05-01

    Smectites, clay minerals commonly found in soils and sediments, vary widely in their ability to adsorb organic chemicals. Recent research has demonstrated the importance of surface charge density and properties of exchangeable cations in controlling the affinity of smectites for organic molecules. In this study, we induced hysteresis in the crystalline swelling of smectites to test the hypothesis that the extent of crystalline swelling (or interlayer hydration status) has a large influence on the ability of smectites to adsorb atrazine from aqueous systems. Air-dried K-saturated Panther Creek (PC) smectite swelled less (d(001) = 1.38 nm) than never-dried K-PC (d(001) = 1.7 nm) when rehydrated in 20 mM KCl. Correspondingly, the air-dried-rehydrated K-PC had an order of magnitude greater affinity for atrazine relative to the never-dried K-PC. Both air-dried-rehydrated and never-dried Ca-PC expanded to approximately 2.0 nm in 10 mM CaCl2 and both samples had similar affinities for atrazine that were slightly lower than that of never-dried K-PC. The importance of interlayer hydration status in controlling sorption affinity was confirmed by molecular modeling, which revealed much greater interaction between interlayer water molecules and atrazine in a three-layer hydrate relative to a one-layer hydrate. The entropy change on moving atrazine from a fully hydrated state in the bulk solution to a partially hydrated state in the smectite interlayers is believed to be a major factor influencing sorption affinity. In an application test, choice of background solution (20 mM KCl versus 10 mM CaCl2) and air-drying treatments significantly affected atrazine sorption affinities for three-smectitic soils; however, the trends were not consistent with those observed for the reference smectite. Further, extending the initial rehydration time from 24 to 240 h (prior to adding atrazine) significantly decreased the soil's sorption affinity for atrazine. We conclude that interlayer

  14. Quantification of the Intracellular Life Time of Water Molecules to Measure Transport Rates of Human Aquaglyceroporins.

    Science.gov (United States)

    Palmgren, Madelene; Hernebring, Malin; Eriksson, Stefanie; Elbing, Karin; Geijer, Cecilia; Lasič, Samo; Dahl, Peter; Hansen, Jesper S; Topgaard, Daniel; Lindkvist-Petersson, Karin

    2017-12-01

    Orthodox aquaporins are transmembrane channel proteins that facilitate rapid diffusion of water, while aquaglyceroporins facilitate the diffusion of small uncharged molecules such as glycerol and arsenic trioxide. Aquaglyceroporins play important roles in human physiology, in particular for glycerol metabolism and arsenic detoxification. We have developed a unique system applying the strain of the yeast Pichia pastoris, where the endogenous aquaporins/aquaglyceroporins have been removed and human aquaglyceroporins AQP3, AQP7, and AQP9 are recombinantly expressed enabling comparative permeability measurements between the expressed proteins. Using a newly established Nuclear Magnetic Resonance approach based on measurement of the intracellular life time of water, we propose that human aquaglyceroporins are poor facilitators of water and that the water transport efficiency is similar to that of passive diffusion across native cell membranes. This is distinctly different from glycerol and arsenic trioxide, where high glycerol transport efficiency was recorded.

  15. Influence of fluorosurfactants on hydrate formation rates

    Energy Technology Data Exchange (ETDEWEB)

    Kim, C.U.; Jeong, K.E.; Chae, H.J.; Jeong, S.Y. [Korea Reasearch Inst. of Chemical Technology, Alternative Chemicals/Fuel Research Center, Yuseong-Gu, Daejon (Korea, Republic of)

    2008-07-01

    Gas hydrates, or clathrates, are ice-like solids that forms when natural gas is in contact with liquid water or ice under high pressure and low temperature. There is significant interest in studying the storage and transportation of gas in the form of hydrates. However, a critical problem impacting the industrial application of gas hydrates for storage and transportation of natural gas is the slow formation rate of natural gas hydrate. Researchers have previously reported on the promotion effect of some additives on gas hydrate formation and hydrate gas content. Fluorosurfactants are significantly superior to nonfluorinated surfactants in wetting action, as well as stability in harsh environments, both thermal and chemical. This paper discussed an experimental investigation into the effects of fluorosurfactants with different ionic types on the formation of methane hydrate. The surfactants used were FSN-100 of DuPont Zonyl as non-ionic surfactant and FC-143 of DuPont as anionic surfactant. The paper discussed the experimental apparatus for methane hydrate formation. It also discussed hydrate formation kinetics and the series of hydrate formation experiments that were conducted in the presence of fluorosurfactants. Last, the paper explored the results of the study. It was concluded that anionic fluorosurfactant of FC-143 had a better promoting effect on methane hydrate formation compared with nonionic surfactant of FSN-100. 8 refs., 2 tabs., 2 figs.

  16. Investigation of the Methane Hydrate Formation by Cavitation Jet

    Science.gov (United States)

    Morita, H.; Nagao, J.

    2015-12-01

    Methane hydrate (hereafter called "MH") is crystalline solid compound consisting of hydrogen-bonded water molecules forming cages and methane gas molecules enclosed in the cage. When using MH as an energy resource, MH is dissociated to methane gas and water and collect only the methane gas. The optimum MH production method was the "depressurization method". Here, the production of MH means dissociating MH in the geologic layers and collecting the resultant methane gas by production systems. In the production of MH by depressurization method, MH regeneration was consider to important problem for the flow assurance of MH production system. Therefore, it is necessary to clarify the effect of flow phenomena in the pipeline on hydrate regeneration. Cavitation is one of the flow phenomena which was considered a cause of MH regeneration. Large quantity of microbubbles are produced by cavitation in a moment, therefore, it is considered to promote MH formation. In order to verify the possible of MH regeneration by cavitation, it is necessary to detailed understanding the condition of MH formation by cavitation. As a part of a Japanese National hydrate research program (MH21, funded by METI), we performed a study on MH formation using by cavitation. The primary objective of this study is to demonstrate the formation MH by using cavitation in the various temperature and pressure condition, and to clarify the condition of MH formation by using observation results.

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

    International Nuclear Information System (INIS)

    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, e aq - , 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 e aq - /OH, respectively, were the following: chloronitromethane (3.01 ± 0.40) x 10 10 /(1.94 ± 0.32) x 10 8 ; dichloronitromethane (3.21 ± 0.17) x 10 10 /(5.12 ± 0.77) x 10 8 ; bromonitromethane (3.13 ± 0.06) x 10 10 /(8.36 ± 0.57) x 107; dibromonitromethane (3.07 ± 0.40) x 10 10 /(4.75 ± 0.98) x 10 8 ; tribromonitromethane (2.29 ± 0.39) x 10 10 /(3.25 ± 0.67) x 10 8 ; bromochloronitromethane (2.93 ± 0.47) x 10 10 /(4.2 ± 1.1) x 10 8 ; bromodichloronitromethane (2.68 ± 0.13) x 10 10 /(1.02 ± 0.15) x 10 8 ; and dibromochloronitromethane (2.95 ± 0.43) x 10 10 /(1.80 ± 0.31) x 10 8 at room temperature and pH ∼7. Comparison data were also obtained for hydroxyl radical reaction with bromoform (1.50 ± 0.05) x 10 8 , bromodichloromethane (7.11 ± 0.26) x 10 7 , and chlorodibromomethane (8.31 ± 0.25) x 10 7 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

  18. Single-Molecule Imaging of DNAs with Sticky Ends at Water/Fused Silica Interface

    Energy Technology Data Exchange (ETDEWEB)

    Isailovic, Slavica [Iowa State Univ., Ames, IA (United States)

    2005-01-01

    Total internal reflection fluorescence microscopy (TIRFM) was used to study intermolecular interactions of DNAs with unpaired (sticky) ends of different lengths at water/fused silica interface at the single-molecule level. Evanescent field residence time, linear velocity and adsorption/desorption frequency were measured in a microchannel for individual DNA molecules from T7, Lambda, and PSP3 phages at various pH values. The longest residence times and the highest adsorption/desorption frequencies at the constant flow at pH 5.5 were found for PSP3 DNA, followed by lower values for Lambda DNA, and the lowest values for T7 DNA. Since T7, Lambda, and PSP3 DNA molecules contain none, twelve and nineteen unpaired bases, respectively, it was concluded that the affinity of DNAs for the surface increases with the length of the sticky ends. This confirms that hydrophobic and hydrogen-bonding interactions between sticky ends and fused-silica surface are driving forces for DNA adsorption at the fused-silica surface. Described single-molecule methodology and results therein can be valuable for investigation of interactions in liquid chromatography, as well as for design of DNA hybridization sensors and drug delivery systems.

  19. Modeling the Release Kinetics of Poorly Water-Soluble Drug Molecules from Liposomal Nanocarriers

    Directory of Open Access Journals (Sweden)

    Stephan Loew

    2011-01-01

    Full Text Available Liposomes are frequently used as pharmaceutical nanocarriers to deliver poorly water-soluble drugs such as temoporfin, cyclosporine A, amphotericin B, and paclitaxel to their target site. Optimal drug delivery depends on understanding the release kinetics of the drug molecules from the host liposomes during the journey to the target site and at the target site. Transfer of drugs in model systems consisting of donor liposomes and acceptor liposomes is known from experimental work to typically exhibit a first-order kinetics with a simple exponential behavior. In some cases, a fast component in the initial transfer is present, in other cases the transfer is sigmoidal. We present and analyze a theoretical model for the transfer that accounts for two physical mechanisms, collisions between liposomes and diffusion of the drug molecules through the aqueous phase. Starting with the detailed distribution of drug molecules among the individual liposomes, we specify the conditions that lead to an apparent first-order kinetic behavior. We also discuss possible implications on the transfer kinetics of (1 high drug loading of donor liposomes, (2 attractive interactions between drug molecules within the liposomes, and (3 slow transfer of drugs between the inner and outer leaflets of the liposomes.

  20. Structural analysis on mutation residues and interfacial water molecules for human TIM disease understanding

    Science.gov (United States)

    2013-01-01

    Background Human triosephosphate isomerase (HsTIM) deficiency is a genetic disease caused often by the pathogenic mutation E104D. This mutation, located at the side of an abnormally large cluster of water in the inter-subunit interface, reduces the thermostability of the enzyme. Why and how these water molecules are directly related to the excessive thermolability of the mutant have not been investigated in structural biology. Results This work compares the structure of the E104D mutant with its wild type counterparts. It is found that the water topology in the dimer interface of HsTIM is atypical, having a "wet-core-dry-rim" distribution with 16 water molecules tightly packed in a small deep region surrounded by 22 residues including GLU104. These water molecules are co-conserved with their surrounding residues in non-archaeal TIMs (dimers) but not conserved across archaeal TIMs (tetramers), indicating their importance in preserving the overall quaternary structure. As the structural permutation induced by the mutation is not significant, we hypothesize that the excessive thermolability of the E104D mutant is attributed to the easy propagation of atoms' flexibility from the surface into the core via the large cluster of water. It is indeed found that the B factor increment in the wet region is higher than other regions, and, more importantly, the B factor increment in the wet region is maintained in the deeply buried core. Molecular dynamics simulations revealed that for the mutant structure at normal temperature, a clear increase of the root-mean-square deviation is observed for the wet region contacting with the large cluster of interfacial water. Such increase is not observed for other interfacial regions or the whole protein. This clearly suggests that, in the E104D mutant, the large water cluster is responsible for the subunit interface flexibility and overall thermolability, and it ultimately leads to the deficiency of this enzyme. Conclusions Our study

  1. IR reflectance spectroscopy of carbon dioxide clathrate hydrates. Implications for Saturn's icy moons.

    Science.gov (United States)

    Oancea, A.; Grasset, O.; Le Menn, E.; Bezacier, L.; Bollengier, O.; Le Mouélic, S.; Tobie, G.

    2012-04-01

    A CO2 spectral band was discovered by VIMS on the Saturn's satellites Dione, Hyperion, Iapetus and Phoebe [1]. The band position on the three first satellites corresponds to CO2 trapped in a complex material, but no indication exists whether this latter is water ice or some mineral or complex organic compound [1]. On Phoebe, the CO2 spectral band is consistent with solid CO2 or CO2 molecules trapped in the small cages of a clathrate hydrate structure [2]. It is thought that clathrate hydrates could play a significant role in the chemistry of the solar nebula [3] and in the physical evolution of astrophysical objects [4]. But so far, no clathrate hydrate structure has been observed in astrophysical environments. Moreover, identification of molecules trapped in a clathrate hydrate structure is extremely difficult because of the strong IR vibration modes of the water ice matrix. In this work, experimental IR reflectance spectra for CO2 clathrate hydrates are studied on grains and films. Clathrates are synthesized in a high pressure autoclave at low temperatures. IR spectral analysis is made with a low pressure and low temperature cryostat. These experimental conditions - 80 spectrum will be presented. A comparison between the absorption bands of CO2 clathrate hydrates obtained in our lab and CO2 absorption bands as detected by VIMS on the icy satellites of Saturn will be shown. This experimental work confirms that VIMS data are not consistent with the presence of structure I CO2 clathrate hydrates on the surface of the icy moons. Possibility of having metastable structure II still remains unsolved and will be discussed. [1] Dalton et al., Space Sci. Rev. 2010, 153 : 113-154. [2] Cruikshank D.P. et al, Icarus, 2010, 206: 561-572. [3] Mousis O. et al , Ap. J. 2009, 691: 1780-1786. [4] Choukroun M. et al, in Solar System Ices, edited by Castillo-Rogez, J. et al., 2011.

  2. Experimental investigation of smectite hydration from the simulation of 001 X-ray diffraction lines. Implications for the characterization of mineralogical modifications of the 'argilite' from the Meuse - Haute Marne site as a result of a thermal perturbation

    International Nuclear Information System (INIS)

    Ferrage, E.

    2004-10-01

    The structural modifications affecting the reactive mineral constituents of the clay barriers (smectite) and possibly resulting from the thermal pulse related to nuclear waste storage are essentially limited to the amount and location of the layer charge deficit. These modifications likely impact the hydration properties of these minerals, and a specific methodology has thus been developed to describe, using simulation of X-ray diffraction profiles (001 reflections), these hydration properties and specifically the heterogeneity resulting from the inter-stratification of different layer types, each exhibiting a specific hydration state. The detailed study of the hydration properties of a low-charge montmorillonite (octahedral charge) has shown that the affinity of the interlayer cation for water rules the hydration state and the thickness of hydrated smectite layers. If the layer charge is increased, the transition between the different hydration states is shifted, following a water desorption isotherm, towards lower relative humidities. In addition, the hydration of studied beidellites (tetrahedral charge) was shown to be more heterogeneous than that of montmorillonites. The developed methodology also allowed describing the structural modifications resulting from a chemical perturbation (chlorinated anionic background, pH). Finally, the link between the thickness of elementary layers and the amount of interlayer water molecules has been evidenced. A new structure model has also been determined for these interlayer species allowing an improved description of their positional distribution in bi-hydrated interlayers. (author)

  3. Late Glacial temperature and precipitation changes in the lowland Neotropics by tandem measurement of δ 18O in biogenic carbonate and gypsum hydration water

    Science.gov (United States)

    Hodell, David A.; Turchyn, Alexandra V.; Wiseman, Camilla J.; Escobar, Jaime; Curtis, Jason H.; Brenner, Mark; Gilli, Adrian; Mueller, Andreas D.; Anselmetti, Flavio; Ariztegui, Daniel; Brown, Erik T.

    2012-01-01

    We applied a new method to reconstruct paleotemperature in the tropics during the last deglaciation by measuring oxygen isotopes of co-occurring gypsum hydration water and biogenic carbonate in sediment cores from two lakes on the Yucatan Peninsula. Oxygen and hydrogen isotope values of interstitial and gypsum hydration water indicate that the crystallization water preserves the isotopic signal of the lake water, and has not undergone post-depositional isotopic exchange with sediment pore water. The estimated lake water δ18O is combined with carbonate δ18O to calculate paleotemperature. Three paired measurements of 1200-yr-old gypsum and gastropod aragonite from Lake Chichancanab, Mexico, yielded a mean temperature of 26 °C (range 23-29.5 °C), which is consistent with the mean and range of mean annual temperatures (MAT) in the region today. Paired measurements of ostracods, gastropods, and gypsum hydration water samples were measured in cores from Lake Petén Itzá, Guatemala, spanning the Late Glacial and early Holocene period (18.5-10.4 ka). The lowest recorded temperatures occurred at the start of Heinrich Stadial (HS) 1 at 18.5 ka. Inferred temperatures from benthic ostracods ranged from 16 to 20 °C during HS 1, which is 6-10 °C cooler than MAT in the region today, whereas temperatures derived from shallow-water gastropods were generally warmer (20-25 °C), reflecting epilimnetic temperatures. The derived temperatures support previous findings of greater tropical cooling on land in Central America during the Late Glacial than indicated by nearby marine records. Temperature increased in two steps during the last deglaciation. The first occurred during the Bolling-Allerod (B-A; from 14.7 to 13 ka) when temperature rose to 20-24 °C towards the end of this period. The second step occurred at 10.4 ka near the beginning of the Holocene when ostracod-inferred temperature rose to 26 °C, reflecting modern hypolimnetic temperature set during winter, whereas

  4. 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....

  5. Mixing of alcohol and water molecules studied by neutron probe. Structure and dynamics

    International Nuclear Information System (INIS)

    Yoshida, Koji

    2001-01-01

    Structure of water/alcohol mixing solution was studied by three methods such as an isotope-exchanged neutron scattering method, RISM (Reference Interaction Site Model) integral equation and a neutron spin echo method. The principle of methods, experiments and results were reported. The results of experiments of water/tert-butyl alcohol (TBA) solution by the isotope-exchange neutron scattering method showed TBA molecule associated with each other through end methyl group. Especially this effect was the largest at x TBA = 0.06 and decreased with increasing the concentration of TBA. However, hydrogen bonding of TBA was very rare at x TBA = 0.06. By the partial radial distribution function obtained from RISM integral equation, it indicated that the structure of pure TBA became chain structure by hydrogen bond but changed to the structure contacted directly each hydrophobic group with increasing the concentration of water. Water/2-butoxyethanol (BE) mixing solution was measured by a neutron spin echo method. The activation energy of the diffusion coefficients obtained agreed to the energy of hydrogen bonding. The temperature response of diffusion coefficients showed the inverse of the experimental results obtained by the dynamic light scattering method. The difference between two measurement methods was different time scale and space scale. Namely, the object of the neutron scattering method is nano meter and nano second, but one of light scattering method many times over. It was proved from the above results that there was the cluster consisted of the same kind of molecule in the homogeneous two components solution, but the cluster was not stable and constantly exchanged with molecule, where the production and decay of the cluster is repeated at about nano sec. (S.Y.)

  6. Experimental investigation of methane release from hydrate formation in sandstone through both hydrate dissociation and CO{sub 2} sequestration

    Energy Technology Data Exchange (ETDEWEB)

    Husebo, J.; Graue, A.; Kvamme, B. [Bergen Univ., Bergen (Norway). Dept. of Physics and Technology; Stevens, J.; Howard, J.J. [ConocoPhillips, Ponca City, OK (United States); Baldwin, B.A. [Green Country Petrophysics LLC, Dewey, OK (United States)

    2008-07-01

    Large amounts of natural gas trapped in hydrate reservoirs are found in Arctic regions and in deep offshore locations around the world. Natural gas production from hydrate deposits offer significant potential for future energy needs. However, research is needed in order to propose potential production schemes for natural gas hydrates. Natural gas molecules can be freed from hydrate structured cages by depressurization, by heating and by exposing the hydrate to a substance that will form a thermodynamically more stable hydrate structure. This paper provided a comparison of two approaches for releasing methane from methane hydrate in porous sandstone. The study scope covered the dissociation rate of methane hydrate in porous media through depressurization, and also referred to previous work done on producing methane from hydrates in sandstone while sequestering carbon dioxide (CO{sub 2}). The study was conducted in a laboratory setting. The paper discussed the experimental design which included the placing of a pressure- and temperature-controlled sample holder inside the bore of a magnetic resonance imager. The experimental procedures were then outlined, with reference to hydrate formation; carbon dioxide sequestration; hydrate dissociation experiments with constant volume; and hydrate dissociation experiments at constant pressure. The constant volume experiments demonstrated that in order to dissociate a large amount of hydrate, the initial depressurization had to be significantly lower than the hydrate stability pressure. 9 refs., 9 figs.

  7. A novel technique using DNA denaturation to detect multiply induced single-strand breaks in a hydrated plasmid DNA molecule by X-ray and 4He2+ ion irradiation

    International Nuclear Information System (INIS)

    Yokoya, A.; Shikazono, N.; Fujii, K.; Noguchi, M.; Urushibara, A.

    2011-01-01

    To detect multiple single-strand breaks (SSBs) produced in plasmid DNA molecules by direct energy deposition from radiation tracks, we have developed a novel technique using DNA denaturation by which irradiated DNA is analysed as single-strand DNA (SS-DNA). The multiple SSBs that arise in both strands of DNA, but do not induce a double-strand break, are quantified as loss of SS-DNA using agarose gel electrophoresis. We have applied this method to X-ray and 4 He 2+ ion-irradiated samples of fully hydrated pUC18 plasmid DNA. The fractions of both SS-DNA and closed circular DNA (CC-DNA) exponentially decrease with the increasing dose of X rays and 4 He 2+ ions. The efficiency of the loss of SS-DNA was half that of CC-DNA for both types of irradiation, indicating that one of two strands in DNA is not broken when one SSB is produced in CC-DNA by irradiation. Contrary to our initial expectation, these results indicate that SSBs are not multiply induced even by high linear energy transfer radiation distributed in both strands. (authors)

  8. Elevated Serum Osmolality and Total Water Deficit Indicate Impaired Hydration Status in Residents of Long-Term Care Facilities Regardless of Low or High Body Mass Index.

    Science.gov (United States)

    Marra, Melissa Ventura; Simmons, Sandra F; Shotwell, Matthew S; Hudson, Abbie; Hollingsworth, Emily K; Long, Emily; Kuertz, Brittany; Silver, Heidi J

    2016-05-01

    Dehydration is typically associated with underweight and malnutrition in long-term care (LTC) settings. Evidence is lacking regarding the influence of the rising prevalence of overweight and obesity on risk factors, prevalence, and presentation of dehydration. The aim of this study was to objectively assess hydration status and the adequacy of total water intake, and determine relationships between hydration status, total water intake, and body mass index (BMI) in LTC residents. A cross-sectional analysis of baseline data was performed. Baseline data from 247 subjects recruited from eight community-based LTC facilities participating in two randomized trials comparing nutrient and cost-efficacy of between-meal snacks vs oral nutrition supplements (ONS). Hydration status was assessed by serum osmolality concentration and total water intakes were quantified by weighed food, beverage, water, and ONS intake. Simple and multiple linear regression methods were applied. Forty-nine (38.3%) subjects were dehydrated (>300 mOsm/kg) and another 39 (30.5%) had impending dehydration (295 to 300 mOsm/kg). The variance in serum osmolality was significantly accounted for by blood urea nitrogen level, mental status score, and having diabetes (R(2)=0.46; PTotal water intake averaged 1,147.2±433.1 mL/day. Thus, 96% to 100% of subjects did not meet estimated requirements, with a deficit range of 700 to 1,800 mL/day. The variance in total water intake was significantly accounted for by type of liquid beverages (thin vs thick), type of ONS, total energy intake, total activities of daily living dependence, sex, and BMI (R(2)=0.56; Ptotal water intake is prevalent in LTC residents across all BMI categories. Type of liquid beverages, type of ONS, and type of between-meal snacks are factors that could be targeted for nutrition interventions designed to prevent or reverse dehydration. Copyright © 2016 Academy of Nutrition and Dietetics. Published by Elsevier Inc. All rights reserved.

  9. An oil-soluble extract of Rubus idaeus cells enhances hydration and water homeostasis in skin cells.

    Science.gov (United States)

    Tito, A; Bimonte, M; Carola, A; De Lucia, A; Barbulova, A; Tortora, A; Colucci, G; Apone, F

    2015-12-01

    Raspberry plants, belonging to the species of Rubus idaeus, are known for their excellent therapeutic properties as they are particularly rich in compounds with strong antioxidant activity, which promote health and well-being of human cells. Besides their high content of phenolic compounds, Rubus plants are rich in oil-soluble compounds, which are also primary components of the hydrolipidic film barrier of the skin. As plant cell cultures represented a valuable system to produce interesting compounds and ingredients for cosmetic applications, we developed liquid suspension cultures from Rubus idaeus leaves and used them to obtain an active ingredient aimed at improving hydration and moisturization capacity in the skin. Rubus idaeus cells, grown in the laboratory under sterile and controlled conditions as liquid suspension cultures, were processed to obtain an oil-soluble (liposoluble) extract, containing phenolic compounds and a wide range of fatty acids. The extract was tested on cultured keratinocytes and fibroblasts and then on the skin in vivo, to assess its cosmetic activities. When tested on skin cell cultures, the extract induced the genes responsible for skin hydration, such as aquaporin 3, filaggrin, involucrin and hyaluronic acid synthase, and stimulated the expression and the activity of the enzyme glucocerebrosidase, involved in ceramide production. Moreover, the liposoluble extract increased the synthesis of the extracellular matrix components in cultured fibroblasts and showed a remarkable skin-hydrating capacity when tested on human skin in vivo. Thanks to these activities, the Rubus idaeus liposoluble extract has several potential applications in skin care cosmetics: it can be used as hydrating and moisturizing ingredient in face and body lotions, and as anti-ageing product in face creams specifically designed to fight wrinkle formation. © 2015 Society of Cosmetic Scientists and the Société Française de Cosmétologie.

  10. Ab Initio Density Functional Theory Investigation of the Interaction between Carbon Nanotubes and Water Molecules during Water Desalination Process

    Directory of Open Access Journals (Sweden)

    Loay A. Elalfy

    2013-01-01

    Full Text Available Density functional theory calculations using B3LYP/3-21G level of theory have been implemented on 6 carbon nanotubes (CNTs structures (3 zigzag and 3 armchair CNTs to study the energetics of the reverse osmosis during water desalination process. Calculations of the band gap, interaction energy, highest occupied molecular orbital, lowest unoccupied molecular orbital, electronegativity, hardness, and pressure of the system are discussed. The calculations showed that the water molecule that exists inside the CNT is about 2-3 Å away from its wall. The calculations have proven that the zigzag CNTs are more efficient for reverse osmosis water desalination process than armchair CNTs as the reverse osmosis process requires pressure of approximately 200 MPa for armchair CNTs, which is consistent with the values used in molecular dynamics simulations, while that needed when using zigzag CNTs was in the order of 60 MPa.

  11. Multipole moments of water molecules in clusters and ice Ih from first principles calculations

    International Nuclear Information System (INIS)

    Batista, E.R.; Xantheas, S.S.; Jonsson, H.

    1999-01-01

    We have calculated molecular multipole moments for water molecules in clusters and in ice Ih by partitioning the charge density obtained from first principles calculations. Various schemes for dividing the electronic charge density among the water molecules were used. They include Bader close-quote s zero flux surfaces and Voronoi partitioning schemes. A comparison was also made with an induction model including dipole, dipole-quadrupole, quadrupole-quadrupole polarizability and first hyperpolarizability as well as fixed octopole and hexadecapole moments. We have found that the different density partitioning schemes lead to widely different values for the molecular multipoles, illustrating how poorly defined molecular multipoles are in clusters and condensed environments. For instance, the magnitude of the molecular dipole moment in ice Ih ranges between 2.3 D and 3.1 D depending on the partitioning scheme used. Within each scheme, though, the value for the molecular dipole moment in ice is larger than in the hexamer. The magnitude of the molecular dipole moment in the clusters shows a monotonic increase from the gas phase value to the one in ice Ih, with the molecular dipole moment in the water ring hexamer being smaller than the one in ice Ih for all the partitioning schemes used. copyright 1999 American Institute of Physics

  12. Electric double-layer capacitor based on an ionic clathrate hydrate.

    Science.gov (United States)

    Lee, Wonhee; Kwon, Minchul; Park, Seongmin; Lim, Dongwook; Cha, Jong-Ho; Lee, Huen

    2013-07-01

    Herein, we suggest a new approach to an electric double-layer capacitor (EDLC) that is based on a proton-conducting ionic clathrate hydrate (ICH). The ice-like structures of clathrate hydrates, which are comprised of host water molecules and guest ions, make them suitable for applications in EDLC electrolytes, owing to their high proton conductivities and thermal stabilities. The carbon materials in the ICH Me4NOH⋅5 H2O show a high specific capacitance, reversible charge-discharge behavior, and a long cycle life. The ionic-hydrate complex provides the following advantages in comparison with conventional aqueous and polymer electrolytes: 1) The ICH does not cause leakage problems under normal EDLC operating conditions. 2) The hydrate material can be utilized itself, without requiring any pre-treatments or activation for proton conduction, thus shortening the preparation procedure of the EDLC. 3) The crystallization of the ICH makes it possible to tailor practical EDLC dimensions because of its fluidity as a liquid hydrate. 4) The hydrate solid electrolyte exhibits more-favorable electrochemical stability than aqueous and polymer electrolytes. Therefore, ICH materials are expected to find practical applications in versatile energy devices that incorporate electrochemical systems. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  13. Continuum Navier-Stokes modelling of water ow past fullerene molecules

    DEFF Research Database (Denmark)

    Walther, J. H.; Popadic, A.; Koumoutsakos, P.

    We present continuum simulations of water flow past fullerene molecules. The governing Navier-Stokes equations are complemented with the Navier slip boundary condition with a slip length that is extracted from related molecular dynamics simulations. We find that several quantities of interest...... as computed by the present model are in good agreement with results from atomistic and atomistic-continuum simulations at a fraction of the computational cost. We simulate the flow past a single fullerene and an array of fullerenes and demonstrate that such nanoscale flows can be computed efficiently...

  14. Continuum Navier-Stokes modelling of water flow past fullerene molecules

    DEFF Research Database (Denmark)

    Walther, J. H.; Popadic, A.; Koumoutsakos, P.

    We present continuum simulations of water flow past fullerene molecules. The governing Navier-Stokes equations are complemented with the Navier slip boundary condition with a slip length that is extracted from related molecular dynamics simulations. We find that several quantities of interest...... as computed by the present model are in good agreement with results from atomistic and atomistic-continuum simulations at a fraction of the computational cost. We simulate the flow past a single fullerene and an array of fullerenes and demonstrate that such nanoscale flows can be computed efficiently...

  15. Explicit Consideration of Water Molecules to Study Vibrational Circular DICHROÎSM of Monosaccharide's

    Science.gov (United States)

    Moussi, Sofiane; Ouamerali, Ourida

    2014-06-01

    Carbohydrates have multiples roles in biological systems. It has been found that the glycoside bond is fundamentally important in many aspects of chemistry and biology and forms the basis of carbohydrate chemistry. That means the stereochemical information, namely, glycosidic linkages α or β, gives an significant features of the carbohydrate glycosidation position of the glycosylic acceptor. For these reasons, much effort was made for the synthesis and analysis of the glycoside bond. Vibrational circular dichroism VCD has some advantages over conventional electronic circular dichroism (ECD) due to the applicability to all organic molecules and the reliability of ab initio quantum calculation. However, for a molecule with many chiral centers such as carbohydrates, determination of the absolute configuration tends to be difficult because the information from each stereochemical center is mixed and averaged over the spectrum. In the CH stretching region, only two VCD studies on carbohydrates have been reported and spectra--structure correlation, as determined for the glycoside band, remains to be investigated. T. Taniguchi and collaborators report that methyl glycosides exhibit a characteristic VCD peak, the sign of which solely reflects the C-1 absolute configuration. This work is a theoretical contribution to study the behaviour of VCD spectrum's of the monosaccharides when the water molecules are taken explicitly. This study is focused on six different monosaccharides in theirs absolute configuration R and S. We used the method of density functional theory DFT by means of the B3LYP hybrid functional and 6-31G * basis set.

  16. Fire extinction utilizing carbon dioxide hydrate

    Energy Technology Data Exchange (ETDEWEB)

    Hatakeyama, T.; Aida, E.; Yokomori, T.; Ohmura, R.; Ueda, T. [Keio Univ., Hiyoshi, Kohoku-ku, Yokohama (Japan)

    2008-07-01

    Clathrate hydrates formed with nonflammable gases may be suitable for use as fire extinguishing agents because dissociation of the hydrates results in the temperature decrease in the combustion field and the nonflammable gases released from the dissociated hydrates prevent the supply of the oxygen to the combustion field. This paper discussed experiments in which ordinary ice and dry ice were used to evaluate the performance of CO{sub 2} hydrate as a fire extinguishing agent. The paper described the apparatus and procedure for the preparation of CO{sub 2} hydrate crystals. A schematic of the reactor to form CO{sub 2} hydrate and a photograph of CO{sub 2} hydrate crystal formed in the study were also presented. Other illustrations, photographs, and tables that were presented included a schematic diagram of the experimental apparatus used for the flame extinction experiments; a photograph of CO{sub 2} hydrate powder; sequential video graphs of the flame extinction by the supply of CO{sub 2} hydrate crystals to the methanol pool flame and the relevant illustration; and heat of CO{sub 2} hydrate dissociation, water vaporization and sublimation of dry ice. It was concluded that the critical mass of the CO{sub 2} hydrate required to extinguish a flame was much less than that of ordinary ice, indicating the superiority of CO{sub 2} hydrate to the ice. In addition, the experiments also revealed that the size of the CO{sub 2} hydrate particles had a significant effect on the performance of flame extinction. 5 refs., 2 tabs., 7 figs.

  17. Free energy of hydration of niobium oxide

    International Nuclear Information System (INIS)

    Plodinec, M.J.

    1996-01-01

    Some of the glasses being formulated by SRTC researchers contain niobium oxide. In this report, the free energy of hydration of the oxide is calculated from the free energies of formation of the oxide, the hydroxide, and water. This value can be used in calculations of the free energy of hydration of glasses containing niobium

  18. Water and oxygen induced degradation of small molecule organic solar cells

    DEFF Research Database (Denmark)

    Hermenau, Martin; Riede, Moritz; Leo, Karl

    2011-01-01

    Small molecule organic solar cells were studied with respect to water and oxygen induced degradation by mapping the spatial distribution of reaction products in order to elucidate the degradation patterns and failure mechanisms. The active layers consist of a 30 nm bulk heterojunction formed......,4′-diamine p-doped with C60F36 (MeO-TPD:C60F36), which acted as hole transporting layer. Indium-tin-oxide (ITO) and aluminum served as hole and electron collecting electrode, respectively. Time-of-flight secondary ion mass spectrometry (TOF-SIMS) and X-ray photoelectron spectroscopy (XPS) in conjunction...... of aluminum oxide at the BPhen/Al interface, and diffusion of water into the ZnPc:C60 layer where ZnPc becomes oxidized. Finally, diffusion from the electrodes was found to have no or a negligible effect on the device lifetime....

  19. Experimental Determination of Refractive Index of Gas Hydrates

    DEFF Research Database (Denmark)

    Bylov, Martin; Rasmussen, Peter

    1997-01-01

    . 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......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...

  20. Development of hydrate risk quantification in oil and gas production

    Science.gov (United States)

    Chaudhari, Piyush N.

    Subsea flowlines that transport hydrocarbons from wellhead to the processing facility face issues from solid deposits such as hydrates, waxes, asphaltenes, etc. The solid deposits not only affect the production but also pose a safety concern; thus, flow assurance is significantly important in designing and operating subsea oil and gas production. In most subsea oil and gas operations, gas hydrates form at high pressure and low temperature conditions, causing the risk of plugging flowlines, with a undesirable impact on production. Over the years, the oil and gas industry has shifted their perspective from hydrate avoidance to hydrate management given several parameters such as production facility, production chemistry, economic and environmental concerns. Thus, understanding the level of hydrate risk associated with subsea flowlines is an important in developing efficient hydrate management techniques. In the past, hydrate formation models were developed for various flow-systems (e.g., oil dominated, water dominated, and gas dominated) present in the oil and gas production. The objective of this research is to extend the application of the present hydrate prediction models for assessing the hydrate risk associated with subsea flowlines that are prone to hydrate formation. It involves a novel approach for developing quantitative hydrate risk models based on the conceptual models built from the qualitative knowledge obtained from experimental studies. A comprehensive hydrate risk model, that ranks the hydrate risk associated with the subsea production system as a function of time, hydrates, and several other parameters, which account for inertial, viscous, interfacial forces acting on the flow-system, is developed for oil dominated and condensate systems. The hydrate plugging risk for water dominated systems is successfully modeled using The Colorado School of Mines Hydrate Flow Assurance Tool (CSMHyFAST). It is found that CSMHyFAST can be used as a screening tool in

  1. Accuracy of free energies of hydration using CM1 and CM3 atomic charges.

    Science.gov (United States)

    Udier-Blagović, Marina; Morales De Tirado, Patricia; Pearlman, Shoshannah A; Jorgensen, William L

    2004-08-01

    Absolute free energies of hydration (DeltaGhyd) have been computed for 25 diverse organic molecules using partial atomic charges derived from AM1 and PM3 wave functions via the CM1 and CM3 procedures of Cramer, Truhlar, and coworkers. Comparisons are made with results using charges fit to the electrostatic potential surface (EPS) from ab initio 6-31G* wave functions and from the OPLS-AA force field. OPLS Lennard-Jones parameters for the organic molecules were used together with the TIP4P water model in Monte Carlo simulations with free energy perturbation theory. Absolute free energies of hydration were computed for OPLS united-atom and all-atom methane by annihilating the solutes in water and in the gas phase, and absolute DeltaGhyd values for all other molecules were computed via transformation to one of these references. Optimal charge scaling factors were determined by minimizing the unsigned average error between experimental and calculated hydration free energies. The PM3-based charge models do not lead to lower average errors than obtained with the EPS charges for the subset of 13 molecules in the original study. However, improvement is obtained by scaling the CM1A partial charges by 1.14 and the CM3A charges by 1.15, which leads to average errors of 1.0 and 1.1 kcal/mol for the full set of 25 molecules. The scaled CM1A charges also yield the best results for the hydration of amides including the E/Z free-energy difference for N-methylacetamide in water. Copyright 2004 Wiley Periodicals, Inc.

  2. Diffusion of water adsorbed in hydrotalcite: neutron scattering Study

    Energy Technology Data Exchange (ETDEWEB)

    Mitra, S [Solid State Physics Division, Bhabha Atomic Research Centre, Mumbai (India); Pramanik, A [Unilever Research India, Bangalore 500 066 (India); Chakrabarty, D [Godrej Sara Lee Limited, Research and Development Centre, Mumbai 400 079 (India); Juranyi, F [Laboratory for Neutron Scattering, ETHZ and PSI, CH-5232 Villigen PSI (Switzerland); Gautam, S [Solid State Physics Division, Bhabha Atomic Research Centre, Mumbai (India); Mukhopadhyay, R [Solid State Physics Division, Bhabha Atomic Research Centre, Mumbai (India)

    2007-12-15

    Layered double hydroxides (LDH) are a class of ionic lamellar solids with positively charged layers of two kinds of metallic cations and exchangeable hydrated anions. Quasi-elastic neutron scattering (QENS) measurements are performed in this type of LDH structured hydrated hydrotalcite sample to study the dynamical behaviour of the water in geometric confinement within the layers. Dynamical parameters correspond to the confined water molecules revealed that depending on the amount of excess water present, behaves differently and approaches bulk values at high concentration. Both translational and rotational dynamical parameters showed that at very low concentration of excess water, water molecules are attached to the surfaces and show the confinement effect.

  3. Conserved hydrogen bonds and water molecules in MDR HIV-1 protease substrate complexes

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Zhigang [Wayne State Univ., Detroit, MI (United States); Case Western Reserve Univ., Cleveland, OH (United States); Harbor Hospital Baltimore, MD (United States); Wang, Yong [Wayne State Univ., Detroit, MI (United States); Yedidi, Ravikiran S. [Wayne State Univ., Detroit, MI (United States); National Institutes of Health, Bethesda, MD (United States); Dewdney, Tamaria G. [Wayne State Univ., Detroit, MI (United States); Reiter, Samuel J. [Wayne State Univ., Detroit, MI (United States); Brunzelle, Joseph S. [Northwestern Univ. Feinberg School of Medicine, Chicago, IL (United States); Kovari, Iulia A. [Wayne State Univ., Detroit, MI (United States); Kovari, Ladislau C. [Wayne State Univ., Detroit, MI (United States)

    2012-12-19

    Success of highly active antiretroviral therapy (HAART) in anti-HIV therapy is severely compromised by the rapidly developing drug resistance. HIV-1 protease inhibitors, part of HAART, are losing their potency and efficacy in inhibiting the target. Multi-drug resistant (MDR) 769 HIV-1 protease (resistant mutations at residues 10, 36, 46, 54, 62, 63, 71, 82, 84, 90) was selected for the present study to understand the binding to its natural substrates. The nine crystal structures of MDR769 HIV-1 protease substrate hepta-peptide complexes were analyzed in order to reveal the conserved structural elements for the purpose of drug design against MDR HIV-1 protease. Our structural studies demonstrated that highly conserved hydrogen bonds between the protease and substrate peptides, together with the conserved crystallographic water molecules, played a crucial role in the substrate recognition, substrate stabilization and protease stabilization. Additionally, the absence of the key flap-ligand bridging water molecule might imply a different catalytic mechanism of MDR769 HIV-1 protease compared to that of wild type (WT) HIV-1 protease.

  4. Tuning dissociation using isoelectronically doped graphene and hexagonal boron nitride: Water and other small molecules

    Energy Technology Data Exchange (ETDEWEB)

    Al-Hamdani, Yasmine S. [Thomas Young Centre and London Centre for Nanotechnology, 17–19 Gordon Street, London WC1H 0AH (United Kingdom); Department of Chemistry, University College London, 20 Gordon Street, London WC1H 0AJ (United Kingdom); Alfè, Dario [Thomas Young Centre and London Centre for Nanotechnology, 17–19 Gordon Street, London WC1H 0AH (United Kingdom); Department of Earth Sciences, University College London, Gower Street, London WC1E 6BT (United Kingdom); Lilienfeld, O. Anatole von [Institute of Physical Chemistry and National Center for Computational Design and Discovery of Novel Materials (MARVEL), Department of Chemistry, University of Basel, Klingelbergstrasse 80, CH-4056 Basel (Switzerland); Michaelides, Angelos, E-mail: angelos.michaelides@ucl.ac.uk [Thomas Young Centre and London Centre for Nanotechnology, 17–19 Gordon Street, London WC1H 0AH (United Kingdom); Department of Physics and Astronomy, University College London, Gower Street, London WC1E 6BT (United Kingdom)

    2016-04-21

    Novel uses for 2-dimensional materials like graphene and hexagonal boron nitride (h-BN) are being frequently discovered especially for membrane and catalysis applications. Still however, a great deal remains to be understood about the interaction of environmentally and industrially relevant molecules such as water with these materials. Taking inspiration from advances in hybridising graphene and h-BN, we explore using density functional theory, the dissociation of water, hydrogen, methane, and methanol on graphene, h-BN, and their isoelectronic doped counterparts: BN doped graphene and C doped h-BN. We find that doped surfaces are considerably more reactive than their pristine counterparts and by comparing the reactivity of several small molecules, we develop a general framework for dissociative adsorption. From this a particularly attractive consequence of isoelectronic doping emerges: substrates can be doped to enhance their reactivity specifically towards either polar or non-polar adsorbates. As such, these substrates are potentially viable candidates for selective catalysts and membranes, with the implication that a range of tuneable materials can be designed.

  5. Identification of Carboxylate, Phosphate, and Phenoxide Functionalities in Deprotonated Molecules Related to Drug Metabolites via Ion-Molecule Reactions with water and Diethylhydroxyborane

    Science.gov (United States)

    Zhu, Hanyu; Ma, Xin; Kong, John Y.; Zhang, Minli; Kenttämaa, Hilkka I.

    2017-10-01

    Tandem mass spectrometry based on ion-molecule reactions has emerged as a powerful tool for structural elucidation of ionized analytes. However, most currently used reagents were designed to react with protonated analytes, making them suboptimal for acidic analyte