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Sample records for prevents hydrate formation

  1. Rapid gas hydrate formation process

    Science.gov (United States)

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

    2013-01-15

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

  2. Hydrate formation in drilling fluids: prevention and countering; Formacao de hidratos em fluidos de perfuracao: prevencao e controle

    Energy Technology Data Exchange (ETDEWEB)

    Villas Boas, Mario Barbosa [PETROBRAS, Macae, RJ (Brazil). Distrito de Perfuracao do Sudeste. Setor de Fluidos de Perfuracao

    1988-12-31

    The possibility of hydrates forming during deep water well drilling is analyzed under conditions typical of the state of Rio de Janeiro`s coastal ocean bed. Relying on an extensive review of technical literature, an effort has been made to ascertain the conditions which favor the occurrence of such hydrates in gas-contaminated water-based drilling muds. Based on this study, methods are proposed for preventing and countering this problem. (author) 58 refs., 10 figs.

  3. 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.

  4. 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)

  5. Hydrates prevention during deep-water formation gas well test; 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 [Unidade de Operacoes de Exploracao e Producao do Espirito Santo. Engenharia de Producao. Gerencia de Engenharia de Poco, ES (Brazil)], e-mail: renatocr@petrobras.com.br; Freitas, Alexandre Mussumeci Valim de [Centro de Pesquisas da Petrobras (CENPES). Gerencia de Tecnologia de Elevacao e Escoamento da Producao (Brazil)], e-mail: amfreitas@petrobras.com.br; Nishimura, Nelson Satiro [E and P Engenharia de Producao. Reservas e Reservatorios. Gerencia de Avaliacao de Reservatorios (Brazil)], e-mail: nishimura@petrobras.com.br

    2010-06-15

    This study examines the situation of a deep water formation test for a gas well in which simulations were made to identify possible pairs of points (Pressure versus Temperature), favorable to hydrate formation. Furthermore, the values obtained in the simulation were compared with the values registered during the formation test for the Alfa well in the Beta Field. With this information, an evaluation was made of the necessity to inject inhibitors intended to prevent hydrate formation in each test phase. In a wider sense, the study's objective was to recommend the volumes of hydrate inhibitors to be injected in each phase of a deep water formation test of a gas well to assure the operation be done without the risk of hydrate formation. (author)

  6. Study of Formation Mechanisms of Gas Hydrate

    Science.gov (United States)

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

    2015-04-01

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

  7. Glacial Cycles Influence Marine Methane Hydrate Formation

    Science.gov (United States)

    Malinverno, A.; Cook, A. E.; Daigle, H.; Oryan, B.

    2018-01-01

    Methane hydrates in fine-grained continental slope sediments often occupy isolated depth intervals surrounded by hydrate-free sediments. As they are not connected to deep gas sources, these hydrate deposits have been interpreted as sourced by in situ microbial methane. We investigate here the hypothesis that these isolated hydrate accumulations form preferentially in sediments deposited during Pleistocene glacial lowstands that contain relatively large amounts of labile particulate organic carbon, leading to enhanced microbial methanogenesis. To test this hypothesis, we apply an advection-diffusion-reaction model with a time-dependent organic carbon deposition controlled by glacioeustatic sea level variations. In the model, hydrate forms in sediments with greater organic carbon content deposited during the penultimate glacial cycle ( 120-240 ka). The model predictions match hydrate-bearing intervals detected in three sites drilled on the northern Gulf of Mexico continental slope, supporting the hypothesis of hydrate formation driven by enhanced organic carbon burial during glacial lowstands.

  8. Formation rate of natural gas hydrate

    Energy Technology Data Exchange (ETDEWEB)

    Mork, Marit

    2002-07-01

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

  9. 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

  10. 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.

  11. A prediction method of natural gas hydrate formation in deepwater gas well and its application

    Directory of Open Access Journals (Sweden)

    Yanli Guo

    2016-09-01

    Full Text Available To prevent the deposition of natural gas hydrate in deepwater gas well, the hydrate formation area in wellbore must be predicted. Herein, by comparing four prediction methods of temperature in pipe with field data and comparing five prediction methods of hydrate formation with experiment data, a method based on OLGA & PVTsim for predicting the hydrate formation area in wellbore was proposed. Meanwhile, The hydrate formation under the conditions of steady production, throttling and shut-in was predicted by using this method based on a well data in the South China Sea. The results indicate that the hydrate formation area decreases with the increase of gas production, inhibitor concentrations and the thickness of insulation materials and increases with the increase of thermal conductivity of insulation materials and shutdown time. Throttling effect causes a plunge in temperature and pressure in wellbore, thus leading to an increase of hydrate formation area.

  12. Controls on Gas Hydrate Formation and Dissociation

    Energy Technology Data Exchange (ETDEWEB)

    Miriam Kastner; Ian MacDonald

    2006-03-03

    The main objectives of the project were to monitor, characterize, and quantify in situ the rates of formation and dissociation of methane hydrates at and near the seafloor in the northern Gulf of Mexico, with a focus on the Bush Hill seafloor hydrate mound; to record the linkages between physical and chemical parameters of the deposits over the course of one year, by emphasizing the response of the hydrate mound to temperature and chemical perturbations; and to document the seafloor and water column environmental impacts of hydrate formation and dissociation. For these, monitoring the dynamics of gas hydrate formation and dissociation was required. The objectives were achieved by an integrated field and laboratory scientific study, particularly by monitoring in situ formation and dissociation of the outcropping gas hydrate mound and of the associated gas-rich sediments. In addition to monitoring with the MOSQUITOs, fluid flow rates and temperature, continuously sampling in situ pore fluids for the chemistry, and imaging the hydrate mound, pore fluids from cores, peepers and gas hydrate samples from the mound were as well sampled and analyzed for chemical and isotopic compositions. In order to determine the impact of gas hydrate dissociation and/or methane venting across the seafloor on the ocean and atmosphere, the overlying seawater was sampled and thoroughly analyzed chemically and for methane C isotope ratios. At Bush hill the pore fluid chemistry varies significantly over short distances as well as within some of the specific sites monitored for 440 days, and gas venting is primarily focused. The pore fluid chemistry in the tub-warm and mussel shell fields clearly documented active gas hydrate and authigenic carbonate formation during the monitoring period. The advecting fluid is depleted in sulfate, Ca Mg, and Sr and is rich in methane; at the main vent sites the fluid is methane supersaturated, thus bubble plumes form. The subsurface hydrology exhibits both

  13. Thermodynamic inhibitor performance extender that, effectively and economically prevent hydrate formation in the oil field production systems

    Energy Technology Data Exchange (ETDEWEB)

    Allenson, Stephen; Johnston, Angela [Nalco Energy Services, Sugar Land, TX (United States)

    2008-07-01

    This paper presents the development of a new additive that was developed to improve the effectiveness of the treatment two to four fold when added to the thermodynamic hydrate inhibitor (THI). Consequently, the THI/additive treatment can now enable the system to handle two to four times the amount of water production or can allow treatment of the same amount of water at half to quarter the dosage of THI. This new additive extends the performance of the THI and allows for a significant increase in production or a significant drop in the amount of THI usage with a corresponding drop in cost. This paper will further discuss the overall process of THI enhancement and will present several case studies where the enhanced THI has been successfully applied. (author)

  14. Effect of hydrate formation-dissociation on emulsion stability using DSC and visual techniques

    Energy Technology Data Exchange (ETDEWEB)

    Lachance, J.W.; Dendy Sloan, E.; Koh, C.A. [Colorado School of Mines, Golden, CO (United States). Center for Hydrates Research

    2008-07-01

    Many flow assurance operators are now focusing on preventing hydrates from agglomerating and forming plugs within pipelines. A key factor in reducing plug formation in oil-dominated systems is the stability of emulsified water in gas hydrate formation. In this study, differential scanning calorimetry (DSC) studies were used to show that gas hydrate formation has a destabilizing effect on water and oil emulsions, and can result in a free water phase through the coalescence and agglomeration of dissociated hydrate particles. The study focused on investigating the ability of the hydrates to stay segregated with hydrate formation. The stability of water-in-oil emulsions with hydrate formation was investigated with a range of different crude oils with varying emulsion stability levels. Thermal properties were measured at both atmospheric and pressurized conditions. Thermocouples in the calorimetric furnace were used to measure the temperature difference between reference and sample cells. Emulsion stability was measured over a 1-month time period. Results of the study showed that hydrate formation and dissociation destabilizes emulsions. However, the asphaltene fraction in crude oils resists hydrate-induced destabilization. The stability of the emulsion increased when asphaltene content increased. It was concluded that emulsion stability is a key factor in preventing agglomeration in flow lines. 14 refs., 3 tabs., 8 figs.

  15. Hydrophobic amino acids as a new class of kinetic inhibitors for gas hydrate formation

    Science.gov (United States)

    Sa, Jeong-Hoon; Kwak, Gye-Hoon; Lee, Bo Ram; Park, Da-Hye; Han, Kunwoo; Lee, Kun-Hong

    2013-08-01

    As the foundation of energy industry moves towards gas, flow assurance technology preventing pipelines from hydrate blockages becomes increasingly significant. However, the principle of hydrate inhibition is still poorly understood. Here, we examined natural hydrophobic amino acids as novel kinetic hydrate inhibitors (KHIs), and investigated hydrate inhibition phenomena by using them as a model system. Amino acids with lower hydrophobicity were found to be better KHIs to delay nucleation and retard growth, working by disrupting the water hydrogen bond network, while those with higher hydrophobicity strengthened the local water structure. It was found that perturbation of the water structure around KHIs plays a critical role in hydrate inhibition. This suggestion of a new class of KHIs will aid development of KHIs with enhanced biodegradability, and the present findings will accelerate the improved control of hydrate formation for natural gas exploitation and the utilization of hydrates as next-generation gas capture media.

  16. 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.

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

    KAUST Repository

    Jang, Jaewon

    2016-06-20

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

  18. Ethylene Separation via Hydrate Formation in W/O Emulsions

    Directory of Open Access Journals (Sweden)

    Yong Pan

    2015-05-01

    Full Text Available An hybrid absorption-hydration method was adopted to recover C2H4 from C2H4/CH4 binary gas mixtures and the hydrate formation conditions of C2H4/CH4 mixtures was studied experimentally in diesel in water (w/o emulsions. Span 20 at a concentration of 1.0 wt% in the aqueous phase was added to form water in diesel emulsions before hydrate formation and then hydrate in diesel slurry was separated after hydrate formation. The influences of initial gas-liquid volume ratio (53–142, pressure (3.4–5.4 MPa, temperature (274.15–278.15 K, water cuts (10–30 vol%, and the mole fraction of C2H4 in feed gas (13.19–80.44 mol% upon the C2H4 separation efficiency were systematically investigated. The experimental results show that ethylene can be enriched in hydrate slurry phase with high separation factor (S and recovery ratio (R. Most hydrate formation finished in 20 min, after that, the hydrate formation rate became very slow. The conclusion is useful for determining the suitable operation conditions when adopting an absorption-hydration method to separate C2H4/CH4.

  19. Formation of hydrate plug within rectangular natural gas passage

    Energy Technology Data Exchange (ETDEWEB)

    Seong, K.; Song, M.H.; Ahn, J.H.; Yoo, K.S. [Dong Guk Univ., Joong-ku, Seoul (Korea, Republic of)

    2008-07-01

    Oil and gas reservoirs in off-shore shallow areas are being depleted. At the same time, the industry is expanding its production sites into deeper waters resulting in higher pressure and lower temperature and more isolated locations. In response, connecting pipelines have been extended, but because of these pressure, temperature and distance changes in pipelines, a more favorable condition for hydrate formation is created, making the problem of flow assurance more critical for safe and economic operations at deep off-shore oil and gas production sites. Another challenge in flow assurance lies in hydrate formation and potential blockage due to hydrate plugs in gas pipelines, where no free water phase is present. This paper presented an experimental study that examined the formation and the growth of hydrates from a gas mixture of methane and propane with different moisture concentrations. The hydrates were formed in a rectangular passage cooled to temperatures below equilibrium hydrate formation temperature. The paper described the experimental procedure and apparatus that was designed and fabricated for the study. A schematic layout of the hydrate formation and plug test experimental apparatus was illustrated. The paper also described the results of two sets of experiments that were conducted. It was concluded that with enough moisture content, hydrates formed without a fresh water phase under equilibrium conditions. It was also concluded that the results of the study could be used in verifying numerical models developed to predict hydrate plugging of natural gas pipelines. 4 refs., 6 figs.

  20. Characteristics of SF{sub 6} gas hydrate formation mechanisms (kinetics) and surfactants effects on hydrate formation rate

    Energy Technology Data Exchange (ETDEWEB)

    Lee, B.; Lee, H.; Kim, Y.D. [Pusan National Univ., Busan (Korea, Republic of). School of Materials Science and Engineering; Kim, Y.S.; Lee, J.D. [Korea Inst. of Industrial Technology, Busan (Korea, Republic of). Advanced Energy Resource Development Team

    2008-07-01

    Sulfur hexafluoride (SF{sub 6}) is used as an insulating gas in a variety of industrial applications, and is a potent greenhouse gas (GHG). Gas hydrates are stable crystalline compounds formed by water and natural gas molecules that have relatively large cavities that can be occupied by guest molecules. SF{sub 6} gas is able to form hydrates at relatively mild conditions. This study investigated the hydrate formation mechanisms of SF{sub 6} gas, and presented a potential hydration treatment for the gas. The effects of surface active agents on SF{sub 6} gas hydrate formation were examined experimentally using Tween 20, sodium dodecyl sulfate (SDS) and linear alkyl benzene sulfonate (LABS). The surfactants showed promoter behaviour for SF{sub 6} gas hydrate formation. Formation rates occurred in 2 stages, with rates rapidly increasing during the second phase. The inflection point occurred approximately 30 minutes after the hydrate nucleation point. Results indicated the existence of a critical concentration of surfactants. It was concluded that SF{sub 6} gas hydrate formation rates were increased by the addition of surfactants. Further studies are needed to investigate 2-stage hydrate formation rates. 18 refs., 4 figs.

  1. Separation of water through gas hydrate formation

    DEFF Research Database (Denmark)

    Boch Andersen, Torben; Thomsen, Kaj

    2009-01-01

    Gas hydrate is normally recognized as a troublemaker in the oil and gas industry. However, gas hydrate has some interesting possibilities when used in connection with separation of water. Nordic Sugar has investigated the possibility of using gas hydrates for concentration of sugar juice. The goa...... volumes and the needs for high pressure. The process could be interesting for concentration of heat sensitive, high value products...

  2. Formation of nitric acid hydrates - A chemical equilibrium approach

    Science.gov (United States)

    Smith, Roland H.

    1990-01-01

    Published data are used to calculate equilibrium constants for reactions of the formation of nitric acid hydrates over the temperature range 190 to 205 K. Standard enthalpies of formation and standard entropies are calculated for the tri- and mono-hydrates. These are shown to be in reasonable agreement with earlier calorimetric measurements. The formation of nitric acid trihydrate in the polar stratosphere is discussed in terms of these equilibrium constants.

  3. Hydrate formation in heterogeneous sediments: To what extent does hydrate distribution record the local environmental history?

    Science.gov (United States)

    Rempel, A. W.; VanderBeek, B. P.

    2017-12-01

    deeper source region. These results hold promise for using observations of hydrate distribution within anomalous deposits, together with measured sediment properties to infer pore fluid advection rates and formation time scales during reservoir emplacement.

  4. 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...

  5. Synergistic kinetic inhibition of natural gas hydrate formation

    DEFF Research Database (Denmark)

    Daraboina, Nagu; Malmos, Christine; von Solms, Nicolas

    2013-01-01

    Rocking cells were used to investigate the natural gas hydrate formation and decomposition in the presence of kinetic inhibitor, Luvicap. In addition, the influence of poly ethylene oxide (PEO) and NaCl on the performance of Luvicap was investigated using temperature ramping and isothermal...... to decompose completely. One should consider this complex inhibitor-mediated hydrate formation and decomposition kinetics when screening and designing kinetic inhibitors for field applications....

  6. Effects of excipients on hydrate formation in wet masses containing theophylline

    DEFF Research Database (Denmark)

    Airaksinen, Sari; Luukkonen, Pirjo; Jørgensen, Anna

    2003-01-01

    its dissolution rate. The aim of this study was to investigate whether excipients, such as alpha-lactose monohydrate or the highly water absorbing silicified microcrystalline cellulose (SMCC) can influence the hydrate formation of theophylline. In particular, the aim was to study if SMCC offers...... protection against the formation of theophylline monohydrate relative to alpha-lactose monohydrate in wet masses after an overnight equilibration and the stability of final granules during controlled storage. In addition, the aim was to study the use of spectroscopic methods to identify hydrate formation...... in the formulations containing excipients. Off-line evaluation of materials was performed using X-ray powder diffractometry, near infrared and Raman spectroscopy. alpha-Lactose monohydrate with minimal water absorbing potential was not able to prevent but enhanced hydrate formation of theophylline. Even though SMCC...

  7. Increasing Gas Hydrate Formation Temperature for Desalination of High Salinity Produced Water with Secondary Guests

    Energy Technology Data Exchange (ETDEWEB)

    Cha, Jong-Ho; Seol, Yongkoo

    2013-10-07

    We suggest a new gas hydrate-based desalination process using water-immiscible hydrate formers; cyclopentane (CP) and cyclohexane (CH) as secondary hydrate guests to alleviate temperature requirements for hydrate formation. The hydrate formation reactions were carried out in an isobaric condition of 3.1 MPa to find the upper temperature limit of CO2 hydrate formation. Simulated produced water (8.95 wt % salinity) mixed with the hydrate formers shows an increased upper temperature limit from -2 °C for simple CO2 hydrate to 16 and 7 °C for double (CO2 + CP) and (CO2 + CH) hydrates, respectively. The resulting conversion rate to double hydrate turned out to be similar to that with simple CO2 hydrate at the upper temperature limit. Hydrate formation rates (Rf) for the double hydrates with CP and CH are shown to be 22 and 16 times higher, respectively, than that of the simple CO2 hydrate at the upper temperature limit. Such mild hydrate formation temperature and fast formation kinetics indicate increased energy efficiency of the double hydrate system for the desalination process. Dissociated water from the hydrates shows greater than 90% salt removal efficiency for the hydrates with the secondary guests, which is also improved from about 70% salt removal efficiency for the simple hydrates.

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

    Science.gov (United States)

    Rogers, Rudy E.; Zhong, Yu

    2002-01-01

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

  9. Hydrate prevention in petroleum production sub sea system

    Energy Technology Data Exchange (ETDEWEB)

    Rodrigues, Paula L.F.; Rocha, Humberto A.R. [Universidade Estacio de Sa (UNESA), Rio de Janeiro, RJ (Brazil); Rodrigues, Antonio P. [Universidade Federal do Rio Grande do Norte (UFRN), Natal, RN (Brazil)

    2012-07-01

    In spite of the merits of the several hydrate prevention techniques used nowadays, such as: chemical product injection for inhibition and use of thick thermal insulate lines; hydrates per times happen and they are responsible for considerable production losses. Depressurization techniques can be used so much for prevention as in the remediation. Some hydrate removal techniques need a rig or vessel, resources not readily available and with high cost, reason that limits such techniques just for remediation and not for prevention. In the present work it is proposed and described an innovative depressurization system, remote and resident, for hydrate prevention and removal, applicable as for individual sub sea wells as for grouped wells by manifold. Based on low cost jet pumps, without movable parts and with a high reliability, this technique allows hydrate prevention or remediation in a fast and remote way, operated from the production unit. The power fluid line and fluid return line can be integrated in the same umbilical or annulus line structure, without significant increase in the construction costs and installation. It is not necessary to wait for expensive resource mobilization, sometimes not available quickly, such as: vessels or rigs. It still reduces the chemical product consumption and permits to depressurized stopped lines. Other additional advantage, depressurization procedure can be used in the well starting, removing fluid until riser emptying. (author)

  10. 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

  11. Formation of methane hydrate from polydisperse ice powders.

    Science.gov (United States)

    Kuhs, Werner F; Staykova, Doroteya K; Salamatin, Andrey N

    2006-07-06

    Neutron diffraction runs and gas-consumption experiments based on pressure-volume-temperature measurements are conducted to study the kinetics of methane hydrate formation from hydrogenated and deuterated ice powder samples in the temperature range of 245-270 K up to high degrees of transformation. An improved theory of the hydrate growth in a polydisperse ensemble of randomly packed ice spheres is developed to provide a quantitative interpretation of the data in terms of kinetic model parameters. This paper continues the research line of our earlier study which was limited to the monodisperse case and shorter reaction times (Staykova et al., 2003). As before, we distinguish the process of initial hydrate film spreading over the ice particle surface (stage I) and the subsequent hydrate shell growth (stage II) which includes two steps, i.e., an interfacial clathration reaction and the gas and water transport (diffusion) through the hydrate layer surrounding the shrinking ice cores. Although kinetics of hydrate formation at stage II is clearly dominated by the diffusion mechanism which becomes the limiting step at temperatures above 263 K, both steps are shown to be essential at lower temperatures. The permeation coefficient D is estimated as (1.46 +/- 0.44) x 10(-12) m2/h at 263 K with an activation energy Q(D) approximately 52.1 kJ/mol. This value is close to the energy of breaking hydrogen bonds in ice Ih and suggests that this process is the rate-limiting step in hydrate formation from ice in the slower diffusion-controlled part of the reaction.

  12. The method of predicting the process of condensation of moisture and hydrate formation in the gas pipeline

    OpenAIRE

    Хвостова, Олена Вікторівна

    2014-01-01

    The problem of ensuring the required value of one of the natural gas quality indicators during its transportation to the consumer - moisture content is considered in the paper. The method for predicting possible moisture condensation and hydrate formation processes in gas pipelines considering mixing gas flows with different moisture content was developed.Predicting the moisture condensation and hydrate formation in gas pipelines is an actual task since a timely prevention of these processes ...

  13. 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.

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

    Science.gov (United States)

    Grasso, Giovanny A.

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

  15. 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

  16. Effect of solidification and peculiarities of hydrate formation

    International Nuclear Information System (INIS)

    Svatovskaya, L.B.; Sychev, M.M.

    1978-01-01

    Solidification of dispersed systems: of CaCl 2 -H 2 O, SrCl 2 -H 2 O, MgSO 4 -H 2 O, ZnSO 4 -H 2 O, CoSO 4 -H 2 O, FeSO 4 -H 2 O is considered. It is shown that conditions of high ''solid-liquid'' values bring about metastable intermediate phases, which provides the opportunity of using solidification effect to study the mechanism of some inorganic reactions. The data obtained permit to consider hydration reactions in these systems to be additive reactions and to take place according to the associative mechanism. Outlined are correlations between heat of formation of initial and hydrate phases and the strength of artificial stone

  17. Effect of three representative surfactants on methane hydrate formation rate and induction time

    Directory of Open Access Journals (Sweden)

    Mostafa keshavarz Moraveji

    2017-06-01

    Full Text Available The effects of three types of surfactants on methane hydrate formation process were investigated. Three different classes of surfactants involving anionic (sodium dodecyl sulfonate, cationic (hexadecyl trimethyl ammonium bromide and non-ionic (poly oxy ethylene (40 octyl phenyl ether have been used. Thermodynamics of hydrate formation, formation rate, kinetic constants and induction time in the presence of surfactants with various concentrations were analyzed. Critical micelle concentrations (CMCs of these surfactants in water were determined by induction time measurements in various concentrations under methane hydrate formation conditions. The critical micelle concentration (CMC at the methane hydrate formation conditions for SDS, HTABr and TritonX-405 solutions were obtained at 450, 380 and 950 ppm, respectively. The experimental results indicated that hydrate formation rate increased with the use of surfactants for all concentrations and induction time decreased. It was found that for surfactants, CMC at hydrate formation conditions was less than CMC at ambient conditions.

  18. Methane Hydrate Formation and Dissociation in the Presence of Silica Sand and Bentonite Clay

    Directory of Open Access Journals (Sweden)

    Kumar Saw V.

    2015-11-01

    Full Text Available The formation and dissociation of methane hydrates in a porous media containing silica sand of different sizes and bentonite clay were studied in the presence of synthetic seawater with 3.55 wt% salinity. The phase equilibrium of methane hydrate under different experimental conditions was investigated. The effects of the particle size of silica sand as well as a mixture of bentonite clay and silica sand on methane hydrate formation and its dissociation were studied. The kinetics of hydrate formation was studied under different subcooling conditions to observe its effects on the induction time of hydrate formation. The amount of methane gas encapsulated in hydrate was computed using a real gas equation. The Clausius-Clapeyron equation is used to estimate the enthalpy of hydrate dissociation with measured phase equilibrium data.

  19. CO2 + N2O mixture gas hydrate formation kinetics and effect of soil minerals on mixture-gas hydrate formation process

    Science.gov (United States)

    Enkh-Amgalan, T.; Kyung, D.; Lee, W.

    2012-12-01

    CO2 mitigation is one of the most pressing global scientific topics in last 30 years. Nitrous oxide (N2O) is one of the main greenhouse gases (GHGs) defined by the Kyoto Protocol and its global warming potential (GWP) of one metric ton is equivalent to 310 metric tons of CO2. They have similar physical and chemical properties and therefore, mixture-gas (50% CO2 + 50% N2O) hydrate formation process was studied experimentally and computationally. There were no significant research to reduce N20 gas and we tried to make hydrate to mitigate N20 and CO2 in same time. Mixture gas hydrate formation periods were approximately two times faster than pure N2O hydrate formation kinetic in general. The fastest induction time of mixture-gas hydrate formation observed in Illite and Quartz among various soil mineral suspensions. It was also observed that hydrate formation kinetic was faster with clay mineral suspensions such as Nontronite, Sphalerite and Montmorillonite. Temperature and pressure change were not significant on hydrate formation kinetic; however, induction time can be significantly affected by various chemical species forming under the different suspension pHs. The distribution of chemical species in each mineral suspension was estimated by a chemical equilibrium model, PHREEQC, and used for the identification of hydrate formation characteristics in the suspensions. With the experimental limitations, a study on the molecular scale modeling has a great importance for the prediction of phase behavior of the gas hydrates. We have also performed molecular dynamics computer simulations on N2O and CO2 hydrate structures to estimate the residual free energy of two-phase (hydrate cage and guest molecule) at three different temperature ranges of 260K, 273K, and 280K. The calculation result implies that N2O hydrates are thermodynamically stable at real-world gas hydrate existing condition within given temperature and pressure. This phenomenon proves that mixture-gas could be

  20. Hysteresis of methane hydrate formation/decomposition at subsea geological conditions

    International Nuclear Information System (INIS)

    Klapproth, Alice; Piltz, Ross; Peterson, Vanessa K.; Kennedy, Shane J.; Kozielski, Karen A.; Hartley, Patrick G.

    2009-01-01

    Full text: Gas hydrates are a major risk when transporting oil and gas in offshore subsea pipelines. Under typical conditions in these pipelines (at high pressure and low temperature) the formation of gas hydrates is favourable. The hydrates form large solid plugs that can block pipelines and can even cause them to burst. This represents a major problem for the gas mining industry, which currently goes to extreme measures to reduce the risk of hydrate formation because there is no reliable experimental data on hydrate processes. The mechanisms of gas hydrate formation, growth and inhibition are poorly understood. A clear understanding of the fundamental processes will allow development of cost effective technologies to avoid production losses in gas pipelines. We are studying the nucleation of the methane hydrates by measuring the hysteresis of hydrate formation/decomposition by neutron diffraction. When a gas hydrate is decomposed (melted) the resulting water has a 'supposed memory effect' raising the probability of rapid hydrate reformation. This rapid reformation does not occur for pure water where nucleation can be delayed by several hours (induction time) due to metastability [1]. The memory effect can only be destroyed by extreme heating of the effected area. Possible causes of this effect include residual water structure, persistent hydrate crystal lites remaining in solution and remaining dissolved gas. We will compare the kinetics of formation and the stability region of hydrate formation of 'memory' water for comparison with pure water. This information has important implications for the oil and gas industry because it should provide a better understanding of the role of multiple dissociation and reformation of gas hydrates in plug formation.

  1. Formation of natural gas hydrates in marine sediments 1. Conceptual model of gas hydrate growth conditioned by host sediment properties

    Science.gov (United States)

    Clennell, M.B.; Hovland, M.; Booth, J.S.; Henry, P.; Winters, W.J.

    1999-01-01

    The stability of submarine gas hydrates is largely dictated by pressure and temperature, gas composition, and pore water salinity. However, the physical properties and surface chemistry of deep marine sediments may also affect the thermodynamic state, growth kinetics, spatial distributions, and growth forms of clathrates. Our conceptual model presumes that gas hydrate behaves in a way analogous to ice in a freezing soil. Hydrate growth is inhibited within fine-grained sediments by a combination of reduced pore water activity in the vicinity of hydrophilic mineral surfaces, and the excess internal energy of small crystals confined in pores. The excess energy can be thought of as a "capillary pressure" in the hydrate crystal, related to the pore size distribution and the state of stress in the sediment framework. The base of gas hydrate stability in a sequence of fine sediments is predicted by our model to occur at a lower temperature (nearer to the seabed) than would be calculated from bulk thermodynamic equilibrium. Capillary effects or a build up of salt in the system can expand the phase boundary between hydrate and free gas into a divariant field extending over a finite depth range dictated by total methane content and pore-size distribution. Hysteresis between the temperatures of crystallization and dissociation of the clathrate is also predicted. Growth forms commonly observed in hydrate samples recovered from marine sediments (nodules, and lenses in muds; cements in sands) can largely be explained by capillary effects, but kinetics of nucleation and growth are also important. The formation of concentrated gas hydrates in a partially closed system with respect to material transport, or where gas can flush through the system, may lead to water depletion in the host sediment. This "freeze-drying" may be detectable through physical changes to the sediment (low water content and overconsolidation) and/or chemical anomalies in the pore waters and metastable

  2. Surface Assisted Formation of methane Hydrates on Ice and Na Montmorillonite Clay

    Energy Technology Data Exchange (ETDEWEB)

    Gordon, Margaret Ellen [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Teich-McGoldrick, Stephanie [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Cygan, Randall Timothy [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Meserole, Stephen P. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Rodriguez, Mark A. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)

    2015-07-01

    Methane hydrates are extremely important naturally-occurring crystalline materials that impact climate change, energy resources, geological hazards, and other major environmental issues. Whereas significant experimental effort has been completed to understanding the bulk thermodynamics of methane hydrate assemblies, little is understood on heterogeneous nucleation and growth of methane hydrates in clay-rich environments. Controlled synthesis experiments were completed at 265-285 K and 6.89 MPa to examine the impact of montmorillonite surfaces in clay-ice mixtures to nucleate and form methane hydrate. The results suggest that the hydrophilic and methane adsorbing properties of Namontmorillonite reduce the nucleation period of methane hydrate formation in pure ice systems.

  3. Hydration for the prevention of contrast medium-induced nephropathy. An update

    International Nuclear Information System (INIS)

    Heinrich, M.; Uder, M.

    2006-01-01

    Contrast medium-induced nephropathy (CIN) continues to be one of the most common causes of hospital-acquired acute renal failure. Since most of the clinical studies on the prophylactic use of different drugs to prevent CIN produced disappointing results, hydration remains the mainstay of prophylaxis. A number of recent prospective randomized trials provided further evidence of the effectiveness of hydration and relevant information regarding the optimization of hydration protocols. It was shown that a bolus hydration solely during examination is not sufficient to prevent CIN. In addition, isotonic 0.9% saline was superior to the commonly used halfisotonic 0.45% saline in another trial. An outpatient hydration protocol including oral hydration before the examination followed by forced intravenous hydration over 6 hrs. beginning 30 to 60 min. prior to examination seems to be comparable to the usual hydration over 24 hrs. Another hydration protocol, which could also be very attractive especially for outpatients, included the infusion of sodium bicarbonate. In a recent trial, hydration with sodium bicarbonate, given as a bolus for 1 hr. prior to examination followed by an infusion for 6 hrs. after examination, was more effective than hydration with sodium chloride for the prophylaxis of CIN. However, there is still a lack of large-scale, multi-center trials comparing different hydration protocols and investigating their influence on clinically relevant endpoints such as mortality or the need for dialysis. (orig.)

  4. Deep-ocean field test of methane hydrate formation from a remotely operated vehicle

    Science.gov (United States)

    Brewer, Peter G.; Orr, Franklin M., Jr.; Friederich, Gernot; Kvenvolden, Keith A.; Orange, Daniel L.; McFarlane, James; Kirkwood, William

    1997-05-01

    We have observed the process of formation of clathrate hydrates of methane in experiments conducted on the remotely operated vehicle (ROV) Ventana in the deep waters of Monterey Bay. A tank of methane gas, acrylic tubes containing seawater, and seawater plus various types of sediment were carried down on Ventana to a depth of 910 m where methane gas was injected at the base of the acrylic tubes by bubble stream. Prior calculations had shown that the local hydrographic conditions gave an upper limit of 525 m for the P-T boundary defining methane hydrate formation or dissociation at this site, and thus our experiment took place well within the stability range for this reaction to occur. Hydrate formation in free seawater occurred within minutes as a buoyant mass of translucent hydrate formed at the gas-water interface. In a coarse sand matrix the filling of the pore spaces with hydrate turned the sand column into a solidified block, which gas pressure soon lifted and ruptured. In a fine-grained black mud the gas flow carved out flow channels, the walls of which became coated and then filled with hydrate in larger discrete masses. Our experiment shows that hydrate formation is rapid in natural seawater, that sediment type strongly influences the patterns of hydrate formation, and that the use of ROV technologies permits the synthesis of large amounts of hydrate material in natural systems under a variety of conditions so that fundamental research on the stability and growth of these substances is possible.

  5. Natural gas hydrate formation and inhibition in gas/crude oil/aqueous systems

    DEFF Research Database (Denmark)

    Daraboina, Nagu; Pachitsas, Stylianos; von Solms, Nicolas

    2015-01-01

    Gas hydrate formation in multi phase mixtures containing an aqueous phase (with dissolved salts), reservoir fluid (crude oil) and natural gas phase was investigated by using a standard rocking cell (RC-5) apparatus. The hydrate formation temperature was reduced in the presence of crude oils...... of the biodegradable commercial kinetic inhibitor (Luvicap-Bio) on natural gas hydrate formation with and without crude oil (30%) was investigated. The strength of kinetic inhibitor was not affected by salts, but decreased significantly in the presence of crude oil. Data for hydrate formation at practical conditions...... inhibition mechanisms and potentially a competition among inhibition-promotion mechanisms. Moreover, the hydrate formation time has been determined at different water cuts in each crude oil and it was found that the inhibition capability increases with an increase in the oil content. The effect...

  6. The impact of permafrost-associated microorganisms on hydrate formation kinetics

    Science.gov (United States)

    Luzi-Helbing, Manja; Liebner, Susanne; Spangenberg, Erik; Wagner, Dirk; Schicks, Judith M.

    2016-04-01

    The relationship between gas hydrates, microorganisms and the surrounding sediment is extremely complex: On the one hand, microorganisms producing methane provide the prerequisite for gas hydrate formation. As it is known most of the gas incorporated into natural gas hydrates originates from biogenic sources. On the other hand, as a result of microbial activity gas hydrates are surrounded by a great variety of organic compounds which are not incorporated into the hydrate structure but may influence the formation or degradation process. For gas hydrate samples from marine environments such as the Gulf of Mexico a direct association between microbes and gas hydrates was shown by Lanoil et al. 2001. It is further assumed that microorganisms living within the gas hydrate stability zone produce biosurfactants which were found to enhance the hydrate formation process significantly and act as nucleation centres (Roger et al. 2007). Another source of organic compounds is sediment organic matter (SOM) originating from plant material or animal remains which may also enhance hydrate growth. So far, the studies regarding this relationship were focused on a marine environment. The scope of this work is to extend the investigations to microbes originating from permafrost areas. To understand the influence of microbial activity in a permafrost environment on the methane hydrate formation process and the stability conditions of the resulting hydrate phase we will perform laboratory studies. Thereby, we mimic gas hydrate formation in the presence and absence of methanogenic archaea (e.g. Methanosarcina soligelidi) and other psychrophilic bacteria isolated from permafrost environments of the Arctic and Antarctic to investigate their impact on hydrate induction time and formation rates. Our results may contribute to understand and predict the occurrences and behaviour of potential gas hydrates within or adjacent to the permafrost. Lanoil BD, Sassen R, La Duc MT, Sweet ST, Nealson KH

  7. Kinetics of gas hydrate formation in a water-oil-gas system

    Energy Technology Data Exchange (ETDEWEB)

    Talatori, S.; Barth, T. [Bergen Univ., Bergen (Norway). Dept. of Chemistry; Fotland, P. [StatoilHydro Research and Development Centre, Sandsli (Norway)

    2008-07-01

    Gas hydrates are crystalline compounds consisting of polyhedral water cavities which enclathrate small gas molecules. They are formed at certain pressure-temperature conditions where gas and water are present. Gas hydrate formation is of significant importance for flow assurance in oil pipelines at high pressures and/or low temperatures. It is therefore necessary to understand the kinetics of gas hydrate formation for the kinetic inhibition of the hydrates. This paper presented a kinetic model for the growth of gas hydrates and tested it against experimental hydrate kinetic data. The model was based on the Kolmogorov Johnson Mehl Avrami (KJMA) formula employed for a polynuclear mechanism and was found to fit the experimental data. A method was developed in which the mass of formed hydrates was calculated at different stirring rates from the experimental pressure and temperature recorded during the hydrate formation. The gas compositions predicted by the method were verified by comparison with the real compositions as obtained by analysis using a Hewlett Packard HP 6890 Series GC Plus. The paper described the experimental materials, procedures, and methods. It was concluded that linearization of the model specified the type of the nucleation and growth for all the kinetic data at each stirring rate. The effect of stirring rate on the kinetics of hydrate formation for the three stirring rates in the system showed acceleration of the hydrate formation when increasing the stirring rate from 300 to 600 rpm. More hydrates nucleated as stirring rates increased. It was recommended that in order to reach more definite conclusions, it would be necessary to repeat the measurements as well as conduct testing of other oils. 11 refs., 11 figs.

  8. Inhibition of Methane Hydrate Formation by Ice-Structuring Proteins

    DEFF Research Database (Denmark)

    Jensen, Lars; Ramløv, Hans; Thomsen, Kaj

    2010-01-01

    , assumed biodegradable, are capable of inhibiting the growth of methane hydrate (a structure I hydrate). The ISPs investigated were type III HPLC12 (originally identified in ocean pout) and ISP type III found in meal worm (Tenebrio molitor). These were compared to polyvinylpyrrolidone (PVP) a well......-known kinetic hydrate inhibitor. The results revealed that adding ISP in sufficient amounts caused the appearance of an initial nonlinear growth period. At a certain point during the growth process the growth pattern changed to linear which is identical to the growth observed for methane hydrate in the absence...... of inhibitors. The profile of the nonlinear growth was concentration-dependent but also dependent on the stirring rate. ISP type III HPLC12 decreased the growth rate of methane hydrate during the linear growth period by 17−75% at concentrations of 0.01−0.1 wt % (0.014−0.14 mM) while ISP from Tenebrio molitor...

  9. A polyether glycol derived from cashew nutshell as a kinetic inhibitor for methane hydrate formation

    Energy Technology Data Exchange (ETDEWEB)

    Ferreira, Jorge Cesar; Esteves, Pierre M., E-mail: pesteves@iq.ufrj.br [Instituto de Quimica, Universidade Federal do Rio de Janeiro, Rio de Janeiro, RJ (Brazil); Teixeira, Adriana [Centro de Pesquisa e Desenvolvimento Leopoldo Americo Miguez de Mello, PETROBRAS, Rio de Janeiro, RJ (Brazil)

    2012-07-01

    The polyether glycol derived from cashew nutshell liquid inhibited the formation of methane hydrate. The polymer proved to be more efficient than the polyvinyl pyrrolidone-poly(N-vinyl) caprolactam (PVP-PVCap) co-polymer under tested conditions (CH{sub 4}, 1470 psi and 4 degree C), being the latter one of the best commercially available hydrate inhibitors. (author)

  10. 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 ...

  11. 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.

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

    Directory of Open Access Journals (Sweden)

    Chang-Yu Sun

    2013-02-01

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

  13. Gas Hydrate Formation Amid Submarine Canyon Incision: Investigations From New Zealand's Hikurangi Subduction Margin

    Science.gov (United States)

    Crutchley, G. J.; Kroeger, K. F.; Pecher, I. A.; Mountjoy, J. J.; Gorman, A. R.

    2017-12-01

    We investigate gas hydrate system dynamics beneath a submarine canyon on New Zealand's Hikurangi subduction margin using seismic reflection data and petroleum systems modeling. High seismic velocities just above the base of gas hydrate stability (BGHS) indicate that concentrated gas hydrates exist beneath the canyon. Two-dimensional gas hydrate formation modeling shows how the process of canyon incision at this location alters the distribution and concentration of gas hydrate. The key modeling result is that free gas is trapped beneath the gas hydrate layer and then "captured" into a concentrated gas hydrate deposit as a result of a downward-shift in the BGHS driven by canyon incision. Our study thus provides new insight into the functioning of this process. From our data, we also conceptualize two other models to describe how canyons could significantly change gas hydrate distribution and concentration. One scenario is related to deflection of fluid flow pathways from over-pressured regions at the BGHS toward the canyon, and the other is based on relationships between simultaneous seafloor uplift and canyon incision. The relationships and processes described are of global relevance because of considerations of gas hydrate as an energy resource and the influence of both submarine canyons and gas hydrate systems on seafloor biodiversity.

  14. Modeling the formation of methane hydrate-bearing intervals in fine-grained sediments

    Energy Technology Data Exchange (ETDEWEB)

    Malinverno, Alberto; Cook, Ann; Daigle, Hugh

    2016-09-30

    Sediment grain size exerts a fundamental control on how methane hydrates are distributed within the pore space. Fine-grained muds are the predominant sediments in continental margins, and hydrates in these sediments have often been observed in semi-vertical veins and fractures. In several instances, these hydrate veins/fractures are found in discrete depth intervals a few tens meters thick within the gas hydrate stability zone (GHSZ) surrounded by hydrate-free sediments above and below. As they are not obviously connected with free gas occurring beneath the base of the GHSZ, these isolated hydrate-bearing intervals have been interpreted as formed by microbial methane generated in situ. To investigate further the formation of these hydrate deposits, we applied a time-dependent advection-diffusion-reaction model that includes the effects of sedimentation, solute diffusion, and microbial methane generation. The microbial methane generation term depends on the amount of metabolizable organic carbon deposited at the seafloor, which is degraded at a prescribed rate resulting in methane formation beneath the sulfate reduction zone. In the model, methane hydrate precipitates once the dissolved methane concentration is greater than solubility, or hydrate dissolves if concentration goes below solubility. If the deposition of organic carbon at the seafloor is kept constant in time, we found that the predicted amounts of hydrate formed in discrete intervals within the GHSZ are much less than those estimated from observations. We then investigated the effect of temporal variations in the deposition of organic carbon. If greater amounts of organic carbon are deposited during some time interval, methane generation is enhanced during burial in the corresponding sediment interval. With variations in organic carbon deposition that are consistent with observations in continental margin sediments, we were able to reproduce the methane hydrate contents estimated in discrete depth

  15. Thermodynamic simulations of hydrate formation from gas mixtures in batch operations

    International Nuclear Information System (INIS)

    Kobayashi, Takehito; Mori, Yasuhiko H.

    2007-01-01

    This paper deals with the hydrate formation from mixed hydrate-forming gases such as natural gas to be converted to hydrates for the purpose of its storage and biogases from which carbon dioxide is to be separated by hydrate formation. When a batch operation is selected for processing such a gas mixture in a closed reactor, we need to predict the evolution of the thermodynamic and compositional states inside the reactor during the operation. We have contrived a simulation scheme that allows us to estimate the simultaneous changes in the composition of the residual gas, the structure of the hydrate formed and the guest composition in the hydrate, in addition to the change in the system pressure, with the progress of hydrate formation during each operation. This scheme assumes the transient hydrate forming process in a reactor during each operation to be a series of numerous equilibrium states, each slightly deviating from the preceding state. That is, a thermodynamic system composed of the contents of the reactor is assumed to be subjected to a quasi-static, irreversible change in state, instantaneously keeping itself in thermodynamic equilibrium. The paper demonstrates a simulation of a process of hydrate formation from a methane + propane mixture and compares its results to relevant experimental results reported by Uchida et al. [Uchida T, Morikawa M, Takeya S, Ikeda IY, Ohmura R, Nagao J, et al. Two-step formation of methane-propane mixed gas hydrates in a batch-type reactor. AIChE J 2004;50(2):518-23

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2010-07-01

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

  17. The combined effect of thermodynamic promoters tetrahydrofuran and cyclopentane on the kinetics of flue gas hydrate formation

    DEFF Research Database (Denmark)

    Daraboina, Nagu; von Solms, Nicolas

    2015-01-01

    ) hydrate formation using a rocking cell apparatus. Hydrate formation and decomposition kinetics were investigated by constant cooling (hydrate nucleation temperature) and isothermal (hydrate nucleation time) methods. Improved (synergistic) hydrate formation kinetics (hydrate nucleation and growth) were......Carbon dioxide (CO2) capture through hydrate crystallization is a promising method among the new approaches for mitigating carbon emissions into the atmosphere. In this work, we investigate a combination of tetrahydrofuran (THF) and cyclopentane (CP) on the kinetics of flue gas (CO2:20 mol %/N2...... observed when THF and CP were present together compared to the individual THF and CP systems. Moreover, the complete hydrate decomposition temperature of CO2/N2/CP/THF hydrate was found to be slightly higher compared to the individual promoter (CO2/N2/CP and CO2/N2/THF) systems. The combined use...

  18. Methane Hydrate Distribution from Prolonged and Repeated Formation in Natural and Compacted Sand Samples: X-Ray CT Observations

    Directory of Open Access Journals (Sweden)

    Emily V. L. Rees

    2011-01-01

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

  19. Hydration characteristics and structure formation of cement pastes containing metakaolin

    Directory of Open Access Journals (Sweden)

    Dvorkin Leonid

    2018-01-01

    Full Text Available Metakaolin (MK is one of the most effective mineral admixtures for cement-based composites. The deposits of kaolin clays are wide-spread in the world. Metakaolin is comparable to silica fume as an active mineral admixture for cement-based composites. In this paper, the rheological and mechanical properties of cement paste containing metakaolin are investigated. The effect of MK is more evident at “tight” hydration conditions within mixtures with low water-cement ratio, provided by application of superplasticizers. The cement is replaced with 0 to 15% metakaolin, and superplasticizer content ranged from 0 to 1.5% by weight of cementitious materials (i.e. cement and metakaolin. An equation is derived to describe the relationship between the metakaolin and superplasticizer content and consistency of pastes. There is a linear dependence between metakalolin content and water demand. Second-degree polynomial describe the influence of superplasticizer content. The application of SP and MK may produce cement-water suspensions with water-retaining capacity at 50-70% higher than control suspensions. The investigation of initial structure forming of cement pastes with SP-MK composite admixture indicates the extension of coagulation structure forming phase comparing to the pastes without additives. Crystallization stage was characterized by more intensive strengthening of the paste with SP-MK admixture comparing to the paste without admixtures and paste with SP. Results on the porosity parameters for hardened cement paste indicate a decrease in the average diameter of pores and refinement of pore structure in the presence of metakaolin. A finer pore structure associated with an increase in strength. X-ray analysis data reveal a growing number of small-crystalline low-alkaline calcium hydrosilicates and reducing portlandite content, when MK dosage increases. Scanning electron microscopy (SEM data confirm, that hardened cement paste containing MK has

  20. Gas Hydrate Formation Probability Distributions: The Effect of Shear and Comparisons with Nucleation Theory.

    Science.gov (United States)

    May, Eric F; Lim, Vincent W; Metaxas, Peter J; Du, Jianwei; Stanwix, Paul L; Rowland, Darren; Johns, Michael L; Haandrikman, Gert; Crosby, Daniel; Aman, Zachary M

    2018-03-13

    Gas hydrate formation is a stochastic phenomenon of considerable significance for any risk-based approach to flow assurance in the oil and gas industry. In principle, well-established results from nucleation theory offer the prospect of predictive models for hydrate formation probability in industrial production systems. In practice, however, heuristics are relied on when estimating formation risk for a given flowline subcooling or when quantifying kinetic hydrate inhibitor (KHI) performance. Here, we present statistically significant measurements of formation probability distributions for natural gas hydrate systems under shear, which are quantitatively compared with theoretical predictions. Distributions with over 100 points were generated using low-mass, Peltier-cooled pressure cells, cycled in temperature between 40 and -5 °C at up to 2 K·min -1 and analyzed with robust algorithms that automatically identify hydrate formation and initial growth rates from dynamic pressure data. The application of shear had a significant influence on the measured distributions: at 700 rpm mass-transfer limitations were minimal, as demonstrated by the kinetic growth rates observed. The formation probability distributions measured at this shear rate had mean subcoolings consistent with theoretical predictions and steel-hydrate-water contact angles of 14-26°. However, the experimental distributions were substantially wider than predicted, suggesting that phenomena acting on macroscopic length scales are responsible for much of the observed stochastic formation. Performance tests of a KHI provided new insights into how such chemicals can reduce the risk of hydrate blockage in flowlines. Our data demonstrate that the KHI not only reduces the probability of formation (by both shifting and sharpening the distribution) but also reduces hydrate growth rates by a factor of 2.

  1. CO2-SO2 clathrate hydrate formation on early Mars

    Directory of Open Access Journals (Sweden)

    Chassefière E.

    2014-02-01

    Full Text Available Most sulfate minerals discovered on Mars are dated no earlier than the Hesperian. We showed, using a 1-D radiative-convective-photochemical model, that clathrate formation during the Noachian would have buffered the atmospheric CO2 pressure of early Mars at ~2 bar and maintained a global average surface temperature ~230 K. Because clathrates trap SO2 more favorably than CO2, all volcanically outgassed sulfur would have been trapped in Noachian Mars cryosphere, preventing a significant formation of sulfate minerals during the Noachian and inhibiting carbonates from forming at the surface in acidic water resulting from the local melting of the SO2- rich cryosphere. The massive formation of sulfate minerals at the surface of Mars during the Hesperian could be the consequence of a drop of the CO2 pressure below a 2-bar threshold value at the late Noachian-Hesperian transition, which would have released sulfur gases into the atmosphere from both the Noachian sulfur-rich cryosphere and still active Tharsis volcanism. Our hypothesis could allow to explain the formation of chaotic terrains and outflow channels, and the occurrence of episodic warm episodes facilitated by the release of SO2 to the atmosphere. These episodes could explain the formation of valley networks and the degradation of impact craters, but remain to be confirmed by further modeling.

  2. Systematic review: periprocedural hydration in the prevention of post-ERCP pancreatitis

    NARCIS (Netherlands)

    Smeets, X. J. N. M.; da Costa, D. W.; Besselink, M. G.; Bruno, M. J.; Fockens, P.; Mulder, C. J. J.; van der Hulst, R. W.; Vleggaar, F. P.; Timmer, R.; Drenth, J. P. H.; van Geenen, E. J. M.

    2016-01-01

    With an overall incidence of 3.5%, pancreatitis is the most frequent complication of endoscopic retrograde cholangiopancreatography (ERCP). Periprocedural hydration may prevent post-ERCP pancreatitis by maintaining pancreatic microperfusion, thereby inhibiting the pancreatic inflammatory response.

  3. Controlled formation of cyclopentane hydrate suspensions via capillary-driven jet break-up

    Science.gov (United States)

    Geri, Michela; McKinley, Gareth

    2017-11-01

    Clathrate hydrates are crystalline compounds that form when a lattice of hydrogen-bonded water molecules is filled by guest molecules sequestered from an adjacent gas or liquid phase. Being able to rapidly produce and transport synthetic hydrates is of great interest given their significant potential as a clean energy source and safe option for hydrogen storage. We propose a new method to rapidly produce cyclopentane hydrate suspensions at ambient pressure with tunable particle size distribution by taking advantage of the Rayleigh-Plateau instability to form a mono-disperse stream of droplets during the controlled break-up of a water jet. The droplets are immediately frozen into ice particles through immersion in a subcooled reservoir and converted into hydrates with a dramatic reduction in the nucleation induction time. By measuring the evolution of the rheological properties with time, we monitor the process of hydrates formation via surface crystallization and agglomeration with different droplet size distributions. This new method enables us to gain new insights into hydrate formation and transport which was previously hindered by uncontrolled droplet formation and hydrate nucleation processes. MITei Chevron Fellowship.

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

    Science.gov (United States)

    Vijayamohan, Prithvi

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

  5. An innovative approach to enhance methane hydrate formation kinetics with leucine for energy storage application

    International Nuclear Information System (INIS)

    Veluswamy, Hari Prakash; Kumar, Asheesh; Kumar, Rajnish; Linga, Praveen

    2017-01-01

    Highlights: • Innovative combinatorial hybrid approach to reduce nucleation stochasticity and enhance hydrate growth. • Methane hydrate growth curves are similar in UTR and STR configurations in presence of leucine. • Amalgamation of stirred (STR) and unstirred (UTR) configuration is demonstrated. • Reliable method for scale up and commercial production of Solidified Natural Gas (SNG). - Abstract: Natural gas storage in clathrate hydrates or solidified natural gas (SNG) offers the safest, cleanest and the most compact mode of storage aided by the relative ease in natural gas (NG) recovery with minimal cost compared to known conventional methods of NG storage. The stochastic nature of hydrate nucleation and the slow kinetics of hydrate growth are major challenges that needs to be addressed on the SNG production side. A deterministic and fast nucleation coupled with rapid crystallization kinetics would empower this beneficial technology for commercial application. We propose a hybrid combinatorial approach of methane hydrate formation utilizing the beneficial aspect of environmentally benign amino acid (leucine) as a kinetic promoter by combining stirred and unstirred reactor operation. This hybrid approach is simple, can easily be implemented and scaled-up to develop an economical SNG technology for efficient storage of natural gas on a large scale. Added benefits include the minimal energy requirement during hydrate growth resulting in overall cost reduction for SNG technology.

  6. Modeling the methane hydrate formation in an aqueous film submitted to steady cooling

    Energy Technology Data Exchange (ETDEWEB)

    Avendano-Gomez, J.R. [ESIQIE, Laboratorio de Ingenieria Quimica Ambiental, Mexico (Mexico). Inst. Politecnico Nacional; Garcia-Sanchez, F. [Laboratorio de Termodinamica, Mexico (Mexico). Inst. Mexicano del Petroleo; Gurrola, D.V. [UPIBI, Laboratorio de Diseno de Plantas, Mexico (Mexico). Inst. Politecnico Nacional

    2008-07-01

    Gas hydrates, or clathrate hydrates, are ice-like compounds that results from the kinetic process of crystallization of an aqueous solution supersaturated with a dissolved gas. This paper presented a model that took into account two factors involved in the hydrate crystallization, notably the stochastic nature of crystallization that causes sub-cooling and the heat resulting from the exothermic enthalpy of hydrate formation. The purpose of this study was to model the thermal evolution inside a hydrate forming system which was submitted to an imposed steady cooling. The study system was a cylindrical thin film of aqueous solution at 19 Mpa. The study involved using methane as the hydrate forming molecule. It was assumed that methane was homogeneously dissolved in the aqueous phase. Ethane hydrate was formed through a kinetic process of nucleation and crystallization. In order to predict the onset time of nucleation, the induction time needed to be considered. This paper discussed the probability of nucleation as well as the estimation of the rate of nucleation. It also presented the mathematical model and boundary conditions. These included assumptions and derivation of the model; boundary conditions; initial conditions; and numerical solution of the model equation. It was concluded that the heat source must be considered when investigating crystallization effects. 34 refs., 2 tabs., 2 figs.

  7. Influence of formation temperature and inhibitor concentration on the dissociation temperature for hydrates formed with polyvinyl caprolactam

    Energy Technology Data Exchange (ETDEWEB)

    Gulbrandsen, A.C. [StatoilHydro, Stavanger (Norway); Svartaas, T.M. [Stavanger Univ., Stavanger (Norway). Dept. of Petroleum Engineering

    2008-07-01

    Kinetic inhibitors are used to delay hydrate nucleation and crystal growth in oil and gas pipelines. This study examined inhibitor containing systems for gas hydrates with kinetic inhibitors. Poly Vinyl Caprolactam (PVCap) was added to the water phase of structure 1 (s-1) and structure 2 (s-2) hydrates and experiments were conducted to determine dissociation temperatures for various formation temperatures and PVCap concentrations. Data obtained during the experiments were then compared with values calculated using a hydrate simulator tool called CSMHYD. The difference between the values calculated by the model and the experimental values demonstrated that both formation temperature and concentration influenced dissociation temperature. Dissociation temperatures for hydrates formed at lower degrees of subcooling were higher than hydrates formed at higher degrees of subcooling. It was concluded that increases in pressure diminished the influence of the hydrate formation temperature. Dissociation temperatures increased when kinetic inhibitor volumes were increased. 4 refs., 7 figs.

  8. 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).

  9. Hydrate formation during wet granulation studied by spectroscopic methods and multivariate analysis

    DEFF Research Database (Denmark)

    Jørgensen, Anna; Rantanen, Jukka; Karjalainen, Milja

    2002-01-01

    PURPOSE: The aim was to follow hydrate formation of two structurally related drugs, theophylline and caffeine, during wet granulation using fast and nondestructive spectroscopic methods. METHODS: Anhydrous theophylline and caffeine were granulated with purified water. Charge-coupled device (CCD......) Raman spectroscopy was compared with near-infrared spectroscopy (NIR) in following hydrate formation of drugs during wet granulation (off-line). To perform an at-line process analysis, the effect of water addition was monitored by NIR spectroscopy and principal components analysis (PCA). The changes...... in the crystal arrangements were verified by using X-ray powder diffraction (XRPD). RESULTS: Hydrate formation of theophylline and caffeine could be followed by CCD Raman spectroscopy. The NIR and Raman spectroscopic results were consistent with each other. NIR revealed the state of water, and Raman spectroscopy...

  10. 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.

  11. Hydrate formation during wet granulation studied by spectroscopic methods and multivariate analysis

    DEFF Research Database (Denmark)

    Jørgensen, Anna; Rantanen, Jukka; Karjalainen, Milja

    2002-01-01

    PURPOSE: The aim was to follow hydrate formation of two structurally related drugs, theophylline and caffeine, during wet granulation using fast and nondestructive spectroscopic methods. METHODS: Anhydrous theophylline and caffeine were granulated with purified water. Charge-coupled device (CCD......) Raman spectroscopy was compared with near-infrared spectroscopy (NIR) in following hydrate formation of drugs during wet granulation (off-line). To perform an at-line process analysis, the effect of water addition was monitored by NIR spectroscopy and principal components analysis (PCA). The changes...

  12. 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%.

  13. Hydrate plug formation prediction tool : an increasing need for flow assurance in the oil industry

    Energy Technology Data Exchange (ETDEWEB)

    Kinnari, K.; Labes-Carrier, C.; Lunde, K. [StatoilHydro, Stavanger (Norway); Hemmingsen, P. [StatoilHydro, Trondheim (Norway); Davies, S.R.; Boxall, J.A.; Koh, C.A.; Sloan, E.D. [Colorado School of Mines, Golden, CO (United States)

    2008-07-01

    This paper outlined the current understanding of the mechanisms for hydrate formation, agglomeration and plugging of pipelines. The Colorado School of Mines Hydrate Kinetics (CSMHyK) model was developed to meet the industrial needs of predicting hydrate plugging and to reduce the extent of such events. This paper described the main application domains and features of this newly developed model whose current version is the first step towards describing the complex mechanisms in multiphase systems. The model is based on the gradual increase in the viscosity of a hydrate slurry. Different operational scenarios where hydrate plugging might occur were described in this paper. The CSMHyK has recently been implemented in the transient multiphase flow simulator OLGA as a separate module. Examples using the current model in several operational scenarios demonstrated some of its important capabilities in improving facility design and operation. The results from these examples and the operational scenarios analysis were used to discuss the future development needs of the CSMHyK model. It was concluded that the model should be extended to include the aspects of hydrate growth which is likely controlled by the mass and heat transfer in the close vicinity of growing particles. Further model development will include the possibility of forming large agglomerates, depositions on the wall and jamming the pipe by detached deposits. 6 refs., 7 figs.

  14. Evaluation of the geological relationships to gas hydrate formation and stability

    Energy Technology Data Exchange (ETDEWEB)

    1986-01-01

    Although there are many publications pertaining to gas hydrates, their formation and stability in various geological conditions are poorly known. Therefore, for the same reasons and because of the very broad scope of our research, limited amount and extremely dispersed information, the study regions are very large. Moreover, almost without exception the geological environments controlling gas hydrates formation and stability of the studied regions are very complex. The regions studied (completed and partially completed - total 17 locations) during the reporting period, particularly the Gulf of Mexico and the Middle America Trench, are the most important in this entire research project. In the past, both of these regions have been extensively studied, the presence of gas hydrates confirmed and samples recovered. In our investigation it was necessary not only to review all previous data and interpretations, but to do a thorough analysis of the basins, and a critical evaluation of an previously reported and publicly available but not published information.

  15. Measurements of relevant parameters in the formation of clathrate hydrates by a novel experimental apparatus

    Energy Technology Data Exchange (ETDEWEB)

    Arca, S.; Di Profio, P.; Germani, R.; Savelli, G. [Perugia Univ., CEMIN, Perugia (Italy). Dept. of Chemistry

    2008-07-01

    There is a growing interest in understanding the thermodynamics and kinetics of clathrate hydrate formation. This paper presented a study that involved the design, construction, calibration, and testing of a new apparatus that could obtain as many parameters as possible in a single formation batch and that could measure unexplored clathrate hydrate parameters. The apparatus was capable of measuring equilibrium phases involving gaseous components. The paper described the conceptual design as well as the chamber, pressure line, temperature control, liquid addition line, and conductometric probe. The paper also discussed data acquisition, stirring, measurement examples, and internal illumination and video monitoring. It was concluded that refining measurements, particularly those concerning kinetic characterizations, is important in order to clarify several uncertain kinetic behaviors of clathrate hydrates. 6 refs., 16 figs.

  16. Complex formation constant and hydration number change of aqua-rare earth ions

    International Nuclear Information System (INIS)

    Kanno, H.

    1998-01-01

    Full text: It is now well established that the inner-sphere hydration number of aqua-rare earth ions changes from nine to eight in the middle of the rare earth series. This hydration number change greatly affects the complex formation of rare earth ions as we observe irregular variations in most series behaviours of the complex formation constant (K) in aqueous solution systems when K being plotted against 1/r or r (r is ionic radius of rare earth ion). Furthermore, it shows very anomalous concentration dependence in the sense that nona-aqua Ln 3+ ion increases in number with increase in salt concentration in aqueous rare earth salt solution (salt chloride, perchlorate). In this report, a theoretical derivation of the formation constant (K) for the inner-sphere complex formation of rare earth ions with a monodentate ligand was made by taking account of both the hydration number change in the middle of the series and its anomalous salt concentration dependence. The series behaviour of the formation constant against 1/r (or r) is successfully explained with using the empirical finding that K varies almost linearly with 1/r (or r) in the region where only one hydration number dominates. This success is also taken as evidence that the anomalous salt concentration dependence of the hydration number change is caused by the outer-sphere complex formation of rare earth ions with the condition that nona-aqua rare earth ions form outer-sphere complexes more easily than octa-aqua ions

  17. The potential for methane hydrate formation in deep repositories of spent nuclear fuel in granitic rocks

    International Nuclear Information System (INIS)

    Tohidi, Bahman; Chapoy, Antonin; Smellie, John; Puigdomenech, Ignasi

    2010-12-01

    The main aim of this work was to establish whether the pertaining pressure and temperature conditions and dissolved gas concentration in groundwater is conducive to gas hydrate formation using a modelling approach. The hydrate stability pressure-temperature zone of dissolved methane in the presence of salt has been obtained through calculations which show that a decrease in the system pressure and/or an increase in salt concentration favours hydrate formation, as both factors reduce equilibrium gas solubility in the aqueous phase. This behaviour is unlike that of the system including a gas phase, where the water phase is always saturated with methane, and hence the methane solubility in water is not a limiting factor. The main conclusion is that hydrate formation is not possible at the reported methane concentrations and water salinities for the Forsmark and Laxemar sites in Sweden and Olkiluoto in Finland. At the highest salinities and methane concentrations encountered, namely ∼0.00073 mole fraction methane and ∼10 mass % NaCl at a depth of 1,000 m in Olkiluoto, Finland, hydrates could form if the system temperatures and pressures are below 2.5 deg C and 60 bar, respectively, i.e. values that are much lower than those prevailing at that depth (∼20 deg C and ∼100 bar, respectively). Furthermore, the calculated results provide the necessary data to estimate the effect of increase in dissolved methane concentration on potential hydrate formation, as well as two phase flow. The available depth dependency of methane concentration at the sites studied in Sweden and Finland was used in another study to estimate the diffusive flow of methane in the rock volumes. These diffusion rates, which are highest at Olkiluoto, indicate that even if the conditions were to become favourable to methane hydrate formation, then it would take several millions of years before a thin layer of hydrates could be formed, a condition which is outside the required period of satisfactory

  18. The potential for methane hydrate formation in deep repositories of spent nuclear fuel in granitic rocks

    Energy Technology Data Exchange (ETDEWEB)

    Tohidi, Bahman; Chapoy, Antonin (Hydrafact Ltd, Inst. of Petroleum Engineering, Heriot-Watt Univ., Edinburgh (United Kingdom)); Smellie, John (Conterra AB, Uppsala (Sweden)); Puigdomenech, Ignasi (Swedish Nuclear Fuel and Waste Management Co., Stockholm (Sweden))

    2010-12-15

    The main aim of this work was to establish whether the pertaining pressure and temperature conditions and dissolved gas concentration in groundwater is conducive to gas hydrate formation using a modelling approach. The hydrate stability pressure-temperature zone of dissolved methane in the presence of salt has been obtained through calculations which show that a decrease in the system pressure and/or an increase in salt concentration favours hydrate formation, as both factors reduce equilibrium gas solubility in the aqueous phase. This behaviour is unlike that of the system including a gas phase, where the water phase is always saturated with methane, and hence the methane solubility in water is not a limiting factor. The main conclusion is that hydrate formation is not possible at the reported methane concentrations and water salinities for the Forsmark and Laxemar sites in Sweden and Olkiluoto in Finland. At the highest salinities and methane concentrations encountered, namely approx0.00073 mole fraction methane and approx10 mass % NaCl at a depth of 1,000 m in Olkiluoto, Finland, hydrates could form if the system temperatures and pressures are below 2.5 deg C and 60 bar, respectively, i.e. values that are much lower than those prevailing at that depth (approx20 deg C and approx100 bar, respectively). Furthermore, the calculated results provide the necessary data to estimate the effect of increase in dissolved methane concentration on potential hydrate formation, as well as two phase flow. The available depth dependency of methane concentration at the sites studied in Sweden and Finland was used in another study to estimate the diffusive flow of methane in the rock volumes. These diffusion rates, which are highest at Olkiluoto, indicate that even if the conditions were to become favourable to methane hydrate formation, then it would take several millions of years before a thin layer of hydrates could be formed, a condition which is outside the required period of

  19. An Experimental and Theoretical Study of CO2 Hydrate Formation Systems

    DEFF Research Database (Denmark)

    Tzirakis, Fragkiskos

    Appendix E) using as promoters tetra-n-butyl ammonium salts of bromide, fluoride and cyclopentane in collaboration with MINESParisTech in France. These chemicals are well known for their reduction capabilities of hydrate formation pressure. The results are in good accordance with the literature. Moreover...

  20. 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

    Formation of hydrates in gas transmission lines due to high pressures and low temperatures is a serious problem in the oil and gas industry with potential hazards and/or economic losses. Kinetic hydrate inhibitors are water soluble polymeric compounds that prevent or delay hydrate formation. This...

  1. Formation of Methane Hydrate in the Presence of Natural and Synthetic Nanoparticles.

    Science.gov (United States)

    Cox, Stephen J; Taylor, Diana J F; Youngs, Tristan G A; Soper, Alan K; Totton, Tim S; Chapman, Richard G; Arjmandi, Mosayyeb; Hodges, Michael G; Skipper, Neal T; Michaelides, Angelos

    2018-03-07

    Natural gas hydrates occur widely on the ocean-bed and in permafrost regions, and have potential as an untapped energy resource. Their formation and growth, however, poses major problems for the energy sector due to their tendency to block oil and gas pipelines, whereas their melting is viewed as a potential contributor to climate change. Although recent advances have been made in understanding bulk methane hydrate formation, the effect of impurity particles, which are always present under conditions relevant to industry and the environment, remains an open question. Here we present results from neutron scattering experiments and molecular dynamics simulations that show that the formation of methane hydrate is insensitive to the addition of a wide range of impurity particles. Our analysis shows that this is due to the different chemical natures of methane and water, with methane generally excluded from the volume surrounding the nanoparticles. This has important consequences for our understanding of the mechanism of hydrate nucleation and the design of new inhibitor molecules.

  2. Sodium bicarbonate-based hydration prevents contrast-induced nephropathy: a meta-analysis

    Directory of Open Access Journals (Sweden)

    Tamhane Umesh

    2009-05-01

    Full Text Available Abstract Background Contrast-induced nephropathy is the leading cause of in-hospital acute renal failure. This side effect of contrast agents leads to increased morbidity, mortality, and health costs. Ensuring adequate hydration prior to contrast exposure is highly effective at preventing this complication, although the optimal hydration strategy to prevent contrast-induced nephropathy still remains an unresolved issue. Former meta-analyses and several recent studies have shown conflicting results regarding the protective effect of sodium bicarbonate. The objective of this study was to assess the effectiveness of normal saline versus sodium bicarbonate for prevention of contrast-induced nephropathy. Methods The study searched MEDLINE, EMBASE, Cochrane databases, International Pharmaceutical Abstracts database, ISI Web of Science (until 15 December 2008, and conference proceedings for randomized controlled trials that compared normal saline with sodium bicarbonate-based hydration regimen regarding contrast-induced nephropathy. Random-effects models were used to calculate summary odds ratios. Results A total of 17 trials including 2,633 subjects were pooled. Pre-procedural hydration with sodium bicarbonate was associated with a significant decrease in the rate of contrast-induced nephropathy (odds ratios 0.52; 95% confidence interval 0.34–0.80, P = 0.003. Number needed to treat to prevent one case of contrast-induced nephropathy was 16 (95% confidence interval 10–34. No significant differences in the rates of post-procedure hemodialysis (P = 0.20 or death (P = 0.53 was observed. Conclusion Sodium bicarbonate-based hydration was found to be superior to normal saline in prevention of contrast-induced nephropathy in this updated meta-analysis.

  3. The big fat LARS - a LArge Reservoir Simulator for hydrate formation and gas production

    Science.gov (United States)

    Beeskow-Strauch, Bettina; Spangenberg, Erik; Schicks, Judith M.; Giese, Ronny; Luzi-Helbing, Manja; Priegnitz, Mike; Klump, Jens; Thaler, Jan; Abendroth, Sven

    2013-04-01

    Simulating natural scenarios on lab scale is a common technique to gain insight into geological processes with moderate effort and expenses. Due to the remote occurrence of gas hydrates, their behavior in sedimentary deposits is largely investigated on experimental set ups in the laboratory. In the framework of the submarine gas hydrate research project (SUGAR) a large reservoir simulator (LARS) with an internal volume of 425 liter has been designed, built and tested. To our knowledge this is presently a word-wide unique set up. Because of its large volume it is suitable for pilot plant scale tests on hydrate behavior in sediments. That includes not only the option of systematic tests on gas hydrate formation in various sedimentary settings but also the possibility to mimic scenarios for the hydrate decomposition and subsequent natural gas extraction. Based on these experimental results various numerical simulations can be realized. Here, we present the design and the experimental set up of LARS. The prerequisites for the simulation of a natural gas hydrate reservoir are porous sediments, methane, water, low temperature and high pressure. The reservoir is supplied by methane-saturated and pre-cooled water. For its preparation an external gas-water mixing stage is available. The methane-loaded water is continuously flushed into LARS as finely dispersed fluid via bottom-and-top-located sparger. The LARS is equipped with a mantle cooling system and can be kept at a chosen set temperature. The temperature distribution is monitored at 14 reasonable locations throughout the reservoir by Pt100 sensors. Pressure needs are realized using syringe pump stands. A tomographic system, consisting of a 375-electrode-configuration is attached to the mantle for the monitoring of hydrate distribution throughout the entire reservoir volume. Two sets of tubular polydimethylsiloxan-membranes are applied to determine gas-water ratio within the reservoir using the effect of permeability

  4. Investigation of Methane Hydrate Formation in a Recirculating Flow Loop: Modeling of the Kinetics and Tests of Efficiency of Chemical Additives on Hydrate Inhibition Étude de la formation de l'hydrate de méthane dans une conduite de recirculation : modélisation de la cinétique et tests d'efficacité d'additifs chimiques inhibiteurs d'hydrates de gaz

    Directory of Open Access Journals (Sweden)

    Peytavy J. L.

    2006-12-01

    Full Text Available Gas hydrates can be formed when light gases, such as the components of natural gas, come into contact with water under particular conditions of temperature and pressure. These solid compounds give rise to problems in natural gas and oil industry because they can plug pipelines and process equipment. To prevent hydrate formation methanol and glycols are commonly and extensively used as inhibitors. Today, the thermodynamic equilibria of hydrate formation are well known, but the kinetics of gas hydrate formation and growth has to be studied in order to find means of controlling these processes and to explore the mechanisms for hydrate formation that follows non equilibrium laws. The present work deals with the kinetics of methane hydrate formation studied in a laboratory loop where the liquid blend saturated with methane is circulated up to a pressure of 75 bar. Pressure is maintained at a constant value during experimental runs by means of methane gas make-up. First the effects of pressure (35-75 bar, liquid velocity (0. 5-3 m/s, liquid cooling temperature ramp (2-15°C/h, and liquid hydrocarbon amount (0-96%, on hydrate formation kinetics are investigated. Then a new method is proposed to predict firstly the thermodynamic conditions (pressure and temperature at the maximum values of the growth rate of methane hydrate and secondly the methane hydrate growth rate. A good agreement is found between calculated and experimental data. Finally the evaluation of the efficiency of some kinetic additives and some surfactants developed to avoid either nucleation or crystal growth and agglomeration of methane hydrates is tested based on the proposed experimental procedure. Les hydrates de gaz des composés légers du gaz naturel se forment lorsque ceux-ci entrent en contact avec l'eau dans certaines conditions de température et de pression. Ces composés solides sont nuisibles pour les industries gazière et pétrolière car des bouchons solides peuvent

  5. Ferric citrate hydrate, a new phosphate binder, prevents the complications of secondary hyperparathyroidism and vascular calcification.

    Science.gov (United States)

    Iida, Akio; Kemmochi, Yusuke; Kakimoto, Kochi; Tanimoto, Minako; Mimura, Takayuki; Shinozaki, Yuichi; Uemura, Atsuhiro; Matsuo, Akira; Matsushita, Mutsuyoshi; Miyamoto, Ken-ichi

    2013-01-01

    Ferric citrate hydrate (JTT-751) is being developed as a treatment for hyperphosphatemia in chronic kidney disease patients, and shows serum phosphorus-reducing effects on hyperphosphatemia in hemodialysis patients. We examined whether JTT-751 could reduce phosphorus absorption in normal rats and prevent the progression of ectopic calcification, secondary hyperparathyroidism and bone abnormalities in chronic renal failure (CRF) rats. Normal rats were fed a diet containing 0.3, 1 or 3% JTT-751 for 7 days. The effects of JTT-751 on phosphorus absorption were evaluated with fecal and urinary phosphorus excretion. Next, a CRF model simulating hyperphosphatemia was induced by feeding rats a 0.75% adenine diet. After 21 days of starting the adenine diet feeding, 1 or 3% JTT-751 was administered for 35 days by dietary admixture. The serum phosphorus levels and mineral parameters were measured. Calcification in the aorta was examined biochemically and histopathologically. Hyperparathyroidism and bone abnormalities were evaluated by histopathological analysis of the parathyroid and femur, respectively. In normal rats, JTT-751 increased fecal phosphorus excretion and reduced phosphorus absorption and urinary phosphorus excretion. In CRF rats, JTT-751 reduced serum phosphorus levels, the calcium-phosphorus product and calcium content in the aorta. Serum intact parathyroid hormone levels and the incidence and severity of parathyroid hyperplasia were also decreased. JTT-751 reduced femoral bone fibrosis, porosity and osteoid formation. JTT-751 could bind with phosphate in the gastrointestinal tract, increase fecal phosphorus excretion and reduce phosphorus absorption. JTT-751 could prevent the progression of ectopic calcification, secondary hyperparathyroidism and bone abnormalities in rats. Copyright © 2013 S. Karger AG, Basel.

  6. CALCIUM ORTHOPHOSPHATES HYDRATES: FORMATION, STABILITY AND INFLUENCE ON STANDARD PROPERTIES OF PORTLAND CEMENT

    Directory of Open Access Journals (Sweden)

    Kaziliunas A.

    2013-12-01

    Full Text Available Preparation of phosphogypsum to produce the binders requires a much higher input than preparation of natural gypsum stone. This makes it uncompetitive material. The investigations presented therein are meant to reduce this input by looking for the ways of rendering impurities harmless. Soluble acid orthophosphates are the main harmful impurity of phosphogypsum. The studies show that dry insoluble calcium orthophosphates hydrates (1.09 % and 2.18 % P2O5 in gypsum have little effect on W/C, setting times and soundness of Portland cement pastes. Insoluble calcium orthophosphates hydrates {CaHPO4∙2H2O, Ca8(HPO42(PO44∙5H2O and Ca9(HPO4(PO45(OH∙4H2O} formed in acidic medium (pH = 4.2 - 5.9 have been destroyed in alkaline medium and reduce standard compressive strength of cement up to 28 %. Calcium orthophosphates hydrates of hydroxyapatite group are stable in alcaline medium, while in dry state they reduce the standard compressive strength of cement until 10 %, but their suspensions prolong setting times of Portland cement as soluble orthophosphates – 2 - 3 times. Alkalis in cement increase pH of paste, but do not change the process of formation of calcium orthophosphates hydrates of hydroxyapatite group: it takes place through an intermediate phase - CaHPO4·2H2O, whose transformation into apatite lasts for 2 - 3 months.

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

    Science.gov (United States)

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

    2016-08-01

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

  8. Characterization of methane-hydrate formation inferred from insitu Vp-density relationship for hydrate-bearing sediment cores obtained off the eastern coast of India

    Science.gov (United States)

    Kinoshita, M.; Hamada, Y.; Hirose, T.; Yamada, Y.

    2017-12-01

    In 2015, the Indian National Gas Hydrate Program (NGHP) Drilling Expedition 02 was carried out off the eastern margin of the Indian Peninsula in order to investigate distribution and occurrence of gas hydrates. From 25 drill sites, downhole logging data, cored samples, and drilling performance data were collected. One of the target areas (area B) is located on the axial and flank of an anticline, where the BSR is identified 100 m beneath the summit of anticline. 3 sites were drilled in the crest. The lower potential hydrate zone II was suggested by downhole logging (LWD) at 270-290 m below seafloor across the top of anticline. Core samples from this interval is characterized by a higher natural gamma radiation, gamma-ray-based higher bulk density and lower porosity, and higher electrical resistivity. All these features are in good agreement with LWD results. During this expedition, numerous special core sampling operations (PCAT) were carried out, keeping its insitu pressure in a pressure-tight vessel. They enabled acquiring insitu P-wave velocity and gamma-ray attenuation density measurements. In-situ X-CT images exhibit very clear hydrate distribution as lower density patches. Hydrate-bearing sediments exhibit a Vp-density trend that is clearly different from the ordinary formation. Vp values are significantly higher than 2 km/s whereas the density remains constant at 2-2.2 g/cm3 in hydrate zones. At some hydrate-bearing sediments, we noticed that Vp is negatively correlated to the density in the deeper portion (235-285 mbsf). On the other hand, in the shallower portion they are positively correlated. From lithostratigraphy the shallower portion consists of sand, whereas deeper portion are silty-clay dominant. We infer that the sand-dominant, shallower hydrate is a pore-filling type, and Vp is correlated positively to density. On the other hand, the clay-dominant, deeper hydrate is filled in vertical veins, and Vp is negatively correlated to density. Negative

  9. Modeling hydrate formation conditions in the presence of electrolytes and polar inhibitor solutions

    International Nuclear Information System (INIS)

    Osfouri, Shahriar; Azin, Reza; Gholami, Reza; Izadpanah, Amir Abbas

    2015-01-01

    Highlights: • A new predictive model is proposed for prediction of hydrate formation pressures. • A new local composition model was used to evaluate water activity in the presence of electrolyte. • MEG, DEG and TEG were used to test ability of the proposed model in the presence of polar inhibitors. • Cage occupancies by methane for the small cage were higher than carbon dioxide for gas mixtures. • The proposed model gives better match with experimental data in mixed electrolyte solutions. - Abstract: In this paper, a new predictive model is proposed for prediction of gas hydrate formation conditions in the presence of single and mixed electrolytes and solutions containing both electrolyte and a polar inhibitor such as monoethylene glycol (MEG), diethylene glycol (DEG) and triethylene glycol (TEG). The proposed model is based on the γ–φ approach, which uses modified Patel–Teja equation of state (VPT EOS) for characterizing the vapor phase, the solid solution theory by van der Waals and Platteeuw for modeling the hydrate phase, the non-electrolyte NRTL-NRF local composition model and Pitzer–Debye–Huckel equation as short-range and long-range contributions to calculate water activity in single electrolyte solutions. Also, the Margules equation was used to determine the activity of water in solutions containing polar inhibitor (glycols). The model predictions are in acceptable agreement with experimental data. For single electrolyte solutions, the model predictions are similar to available models, while for mixtures of electrolytes and mixtures of electrolytes and inhibitors, the proposed model gives significantly better predictions. In addition, the absolute average deviation of hydrate formation pressures (AADP) for 144 experimental data in solutions containing single electrolyte is 5.86% and for 190 experimental data in mixed electrolytes solutions is 5.23%. Furthermore, the proposed model has an AADP of 14.13%, 5.82% and 5.28% in solutions

  10. Investigation into the Formation and Adhesion of Cyclopentane Hydrates on Mechanically Robust Vapor-Deposited Polymeric Coatings.

    Science.gov (United States)

    Sojoudi, Hossein; Walsh, Matthew R; Gleason, Karen K; McKinley, Gareth H

    2015-06-09

    Blockage of pipelines by formation and accumulation of clathrate hydrates of natural gases (also called gas hydrates) can compromise project safety and economics in oil and gas operations, particularly at high pressures and low temperatures such as those found in subsea or arctic environments. Cyclopentane (CyC5) hydrate has attracted interest as a model system for studying natural gas hydrates, because CyC5, like typical natural gas hydrate formers, is almost fully immiscible in water; and thus CyC5 hydrate formation is governed not only by thermodynamic phase considerations but also kinetic factors such as the hydrocarbon/water interfacial area, as well as mass and heat transfer constraints, as for natural gas hydrates. We present a macroscale investigation of the formation and adhesion strength of CyC5 hydrate deposits on bilayer polymer coatings with a range of wettabilities. The polymeric bilayer coatings are developed using initiated chemical vapor deposition (iCVD) of a mechanically robust and densely cross-linked polymeric base layer (polydivinylbenzene or pDVB) that is capped with a covalently attached thin hydrate-phobic fluorine-rich top layer (poly(perfluorodecyl acrylate) or pPFDA). The CyC5 hydrates are formed from CyC5-in-water emulsions, and differential scanning calorimetry (DSC) is used to confirm the thermal dissociation properties of the solid hydrate deposits. We also investigate the adhesion of the CyC5 hydrate deposits on bare and bilayer polymer-coated silicon and steel substrates. Goniometric measurements with drops of CyC5-in-water emulsions on the coated steel substrates exhibit advancing contact angles of 148.3 ± 4.5° and receding contact angles of 142.5 ± 9.8°, indicating the strongly emulsion-repelling nature of the iCVD coatings. The adhesion strength of the CyC5 hydrate deposits is reduced from 220 ± 45 kPa on rough steel substrates to 20 ± 17 kPa on the polymer-coated steel substrates. The measured strength of CyC5 hydrate

  11. A study of the methane hydrate formation by in situ turbidimetry

    Energy Technology Data Exchange (ETDEWEB)

    Herri, J.M.

    1996-02-02

    The study of the Particle Size Distribution (PSD) during the processes of crystallization is a subject of considerable interest, notably in the offshore exploitation of liquid fuels where the gas hydrate crystallization can plug production, treatment and transport facilities. The classical remedy to this problem is mainly thermodynamic additives such as alcohols or salts, but a new way of research is the use of dispersant additives which avoid crystals formation. In this paper, we show an original apparatus that is able to measure in situ the polychromatic UV-Visible turbidity spectrum in a pressurised reactor. We apply this technology to the calculation of the PSD during the crystallization of methane hydrate particles in a stirred semi-batch tank reactor. We discuss the mathematics treatment of the turbidity spectrum in order to determine the PSD and especially the method of matrix inversion with constraint. Moreover, we give a method to calculate theoretically the refractive index of the hydrate particles and we validate it experimentally with the methane hydrate particles. We apply this technology to the study of the crystallization of methane hydrate from pure liquid water and methane gas into the range of temperature [0-2 deg. C], into the range of pressure [30-100 bars] and into the range of stirring rate [0-600 rpm]. We produce a set of experiments concerning these parameters. Then we realize a model of the crystallization taking into account the processes of nucleation, of growth, of agglomeration and flotation. We compare this model with the experimental results concerning the complex influence of stirring rate at 1 deg. C and 30 bars. Then, we investigate the influence of additives such as Fontainebleau Sand, Potassium Chloride and a surfactant such as Poly-Vinyl-Pyrrolydone. (authors). 133 refs., 210 figs., 54 tabs.

  12. Detection of Occupancy Differences in Methane Gas Hydrates by Raman Spectroscopy

    DEFF Research Database (Denmark)

    Hansen, Susanne Brunsgaard; Berg, Rolf W.; Stenby, Erling Halfdan

    2004-01-01

    of reservoir fluids due to plugging. Methods to prevent hydrate formation are in use, e.g. by injection of inhibitors. From environmental and security points of view an easy way to detect hydrate formation is of interest. We have tried to detect methane hydrate formation by use of Raman spectroscopy....

  13. Saline Alone vs Saline plus Mannitol Hydration for the Prevention of Acute Cisplatin Nephrotoxicity: A Randomized Trial

    Science.gov (United States)

    2017-10-15

    REPORT TYPE 10/15/2017 Presentation 4. TITLE AND SUBTITLE Saline Alone vs Saline plus Mannitol Hydration for the Prevention of Acute Cisplatin ...Saline plus Mannitol Hydration for the Prevention of Acute Cisplatin Nephrotoxicity: A Randomized Trial Wilfred Dela Cruz, Frederick Flynt, Sandra...America Background Cisplatin is widely used as an effective chemotherapy in diverse neoplasms and is associated with renal toxicity. Several studies

  14. Modeling the Formation of Hydrate-Filled Veins in Fine-Grained Sediments from in Situ Microbial Methane

    Energy Technology Data Exchange (ETDEWEB)

    Malinverno, Alberto [Lamont-Doherty Earth Observatory, Palisades, NY (United States); Cook, Ann [The Ohio State Univ., Columbus, OH (United States); Daigle, Hugh [Univ. of Texas, Austin, TX (United States)

    2016-12-16

    Continental margin sediments are dominantly fine-grained silt and clay, and methane hydrates in these sediments are often found in semi-vertical veins and fractures. In several instances, these hydrate veins occupy discrete depth intervals that are a few tens of meters thick and are surrounded by hydrate-free sediments. As they are not connected with gas sources beneath the base of the gas hydrate stability zone (GHSZ), these isolated hydrate-bearing intervals have been interpreted as formed by in situ microbial methane. To investigate the formation of these hydrate deposits, we applied a time-dependent advection-diffusion-reaction model that includes the effects of sedimentation, compaction, solute diffusion, and microbial methane generation. Microbial methane generation depends on the amount of metabolizable organic carbon deposited at the seafloor, whose progressive degradation produces methane beneath the sulfate reduction zone. If the amount of organic carbon entering the methanogenic zone is kept constant in time, we found that the computed amounts of hydrate formed in discrete intervals within the GHSZ are well below those estimated from observations. On the other hand, if the deposition of organic carbon is higher in a given time interval, methane generation during burial is more intense in the corresponding sediment interval, resulting in enhanced hydrate formation. With variations in organic carbon deposition comparable to those generally observed in continental margins, our model was able to reproduce the methane hydrate contents that were estimated from drilling. These results support the suggestion that in situ microbial generation associated with transient organic carbon deposition is the source of methane that forms isolated intervals of hydrate-filled veins in fine-grained sediments.

  15. Formation of natural gas hydrates in marine sediments. Gas hydrate growth and stability conditioned by host sediment properties

    Science.gov (United States)

    Clennell, M.B.; Henry, P.; Hovland, M.; Booth, J.S.; Winters, W.J.; Thomas, M.

    2000-01-01

    The stability conditions of submarine gas hydrates (methane clathrates) are largely dictated by pressure, temperature, gas composition, and pore water salinity. However, the physical properties and surface chemistry of the host sediments also affect the thermodynamic state, growth kinetics, spatial distributions, and growth forms of clathrates. Our model presumes that gas hydrate behaves in a way analogous to ice in the pores of a freezing soil, where capillary forces influence the energy balance. Hydrate growth is inhibited within fine-grained sediments because of the excess internal phase pressure of small crystals with high surface curvature that coexist with liquid water in small pores. Therefore, the base of gas hydrate stability in a sequence of fine sediments is predicted by our model to occur at a lower temperature, and so nearer to the seabed than would be calculated from bulk thermodynamic equilibrium. The growth forms commonly observed in hydrate samples recovered from marine sediments (nodules, sheets, and lenses in muds; cements in sand and ash layers) can be explained by a requirement to minimize the excess of mechanical and surface energy in the system.

  16. Research on the nanolevel influence of surfactants on structure formation of the hydrated Portland cement compositions

    Directory of Open Access Journals (Sweden)

    Guryanov Alexander

    2016-01-01

    Full Text Available The research of the structure formation process on a nanolevel of the samples of hydrated Portland cement compositions containing the modifying additives has been conducted with the help of small angle neutron scattering method. Carbonate and aluminum alkaline slimes as well as the complex additives containing surfactants were used as additives. The influence of slimes and surfactants on structural parameters change of Portland cement compositions of the average size of the disseminating objects, fractal dimension samples is considered. These Portland cement compositions are shown to be fractal clusters.

  17. Formation of Sclerotic Hydrate Deposits in a Pipe for Extraction of a Gas from a Dome Separator

    Science.gov (United States)

    Urazov, R. R.; Chiglinstev, I. A.; Nasyrov, A. A.

    2017-09-01

    The theory of formation of hydrate deposits on the walls of a pipe for extraction of a gas from a dome separator designed for the accident-related collection of hydrocarbons on the ocean floor is considered. A mathematical model has been constructed for definition of a steady movement of a gas in such a pipe with gas-hydrate deposition under the conditions of changes in the velocity, temperature, pressure, and moisture content of the gas flow.

  18. Study of formation and stability conditions of gas hydrates in drilling fluids; Etude des conditions de formation et de stabilite des hydrates de gaz dans les fluides de forage

    Energy Technology Data Exchange (ETDEWEB)

    Kharrat, M.

    2004-10-15

    Drilling fluids are complex media, in which solid particles are in suspension in a water-in-oil emulsion. The formation of gas hydrates in these fluids during off shore drilling operations has been suspected to be the cause of serious accidents. The purpose of this thesis is the study of the formation conditions as well as the stability of gas hydrates in complex fluids containing water-in-oil emulsions. The technique of high-pressure differential scanning calorimetry was used to characterise the conditions of hydrates formation and dissociation. Special attention has first been given to the validation of thermodynamic measurements in homogeneous solutions, in the pressure range 4 to 12 Mpa; the results were found to be in good agreement with literature data, as well as with modelling results. The method was then applied to water-in-oil emulsion, used as a model for real drilling fluids. It was proven that thermodynamics of hydrate stability are not significantly influenced by the state of dispersion of the water phase. On the other hand, the kinetics of formation and the amount of hydrates formed are highly increased by the dispersion. Applying the technique to real drilling fluids confirmed the results obtained in emulsions. Results interpretation allowed giving a representation of the process of hydrate formation in emulsion. Empirical modelling was developed to compute the stability limits of methane hydrate in the presence of various inhibitors, at pressures ranging from ambient to 70 MPa. Isobaric phase diagrams were constructed, that allow predicting the inhibiting efficiency of sodium chloride and calcium chloride at constant pressure, from 0,25 to 70 MPa. (author)

  19. Do Pleistocene Glacial-Interglacial Cycles Control Methane Hydrate Formation? An Example from Green Canyon, Gulf of Mexico

    Science.gov (United States)

    Oryan, B.; Malinverno, A.; Goldberg, D.; Fortin, W.

    2017-12-01

    Well GC955-H was drilled in the Green Canyon region under the Gulf of Mexico Gas Hydrates Joint Industry Project in 2009. Logging-while-drilling resistivity logs obtained at the well indicate that the saturation of gas hydrate varies between high and low values in an alternating fashion. This trend is observed from 180 to 360mbsf, depths that correspond to the Late Pleistocene. Similar gas hydrate saturation patterns have been observed in other Gulf of Mexico locations (Walker Ridge sites WR313-G and 313-H) in Late Pleistocene sediments. Our hypothesis is that these variations in saturation can be explained by sea level changes through time during glacial-interglacial cycles. A higher amount of organic matter is deposited and buried in the sediment column during glacial intervals when sea level is low. Microbes in the sediment column degrade organic matter and produce methane gas as a byproduct. Higher availability of organic matter in the sediment column can increase the concentration of methane in the sediment pore water and in turn lead to the formation of gas hydrate. We use a time-dependent numerical model of the formation of gas hydrate to test this hypothesis. The model predicts the volume and distribution of gas hydrates using mass balance equations. Model inputs include in situ porosity determined from bulk density logs; local thermal gradient estimated from the depth of the bottom of the gas hydrate stability zone in proximity to the well; and sedimentation rate determined using the biostratigraphy of an industry well in the vicinity of GC955-H. Initial results show a good match between gas hydrate saturation predicted by the model and resistivity logs obtained in the well. We anticipate that this correlation will establish whether a causal link exists between the saturation of gas hydrate in this reservoir and glacioeustatic sea level changes in the Late Pleistocene.

  20. Fundamentals and applications of gas hydrates.

    Science.gov (United States)

    Koh, Carolyn A; Sloan, E Dendy; Sum, Amadeu K; Wu, David T

    2011-01-01

    Fundamental understanding of gas hydrate formation and decomposition processes is critical in many energy and environmental areas and has special importance in flow assurance for the oil and gas industry. These areas represent the core of gas hydrate applications, which, albeit widely studied, are still developing as growing fields of research. Discovering the molecular pathways and chemical and physical concepts underlying gas hydrate formation potentially can lead us beyond flowline blockage prevention strategies toward advancing new technological solutions for fuel storage and transportation, safely producing a new energy resource from natural deposits of gas hydrates in oceanic and arctic sediments, and potentially facilitating effective desalination of seawater. The state of the art in gas hydrate research is leading us to new understanding of formation and dissociation phenomena that focuses on measurement and modeling of time-dependent properties of gas hydrates on the basis of their well-established thermodynamic properties.

  1. 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).

  2. Comparison of intelligent systems, artificial neural networks and neural fuzzy model for prediction of gas hydrate formation rate

    Directory of Open Access Journals (Sweden)

    Mohammad Javad Jalalnezhad

    2014-05-01

    Full Text Available The main objective of this study was to present a novel approach for predication of gas hydrate formation rate based on the Intelligent Systems. Using a data set including about 470 data obtained from flow tests in a mini-loop apparatus, different predictive models were developed. From the results predicted by these models, it can be pointed out that the developed models can be used as powerful tools for prediction of gas hydrate formation rate with total errors of less than 4%.

  3. Thermodynamics of Uranyl Minerals: Enthalpies of Formation of Uranyl Oxide Hydrates

    Energy Technology Data Exchange (ETDEWEB)

    K. Kubatko; K. Helean; A. Navrotsky; P.C. Burns

    2005-05-11

    The enthalpies of formation of seven uranyl oxide hydrate phases and one uranate have been determined using high-temperature oxide melt solution calorimetry: [(UO{sub 2}){sub 4}O(OH){sub 6}](H{sub 2}O){sub 5}, metaschoepite; {beta}-UO{sub 2}(OH){sub 2}; CaUO{sub 4}; Ca(UO{sub 2}){sub 6}O{sub 4}(OH){sub 6}(H{sub 2}O){sub 8}, becquerelite; Ca(UO{sub 2}){sub 4}O{sub 3}(OH){sub 4}(H{sub 2}O){sub 2}; Na(UO{sub 2})O(OH), clarkeite; Na{sub 2}(UO{sub 2}){sub 6}O{sub 4}(OH){sub 6}(H{sub 2}O){sub 7}, the sodium analogue of compreignacite and Pb{sub 3}(UO{sub 2}){sub 8}O{sub 8}(OH){sub 6}(H{sub 2}O){sub 2}, curite. The enthalpy of formation from the binary oxides, {Delta}H{sub f-ox}, at 298 K was calculated for each compound from the respective drop solution enthalpy, {Delta}H{sub ds}. The standard enthalpies of formation from the elements, {Delta}H{sub f}{sup o}, at 298 K are -1791.0 {+-} 3.2, -1536.2 {+-} 2.8, -2002.0 {+-} 3.2, -11389.2 {+-} 13.5, -6653.1 {+-} 13.8, -1724.7 {+-} 5.1, -10936.4 {+-} 14.5 and -13163.2 {+-} 34.4 kJ mol{sup -1}, respectively. These values are useful in exploring the stability of uranyl oxide hydrates in auxiliary chemical systems, such as those expected in U-contaminated environments.

  4. Acoustic Investigations of Gas and Gas Hydrate Formations, Offshore Southwestern Black Sea*

    Science.gov (United States)

    Kucuk, H. M.; Dondurur, D.; Ozel, O.; Atgin, O.; Sinayuc, C.; Merey, S.; Parlaktuna, M.; Cifci, G.

    2015-12-01

    The Black Sea is a large intercontinental back-arc basin with relatively high sedimentation rate. The basin was formed as two different sub-basins divided by Mid-Black Sea Ridge. The ridge is completely buried today and the Black Sea became a single basin in the early Miocene that is currently anoxic. Recent acoustic investigations in the Black Sea indicate potential for gas hydrate formation and gas venting. A total of 2500 km multichannel seismic, Chirp sub-bottom profiler and multibeam bathymetry data were collected during three different expeditions in 2010 and 2012 along the southwestern margin of the Black Sea. Box core sediment samples were collected for gas cromatography analysis. Wide spread BSRs and multiple BSRs are observed in the seismic profiles and may be categorized into two different types: cross-cutting BSRs (transecting sedimentary strata) and amplitude BSRs (enhanced reflections). Both types mimic the seabed reflection with polarity reversal. Some undulations of the BSR are observed along seismic profiles probably caused by local pressure and/or temperature changes. Shallow gas sources and chimney vents are clearly indicated by bright reflection anomalies in the seismic data. Gas cromatography results indicate the presence of methane and various components of heavy hydrocarbons, including Hexane. These observations suggest that the gas forming hydrate in the southwestern Black Sea may originate from deeper thermogenic hydrocarbon sources. * This study is supported by 2214-A programme of The Scientific and Technological Research Council of Turkey (TÜBITAK).

  5. Experimental study and thermodynamic modeling of CO2 gas hydrate formation in presence of zinc oxide nanoparticles

    International Nuclear Information System (INIS)

    Mohammadi, Mohsen; Haghtalab, Ali; Fakhroueian, Zahra

    2016-01-01

    Highlights: • Nanofluids enhance heat and mass transfer and affect on kinetic and thermodynamics. • The ZnO nanoparticles in liquid affect on kinetics and P-T curve of CO 2 hydrate. • ZnO nanoparticles enhance the growth rate and gas storage in CO 2 hydrate. • A thermodynamic modeling of CO 2 hydrate proposed in the presence of nanoparticles. • Water activity in ZnO + nanofluid was affected by enhancement of the CO 2 solubility. - Abstract: The effect of synthesized zinc oxide (ZnO) nanoparticles was investigated on the kinetic and thermodynamic equilibrium conditions of CO 2 hydrate formation. The amount of the gas consumption was measured and compared for the four sample fluids: pure water, aqueous solution of sodium dodecyl sulfate (SDS), water-based ZnO-nanofluid and water-based ZnO-nanofluid in the presence of SDS (0.001 mass fraction). The time of hydrate growth decreased and the amount of the storage gas enhanced in the presence of nanoparticles. Moreover, the nanoparticles size effect besides the CO 2 solubility enhancement in ZnO-nanofluid led to the reduction of water activity, so that the equilibrium curve of hydrate formation was shifted to higher pressures. A new correlation for Henry’s law constant was obtained using CO 2 -solubility data in ZnO-nanofluid. Finally using this correlation, the water activity was calculated through the Chen–Guo approach to propose a thermodynamic method for prediction of the equilibrium hydrate formation conditions in the presence of the nanoparticles.

  6. Assessing Hydrate Formation in Natural Gas Pipelines Under Transient Operation / Ocena zjawiska tworzenia się hydratów w warunkach nieustalonego przepływu gazu w gazociągach

    Science.gov (United States)

    Osiadacz, Andrzej

    2013-03-01

    This work presents a transient, non-isothermal compressible gas flow model that is combined with a hydrate phase equilibrium model. It enables, to determine whether hydrates could form under existing operating conditions in natural gas pipelines. In particular, to determine the time and location at which the natural gas enters the hydrate formation region. The gas flow is described by a set of partial differential equations resulting from the conservation of mass, momentum, and energy. Real gas effects are determined by the predictive Soave-Redlich-Kwong group contribution method. By means of statistical mechanics, the hydrate model is formulated combined with classical thermodynamics of phase equilibria for systems that contain water and both hydrate forming and non-hydrate forming gases as function of pressure, temperature, and gas composition. To demonstrate the applicability a case study is conducted.

  7. Role of excipients in hydrate formation kinetics of theophylline in wet masses studied by near-infrared spectroscopy

    DEFF Research Database (Denmark)

    Jørgensen, Anna C; Airaksinen, Sari; Karjalainen, Milja

    2004-01-01

    . Anhydrous theophylline was chosen as the hydrate-forming model drug compound and two excipients, silicified microcrystalline cellulose (SMCC) and alpha-lactose monohydrate, with different water absorbing properties, were used in formulation. An early stage of wet massing was studied with anhydrous...... theophylline and its 1:1 (w/w) mixtures with alpha-lactose monohydrate and SMCC with 0.1g/g of purified water. The changes in the state of water were monitored using near-infrared spectroscopy, and the conversion of the crystal structure was verified using X-ray powder diffraction (XRPD). SMCC decreased...... the hydrate formation rate by absorbing water, but did not inhibit it. The results suggest that alpha-lactose monohydrate slightly increased the hydrate formation rate in comparison with a mass comprising only anhydrous theophylline....

  8. Thermodynamic analysis of hydrates formation in drilling activities; Analise termodinamica da formacao de hidratos em atividades de perfuracao

    Energy Technology Data Exchange (ETDEWEB)

    Baptista, Joao Marcelo Mussi; Rossi, Luciano Fernando dos Santos; Morales, Rigoberto E.M. [Universidade Tecnologica Federal do Parana (UTFPR), Curitiba, PR (Brazil)], e-mail: joaommussi@yahoo.com.br, e-mail: lfrossi@cefetpr.br, e-mail: rmorales@cefetpr.br

    2006-07-01

    The present work has for objective to present an analysis of hydrates formation in drilling activities. This analysis presents a study of the state conditions for gas hydrates formation in inhibitors containing systems (salts and alcohols, separately). To describe the nonidealities of liquid phase in electrolytic solutions, the activity coefficient model of Debye-Hueckel is used, as [4], and to describe the influence of alcohols in the activity of water, the UNQUAC model is used, as Parrish and Prausnitz. The hydrate phase is described by thermodynamic statistic model of van der Waals and Platteeuw, and the gaseous phase fugacities are modeled by the Peng-Robinson Equation of State. Some results are presented for saline inhibitors, and for methanol and ethyleneglycol. (author)

  9. The investigation of lithium formate hydrate, sodium dithionate and N-methyl taurine as clinical EPR dosimeters

    International Nuclear Information System (INIS)

    Lelie, S.; Hole, E.O.; Duchateau, M.; Schroeyers, W.; Schreurs, S.; Verellen, D.

    2013-01-01

    Introduction: EPR-dosimetry using L-α-alanine is an established method for measuring high doses of ionizing radiation. However, since a minimum dose of approximately 4 Gy is required to achieve sufficient low uncertainties (1–2%) for clinical application, alternative dosimeter materials are being inquired. Lithium formate (LiFo) monohydrate has been studied by several groups and has revealed several promising properties in the low dose region (<4 Gy). The fading properties, however, are somewhat unpredictable, and depend on properties not yet fully uncovered. This paper reports the results from a study of lithium formate hydrate and N-methyl taurine as potential low dose EPR dosimeters. Methods and materials: Pellet shaped dosimeters of lithium formate monohydrate, lithium formate hydrate, sodium dithionate and N-methyl taurine were produced using a manual Weber press, L-α-alanine was obtained from Harwell dosimeters and irradiated using 60 kV and 6 MV X-ray beams, and Co-60 gamma-rays to a dose of 30 Gy and dose ranges of 0.5–100 Gy and 2–20 Gy respectively. The dosimeters were measured using an Electron Paramagnetic Resonance (EPR)-spectrometer. The detector responses for 6 MV and Co-60 radiation beams, the fading behaviors and signal shape in time were investigated. Results: Lithium formate monohydrate and lithium formate hydrate are apparently associated with near identical EPR-spectra (mainly one broad line), and the same spectrum arises for all radiation energies investigated. The shape of the EPR resonance remains constant with time, but the intensities decreases, and the fading is more prominent for the monohydrate than for the hydrate. The EPR resonance associated with N-methyl taurine is more complex than the resonance associated with LiFo and it changes with time, implying radical transitions and growth. Conclusions: The study showed that lithium formate hydrate is a strong candidate for EPR dosimetry with slightly better fading characteristics

  10. Experimental study on hydration damage mechanism of shale from the Longmaxi Formation in southern Sichuan Basin, China

    Directory of Open Access Journals (Sweden)

    Xiangjun Liu

    2016-03-01

    Full Text Available As a serious problem in drilling operation, wellbore instability restricts efficient development of shale gas. The interaction between the drilling fluid and shale with hydration swelling property would have impact on the generation and propagation mechanism of cracks in shale formation, leading to wellbore instability. In order to investigate the influence of the hydration swelling on the crack propagation, mineral components and physicochemical properties of shale from the Lower Silurian Longmaxi Formation (LF were investigated by using the XRD analysis, cation exchange capabilities (CEC analysis, and SEM observation, and we researched the hydration mechanism of LF shale. Results show that quartz and clay mineral are dominated in mineral composition, and illite content averaged 67% in clay mineral. Meanwhile, CEC of the LF shale are 94.4 mmol/kg. The process of water intruding inside shale along microcracks was able to be observed through high power microscope, meanwhile, the hydration swelling stress would concentrate at the crack tip. The microcracks would propagate, bifurcate and connect with each other, with increase of water immersing time, and it would ultimately develop into macro-fracture. Moreover, the macrocracks extend and coalesce along the bedding, resulting in the rock failure into blocks. Hydration swelling is one of the major causes that lead to wellbore instability of the LF shale, and therefore improving sealing capacity and inhibition of drilling fluid system is an effective measure to stabilize a borehole.

  11. Relation between methane hydrate-bearing formations and geological phenomena on the seafloor in the eastern Nankai trough

    Energy Technology Data Exchange (ETDEWEB)

    Nagakubo, S.; Kobayashi, T.; Inamori, T.; Saeki, T.; Shimoda, N.; Fujii, T. [Japan Oil, Gas and Metals National Corp., Chiba (Japan). Technology Research Center; Morita, S.; Tanahashi, M. [National Inst. of Advanced Industrial Science and Technology, Tsukuba (Japan). Inst. for Geo-Resources and Environment

    2008-07-01

    Bathymetric and sea floor amplitude maps of the Tokai-Oki area, Daini-Atsumi Knoll, and Kumao-Nada areas were constructed using data obtained from 3-D seismic surveys. The study examined the control factors of fluid migration between methane hydrate formations and the sea floor. The aim of the study was to understand the relationship between methane hydrate-bearing formation and geological phenomena in the eastern Nankai trough. Sea floor geological features in the region include canyons, pockmarks, landslides, and undulations. The study identified methane seeps with biological colonies, bacteria mats and methane-enriched pore water. Strong sea floor amplitudes corresponded with distributions of carbonate outcrops and methane-bearing fluids around the BSR. The study showed that the principle geological control factors for fluid migration between methane hydrate-bearing formations and the sea floor are permeable sandy sediments; shallow faults; and natural hydraulic fractures. Significant shallow anomalies were observed in the Daini-Atsumi Knoll area. Sandy sediments derived from turbidites control the distributions of bottom simulating reflectors. It was concluded that permeable sandy sediments may play an important role in fluid migration between methane hydrate-bearing formations and the sea floor. 12 refs., 13 figs.

  12. Effect of conditioners upon the thermodynamics and kinetics of methane hydrate formation. A preliminary structure-properties relationship study

    Energy Technology Data Exchange (ETDEWEB)

    Di Profio, Pietro; Arca, Simone; Germani, Raimondo; Savelli, Gianfranco

    2005-07-01

    The synthesis and stability of gas hydrates was found to be heavily affected by the presence of small quantities of additives, or conditioners, particularly surfactants. In a recent work, we showed that the enhancement of hydrate formation, both from previously described and newly synthesized surfactants, is probably due to surfactant monomers, rather than micelles, and that the features of hydrate induction time should not be used as a measure of critical micelle concentration. In the present paper, we discuss the results of a structure-properties relationship study in which a preliminary attempt to relate the structural features of several amphiphilic additives to some kinetic and thermodynamic parameters of methane hydrate formation - e.g., induction times, rate of formation, occupancy, etc. - is conducted. According to the present study, it is found that, for a particular conditioner, a reduction of induction time does not correlate to an increase of the formation rate and occupancy, and vice versa. This may be related to the nature of chemical moieties forming a particular amphiphile (e.g., the hydrophobic tail, head group, counterion, etc.). The understanding of the mechanisms by which those moieties play their differential role may be the key tool to the design and synthesis of tailored conditioners. (Author)

  13. Crack formation and prevention in colloidal drops

    Science.gov (United States)

    Kim, Jin Young; Cho, Kun; Ryu, Seul-A.; Kim, So Youn; Weon, Byung Mook

    2015-08-01

    Crack formation is a frequent result of residual stress release from colloidal films made by the evaporation of colloidal droplets containing nanoparticles. Crack prevention is a significant task in industrial applications such as painting and inkjet printing with colloidal nanoparticles. Here, we illustrate how colloidal drops evaporate and how crack generation is dependent on the particle size and initial volume fraction, through direct visualization of the individual colloids with confocal laser microscopy. To prevent crack formation, we suggest use of a versatile method to control the colloid-polymer interactions by mixing a nonadsorbing polymer with the colloidal suspension, which is known to drive gelation of the particles with short-range attraction. Gelation-driven crack prevention is a feasible and simple method to obtain crack-free, uniform coatings through drying-mediated assembly of colloidal nanoparticles.

  14. Methane Hydrate Formation from Enhanced Organic Carbon Burial During Glacial Lowstands: Examples from the Gulf of Mexico

    Energy Technology Data Exchange (ETDEWEB)

    Malinverno, Alberto; Cook, Ann; Daigle, Hugh; Oryan, Bar

    2017-12-15

    Methane hydrates in fine-grained marine sediments are often found within veins and fractures occupying discrete depth intervals that are surrounded by hydrate-free sediments. As they are not connected with gas sources beneath the base of the methane hydrate stability zone (MHSZ), these isolated hydrate-bearing intervals have been interpreted as formed by in situ microbial methane. We investigate here the hypothesis that these hydrate deposits form in sediments that were deposited during glacial lowstands and contain higher amounts of labile particulate organic carbon (POC), leading to enhanced microbial methanogenesis. During Pleistocene lowstands, river loads are deposited near the steep top of the continental slope and turbidity currents transport organic-rich, fine-grained sediments to deep waters. Faster sedimentation rates during glacial periods result in better preservation of POC because of decreased exposure times to oxic conditions. The net result is that more labile POC enters the methanogenic zone and more methane is generated in these sediments. To test this hypothesis, we apply an advection-diffusion-reaction model with a time-dependent deposition of labile POC at the seafloor controlled by glacioeustatic sea level variations in the last 250 kyr. The model is run for parameters estimated at three sites drilled by the 2009 Gulf of Mexico Joint Industry Project: Walker Ridge in the Terrebonne Basin (WR313-G and WR313-H) and Green Canyon near the canyon embayment into the Sigsbee Escarpment (GC955-H). In the model, gas hydrate forms in sediments with higher labile POC content deposited during the glacial cycle between 230 and 130 kyr (marine isotope stages 6 and 7). The corresponding depth intervals in the three sites contain hydrates, as shown by high bulk electrical resistivities and resistive subvertical fracture fills. This match supports the hypothesis that enhanced POC burial during glacial lowstands can result in hydrate formation from in situ

  15. Methane Hydrate Formation from Enhanced Organic Carbon Burial During Glacial Lowstands: Examples from the Gulf of Mexico

    Science.gov (United States)

    Malinverno, A.; Cook, A.; Daigle, H.; Oryan, B.

    2017-12-01

    Methane hydrates in fine-grained marine sediments are often found within veins and fractures occupying discrete depth intervals that are surrounded by hydrate-free sediments. As they are not connected with gas sources beneath the base of the methane hydrate stability zone (MHSZ), these isolated hydrate-bearing intervals have been interpreted as formed by in situ microbial methane. We investigate here the hypothesis that these hydrate deposits form in sediments that were deposited during glacial lowstands and contain higher amounts of labile particulate organic carbon (POC), leading to enhanced microbial methanogenesis. During Pleistocene lowstands, river loads are deposited near the steep top of the continental slope and turbidity currents transport organic-rich, fine-grained sediments to deep waters. Faster sedimentation rates during glacial periods result in better preservation of POC because of decreased exposure times to oxic conditions. The net result is that more labile POC enters the methanogenic zone and more methane is generated in these sediments. To test this hypothesis, we apply an advection-diffusion-reaction model with a time-dependent deposition of labile POC at the seafloor controlled by glacioeustatic sea level variations in the last 250 kyr. The model is run for parameters estimated at three sites drilled by the 2009 Gulf of Mexico Joint Industry Project: Walker Ridge in the Terrebonne Basin (WR313-G and WR313-H) and Green Canyon near the canyon embayment into the Sigsbee Escarpment (GC955-H). In the model, gas hydrate forms in sediments with higher labile POC content deposited during the glacial cycle between 230 and 130 kyr (marine isotope stages 6 and 7). The corresponding depth intervals in the three sites contain hydrates, as shown by high bulk electrical resistivities and resistive subvertical fracture fills. This match supports the hypothesis that enhanced POC burial during glacial lowstands can result in hydrate formation from in situ

  16. Study of electrical conductivity response upon formation of ice and gas hydrates from salt solutions by a second generation high pressure electrical conductivity probe

    Science.gov (United States)

    Sowa, Barbara; Zhang, Xue Hua; Kozielski, Karen A.; Dunstan, Dave E.; Hartley, Patrick G.; Maeda, Nobuo

    2014-11-01

    We recently reported the development of a high pressure electrical conductivity probe (HP-ECP) for experimental studies of formation of gas hydrates from electrolytes. The onset of the formation of methane-propane mixed gas hydrate from salt solutions was marked by a temporary upward spike in the electrical conductivity. To further understand hydrate formation a second generation of window-less HP-ECP (MkII), which has a much smaller heat capacity than the earlier version and allows access to faster cooling rates, has been constructed. Using the HP-ECP (MkII) the electrical conductivity signal responses of NaCl solutions upon the formation of ice, tetrahydrofuran hydrates, and methane-propane mixed gas hydrate has been measured. The concentration range of the NaCl solutions was from 1 mM to 3M and the driving AC frequency range was from 25 Hz to 5 kHz. This data has been used to construct an "electrical conductivity response phase diagrams" that summarize the electrical conductivity response signal upon solid formation in these systems. The general trend is that gas hydrate formation is marked by an upward spike in the conductivity at high concentrations and by a drop at low concentrations. This work shows that HP-ECP can be applied in automated measurements of hydrate formation probability distributions of optically opaque samples using the conductivity response signals as a trigger.

  17. Prediction of hydrate formation temperature by both statistical models and artificial neural network approaches

    International Nuclear Information System (INIS)

    Zahedi, Gholamreza; Karami, Zohre; Yaghoobi, Hamed

    2009-01-01

    In this study, various estimation methods have been reviewed for hydrate formation temperature (HFT) and two procedures have been presented. In the first method, two general correlations have been proposed for HFT. One of the correlations has 11 parameters, and the second one has 18 parameters. In order to obtain constants in proposed equations, 203 experimental data points have been collected from literatures. The Engineering Equation Solver (EES) and Statistical Package for the Social Sciences (SPSS) soft wares have been employed for statistical analysis of the data. Accuracy of the obtained correlations also has been declared by comparison with experimental data and some recent common used correlations. In the second method, HFT is estimated by artificial neural network (ANN) approach. In this case, various architectures have been checked using 70% of experimental data for training of ANN. Among the various architectures multi layer perceptron (MLP) network with trainlm training algorithm was found as the best architecture. Comparing the obtained ANN model results with 30% of unseen data confirms ANN excellent estimation performance. It was found that ANN is more accurate than traditional methods and even our two proposed correlations for HFT estimation.

  18. Analysis of formation pressure test results in the Mount Elbert methane hydrate reservoir through numerical simulation

    Science.gov (United States)

    Kurihara, M.; Sato, A.; Funatsu, K.; Ouchi, H.; Masuda, Y.; Narita, H.; Collett, T.S.

    2011-01-01

    Targeting the methane hydrate (MH) bearing units C and D at the Mount Elbert prospect on the Alaska North Slope, four MDT (Modular Dynamic Formation Tester) tests were conducted in February 2007. The C2 MDT test was selected for history matching simulation in the MH Simulator Code Comparison Study. Through history matching simulation, the physical and chemical properties of the unit C were adjusted, which suggested the most likely reservoir properties of this unit. Based on these properties thus tuned, the numerical models replicating "Mount Elbert C2 zone like reservoir" "PBU L-Pad like reservoir" and "PBU L-Pad down dip like reservoir" were constructed. The long term production performances of wells in these reservoirs were then forecasted assuming the MH dissociation and production by the methods of depressurization, combination of depressurization and wellbore heating, and hot water huff and puff. The predicted cumulative gas production ranges from 2.16??106m3/well to 8.22??108m3/well depending mainly on the initial temperature of the reservoir and on the production method.This paper describes the details of modeling and history matching simulation. This paper also presents the results of the examinations on the effects of reservoir properties on MH dissociation and production performances under the application of the depressurization and thermal methods. ?? 2010 Elsevier Ltd.

  19. Prediction of Gas Hydrate Formation Conditions in Aqueous Solutions of Single and Mixed Electrolytes

    DEFF Research Database (Denmark)

    Zuo, You-Xiang; Stenby, Erling Halfdan

    1997-01-01

    In this paper, the extended Patel-Teja equation of state was modified to describe non-ideality of the liquid phase containing water and electrolytes accurately. The modified Patel-Teja equation of state (MPT EOS) was utilized to develop a predictive method for gas hydrate equilibria. The new method...... employs the Barkan and Sheinin hydrate model for the description of the hydrate phase, the original Patel-Teja equation of state for the vapor phase fugacities, and the MPT EOS (instead of the activity coefficient model) for the activity of water in the aqueous phase. The new method has succesfully...

  20. Thermodynamic promotion of carbon dioxide-clathrate hydrate formation by tetrahydrofuran, cyclopentane and their mixtures

    DEFF Research Database (Denmark)

    Herslund, Peter Jørgensen; Thomsen, Kaj; Abildskov, Jens

    2013-01-01

    Gas clathrate hydrate dissociation pressures are reported for mixtures of carbon dioxide, water and thermodynamic promoters forming structure II hydrates.Hydrate (H)-aqueous liquid (Lw)-vapour (V) equilibrium pressures for the ternary system composed of water, tetrahydrofuran (THF), and carbon......) equilibrium data are presented for the ternary system of water-cyclopentane-carbon dioxide at temperatures ranging from 285.2K down to 275.5K.New four-phase H-Lw-La-V equilibrium data for the quaternary system water-THF-cyclopentane-carbon dioxide are presented in the temperature range from 275.1K to 286.6K....... It is shown that upon adding THF to the pure aqueous phase to form a 4mass percent solution, the equilibrium pressure of the formed hydrates may be lowered compared to the ternary system of water, cyclopentane and carbon dioxide. © 2013 Elsevier Ltd....

  1. Hydrate-phobic surfaces: fundamental studies in clathrate hydrate adhesion reduction.

    Science.gov (United States)

    Smith, J David; Meuler, Adam J; Bralower, Harrison L; Venkatesan, Rama; Subramanian, Sivakumar; Cohen, Robert E; McKinley, Gareth H; Varanasi, Kripa K

    2012-05-07

    Clathrate hydrate formation and subsequent plugging of deep-sea oil and gas pipelines represent a significant bottleneck for deep-sea oil and gas operations. Current methods for hydrate mitigation are expensive and energy intensive, comprising chemical, thermal, or flow management techniques. In this paper, we present an alternate approach of using functionalized coatings to reduce hydrate adhesion to surfaces, ideally to a low enough level that hydrodynamic shear stresses can detach deposits and prevent plug formation. Systematic and quantitative studies of hydrate adhesion on smooth substrates with varying solid surface energies reveal a linear trend between hydrate adhesion strength and the practical work of adhesion (γ(total)[1 + cos θ(rec)]) of a suitable probe liquid, that is, one with similar surface energy properties to those of the hydrate. A reduction in hydrate adhesion strength by more than a factor of four when compared to bare steel is achieved on surfaces characterized by low Lewis acid, Lewis base, and van der Waals contributions to surface free energy such that the practical work of adhesion is minimized. These fundamental studies provide a framework for the development of hydrate-phobic surfaces, and could lead to passive enhancement of flow assurance and prevention of blockages in deep-sea oil and gas operations.

  2. Prevention of organic iodide formation in BWR's

    International Nuclear Information System (INIS)

    Karjunen, T.; Laitinen, T.; Piippo, J.; Sirkiae, P.

    1996-01-01

    During an accident, many different forms of iodine may emerge. Organic iodides, such as methyl iodide and ethyl iodide, are relatively volatile, and thus their appearance leads to increased concentration of gaseous iodine. Since organic iodides are also relatively immune to most accident mitigation measures, such as sprays and filters, they can affect the accident source term significantly even when only a small portion of iodine is in organic form. Formation of organic iodides may not be limited by the amount of organic substances available. Excessive amounts of methane can be produced, for example, during oxidation of boron carbide, which is used in BWR's as a neutron absorber material. Another important source is cable insulation. In a BWR, a large quantity of cables is placed below the pressure vessel. Thus a large quantity of pyrolyse gases will be produced, should the vessel fail. Organic iodides can be formed as a result of many different reactions, but at least in certain conditions the main reaction takes place between an organic radical produced by radiolysis and elemental iodine. A necessary requirement for prevention of organic iodide production is therefore that the pH in the containment water pools is kept high enough to eliminate formation of elemental iodine. In a typical BWR the suppression pool water is usually unbuffered. As a result, the pH may be dominated by chemicals introduced during an accident. If no system for adding basic chemicals is operable, the main factor affecting pool water pH may be hydrochloric acid released during cable degradation. Should this occur, the conditions could be very favorable for production of elemental iodine and, consequently, formation of organic iodides. Although high pH is necessary for iodine retention, it could have also adverse effects. High pH may, for example, accelerate corrosion of containment materials and alter the characteristics of the solid corrosion products. (author) 6 figs., 1 tab., 13 refs

  3. Influence of Countercation Hydration Enthalpies on the Formation of Molecular Complexes: A Thorium-Nitrate Example.

    Science.gov (United States)

    Jin, Geng Bang; Lin, Jian; Estes, Shanna L; Skanthakumar, S; Soderholm, L

    2017-12-13

    The influence of countercations (A n+ ) in directing the composition of monomeric metal-ligand (ML) complexes that precipitate from solution are often overlooked despite the wide usage of A n+ in materials synthesis. Herein, we describe a correlation between the composition of ML complexes and A + hydration enthalpies found for two related series of thorium (Th)-nitrate molecular compounds obtained by evaporating acidic aqueous Th-nitrate solutions in the presence of A + counterions. Analyses of their chemical composition and solid-state structures demonstrate that A + not only affects the overall solid-state packing of the Th-nitrato complexes but also influences the composition of the Th-nitrato monomeric anions themselves. Trends in composition and structure are found to correlate with A + hydration enthalpies, such that the A + with smaller hydration enthalpies associate with less hydrated and more anionic Th-nitrato complexes. This perspective, broader than the general assumption of size and charge as the dominant influence of A n+ , opens a new avenue for the design and synthesis of targeted metal-ligand complexes.

  4. Investigating the influence of lithologic heterogeneity on gas hydrate formation and methane recycling at the base of the gas hydrate stability zone in channelized systems

    Energy Technology Data Exchange (ETDEWEB)

    Daigle, Hugh; Nole, Michael; Cook, Ann; Malinverno, Alberto

    2017-12-14

    In marine environments, gas hydrate preferentially accumulates in coarse-grained sediments. At the meso- to micro-scale, however, hydrate distribution in these coarse-grained units is often heterogeneous. We employ a methane hydrate reservoir simulator coupling heat and mass transfer as well as capillary effects to investigate how capillary controls on methane solubility affect gas and hydrate accumulations in reservoirs characterized by graded bedding and alternating sequences of coarse-grained sands and fine-grained silt and clay. Simulations bury a channelized reservoir unit encased in homogeneous, fine-grained material characterized by small pores (150 nm) and low permeability (~1 md in the absence of hydrate). Pore sizes within each reservoir bed between vary between coarse sand and fine silt. Sands have a median pore size of 35 microns and a lognormal pore size distribution. We also investigate how the amount of labile organic carbon (LOC) affects hydrate growth due to microbial methanogenesis within the sediments. In a diffusion-dominated system, methane movies into reservoir layers along spatial gradients in dissolved methane concentration. Hydrate grows in such a way as to minimize these concentration gradients by accumulating slower in finer-grained reservoir layers and faster in coarser-grained layers. Channelized, fining-upwards sediment bodies accumulate hydrate first along their outer surfaces and thence inward from top to bottom. If LOC is present in thin beds within the channel, higher saturations of hydrate will be distributed more homogeneously throughout the unit. When buried beneath the GHSZ, gas recycling can occur only if enough hydrate is present to form a connected gas phase upon dissociation. Simulations indicate that this is difficult to achieve for diffusion-dominated systems, especially those with thick GHSZs and/or small amounts of LOC. However, capillary-driven fracturing behavior may be more prevalent in settings with thick GHSZs.

  5. Surface coating for prevention of crust formation

    Energy Technology Data Exchange (ETDEWEB)

    Kronberg, J.W.

    1994-05-24

    A flexible surface coating which promotes the removal of deposits as they reach the surface by preventing adhesion and crust formation is disclosed. Flexible layers are attached to each side of a flexible mesh substrate comprising of a plurality of zones composed of one or more neighboring cells, each zone having a different compressibility than its adjacent zones. The substrate is composed of a mesh made of strands and open cells. The cells may be filled with foam. Studs or bearings may also be positioned in the cells to increase the variation in compressibility and thus the degree of flexing of the coating. Surface loading produces varying amounts of compression from point to point causing the coating to flex as deposits reach it, breaking up any hardening deposits before a continuous crust forms. Preferably one or more additional layers are also used, such as an outer layer of a non-stick material such as TEFLON, which may be pigmented, and an inner, adhesive layer to facilitate applying the coating to a surface. 5 figs.

  6. Inhibition of hydrate formation by kinetic inhibitors. Literature study; Inhibierung von Erdgashydraten durch kinetische Inhibitoren. Literaturstudie

    Energy Technology Data Exchange (ETDEWEB)

    Eberhardt, E.; Meyn, V.; Rahimian, I. [Institut fuer Erdoel- und Erdgasforschung, Clausthal-Zellerfeld (Germany)

    2000-04-01

    The aim of this study was to represent the state-of-the art of the inhibition of gas hydrates. Corresponding to recent publications the kinetic inhibition was considered in particular. Special inhibitors were validated using a set of criteria derived from different experimental test methods. Best results were obtained by the application of terpolymer VC-713 especially in relation to nucleation and crystal growth, followed by PVCap (polyvinylcaprolactame) and THI (threshold hydrate inhibitor), the chemical structure of which is derived from the antifreeze glycopeptids of antarcitc winter flounder. (orig.) [German] Die vorliegende Literaturstudie gibt den derzeitigen Stand der Kenntnis zur Inhibierung von Gashydraten wieder. Entsprechend der neueren Literatur wird insbesondere auf die kinetische Inhibierung eingegangen. Zur Beurteilung der verschiedenen Inhibitoren werden Bewertungskriterien zur Validierung der mit unterschiedlichen Untersuchungsmethoden erzielten experimentellen Ergebnisse angegeben. Anhand dieser Vorgehensweise zeigte sich, dass mit dem Terpolymer VC-713 die besten Ergebnisse, insbesondere im Hinblick auf Keimbildung und Wachstum, erzielt werden konnten. Sehr gute Ergebnisse wurden auch mit dem Polyvinylcaprolactam (PVCap) und den aus den Antigefrierpeptiden der antarktischen Winterflunder abgeleiteten Threshold Hydrate Inhibitoren (THI) erhalten. (orig.)

  7. Prediction of induction time for methane hydrate formation in the presence or absence of THF in flow loop system by Natarajan model

    Science.gov (United States)

    Talaghat, Mohammad Reza; Jokar, Seyyed Mohammad

    2018-03-01

    The induction time is a time interval to detect the initial hydrate formation, which is counted from the moment when the stirrer is turned on until the first detection of hydrate formation. The main objective of the present work is to predict and measure the induction time of methane hydrate formation in the presence or absence of tetrahydrofuran (THF) as promoter in the flow loop system. A laboratory flow mini-loop apparatus was set up to measure the induction time of methane hydrate formation. The induction time is predicted using developed Kashchiev and Firoozabadi model and modified model of Natarajan for a flow loop system. Furthermore, the effects of volumetric flow rate of the fluid on the induction time were investigated. The results of the models were compared with experimental data. They show that the induction time of hydrate formation in the presence of THF is very short at high pressure and high volumetric flow rate of the fluid. It decreases with increasing pressure and liquid volumetric flow rate. It is also shown that the modified Natarajan model is more accurate than the Kashchiev and Firoozabadi ones in prediction of the induction time.

  8. Hydrate promoting capabilities of some in water soluble and insoluble organics on the formation of methane gas hydrate; Action benefique de composes organique soluble ou insoluble dans l'eau sur la formation du methane hydrate

    Energy Technology Data Exchange (ETDEWEB)

    Mooijer, M.M.; Heuvel, V.D.; Reuvers, M.; Deugd, R.M. de; Peters, C.J.; Swaan Arons, J. de [Delft University of Technology, Faculty of Applied Sciences, Laboratory of Applied Thermodynamics and Phase Equilibria, Delft (Netherlands)

    2000-07-01

    Sodium chloride (NaCl) has a strong pressure enhancing effect on the three-phase equilibrium liquid water - hydrate - vapour (L{sub w}-H-V) in the ternary system water + methane + sodium chloride (H{sub 2}O+CH{sub 4}+NaCl). Recently, however, it became apparent that certain in water soluble and insoluble organic components have the opposite effect on the equilibrium pressure of the three-phase equilibrium L{sub w}-H-V. Compared to the hydrate equilibrium pressure of the organic free system, pressure reductions as high as 80% have been observed. This contribution reports on experimental results of the competitive effect, on the equilibrium pressure of the three-phase equilibrium L{sub w}-H-V, of both NaCl and the organic component 1,3-dioxolane, which is soluble in water. Also the in water insoluble organics tetrahydropyran, cyclo-butanone, methyl-cyclohexane, fluoroform and tetrafluoromethane and their effects are considered. (authors)

  9. Field investigation and spectral characterization of Banded Iron Formation, Odisha, India: Implications to hydration processes on Mars

    Science.gov (United States)

    Singh, M.; Singhal, J.; Rajesh, V. J.

    2015-10-01

    Banded iron formations are major rock units having hematite layers intermittent with silica rich layers and formed mainly by the sedimentary processes during Late-Archaean to Mid-Proterozoic time period. They found their significance as a major iron-ore deposits and the first terrestrial rock bodies with existing life signatures on Earth. Here, we propose Odisha BIFs as a probable analogue site to the martian layered hematite deposit and its implications in inferring the sedimentary processes,hydration and astrobiological activities on Mars. Hyperspectral analysis identifies the optimum bands for the identification of similar type of deposits on Mars. Odisha BIFs have been found well comparable with the existing analogue sites of Lake Superior and Carajas Formation, Brazil.

  10. Coprecipitation of radium on hydrated manganese dioxide in the presence of precipitate formation

    International Nuclear Information System (INIS)

    Bartikova, O.; Jedinakova, V.

    1984-01-01

    Optimal conditions were determined of radium precipitation on hydrated manganese dioxide. Parameters investigated included: manganese dichloride and sodium hypochlorite concentrations, pH value, stirring time and the presence of flocculants. The following conditions were found to be optimal: pH 10.3, manganese dichloride concentration 0.4 g/dm 3 , sodium hypochlorite concentration 0.3 g/dm 3 , stirring time 2 mins. Sedimentation may be accelerated and decontamination increased by 1.5% by adding a 1 μg/dm 3 concentration of the flocculant Prestol. The probable sorption mechanism was derived from sorption isotherms and measured X-ray spectra. (author)

  11. Vacancy ordering and superstructure formation in dry and hydrated strontium tantalate perovskites: A TEM perspective

    DEFF Research Database (Denmark)

    Ashok, Anuradha M.; Haavik, Camilla; Norby, Poul

    2014-01-01

    Crystal structures of Sr4(Sr2Ta2)O11 and Sr4(Sr1.92Ta2.08)O11.12, synthesized by solid state reaction technique in dry and hydrated state have been studied mainly using Transmission Electron Microscopy. Due to the lesser ability of X-rays to probe details in oxygen sublattice, the change in crystal...... and corresponding unit cells of all the perovskites based on the ordering of oxygen vacancies is deduced. Crystal unit cells based on the observations are proposed with ideal atomic coordinates. Finally an attempt is made to explain the water uptake behaviour of these perovskites based on the proposed crystal...

  12. The genetic source and timing of hydrocarbon formation in gas hydrate reservoirs in Green Canyon, Block GC955

    Science.gov (United States)

    Moore, M. T.; Darrah, T.; Cook, A.; Sawyer, D.; Phillips, S.; Whyte, C. J.; Lary, B. A.

    2017-12-01

    Although large volumes of gas hydrates are known to exist along continental slopes and below permafrost, their role in the energy sector and the global carbon cycle remains uncertain. Investigations regarding the genetic source(s) (i.e., biogenic, thermogenic, mixed sources of hydrocarbon gases), the location of hydrocarbon generation, (whether hydrocarbons formed within the current reservoir formations or underwent migration), rates of clathrate formation, and the timing of natural gas formation/accumulation within clathrates are vital to evaluate economic potential and enhance our understanding of geologic processes. Previous studies addressed some of these questions through analysis of conventional hydrocarbon molecular (C1/C2+) and stable isotopic (e.g., δ13C-CH4, δ2H-CH4, δ13C-CO2) composition of gases, water chemistry and isotopes (e.g., major and trace elements, δ2H-H2O, δ18O-H2O), and dissolved inorganic carbon (δ13C-DIC) of natural gas hydrate systems to determine proportions of biogenic and thermogenic gas. However, the effects from contributions of mixing, transport/migration, methanogenesis, and oxidation in the subsurface can complicate the first-order application of these techniques. Because the original noble gas composition of a fluid is preserved independent of microbial activity, chemical reactions, or changes in oxygen fugacity, the integration of noble gas data can provide both a geochemical fingerprint for sources of fluids and an additional insight as to the uncertainty between effects of mixing versus post-genetic modification. Here, we integrate inert noble gases (He, Ne, Ar, and associated isotopes) with these conventional approaches to better constrain the source of gas hydrate formation and the residence time of fluids (porewaters and natural gases) using radiogenic 4He ingrowth techniques in cores from two boreholes collected as part of the University of Texas led UT-GOM2-01 drilling project. Pressurized cores were extracted from

  13. Photosensitive Cationic Azobenzene Surfactants: Thermodynamics of Hydration and the Complex Formation with Poly(methacrylic acid).

    Science.gov (United States)

    Montagna, Maria; Guskova, Olga

    2018-01-09

    In this computational work, we investigate the photosensitive cationic surfactants with the trimethylammonium or polyamine hydrophilic head and the azobenzene-containing hydrophobic tail. The azobenzene-based molecules are known to undergo a reversible trans-cis-trans isomerization reaction when subjected to UV-visible light irradiation. Combining the density functional theory and the all-atom molecular dynamics simulations, the structural and the hydration properties of the trans- and the cis-isomers and their interaction with the oppositely charged poly(methacrylic acid) in aqueous solution are investigated. We establish and quantify the correlations of the molecular structure and the isomerization state of the surfactants and their hydrophilicity/hydrophobicity and the self-assembling altered by light. For this reason, we compare the hydration free energies of the trans- and the cis-isomers. Moreover, the investigations of the interaction strength between the azobenzene molecules and the polyanion provide additional elucidations of the recent experimental and theoretical studies on the light triggered reversible deformation behavior of the microgels and the polymer brushes loaded with azobenzene surfactants.

  14. Optimum potassium chloride concentration to reduce hydration capacity of clay formations; Concentracao otima de cloreto de potassio para reduzir a capacidade de hidratacao das formacoes argilosas

    Energy Technology Data Exchange (ETDEWEB)

    Machado, Jose Carlos Vieira [PETROBRAS, Salvador, BA (Brazil). Centro de Recursos Humanos Norte-Nordeste. Setor de Programas de Perfuracao; Oliveira, Manoel Martins de [PETROBRAS, BA (Brazil). Distrito de Perfuracao. Div. de Tecnicas de Perfuracao

    1988-12-31

    An experimental method for ascertaining the optimal concentration of potassium chloride for reducing the hydration and dispersion capacity of clayey formations sensitive to water-based fluids is described. Under this method, filtering time for disperse systems prepared from clayey formation samples is measured. A discussion is offered on theoretical aspects of hydration, expansion, and dispersion of clayey rocks in response to the variations in stress equilibrium states produced by these phenomena when a hole (well) is opened in the rock. The state of the art of this technological branch is also described. (author) 10 refs., 5 figs., 4 tabs.

  15. Evaluation of the geological relationships to gas hydrate formation and stability. Second annual technical progress report, October 1, 1985--September 30, 1986

    Energy Technology Data Exchange (ETDEWEB)

    1986-12-31

    Although there are many publications pertaining to gas hydrates, their formation and stability in various geological conditions are poorly known. Therefore, for the same reasons and because of the very broad scope of our research, limited amount and extremely dispersed information, the study regions are very large. Moreover, almost without exception the geological environments controlling gas hydrates formation and stability of the studied regions are very complex. The regions studied (completed and partially completed - total 17 locations) during the reporting period, particularly the Gulf of Mexico and the Middle America Trench, are the most important in this entire research project. In the past, both of these regions have been extensively studied, the presence of gas hydrates confirmed and samples recovered. In our investigation it was necessary not only to review all previous data and interpretations, but to do a thorough analysis of the basins, and a critical evaluation of an previously reported and publicly available but not published information.

  16. Observations of CO{sub 2} clathrate hydrate formation and dissolution under deep-ocean disposal conditions

    Energy Technology Data Exchange (ETDEWEB)

    Warzinski, R.P.; Cugini, A.V. [Department of Energy, Pittsburgh, PA (United States); Holder, G.D. [Univ. of Pittsburgh, Pittsburgh, PA (United States)

    1995-11-01

    Disposal of anthropogenic emissions of CO{sub 2} may be required to mitigate rises in atmospheric levels of this greenhouse gas if other measures are ineffective and the worst global warming scenarios begin to occur. Long-term storage of large quantities of CO{sub 2} has been proposed, but the feasibility of large land and ocean disposal options remains to be established. Determining the fate of liquid CO{sub 2} injected into the ocean at depths greater than 500 m is complicated by uncertainties associated with the physical behavior of CO{sub 2} under these conditions, in particular the possible formation of the ice-like CO{sub 2} clathrate hydrate. Resolving this issue is key to establishing the technical feasibility of this option. Experimental and theoretical work in this area is reported.

  17. Geological evolution and analysis of confirmed or suspected gas hydrate localities: Volume 10, Basin analysis, formation and stability of gas hydrates of the Aleutian Trench and the Bering Sea

    Energy Technology Data Exchange (ETDEWEB)

    Krason, J.; Ciesnik, M.

    1987-01-01

    Four major areas with inferred gas hydrates are the subject of this study. Two of these areas, the Navarin and the Norton Basins, are located within the Bering Sea shelf, whereas the remaining areas of the Atka Basin in the central Aleutian Trench system and the eastern Aleutian Trench represent a huge region of the Aleutian Trench-Arc system. All four areas are geologically diverse and complex. Particularly the structural features of the accretionary wedge north of the Aleutian Trench still remain the subjects of scientific debates. Prior to this study, suggested presence of the gas hydrates in the four areas was based on seismic evidence, i.e., presence of bottom simulating reflectors (BSRs). Although the disclosure of the BSRs is often difficult, particularly under the structural conditions of the Navarin and Norton basins, it can be concluded that the identified BSRs are mostly represented by relatively weak and discontinuous reflectors. Under thermal and pressure conditions favorable for gas hydrate formation, the relative scarcity of the BSRs can be attributed to insufficient gas supply to the potential gas hydrate zone. Hydrocarbon gas in sediment may have biogenic, thermogenic or mixed origin. In the four studied areas, basin analysis revealed limited biogenic hydrocarbon generation. The migration of the thermogenically derived gases is probably diminished considerably due to the widespread diagenetic processes in diatomaceous strata. The latter processes resulted in the formation of the diagenetic horizons. The identified gas hydrate-related BSRs seem to be located in the areas of increased biogenic methanogenesis and faults acting as the pathways for thermogenic hydrocarbons.

  18. New Insights into Solid Form Stability and Hydrate Formation: o-Phenanthroline HCl and Neocuproine HCl

    Directory of Open Access Journals (Sweden)

    Doris E. Braun

    2017-12-01

    Full Text Available The moisture- and temperature dependent stabilities and interrelation pathways of the practically relevant solid forms of o-phenanthroline HCl (1 and neocuproine HCl (2 were investigated using thermal analytical techniques (HSM, DSC and TGA and gravimetric moisture sorption/desorption studies. The experimental stability data were correlated with the structural changes observed upon dehydration and the pairwise interaction and lattice energies calculated. For 1 the monohydrate was identified as the only stable form under conditions of RH typically found during production and storage, but at RH values >80% deliquescence occurs. The second compound, 2, forms an anhydrate and two different hydrates, mono- (2-Hy1 and trihydrate (2-Hy3. The 2-Hy1 structure was solved from SCXRD data and the anhydrate structure derived from a combination of PXRD and CSP. Depending on the environmental conditions (moisture either 2-Hy1 or 2-Hy3 is the most sable solid form of 2 at RT. The monohydrates 1-Hy1 and 2-Hy1 show a high enthalpic stabilization (≥20 kJ mol−1 relative to the anhydrates. The anhydrates are unstable at ambient conditions and readily transform to the monohydrates even in the presence of traces of moisture. This study demonstrates how the right combination of experiment and theory can unravel the properties and interconversion pathways of solid forms.

  19. Gas hydrate nucleation

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1997-12-31

    The overall aim of the project was to gain more knowledge about the kinetics of gas hydrate formation especially the early growth phase. Knowledge of kinetics of gas hydrate formation is important and measurements of gas hydrate particle size and concentration can contribute to improve this knowledge. An experimental setup for carrying out experimental studies of the nucleation and growth of gas hydrates has been constructed and tested. Multi wavelength extinction (MWE) was the experimental technique selected for obtaining particle diameter and concentration. The principle behind MWE is described as well as turbidity spectrum analysis that in an initial stage of the project was considered as an alternative experimental technique. Details of the experimental setup and its operation are outlined. The measuring cell consists of a 1 litre horizontal tube sustaining pressures up to 200 bar. Laser light for particle size determination can be applied through sapphire windows. A description of the various auxiliary equipment and of another gas hydrate cell used in the study are given. A computer program for simulation and analysis of gas hydrate experiments is based on the gas hydrate kinetics model proposed by Skovborg and Rasmussen (1993). Initial measurements showed that knowledge of the refractive index of gas hydrates was important in order to use MWE. An experimental determination of the refractive index of methane and natural gas hydrate is described. The test experiments performed with MWE on collectives of gas hydrate particles and experiments with ethane, methane and natural gas hydrate are discussed. Gas hydrate particles initially seem to grow mainly in size and at latter stages in number. (EG) EFP-94; 41 refs.

  20. Theoretical studies on microstructures, stabilities and formation conditions of some sour gas in the type I, II, and H clathrate hydrates

    Science.gov (United States)

    Zhang, Xuran; Qiu, Nianxiang; Huang, Qing; Zha, Xianhu; He, Jian; Li, Yongfeng; Du, Shiyu

    2018-02-01

    Clathrate hydrates are well known for the water cage structures and the capability of encapsulating natural gas, generally considered as sour gas if containing appreciable amount of hydrogen sulfide. Using the ab initio calculations at the wB97X-D/6-311++G(2d,2p) level, we have investigated systematically the microstructures of five standard water cavities (ID, D, T, H and I) with single and multiple hydrogen sulfide inside. The interaction energies and deformation energies are predicted to ensure the stabilities and maximum occupancies of cages. In addition, the Gibbs free energies forming various water cavities enclosing CH4 and H2S molecules at temperature range 253 K-283 K are also calculated to explore the selectivity on hydrate types and corresponding formation conditions. The results from this work may provide new insight into the theory for the replacement scheme in the exploitation of natural gas hydrate.

  1. Thirst beats hunger - declining hydration during drought prevents carbon starvation in Norway spruce saplings.

    Science.gov (United States)

    Hartmann, Henrik; Ziegler, Waldemar; Kolle, Olaf; Trumbore, Susan

    2013-10-01

    Drought-induced tree mortality results from an interaction of several mechanisms. Plant water and carbon relations are interdependent and assessments of their individual contributions are difficult. Because drought always affects both plant hydration and carbon assimilation, it is challenging to disentangle their concomitant effects on carbon balance and carbon translocation. Here, we report results of a manipulation experiment specifically designed to separate drought effects on carbon and water relations from those on carbon translocation. In a glasshouse experiment, we manipulated the carbon balance of Norway spruce saplings exposed to either drought or carbon starvation (CO2 withdrawal), or both treatments, and compared the dynamics of carbon exchange, allocation and storage in different tissues. Drought killed trees much faster than did carbon starvation. Storage C pools were not depleted at death for droughted trees as they were for starved, well-watered trees. Hence drought has a significant detrimental effect on a plant's ability to utilize stored carbon. Unless they can be transported to where they are needed, sufficient carbon reserves alone will not assure survival of a drought except under specific conditions, such as moderate drought, or in species that maintain plant water relations required for carbon re-mobilization. © 2013 No claim to original German goverment works New Phytologist © 2013 New Phytologist Trust.

  2. Molecular analysis of petroleum derived compounds that adsorb onto gas hydrate surfaces

    International Nuclear Information System (INIS)

    Borgund, Anna E.; Hoiland, Sylvi; Barth, Tanja; Fotland, Per; Askvik, Kjell M.

    2009-01-01

    Field observations have shown that some streams of water, gas and crude oil do not form gas hydrate plugs during petroleum production even when operating within thermodynamic conditions for hydrate formation. Also, when studied under controlled laboratory conditions, some oils are found to form hydrate dispersed systems whereas others form plugs. Oils with low tendency to form hydrate plugs are believed to contain natural hydrate plug inhibiting components (NICs) that adsorb onto the hydrate surface, making them less water-wet and preventing the particles from agglomerating into large hydrate clusters. The molecular structure of the NICs is currently unknown. In this work, hydrate adsorbing components were extracted from crude oils using freon hydrates as an extraction phase. The fractions were found to be enriched in polar material, and more polar material is associated with hydrates generated in biodegraded crude oils than in non-biodegraded oils. Various fractionation schemes and analytical techniques have been applied in the search for molecular characterisation. The average molecular weights were found to be approximately 500 g/mole. GC-MS chromatograms show a large UCM (Unresolved Complex Mixture). Thus, GC-MS has a limited potential for identification of compounds. A commercial biosurfactant was used as a model compound in the search for similar structures in the extracts. The results from analysis of the hydrate adsorbing components suggest that the type and structure are more important for hydrate morphology than the amount of material adsorbed.

  3. Gas hydrate formation and dissipation histories in the northern margin of Canada: Beaufort-Mackenzie and the Sverdrup Basins

    Czech Academy of Sciences Publication Activity Database

    Majorowicz, J.; Osadetz, K.; Šafanda, Jan

    2012-01-01

    Roč. 2012, č. 1 (2012), 879393/1-879393/17 ISSN 1687-8833 Institutional research plan: CEZ:AV0Z30120515 Keywords : gas hydrates * Canadian Arctic continental margin * permafrost Subject RIV: DC - Siesmology, Volcanology, Earth Structure

  4. Implementation of subsea system to monitor in-situ temperature and formation pressure in methane hydrates sediments for the production test in 2017, offshore Japan

    Science.gov (United States)

    Nishimoto, K.

    2016-12-01

    The methane hydrates phase changes, from solid to fluid, is governed by pressure drop and heat transportation through a geological formation. For the world's first offshore production test of methane hydrates conducted in 2013, the MH21 research team installed distributed temperature sensing (DTS) cables and array type resistance temperature devices (RTD) behind the casings of the monitoring wells. The temperature monitoring was continued over the period of 18 months. As a result, the thermal response of the methane hydrate-bearing sediment during depressurization was observed, and the obtained data was used to evaluate the methane dissociation behavior and to estimate the dissociation front radius from a producer well. The second offshore production test is planned in the same area in 2017 with the extended period up to one month. Two sets of a pair of monitoring and producer well were drilled in 2016. A pair of monitoring and producer wells is only 20m apart. An improved monitoring system is prepared for the second test with additional pressure measurement capability with new features of subsea system. The planed formation pressure measurement is expected to contribute not only for the evaluation of methane hydrate phase changes and estimation of its areal distribution but also the analyzing the interference in the vicinity of the producer wells from the geo-mechanical point of view. The DTS resolution was improved with longer averaging time than the previously utilized system. To accomplish the continuous acquisition up running over longer than 18 months to cover pre-flow and post-flow periods, the subsea acquisition system was equipped with an exchangeable subsea batteries by ROV. As for the surface communication method, the acoustic transponder was added in the subsea system. In this technical presentation, the improvements on the monitoring system are discussed and the scientific objectives for new measurements such as formation pressure are presented.

  5. Hydration and ion pair formation in common aqueous La(III) salt solutions--a Raman scattering and DFT study.

    Science.gov (United States)

    Rudolph, Wolfram W; Irmer, Gert

    2015-01-07

    Raman spectra of aqueous lanthanum perchlorate, triflate (trifluorosulfonate), chloride and nitrate solutions were measured over a broad concentration (0.121-3.050 mol L(-1)) range at room temperature (23 °C). A very weak mode at 343 cm(-1) with a full width at half height at 49 cm(-1) in the isotropic spectrum suggests that the nona-aqua La(III) ion is thermodynamically stable in dilute perchlorate solutions (∼0.2 mol L(-1)) while in concentrated perchlorate solutions outer-sphere ion pairs and contact ion pairs are formed. The La(3+) nona-hydrate was also detected in a 1.2 mol L(-1) La(CF3SO3)3(aq). In lanthanum chloride solutions chloro-complex formation was detected over the measured concentration range from 0.5-3.050 mol L(-1). The chloro-complexes in LaCl3(aq) are fairly weak and disappear with dilution. At a concentration La(OH2)(9-n)Cln](+3-n) (n = 1-3) were formed. The La(NO3)3(aq) spectra were compared with a spectrum of a 0.409 mol L(-1) NaNO3(aq) and it was concluded that in La(NO3)3(aq) over the concentration range from 0.121-1.844 mol L(-1), nitrato-complexes, [La(OH2)(9-n)(NO3)n](+3-n) (n = 1, 2) were formed. These nitrato-complexes are quite weak and disappear with dilution La(OH2)9](3+) with the polarizable dielectric continuum are in good agreement with data from recent structural experimental measurements and high quality simulations. The DFT frequency of the La-O stretching mode at 328.2 cm(-1), is only slightly smaller than the experimental one.

  6. Modelling the response of the Cased Hole Formation Resistivity tool in order to determine the depth of gas hydrate dissociation during the thermal test in the JAPEX/JNOC/GSC et al. Mallik 5L-38 gas hydrate production research well

    Energy Technology Data Exchange (ETDEWEB)

    Anderson, B. [Schlumberger-Doll Research, Ridgefield, CT (United States); Dubourg, I. [Etudes et Productions Schlumberger, Clamart (France); Collett, T.S. [United States Geological Survey, Denver, CO (United States); Lewis, R.E. [Schlumberger Oilfield Services, Oklahoma City, OK (United States)

    2005-07-01

    The physical response of a gas hydrate deposit to various advanced production methods was field tested at the JAPEX/JNOC/GSC et al. Mallik 5L-38 gas hydrate production research well. The annular radius of gas hydrate dissociation that occurred around the wellbore during the thermal test in the Mallik 5L-38 well was determined using iterative forward modelling of Cased Hole Formation Resistivity (CHFR) well logs. According to modeling results, the radius of gas hydrate dissociation had large local variations and was far from uniform. A comparison of CHFR modeling results and measured gas volumes at the surface suggest that most of the gas produced during the thermal test in the Mallik 5L-38 well was accurately measured at the surface. It was concluded that the CHFR modelling method is a promising method to evaluate future gas hydrate dissociation in single-wells.

  7. EFFECT OF K₂O AND MgO ON THE FORMATION AND HYDRATION ACTIVITY OF Ba-BEARING CALCIUM SULFOALUMINATE

    Directory of Open Access Journals (Sweden)

    Weibo Shen

    2016-12-01

    Full Text Available Ba-bearing calcium sulfoaluminate (C2.75B1.25A₃$ is characterized by rapid hydration rate and volume stability, as a constituent of the low-CO₂ alternative clinker. In this paper, the effect of K₂O and MgO on the formation and hydration activity of Ba-bearing calcium sulfoaluminate was studied. Results show that according to DSC-TA curves 0.5-0.8 wt.% K₂O can reduce the decomposition temperature of CaCO₃ about 10-23 °C and the decomposition temperature of C2.75B1.25A3$ about 10-16°C. And 4.0 ∼5.0 wt.% MgO can reduce the decomposition temperature of CaCO₃ about 10-23°C and the decomposition temperature of C2.75B1.25A₃$ about 10-16°C.The effect of MgO on hydration activity of C2.75B1.25A₃$ is a little better than that of K₂O. This may be due to the reason that MgO, especially at the optimum dosage of 3.0∼ 4.0 wt.%, favors the formation of C2.75B1.25A₃$ mineral with little impurities such as BaAlO4 which is obtained from the analysis of XRD. From the released hydration heat rate and cumulative heat release results it is found that 0.5-1.1 wt.% K₂O and 2.0-4.0 wt.% MgO promote the hydration of C2.75B1.25A₃$ because of the lattice distortion and defects. Appropriate amount of MgO (2.0-4.0 wt.% and K₂O (0.8 wt.% can improve the compressive strength and ensure it steady growth with the increase of curing ages. But 1.4 wt.% K₂O and 5.0 wt.% MgO caused BaSO₄ and BaAlO₄ to extend the hydration of C2.75B1.25A₃$ and reduce the compressive strengths at both early ages and late ages.

  8. Modeling the kinetics of hydrates formation using phase field method under similar conditions of petroleum pipelines; Modelagem da cinetica de formacao de hidratos utilizando o Modelo do Campo de Fase em condicoes similares a dutos de petroleo

    Energy Technology Data Exchange (ETDEWEB)

    Oliveira, Mabelle Biancardi; Castro, Jose Adilson de; Silva, Alexandre Jose da [Universidade Federal Fluminense (UFF), Volta Redonda, RJ (Brazil). Programa de Pos-Graduacao em Engenharia Metalurgica], e-mails: mabelle@metal.eeimvr.uff.br; adilson@metal.eeimvr.uff.br; ajs@metal.eeimvr.uff.br

    2008-10-15

    Natural hydrates are crystalline compounds that are ice-like formed under oil extraction transportation and processing. This paper deals with the kinetics of hydrate formation by using the phase field approach coupled with the transport equation of energy. The kinetic parameters of the hydrate formation were obtained by adjusting the proposed model to experimental results in similar conditions of oil extraction. The effect of thermal and nucleation conditions were investigated while the rate of formation and morphology were obtained by numerical computation. Model results of kinetics growth and morphology presented good agreement with the experimental ones. Simulation results indicated that super-cooling and pressure were decisive parameters for hydrates growth, morphology and interface thickness. (author)

  9. Wine protein haze: mechanisms of formation and advances in prevention.

    Science.gov (United States)

    Van Sluyter, Steven C; McRae, Jacqui M; Falconer, Robert J; Smith, Paul A; Bacic, Antony; Waters, Elizabeth J; Marangon, Matteo

    2015-04-29

    Protein haze is an aesthetic problem in white wines that can be prevented by removing the grape proteins that have survived the winemaking process. The haze-forming proteins are grape pathogenesis-related proteins that are highly stable during winemaking, but some of them precipitate over time and with elevated temperatures. Protein removal is currently achieved by bentonite addition, an inefficient process that can lead to higher costs and quality losses in winemaking. The development of more efficient processes for protein removal and haze prevention requires understanding the mechanisms such as the main drivers of protein instability and the impacts of various wine matrix components on haze formation. This review covers recent developments in wine protein instability and removal and proposes a revised mechanism of protein haze formation.

  10. The Methane Hydrate Reservoir System

    Science.gov (United States)

    Flemings, P. B.; Liu, X.

    2007-12-01

    We use multi phase flow modeling and field examples (Hydrate Ridge, offshore Oregon and Blake Ridge, offshore North Carolina) to demonstrate that the methane hydrate reservoir system links traditional and non- traditional hydrocarbon system components: free gas flow is a fundamental control on this system. As in a traditional hydrocarbon reservoir, gas migrates into the hydrate reservoir as a separate phase (secondary migration) where it is trapped in a gas column beneath the base of the hydrate layer. With sufficient gas supply, buoyancy forces exceed either the capillary entry pressure of the cap rock or the fracture strength of the cap rock, and gas leaks into the hydrate stability zone, or cap rock. When gas enters the hydrate stability zone and forms hydrate, it becomes a very non traditional reservoir. Free gas forms hydrate, depletes water, and elevates salinity until pore water is too saline for further hydrate formation: salinity and hydrate concentration increase upwards from the base of the regional hydrate stability zone (RHSZ) to the seafloor and the base of the hydrate stability zone has significant topography. Gas chimneys couple the free gas zone to the seafloor through high salinity conduits that are maintained at the three-phase boundary by gas flow. As a result, significant amounts of gaseous methane can bypass the RHSZ, which implies a significantly smaller hydrate reservoir than previously envisioned. Hydrate within gas chimneys lie at the three-phase boundary and thus small increases in temperature or decreases in pressure can immediately transport methane into the ocean. This type of hydrate deposit may be the most economical for producing energy because it has very high methane concentrations (Sh > 70%) located near the seafloor, which lie on the three-phase boundary.

  11. A study on dehydration of rare earth chloride hydrate

    International Nuclear Information System (INIS)

    Cho, Yong Zun; Eun, Hee Chul; Son, Sung Mo; Lee, Tae Kyo; Hwang, Taek Sung

    2012-01-01

    The dehydration schemes of rare earth (La, Ce, Nd, Pr, Sm. Eu, Gd, Y) chloride hydrates was investigated by using a dehydration apparatus. To prevent the formation of the rare earth oxychlorides, the operation temperature was changed step by step (80→150→230 degree C) based on the TGA (thermo-gravimetric analysis) results of the rare earth chloride hydrates. A vacuum pump and preheated Ar gas were used to effectively remove the evaporated moisture and maintain an inert condition in the dehydration apparatus. The dehydration temperature of the rare earth chloride hydrate was increased when the atomic number of the rare earth nuclide was increased. The content of the moisture in the rare earth chloride hydrate was decreased below 10% in the dehydration apparatus.

  12. Gas hydrate formation in deep-sea sediments - on the role of sediment-mechanical process determination; Gashydratbildung in Tiefseesedimenten - zur Rolle der sedimentmechanischen Prozesssteuerung

    Energy Technology Data Exchange (ETDEWEB)

    Feeser, V. [Kiel Univ. (Germany). Geologisch-Palaeontologisches Inst.

    1997-12-31

    Slope failures in gas hydrate regions are encountered throughout the oceans. The stability of seafloor slopes can be assessed and predicted by means of calculation methods based on mechanical laws and parameters which describe the deformation behaviour and/or mechanical strength of the slope-forming sediments. Thermodynamic conditions conducive to the formation of gas hydrates in marine sediments differ from conditions prevailing in exclusively water-filled systems. The present contribution describes the relevant energetic conditions on the basis of a simple spherical model giving due consideration to petrographic parameters. Depending on pore size distribution, lithological stress conditions, pore water pressure, and sediment strength gas hydrates will either develop as a cementing phase or as segregated lenses. (MSK) [Deutsch] In den Weltmeeren ereignen sich immer wieder Hangrutschungen in Gashydratgebieten. Die zur Beurteilung und Prognonse von Hangstabilitaeten zu verwendenden Berechnungsverfahren erfordern Stoffgesetze und Parameter, welche das Deformations-und/oder Festigkeitsverhalten der hangbildenden Sedimente beschreiben. Die thermodynamischen Bildungsbedingungen von Gashydraten in marinen Sedimenten unterscheiden sich von den Bedingungen in ausschliesslich wassergefuellten Systemen. Unter Einbeziehung petrographischer Eigenschaften werden die energetischen Bedingungen beschrieben. Dazu dient ein einfaches Kugelmodell. Je nach vorhandenem Porenraumspektrum, lithostatischen Spannungsverhaeltnissen, Porenwasserdruck und Sedimentfestigkeit wachsen Gashydrate als Porenraumzement oder als segregierte Linsen.

  13. Methane Production and Carbon Capture by Hydrate Swapping

    DEFF Research Database (Denmark)

    Mu, Liang; von Solms, Nicolas

    2017-01-01

    There are essentially two different approaches to producing methane from natural gas hydrate reservoirs, either bring the hydrate out of its thermodynamic stability region or expose the hydrate to a substance that will form a more stable hydrate structure, forcing an in situ swapping of the trapped...... in small hydrate cages, as long as the equilibrium formation pressure of (CO2 + N2) binary gas hydrate is below that of methane hydrate, even though adding nitrogen to carbon dioxide reduces the thermodynamic driving force for the formation of a new hydrate. When other conditions are similar, the methane...

  14. Fluid hydration to prevent post-ERCP pancreatitis in average- to high-risk patients receiving prophylactic rectal NSAIDs (FLUYT trial): study protocol for a randomized controlled trial.

    Science.gov (United States)

    Smeets, Xavier J N M; da Costa, David W; Fockens, Paul; Mulder, Chris J J; Timmer, Robin; Kievit, Wietske; Zegers, Marieke; Bruno, Marco J; Besselink, Marc G H; Vleggaar, Frank P; van der Hulst, Rene W M; Poen, Alexander C; Heine, Gerbrand D N; Venneman, Niels G; Kolkman, Jeroen J; Baak, Lubbertus C; Römkens, Tessa E H; van Dijk, Sven M; Hallensleben, Nora D L; van de Vrie, Wim; Seerden, Tom C J; Tan, Adriaan C I T L; Voorburg, Annet M C J; Poley, Jan-Werner; Witteman, Ben J; Bhalla, Abha; Hadithi, Muhammed; Thijs, Willem J; Schwartz, Matthijs P; Vrolijk, Jan Maarten; Verdonk, Robert C; van Delft, Foke; Keulemans, Yolande; van Goor, Harry; Drenth, Joost P H; van Geenen, Erwin J M

    2018-04-02

    Post-endoscopic retrograde cholangiopancreatography (ERCP) pancreatitis (PEP) is the most common complication of ERCP and may run a severe course. Evidence suggests that vigorous periprocedural hydration can prevent PEP, but studies to date have significant methodological drawbacks. Importantly, evidence for its added value in patients already receiving prophylactic rectal non-steroidal anti-inflammatory drugs (NSAIDs) is lacking and the cost-effectiveness of the approach has not been investigated. We hypothesize that combination therapy of rectal NSAIDs and periprocedural hydration would significantly lower the incidence of post-ERCP pancreatitis compared to rectal NSAIDs alone in moderate- to high-risk patients undergoing ERCP. The FLUYT trial is a multicenter, parallel group, open label, superiority randomized controlled trial. A total of 826 moderate- to high-risk patients undergoing ERCP that receive prophylactic rectal NSAIDs will be randomized to a control group (no fluids or normal saline with a maximum of 1.5 mL/kg/h and 3 L/24 h) or intervention group (lactated Ringer's solution with 20 mL/kg over 60 min at start of ERCP, followed by 3 mL/kg/h for 8 h thereafter). The primary endpoint is the incidence of post-ERCP pancreatitis. Secondary endpoints include PEP severity, hydration-related complications, and cost-effectiveness. The FLUYT trial design, including hydration schedule, fluid type, and sample size, maximize its power of identifying a potential difference in post-ERCP pancreatitis incidence in patients receiving prophylactic rectal NSAIDs. EudraCT: 2015-000829-37 . Registered on 18 February 2015. 13659155 . Registered on 18 May 2015.

  15. Phase equilibria with hydrate formation in H2O + CO2 mixtures modeled with reference equations of state

    Czech Academy of Sciences Publication Activity Database

    Jäger, A.; Vinš, Václav; Gernert, J.; Span, R.; Hrubý, Jan

    2013-01-01

    Roč. 338, Januar (2013), s. 100-113 ISSN 0378-3812 R&D Projects: GA ČR(CZ) GPP101/11/P046; GA ČR(CZ) GAP101/11/1593 Institutional support: RVO:61388998 Keywords : carbon dioxide * gas hydrate * modeling Subject RIV: BJ - Thermodynamics Impact factor: 2.241, year: 2013 http://www.sciencedirect.com/science/article/pii/S0378381212005158

  16. 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.

  17. Enzymatic treatment for preventing biofilm formation in the paper industry.

    Science.gov (United States)

    Torres, Claudia Esperanza; Lenon, Giles; Craperi, Delphine; Wilting, Reinhard; Blanco, Angeles

    2011-10-01

    Microbiological control programmes at industrial level should aim at reducing both the detrimental effects of microorganisms on the process and the environmental impact associated to the use of biocides as microbiological control products. To achieve this target, new efficient and environmentally friendly products are required. In this paper, 17 non-specific, commercial enzymatic mixtures were tested to assess their efficacy for biofilm prevention and control at laboratory and pilot plant scale. Pectin methylesterase, an enzyme found in the formulation of two of the mixtures tested, was identified as an active compound able to reduce biofilm formation by 71% compared to control tests.

  18. 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 ...

  19. Formation of low-T hydrated silicates in modern microbialites from Mexico and implications for microbial fossilization

    Directory of Open Access Journals (Sweden)

    Nina eZeyen

    2015-10-01

    Full Text Available Microbialites are organo-sedimentary rocks found in abundance throughout the geological record back to ~3.5 Ga. Interpretations of the biological and environmental conditions under which they formed rely on comparisons with modern microbialites. Therefore, a better characterization of diverse modern microbialites is crucial to improve such interpretations. Here, we studied modern microbialites from three Mexican alkaline crater lakes: Quechulac, La Preciosa and Atexcac. The geochemical analyses of water solutions showed that they were supersaturated to varying extents with several mineral phases, including aragonite, calcite, hydromagnesite, as well as hydrated Mg-silicates. Consistently, X-ray diffraction and Fourier transform infrared spectroscopy analyses revealed that microbialites are composed of a diversity of mineral phases including aragonite and sometimes calcite, hydromagnesite, and more interestingly, a poorly-crystalline hydrated silicate phase. Coupling of scanning electron microscopy with energy dispersive X-ray spectrometry microanalyses on polished sections showed that this latter phase is abundant, authigenic, magnesium-rich and sometimes associated with iron and manganese. This mineral phase is similar to kerolite, a hydrated poorly crystalline talc-like phase (Mg3Si4O10(OH2·nH2O. Diverse microfossils were permineralized by this silicate phase. Some of them were imaged in 3D by FIB-tomography showing that their morphologically was exquisitely preserved down to the few nm-scale. The structural and chemical features of these fossils were further studied using a combination of transmission electron microscopy and scanning transmission X-ray microscopy at the carbon and magnesium K-edges and iron L2,3-edges. These results showed that organic carbon is pervasively associated with kerolite. Overall, it is suggested that the poorly-crystalline hydrated magnesium-rich silicate forms in many alkaline lakes and has a strong potential

  20. 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.

  1. 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

    Blake Ridge in the Atlantic Ocean in 1995, have also contributed greatly to our understanding of the geologic controls on the formation, occurrence, and stability of gas hydrates in marine environments. For the most part methane hydrate research expeditions carried out by the ODP and IODP provided the foundation for our scientific understanding of gas hydrates. The methane hydrate research efforts under ODP-­‐IODP have mostly dealt with the assessment of the geologic controls on the occurrence of gas hydrate, with a specific goal to study the role methane hydrates may play in the global carbon cycle.Over the last 10 years, national led methane hydrate research programs, along with industry interest have led to the development and execution of major methane hydrate production field test programs. Two of the most important production field testing programs have been conducted at the Mallik site in the Mackenzie River Delta of Canada and in the Eileen methane hydrate accumulation on the North Slope of Alaska. Most recently we have also seen the completion of the world’s first marine methane hydrate production test in the Nankai Trough in the offshore of Japan. Industry interest in gas hydrates has also included important projects that have dealt with the assessment of geologic hazards associated with the presence of hydrates.The scientific drilling and associated coring, logging, and borehole monitoring technologies developed in the long list of methane hydrate related field studies are one of the most important developments and contributions associated with methane hydrate research and development activities. Methane hydrate drilling has been conducted from advanced scientific drilling platforms like the JOIDES Resolution and the D/V Chikyu, which feature highly advanced integrated core laboratories and borehole logging capabilities. Hydrate research drilling has also included the use of a wide array of industry, geotechnical and multi-­‐service ships. All of

  2. 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.

  3. Last 20 years of gas hydrates in the oil industry : challenges and achievements in predicting pipeline blockage

    Energy Technology Data Exchange (ETDEWEB)

    Estanga, D.A.; Creek, J.; Subramanian, S.; Kini, R.A. [Chevron Energy Technology Co., Houston, TX (United States)

    2008-07-01

    This paper reviewed how the successes of the past 20 years have shaped the new hydrate focus. It also outlined innovative tools for hydrate plugging prediction. Tools such as CSMHyK-OLGA were developed to address the design and operational challenges associated with offshore production regarding flow assurance in the area of gas hydrates. The effort to understand the complex behavior of gas hydrates in multiphase flow has resulted in new hydrate blockage models. Although the hydrate community continues to debate the impact of kinetics, agglomeration, and oil chemistry effects on hydrate blockage formation in pipelines and wellbores, the petroleum industry still relies on thermodynamic strategies that completely prevent hydrates in production systems. However, these complex strategies such as thermal insulation, electric heating, dead oil displacement, and methanol injection are costly, particularly for marginal fields. As such, research continues in developing a comprehensive multiphase flow simulator capable of handling the transient aspects of production operations, notably shut-in, restart, blowdown and blockage prediction. Model predictions are leading to new operating strategies based on risk management approach. This paper discussed the challenges and opportunities that have shifted the focus from prevention of hydrates to prevention of blockage. Some initial successes in the development of a first generation empirical tool for the prediction of hydrate blockages in flow lines were also presented along with new experimental data that explained how hydrate blockages can manifest in the field. It was concluded that additional research is needed to solve the problem of hydrate plugging mechanism. 12 refs., 6 figs.

  4. Novel thermosensitive hydrogel for preventing formation of abdominal adhesions

    Directory of Open Access Journals (Sweden)

    Gao X

    2013-07-01

    Full Text Available Xiang Gao,1,2 Xiaohui Deng,3 Xiawei Wei,2 Huashan Shi,2 Fengtian Wang,2 Tinghong Ye,2 Bin Shao,2 Wen Nie,2 Yuli Li,2 Min Luo,2 Changyang Gong,2 Ning Huang1 1Department of Pathophysiology, College of Preclinical and Forensic Medical Sciences, Sichuan University, Chengdu, 2State Key Laboratory of Biotherapy and Cancer Center, West China Hospital, West China Medical School, Sichuan University, Chengdu, 3Department of Human Anatomy, Xinxiang Medical University, Xinxiang, People’s Republic of China Abstract: Adhesions can form after almost any type of abdominal surgery. Postoperative adhesions can be prevented by improved surgical techniques, such as reducing surgical trauma, preventing ischemia, and avoiding exposure of the peritoneal cavity to foreign materials. Although improved surgical techniques can potentially reduce formation of adhesions, they cannot be eliminated completely. Therefore, finding more effective methods to prevent postoperative adhesions is imperative. Recently, we found that a novel thermosensitive hydrogel, ie, poly(ε-caprolactone-poly(ethylene glycol-poly(ε-caprolactone (PCEC had the potential to prevent postoperative adhesions. Using the ring-opening polymerization method, we prepared a PCEC copolymer which could be dissolved and assembled at 55°C into PCEC micelles with mean size of 25 nm. At body temperature, a solution containing PCEC micelles could convert into a hydrogel. The PCEC copolymer was biodegradable and had low toxicity in vitro and in vivo. We found that most animals in a hydrogel-treated group (n = 10 did not develop adhesions. In contrast, 10 untreated animals developed adhesions that could only be separated by sharp dissection (P < 0.001. The hydrogel could adhere to peritoneal wounds and degraded gradually over 7–9 days, transforming into a viscous fluid that was completely absorbed within 12 days. The injured parietal and visceral peritoneum remesothelialized over about seven and nine days

  5. Collaborative Falls Prevention: Interprofessional Team Formation, Implementation, and Evaluation.

    Science.gov (United States)

    Lasater, Kathie; Cotrell, Victoria; McKenzie, Glenise; Simonson, William; Morgove, Megan W; Long, Emily E; Eckstrom, Elizabeth

    2016-12-01

    As health care rapidly evolves to promote person-centered care, evidence-based practice, and team-structured environments, nurses must lead interprofessional (IP) teams to collaborate for optimal health of the populations and more cost-effective health care. Four professions-nursing, medicine, social work, and pharmacy-formed a teaching team to address fall prevention among older adults in Oregon using an IP approach. The teaching team developed training sessions that included interactive, evidence-based sessions, followed by individualized team coaching. This article describes how the IP teaching team came together to use a unique cross-training approach to teach each other. They then taught and coached IP teams from a variety of community practice settings to foster their integration of team-based falls-prevention strategies into practice. After coaching 25 teams for a year each, the authors present the lessons learned from the teaching team's formation and experiences, as well as feedback from practice team participants that can provide direction for other IP teams. J Contin Educ Nurs. 2016;47(12):545-550. Copyright 2016, SLACK Incorporated.

  6. Influence of a synergist on the dissociation of gas hydrates formed in the presence of the kinetic inhibitor polyvinyl caprolactam

    Energy Technology Data Exchange (ETDEWEB)

    Gulbrandsen, A.C. [StatoilHydro, Stavanger (Norway); Svartaas, T.M. [Stavanger Univ., Stavanger (Norway). Dept. of Petroleum Engineering

    2008-07-01

    Conventional chemical methods used to prevent natural gas hydrate plugs in oil and gas production lines are costly and can lead to pipeline corrosion. Polymer-based kinetic inhibitors are now being used to prevent hydrate nucleation and growth, and recent research has shown that the addition of small amounts of glycol ethers substantially improve the performance of the polymers. In this study, gas hydrates were formed from solutions containing Poly Vinyl Caprolactam (PVCap), or INHIBEX, a liquid mixture containing 50 wt per cent PVCAP 2k and 50 wt per cent butyl glycol. Laboratory experiments were conducted using a stirred cell. Hydrate formation was induced by magnetic stirring. Hydrates were then dissociated by increasing the cell temperature. Doses of 1500 ppm and 3000 ppm of the INHIBEX concentration were tested in the cell. Dissociation temperatures were then compared for hydrates formed in the presence of PVCap and INHIBEX. The influence of the INHIBEX concentration on dissociation temperature was also investigated. Results of the study showed that hydrates containing INHIBEX dissociated at lower temperatures than hydrate systems using PVCap. INHIBEX mixtures formed using 3000 ppm of INHIBEX had higher dissociation temperatures than mixtures with INHIBEX at 1500 ppm. It was concluded that the hydrophobicity of the alkoxy group within the glycol ethers caused the molecules to associate with the dissolved polymers. The presence of butyl glycol decreased the hydrate dissociation temperature observed for PVCap systems. 4 refs., 2 tabs., 6 figs.

  7. Prevention of organic iodide formation in BWR`s

    Energy Technology Data Exchange (ETDEWEB)

    Karjunen, T. [Finnish Centre for Radiation and Nuclear Safety, Helsinki (Finland); Laitinen, T.; Piippo, J.; Sirkiae, P. [VTT Manufacturing Technology (Finland)

    1996-12-01

    During an accident, many different forms of iodine may emerge. Organic iodides, such as methyl iodide and ethyl iodide, are relatively volatile, and thus their appearance leads to increased concentration of gaseous iodine. Since organic iodides are also relatively immune to most accident mitigation measures, such as sprays and filters, they can affect the accident source term significantly even when only a small portion of iodine is in organic form. Formation of organic iodides may not be limited by the amount of organic substances available. Excessive amounts of methane can be produced, for example, during oxidation of boron carbide, which is used in BWR`s as a neutron absorber material. Another important source is cable insulation. In a BWR, a large quantity of cables is placed below the pressure vessel. Thus a large quantity of pyrolyse gases will be produced, should the vessel fail. Organic iodides can be formed as a result of many different reactions, but at least in certain conditions the main reaction takes place between an organic radical produced by radiolysis and elemental iodine. A necessary requirement for prevention of organic iodide production is therefore that the pH in the containment water pools is kept high enough to eliminate formation of elemental iodine. In a typical BWR the suppression pool water is usually unbuffered. As a result, the pH may be dominated by chemicals introduced during an accident. If no system for adding basic chemicals is operable, the main factor affecting pool water pH may be hydrochloric acid released during cable degradation. Should this occur, the conditions could be very favorable for production of elemental iodine and, consequently, formation of organic iodides. Although high pH is necessary for iodine retention, it could have also adverse effects. High pH may, for example, accelerate corrosion of containment materials and alter the characteristics of the solid corrosion products. (author) 6 figs., 1 tab., 13 refs.

  8. Thermoresponsive Microcarriers for Smart Release of Hydrate Inhibitors under Shear Flow.

    Science.gov (United States)

    Lee, Sang Seok; Park, Juwoon; Seo, Yutaek; Kim, Shin-Hyun

    2017-05-24

    The hydrate formation in subsea pipelines can cause oil and gas well blowout. To avoid disasters, various chemical inhibitors have been developed to prevent or delay the hydrate formation and growth. Nevertheless, direct injection of the inhibitors results in environmental contamination and cross-suppression of inhibition performance in the presence of other inhibitors against corrosion and/or formation of scale, paraffin, and asphaltene. Here, we suggest a new class of microcarriers that encapsulate hydrate inhibitors at high concentration and release them on demand without active external triggering. The key to the success in microcarrier design lies in the temperature dependence of polymer brittleness. The microcarriers are microfluidically created to have an inhibitor-laden water core and polymer shell by employing water-in-oil-in-water (W/O/W) double-emulsion drops as a template. As the polymeric shell becomes more brittle at a lower temperature, there is an optimum range of shell thickness that renders the shell unstable at temperature responsible for hydrate formation under a constant shear flow. We precisely control the shell thickness relative to the radius by microfluidics and figure out the optimum range. The microcarriers with the optimum shell thickness are selectively ruptured by shear flow only at hydrate formation temperature and release the hydrate inhibitors. We prove that the released inhibitors effectively retard the hydrate formation without reduction of their performance. The microcarriers that do not experience the hydration formation temperature retain the inhibitors, which can be easily separated from ruptured ones for recycling by exploiting the density difference. Therefore, the use of microcarriers potentially minimizes the environmental damages.

  9. Gas hydrates

    Digital Repository Service at National Institute of Oceanography (India)

    Ramprasad, T.

    Fuels in India’s Energy Future. Workshop on “Alternate Fuels in India’s Energy Future”, held at Hotel International, New Delhi,19 Sept 2006 , Jointly organised by CII,ERM and British High Commission Bangs, N.L., D.S. Sawyer, X. Golovchenko... hydrates: relevance to world margin stability and climatic change, Tutorial book: Gent, Belgium, pp. 1-37. Sloan, E. D., 1998, Clathrate hydrates of natural gases. 2 nd edition: Marcel Dekker, Inc., New York, pp705. Stakes...

  10. THE EFFECT OF GAS HYDRATES DISSOCIATION AND DRILLING FLUIDS INVASION UPON BOREHOLE STABILITY IN OCEANIC GAS HYDRATES-BEARING SEDIMENT

    Science.gov (United States)

    Ning, F.; Wu, N.; Jiang, G.; Zhang, L.

    2009-12-01

    bohole. If the formation has a low permeability and is heated quickly, the dissociated gas and water couldn’t flow away in time, which is likely to bring a hazard of excess pore pressure. Especially in the area near the wall of borehole, the increase degree of pore pressure is high than other area because the dissociation of gas hydrates is relatively violent and hydraulic gradient is bigger. We also studied the distribution of water saturation around borehole after 10min, 30min and 60min respectively. It revealed that along with the invasion of drilling fluid and dissociation of gas hydrate, the degree of water saturation increased gradually. The effect of gas hydrate dissociation and drilling fluids invasion on borehole stability is to weaken mechanical properties of wellbore and change the pore pressure, then changes the effective stress of gas hydrates-bearing sediment. So temperature, pressure in the borehole and filter loss of drilling fluids should be controlled strictly to prevent gas hydrates from decomposing largely and in order to keep the borehole stability in the gas hydrates-bearing formations.

  11. Gas hydrates in gas storage caverns; Gashydrate bei der Gaskavernenspeicherung

    Energy Technology Data Exchange (ETDEWEB)

    Groenefeld, P. [Kavernen Bau- und Betriebs-GmbH, Hannover (Germany)

    1997-12-31

    Given appropriate pressure and temperature conditions the storage of natural gas in salt caverns can lead to the formation of gas hydrates in the producing well or aboveground operating facilities. This is attributable to the stored gas becoming more or less saturated with water vapour. The present contribution describes the humidity, pressure, and temperature conditions conducive to gas hydrate formation. It also deals with the reduction of the gas removal capacity resulting from gas hydrate formation, and possible measures for preventing hydrate formation such as injection of glycol, the reduction of water vapour absorption from the cavern sump, and dewatering of the cavern sump. (MSK) [Deutsch] Bei der Speicherung von Erdgas in Salzkavernen kann es unter entsprechenden Druck- und Temperaturverhaeltnissen zur Gashydratbildung in den Foerdersonden oder obertaegigen Betriebseinrichtungen kommen, weil sich das eingelagerte Gas mehr oder weniger mit Wasserdampf aufsaettigt. Im Folgenden werden die Feuchtigkeits-, Druck- und Temperaturbedingungen, die zur Hydratbildung fuehren erlaeutert. Ebenso werden die Verringerung der Auslagerungskapazitaet durch die Hydratbildung, Massnahmen zur Verhinderung der Hydratbildung wie die Injektion von Glykol, die Verringerung der Wasserdampfaufnahme aus dem Kavernensumpf und die Entwaesserung der Kavernensumpfs selbst beschrieben.

  12. Randomized clinical trial of prevention of seroma formation after mastectomy by local methylprednisolone injection

    DEFF Research Database (Denmark)

    Qvamme, G; Axelsson, C. K.; Lanng, C

    2015-01-01

    BACKGROUND: Seroma formation, the most prevalent postoperative complication after mastectomy, is an inflammatory process that is potentially preventable via local steroid administration. This study investigated the effect of local steroid administration on seroma formation. METHODS: This was a do...

  13. Flow assurance intervention, hydrates remediation

    Energy Technology Data Exchange (ETDEWEB)

    Mancini, Christopher S. [Oceaneering International Inc., Houston, TX (United States)

    2012-07-01

    This paper addresses the issues of removing hydrates in sub sea flow lines and associated equipment with an Remotely Operated Vehicle (ROV) of opportunity and a multi-service-vessel (MSV). The paper is split into three topics: the equipment used with the ROV, assessing the interface points and handling fluids produced from drawing down the pressure. Each section is explained thoroughly and backed up with real world experience. The equipment section details information from actual jobs performed and why the particular components were utilized. The system is generally contained in an ROV mounted skid. Pumps are utilized to draw down the pressure inside the hydrated section of equipment, removing one of the three necessary components for hydrates formation. Once the section is pumped down, several options exist for handling the fluids pumped out of the system: pumping to surface, re-injection into the well, or injection into an operating flow line. This method of hydrates remediation is both economical and timely. Hydrate blockages form in low temperatures and high pressures. Reducing the pressure or increasing the temperature so the conditions lie to the right of the hydrate dissociation curve will slowly decompose the blockage. Depressurization and the use of MEG or methanol will give favorable conditions to remove the hydrate plug. Oceaneering has the capabilities to remove hydrates using the FRS in conjunction with an installation vessel to dispose of the gas and fluid removed from the flow line. Hydrate remediation techniques should be implemented into the initial design to reduce costs later. The cost of stopped production combined with the day rate for equipment needed for hydrate removal outweighs the costs if no technique is utilized. (author)

  14. Structure and composition analysis of natural gas hydrates: 13C NMR spectroscopic and gas uptake measurements of mixed gas hydrates.

    Science.gov (United States)

    Seo, Yutaek; Kang, Seong-Pil; Jang, Wonho

    2009-09-03

    Gas hydrates are becoming an attractive way of storing and transporting large quantities of natural gas, although there has been little effort to understand the preferential occupation of heavy hydrocarbon molecules in hydrate cages. In this work, we present the formation kinetics of mixed hydrate based on a gas uptake measurement during hydrate formation, and how the compositions of the hydrate phase are varied under corresponding formation conditions. We also examine the effect of silica gel pores on the physical properties of mixed hydrate, including thermodynamic equilibrium, formation kinetics, and hydrate compositions. It is expected that the enclathration of ethane and propane is faster than that of methane early stage hydrate formation, and later methane becomes the dominant component to be enclathrated due to depletion of heavy hydrocarbons in the vapor phase. The composition of the hydrate phase seems to be affected by the consumed amount of natural gas, which results in a variation of heating value of retrieved gas from mixed hydrates as a function of formation temperature. 13C NMR experiments were used to measure the distribution of hydrocarbon molecules over the cages of hydrate structure when it forms either from bulk water or water in silica gel pores. We confirm that 70% of large cages of mixed hydrate are occupied by methane molecules when it forms from bulk water; however, only 19% of large cages of mixed hydrate are occupied by methane molecules when it forms from water in silica gel pores. This result indicates that the fractionation of the hydrate phase with heavy hydrocarbon molecules is enhanced in silica gel pores. In addition when heavy hydrocarbon molecules are depleted in the vapor phase during the formation of mixed hydrate, structure I methane hydrate forms instead of structure II mixed hydrate and both structures coexist together, which is also confirmed by 13C NMR spectroscopic analysis.

  15. Skin hydration effects, film formation time, and physicochemical properties of a moisture mask containing Monostroma nitidium water-soluble mucilage.

    Science.gov (United States)

    Chen, Rong Huei; Chen, Weei Yuu

    2003-01-01

    The objectives of the study were to explore the effects of using the water-soluble mucilage of Monostroma nitidium to replace the humectant and half of the thickening agent on the rheological properties, color, storage stability, water-holding capacity, and film formation time of moisture masks thus prepared. Results showed that moisture masks containing water-soluble mucilage were pseudoplaxtic fluids. The apparent viscosity of these moisture masks decreased with increasing shear rate but increased with increasing concentration of the aqueous extracts used. The water-holding capacity of moisture masks containing 1% aqueous extracts and 1% hydroxyethyl cellulose (HEC) were similar to those containing 2% HEC and 5% 1-3 butadiene (humectant) but better than those containing 2% methyl cellulose (MC) and 5% humectant. The film formation time of moisture masks containing different concentrations of aqueous extracts decreased with increasing concentration of the aqueous extract used. The storage stability of a moisture mask containing 1% aqueous extract and 1% HEC was similar to that containing 2% HEC and 5% humectant and better than those containing 2% MC and 5% humectant. The safety test resulted in no erythema based on the Draize score test. The pH was between 7.1 and 7.5 for all moisture masks studied.

  16. Preparation of americium metal of high purity and determination of the heat of formation of the hydrated trivalent americium ion

    International Nuclear Information System (INIS)

    Spirlet, J.C.

    1975-10-01

    In order to redetermine some physical and chemical properties of americium metal, several grams of Am-241 have been prepared by two independent methods: lanthanum reduction of the oxide and thermal dissociation of the intermetallic compound Pt 5 Am. After its separation from excess lanthanum or alloy constituent by evaporation, americium metal was further purified by sublimation at 1100 deg C and 10 -6 Torr. Irrespective of the method of preparation, the americium samples displayed the same d.h.c.p. crystal structure. As determined by vacuum hot extraction, the oxygen, nitrogen and hydrogen contents are equal to or smaller than 250, 50 and 20 ppm, respectively. The heats of solution of americium metal (d.c.h.p. structure) in aqueous hydrochloric acid solutions have been measured at 298.15+-0.05K. The standard enthalpy of formation of Am 3+ (aq) is obtained as -616.7+-1.2 kJ mol -1 [fr

  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. Does vitamin E-blended UHMWPE prevent biofilm formation?

    Science.gov (United States)

    Williams, Dustin L; Vinciguerra, John; Lerdahl, Julia M; Bloebaum, Roy D

    2015-03-01

    Biofilm-related periprosthetic infections are catastrophic to patients and clinicians. Data suggest the addition of vitamin E to UHMWPE may have the ability to reduce biofilm formation on the surface of UHMWPE; however, previous studies were performed using stagnant broth solutions that may not have simulated a physiologic environment. In addition, the observed differences in levels of bacterial attachment, though statistically significant, may not be clinically significant. We blended vitamin E with UHMWPE material and tested it for the ability to resist biofilm formation using a clinical isolate of methicillin-resistant Staphylococcus aureus (MRSA). Three additional materials were tested for comparison: highly crosslinked UHMWPE, compression-molded UHMWPE, and polyetheretherketone. We also determined whether the surface roughness of these materials facilitated biofilm formation. Using a flow cell system, samples of each material type were placed into separate chambers. A 10% solution of brain-heart infusion broth containing 10(5) colony-forming units (CFUs)/mL was flowed through the flow cell over 48 hours. The number of bacteria that adhered to the surface was quantified and biofilm formation was observed qualitatively using scanning electron microscopy. Optical profilometry was used to determine the surface roughness of each material type. Vitamin E-blended UHMWPE did not reduce biofilm formation of a clinically relevant strain of MRSA compared to materials that did not have vitamin E. More specifically, vitamin E-blended materials had similar amounts of biofilm formation (~ 8 log10 CFUs/cm(2)) compared to materials not containing vitamin E (~ 8.1 log10 CFUs/cm(2)) (p > 0.4). The roughness of vitamin E-blended material surfaces (mean ± SD: 1.85 ± 0.46 µm) compared to that of materials without vitamin E (2.06 ± 1.24 µm) did not appear to influence biofilm formation. Under physiologically relevant conditions, vitamin E-blended UHMWPE did not have the ability

  19. 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

  20. Methane Recovery from Hydrate-bearing Sediments

    Energy Technology Data Exchange (ETDEWEB)

    J. Carlos Santamarina; Costas Tsouris

    2011-04-30

    Gas hydrates are crystalline compounds made of gas and water molecules. Methane hydrates are found in marine sediments and permafrost regions; extensive amounts of methane are trapped in the form of hydrates. Methane hydrate can be an energy resource, contribute to global warming, or cause seafloor instability. This study placed emphasis on gas recovery from hydrate bearing sediments and related phenomena. The unique behavior of hydrate-bearing sediments required the development of special research tools, including new numerical algorithms (tube- and pore-network models) and experimental devices (high pressure chambers and micromodels). Therefore, the research methodology combined experimental studies, particle-scale numerical simulations, and macro-scale analyses of coupled processes. Research conducted as part of this project started with hydrate formation in sediment pores and extended to production methods and emergent phenomena. In particular, the scope of the work addressed: (1) hydrate formation and growth in pores, the assessment of formation rate, tensile/adhesive strength and their impact on sediment-scale properties, including volume change during hydrate formation and dissociation; (2) the effect of physical properties such as gas solubility, salinity, pore size, and mixed gas conditions on hydrate formation and dissociation, and it implications such as oscillatory transient hydrate formation, dissolution within the hydrate stability field, initial hydrate lens formation, and phase boundary changes in real field situations; (3) fluid conductivity in relation to pore size distribution and spatial correlation and the emergence of phenomena such as flow focusing; (4) mixed fluid flow, with special emphasis on differences between invading gas and nucleating gas, implications on relative gas conductivity for reservoir simulations, and gas recovery efficiency; (5) identification of advantages and limitations in different gas production strategies with

  1. Causes and preventive management of scale formation in oilfield ...

    African Journals Online (AJOL)

    ... removal of at least one scaling component from the system, pH reduction, choosing a surface that resists scale adhesion, application of physical fields example magnetic or electrostatic, the use of scale inhibitors and proactive application of scale prediction models or soft wares. Keywords: Scale formation, oilfield systems ...

  2. Prevention of biofilm formation in dialysis water treatment systems.

    Science.gov (United States)

    Smeets, Ed; Kooman, Jeroen; van der Sande, Frank; Stobberingh, Ellen; Frederik, Peter; Claessens, Piet; Grave, Willem; Schot, Arend; Leunissen, Karel

    2003-04-01

    Biofilm formations in dialysis systems may be relevant because they continuously release bacterial compounds and are resistant against disinfection. The aim of the study was to compare the development of biofilm between a water treatment system based on a single reverse osmosis unit producing purified dialysate water [bacterial count, 350 colony-forming unit (CFU)/L] (center A) and a water treatment system based on double reverse osmosis and electric deionization, which is continuously disinfected with ultraviolet light and treated with ozone once a week (bacterial count, 1 CFU/L) (center B). During a period of 12 weeks, biofilm formation was studied in the tubing segment between the water piping and the dialysis module, using four dialysis monitors in each center. On a weekly basis, tubing samples of 5 cm length (N = 96) were taken under aseptic conditions and investigated for microbiologic contamination [cystine lactose electrolyte-deficient (CLED) Agar], endotoxin levels [limulus amoeben lysate (LAL) gel test, cutoff value, 0.0125 EU/mL], and biofilm formation [electron scanning microscopy (SEM)]. In center A, tube cultures were positive (>100 CFU/mL) in 16% of samples at 22 degrees C and 37 degrees C, compared to 3% of samples of center B (P tubing samples of center A and negative in all of the samples of center B (P < 0.05). Biofilm was present in 91.7% of the samples of center A (Fig. 1), and only present in one sample (taken after 9 weeks) of center B (P < 0.05) (Fig. 2). In center A, biofilm formation was already observed after 1 week. In contrast to a standard water treatment system producing purified water, the use of a system producing highly purified water, which is also treated with regular disinfection procedures, leads to a significant reduction in biofilm formation, bacterial growth, and endotoxin levels in a highly vulnerable part of a water treatment system.

  3. Hydrates plugs dissociation in pipelines; Dissociation des bouchons d'hydrates de gaz dans les conduites petrolieres sous-marines

    Energy Technology Data Exchange (ETDEWEB)

    Nguyen Hong, D.

    2005-03-15

    Natural gas hydrates plugs cause problems during drilling, well operations, production, transportation and processing of oil and gas. Especially, it is a very serious problem in off-shore oil transportation where low temperature and high pressure become more and more favourable to gas hydrate formation as the new production wells are more and more deeper. Up to now, although many studies have been developed concerning the possibility of preventing pipe plugging, there is limited information in open literature on hydrate plugs dissociation and all models in literature are numerically complicated. In this study, hydrate plugs are formed from water in n-dodecane mixture with addition of a dispersant E102B in two different experimental apparatus in order to obtain hydrates plugs with different sizes (diameter of 7, 10.75 and 12 cm). Then, the plugs are dissociated by the method of two-sided depressurization. In this paper, we propose a numerical model which describes the dissociation of gas hydrate plugs in pipelines. The numerical model, which is constructed for cylindrical coordinates and for two-sided pressurization, is based on enthalpy method. We present also an approximate analytical model which has an average error 2.7 % in comparison with the numerical model. The excellent agreement between our experimental results, literature data and the two models shows that the models give a good prediction independently of the pipeline diameter, plug porosity and gas. The simplicity of the analytical model will make it easier in industrial applications. (author)

  4. Excess pore pressure and slope failures resulting from gas-hydrates dissociation and dissolution

    OpenAIRE

    Sultan, Nabil

    2007-01-01

    Parameters affecting gas hydrate formation include temperature, pore pressure, gas chemistry, and pore-water salinity. Any change in the equilibrium of these parameters may result in dissociation (gas-hydrate turns into free gas/water mixture) and/or dissolution (gas-hydrate becomes mixture of water and dissolved gas) of the gas hydrate. While, gas-hydrate dissociation at the base of the Gas Hydrate Occurrence Zone (GHOZ) is often considered as a major cause of sediment deformation and submar...

  5. Thermal conductivity of hydrate-bearing sediments

    Science.gov (United States)

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

    2009-01-01

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

  6. Hydrate-Bearing Clayey Sediments: Morphology, Physical Properties, Production and Engineering/Geological Implications

    Energy Technology Data Exchange (ETDEWEB)

    Dai, Sheng [Georgia Tech Research Corporation, Atlanta, GA (United States); Santamarina, J. Carlos [King Abdulaziz Univ., Jeddah (Saudi Arabia)

    2017-12-30

    Fine-grained sediments host more than 90 percent of global gas hydrate accumulation. However, hydrate formation in clay-dominated sediments is less understood and characterized than other types of hydrate occurrence. There is an inadequate understanding of hydrate formation mechanisms, segregation structures, hydrate lens topology, system connectivity, and physical macro-scale properties of clay-dominated hydrate-bearing sediments. This situation hinders further analyses of the global carbon budget as well as engineering challenges/solutions related to hydrate instability and production. This project studies hydrate-bearing clay-dominated sediments with emphasis on the enhanced fundamental understanding of hydrate formation and resulting morphology, the development laboratory techniques to emulate natural hydrate formations, the assessment of analytical tools to predict physical properties, the evaluation of engineering and geological implications, and the advanced understanding of gas production potential from finegrained sediments.

  7. Gas Hydrate Storage of Natural Gas

    Energy Technology Data Exchange (ETDEWEB)

    Rudy Rogers; John Etheridge

    2006-03-31

    Environmental and economic benefits could accrue from a safe, above-ground, natural-gas storage process allowing electric power plants to utilize natural gas for peak load demands; numerous other applications of a gas storage process exist. A laboratory study conducted in 1999 to determine the feasibility of a gas-hydrates storage process looked promising. The subsequent scale-up of the process was designed to preserve important features of the laboratory apparatus: (1) symmetry of hydrate accumulation, (2) favorable surface area to volume ratio, (3) heat exchanger surfaces serving as hydrate adsorption surfaces, (4) refrigeration system to remove heat liberated from bulk hydrate formation, (5) rapid hydrate formation in a non-stirred system, (6) hydrate self-packing, and (7) heat-exchanger/adsorption plates serving dual purposes to add or extract energy for hydrate formation or decomposition. The hydrate formation/storage/decomposition Proof-of-Concept (POC) pressure vessel and supporting equipment were designed, constructed, and tested. This final report details the design of the scaled POC gas-hydrate storage process, some comments on its fabrication and installation, checkout of the equipment, procedures for conducting the experimental tests, and the test results. The design, construction, and installation of the equipment were on budget target, as was the tests that were subsequently conducted. The budget proposed was met. The primary goal of storing 5000-scf of natural gas in the gas hydrates was exceeded in the final test, as 5289-scf of gas storage was achieved in 54.33 hours. After this 54.33-hour period, as pressure in the formation vessel declined, additional gas went into the hydrates until equilibrium pressure/temperature was reached, so that ultimately more than the 5289-scf storage was achieved. The time required to store the 5000-scf (48.1 hours of operating time) was longer than designed. The lower gas hydrate formation rate is attributed to a

  8. Entrapment of Hydrate-coated Gas Bubbles into Oil and Separation of Gas and Hydrate-film; Seafloor Experiments with ROV

    Science.gov (United States)

    Hiruta, A.; Matsumoto, R.

    2015-12-01

    We trapped gas bubbles emitted from the seafloor into oil-containing collector and observed an unique phenomena. Gas hydrate formation needs water for the crystal lattice; however, gas hydrates in some areas are associated with hydrophobic crude oil or asphalt. In order to understand gas hydrate growth in oil-bearing sediments, an experiment with cooking oil was made at gas hydrate stability condition. We collected venting gas bubbles into a collector with canola oil during ROV survey at a gas hydrate area in the eastern margin of the Sea of Japan. When the gas bubbles were trapped into collector with oil, gas phase appeared above the oil and gas hydrates, between oil and gas phase. At this study area within gas hydrate stability condition, control experiment with oil-free collector suggested that gas bubbles emitted from the seafloor were quickly covered with gas hydrate film. Therefore it is improbable that gas bubbles entered into the oil phase before hydrate skin formation. After the gas phase formation in oil-containing collector, the ROV floated outside of hydrate stability condition for gas hydrate dissociation and re-dived to the venting site. During the re-dive within hydrate stability condition, gas hydrate was not formed. The result suggests that moisture in the oil is not enough for hydrate formation. Therefore gas hydrates that appeared at the oil/gas phase boundary were already formed before bubbles enter into the oil. Hydrate film is the only possible origin. This observation suggests that hydrate film coating gas hydrate was broken at the sea water/oil boundary or inside oil. Further experiments may contribute for revealing kinetics of hydrate film and formation. This work was a part of METI (Ministry of Economy, Trade and Industry)'s project entitled "FY2014 Promoting research and development of methane hydrate". We also appreciate support of AIST (National Institute of Advanced Industrial Science and Technology).

  9. Protons in hydrated protein powders

    International Nuclear Information System (INIS)

    Careri, G.; Bruni, F.; Consolini, G.

    1995-01-01

    Previous work from this laboratory has shown that hydrated lysozyme powders exhibit a dielectric behaviour, due to proton conductivity, explainable within the frame of percolation theory. Long range proton displacement appears only above the critical hydration for percolation, when the 2-dimensional motion takes place on fluctuating clusters of hydrogen-bonded water molecules adsorbed on the protein surface. The emergence of biological function, enzyme catalysis, was found to coincide with the critical hydration for percolation. More recently, we have evaluated the protonic conductivity of hydrated lysozyme powders, from room down to liquid N 2 temperature. In the high temperature limit a classical isotopic effect can be detected, and the conductivity follows the familiar Arrhenius law for thermally activated hopping. In the low temperature region the conductivity shows a temperature dependence in agreement with prediction by the theory of dissipative quantum tunneling. Below room temperature the static dielectric constant, and the dielectric relaxation time for charge transport showed an increase likely to be identified with the formation of a polaronic-solitonic species as predicted by the theory of proton transport in water chains, a species which displays a larger effective mass and a larger dipole moment that the usual hydrated protonic defects. The purpose of this paper is twofold. In the first section we present a tutorial report of some previous experimental results on proton displacement in slightly hydrated biological systems at room temperature, to show that in these systems the emergence of biological systems at room temperature, to show that in these systems the emergence of biological function coincides with the onset of percolative pathways in the water molecules network adsorbed on the surface of biomolecules. In the second section, we report on preliminary data on the dielectric relaxation of hydrated lysozyme below room temperature, to suggest

  10. 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

  11. Investigations into surfactant/gas hydrate relationship

    Energy Technology Data Exchange (ETDEWEB)

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

    2007-03-15

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

  12. Clathrate hydrate tuning for technological purposes

    Science.gov (United States)

    di Profio, Pietro; Germani, Raimondo; Savelli, Gianfranco

    2010-05-01

    Gas hydrates are being increasingly considered as convenient media for gas storage and transportation as the knowledge of their properties increases, in particular as relates to methane and hydrogen. Clathrate hydrates may also represent a feasible sequestration technology for carbon dioxide, due to a well defined P/T range of stability, and several research programs are addressing this possibility. Though the understanding of the molecular structure and supramolecular interactions which are responsible of most properties of hydrates have been elucitated in recent years, the underlying theoretical physico-chemical framework is still poor, especially as relates to the role of "conditioners" (inhibitors and promoters) from the molecular/supramolecular point of view. In the present communication we show some results from our research approach which is mainly focused on the supramolecular properties of clathrate hydrate systems - and their conditioners - as a way to get access to a controlled modulation of the formation, dissociation and stabilization of gas hydrates. In particular, this communication will deal with: (a) a novel, compact apparatus for studying the main parameters of formation and dissociation of gas hydrates in a one-pot experiment, which can be easily and rapidly carried out on board of a drilling ship;[1] (b) the effects of amphiphile molecules (surfactants) as inhibitors or promoters of gas hydrate formation;[2] (c) a novel nanotechnology for a reliable and quick production of hydrogen hydrates, and its application to fuel cells;[3,4] and (d) the development of a clathrate hydrate tecnology for the sequestration and geological storage of man-made CO2, possibly with concomitant recovery of natural gas from NG hydrate fields. Furthermore, the feasibility of catalyzing the reduction of carbon dioxide to energy-rich species by hydrates is being investigated. [1] Di Profio, P., Germani, R., Savelli, G., International Patent Application PCT/IT2006

  13. Artificial Hydration and Nutrition

    Science.gov (United States)

    ... Crisis Situations Pets and Animals myhealthfinder Food and Nutrition Healthy Food Choices Weight Loss and Diet Plans ... Your Health Resources Healthcare Management Artificial Hydration and Nutrition Artificial Hydration and Nutrition Share Print Patients who ...

  14. Nicorandil prevents sirolimus-induced production of reactive oxygen species, endothelial dysfunction, and thrombus formation

    Directory of Open Access Journals (Sweden)

    Ken Aizawa

    2015-03-01

    Full Text Available Sirolimus (SRL is widely used to prevent restenosis after percutaneous coronary intervention. However, its beneficial effect is hampered by complications of thrombosis. Several studies imply that reactive oxygen species (ROS play a critical role in endothelial dysfunction and thrombus formation. The present study investigated the protective effect of nicorandil (NIC, an anti-angina agent, on SRL-associated thrombosis. In human coronary artery endothelial cells (HCAECs, SRL stimulated ROS production, which was prevented by co-treatment with NIC. The preventive effect of NIC on ROS was abolished by 5-hydroxydecanoate but not by 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one. NIC also inhibited SRL-induced up-regulation of NADPH oxidase subunit p22phox mRNA. Co-treatment with NIC and SRL significantly up-regulated superoxide dismutase 2. NIC treatment significantly improved SRL-induced decrease in viability of HCAECs. The functional relevance of the preventive effects of NIC on SRL-induced ROS production and impairment of endothelial viability was investigated in a mouse model of thrombosis. Pretreatment with NIC inhibited the SRL-induced acceleration of FeCl3-initiated thrombus formation and ROS production in the testicular arteries of mice. In conclusion, NIC prevented SRL-induced thrombus formation, presumably due to the reduction of ROS and to endothelial protection. The therapeutic efficacy of NIC could represent an additional option in the prevention of SRL-related thrombosis.

  15. Novel understanding of calcium silicate hydrate from dilute hydration

    KAUST Repository

    Zhang, Lina

    2017-05-13

    The perspective of calcium silicate hydrate (C-S-H) is still confronting various debates due to its intrinsic complicated structure and properties after decades of studies. In this study, hydration at dilute suspension of w/s equaling to 10 was conducted for tricalcium silicate (C3S) to interpret long-term hydration process and investigate the formation, structure and properties of C-S-H. Based on results from XRD, IR, SEM, NMR and so forth, loose and dense clusters of C-S-H with analogous C/S ratio were obtained along with the corresponding chemical formulae proposed as Ca5Si4O13∙6.2H2O. Crystalline structure inside C-S-H was observed by TEM, which was allocated at the foil-like proportion as well as the edge of wrinkles of the product. The long-term hydration process of C3S in dilute suspension could be sketchily described as migration of calcium hydroxide and in-situ growth of C-S-H with equilibrium silicon in aqueous solution relatively constant and calcium varied.

  16. Gas hydrate and humans

    Science.gov (United States)

    Kvenvolden, K.A.

    2000-01-01

    The potential effects of naturally occurring gas hydrate on humans are not understood with certainty, but enough information has been acquired over the past 30 years to make preliminary assessments possible. Three major issues are gas hydrate as (1) a potential energy resource, (2) a factor in global climate change, and (3) a submarine geohazard. The methane content is estimated to be between 1015 to 1017 m3 at STP and the worldwide distribution in outer continental margins of oceans and in polar regions are significant features of gas hydrate. However, its immediate development as an energy resource is not likely because there are various geological constraints and difficult technological problems that must be solved before economic recovery of methane from hydrate can be achieved. The role of gas hydrate in global climate change is uncertain. For hydrate methane to be an effective greenhouse gas, it must reach the atmosphere. Yet there are many obstacles to the transfer of methane from hydrate to the atmosphere. Rates of gas hydrate dissociation and the integrated rates of release and destruction of the methane in the geo/hydro/atmosphere are not adequately understood. Gas hydrate as a submarine geohazard, however, is of immediate and increasing importance to humans as our industrial society moves to exploit seabed resources at ever-greater depths in the waters of our coastal oceans. Human activities and installations in regions of gas-hydrate occurrence must take into account the presence of gas hydrate and deal with the consequences of its presence.

  17. Method for production of hydrocarbons from hydrates

    Science.gov (United States)

    McGuire, Patrick L.

    1984-01-01

    A method of recovering natural gas entrapped in frozen subsurface gas hydrate formations in arctic regions. A hot supersaturated solution of CaCl.sub.2 or CaBr.sub.2, or a mixture thereof, is pumped under pressure down a wellbore and into a subsurface hydrate formation so as to hydrostatically fracture the formation. The CaCl.sub.2 /CaBr.sub.2 solution dissolves the solid hydrates and thereby releases the gas entrapped therein. Additionally, the solution contains a polymeric viscosifier, which operates to maintain in suspension finely divided crystalline CaCl.sub.2 /CaBr.sub.2 that precipitates from the supersaturated solution as it is cooled during injection into the formation.

  18. The use of theory based semistructured elicitation questionnaires: formative research for CDC's Prevention Marketing Initiative.

    Science.gov (United States)

    Middlestadt, S E; Bhattacharyya, K; Rosenbaum, J; Fishbein, M; Shepherd, M

    1996-01-01

    Through one of its many HIV prevention programs, the Prevention Marketing Initiative, the Centers for Disease Control and Prevention promotes a multifaceted strategy for preventing the sexual transmission of HIV/AIDS among people less than 25 years of age. The Prevention Marketing Initiative is an application of marketing and consumer-oriented technologies that rely heavily on behavioral research and behavior change theories to bring the behavioral and social sciences to bear on practical program planning decisions. One objective of the Prevention Marketing Initiative is to encourage consistent and correct condom use among sexually active young adults. Qualitative formative research is being conducted in several segments of the population of heterosexually active, unmarried young adults between 18 and 25 using a semistructured elicitation procedure to identify and understand underlying behavioral determinants of consistent condom use. The purpose of this paper is to illustrate the use of this type of qualitative research methodology in designing effective theory-based behavior change interventions. Issues of research design and data collection and analysis are discussed. To illustrate the methodology, results of content analyses of selected responses to open-ended questions on consistent condom use are presented by gender (male, female), ethnic group (white, African American), and consistency of condom use (always, sometimes). This type of formative research can be applied immediately to designing programs and is invaluable for valid and relevant larger-scale quantitative research.

  19. Comparative Assessment of Advanced Gay Hydrate Production Methods

    Energy Technology Data Exchange (ETDEWEB)

    M. D. White; B. P. McGrail; S. K. Wurstner

    2009-06-30

    Displacing natural gas and petroleum with carbon dioxide is a proven technology for producing conventional geologic hydrocarbon reservoirs, and producing additional yields from abandoned or partially produced petroleum reservoirs. Extending this concept to natural gas hydrate production offers the potential to enhance gas hydrate recovery with concomitant permanent geologic sequestration. Numerical simulation was used to assess a suite of carbon dioxide injection techniques for producing gas hydrates from a variety of geologic deposit types. Secondary hydrate formation was found to inhibit contact of the injected CO{sub 2} regardless of injectate phase state, thus diminishing the exchange rate due to pore clogging and hydrate zone bypass of the injected fluids. Additional work is needed to develop methods of artificially introducing high-permeability pathways in gas hydrate zones if injection of CO{sub 2} in either gas, liquid, or micro-emulsion form is to be more effective in enhancing gas hydrate production rates.

  20. Spectroscopic methods in gas hydrate research.

    Science.gov (United States)

    Rauh, Florian; Mizaikoff, Boris

    2012-01-01

    Gas hydrates are crystalline structures comprising a guest molecule surrounded by a water cage, and are particularly relevant due to their natural occurrence in the deep sea and in permafrost areas. Low molecular weight molecules such as methane and carbon dioxide can be sequestered into that cage at suitable temperatures and pressures, facilitating the transition to the solid phase. While the composition and structure of gas hydrates appear to be well understood, their formation and dissociation mechanisms, along with the dynamics and kinetics associated with those processes, remain ambiguous. In order to take advantage of gas hydrates as an energy resource (e.g., methane hydrate), as a sequestration matrix in (for example) CO(2) storage, or for chemical energy conservation/storage, a more detailed molecular level understanding of their formation and dissociation processes, as well as the chemical, physical, and biological parameters that affect these processes, is required. Spectroscopic techniques appear to be most suitable for analyzing the structures of gas hydrates (sometimes in situ), thus providing access to such information across the electromagnetic spectrum. A variety of spectroscopic methods are currently used in gas hydrate research to determine the composition, structure, cage occupancy, guest molecule position, and binding/formation/dissociation mechanisms of the hydrate. To date, the most commonly applied techniques are Raman spectroscopy and solid-state nuclear magnetic resonance (NMR) spectroscopy. Diffraction methods such as neutron and X-ray diffraction are used to determine gas hydrate structures, and to study lattice expansions. Furthermore, UV-vis spectroscopic techniques and scanning electron microscopy (SEM) have assisted in structural studies of gas hydrates. Most recently, waveguide-coupled mid-infrared spectroscopy in the 3-20 μm spectral range has demonstrated its value for in situ studies on the formation and dissociation of gas

  1. Formative research in a school-based obesity prevention program for Native American school children (Pathways)

    Science.gov (United States)

    Gittelsohn, Joel; Evans, Marguerite; Helitzer, Deborah; Anliker, Jean; Story, Mary; Metcalfe, Lauve; Davis, Sally; Cloud, Patty Iron

    2016-01-01

    This paper describes how formative research was developed and implemented to produce obesity prevention interventions among school children in six different Native American nations that are part of the Pathways study. The formative assessment work presented here was unique in several ways: (1) it represents the first time formative research methods have been applied across multiple Native American tribes; (2) it is holistic, including data collection from parents, children, teachers, administrators and community leaders; and (3) it was developed by a multi-disciplinary group, including substantial input from Native American collaborators. The paper describes the process of developing the different units of the protocol, how data collection was implemented and how analyses were structured around the identification of risk behaviors. An emphasis is placed on describing which units of the formative assessment protocol were most effective and which were less effective. PMID:10181023

  2. 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.

  3. Origins of hydration lubrication.

    Science.gov (United States)

    Ma, Liran; Gaisinskaya-Kipnis, Anastasia; Kampf, Nir; Klein, Jacob

    2015-01-14

    Why is friction in healthy hips and knees so low? Hydration lubrication, according to which hydration shells surrounding charges act as lubricating elements in boundary layers (including those coating cartilage in joints), has been invoked to account for the extremely low sliding friction between surfaces in aqueous media, but not well understood. Here we report the direct determination of energy dissipation within such sheared hydration shells. By trapping hydrated ions in a 0.4-1 nm gap between atomically smooth charged surfaces as they slide past each other, we are able to separate the dissipation modes of the friction and, in particular, identify the viscous losses in the subnanometre hydration shells. Our results shed light on the origins of hydration lubrication, with potential implications both for aqueous boundary lubricants and for biolubrication.

  4. Control and prevention of ice formation and accretion on heat exchangers for ventilation systems

    DEFF Research Database (Denmark)

    Rahimi, Maral; Afshari, Alireza

    2015-01-01

    In cold climates, the application of mechanical ventilation systems with heat recovery like are airto-air exchangers is used for reducing energy consumption for heating buildings by transferring heat exhausted air to supply air. However, increase efficiency of heat exchanger results in lower...... exhaust air temperatures and Ice formation on heat exchanger fins, which can cause problem and is not favourable. Therefore, prevention and control of ice formation on heat exchangers is necessary. The existing methods are divided into two different methods: active and passive ice control methods...

  5. Indian National Gas Hydrate Program Expedition 01 report

    Science.gov (United States)

    Collett, Timothy S.; Riedel, M.; Boswell, R.; Presley, J.; Kumar, P.; Sathe, A.; Sethi, A.; Lall, M.V.; ,

    2015-01-01

    Gas hydrate is a naturally occurring “ice-like” combination of natural gas and water that has the potential to serve as an immense resource of natural gas from the world’s oceans and polar regions. However, gas-hydrate recovery is both a scientific and a technical challenge and much remains to be learned about the geologic, engineering, and economic factors controlling the ultimate energy resource potential of gas hydrate. The amount of natural gas contained in the world’s gas-hydrate accumulations is enormous, but these estimates are speculative and range over three orders of magnitude from about 2,800 to 8,000,000 trillion cubic meters of gas. By comparison, conventional natural gas accumulations (reserves and undiscovered, technically recoverable resources) for the world are estimated at approximately 440 trillion cubic meters. Gas recovery from gas hydrate is hindered because the gas is in a solid form and because gas hydrate commonly occurs in remote Arctic and deep marine environments. Proposed methods of gas recovery from gas hydrate generally deal with disassociating or “melting” in situ gas hydrate by heating the reservoir beyond the temperature of gas-hydrate formation, or decreasing the reservoir pressure below hydrate equilibrium. The pace of energy-related gas hydrate assessment projects has accelerated over the past several years.

  6. 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.)

  7. A numerical study of natural hydrate formation kinetics in petroleum pipelines by the phase field method: influence of the model parameters; Estudo da cinetica de formacao de hidratos em dutos de petroleo pelo metodo do campo de fase: influencia dos parametros do modelo

    Energy Technology Data Exchange (ETDEWEB)

    Oliveira, Mabelle Biancardi; Castro, Jose Adilson de; Silva, Alexandre Jose da; Ferreira, Alexandre Furtado [Universidade Federal Fluminense (UFF), Volta Redonda, RJ (Brazil). Pos-Graduacao em Engenharia Metalurgica], e-mail: mabelle@metal.eeimvr.uff.br, e-mail: adilson@metal.eeimvr.uff.br, e-mail: ajs@metal.eeimvr.uff.br, e-mail: furtado@metal.eeimvr.uff.br

    2006-07-01

    The objective of this work is to study the influence of the parameters of the phase field model field on the formation of natural hydrates. It was investigated parameters such as superficial tension, effect of the super-cooling, homogeneous and heterogeneous nucleation. The influence of these parameters was analyzed according to morphology of the interface and the rate of formation. The mathematical model to describe the evolution of the natural hydrates formation is based on the simultaneous solution of the phase and energy equations. The finite volume numerical method was used to discretize the governing differential equations. Results of the simulation indicated that the reduction of the superficial tension leads to the increase of the surface rugosity, interface thickness and instability of the interface resulting in a decrease of the rate growth. In order to investigate the nucleation effect of the natural hydrates, two conditions had been simulated a) the random distribution of nuclei: where the evolution of formed hydrates suffered coalescence and the kinetic decreased due to impingement of hydrates regions and b) Nucleation in the pipeline wall, where rough interfaces were observed. (author)

  8. Parathyroid hormone may maintain bone formation in hibernating black bears (Ursus americanus) to prevent disuse osteoporosis.

    Science.gov (United States)

    Donahue, Seth W; Galley, Sarah A; Vaughan, Michael R; Patterson-Buckendahl, Patricia; Demers, Laurence M; Vance, Josef L; McGee, Meghan E

    2006-05-01

    Mechanical unloading of bone causes an imbalance in bone formation and resorption leading to bone loss and increased fracture risk. Black bears (Ursus americanus) are inactive for up to six months during hibernation, yet bone mineral content and strength do not decrease with disuse or aging. To test whether hibernating bears have biological mechanisms to prevent disuse osteoporosis, we measured the serum concentrations of hormones and growth factors involved in bone metabolism and correlated them with the serum concentration of a bone formation marker (osteocalcin). Serum was obtained from black bears over a 7-month duration that included periods of activity and inactivity. Both resorption and formation markers increased during hibernation, suggesting high bone turnover occurred during inactivity. However, bone formation appeared to be balanced with bone resorption. The serum concentration of parathyroid hormone (PTH) was higher in the hibernation (P=0.35) and post-hibernation (P=0.006) seasons relative to pre-hibernation levels. Serum leptin was lower (Phibernation relative to pre-hibernation and hibernation periods. Insulin-like growth factor I (IGF-I) decreased (Phibernation relative to pre-hibernation and reached its highest value during remobilization. There was no difference (P=0.64) in 25-OH vitamin D between the three seasons. Serum osteocalcin (bone formation marker) was significantly correlated with PTH, but not with leptin, IGF-I or 25-OH vitamin D. Osteocalcin and PTH were positively correlated when samples from all seasons were pooled and when only hibernation samples were considered, raising the possibility that the anabolic actions of PTH help maintain bone formation to prevent disuse osteoporosis. Prostaglandin E(2) (PGE(2)) release from MC3T3 osteoblastic cells was significantly affected by treatment with bear serum from different seasons (i.e. hibernation versus active periods). The seasonal changes in PGE(2) release showed trends similar to the

  9. Exploitation of subsea gas hydrate reservoirs

    Science.gov (United States)

    Janicki, Georg; Schlüter, Stefan; Hennig, Torsten; Deerberg, Görge

    2016-04-01

    Natural gas hydrates are considered to be a potential energy resource in the future. They occur in permafrost areas as well as in subsea sediments and are stable at high pressure and low temperature conditions. According to estimations the amount of carbon bonded in natural gas hydrates worldwide is two times larger than in all known conventional fossil fuels. Besides technical challenges that have to be overcome climate and safety issues have to be considered before a commercial exploitation of such unconventional reservoirs. The potential of producing natural gas from subsea gas hydrate deposits by various means (e.g. depressurization and/or injection of carbon dioxide) is numerically studied in the frame of the German research project »SUGAR«. The basic mechanisms of gas hydrate formation/dissociation and heat and mass transport in porous media are considered and implemented into a numerical model. The physics of the process leads to strong non-linear couplings between hydraulic fluid flow, hydrate dissociation and formation, hydraulic properties of the sediment, partial pressures and seawater solution of components and the thermal budget of the system described by the heat equation. This paper is intended to provide an overview of the recent development regarding the production of natural gas from subsea gas hydrate reservoirs. It aims at giving a broad insight into natural gas hydrates and covering relevant aspects of the exploitation process. It is focused on the thermodynamic principles and technological approaches for the exploitation. The effects occurring during natural gas production within hydrate filled sediment layers are identified and discussed by means of numerical simulation results. The behaviour of relevant process parameters such as pressure, temperature and phase saturations is described and compared for different strategies. The simulations are complemented by calculations for different safety relevant problems.

  10. The educative prevention of the early stage of educationist’s formation.

    OpenAIRE

    Marta Alfonso Nazco; Evaristo Reinoso Porra; Ana Consuelo Figueroa Carbonell

    2010-01-01

    The article introduces a characterization of the educative prevention stage at the early professional formation process of educacionist in Sancti Spìritus province. The study is done by the indication analysis of assistant, learning, permanence and behavior at youths who course pedagogical carrers, and haven’t expressed a desire stage yet. The main shown results dealt with the assumption of the searching variables and its indicators, the construction of instruments and the definition of aspec...

  11. Formative research to inform intervention development for diabetes prevention in the Republic of the Marshall Islands.

    Science.gov (United States)

    Cortes, L M; Gittelsohn, J; Alfred, J; Palafox, N A

    2001-12-01

    Formative research was conducted in the Republic of the Marshall Islands to help develop a diabetes prevention intervention. Methods included in-depth interviews, semistructured interviews, and direct observation of household behaviors in urban and remote settings. Foods were classified into two main conceptual spheres: foods from the islands/Marshallese foods and imported/American foods. Diabetes (nanimij in tonal) is a highly salient illness and is believed to be caused by foods high in fat and sugar, consumption of imported/American foods, family background, and the atomic bomb testing. Physical activity and eating a traditional diet were viewed as important for preventing diabetes. The traditional belief system links a large body with health, and a thin body with illness; however, perceptions are changing with increased acculturation and education about the health risks of obesity. These findings were used to develop a diabetes prevention home visit intervention currently being implemented and evaluated in Marshallese households.

  12. Effect of isotopy and temperature on hydration of alkanols

    Energy Technology Data Exchange (ETDEWEB)

    Korolev, V.P.; Batov, D.V.; Krestov, G.A.

    1987-07-10

    The authors determine isotope and temperature effects on the hydration of alkanols at a temperature of 278.15 K in solutions of water and heavy water. Aspects of isotopic exchange between hydrogen and deuterium are given as are enthalpies of hydration, evaporation, and dissolution for the alkanols. The possibility of weak hydrogen bond formation was examined.

  13. Putting the Deep Biosphere and Gas Hydrates on the Map

    Science.gov (United States)

    Sikorski, Janelle J.; Briggs, Brandon R.

    2016-01-01

    Microbial processes in the deep biosphere affect marine sediments, such as the formation of gas hydrate deposits. Gas hydrate deposits offer a large source of natural gas with the potential to augment energy reserves and affect climate and seafloor stability. Despite the significant interdependence between life and geology in the ocean, coverage…

  14. Nuclear Well Log Properties of Natural Gas Hydrate Reservoirs

    Science.gov (United States)

    Burchwell, A.; Cook, A.

    2015-12-01

    Characterizing gas hydrate in a reservoir typically involves a full suite of geophysical well logs. The most common method involves using resistivity measurements to quantify the decrease in electrically conductive water when replaced with gas hydrate. Compressional velocity measurements are also used because the gas hydrate significantly strengthens the moduli of the sediment. At many gas hydrate sites, nuclear well logs, which include the photoelectric effect, formation sigma, carbon/oxygen ratio and neutron porosity, are also collected but often not used. In fact, the nuclear response of a gas hydrate reservoir is not known. In this research we will focus on the nuclear log response in gas hydrate reservoirs at the Mallik Field at the Mackenzie Delta, Northwest Territories, Canada, and the Gas Hydrate Joint Industry Project Leg 2 sites in the northern Gulf of Mexico. Nuclear logs may add increased robustness to the investigation into the properties of gas hydrates and some types of logs may offer an opportunity to distinguish between gas hydrate and permafrost. For example, a true formation sigma log measures the thermal neutron capture cross section of a formation and pore constituents; it is especially sensitive to hydrogen and chlorine in the pore space. Chlorine has a high absorption potential, and is used to determine the amount of saline water within pore spaces. Gas hydrate offers a difference in elemental composition compared to water-saturated intervals. Thus, in permafrost areas, the carbon/oxygen ratio may vary between gas hydrate and permafrost, due to the increase of carbon in gas hydrate accumulations. At the Mallik site, we observe a hydrate-bearing sand (1085-1107 m) above a water-bearing sand (1107-1140 m), which was confirmed through core samples and mud gas analysis. We observe a decrease in the photoelectric absorption of ~0.5 barnes/e-, as well as an increase in the formation sigma readings of ~5 capture units in the water-bearing sand as

  15. Ecological and climatic consequences of phase instability of gas hydrates on the ocean bed

    Science.gov (United States)

    Balanyuk, I.; Dmitrievsky, A.; Akivis, T.; Chaikina, O.

    2009-04-01

    energy and gas that leads to explosion. Methane is the main natural source for power engineering specialists. It is transported by pipelines, and gas hydrate is dangerous in this case too. It can block the gas pipeline system forming the so-called "trombus" of "thermal ice". After that the pipes have to be opened. The mess of this strange ice discovered melts immediately releasing methane and water vapor. The trombus formation can be prevented by the temperature increase or the pressure decrease. Both methods are very uncomfortable under the conditions the pipelines work. The better method is thorough drying up of the gas because gas hydrate obviously cannot be formed without water. Gas hydrates attract attention not only as a fuel and chemical stuff but in relation to a serious anxiety of strong ecological and climatic problems that can occur as a result of methane release to the atmosphere due to both gas hydrate deposits development and minor changes in thermodynamic conditions in the vicinity of a threshold of gas hydrate phase stability. One of the most probable causes is the global warming of the Earth due to the hothouse effect because the specific absorption of the Earth heat radiation by methane (radiation effectivity) is 21 times higher than its absorption by carbonic gas. Analysis of the air trapped by polar ice show that contemporary increase of methane concentration in the atmosphere is unexampled for the last 160 thousands of years. The sources of this increase are not clear. Observer and latent methane bursts during natural gas hydrates decomposition can be considered as a probable source. Amount of methane hided in natural gas hydrates is 3000 times higher its amount in the atmosphere. Release of this hothouse potential would have terrible consequences for the humanity. The warming can cause further gas hydrates decomposition and released methane will cause the following warming. Thus, self-accelerating process can start. The most vulnerable for the

  16. The role of hydration in vocal fold physiology.

    Science.gov (United States)

    Sivasankar, Mahalakshmi; Leydon, Ciara

    2010-06-01

    Increased vocal fold hydration is a popular target in the prevention and management of voice disorders. Current intervention strategies focus on enhancing both systemic (internal) and superficial (surface) hydration. We review relevant bench and human research on the role of hydration in vocal fold physiology. Bench and human studies provide converging evidence that systemic and superficial dehydration are detrimental to vocal fold physiology. Dehydration challenges increase the viscous properties of excised vocal fold tissue. Systemic, superficial, and combined drying challenges increase aerodynamic and acoustic measures of voice production in speakers. Emerging theoretical and clinical data suggest that increasing both systemic and superficial hydration levels may benefit voice production; however, robust evidence for positive outcomes of hydration treatments is lacking. Increased systemic and superficial vocal fold hydration as a component of vocal hygiene may improve overall health and efficiency of the vocal apparatus. However, continued exploration of biological mechanisms regulating vocal fold hydration is needed to optimize clinical hydration interventions. Specifically, the development of hydration treatments that maximize positive phonatory outcomes will necessitate understanding of the signaling pathways linking systemic and superficial hydration.

  17. Raman spectroscopic measurements on fluoromethane clathrate hydrates

    Energy Technology Data Exchange (ETDEWEB)

    Uchida, T. [Hokkaido Univ., Sapporo (Japan). Graduate School of Engineering, Div. of Applied Physics; Ohmura, R. [Keio Univ., Kohoku-ku, Yokohama (Japan). Dept. of Mechanical Engineering; Hori, A. [Kitami Inst. of Technology, Kitami (Japan). Course of Civil Engineering

    2008-07-01

    The occupation of guest molecules in clathrate-structure cages is of interest to researchers, since this property is involved in the estimation of guest molecule density, the stability of clathrate hydrates, and other features. However, such occupation is known to be non-stoichiometric. It remains difficult to accurately estimate the total amount of natural gases in the hydrates located in the deep ocean or in permafrost. This paper discussed the systematic observations of fluoromethane clathrate hydrates using Raman spectroscopy in conjunction with previously obtained Raman spectra for methane (CH{sub 4}) hydrate. Four types of fluoromethane were utilized as standard guest molecules to investigate cage occupation in the hydrates, as all of them were included in the same crystal structure and shared similar functional groups. The types of fluoromethane that were used included fluoromethane (CH{sub 3}F), difluoromethane (CH{sub 2}F{sub 2}), trifluoromethane (CHF{sub 3}), and tetrafluoromethane (CF{sub 4}). The paper discussed the experimental methods including the temperature and pressure conditions of fluorocarbon hydrate formation. It was concluded that the summary of the Raman peak positions of fluoromethane molecules indicate that the influence of deuterized host molecules on the intramolecular vibration frequencies is less than that suggested by experimental error. The obtained data were confirmed to agree with the empirical model for the Raman peak positions on guest molecules, when the relative position of the guest molecule in a host cage structure is considered. 28 refs., 1 tab., 7 figs.

  18. Thermal conductivity measurements in unsaturated hydrate-bearing sediments

    Science.gov (United States)

    Dai, Sheng; Cha, Jong-Ho; Rosenbaum, Eilis J.; Zhang, Wu; Seol, Yongkoo

    2015-08-01

    Current database on the thermal properties of hydrate-bearing sediments remains limited and has not been able to capture their consequential changes during gas production where vigorous phase changes occur in this unsaturated system. This study uses the transient plane source (TPS) technique to measure the thermal conductivity of methane hydrate-bearing sediments with various hydrate/water/gas saturations. We propose a simplified method to obtain thermal properties from single-sided TPS signatures. Results reveal that both volume fraction and distribution of the pore constituents govern the thermal conductivity of unsaturated specimens. Thermal conductivity hysteresis is observed due to water redistribution and fabric change caused by hydrate formation and dissociation. Measured thermal conductivity increases evidently when hydrate saturation Sh > 30-40%, shifting upward from the geometric mean model prediction to a Pythagorean mixing model. These observations envisage a significant drop in sediment thermal conductivity when residual hydrate/water saturation falls below ~40%, hindering further gas production.

  19. Towards bio-silicon interfaces: formation of an ultra-thin self-hydrated artificial membrane composed of dipalmitoylphosphatidylcholine (DPPC) and chitosan deposited in high vacuum from the gas-phase.

    Science.gov (United States)

    Retamal, María J; Cisternas, Marcelo A; Gutierrez-Maldonado, Sebastian E; Perez-Acle, Tomas; Seifert, Birger; Busch, Mark; Huber, Patrick; Volkmann, Ulrich G

    2014-09-14

    The recent combination of nanoscale developments with biological molecules for biotechnological research has opened a wide field related to the area of biosensors. In the last years, device manufacturing for medical applications adapted the so-called bottom-up approach, from nanostructures to larger devices. Preparation and characterization of artificial biological membranes is a necessary step for the formation of nano-devices or sensors. In this paper, we describe the formation and characterization of a phospholipid bilayer (dipalmitoylphosphatidylcholine, DPPC) on a mattress of a polysaccharide (Chitosan) that keeps the membrane hydrated. The deposition of Chitosan (~25 Å) and DPPC (~60 Å) was performed from the gas phase in high vacuum onto a substrate of Si(100) covered with its native oxide layer. The layer thickness was controlled in situ using Very High Resolution Ellipsometry (VHRE). Raman spectroscopy studies show that neither Chitosan nor DPPC molecules decompose during evaporation. With VHRE and Atomic Force Microscopy we have been able to detect phase transitions in the membrane. The presence of the Chitosan interlayer as a water reservoir is essential for both DPPC bilayer formation and stability, favoring the appearance of phase transitions. Our experiments show that the proposed sample preparation from the gas phase is reproducible and provides a natural environment for the DPPC bilayer. In future work, different Chitosan thicknesses should be studied to achieve a complete and homogeneous interlayer.

  20. Towards bio-silicon interfaces: Formation of an ultra-thin self-hydrated artificial membrane composed of dipalmitoylphosphatidylcholine (DPPC) and chitosan deposited in high vacuum from the gas-phase

    Energy Technology Data Exchange (ETDEWEB)

    Retamal, María J., E-mail: moretama@uc.cl; Cisternas, Marcelo A.; Seifert, Birger; Volkmann, Ulrich G. [Instituto de Física, Pontificia Universidad Católica de Chile, Avda. Vicuña Mackenna 4860, 7820436 Santiago (Chile); Centro de Investigación en Nanotecnología y Materiales Avanzados (CIEN-UC), Pontificia Universidad Católica de Chile, Avda. Vicuña Mackenna 4860, 7820436 Santiago (Chile); Gutierrez-Maldonado, Sebastian E.; Perez-Acle, Tomas [Computational Biology Lab (DLab), Fundación Ciencia y Vida, Av. Zañartu 1482, Santiago (Chile); Centro Interdisciplinario de Neurociencias de Valparaiso (CINV), Universidad de Valparaiso, Pasaje Harrington 287, Valparaiso (Chile); Busch, Mark; Huber, Patrick [Institute of Materials Physics and Technology, Hamburg University of Technology (TUHH), D-21073 Hamburg-Harburg (Germany)

    2014-09-14

    The recent combination of nanoscale developments with biological molecules for biotechnological research has opened a wide field related to the area of biosensors. In the last years, device manufacturing for medical applications adapted the so-called bottom-up approach, from nanostructures to larger devices. Preparation and characterization of artificial biological membranes is a necessary step for the formation of nano-devices or sensors. In this paper, we describe the formation and characterization of a phospholipid bilayer (dipalmitoylphosphatidylcholine, DPPC) on a mattress of a polysaccharide (Chitosan) that keeps the membrane hydrated. The deposition of Chitosan (∼25 Å) and DPPC (∼60 Å) was performed from the gas phase in high vacuum onto a substrate of Si(100) covered with its native oxide layer. The layer thickness was controlled in situ using Very High Resolution Ellipsometry (VHRE). Raman spectroscopy studies show that neither Chitosan nor DPPC molecules decompose during evaporation. With VHRE and Atomic Force Microscopy we have been able to detect phase transitions in the membrane. The presence of the Chitosan interlayer as a water reservoir is essential for both DPPC bilayer formation and stability, favoring the appearance of phase transitions. Our experiments show that the proposed sample preparation from the gas phase is reproducible and provides a natural environment for the DPPC bilayer. In future work, different Chitosan thicknesses should be studied to achieve a complete and homogeneous interlayer.

  1. Formative research in clinical trial development: attitudes of patients with arthritis in enhancing prevention trials

    Science.gov (United States)

    Taylor, Holly A; Sugarman, Jeremy; Pisetsky, David S; Bathon, Joan

    2007-01-01

    In preparation for randomised controlled trials (RCTs) of disease‐modifying antirheumatic drugs in patients with early inflammatory arthritis (EIA), formative research was conducted to enhance the design of such trials. The objectives of this research were to (1) determine patients' educational needs as they relate to the necessary elements of informed consent; and (2) assess patients' interest in enrolling in a hypothetical prevention trial. In‐depth interviews were conducted with nine patients. Seven patients were women and all but one white. The mean age was 48 years. During the 4‐month enrolment period, only three patients with EIA were identified; six patients with longer duration of symptoms were also interviewed. Most patients were able to express the primary aim of a hypothetical prevention trial presented. Factors cited by patients favouring enrolment were potential for direct medical benefit and knowledge that they would be withdrawn from the trial if they developed symptoms. Factors cited by patients against enrolment were the inclusion of a placebo and general uncertainty regarding treatment required by the RCT design. Pending larger‐scale empirical projects to explore patients' attitudes about prevention trials, small‐scale formative research in advance of such trials ought to be conducted. PMID:16984939

  2. Mechanism of gypsum hydration

    Directory of Open Access Journals (Sweden)

    Pacheco, G.

    1991-06-01

    Full Text Available There is an hypothesis that the mechanism o f gypsum hydration and dehydration is performed through two simultaneous phenomena. In this study we try to clear up this phenomenon using chlorides as accelerators or a mixture of ethanol-methanol as retarders to carry out the gypsum setting. Natural Mexican gypsum samples and a hemihydrate prepared in the laboratory are used. The following analytical techniques are used: MO, DRX, DTA, TG and DTG. In agreement with the obtained results, it can be concluded: that colloid formation depends on the action of accelerators or retarders and the crystals are a consequence of the quantity of hemihydrate formed.

    En el mecanismo de hidratación y deshidratación del yeso existe la hipótesis de que éste se efectúa por dos fenómenos simultáneos. Este estudio intenta esclarecer estos fenómenos, empleando: cloruros como aceleradores o mezcla etanol-metanol como retardadores para efectuar el fraguado del yeso. Se emplean muestras de yeso de origen natural mexicano y hemihydrate preparado en laboratorio; se utilizan técnicas analíticas: MO, DRX, DTA, TG y DTG. De acuerdo a los resultados obtenidos se puede deducir: que la formación del coloide depende de la acción de los agentes aceleradores o retardadores y que los cristales son consecuencia de la cantidad de hemihidrato formado.

  3. 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.

  4. In-situ gas hydrate hydrate saturation estimated from various well logs at the Mount Elbert Gas Hydrate Stratigraphic Test Well, Alaska North Slope

    Science.gov (United States)

    Lee, M.W.; Collett, T.S.

    2011-01-01

    In 2006, the U.S. Geological Survey (USGS) completed detailed analysis and interpretation of available 2-D and 3-D seismic data and proposed a viable method for identifying sub-permafrost gas hydrate prospects within the gas hydrate stability zone in the Milne Point area of northern Alaska. To validate the predictions of the USGS and to acquire critical reservoir data needed to develop a long-term production testing program, a well was drilled at the Mount Elbert prospect in February, 2007. Numerous well log data and cores were acquired to estimate in-situ gas hydrate saturations and reservoir properties.Gas hydrate saturations were estimated from various well logs such as nuclear magnetic resonance (NMR), P- and S-wave velocity, and electrical resistivity logs along with pore-water salinity. Gas hydrate saturations from the NMR log agree well with those estimated from P- and S-wave velocity data. Because of the low salinity of the connate water and the low formation temperature, the resistivity of connate water is comparable to that of shale. Therefore, the effect of clay should be accounted for to accurately estimate gas hydrate saturations from the resistivity data. Two highly gas hydrate-saturated intervals are identified - an upper ???43 ft zone with an average gas hydrate saturation of 54% and a lower ???53 ft zone with an average gas hydrate saturation of 50%; both zones reach a maximum of about 75% saturation. ?? 2009.

  5. The U.S. Geological Survey’s Gas Hydrates Project

    Science.gov (United States)

    Ruppel, Carolyn D.

    2018-01-17

    The Gas Hydrates Project at the U.S. Geological Survey (USGS) focuses on the study of methane hydrates in natural environments. The project is a collaboration between the USGS Energy Resources and the USGS Coastal and Marine Geology Programs and works closely with other U.S. Federal agencies, some State governments, outside research organizations, and international partners. The USGS studies the formation and distribution of gas hydrates in nature, the potential of hydrates as an energy resource, and the interaction between methane hydrates and the environment. The USGS Gas Hydrates Project carries out field programs and participates in drilling expeditions to study marine and terrestrial gas hydrates. USGS scientists also acquire new geophysical data and sample sediments, the water column, and the atmosphere in areas where gas hydrates occur. In addition, project personnel analyze datasets provided by partners and manage unique laboratories that supply state-of-the-art analytical capabilities to advance national and international priorities related to gas hydrates.

  6. Irrigation port hydration in phacoemulsification surgery.

    Science.gov (United States)

    Suzuki, Hisaharu; Masuda, Yoichiro; Hamajima, Yuki; Takahashi, Hiroshi

    2018-01-01

    In most cases, hydration is performed by water injection into the stromal tissue with a needle. The technique is simple, however it is sometimes troublesome. We describe a simple technique for hydrating the corneal stroma in cataract surgery using an irrigation port. The technique began by pushing the irrigation port against the corneal stroma for a few seconds during phacoemulsification, which generated edema in the corneal incision that subsequently prevented leakage. This procedure is called the hydration using irrigation port (HYUIP) technique. A total of 60 eyes were randomized and placed in two groups, 30 eyes underwent surgeries using the HYUIP technique (HYUIP group) and 30 eyes underwent surgeries without the HYUIP technique (control). The three points evaluated during each surgery included 1) the occurrence of anterior chamber collapse during the pulling out of the I/A tip after inserting the intraocular lens, 2) the need for conventional hydration, and 3) watertight completion at the end stage of surgery. The anterior chamber collapse and the need for conventional hydration were significantly smaller in the HYUIP group compared to the control group. Regarding the self-sealing completion, no significant difference was observed between the two groups. The HYUIP technique is an effective method for creating self-sealing wound. In addition, this technique helps to prevent anterior chamber collapse.

  7. Application of chimeric glucanase comprising mutanase and dextranase for prevention of dental biofilm formation.

    Science.gov (United States)

    Otsuka, Ryoko; Imai, Susumu; Murata, Takatoshi; Nomura, Yoshiaki; Okamoto, Masaaki; Tsumori, Hideaki; Kakuta, Erika; Hanada, Nobuhiro; Momoi, Yasuko

    2015-01-01

    Water-insoluble glucan (WIG) produced by mutans streptococci, an important cariogenic pathogen, plays an important role in the formation of dental biofilm and adhesion of biofilm to tooth surfaces. Glucanohydrolases, such as mutanase (α-1,3-glucanase) and dextranase (α-1,6-glucanase), are able to hydrolyze WIG. The purposes of this study were to construct bi-functional chimeric glucanase, composed of mutanase and dextranase, and to examine the effects of this chimeric glucanase on the formation and decomposition of biofilm. The mutanase gene from Paenibacillus humicus NA1123 and the dextranase gene from Streptococcus mutans ATCC 25175 were cloned and ligated into a pE-SUMOstar Amp plasmid vector. The resultant his-tagged fusion chimeric glucanase was expressed in Escherichia coli BL21 (DE3) and partially purified. The effects of chimeric glucanase on the formation and decomposition of biofilm formed on a glass surface by Streptococcus sobrinus 6715 glucosyltransferases were then examined. This biofilm was fractionated into firmly adherent, loosely adherent, and non-adherent WIG fractions. Amounts of WIG in each fraction were determined by a phenol-sulfuric acid method, and reducing sugars were quantified by the Somogyi-Nelson method. Chimeric glucanase reduced the formation of the total amount of WIG in a dose-dependent manner, and significant reductions of WIG in the adherent fraction were observed. Moreover, the chimeric glucanase was able to decompose biofilm, being 4.1 times more effective at glucan inhibition of biofilm formation than a mixture of dextranase and mutanase. These results suggest that the chimeric glucanase is useful for prevention of dental biofilm formation. © 2014 The Societies and Wiley Publishing Asia Pty Ltd.

  8. Chemoselective Methylation of Phenolic Hydroxyl Group Prevents Quinone Methide Formation and Repolymerization During Lignin Depolymerization

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Kwang Ho; Dutta, Tanmoy; Walter, Eric D.; Isern, Nancy G.; Cort, John R.; Simmons, Blake A.; Singh, Seema

    2017-03-30

    Chemoselective blocking of the phenolic hydroxyl (Ar-OH) group by methylation was found to suppress secondary repolymerization and charring during lignin depolymerization. Methylation of Ar-OH prevents formation of reactive quinone methide intermediates, which are partly responsible for undesirable secondary repolymerization reactions. Instead, this structurally modified lignin produces more relatively low molecular weight products from lignin depolymerization compared to unmodified lignin. This result demonstrates that structural modification of lignin is desirable for production of low molecular weight phenolic products. This approach could be directed toward alteration of natural lignification processes to produce biomass more amenable to chemical depolymerization.

  9. 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

  10. Effect of Resveratrol on the Prevention of Intra-Abdominal Adhesion Formation in a Rat Model

    Directory of Open Access Journals (Sweden)

    Guangbing Wei

    2016-06-01

    Full Text Available Background: Intra-abdominal adhesions are a very common complication following abdominal surgery. Our previous studies have demonstrated that the inhibition of inflammation at the sites of peritoneal injury can prevent the formation of intra-abdominal adhesions. Resveratrol is a natural extract with a broad range of anti-inflammatory effects. Therefore, we propose that resveratrol can reduce the formation of intra-abdominal adhesions after surgery. The aim of this study was to investigate the effect of resveratrol on intra-abdominal adhesion prevention in a rat model with surgery-induced peritoneal adhesions. Materials and Methods: The cecum wall and its opposite parietal peritoneum were abraded following laparotomy to induce intra-abdominal adhesion formation. Varying doses of resveratrol were administered to the animals. On the eighth day after surgery, the adhesion score was assessed using a visual scoring system. Picrosirius red staining and a hydroxyproline assay were used to assess the amount of collagen deposition in the adhesion tissues. The levels of serum interleukin-6 (IL-6, tumor necrosis factor (TNF-α, and transforming growth factor beta-1 (TGF-β1 were determined by an enzyme-linked immunosorbent assay (ELISA. Western blotting was performed to determine the protein expression of TGF-β1, fibrinogen, and α-smooth muscle actin (α-SMA in rat peritoneal adhesion tissue. Real-time RT-PCR was performed to quantify the mRNA expression of TGF-β1, fibrinogen, and α-SMA. Results: Resveratrol significantly reduced intra-abdominal adhesion formation and fibrin deposition in the rat model. Furthermore, resveratrol significantly reduced the serum levels of IL-6, TNF-α, and TGF-β1. The protein and mRNA expression of TGF-β1, fibrinogen, and α-SMA in the rat peritoneum and adhesion tissues were also down-regulated due to resveratrol intervention. Conclusion: Resveratrol can effectively prevent the formation of postoperative intra

  11. Experimental Study of Gas Hydrate Dynamics

    Science.gov (United States)

    Fandino, O.; Ruffine, L.

    2011-12-01

    Important quantities of methane and other gases are trapped below the seafloor and in the permafrost by an ice-like solid, called gas hydrates or clathrate hydrates. The latter is formed when water is mixing with different gases at high pressures and low temperatures. Due to a their possible use as a source of energy [1] or the problematic related to flow assurance failure in pipelines [2] the understanding of their processes of formation/destabilisation of these structures becomes a goal for many laboratories research as well as industries. In this work we present an experimental study on the stochastic behaviour of hydrate formation from a bulk phase. The method used here for the experiments was to repeat several time the same hydrate formation procedure and to notice the different from one experiment to another. A variable-volume type high-pressure apparatus with two sapphire windows was used. This device, already presented by Ruffine et al.[3], allows us to perform both kinetics and phase equilibrium measurements. Three initial pressure conditions were considered here, 5.0 MPa, 7.5 MPa and 10.0 MPa. Hydrates have been formed, then allowed to dissociate by stepwise heating. The memory effect has also been investigated after complete dissociation. It turned out that, although the thermodynamics conditions of formation and/or destabilization were reproducible. An attempt to determine the influence of pressure on the nucleation induction time will be discussed. References 1. Sum, A. K.; Koh, C. A.; Sloan, E. D., Clathrate Hydrates: From Laboratory Science to Engineering Practice. Industrial & Engineering Chemistry Research 2009, 48, 7457-7465. 2. Sloan, E. D., A changing hydrate paradigm-from apprehension to avoidance to risk management. Fluid Phase Equilibria 2005, 228, 67-74. 3. Ruffine, L.; Donval, J. P.; Charlou, J. L.; Cremière, A.; Zehnder, B. H., Experimental study of gas hydrate formation and destabilisation using a novel high-pressure apparatus. Marine

  12. Gypsum hydration: a theoretical and experimental study

    NARCIS (Netherlands)

    Yu, Qingliang; Brouwers, Jos; de Korte, A.C.J.; Fischer, H.B; Bode, K.A.

    2009-01-01

    Calcium sulphate dihydrate (CaSO4·2H2O or gypsum) is used widely as building material because of its excellent fire resistance, aesthetics, and low price. Hemihydrate occurs in two formations of α- and β-type. Among them β-hemihydrate is mainly used to produce gypsum plasterboard since the hydration

  13. METHANE HYDRATE PRODUCTION FROM ALASKAN PERMAFROST

    Energy Technology Data Exchange (ETDEWEB)

    Richard Sigal; Kent Newsham; Thomas Williams; Barry Freifeld; Timothy Kneafsey; Carl Sondergeld; Shandra Rai; Jonathan Kwan; Stephen Kirby; Robert Kleinberg; Doug Griffin

    2005-02-01

    Natural-gas hydrates have been encountered beneath the permafrost and considered a nuisance by the oil and gas industry for years. Engineers working in Russia, Canada and the USA have documented numerous drilling problems, including kicks and uncontrolled gas releases, in arctic regions. Information has been generated in laboratory studies pertaining to the extent, volume, chemistry and phase behavior of gas hydrates. Scientists studying hydrate potential agree that the potential is great--on the North Slope of Alaska alone, it has been estimated at 590 TCF. However, little information has been obtained on physical samples taken from actual rock containing hydrates. The work scope drilled and cored a well The Hot Ice No. 1 on Anadarko leases beginning in FY 2003 and completed in 2004. An on-site core analysis laboratory was built and utilized for determining the physical characteristics of the hydrates and surrounding rock. The well was drilled from a new Anadarko Arctic Platform that has a minimal footprint and environmental impact. The final efforts of the project are to correlate geology, geophysics, logs, and drilling and production data and provide this information to scientists developing reservoir models. No gas hydrates were encountered in this well; however, a wealth of information was generated and is contained in this report. The Hot Ice No. 1 well was drilled from the surface to a measured depth of 2300 ft. There was almost 100% core recovery from the bottom of surface casing at 107 ft to total depth. Based on the best estimate of the bottom of the methane hydrate stability zone (which used new data obtained from Hot Ice No. 1 and new analysis of data from adjacent wells), core was recovered over its complete range. Approximately 580 ft of porous, mostly frozen, sandstone and 155 of conglomerate were recovered in the Ugnu Formation and approximately 215 ft of porous sandstone were recovered in the West Sak Formation. There were gas shows in the bottom

  14. A randomized controlled trial comparing hydration therapy to additional hemodialysis or N-acetylcysteine for the prevention of contrast medium-induced nephropathy: the Dialysis-versus-Diuresis (DVD) Trial.

    Science.gov (United States)

    Reinecke, H; Fobker, M; Wellmann, J; Becke, B; Fleiter, J; Heitmeyer, C; Breithardt, G; Hense, H-W; Schaefer, R M

    2007-03-01

    Contrast medium-induced nephropathy (CIN) is a serious complication with increasing frequency and an unfavorable prognosis. Previous analyses of surrogate parameters have suggested beneficial effects of hemodialysis that are assessed in this randomized clinical trial. We performed a prospective single-center trial in 424 consecutive patients with serum creatinine concentrations between 1.3- 3.5 mg/dl who underwent elective coronary angiography. Patients were randomized to one of three treatment strategies with all patients receiving pre- and postprocedural hydration: One group received no additional therapy, patients in the second group were hemodialyzed once, and the third group received oral N-acetylcysteine. The frequency of CIN (defined as an increase in serum creatinine>or=0.5 mg/dl) from 48 to 72 h after catheterization was 6.1% in the hydration-only group, 15.9% with hemodialysis treatment, and 5.3% in the N-ACC group (intention-to-treat analysis; P=0.008). There were no differences between the treatment groups with regard to increased (>or=0.5 mg/dl) serum creatinine concentrations after 30-60 days (4.8%, 5.1%, and 3.1%, respectively; P=0.700). Analyses of long-term follow-up (range 63 to 1316 days) by Cox regressions models of the study groups found quite similar survival rates (P=0.500). In contrast to other (retrospective) studies, long-term survival of patients with vs those without CIN within 72 h was not different, but patients who still had elevated creatinine concentrations at 30-60 days suffered from a markedly higher 2-year mortality (46% vs 17%, P=0.002). In conclusion, hemodialysis in addition to hydration therapy for the prevention of CIN provided no evidence for any outcome benefit but evidence for probable harm. Increased creatinine concentrations at 30-60 days, but not within 72 h, were associated with markedly reduced long-term survival.

  15. Three types of gas hydrate reservoirs in the Gulf of Mexico identified in LWD data

    Science.gov (United States)

    Lee, Myung Woong; Collett, Timothy S.

    2011-01-01

    High quality logging-while-drilling (LWD) well logs were acquired in seven wells drilled during the Gulf of Mexico Gas Hydrate Joint Industry Project Leg II in the spring of 2009. These data help to identify three distinct types of gas hydrate reservoirs: isotropic reservoirs in sands, vertical fractured reservoirs in shale, and horizontally layered reservoirs in silty shale. In general, most gas hydratebearing sand reservoirs exhibit isotropic elastic velocities and formation resistivities, and gas hydrate saturations estimated from the P-wave velocity agree well with those from the resistivity. However, in highly gas hydrate-saturated sands, resistivity-derived gas hydrate-saturation estimates appear to be systematically higher by about 5% over those estimated by P-wave velocity, possibly because of the uncertainty associated with the consolidation state of gas hydrate-bearing sands. Small quantities of gas hydrate were observed in vertical fractures in shale. These occurrences are characterized by high formation resistivities with P-wave velocities close to those of water-saturated sediment. Because the formation factor varies significantly with respect to the gas hydrate saturation for vertical fractures at low saturations, an isotropic analysis of formation factor highly overestimates the gas hydrate saturation. Small quantities of gas hydrate in horizontal layers in shale are characterized by moderate increase in P-wave velocities and formation resistivities and either measurement can be used to estimate gas hydrate saturations.

  16. Simulating the effect of hydrate dissociation on wellhead stability during oil and gas development in deepwater

    Science.gov (United States)

    Li, Qingchao; Cheng, Yuanfang; Zhang, Huaiwen; Yan, Chuanliang; Liu, Yuwen

    2018-02-01

    It is well known that methane hydrate has been identified as an alternative resource due to its massive reserves and clean property. However, hydrate dissociation during oil and gas development (OGD) process in deep water can affect the stability of subsea equipment and formation. Currently, there is a serious lack of studies over quantitative assessment on the effects of hydrate dissociation on wellhead stability. In order to solve this problem, ABAQUS finite element software was used to develop a model and to evaluate the behavior of wellhead caused by hydrate dissociation. The factors that affect the wellhead stability include dissociation range, depth of hydrate formation and mechanical properties of dissociated hydrate region. Based on these, series of simulations were carried out to determine the wellhead displacement. The results revealed that, continuous dissociation of hydrate in homogeneous and isotropic formations can causes the non-linear increment in vertical displacement of wellhead. The displacement of wellhead showed good agreement with the settlement of overlying formations under the same conditions. In addition, the shallower and thicker hydrate formation can aggravate the influence of hydrate dissociation on the wellhead stability. Further, it was observed that with the declining elastic modulus and Poisson's ratio, the wellhead displacement increases. Hence, these findings not only confirm the effect of hydrate dissociation on the wellhead stability, but also lend support to the actions, such as cooling the drilling fluid, which can reduce the hydrate dissociation range and further make deepwater operations safer and more efficient.

  17. Developing a diabetes prevention education programme for community health-care workers in Thailand: formative findings.

    Science.gov (United States)

    Sranacharoenpong, Kitti; Hanning, Rhona M

    2011-10-01

    The aim of this study was to investigate barriers to and supports for implementing a diabetes prevention education programme for community health-care workers (CHCWs) in Chiang Mai province, Thailand. The study also aimed to get preliminary input into the design of a tailored diabetes prevention education programme for CHCWs. Thailand has faced under-nutrition and yet, paradoxically, the prevalence of diseases of over-nutrition, such as obesity and diabetes, has escalated. As access to diabetes prevention programme is limited in Thailand, especially in rural and semi-urban areas, it becomes critical to develop a health information delivery system that is relevant, cost-effective, and sustainable. Health-care professionals (n = 12) selected from health centres within one district participated in in-depth interviews. In addition, screened people at risk for diabetes participated in interviews (n = 8) and focus groups (n = 4 groups, 23 participants). Coded transcripts from audio-taped interviews or focus groups were analysed by hand and using NVivo software. Concept mapping illustrated the findings. Health-care professionals identified potential barriers to programme success as a motivation for regular participation, and lack of health policy support for programme sustainability. Health-care professionals identified opportunities to integrate health promotion and disease prevention into CHCWs' duties. Health-care professionals recommended small-group workshops, hands-on learning activities, case studies, and video presentations that bring knowledge to practice within their cultural context. CHCWs should receive a credit for continuing study. People at risk for diabetes lacked knowledge of nutrition, diabetes risk factors, and resources to access health information. They desired two-way communication with CHCWs. Formative research supports the need for an effective, sustainable programme to support knowledge translation to CHCWs and at-risk populations in the

  18. Prevention of H-Aggregates Formation in Cy5 Labeled Macromolecules

    Directory of Open Access Journals (Sweden)

    Jing Kang

    2010-01-01

    Full Text Available H-aggregates of the cyanine dye Cy5 are formed during covalent linkage to the cationic macromolecule Poly(allylamine (PAH. The nonfluorescent H-aggregates strongly restrict the usage of the dye for analytical purposes and prevent a quantitative determination of the labeled macromolecules. The behavior of the H-aggregates has been studied by investigation of the absorption and fluorescence spectra of the dye polymer in dependence on solvent, label degree and additional sulfonate groups. H-aggregate formation is caused by an inhomogeneous distribution of the Cy5 molecules on the polymer chain. The H-aggregates can be destroyed by conformational changes of the PAH induced by interactions with polyanions or in organic solvents. It has been found that the polymer labeling process in high content of organic solvents can prevent the formation of H-aggregates. The results offer a better understanding and improvement of the use of the Cy5 dye for labeling purposes in fluorescence detection of macromolecules.

  19. Methylene blue 1% solution on the prevention of intraperitoneal adhesion formation in a dog model

    Directory of Open Access Journals (Sweden)

    Marco Augusto Machado Silva

    Full Text Available Intraperitoneal adhesions usually are formed after abdominal surgeries and may cause technical difficulties during surgical intervention, chronic abdominal pain and severe obstructions of the gastrointestinal tract. The current study aimed to evaluate the efficacy of methylene blue (MB 1% solution on the prevention of intraperitoneal postsurgical adhesion formation in a canine surgical trauma model. Twenty bitches were submitted to falciform ligament resection, omentectomy, ovariohysterectomy and scarification of a colonic segment. Prior to abdominal closure, 10 bitches received 1mg kg-1 MB intraperitoneally (MB group and 10 bitches received no treatment (control group, CT. On the 15th postoperative day the bitches were submitted to laparoscopy to assess adhesions. The mean adhesion scores were 13.9 (±5.6 for MB group and 20.5 (±6.4 for the CT group (P=0,043. In conclusion, the 1% MB solution was efficient on the prevention of intraperitoneal postoperative adhesion formation in bitches, especially those involving the colonic serosa.

  20. Can Dietary Polyphenols Prevent the Formation of Toxic Compounds from Maillard Reaction?

    Science.gov (United States)

    Del Turco, Serena; Basta, Giuseppina

    2016-01-01

    Polyphenols are functional compounds in edible vegetable and food such as tea, coffee and red wine and increasing evidence demonstrates a positive link between consumption of polyphenol-rich foods and disease prevention. In this review we have focused on the current knowledge of the potential anti-glycation effects of polyphenols, particularly in regard to their influence on Maillard reaction, a non-enzymatic reaction between amino acids and reducing sugars that contributes to the production of toxic compounds, mainly reactive carbonyl species, advanced glycation end-products (AGEs) and other toxicants. The Maillard reaction occurs in the human body during hyperglycemic condition, but it is well known as browning reaction in thermally processed foods and it is responsible for flavor and toxicant formation. Dietary polyphenols can have anti-glycation effects and actively participate in Maillard reaction, mitigating the AGE formation and the heat-induced production of toxic compounds. In a time in which the role of a healthy diet in the prevention of chronic diseases is welcome and the borderline between food and medicine is becoming very thin, an improved mechanistic knowledge of how polyphenols can function to reduce harmful and unhealthy substances is mandatory.

  1. Niclosamide prevents the formation of large ubiquitin-containing aggregates caused by proteasome inhibition.

    Directory of Open Access Journals (Sweden)

    Esther Gies

    2010-12-01

    Full Text Available Protein aggregation is a hallmark of many neurodegenerative diseases and has been linked to the failure to degrade misfolded and damaged proteins. In the cell, aberrant proteins are degraded by the ubiquitin proteasome system that mainly targets short-lived proteins, or by the lysosomes that mostly clear long-lived and poorly soluble proteins. Both systems are interconnected and, in some instances, autophagy can redirect proteasome substrates to the lysosomes.To better understand the interplay between these two systems, we established a neuroblastoma cell population stably expressing the GFP-ubiquitin fusion protein. We show that inhibition of the proteasome leads to the formation of large ubiquitin-containing inclusions accompanied by lower solubility of the ubiquitin conjugates. Strikingly, the formation of the ubiquitin-containing aggregates does not require ectopic expression of disease-specific proteins. Moreover, formation of these focused inclusions caused by proteasome inhibition requires the lysine 63 (K63 of ubiquitin. We then assessed selected compounds that stimulate autophagy and found that the antihelmintic chemical niclosamide prevents large aggregate formation induced by proteasome inhibition, while the prototypical mTORC1 inhibitor rapamycin had no apparent effect. Niclosamide also precludes the accumulation of poly-ubiquitinated proteins and of p62 upon proteasome inhibition. Moreover, niclosamide induces a change in lysosome distribution in the cell that, in the absence of proteasome activity, may favor the uptake into lysosomes of ubiquitinated proteins before they form large aggregates.Our results indicate that proteasome inhibition provokes the formation of large ubiquitin containing aggregates in tissue culture cells, even in the absence of disease specific proteins. Furthermore our study suggests that the autophagy-inducing compound niclosamide may promote the selective clearance of ubiquitinated proteins in the absence

  2. Geomechanical Performance of Hydrate-Bearing Sediment in Offshore Environments

    Energy Technology Data Exchange (ETDEWEB)

    Stephen Holditch; Tad Patzek; Jonny Rutqvist; George Moridis; Richard Plumb

    2008-03-31

    The objective of this multi-year, multi-institutional research project was to develop the knowledge base and quantitative predictive capability for the description of geomechanical performance of hydrate-bearing sediments (hereafter referred to as HBS) in oceanic environments. The focus was on the determination of the envelope of hydrate stability under conditions typical of those related to the construction and operation of offshore platforms. We have developed a robust numerical simulator of hydrate behavior in geologic media by coupling a reservoir model with a commercial geomechanical code. We also investigated the geomechanical behavior of oceanic HBS using pore-scale models (conceptual and mathematical) of fluid flow, stress analysis, and damage propagation. The objective of the UC Berkeley work was to develop a grain-scale model of hydrate-bearing sediments. Hydrate dissociation alters the strength of HBS. In particular, transformation of hydrate clusters into gas and liquid water weakens the skeleton and, simultaneously, reduces the effective stress by increasing the pore pressure. The large-scale objective of the study is evaluation of geomechanical stability of offshore oil and gas production infrastructure. At Lawrence Berkeley National Laboratory (LBNL), we have developed the numerical model TOUGH + Hydrate + FLAC3D to evaluate how the formation and disassociation of hydrates in seafloor sediments affects seafloor stability. Several technical papers were published using results from this model. LBNL also developed laboratory equipment and methods to produce realistic laboratory samples of sediments containing gas hydrates so that mechanical properties could be measured in the laboratory. These properties are required to run TOUGH + Hydrate + FLAC3D to evaluate seafloor stability issues. At Texas A&M University we performed a detailed literature review to determine what gas hydrate formation properties had been measured and reported in the literature. We

  3. Investigating the Metastability of Clathrate Hydrates for Energy Storage

    Energy Technology Data Exchange (ETDEWEB)

    Koh, Carolyn Ann [Colorado School of Mines, Golden, CO (United States)

    2014-11-18

    Important breakthrough discoveries have been achieved from the DOE award on the key processes controlling the synthesis and structure-property relations of clathrate hydrates, which are critical to the development of clathrate hydrates as energy storage materials. Key achievements include: (i) the discovery of key clathrate hydrate building blocks (stable and metastable) leading to clathrate hydrate nucleation and growth; (ii) development of a rapid clathrate hydrate synthesis route via a seeding mechanism; (iii) synthesis-structure relations of H2 + CH4/CO2 binary hydrates to control thermodynamic requirements for energy storage and sequestration applications; (iv) discovery of a new metastable phase present during clathrate hydrate structural transitions. The success of our research to-date is demonstrated by the significant papers we have published in high impact journals, including Science, Angewandte Chemie, J. Am. Chem. Soc. Intellectual Merits of Project Accomplishments: The intellectual merits of the project accomplishments are significant and transformative, in which the fundamental coupled computational and experimental program has provided new and critical understanding on the key processes controlling the nucleation, growth, and thermodynamics of clathrate hydrates containing hydrogen, methane, carbon dioxide, and other guest molecules for energy storage. Key examples of the intellectual merits of the accomplishments include: the first discovery of the nucleation pathways and dominant stable and metastable structures leading to clathrate hydrate formation; the discovery and experimental confirmation of new metastable clathrate hydrate structures; the development of new synthesis methods for controlling clathrate hydrate formation and enclathration of molecular hydrogen. Broader Impacts of Project Accomplishments: The molecular investigations performed in this project on the synthesis (nucleation & growth)-structure-stability relations of clathrate

  4. Prevention of Risky Sexual Behaviour through the Formation of Psychological Readiness to Parenthood

    Directory of Open Access Journals (Sweden)

    Krysko A.A.,

    2018-04-01

    Full Text Available In the world there are tendencies of early entering into sexual relations and simultaneous withdrawal of the age of marriage, an increase in the number of early pregnancies and abortions among minors. Existing programs for the prevention of risky sexual behavior are ineffective, since they are one-time, narrowly focused. The author presents the results of an experiment on the prevention of risky sexual behavior in adolescents based on the formation of their ideas of parenting and child-parent relations, and through the prism of this topic, allowing to build an image of reproductive behavior in the present and future. The program is designed taking into account the psychology of modern adolescents, in accordance with the principles of awareness and responsibility, is based on a restorative approach and resource approach to the formation of psychological readiness for parenthood M.E. Lantsburg. The program for the development of psychological preparedness for parenting in adolescents has two targets: the nearest: preventing adolescent pregnancy and reducing its negative consequences in the event of an early pregnancy, and strategic - preparing for the planning and birth of the coveted child in the future. The results prove that the adolescents' views about the family depend both on the experiences they experienced in their own childhood and on the trends in the social and political space discussed in this topic. The study showed that adolescents' views on sexual relations, family and parenthood can be purposefully influenced through a program based on the knowledge of age-related psychology, resource and recovery approaches and using interactive methods of teaching relevant to this age group.

  5. Hydration process of nuclear-waste glass: an interim report

    International Nuclear Information System (INIS)

    Bates, J.K.; Jardine, L.J.; Steindler, M.J.

    1982-07-01

    Aging of simulated nuclear waste glass by contact with a controlled-temperature, humid atmosphere results in the formation of a double hydration layer penetrating the glass, as well as the formation of minerals on the glass surface. The hydration process can be described by Arrhenius behavior between 120 and 240 0 C. Results suggest that simulated aging reactions are necessary for demonstrating that nuclear waste forms can meet projected Nuclear Regulatory Commission regulations. 16 figures, 4 tables

  6. 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.

  7. A failure of matrix metalloproteinase inhibition in the prevention of rat intracranial aneurysm formation

    International Nuclear Information System (INIS)

    Kaufmann, T.J.; Kallmes, D.F.; Marx, W.F.

    2006-01-01

    We tested the hypothesis that nonspecific matrix metalloproteinase (MMP) inhibition with doxycycline would decrease the incidence of intracranial aneurysm formation in a rat aneurysm model. We performed common carotid artery ligation on 96 Long-Evans rats. A treatment group of 48 animals was chosen at random to receive oral doxycycline (3 mg/kg) in addition to standard rat chow, and the control group of 48 animals received standard rat chow only. The major circle of Willis arteries was dissected at 1 year following carotid ligation, and the proportions of animals with aneurysms were compared between groups using Fisher's exact test. Four animals given oral doxycycline and ten control animals expired before 1 year. Of the examined animals, eight saccular intracranial aneurysms were found in 8 of 45 animals which had received doxycycline (17.8%) and seven saccular intracranial aneurysms were found in 7 of 37 control animals (18.9%). There was no significant difference in aneurysm formation between the doxycycline-treated and control groups (P=0.894). Nonspecific MMP inhibition with doxycycline is not effective in preventing intracranial aneurysm formation in a rat model. (orig.)

  8. Antifreeze proteins: Adsorption to ice, silica and gas hydrates

    Energy Technology Data Exchange (ETDEWEB)

    Zeng, Huang; Brown, Alan; Wathen, Brent; Ripmeester, John A.; Walker, VIrginia K.

    2005-07-01

    Certain organisms survive under freezing conditions that could otherwise prove fatal by the synthesis of antifreeze proteins (AFPs). AFPs adsorb to the surface of microscopic ice crystals and prevent further ice growth, resulting in a noncolligative freezing point depression. Type I AFP from the winter flounder (wfAFP) is an alfa-helical, alanine-rich serum protein that helps protect against innoculative freezing from ice-laden seas. The AFP of a moth from the boreal forest, Choristoneura fumiferana (Cf), is a beta-helical threonine-rich protein that helps prevent freezing at the overwintering, caterpillar stage. In contrast, the beta-roll AFP from the grass, Lolium perenne (Lp), confers little freezing point depression and the plants readily freeze. Remarkably, AFPs also adsorb to tetrahyrofuran (THF) hydrate, changing the hydrate's octahedral morphology and, as well, inhibiting the growth of THF and gas hydrates. The hyperactive CfAFP, with 30-100 times the activity of wfAFP toward ice, showed far greater nucleation inhibition for THF hydrate than did a commercial hydrate inhibitor, poly(N-vinylpyrrolidone) (PVP). Active AFPs were also judged to be superior to PVP in that they inhibited the memory effect, a phenomenon whereby hydrate reforms at a faster rate soon after melting. An inactive mutant wfAFP, with an amino acid substitution at the ice-binding site, also reduced the growth of THF hydrate but was ineffective at suppressing hydrate reformation. These results suggest that the molecular properties important for ice adsorption and inhibition of hydrate reformation may be similar, and are distinct from those required for hydrate growth inhibition. The different AFPs also show markedly different aggregations on a third hydrophilic substrate, silica. Together these studies suggest that AFP adsorption to ice, hydrates and silica depends on the overall structure, specific residues and protein-protein interactions. (Author)

  9. THz characterization of hydrated and anhydrous materials

    Science.gov (United States)

    Sokolnikov, Andre

    2011-06-01

    The characterization of anhydrous and hydrated forms of materials is of great importance to science and industry. Water content poses difficulties for successful identification of the material structure by THz radiation. However, biological tissues and hydrated forms of nonorganic substances still may be investigated by THz radiation. This paper outlines the range of possibilities of the above characterization, as well as provides analysis of the physical mechanism that allows or prevents penetration of THz waves through the substance. THz-TDS is used to measure the parameters of the characterization of anhydrous and hydrated forms of organic and nonorganic samples. Mathematical methods (such as prediction models of time-series analysis) are used to help identifying the absorption coefficient and other parameters of interest. The discovered dependencies allow designing techniques for material identification/characterization (e.g. of drugs, explosives, etc. that may have water content). The results are provided.

  10. Development and formative evaluation of a family-centred adolescent HIV prevention programme in South Africa.

    Science.gov (United States)

    Visser, Maretha; Thurman, Tonya R; Spyrelis, Alexandra; Taylor, Tory M; Nice, Johanna K; Finestone, Michelle

    2018-03-06

    Preventing HIV among young people is critical to achieving and sustaining global epidemic control. Evidence from Western settings suggests that family-centred prevention interventions may be associated with greater reductions in risk behaviour than standard adolescent-only models. Despite this, family-centred models for adolescent HIV prevention are nearly non-existent in South Africa - home to more people living with HIV than any other country. This paper describes the development and formative evaluation of one such intervention: an evidence-informed, locally relevant, adolescent prevention intervention engaging caregivers as co-participants. The programme, originally consisting of 19 sessions for caregivers and 14 for adolescents, was piloted with 12 groups of caregiver-adolescent dyads by community-based organizations (CBOs) in KwaZulu-Natal and Gauteng provinces. Literature and expert reviews were employed in the development process, and evaluation methods included analysis of attendance records, session-level fidelity checklists and facilitator feedback forms collected during the programme pilot. Facilitator focus group discussions and an implementer programme workshop were also held. Results highlighted the need to enhance training content related to cognitive behavioural theory and group management techniques, as well as increase the cultural relevance of activities in the curriculum. Participant attendance challenges were also identified, leading to a shortened and simplified session set. Findings overall were used to finalize materials and guidance for a revised 14-week group programme consisting of individual and joint sessions for adolescents and their caregivers, which may be implemented by community-based facilitators in other settings. Copyright © 2018 Elsevier Ltd. All rights reserved.

  11. Overexpression of Catalase in Vascular Smooth Muscle Cells Prevents the Formation of Abdominal Aortic Aneurysms

    Science.gov (United States)

    Parastatidis, Ioannis; Weiss, Daiana; Joseph, Giji; Taylor, W Robert

    2013-01-01

    Objective Elevated levels of oxidative stress have been reported in abdominal aortic aneurysms (AAA), but which reactive oxygen species (ROS) promotes the development of AAA remains unclear. Here we investigate the effect of the hydrogen peroxide (H2O2) degrading enzyme catalase on the formation of AAA. Approach and Results AAA were induced with the application of calcium chloride (CaCl2) on mouse infrarenal aortas. The administration of PEG-catalase, but not saline, attenuated the loss of tunica media and protected against AAA formation (0.91±0.1 mm vs. 0.76±0.09 mm). Similarly, in a transgenic mouse model, catalase over-expression in the vascular smooth muscle cells (VSMC) preserved the thickness of tunica media and inhibited aortic dilatation by 50% (0.85±0.14 mm vs. 0.57±0.08 mm). Further studies showed that injury with CaCl2 decreased catalase expression and activity in the aortic wall. Pharmacologic administration or genetic over-expression of catalase restored catalase activity and subsequently decreased matrix metalloproteinase activity. In addition, a profound reduction in inflammatory markers and VSMC apoptosis was evident in aortas of catalase over-expressing mice. Interestingly, as opposed to infusion of PEG-catalase, chronic over-expression of catalase in VSMC did not alter the total aortic H2O2 levels. Conclusions The data suggest that a reduction in aortic wall catalase activity can predispose to AAA formation. Restoration of catalase activity in the vascular wall enhances aortic VSMC survival and prevents AAA formation primarily through modulation of matrix metalloproteinase activity. PMID:23950141

  12. A new aluminium-hydrate species in hydrated Portland cements characterized by 27Al and 29Si MAS NMR spectroscopy

    International Nuclear Information System (INIS)

    Andersen, Morten Daugaard; Jakobsen, Hans J.; Skibsted, Jorgen

    2006-01-01

    Recent 27 Al MAS NMR studies of hydrated Portland cements and calcium-silicate-hydrate (C-S-H) phases have shown a resonance from Al in octahedral coordination, which cannot be assigned to the well-known aluminate species in hydrated Portland cements. This resonance, which exhibits the isotropic chemical shift δ iso = 5.0 ppm and the quadrupole product parameter P Q = 1.2 MHz, has been characterized in detail by 27 Al MAS and 27 Al{ 1 H} CP/MAS NMR for different hydrated white Portland cements and C-S-H phases. These experiments demonstrate that the resonance originates from an amorphous or disordered aluminate hydrate which contains Al(OH) 6 3- or O x Al(OH) 6-x (3+x)- units. The formation of the new aluminate hydrate is related to the formation of C-S-H at ambient temperatures, however, it decomposes by thermal treatment at temperatures of 70-90 o C. From the experiments in this work it is proposed that the new aluminate hydrate is either an amorphous/disordered aluminate hydroxide or a calcium aluminate hydrate, produced as a separate phase or as a nanostructured surface precipitate on the C-S-H phase. Finally, the possibilities of Al 3+ for Ca 2+ substitution in the principal layers and interlayers of the C-S-H structure are discussed

  13. The Role of Antimicrobial Peptides in Preventing Multidrug-Resistant Bacterial Infections and Biofilm Formation

    Directory of Open Access Journals (Sweden)

    Kyung-Soo Hahm

    2011-09-01

    Full Text Available Over the last decade, decreasing effectiveness of conventional antimicrobial-drugs has caused serious problems due to the rapid emergence of multidrug-resistant pathogens. Furthermore, biofilms, which are microbial communities that cause serious chronic infections and dental plaque, form environments that enhance antimicrobial resistance. As a result, there is a continuous search to overcome or control such problems, which has resulted in antimicrobial peptides being considered as an alternative to conventional drugs. Antimicrobial peptides are ancient host defense effector molecules in living organisms. These peptides have been identified in diverse organisms and synthetically developed by using peptidomimic techniques. This review was conducted to demonstrate the mode of action by which antimicrobial peptides combat multidrug-resistant bacteria and prevent biofilm formation and to introduce clinical uses of these compounds for chronic disease, medical devices, and oral health. In addition, combinations of antimicrobial peptides and conventional drugs were considered due to their synergetic effects and low cost for therapeutic treatment.

  14. Steps in the design, development and formative evaluation of obesity prevention-related behavior change trials

    Directory of Open Access Journals (Sweden)

    Baranowski Janice

    2009-01-01

    Full Text Available Abstract Obesity prevention interventions through dietary and physical activity change have generally not been effective. Limitations on possible program effectiveness are herein identified at every step in the mediating variable model, a generic conceptual framework for understanding how interventions may promote behavior change. To minimize these problems, and thereby enhance likely intervention effectiveness, four sequential types of formative studies are proposed: targeted behavior validation, targeted mediator validation, intervention procedure validation, and pilot feasibility intervention. Implementing these studies would establish the relationships at each step in the mediating variable model, thereby maximizing the likelihood that an intervention would work and its effects would be detected. Building consensus among researchers, funding agencies, and journal editors on distinct intervention development studies should avoid identified limitations and move the field forward.

  15. Bryophyllum pinnatum leaf extracts prevent formation of renal calculi in lithiatic rats

    Directory of Open Access Journals (Sweden)

    Mahendra Yadav

    2016-01-01

    Full Text Available Background: Bryophyllum pinnatum, commonly known as Pattharcaṭṭa, is used traditionally in ethnomedicinal practices for the treatment of kidney stone and urinary insufficiency. Aim: The present study evaluated the effect of Bryophyllum pinnatum on ethylene glycol (EG-induced renal calculi in rats. Materials and Methods: Renal calculi were induced in rats by administration of 0.75% EG in drinking water and co-treated orally with standard drug, Cystone (750 mg/kg, or alcoholic and hydro-alcoholic extracts in doses of 100, 200 and 400 mg/kg for 28 days. Weekly body weights were recorded. On day 29, urolithiasis was confirmed by assessing the urinary parameters (urine volume, pH, uric acid, calcium, phosphorus, oxalate, magnesium and creatinine clearance, serum biochemical parameters (creatinine, uric acid, urea, calcium, phosphorus and magnesium, oxidative stress parameters and histology of kidney. Results: Treatment with extracts attenuated the EG-induced decrease in body weight and elevation in urinary parameters (uric acid, calcium, phosphorus and oxalate and serum biochemical parameters (creatinine, uric acid, urea, calcium, phosphorus and magnesium. Extract treatment also reversed EG-induced decrease in urine volume, pH, magnesium and creatinine clearance, oxidative and histological damages in kidneys. Results were comparable to standard drug, Cystone. Results indicated that EG administration caused renal calculi formation which is prevented by treatment with extracts. The observed antilithiatic effect may be attributed to the presence of high content of phenolics, flavonoids and saponins in the extracts. Conclusion: Bryophyllum pinnatum leaves showed preventive effect against renal calculi formation and validates its ethnomedicinal use in urinary disorders. It further supports its therapeutic potential for the treatment of urinary calculi.

  16. Detecting gas hydrate behavior in crude oil using NMR.

    Science.gov (United States)

    Gao, Shuqiang; House, Waylon; Chapman, Walter G

    2006-04-06

    Because of the associated experimental difficulties, natural gas hydrate behavior in black oil is poorly understood despite its grave importance in deep-water flow assurance. Since the hydrate cannot be visually observed in black oil, traditional methods often rely on gas pressure changes to monitor hydrate formation and dissociation. Because gases have to diffuse through the liquid phase for hydrate behavior to create pressure responses, the complication of gas mass transfer is involved and hydrate behavior is only indirectly observed. This pressure monitoring technique encounters difficulties when the oil phase is too viscous, the amount of water is too small, or the gas phase is absent. In this work we employ proton nuclear magnetic resonance (NMR) spectroscopy to observe directly the liquid-to-solid conversion of the water component in black oil emulsions. The technique relies on two facts. The first, well-known, is that water becomes essentially invisible to liquid state NMR as it becomes immobile, as in hydrate or ice formation. The second, our recent finding, is that in high magnetic fields of sufficient homogeneity, it is possible to distinguish water from black oil spectrally by their chemical shifts. By following changes in the area of the water peak, the process of hydrate conversion can be measured, and, at lower temperatures, the formation of ice. Taking only seconds to accomplish, this measurement is nearly direct in contrast to conventional techniques that measure the pressure changes of the whole system and assume these changes represent formation or dissociation of hydrates - rather than simply changes in solubility. This new technique clearly can provide accurate hydrate thermodynamic data in black oils. Because the technique measures the total mobile water with rapidity, extensions should prove valuable in studying the dynamics of phase transitions in emulsions.

  17. Formative evaluation of the telecare fall prevention project for older veterans

    Directory of Open Access Journals (Sweden)

    Saliba Debra

    2011-05-01

    Full Text Available Abstract Background Fall prevention interventions for community-dwelling older adults have been found to reduce falls in some research studies. However, wider implementation of fall prevention activities in routine care has yielded mixed results. We implemented a theory-driven program to improve care for falls at our Veterans Affairs healthcare facility. The first project arising from this program used a nurse advice telephone line to identify patients' risk factors for falls and to triage patients to appropriate services. Here we report the formative evaluation of this project. Methods To evaluate the intervention we: 1 interviewed patient and employee stakeholders, 2 reviewed participating patients' electronic health record data and 3 abstracted information from meeting minutes. We describe the implementation process, including whether the project was implemented according to plan; identify barriers and facilitators to implementation; and assess the incremental benefit to the quality of health care for fall prevention received by patients in the project. We also estimate the cost of developing the pilot project. Results The project underwent multiple changes over its life span, including the addition of an option to mail patients educational materials about falls. During the project's lifespan, 113 patients were considered for inclusion and 35 participated. Patient and employee interviews suggested support for the project, but revealed that transportation to medical care was a major barrier in following up on fall risks identified by nurse telephone triage. Medical record review showed that the project enhanced usual medical care with respect to home safety counseling. We discontinued the program after 18 months due to staffing limitations and competing priorities. We estimated a cost of $9194 for meeting time to develop the project. Conclusions The project appeared feasible at its outset but could not be sustained past the first cycle of

  18. Formative evaluation of the telecare fall prevention project for older veterans.

    Science.gov (United States)

    Miake-Lye, Isomi M; Amulis, Angel; Saliba, Debra; Shekelle, Paul G; Volkman, Linda K; Ganz, David A

    2011-05-23

    Fall prevention interventions for community-dwelling older adults have been found to reduce falls in some research studies. However, wider implementation of fall prevention activities in routine care has yielded mixed results. We implemented a theory-driven program to improve care for falls at our Veterans Affairs healthcare facility. The first project arising from this program used a nurse advice telephone line to identify patients' risk factors for falls and to triage patients to appropriate services. Here we report the formative evaluation of this project. To evaluate the intervention we: 1) interviewed patient and employee stakeholders, 2) reviewed participating patients' electronic health record data and 3) abstracted information from meeting minutes. We describe the implementation process, including whether the project was implemented according to plan; identify barriers and facilitators to implementation; and assess the incremental benefit to the quality of health care for fall prevention received by patients in the project. We also estimate the cost of developing the pilot project. The project underwent multiple changes over its life span, including the addition of an option to mail patients educational materials about falls. During the project's lifespan, 113 patients were considered for inclusion and 35 participated. Patient and employee interviews suggested support for the project, but revealed that transportation to medical care was a major barrier in following up on fall risks identified by nurse telephone triage. Medical record review showed that the project enhanced usual medical care with respect to home safety counseling. We discontinued the program after 18 months due to staffing limitations and competing priorities. We estimated a cost of $9194 for meeting time to develop the project. The project appeared feasible at its outset but could not be sustained past the first cycle of evaluation due to insufficient resources and a waning of local

  19. Inhibition of multidrug efflux as a strategy to prevent biofilm formation.

    Science.gov (United States)

    Baugh, Stephanie; Phillips, Charlotte R; Ekanayaka, Aruna S; Piddock, Laura J V; Webber, Mark A

    2014-03-01

    We have recently shown that inactivation of any of the multidrug efflux systems of Salmonella results in loss of the ability to form a competent biofilm. The aim of this study was to determine the mechanism linking multidrug efflux and biofilm formation, and to determine whether inhibition of efflux is a viable antibiofilm strategy. Mutants lacking components of the AcrAB-TolC system in Salmonella enterica serovar Typhimurium were investigated for their ability to aggregate, produce biofilm matrix components and form a biofilm. The potential for export of a biofilm-relevant substrate via efflux pumps was investigated and expression of genes that regulate multidrug efflux and production of biofilm matrix components was measured. The ability of efflux inhibitors carbonyl cyanide m-chlorophenylhydrazone, chlorpromazine and phenyl-arginine-β-naphthylamide to prevent biofilm formation by Escherichia coli, Pseudomonas aeruginosa and Staphylococcus aureus under static and flow conditions was assessed. Mutants of Salmonella Typhimurium that lack TolC or AcrB, but surprisingly not AcrA, were compromised in their ability to form biofilms. This defect was not related to changes in cellular hydrophobicity, aggregative ability or export of any biofilm-specific factor. The biofilm defect resulted from transcriptional repression of curli biosynthesis genes and consequent inhibition of production of curli. All three efflux inhibitors significantly reduced biofilm production in both static and flow biofilm assays, although different concentrations of each inhibitor were most active against each species. This work shows that both genetic inactivation and chemical inhibition of efflux pumps results in transcriptional repression of biofilm matrix components and a lack of biofilm formation. Therefore, inhibition of efflux is a promising antibiofilm strategy.

  20. A density functional theory study of the hydrates of NH{sub 3}{center_dot}H{sub 2}SO{sub 4} and its implications for the formation of new atmospheric particles

    Energy Technology Data Exchange (ETDEWEB)

    Ianni, J.C.; Bandy, A.R. [Drexel Univ., Philadelphia, PA (United States). Dept. of Chemistry

    1999-04-15

    The interest in tropospheric and stratospheric aerosols has risen in past years. This is primarily due to the fact that aerosols in the troposphere and stratosphere are altering the earth`s climate by scattering radiation directly or indirectly by changing the reflectivity of clouds. They have also been involved in indirectly depleting the Antarctic stratospheric ozone layer by converting relatively inert chlorine species to photochemically reactive species which are well-known ozone-destroying species. Density functional molecular orbital theory was used at the B3LYP/6-311++G(2d,2p)//B3LYP/6-311++G(2d,2p) level of theory to study the hydrates of NH{sub 3}{center_dot}H{sub 2}SO{sub 4}{center_dot}nH{sub 2}O for n = 0--5 and NH{sub 3}{center_dot}(H{sub 2}SO{sub 4}){sub 2}{center_dot}H{sub 2}O. Neutrals of the first four NH{sub 3}{center_dot}H{sub 2}SO{sub 4}{center_dot}nH{sub 2}O clusters (n = 0--4) spontaneously formed and were determined to be hydrogen-bonded molecular complexes of H{sub 2}SO{sub 4}, H{sub 2}O, and NH{sub 3}. Double ions (clusters containing a NH{sub 4}{sup +} cation and a HSO{sub 4}{sup {minus}} anion) spontaneously formed in clusters of NH{sub 3}{center_dot}{approximately}H{sub 2}SO{sub 4}{center_dot}nH{sub 2}O where n = 1--5. The energetics of the hydration and isomerization reactions also were calculated. Double ions are not energetically favorable until NH{sub 3}{center_dot}H{sub 2}SO{sub 4}{center_dot}4H{sub 2}O. The free energy of formation from free NH{sub 3} and H{sub 2}SO{sub 4}{center_dot}nH{sub 2}O had a maximum at n = 3 at room temperature with {Delta}G {approx} {minus}3 kcal/mol. NH{sub 3}{center_dot}(H{sub 2}SO{sub 4}){sub 2}{center_dot}H{sub 2}O was studied to see if NH{sub 3} can initiate new atmospheric particle growth. It has been shown that NH{sub 3} has no role in the initialization of new atmospheric particles.

  1. Simulation of subsea gas hydrate exploitation

    Science.gov (United States)

    Janicki, Georg; Schlüter, Stefan; Hennig, Torsten; Deerberg, Görge

    2014-05-01

    The recovery of methane from gas hydrate layers that have been detected in several subsea sediments and permafrost regions around the world is a promising perspective to overcome future shortages in natural gas supply. Being aware that conventional natural gas resources are limited, research is going on to develop technologies for the production of natural gas from such new sources. Thus various research programs have started since the early 1990s in Japan, USA, Canada, India, and Germany to investigate hydrate deposits and develop required technologies. In recent years, intensive research has focussed on the capture and storage of CO2 from combustion processes to reduce climate impact. While different natural or man-made reservoirs like deep aquifers, exhausted oil and gas deposits or other geological formations are considered to store gaseous or liquid CO2, the storage of CO2 as hydrate in former methane hydrate fields is another promising alternative. Due to beneficial stability conditions, methane recovery may be well combined with CO2 storage in the form of hydrates. Regarding technological implementation many problems have to be overcome. Especially mixing, heat and mass transfer in the reservoir are limiting factors causing very long process times. Within the scope of the German research project »SUGAR« different technological approaches for the optimized exploitation of gas hydrate deposits are evaluated and compared by means of dynamic system simulations and analysis. Detailed mathematical models for the most relevant chemical and physical processes are developed. The basic mechanisms of gas hydrate formation/dissociation and heat and mass transport in porous media are considered and implemented into simulation programs. Simulations based on geological field data have been carried out. The studies focus on the potential of gas production from turbidites and their fitness for CO2 storage. The effects occurring during gas production and CO2 storage within

  2. Protein hydration and dynamics

    International Nuclear Information System (INIS)

    Nakagawa, Hiroshi; Kataoka, Mikio

    2015-01-01

    Inelastic neutron scattering can measure the protein thermal fluctuations under the physiological aqueous environment, especially it is powerful to observe the low-energy protein dynamics in THz region, which are revealed theoretically to be coupled with solvations. Neutron enables the selective observation of protein and hydration water by deuteration. The complementary analysis with molecular dynamics simulation is also effective for the study of protein hydration. Some examples of the application toward the understanding of molecular basis of protein functions will be introduced. (author)

  3. Investigation of the Flow Characteristics of Methane Hydrate Slurries with Low Flow Rates

    Directory of Open Access Journals (Sweden)

    Cuiping Tang

    2017-01-01

    Full Text Available Gas hydrate blockage in pipelines during offshore production becomes a major problem with increasing water depth. In this work, a series of experiments on gas hydrate formation in a flow loop was performed with low flow rates of 0.33, 0.66, and 0.88 m/s; the effects of the initial subcooling, flow rate, pressure, and morphology were investigated for methane hydrate formation in the flow loop. The results indicate that the differential pressure drop (ΔP across two ends of the horizontal straight pipe increases with increasing hydrate concentration at the early stage of gas hydrate formation. When the flow rates of hydrate fluid are low, the higher the subcooling is, the faster the transition of the hydrates macrostructures. Gas hydrates can agglomerate, and sludge hydrates appear at subcoolings of 6.5 and 8.5 °C. The difference between the ΔP values at different flow rates is small, and there is no obvious influence of the flow rates on ΔP. Three hydrate macrostructures were observed: slurry-like, sludge-like, and their transition. When the initial pressure is 8.0 MPa, large methane hydrate blockages appear at the gas hydrate concentration of approximately 7%. Based on the gas–liquid two-phase flow model, a correlation between the gas hydrate concentration and the value of ΔP is also presented. These results can enrich the kinetic data of gas hydrate formation and agglomeration and provide guidance for oil and gas transportation in pipelines.

  4. cAMP prevents TNF-induced apoptosis through inhibiting DISC complex formation in rat hepatocytes

    Energy Technology Data Exchange (ETDEWEB)

    Bhattacharjee, Rajesh [Department of Surgery, University of Pittsburgh Medical Center, Pittsburgh, PA 15213 (United States); Xiang, Wenpei [Department of Surgery, University of Pittsburgh Medical Center, Pittsburgh, PA 15213 (United States); Family Planning Research Institute, Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430030, People' s Republic of China (China); Wang, Yinna [Vascular Medicine Institute, University of Pittsburgh School of Medicine, 10051-5A BST 3, 3501 Fifth Avenue, Pittsburgh, PA 15261 (United States); Zhang, Xiaoying [Department of Medicine/Endocrinology Division, University of Pittsburgh Medical Center, 200 Lothrop St., Pittsburgh, PA 15213 (United States); Billiar, Timothy R., E-mail: billiartr@upmc.edu [Department of Surgery, University of Pittsburgh Medical Center, Pittsburgh, PA 15213 (United States)

    2012-06-22

    that cAMP exerts its affect at the proximal level of TNF signaling by inhibiting the formation of the DISC complex upon the binding of TNF to TNFR1. In conclusion, our study shows that cAMP prevents TNF + ActD-induced apoptosis in rat hepatocytes by inhibiting DISC complex formation.

  5. A DFT-based comparative equilibrium study of thermal dehydration and hydrolysis of CaCl₂ hydrates and MgCl₂ hydrates for seasonal heat storage.

    Science.gov (United States)

    Pathak, Amar Deep; Nedea, Silvia; Zondag, Herbert; Rindt, Camilo; Smeulders, David

    2016-04-21

    Salt hydrates store solar energy in chemical form via a reversible dehydration-hydration reaction. However, as a side reaction to dehydration, hydrolysis (HCl formation) may occur in chloride based salt hydrates (specially in MgCl2 hydrates), affecting the durability of the storage system. The mixture of CaCl2 and MgCl2 hydrates has been shown experimentally to have exceptional cycle stability and improved kinetics. However, the optimal operating conditions for the mixture are unknown. To understand the appropriate balance between dehydration and hydrolysis kinetics in the mixtures, it is essential to gain in-depth insight into the mixture components. We present a GGA-DFT level study to investigate the various gaseous structures of CaCl2 hydrates and to understand the relative stability of their conformers. The hydration strength and relative stability of conformers are dominated by electrostatic interactions. A wide network of intramolecular homonuclear and heteronuclear hydrogen bonds is observed in CaCl2 hydrates. Equilibrium product concentrations are obtained during dehydration and hydrolysis reactions under various temperature and pressure conditions. The trend of the dehydration curve with temperature in CaCl2 hydrates is similar to the experiments. Comparing these results to those of MgCl2 hydrates, we find that CaCl2 hydrates are more resistant towards hydrolysis in the temperature range of 273-800 K. Specifically, the present study reveals that the onset temperatures of HCl formation, a crucial design parameter for MgCl2 hydrates, are lower than for CaCl2 hydrates except for the mono-hydrate.

  6. Contribution of formative research to design an environmental program for obesity prevention in schools in Mexico City.

    Science.gov (United States)

    Bonvecchio, Anabelle; Théodore, Florence L; Safdie, Margarita; Duque, Tiffany; Villanueva, María Ángeles; Torres, Catalina; Rivera, Juan

    2014-01-01

    This paper describes the methods and key findings of formative research conducted to design a school-based program for obesity prevention. Formative research was based on the ecological model and the principles of social marketing. A mixed method approach was used. Qualitative (direct observation, indepth interviews, focus group discussions and photo-voice) and quantitative (closed ended surveys, checklists, anthropometry) methods were employed. Formative research key findings, including barriers by levels of the ecological model, were used for designing a program including environmental strategies to discourage the consumption of energy dense foods and sugar beverages. Formative research was fundamental to developing a context specific obesity prevention program in schools that seeks environment modification and behavior change.

  7. Ultraviolet light-irradiated photocrosslinkable chitosan hydrogel to prevent bone formation in both rat skull and fibula bone defects.

    Science.gov (United States)

    Tsuda, Yoshifumi; Hattori, Hidemi; Tanaka, Yoshihiro; Ishihara, Masayuki; Kishimoto, Satoko; Amako, Masatoshi; Arino, Hiroshi; Nemoto, Koichi

    2013-09-01

    In the field of orthopaedic surgery, an orthopaedic surgeon sometimes requires to suppress excessive bone formation, such as ectopic bone formation, ossifying myositis and radio-ulnar synostosis, etc. Ultraviolet (UV) light irradiation of a photocrosslinkable chitosan (Az-CH-LA) generates an insoluble hydrogel within 30 s. The purpose of this study was to evaluate the ability of the photocrosslinked chitosan hydrogel (PCH) to inhibit bone formation in an experimental model of bone defect. Rat calvarium and fibula were surgically injured and PCH was implanted into the resultant bone defects. The PCH implants significantly prevented bone formation in the bone defects during the 4 and 8 week observation periods. In the PCH-treated defects, fibrous tissues infiltrated by inflammatory cells were formed by day 7, completely filling the bone defects. In addition to these findings, expression of osteocalcin and runt-related gene 2 (RUNX2) mRNA, both markers of bone formation, was lower in the PCH-treated defects than in the controls. In contrast, collagen type 1α2 and α-smooth muscle actin (α-SMA) mRNA levels were significantly higher in the PCH-treated defects after 1 week. PCH stimulated the formation of fibrous tissue in bone defects while inhibiting bone formation. Thus, PCH might be a promising new therapeutic biomaterial for the prevention of bone formation in orthopaedic surgery. Copyright © 2012 John Wiley & Sons, Ltd.

  8. Aluminum Sulfate 18 Hydrate

    Science.gov (United States)

    Young, Jay A.

    2004-01-01

    A chemical laboratory information profile (CLIP) of the chemical, aluminum sulfate 18 hydrate, is presented. The profile lists physical and harmful properties, exposure limits, reactivity risks, and symptoms of major exposure for the benefit of teachers and students using the chemical in the laboratory.

  9. Novel application for the prevention and treatment of Staphylococcus aureus biofilm formation

    Science.gov (United States)

    Traba, Christian

    Formation of bacterial biofilms at solid-liquid interfaces creates numerous problems in both industrial and biomedical sciences. In this dissertation, the application of plasma from two very different facets was studied. In part one, the susceptibility of pre-formed Staphylococcus aureus biofilms on biomaterials to different plasmas was investigated. It was found that the distinct chemical/physical properties of plasmas generated from oxygen, nitrogen, and argon all demonstrated very potent but very different anti-biofilm mechanisms of action. An in depth analysis of these results show: 1) different reactive species produced in each plasma demonstrate specific activity, and 2) the commonly associated etching effect could be manipulated and even controlled, depending on experimental conditions and the discharge gas. These studies provide insights into the anti-biofilm mechanisms of plasma as well as the effects of different reactive species on biofilm inactivation. Under experimental parameters, bacterial cells in Staphylococcus aureus biofilms were killed (>99.9%) by plasmas within minutes of exposure and no bacteria nor biofilm re-growth from discharge gas treated biofilms was observed throughout the life-span of the re-growth experiment. The decontamination ability of plasmas for the treatment of biofilm related infections on biomedical materials was confirmed and novel applications involving the use of low power argon and oxygen for the treatment of biofilm contaminated biomaterials and indwelling devices is proposed. The second facet of this dissertation explores the interaction between biofilm forming Staphylococcus aureus bacteria on different antibacterial/anti-biofilm surfaces. The antibiotic-free anti-fouling surfaces constructed in this study were generated from the plasma-assisted graft polymerization technique. These sophisticated surfaces were stable, biocompatible and capable of preventing biofilm formation on biomaterials and medical devices. Under

  10. Preventing Pressure Sores

    Medline Plus

    Full Text Available ... L Sarah Harrison, OT Anne Bryden, OT The Role of the Social Worker after Spinal Cord Injury ... do to prevent pressure sores? play_arrow What role does diet and hydration play in preventing pressure ...

  11. Preventing Pressure Sores

    Medline Plus

    Full Text Available ... to prevent pressure sores? play_arrow What is “skin tolerance” and how can it be ... play_arrow What role does diet and hydration play in preventing pressure sores among ...

  12. Assessing the conditions favorable for the occurrence of gas hydrate in the Tuonamu area Qiangtang basin, Qinghai–Tibetan, China

    International Nuclear Information System (INIS)

    He Jianglin; Wang Jian; Fu Xiugen; Zheng Chenggang; Chen Yanting

    2012-01-01

    Highlights: ► This is a pioneer research on the exploration of gas hydrate in Qiangtang basin. ► The factors influencing the stable of gas hydrate in Tuonamu area were studied. ► Simulation shows that gas hydrate stable zone is about 300 m thick in target area. ► Source condition is the key factor for the formation of gas hydrate in this area. ► The areas around the deeper faults are favorable targets for gas hydrate. - Abstract: Qiangtang basin, which is located in the largest continuous permafrost area in Qinghai–Tibetan Plateau, is expected to be a strategic area of gas hydrate exploitation in China. However, relatively little work has been done on the exploration of gas hydrate in this area. In this work, we evaluated the factors controlling the formation of gas hydrate in the Tuonamu area and provided a preliminary insight into gas hydrate distribution in it on the basis of the core samples, seismic data and laboratory analysis. It can be concluded that the source rock in the deeper formation would be dominant thermogenic source for the formation of gas hydrate in Tuonamu area. The thickness of gas hydrate stable zone in this area is about 300 m. The gas hydrate in the area most probably is in the form of gas-hydrate-water. The source condition is the key factor for the formation of gas hydrate and the gas hydrate layer would be mainly present in the form of interlayer in this area. The areas around the deeper faults are the favorable targets for the exploration of gas hydrate in the Tuonamu area.

  13. Calcium and magnesium silicate hydrates

    International Nuclear Information System (INIS)

    Lothenbach, B.; L'Hopital, E.; Nied, D.; Achiedo, G.; Dauzeres, A.

    2015-01-01

    Deep geological disposals are planed to discard long-lived intermediate-level and high-level radioactive wastes. Clay-based geological barriers are expected to limit the ingress of groundwater and to reduce the mobility of radioelements. In the interaction zone between the cement and the clay based material alteration can occur. Magnesium silicate hydrates (M-S-H) have been observed due to the reaction of magnesium sulfate containing groundwater with cements or in the interaction zone between low-pH type cement and clays. M-S-H samples synthesized in the laboratory showed that M-S-H has a variable composition within 0.7 ≤ Mg/Si ≤ 1.5. TEM/EDS analyses show an homogeneous gel with no defined structure. IR and 29 Si NMR data reveal a higher polymerization degree of the silica network in M-S-H compared to calcium silicate hydrates (C-S-H). The presence of mainly Q 3 silicate tetrahedrons in M-S-H indicates a sheet like or a triple-chain silica structure while C-S-H is characterised by single chain-structure. The clear difference in the silica structure and the larger ionic radius of Ca 2+ (1.1 Angstrom) compared to Mg 2+ (0.8 Angstrom) make the formation of an extended solid solution between M-S-H and C-S-H gel improbable. In fact, the analyses of synthetic samples containing both magnesium and calcium in various ratios indicate the formation of separate M-S-H and C-S-H gels with no or very little uptake of magnesium in CS-H or calcium in M-S-H

  14. Prevention of biofilm formation by dairy products and N-acetylcysteine on voice prostheses in an artificial throat

    NARCIS (Netherlands)

    Schwandt, LQ; Van Weissenbruch, R; Stokroos, [No Value; Van der Mei, HC; Busscher, HJ; Albers, FWJ

    Objective - To evaluate the preventive effect of buttermilk, Yakult Light fermented milk drink and N-acetylcysteine on biofilm formation on voice prostheses in vitro. Material and Methods - Groningen button and Provox(R) 2 voice prostheses were inoculated with a mixture of bacteria and yeasts

  15. An effective medium inversion algorithm for gas hydrate quantification and its application to laboratory and borehole measurements of gas hydrate-bearing sediments

    Science.gov (United States)

    Chand, S.; Minshull, T.A.; Priest, J.A.; Best, A.I.; Clayton, C.R.I.; Waite, W.F.

    2006-01-01

    The presence of gas hydrate in marine sediments alters their physical properties. In some circumstances, gas hydrate may cement sediment grains together and dramatically increase the seismic P- and S-wave velocities of the composite medium. Hydrate may also form a load-bearing structure within the sediment microstructure, but with different seismic wave attenuation characteristics, changing the attenuation behaviour of the composite. Here we introduce an inversion algorithm based on effective medium modelling to infer hydrate saturations from velocity and attenuation measurements on hydrate-bearing sediments. The velocity increase is modelled as extra binding developed by gas hydrate that strengthens the sediment microstructure. The attenuation increase is modelled through a difference in fluid flow properties caused by different permeabilities in the sediment and hydrate microstructures. We relate velocity and attenuation increases in hydrate-bearing sediments to their hydrate content, using an effective medium inversion algorithm based on the self-consistent approximation (SCA), differential effective medium (DEM) theory, and Biot and squirt flow mechanisms of fluid flow. The inversion algorithm is able to convert observations in compressional and shear wave velocities and attenuations to hydrate saturation in the sediment pore space. We applied our algorithm to a data set from the Mallik 2L–38 well, Mackenzie delta, Canada, and to data from laboratory measurements on gas-rich and water-saturated sand samples. Predictions using our algorithm match the borehole data and water-saturated laboratory data if the proportion of hydrate contributing to the load-bearing structure increases with hydrate saturation. The predictions match the gas-rich laboratory data if that proportion decreases with hydrate saturation. We attribute this difference to differences in hydrate formation mechanisms between the two environments.

  16. The Hydrated Electron

    Science.gov (United States)

    Herbert, John M.; Coons, Marc P.

    2017-05-01

    Existence of a hydrated electron as a byproduct of water radiolysis was established more than 50 years ago, yet this species continues to attract significant attention due to its role in radiation chemistry, including DNA damage, and because questions persist regarding its detailed structure. This work provides an overview of what is known in regards to the structure and spectroscopy of the hydrated electron, both in liquid water and in clusters [Formula: see text], the latter of which provide model systems for how water networks accommodate an excess electron. In clusters, the existence of both surface-bound and internally bound states of the excess electron has elicited much debate, whereas in bulk water there are questions regarding how best to understand the structure of the excess electron's spin density. The energetics of the equilibrium species e-(aq) and its excited states, in bulk water and at the air/water interface, are also addressed.

  17. Formative research to develop theory-based messages for a Western Australian child drowning prevention television campaign: study protocol.

    Science.gov (United States)

    Denehy, Mel; Crawford, Gemma; Leavy, Justine; Nimmo, Lauren; Jancey, Jonine

    2016-05-20

    Worldwide, children under the age of 5 years are at particular risk of drowning. Responding to this need requires the development of evidence-informed drowning prevention strategies. Historically, drowning prevention strategies have included denying access, learning survival skills and providing supervision, as well as education and information which includes the use of mass media. Interventions underpinned by behavioural theory and formative evaluation tend to be more effective, yet few practical examples exist in the drowning and/or injury prevention literature. The Health Belief Model and Social Cognitive Theory will be used to explore participants' perspectives regarding proposed mass media messaging. This paper describes a qualitative protocol to undertake formative research to develop theory-based messages for a child drowning prevention campaign. The primary data source will be focus group interviews with parents and caregivers of children under 5 years of age in metropolitan and regional Western Australia. Qualitative content analysis will be used to analyse the data. This study will contribute to the drowning prevention literature to inform the development of future child drowning prevention mass media campaigns. Findings from the study will be disseminated to practitioners, policymakers and researchers via international conferences, peer and non-peer-reviewed journals and evidence summaries. The study was submitted and approved by the Curtin University Human Research Ethics Committee. Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://www.bmj.com/company/products-services/rights-and-licensing/

  18. Modeling Hydrates and the Gas Hydrate Markup Language

    Directory of Open Access Journals (Sweden)

    Weihua Wang

    2007-06-01

    Full Text Available Natural gas hydrates, as an important potential fuels, flow assurance hazards, and possible factors initiating the submarine geo-hazard and global climate change, have attracted the interest of scientists all over the world. After two centuries of hydrate research, a great amount of scientific data on gas hydrates has been accumulated. Therefore the means to manage, share, and exchange these data have become an urgent task. At present, metadata (Markup Language is recognized as one of the most efficient ways to facilitate data management, storage, integration, exchange, discovery and retrieval. Therefore the CODATA Gas Hydrate Data Task Group proposed and specified Gas Hydrate Markup Language (GHML as an extensible conceptual metadata model to characterize the features of data on gas hydrate. This article introduces the details of modeling portion of GHML.

  19. Magnesium prevents vascular calcification in vitro by inhibition of hydroxyapatite crystal formation.

    NARCIS (Netherlands)

    Braake, A.D. ter; Tinnemans, P.T.; Shanahan, C.M.; Hoenderop, J.G.J.; Baaij, J.H.F. de

    2018-01-01

    Magnesium has been shown to effectively prevent vascular calcification associated with chronic kidney disease. Magnesium has been hypothesized to prevent the upregulation of osteoblastic genes that potentially drives calcification. However, extracellular effects of magnesium on hydroxyapatite

  20. Gogo receptor contributes to retinotopic map formation and prevents R1-6 photoreceptor axon bundling.

    Directory of Open Access Journals (Sweden)

    Irina Hein

    Full Text Available BACKGROUND: Topographic maps form the basis of neural processing in sensory systems of both vertebrate and invertebrate species. In the Drosophila visual system, neighboring R1-R6 photoreceptor axons innervate adjacent positions in the first optic ganglion, the lamina, and thereby represent visual space as a continuous map in the brain. The mechanisms responsible for the establishment of retinotopic maps remain incompletely understood. RESULTS: Here, we show that the receptor Golden goal (Gogo is required for R axon lamina targeting and cartridge elongation in a partially redundant fashion with local guidance cues provided by neighboring axons. Loss of function of Gogo in large clones of R axons results in aberrant R1-R6 fascicle spacing. Gogo affects target cartridge selection only indirectly as a consequence of the disordered lamina map. Interestingly, small clones of gogo deficient R axons perfectly integrate into a proper retinotopic map suggesting that surrounding R axons of the same or neighboring fascicles provide complementary spatial guidance. Using single photoreceptor type rescue, we show that Gogo expression exclusively in R8 cells is sufficient to mediate targeting of all photoreceptor types in the lamina. Upon lamina targeting and cartridge selection, R axons elongate within their individual cartridges. Interestingly, here Gogo prevents bundling of extending R1-6 axons. CONCLUSION: Taken together, we propose that Gogo contributes to retinotopic map formation in the Drosophila lamina by controlling the distribution of R1-R6 axon fascicles. In a later developmental step, the regular position of R1-R6 axons along the lamina plexus is crucial for target cartridge selection. During cartridge elongation, Gogo allows R1-R6 axons to extend centrally in the lamina cartridge.

  1. Prevention of Human Lymphoproliferative Tumor Formation in Ovarian Cancer Patient-Derived Xenografts

    Directory of Open Access Journals (Sweden)

    Kristina A. Butler

    2017-08-01

    Full Text Available Interest in preclinical drug development for ovarian cancer has stimulated development of patient-derived xenograft (PDX or tumorgraft models. However, the unintended formation of human lymphoma in severe combined immunodeficiency (SCID mice from Epstein-Barr virus (EBV–infected human lymphocytes can be problematic. In this study, we have characterized ovarian cancer PDXs which developed human lymphomas and explore methods to suppress lymphoproliferative growth. Fresh human ovarian tumors from 568 patients were transplanted intraperitoneally in SCID mice. A subset of PDX models demonstrated atypical patterns of dissemination with mediastinal masses, hepatosplenomegaly, and CD45-positive lymphoblastic atypia without ovarian tumor engraftment. Expression of human CD20 but not CD3 supported a B-cell lineage, and EBV genomes were detected in all lymphoproliferative tumors. Immunophenotyping confirmed monoclonal gene rearrangements consistent with B-cell lymphoma, and global gene expression patterns correlated well with other human lymphomas. The ability of rituximab, an anti-CD20 antibody, to suppress human lymphoproliferation from a patient's ovarian tumor in SCID mice and prevent growth of an established lymphoma led to a practice change with a goal to reduce the incidence of lymphomas. A single dose of rituximab during the primary tumor heterotransplantation process reduced the incidence of CD45-positive cells in subsequent PDX lines from 86.3% (n = 117 without rituximab to 5.6% (n = 160 with rituximab, and the lymphoma rate declined from 11.1% to 1.88%. Taken together, investigators utilizing PDX models for research should routinely monitor for lymphoproliferative tumors and consider implementing methods to suppress their growth.

  2. The effect of hydrate promoters on gas uptake.

    Science.gov (United States)

    Xu, Chun-Gang; Yu, Yi-Song; Ding, Ya-Long; Cai, Jing; Li, Xiao-Sen

    2017-08-16

    Gas hydrate technology is considered as a promising technology in the fields of gas storage and transportation, gas separation and purification, seawater desalination, and phase-change thermal energy storage. However, to date, the technology is still not commercially used mainly due to the low gas hydrate formation rate and the low gas uptake. In this study, the effect of hydrate promoters on gas uptake was systematically studied and analyzed based on hydrate-based CH 4 storage and CO 2 capture from CO 2 /H 2 gas mixture experiments. Raman spectroscopy, Fourier transform infrared spectroscopy (FTIR) and gas chromatography (GC) were employed to analyze the microstructures and gas compositions. The results indicate that the effect of the hydrate promoter on the gas uptake depends on the physical and chemical properties of the promoter and gas. A strong polar ionic promoter is not helpful towards obtaining the ideal gas uptake because a dense hydrate layer is easily formed at the gas-liquid interface, which hinders gas diffusion from the gas phase to the bulk solution. For a weak polar or non-polar promoter, the gas uptake depends on the dissolution characteristics among the different substances in the system. The lower the mutual solubility among the substances co-existing in the system, the higher the independence among the substances in the system; this is so that each phase has an equal chance to occupy the hydrate cages without or with small interactions, finally leading to a relatively high gas uptake.

  3. Kinetic studies of methane-ethane mixed gas hydrates by neutron diffraction and Raman spectroscopy.

    Science.gov (United States)

    Murshed, M Mangir; Kuhs, Werner F

    2009-04-16

    In situ formations of CH(4)-C(2)H(6) mixed gas hydrates were made using high flux neutron diffraction at 270 K and 5 MPa. For this purpose, a feed gas composition of CH(4) and C(2)H(6) (95 mol% CH(4)) was employed. The rates of transformation of spherical grains of deuterated ice Ih into hydrates were measured by time-resolved neutron powder diffraction on D20 at ILL, Grenoble. Phase fractions of the crystalline constituents were obtained from Rietveld refinements. A concomitant formation of structure type I (sI) and structure type II (sII) hydrates were observed soon after the gas pressure was applied. The initial fast formation of sII hydrate reached its maximum volume and started declining very slowly. The formation of sI hydrate followed a sigmoid growth kinetics that slowed down due to diffusion limitation. This observation has been interpreted in terms of a kinetically favored nucleation of the sII hydrate along with a slow transformation into sI. Both powder diffraction and Raman spectroscopic results suggest that a C(2)H(6)-rich sII hydrate was formed at the early part of the clathration, which slowly decreased to approximately 3% after a reaction of 158 days as confirmed by synchrotron XRD. The final persistence of a small portion of sII hydrate points to a miscibility gap between CH(4)-rich sI and C(2)H(6)-rich sII hydrates.

  4. MORPHOLOGY OF METHANE HYDRATE HOST SEDIMENTS.

    Energy Technology Data Exchange (ETDEWEB)

    JONES,K.W.; FENG,H.; TOMOV,S.; WINTER,W.J.; EATON,M.; MAHAJAN,D.

    2004-12-01

    Results from simulated experiments in several laboratories show that host sediments influence hydrate formation in accord with known heterogeneity of host sediments at sites of gas hydrate occurrence (1). For example, in Mackenzie Delta, NWT Canada (Mallik 2L-38 well), coarser-grained units (pore-filling model) are found whereas in the Gulf of Mexico, the found hydrate samples do not appear to be lithologically controlled. We have initiated a systematic study of sediments, initially focusing on samples from various depths at a specific site, to establish a correlation with hydrate occurrence (or variations thereof) to establish differences in their microstructure, porosity, and other associated properties. The synchrotron computed microtomography (CMT) set-up at the X-27A tomography beam line at the National Synchrotron Light Source (NSLS), Brookhaven National Laboratory was used as a tool to study sediments from Blake Ridge at three sub bottom depths of 0.2, 50, and 667 meters. Results from the tomographic analysis of the deepest sample (667 m) are presented here to illustrate how tomography can be used to obtain new insights into the structures of methane hydrate host sediments. The investigation shows the internal grain/pore space resolution in the microstructure and a 3-D visualization of the connecting pathways obtained following data segmentation into pore space and grains within the sediment sample. The analysis gives the sample porosity, specific surface area, mean particle size, and tortuosity, as well. An earlier report on the experimental program has been given by Mahajan et al. (2).

  5. Rheological properties of hydrate suspensions in asphaltenic crude oils; Proprietes rheologiques de suspensions d'hydrate dans des bruts asphalteniques

    Energy Technology Data Exchange (ETDEWEB)

    Marques de Toledo Camargo, R.

    2001-03-01

    The development of offshore oil exploitation under increasing water depths has forced oil companies to increase their understanding of gas hydrate formation and transportation in multiphase flow lines in which a liquid hydrocarbon phase is present. This work deals with the flow behaviour of hydrate suspensions in which a liquid hydrocarbon is the continuous phase. Three different liquid hydrocarbons are used: an asphaltenic crude oil, a condensate completely free of asphaltenes and a mixture between the asphaltenic oil and heptane. The rheological characterisation of hydrate suspensions is the main tool employed. Two original experimental devices are used: a PVT cell adapted to operate as a Couette type rheometer and a semi-industrial flow loop. Hydrate suspensions using the asphaltenic oil showed shear-thinning behaviour and thixotropy. This behaviour is typically found in flocculated systems, in which the particles attract each other forming flocs of aggregated particles at low shear rates. The suspensions using the condensate showed Newtonian behaviour. Their relative viscosities were high, which suggests that an aggregation process between hydrate particles takes. place during hydrate formation. Finally, hydrate suspensions using the mixture asphaltenic oil-heptane showed shear-thinning behaviour, thixotropy and high relative viscosity. From these results it can be inferred that, after the achievement of the hydrate formation process, the attractive forces between hydrate particles are weak. making unlikely pipeline obstruction by an aggregation process. Nevertheless, during the hydrate formation, these attractive forces can be sufficiently high. It seems that the hydrate surface wettability is an important parameter in this phenomena. (author)

  6. 3D pore-type digital rock modeling of natural gas hydrate for permafrost and numerical simulation of electrical properties

    Science.gov (United States)

    Dong, Huaimin; Sun, Jianmeng; Lin, Zhenzhou; Fang, Hui; Li, Yafen; Cui, Likai; Yan, Weichao

    2018-02-01

    Natural gas hydrate is being considered as an alternative energy source for sustainable development and has become a focus of research throughout the world. In this paper, based on CT scanning images of hydrate reservoir rocks, combined with the microscopic distribution of hydrate, a diffusion limited aggregation (DLA) model was used to construct 3D hydrate digital rocks of different distribution types, and the finite-element method was used to simulate their electrical characteristics in order to study the influence of different hydrate distribution types, hydrate saturation and formation of water salinity on electrical properties. The results show that the hydrate digital rocks constructed using the DLA model can be used to characterize the microscopic distribution of different types of hydrates. Under the same conditions, the resistivity of the adhesive hydrate digital rock is higher than the cemented and scattered type digital rocks, and the resistivity of the scattered hydrate digital rock is the smallest among the three types. Besides, the difference in the resistivity of the different types of hydrate digital rocks increases with an increase in hydrate saturation, especially when the saturation is larger than 55%, and the rate of increase of each of the hydrate types is quite different. Similarly, the resistivity of the three hydrate types decreases with an increase in the formation of water salinity. The single distribution hydrate digital rock constructed, combined with the law of microscopic distribution and influence of saturation on the electrical properties, can effectively improve the accuracy of logging identification of hydrate reservoirs and is of great significance for the estimation of hydrate reserves.

  7. Dongsha Area Gas-hydrate Petroleum System in northern Slope of the South China Sea

    Science.gov (United States)

    Pibo, Su; Zhibin, Sha

    2015-04-01

    In recent years, significant progress has been made in addressing key issues on the formation, occurrence,and stability of gas hydrate in nature. The concept of a gas-hydrate petroleum system, similar to the system that guides current conventional oil and gas exploration,is gaining acceptance.A gas-hydrate petroleum systems model is a digital data model of a gas-hydrate petroleum system in which the interrelated processes and their results can be simulated by numerical modeling.A new module of gas-hydrate petroleum system simulating can predict the thickness of the gas hydrate stability field, the generation and migration of biogenic and thermogenic methane gas,and its accumulation as gas hydrates in gas hydrate stability field. Dongsha area is located to eastern part of the Pearl River Mouth basin, and is one of the key hydrate-exploration areas in China. However, the gas hydrate petroleum system and basin modeling in Dongsha area haven't been paid enough attention. In the paper,geological conditions for gas hydrate formation have been naturally prepared on the Dong sha area.The paper first analyzed the geological-tectonic conditions of gas hydrate formation in Dongsha area,and selected the typical sections in Dong sha uplift area and southwest taiwan basin.The geological models of gas hydrate reservoir in the two study area were constructed through the typical seismic image.The typical seismic lines are obtained from the two study area by Guangzhou Marine Geological Survey.In combination with physical,thermal and geochemical data,the match condition of gas hydrate formation was studied.by sedimentary basin simulation technique.The research results is as followed:1.In southwest taiwan basin Basin, thermal developing history is low in deep department stratum,Source of gas of hydrate come from shallower biogenic gas;2.In Dongsha uplift areas,the thickness of Cenozoic is thin and the Sediment is limited,so biogenic gas was scarce,Source of gas of hydrate come from a

  8. Manufacture of Methane Hydrate using Carbon Nano Tubes

    International Nuclear Information System (INIS)

    Park, Sung Seek

    2010-02-01

    . Therefore, it is found that NaCl acts as a inhibitor. Also, when the multi wall carbon nanotubes of 0.004 wt% was added to pure water, the amount of consumed gas was about 300% higher than that in pure water and the hydrate formation time decreased at the low subcooling temperature

  9. Hydrate plugging or slurry flow : effect of key variables

    Energy Technology Data Exchange (ETDEWEB)

    Dellecase, E.; Geraci, G.; Barrios, L.; Estanga, D.; Domingues, R.; Volk, M. [Tulsa Univ., Tulsa, OK (United States)

    2008-07-01

    Although oil and gas companies have proven design criteria and proper operating procedures to prevent hydrate plugs from forming, hydrates remain the primary issue in flow assurance. The costs associated with hydrate prevention affect project economics, particularly in deepwater pipelines. As such, there is an interest in developing a technology that allows hydrates to be transported as a slurry, while avoiding plugs. The feasibility of managing such hydrate flow was investigated. This study used a hydrate flow loop to investigate the effects of flow conditions on the transportability of a slurry in both steady-state and restart conditions. For most cases, uninhibited steady-state slurry flow conditions above 25 per cent water-cut were marginal, and most likely not feasible at 50 per cent water-cut or above. Liquid loading and velocity appeared to have a marginal effect on plugging tendency. However, minimum velocity may be needed to guarantee slurry transportation. Some of the important parameters and key variables that determine if a plug will form, particularly in restart conditions, include oil-water dispersion properties; oil-water phase segregation on the plugging tendency of model fluids; the location and state of the water; and the flow pattern. It was concluded that the plugging behaviour of oil systems changes with these variables, and with the oil-water chemistry. As such, specific strategies must be developed for each field. 4 refs., 1 tab., 14 figs.

  10. Gas hydrates of the Black sea sediment section

    International Nuclear Information System (INIS)

    Byakov, Y.A.; Kruglyakova, R.P.; Kruglyakova, M.V.

    2002-01-01

    Full text : This article shows how gas formation and its genesis in the Black sea sediments forms two types of gas hydrates. The first is diagenetic, formed from biochemical methane. The second type is thermogenic, formed from the thermogenic gases and represented not only by methane, but also by its light homologues, like ethane and propane. The most favourable area for formation of the gas hydrates of the first type in the Black sea is the foot of the continental slope and areas of underwater cones of paleorivers drift-over. Gas hydrates of the second type are accumulated in the areas of underwater mud volcanoes. In accordance with the results of seismic and seismoacoustic studies in deposited thickness of the Black sea the specific anomalies of the BSR and VAMP's types are revealed that associate with the foot of gas hydrate deposits. Two gas hydrates are distinguished according to sources of gas supply and genesis : type 1 - diagenetic, type 2 - thermogenic. When some critique is reached the gas hydrate trap breaks and volcanic eruption occurs. Thus, occurrence of underwater volcanism may testify the presence of deposits.

  11. Clinical study on orofacial photonic hydration using phototherapy and biomaterials

    Science.gov (United States)

    Lizarelli, Rosane F. Z.; Grandi, Natália D. P.; Florez, Fernando L. E.; Grecco, Clovis; Lopes, Luciana A.

    2015-06-01

    Skin hydration is important to prevent aging and dysfunction of orofacial system. Nowadays, it is known that cutaneous system is linked to muscle system, then every dentist need to treat healthy facial skin, as lips, keeping orofacial functions healthy. Thirty-two patients were treated using laser and led therapy single or associated to biomaterials (dermo-cosmetics) searching for the best protocol to promote skin hydration. Using a peace of equipment to measure electric impedance, percentage of water and oil from skin, before and after different treatments were analyzed. Statistic tests using 5% and 0.1% of significance were applied and results showed that light could improve hydration of epidermis layer of facial skin. Considering just light effect, using infrared laser followed by blue led system is more effective to hydration than just blue led system application. Considering dermo-cosmetic and light, the association between both presented the best result.

  12. Molecular mechanisms responsible for hydrate anti-agglomerant performance.

    Science.gov (United States)

    Phan, Anh; Bui, Tai; Acosta, Erick; Krishnamurthy, Pushkala; Striolo, Alberto

    2016-09-28

    Steered and equilibrium molecular dynamics simulations were employed to study the coalescence of a sI hydrate particle and a water droplet within a hydrocarbon mixture. The size of both the hydrate particle and the water droplet is comparable to that of the aqueous core in reverse micelles. The simulations were repeated in the presence of various quaternary ammonium chloride surfactants. We investigated the effects due to different groups on the quaternary head group (e.g. methyl vs. butyl groups), as well as different hydrophobic tail lengths (e.g. n-hexadecyl vs. n-dodecyl tails) on the surfactants' ability to prevent coalescence. Visual inspection of sequences of simulation snapshots indicates that when the water droplet is not covered by surfactants it is more likely to approach the hydrate particle, penetrate the protective surfactant film, reach the hydrate surface, and coalesce with the hydrate than when surfactants are present on both surfaces. Force-distance profiles obtained from steered molecular dynamics simulations and free energy profiles obtained from umbrella sampling suggest that surfactants with butyl tripods on the quaternary head group and hydrophobic tails with size similar to the solvent molecules can act as effective anti-agglomerants. These results qualitatively agree with macroscopic experimental observations. The simulation results provide additional insights, which could be useful in flow assurance applications: the butyl tripod provides adhesion between surfactants and hydrates; when the length of the surfactant tail is compatible with that of the hydrocarbon in the liquid phase a protective film can form on the hydrate; however, once a molecularly thin chain of water molecules forms through the anti-agglomerant film, connecting the water droplet and the hydrate, water flows to the hydrate and coalescence is inevitable.

  13. Gas Hydrate Stability and Sampling: The Future as Related to the Phase Diagram

    Directory of Open Access Journals (Sweden)

    E. Dendy Sloan

    2010-12-01

    Full Text Available The phase diagram for methane + water is explained, in relation to hydrate applications, such as in flow assurance and in nature. For natural applications, the phase diagram determines the regions for hydrate formation for two- and three-phase conditions. Impacts are presented for sample preparation and recovery. We discuss an international study for “Round Robin” hydrate sample preparation protocols and testing.

  14. Gas hydrate stability and sampling: the future as related to the phase diagram

    Energy Technology Data Exchange (ETDEWEB)

    Sloan, E. D.; Koh, C. A.; Sum, A. K. [Center for Hydrate Research, Chemical Engineering Department, Colorado School of Mines, 1500 Illinois Street, Golden, CO 80401 (United States)

    2010-12-15

    The phase diagram for methane plus water is explained, in relation to hydrate applications, such as in flow assurance and in nature. For natural applications, the phase diagram determines the regions for hydrate formation for two- and three-phase conditions. Impacts are presented for sample preparation and recovery. We discuss an international study for 'Round Robin' hydrate sample preparation protocols and testing. (authors)

  15. 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

  16. Modelling porewater chemistry in hydrated Portland cement

    International Nuclear Information System (INIS)

    Berner, U.R.

    1987-01-01

    Extensive employment of concrete is foreseen in radioactive waste repositories. A prerequisite for modelling the interactions between concrete and formation waters is characterization of the concrete system. Available experimental data from high pressure squeezing of cement pore-water indicate that, besides the high pH due to alkali hydroxide dissolution, cement composition itself influences the solubility determining solid phases. A model which simulates the hydration of Portland cement assuming complete hydration of the main clinker minerals is presented. The model also includes parameters describing the reactions between the cement and blending agents. Comparison with measured pore-water data generally gives a consistent picture and, as expected, the model gives correct predictions for pure Portland cements. For blended cements, the required additional parameters can, to some extent, be derived from pore-water analysis. 14 references, 1 figure, 4 tables

  17. Prevention

    Science.gov (United States)

    ... Error processing SSI file About Heart Disease & Stroke Prevention Heart disease and stroke are an epidemic in ... secondhand smoke. Barriers to Effective Heart Disease & Stroke Prevention Many people with key risk factors for heart ...

  18. X-ray CT Observations of Methane Hydrate Distribution Changes over Time in a Natural Sediment Core from the BPX-DOE-USGS Mount Elbert Gas Hydrate Stratigraphic Test Well

    Energy Technology Data Exchange (ETDEWEB)

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

    2010-03-01

    When maintained under hydrate-stable conditions, methane hydrate in laboratory samples is often considered a stable and immobile solid material. Currently, there do not appear to be any studies in which the long-term redistribution of hydrates in sediments has been investigated in the laboratory. These observations are important because if the location of hydrate in a sample were to change over time (e.g. by dissociating at one location and reforming at another), the properties of the sample that depend on hydrate saturation and pore space occupancy would also change. Observations of hydrate redistribution under stable conditions are also important in understanding natural hydrate deposits, as these may also change over time. The processes by which solid hydrate can move include dissociation, hydrate-former and water migration in the gas and liquid phases, and hydrate formation. Chemical potential gradients induced by temperature, pressure, and pore water or host sediment chemistry can drive these processes. A series of tests were performed on a formerly natural methane-hydrate-bearing core sample from the BPX-DOE-USGS Mount Elbert Gas Hydrate Stratigraphic Test Well, in order to observe hydrate formation and morphology within this natural sediment, and changes over time using X-ray computed tomography (CT). Long-term observations (over several weeks) of methane hydrate in natural sediments were made to investigate spatial changes in hydrate saturation in the core. During the test sequence, mild buffered thermal and pressure oscillations occurred within the sample in response to laboratory temperature changes. These oscillations were small in magnitude, and conditions were maintained well within the hydrate stability zone.

  19. Prevention of Addictive Behavior Based on the Formation of Teenagers' Resilience

    Science.gov (United States)

    Zeleeva, Vera P.; Shubnikova, Ekaterina G.

    2016-01-01

    The relevance of the study is due to the development of a new stage of prevention and the need to justify new educational goals and objectives of the pedagogical prevention of addictive behavior in the educational environment. The purpose of this article is to examine the totality of the necessary and sufficient individual resources, that are…

  20. Hydrate-CASM for modeling Methane Hydrate-Bearing Sediments

    Science.gov (United States)

    De La Fuente Ruiz, M.; Vaunat, J.; Marin Moreno, H.

    2017-12-01

    A clear understanding of the geomechanical behavior of methane hydrate-bearing sediments (MHBS) is crucial to assess the stability of the seafloor and submarine infrastructures to human and natural loading changes. Here we present the Hydrate-CASM, a new elastoplastic constitutive model to predict the geomechanical behavior of MHBS. Our model employs the critical state model CASM (Clay and Sand Model) because of its flexibility in describing the shape of the yield surface and its proven ability to predict the mechanical behavior of sands, the most commercially viable hydrate reservoirs. The model considers MHBS as a deformable elastoplastic continuum, and hydrate-related changes in the stress-strain behavior are predicted by a densification mechanism. The densification attributes the mechanical contribution of hydrate to; a reduction of the available void ratio; a decrease of the swelling line slope; and an increase of the volumetric yield stress. It is described by experimentally derived physical parameters except from the swelling slope coefficient that requires empirical calibration. The Hydrate-CASM is validated against published triaxial laboratory tests performed at different confinement stresses, hydrate saturations, and hydrate morphologies. During the validation, we focused on capturing the mechanical behavior of the host sediment and consider perturbations of the sediment's mechanical properties that could result from the sample preparation. Our model successfully captures the experimentally observed influence of hydrate saturation in the magnitude and trend of the stiffness, shear strength, and dilatancy of MHBS. Hence, we propose that hydrate-related densification changes might be a major factor controlling the geomechanical response of MHBS.

  1. Cryopegs as destabilization factor of intra-permafrost gas hydrates

    Science.gov (United States)

    Chuvilin, Evgeny; Bukhanov, Boris; Istomin, Vladimir

    2016-04-01

    A characteristic feature of permafrost soils in the Arctic is widespread intra-permafrost unfrozen brine lenses - cryopegs. They are often found in permafrost horizons in the north part of Western Siberia, in particular, on the Yamal Peninsula. Cryopegs depths in permafrost zone can be tens and hundreds of meters from the top of frozen strata. The chemical composition of natural cryopegs is close to sea waters, but is characterized by high mineralization. They have a sodium-chloride primary composition with a minor amount of sulphate. Mineralization of cryopegs brine is often hundreds of grams per liter, and the temperature is around -6…-8 °C. The formation of cryopegs in permafrost is associated with processes of long-term freezing of sediments and cryogenic concentration of salts and salt solutions in local areas. The cryopegs' formation can take place in the course of permafrost evolution at the sea transgressions and regressions during freezing of saline sea sediments. Very important feature of cryopegs in permafrost is their transformation in the process of changing temperature and pressure conditions. As a result, the salinity and chemical composition are changed and in addition the cryopegs' location can be changed during their migration. The cryopegs migration violates the thermodynamic conditions of existence intra-permafrost gas hydrate formations, especially the relic gas hydrates deposits, which are situated in the shallow permafrost up to 100 meters depth in a metastable state [1]. The interaction cryopegs with gas hydrates accumulations can cause decomposition of intra-permafrost hydrates. Moreover, the increasing of salt and unfrozen water content in sedimentary rocks sharply reduce the efficiency of gas hydrates self-preservation in frozen soils. It is confirmed by experimental investigations of interaction of frozen gas hydrate bearing sediments with salt solutions [2]. So, horizons with elevated pressure can appear, as a result of gas hydrate

  2. Molecular dynamics simulation of the intercalation behaviors of methane hydrate in montmorillonite.

    Science.gov (United States)

    Yan, KeFeng; Li, XiaoSen; Xu, ChunGang; Lv, QiuNan; Ruan, XuKe

    2014-06-01

    The formation and mechanism of CH4 hydrate intercalated in montmorillonite are investigated by molecular dynamics (MD) simulation. The formation process of CH4 hydrate in montmorillonite with 1 ~ 8 H2O layers is observed. In the montmorillonite, the "surface H2O" constructs the network by hydrogen bonds with the surface Si-O ring of clay, forming the surface cage. The "interlayer H2O" constructs the network by hydrogen bonds, forming the interlayer cage. CH4 molecules and their surrounding H2O molecules form clathrate hydrates. The cation of montmorillonite has a steric effect on constructing the network and destroying the balance of hydrogen bonds between the H2O molecules, distorting the cage of hydrate in clay. Therefore, the cages are irregular, which is unlike the ideal CH4 clathrate hydrates cage. The pore size of montmorillonite is another impact factor to the hydrate formation. It is quite easier to form CH4 hydrate nucleation in montmorillonite with large pore size than in montmorillonite with small pore. The MD work provides the constructive information to the investigation of the reservoir formation for natural gas hydrate (NGH) in sediments.

  3. Parametric study of the physical properties of hydrate-bearing sand, silt, and clay sediments: 2. Small-strain mechanical properties

    Science.gov (United States)

    Lee, J.Y.; Francisca, F.M.; Santamarina, J.C.; Ruppel, C.

    2010-01-01

    The small-strain mechanical properties (e.g., seismic velocities) of hydrate-bearing sediments measured under laboratory conditions provide reference values for calibration of logging and seismic exploration results acquired in hydrate-bearing formations. Instrumented cells were designed for measuring the compressional (P) and shear (S) velocities of sand, silts, and clay with and without hydrate and subject to vertical effective stresses of 0.01 to 2 MPa. Tetrahydrofuran (THF), which is fully miscible in water, was used as the hydrate former to permit close control over the hydrate saturation Shyd and to produce hydrate from dissolved phase, as methane hydrate forms in most natural marine settings. The results demonstrate that laboratory hydrate formation technique controls the pattern of P and S velocity changes with increasing Shyd and that the small-strain properties of hydrate-bearing sediments are governed by effective stress, δ'v and sediment specific surface. The S velocity increases with hydrate saturation owing to an increase in skeletal shear stiffness, particularly when hydrate saturation exceeds Shyd≈ 0.4. At very high hydrate saturations, the small strain shear stiffness is determined by the presence of hydrates and becomes insensitive to changes in effective stress. The P velocity increases with hydrate saturation due to the increases in both the shear modulus of the skeleton and the bulk modulus of pore-filling phases during fluid-to-hydrate conversion. Small-strain Poisson's ratio varies from 0.5 in soft sediments lacking hydrates to 0.25 in stiff sediments (i.e., subject to high vertical effective stress or having high Shyd). At Shyd ≥ 0.5, hydrate hinders expansion and the loss of sediment stiffness during reduction of vertical effective stress, meaning that hydrate-rich natural sediments obtained through pressure coring should retain their in situ fabric for some time after core retrieval if the cores are maintained within the hydrate

  4. Formative evaluation of the telecare fall prevention project for older veterans

    OpenAIRE

    Miake-Lye, Isomi M; Amulis, Angel; Saliba, Debra; Shekelle, Paul G; Volkman, Linda K; Ganz, David A

    2011-01-01

    Abstract Background Fall prevention interventions for community-dwelling older adults have been found to reduce falls in some research studies. However, wider implementation of fall prevention activities in routine care has yielded mixed results. We implemented a theory-driven program to improve care for falls at our Veterans Affairs healthcare facility. The first project arising from this program used a nurse advice telephone line to identify patients' risk factors for falls and to triage pa...

  5. In Situ Raman Detection of Gas Hydrates Exposed on the Seafloor of the South China Sea

    Science.gov (United States)

    Zhang, Xin; Du, Zengfeng; Luan, Zhendong; Wang, Xiujuan; Xi, Shichuan; Wang, Bing; Li, Lianfu; Lian, Chao; Yan, Jun

    2017-10-01

    Gas hydrates are usually buried in sediments. Here we report the first discovery of gas hydrates exposed on the seafloor of the South China Sea. The in situ chemical compositions and cage structures of these hydrates were measured at the depth of 1,130 m below sea level using a Raman insertion probe (RiP-Gh) that was carried and controlled by a remotely operated vehicle (ROV) Faxian. This in situ analytical technique can avoid the physical and chemical changes associated with the transport of samples from the deep sea to the surface. Natural gas hydrate samples were analyzed at two sites. The in situ spectra suggest that the newly formed hydrate was Structure I but contains a small amount of C3H8 and H2S. Pure gas spectra of CH4, C3H8, and H2S were also observed at the SCS-SGH02 site. These data represent the first in situ proof that free gas can be trapped within the hydrate fabric during rapid hydrate formation. We provide the first in situ confirmation of the hydrate growth model for the early stages of formation of crystalline hydrates in a methane-rich seafloor environment. Our work demonstrates that natural hydrate deposits, particularly those in the early stages of formation, are not monolithic single structures but instead exhibit significant small-scale heterogeneities due to inclusions of free gas and the surrounding seawater, there inclusions also serve as indicators of the likely hydrate formation mechanism. These data also reinforce the importance of correlating visual and in situ measurements when characterizing a sampling site.

  6. Cranberry-derived proanthocyanidins prevent formation of Candida albicans biofilms in artificial urine through biofilm- and adherence-specific mechanisms.

    Science.gov (United States)

    Rane, Hallie S; Bernardo, Stella M; Howell, Amy B; Lee, Samuel A

    2014-02-01

    Candida albicans is a common cause of nosocomial urinary tract infections (UTIs) and is responsible for increased morbidity and healthcare costs. Moreover, the US Centers for Medicare & Medicaid Services no longer reimburse for hospital-acquired catheter-associated UTIs. Thus, development of specific approaches for the prevention of Candida urinary infections is needed. Cranberry juice-derived proanthocyanidins (PACs) have efficacy in the prevention of bacterial UTIs, partially due to anti-adherence properties, but there are limited data on their use for the prevention and/or treatment of Candida UTIs. Therefore, we sought to systematically assess the in vitro effect of cranberry-derived PACs on C. albicans biofilm formation in artificial urine. C. albicans biofilms in artificial urine were coincubated with cranberry PACs at serially increasing concentrations and biofilm metabolic activity was assessed using the XTT assay in static microplate and silicone disc models. Cranberry PAC concentrations of ≥16 mg/L significantly reduced biofilm formation in all C. albicans strains tested, with a paradoxical effect observed at high concentrations in two clinical isolates. Further, cranberry PACs were additive in combination with traditional antifungals. Cranberry PACs reduced C. albicans adherence to both polystyrene and silicone. Supplementation of the medium with iron reduced the efficacy of cranberry PACs against biofilms. These findings indicate that cranberry PACs have excellent in vitro activity against C. albicans biofilm formation in artificial urine. We present preliminary evidence that cranberry PAC activity against C. albicans biofilm formation is due to anti-adherence properties and/or iron chelation.

  7. TOUGH+Hydrate v1.0 User's Manual: A Code for the Simulation of System Behavior in Hydrate-Bearing Geologic Media

    Energy Technology Data Exchange (ETDEWEB)

    Moridis, George; Moridis, George J.; Kowalsky, Michael B.; Pruess, Karsten

    2008-03-01

    TOUGH+HYDRATE v1.0 is a new code for the simulation of the behavior of hydrate-bearing geologic systems. By solving the coupled equations of mass and heat balance, TOUGH+HYDRATE can model the non-isothermal gas release, phase behavior and flow of fluids and heat under conditions typical of common natural CH{sub 4}-hydrate deposits (i.e., in the permafrost and in deep ocean sediments) in complex geological media at any scale (from laboratory to reservoir) at which Darcy's law is valid. TOUGH+HYDRATE v1.0 includes both an equilibrium and a kinetic model of hydrate formation and dissociation. The model accounts for heat and up to four mass components, i.e., water, CH{sub 4}, hydrate, and water-soluble inhibitors such as salts or alcohols. These are partitioned among four possible phases (gas phase, liquid phase, ice phase and hydrate phase). Hydrate dissociation or formation, phase changes and the corresponding thermal effects are fully described, as are the effects of inhibitors. The model can describe all possible hydrate dissociation mechanisms, i.e., depressurization, thermal stimulation, salting-out effects and inhibitor-induced effects. TOUGH+HYDRATE is the first member of TOUGH+, the successor to the TOUGH2 [Pruess et al., 1991] family of codes for multi-component, multiphase fluid and heat flow developed at the Lawrence Berkeley National Laboratory. It is written in standard FORTRAN 95, and can be run on any computational platform (workstation, PC, Macintosh) for which such compilers are available.

  8. Modelling of tetrahydrofuran promoted gas hydrate systems for carbon dioxide capture processes

    DEFF Research Database (Denmark)

    Herslund, Peter Jørgensen; Thomsen, Kaj; Abildskov, Jens

    2014-01-01

    hydrate process, operates isothermally at a temperature of 280. K. Applying three consecutive hydrate formation/dissociation stages (three-stage capture process), a carbon dioxide-rich product (97. mol%) is finally delivered at a temperature of 280. K and a pressure of 3.65. MPa. The minimum pressure...... to produce a 96. mol% carbon dioxide-rich product stream. This stream is delivered at 280. K and a pressure of 0.17. MPa. The present modelling study suggests several drawbacks of using tetrahydrofuran as a thermodynamic hydrate promoter, when applied in low-pressure, hydrate-based gas separation processes...... of water, tetrahydrofuran, carbon dioxide and nitrogen. The applied model incorporates the Cubic-Plus-Association (CPA) equation of state for the fluid phase description and the van der Waals-Platteeuw hydrate model for the solid (hydrate) phase. Six binary pairs are studied for their fluid phase behaviour...

  9. Hydration of Blended Portland Cements Containing Calcium-Aluminosilicate Glass Powder and Limestone

    DEFF Research Database (Denmark)

    Moesgaard, Mette; Poulsen, S.L.; Herfort, D.

    2012-01-01

    This work investigates the hydration of blended Portland cement containing 30 wt.% Na2O-CaO-Al2O3-SiO2 (NCAS) glass particles either as the only supplementary cementitious material (SCM) or in combination with limestone, using 29Si MAS NMR, powder XRD, and thermal analyses. The NCAS glass...... of hydration. The hydrated glass contributes to the formation of the calcium-silicate-hydrate (C-S-H) phase, consuming a part of the Portlandite (Ca(OH)2) formed during hydration of the Portland cement. Furthermore, the presence of the glass and limestone particles, alone or in combination, results...... in an accelerated hydration for alite (Ca3SiO5), the main constituent of Portland cement. A higher degree of limestone reaction has been observed in the blend containing both limestone and NCAS glass as compared to the limestone – Portland mixture. This reflects that limestone reacts with a part of the alumina...

  10. Nonequilibrium Thermodynamics of Hydrate Growth on a Gas-Liquid Interface

    Science.gov (United States)

    Fu, Xiaojing; Cueto-Felgueroso, Luis; Juanes, Ruben

    2018-04-01

    We develop a continuum-scale phase-field model to study gas-liquid-hydrate systems far from thermodynamic equilibrium. We design a Gibbs free energy functional for methane-water mixtures that recovers the isobaric temperature-composition phase diagram under thermodynamic equilibrium conditions. The proposed free energy is incorporated into a phase-field model to study the dynamics of hydrate formation on a gas-liquid interface. We elucidate the role of initial aqueous concentration in determining the direction of hydrate growth at the interface, in agreement with experimental observations. Our model also reveals two stages of hydrate growth at an interface—controlled by a crossover in how methane is supplied from the gas and liquid phases—which could explain the persistence of gas conduits in hydrate-bearing sediments and other nonequilibrium phenomena commonly observed in natural methane hydrate systems.

  11. Preventive effects of a phospholipid polymer coating on PMMA on biofilm formation by oral streptococci

    Science.gov (United States)

    Shibata, Yukie; Yamashita, Yoshihisa; Tsuru, Kanji; Ishihara, Kazuhiko; Fukazawa, Kyoko; Ishikawa, Kunio

    2016-12-01

    The regulation of biofilm formation on dental materials such as denture bases is key to oral health. Recently, a biocompatible phospholipid polymer, poly(2-methacryloyloxyethyl phosphorylcholine-co-n-butyl methacrylate) (PMB) coating, was reported to inhibit sucrose-dependent biofilm formation by Streptococcus mutans, a cariogenic bacterium, on the surface of poly(methyl methacrylate) (PMMA) denture bases. However, S. mutans is a minor component of the oral microbiome and does not play an important role in biofilm formation in the absence of sucrose. Other, more predominant oral streptococci must play an indispensable role in sucrose-independent biofilm formation. In the present study, the effect of PMB coating on PMMA was evaluated using various oral streptococci that are known to be initial colonizers during biofilm formation on tooth surfaces. PMB coating on PMMA drastically reduced sucrose-dependent tight biofilm formation by two cariogenic bacteria (S. mutans and Streptococcus sobrinus), among seven tested oral streptococci, as described previously [N. Takahashi, F. Iwasa, Y. Inoue, H. Morisaki, K. Ishihara, K. Baba, J. Prosthet. Dent. 112 (2014) 194-203]. Streptococci other than S. mutans and S. sobrinus did not exhibit tight biofilm formation even in the presence of sucrose. On the other hand, all seven species of oral streptococci exhibited distinctly reduced glucose-dependent soft biofilm retention on PMB-coated PMMA. We conclude that PMB coating on PMMA surfaces inhibits biofilm attachment by initial colonizer oral streptococci, even in the absence of sucrose, indicating that PMB coating may help maintain clean conditions on PMMA surfaces in the oral cavity.

  12. High pressure rheology of gas hydrate formed from multiphase systems using modified Couette rheometer

    Science.gov (United States)

    Pandey, Gaurav; Linga, Praveen; Sangwai, Jitendra S.

    2017-02-01

    Conventional rheometers with concentric cylinder geometries do not enhance mixing in situ and thus are not suitable for rheological studies of multiphase systems under high pressure such as gas hydrates. In this study, we demonstrate the use of modified Couette concentric cylinder geometries for high pressure rheological studies during the formation and dissociation of methane hydrate formed from pure water and water-decane systems. Conventional concentric cylinder Couette geometry did not produce any hydrates in situ and thus failed to measure rheological properties during hydrate formation. The modified Couette geometries proposed in this work observed to provide enhanced mixing in situ, thus forming gas hydrate from the gas-water-decane system. This study also nullifies the use of separate external high pressure cell for such measurements. The modified geometry was observed to measure gas hydrate viscosity from an initial condition of 0.001 Pa s to about 25 Pa s. The proposed geometries also possess the capability to measure dynamic viscoelastic properties of hydrate slurries at the end of experiments. The modified geometries could also capture and mimic the viscosity profile during the hydrate dissociation as reported in the literature. The present study acts as a precursor for enhancing our understanding on the rheology of gas hydrate formed from various systems containing promoters and inhibitors in the context of flow assurance.

  13. 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

  14. Mesostructure from hydration gradients in demosponge biosilica.

    Science.gov (United States)

    Neilson, James R; George, Nathan C; Murr, Meredith M; Seshadri, Ram; Morse, Daniel E

    2014-04-22

    Organisms of the phylum Porifera, that is, sponges, utilize enzymatic hydrolysis to concatenate bioavailable inorganic silicon to produce lightweight, strong, and often flexible skeletal elements called spicules. In their optical transparency, these remarkable biomaterials resemble fused silica, despite having been formed under ambient marine biological conditions. Although previous studies have elucidated the chemical mechanisms of spicule formation and revealed the extensive hydration of these glasses, their precise composition and local and medium-range structures had not been determined. We have employed a combination of compositional analysis, (1) H and (29) Si solid-state nuclear magnetic resonance spectroscopy, and synchrotron X-ray total scattering to characterize spicule-derived silica produced by the demosponge Tethya aurantia. These studies indicate that the materials are highly hydrated, but in an inhomogeneous manner. The spicule-derived silica is, on average, perfectly dense for the given extent of hydration and regions of fully condensed and unstrained SiO networks persist throughout each monolithic spicule. To accommodate chemical strain and defects, the extensive hydration is concentrated in distinct regions that give rise to mesostructural features. The chemistry responsible for producing spicule silica resembles hydrolytic sol-gel processing, which offers exceptional control over the precise local atomic arrangement of materials. However, the specific processing involved in forming the sponge spicule silica further results in regions of fully condensed silica coexisting with regions of incomplete condensation. This mesostructure suggests a mechanism for atomistic defect tolerance and strain relief that may account for the unusual mechanical properties of the biogenic spicules. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  15. Guideline adherence for identification and hydration of high-risk hospital patients for contrast-induced nephropathy.

    NARCIS (Netherlands)

    Schilp, J.; Blok, C. de; Langelaan, M.; Spreeuwenberg, P.; Wagner, C.

    2014-01-01

    Background: Contrast-induced nephropathy (CIN) is a common cause of acute renal failure in hospital patients. To prevent CIN, identification and hydration of high-risk patients is important. Prevention of CIN by hydration of high-risk patients was one of the themes to be implemented in the Dutch

  16. Guideline adherence for identification and hydration of high-risk hospital patients for contrast-induced nephropathy

    NARCIS (Netherlands)

    Schilp, J.; de Blok, C.; Langelaan, M.; Spreeuwenberg, P.; Wagner, C.

    2014-01-01

    Background: Contrast-induced nephropathy (CIN) is a common cause of acute renal failure in hospital patients. To prevent CIN, identification and hydration of high-risk patients is important. Prevention of CIN by hydration of high-risk patients was one of the themes to be implemented in the Dutch

  17. A new experimental method to prevent paraffin - wax formation on the crude oil wells: A field case study in Libya

    Directory of Open Access Journals (Sweden)

    Elhaddad Elnori E.

    2015-01-01

    Full Text Available Wax formation and deposition is one of the most common problems in oil producing wells. This problem occurs as a result of the reduction of the produced fluid temperature below the wax appearance temperature (range between 46°C and 50°C and the pour point temperature (range between 42°C and 44°C. In this study, two new methods for preventing wax formation were implemented on three oil wells in Libya, where the surface temperature is, normally, 29°C. In the first method, the gas was injected at a pressure of 83.3 bar and a temperature of 65°C (greater than the pour point temperature during the gas-lift operation. In the second method, wax inhibitors (Trichloroethylene-xylene (TEX, Ethylene copolymers, and Comb polymers were injected down the casings together with the gas. Field observations confirmed that by applying these techniques, the production string was kept clean and no wax was formed. The obtained results show that the wax formation could be prevented by both methods.

  18. Comparison of the physical and geotechnical properties of gas-hydrate-bearing sediments from offshore India and other gas-hydrate-reservoir systems

    Science.gov (United States)

    Winters, William J.; Wilcox-Cline, R.W.; Long, P.; Dewri, S.K.; Kumar, P.; Stern, Laura A.; Kerr, Laura A.

    2014-01-01

    The sediment characteristics of hydrate-bearing reservoirs profoundly affect the formation, distribution, and morphology of gas hydrate. The presence and type of gas, porewater chemistry, fluid migration, and subbottom temperature may govern the hydrate formation process, but it is the host sediment that commonly dictates final hydrate habit, and whether hydrate may be economically developed.In this paper, the physical properties of hydrate-bearing regions offshore eastern India (Krishna-Godavari and Mahanadi Basins) and the Andaman Islands, determined from Expedition NGHP-01 cores, are compared to each other, well logs, and published results of other hydrate reservoirs. Properties from the hydrate-free Kerala-Konkan basin off the west coast of India are also presented. Coarser-grained reservoirs (permafrost-related and marine) may contain high gas-hydrate-pore saturations, while finer-grained reservoirs may contain low-saturation disseminated or more complex gas-hydrates, including nodules, layers, and high-angle planar and rotational veins. However, even in these fine-grained sediments, gas hydrate preferentially forms in coarser sediment or fractures, when present. The presence of hydrate in conjunction with other geologic processes may be responsible for sediment porosity being nearly uniform for almost 500 m off the Andaman Islands.Properties of individual NGHP-01 wells and regional trends are discussed in detail. However, comparison of marine and permafrost-related Arctic reservoirs provides insight into the inter-relationships and common traits between physical properties and the morphology of gas-hydrate reservoirs regardless of location. Extrapolation of properties from one location to another also enhances our understanding of gas-hydrate reservoir systems. Grain size and porosity effects on permeability are critical, both locally to trap gas and regionally to provide fluid flow to hydrate reservoirs. Index properties corroborate more advanced

  19. Grain-scale imaging and compositional characterization of cryo-preserved India NGHP 01 gas-hydrate-bearing cores

    Science.gov (United States)

    Stern, Laura A.; Lorenson, T.D.

    2014-01-01

    We report on grain-scale characteristics and gas analyses of gas-hydrate-bearing samples retrieved by NGHP Expedition 01 as part of a large-scale effort to study gas hydrate occurrences off the eastern-Indian Peninsula and along the Andaman convergent margin. Using cryogenic scanning electron microscopy, X-ray spectroscopy, and gas chromatography, we investigated gas hydrate grain morphology and distribution within sediments, gas hydrate composition, and methane isotopic composition of samples from Krishna–Godavari (KG) basin and Andaman back-arc basin borehole sites from depths ranging 26 to 525 mbsf. Gas hydrate in KG-basin samples commonly occurs as nodules or coarse veins with typical hydrate grain size of 30–80 μm, as small pods or thin veins 50 to several hundred microns in width, or disseminated in sediment. Nodules contain abundant and commonly isolated macropores, in some places suggesting the original presence of a free gas phase. Gas hydrate also occurs as faceted crystals lining the interiors of cavities. While these vug-like structures constitute a relatively minor mode of gas hydrate occurrence, they were observed in near-seafloor KG-basin samples as well as in those of deeper origin (>100 mbsf) and may be original formation features. Other samples exhibit gas hydrate grains rimmed by NaCl-bearing material, presumably produced by salt exclusion during original hydrate formation. Well-preserved microfossil and other biogenic detritus are also found within several samples, most abundantly in Andaman core material where gas hydrate fills microfossil crevices. The range of gas hydrate modes of occurrence observed in the full suite of samples suggests a range of formation processes were involved, as influenced by local in situconditions. The hydrate-forming gas is predominantly methane with trace quantities of higher molecular weight hydrocarbons of primarily microbial origin. The composition indicates the gas hydrate is Structure I.

  20. Prevention

    Science.gov (United States)

    ... Contact Aging & Health A to Z Find a Geriatrics Healthcare Professional Medications & Older Adults Making Your Wishes ... Prevention Hearing Loss Heart Attack High Blood Pressure Nutrition Osteoporosis Shingles Skin Cancer Related News Quitting Smoking, ...

  1. Chlorhexidine efficacy in preventing lesion formation in enamel and dentine: an in situ study

    NARCIS (Netherlands)

    van Strijp, A.J.P.; Gerardu, V.A.M.; Buijs, M.J.; van Loveren, C.; ten Cate, J.M.

    2008-01-01

    Background: Clinical studies on the caries-preventive properties of chlorhexidine mouthrinses are limited and the results are inconclusive. Aim: The aim of this study was to elucidate the contribution of a 0.2% chlorhexidine mouthrinse to the protection of enamel and dentine against

  2. Catalysis of gas hydrates by biosurfactants in seawater-saturated sand/clay

    Energy Technology Data Exchange (ETDEWEB)

    Rogers, R. E.; Kothapalli, C.; Lee, M.S. [Mississippi State University, Swalm School of Chemical Engineering, MS (United States); Woolsey, J. R. [University of Mississippi, Centre of Marine Resources and Environmental Technology, MS (United States)

    2003-10-01

    Large gas hydrate mounds have been photographed in the seabed of the Gulf of Mexico and elsewhere. According to industry experts, the carbon trapped within gas hydrates is two or three times greater than all known crude oil, natural gas and coal reserves in the world. Gas hydrates, which are ice-like solids formed from the hydrogen bonding of water as water temperature is lowered under pressure to entrap a suitable molecular-size gas in cavities of the developing crystal structure, are found below the ocean floor to depths exhibiting temperature and pressure combinations within the appropriate limits. The experiments described in this study attempt to ascertain whether biosurfactant byproducts of microbial activity in seabeds could catalyze gas hydrate formation. Samples of five possible biosurfactants classifications were used in the experiments. Results showed that biosurfactants enhanced hydrate formation rate between 96 per cent and 288 percent, and reduced hydrate induction time 20 per cent to 71 per cent relative to the control. The critical micellar concentration of rhamnolipid/seawater solution was found to be 13 ppm at hydrate-forming conditions. On the basis of these results it was concluded that minimal microbial activity in sea floor sands could achieve the threshold concentration of biosurfactant that would greatly promote hydrate formation. 28 refs., 2 tabs., 4 figs.

  3. Streptomyces lunalinharesii 235 prevents the formation of a sulfate-reducing bacterial biofilm

    Directory of Open Access Journals (Sweden)

    Juliana Pacheco da Rosa

    Full Text Available ABSTRACT Streptomyces lunalinharesii strain 235 produces an antimicrobial substance that is active against sulfate reducing bacteria, the major bacterial group responsible for biofilm formation and biocorrosion in petroleum reservoirs. The use of this antimicrobial substance for sulfate reducing bacteria control is therefore a promising alternative to chemical biocides. In this study the antimicrobial substance did not interfere with the biofilm stability, but the sulfate reducing bacteria biofilm formation was six-fold smaller in carbon steel coupons treated with the antimicrobial substance when compared to the untreated control. A reduction in the most probable number counts of planktonic cells of sulfate reducing bacteria was observed after treatments with the sub-minimal inhibitory concentration, minimal inhibitory concentration, and supra-minimal inhibitory concentration of the antimicrobial substance. Additionally, when the treated coupons were analyzed by scanning electron microscopy, the biofilm formation was found to be substantially reduced when the supra-minimal inhibitory concentration of the antimicrobial substance was used. The coupons used for the biofilm formation had a small weight loss after antimicrobial substance treatment, but corrosion damage was not observed by scanning electron microscopy. The absence of the dsrA gene fragment in the scraped cell suspension after treatment with the supra-minimal inhibitory concentration of the antimicrobial substance suggests that Desulfovibrio alaskensis was not able to adhere to the coupons. This is the first report on an antimicrobial substance produced by Streptomyces active against sulfate reducing bacteria biofilm formation. The application of antimicrobial substance as a potential biocide for sulfate reducing bacteria growth control could be of great interest to the petroleum industry.

  4. Modelling the effects of waste components on cement hydration

    NARCIS (Netherlands)

    van Eijk, R.J.; Brouwers, Jos

    2000-01-01

    Ordinary Portland Cement (OPC) is often used for the Solidification/Stabilization (S/S) of waste containing heavy metals and salts. These waste componenents will precipitate in the form of insoluble compounds onto unreacted cement clinker grains preventing further hydration. In this study the long

  5. Controlled release of chlorhexidine from a mesoporous silica-containing macroporous titanium dental implant prevents microbial biofilm formation.

    Science.gov (United States)

    De Cremer, K; Braem, A; Gerits, E; De Brucker, K; Vandamme, K; Martens, J A; Michiels, J; Vleugels, J; Cammue, B P; Thevissen, K

    2017-01-11

    Roughened surfaces are increasingly being used for dental implant applications as the enlarged contact area improves bone cell anchorage, thereby facilitating osseointegration. However, the additional surface area also entails a higher risk for the development of biofilm associated infections, an etiologic factor for many dental ailments, including peri-implantitis. To overcome this problem, we designed a dental implant composed of a porous titanium-silica (Ti/SiO2) composite material and containing an internal reservoir that can be loaded with antimicrobial compounds. The composite material consists of a sol-gel derived mesoporous SiO2 diffusion barrier integrated in a macroporous Ti load-bearing structure obtained by powder metallurgical processing. The antimicrobial compounds can diffuse through the porous implant walls, thereby reducing microbial biofilm formation on the implant surface. A continuous release of µM concentrations of chlorhexidine through the Ti/SiO2 composite material was measured, without initial burst effect, over at least 10 days and using a 5 mM chlorhexidine solution in the implant reservoir. Metabolic staining, CFU counting and visualisation by scanning electron microscopy confirmed that Streptococcus mutans biofilm formation on the implant surface was almost completely prevented due to chlorhexidine release (preventive setup). Moreover, we demonstrated efficacy of released chlorhexidine against mature Streptococcus mutans biofilms (curative setup). In conclusion, we provide a proof of concept of the sustained release of chlorhexidine, one of the most widely used oral antiseptics, through the Ti/SiO2 material thereby preventing and eradicating biofilm formation on the surface of the dental implant. In principle, our flexible design allows for the use of any bioactive compound, as discussed.

  6. Influence of Physical Activity and Ambient Temperature on Hydration: The European Hydration Research Study (EHRS

    Directory of Open Access Journals (Sweden)

    Ricardo Mora-Rodriguez

    2016-04-01

    Full Text Available This study explored the effects of physical activity (PA and ambient temperature on water turnover and hydration status. Five-hundred seventy three healthy men and women (aged 20–60 years from Spain, Greece and Germany self-reported PA, registered all food and beverage intake, and collected 24-h urine during seven consecutive days. Fasting blood samples were collected at the onset and end of the study. Food moisture was assessed using nutritional software to account for all water intake which was subtracted from daily urine volume to allow calculation of non-renal water loss (i.e., mostly sweating. Hydration status was assessed by urine and blood osmolality. A negative association was seen between ambient temperature and PA (r = −0.277; p < 0.001. Lower PA with high temperatures did not prevent increased non-renal water losses (i.e., sweating and elevated urine and blood osmolality (r = 0.218 to 0.163 all p < 0.001. When summer and winter data were combined PA was negatively associated with urine osmolality (r = −0.153; p = 0.001. Our data suggest that environmental heat acts to reduce voluntary PA but this is not sufficient to prevent moderate dehydration (increased osmolality. On the other hand, increased PA is associated with improved hydration status (i.e., lower urine and blood osmolality.

  7. 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.

  8. Low-δD hydration rinds in Yellowstone perlites record rapid syneruptive hydration during glacial and interglacial conditions

    Science.gov (United States)

    Bindeman, Ilya N.; Lowenstern, Jacob B.

    2016-01-01

    Hydration of silicic volcanic glass forms perlite, a dusky, porous form of altered glass characterized by abundant “onion-skin” fractures. The timing and temperature of perlite formation are enigmatic and could plausibly occur during eruption, during post-eruptive cooling, or much later at ambient temperatures. To learn more about the origin of natural perlite, and to fingerprint the hydration waters, we investigated perlitic glass from several synglacial and interglacial rhyolitic lavas and tuffs from the Yellowstone volcanic system. Perlitic cores are surrounded by a series of conchoidal cracks that separate 30- to 100-µm-thick slivers, likely formed in response to hydration-induced stress. H2O and D/H profiles confirm that most D/H exchange happens together with rapid H2O addition but some smoother D/H variations may suggest separate minor exchange by deuterium atom interdiffusion following hydration. The hydrated rinds (2–3 wt% H2O) transition rapidly (within 30 µm, or by 1 wt% H2O per 10 µm) to unhydrated glass cores. This is consistent with quenched “hydration fronts” where H2O diffusion coefficients are strongly dependent on H2O concentrations. The chemical, δ18O, and δD systematics of bulk glass records last equilibrium between ~110 and 60 °C without chemical exchange but with some δ18O exchange. Similarly, the δ18O of water extracted from glass by rapid heating suggests that water was added to the glass during cooling at higher rates of diffusion at 60–110 °C temperatures, compared with values expected from extrapolation of high-temperature (>400 °C) experimental data. The thick hydration rinds in perlites, measuring hundreds of microns, preserve the original D/H values of hydrating water as a recorder of paleoclimate conditions. Measured δD values in perlitic lavas are −150 to −191 or 20–40 ‰ lower than glass hydrated by modern Yellowstone waters. This suggests that Yellowstone perlites record the low-δD signature

  9. Environment of estates and crime prevention through urban environment formation and modification

    Directory of Open Access Journals (Sweden)

    Matlovičová Kvetoslava

    2016-01-01

    Full Text Available Due to the significant impact of criminality on the quality of life in a particular territory, criminality is attracting more and more attention from local authorities which are trying to reduce it. In this respect, the concept of CPTED (Crime Prevention Through Environmental Design which is quite often used out­side of Slovakia and is based on prevention of criminality through the appropriate design of urban environments, seems to be useful. The study offers the characteristics of CPTED principles and also suggests possibilities for its application within innercity criminality on model territories of the city of Prešov (Slovakia as an usable way of reducing crime in other mainly East-central European cities.

  10. Corrosive inorganic contamination on wafer surfaces after nickel-iron electroplating formation mechanisms and prevention

    Energy Technology Data Exchange (ETDEWEB)

    Kritzer, P. [Freudenberg Nonwovens KG, Technical Nonwovens Div., Weinheim (Germany); Diel, W.; Barber, P.H. [IBM Speichersysteme Deutschland GmbH, Mainz (Germany); Romankiw, L.T. [IBM Watson Research Center, Yorktown Heights, NY (United States)

    2001-11-01

    Electroplating of Nickel-Iron alloys is widely used in the production of magnetic heads for storage systems. Usually, the plating process is performed in acidic, salt-containing solutions. After the plating step, a complete removal of the plating salts is necessary to receive a clean surface. In disadvantageous cases, a precipitation of sticky particles is observed that cannot be removed from the plated surface without damaging the surface. Some of these substances (esp. nickel sulfates) might lead to severe local corrosion and thus might act as ''time-bomb'' in the later product. Non-corrosive precipitations (i.e. nickel hydroxides) strongly hinder or even prevent the following production steps. In the present paper, the mechanisms of the origin of the different kinds of precipitation are described and the principle actions for their prevention are given. An outlook is given for other possible technical applications. (orig.)

  11. Control and Prevention of Ice Formation on the Surface of an Aluminum Alloy

    DEFF Research Database (Denmark)

    Rahimi, Maral

    In cold climates, mechanical ventilation systems with heat recovery, e.g. air-to-air exchangers, are often used to reduce energy demand for heating by recovering the heat from the exhausted air. This, however, creates a risk of ice accretion on the fins of the heat exchanger as warm and humid...... exhausted air cools down. Due to the reduction in heat exchanger efficiency due to ice formation, this phenomenon has been studied for many decades. There are two approaches to controlling ice formation on heat exchangers: active and passive. The active methods, e.g. bypass, recirculation, preheating etc......., require energy and consequently reduce the overall efficiency of the system. They are not addressed in this work and have already been studied extensively by many researchers. The passive methods, which are related to the surface characteristics of the heat exchanger fins and their effect on the initial...

  12. UV-Induced prevention of biofilm formation inside medical tubes and catheters

    DEFF Research Database (Denmark)

    Pedersen, Jens Kristian Mølgaard; Nielsen, Kristian; Bang, Ole

    2014-01-01

    Biofilm formation inside medical tubes and catheters may often cause unwanted infections, illness andimpaired wound healing during medical treatment, resulting in extended hospitalization and - in worst case– life threatening conditions of the patients. In fact, it is estimated, that the infectio......-light propagation or by other meansintegrating optical fiber technology into the tube walls, such as to gradually release UV-light into theinterior, efficiently killing off bacteria present inside....

  13. Kaempferide Prevents Titanium Particle Induced Osteolysis by Suppressing JNK Activation during Osteoclast Formation.

    Science.gov (United States)

    Jiao, Zixian; Xu, Weifeng; Zheng, Jisi; Shen, Pei; Qin, An; Zhang, Shanyong; Yang, Chi

    2017-11-30

    Kaempferide (KF) is an O-methylated flavonol, a natural plant extract, which is often found in Kaempferia galanga. It has a variety of effects including anti-carcinogenic, anti-inflammatory, anti-oxidant, anti-bacterial and anti-viral properties. In this study, we aimed to investigate whether KF effectively inhibits titanium particle induced calvarial bone loss via down regulation of the JNK signaling pathway. In the mice with titanium particle induced calvarial osteolysis, the Low dose of KF mildly reduced the resorption pits while in the high dose group, fewer scattered pits were observed on the surface of calvarium. Histological examination showed fewer osteoclasts formation in the KF group. In mouse bone marrow macrophages (BMMs) and RAW264.7 cells, KF significantly inhibited the osteoclast formation and bone resorption at 12.5 μM. However, KF does not affect the mature osteoclast F-actin ring formation. But when being co-treated with KF and anisomycin, BMMs differentiated into mature osteoclasts. At the molecular levels, the JNK phosphorylation was inhibited and the osteoclastogenesis-related specific gene expression including V-ATPase d2, TRAP, calcitonin receptor (CTR), c-Fos and NFATc1 was markedly suppressed. In conclusion, these results indicated that KF is a promising agent in the treatment of osteoclast-related diseases.

  14. Antioxidant Compounds in Traditional Indian Pickles May Prevent the Process-Induced Formation of Benzene.

    Science.gov (United States)

    Kharat, Mahesh M; Adiani, Vanshika; Variyar, Prasad; Sharma, Arun; Singhal, Rekha S

    2016-01-01

    Pickles in the Indian market contain ascorbic acid from the raw material used and benzoate as an added preservative that are involved in the formation of benzene in soft drinks. In this work, 24 market pickle samples were surveyed for benzene content, as well as its precursors and other constituents that influence its formation. The analysis showed that pickle samples were high in acid content (low pH) and showed significant amount of ascorbic acid, minerals (Cu and Fe), and benzoic acid present in them. Also, most samples exhibited high antioxidant activity that might be attributed to the ingredients used, such as fruits and spices. The solid-phase microextraction headspace gas chromatography-mass spectrometry method was developed in-house for benzene analysis. Eleven of 24 samples had benzene, with the highest concentration of 4.36 ± 0.82 μg of benzene per kg of pickle for a lime pickle that was also reported to have highest benzoic acid and considerably less hydroxyl radical ((•)OH) scavenging activity. However, benzene levels for all 11 samples were considerably below the World Health Organization regulatory limit of 10 μg/kg for benzene in mineral water. Studies on model systems revealed that the high antioxidant activity of Indian pickles may have had a strong inhibitory effect on benzene formation.

  15. Influences of additives on the gas hydrate cool storage process in a new gas hydrate cool storage system

    International Nuclear Information System (INIS)

    Bi Yuehong; Guo Tingwei; Zhu Tingying; Zhang Liang; Chen Lingen

    2006-01-01

    Experimental research on the crystallization process of the gas hydrate HCFC141b is performed for this paper. The influences of different proportions of calcium hypochlorite or benzenesulfonic acid sodium salt on the crystallization process are studied. The results show that the degree of subcooling of formation is obviously decreased, and the formation rate of the gas hydrate is greatly accelerated by adding reasonable proportions of the additives. The degree of subcooling of formation decreases 0.78 deg. C by adding benzenesulfonic acid sodium salt of 0.03%, and the formation rate of the gas hydrate increases 0.2 g/s by adding calcium hypochlorite of 0.08%. In the cool storage system, clathrate hydrates can be formed effectively, and thermal energy can be stored efficiently. When adding benzenesulfonic acid sodium salt of 0.03%, the cold energy stored is 4.74 MJ, and the cool storage density is 206.07 MJ/m 3 . The performance of this cool storage system can meet the needs of practical air conditioning engineering

  16. Electrical Conductive Mechanism of Gas Hydrate-Bearing Reservoirs in the Permafrost Region of Qilian Mountain

    Science.gov (United States)

    Peng, C.; Zou, C.; Tang, Y.; Liu, A.; Hu, X.

    2017-12-01

    In the Qilian Mountain, gas hydrates not only occur in pore spaces of sandstones, but also fill in fractures of mudstones. This leads to the difficulty in identification and evaluation of gas hydrate reservoir from resistivity and velocity logs. Understanding electrical conductive mechanism is the basis for log interpretation. However, the research is insufficient in this area. We have collected well logs from 30 wells in this area. Well logs and rock samples from DK-9, DK-11 and DK-12 wells were used in this study. The experiments including SEM, thin section, NMR, XRD, synthesis of gas hydrate in consolidated rock cores under low temperature and measurement of their resistivity and others were performed for understanding the effects of pore structure, rock composition, temperature and gas hydrate on conductivity. The results show that the porosity of reservoir of pore filling type is less than 10% and its clay mineral content is high. As good conductive passages, fractures can reduce resistivity of water-saturated rock. If fractures in the mudstone are filled by calcite, resistivity increases significantly. The resistivity of water-saturated rock at 2°C is twice of that at 18°C. The gas hydrate formation process in the sandstone was studied by resistivity recorded in real time. In the early stage of gas hydrate formation, the increase of residual water salinity may lead to the decrease of resistivity. In the late stage of gas hydrate formation, the continuity decrease of water leads to continuity increase of resistivity. In summary, fractures, rock composition, temperature and gas hydrate are important factors influencing resistivity of formation. This study is helpful for more accurate evaluation of gas hydrate from resistivity log. Acknowledgment: We acknowledge the financial support of the National Special Program for Gas Hydrate Exploration and Test-production (GZH201400302).

  17. Prevention

    DEFF Research Database (Denmark)

    Halken, S; Høst, A

    2001-01-01

    , breastfeeding should be encouraged for 4-6 months. In high-risk infants a documented extensively hydrolysed formula is recommended if exclusive breastfeeding is not possible for the first 4 months of life. There is no evidence for preventive dietary intervention neither during pregnancy nor lactation...... populations. These theories remain to be documented in proper, controlled and prospective studies. Breastfeeding and the late introduction of solid foods (>4 months) is associated with a reduced risk of food allergy, atopic dermatitis, and recurrent wheezing and asthma in early childhood. In all infants....... Preventive dietary restrictions after the age of 4-6 months are not scientifically documented....

  18. 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

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

    Energy Technology Data Exchange (ETDEWEB)

    Fratini, Emiliano [Department of Chemistry and CSGI, University of Florence, via della Lastruccia 3-Sesto Fiorentino, I-50019 Florence (Italy); Ridi, Francesca [Department of Chemistry and CSGI, University of Florence, via della Lastruccia 3-Sesto Fiorentino, I-50019 Florence (Italy); Chen, Sow-Hsin [Department of Nuclear Science and Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139 (United States); Baglioni, Piero [Department of Chemistry and CSGI, University of Florence, via della Lastruccia 3-Sesto Fiorentino, I-50019 Florence (Italy)

    2006-09-13

    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{sub 3}S, C{sub 2}S) and aluminates (C{sub 3}A, C{sub 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{sup -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 {sup 1}H-NMR. Additional information is obtained by scanning electron microscopy (SEM), ultra small angle neutron

  20. TOUGH+HYDRATE v1.2 User's Manual: A Code for the Simulation of System Behavior in Hydrate-Bearing Geologic Media

    Energy Technology Data Exchange (ETDEWEB)

    Moridis, George J. [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Kowalsky, Michael B. [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Pruess, Karsten [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)

    2012-08-01

    TOUGH+HYDRATE v1.2 is a code for the simulation of the behavior of hydratebearing geologic systems, and represents the second update of the code since its first release [Moridis et al., 2008]. By solving the coupled equations of mass and heat balance, TOUGH+HYDRATE can model the non-isothermal gas release, phase behavior and flow of fluids and heat under conditions typical of common natural CH4-hydrate deposits (i.e., in the permafrost and in deep ocean sediments) in complex geological media at any scale (from laboratory to reservoir) at which Darcy’s law is valid. TOUGH+HYDRATE v1.2 includes both an equilibrium and a kinetic model of hydrate formation and dissociation. The model accounts for heat and up to four mass components, i.e., water, CH4, hydrate, and water-soluble inhibitors such as salts or alcohols. These are partitioned among four possible phases (gas phase, liquid phase, ice phase and hydrate phase). Hydrate dissociation or formation, phase changes and the corresponding thermal effects are fully described, as are the effects of inhibitors. The model can describe all possible hydrate dissociation mechanisms, i.e., depressurization, thermal stimulation, salting-out effects and inhibitor-induced effects. TOUGH+HYDRATE is a member of TOUGH+, the successor to the TOUGH2 [Pruess et al., 1991] family of codes for multi-component, multiphase fluid and heat flow developed at the Lawrence Berkeley National Laboratory. It is written in standard FORTRAN 95/2003, and can be run on any computational platform (workstation, PC, Macintosh) for which such compilers are available.

  1. Study on gas hydrate as a new energy resource in the 21th century

    Energy Technology Data Exchange (ETDEWEB)

    Ryu, Byeong-Jae; Kwak Young-Hoon; Kim, Won-Sik [Korea Institute of Geology Mining and Materials, Taejon (KR)] (and others)

    1999-12-01

    Natural gas hydrate, a special type of clathrate hydrates, is a metastable solid compound which mainly consists of methane and water, and generally called as gas hydrate. It is stable in the specific low-temperature/high-pressure conditions. Gas hydrates play an important role as major reservoir of methane on the earth. On the other hand, the formation and dissociation of gas hydrates could cause the plugging in pipeline, gas kick during production, atmospheric pollution and geohazard. To understand the formation and dissociation of the gas hydrate, the experimental equilibrium conditions of methane hydrate were measured in pure water, 3 wt.% NaCl and MgCl{sub 2} solutions. The equilibrium conditions of propane hydrates were also measured in pure water. The relationship between methane hydrate formation time and overpressure was also analyzed through the laboratory work. The geophysical surveys using air-gun system and multibeam echo sounder were implemented to develop exploration techniques and to evaluate the gas hydrate potential in the East Sea, Korea. General indicators of submarine gas hydrates on seismic data is commonly inferred from the BSR developed parallel to the see floor, amplitude blanking at the upper part of the BSR, and phase reversal and decrease of the interval velocity at BSR. The field data were processed using Geobit 2.9.5 developed by KIGAM to detect the gas hydrate indicators. The accurate velocity analysis was performed by XVA (X-window based Velocity Analysis). Processing results show that the strong reflector occurred parallel to the sea floor were shown at about 1800 ms two way travel time. The interval velocity decrease at this strong reflector and at the reflection phase reversal corresponding to the reflection at the sea floor. Gas hydrate stability field in the study area was determined using the data of measured hydrate equilibrium condition, hydrothermal gradient and geothermal gradient. The depth of BSR detected in the seismic

  2. PDZK1 prevents neointima formation via suppression of breakpoint cluster region kinase in vascular smooth muscle.

    Directory of Open Access Journals (Sweden)

    Wan Ru Lee

    Full Text Available Scavenger receptor class B, type I (SR-BI and its adaptor protein PDZK1 mediate responses to HDL cholesterol in endothelium. Whether the receptor-adaptor protein tandem serves functions in other vascular cell types is unknown. The current work determined the roles of SR-BI and PDZK1 in vascular smooth muscle (VSM. To evaluate possible VSM functions of SR-BI and PDZK1 in vivo, neointima formation was assessed 21 days post-ligation in the carotid arteries of wild-type, SR-BI-/- or PDZK1-/- mice. Whereas neointima development was negligible in wild-type and SR-BI-/-, there was marked neointima formation in PDZK1-/- mice. PDZK1 expression was demonstrated in primary mouse VSM cells, and compared to wild-type cells, PDZK1-/- VSM displayed exaggerated proliferation and migration in response to platelet derived growth factor (PDGF. Tandem affinity purification-mass spectrometry revealed that PDZK1 interacts with breakpoint cluster region kinase (Bcr, which contains a C-terminal PDZ binding sequence and is known to enhance responses to PDGF in VSM. PDZK1 interaction with Bcr in VSM was demonstrated by pull-down and by coimmunoprecipitation, and the augmented proliferative response to PDGF in PDZK1-/- VSM was abrogated by Bcr depletion. Furthermore, compared with wild-type Bcr overexpression, the introduction of a Bcr mutant incapable of PDZK1 binding into VSM cells yielded an exaggerated proliferative response to PDGF. Thus, PDZK1 has novel SR-BI-independent function in VSM that affords protection from neointima formation, and this involves PDZK1 suppression of VSM cell proliferation via an inhibitory interaction with Bcr.

  3. Licochalcone A Prevents Platelet Activation and Thrombus Formation through the Inhibition of PLCγ2-PKC, Akt, and MAPK Pathways.

    Science.gov (United States)

    Lien, Li-Ming; Lin, Kuan-Hung; Huang, Li-Ting; Tseng, Mei-Fang; Chiu, Hou-Chang; Chen, Ray-Jade; Lu, Wan-Jung

    2017-07-12

    Platelet activation is involved in cardiovascular diseases, such as atherosclerosis and ischemic stroke. Licochalcone A (LA), an active ingredient of licorice, exhibits multiple biological activities such as anti-oxidation and anti-inflammation. However, its role in platelet activation remains unclear. Therefore, the study investigated the antiplatelet mechanism of LA. Our data revealed that LA (2-10 μM) concentration dependently inhibited platelet aggregation induced by collagen, but not thrombin and U46619. LA markedly attenuated collagen-stimulated ATP release, P-selectin secretion, calcium mobilization, and GPIIbIIIa activation, but did not interfere with the collagen binding to platelets. Moreover, LA significantly reduced the activation of PLCγ2, PKC, Akt and MAPKs. Thus, LA attenuates platelet activation, possibly by inhibiting collagen receptor downstream signaling but not by blocking the collagen receptors. In addition, LA prevented adenosine diphosphate (ADP)-induced acute pulmonary thrombosis, fluorescein sodium-induced platelet thrombus formation, and middle cerebral artery occlusion/reperfusion-induced brain injury in mice, but did not affect normal hemostasis. This study demonstrated that LA effectively reduced platelet activation and thrombus formation, in part, through the inhibition of PLCγ2-PKC, Akt, and MAPK pathways, without the side effect of bleeding. These findings also indicate that LA may provide a safe and alternative therapeutic approach for preventing thromboembolic disorders such as stroke.

  4. Sustained prevention of biofilm formation on a novel silicone matrix suitable for medical devices

    DEFF Research Database (Denmark)

    Steffensen, Søren Langer; Merete H., Vestergaard,; Jensen, Minna Grønning

    2015-01-01

    ciprofloxacin was loaded into the polymer matrix by a post-polymerization loading procedure. Sustained release of ciprofloxacin was demonstrated, and the release could be controlled by varying the hydrogel content in the range 13–38% (w/w) and by changing the concentration of ciprofloxacin during loading...... in the range of 1–20 mg/mL. Devices containing 25% (w/w) hydrogel and loaded with ciprofloxacin displayed a strong antibacterial effect against Staphylococcus aureus bacterial colonization and subsequent biofilm formation on the device material was inhibited for 29 days. In conclusion, the hydrogel...

  5. Radiation-induced formation of 8-hydroxy-2'-deoxyguanosine and its prevention by scavengers

    DEFF Research Database (Denmark)

    Fischer-Nielsen, A; Jeding, I B; Loft, S

    1994-01-01

    measured 8-OHdG formation in calf thymus DNA exposed to ionizing radiation under conditions generating either hydroxyl radicals (OH.), superoxide anions (O2-) or both. Additionally, we investigated the relationship between the scavenger effect of the drug 5-aminosalicylic acid (5-ASA) and increasing OH...... and 100 Gy radiation, i.e. within a wide range of OH. exposure, which is useful information considering clinical applications where the exact amount of ROS formed is unknown. Both 5-ASA and ascorbate at low concentrations (

  6. Sensitivity Analysis of Gas Production from Class 2 and Class 3 Hydrate Deposits

    Energy Technology Data Exchange (ETDEWEB)

    Reagan, Matthew; Moridis, George; Zhang, Keni

    2008-05-01

    Gas hydrates are solid crystalline compounds in which gas molecules are lodged within the lattices of an ice-like crystalline solid. The vast quantities of hydrocarbon gases trapped in hydrate formations in the permafrost and in deep ocean sediments may constitute a new and promising energy source. Class 2 hydrate deposits are characterized by a Hydrate-Bearing Layer (HBL) that is underlain by a saturated zone of mobile water. Class 3 hydrate deposits are characterized by an isolated Hydrate-Bearing Layer (HBL) that is not in contact with any hydrate-free zone of mobile fluids. Both classes of deposits have been shown to be good candidates for exploitation in earlier studies of gas production via vertical well designs - in this study we extend the analysis to include systems with varying porosity, anisotropy, well spacing, and the presence of permeable boundaries. For Class 2 deposits, the results show that production rate and efficiency depend strongly on formation porosity, have a mild dependence on formation anisotropy, and that tighter well spacing produces gas at higher rates over shorter time periods. For Class 3 deposits, production rates and efficiency also depend significantly on formation porosity, are impacted negatively by anisotropy, and production rates may be larger, over longer times, for well configurations that use a greater well spacing. Finally, we performed preliminary calculations to assess a worst-case scenario for permeable system boundaries, and found that the efficiency of depressurization-based production strategies are compromised by migration of fluids from outside the system.

  7. Detection of gas hydrate with downhole logs and assessment of gas hydrate concentrations (saturations) and gas volumes on the Blake Ridge with electrical resistivity log data

    Science.gov (United States)

    Collett, T.S.; Ladd, J.

    2000-01-01

    Let 164 of the Ocean Drilling Program was designed to investigate the occurrence of gas hydrate in the sedimentary section beneath the Blake Ridge on the southeastern continental margin of North America. Site 994, and 997 were drilled on the Blake Ridge to refine our understanding of the in situ characteristics of natural gas hydrate. Because gas hydrate is unstable at surface pressure and temperature conditions, a major emphasis was placed on the downhole logging program to determine the in situ physical properties of the gas hydrate-bearing sediments. Downhole logging tool strings deployed on Leg 164 included the Schlumberger quad-combination tool (NGT, LSS/SDT, DIT, CNT-G, HLDT), the Formation MicroScanner (FMS), and the Geochemical Combination Tool (GST). Electrical resistivity (DIT) and acoustic transit-time (LSS/SDT) downhole logs from Sites 994, 995, and 997 indicate the presence of gas hydrate in the depth interval between 185 and 450 mbsf on the Blake Ridge. Electrical resistivity log calculations suggest that the gas hydrate-bearing sedimentary section on the Blake Ridge may contain between 2 and 11 percent bulk volume (vol%) gas hydrate. We have determined that the log-inferred gas hydrates and underlying free-gas accumulations on the Blake Ridge may contain as much as 57 trillion m3 of gas.

  8. Elevated gas hydrate saturation within silt and silty clay sediments in the Shenhu area, South China Sea

    Science.gov (United States)

    Wang, Xiujuan; Hutchinson, Deborah R.; Wu, Shiguo; Yang, Shengxiong; Guo, Yiqun

    2011-01-01

    Gas hydrate saturations were estimated using five different methods in silt and silty clay foraminiferous sediments from drill hole SH2 in the South China Sea. Gas hydrate saturations derived from observed pore water chloride values in core samples range from 10 to 45% of the pore space at 190–221 m below seafloor (mbsf). Gas hydrate saturations estimated from resistivity (Rt) using wireline logging results are similar and range from 10 to 40.5% in the pore space. Gas hydrate saturations were also estimated by P wave velocity obtained during wireline logging by using a simplified three-phase equation (STPE) and effective medium theory (EMT) models. Gas hydrate saturations obtained from the STPE velocity model (41.0% maximum) are slightly higher than those calculated with the EMT velocity model (38.5% maximum). Methane analysis from a 69 cm long depressurized core from the hydrate-bearing sediment zone indicates that gas hydrate saturation is about 27.08% of the pore space at 197.5 mbsf. Results from the five methods show similar values and nearly identical trends in gas hydrate saturations above the base of the gas hydrate stability zone at depths of 190 to 221 mbsf. Gas hydrate occurs within units of clayey slit and silt containing abundant calcareous nannofossils and foraminifer, which increase the porosities of the fine-grained sediments and provide space for enhanced gas hydrate formation. In addition, gas chimneys, faults, and fractures identified from three-dimensional (3-D) and high-resolution two-dimensional (2-D) seismic data provide pathways for fluids migrating into the gas hydrate stability zone which transport methane for the formation of gas hydrate. Sedimentation and local canyon migration may contribute to higher gas hydrate saturations near the base of the stability zone.

  9. Using Carbon Dioxide to Enhance Recovery of Methane from Gas Hydrate Reservoirs: Final Summary Report

    Energy Technology Data Exchange (ETDEWEB)

    McGrail, B. Peter; Schaef, Herbert T.; White, Mark D.; Zhu, Tao; Kulkarni, Abhijeet S.; Hunter, Robert B.; Patil, Shirish L.; Owen, Antionette T.; Martin, P F.

    2007-09-01

    Carbon dioxide sequestration coupled with hydrocarbon resource recovery is often economically attractive. Use of CO2 for enhanced recovery of oil, conventional natural gas, and coal-bed methane are in various stages of common practice. In this report, we discuss a new technique utilizing CO2 for enhanced recovery of an unconventional but potentially very important source of natural gas, gas hydrate. We have focused our attention on the Alaska North Slope where approximately 640 Tcf of natural gas reserves in the form of gas hydrate have been identified. Alaska is also unique in that potential future CO2 sources are nearby, and petroleum infrastructure exists or is being planned that could bring the produced gas to market or for use locally. The EGHR (Enhanced Gas Hydrate Recovery) concept takes advantage of the physical and thermodynamic properties of mixtures in the H2O-CO2 system combined with controlled multiphase flow, heat, and mass transport processes in hydrate-bearing porous media. A chemical-free method is used to deliver a LCO2-Lw microemulsion into the gas hydrate bearing porous medium. The microemulsion is injected at a temperature higher than the stability point of methane hydrate, which upon contacting the methane hydrate decomposes its crystalline lattice and releases the enclathrated gas. Small scale column experiments show injection of the emulsion into a CH4 hydrate rich sand results in the release of CH4 gas and the formation of CO2 hydrate

  10. Phase field theory modeling of methane fluxes from exposed natural gas hydrate reservoirs

    Science.gov (United States)

    Kivelä, Pilvi-Helinä; Baig, Khuram; Qasim, Muhammad; Kvamme, Bjørn

    2012-12-01

    Fluxes of methane from offshore natural gas hydrate into the oceans vary in intensity from massive bubble columns of natural gas all the way down to fluxes which are not visible within human eye resolution. The driving force for these fluxes is that methane hydrate is not stable towards nether minerals nor towards under saturated water. As such fluxes of methane from deep below hydrates zones may diffuse through fluid channels separating the hydrates from minerals surfaces and reach the seafloor. Additional hydrate fluxes from hydrates dissociating towards under saturated water will have different characteristics depending on the level of dynamics in the actual reservoirs. If the kinetic rate of hydrate dissociation is smaller than the mass transport rate of distributing released gas into the surrounding water through diffusion then hydrodynamics of bubble formation is not an issue and Phase Field Theory (PFT) simulations without hydrodynamics is expected to be adequate [1, 2]. In this work we present simulated results corresponding to thermodynamic conditions from a hydrate field offshore Norway and discuss these results with in situ observations. Observed fluxes are lower than what can be expected from hydrate dissociating and molecularly diffusing into the surrounding water. The PFT model was modified to account for the hydrodynamics. The modified model gave higher fluxes, but still lower than the observed in situ fluxes.

  11. Biosurfactants prevent in vitro Candida albicans biofilm formation on resins and silicon materials for prosthetic devices.

    Science.gov (United States)

    Cochis, Andrea; Fracchia, Letizia; Martinotti, Maria Giovanna; Rimondini, Lia

    2012-06-01

    The aim of this study was to evaluate in vitro the preventive antiadhesion activity of biosurfactants against Candida albicans biofilm. Disks of silicon and acrylic resin for denture prostheses were precoated with increasing concentrations of biosurfactants obtained from endophyte biofilms selected from Robinia pseudoacacia and from Nerium oleander, and afterward infected with C. albicans cells. The number of biofilm cells were detected by colony-forming unit (CFU) counting, cell viability was established by the 2,3-bis(2-methoxy-4-nitro-5-sulphophenyl)-5-[(phenyl amino)carbonyl]-2H-tetrazolium hydroxide (XTT) assay, and biosurfactant cytotoxicity was evaluated by the [3-(4,5-dimethyliazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulphophenyl)-2H-tetrazolium] (MTT) assay. Chlorhexidine was used as control. Precoating with biosurfactants caused a greater reduction (P biosurfactants was observed at low concentrations (78.12 μg/mL and 156.12 μg/mL) which were noncytotoxic. This study demonstrated the preventive antiadhesion activity of biosurfactants against C. albicans biofilm. These agents are amphiphilic, interfere with microbial adhesion, and demonstrate cycompatibility with epithelial cells and fibroblasts. Copyright © 2012 Elsevier Inc. All rights reserved.

  12. [Calculus formation in the prostatic cavity after transurethral resection of the prostate: causes, treatment and prevention].

    Science.gov (United States)

    Wei, Zhi-Feng; Xu, Xiao-Feng; Cheng, Wen; Zhou, Wen-Quan; Ge, Jing-Ping; Zhang, Zheng-Yu; Gao, Jian-Ping

    2012-05-01

    To study the causes, clinical manifestations, treatment and prevention of calculus that develops in the prostatic cavity after transurethral resection of the prostate. We reported 11 cases of calculus that developed in the prostatic cavity after transurethral resection or transurethral plasmakinetic resection of prostate. The patients complained of repeated symptoms of frequent micturition, urgent micturition and urodynia after operation, accompanied with urinary tract infection and some with urinary obstruction, which failed to respond to anti-infective therapies. Cystoscopy revealed calculi in the prostatic cavity, with eschar, sphacelus, uneven wound surface and small diverticula in some cases. After diagnosis, 1 case was treated by holmium laser lithotripsy and a second transurethral resection of the prostate, while the other 10 had the calculi removed under the cystoscope, followed by 1 -2 weeks of anti-infective therapy. After treatment, all the 11 cases showed normal results of routine urinalysis, and no more symptoms of frequent micturition, urgent micturition and urodynia. Three- to six-month follow-up found no bladder irritation symptoms and urinary tract infection. Repeated symptoms of frequent micturition, urgent micturition, urodynia and urinary tract infection after transurethral resection of the prostate should be considered as the indicators of calculus in the prostatic cavity, which can be confirmed by cystoscopy. It can be treated by lithotripsy or removal of the calculus under the cystoscope, or even a second transurethral resection of the prostate. For its prevention, excessive electric coagulation and uneven wound surface should be avoided and anti-infection treatment is needed.

  13. Extract of Ulmus macrocarpa Hance prevents thrombus formation through antiplatelet activity.

    Science.gov (United States)

    Yang, Won-Kyung; Lee, Jung-Jin; Sung, Yoon-Young; Kim, Dong-Seon; Myung, Chang-Seon; Kim, Ho Kyoung

    2013-09-01

    Ulmus macrocarpa Hance (Ulmaceae) has been used as a traditional oriental medicine for the treatment of edema, mastitis, gastric cancer and inflammation. The aim of this study was to investigate the effects of Ulmus macrocarpa extract (UME) on thrombus formation in vivo, platelet activation ex vivo and fibrinolytic activity in vitro. To identify the antithrombotic activity of UME in vivo, we used an arterial thrombosis model. UME delayed the occlusion time by 13.4 and 13.9 min at doses of 300 and 600 mg/kg, respectively. UME significantly inhibited ex vivo platelet aggregation induced by collagen and adenosine 5'-diphosphate (ADP), respectively, but did not affect the coagulation times following activated partial thromboplastin and prothrombin activation. Therefore, to investigate the antiplatelet effect of UME, the effect of UME on collagen and ADP-induced platelet aggregation in vitro was examined. UME exhibited antiplatelet aggregation activity, induced by ADP and collagen. Furthermore, the fibrinolytic activity of UME was investigated. The results showed that UME significantly increased fibrinolysis at 1,000 mg/ml. In conclusion, the results suggested that UME may significantly inhibit artery thrombus formation in vivo, potentially due to antiplatelet activity, and also exhibits potential as a clot‑dissolving agent for thrombolytic therapy.

  14. Improving Prevention Curricula: Lessons Learned Through Formative Research on the Youth Message Development Curriculum

    Science.gov (United States)

    GREENE, KATHRYN; CATONA, DANIELLE; ELEK, ELVIRA; MAGSAMEN-CONRAD, KATE; BANERJEE, SMITA C.; HECHT, MICHAEL L.

    2016-01-01

    This article describes formative research (a pilot study, interviews, and focus groups) conducted as part of a feasibility test of 2 versions (Analysis vs. Planning) of a brief media literacy intervention titled Youth Message Development (YMD). The intervention targets high school student alcohol use with activities to understand persuasion strategies, increase counter-arguing, and then apply these new skills to ad analysis or a more engaging ad poster planning activity. Based on the theory of active involvement (Greene, 2013), the Planning curriculum is proposed to be more effective than the Analysis curriculum. Overall, results of the formative research indicated that students (N = 182) and mentors/teachers (N = 53) perceived the YMD Planning curriculum as more interesting, involving, and novel, and these ratings were associated with increased critical thinking about the impact of advertising, lower alcohol use intentions, and fewer positive expectations about the effects of alcohol use. Qualitative feedback indicated a need to supplement alcohol-focused ad stimuli with ads targeting other advertising images, use incentives and competition-based activities to further enhance student motivation, and provide flexibility to enhance the appropriateness of the curriculum to various settings. These concerns led to the development of a revised curriculum and plans for further study. PMID:27684111

  15. Superhydrophilic nanopillar-structured quartz surfaces for the prevention of biofilm formation in optical devices

    Science.gov (United States)

    Han, Soo; Ji, Seungmuk; Abdullah, Abdullah; Kim, Duckil; Lim, Hyuneui; Lee, Donghyun

    2018-01-01

    Bacterial biofilm formation on optical devices such as contact lenses, optical glasses, endoscopic devices, and microscopic slides and lenses are major concerns in the field of medicine and biomedical engineering. To solve these problems, here we present the first report of superhydrophilic transparent nanopillar-structured surfaces with bactericidal properties. To construct bactericidal surfaces, we imitated a topological mechanism found in nature in which nanopillar-structured surfaces cause a mechanical disruption of the outer cell membranes of bacteria, resulting in bacterial cell death. We used nanosphere lithography to fabricate nanopillars with various sharpnesses and heights on a quartz substrate. Water contact angle and light reflectance measurements revealed superhydrophilic, antifogging and antireflective properties, which are important for use in optical devices. To determine bactericidal efficiency, the fabricated surfaces were incubated and tested against two Gram-negative bacteria associated with biofilm formation and various diseases in humans, Pseudomonas aeruginosa and Escherichia coli. The highest bactericidal activity was achieved with nanopillars that measured 300 nm in height and 10 nm in apex diameter. Quartz substrates patterned with such nanopillars killed ∼38,000 P. aeruginosa and ∼27,000 E. coli cells cm-2 min-1, respectively. Thus, the newly designed nanopillar-structured bactericidal surfaces are suitable for use in the development of superhydrophilic and transparent optical devices.

  16. Coupled numerical modeling of gas hydrates bearing sediments from laboratory to field-scale conditions

    Science.gov (United States)

    Sanchez, M. J.; Santamarina, C.; Gai, X., Sr.; Teymouri, M., Sr.

    2017-12-01

    Stability and behavior of Hydrate Bearing Sediments (HBS) are characterized by the metastable character of the gas hydrate structure which strongly depends on thermo-hydro-chemo-mechanical (THCM) actions. Hydrate formation, dissociation and methane production from hydrate bearing sediments are coupled THCM processes that involve, amongst other, exothermic formation and endothermic dissociation of hydrate and ice phases, mixed fluid flow and large changes in fluid pressure. The analysis of available data from past field and laboratory experiments, and the optimization of future field production studies require a formal and robust numerical framework able to capture the very complex behavior of this type of soil. A comprehensive fully coupled THCM formulation has been developed and implemented into a finite element code to tackle problems involving gas hydrates sediments. Special attention is paid to the geomechanical behavior of HBS, and particularly to their response upon hydrate dissociation under loading. The numerical framework has been validated against recent experiments conducted under controlled conditions in the laboratory that challenge the proposed approach and highlight the complex interaction among THCM processes in HBS. The performance of the models in these case studies is highly satisfactory. Finally, the numerical code is applied to analyze the behavior of gas hydrate soils under field-scale conditions exploring different features of material behavior under possible reservoir conditions.

  17. Influence of Fines Content on the Mechanical Behavior of Methane Hydrate-Bearing Sediments

    Science.gov (United States)

    Hyodo, Masayuki; Wu, Yang; Nakashima, Koji; Kajiyama, Shintaro; Nakata, Yukio

    2017-10-01

    Methane hydrate-bearing sediments with different amounts of fines content and at three densities were artificially prepared under controlled temperature and pressure conditions. The void ratios of specimens after isotropic consolidation tend to decrease with a rise in fines content. The fines particles enter into the pore space between sand grains and densify the specimens. A series of triaxial compression tests were performed to systematically investigate the influences of fines content and density on the shear properties of hydrate-free sediments and methane hydrate-bearing sediments. The test results demonstrate that a rise in fines content within methane hydrate-bearing sediments significantly enhances peak shear strength and promotes dilation behavior. These influences are particularly prominent for specimens at loose packing state. A decrease in void ratio increases the shear strength and stiffness of hydrate-free sediments and methane hydrate-bearing sediments containing fines content of 0% and 8.9%. It is noted that the formation of methane hydrate in samples with varying amounts of fines content increases the stress ratios at the critical state. The addition of fines particles into coarse-grained sand grains alters the internal microstructure of sand matrix and the hydrate formation pattern in the pore space between sand grains and fines particles.

  18. Photoprotection by Cichorum endivia extracts: prevention of UVB-induced erythema, pyrimidine dimer formation and IL-6 expression.

    Science.gov (United States)

    Enk, C D; Hochberg, M; Torres, A; Lev, O; Dor, I; Srebnik, M; Dembitsky, V M

    2004-01-01

    In the gradual process of evolution, plants have developed natural sun protecting substances that enable continuous survival under direct and intense ultraviolet (UV) radiation. As part of our studies of plant-derived pigments that might constitute an alternative to conventional sunscreens, we have tested the ethanolic extracts of roots, stalks, and inflorescences of populations of wild Cichorum endivia subsp. Divaricatum (Asteraceae) in terms of protection against sunburn, and in prevention of UVB-induced pyrimidine dimer formation and IL-6 mRNA expression in the human keratinocyte cell line, HaCaT. Using ELISA technique for detection of pyrimidine dimers and RT-PCR for detection of IL-6, we found that the ethanolic extract of C. endivia roots absorbs radiation in the UVB spectrum and partially prevents induction of pyrimidine dimers and IL-6 expression. Application of the root extract on the skin prior to UVB irradiation totally prevented erythema. Our findings suggest that C. endivia extracts might possess sun-protective qualities that make them useful as sunscreens. Copyright 2004 S. Karger AG, Basel

  19. Natural gas hydrates and the mystery of the Bermuda Triangle

    Energy Technology Data Exchange (ETDEWEB)

    Gruy, H.J.

    1998-03-01

    Natural gas hydrates occur on the ocean floor in such great volumes that they contain twice as much carbon as all known coal, oil and conventional natural gas deposits. Releases of this gas caused by sediment slides and other natural causes have resulted in huge slugs of gas saturated water with density too low to float a ship, and enough localized atmospheric contamination to choke air aspirated aircraft engines. The unexplained disappearances of ships and aircraft along with their crews and passengers in the Bermuda Triangle may be tied to the natural venting of gas hydrates. The paper describes what gas hydrates are, their formation and release, and their possible link to the mystery of the Bermuda Triangle.

  20. Behavior of gas seep bubbles below the hydrate stability zone

    Science.gov (United States)

    Wang, B.; Jun, I.; Hutschenreuter, K.; Socolofsky, S. A.; Kessler, J. D.; Lavery, A.; Breier, J. A., Jr.; Seewald, J.

    2016-02-01

    Two research cruises (GISR G07 and G08) have been carried out during 2014-2015 to study the behavior of natural gas seep plumes escaping on the seafloor below the hydrate stability zone at MC 118 and GC 600 in the Gulf of Mexico. Quantitative image measurements suggest both temporal and spatial variation of the bubble size and gas flow rate. Hydrate formation on the natural gas seep bubbles was a very fast process in the deep sea environment (890 and 1200 m depth), where the measured methane concentration in water close to the source was also saturated. The measured rise velocities of the bubbles differed significantly from the predicted terminal velocities using empirical equations in Clift et al. (1978). The measured bubble characteristics (size distribution and flow rate) were provided as input to a bubble dissolution model, which accounts for the effect of hydrate on the mass transfer coefficient. The model shows results consistent with the measurements.

  1. Dental calculus: recent insights into occurrence, formation, prevention, removal and oral health effects of supragingival and subgingival deposits.

    Science.gov (United States)

    White, D J

    1997-10-01

    radius of plaque induced periodontal injury. Removal of subgingival plaque and calculus remains the cornerstone of periodontal therapy. Calculus formation is the result of petrification of dental plaque biofilm, with mineral ions provided by bathing saliva or crevicular fluids. Supragingival calculus formation can be controlled by chemical mineralization inhibitors, applied in toothpastes or mouthrinses. These agents act to delay plaque calcification, keeping deposits in an amorphous non-hardened state to facilitate removal with regular hygiene. Clinical efficacy for these agents is typically assessed as the reduction in tartar area coverage on the teeth between dental cleaning. Research shows that topically applied mineralization inhibitors can also influence adhesion and hardness of calculus deposits on the tooth surface, facilitating removal. Future research in calculus may include the development of improved supragingival tartar control formulations, the development of treatments for the prevention of subgingival calculus formation, the development of improved methods for root detoxification and debridement and the development and application of sensitive diagnostic methods to assess subgingival debridement efficacy.

  2. 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.

  3. Measures to prevent foam formation in the anaerobic digestion of sugar beet in biogas plants

    Directory of Open Access Journals (Sweden)

    Lucie Moeller

    2017-01-01

    Full Text Available The occurrence of persistent foaming is observed in many anaerobic digesters that have sugar beet as their feedstock. The formation of foam entails a significant risk of damage to biogas plants, as gas pipes can become blocked. For this reason, foaming tests have been conducted to investigate which measures lead to reductions in foam development. It was found that generally available fertilizers such as urea, ammonium nitrate and calcium cyanamide have a foam-reducing effect. However, batch fermentation tests showed inhibition of biogas production at higher concentrations of these substances, which means that they should be used with care. Calcium cyanamide was found to be very unsuitable, as this substance inhibited biogas production even at low concentrations and caused the fermentation process to come to a complete stop at higher concentrations.

  4. Numerical Simulations for Enhanced Methane Recovery from Gas Hydrate Accumulations by Utilizing CO2 Sequestration

    Science.gov (United States)

    Sridhara, Prathyusha

    In 2013, the International Energy Outlook (EIA, 2013) projected that global energy demand will grow by 56% between 2010 and 2040. Despite strong growth in renewable energy supplies, much of this growth is expected to be met by fossil fuels. Concerns ranging from greenhouse gas emissions and energy security are spawning new interests for other sources of energy including renewable and unconventional fossil fuel such as shale gas and oil as well as gas hydrates. The production methods as well as long-term reservoir behavior of gas hydrate deposits have been under extensive investigation. Reservoir simulators can be used to predict the production potentials of hydrate formations and to determine which technique results in enhanced gas recovery. In this work, a new simulation tool, Mix3HydrateResSim (Mix3HRS), which accounts for complex thermodynamics of multi-component hydrate phase comprised of varying hydrate solid crystal structure, is used to perform the CO2-assisted production technique simulations from CH4 hydrate accumulations. The simulator is one among very few reservoir simulators which can simulate the process of CH4 substitution by CO2 (and N2 ) in the hydrate lattice. Natural gas hydrate deposits around the globe are categorized into three different classes based on the characteristics of the geological sediments present in contact with the hydrate bearing deposits. Amongst these, the Class 2 hydrate accumulations predominantly confirmed in the permafrost and along seashore, are characterized by a mobile aqueous phase underneath a hydrate bearing sediment. The exploitation of such gas hydrate deposits results in release of large amounts of water due to the presence of permeable water-saturated sediments encompassing the hydrate deposits, thus lowering the produced gas rates. In this study, a suite of numerical simulation scenarios with varied complexity are considered which aimed at understanding the underlying changes in physical, thermodynamic and

  5. Acoustical method of whole-body hydration status monitoring

    Science.gov (United States)

    Sarvazyan, A. P.; Tsyuryupa, S. N.; Calhoun, M.; Utter, A.

    2016-07-01

    An acoustical handheld hydration monitor (HM) for assessing the water balance of the human body was developed. Dehydration is a critical public health problem. Many elderly over age of 65 are particularly vulnerable as are infants and young children. Given that dehydration is both preventable and reversible, the need for an easy-to-perform method for the detection of water imbalance is of the utmost clinical importance. The HM is based on an experimental fact that ultrasound velocity in muscle is a linear function of water content and can be referenced to the hydration status of the body. Studies on the validity of HM for the assessment of whole-body hydration status were conducted in the Appalachian State University, USA, on healthy young adults and on elderly subjects residing at an assisted living facility. The HM was able to track changes in total body water during periods of acute dehydration and rehydration in athletes and day-to-day and diurnal variability of hydration in elderly. Results of human studies indicate that HM has a potential to become an efficient tool for detecting abnormal changes in the body hydration status.

  6. Integrating Natural Gas Hydrates in the Global Carbon Cycle

    Energy Technology Data Exchange (ETDEWEB)

    David Archer; Bruce Buffett

    2011-12-31

    We produced a two-dimensional geological time- and basin-scale model of the sedimentary margin in passive and active settings, for the simulation of the deep sedimentary methane cycle including hydrate formation. Simulation of geochemical data required development of parameterizations for bubble transport in the sediment column, and for the impact of the heterogeneity in the sediment pore fluid flow field, which represent new directions in modeling methane hydrates. The model is somewhat less sensitive to changes in ocean temperature than our previous 1-D model, due to the different methane transport mechanisms in the two codes (pore fluid flow vs. bubble migration). The model is very sensitive to reasonable changes in organic carbon deposition through geologic time, and to details of how the bubbles migrate, in particular how efficiently they are trapped as they rise through undersaturated or oxidizing chemical conditions and the hydrate stability zone. The active margin configuration reproduces the elevated hydrate saturations observed in accretionary wedges such as the Cascadia Margin, but predicts a decrease in the methane inventory per meter of coastline relative to a comparable passive margin case, and a decrease in the hydrate inventory with an increase in the plate subduction rate.

  7. Gas Hydrate Research Database and Web Dissemination Channel

    Energy Technology Data Exchange (ETDEWEB)

    Micheal Frenkel; Kenneth Kroenlein; V Diky; R.D. Chirico; A. Kazakow; C.D. Muzny; M. Frenkel

    2009-09-30

    To facilitate advances in application of technologies pertaining to gas hydrates, a United States database containing experimentally-derived information about those materials was developed. The Clathrate Hydrate Physical Property Database (NIST Standard Reference Database {number_sign} 156) was developed by the TRC Group at NIST in Boulder, Colorado paralleling a highly-successful database of thermodynamic properties of molecular pure compounds and their mixtures and in association with an international effort on the part of CODATA to aid in international data sharing. Development and population of this database relied on the development of three components of information-processing infrastructure: (1) guided data capture (GDC) software designed to convert data and metadata into a well-organized, electronic format, (2) a relational data storage facility to accommodate all types of numerical and metadata within the scope of the project, and (3) a gas hydrate markup language (GHML) developed to standardize data communications between 'data producers' and 'data users'. Having developed the appropriate data storage and communication technologies, a web-based interface for both the new Clathrate Hydrate Physical Property Database, as well as Scientific Results from the Mallik 2002 Gas Hydrate Production Research Well Program was developed and deployed at http://gashydrates.nist.gov.

  8. Energy resource potential of natural gas hydrates

    Science.gov (United States)

    Collett, T.S.

    2002-01-01

    The discovery of large gas hydrate accumulations in terrestrial permafrost regions of the Arctic and beneath the sea along the outer continental margins of the world's oceans has heightened interest in gas hydrates as a possible energy resource. However, significant to potentially insurmountable technical issues must be resolved before gas hydrates can be considered a viable option for affordable supplies of natural gas. The combined information from Arctic gas hydrate studies shows that, in permafrost regions, gas hydrates may exist at subsurface depths ranging from about 130 to 2000 m. The presence of gas hydrates in offshore continental margins has been inferred mainly from anomalous seismic reflectors, known as bottom-simulating reflectors, that have been mapped at depths below the sea floor ranging from about 100 to 1100 m. Current estimates of the amount of gas in the world's marine and permafrost gas hydrate accumulations are in rough accord at about 20,000 trillion m3. Disagreements over fundamental issues such as the volume of gas stored within delineated gas hydrate accumulations and the concentration of gas hydrates within hydrate-bearing strata have demonstrated that we know little about gas hydrates. Recently, however, several countries, including Japan, India, and the United States, have launched ambitious national projects to further examine the resource potential of gas hydrates. These projects may help answer key questions dealing with the properties of gas hydrate reservoirs, the design of production systems, and, most important, the costs and economics of gas hydrate production.

  9. Surface zwitterionization: Effective method for preventing oral bacterial biofilm formation on hydroxyapatite surfaces

    Science.gov (United States)

    Lee, Myoungjin; Kim, Heejin; Seo, Jiae; Kang, Minji; Kang, Sunah; Jang, Joomyung; Lee, Yan; Seo, Ji-Hun

    2018-01-01

    In this study, we conducted surface zwitterionization of hydroxyapatite (HA) surfaces by immersing them in the zwitterionic polymer solutions to provide anti-bacterial properties to the HA surface. Three different monomers containing various zwitterionic groups, i.e., phosphorylcholine (PC), sulfobetaine (SB), and carboxybetaine (CB), were copolymerized with the methacrylic monomer containing a Ca2+-binding moiety, using the free radical polymerization method. As a control, functionalization of the copolymer containing the Ca2+-binding moiety was synthesized using a hydroxy group. The stable immobilization of the zwitterionic functional groups was confirmed by water contact angle analysis and X-ray photoelectron spectroscopy (XPS) measurement conducted after the sonication process. The zwitterionized HA surface showed significantly decreased protein adsorption, whereas the hydroxyl group-coated HA surface showed limited efficacy. The anti-bacterial adhesion property was confirmed by conducting Streptococcus mutans (S. mutans) adhesion tests for 6 h and 24 h. When furanone C-30, a representative anti-quorum sensing molecule for S. mutans, was used, only a small amount of bacteria adhered after 6 h and the population did not increase after 24 h. In contrast, zwitterionized HA surfaces showed almost no bacterial adhesion after 6 h and the effect was retained for 24 h, resulting in the lowest level of oral bacterial adhesion. These results confirm that surface zwitterionization is a promising method to effectively prevent oral bacterial adhesion on HA-based materials.

  10. High wind speeds prevent formation of a distinct bacterioneuston community in the sea-surface microlayer.

    Science.gov (United States)

    Rahlff, Janina; Stolle, Christian; Giebel, Helge-Ansgar; Brinkhoff, Thorsten; Ribas-Ribas, Mariana; Hodapp, Dorothee; Wurl, Oliver

    2017-05-01

    The sea-surface microlayer (SML) at the boundary between atmosphere and hydrosphere represents a demanding habitat for bacteria. Wind speed is a crucial but poorly studied factor for its physical integrity. Increasing atmospheric burden of CO2, as suggested for future climate scenarios, may particularly act on this habitat at the air-sea interface. We investigated the effect of increasing wind speeds and different pCO2 levels on SML microbial communities in a wind-wave tunnel, which offered the advantage of low spatial and temporal variability. We found that enrichment of bacteria in the SML occurred solely at a U10 wind speed of ≤5.6 m s-1 in the tunnel and ≤4.1 m s-1 in the Baltic Sea. High pCO2 levels further intensified the bacterial enrichment in the SML during low wind speed. In addition, low wind speed and pCO2 induced the formation of a distinctive bacterial community as revealed by 16S rRNA gene fingerprints and influenced the presence or absence of individual taxonomic units within the SML. We conclude that physical stability of the SML below a system-specific wind speed threshold induces specific bacterial communities in the SML entailing strong implications for ecosystem functioning by wind-driven impacts on habitat properties, gas exchange and matter cycling processes. © FEMS 2017.

  11. Oral Administration of Thioflavin T Prevents Beta Amyloid Plaque Formation in Double Transgenic AD Mice.

    Science.gov (United States)

    Sarkar, Sumit; Raymick, James; Ray, Balmiki; Lahiri, Debomoy K; Paule, Merle G; Schmued, Larry

    2015-01-01

    Alzheimer's disease (AD) is a progressive neurodegenerative disorder and the fourth leading cause of death in the United States and most common cause of adult-onset dementia. The major hallmarks of AD are the formation of senile amyloid plaques made of beta amyloid and neurofibrillary tangles (NFT) which are primarily composed of phosphorylated tau protein. Although numerous agents have been considered as providing protection against AD, identification of potential agents with neuroprotective ability is limited. Thioflavin T has been used in the past to stain amyloid beta plaques in brain. In this study, Thioflavin T (ThT) and vehicle (infant formula) were administered orally by gavage to transgenic (B6C3 APP PS1; AD-Tg) mice beginning at 4 months age and continuing until sacrifice at 9 months of age at 40 mg/kg dose. The number of amyloid plaques was reduced dramatically by ThT treatment in both male and female transgenic mice compared to those in control mice. Additionally, GFAP and Amylo-Glo labeling suggest that astrocytic hypertrophy is minimized in ThT-treated animals. Similarly, CD68 labeling, which detects activated microglia, along with Amylo-Glo labeling, suggests that microglial activation is significantly less in ThT-treated mice. Both Aβ-40 and Aβ-42 concentrations in blood rose significantly in the ThT-treated animals suggesting that ThT may inhibit the deposition, degradation, and/or clearance of Aβ plaques in brain.

  12. Intraperitoneal tenoxicam to prevent abdominal adhesion formation in a rat peritonitis model.

    Science.gov (United States)

    Ezberci, Fikret; Bulbuloglu, Ertan; Ciragil, Pinar; Gul, Mustafa; Kurutas, Ergul Belge; Bozkurt, Serdar; Kale, I Taner

    2006-01-01

    We investigated the effects of intraperitoneal tenoxicam on the development of postoperative intra-abdominal adhesions and oxidative stress in a model of bacterial peritonitis. Bacterial peritonitis was induced in 24 rats by cecal ligation and puncture. The rats were randomly assigned to one of three groups. Group 1 (n = 8) received 2 ml saline intraperitoneally, group 2 (n = 8) received 2 ml (0.5 mg/kg) tenoxicam (Oksamen) intraperitoneally, and group 3 (n = 8) was a control, which did not receive any injection. All animals were killed 14 days later so we could assess the adhesion score and measure anastomotic bursting pressures. Tissue antioxidant levels were measured in 1-g tissue samples taken from the abdominal wall. The adhesion score was significantly lower in the tenoxicam group than in the saline and control groups. The anastomotic bursting pressures were higher in the saline and tenoxicam groups than in the control group. The catalase (CAT) levels were higher in the saline and tenoxicam groups than in the control group. The malondialdehyde (MDH) levels were higher in the saline group than in the tenoxicam and control groups. Intraperitoneal tenoxicam inhibited the formation of postoperative intra-abdominal adhesions without compromising wound healing in this bacterial peritonitis rat model. Tenoxicam also decreased the oxidative stress during peritonitis.

  13. Clinker mineral hydration at reduced relative humidities

    DEFF Research Database (Denmark)

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

    1999-01-01

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

  14. Production-test planning for the JAPEX/JNOC/GSC et al. Mallik 5L-38 gas hydrate production research well

    Energy Technology Data Exchange (ETDEWEB)

    Satoh, T. [Japan Petroleum Exploration Co. Ltd., Tokyo (Japan); Dallimore, S. [Geological Survey of Canada, Sidney, BC (Canada); Collett, T. [United States Geological Survey, Denver, CO (United States); Inoue, T. [Japan National Oil Corp., Chiba (Japan); Hancock, S.H.; Weatherill, B. [APA Petroleum Engineering Ltd., Calgary, AB (Canada); Moridis, G.J. [California Univ., Berkeley, CA (United States). Lawrence Berkeley National Laboratory

    2005-07-01

    The development of the gas hydrate production-test experiments for the JAPEX/JNOC/GSC et al. Mallik 5L-38 well was reviewed. The research well was drilled to confirm the feasibility of natural gas production from gas hydrate deposits by depressurization and thermal stimulation, and to collect enough data to determine relevant gas hydrate formation properties. The production of the free-gas interval at the base of the gas hydrate stability zone was examined along with other tests for gas hydrate accumulation at the Mallik well. This perforated the hydrate interval to allow for both small and large-scale pressure drawdown tests directly in a gas hydrate zone. Other gas hydrate accumulation tests included inhibitor stimulations; horizontal wells; complex multiple-well experiments; and thermal stimulations. Modern pressure transient analysis techniques were also used to analyze the bottomhole data.

  15. Life Origination Hydrate Hypothesis (LOH-Hypothesis).

    Science.gov (United States)

    Ostrovskii, Victor; Kadyshevich, Elena

    2012-01-04

    The paper develops the Life Origination Hydrate Hypothesis (LOH-hypothesis), according to which living-matter simplest elements (LMSEs, which are N-bases, riboses, nucleosides, nucleotides), DNA- and RNA-like molecules, amino-acids, and proto-cells repeatedly originated on the basis of thermodynamically controlled, natural, and inevitable processes governed by universal physical and chemical laws from CH4, niters, and phosphates under the Earth's surface or seabed within the crystal cavities of the honeycomb methane-hydrate structure at low temperatures; the chemical processes passed slowly through all successive chemical steps in the direction that is determined by a gradual decrease in the Gibbs free energy of reacting systems. The hypothesis formulation method is based on the thermodynamic directedness of natural movement and consists ofan attempt to mentally backtrack on the progression of nature and thus reveal principal milestones alongits route. The changes in Gibbs free energy are estimated for different steps of the living-matter origination process; special attention is paid to the processes of proto-cell formation. Just the occurrence of the gas-hydrate periodic honeycomb matrix filled with LMSEs almost completely in its final state accounts for size limitation in the DNA functional groups and the nonrandom location of N-bases in the DNA chains. The slowness of the low-temperature chemical transformations and their "thermodynamic front" guide the gross process of living matter origination and its successive steps. It is shown that the hypothesis is thermodynamically justified and testable and that many observed natural phenomena count in its favor.

  16. Life Origination Hydrate Hypothesis (LOH-Hypothesis

    Directory of Open Access Journals (Sweden)

    Victor Ostrovskii

    2012-01-01

    Full Text Available The paper develops the Life Origination Hydrate Hypothesis (LOH-hypothesis, according to which living-matter simplest elements (LMSEs, which are N-bases, riboses, nucleosides, nucleotides, DNA- and RNA-like molecules, amino-acids, and proto-cells repeatedly originated on the basis of thermodynamically controlled, natural, and inevitable processes governed by universal physical and chemical laws from CH4, niters, and phosphates under the Earth's surface or seabed within the crystal cavities of the honeycomb methane-hydrate structure at low temperatures; the chemical processes passed slowly through all successive chemical steps in the direction that is determined by a gradual decrease in the Gibbs free energy of reacting systems. The hypothesis formulation method is based on the thermodynamic directedness of natural movement and consists ofan attempt to mentally backtrack on the progression of nature and thus reveal principal milestones alongits route. The changes in Gibbs free energy are estimated for different steps of the living-matter origination process; special attention is paid to the processes of proto-cell formation. Just the occurrence of the gas-hydrate periodic honeycomb matrix filled with LMSEs almost completely in its final state accounts for size limitation in the DNA functional groups and the nonrandom location of N-bases in the DNA chains. The slowness of the low-temperature chemical transformations and their “thermodynamic front” guide the gross process of living matter origination and its successive steps. It is shown that the hypothesis is thermodynamically justified and testable and that many observed natural phenomena count in its favor.

  17. Constraining gas hydrate occurrence in the northern Gulf of Mexico continental slope : fine scale analysis of grain-size in hydrate-bearing sediments

    Energy Technology Data Exchange (ETDEWEB)

    Hangsterfer, A.; Driscoll, N.; Kastner, M. [Scripps Inst. of Oceanography, La Jolla, CA (United States). Geosciences Research Division

    2008-07-01

    Methane hydrates can form within the gas hydrate stability zone (GHSZ) in sea beds. The Gulf of Mexico (GOM) contains an underlying petroleum system and deeply buried, yet dynamic salt deposits. Salt tectonics and fluid expulsion upward through the sediment column result in the formation of fractures, through which high salinity brines migrate into the GHSZ, destabilizing gas hydrates. Thermogenic and biogenic hydrocarbons also migrate to the seafloor along the GOMs northern slope, originating from the thermal and biogenic degradation of organic matter. Gas hydrate occurrence can be controlled by either primary permeability, forming in coarse-grained sediment layers, or by secondary permeability, forming in areas where hydrofracture and faulting generate conduits through which hydrocarbon-saturated fluids flow. This paper presented a study that attempted to determine the relationship between grain-size, permeability, and gas hydrate distribution. Grain-size analyses were performed on cores taken from Keathley Canyon and Atwater Valley in the GOM, on sections of cores that both contained and lacked gas hydrate. Using thermal anomalies as proxies for the occurrence of methane hydrate within the cores, samples of sediment were taken and the grain-size distributions were measured to see if there was a correlation between gas hydrate distribution and grain-size. The paper described the methods, including determination of hydrate occurrence and core analysis. It was concluded that gas hydrate occurrence in Keathley Canyon and Atwater Valley was constrained by secondary permeability and was structurally controlled by hydrofractures and faulting that acted as conduits through which methane-rich fluids flowed. 11 refs., 2 tabs., 5 figs.

  18. Prevention of Bacterial Biofilm Formation on Soft Contact Lenses Using Natural Compounds.

    Science.gov (United States)

    El-Ganiny, Amira M; Shaker, Ghada H; Aboelazm, Abeer A; El-Dash, Heba A

    2017-12-01

    In eye care field, contact lenses (CL) have a great impact on improving vision, but their use can be limited by ocular infection. CL- associated infections can be reduced by good attention to CL storage case practice. CL-care solutions should be able to control microbial growth on CL. The aim of the study was to evaluate and compare the efficacy of CL-care solutions (found in Egyptian market) with some natural compounds in removal and inhibition of bacterial biofilm formed on soft CL. Clinical isolates were recovered from patients having conjunctivitis from Benha University Hospital and identified microbiologically. Quantification of biofilm was done using microtiter plate assay. Three multipurpose CL-care solutions were examined for their ability to remove and inhibit biofilm. Also four natural extracts having antibacterial activity and are safe on eye were tested for their anti-biofilm activity. The major bacterial isolates from eye infections were Pseudomonas aeruginosa (36%) and Staphylococcus spp. (37.8%). Only 33.3% of isolates showed ability to produce weak to moderate biofilm. The tested multi-purpose CL-care solutions showed moderate ability to remove preformed biofilm. Among the tested natural compounds, Calendula officinalis and Buddleja salviifolia extracts showed an excellent efficacy in inhibition of biofilm and also removal of preformed biofilm. This study demonstrated that isolates from infected eye and CL-cases showed weak to moderate biofilm formation. Calendula officinalis and Buddleja salviifolia extracts showed excellent effect on inhibition and removal of biofilm, these extracts could be added into CL-care solutions which could markedly reduce eye-infections during CL-wear.

  19. Candesartan restores pressure-induced vasodilation and prevents skin pressure ulcer formation in diabetic mice.

    Science.gov (United States)

    Danigo, Aurore; Nasser, Mohamad; Bessaguet, Flavien; Javellaud, James; Oudart, Nicole; Achard, Jean-Michel; Demiot, Claire

    2015-02-18

    Angiotensin II type 1 receptor (AT1R) blockers have beneficial effects on neurovascular complications in diabetes and in organ's protection against ischemic episodes. The present study examines whether the AT1R blocker candesartan (1) has a beneficial effect on diabetes-induced alteration of pressure-induced vasodilation (PIV, a cutaneous physiological neurovascular mechanism which could delay the occurrence of tissue ischemia), and (2) could be protective against skin pressure ulcer formation. Male Swiss mice aged 5-6 weeks were randomly assigned to four experimental groups. In two groups, diabetes was induced by a single intraperitoneal injection of streptozotocin (STZ, 200 mg.kg(-1)). After 6 weeks, control and STZ mice received either no treatment or candesartan (1 mg/kg-daily in drinking water) during 2 weeks. At the end of treatment (8 weeks of diabetes duration), C-fiber mediated nociception threshold, endothelium-dependent vasodilation and PIV were assessed. Pressure ulcers (PUs) were then induced by pinching the dorsal skin between two magnetic plates for three hours. Skin ulcer area development was assessed during three days, and histological examination of the depth of the skin lesion was performed at day three. After 8 weeks of diabetes, the skin neurovascular functions (C-fiber nociception, endothelium-dependent vasodilation and PIV) were markedly altered in STZ-treated mice, but were fully restored by treatment with candesartan. Whereas in diabetes mice exposure of the skin to pressure induced wide and deep necrotic lesions, treatment with candersartan restored their ability to resist to pressure-induced ulceration as efficiently as the control mice. Candesartan decreases the vulnerability to pressure-induced ulceration and restores skin neurovascular functions in mice with STZ-induced established diabetes.

  20. Time-resolved in situ neutron diffraction studies of gas hydrate: transformation of structure II (sII) to structure I (sI).

    Science.gov (United States)

    Halpern, Y; Thieu, V; Henning, R W; Wang, X; Schultz, A J

    2001-12-26

    We report the in situ observation from diffraction data of the conversion of a gas hydrate with the structure II (sII) lattice to one with the structure I (sI) lattice. Initially, the in situ formation, dissociation, and reactivity of argon gas clathrate hydrate was investigated by time-of-flight neutron powder diffraction at temperatures ranging from 230 to 263 K and pressures up to 5000 psi (34.5 MPa). These samples were prepared from deuterated ice crystals and transformed to hydrate by pressurizing the system with argon gas. Complete transformation from D(2)O ice to sII Ar hydrate was observed as the sample temperature was slowly increased through the D(2)O ice melting point. The transformation of sII argon hydrate to sI hydrate was achieved by removing excess Ar gas and exposing the hydrate to liquid CO(2) by pressurizing the Ar hydrate with CO(2). Results suggest the sI hydrate formed from CO(2) exchange in argon sII hydrate is a mixed Ar/CO(2) hydrate. The proposed exchange mechanism is consistent with clathrate hydrate being an equilibrium system in which guest molecules are exchanging between encapsulated molecules in the solid hydrate and free molecules in the surrounding gas or liquid phase.

  1. The chloride channel inhibitor NS3736 [corrected] prevents bone resorption in ovariectomized rats without changing bone formation

    DEFF Research Database (Denmark)

    Schaller, Sophie; Henriksen, Kim; Sveigaard, Christina

    2004-01-01

    Chloride channel activity is essential for osteoclast function. Consequently, inhibition of the osteoclastic chloride channel should prevent bone resorption. Accordingly, we tested a chloride channel inhibitor on bone turnover and found that it inhibits bone resorption without affecting bone...... for osteoporosis, daily treatment with 30 mg/kg orally protected bone strength and BMD by approximately 50% 6 weeks after surgery. Most interestingly, bone formation assessed by osteocalcin, mineral apposition rate, and mineralized surface index was not inhibited. MATERIALS AND METHODS: Analysis of chloride......, appearing mainly in osteoclasts, ovaries, appendix, and Purkinje cells. This highly selective distribution predicts that inhibition of ClC-7 should specifically target osteoclasts in vivo. We suggest that NS3736 is inhibiting ClC-7, leading to a bone-specific effect in vivo. RESULTS AND CONCLUSION...

  2. Moessbauer and calorimetric studies of portland cement hydration in the presence of black gram pulse

    International Nuclear Information System (INIS)

    Rai, Sarita; Kurian, Sajith; Dwivedi, V. N.; Das, S. S.; Singh, N. B.; Gajbhiye, N. S.

    2009-01-01

    Effect of different concentrations of naturally occurring admixture in the form of fine powder of black gram pulse (BGP) on the hydration of Portland cement was studied by isothermal calorimetry and 57 Fe Moessbauer spectroscopy. The spectra were recorded for anhydrous cement and the hydration products at room temperature and 77 K. In the presence of BGP, the spectra showed superparamagnetic doublets at room temperature and the sextet at 77 K, due to the presence of fine particles of iron containing component. Moessbauer studies of hydration products confirmed the formation of nanosize hydration products containing Fe 3+ . The isomer shift (δ) and the quadrupole splitting (ΔE Q ) values of C 4 AF in the cement confirmed iron in an octahedral and tetrahedral environment with +3 oxidation state. The high value of quadrupole splitting showed the high asymmetry of the electron environment around the iron atom. The overall mechanism of the hydration of cement in presence of BGP is discussed.

  3. Dry heat treatment affects wheat bran surface properties and hydration kinetics.

    Science.gov (United States)

    Jacobs, Pieter J; Hemdane, Sami; Delcour, Jan A; Courtin, Christophe M

    2016-07-15

    Heat stabilization of wheat bran aims at inactivation of enzymes which may cause rancidity and processability issues. Such treatments may however cause additional unanticipated phenomena which may affect wheat bran technological properties. In this work, the impact of toasting on wheat bran hydration capacity and hydration kinetics was studied. Hydration properties were assessed using the Enslin-Neff and drainage centrifugation water retention capacity methods, thermogravimetric analysis and contact angle goniometry, next to more traditional methods. While equilibrium hydration properties of bran were not affected by the heat treatment, the rate at which the heat treated bran hydrated was, however, very significantly reduced compared to the untreated bran. This phenomenon was found to originate from the formation of a lipid coating during the treatment rendering the bran surface hydrophobic. These insights help to understand and partially account for the modified processability of heat treated bran in food applications. Copyright © 2016 Elsevier Ltd. All rights reserved.

  4. Prevention of parastomal hernias with 3D funnel meshes in intraperitoneal onlay position by placement during initial stoma formation.

    Science.gov (United States)

    Köhler, G; Hofmann, A; Lechner, M; Mayer, F; Wundsam, H; Emmanuel, K; Fortelny, R H

    2016-02-01

    In patients with terminal ostomies, parastomal hernias (PSHs) occur on a frequent basis. They are commonly associated with various degrees of complaints and occasionally lead to life-threatening complications. Various strategies and measures have been tested and evaluated, but to date there is a lack of published evidence with regard to the best surgical technique for the prevention of PSH development. We conducted a retrospective analysis of prospectively collected data of eighty patients, who underwent elective permanent ostomy formation between 2009 and 2014 by means of prophylactic implantation of a three-dimensional (3D) funnel mesh in intraperitoneal onlay (IPOM) position. PSH developed in three patients (3.75%). No mesh-related complications were encountered and none of the implants had to be removed. Ostomy-related complications had to be noted in seven (8.75%) cases. No manifestation of ostomy prolapse occurred. Follow-up time was a median 21 (range 3-47) months. The prophylactical implantation of a specially shaped, 3D mesh implant in IPOM technique during initial formation of a terminal enterostomy is safe, highly efficient and comparatively easy to perform. As opposed to what can be achieved with flat or keyhole meshes, the inner boundary areas of the ostomy itself can be well covered and protected from the surging viscera with the 3D implants. At the same time, the vertical, tunnel-shaped part of the mesh provides sufficient protection from an ostomy prolapse. Further studies will be needed to compare the efficacy of various known approaches to PSH prevention.

  5. Gender- and hydration- associated differences in the physiological response to spinning.

    Science.gov (United States)

    Ramos-Jiménez, Arnulfo; Hernández-Torres, Rosa Patricia; Wall-Medrano, Abraham; Torres-Durán, Patricia Victoria; Juárez-Oropeza, Marco Antonio; Viloria, María; Villalobos-Molina, Rafael

    2014-03-01

    There is scarce and inconsistent information about gender-related differences in the hydration of sports persons, as well as about the effects of hydration on performance, especially during indoor sports. To determine the physiological differences between genders during in indoor physical exercise, with and without hydration. 21 spinning sportspeople (12 men and 9 women) participated in three controlled, randomly assigned and non-sequential hydration protocols, including no fluid intake and hydration with plain water or a sports drink (volume adjusted to each individual every 15 min), during 90 min of spinning exercise. The response variables included body mass, body temperature, heart rate and blood pressure. During exercise without hydration, men and women lost ~2% of body mass, and showed higher body temperature (~0.2°C), blood pressure (~4 mmHg) and heart rate (~7 beats/min) compared to exercises with hydration. Body temperature and blood pressure were higher for men than for women during exercise without hydration, differences not observed during exercise with hydration. Between 42-99% of variance in body temperature, blood pressure and heart rate could be explained by the physical characteristics of subjects and the work done. During exercise with hydration (either with water or sport drink), the physiological response was similar for both genders. Exercise without hydration produced physical stress, which could be prevented with either of the fluids (plain water was sufficient). Gender differences in the physiological response to spinning (body temperature, mean blood pressure and heart rate) can be explained in part by the distinct physical characteristics of each individual. Copyright AULA MEDICA EDICIONES 2014. Published by AULA MEDICA. All rights reserved.

  6. Comparative evaluation of turmeric and chlorhexidine gluconate mouthwash in prevention of plaque formation and gingivitis: a clinical and microbiological study.

    Science.gov (United States)

    Waghmare, P F; Chaudhari, A U; Karhadkar, V M; Jamkhande, A S

    2011-07-01

    To compare the efficacy of turmeric mouthwash and chlorhexidine gluconate mouthwash in prevention of gingivitis and plaque formation. A total of 100 randomly selected subjects visiting the Department of Periodontology at Bharati Vidyapeeth Deemed University, Dental College and Hospital, were considered for the study. The gingival index (GI) by Loe and Silness was recorded which was followed by Turesky- Gilmore-Glickman modification of Quigley Hein plaque index (TQHPI) at 0, 14 and 21 days. Individuals who gave an informed consent, subjects in the age group of 25 to 35 years with having fair and poor gingival index scores and a score >1 for plaque index, were included in the study. Results showed statistically significant reduction (p plaque index (PI) with chlorhexidine gluconate mouthwash when compared with turmeric mouthwash. No significant difference in mean gingival index (GI) was seen when chlorhexidine mouthwash was compared with turmeric mouthwash. Significant reduction in total microbial count (p chlorhexidine mouthwash was compared with turmeric mouthwash. From the above observations, it can be concluded that chlorhexidine gluconate as well as turmeric mouthwash can be effectively used as an adjunct to mechanical plaque control methods in prevention of plaque and gingivitis. Chlorhexidine gluconate has been found to be more effective when antiplaque property was considered. From this study, it could be stated that turmeric is definitely a good adjunct to mechanical plaque control. Further studies are required on turmeric based mouthwash to establish it as a low cost plaque control measure.

  7. Antibacterial activity of Thymoquinone, an active principle of Nigella sativa and its potency to prevent bacterial biofilm formation

    Directory of Open Access Journals (Sweden)

    Bakhrouf Amina

    2011-04-01

    Full Text Available Abstract Background Thymoquinone is an active principle of Nigella sativa seed known as "Habbah Al-Sauda" in Arabic countries and "Sinouj" in Tunisia. Bacterial biofilms tend to exhibit significant tolerance to antimicrobials drugs during infections. Methods The antibacterial activity of Thymoquinone (TQ and its biofilm inhibition potencies were investigated on 11 human pathogenic bacteria. The growth and development of the biofilm were assessed using the crystal violet (CV and the 2, 3-bis [2-methyloxy-4-nitro-5-sulfophenyl]-2H-tetrazolium-5-carboxanilide (XTT reduction assay. Results TQ exhibited a significant bactericidal activity against the majority of the tested bacteria (MICs values ranged from 8 to 32 μg/ml especially Gram positive cocci (Staphylococcus aureus ATCC 25923 and Staphylococcus epidermidis CIP 106510. Crystal violet assay demonstrated that the minimum biofilm inhibition concentration (BIC50 was reached with 22 and 60 μg/ml for Staphylococcus aureus ATCC 25923 and Staphylococcus epidermidis CIP 106510 respectively. In addition our data revealed that cells oxidative activity was influenced by TQ supplementation. In the same way, TQ prevented cell adhesion to glass slides surface. Conclusion The ability of TQ to prevent biofilm formation warrants further investigation to explore its use as bioactive substances with antibiofilm potential.

  8. A metagenomic study of the preventive effect of Lactobacillus rhamnosus GG on intestinal polyp formation in ApcMin/+mice.

    Science.gov (United States)

    Ni, Y; Wong, V H Y; Tai, W C S; Li, J; Wong, W Y; Lee, M M L; Fong, F L Y; El-Nezami, H; Panagiotou, G

    2017-03-01

    To investigate the in vivo effects of Lactobacillus rhamnosus GG (LGG) on intestinal polyp development and the interaction between this single-organism probiotic and the gut microbiota therein. The Apc Min/+ mouse model was used to study the potential preventive effect of LGG on intestinal polyposis, while shotgun metagenomic sequencing was employed to characterize both taxonomic and functional changes within the gut microbial community. We found that the progression of intestinal polyps in the control group altered the community functional profile remarkably despite small variation in the taxonomic diversity. In comparison, the consumption of LGG helped maintain the overall functional potential and taxonomic profile in the resident microbes, thereby leading to a 25% decrease of total polyp counts. Furthermore, we found that LGG enriched those microbes or microbial activities related to short-chain fatty acid production (e.g. Roseburia and Coprococcus), as well as suppressed the ones that can lead to inflammation (e.g. Bilophila wadsworthia). Our study using shotgun metagenomics highlights how single probiotic LGG may exert its beneficial effects and decrease polyp formation in mice by maintaining gut microbial functionality. This probiotic intervention targeting microbiota may be used in conjugation with other dietary supplements or drugs as part of prevention strategies for early-stage colon cancer, after further clinical validations in human. © 2016 The Society for Applied Microbiology.

  9. 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).

  10. NATURAL GAS HYDRATES STORAGE PROJECT PHASE II. CONCEPTUAL DESIGN AND ECONOMIC STUDY

    Energy Technology Data Exchange (ETDEWEB)

    R.E. Rogers

    1999-09-27

    DOE Contract DE-AC26-97FT33203 studied feasibility of utilizing the natural-gas storage property of gas hydrates, so abundantly demonstrated in nature, as an economical industrial process to allow expanded use of the clean-burning fuel in power plants. The laboratory work achieved breakthroughs: (1) Gas hydrates were found to form orders of magnitude faster in an unstirred system with surfactant-water micellar solutions. (2) Hydrate particles were found to self-pack by adsorption on cold metal surfaces from the micellar solutions. (3) Interstitial micellar-water of the packed particles were found to continue forming hydrates. (4) Aluminum surfaces were found to most actively collect the hydrate particles. These laboratory developments were the bases of a conceptual design for a large-scale process where simplification enhances economy. In the design, hydrates form, store, and decompose in the same tank in which gas is pressurized to 550 psi above unstirred micellar solution, chilled by a brine circulating through a bank of aluminum tubing in the tank employing gas-fired refrigeration. Hydrates form on aluminum plates suspended in the chilled micellar solution. A low-grade heat source, such as 110 F water of a power plant, circulates through the tubing bank to release stored gas. The design allows a formation/storage/decomposition cycle in a 24-hour period of 2,254,000 scf of natural gas; the capability of multiple cycles is an advantage of the process. The development costs and the user costs of storing natural gas in a scaled hydrate process were estimated to be competitive with conventional storage means if multiple cycles of hydrate storage were used. If more than 54 cycles/year were used, hydrate development costs per Mscf would be better than development costs of depleted reservoir storage; above 125 cycles/year, hydrate user costs would be lower than user costs of depleted reservoir storage.

  11. Formative research and strategic development of a physical activity component to a social marketing campaign for obesity prevention in preschoolers.

    Science.gov (United States)

    Bellows, Laura; Anderson, Jennifer; Gould, Susan Martin; Auld, Garry

    2008-06-01

    The prevalence of overweight in childhood, including preschoolers, continues to rise. While efforts focusing on school-aged children are encouraging, obesity prevention programs to address nutrition and physical activity in the child care center are lacking. Food Friends is a successfully evaluated nutrition program aimed at enhancing preschoolers' food choices, the addition of a physical activity program would improve the programs overall efforts to establish healthful habits early in life. This study describes the formative research conducted with secondary influencers of preschoolers-teachers and parents-for the development of a physical activity program. Key informant interviews and focus group discussions were conducted with preschool teachers and parents, respectively, to examine current physical activity practices, as well as attitudes, opinions, and desired wants and needs for physical activity materials. Findings illustrate that teachers provided physical activity; however, most did not use a structured program. Teachers identified time, space and equipment as barriers to providing activity in their classroom. Focus group findings identified activities of preschoolers', parents' perceptions of the adequacy of activity levels, and items to help parents engage their children in more physical activity. Barriers were also identified by parents and included time, safety, inclement weather, and lack of knowledge and self-efficacy. Findings from this formative research were used to develop a marketing strategy to guide the development of a physical activity component, Food Friends Get Movin' with Mighty Moves , as part of a larger social marketing campaign aimed to decrease the risk for obesity in low-income preschoolers.

  12. Prevention of biofilm formation by dairy products and N-acetylcysteine on voice prostheses in an artificial throat.

    Science.gov (United States)

    Schwandt, Leonora Q; Van Weissenbruch, Ranny; Stokroos, Ietse; Van der Mei, Henny C; Busscher, Henk J; Albers, Frans W J

    2004-08-01

    To evaluate the preventive effect of buttermilk, Yakult Light fermented milk drink and N-acetylcysteine on biofilm formation on voice prostheses in vitro. Groningen button and Provox 2 voice prostheses were inoculated with a mixture of bacteria and yeasts isolated from previously explanted Groningen button voice prostheses. After 5 h, separate throats were flushed with buttermilk, Yakult Light fermented milk drink, N-acetylcysteine or phosphate-buffered saline, which served as a control. After 7 days, the microflora on each voice prosthesis was determined. On Groningen button voice prostheses, buttermilk, Yakult Light fermented milk drink and N-acetylcysteine all reduced the amount of both bacteria and yeasts. On Provox 2 voice prostheses, buttermilk, Yakult Light fermented milk drink and N-acetylcysteine reduced the amount of bacteria but, conversely, increased the amount of yeasts. These in vitro experiments demonstrate that biofilm formation on voice prostheses is reduced in an artificial throat by the use of buttermilk, Yakult Light fermented milk drink and N-acetylcysteine. However, the structural differences between the type of voice prostheses may influence the ultimate effects.

  13. Pathobiology of cholesterol gallstone disease: from equilibrium ternary phase diagram to agents preventing cholesterol crystallization and stone formation.

    Science.gov (United States)

    Portincasa, Piero; Moschetta, Antonio; Calamita, Giuseppe; Margari, Antonio; Palasciano, Giuseppe

    2003-03-01

    The primum movens in cholesterol gallstone formation is hypersecretion of hepatic cholesterol, chronic surpersaturation of bile with cholesterol and rapid precipitation of cholesterol crystals in the gallbladder from cholesterol-enriched vesicles. Associated events include biochemical defects (increased biliary mucin, and increased proportions of hydrophobic bile salts in the intestine and gallbladder), motility defects (gallbladder smooth muscle hypocontractility in vitro and gallbladder stasis in vivo, sluggish intestinal transit), and an abnormal genetic background. The study of physical-chemical factors and pathways leading to cholesterol crystallization in bile has clinical relevance and the task can be carried out in different ways. The lithogenicity of bile is investigated in artificial model biles made by three biliary lipids - cholesterol, bile salts and phospholipids - variably combined in systems plotting within the equilibrium ternary phase diagram; also, crystallization propensity of ex vivo incubated human bile is studied by biochemical analysis of precipitated crystals, polarizing quantitative light microscopy and turbidimetric methods. The present review will focus on the recent advances in the field of pathobiology of cholesterol gallstones, by underscoring the role of early events like water transport, lipid transport, crystallization phenomena - including a genetic background - in gallstone pathogenesis. Agents delaying or preventing precipitation of cholesterol crystals and gallstone formation in bile will also be discussed.

  14. A combined road weather forecast system to prevent road ice formation in the Adige Valley (Italy)

    Science.gov (United States)

    Di Napoli, Claudia; Piazza, Andrea; Antonacci, Gianluca; Todeschini, Ilaria; Apolloni, Roberto; Pretto, Ilaria

    2016-04-01

    Road ice is a dangerous meteorological hazard to a nation's transportation system and economy. By reducing the pavement friction with vehicle tyres, ice formation on pavements increases accident risk and delays travelling times thus posing a serious threat to road users' safety and the running of economic activities. Keeping roads clear and open is therefore essential, especially in mountainous areas where ice is likely to form during the winter period. Winter road maintenance helps to restore road efficiency and security, and its benefits are up to 8 times the costs sustained for anti-icing strategies [1]. However, the optimization of maintenance costs and the reduction of the environmental damage from over-salting demand further improvements. These can be achieved by reliable road weather forecasts, and in particular by the prediction of road surface temperatures (RSTs). RST is one of the most important parameters in determining road surface conditions. It is well known from literature that ice forms on pavements in high-humidity conditions when RSTs are below 0°C. We have therefore implemented an automatic forecast system to predict critical RSTs on a test route along the Adige Valley complex terrain, in the Italian Alps. The system considers two physical models, each computing heat and energy fluxes between the road and the atmosphere. One is Reuter's radiative cooling model, which predicts RSTs at sunrise as a function of surface temperatures at sunset and the time passed since then [2]. One is METRo (Model of the Environment and Temperature of Roads), a road weather forecast software which also considers heat conduction through road material [3]. We have applied the forecast system to a network of road weather stations (road weather information system, RWIS) installed on the test route [4]. Road and atmospheric observations from RWIS have been used as initial conditions for both METRo and Reuter's model. In METRo observations have also been coupled to

  15. A randomised controlled trial on melatonin and rosiglitazone for prevention of adhesion formation in a rat uterine horn model.

    Science.gov (United States)

    Aksakal, Orhan; Yilmaz, Bulent; Gungor, Tayfun; Sirvan, Levent; Sut, Necdet; Inan, Ismet; Kalyoncu, Senol; Mollamahmutoglu, Leyla

    2010-07-01

    To investigate the effectiveness of melatonin and rosiglitazone in reducing postoperative adhesion formation in a rat uterine horn model. Thirty non-pregnant female Wistar albino rats, weighing 180-220 g, were used as a model for postoperative adhesion formation. The rats were randomised into three groups after seven standard lesions were inflicted in a 2-cm segment of each uterine horn and lower abdominal sidewall using bipolar cauterisation. The rats were treated with 10 mg/kg, intraperitoneal melatonin, and 1 mg/kg per day peroral rosiglitazone. No medication was given to the control group. As much as 20 uterine horns of 10 rats were evaluated in each group. Extent, severity, and degree of the adhesions to the uterine horns and, inflammation and fibrosis scores (histopathologically) were evaluated after 2 weeks of the treatment. There was no mortality in the groups and all of the rats recovered without incident after operation. Rosiglitazone group had lower adhesion scores [median (min-max ranges)] regarding extent, severity, and degree of the adhesions [0 (0-3), 0 (0-3) and 0 (0-3), respectively], which were significantly different (P < 0.001, P < 0.05 and P < 0.01, respectively) from those of the controls [1 (0-3), 2 (0-2) and 2 (0-3), respectively]; however, there were no statistically significant differences between rosiglitazone versus melatonin groups [1 (0-4), 2 (0-3) and 1 (0-3), respectively] and melatonin versus control groups. Moreover, no significant differences were determined between groups regarding histopathologic findings. Rosiglitazone, but not melatonin, is effective in prevention of adhesion formation in a rat uterine horn model.

  16. Modeling pure methane hydrate dissociation using a numerical simulator from a novel combination of X-ray computed tomography and macroscopic data

    Energy Technology Data Exchange (ETDEWEB)

    Gupta, A.; Moridis, G.J.; Kneafsey, T.J.; Sloan, Jr., E.D.

    2009-08-15

    The numerical simulator TOUGH+HYDRATE (T+H) was used to predict the transient pure methane hydrate (no sediment) dissociation data. X-ray computed tomography (CT) was used to visualize the methane hydrate formation and dissociation processes. A methane hydrate sample was formed from granular ice in a cylindrical vessel, and slow depressurization combined with thermal stimulation was applied to dissociate the hydrate sample. CT images showed that the water produced from the hydrate dissociation accumulated at the bottom of the vessel and increased the hydrate dissociation rate there. CT images were obtained during hydrate dissociation to confirm the radial dissociation of the hydrate sample. This radial dissociation process has implications for dissociation of hydrates in pipelines, suggesting lower dissociation times than for longitudinal dissociation. These observations were also confirmed by the numerical simulator predictions, which were in good agreement with the measured thermal data during hydrate dissociation. System pressure and sample temperature measured at the sample center followed the CH{sub 4} hydrate L{sub w}+H+V equilibrium line during hydrate dissociation. The predicted cumulative methane gas production was within 5% of the measured data. Thus, this study validated our simulation approach and assumptions, which include stationary pure methane hydrate-skeleton, equilibrium hydrate-dissociation and heat- and mass-transfer in predicting hydrate dissociation in the absence of sediments. It should be noted that the application of T+H for the pure methane hydrate system (no sediment) is outside the general applicability limits of T+H.

  17. [NMF and cosmetology of cutaneous hydration].

    Science.gov (United States)

    Marty, J-P

    2002-01-01

    In the stratum corneum, the water binds to the intracellular hygroscopic and hydrosoluble substances called "natural moisturizing factors" or NMF. These "natural moisturizing factors" contained in the corneocytes are formed during epidermal differentiation and may represent up to 10 p. cent of the corneocyte mass. They are principally amino acids, carboxylic pyrrolidone acid, lactic acid, urea, glucose and mineral ions. Keratinization plays an important part in the formation of NMF that exhibit strong osmotic potential attracting the water molecules. The binding of water to NMF is the static aspect of cutaneous hydration. The second, dynamic, aspect is related to the selective permeability of the stratum corneum and to its lipid barrier properties, the permeability of which depends on the integrity and nature of the inter-corneocyte lipids and their lamellar organization between the cells. In these conditions, hydration cosmetics rely on two concepts that can be isolated or associated: the supply of hydrophilic substances to the stratum corneum, capable of attracting and retaining water (moisturizer) or capable of restoring the barrier in order to restore normal water loss or of protecting it against aggression (occlusive).

  18. Evaluation of superpave mixtures containing hydrated lime.

    Science.gov (United States)

    2013-07-01

    The use of hydrated lime in Hot-Mix Asphalt (HMA) mixtures can reduce permanent deformation, long-term aging, and moisture : susceptibility of mixtures. In addition, hydrated lime increases the stiffness and fatigue resistance of mixtures. This study...

  19. Implications of hydration depletion in the in vitro starch digestibility of white bread crumb and crust.

    Science.gov (United States)

    Martínez, Mario M; Román, Laura; Gómez, Manuel

    2018-01-15

    The objective of this study was to provide understanding about the efficacy of decreasing dough hydration to slow down starch digestibility in white bread. Breads were made with 45 (low hydration bread, LHB), 60 (intermediate hydration bread, IHB) and 75% (high hydration bread, HHB) water (flour basis). A hydration depletion down to 45%, which is close to the minimum hydration found in commercially available white bread, did not prevent the starch in the crumb from complete gelatinization. However, LHB and IHB crumbs were more resistant to physical breakdown during in vitro digestion than HHB crumbs, resulting in a 96.81% increase of slowly digestible starch (SDS) from 75 to 45% dough hydration. The degree of gelatinization in crust samples was significantly reduced with a depletion in the dough hydration, ranging from 29.90 to 44.36%, which led to an increase of SDS from 7.41 in HHB to 13.78% in LHB (bread basis). Copyright © 2017 Elsevier Ltd. All rights reserved.

  20. Permafrost-associated gas hydrate: is it really approximately 1% of the global system?

    Science.gov (United States)

    Ruppel, Carolyn

    2015-01-01

    Permafrost-associated gas hydrates are often assumed to contain ∼1 % of the global gas-in-place in gas hydrates based on a study26 published over three decades ago. As knowledge of permafrost-associated gas hydrates has grown, it has become clear that many permafrost-associated gas hydrates are inextricably linked to an associated conventional petroleum system, and that their formation history (trapping of migrated gas in situ during Pleistocene cooling) is consistent with having been sourced at least partially in nearby thermogenic gas deposits. Using modern data sets that constrain the distribution of continuous permafrost onshore5 and subsea permafrost on circum-Arctic Ocean continental shelves offshore and that estimate undiscovered conventional gas within arctic assessment units,16 the done here reveals where permafrost-associated gas hydrates are most likely to occur, concluding that Arctic Alaska and the West Siberian Basin are the best prospects. A conservative estimate is that 20 Gt C (2.7·1013 kg CH4) may be sequestered in permafrost-associated gas hydrates if methane were the only hydrate-former. This value is slightly more than 1 % of modern estimates (corresponding to 1600 Gt C to 1800 Gt C2,22) for global gas-in-place in methane hydrates and about double the absolute estimate (11.2 Gt C) made in 1981.26

  1. 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.

  2. Evaluation of hydration indexes in kale leaves

    OpenAIRE

    Calbo, Adonai G.; Ferreira, Marcos D.

    2011-01-01

    Hydration indexes are practical variables for quantifying plant water stress and can be useful for agronomic purposes. Three adapted hydration indexes based on relative water content, volumetric hydration, and leaf turgor pressure were evaluated in kale (Brassica oleracea var. acephala) leaf segments. Relative water content and volumetric hydration were measured in leaf segments after a water infiltration procedure with the aim of filling its large intercellular volumes (@18%v/v). The infiltr...

  3. Rates and mechanisms of conversion of ice nanocrystals to hydrates of HCl and HBr: acid diffusion in the ionic hydrates.

    Science.gov (United States)

    Devlin, J Paul; Gulluru, Dheeraj B; Buch, Victoria

    2005-03-03

    This FTIR study focuses on solid-state chemistry associated with formation and interconversion of the ionic HX (X = Cl, Br) hydrates. Kinetic data are reported for conversions of ice nanocrystal arrays exposed to the saturation pressure of the acids in the 110 approximately 125 K range. The product is amorphous acid dihydrate in the case of HBr, and amorphous monohydrate for HCl. The rate-determining step is identified as HX diffusion through the hydrate product crust toward the interfacial reaction zone, rather than diffusion through ice, as commonly believed. Slowing of the conversion process is thus observed with increasing thickness of the crust. The diffusion coefficient (D(e)) and activation energy values for HX diffusion through the hydrates were evaluated with the help of the shrinking-core model. Hydrate crystallization occurs as a separate step, upon heating above 130 K. Subsequently, rates of reversible transitions between crystal di- and monohydrates were observed upon exposure to acid vapor and acid evacuation. In conversion from di- to monohydrate, the rate slows after fast formation of several layers; subsequently, diffusion through the product crust appears to be the rate-controlling step. The activation energy for HBr diffusion through crystal dihydrate is found to be significantly higher than that for the amorphous analogue. Conjecture is offered for a molecular mechanism of HX transport through the crystal hydrate, based on (i) spectroscopic/computational evidence for the presence of molecular HX bonded to X(-) in each of the ionic hydrate phases and (ii) the relative E(a) values found for HBr and HCl diffusion. Monte Carlo modeling suggests acid transport to the reaction zone along boundaries between "nanocrystallites" generated by multiple hydrate nucleation events at the particle surfaces. The reverse conversion, of crystalline monohydrate particles to the dihydrate phase, as well as dihydrate to trihydrate, displays nearly constant rate

  4. Onset and stability of gas hydrates under permafrost in an environment of surface climatic change : past and future

    International Nuclear Information System (INIS)

    Majorowicz, J.A.; Osadetz, K.; Safanda, J.

    2008-01-01

    This paper presented a model designed to simulate permafrost and gas hydrate formation in a changing surface temperature environment in the Beaufort-Mackenzie Basin (BMB). The numerical model simulated surface forcing due to general cooling trends that began in the late Miocene era. This study modelled the onset of permafrost formation and subsequent gas hydrate formation in the changing surface temperature environment for the BMB. Paleoclimatic data were used. The 1-D model was constrained by deep heat flow from well bottom hole temperatures; conductivity; permafrost thickness; and the thickness of the gas hydrates. The model used latent heat effects for the ice-bearing permafrost and hydrate intervals. Surface temperatures for glacial and interglacial histories for the last 14 million years were considered. The model also used a detailed Holocene temperature history as well as a scenario in which atmospheric carbon dioxide (CO 2 ) levels were twice as high as current levels. Two scenarios were considered: (1) the formation of gas hydrates from gas entrapped under geological seals; and (2) the formation of gas hydrates from gas located in free pore spaces simultaneously with permafrost formation. Results of the study showed that gas hydrates may have formed at a depth of 0.9 km only 1 million years ago. Results of the other modelling scenarios suggested that the hydrates formed 6 million years ago, when temperature changes caused the gas hydrate layer to expand both downward and upward. Detailed models of more recent glacial and interglacial histories showed that the gas hydrate zones will persist under the thick body of the BMB permafrost through current interglacial warming as well as in scenarios where atmospheric CO 2 is doubled. 28 refs., 13 figs

  5. Hydration kinetics for the alite, belite, and calcium aluminate phase in Portland cements from 27Al and 29Si MAS NMR spectroscopy

    DEFF Research Database (Denmark)

    Skibsted, Jørgen; Jensen, Ole Mejlhede; Jakobsen, Hans Jørgen

    1997-01-01

    29Si magic-angle spinning (MAS) NMR spectroscopy is shown to be a valuable tool for obtaining the quantities of alite and belite in hydrated Portland cements. The hydration (1-180 days) of a white Portland cement with 10 wt.% silica fume added is investigated and the degrees of hydration for alite...... belite, and silica fume are determined. It is demonstrated that 27Al MAS NMR spectra of hydrated Portland cements can give quantitative information about the formation of ettringite and the conversion of this phase to monosulphate during hydration....

  6. Hydration mechanism and leaching behavior of bauxite-calcination-method red mud-coal gangue based cementitious materials

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Na; Li, Hongxu [School of Metallurgical and Ecological Engineering, University of Science and Technology Beijing, Beijing 100083 (China); Beijing Key Laboratory of Rare and Precious Metals Green Recycling and Extraction, University of Science and Technology Beijing, Beijing 100083 (China); Liu, Xiaoming, E-mail: liuxm@ustb.edu.cn [School of Metallurgical and Ecological Engineering, University of Science and Technology Beijing, Beijing 100083 (China); Beijing Key Laboratory of Rare and Precious Metals Green Recycling and Extraction, University of Science and Technology Beijing, Beijing 100083 (China)

    2016-08-15

    Highlights: • Nanocrystalline regions in size of ∼5 nm were found in the amorphous C-A-S-H gel. • A hydration model was proposed to clarify the hydration mechanism. • The developed cementitious materials are environmentally acceptable. - Abstract: A deep investigation on the hydration mechanism of bauxite-calcination-method red mud-coal gangue based cementitious materials was conducted from viewpoints of hydration products and hydration heat analysis. As a main hydration product, the microstructure of C-A-S-H gel was observed using high resolution transmission electron microscopy. It was found that the C-A-S-H gel is composed of amorphous regions and nanocrystalline regions. Most of regions in the C-A-S-H gel are amorphous with continuous distribution, and the nanocrystalline regions on scale of ∼5 nm are dispersed irregularly within the amorphous regions. The hydration heat of red mud-coal gangue based cementitious materials is much lower than that of the ordinary Portland cement. A hydration model was proposed for this kind of cementitious materials, and the hydration process mainly consists of four stages which are dissolution of materials, formation of C-A-S-H gels and ettringite, cementation of hydration products, and polycondensation of C-A-S-H gels. There are no strict boundaries among these four basic stages, and they proceed crossing each other. Moreover, the leaching toxicity tests were also performed to prove that the developed red mud-coal gangue based cementitious materials are environmentally acceptable.

  7. 3-D basin-scale reconstruction of natural gas hydrate system of the Green Canyon, Gulf of Mexico

    Science.gov (United States)

    Burwicz, Ewa; Reichel, Thomas; Wallmann, Klaus; Rottke, Wolf; Haeckel, Matthias; Hensen, Christian

    2017-05-01

    Our study presents a basin-scale 3-D modeling solution, quantifying and exploring gas hydrate accumulations in the marine environment around the Green Canyon (GC955) area, Gulf of Mexico. It is the first modeling study that considers the full complexity of gas hydrate formation in a natural geological system. Overall, it comprises a comprehensive basin reconstruction, accounting for depositional and transient thermal history of the basin, source rock maturation, petroleum components generation, expulsion and migration, salt tectonics, and associated multistage fault development. The resulting 3-D gas hydrate distribution in the Green Canyon area is consistent with independent borehole observations. An important mechanism identified in this study and leading to high gas hydrate saturation (>80 vol %) at the base of the gas hydrate stability zone (GHSZ) is the recycling of gas hydrate and free gas enhanced by high Neogene sedimentation rates in the region. Our model predicts the rapid development of secondary intrasalt minibasins situated on top of the allochthonous salt deposits which leads to significant sediment subsidence and an ensuing dislocation of the lower GHSZ boundary. Consequently, large amounts of gas hydrates located in the deepest parts of the basin dissociate and the released free methane gas migrates upward to recharge the GHSZ. In total, we have predicted the gas hydrate budget for the Green Canyon area that amounts to ˜3256 Mt of gas hydrate, which is equivalent to ˜340 Mt of carbon (˜7 × 1011 m3 of CH4 at STP conditions), and consists mostly of biogenic hydrates.

  8. Hydrate crystallization at oil-water interface, the effect of nonionic surfactants

    Science.gov (United States)

    Rosenfeld, Liat; Dann, Kevin; Rosenfeld Team

    2017-11-01

    Gas hydrates pose economic and environmental risks to the oil and gas industry when plug formation occurs in pipelines. A novel approach using interfacial rheology and visualization techniques was applied to understand cyclopentane clathrate hydrate formation in the presence of nonionic surfactant to achieve hydrate inhibition at low percent weight compared to thermodynamic inhibitors. The hydrate-inhibiting performance of various surfactants on a manually nucleated 2 μL droplet showed a morphological shift in crystallization from planar shell growth to conical growth. Monitoring the internal pressure of the water droplet undergoing hydrate crystallization provides information on the change of interfacial tension during crystallization process. At low surfactant concentrations, planar hydrate crystal was formed and decreasing interfacial tension was observed. At high surfactant concentration, crystal morphology was shifted to conical. Interfacial tension measurements reveal oscillations of interfacial tension during the crystallization process. The oscillatory behavior of the interfacial tension is a result of the growth and release of the hydrate cones from the surface of the droplet.

  9. Hydration modeling of calcium sulphates

    NARCIS (Netherlands)

    de Korte, A.C.J.; Brouwers, H.J.H.; Al-Mattarneh, Hashem; Mustapha, Kamal N.; Nuruddin, Muhd Fadhil

    2008-01-01

    The CEMHYD3D model has been extended at the University of Twente in the last ten years [1,2]. At present the cement hydration model is extended for the use of gypsum. Although gypsum was present in the model already, the model was not suitable for high contents of gypsum and did not include the

  10. 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.

  11. Digital Bangladesh: Using Formative Research to Develop Phone Messages for the Prevention and Control of Diabetes in Rural Bangladesh.

    Directory of Open Access Journals (Sweden)

    Hannah Maria Jennings

    2015-10-01

    Full Text Available Background: As with many low-income countries, diabetes is an increasing issue in Bangladesh affecting an estimated 20% to 30% of the population either as intermediate hyperglycaemia or fully expressed diabetes mellitus (Bhowmik et al., 2012. The Bangladesh D-MAGIC project is a cluster randomised control trial to test the effectiveness of interventions to improve detection, management and control of diabetes in rural Bangladesh. One of these interventions is an mHealth intervention, which involves sending health promotion voice messages to individuals’ mobile phones to target diabetes prevention and management. In-depth formative research (interviews and focus group discussions has been undertaken in rural Faridpur District in order to gain a greater understanding of people’s beliefs, practices and behaviour regarding diabetes prevention and control and their access to and use of mobile phones. The findings of the research, used within the COM-B framework (Michie et al 2011, are being used to inform and appropriately tailor the voice messages to the needs of the target population. This presentation will highlight key findings of the formative research and discuss how these findings are being used to design the mHealth intervention. Aim: To identify key issues for the content and delivery of voice messages regarding the prevention and control of diabetes in rural Bangladesh through in-depth formative research. Methods: We conducted sixteen semi-structured interviews with purposively sampled diabetics, non-diabetics and health professionals. In addition, nine focus group discussions with diabetics and non-diabetics were conducted in villages in three sub-districts of Faridpur. We explored beliefs and behaviour regarding diet, exercise, smoking, stress and care-seeking. The findings from the interviews and focus group discussions were analysed thematically, and specific enablers and barriers to behaviour change related to diabetes identified

  12. Hydrated phases and pore solution composition in cementsolidified saltstone waste forms

    Directory of Open Access Journals (Sweden)

    Philip J.

    2013-07-01

    Full Text Available The mineral phases and pore solution composition of hydrated cementsolidified synthetic saltstone waste forms are quantified using thermogravimetric analysis, quantitative X-ray powder diffraction, and inductively coupled plasma atomic emission spectroscopy. Although the synthetic waste contained additional sulfate, the overall chemistry of the system suppressed the formation of sulfate-bearing mineral phases. This was corroborated by the pore solution analysis that indicated very high sulfur concentrations. After one year of hydration, the mineral phases present and the composition of the pore solution are stable, and are generally consistent with expectations based on the hydration of high volume portland cement replacement mixtures.

  13. 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.

  14. Hydration mechanisms of mineral trioxide aggregate.

    Science.gov (United States)

    Camilleri, J

    2007-06-01

    To report the hydration mechanism of white mineral trioxide aggregate (White MTA, Dentsply, Tulsa Dental Products, Tulsa, OK, USA). The chemical constitution of white MTA was studied by viewing the powder in polished sections under the scanning electron microscope (SEM). The hydration of both white MTA and white Portland cement (PC) was studied by characterizing cement hydrates viewed under the SEM, plotting atomic ratios, performing quantitative energy dispersive analyses with X-ray (EDAX) and by calculation of the amount of anhydrous clinker minerals using the Bogue calculation. Un-hydrated MTA was composed of impure tri-calcium and di-calcium silicate and bismuth oxide. The aluminate phase was scarce. On hydration the white PC produced a dense structure made up of calcium silicate hydrate, calcium hydroxide, monosulphate and ettringite as the main hydration products. The un-reacted cement grain was coated with a layer of hydrated cement. In contrast MTA produced a porous structure on hydration. Levels of ettringite and monosulphate were low. Bismuth oxide was present as un-reacted powder but also incorporated with the calcium silicate hydrate. White MTA was deficient in alumina suggesting that the material was not prepared in a rotary kiln. On hydration this affected the production of ettringite and monosulphate usually formed on hydration of PC. The bismuth affected the hydration mechanism of MTA; it formed part of the structure of C-S-H and also affected the precipitation of calcium hydroxide in the hydrated paste. The microstructure of hydrated MTA would likely be weaker when compared with that of PC.

  15. In-Situ Sampling and Characterization of Naturally Occurring Marine Methane Hydrate Using the D/V JOIDES Resolution

    Energy Technology Data Exchange (ETDEWEB)

    Rack, Frank; Bohrmann, Gerhard; Trehu, Anne; Storms, Michael; Schroeder, Derryl

    2002-09-30

    The primary accomplishment of the JOI Cooperative Agreement with DOE/NETL in this quarter was the deployment of tools and measurement systems on ODP Leg 204 to study hydrate deposits on Hydrate Ridge, offshore Oregon from July through September, 2002. During Leg 204, we cored and logged 9 sites on the Oregon continental margin to determine the distribution and concentration of gas hydrates in an accretionary ridge and adjacent slope basin, investigate the mechanisms that transport methane and other gases into the gas hydrate stability zone (GHSZ), and obtain constraints on physical properties of hydrates in situ. A 3D seismic survey conducted in 2000 provided images of potential subsurface fluid conduits and indicated the position of the GHSZ throughout the survey region. After coring the first site, we acquired Logging-While-Drilling (LWD) data at all but one site to provide an overview of downhole physical properties. The LWD data confirmed the general position of key seismic stratigraphic horizons and yielded an initial estimate of hydrate concentration through the proxy of in situ electrical resistivity. These records proved to be of great value in planning subsequent coring. The second new hydrate proxy to be tested was infrared thermal imaging of cores on the catwalk as rapidly as possible after retrieval. The thermal images were used to identify hydrate samples and to map estimate the distribution and texture of hydrate within the cores. Geochemical analyses of interstitial waters and of headspace and void gases provide additional information on the distribution and concentration of hydrate within the stability zone, the origin and pathway of fluids into and through the GHSZ, and the rates at which the process of gas hydrate formation is occurring. Bio- and lithostratigraphic description of cores, measurement of physical properties, and in situ pressure core sampling and thermal measurements complement the data set, providing ground-truth tests of inferred

  16. Role of ultraviolet irradiation and oxidative stress in cataract formation-medical prevention by nutritional antioxidants and metabolic agonists.

    Science.gov (United States)

    Varma, Shambhu D; Kovtun, Svitlana; Hegde, Kavita R

    2011-07-01

    Cataract is a significant cause of visual disability with relatively high incidence. It has been proposed that such high incidence is related to oxidative stress induced by continued intraocular penetration of light and consequent photochemical generation of reactive oxygen species, such as superoxide and singlet oxygen and their derivatization to other oxidants, such as hydrogen peroxide and hydroxyl radical. The latter two can also interact to generate singlet oxygen by Haber-Weiss reaction. It has been proposed that in addition to the endogenous enzymatic antioxidant enzymes, the process can be inhibited by many nutritional and metabolic oxyradical scavengers, such as ascorbate, vitamin E, pyruvate, and xanthine alkaloids, such as caffeine. Initial verification of the hypothesis has been done primarily by rat and mouse lens organ culture studies under ambient as well as ultraviolet (UV) light irradiation and determining the effect of such irradiation on its physiology in terms of its efficiency of active membrane transport activity and the levels of certain metabolites such as glutathione and adenosine triphosphate as well as in terms of apoptotic cell death. In vivo studies on the possible prevention of oxidative stress and cataract formation have been conducted by administering pyruvate and caffeine orally in drinking water and by their topical application using diabetic and galactosemic animal models. Photosensitized damage to lens caused by exposure to visible light and UVA has been found to be significantly prevented by ascorbate and pyruvate. Caffeine has been found be effective against UVA and UVB. Oral or topical application of pyruvate has been found to inhibit the formation of cataracts induced by diabetes and galactosemia. Caffeine has also been found to inhibit cataract induced by sodium selenite and high levels of galactose. Studies with diabetes are in progress. Various in vitro and in vivo studies summarized in this review strongly support the

  17. GLP-1 Receptor Agonist Treatment Increases Bone Formation and Prevents Bone Loss in Weight-Reduced Obese Women.

    Science.gov (United States)

    Iepsen, Eva W; Lundgren, Julie R; Hartmann, Bolette; Pedersen, Oluf; Hansen, Torben; Jørgensen, Niklas R; Jensen, Jens-Erik B; Holst, Jens J; Madsbad, Sten; Torekov, Signe S

    2015-08-01

    Recent studies indicate that glucagon-like peptide (GLP)-1 regulates bone turnover, but the effects of GLP-1 receptor agonists (GLP-1 RAs) on bone in obese weight-reduced individuals are unknown. To investigate the role of GLP-1 RAs on bone formation and weight loss-induced bone mass reduction. Randomized control study. Outpatient research hospital clinic. Thirty-seven healthy obese women with body mass index of 34 ± 0.5 kg/m(2) and age 46 ± 2 years. After a low-calorie-diet-induced 12% weight loss, participants were randomized to treatment with or without administration of the GLP-1 RA liraglutide (1.2 mg/d) for 52 weeks. In case of weight gain, up to two meals per day could be replaced with a low-calorie-diet product to maintain the weight loss. Total, pelvic, and arm-leg bone mineral content (BMC) and bone markers [C-terminal telopeptide of type 1 collagen (CTX-1) and N-terminal propeptide of type 1 procollagen (P1NP)] were investigated before and after weight loss and after 52-week weight maintenance. Primary endpoints were changes in BMC and bone markers after 52-week weight maintenance with or without GLP-1 RA treatment. Total, pelvic, and arm-leg BMC decreased during weight maintenance in the control group (P GLP-1 RA increased bone formation by 16% and prevented bone loss after weight loss obtained through a low-calorie diet, supporting its role as a safe weight-lowering agent.

  18. Hydration and Temperature in Tennis - A Practical Review

    OpenAIRE

    Kovacs, Mark S.

    2006-01-01

    Competitive tennis is typically played in warm and hot environments. Because hypohydration will impair tennis performance and increases the risk of heat injury, consumption of appropriate fluid levels is necessary to prevent dehydration and enhance performance. The majority of research in this area has focused on continuous aerobic activity - unlike tennis, which has average points lasting less than ten seconds with rest periods dispersed between each work period. For this reason, hydration a...

  19. Acoustical Method of Whole-Body Hydration Status Monitoring1

    OpenAIRE

    Sarvazyan, A. P.; Tsyuryupa, S. N.; Calhoun, M.; Utter, A.

    2016-01-01

    An acoustical handheld hydration monitor (HM) for assessing the water balance of the human body was developed. Dehydration is a critical public health problem. Many elderly over age of 65 are particularly vulnerable as are infants and young children. Given that dehydration is both preventable and reversible, the need for an easy-to-perform method for the detection of water imbalance is of the utmost clinical importance. The HM is based on an experimental fact that ultrasound velocity in muscl...

  20. Apparatus investigates geological aspects of gas hydrates

    Science.gov (United States)

    Booth, J.S.; Winters, W.J.; Dillon, William P.

    1999-01-01

    The US Geological Survey (USGS), in response to potential geohazards, energy resource potential, and climate issues associated with marine gas hydrates, has developed a laboratory research system that permits hydrate genesis and dissociation under deep-sea conditions, employing user-selected sediment types and pore fluids.The apparatus, GHASTI (gas hydrate and sediment test laboratory instrument), provides a means to link field studies and theory and serves as a tool to improve gas hydrate recognition and assessment, using remote sensing techniques.GHASTLI's use was proven in an exploration well project led by the Geological Survey of Canada and the Japanese National Oil Corp., collaborating with Japan Petroleum Exploration Co. and the USGS. The site was in the Mackenzie Delta region of the Northwest Territories (Mallik 2L-38 drillsite).From tests on natural methane hydrate-bearing sand recovered at about 1,000 m subsurface, the in situ quantity of hydrate was estimated from acoustic properties, and a substantial increase in shear strength due to the presence of the hydrate was measured.1 2GHASTI can mimic a wide range of geologic settings and processes. Initial goals involve improved recognition and mapping of gas hydrate-bearing sediments, understanding factors that control the occurrence and concentration of gas hydrates, knowledge of hydrate's significance to slope failure and foundation problems, and analysis of gas hydrate's potential use as an energy resource.

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

    Energy Technology Data Exchange (ETDEWEB)

    Seol, Yongkoo; Kneafsey, Timothy J.

    2009-06-01

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

  2. Terahertz Time Domain Spectroscopy for Structure-II Gas Hydrates

    DEFF Research Database (Denmark)

    Takeya, Kei; Zhang, Caihong; Kawayama, Iwao

    2009-01-01

    For the nondestructive inspection of gas hydrates, terahertz (THz) time-domain spectroscopy (TDS) was applied to tetrahydrofuran (THF) hydrate and propane hydrate. The absorption of propane hydrate monotonically increases with frequency, similar to the case of ice, while THF hydrate has a charact......For the nondestructive inspection of gas hydrates, terahertz (THz) time-domain spectroscopy (TDS) was applied to tetrahydrofuran (THF) hydrate and propane hydrate. The absorption of propane hydrate monotonically increases with frequency, similar to the case of ice, while THF hydrate has...

  3. Handbook of gas hydrate properties and occurrence

    Energy Technology Data Exchange (ETDEWEB)

    Kuustraa, V.A.; Hammershaimb, E.C.

    1983-12-01

    This handbook provides data on the resource potential of naturally occurring hydrates, the properties that are needed to evaluate their recovery, and their production potential. The first two chapters give data on the naturally occurring hydrate potential by reviewing published resource estimates and the known and inferred occurrences. The third and fourth chapters review the physical and thermodynamic properties of hydrates, respectively. The thermodynamic properties of hydrates that are discussed include dissociation energies and a simplified method to calculate them; phase diagrams for simple and multi-component gases; the thermal conductivity; and the kinetics of hydrate dissociation. The final chapter evaluates the net energy balance of recovering hydrates and shows that a substantial positive energy balance can theoretically be achieved. The Appendices of the Handbook summarize physical and thermodynamic properties of gases, liquids and solids that can be used in designing and evaluating recovery processes of hydrates. 158 references, 67 figures, 47 tables.

  4. Is the Surface of Gas Hydrates Dry?

    Directory of Open Access Journals (Sweden)

    Nobuo Maeda

    2015-06-01

    Full Text Available Adhesion (cohesion and agglomeration properties of gas hydrate particles have been a key to hydrate management in flow assurance in natural gas pipelines. Despite its importance, the relevant data in the area, such as the surface energy and the interfacial energy of gas hydrates with gas and/or water, are scarce; presumably due to the experimental difficulties involved in the measurements. Here we review what is known about the surface energy and the interfacial energy of gas hydrates to date. In particular, we ask a question as to whether pre-melting can occur on the surface of gas hydrates. Surface thermodynamic analyses show that pre-melting is favoured to occur on the surface of gas hydrates, however, not sufficient data are available to assess its thickness. The effects of the existence of pre-melting layers on the cohesion and friction forces between gas hydrate particles are also discussed.

  5. Curcumin Prevents Formation of Polyglutamine Aggregates by Inhibiting Vps36, a Component of the ESCRT-II Complex

    Science.gov (United States)

    Verma, Meenakshi; Sharma, Abhishek; Naidu, Swarna; Bhadra, Ankan Kumar; Kukreti, Ritushree; Taneja, Vibha

    2012-01-01

    Small molecules with antioxidative properties have been implicated in amyloid disorders. Curcumin is the active ingredient present in turmeric and known for several biological and medicinal effects. Adequate evidence substantiates the importance of curcumin in Alzheimer's disease and recent evidence suggests its role in Prion and Parkinson's disease. However, contradictory effects have been suggested for Huntington's disease. This difference provided a compelling reason to investigate the effect of curcumin on glutamine-rich (Q-rich) and non-glutamine-rich (non Q-rich) amyloid aggregates in the well established yeast model system. Curcumin significantly inhibited the formation of htt72Q-GFP (a Q-rich) and Het-s-GFP (a non Q-rich) aggregates in yeast. We show that curcumin prevents htt72Q-GFP aggregation by down regulating Vps36, a component of the ESCRT-II (Endosomal sorting complex required for transport). Moreover, curcumin disrupted the htt72Q-GFP aggregates that were pre-formed in yeast and cured the yeast prion, [PSI +]. PMID:22880132

  6. Low molecular weight heparins prevent the induction of autophagy of activated neutrophils and the formation of neutrophil extracellular traps.

    Science.gov (United States)

    Manfredi, Angelo A; Rovere-Querini, Patrizia; D'Angelo, Armando; Maugeri, Norma

    2017-09-01

    The protection exerted by neutrophils against invading microbes is partially mediated via the generation of neutrophil extracellular traps (NETs). In sterile conditions NETs are damaging species, enriched in autoantigens and endowed with the ability to damage the vessel wall and bystander tissues, to promote thrombogenesis, and to impair wound healing. To identify and reposition agents that can be used to modulate the formation of NETs is a priority in the research agenda. Low molecular weight heparins (LMWH) are currently used, mostly on an empirical basis, in conditions in which NETs play a critical role, such as pregnancy complications associated to autoimmune disease. Here we report that LMWHs induce a profound change in the ability of human neutrophils to generate NETs and to mobilize the content of the primary granules in response to unrelated inflammatory stimuli, such as IL-8, PMA and HMGB1. Autophagy consistently accompanies NET generation in our system and autophagy inhibitors, 3-MA and wortmannin, prevent NET generation. Pretreatment with LMWH in vitro critically jeopardizes neutrophil ability to activate autophagy, a mechanism that might contribute to neutrophil unresponsiveness. Finally, we verified that treatment of healthy volunteers with a single prophylactic dose of parnaparin abrogated the ability of neutrophils to activate autophagy and to generate NETs. Together, these results support the contention that neutrophils, and NET generation in particular, might represent a preferential target of the anti-inflammatory action of LMWH. Copyright © 2016 Elsevier Ltd. All rights reserved.

  7. Hydrate-based technology for CO2 capture from fossil fuel power plants

    International Nuclear Information System (INIS)

    Yang, Mingjun; Song, Yongchen; Jiang, Lanlan; Zhao, Yuechao; Ruan, Xuke; Zhang, Yi; Wang, Shanrong

    2014-01-01

    Graphical abstract: Application of hydrate based technology on carbon dioxide capture and storage (CCS). - Highlights: • Hydrate-based CO 2 –N 2 separation data was obtained for flow in porous media. • Tetrahydrofuran and sodium dodecyl sulphate are used as additives simultaneously. • Solution movement rarely occurs when residual solution saturations are low. • Bothe of pressure and temperature have remarkable impacts on gas compositions. • A suitable operation parameter choice is proposed for hydrate-based CO 2 capture. - Abstract: Hydrate-based CO 2 capture is a promising technology. To obtain fundamental data for a flowing system, we measured the distribution of pore solution to analyse hydrate formation/dissociation and gas separation properties. An orthogonal experiment was carried out to investigate the effects of glass beads, flow rates, pressures and temperatures on it. Magnetic resonance imaging (MRI) images were obtained using a spin echo multi-slice pulse sequence. Hydrate saturations were calculated quantitatively using an MRI mean intensity. The results show that hydrate blockages were frequently present. During the hydrate formation and dissociation process, the movement of the solution occurred in cycles. However, the solution movement rarely occurred for residual solution saturations obtained with a high backpressure. The solution concentrate phenomenon occurred mostly in BZ-04. The highest hydrate saturation was 30.2%, and the lowest was 0.70%. Unlike that in BZ-01, there was no stability present in BZ-02 and BZ-04. The different CO 2 concentrations for the three processes of each cycle verified hydrate formation during the gas flow process. The highest CO 2 concentration was 38.8%, and the lowest one was 11.4%. To obtain high hydrate saturation and good separation effects, the values of 5.00 MPa, 1.0 ml min −1 and 280.00 K were chosen. For the gas flow process, only the pressure had a significant impact on gas composition, and all

  8. The use of silicone occlusive sheeting (Sil-K) and silicone occlusive gel (epiderm) in the prevention of hypertrophic scar formation

    NARCIS (Netherlands)

    Niessen, FB; Spauwen, PHM; Robinson, PH; Fidler, [No Value; Kon, M

    1998-01-01

    The development of hypertrophic scars and keloids is an unsolved problem in the process of found healing. For this reason, a successful treatment to prevent excessive scar formation still has not been found. Over the last decade, however, a promising new treatment has been introduced. Silicone

  9. Low temperature X-ray diffraction studies of natural gas hydrate samples from the Gulf of Mexico

    Energy Technology Data Exchange (ETDEWEB)

    Rawn, C.J. [Oak Ridge National Laboratory, Oak Ridge, TN (United States). Materials Science and Technology Div.; Sassen, R. [Texas A and M Univ., College Station, TX (United States). Geochemical and Environmental Research Group; Ulrich, S.M.; Phelps, T.J. [Oak Ridge National Laboratory, Oak Ridge, TN (United States). Biosciences Div.; Chakoumakos, B.C. [Oak Ridge National Laboratory, Oak Ridge, TN (United States). Neutron Scattering Science Div.; Payzant, E.A. [Oak Ridge National Laboratory, Oak Ridge, TN (United States). Center for Nanophase Materials Science

    2008-07-01

    Quantitative studies of natural clathrate hydrates are hampered by the difficulties associated with obtaining pristine samples for the sea floor without comprising their integrity. This paper discussed X-ray power diffraction studies conducted to measure natural gas hydrate samples obtained from the Green Canyon in the Gulf of Mexico. Data on the hydrate deposits were initially collected in 2002. The X-ray diffraction data were collected in order to examine the structure 2 (s2) gas hydrates as functions of temperature and time. A diffractometer with a theta-theta goniometer modified with a helium closed cycle refrigerator and temperature controller was used. Aragonite, quartz and halite phases were determined in the decomposed sample. Refined phase fractions for both the ice and the s2 hydrate were obtained as a function of temperature. Results of the study demonstrated that the amount of hydrates decreased with increasing temperatures and amounts of time. Large pieces of the hydrate showed heterogenous ice content. Dissociation rates were higher at lower temperatures. It was concluded that unusual trends observed for the smaller lattice parameter of the hydrates resulted from the formation of ice layers that acted as barriers to the released gases and caused increased isostatic pressures around the hydrate core. 9 refs., 6 figs.

  10. Hydration and temperature in tennis - a practical review.

    Science.gov (United States)

    Kovacs, Mark S

    2006-03-01

    Competitive tennis is typically played in warm and hot environments. Because hypohydration will impair tennis performance and increases the risk of heat injury, consumption of appropriate fluid levels is necessary to prevent dehydration and enhance performance. The majority of research in this area has focused on continuous aerobic activity - unlike tennis, which has average points lasting less than ten seconds with rest periods dispersed between each work period. For this reason, hydration and temperature regulation methods need to be specific to the activity. Tennis players can sweat more than 2.5 L·h(-1) and replace fluids at a slower rate during matches than in practice. Latter stages of matches and tournaments are when tennis players are more susceptible to temperature and hydration related problems. Sodium (Na(+)) depletion, not potassium (K(+)), is a key electrolyte in tennis related muscle cramps. However, psychological and competitive factors also contribute. CHO drinks have been shown to promote fluid absorption to a greater degree than water alone, but no performance benefits have been shown in tennis players in short matches. It is advisable to consume a CHO beverage if practice or matches are scheduled longer than 90-120 minutes. Key PointsAlthough substantial research has been performed on temperature and hydration concerns in aerobic activities, there is little information with regard to tennis performance and safetyTennis athletes should be on an individualized hydration schedule, consuming greater than 200ml of fluid every changeover (approximately 15 minutes).Optimum hydration and temperature regulation will reduce the chance of tennis related muscle cramps and performance decrements.

  11. Fluids and hydration in prolonged endurance performance.

    Science.gov (United States)

    Von Duvillard, Serge P; Braun, William A; Markofski, Melissa; Beneke, Ralph; Leithäuser, Renate

    2004-01-01

    Numerous studies have confirmed that performance can be impaired when athletes are dehydrated. Endurance athletes should drink beverages containing carbohydrate and electrolyte during and after training or competition. Carbohydrates (sugars) favor consumption and Na(+) favors retention of water. Drinking during competition is desirable compared with fluid ingestion after or before training or competition only. Athletes seldom replace fluids fully due to sweat loss. Proper hydration during training or competition will enhance performance, avoid ensuing thermal stress, maintain plasma volume, delay fatigue, and prevent injuries associated with dehydration and sweat loss. In contrast, hyperhydration or overdrinking before, during, and after endurance events may cause Na(+) depletion and may lead to hyponatremia. It is imperative that endurance athletes replace sweat loss via fluid intake containing about 4% to 8% of carbohydrate solution and electrolytes during training or competition. It is recommended that athletes drink about 500 mL of fluid solution 1 to 2 h before an event and continue to consume cool or cold drinks in regular intervals to replace fluid loss due to sweat. For intense prolonged exercise lasting longer than 1 h, athletes should consume between 30 and 60 g/h and drink between 600 and 1200 mL/h of a solution containing carbohydrate and Na(+) (0.5 to 0.7 g/L of fluid). Maintaining proper hydration before, during, and after training and competition will help reduce fluid loss, maintain performance, lower submaximal exercise heart rate, maintain plasma volume, and reduce heat stress, heat exhaustion, and possibly heat stroke.

  12. Field Data and the Gas Hydrate Markup Language

    Directory of Open Access Journals (Sweden)

    Ralf Löwner

    2007-06-01

    Full Text Available Data and information exchange are crucial for any kind of scientific research activities and are becoming more and more important. The comparison between different data sets and different disciplines creates new data, adds value, and finally accumulates knowledge. Also the distribution and accessibility of research results is an important factor for international work. The gas hydrate research community is dispersed across the globe and therefore, a common technical communication language or format is strongly demanded. The CODATA Gas Hydrate Data Task Group is creating the Gas Hydrate Markup Language (GHML, a standard based on the Extensible Markup Language (XML to enable the transport, modeling, and storage of all manner of objects related to gas hydrate research. GHML initially offers an easily deducible content because of the text-based encoding of information, which does not use binary data. The result of these investigations is a custom-designed application schema, which describes the features, elements, and their properties, defining all aspects of Gas Hydrates. One of the components of GHML is the "Field Data" module, which is used for all data and information coming from the field. It considers international standards, particularly the standards defined by the W3C (World Wide Web Consortium and the OGC (Open Geospatial Consortium. Various related standards were analyzed and compared with our requirements (in particular the Geographic Markup Language (ISO19136, GML and the whole ISO19000 series. However, the requirements demanded a quick solution and an XML application schema readable for any scientist without a background in information technology. Therefore, ideas, concepts and definitions have been used to build up the modules of GHML without importing any of these Markup languages. This enables a comprehensive schema and simple use.

  13. Gas hydrate decomposition recorded by authigenic barite at pockmark sites of the northern Congo Fan

    Science.gov (United States)

    Kasten, Sabine; Nöthen, Kerstin; Hensen, Christian; Spieß, Volkhard; Blumenberg, Martin; Schneider, Ralph R.

    2012-12-01

    The geochemical cycling of barium was investigated in sediments of pockmarks of the northern Congo Fan, characterized by surface and subsurface gas hydrates, chemosynthetic fauna, and authigenic carbonates. Two gravity cores retrieved from the so-called Hydrate Hole and Worm Hole pockmarks were examined using high-resolution pore-water and solid-phase analyses. The results indicate that, although gas hydrates in the study area are stable with respect to pressure and temperature, they are and have been subject to dissolution due to methane-undersaturated pore waters. The process significantly driving dissolution is the anaerobic oxidation of methane (AOM) above the shallowest hydrate-bearing sediment layer. It is suggested that episodic seep events temporarily increase the upward flux of methane, and induce hydrate formation close to the sediment surface. AOM establishes at a sediment depth where the upward flux of methane from the uppermost hydrate layer counterbalances the downward flux of seawater sulfate. After seepage ceases, AOM continues to consume methane at the sulfate/methane transition (SMT) above the hydrates, thereby driving the progressive dissolution of the hydrates "from above". As a result the SMT migrates downward, leaving behind enrichments of authigenic barite and carbonates that typically precipitate at this biogeochemical reaction front. Calculation of the time needed to produce the observed solid-phase barium enrichments above the present-day depths of the SMT served to track the net downward migration of the SMT and to estimate the total time of hydrate dissolution in the recovered sediments. Methane fluxes were higher, and the SMT was located closer to the sediment surface in the past at both sites. Active seepage and hydrate formation are inferred to have occurred only a few thousands of years ago at the Hydrate Hole site. By contrast, AOM-driven hydrate dissolution as a consequence of an overall net decrease in upward methane flux seems to

  14. Formative research to develop a community-based intervention for chronic disease prevention in Guatemalan school-age children.

    Science.gov (United States)

    Letona, Paola; Ramirez-Zea, Manuel; Caballero, Benjamin; Gittelsohn, Joel

    2014-01-31

    Noncommunicable diseases (NCD) are the most common causes of morbidity and mortality worldwide, even in low- and middle-income countries (LMIC). Recent trends in health promotion emphasize community-based interventions as an important strategy for improving health outcomes. The aim of this study was to conduct formative research regarding the perceptions of NCD risk factors, their influencing factors, and community resources available to aid the development and implementation of a community-based intervention with school-age children. Focus group discussions (n = 18), home visits (n = 30), and individual semi-structured interviews (n = 26) were conducted in three urban communities in Guatemala with school-age children (10-12 years of age), teachers, parents, and local community members (i.e., school principals, school food kiosk vendors, religious leaders, authority representatives). All focus groups and interviews were transcribed verbatim for thematic analysis. Children, parents, and teachers have general knowledge about modifiable risk factors. Adults worried more about tobacco use, as compared to unhealthy diet and physical inactivity in children. Participants identified features at the intrapersonal (e.g., negative emotional state), interpersonal (e.g., peers as role models), and organizational and community levels (e.g., high levels of crime) that influence these risk factors in children. School committees, religious leaders, and government programs and activities were among the positive community resources identified. These findings should help researchers in Guatemala and similar LMIC to develop community-based interventions for NCD prevention in school-age children that are effective, feasible, and culturally acceptable.

  15. THEOS-2 Orbit Design: Formation Flying in Equatorial Orbit and Damage Prevention Technique for the South Atlantic Magnetic Anomaly (SAMA)

    Science.gov (United States)

    Pimnoo, Ammarin

    2016-07-01

    Geo-Informatics and Space Technology Development Agency (GISTDA) has initiative THEOS-2 project after the THEOS-1 has been operated for more than 7 years which is over the lifetime already. THEOS-2 project requires not only the development of earth observation satellite(s), but also the development of the area-based decision making solution platform comprising of data, application systems, data processing and production system, IT infrastructure improvement and capacity building through development of satellites, engineering model, and infrastructures capable of supporting research in related fields. The developing satellites in THEOS-2 project are THAICHOTE-2 and THAICHOTE-3. This paper focuses the orbit design of THAICHOTE-2 & 3. It discusses the satellite orbit design for the second and third EOS of Thailand. In this paper, both THAICHOTE will be simulated in an equatorial orbit as a formation flying which will be compared the productive to THAICHOTE-1 (THEOS-1). We also consider a serious issue in equatorial orbit design, namely the issue of the geomagnetic field in the area of the eastern coast of South America, called the South Atlantic Magnetic Anomaly (SAMA). The high-energy particles of SAMA comprise a radiation environment which can travel through THAICHOTE-2 & 3 material and deposit kinetic energy. This process causes atomic displacement or leaves a stream of charged atoms in the incident particles' wake. It can cause damage to the satellite including reduction of power generated by solar arrays, failure of sensitive electronics, increased background noise in sensors, and exposure of the satellite devices to radiation. This paper demonstrates the loss of ionizing radiation damage and presents a technique to prevent damage from high-energy particles in the SAMA.

  16. Origin Of Methane Gas And Migration Through The Gas Hydrate Stability Zone Beneath The Permafrost Zone

    Science.gov (United States)

    Uchida, T.; Waseda, A.; Namikawa, T.

    2005-12-01

    In 1998 and 2002 Mallik wells were drilled at Mackenzie Delta in the Canadian Arctic that clarified the characteristics of gas hydrate-dominant sandy layers at depths from 890 to 1110 m beneath the permafrost zone. Continuous downhole well log data as well as visible gas hydrates have confirmed pore-space hydrate as intergranular pore filling within sandy layers whose saturations are up to 80% in pore volume, but muddy sediments scarcely contain. Plenty of gas hydrate-bearing sand core samples have been obtained from the Mallik wells. According to grain size distributions pore-space hydrate is dominant in medium- to very fine-grained sandy strata. Methane gas accumulation and original pore space large enough to occur within host sediments may be required for forming highly saturated gas hydrate in pore system. The distribution of a porous and coarser-grained host rock should be one of the important factors to control the occurrence of gas hydrate, as well as physicochemical conditions. Subsequent analyses in sedimentology and geochemistry performed on gas hydrate-bearing sandy core samples also revealed important geologic and sedimentological controls on the formation and concentration of natural gas hydrate. This appears to be a similar mode for conventional oil and gas accumulations. It is necessary for investigating subsurface fluid flow behaviors to evaluate both porosity and permeability of gas hydrate-bearing sandy sediments, and the measurements of water permeability for them indicate that highly saturated sands may have permeability of a few millidarcies. The isotopic data of methane show that hydrocarbon gas contained in gas hydrate is generated by thermogenic decomposition of kerogen in deep mature sediments. Based on geochemical and geological data, methane is inferred to migrate upward closely associated with pore water hundreds of meters into and through the hydrate stability zone partly up to the permafrost zone and the surface along faults and

  17. Natural gas hydrate occurrence and issues

    Science.gov (United States)

    Kvenvolden, K.A.

    1994-01-01

    Naturally occurring gas hydrate is found in sediment of two regions: (1) continental, including continental shelves, at high latitudes where surface temperatures are very cold, and (2) submarine outer continental margins where pressures are very high and bottom-water temperatures are near 0??C. Continental gas hydrate is found in association with onshore and offshore permafrost. Submarine gas hydrate is found in sediment of continental slopes and rises. The amount of methane present in gas hydrate is thought to be very large, but the estimates that have been made are more speculative than real. Nevertheless, at the present time there has been a convergence of ideas regarding the amount of methane in gas hydrate deposits worldwide at about 2 x 1016 m3 or 7 x 1017 ft3 = 7 x 105 Tcf [Tcf = trillion (1012) ft3]. The potentially large amount of methane in gas hydrate and the shallow depth of gas hydrate deposits are two of the principal factors driving research concerning this substance. Such a large amount of methane, if it could be commercially produced, provides a potential energy resource for the future. Because gas hydrate is metastable, changes of surface pressure and temperature affect its stability. Destabilized gas hydrate beneath the sea floor leads to geologic hazards such as submarine mass movements. Examples of submarine slope failures attributed to gas hydrate are found worldwide. The metastability of gas hydrate may also have an effect on climate. The release of methane, a 'greenhouse' gas, from destabilized gas hydrate may contribute to global warming and be a factor in global climate change.

  18. Sedimentological Properties of Natural Gas Hydrates-Bearing Sands in the Nankai Trough and Mallik Areas

    Science.gov (United States)

    Uchida, T.; Tsuji, T.; Waseda, A.

    2009-12-01

    The Nankai Trough parallels the Japanese Island, where extensive BSRs have been interpreted from seismic reflection records. High resolution seismic surveys have definitely indicated gas hydrate distributions, and drilling the MITI Nankai Trough wells in 2000 and the METI Tokai-oki to Kumano-nada wells in 2004 have revealed subsurface gas hydrate in the eastern part of Nankai Trough. In 1998 and 2002 Mallik wells were drilled at Mackenzie Delta in the Canadian Arctic that also clarified the characteristics of gas hydrate-dominant sandy layers at depths from 890 to 1110 m beneath the permafrost zone. During the field operations, the LWD and wire-line well log data were continuously obtained and plenty of gas hydrate-bearing sand cores were recovered. Subsequence sedimentological and geochemical analyses performed on those core samples revealed the crucial geologic controls on the formation and preservation of natural gas hydrate in sediments. Pore-space gas hydrates reside in sandy sediments mostly filling intergranular porosity. Pore waters chloride anomalies, core temperature depression and core observations on visible gas hydrates confirm the presence of pore-space gas hydrates within moderate to thick sandy layers, typically 10 cm to a meter thick. Sediment porosities and pore-size distributions were obtained by mercury porosimetry, which indicate that porosities of gas hydrate-bearing sandy strata are approximately 45 %. According to grain size distribution curves, gas hydrate is dominant in fine- to very fine-grained sandy strata. Gas hydrate saturations are typically up to 80 % in pore volume throughout most of the hydrate-dominant sandy layers, which are estimated by well log analyses as well as pore water chloride anomalies. It is necessary for investigating subsurface fluid flow behaviors to evaluate both porosity and permeability of gas hydrate-bearing sandy sediments, and the measurements of water permeability for them indicated that highly saturated

  19. Substantially self-powered method and apparatus for recovering hydrocarbons from hydrocarbon-containing solid hydrates

    Science.gov (United States)

    Elliott, G.R.B.; Barraclough, B.L.; Vanderborgh, N.E.

    1981-02-19

    A method and apparatus are provided for producing gaseous hydrocarbons from formations comprising solid hydrocarbon hydrates located under either a body of land or a body of water. The vast natural resources of such hydrocarbon hydrates can thus now be economically mined. Relatively warm brine or water is brought down from an elevation above that of the hydrates through a portion of the apparatus, and passes in contact with the hydrates, thus melting them. The liquid then continues up another portion of the apparatus carrying entrained hydrocarbon vapors in the form of bubbles, which can easily be separated from the liquid. After a short startup procedure, the process and apparatus are substantially self-powered.

  20. Effect of Graphene Oxide (GO on the Morphology and Microstructure of Cement Hydration Products

    Directory of Open Access Journals (Sweden)

    Liguo Wang

    2017-12-01

    Full Text Available In this study, the effects of graphene oxide (GO on the microstructure of cement mortars were studied using scanning electron microscopy (SEM, thermogravimetric (TG, and X-ray diffraction (XRD techniques. Cement mortar samples with different proportions of GO (0.02, 0.04, 0.06, and 0.08 wt % based on the weight of cement were prepared. The test results showed that GO affected the crystallization of cement hydration products, C–S–H (calcium silicate hydrate is the main hydrate product and CH (calcium hydroxide. The morphology of hydration products changed with the increase of GO content. Furthermore, the results of XRD analyses showed that the diffraction peak intensity and the crystal grain size of CH (001, (100, (101, and (102 for GO samples increased considerably compared with the control sample. Based on the results, it can be understood that GO can modify the crystal surface of CH, leading to the formation of larger crystals.

  1. Thermodynamic calculations in the system CH4-H2O and methane hydrate phase equilibria

    Science.gov (United States)

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

    2006-01-01

    Using the Gibbs function of reaction, equilibrium pressure, temperature conditions for the formation of methane clathrate hydrate have been calculated from the thermodynamic properties of phases in the system CH4-H 2O. The thermodynamic model accurately reproduces the published phase-equilibria data to within ??2 K of the observed equilibrium boundaries in the range 0.08-117 MPa and 190-307 K. The model also provides an estimate of the third-law entropy of methane hydrate at 273.15 K, 0.1 MPa of 56.2 J mol-1 K-1 for 1/n CH4??H 2O, where n is the hydrate number. Agreement between the calculated and published phase-equilibria data is optimized when the hydrate composition is fixed and independent of the pressure and temperature for the conditions modeled. ?? 2006 American Chemical Society.

  2. Microcrystalline dolomite within massive Japan Sea methane hydrate: origin and development ascertained by inclusions within inclusions.

    Science.gov (United States)

    Snyder, G. T.; Kakizaki, Y.; Matsumoto, R.; Suzuki, Y.; Takahata, N.; Sano, Y.; Tanaka, K.; Tomaru, H.; Imajo, T.; Iguchi, A.

    2017-12-01

    Microcrystalline dolomite grains were recently discovered as inclusions within relatively pure massive gas hydrate recovered from the Joetsu Basin area of the Japan Sea. These grains presumably formed as a consequence of the highly saline conditions in fluid inclusions which developed between coalescing grain boundaries within the growing hydrate. Stable carbon and oxygen isotopic composition of the dolomite is consistent with crystal growth occurring within such fluids. In addition to stable isotopes, we investigate trends in Mg/Ca ratios of the grains as well as the composition of inclusions which exist within the dolomites. Preliminary research shows that these inclusions retain valuable information as to the conditions which existed at the time of formation, as well as the dynamics of these extensive hydrate deposits over time. This study was conducted under the commission from AIST as a part of the methane hydrate research project funded by METI (the Ministry of Economy, Trade and Industry, Japan).

  3. Fractionation of oxygen and hydrogen isotopes at the hydrate gas forming in the sea sediments

    International Nuclear Information System (INIS)

    Pashkina, V.I.; Esikov, A.D.

    1990-01-01

    The paper gives data on isotope composition of interstitial and near-bottom waters sampled in a region of gas-hydrate formation in the Sea of Okhotsk. The studies show that heavy isotopes of oxygen and hydrogen is used in gas-hydrate formation, with the result that isotope composition of its constitution water constitutes δ 18 O=+1.99per mille, δD=+23per mille relatively to SMOW. Formation of autogenic carbonates leads to isotope exchange with interstitial water wich, in turn, changes its primary isotope composition in the direction of increasing of O-18 content. The near-bottom waters are isotope-light relatively to the SMOW standard and to the mean isotope composition of interstitial water in the studied region of gas-hydrate spreading. (orig.) [de

  4. Renal impairment following angiography in well-hydrated patients

    International Nuclear Information System (INIS)

    Brown, J.J.; Bookstein, J.J.; Davis, G.B.; Tainer, L.B.

    1986-01-01

    The authors undertook a prospective study to assess the efficacy of a specific hydration protocol for reducing the risk of renal impairment following angiography. One hundred four patients were infused with 0.5 NS at a rate of 250 ml/hour for 2 hours before angiography, during the angiographic procedure, and for 2 hours after the procedure. Blood urea nitrogen and serum creatinine values were determined before the procedure and on the first and third days after the procedure. The type and dose of contrast material used, the site of injection, and preexisting risk factors for the development of renal impairment were recorded for each patient. None of the patients in the series experienced significant deterioration of renal reaction. In comparison to historical controls, this hydration regimen seems effective in preventing significant postangiographic renal impairment

  5. Accelerated hydration of high silica cements

    International Nuclear Information System (INIS)

    Walker, Colin; Yui, Mikazu

    2012-01-01

    Current Japanese designs for high level radioactive waste (HLW) repositories anticipate the use of both bentonite (buffer and backfill material) and cement based materials. Using hydrated Ordinary Portland Cement (OPC) as a grouting material is undesirable because the associated high pH buffer will have an undisputed detrimental effect on the performance of the bentonite buffer and backfill and of the host rock by changing its porosity. Instead, hydrated low pH cement (LopHC) grouting materials are being developed to provide a pH inferior or equal to 11 to reduce these detrimental effects. LopHC grouting materials use mixtures of superfine OPC (SOPC) clinker and silica fume (SF), and are referred as high silica cements (HSC). The focus of the present study was to identify the development of the unhydrated and hydrated mineral assemblage and the solution chemistry during the hydration of HSC. Since hydration experiments of cementitious materials are notably slow, a ball mill was used to accelerate hydration. This was done for two reasons. Firstly, to develop a method to rapidly hydrate cement based materials without the need for higher temperatures (which can alter the mineral assemblage), and secondly, to ensure that the end point of hydration was reached in a reasonable time frame and so to realize the final mineralogy and solution chemistry of hydrated HSC

  6. 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…

  7. Methane hydrates as potential energy resource: Part 2 - Methane production processes from gas hydrates

    International Nuclear Information System (INIS)

    Demirbas, Ayhan

    2010-01-01

    Three processes have been proposed for dissociation of methane hydrates: thermal stimulation, depressurization, and inhibitor injection. The obvious production approaches involve depressurization, heating and their combinations. The depressurization method is lowering the pressure inside the well and encouraging the methane hydrate to dissociate. Its objective is to lower the pressure in the free-gas zone immediately beneath the hydrate stability zone, causing the hydrate at the base of the hydrate stability zone to decompose. The thermal stimulation method is applied to the hydrate stability zone to raise its temperature, causing the hydrate to decompose. In this method, a source of heat provided directly in the form of injected steam or hot water or another heated liquid, or indirectly via electric or sonic means. This causes methane hydrate to decompose and generates methane gas. The methane gas mixes with the hot water and returns to the surface, where the gas and hot water are separated. The chemical inhibition method seeks to displace the natural-gas hydrate equilibrium condition beyond the hydrate stability zone's thermo-dynamic conditions through injection of a liquid inhibitor chemical adjacent to the hydrate. In this method, inhibitor such as methanol is injected from surface down to methane hydrate-bearing layers. The thermal stimulation method is quite expensive. The chemical inhibitor injection method is also expensive. The depressurization method may prove useful to apply more than one production.

  8. Crystal structure, stability and spectroscopic properties of methane and CO2 hydrates.

    Science.gov (United States)

    Martos-Villa, Ruben; Francisco-Márquez, Misaela; Mata, M Pilar; Sainz-Díaz, C Ignacio

    2013-07-01

    Methane hydrates are highly present in sea-floors and in other planets and their moons. Hence, these compounds are of great interest for environment, global climate change, energy resources, and Cosmochemistry. The knowledge of stability and physical-chemical properties of methane hydrate crystal structure is important for evaluating some new green becoming technologies such as, strategies to produce natural gas from marine methane hydrates and simultaneously store CO2 as hydrates. However, some aspects related with their stability, spectroscopic and other chemical-physical properties of both hydrates are not well understood yet. The structure and stability of crystal structure of methane and CO2 hydrates have been investigated by means of calculations with empirical interatomic potentials and quantum-mechanical methods based on Hartree-Fock and Density Functional Theory (DFT) approximations. Molecular Dynamic simulations have been also performed exploring different configurations reproducing the experimental crystallographic properties. Spectroscopic properties have also been studied. Frequency shifts of the main vibration modes were observed upon the formation of these hydrates, confirming that vibration stretching peaks of C-H at 2915cm(-1) and 2905cm(-1) are due to methane in small and large cages, respectively. Similar effect is observed in the CO2 clathrates. The guest-host binding energy in these clathrates calculated with different methods are compared and discussed in terms of adequacy of empirical potentials and DFT methods for describing the interactions between gas guest and the host water cage, proving an exothermic nature of methane and CO2 hydrates formation process. Copyright © 2013 Elsevier Inc. All rights reserved.

  9. Experiments and Phase-field Modeling of Hydrate Growth at the Interface of Migrating Gas Fingers

    Science.gov (United States)

    Fu, X.; Jimenez-Martinez, J.; Porter, M. L.; Cueto-Felgueroso, L.; Juanes, R.

    2016-12-01

    The fate of methane bubbles escaping from seafloor seeps remains an important research question, as it directly concerns our understanding of the impact of seafloor methane leakage on ocean biogeochemistry. While the physics of rising bubbles in a water column has been studied extensively, the process is poorly understood when the gas bubbles form a hydrate ``crust" during their ascent. Understanding bubble rise, expansion and dissolution under these conditions is essential to determine the fate