Science.gov

Sample records for affect gas transport

  1. Natural gas marketing and transportation

    SciTech Connect

    Not Available

    1991-01-01

    This book covers: Overview of the natural gas industry; Federal regulation of marketing and transportation; State regulation of transportation; Fundamentals of gas marketing contracts; Gas marketing options and strategies; End user agreements; Transportation on interstate pipelines; Administration of natural gas contracts; Structuring transactions with the nonconventional source fuels credit; Take-or-pay wars- a cautionary analysis for the future; Antitrust pitfalls in the natural gas industry; Producer imbalances; Natural gas futures for the complete novice; State non-utility regulation of production, transportation and marketing; Natural gas processing agreements and Disproportionate sales, gas balancing, and accounting to royalty owners.

  2. Gas transport processes in sea ice: How convection and diffusion processes might affect biological imprints, a challenge for modellers

    NASA Astrophysics Data System (ADS)

    Tison, J.-L.; Zhou, J.; Thomas, D. N.; Rysgaard, S.; Eicken, H.; Crabeck, O.; Deleu, F.; Delille, B.

    2012-04-01

    Recent data from a year-round survey of landfast sea ice growth in Barrow (Alaska) have shown how O2/N2 and O2/Ar ratios could be used to pinpoint primary production in sea ice and derive net productivity rates from the temporal evolution of the oxygen concentration at a given depth within the sea ice cover. These rates were however obtained surmising that neither convection, nor diffusion had affected the gas concentration profiles in the ice between discrete ice core collections. This paper discusses examples from three different field surveys (the above-mentioned Barrow experiment, the INTERICE IV tank experiment in Hamburg and a short field survey close to the Kapisilit locality in the South-East Greenland fjords) where convection or diffusion processes have clearly affected the temporal evolution of the gas profiles in the ice, therefore potentially affecting biological signatures. The INTERICE IV and Barrow experiment show that the initial equilibrium dissolved gas entrapment within the skeletal layer basically governs most of the profiles higher up in the sea ice cover during the active sea ice growth. However, as the ice layers age and cool down under the temperature gradient, bubble nucleation occurs while the concentration in the ice goes well above the theoretical one, calculated from brine equilibrium under temperature and salinity changes and observed brine volumes. This phase change locks the gases within the sea ice structure, preventing "degassing" of the ice, as is observed for salts under the mushy layer brine convection process. In some cases, mainly in the early stages of the freezing process (first 10-20 cm) where temperature gradients are strong and the ice still permeable on its whole thickness, repeated convection and bubble nucleation can actually increase the gas concentration in the ice above the one initially acquired within the skeletal layer. Convective processes will also occur on ice decay, when ice permeability is restored and the

  3. Conditioning natural gas for measurement and transportation

    SciTech Connect

    Barnhard, E.E.

    1984-04-01

    This paper discusses methods of conditioning natural gas for measurement and transportation. Gas mixtures measured at the well head or into a gathering system may not yet be conditioned to pipeline standards at the point of measurement, because title to the gas passes from the seller to the buyer at that point. Therefore, it is sometimes necessary to measure the gas flow without complete conditioning and to do it accurately. Careful study of the conditioning steps that the gas has completed, or that must be performed prior to measurement, will affect selection of the measurement equipment and the success of its operation.

  4. Positron transport: The plasma-gas interface

    SciTech Connect

    Marler, J. P.; Petrovic, Z. Lj.; Bankovic, A.; Dujko, S.; Suvakov, M.; Malovic, G.; Buckman, S. J.

    2009-05-15

    Motivated by an increasing number of applications, new techniques in the analysis of electron transport have been developed over the past 30 years or so, but similar methods had yet to be applied to positrons. Recently, an in-depth look at positron transport in pure argon gas has been performed using a recently established comprehensive set of cross sections and well-established Monte Carlo simulations. The key novelty as compared to electron transport is the effect of positronium formation which changes the number of particles and has a strong energy dependence. This coupled with spatial separation by energy of the positron swarm leads to counterintuitive behavior of some of the transport coefficients. Finally new results in how the presence of an applied magnetic field affects the transport coefficients are presented.

  5. Factors affecting gas content in coal beds

    SciTech Connect

    Scott, A.R.; Kaiser, W.R.

    1996-06-01

    Gas content is one of the most important controls on coalbed methane producibility because coal gas production becomes uneconomical if insufficient amounts of gas are sorbed onto the coal surface. Gas content in coal beds is not fixed but changes when equilibrium conditions within the reservoir are disrupted. Therefore, the distribution of gas content varies laterally within individual coal beds, vertically among coals within a single well, and vertically within thicker coal beds. The key hydrogeologic factors affecting gas content variability include gas generation, coal properties, and reservoir conditions. The potential for high gas content depends on thermogenic and secondary biogenic gas generation, which are controlled by burial history (coal rank), maceral composition, and basin hydrodynamics. Coal properties such as ash and moisture content, maceral type, permeability, and diffusion coefficient affect the sorption capacity and diffusion rates in coal beds and, therefore, the final gas content. Reservoir conditions such as pressure and temperature also affect the amount of gases sorbed to the coal surface, whereas coal geometry, hydrogeology, and the presence or absence of permeability barriers determine whether or not gas contents are increased or decreased. Stratigraphic and/or structural trapping concentrates coal gases, resulting in higher gas contents adjacent to permeability barriers; the presence of abnormally high gas contents in lower-rank coals indicates secondary biogenic gas generation and/or conventional trapping of thermogenic or biogenic gases. Gas content decreases in areas of active recharge caused by flushing or in areas of convergent flow where no trapping mechanisms (seals) are present.

  6. Convert natural gas into clean transportation fuels

    SciTech Connect

    Agee, M.A.

    1997-03-01

    A new process economically converts natural gas into synthetic transportation fuels that are free of sulfur, metals, aromatics and are clear in appearance. The process, developed by Syntroleum Corp., is energy self-sufficient and can be implemented in sizes small enough to fit a large number of the world`s gas fields. The process is described.

  7. Modeling gas transport in the Martian subsurface

    NASA Astrophysics Data System (ADS)

    Gloesener, Elodie; Karatekin, Özgür; Dehant, Véronique

    2015-04-01

    Modeling gas transport through Martian subsurface and outgassing processes is essential in the study of atmospheric evolution of Mars. We present an overview of gas transport in Martian soil focusing on water vapor and methane diffusion to explain the recent observations of methane in Martian atmosphere with a diffusive transport model. The range of parameters that have the largest effect on transport in Martian conditions is investigated. Among the possible sources of methane, clathrate hydrates destabilization is one potential mechanism. Hydrate stability zone in subsurface is also investigated. In 2016, ExoMars Trace Gas Orbiter (TGO) will have the capabilities to detect and characterize trace gases in Martian atmosphere and will bring additional information to validate the different possible outgassing scenarios.

  8. Inert gas transport in blood and tissues.

    PubMed

    Baker, A Barry; Farmery, Andrew D

    2011-04-01

    This article establishes the basic mathematical models and the principles and assumptions used for inert gas transfer within body tissues-first, for a single compartment model and then for a multicompartment model. From these, and other more complex mathematical models, the transport of inert gases between lungs, blood, and other tissues is derived and compared to known experimental studies in both animals and humans. Some aspects of airway and lung transfer are particularly important to the uptake and elimination of inert gases, and these aspects of gas transport in tissues are briefly described. The most frequently used inert gases are those that are administered in anesthesia, and the specific issues relating to the uptake, transport, and elimination of these gases and vapors are dealt with in some detail showing how their transfer depends on various physical and chemical attributes, particularly their solubilities in blood and different tissues. Absorption characteristics of inert gases from within gas cavities or tissue bubbles are described, and the effects other inhaled gas mixtures have on the composition of these gas cavities are discussed. Very brief consideration is given to the effects of hyper- and hypobaric conditions on inert gas transport.

  9. Gas transport across hyperthin membranes.

    PubMed

    Wang, Minghui; Janout, Vaclav; Regen, Steven L

    2013-12-17

    The use of organic polymeric membranes to separate gaseous mixtures provides an attractive alternative to other methods such as selective adsorption and cryogenic distillation. The primary advantages of membrane-based separations are their relative energy efficiency and lower costs. Because the flux of a gas across a membrane is inversely proportional to the membrane's thickness, this method relies on fabricating membranes that are as thin as possible. However, as researchers have tried to produce "hyperthin" membranes (less than 100 nm), these membranes often form defects and lose their permeation selectivity. In this Account, we review some of the progress in our laboratories at Lehigh University to create hyperthin membranes with high permeation selectivities. We focus special attention on gaseous permeants that are relevant for the production of clean energy (H2 and CO2 formed from CH4) and the reduction of global warming (CO2 and N2, the major components of flue gas). Our studies make extensive use of Langmuir-Blodgett (LB) methods and porous surfactants derived from calix[6]arenes. We specially designed each surfactant to form cohesive monolayers and multilayers, and we introduced a "gluing" technique, where we cross-link porous surfactants containing quaternary ammonium groups ionically with polymeric counterions. Using ellipsometry, atomic force microscopy, X-ray photoelectron spectroscopy, monolayer isotherm, surface viscosity, and permeation measurements, we have characterized these hyperthin films. While molecular sieving appears to make a significant contribution to the permeation selectivity of some of these membranes, solution-diffusion pathways predominate. We also describe initial studies in which we formed hyperthin films from poly(ethylene glycol)-based polyelectrolytes using layer-by-layer deposition (LbL) methods. We have found remarkably high H2/CO2 and CO2/N2 permeation selectivities with these LB- and LbL-based hyperthin membranes. These

  10. Hot Gas Desulfurization Using Transport Reactors

    SciTech Connect

    Moorehead, E.L.

    1996-12-31

    Sierra Pacific Power Company is building a 100 MW, IGCC power plant based on KRW fluid bed gasifier technology that utilizes transport reactors for hot gas desulfurization and sorbent regeneration. Use of a transport absorber avoids the need for pre-filtration of dust-laden gasifier effluent, while a transport regenerator allows for the use of 100% air without the need for heat exchange equipment. Selection of transport reactors for hot gas desulfurization using a proprietary sorbent, based on testing performed in a transport reactor test unit (TRTU) at the M. W. Kellogg Technology Development Center and in a fixed bed reactor at Morgantown Energy Technology Center (METC), is outlined. The results obtained in these two test facilities and reasons for selecting transport reactors for the IGCC power plant in preference to either fixed bed or fluidized bed reactors are discussed. This paper reviews the evolution of the hot gas desulfurization system designs and includes selected results on H{sub 2}S absorption and regeneration of sulfided sorbent over several absorption/regeneration cycles conducted in the TRTU and the METC fixed bed reactor. The original design for the Sierra Pacific Project was based on fixed bed reactors with zinc ferrite as the sorbent. Owing to the high steam requirements of this sorbent, zinc titanate was selected and tested in a fixed bed reactor and was found unacceptable due to loss of strength on cyclic absorption/regeneration operation. Another sorbent evaluated was Z-Sorb{reg_sign}, a proprietary sorbent developed by Phillips Petroleum Company, was found to have excellent sulfur capacity, structural strength and regenerability. Steam was found unsuitable as fixed bed regenerator diluent, this results in a requirement for a large amount of inert gas, whereas a transport regenerator requires no diluent. The final Sierra design features transport reactors for both desulfurization and regeneration steps using neat air. 3 refs., 3 figs., 2 tabs.

  11. Gas Transport in Polymer-Grafted Nanoparticles

    NASA Astrophysics Data System (ADS)

    Zhang, Kai; Kumar, Sanat

    The efficient separation of gases is crucial for clean energy technologies. With their intrinsic multiscale features and excellent self-assembly properties, polymer-grafted nanoparticles (PGNP) material makes a good candidate for effective gas separation, but the basic understanding of gas transport in PGNPs is still missing. While the nanoparticles cores are spherical, the corona of the PGNPs can be deformed into anisotropic space-filling polygons at high density that are commensurate with the crystal structures (Wigner-Seitz cells). Such deformation indicates that the polymer chains are extended or compressed along different directions and create cavities within the crystals that can help to improve the gas selectivity. We use coarse-grained computer simulations to study the solubility and diffusion of gas molecules inside the crystalline packing of the NP cores. By tuning the degree of polymerization, the surface density of grafting chains and the size of gas molecules, we systematically investigate the dependence of gas transport on these parameters. We find that the void formed by three contacting monomers imposes a critical lengthscale beyond which the transport becomes highly size selective.

  12. Gas controller's paper pipeline - transportation and exchange

    SciTech Connect

    Chapman, R.E. Jr.

    1981-01-01

    When gas supplies began to decline during the 1970s, the US Federal Energy Regulatory Commission promulgated Orders 402 and 402-A to allow curtailed companies to make 60-day emergency purchases. In assisting its customer companies with such transactions, Texas Gas encountered several problems: the gas had to be allocated to each company, the sales required separate billing, the allocated volumes had to be received and delivered, and new contracts were necessary. Another stopgap measure, known as the 533 transportation service, also proved difficult to implement because the gas volumes were usually very small and were often interrupted when regular supplies began to resume. Under the Natural Gas Policy Act of 1978, interstate companies could offer the same gas prices to producers that intrastate companies paid; the NGPA also allowed sales from intra- to interstate companies. These provisions created a greater need for transportation-or-exchange service among all the parties. More recently, the FERC's Order 60 gave interstate companies the power to enter into self-implementing transportation-or-exchange service. Under legal modifications now being considered, pipeline companies will be able to significantly reduce regulatory delays by using blanket certificates.

  13. Conditions and processes affecting radionuclide transport

    USGS Publications Warehouse

    Simmons, Ardyth M.; Neymark, Leonid A.

    2012-01-01

    Understanding of unsaturated-zone transport is based on laboratory and field-scale experiments. Fractures provide advective transport pathways. Sorption and matrix diffusion may contribute to retardation of radionuclides. Conversely, sorption onto mobile colloids may enhance radionuclide transport.

  14. Gas transport behavior of semicrystalline syndiotactic polystyrene

    NASA Astrophysics Data System (ADS)

    Prodpran, Thummanoon

    Solid-state structure, crystalline morphology, crystallization kinetic, and gas transport properties of thermally crystallized semicrystalline syndiotactic polystyrene (s-PS) have been investigated in this study. Solid-state structure of syndiotactic polystyrene (s-PS) after crystallization from the melt and the glassy state was examined by differential scanning calorimetry (DSC), density and wide angle x-ray diffraction analysis (WAXS). The measurements confirmed the low density of both crystalline forms, which in the case of a crystalline form was smaller and in the case of beta crystalline form was slightly larger than the density of the glassy amorphous s-PS. Positron annihilation lifetime spectroscopy (PALS) experiments have been also carried out to study the free volume properties of these materials. The crystalline morphologies of s-PS containing pure alpha and beta phase were examined via atomic force microscopy (AFM) and optical microscopy (OM). The beta crystalline phase exhibited typical spherulitic morphology. The morphology of the a crystalline phase of limiting ordered modification (alpha″-form) consists of individual randomly oriented lamellae imbedded in the matrix of amorphous s-PS. The a crystalline phase of limiting disordered modification (alpha'-form) exhibited small spherulite-like morphology with lack of regular birefringence pattern. The crystalline morphology observations were in good agreement with the crystallization kinetic data. Oxygen and carbon dioxide gas permeability, diffusion and solubility of semicrystalline s-PS containing different crystalline forms were studied as a function of crystallinity. Syndiotactic polystyrene containing the beta crystalline form exhibited decrease of permeability with crystallinity. On the contrary, s-PS containing less dense a crystalline form showed increase of permeability with crystallinity, meaning highly gas permeable to small gas molecules. Unusual gas transport behavior of the alpha

  15. Space Weather affects on Air Transportation

    NASA Astrophysics Data System (ADS)

    Jones, J. B. L.; Bentley, R. D.; Dyer, C.; Shaw, A.

    In Europe, legislation requires the airline industry to monitor the occupational exposure of aircrew to cosmic radiation. However, there are other significant impacts of space weather phenomena on the technological systems used for day-to-day operations which need to be considered by the airlines. These were highlighted by the disruption caused to the industry by the period of significant solar activity in late October and early November 2003. Next generation aircraft will utilize increasingly complex avionics as well as expanding the performance envelopes. These and future generation platforms will require the development of a new air-space management infrastructure with improved position accuracy (for route navigation and landing in bad weather) and reduced separation minima in order to cope with the expected growth in air travel. Similarly, greater reliance will be placed upon satellites for command, control, communication and information (C3I) of the operation. However, to maximize effectiveness of this globally interoperable C3I and ensure seamless fusion of all components for a safe operation will require a greater understanding of the space weather affects, their risks with increasing technology, and the inclusion of space weather information into the operation. This paper will review space weather effects on air transport and the increasing risks for future operations cause by them. We will examine how well the effects can be predicted, some of the tools that can be used and the practicalities of using such predictions in an operational scenario. Initial results from the SOARS ESA Space Weather Pilot Project will also be discussed,

  16. Trace Gas Transport Over Complex Terrain

    NASA Astrophysics Data System (ADS)

    Sun, J.; Burns, S. P.; Delany, A. C.; Oncley, S. P.; Turnipseed, A. A.; Stephens, B. B.; Monson, R. K.; Anderson, D. E.

    2005-12-01

    Carbon dioxide transport at the Niwot Ridge AmeriFlux site was investigated in both gravity and streamline coordinates during a pilot experiment. We found that the nighttime drainage flow and the daytime upslope flow played important roles in the trace gas budget, such as CO2 and water vapor, at this about 6% sloped forest site. Most of time, the canopy flow was decoupled from the air above; the air within the canopy was dominated by drainage and upslope flows while the air above was dominated by prevailing westerlies. At night the flow was stably stratified everywhere but less stable within than above the canopy; while during the day, the air was mostly stable within the canopy layer, especially near the bottom of the canopy, and the layer above was unstable. Protected by the overlying canopy, the drainage flow was responsible for transporting CO2 at night while the stable layer above the canopy prevented upward CO2 transport. In the early morning, the upslope flow transported the nighttime accumulation of moist and CO2-enhanced air up the slope. The reduction of the CO2 concentration in the early morning was associated with photosynthesis, upslope flow, and flux venting. The daytime stable boundary layer within the canopy prevented CO2 venting and provided favorable conditions for CO2 uptake, where the CO2 concentration was relatively high from both local and remote respiration, and both direct and diffused solar radiation were available for photosynthesis. Therefore, both the CO2 respiration at night and the CO2 uptake during the day are underestimated if the horizontal transport of CO2 is not monitored; and the two components may not cancel out.

  17. RAETRAD MODEL OF RADON GAS GENERATION, TRANSPORT, AND INDOOR ENTRY

    EPA Science Inventory

    The report describes the theoretical basis, implementation, and validation of the Radon Emanation and Transport into Dwellings (RAETRAD) model, a conceptual and mathematical approach for simulating radon (222Rn) gas generation and transport from soils and building foundations to ...

  18. BiP negatively affects ricin transport.

    PubMed

    Gregers, Tone F; Skånland, Sigrid S; Wälchli, Sébastien; Bakke, Oddmund; Sandvig, Kirsten

    2013-05-10

    The AB plant toxin ricin binds both glycoproteins and glycolipids at the cell surface via its B subunit. After binding, ricin is endocytosed and then transported retrogradely through the Golgi to the endoplasmic reticulum (ER). In the ER, the A subunit is retrotranslocated to the cytosol in a chaperone-dependent process, which is not fully explored. Recently two separate siRNA screens have demonstrated that ER chaperones have implications for ricin toxicity. ER associated degradation (ERAD) involves translocation of misfolded proteins from ER to cytosol and it is conceivable that protein toxins exploit this pathway. The ER chaperone BiP is an important ER regulator and has been implicated in toxicity mediated by cholera and Shiga toxin. In this study, we have investigated the role of BiP in ricin translocation to the cytosol. We first show that overexpression of BiP inhibited ricin translocation and protected cells against the toxin. Furthermore, shRNA-mediated depletion of BiP enhanced toxin translocation resulting in increased cytotoxicity. BiP-dependent inhibition of ricin toxicity was independent of ER stress. Our findings suggest that in contrast to what was shown with the Shiga toxin, the presence of BiP does not facilitate, but rather inhibits the entry of ricin into the cytosol.

  19. Cryogenic Transport of High-Pressure-System Recharge Gas

    NASA Technical Reports Server (NTRS)

    Ungar, Eugene K,; Ruemmele, Warren P.; Bohannon, Carl

    2010-01-01

    A method of relatively safe, compact, efficient recharging of a high-pressure room-temperature gas supply has been proposed. In this method, the gas would be liquefied at the source for transport as a cryogenic fluid at or slightly above atmospheric pressure. Upon reaching the destination, a simple heating/expansion process would be used to (1) convert the transported cryogenic fluid to the room-temperature, high-pressure gaseous form in which it is intended to be utilized and (2) transfer the resulting gas to the storage tank of the system to be recharged. In conventional practice for recharging high-pressure-gas systems, gases are transported at room temperature in high-pressure tanks. For recharging a given system to a specified pressure, a transport tank must contain the recharge gas at a much higher pressure. At the destination, the transport tank is connected to the system storage tank to be recharged, and the pressures in the transport tank and the system storage tank are allowed to equalize. One major disadvantage of the conventional approach is that the high transport pressure poses a hazard. Another disadvantage is the waste of a significant amount of recharge gas. Because the transport tank is disconnected from the system storage tank when it is at the specified system recharge pressure, the transport tank still contains a significant amount of recharge gas (typically on the order of half of the amount transported) that cannot be used. In the proposed method, the cryogenic fluid would be transported in a suitably thermally insulated tank that would be capable of withstanding the recharge pressure of the destination tank. The tank would be equipped with quick-disconnect fluid-transfer fittings and with a low-power electric heater (which would not be used during transport). In preparation for transport, a relief valve would be attached via one of the quick-disconnect fittings (see figure). During transport, the interior of the tank would be kept at a near

  20. Impact of compression on gas transport in non-woven gas diffusion layers of high temperature polymer electrolyte fuel cells

    NASA Astrophysics Data System (ADS)

    Froning, Dieter; Yu, Junliang; Gaiselmann, Gerd; Reimer, Uwe; Manke, Ingo; Schmidt, Volker; Lehnert, Werner

    2016-06-01

    Gas transport in non-woven gas diffusion layers of a high-temperature polymer electrolyte fuel cell was calculated with the Lattice Boltzmann method. The underlying micro structure was taken from two sources. A real micro structure was analyzed in the synchrotron under the impact of a compression mask mimicking the channel/rib structure of a flow field. Furthermore a stochastic geometry model based on synchrotron X-ray tomography studies was applied. The effect of compression is included in the stochastic model. Gas transport in these micro structures was simulated and the impact of compression was analyzed. Fiber bundles overlaying the micro structure were identified which affect the homogeneity of the gas flow. There are significant deviations between the impact of compression on effective material properties for this type of gas diffusion layers and the Kozeny-Carman equation.

  1. Soil water repellency affects production and transport of CO2 and CH4 in soil

    NASA Astrophysics Data System (ADS)

    Urbanek, Emilia; Qassem, Khalid

    2016-04-01

    Soil moisture is known to be vital in controlling both the production and transport of C gases in soil. Water availability regulates the decomposition rates of soil organic matter by the microorganisms, while the proportion of water/air filled pores controls the transport of gases within the soil and at the soil-atmosphere interface. Many experimental studies and process models looking at soil C gas fluxes assume that soil water is uniformly distributed and soil is easily wettable. Most soils, however, exhibit some degree of soil water repellency (i.e. hydrophobicity) and do not wet spontaneously when dry or moderately moist. They have restricted infiltration and conductivity of water, which also results in extremely heterogeneous soil water distribution. This is a world-wide occurring phenomenon which is particularly common under permanent vegetation e.g. forest, grass and shrub vegetation. This study investigates the effect of soil water repellency on microbial respiration, CO2 transport within the soil and C gas fluxes between the soil and the atmosphere. The results from the field monitoring and laboratory experiments show that soil water repellency results in non-uniform water distribution in the soil which affects the CO2 and CH4 gas fluxes. The main conclusion from the study is that water repellency not only affects the water relations in the soil, but has also a great impact on greenhouse gas production and transport and therefore should be included as an important parameter during the sites monitoring and modelling of gas fluxes.

  2. Coupling between geochemical reactions and multicomponent gas and solute transport in unsaturated media: A reactive transport modeling study

    NASA Astrophysics Data System (ADS)

    Molins, S.; Mayer, K. U.

    2007-05-01

    The two-way coupling that exists between biogeochemical reactions and vadose zone transport processes, in particular gas phase transport, determines the composition of soil gas. To explore these feedback processes quantitatively, multicomponent gas diffusion and advection are implemented into an existing reactive transport model that includes a full suite of geochemical reactions. Multicomponent gas diffusion is described on the basis of the dusty gas model, which accounts for all relevant gas diffusion mechanisms. The simulation of gas attenuation in partially saturated landfill soil covers, methane production, and oxidation in aquifers contaminated by organic compounds (e.g., an oil spill site) and pyrite oxidation in mine tailings demonstrate that both diffusive and advective gas transport can be affected by geochemical reactions. Methane oxidation in landfill covers reduces the existing upward pressure gradient, thereby decreasing the contribution of advective methane emissions to the atmosphere and enhancing the net flux of atmospheric oxygen into the soil column. At an oil spill site, methane oxidation causes a reversal in the direction of gas advection, which results in advective transport toward the zone of oxidation both from the ground surface and the deeper zone of methane production. Both diffusion and advection contribute to supply atmospheric oxygen into the subsurface, and methane emissions to the atmosphere are averted. During pyrite oxidation in mine tailings, pressure reduction in the reaction zone drives advective gas flow into the sediment column, enhancing the oxidation process. In carbonate-rich mine tailings, calcite dissolution releases carbon dioxide, which partly offsets the pressure reduction caused by O2 consumption.

  3. Coupling between geochemical reactions and multicomponent gas and solute transport in unsaturated media: A reactive transport modeling study

    USGS Publications Warehouse

    Molins, S.; Mayer, K.U.

    2007-01-01

    The two-way coupling that exists between biogeochemical reactions and vadose zone transport processes, in particular gas phase transport, determines the composition of soil gas. To explore these feedback processes quantitatively, multicomponent gas diffusion and advection are implemented into an existing reactive transport model that includes a full suite of geochemical reactions. Multicomponent gas diffusion is described on the basis of the dusty gas model, which accounts for all relevant gas diffusion mechanisms. The simulation of gas attenuation in partially saturated landfill soil covers, methane production, and oxidation in aquifers contaminated by organic compounds (e.g., an oil spill site) and pyrite oxidation in mine tailings demonstrate that both diffusive and advective gas transport can be affected by geochemical reactions. Methane oxidation in landfill covers reduces the existing upward pressure gradient, thereby decreasing the contribution of advective methane emissions to the atmosphere and enhancing the net flux of atmospheric oxygen into the soil column. At an oil spill site, methane oxidation causes a reversal in the direction of gas advection, which results in advective transport toward the zone of oxidation both from the ground surface and the deeper zone of methane production. Both diffusion and advection contribute to supply atmospheric oxygen into the subsurface, and methane emissions to the atmosphere are averted. During pyrite oxidation in mine tailings, pressure reduction in the reaction zone drives advective gas flow into the sediment column, enhancing the oxidation process. In carbonate-rich mine tailings, calcite dissolution releases carbon dioxide, which partly offsets the pressure reduction caused by O2 consumption.

  4. Transport of dissolved gas and its ecological impact after a gas release from deepwater.

    PubMed

    Wimalaratne, Malinda R; Yapa, Poojitha D; Nakata, Kisaburo; Premathilake, Lakshitha T

    2015-11-15

    Previous models on simulating gas releases in deepwater were not focused on the dissolved component and its impact on water quality. This paper presents a new model developed for simulating the transport/spread of dissolved methane from an underwater release and its impact on dissolved oxygen in ambient water. Methane dissolves into ambient water from gas phase, direct from hydrate phase, and from dissociating hydrates formed earlier. Dissolved methane affects the dissolved oxygen levels in ambient water due to microbial interaction and possible direct absorption of oxygen into methane bubbles. We use new model simulations of Deepspill field experiments to compare with instantaneous profiles which were unpublished until now. The comparisons are very good with a short time lag, but are within the acceptable discrepancy for models for emergency response and contingency planning. Scenario simulations show the effect on dissolved oxygen due to different methane release situations.

  5. Feed gas contaminant removal in ion transport membrane systems

    DOEpatents

    Underwood, Richard Paul [Allentown, PA; Makitka, III, Alexander; Carolan, Michael Francis [Allentown, PA

    2012-04-03

    An oxygen ion transport membrane process wherein a heated oxygen-containing gas having one or more contaminants is contacted with a reactive solid material to remove the one or more contaminants. The reactive solid material is provided as a deposit on a support. The one or more contaminant compounds in the heated oxygen-containing gas react with the reactive solid material. The contaminant-depleted oxygen-containing gas is contacted with a membrane, and oxygen is transported through the membrane to provide transported oxygen.

  6. ANALYSIS OF FACTORS AFFECTING METHANE GAS RECOVERY FROM SIX LANDFILLS

    EPA Science Inventory

    The report gives results of a pilot study of six U.S. landfills that have methane (CH4) gas recovery systems. NOTE: The study was a first step in developing a field testing program to gather data to identify key variables that affect CH4 generation and to develop an empirical mod...

  7. Ion transport membrane reactor systems and methods for producing synthesis gas

    DOEpatents

    Repasky, John Michael

    2015-05-12

    Embodiments of the present invention provide cost-effective systems and methods for producing a synthesis gas product using a steam reformer system and an ion transport membrane (ITM) reactor having multiple stages, without requiring inter-stage reactant injections. Embodiments of the present invention also provide techniques for compensating for membrane performance degradation and other changes in system operating conditions that negatively affect synthesis gas production.

  8. Root aeration in wetland trees by pressurized gas transport.

    PubMed

    Grosse, W; Frye, J; Lattermann, S

    1992-04-01

    Tracer gas studies and oxygen uptake measurements have shown that pressurized gas transport improves oxygen supply to roots in the wetland tree species Taxodium distichum L. Rich. (Taxodiaceae), Betula pubescens J.F. Ehrh. (Betulaceae), and Populus tremula L. (Salicaceae), but not in Acer pseudoplatanus L. and Ilex aquifolium L., which are found in drier habitats. In the deciduous tree species Betula pubescens and Populus tremula, pressurized gas transport was most evident during the resting period, which is characterized by soil anoxia following waterlogging of the natural habitat. Because pressurized gas transport is found in species of distantly related families, we hypothesize that it helps wetland species survive the initial period of soil flooding before acclimation to waterlogging cccurs.

  9. Cloud draft structure and trace gas transport

    NASA Technical Reports Server (NTRS)

    Scala, John R.; Tao, Wei-Kuo; Thompson, Anne M.; Simpson, Joanne; Garstang, Michael; Pickering, Kenneth E.; Browell, Edward V.; Sachse, Glen W.; Gregory, Gerald L.; Torres, Arnold L.

    1990-01-01

    During the second Amazon Boundary Layer Experiment (ABLE 2B), meteorological observations, chemical measurements, and model simulations are utilized in order to interpret convective cloud draft structure and to analyze its role in transport and vertical distribution of trace gases. One-dimensional photochemical model results suggest that the observed poststorm changes in ozone concentration can be attributed to convective transports rather than photochemical production and the results of a two-dimensional time-dependent cloud model simulation are presented for the May 6, 1987 squall system. The mesoscale convective system exhibited evidence of significant midlevel detrainment in addition to transports to anvil heights. Chemical measurements of O3 and CO obtained in the convective environment are used to predict photochemical production within the troposphere and to corroborate the cloud model results.

  10. How does gas pass? Bubble transport through sediments

    NASA Astrophysics Data System (ADS)

    Fauria, K. E.; Rempel, A. W.

    2009-12-01

    The transport of gas through marine sediments is critical for both the formation and the ultimate fate of gas that is housed temporarily within hydrates. We monitored the gas flux produced by repeated bubble injections into a particle layer that was initially saturated with liquid. The size of ejected bubbles and the period between ejection events were different from the input size and period. Our observations clearly demonstrate bubble break-up as well as coalescence and the formation of preferred bubble migration pathways. We develop an elementary, semi-empirical model to interpret aspects of these results and predict the gas flux expected from a given size distribution of bubble inputs as a function of basic host sediment characteristics. Models of gas transport that use simple modifications to Darcy's law are not adequate to cope with bubble dynamics in the parameter regime that we observe.

  11. Case Study: Natural Gas Regional Transport Trucks

    SciTech Connect

    Laughlin, M.; Burnham, A.

    2016-08-01

    Learn about Ryder System, Inc.'s experience in deploying nearly 200 CNG and LNG heavy-duty trucks and construction and operation of L/CNG stations using ARRA funds. Using natural gas in its fleet, Ryder mitigated the effects of volatile fuel pricing and reduced lifecycle GHGs by 20% and petroleum by 99%.

  12. Enhanced serotonin transporter function during depression in seasonal affective disorder.

    PubMed

    Willeit, Matthäus; Sitte, Harald H; Thierry, Nikolaus; Michalek, Klaus; Praschak-Rieder, Nicole; Zill, Peter; Winkler, Dietmar; Brannath, Werner; Fischer, Michael B; Bondy, Brigitta; Kasper, Siegfried; Singer, Ernst A

    2008-06-01

    Decreased synaptic serotonin during depressive episodes is a central element of the monoamine hypothesis of depression. The serotonin transporter (5-HTT, SERT) is a key molecule for the control of synaptic serotonin levels. Here we aimed to detect state-related alterations in the efficiency of 5-HTT-mediated inward and outward transport in platelets of drug-free depressed patients suffering from seasonal affective disorder (SAD). 5-HTT turnover rate, a measure for the number of inward transport events per minute, and tyramine-induced, 5-HTT-mediated outward transport were assessed at baseline, after 4 weeks of bright light therapy, and in summer using a case-control design in a consecutive sample of 73 drug-free depressed patients with SAD and 70 nonseasonal healthy controls. Patients were drug-naive or medication-free for at least 6 months prior to study inclusion, females patients were studied in the follicular phase of the menstrual cycle. All participants were genotyped for a 5-HTT-promoter polymorphism (5-HTTLPR) to assess the influence of this polymorphism on 5-HTT parameters. Efficiency of 5-HTT-mediated inward (p=0.014) and outward (p=0.003) transport was enhanced in depressed patients. Both measures normalized toward control levels after therapy and in natural summer remission. Changes in outward transport showed a clear correlation with treatment response (rho=0.421, p=0.001). Changes in inward transport were mediated by changes in 5-HTT transport efficiency rather than affinity or density. 5-HTTLPR was not associated with any of the 5-HTT parameters. In sum, we conclude that the 5-HTT is in a hyperfunctional state during depression in SAD and normalizes after light therapy and in natural summer remission.

  13. Noble Gas Tracing of Fluid Transport in Shale Reservoirs

    NASA Astrophysics Data System (ADS)

    Heath, J. E.; Gardner, W. P.; Kuhlman, K. L.; Robinson, D. G.; Bauer, S. J.

    2014-12-01

    We investigate fluid transport mechanisms in a shale reservoir using natural noble gas tracers. Noble gas tracing is promising due to sensitivity of transport to: pore structure and sizes; phase partitioning between groundwater and liquid and gaseous hydrocarbons; and deformation from hydraulic fracturing and creation of surface area. A time-series of over thirty wellhead fluid samples were collected from two hydraulically-fractured wells with different oil-to-gas ratios, along with production data (i.e., flowrate and pressure). Tracer and production data sets can be combined to infer production flow regimes, to estimate reservoir transport parameters, and to improve forecasts of production decline. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000.

  14. Feed gas contaminant control in ion transport membrane systems

    DOEpatents

    Carolan, Michael Francis; Minford, Eric; Waldron, William Emil

    2009-07-07

    Ion transport membrane oxidation system comprising an enclosure having an interior and an interior surface, inlet piping having an internal surface and adapted to introduce a heated feed gas into the interior of the enclosure, and outlet piping adapted to withdraw a product gas from the interior of the enclosure; one or more planar ion transport membrane modules disposed in the interior of the enclosure, each membrane module comprising mixed metal oxide material; and a preheater adapted to heat a feed gas to provide the heated feed gas to the inlet piping, wherein the preheater comprises an interior surface. Any of the interior surfaces of the enclosure, the inlet piping, and the preheater may be lined with a copper-containing metal lining. Alternatively, any of the interior surfaces of the inlet piping and the preheater may be lined with a copper-containing metal lining and the enclosure may comprise copper.

  15. Hot-Gas Filter Testing with a Transport Reactor Gasifier

    SciTech Connect

    Swanson, M.L.; Hajicek, D.R.

    2002-09-18

    Today, coal supplies over 55% of the electricity consumed in the United States and will continue to do so well into the next century. One of the technologies being developed for advanced electric power generation is an integrated gasification combined cycle (IGCC) system that converts coal to a combustible gas, cleans the gas of pollutants, and combusts the gas in a gas turbine to generate electricity. The hot exhaust from the gas turbine is used to produce steam to generate more electricity from a steam turbine cycle. The utilization of advanced hot-gas particulate and sulfur control technologies together with the combined power generation cycles make IGCC one of the cleanest and most efficient ways available to generate electric power from coal. One of the strategic objectives for U.S. Department of Energy (DOE) IGCC research and development program is to develop and demonstrate advanced gasifiers and second-generation IGCC systems. Another objective is to develop advanced hot-gas cleanup and trace contaminant control technologies. One of the more recent gasification concepts to be investigated is that of the transport reactor gasifier, which functions as a circulating fluid-bed gasifier while operating in the pneumatic transport regime of solid particle flow. This gasifier concept provides excellent solid-gas contacting of relatively small particles to promote high gasification rates and also provides the highest coal throughput per unit cross-sectional area of any other gasifier, thereby reducing capital cost of the gasification island.

  16. Temperature-dependent gas transport performance of vertically aligned carbon nanotube/parylene composite membranes.

    PubMed

    Zhang, Lei; Yang, Junhe; Wang, Xianying; Zhao, Bin; Zheng, Guangping

    2014-01-01

    A novel composite membrane consisting of vertically aligned carbon nanotubes (CNTs) and parylene was successfully fabricated. Seamless filling of the spaces in CNT forests with parylene was achieved by a low-pressure chemical vapor deposition (CVD) technique and followed with the Ar/O2 plasma etching to expose CNT tips. Transport properties of various gases through the CNT/parylene membranes were explored. And gas permeances were independent on feed pressure in accordance with the Knudsen model, but the permeance values were over 60 times higher than that predicted by the Knudsen diffusion kinetics, which was attributed to specular momentum reflection inside smooth CNT pores. Gas permeances and enhancement factors over the Knudsen model firstly increased and then decreased with rising temperature, which confirmed the existence of non-Knudsen transport. And surface adsorption diffusion could affect the gas permeance at relatively low temperature. The gas permeance of the CNT/parylene composite membrane could be improved by optimizing operating temperature.

  17. Measurement of gas transport properties for chemical vapor infiltration

    SciTech Connect

    Starr, T.L.; Hablutzel, N.

    1996-12-01

    In the chemical vapor infiltration (CVI) process for fabricating ceramic matrix composites (CMCs), transport of gas phase reactant into the fiber preform is a critical step. The transport can be driven by pressure or by concentration. This report describes methods for measuring this for CVI preforms and partially infiltrated composites. Results are presented for Nicalon fiber cloth layup preforms and composites, Nextel fiber braid preforms and composites, and a Nicalon fiber 3-D weave composite. The results are consistent with a percolating network model for gas transport in CVI preforms and composites. This model predicts inherent variability in local pore characteristics and transport properties, and therefore, in local densification during processing; this may lead to production of gastight composites.

  18. A numerical study of gas transport in human lung models

    NASA Astrophysics Data System (ADS)

    Lin, Ching-Long; Hoffman, Eric A.

    2005-04-01

    Stable Xenon (Xe) gas has been used as an imaging agent for decades in its radioactive form, is chemically inert, and has been used as a ventilation tracer in its non radioactive form during computerized tomography (CT) imaging. Magnetic resonance imaging (MRI) using hyperpolarized Helium (He) gas and Xe has also emerged as a powerful tool to study regional lung structure and function. However, the present state of knowledge regarding intra-bronchial Xe and He transport properties is incomplete. As the use of these gases rapidly advances, it has become critically important to understand the nature of their transport properties and to, in the process, better understand the role of gas density in general in determining regional distribution of respiratory gases. In this paper, we applied the custom developed characteristic-Galerkin finite element method, which solves the three-dimensional (3D) incompressible variable-density Navier-Stokes equations, to study the transport of Xe and He in the CT-based human lung geometries, especially emulating the washin and washout processes. The realistic lung geometries are segmented and reconstructed from CT images as part of an effort to build a normative atlas (NIH HL-064368) documenting airway geometry over 4 decades of age in healthy and disease-state adult humans. The simulation results show that the gas transport process depends on the gas density and the body posture. The implications of these results on the difference between washin and washout time constants are discussed.

  19. Gas transport during in vitro and in vivo preclinical testing of inert gas therapies

    PubMed Central

    Katz, Ira; Palgen, Marc; Murdock, Jacqueline; Martin, Andrew R.; Farjot, Géraldine; Caillibotte, Georges

    2016-01-01

    New gas therapies using inert gases such as xenon and argon are being studied, which require in vitro and in vivo preclinical experiments. Examples of the kinetics of gas transport during such experiments are analyzed in this paper. Using analytical and numerical models, we analyze an in vitro experiment for gas transport to a 96 cell well plate and an in vivo delivery to a small animal chamber, where the key processes considered are the wash-in of test gas into an apparatus dead volume, the diffusion of test gas through the liquid media in a well of a cell test plate, and the pharmacokinetics in a rat. In the case of small animals in a chamber, the key variable controlling the kinetics is the chamber wash-in time constant that is a function of the chamber volume and the gas flow rate. For cells covered by a liquid media the diffusion of gas through the liquid media is the dominant mechanism, such that liquid depth and the gas diffusion constant are the key parameters. The key message from these analyses is that the transport of gas during preclinical experiments can be important in determining the true dose as experienced at the site of action in an animal or to a cell. PMID:27826419

  20. Gas transport during in vitro and in vivo preclinical testing of inert gas therapies.

    PubMed

    Katz, Ira; Palgen, Marc; Murdock, Jacqueline; Martin, Andrew R; Farjot, Géraldine; Caillibotte, Georges

    2016-03-01

    New gas therapies using inert gases such as xenon and argon are being studied, which require in vitro and in vivo preclinical experiments. Examples of the kinetics of gas transport during such experiments are analyzed in this paper. Using analytical and numerical models, we analyze an in vitro experiment for gas transport to a 96 cell well plate and an in vivo delivery to a small animal chamber, where the key processes considered are the wash-in of test gas into an apparatus dead volume, the diffusion of test gas through the liquid media in a well of a cell test plate, and the pharmacokinetics in a rat. In the case of small animals in a chamber, the key variable controlling the kinetics is the chamber wash-in time constant that is a function of the chamber volume and the gas flow rate. For cells covered by a liquid media the diffusion of gas through the liquid media is the dominant mechanism, such that liquid depth and the gas diffusion constant are the key parameters. The key message from these analyses is that the transport of gas during preclinical experiments can be important in determining the true dose as experienced at the site of action in an animal or to a cell.

  1. Heterogeneous processes affecting metal ion transport in the presence of organic ligands: Reactive transport modeling

    NASA Astrophysics Data System (ADS)

    Kantar, Cetin

    2007-04-01

    The development of models to accurately simulate metal ion transport through saturated systems under variable chemical conditions, e.g., in systems containing organic ligands (L) such as natural organic matter (NOM), has two essential aspects: (1) establishing the ability to simulate metal ion sorption to aquifer solids over a range of metal/ligand ratios; and (2) to incorporate this ability to simulate metal speciation over a range in chemical conditions (e.g., pH, ligand activity) into mass transport models. Modeling approaches to evaluate metal ion sorption and transport in the presence of NOM include: (1) isotherm-based transport models, and (2) multicomponent (MC) transport models. The accuracy of transport models depends on how well the chemical interactions affecting metal ion transport in the presence of organic ligands (e.g., metal/ligand complexation) are described in transport equations. The isotherm-based transport models often fail to accurately describe metal ion transport in the presence of NOM since these models treat NOM as a single solute despite the fact that NOM is a multicomponent mixture of subcomponents with different chemical and polyfunctional behavior. On the other hand, the calculations presented in this study suggest that a multicomponent reactive transport model, in conjunction with a mechanistic modeling approach for the description of metal ion binding by NOM in a manner conducive to the application of surface complexation modeling (SCM), can effectively be used as an important predictive tool in simulating metal ion sorption and transport under variable chemical conditions in the presence of NOM.

  2. 75 FR 2126 - Regulations Governing the Conduct of Open Seasons for Alaska Natural Gas Transportation Projects...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-01-14

    ... Gas Transportation Projects; Notice of Alaska Natural Gas Transportation Projects Open Season Pre... season for an Alaska Natural Gas Transportation Project. The Workshop is being hosted by the Alaska... docket, FERC enacted regulations under the Alaska Natural Gas Pipeline Act which established...

  3. Multimodel analysis of anisotropic diffusive tracer-gas transport in a deep arid unsaturated zone

    USGS Publications Warehouse

    Green, Christopher T.; Walvoord, Michelle Ann; Andraski, Brian J.; Striegl, Robert G.; Stonestrom, David A.

    2015-01-01

    Gas transport in the unsaturated zone affects contaminant flux and remediation, interpretation of groundwater travel times from atmospheric tracers, and mass budgets of environmentally important gases. Although unsaturated zone transport of gases is commonly treated as dominated by diffusion, the characteristics of transport in deep layered sediments remain uncertain. In this study, we use a multimodel approach to analyze results of a gas-tracer (SF6) test to clarify characteristics of gas transport in deep unsaturated alluvium. Thirty-five separate models with distinct diffusivity structures were calibrated to the tracer-test data and were compared on the basis of Akaike Information Criteria estimates of posterior model probability. Models included analytical and numerical solutions. Analytical models provided estimates of bulk-scale apparent diffusivities at the scale of tens of meters. Numerical models provided information on local-scale diffusivities and feasible lithological features producing the observed tracer breakthrough curves. The combined approaches indicate significant anisotropy of bulk-scale diffusivity, likely associated with high-diffusivity layers. Both approaches indicated that diffusivities in some intervals were greater than expected from standard models relating porosity to diffusivity. High apparent diffusivities and anisotropic diffusivity structures were consistent with previous observations at the study site of rapid lateral transport and limited vertical spreading of gas-phase contaminants. Additional processes such as advective oscillations may be involved. These results indicate that gases in deep, layered unsaturated zone sediments can spread laterally more quickly, and produce higher peak concentrations, than predicted by homogeneous, isotropic diffusion models.

  4. Transformative Reduction of Transportation Greenhouse Gas Emissions. Opportunities for Change in Technologies and Systems

    SciTech Connect

    Vimmerstedt, Laura; Brown, Austin; Newes, Emily; Markel, Tony; Schroeder, Alex; Zhang, Yimin; Chipman, Peter; Johnson, Shawn

    2015-04-30

    The transportation sector is changing, influenced by concurrent, ongoing, dynamic trends that could dramatically affect the future energy landscape, including effects on the potential for greenhouse gas emissions reductions. Battery cost reductions and improved performance coupled with a growing number of electric vehicle model offerings are enabling greater battery electric vehicle market penetration, and advances in fuel cell technology and decreases in hydrogen production costs are leading to initial fuel cell vehicle offerings. Radically more efficient vehicles based on both conventional and new drivetrain technologies reduce greenhouse gas emissions per vehicle-mile. Net impacts also depend on the energy sources used for propulsion, and these are changing with increased use of renewable energy and unconventional fossil fuel resources. Connected and automated vehicles are emerging for personal and freight transportation systems and could increase use of low- or non-emitting technologies and systems; however, the net effects of automation on greenhouse gas emissions are uncertain. The longstanding trend of an annual increase in transportation demand has reversed for personal vehicle miles traveled in recent years, demonstrating the possibility of lower-travel future scenarios. Finally, advanced biofuel pathways have continued to develop, highlighting low-carbon and in some cases carbon-negative fuel pathways. We discuss the potential for transformative reductions in petroleum use and greenhouse gas emissions through these emerging transportation-sector technologies and trends and present a Clean Transportation Sector Initiative scenario for such reductions, which are summarized in Table ES-1.

  5. Investigating ebullition in a sand column using dissolved gas analysis and reactive transport modeling

    USGS Publications Warehouse

    Amos, Richard T.; Mayer, K. Ulrich

    2006-01-01

    Ebullition of gas bubbles through saturated sediments can enhance the migration of gases through the subsurface, affect the rate of biogeochemical processes, and potentially enhance the emission of important greenhouse gases to the atmosphere. To better understand the parameters controlling ebullition, methanogenic conditions were produced in a column experiment and ebullition through the column was monitored and quantified through dissolved gas analysis and reactive transport modeling. Dissolved gas analysis showed rapid transport of CH4 vertically through the column at rates several times faster than the bromide tracer and the more soluble gas CO2, indicating that ebullition was the main transport mechanism for CH4. An empirically derived formulation describing ebullition was integrated into the reactive transport code MIN3P allowing this process to be investigated on the REV scale in a complex geochemical framework. The simulations provided insights into the parameters controlling ebullition and show that, over the duration of the experiment, 36% of the CH4 and 19% of the CO2 produced were transported to the top of the column through ebullition.

  6. Gas production and transport in artificial sludge depots.

    PubMed

    van Kessel, T; van Kesteren, W G M

    2002-01-01

    This paper presents a study to determine the impact of gas production in dredging sludge on the storage capacity of artificial sludge depots. Gas is produced as a result of the decomposition of organic material present in dredging spoil. This process, in which methane and carbon dioxide are formed, may lead to expansion of sludge layers, partly or even completely counterbalancing consolidation. The study shows that, even with a very conservative estimation of the rate of gas production, accumulation of gas occurs as convective and diffusive transport proceed very slowly. Nucleation of gas bubbles occurs already at a limited oversaturation of pore water. During their growth, bubbles push aside the surrounding grain matrix. Resulting stresses may initiate cracks around bubbles. If these cracks join, they may form channels stretching out to the depot surface and along which gas may escape. However, channels are only stable to a limited depth below which bubble accumulation may continue. The gas content at which sufficient cracks and channels are formed to balance the rate of gas production with the rate of outflow strongly depends on the constitutive properties of the dredging sludge considered. In sludge with a high shear strength (> 10 kPa), stable channels are created already at low deformations. However, a large expansion may occur in sludge with a low strength. The present study shows that accumulation of gas may continue until a bulk density less than that of water is attained. This is equivalent to a gas fraction of about 25-37%, depending on the initial water content of the sludge. Only then can gas escape as a result of instabilities in the sediment matrix. This should be well taken into account during the design and management of artificial depots.

  7. Dissolved gas exsolution to enhance gas production and transport during bench-scale electrical resistance heating

    NASA Astrophysics Data System (ADS)

    Hegele, P. R.; Mumford, K. G.

    2015-05-01

    Condensation of volatile organic compounds in colder zones can be detrimental to the performance of an in situ thermal treatment application for the remediation of chlorinated solvent source zones. A novel method to increase gas production and limit convective heat loss in more permeable, potentially colder, zones involves the injection and liberation of dissolved gas from solution during heating. Bench-scale electrical resistance heating experiments were performed with a dissolved carbon dioxide and sodium chloride solution to investigate exsolved gas saturations and transport regimes at elevated, but sub-boiling, temperatures. At sub-boiling temperatures, maximum exsolved gas saturations of Sg = 0.12 were attained, and could be sustained when the carbon dioxide solution was injected during heating rather than emplaced prior to heating. This gas saturation was estimated to decrease groundwater relative permeability to krw = 0.64. Discontinuous gas transport was observed above saturations of Sg = 0.07, demonstrating the potential of exsolved CO2 to bridge vertical gas transport through colder zones.

  8. Impurity transport through a strongly interacting bosonic quantum gas

    SciTech Connect

    Johnson, T. H.; Clark, S. R.; Bruderer, M.; Jaksch, D.

    2011-08-15

    Using near-exact numerical simulations, we study the propagation of an impurity through a one-dimensional Bose lattice gas for varying bosonic interaction strengths and filling factors at zero temperature. The impurity is coupled to the Bose gas and confined to a separate tilted lattice. The precise nature of the transport of the impurity is specific to the excitation spectrum of the Bose gas, which allows one to measure properties of the Bose gas nondestructively, in principle, by observing the impurity; here we focus on the spatial and momentum distributions of the impurity as well as its reduced density matrix. For instance, we show it is possible to determine whether the Bose gas is commensurately filled as well as the bandwidth and gap in its excitation spectrum. Moreover, we show that the impurity acts as a witness to the crossover of its environment from the weakly to the strongly interacting regime, i.e., from a superfluid to a Mott insulator or Tonks-Girardeau lattice gas, and the effects on the impurity in both of these strongly interacting regimes are clearly distinguishable. Finally, we find that the spatial coherence of the impurity is related to its propagation through the Bose gas.

  9. Lattice gas automata for flow and transport in geochemical systems

    SciTech Connect

    Janecky, D.R.; Chen, S.; Dawson, S.; Eggert, K.C.; Travis, B.J.

    1992-01-01

    Lattice gas automata models are described, which couple solute transport with chemical reactions at mineral surfaces within pore networks. Diffusion in a box calculations are illustrated, which compare directly with Fickian diffusion. Chemical reactions at solid surfaces, including precipitation/dissolution, sorption, and catalytic reaction, can be examined with the model because hydrodynamic transport, solute diffusion and mineral surface processes are all treated explicitly. The simplicity and flexibility of the approach provides the ability to study the interrelationship between fluid flow and chemical reactions in porous materials, at a level of complexity that has not previously been computationally possible.

  10. Lattice gas automata for flow and transport in geochemical systems

    SciTech Connect

    Janecky, D.R.; Chen, S.; Dawson, S.; Eggert, K.C.; Travis, B.J.

    1992-05-01

    Lattice gas automata models are described, which couple solute transport with chemical reactions at mineral surfaces within pore networks. Diffusion in a box calculations are illustrated, which compare directly with Fickian diffusion. Chemical reactions at solid surfaces, including precipitation/dissolution, sorption, and catalytic reaction, can be examined with the model because hydrodynamic transport, solute diffusion and mineral surface processes are all treated explicitly. The simplicity and flexibility of the approach provides the ability to study the interrelationship between fluid flow and chemical reactions in porous materials, at a level of complexity that has not previously been computationally possible.

  11. The Lorentz gas in Kaluza's MHD: Transport equations

    NASA Astrophysics Data System (ADS)

    Sandoval-Villalbazo, Alfredo; Sagaceta-Mejia, Alma Rocio; Mondragon-Suarez, Jose Humberto

    2016-11-01

    Relativistic kinetic theory is applied to the study of the transport processes present in a Lorentz gas, using a geometric five-dimensional space-time. While the conventional transport equations are recovered in the Newtonian limit, it is shown that relativistic corrections to the conduction and diffusion fluxes arise within this formalism. A brief review of the conceptual advantages of the Kaluza-type approach to magnetohydrodynamics is also given. The authors acknowledge support from CONACyT through Grant CB2011/167563.

  12. Possible Pathways for Increasing Natural Gas Use for Transportation (Presentation)

    SciTech Connect

    Zigler, B.

    2014-10-01

    A collaborative partnership of DOE National Laboratories is working with DOE to identify critical RD&D needs to significantly increase the speed and breadth of NG uptake into the transportation sector. Drivers for increased utilization of natural gas for transportation are discussed. Key needs in research, development, and deployment are proposed, as well as possible pathways to address those needs. This presentation is intended to serve as a catalyst to solicit input from stakeholders regarding what technical areas they deem the most important.

  13. Transport coefficients of solid particles immersed in a viscous gas.

    PubMed

    Garzó, Vicente; Fullmer, William D; Hrenya, Christine M; Yin, Xiaolong

    2016-01-01

    Transport properties of a suspension of solid particles in a viscous gas are studied. The dissipation in such systems arises from two sources: inelasticity in particle collisions and viscous dissipation due to the effect of the gas phase on the particles. Here we consider a simplified case in which the mean relative velocity between the gas and solid phases is taken to be zero, such that "thermal drag" is the only remaining gas-solid interaction. Unlike the previous, more general, treatment of the drag force [Garzó et al., J. Fluid Mech. 712, 129 (2012)]JFLSA70022-112010.1017/jfm.2012.404, here we take into account contributions to the (scaled) transport coefficients η^{*} (shear viscosity), κ^{*} (thermal conductivity), and μ^{*} (Dufour-like coefficient) coming from the temperature dependence of the (dimensionless) friction coefficient γ^{*} characterizing the amplitude of the drag force. At moderate densities, the thermal drag model (which is based on the Enskog kinetic equation) is solved by means of the Chapman-Enskog method and the Navier-Stokes transport coefficients are determined in terms of the coefficient of restitution, the solid volume fraction, and the friction coefficient. The results indicate that the effect of the gas phase on η^{*} and μ^{*} is non-negligible (especially in the case of relatively dilute systems) while the form of κ^{*} is the same as the one obtained in the dry granular limit. Finally, as an application of these results, a linear stability analysis of the hydrodynamic equations is carried out to analyze the conditions for stability of the homogeneous cooling state. A comparison with direct numerical simulations shows a good agreement for conditions of practical interest.

  14. Transport of a lattice gas under continuous measurement

    NASA Astrophysics Data System (ADS)

    Cheung, Hil F. H.; Patil, Yogesh Sharad; Madjarov, Ivaylo S.; Chen, Huiyao Y.; Vengalattore, Mukund

    2016-05-01

    The act of measurement has a profound consequence on a quantum system. While this backaction has hitherto been discussed as a limitation to the precision of measurements, it is increasingly being appreciated that measurement backaction is a powerful means of quantum control. We have previously demonstrated that backaction from position measurement can modify the coherent tunneling rate of a lattice gas through the Quantum Zeno effect. By suitably designing measurement landscapes we can control the transport properties of the lattice gas. We describe a quantitative study of lattice gas dynamics under continuous quantum measurement in the context of a quantum to classical transition where the atom dynamics goes from a quantum walk at low measurement strengths to classical diffusion at high measurement strengths. We further discuss the prospect of using disorder measurement landscapes to realize a new form of Anderson localization. This work is supported by the ARO MURI on non-equilibrium dynamics.

  15. Tau phosphorylation affects its axonal transport and degradation

    PubMed Central

    Rodríguez-Martín, Teresa; Cuchillo-Ibáñez, Inmaculada; Noble, Wendy; Nyenya, Fanon; Anderton, Brian H.; Hanger, Diane P.

    2013-01-01

    Phosphorylated forms of microtubule-associated protein tau accumulate in neurofibrillary tangles in Alzheimer's disease. To investigate the effects of specific phosphorylated tau residues on its function, wild type or phosphomutant tau was expressed in cells. Elevated tau phosphorylation decreased its microtubule binding and bundling, and increased the number of motile tau particles, without affecting axonal transport kinetics. In contrast, reducing tau phosphorylation enhanced the amount of tau bound to microtubules and inhibited axonal transport of tau. To determine whether differential tau clearance is responsible for the increase in phosphomimic tau, we inhibited autophagy in neurons which resulted in a 3-fold accumulation of phosphomimic tau compared with wild type tau, and endogenous tau was unaffected. In autophagy-deficient mouse embryonic fibroblasts, but not in neurons, proteasomal degradation of phosphomutant tau was also reduced compared with wild type tau. Therefore, autophagic and proteasomal pathways are involved in tau degradation, with autophagy appearing to be the primary route for clearing phosphorylated tau in neurons. Defective autophagy might contribute to the accumulaton of tau in neurodegenerative diseases. PMID:23601672

  16. Reactive Gas transport in soil: Kinetics versus Local Equilibrium Approach

    NASA Astrophysics Data System (ADS)

    Geistlinger, Helmut; Jia, Ruijan

    2010-05-01

    Gas transport through the unsaturated soil zone was studied using an analytical solution of the gas transport model that is mathematically equivalent to the Two-Region model. The gas transport model includes diffusive and convective gas fluxes, interphase mass transfer between the gas and water phase, and biodegradation. The influence of non-equilibrium phenomena, spatially variable initial conditions, and transient boundary conditions are studied. The objective of this paper is to compare the kinetic approach for interphase mass transfer with the standard local equilibrium approach and to find conditions and time-scales under which the local equilibrium approach is justified. The time-scale of investigation was limited to the day-scale, because this is the relevant scale for understanding gas emission from the soil zone with transient water saturation. For the first time a generalized mass transfer coefficient is proposed that justifies the often used steady-state Thin-Film mass transfer coefficient for small and medium water-saturated aggregates of about 10 mm. The main conclusion from this study is that non-equilibrium mass transfer depends strongly on the temporal and small-scale spatial distribution of water within the unsaturated soil zone. For regions with low water saturation and small water-saturated aggregates (radius about 1 mm) the local equilibrium approach can be used as a first approximation for diffusive gas transport. For higher water saturation and medium radii of water-saturated aggregates (radius about 10 mm) and for convective gas transport, the non-equilibrium effect becomes more and more important if the hydraulic residence time and the Damköhler number decrease. Relative errors can range up to 100% and more. While for medium radii the local equilibrium approach describes the main features both of the spatial concentration profile and the time-dependence of the emission rate, it fails completely for larger aggregates (radius about 100 mm

  17. Field measurements of tracer gas transport by barometric pumping

    SciTech Connect

    Lagus, P.L.; McKinnis, W.B.; Hearst, J.R.; Burkhard, N.R.; Smith, C.F.

    1994-07-28

    Vertical gas motions induced by barometric pressure variations can carry radioactive gases out of the rubblized region produced by an underground nuclear explosion, through overburden rock, into the atmosphere. To better quantify transit time and amount of transport, field experiments were conducted at two sites on Pahute Mesa, Kapelli and Tierra, where radioactive gases had been earlier detected in surface cracks. At each site, two tracer gases were injected into the rubblized chimney 300-400 m beneath the surface and their arrival was monitored by concentration measurements in gas samples extracted from shallow collection holes. The first ``active`` tracer was driven by a large quantity of injected air; the second ``passive`` tracer was introduced with minimal gas drive to observe the natural transport by barometric pumping. Kapelli was injected in the fall of 1990, followed by Tierra in the fall of 1991. Data was collected at both sites through the summer of 1993. At both sites, no surface arrival of tracer was observed during the active phase of the experiment despite the injection of several million cubic feet of air, suggesting that cavity pressurization is likely to induce horizontal transport along high permeability layers rather than vertical transport to the surface. In contrast, the vertical pressure gradients associated with barometric pumping brought both tracers to the surface in comparable concentrations within three months at Kapelli, whereas 15 months elapsed before surface arrival at Tierra. At Kapelli, a quasisteady pumping regime was established, with tracer concentrations in effluent gases 1000 times smaller than concentrations thought to exist in the chimney. Tracer concentrations observed at Tierra were typically an order of magnitude smaller. Comparisons with theoretical calculations suggest that the gases are traveling through {approximately}1 millimeter vertical fractures spaced 2 to 4 meters apart. 6 refs., 18 figs., 3 tabs.

  18. Radionuclide Gas Transport through Nuclear Explosion-Generated Fracture Networks

    NASA Astrophysics Data System (ADS)

    Jordan, Amy B.; Stauffer, Philip H.; Knight, Earl E.; Rougier, Esteban; Anderson, Dale N.

    2015-12-01

    Underground nuclear weapon testing produces radionuclide gases which may seep to the surface. Barometric pumping of gas through explosion-fractured rock is investigated using a new sequentially-coupled hydrodynamic rock damage/gas transport model. Fracture networks are produced for two rock types (granite and tuff) and three depths of burial. The fracture networks are integrated into a flow and transport numerical model driven by surface pressure signals of differing amplitude and variability. There are major differences between predictions using a realistic fracture network and prior results that used a simplified geometry. Matrix porosity and maximum fracture aperture have the greatest impact on gas breakthrough time and window of opportunity for detection, with different effects between granite and tuff simulations highlighting the importance of accurately simulating the fracture network. In particular, maximum fracture aperture has an opposite effect on tuff and granite, due to different damage patterns and their effect on the barometric pumping process. From stochastic simulations using randomly generated hydrogeologic parameters, normalized detection curves are presented to show differences in optimal sampling time for granite and tuff simulations. Seasonal and location-based effects on breakthrough, which occur due to differences in barometric forcing, are stronger where the barometric signal is highly variable.

  19. Radionuclide gas transport through nuclear explosion-generated fracture networks

    SciTech Connect

    Jordan, Amy B.; Stauffer, Philip H.; Knight, Earl E.; Rougier, Esteban; Anderson, Dale N.

    2015-12-17

    Underground nuclear weapon testing produces radionuclide gases which may seep to the surface. Barometric pumping of gas through explosion-fractured rock is investigated using a new sequentially-coupled hydrodynamic rock damage/gas transport model. Fracture networks are produced for two rock types (granite and tuff) and three depths of burial. The fracture networks are integrated into a flow and transport numerical model driven by surface pressure signals of differing amplitude and variability. There are major differences between predictions using a realistic fracture network and prior results that used a simplified geometry. Matrix porosity and maximum fracture aperture have the greatest impact on gas breakthrough time and window of opportunity for detection, with different effects between granite and tuff simulations highlighting the importance of accurately simulating the fracture network. In particular, maximum fracture aperture has an opposite effect on tuff and granite, due to different damage patterns and their effect on the barometric pumping process. From stochastic simulations using randomly generated hydrogeologic parameters, normalized detection curves are presented to show differences in optimal sampling time for granite and tuff simulations. In conclusion, seasonal and location-based effects on breakthrough, which occur due to differences in barometric forcing, are stronger where the barometric signal is highly variable.

  20. Radionuclide Gas Transport through Nuclear Explosion-Generated Fracture Networks

    PubMed Central

    Jordan, Amy B.; Stauffer, Philip H.; Knight, Earl E.; Rougier, Esteban; Anderson, Dale N.

    2015-01-01

    Underground nuclear weapon testing produces radionuclide gases which may seep to the surface. Barometric pumping of gas through explosion-fractured rock is investigated using a new sequentially-coupled hydrodynamic rock damage/gas transport model. Fracture networks are produced for two rock types (granite and tuff) and three depths of burial. The fracture networks are integrated into a flow and transport numerical model driven by surface pressure signals of differing amplitude and variability. There are major differences between predictions using a realistic fracture network and prior results that used a simplified geometry. Matrix porosity and maximum fracture aperture have the greatest impact on gas breakthrough time and window of opportunity for detection, with different effects between granite and tuff simulations highlighting the importance of accurately simulating the fracture network. In particular, maximum fracture aperture has an opposite effect on tuff and granite, due to different damage patterns and their effect on the barometric pumping process. From stochastic simulations using randomly generated hydrogeologic parameters, normalized detection curves are presented to show differences in optimal sampling time for granite and tuff simulations. Seasonal and location-based effects on breakthrough, which occur due to differences in barometric forcing, are stronger where the barometric signal is highly variable. PMID:26676058

  1. Surface Diffusion Effect on Gas Transport in Nanoporous Materials

    NASA Astrophysics Data System (ADS)

    Hori, Takuma; Yoshimoto, Yuta; Takagi, Shu; Kinefuchi, Ikuya

    2016-11-01

    Polymer electrolyte fuel cells are one of the promising candidates for power sources of electric vehicles. For further improvement of their efficiency in high current density operation, a better understanding of oxygen flow inside the cells, which have micro- or nanoporous structures, is necessary. Molecular simulations such as the direct simulation of Monte Carlo (DSMC) are necessary to elucidate flow phenomena in micro- or nanostructures since the Knudsen number is close to unity. Our previous report showed that the oxygen diffusion resistance in porous structures with a characteristic pore size of 100 nm calculated by DSMC agrees well with that measured experimentally. On the other hand, when it comes to the transport in structures with much smaller pore sizes, it is expected that the surface diffusion has a significant impact on gas transport because of their higher specific surface area. Here we present the calculation of gas transport in porous structures with considering surface diffusion. The numerical porous structure models utilized in our simulations are constructed from three-dimensional imaging of materials. The effect of the distance of random walk on the total diffusion resistance in the structures is discussed. This paper is based on results obtained from a project commissioned by the New Energy and Industrial Development Organization (NEDO).

  2. Essays on alternative energy policies affecting the US transportation sector

    NASA Astrophysics Data System (ADS)

    O'Rear, Eric G.

    This dissertation encompasses three essays evaluating the impacts of different policies targeting the greenhouse gas (GHG) emissions, fuel demands, etc. of the transportation sector. Though there are some similarities across the three chapters, each essay stands alone as an independent work. The 2010 US EPA MARKAL model is used in each essay to evaluate policy effects. Essay 1 focuses on the recent increases in Corporate Average Fuel Economy (CAFE) standards, and the implications of a "rebound effect." These increases are compared to a carbon tax generating similar reductions in system-wide emissions. As anticipated, the largest reductions in fuel use by light-duty vehicles (LDV) and emissions are achieved under CAFE. Consideration of the rebound effect does little to distort CAFE benefits. Our work validates many economists' belief that a carbon tax is a more efficient approach. However, because the tax takes advantage of cheaper abatement opportunities in other sectors, reductions in transportation emissions will be much lower than what we observe with CAFE. Essay 2 compares CAFE increases with what some economists suggest would be a much more "efficient" alternative -- a system-wide oil tax internalizing some environmental externalities. Because oil taxes are likely to be implemented in addition to CAFE standards, we consider a combined policy case reflecting this. Our supplementary analysis approximates the appropriate tax rates to produce similar reductions in oil demands as CAFE (CAFE-equivalent tax rates). We discover that taxes result in greater and more cost-effective reductions in system-wide emissions and net oil imports than CAFE. The current fuel tax system is compared to three versions of a national vehicle miles traveled (VMT) tax charged to all LDVs in Essay 3. VMT taxes directly charge motorists for each mile driven and help to correct the problem of eroding tax revenues given the failure of today's fuel taxes to adjust with inflation. Results

  3. Methane transport and emissions from soil as affected by water table and vascular plants

    PubMed Central

    2013-01-01

    Background The important greenhouse gas (GHG) methane is produced naturally in anaerobic wetland soils. By affecting the production, oxidation and transport of methane to the atmosphere, plants have a major influence upon the quantities emitted by wetlands. Different species and functional plant groups have been shown to affect these processes differently, but our knowledge about how these effects are influenced by abiotic factors such as water regime and temperature remains limited. Here we present a mesocosm experiment comparing eight plant species for their effects on internal transport and overall emissions of methane under contrasting hydrological conditions. To quantify how much methane was transported internally through plants (the chimney effect), we blocked diffusion from the soil surface with an agar seal. Results We found that graminoids caused higher methane emissions than forbs, although the emissions from mesocosms with different species were either lower than or comparable to those from control mesocosms with no plant (i.e. bare soil). Species with a relatively greater root volume and a larger biomass exhibited a larger chimney effect, though overall methane emissions were negatively related to plant biomass. Emissions were also reduced by lowering the water table. Conclusions We conclude that plant species (and functional groups) vary in the degree to which they transport methane to the atmosphere. However, a plant with a high capacity to transport methane does not necessarily emit more methane, as it may also cause more rhizosphere oxidation of methane. A shift in plant species composition from graminoids to forbs and/or from low to high productive species may lead to reduction of methane emissions. PMID:24010540

  4. Evolution of natural gas composition: Predictive multi-phase reaction-transport modeling

    SciTech Connect

    Ortoleva, P.J.; Chang, K.A.; Maxwell, J.M.

    1995-12-31

    A computational modeling approach is used to investigate reaction and transport processes affecting natural gas composition over geological time. Three basic stages are integrated -- gas generation from organic solids or liquids, interactions during source rock expulsion to the reservoir and reactions within the reservoir. Multi-phase dynamics is handled by solving the fully coupled problem of phase-to-phase transfer, intra-phase organic and inorganic reactions and redox and other reactions between fluid phase molecules and minerals. Effects of capillarity and relative permeability are accounted for. Correlations will be determined between gas composition, temperature history, the mineralogy of rocks with which the gas was in contact and the composition of source organic phases. Questions of H{sub 2}S scavenging by oxidizing minerals and the production or removal of CO{sub 2} are focused upon. Our three spatial dimensional, reaction-transport simulation approach has great promise for testing general concepts and as a practical tool for the exploration and production of natural gas.

  5. A heterogeneous model for gas transport in carbon molecular sieves.

    PubMed

    Ding, L P; Yuan, Y X; Farooq, S; Bhatia, S K

    2005-01-18

    A dual resistance model with distribution of either barrier or pore diffusional activation energy is proposed in this work for gas transport in carbon molecular sieve (CMS) micropores. This is a novel approach in which the equilibrium is homogeneous, but the kinetics is heterogeneous. The model seems to provide a possible explanation for the concentration dependence of the thermodynamically corrected barrier and pore diffusion coefficients observed in previous studies from this laboratory on gas diffusion in CMS. The energy distribution is assumed to follow the gamma distribution function. It is shown that the energy distribution model can fully capture the behavior described by the empirical model established in earlier studies to account for the concentration dependence of thermodynamically corrected barrier and pore diffusion coefficients. A methodology is proposed for extracting energy distribution parameters, and it is further shown that the extracted energy distribution parameters can effectively predict integral uptake and column breakthrough profiles over a wide range of operating pressures.

  6. Gas gangrene without wound: both lower extremities affected simultaneously.

    PubMed

    Lu, Jun; Wu, Xiao-Tao; Kong, Xiang-Fei; Tang, Wen-Hao; Cheng, Jian-Ming; Wang, Hai-Liang

    2008-10-01

    Gas gangrene is a necrotizing soft tissue infection characterized by muscular necrosis and gas formation. It develops quickly and can cause septic shock and death. In adults, gas gangrene used to be a well-known complication of war wounds. Recently, cases of spontaneous or nontraumatic gas gangrene have been reported in both adults and children. We report a case of nontraumatic gas gangrene involving both the lower extremities simultaneously. Pathogenesis of this fatal soft tissue infection is discussed.We also review the diagnosis and treatment aspects of this entity.

  7. Seismic reflection characteristics of naturally-induced subsidence affecting transportation

    USGS Publications Warehouse

    Miller, R.D.; Xia, J.; Steeples, D.W.

    2009-01-01

    High-resolution seismic reflections have been used effectively to investigate sinkholes formed from the dissolution of a bedded salt unit found throughout most of Central Kansas. Surface subsidence can have devastating effects on transportation structures. Roads, rails, bridges, and pipelines can even be dramatically affected by minor ground instability. Areas susceptible to surface subsidence can put public safety at risk. Subsurface expressions significantly larger than surface depressions are consistently observed on seismic images recorded over sinkholes in Kansas. Until subsidence reaches the ground surface, failure appears to be controlled by compressional forces evidenced by faults with reverse orientation. Once a surface depression forms or dissolution of the salt slows or stops, subsidence structures are consistent with a tensional stress environment with prevalent normal faults. Detecting areas of rapid subsidence potential, prior to surface failure, is the ultimate goal of any geotechnical survey where the ground surface is susceptible to settling. Seismic reflection images have helped correlate active subsidence to dormant paleofeatures, project horizontal growth of active sinkholes based on subsurface structures, and appraise the risk of catastrophic failure. ?? China University of Geosciences (Wuhan) and Springer-Verlag GmbH 2009.

  8. Noble gas transport during devolatilization of oceanic crust

    NASA Astrophysics Data System (ADS)

    Jackson, C.; Smye, A.; Shuster, D. L.; Parman, S. W.; Kelley, S. P.; Hesse, M. A.; Cooper, R. F.

    2014-12-01

    Here we examine the role of slab dehydration in determining the elemental pattern of recycled noble gases. As a first step, we apply newly reported measurements of He-Ne-Ar (light noble gases) solubility and diffusivity in amphibole to parameterize a 1D diffusive-reaction transport model that simulates noble gas behavior during fluid loss from down-going oceanic crust. Recent experiments demonstrate that noble gases are highly soluble in ring-structured minerals, such as amphibole and other common hydrothermal products in slabs [1]. These results suggest that ring-structured minerals have the potential to strongly influence the budget of noble gases input into subduction zones and the elemental fractionations associated with volatile loss from slabs New measurements of He-Ne-Ar solubility in a suite of amphiboles have been completed utilizing the methodology described in [1]. These new measurements confirm that all light noble gases are highly soluble in amphibole, and that noble gas solubility correlates with the availability of unoccupied ring sites. New experimental measurements of He and Ne diffusivity have also been completed using a step-degassing approach at the Berkeley Geochronology Center. These measurements suggest that vacant ring sites in amphibole act to slow noble gas diffusion. We combine the newly acquired He and Ne diffusivity measurements with literature values for Ar diffusivity [2] to parameterize the diffusive-reaction transport model. Application of these data to the diffusive-reaction transport model yields several new insights. The relative mobility of Ne compared to Ar allows for efficient extraction of Ne from "hot" slabs by shallow depths (<50 km), while Ar is effectively retained to deeper depths, potentially past sub-arc conditions. Noble gas partition coefficients sharply increase with depth, following their increasing non-ideality in supercritical fluids, causing noble gases to partition back into minerals from any fluids retained in

  9. Transport properties in semiconductor-gas discharge electronic devices

    NASA Astrophysics Data System (ADS)

    Sadiq, Y.; (Yücel) Kurt, H.; Albarzanji, A. O.; Alekperov, S. D.; Salamov, B. G.

    2009-09-01

    Nonlinear electrical transport of semi-insulating (SI) GaAs detector in semiconductor-gas discharge IR image converter (SGDIC) are studied experimentally for a wide range of the gas pressures ( p = 28-55 Torr), interelectrode distances ( d = 445-525 μm) and inner electrode diameters ( D = 12-22 mm) of photocathode. The destabilization of homogeneous state observed in a planar dc-driven structure is due to nonlinear transport properties of GaAs photocathode. Experimental investigation of electrical instability in SGDIC structure was analyzed using hysteresis, N-shaped negative differential conductivity (NDC) current voltage characteristics (CVC) and dynamic behavior of current in a wide range of feeding voltage ( U = 590-1000 V) under different IR light intensities incident on cathode material. It is established that hysteresis are related to electron capture and emission from EL2 deep center on the detector substrate. We have experimentally investigated domain velocity and electron mobility based on well-understood transferred electron effect (TEE) for abovementioned nonlinear electrical characteristics of SI GaAs. The experimental findings are in good agreement with estimated results reported by other independent authors.

  10. Radionuclide gas transport through nuclear explosion-generated fracture networks

    DOE PAGES

    Jordan, Amy B.; Stauffer, Philip H.; Knight, Earl E.; ...

    2015-12-17

    Underground nuclear weapon testing produces radionuclide gases which may seep to the surface. Barometric pumping of gas through explosion-fractured rock is investigated using a new sequentially-coupled hydrodynamic rock damage/gas transport model. Fracture networks are produced for two rock types (granite and tuff) and three depths of burial. The fracture networks are integrated into a flow and transport numerical model driven by surface pressure signals of differing amplitude and variability. There are major differences between predictions using a realistic fracture network and prior results that used a simplified geometry. Matrix porosity and maximum fracture aperture have the greatest impact on gasmore » breakthrough time and window of opportunity for detection, with different effects between granite and tuff simulations highlighting the importance of accurately simulating the fracture network. In particular, maximum fracture aperture has an opposite effect on tuff and granite, due to different damage patterns and their effect on the barometric pumping process. From stochastic simulations using randomly generated hydrogeologic parameters, normalized detection curves are presented to show differences in optimal sampling time for granite and tuff simulations. In conclusion, seasonal and location-based effects on breakthrough, which occur due to differences in barometric forcing, are stronger where the barometric signal is highly variable.« less

  11. Laboratory Measurements of Fluid Transport Properties on Tight Gas Sandstones and Applications

    NASA Astrophysics Data System (ADS)

    Albrecht, Daniel; Reitenbach, Viktor

    2014-05-01

    Deep gas reservoirs are of great interest for the E&P industry. Large areas of such reservoirs have permeabilities below 1 mD. The reservoir rocks in these areas show a strong stress sensitivity of the fluid transport properties and a considerable productivity decline due to changing stress conditions during the production process. For correct modeling and simulation of Tight Gas reservoirs it is important to know the behavior of the fluid transport properties under the changing stress condition the reservoir experiences. In several measurement series the effects of changing overburden and pore pressure on Rotliegend sandstone samples from north German Tight Gas reservoirs have been quantified and used to set up correlation functions. With the correlation functions from the own measurements and additional data and correlations from literature a Rock Data Catalog has been developed as tool to help reservoir engineers with modeling and simulation of such reservoirs. The Rock Data Catalog consists of the Rock Database and the Correlation Module. The Rock Database contains general and petrophysical rock data. The Correlation Module uses this data to generate secondary data of e.g. in-situ capillary and hydraulic rock properties with appropriate correlation functions. Viability of the economic gas production from Tight Gas Reservoirs strongly depends on reservoir quality. Therefore identification of high quality reservoir parts or so called Sweet Spots for placing production wells and planning hydraulic fracturing stimulation, is one of key issues of the tight gas reservoir characterization and evaluation. The data and correlation functions collected in the Rock Data Catalog could also be used to identify Sweet Spots in Tight Gas reservoirs. Several rock parameters and properties, which affect the fluid flow in a reservoir (like lithology, clay content, water saturation, permeability, pore size distribution) can be identified and used to set up a Sweet Spot Index as a

  12. Gas transport in polybutadiene treated with aqueous bromine

    NASA Astrophysics Data System (ADS)

    Rein, D. H.; Baddour, R. F.; Cohen, R. E.

    1991-10-01

    Diffusion, solubility and permeability coefficients were measured for He, CO2, Ar and CH4 in polybutadiene (PB) and in polybutadiene reacted in the solid state to various extents with aqueous bromine. Analysis of the sorption curves and x ray emission spectra showed that the bromination created a heterogeneous membrane with an outer brominated skin and an unreacted core. At relatively low extent of bromination, the diffusion and permeability coefficients for CO2, Ar and CH4 became immeasurably small after about 3 percent bromination. The ideal separation factor for gas pairs with different molecular size increased with bromination, suggesting applications in gas separation processes. Tailoring the structure of existing commodity polymers through chemical modification is an attractive approach to improving the properties of membranes for gas separation and barrier applications. Systematic alterations of the polymer structure also provide a convenient route for studying the effects of molecular architecture on the permeability. Substitutions to the backbone or side chains affect the intrasegmental mobility and intersegmental chain packing, resulting in changes in gas diffusivity, solubility and permeability coefficients.

  13. Bioinspired gas bubble spontaneous and directional transportation effects in an aqueous medium.

    PubMed

    Ma, Rui; Wang, Jingming; Yang, Zhongjia; Liu, Meng; Zhang, Jingjing; Jiang, Lei

    2015-04-08

    A series of well-ordered, 3D gradient porous interconnected network surfaces composed of micro-nano hierarchical geometries is constructed on a copper wire. A continuous gas film can be trapped around its interface in an aqueous medium acting as an effective channel for gas transportation. Driving by the difference of the Laplace pressure, gas bubbles can be transported spontaneously and directionally.

  14. Impact of Adsorption on Gas Transport in Nanopores

    PubMed Central

    Wu, Tianhao; Zhang, Dongxiao

    2016-01-01

    Given the complex nature of the interaction between gas and solid atoms, the development of nanoscale science and technology has engendered a need for further understanding of gas transport behavior through nanopores and more tractable models for large-scale simulations. In the present paper, we utilize molecular dynamic simulations to demonstrate the behavior of gas flow under the influence of adsorption in nano-channels consisting of illite and graphene, respectively. The results indicate that velocity oscillation exists along the cross-section of the nano-channel, and the total mass flow could be either enhanced or reduced depending on variations in adsorption under different conditions. The mechanisms can be explained by the extra average perturbation stress arising from density oscillation via the novel perturbation model for micro-scale simulation, and approximated via the novel dual-region model for macro-scale simulation, which leads to a more accurate permeability correction model for industrial applications than is currently available. PMID:27020130

  15. Factors Of Environmental Safety And Environmentally Efficient Technologies Transportation Facilities Gas Transportation Industry

    NASA Astrophysics Data System (ADS)

    Vasiliev, Bogdan U.

    2017-01-01

    The stable development of the European countries depends on a reliable and efficient operation of the gas transportation system (GTS). With high reliability of GTS it is necessary to ensure its industrial and environmental safety. In this article the major factors influencing on an industrial and ecological safety of GTS are analyzed, sources of GTS safety decreasing is revealed, measures for providing safety are proposed. The article shows that use of gas-turbine engines of gas-compressor units (GCU) results in the following phenomena: emissions of harmful substances in the atmosphere; pollution by toxic waste; harmful noise and vibration; thermal impact on environment; decrease in energy efficiency. It is shown that for the radical problem resolution of an industrial and ecological safety of gas-transmission system it is reasonable to use gas-compressor units driven by electric motors. Their advantages are shown. Perspective technologies of these units and experience of their use in Europe and the USA are given in this article.

  16. Universal spin transport in a strongly interacting Fermi gas.

    PubMed

    Sommer, Ariel; Ku, Mark; Roati, Giacomo; Zwierlein, Martin W

    2011-04-14

    Transport of fermions, particles with half-integer spin, is central to many fields of physics. Electron transport runs modern technology, defining states of matter such as superconductors and insulators, and electron spin is being explored as a new carrier of information. Neutrino transport energizes supernova explosions following the collapse of a dying star, and hydrodynamic transport of the quark-gluon plasma governed the expansion of the early Universe. However, our understanding of non-equilibrium dynamics in such strongly interacting fermionic matter is still limited. Ultracold gases of fermionic atoms realize a pristine model for such systems and can be studied in real time with the precision of atomic physics. Even above the superfluid transition, such gases flow as an almost perfect fluid with very low viscosity when interactions are tuned to a scattering resonance. In this hydrodynamic regime, collective density excitations are weakly damped. Here we experimentally investigate spin excitations in a Fermi gas of (6)Li atoms, finding that, in contrast, they are maximally damped. A spin current is induced by spatially separating two spin components and observing their evolution in an external trapping potential. We demonstrate that interactions can be strong enough to reverse spin currents, with components of opposite spin reflecting off each other. Near equilibrium, we obtain the spin drag coefficient, the spin diffusivity and the spin susceptibility as a function of temperature on resonance and show that they obey universal laws at high temperatures. In the degenerate regime, the spin diffusivity approaches a value set by [planck]/m, the quantum limit of diffusion, where [planck]/m is Planck's constant divided by 2π and m the atomic mass. For repulsive interactions, our measurements seem to exclude a metastable ferromagnetic state.

  17. Prospects of and Problems in Using Natural Gas for Motor Transport in RUSSIA

    NASA Astrophysics Data System (ADS)

    Chikishev, E.; Ivanov, A.; Anisimov, I.; Chainikov, D.

    2016-08-01

    This article is devoted to increasing the use of natural gas in Russia as a measure to decrease the negative influence of motor transport on the environment. A brief analysis of the global fleet of natural gas vehicles is provided above. The documents accepted in Russia to promote public awareness of compressed natural gas in transport are submitted. The basic reasons keeping the growth of natural gas vehicle fleets in Russia consist of weak branching of refuelling stations; difficulty in determining the actual amount of compressed natural gas required; and control methods of the consumption of gas fuel. The offers promoting the growth of the fleet of natural gas vehicles are given.

  18. Glucocorticoid affects dendritic transport of BDNF-containing vesicles.

    PubMed

    Adachi, Naoki; Numakawa, Tadahiro; Nakajima, Shingo; Fukuoka, Masashi; Odaka, Haruki; Katanuma, Yusuke; Ooshima, Yoshiko; Hohjoh, Hirohiko; Kunugi, Hiroshi

    2015-08-04

    Brain-derived neurotrophic factor (BDNF) is essential for neuronal survival, differentiation, and functions in the central nervous system (CNS). Because BDNF protein is sorted into secretory vesicles at the trans-Golgi network in the cell body after translation, transport of BDNF-containing vesicles to the secretion sites is an important process for its function. Here we examined the effect of dexamethasone (DEX), a synthetic glucocorticoid, on BDNF-containing vesicle transport and found that DEX decreased the proportion of stationary vesicles and increased velocity of the microtubule-based vesicle transport in dendrites of cortical neurons. Furthermore, DEX increased huntingtin (Htt) protein levels via glucocorticoid receptor (GR) activation, and reduction in the amount of Htt by a specific shRNA reversed the action of DEX on BDNF vesicle transport. Given that Htt protein is a positive regulator for the microtubule-dependent vesicular transport in neurons, our data suggest that glucocorticoid stimulates BDNF vesicle transport through upregulation of Htt protein levels.

  19. 30 CFR 250.120 - How does injecting, storing, or treating gas affect my royalty payments?

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 30 Mineral Resources 2 2013-07-01 2013-07-01 false How does injecting, storing, or treating gas... ENFORCEMENT, DEPARTMENT OF THE INTERIOR OFFSHORE OIL AND GAS AND SULPHUR OPERATIONS IN THE OUTER CONTINENTAL SHELF General Performance Standards § 250.120 How does injecting, storing, or treating gas affect...

  20. Element variations in rhyolitic magma resulting from gas transport

    NASA Astrophysics Data System (ADS)

    Berlo, K.; Tuffen, H.; Smith, V. C.; Castro, J. M.; Pyle, D. M.; Mather, T. A.; Geraki, K.

    2013-11-01

    Tuffisite veins are glass-filled fractures formed when magma fragments during degassing within the conduit. These veins form transient channels through which exsolved gases can escape from magma. The purpose of this study is to determine the extent to which chemical heterogeneity within the melt results from gas transport, and assess how this can be used to study magma degassing. Two tuffisite veins from contrasting rhyolitic eruptions at Torfajökull (Iceland) and Chaitén (Chile) were studied in detail. The tuffisite vein from Torfajökull is from a shallow dissected conduit (∼70 ka) that fed a degassed lava flow, while the sample from Chaitén was a bomb ejected during the waning phases of Plinian activity in May 2008. The results of detailed in situ chemical analyses (synchrotron XRF, FTIR, LA-ICP-MS) show that in both veins larger vesiculated fragments are enriched in volatile elements (Torfajökull: H, Li, Cl; Chaitén: Li, Cl, Cu, Zn, As, Sn, Sb) compared to the host, while the surrounding smaller particles are depleted in the Torfajökull vein (Li, Cl, Zn, Br, Rb, Pb), but enriched in the Chaitén vein (K, Cu, Zn, As, Mo, Sb, Pb). The lifespans of both veins and the fluxes of gas and particles through them can be estimated using diffusion profiles and enrichment factors. The Torfajökull vein had a longer lifespan (∼a day) and low particle velocities (∼cm/s), while the Chaitén vein was shorter lived (<1 h) with a high gas velocity (∼m/s). These differences are consistent with the contrasting eruption mechanisms (effusive vs. explosive). The amount of magma that degassed through the Chaitén vein is more than ten times the volume of the vein itself, requiring the vein to tap into pre-exsolved gas pockets. This study highlights that tuffisite veins are highly efficient gas pathways and thereby impart chemical diversity in volatile elements on the melt.

  1. Fuel-mix, fuel efficiency, and transport demand affect prospects for biofuels in northern Europe.

    PubMed

    Bright, Ryan M; Strømman, Anders Hammer

    2010-04-01

    Rising greenhouse gas (GHG) emissions in the road transport sector represents a difficult mitigation challenge due to a multitude of intricate factors, namely the dependency on liquid energy carriers and infrastructure lock-in. For this reason, low-carbon renewable energy carriers, particularly second generation biofuels, are often seen as a prominent candidate for realizing reduced emissions and lowered oil dependency over the medium- and long-term horizons. However, the overarching question is whether advanced biofuels can be an environmentally effective mitigation strategy in the face of increasing consumption and resource constraints. Here we develop both biofuel production and road transport consumption scenarios for northern Europe-a region with a vast surplus of forest bioenergy resources-to assess the potential role that forest-based biofuels may play over the medium- and long-term time horizons using an environmentally extended, multiregion input-output model. Through scenarios, we explore how evolving vehicle technologies and consumption patterns will affect the mitigation opportunities afforded by any future supply of forest biofuels. We find that in a scenario involving ambitious biofuel targets, the size of the GHG mitigation wedge attributed to the market supply of biofuels is severely reduced under business-as-usual growth in consumption in the road transport sector. Our results indicate that climate policies targeting the road transport sector which give high emphases to reducing demand (volume), accelerating the deployment of more fuel-efficient vehicles, and promoting altered consumption patterns (structure) can be significantly more effective than those with single emphasis on expanded biofuel supply.

  2. Kinetically influenced terms for solute transport affected by heterogeneous and homogeneous classical reactions

    USGS Publications Warehouse

    Bahr, J.M.

    1990-01-01

    This paper extends a four-step derivation procedure, previously presented for cases of transport affected by surface reactions, to transport problems involving homogeneous reactions. Derivations for these classes of reactions are used to illustrate the manner in which mathematical differences between reaction classes are reflected in the mathematical derivation procedures required to identify kinetically influenced terms. Simulation results for a case of transport affected by a single solution phase complexation reaction and for a case of transport affected by a precipitation-dissolution reaction are used to demonstrate the nature of departures from equilibrium-controlled transport as well as the use of kinetically influenced terms in determining criteria for the applicability of the local equilibrium assumption. A final derivation for a multireaction problem demonstrates the application of the generalized procedure to a case of transport affected by reactions of several classes. -from Author

  3. Increasing The Use Of Natural Gas On Motor Transport By An Efficient Location Of The NGV RS (On The Example Of Tyumen)

    NASA Astrophysics Data System (ADS)

    Chikishev, E.; Chainikov, D.; Anisimov, I.

    2017-01-01

    This article is devoted to increasing the use of natural gas on the basis of an efficient territorial and quantitative location of natural gas refuelling stations (NGV RS). The key factors which can affect it are offered. On the basis of the chosen factors on the example of Tyumen the option of a territorial location of 4 NGV RS capable to satisfy the demand for natural gas by motor transport in the short term is considered. Increased use of natural gas (NG) on motor transport allows to reduce the negative impact on the environment from harmful substances emitted with exhaust gases.

  4. Technology assessment of future intercity passenger transporation systems. Volume 2: Identification of issues affecting intercity transportation

    NASA Technical Reports Server (NTRS)

    1976-01-01

    Papers on major issues and trends that affect the future of intercity transportation are presented. Specific areas covered include: political, social, technological, institutional, and economic mechanisms, the workings of which determine how future intercity transporation technologies will evolve and be put into service; the major issues of intercity transportation from the point of view of reform, including candidate transporation technologies; and technical analysis of trends affecting the evolution of intercity transportation technologies.

  5. Common inconsistencies in modeling gas transport in porous electrodes: The dusty-gas model and the Fick law

    NASA Astrophysics Data System (ADS)

    Bertei, A.; Nicolella, C.

    2015-04-01

    The paper shows as two assumptions typically made in modeling gas transport in solid oxide fuel cell electrodes, i.e., a) uniform pressure in the dusty-gas model, and b) validity of the Bosanquet formula in the Fick model, may lead to serious inconsistencies (such as molar fractions that do not sum up to one or fluxes that do not obey reaction stoichiometry), thus nullifying the efforts of the mechanistic modeling of transport phenomena. The nature of the inconsistent use of the models is explained with clear examples, then the correct implementation of the gas transport models is discussed. The study aims to promote a coherent physically-based modeling of gas transport phenomena in porous electrodes in order to assist their rational design.

  6. Investigating the role of gas bubble formation and entrapment in contaminated aquifers: Reactive transport modelling

    NASA Astrophysics Data System (ADS)

    Amos, Richard T.; Ulrich Mayer, K.

    2006-09-01

    In many natural and contaminated aquifers, geochemical processes result in the production or consumption of dissolved gases. In cases where methanogenesis or denitrification occurs, the production of gases may result in the formation and growth of gas bubbles below the water table. Near the water table, entrapment of atmospheric gases during water table rise may provide a significant source of O 2 to waters otherwise depleted in O 2. Furthermore, the presence of bubbles will affect the hydraulic conductivity of an aquifer, resulting in changes to the groundwater flow regime. The interactions between physical transport, biogeochemical processes, and gas bubble formation, entrapment and release is complex and requires suitable analysis tools. The objective of the present work is the development of a numerical model capable of quantitatively assessing these processes. The multicomponent reactive transport code MIN3P has been enhanced to simulate bubble growth and contraction due to in-situ gas production or consumption, bubble entrapment due to water table rise and subsequent re-equilibration of the bubble with ambient groundwater, and permeability changes due to trapped gas phase saturation. The resulting formulation allows for the investigation of complex geochemical systems where microbially mediated redox reactions both produce and consume gases as well as affect solution chemistry, alkalinity, and pH. The enhanced model has been used to simulate processes in a petroleum hydrocarbon contaminated aquifer where methanogenesis is an important redox process. The simulations are constrained by data from a crude oil spill site near Bemidji, MN. Our results suggest that permeability reduction in the methanogenic zone due to in-situ formation of gas bubbles, and dissolution of entrapped atmospheric bubbles near the water table, both work to attenuate the dissolved gas plume emanating from the source zone. Furthermore, the simulations demonstrate that under the given

  7. Investigating the role of gas bubble formation and entrapment in contaminated aquifers: Reactive transport modelling

    USGS Publications Warehouse

    Amos, Richard T.; Mayer, K. Ulrich

    2006-01-01

    In many natural and contaminated aquifers, geochemical processes result in the production or consumption of dissolved gases. In cases where methanogenesis or denitrification occurs, the production of gases may result in the formation and growth of gas bubbles below the water table. Near the water table, entrapment of atmospheric gases during water table rise may provide a significant source of O2 to waters otherwise depleted in O2. Furthermore, the presence of bubbles will affect the hydraulic conductivity of an aquifer, resulting in changes to the groundwater flow regime. The interactions between physical transport, biogeochemical processes, and gas bubble formation, entrapment and release is complex and requires suitable analysis tools. The objective of the present work is the development of a numerical model capable of quantitatively assessing these processes. The multicomponent reactive transport code MIN3P has been enhanced to simulate bubble growth and contraction due to in-situ gas production or consumption, bubble entrapment due to water table rise and subsequent re-equilibration of the bubble with ambient groundwater, and permeability changes due to trapped gas phase saturation. The resulting formulation allows for the investigation of complex geochemical systems where microbially mediated redox reactions both produce and consume gases as well as affect solution chemistry, alkalinity, and pH. The enhanced model has been used to simulate processes in a petroleum hydrocarbon contaminated aquifer where methanogenesis is an important redox process. The simulations are constrained by data from a crude oil spill site near Bemidji, MN. Our results suggest that permeability reduction in the methanogenic zone due to in-situ formation of gas bubbles, and dissolution of entrapped atmospheric bubbles near the water table, both work to attenuate the dissolved gas plume emanating from the source zone. Furthermore, the simulations demonstrate that under the given

  8. Benthic processes affecting contaminant transport in Upper Klamath Lake, Oregon

    USGS Publications Warehouse

    Kuwabara, James S.; Topping, Brent R.; Carter, James L.; Carlson, Rick A; Parchaso, Francis; Fend, Steven V.; Stauffer-Olsen, Natalie; Manning, Andrew J.; Land, Jennie M.

    2016-09-30

    Executive SummaryMultiple sampling trips during calendar years 2013 through 2015 were coordinated to provide measurements of interdependent benthic processes that potentially affect contaminant transport in Upper Klamath Lake (UKL), Oregon. The measurements were motivated by recognition that such internal processes (for example, solute benthic flux, bioturbation and solute efflux by benthic invertebrates, and physical groundwater-surface water interactions) were not integrated into existing management models for UKL. Up until 2013, all of the benthic-flux studies generally had been limited spatially to a number of sites in the northern part of UKL and limited temporally to 2–3 samplings per year. All of the benthic invertebrate studies also had been limited to the northern part of the lake; however, intensive temporal (weekly) studies had previously been completed independent of benthic-flux studies. Therefore, knowledge of both the spatial and temporal variability in benthic flux and benthic invertebrate distributions for the entire lake was lacking. To address these limitations, we completed a lakewide spatial study during 2013 and a coordinated temporal study with weekly sampling of benthic flux and benthic invertebrates during 2014. Field design of the spatially focused study in 2013 involved 21 sites sampled three times as the summer cyanobacterial bloom developed (that is, May 23, June 13, and July 3, 2013). Results of the 27-week, temporally focused study of one site in 2014 were summarized and partitioned into three periods (referred to herein as pre-bloom, bloom and post-bloom periods), each period involving 9 weeks of profiler deployments, water column and benthic sampling. Partitioning of the pre-bloom, bloom, and post-bloom periods were based on water-column chlorophyll concentrations and involved the following date intervals, respectively: April 15 through June 10, June 17 through August 13, and August 20 through October 16, 2014. To examine

  9. Arc Deflection Length Affected by Transverse Rotating Magnetic Field with Lateral Gas

    NASA Astrophysics Data System (ADS)

    Shiino, Toru; Ishii, Yoko; Yamamoto, Shinji; Iwao, Toru; High Current Energy Laboratory (HiCEL) Team

    2016-10-01

    Gas metal arc welding using shielding gas is often used in the welding industry. However, the arc deflection affected by lateral gas is problem because of inappropriate heat transfer. Shielding gas is used in order to prevent the instability affected by the arc deflection. However, the shielding gas causes turbulence, then blowhole of weld defect occurs because the arc affected by the instability is contaminated by the air. Thus, the magnetic field is applied to the arc in order to stabilize the arc using low amount of shielding gas. The method of applying the transverse rotating magnetic field (RMF) to the arc is one of the methods to prevent the arc instability. The RMF drives the arc because of electromagnetic force. The driven arc is considered to be prevented to arc deflection of lateral gas because the arc is restrained by the magnetic field because of the driven arc. In addition, it is assume the RMF prevented to the arc deflection of lateral gas from the multiple directions. In this paper, the arc deflection length affected by the RMF with lateral gas was elucidated in order to know the effect of the RMF for arc stabilization. Specifically, the arc deflection length affected by the magnetic frequency and the magnetic flux density is measured by high speed video camera. As a result, the arc deflection length decreases with increasing magnetic frequency, and the arc deflection length increases with increasing the magnetic flux density.

  10. Transportation and Greenhouse Gas Emissions Trading. Final Technical Report

    SciTech Connect

    Steve Winkelman; Tim Hargrave; Christine Vanderlan

    1999-10-01

    The authors conclude in this report that an upstream system would ensure complete regulatory coverage of transportation sector emissions in an efficient and feasible manner, and as such represents a key component of a national least-cost GHG emissions abatement strategy. The broad coverage provided by an upstream system recommends this approach over vehicle-maker based approaches, which would not cover emissions from heavy-duty vehicles and the aviation, marine and off-road sub-sectors. The on-road fleet approach unfairly and inefficiently burdens vehicle manufacturers with responsibility for emissions that they cannot control. A new vehicles approach would exclude emissions from vehicles on the road prior to program inception. The hybrid approach faces significant technical and political complications, and it is not clear that the approach would actually change behavior among vehicle makers and users, which is its main purpose. They also note that a trading system would fail to encourage many land use and infrastructure measures that affect VMT growth and GHG emissions. They recommend that this market failure be addressed by complementing the trading system with a program specifically targeting land use- and infrastructure-related activities. A key issue that must be addressed in designing a national GHG control strategy is whether or not it is necessary to guarantee GHG reductions from the transport sector. Neither an upstream system nor a downstream approach would do so, since both would direct capital to the least-cost abatement opportunities wherever they were found. They review two reasons why it may be desirable to force transportation sector reductions: first, that the long-term response to climate change will require reductions in all sectors; and second, the many ancillary benefits associated with transportation-related, and especially VMT-related, emissions reduction activities. If policy makers find it desirable to establish transportation

  11. Properties of nanoparticles affecting simulation of fibrous gas filter performance

    NASA Astrophysics Data System (ADS)

    Tronville, Paolo; Rivers, Richard

    2015-05-01

    Computational Fluid Dynamics (CFD) codes allow detailed simulation of the flow of gases through fibrous filter media. When the pattern of gas flow between fibers has been established, simulated particles of any desired size can be “injected” into the entering gas stream, and their paths under the influence of aerodynamic drag, Brownian motion and electrostatic forces tracked. Particles either collide with a fiber, or pass through the entire filter medium. They may bounce off the fiber surface, or adhere firmly to the surface or to particles previously captured. Simulated injection of many particles at random locations in the entering stream allows the average probability of capture to be calculated. Many particle properties must be available as parameters for the equations defining the forces on particles in the gas stream, at the moment of contact with a fiber, and after contact. Accurate values for all properties are needed, not only for predicting particle capture in actual service, but also to validate models for media geometries and computational procedures used in CFD. We present a survey of existing literature on the properties influencing nanoparticle dynamics and adhesion.

  12. 75 FR 6370 - Regulations Governing the Conduct of Open Seasons for Alaska Natural Gas Transportation Projects...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-02-09

    ... Energy Regulatory Commission Regulations Governing the Conduct of Open Seasons for Alaska Natural Gas Transportation Projects; Notice of Alaska Natural Gas Transportation Projects Open Season Pre-Filing Workshop... hold a workshop on the procedures and process for holding and commenting on an open season for...

  13. Positron transport and thermalization - the plasma-gas interface

    NASA Astrophysics Data System (ADS)

    Marler, Joan

    2008-11-01

    Low energy positrons are now used in many fields including atomic physics, material science and medicine [1]. Plasma physics is providing new tools for this research, including Penning-Malmberg buffer-gas traps to accumulate positrons and the use of rotating electric fields (the ``rotating wall'' technique) to compress positrons radially and create tailored beams [1]. These devices (now available commercially), which rely in key instances on positron-neutral interactions, are a convenient way to create plasmas and beams for a variety of applications. A deeper understanding of the relevant cooling and loss mechanisms is required to take full advantage of this technology. This talk focuses on a recent study of positrons in such a tenuous gaseous environment in the presence of an applied electric field [2]. Energy-resolved collision cross sections and a Monte Carlo code modified to include positrionium (Ps) formation are used to obtain transport coefficients and the thermalization and Ps-formation rates. A markedly different type of negative differential conductivity is observed (i.e., not seen in electron systems), due to the non-conservative nature of the Ps-formation process. It is particularly prominent in gases with large, highly energy dependent Ps-formation cross sections. The relevance of these calculations to other positron applications will also be discussed, including a currently planned study of positrons in gaseous water. It is hoped that these calculations will inspire a new generation of positron transport experiments.*Work done in collaboration with Z.Lj. Petrovi'c, A. Bankovi'c, M. Suvakov, G. Malovi'c, S. Dujko, S.J. Buckman. 1. C. M. Surko and R. G. Greaves, Phys. Plasmas 11, 2333-2348 (2004).2. A. Bankovi'c, J. P. Marler, M. Suvakov, G. Malovi'c, and Z. Lj. Petrovi'c, Nucl. Instrum. and Meth. in Phys. Res. B 266, 462-465 (2008).

  14. Radon as a tracer of biogenic gas equilibration and transport from methane-saturated sediments

    NASA Technical Reports Server (NTRS)

    Martens, Christopher S.; Chanton, Jeffrey P.

    1989-01-01

    Data on Rn-222 activity in methane-rich gas bubbles from anoxic coastal sediments of Cape Lookout Bight, North Carolina, were used to determine gas equilibration with pore waters and the rates of ebullitive stripping and transport of gases to overlying waters and the atmosphere. Results showed that, during summer months, the bubble ebullition process strips and transports 1.9-4.8 percent/day of the standing crop of radon (and, by inference, other gases equilibrated with gas bubbles) in surface sediments of Cape Lookout Bight to the troposphere. Thus, the ebullitive mode of gas transport represents an effective mechanism for delivering reduced biogenic gases directly to the atmosphere.

  15. Gibberellins inhibit adventitious rooting in hybrid aspen and Arabidopsis by affecting auxin transport.

    PubMed

    Mauriat, Mélanie; Petterle, Anna; Bellini, Catherine; Moritz, Thomas

    2014-05-01

    Knowledge of processes involved in adventitious rooting is important to improve both fundamental understanding of plant physiology and the propagation of numerous plants. Hybrid aspen (Populus tremula × tremuloïdes) plants overexpressing a key gibberellin (GA) biosynthesis gene (AtGA20ox1) grow rapidly but have poor rooting efficiency, which restricts their clonal propagation. Therefore, we investigated the molecular basis of adventitious rooting in Populus and the model plant Arabidopsis. The production of adventitious roots (ARs) in tree cuttings is initiated from the basal stem region, and involves the interplay of several endogenous and exogenous factors. The roles of several hormones in this process have been characterized, but the effects of GAs have not been fully investigated. Here, we show that a GA treatment negatively affects the numbers of ARs produced by wild-type hybrid aspen cuttings. Furthermore, both hybrid aspen plants and intact Arabidopsis seedlings overexpressing AtGA20ox1, PttGID1.1 or PttGID1.3 genes (with a 35S promoter) produce few ARs, although ARs develop from the basal stem region of hybrid aspen and the hypocotyl of Arabidopsis. In Arabidopsis, auxin and strigolactones are known to affect AR formation. Our data show that the inhibitory effect of GA treatment on adventitious rooting is not mediated by perturbation of the auxin signalling pathway, or of the strigolactone biosynthetic and signalling pathways. Instead, GAs appear to act by perturbing polar auxin transport, in particular auxin efflux in hybrid aspen, and both efflux and influx in Arabidopsis.

  16. Trace gas transport out of the Indian Summer Monsoon

    NASA Astrophysics Data System (ADS)

    Tomsche, Laura; Pozzer, Andrea; Zimmermann, Peter; Parchatka, Uwe; Fischer, Horst

    2016-04-01

    The trace gas transport out of the Indian summer monsoon was investigated during the aircraft campaign OMO (Oxidation Mechanism Observations) with the German research aircraft HALO (High Altitude and Long Range Research Aircraft) in July/August 2015. HALO was based at Paphos/Cyprus and also on Gan/Maledives. Flights took place over the Mediterranean Sea, the Arabian Peninsula and the Arabian Sea. In this work the focus is on the distribution of carbon monoxide (CO) and methane (CH4) in the upper troposphere. They were measured with the laser absorption spectrometer TRISTAR on board of HALO. During the Indian summer monsoon strong convection takes place over India and the Bay of Bengal. In this area the population is high accompanied by many emission sources e.g. wetlands and cultivation of rice. Consequently the boundary layer is polluted containing high concentrations of trace gases like methane and carbon monoxide. Due to vertical transport these polluted air masses are lifted to the upper troposphere. Here they circulate with the so called Asian monsoon anticyclone. In the upper troposphere polluted air masses lead to a change in the chemical composition thus influence the chemical processes. Furthermore the anticyclone spreads the polluted air masses over a larger area. Thus the outflow of the anticyclone in the upper troposphere leads to higher concentrations of trace gases over the Arabian Sea, the Arabian Peninsula and also over the eastern part of North Africa and the eastern part of the Mediterranean Sea. During OMO higher concentrations of methane and carbon monoxide were detected at altitudes between 11km and 15km. The highest measured concentrations of carbon monoxide and methane were observed over Oman. The CO concentration in the outflow of the monsoon exceeds background levels by 10-15ppb. However the enhancement in the concentration is not obviously connected to the monsoon due to the natural variability in the troposphere. The enhancement in the

  17. Seasonal difference in brain serotonin transporter binding predicts symptom severity in patients with seasonal affective disorder.

    PubMed

    Mc Mahon, Brenda; Andersen, Sofie B; Madsen, Martin K; Hjordt, Liv V; Hageman, Ida; Dam, Henrik; Svarer, Claus; da Cunha-Bang, Sofi; Baaré, William; Madsen, Jacob; Hasholt, Lis; Holst, Klaus; Frokjaer, Vibe G; Knudsen, Gitte M

    2016-05-01

    Cross-sectional neuroimaging studies in non-depressed individuals have demonstrated an inverse relationship between daylight minutes and cerebral serotonin transporter; this relationship is modified by serotonin-transporter-linked polymorphic region short allele carrier status. We here present data from the first longitudinal investigation of seasonal serotonin transporter fluctuations in both patients with seasonal affective disorder and in healthy individuals. Eighty (11)C-DASB positron emission tomography scans were conducted to quantify cerebral serotonin transporter binding; 23 healthy controls with low seasonality scores and 17 patients diagnosed with seasonal affective disorder were scanned in both summer and winter to investigate differences in cerebral serotonin transporter binding across groups and across seasons. The two groups had similar cerebral serotonin transporter binding in the summer but in their symptomatic phase during winter, patients with seasonal affective disorder had higher serotonin transporter than the healthy control subjects (P = 0.01). Compared to the healthy controls, patients with seasonal affective disorder changed their serotonin transporter significantly less between summer and winter (P < 0.001). Further, the change in serotonin transporter was sex- (P = 0.02) and genotype- (P = 0.04) dependent. In the patients with seasonal affective disorder, the seasonal change in serotonin transporter binding was positively associated with change in depressive symptom severity, as indexed by Hamilton Rating Scale for Depression - Seasonal Affective Disorder version scores (P = 0.01). Our findings suggest that the development of depressive symptoms in winter is associated with a failure to downregulate serotonin transporter levels appropriately during exposure to the environmental stress of winter, especially in individuals with high predisposition to affective disorders.media-1vid110.1093/brain/aww043_video_abstractaww043_video_abstract.

  18. TRU waste transportation -- The flammable gas generation problem

    SciTech Connect

    Connolly, M.J.; Kosiewicz, S.T.

    1997-11-01

    The Nuclear Regulatory Commission (NRC) has imposed a flammable gas (i.e., hydrogen) concentration limit of 5% by volume on transuranic (TRU) waste containers to be shipped using the TRUPACT-II transporter. This concentration is the lower explosive limit (LEL) in air. This was done to minimize the potential for loss of containment during a hypothetical 60 day period. The amount of transuranic radionuclide that is permissible for shipment in TRU waste containers has been tabulated in the TRUPACT-II Safety Analysis Report for Packaging (SARP, 1) to conservatively prevent accumulation of hydrogen above this 5% limit. Based on the SARP limitations, approximately 35% of the TRU waste stored at the Idaho National Engineering and Environmental Lab (INEEL), Los Alamos National Lab (LANL), and Rocky Flats Environmental Technology Site (RFETS) cannot be shipped in the TRUPACT-II. An even larger percentage of the TRU waste drums at the Savannah River Site (SRS) cannot be shipped because of the much higher wattage loadings of TRU waste drums in that site`s inventory. This paper presents an overview of an integrated, experimental program that has been initiated to increase the shippable portion of the Department of Energy (DOE) TRU waste inventory. In addition, the authors will estimate the anticipated expansion of the shippable portion of the inventory and associated cost savings. Such projection should provide the TRU waste generating sites a basis for developing their TRU waste workoff strategies within their Ten Year Plan budget horizons.

  19. Influences of interfacial resistances on gas transport through carbon nanotube membranes.

    PubMed

    Newsome, David A; Sholl, David S

    2006-09-01

    Carbon nanotubes have significant promise as gas separation membranes. Gas permeation through nanopores involves mass transfer resistances from molecules entering and leaving pores (so-called surface resistances) and diffusion within the pores. We use molecular simulations to give the first estimates of surface resistances for gas transport through nanotubes. For CH4 transport through (20,0) carbon nanotubes at 300 K, surface resistances are small for nanotubes 5-10 mum in length but can be significant for shorter nanotubes.

  20. Gas Transport Parameters for Landfill Cover Soils: Effects of Soil Compaction and Water Blockages

    NASA Astrophysics Data System (ADS)

    Wickramarachchi, P. N.; Hamamoto, S.; Kawamoto, K.; Nawagamuwa, U.; Komatsu, T.; Moldrup, P.

    2009-12-01

    Recently, landfill sites have been emerging in greenhouse warming scenarios as a significant source of atmospheric CH4. landfill management strategies have mainly addressed the problem of preventing groundwater contamination and reduction of leachate generation. Being one of the largest source of anthropogenic CH4 emission , the final cover system should also be designed for minimizing the biogas migration into the atmosphere or the areas surrounding the landfill. Compared to the intensive research efforts on hydraulic performances of landfill final cover soil , there are few studies about gas transport characteristics of landfill cover soils. Therefore, the effects of soil physical properties such as bulk density (i.e., compaction level), soil particle size and water blockage effects on the gas exchange in t highly compacted final cover soil are largely unknown. The gas exchange through the final cover soils is controlled by advective and diffusive gas transport. Air permeability (ka) governs the advective gas transport while the soil-gas diffusion coefficient (Dp) governs diffusive gas transport . In this study, the effects of compaction level and water blockage effects on ka and Dp for two landfill final cover soils were investigated. The disturbed soil samples were taken from landfill final covers in Japan and Sri Lanka. A compaction tests were performed for the soil samples with two different size fractions (< 35 mm and < 2.0 mm). In the compaction tests at field water content , the soil samples were repacked into soil cores (i.d. 15-cm, length 12-cm) at two different compaction levels (2700 kN/m2 and 600 kN/m2). After the compaction tests, ka and Dp were measured and then samples were saturated and subsequently drained at different soil-water matric potential (pF; pF equals to log(-ɛ) where ɛ is soil-water matric potential in cm H2O) of 1.5, 2.0, 3.0, 4.1, and with air-dried (pF 6.0) and oven-dried (pF 6.9) conditions. Results showed that measured Dp values

  1. Natural gas: Marine transportation. (Latest citations from Oceanic Abstracts). Published Search

    SciTech Connect

    Not Available

    1994-04-01

    The bibliography contains citations concerning the design, construction, and operation of ships for the transport of liquified natural gas. Topics include safety devices, materials handling equipment for loading and unloading liquified natural gas, new hull and vessel designs, gas turbine propulsion systems, cargo tank designs and requirements, and liguid load dynamics. (Contains 250 citations and includes a subject term index and title list.)

  2. Natural gas: Marine transportation. (Latest citations from Oceanic Abstracts). Published Search

    SciTech Connect

    Not Available

    1992-11-01

    The bibliography contains citations concerning the design, construction, and operation of ships for the transport of liquified natural gas. Topics include safety devices, materials handling equipment for loading and unloading liquified natural gas, new hull and vessel designs, gas turbine propulsion systems, cargo tank designs and requirements, and liguid load dynamics. (Contains 250 citations and includes a subject term index and title list.)

  3. Acoustic reflectometry esophageal profiles minimally affected by massive gas ventilation.

    PubMed

    Raphael, David T; Crookes, Peter; Arnaudov, Dimiter; Benbassat, Maxim

    2005-10-01

    Acoustic reflectometry can be used to distinguish between breathing tube placement in an esophagus vs the trachea via characteristic area-distance profiles for both cavities. In the cardiopulmonary resuscitation setting, capnography may be useless because the patient has little or no pulmonary circulation. With the breathing tube in the esophagus, can massive ventilation with a manual resuscitation bag, as might occur in the cardiopulmonary resuscitation setting, markedly alter the form of the obtained esophageal reflectometry profile? Nine hounds were induced, endotracheally intubated, mechanically ventilated, and anesthetized. Area-distance profiles were obtained with a 2-microphone acoustic reflectometer customized to measure areas up to 50 cm. Acoustic reflectometer profiles were obtained in intubated esophagi as follows: (1) baseline nonventilated state, (2) after aggressive 2-handed manual ventilation with high inspiratory pressures, rapid respiratory rates, and large tidal volumes for periods of 0.5, 1, and 1.5 minutes, upon detachment of the resuscitation bag, and (3) after esophagogastric decompression. We hypothesized that massive gas ventilation has no effect on the esophageal peak areas (null hypothesis), and used a paired t test for statistical significance (P < .05). For times of 0.5, 1.0, and 1.5 minutes, the ventilation volumes (mean +/- SD) were 25 +/- 7, 49 +/- 8, and 70 +/- 18 L. Massive gas ventilation caused minimal broadening and slight distal spread of the basal "hump". The mean peak area change was 0.18 +/- 0.35 cm2. For a paired t test (n = 9, df = 8), the corresponding t value was 1.54, with a P value of .16, which was incompatible with the null hypothesis. The experimental observations indicate a minimal effect of massive gas ventilation on the acoustic reflectometry esophageal profile. Hence, operator recognition of the altered canine acoustic reflectometer profile as that of an esophageal cavity is maintained, indicating that acoustic

  4. Ozone gas affects the physical and chemical properties of wheat (Triticum aestivum L.) starch

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Ozone can oxidize hydroxyl groups present at C2, C3, and C6 positions on the starch molecule and affect its physicochemical properties. In this experiment, bread wheat flour and isolated wheat starch were treated with ozone gas (1,500 ppm, gas flow rate 2.5 L/minutes) for 45 minutes and 30 minutes, ...

  5. The hydrology of northern peatlands as affected by biogenic gas: Current developments and research needs

    USGS Publications Warehouse

    Rosenberry, D.O.; Glaser, P.H.; Siegel, D.I.

    2006-01-01

    Recent research indicates that accumulation and release of biogenic gas from northern peatlands may substantially affect future climate. Sudden release of free-phase gas bubbles into the atmosphere may preclude the conversion of methane to carbon dioxide in the uppermost oxic layer of the peat, resulting in greater contribution of methane to the atmosphere than is currently estimated. The hydrology of these peatlands also affects and is affected by this process, especially when gas is released suddenly and episodically. Indirect hydrological evidence indicates that ebullitive gas releases are relatively frequent in some peatlands and time-averaged rates may be significantly greater than diffusive releases. Estimates of free-phase gas contained in peat have ranged from 0 to nearly 20% of the peat volume. Abrupt changes in the volume of gas may alter hydraulic gradients and movement of water and solutes in peat, which in turn could alter composition and fluxes of the gas. Peat surfaces also move vertically and horizontally in response to accumulation and release of free-phase gas. Future research should address the distribution, temporal variability, and relative significance of ebullition in peatlands and the consequent hydrological responses to these gas-emission events. Copyright ?? 2006 John Wiley & Sons, Ltd.

  6. Transport of Gas and Solutes in Permeable Estuarine Sediments

    DTIC Science & Technology

    2008-01-01

    subsurface methane accumulations that formed gas layers up to 2 cm thick at 3 to 10 cm sediment depth. This gas was collected in the chambers and the...reactive solutes in the surface layers of the bed. Gas producing organisms benefit from this filtration, i.e. methanogens from the filtration of organic

  7. Reduced soil wettability can affect greenhouse gas fluxes

    NASA Astrophysics Data System (ADS)

    Urbanek, Emilia; Qassem, Khalid

    2015-04-01

    Soil moisture is known to be an important factor affecting the carbon (C) dynamics in soils including decomposition of organic matter and exchange of gases like CO2 and CH4 between the soil and the atmosphere. Most studies and process models looking at the soil C dynamics assume, however, that soils are easily wettable and water is relatively uniformly distributed within the soil pores. Most soils, however, do not wet spontaneously when dry or moderately moist, but instead exhibit some degree of soil water repellency (i.e. hydrophobicity), which can restrict infiltration and conductivity of water for weeks or months. This is world-wide occurring phenomenon which affects all soil textural types but is particularly common under permanent vegetation e.g. forest, grass and shrub vegetation. Soil water repellency is most profound during drier seasons, when the soil moisture content is relatively low. Although prolonged contact with water can gradually decrease water repellency, some soils do not recover to being completely wettable even after very wet winter months or substantial rainfall events. It has been recognized that with the predicted climatic changes the phenomenon of soil water repellency will become even more pronounced and severe, additionally it may occur in the areas and climatic zones where the effect have not been currently recognized. One of the main implications of soil water repellency is restricted water infiltration and reduced conductivity, which results in reduced soil water availability for plants and soil biota, even after prolonged periods of rainfall. As the process of C mineralization and consequently CO2 efflux from soil is driven by the accessibility of organic matter to decomposing organisms, which in turn is directly dependent on (i) soil moisture and (ii) soil temperature it is, therefore hypothesised that carbon decomposition and CO2 efflux in water repellent soils will also be affected when soil in the water repellent state. The CO2

  8. Ion transport membrane module and vessel system with directed internal gas flow

    DOEpatents

    Holmes, Michael Jerome; Ohrn, Theodore R.; Chen, Christopher Ming-Poh

    2010-02-09

    An ion transport membrane system comprising (a) a pressure vessel having an interior, an inlet adapted to introduce gas into the interior of the vessel, an outlet adapted to withdraw gas from the interior of the vessel, and an axis; (b) a plurality of planar ion transport membrane modules disposed in the interior of the pressure vessel and arranged in series, each membrane module comprising mixed metal oxide ceramic material and having an interior region and an exterior region; and (c) one or more gas flow control partitions disposed in the interior of the pressure vessel and adapted to change a direction of gas flow within the vessel.

  9. Transport of fission products with a helium gas-jet at TRIGA-SPEC

    NASA Astrophysics Data System (ADS)

    Eibach, M.; Beyer, T.; Blaum, K.; Block, M.; Eberhardt, K.; Herfurth, F.; Geppert, C.; Ketelaer, J.; Ketter, J.; Krämer, J.; Krieger, A.; Knuth, K.; Nagy, Sz.; Nörtershäuser, W.; Smorra, C.

    2010-02-01

    A helium gas-jet system for the transport of fission products from the research reactor TRIGA Mainz has been developed, characterized and tested within the TRIGA-SPEC experiment. For the first time at TRIGA Mainz carbon aerosol particles have been used for the transport of radionuclides from a target chamber with high efficiency. The radionuclides have been identified by means of γ-spectroscopy. Transport time, efficiency as well as the absolute number of transported radionuclides for several species have been determined. The design and the characterization of the gas-jet system are described and discussed.

  10. Near-surface physics during convection affecting air-water gas transfer

    NASA Astrophysics Data System (ADS)

    Fredriksson, S. T.; Arneborg, L.; Nilsson, H.; Handler, R. A.

    2016-05-01

    The gas flux at the water surface is affected by physical processes including turbulence from wind shear, microscale wave breaking, large-scale breaking, and convection due to heat loss at the surface. The main route in the parameterizations of the gas flux has been to use the wind speed as a proxy for the gas flux velocity, indirectly taking into account the dependency of the wind shear and the wave processes. The interest in the contributions from convection processes has increased as the gas flux from inland waters (with typically lower wind and sheltered conditions) now is believed to play a substantial role in the air-water gas flux budget. The gas flux is enhanced by convection through the mixing of the mixed layer as well as by decreasing the diffusive boundary layer thickness. The direct numerical simulations performed in this study are shown to be a valuable tool to enhance the understanding of this flow configuration often present in nature.

  11. Role of transportation in the persuasion process: cognitive and affective responses to antidrug narratives.

    PubMed

    Banerjee, Smita C; Greene, Kathryn

    2012-01-01

    This study examined transportation effects of first- and third-person narratives as well as the role of transportation in the persuasion process. In particular, the authors evaluated the role of transportation in affecting cognitive and affective responses. Last, they addressed the relation between (a) cognitive and affective responses and (b) antidrug expectancies. Participants were 500 undergraduate students at a large northern university in the United Kingdom who were randomly assigned to 1 of 2 conditions: first- or third-person narratives on cocaine use. The results demonstrated that there was no difference between first- and third-person narratives in terms of transportation. However, overall, greater transportation was associated with more favorable cognitive responses, and more favorable cognitive response was associated with stronger anticocaine expectancies. In terms of affective responses, results indicated the mediating role of sadness and contentment in the association between transportation and anticocaine expectancies. In particular, increased transportation was associated with greater sadness and lower contentment. Lower sadness and contentment were associated with stronger anticocaine expectancies. Important theoretical and empirical implications are discussed.

  12. Modeling of Gas Production from Shale Reservoirs Considering Multiple Transport Mechanisms.

    PubMed

    Guo, Chaohua; Wei, Mingzhen; Liu, Hong

    2015-01-01

    Gas transport in unconventional shale strata is a multi-mechanism-coupling process that is different from the process observed in conventional reservoirs. In micro fractures which are inborn or induced by hydraulic stimulation, viscous flow dominates. And gas surface diffusion and gas desorption should be further considered in organic nano pores. Also, the Klinkenberg effect should be considered when dealing with the gas transport problem. In addition, following two factors can play significant roles under certain circumstances but have not received enough attention in previous models. During pressure depletion, gas viscosity will change with Knudsen number; and pore radius will increase when the adsorption gas desorbs from the pore wall. In this paper, a comprehensive mathematical model that incorporates all known mechanisms for simulating gas flow in shale strata is presented. The objective of this study was to provide a more accurate reservoir model for simulation based on the flow mechanisms in the pore scale and formation geometry. Complex mechanisms, including viscous flow, Knudsen diffusion, slip flow, and desorption, are optionally integrated into different continua in the model. Sensitivity analysis was conducted to evaluate the effect of different mechanisms on the gas production. The results showed that adsorption and gas viscosity change will have a great impact on gas production. Ignoring one of following scenarios, such as adsorption, gas permeability change, gas viscosity change, or pore radius change, will underestimate gas production.

  13. Modeling of Gas Production from Shale Reservoirs Considering Multiple Transport Mechanisms

    PubMed Central

    Guo, Chaohua; Wei, Mingzhen; Liu, Hong

    2015-01-01

    Gas transport in unconventional shale strata is a multi-mechanism-coupling process that is different from the process observed in conventional reservoirs. In micro fractures which are inborn or induced by hydraulic stimulation, viscous flow dominates. And gas surface diffusion and gas desorption should be further considered in organic nano pores. Also, the Klinkenberg effect should be considered when dealing with the gas transport problem. In addition, following two factors can play significant roles under certain circumstances but have not received enough attention in previous models. During pressure depletion, gas viscosity will change with Knudsen number; and pore radius will increase when the adsorption gas desorbs from the pore wall. In this paper, a comprehensive mathematical model that incorporates all known mechanisms for simulating gas flow in shale strata is presented. The objective of this study was to provide a more accurate reservoir model for simulation based on the flow mechanisms in the pore scale and formation geometry. Complex mechanisms, including viscous flow, Knudsen diffusion, slip flow, and desorption, are optionally integrated into different continua in the model. Sensitivity analysis was conducted to evaluate the effect of different mechanisms on the gas production. The results showed that adsorption and gas viscosity change will have a great impact on gas production. Ignoring one of following scenarios, such as adsorption, gas permeability change, gas viscosity change, or pore radius change, will underestimate gas production. PMID:26657698

  14. Evaluating Gas-Phase Transport And Detection Of Noble Gas Signals From Underground Nuclear Explosions Using Chemical Tracers

    NASA Astrophysics Data System (ADS)

    Carrigan, C. R.; Hunter, S. L.; Sun, Y.; Wagoner, J. L.; Ruddle, D.; Anderson, G.; Felske, D.; Myers, K.; Zucca, J. J.; Emer, D. F.; Townsend, M.; Drellack, S.; Chipman, V.; Snelson, C. M.

    2013-12-01

    The 1993 Non-Proliferation Experiment (NPE) involved detonating 1 kiloton of chemical explosive in a subsurface cavity which also contained bottles of tracer gases (ref 1). That experiment provided an improved understanding of transport processes relevant to the detection of noble gas signals at the surface emanating from a clandestine underground nuclear explosion (UNE). As an alternative to performing large chemical detonations to simulate gas transport from UNEs, we have developed a test bed for subsurface gas transport, sampling and detection studies using a former UNE cavity. The test bed site allows for the opportunity to evaluate pathways to the surface created by the UNE as well as possible transport mechanisms including barometric pumping and cavity pressurization (ref 2). With the test bed we have monitored long-term chemical tracers as well as newly injected tracers. In order to perform high temporal resolution tracer gas monitoring, we have also developed a Subsurface Gas Smart Sampler (SGSS) which has application during an actual On Site Inspection (OSI) and is available for deployment in OSI field exercises planned for 2014. Deployment of five SGSS at the remote test bed has provided unparalleled detail concerning relationships involving tracer gas transport to the surface, barometric fluctuations and temporal variations in the natural radon concentration. We anticipate that the results of our tracer experiments will continue to support the development of improved noble gas detection technology for both OSI and International Monitoring System applications. 1. C.R. Carrigan et al., 1996, Nature, 382, p. 528. 2. Y. Sun and C.R. Carrigan, 2012, Pure Appl. Geophys., DOI 10.1007/s00024-012-0514-4.

  15. Operational Challenges in Gas-To-Liquid (GTL) Transportation Through Trans Alaska Pipeline System (TAPS)

    SciTech Connect

    Godwin A. Chukwu; Santanu Khataniar; Shirish Patil; Abhijit Dandekar

    2006-06-30

    Oil production from Alaskan North Slope oil fields has steadily declined. In the near future, ANS crude oil production will decline to such a level (200,000 to 400,000 bbl/day) that maintaining economic operation of the Trans-Alaska Pipeline System (TAPS) will require pumping alternative products through the system. Heavy oil deposits in the West Sak and Ugnu formations are a potential resource, although transporting these products involves addressing important sedimentation issues. One possibility is the use of Gas-to-Liquid (GTL) technology. Estimated recoverable gas reserves of 38 trillion cubic feet (TCF) on the North Slope of Alaska can be converted to liquid with GTL technology and combined with the heavy oils for a product suitable for pipeline transport. Issues that could affect transport of this such products through TAPS include pumpability of GTL and crude oil blends, cold restart of the pipeline following a prolonged winter shutdown, and solids deposition inside the pipeline. This study examined several key fluid properties of GTL, crude oil and four selected blends under TAPS operating conditions. Key measurements included Reid Vapor Pressure, density and viscosity, PVT properties, and solids deposition. Results showed that gel strength is not a significant factor for the ratios of GTL-crude oil blend mixtures (1:1; 1:2; 1:3; 1:4) tested under TAPS cold re-start conditions at temperatures above - 20 F, although Bingham fluid flow characteristics exhibited by the blends at low temperatures indicate high pumping power requirements following prolonged shutdown. Solids deposition is a major concern for all studied blends. For the commingled flow profile studied, decreased throughput can result in increased and more rapid solid deposition along the pipe wall, resulting in more frequent pigging of the pipeline or, if left unchecked, pipeline corrosion.

  16. Purge gas protected transportable pressurized fuel cell modules and their operation in a power plant

    DOEpatents

    Zafred, P.R.; Dederer, J.T.; Gillett, J.E.; Basel, R.A.; Antenucci, A.B.

    1996-11-12

    A fuel cell generator apparatus and method of its operation involves: passing pressurized oxidant gas and pressurized fuel gas into modules containing fuel cells, where the modules are each enclosed by a module housing surrounded by an axially elongated pressure vessel, and where there is a purge gas volume between the module housing and pressure vessel; passing pressurized purge gas through the purge gas volume to dilute any unreacted fuel gas from the modules; and passing exhaust gas and circulated purge gas and any unreacted fuel gas out of the pressure vessel; where the fuel cell generator apparatus is transportable when the pressure vessel is horizontally disposed, providing a low center of gravity. 11 figs.

  17. Vadose zone attenuation of organic compounds at a crude oil spill site - Interactions between biogeochemical reactions and multicomponent gas transport

    USGS Publications Warehouse

    Molins, S.; Mayer, K.U.; Amos, R.T.; Bekins, B.A.

    2010-01-01

    balance. Overall, the model was successful in capturing the complex interactions between biogeochemical reactions and multicomponent gas transport processes. However, despite employing a process-based modeling approach, honoring observed parameter ranges, and generally obtaining good agreement between field observations and model simulations, accurate quantification of natural attenuation rates remains difficult. The modeling results are affected by uncertainties regarding gas phase saturations, tortuosities, and the magnitude of CH4 and CO2 flux from the smear zone. These findings highlight the need to better delineate gas fluxes at the model boundaries, which will help constrain contaminant degradation rates, and ultimately source zone longevity. ?? 2009 Elsevier B.V.

  18. Natural Gas Transportation - Infrastructure Issues and Operational Trends

    EIA Publications

    2001-01-01

    This report examines how well the current national natural gas pipeline network has been able to handle today's market demand for natural gas. In addition, it identifies those areas of the country where pipeline utilization is continuing to grow rapidly and where new pipeline capacity is needed or is planned over the next several years.

  19. Histidines in potential substrate recognition sites affect thyroid hormone transport by monocarboxylate transporter 8 (MCT8).

    PubMed

    Braun, Doreen; Lelios, Iva; Krause, Gerd; Schweizer, Ulrich

    2013-07-01

    Mutations in monocarboxylate transporter 8 (MCT8; SLC16A2) cause the Allan-Herndon-Dudley syndrome, a severe X-linked psychomotor retardation syndrome. MCT8 belongs to the major facilitator superfamily of 12 transmembrane-spanning proteins and transports thyroid hormones across the blood-brain barrier and into neurons. How MCT8 distinguishes thyroid hormone substrates from structurally closely related compounds is not known. The goal of this study was to identify critical amino acids along the transport channel cavity, which participate in thyroid hormone recognition. The fact that T3 is bound between a His-Arg clamp in the crystal structure of the T3 receptor/T3 complex prompted us to investigate whether such a motif might potentially be relevant for T3 recognition in MCT8. We therefore replaced candidate histidines and arginines by site-directed mutagenesis and performed activity assays in MDCK-1 cells and Xenopus oocytes. Histidines were replaced by alanine, phenylalanine, and glutamine to probe for molecular properties like aromatic ring structure and H-bonding properties. It was found that some mutations in His192 and His415 significantly changed substrate transport kinetics. Arg301 at the intracellular end of the substrate channel is at an ideal distance to His415 to participate in a His-Arg clamp and mutation to alanine-abrogated hormone transport. Molecular modeling demonstrates a perfect fit of T3 poised into the substrate channel between His415 and Arg301 and observing the same geometry as in the T3 receptor.

  20. Engineering development of ceramic membrane reactor system for converting natural gas to hydrogen and synthesis gas for liquid transportation fuels

    SciTech Connect

    1998-07-01

    The objective of this contract is to research, develop and demonstrate a novel ceramic membrane reactor system for the low-cost conversion of natural gas to synthesis gas and hydrogen for liquid transportation fuels: the ITM Syngas process. Through an eight-year, three-phase program, the technology will be developed and scaled up to obtain the technical, engineering, operating and economic data necessary for the final step to full commercialization of the Gas-to-Liquids (GTL) conversion technology. This report is a summary of activities through June 1998.

  1. Molecular Dynamics Simulations of Gas Transport in Polymer Films

    NASA Astrophysics Data System (ADS)

    Whitley, David; Butler, Simon; Adolf, David

    2010-03-01

    Parallel molecular dynamics simulations have been carried out to determine the permeability of O2 and N2 through polyethylene terephthalate, polypropylene and cis(1-4) polybutadiene. The permeability of both mixed and unmixed gas penetrants is studied within films of these well known gas barrier polymers. Results are obtained either through the solubility and diffusion (i.e. P=D*S) or via the permeability directly. Encouraging results are obtained. Additional analysis focuses on ``unmixed/mixed gas'' intracomparisons of the simulated permeability data in addition to corresponding penetrant and host polymer local dynamics.

  2. Changes in U.S. Natural Gas Transportation Infrastructure in 2004

    EIA Publications

    2005-01-01

    This report looks at the level of growth that occurred within the U.S. natural gas transportation network during 2004. In addition, it includes discussion and an analysis of recent gas pipeline development activities and an examination of additional projects proposed for completion over the next several years.

  3. Water Transport Characteristics of Gas Diffusion Layer in a PEM Fuel Cell

    SciTech Connect

    Damle, Ashok S; Cole, J Vernon

    2008-12-01

    A presentation addressing the following: Water transport in PEM Fuel Cells - a DoE Project 1. Gas Diffusion Layer--Role and Characteristics 2. Capillary Pressure Determinations of GDL Media 3. Gas Permeability Measurements of GDL Media 4. Conclusions and Future Activities

  4. Methodology for in situ gas sampling, transport and laboratory analysis of gases from stranded cetaceans

    PubMed Central

    de Quirós, Yara Bernaldo; González-Díaz, Óscar; Saavedra, Pedro; Arbelo, Manuel; Sierra, Eva; Sacchini, Simona; Jepson, Paul D.; Mazzariol, Sandro; Di Guardo, Giovanni; Fernández, Antonio

    2011-01-01

    Gas-bubble lesions were described in cetaceans stranded in spatio-temporal concordance with naval exercises using high-powered sonars. A behaviourally induced decompression sickness-like disease was proposed as a plausible causal mechanism, although these findings remain scientifically controversial. Investigations into the constituents of the gas bubbles in suspected gas embolism cases are highly desirable. We have found that vacuum tubes, insulin syringes and an aspirometer are reliable tools for in situ gas sampling, storage and transportation without appreciable loss of gas and without compromising the accuracy of the analysis. Gas analysis is conducted by gas chromatography in the laboratory. This methodology was successfully applied to a mass stranding of sperm whales, to a beaked whale stranded in spatial and temporal association with military exercises and to a cetacean chronic gas embolism case. Results from the freshest animals confirmed that bubbles were relatively free of gases associated with putrefaction and consisted predominantly of nitrogen. PMID:22355708

  5. Methodology for in situ gas sampling, transport and laboratory analysis of gases from stranded cetaceans

    NASA Astrophysics Data System (ADS)

    de Quirós, Yara Bernaldo; González-Díaz, Óscar; Saavedra, Pedro; Arbelo, Manuel; Sierra, Eva; Sacchini, Simona; Jepson, Paul D.; Mazzariol, Sandro; di Guardo, Giovanni; Fernández, Antonio

    2011-12-01

    Gas-bubble lesions were described in cetaceans stranded in spatio-temporal concordance with naval exercises using high-powered sonars. A behaviourally induced decompression sickness-like disease was proposed as a plausible causal mechanism, although these findings remain scientifically controversial. Investigations into the constituents of the gas bubbles in suspected gas embolism cases are highly desirable. We have found that vacuum tubes, insulin syringes and an aspirometer are reliable tools for in situ gas sampling, storage and transportation without appreciable loss of gas and without compromising the accuracy of the analysis. Gas analysis is conducted by gas chromatography in the laboratory. This methodology was successfully applied to a mass stranding of sperm whales, to a beaked whale stranded in spatial and temporal association with military exercises and to a cetacean chronic gas embolism case. Results from the freshest animals confirmed that bubbles were relatively free of gases associated with putrefaction and consisted predominantly of nitrogen.

  6. Methodology for in situ gas sampling, transport and laboratory analysis of gases from stranded cetaceans.

    PubMed

    Bernaldo de Quirós, Yara; González-Díaz, Oscar; Saavedra, Pedro; Arbelo, Manuel; Sierra, Eva; Sacchini, Simona; Jepson, Paul D; Mazzariol, Sandro; Di Guardo, Giovanni; Fernández, Antonio

    2011-01-01

    Gas-bubble lesions were described in cetaceans stranded in spatio-temporal concordance with naval exercises using high-powered sonars. A behaviourally induced decompression sickness-like disease was proposed as a plausible causal mechanism, although these findings remain scientifically controversial. Investigations into the constituents of the gas bubbles in suspected gas embolism cases are highly desirable. We have found that vacuum tubes, insulin syringes and an aspirometer are reliable tools for in situ gas sampling, storage and transportation without appreciable loss of gas and without compromising the accuracy of the analysis. Gas analysis is conducted by gas chromatography in the laboratory. This methodology was successfully applied to a mass stranding of sperm whales, to a beaked whale stranded in spatial and temporal association with military exercises and to a cetacean chronic gas embolism case. Results from the freshest animals confirmed that bubbles were relatively free of gases associated with putrefaction and consisted predominantly of nitrogen.

  7. Transport and sorting of the solanum tuberosum sucrose transporter SUT1 is affected by posttranslational modification.

    PubMed

    Krügel, Undine; Veenhoff, Liesbeth M; Langbein, Jennifer; Wiederhold, Elena; Liesche, Johannes; Friedrich, Thomas; Grimm, Bernhard; Martinoia, Enrico; Poolman, Bert; Kühn, Christina

    2008-09-01

    The plant sucrose transporter SUT1 from Solanum tuberosum revealed a dramatic redox-dependent increase in sucrose transport activity when heterologously expressed in Saccharomyces cerevisiae. Plant plasma membrane vesicles do not show any change in proton flux across the plasma membrane in the presence of redox reagents, indicating a SUT1-specific effect of redox reagents. Redox-dependent sucrose transport activity was confirmed electrophysiologically in Xenopus laevis oocytes with SUT1 from maize (Zea mays). Localization studies of green fluorescent protein fusion constructs showed that an oxidative environment increased the targeting of SUT1 to the plasma membrane where the protein concentrates in 200- to 300-nm raft-like microdomains. Using plant plasma membranes, St SUT1 can be detected in the detergent-resistant membrane fraction. Importantly, in yeast and in plants, oxidative reagents induced a shift in the monomer to dimer equilibrium of the St SUT1 protein and increased the fraction of dimer. Biochemical methods confirmed the capacity of SUT1 to form a dimer in plants and yeast cells in a redox-dependent manner. Blue native PAGE, chemical cross-linking, and immunoprecipitation, as well as the analysis of transgenic plants with reduced expression of St SUT1, confirmed the dimerization of St SUT1 and Sl SUT1 (from Solanum lycopersicum) in planta. The ability to form homodimers in plant cells was analyzed by the split yellow fluorescent protein technique in transiently transformed tobacco (Nicotiana tabacum) leaves and protoplasts. Oligomerization seems to be cell type specific since under native-like conditions, a phloem-specific reduction of the dimeric form of the St SUT1 protein was detectable in SUT1 antisense plants, whereas constitutively inhibited antisense plants showed reduction only of the monomeric form. The role of redox control of sucrose transport in plants is discussed.

  8. Natural gas: Marine transportation. (Latest citations from Oceanic Abstracts). Published Search

    SciTech Connect

    1997-01-01

    The bibliography contains citations concerning the design, construction, and operation of ships for the transport of liquified natural gas. Topics include safety devices, materials handling equipment for loading and unloading liquified natural gas, new hull and vessel designs, gas turbine propulsion systems, cargo tank designs and requirements, and liguid load dynamics. (Contains 50-250 citations and includes a subject term index and title list.) (Copyright NERAC, Inc. 1995)

  9. Natural gas: Marine transportation. (Latest citations from Oceanic abstracts). Published Search

    SciTech Connect

    1996-02-01

    The bibliography contains citations concerning the design, construction, and operation of ships for the transport of liquified natural gas. Topics include safety devices, materials handling equipment for loading and unloading liquified natural gas, new hull and vessel designs, gas turbine propulsion systems, cargo tank designs and requirements, and liguid load dynamics. (Contains 50-250 citations and includes a subject term index and title list.) (Copyright NERAC, Inc. 1995)

  10. Transport of Gas and Solutes in Permeable Estuarine Sediments

    DTIC Science & Technology

    2010-09-30

    collection of information if it does not display a currently valid OMB control number. 1. REPORT DATE 2010 2. REPORT TYPE 3. DATES COVERED 00-00...thereby also gas ebullition , the bubble traps collect bubbles under the natural flow conditions. − Determination of gas composition. The...characteristics of bubble ebullition in a shallow coastal environment with strong benthic photosynthesis (May 26-28). The goal was to determine the spatial and

  11. Water and greenhouse gas tradeoffs associated with a transition to a low carbon transportation system

    EPA Science Inventory

    Transportation fuels are heavily dominated by the use of petroleum, but concerns over oil depletion, energy security, and greenhouse gas emissions from petroleum combustion are driving the search for alternatives. As we look to shift away from petroleum-based transportation fuels...

  12. Gas transport in unsaturated porous media: the adequacy of Fick's law

    USGS Publications Warehouse

    Thorstenson, D.C.; Pollock, D.W.

    1989-01-01

    The increasing use of natural unsaturated zones as repositories for landfills and disposal sites for hazardous wastes (chemical and radioactive) requires a greater understanding of transport processes in the unsaturated zone. For volatile constituents an important potential transport mechanism is gaseous diffusion. Diffusion, however, cannot be treated as an independent isolated transport mechanism. A complete understanding of multicomponent gas transport in porous media (unsaturated zones) requires a knowledge of Knudsen transport, the molecular and nonequimolar components of diffusive flux, and viscous (pressure driven) flux. This review presents a brief discussion of the underlying principles and interrelationships among each of the above flux mechanisms. -from Authors

  13. (220)Rn/(222)Rn isotope pair as a natural proxy for soil gas transport.

    PubMed

    Huxol, Stephan; Brennwald, Matthias S; Henneberger, Ruth; Kipfer, Rolf

    2013-12-17

    Radon (Rn) is a naturally occurring radioactive noble gas, which is ubiquitous in soil gas. Especially, its long-lived isotope (222)Rn (half-life: 3.82 d) gained widespread acceptance as a tracer for gas transport in soils, while the short-lived (220)Rn (half-life: 55.6 s) found less interest in environmental studies. However, in some cases, the application of (222)Rn as a tracer in soil gas is complex as its concentrations can be influenced by changes of the transport conditions or of the (222)Rn production of the soil material. Due to the different half-lives of (220)Rn and (222)Rn, the distances that can be traveled by the respective isotopes before decay differ significantly, with (220)Rn migrating over much shorter distances than (222)Rn. Therefore, the soil gas concentrations of (220)Rn and (222)Rn are influenced by processes on different length scales. In laboratory experiments in a sandbox, we studied the different transport behaviors of (220)Rn and (222)Rn resulting from changing the boundary conditions for diffusive transport and from inducing advective gas movements. From the results gained in the laboratory experiments, we propose the combined analysis of (220)Rn and (222)Rn to determine gas transport processes in soils. In a field study on soil gases in the cover soil of a capped landfill we applied the combined analysis of (220)Rn and (222)Rn in soil gas for the first time and showed the feasibility of this approach to characterize soil gas transport processes.

  14. Gas production and transport during bench-scale electrical resistance heating of water and trichloroethene.

    PubMed

    Hegele, P R; Mumford, K G

    2014-09-01

    The effective remediation of chlorinated solvent source zones using in situ thermal treatment requires successful capture of gas that is produced. Replicate electrical resistance heating experiments were performed in a thin bench-scale apparatus, where water was boiled and pooled dense non-aqueous phase liquid (DNAPL) trichloroethene (TCE) and water were co-boiled in unconsolidated silica sand. Quantitative light transmission visualization was used to assess gas production and transport mechanisms. In the water boiling experiments, nucleation, growth and coalescence of the gas phase into connected channels were observed at critical gas saturations of Sgc=0.233±0.017, which allowed for continuous gas transport out of the sand. In experiments containing a colder region above a target heated zone, condensation prevented the formation of steam channels and discrete gas clusters that mobilized into colder regions were trapped soon after discontinuous transport began. In the TCE-water experiments, co-boiling at immiscible fluid interfaces resulted in discontinuous gas transport above the DNAPL pool. Redistribution of DNAPL was also observed above the pool and at the edge of the vapor front that propagated upwards through colder regions. These results suggest that the subsurface should be heated to water boiling temperatures to facilitate gas transport from specific locations of DNAPL to extraction points and reduce the potential for DNAPL redistribution. Decreases in electric current were observed at the onset of gas phase production, which suggests that coupled electrical current and temperature measurements may provide a reliable metric to assess gas phase development.

  15. Gas production and transport during bench-scale electrical resistance heating of water and trichloroethene

    NASA Astrophysics Data System (ADS)

    Hegele, P. R.; Mumford, K. G.

    2014-09-01

    The effective remediation of chlorinated solvent source zones using in situ thermal treatment requires successful capture of gas that is produced. Replicate electrical resistance heating experiments were performed in a thin bench-scale apparatus, where water was boiled and pooled dense non-aqueous phase liquid (DNAPL) trichloroethene (TCE) and water were co-boiled in unconsolidated silica sand. Quantitative light transmission visualization was used to assess gas production and transport mechanisms. In the water boiling experiments, nucleation, growth and coalescence of the gas phase into connected channels were observed at critical gas saturations of Sgc = 0.233 ± 0.017, which allowed for continuous gas transport out of the sand. In experiments containing a colder region above a target heated zone, condensation prevented the formation of steam channels and discrete gas clusters that mobilized into colder regions were trapped soon after discontinuous transport began. In the TCE-water experiments, co-boiling at immiscible fluid interfaces resulted in discontinuous gas transport above the DNAPL pool. Redistribution of DNAPL was also observed above the pool and at the edge of the vapor front that propagated upwards through colder regions. These results suggest that the subsurface should be heated to water boiling temperatures to facilitate gas transport from specific locations of DNAPL to extraction points and reduce the potential for DNAPL redistribution. Decreases in electric current were observed at the onset of gas phase production, which suggests that coupled electrical current and temperature measurements may provide a reliable metric to assess gas phase development.

  16. Engineering Development of Ceramic Membrane Reactor System for Converting Natural Gas to Hydrogen and Synthesis Gas for Liquid Transportation Fuels

    SciTech Connect

    Air Products and Chemicals

    2008-09-30

    An Air Products-led team successfully developed ITM Syngas technology from the concept stage to a stage where a small-scale engineering prototype was about to be built. This technology produces syngas, a gas containing carbon monoxide and hydrogen, by reacting feed gas, primarily methane and steam, with oxygen that is supplied through an ion transport membrane. An ion transport membrane operates at high temperature and oxygen ions are transported through the dense membrane's crystal lattice when an oxygen partial pressure driving force is applied. This development effort solved many significant technical challenges and successfully scaled-up key aspects of the technology to prototype scale. Throughout the project life, the technology showed significant economic benefits over conventional technologies. While there are still on-going technical challenges to overcome, the progress made under the DOE-funded development project proved that the technology was viable and continued development post the DOE agreement would be warranted.

  17. Facilities, breed and experience affect ease of sheep handling: the livestock transporter's perspective.

    PubMed

    Burnard, C L; Pitchford, W S; Hocking Edwards, J E; Hazel, S J

    2015-08-01

    An understanding of the perceived importance of a variety of factors affecting the ease of handling of sheep and the interactions between these factors is valuable in improving profitability and welfare of the livestock. Many factors may contribute to animal behaviour during handling, and traditionally these factors have been assessed in isolation under experimental conditions. A human social component to this phenomenon also exists. The aim of this study was to gain a deeper understanding of the importance of a variety of factors affecting ease of handling, and the interactions between these from the perspective of the livestock transporter. Qualitative interviews were used to investigate the factors affecting sheep behaviour during handling. Interview transcripts underwent thematic analysis. Livestock transporters discussed the effects of attitudes and behaviours towards sheep, helpers, facilities, distractions, environment, dogs and a variety of sheep factors including breed, preparation, experience and sex on sheep behaviour during handling. Transporters demonstrated care and empathy and stated that patience and experience were key factors determining how a person might deal with difficult sheep. Livestock transporters strongly believed facilities (ramps and yards) had the greatest impact, followed by sheep experience (naivety of the sheep to handling and transport) and breed. Transporters also discussed the effects of distractions, time of day, weather, dogs, other people, sheep preparation, body condition and sheep sex on ease of handling. The concept of individual sheep temperament was indirectly expressed.

  18. Coupling of hydrologic transport and chemical reactions in a stream affected by acid mine drainage

    USGS Publications Warehouse

    Kimball, B.A.; Broshears, R.E.; Bencala, K.E.; McKnight, Diane M.

    1994-01-01

    Experiments in St. Kevin Gulch, an acid mine drainage stream, examined the coupling of hydrologic transport to chemical reactions affecting metal concentrations. Injection of LiCl as a conservative tracer was used to determine discharge and residence time along a 1497-m reach. Transport of metals downstream from inflows of acidic, metal-rich water was evaluated based on synoptic samples of metal concentrations and the hydrologic characteristics of the stream. Transport of SO4 and Mn was generally conservative, but in the subreaches most affected by acidic inflows, transport was reactive. Both 0.1-??m filtered and particulate Fe were reactive over most of the stream reach. Filtered Al partitioned to the particulate phase in response to high instream concentrations. Simulations that accounted for the removal of SO4, Mn, Fe, and Al with first-order reactions reproduced the steady-state profiles. The calculated rate constants for net removal used in the simulations embody several processes that occur on a stream-reach scale. The comparison between rates of hydrologie transport and chemical reactions indicates that reactions are only important over short distances in the stream near the acidic inflows, where reactions occur on a comparable time scale with hydrologic transport and thus affect metal concentrations.

  19. Thinking on Sichuan-Chongqing gas pipeline transportation system reform under market-oriented conditions

    NASA Astrophysics Data System (ADS)

    Duan, Yanzhi

    2017-01-01

    The gas pipeline networks in Sichuan and Chongqing (Sichuan-Chongqing) region have formed a fully-fledged gas pipeline transportation system in China, which supports and promotes the rapid development of gas market in Sichuan-Chongqing region. In the circumstances of further developed market-oriented economy, it is necessary to carry out further the pipeline system reform in the areas of investment/financing system, operation system and pricing system to lay a solid foundation for improving future gas production and marketing capability and adapting itself to the national gas system reform, and to achieve the objectives of multiparty participated pipeline construction, improved pipeline transportation efficiency and fair and rational pipeline transportation prices. In this article, main thinking on reform in the three areas and major deployment are addressed, and corresponding measures on developing shared pipeline economy, providing financial support to pipeline construction, setting up independent regulatory agency to enhance the industrial supervision for gas pipeline transportation, and promoting the construction of regional gas trade market are recommended.

  20. Oxygen transport membrane based advanced power cycle with low pressure synthesis gas slip stream

    DOEpatents

    Kromer, Brian R.; Litwin, Michael M.; Kelly, Sean M.

    2016-09-27

    A method and system for generating electrical power in which a high pressure synthesis gas stream generated in a gasifier is partially oxidized in an oxygen transport membrane based reactor, expanded and thereafter, is combusted in an oxygen transport membrane based boiler. A low pressure synthesis gas slip stream is split off downstream of the expanders and used as the source of fuel in the oxygen transport membrane based partial oxidation reactors to allow the oxygen transport membrane to operate at low fuel pressures with high fuel utilization. The combustion within the boiler generates heat to raise steam to in turn generate electricity by a generator coupled to a steam turbine. The resultant flue gas can be purified to produce a carbon dioxide product.

  1. Appraisal of transport and deformation in shale reservoirs using natural noble gas tracers

    SciTech Connect

    Heath, Jason E.; Kuhlman, Kristopher L.; Robinson, David G.; Bauer, Stephen J.; Gardner, William Payton

    2015-09-01

    This report presents efforts to develop the use of in situ naturally-occurring noble gas tracers to evaluate transport mechanisms and deformation in shale hydrocarbon reservoirs. Noble gases are promising as shale reservoir diagnostic tools due to their sensitivity of transport to: shale pore structure; phase partitioning between groundwater, liquid, and gaseous hydrocarbons; and deformation from hydraulic fracturing. Approximately 1.5-year time-series of wellhead fluid samples were collected from two hydraulically-fractured wells. The noble gas compositions and isotopes suggest a strong signature of atmospheric contribution to the noble gases that mix with deep, old reservoir fluids. Complex mixing and transport of fracturing fluid and reservoir fluids occurs during production. Real-time laboratory measurements were performed on triaxially-deforming shale samples to link deformation behavior, transport, and gas tracer signatures. Finally, we present improved methods for production forecasts that borrow statistical strength from production data of nearby wells to reduce uncertainty in the forecasts.

  2. Quantum transport through a Tonks-Girardeau gas.

    PubMed

    Palzer, Stefan; Zipkes, Christoph; Sias, Carlo; Köhl, Michael

    2009-10-09

    We investigate the propagation of spin impurity atoms through a strongly interacting one-dimensional Bose gas. The initially well localized impurities are accelerated by a constant force, very much analogous to electrons subject to a bias voltage, and propagate as a one-dimensional impurity spin wave packet. We follow the motion of the impurities in situ and characterize the interaction induced dynamics. We observe a very complex nonequilibrium dynamics, including the emergence of large density fluctuations in the remaining Bose gas, and multiple scattering events leading to dissipation of the impurity's motion.

  3. State policies affecting natural gas consumption (Notice of inquiry issued on August 14, 1992)

    SciTech Connect

    Lemon, R.; Kamphuis-Zatopa, W.

    1993-03-25

    On August 14, 1992, the United States Department of Energy issued a Request for Comments Concerning State Policies Affecting Natural Gas Consumption. This Notice of (NOI) noted the increasing significance of the role played by states and sought to gain better understanding of how state policies impact the gas industry. The general trend toward a. more competitive marketplace for natural gas, as well as recent regulatory and legislative changes at the Federal level, are driving State regulatory agencies to reevaluate how they regulate natural gas. State action is having a significant impact on the use of natural gas for generating electricity, as well as affecting the cost-effective trade-off between conservation expenditures and gas use. Additionally, fuel choice has an impact upon the environment and national energy security. In light of these dimensions, the Department of Energy initiated this study of State regulation. The goals of this NOI are: (1) help DOE better understand the impact of State policies on the efficient use of gas; (2) increase the awareness of the natural gas industry and Federal and State officials to the important role of State policies and regulations; (3) create an improved forum for dialogue on State and Federal natural gas issues; and, (4) develop a consensus on an analytical agenda that would be most helpful in addressing the regulatory challenges faced by the States. Ninety-seven parties filed comments, and of these ninety-seven, fifteen parties filed reply comments. Appendix One lists these parties. This report briefly syntheses the comments received. The goal is to assist parties to judging the extent of consensus on the problems posed and the remedies suggested, aid in identifying future analytical analyses, and assist parties in assessing differences in strategies and regulatory philosophies which shape these issues and their resolution.

  4. Greenhouse Gas Emissions Driven by the Transportation of Goods Associated with French Consumption.

    PubMed

    Hawkins, Troy R; Dente, Sebastien M R

    2010-11-15

    The transportation of goods plays a significant role in the overall greenhouse gas emissions from consumption. This study investigates the connections between French household consumption and production and transportation-related emissions throughout product supply chains. Here a two-region, environmentally extended input-output model is combined with a novel detailed, physical-unit transportation model to examine the connection between product, location of production, choice of transport mode, and greenhouse gas emissions. Total emissions associated with French household consumption are estimated to be 627 MtCO2e, or 11 tCO2e per capita. Of these, 3% are associated with the transportation of goods within France and 10% with transport of goods outside or into France. We find that most transport originating in northern Europe is by road, whereas most transport from other regions is conducted by sea and ocean transport. Rail, inland water, and air transportation play only a minor role in terms of mass, tonne-kilometers, and greenhouse gas emissions. By product, transport of coal and coke and intermediate goods make the largest contribution to overall freight transport emissions associated with French household consumption. In terms of mass, most goods are transported by road while in terms of tonne-kilometers, sea and ocean transport plays the largest role. Road transport contributes the highest share to the transport of all goods with the exceptions of coal and coke and petroleum. We examine the potential for emissions reductions associated with shifting 10% of direct imports by air freight to sea and ocean or road transport and find that the potential reductions are less than 0.03% of total emissions associated with French consumption. We also consider shifting 10% of direct imports by road transport to rail or inland water and find potential reductions on the order of 0.4−0.5% of the total or 3−4% of the freight transport emissions associated with French

  5. Analysis of volatile phase transport in soils using natural radon gas as a tracer

    SciTech Connect

    Chen, C.; Thomas, D.M.

    1992-12-31

    We have conducted a field study of soil gas transport processes using radon gas as a naturally occurring tracer. The .experiment monitored soil gas radon activity, soil moisture, and soil temperature at three depths in the shallow soil column; barometric pressure, rainfall and wind speed were monitored at the soil surface. Linear and multiple regression analysis of the data sets has shown that the gas phase radon activities under natural environmental conditions are influenced by soil moisture content, barometric pressure variations, soil temperature and soil structure. The effect of wind speed on subsurface radon activities under our field conditions has not been demonstrated.

  6. Analysis of volatile phase transport in soils using natural radon gas as a tracer

    SciTech Connect

    Chen, C.; Thomas, D.M.

    1992-01-01

    We have conducted a field study of soil gas transport processes using radon gas as a naturally occurring tracer. The .experiment monitored soil gas radon activity, soil moisture, and soil temperature at three depths in the shallow soil column; barometric pressure, rainfall and wind speed were monitored at the soil surface. Linear and multiple regression analysis of the data sets has shown that the gas phase radon activities under natural environmental conditions are influenced by soil moisture content, barometric pressure variations, soil temperature and soil structure. The effect of wind speed on subsurface radon activities under our field conditions has not been demonstrated.

  7. Overview of U.S. Legislation and Regulations Affecting Offshore Natural Gas and Oil Activity

    EIA Publications

    2005-01-01

    This article presents a summary of the legislative and regulatory regime that affects natural gas and oil exploration and production in offshore regions of the United States. It discusses the role and importance of these areas as well as the competing interests surrounding ownership, production, exploration and conservation.

  8. METHANOL PRODUCTION FROM BIOMASS AND NATURAL GAS AS TRANSPORTATION FUEL

    EPA Science Inventory

    Two processes are examined for production of methanol. They are assessed against the essential requirements of a future alternative fuel for road transport: that it (i) is producible in amounts comparable to the 19 EJ of motor fuel annually consumed in the U.S., (ii) minimizes em...

  9. Unified Measurement System with Suction Control for Gas Transport Parameters in Porous Media

    NASA Astrophysics Data System (ADS)

    Kawamoto, K.; Rouf, M. A.; Hamamoto, S.; Sakaki, T.; Komatsu, T.; Moldrup, P.

    2010-12-01

    Pore geometric parameters including pore size distribution, total and air-filled porosities, pore tortuosity and connectivity strongly influence air flow in porous media, and, thus, characterize gas transport parameters such as gas diffusion coefficient Dp and air permeability ka. In this study, the gas transport parameters were measured for porous media with varying textures under repeated drying and wetting cycles using a newly-developed measurement system, and the hysteretic behaviors in the gas transport parameters were examined. A unified measurement system with suction control (UMS_SC) was developed for measuring soil water characteristics curve and gas transport parameters sequentially under drying and wetting cycles. It consisted of a porous plate, diffusion chamber, sample ring (15 cm in inner diameter and 12 cm in height), tensiometer, soil moisture sensor, oxygen electrodes and air pressure gauges. Soil water characteristics curve and gas transport parameters (gas diffusion coefficient Dp and air permeability ka) for differently textured materials including sand, molten slag , and a mixture material of MS and volcanic ash soil were measured under repeated drying and wetting cycles. The measurement for each porous material was initiated from a full saturation and suction head was increased/decreased in steps in the drainage/wetting cycles. Moreover, independent measurements of Dp and ka were carried out for repacked air-dried samples using a cylindrical mold (15 cm in inner diameter and 12 cm in height) in order to obtain the Dp and ka values at a full dry condition. The newly-developed UMS_SC performed well for the applied suction head less than 50 cm of water with corresponding saturation of roughly 0.3-0.5. The gas transport parameters were well measured at each suction head level under repeated drying and wetting cycles, and the measured gas transport parameters including the independent measurements were verified by literature data as well as

  10. Membrane transporters and protein traffic networks differentially affecting metal tolerance: a genomic phenotyping study in yeast

    PubMed Central

    Ruotolo, Roberta; Marchini, Gessica; Ottonello, Simone

    2008-01-01

    Background The cellular mechanisms that underlie metal toxicity and detoxification are rather variegated and incompletely understood. Genomic phenotyping was used to assess the roles played by all nonessential Saccharomyces cerevisiae proteins in modulating cell viability after exposure to cadmium, nickel, and other metals. Results A number of novel genes and pathways that affect multimetal as well as metal-specific tolerance were discovered. Although the vacuole emerged as a major hot spot for metal detoxification, we also identified a number of pathways that play a more general, less direct role in promoting cell survival under stress conditions (for example, mRNA decay, nucleocytoplasmic transport, and iron acquisition) as well as proteins that are more proximally related to metal damage prevention or repair. Most prominent among the latter are various nutrient transporters previously not associated with metal toxicity. A strikingly differential effect was observed for a large set of deletions, the majority of which centered on the ESCRT (endosomal sorting complexes required for transport) and retromer complexes, which - by affecting transporter downregulation and intracellular protein traffic - cause cadmium sensitivity but nickel resistance. Conclusion The data show that a previously underestimated variety of pathways are involved in cadmium and nickel tolerance in eukaryotic cells. As revealed by comparison with five additional metals, there is a good correlation between the chemical properties and the cellular toxicity signatures of various metals. However, many conserved pathways centered on membrane transporters and protein traffic affect cell viability with a surprisingly high degree of metal specificity. PMID:18394190

  11. Oocyte aging-induced Neuronatin (NNAT) hypermethylation affects oocyte quality by impairing glucose transport in porcine

    PubMed Central

    Gao, Ying-Ying; Chen, Li; Wang, Tao; Nie, Zheng-Wen; Zhang, Xia; Miao, Yi-Liang

    2016-01-01

    DNA methylation plays important roles in regulating many physiological behaviors; however, few studies were focused on the changes of DNA methylation during oocyte aging. Early studies showed that some imprinted genes’ DNA methylation had been changed in aged mouse oocytes. In this study, we used porcine oocytes to test the hypothesis that oocyte aging would alter DNA methylation pattern of genes and disturb their expression in age oocytes, which affected the developmental potential of oocytes. We compared several different types of genes and found that the expression and DNA methylation of Neuronatin (NNAT) were disturbed in aged oocytes significantly. Additional experiments demonstrated that glucose transport was impaired in aged oocytes and injection of NNAT antibody into fresh oocytes led to the same effects on glucose transport. These results suggest that the expression of NNAT was declined by elevating DNA methylation, which affected oocyte quality by decreasing the ability of glucose transport in aged oocytes. PMID:27782163

  12. Transport of Gas and Solutes in Permeable Estuarine Sediments

    DTIC Science & Technology

    2011-09-30

    from the upper 10 cm and even deeper layers of shallow sands typically is photosynthetically active when exposed to light . For two dimensional plots of...ultrasonic and optical methods on sediment cores maintained at in-situ pressure, light and temperature and without changing the orientation of the...core. − Mapping of the spatial and temporal distribution of high sedimentary photosynthetic production and sites for free gas development

  13. Connexin-deficiency affects expression levels of glial glutamate transporters within the cerebrum.

    PubMed

    Unger, Tina; Bette, Stefanie; Zhang, Jiong; Theis, Martin; Engele, Jürgen

    2012-01-06

    The glial glutamate transporter subtypes, GLT-1/EAAT-2 and GLAST/EAAT-1 clear the bulk of extracellular glutamate and are severely dysregulated in various acute and chronic brain diseases. Despite the previous identification of several extracellular factors modulating glial glutamate transporter expression, our knowledge of the regulatory network controlling glial glutamate transport in health and disease still remains incomplete. In studies with cultured cortical astrocytes, we previously obtained evidence that glial glutamate transporter expression is also affected by gap junctions/connexins. To assess whether gap junctions would likewise control the in vivo expression of glial glutamate transporters, we have now assessed their expression levels in brains of conditional Cx43 knockout mice, total Cx30 knockouts, as well as Cx43/Cx30 double knockouts. We found that either knocking out Cx30, Cx43, or both increases GLT-1/EAAT-2 protein levels in the cerebral cortex to a similar extent. By contrast, GLAST/EAAT-1 protein levels maximally increased in cerebral cortices of Cx30/Cx43 double knockouts, implying that gap junctions differentially affect the expression of GLT-1/EAAT-2 and GLAST/EAAT-1. Quantitative PCR analysis further revealed that increases in glial glutamate transporter expression are brought about by transcriptional and translational/posttranslational processes. Moreover, GLT-1/EAAT-2- and GLAST/EAAT-1 protein levels remained unchanged in the hippocampi of Cx43/Cx30 double knockouts when compared to Cx43fl/fl controls, indicating brain region-specific effects of gap junctions on glial glutamate transport. Since astrocytic gap junction coupling is affected in various forms of brain injuries, our findings point to gap junctions/connexins as important regulators of glial glutamate turnover in the diseased cerebral cortex.

  14. Transportation Energy Futures Series: Effects of the Built Environment on Transportation: Energy Use, Greenhouse Gas Emissions, and Other Factors

    SciTech Connect

    Porter, C. D.; Brown, A.; Dunphy, R. T.; Vimmerstedt, L.

    2013-03-01

    Planning initiatives in many regions and communities aim to reduce transportation energy use, decrease emissions, and achieve related environmental benefits by changing land use. This report reviews and summarizes findings from existing literature on the relationship between the built environment and transportation energy use and greenhouse gas emissions, identifying results trends as well as potential future actions. The indirect influence of federal transportation and housing policies, as well as the direct impact of municipal regulation on land use are examined for their effect on transportation patterns and energy use. Special attention is given to the 'four D' factors of density, diversity, design and accessibility. The report concludes that policy-driven changes to the built environment could reduce transportation energy and GHG emissions from less than 1% to as much as 10% by 2050, the equivalent of 16%-18% of present-day urban light-duty-vehicle travel. This is one of a series of reports produced as a result of the Transportation Energy Futures (TEF) project, a Department of Energy-sponsored multi-agency project initiated to pinpoint underexplored strategies for abating GHGs and reducing petroleum dependence related to transportation.

  15. Transportation Energy Futures Series. Effects of the Built Environment on Transportation. Energy Use, Greenhouse Gas Emissions, and Other Factors

    SciTech Connect

    Porter, C. D.; Brown, A.; Dunphy, R. T.; Vimmerstedt, L.

    2013-03-15

    Planning initiatives in many regions and communities aim to reduce transportation energy use, decrease emissions, and achieve related environmental benefits by changing land use. This report reviews and summarizes findings from existing literature on the relationship between the built environment and transportation energy use and greenhouse gas emissions, identifying results trends as well as potential future actions. The indirect influence of federal transportation and housing policies, as well as the direct impact of municipal regulation on land use are examined for their effect on transportation patterns and energy use. Special attention is given to the 'four D' factors of density, diversity, design and accessibility. The report concludes that policy-driven changes to the built environment could reduce transportation energy and GHG emissions from less than 1% to as much as 10% by 2050, the equivalent of 16%-18% of present-day urban light-duty-vehicle travel. This is one of a series of reports produced as a result of the Transportation Energy Futures (TEF) project, a Department of Energy-sponsored multi-agency project initiated to pinpoint underexplored strategies for abating GHGs and reducing petroleum dependence related to transportation.

  16. Transport of Gas and Solutes in Permeable Estuarine Sediments

    DTIC Science & Technology

    2009-01-01

    information if it does not display a currently valid OMB control number. 1. REPORT DATE 2009 2. REPORT TYPE 3. DATES COVERED 00-00-2009 to 00-00...fluorescent light to investigate bubble production in surface sands under controlled conditions. 2 Effect of ebullition on subsurface-surface...solute exchange. The effect of ebullition , the movement of bubbles from one medium to another, on inert solute tracer transport through coarse-grained

  17. DIRECT COMPARISON OF KINETIC AND LOCAL EQUILIBRIUM FORMULATIONS FOR SOLUTE TRANSPORT AFFECTED BY SURFACE REACTIONS.

    USGS Publications Warehouse

    Bahr, Jean M.; Rubin, Jacob

    1987-01-01

    Modeling transport of reacting solutes in porous media often requires a choice between models based on the local equilibrium assumption (LEA) and models involving reaction kinetics. Direct comparison of the mathematical formulations for these two types of transport models can aid in this choice. For cases of transport affected by surface reaction, such a comparison is made possible by a new derivation procedure. This procedure yields a kinetics-based formulation that is the sum of the LEA formulation and one or more kinetically influenced terms. The dimensionless form of the new kinetics-based formulation facilitates identification of critical parameter groupings which control the approach to transport behavior consistent with LEA model predictions. Results of numerical experiments demonstrate that criteria for LEA applicability can be expressed conveniently in terms of these parameter groupings. The derivation procedure is demonstrated for examples of surface reactions including first-order reversible sorption, Langmuir-type kinetics and binary, homovalent ion exchange.

  18. [Vertical transporting risk of nitrogen in purple soil affected by surfactant].

    PubMed

    Chen, Yu-cheng; Yang, Zhi-min; Jiang, Ling; Chen, Qing-hu; Gao, Meng

    2010-07-01

    The simulated leaching experiment was conducted to determine the effects of surfactant of sodium dodecyl benzene sulphonate (SDBS) on vertical transporting of nitrogen in purple soil. SDBS could reduce NH4+ -N loss from soil, and the higher concentration of SDBS, the less loss. SDBS could increase NO3- -N loss from soil, and the order of accumulation loss is SDBS100 > SDBS40 > SDBS0 > SDBS5. Lower concentration SDBS decrease TKN loss, but higher concentration SDBS had a reverse effect, and compared with SDBS0, the accumulation loss TKN of SDBS40, SDBS100 increased by 16.8%, 22.36%, respectively. SDBS could affect vertical transporting of nitrogen in purple soil, that is, the significant down-transporting of nitrogen was observed after leaching with SDBS, and the higher concentration of SDBS, the more obviously transporting trend.

  19. Energy policy act transportation study: Interim report on natural gas flows and rates

    SciTech Connect

    1995-11-17

    This report, Energy Policy Act Transportation Study: Interim Report on Natural Gas Flows and Rates, is the second in a series mandated by Title XIII, Section 1340, ``Establishment of Data Base and Study of Transportation Rates,`` of the Energy Policy Act of 1992 (P.L. 102--486). The first report Energy Policy Act Transportation Study: Availability of Data and Studies, was submitted to Congress in October 1993; it summarized data and studies that could be used to address the impact of legislative and regulatory actions on natural gas transportation rates and flow patterns. The current report presents an interim analysis of natural gas transportation rates and distribution patterns for the period from 1988 through 1994. A third and final report addressing the transportation rates and flows through 1997 is due to Congress in October 2000. This analysis relies on currently available data; no new data collection effort was undertaken. The need for the collection of additional data on transportation rates will be further addressed after this report, in consultation with the Congress, industry representatives, and in other public forums.

  20. Decreased vesicular monoamine transporter 2 (VMAT2) and dopamine transporter (DAT) function in knockout mice affects aging of dopaminergic systems

    PubMed Central

    Hall, F. S.; Itokawa, K.; Schmitt, A.; Moessner, R.; Sora, I.; Lesch, K. P.; Uhl, G. R.

    2013-01-01

    Dopamine (DA) is accumulated and compartmentalized by the dopamine transporter (DAT; SLC3A6) and the vesicular monoamine transporter 2 (VMAT2; SLC18A2). These transporters work at the plasma and vesicular membranes of dopaminergic neurons, respectively, and thus regulate levels of DA in neuronal compartments that include the extravesicular cytoplasmic compartment. DA in this compartment has been hypothesized to contribute to oxidative damage that can reduce the function of dopaminergic neurons in aging brains and may contribute to reductions in dopaminergic neurochemical markers, locomotor behavior and responses to dopaminergic drugs that are found in aged animals. The studies reported here examined aged mice with heterozygous deletions of VMAT2 or of DAT, which each reduce transporter expression to about 50% of levels found in wild-type (WT) mice. Aged mice displayed reduced locomotor responses under a variety of circumstances, including in response to locomotor stimulants, as well as changes in monoamine levels and metabolites in a regionally dependent manner. Several effects of aging were more pronounced in heterozygous VMAT2 knockout (KO) mice, including aging induced reductions in locomotion and reduced locomotor responses to cocaine. By contrast, some effects of aging were reduced or not observed in heterozygous DAT KO mice. These findings support the idea that altered DAT and VMAT2 expression affect age-related changes in dopaminergic function. These effects are most likely mediated by alterations in DA compartmentalization, and might be hypothesized to be more exacerbated by other factors that affect the metabolism of cytosolic DA. PMID:23978383

  1. MR Imaging of Apparent 3He Gas Transport in Narrow Pipes and Rodent Airways

    SciTech Connect

    Minard, Kevin R.; Jacob, Rick E.; Laicher, Gernot; Einstein, Daniel R.; Kuprat, Andrew P.; Corley, Richard A.

    2008-10-01

    High sensitivity makes hyperpolarized 3He an attractive signal source for visualizing gas flow with magnetic resonance (MR) imaging. Its rapid Brownian motion, however, can blur observed flow lamina and alter measured diffusion rates when excited nuclei traverse shear-induced velocity gradients during data acquisition. Here, both effects are described analytically, and predicted values for measured transport during laminar flow through a straight, 3.2-mm-diameter pipe are validated using two-dimensional (2D) constant-time images of different binary gas mixtures. Results show explicitly how measured transport in narrow conduits is characterized by apparent values that depend on underlying gas dynamics and imaging time. In ventilated rats, this is found to obscure acquired airflow images. Flow splitting at airway branches is still evident, however, and use of 3D vector flow mapping is shown to provide a quantitative view of pulmonary gas supply that highlights the correlation of airflow dynamics with lung structure.

  2. Transport Membrane Condenser for Water and Energy Recovery from Power Plant Flue Gas

    SciTech Connect

    Dexin Wang

    2012-03-31

    The new waste heat and water recovery technology based on a nanoporous ceramic membrane vapor separation mechanism has been developed for power plant flue gas application. The recovered water vapor and its latent heat from the flue gas can increase the power plant boiler efficiency and reduce water consumption. This report describes the development of the Transport Membrane Condenser (TMC) technology in details for power plant flue gas application. The two-stage TMC design can achieve maximum heat and water recovery based on practical power plant flue gas and cooling water stream conditions. And the report includes: Two-stage TMC water and heat recovery system design based on potential host power plant coal fired flue gas conditions; Membrane performance optimization process based on the flue gas conditions, heat sink conditions, and water and heat transport rate requirement; Pilot-Scale Unit design, fabrication and performance validation test results. Laboratory test results showed the TMC system can exact significant amount of vapor and heat from the flue gases. The recovered water has been tested and proved of good quality, and the impact of SO{sub 2} in the flue gas on the membrane has been evaluated. The TMC pilot-scale system has been field tested with a slip stream of flue gas in a power plant to prove its long term real world operation performance. A TMC scale-up design approach has been investigated and an economic analysis of applying the technology has been performed.

  3. Opportunities for Synergy Between Natural Gas and Renewable Energy in the Electric Power and Transportation Sectors

    SciTech Connect

    Lee, A.; Zinaman, O.; Logan, J.

    2012-12-01

    Use of both natural gas and renewable energy has grown significantly in recent years. Both forms of energy have been touted as key elements of a transition to a cleaner and more secure energy future, but much of the current discourse considers each in isolation or concentrates on the competitive impacts of one on the other. This paper attempts, instead, to explore potential synergies of natural gas and renewable energy in the U.S. electric power and transportation sectors.

  4. PARTICLE TRANSPORTATION AND DEPOSITION IN HOT GAS FILTER VESSELS - A COMPUTATIONAL AND EXPERIMENTAL MODELING APPROACH

    SciTech Connect

    Goodarz Ahmadi

    2002-07-01

    In this project, a computational modeling approach for analyzing flow and ash transport and deposition in filter vessels was developed. An Eulerian-Lagrangian formulation for studying hot-gas filtration process was established. The approach uses an Eulerian analysis of gas flows in the filter vessel, and makes use of the Lagrangian trajectory analysis for the particle transport and deposition. Particular attention was given to the Siemens-Westinghouse filter vessel at Power System Development Facility in Wilsonville in Alabama. Details of hot-gas flow in this tangential flow filter vessel are evaluated. The simulation results show that the rapidly rotation flow in the spacing between the shroud and the vessel refractory acts as cyclone that leads to the removal of a large fraction of the larger particles from the gas stream. Several alternate designs for the filter vessel are considered. These include a vessel with a short shroud, a filter vessel with no shroud and a vessel with a deflector plate. The hot-gas flow and particle transport and deposition in various vessels are evaluated. The deposition patterns in various vessels are compared. It is shown that certain filter vessel designs allow for the large particles to remain suspended in the gas stream and to deposit on the filters. The presence of the larger particles in the filter cake leads to lower mechanical strength thus allowing for the back-pulse process to more easily remove the filter cake. A laboratory-scale filter vessel for testing the cold flow condition was designed and fabricated. A laser-based flow visualization technique is used and the gas flow condition in the laboratory-scale vessel was experimental studied. A computer model for the experimental vessel was also developed and the gas flow and particle transport patterns are evaluated.

  5. Unifying diffusion and seepage for nonlinear gas transport in multiscale porous media

    NASA Astrophysics Data System (ADS)

    Song, Hongqing; Wang, Yuhe; Wang, Jiulong; Li, Zhengyi

    2016-09-01

    We unify the diffusion and seepage process for nonlinear gas transport in multiscale porous media via a proposed new general transport equation. A coherent theoretical derivation indicates the wall-molecule and molecule-molecule collisions drive the Knudsen and collective diffusive fluxes, and constitute the system pressure across the porous media. A new terminology, nominal diffusion coefficient can summarize Knudsen and collective diffusion coefficients. Physical and numerical experiments show the support of the new formulation and provide approaches to obtain the diffusion coefficient and permeability simultaneously. This work has important implication for natural gas extraction and greenhouse gases sequestration in geological formations.

  6. Evaluation of septum-capped vials for storage of gas samples during air transport.

    PubMed

    Glatzel, Stephan; Well, Reinhard

    2008-01-01

    In order to provide information on the suitability of commonly used gas storage vials for air transport, we tested two vial types on their ability to preserve defined nitrous oxide concentrations and excess pressure when exposed to low pressure, low temperature and puncture by needles. Unlike in Crimp Cap vials, in Exetainers no nitrous oxide loss following low pressure storage was detectable. Tightness of Exetainers following multiple puncture was best using a small needle diameter. Pressure loss following 5, 10, or 25 punctures was lowest in the Exetainers. We conclude that Exetainers are suitable for storing gas samples for an extended period of time during aircraft transport.

  7. Gas transport model for chemical vapor infiltration. Topical report

    SciTech Connect

    Starr, T.L.

    1995-05-01

    A node-bond percolation model is presented for the gas permeability and pore surface area of the coarse porosity in woven fiber structures during densification by chemical vapor infiltration (CVI). Model parameters include the number of nodes per unit volume and their spatial distribution, and the node and bond radii and their variability. These parameters relate directly to structural features of the weave. Some uncertainty exists in the proper partition of the porosity between {open_quotes}node{close_quotes} and{open_quote}bond{close_quotes} and between intra-tow and inter-tow, although the total is constrained by the known fiber loading in the structure. Applied to cloth layup preforms the model gives good agreement with the limited number of available measurements.

  8. Transport of Gas and Solutes in Permeable Estuarine Sediments

    DTIC Science & Technology

    2012-09-30

    is demonstrated by measuring the spatial and temporal distribution of small bubbles produced by photosynthesis in sublittoral sands. − We...document contains color images. 14. ABSTRACT 15. SUBJECT TERMS 16. SECURITY CLASSIFICATION OF: 17. LIMITATION OF ABSTRACT SAR 18. NUMBER OF...column Oxygen bubbles produced by photosynthesis in the sediment affect the concentrations of dissolved gases in the pore water. As soon these oxygen

  9. Psychostimulants affect dopamine transmission through both dopamine transporter-dependent and independent mechanisms.

    PubMed

    dela Peña, Ike; Gevorkiana, Ruzanna; Shi, Wei-Xing

    2015-10-05

    The precise mechanisms by which cocaine and amphetamine-like psychostimulants exert their reinforcing effects are not yet fully defined. It is widely believed, however, that these drugs produce their effects by enhancing dopamine neurotransmission in the brain, especially in limbic areas such as the nucleus accumbens, by inducing dopamine transporter-mediated reverse transport and/or blocking dopamine reuptake though the dopamine transporter. Here, we present the evidence that aside from dopamine transporter, non-dopamine transporter-mediated mechanisms also participate in psychostimulant-induced dopamine release and contribute to the behavioral effects of these drugs, such as locomotor activation and reward. Accordingly, psychostimulants could increase norepinephrine release in the prefrontal cortex, the latter then alters the firing pattern of dopamine neurons resulting in changes in action potential-dependent dopamine release. These alterations would further affect the temporal pattern of dopamine release in the nucleus accumbens, thereby modifying information processing in that area. Hence, a synaptic input to a nucleus accumbens neuron may be enhanced or inhibited by dopamine depending on its temporal relationship to dopamine release. Specific temporal patterns of dopamine release may also be required for certain forms of synaptic plasticity in the nucleus accumbens. Together, these effects induced by psychostimulants, mediated through a non-dopamine transporter-mediated mechanism involving norepinephrine and the prefrontal cortex, may also contribute importantly to the reinforcing properties of these drugs.

  10. Trace gas exchanges and transports over the Amazonian rain forest

    NASA Technical Reports Server (NTRS)

    Garstang, Michael; Greco, Steve; Scala, John; Harriss, Robert; Browell, Edward; Sachse, Glenn; Simpson, Joanne; Tao, Wei-Kuo; Torres, Arnold

    1986-01-01

    Early results are presented from a program to model deep convective transport of chemical species by means of in situ data collection and numerical models. Data were acquired during the NASA GTE Amazon Boundary Layer Experiment in July-August 1985. Airborne instrumentation, including a UV-DIAL system, collected data on the O3, CO, NO, temperature and water vapor profiles from the surface to 400 mb altitude, while GOES imagery tracked convective clouds over the study area. A two-dimensional cloud model with small amplitude random temperature fluctuations at low levels, which simulated thermals, was used to describe the movements of the chemical species sensed in the convective atmosphere. The data was useful for evaluating the accuracy of the cloud model, which in turn was effective in describing the circulation of the chemical species.

  11. 40 CFR 60.5400 - What equipment leak standards apply to affected facilities at an onshore natural gas processing...

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... affected facilities at an onshore natural gas processing plant? 60.5400 Section 60.5400 Protection of... NEW STATIONARY SOURCES Standards of Performance for Crude Oil and Natural Gas Production, Transmission... natural gas processing plant? This section applies to the group of all equipment, except...

  12. 40 CFR 60.5400 - What equipment leak standards apply to affected facilities at an onshore natural gas processing...

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... affected facilities at an onshore natural gas processing plant? 60.5400 Section 60.5400 Protection of... NEW STATIONARY SOURCES Standards of Performance for Crude Oil and Natural Gas Production, Transmission... natural gas processing plant? This section applies to the group of all equipment, except...

  13. Probabilities of adverse weather affecting transport in Europe: climatology and scenarios up to the 2050s

    NASA Astrophysics Data System (ADS)

    Vajda, A.; Tuomenvirta, H.; Jokinen, P.; Luomaranta, A.; Makkonen, L.; Tikanmäki, M.; Groenemeijer, P.; Saarikivi, P.; Michaelides, S.; Papadakis, M.; Tymvios, F.; Athanasatos, S.

    2012-04-01

    This paper provides the first comprehensive climatology of the adverse and extreme weather events affecting the European transport system by estimating the frequency (or probability) of phenomena for the present climate (1971-2000) and an overview of the projected changes in some of these extremes in the future climate until the 2050s. The research was carried out within the framework of the EWENT Project that addresses the European Union (EU) policies and strategies related to climate change, with a particular focus on extreme weather impacts on the EU transportation system. This project is funded by the Seventh Framework Programme (Transports, call ID FPT7-TPT-2008-RTD-1). The analyzed phenomena are wind, snow, blizzards, heavy precipitation, cold spells and heat waves. In addition, reduced visibility conditions determined by fog and dust events, small-scale phenomena affecting the transport system, such as thunderstorms, lightning, large hail and tornadoes and events damaging infrastructure of the transport system, have been considered. Frequency and probability analysis of past and present ex¬tremes were performed using observational and atmospheric reanalysis data. Future changes in the probability of severe events were assessed based on six regional climate model simulations produced in the FP6 ENSEMBLES project (http://www.ensembles-eu.org/). To facilitate the assessment of impacts and consequences of extreme phenomena on a continental level, the WP2 Deliverable introduces a regionalization of the European extreme phenomena, defining the climate zones with similarities in extreme phenomena. The projected changes as well as large natural variability in weather extremes on the transportation network will have impacts of both signs. The decline of extreme cold and snowfall over most of the continent implies a positive impact on road, rail, inland water and air transportation, e.g., by reducing snow removal. However, even with a general decreasing trend in

  14. Analysis of volatile-phase transport in soils using natural radon gas as a tracer

    SciTech Connect

    Chen, C.; Thomas, D.M.

    1994-01-01

    We have conducted a field study of soil gas transport processes using radon gas as a naturally occurring tracer. The experiment monitored soil gas radon activity, soil moisture, and soil temperature at depth; barometric pressure, rainfall, and wind speed were monitored at the soil surface. Linear and multiple regression analysis under natural environmental conditions are influenced by soil moisture content, barometric pressure variations, soil temperature, and soil structure. The effect of wind speed on subsurface radon activities under our field conditions has not been observed. 25 refs., 12 figs., 1 tab.

  15. Study of effective transport properties of fresh and aged gas diffusion layers

    NASA Astrophysics Data System (ADS)

    Bosomoiu, Magdalena; Tsotridis, Georgios; Bednarek, Tomasz

    2015-07-01

    Gas diffusion layers (GDLs) play an important role in proton exchange membrane fuel cells (PEMFCs) for the diffusion of reactant and the removal of product water. In the current study fresh and aged GDLs (Sigracet® GDL34BC) were investigated by X-ray computed tomography to obtain a representative 3D image of the real GDL structure. The examined GDL samples are taken from areas located under the flow channel and under the land. Additionally, a brand new Sigracet® GDL34BC was taken as a reference sample in order to find out the impact of fuel cell assembly on GDL. The produced 3D image data were used to calculate effective transport properties such as thermal and electrical conductivity, diffusivity, permeability and capillary pressure curves of the dry and partially saturated GDL. The simulation indicates flooding by product water occurs at contact angles lower than 125° depending on sample porosity. In addition, GDL anisotropy significantly affects the permeability as well as thermal and electrical conductivities. The calculated material bulk properties could be next used as input for CFD modelling of PEM fuel cells where GDL is usually assumed layer-like and homogeneous. Tensor material parameters allow to consider GDL anisotropy and lead to more realistic results.

  16. How AGN and SN Feedback Affect Mass Transport and Black Hole Growth in High-redshift Galaxies

    NASA Astrophysics Data System (ADS)

    Prieto, Joaquin; Escala, Andrés; Volonteri, Marta; Dubois, Yohan

    2017-02-01

    Using cosmological hydrodynamical simulations, we study the effect of supernova (SN) and active galactic nucleus (AGN) feedback on the mass transport (MT) of gas onto galactic nuclei and the black hole (BH) growth down to redshift z∼ 6. We study the BH growth in relation to the MT processes associated with gravity and pressure torques and how they are modified by feedback. Cosmological gas funneled through cold flows reaches the galactic outer region close to freefall. Then torques associated with pressure triggered by gas turbulent motions produced in the circumgalactic medium by shocks and explosions from SNe are the main source of MT beyond the central ∼100 pc. Due to high concentrations of mass in the central galactic region, gravitational torques tend to be more important at high redshift. The combined effect of almost freefalling material and both gravity and pressure torques produces a mass accretion rate of order ∼ 1 {M}ȯ yr‑1 at approximately parsec scales. In the absence of SN feedback, AGN feedback alone does not affect significantly either star formation or BH growth until the BH reaches a sufficiently high mass of ∼ {10}6 {M}ȯ to self-regulate. SN feedback alone, instead, decreases both stellar and BH growth. Finally, SN and AGN feedback in tandem efficiently quench the BH growth, while star formation remains at the levels set by SN feedback alone, due to the small final BH mass, ∼few times {10}5 {M}ȯ . SNe create a more rarefied and hot environment where energy injection from the central AGN can accelerate the gas further.

  17. Rapid vertical trace gas transport by an isolated midlatitude thunderstorm

    NASA Astrophysics Data System (ADS)

    Hauf, Thomas; Schulte, Peter; Alheit, Reiner; Schlager, Hans

    1995-11-01

    During the cloud dynamics and chemistry field experiment CLEOPATRA in the summer of 1992 in southern Germany, the Deutsche Forschungsanstalt für Luft- und Raumfahrt (DLR) (German Aerospace Research Establishment) research aircraft Falcon traversed four times the anvil of a severe, isolated thunderstorm. The first two traverses were at 8 km altitude and close to the anvil cloud base, while the second two traverses were at 10 km. During the 8-km traverse, measured ozone mixing ratios dropped by 13 parts per billion by volume (ppbv) from the ambient cloud free environment to the anvil cloud, while water vapor increased by 0.3 g kg-1. At the 10-km traverses, ozone dropped by 25 ppbv, while water vapor increased by 0.18 g kg-1. Three-dimensional numerical thunderstorm simulations were performed to understand the cause of these changes. The simulations included the transport of two chemical inert tracers. Ozone was assumed to be one of them. The initial ozone profile was composed from an ozone routine sounding and the in situ Falcon measurements prior to the thunderstorm development. The second tracer is typical for a surface released pollutant with a nonzero, constant value in the boundary layer but zero above it. The redistribution of both tracers by the storm is calculated and compared with the observations. For the anvil penetration at 10 km, the calculated difference in ozone mixing ratios is 21 ppbv, while for water vapor an increase of 0.25 g kg-1 was found, in good agreement with the observations. To validate the model results, the radar reflectivity was calculated from simulated fields of cloud water, rain, graupel, hail, and snow and ice crystals and compared with observed values. With respect to maximum reflectivity values and spatial scales, again, excellent agreement was achieved. It is concluded that the rapid transport from the boundary layer directly into the anvil level is the most likely cause of the observed ozone decrease and water vapor increase

  18. Role of plant-mediated gas transport in CH4 emissions from Phragmites-dominated peatlands

    NASA Astrophysics Data System (ADS)

    van den Berg, Merit; Ingwersen, Joachim; van den Elzen, Eva; Lamers, Leon P. M.; Streck, Thilo

    2016-04-01

    A large part of the methane (CH4) produced in peatlands is directly oxidized and the extent of its oxidation depends on the gas transport pathway. In wetland ecosystems, CH4 can be transported from the soil to the atmosphere via diffusion, ebullition and via aerenchyma of roots and stems of vascular plants. Compared to other wetland plants, the very common species Phragmites australis (Common reed) appears to have a high ability to transport gases between the soil and atmosphere. The gas exchange within Phragmites plants takes place via convective flow through the culm, which is believed to be achieved by a humidity-induced pressure gradient and is more than 5-times as efficient as diffusion. By this mechanism, CH4 surpasses the upper (oxic) soil layers and therefore oxidation of CH4 may well be reduced. On the other hand, transport of oxygen in Phragmites plants tends to enhance O2concentration in the rhizosphere, which will foster CH4oxidation in deeper soil layers. It is therefore unknown whether humidity-induced convection leads to higher or lower overall CH4 emission in Phragmites, which is essential to understand their role in the emissions from these very common peatland types. To investigate whether this internal gas transport mechanism of reed promotes or reduces CH4 fluxes to the atmosphere, we conducted manipulative field experiments in a large Phragmites peatland in South-West Germany in October 2014 and July 2015. Using large chambers, we compared CH4 fluxes from intact plots, plots with cut reed, and plots with cut + sealed reed to exclude gas transport through the plants. Additionally, pore water samples from the plots were analyzed for possible changes in soil chemistry due to the change of oxygen transport into the soil by the treatments. Based on our results, we will explain the potential role of rhizosphere oxygenation and convective flow on CH4 emissions from Phragmites-dominated peatlands in relation to other environmental condition.

  19. Evaluation of soil-gas transport of organic chemicals into residential buildings: Final report

    SciTech Connect

    Hodgson, A.T.; Garbesi, K.; Sextro, R.G.; Daisey, J.M.

    1988-06-01

    This investigation consisted of theoretical, laboratory, and field study phases with the overall objective of determining the importance of pressure-driven flow of soil gas in the transport of volatile organic compounds (VOC) from soil into a house. In the first phase, the mechanisms of advection, diffusion, and retardation of VOC in soil were evaluated. Using the theory of fluid mechanics and empirical for equilibrium partitioning of VOC among gas, aqueous, and solid phase of soil, a one-dimensional advection-diffusion equation or the transport of gas-phase VOC through soil was developed. An experimental apparatus and method were developed for the direct observation of pressure-driven transport of VOC through soil under controlled laboratory conditions. The retardation of sulfur hexafluoride (SF/sub 6/) and hexafluorobenzene with respect to the flow of the bulk gas was measured in soil-column experiments using different soils and soil-moisture conditions. The results were in good agreement with theoretical predictions. Since SF/sub 6/ was not lost by sorption to soil, it was selected for use as a tracer gas in the field study to study the advective flow of soil gas. The overall objective of the investigation was directly addressed by the field study. This study was conducted at a house which has a basement and which was located adjacent to a covered municipal landfill. The soil at the site was characterized, pressure coupling between the basement and surrounding soil was measured, the entry rate of soil gas as a function of basement depressurization was measured, and VOC in soil gas, indoor air and outdoor air were quantified. 46 refs., 18 figs., 11 tabs.

  20. Factors affecting body weight loss during commercial long haul transport of cattle in North America.

    PubMed

    González, L A; Schwartzkopf-Genswein, K S; Bryan, M; Silasi, R; Brown, F

    2012-10-01

    The objective of the present study was to identify and quantify several factors affecting shrink in cattle during commercial long-haul transport (≥400 km; n = 6,152 journeys). Surveys were designed and delivered to transport carriers to collect relevant information regarding the characteristics of animals, time of loading, origin and destination, and loaded weight before and after transport. In contrast to fat cattle, feeder cattle exhibited greater shrink (4.9 vs. 7.9 ± 0.2% of BW, respectively; P < 0.01), and experienced longer total transport durations (12.4 vs. 14.9 ± 0.99, respectively; P < 0.01) due to border crossing protocols which require mandatory animal inspection. Shrink was greater (P < 0.001) for feeder cattle loaded at ranches/farms and feed yards compared with those loaded at auction markets. Cattle loaded during the afternoon and evening shrank more than those loaded during the night and morning (P < 0.05). Shrinkage was less in cattle transported by truck drivers having 6 or more years of experience hauling livestock compared with those with 5 yr or less (P < 0.05). Shrink increased with both midpoint ambient temperature (% of BW/°C; P < 0.001) and time on truck (% of BW/h; P < 0.001). Temperature and time on truck had a multiplicative effect on each other because shrink increased most rapidly in cattle transported for both longer durations and at higher ambient temperatures (P < 0.001). The rate of shrink over time (% of BW/h) was greatest in cull cattle, intermediate in calves and feeder cattle, and slowest in fat cattle (P < 0.05) but such differences disappeared when the effects of place of origin, loading time, and experience of truck drivers were included in the model. Cull cattle, calves and feeder cattle appear to be more affected by transport compared with fat cattle going to slaughter because of greater shrink. Several factors should be considered when developing guidelines to reduce cattle transport stress and shrink including type

  1. FACTORS IN GEOTROPOSPHERIC PARTICLE-GAS TRANSPORT OF SEMIVOLATILE ORGANIC COMPOUNDS

    EPA Science Inventory

    Semivolatile organic compounds (SVOCs) can exist in solid, liquid, or gas phases under ambient environmental conditions. The geotropospheric transport of SVOCs varies according to the particle type. Two classes of SVOCs and two types of particles were analyzed to determine possib...

  2. Gas effect on transport rates of ZnSe in closed ampoules

    NASA Astrophysics Data System (ADS)

    Muranoi, Tetsuo; Shiohara, Tetsuya; Sotokawa, Akio; Yoshida, Hisayoshi; Isobe, Shuichi; Kanbe, Nobutaka

    1995-01-01

    Gas effects on the transport rates of ZnSe in closed systems were investigated. An ampoule (10 mm × 90 mm) was fabricated from a quartz tube which had been cleaned in a hydrogen flow at about 1000°C for 5 hours. The source material was polycrystalline ZnSe of 6N purity with about a 3 to 6 mm particle size. Ar, H 2 or He gas was introduced under pressure p, along with the source. The ampoule was sealed and placed in an electric furnace for 15 hours. The source temperature was 1069°C, and the growth end temperature was 1048°C. Here, the transport rate was defined as J. Jargon started to decrease at pargon = 9 Torr, Jhydrogen decreased at phydrogen = 45 Torr, and Jhelium was almost constant in all over the phelium range. The thermal conductivity of helium is almost 10 times that of argon gas, but similar to that of hydrogen gas. It was considered that Jhydrogen was intermediate between Jhelium and Jargon since hydrogen is a reactive gas. It was concluded that Jargon and Jhydrogen had a diffusion limited mass transport region.

  3. Yeast culture supplement during nursing and transport affects immunity and intestinal microbial ecology of weanling pigs.

    PubMed

    Weedman, S M; Rostagno, M H; Patterson, J A; Yoon, I; Fitzner, G; Eicher, S D

    2011-06-01

    The objectives of this study were to determine the influence of a Saccharomyces cerevisiae fermentation product on innate immunity and intestinal microbial ecology after weaning and transport stress. In a randomized complete block design, before weaning and in a split-plot analysis of a 2 × 2 factorial arrangement of yeast culture (YY) and transport (TT) after weaning, 3-d-old pigs (n = 108) were randomly assigned within litter (block) to either a control (NY, milk only) or yeast culture diet (YY; delivered in milk to provide 0.1 g of yeast culture product/kg of BW) from d 4 to 21. At weaning (d 21), randomly, one-half of the NY and YY pigs were assigned to a 6-h transport (NY-TT and YY-TT) before being moved to nursery housing, and the other one-half were moved directly to nursery housing (NY-NT and YY-NT, where NT is no transport). The yeast treatment was a 0.2% S. cerevisiae fermentation product and the control treatment was a 0.2% grain blank in feed for 2 wk. On d 1 before transport and on d 1, 4, 7, and 14 after transport, blood was collected for leukocyte assays, and mesenteric lymph node, jejunal, and ileal tissue, and jejunal, ileal, and cecal contents were collected for Toll-like receptor expression (TLR); enumeration of Escherichia coli, total coliforms, and lactobacilli; detection of Salmonella; and microbial analysis. After weaning, a yeast × transport interaction for ADG was seen (P = 0.05). Transport affected (P = 0.09) ADFI after weaning. Yeast treatment decreased hematocrit (P = 0.04). A yeast × transport interaction was found for counts of white blood cells (P = 0.01) and neutrophils (P = 0.02) and for the neutrophil-to-lymphocyte ratio (P = 0.02). Monocyte counts revealed a transport (P = 0.01) effect. Interactions of yeast × transport (P = 0.001) and yeast × transport × day (P = 0.09) for TLR2 and yeast × transport (P = 0.08) for TLR4 expression in the mesenteric lymph node were detected. Day affected lactobacilli, total coliform, and E

  4. Interacting Physical and Biological Processes Affecting Nutrient Transport Through Human Dominated Landscapes

    NASA Astrophysics Data System (ADS)

    Finlay, J. C.

    2015-12-01

    Human activities increasingly dominate biogeochemical cycles of limiting nutrients on Earth. Urban and agricultural landscapes represent the largest sources of excess nutrients that drive water quality degradation. The physical structure of both urban and agricultural watersheds has been extensively modified, and these changes have large impacts on water and nutrient transport. Despite strong physical controls over nutrient transport in human dominated landscapes, biological processes play important roles in determining the fates of both nitrogen and phosphorus. This talk uses examples from research in urban and agricultural watersheds in the Midwestern USA to illustrate interactions of physical and biological controls over nutrient cycles that have shifted nitrogen (N) and phosphorus (P) sources and cycling in unexpected ways in response to management changes. In urban watersheds, efforts to improve water quality have been hindered by legacy sources of phosphorus added to storm water through transport to drainage systems by vegetation. Similarly, reductions in field erosion in agricultural watersheds have not led to major reductions in phosphorus transport, because of continued release of biological sources of P. Where management of phosphorus has been most effective in reducing eutrophication of lakes, decreases in N removal processes have led to long term increases in N concentration and transport. Together, these examples show important roles for biological processes affecting nutrient movement in highly modified landscapes. Consideration of the downstream physical and biological responses of management changes are thus critical toward identification of actions that will most effectively reduce excess nutrients watersheds and coastal zones.

  5. Growth dynamics and gas transport mechanism of nanobubbles in graphene liquid cells.

    PubMed

    Shin, Dongha; Park, Jong Bo; Kim, Yong-Jin; Kim, Sang Jin; Kang, Jin Hyoun; Lee, Bora; Cho, Sung-Pyo; Hong, Byung Hee; Novoselov, Konstantin S

    2015-02-02

    Formation, evolution and vanishing of bubbles are common phenomena in nature, which can be easily observed in boiling or falling water, carbonated drinks, gas-forming electrochemical reactions and so on. However, the morphology and the growth dynamics of the bubbles at nanoscale have not been fully investigated owing to the lack of proper imaging tools that can visualize nanoscale objects in the liquid phase. Here, we demonstrate for the first time that the nanobubbles in water encapsulated by graphene membrane can be visualized by in-situ ultra-high vacuum transmission electron microscopy. Our microscopic results indicate two distinct growth mechanisms of merging nanobubbles and the existence of a critical radius of nanobubbles that determines the unusually long stability of nanobubbles. Interestingly, the gas transport through ultrathin water membranes at nanobubble interface is free from dissolution, which is clearly different from conventional gas transport that includes condensation, transmission and evaporation.

  6. Growth dynamics and gas transport mechanism of nanobubbles in graphene liquid cells

    NASA Astrophysics Data System (ADS)

    Shin, Dongha; Park, Jong Bo; Kim, Yong-Jin; Kim, Sang Jin; Kang, Jin Hyoun; Lee, Bora; Cho, Sung-Pyo; Hong, Byung Hee; Novoselov, Konstantin S.

    2015-02-01

    Formation, evolution and vanishing of bubbles are common phenomena in nature, which can be easily observed in boiling or falling water, carbonated drinks, gas-forming electrochemical reactions and so on. However, the morphology and the growth dynamics of the bubbles at nanoscale have not been fully investigated owing to the lack of proper imaging tools that can visualize nanoscale objects in the liquid phase. Here, we demonstrate for the first time that the nanobubbles in water encapsulated by graphene membrane can be visualized by in-situ ultra-high vacuum transmission electron microscopy. Our microscopic results indicate two distinct growth mechanisms of merging nanobubbles and the existence of a critical radius of nanobubbles that determines the unusually long stability of nanobubbles. Interestingly, the gas transport through ultrathin water membranes at nanobubble interface is free from dissolution, which is clearly different from conventional gas transport that includes condensation, transmission and evaporation.

  7. Characterization of Gas Transport Properties of Fractured Rocks By Borehole and Chamber Tests.

    NASA Astrophysics Data System (ADS)

    Shimo, M.; Shimaya, S.; Maejima, T.

    2014-12-01

    Gas transport characteristics of fractured rocks is a great concern to variety of engineering applications such as underground storage of LPG, nuclear waste disposal, CCS and gas flooding in the oil field. Besides absolute permeability, relative permeability and capillary pressure as a function of water saturation have direct influences to the results of two phase flow simulation. However, number of the reported gas flow tests for fractured rocks are limited, therefore, the applicability of the conventional two-phase flow functions used for porous media, such as Mualem-van Genuchten model, to prediction of the gas transport in the fractured rock mass are not well understood. The authors conducted the two types of in-situ tests, with different scales, a borehole gas-injection test and a chamber gas-injection test in fractured granitic rock. These tests were conducted in the Cretaceous granitic rocks at the Namikata underground LPG storage cavern construction site in Ehime Prefecture in Japan, preceding to the cavern scale gas-tightness test. A borehole injection test was conducted using vertical and sub-vertical boreholes drilled from the water injection tunnel nearly at the depth of the top of the cavern, EL-150m. A new type downhole gas injection equipment that is capable to create a small 'cavern' within a borehole was developed. After performing a series of preliminary tests to investigate the hydraulic conductivity and gas-tightness, i.e. threshold pressure, gas injection tests were conducted under different gas pressure. Fig.1 shows an example of the test results From a chamber test using a air pressurizing chamber with volume of approximately166m3, the gas-tightness was confirmed within the uncertainty of 22Pa under the storage pressure of 0.7MPa, however, significant air leakage occurred possibly through an open fracture intersecting the chamber just after cavern pressure exceeds the initial hydrostatic pressure at the ceiling level of the chamber. Anomalies

  8. Factors affecting gas migration and contaminant redistribution in heterogeneous porous media subject to electrical resistance heating.

    PubMed

    Munholland, Jonah L; Mumford, Kevin G; Kueper, Bernard H

    2016-01-01

    A series of intermediate-scale laboratory experiments were completed in a two-dimensional flow cell to investigate gas production and migration during the application of electrical resistance heating (ERH) for the removal of dense non-aqueous phase liquids (DNAPLs). Experiments consisted of heating water in homogeneous silica sand and heating 270 mL of trichloroethene (TCE) and chloroform (CF) DNAPL pools in heterogeneous silica sands, both under flowing groundwater conditions. Spatial and temporal distributions of temperature were measured using thermocouples and observations of gas production and migration were collected using front-face image capture throughout the experiments. Post-treatment soil samples were collected and analyzed to assess DNAPL removal. Results of experiments performed in homogeneous sand subject to different groundwater flow rates showed that high groundwater velocities can limit subsurface heating rates. In the DNAPL pool experiments, temperatures increased to achieve DNAPL-water co-boiling, creating estimated gas volumes of 131 and 114 L that originated from the TCE and CF pools, respectively. Produced gas migrated vertically, entered a coarse sand lens and subsequently migrated laterally beneath an overlying capillary barrier to outside the heated treatment zone where 31-56% of the original DNAPL condensed back into a DNAPL phase. These findings demonstrate that layered heterogeneity can potentially facilitate the transport of contaminants outside the treatment zone by mobilization and condensation of gas phases during ERH applications. This underscores the need for vapor phase recovery and/or control mechanisms below the water table during application of ERH in heterogeneous porous media during the co-boiling stage, which occurs prior to reaching the boiling point of water.

  9. Factors affecting gas migration and contaminant redistribution in heterogeneous porous media subject to electrical resistance heating

    NASA Astrophysics Data System (ADS)

    Munholland, Jonah L.; Mumford, Kevin G.; Kueper, Bernard H.

    2016-01-01

    A series of intermediate-scale laboratory experiments were completed in a two-dimensional flow cell to investigate gas production and migration during the application of electrical resistance heating (ERH) for the removal of dense non-aqueous phase liquids (DNAPLs). Experiments consisted of heating water in homogeneous silica sand and heating 270 mL of trichloroethene (TCE) and chloroform (CF) DNAPL pools in heterogeneous silica sands, both under flowing groundwater conditions. Spatial and temporal distributions of temperature were measured using thermocouples and observations of gas production and migration were collected using front-face image capture throughout the experiments. Post-treatment soil samples were collected and analyzed to assess DNAPL removal. Results of experiments performed in homogeneous sand subject to different groundwater flow rates showed that high groundwater velocities can limit subsurface heating rates. In the DNAPL pool experiments, temperatures increased to achieve DNAPL-water co-boiling, creating estimated gas volumes of 131 and 114 L that originated from the TCE and CF pools, respectively. Produced gas migrated vertically, entered a coarse sand lens and subsequently migrated laterally beneath an overlying capillary barrier to outside the heated treatment zone where 31-56% of the original DNAPL condensed back into a DNAPL phase. These findings demonstrate that layered heterogeneity can potentially facilitate the transport of contaminants outside the treatment zone by mobilization and condensation of gas phases during ERH applications. This underscores the need for vapor phase recovery and/or control mechanisms below the water table during application of ERH in heterogeneous porous media during the co-boiling stage, which occurs prior to reaching the boiling point of water.

  10. A computer model of gas generation and transport within TRU waste drums

    SciTech Connect

    Smith, F.G. III

    1988-06-01

    A computer model has been developed to predict radiolytic gas generation and transport within Transuranic (TRU) waste drums and surrounding enclosures. Gas generation from the radiolytic decomposition of organic material contaminated with plutonium is modeled and the concentrations of gas throughout the waste drum and enclosures are determined using a diffusional transport model. The model accurately reproduces experimentally measured gas concentrations. With polyethylene waste in unvented drums, the model predicts that the concentration of hydrogen gas can exceed 4 mole percent (lower flammable limit) with only about 5 curies of plutonium. If the drum liner is punctured and an unrestricted 0.75-in. carbon composite filter vent is installed in the drum lid, the plutonium loading can be increased to 240 Ci without generating flammable gas mixtures. Larger diameter filters can be used to increase the curie loading. The model has been used to show that shipments of 1000 Ci of plutonium-238 contaminated waste from Savannah River to the WIPP site are feasible using the TRUPACT shipping container. 10 refs., 17 figs., 6 tabs.

  11. Affective Neural Responses Modulated by Serotonin Transporter Genotype in Clinical Anxiety and Depression

    PubMed Central

    Oathes, Desmond J.; Hilt, Lori M.; Nitschke, Jack B.

    2015-01-01

    Serotonin transporter gene variants are known to interact with stressful life experiences to increase chances of developing affective symptoms, and these same variants have been shown to influence amygdala reactivity to affective stimuli in non-psychiatric populations. The impact of these gene variants on affective neurocircuitry in anxiety and mood disorders has been studied less extensively. Utilizing a triallelic assay (5-HTTLPR and rs25531) to assess genetic variation linked with altered serotonin signaling, this fMRI study investigated genetic influences on amygdala and anterior insula activity in 50 generalized anxiety disorder patients, 26 of whom also met DSM-IV criteria for social anxiety disorder and/or major depressive disorder, and 39 healthy comparison subjects. A Group x Genotype interaction was observed for both the amygdala and anterior insula in a paradigm designed to elicit responses in these brain areas during the anticipation of and response to aversive pictures. Patients who are S/LG carriers showed less activity than their LA/LA counterparts in both regions and less activity than S/LG healthy comparison subjects in the amygdala. Moreover, patients with greater insula responses reported higher levels of intolerance of uncertainty, an association that was particularly pronounced for patients with two LA alleles. A genotype effect was not established in healthy controls. These findings link the serotonin transporter gene to affective circuitry findings in anxiety and depression psychopathology and further suggest that its impact on patients may be different from effects typically observed in healthy populations. PMID:25675343

  12. 3-D simulation of gases transport under condition of inert gas injection into goaf

    NASA Astrophysics Data System (ADS)

    Liu, Mao-Xi; Shi, Guo-Qing; Guo, Zhixiong; Wang, Yan-Ming; Ma, Li-Yang

    2016-12-01

    To prevent coal spontaneous combustion in mines, it is paramount to understand O2 gas distribution under condition of inert gas injection into goaf. In this study, the goaf was modeled as a 3-D porous medium based on stress distribution. The variation of O2 distribution influenced by CO2 or N2 injection was simulated based on the multi-component gases transport and the Navier-Stokes equations using Fluent. The numerical results without inert gas injection were compared with field measurements to validate the simulation model. Simulations with inert gas injection show that CO2 gas mainly accumulates at the goaf floor level; however, a notable portion of N2 gas moves upward. The evolution of the spontaneous combustion risky zone with continuous inert gas injection can be classified into three phases: slow inerting phase, rapid accelerating inerting phase, and stable inerting phase. The asphyxia zone with CO2 injection is about 1.25-2.4 times larger than that with N2 injection. The efficacy of preventing and putting out mine fires is strongly related with the inert gas injecting position. Ideal injections are located in the oxidation zone or the transitional zone between oxidation zone and heat dissipation zone.

  13. Advances in Understanding Sorption and Transport Processes Affecting the Fate of Environmental Pollutants in the Subsurface

    NASA Astrophysics Data System (ADS)

    Karapanagioti, H. K.; Werner, D.; Werth, C.

    2012-04-01

    The results of a call for a special issue that is now in press by the Journal of Contaminant Hydrology will be presented. This special issue is edited by the authors and is entitled "Sorption and Transport Processes Affecting the Fate of Environmental Pollutants in the Subsurface". A short abstract of each paper will be presented along with the most interesting results. Nine papers were accepted. Pollutants studied include: biocolloids, metals (arsenic, chromium, nickel), organic compounds such as hydrocarbons, chlorinated hydrocarbons, micropollutants (PAHs, PCBs), pesticides (glyphosate, 2,4-D). Findings presented in the papers include a modified batch reactor system to study equilibrium-reactive transport problems of metals. Column studies along with theoretical approximations evaluate the combined effects of grain size and pore water velocity on the transport in water saturated porous media of three biocolloids. A polluted sediment remediation method is evaluated considering site-specific conditions through monitoring results and modelling. A field study points to glogging and also sorption as mechanisms affecting the effectiveness of sub-surface flow constructed wetlands. A new isotherm model combining modified traditionally used isotherms is proposed that can be used to simulate pH-dependent metal adsorption. Linear free energy relationships (LFERs) demonstrate ability to predict slight isotope shifts into the groundwater due to sorption. Possible modifications that improve the reliability of kinetic models and parameter values during the evaluation of experiments that assess the sorption of pesticides on soils are tested. Challenges in selecting groundwater pollutant fate and transport models that account for the effect of grain-scale sorption rate limitations are evaluated based on experimental results and are discussed based on the Damköhler number. Finally, a thorough review paper presents the impact of mineral micropores on the transport and fate of

  14. Cold flame on Biofilm - Transport of Plasma Chemistry from Gas to Liquid Phase

    NASA Astrophysics Data System (ADS)

    Kong, Michael

    2014-10-01

    One of the most active and fastest growing fields in low-temperature plasma science today is biological effects of gas plasmas and their translation in many challenges of societal importance such as healthcare, environment, agriculture, and nanoscale fabrication and synthesis. Using medicine as an example, there are already three FDA-approved plasma-based surgical procedures for tissue ablation and blood coagulation and at least five phase-II clinical trials on plasma-assisted wound healing therapies. A key driver for realizing the immense application potential of near room-temperature ambient pressure gas plasmas, commonly known as cold atmospheric plasmas or CAP, is to build a sizeable interdisciplinary knowledge base with which to unravel, optimize, and indeed design how reactive plasma species interact with cells and their key components such as protein and DNA. Whilst a logical objective, it is a formidable challenge not least since existing knowledge of gas discharges is largely in the gas-phase and therefore not directly applicable to cell-containing matters that are covered by or embedded in liquid (e.g. biofluid). Here, we study plasma inactivation of biofilms, a jelly-like structure that bacteria use to protect themselves and a major source of antimicrobial resistance. As 60--90% of biofilm is made of water, we develop a holistic model incorporating physics and chemistry in the upstream CAP-generating region, a plasma-exit region as a buffer for as-phase transport, and a downstream liquid region bordering the gas buffer region. A special model is developed to account for rapid chemical reactions accompanied the transport of gas-phase plasma species through the gas-liquid interface and for liquid-phase chemical reactions. Numerical simulation is used to illustrate how key reactive oxygen species (ROS) are transported into the liquid, and this is supported with experimental data of both biofilm inactivation using plasmas and electron spin spectroscopy (ESR

  15. Gas Transport Parameters for Landfill Final Cover Soil: Measurements and Model Modification by Dry Bulk Density

    NASA Astrophysics Data System (ADS)

    Wickramarachchi, P. N.; Kawamoto, K.; Hamamoto, S.; Nagamori, M.; Moldrup, P.; Komatsu, T.

    2011-12-01

    Landfill sites have been emerging in greenhouse warming scenarios as a significant source of atmospheric methane (CH4). Until recently, landfill management strategies have mainly addressed the problem of preventing groundwater contamination and reduction of leachate generation. Being one of the largest sources of anthropogenic CH4 emission, the final cover system should also be designed for minimizing the greenhouse gases migration into the atmosphere or the areas surrounding the landfill while securing the hydraulic performance. Compared to the intensive research efforts on hydraulic performances of landfill final cover soil, few studies about gas transport characteristics of landfill cover soils have been done. However, recent soil-gas studies implied that the effects of soil physical properties such as bulk density (i.e., compaction level), soil particle size are key parameters to understand landfill gaseous performance. The gas exchange through the final cover soils is controlled by advective and diffusive gas transport. Air permeability (ka) governs the advective gas transport while the soil-gas diffusion coefficient (Dp) governs diffusive gas transport. In this study, the effects of compaction level and particle size fraction effects on ka and Dp for landfill final cover soil was investigated. The disturbed soil samples were taken from landfill final cover in Japan. A compaction tests were performed for the soil samples with two different size fractions (< 35 mm and < 2.0 mm). In the compaction tests at field water content , the soil samples were repacked into soil cores (i.d. 15-cm, length 12-cm, 2120 cm3) at two different compaction levels [(MP):2700 kN/m2 and (SP):600 kN/m2]. After the compaction tests, ka and Dp were measured and then samples were saturated and subsequently drained at different soil-water matric potential of 0.98, 2.94, 9.81, 1235 kPa and with air-dried and oven-dried conditions. Results showed that measured Dp and ka values for the

  16. Preliminary assessment of the availability of U.S. natural gas resources to meet U.S. transportation energy demand.

    SciTech Connect

    Singh, M. K.; Moore, J. S.

    2002-03-04

    Recent studies have indicated that substitutes for conventional petroleum resources will be needed to meet U.S. transportation energy demand in the first half of this century. One possible substitute is natural gas which can be used as a transportation fuel directly in compressed natural gas or liquefied natural gas vehicles or as resource fuel for the production of hydrogen for fuel cell vehicles. This paper contains a preliminary assessment of the availability of U.S. natural gas resources to meet future U.S. transportation fuel demand. Several scenarios of natural gas demand, including transportation demand, in the U.S. to 2050 are developed. Natural gas resource estimates for the U. S. are discussed. Potential Canadian and Mexican exports to the U.S. are estimated. Two scenarios of potential imports from outside North America are also developed. Considering all these potential imports, U.S. natural gas production requirements to 2050 to meet the demand scenarios are developed and compared with the estimates of U.S. natural gas resources. The comparison results in a conclusion that (1) given the assumptions made, there are likely to be supply constraints on the availability of U.S. natural gas supply post-2020 and (2) if natural gas use in transportation grows substantially, it will have to compete with other sectors of the economy for that supply-constrained natural gas.

  17. Pulsatile Flow and Gas Transport of Blood over an Array of Cylinders

    NASA Astrophysics Data System (ADS)

    Chan, Kit Yan

    2005-11-01

    In the artificial lung, blood passes through an array of micro-fibers and the gas transfer is strongly dependent on the flow field. The blood flow is unsteady and pulsatile. We have numerically simulated pulsatile flow and gas transfer of blood (modeled as a Casson fluid) over arrays of cylindrical micro-fibers. Oxygen and carbon dioxide are assumed to be in local equilibrium with hemoglobin in blood; and the carbon dioxide facilitated oxygen transport is incorporated into the model by allowing the coupling of carbon dioxide partial pressure and oxygen saturation. The pulsatile flow inputs considered are the sinusoidal and the cardiac waveforms. The squared and staggered arrays of arrangement of the cylinders are considered in this study. Gas transport can be enhanced by: increasing the oscillation frequency; increasing the Reynolds number; increasing the oscillation amplitude; decreasing the void fraction; the use of the cardiac pulsatile input. The overall gas transport is greatly enhanced by the presence of hemoglobin in blood even though the non-Newtonian effect of blood tends to decrease the size and strength of vortices. The pressure drop is also presented as it is an important design parameter confronting the heart.

  18. Using a Gas-Phase Tracer Test to Characterize the Impact of Landfill Gas Generation on Advective-Dispersive Transport of VOCs in the Vadose Zone

    PubMed Central

    Monger, Gregg R.; Duncan, Candice Morrison; Brusseau, Mark L.

    2015-01-01

    A gas-phase tracer test (GTT) was conducted at a landfill in Tucson, AZ, to help elucidate the impact of landfill gas generation on the transport and fate of chlorinated aliphatic volatile organic contaminants (VOCs). Sulfur hexafluoride (SF6) was used as the non-reactive gas tracer. Gas samples were collected from a multiport monitoring well located 15.2 m from the injection well, and analyzed for SF6, CH4, CO2, and VOCs. The travel times determined for SF6 from the tracer test are approximately two to ten times smaller than estimated travel times that incorporate transport by only gas-phase diffusion. In addition, significant concentrations of CH4 and CO2 were measured, indicating production of landfill gas. Based on these results, it is hypothesized that the enhanced rates of transport observed for SF6 are caused by advective transport associated with landfill gas generation. The rates of transport varied vertically, which is attributed to multiple factors including spatial variability of water content, refuse mass, refuse permeability, and gas generation. PMID:26380532

  19. Using a Gas-Phase Tracer Test to Characterize the Impact of Landfill Gas Generation on Advective-Dispersive Transport of VOCs in the Vadose Zone.

    PubMed

    Monger, Gregg R; Duncan, Candice Morrison; Brusseau, Mark L

    2014-12-01

    A gas-phase tracer test (GTT) was conducted at a landfill in Tucson, AZ, to help elucidate the impact of landfill gas generation on the transport and fate of chlorinated aliphatic volatile organic contaminants (VOCs). Sulfur hexafluoride (SF6) was used as the non-reactive gas tracer. Gas samples were collected from a multiport monitoring well located 15.2 m from the injection well, and analyzed for SF6, CH4, CO2, and VOCs. The travel times determined for SF6 from the tracer test are approximately two to ten times smaller than estimated travel times that incorporate transport by only gas-phase diffusion. In addition, significant concentrations of CH4 and CO2 were measured, indicating production of landfill gas. Based on these results, it is hypothesized that the enhanced rates of transport observed for SF6 are caused by advective transport associated with landfill gas generation. The rates of transport varied vertically, which is attributed to multiple factors including spatial variability of water content, refuse mass, refuse permeability, and gas generation.

  20. Stomatal control of gas-exchange is related to assimilate transport from leaves

    NASA Astrophysics Data System (ADS)

    Nikinmaa, E.; Holtta, T.; Sevanto, S.; Makela, A.; Hari, P.; Vesala, T.

    2009-04-01

    In land plants, the carbon fluxes are closely associated with those of water. The loss of water from leaves pulls water from soil in plants. High transpiration relative to compensating water flux from soil increases the tension of water column that may lead to its rupture and catastrophic dysfunction of the xylem if the transpiration rate is not regulated. Modification of the size of stomatal openings in leaves regulates the interconnected fluxes of water and carbon. Stomatal regulation of transpiration has direct influence also on the carbon transport from source leaves to sinks. Under given conditions, the water tension of xylem in leaves is linearly related to stomatal conductance while the assimilation rate, which is linked to the loading capacity, has saturating relationship with stomatal conductance. High sugar loading at source could compensate for the high water tension in xylem resulting from eg. high transpiration. However, excessive loading rate of the most commonly transported sugar, sucrose, causes rapid viscosity build up that effectively blocks the phloem transport. Assimilate transport from the shoot is a clear requirement for continuous photosynthetic production in leaves. Without transport the storage capacity of the leaves would be rapidly exhausted and accumulation of excess sugars in leaves lead to downregulation of photosynthesis. In this presentation we study the stomatal response to environment and its linkage to xylem and phloem tranport with dynamic model. We hypothesize that stomatal reaction to environment would maintain maximal assimilate transport in phloem under those conditions. We added to the xylem phloem transport model stomatal control of leaf gas-exchange, light and CO2 concentration dependent photosynthesis rate and carbon storage in leaf. For each time step we varied the stomatal conductance and selected the sollution that maximised the transport of assimilates in phloem. Our hypothesis reproduced realistically stomatal

  1. Transport coefficients for relativistic gas mixtures of hard-sphere particles

    NASA Astrophysics Data System (ADS)

    Kremer, Gilberto M.; Moratto, Valdemar

    2017-04-01

    In the present work, we calculate the transport coefficients for a relativistic binary mixture of diluted gases of hard-sphere particles. The gas mixture under consideration is studied within the relativistic Boltzmann equation in the presence of a gravitational field described by the isotropic Schwarzschild metric. We obtain the linear constitutive equations for the thermodynamic fluxes. The driving forces for the fluxes of particles and heat will appear with terms proportional to the gradient of gravitational potential. We discuss the consequences of the gravitational dependence on the driving forces. We obtain general integral expressions for the transport coefficients and evaluate them by assuming a hard-sphere interaction amongst the particles when they collide and not very disparate masses and diameters of the particles of each species. The obtained results are expressed in terms of their temperature dependence through the relativistic parameter which gives the ratio of the rest energy of the particles and the thermal energy of the gas mixture. Plots are given to analyze the behavior of the transport coefficients with respect to the temperature when small variations in masses and diameters of the particles of the species are present. We also analyze for each coefficient the corresponding limits to a single gas so the non-relativistic and ultra-relativistic limiting cases are recovered as well. Furthermore, we show that the transport coefficients have a dependence on the gravitational field.

  2. Multi-walled carbon nanotubes affect drug transport across cell membrane in rat astrocytes

    NASA Astrophysics Data System (ADS)

    Chen, Xiao; Schluesener, Hermann J.

    2010-03-01

    The impact of carbon nanotubes on the cell membrane is an aspect of particular importance and interest in the study of carbon nanotubes' interactions with living systems. One of the many functions of the cell membrane is to execute substance transport into and out of the cell. We investigated the influence of multi-walled carbon nanotubes (MWCNTs) on the transport of several compounds across in the cell membrane of rat astrocytes using flow cytometry. These compounds are fluorescein diacetate, carboxyfluorescein diacetate, rhodamine 123 and doxorubicin, which are prosubstrate/substrates of multidrug transporter proteins. Results showed that MWCNTs significantly inhibited cellular uptake of doxorubicin but not the other drugs and the mode of loading made a significant difference in doxorubicin uptake. Retention of fluorescein, carboxyfluorescein and rhodamine 123 was remarkably higher in MWCNT-exposed cells after an efflux period. A kinetics study also demonstrated slower efflux of intracellular fluorescein and rhodamine 123. Data presented in this paper suggest that MWCNTs could affect drug transport across cell membranes. The implications of the findings are discussed.

  3. The Integration of a Structural Water Gas Shift Catalyst with a Vanadium Alloy Hydrogen Transport Device

    SciTech Connect

    Barton, Thomas; Argyle, Morris; Popa, Tiberiu

    2009-06-30

    This project is in response to a requirement for a system that combines water gas shift technology with separation technology for coal derived synthesis gas. The justification of such a system would be improved efficiency for the overall hydrogen production. By removing hydrogen from the synthesis gas stream, the water gas shift equilibrium would force more carbon monoxide to carbon dioxide and maximize the total hydrogen produced. Additional benefit would derive from the reduction in capital cost of plant by the removal of one step in the process by integrating water gas shift with the membrane separation device. The answer turns out to be that the integration of hydrogen separation and water gas shift catalysis is possible and desirable. There are no significant roadblocks to that combination of technologies. The problem becomes one of design and selection of materials to optimize, or at least maximize performance of the two integrated steps. A goal of the project was to investigate the effects of alloying elements on the performance of vanadium membranes with respect to hydrogen flux and fabricability. Vanadium was chosen as a compromise between performance and cost. It is clear that the vanadium alloys for this application can be produced, but the approach is not simple and the results inconsistent. For any future contracts, large single batches of alloy would be obtained and rolled with larger facilities to produce the most consistent thin foils possible. Brazing was identified as a very likely choice for sealing the membranes to structural components. As alloying was beneficial to hydrogen transport, it became important to identify where those alloying elements might be detrimental to brazing. Cataloging positive and negative alloying effects was a significant portion of the initial project work on vanadium alloying. A water gas shift catalyst with ceramic like structural characteristics was the second large goal of the project. Alumina was added as a

  4. Capillary transport of H2 gas generated locally in renal tissue.

    PubMed

    Kirkebø, A; Oien, A H; Aukland, K

    1983-01-01

    Previous measurements by microspheres have shown a higher blood flow in outer cortex and a lower blood flow in inner cortex than found by diffusible tracers. During vasodilation microspheres have indicated a disproportionate increase in deep cortical blood flow, whereas diffusible tracer distributions remained unchanged. These discrepancies could possibly be explained by a variable net inward transport of diffusible tracers in postglomerular vessels, the transport existing in control, but disappearing during vasodilation. To test this hypothesis H2 gas was produced electrolytically for 1 s at a platinum electrode in midcortex and the resulting gas concentration curve measured polarographically at two electrodes placed above and below the source. Analysis of a mathematical model showed that the ratio of the curve maxima at the two electrodes (Cmo/Cmi) would best reveal a radial net transport. Average Cmo/Cmi at 25 positions in 7 clamped dog kidneys was close to unity, but rose to 1.24 at control flow. During acetylcholine infusion Cmo/Cmi rose to 1.68. Local washout rates at the two electrodes increased equally. Calculations indicated a small outwardly directed net transport in control (3 X 10(-4) cm/s), becoming slightly reinforced during vasodilation (5 X 10(-4) cm/s). Thus the control transport direction is opposite to the hypothesis, and the change during vasodilation was estimated to be too small to explain the disparity between diffusible tracer uptake and microsphere distribution in control. H2 concentration maximum was obtained earlier under control flow than in the clamped kidney, indicating an increase in apparent D of the gas in tissue from 3 X 10(-5) cm2/s to 5 X 10(-5) cm2/s, probably due to mixing of H2 gas in the capillary net work.

  5. New Natural Gas Storage and Transportation Capabilities Utilizing Rapid Methane Hydrate Formation Techniques

    SciTech Connect

    Brown, T.D.; Taylor, C.E.; Bernardo, M.

    2010-01-01

    Natural gas (methane as the major component) is a vital fossil fuel for the United States and around the world. One of the problems with some of this natural gas is that it is in remote areas where there is little or no local use for the gas. Nearly 50 percent worldwide natural gas reserves of ~6,254.4 trillion ft3 (tcf) is considered as stranded gas, with 36 percent or ~86 tcf of the U.S natural gas reserves totaling ~239 tcf, as stranded gas [1] [2]. The worldwide total does not include the new estimates by U.S. Geological Survey of 1,669 tcf of natural gas north of the Arctic Circle, [3] and the U.S. ~200,000 tcf of natural gas or methane hydrates, most of which are stranded gas reserves. Domestically and globally there is a need for newer and more economic storage, transportation and processing capabilities to deliver the natural gas to markets. In order to bring this resource to market, one of several expensive methods must be used: 1. Construction and operation of a natural gas pipeline 2. Construction of a storage and compression facility to compress the natural gas (CNG) at 3,000 to 3,600 psi, increasing its energy density to a point where it is more economical to ship, or 3. Construction of a cryogenic liquefaction facility to produce LNG, (requiring cryogenic temperatures at <-161 °C) and construction of a cryogenic receiving port. Each of these options for the transport requires large capital investment along with elaborate safety systems. The Department of Energy's Office of Research and Development Laboratories at the National Energy Technology Laboratory (NETL) is investigating new and novel approaches for rapid and continuous formation and production of synthetic NGHs. These synthetic hydrates can store up to 164 times their volume in gas while being maintained at 1 atmosphere and between -10 to -20°C for several weeks. Owing to these properties, new process for the economic storage and transportation of these synthetic hydrates could be envisioned

  6. A gas-kinetic BGK scheme for semiclassical Boltzmann hydrodynamic transport

    NASA Astrophysics Data System (ADS)

    Shi, Yu-Hsin; Yang, J. Y.

    2008-11-01

    A class of gas-kinetic BGK schemes for solving quantum hydrodynamic transport based on the semiclassical Boltzmann equation with the relaxation time approximation is presented. The derivation is a generalization to the development of Xu [K. Xu, A gas-kinetic BGK scheme for the Navier-Stokes equations and its connection with artificial dissipation and Godunov method, from gas-kinetic theory, J. Comput. Phys. 171 (2001) 289-335] for the classical gas. Both Bose-Einstein and Fermi-Dirac gases are considered. Some new features due to the quantum equilibrium distributions are delineated. The first-order Chapman-Enskog expansion of the quantum BGK-Boltzmann equation is derived. The coefficients of shear viscosity and thermal conductivity of a quantum gas are given. The van Leer's limiter is used to interpolate and construct the distribution on interface to achieve second-order accuracy. The present quantum gas-kinetic BGK scheme recovers the Xu's scheme when the classical limit is taken. Several one-dimensional quantum gas flows in a shock tube are computed to illustrate the present method.

  7. Optimization problems in natural gas transportation systems. A state-of-the-art review

    SciTech Connect

    Ríos-Mercado, Roger Z.; Borraz-Sánchez, Conrado

    2015-03-24

    Our paper provides a review on the most relevant research works conducted to solve natural gas transportation problems via pipeline systems. The literature reveals three major groups of gas pipeline systems, namely gathering, transmission, and distribution systems. In this work, we aim at presenting a detailed discussion of the efforts made in optimizing natural gas transmission lines.There is certainly a vast amount of research done over the past few years on many decision-making problems in the natural gas industry and, specifically, in pipeline network optimization. In this work, we present a state-of-the-art survey focusing on specific categories that include short-term basis storage (line-packing problems), gas quality satisfaction (pooling problems), and compressor station modeling (fuel cost minimization problems). We also discuss both steady-state and transient optimization models highlighting the modeling aspects and the most relevant solution approaches known to date. Although the literature on natural gas transmission system problems is quite extensive, this is, to the best of our knowledge, the first comprehensive review or survey covering this specific research area on natural gas transmission from an operations research perspective. Furthermore, this paper includes a discussion of the most important and promising research areas in this field. Hence, our paper can serve as a useful tool to gain insight into the evolution of the many real-life applications and most recent advances in solution methodologies arising from this exciting and challenging research area of decision-making problems.

  8. Liquid natural gas as a transportation fuel in the heavy trucking industry. Final technical report

    SciTech Connect

    Sutton, W.H.

    1997-06-30

    This report encompasses the second year of a proposed three year project with emphasis focused on fundamental research issues in Use of Liquid Natural Gas as a Transportation Fuel in the Heavy Trucking Industry. These issues may be categorized as (1) direct diesel replacement with LNG fuel, and (2) long term storage/utilization of LNG vent gases produced by tank storage and fueling/handling operation. The results of this work are expected to enhance utilization of LNG as a transportation fuel. The paper discusses the following topics: (A) Fueling Delivery to the Engine, Engine Considerations, and Emissions: (1) Atomization and/or vaporization of LNG for direct injection diesel-type natural gas engines; (2) Fundamentals of direct replacement of diesel fuel by LNG in simulated combustion; (3) Distribution of nitric oxide and emissions formation from natural gas injection; and (B) Short and long term storage: (1) Modification by partial direct conversion of natural gas composition for improved storage characteristics; (2) LNG vent gas adsorption and recovery using activate carbon and modified adsorbents; (3) LNG storage at moderate conditions.

  9. Application of CFRP with High Hydrogen Gas Barrier Characteristics to Fuel Tanks of Space Transportation System

    NASA Astrophysics Data System (ADS)

    Yonemoto, Koichi; Yamamoto, Yuta; Okuyama, Keiichi; Ebina, Takeo

    In the future, carbon fiber reinforced plastics (CFRPs) with high hydrogen gas barrier performance will find wide applications in all industrial hydrogen tanks that aim at weight reduction; the use of such materials will be preferred to the use of conventional metallic materials such as stainless steel or aluminum. The hydrogen gas barrier performance of CFRP will become an important issue with the introduction of hydrogen-fuel aircraft. It will also play an important role in realizing fully reusable space transportation system that will have high specific tensile CFRP structures. Such materials are also required for the manufacture of high-pressure hydrogen gas vessels for use in the fuel cell systems of automobiles. This paper introduces a new composite concept that can be used to realize CFRPs with high hydrogen gas barrier performance for applications in the cryogenic tanks of fully reusable space transportation system by the incorporation of a nonmetallic crystal layer, which is actually a dense and highly oriented clay crystal laminate. The preliminary test results show that the hydrogen gas barrier characteristics of this material after cryogenic heat shocks and cyclic loads are still better than those of other polymer materials by approximately two orders of magnitude.

  10. Comparison between transport parameters for K+ and Li+ in 1, 2-dimethoxy ethane (DXE) gas

    NASA Astrophysics Data System (ADS)

    Nikitović, Ž.; Gilić, M.; Raspopović, Z.; Stojanović, V.

    2016-10-01

    In this paper, a theoretical study of 1, 2-dimethoxy ethane (DXE) and \\text{K}^+/\\text{Li}+ binary mixture in low-temperature plasmas is reported. The most probable reactions of alkali metal ions K+ and Li+ with dimethoxy ethane molecule and its fragment ions are selected in order to obtain appropriate gas phase enthalpies of formation for the products. The scattering cross-sections set as a function of kinetic energy and transport parameters as a function of E/N (E is the electric field, N the gas density) were obtained by using the Monte Carlo technique.

  11. Studies on gas transport through dry cellulose acetate membranes prepared by solvent exchange technique

    SciTech Connect

    Lui, A.; Talbot, F.D.F.; Sourirajan, S.; Fouda, A.; Matsuura, T.

    1988-10-01

    The mechanism of gas transport through pores on the surface of dry cellulose acetate membranes under pressure was identified for membranes prepared by the solvent exchange technique using pure gas permeation rate data. The pure gases were helium, methane and carbon dioxide. The variables involved in the membrane preparation variables involved in the membrane preparation are the shrinkage temperature, the first solvent, the second solvent and the combinations thereof. Different conditions of membrane preparation produce different pore sizes. Depending on this pore size, one of the following mechanisms becomes dominant: Knudsen, surface and size exclusion.

  12. Modeling Transport in Gas Chromatography Columns for the Micro-ChemLab

    SciTech Connect

    ADKINS,DOUGLAS R.; FRYE-MASON,GREGORY CHARLES; HUDSON,MARY L.; KOTTENSTETTE,RICHARD; MATZKE,CAROLYN M.; SALINGER,ANDREW G.; SHADID,JOHN N.; WONG, CHUNGNIN CHANN

    1999-09-01

    The gas chromatography (GC) column is a critical component in the microsystem for chemical detection ({mu}ChemLab{trademark}) being developed at Sandia. The goal is to etch a meter-long GC column onto a 1-cm{sup 2} silicon chip while maintaining good chromatographic performance. Our design strategy is to use a modeling and simulation approach. We have developed an analytical tool that models the transport and surface interaction process to achieve an optimized design of the GC column. This analytical tool has a flow module and a separation module. The flow module considers both the compressibility and slip flow effects that may significantly influence the gas transport in a long and narrow column. The separation module models analyte transport and physico-chemical interaction with the coated surface in the GC column. It predicts the column efficiency and performance. Results of our analysis will be presented in this paper. In addition to the analytical tool, we have also developed a time-dependent adsorption/desorption model and incorporated this model into a computational fluid dynamics (CFD) code to simulate analyte transport and separation process in GC columns. CFD simulations can capture the complex three-dimensional flow and transport dynamics, whereas the analytical tool cannot. Different column geometries have been studied, and results will be presented in this paper. Overall we have demonstrated that the modeling and simulation approach can guide the design of the GC column and will reduce the number of iterations in the device development.

  13. Numerical simulation of the environmental impact of hydraulic fracturing of tight/shale gas reservoirs on near-surface groundwater: Background, base cases, shallow reservoirs, short-term gas, and water transport

    PubMed Central

    Reagan, Matthew T; Moridis, George J; Keen, Noel D; Johnson, Jeffrey N

    2015-01-01

    Hydrocarbon production from unconventional resources and the use of reservoir stimulation techniques, such as hydraulic fracturing, has grown explosively over the last decade. However, concerns have arisen that reservoir stimulation creates significant environmental threats through the creation of permeable pathways connecting the stimulated reservoir with shallower freshwater aquifers, thus resulting in the contamination of potable groundwater by escaping hydrocarbons or other reservoir fluids. This study investigates, by numerical simulation, gas and water transport between a shallow tight-gas reservoir and a shallower overlying freshwater aquifer following hydraulic fracturing operations, if such a connecting pathway has been created. We focus on two general failure scenarios: (1) communication between the reservoir and aquifer via a connecting fracture or fault and (2) communication via a deteriorated, preexisting nearby well. We conclude that the key factors driving short-term transport of gas include high permeability for the connecting pathway and the overall volume of the connecting feature. Production from the reservoir is likely to mitigate release through reduction of available free gas and lowering of reservoir pressure, and not producing may increase the potential for release. We also find that hydrostatic tight-gas reservoirs are unlikely to act as a continuing source of migrating gas, as gas contained within the newly formed hydraulic fracture is the primary source for potential contamination. Such incidents of gas escape are likely to be limited in duration and scope for hydrostatic reservoirs. Reliable field and laboratory data must be acquired to constrain the factors and determine the likelihood of these outcomes. Key Points: Short-term leakage fractured reservoirs requires high-permeability pathways Production strategy affects the likelihood and magnitude of gas release Gas release is likely short-term, without additional driving forces PMID

  14. Interrelated structures of the transport shock and collisional relaxation layer in a multitemperature, multilevel ionized gas

    NASA Technical Reports Server (NTRS)

    Vinolo, A. R.; Clarke, J. H.

    1972-01-01

    The gas dynamic structures of the transport shock and the downstream collisional relaxation layer are evaluated for partially ionized monatomic gases. Elastic and inelastic collisional nonequilibrium effects are taken into consideration. Three electronic levels are accounted for in the microscopic model of the atom. Nonequilibrium processes with respect to population of levels and species plus temperature are considered. By using an asymptotic technique the shock morphology is found on a continuum flow basis. The asymptotic procedure gives two distinct layers in which the nonequilibrium effects to be considered are different. A transport shock appears as the inner solution to an outer collisional relaxation layer in which the gas reaches local equilibrium. A family of numerical examples is displayed for different flow regimes. Argon and helium models are used in these examples.

  15. Electronic transport properties of BN sheet on adsorption of ammonia (NH3) gas.

    PubMed

    Srivastava, Anurag; Bhat, Chetan; Jain, Sumit Kumar; Mishra, Pankaj Kumar; Brajpuriya, Ranjeet

    2015-03-01

    We report the detection of ammonia gas through electronic and transport properties analysis of boron nitride sheet. The density functional theory (DFT) based ab initio approach has been used to calculate the electronic and transport properties of BN sheet in presence of ammonia gas. Analysis confirms that the band gap of the sheet increases due to presence of ammonia. Out of different positions, the bridge site is the most favorable position for adsorption of ammonia and the mechanism of interaction falls between weak electrostatic interaction and chemisorption. On relaxation, change in the bond angles of the ammonia molecule in various configurations has been reported with the distance between NH3 and the sheet. An increase in the transmission of electrons has been observed on increasing the bias voltage and I-V relationship. This confirms that, the current increases on applying the bias when ammonia is introduced while a very small current flows for pure BN sheet.

  16. Treating cattle with antibiotics affects greenhouse gas emissions, and microbiota in dung and dung beetles.

    PubMed

    Hammer, Tobin J; Fierer, Noah; Hardwick, Bess; Simojoki, Asko; Slade, Eleanor; Taponen, Juhani; Viljanen, Heidi; Roslin, Tomas

    2016-05-25

    Antibiotics are routinely used to improve livestock health and growth. However, this practice may have unintended environmental impacts mediated by interactions among the wide range of micro- and macroorganisms found in agroecosystems. For example, antibiotics may alter microbial emissions of greenhouse gases by affecting livestock gut microbiota. Furthermore, antibiotics may affect the microbiota of non-target animals that rely on dung, such as dung beetles, and the ecosystem services they provide. To examine these interactions, we treated cattle with a commonly used broad-spectrum antibiotic and assessed downstream effects on microbiota in dung and dung beetles, greenhouse gas fluxes from dung, and beetle size, survival and reproduction. We found that antibiotic treatment restructured microbiota in dung beetles, which harboured a microbial community distinct from those in the dung they were consuming. The antibiotic effect on beetle microbiota was not associated with smaller size or lower numbers. Unexpectedly, antibiotic treatment raised methane fluxes from dung, possibly by altering the interactions between methanogenic archaea and bacteria in rumen and dung environments. Our findings that antibiotics restructure dung beetle microbiota and modify greenhouse gas emissions from dung indicate that antibiotic treatment may have unintended, cascading ecological effects that extend beyond the target animal.

  17. Liquefied natural gas as a transportation fuel for heavy-duty trucks: Volume I

    SciTech Connect

    1997-12-01

    This document contains Volume 1 of a three-volume manual designed for use with a 2- to 3-day liquefied natural gas (LNG) training course. Transportation and off-road agricultural, mining, construction, and industrial applications are discussed. This volume provides a brief introduction to the physics and chemistry of LNG; an overview of several ongoing LNG projects, economic considerations, LNG fuel station technology, LNG vehicles, and a summary of federal government programs that encourage conversion to LNG.

  18. Barometric gas transport along faults and its application to nuclear test-ban monitoring

    SciTech Connect

    Carrigan, C. R.; Heinle, R. A.; Hudson, G. B.; Nitao, J. J.; Zucca, J. J.

    1997-06-01

    Underground nuclear explosions produce a unique but evanescent set of radionuclide gases that potentially can be used in the context of an on-site, test-ban monitoring program to differentiate them from other detected events such as earthquakes or mining activity. In Part I of this report we describe an experiment to evaluate the upward transport of gases from an underground explosion using two gas tracers with very different diffusivities that were released in a 400- m-deep, chemical explosive detonation. The less diffusive (more massive) tracer was detected on a nearby geologic fault 50 days following the detonation while the more diffusive tracer was-- detected 375 days after release. Computer simulations indicate that the arrival time and the chromatographic behavior of transport are characteristic of barometrically induced flow in a fractured, porous matrix regime. For a hypothetical 1-kiloton fission explosion subject to the same weather and gas transport conditions of the chemical explosion, simulations predict the delectability of argon-37 after 80 days in spite of depletion by radioactive decay. Largely because of the earlier arrival of xenon-133, owing to its lower binary gas diffusivity, the exceedingly short lived isotope should also be detectable-arriving about 30 days earlier than argon. in Part II we consider that our prediction of the delectability of argon and xenon is based upon the small volume (0.00001 M3) sampling technique of the NPE tracer-gas sampling study while actual sampling for radionuclides would involve drawing much larger volume (possibly 0.1- 1 M3) gas samples from the near-surface.

  19. Transport of Gas Phase Radionuclides in a Fractured, Low-Permeability Reservoir

    NASA Astrophysics Data System (ADS)

    Cooper, C. A.; Chapman, J.

    2001-12-01

    The U.S. Atomic Energy Commission (predecessor to the Department of Energy, DOE) oversaw a joint program between industry and government in the 1960s and 1970s to develop technology to enhance production from low-permeability gas reservoirs using nuclear stimulation rather than conventional means (e.g., hydraulic and/or acid fracturing). Project Rio Blanco, located in the Piceance Basin, Colorado, was the third experiment under the program. Three 30-kiloton nuclear explosives were placed in a 2134 m deep well at 1780, 1899, and 2039 m below the land surface and detonated in May 1973. Although the reservoir was extensively fractured, complications such as radionuclide contamination of the gas prevented production and subsequent development of the technology. Two-dimensional numerical simulations were conducted to identify the main transport processes that have occurred and are currently occurring in relation to the detonations, and to estimate the extent of contamination in the reservoir. Minor modifications were made to TOUGH2, the multiphase, multicomponent reservoir simulator developed at Lawrence Berkeley National Laboratories. The simulator allows the explicit incorporation of fractures, as well as heat transport, phase change, and first order radionuclide decay. For a fractured two-phase (liquid and gas) reservoir, the largest velocities are of gases through the fractures. In the gas phase, tritium and one isotope of krypton are the principle radionuclides of concern. However, in addition to existing as a fast pathway, fractures also permit matrix diffusion as a retardation mechanism. Another retardation mechanism is radionuclide decay. Simulations show that incorporation of fractures can significantly alter transport rates, and that radionuclides in the gas phase can preferentially migrate upward due to the downward gravity drainage of liquid water in the pores. This project was funded by the National Nuclear Security Administration, Nevada Operations Office

  20. Transport of gas-phase radionuclides in a fractured, low-permeability reservoir

    SciTech Connect

    Clay Cooper; Jenny Chapman

    2001-12-01

    The U.S. Atomic Energy Commission (predecessor to the U.S. Department of Energy, DOE) oversaw a joint program between industry and government in the 1960s and 1970s to develop technology to enhance production from low-permeability gas reservoirs using nuclear stimulation rather than conventional means (e.g., hydraulic and/or acid fracturing). Project Rio Blanco, located in the Piceance Basin, Colorado, was the third experiment under the program. Three 30-kiloton nuclear explosives were placed in a 2,134-m-deep well at 1,780, 1,899, and 2,039 m below the land surface and detonated in May 1973. Although the reservoir was extensively fractured, complications such as radionuclide contamination of the gas prevented production and subsequent development of the technology. Two-dimensional numerical simulations were conducted to identify the main transport processes that have occurred and are currently occurring in relation to the detonations, and to estimate the extent of contamination in the reservoir. Minor modifications were made to TOUGH2, the multiphase, multicomponent reservoir simulator developed at Lawrence Berkeley National Laboratories. The simulator allows the explicit incorporation of fractures, as well as heat transport, phase change, and first-order radionuclide decay. For a fractured, two-phase (liquid and gas) reservoir, the largest velocities are of gases through the fractures. In the gas phase, tritium and one isotope of krypton are the principal radionuclides of concern. However, in addition to existing as a fast pathway, fractures also permit matrix diffusion as a retardation mechanism. Another retardation mechanism is radionuclide decay. Simulations show that incorporation of fractures can significantly alter transport rates, and that radionuclides in the gas phase can preferentially migrate upward due to the downward gravity drainage of liquid water in the pores.

  1. Does nitrogen gas bubbled through a low density polymer gel dosimeter solution affect the polymerization process?

    PubMed Central

    Shahbazi-Gahrouei, Daryoush; Gholami, Mehrdad; Pourfallah, Tayyeb Allahverdi; Keshtkar, Mohammad

    2015-01-01

    Background: On account of the lower electron density in the lung tissue, the dose distribution in the lung cannot be verified with the existing polymer gel dosimeters. Thus, the aims of this study are to make a low density polymer gel dosimeter and investigate the effect of nitrogen gas bubbles on the R2 responses and its homogeneity. Materials and Methods: Two different types of low density polymer gel dosimeters were prepared according to a composition proposed by De Deene, with some modifications. In the first type, no nitrogen gas was perfused through the gel solution and water. In the second type, to expel the dissolved oxygen, nitrogen gas was perfused through the water and gel solution. The post-irradiation times in the gels were 24 and 5 hours, respectively, with and without perfusion of nitrogen gas through the water and gel solution. Results: In the first type of gel, there was a linear correlation between the doses and R2 responses from 0 to 12 Gy. The fabricated gel had a higher dynamic range than the other low density polymer gel dosimeter; but its background R2 response was higher. In the second type, no difference in R2 response was seen in the dose ranges from 0 to 18 Gy. Both gels had a mass density between 0.35 and 0.45 g.cm-3 and CT values of about -650 to -750 Hounsfield units. Conclusion: It appeared that reactions between gelatin-free radicals and monomers, due to an increase in the gel temperature during rotation in the household mixer, led to a higher R2-background response. In the second type of gel, it seemed that the collapse of the nitrogen bubbles was the main factor that affected the R2-responses. PMID:26015914

  2. Fuel-cycle greenhouse gas emissions impacts of alternative transportation fuels and advanced vehicle technologies.

    SciTech Connect

    Wang, M. Q.

    1998-12-16

    At an international conference on global warming, held in Kyoto, Japan, in December 1997, the United States committed to reduce its greenhouse gas (GHG) emissions by 7% over its 1990 level by the year 2012. To help achieve that goal, transportation GHG emissions need to be reduced. Using Argonne's fuel-cycle model, I estimated GHG emissions reduction potentials of various near- and long-term transportation technologies. The estimated per-mile GHG emissions results show that alternative transportation fuels and advanced vehicle technologies can help significantly reduce transportation GHG emissions. Of the near-term technologies evaluated in this study, electric vehicles; hybrid electric vehicles; compression-ignition, direct-injection vehicles; and E85 flexible fuel vehicles can reduce fuel-cycle GHG emissions by more than 25%, on the fuel-cycle basis. Electric vehicles powered by electricity generated primarily from nuclear and renewable sources can reduce GHG emissions by 80%. Other alternative fuels, such as compressed natural gas and liquefied petroleum gas, offer limited, but positive, GHG emission reduction benefits. Among the long-term technologies evaluated in this study, conventional spark ignition and compression ignition engines powered by alternative fuels and gasoline- and diesel-powered advanced vehicles can reduce GHG emissions by 10% to 30%. Ethanol dedicated vehicles, electric vehicles, hybrid electric vehicles, and fuel-cell vehicles can reduce GHG emissions by over 40%. Spark ignition engines and fuel-cell vehicles powered by cellulosic ethanol and solar hydrogen (for fuel-cell vehicles only) can reduce GHG emissions by over 80%. In conclusion, both near- and long-term alternative fuels and advanced transportation technologies can play a role in reducing the United States GHG emissions.

  3. Does Membrane Thickness Affect the Transport of Selective Ions Mediated by Ionophores in Synthetic Membranes?

    PubMed

    Lomora, Mihai; Dinu, Ionel Adrian; Itel, Fabian; Rigo, Serena; Spulber, Mariana; Palivan, Cornelia G

    2015-08-31

    Biomimetic polymer nanocompartments (polymersomes) with preserved architecture and ion-selective membrane permeability represent cutting-edge mimics of cellular compartmentalization. Here it is studied whether the membrane thickness affects the functionality of ionophores in respect to the transport of Ca(2+) ions in synthetic membranes of polymersomes, which are up to 2.6 times thicker than lipid membranes (5 nm). Selective permeability toward calcium ions is achieved by proper insertion of ionomycin, and demonstrated by using specific fluorescence markers encapsulated in their inner cavities. Preservation of polymersome architecture is shown by a combination of light scattering, transmission electron microscopy, and fluorescence spectroscopy. By using a combination of stopped-flow and fluorescence spectroscopy, it is shown that ionomycin can function and transport calcium ions across polymer membranes with thicknesses in the range 10.7-13.4 nm (7.1-8.9 times larger than the size of the ionophore). Thicker membranes induce a decrease in transport, but do not block it due to the intrinsic flexibility of these synthetic membranes. The design of ion selective biomimetic nanocompartments represents a new path toward the development of cellular ion nanosensors and nano-reactors, in which calcium sensitive biomacromolecules can be triggered for specific biological functions.

  4. Activity of erdosteine on mucociliary transport in patients affected by chronic bronchitis.

    PubMed

    Olivieri, D; Del Donno, M; Casalini, A; D'Ippolito, R; Fregnan, G B

    1991-01-01

    The influence of erdosteine (a mucomodulator endowed with mucolytic and antioxidant properties) on human mucociliary transport (MCT) was investigated in a double-blind placebo controlled study. Sixteen former smokers affected by chronic bronchitis, preselected for their mucociliary responsiveness to an inhaled beta 2-agonist, were divided into two groups (matched by number, sex, age and FEV1%) and orally treated with placebo or erdosteine (300 mg t.i.d.) for 8 days. Their MCT was assessed by the bronchofiberscopy technique just before starting the treatment and at the end of the treatment. The pretreatment mucus transport velocity in these patients was significantly decreased with respect to healthy subjects. The erdosteine treatment induced a significant improvement of MCT while placebo was inactive (mean % variation +/- SE against their baseline values being +60.4 +/- 18.4 and -3.0 +/- 5.9, respectively). This peculiar activity of erdosteine on mucus transport may be of clinical usefulness in chronic bronchitic patients and it can be added to beta 2-agonist to restore the decreased MCT.

  5. Modeling of transport phenomena during gas hydrate decomposition by depressurization and/or thermal stimulation

    NASA Astrophysics Data System (ADS)

    Abendroth*, Sven; Klump, Jens; Thaler, Jan; Schicks, Judith M.

    2013-04-01

    In the context of the German joint project SUGAR (Submarine Gas Hydrate Reservoirs: exploration, extraction and transport) we conducted a series of experiments in the LArge Reservoir Simulator (LARS) at the German Research Centre of Geosciences Potsdam (Beeskow-Strauch et al., this volume). These experiments allow us to investigate the formation and dissociation of hydrates at large scale laboratory conditions. Processes inside LARS are modeled to study the effects of sediment properties as well as physical and chemical processes on parameters such as hydrate dissociation rate and methane production rate. The experimental results from LARS are used to provide details about processes inside the pressure vessel, validate the models through history matching, and feed back into the design of future experiments. In experiments in LARS the amount of methane produced from gas hydrates was much lower than expected. Previously published models predict a methane production rate higher than the observed in experiments and field studies (Uddin and Wright 2005; Uddin et al. 2010; Wright et al. 2011). The authors of the aforementioned studies point out that the current modeling approach overestimates the gas production rate when modeling gas production by depressurization. Uddin and Wright (2005) suggested that trapping of gas bubbles inside the porous medium is responsible for the reduced gas production rate. They point out that this behavior of multi-phase flow is not well explained by a "residual oil" model, but rather resembles a "foamy oil" model. Our study applies Uddin's (2010) "foamy oil" model and combines it with history matches of our experiments in LARS. First results indicate a better agreement between experimental and model results when using the "foamy oil" model instead of conventional models featuring gas flow in water. Further experiments with LARS, including hydrate dissociation by depressurization and thermal stimulation by in-situ combustion will be used to

  6. Synthesis and Transport Properties of Novel MOF/PIM-1/MOF Sandwich Membranes for Gas Separation.

    PubMed

    Fuoco, Alessio; Khdhayyer, Muhanned R; Attfield, Martin P; Esposito, Elisa; Jansen, Johannes C; Budd, Peter M

    2017-02-11

    Metal-organic frameworks (MOFs) were supported on polymer membrane substrates for the fabrication of composite polymer membranes based on unmodified and modified polymer of intrinsic microporosity (PIM-1). Layers of two different MOFs, zeolitic imidazolate framework-8 (ZIF-8) and Copper benzene tricarboxylate ((HKUST-1), were grown onto neat PIM-1, amide surface-modified PIM-1 and hexamethylenediamine (HMDA) -modified PIM-1. The surface-grown crystalline MOFs were characterized by a combination of several techniques, including powder X-ray diffraction, infrared spectroscopy and scanning electron microscopy to investigate the film morphology on the neat and modified PIM-1 membranes. The pure gas permeabilities of He, H₂, O₂, N₂, CH₄, CO₂ were studied to understand the effect of the surface modification on the basic transport properties and evaluate the potential use of these membranes for industrially relevant gas separations. The pure gas transport was discussed in terms of permeability and selectivity, highlighting the effect of the MOF growth on the diffusion coefficients of the gas in the new composite polymer membranes. The results confirm that the growth of MOFs on polymer membranes can enhance the selectivity of the appropriately functionalized PIM-1, without a dramatic decrease of the permeability.

  7. Synthesis and Transport Properties of Novel MOF/PIM-1/MOF Sandwich Membranes for Gas Separation

    PubMed Central

    Fuoco, Alessio; Khdhayyer, Muhanned R.; Attfield, Martin P.; Esposito, Elisa; Jansen, Johannes C.; Budd, Peter M.

    2017-01-01

    Metal-organic frameworks (MOFs) were supported on polymer membrane substrates for the fabrication of composite polymer membranes based on unmodified and modified polymer of intrinsic microporosity (PIM-1). Layers of two different MOFs, zeolitic imidazolate framework-8 (ZIF-8) and Copper benzene tricarboxylate ((HKUST-1), were grown onto neat PIM-1, amide surface-modified PIM-1 and hexamethylenediamine (HMDA) -modified PIM-1. The surface-grown crystalline MOFs were characterized by a combination of several techniques, including powder X-ray diffraction, infrared spectroscopy and scanning electron microscopy to investigate the film morphology on the neat and modified PIM-1 membranes. The pure gas permeabilities of He, H2, O2, N2, CH4, CO2 were studied to understand the effect of the surface modification on the basic transport properties and evaluate the potential use of these membranes for industrially relevant gas separations. The pure gas transport was discussed in terms of permeability and selectivity, highlighting the effect of the MOF growth on the diffusion coefficients of the gas in the new composite polymer membranes. The results confirm that the growth of MOFs on polymer membranes can enhance the selectivity of the appropriately functionalized PIM-1, without a dramatic decrease of the permeability. PMID:28208658

  8. Effects of a Rotating Magnetic Field on Gas Transport During Detached Crystal Growth in Space

    NASA Technical Reports Server (NTRS)

    Walker, John S.; Volz, Martin P.; Szofran, Frank R.; Motakef, Shariar; Curreri, Peter A. (Technical Monitor)

    2002-01-01

    During the detached Bridgman growth of semiconductor crystals, the melt has a short free surface which is detached from the ampoule wall near the crystal-melt interface, thus eliminating the crystal defects caused by contact with the ampoule wall. Recent modelling has indicated that initiation and continuation of detached growth depends on the rate of transport of dissolved gas from the crystal-melt interface, where gas is rejected into the melt, to the detached free surface, where evaporating gas maintains the pressure on the free surface. Here we use numerical modelling to investigate whether the application of a rotating magnetic field increases or decreases the transport of rejected gas to the detached free surface. Unfortunately the results show that a rotating magnetic field almost always decreases the evaporation rate at the detached free surface. The exception is an insignificant increase for a short period at the beginning of crystal growth for a few circumstances. The evaporation rate decreases as the strength of the rotating magnetic field is increased.

  9. Exploring the dynamic behaviors and transport properties of gas molecules in a transmembrane cyclic peptide nanotube.

    PubMed

    Li, Rui; Fan, Jianfen; Li, Hui; Yan, Xiliang; Yu, Yi

    2013-12-05

    The dynamic behaviors and transport properties of O2, CO2, and NH3 molecules through a transmembrane cyclic peptide nanotube (CPNT) of 8×cyclo-(WL)4/POPE have been investigated by steered molecular dynamics (SMD) simulations and adaptive biasing force (ABF) samplings. Different external forces are needed for three gas molecules to enter the channel. The periodic change of the pulling force curve for a gas traveling through the channel mainly arises from the regular and periodic arrangement of the composed CP subunits of the CPNT. Radial distribution functions (RDFs) between gas and water disclose the density decrease of channel water, which strongly aggravates the discontinuity of H-bond formation between a gas molecule and the neighboring water. Compared to hardly any H-bond formation between CO2 (or O2) and the framework of the CPNT, NH3 can form abundant H-bonds with the carbonyl/amide groups of the CPNT, leading to a fierce competition to NH3-water H-bonded interactions. In addition to direct H-bonded interactions, all three gases can form water bridges with the tube. The potential profile of mean force coincides with the occurring probability of a gas molecule along the tube axis. The energy barriers at two mouths of the CPNT elucidate the phenomenon that CO2 and O2 are thoroughly confined in the narrow lumen while NH3 can easily go outside the tube. Intermolecular interactions of each gas with channel water and the CPNT framework and the formation of H-bonds and water bridges illuminate the different gas translocation behaviors. The results uncover interesting and comprehensive mechanisms underlying the permeation characteristics of three gas molecules traveling through a transmembrane CPNT.

  10. Energy utilization and greenhouse-gas emissions: Transportation sector, topical report

    SciTech Connect

    Darrow, K.G.

    1992-06-01

    The objective of the report is to compare the emissions of greenhouse gases for alternative end-use technologies in the transportation sector. Scientists assert that global warming is occurring and will continue to occur as a result of increasing concentrations of certain gases in the atmosphere. Carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O) are the focus of this analysis because they are believed to cause three-fourths of the global warming effect and because energy production and use are a significant source of these emissions. Greenhouse gas emissions in the energy sector occur during energy production, conversion, transportation and end-use. This analysis compares alternative transportation sector fuel/technology choices in terms of their total fuel-cycle emissions of greenhouse gases. The emphasis of this report is on the end use comparison. The fuel-cycle emissions comparison was developed in a companion report.

  11. Model simulation and experiments of flow and mass transport through a nano-material gas filter

    SciTech Connect

    Yang, Xiaofan; Zheng, Zhongquan C.; Winecki, Slawomir; Eckels, Steve

    2013-11-01

    A computational model for evaluating the performance of nano-material packed-bed filters was developed. The porous effects of the momentum and mass transport within the filter bed were simulated. For the momentum transport, an extended Ergun-type model was employed and the energy loss (pressure drop) along the packed-bed was simulated and compared with measurement. For the mass transport, a bulk dsorption model was developed to study the adsorption process (breakthrough behavior). Various types of porous materials and gas flows were tested in the filter system where the mathematical models used in the porous substrate were implemented and validated by comparing with experimental data and analytical solutions under similar conditions. Good agreements were obtained between experiments and model predictions.

  12. Influence of the Gas-Water Interface on Transport of Microorganisms through Unsaturated Porous Media

    PubMed Central

    Wan, Jiamin; Wilson, John L.; Kieft, Thomas L.

    1994-01-01

    In this article, a new mechanism influencing the transport of microorganisms through unsaturated porous media is examined, and a new method for directly visualizing bacterial behavior within a porous medium under controlled chemical and flow conditions is introduced. Resting cells of hydrophilic and relatively hydrophobic bacterial strains isolated from groundwater were used as model microorganisms. The degree of hydrophobicity was determined by contact-angle measurements. Glass micromodels allowed the direct observation of bacterial behavior on a pore scale, and three types of sand columns with different gas saturations provided quantitative measurements of the observed phenomena on a porous medium scale. The reproducibility of each break-through curve was established in three to five repeated experiments. The data collected from the column experiments can be explained by phenomena directly observed in the micromodel experiments. The retention rate of bacteria is proportional to the gas saturation in porous media because of the preferential sorption of bacteria onto the gas-water interface over the solid-water interface. The degree of sorption is controlled mainly by cell surface hydrophobicity under the simulated groundwater conditions because of hydrophobic forces between the organisms and the interfaces. The sorption onto the gas-water interface is essentially irreversible because of capillary forces. This preferential and irreversible sorption at the gas-water interface strongly influences the movement and spatial distribution of microorganisms. Images PMID:16349180

  13. Revisiting low-fidelity two-fluid models for gas-solids transport

    NASA Astrophysics Data System (ADS)

    Adeleke, Najeem; Adewumi, Michael; Ityokumbul, Thaddeus

    2016-08-01

    Two-phase gas-solids transport models are widely utilized for process design and automation in a broad range of industrial applications. Some of these applications include proppant transport in gaseous fracking fluids, air/gas drilling hydraulics, coal-gasification reactors and food processing units. Systems automation and real time process optimization stand to benefit a great deal from availability of efficient and accurate theoretical models for operations data processing. However, modeling two-phase pneumatic transport systems accurately requires a comprehensive understanding of gas-solids flow behavior. In this study we discuss the prevailing flow conditions and present a low-fidelity two-fluid model equation for particulate transport. The model equations are formulated in a manner that ensures the physical flux term remains conservative despite the inclusion of solids normal stress through the empirical formula for modulus of elasticity. A new set of Roe-Pike averages are presented for the resulting strictly hyperbolic flux term in the system of equations, which was used to develop a Roe-type approximate Riemann solver. The resulting scheme is stable regardless of the choice of flux-limiter. The model is evaluated by the prediction of experimental results from both pneumatic riser and air-drilling hydraulics systems. We demonstrate the effect and impact of numerical formulation and choice of numerical scheme on model predictions. We illustrate the capability of a low-fidelity one-dimensional two-fluid model in predicting relevant flow parameters in two-phase particulate systems accurately even under flow regimes involving counter-current flow.

  14. Ground transport stress affects bacteria in the rumen of beef cattle: A real-time PCR analysis.

    PubMed

    Deng, Lixin; He, Cong; Zhou, Yanwei; Xu, Lifan; Xiong, Huijun

    2016-10-03

    Transport stress syndrome often appears in beef cattle during ground transportation, leading to changes in their capacity to digest food due to changes in rumen microbiota. The present study aimed to analyze bacteria before and after cattle transport. Eight Xianan beef cattle were transported over 1000 km. Rumen fluid and blood were sampled before and after transport. Real-time PCR was used to quantify rumen bacteria. Cortisol and adrenocorticotrophic hormone (ACTH) were measured. Cortisol and ACTH were increased on day 1 after transportation and decreased by day 3. Cellulolytic bacteria (Fibrobacter succinogenes and Ruminococcus flavefaciens), Ruminococcus amylophilus and Prevotella albensis were increased at 6 h and declined by 15 days after transport. There was a significant reduction in Succinivibrio dextrinosolvens, Prevotella bryantii, Prevotella ruminicola and Anaerovibrio lipolytica after transport. Rumen concentration of acetic acid increased after transport, while rumen pH and concentrations of propionic and butyric acids were decreased. Body weight decreased by 3 days and increased by 15 days after transportation. Using real-time PCR analysis, we detected changes in bacteria in the rumen of beef cattle after transport, which might affect the growth of cattle after transport.

  15. Optimization problems in natural gas transportation systems. A state-of-the-art review

    DOE PAGES

    Ríos-Mercado, Roger Z.; Borraz-Sánchez, Conrado

    2015-03-24

    Our paper provides a review on the most relevant research works conducted to solve natural gas transportation problems via pipeline systems. The literature reveals three major groups of gas pipeline systems, namely gathering, transmission, and distribution systems. In this work, we aim at presenting a detailed discussion of the efforts made in optimizing natural gas transmission lines.There is certainly a vast amount of research done over the past few years on many decision-making problems in the natural gas industry and, specifically, in pipeline network optimization. In this work, we present a state-of-the-art survey focusing on specific categories that include short-termmore » basis storage (line-packing problems), gas quality satisfaction (pooling problems), and compressor station modeling (fuel cost minimization problems). We also discuss both steady-state and transient optimization models highlighting the modeling aspects and the most relevant solution approaches known to date. Although the literature on natural gas transmission system problems is quite extensive, this is, to the best of our knowledge, the first comprehensive review or survey covering this specific research area on natural gas transmission from an operations research perspective. Furthermore, this paper includes a discussion of the most important and promising research areas in this field. Hence, our paper can serve as a useful tool to gain insight into the evolution of the many real-life applications and most recent advances in solution methodologies arising from this exciting and challenging research area of decision-making problems.« less

  16. Gas transport by thermal transpiration in micro-channels -- A numerical study

    SciTech Connect

    Wong, C.C.; Hudson, M.L.; Potter, D.L.; Bartel, T.J.

    1998-08-01

    A reliable micro gas pump is an essential element to the development of many micro-systems for chemical gas analyses. At Sandia, the authors are exploring a different pumping mechanism, gas transport by thermal transpiration. Thermal transpiration refers to the rarefied gas dynamics developed in a micro-channel with a longitudinal temperature gradient. To investigate the potential of thermal transpiration for gas pumping in micro-systems, the authors have performed simulations and model analysis to design micro-devices and to assess their design performance before the fabrication process. The effort is to apply ICARUS (a Direct Simulation Monte Carlo code developed at Sandia) to characterize the fluid transport and evaluate the design performance. The design being considered has two plenums at different temperatures (hot and cold) separated by a micro-channel of 0.1 micron wide and 1 micron long. The temperature difference between the two plenums is 30 kelvin. ICARUS results, a quasi-steady analysis, predicts a net flow through the micro-channel with a velocity magnitude of about 0.4 m/s due to temperature gradient at the wall (thermal creep flow) at the early time. Later as the pressure builds up in the hot plenum, flow is reversed. Eventually when the system reaches steady state equilibrium, the net flow becomes zero. The thermal creep effect is compensated by the thermo-molecular pressure effect. This result demonstrates that it is important to include the thermo-molecular pressure effect when designing a pumping mechanism based on thermal transpiration. The DSMC technique can model this complex thermal transpiration problem.

  17. GH-3PAD - a new numerical solver for multiphase transport in porous media - new insights on gas hydrate and free gas co-existence

    NASA Astrophysics Data System (ADS)

    Burwicz, E.; Rupke, L.; Wallmann, K.

    2013-12-01

    Gas Hydrate-3 Phase Advanced Dynamics (GH-3PAD) code has been developed to study the geophysical and biochemical processes associated with gas hydrate as well as free methane gas formation and dissolution in marine sediments. Biochemical processes influencing in-situ organic carbon decay and, therefore, gas hydrate formation, such as Anaerobic Oxidation of Methane (AOM), sulfate reduction, and methanogenesis have been considered. The new model assumes a Lagrangian reference frame that is attached to the deposited sedimentary layers, which compact according to their individual lithological properties. Differential motion of the pore fluids and free gas is modeled as Darcy flow. Gas hydrate and free gas formation is either controlled by 1) instant gas hydrate crystallization assuming local thermodynamical equilibrium or by a 2) kinetically controlled rate of gas hydrate growth. The thermal evolution is computed from an energy equation that includes contributions from all phases present in the model (sediment grains, saline pore fluids, gas hydrate, and free gas). A first application of the GH-3PAD model has been the Blake Ridge Site, offshore South Carolina. Here seismic and well data points to the out-of-equilibrium co-existence of gas hydrate and free gas. It has been reported that these two distinct phases appear within sediment column with a gaseous phase tending to migrate upwards throughout the Gas Hydrate Stability Zone (GHSZ) until it reaches the seafloor despite relatively low gas hydrate content (4 - 7 vol. % after Paull et al., 1996). With the GH-3PAD model we quantify the complex transport- reaction processes that control three phase (gas hydrate, free gas, and dissolved CH4) out-of-equilibrium state. References: Paull C. K., Matsumoto R., Wallace P. J., 1996. 9. Site 997, Shipboard Scientific Party. Proceeding of the Ocean Drilling Program, Initial Reports, Vol. 164.

  18. Describing and compensating gas transport dynamics for accurate instantaneous emission measurement

    NASA Astrophysics Data System (ADS)

    Weilenmann, Martin; Soltic, Patrik; Ajtay, Delia

    Instantaneous emission measurements on chassis dynamometers and engine test benches are becoming increasingly usual for car-makers and for environmental emission factor measurement and calculation, since much more information about the formation conditions can be extracted than from the regulated bag measurements (integral values). The common exhaust gas analysers for the "regulated pollutants" (carbon monoxide, total hydrocarbons, nitrogen oxide, carbon dioxide) allow measurement at a rate of one to ten samples per second. This gives the impression of having after-the-catalyst emission information with that chronological precision. It has been shown in recent years, however, that beside the reaction time of the analysers, the dynamics of gas transport in both the exhaust system of the car and the measurement system last significantly longer than 1 s. This paper focuses on the compensation of all these dynamics convoluting the emission signals. Most analysers show linear and time-invariant reaction dynamics. Transport dynamics can basically be split into two phenomena: a pure time delay accounting for the transport of the gas downstream and a dynamic signal deformation since the gas is mixed by turbulence along the way. This causes emission peaks to occur which are smaller in height and longer in time at the sensors than they are after the catalyst. These dynamics can be modelled using differential equations. Both mixing dynamics and time delay are constant for modelling a raw gas analyser system, since the flow in that system is constant. In the exhaust system of the car, however, the parameters depend on the exhaust volume flow. For gasoline cars, the variation in overall transport time may be more than 6 s. It is shown in this paper how all these processes can be described by invertible mathematical models with the focus on the more complex case of the car's exhaust system. Inversion means that the sharp emission signal at the catalyst out location can be

  19. Mass-transport deposits: the role of gas in their triggering and final morphology

    NASA Astrophysics Data System (ADS)

    Imbert, Patrice

    2013-04-01

    Mass failure on continental slopes occurs when and where the shear stress at a certain level below the seafloor exceeds the resistance to shear of that level. A number of processes may cause this disequilibrium, including tectonic activity, excess sedimentation, etc. In several cases that will be presented from both seismic and outcrop data, it seems that gas migration plays a crucial role in defining the morphology of the basal surface. The clearest examples come from three separate sedimentary basins. In those three examples, the basal décollement of large-scale mass-transport deposits (MTDs), follows one stratigraphic level over most of the surveyed area, but locally jumps down to a ca. 100-m deeper level. These downward shifts in the basal surface occur right above the crest of underlying structural highs. The coincidence of this morphology with the deeper structure and in some cases with the presence of seismic indications of gas just below strongly suggest that gas did play a role in the location of the anomaly. Another seismic example shows numerous bright amplitude patches at the base of an MTD. The distribution of these anomalies, below relative thins of the transported mass, may indicate degassing by pressure decrease during, and maybe for some time after the gliding. Finally, a Cretaceous outcrop in SE France shows tubular carbonate concretions with a negative anomaly of 13C, interpreted to be diagnostic of methane-derived carbonates, just below the base of a 20-m thick slump. The following processes are envisioned to account for the relationship observed or inferred between anomalies in MTD morphology and gas migration pathways, and may not be mutually exclusive: • Processes initiated by the failure: local anomalies of the décollement surface - Pressure decrease by the spreading out of a failing mass of sediment may cause gas exsolution below the failure along gas migration pathways. Exsolution would then induce local loss of shear strength, and

  20. Event-based stormwater quality and quantity loadings from elevated urban infrastructure affected by transportation.

    PubMed

    Sansalone, John J; Hird, Jonathan P; Cartledge, Frank K; Tittlebaum, Marty E

    2005-01-01

    Urban-rainfall runoff affected by transportation is a complex matrix of a very wide gradation of particulate matter (< 1 to > 10 000 microm) and dissolved inorganic and organic constituents. Particulate matter transported by rainfall runoff can be a significant vector for many reactive particulate-bound constituents, particularly metal elements. The water quality and hydrology of nine events from a representative elevated section of Interstate 10 (I-10) (eastbound average daily traffic load of 70 400 vehicles) in Baton Rouge, Louisiana, were characterized and compared with respect to the passage of each hydrograph. Residence time on the paved concrete surface was less than 30 minutes for all events. Results indicate that event-mean concentrations (EMCs) of particulate matter as total-suspended solids (TSS) (138 to 561 mg/L) and chemical-oxygen demand (COD) (128 to 1440 mg/L) were greater than those found in untreated municipal wastewater from the same service area. Particulate-matter dissolution and COD partitioned as a function of pH, pavement residence time, and organic content. In general, delivery of mass for aggregate indices, such as particulate matter (measured as TSS) and COD mass, were driven by the hydrology of the event, while concentrations of aggregate-constituent measurements, such as total-dissolved solids (TDS), illustrated an exponential-type decline during the rising limb of the hydrograph. Despite the short residence times, wide solids gradation, partitioning, and complexity of the rainfall-runoff chemistry, conductivity and dissolved solids were strongly correlated. Characterization of the transport and loads of constituents in urban-rainfall runoff, as a function of hydrology, is a necessary first step when considering treatability, structural or nonstructural controls, and mass trading for discharges from paved infrastructure.

  1. Facilitated transport ceramic membranes for high-temperature gas cleanup. Final report, February 1990--April 1994

    SciTech Connect

    Quinn, R.; Minford, E.; Damle, A.S.; Gangwal, S.K.; Hart, B.A.

    1994-04-01

    The objective of this program was to demonstrate the feasibility of developing high temperature, high pressure, facilitated transport ceramic membranes to control gaseous contaminants in Integrated Gasification Combined Cycle (IGCC) power generation systems. Meeting this objective requires that the contaminant gas H{sub 2}S be removed from an IGCC gas mixture without a substantial loss of the other gaseous components, specifically H{sub 2} and CH{sub 4}. As described above this requires consideration of other, nonconventional types of membranes. The solution evaluated in this program involved the use of facilitated transport membranes consisting of molten mixtures of alkali and alkaline earth carbonate salts immobilized in a microporous ceramic support. To accomplish this objective, Air Products and Chemicals, Inc., Golden Technologies Company Inc., and Research Triangle Institute worked together to develop and test high temperature facilitated membranes for the removal of H{sub 2}S from IGCC gas mixtures. Three basic experimental activities were pursued: (1) evaluation of the H{sub 2}S chemistry of a variety of alkali and alkaline earth carbonate salt mixtures; (2) development of microporous ceramic materials which were chemically and physically compatible with molten carbonate salt mixtures under IGCC conditions and which could function as a host to support a molten carbonate mixture and; (3) fabrication of molten carbonate/ceramic immobilized liquid membranes and evaluation of these membranes under conditions approximating those found in the intended application. Results of these activities are presented.

  2. Analysis of CO2 Separation from Flue Gas, Pipeline Transportation, and Sequestration in Coal

    SciTech Connect

    Eric P. Robertson

    2007-09-01

    This report was written to satisfy a milestone of the Enhanced Coal Bed Methane Recovery and CO2 Sequestration task of the Big Sky Carbon Sequestration project. The report begins to assess the costs associated with separating the CO2 from flue gas and then injecting it into an unminable coal seam. The technical challenges and costs associated with CO2 separation from flue gas and transportation of the separated CO2 from the point source to an appropriate sequestration target was analyzed. The report includes the selection of a specific coal-fired power plant for the application of CO2 separation technology. An appropriate CO2 separation technology was identified from existing commercial technologies. The report also includes a process design for the chosen technology tailored to the selected power plant that used to obtain accurate costs of separating the CO2 from the flue gas. In addition, an analysis of the costs for compression and transportation of the CO2 from the point-source to an appropriate coal bed sequestration site was included in the report.

  3. Radon as a natural tracer for gas transport within uranium waste rock piles.

    PubMed

    Silva, N C; Chagas, E G L; Abreu, C B; Dias, D C S; Lopez, D; Guerreiro, E T Z; Alberti, H L C; Braz, M L; Branco, O; Fleming, P

    2014-07-01

    Acid mine drainage (AMD) has been identified as the main cause for outflow of acid water and radioactive/non-radioactive contaminants. AMD encompasses pyrites oxidation when water and oxygen are available. AMD was identified in uranium waste rock piles (WRPs) of Indústrias Nucleares do Brasil-Caldas facility (Brazilian uranium mine), resulting in high costs for water treatment. AMD reduction is the main challenge, and scientific investigation has been conducted to understand oxygen and water transportation within WRPs, where 222Rn is used as natural tracer for oxygen transportation. The study consists of soil radon gas mapping in the top layer of WRP4 using active soil gas pumping, radon adsorption in active charcoal and 222Rn determination using high-resolution gamma-ray spectrometry. A sampling network of 71 points was built where samples were collected at a depth of 40 cm. Soil radon gas concentration ranged from 33.7 to 1484.2 kBq m(-3) with mean concentration of 320.7±263.3 kBq m(-3).

  4. Hybrid life-cycle assessment of natural gas based fuel chains for transportation.

    PubMed

    Strømman, Anders Hammer; Solli, Christian; Hertwich, Edgar G

    2006-04-15

    This research compares the use of natural gas, methanol, and hydrogen as transportation fuels. These three fuel chains start with the extraction and processing of natural gas in the Norwegian North Sea and end with final use in Central Europe. The end use is passenger transportation with a sub-compact car that has an internal combustion engine for the natural gas case and a fuel cell for the methanol and hydrogen cases. The life cycle assessment is performed by combining a process based life-cycle inventory with economic input-output data. The analysis shows that the potential climate impacts are lowest for the hydrogen fuel scenario with CO2 deposition. The hydrogen fuel chain scenario has no significant environmental disadvantage compared to the other fuel chains. Detailed analysis shows that the construction of the car contributes significantly to most impact categories. Finally, it is shown how the application of a hybrid inventory model ensures a more complete inventory description compared to standard process-based life-cycle assessment. This is particularly significant for car construction which would have been significantly underestimated in this study using standard process life-cycle assessment alone.

  5. Exploring Factors Affecting Emergency Medical Services Staffs' Decision about Transporting Medical Patients to Medical Facilities

    PubMed Central

    Seyedin, Hesam; Jamshidi-Orak, Roohangiz

    2014-01-01

    Transfer of patients in medical emergency situations is one of the most important missions of emergency medical service (EMS) staffs. So this study was performed to explore affecting factors in EMS staffs' decision during transporting of patients in medical situations to medical facilities. The participants in this qualitative study consisted of 18 EMS staffs working in prehospital care facilities in Tehran, Iran. Data were gathered through semistructured interviews. The data were analyzed using a content analysis approach. The data analysis revealed the following theme: “degree of perceived risk in EMS staffs and their patients.” This theme consisted of two main categories: (1) patient's condition' and (2) the context of the EMS mission'. The patent's condition category emerged from “physical health statuses,” “socioeconomic statuses,” and “cultural background” subcategories. The context of the EMS mission also emerged from two subcategories of “characteristics of the mission” and EMS staffs characteristics'. EMS system managers can consider adequate technical, informational, financial, educational, and emotional supports to facilitate the decision making of their staffs. Also, development of an effective and user-friendly checklist and scoring system was recommended for quick and easy recognition of patients' needs for transportation in a prehospital situation. PMID:24891953

  6. Exploring Factors Affecting Emergency Medical Services Staffs' Decision about Transporting Medical Patients to Medical Facilities.

    PubMed

    Ebrahimian, Abbasali; Seyedin, Hesam; Jamshidi-Orak, Roohangiz; Masoumi, Gholamreza

    2014-01-01

    Transfer of patients in medical emergency situations is one of the most important missions of emergency medical service (EMS) staffs. So this study was performed to explore affecting factors in EMS staffs' decision during transporting of patients in medical situations to medical facilities. The participants in this qualitative study consisted of 18 EMS staffs working in prehospital care facilities in Tehran, Iran. Data were gathered through semistructured interviews. The data were analyzed using a content analysis approach. The data analysis revealed the following theme: "degree of perceived risk in EMS staffs and their patients." This theme consisted of two main categories: (1) patient's condition' and (2) the context of the EMS mission'. The patent's condition category emerged from "physical health statuses," "socioeconomic statuses," and "cultural background" subcategories. The context of the EMS mission also emerged from two subcategories of "characteristics of the mission" and EMS staffs characteristics'. EMS system managers can consider adequate technical, informational, financial, educational, and emotional supports to facilitate the decision making of their staffs. Also, development of an effective and user-friendly checklist and scoring system was recommended for quick and easy recognition of patients' needs for transportation in a prehospital situation.

  7. Factors affecting pesticide occurrence and transport in a large Midwestern river basin

    USGS Publications Warehouse

    Crawford, Charles G.

    2001-01-01

    Several factors affect the occurrence and transport of pesticides in surface waters of the 29,400 km2 White River Basin in Indiana. A relationship was found between pesticide use and the average annual concentration of that pesticide in the White River, although this relationship varies for different classes of pesticides. About one percent of the mass applied of each of the commonly used agricultural herbicides was transported from the basin via the White River. Peak pesticide concentrations were typically highest in late spring or early summer and were associated with periods of runoff following application. Concentrations of diazinon were higher in an urban basin than in two agricultural basins, corresponding to the common use of this insecticide on lawns and gardens in urban areas. Concentrations of atrazine, a corn herbicide widely used in the White River Basin, were higher in an agricultural basin with permeable, well-drained soils, than in an agricultural basin with less permeable, more poorly drained soils. Although use of butylate and cyanazine was comparable in the White River Basin between 1992 and 1994, concentrations in the White River of butylate, which is incorporated into soil, were substantially less than for cyanazine, which is typically applied to the soil surface.

  8. Gas Transport and Control in Thick-Liquid Inertial Fusion PowerPlants

    SciTech Connect

    Debonnel, Christophe Sylvain

    2006-01-01

    Among the numerous potential routes to a commercial fusion power plant, the inertial path with thick-liquid protection is explored in this doctoral dissertation. Gas dynamics phenomena in such fusion target chambers have been investigated since the early 1990s with the help of a series of simulation codes known as TSUNAMI. For this doctoral work, the code was redesigned and rewritten entirely to enable the use of modern programming techniques, languages and software; improve its user-friendliness; and refine its ability to model thick-liquid protected chambers. The new ablation and gas dynamics code is named “Visual Tsunami” to emphasize its graphics-based pre- and post-processors. It is aimed at providing a versatile and user-friendly design tool for complex systems for which transient gas dynamics phenomena play a key role. Simultaneously, some of these improvements were implemented in a previous version of the code; the resulting code constitutes the version 2.8 of the TSUNAMI series. Visual Tsunami was used to design and model the novel Condensation Debris Experiment (CDE), which presents many aspects of a typical Inertial Fusion Energy (IFE) system and has therefore been used to exercise the code. Numerical and experimental results are in good agreement. In a heavy-ion IFE target chamber, proper beam and target propagation set stringent requirements for the control of ablation debris transport in the target chamber and beam tubes. When the neutralized ballistic transport mode is employed, the background gas density should be adequately low and the beam tube metallic surfaces upstream of the neutralizing region should be free of contaminants. TSUNAMI 2.8 was used for the first simulation of gas transport through the complex geometry of the liquid blanket of a hybrid target chamber and beam lines. Concurrently, the feasibility of controlling the gas density was addressed with a novel beam tube design, which introduces magnetic shutters and a long low

  9. Calculation of effective transport properties of partially saturated gas diffusion layers

    NASA Astrophysics Data System (ADS)

    Bednarek, Tomasz; Tsotridis, Georgios

    2017-02-01

    A large number of currently available Computational Fluid Dynamics numerical models of Polymer Electrolyte Membrane Fuel Cells (PEMFC) are based on the assumption that porous structures are mainly considered as thin and homogenous layers, hence the mass transport equations in structures such as Gas Diffusion Layers (GDL) are usually modelled according to the Darcy assumptions. Application of homogenous models implies that the effects of porous structures are taken into consideration via the effective transport properties of porosity, tortuosity, permeability (or flow resistance), diffusivity, electric and thermal conductivity. Therefore, reliable values of those effective properties of GDL play a significant role for PEMFC modelling when employing Computational Fluid Dynamics, since these parameters are required as input values for performing the numerical calculations. The objective of the current study is to calculate the effective transport properties of GDL, namely gas permeability, diffusivity and thermal conductivity, as a function of liquid water saturation by using the Lattice-Boltzmann approach. The study proposes a method of uniform water impregnation of the GDL based on the "Fine-Mist" assumption by taking into account the surface tension of water droplets and the actual shape of GDL pores.

  10. Technical, economic, and environmental impact study of converting Uzbekistan transportation fleets to natural gas operation. Export trade information

    SciTech Connect

    1997-04-30

    This study, conducted by Radian International, was funded by the U.S. Trade and Development Agency. The report assesses the feasibility (technical, economic and environmental) of converting the Uzbek transportation fleets to natural gas operation. The study focuses on the conversion of high fuel use vehicles and locomotives to liquefied natural gas (LNG) and the conversion of moderate fuel use veicles to compressed natural gas (CNG). The report is divided into the following sections: Executive Summary; (1.0) Introduction; (2.0) Country Background; (3.0) Characterization of Uzbek Transportation Fuels; (4.0) Uzbek Vehicle and Locomotive Fleet Characterization; (5.0) Uzbek Natural Gas Vehicle Conversion Shops; (6.0) Uzbek Natural Gas Infrastructure; (7.0) Liquefied Natural Gas (LNG) for Vehicular Fuel in Uzbekistan; (8.0) Economic Feasibility Study; (9.0) Environmental Impact Analysis; References; Appendices A - S.

  11. Proteomics of juvenile senegal sole (Solea senegalensis) affected by gas bubble disease in hyperoxygenated ponds.

    PubMed

    Salas-Leiton, E; Cánovas-Conesa, B; Zerolo, R; López-Barea, J; Cañavate, J P; Alhama, J

    2009-01-01

    Solea senegalensis is a commercial flat fish traditionally farmed in earth ponds in coastal wetlands that might also become important to more intensive aquaculture. Gas bubble disease (GBD) is a potential risk for outdoor fish farming, particularly in certain periods of the year, related to improper management leading to macroalgae blooms. Physical-chemical conditions inducing hyperoxia, including radiation, temperature, and high levels of dissolved oxygen, have been monitored in fish affected by GBD together with observed symptoms. Exophthalmia, subcutaneous emphysemas, obstruction of gill lamellae, hemorrhages, and anomalous swimming were the main effects of oxygen supersaturation. A proteomic study was carried out for the first time under aquaculture conditions and protein expression changes are described for fish that were subject to hyperoxic conditions. Proteins identified in gill of GBD-affected fish are related to oxidative alteration of cytoskeleton structure/function (beta-tubulin, beta-actin), motility (light myosin chain, alpha-tropomyosin), or regulatory pathways (calmodulin, Raf kinase inhibitor protein), reflecting the central role of gill in oxygen exchange. Hepatic proteins identified are related to protein oxidative damages (beta-globin, FABPs), protection from oxidative stress (DCXR, GNMT), and inflammatory response (C3), in agreement with the predominant metabolic role of liver. Comparison of protein expression patterns and protein identification are suggested as potentially specific hyperoxia biomarkers that would facilitate prevention of GBD outbreaks.

  12. Greenhouse gas simulations with a coupled meteorological and transport model: the predictability of CO2

    NASA Astrophysics Data System (ADS)

    Polavarapu, Saroja M.; Neish, Michael; Tanguay, Monique; Girard, Claude; de Grandpré, Jean; Semeniuk, Kirill; Gravel, Sylvie; Ren, Shuzhan; Roche, Sébastien; Chan, Douglas; Strong, Kimberly

    2016-09-01

    A new model for greenhouse gas transport has been developed based on Environment and Climate Change Canada's operational weather and environmental prediction models. When provided with realistic posterior fluxes for CO2, the CO2 simulations compare well to NOAA's CarbonTracker fields and to near-surface continuous measurements, columns from the Total Carbon Column Observing Network (TCCON) and NOAA aircraft profiles. This coupled meteorological and tracer transport model is used to study the predictability of CO2. Predictability concerns the quantification of model forecast errors and thus of transport model errors. CO2 predictions are used to compute model-data mismatches when solving flux inversion problems and the quality of such predictions is a major concern. Here, the loss of meteorological predictability due to uncertain meteorological initial conditions is shown to impact CO2 predictability. The predictability of CO2 is shorter than that of the temperature field and increases near the surface and in the lower stratosphere. When broken down into spatial scales, CO2 predictability at the very largest scales is mainly due to surface fluxes but there is also some sensitivity to the land and ocean surface forcing of meteorological fields. The predictability due to the land and ocean surface is most evident in boreal summer when biospheric uptake produces large spatial gradients in the CO2 field. This is a newly identified source of uncertainty in CO2 predictions but it is expected to be much less significant than uncertainties in fluxes. However, it serves as an upper limit for the more important source of transport error and loss of predictability, which is due to uncertain meteorological analyses. By isolating this component of transport error, it is demonstrated that CO2 can only be defined on large spatial scales due to the presence of meteorological uncertainty. Thus, for a given model, there is a spatial scale below which fluxes cannot be inferred simply

  13. Switch-Loop Flexibility Affects Transport of Large Drugs by the Promiscuous AcrB Multidrug Efflux Transporter

    PubMed Central

    Cha, Hi-jea; Müller, Reinke T.

    2014-01-01

    Multidrug efflux transporters recognize a variety of structurally unrelated compounds for which the molecular basis is poorly understood. For the resistance nodulation and cell division (RND) inner membrane component AcrB of the AcrAB-TolC multidrug efflux system from Escherichia coli, drug binding occurs at the access and deep binding pockets. These two binding areas are separated by an 11-amino-acid-residue-containing switch loop whose conformational flexibility is speculated to be essential for drug binding and transport. A G616N substitution in the switch loop has a distinct and local effect on the orientation of the loop and on the ability to transport larger drugs. Here, we report a distinct phenotypical pattern of drug recognition and transport for the G616N variant, indicating that drug substrates with minimal projection areas of >70 Å2 are less well transported than other substrates. PMID:24914123

  14. Monitoring suspended sediment transport in an ice-affected river using acoustic Doppler current profilers

    NASA Astrophysics Data System (ADS)

    Moore, S. A.; Ghareh Aghaji Zare, S.; Rennie, C. D.; Ahmari, H.; Seidou, O.

    2013-12-01

    Quantifying sediment budgets and understanding the processes which control fluvial sediment transport is paramount to monitoring river geomorphology and ecological habitat. In regions that are subject to freezing there is the added complexity of ice. River ice processes impact flow distribution, water stage and sediment transport. Ice processes typically have the largest impact on sediment transport and channel morphodynamics when ice jams occur during ice cover formation and breakup. Ice jams may restrict flow and cause local acceleration when released. Additionally, ice can mechanically scour river bed and banks. Under-ice sediment transport measurements are lacking due to obvious safety and logistical reasons, in addition to a lack of adequate measurement techniques. Since some rivers can be covered in ice during six months of the year, the lack of data in winter months leads to large uncertainty in annual sediment load calculations. To address this problem, acoustic profilers are being used to monitor flow velocity, suspended sediment and ice processes in the Lower Nelson River, Manitoba, Canada. Acoustic profilers are ideal for under-ice sediment flux measurements since they can be operated autonomously and continuously, they do not disturb the flow in the zone of measurement and acoustic backscatter can be related to sediment size and concentration. In March 2012 two upward-facing profilers (1200 kHz acoustic Doppler current profiler, 546 KHz acoustic backscatter profiler) were installed through a hole in the ice on the Nelson River, 50 km downstream of the Limestone Generating Station. Data were recorded for four months, including both stable cover and breakup periods. This paper presents suspended sediment fluxes calculated from the acoustic measurements. Velocity data were used to infer the vertical distribution of sediment sizes and concentrations; this information was then used in the interpretation of the backscattered intensity data. It was found that

  15. Dopamine Transporter Gene Variant Affecting Expression in Human Brain is Associated with Bipolar Disorder

    PubMed Central

    Pinsonneault, Julia K; Han, Dawn D; Burdick, Katherine E; Kataki, Maria; Bertolino, Alessandro; Malhotra, Anil K; Gu, Howard H; Sadee, Wolfgang

    2011-01-01

    The gene encoding the dopamine transporter (DAT) has been implicated in CNS disorders, but the responsible polymorphisms remain uncertain. To search for regulatory polymorphisms, we measured allelic DAT mRNA expression in substantia nigra of human autopsy brain tissues, using two marker SNPs (rs6347 in exon 9 and rs27072 in the 3′-UTR). Allelic mRNA expression imbalance (AEI), an indicator of cis-acting regulatory polymorphisms, was observed in all tissues heterozygous for either of the two marker SNPs. SNP scanning of the DAT locus with AEI ratios as the phenotype, followed by in vitro molecular genetics studies, demonstrated that rs27072 C>T affects mRNA expression and translation. Expression of the minor T allele was dynamically regulated in transfected cell cultures, possibly involving microRNA interactions. Both rs6347 and rs3836790 (intron8 5/6 VNTR) also seemed to affect DAT expression, but not the commonly tested 9/10 VNTR in the 3′UTR (rs28363170). All four polymorphisms (rs6347, intron8 5/6 VNTR, rs27072 and 3′UTR 9/10 VNTR) were genotyped in clinical cohorts, representing schizophrenia, bipolar disorder, depression, and controls. Only rs27072 was significantly associated with bipolar disorder (OR=2.1, p=0.03). This result was replicated in a second bipolar/control population (OR=1.65, p=0.01), supporting a critical role for DAT regulation in bipolar disorder. PMID:21525861

  16. Does low gas permeability of rigid-shelled gekkotan eggs affect embryonic development?

    PubMed

    Andrews, Robin M; Thompson, Michael B; Greene, Virginia W

    2013-06-01

    Parchment-shelled eggs are characteristic of most squamates, including the basal clades of gekkotan lizards. The majority of gekkotan lizards, however, produce rigid-shelled eggs that are highly impermeable to gas exchange; eggs are laid in dry sites and experience a net loss of water during incubation. We tested the hypothesis that the 1,000-fold lower rate of oxygen diffusion through the shells of rigid- compared to parchment-shelled eggs imposes a physiological cost on development. To do this, we contrasted species with rigid and with parchment shells with regards to (1) rates of embryonic metabolism and (2) rates and patterns of development of the yolk sac and chorioallantois, the vascularized extra-embryonic membranes that transport oxygen to embryonic tissues. Metabolic rates of embryos from the rigid-shelled eggs of Gehyra variegata did not differ from those of the parchment-shelled eggs of Oedura lesueurii. Moreover, maximum metabolic rates of gekkotans with rigid shells did not differ from those of gekkotan or scincid lizards with parchment shells. In contrast, the yolk sac covered more of the surface area of the egg at oviposition, and the chorioallantois reached its full extent earlier for the species with rigid shelled eggs (Chondrodactylus turneri, G. variegata) than for the species with parchment-shelled eggs (Eublepharis macularius, O. lesueurii). Differences in the temporal patterns of yolk sac and chorioallantois development would thus serve to compensate for low rates of oxygen diffusion through rigid shells of gekkotans.

  17. A case study of electrostatic accidents in the process of oil-gas storage and transportation

    NASA Astrophysics Data System (ADS)

    Hu, Yuqin; Wang, Diansheng; Liu, Jinyu; Gao, Jianshen

    2013-03-01

    Ninety nine electrostatic accidents were reviewed, based on information collected from published literature. All the accidents over the last 30 years occurred during the process of oil-gas storage and transportation. Statistical analysis of these accidents was performed based on the type of complex conditions where accidents occurred, type of tanks and contents, and type of accidents. It is shown that about 85% of the accidents occurred in tank farms, gas stations or petroleum refineries, and 96% of the accidents included fire or explosion. The fishbone diagram was used to summarize the effects and the causes of the effects. The results show that three major reasons were responsible for accidents, including improper operation during loading and unloading oil, poor grounding and static electricity on human bodies, which accounted for 29%, 24% and 13% of the accidents, respectively. Safety actions are suggested to help operating engineers to handle similar situations in the future.

  18. Gas transport and bubble collapse in rhyolitic magma: an experimental approach

    NASA Astrophysics Data System (ADS)

    Westrich, Henry R.; Eichelberger, John C.

    1994-12-01

    A series of experiments was conducted to test concepts of porous flow degassing of rhyolitic magma during ascent and of the subsequent collapse of vesicles in degassed magma to form obsidian. Dense, synthetically hydrated, natural glasses were pressurized under water-saturated conditions and then decompressed to achieve a range of porosities in the presence of a tracer vapor, D2O. Rapid isotopic exchange indicative of vapor transport rather than of simple diffusion occurred at a porosity >60 vol.%, in accord with earlier gas permeability measurements on cold natural samples. In another series of experiments, natural and synthetic pumices, vesiculated by degassing to atmospheric pressure, rapidly collapsed to dense glass on repressurization to the modest pressures prevailing in lava flows. No relict bubble textures remained. These results support the hypothesis that effusive eruptions result from the syneruptive escape of gas from permeable magmatic foam, and that a process analogous to welding yields dense lavas when such foams are extruded.

  19. Transport simulations of the pre-thermal-quench phase in ASDEX Upgrade massive gas injection experiments

    NASA Astrophysics Data System (ADS)

    Fable, E.; Pautasso, G.; Lehnen, M.; Dux, R.; Bernert, M.; Mlynek, A.; the ASDEX Upgrade Team

    2016-02-01

    The pre-thermal-quench (PTQ) phase of the massive gas injection (MGI) scenario to terminate the tokamak plasma discharge is studied by means of one-dimensional (1D) transport simulations. This phase is characterized by the cold-front penetration in the hot plasma after the gas has been released from the valves, and before the actual thermal quench takes place, with consequent plasma disruption at lower stored energy. The comparison between the simulations and the ASDEX Upgrade (AUG) experiments allows to gain insight in the observed dependencies and time scales. Despite the genuine three-dimensional structure of the problem, it is shown that the 1D simulations are already giving experimentally relevant answers, the reason for which will be discussed in detail. Influence of unknown parameters and simplifying assumptions are also discussed.

  20. Should we transport coal, gas, or electricity: cost, efficiency, and environmental implications.

    PubMed

    Bergerson, Joule A; Lave, Lester B

    2005-08-15

    We examine the life cycle costs, environmental discharges, and deaths of moving coal via rail, coal gas via pipeline, and electricity via wire from the Powder River Basin (PRB) in Wyoming to Texas. Which method has least social cost depends on how much additional investment in rail line, transmission, or pipeline infrastructure is required, as well as how much and how far energy is transported. If the existing rail lines have unused capacity, coal by rail is the cheapest method (up to 200 miles of additional track could be added). If no infrastructure exists, greater distances and larger amounts of energy favor coal by rail and gasified coal by pipeline over electricity transmission. For 1,000 miles and 9 gigawatts of power, a gas pipeline is cheapest, has less environmental discharges, uses less land, and is least obtrusive.

  1. Stoichiometry dependent electron transport and gas sensing properties of indium oxide nanowires.

    PubMed

    Gali, Pradeep; Sapkota, Gopal; Syllaios, A J; Littler, Chris; Philipose, U

    2013-06-07

    The effect of stoichiometry of single crystalline In2O3 nanowires on electrical transport and gas sensing was investigated. The nanowires were synthesized by vapor phase transport and had diameters ranging from 80 to 100 nm and lengths between 10 and 20 μm, with a growth direction of [001]. Transport measurements revealed n-type conduction, attributed to the presence of oxygen vacancies in the crystal lattice. As-grown In2O3 nanowires were shown to have a carrier concentration of ≈5 × 10(17) cm(-3), while nanowires that were annealed in wet O2 showed a reduced carrier concentration of less than 10(16) cm(-3). Temperature dependent conductivity measurements on the as-grown nanowires and analysis of the thermally activated Arrhenius conduction for the temperature range of 77-350 K yielded an activation energy of 0.12 eV. This is explained on the basis of carrier exchange that occurs between the surface states and the bulk of the nanowire, resulting in a depleted surface layer of thickness of the order of the Debye length (LD), estimated to be about 3-4 nm for the as-grown nanowires and about 10 times higher for the more stoichiometric nanowires. Significant changes in the electrical conductance of individual In2O3 nanowires were also observed within several seconds of exposure to NH3 and O2 gas molecules at room temperature, thus demonstrating the potential use of In2O3 nanowires as efficient miniaturized chemical sensors. The sensing mechanism is dominated by the nanowire channel conductance, and a simple energy band diagram is used to explain the change in conductivity when gas molecules adsorbed on the nanowire surface influence its electrical properties. Less stoichiometric nanowires were found to be more sensitive to oxidizing gases while more stoichiometric nanowires showed significantly enhanced response to reducing gases.

  2. Control of Chemical, Thermal, and Gas Transport Properties in Dense Phosphazene Polymer Membranes.

    SciTech Connect

    Christopher J. Orme; Frederick F. Stewart; Mark L. Stone; Mason K. Harrup; Thomas A. Luther; Eric S. Peterson

    2005-10-01

    Polyphosphazenes are hybrid polymers having organic pendant groups attached to an inorganic backbone. Phosphazene polymers can be tailored to specific applications through the attachment of a variety of different pendant groups to the phosphazene backbone. Applications for which these polymers have proven useful include solid polymer electrolytes for batteries and fuel cells, as well as, membranes for gas and liquid separations. In past work, phosphazene polymers have been synthesized using mixtures of pendant groups with differing chemical affinities. Specific ratios of hydrophobic and hydrophilic pendant groups were placed on the phosphazene backbone with a goal of demonstrating control of solubility, and therefore chemical selectivity. In this work, a series of phosphazene homo-polymers were synthesized having varying amounts of hydrophobic and hydrophilic character on each individual pendant group. Polymers were synthesized having a hydrophilic portion next to the polymer backbone and the hydrophobic portion on the terminal end of the pendant group. The effects of these combined hydrophobic/hydrophilic pendant groups on polymer morphology and gas transport properties are presented. The following data will be addressed: thermal characterization, pure gas permeability on seven gases (Ar, H2, O2, N2, CO2, and CH4 ), and ideal selectivity for the gas pairs: O2/N2, H2/CO2, CO2/H2, CO2/CH4 and CO2/N2.

  3. Estimation of rates of aerobic hydrocarbon biodegradation by simulation of gas transport in the unsaturated zone

    USGS Publications Warehouse

    Lahvis, M.A.; Baehr, A.L.

    1996-01-01

    The distribution of oxygen and carbon dioxide gases in the unsaturated zone provides a geochemical signature of aerobic hydrocarbon degradation at petroleum product spill sites. The fluxes of these gases are proportional to the rate of aerobic biodegradation and are quantified by calibrating a mathematical transport model to the oxygen and carbon dioxide gas concentration data. Reaction stoichiometry is assumed to convert the gas fluxes to a corresponding rate of hydrocarbon degradation. The method is applied at a gasoline spill site in Galloway Township, New Jersey, to determine the rate of aerobic degradation of hydrocarbons associated with passive and bioventing remediation field experiments. At the site, microbial degradation of hydrocarbons near the water table limits the migration of hydrocarbon solutes in groundwater and prevents hydrocarbon volatilization into the unsaturated zone. In the passive remediation experiment a site-wide degradation rate estimate of 34,400 g yr-1 (11.7 gal. yr-1) of hydrocarbon was obtained by model calibration to carbon dioxide gas concentration data collected in December 1989. In the bioventing experiment, degradation rate estimates of 46.0 and 47.9 g m-2 yr-1 (1.45 x 10-3 and 1.51 x 10-3 gal. ft.-2 yr-1) of hydrocarbon were obtained by model calibration to oxygen and carbon dioxide gas concentration data, respectively. Method application was successful in quantifying the significance of a naturally occurring process that can effectively contribute to plume stabilization.

  4. Estimation of rates of aerobic hydrocarbon biodegradation by simulation of gas transport in the unsaturated zone

    NASA Astrophysics Data System (ADS)

    Lahvis, Matthew A.; Baehr, Arthur L.

    1996-07-01

    The distribution of oxygen and carbon dioxide gases in the unsaturated zone provides a geochemical signature of aerobic hydrocarbon degradation at petroleum product spill sites. The fluxes of these gases are proportional to the rate of aerobic biodegradation and are quantified by calibrating a mathematical transport model to the oxygen and carbon dioxide gas concentration data. Reaction stoichiometry is assumed to convert the gas fluxes to a corresponding rate of hydrocarbon degradation. The method is applied at a gasoline spill site in Galloway Township, New Jersey, to determine the rate of aerobic degradation of hydrocarbons associated with passive and bioventing remediation field experiments. At the site, microbial degradation of hydrocarbons near the water table limits the migration of hydrocarbon solutes in groundwater and prevents hydrocarbon volatilization into the unsaturated zone. In the passive remediation experiment a site-wide degradation rate estimate of 34,400 gyr-1 (11.7 gal. yr-1) of hydrocarbon was obtained by model calibration to carbon dioxide gas concentration data collected in December 1989. In the bioventing experiment, degradation rate estimates of 46.0 and 47.9 gm-2yr-1 (1.45×10-3 and 1.51×10-3 gal.ft.-2yr-1) of hydrocarbon were obtained by model calibration to oxygen and carbon dioxide gas concentration data, respectively. Method application was successful in quantifying the significance of a naturally occurring process that can effectively contribute to plume stabilization.

  5. Gas transport in unsaturated porous media: The adequacy of Fick's law

    NASA Astrophysics Data System (ADS)

    Thorstenson, D. C.; Pollock, D. W.

    1989-02-01

    The increasing use of natural unsaturated zones as repositories for landfills and disposal sites for hazardous wastes (chemical and radioactive) requires a greater understanding of transport processes in the unsaturated zone. For volatile constituents an important potential transport mechanism is gaseous diffusion. Diffusion, however, cannot be treated as an independent isolated transport mechanism. A complete understanding of multicomponent gas transport in porous media (unsaturated zones) requires a knowledge of Knudsen transport, the molecular and nonequimolar components of diffusive flux, and viscous (pressure driven) flux. The constitutive equations relating these flux components are available from the "dusty gas" model of Mason et al. (1967). This review presents a brief discussion of the underlying principles and interrelationships among each of the above flux mechanisms. Some aspects of these transport mechanisms are, to our knowledge, generally unrecognized in the Earth science literature. The principles underlying the transport mechanisms are illustrated with binary systems; the constitutive equations are then cast in forms thought to be most useful for the study of natural unsaturated zones. The viscous and diffusive fluxes are coupled in the constitutive equations through the Knudsen diffusivities; a knowledge of Knudsen diffusivities is necessary to calculate the viscous component of flux and pressure gradients. The Knudsen diffusivities can be calculated from measurements of the Klinkenberg effect. Two examples are presented showing that in natural systems, very small pressure gradients (1 Pa/m or less) can produce viscous fluxes greater than or equal to diffusive fluxes and that, conversely, pressure gradients of this magnitude can be generated by diffusive processes. The example calculations show that major concentration gradients can be developed for stagnant (zero flux, nonreactive) gases. A method is presented for approximating the viscous and

  6. Pore Network Modeling of Multiphase Transport in Polymer Electrolyte Membrane Fuel Cell Gas Diffusion Layers

    NASA Astrophysics Data System (ADS)

    Fazeli, Mohammadreza

    In this thesis, pore network modeling was used to study how the microstructure of the polymer electrolyte membrane (PEM) fuel cell gas diffusion layer (GDL) influences multiphase transport within the composite layer. An equivalent pore network of a GDL was used to study the effects of GDL/catalyst layer condensation points and contact quality on the spatial distribution of liquid water in the GDL. Next, pore networks extracted from synchrotron-based micro-computed tomography images of compressed GDLs were employed to simulate liquid water transport in GDL materials over a range of compression pressures, and favorable GDL compression values for preferred liquid water distributions were found for two commercially available GDL materials. Finally, a technique was developed for calculating the oxygen diffusivity in carbon paper substrates with a microporous layer (MPL) coating through pore network modeling. A hybrid network was incorporated into the pore network model, and effective diffusivity predictions of MPL coated GDL materials were obtained.

  7. Barometric gas transport along geologic faults and its application to nuclear test-ban monitoring

    SciTech Connect

    Carrigan, C.R.; Heinle, R.A.; Hudson, G.B.; Nitao, J.J.

    1996-10-01

    Nuclear explosions produce unique but rapidly decaying radionuclide gases that potentially can be used in the context of a test-ban monitoring program to identify clandestine underground testing activity. To evaluate the upward transport of such gases from an underground explosion, two, non-radioactive gas tracers, spanning a 49-fold difference in species mass, were released in a 400-m-deep, chemical explosive detonation. The more massive tracer was first detected on a fault 50 days following the detonation while the other tracer was detected 375 days after release. Models indicate that both the time scale of arrival and chromatographic behavior of transport are characteristic of barometrically induced flow in a fracture- matrix regime. For a 1-kiloton fission explosion, simulations predict that short-lived isotopes of argon and xenon would be detectable on nearby geologic faults.

  8. Investigation of Gas Phase Transport Mechanisms in Unsaturated Zones Under Natural Conditions

    NASA Astrophysics Data System (ADS)

    You, K.; Zhan, H.

    2012-12-01

    Diffusive flux is traditionally treated as the dominant mechanism for gas transport in unsaturated zones without active disturbance. However, some researchers have found that the pressure-driven and density-driven advective flux may also be important under certain conditions. This article conducts a comprehensive study of the diffusive, pressure-driven and density-driven advective fluxes of the gas phase volatile organic compounds (VOCs) in the unsaturated zone under various hydrogeological conditions. The presence of a less or more permeable layer at ground surface in a heterogeneous unsaturated zone is investigated for their influence on the time-averaged advective and diffusive fluxes. Our developed numerical solution is applied to interpret a field study of the trichloroethylene contamination in the unsaturated zone at Picatinny Arsenal in Morris County, New Jersey. Results show that under most of the field conditions the time-averaged advective flux is one to three orders of magnitude smaller than the diffusive flux, and the influence of the density-driven flux on the advective flux is undetectable. The time-averaged advective flux is comparable in magnitude with the diffusive flux only in a deep unsaturated zone (thickness greater than 15 m), or when the gas-filled porosity is less than 0.05, or the magnitude of the water table fluctuation is greater than 0.2 m for the default parameters used in this study. A less permeable layer at ground surface increases the total flux of VOCs under it, while a permeable layer at ground surface increases the total flux in it. The error induced by fixing the water table position but allowing the fluctuation of water table moving velocity is negligible for predicting the gas phase VOCs transport in an unsaturated zone at non-coastal sites.

  9. Understanding how hydrodynamics affects particle transport in saturated fractures using modelling and experimental results

    NASA Astrophysics Data System (ADS)

    Cianflone, S.; Lakhian, V.; Dickson, S. E.

    2013-12-01

    Approximately 35% of Canadians and Americans utilize groundwater for drinking water and as such, it is essential to understand the mechanisms which may jeopardize this resource. Porous media aquifers typically provide significant removal of particulate contaminants (eg. viruses, bacteria); however, fractures in fractured rock aquifers and aquitards often provide pathways for particles to move in greater numbers and speed than in porous media. Thus, understanding flow and transport in fractures is important for the preservation and use of groundwater sources. Models based on coupling flow and transport equations can be used in understanding transport in fractures. Both experiments and simulations have shown that there are inconsistencies in current transport, attachment and detachment theory, particularly when particle size is varied. The assumption that hydrodynamic effects do not significantly affect transport of particles is likely untrue. As well, it has been shown that preferential flow paths occur in fractures, but the effects of path specific properties such as fracture geometry have yet to be thoroughly explored. It has been observed that eddies caused by local changes in geometry exist in fractures in the environment and models have demonstrated that such eddies will retard the flow of particles. In this work, two 2D fractures were randomly generated with a mean aperture of approximately 2mm. Finite element software, COMSOL Multiphysics, generated flow fields through the fractures by numerically solving the steady-state Navier-Stokes equation for varied flow rates. Eddies were observed in one of the fractures at both low (~1 m/day) and high (>100 m/day) velocities. A program was written using random walk particle tracking to simulate transport. Theories of attachment, detachment and matrix flow are not included in this model in order to isolate hydrodynamic forces. In combination with the modelling procedure, the two fractures were inscribed into pieces of

  10. Corn Ethanol: The Surprisingly Effective Route for Natural Gas Consumption in the Transportation Sector

    SciTech Connect

    Szybist, James P.; Curran, Scott

    2015-05-01

    Proven reserves and production of natural gas (NG) in the United States have increased dramatically in the last decade, due largely to the commercialization of hydraulic fracturing. This has led to a plentiful supply of NG, resulting in a significantly lower cost on a gallon of gasoline-equivalent (GGE) basis. Additionally, NG is a domestic, non-petroleum source of energy that is less carbon-intensive than coal or petroleum products, and thus can lead to lower greenhouse gas emissions. Because of these factors, there is a desire to increase the use of NG in the transportation sector in the United States (U.S.). However, using NG directly in the transportation sector requires that several non-trivial challenges be overcome. One of these issues is the fueling infrastructure. There are currently only 1,375 NG fueling stations in the U.S. compared to 152,995 fueling stations for gasoline in 2014. Additionally, there are very few light-duty vehicles that can consume this fuel directly as dedicated or bi-fuel options. For example, in model year 2013Honda was the only OEM to offer a dedicated CNG sedan while a number of others offered CNG options as a preparation package for LD trucks and vans. In total, there were a total of 11 vehicle models in 2013 that could be purchased that could use natural gas directly. There are additional potential issues associated with NG vehicles as well. Compared to commercial refueling stations, the at-home refueling time for NG vehicles is substantial – a result of the small compressors used for home refilling. Additionally, the methane emissions from both refueling (leakage) and from tailpipe emissions (slip) from these vehicles can add to their GHG footprint, and while these emissions are not currently regulated it could be a barrier in the future, especially in scenarios with broad scale adoption of CNG vehicles. However, NG consumption already plays a large role in other sectors of the economy, including some that are important to

  11. Transport characteristics of gas phase ozone in unsaturated porous media for in-situ chemical oxidation.

    SciTech Connect

    Choi, H.; Lim, H-N; Kang, J-W; Hwang, T-M; Kim, J.; Environmental Research; Kwangju Inst. of Science and Technology; Yonsei Univ.

    2002-07-01

    Laboratory column experiments were conducted by employing various porous media to delineate the characteristics of gaseous ozone transport in the unsaturated zone under various conditions. Water content, soil organic matter (SOM), and metal oxides (MOs) were found to be the factors most influential in the fate and transport of gaseous ozone in unsaturated porous media. The migration velocity of the gaseous ozone front was inversely proportional to the MO content of the porous media. Increased water content at fixed gas flux decreased the ozone breakthrough time proportionally as a result of reduced gas pore volume (PV) in the column, and increased pore water interfered with reactions of gaseous ozone with SOM and MOs on the surface of porous media. The feasibility of in-situ ozone injection for the remediation of unsaturated soils contaminated with either phenanthrene or diesel-range organics (DROs) was investigated under various conditions. The maximum removal after 1 h of ozone injection was achieved in columns packed with baked sand, followed, in descending order, by glass beads and by sand, indicating that catalytic ozone decomposition with MOs in columns packed with baked sand enhanced hydroxyl radical formation and resulted in increased contaminant removal. Overall removal efficiency of multicomponent C{sub 10}-C{sub 24} DROs after 14 h of ozonation was 78.7%. Ozone transport was retarded considerably because of the high ozone demand of DROs, requiring more than 6 h for the gaseous ozone to initially break through the soil column under the experimental conditions tested in this study. Overall, gaseous ozone was readily delivered and transported to remediate unsaturated soils contaminated with phenanthrene and DROs.

  12. Interrelated structures of the transport shock and collisional relaxation layer in a multitemperature, multilevel ionized gas

    NASA Technical Reports Server (NTRS)

    Vinolo, A. R.; Clarke, J. H.

    1973-01-01

    The gas dynamic structures of the transport shock and the downstream collisional relaxation layer are evaluated for partially ionized monatomic gases. Elastic and inelastic collisional nonequilibrium effects are taken into consideration. In the microscopic model of the atom, three electronic levels are accounted for. By using an asymptotic technique, the shock morphology is found on a continuum flow basis. This procedure gives two distinct layers in which the nonequilibrium effects to be considered are different. A transport shock appears as the inner solution to an outer collisional relaxation layer. The results show four main interesting points: (1) on structuring the transport shock, ionization and excitation rates must be included in the formulation, since the flow is not frozen with respect to the population of the different electronic levels; (2) an electron temperature precursor appears at the beginning of the transport shock; (3) the collisional layer is rationally reduced to quadrature for special initial conditions, which (4) are obtained from new Rankine-Hugoniot relations for the inner shock.

  13. The impact of ice layers on gas transport through firn at the North Greenland Eemian Ice Drilling (NEEM) site, Greenland

    NASA Astrophysics Data System (ADS)

    Keegan, K.; Albert, M. R.; Baker, I.

    2014-10-01

    Typically, gas transport through firn is modeled in the context of an idealized firn column. However, in natural firn, imperfections are present, which can alter transport dynamics and therefore reduce the accuracy of reconstructed climate records. For example, ice layers have been found in several firn cores collected in the polar regions. Here, we examined the effects of two ice layers found in a NEEM, Greenland firn core on gas transport through the firn. These ice layers were found to have permeability values of 3.0 and 4.0 × 10-10 m2, and are therefore not impermeable layers. However, the shallower ice layer was found to be significantly less permeable than the surrounding firn, and can therefore retard gas transport. Large closed bubbles were found in the deeper ice layer, which will have an altered gas composition than that expected because they were closed near the surface after the water phase was present. The bubbles in this layer represent 12% of the expected closed porosity of this firn layer after the firn-ice transition depth is reached, and will therefore bias the future ice core gas record. The permeability and thickness of the ice layers at the North Greenland Eemian Ice Drilling (NEEM) site suggest that they do not disrupt the firn-air concentration profiles and that they do not need to be accounted for in gas transport models at NEEM.

  14. Blood lactate concentrations are mildly affected by mobile gas exchange measurements.

    PubMed

    Scharhag-Rosenberger, F; Wochatz, M; Otto, C; Cassel, M; Mayer, F; Scharhag, J

    2014-06-01

    We sought to investigate the effects of wearing a mobile respiratory gas analysis system during a treadmill test on blood lactate (bLa) concentrations and commonly applied bLa thresholds. A total of 16 recreational athletes (31±3 years, VO2max: 58±6 ml · min(-1) · kg(-1)) performed one multistage treadmill test with and one without gas exchange measurements (GEM and noGEM). The whole bLa curve, the lactate threshold (LT), the individual anaerobic thresholds according to Stegmann (IATSt) and Dickhuth (IATDi), and a fixed bLa concentration of 4 mmol ∙ l(-1) (OBLA) were evaluated. The bLa curve was shifted slightly leftward in GEM compared to noGEM (P<0.05), whereas the heart rate response was not different between conditions (P=0.89). There was no difference between GEM and noGEM for LT (2.61±0.34 vs. 2.64±0.39 m · s(-1), P=0.49) and IATSt (3.47±0.42 vs. 3.55±0.47 m · s(-1), P=0.12). However, IATDi (3.57±0.39 vs. 3.66±0.44 m · s(-1), P<0.01) and OBLA (3.85±0.46 vs. 3.96±0.47 m · s(-1), P<0.01) occurred at slower running velocities in GEM. The bLa response to treadmill tests is mildly affected by wearing a mobile gas analysis system. This also applies to bLa thresholds located at higher exercise intensities. While the magnitude of the effects is of little importance for recreational athletes, it might be relevant for elite athletes and scientific studies.

  15. Pore network modeling to explore the effects of compression on multiphase transport in polymer electrolyte membrane fuel cell gas diffusion layers

    NASA Astrophysics Data System (ADS)

    Fazeli, Mohammadreza; Hinebaugh, James; Fishman, Zachary; Tötzke, Christian; Lehnert, Werner; Manke, Ingo; Bazylak, Aimy

    2016-12-01

    Understanding how compression affects the distribution of liquid water and gaseous oxygen in the polymer electrolyte membrane fuel cell gas diffusion layer (GDL) is vital for informing the design of improved porous materials for effective water management strategies. Pore networks extracted from synchrotron-based micro-computed tomography images of compressed GDLs were employed to simulate liquid water transport in GDL materials over a range of compression pressures. The oxygen transport resistance was predicted for each sample under dry and partially saturated conditions. A favorable GDL compression value for a preferred liquid water distribution and oxygen diffusion was found for Toray TGP-H-090 (10%), yet an optimum compression value was not recognized for SGL Sigracet 25BC. SGL Sigracet 25BC exhibited lower transport resistance values compared to Toray TGP-H-090, and this is attributed to the additional diffusion pathways provided by the microporous layer (MPL), an effect that is particularly significant under partially saturated conditions.

  16. Fire and drought affect plant communities and the greenhouse gas balance in a Mediterranean shrubland

    NASA Astrophysics Data System (ADS)

    Moreno, José M.; Parra, Antonio; Dannenmann, Michael; Ramírez, David A.; Diaz-Pines, Eugenio; Tejedor, Javier; Kitzler, Barbara; Karhu, Kristina; Resco, Victor; Povoas, Luciano

    2010-05-01

    Predicted changes in the seasonality and amount of rainfall under a changing climate have the potential to dramatically alter ecosystem function and species composition. Moreover, in fire-prone ecosystems, the joint effects of fire and increasing aridity may create irreversible changes to the services these ecosystems provide. To understand the effects of increasing drought and fire in a Mediterranean shrubland, we implemented an automated rainfall manipulation system, with rain-out shelters which automatically fold and unfold when conditions are rainy and dry, respectively. In January 2009, we implemented five different treatments, where annual precipitation was reduced by diminishing summer rainfall from the long-term historical average, up to a 40% reduction, following IPCC scenarios. In September 2009, we uninstalled all the shelters to burn the different plots, and reinstalled the shelters immediately afterwards. In this talk, we will present the preliminary results of an integrated experiment which aims at understanding the concomitant effects of fire and different drought intensities on the species composition and greenhouse gas balance (CO2, N2O and CH4) of a Mediterranean shrubland. We observed that plant growth was more severely affected by drought in the more shallow-rooted, malacophyllous shrub (from 116 to -7.2 mg/g/d in Cistus ladanifer), than in a deeper-rooted heather (from 5.5 to 66.9 mg/g/day in Erica arborea). This growth response was mediated by species-specific differences in hydraulics, leaf morphology and photosynthetic gas exchange of each species. Analyses of changes in species composition after fire are currently undergoing. The precipitation reduction treatments exerted drought stress on CH4 oxidizing microorganisms and thus reduced the CH4 sink strength of the ecosystem during the pre-fire period. Furthermore, the net CH4 uptake at the soil-atmosphere interface was reduced by the fire for a period of at least one month. Pedosphere

  17. An approximate calculation of advective gas-phase transport of 14C at Yucca Mountain, Nevada

    NASA Astrophysics Data System (ADS)

    Knapp, R. B.

    1990-01-01

    A quasilinear partial differential equation, which describes gas-phase transport of a 14C kinematic wave through a porous medium, is derived, its sensitivity to system variables is analyzed and it is applied to one possible release scenarion at the porposed Yucca Mountain, Nevada high-level radioactive waste repository. Advection, isotope exchange between CO 2 in a flowing gas phase and HCO 3- in a static aqueous phase, and radioactive decay are incorporated. The governing equation is solved analytically by the method of characteristics. The mass fraction of 14C in the gas phase,X 14g, is controlled by radioactive decay. The relatively long half-line of 14C, about 5720 years, and the relatively shallow proposed burial depth of the radioactive waste, about 350m, requires significant retardation of the 14C wave velocity for significant reduction in X 14g. 14C wave velocity is most sensitive to temperature and pH which control the distribution of total carbon between gas and liquid phase; the greater the partitioning of carbon into the liquid phase, the greater the retardation of the 14C wave velocity and the greater the ultimate reduction in X 14g from initial conditions. Partitioning of total carbon into the liquid phase is greatest at low temperatures, < 100° C, and high pH values, > 8. Increasing water saturation also tends to retard 14C wave velocity but to a lesser extent. The governing equation has been applied using conditions that may possibly occur at the proposed Yucca Mountain repository. Calculations indicate that the 14C wave takes about 5900 years to reach the surface with a X 14g equal to 25 ppm. Diffusion and dispersion are not of major importance for these conditions. These calculations are approximate due to the number of assumptions involved. Discharge of 14C into the gas before the selected time would accelerate wave arrival and increase the amount of 14C reaching the surface.

  18. Modeling gravity effects on water retention and gas transport characteristics in plant growth substrates

    NASA Astrophysics Data System (ADS)

    Chamindu Deepagoda, T. K. K.; Jones, Scott B.; Tuller, Markus; de Jonge, Lis Wollesen; Kawamoto, Ken; Komatsu, Toshiko; Moldrup, Per

    2014-08-01

    Growing plants to facilitate life in outer space, for example on the International Space Station (ISS) or at planned deep-space human outposts on the Moon or Mars, has received much attention with regard to NASA's advanced life support system research. With the objective of in situ resource utilization to conserve energy and to limit transport costs, native materials mined on Moon or Mars are of primary interest for plant growth media in a future outpost, while terrestrial porous substrates with optimal growth media characteristics will be useful for onboard plant growth during space missions. Due to limited experimental opportunities and prohibitive costs, liquid and gas behavior in porous substrates under reduced gravity conditions has been less studied and hence remains poorly understood. Based on ground-based measurements, this study examined water retention, oxygen diffusivity and air permeability characteristics of six plant growth substrates for potential applications in space, including two terrestrial analogs for lunar and Martian soils and four particulate substrates widely used in reduced gravity experiments. To simulate reduced gravity water characteristics, the predictions for ground-based measurements (1 - g) were scaled to two reduced gravity conditions, Martian gravity (0.38 - g) and lunar gravity (0.16 - g), following the observations in previous reduced gravity studies. We described the observed gas diffusivity with a recently developed model combined with a new approach that estimates the gas percolation threshold based on the pore size distribution. The model successfully captured measured data for all investigated media and demonstrated the implications of the poorly-understood shift in gas percolation threshold with improved gas percolation in reduced gravity. Finally, using a substrate-structure parameter related to the gaseous phase, we adequately described the air permeability under reduced gravity conditions.

  19. Field-scale sulfur hexafluoride tracer experiment to understand long distance gas transport in the deep unsaturated zone

    USGS Publications Warehouse

    Walvoord, Michelle Ann; Andraski, Brian; Green, Christopher T.; Stonestrom, David A.; Striegl, Robert G.

    2014-01-01

    A natural gradient SF6 tracer experiment provided an unprecedented evaluation of long distance gas transport in the deep unsaturated zone (UZ) under controlled (known) conditions. The field-scale gas tracer test in the 110-m-thick UZ was conducted at the U.S. Geological Survey’s Amargosa Desert Research Site (ADRS) in southwestern Nevada. A history of anomalous (theoretically unexpected) contaminant gas transport observed at the ADRS, next to the first commercial low-level radioactive waste disposal facility in the United States, provided motivation for the SF6 tracer study. Tracer was injected into a deep UZ borehole at depths of 15 and 48 m, and plume migration was observed in a monitoring borehole 9 m away at various depths (0.5–109 m) over the course of 1 yr. Tracer results yielded useful information about gas transport as applicable to the spatial scales of interest for off-site contaminant transport in arid unsaturated zones. Modeling gas diffusion with standard empirical expressions reasonably explained SF6 plume migration, but tended to underpredict peak concentrations for the field-scale experiment given previously determined porosity information. Despite some discrepancies between observations and model results, rapid SF6 gas transport commensurate with previous contaminant migration was not observed. The results provide ancillary support for the concept that apparent anomalies in historic transport behavior at the ADRS are the result of factors other than nonreactive gas transport properties or processes currently in effect in the undisturbed UZ.

  20. Non-steroidal anti-inflammatory drugs affect the methotrexate transport in IEC-6 cells.

    PubMed

    Sosogi, Aiko; Gao, Feng; Tomimatsu, Takashi; Hirata, Koji; Horie, Toshiharu

    2003-06-13

    Methotrexate (MTX) is used not only for the cancer chemotherapy but also for the treatment of rheumatic disease, often together with non-steroidal anti-inflammatory drugs (NSAIDs). MTX is actively cotransported with H(+) in the small intestine, mediated by a reduced folate carrier (RFC). The coadministration of some NSAIDs with MTX to rats caused a decrease of MTX absorption through the small intestine. This may be due to the uncoupling effect of oxidative phosphorylation of the NSAIDs. The present study investigated whether flufenamic acid, diclofenac and indomethacin, NSAIDs, decreased ATP content of rat-derived intestinal epithelial cell line IEC-6 cells and affected the MTX transport in IEC-6 cells. The MTX uptake in IEC-6 cells was dependent on medium pH and maximum around pH 4.5-5.5. The MTX uptake was composed of a transport inhibited by 4, 4'-diisothiocyanostilbene-2, 2'-disulfonic acid (DIDS) and a non-saturable one. The DIDS-sensitive component in the MTX uptake showed a saturation kinetics (Michaelis-Menten constant (Km): 3.91 +/- 0.52 microM, Maximum velocity (Vmax): 94.66 +/- 6.56 pmol/mg protein/5 min). The cellular ATP content in IEC-6 cells decreased significantly at 30 min after the cells were started to incubate with the NSAIDs (250 microM flufenamic acid, 500 microM diclofenac and 500 microM indomethacin). The MTX uptake in IEC-6 cells in the presence of the NSAIDs decreased with the reduction of cellular ATP content and showed a good correlation with the ATP content (correlation coefficient: 0.982). Thus it seems likely that the ATP content in IEC-6 cells with the NSAIDs decreased due to the uncoupling effect of oxidative phosphorylation of the NSAIDs, resulting in the inhibition of the secondary active transport of MTX in IEC-6 cells. The present results also suggest that IEC-6 cells are useful to evaluate the drug interaction relating to this carrier system.

  1. Alpha-Synuclein affects neurite morphology, autophagy, vesicle transport and axonal degeneration in CNS neurons

    PubMed Central

    Koch, J C; Bitow, F; Haack, J; d'Hedouville, Z; Zhang, J-N; Tönges, L; Michel, U; Oliveira, L M A; Jovin, T M; Liman, J; Tatenhorst, L; Bähr, M; Lingor, P

    2015-01-01

    Many neuropathological and experimental studies suggest that the degeneration of dopaminergic terminals and axons precedes the demise of dopaminergic neurons in the substantia nigra, which finally results in the clinical symptoms of Parkinson disease (PD). The mechanisms underlying this early axonal degeneration are, however, still poorly understood. Here, we examined the effects of overexpression of human wildtype alpha-synuclein (αSyn-WT), a protein associated with PD, and its mutant variants αSyn-A30P and -A53T on neurite morphology and functional parameters in rat primary midbrain neurons (PMN). Moreover, axonal degeneration after overexpression of αSyn-WT and -A30P was analyzed by live imaging in the rat optic nerve in vivo. We found that overexpression of αSyn-WT and of its mutants A30P and A53T impaired neurite outgrowth of PMN and affected neurite branching assessed by Sholl analysis in a variant-dependent manner. Surprisingly, the number of primary neurites per neuron was increased in neurons transfected with αSyn. Axonal vesicle transport was examined by live imaging of PMN co-transfected with EGFP-labeled synaptophysin. Overexpression of all αSyn variants significantly decreased the number of motile vesicles and decelerated vesicle transport compared with control. Macroautophagic flux in PMN was enhanced by αSyn-WT and -A53T but not by αSyn-A30P. Correspondingly, colocalization of αSyn and the autophagy marker LC3 was reduced for αSyn-A30P compared with the other αSyn variants. The number of mitochondria colocalizing with LC3 as a marker for mitophagy did not differ among the groups. In the rat optic nerve, both αSyn-WT and -A30P accelerated kinetics of acute axonal degeneration following crush lesion as analyzed by in vivo live imaging. We conclude that αSyn overexpression impairs neurite outgrowth and augments axonal degeneration, whereas axonal vesicle transport and autophagy are severely altered. PMID:26158517

  2. 40 CFR 60.5410 - How do I demonstrate initial compliance with the standards for my gas well affected facility, my...

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... affected facility, and my equipment leaks and sweetening unit affected facilities at onshore natural gas... Performance for Crude Oil and Natural Gas Production, Transmission and Distribution § 60.5410 How do I... at onshore natural gas processing plants? You must determine initial compliance with the...

  3. 40 CFR 60.5410 - How do I demonstrate initial compliance with the standards for my gas well affected facility, my...

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... affected facility, and my equipment leaks and sweetening unit affected facilities at onshore natural gas... Performance for Crude Oil and Natural Gas Production, Transmission and Distribution § 60.5410 How do I... at onshore natural gas processing plants? You must determine initial compliance with the...

  4. Risks in the transport and storage of liquefied natural gas. Sub-project 5-2: Investigation into building damage

    NASA Astrophysics Data System (ADS)

    Gouwens, C.; Dragosavic, M.

    The large reserves and increasing use of natural gas as a source of energy have resulted in its storage and transport becoming an urgent problem. Since a liquid of the same mass occupies only a fraction of the volume of a gas, it is economical to store natural gas as a liquid. Liquefied natural gas is stored in insulated tanks and also carried by ship at a temperature of -160 C to 170 C. If a serious accident allows the LNG to escape, a gas cloud forms. The results of a possible explosion from such a gas cloud are studied. The development of a leak, escape and evaporation, size and propagation of the gas cloud, the explosive pressures to be expected and the results on the environment are investigated. Damage to buildings is examined making use of the preliminary conclusions of the other sub-projects and especially the explosive pressures.

  5. An analysis of pollutant gas transport and absorption in pulmonary airways

    SciTech Connect

    Grotberg, J.B.; Sheth, B.V.; Mockros, L.F. )

    1990-05-01

    A mathematical model of ozone absorption, or for any soluble gas that has similar transport properties, is developed for a branching network of liquid-lined cylinders. In particular, we investigate specific flow regimes for finite length tubes where boundary layer phenomena and entrance effects exist in high Reynolds and Peclet (Pe) number airways. The smaller airways which have lower Reynolds and Peclet number flows are modelled by incorporating the detailed analysis found in (10) and modifying it for airways which have alveolated surfaces. We also consider a reacting gas and treat specific regimes where the reaction front is located at the air-liquid interface, within the liquid or at the liquid-tissue interface. Asymptotic methods are used in regions of the tracheobronchial tree where Pe much less than 1 and Pe much greater than 1. In addition, the fact that the radial transport parameter gamma much less than 1 for this toxin, and others such as nitrous oxides, is employed to simplify the analysis. The ozone concentrations, airway absorption and tissue dose are examined as a function of airway generation for several values of the governing parameters. The general result is a maximal dosing in airway generations 17 to 18 that is much larger (up to an order of magnitude) than the predictions of previous theories.

  6. Localization of the porous partition responsible for pressurized gas transport in Alnus glutinosa (L.) Gaertn.

    PubMed

    Buchel, H B; Grosse, W

    1990-09-01

    The pressurized gas transport which improves the oxygen supply of the roots of the wetland tree black alder (Alnus glutinosa (L.) Gaertn.), is based on the existence of a thermo-osmotically active porous tissue partition in the lower part of the trunk with pore diameters in the range of, or smaller than, the mean free path length of the gas molecules (e.g., 70 nm for O(2) at 20 degrees C and 100 kPa). Anatomical studies have shown that only the cambial layer or the phellogen of the lenticels have intercellular spaces small enough to be responsible for thermo-osmotic activity. The final localization of the thermo-osmotically active partition and the determination of the pore sizes were done by diffusion and effusion experiments with basal trunk pieces of 3- to 4-year-old trees. The mean pore sizes of the intercellular system were not smaller than 100 nm in diameter in the cambial layer separating the bark from the wood, but 14 +/- 7 nm in diameter in the phellogen underlying the lenticels. Because of these small pores, the phellogen of the lenticels is the significant thermo-osmotically active partition for the transport of air to the root system in black alder.

  7. Geochemical factors affecting radionuclide transport through near and far fields at a Low-Level Waste Disposal Site

    SciTech Connect

    Kaplan, D.I.; Seme, R.J.; Piepkho, M.G.

    1995-03-01

    The concentration of low-level waste (LLW) contaminants in groundwater is determined by the amount of contaminant present in the solid waste, rate of release from the waste and surrounding barriers, and a number of geochemical processes including adsorption, desorption, diffusion, precipitation, and dissolution. To accurately predict radionuclide transport through the subsurface, it is essential that the important geochemical processes affecting radionuclide transport be identified and, perhaps more importantly, accurately quantified and described in a mathematically defensible manner.

  8. A Comprehensive Model for Real Gas Transport in Shale Formations with Complex Non-planar Fracture Networks

    NASA Astrophysics Data System (ADS)

    Yang, Ruiyue; Huang, Zhongwei; Yu, Wei; Li, Gensheng; Ren, Wenxi; Zuo, Lihua; Tan, Xiaosi; Sepehrnoori, Kamy; Tian, Shouceng; Sheng, Mao

    2016-11-01

    A complex fracture network is generally generated during the hydraulic fracturing treatment in shale gas reservoirs. Numerous efforts have been made to model the flow behavior of such fracture networks. However, it is still challenging to predict the impacts of various gas transport mechanisms on well performance with arbitrary fracture geometry in a computationally efficient manner. We develop a robust and comprehensive model for real gas transport in shales with complex non-planar fracture network. Contributions of gas transport mechanisms and fracture complexity to well productivity and rate transient behavior are systematically analyzed. The major findings are: simple planar fracture can overestimate gas production than non-planar fracture due to less fracture interference. A “hump” that occurs in the transition period and formation linear flow with a slope less than 1/2 can infer the appearance of natural fractures. The sharpness of the “hump” can indicate the complexity and irregularity of the fracture networks. Gas flow mechanisms can extend the transition flow period. The gas desorption could make the “hump” more profound. The Knudsen diffusion and slippage effect play a dominant role in the later production time. Maximizing the fracture complexity through generating large connected networks is an effective way to increase shale gas production.

  9. A Comprehensive Model for Real Gas Transport in Shale Formations with Complex Non-planar Fracture Networks

    PubMed Central

    Yang, Ruiyue; Huang, Zhongwei; Yu, Wei; Li, Gensheng; Ren, Wenxi; Zuo, Lihua; Tan, Xiaosi; Sepehrnoori, Kamy; Tian, Shouceng; Sheng, Mao

    2016-01-01

    A complex fracture network is generally generated during the hydraulic fracturing treatment in shale gas reservoirs. Numerous efforts have been made to model the flow behavior of such fracture networks. However, it is still challenging to predict the impacts of various gas transport mechanisms on well performance with arbitrary fracture geometry in a computationally efficient manner. We develop a robust and comprehensive model for real gas transport in shales with complex non-planar fracture network. Contributions of gas transport mechanisms and fracture complexity to well productivity and rate transient behavior are systematically analyzed. The major findings are: simple planar fracture can overestimate gas production than non-planar fracture due to less fracture interference. A “hump” that occurs in the transition period and formation linear flow with a slope less than 1/2 can infer the appearance of natural fractures. The sharpness of the “hump” can indicate the complexity and irregularity of the fracture networks. Gas flow mechanisms can extend the transition flow period. The gas desorption could make the “hump” more profound. The Knudsen diffusion and slippage effect play a dominant role in the later production time. Maximizing the fracture complexity through generating large connected networks is an effective way to increase shale gas production. PMID:27819349

  10. 30 CFR 250.120 - How does injecting, storing, or treating gas affect my royalty payments?

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... royalty payments? (a) If you produce gas from an OCS lease and inject it into a reservoir on the lease or... sell the gas from the reservoir. (b) If you produce gas from an OCS lease and store it according to 30 CFR 550.119, you must pay royalty before injecting it into the storage reservoir. (c) If you...

  11. 30 CFR 250.120 - How does injecting, storing, or treating gas affect my royalty payments?

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... royalty payments? (a) If you produce gas from an OCS lease and inject it into a reservoir on the lease or... sell the gas from the reservoir. (b) If you produce gas from an OCS lease and store it according to 30 CFR 550.119, you must pay royalty before injecting it into the storage reservoir. (c) If you...

  12. Oxygen transport from the atmosphere to soil gas beneath a slab-on-grade foundation overlying petroleum-impacted soil.

    PubMed

    Lundegard, Paul D; Johnson, Paul C; Dahlen, Paul

    2008-08-01

    Modeling and field study results suggest that, in the case of a building overlying an aerobically biodegradable vapor source (i.e., petroleum-impacted soil), the significance of vapor intrusion into the building depends on the source vapor concentration, the relative position of the vapor source and building, and the rate of O2 transport from the atmosphere to the soil gas beneath the building. This work quantified the latter at a house having about a 250 m2 slab-on-grade foundation footprint. It was constructed on 1.5 m of clean fill overlying a petroleum hydrocarbon-impacted soil layer undergoing methanogenesis. Soil gas O2 and CH4 profiles adjacent to and beneath the foundation were measured and then the soil gas beneath the slab was rapidly displaced with N2. The natural replenishment of O2 was monitored for 90 days using in situ O2 sensors, and the responses with time were similar, independent of location. The O2 replenishment rate was about 2500 g-O2/d immediately after the N2 flood and then it declined to 200-500 g-O2/d over 30 days. Weather events affected the O2 replenishment rate; an increase occurred during a strong wind period (> 3 m/s), and a decrease occurred during a heavy rainfall event. The spatial and temporal patterns in the O2 sensor responses and quantified O2 replenishment rates could not be accounted for by simple mechanistic hypotheses involving lateral diffusion or advection through the bulk soil, and instead the data suggest rapid replenishment immediately below the foundation followed by downward diffusion.

  13. Factors that affect the efficiency of antisense oligodeoxyribonucleotide transfection by insonated gas-filled lipid microbubbles

    NASA Astrophysics Data System (ADS)

    Zhao, Ying-Zheng; Lu, Cui-Tao

    2008-03-01

    Objective: To investigate the factors that affect the efficiency of antisense oligodeoxyribonucleotide(AS-ODNs) transfection by insonated gas-filled lipid microbubbles. Methods: Lipid microbubbles filled with two types of gases-air and C3F8, were prepared respectively. An AS-ODNs sequence HA824 and a breast cancer cell line SK-BR-3 were used to define the various operating variables determining the transfection efficiency of insonated microbubbles. Two mixing methods, three levels of mixing speed, different mixing durations and various ultrasound initiation time after mixing were examined respectively. Transfection efficiency was detected by fluorescence microscopy. Results: C3F8 microbubbles gave higher levels of AS-ODNs transfection efficiency than air microbubbles in all test conditions. Transfection efficiency resulted from mixing method A (incubation of HA824 and microbubbles before mixing cells) did not show significant difference with that of mixing method B (without incubation of HA824 and microbubbles before mixing cells). Mixing speed, duration of mixing and ultrasound initiation time after mixing were central to determining HA824 transfection efficiency in vitro. The optimum parameters for SK-BR-3 cells were found at a mixing speed of 40-50 rpm for 30-60 s with less than 60 s delay before ultrasound. Conclusion: Ultrasound-mediated AS-ODNs transfection enhanced by C3F8-filled lipid microbubbles represents an effective avenue for AS-ODNs transfer.

  14. Influence of the microstructure on the charge transport in semiconductor gas discharge electronic devices

    NASA Astrophysics Data System (ADS)

    Sadiq, Y.; Aktas, K.; Acar, S.; Salamov, B. G.

    2010-06-01

    Experimental results with nonlinear features and hysteresis characteristics in the pre-breakdown Townsend discharge regime is studied experimentally for a planar microstructure with a GaAs photocathode, an interelectrode gap thickness of 445 μm and gas pressure in the range 28-66 Torr. An investigation of the effect of the voltage amplitude on the dynamics of transient processes in the semiconductor gas discharge microstructure was made to explain the mechanism of the current decay. A linearly increasing voltage (i.e. 3 V s and 5 V s voltage rate) was applied to the system to study current instability. The nonlinear transport mechanism of carriers through the cross-section of the discharge gap i.e. the appearance of the spatio-temporal self-organization of a nonlinear dissipative system, non-equilibrium electron motion and autocatalytic effect of carrier accumulation in the gas layer attributed to decrease of current with the increase of applied voltage. It is established that the pre-breakdown current decreases anomalously with increase of the feeding voltage and illumination intensity on the photocathode. The current density change through the cross-section of the discharge gap, i.e. the appearance of the spatio-temporal self-organization of nonlinear dissipative systems, causes these observed effects. On the other hand, the oscillatory current with non-monotonic N-shaped and hysteresis peculiarities in post-breakdown region is known to be related to a nonlinear mechanism of carrier transport in the semiconductor material caused by EL2 defect centres.

  15. Simulation of gas phase transport of carbon-14 at Yucca Mountain, Nevada, USA

    USGS Publications Warehouse

    Lu, N.; Ross, B.

    1994-01-01

    We have simulated gas phase transport of Carbon-14 at Yucca Mountain, Nevada. Three models were established to calculate travel time of Carbon-14 from the potential repository to the mountain surface: a geochemical model for retardation factors, a coupled gas-flow and heat transfer model for temperature and gas flow fields, and a particle tracker for travel time calculation. The simulations used three parallel, east-west cross-sections that were taken from the Sandia National Laboratories Interactive Graphics Information System (IGIS). Assuming that the repository is filled with 30- year-old waste at an initial areal power density of 57 kw/acre, we found that repository temperatures remain above 60??C for more than 10,000 years. For a tuff permeability of 10-7 cm2, Carbon-14 travel times to the surface are mostly less than 1,000 years, for particles starting at any time within the first 10,000 years. If the tuff permeability is 10-8 cm2, however, Carbon- 14 travel times to the surface range from 3,000 to 12,000 years, for particle starting within the 10,000 years.

  16. Alteration of natural (37)Ar activity concentration in the subsurface by gas transport and water infiltration.

    PubMed

    Guillon, Sophie; Sun, Yunwei; Purtschert, Roland; Raghoo, Lauren; Pili, Eric; Carrigan, Charles R

    2016-05-01

    High (37)Ar activity concentration in soil gas is proposed as a key evidence for the detection of underground nuclear explosion by the Comprehensive Nuclear Test-Ban Treaty. However, such a detection is challenged by the natural background of (37)Ar in the subsurface, mainly due to Ca activation by cosmic rays. A better understanding and improved capability to predict (37)Ar activity concentration in the subsurface and its spatial and temporal variability is thus required. A numerical model integrating (37)Ar production and transport in the subsurface is developed, including variable soil water content and water infiltration at the surface. A parameterized equation for (37)Ar production in the first 15 m below the surface is studied, taking into account the major production reactions and the moderation effect of soil water content. Using sensitivity analysis and uncertainty quantification, a realistic and comprehensive probability distribution of natural (37)Ar activity concentrations in soil gas is proposed, including the effects of water infiltration. Site location and soil composition are identified as the parameters allowing for a most effective reduction of the possible range of (37)Ar activity concentrations. The influence of soil water content on (37)Ar production is shown to be negligible to first order, while (37)Ar activity concentration in soil gas and its temporal variability appear to be strongly influenced by transient water infiltration events. These results will be used as a basis for practical CTBTO concepts of operation during an OSI.

  17. Transcription factor organic cation transporter 1 (OCT-1) affects the expression of porcine Klotho (KL) gene

    PubMed Central

    Zhou, Jiawei

    2016-01-01

    Klotho (KL), originally discovered as an aging suppressor, is a membrane protein that shares sequence similarity with the β-glucosidase enzymes. Recent reports showed Klotho might play a role in adipocyte maturation and systemic glucose metabolism. However, little is known about the transcription factors involved in regulating the expression of porcine KL gene. Deletion fragment analysis identified KL-D2 (−418 bp to −3 bp) as the porcine KL core promoter. MARC0022311SNP (A or G) in KL intron 1 was detected in Landrace × DIV pigs using the Porcine SNP60 BeadChip. The pGL-D2-A and pGL-D2-G were constructed with KL-D2 and the intron fragment of different alleles and relative luciferase activity of pGL3-D2-G was significantly higher than that of pGL3-D2-A in the PK cells and ST cells. This was possibly the result of a change in KL binding ability with transcription factor organic cation transporter 1 (OCT-1), which was confirmed using electrophoretic mobility shift assays (EMSA) and chromatin immune-precipitation (ChIP). Moreover, OCT-1 regulated endogenous KL expression by RNA interference experiments. Our study indicates SNP MARC0022311 affects porcine KL expression by regulating its promoter activity via OCT-1. PMID:27478698

  18. The addition of organic carbon and nitrate affects reactive transport of heavy metals in sandy aquifers.

    PubMed

    Satyawali, Yamini; Seuntjens, Piet; Van Roy, Sandra; Joris, Ingeborg; Vangeel, Silvia; Dejonghe, Winnie; Vanbroekhoven, Karolien

    2011-04-25

    Organic carbon introduction in the soil to initiate remedial measures, nitrate infiltration due to agricultural practices or sulphate intrusion owing to industrial usage can influence the redox conditions and pH, thus affecting the mobility of heavy metals in soil and groundwater. This study reports the fate of Zn and Cd in sandy aquifers under a variety of plausible in-situ redox conditions that were induced by introduction of carbon and various electron acceptors in column experiments. Up to 100% Zn and Cd removal (from the liquid phase) was observed in all the four columns, however the mechanisms were different. Metal removal in column K1 (containing sulphate), was attributed to biological sulphate reduction and subsequent metal precipitation (as sulphides). In the presence of both nitrate and sulphate (K2), the former dominated the process, precipitating the heavy metals as hydroxides and/or carbonates. In the presence of sulphate, nitrate and supplemental iron (Fe(OH)(3)) (K3), metal removal was also due to precipitation as hydroxides and/or carbonates. In abiotic column, K4, (with supplemental iron (Fe(OH)(3)), but no nitrate), cation exchange with soil led to metal removal. The results obtained were modeled using the reactive transport model PHREEQC-2 to elucidate governing processes and to evaluate scenarios of organic carbon, sulphate and nitrate inputs.

  19. Hyperosmotic and isosmotic shrinkage differentially affect protein phosphorylation and ion transport.

    PubMed

    Koltsova, Svetlana V; Akimova, Olga A; Kotelevtsev, Sergei V; Grygorczyk, Ryszard; Orlov, Sergei N

    2012-02-01

    In the present work, we compared the outcome of hyperosmotic and isosmotic shrinkage on ion transport and protein phosphorylation in C11-MDCK cells resembling intercalated cells from collecting ducts and in vascular smooth muscle cells (VSMC) from the rat aorta. Hyperosmotic shrinkage was triggered by cell exposure to hypertonic medium, whereas isosmotic shrinkage was evoked by cell transfer from an hypoosmotic to an isosmotic environment. Despite a similar cell volume decrease of 40%-50%, the consequences of hyperosmotic and isosmotic shrinkage on cellular functions were sharply different. In C11-MDCK and VSMC, hyperosmotic shrinkage completely inhibited Na(+),K(+)-ATPase and Na(+),P(i) cotransport. In contrast, in both types of cells isosmotic shrinkage slightly increased rather than suppressed Na(+),K(+)-ATPase and did not change Na(+),P(i) cotransport. In C11-MDCK cells, phosphorylation of JNK1/2 and Erk1/2 mitogen-activated protein kinases was augmented in hyperosmotically shrunken cells by ∼7- and 2-fold, respectively, but was not affected in cells subjected to isosmotic shrinkage. These results demonstrate that the data obtained in cells subjected to hyperosmotic shrinkage cannot be considered as sufficient proof implicating cell volume perturbations in the regulation of cellular functions under isosmotic conditions.

  20. Improving the accuracy of vehicle emissions profiles for urban transportation greenhouse gas and air pollution inventories.

    PubMed

    Reyna, Janet L; Chester, Mikhail V; Ahn, Soyoung; Fraser, Andrew M

    2015-01-06

    Metropolitan greenhouse gas and air emissions inventories can better account for the variability in vehicle movement, fleet composition, and infrastructure that exists within and between regions, to develop more accurate information for environmental goals. With emerging access to high quality data, new methods are needed for informing transportation emissions assessment practitioners of the relevant vehicle and infrastructure characteristics that should be prioritized in modeling to improve the accuracy of inventories. The sensitivity of light and heavy-duty vehicle greenhouse gas (GHG) and conventional air pollutant (CAP) emissions to speed, weight, age, and roadway gradient are examined with second-by-second velocity profiles on freeway and arterial roads under free-flow and congestion scenarios. By creating upper and lower bounds for each factor, the potential variability which could exist in transportation emissions assessments is estimated. When comparing the effects of changes in these characteristics across U.S. cities against average characteristics of the U.S. fleet and infrastructure, significant variability in emissions is found to exist. GHGs from light-duty vehicles could vary by -2%-11% and CAP by -47%-228% when compared to the baseline. For heavy-duty vehicles, the variability is -21%-55% and -32%-174%, respectively. The results show that cities should more aggressively pursue the integration of emerging big data into regional transportation emissions modeling, and the integration of these data is likely to impact GHG and CAP inventories and how aggressively policies should be implemented to meet reductions. A web-tool is developed to aide cities in improving emissions uncertainty.

  1. State policies affecting natural gas consumption (Notice of inquiry issued on August 14, 1992). Summary of comments

    SciTech Connect

    Lemon, R.; Kamphuis-Zatopa, W.

    1993-03-25

    On August 14, 1992, the United States Department of Energy issued a Request for Comments Concerning State Policies Affecting Natural Gas Consumption. This Notice of (NOI) noted the increasing significance of the role played by states and sought to gain better understanding of how state policies impact the gas industry. The general trend toward a. more competitive marketplace for natural gas, as well as recent regulatory and legislative changes at the Federal level, are driving State regulatory agencies to reevaluate how they regulate natural gas. State action is having a significant impact on the use of natural gas for generating electricity, as well as affecting the cost-effective trade-off between conservation expenditures and gas use. Additionally, fuel choice has an impact upon the environment and national energy security. In light of these dimensions, the Department of Energy initiated this study of State regulation. The goals of this NOI are: (1) help DOE better understand the impact of State policies on the efficient use of gas; (2) increase the awareness of the natural gas industry and Federal and State officials to the important role of State policies and regulations; (3) create an improved forum for dialogue on State and Federal natural gas issues; and, (4) develop a consensus on an analytical agenda that would be most helpful in addressing the regulatory challenges faced by the States. Ninety-seven parties filed comments, and of these ninety-seven, fifteen parties filed reply comments. Appendix One lists these parties. This report briefly syntheses the comments received. The goal is to assist parties to judging the extent of consensus on the problems posed and the remedies suggested, aid in identifying future analytical analyses, and assist parties in assessing differences in strategies and regulatory philosophies which shape these issues and their resolution.

  2. Accounting for exhaust gas transport dynamics in instantaneous emission models via smooth transition regression.

    PubMed

    Kamarianakis, Yiannis; Gao, H Oliver

    2010-02-15

    Collecting and analyzing high frequency emission measurements has become very usual during the past decade as significantly more information with respect to formation conditions can be collected than from regulated bag measurements. A challenging issue for researchers is the accurate time-alignment between tailpipe measurements and engine operating variables. An alignment procedure should take into account both the reaction time of the analyzers and the dynamics of gas transport in the exhaust and measurement systems. This paper discusses a statistical modeling framework that compensates for variable exhaust transport delay while relating tailpipe measurements with engine operating covariates. Specifically it is shown that some variants of the smooth transition regression model allow for transport delays that vary smoothly as functions of the exhaust flow rate. These functions are characterized by a pair of coefficients that can be estimated via a least-squares procedure. The proposed models can be adapted to encompass inherent nonlinearities that were implicit in previous instantaneous emissions modeling efforts. This article describes the methodology and presents an illustrative application which uses data collected from a diesel bus under real-world driving conditions.

  3. The impact of thermal conductivity and diffusion rates on water vapor transport through gas diffusion layers

    NASA Astrophysics Data System (ADS)

    Burlatsky, Sergei F.; Atrazhev, Vadim V.; Gummalla, Mallika; Condit, Dave A.; Liu, Fuqiang

    Proper water management in a hydrogen-fueled polymer electrolyte membrane (PEM) fuel cell is critical for performance and durability. A mathematical model has been developed to elucidate the effect of thermal conductivity and water vapor diffusion coefficient in the gas diffusion layers (GDLs). The fraction of product water removed in the vapor phase through the GDL as a function of GDL properties/set of material and component parameters and operating conditions has been calculated. The current model enables identification of conditions wherein condensation occurs in each GDL component. The model predicts the temperature gradient across various components of a PEM fuel cell, providing insight into the overall mechanism of water transport in a given cell design. The water condensation conditions and transport mode in the GDL components depend on the combination of water vapor diffusion coefficients and thermal conductivities of the GDL components. Different types of GDLs and water transport scenarios are defined in this work, based on water condensation in the GDL and fraction of water that the GDL removes through the vapor phase, respectively.

  4. Mass-transport-controlled, large-area, uniform deposition of carbon nanofibers and their application in gas diffusion layers of fuel cells.

    PubMed

    Tang, Xian; Xie, Zhiyong; Huang, Qizhong; Chen, Guofen; Hou, Ming; Yi, Baolian

    2015-05-07

    The effect of mass transport on the growth characteristics of large-area vapor-grown carbon nanofibers (CNFs) was investigated by adjusting the substrate deposition angle (α). The catalyst precursor solution was coated onto one side of a 2D porous carbon paper substrate via a decal printing method. The results showed that the CNFs were grown on only one side of the substrate and α was found to significantly affect the growth uniformity. At α = 0°, the growth thickness, the density, the microstructure and the yield of the CNF film were uniform across the substrate surface, whereas the growth uniformity decreased with increasing α, suggesting that the large-area CNF deposition processes were mass-transport-controlled. Computational fluid dynamics simulations of the gas diffusion processes revealed the homogeneous distributions of the carbon-source-gas concentration, pressure, and velocity near the substrate surface at α = 0°, which were the important factors in achieving the mass-transport-limited uniform CNF growth. The homogeneity of the field distributions decreased with increasing α, in accordance with the variation in the growth uniformity with α. When used as a micro-porous layer, the uniform CNF film enabled higher proton exchange membrane fuel cell performance in comparison with commercial carbon black by virtue of its improved electronic and mass-transport properties confirmed by the electrochemical impedance spectroscopy results.

  5. Numerical Simulation of Subsurface Transport and Groundwater Impacts from Hydraulic Fracturing of Tight/Shale Gas Reservoirs

    NASA Astrophysics Data System (ADS)

    Reagan, M. T.; Moridis, G. J.; Keen, N. D.

    2014-12-01

    The use of reservoir stimulation techniques, such as hydraulic fracturing, has grown tremendously over the last decade, and concerns have arisen that reservoir stimulation creates environmental threats through the creation of permeable pathways that could connect the stimulated reservoir to shallower groundwater aquifers. This study investigates, by numerical simulation, gas and water transport between a deeper tight-gas reservoir and a shallower overlying groundwater aquifer following hydraulic fracturing operations, assuming that the formation of a connecting pathway has already occurred. We focus on two general transport scenarios: 1) communication between the reservoir and aquifer via a connecting fracture or fault and 2) communication via a deteriorated, preexisting nearby well. The simulations explore a range of permeabilities and geometries over time scales, and evaluate the mechanisms and factors that could lead to the escape of gas or reservoir fluid and the contamination of groundwater resources. We also examine the effects of overpressured reservoirs, and explore long-term transport processes as part of a continuing study. We conclude that the key factors driving short-term transport of gas include high permeability for the connecting pathway and the overall volume of the connecting feature. Gas production from the reservoir via a horizontal well is likely to mitigate release through the reduction of available free gas and the lowering of reservoir pressure. We also find that fractured tight-gas reservoirs are unlikely to act as a continuing source of large volumes of migrating gas, and incidents of gas escape are likely to be limited in duration and scope. Reliable field and laboratory data must be acquired to constrain the factors and determine the likelihood of these outcomes.

  6. "Who's been feeding in my bed?" Benthivorous fish affect fluvial sediment transport - fact or fairy tale?

    NASA Astrophysics Data System (ADS)

    Rice, Stephen; Pledger, Andrew; Smith, James; Toone, Julia

    2016-04-01

    Many species of fish are benthivorous - they forage for food in the river bed - and their foraging disturbs, displaces and sorts bed materials with implications for fluvial sediment transport. Flume experiments have confirmed that benthic foraging by Barbel (Barbus barbus (L.)) and Chub (Squalius cephalus (L.)) modifies the structure and topography of water-worked gravels, thereby increasing particle entrainment probabilities and the quantity of sediment mobilised during experimental high flows. Field experiments and observations have demonstrated the impact of foraging on patch-scale bed disturbance, gravel structure, grain displacements and grain-size sorting. Initial ex-situ experiments support the suggestion that in low gradient rivers, shoals of fish like Bream (Abramis brama (L.)) entrain fine bed sediments, adding a biotic surcharge to the suspended sediment flux and modifying bed topography. These results underpin a novel proposal: that there is an aggregate, cumulative effect of benthic foraging on fluvial sediment transport at larger scales, including at scales where the contribution to sediment movement and river channel behaviour generates management concerns. Evaluating this proposal is a long-term goal, which is based on two intermediate objectives: to develop deeper mechanistic understanding of foraging impacts and to establish the spatial and temporal extent of geomorphologically significant feeding behaviours in river systems. The latter is crucial because field data are currently limited to a single reach on one UK river. It is reasonable to hypothesise that foraging impacts are spatially and temporally widespread because obligate and opportunistic benthic feeding is common and fish feed throughout their life. However, the effectiveness of foraging as a geomorphological process is likely to vary with factors including substrate size, fish community composition, food availability, water temperature, river flows and seasonal changes in fish

  7. Numerical simulation of the environmental impact of hydraulic fracturing of tight/shale gas reservoirs on near-surface ground water: background, base cases, shallow reservoirs, short-term gas and water transport

    EPA Pesticide Factsheets

    Researchers examined gas and water transport between a deep tight shale gas reservoir and a shallow overlying aquifer in the two years following hydraulic fracturing, assuming a pre-existing connecting pathway.

  8. Environmental factors influencing trace house gas production in permafrost-affected soils

    NASA Astrophysics Data System (ADS)

    Walz, Josefine; Knoblauch, Christian; Böhme, Luisa; Pfeiffer, Eva-Maria

    2016-04-01

    The permafrost-carbon feedback has been identified as a major feedback mechanism to climate change. Soil organic matter (SOM) decomposition in the active layer and thawing permafrost is an important source of atmospheric carbon dioxide (CO2) and methane (CH4). Decomposability and potential CO2 and CH4 production are connected to the quality of SOM. SOM quality varies with vegetation composition, soil type, and soil depth. The regulating factors affecting SOM decomposition in permafrost landscapes are not well understood. Here, we incubated permafrost-affected soils from a polygonal tundra landscape in the Lena Delta, Northeast Siberia, to examine the influence of soil depth, oxygen availability, incubation temperature, and fresh organic matter addition on trace gas production. CO2 production was always highest in topsoil (0 - 10 cm). Subsoil (10 - 50 cm) and permafrost (50 - 90 cm) carbon did not differ significantly in their decomposability. Under anaerobic conditions, less SOM was decomposed than under aerobic conditions. However, in the absence of oxygen, CH4 can also be formed, which has a substantially higher warming potential than CO2. But, within the four-month incubation period (approximate period of thaw), methanogenesis played only a minor role with CH4 contributing 1-30% to the total anaerobic carbon release. Temperature and fresh organic matter addition had a positive effect on SOM decomposition. Across a temperature gradient (1, 4, 8°C) aerobic decomposition in topsoil was less sensitive to temperature than in subsoil or permafrost. The addition of labile plant organic matter (13C-labelled Carex aquatilis, a dominant species in the region) significantly increased overall CO2 production across different depths and temperatures. Partitioning the total amount of CO2 in samples amended with Carex material into SOM-derived CO2 and Carex-derived CO2, however, revealed that most of the additional CO2 could be assigned to the organic carbon from the amendment

  9. Transport and Sorting of the Solanum tuberosum Sucrose Transporter SUT1 Is Affected by Posttranslational Modification[W

    PubMed Central

    Krügel, Undine; Veenhoff, Liesbeth M.; Langbein, Jennifer; Wiederhold, Elena; Liesche, Johannes; Friedrich, Thomas; Grimm, Bernhard; Martinoia, Enrico; Poolman, Bert; Kühn, Christina

    2008-01-01

    The plant sucrose transporter SUT1 from Solanum tuberosum revealed a dramatic redox-dependent increase in sucrose transport activity when heterologously expressed in Saccharomyces cerevisiae. Plant plasma membrane vesicles do not show any change in proton flux across the plasma membrane in the presence of redox reagents, indicating a SUT1-specific effect of redox reagents. Redox-dependent sucrose transport activity was confirmed electrophysiologically in Xenopus laevis oocytes with SUT1 from maize (Zea mays). Localization studies of green fluorescent protein fusion constructs showed that an oxidative environment increased the targeting of SUT1 to the plasma membrane where the protein concentrates in 200- to 300-nm raft-like microdomains. Using plant plasma membranes, St SUT1 can be detected in the detergent-resistant membrane fraction. Importantly, in yeast and in plants, oxidative reagents induced a shift in the monomer to dimer equilibrium of the St SUT1 protein and increased the fraction of dimer. Biochemical methods confirmed the capacity of SUT1 to form a dimer in plants and yeast cells in a redox-dependent manner. Blue native PAGE, chemical cross-linking, and immunoprecipitation, as well as the analysis of transgenic plants with reduced expression of St SUT1, confirmed the dimerization of St SUT1 and Sl SUT1 (from Solanum lycopersicum) in planta. The ability to form homodimers in plant cells was analyzed by the split yellow fluorescent protein technique in transiently transformed tobacco (Nicotiana tabacum) leaves and protoplasts. Oligomerization seems to be cell type specific since under native-like conditions, a phloem-specific reduction of the dimeric form of the St SUT1 protein was detectable in SUT1 antisense plants, whereas constitutively inhibited antisense plants showed reduction only of the monomeric form. The role of redox control of sucrose transport in plants is discussed. PMID:18790827

  10. Large herbivore grazing affects the vegetation structure and greenhouse gas balance in a high arctic mire

    NASA Astrophysics Data System (ADS)

    Falk, Julie Maria; Schmidt, Niels Martin; Christensen, Torben R.; Ström, Lena

    2015-04-01

    Herbivory is an important part of most ecosystems and affects the ecosystems’ carbon balance both directly and indirectly. Little is known about herbivory and its impact on the carbon balance in high arctic mire ecosystems. We hypothesized that trampling and grazing by large herbivores influences the vegetation density and composition and thereby also the carbon balance. In 2010, we established fenced exclosures in high arctic Greenland to prevent muskoxen (Ovibos moschatus) from grazing. During the growing seasons of 2011 to 2013 we measured CO2 and CH4 fluxes in these ungrazed blocks and compared them to blocks subjected to natural grazing. Additionally, we measured depth of the water table and active layer, soil temperature, and in 2011 and 2013 an inventory of the vegetation density and composition were made. In 2013 a significant decrease in total number of vascular plant (33-44%) and Eriophorum scheuchzeri (51-53%) tillers were found in ungrazed plots, the moss-layer and amount of litter had also increased substantially in these plots. This resulted in a significant decrease in net ecosystem uptake of CO2 (47%) and likewise a decrease in CH4 emission (44%) in ungrazed plots in 2013. While the future of the muskoxen in a changing arctic is unknown, this experiment points to a potentially large effect of large herbivores on the carbon balance in natural Arctic ecosystems. It thus sheds light on the importance of grazing mammals, and hence adds to our understanding of natural ecosystem greenhouse gas balance in the past and in the future.

  11. Analysis of Transportation and Logistics Challenges Affecting the Deployment of Larger Wind Turbines: Summary of Results

    SciTech Connect

    Cotrell, J.; Stehly, T.; Johnson, J.; Roberts, J. O.; Parker, Z.; Scott, G.; Heimiller, D.

    2014-01-01

    There is relatively little literature that characterizes transportation and logistics challenges and the associated effects on U.S. wind markets. The objectives of this study were to identify the transportation and logistics challenges, assess the associated impacts, and provide recommendations for strategies and specific actions to address the challenges. The authors primarily relied on interviews with wind industry project developers, original equipment manufacturers, and transportation and logistics companies to obtain the information and industry perspectives needed for this study. They also reviewed published literature on trends and developments in increasing wind turbine size, logistics, and transportation issues.

  12. Peclet number as affected by molecular diffusion controls transient anomalous transport in alluvial aquifer-aquitard complexes

    USGS Publications Warehouse

    Zhang, Yong; Green, Christopher T.; Tick, Geoffrey R.

    2015-01-01

    This study evaluates the role of the Peclet number as affected by molecular diffusion in transient anomalous transport, which is one of the major knowledge gaps in anomalous transport, by combining Monte Carlo simulations and stochastic model analysis. Two alluvial settings containing either short- or long-connected hydrofacies are generated and used as media for flow and transport modeling. Numerical experiments show that 1) the Peclet number affects both the duration of the power-law segment of tracer breakthrough curves (BTCs) and the transition rate from anomalous to Fickian transport by determining the solute residence time for a given low-permeability layer, 2) mechanical dispersion has a limited contribution to the anomalous characteristics of late-time transport as compared to molecular diffusion due to an almost negligible velocity in floodplain deposits, and 3) the initial source dimensions only enhance the power-law tail of the BTCs at short travel distances. A tempered stable stochastic (TSS) model is then applied to analyze the modeled transport. Applications show that the time-nonlocal parameters in the TSS model relate to the Peclet number, Pe. In particular, the truncation parameter in the TSS model increases nonlinearly with a decrease in Pe due to the decrease of the mean residence time, and the capacity coefficient increases with an increase in molecular diffusion which is probably due to the increase in the number of immobile particles. The above numerical experiments and stochastic analysis therefore reveal that the Peclet number as affected by molecular diffusion controls transient anomalous transport in alluvial aquifer–aquitard complexes.

  13. Peclet number as affected by molecular diffusion controls transient anomalous transport in alluvial aquifer-aquitard complexes.

    PubMed

    Zhang, Yong; Green, Christopher T; Tick, Geoffrey R

    2015-01-01

    This study evaluates the role of the Peclet number as affected by molecular diffusion in transient anomalous transport, which is one of the major knowledge gaps in anomalous transport, by combining Monte Carlo simulations and stochastic model analysis. Two alluvial settings containing either short- or long-connected hydrofacies are generated and used as media for flow and transport modeling. Numerical experiments show that 1) the Peclet number affects both the duration of the power-law segment of tracer breakthrough curves (BTCs) and the transition rate from anomalous to Fickian transport by determining the solute residence time for a given low-permeability layer, 2) mechanical dispersion has a limited contribution to the anomalous characteristics of late-time transport as compared to molecular diffusion due to an almost negligible velocity in floodplain deposits, and 3) the initial source dimensions only enhance the power-law tail of the BTCs at short travel distances. A tempered stable stochastic (TSS) model is then applied to analyze the modeled transport. Applications show that the time-nonlocal parameters in the TSS model relate to the Peclet number, Pe. In particular, the truncation parameter in the TSS model increases nonlinearly with a decrease in Pe due to the decrease of the mean residence time, and the capacity coefficient increases with an increase in molecular diffusion which is probably due to the increase in the number of immobile particles. The above numerical experiments and stochastic analysis therefore reveal that the Peclet number as affected by molecular diffusion controls transient anomalous transport in alluvial aquifer-aquitard complexes.

  14. Study on a gas transport system based on thermal induced flow

    NASA Astrophysics Data System (ADS)

    Matsumoto, Hiroaki; Mihara, Kai; Yamagishi, Daigo; Morokuma, Takayuki

    2016-11-01

    In this study, the performance of a rarefied gas transport system which works by thermal induced flow was studied experimentally. The driving force of the pump system presented in this study is thermal creep flow around the edge of a small circular plate. The thermal induced flow is generated by irradiating the plates, which are colored black on one side and white on the other. The system was constructed by arranging a series of such plates in a glass pipe which was connected to two vessels and irradiated with an infrared lamp. It was observed that the ratio of pressures in the two vessels was about 96% when the temperature difference between the black and white surfaces of the plates was about 40 °C.

  15. Free volumes and gas transport in polymers: amine-modified epoxy resins as a case study.

    PubMed

    Patil, Pushkar N; Roilo, David; Brusa, Roberto S; Miotello, Antonio; Aghion, Stefano; Ferragut, Rafael; Checchetto, Riccardo

    2016-02-07

    The CO2 transport process was studied in a series of amine-modified epoxy resins having different cross-linking densities but the same chemical environment for the penetrant molecules. Positron Annihilation Lifetime Spectroscopy (PALS) was used to monitor the free volume structure of the samples and experimentally evaluate their fractional free volume fh(T) and its temperature evolution. The analysis of the free volume hole size distribution showed that all the holes have a size large enough to accommodate the penetrant molecules at temperatures T above the glass transition temperature Tg. The measured gas diffusion constants at T > Tg have been reproduced in the framework of the free volume theory of diffusion using a novel procedure based on the use of fh(T) as an input experimental parameter.

  16. Investigation of some numerical issues in a chemistry-transport model: Gas-phase simulations

    NASA Astrophysics Data System (ADS)

    Mallet, Vivien; Pourchet, AdéLaïDe; QuéLo, Denis; Sportisse, Bruno

    2007-08-01

    Many numerical strategies have been specifically developed for chemistry-transport models. Since no exact solutions are available for 3-D real problems, there are only few insights to choose between alternative numerical schemes and approximations, or to estimate the performance discrepancy between two approaches. However it is possible to assess the importance of numerical approximations through the comparison of different strategies. We estimated the impact of several numerical schemes for advection, diffusion and stiff chemistry. We also addressed operator splitting with different methods and operator orders. The study is performed with a gas-phase Eulerian model from the modeling platform Polyphemus. It is applied to ozone forecasts mainly over Europe, with focus on a few key species: ozone, nitric oxide, nitrogen dioxide, sulfur dioxide and hydroxy radical. The outcome is a ranking of the most sensitive numerical choices. It stresses the prominent impact of the advection scheme and of the splitting time step.

  17. A demonstration of a whole core neutron transport method in a gas cooled reactor

    SciTech Connect

    Connolly, K. J.; Rahnema, F.

    2013-07-01

    This paper illustrates a capability of the whole core transport method COMET. Building on previous works which demonstrated the accuracy of the method, this work serves to emphasize the robust capability of the method while also accentuating its efficiency. A set of core configurations is presented based on an operating gas-cooled thermal reactor, Japan's HTTR, and COMET determines the eigenvalue and fission density profile throughout each core configuration. Results for core multiplication factors are compared to MCNP for accuracy and also to compare runtimes. In all cases, the values given by COMET differ by those given by MCNP by less than the uncertainty inherent in the stochastic solution procedure, however, COMET requires runtimes shorter on the order of a few hundred. Figures are provided illustrating the whole core fission density profile, with segments of pins explicitly modeled individually, so that pin-level neutron flux behavior can be seen without any approximation due to simplification strategies such as homogenization. (authors)

  18. Understanding and modelling dissolved gas transport in the bedrock of three Fennoscandian sites

    NASA Astrophysics Data System (ADS)

    Trinchero, Paolo; Delos, Anne; Molinero, Jorge; Dentz, Marco; Pitkänen, Petteri

    2014-05-01

    The origin and transport of dissolved gases in the geosphere is of interest for assessment studies of nuclear waste repositories. In this paper, we analyse available field measurements of helium, methane and hydrogen at three Fennoscandian sites: Forsmark and Laxemar in Sweden and Olkiluoto in Finland. The field data are interpreted using different analytical models all based on the one-dimensional diffusion equation. The results of the different models provide estimates about the amount of deep gas flux, the in situ production and the groundwater residence time of the considered sites. The computed helium fluxes, which fall within the lower range of crustal degassing fluxes reported by Torgersen (2010), are strictly related with the high tightness of the considered fracture media. The very high estimates of groundwater residence time indicate that, at the considered depths, there are only very few flowing fractures while in the rest of the fractured domain groundwater has been almost motionless during a whole glacial cycle.

  19. Building-Resolved CFD Simulations for Greenhouse Gas Transport and Dispersion over Washington DC / Baltimore

    NASA Astrophysics Data System (ADS)

    Prasad, K.; Lopez-Coto, I.; Ghosh, S.; Mueller, K.; Whetstone, J. R.

    2015-12-01

    The North-East Corridor project aims to use a top-down inversion methodology to quantify sources of Greenhouse Gas (GHG) emissions over urban domains such as Washington DC / Baltimore with high spatial and temporal resolution. Atmospheric transport of tracer gases from an emission source to a tower mounted receptor are usually conducted using the Weather Research and Forecasting (WRF) model. For such simulations, WRF employs a parameterized turbulence model and does not resolve the fine scale dynamics generated by the flow around buildings and communities comprising a large city. The NIST Fire Dynamics Simulator (FDS) is a computational fluid dynamics model that utilizes large eddy simulation methods to model flow around buildings at length scales much smaller than is practical with WRF. FDS has the potential to evaluate the impact of complex urban topography on near-field dispersion and mixing difficult to simulate with a mesoscale atmospheric model. Such capabilities may be important in determining urban GHG emissions using atmospheric measurements. A methodology has been developed to run FDS as a sub-grid scale model within a WRF simulation. The coupling is based on nudging the FDS flow field towards that computed by WRF, and is currently limited to one way coupling performed in an off-line mode. Using the coupled WRF / FDS model, NIST will investigate the effects of the urban canopy at horizontal resolutions of 10-20 m in a domain of 12 x 12 km. The coupled WRF-FDS simulations will be used to calculate the dispersion of tracer gases in the North-East Corridor and to evaluate the upwind areas that contribute to tower observations, referred to in the inversion community as influence functions. Results of this study will provide guidance regarding the importance of explicit simulations of urban atmospheric turbulence in obtaining accurate estimates of greenhouse gas emissions and transport.

  20. The influence of soil gas transport properties on methane oxidation in a selection of northern European soils

    NASA Astrophysics Data System (ADS)

    Ball, B. C.; Smith, K. A.; Klemedtsson, L.; Brumme, R.; Sitaula, B. K.; Hansen, S.; Priemé, A.; MacDonald, J.; Horgan, G. W.

    1997-10-01

    The oxidation of atmospheric methane in soils was measured in situ at a selection of sites in northern Europe, mainly under forest but also under moorland and agricultural arable land and grassland. Our objective was to examine how land use, soil type, and location affected methane oxidation through their impact on gas diffusivity and air permeability. Gas diffusivity at the soil surface and, in some cases, after removal of any surface organic layer was measured in situ using Freon-22 tracer in a portable probe. For about half of the sites, gas diffusivity was also measured in intact topsoil core samples in the laboratory using krypton 85. Air permeability and porosity were also measured on these cores. Although the method of measurement of CH4 oxidation varied between sites, the same techniques were used to measure soil physical properties at all sites. CH4 oxidation rates ranged from 0 to 2.5 mg m-2 d-1. Diffusivity also covered a very wide range, being lowest in loam cores from wet grassland in Norway and highest in relatively dry, sandy soils in Denmark and Scotland. CH4 oxidation tended to increase with gas diffusivity measured in situ at the soil surface, though the relationship was poor at high diffusivities, presumably because CH4 oxidation was not limited by diffusion. Removal of the surface organic layer reduced in situ diffusivity at the surface and improved its relationship with CH4 oxidation rate. Sites where soils had well-developed structure and a loose and permeable organic layer at the surface tended to have the highest CH4 oxidation rates. Core measurements, particularly of air permeability, could not be obtained at some sites owing to the inability to take suitable samples. Diffusivity measured in cores generally decreased with increasing depth of sampling in the topsoil, with the 50-to 100-mm depth giving the best correlation with CH4 uptake; cores from within this layer also gave the highest CH4 oxidation during laboratory incubation. Effective

  1. Analysis of selected energy security issues related to US crude oil and natural gas exploration, development, production, transportation and processing. Final report, Task 13

    SciTech Connect

    Not Available

    1990-10-01

    In July 1989, President Bush directed the Secretary of Energy to initiate the development of a comprehensive National Energy Strategy (NES) built upon a national consensus. The overall principle for the NES, as defined by the President and articulated by the Economic Policy Council (EPC), is the continuation of the successful policy of market reliance, consistent with the following goals: Balancing of energy, economic, and environmental concerns; and reduced dependence by the US and its friends and allies on potentially unreliable energy suppliers. The analyses presented in this report draw upon a large body of work previously conducted for DOE/Office of Fossil Energy, the US Department of Interior/Minerals Management Service (DOI/MMS), and the Gas Research Institute (GRI), referenced throughout the text of this report. This work includes assessments in the following areas: the potential of advanced oil and gas extraction technologies as improved through R&D, along with the successful transfer of these technologies to the domestic petroleum industry; the economic and energy impacts of environmental regulations on domestic oil and gas exploration, production, and transportation; the potential of tax incentives to stimulate domestic oil and gas development and production; the potential environmental costs associated with various options for leasing for US oil and gas resources in the Outer Continental Shelf (OCS); and the economic impacts of environmental regulations affecting domestic crude oil refining.

  2. Porewater methane transport within the gas vesicles of diurnally migrating Chaoborus spp.: An energetic advantage.

    PubMed

    McGinnis, Daniel F; Flury, Sabine; Tang, Kam W; Grossart, Hans-Peter

    2017-03-14

    Diurnally-migrating Chaoborus spp. reach populations of up to 130,000 individuals m(-2) in lakes up to 70 meters deep on all continents except Antarctica. Linked to eutrophication, migrating Chaoborus spp. dwell in the anoxic sediment during daytime and feed in the oxic surface layer at night. Our experiments show that by burrowing into the sediment, Chaoborus spp. utilize the high dissolved gas partial pressure of sediment methane to inflate their tracheal sacs. This mechanism provides a significant energetic advantage that allows the larvae to migrate via passive buoyancy rather than more energy-costly swimming. The Chaoborus spp. larvae, in addition to potentially releasing sediment methane bubbles twice a day by entering and leaving the sediment, also transport porewater methane within their gas vesicles into the water column, resulting in a flux of 0.01-2 mol m(-2) yr(-1) depending on population density and water depth. Chaoborus spp. emerging annually as flies also result in 0.1-6 mol m(-2) yr(-1) of carbon export from the system. Finding the tipping point in lake eutrophication enabling this methane-powered migration mechanism is crucial for ultimately reconstructing the geographical expansion of Chaoborus spp., and the corresponding shifts in the lake's biogeochemistry, carbon cycling and food web structure.

  3. Lattice Boltzmann Simulation of Shale Gas Transport in Organic Nano-Pores

    PubMed Central

    Zhang, Xiaoling; Xiao, Lizhi; Shan, Xiaowen; Guo, Long

    2014-01-01

    Permeability is a key parameter for investigating the flow ability of sedimentary rocks. The conventional model for calculating permeability is derived from Darcy's law, which is valid only for continuum flow in porous rocks. We discussed the feasibility of simulating methane transport characteristics in the organic nano-pores of shale through the Lattice Boltzmann method (LBM). As a first attempt, the effects of high Knudsen number and the associated slip flow are considered, whereas the effect of adsorption in the capillary tube is left for future work. Simulation results show that at small Knudsen number, LBM results agree well with Poiseuille's law, and flow rate (flow capacity) is proportional to the square of the pore scale. At higher Knudsen numbers, the relaxation time needs to be corrected. In addition, velocity increases as the slip effect causes non negligible velocities on the pore wall, thereby enhancing the flow rate inside the pore, i.e., the permeability. Therefore, the LBM simulation of gas flow characteristics in organic nano-pores provides an effective way of evaluating the permeability of gas-bearing shale. PMID:24784022

  4. Measurement of gas transport through fiber preforms and densified composites for chemical vapor infiltration

    SciTech Connect

    Starr, T.L.; Hablutzel, N.

    1998-05-01

    Gas transport via pressure-driven permeation or via concentration-driven diffusion is a key step in the chemical vapor infiltration (CVI) process. This paper describes methods for the measurement of these properties for CVI preforms and partially infiltrated composites. Results are presented for Nicalon-fiber cloth layup preforms and composites, Nextel-fiber braid preforms and composites, and a Nicalon-fiber three-dimensional (3-D) weave composite. The permeability of Nicalon cloth layup preforms is strongly dependent on the packing density over the range of 29--40 vol% but is only weakly dependent on the orientation of the alternating cloth layers. The permeability of Nextel braid preforms is dependent on the thread count and the weight for cloths with similar construction and packing density. The gas permeability of the finer wave (6.3 tows/cm (16 tows/in.)) is approximately one-half that of the coarser weave (3.5 tows/cm (9 tows/in.)). Results are reported for a small number of infiltrated composites with Nextel fiber reinforcement. Attempts to mount a Nicalon-fiber 3-D weave preform specimen have been unsuccessful. Results for a small number of composite specimens with 3-D weave reinforcement are reported.

  5. Lattice Boltzmann simulation of shale gas transport in organic nano-pores.

    PubMed

    Zhang, Xiaoling; Xiao, Lizhi; Shan, Xiaowen; Guo, Long

    2014-05-02

    Permeability is a key parameter for investigating the flow ability of sedimentary rocks. The conventional model for calculating permeability is derived from Darcy's law, which is valid only for continuum flow in porous rocks. We discussed the feasibility of simulating methane transport characteristics in the organic nano-pores of shale through the Lattice Boltzmann method (LBM). As a first attempt, the effects of high Knudsen number and the associated slip flow are considered, whereas the effect of adsorption in the capillary tube is left for future work. Simulation results show that at small Knudsen number, LBM results agree well with Poiseuille's law, and flow rate (flow capacity) is proportional to the square of the pore scale. At higher Knudsen numbers, the relaxation time needs to be corrected. In addition, velocity increases as the slip effect causes non negligible velocities on the pore wall, thereby enhancing the flow rate inside the pore, i.e., the permeability. Therefore, the LBM simulation of gas flow characteristics in organic nano-pores provides an effective way of evaluating the permeability of gas-bearing shale.

  6. Lattice Boltzmann Simulation of Shale Gas Transport in Organic Nano-Pores

    NASA Astrophysics Data System (ADS)

    Zhang, Xiaoling; Xiao, Lizhi; Shan, Xiaowen; Guo, Long

    2014-05-01

    Permeability is a key parameter for investigating the flow ability of sedimentary rocks. The conventional model for calculating permeability is derived from Darcy's law, which is valid only for continuum flow in porous rocks. We discussed the feasibility of simulating methane transport characteristics in the organic nano-pores of shale through the Lattice Boltzmann method (LBM). As a first attempt, the effects of high Knudsen number and the associated slip flow are considered, whereas the effect of adsorption in the capillary tube is left for future work. Simulation results show that at small Knudsen number, LBM results agree well with Poiseuille's law, and flow rate (flow capacity) is proportional to the square of the pore scale. At higher Knudsen numbers, the relaxation time needs to be corrected. In addition, velocity increases as the slip effect causes non negligible velocities on the pore wall, thereby enhancing the flow rate inside the pore, i.e., the permeability. Therefore, the LBM simulation of gas flow characteristics in organic nano-pores provides an effective way of evaluating the permeability of gas-bearing shale.

  7. Gas Transport and Density Control in the HYLIFE Heavy-Ion Beam Lines

    SciTech Connect

    Debonnel, Christophe S.; Welch, Dale R.; Rose, David V.; Lawrence, Simon S.Yu; Peterson, Per F

    2003-05-15

    The effective propagation and focusing of heavy-ion beams in the final-focus magnet region of inertial fusion target chambers require controlling the background gas density and pressure in the beam tubes. Liquid vortexes will coat the inside of the tubes next to the beam ports and will help eliminate the need for mechanical shutters to mitigate the venting of target chamber background gas into the final-focus magnet region. Before the neutralizing region, the beam space charge is high, and ablation and target debris deposition in the final-focus magnet region may cause voltage breakdown. Previous studies focused on evaluating the amount of target chamber debris reaching the entrance of the beam ports. The TSUNAMI code has now been used to assess the density, temperature, and velocity of the vortex debris transported {approx}3 m up the beam tubes and reaching the final-focus magnet region, assuming that the liquid vortexes are perfectly absorbing surfaces. To further mitigate debris deposition in the final-focus magnet region, and prevent voltage breakdown, a 'magnetic shutter' has been envisaged to divert the debris out of the final-focus region. This shutter will prevent the hot ablation debris from reaching the magnet region and, coupled to some ionizing scheme, will conveniently suppress early ingression of debris into the final-focus magnet region.

  8. Effect of transition from slip to free molecular flow on gas transport in porous media

    NASA Astrophysics Data System (ADS)

    Bravo, Maria Cecilia

    2007-10-01

    Traditional models, such as the advection-diffusion and the dusty gas models, overlook the contribution of the transition flow regime between the slip and the free molecular flow, on the gas transport in porous media. In this work we demonstrate that, due to the existence of this intermediate regime, the Klinkenberg [Drill. & Prod. Prac. 1941, 200 (1941)] parameter b depends on the pressure. Reported experiments were used to corroborate such an effect and a formulation that extends the Klinkenberg equation—to include the effect of a region at pore scale where both molecule-molecule and molecule-wall interactions are important—was developed. The mathematical form of the extended Klinkenberg equation remains the same, but the slippage Klinkenberg's parameter b is now a generalized parameter that is a function of Knudsen's number. It was demonstrated that the widely accepted relation between the parameter b and the Knudsen diffusion coefficient is a good approximation just for Knudsen numbers corresponding to the free molecular flow regime. The model proposed in this paper reproduces the experimental data and predicts practical situations where important errors on total flow rate can be expected if the transition flow regime is neglected in the formalism.

  9. Porewater methane transport within the gas vesicles of diurnally migrating Chaoborus spp.: An energetic advantage

    PubMed Central

    McGinnis, Daniel F.; Flury, Sabine; Tang, Kam W.; Grossart, Hans-Peter

    2017-01-01

    Diurnally-migrating Chaoborus spp. reach populations of up to 130,000 individuals m−2 in lakes up to 70 meters deep on all continents except Antarctica. Linked to eutrophication, migrating Chaoborus spp. dwell in the anoxic sediment during daytime and feed in the oxic surface layer at night. Our experiments show that by burrowing into the sediment, Chaoborus spp. utilize the high dissolved gas partial pressure of sediment methane to inflate their tracheal sacs. This mechanism provides a significant energetic advantage that allows the larvae to migrate via passive buoyancy rather than more energy-costly swimming. The Chaoborus spp. larvae, in addition to potentially releasing sediment methane bubbles twice a day by entering and leaving the sediment, also transport porewater methane within their gas vesicles into the water column, resulting in a flux of 0.01–2 mol m−2 yr−1 depending on population density and water depth. Chaoborus spp. emerging annually as flies also result in 0.1–6 mol m−2 yr−1 of carbon export from the system. Finding the tipping point in lake eutrophication enabling this methane-powered migration mechanism is crucial for ultimately reconstructing the geographical expansion of Chaoborus spp., and the corresponding shifts in the lake’s biogeochemistry, carbon cycling and food web structure. PMID:28290556

  10. Porewater methane transport within the gas vesicles of diurnally migrating Chaoborus spp.: An energetic advantage

    NASA Astrophysics Data System (ADS)

    McGinnis, Daniel F.; Flury, Sabine; Tang, Kam W.; Grossart, Hans-Peter

    2017-03-01

    Diurnally-migrating Chaoborus spp. reach populations of up to 130,000 individuals m‑2 in lakes up to 70 meters deep on all continents except Antarctica. Linked to eutrophication, migrating Chaoborus spp. dwell in the anoxic sediment during daytime and feed in the oxic surface layer at night. Our experiments show that by burrowing into the sediment, Chaoborus spp. utilize the high dissolved gas partial pressure of sediment methane to inflate their tracheal sacs. This mechanism provides a significant energetic advantage that allows the larvae to migrate via passive buoyancy rather than more energy-costly swimming. The Chaoborus spp. larvae, in addition to potentially releasing sediment methane bubbles twice a day by entering and leaving the sediment, also transport porewater methane within their gas vesicles into the water column, resulting in a flux of 0.01–2 mol m‑2 yr‑1 depending on population density and water depth. Chaoborus spp. emerging annually as flies also result in 0.1–6 mol m‑2 yr‑1 of carbon export from the system. Finding the tipping point in lake eutrophication enabling this methane-powered migration mechanism is crucial for ultimately reconstructing the geographical expansion of Chaoborus spp., and the corresponding shifts in the lake’s biogeochemistry, carbon cycling and food web structure.

  11. Modeling of off-gas emissions from wood pellets during marine transportation.

    PubMed

    Pa, Ann; Bi, Xiaotao T

    2010-10-01

    After a fatal accident during the discharge of wood pellets at Helsingborg, emissions from pellets during marine transportation became a concern for the safe handling and storage of wood pellets. In this paper, a two-compartment model has been developed for the first time to predict the concentrations of CO, CO₂, CH₄, and O₂ inside the cargo ship and the time and rate of forced ventilation required before the safe entry into the stairway adjacent to the storage hatch. The hatch and stairway are treated as two perfectly mixed tanks. The gas exchange rate between these two rooms and the gas exchange rate with the atmosphere are fitted to satisfy a measured tracer final concentration of 33 p.p.m.v. in the stairway and an average final hatch to stairway CO, CO₂, and CH₄ concentration ratio of 1.62 based on measurement from five other hatch and stairway systems. The reaction kinetics obtained from a laboratory unit using a different batch of pellets, however, need to be scaled in order to bring the prediction to close agreement with onboard measured emission data at the end of voyage. Using the adjusted kinetic data, the model was able to predict the general trend of data recorded in the first 12.5 days of the voyage. Further validation, however, requires the data recorded over the whole journey. The model was applied to predict the effect of ocean temperature on the off-gas emissions and the buildup of concentrations in the hatch and stairway. For safe entry to the cargo ship, the current model predicted that a minimal ventilation rate of 4.4 hr⁻¹ is required for the stairway's CO concentration to lower to a safe concentration of 25 p.p.m.v. At 4.4 hr⁻¹, 10 min of ventilation time is required for the safe entry into the stairway studied.

  12. Transport coefficients of a granular gas of inelastic rough hard spheres.

    PubMed

    Kremer, Gilberto M; Santos, Andrés; Garzó, Vicente

    2014-08-01

    The Boltzmann equation for inelastic and rough hard spheres is considered as a model of a dilute granular gas. In this model, the collisions are characterized by constant coefficients of normal and tangential restitution, and hence the translational and rotational degrees of freedom are coupled. A normal solution to the Boltzmann equation is obtained by means of the Chapman-Enskog method for states near the homogeneous cooling state. The analysis is carried out to first order in the spatial gradients of the number density, the flow velocity, and the granular temperature. The constitutive equations for the momentum and heat fluxes and for the cooling rate are derived, and the associated transport coefficients are expressed in terms of the solutions of linear integral equations. For practical purposes, a first Sonine approximation is used to obtain explicit expressions of the transport coefficients as nonlinear functions of both coefficients of restitution and the moment of inertia. Known results for purely smooth inelastic spheres and perfectly elastic and rough spheres are recovered in the appropriate limits.

  13. Electrical detection of spin transport in Si two-dimensional electron gas systems

    NASA Astrophysics Data System (ADS)

    Chang, Li-Te; Fischer, Inga Anita; Tang, Jianshi; Wang, Chiu-Yen; Yu, Guoqiang; Fan, Yabin; Murata, Koichi; Nie, Tianxiao; Oehme, Michael; Schulze, Jörg; Wang, Kang L.

    2016-09-01

    Spin transport in a semiconductor-based two-dimensional electron gas (2DEG) system has been attractive in spintronics for more than ten years. The inherent advantages of high-mobility channel and enhanced spin-orbital interaction promise a long spin diffusion length and efficient spin manipulation, which are essential for the application of spintronics devices. However, the difficulty of making high-quality ferromagnetic (FM) contacts to the buried 2DEG channel in the heterostructure systems limits the potential developments in functional devices. In this paper, we experimentally demonstrate electrical detection of spin transport in a high-mobility 2DEG system using FM Mn-germanosilicide (Mn(Si0.7Ge0.3)x) end contacts, which is the first report of spin injection and detection in a 2DEG confined in a Si/SiGe modulation doped quantum well structure (MODQW). The extracted spin diffusion length and lifetime are l sf = 4.5 μm and {τ }{{s}}=16 {{ns}} at 1.9 K respectively. Our results provide a promising approach for spin injection into 2DEG system in the Si-based MODQW, which may lead to innovative spintronic applications such as spin-based transistor, logic, and memory devices.

  14. Subsurface fate and transport of cyanide species at a manufactured-gas plant site

    SciTech Connect

    Ghosh, R.S.; Dzombak, D.A.; Luthy, R.G.; Nakles, D.V.

    1999-10-01

    Cyanide is present at manufactured-gas plant (MGP) sites in oxide-box residuals, which were often managed on-site as fill during active operations. Cyanide can leach from these materials, causing groundwater contamination. Speciation, fate, and transport of cyanide in a sand-gravel aquifer underlying an MGP site in the upper Midwest region of the US were studied through characterization, monitoring, and modeling of a plume of cyanide-contaminated groundwater emanating from the site. Results indicate that cyanide in the groundwater is primarily in the form of iron-cyanide complexes (>98%), that these complexes are stable under the conditions of the aquifer, and that they are transported as nonreactive solutes in the sand-gravel aquifer material. Weak-acid-dissociable cyanide, which represents a minute fraction of total cyanide in the site groundwater, may undergo chemical-biological degradation in the sand-gravel aquifer. It seems that dilution may be the only natural attenuation mechanism for iron-cyanide complexes in sand-gravel aquifers at MGP sites.

  15. Estimating the health benefits from natural gas use in transport and heating in Santiago, Chile.

    PubMed

    Mena-Carrasco, Marcelo; Oliva, Estefania; Saide, Pablo; Spak, Scott N; de la Maza, Cristóbal; Osses, Mauricio; Tolvett, Sebastián; Campbell, J Elliott; Tsao, Tsao Es Chi-Chung; Molina, Luisa T

    2012-07-01

    Chilean law requires the assessment of air pollution control strategies for their costs and benefits. Here we employ an online weather and chemical transport model, WRF-Chem, and a gridded population density map, LANDSCAN, to estimate changes in fine particle pollution exposure, health benefits, and economic valuation for two emission reduction strategies based on increasing the use of compressed natural gas (CNG) in Santiago, Chile. The first scenario, switching to a CNG public transportation system, would reduce urban PM2.5 emissions by 229 t/year. The second scenario would reduce wood burning emissions by 671 t/year, with unique hourly emission reductions distributed from daily heating demand. The CNG bus scenario reduces annual PM2.5 by 0.33 μg/m³ and up to 2 μg/m³ during winter months, while the residential heating scenario reduces annual PM2.5 by 2.07 μg/m³, with peaks exceeding 8 μg/m³ during strong air pollution episodes in winter months. These ambient pollution reductions lead to 36 avoided premature mortalities for the CNG bus scenario, and 229 for the CNG heating scenario. Both policies are shown to be cost-effective ways of reducing air pollution, as they target high-emitting area pollution sources and reduce concentrations over densely populated urban areas as well as less dense areas outside the city limits. Unlike the concentration rollback methods commonly used in public policy analyses, which assume homogeneous reductions across a whole city (including homogeneous population densities), and without accounting for the seasonality of certain emissions, this approach accounts for both seasonality and diurnal emission profiles for both the transportation and residential heating sectors.

  16. Assessment of an atmospheric transport model for annual inverse estimates of California greenhouse gas emissions

    NASA Astrophysics Data System (ADS)

    Bagley, Justin E.; Jeong, Seongeun; Cui, Xinguang; Newman, Sally; Zhang, Jingsong; Priest, Chad; Campos-Pineda, Mixtli; Andrews, Arlyn E.; Bianco, Laura; Lloyd, Matthew; Lareau, Neil; Clements, Craig; Fischer, Marc L.

    2017-02-01

    Atmospheric inverse estimates of gas emissions depend on transport model predictions, hence driving a need to assess uncertainties in the transport model. In this study we assess the uncertainty in WRF-STILT (Weather Research and Forecasting and Stochastic Time-Inverted Lagrangian Transport) model predictions using a combination of meteorological and carbon monoxide (CO) measurements. WRF configurations were selected to minimize meteorological biases using meteorological measurements of winds and boundary layer depths from surface stations and radar wind profiler sites across California. We compare model predictions with CO measurements from four tower sites in California from June 2013 through May 2014 to assess the seasonal biases and random errors in predicted CO mixing ratios. In general, the seasonal mean biases in boundary layer wind speed (< 0.5 m/s), direction (< 15°), and boundary layer height (< 200 m) were small. However, random errors were large ( 1.5-3.0 m/s for wind speed, 40-60° for wind direction, and 300-500 m for boundary layer height). Regression analysis of predicted and measured CO yielded near-unity slopes (i.e., within 1.0 ± 0.20) for the majority of sites and seasons, though a subset of sites and seasons exhibit larger ( 30%) uncertainty, particularly when weak winds combined with complex terrain in the South Central Valley of California. Looking across sites and seasons, these results suggest that WRF-STILT simulations are sufficient to estimate emissions of CO to up to 15% on annual time scales across California.

  17. Chemical Potential of Triethylene Glycol Adsorbed on Surfaces Relevant to Gas Transport and Processing - Studies Using Molecular Dynamics Simulations

    NASA Astrophysics Data System (ADS)

    Kvamme, B.; Olsen, R.; Sjöblom, S.; Leirvik, K. N.; Kuznetsova, T.

    2014-12-01

    Natural gas will inevitably contain trace amounts of water and other impurities during different stages of processing and transport. Glycols, such as triethylene glycol (TEG), will in many cases follow the water. The glycol contents of the gas can originate from preceding glycol-drying units or it can be a residue from the direct injection of glycols used to prevent hydrate formation. Thus, it is important to know how glycol contents will affect the different paths leading to hydrate formation. Glycols may in some cases dominate the condensed water phase. If this occurs, it will lead to the well-documented shift in the hydrate stability curve, due to the altered activity of the water. A great deal of information on the molecular path of a glycol through the system can be obtained from calculating the chemical potential. Due to difficulties in measuring interfacial chemical potentials, these often need to be estimated using theoretical tools. We used molecular dynamics (MD) to study how TEG behaves in the vicinity of mineral surfaces such as calcite and hematite. Many methods exist for estimating chemical potentials based on MD trajectories. These include techniques such as free energy perturbation theory (FEP) and thermodynamic integration (TI). Such methods require sufficient sampling of configurations where free energy is to be estimated. Thus, it can be difficult to estimate chemical potentials on surfaces. There are several methods to circumvent this problem, such as blue moon sampling and umbrella sampling. These have been considered and the most important have been used to estimate chemical potentials of TEG adsorbed on the mineral surfaces. The resulting chemical potentials were compared to the chemical potential of TEG in bulk water, which was estimated using temperature thermodynamic integration.

  18. Gas transport below artificial recharge ponds: insights from dissolved noble gases and a dual gas (SF6 and 3He) tracer experiment.

    PubMed

    Clark, Jordan F; Hudson, G Bryant; Avisar, Dror

    2005-06-01

    A dual gas tracer experiment using sulfur hexafluoride (SF6) and an isotope of helium (3He) and measurements of dissolved noble gases was performed at the El Rio spreading grounds to examine gas transport and trapped air below an artificial recharge pond with a very high recharge rate (approximately 4 m day(-1)). Noble gas concentrations in the groundwater were greater than in surface water due to excess air formation showing that trapped air exists below the pond. Breakthrough curves of SF6 and 3He at two nearby production wells were very similar and suggest that nonequilibrium gas transfer was occurring between the percolating water and the trapped air. At one well screened between 50 and 90 m below ground, both tracers were detected after 5 days and reached a maximum at approximately 24 days. Despite the potential dilution caused by mixing within the production well, the maximum concentration was approximately 25% of the mean pond concentration. More than 50% of the SF6 recharged was recovered by the production wells during the 18 month long experiment. Our results demonstrate that at artificial recharge sites with high infiltration rates and moderately deep water tables, transport times between recharge locations and wells determined with gas tracer experiments are reliable.

  19. Potassium nutrition and water availability affect phloem transport of photosynthetic carbon in eucalypt trees

    NASA Astrophysics Data System (ADS)

    Epron, Daniel; Cabral, Osvaldo; Laclau, Jean-Paul; Dannoura, Masako; Packer, Ana Paula; Plain, Caroline; Battie-Laclau, Patricia; Moreira, Marcelo; Trivelin, Paulo; Bouillet, Jean-Pierre; Gérant, Dominique; Nouvellon, Yann

    2015-04-01

    Potassium fertilisation strongly affects growth and carbon partitioning of eucalypt on tropical soil that are strongly weathered. In addition, potassium fertilization could be of great interest in mitigating the adverse consequences of drought in planted forests, as foliar K concentrations influence osmotic adjustment, stomatal regulation and phloem loading. Phloem is the main pathway for transferring photosynthate from source leaves to sink organs, thus controlling growth partitioning among the different tree compartments. But little is known about the effect of potassium nutrition on phloem transport of photosynthetic carbon and on the interaction between K nutrition and water availability. In situ 13C pulse labelling was conducted on tropical eucalypt trees (Eucalyptus grandis L.) grown in a trial plantation with plots in which 37% of throughfall were excluded (about 500 mm/yr) using home-made transparent gutters (-W) or not (+W) and plots that received 0.45 mol K m-2 applied as KCl three months after planting (+K) or not (-K). Three trees were labelled in each of the four treatments (+K+W, +K-W, -K+W and -K-W). Trees were labelled for one hour by injecting pure 13CO2 in a 27 m3 whole crown chamber. We estimated the velocity of carbon transfer in the trunk by comparing time lags between the uptake of 13CO2 and its recovery in trunk CO2 efflux recorded by off axis integrated cavity output spectroscopy (Los Gatos Research) in two chambers per tree, one just under the crown and one at the base of the trunk. We analyzed the dynamics of the label recovered in the foliage and in the phloem sap by analysing carbon isotope composition of bulk leaf organic matter and phloem extracts using an isotope ratio mass spectrometer. The velocity of carbon transfer in the trunk and the initial rate 13C disappearance from the foliage were much higher in +K trees than in -K trees with no significant effect of rainfall. The volumetric flow of phloem, roughly estimated by multiplying

  20. Tracing natural gas transport into shallow groundwater using dissolved nitrogen and alkane chemistry in Parker County, Texas

    NASA Astrophysics Data System (ADS)

    Larson, T.; Nicot, J. P.; Mickler, P. J.; Darvari, R.

    2015-12-01

    Dissolved methane in shallow groundwater drives public concern about the safety of hydraulic fracturing. We report dissolved alkane and nitrogen gas concentrations and their stable isotope values (δ13C and δ15N, respectively) from 208 water wells in Parker county, Texas. These data are used to differentiate 'stray' natural gas and low temperature microbial methane, and (2) estimate the ratio of stray gas to groundwater. The ratio of (gas-phase) stray natural gas to groundwater is estimated by correlating dissolved methane and nitrogen concentrations and dissolved nitrogen δ15N values. Our hypothesis is groundwater exposed to high volumes of stray natural gas have high dissolved methane concentrations and low dissolved nitrogen concentrations and δ15N values. Alternatively, groundwater exposed to low volumes of stray gas-phase natural gas have elevated dissolved methane, but the concentration of dissolved nitrogen and its d15N value is atmospheric. A cluster of samples in Parker county have high concentrations of dissolved methane (>10mg/L) with d13Cmethane and alkane ratios (C1/C2+C3) typical of natural gas from the Barnett Shale and the Strawn Formation. Coupling dissolved nitrogen concentrations and δ15N values with these results, we suggest that few of the wells in this cluster preserve large gas to water ratios. Many samples with high dissolved methane concentrations have atmospheric dissolved nitrogen concentrations and δ15N values, providing evidence against high flux natural gas transport into shallow groundwater. These results demonstrate that dissolved nitrogen chemistry, in addition to dissolved alkane and noble gas measurements, may be useful to discern sources of dissolved methane and estimate ratios of stray natural gas-water ratios.

  1. Low-Carbon Natural Gas for Transportation: Well-to-Wheels Emissions and Potential Market Assessment in California

    SciTech Connect

    Penev, Michael; Melaina, Marc; Bush, Brian; Muratori, Matteo; Warner, Ethan; Chen, Yuche

    2016-12-01

    This report improves on the understanding of the long-term technology potential of low-carbon natural gas (LCNG) supply pathways by exploring transportation market adoption potential through 2035 in California. Techno-economic assessments of each pathway are developed to compare the capacity, cost, and greenhouse gas (GHG) emissions of select LCNG production pathways. The study analyzes the use of fuel from these pathways in light-, medium-, and heavy-duty vehicle applications. Economic and life-cycle GHG emissions analysis suggest that landfill gas resources are an attractive and relatively abundant resource in terms of cost and GHG reduction potential, followed by waste water treatment plants and biomass with gasification and methanation. Total LCNG production potential is on the order of total natural gas demand anticipated in a success scenario for future natural gas vehicle adoption by 2035 across light-, medium-, and heavy-duty vehicle markets (110 trillion Btu/year).

  2. A fully coupled model for water-gas-heat reactive transport with methane oxidation in landfill covers.

    PubMed

    Ng, C W W; Feng, S; Liu, H W

    2015-03-01

    Methane oxidation in landfill covers is a complex process involving water, gas and heat transfer as well as microbial oxidation. The coupled phenomena of microbial oxidation, water, gas, and heat transfer are not fully understood. In this study, a new model is developed that incorporates water-gas-heat coupled reactive transport in unsaturated soil with methane oxidation. Effects of microbial oxidation-generated water and heat are included. The model is calibrated using published data from a laboratory soil column test. Moreover, a series of parametric studies are carried out to investigate the influence of microbial oxidation-generated water and heat, initial water content on methane oxidation efficiency. Computed and measured results of gas concentration and methane oxidation rate are consistent. It is found that the coupling effects between water-gas-heat transfer and methane oxidation are significant. Ignoring microbial oxidation-generated water and heat can result in a significant difference in methane oxidation efficiency by 100%.

  3. Transport of methane and noble gases during gas push-pull tests in variably saturated porous media.

    PubMed

    Gómez, Katherine; Gonzalez-Gil, Graciela; Schroth, Martin H; Zeyer, Josef

    2008-04-01

    The gas push-pull test (GPPT) is a single-well gas-tracer method to quantify in situ rates of CH4 oxidation in soils. To improve the design and interpretation of GPPT field experiments, gas component transport during GPPTs was examined in abiotic porous media over a range of water saturations (0.0 < or = Sw < or = 0.61). A series of GPPTs using He, Ne, and Ar as tracers for CH4 were performed at two injection/extraction gas flow rates (approximately 200 and approximately 700 mL min(-1)) in a laboratory tank. Extraction phase breakthrough curves and mass recovery curves of the gaseous components became more similar at higher Sw as water in the pore space restricted diffusive gas-phase transport. Diffusional fractionation of the stable carbon isotopes of CH4 during the extraction period of GPPTs also decreased with increasing Sw (particularly when Sw > 0.42). Gas-component transport during GPPTs was numerically simulated using estimated hydraulic parameters for the porous media and no fitting of data for the GPPTs. Numerical simulations accurately predicted the relative decline of the gaseous components in the breakthrough curves, but slightly overestimated recoveries at low Sw (< or = 0.35) and underestimated recoveries at high Sw (> or = 0.49). Comparison of numerical simulations considering and not considering air-water partitioning indicated that removal of gaseous components through dissolution in pore water was not significant during GPPTs, even at Sw = 0.61. These data indicate that Ar is a good tracer for CH4 physical transport over the full range of Sw studied, whereas, at Sw > 0.61, any of the tracers could be used. Greater mass recovery at higher Sw raises the possibility to reduce gas flow rates, thereby extending GPPT times in environments such as tundra soils where low activity due to low temperatures may require longer test times to establish a quantifiable difference between reactant and tracer breakthrough curves.

  4. Ammonia gas transport and reactions in unsaturated sediments: implications for use as an amendment to immobilize inorganic contaminants.

    PubMed

    Zhong, L; Szecsody, J E; Truex, M J; Williams, M D; Liu, Y

    2015-05-30

    Use of gas-phase amendments for in situ remediation of inorganic contaminants in unsaturated sediments of the vadose zone may be advantageous, but there has been limited development and testing of gas remediation technologies. Treatment with ammonia gas has a potential for use in treating inorganic contaminants (such as uranium) because it induces a high pore-water pH, causing mineral dissolution and subsequent formation of stable precipitates that decrease the mobility of some contaminants. For field application of this treatment, further knowledge of ammonia transport in porous media and the geochemical reactions induced by ammonia treatment is needed. Laboratory studies were conducted to support calculations needed for field treatment design, to quantify advective and diffusive ammonia transport in unsaturated sediments, to evaluate inter-phase (gas/sediment/pore water) reactions, and to study reaction-induced pore-water chemistry changes as a function of ammonia delivery conditions, such as flow rate, gas concentration, and water content. Uranium-contaminated sediment was treated with ammonia gas to demonstrate U immobilization. Ammonia gas quickly partitions into sediment pore water and increases the pH up to 13.2. Injected ammonia gas advection front movement can be reasonably predicted by gas flow rate and equilibrium partitioning. The ammonia gas diffusion rate is a function of the water content in the sediment. Sodium, aluminum, and silica pore-water concentrations increase upon exposure to ammonia and then decline as aluminosilicates precipitate when the pH declines due to buffering. Up to 85% of the water-leachable U was immobilized by ammonia treatment.

  5. Analysis of Transportation and Logistics Challenges Affecting the Deployment of Larger Wind Turbines: Summary of Results

    SciTech Connect

    J. Cotrell, T. Stehly, J. Johnson, J. O. Roberts, Z. Parker, G. Scott, and D. Heimiller

    2014-01-28

    The objectives of this study were to identify the transportation and logistics challenges, assess the associated impacts, and provide recommendations for strategies and specific actions to address the challenges.

  6. Putative Membrane-Bound Transporters MFSD14A and MFSD14B Are Neuronal and Affected by Nutrient Availability

    PubMed Central

    Lekholm, Emilia; Perland, Emelie; Eriksson, Mikaela M.; Hellsten, Sofie V.; Lindberg, Frida A.; Rostami, Jinar; Fredriksson, Robert

    2017-01-01

    Characterization of orphan transporters is of importance due to their involvement in cellular homeostasis but also in pharmacokinetics and pharmacodynamics. The tissue and cellular localization, as well as function, is still unknown for many of the solute carriers belonging to the major facilitator superfamily (MFS) Pfam clan. Here, we have characterized two putative novel transporters MFSD14A (HIAT1) and MFSD14B (HIATL1) in the mouse central nervous system and found protein staining throughout the adult mouse brain. Both transporters localized to neurons and MFSD14A co-localized with the Golgi marker Giantin in primary embryonic cortex cultures, while MFSD14B staining co-localized with an endoplasmic retention marker, KDEL. Based on phylogenetic clustering analyses, we predict both to have organic substrate profiles, and possible involvement in energy homeostasis. Therefore, we monitored gene regulation changes in mouse embryonic primary cultures after amino acid starvations and found both transporters to be upregulated after 3 h of starvation. Interestingly, in mice subjected to 24 h of food starvation, both transporters were downregulated in the hypothalamus, while Mfsd14a was also downregulated in the brainstem. In addition, in mice fed a high fat diet (HFD), upregulation of both transporters was seen in the striatum. Both MFSD14A and MFSD14B were intracellular neuronal membrane-bound proteins, expressed in the Golgi and Endoplasmic reticulum, affected by both starvation and HFD to varying degree in the mouse brain. PMID:28179877

  7. Development and evaluation of a transportable fast gas chromatograph for the monitoring of organic vapors in air

    SciTech Connect

    Gonzalez, J.A.; Levine, S.P.; Berkley, R.E.

    1993-01-01

    Gas chromatography has the potential to be a real-time or near real-time monitoring method for organics in air. A transportable fast GC with FID/ECD and PID/ECD configurations has been developed. Preliminary evaluation has shown that all design features and improvements of the instrument worked successfully.

  8. The transportation of fine arts materials aboard the space shuttle Columbia. GAS payload No. 481: Vertical horizons

    NASA Technical Reports Server (NTRS)

    Kurtz, Ellery; Wishnow, Howard

    1988-01-01

    The Vertical Horizons experiment represents an initial investigation into the transportation of fine arts materials aboard a space shuttle. Within the confines of a GAS canister, artist quality fine arts materials were packaged and exposed to the rigors of space flight in an attempt to identify adverse effects.

  9. Plant water use efficiency over geological time--evolution of leaf stomata configurations affecting plant gas exchange.

    PubMed

    Assouline, Shmuel; Or, Dani

    2013-01-01

    Plant gas exchange is a key process shaping global hydrological and carbon cycles and is often characterized by plant water use efficiency (WUE - the ratio of CO2 gain to water vapor loss). Plant fossil record suggests that plant adaptation to changing atmospheric CO2 involved correlated evolution of stomata density (d) and size (s), and related maximal aperture, amax . We interpreted the fossil record of s and d correlated evolution during the Phanerozoic to quantify impacts on gas conductance affecting plant transpiration, E, and CO2 uptake, A, independently, and consequently, on plant WUE. A shift in stomata configuration from large s-low d to small s-high d in response to decreasing atmospheric CO2 resulted in large changes in plant gas exchange characteristics. The relationships between gas conductance, gws , A and E and maximal relative transpiring leaf area, (amax ⋅d), exhibited hysteretic-like behavior. The new WUE trend derived from independent estimates of A and E differs from established WUE-CO2 trends for atmospheric CO2 concentrations exceeding 1,200 ppm. In contrast with a nearly-linear decrease in WUE with decreasing CO2 obtained by standard methods, the newly estimated WUE trend exhibits remarkably stable values for an extended geologic period during which atmospheric CO2 dropped from 3,500 to 1,200 ppm. Pending additional tests, the findings may affect projected impacts of increased atmospheric CO2 on components of the global hydrological cycle.

  10. Deep earthquakes beneath mount st. Helens: evidence for magmatic gas transport?

    PubMed

    Weaver, C S; Zollweg, J E; Malone, S D

    1983-09-30

    Small-magnitude earthquakes began beneath Mount St. Helens 40 days before the eruption of 20 March 1982. Unlike earlier preeruption seismicity for this volcano, which had been limited to shallow events (less than 3 kilometers), many of these earthquakes were deep (between 5 and 11 kilometers). The location of these preeruptive events at such depth indicates that a larger volume of the volcanic system was affected prior to the 20 March eruption than prior to any of the earlier dome-building eruptions. The depth-time relation between the deep earthquakes and the explosive onset of the eruption is compatible with the upward migration of magmatic gas released from a separate deep reservoir.

  11. Deep earthquakes beneath Mount St. Helens: Evidence for magmatic gas transport?

    USGS Publications Warehouse

    Weaver, C.S.; Zollweg, J.E.; Malone, S.D.

    1983-01-01

    Small-magnitude earthquakes began beneath Mount St. Helens 40 days before the eruption of 20 March 1982. Unlike earlier preeruption seismicity for this volcano, which had been limited to shallow events (less than 3 kilometers), many of these earthquakes were deep (between 5 and 11 kilometers). The location of these preeruptive events at such depth indicates that a larger volume of the volcanic system was affected prior to the 20 March eruption than prior to any of the earlier dome-building eruptions. The depth-time relation between the deep earthquakes and the explosive onset of the eruption is compatible with the upward migration of magmatic gas released from a separate deep reservoir.

  12. Analysis of matrix effects critical to microbial transport in organic waste-affected soils across laboratory and field scales

    NASA Astrophysics Data System (ADS)

    Unc, Adrian; Goss, Michael J.; Cook, Simon; Li, Xunde; Atwill, Edward R.; Harter, Thomas

    2012-06-01

    Organic waste applications to soil (manure, various wastewaters, and biosolids) are among the most significant sources of bacterial contamination in surface and groundwater. Transport of bacteria through the vadose zone depends on flow path geometry and stability and is mitigated by interaction between soil, soil solution, air-water interfaces, and characteristics of microbial surfaces. After initial entry, the transport through soil depends on continued entrainment of bacteria and resuspension of those retained in the porous structure. We evaluated the retention of bacteria-sized artificial microspheres, varying in diameter and surface charge and applied in different suspending solutions, by a range of sieved soils contained in minicolumns, the transport of hydrophobic bacteria-sized microspheres through undisturbed soil columns as affected by waste type under simulated rainfall, and the field-scale transport of Enterococcus spp. to an unconfined sandy aquifer after the application of liquid manure. Microsphere retention reflected microsphere properties. The soil type and suspending solution affected retention of hydrophilic but not hydrophobic particles. Retention was not necessarily facilitated by manure-microsphere-soil interactions but by manure-soil interactions. Undisturbed column studies confirmed the governing role of waste type on vadose-zone microsphere transport. Filtration theory applied as an integrated analysis of transport across length scales showed that effective collision efficiency depended on the distance of travel. It followed a power law behavior with the power coefficient varying from ˜0.4 over short distances to >0.9 over 1 m (i.e., very little filtration for a finite fraction of biocolloids), consistent with reduced influence of soil solution and biocolloid properties at longer travel distances.

  13. Influence of state-to-state vibrational distributions on transport coefficients of a single gas

    NASA Astrophysics Data System (ADS)

    Kustova, Elena V.; Kremer, Gilberto M.

    2016-11-01

    In this work the influence of the size of vibrationally and rotationally excited molecules on the collision integrals required for the calculation of state-to-state transport coefficients is discussed. Several diatomic molecules are considered: N2, O2, NO, H2, Cl2. It is shown that whereas the molecular size is not affected by rotational excitation, it strongly depends on the vibrational state. Particular emphasis is given to the shear viscosity and thermal conductivity coefficients calculated in the temperature range 2 500-20 000 K for equilibrium Boltzmann vibrational distributions. It is shown that under conditions of local thermal equilibrium, the effect of vibrational excitation on the shear viscosity and thermal conductivity coefficients are found to be negligible for temperatures below 5 000 K, except for the case of Cl2 molecule where at 5 000 K the effect is about 10%. For T > 10 000 K, the contribution of excited states becomes important and reaches 10-25%.

  14. Benefits on public health from transport-related greenhouse gas mitigation policies in Southeastern European cities.

    PubMed

    Sarigiannis, D A; Kontoroupis, P; Nikolaki, S; Gotti, A; Chapizanis, D; Karakitsios, S

    2017-02-01

    Climate change is a major environmental threat of our time. Cities have a significant impact on greenhouse gas emissions as most of the traffic, industry, commerce and more than 50% of world population is situated in urban areas. Southern Europe is a region that faces financial turmoil, enhanced migratory fluxes and climate change pressure. The case study of Thessaloniki is presented, one of the only two cities in Greece with established climate change action plans. The effects of feasible traffic policies in year 2020 are assessed and their potential health impact is compared to a business as usual scenario. Two types of measures are investigated: operation of underground rail in the city centre and changes in fleet composition. Potential co-benefits from reduced greenhouse gas emissions on public health by the year 2020 are computed utilizing state-of-the-art concentration response functions for PMx, NO2 and C6H6. Results show significant environmental health and monetary co-benefits when the city metro is coupled with appropriate changes in the traffic composition. Monetary savings due to avoided mortality or leukaemia incidence corresponding to the reduction in PM10, PM2.5, NO2 and C6H6 exposure will be 56.6, 45, 37.7 and 1.0 million Euros respectively. Promotion of 'green' transportation in the city (i.e. the wide use of electric vehicles), will provide monetary savings from the reduction in PM10, PM2.5, NO2 and C6H6 exposure up to 60.4, 49.1, 41.2 and 1.08 million Euros. Overall, it was shown that the respective GHG emission reduction policies resulted in clear co-benefits in terms of air quality improvement, public health protection and monetary loss mitigation.

  15. Spatial and intertemporal arbitrage in the California natural gas transportation and storage network

    NASA Astrophysics Data System (ADS)

    Uria Martinez, Rocio

    Intertemporal and spatial price differentials should provide the necessary signals to allocate a commodity efficiently inside a network. This dissertation investigates the extent to which decisions in the California natural gas transportation and storage system are taken with an eye on arbitrage opportunities. Daily data about flows into and out of storage facilities in California over 2002-2006 and daily spreads on the NYMEX futures market are used to investigate whether the injection profile is consistent with the "supply-of-storage" curve first observed by Working for wheat. Spatial price differentials between California and producing regions fluctuate throughout the year, even though spot prices at trading hubs across North America are highly correlated. In an analysis of "residual supply", gas volumes directed to California are examined for the influence of those fluctuations in locational differentials. Daily storage decisions in California do seem to be influenced by a daily price signal that combines the intertemporal spread and the locational basis between California and the Henry Hub, in addition to strong seasonal and weekly cycles. The timing and magnitude of the response differs across storage facilities depending on the regulatory requirements they face and the type of customers they serve. In contrast, deviations in spatial price differentials from the levels dictated by relative seasonality in California versus competing regions do not trigger significant reallocations of flows into California. Available data for estimation of both the supply-of-storage and residual-supply curves aggregate the behavior of many individuals whose motivations and attentiveness to prices vary. The resulting inventory and flow profiles differ from those that a social planner would choose to minimize operating costs throughout the network. Such optimal allocation is deduced from a quadratic programming model, calibrated to 2004-2005, that acknowledges relative seasonality

  16. Poly-use multi-level sampling system for soil-gas transport analysis in the vadose zone.

    PubMed

    Nauer, Philipp A; Chiri, Eleonora; Schroth, Martin H

    2013-10-01

    Soil-gas turnover is important in the global cycling of greenhouse gases. The analysis of soil-gas profiles provides quantitative information on below-ground turnover and fluxes. We developed a poly-use multi-level sampling system (PMLS) for soil-gas sampling, water-content and temperature measurement with high depth resolution and minimal soil disturbance. It is based on perforated access tubes (ATs) permanently installed in the soil. A multi-level sampler allows extraction of soil-gas samples from 20 locations within 1 m depth, while a capacitance probe is used to measure volumetric water contents. During idle times, the ATs are sealed and can be equipped with temperature sensors. Proof-of-concept experiments in a field lysimeter showed good agreement of soil-gas samples and water-content measurements compared with conventional techniques, while a successfully performed gas-tracer test demonstrated the feasibility of the PMLS to determine soil-gas diffusion coefficients in situ. A field application of the PMLS to quantify oxidation of atmospheric CH4 in a field lysimeter and in the forefield of a receding glacier yielded activity coefficients and soil-atmosphere fluxes well in agreement with previous studies. With numerous options for customization, the presented tool extends the methodological choices to investigate soil-gas transport in the vadose zone.

  17. Analysis of Time-Varying, Stochastic Gas Transport through Graphene Membranes.

    PubMed

    Drahushuk, Lee W; Wang, Luda; Koenig, Steven P; Bunch, J Scott; Strano, Michael S

    2016-01-26

    Molecular transport measurements through isolated nanopores can greatly inform our understanding of how such systems can select for molecular size and shape. In this work, we present a detailed analysis of experimental gas permeation data through single layer graphene membranes under batch depletion conditions parametric in starting pressure for He, H2, Ne, and CO2 between 100 and 670 kPa. We show mathematically that the observed intersections of the membrane deflection curves parametric in starting pressure are indicative of a time dependent membrane permeance (pressure normalized molecular flow). Analyzing these time dependent permeance data for He, Ne, H2, and CO2 shows remarkably that the latter three gases exhibit discretized permeance values that are temporally repeated. Such quantized fluctuations (called "gating" for liquid phase nanopore and ion channel systems) are a hallmark of isolated nanopores, since small, but rapid changes in the transport pathway necessarily influence a single detectable flux. We analyze the fluctuations using a Hidden Markov model to fit to discrete states and estimate the activation barrier for switching at 1.0 eV. This barrier is and the relative fluxes are consistent with a chemical bond rearrangement of an 8-10 atom vacancy pore. Furthermore, we use the relations between the states given by the Markov network for few pores to determine that three pores, each exhibiting two state switching, are responsible for the observed fluctuations; and we compare simulated control data sets with and without the Markov network for comparison and to establish confidence in our evaluation of the limited experimental data set.

  18. Vapour transport of rare earth elements (REE) in volcanic gas: Evidence from encrustations at Oldoinyo Lengai

    NASA Astrophysics Data System (ADS)

    Gilbert, C. D.; Williams-Jones, A. E.

    2008-10-01

    Fumarolic encrustations and natrocarbonatite lava from the active crater of Oldoinyo Lengai volcano, Tanzania, were sampled and analysed. Two types of encrustation were distinguished on the basis of their REE content, enriched (~ 2800-5600 × [REE chondrite]) and depleted (~ 100-200 × [REE chondrite]) relative to natrocarbonatite (1700-1900 × [REE chondrite]. REE-enriched encrustations line the walls of actively degassing fumaroles, whereas REE-depleted encrustations occur mainly along cracks in and as crusts on cooling natrocarbonatite lava flows; one of the low REE encrustation samples was a stalactite from the wall of a possible fumarole. The encrustations are interpreted to have different origins, the former precipitating from volcanic gas and the latter from meteoric/ground water converted to steam by the heat of the overlying lava flow(s). REE-profiles of encrustations and natrocarbonatite are parallel, suggesting that there was no preferential mobilization of specific REE by either volcanic vapour or meteoric water vapour. The elevated REE-content of the first group of encrustations suggests that direct REE-transport from natrocarbonatite to volcanic vapour is possible. The REE trends observed in samples precipitating directly from the volcanic vapour cannot be explained by dry volatility based on the available data as there is no evidence in the encrustation compositions of the greatly enhanced volatility predicted for Yb and Eu. The observed extreme REE-fractionation with steep La/Sm slopes parallel to those of the natrocarbonatite reflects solvation and complexation reactions in the vapour phase that did not discriminate amongst the different REE or similar transport of REE in both the natrocarbonatite magma and its exsolving vapour. The low concentrations of REE in the encrustations produced by meteoric vapour suggest that the temperature was too low or that this vapour did not contain the ligands necessary to permit significant mobilization of the REE.

  19. Fosfomycin resistance plasmids do not affect fosfomycin transport into Escherichia coli.

    PubMed Central

    León, J; García-Lobo, J M; Ortiz, J M

    1982-01-01

    Escherichia coli cells carrying fosfomycin resistance plasmids were able to take up fosfomycin from the medium to the same extent as plasmid-free bacteria. The antibiotic entered the plasmid-harboring cells by means of the glpT and uhp transport systems, as is the case with susceptible bacteria. Active fosfomycin could be detected in soluble extracts of cells which had previously been incubated in the presence of the antibiotic. Furthermore, fosfomycin resistance plasmids did not confer on E. coli cells resistance to the novel antibiotic FR-31564, which is incorporated by the same transport systems as fosfomycin. We conclude that, in contrast to chromosomal resistance mutants, altered transport does not play a role in the plasmid-encoded fosfomycin resistance mechanism. PMID:7044304

  20. Dietary inulin affects the morphology but not the sodium-dependent glucose and glutamine transport in the jejunum of broilers.

    PubMed

    Rehman, H; Rosenkranz, C; Böhm, J; Zentek, J

    2007-01-01

    Inulin, a prebiotic, is a fermentable oligosaccharide that may affect the intestinal mucosal architecture and the electrophysiological parameters. The effects of a diet with added inulin were tested on the jejunal morphology and electrogenic transport of Glc and Gln from the jejunal mucosa in broilers. Short-circuit current and transmucosal tissue resistance of jejunal flaps were measured in Ussing chambers. The feeding experiment was carried out in broilers (n = 40) using 1% inulin with an application period of 5 wk. The inulin-containing diet resulted in longer jejunal villi (P < 0.05) and deeper crypts (P < 0.01) than in control birds without affecting villus:crypt depth. Basal short-circuit current value remained unaffected by dietary treatment. Inulin supplementation did not modify the electrogenic transport of Glc and Gln in the jejunal mucosa. The basal value of transmucosal tissue resistance was significantly lower (P < 0.001) in the inulin-fed group compared with the control group. In conclusion, inulin supplementation affected the jejunal mucosal architecture but did not modify the electrogenic transport of Glc and amino acid under present experimental condition.

  1. Net greenhouse gas emissions affected by sheep grazing under dryland cropping systems

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Sheep grazing to control weeds during fallow may influence greenhouse gas (GHG) emissions by consuming crop residue and returning feces and urine to the soil. We evaluated the effect of sheep grazing compared to herbicide application for weed control on soil temperature and water content at the 0- t...

  2. Soil greenhouse gas emissions affected by sheep grazing under dryland cropping systems

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Sheep grazing to control weeds during fallow may influence soil greenhouse gas (CO2, N2O, and CH4) emissions by consuming crop residue and returning feces and urine to the soil. An experiment was conducted to evaluate the effect of sheep grazing compared to herbicide application on soil temperature ...

  3. Sub-surface soil carbon changes affects biofuel greenhouse gas emissions

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Changes in direct soil organic carbon (SOC) can have a major impact on overall greenhouse gas (GHG) emissions from biofuels when using life-cycle assessment (LCA). Estimated changes in SOC, when accounted for in an LCA, are typically derived from near-surface soil depths (<30 cm). Changes in subsurf...

  4. Net global warming potential and greenhouse gas intensity affected by cropping sequence and nitrogen fertilization

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Little information is available about management practice effects on the net global warming potential (GWP) and greenhouse gas intensity (GHGI) under dryland cropping systems. We evaluated the effects of cropping sequences (conventional-tillage malt barley [Hordeum vulgaris L.]–fallow [CTB-F], no-ti...

  5. Manure and inorganic N affect trace gas emissions under semi-arid irrigated corn

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Dairy manure is often applied to cropped soils as a substitute for inorganic N fertilizers, but the impacts of manure on soil greenhouse gas (GHG) fluxes, yields and soil N are uncertain in the semi-arid western U.S. Soil carbon dioxide (CO2-C), methane (CH4-C), and nitrous oxide (N2O-N) emissions ...

  6. Ecosystem Warming Affects Vertical Distribution of Leaf Gas Exchange Properties and Water Relations of Spring Wheat

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The vertical distribution of gas exchange and water relations responses to full-season in situ infrared (IR) warming were evaluated for hard red spring wheat (Triticum aestivum L. cv. Yecora Rojo) grown in an open field in a semiarid desert region of the Southwest USA. A Temperature Free-Air Contro...

  7. [Aero-transport of a MDR-TB affected patient with bio-containment systems].

    PubMed

    Lastilla, M; Bisetti, R; Autore, A; Aragonese, F; Di Stefano, M; Sarlo, O

    2007-01-01

    The Italian Air Force medical service, in order to attend to its duty, has to deal with the search, rescue and aero-medical evacuation of the wounded and sick. Due to the increase of air transportation, the likelihood of contracting disease, such as haemorrhagic fevers has risen and it is necessary to know how to treat a patient abroad suffering from severe infectious disease without running any risk either for the medical personnel or for the air crew. The military sanitary service of the Air Force has been preparing for this purpose through a meticulous preparation in Italy and in the USA in order to satisfy these need and through the use of stretchers specifically designed to transport highly contagious patients: Aircraft Transit Isolators (ATIs) and Stretcher Transit Isolators (STIs). These particular medical tools are provided by filter HEPA and they are completely insulated in a PVC envelope. The former (ATI) is used to transport the patient by airplane, the latter is used for road travel. Last January 24th the first real mission was performed transporting a severe TBC-MDR (case) from Alghero to Milan. All went well and the patient left the hospital of Sondalo two months later.

  8. 77 FR 59840 - Statutory Amendments Affecting Transportation of Agricultural Commodities and Farm Supplies

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-10-01

    ... retail store deliveries. Thus, it is clear Congress intended to limit this exemption to retail... transportation from a retail distribution point of the farm supply to a location (farm or other location where the farm supply product would be used) within a 100 air-mile radius of the retail distribution...

  9. Yeast culture supplement during nursing and transport affects immunity and intestinal microbial ecology of weanling pigs

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Weaning and transport stress can have a negative impact on the piglet's immune system and intestinal microbiota. The objective of this study was to determine the influence of a yeast product on innate immunity and microbial ecology of the gastrointestinal tract following stress of weaning and trans...

  10. Runoff nutrient transport as affected by land application method, swine growth stage, and runoff rate

    Technology Transfer Automated Retrieval System (TEKTRAN)

    This study was conducted to measure the effects of slurry application method, swine growth stage, and flow rate on runoff nutrient transport. Swine slurry was obtained from production units containing grower pigs, finisher pigs, or sows and gilts. The swine slurry was applied using broadcast, disk, ...

  11. Intestinal microbial affects of yeast products on weaned and transport stressed pigs

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Study objectives were to determine effects of a commercially available yeast product (XPC, Diamond-V Mills) and stress of transportation on total Enterobacteriaceae, Escherichia coli, coliforms, and Lactobacilli populations in the intestine of weaning pigs. In a RCB design with a 2 x 2 factorial ar...

  12. A mutation in protein phosphatase 2A regulatory subunit A affects auxin transport in Arabidopsis

    NASA Technical Reports Server (NTRS)

    Garbers, C.; DeLong, A.; Deruere, J.; Bernasconi, P.; Soll, D.; Evans, M. L. (Principal Investigator)

    1996-01-01

    The phytohormone auxin controls processes such as cell elongation, root hair development and root branching. Tropisms, growth curvatures triggered by gravity, light and touch, are also auxin-mediated responses. Auxin is synthesized in the shoot apex and transported through the stem, but the molecular mechanism of auxin transport is not well understood. Naphthylphthalamic acid (NPA) and other inhibitors of auxin transport block tropic curvature responses and inhibit root and shoot elongation. We have isolated a novel Arabidopsis thaliana mutant designated roots curl in NPA (rcn1). Mutant seedlings exhibit altered responses to NPA in root curling and hypocotyl elongation. Auxin efflux in mutant seedlings displays increased sensitivity to NPA. The rcn1 mutation was transferred-DNA (T-DNA) tagged and sequences flanking the T-DNA insert were cloned. Analysis of the RCN1 cDNA reveals that the T-DNA insertion disrupts a gene for the regulatory A subunit of protein phosphatase 2A (PP2A-A). The RCN1 gene rescues the rcn1 mutant phenotype and also complements the temperature-sensitive phenotype of the Saccharomyces cerevisiae PP2A-A mutation, tpd3-1. These data implicate protein phosphatase 2A in the regulation of auxin transport in Arabidopsis.

  13. A mutation in protein phosphatase 2A regulatory subunit A affects auxin transport in Arabidopsis.

    PubMed Central

    Garbers, C; DeLong, A; Deruére, J; Bernasconi, P; Söll, D

    1996-01-01

    The phytohormone auxin controls processes such as cell elongation, root hair development and root branching. Tropisms, growth curvatures triggered by gravity, light and touch, are also auxin-mediated responses. Auxin is synthesized in the shoot apex and transported through the stem, but the molecular mechanism of auxin transport is not well understood. Naphthylphthalamic acid (NPA) and other inhibitors of auxin transport block tropic curvature responses and inhibit root and shoot elongation. We have isolated a novel Arabidopsis thaliana mutant designated roots curl in NPA (rcn1). Mutant seedlings exhibit altered responses to NPA in root curling and hypocotyl elongation. Auxin efflux in mutant seedlings displays increased sensitivity to NPA. The rcn1 mutation was transferred-DNA (T-DNA) tagged and sequences flanking the T-DNA insert were cloned. Analysis of the RCN1 cDNA reveals that the T-DNA insertion disrupts a gene for the regulatory A subunit of protein phosphatase 2A (PP2A-A). The RCN1 gene rescues the rcn1 mutant phenotype and also complements the temperature-sensitive phenotype of the Saccharomyces cerevisiae PP2A-A mutation, tpd3-1. These data implicate protein phosphatase 2A in the regulation of auxin transport in Arabidopsis. Images PMID:8641277

  14. Oxic and anoxic conditions affect arsenic (As) accumulation and arsenite transporter expression in rice.

    PubMed

    Wu, Chuan; Huang, Liu; Xue, Sheng-Guo; Pan, Wei-Song; Zou, Qi; Hartley, William; Wong, Ming-Hung

    2017-02-01

    Arsenic (As) exposure from rice consumption has now become a global health issue. This study aimed to investigate the effects of rice rhizosphere oxic conditions on silicate transporter (responsible for arsenite transportation) expressions, and on As accumulation and speciation in four rice genotypes, including two hybrid genotypes (Xiangfengyou9, Shenyou9586) and two indica subspecies (Xiangwanxian17, Xiangwanxian12). Oxic and anoxic treatments have different effects on root length (p < 0.001) and weight (p < 0.05). Total As concentrations in roots were dramatically lower in oxic treatments (88.8-218 mg/kg), compared to anoxic treatments (147-243 mg/kg) (p < 0.001). Moreover, root and shoot arsenite concentrations in oxic treatments were lower than that in anoxic treatments in arsenite treatments. The relative abundance of silicate transporter expressions displayed a trend of down-regulation in oxic treatments compared to anoxic treatments, especially significantly different for Xiangwanxian17, Xiangwanxian12 in Lsi1 expressions (p < 0.05), Xiangfengyou9, Shenyou9586, Xiangwanxian17 in Lsi2 expressions (p < 0.05). However, there were no significant differences of transporter expressions in different As treatments and genotypes. It may be a possible reason for low As accumulation in rice growing aerobically compared to flooded condition and a potential route to reduce the health risk of As in rice.

  15. An experimental trace gas investigation of fluid transport and mixing in a circular-to-rectangular transition duct

    NASA Technical Reports Server (NTRS)

    Reichert, B. A.; Hingst, W. R.; Okiishi, T. H.

    1991-01-01

    An ethylene trace gas technique was used to map out fluid transport and mixing within a circular to rectangular transition duct. Ethylene gas was injected at several points in a cross stream plane upstream of the transition duct. Ethylene concentration contours were determined at several cross stream measurement planes spaced axially within the duct. The flow involved a uniform inlet flow at a Mach number level of 0.5. Statistical analyses were used to quantitatively interpret the trace gas results. Also, trace gas data were considered along with aerodynamic and surface flow visualization results to ascertain transition duct flow phenomena. Convection of wall boundary layer fluid by vortices produced regions of high total pressure loss in the duct. The physical extent of these high loss regions is governed by turbulent diffusion.

  16. Electrification of the transportation sector offers limited country-wide greenhouse gas reductions

    NASA Astrophysics Data System (ADS)

    Meinrenken, Christoph J.; Lackner, Klaus S.

    2014-03-01

    Compared with conventional propulsion, plugin and hybrid vehicles may offer reductions in greenhouse gas (GHG) emissions, regional air/noise pollution, petroleum dependence, and ownership cost. Comparing only plugins and hybrids amongst themselves, and focusing on GHG, relative merits of different options have been shown to be more nuanced, depending on grid-carbon-intensity, range and thus battery manufacturing and weight, and trip patterns. We present a life-cycle framework to compare GHG emissions for three drivetrains (plugin-electricity-only, gasoline-only-hybrid, and plugin-hybrid) across driving ranges and grid-carbon-intensities, for passenger cars, vans, buses, or trucks (well-to-wheel plus storage manufacturing). Parameter and model uncertainties are quantified via sensitivity analyses. We find that owing to the interplay of range, GHG/km, and portions of country-wide kms accessible to electrification, GHG reductions achievable from plugins (whether electricity-only or hybrids) are limited even when assuming low-carbon future grids. Furthermore, for policy makers considering GHG from electricity and transportation sectors combined, plugin technology may in fact increase GHG compared to gasoline-only-hybrids, regardless of grid-carbon-intensity.

  17. Transport Properties of He-N{sub 2} Binary Gas Mixtures for CBC Space Applications

    SciTech Connect

    Tournier, Jean-Michel P.; El-Genk, Mohamed S.

    2008-01-21

    In order to reduce the size and mass of the single-shaft turbo-machines, with little impact on the size of the heat transfer components in the CBC loop, He-Xe binary mixture with a molecular weight of 40 g/mole has been the working fluid of choice in space nuclear reactor power systems with Close Brayton Cycle (CBC) for energy conversion. This working fluid is also a suitable coolant for the fission reactors heat source designed with fast neutron energy spectra. For space nuclear reactors with thermal neutron energy spectra, however, the high capture neutron cross-section of Xe will reduce the beginning-of-life excess reactivity of the reactor, decreasing its effective operation lifetime. In addition, the neutron activation of Xe in the reactor will introduce a radioactivity source term in the CBC loop. Alternative working fluids with no activation concerns and comparable performance are N{sub 2} and the binary mixtures of He-N{sub 2}. This paper calculates the transport properties of these working fluids and compares their values to those of noble gas binary mixtures at the temperatures and pressures expected in CBC space reactor power system applications. Also investigated is the impact of using these working fluids on the pressure losses, heat transfer coefficient, and the aerodynamic loading of the blades in the CBC turbo-machines.

  18. Transport of manure-borne testosterone in soils affected by artificial rainfall events.

    PubMed

    Qi, Yong; Zhang, Tian C

    2016-04-15

    Information is very limited on fate and transport of steroidal hormones in soils. In this study, the rainfall simulation tests were conducted with a soil slab reactor to investigate the transport of manure-borne testosterone in a silty-clay loam soil under six controllable operation conditions (i.e., three rainfall intensities and two tillage practices). The properties [e.g., rainwater volume, particle size distribution (PSD)] of the slurry samples collected in runoff and leachate at different time intervals were measured; their correlation with the distribution of testosterone among runoff, leachate and soil matrix was analyzed. The results indicated that more than 88% of the testosterone was held by the applied manure and/or soil matrix even under the rainfall intensity of 100-year return frequency. The runoff facilitated testosterone transport through both dissolved and particle-associated phases, with the corresponding mass ratio being ∼7 to 3. Soil particles collected through runoff were mainly silt-sized aggregates (STA) and clays, indicating the necessity of using partially-dispersed soil particles as testing materials to conduct batch tests (e.g., sorption/desorption). No testosterone was detected at the soil depth >20 cm or in the leachate samples, indicating that transport of testosterone through the soil is very slow when there is no preferential flow. Tillage practice could impede the transport of testosterone in runoff. For the first time, results and the methodologies of this study allow one to quantify the hormone distribution among runoff, leachate and soil matrix at the same time and to obtain a comprehensive picture of the F/T of manure-borne testosterone in soil-water environments.

  19. Ammonia Gas Transport and Reactions in Unsaturated Sediments: Implications for Use as an Amendment to Immobilize Inorganic Contaminants

    SciTech Connect

    Zhong, Lirong; Szecsody, James E.; Truex, Michael J.; Williams, Mark D.; Liu, Yuanyuan

    2015-05-01

    Use of gas-phase amendments for in situ remediation of inorganic contaminants in unsaturated sediments of the vadose zone may be advantageous, but there has been limited development and testing of gas remediation technologies. Treatment with ammonia gas has been studied and has a potential for use in treating inorganic contaminants such as uranium because it induces a high pore-water pH causing mineral dissolution and subsequent formation of stable precipitates that decrease the mobility of some contaminants. For field application, knowledge of ammonia transport and the geochemical reactions induced by ammonia is needed. Laboratory studies were conducted to support calculations needed for field treatment design, to quantify advective and diffusive ammonia transport in unsaturated sediments, to evaluate reactions among gas, sediment, and water, and to study reaction-induced pore-water chemistry changes as a function of ammonia delivery conditions. Ammonia gas quickly partitions into sediment pore water and increases pH up to 13.2. Injected ammonia gas front movement can be reasonably predicted by gas flow rate and equilibrium partitioning. The ammonia gas diffusion rate is a function of the water content in the sediment. Measured diffusion front movement was 0.05, 0.03, and 0.02 cm/hr. in sediments with 2.0%, 8.7%, and 13.0% water content, respectively. Sodium, aluminum, and silica pore-water concentrations increase on exposure to ammonia and then decline as aluminosilicates precipitate with declining pH. When uranium is present in the sediment and pore water, up to 85% of the water-leachable uranium was immobilized by ammonia treatment.

  20. Influence of chemical structure on hydration and gas transport mechanisms of sulfonated poly(aryl ether ketone) membranes.

    PubMed

    Simon, Sandra; Espuche, Eliane; Gouanvé, Fabrice; Chauveau, Edouard; Marestin, Catherine; Mercier, Régis

    2012-10-25

    This work reports the influence of the chemical structure of two sulfonated poly(aryl ether ketone)s (SPAEK) on the hydration and gas transport mechanism of thin membranes made thereupon. For this purpose, two sulfonated poly(aryl ether ketone)s having the same ionic exchange capacity (IEC) but bearing a different repartition of the sulfonic acid groups along the polymer backbone were prepared. These polymers were synthesized by direct copolymerization of two specific sulfonated precursors, bisphenol AF and 4,4'-difluorobenzophenone. The morphology of the membranes was studied by transmission electron microscopy, and the thermal properties of the ionomers were determined from differential scanning calorimetry and thermogravimetric analyses. A detailed analysis of the water sorption isotherms and kinetics was performed. The gas transport properties were also determined for He, H(2), and CO(2) in the full range of water activity. From the detailed analysis of the water sorption isotherm and of the relative contributions of the Fickian diffusion and relaxation phenomena, a water sorption mechanism was proposed in relation with the SPAEK architectures and polymers' chain mobility. This mechanism allowed explaining the different evolution of the gas transport properties observed as a function of the gas nature and hydration rate.

  1. How does metallicity affect the gas and dust properties of galaxies?

    NASA Astrophysics Data System (ADS)

    Madden, Suzanne C.; Cormier, Diane; Rémy-Ruyer, Aurélie

    Comparison of the ISM properties of a wide range of metal poor galaxies with normal metal-rich galaxies reveals striking differences. We find that the combination of the low dust abundance and the active star formation results in a very porous ISM filled with hard photons, heating the dust in dwarf galaxies to overall higher temperatures than their metal-rich counterparts. This results in photodissociation of molecular clouds to greater depths, leaving relatively large PDR envelopes and difficult-to-detect CO cores. From detailed modeling of the low-metallicity ISM, we find significant fractions of CO-dark H2 - a reservoir of molecular gas not traced by CO, but present in the [CII] and [CI]-emitting envelopes. Self-consistent analyses of the neutral and ionized gas diagnostics along with the dust SED is the necessary way forward in uncovering the multiphase structure of galaxies.

  2. Purge gas protected transportable pressurized fuel cell modules and their operation in a power plant

    DOEpatents

    Zafred, Paolo R.; Dederer, Jeffrey T.; Gillett, James E.; Basel, Richard A.; Antenucci, Annette B.

    1996-01-01

    A fuel cell generator apparatus and method of its operation involves: passing pressurized oxidant gas, (O) and pressurized fuel gas, (F), into fuel cell modules, (10 and 12), containing fuel cells, where the modules are each enclosed by a module housing (18), surrounded by an axially elongated pressure vessel (64), where there is a purge gas volume, (62), between the module housing and pressure vessel; passing pressurized purge gas, (P), through the purge gas volume, (62), to dilute any unreacted fuel gas from the modules; and passing exhaust gas, (82), and circulated purge gas and any unreacted fuel gas out of the pressure vessel; where the fuel cell generator apparatus is transpatable when the pressure vessel (64) is horizontally disposed, providing a low center of gravity.

  3. Correlation between gas compositions and physical phenomena affecting the reservoir fluid in Palinpinon geothermal field (Philippines)

    SciTech Connect

    D'More F.; Nuti, S.; Ruaya, J.R.; Ramos-Candelaria, M.N.; Seastres, J.S.

    1993-01-28

    Using thermodynamic gas equilibria to calculate temperature and steam fraction in the reservoir, three main physical phenomena due to exploitation of Palinpinon field are identified. 1) Pressure drawdown producing a local increase in the computed steam fraction, with the fluid maintaining high temperature values (close to 300°C). Strong decline in flow rate is observed. 2) Irreversible steam losses from the original high temperature liquid phase during its ascent through fractures in upper zones of the reservoir. Steam is generally lost at temperatures (e.g. 240°C) lower then those of the original aquifer. 3) Dilution and cooling effects due to reinjection fluid returns. These are function of the local geostructural conditions linking through fractures the injectors and production wells. The computed fraction of the recovered reinjected brine can in some case exceed 80% of the total produced fluid. At the same time the computed gas equilibration temperatures can decline from 280-300°C to as low as 215-220°C. Comparing these values with the well bottom measured temperatures, the proposed methodology based on gas chemistry gives more reliable temperature estimate than water chemistry based geothermometers for fluids with high fractions of injected brine.

  4. Allocation, stress tolerance and carbon transport in plants: how does phloem physiology affect plant ecology?

    PubMed

    Savage, Jessica A; Clearwater, Michael J; Haines, Dustin F; Klein, Tamir; Mencuccini, Maurizio; Sevanto, Sanna; Turgeon, Robert; Zhang, Cankui

    2016-04-01

    Despite the crucial role of carbon transport in whole plant physiology and its impact on plant-environment interactions and ecosystem function, relatively little research has tried to examine how phloem physiology impacts plant ecology. In this review, we highlight several areas of active research where inquiry into phloem physiology has increased our understanding of whole plant function and ecological processes. We consider how xylem-phloem interactions impact plant drought tolerance and reproduction, how phloem transport influences carbon allocation in trees and carbon cycling in ecosystems and how phloem function mediates plant relations with insects, pests, microbes and symbiotes. We argue that in spite of challenges that exist in studying phloem physiology, it is critical that we consider the role of this dynamic vascular system when examining the relationship between plants and their biotic and abiotic environment.

  5. Quantifying the effect of settlement and gas on solute flow and transport through treated municipal solid waste

    NASA Astrophysics Data System (ADS)

    Woodman, N. D.; Siddiqui, A. A.; Powrie, W.; Stringfellow, A.; Beaven, R. P.; Richards, D. J.

    2013-10-01

    The effect of degradation and settlement on transport properties of mechanically and biologically treated (MBT) waste was examined by applying three different tracers to two waste columns (~ 0.5 m diameter) in a series of closed-loop experiments. One column was allowed to biodegrade and the other was bio-suppressed. Permeability and drainable porosity were reduced by settlement, in line with previous results. A dual-porosity model performed well against the data and suggested that more preferential flow occurred early on in the un-degraded column. Diffusion timescales were found to be between 0.8 and 6 days. Volumetric water contents of the mobile region were found to be small in the bio-suppressed cell (~ 0.01) and even smaller values were found in the degrading waste, possibly due to displacement by gas. Once either settlement or gas production had disrupted this pattern into a more even flow, subsequent compression made little difference to the diffusion time-scale. This may indicate that transport was thereafter dominated by other aspects of the waste structure such as the distribution of low-permeability objects. The presence of gas in the degrading waste reduced the volumetric water content through displacement. The model indicated that the gas was primarily located in the more mobile porosity fraction. Primary compression of the degrading waste tended to squeeze this gas out of the waste in preference to water.

  6. Wave-induced mass transport affects daily Escherichia coli fluctuations in nearshore water

    USGS Publications Warehouse

    Ge, Zhongfu; Whitman, Richard L.; Nevers, Meredith B.; Phanikumar, Mantha S.

    2012-01-01

    Characterization of diel variability of fecal indicator bacteria concentration in nearshore waters is of particular importance for development of water sampling standards and protection of public health. Significant nighttime increase in Escherichia coli (E. coli) concentration in beach water, previously observed at marine sites, has also been identified in summer 2000 from fixed locations in waist- and knee-deep waters at Chicago 63rd Street Beach, an embayed, tideless, freshwater beach with low currents at night (approximately 0.015 m s–1). A theoretical model using wave-induced mass transport velocity for advection was developed to assess the contribution of surface waves to the observed nighttime E. coli replenishment in the nearshore water. Using average wave conditions for the summer season of year 2000, the model predicted an amount of E. coli transported from water of intermediate depth, where sediment resuspension occurred intermittently, that would be sufficient to have elevated E. coli concentration in the surf and swash zones as observed. The nighttime replenishment of E. coli in the surf and swash zones revealed here is an important phase in the cycle of diel variations of E. coli concentration in nearshore water. According to previous findings in Ge et al. (Environ. Sci. Technol. 2010, 44, 6731–6737), enhanced current circulation in the embayment during the day tends to displace and deposit material offshore, which partially sets up the system by the early evening for a new period of nighttime onshore movement. This wave-induced mass transport effect, although facilitating a significant base supply of material shoreward, can be perturbed or significantly influenced by high currents (orders of magnitude larger than a typical wave-induced mass transport velocity), current-induced turbulence, and tidal forcing.

  7. Temperature affects transport of polysaccharides and proteins in articular cartilage explants.

    PubMed

    Moeini, Mohammad; Lee, Kwan-Bong; Quinn, Thomas M

    2012-07-26

    Solute transport phenomena mediate many aspects of the physiology and contrast agent-based clinical imaging of articular cartilage. Temperatures up to 10°C below standard body temperature (37°C) are common in articulating joints during normal activities and clinically (e.g. cold treatment of injuries). Therefore it is of interest to characterize the effects of temperature changes on solute transport parameters in cartilage. A range of fluorescent solutes including fluorescein isothiocyanate, 4 and 40kDa dextrans, myoglobin, insulin and chondroitin sulfate were prepared and used in assays of solute effective partition coefficient and effective diffusivity in bovine intermediate zone articular cartilage explants maintained at 10, 22 or 37°C. Trends for increasing partition coefficient with increasing temperature were evident for all solutes except chondroitin sulfate, with significant changes between 22 and 37°C for 4kDa dextran, insulin and myoglobin. Diffusivities of most solutes tested also tended to increase with increasing temperature, with significant changes between 10 and 22°C for FITC, 40kDa dextran and myoglobin. Oddly, insulin diffusivity decreased significantly as temperature increased from 22 to 37°C while chondroitin sulfate diffusivity exhibited no clear temperature dependence. These results highlight solute-specific temperature dependences of transport phenomena which may depend upon molecular weight, chemical structure, molecular conformation, and solute-matrix and solute-solute interactions. The articular cartilage explants themselves exhibited small but significant changes in water and glycosaminoglycan contents during experiments, underscoring the importance of solute-matrix interactions. Solute transport parameters in cartilage and their temperature dependences are therefore not easily predicted, and case-by-case experimental determination may be essential.

  8. Wave-induced mass transport affects daily Escherichia coli fluctuations in nearshore water.

    PubMed

    Ge, Zhongfu; Whitman, Richard L; Nevers, Meredith B; Phanikumar, Mantha S

    2012-02-21

    Characterization of diel variability of fecal indicator bacteria concentration in nearshore waters is of particular importance for development of water sampling standards and protection of public health. Significant nighttime increase in Escherichia coli (E. coli) concentration in beach water, previously observed at marine sites, has also been identified in summer 2000 from fixed locations in waist- and knee-deep waters at Chicago 63rd Street Beach, an embayed, tideless, freshwater beach with low currents at night (approximately 0.015 m s(-1)). A theoretical model using wave-induced mass transport velocity for advection was developed to assess the contribution of surface waves to the observed nighttime E. coli replenishment in the nearshore water. Using average wave conditions for the summer season of year 2000, the model predicted an amount of E. coli transported from water of intermediate depth, where sediment resuspension occurred intermittently, that would be sufficient to have elevated E. coli concentration in the surf and swash zones as observed. The nighttime replenishment of E. coli in the surf and swash zones revealed here is an important phase in the cycle of diel variations of E. coli concentration in nearshore water. According to previous findings in Ge et al. (Environ. Sci. Technol. 2010, 44, 6731-6737), enhanced current circulation in the embayment during the day tends to displace and deposit material offshore, which partially sets up the system by the early evening for a new period of nighttime onshore movement. This wave-induced mass transport effect, although facilitating a significant base supply of material shoreward, can be perturbed or significantly influenced by high currents (orders of magnitude larger than a typical wave-induced mass transport velocity), current-induced turbulence, and tidal forcing.

  9. Mechanisms affecting the transport and retention of bacteria, bacteriophage and microspheres in laboratory-scale saturated fractures

    NASA Astrophysics Data System (ADS)

    Seggewiss, G.; Dickson, S. E.

    2013-12-01

    Groundwater is becoming an increasingly important water source due to the ever-increasing demands from agricultural, residential and industrial consumers. In search of more secure sources, wells are routinely finished over large vertical depths in bedrock aquifers, creating new hydraulic pathways and thus increasing the risk of cross contamination. Moreover, hydraulic pathways are also being altered and created by increasing water withdrawal rates from these wells. Currently, it is not well understood how biological contaminants are transported through, and retained in, fractured media thereby making risk assessment and land use decisions difficult. Colloid transport within fractured rock is a complex process with several mechanisms affecting transport and retention, including: advection, hydrodynamic dispersion, diffusion, size exclusion, adsorption, and decay. Several researchers have investigated the transport of bacteria, bacteriophage, and microspheres (both carboxylated and plain) to evaluate the effects of surface properties and size on transport and retention. These studies have suggested that transport is highly dependent on the physico-chemical properties of the particle, the fracture, and the carrying fluid. However, these studies contain little detail regarding the specific mechanisms responsible for transport beyond speculating about their existence. Further, little work has been done to compare the transport of these particulate materials through the same fracture, allowing for direct observations based on particulate size and surface properties. This research examines the similarities and differences in transport and retention between four different particles through two different laboratory-scale, saturated fractures. This work is designed to explore the effects of particle size, surface properties, ionic strength of the carrying solution, and aperture field characteristics on transport and retention in single, saturated fractures. The particulates

  10. Proteins affecting thylakoid morphology - the key to understanding vesicle transport in chloroplasts?

    PubMed

    Lindquist, Emelie; Aronsson, Henrik

    2014-01-01

    We recently showed that a Rab protein, CPRabA5e (CP = chloroplast localized), is located in chloroplasts of Arabidopsis thaliana where it is involved in various processes, such as thylakoid biogenesis and vesicle transport. Using a yeast two-hybrid method, CPRabA5e was shown to interact with a number of chloroplast proteins, including the CURVATURE THYLAKOID 1A (CURT1A) protein and the light-harvesting chlorophyll a/b binding protein (LHCB1.5). CURT1A has recently been shown to modify thylakoid architecture by inducing membrane curvature in grana, whereas LHCB1.5 is a protein of PSII (Photosystem II) facilitating light capture. LHCB1.5 is imported to chloroplasts and transported to thylakoid membranes using the post-translational Signal Recognition Particle (SRP) pathway. With this information as starting point, we here discuss their subsequent protein-protein interactions, given by the literature and Interactome 3D. CURT1A itself and several of the proteins interacting with CURT1A and LHCB1.5 have relations to vesicle transport and thylakoid morphology, which are also characteristics of cprabA5e mutants. This highlights the previous hypothesis of an alternative thylakoid targeting pathway for LHC proteins using vesicles, in addition to the SRP pathway.

  11. STP-ECRTS - THERMAL AND GAS ANALYSES FOR SLUDGE TRANSPORT AND STORAGE CONTAINER (STSC) STORAGE AT T PLANT

    SciTech Connect

    CROWE RD; APTHORPE R; LEE SJ; PLYS MG

    2010-04-29

    The Sludge Treatment Project (STP) is responsible for the disposition of sludge contained in the six engineered containers and Settler tank within the 105-K West (KW) Basin. The STP is retrieving and transferring sludge from the Settler tank into engineered container SCS-CON-230. Then, the STP will retrieve and transfer sludge from the six engineered containers in the KW Basin directly into a Sludge Transport and Storage Containers (STSC) contained in a Sludge Transport System (STS) cask. The STSC/STS cask will be transported to T Plant for interim storage of the STSC. The STS cask will be loaded with an empty STSC and returned to the KW Basin for loading of additional sludge for transportation and interim storage at T Plant. CH2MHILL Plateau Remediation Company (CHPRC) contracted with Fauske & Associates, LLC (FAI) to perform thermal and gas generation analyses for interim storage of STP sludge in the Sludge Transport and Storage Container (STSCs) at T Plant. The sludge types considered are settler sludge and sludge originating from the floor of the KW Basin and stored in containers 210 and 220, which are bounding compositions. The conditions specified by CHPRC for analysis are provided in Section 5. The FAI report (FAI/10-83, Thermal and Gas Analyses for a Sludge Transport and Storage Container (STSC) at T Plant) (refer to Attachment 1) documents the analyses. The process considered was passive, interim storage of sludge in various cells at T Plant. The FATE{trademark} code is used for the calculation. The results are shown in terms of the peak sludge temperature and hydrogen concentrations in the STSC and the T Plant cell. In particular, the concerns addressed were the thermal stability of the sludge and the potential for flammable gas mixtures. This work was performed with preliminary design information and a preliminary software configuration.

  12. CASCADER: An M-chain gas-phase radionuclide transport and fate model. Volume 4 -- Users guide to CASCADR9

    SciTech Connect

    Cawlfield, D.E.; Emer, D.F.; Lindstrom, F.T.; Shott, G.J.

    1993-09-01

    Chemicals and radionuclides move either in the gas-phase, liquid-phase, or both phases in soils. They may be acted upon by either biological or abiotic processes through advection and/or dispersion. Additionally during the transport of parent and daughter radionuclides in soil, radionuclide decay may occur. This version of CASCADER called CASCADR9 starts with the concepts presented in volumes one and three of this series. For a proper understanding of how the model works, the reader should read volume one first. Also presented in this volume is a set of realistic scenarios for buried sources of radon gas, and the input and output file structure for CASCADER9.

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

    NASA Astrophysics Data System (ADS)

    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

  14. Survey of regulations affecting emissions from residential, gas-fired appliances. Topical report, January-December 1993

    SciTech Connect

    Benedek, K.; Goodman, T.

    1994-01-01

    The purpose of the project was to provide the U.S. gas industry with: an accurate database of existing emissions standards that may affect the use of natural gas in the U.S. residential sector; and a view of national and world-wide environmental trends that may provide insight into the future of U.S. emissions regulations and consumer interest in environmentally friendly technologies. In the U.S., the state of California has established a limit of 40 Nanogram/Jorale for NOx emissions from residential appliances in six air pollution control districts. The trend in the U.S. is for emission regulations to move away from traditional standards, toward market-based control strategies.

  15. Simulation of electron beam formation and transport in a gas-filled electron-optical system with a plasma emitter

    NASA Astrophysics Data System (ADS)

    Grishkov, A. A.; Kornilov, S. Yu.; Rempe, N. G.; Shidlovskiy, S. V.; Shklyaev, V. A.

    2016-07-01

    The results of computer simulations of the electron-optical system of an electron gun with a plasma emitter are presented. The simulations are performed using the KOBRA3-INP, XOOPIC, and ANSYS codes. The results describe the electron beam formation and transport. The electron trajectories are analyzed. The mechanisms of gas influence on the energy inhomogeneity of the beam and its current in the regions of beam primary formation, acceleration, and transport are described. Recommendations for optimizing the electron-optical system with a plasma emitter are presented.

  16. Heat and particle transport in a one-dimensional hard-point gas model with on-site potential

    SciTech Connect

    Wang, Lei

    2015-05-15

    Heat and particle transport in a one-dimensional hard-point gas of elastically colliding particles are studied. In the nonequal mass case, due to the presence of on-site potential, the heat conduction of the model obeys the Fourier law and all the transport coefficients asymptotically approach constants in the thermodynamic limit. The thermoelectric figure of merit ZT increases slowly with the system length L and is proportional to the height of the potential barriers H in high H regime. These findings may serve as a guide for future theoretical and experimental studies.

  17. Meteorological Processes Affecting the Transport of Emissions from the Navajo Generating Station to Grand Canyon National Park.

    NASA Astrophysics Data System (ADS)

    Lindsey, Charles G.; Chen, Jun; Dye, Timothy S.; Willard Richards, L.; Blumenthal, Donald L.

    1999-08-01

    During the 1990 Navajo Generating Station (NGS) Winter Visibility Study, a network of surface and upper-air meteorological measurement systems was operated in and around Grand Canyon National Park to investigate atmospheric processes in complex terrain that affected the transport of emissions from the nearby NGS. This network included 15 surface monitoring stations, eight balloon sounding stations (equipped with a mix of rawinsonde, tethersonde, and Airsonde sounding systems), three Doppler radar wind profilers, and four Doppler sodars. Measurements were made from 10 January through 31 March 1990. Data from this network were used to prepare objectively analyzed wind fields, trajectories, and streak lines to represent transport of emissions from the NGS, and to prepare isentropic analyses of the data. The results of these meteorological analyses were merged in the form of a computer animation that depicted the streak line analyses along with measurements of perfluorocarbon tracer, SO2, and sulfate aerosol concentrations, as well as visibility measurements collected by an extensive surface monitoring network. These analyses revealed that synoptic-scale circulations associated with the passage of low pressure systems followed by the formation of high pressure ridges accompanied the majority of cases when NGS emittants appeared to be transported to the Grand Canyon. The authors' results also revealed terrain influences on transport within the topography of the study area, especially mesoscale flows inside the Lake Powell basin and along the plain above the Marble Canyon.

  18. Transcription of hexose transporters of Saccharomyces cerevisiae is affected by change in oxygen provision

    PubMed Central

    Rintala, Eija; Wiebe, Marilyn G; Tamminen, Anu; Ruohonen, Laura; Penttilä, Merja

    2008-01-01

    Background The gene family of hexose transporters in Saccharomyces cerevisiae consists of 20 members; 18 genes encoding transporters (HXT1-HXT17, GAL2) and two genes encoding sensors (SNF3, RGT2). The effect of oxygen provision on the expression of these genes was studied in glucose-limited chemostat cultivations (D = 0.10 h-1, pH 5, 30°C). Transcript levels were measured from cells grown in five steady state oxygen levels (0, 0.5, 1, 2.8 and 20.9% O2), and from cells under conditions in which oxygen was introduced to anaerobic cultures or removed from cultures receiving oxygen. Results The expression pattern of the HXT gene family was distinct in cells grown under aerobic, hypoxic and anaerobic conditions. The transcription of HXT2, HXT4 and HXT5 was low when the oxygen concentration in the cultures was low, both under steady state and non-steady state conditions, whereas the expression of HXT6, HXT13 and HXT15/16 was higher in hypoxic than in fully aerobic or anaerobic conditions. None of the HXT genes showed higher transcript levels in strictly anaerobic conditions. Expression of HXT9, HXT14 and GAL2 was not detected under the culture conditions studied. Conclusion When oxygen becomes limiting in a glucose-limited chemostat cultivation, the glucose uptake rate per cell increases. However, the expression of none of the hexose transporter encoding genes was increased in anaerobic conditions. It thus seems that the decrease in the moderately low affinity uptake and consequently the relative increase of high affinity uptake may itself allow the higher specific glucose consumption rate to occur in anaerobic compared to aerobic conditions. PMID:18373847

  19. Calcium transport in bovine rumen epithelium as affected by luminal Ca concentrations and Ca sources

    PubMed Central

    Schröder, Bernd; Wilkens, Mirja R; Ricken, Gundula E; Leonhard-Marek, Sabine; Fraser, David R; Breves, Gerhard

    2015-01-01

    The quantitative role of different segments of the gastrointestinal tract for Ca absorption, the respective mechanisms, and their regulation are not fully identified for ruminants, that is, cattle. In different in vitro experiments the forestomach wall has been demonstrated to be a major site for active Ca absorption in sheep and goats. In order to further clarify the role of the bovine rumen for Ca transport with special attention to luminal Ca concentrations, its ionic form, and pH, electrophysiological and unidirectional flux rate measurements were performed with isolated bovine rumen epithelial tissues. For Ca flux studies (Jms, Jsm) in vitro Ussing chamber technique was applied. Standard RT-PCR method was used to characterize TRPV6 and PMCA1 as potential contributors to transepithelial active Ca transport. At Ca concentrations of 1.2 mmol L−1 on both sides of the tissues, Jms were higher than Jsm resulting under some conditions in significant Ca net flux rates (Jnet), indicating the presence of active Ca transport. In the absence of an electrical gradient, Jnet could significantly be stimulated in the presence of luminal short-chain fatty acids (SCFAs). Increasing the luminal Ca concentrations up to 11.2 mmol L−1 resulted in significant increases in Jms without influencing Jsm. Providing Ca in its form as respective chloride, formate, or propionate salts there was no significant effect on Jms. No transcripts specific for Ca channel TRPV6 could be demonstrated. Our results indicate different mechanisms for Ca absorption in bovine rumen as compared with those usually described for the small intestines. PMID:26564067

  20. Natural Gas Processing: The Crucial Link Between NG Production & Its Transportation to Market

    EIA Publications

    2006-01-01

    This special report examines the processing plant segment of the natural gas industry, providing a discussion and an analysis of how the gas processing segment has changed following the restructuring of the natural gas industry in the 1990s and the trends that have developed during that time.

  1. Mapping of a genetic locus that affects glycerol 3-phosphate transport in Bacillus subtilis.

    PubMed Central

    Lindgren, V

    1978-01-01

    Two types of fosfomycin-resistant mutants of Bacillus subtilis were isolated. Mutants of the first type (GlpT mutants) were resistant to at least 200 microgram of fosfomycin per ml and failed to take up exogenous glycerol 3-phosphate. Mutants of the second type were resistant to lower concentrations of fosfomycin and transported glycerol-3-phosphate as efficiently as wild-type bacteria. The glpT mutations, but not the mutations in the second type of fosfomycin-resistant mutants, map in the cysA-aroI region of the B. subtilis chromosome. PMID:415047

  2. Factors Affecting the Corporate Decision-Making Process of Air Transport Manufacturers

    NASA Technical Reports Server (NTRS)

    Ollila, R. G.; Hill, J. D.; Noton, B. R.; Duffy, M. A.; Epstein, M. M.

    1976-01-01

    Fuel economy is a pivotal question influencing the future sale and utilization of commercial aircraft. The NASA Aircraft Energy Efficiency (ACEE) Program Office has a program intended to accelerate the readiness of advanced technologies for energy efficient aircraft. Because the decision to develop a new airframe or engine is a major financial hazard for manufacturers, it is important to know what factors influence the decision making process. A method is described for identifying and ranking individuals and organizations involved at each stage of commercial air transport development, and the barriers that must be overcome in adopting new technologies.

  3. From producer to consumer: greenhouse tomato quality as affected by variety, maturity stage at harvest, transport conditions, and supermarket storage.

    PubMed

    Verheul, Michèl J; Slimestad, Rune; Tjøstheim, Irene Holta

    2015-05-27

    Possible causes for differences in quality traits at the time of buying were studied in two widely different red tomato types. Three maturity stages were harvested from commercial greenhouses and transferred immediately to controlled environments simulating different storage, transport, and supermarket conditions. Results show significant differences in development of color, fruit firmness, contents of soluble solids (SSC), titratable acids (TTA), phenolics, and carotenoids from harvest to sale, as related to postharvest conditions. Fruit firmness, SSC, and TTA of vine-ripened red cherry tomatoes was 30, 55 and 11% higher than for those harvested at breakers and ripened to red. Temperature, light, UVC radiation, or ethylene during 4 days transport affected tomato quality traits, and differences persisted during 3 weeks of supermarket storage. Ethylene exposure gave a 3.7-fold increase in lycopene content in cherry tomatoes, whereas UVC hormesis revealed a 6-fold increase compared with the control. Results can be used to update recommendations concerning optimal handling.

  4. Transportation Energy Futures Series. Effects of Travel Reduction and Efficient Driving on Transportation. Energy Use and Greenhouse Gas Emissions

    SciTech Connect

    Porter, C. D.; Brown, A.; DeFlorio, J.; McKenzie, E.; Tao, W.; Vimmerstedt, L.

    2013-03-01

    Since the 1970s, numerous transportation strategies have been formulated to change the behavior of drivers or travelers by reducing trips, shifting travel to more efficient modes, or improving the efficiency of existing modes. This report summarizes findings documented in existing literature to identify strategies with the greatest potential impact. The estimated effects of implementing the most significant and aggressive individual driver behavior modification strategies range from less than 1% to a few percent reduction in transportation energy use and GHG emissions. Combined strategies result in reductions of 7% to 15% by 2030. Pricing, ridesharing, eco-driving, and speed limit reduction/enforcement strategies are widely judged to have the greatest estimated potential effect, but lack the widespread public acceptance needed to accomplish maximum results. This is one of a series of reports produced as a result of the Transportation Energy Futures (TEF) project, a Department of Energy-sponsored multi-agency project initiated to pinpoint underexplored strategies for abating GHGs and reducing petroleum dependence related to transportation.

  5. Transportation Energy Futures Series: Effects of Travel Reduction and Efficient Driving on Transportation: Energy Use and Greenhouse Gas Emissions

    SciTech Connect

    Porter, C. D.; Brown, A.; DeFlorio, J.; McKenzie, E.; Tao, W.; Vimmerstedt, L.

    2013-03-01

    Since the 1970s, numerous transportation strategies have been formulated to change the behavior of drivers or travelers by reducing trips, shifting travel to more efficient modes, or improving the efficiency of existing modes. This report summarizes findings documented in existing literature to identify strategies with the greatest potential impact. The estimated effects of implementing the most significant and aggressive individual driver behavior modification strategies range from less than 1% to a few percent reduction in transportation energy use and GHG emissions. Combined strategies result in reductions of 7% to 15% by 2030. Pricing, ridesharing, eco-driving, and speed limit reduction/enforcement strategies are widely judged to have the greatest estimated potential effect, but lack the widespread public acceptance needed to accomplish maximum results. This is one of a series of reports produced as a result of the Transportation Energy Futures (TEF) project, a Department of Energy-sponsored multi-agency project initiated to pinpoint underexplored strategies for abating GHGs and reducing petroleum dependence related to transportation.

  6. Processes affecting the transport of nitrogen in groundwater and factors related to slope position

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Nitrate (NO3-) pollution of water resources has been a major problem for years, causing contaminated water supplies, harmful effects on human health, and widespread eutrophication of fresh water resources. The main objectives of this study were to: 1) understand the processes affecting NO3- transpor...

  7. Vasomotor tone does not affect perfusion heterogeneity and gas exchange in normal primate lungs during normoxia

    NASA Technical Reports Server (NTRS)

    Glenny, R. W.; Robertson, H. T.; Hlastala, M. P.

    2000-01-01

    To determine whether vasoregulation is an important cause of pulmonary perfusion heterogeneity, we measured regional blood flow and gas exchange before and after giving prostacyclin (PGI(2)) to baboons. Four animals were anesthetized with ketamine and mechanically ventilated. Fluorescent microspheres were used to mark regional perfusion before and after PGI(2) infusion. The lungs were subsequently excised, dried inflated, and diced into approximately 2-cm(3) pieces (n = 1,208-1,629 per animal) with the spatial coordinates recorded for each piece. Blood flow to each piece was determined for each condition from the fluorescent signals. Blood flow heterogeneity did not change with PGI(2) infusion. Two other measures of spatial blood flow distribution, the fractal dimension and the spatial correlation, did not change with PGI(2) infusion. Alveolar-arterial O(2) differences did not change with PGI(2) infusion. We conclude that, in normal primate lungs during normoxia, vasomotor tone is not a significant cause of perfusion heterogeneity. Despite the heterogeneous distribution of blood flow, active regulation of regional perfusion is not required for efficient gas exchange.

  8. Transport Regimes of Air Masses Affecting the Tropospheric Composition of the Canadian and European Arctic During RACEPAC 2014 and NETCARE 2014/2015

    NASA Astrophysics Data System (ADS)

    Bozem, H.; Hoor, P. M.; Koellner, F.; Kunkel, D.; Schneider, J.; Schulz, C.; Herber, A. B.; Borrmann, S.; Wendisch, M.; Ehrlich, A.; Leaitch, W. R.; Willis, M. D.; Burkart, J.; Thomas, J. L.; Abbatt, J.

    2015-12-01

    The Arctic is warming much faster than any other place in the world and undergoes a rapid change dominated by a changing climate in this region. The impact of polluted air masses traveling to the Arctic from various remote sources significantly contributes to the observed climate change, in contrast there are additional local emission sources contributing to the level of pollutants (trace gases and aerosol). Processes affecting the emission and transport of these pollutants are not well understood and need to be further investigated. We present aircraft based trace gas measurements in the Arctic during RACEPAC (2014) and NETCARE (2014 and 2015) with the Polar 6 aircraft of Alfred Wegener Institute (AWI) covering an area from 134°W to 17°W and 68°N to 83°N. We focus on cloud, aerosol and general transport processes of polluted air masses into the high Arctic. Based on CO and CO2 measurements and kinematic 10-day back trajectories we analyze the transport regimes prevalent during spring (RACEPAC 2014 and NETCARE 2015) and summer (NETCARE 2014) in the observed region. Whereas the eastern part of the Canadian Arctic is affected by air masses with their origin in Asia, in the central and western parts of the Canadian and European Arctic air masses from North America are predominant at the time of the measurement. In general the more northern parts of the Arctic were relatively unaffected by pollution from mid-latitudes since air masses mostly travel within the polar dome, being quite isolated. Associated mixing ratios of CO and CO2 fit into the seasonal cycle observed at NOAA ground stations throughout the Arctic, but show a more mid-latitudinal characteristic at higher altitudes. The transition is remarkably sharp and allows for a chemical definition of the polar dome. At low altitudes, synoptic disturbances transport polluted air masses from mid-latitudes into regions of the polar dome. These air masses contribute to the Arctic pollution background, but also

  9. Transport of Chemical Vapors from Subsurface Sources to Atmosphere as Affected by Shallow Subsurface and Atmospheric Conditions

    NASA Astrophysics Data System (ADS)

    Rice, A. K.; Smits, K. M.; Hosken, K.; Schulte, P.; Illangasekare, T. H.

    2012-12-01

    Understanding the movement and modeling of chemical vapor through unsaturated soil in the shallow subsurface when subjected to natural atmospheric thermal and mass flux boundary conditions at the land surface is of importance to applications such as landmine detection and vapor intrusion into subsurface structures. New, advanced technologies exist to sense chemical signatures at the land/atmosphere interface, but interpretation of these sensor signals to make assessment of source conditions remains a challenge. Chemical signatures are subject to numerous interactions while migrating through the unsaturated soil environment, attenuating signal strength and masking contaminant source conditions. The dominant process governing movement of gases through porous media is often assumed to be Fickian diffusion through the air phase with minimal or no quantification of other processes contributing to vapor migration, such as thermal diffusion, convective gas flow due to the displacement of air, expansion/contraction of air due to temperature changes, temporal and spatial variations of soil moisture and fluctuations in atmospheric pressure. Soil water evaporation and interfacial mass transfer add to the complexity of the system. The goal of this work is to perform controlled experiments under transient conditions of soil moisture, temperature and wind at the land/atmosphere interface and use the resulting dataset to test existing theories on subsurface gas flow and iterate between numerical modeling efforts and experimental data. Ultimately, we aim to update conceptual models of shallow subsurface vapor transport to include conditionally significant transport processes and inform placement of mobile sensors and/or networks. We have developed a two-dimensional tank apparatus equipped with a network of sensors and a flow-through head space for simulation of the atmospheric interface. A detailed matrix of realistic atmospheric boundary conditions was applied in a series of

  10. TRANSPORT

    EPA Science Inventory

    Presentation outline: transport principles, effective solubility; gasoline composition; and field examples (plume diving).
    Presentation conclusions: MTBE transport follows from - phyiscal and chemical properties and hydrology. Field examples show: MTBE plumes > benzene plu...

  11. Geologic and societal factors affecting the international oceanic transport of aggregate

    USGS Publications Warehouse

    Langer, W.H.

    1995-01-01

    Crushed stone and sand and gravel are the two main sources of natural aggregate, and together comprise approximately half the volume and tonnage of mined material in the United States. Natural aggregate is a bulky, heavy material without special or unique properties, and it is commonly used near its source of production to minimize haulage cost. However, remoteness is no longer an absolute disqualifier for the production of aggregate. Today interstate aggregate routinely is shipped hundreds of kilometers by rail and barge. In addition, during 1992, the United States imported 1,317,000 metric tons of aggregate from Canada and 1,531,000 metric tons from Mexico. A number of ports on the Atlantic Coast and Gulf Coast of the United States receive imports of crushed stone from foreign sources for transport to various parts of the eastern United States. These areas either lack adequate supplies of aggregate or are augmenting their supplies because they have difficulties meeting current demand. These difficulties may include poor stone quality, environmental permitting problems, or transportation. Certain societal and geologic conditions of New York City and Philadelphia along the Atlantic Coast, and Tampa and New Orleans along the Gulf Coast, are discussed to demonstrate the different combinations of issues that contribute to the economic viability of importing crushed stone. ?? 1995 Oxford University Press.

  12. The Role of EPS in Microhydrology and Transport Processes Affecting Microbial Activity in Unsaturated Porous Media

    NASA Astrophysics Data System (ADS)

    Or, D.; Phutane, S.

    2005-12-01

    Extra-cellular Polymeric Substances (EPS) refers to biopolymers excreted and surrounding soil bacterial cells (and other biota) forming the scaffolding for colonies and serving a wide array of transport, nutrient entrapment, and mechanical functions. In essence, EPS is a porous matrix through which aqueous, gaseous and nutrient fluxes flow to supply the embedded bacterial cells. The large water holding capacity and retarded water loss rates of EPS dampens rapid fluctuations in hydration status of host porous medium which sustain higher diffusion fluxes than in surrounding porous medium, and shelters microbial cells from effect of rapid desiccation or rewetting. The morphology of EPS changes from an open well-hydrated bioweb to dense and highly cross-linked structure under dry conditions. Such morphological changes are accompanied by enhanced mechanical strength and retardation of water loss that provide additional time for physiological adaptation to desiccation. Additional capacitance results from the disparity in dynamic hydrological properties between EPS and soil that promotes water entrapment in EPS during rapid drainage. EPS may also trap dissolved nutrients that may be unevenly distributed and irregularly supplied in unsaturated environments, thereby increasing nutrient availability in the microhabitat and offsetting decreased supply by diffusion during drying. The remarkable transport and mechanical properties of EPS makes it an important stabilizing agent for soil aggregation and even minute amounts of EPS may significantly alter macroscopic hydrological properties of host porous medium.

  13. Simulation of runaway electrons, transport affected by J-TEXT resonant magnetic perturbation

    NASA Astrophysics Data System (ADS)

    Jiang, Z. H.; Wang, X. H.; Chen, Z. Y.; Huang, D. W.; Sun, X. F.; Xu, T.; Zhuang, G.

    2016-09-01

    The topology of a magnetic field and transport properties of runaway electrons can be changed by a resonant magnetic perturbation field. The J-TEXT magnetic topology can be effectively altered via static resonant magnetic perturbation (SRMP) and dynamic resonant magnetic perturbation (DRMP). This paper studies the effect of resonant magnetic perturbation (RMP) on the confinement of runaway electrons via simulating their drift orbits in the magnetic perturbation field and calculating the orbit losses for different runaway initial energies and different runaway electrons, initial locations. The model adopted is based on Hamiltonian guiding center equations for runaway electrons, and the J-TEXT magnetic turbulences and RMP are taken into account. The simulation indicates that the loss rate of runaway electrons is sensitive to the radial position of electrons. The loss of energetic runaway beam is dominated by the shrinkage of the confinement region. Outside the shrinkage region of the runaway electrons are lost rapidly. Inside the shrinkage region the runaway beam is confined very well and is less sensitive to the magnetic perturbation. The experimental result on the response of runaway transport to the application RMP indicates that the loss of runaway electrons is dominated by the shrinkage of the confinement region, other than the external magnetic perturbation.

  14. Structure and function of subsurface microbial communities affecting radionuclide transport and bioimmobilization

    SciTech Connect

    Kostka, Joel E.; Prakash, Om; Green, Stefan J.; Akob, Denise; Jasrotia, Puja; Kerkhof, Lee; Chin, Kuk-Jeong; Sheth, Mili; Keller, Martin; Venkateswaran, Amudhan; Elkins, James G.; Stucki, Joseph W.

    2012-05-01

    Our objectives were to: 1) isolate and characterize novel anaerobic prokaryotes from subsurface environments exposed to high levels of mixed contaminants (U(VI), nitrate, sulfate), 2) elucidate the diversity and distribution of metabolically active metal- and nitrate-reducing prokaryotes in subsurface sediments, and 3) determine the biotic and abiotic mechanisms linking electron transport processes (nitrate, Fe(III), and sulfate reduction) to radionuclide reduction and immobilization. Mechanisms of electron transport and U(VI) transformation were examined under near in situ conditions in sediment microcosms and in field investigations. Field sampling was conducted at the Oak Ridge Field Research Center (ORFRC), in Oak Ridge, Tennessee. The ORFRC subsurface is exposed to mixed contamination predominated by uranium and nitrate. In short, we effectively addressed all 3 stated objectives of the project. In particular, we isolated and characterized a large number of novel anaerobes with a high bioremediation potential that can be used as model organisms, and we are now able to quantify the function of subsurface sedimentary microbial communities in situ using state-of-the-art gene expression methods (molecular proxies).

  15. Intronless mRNA transport elements may affect multiple steps of pre-mRNA processing.

    PubMed Central

    Huang, Y; Wimler, K M; Carmichael, G G

    1999-01-01

    We have reported recently that a small element within the mouse histone H2a-coding region permits efficient cytoplasmic accumulation of intronless beta-globin cDNA transcripts. This sequence lowers the levels of spliced products from intron-containing constructs and can functionally replace Rev and the Rev-responsive element (RRE) in the nuclear export of unspliced HIV-1-related mRNAs. In work reported here, we further investigate the molecular mechanisms by which this element might work. We demonstrate here through both in vivo and in vitro assays that, in addition to promoting mRNA nuclear export, this element acts as a polyadenylation enhancer and as a potent inhibitor of splicing. Surprisingly, two other described intronless mRNA transport elements (from the herpes simplex virus thymidine kinase gene and hepatitis B virus) appear to function in a similar manner. These findings prompt us to suggest that a general feature of intronless mRNA transport elements might be a collection of phenotypes, including the inhibition of splicing and the enhancement of both polyadenylation and mRNA export. PMID:10075934

  16. Arbuscular mycorrhiza affects nickel translocation and expression of ABC transporter and metallothionein genes in Festuca arundinacea.

    PubMed

    Shabani, Leila; Sabzalian, Mohammad R; Mostafavi pour, Sodabeh

    2016-01-01

    Mycorrhizal fungi are key microorganisms for enhancing phytoremediation of soils contaminated with heavy metals. In this study, the effects of the arbuscular mycorrhizal fungus (AMF) Funneliformis mosseae (=Glomus mosseae) on physiological and molecular mechanisms involved in the nickel (Ni) tolerance of tall fescue (Festuca arundinacea = Schedonorus arundinaceus) were investigated. Nickel addition had a pronounced negative effect on tall fescue growth and photosynthetic pigment contents, as well as on AMF colonization. Phosphorus content increased markedly in mycorrhizal plants (M) compared to non-inoculated (NM) ones. However, no significant difference was observed in root carbohydrate content between AMF-inoculated and non-inoculated plants. For both M and NM plants, Ni concentrations in shoots and roots increased according to the addition of the metal into soil, but inoculation with F. mosseae led to significantly lower Ni translocation from roots to the aboveground parts compared to non-inoculated plants. ABC transporter and metallothionein transcripts accumulated to considerably higher levels in tall fescue plants colonized by F. mosseae than in the corresponding non-mycorrhizal plants. These results highlight the importance of mycorrhizal colonization in alleviating Ni-induced stress by reducing Ni transport from roots to shoots of tall fescue plants.

  17. Do ATP-binding cassette transporters cause pharmacoresistance in epilepsy? Problems and approaches in determining which antiepileptic drugs are affected.

    PubMed

    Löscher, Wolfgang; Luna-Tortós, Carlos; Römermann, Kerstin; Fedrowitz, Maren

    2011-01-01

    Resistance to multiple antiepileptic drugs (AEDs) is a common problem in epilepsy, affecting at least 30% of patients. One prominent hypothesis to explain this resistance suggests an inadequate penetration or excess efflux of AEDs across the blood - brain barrier (BBB) as a result of overexpressed efflux transporters such as P-glycoprotein (Pgp), the encoded product of the multidrug resistance- 1 (MDR1, ABCB1) gene. Pgp and MDR1 are markedly increased in epileptogenic brain tissue of patients with AED-resistant partial epilepsy and following seizures in rodent models of partial epilepsy. In rodent models, AED-resistant rats exhibit higher Pgp levels than responsive animals; increased Pgp expression is associated with lower brain levels of AEDs; and, most importantly, co-administration of Pgp inhibitors reverses AED resistance. Thus, it is reasonable to conclude that Pgp plays a significant role in mediating resistance to AEDs in rodent models of epilepsy - however, whether this phenomenon extends to at least some human refractory epilepsy remains unclear, particularly because it is still a matter of debate which AEDs, if any, are transported by human Pgp. The difficulty in determining which AEDs are substrates of human Pgp is mainly a consequence of the fact that AEDs are highly permeable compounds, which are not easily identified as Pgp substrates in in vitro models of the BBB, such as monolayer (Transwell(®)) efflux assays. By using a modified assay (concentration equilibrium transport assay; CETA), which minimizes the influence of high transcellular permeability, two groups have recently demonstrated that several major AEDs are transported by human Pgp. Importantly, it was demonstrated in these studies that Pgp-mediated transport highly depends on the AED concentration and may not be identified if concentrations below or above the therapeutic range are used. In addition to the efflux transporters, seizure-induced alterations in BBB integrity and activity of

  18. Water Transport in the Micro Porous Layer and Gas Diffusion Layer of a Polymer Electrolyte Fuel Cell

    NASA Astrophysics Data System (ADS)

    Qin, C.; Hassanizadeh, S. M.

    2015-12-01

    In this work, a recently developed dynamic pore-network model is presented [1]. The model explicitly solves for both water pressure and capillary pressure. A semi-implicit scheme is used in updating water saturation in each pore body, which considerably increases the numerical stability at low capillary number values. Furthermore, a multiple-time-step algorithm is introduced to reduce the computational effort. A number of case studies of water transport in the micro porous layer (MPL) and gas diffusion layer (GDL) are conducted. We illustrate the role of MPL in reducing water flooding in the GDL. Also, the dynamic water transport through the MPL-GDL interface is explored in detail. This information is essential to the reduced continua model (RCM), which was developed for multiphase flow through thin porous layers [2, 3]. C.Z. Qin, Water transport in the gas diffusion layer of a polymer electrolyte fuel cell: dynamic pore-network modeling, J Electrochimical. Soci., 162, F1036-F1046, 2015. C.Z. Qin and S.M. Hassanizadeh, Multiphase flow through multilayers of thin porous media: general balance equations and constitutive relationships for a solid-gas-liquid three-phase system, Int. J. Heat Mass Transfer, 70, 693-708, 2014. C.Z. Qin and S.M. Hassanizadeh, A new approach to modeling water flooding in a polymer electrolyte fuel cell, Int. J. Hydrogen Energy, 40, 3348-3358, 2015.

  19. Colonic epithelial ion transport is not affected in patients with diverticulosis

    PubMed Central

    Osbak, Philip S; Bindslev, Niels; Poulsen, Steen S; Kaltoft, Nicolai; Tilotta, Maria C; Hansen, Mark B

    2007-01-01

    Background Colonic diverticular disease is a bothersome condition with an unresolved pathogenesis. It is unknown whether a neuroepithelial dysfunction is present. The aim of the study was two-fold; (1) to investigate colonic epithelial ion transport in patients with diverticulosis and (2) to adapt a miniaturized Modified Ussing Air-Suction (MUAS) chamber for colonic endoscopic biopsies. Methods Biopsies were obtained from the sigmoid part of the colon. 86 patients were included. All patients were referred for colonoscopy on suspicion of neoplasia and they were without pathological findings at colonoscopy (controls) except for diverticulosis in 22 (D-patients). Biopsies were mounted in MUAS chambers with an exposed area of 5 mm2. Electrical responses to various stimulators and inhibitors of ion transport were investigated together with histological examination. The MUAS chamber was easy to use and reproducible data were obtained. Results Median basal short circuit current (SCC) was 43.8 μA·cm-2 (0.8 – 199) for controls and 59.3 μA·cm-2 (3.0 – 177.2) for D-patients. Slope conductance was 77.0 mS·cm-2 (18.6 – 204.0) equal to 13 Ω·cm2 for controls and 96.6 mS·cm-2 (8.4 – 191.4) equal to 10.3 Ω·cm2 for D-patients. Stimulation with serotonin, theophylline, forskolin and carbachol induced increases in SCC in a range of 4.9 – 18.6 μA·cm-2, while inhibition with indomethacin, bumetanide, ouabain and amiloride decreased SCC in a range of 6.5 – 27.4 μA·cm-2, and all with no significant differences between controls and D-patients. Histological examinations showed intact epithelium and lamina propria before and after mounting for both types of patients. Conclusion We conclude that epithelial ion transport is not significantly altered in patients with diverticulosis and that the MUAS chamber can be adapted for studies of human colonic endoscopic biopsies. PMID:17888183

  20. The outlook for aeronautics, 1980 - 2000 - Study report. [trends affecting civil air transportation and defense

    NASA Technical Reports Server (NTRS)

    1976-01-01

    Trends in civil and military aviation in the period 1980-2000 are examined in terms of the role that NASA should play in aeronautical research and development during this period. Factors considered include the pattern of industry and government relationships, the character of the aircraft to be developed, and the technology advances that will be required as well as demographic, economic, and social factors. Trends are expressed in terms of the most probable developments in civil air transportation and air defense and several characteristically different directions for future development are defined. The longer term opportunities created by developments in air transporation extending into the next century are also examined. Within this framework, a preferred NASA role and a preferred set of objectives are formulated for the research and technology which should be undertaken by NASA during the period 1976-1985.

  1. Parental vitamin deficiency affects the embryonic gene expression of immune-, lipid transport- and apolipoprotein genes

    PubMed Central

    Skjærven, Kaja H.; Jakt, Lars Martin; Dahl, John Arne; Espe, Marit; Aanes, Håvard; Hamre, Kristin; Fernandes, Jorge M. O.

    2016-01-01

    World Health Organization is concerned for parental vitamin deficiency and its effect on offspring health. This study examines the effect of a marginally dietary-induced parental one carbon (1-C) micronutrient deficiency on embryonic gene expression using zebrafish. Metabolic profiling revealed a reduced 1-C cycle efficiency in F0 generation. Parental deficiency reduced the fecundity and a total of 364 genes were differentially expressed in the F1 embryos. The upregulated genes (53%) in the deficient group were enriched in biological processes such as immune response and blood coagulation. Several genes encoding enzymes essential for the 1-C cycle and for lipid transport (especially apolipoproteins) were aberrantly expressed. We show that a parental diet deficient in micronutrients disturbs the expression in descendant embryos of genes associated with overall health, and result in inherited aberrations in the 1-C cycle and lipid metabolism. This emphasises the importance of parental micronutrient status for the health of the offspring. PMID:27731423

  2. Parental vitamin deficiency affects the embryonic gene expression of immune-, lipid transport- and apolipoprotein genes

    NASA Astrophysics Data System (ADS)

    Skjærven, Kaja H.; Jakt, Lars Martin; Dahl, John Arne; Espe, Marit; Aanes, Håvard; Hamre, Kristin; Fernandes, Jorge M. O.

    2016-10-01

    World Health Organization is concerned for parental vitamin deficiency and its effect on offspring health. This study examines the effect of a marginally dietary-induced parental one carbon (1-C) micronutrient deficiency on embryonic gene expression using zebrafish. Metabolic profiling revealed a reduced 1-C cycle efficiency in F0 generation. Parental deficiency reduced the fecundity and a total of 364 genes were differentially expressed in the F1 embryos. The upregulated genes (53%) in the deficient group were enriched in biological processes such as immune response and blood coagulation. Several genes encoding enzymes essential for the 1-C cycle and for lipid transport (especially apolipoproteins) were aberrantly expressed. We show that a parental diet deficient in micronutrients disturbs the expression in descendant embryos of genes associated with overall health, and result in inherited aberrations in the 1-C cycle and lipid metabolism. This emphasises the importance of parental micronutrient status for the health of the offspring.

  3. Initial Sediment Transport Model of the Mining-Affected Aries River Basin, Romania

    USGS Publications Warehouse

    Friedel, Michael J.; Linard, Joshua I.

    2008-01-01

    The Romanian government is interested in understanding the effects of existing and future mining activities on long-term dispersal, storage, and remobilization of sediment-associated metals. An initial Soil and Water Assessment Tool (SWAT) model was prepared using available data to evaluate hypothetical failure of the Valea Sesei tailings dam at the Rosia Poieni mine in the Aries River basin. Using the available data, the initial Aries River Basin SWAT model could not be manually calibrated to accurately reproduce monthly streamflow values observed at the Turda gage station. The poor simulation of the monthly streamflow is attributed to spatially limited soil and precipitation data, limited constraint information due to spatially and temporally limited streamflow measurements, and in ability to obtain optimal parameter values when using a manual calibration process. Suggestions to improve the Aries River basin sediment transport model include accounting for heterogeneity in model input, a two-tier nonlinear calibration strategy, and analysis of uncertainty in predictions.

  4. Long-term transport behavior of psychoactive compounds in sewage-affected groundwater

    NASA Astrophysics Data System (ADS)

    Nham, Hang Thuy Thi; Greskowiak, Janek; Hamann, Enrico; Meffe, Raffaella; Hass, Ulrike; Massmann, Gudrun

    2016-11-01

    The present study provides a model-based characterization of the long-term transport behavior of five psychoactive compounds (meprobamate, pyrithyldione, primidone, phenobarbital and phenylethylmalonamide) introduced into groundwater via sewage irrigation in Berlin, Germany. Compounds are still present in the groundwater despite the sewage farm closure in the year 1980. Due to the limited information on (i) compound concentrations in the source water and (ii) substance properties, a total of 180 cross-sectional model realizations for each compound were carried out, covering a large range of possible parameter combinations. Results were compared with the present-day contamination patterns in the aquifer and the most likely scenarios were identified based on a number of model performance criteria. The simulation results show that (i) compounds are highly persistent under the present field conditions, and (ii) sorption is insignificant. Thus, back-diffusion from low permeability zones appears as the main reason for the compound retardation.

  5. Ocean plankton. Environmental characteristics of Agulhas rings affect interocean plankton transport.

    PubMed

    Villar, Emilie; Farrant, Gregory K; Follows, Michael; Garczarek, Laurence; Speich, Sabrina; Audic, Stéphane; Bittner, Lucie; Blanke, Bruno; Brum, Jennifer R; Brunet, Christophe; Casotti, Raffaella; Chase, Alison; Dolan, John R; d'Ortenzio, Fabrizio; Gattuso, Jean-Pierre; Grima, Nicolas; Guidi, Lionel; Hill, Christopher N; Jahn, Oliver; Jamet, Jean-Louis; Le Goff, Hervé; Lepoivre, Cyrille; Malviya, Shruti; Pelletier, Eric; Romagnan, Jean-Baptiste; Roux, Simon; Santini, Sébastien; Scalco, Eleonora; Schwenck, Sarah M; Tanaka, Atsuko; Testor, Pierre; Vannier, Thomas; Vincent, Flora; Zingone, Adriana; Dimier, Céline; Picheral, Marc; Searson, Sarah; Kandels-Lewis, Stefanie; Acinas, Silvia G; Bork, Peer; Boss, Emmanuel; de Vargas, Colomban; Gorsky, Gabriel; Ogata, Hiroyuki; Pesant, Stéphane; Sullivan, Matthew B; Sunagawa, Shinichi; Wincker, Patrick; Karsenti, Eric; Bowler, Chris; Not, Fabrice; Hingamp, Pascal; Iudicone, Daniele

    2015-05-22

    Agulhas rings provide the principal route for ocean waters to circulate from the Indo-Pacific to the Atlantic basin. Their influence on global ocean circulation is well known, but their role in plankton transport is largely unexplored. We show that, although the coarse taxonomic structure of plankton communities is continuous across the Agulhas choke point, South Atlantic plankton diversity is altered compared with Indian Ocean source populations. Modeling and in situ sampling of a young Agulhas ring indicate that strong vertical mixing drives complex nitrogen cycling, shaping community metabolism and biogeochemical signatures as the ring and associated plankton transit westward. The peculiar local environment inside Agulhas rings may provide a selective mechanism contributing to the limited dispersal of Indian Ocean plankton populations into the Atlantic.

  6. Enkephalin affects ion transport via the enteric nervous system in guinea-pig ileum.

    PubMed

    Schulzke, J D; Fromm, M; Riecken, E O; Reutter, W

    1990-04-01

    The endogenous opioid enkephalin drives ion transport towards absorption. To determine the site and mechanism of this effect, fractionated stripping of guinea-pig ileum was carried out. The muscularis propria, including myenteric plexus, was removed by partial stripping. The submucosa, including the submucosal plexus, plus the muscularis mucosae were removed by total stripping. For binding studies, epithelial cells were removed by the method of Weiser leaving the lamina propria mucosae with the mucosal plexus. Radio-receptor-assay with (3H)2-D-ala-5-D-leu-enkephalin revealed enkephalin binding sites in the submucosa plus muscularis mucosae (KD = 3.6 nmol l-1; Vmax = 7.3 fmol mg-1) and in the lamina propria mucosae (KD = 4.2 nmol l-1; Vmax = 5.1 fmol mg-1. The binding was stereospecific in both layers. No binding was detected on epithelial cells. In the Ussing chamber, partially stripped ileum exhibited spontaneous ISC which was abolished by addition of tetrodotoxin (TTX) or by total stripping indicating that this ISC was neuronally stimulated by the submucosal plexus. Electrogenic chloride secretion was identified as contributing to this ISC, since the TTX-sensitive part of ISC in the partially stripped ileum was lacking in Cl- and HCO3-free medium, reappeared after addition of Cl consistent with Michaelis-Menten kinetics (Km = 19 nmol l-1) and was reversed by serosal addition of bumetanide. In addition, enkephalin increased electroneutral NaCl-absorption as obtained by Na- and Cl-flux measurements. Enkephalin decreased this spontaneous neuronally stimulated electrogenic Cl-secretion in the partially stripped ileum, but had no effect in totally stripped ileum if ISC was stimulated at the cellular level by theophylline or PGE1. We conclude that ganglia located in the submucosal plexus regulate intestinal ion transport. Enkephalin acts by presynaptic inhibition via receptors on these neurons in the submucosa and/or via receptors on their neurites in the lamina

  7. Soil structure, colloids, and chemical transport as affected by short-term reducing conditions: a laboratory study

    NASA Astrophysics Data System (ADS)

    de-Campos, A. B.; Mamedov, A. I.; Huang, C.; Wagner, L. E.

    2008-12-01

    Upland soils in the Midwestern US often undergo reducing conditions when soils are temporally flooded during the spring and remain water saturated for days or weeks. Short-term reducing conditions change the chemistry of the soil and may affect soil structure and solution chemical transport. The effects of short-term reducing conditions on chemical and physical properties of the soils, colloids, and associated chemical/nutrients transport are still not well understood and was the objective of our study. A biogeochemical reactor was built to achieve reducing conditions. Three cultivated and three uncultivated soils with different organic carbon contents were incubated in the reactor for 1 hour and 3 days under anaerobic conditions. Effects of the redox state on soil structure (pore size distribution) and drainable porosity, colloids mobility, and chemical transport were determined using high energy moisture characteristic and analytical methods. After each treatment, the soil solution was collected for redox potential (Eh), pH, and electrical conductivity (EC) measurements, and chemical analysis of metals (Ca, Mg, K), nutrients (N, P), and dissolved organic carbon. Strongly reducing conditions were achieved after 3 days of incubation and were followed by a decrease in soil porosity and an increase in pH, EC, clay dispersion, swelling, colloids mobility, and associated chemical transport. The trend for each soil depended on their initial structural stability and chemical properties. The structure of cultivated soils and the leaching of nutrients and carbon from uncultivated soils were more sensitive to the redox state. A strong correlation was found between changes in Eh and drainable porosity. The role of short-term reducing conditions on changes in redox sensitive elements, organic matter decomposition, pH, and EC and their influence on soil structure and soil particles or colloids/chemical transport for both soil groups are discussed in the paper. This study

  8. The Effects of SF6-Cu Mixture on the Arc Characteristics in a Medium Voltage Puffer Gas Circuit Breaker due to Variation of Thermodynamic Properties and Transport Coefficients

    NASA Astrophysics Data System (ADS)

    Vahid, Abbasi; Ahmad, Gholami; Kaveh, Niayesh

    2013-06-01

    In a gas circuit breaker, metal vapor resulting from electrode erosion is injected into the arc plasma. The arc then burns in a mixture of SF6 and electrode vapor, which has properties significantly different from those of pure SF6. Thermodynamic properties and transport coefficients of thermal plasmas formed in SF6-copper vapor mixtures change as a function of temperature and pressure. The property that is mostly affected by the presence of copper is electrical conductivity, which is important in magnetohydrodynamic (MHD) analysis. In this study, the transport coefficients of SF6 in the presence of 10 percent copper are considered as the basis of MHD simulation. Comparisons are made between the results during arc formation for pure SF6 and SF6-Cu mixture in a medium voltage (MV) circuit breaker. According to the transport coefficients influenced by the SF6-Cu mixture, the distribution of the electric potential, temperature, electromagnetic force density and current density of the arc column are presented and discussed. Also, the arc stability and pinch effect near current zero with 3-D simulation are investigated, which is advantageous to improving the efficiency of arc plasma simulation.

  9. Acute exposure to gas-supersaturated water does not affect reproductive success of female adult chinook salmon late in maturation

    USGS Publications Warehouse

    Gale, William L.; Maule, A.G.; Postera, A.; Peters, M.H.

    2004-01-01

    At times, total dissolved gas concentrations in the Columbia and Snake rivers have been elevated due to involuntary spill from high spring runoff and voluntary spill used as a method to pass juvenile salmonids over dams. The goal of this project was to determine if acute exposure to total dissolved gas supersaturation (TDGS) affects the reproductive performance of female chinook salmon late in their maturation. During this study, adult female spring chinook salmon were exposed to mean TDGS levels of 114.1 % to 125.5%. We ended exposures at first mortality, or at the appearance of impending death. Based on this criterion, exposures lasted from 10 to 68 h and were inversely related to TDGS. There was no effect of TDGS on pre-spawning mortality or fecundity when comparing treatment fish to experimental controls or the general hatchery population four to six weeks after exposures. Egg quality, based on egg weight and egg diameter, did not differ between treatment and control fish. Fertilization rate and survival to eyed-stage was high (>94%) for all groups. With the exception of Renibacterium salmoninarum (the causative agent of bacterial kidney disease; BKD), no viral or bacterial fish pathogens were isolated from experimental fish. The prevalence (about 45%) and severity of R. salmoninarum did not differ among the groups or the general hatchery population. We conclude that these acute exposures to moderate levels of gas-supersaturated water-perhaps similar to that experienced by immigrating adult salmon as they approach and pass a hydropower dam on the Columbia River-did not affect reproductive success of female chinook salmon late in their maturation. These results are most applicable to summer and fall chinook salmon, which migrate in the summer/fall and spawn shortly after reaching their natal streams. Published in 2004 by John Wiley and Sons, Ltd.

  10. Staufen Recruitment into Stress Granules Does Not Affect Early mRNA Transport in Oligodendrocytes

    PubMed Central

    Thomas, María G.; Tosar, Leandro J. Martinez; Loschi, Mariela; Pasquini, Juana M.; Correale, Jorge; Kindler, Stefan; Boccaccio, Graciela L.

    2005-01-01

    Staufen is a conserved double-stranded RNA-binding protein required for mRNA localization in Drosophila oocytes and embryos. The mammalian homologues Staufen 1 and Staufen 2 have been implicated in dendritic RNA targeting in neurons. Here we show that in rodent oligodendrocytes, these two proteins are present in two independent sets of RNA granules located at the distal myelinating processes. A third kind of RNA granules lacks Staufen and contains major myelin mRNAs. Myelin Staufen granules associate with microfilaments and microtubules, and their subcellular distribution is affected by polysome-disrupting drugs. Under oxidative stress, both Staufen 1 and Staufen 2 are recruited into stress granules (SGs), which are stress-induced organelles containing transiently silenced messengers. Staufen SGs contain the poly(A)-binding protein (PABP), the RNA-binding proteins HuR and TIAR, and small but not large ribosomal subunits. Staufen recruitment into perinuclear SGs is paralleled by a similar change in the overall localization of polyadenylated RNA. Under the same conditions, the distribution of recently transcribed and exported mRNAs is not affected. Our results indicate that Staufen 1 and Staufen 2 are novel and ubiquitous SG components and suggest that Staufen RNPs are involved in repositioning of most polysomal mRNAs, but not of recently synthesized transcripts, during the stress response. PMID:15525674

  11. Information technology and road transport industry: how does IT affect the lorry driver?

    PubMed

    de Croon, Einar M; Kuijer, P Paul F M; Broersen, Jake P J; Frings-Dresen, Monique H W

    2004-07-01

    A quasi-experimental design was used to study the effect of on board computer-systems (OBC-systems) on the Dutch lorry drivers' psychosocial work environment (i.e., control and demands) and coinciding mental health (i.e., need for recovery after work) and job attitudes (i.e., organisational commitment). The intervention group (n = 26) started working with an OBC-system between 1998 and 2000 and was compared with two matched reference groups (n = 26 in both groups). All participants were from a cohort of 650 drivers who participated in a prospective study on occupational stress and health. All outcome variables were quantified by standardised and validated questionnaires. Results showed that the application of OBC-systems negatively affected the drivers' job control and organisational commitment. However, OBC-systems did not influence the drivers' psychological job demands and need for recovery after work. Accordingly, it is concluded that the application of OBC-systems negatively affects the lorry driver's psychosocial work environment and job attitudes.

  12. Radiation and gas conduction heat transport across a helium dewer multilayer insulation system

    SciTech Connect

    Green, M.A.

    1995-02-01

    This report describes a method for calculating mixed heat transfer through the multilayer insulation used to insulated a 4K liquid helium cryostat. The method described permits one to estimate the insulation potential for a multilayer insulation system from first principles. The heat transfer regimes included are: radiation, conduction by free molecule gas conduction, and conduction through continuum gas conduction. Heat transfer in the transition region between the two gas conduction regimes is also included.

  13. Radiation and gas conduction heat transport across a helium dewar multilayer insulation system

    SciTech Connect

    Green, M.A.

    1994-10-10

    This report describes a method for calculating mixed heat transfer through the multilayer insulation used to insulate a 4 K liquid helium cryostat. The method described here permits one to estimate the insulation potential for a multilayer insulation system from first principles. The heat transfer regimes included are: radiation, conduction by free molecule gas conduction, and conduction through continuum gas conduction. Heat transfer in the transition region between the two gas conduction regimes is also included.

  14. Characterizing multiple timescales of stream and storage zone interaction that affect solute fate and transport in streams

    USGS Publications Warehouse

    Choi, J.; Harvey, J.W.; Conklin, M.H.

    2000-01-01

    The fate of contaminants in streams and rivers is affected by exchange and biogeochemical transformation in slowly moving or stagnant flow zones that interact with rapid flow in the main channel. In a typical stream, there are multiple types of slowly moving flow zones in which exchange and transformation occur, such as stagnant or recirculating surface water as well as subsurface hyporheic zones. However, most investigators use transport models with just a single storage zone in their modeling studies, which assumes that the effects of multiple storage zones can be lumped together. Our study addressed the following question: Can a single-storage zone model reliably characterize the effects of physical retention and biogeochemical reactions in multiple storage zones? We extended an existing stream transport model with a single storage zone to include a second storage zone. With the extended model we generated 500 data sets representing transport of nonreactive and reactive solutes in stream systems that have two different types of storage zones with variable hydrologic conditions. The one storage zone model was tested by optimizing the lumped storage parameters to achieve a best fit for each of the generated data sets. Multiple storage processes were categorized as possessing I, additive; II, competitive; or III, dominant storage zone characteristics. The classification was based on the goodness of fit of generated data sets, the degree of similarity in mean retention time of the two storage zones, and the relative distributions of exchange flux and storage capacity between the two storage zones. For most cases (> 90%) the one storage zone model described either the effect of the sum of multiple storage processes (category I) or the dominant storage process (category III). Failure of the one storage zone model occurred mainly for category II, that is, when one of the storage zones had a much longer mean retention time (t(s) ratio > 5.0) and when the dominance of

  15. Factors Affecting the Capture Efficiency of a Fume Extraction Torch for Gas Metal Arc Welding

    PubMed Central

    Bonthoux, Francis

    2016-01-01

    Welding fumes are classified as Group 2B ‘possibly carcinogenic’ and this prompts to the implementation of local exhaust ventilation (LEV). The fume extraction torch with LEV integrated into the tool is the most attractive solution but its capture efficiency is often disappointing in practice. This study assesses the main parameters affecting fume capture efficiency namely the extraction flow rate, the positioning of the suction openings on the torch, the angle of inclination of the torch to the workpiece during welding, the metal transfer modes, and the welding deposition rate. The theoretical velocity induced by suction, estimated from the extraction flow rate and the position of the suction openings, is the main parameter affecting effectiveness of the device. This is the design parameter and its value should never be <0.25 m s−1. The angle of the torch relative to the workpiece also has a great deal of influence. To improve efficiency, work station layouts need to favour positions where the torch is held with angles closer to perpendicular (<15°). Welding with high deposition rates (>1.1g s−1) and spray transfer leads to low capture efficiency if induced velocities are <0.5 m s−1. The results of the study can be used in the design of integrated on-torch extraction systems and provide information for fixing system objectives. PMID:27074798

  16. Clinically used selective estrogen receptor modulators affect different steps of macrophage-specific reverse cholesterol transport.

    PubMed

    Fernández-Suárez, María E; Escolà-Gil, Joan C; Pastor, Oscar; Dávalos, Alberto; Blanco-Vaca, Francisco; Lasunción, Miguel A; Martínez-Botas, Javier; Gómez-Coronado, Diego

    2016-09-07

    Selective estrogen receptor modulators (SERMs) are widely prescribed drugs that alter cellular and whole-body cholesterol homeostasis. Here we evaluate the effect of SERMs on the macrophage-specific reverse cholesterol transport (M-RCT) pathway, which is mediated by HDL. Treatment of human and mouse macrophages with tamoxifen, raloxifene or toremifene induced the accumulation of cytoplasmic vesicles of acetyl-LDL-derived free cholesterol. The SERMs impaired cholesterol efflux to apolipoprotein A-I and HDL, and lowered ABCA1 and ABCG1 expression. These effects were not altered by the antiestrogen ICI 182,780 nor were they reproduced by 17β-estradiol. The treatment of mice with tamoxifen or raloxifene accelerated HDL-cholesteryl ester catabolism, thereby reducing HDL-cholesterol concentrations in serum. When [(3)H]cholesterol-loaded macrophages were injected into mice intraperitoneally, tamoxifen, but not raloxifene, decreased the [(3)H]cholesterol levels in serum, liver and feces. Both SERMs downregulated liver ABCG5 and ABCG8 protein expression, but tamoxifen reduced the capacity of HDL and plasma to promote macrophage cholesterol efflux to a greater extent than raloxifene. We conclude that SERMs interfere with intracellular cholesterol trafficking and efflux from macrophages. Tamoxifen, but not raloxifene, impair M-RCT in vivo. This effect is primarily attributable to the tamoxifen-mediated reduction of the capacity of HDL to promote cholesterol mobilization from macrophages.

  17. Clinically used selective estrogen receptor modulators affect different steps of macrophage-specific reverse cholesterol transport

    PubMed Central

    Fernández-Suárez, María E.; Escolà-Gil, Joan C.; Pastor, Oscar; Dávalos, Alberto; Blanco-Vaca, Francisco; Lasunción, Miguel A.; Martínez-Botas, Javier; Gómez-Coronado, Diego

    2016-01-01

    Selective estrogen receptor modulators (SERMs) are widely prescribed drugs that alter cellular and whole-body cholesterol homeostasis. Here we evaluate the effect of SERMs on the macrophage-specific reverse cholesterol transport (M-RCT) pathway, which is mediated by HDL. Treatment of human and mouse macrophages with tamoxifen, raloxifene or toremifene induced the accumulation of cytoplasmic vesicles of acetyl-LDL-derived free cholesterol. The SERMs impaired cholesterol efflux to apolipoprotein A-I and HDL, and lowered ABCA1 and ABCG1 expression. These effects were not altered by the antiestrogen ICI 182,780 nor were they reproduced by 17β-estradiol. The treatment of mice with tamoxifen or raloxifene accelerated HDL-cholesteryl ester catabolism, thereby reducing HDL-cholesterol concentrations in serum. When [3H]cholesterol-loaded macrophages were injected into mice intraperitoneally, tamoxifen, but not raloxifene, decreased the [3H]cholesterol levels in serum, liver and feces. Both SERMs downregulated liver ABCG5 and ABCG8 protein expression, but tamoxifen reduced the capacity of HDL and plasma to promote macrophage cholesterol efflux to a greater extent than raloxifene. We conclude that SERMs interfere with intracellular cholesterol trafficking and efflux from macrophages. Tamoxifen, but not raloxifene, impair M-RCT in vivo. This effect is primarily attributable to the tamoxifen-mediated reduction of the capacity of HDL to promote cholesterol mobilization from macrophages. PMID:27601313

  18. Desiccation of sediments affects assimilate transport within aquatic plants and carbon transfer to microorganisms.

    PubMed

    von Rein, I; Kayler, Z E; Premke, K; Gessler, A

    2016-11-01

    With the projected increase in drought duration and intensity in future, small water bodies, and especially the terrestrial-aquatic interfaces, will be subjected to longer dry periods with desiccation of the sediment. Drought effects on the plant-sediment microorganism carbon continuum may disrupt the tight linkage between plants and microbes which governs sediment carbon and nutrient cycling, thus having a potential negative impact on carbon sequestration of small freshwater ecosystems. However, research on drought effects on the plant-sediment carbon transfer in aquatic ecosystems is scarce. We therefore exposed two emergent aquatic macrophytes, Phragmites australis and Typha latifolia, to a month-long summer drought in a mesocosm experiment. We followed the fate of carbon from leaves to sediment microbial communities with (13) CO2 pulse labelling and microbial phospholipid-derived fatty acid (PLFA) analysis. We found that drought reduced the total amount of carbon allocated to stem tissues but did not delay the transport. We also observed an increase in accumulation of (13) C-labelled sugars in roots and found a reduced incorporation of (13) C into the PLFAs of sediment microorganisms. Drought induced a switch in plant carbon allocation priorities, where stems received less new assimilates leading to reduced starch reserves whilst roots were prioritised with new assimilates, suggesting their use for osmoregulation. There were indications that the reduced carbon transfer from roots to microorganisms was due to the reduction of microbial activity via direct drought effects rather than to a decrease in root exudation or exudate availability.

  19. Some factors affecting phosphate transport in a perfused rat heart preparation.

    PubMed Central

    Medina, G; Illingworth, J

    1980-01-01

    Pi uptake by a perfused rat heart preparation did not require the presence of any other permeant anion, but was markedly dependent on the extracellular Na+ concentration and accelerated when tissue oxygenation was inadequate. Pi efflux was also independent of other permeant anions, but apparently varied with the intracellular Na+ concentration. Cardiac Pi efflux was not sensitive to a number of inhibitors that clock Cl- movement in heart and other tissues. Both uptake and efflux apparently proceed via a reversible electroneutral co-transport system linked to the transmembrane Na+ gradient. Pi uptake was independent of cardiac work load, but the efflux rate was sharply accelerated after an increase in aortic pressure development, with a slow return towards basal values during sustained periods of high work output. An inverted biphasic effect on the efflux rate was observed after a reduction in cardiac work load. Mild hypoxia and respiratory and metabolic acidosis each resulted in a transient acceleration of Pi efflux followed by a return towards basal values during prolonged exposure to the stimulus, whereas respiratory and metabolic alkalosis produced a similar but inverted response. The origin of these phasic effects on Pi efflux remains to be identified at present. PMID:7396864

  20. How non-adiabatic passing electron layers of linear microinstabilities affect turbulent transport

    NASA Astrophysics Data System (ADS)

    Dominski, J.; Brunner, S.; Görler, T.; Jenko, F.; Told, D.; Villard, L.

    2015-06-01

    The response of passing electrons in ion temperature gradient and trapped electron mode microturbulence regimes is investigated in tokamak geometry making use of the flux-tube version of the gyrokinetic code GENE. Results are obtained using two different electron models, fully kinetic and hybrid in which passing particles are forced to respond adiabatically, while trapped are handled kinetically. Comparing linear eigenmodes obtained with these two models enables to systematically isolate fine radial structures located at corresponding mode rational surfaces, clearly resulting from the non-adiabatic passing-electron response. Non-linear simulations show that these fine structures on the non-axisymmetric modes survive in the turbulent phase. Furthermore, through non-linear coupling to axisymmetric modes, they induce radial modulations in the effective profiles of density, ion/electron temperature, and E × B shearing rate. Finally, the passing-electron channel is shown to significantly contribute to the transport levels, at least in our ion temperature gradient case. Also shown is that the passing electrons significantly influence the E × B saturation mechanism of turbulence fluxes.

  1. Hydrostatic pressure affects selective tidal stream transport in the North Sea brown shrimp (Crangon crangon).

    PubMed

    Tielmann, Moritz; Reiser, Stefan; Hufnagl, Marc; Herrmann, Jens-Peter; Eckardt, André; Temming, Axel

    2015-10-01

    The brown shrimp (Crangon crangon) is a highly abundant invertebrate in the North Sea, with its life cycle stages ranging from deep offshore spawning to shallow onshore nursery areas. To overcome the long distances between these two habitats, brown shrimp are suspected to use selective tidal stream transport (STST), moving with the cyclic tide currents towards their preferred water depths. However, it is not known which stimulus actually triggers STST behavior in brown shrimp. In this work, we determined the influence of different hyperbaric pressures on STST behavior of juvenile brown shrimp. Brown shrimp activity was recorded in a hyperbaric pressure chamber that supplied constant and dynamic pressure conditions simulating different depths, with and without a tidal cycle. Subsequent wavelet and Fourier analysis were performed to determine the periodicity in the activity data. The results of the experiments show that STST behavior in brown shrimp varies with pressure and therefore with depth. We further show that STST behavior can be initiated by cyclic pressure changes. However, an interaction with one or more other environmental triggers remains possible. Furthermore, a security ebb-tide activity was identified that may serve to avoid potential stranding in shallow waters and is 'remembered' by shrimp for about 1.5 days without contact with tidal triggers.

  2. Selective transport of amino acids into the gas phase: driving forces for amino acid solubilization in gas-phase reverse micelles.

    PubMed

    Fang, Yigang; Bennett, Andrew; Liu, Jianbo

    2011-01-28

    We report a study on encapsulation of various amino acids into gas-phase sodium bis(2-ethylhexyl) sulfosuccinate (NaAOT) reverse micelles, using electrospray ionization guided-ion-beam tandem mass spectrometry. Collision-induced dissociation of mass-selected reverse micellar ions with Xe was performed to probe structures of gas-phase micellar assemblies, identify solute-surfactant interactions, and determine preferential incorporation sites of amino acids. Integration into gas-phase reverse micelles depends upon amino acid hydrophobicity and charge state. For examples, glycine and protonated amino acids (such as protonated tryptophan) are encapsulated within the micellar core via electrostatic interactions; while neutral tryptophan is adsorbed in the surfactant layer. As verified using model polar hydrophobic compounds, the hydrophobic effect and solute-interface hydrogen-bonding do not provide sufficient driving force needed for interfacial solubilization of neutral tryptophan. Neutral tryptophan, with a zwitterionic structure, is intercalated at the micellar interface between surfactant molecules through complementary effects of electrostatic interactions between tryptophan backbone and AOT polar heads, and hydrophobic interactions between tryptophan side chain and AOT alkyl tails. Protonation of tryptophan could significantly improve its incorporation capacity into gas-phase reverse micelles, and displace its incorporation site from the micellar interfacial zone to the core; protonation of glycine, on the other hand, has little effect on its encapsulation capacity. Another interesting observation is that amino acids of different isoelectric points could be selectively encapsulated into, and transported by, reverse micelles from solution to the gas phase, based upon their competition for protonation and subsequent encapsulation within the micellar core.

  3. Quantitative Analysis of Major Factors Affecting Black Carbon Transport and Concentrations in the Unique Atmospheric Structures of Urban Environment

    NASA Astrophysics Data System (ADS)

    Liang, Marissa Shuang

    Black carbon (BC) from vehicular emission in transportation is a principal component of particulate matters ≤ 2.5 mum (PM2.5). PM2.5 and other diesel emission pollutants (e.g., NOx) are regulated by the Clean Air Act (CAA) according to the National Ambient Air Quality standards (NAAQS). This doctoral dissertation details a study on transport behaviors of black carbon and PM2.5 from transportation routes, their relations with the atmospheric structure of an urban formation, and their relations with the use of biodiesel fuels. The results have implications to near-road risk assessment and to the development of sustainable transportation solutions in urban centers. The first part of study quantified near-roadside black carbon transport as a function of particulate matter (PM) size and composition, as well as microclimatic variables (temperature and wind fields) at the interstate highway I-75 in northern Cincinnati, Ohio. Among variables examined, wind speed and direction significantly affect the roadside transport of black carbon and hence its effective emission factor. Observed non-Gaussian dispersion occurred during low wind and for wind directions at acute angles or upwind to the receptors, mostly occurring in the morning hours. Meandering of air pollutant mass under thermal inversion is likely the driving force. In contrary, Gaussian distribution predominated in daytime of strong downwinds. The roles of urban atmospheric structure, wind fields, and the urban heat island (UHI) effects were further examined on pollutant dispersion and transport. Spatiotemporal variations of traffic flow, atmospheric structure, ambient temperature and PM2.5 concentration data from 14 EPA-certified NAAQS monitoring stations, were analyzed in relation to land-use in the Cincinnati metropolitan area. The results show a decade-long UHI effects with higher interior temperature than that in exurban, and a prominent nocturnal thermal inversion frequent in urban boundary layer. The

  4. Molecular valves for controlling gas phase transport made from discrete ångström-sized pores in graphene.

    PubMed

    Wang, Luda; Drahushuk, Lee W; Cantley, Lauren; Koenig, Steven P; Liu, Xinghui; Pellegrino, John; Strano, Michael S; Bunch, J Scott

    2015-09-01

    An ability to precisely regulate the quantity and location of molecular flux is of value in applications such as nanoscale three-dimensional printing, catalysis and sensor design. Barrier materials containing pores with molecular dimensions have previously been used to manipulate molecular compositions in the gas phase, but have so far been unable to offer controlled gas transport through individual pores. Here, we show that gas flux through discrete ångström-sized pores in monolayer graphene can be detected and then controlled using nanometre-sized gold clusters, which are formed on the surface of the graphene and can migrate and partially block a pore. In samples without gold clusters, we observe stochastic switching of the magnitude of the gas permeance, which we attribute to molecular rearrangements of the pore. Our molecular valves could be used, for example, to develop unique approaches to molecular synthesis that are based on the controllable switching of a molecular gas flux, reminiscent of ion channels in biological cell membranes and solid-state nanopores.

  5. GPI anchor attachment is required for Gas1p transport from the endoplasmic reticulum in COP II vesicles.

    PubMed Central

    Doering, T L; Schekman, R

    1996-01-01

    Inositol starvation of auxotrophic yeast interrupts glycolipid biosynthesis and prevents lipid modification of a normally glycosyl phosphatidylinositol (GPI)-linked protein, Gas1p. The unanchored Gas1p precursor undergoes progressive modification in the endoplasmic reticulum (ER), but is not modified by Golgi-specific glycosylation. Starvation-induced defects in anchor assembly and protein processing are rapid, and occur without altered maturation of other proteins. Cells remain competent to manufacture anchor components and to process Gas1p efficiently once inositol is restored. Newly synthesized Gas1p is packaged into vesicles formed in vitro from perforated yeast spheroplasts incubated with either yeast cytosol or the purified Sec proteins (COP II) required for vesicle budding from the ER. In vitro synthesized vesicles produced by inositol-starved membranes do not contain detectable Gas1p. These studies demonstrate that COP II components fulfill the soluble protein requirements for packaging a GPI-anchored protein into ER-derived transport vesicles. However, GPI anchor attachment is required for this packaging to occur. Images PMID:8598201

  6. Does manure management affect the latent greenhouse gas emitting potential of livestock manures?

    PubMed

    Pratt, Chris; Redding, Matthew; Hill, Jaye; Jensen, Paul D

    2015-12-01

    With livestock manures being increasingly sought as alternatives to costly synthetic fertilisers, it is imperative that we understand and manage their associated greenhouse gas (GHG) emissions. Here we provide the first dedicated assessment into how the GHG emitting potential of various manures responds to the different stages of the manure management continuum (e.g., from feed pen surface vs stockpiled). The research is important from the perspective of manure application to agricultural soils. Manures studied included: manure from beef feedpen surfaces and stockpiles; poultry broiler litter (8-week batch); fresh and composted egg layer litter; and fresh and composted piggery litter. Gases assessed were methane (CH4) and nitrous oxide (N2O), the two principal agricultural GHGs. We employed proven protocols to determine the manures' ultimate CH4 producing potential. We also devised a novel incubation experiment to elucidate their N2O emitting potential; a measure for which no established methods exist. We found lower CH4 potentials in manures from later stages in their management sequence compared with earlier stages, but only by a factor of 0.65×. Moreover, for the beef manures this decrease was not significant (P<0.05). Nitrous oxide emission potential was significantly positively (P<0.05) correlated with C/N ratios yet showed no obvious relationship with manure management stage. Indeed, N2O emissions from the composted egg manure were considerably (13×) and significantly (P<0.05) higher than that of the fresh egg manure. Our study demonstrates that manures from all stages of the manure management continuum potentially entail significant GHG risk when applied to arable landscapes. Efforts to harness manure resources need to account for this.

  7. Soil greenhouse gas emissions affected by irrigation, tillage, crop rotation, and nitrogen fertilization.

    PubMed

    Sainju, Upendra M; Stevens, William B; Caesar-Tonthat, Thecan; Liebig, Mark A

    2012-01-01

    Management practices, such as irrigation, tillage, cropping system, and N fertilization, may influence soil greenhouse gas (GHG) emissions. We quantified the effects of irrigation, tillage, crop rotation, and N fertilization on soil CO, NO, and CH emissions from March to November, 2008 to 2011 in a Lihen sandy loam in western North Dakota. Treatments were two irrigation practices (irrigated and nonirrigated) and five cropping systems (conventional-tilled malt barley [ L.] with N fertilizer [CT-N], conventional-tilled malt barley with no N fertilizer [CT-C], no-tilled malt barley-pea [ L.] with N fertilizer [NT-PN], no-tilled malt barley with N fertilizer [NT-N], and no-tilled malt barley with no N fertilizer [NT-C]). The GHG fluxes varied with date of sampling and peaked immediately after precipitation, irrigation, and/or N fertilization events during increased soil temperature. Both CO and NO fluxes were greater in CT-N under the irrigated condition, but CH uptake was greater in NT-PN under the nonirrigated condition than in other treatments. Although tillage and N fertilization increased CO and NO fluxes by 8 to 30%, N fertilization and monocropping reduced CH uptake by 39 to 40%. The NT-PN, regardless of irrigation, might mitigate GHG emissions by reducing CO and NO emissions and increasing CH uptake relative to other treatments. To account for global warming potential for such a practice, information on productions associated with CO emissions along with NO and CH fluxes is needed.

  8. STRUCTURE AND FUNCTION OF SUBSURFACE MICROBIAL COMMUNITIES AFFECTING RADIONUCLIDE TRANSPORT AND BIOIMMOBILIZATION

    SciTech Connect

    Joel E. Kostka; Lee Kerkhof; Kuk-Jeong Chin; Martin Keller; Joseph W. Stucki

    2011-06-15

    The objectives of this project were to: (1) isolate and characterize novel anaerobic prokaryotes from subsurface environments exposed to high levels of mixed contaminants (U(VI), nitrate, sulfate), (2) elucidate the diversity and distribution of metabolically active metal- and nitrate-reducing prokaryotes in subsurface sediments, and (3) determine the biotic and abiotic mechanisms linking electron transport processes (nitrate, Fe(III), and sulfate reduction) to radionuclide reduction and immobilization. Mechanisms of electron transport and U(VI) transformation were examined under near in situ conditions in sediment microcosms and in field investigations at the Oak Ridge Field Research Center (ORFRC), in Oak Ridge, Tennessee, where the subsurface is exposed to mixed contamination predominated by uranium and nitrate. A total of 20 publications (16 published or 'in press' and 4 in review), 10 invited talks, and 43 contributed seminars/ meeting presentations were completed during the past four years of the project. PI Kostka served on one proposal review panel each year for the U.S. DOE Office of Science during the four year project period. The PI leveraged funds from the state of Florida to purchase new instrumentation that aided the project. Support was also leveraged by the PI from the Joint Genome Institute in the form of two successful proposals for genome sequencing. Draft genomes are now available for two novel species isolated during our studies and 5 more genomes are in the pipeline. We effectively addressed each of the three project objectives and research highlights are provided. Task I - Isolation and characterization of novel anaerobes: (1) A wide range of pure cultures of metal-reducing bacteria, sulfate-reducing bacteria, and denitrifying bacteria (32 strains) were isolated from subsurface sediments of the Oak Ridge Field Research Center (ORFRC), where the subsurface is exposed to mixed contamination of uranium and nitrate. These isolates which are new

  9. [Mental health of gas and gas-transport industry workers as an indispensable condition of their efficient occupational activity].

    PubMed

    Polozhiĭ, B S

    2013-01-01

    Mental health workers in industry is a major health and social resource of any developed country. Unfortunately, Russia's level of mental health workers is unfavorable level. We have conducted a survey of employees psychoprophylactic mass of the gas industry, which occupies a leading position in the economy. Found that the prevalence of mental disorders in this professional group is 187 per 1,000 workers. In this case, 99.3% of employees with mental health problems of mentally ill for a long time, they do not receive appropriate treatment. Leading position in the structure occupy disorder with anxious and depressive symptoms, about 75% of all cases. In the treatment of these patients showed the highest efficiency Luvox, which is one of the most appropriate products in a production environment.

  10. Plasma metabolomic profiling of dairy cows affected with ketosis using gas chromatography/mass spectrometry

    PubMed Central

    2013-01-01

    Background Ketosis is an important problem for dairy cows` production performance. However, it is still little known about plasma metabolomics details of dairy ketosis. Results A gas chromatography/mass spectrometry (GC/MS) technique was used to investigate plasma metabolic differences in cows that had clinical ketosis (CK, n=22), subclinical ketosis (SK, n=32), or were clinically normal controls (NC, n=22). The endogenous plasma metabolome was measured by chemical derivatization followed by GC/MS, which led to the detection of 267 variables. A two-sample t-test of 30, 32, and 13 metabolites showed statistically significant differences between SK and NC, CK and NC, and CK and SK, respectively. Orthogonal signal correction-partial least-square discriminant analysis (OPLS-DA) revealed that the metabolic patterns of both CK and SK were mostly similar, with the exception of a few differences. The development of CK and SK involved disturbances in many metabolic pathways, mainly including fatty acid metabolism, amino acid metabolism, glycolysis, gluconeogenesis, and the pentose phosphate pathway. A diagnostic model arbitrary two groups was constructed using OPLS-DA and receiver–operator characteristic curves (ROC). Multivariate statistical diagnostics yielded the 19 potential biomarkers for SK and NC, 31 for CK and NC, and 8 for CK and SK with area under the curve (AUC) values. Our results showed the potential biomarkers from CK, SK, and NC, including carbohydrates, fatty acids, amino acids, even sitosterol and vitamin E isomers, etc. 2-piperidinecarboxylic acid and cis-9-hexadecenoic acid were closely associated with metabolic perturbations in ketosis as Glc, BHBA and NEFA for dealing with metabolic disturbances of ketosis in clinical practice. However, further research is needed to explain changes of 2,3,4-trihydroxybutyric acid, 3,4-dihydroxybutyric acid, α-aminobutyric acid, methylmalonic acid, sitosterol and α-tocopherol in CK and SK, and to reveal differences

  11. Greenhouse gas balance of mountain dairy farms as affected by grassland carbon sequestration.

    PubMed

    Salvador, Sara; Corazzin, Mirco; Romanzin, Alberto; Bovolenta, Stefano

    2017-03-30

    Recent studies on milk production have often focused on environmental impacts analysed using the Life Cycle Assessment (LCA) approach. In grassland-based livestock systems, soil carbon sequestration might be a potential sink to mitigate greenhouse gas (GHG) balance. Nevertheless, there is no commonly shared methodology. In this work, the GHG emissions of small-scale mountain dairy farms were assessed using the LCA approach. Two functional units, kg of Fat and Protein Corrected Milk (FPCM) and Utilizable Agricultural Land (UAL), and two different emissions allocations methods, no allocation and physical allocation, which accounts for the co-product beef, were considered. Two groups of small-scale dairy farms were identified based on the Livestock Units (LU) reared: <30 LU (LLU) and >30 LU (HLU). Before considering soil carbon sequestration in LCA, performing no allocation methods, LLU farms tended to have higher GHG emission than HLU farms per kg of FPCM (1.94 vs. 1.59 kg CO2-eq/kg FPCM, P ≤ 0.10), whereas the situation was reversed upon considering the m(2) of UAL as a functional unit (0.29 vs. 0.89 kg CO2-eq/m(2), P ≤ 0.05). Conversely, considering physical allocation, the difference between the two groups became less noticeable. When the contribution from soil carbon sequestration was included in the LCA and no allocation method was performed, LLU farms registered higher values of GHG emission per kg of FPCM than HLU farms (1.38 vs. 1.10 kg CO2-eq/kg FPCM, P ≤ 0.05), and the situation was likewise reversed in this case upon considering the m(2) of UAL as a functional unit (0.22 vs. 0.73 kg CO2-eq/m(2), P ≤ 0.05). To highlight how the presence of grasslands is crucial for the carbon footprint of small-scale farms, this study also applied a simulation for increasing the forage self-sufficiency of farms to 100%. In this case, an average reduction of GHG emission per kg of FPCM of farms was estimated both with no allocation and with physical

  12. H2O2-Induced Oxidative Stress Affects SO4= Transport in Human Erythrocytes

    PubMed Central

    Morabito, Rossana; Romano, Orazio; La Spada, Giuseppa; Marino, Angela

    2016-01-01

    The aim of the present investigation was to verify the effect of H2O2-induced oxidative stress on SO4= uptake through Band 3 protein, responsible for Cl-/HCO3- as well as for cell membrane deformability, due to its cross link with cytoskeletal proteins. The role of cytoplasmic proteins binding to Band 3 protein has been also considered by assaying H2O2 effects on hemoglobin-free resealed ghosts of erythrocytes. Oxidative conditions were induced by 30 min exposure of human erythrocytes to different H2O2 concentrations (10 to 300 μM), with or without GSH (glutathione, 2 mM) or curcumin (10 μM), compounds with proved antioxidant properties. Since SO4= influx through Band 3 protein is slower and better controllable than Cl- or HCO3- exchange, the rate constant for SO4= uptake was measured to prove anion transport efficiency, while MDA (malondialdehyde) levels and –SH groups were estimated to quantify the effect of oxidative stress. H2O2 induced a significant decrease in rate constant for SO4= uptake at both 100 and 300 μM H2O2. This reduction, observed in erythrocytes but not in resealed ghosts and associated to increase in neither MDA levels nor in –SH groups, was impaired by both curcumin and GSH, whereas only curcumin effectively restored H2O2-induced changes in erythrocytes shape. Our results show that: i) 30 min exposure to 300 μM H2O2 reduced SO4= uptake in human erythrocytes; ii) oxidative damage was revealed by the reduction in rate constant for SO4= uptake, but not by MDA or –SH groups levels; iii) the damage was produced via cytoplasmic components which cross link with Band 3 protein; iv) the natural antioxidant curcumin may be useful in protecting erythrocytes from oxidative injury; v) SO4= uptake through Band 3 protein may be reasonably suggested as a tool to monitor erythrocytes function under oxidative conditions possibly deriving from alcohol consumption, use of drugs, radiographic contrast media administration, hyperglicemia or

  13. H2O2-Induced Oxidative Stress Affects SO4= Transport in Human Erythrocytes.

    PubMed

    Morabito, Rossana; Romano, Orazio; La Spada, Giuseppa; Marino, Angela

    2016-01-01

    The aim of the present investigation was to verify the effect of H2O2-induced oxidative stress on SO4= uptake through Band 3 protein, responsible for Cl-/HCO3- as well as for cell membrane deformability, due to its cross link with cytoskeletal proteins. The role of cytoplasmic proteins binding to Band 3 protein has been also considered by assaying H2O2 effects on hemoglobin-free resealed ghosts of erythrocytes. Oxidative conditions were induced by 30 min exposure of human erythrocytes to different H2O2 concentrations (10 to 300 μM), with or without GSH (glutathione, 2 mM) or curcumin (10 μM), compounds with proved antioxidant properties. Since SO4= influx through Band 3 protein is slower and better controllable than Cl- or HCO3- exchange, the rate constant for SO4= uptake was measured to prove anion transport efficiency, while MDA (malondialdehyde) levels and -SH groups were estimated to quantify the effect of oxidative stress. H2O2 induced a significant decrease in rate constant for SO4= uptake at both 100 and 300 μM H2O2. This reduction, observed in erythrocytes but not in resealed ghosts and associated to increase in neither MDA levels nor in -SH groups, was impaired by both curcumin and GSH, whereas only curcumin effectively restored H2O2-induced changes in erythrocytes shape. Our results show that: i) 30 min exposure to 300 μM H2O2 reduced SO4= uptake in human erythrocytes; ii) oxidative damage was revealed by the reduction in rate constant for SO4= uptake, but not by MDA or -SH groups levels; iii) the damage was produced via cytoplasmic components which cross link with Band 3 protein; iv) the natural antioxidant curcumin may be useful in protecting erythrocytes from oxidative injury; v) SO4= uptake through Band 3 protein may be reasonably suggested as a tool to monitor erythrocytes function under oxidative conditions possibly deriving from alcohol consumption, use of drugs, radiographic contrast media administration, hyperglicemia or neurodegenerative

  14. Fusarium Oxysporum Volatiles Enhance Plant Growth Via Affecting Auxin Transport and Signaling.

    PubMed

    Bitas, Vasileios; McCartney, Nathaniel; Li, Ningxiao; Demers, Jill; Kim, Jung-Eun; Kim, Hye-Seon; Brown, Kathleen M; Kang, Seogchan

    2015-01-01

    Volatile organic compounds (VOCs) have well-documented roles in plant-plant communication and directing animal behavior. In this study, we examine the less understood roles of VOCs in plant-fungal relationships. Phylogenetically and ecologically diverse strains of Fusarium oxysporum, a fungal species complex that often resides in the rhizosphere of assorted plants, produce volatile compounds that augment shoot and root growth of Arabidopsis thaliana and tobacco. Growth responses of A. thaliana hormone signaling mutants and expression patterns of a GUS reporter gene under the auxin-responsive DR5 promoter supported the involvement of auxin signaling in F. oxysporum volatile-mediated growth enhancement. In addition, 1-naphthylthalamic acid, an inhibitor of auxin efflux, negated F. oxysporum volatile-mediated growth enhancement in both plants. Comparison of the profiles of volatile compounds produced by F. oxysporum strains that differentially affected plant growth suggests that the relative compositions of both growth inhibitory and stimulatory compounds may determine the degree of plant growth enhancement. Volatile-mediated signaling between fungi and plants may represent a potentially conserved, yet mostly overlooked, mechanism underpinning plant-fungus interactions and fungal niche adaption.

  15. Fusarium Oxysporum Volatiles Enhance Plant Growth Via Affecting Auxin Transport and Signaling

    PubMed Central

    Bitas, Vasileios; McCartney, Nathaniel; Li, Ningxiao; Demers, Jill; Kim, Jung-Eun; Kim, Hye-Seon; Brown, Kathleen M.; Kang, Seogchan

    2015-01-01

    Volatile organic compounds (VOCs) have well-documented roles in plant-plant communication and directing animal behavior. In this study, we examine the less understood roles of VOCs in plant-fungal relationships. Phylogenetically and ecologically diverse strains of Fusarium oxysporum, a fungal species complex that often resides in the rhizosphere of assorted plants, produce volatile compounds that augment shoot and root growth of Arabidopsis thaliana and tobacco. Growth responses of A. thaliana hormone signaling mutants and expression patterns of a GUS reporter gene under the auxin-responsive DR5 promoter supported the involvement of auxin signaling in F. oxysporum volatile-mediated growth enhancement. In addition, 1-naphthylthalamic acid, an inhibitor of auxin efflux, negated F. oxysporum volatile-mediated growth enhancement in both plants. Comparison of the profiles of volatile compounds produced by F. oxysporum strains that differentially affected plant growth suggests that the relative compositions of both growth inhibitory and stimulatory compounds may determine the degree of plant growth enhancement. Volatile-mediated signaling between fungi and plants may represent a potentially conserved, yet mostly overlooked, mechanism underpinning plant-fungus interactions and fungal niche adaption. PMID:26617587

  16. Common gas phase molecules from fungi affect seed germination and plant health in Arabidopsis thaliana

    PubMed Central

    2014-01-01

    Fungal volatile organic compounds (VOCs) play important ecophysiological roles in mediating inter-kingdom signaling with arthropods but less is known about their interactions with plants. In this study, Arabidopsis thaliana was used as a model in order to test the physiological effects of 23 common vapor-phase fungal VOCs that included alcohols, aldehydes, ketones, and other chemical classes. After exposure to a shared atmosphere with the 23 individual VOCs for 72 hrs, seeds were assayed for rate of germination and seedling formation; vegetative plants were assayed for fresh weight and chlorophyll concentration. All but five of the VOCs tested (1-decene, 2-n-heptylfuran, nonanal, geosmin and -limonene) had a significant effect in inhibiting either germination, seedling formation or both. Seedling formation was entirely inhibited by exposure to 1-octen-3-one, 2-ethylhexanal, 3-methylbutanal, and butanal. As assayed by a combination of fresh weight and chlorophyll concentration, 2-ethylhexanal had a negative impact on two-week-old vegetative plants. Three other compounds (1-octen-3-ol, 2-ethylhexanal, and 2-heptylfuran) decreased fresh weight alone. Most of the VOCs tested did not change the fresh weight or chlorophyll concentration of vegetative plants. In summary, when tested as single compounds, fungal VOCs affected A. thaliana in positive, negative or neutral ways. PMID:25045602

  17. Trace Gas Transport in the Troposphere and the Interpretation of In-Situ Concentration Measurements

    NASA Technical Reports Server (NTRS)

    Plumb, R. Alan

    2000-01-01

    The research conducted comprised two sub-projects: 1) definition of the major transport pathways in the troposphere with focus on low-level transport in baroclinic systems, and (2) investigation, and assessment of the usefulness of, tracer-tracer correlations in the troposphere.

  18. Technological Change and Its Labor Impact in Five Energy Industries. Coal Mining/Oil and Gas Extraction/Petroleum Refining/Petroleum Pipeline Transportation/Electric and Gas Utilities.

    ERIC Educational Resources Information Center

    Bureau of Labor Statistics (DOL), Washington, DC.

    This bulletin appraises major technological changes emerging in five American industries (coal mining, oil and gas extraction, petroleum refining, petroleum pipeline transportation, and electric and gas utilities) and discusses the impact of these changes on productivity and occupations over the next five to ten years. Its separate reports on each…

  19. Theoretical and Experimental Investigation of Gas Flows, Powder Transport and Heating in Coaxial Laser Direct Metal Deposition (DMD) Process

    NASA Astrophysics Data System (ADS)

    Kovalev, O. B.; Zaitsev, A. V.; Novichenko, D.; Smurov, I.

    2011-03-01

    The results of theoretical and experimental investigations of direct metal deposition (DMD) processes involving a CO2-laser with the power up to 5 kW and wave length of 10.6 μm are presented. The physical and mathematical model of multi-layer gas flows with gas-jet transportation of metal powder particles has been developed. To simulate the flows of carrier and shaping gases in annular channels of a triple coaxial nozzle, Navier-Stokes equations were applied for an axisymmetric flow. Thermodynamics and powder particles transport are calculated from a discrete-trajectory model with due regard to particle collision with solid walls of the transport nozzle. It is shown that particles may overheat on their way between the nozzle and substrate; the overheating depends on the trajectories by which particles move, on their size, and time of their retention in the laser-radiation region. The results of performed experimental researches on DMD processes visualization are presented. Some results of numerical simulation and experimental data are compared and analyzed.

  20. A reactive transport modelling approach to assess the leaching potential of hydraulic fracturing fluids associated with coal seam gas extraction

    NASA Astrophysics Data System (ADS)

    Mallants, Dirk; Simunek, Jirka; Gerke, Kirill

    2015-04-01

    Coal Seam Gas production generates large volumes of "produced" water that may contain compounds originating from the use of hydraulic fracturing fluids. Such produced water also contains elevated concentrations of naturally occurring inorganic and organic compounds, and usually has a high salinity. Leaching of produced water from storage ponds may occur as a result of flooding or containment failure. Some produced water is used for irrigation of specific crops tolerant to elevated salt levels. These chemicals may potentially contaminate soil, shallow groundwater, and groundwater, as well as receiving surface waters. This paper presents an application of scenario modelling using the reactive transport model for variably-saturated media HP1 (coupled HYDRUS-1D and PHREEQC). We evaluate the fate of hydraulic fracturing chemicals and naturally occurring chemicals in soil as a result of unintentional release from storage ponds or when produced water from Coal Seam Gas operations is used in irrigation practices. We present a review of exposure pathways and relevant hydro-bio-geo-chemical processes, a collation of physico-chemical properties of organic/inorganic contaminants as input to a set of generic simulations of transport and attenuation in variably saturated soil profiles. We demonstrate the ability to model the coupled processes of flow and transport in soil of contaminants associated with hydraulic fracturing fluids and naturally occurring contaminants.

  1. Physics-based, reduced-order gas cloud with radiative transport model for rapid simulation of hyperspectral infrared sensors

    NASA Astrophysics Data System (ADS)

    Kottke, Peter A.; Fedorov, Andrei G.

    2012-05-01

    We have developed a reduced-order, physics-based model of gas cloud transport and combined it with an approximate formulation of the equation of radiative transport to enable efficient prediction of spectral irradiation for simulation of hyperspectral infrared sensors. The resulting combined model is easily implemented, providing a rapid and flexible in silico experimentation capability. The gas cloud model is based on the entrainment hypothesis and predicts cloud trajectories in three-dimensions, with elevation changes occurring primarily due to buoyancy effects and with spreading and accompanying dilution and cooling occurring due to a turbulence dominated growth mechanism. The radiation transport model is simplified through an approximate treatment of scattering that transforms the governing equation from an integro-differential equation to an ordinary differential equation. The conjugate model has been combined with a simple sensor model and has been validated through comparison to results from large-scale field tests. The utility of the simulations has also been demonstrated through inclusion in a larger algorithm development and analysis program, the chem/bio algorithm development kit.

  2. The influence of the intensity of electric field on methane-air mixed gas discharge electron transport parameters

    NASA Astrophysics Data System (ADS)

    Shen, Shuang-yan; Jin, Xing; Zhang, Peng

    2016-10-01

    Plasma enhanced ignition is an important way in the field of ignition auxiliary. It has got wide attention throughout the researchers both at home and abroad. The plasma is usually added in the form of discharge. It makes a big difference in the discharge form according to different discharge unit, different kinds of electric field and different kinds of discharge medium. Variety of methods could be used to characterize the parameters of the plasma. The electron transport parameter is an important variable during the process of the plasma discharge. The mathematical model was set up to calculate the electron transport parameters in different reduced electric intensity. The electrons meet the Boltzmann equations in plasma system. Reasonable methods were used to simplify the Boltzmann equations. The electron transport parameters of methane-air mixed gas at the same equivalent ratio and pressure in different reduced electric field were calculated. The calculation results show that the EEDF turns to the right with the increasing of reduced electric field. The average electron energy and average electron energy of the mixed gas increases linearly with the increasing of reduced electric field. The increasing of reduced electric field enhances the electronic/energy diffusion effect and the enhancing effect is more apparent when the reduced electric field is high. The increasing of reduced electric field restrains the electron diffusion and energy transference restrains from the trend of the change. The inhibition effect is weakening with the increasing of the reduced electric field.

  3. Soil-Gas Identification of Environmental Factors Affecting CO2 Concentrations Beneath a Playa Wetland: Implications for Soil-Gas Monitoring at Carbon Storage Sites

    NASA Astrophysics Data System (ADS)

    Romanak, K.; Bennett, P.

    2009-12-01

    support significant carbonate dissolution resulting from reaction of CO2 with infiltrating water and soil carbonate. Results of the study show that the degree of carbon reactivity within a near-surface environment limits the effectiveness of shallow subsurface and surface-flux soil-gas monitoring at engineered carbon repositories. When carbon reactivity is at a maximum, CO2 cycling is complex and input of exogenous CO2 into the system is difficult to constrain and quantify. A summary of the factors that define carbon reactivity and their affects on near-surface soil-gas monitoring at geologic carbon storage sites is presented, along with recommendations for site evaluation with regard to near-surface monitoring.

  4. Letter Report: Scoping Analysis of Gas Phase Transport from the Rulison Underground Nuclear Test

    SciTech Connect

    Clay Cooper

    2004-05-06

    This letter report documents the results of a computer model to quantify the travel time of tritium (radioactive hydrogen) from an underground nuclear detonation in 1969 toward a proposed producing gas well located 1,500 feet (457 meters) away.

  5. AN INQUIRY INTO THE STRUCTURAL CONDITIONS AFFECTING FLUID TRANSPORT IN THE INTERSTITIAL TISSUE OF THE SKIN

    PubMed Central

    McMaster, Philip D.

    1941-01-01

    With the aim of determining the structural conditions which affect fluid movement in the cutaneous connective tissue of mice, various test fluids were brought into contact with it under conditions such that neither blood vessels nor lymphatics were directly entered. Locke's solution, mouse serum, and a mixture of Locke's solution with a dye which causes edema were all employed. At atmospheric pressure, Locke's solution entered the tissues intermittently. When subjected to very low pressures it continued to enter the skin intermittently and at approximately the same rate. At pressures above 4.5 cm. of water, however, the flow became continuous but it did not increase in rate significantly until pressures of about 8.5 cm. were employed. There was no relationship between the rate of flow and the pressure employed. At a pressure of about 8.5 cm. the resistance of the tissues seemed to give way abruptly as if the formed elements had been separated. This has been termed the "breaking point." After it had been reached each further increase of pressure produced a proportionately greater inflow. Under the conditions of our experiments, the dye-Locke"s solution and also the homologous serum failed to enter the tissues at atmospheric pressure. It was necessary to subject these fluids to pressure to force them into the skin at the same rate at which the Locke's solution entered it spontaneously. Under these circumstances the dye-Locke's solution and the serum entered the skin continuously, not intermittently like the plain Locke's solution. As the pressure was gradually raised, no significant increase of flow into the tissues occurred until a point was reached, on the average 8.5 cm. of water, at which fluid suddenly began to enter very rapidly. This point, the "breaking point" already mentioned, was reached at the same pressure irrespective of the character of the fluid employed, showing that the phenomenon was produced by the fluid bulk. Once it had been attained, further

  6. A study of the physical-chemical mechanisms and variables which affect the transport of inorganic and organic heterogeneous systems

    SciTech Connect

    Anderson, M.A.; Zeltner, W.A.

    1990-07-01

    In order to model transport of dissolved ions in subsurface environments, one should understand how these ions interact with solid phase adsorbents. Our primary goal has been investigating the reaction mechanisms which affect microcontaminant partitioning between aqueous solutions and solid phase adsorbents, using goethite ({alpha}-FeOOH) as a model adsorbent. Cylindrical internal reflection -- Fourier transform infrared (CIR-FTIR) spectroscopy has been developed as the primary technique for this study. Wet chemical adsorption studies, acoustophoresis and electrophoretic mobility have been used to obtain supporting information as needed. Phenol and o-nitrophenol did not adsorb to goethite. Benzoate, phthalate and p-hydroxybenzoate all adsorbed via a bidentate mechanism to two adjacent iron atoms, while salicylate and 2,4-dihydroxybenzoate formed a chelate complex to single iron atoms. Phosphate adsorption was predominately bidentate.

  7. Tritium Transport at the Rulison Site, a Nuclear-stimulated Low-permeability Natural Gas Reservoir

    SciTech Connect

    C. Cooper; M. Ye; J. Chapman

    2008-04-01

    The U.S. Department of Energy (DOE) and its predecessor agencies conducted a program in the 1960s and 1970s that evaluated technology for the nuclear stimulation of low-permeability natural gas reservoirs. The second project in the program, Project Rulison, was located in west-central Colorado. A 40-kiltoton nuclear device was detonated 2,568 m below the land surface in the Williams Fork Formation on September 10, 1969. The natural gas reservoirs in the Williams Fork Formation occur in low permeability, fractured sandstone lenses interbedded with shale. Radionuclides derived from residual fuel products, nuclear reactions, and activation products were generated as a result of the detonation. Most of the radionuclides are contained in a cooled, solidified melt glass phase created from vaporized and melted rock that re-condensed after the test. Of the mobile gas-phase radionuclides released, tritium ({sup 3}H or T) migration is of most concern. The other gas-phase radionuclides ({sup 85}Kr, {sup 14}C) were largely removed during production testing in 1969 and 1970 and are no longer present in appreciable amounts. Substantial tritium remained because it is part of the water molecule, which is present in both the gas and liquid (aqueous) phases. The objectives of this work are to calculate the nature and extent of tritium contamination in the subsurface from the Rulison test from the time of the test to present day (2007), and to evaluate tritium migration under natural-gas production conditions to a hypothetical gas production well in the most vulnerable location outside the DOE drilling restriction. The natural-gas production scenario involves a hypothetical production well located 258 m horizontally away from the detonation point, outside the edge of the current drilling exclusion area. The production interval in the hypothetical well is at the same elevation as the nuclear chimney created by the detonation, in order to evaluate the location most vulnerable to

  8. Numerical modeling of landfill gas and heat transport in the deformable MSW landfill body. Part 1. Development of the model

    NASA Astrophysics Data System (ADS)

    Kutsyi, D. V.

    2015-06-01

    The article is devoted to studying the parameters of wells that are used as part of vertical gas extraction systems for degassing landfills. To this end, approaches to modeling the main processes occurring in the landfill's porous medium are considered. The considered approaches served as a basis for elaborating a thermophysical gas and heat transport model that takes into account variation in the hydrodynamic properties of wastes resulting from their secondary settlement. The adequacy of the results obtained using the developed model is confirmed by the data of classic works. The effect the secondary settlement of wastes has on the distribution of pressure and temperature in the landfill body is determined. It is shown that compaction of wastes due to their secondary settlement results in a growth of pressure by 40% on the average.

  9. Climate impacts of air quality policy: switching to a natural gas-fueled public transportation system in New Delhi.

    PubMed

    Reynolds, Conor C O; Kandlikar, Milind

    2008-08-15

    Between 2001 and 2003, public transport vehicles in New Delhi were required to switch their fuel to natural gas in an attemptto reduce their air pollution impacts. This study examines the climatic impacts of New Delhi's fuel switching policy, and outlines implications for such efforts in rapidly industrializing countries. Natural gas is mostly composed of methane, an important greenhouse gas. Emitted aerosols (black carbon, particulate organic carbon, and sulfate) also cause radiative forcing. We find that methane and black carbon emissions are critical contributors to the change in carbon dioxide equivalent [CO2(e)] emissions. In New Delhi, the switch to natural gas results in a 30% increase in CO2(e) when the impact of aerosols is not considered. However, when aerosol emissions are taken into account in our model, the net effect of the switch is estimated to be a 10% reduction in CO2(e), and there may be as much as a 30% reduction in CO2(e). There is significant potential for emissions reductions through the United Nations Framework Convention on Climate Change (UNFCCC) Clean Development Mechanism for such fuel switching projects.

  10. Measurement of the emission rate of an aerosol source--comparison of aerosol and gas transport coefficients.

    PubMed

    Bémer, D; Callé, S; Godinot, S; Régnier, R; Dessagne, J M

    2000-12-01

    A measuring method of the emission rate of an atmospheric pollutant source, based on the use of a tracer gas (helium) and developed in the case of a gaseous source, was tested for an aerosol source. The influence of both particle sedimentation and wall depositions was studied. The transport coefficients of the tracer gas and of alumina particles of various particle sizes (MMAD from 8 to 36 microns) were measured on a vertical axis close to the source, in a 71 m3 room swept by a piston flow. The measurements clearly demonstrated the predominant influence of sedimentation in the case of particles with aerodynamic diameters greater than 10 microns. Particle wall deposition was determined by measuring the gas and particle concentration decay in the ventilated room. To do this, a new tracing method using a fluorescent aerosol was developed. The measured aerosol deposition rates are much higher than those calculated from the formula of Corner for a cubical volume. Aerosol sedimentation and wall deposition are two phenomena limiting the use of a tracer gas to measure the aerosol emission rate. The chemical substances and materials used in work premises are likely to be released into the atmosphere and lead to the formation of pollutants. These emissions stem from either physical or chemical processes (evaporation of a solvent) or from mechanical processes (dispersion of oil droplets at the source of mists).

  11. Working process study of a novel scroll type multiphase pump for the transportation of gas-liquid mixtures

    NASA Astrophysics Data System (ADS)

    Wang, J.; Zha, H. B.; Zhang, X. H.; Zhang, D. H.

    2012-11-01

    A novel scroll type multiphase pump was proposed to transport gas-liquid two-phase mixture. There is a pressure unloading gap from compression chambers to the discharge port by constructing scroll wrap profile with variational meshing clearance in this scroll multiphase pump. In the working process when the volume of working chamber decreases, the pressure of gas-liquid mixtures increases gradually, at the same time small amounts of gas-liquid mixture are pushed to the discharge port from compression chambers through the pressure unloading gap. Therefore, this multiphase pump has an advantage of unloading pressure method automatically, and the frequently problem of liquid impacting in volume multiphase pump is solved. The safety and reliability of volumetric multiphase pump are improved, and the scope of multiphase pump of the gas-liquid ratio is expanded. The working process and the performance characteristics of scroll multiphase pump were analyzed too, and the generation method of scroll wrap profile with variational meshing clearance was investigated. The equations of the profile were obtained, and the changing principle of the working volume and the meshing clearance were analyzed. The geometric theory of scroll multiphase pump was formed. All of that lay the theoretical foundation for engineering design of this novel scroll.

  12. Assessing factors affecting the thermal properties of a passive thermal refuge using three-dimensional hydrodynamic flow and transport modeling

    USGS Publications Warehouse

    Decker, Jeremy D.; Swain, Eric D.; Stith, Bradley M.; Langtimm,