WorldWideScience

Sample records for cell water dynamics

  1. Water Dynamics in Living Cells and Tumor Cell Migration in Confined Microenvironments

    Science.gov (United States)

    Sun, Sean

    More than 70% of the total mass in living cells is water. In most biological scenarios water serves as a passive medium responsible for solvation and proper functioning of proteins. However, it has been long recognized that there are situations where dynamic transport of water in cells is important. First, cells actively transport water in order to maintain its volume, and because cell volume directly influences cell shape and internal hydrostatic pressure, it is a critical aspect of cell mechanics. Furthermore, cell volume is coupled to protein synthesis which ultimately determines the cell size. Therefore water transport and cell volume dynamics ultimately impact cell growth and division. Second, epithelial cells in organs such as the eye and kidney actively transport water across the cell membrane and the epithelial layer. Indeed, water channels such as aquaporins increase water permeability of the membrane and facilitate this transport. Recent, we have shown that in confined microenvironments, active transport of water is responsible for actin-independent cell movement in confined spaces, especially for cancer cells. These results suggest that cells actively control its water content. The active regulation of water content is a crucial aspect of cell dynamics. We will discuss a theoretical model of cell pressure/volume control. Implications of this model for active cell dynamics in multi-cellular epithelial sheets will be discussed.

  2. Reversibility, Water-Mediated Switching, and Directed Cell Dynamics

    OpenAIRE

    J. C. Phillips

    2008-01-01

    Reversible switching of the complex network dynamics of proteins is mimicked in selected network glasses and compacted small carbohydrate molecules. Protein transitions occur on long time scales ~ us -ms, evocative of the exponentially large viscosities found in glass-forming supercooled liquids just above the glass transition; in searching for mechanisms for reversibly slowed "geared activation", Kauzmann was led from proteins to glasses. I show here that selected network glasses and small c...

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

    Science.gov (United States)

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

    2015-03-01

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

  4. Molecular Dynamics Simulations of a Cyclic DP-240 Amylose Fragment in a Periodic Cell: Glass Transition Temperature and Water Diffusion

    Science.gov (United States)

    Molecular dynamics simulations using AMB06C, an in-house carbohydrate force field, (NPT ensembles, 1atm) were carried out on a periodic cell that contained a cyclic-DP-240 amylose fragment and TIP3P water molecules. Molecular conformation and movement of the amylose fragment and water molecules at ...

  5. Collective dynamics of water in the living cell and in bulk liquid. New physical models and biological inferences

    OpenAIRE

    Preoteasa, Eugen A.; Apostol, Marian V.

    2008-01-01

    In the frame of collective dynamics in water, models built on elementary excitations and long-range electromagnetic interactions in the cell and bulk liquid are presented. Making use of the low effective mass of water coherence domains (CDs), we examined the relevance of simple quantum models to cellular characteristics. A hypothesis of CDs Bose-type condensation, and models of CD in spherical wells with impenetrable and semipenetrable walls, and of an isotropic oscillator consisting of two i...

  6. Modelling and Validation of Water Hydration of PEM Fuel Cell Membrane in Dynamic Operations

    DEFF Research Database (Denmark)

    Liso, Vincenzo; Nielsen, Mads Pagh

    2015-01-01

    and considers the water adsorption/desorption phenomena in the membrane. The effect of diffusivity, surface roughness and water content driving force is considered. The model is validated against experimental data. Many studies have considered the fuel cell membrane to be in equilibrium condition...

  7. Collective dynamics of water in the living cell and in bulk liquid. New physical models and biologcial infereneces

    CERN Document Server

    Preoteasa, Eugen A

    2008-01-01

    In the frame of collective dynamics in water, models built on elementary excitations and long-range electromagnetic interactions in the cell and bulk liquid are presented. Making use of the low effective mass of water coherence domains (CDs), we examined the relevance of simple quantum models to cellular characteristics. A hypothesis of CDs Bose-type condensation, and models of CD in spherical wells with impenetrable and semipenetrable walls, and of an isotropic oscillator consisting of two interacting CDs were investigated. Estimated cellular volumes matched to medium-sized bacteria and small prokaryotes, and to some organelles in eukaryotic cells. Also, the cytotoxic effects of heavy water in eukaryotes were explained. In another approach we proposed a plasmon-like model of hydrogen-oxygen ionic plasma in liquid water. In addition to plasmonic oscillations, the model predicted sound-like non-equilibrium elementary excitations that we called densitons (the sound anomaly of water), the vaporization heat and t...

  8. Systems analysis of guard cell membrane transport for enhanced stomatal dynamics and water use efficiency.

    Science.gov (United States)

    Wang, Yizhou; Hills, Adrian; Blatt, Michael R

    2014-04-01

    Stomatal transpiration is at the center of a crisis in water availability and crop production that is expected to unfold over the next 20 to 30 years. Global water usage has increased 6-fold in the past 100 years, twice as fast as the human population, and is expected to double again before 2030, driven mainly by irrigation and agriculture. Guard cell membrane transport is integral to controlling stomatal aperture and offers important targets for genetic manipulation to improve crop performance. However, its complexity presents a formidable barrier to exploring such possibilities. With few exceptions, mutations that increase water use efficiency commonly have been found to do so with substantial costs to the rate of carbon assimilation, reflecting the trade-off in CO₂ availability with suppressed stomatal transpiration. One approach yet to be explored in detail relies on quantitative systems analysis of the guard cell. Our deep knowledge of transport and homeostasis in these cells gives real substance to the prospect for reverse engineering of stomatal responses, using in silico design in directing genetic manipulation for improved water use and crop yields. Here we address this problem with a focus on stomatal kinetics, taking advantage of the OnGuard software and models of the stomatal guard cell recently developed for exploring stomatal physiology. Our analysis suggests that manipulations of single transporter populations are likely to have unforeseen consequences. Channel gating, especially of the dominant K⁺ channels, appears the most favorable target for experimental manipulation. PMID:24596330

  9. Dynamic water management of polymer electrolyte membrane fuel cells using intermittent RH control

    KAUST Repository

    Hussaini, I.S.

    2010-06-01

    A novel method of water management of polymer electrolyte membrane (PEM) fuel cells using intermittent humidification is presented in this study. The goal is to maintain the membrane close to full humidification, while eliminating channel flooding. The entire cycle is divided into four stages: saturation and de-saturation of the gas diffusion layer followed by de-hydration and hydration of membrane. By controlling the duration of dry and humid flows, it is shown that the cell voltage can be maintained within a narrow band. The technique is applied on experimental test cells using both plain and hydrophobic materials for the gas diffusion layer and an improvement in performance as compared to steady humidification is demonstrated. Duration of dry and humid flows is determined experimentally for several operating conditions. © 2010 Elsevier B.V. All rights reserved.

  10. Dynamics and thermodynamics of water

    Energy Technology Data Exchange (ETDEWEB)

    Kumar, Pradeep; Stanley, H Eugene [Center for Studies in Physics and Biology, Rockefeller University, New York, NY 10021 (United States); Franzese, Giancarlo [Departament de Fisica Fonamental, Universitat de Barcelona, Diagonal 647, Barcelona 08028 (Spain)], E-mail: pradeep.kumar@rockefeller.edu, E-mail: gfranzese@ub.edu, E-mail: hes@bu.edu

    2008-06-18

    On decreasing the temperature T, the correlation time {tau} of supercooled water displays a dynamic crossover from non-Arrhenius dynamics (with T-dependent activation energy) at high T to Arrhenius dynamics (with constant activation energy) at low T. Simulations for water models show that this crossover occurs at the locus of maximum isobaric specific heat in the pressure-temperature (P-T) plane. Results of simulations show also that at this locus there is a sharp change of local structure: more tetrahedral below the locus, and less tetrahedral above it. Furthermore, in water solutions with proteins or DNA, simulations show that in correspondence with this locus there is a crossover in the dynamics of the biomolecules, a phenomenon commonly known as the protein glass transition. To clarify the relation of the dynamic crossover with the thermodynamics of water, we study the dynamics of a cell model of water which can be tuned to exhibit: (1) a first-order phase transition line that separates the liquids of high and low densities at low temperatures; this phase transition line terminates at a liquid-liquid critical point (LLCP), from which departs the Widom line T{sub W}(P), i.e. the line of maximum isobaric specific heat in the P-T plane; (2) the singularity-free (SF) scenario, under which the system exhibits water-like anomalies but with no finite temperature liquid-liquid critical point. We find that the dynamic crossover is present in both the LLCP and the SF cases. Moreover, on the basis of the study of the probability p{sub B} of forming a bond, we propose and verify a relation between dynamics and thermodynamics that is able to show how the crossover is a consequence of a local relaxation process associated with breaking a bond and reorienting the molecule. We further find a distinct difference in pressure dependence of the dynamic crossover between the LLCP and SF scenarios, which may help in resolving which of the scenarios correctly explains the anomalous

  11. Dynamics and thermodynamics of water

    International Nuclear Information System (INIS)

    On decreasing the temperature T, the correlation time τ of supercooled water displays a dynamic crossover from non-Arrhenius dynamics (with T-dependent activation energy) at high T to Arrhenius dynamics (with constant activation energy) at low T. Simulations for water models show that this crossover occurs at the locus of maximum isobaric specific heat in the pressure-temperature (P-T) plane. Results of simulations show also that at this locus there is a sharp change of local structure: more tetrahedral below the locus, and less tetrahedral above it. Furthermore, in water solutions with proteins or DNA, simulations show that in correspondence with this locus there is a crossover in the dynamics of the biomolecules, a phenomenon commonly known as the protein glass transition. To clarify the relation of the dynamic crossover with the thermodynamics of water, we study the dynamics of a cell model of water which can be tuned to exhibit: (1) a first-order phase transition line that separates the liquids of high and low densities at low temperatures; this phase transition line terminates at a liquid-liquid critical point (LLCP), from which departs the Widom line TW(P), i.e. the line of maximum isobaric specific heat in the P-T plane; (2) the singularity-free (SF) scenario, under which the system exhibits water-like anomalies but with no finite temperature liquid-liquid critical point. We find that the dynamic crossover is present in both the LLCP and the SF cases. Moreover, on the basis of the study of the probability pB of forming a bond, we propose and verify a relation between dynamics and thermodynamics that is able to show how the crossover is a consequence of a local relaxation process associated with breaking a bond and reorienting the molecule. We further find a distinct difference in pressure dependence of the dynamic crossover between the LLCP and SF scenarios, which may help in resolving which of the scenarios correctly explains the anomalous behavior of

  12. Proton-Induced Trap States, Injection and Recombination Dynamics in Water-Splitting Dye-Sensitized Photoelectrochemical Cells.

    Science.gov (United States)

    McCool, Nicholas S; Swierk, John R; Nemes, Coleen T; Saunders, Timothy P; Schmuttenmaer, Charles A; Mallouk, Thomas E

    2016-07-01

    Water-splitting dye-sensitized photoelectrochemical cells (WS-DSPECs) utilize a sensitized metal oxide and a water oxidation catalyst in order to generate hydrogen and oxygen from water. Although the Faradaic efficiency of water splitting is close to unity, the recombination of photogenerated electrons with oxidized dye molecules causes the quantum efficiency of these devices to be low. It is therefore important to understand recombination mechanisms in order to develop strategies to minimize them. In this paper, we discuss the role of proton intercalation in the formation of recombination centers. Proton intercalation forms nonmobile surface trap states that persist on time scales that are orders of magnitude longer than the electron lifetime in TiO2. As a result of electron trapping, recombination with surface-bound oxidized dye molecules occurs. We report a method for effectively removing the surface trap states by mildly heating the electrodes under vacuum, which appears to primarily improve the injection kinetics without affecting bulk trapping dynamics, further stressing the importance of proton control in WS-DSPECs. PMID:27295276

  13. Water management studies in PEM fuel cells, part III: Dynamic breakthrough and intermittent drainage characteristics from GDLs with and without MPLs

    Energy Technology Data Exchange (ETDEWEB)

    Lu, Zijie; Daino, Michael M.; Rath, Cody; Kandlikar, Satish G. [Mechanical Engineering Department, Rochester Institute of Technology, 76 Lomb Memorial Dr., Rochester, NY 14623 (United States)

    2010-05-15

    The transport of liquid water and gaseous reactants through a gas diffusion layer (GDL) is one of the most important water management issues in a proton exchange membrane fuel cell (PEMFC). In this work, the liquid water breakthrough dynamics, characterized by the capillary pressure and water saturation, across GDLs with and without a microporous layer (MPL) are studied in an ex-situ setup which closely simulates a real fuel cell configuration and operating conditions. The results reveal that recurrent breakthroughs are observed for all of the GDL samples tested, indicating the presence of an intermittent water drainage mechanism in the GDL. This is accounted for by the breakdown and redevelopment of the continuous water paths during water drainage as demonstrated by Haines jumps. For GDL samples without MPL, a dynamic change of breakthrough locations is observed, which originates from the rearrangement of the water configuration in the GDL following the drainage. For GDL samples with MPL, no dynamic change of breakthrough location can be found and the water saturation is significantly lower than the samples without MPL. These results suggest that the MPL not only limits the number of water entry locations into the GDL (such that the water saturation is drastically reduced), but also stabilizes the water paths (or morphology). The effect of MPL on the two-phase flow dynamics in gas channels is also studied with multi-channel flow experiments. The most important result is that GDL without MPL promotes film flow and shifts the slug-to-film flow transition to lower air flow rates, compared with the case of GDL with MPL. This is closely related to the larger number of water breakthrough locations through GDL without MPL, which promotes the formation of water film. (author)

  14. Ultrafast dynamics of interfacial water

    OpenAIRE

    Hsieh, C.-S.

    2014-01-01

    We survey the dynamics of the interfacial water at the air/water interface. We reveal that the ultrafast vibrational energy transfer dynamics and spectral diffusion of the OH stretch mode at the interface differs from those in the bulk significantly; the rotational motion is 3 times faster than in the bulk and energy relaxation is dominated by the rotational dynamics as well as the vibrational energy transfer from the free OH group to the H-bonded OH groups of a water molecule with the free O...

  15. Linking water and permafrost dynamics

    OpenAIRE

    Sjöberg, Ylva

    2015-01-01

    The extent and dynamics of permafrost are tightly linked to the distribution and movement of water in arctic landscapes. As the Arctic warms more rapidly than the global average, profound changes are expected in both permafrost and hydrology; however, much is still not known about the interactions between these two systems. The aim of this thesis is to provide new knowledge on the links between permafrost and hydrology under varying environmental conditions and across different scales. The ob...

  16. Microbial Cell Dynamics Lab (MCDL)

    Data.gov (United States)

    Federal Laboratory Consortium — The Microbial Cell Dynamics Laboratory at PNNL enables scientists to study the molecular details of microbes under relevant environmental conditions. The MCDL seeks...

  17. Dynamized Preparations in Cell Culture

    Directory of Open Access Journals (Sweden)

    Ellanzhiyil Surendran Sunila

    2009-01-01

    Full Text Available Although reports on the efficacy of homeopathic medicines in animal models are limited, there are even fewer reports on the in vitro action of these dynamized preparations. We have evaluated the cytotoxic activity of 30C and 200C potencies of ten dynamized medicines against Dalton's Lymphoma Ascites, Ehrlich's Ascites Carcinoma, lung fibroblast (L929 and Chinese Hamster Ovary (CHO cell lines and compared activity with their mother tinctures during short-term and long-term cell culture. The effect of dynamized medicines to induce apoptosis was also evaluated and we studied how dynamized medicines affected genes expressed during apoptosis. Mother tinctures as well as some dynamized medicines showed significant cytotoxicity to cells during short and long-term incubation. Potentiated alcohol control did not produce any cytotoxicity at concentrations studied. The dynamized medicines were found to inhibit CHO cell colony formation and thymidine uptake in L929 cells and those of Thuja, Hydrastis and Carcinosinum were found to induce apoptosis in DLA cells. Moreover, dynamized Carcinosinum was found to induce the expression of p53 while dynamized Thuja produced characteristic laddering pattern in agarose gel electrophoresis of DNA. These results indicate that dynamized medicines possess cytotoxic as well as apoptosis-inducing properties.

  18. Water dynamics at the nanoscale

    Directory of Open Access Journals (Sweden)

    C.Masciovecchi

    2008-03-01

    Full Text Available The recent construction of an Inelastic UltraViolet Scattering (IUVS beamline at the ELETTRA Synchrotron Light Laboratory opens new possibilities for studying the density fluctuation spectrum, S(Q,E, of disordered systems in the mesoscopic momentum (Q and energy (E transfer region not accessible by other spectroscopic techniques. As an example of possible application of IUVS technique we will discuss the new insights provided in the case of water dynamics. From the analysis of IUVS spectra we were able to measure the temperature and pressure dependencies of structural relaxation time (τ in water. In the case of room-pressure water the values of τ, as derived by IUVS, are fairly consistent with previous determinations and, most important, its temperature dependence agrees with Mode Coupling Theory (MCT predictions. Moreover we found that τ decreases with increasing pressure at fixed temperature. The observed trend demonstrates that the structural relaxation phenomenology is strongly affected by the applied pressure. However, further investigations are necessary in order to clarify the physical meaning of these preliminary experimental results.

  19. Dynamized Preparations in Cell Culture

    OpenAIRE

    Girija Kuttan; Korengath Chandran Preethi; Ramadasan Kuttan; Ellanzhiyil Surendran Sunila

    2009-01-01

    Although reports on the efficacy of homeopathic medicines in animal models are limited, there are even fewer reports on the in vitro action of these dynamized preparations. We have evaluated the cytotoxic activity of 30C and 200C potencies of ten dynamized medicines against Dalton's Lymphoma Ascites, Ehrlich's Ascites Carcinoma, lung fibroblast (L929) and Chinese Hamster Ovary (CHO) cell lines and compared activity with their mother tinctures during short-term and long-term cell culture. The ...

  20. Inhomogeneous dynamics in confined water nanodroplets.

    Science.gov (United States)

    Dokter, Adriaan M; Woutersen, Sander; Bakker, Huib J

    2006-10-17

    The effect of confinement on the dynamical properties of liquid water was studied by mid-infrared ultrafast pump-probe spectroscopy on HDO:D2O in reverse micelles. By preparing water-containing reverse micelles of different well defined sizes, we varied the degree of geometric confinement in water nanodroplets with radii ranging from 0.2 to 4.5 nm. We find that water molecules located near the interface confining the droplet exhibit slower vibrational energy relaxation and have a different spectral absorption than those located in the droplet core. As a result, we can measure the orientational dynamics of these different types of water with high selectivity. We observe that the water molecules in the core show similar orientational dynamics as bulk water and that the water layer solvating the interface is highly immobile. PMID:17028175

  1. Ultrafast dynamics of water in cationic micelles.

    Science.gov (United States)

    Dokter, Adriaan M; Woutersen, Sander; Bakker, Huib J

    2007-03-28

    The effect of confinement on the dynamical properties of liquid water is investigated for water enclosed in cationic reverse micelles. The authors performed mid-infrared ultrafast pump-probe spectroscopy on the OH-stretch vibration of isotopically diluted HDO in D(2)O in cetyltrimethylammonium bromide (CTAB) reverse micelles of various sizes. The authors observe that the surfactant counterions are inhomogeneously distributed throughout the reverse micelle, and that regions of extreme salinity occur near the interfacial Stern layer. The authors find that the water molecules in the core of the micelles show similar orientational dynamics as bulk water, and that water molecules in the counterion-rich interfacial region are much less mobile. An explicit comparison is made with the dynamics of water confined in anionic sodium bis(2-ethythexyl) sulfosuccinate (AOT) reverse micelles. The authors find that interfacial water in cationic CTAB reverse micelles has a higher orientational mobility than water in anionic AOT reverse micelles. PMID:17411144

  2. Ultrafast dynamics of water in cationic micelles

    Science.gov (United States)

    Dokter, Adriaan M.; Woutersen, Sander; Bakker, Huib J.

    2007-03-01

    The effect of confinement on the dynamical properties of liquid water is investigated for water enclosed in cationic reverse micelles. The authors performed mid-infrared ultrafast pump-probe spectroscopy on the OH-stretch vibration of isotopically diluted HDO in D2O in cetyltrimethylammonium bromide (CTAB) reverse micelles of various sizes. The authors observe that the surfactant counterions are inhomogeneously distributed throughout the reverse micelle, and that regions of extreme salinity occur near the interfacial Stern layer. The authors find that the water molecules in the core of the micelles show similar orientational dynamics as bulk water, and that water molecules in the counterion-rich interfacial region are much less mobile. An explicit comparison is made with the dynamics of water confined in anionic sodium bis(2-ethythexyl) sulfosuccinate (AOT) reverse micelles. The authors find that interfacial water in cationic CTAB reverse micelles has a higher orientational mobility than water in anionic AOT reverse micelles.

  3. Excess water dynamics in hydrotalcite: QENS study

    Indian Academy of Sciences (India)

    S Mitra; A Pramanik; D Chakrabarty; R Mukhopadhyay

    2004-08-01

    Results of the quasi-elastic neutron scattering (QENS) measurements on the dynamics of excess water in hydrotalcite sample with varied content of excess water are reported. Translational motion of excess water can be best described by random translational jump diffusion model. The observed increase in translational diffusivity with increase in the amount of excess water is attributed to the change in binding of the water molecules to the host layer.

  4. Dynamics of confined water. Proton dynamics

    International Nuclear Information System (INIS)

    Quasi-elastic neutron scattering(QENS) at small momentum transfer(Q) is related to the self-diffusion and that at higher momentum transfer related local jump motion. Motions of hydrogen in inorganic oxides, porous materials and organic polymer gels were constituted through the moving with water molecules, local jump between trapped sites and other moving modes. The QENS experiments provided the Q and energy(ω) transfer region, which correspond with each moving modes. As the obtained broad QENS spectra contain many moving modes, careful analyses should be necessary by reliable experimental data using a facility with high-resolution, wide momentum-transfer spectrometer and high neutron flux. (author)

  5. Epidermal stem cell dynamics

    OpenAIRE

    Sieber-Blum, Maya

    2011-01-01

    Wong and Reiter have explored the possibility that hair follicle stem cells can give rise to basal cell carcinoma (BCC). They expressed in mice an inducible human BCC-derived oncogenic allele of Smoothened, SmoM2, under the control of either the cytokeratin 14 (K14) or cytokeratin 15 (K15) promoter. Smoothened encodes a G-protein-coupled receptor protein in the hedgehog pathway, the misregulation of which is implicated in BCC and other human cancers. Chronic injury is thought to be a contribu...

  6. Dynamic Programming Applications in Water Resources

    Science.gov (United States)

    Yakowitz, Sidney

    1982-08-01

    The central intention of this survey is to review dynamic programming models for water resource problems and to examine computational techniques which have been used to obtain solutions to these problems. Problem areas surveyed here include aqueduct design, irrigation system control, project development, water quality maintenance, and reservoir operations analysis. Computational considerations impose severe limitation on the scale of dynamic programming problems which can be solved. Inventive numerical techniques for implementing dynamic programming have been applied to water resource problems. Discrete dynamic programming, differential dynamic programming, state incremental dynamic programming, and Howard's policy iteration method are among the techniques reviewed. Attempts have been made to delineate the successful applications, and speculative ideas are offered toward attacking problems which have not been solved satisfactorily.

  7. Dynamics of Water Jet in Water Jet Looms

    Institute of Scientific and Technical Information of China (English)

    李克让; 陈明

    2001-01-01

    On the base of the study on dynamics of water jet in water jet looms, the parameters of water jet mechanism which affect the speed of water jet are analyzed and optimized. So the stability of the water jet can be improved to raise the speed of water jet as well as weft insertion rate and to enlarge the width of woven fabrics a lot. At the same time it also points out that to increase water jet speed and to prolong its affective jet time depend mainly on the accretion of spring rate (constant)of stiffness and the diminution of plunger's cross sectional area respectively.

  8. Water losses dynamic modelling in water distribution networks

    Science.gov (United States)

    Puleo, Valeria; Milici, Barbara

    2015-12-01

    In the last decades, one of the main concerns of the water system managers have been the minimisation of water losses, that frequently reach values of 30% or even 70% of the volume supplying the water distribution network. The economic and social costs associated with water losses in modern water supply systems are rapidly rising to unacceptably high levels. Furthermore, the problem of the water losses assumes more and more importance mainly when periods of water scarcity occur or when not sufficient water supply takes part in areas with fast growth. In the present analysis, a dynamic model was used for estimating real and apparent losses of a real case study. A specific nodal demand model reflecting the user's tank installation and a specific apparent losses module were implemented. The results from the dynamic model were compared with the modelling estimation based on a steady-state approach.

  9. Fuel-Cell Water Separator

    Science.gov (United States)

    Burke, Kenneth Alan; Fisher, Caleb; Newman, Paul

    2010-01-01

    The main product of a typical fuel cell is water, and many fuel-cell configurations use the flow of excess gases (i.e., gases not consumed by the reaction) to drive the resultant water out of the cell. This two-phase mixture then exits through an exhaust port where the two fluids must again be separated to prevent the fuel cell from flooding and to facilitate the reutilization of both fluids. The Glenn Research Center (GRC) has designed, built, and tested an innovative fuel-cell water separator that not only removes liquid water from a fuel cell s exhaust ports, but does so with no moving parts or other power-consuming components. Instead it employs the potential and kinetic energies already present in the moving exhaust flow. In addition, the geometry of the separator is explicitly intended to be integrated into a fuel-cell stack, providing a direct mate with the fuel cell s existing flow ports. The separator is also fully scalable, allowing it to accommodate a wide range of water removal requirements. Multiple separators can simply be "stacked" in series or parallel to adapt to the water production/removal rate. GRC s separator accomplishes the task of water removal by coupling a high aspect- ratio flow chamber with a highly hydrophilic, polyethersulfone membrane. The hydrophilic membrane readily absorbs and transports the liquid water away from the mixture while simultaneously resisting gas penetration. The expansive flow path maximizes the interaction of the water particles with the membrane while minimizing the overall gas flow restriction. In essence, each fluid takes its corresponding path of least resistance, and the two fluids are effectively separated. The GRC fuel-cell water separator has a broad range of applications, including commercial hydrogen-air fuel cells currently being considered for power generation in automobiles.

  10. Towed Water Turbine Computational Fluid Dynamics Analysis

    OpenAIRE

    Maughan, Robert G.

    2013-01-01

    Computational fluid dynamics can be used to predict operating conditions of towed water turbines which are used in long distance sailing applications to meet electrical demands. The design consists of a turbine fastened to a shaft which is attached to a generator by a rope. The turbine is pulled in water behind a sailboat and torque is transmitted through the rope to turn the onboard generator and produce power. Torque curves from an alternator, generator, and from computational fluid dynamic...

  11. Shape dynamics of growing cell walls

    OpenAIRE

    Banerjee, Shiladitya; Scherer, Norbert F.; Dinner, Aaron R.

    2015-01-01

    We introduce a general theoretical framework to study the shape dynamics of actively growing and remodeling surfaces. Using this framework we develop a physical model for growing bacterial cell walls and study the interplay of cell shape with the dynamics of growth and constriction. The model allows us to derive constraints on cell wall mechanical energy based on the observed dynamics of cell shape. We predict that exponential growth in cell size requires a constant amount of cell wall energy...

  12. In-situ observation of dynamic water behavior in polymer electrolyte fuel cell by combined method of Small-Angle Neutron Scattering and Neutron Radiography

    International Nuclear Information System (INIS)

    In-situ observation was conducted on an operating polymer electrolyte fuel cell with a combined method of small-angle neutron scattering (SANS) and neutron radiography (NR). The combined measurement system has been recently developed to visualize water in a wide length scale from nano- to millimeter and successfully detected a spatial distribution of the water generated in individual cell elements; NR macroscopically detected the water in a gas diffusion layer and a flow-field, whereas SANS microscopically did in a membrane electrode assembly. In particular SANS was found to be a strong tool to make a rather precise analysis on the water content inside of ion conducting channels of polymer electrolyte membrane.

  13. Wetting dynamics of a water nanodrop on graphene.

    Science.gov (United States)

    Andrews, Joseph Eugene; Sinha, Shayandev; Chung, Peter W; Das, Siddhartha

    2016-09-14

    Water-graphene wetting interactions are central to several applications such as desalination, water filtration, electricity generation, biochemical sensing, fabrication of fuel cells, and many more. While substantial attention has been devoted to probe the wetting statics of a water drop on graphene, unraveling the possible wetting translucency nature of graphene, very little research has been done on the dynamics of wetting of water drops on graphene-coated solids or free-standing graphene layers. In this paper, we employ molecular dynamics (MD) simulations to study the contact and the spreading of a water nanodrop, quantifying its wetting dynamics, on supported and free-standing graphene. We demonstrate that nanoscale water drops establish contact with graphene by forming patches on graphene, and this patch formation is hastened for graphene layer(s) supported on hydrophilic solids. More importantly, our results demonstrate that the nanodrop spreading dynamics, regardless of the number of graphene layers or the nature of the underlying solid, obey the half-power law, i.e., r∼t(1/2) (where r is the wetting contact radius and t is the spreading time) for the entire timespan of spreading except towards the very end of the spreading lifetime when the spreading stops. Such a spreading behavior is exactly analogous to the spreading dynamics of nanodroplets for standard solids - this is in sharp contrast to the wetting statics of graphene where the wetting translucency effect makes graphene different from other standard solids. PMID:27306955

  14. Vibrational dynamics of hydration water in amylose

    CERN Document Server

    Cavatorta, F; Albanese, G; Angelini, N

    2002-01-01

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

  15. Water dynamics in glass ionomer cements

    Science.gov (United States)

    Berg, M. C.; Jacobsen, J.; Momsen, N. C. R.; Benetti, A. R.; Telling, M. T. F.; Seydel, T.; Bordallo, H. N.

    2016-07-01

    Glass ionomer cements (GIC) are an alternative for preventive dentistry. However, these dental cements are complex systems where important motions related to the different states of the hydrogen atoms evolve in a confined porous structure. In this paper, we studied the water dynamics of two different liquids used to prepare either conventional or resin-modified glass ionomer cement. By combining thermal analysis with neutron scattering data we were able to relate the water structure in the liquids to the materials properties.

  16. Origin of subdiffusion of water molecules on cell membrane surfaces

    CERN Document Server

    Yamamoto, Eiji; Yasui, Masato; Yasuoka, Kenji

    2014-01-01

    Water molecules play an important role in providing unique environments for biological reactions on cell membranes. It is widely believed that water molecules form bridges that connect lipid molecules and stabilize cell membranes. Using all-atom molecular dynamics simulations, we show that translational and rotational diffusion of water molecules on lipid membrane surfaces exhibit subdiffusion. Moreover, we provide evidence that both divergent mean trapping time (continuous-time random walk) and long-correlated noise (fractional Brownian motion) contribute to this subdiffusion. These results suggest that subdiffusion on cell membranes causes the water retardation, an enhancement of cell membrane stability, and a higher reaction efficiency.

  17. Shape dynamics of growing cell walls

    CERN Document Server

    Banerjee, Shiladitya; Dinner, Aaron R

    2015-01-01

    We introduce a general theoretical framework to study the shape dynamics of actively growing and remodeling surfaces. Using this framework we develop a physical model for growing bacterial cell walls and study the interplay of cell shape with the dynamics of growth and constriction. The model allows us to derive constraints on cell wall mechanical energy based on the observed dynamics of cell shape. We predict that exponential growth in cell size requires a constant amount of cell wall energy to be dissipated per unit volume. We use the model to understand and contrast growth in bacteria with different shapes such as spherical, ellipsoidal, cylindrical and toroidal morphologies. Coupling growth to cell wall constriction, we predict a discontinuous shape transformation, from partial constriction to cell division, as a function of the chemical potential driving cell-wall synthesis. Our model for cell wall energy and shape dynamics relates growth kinetics with cell geometry, and provides a unified framework to d...

  18. Dynamic characteristics of an automotive fuel cell system for transitory load changes

    OpenAIRE

    Rabbani, Raja Abid; Rokni, Masoud

    2013-01-01

    A dynamic model of Polymer Electrolyte Membrane Fuel Cell (PEMFC) system is developed to investigate the behavior and transient response of a fuel cell system for automotive applications. Fuel cell dynamics are subjected to reactant flows, heat management and water transportation inside the fuel cell. Therefore, a control-oriented model has been devised in Aspen Plus Dynamics, which accommodates electrochemical, thermal, feed flow and water crossover models in addition to two-phase calculatio...

  19. Dynamics of water confined in clay minerals

    International Nuclear Information System (INIS)

    Ultrafast infrared spectroscopy of the O-D stretching mode of dilute HOD in H2O probes the local environment and the hydrogen bond network of confined water. The dynamics of water molecules confined in the interlayer space of montmorillonites (Mt) and in interaction with two types of cations (Li+ and Ca2+) but also with the negatively charged siloxane surface are studied. The results evidence that the OD vibrational dynamics is significantly slowed down in confined media: it goes from 1.7 ps in neat water to 2.6 Ps in the case of Li+ cations with two water pseudo-layers (2.2-2.3 ps in the case of Ca2+ cations) and to 4.7 ps in the case of Li+ cations with one water pseudo-layer. No significant difference between the two cations is noticed. In this 2D confined geometry (the interlayer space being about 0.6 nm for two water pseudo-layers), the relaxation time constants obtained are comparable to the ones measured in analogous concentrated salt solutions. Nevertheless, and in strong opposition to the observations performed in the liquid phase, anisotropy experiments evidence the absence of rotational motions on a 5 ps time scale, proving that the hydrogen bond network in the interlayer space of the clay mineral is locked at this time scale. (authors)

  20. Dynamics and reactivity of confined water

    International Nuclear Information System (INIS)

    In the context of new sustainable energy sources quest, the nuclear energy remains a key solution. However, with the development of nuclear technology, problems relating to nuclear waste disposal arise; thus, the radiolysis of water in confined media is extremely important with respect to matters related to long time storage of nuclear waste. Studies in model porous media would allow the projection of a confined water radiolysis simulator. A first step in this direction was made by studying the radiolysis of water confined in Vycor and CPG glasses; this study continues the trend set and investigates the effects of confinement in metal materials upon the water radiolysis allowing the understanding of metal - water radiation induced corrosion. A further/complete understanding of the radiolytic process under confinement requires knowledge of the effect of confinement upon the dynamics of confined molecules and on the evolution of the species produced upon ionizing radiation. In this respect, we have used the OH vibrator as a probe of the hydrogen bond network properties and thus investigated the dynamics of confined water using IR time resolved spectroscopy. The evolution of the hydrated electron under confinement was studied on a nano and picosecond time scale using UV pump - visible probe technique and single shot spectroscopy. (author)

  1. Transcriptome Dynamics of Pseudomonas putida KT2440 under Water Stress

    DEFF Research Database (Denmark)

    Gülez, Gamze; Dechesne, Arnaud; Workman, Christopher;

    2012-01-01

    Water deprivation can be a major stressor to microbial life in surface and subsurface soil. In unsaturated soils, the matric potential (Ψm) is often the main component of the water potential, which measures the thermodynamic availability of water. A low matric potential usually translates into...... water forming thin liquid films in the soil pores. Little is known of how bacteria respond to such conditions, where, in addition to facing water deprivation that might impair their metabolism, they have to adapt their dispersal strategy as swimming motility may be compromised. Using the pressurized...... porous surface model (PPSM), which allows creation of thin liquid films by controlling Ψm, we examined the transcriptome dynamics of Pseudomonas putida KT2440. We identified the differentially expressed genes in cells exposed to a mild matric stress (–0.4 MPa) for 4, 24, or 72 h. The major response was...

  2. Simulation of Boiling Water Reactor dynamics

    International Nuclear Information System (INIS)

    This master thesis describes a mathematical model of a boiling water reactor and address the dynamic behaviour of the neutron kinetics, boilding dynamics and pressur stability. The simulation have been done using the SIMNON-program. The meaning were that the result from this work possibly would be adjust to supervision methods suitable for application in computer systems. This master thesis in automatic control has been done at the Department of Automatic Control, Lund Institute of Technology. The initiative to the work came from Sydkraft AB. (author)

  3. Dynamical Transition of Protein-Hydration Water

    Science.gov (United States)

    Doster, W.; Busch, S.; Gaspar, A. M.; Appavou, M.-S.; Wuttke, J.; Scheer, H.

    2010-03-01

    Thin layers of water on biomolecular and other nanostructured surfaces can be supercooled to temperatures not accessible with bulk water. Chen et al. [Proc. Natl. Acad. Sci. U.S.A. 103, 9012 (2006)]PNASA60027-842410.1073/pnas.0602474103 suggested that anomalies near 220 K observed by quasielastic neutron scattering can be explained by a hidden critical point of bulk water. Based on more sensitive measurements of water on perdeuterated phycocyanin, using the new neutron backscattering spectrometer SPHERES, and an improved data analysis, we present results that show no sign of such a fragile-to-strong transition. The inflection of the elastic intensity at 220 K has a dynamic origin that is compatible with a calorimetric glass transition at 170 K. The temperature dependence of the relaxation times is highly sensitive to data evaluation; it can be brought into perfect agreement with the results of other techniques, without any anomaly.

  4. Numerical Simulations of Droplet Dynamics in PEM Fuel Cell Microchannels

    Science.gov (United States)

    Cauble, Eric; Owkes, Mark

    2015-11-01

    Proton exchange membrane (PEM) fuel cells are of beneficial interest due to their capability of producing clean energy with zero emissions. An important design challenge hindering the performance of fuel cells is controlling water removal to maintain a hydrated membrane while avoiding excess water that may lead to channel blockage. Fuel cell water management requires a detailed knowledge of multiphase flow dynamics within microchannels. Direct observation of gas-liquid flows is difficult due to the small scale and viewing obstructions of the channels within the fuel cell. Instead, this work uses a CFD approach to compute the formation and dynamics of droplets in fuel cell channels. The method leverages a conservative volume-of-fluid (VOF) formulation coupled with a novel methodology to track dynamic contact angles. We present details of the numerical approach and simulation results relevant to water management in PEM fuel cells. In particular, it is shown that variation of the contact hysteresis angle influences the wetting properties of the droplet and significantly impacts water transport throughout the a fuel cell channel.

  5. Vibrational Spectroscopy and Dynamics of Water.

    Science.gov (United States)

    Perakis, Fivos; Marco, Luigi De; Shalit, Andrey; Tang, Fujie; Kann, Zachary R; Kühne, Thomas D; Torre, Renato; Bonn, Mischa; Nagata, Yuki

    2016-07-13

    We present an overview of recent static and time-resolved vibrational spectroscopic studies of liquid water from ambient conditions to the supercooled state, as well as of crystalline and amorphous ice forms. The structure and dynamics of the complex hydrogen-bond network formed by water molecules in the bulk and interphases are discussed, as well as the dissipation mechanism of vibrational energy throughout this network. A broad range of water investigations are addressed, from conventional infrared and Raman spectroscopy to femtosecond pump-probe, photon-echo, optical Kerr effect, sum-frequency generation, and two-dimensional infrared spectroscopic studies. Additionally, we discuss novel approaches, such as two-dimensional sum-frequency generation, three-dimensional infrared, and two-dimensional Raman terahertz spectroscopy. By comparison of the complementary aspects probed by various linear and nonlinear spectroscopic techniques, a coherent picture of water dynamics and energetics emerges. Furthermore, we outline future perspectives of vibrational spectroscopy for water researches. PMID:27096701

  6. Macromolecular Dynamics in Red Blood Cells Investigated Using Neutron Spectroscopy

    CERN Document Server

    Stadler, Andreas Maximilian; Demmel, Franz; Artmann, Gerhard; 10.1098/rsif.2010.0306

    2011-01-01

    We present neutron scattering measurements on the dynamics of hemoglobin (Hb) in human red blood cells in vivo. Global and internal Hb dynamics were measured in the ps to ns time- and {\\AA} length-scale using quasielastic neutron backscattering spectroscopy. We observed the cross-over from global Hb short-time to long-time self-diffusion. Both short- and long-time diffusion coefficients agree quantitatively with predicted values from hydrodynamic theory of non-charged hard-sphere suspensions when a bound water fraction of around 0.23g H2O/ g Hb is taken into account. The higher amount of water in the cells facilitates internal protein fluctuations in the ps time-scale when compared to fully hydrated Hb powder. Slower internal dynamics of Hb in red blood cells in the ns time-range were found to be rather similar to results obtained with fully hydrated protein powders, solutions and E. coli cells.

  7. Epigenetic dynamics across the cell cycle

    DEFF Research Database (Denmark)

    Kheir, Tony Bou; Lund, Anders H.

    2010-01-01

    Progression of the mammalian cell cycle depends on correct timing and co-ordination of a series of events, which are managed by the cellular transcriptional machinery and epigenetic mechanisms governing genome accessibility. Epigenetic chromatin modifications are dynamic across the cell cycle...... a correct inheritance of epigenetic chromatin modifications to daughter cells. In this chapter, we summarize the current knowledge on the dynamics of epigenetic chromatin modifications during progression of the cell cycle....

  8. Water reactive hydrogen fuel cell power system

    Science.gov (United States)

    Wallace, Andrew P; Melack, John M; Lefenfeld, Michael

    2014-01-21

    A water reactive hydrogen fueled power system includes devices and methods to combine reactant fuel materials and aqueous solutions to generate hydrogen. The generated hydrogen is converted in a fuel cell to provide electricity. The water reactive hydrogen fueled power system includes a fuel cell, a water feed tray, and a fuel cartridge to generate power for portable power electronics. The removable fuel cartridge is encompassed by the water feed tray and fuel cell. The water feed tray is refillable with water by a user. The water is then transferred from the water feed tray into a fuel cartridge to generate hydrogen for the fuel cell which then produces power for the user.

  9. Photonic water dynamically responsive to external stimuli.

    Science.gov (United States)

    Sano, Koki; Kim, Youn Soo; Ishida, Yasuhiro; Ebina, Yasuo; Sasaki, Takayoshi; Hikima, Takaaki; Aida, Takuzo

    2016-01-01

    Fluids that contain ordered nanostructures with periodic distances in the visible-wavelength range, anomalously exhibit structural colours that can be rapidly modulated by external stimuli. Indeed, some fish can dynamically change colour by modulating the periodic distance of crystalline guanine sheets cofacially oriented in their fluid cytoplasm. Here we report that a dilute aqueous colloidal dispersion of negatively charged titanate nanosheets exhibits structural colours. In this 'photonic water', the nanosheets spontaneously adopt a cofacial geometry with an ultralong periodic distance of up to 675 nm due to a strong electrostatic repulsion. Consequently, the photonic water can even reflect near-infrared light up to 1,750 nm. The structural colour becomes more vivid in a magnetic flux that induces monodomain structural ordering of the colloidal dispersion. The reflective colour of the photonic water can be modulated over the entire visible region in response to appropriate physical or chemical stimuli. PMID:27572806

  10. Regulation of Water in Plant Cells

    Science.gov (United States)

    Kowles, Richard V.

    2010-01-01

    Cell water relationships are important topics to be included in cell biology courses. Differences exist in the control of water relationships in plant cells relative to control in animal cells. One important reason for these differences is that turgor pressure is a consideration in plant cells. Diffusion and osmosis are the underlying factors…

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

    International Nuclear Information System (INIS)

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

  12. Dynamic regulation of aquaporin-4 water channels in neurological disorders.

    Science.gov (United States)

    Hsu, Ying; Tran, Minh; Linninger, Andreas A

    2015-10-01

    Aquaporin-4 water channels play a central role in brain water regulation in neurological disorders. Aquaporin-4 is abundantly expressed at the astroglial endfeet facing the cerebral vasculature and the pial membrane, and both its expression level and subcellular localization significantly influence brain water transport. However, measurements of aquaporin-4 levels in animal models of brain injury often report opposite trends of change at the injury core and the penumbra. Furthermore, aquaporin-4 channels play a beneficial role in brain water clearance in vasogenic edema, but a detrimental role in cytotoxic edema and exacerbate cell swelling. In light of current evidence, we still do not have a complete understanding of the role of aquaporin-4 in brain water transport. In this review, we propose that the regulatory mechanisms of aquaporin-4 at the transcriptional, translational, and post-translational levels jointly regulate water permeability in the short and long time scale after injury. Furthermore, in order to understand why aquaporin-4 channels play opposing roles in cytotoxic and vasogenic edema, we discuss experimental evidence on the dynamically changing osmotic gradients between blood, extracellular space, and the cytosol during the formation of cytotoxic and vasogenic edema. We conclude with an emerging picture of the distinct osmotic environments in cytotoxic and vasogenic edema, and propose that the directions of aquaporin-4-mediated water clearance in these two types of edema are distinct. The difference in water clearance pathways may provide an explanation for the conflicting observations of the roles of aquaporin-4 in edema resolution. PMID:26526878

  13. Polarizable water model for Dissipative Particle Dynamics

    Science.gov (United States)

    Pivkin, Igor; Peter, Emanuel

    2015-11-01

    Dissipative Particle Dynamics (DPD) is an efficient particle-based method for modeling mesoscopic behavior of fluid systems. DPD forces conserve the momentum resulting in a correct description of hydrodynamic interactions. Polarizability has been introduced into some coarse-grained particle-based simulation methods; however it has not been done with DPD before. We developed a new polarizable coarse-grained water model for DPD, which employs long-range electrostatics and Drude oscillators. In this talk, we will present the model and its applications in simulations of membrane systems, where polarization effects play an essential role.

  14. THE INTERIOR DYNAMICS OF WATER PLANETS

    International Nuclear Information System (INIS)

    The ever-expanding catalog of detected super-Earths calls for theoretical studies of their properties in the case of a substantial water layer. This work considers such water planets with a range of masses and water mass fractions (2-5 MEarth, 0.02%-50% H2O). First, we model the thermal and dynamical structure of the near-surface for icy and oceanic surfaces, finding separate regimes where the planet is expected to maintain a subsurface liquid ocean and where it is expected to exhibit ice tectonics. Newly discovered exoplanets may be placed into one of these regimes given estimates of surface temperature, heat flux, and gravity. Second, we construct a parameterized convection model for the underlying ice mantle of higher ice phases, finding that materials released from the silicate-iron core should traverse the ice mantle on the timescale of 0.1 to 100 megayears. We present the dependence of the overturn times of the ice mantle and the planetary radius on total mass and water mass fraction. Finally, we discuss the implications of these internal processes on atmospheric observables.

  15. Salt—Water Dynamics in Soils:II.Effect of Precipitation on SaltWater Dynamics

    Institute of Scientific and Technical Information of China (English)

    YOUWEN-RUI; MENGFAN-HUA

    1992-01-01

    Through a simulation test carried out with soil columns (61.8cm in diameter),the effect of precipitation on salt-water dynamics in soils was studied by in-situ monitoring of salt-water dynamics using soil salinity sensors and tensioneters.The results show that in the profile of whole silty loam soil,the surface runoff volume due to precipitation and the salt-leaching role of infiltrated precipitation increased with the depth of ground water;and in the profile with an intercalated bed of clay or with a thick upper layer of clay,the amount of surface runoff was greater but the salt-leaching role of precipitation was smaller than those in the profile of whole silty loam soil.In case of soil water being supplemented by precipitation,the evaporation of groundwater in the soil columns reduced,resulting in a great decline of salt accumulation from soil profile to surface soil.The effect of precipitation on the water regime of soil profile was performed via both water infiltration and water pressure transfer.The direct infiltration depth of precipitation was less than 1m in general,but water pressure transfer could go up to groundwater surface directly.

  16. Dynamic modelling of Industrial Heavy Water Plant

    International Nuclear Information System (INIS)

    The dynamic behavior of the isotopic enrichment unites of the Industrial Heavy Water Plant, located in Arroyito, Neuquen, Argentina, was modeled and simulated in the present work. Dynamic models of the chemical and isotopic interchange processes existent in the plant, were developed. This served as a base to obtain representative models of the different unit and control systems. The developed models were represented in a modular code for each unit. Each simulator consists of approximately one hundred non-linear-first-order differential equations and some other algebraic equation, which are time resolved by the code. The different simulators allow to change a big number of boundary conditions and the control systems set point for each simulation, so that the program become very versatile. The output of the code allows to see the evolution through time of the variables of interest. An interface which facilitates the use of the first enrichment stage simulator was developed. This interface allows an easy access to generate wished events during the simulation and includes the possibility to plot evolution of the variables involved. The obtained results agree with the expected tendencies. The calculated nominal steady state matches by the manufacturer. The different steady states obtained, agree with previous works. The times and tendencies involved in the transients generated by the program, are in good agreement with the experience obtained at the plant. Based in the obtained results, it is concluded that the characteristic times of the plant are determined by the masses involved in the process. Different characteristics in the system dynamic behavior were generated with the different simulators, and were validated by plant personnel. This work allowed to understand the different process involved in the heavy water manufacture, and to develop a very useful tool for the personnel of the plant. (author). 14 refs., figs., tabs. plant. (author). 14 refs., figs., tabs

  17. Non linear dynamics of boiling water reactor dynamical system

    International Nuclear Information System (INIS)

    The fifth order phenomenological model of March-Leuba for boiling water reactors include the point reactor kinetics equations for neutron balance and effective delayed neutron precursor groups with one node representation of the heat transfer process and channel thermal hydraulics. This nonlinear mathematical model consists five coupled nonlinear ordinary differential equations. The reactivity feedback (void coefficient of reactivity as well as the fuel temperature coefficient of reactivity), heat transfer process and momentum balance are major reasons for the appearance of nonlinearity in this dynamical system. The linear stability of a dynamical system with the existence of nonlinearity cannot predict a true picture of the stability characteristics of dynamical system; hence nonlinear stability analyses become an essential part to predict the global stable region on the stability map. The linear stable region is analyzed by the eigenvalues. In this stable region all the eigenvalues have negative real parts, but when pair of one of the complex eigenvalues passes transversely through imaginary axis, the dynamical system loses or gain its stability via a Hopf bifurcation and limit cycles emerges from the tip. The study of eigenvalues can predict a few bifurcations. The first Lyapunov coefficient and normal form coefficients can be used for the detection of other bifurcations in the systems. Stable or unstable limit cycles excite from these Hopf points. These limits cycles gains or loses their stability via limit point bifurcation of cycles, period doubling bifurcation of cycles and Neimark-Sacker bifurcation of cycles when one of the parameters of the nuclear dynamical system is varied. The stability of these limit cycles can be studied by Floquet theory and Lyapunov coefficient, but the bifurcations of limit cycles can be investigated only by critical Floquet multiplier which is basically the eigenvalue of the monodromy matrices. The cascade of period doubling

  18. Dynamic characteristics of an automotive fuel cell system for transitory load changes

    DEFF Research Database (Denmark)

    Rabbani, Raja Abid; Rokni, Masoud

    2013-01-01

    A dynamic model of Polymer Electrolyte Membrane Fuel Cell (PEMFC) system is developed to investigate the behavior and transient response of a fuel cell system for automotive applications. Fuel cell dynamics are subjected to reactant flows, heat management and water transportation inside the fuel...

  19. Cell Division, Differentiation and Dynamic Clustering

    CERN Document Server

    Kaneko, K; Kaneko, Kunihiko; Yomo, Tetsuya

    1993-01-01

    A novel mechanism for cell differentiation is proposed, based on the dynamic clustering in a globally coupled chaotic system. A simple model with metabolic reaction, active transport of chemicals from media, and cell division is found to show three successive stages with the growth of the number of cells; coherent growth, dynamic clustering, and fixed cell differentiation. At the last stage, disparity in activities, germ line segregation, somatic cell differentiation, and homeochaotic stability against external perturbation are found. Our results, in consistency with the experiments of the preceding paper, imply that cell differentiation can occur without a spatial pattern. From dynamical systems viewpoint, the new concept of ``open chaos" is proposed, as a novel and general scenario for systems with growing numbers of elements, also seen in economics and sociology.A

  20. Hydrogen-Bond Dynamics of Water in Ionic Solutions

    Science.gov (United States)

    Bakker, H. J.; Kropman, M. F.; Omta, A. W.; Woutersen, S.

    We study the effects of ions on the structure and dynamics of the hydrogen bonds in liquid water. As a technique we use femtosecond two-color mid-infrared spectroscopy, since this technique allows a clear distinction of the dynamics of the first solvation (hydration) shell of water molecules from the dynamics of bulk water. We find that water molecules in the first hydration shell of the halogenic anions Cl, and I show much slower hydrogen-bond dynamics than water molecules in the pure liquid. We also observe that the first hydration shell shows very slow collective orientational dynamics, and forms a rigid, long-living structure. Finally, we find that ions have surprisingly little effect on the hydrogen-bond dynamics of water molecules outside the first hydration shell, which implies that ions do not enhance or weaken the hydrogen-bond network of liquid water.

  1. Experimental Study of the Morphology and Dynamics of Gas-Laden Layers Under the Anodes in an Air-Water Model of Aluminum Reduction Cells

    Science.gov (United States)

    Vékony, Klára; Kiss, László I.

    2012-10-01

    The bubble layer formed under an anode and the bubble-induced flow play a significant role in the aluminum electrolysis process. The bubbles covering the anode bottom reduce the efficient surface that can carry current. In our experiments, we filmed and studied the bubble layer under the anode in a real-size air-water electrolysis cell model. Three different flow regimes were found depending on the gas generation rate. The covering factor was found to be proportional to the gas generation rate and inversely proportional to the angle of inclination. A correlation between the average height of the entire bubble layer and the position under the anode was determined. From this correlation and the measured contact sizes, the volume of the accumulated gas was calculated. The sweeping effect of large bubbles was observed. Moreover, the small bubbles under the inner edge of the anode were observed to move backward as a result of the escape of huge gas pockets, which means large momentum transport occurs in the bath.

  2. American coot collective on-water dynamics

    CERN Document Server

    Trenchard, Hugh

    2012-01-01

    American coot (Fulica americana) flocks exhibit water surface (two-dimensional) collective dynamics that oscillate between two primary phases: a disordered phase of low density and non-uniform coot body orientations; a synchronized phase characterized by high density, uniform body orientations and speed. For this small-scale study, data was obtained for flocks of 10 to ~250 members for these phases. Approximate durations of phase occurrences were recorded for different flock sizes and for both relatively calm and severe weather conditions. Results indicate that for timed durations of up to ~ 2 hours, small flocks (10 coots) exhibit a comparatively high disordered/synchronized phase ratio (PR) in relatively warm and well-sheltered conditions (substantially >1); large flocks (~100 or more) generally exhibit a PR near 1, while large flocks spend comparatively more time in a disordered phase in relatively calm conditions (PR somewhat >1), and spend more time in a synchronized phase during severe conditions (PR &l...

  3. Functional dynamics of cell surface membrane proteins

    Science.gov (United States)

    Nishida, Noritaka; Osawa, Masanori; Takeuchi, Koh; Imai, Shunsuke; Stampoulis, Pavlos; Kofuku, Yutaka; Ueda, Takumi; Shimada, Ichio

    2014-04-01

    Cell surface receptors are integral membrane proteins that receive external stimuli, and transmit signals across plasma membranes. In the conventional view of receptor activation, ligand binding to the extracellular side of the receptor induces conformational changes, which convert the structure of the receptor into an active conformation. However, recent NMR studies of cell surface membrane proteins have revealed that their structures are more dynamic than previously envisioned, and they fluctuate between multiple conformations in an equilibrium on various timescales. In addition, NMR analyses, along with biochemical and cell biological experiments indicated that such dynamical properties are critical for the proper functions of the receptors. In this review, we will describe several NMR studies that revealed direct linkage between the structural dynamics and the functions of the cell surface membrane proteins, such as G-protein coupled receptors (GPCRs), ion channels, membrane transporters, and cell adhesion molecules.

  4. Water dynamics clue to key residues in protein folding

    International Nuclear Information System (INIS)

    A computational method independent of experimental protein structure information is proposed to recognize key residues in protein folding, from the study of hydration water dynamics. Based on all-atom molecular dynamics simulation, two key residues are recognized with distinct water dynamical behavior in a folding process of the Trp-cage protein. The identified key residues are shown to play an essential role in both 3D structure and hydrophobic-induced collapse. With observations on hydration water dynamics around key residues, a dynamical pathway of folding can be interpreted.

  5. Hierarchic Theory of Condensed Matter Role of water in protein dynamics, function and cancer emergency

    CERN Document Server

    Kaivarainen, A

    2000-01-01

    1. Role of inter-domain water clusters in large-scale dynamics of proteins; 2. Description of large-scale dynamics of proteins based on generalized Stokes-Einstein and Eyring-Polany equation; 3. Dynamic model of protein-ligand complexes formation; 4. The life-time of quasiparticles and frequencies of their excitation; 5. Mesoscopic mechanism of enzyme catalysis; 6. The mechanism of ATP hydrolysis energy utilization in muscle contraction and protein polymerization; 7. Water activity as a regulative factor in the intra- and inter-cell processes; 8. Water and cancer.

  6. Sensitivity Analysis of Centralized Dynamic Cell Selection

    DEFF Research Database (Denmark)

    Lopez, Victor Fernandez; Alvarez, Beatriz Soret; Pedersen, Klaus I.;

    2016-01-01

    mechanism and solutions involving cell switching in general. Simulation results show that such solutions can greatly benefit from the use of receivers with interference suppression capabilities and a larger number of antennas, with a maximum data rate gain of 120%. High performance gains are observed with...... two different traffic models, and it is not necessary to be able to connect to a large number of cells in order to reap most of the benefits of the centralized dynamic cell selection....

  7. Effect of urea on the structural dynamics of water

    OpenAIRE

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

    2006-01-01

    We use polarization-resolved mid-infrared pump-probe spectroscopy to study the effect of urea on the structure and dynamics of water. Surprisingly, we find that, even at high concentrations of urea (8 M), the orientational dynamics of most water molecules are the same as in pure liquid water, showing that urea has a negligible effect on the hydrogen-bond dynamics of these molecules. However, a small fraction of the water molecules (approximately one water molecule per urea molecule) turns out...

  8. Dynamics and mechanism of ultrafast water-protein interactions.

    Science.gov (United States)

    Qin, Yangzhong; Wang, Lijuan; Zhong, Dongping

    2016-07-26

    Protein hydration is essential to its structure, dynamics, and function, but water-protein interactions have not been directly observed in real time at physiological temperature to our awareness. By using a tryptophan scan with femtosecond spectroscopy, we simultaneously measured the hydration water dynamics and protein side-chain motions with temperature dependence. We observed the heterogeneous hydration dynamics around the global protein surface with two types of coupled motions, collective water/side-chain reorientation in a few picoseconds and cooperative water/side-chain restructuring in tens of picoseconds. The ultrafast dynamics in hundreds of femtoseconds is from the outer-layer, bulk-type mobile water molecules in the hydration shell. We also found that the hydration water dynamics are always faster than protein side-chain relaxations but with the same energy barriers, indicating hydration shell fluctuations driving protein side-chain motions on the picosecond time scales and thus elucidating their ultimate relationship. PMID:27339138

  9. Dynamical evolution of sand ripples under water.

    Science.gov (United States)

    Stegner, A; Wesfreid, J E

    1999-10-01

    We have performed an experimental study on the evolution of sand ripples formed under the action of an oscillatory flow. An annular sand-water cell was used in order to investigate a wide range of parameters. The sand ripples follow an irreversible condensation mechanism from small to large wavelength until a final state is reached. The wavelength and the shape of these stable sand patterns are mainly governed by the fluid displacement and the static angle of the granular media. A strong hysteresis affects the evolution of steep ripples. When the acceleration of the sand bed reaches a critical value, the final pattern is modified by the superficial fluidization of the sand layer. PMID:11970264

  10. Experimental investigation of dynamic responses of a transparent PEM fuel cell to step changes in cell current density with operating temperature

    International Nuclear Information System (INIS)

    The dynamic responses of a proton exchange membrane fuel cell (PEMFC) are closely related to the novel water management technique used for the efficient operation of automotive PEMFCs. In order to better understand the dynamic water transport during cell transients, this paper presents an experimental investigation of the transient response of a cell under fully humidified conditions. The cell dynamic performance was measured by employing a transparent cell and investigated with visualization images of the water distribution in the flow channels. Furthermore, the effect of the operating temperature on the cell transients was examined. The results show that the cell dynamic behavior for the tested operating temperature (30-50 .deg. C) conditions is mainly governed by water transport characteristics related to cathode flooding. Also, we show that the time needed for the cell to reach steady-state after a current density step increase is retarded due to excessive water accumulation inside the cell at lower operating temperatures

  11. A dynamic simulation tool for hydrogen fuel cell vehicles

    Science.gov (United States)

    Moore, R. M.; Hauer, K. H.; Friedman, D.; Cunningham, J.; Badrinarayanan, P.; Ramaswamy, S.; Eggert, A.

    This paper describes a dynamic fuel cell vehicle simulation (FCVSim) tool for the load-following direct-hydrogen (DH) fuel cell vehicle. The emphasis is on simulation of the direct-hydrogen fuel cell system (FC System) within the vehicle simulation tool. This paper is focused on the subsystems that are specific to the load-following direct-hydrogen model. The four major subsystems discussed are the fuel cell stack, the air supply, the water and thermal management (WTM), and the hydrogen supply. The discussion provides the details of these subsystem simulations. The basic vehicle configuration has been previously outlined by Hauer [An Analysis Tool For Fuel Cell Vehicle Hardware and Software (Controls) with an Application to Fuel Economy Comparisons of Alternative System Designs, Dissertation, UC California, Davis, USA, 2001] and Hauer and Moore [Fuel Cells for Automotive Applications, Professional Engineering Publishing, 2003, pp. 157-177, ISBN 1860584233] and is only briefly reviewed in this paper.

  12. Cell-wall dynamics in growing bacteria

    Science.gov (United States)

    Furchtgott, Leon; Wingreen, Ned; Huang, Kerwyn Casey

    2010-03-01

    Bacterial cells come in a large variety of shapes, and cell shape plays an important role in the regulation of many biological functions. Cell shape in bacterial cells is dictated by a cell wall composed of peptidoglycan, a polymer made up of long, stiff glycan strands and flexible peptide crosslinks. Although much is understood about the structural properties of peptidoglycan, little is known about the dynamics of cell wall organization in bacterial cells. In particular, during cell growth, how does the bacterial cell wall continuously expand and reorganize while maintaining cell shape? In order to investigate this question quantitatively, we model the cell wall of the Gram-negative bacterium Escherichia coli using a simple elastic model, in which glycan and peptide subunits are treated as springs with different spring constants and relaxed lengths. We consider the peptidoglycan network as a single-layered network of these springs under tension due to an internal osmotic pressure. Within this model, we simulate possible hypotheses for cell growth as different combinations of addition of new springs and breakage of old springs.

  13. Mitochondrial dynamics and the cell cycle

    Science.gov (United States)

    Nuclear-mitochondrial (NM) communication impacts many aspects of plant development including vigor, sterility and viability. Dynamic changes in mitochondrial number, shape, size, and cellular location takes place during the cell cycle possibly impacting the process itself and leading to distribution...

  14. Water balance in fuel cells systems

    International Nuclear Information System (INIS)

    Fuel cell systems are attractive for their high efficiency (i.e., electric power generated per weight/volume of fuel,) and lower emissions. These systems are being developed for applications that include transportation (propulsion and auxiliary), remote stationary, and portable. Where these systems use on-board fuel processing of available fuels, the fuel processor requires high-purity water. For utility applications, this water may be available on-site, but for most applications, the process water must be recovered from the fuel cell system exhaust gas. For such applications, it is critically important that the fuel cell system be a net water-producing device. A variety of environmental conditions (e.g., ambient temperature, pressure), fuel cell system design, and operating conditions determine whether the fuel cell system is water-producing or water-consuming. This paper will review and discuss the conditions that determine the net-water balance of a generic fuel cell system and identify some options that will help meet the water needs of the fuel processor

  15. Retardation of Bulk Water Dynamics by Disaccharide Osmolytes

    CERN Document Server

    Shukla, Nimesh; Chen, Lee; Chergui, Majed; Othon, Christina M

    2016-01-01

    The bioprotective nature of disaccharides is hypothesized to derive from the modification of the hydrogen bonding network of water which protects biomolecules through lowered water activity at the protein interface. Using ultrafast fluorescence spectroscopy we measured the relaxation of bulk water dynamics around the induced dipole moment of two fluorescent probes (Lucifer Yellow Ethylenediamine and Tryptophan). Our results indicate a reduction in bulk water reorganization rate of approximately of 30%. We observe this retardation in the low concentration regime measured at 0.1M and 0.25 M, far below the onset of glassy dynamics. This reduction in water activity could be significant in crowded biological systems, contributing to global change in protein energy landscape, resulting in a significant enhancement of protein stability under environmental stress. We observed similar dynamic reduction for two disaccharide osmolytes, sucrose and trehalose, with trehalose being the more effective dynamic reducer.

  16. Water dynamics for North Carolina v. Vinifera

    Science.gov (United States)

    As North Carolina wine grape (V. vinifera) production intensifies, the importance of water management must be addressed. Grape yield and composition, and consequently wine quality, are profoundly influenced by the water regime under which the grapes were produced. Despite the importance of water man...

  17. Transcriptome dynamics of Pseudomonas putida KT2440 under water stress.

    Science.gov (United States)

    Gülez, Gamze; Dechesne, Arnaud; Workman, Christopher T; Smets, Barth F

    2012-02-01

    Water deprivation can be a major stressor to microbial life in surface and subsurface soil. In unsaturated soils, the matric potential (Ψ(m)) is often the main component of the water potential, which measures the thermodynamic availability of water. A low matric potential usually translates into water forming thin liquid films in the soil pores. Little is known of how bacteria respond to such conditions, where, in addition to facing water deprivation that might impair their metabolism, they have to adapt their dispersal strategy as swimming motility may be compromised. Using the pressurized porous surface model (PPSM), which allows creation of thin liquid films by controlling Ψ(m), we examined the transcriptome dynamics of Pseudomonas putida KT2440. We identified the differentially expressed genes in cells exposed to a mild matric stress (-0.4 MPa) for 4, 24, or 72 h. The major response was detected at 4 h before gradually disappearing. Upregulation of alginate genes was notable in this early response. Flagellar genes were not downregulated, and the microarray data even suggested increasing expression as the stress prolonged. Moreover, we tested the effect of polyethylene glycol 8000 (PEG 8000), a nonpermeating solute often used to simulate Ψ(m), on the gene expression profile and detected a different profile than that observed by directly imposing Ψ(m). This study is the first transcriptome profiling of KT2440 under directly controlled Ψ(m) and also the first to show the difference in gene expression profiles between a PEG 8000-simulated and a directly controlled Ψ(m). PMID:22138988

  18. Hydrological dynamics of water sources in a Mediterranean lagoon

    Directory of Open Access Journals (Sweden)

    C. Stumpp

    2014-07-01

    Full Text Available Lagoons are important ecosystems occupying large coastal areas worldwide. Lagoons contain various mixtures of marine and freshwater sources which are highly dynamic in time. However, it often remains a challenge to identify and quantify dynamic changes of water sources, particularly in heterogeneous lagoon systems like the Köycegiz-Dalyan Lagoon (KDL, which is located at the southwest of Turkey on the Mediterranean Sea coast. The objective of this study was to quantify different contributions of potential water sources i.e. surface water, groundwater and seawater in the lagoon and how these water sources changed over time and space. In the wet and dry season stable isotopes of water, chloride concentration (Cl- and salinity were measured in two depths in the lagoon and surrounding water bodies (sea, lake, groundwater. Different components of water sources were quantified with a three component endmember mixing analysis. Differences in Cl- and stable isotopes over time indicated the dynamic behaviour of the system. Generally, none of the groundwater samples was impacted by water of the Mediterranean Sea. During the wet season, most of the lagoon water (>95% was influenced by freshwater and vertically well mixed. During the dry season, high Cl- in the deeper sampling locations indicated a high contribution of marine water throughout the entire lagoon system due to salt water intrusion. However, a distinct layering in the lagoon was obvious from low Cl- and depleted isotope contents close to the surface supporting freshwater inflow into the system even during the dry season. Besides temporal dynamics also spatial heterogeneities were identified. Changes in water sources were most evident in the main lagoon channel compared to more isolate lagoon lakes, which were influenced by marine water even in the wet season, and compared to side branches indicating slower turnover times. We found that environmental tracers helped to quantify contributions of

  19. Residential water use and landscape vegetation dynamics in Los Angeles

    OpenAIRE

    Mini, Caroline

    2013-01-01

    This research contributes to a better understanding of the dynamics of single-family water consumption associated with vegetation in semi-arid cities. The innovative research approach couples long-term water consumption data with remote-sensing based products, socio-demographic, land cover, landscaping and climate data analyzed with multidisciplinary techniques. Accurate water demand forecasting and long-term conservation planning are required to meet future urban water needs relying on a set...

  20. Anomalies of water and hydrogen bond dynamics in hydrophobic nanoconfinement

    Energy Technology Data Exchange (ETDEWEB)

    Kumar, Pradeep [Center for Studies in Physics and Biology, Rockefeller University, 1230 York Avenue, New York, NY 10021 (United States); Han, Sungho; Stanley, H Eugene [Center for Polymer Studies and Department of Physics, Boston University, Boston, MA 02215 (United States)

    2009-12-16

    Using molecular dynamic (MD) simulations of the TIP5P model of water, we investigate the effect of hydrophobic confinement on the anomalies of liquid water. For confinement length Lz = 1.1 nm, such that there are 2-3 molecular layers of water, we find the presence of the bulk-like density and diffusion anomaly in the lateral directions. However, the lines of these anomalies in the P-T plane are shifted to lower temperatures (DELTATapprox40 K) and pressures compared to bulk water. Furthermore, we introduce a method to calculate the effective diffusion constant along the confinement direction and find that the diffusion anomaly is absent. Moreover, we investigate the hydrogen bond dynamics of confined water and find that the hydrogen bond dynamics preserves the characteristics of HB dynamics in bulk water, such as a non-exponential behavior followed by an exponential tail of HB lifetime probability distributions and an Arrhenius temperature dependence of the average HB lifetime. The average number and lifetime of HBs decrease in confined water compared to bulk water at the same temperature. This reduction may be the origin of the reasons for the different physical properties of confined water from bulk water, such as the 40 K temperature shift.

  1. Phase transitions and dynamics of bulk and interfacial water

    Energy Technology Data Exchange (ETDEWEB)

    Franzese, G; Hernando-Martinez, A [Departament de Fisica Fonamental, Universitat de Barcelona, Diagonal 647, Barcelona 08028 (Spain); Kumar, P [Center for Studies in Physics and Biology, Rockefeller University, 1230 York Avenue, New York, NY 10021 (United States); Mazza, M G; Stokely, K; Strekalova, E G; Stanley, H E [Center for Polymer Studies and Department of Physics, Boston University, Boston, MA 02215 (United States); De los Santos, F, E-mail: gfranzese@ub.ed [Departamento de Electromagnetismo y Fisica de la Materia, Universidad de Granada, Fuentenueva s/n, 18071 Granada (Spain)

    2010-07-21

    New experiments on water at the surface of proteins at very low temperature display intriguing dynamic behaviors. The extreme conditions of these experiments make it difficult to explore the wide range of thermodynamic state points needed to offer a suitable interpretation. Detailed simulations suffer from the same problem, where equilibration times at low temperature become extremely long. We show how Monte Carlo simulations and mean field calculations using a tractable model of water help interpret the experimental results. Here we summarize the results for bulk water and investigate the thermodynamic and dynamic properties of supercooled water at an interface.

  2. Water injected fuel cell system compressor

    Science.gov (United States)

    Siepierski, James S.; Moore, Barbara S.; Hoch, Martin Monroe

    2001-01-01

    A fuel cell system including a dry compressor for pressurizing air supplied to the cathode side of the fuel cell. An injector sprays a controlled amount of water on to the compressor's rotor(s) to improve the energy efficiency of the compressor. The amount of water sprayed out the rotor(s) is controlled relative to the mass flow rate of air inputted to the compressor.

  3. Hydrological dynamics of water sources in a Mediterranean lagoon

    Science.gov (United States)

    Stumpp, C.; Ekdal, A.; Gönenc, I. E.; Maloszewski, P.

    2014-12-01

    Lagoons are important ecosystems occupying large coastal areas worldwide. Lagoons contain various mixtures of marine and freshwater sources which are highly dynamic in time. However, it often remains a challenge to identify and quantify dynamic changes of water sources, particularly in heterogeneous lagoon systems like the Köycegiz-Dalyan lagoon (KDL), which is located at the south-west of Turkey on the Mediterranean Sea coast. The objective of this study was to quantify different contributions of potential water sources i.e. surface water, groundwater and seawater in the lagoon and how these water sources changed over time and space. In the wet- and dry-season stable isotopes of water, chloride concentration (Cl-) and salinity were measured in two depths in the lagoon and surrounding water bodies (sea, lake, groundwater). Different components of water sources were quantified with a three component endmember mixing analysis. Differences in Cl- and stable isotopes over time indicated the dynamic behaviour of the system. Generally, none of the groundwater samples was impacted by water of the Mediterranean Sea. During the wet season, most of the lagoon water (> 95%) was influenced by freshwater and vertically well mixed. During the dry season, high Cl- in the deeper sampling locations indicated a high contribution of marine water throughout the entire lagoon system due to saltwater intrusion. However, a distinct layering in the lagoon was obvious from low Cl- and depleted isotope contents close to the surface supporting freshwater inflow into the system even during the dry season. Besides temporal dynamics also spatial heterogeneities were identified. Changes in water sources were most evident in the main lagoon channel compared to more isolate lagoon lakes, which were influenced by marine water even in the wet season, and compared to side branches indicating slower turnover times. We found that environmental tracers helped to quantify highly dynamic and

  4. Dynamics of hydrogen bonds in water and consequences for the unusual behaviour of supercooled water

    Indian Academy of Sciences (India)

    José Teixeira

    2008-10-01

    The dynamics of liquid water is evaluated by the coherent quasi-elastic scattering at two different momentum transfers, in order to discriminate hydrogen bond life-time from molecular dynamics. The results indicate a possible issue for the puzzle of the behaviour of supercooled water.

  5. Ultrafast dynamics of water at the water-air interface studied by femtosecond surface vibrational spectroscopy

    Directory of Open Access Journals (Sweden)

    Bakker Huib J.

    2013-04-01

    Full Text Available We study the dynamics of water molecules at the water-air interface, using surfacespecific two-dimensional infrared sum-frequency generation (2D-SFG spectroscopy. The data reveal the occurrence of surprisingly fast energy transfer and reorientational dynamics at aqueous interfaces.

  6. Dynamic combinatorial chemistry with diselenides and disulfides in water

    DEFF Research Database (Denmark)

    Rasmussen, Brian; Sørensen, Anne; Gotfredsen, Henrik;

    2014-01-01

    Diselenide exchange is introduced as a reversible reaction in dynamic combinatorial chemistry in water. At neutral pH, diselenides are found to mix with disulfides and form dynamic combinatorial libraries of diselenides, disulfides, and selenenylsulfides. This journal is © the Partner Organisations...

  7. Dynamic contact angle of water-based titanium oxide nanofluid

    OpenAIRE

    Radiom, Milad; Yang, Chun; Chan, Weng Kong

    2013-01-01

    Abstract This paper presents an investigation into spreading dynamics and dynamic contact angle of TiO2-deionized water nanofluids. Two mechanisms of energy dissipation, (1) contact line friction and (2) wedge film viscosity, govern the dynamics of contact line motion. The primary stage of spreading has the contact line friction as the dominant dissipative mechanism. At the secondary stage of spreading, the wedge film viscosity is the dominant dissipative mechanism. A theoretical model based ...

  8. Dynamical Adaptation in Terrorist Cells/Networks

    DEFF Research Database (Denmark)

    Hussain, Dil Muhammad Akbar; Ahmed, Zaki

    2010-01-01

    followers etc. In this research we analyze and predict the most likely role a particular node can adapt once a member of the network is either killed or caught. The adaptation is based on computing Bayes posteriori probability of each node and the level of the said node in the network structure.......Typical terrorist cells/networks have dynamical structure as they evolve or adapt to changes which may occur due to capturing or killing of a member of the cell/network. Analytical measures in graph theory like degree centrality, betweenness and closeness centralities are very common and have long...

  9. Dynamics of hydration water in protein

    International Nuclear Information System (INIS)

    Incoherent quasi-elastic neutron scattering studies of in vivo deuterated C-phycocyanin, at different levels of hydration, have been made. We show that the mobility at high temperature, (∝300 K) of the water molecules near the protein surface can be described by relatively simple models. At full hydration the high temperature data can be interpreted using a model where each water molecule is diffusing in a confined space of 3 A in radius. At low hydration, and 298 K, the diffusional behaviour is typical of jump diffusion with a residence time 10 times larger than the one in bulk water at the same temperature. (orig.)

  10. The diffusive dynamics of water confined in ganglioside micelles

    Science.gov (United States)

    Cantù, L.; Cavatorta, F.; Corti, M.; Del Favero, E.; Deriu, A.

    1997-02-01

    We have investigated by QENS the dynamics of water associated to gangliosides. The dependence of the QENS line-broadening versus Q indicates that proton diffusion is restricted when investigated over scale lengths of about 6-8 Å; at smaller distances the diffusivity parameters are similar to those of pure water at a lower temperature.

  11. Soil Water Dynamics In Central Europe and Brazil

    DEFF Research Database (Denmark)

    Klein, Markus; Mahler, Claudio F.; Trapp, Stefan;

    2000-01-01

    The comprehension of the soil water dynamics is important for the study of environmental processes. Precipitation, temperature, and water balance of Rio de Janeiro, Southeast Brazil and locations in Germany, Central Europe, are significantly different. Experience from one region could not be used...

  12. Structure and dynamics of supercooled water in neutral confinements

    Science.gov (United States)

    Klameth, F.; Vogel, M.

    2013-04-01

    We perform molecular dynamics simulations to study the structure and dynamics of liquid water in neutral nanopores, which are generated by pinning a suitable subset of water molecules in an equilibrium configuration of a bulk system. It is found that such neutral confinement does not disturb the structure of water, in particular, the local tetrahedral order, while it imposes a pronounced spatial inhomogeneity on the dynamics of water. Specifically, when the pore wall is approached, hopping motion sets in and water dynamics slows down. We show that the logarithm of the correlation time is an exponential function of the distance to the wall, indicating a tremendous gradient of water mobility across the confinement. Upon cooling, the length scale associated with this exponential distance dependence and, thus, the range of the wall effect increases, at least down to the critical temperature of mode coupling theory, Tc. Also, the temperature dependence of water dynamics varies across the pore, i.e., fragility is high in the pore center, while it is low near the pore wall. Due to all these effects, time-temperature superposition is violated. Our observations for a neutral confinement reveal that specific interactions at hydrophilic or hydrophobic walls are not the main cause of spatially inhomogeneous dynamics of confined water. In view of similarities with the behavior of Lennard-Jones liquids in neutral confinements, one may rather speculate that the effects observed for confined water are general and result from the existence of a static contribution to the energy landscape, which is imprinted by an immobile environment.

  13. Dynamical Crossover in Hot Dense Water: The Hydrogen Bond Role.

    Science.gov (United States)

    Ranieri, Umbertoluca; Giura, Paola; Gorelli, Federico A; Santoro, Mario; Klotz, Stefan; Gillet, Philippe; Paolasini, Luigi; Koza, Michael Marek; Bove, Livia E

    2016-09-01

    We investigate the terahertz dynamics of liquid H2O as a function of pressure along the 450 K isotherm, by coupled quasielastic neutron scattering and inelastic X-ray scattering experiments. The pressure dependence of the single-molecule dynamics is anomalous in terms of both microscopic translation and rotation. In particular, the Stokes-Einstein-Debye equations are shown to be violated in hot water compressed to the GPa regime. The dynamics of the hydrogen bond network is only weakly affected by the pressure variation. The time scale of the structural relaxation driving the collective dynamics increases by a mere factor of 2 along the investigated isotherm, and the structural relaxation strength turns out to be almost pressure independent. Our results point at the persistence of the hydrogen bond network in hot dense water up to ice VII crystallization, thus questioning the long-standing perception that hydrogen bonds are broken in liquid water under the effect of compression. PMID:27479235

  14. Tight Coupling of Metabolic Oscillations and Intracellular Water Dynamics in Saccharomyces cerevisiae

    DEFF Research Database (Denmark)

    Thoke, Henrik Seir; Tobiesen, Asger; Brewer, Jonathan R.;

    2015-01-01

    We detected very strong coupling between the oscillating concentration of ATP and the dynamics of intracellular water during glycolysis in Saccharomyces cerevisiae. Our results indicate that: i) dipolar relaxation of intracellular water is heterogeneous within the cell and different from dilute c......2O in a dose-dependent manner. These results offer a new insight into the coupling of an emergent intensive physicochemical property of the cell, i.e. cell-wide water dipolar relaxation, and a central metabolite (ATP) produced by a robustly oscillating metabolic process.......We detected very strong coupling between the oscillating concentration of ATP and the dynamics of intracellular water during glycolysis in Saccharomyces cerevisiae. Our results indicate that: i) dipolar relaxation of intracellular water is heterogeneous within the cell and different from dilute...... conditions, ii) water dipolar relaxation oscillates with glycolysis and in phase with ATP concentration, iii) this phenomenon is scale-invariant from the subcellular to the ensemble of synchronized cells and, iv) the periodicity of both glycolytic oscillations and dipolar relaxation are equally affected by D...

  15. Evolution of water dynamics in the Prussian blue

    Directory of Open Access Journals (Sweden)

    Mitra S.

    2015-01-01

    Full Text Available Crystal water plays a crucial role towards the multifunctional properties of Prussian blue and its analogue (PBA compounds. We have investigated the dynamics of crystal water in Prussian blue (PB, Fe(III4[Fe(II(CN6]3. 14 H2 O using Quasielastic Neutron Scattering (QENS. In PB, water molecules exist in the spherical cavity, created due to the vacant sites of Fe(CN6 units, and also at interstitial sites. QENS data showed that dynamics evolves with increase in temperature. The observed dynamics has been correlated quantitatively with the different water molecules that exist at different sites of the lattice. It is found that only the non-coordinated water molecules contribute to the dynamics at low temperature, and others start contributing progressively with increasing temperature. A detailed data analysis showed that the water molecules undergo a localized translational diffusion. The estimated spatial domain of dynamics is found to be compatible with the geometry of the structure.

  16. Using Ethanol to Investigate Dynamic Soil Water Repellency

    Science.gov (United States)

    Smith, James E.; Beatty, Sarah M.

    2016-04-01

    Large gaps remain in our fundamental understanding of the behaviour of water in dynamically repellent soils. By investigating these systems using other miscible fluids that minimize or eliminate repellency, e.g. ethanol, we seek to better understand and quantify soil water repellency. The advantages of the enhanced wettability of water repellent soils to other miscible fluids, however, come with complications including shifts in effective pore water pressures induced through variable interfacial tensions as well as differences in fluid mobility due to variable fluid viscosities and densities. With these considerations in mind, we compare and contrast the observed behaviours of fluid infiltration and retention in dynamically hydrophobic soils and hydrophilic soils. We conducted field and laboratory studies using tension disc infiltrometers along with water and ethanol solutions to investigate dynamic repellency in post-wildfire soils from Northern Ontario, Canada. Tension infiltrometers maintain a constant negative liquid pressure at the surface which proved to be useful for isolating wettable behaviours sensitive to dynamic changes in wettability. We present the data and system conceptualised and explained through contact angle dynamics and variable fractional wettability of the soil. The limitations of extending hydrophilic concepts and hydraulic functions to hydrophobic soils are discussed along with persistent challenges to advance our ability to simulate and predict system behaviours in naturally occurring water repellent soils.

  17. Cell list algorithms for nonequilibrium molecular dynamics

    Science.gov (United States)

    Dobson, Matthew; Fox, Ian; Saracino, Alexandra

    2016-06-01

    We present two modifications of the standard cell list algorithm that handle molecular dynamics simulations with deforming periodic geometry. Such geometry naturally arises in the simulation of homogeneous, linear nonequilibrium flow modeled with periodic boundary conditions, and recent progress has been made developing boundary conditions suitable for general 3D flows of this type. Previous works focused on the planar flows handled by Lees-Edwards or Kraynik-Reinelt boundary conditions, while the new versions of the cell list algorithm presented here are formulated to handle the general 3D deforming simulation geometry. As in the case of equilibrium, for short-ranged pairwise interactions, the cell list algorithm reduces the computational complexity of the force computation from O(N2) to O(N), where N is the total number of particles in the simulation box. We include a comparison of the complexity and efficiency of the two proposed modifications of the standard algorithm.

  18. Dynamics and stability of a vertical water bridge

    CERN Document Server

    Namin, Reza Montazeri

    2013-01-01

    A vertical connection of water is formed when a high voltage electrode is dipped in and pulled out of a container of deionized water. We considered the formation, stability and dynamical characteristics of this vertical water bridge. For the first time in this field, we observed instabilities in the bridge that led to an oscillatory behaviour which is categorized in three dynamical regimes and supplied explanations on the physics behind these varied motions. We report the formation of macroscopic droplets during this motion, which their dynamics revealed that they are electrically charged. In some cases the droplets would be levitating when the electric force opposes the gravity. Also the steady bridge is thoroughly studied regarding its geometry and a set of quantitative data is presented using dimensionless numbers, which brings the possibility of direct quantitative comparison between theory and experiments. Our results shed light on the physics behind this phenomenon and the horizontal water bridge, which...

  19. Molecular dynamics insights into human aquaporin 2 water channel.

    Science.gov (United States)

    Binesh, A R; Kamali, R

    2015-12-01

    In this study, the first molecular dynamics simulation of the human aquaporin 2 is performed and for a better understanding of the aquaporin 2 permeability performance, the characteristics of water transport in this protein channel and key biophysical parameters of AQP2 tetramer including osmotic and diffusive permeability constants and the pore radius are investigated. For this purpose, recently recovered high resolution X-ray crystal structure of` the human aquaporin 2 is used to perform twenty nanosecond molecular dynamics simulation of fully hydrated tetramer of this protein embedded in a lipid bilayer. The resulting water permeability characteristics of this protein channel showed that the water permeability of the human AQP2 is in a mean range in comparison with other human aquaporins family. Finally, the results reported in this research demonstrate that molecular dynamics simulation of human AQP2 provided useful insights into the mechanisms of water permeation and urine concentration in the human kidney. PMID:26489820

  20. Nonlinear Dynamic Characteristics of Oil-in-Water Emulsions

    Science.gov (United States)

    Yin, Zhaoqi; Han, Yunfeng; Ren, Yingyu; Yang, Qiuyi; Jin, Ningde

    2016-08-01

    In this article, the nonlinear dynamic characteristics of oil-in-water emulsions under the addition of surfactant were experimentally investigated. Firstly, based on the vertical upward oil-water two-phase flow experiment in 20 mm inner diameter (ID) testing pipe, dynamic response signals of oil-in-water emulsions were recorded using vertical multiple electrode array (VMEA) sensor. Afterwards, the recurrence plot (RP) algorithm and multi-scale weighted complexity entropy causality plane (MS-WCECP) were employed to analyse the nonlinear characteristics of the signals. The results show that the certainty is decreasing and the randomness is increasing with the increment of surfactant concentration. This article provides a novel method for revealing the nonlinear dynamic characteristics, complexity, and randomness of oil-in-water emulsions with experimental measurement signals.

  1. Protein Dynamics in Organic Media at Varying Water Activity Studied by Molecular Dynamics Simulation

    DEFF Research Database (Denmark)

    Wedberg, Nils Hejle Rasmus Ingemar; Abildskov, Jens; Peters, Günther H.J.

    2012-01-01

    In nonaqueous enzymology, control of enzyme hydration is commonly approached by fixing the thermodynamic water activity of the medium. In this work, we present a strategy for evaluating the water activity in molecular dynamics simulations of proteins in water/organic solvent mixtures. The method...... relies on determining the water content of the bulk phase and uses a combination of Kirkwood−Buff theory and free energy calculations to determine corresponding activity coefficients. We apply the method in a molecular dynamics study of Candida antarctica lipase B in pure water and the organic solvents...... methanol, tert-butyl alcohol, methyl tert-butyl ether, and hexane, each mixture at five different water activities. It is shown that similar water activity yields similar enzyme hydration in the different solvents. However, both solvent and water activity are shown to have profound effects on enzyme...

  2. A dynamic analysis of water footprint of Jinghe River basin

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    Water footprint in a region is defined as the volume of water needed for the production of goods and services consumed by the local people. Ecosystem services are a kind of important services, so ecological water use is one necessary component in water footprint. Water footprint is divided into green water footprint and blue water footprint but the former one is often ignored. In this paper water footprint includes blue water needed by agricultural irrigation, industrial and domestic water demand, and green water needed by crops, economic forests, livestock products, forestlands and grasslands. The study calculates the footprint of the Jinghe River basin in 1990,1995, 2000 and 2005 with quarto methods. Results of research show that water footprints reached 164.1 × 108m3, 175.69×108m3 and 178.45×108m3 respectively in 1990, 1995 and 2000 including that of ecological water use, but reached 77.68×108m3, 94.24×108m3, 92.92×108m3 and 111.36×108m3 respectively excluding that of ecological water use. Green water footprint is much more than blue water footprint: thereby, green water plays an important role in economic development and ecological construction. The dynamic change of water footprints stows that blue water use increases rapidly and that the ecological water use is occupied by economic and domestic water use. The change also shows that water use is transferred from primary industry to secondary industry. In primary industry, it is transferred from crops farming to forestry and animal agriculture. The factors impelling the change include development anticipation on economy, government policies, readjustment of the industrial structure, population growth, the raise of urbanization level, and structural change of consumption, low level of water-saving and poor ability of waste water treatment. With blue water use per unit, green water use per unit, blue water use structure and green water use structure, we analyzed the difference of the six ecological

  3. Evidence on dynamic effects in the water content – water potential relation of building materials

    DEFF Research Database (Denmark)

    Scheffler, Gregor Albrecht; Plagge, Rudolf

    2008-01-01

    moisture storage characteristic is process dependent with varying significance for the numerical simulation. On the basis of different building materials, a comprehensive instantaneous profile measurement study has been accomplished. Profiles of water content and relative humidity were obtained during a...... static and dynamic moisture storage data and the more pronounced was the corresponding dynamic hysteresis. The paper thus provides clear experimental evidence on dynamic effects in the water content – water potential relation of building materials. By that, data published by previous authors as Topp et...

  4. Structure and dynamics of water in nanoscopic spheres and tubes.

    Science.gov (United States)

    van der Loop, Tibert H; Ottosson, Niklas; Lotze, Stephan; Kentzinger, Emmanuel; Vad, Thomas; Sager, Wiebke F C; Bakker, Huib J; Woutersen, Sander

    2014-11-14

    We study the reorientation dynamics of liquid water confined in nanometer-sized reverse micelles of spherical and cylindrical shape. The size and shape of the micelles are characterized in detail using small-angle x-ray scattering, and the reorientation dynamics of the water within the micelles is investigated using GHz dielectric relaxation spectroscopy and polarization-resolved infrared pump-probe spectroscopy on the OD-stretch mode of dilute HDO:H2O mixtures. We find that the GHz dielectric response of both the spherical and cylindrical reverse micelles can be well described as a sum of contributions from the surfactant, the water at the inner surface of the reversed micelles, and the water in the core of the micelles. The Debye relaxation time of the core water increases from the bulk value τ(H2O) of 8.2 ± 0.1 ps for the largest reverse micelles with a radius of 3.2 nm to 16.0 ± 0.4 ps for the smallest micelles with a radius of 0.7 nm. For the nano-spheres the dielectric response of the water is approximately ∼6 times smaller than expected from the water volume fraction and the bulk dielectric relaxation of water. We find that the dielectric response of nano-spheres is more attenuated than that of nano-tubes of identical composition (water-surfactant ratio), whereas the reorientation dynamics of the water hydroxyl groups is identical for the two geometries. We attribute the attenuation of the dielectric response compared to bulk water to a local anti-parallel ordering of the molecular dipole moments. The difference in attenuation between nano-spheres and nano-cylinders indicates that the anti-parallel ordering of the water dipoles is more pronounced upon spherical than upon cylindrical nanoconfinement. PMID:25399200

  5. Structure and dynamics of water in nanoscopic spheres and tubes

    Science.gov (United States)

    van der Loop, Tibert H.; Ottosson, Niklas; Lotze, Stephan; Kentzinger, Emmanuel; Vad, Thomas; Sager, Wiebke F. C.; Bakker, Huib J.; Woutersen, Sander

    2014-11-01

    We study the reorientation dynamics of liquid water confined in nanometer-sized reverse micelles of spherical and cylindrical shape. The size and shape of the micelles are characterized in detail using small-angle x-ray scattering, and the reorientation dynamics of the water within the micelles is investigated using GHz dielectric relaxation spectroscopy and polarization-resolved infrared pump-probe spectroscopy on the OD-stretch mode of dilute HDO:H2O mixtures. We find that the GHz dielectric response of both the spherical and cylindrical reverse micelles can be well described as a sum of contributions from the surfactant, the water at the inner surface of the reversed micelles, and the water in the core of the micelles. The Debye relaxation time of the core water increases from the bulk value τ_H_2O of 8.2 ± 0.1 ps for the largest reverse micelles with a radius of 3.2 nm to 16.0 ± 0.4 ps for the smallest micelles with a radius of 0.7 nm. For the nano-spheres the dielectric response of the water is approximately ˜6 times smaller than expected from the water volume fraction and the bulk dielectric relaxation of water. We find that the dielectric response of nano-spheres is more attenuated than that of nano-tubes of identical composition (water-surfactant ratio), whereas the reorientation dynamics of the water hydroxyl groups is identical for the two geometries. We attribute the attenuation of the dielectric response compared to bulk water to a local anti-parallel ordering of the molecular dipole moments. The difference in attenuation between nano-spheres and nano-cylinders indicates that the anti-parallel ordering of the water dipoles is more pronounced upon spherical than upon cylindrical nanoconfinement.

  6. Dynamics of water in prussian blue analogues: Neutron scattering study

    Science.gov (United States)

    Sharma, V. K.; Mitra, S.; Thakur, N.; Yusuf, S. M.; Juranyi, Fanni; Mukhopadhyay, R.

    2014-07-01

    Dynamics of crystal water in Prussian blue (PB), Fe(III)4[Fe(II)(CN)6]3.14H2O and its analogue Prussian green (PG), ferriferricynaide, Fe(III)4[Fe(III)(CN)6]4.16H2O have been investigated using Quasielastic Neutron Scattering (QENS) technique. PB and its analogue compounds are important materials for their various interesting multifunctional properties. It is known that crystal water plays a crucial role towards the multifunctional properties of Prussian blue analogue compounds. Three structurally distinguishable water molecules: (i) coordinated water molecules at empty nitrogen sites, (ii) non-coordinated water molecules in the spherical cavities, and (iii) at interstitial sites exist in PB. Here spherical cavities are created due to the vacant sites of Fe(CN)6 units. However, PG does not have any such vacant N or Fe(CN)6 units, and only one kind of water molecules, exists only at interstitial sites. QENS experiments have been carried out on both the compounds in the temperature range of 260-360 K to elucidate the dynamical behavior of different kinds of water molecules. Dynamics is found to be much more pronounced in case of PB, compared to PG. A detailed data analysis showed that localized translational diffusion model could describe the observed data for both PB and PG systems. The average diffusion coefficient is found to be much larger in the PB than PG. The obtained domain of dynamics is found to be consistent with the geometry of the structure of the two systems. Combining the data of the two systems, a quantitative estimate of the dynamics, corresponding to the water molecules at different locations is made.

  7. On the dynamics of bubbles in boiling water

    International Nuclear Information System (INIS)

    Research highlights: → We devote this work to investigate the bubbles dynamics in boiling water. → A simple experiment of laser scattering was designed to obtain dynamical features. → Correlations and non-exponential distributions were found. → A simple model was able to describe several aspects of the system. - Abstract: We investigate the dynamics of many interacting bubbles in boiling water by using a laser scattering experiment. Specifically, we analyze the temporal variations of a laser intensity signal which passed through a sample of boiling water. Our empirical results indicate that the return interval distribution of the laser signal does not follow an exponential distribution; contrariwise, a heavy-tailed distribution has been found. Additionally, we compare the experimental results with those obtained from a minimalist phenomenological model, finding a good agreement.

  8. Slow dynamics of supercooled water confined in nanoporous silica materials

    Science.gov (United States)

    Liu, L.; Faraone, A.; Mou, C.-Y.; Yen, C.-W.; Chen, S.-H.

    2004-11-01

    We review our incoherent quasielastic neutron scattering (QENS) studies of the dynamics of supercooled water confined in nanoporous silica materials. QENS data were analysed by using the relaxing cage model (RCM) previously developed by us. We first use molecular dynamics (MD) simulation of the extended simple point charge model (SPC/E) for bulk supercooled water to establish the validity of the RCM, which applies to both the translational and rotational motion of water molecules. We then assume that the dynamics of water molecules in the vicinity of a hydrophilic surface is similar to a bulk water at an equivalent lower supercooled temperature. This analogy was experimentally demonstrated in previous investigations of water in Vycor glasses and near hydrophilic protein surfaces. Studies were made of supercooled water in MCM-41-S (pore sizes 25, 18, and 14 Å) and MCM-48-S (pore size 22 Å) using three QENS spectrometers of respective energy resolutions 1, 30, and 60 µeV, covering the temperature range from 325 to 200 K. Five quantities are extracted from the analysis: they are β, the stretch exponent characterizing the α-relaxation βγ, the exponent determining the power-law dependence of the relaxation time on Q; \\langle \\tau_{0} \\rangle , the Q-independent pre-factor for the average translational relaxation time; \\langle \\tau _{{\\mathrm {R}}_{1}} \\rangle , the relaxation time for the first-order rotational correlation function; and \\langle \\tau _{{\\mathrm {R}}_{2}} \\rangle , the relaxation time for the second-order rotational correlation function. We discuss the temperature dependence of these parameters and note that, in particular, the dynamics is rapidly slowing down at temperature around 220 K, signalling the onset of a structural arrest transition of liquid water into an amorphous solid water.

  9. Water and polymer dynamics in highly crosslinked polyamide membranes

    Science.gov (United States)

    Frieberg, Bradley; Chan, Edwin; Tyagi, Madhu; Stafford, Christopher; Soles, Christopher

    Highly crosslinked polyamides for reverse osmosis are the state-of-the-art active material in membranes for desalination. The thin film composite membrane structure that is used commercially has been empirically designed to selectively allow the passage of water molecules and minimize the passage of solutes such as salt. However, due to the large roughness and variability of the polyamide layer, there is a limited understanding of the structure-property relationship for these materials as well as the transport mechanism. To better understand the water transport mechanism we measure the water and polymer dynamics of polyamide membranes using quasi-elastic neutron scattering (QENS). By hydrating the membrane with deuterated water, we are able to isolate the dynamics of the hydrogenated membrane on the pico- and nanosecond time scales. By subsequently hydrating the membranes with hydrogenated water, the QENS measurements on the same times scales reveal information about both the translational and rotational dynamics of water confined within the polyamide membrane. Further understanding of the water diffusion mechanism will establish design rules in which the performance of future membrane materials can be improved.

  10. Imaging the molecular dynamics of dissociative electron attachment to water

    Energy Technology Data Exchange (ETDEWEB)

    Adaniya, Hidihito; Rudek, B.; Osipov, Timur; Haxton, Dan; Weber, Thorsten; Rescigno, Thomas N.; McCurdy, C.W.; Belkacem, Ali

    2009-10-19

    Momentum imaging experiments on dissociative electron attachment to the water molecule are combined with ab initio theoretical calculations of the angular dependence of the quantum mechanical amplitude for electron attachment to provide a detailed picture of the molecular dynamics of dissociation attachment via the two lowest energy Feshbach resonances. The combination of momentum imaging experiments and theory can reveal dissociation dynamics for which the axial recoil approximation breaks down and thus provides a powerful reaction microscope for DEA to polyatomics.

  11. Hydrological dynamics of water sources in a Mediterranean lagoon

    OpenAIRE

    Stumpp, C.; A. Ekdal; Gönenc, I. E.; P. Maloszewski

    2014-01-01

    Lagoons are important ecosystems occupying large coastal areas worldwide. Lagoons contain various mixtures of marine and freshwater sources which are highly dynamic in time. However, it often remains a challenge to identify and quantify dynamic changes of water sources, particularly in heterogeneous lagoon systems like the Köycegiz–Dalyan lagoon (KDL), which is located at the south-west of Turkey on the Mediterranean Sea coast. The objective of this study was to quantify dif...

  12. Hydrological dynamics of water sources in a Mediterranean lagoon

    OpenAIRE

    Stumpp, C.; A. Ekdal; Gönenc, I. E.; P. Maloszewski

    2014-01-01

    Lagoons are important ecosystems occupying large coastal areas worldwide. Lagoons contain various mixtures of marine and freshwater sources which are highly dynamic in time. However, it often remains a challenge to identify and quantify dynamic changes of water sources, particularly in heterogeneous lagoon systems like the Köycegiz-Dalyan Lagoon (KDL), which is located at the southwest of Turkey on the Mediterranean Sea coast. The objective of this study was...

  13. Dynamics of Gravity-Capillary Solitary Waves in Deep Water

    OpenAIRE

    Wang, Zhan; Milewski, Paul A.

    2012-01-01

    The dynamics of solitary gravity-capillary water waves propagating on the surface of a three-dimensional fluid domain is studied numerically. In order to accurately compute complex time dependent solutions, we simplify the full potential flow problem by taking a cubic truncation of the scaled Dirichlet-to-Neumann operator for the normal velocity on the free surface. This approximation agrees remarkably well with the full equations for the bifurcation curves, wave profiles and the dynamics of ...

  14. Water vapor and the dynamics of climate changes

    OpenAIRE

    Schneider, Tapio; O'Gorman, Paul A.; Levine, Xavier

    2009-01-01

    Water vapor is not only Earth's dominant greenhouse gas. Through the release of latent heat when it condenses, it also plays an active role in dynamic processes that shape the global circulation of the atmosphere and thus climate. Here we present an overview of how latent heat release affects atmosphere dynamics in a broad range of climates, ranging from extremely cold to extremely warm. Contrary to widely held beliefs, atmospheric circulation statistics can change nonmonotonically with globa...

  15. Estimating Biofuel Feedstock Water Footprints Using System Dynamics

    Energy Technology Data Exchange (ETDEWEB)

    Inman, Daniel; Warner, Ethan; Stright, Dana; Macknick, Jordan; Peck, Corey

    2016-07-01

    Increased biofuel production has prompted concerns about the environmental tradeoffs of biofuels compared to petroleum-based fuels. Biofuel production in general, and feedstock production in particular, is under increased scrutiny. Water footprinting (measuring direct and indirect water use) has been proposed as one measure to evaluate water use in the context of concerns about depleting rural water supplies through activities such as irrigation for large-scale agriculture. Water footprinting literature has often been limited in one or more key aspects: complete assessment across multiple water stocks (e.g., vadose zone, surface, and ground water stocks), geographical resolution of data, consistent representation of many feedstocks, and flexibility to perform scenario analysis. We developed a model called BioSpatial H2O using a system dynamics modeling and database framework. BioSpatial H2O could be used to consistently evaluate the complete water footprints of multiple biomass feedstocks at high geospatial resolutions. BioSpatial H2O has the flexibility to perform simultaneous scenario analysis of current and potential future crops under alternative yield and climate conditions. In this proof-of-concept paper, we modeled corn grain (Zea mays L.) and soybeans (Glycine max) under current conditions as illustrative results. BioSpatial H2O links to a unique database that houses annual spatially explicit climate, soil, and plant physiological data. Parameters from the database are used as inputs to our system dynamics model for estimating annual crop water requirements using daily time steps. Based on our review of the literature, estimated green water footprints are comparable to other modeled results, suggesting that BioSpatial H2O is computationally sound for future scenario analysis. Our modeling framework builds on previous water use analyses to provide a platform for scenario-based assessment. BioSpatial H2O's system dynamics is a flexible and user

  16. Quantum tunneling and vibrational dynamics of ultra-confined water

    Science.gov (United States)

    Kolesnikov, Alexander I.; Anovitz, Lawrence M.; Ehlers, Georg; Mamontov, Eugene; Podlesnyak, Andrey; Prisk, Timothy R.; Seel, Andrew; Reiter, George F.

    2015-03-01

    Vibrational dynamics of ultra-confined water in single crystals beryl, the structure of which contains ~ 5 Å diameter channels along the c-axis was studied with inelastic (INS), quasi-elastic (QENS) and deep inelastic (DINS) neutron scattering. The results reveal significantly anisotropic dynamical behavior of confined water, and show that effective potential experienced by water perpendicular to the channels is significantly softer than along them. The observed 7 peaks in the INS spectra (at energies 0.25 to 15 meV), based on their temperature and momentum transfer dependences, are explained by transitions between the split ground states of water in beryl due to water quantum tunneling between the 6-fold equivalent positions across the channels. DINS study of beryl at T=4.3 K shows narrow, anisotropic water proton momentum distribution with corresponding kinetic energy, EK=95 meV, which is much less than was previously observed in bulk water (~150 meV). We believe that the exceptionally small EK in beryl is a result of water quantum tunneling ∖ delocalization in the nanometer size confinement and weak water-cage interaction. The neutron experiment at ORNL was sponsored by the Sci. User Facilities Div., BES, U.S. DOE. This research was sponsored by the Div. Chemical Sci, Geosciences, and Biosciences, BES, U.S. DOE. The STFC RAL is thanked for access to ISIS neutron facilities.

  17. Hydration water in dynamics of a hydrated beta-lactoglobulin

    Science.gov (United States)

    Yoshida, K.; Yamaguchi, T.; Bellissent-Funel, M.-C.; Longeville, S.

    2007-02-01

    Incoherent spin-echo signals of a hydrated β-lactoglobulin protein were investigated, at 275 and 293 K. The intermediate scattering functions I(Q,t) were divided in two contributions from surface water and protein, respectively. On one hand, the dynamics of the surface water follows a KWW stretched exponential function (the exponent is ~0.5), on the other hand, that of the protein follows a single exponential. The present results are consistent with our previous results of hydrated C-phycocyanin combining elastic and quasielastic neutron scattering and by molecular dynamics simulation.

  18. Mechanosensing Dynamics of Red blood Cells

    Science.gov (United States)

    Wan, Jiandi

    2015-11-01

    Mechanical stress-induced deformation of human red blood cells (RBCs) plays important physiopathological roles in oxygen delivery, blood rheology, transfusion, and malaria. Recent studies demonstrate that, in response to mechanical deformation, RBCs release adenosine-5'-triphosphate (ATP), suggesting the existence of mechanotransductive pathways in RBCs. Most importantly, the released ATP from RBCs regulates vascular tone and impaired release of ATP from RBCs has been linked to diseases such as type II diabetes and cystic fibrosis. To date, however, the mechanisms of mechanotransductive release of ATP from RBCs remain unclear. Given that RBCs experience shear stresses continuously during the circulation cycle and the released ATP plays a central role in vascular physiopathology, understanding the mechanotransductive release of ATP from RBCs will provide not only fundamental insights to the role of RBCs in vascular homeostasis but also novel therapeutic strategies for red cell dysfunction and vascular disease. This talk describes the main research in my group on integrating microfluidic-based approaches to study the mechanosensing dynamics of RBCs. Specifically, I will introduce a micro?uidic approach that can probe the dynamics of shear-induced ATP release from RBCs with millisecond resolution and provide quantitative understandings of the mechanosensitive ATP release processes in RBCs. Furthermore, I will also describe our recent findings about the roles of the Piezo1 channel, a newly discovered mechanosensitive cation channel in the mechanotransductive ATP release in RBCs. Last, possible functions of RBCs in the regulation of cerebral blood flow will be discussed.

  19. Neutron Scattering Study of the Dynamics of Water in Ettringite

    Science.gov (United States)

    Hartman, Michael; Berliner, Ronald; Herwig, Kenneth

    2004-03-01

    Ettringite, Ca_6[Al(OH)_6]_2(SO_4)_3textbullet26H_2O, is an important hydration product in ordinary Portland cements, controlling the initial rate of set of the aluminate phase. Ettringite is also implicated in cement degradation mechanism for cement structures exposed to ground waters or contaminant waters containing high sulfate concentrations. As part of a larger experimental program to understand the structure and dynamics of ettringite, we have investigated the dynamics of water contained in ettringite using quasielastic neutron scattering on the QENS instrument at IPNS. Measurements were taken at 250K, 298K, and 323K on ettringite equilibrated at various relative humidities. It was found that the data were best fit with a model for isotropic rotation. Of the hydrogen atoms present, approximately 10% were observed to participate in the isotropic rotation suggesting that it was the waters present in the channel sites that were undergoing the reorientational motion.

  20. Nonlinear dynamics of rotating shallow water methods and advances

    CERN Document Server

    Zeitlin, Vladimir

    2007-01-01

    The rotating shallow water (RSW) model is of wide use as a conceptual tool in geophysical fluid dynamics (GFD), because, in spite of its simplicity, it contains all essential ingredients of atmosphere and ocean dynamics at the synoptic scale, especially in its two- (or multi-) layer version. The book describes recent advances in understanding (in the framework of RSW and related models) of some fundamental GFD problems, such as existence of the slow manifold, dynamical splitting of fast (inertia-gravity waves) and slow (vortices, Rossby waves) motions, nonlinear geostrophic adjustment and wa

  1. Hydrogen bond dynamics in liquid water: Ab initio molecular dynamics simulation

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Cheolhee; Kim, Eunae [College of Pharmacy, Chosun University, Gwangju (Korea, Republic of); Yeom, Min Sun [Korea Institute of Science and Technology Information, Daejeon (Korea, Republic of)

    2016-01-15

    The effect of intermolecular interaction on the distribution of the harmonic vibrational frequencies of water molecules was investigated through ab initio molecular dynamics simulations based on the Born-Oppenheimer approach. For single water, the effect of the dynamics of the oxygen atom in single water and the simulation time step on the frequency distribution were examined. The distributions of the OH stretching and HOH bending vibrational frequencies of liquid water were compared to those of single water. The probability distributions of the change in OH bond length and the lifetime of the dangling OH bond were also obtained. The distribution of the frequencies was strongly affected by the long lifetime of the dangling OH bond, resulting in the formation of hydrogen bonds between water molecules.

  2. Evaluation of water distribution system monitoring using stochastic dynamic modeling

    OpenAIRE

    Jones, Philip Edward James

    1992-01-01

    A stochastic dynamic constituent transport model was developed, capable of simulating the operation of a water distribution system containing pumps and storage tanks, and subject to random demands and contaminant inputs. Long term operation of a hypothetical small town water supply system containing one pump station and one storage tank was simulated while the system was subjected to external contaminant inputs. Repeated simulations were made under different regimes of exter...

  3. Ultrafast vibrational dynamics of water confined in phospholipid reverse micelles

    Directory of Open Access Journals (Sweden)

    Elsaesser T.

    2013-03-01

    Full Text Available We study the ultrafast dynamics of OH stretching and bending vibrations of water inside dioleoylphosphatidylcholine (DOPC reverse micelles in a wide range of hydration. A strong hydration level dependence for the spectral diffusion rates is found and explained by the distinctly different environment for single water molecules bound to the anionic phosphate group. We show that the energy relaxation pathway of the OH stretching vibration at low hydration level involves the OH bending.

  4. A peptide’s perspective of water dynamics

    International Nuclear Information System (INIS)

    Graphical abstract: This perspective focuses on examining the fast components of the water dynamics near peptides and probing the local water at a residue level in proteins using 2D IR spectroscopy. Display Omitted Highlights: ► 2D IR spectroscopy reveals the vibrational frequency dynamics of protein amide I modes from nearby water molecules. ► The evolution of the shape of the 2D IR spectra of aqueous amides characterizes the amide vibrational frequency correlations. ► Benchmarks for interpreting 2D IR spectra of complex biomolecules are thereby created. ► In one example the dynamics of water molecules confined in a viral proton channel are examined. ► In another, the water in fibrils is revealed by the 2D IR spectral shape evolution. - Abstract: This perspective is focused on amide groups of peptides interacting with water. 2D IR spectroscopy has already enabled structural aspects of the peptide backbone to be determined through its ability to measure the coupling between different amide-I modes. Here we describe why nonlinear IR is emerging as the method of choice to examine the fast components of the water dynamics near peptides and how isotopically edited peptide links can be used to probe the local water at a residue level in proteins. This type of research necessarily involves an intimate mix of theory and experiment. The description of the results is underpinned by relatively well established quantum-statistical theories that describe the important manifestations of peptide vibrational frequency fluctuations.

  5. Stable isotopes as indicators of soil water dynamics in watersheds

    International Nuclear Information System (INIS)

    Stream water quality and quantity depend on discharge rates of water and nutrients from soils. However, soil-water storage is very dynamic and strongly influenced by plants. Stable isotopes of oxygen and hydrogen were analyzed to quantify spatial and temporal changes in evaporation, transpiration and stream discharge in a gauged watershed with dry summers and wet winters. The isotope data indicate that plant and soil water have been affected by evaporation. In contrast, stream water is not evaporated, though discharge rates show diurnal cycles driven by transpiration. It is concluded that two separate pools of water are held within the soil. One is a faster moving pool held at relatively weak matric potentials, making it more subject to gravitational transport to streams. The other pool is held more tightly by matric forces, has a longer residence time within the soil, and will more likely be evaporated or taken up by plants. (author)

  6. Fluorescent tags to explore cell wall structure and dynamics

    OpenAIRE

    Gonneau, Martine; Höfte, Herman; Vernhettes, Samantha

    2012-01-01

    Plant cell walls are highly dynamic and heterogeneous structures, which vary between cell types, growth stages but also between microdomains within a single cell wall. In this review, we summarize the imaging techniques using fluorescent tags that are currently being used and which should in the coming years revolutionize our understanding of the dynamics of cell wall architecture and the cellular processes involved in the synthesis of cell wall components.

  7. Socioeconomic dynamics of water quality in the Egyptian Nile

    Science.gov (United States)

    Malik, Maheen; Nisar, Zainab; Karakatsanis, Georgios

    2016-04-01

    The Nile River remains the most important source of freshwater for Egypt as it accounts for nearly all of the country's drinking and irrigation water. About 95% of the total population is accounted to live along the Banks of the Nile(1). Therefore, water quality deterioration in addition to general natural scarcity of water in the region(2) is the main driver for carrying out this study. What further aggravates this issue is the water conflict in the Blue Nile region. The study evaluates different water quality parameters and their concentrations in the Egyptian Nile; further assessing the temporal dynamics of water quality in the area with (a) the Environmental Kuznets Curve (EKC)(3) and (b) the Jevons Paradox (JP)(4) in order to identify water quality improvements or degradations using selected socioeconomic variables(5). For this purpose various environmental indicators including BOD, COD, DO, Phosphorus and TDS were plotted against different economic variables including Population, Gross Domestic Product (GDP), Annual Fresh Water Withdrawal and Improved Water Source. Mathematically, this was expressed by 2nd and 3rd degree polynomial regressions generating the EKC and JP respectively. The basic goal of the regression analysis is to model and highlight the dynamic trend of water quality indicators in relation to their established permissible limits, which will allow the identification of optimal future water quality policies. The results clearly indicate that the dependency of water quality indicators on socioeconomic variables differs for every indicator; while COD was above the permissible limits in all the cases despite of its decreasing trend in each case, BOD and phosphate signified increasing concentrations for the future, if they continue to follow the present trend. This could be an indication of rebound effect explained by the Jevons Paradox i.e. water quality deterioration after its improvement, either due to increase of population or intensification

  8. Ordered water monolayer on ionic model substrates studied by molecular dynamics simulations

    International Nuclear Information System (INIS)

    The molecular behaviors of interfacial water molecules at the solid/liquid interface are of a fundamental significance in a diverse set of technical and scientific contexts, thus have drawn extensive attentions. On certain surfaces, the water monolayer may exhibit an ordered feature, which may result in the novel wetting phenomenon. In this article, based on the molecular dynamics simulations, we make a detailed structure analysis of the ordered water monolayer on ionic model surface with graphene-like hexagonal lattices under various charges and unit cell sizes. We carefully analyze the water density profiles and potential of mean force, which are the origin of the special hexagonal ordered water structures near the solid surface. The number of hydrogen bonds of the ordered water monolayer near the solid surface is carefully investigated. (authors)

  9. Dynamic water accounting in heavily committed river basins

    Science.gov (United States)

    Tilmant, Amaury; Marques, Guilherme

    2014-05-01

    Many river basins throughout the world are increasingly under pressure as water demands keep rising due to population growth, industrialization, urbanization and rising living standards. In the past, the typical answer to meet those demands focused on the supply-side and involved the construction of hydraulic infrastructures to capture more water from surface water bodies and from aquifers. As river basins were being more and more developed, downstream water users and ecosystems have become increasingly dependant on the management actions taken by upstream users. The increased interconnectedness between water users, aquatic ecosystems and the built environment is further compounded by climate change and its impact on the water cycle. Those pressures mean that it has become increasingly important to measure and account for changes in water fluxes and their corresponding economic value as they progress throughout the river system. Such basin water accounting should provide policy makers with important information regarding the relative contribution of each water user, infrastructure and management decision to the overall economic value of the river basin. This paper presents a dynamic water accounting approach whereby the entire river basin is considered as a value chain with multiple services including production and storage. Water users and reservoirs operators are considered as economic agents who can exchange water with their hydraulic neighbors at a price corresponding to the marginal value of water. Effective water accounting is made possible by keeping track of all water fluxes and their corresponding transactions using the results of a hydro-economic model. The proposed approach is illustrated with the Eastern Nile River basin in Africa.

  10. Dynamic cell culture system (7-IML-1)

    Science.gov (United States)

    Cogoli, Augusto

    1992-01-01

    This experiment is one of the Biorack experiments being flown on the International Microgravity Laboratory 1 (MIL-1) mission as part of an investigation studying cell proliferation and performance in space. One of the objectives of this investigation is to assess the potential benefits of bioprocessing in space with the ultimate goal of developing a bioreactor for continuous cell cultures in space. This experiment will test the operation of an automated culture chamber that was designed for use in a Bioreactor in space. The device to be tested is called the Dynamic Cell Culture System (DCCS). It is a simple device in which media are renewed or chemicals are injected automatically, by means of osmotic pumps. This experiment uses four Type I/O experiment containers. One DCCS unit, which contains a culture chamber with renewal of medium and a second chamber without a medium supply fits in each container. Two DCCS units are maintained under zero gravity conditions during the on-orbit period. The other two units are maintained under 1 gh conditions in a 1 g centrifuge. The schedule for incubator transfer is given.

  11. Analysis of Dynamic Characteristics of Water Injection Pump

    International Nuclear Information System (INIS)

    Water injection pump outputs oil with high pressure during this process, seawater is injected into the well to recover the well pressure and maintain high productivity. A water injection pump has high productivity, and herefore, it serves as a key piece of equipment in marine plants. In this light, water injection pumps are being studied widely in industry. In this study, the rotor dynamics is analyzed to determine the natural frequency according to the bearing stiffness and operation speed change. This study aims to establish the pump reliability through critical speed, stability, and unbalance response analysis

  12. Protein Dynamics in Individual Human Cells: Experiment and Theory

    OpenAIRE

    Cohen, Ariel Aharon; Kalisky, Tomer; Mayo, Avi; Geva-Zatorsky, Naama; Danon, Tamar; Issaeva, Irina; Perzov, Natalie; Sigal, Alex; Alon, Uri; Isalan, Mark; Kopito, Ronen; Milo, Ron

    2009-01-01

    A current challenge in biology is to understand the dynamics of protein circuits in living human cells. Can one define and test equations for the dynamics and variability of a protein over time? Here, we address this experimentally and theoretically, by means of accurate time-resolved measurements of endogenously tagged proteins in individual human cells. As a model system, we choose three stable proteins displaying cell-cycle–dependant dynamics. We find that protein accumulation with time pe...

  13. Understanding the dynamics of water availability and use in China

    Energy Technology Data Exchange (ETDEWEB)

    Thomas, R.P.; Conrad, S.H.; Jeppesen, D.M.; Engi, E.

    1997-07-01

    This report presents the preliminary results of an analysis of China`s water resources, part of an effort undertaken by the National Intelligence Council Medea scientists to improve the understanding of future food production and consumption in the People`s Republic of China. A dynamic water model was developed to simulate the hydrological budgetary processes in five river drainage basins located in northeastern, central, and southern China: the Chang Jiang (Yangtse River), Huanghe (Yellow River), Haihe, Huaihe, and Liaohe. The model was designed to assess the effects of changes in urban, industrial, and agricultural water use requirements on the availability of water in each basin and to develop estimates of the water surpluses and/or deficits in China through the year 2025. The model imposes a sustainable yield constraint, that is, groundwater extraction is not allowed to exceed the sustainable yield; if the available water does not meet the total water use requirements, a deficit results. An agronomic model was also developed to generate projections of the water required to service China`s agricultural sector and compare China`s projected grain production with projected grain consumption requirements to estimate any grain surplus and/or deficit. In future refinements, the agronomic model will interface directly with the water model to provide for the exchange of information on projected water use requirements and available water. The preliminary results indicate that the Chang Jiang basin will have a substantial surplus of water through 2025 and that the Haihe basin is in an ongoing situation. The agricultural water use requirements based on grain production indicate that an agricultural water deficit in the Haihe basin begins before the onset of the modeling period (1980) and steadily worsens through 2025. This assumption is confirmed by reports that groundwater mining is already under way in the most intensely cultivated and populated areas of northern China.

  14. Molecular dynamics study of the water/n-alkane interface

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    Molecular dynamics simulations on the interface between liquid water and liquid n-alkane (including octane, nonane, decane, undecane and dodecane) have been performed with the purpose to study the interfacial properties: (Ⅰ) density profile; (Ⅱ) molecular orientation; (Ⅲ) interfacial tension and the temperature effect on the interfacial tension. Simulation results show that at the interface the structures of both water and n-alkane are different from those in the bulk. Water has an orientational preference due to the number of hydrogen bonds per molecule maximized. N-alkane has a more lateral orientation with respect to the interface in order to be in close contact with water. The calculated individual phase bulk density and interfacial tension of water/n-alkane systems are in good agreement with the corresponding experimental ones.

  15. Water dynamics in a bean crop (Phaseolus vulgaris)

    International Nuclear Information System (INIS)

    The dynamics of water was studied at 'La Tola', Experimental Teaching Center of the Central University of Ecuador, in a Sandy-Ioan, typic Haplustoll soil, in wich beans were growing. All the components of the crop water balance were determined. Real evapotranspiration was in direct relation to the growth of the crop, reaching its maximum value of 4.9 mm day-1, at pod setting, then decreasing slowly until maturation of the kernels. Up to 1 meter depth, water loss by drainage depended on rainfall, reaching up to 24% of the total water loss: the soil layer supplying most of the water for the use of the crop was between 0-40 cm, where the root activity was greatest

  16. Understanding water: Molecular dynamics simulations of solubilized and crystallized myoglobin

    Energy Technology Data Exchange (ETDEWEB)

    Wei Gu; Garcia, A.E.; Schoenborn, B.P. [Los Alamos National Laboratory, NM (United States)

    1994-12-31

    Molecular dynamics simulations were performed on CO myoglobin to evaluate the stability of the bound water molecules as determined in a neutron diffraction analysis. The myoglobin structure derived from the neutron analysis provided the starting coordinate set used in the simulations. The simulations show that only a few water molecules are tightly bound to protein atoms, while most solvent molecules are labile, breaking and reforming hydrogen bonds. Comparison between myoglobin in solution and in a single crystal highlighted some of the packing effects on the solvent structure and shows that water solvent plays an indispensable role in protein dynamics and structural stability. The described observations explain some of the differences in the experimental results of protein hydration as observed in NMR, neutron and X-ray diffraction studies.

  17. Development of Nanofluidic Cells for Ultrafast X-ray Studies of Water

    International Nuclear Information System (INIS)

    In order to study the molecular structure and dynamics of liquid water with soft x-ray probes, samples with nanoscale dimensions are needed. This paper describes a simple method for preparing nanofluidic water cells. The idea is to confine a thin layer of water between two silicon nitride windows. The windows are 1 mm x 1 mm and 0.5 mm x 0.5 mm in size and have a thickness of 150 nm. The thickness of the water layer was measured experimentally by probing the infrared spectrum of water in the cells with a Fourier Transform InfraRed (FTIR) apparatus and from soft x-ray static measurements at the Advanced Light Source (ALS) at Lawrence Berkeley National Laboratory. Water layers ranging from 10 nm to more than 2 (micro)m were observed. Evidence for changes in the water structure compared to bulk water is observed in the ultrathin cells

  18. Orientational and translational dynamics of polyether/water solutions.

    Science.gov (United States)

    Sturlaugson, Adam L; Fruchey, Kendall S; Lynch, Stephen R; Aragón, Sergio R; Fayer, Michael D

    2010-04-29

    Optical heterodyne-detected optical Kerr effect (OHD-OKE) experiments and pulsed field-gradient spin-echo NMR (PFGSE-NMR) experiments were performed to measure the rotational and translational diffusion constants of a polyether, tetraethylene glycol dimethyl ether (TEGDE), in binary mixtures with water over concentrations ranging from pure TEGDE to approaching infinite dilution. In addition, hydrodynamic calculations of the rotational and translational diffusion constants for several rigid TEGDE conformations in the neat liquid and in the infinitely dilute solution were performed to supplement the experimental data. The rotational relaxation data follow the Debye-Stokes-Einstein (DSE) equation within experimental error over the entire water concentration range. The agreement with the DSE equation indicates that there is no significant structural change of the polyether as the water content is changed. In contrast to the rotational dynamics, the translational diffusion data show a distinct deviation from Stokes-Einstein (SE) behavior. As the water content of the mixture is reduced, the translational diffusion rate decreases less rapidly than the increase in viscosity alone predicts until the water/TEGDE mole ratio of 7:1 is reached. Upon further reduction of water content, the translational diffusion tracks the viscosity. Comparison of the translational data with the rotational data and the hydrodynamic computations shows that the translational dynamics cannot be explained by a molecular shape change and that the low water fraction solutions are the ones that deviate from hydrodynamic behavior. A conjecture is presented as a possible explanation for the different behaviors of the rotational and translational dynamics. PMID:20373773

  19. Fluorescent tags to explore cell wall structure and dynamics.

    OpenAIRE

    Martine eGonneau; Herman eHöfte; Samantha eVernhettes

    2012-01-01

    Plant cell walls are highly dynamic and heterogeneic structures, which vary between celltypes, growth stages but also between microdomains within a single cell wall. In this review, we summarize the imaging techniques using fluorescent tags that are currently being used and which should in the coming years revolutionize our understanding of the dynamics of cell wall architecture and the cellular processes involved in synthesis of cell wall components.

  20. Water-Mediated Energy Dynamics in a Homodimeric Hemoglobin.

    Science.gov (United States)

    Leitner, David M

    2016-05-01

    We examine energy dynamics in the unliganded and liganded states of the homodimeric hemoglobin from Scapharca inaequivalvis (HbI), which exhibits cooperativity mediated by the cluster of water molecules at the interface upon ligand binding and dissociation. We construct and analyze a dynamic network in which nodes representing the residues, hemes, and water cluster are connected by edges that represent energy transport times, as well as a nonbonded network (NBN) indicating regions that respond rapidly to local strain within the protein via nonbonded interactions. One of the two largest NBNs includes the Lys30-Asp89 salt bridge critical for stabilizing the dimer. The other includes the hemes and surrounding residues, as well as, in the unliganded state, the cluster of water molecules between the globules. Energy transport in the protein appears to be controlled by the Lys30-Asp89 salt bridge critical for stabilizing the dimer, as well as the interface water cluster in the unliganded state. Possible connections between energy transport dynamics in response to local strain identified here and allosteric transitions in HbI are discussed. PMID:27065192

  1. Validation of the dynamic model for a pressurized water reactor

    International Nuclear Information System (INIS)

    Dynamic model validation is a necessary procedure to assure that the developed empirical or physical models are satisfactorily representing the dynamic behavior of the actual plant during normal or abnormal transients. For small transients, physical models which represent isolated core, isolated steam generator and the overall pressurized water reactor are described. Using data collected during the step power changes that occured during the startup procedures, comparisons of experimental and actual transients are given at 30% and 100% of full power. The agreement between the transients derived from the model and those recorded on the plant indicates that the developed models are well suited for use for functional or control studies

  2. Fluid dynamics and noise in bacterial cell-cell and cell-surface scattering

    CERN Document Server

    Drescher, Knut; Cisneros, Luis H; Ganguly, Sujoy; Goldstein, Raymond E; 10.1073/pnas.1019079108

    2011-01-01

    Bacterial processes ranging from gene expression to motility and biofilm formation are constantly challenged by internal and external noise. While the importance of stochastic fluctuations has been appreciated for chemotaxis, it is currently believed that deterministic long-range fluid dynamical effects govern cell-cell and cell-surface scattering - the elementary events that lead to swarming and collective swimming in active suspensions and to the formation of biofilms. Here, we report the first direct measurements of the bacterial flow field generated by individual swimming Escherichia coli both far from and near to a solid surface. These experiments allowed us to examine the relative importance of fluid dynamics and rotational diffusion for bacteria. For cell-cell interactions it is shown that thermal and intrinsic stochasticity drown the effects of long-range fluid dynamics, implying that physical interactions between bacteria are determined by steric collisions and near-field lubrication forces. This dom...

  3. Molecular Dynamics Investigation of Benzene in Supercritical Water

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    Microscopic structure and diffusion properties of benzene in ambient water (298 K, 0.1 MPa) and super critical water (673-773 K, 25-35 MPa) are investigated by molecular dynamics simulation with site-site models. It is found that at the ambient condition, the water molecules surrounding a benzene molecule form a hydrogen bond network. The hydrogen bond interaction between supercritical water molecules decreases dramatically under supercritical conditions. The diffusion coefficients of both the solute molecule and solvent molecule at supercritical conditions increase by 30-180 times than those at the ambient condition. With the temperature approaching the critical temperature, the change of diffusion coefficient with pressure becomes pronounced.

  4. Molecular Dynamics Simulations of Carbon Nanotubes in Water

    Science.gov (United States)

    Walther, J. H.; Jaffe, R.; Halicioglu, T.; Koumoutsakos, P.

    2000-01-01

    We study the hydrophobic/hydrophilic behavior of carbon nanotubes using molecular dynamics simulations. The energetics of the carbon-water interface are mainly dispersive but in the present study augmented with a carbon quadrupole term acting on the charge sites of the water. The simulations indicate that this contribution is negligible in terms of modifying the structural properties of water at the interface. Simulations of two carbon nanotubes in water display a wetting and drying of the interface between the nanotubes depending on their initial spacing. Thus, initial tube spacings of 7 and 8 A resulted in a drying of the interface whereas spacing of > 9 A remain wet during the course of the simulation. Finally, we present a novel particle-particle-particle-mesh algorithm for long range potentials which allows for general (curvilinear) meshes and "black-box" fast solvers by adopting an influence matrix technique.

  5. Short time dynamics of water coalescence on a flat water pool

    CERN Document Server

    Lim, Su Jin; Fezzaa, Kamel; Weon, Byung Mook

    2016-01-01

    Coalescence is an important hydrodynamic event that frequently takes place in nature as well as in industry. Here we provide an experimental study on short time dynamics of water coalescence, particularly when a water droplet comes in contact with a flat water surface, by utilizing high-resolution high-penetration ultrafast X-ray microscopy. Our results demonstrate a possibility that an extreme curvature difference between a drop and a flat surface can significantly modify the hydrodynamics of water coalescence, which is unexpected in the existing theory. We suggest a plausible explanation for why coalescence can be modified by an extreme curvature difference.

  6. The interplay between dynamic heterogeneities and structure of bulk liquid water: A molecular dynamics simulation study

    International Nuclear Information System (INIS)

    In order to study the interplay between dynamical heterogeneities and structural properties of bulk liquid water in the temperature range 130–350 K, thus including the supercooled regime, we use the explicit trend of the distribution functions of some molecular properties, namely, the rotational relaxation constants, the atomic mean-square displacements, the relaxation of the cross correlation functions between the linear and squared displacements of H and O atoms of each molecule, the tetrahedral order parameter q and, finally, the number of nearest neighbors (NNs) and of hydrogen bonds (HBs) per molecule. Two different potentials are considered: TIP4P-Ew and a model developed in this laboratory for the study of nanoconfined water. The results are similar for the dynamical properties, but are markedly different for the structural characteristics. In particular, for temperatures higher than that of the dynamic crossover between “fragile” (at higher temperatures) and “strong” (at lower temperatures) liquid behaviors detected around 207 K, the rotational relaxation of supercooled water appears to be remarkably homogeneous. However, the structural parameters (number of NNs and of HBs, as well as q) do not show homogeneous distributions, and these distributions are different for the two water models. Another dynamic crossover between “fragile” (at lower temperatures) and “strong” (at higher temperatures) liquid behaviors, corresponding to the one found experimentally at T∗ ∼ 315 ± 5 K, was spotted at T∗ ∼ 283 K and T∗ ∼ 276 K for the TIP4P-Ew and the model developed in this laboratory, respectively. It was detected from the trend of Arrhenius plots of dynamic quantities and from the onset of a further heterogeneity in the rotational relaxation. To our best knowledge, it is the first time that this dynamical crossover is detected in computer simulations of bulk water. On the basis of the simulation results, the possible mechanisms of the

  7. Dynamic Ice-Water Interactions Form Europa's Chaos Terrains

    Science.gov (United States)

    Blankenship, D. D.; Schmidt, B. E.; Patterson, G. W.; Schenk, P.

    2011-12-01

    Unique to the surface of Europa, chaos terrain is diagnostic of the properties and dynamics of its icy shell. We present a new model that suggests large melt lenses form within the shell and that water-ice interactions above and within these lenses drive the production of chaos. This model is consistent with key observations of chaos, predicts observables for future missions, and indicates that the surface is likely still active today[1]. We apply lessons from ice-water interaction in the terrestrial cryosphere to hypothesize a dynamic lense-collapse model to for Europa's chaos terrain. Chaos terrain morphology, like that of Conamara chaos and Thera Macula, suggests a four-phase formation [1]: 1) Surface deflection occurs as ice melts over ascending thermal plumes, as regularly occurs on Earth as subglacial volcanoes activate. The same process can occur at Europa if thermal plumes cause pressure melt as they cross ice-impurity eutectics. 2) Resulting hydraulic gradients and driving forces produce a sealed, pressurized melt lense, akin to the hydraulic sealing of subglacial caldera lakes. On Europa, the water cannot escape the lense due to the horizontally continuous ice shell. 3) Extension of the brittle ice lid above the lense opens cracks, allowing for the ice to be hydrofractured by pressurized water. Fracture, brine injection and percolation within the ice and possible iceberg toppling produces ice-melange-like granular matrix material. 4) Refreezing of the melt lense and brine-filled pores and cracks within the matrix results in raised chaos. Brine soaking and injection concentrates the ice in brines and adds water volume to the shell. As this englacial water freezes, the now water-filled ice will expand, not unlike the process of forming pingos and other "expansion ice" phenomena on Earth. The refreezing can raise the surface and create the oft-observed matrix "domes" In this presentation, we describe how catastrophic ice-water interactions on Earth have

  8. Shock induced phase transition of water: Molecular dynamics investigation

    Energy Technology Data Exchange (ETDEWEB)

    Neogi, Anupam, E-mail: anupamneogi@atdc.iitkgp.ernet.in [Advanced Technology Development Center, Indian Institute of Technology Kharagpur, Kharagpur 721302 (India); Mitra, Nilanjan, E-mail: nilanjan@civil.iitkgp.ernet.in [Department of Civil Engineering, Indian Institute of Technology Kharagpur, Kharagpur 721302 (India)

    2016-02-15

    Molecular dynamics simulations were carried out using numerous force potentials to investigate the shock induced phenomenon of pure bulk liquid water. Partial phase transition was observed at single shock velocity of 4.0 km/s without requirement of any external nucleators. Change in thermodynamic variables along with radial distribution function plots and spectral analysis revealed for the first time in the literature, within the context of molecular dynamic simulations, the thermodynamic pathway leading to formation of ice VII from liquid water on shock loading. The study also revealed information for the first time in the literature about the statistical time-frame after passage of shock in which ice VII formation can be observed and variations in degree of crystallinity of the sample over the entire simulation time of 100 ns.

  9. Shock induced phase transition of water: Molecular dynamics investigation

    International Nuclear Information System (INIS)

    Molecular dynamics simulations were carried out using numerous force potentials to investigate the shock induced phenomenon of pure bulk liquid water. Partial phase transition was observed at single shock velocity of 4.0 km/s without requirement of any external nucleators. Change in thermodynamic variables along with radial distribution function plots and spectral analysis revealed for the first time in the literature, within the context of molecular dynamic simulations, the thermodynamic pathway leading to formation of ice VII from liquid water on shock loading. The study also revealed information for the first time in the literature about the statistical time-frame after passage of shock in which ice VII formation can be observed and variations in degree of crystallinity of the sample over the entire simulation time of 100 ns

  10. Water Dynamics in Shewanella oneidensis at Ambient and High Pressure using Quasi-Elastic Neutron Scattering

    Science.gov (United States)

    Foglia, Fabrizia; Hazael, Rachael; Simeoni, Giovanna G.; Appavou, Marie-Sousai; Moulin, Martine; Haertlein, Michael; Trevor Forsyth, V.; Seydel, Tilo; Daniel, Isabelle; Meersman, Filip; McMillan, Paul F.

    2016-01-01

    Quasielastic neutron scattering (QENS) is an ideal technique for studying water transport and relaxation dynamics at pico- to nanosecond timescales and at length scales relevant to cellular dimensions. Studies of high pressure dynamic effects in live organisms are needed to understand Earth’s deep biosphere and biotechnology applications. Here we applied QENS to study water transport in Shewanella oneidensis at ambient (0.1 MPa) and high (200 MPa) pressure using H/D isotopic contrast experiments for normal and perdeuterated bacteria and buffer solutions to distinguish intracellular and transmembrane processes. The results indicate that intracellular water dynamics are comparable with bulk diffusion rates in aqueous fluids at ambient conditions but a significant reduction occurs in high pressure mobility. We interpret this as due to enhanced interactions with macromolecules in the nanoconfined environment. Overall diffusion rates across the cell envelope also occur at similar rates but unexpected narrowing of the QENS signal appears between momentum transfer values Q = 0.7-1.1 Å-1 corresponding to real space dimensions of 6-9 Å. The relaxation time increase can be explained by correlated dynamics of molecules passing through Aquaporin water transport complexes located within the inner or outer membrane structures.

  11. Discharging dynamics in an electrolytic cell.

    Science.gov (United States)

    Feicht, Sarah E; Frankel, Alexandra E; Khair, Aditya S

    2016-07-01

    We analyze the dynamics of a discharging electrolytic cell comprised of a binary symmetric electrolyte between two planar, parallel blocking electrodes. When a voltage is initially applied, ions in the electrolyte migrate towards the electrodes, forming electrical double layers. After the system reaches steady state and the external current decays to zero, the applied voltage is switched off and the cell discharges, with the ions eventually returning to a uniform spatial concentration. At voltages on the order of the thermal voltage V_{T}=k_{B}T/q≃25 mV, where k_{B} is Boltzmann's constant, T is temperature, and q is the charge of a proton, experiments on surfactant-doped nonpolar fluids observe that the temporal evolution of the external current during charging and discharging is not symmetric [V. Novotny and M. A. Hopper, J. Electrochem. Soc. 126, 925 (1979)JESOAN0013-465110.1149/1.2129195; P. Kornilovitch and Y. Jeon, J. Appl. Phys. 109, 064509 (2011)JAPIAU0021-897910.1063/1.3554445]. In fact, at sufficiently large voltages (several V_{T}), the current during discharging is no longer monotonic: it displays a "reverse peak" before decaying in magnitude to zero. We analyze the dynamics of discharging by solving the Poisson-Nernst-Planck equations governing ion transport via asymptotic and numerical techniques in three regimes. First, in the "linear regime" when the applied voltage V is formally much less than V_{T}, the charging and discharging currents are antisymmetric in time; however, the potential and charge density profiles during charging and discharging are asymmetric. The current evolution is on the RC timescale of the cell, λ_{D}L/D, where L is the width of the cell, D is the diffusivity of ions, and λ_{D} is the Debye length. Second, in the (experimentally relevant) thin-double-layer limit ε=λ_{D}/L≪1, there is a "weakly nonlinear" regime defined by V_{T}≲V≲V_{T}ln(1/ε), where the bulk salt concentration is uniform; thus the RC timescale of

  12. Bubble dynamics in a variable gap Hele-Shaw cell

    Science.gov (United States)

    Piedra, Saul; Domiguez, Roberto; Ramos, Eduardo

    2015-11-01

    We present observations of the dynamics of individual air bubbles ascending in a Hele-Shaw cell filled with water. Cells with gaps of 1 mm, 1.5 and 2.5 mm are used and the volume of the bubbles is such that we observe bubbles with apparent diameter from 2 mm to 7.3 mm. Given that we work with air and water in all experiments, the Morton number is constant and equal to 2 . 5 ×10-11 . The results are given in terms of the Eotvos, Archimedes and Reynolds numbers, and the trajectories and wakes of the bubbles are described as functions of the gap. In all cases we observe a linear relationship between the Reynolds and Archimedes numbers, but the proportionality constant varies with the gap. Also, although the wake is composed of alternating vortices similar to the von Karman vortex street, the size and location of the vortices vary with the gap. The analysis of some features of the observations and the description of the shape of the bubbles and dominant forces are made with a two dimensional numerical solution of the conservation equations using a front tracking strategy.

  13. Dynamic modeling of an air source heat pump water heater

    OpenAIRE

    Fardoun, Farouk; Ibrahim, Oussama; Zoughaib, Assaad

    2011-01-01

    International audience This paper presents a dynamic simulation model to predict the performance of an air source heat pump water heater (ASHPWH). The mathematical model consists of submodels of the basic system components i.e. evaporator, condenser, compressor, and expansion valve. These submodels were built based on fundamental principles of heat transfer, thermodynamics, fluid mechanics, empirical relationships and manufacturer's data as necessary. The model simulation was carried out u...

  14. Mechanisms of Acceleration and Retardation of Water Dynamics by Ions

    Czech Academy of Sciences Publication Activity Database

    Stirnemann, G.; Wernersson, Erik; Jungwirth, Pavel; Laage, D.

    2013-01-01

    Roč. 135, č. 32 (2013), s. 11824-11831. ISSN 0002-7863 R&D Projects: GA ČR GBP208/12/G016 Grant ostatní: European Research Council(XE) FP7-279977 Institutional support: RVO:61388963 Keywords : ions * water * molecular dynamics * NMR * IR Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 11.444, year: 2013

  15. Estimation of water diffusivity parameters on grape dynamic drying

    OpenAIRE

    Ramos, Inês N.; Miranda, João M.R.; Brandão, Teresa R. S.; Cristina L.M. Silva

    2010-01-01

    A computer program was developed, aiming at estimating water diffusivity parameters in a dynamic drying process with grapes, assessing the predictability of corresponding non-isothermal drying curves. It numerically solves Fick’s second law for a sphere, by explicit finite differences, in a shrinking system, with anisotropic properties and changing boundary conditions. Experiments were performed in a pilot convective dryer, with simulated air conditions observed in a solar dryer, for modellin...

  16. Microscopic dynamics of nanoparticle monolayers at air-water interface.

    Science.gov (United States)

    Bhattacharya, R; Basu, J K

    2013-04-15

    We present results of surface mechanical and particle tracking measurements of nanoparticles trapped at the air-water interface as a function of their areal density. We monitor both the surface pressure (Π) and isothermal compression modulus (ϵ) as well as the dynamics of nanoparticle clusters, using fluorescence confocal microscopy while they are compressed to very high density near the two dimensional close packing density Φ∼0.82. We observe non-monotonic variation in both ϵ and the dynamic heterogeneity, characterized by the dynamical susceptibility χ4 with Φ, in such high density monolayers. We provide insight into the underlying nature of such transitions in close packed high density nanoparticle monolayers in terms of the morphology and flexibility of these soft colloidal particles. We discuss the significance our results in the context of related studies on two dimensional granular or colloidal systems. PMID:23411354

  17. Dynamics of Gravity-Capillary Solitary Waves in Deep Water

    CERN Document Server

    Wang, Zhan

    2012-01-01

    The dynamics of solitary gravity-capillary water waves propagating on the surface of a three-dimensional fluid domain is studied numerically. In order to accurately compute complex time dependent solutions, we simplify the full potential flow problem by taking a cubic truncation of the scaled Dirichlet-to-Neumann operator for the normal velocity on the free surface. This approximation agrees remarkably well with the full equations for the bifurcation curves, wave profiles and the dynamics of solitary waves for a two-dimensional fluid domain. Fully localised solitary waves are then computed in the three-dimensional problem and the stability and interaction of both line and localized solitary waves are investigated via numerical time integration of the equations. The solitary wave branches are indexed by their finite energy at small amplitude, and the dynamics of the solitary waves is complex involving nonlinear focussing of wave packets, quasi-elastic collisions, and the generation of propagating, spatially lo...

  18. Protein-water dynamics in antifreeze protein III activity

    Science.gov (United States)

    Xu, Yao; Bäumer, Alexander; Meister, Konrad; Bischak, Connor G.; DeVries, Arthur L.; Leitner, David M.; Havenith, Martina

    2016-03-01

    We combine Terahertz absorption spectroscopy (THz) and molecular dynamics (MD) simulations to investigate the underlying molecular mechanism for the antifreeze activity of one class of antifreeze protein, antifreeze protein type III (AFP-III) with a focus on the collective water hydrogen bond dynamics near the protein. After summarizing our previous work on AFPs, we present a new investigation of the effects of cosolutes on protein antifreeze activity by adding sodium citrate to the protein solution of AFP-III. Our results reveal that for AFP-III, unlike some other AFPs, the addition of the osmolyte sodium citrate does not affect the hydrogen bond dynamics at the protein surface significantly, as indicated by concentration dependent THz measurements. The present data, in combination with our previous THz measurements and molecular simulations, confirm that while long-range solvent perturbation is a necessary condition for the antifreeze activity of AFP-III, the local binding affinity determines the size of the hysteresis.

  19. Water and suspended sediment dynamics in the Sungai Selangor estuary

    International Nuclear Information System (INIS)

    Observations of salinity, temperature, suspended sediment concentration (SSC) and tidal current velocity were made in the lower and along the longitudinal axis sungai Selangor estuary over near-spring cycles. The variations of these parameters at the measurement stations and along the channel are presented to illustrate the water and sediment dynamics in the estuary. The results shows that the Sungai Selangor estuary changes from a partially-mixed type during neaps to a well-mixed one during springs. promoted by stronger tidal energy during the higher tidal ranges. The strong neap density stratification is also promoted by the high river discharges during the measurement period maximum concentration of suspended sediment 2000 mg,'/) occurs during maximum current velocities both during flood and ebb. The maximum salinity was achieved during high water slack but the salt water was totally flushed out of estuary during low water springs. The longitudinal axis measurement indicates that a partially-developed zone of turbidity maximum with a sediment concentration over 1000 mg/l was observed at the limit of salt water intrusion in salinity range less than 1 ppt. Tidal pumping as oppose to the estuarine circulation is the more dominant factor in the maximum formation as the salt water is totally excluded at low water. (author)

  20. Dynamic positioning of semi cost effective for shallow water exploration

    International Nuclear Information System (INIS)

    This paper reports that the use of a dynamic positioning (DP) system for station keeping a semisubmersible in water depths as shallow as 101 m (330 ft) has allowed substantial cost savings for short duration exploration wells in the North Sea. BP Exploration Operating Co. Ltd.'s semisubmersible drilling unit Ocean Alliance is capable of drilling exploration wells in anchored mode in water depths to about 550 m and in dynamic positioning mode in water depths to approximately 1,370 m. The design of the DP system offers total redundancy of every component. The dynamic positioning system maintains vessel position and heading through automatic control of the direction and amount of thrust from the vessel's engines to counteract the environmental forces. To carry out this function, the DP system must have the following basic subsystems: A method of measuring external forces; A method of measuring the vessel's position; A method of calculating required counter forces; A method of providing counter forces; and A method of providing a man/machine interface

  1. Dynamics of the global virtual water trade network

    Science.gov (United States)

    Dalin, C.; Konar, M.; Hanasaki, N.; Rodriguez-Iturbe, I.

    2011-12-01

    Water resources are under increasing pressure from population growth, socio-economic development and climate change. Since agriculture is by far the most freshwater-consuming process, the international food trade may be a way of transferring water resources to water-scarce countries, and of saving water globally by encouraging trade from water-efficient countries to less water-efficient countries. We applied complex network theory to analyze the dynamics of the global virtual water trade network. Our goal was to assess how the properties of the virtual water trade network changed in time, and how these changes are related to national policies, economic and weather conditions or events. We found that, on average, the number of trade partners of each country in the network doubled from 1986 to 2007, while the volume of water associated with food trade tripled. Despite this growth of the network, we found that the shape of the network properties distributions remained similar: for all years studied, the degree distribution is well fitted by an exponential distribution and the strength distribution compares well with a stretched exponential distribution, indicating high heterogeneity of flows between nations. Other global network structure characteristics, such as the power law relationship between node strength and node degree, dissasortative behavior and weighted rich club phenomenon were also stable through the 22 year-period. However, there are significant changes at the country and link scale of analysis. The USA has remained the world's top exporter of virtual water, while, since 2001, China has been the world's largest virtual water importer, a position formerly occupied by Russia and Japan. The sharp increase in China's virtual water imports is mostly due to its increased soybean imports, following a domestic policy shift regarding the soy trade in 2000 and 2001. Importantly, the food trade has led to enhanced savings in global water resources over the last few

  2. Dynamic Stackelberg game model for water rationalization in drought emergency

    Science.gov (United States)

    Kicsiny, R.; Piscopo, V.; Scarelli, A.; Varga, Z.

    2014-09-01

    In water resource management, in case of a limited resource, there is a conflict situation between different consumers. In this paper, a dynamic game-theoretical model is suggested for the solution of such conflict. Let us suppose that in a region, water supply is based on a given aquifer, from which a quantity of effective reserve can be used without damaging the aquifer, and a long drought is foreseen. The use of water is divided between the social sector represented by the local authority, and the production sector, in our case, simplified to a single agricultural producer using water for irrigation; they are the players in the game. For a fixed time period, every day, a given amount is available, from which first the authority, then the producer takes a proportion, which corresponds to the strategy choices of the players. A price function is given, which depends on the total available reserve, the payoffs of both players are quantified as their net incomes for the whole period: for the producer: profit from selling the product minus price of water and tax paid, for the authority: tax received plus the gain for the authority from selling the water bought to the social sector minus price of water purchased. A solution (equilibrium) of the game consists of such strategy choices of both players, with which each player maximizes her/his total payoff (over the whole time horizon of the game) provided that the other player also maximizes her/his own payoff. In the paper, in a mathematical model for the above conflict situation, a deterministic continuum-strategy two-player discrete-time dynamic Stackelberg game with fixed finite time duration and closed-loop information structure is proposed, where the authority is “leader” and the producer is “follower”. The algorithms for the solution of the game are based on recent theoretical results of the authors. Illustrative numerical examples are also given.

  3. Water savings potentials of irrigation systems: dynamic global simulation

    Science.gov (United States)

    Jägermeyr, J.; Gerten, D.; Heinke, J.; Schaphoff, S.; Kummu, M.; Lucht, W.

    2015-04-01

    Global agricultural production is heavily sustained by irrigation, but irrigation system efficiencies are often surprisingly low. However, our knowledge of irrigation efficiencies is mostly confined to rough indicative estimates for countries or regions that do not account for spatio-temporal heterogeneity due to climate and other biophysical dependencies. To allow for refined estimates of global agricultural water use, and of water saving and water productivity potentials constrained by biophysical processes and also non-trivial downstream effects, we incorporated a dynamic representation of the three major irrigation systems (surface, sprinkler, and drip) into a process-based bio- and agrosphere model, LPJmL. Based on this enhanced model we provide a gridded worldmap of dynamically retrieved irrigation efficiencies reflecting differences in system types, crop types, climatic and hydrologic conditions, and overall crop management. We find pronounced regional patterns in beneficial irrigation efficiency (a refined irrigation efficiency indicator accounting for crop-productive water consumption only), due to differences in these features, with lowest values ( 60%) in Europe and North America. We arrive at an estimate of global irrigation water withdrawal of 2396 km3 (2004-2009 average); irrigation water consumption is calculated to be 1212 km3, of which 511 km3 are non-beneficially consumed, i.e. lost through evaporation, interception, and conveyance. Replacing surface systems by sprinkler or drip systems could, on average across the world's river basins, reduce the non-beneficial consumption at river basin level by 54 and 76%, respectively, while maintaining the current level of crop yields. Accordingly, crop water productivity would increase by 9 and 15%, respectively, and by much more in specific regions such as in the Indus basin. This study significantly advances the global quantification of irrigation systems while providing a framework for assessing potential

  4. A simplified model to predict diurnal water temperature dynamics in a shallow tropical water pool

    OpenAIRE

    K. P. Paaijmans; Heusinkveld, B.G.; Jacobs, A. F. G.

    2008-01-01

    Water temperature is a critical regulator in the growth and development of malaria mosquito immatures, as they are poikilothermic. Measuring or estimating the diurnal temperature ranges to which these immatures are exposed is of the utmost importance, as these immatures will develop into adults that can transmit malaria. Recent attempts to predict the daily water temperature dynamics in mosquito breeding sites in Kenya have been successful. However, the developed model may be too complex, as ...

  5. Electrochemical Cell with Improved Water or Gas Management

    Science.gov (United States)

    Smith, William F. (Inventor); McElroy, James F. (Inventor); LaGrange, Jay W. (Inventor)

    2015-01-01

    An electrochemical cell having a water/gas porous separator prepared from a polymeric material and one or more conductive cell components that pass through, or are located in close proximity to, the water/gas porous separator, is provided. The inventive cell provides a high level of in-cell electrical conductivity.

  6. Water dynamics in the rhizosphere - a new model of coupled water uptake and mucilage exudation

    Science.gov (United States)

    Kroener, Eva; Holz, Maire; Ahmed, Mutez; Zarebanadkouki, Mohsen; Bittelli, Marco; Carminati, Andrea

    2016-04-01

    The flow of water from soil to plant roots is affected by the narrow region of soil close to the roots, the so-called rhizosphere. The rhizosphere is influenced by mucilage, a polymeric gel exuded by roots that alters the hydraulic properties of the rhizosphere. Here we present a model that accounts for: (a) an increase in equilibrium water retention curve caused by the water holding capacity of mucilage, (b) a reduction of hydraulic conductivity at a given water content due to the higher viscosity of mucilage and (c) the swelling and shrinking dynamics by decoupling water content and water potential and introducing a non-equilibrium water retention curve. The model has been tested for mixtures of soil and mucilage and we applied it to simulate observations of previous experiments with real plants growing in soil that show evidences of altered hydraulic dynamics in the rhizosphere. Furthermore we present results about how the parameters of the model depend on soil texture and root age. Finally we couple our hydraulic model to a diffusion model of mucilage into the soil. Opposed to classical solute transport models here the water flow in the rhizosphere is affected by the concentration distribution of mucilage.

  7. Dynamics of water and solute transport in polymeric reverse osmosis membranes via molecular dynamics simulations

    CERN Document Server

    Shen, Meng; Lueptow, Richard M

    2016-01-01

    The Angstrom-scale transport characteristics of water and six different solutes, methanol, ethanol, 2-propanol, urea, Na+, and Cl-, were studied for a polyamide reverse osmosis (RO) membrane, FT-30, using non-equilibrium molecular dynamics (NEMD) simulations. Results indicate that water transport increases with an increasing fraction of connected percolated free volume, or water-accessible open space, in the membrane polymer structure. This free volume is enhanced by the dynamic structure of the membrane at the molecular level as it swells when hydrated and vibrates due to molecular collisions allowing a continuous path connecting the opposite membrane surfaces. The tortuous paths available for transport of solutes result in Brownian motion of solute molecules and hopping from pore to pore as they pass through the polymer network structure of the membrane. The transport of alcohol solutes decreases for solutes with larger Van der Waals volume, which corresponds to less available percolated free volume, or sol...

  8. Molecular dynamics simulations of water permeation across Nafion membrane interfaces.

    Science.gov (United States)

    Daly, Kevin B; Benziger, Jay B; Panagiotopoulos, Athanassios Z; Debenedetti, Pablo G

    2014-07-24

    Permeation of water across the membrane/vapor and membrane/liquid-water interfaces of Nafion is studied using nonequilibrium molecular dynamics (NEMD) simulations, providing direct calculations of mass-transfer resistance. Water mass transfer within one nanometer of the vapor interface is shown to be 2 orders of magnitude slower than at any other point within the membrane, in qualitative agreement with permeation experiments. This interfacial resistance is much stronger than the resistance suggested by prior simulation work calculating self-diffusivity near the interface. The key difference between the prior approach and the NEMD approach is that the NEMD approach implicitly incorporates changes in solubility in the direction normal to the interface. Water is shown to be very insoluble near the vapor interface, which is rich in hydrophobic perfluorocarbon chains, in agreement with advancing contact angle experiments. Hydrophilic side chains are buried beneath this hydrophobic layer and aligned toward the interior of the membrane. Hydrophilic pores are not exposed to the vapor interface as proposed in prior theoretical work. At the membrane/liquid-water interface, highly swollen polymer chains extend into the liquid-water phase, forming a nanoscopically rough interface that is consistent with atomic force microscopy experiments. In these swollen conformations, hydrophilic side chains are exposed to the liquid-water phase, suggesting that the interface is hydrophilic, in agreement with receding contact angle experiments. The mass-transfer resistance of this interface is negligible compared to that of the bulk, in qualitative agreement with permeation experiments. The water activity at the vapor and liquid-water interfaces are nearly the same, yet large conformational and transport differences are observed, consistent with a mass-transfer-based understanding of Schroeder's paradox for Nafion. PMID:24971638

  9. A molecular dynamics study on surface properties of supercooled water

    Institute of Scientific and Technical Information of China (English)

    L(U) Yongjun; WEI Bingbo

    2006-01-01

    Molecular dynamics simulations were performed to study the surface properties of water in a temperature range from 228 to 293 K by using the extended simple point charge (SPC/E) and four-site TIP4P potentials. The calculated surface tension increases with the decrease of temperature, and moreover the slopes of the surface tension-temperature curves show a weak rise below 273 K, whereas no obvious anomalies appear near 228 K, which accords with the previous experiments. Compared with the measured values, the SPC/E potential shows a good agreement, and the TIP4P potential scription of the surface structure of supercooled water for the SPC/E. When simulating the orientational distributions of water molecules near the surface, the SPC/E potential produces higher ordering and larger surface potentials than the TIP4P potential.

  10. Molecular dynamics of a water jet from a carbon nanotube.

    Science.gov (United States)

    Hanasaki, Itsuo; Yonebayashi, Toru; Kawano, Satoyuki

    2009-04-01

    A carbon nanotube (CNT) can be viewed as a molecular nozzle. It has a cylindrical shape of atomistic regularity, and the diameter can be even less than 1 nm. We have conducted molecular-dynamics simulations of water jet from a (6,6) CNT that confines water in a form of single-file molecular chain. The results show that the water forms nanoscale clusters at the outlet and they are released intermittently. The jet breakup is dominated by the thermal fluctuations, which leads to the strong dependence on the temperature. The cluster size n decreases and the release frequency f increases at higher temperatures. The f roughly follows the reaction kinetics by the transition state theory. The speed of a cluster is proportional to the 1/sqrt[n] because of the central limit theorem. These properties make great contrast with the macroscopic liquid jets. PMID:19518333

  11. Non-Equilibrium Water-Glassy Polymer Dynamics

    Science.gov (United States)

    Davis, Eric; Minelli, Matteo; Baschetti, Marco; Sarti, Giulio; Elabd, Yossef

    2012-02-01

    For many applications (e.g., medical implants, packaging), an accurate assessment and fundamental understanding of the dynamics of water-glassy polymer interactions is of great interest. In this study, sorption and diffusion of pure water in several glassy polymers films, such as poly(styrene) (PS), poly(methyl methacrylate) (PMMA), poly(lactide) (PLA), were measured over a wide range of vapor activities and temperatures using several experimental techniques, including quartz spring microbalance (QSM), quartz crystal microbalance (QCM), and time-resolved Fourier transform infrared-attenuated total reflectance (FTIR-ATR) spectroscopy. Non-Fickian behavior (diffusion-relaxation phenomena) was observed by all three techniques, while FTIR-ATR spectroscopy also provides information about the distribution of the states of water and water transport mechanisms on a molecular-level. Specifically, the states of water are significantly different in PS compared to PMMA and PLA. Additionally, a purely predictive non-equilibrium lattice fluid (NELF) model was applied to predict the sorption isotherms of water in these glassy polymers.

  12. Molecular dynamics of the water liquid-vapor interface

    Science.gov (United States)

    Wilson, M. A.; Pohorille, A.; Pratt, L. R.; MacElroy, R. D. (Principal Investigator)

    1987-01-01

    The results of molecular dynamics calculations on the equilibrium interface between liquid water and its vapor at 325 K are presented. For the TIP4P model of water intermolecular pair potentials, the average surface dipole density points from the vapor to the liquid. The most common orientations of water molecules have the C2 nu molecular axis roughly parallel to the interface. The distributions are quite broad and therefore compatible with the intermolecular correlations characteristic of bulk liquid water. All near-neighbor pairs in the outermost interfacial layers are hydrogen bonded according to the common definition adopted here. The orientational preferences of water molecules near a free surface differ from those near rigidly planar walls which can be interpreted in terms of patterns found in hexagonal ice 1. The mean electric field in the interfacial region is parallel to the mean polarization which indicates that attention cannot be limited to dipolar charge distributions in macroscopic descriptions of the electrical properties of this interface. The value of the surface tension obtained is 132 +/- 46 dyn/cm, significantly different from the value for experimental water of 68 dyn/cm at 325 K.

  13. Salt—Water Dynamics in Soils:I.Salt—Water Dynamics in Unsaturated Soils Under Stable Evaporation Condition

    Institute of Scientific and Technical Information of China (English)

    YOUWEN-RUI; MENGFAN-HUA; 等

    1992-01-01

    A long term simulation test on salt-water dynamics in unsaturated soils with different groundwater depths and soil texture profiles under stable evaporation condition was conducted.Salinity sensors and tensiometers were used to monitor salt and water variation in soils.The experiment revealed that in the process of fresh groundwater moving upwards by capillary rise in the column,the salts in subsoil were brought upwards and accumulated in the surface soil,and consequently the salinization of surface soil took place.The rate of salt accumulation is determined mainly by the volume of capillary water flow and the conditions of salts contained in the soil profile.Water flux in soils decreased obviously when groundwater depths fell below 1.5m.When there was an interbedded clay layer 30cm in thickness in the silty loam soil profile or a clay layer 100cm in thickness at the top layer,the water flux was 3-5 times less than in the soil profile of homogeneous silty loam soil.Therefore,the rate of salt accumulation was decreased and the effect of variation of groundwater depth on the water flux in soils was weakened comparatively.If there was precipitation or irrigation supplying water to the soil,the groundwater could rarely take a direct part in the process of salt accumulation in surface soil,especially,in soil profiles with an interbedded stratum or a clayey surface soil layer.

  14. Linking Hydrology and Atmospheric Sciences in Continental Water Dynamics Modeling

    Science.gov (United States)

    David, C. H.; Gochis, D. J.; Maidment, D. R.; Wilhelmi, O.

    2006-12-01

    Atmospheric observation and model output datasets as well as hydrologic datasets are increasingly becoming available on a continental scale. Although the availability of these datasets could allow large-scale water dynamics modeling, the different objects and semantics used in atmospheric science and hydrology set barriers to their interoperability. Recent work has demonstrated the feasibility for modeling terrestrial water dynamics for the continental United States of America. Continental water dynamics defines the interaction of the hydrosphere, the land surface and subsurface at spatial scales ranging from point to continent. The improved version of the National Hydrographic Dataset (NHDPlus, an integrated suite of geospatial datasets stored in a vector and raster GIS format) was used as hydrologic and elevation data input to the Noah community Land Surface Model, developed at NCAR. Noah was successfully run on a watershed in the Ohio River Basin with NHDPlus inputs. The use of NHDPlus as input data for Noah is a crucial improvement for community modeling efforts allowing users to by-pass much of the time consumed in Digital Elevation Model and hydrological network processing. Furthermore, the community Noah land surface model, in its hydrologically-enhanced configuration, is capable of providing flow inputs for a river dynamics model. Continued enhancement of Noah will, as a consequence, be beneficial to the atmospheric science community as well as to the hydrologic community. Ongoing research foci include using a diversity of weather drivers as an input to Noah, and investigation of how to use land surface model outputs for river forecasting, using both the ArcHydro and OpenMI frameworks.

  15. Salt—Water Dynamics in Highly Salinized Topsoil of Salt—Affected Soil During Water Infiltration

    Institute of Scientific and Technical Information of China (English)

    WANGXUE-FENG; YOUWEN-RUI; 等

    1991-01-01

    Continuous monitoring of salt and water movement in the soil profile of highly salinized topsoil under steadystate infiltration was conducted.It gives that salt and water dynamics during convection-diffusion period can be divided into three stages:1.formation of a salt peak,2.the salt peak moving downwards till the appearance of the summit of the salt peak,3.the salt peak moving further downwards with the peak value decreasing.Results show that the maximum salt peak appears at the same depth if soil texture and outflow condition are the same.Factors affecting salt and water movement and ion components in the outflow solution underinfiltration are discussed.

  16. Defining dynamic pelagic habitats in oceanic waters off eastern Australia

    Science.gov (United States)

    Hobday, A. J.; Young, J. W.; Moeseneder, C.; Dambacher, J. M.

    2011-03-01

    Although many species in the pelagic ocean are widespread, they are not randomly distributed. These species may have associations with particular water masses or habitats, but to best understand patterns in the ocean, these habitats must be identified. Previous efforts have produced static or seasonal climatologies, which still represent smearing over habitats. The Eastern Tuna and Billfish Longline Fishery (ETBF) targets a range of high trophic level species in oceanic waters off eastern Australia. In this study, dynamic ocean habitats in the region were identified for each month based on cluster analysis of five oceanographic variables averaged at a monthly time scale and a spatial scale of 0.5° for the period 1995-2006. A total of seven persistent habitats were identified off eastern Australia with intra and interannual variation in size and location, indicating the importance of spatial and temporal variation in the dynamics of the region. The degree to which these dynamic habitats were distinguished was tested using (i) stable isotope analysis of top fish predators caught in the region and (ii) estimates of variation in estimated abundance generated from catch data from the fishery. More precise estimates (measured as lower total CV) of isotopic values from swordfish ( Xiphias gladius), yellowfin tuna ( Thunnus albacares) and albacore ( Thunnus alalunga) were obtained for 4 of 6 isotope comparisons using the dynamic habitat groupings, which indicate that stratifying by pelagic habitat improved precision. Dynamic habitats produced more precise abundance estimates for 7 of 8 large pelagic species examined, with an average reduction in total CV of 19% compared to when abundance was estimated based on static habitat stratification. These findings could be used to guide development of effective monitoring strategies that can distinguish patterns due to environmental variation, and in the longer term, climate change.

  17. Multispectral fingerprinting for improved in vivo cell dynamics analysis

    Directory of Open Access Journals (Sweden)

    Cooper Cameron HJ

    2010-09-01

    Full Text Available Abstract Background Tracing cell dynamics in the embryo becomes tremendously difficult when cell trajectories cross in space and time and tissue density obscure individual cell borders. Here, we used the chick neural crest (NC as a model to test multicolor cell labeling and multispectral confocal imaging strategies to overcome these roadblocks. Results We found that multicolor nuclear cell labeling and multispectral imaging led to improved resolution of in vivo NC cell identification by providing a unique spectral identity for each cell. NC cell spectral identity allowed for more accurate cell tracking and was consistent during short term time-lapse imaging sessions. Computer model simulations predicted significantly better object counting for increasing cell densities in 3-color compared to 1-color nuclear cell labeling. To better resolve cell contacts, we show that a combination of 2-color membrane and 1-color nuclear cell labeling dramatically improved the semi-automated analysis of NC cell interactions, yet preserved the ability to track cell movements. We also found channel versus lambda scanning of multicolor labeled embryos significantly reduced the time and effort of image acquisition and analysis of large 3D volume data sets. Conclusions Our results reveal that multicolor cell labeling and multispectral imaging provide a cellular fingerprint that may uniquely determine a cell's position within the embryo. Together, these methods offer a spectral toolbox to resolve in vivo cell dynamics in unprecedented detail.

  18. Dynamically slow processes in supercooled water confined between hydrophobic plates

    Energy Technology Data Exchange (ETDEWEB)

    Franzese, Giancarlo [Departamento de Fisica Fundamental, Universidad de Barcelona, Diagonal 647, Barcelona 08028 (Spain); Santos, Francisco de los, E-mail: gfranzese@ub.ed, E-mail: fdlsant@ugr.e [Departamento de Electromagnetismo y Fisica de la Materia, Universidad de Granada, Fuentenueva s/n, 18071 Granada (Spain)

    2009-12-16

    We study the dynamics of water confined between hydrophobic flat surfaces at low temperature. At different pressures, we observe different behaviors that we understand in terms of the hydrogen bond dynamics. At high pressure, the formation of the open structure of the hydrogen bond network is inhibited and the surfaces can be rapidly dried (dewetted) by formation of a large cavity with decreasing temperature. At lower pressure we observe strong non-exponential behavior of the correlation function, but with no strong increase of the correlation time. This behavior can be associated, on the one hand, to the rapid ordering of the hydrogen bonds that generates heterogeneities and, on the other hand, to the lack of a single timescale as a consequence of the cooperativity in the vicinity of the liquid-liquid critical point that characterizes the phase diagram at low temperature of the water model considered here. At very low pressures, the gradual formation of the hydrogen bond network is responsible for the large increase of the correlation time and, eventually, the dynamical arrest of the system, with a strikingly different dewetting process, characterized by the formation of many small cavities.

  19. Hydro-dynamic damping theory in flowing water

    International Nuclear Information System (INIS)

    Fluid-structure interaction (FSI) has a major impact on the dynamic response of the structural components of hydroelectric turbines. On mid-head to high-head Francis runners, the rotor-stator interaction (RSI) phenomenon always has to be considered carefully during the design phase to avoid operational issues later on. The RSI dynamic response amplitudes are driven by three main factors: (1) pressure forcing amplitudes, (2) excitation frequencies in relation to natural frequencies and (3) damping. The prediction of the two first factors has been largely documented in the literature. However, the prediction of fluid damping has received less attention in spite of being critical when the runner is close to resonance. Experimental damping measurements in flowing water on hydrofoils were presented previously. Those results showed that the hydro-dynamic damping increased linearly with the flow. This paper presents development and validation of a mathematical model, based on momentum exchange, to predict damping due to fluid structure interaction in flowing water. The model is implemented as an analytical procedure for simple structures, such as cantilever beams, but is also implemented in more general ways using three different approaches for more complex structures such as runner blades: a finite element procedure, a CFD modal work based approach and a CFD 1DOF approach. The mathematical model and all three implementation approaches are shown to agree well with experimental results

  20. Cavitation in confined water: ultra-fast bubble dynamics

    Science.gov (United States)

    Vincent, Olivier; Marmottant, Philippe

    2012-02-01

    In the hydraulic vessels of trees, water can be found at negative pressure. This metastable state, corresponding to mechanical tension, is achieved by evaporation through a porous medium. It can be relaxed by cavitation, i.e. the sudden nucleation of vapor bubbles. Harmful for the tree due to the subsequent emboli of sap vessels, cavitation is on the contrary used by ferns to eject spores very swiftly. We will focus here on the dynamics of the cavitation bubble, which is of primary importance to explain the previously cited natural phenomena. We use the recently developed method of artificial tress, using transparent hydrogels as the porous medium. Our experiments, on water confined in micrometric hydrogel cavities, show an extremely fast dynamics: bubbles are nucleated at the microsecond timescale. For cavities larger than 100 microns, the bubble ``rings'' with damped oscillations at MHz frequencies, whereas for smaller cavities the oscillations become overdamped. This rich dynamics can be accounted for by a model we developed, leading to a modified Rayleigh-Plesset equation. Interestingly, this model predicts the impossibility to nucleate bubbles above a critical confinement that depends on liquid negative pressure and corresponds to approximately 100 nm for 20 MPa tensions.

  1. Slow dynamics in dense oil-water emulsions studied using dynamic light scattering

    International Nuclear Information System (INIS)

    The 3D-echo-DLS (dynamic light scattering) flat cell light scattering instrument (3D-echo-DLS-FCLSI) presents the possibility of measuring slow dynamics of turbid and concentrated colloidal systems. It combines a modified 3D-DLS component and an echo-DLS component with the flat cell light scattering instrument. While the 3D-DLS suppresses multiple scattering, the echo-DLS allows measurements of slow dynamics or even on non-ergodic systems. The advantage of the thin flat cell is that it increases the transmission and reduces multiple scattering; i.e., singly scattered light that is required by the 3D-DLS is still available from dense turbid systems. In the first part of this contribution the 3D-echo-DLS-FCLSI is introduced and the instrumental performance is presented. The second part of the paper is concerned with the ageing behavior of dense fluids in a flat cell, and with confinement effects. Here, we show that ageing is strongly influenced by the process of filling of the flat cell. In some cases complementary methods can be utilized to measure special properties of the system; e.g., the multispeckle method is most appropriate for measuring heterogeneity effects. In the last part of the paper we compare glass transition measurements of an index-matched emulsion carried out using the 3D-echo-DLS-FCLSI and using the multispeckle instrument. We still find an α-relaxation in the glassy state.

  2. Single cell migration dynamics mediated by geometric confinement.

    Science.gov (United States)

    Zhang, Hua; Hou, Ruixia; Xiao, Peng; Xing, Rubo; Chen, Tao; Han, Yanchun; Ren, Penggang; Fu, Jun

    2016-09-01

    The migration dynamics of cells plays a key role in tissue engineering and regenerative medicine. Previous studies mostly focus on regulating stem cell fate and phenotype by biophysical cues. In contrast, less is known about how the geometric cues mediate the migration dynamics of cells. Here, we fabricate graphene oxide (GO) microstripes on cell non-adhesive PEG substrate by using micromolding in capillary (MIMIC) method. Such micropatterns with alternating cell adhesion and cell resistance enable an effective control of selective adhesion and migration of single cells. The sharp contrast in cell adhesion minimizes the invasion of cells into the PEG patterns, and thereby strongly confines the cells on GO microstripes. As a result, the cells are forced to adapt highly polarized, elongated, and oriented geometry to fit the patterns. A series of pattern widths have been fabricated to modulate the extent of cell deformation and polarization. Under strong confinement, the cytoskeleton contractility, intracellular traction, and actin filament elongation are highly promoted, which result in enhanced cell migration along the patterns. This work provides an important insight into developing combinatorial graphene-based patterns for the control of cell migration dynamics, which is of great significance for tissue engineering and regenerative medicine. PMID:27137805

  3. A dynamic knowledge model for water management in maize

    Institute of Scientific and Technical Information of China (English)

    GUO Yinqiao; LIN Yuping; ZHAO Chuande; WANG Wenxin; LI Cundong

    2007-01-01

    Farmland irrigation management and model establishment are always core and difficult contents in crop simulation.This research was focused on exerting the establishment theory of knowledge model,and applying the systematic analysis method and mathematic modeling technology to knowledge expression system of maize water management.Based on soil water balance,a dynamic knowledge model with systematic and wide-application characteristics for maize water management was developed,after periodically quantifying the relationship of irrigation ration between cultivars' characteristics and environmental factors.Cases were studied on the knowledge model with the data sets of normal year in different eco-sites and those of different rain years in the same eco-sites.The results showed that there was no difference in water saving in normal years under different eco-sites,irrigation schedule changes with eco-sites greatly;but a more obvious difference in different rain years of the same eco-sites existing,with 8.6% and 31.9% of water saving in both more rainfall and normal rainfall years,respectively.Additionally,irrigation in the seedling stage did not change with year types,but it did in Knurling and filling stages.This can be concluded that the irrigation regime designed by the model is well coherent to the actual planting system,which indicated that the model had good decision-making and applicability.

  4. Dynamic Adsorptive Removal of Toxic Chemicals for Purification of Water

    Directory of Open Access Journals (Sweden)

    Amit Saxena

    2005-04-01

    Full Text Available To determine the efficiency of carbon column for the removal of toxic chemicals from water, the adsorption of phenol in concentration range from 0.600 glt to 1.475 gll was studied on activecarbon of 80 CTC grade, 12 X 30 BSS particle size, 1280 m2/g surface area, and of coconut shell origin, under dynamic conditions at space velocity from 0.318 min-' to 4.24 min-' at 25 'C. The carbon column of 100 cm length and 2 cm diameter was found to be removing phenol from the aqueous solution of concentration 1.475 gll up to 84 min at 0.678 min-' space velocity at 5.0 ppm phenol breakthrough concentration. However, no phenol was observed in carbon-treated water after 80 min. The service life of carbon column (100 cm lengthX25 cm diameter was assessed through the water purification system developed at the Defence Laboratory, Jodhpur and was determined to be 4.095 days with twoas factor of safety for 10 ppm initial concentration of phenol at 0.678 min-' space velocity (corresponding to water flow rate. Effects of carbon bed length, water flow rate, and the phenol concentration were also studied.

  5. Spatial dynamics of water management in irrigated agriculture

    Science.gov (United States)

    Muralidharan, Daya; Knapp, Keith C.

    2009-05-01

    Irrigated agriculture provides 40% of worldwide food supplies but uses large amounts of scarce freshwater and contributes to environmental degradation. At the very core of this problem lie decisions made by irrigators subject to biophysical relations. This research develops a microeconomic model of irrigation management taking into account the dynamics of plant growth over the season, spatial variability in infiltration of applied irrigation water, and fundamental principles from subsurface hydrology. The analysis shows that spatial variability in water infiltration common to traditional irrigation systems increases both applied irrigation water and deep percolation flows by very substantial amounts compared to uniform infiltration. The analysis demonstrates that efficient irrigation management can significantly reduce both applied water and deep percolation at relatively low costs, at least up to a certain level. A long-run analysis of optimal irrigation systems including capital costs indicates that traditional furrow systems are economically efficient over a wide range of water prices and deep percolation costs. Overall, the results indicate that optimal irrigation management can achieve significant resource conservation and pollution control with low loss in agricultural net benefits and without land retirement, investment in capital-intensive systems, or crop switching.

  6. Internal dynamics of a living cell nucleus investigated by dynamic light scattering

    Science.gov (United States)

    Suissa, M.; Place, C.; Goillot, E.; Freyssingeas, E.

    2008-08-01

    Recent progresses in cellular biology have shown that the nucleus of a living cell is a structured integration of many functional domains with a complex spatial organization. This organization, as well as molecular and biochemical processes, is time regulated. In the past years many investigations have been performed using fluorescent microscopy techniques to study the internal dynamics of the nucleus of a living cell. These investigations, however, have never focussed on the global internal dynamics of the nucleus, which is still unknown. In this article we present an original light scattering experimental device that we built to investigate this dynamics during biological processes. By means of this experimental set-up, we investigated the global dynamics of the nucleus of a living cell treated with a DNA replication inhibitor. This dynamics presents different and independent kinds of relaxation well separated in time that vary as a function of the cell cycle phases.

  7. Rotor dynamic investigation of a pressurized water reactor coolant pump

    International Nuclear Information System (INIS)

    As a result of high vibration levels of Westinghouse Reactor Coolant Pumps installed at a large Northeast utility plant, Rotor Dynamic studies were conducted coupled with on site measurements. Stability analysis, non-synchronous response and synchronous investigations were completed. It was concluded that the high vibration levels were primarily due to excessive impeller unbalance which was aggravated by the tendency of the rotor to whirl in the 360 degree plain water lubricated journal bearing. The analysis indicated that vibration frequencies can vary along the rotor. Specifically, a predominant synchronous response at the coupling does not rule out a dominant half frequency whirl at the bearing and the impeller. Thus, measurements made at the coupling could be misleading. A tilting-pad design was analytically tested and was predicted to provide whirl-free response and improve overall dynamic characteristics. However, tight clearances are required to limit unbalance response

  8. Water condensation in Gas Diffusion Layers of PEM Fuel cells

    OpenAIRE

    Straubhaar, Benjamin; Pauchet, Joël; Prat, Marc

    2015-01-01

    The fundamental understanding of water transport in PEMFCs is still a major challenge in direct relation with the water management issue, i.e., the ability to maintain a good dynamic balance of water in the membrane-electrode assembly during operation. In the present effort we concentrate on the water transfer mechanisms occurring in the gas diffusion layer (GDL) on the cathode side. In – situ visualizations of liquid water in GDL [1] and evaluations of temperature variations across the GDL [...

  9. The Widom line and dynamical crossover in supercritical water: Popular water models versus experiments

    Energy Technology Data Exchange (ETDEWEB)

    Corradini, D. [Center for Polymer Studies and Department of Physics, Boston University, 590 Commonwealth Avenue, Boston, Massachusetts 02215 (United States); Rovere, M. [Dipartimento di Matematica e Fisica, Università Roma Tre, Via della Vasca Navale 84, I-00146 Rome (Italy); Gallo, P., E-mail: gallop@fis.uniroma3.it [Dipartimento di Matematica e Fisica, Università Roma Tre, Via della Vasca Navale 84, I-00146 Rome (Italy); INFN Sez. Roma Tre, Via della Vasca Navale 84, I-00146 Rome (Italy)

    2015-09-21

    In a previous study [Gallo et al., Nat. Commun. 5, 5806 (2014)], we have shown an important connection between thermodynamic and dynamical properties of water in the supercritical region. In particular, by analyzing the experimental viscosity and the diffusion coefficient obtained in simulations performed using the TIP4P/2005 model, we have found that the line of response function maxima in the one phase region, the Widom line, is connected to a crossover from a liquid-like to a gas-like behavior of the transport coefficients. This is in agreement with recent experiments concerning the dynamics of supercritical simple fluids. We here show how different popular water models (TIP4P/2005, TIP4P, SPC/E, TIP5P, and TIP3P) perform in reproducing thermodynamic and dynamic experimental properties in the supercritical region. In particular, the comparison with experiments shows that all the analyzed models are able to qualitatively predict the dynamical crossover from a liquid-like to a gas-like behavior upon crossing the Widom line. Some of the models perform better in reproducing the pressure-temperature slope of the Widom line of supercritical water once a rigid shift of the phase diagram is applied to bring the critical points to coincide with the experimental ones.

  10. The Widom line and dynamical crossover in supercritical water: Popular water models versus experiments

    International Nuclear Information System (INIS)

    In a previous study [Gallo et al., Nat. Commun. 5, 5806 (2014)], we have shown an important connection between thermodynamic and dynamical properties of water in the supercritical region. In particular, by analyzing the experimental viscosity and the diffusion coefficient obtained in simulations performed using the TIP4P/2005 model, we have found that the line of response function maxima in the one phase region, the Widom line, is connected to a crossover from a liquid-like to a gas-like behavior of the transport coefficients. This is in agreement with recent experiments concerning the dynamics of supercritical simple fluids. We here show how different popular water models (TIP4P/2005, TIP4P, SPC/E, TIP5P, and TIP3P) perform in reproducing thermodynamic and dynamic experimental properties in the supercritical region. In particular, the comparison with experiments shows that all the analyzed models are able to qualitatively predict the dynamical crossover from a liquid-like to a gas-like behavior upon crossing the Widom line. Some of the models perform better in reproducing the pressure-temperature slope of the Widom line of supercritical water once a rigid shift of the phase diagram is applied to bring the critical points to coincide with the experimental ones

  11. The interplay between dynamic heterogeneities and structure of bulk liquid water: A molecular dynamics simulation study

    Energy Technology Data Exchange (ETDEWEB)

    Demontis, Pierfranco; Suffritti, Giuseppe B. [Dipartimento di Chimica e Farmacia, Università degli studi di Sassari, Sassari (Italy); Consorzio Interuniversitario Nazionale per la Scienza e Tecnologia dei Materiali (INSTM), Unità di ricerca di Sassari, Via Vienna, 2, I-07100 Sassari (Italy); Gulín-González, Jorge [Grupo de Matemática y Física Computacionales, Universidad de las Ciencias Informáticas (UCI), Carretera a San Antonio de los Baños, Km 21/2, La Lisa, La Habana (Cuba); Masia, Marco [Dipartimento di Chimica e Farmacia, Università degli studi di Sassari, Sassari (Italy); Consorzio Interuniversitario Nazionale per la Scienza e Tecnologia dei Materiali (INSTM), Unità di ricerca di Sassari, Via Vienna, 2, I-07100 Sassari (Italy); Istituto Officina dei Materiali del CNR, UOS SLACS, Via Vienna 2, 07100 Sassari (Italy); Sant, Marco [Dipartimento di Chimica e Farmacia, Università degli studi di Sassari, Sassari (Italy)

    2015-06-28

    In order to study the interplay between dynamical heterogeneities and structural properties of bulk liquid water in the temperature range 130–350 K, thus including the supercooled regime, we use the explicit trend of the distribution functions of some molecular properties, namely, the rotational relaxation constants, the atomic mean-square displacements, the relaxation of the cross correlation functions between the linear and squared displacements of H and O atoms of each molecule, the tetrahedral order parameter q and, finally, the number of nearest neighbors (NNs) and of hydrogen bonds (HBs) per molecule. Two different potentials are considered: TIP4P-Ew and a model developed in this laboratory for the study of nanoconfined water. The results are similar for the dynamical properties, but are markedly different for the structural characteristics. In particular, for temperatures higher than that of the dynamic crossover between “fragile” (at higher temperatures) and “strong” (at lower temperatures) liquid behaviors detected around 207 K, the rotational relaxation of supercooled water appears to be remarkably homogeneous. However, the structural parameters (number of NNs and of HBs, as well as q) do not show homogeneous distributions, and these distributions are different for the two water models. Another dynamic crossover between “fragile” (at lower temperatures) and “strong” (at higher temperatures) liquid behaviors, corresponding to the one found experimentally at T{sup ∗} ∼ 315 ± 5 K, was spotted at T{sup ∗} ∼ 283 K and T{sup ∗} ∼ 276 K for the TIP4P-Ew and the model developed in this laboratory, respectively. It was detected from the trend of Arrhenius plots of dynamic quantities and from the onset of a further heterogeneity in the rotational relaxation. To our best knowledge, it is the first time that this dynamical crossover is detected in computer simulations of bulk water. On the basis of the simulation results, the possible

  12. Supply-based dynamic Ramsey pricing: Avoiding water shortages

    Science.gov (United States)

    Saǧlam, Yiǧit

    2015-01-01

    In many countries, current water-pricing policies are dictated by the sole objective of financial breaking even. This results in large withdrawals, which are not sustainable in the long run, hence not optimal. In this paper, we derive the optimal dynamic pricing policy, which targets efficient distribution while breaking even through a rebate scheme. Using data from Turkey, we estimate the demand for water by user groups. We carry out simulations to compare the effects of the current and optimal pricing policies on the frequency and severity of shortages. We find that, under the policy of break-even prices, the supplier runs into a shortage every 8 years. In contrast, if the prices were to set optimally, shortages would be practically nonexistent over the next century.

  13. Exploring Neural Cell Dynamics with Digital Holographic Microscopy

    KAUST Repository

    Marquet, Pierre

    2013-04-21

    In this talk, I will present how digital holographic microscopy, as a powerful quantitative phase technique, can non-invasively measure cell dynamics and especially resolve local neuronal network activity through simultaneous multiple site optical recording.

  14. F-pili dynamics by live-cell imaging

    OpenAIRE

    Clarke, Margaret; Maddera, Lucinda; Harris, Robin L.; Silverman, Philip M.

    2008-01-01

    Bacteria have evolved numerous mechanisms for cell–cell communication, many of which have important consequences for human health. Among these is conjugation, the direct transfer of DNA from one cell to another. For Gram-negative bacteria, conjugation requires thin, flexible filaments (conjugative pili) that are elaborated by DNA donor cells. The structure, function, and especially the dynamics of conjugative pili are poorly understood. Here, we have applied live-cell imaging to characterize ...

  15. IMAGING RED BLOOD CELL DYNAMICS BY QUANTITATIVE PHASE MICROSCOPY

    OpenAIRE

    Popescu, Gabriel; Park, YoungKeun; Choi, Wonshik; Dasari, Ramachandra R.; Michael S. Feld; Badizadegan, Kamran

    2008-01-01

    Red blood cells (RBCs) play a crucial role in health and disease, and structural and mechanical abnormalities of these cells have been associated with important disorders such as Sickle cell disease and hereditary cytoskeletal abnormalities. Although several experimental methods exist for analysis of RBC mechanical properties, optical methods stand out as they enable collecting mechanical and dynamic data from live cells without physical contact and without the need for exogenous contrast age...

  16. Protein dynamics in individual human cells: experiment and theory.

    Directory of Open Access Journals (Sweden)

    Ariel Aharon Cohen

    Full Text Available A current challenge in biology is to understand the dynamics of protein circuits in living human cells. Can one define and test equations for the dynamics and variability of a protein over time? Here, we address this experimentally and theoretically, by means of accurate time-resolved measurements of endogenously tagged proteins in individual human cells. As a model system, we choose three stable proteins displaying cell-cycle-dependant dynamics. We find that protein accumulation with time per cell is quadratic for proteins with long mRNA life times and approximately linear for a protein with short mRNA lifetime. Both behaviors correspond to a classical model of transcription and translation. A stochastic model, in which genes slowly switch between ON and OFF states, captures measured cell-cell variability. The data suggests, in accordance with the model, that switching to the gene ON state is exponentially distributed and that the cell-cell distribution of protein levels can be approximated by a Gamma distribution throughout the cell cycle. These results suggest that relatively simple models may describe protein dynamics in individual human cells.

  17. Dynamics of water trimer in femtosecond laser pulses

    Science.gov (United States)

    Wang, Zhiping; Zhang, Fengshou; Xu, Xuefeng; Wang, Yanbiao; Qian, Chaoyi

    2016-07-01

    With the help of the time-dependent local-density approximation (TDLDA) coupled non-adiabatically to molecular dynamics (MD), we studied both the static properties and irradiation dynamics of water trimer subject to the short and intense femtosecond laser field. It is shown that the optimized geometry and the optical absorption strength of the water trimer accord well with results in literature. Three typical possible irradiated scenarios of water trimer which are “normal oscillation”, “dissociation and formation” and “pure OH dissociation” are exhibited by investigating the ionization and the level depletion related to electrons as well as the OH bonds, proton-transfer, the intermolecular distance and the kinetic energy connected with ions. In three scenarios, the behaviors of water trimer can be attributed to the sequential combination of responses of the electrons emission, the proton-transfer, OH vibration and rotation, OH dissociation and hydroxyl formation, respectively. The relevant time scales of the first proton-transfer and OH dissociation are identified as 13 fs and 10-20 fs, respectively. The study of kinetic energies of ions show that the kinetic energies of the remaining ions are all below 4.5 eV and outgoing hydrogen ions carry a kinetic energy about 5-12 eV. Furthermore, it is found that in the tunneling ionization situations the depletion is fairly shared between the various levels except the most deep occupied electronic level while in the multiphotonic ionization case the electron loss comes from all single-electron levels and the HOMO level contributes the most.

  18. Mitochondrial Dynamics Controls T Cell Fate through Metabolic Programming.

    Science.gov (United States)

    Buck, Michael D; O'Sullivan, David; Klein Geltink, Ramon I; Curtis, Jonathan D; Chang, Chih-Hao; Sanin, David E; Qiu, Jing; Kretz, Oliver; Braas, Daniel; van der Windt, Gerritje J W; Chen, Qiongyu; Huang, Stanley Ching-Cheng; O'Neill, Christina M; Edelson, Brian T; Pearce, Edward J; Sesaki, Hiromi; Huber, Tobias B; Rambold, Angelika S; Pearce, Erika L

    2016-06-30

    Activated effector T (TE) cells augment anabolic pathways of metabolism, such as aerobic glycolysis, while memory T (TM) cells engage catabolic pathways, like fatty acid oxidation (FAO). However, signals that drive these differences remain unclear. Mitochondria are metabolic organelles that actively transform their ultrastructure. Therefore, we questioned whether mitochondrial dynamics controls T cell metabolism. We show that TE cells have punctate mitochondria, while TM cells maintain fused networks. The fusion protein Opa1 is required for TM, but not TE cells after infection, and enforcing fusion in TE cells imposes TM cell characteristics and enhances antitumor function. Our data suggest that, by altering cristae morphology, fusion in TM cells configures electron transport chain (ETC) complex associations favoring oxidative phosphorylation (OXPHOS) and FAO, while fission in TE cells leads to cristae expansion, reducing ETC efficiency and promoting aerobic glycolysis. Thus, mitochondrial remodeling is a signaling mechanism that instructs T cell metabolic programming. PMID:27293185

  19. A positive feedback cell signaling nucleation model of astrocyte dynamics

    OpenAIRE

    MacDonald, Christopher L.; Silva, Gabriel A.

    2013-01-01

    We constructed a model of calcium signaling in astrocyte neural glial cells that incorporates a positive feedback nucleation mechanism, whereby small microdomain increases in local calcium can stochastically produce global cellular and intercellular network scale dynamics. The model is able to simultaneously capture dynamic spatial and temporal heterogeneities associated with intracellular calcium transients in individual cells and intercellular calcium waves (ICW) in spatially realistic netw...

  20. Chicago's water market: Dynamics of demand, prices and scarcity rents

    Science.gov (United States)

    Ipe, V.C.; Bhagwat, S.B.

    2002-01-01

    Chicago and its suburbs are experiencing an increasing demand for water from a growing population and economy and may experience water scarcity in the near future. The Chicago metropolitan area has nearly depleted its groundwater resources to a point where interstate conflicts with Wisconsin could accompany an increased reliance on those sources. Further, the withdrawals from Lake Michigan is limited by the Supreme Court decree. The growing demand and indications of possible scarcity suggest a need to reexamine the pricing policies and the dynamics of demand. The study analyses the demand for water and develops estimates of scarcity rents for water in Chicago. The price and income elasticities computed at the means are -0.002 and 0.0002 respectively. The estimated scarcity rents ranges from $0.98 to $1.17 per thousand gallons. The results indicate that the current prices do not fully account for the scarcity rents and suggest a current rate with in the range $1.53 to $1.72 per thousand gallons.

  1. Integrated system dynamics toolbox for water resources planning.

    Energy Technology Data Exchange (ETDEWEB)

    Reno, Marissa Devan; Passell, Howard David; Malczynski, Leonard A.; Peplinski, William J.; Tidwell, Vincent Carroll; Coursey, Don (University of Chicago, Chicago, IL); Hanson, Jason (University of New Mexico, Albuquerque, NM); Grimsrud, Kristine (University of New Mexico, Albuquerque, NM); Thacher, Jennifer (University of New Mexico, Albuquerque, NM); Broadbent, Craig (University of New Mexico, Albuquerque, NM); Brookshire, David (University of New Mexico, Albuquerque, NM); Chemak, Janie (University of New Mexico, Albuquerque, NM); Cockerill, Kristan (Cockeril Consulting, Boone, NC); Aragon, Carlos (New Mexico Univeristy of Technology and Mining (NM-TECH), Socorro, NM); Hallett, Heather (New Mexico Univeristy of Technology and Mining (NM-TECH), Socorro, NM); Vivoni, Enrique (New Mexico Univeristy of Technology and Mining (NM-TECH), Socorro, NM); Roach, Jesse

    2006-12-01

    Public mediated resource planning is quickly becoming the norm rather than the exception. Unfortunately, supporting tools are lacking that interactively engage the public in the decision-making process and integrate over the myriad values that influence water policy. In the pages of this report we document the first steps toward developing a specialized decision framework to meet this need; specifically, a modular and generic resource-planning ''toolbox''. The technical challenge lies in the integration of the disparate systems of hydrology, ecology, climate, demographics, economics, policy and law, each of which influence the supply and demand for water. Specifically, these systems, their associated processes, and most importantly the constitutive relations that link them must be identified, abstracted, and quantified. For this reason, the toolbox forms a collection of process modules and constitutive relations that the analyst can ''swap'' in and out to model the physical and social systems unique to their problem. This toolbox with all of its modules is developed within the common computational platform of system dynamics linked to a Geographical Information System (GIS). Development of this resource-planning toolbox represents an important foundational element of the proposed interagency center for Computer Aided Dispute Resolution (CADRe). The Center's mission is to manage water conflict through the application of computer-aided collaborative decision-making methods. The Center will promote the use of decision-support technologies within collaborative stakeholder processes to help stakeholders find common ground and create mutually beneficial water management solutions. The Center will also serve to develop new methods and technologies to help federal, state and local water managers find innovative and balanced solutions to the nation's most vexing water problems. The toolbox is an important step toward

  2. Molecular Dynamics of a Water-Lipid Bilayer Interface

    Science.gov (United States)

    Wilson, Michael A.; Pohorille, Andrew

    1994-01-01

    We present results of molecular dynamics simulations of a glycerol 1-monooleate bilayer in water. The total length of analyzed trajectories is 5ns. The calculated width of the bilayer agrees well with the experimentally measured value. The interior of the membrane is in a highly disordered fluid state. Atomic density profile, orientational and conformational distribution functions, and order parameters indicate that disorder increases toward the center of the bilayer. Analysis of out-of-plane thermal fluctuations of the bilayer surfaces occurring at the time scale of the present calculations reveals that the distribution of modes agrees with predictions of the capillary wave model. Fluctuations of both bilayer surfaces are uncorrelated, yielding Gaussian distribution of instantaneous widths of the membrane. Fluctuations of the width produce transient thinning defects in the bilayer which occasionally span almost half of the membrane. The leading mechanism of these fluctuations is the orientational and conformational motion of head groups rather than vertical motion of the whole molecules. Water considerably penetrates the head group region of the bilayer but not its hydrocarbon core. The total net excess dipole moment of the interfacial water points toward the aqueous phase, but the water polarization profile is non-monotonic. Both water and head groups significantly contribute to the surface potential across the interface. The calculated sign of the surface potential is in agreement with that from experimental measurements, but the value is markedly overestimated. The structural and electrical properties of the water-bilayer system are discussed in relation to membrane functions, in particular transport of ions and nonelectrolytes across membranes.

  3. Holistic irrigation water management approach based on stochastic soil water dynamics

    Science.gov (United States)

    Alizadeh, H.; Mousavi, S. J.

    2012-04-01

    Appreciating the essential gap between fundamental unsaturated zone transport processes and soil and water management due to low effectiveness of some of monitoring and modeling approaches, this study presents a mathematical programming model for irrigation management optimization based on stochastic soil water dynamics. The model is a nonlinear non-convex program with an economic objective function to address water productivity and profitability aspects in irrigation management through optimizing irrigation policy. Utilizing an optimization-simulation method, the model includes an eco-hydrological integrated simulation model consisting of an explicit stochastic module of soil moisture dynamics in the crop-root zone with shallow water table effects, a conceptual root-zone salt balance module, and the FAO crop yield module. Interdependent hydrology of soil unsaturated and saturated zones is treated in a semi-analytical approach in two steps. At first step analytical expressions are derived for the expected values of crop yield, total water requirement and soil water balance components assuming fixed level for shallow water table, while numerical Newton-Raphson procedure is employed at the second step to modify value of shallow water table level. Particle Swarm Optimization (PSO) algorithm, combined with the eco-hydrological simulation model, has been used to solve the non-convex program. Benefiting from semi-analytical framework of the simulation model, the optimization-simulation method with significantly better computational performance compared to a numerical Mote-Carlo simulation-based technique has led to an effective irrigation management tool that can contribute to bridging the gap between vadose zone theory and water management practice. In addition to precisely assessing the most influential processes at a growing season time scale, one can use the developed model in large scale systems such as irrigation districts and agricultural catchments. Accordingly

  4. Dynamics of Nano-Confined Water under Pressure

    Energy Technology Data Exchange (ETDEWEB)

    Omar Diallo, Souleymane [ORNL; Jazdzewska, Monika [Adam Mickiewicz University, Poland; Palmer, Jeremy [North Carolina State University; Mamontov, Eugene [ORNL; Gubbins, Dr. K. E. [North Carolina State University; Sliwinska-Bartkowiak, M [Adam Mickiewicz University, Poland

    2013-01-01

    We report a study of the effects of pressure on the diffusivity of water molecules confined in single- wall carbon nanotubes (SWNT) with average mean pore diameter of 16 A. The measurements were carried out using high-resolution neutron scattering, over the temperature range 220 T 260 K, and at two pressure conditions: ambient and elevated pressure. The high pressure data were collected at constant volume on cooling, with P varying from 1.92 kbar at temperature T = 260 K to 1.85 kbar at T = 220 K. Analysis of the observed dynamic structure factor S(Q, E) reveals the presence of two relaxation processes, a faster diffusion component (FC) associated with the motion of caged or restricted molecules, and a slower component arising from the free water molecules diffusing within the SWNT matrix. While the temperature dependence of the slow relaxation time exhibits a Vogel-Fulcher-Tammann law and is non-Arrhenius in nature, the faster component follows an Arrhenius exponential law at both pressure conditions. The application of pressure remarkably slows down the overall molecular dynamics, in agreement with previous observations, but most notably affects the slow relaxation. The faster relaxation shows marginal or no change with pressure within the experimental conditions.

  5. A Multiagent Dynamic Assessment Approach for Water Quality Based on Improved Q-Learning Algorithm

    OpenAIRE

    Jianjun Ni; Li Ren; Minghua Liu; Daqi Zhu

    2013-01-01

    The dynamic water quality assessment is a challenging and critical issue in water resource management systems. To deal with this complex problem, a dynamic water assessment model based on multiagent technology is proposed, and an improved Q-learning algorithm is used in this paper. In the proposed Q-learning algorithm, a fuzzy membership function and a punishment mechanism are introduced to improve the learning speed of Q-learning algorithm. The dynamic water quality assessment for different ...

  6. [Functionally-relevant conformational dynamics of water-soluble proteins].

    Science.gov (United States)

    Novikov, G V; Sivozhelezov, V S; Shaĭtan, K V

    2013-01-01

    A study is reported of the functional-relevant dynamics of three typical water-soluble proteins: Calmodulin, Src-tyrosine kinase as well as repressor of Trp operon. Application of the state-of-art methods of structural bioinformatics allowed to identify dynamics seen in the X-ray structures of the investigated proteins associated with their specific biological functions. In addition, Normal Mode analysis technique revealed the most probable directions of the functionally-relevant motions for all that proteins were also predicted. Importantly, overall type of the motions observed on the lowest-frequency modes was very similar to the motions seen from the analysis of the X-ray data of the examined macromolecules. Thereby it was shown that the large-scale as well as local conformational motions of the proteins might be predetermined already at the level of their tertiary structures. In particular, the determining factor might be the specific fold of the alpha-helixes. Thus functionally-relevant in vivo dynamics of the investigated proteins might be evolutionally formed by means of natural selection at the level of the spatial topology. PMID:23705506

  7. A Population Dynamics Analysis of the Interaction between Adaptive Regulatory T Cells and Antigen Presenting Cells

    OpenAIRE

    Fouchet, David; Regoes, Roland

    2008-01-01

    Background Regulatory T cells are central actors in the maintenance of tolerance of self-antigens or allergens and in the regulation of the intensity of the immune response during infections by pathogens. An understanding of the network of the interaction between regulatory T cells, antigen presenting cells and effector T cells is starting to emerge. Dynamical systems analysis can help to understand the dynamical properties of an interaction network and can shed light on the different tasks t...

  8. Modeling and simulation of the dynamic behavior of portable proton exchange membrane fuel cells

    Energy Technology Data Exchange (ETDEWEB)

    Ziegler, C.

    2005-07-01

    In order to analyze the operational behavior, a mathematical model of planar self-breathing fuel cells is developed and validated in Chapter 3 of this thesis. The multicomponent transport of the species is considered as well as the couplings between the transport processes of heat, charge, and mass and the electrochemical reactions. Furthermore, to explain the oxygen mass transport limitation in the porous electrode of the cathode side an agglomerate model for the oxygen reduction reaction is developed. In Chapter 4 the important issue of liquid water generation and transport in PEMFCs is addressed. One of the major tasks when operating this type of fuel cell is avoiding the complete flooding of the PEMFC during operation. A one-dimensional and isothermal model is developed that is based on a coupled system of partial differential equations. The model contains a dynamic and two-phase description of the proton exchange membrane fuel cell. The mass transport in the gas phase and in the liquid phase is considered as well as the phase transition between liquid water and water vapor. The transport of charges and the electrochemical reactions are part of the model. Flooding effects that are caused by liquid water accumulation are described by this model. Moreover, the model contains a time-dependent description of the membrane that accounts for Schroeder's paradox. The model is applied to simulate cyclic voltammograms. Chapter 5 is focused on the dynamic investigation of PEMFC stacks. Understanding the dynamic behavior of fuel cell stacks is important for the operation and control of fuel cell stacks. Using the single cell model of Chapter 3 and the dynamic model of Chapter 4 as basis, a mathematical model of a PEMFC stack is developed. However, due to the complexity of a fuel cell stack, the spatial resolution and dynamic description of the liquid water transport are not accounted for. These restrictions allow for direct comparison between the solution variables of

  9. Observation of dynamic water microadsorption on Au surface

    Energy Technology Data Exchange (ETDEWEB)

    Huang, Xiaokang, E-mail: xiaokang.huang@tqs.com; Gupta, Gaurav; Gao, Weixiang; Tran, Van; Nguyen, Bang; McCormick, Eric; Cui, Yongjie; Yang, Yinbao; Hall, Craig; Isom, Harold [TriQuint Semiconductor, Inc., 500 W Renner Road, Richardson, Texas 75080 (United States)

    2014-05-15

    Experimental and theoretical research on water wettability, adsorption, and condensation on solid surfaces has been ongoing for many decades because of the availability of new materials, new detection and measurement techniques, novel applications, and different scales of dimensions. Au is a metal of special interest because it is chemically inert, has a high surface energy, is highly conductive, and has a relatively high melting point. It has wide applications in semiconductor integrated circuitry, microelectromechanical systems, microfluidics, biochips, jewelry, coinage, and even dental restoration. Therefore, its surface condition, wettability, wear resistance, lubrication, and friction attract a lot of attention from both scientists and engineers. In this paper, the authors experimentally investigated Au{sub 2}O{sub 3} growth, wettability, roughness, and adsorption utilizing atomic force microscopy, scanning electron microscopy, reflectance spectrometry, and contact angle measurement. Samples were made using a GaAs substrate. Utilizing a super-hydrophilic Au surface and the proper surface conditions of the surrounding GaAs, dynamic microadsorption of water on the Au surface was observed in a clean room environment. The Au surface area can be as small as 12 μm{sup 2}. The adsorbed water was collected by the GaAs groove structure and then redistributed around the structure. A model was developed to qualitatively describe the dynamic microadsorption process. The effective adsorption rate was estimated by modeling and experimental data. Devices for moisture collection and a liquid channel can be made by properly arranging the wettabilities or contact angles of different materials. These novel devices will be very useful in microfluid applications or biochips.

  10. Dynamically constrained pipeline for tracking neural progenitor cells

    DEFF Research Database (Denmark)

    Vestergaard, Jacob Schack; Dahl, Anders; Holm, Peter;

    2013-01-01

    . A mitosis detector constructed from empirical observations of cells in a pre-mitotic state interacts with the graph formulation to dynamically allow for cell mitosis when appropriate. Track consistency is ensured by introducing pragmatic constraints and the notion of blob states. We validate the...

  11. Antigen dynamics of follicular dendritic cells

    NARCIS (Netherlands)

    Heesters, B.A.

    2015-01-01

    Stromal-derived follicular dendritic cells (FDCs) are a major depot for antigen that are essential for formation of germinal centers, the site where memory and effector B cells differentiate and high-affinity antibody production takes place. Historically, FDCs have been characterized as ‘accessory’

  12. Ring localized structures in nonlinear shallow water wave dynamics

    International Nuclear Information System (INIS)

    The nonlinear dynamics of the concentric shallow water waves is described by means of the cylindrical Korteweg-de Vries equation, often referred to as the concentric Korteweg-de Vries equation (cKdVE). By using the mapping that transforms a cKdVE into the standard one – hereafter also referred to as the planar Korteweg-de Vries equation (KdVE) – the spatiotemporal evolution of a cylindrical surface water wave, corresponding to a tilted cylindrical bright soliton, is described. The usual representation of a tilted soliton is 'non-physical'; here the cylindrical coordinate and the retarded time play the role of time-like and space-like variables, respectively. However, we show that, when we express such analytical solution of the cKdVE in the appropriate representation in terms of the two horizontal space coordinates, say X and Y, and the 'true' time, say T, this non-physical character disappears. The analysis is then carried out numerically to consider the surface water wave evolution corresponding to initially localized structures with standard boundary conditions, such as bright soliton, Gaussian and Lorentzian profiles. A comparison among those profiles is finally presented

  13. (17)O NMR Investigation of Water Structure and Dynamics.

    Science.gov (United States)

    Keeler, Eric G; Michaelis, Vladimir K; Griffin, Robert G

    2016-08-18

    The structure and dynamics of the bound water in barium chlorate monohydrate were studied with (17)O nuclear magnetic resonance (NMR) spectroscopy in samples that are stationary and spinning at the magic-angle in magnetic fields ranging from 14.1 to 21.1 T. (17)O NMR parameters of the water were determined, and the effects of torsional oscillations of the water molecule on the (17)O quadrupolar coupling constant (CQ) were delineated with variable temperature MAS NMR. With decreasing temperature and reduction of the librational motion, we observe an increase in the experimentally measured CQ explaining the discrepancy between experiments and predictions from density functional theory. In addition, at low temperatures and in the absence of (1)H decoupling, we observe a well-resolved (1)H-(17)O dipole splitting in the spectra, which provides information on the structure of the H2O molecule. The splitting arises because of the homogeneous nature of the coupling between the two (1)H-(17)O dipoles and the (1)H-(1)H dipole. PMID:27454747

  14. Insights into the Cell Shape Dynamics of Migrating Dictyostelium discoideum

    Science.gov (United States)

    Driscoll, Meghan; Homan, Tess; McCann, Colin; Parent, Carole; Fourkas, John; Losert, Wolfgang

    2010-03-01

    Dynamic cell shape is a highly visible manifestation of the interaction between the internal biochemical state of a cell and its external environment. We analyzed the dynamic cell shape of migrating cells using the model system Dictyostelium discoideum. Applying a snake algorithm to experimental movies, we extracted cell boundaries in each frame and followed local boundary motion over long time intervals. Using a local motion measure that corresponds to protrusive/retractive activity, we found that protrusions are intermittent and zig-zag, whereas retractions are more sustained and straight. Correlations of this local motion measure reveal that protrusions appear more localized than retractions. Using a local shape measure, curvature, we also found that small peaks in boundary curvature tend to originate at the front of cells and propagate backwards. We will review the possible cytoskeletal origin of these mechanical waves.

  15. Effect of temperature and glycerol on the hydrogen-bond dynamics of water

    OpenAIRE

    GhattyVenkataKrishna, Pavan K.; Uberbacher, Edward C.

    2015-01-01

    The effect of glycerol, water and glycerol-water binary mixtures on the structure and dynamics of biomolecules has been well studied. However, a lot remains to be learned about the effect of varying glycerol concentration and temperature on the dynamics of water. We have studied the effect of concentration and temperature on the hydrogen bonded network formed by water molecules. A strong correlation between the relaxation time of the network and average number of hydrogen bonds per water mole...

  16. Dynamic instability of genomic methylation patterns in pluripotent stem cells

    Directory of Open Access Journals (Sweden)

    Ooi Steen KT

    2010-09-01

    Full Text Available Abstract Background Genomic methylation patterns are established during gametogenesis, and perpetuated in somatic cells by faithful maintenance methylation. There have been previous indications that genomic methylation patterns may be less stable in embryonic stem (ES cells than in differentiated somatic cells, but it is not known whether different mechanisms of de novo and maintenance methylation operate in pluripotent stem cells compared with differentiating somatic cells. Results In this paper, we show that ablation of the DNA methyltransferase regulator DNMT3L (DNA methyltransferase 3-like in mouse ES cells renders them essentially incapable of de novo methylation of newly integrated retroviral DNA. We also show that ES cells lacking DNMT3L lose DNA methylation over time in culture, suggesting that DNA methylation in ES cells is the result of dynamic loss and gain of DNA methylation. We found that wild-type female ES cells lose DNA methylation at a much faster rate than do male ES cells; this defect could not be attributed to sex-specific differences in expression of DNMT3L or of any DNA methyltransferase. We also found that human ES and induced pluripotent stem cell lines showed marked but variable loss of methylation that could not be attributed to sex chromosome constitution or time in culture. Conclusions These data indicate that DNA methylation in pluripotent stem cells is much more dynamic and error-prone than is maintenance methylation in differentiated cells. DNA methylation requires DNMT3L in stem cells, but DNMT3L is not expressed in differentiating somatic cells. Error-prone maintenance methylation will introduce unpredictable phenotypic variation into clonal populations of pluripotent stem cells, and this variation is likely to be much more pronounced in cultured female cells. This epigenetic variability has obvious negative implications for the clinical applications of stem cells.

  17. Dynamic friction measurements on living HeLa cells

    Science.gov (United States)

    Goulet, Marc-Antoni; Colbert, Marie-Josée; Dalnoki-Veress, Kari

    2008-03-01

    The interaction of cells with various interfaces, and especially man-made surfaces, is an active field of research. In our experiment we use a micropipette to measure both the friction and normal force as a cell slides across a surface. A thin substrate, coated with Poly-L-Lysine is brought into contact with a HeLa cell. The adjustable substrate motion is used to study the response of the cell at various normal forces and speeds. Analysis of the micropipette provides dynamic measurements of both the friction and normal force. With our novel setup we are able to probe the attachment/detachment process of living cells.

  18. Spatial dynamics of estuarine water surface temperature from airborne remote sensing

    Science.gov (United States)

    Hedger, Richard D.; Malthus, Tim J.; Folkard, Andrew M.; Atkinson, Peter M.

    2007-02-01

    This paper examines the applicability of airborne remote sensing to the characterization and quantification of the spatial dynamics of water surface temperature (WST) within estuaries. For this, a series of successive airborne Thematic Mapper thermal images was acquired of Kirkcudbright Bay, an estuary in the United Kingdom, on two dates. Spatial dynamics were determined by two techniques: (1) qualitatively, which involved interpreting features 'by eye'; and (2) by the velocimetric technique of maximum cross correlation (MCC). Qualitatively, complex spatial dynamics were identified over a wide range of spatial and temporal scales, associated with the creation and dissipation of eddies, and the convergence and divergence of fronts, all of which were superimposed on the synoptic tidal flow. MCC was effective for producing synoptic velocity fields, but the minimum cell size was constrained by image noise, limiting the ability to analyze small-scale spatial dynamics. The effectiveness of MCC was related to the ratio of spatially correlated variance to spatially independent variance, as estimated from the variogram. Suggestions for optimizing the application of airborne remote sensing to estuarine spatial dynamics are presented.

  19. Modeling water table dynamics in managed and restored peatlands

    Science.gov (United States)

    Cresto Aleina, Fabio; Rasche, Livia; Hermans, Renée; Subke, Jens-Arne; Schneider, Uwe; Brovkin, Victor

    2016-04-01

    European peatlands have been extensively managed over past centuries. Typical management activities consisted of drainage and afforestation, which lead to considerable damage to the peat and potentially significant carbon loss. Recent efforts to restore previously managed peatlands have been carried out throughout Europe. These restoration efforts have direct implications for water table depth and greenhouse gas emissions, thus impacting on the ecosystem services provided by peatland areas. In order to quantify the impact of peatland restoration on water table depth and greenhouse gas budget, We coupled the Environmental Policy Integrated Climate (EPIC) model to a process-based model for methane emissions (Walter and Heimann, 2000). The new model (EPIC-M) can potentially be applied at the European and even at the global scale, but it is yet to be tested and evaluated. We present results of this new tool from different peatlands in the Flow Country, Scotland. Large parts of the peatlands of the region have been drained and afforested during the 1980s, but since the late 1990s, programs to restore peatlands in the Flow Country have been enforced. This region offers therefore a range of peatlands, from near pristine, to afforested and drained, with different resoration ages in between, where we can apply the EPIC-M model and validate it against experimental data from all land stages of restoration Goals of this study are to evaluate the EPIC-M model and its performances against in situ measurements of methane emissions and water table changes in drained peatlands and in restored ones. Secondly, our purpose is to study the environmental impact of peatland restoration, including methane emissions, due to the rewetting of drained surfaces. To do so, we forced the EPIC-M model with local meteorological and soil data, and simulated soil temperatures, water table dynamics, and greenhouse gas emissions. This is the first step towards a European-wide application of the EPIC

  20. Approximate dynamic fault tree calculations for modelling water supply risks

    International Nuclear Information System (INIS)

    Traditional fault tree analysis is not always sufficient when analysing complex systems. To overcome the limitations dynamic fault tree (DFT) analysis is suggested in the literature as well as different approaches for how to solve DFTs. For added value in fault tree analysis, approximate DFT calculations based on a Markovian approach are presented and evaluated here. The approximate DFT calculations are performed using standard Monte Carlo simulations and do not require simulations of the full Markov models, which simplifies model building and in particular calculations. It is shown how to extend the calculations of the traditional OR- and AND-gates, so that information is available on the failure probability, the failure rate and the mean downtime at all levels in the fault tree. Two additional logic gates are presented that make it possible to model a system's ability to compensate for failures. This work was initiated to enable correct analyses of water supply risks. Drinking water systems are typically complex with an inherent ability to compensate for failures that is not easily modelled using traditional logic gates. The approximate DFT calculations are compared to results from simulations of the corresponding Markov models for three water supply examples. For the traditional OR- and AND-gates, and one gate modelling compensation, the errors in the results are small. For the other gate modelling compensation, the error increases with the number of compensating components. The errors are, however, in most cases acceptable with respect to uncertainties in input data. The approximate DFT calculations improve the capabilities of fault tree analysis of drinking water systems since they provide additional and important information and are simple and practically applicable.

  1. Membrane Organization and Dynamics in Cell Polarity

    OpenAIRE

    Orlando, Kelly; Guo, Wei

    2009-01-01

    The establishment and maintenance of cell polarity is important to a wide range of biological processes ranging from chemotaxis to embryogenesis. An essential feature of cell polarity is the asymmetric organization of proteins and lipids in the plasma membrane. In this article, we discuss how polarity regulators such as small GTP-binding proteins and phospholipids spatially and kinetically control vesicular trafficking and membrane organization. Conversely, we discuss how membrane trafficking...

  2. Coupling all-atom molecular dynamics simulations of ions in water with Brownian dynamics

    CERN Document Server

    Erban, Radek

    2015-01-01

    Molecular dynamics (MD) simulations of ions (K$^+$, Na$^+$, Ca$^{2+}$ and Cl$^-$) in aqueous solutions are investigated. Water is described using the SPC/E model. A stochastic coarse-grained description for ion behaviour is presented and parameterized using MD simulations. It is given as a system of coupled stochastic and ordinary differential equations, describing the ion position, velocity and acceleration. The stochastic coarse-grained model provides an intermediate description between all-atom MD simulations and Brownian dynamics (BD) models. It is used to develop a multiscale method which uses all-atom MD simulations in parts of the computational domain and (less detailed) BD simulations in the remainder of the domain.

  3. Vegetation dynamics and soil water balance in a water-limited Mediterranean ecosystem on Sardinia, Italy

    Directory of Open Access Journals (Sweden)

    N. Montaldo

    2008-01-01

    Full Text Available Mediterranean ecosystems are commonly heterogeneous savanna-like ecosystems, with contrasting plant functional types (PFTs, e.g., grass and woody vegetation competing for the water use. Mediterranean ecosystems are also commonly characterized by strong inter-annual rainfall variability, which influences the distributions of PFTs that vary spatially and temporally. With the objective to investigate interactions between vegetation dynamics, soil water budget and land-surface fluxes in a water-limited ecosystem, an extensive field campaign in a Mediterranean setting was performed. Also a vegetation dynamic model (VDM is coupled to a 3-component (bare soil, grass and woody vegetation Land surface model (LSM. The case study is in Orroli, situated in the mid-west of Sardegna within the Flumendosa river basin. The landscape is a mixture of Mediterranean patchy vegetation types: trees, including wild olives and cork oaks, different shrubs and herbaceous species. Land surface fluxes, soil moisture and vegetation growth were monitored during the May 2003–June 2006 period. Interestingly, hydrometeorological conditions of the monitored years strongly differ, with dry and wet years in turn, such that a wide range of hydrometeorological conditions can be analyzed. The coupled VDM-LSM model is successfully tested for the case study, demonstrating high model performance for the wide range of eco-hydrologic conditions. The use of the VDM in the LSM is demonstrated to be essential when studying the climate-soil-vegetation interactions of these water-limited ecosystems. Results demonstrate also that vegetation dynamics are strongly influenced by the inter-annual variability of atmospheric forcing, with grass leaf area index changing significantly each spring season according to seasonal rainfall amount.

  4. Chemical "Double Slits": dynamical interference of photodissociation pathways in water

    Science.gov (United States)

    Dixon; Hwang; Yang; Harich; Lin; Yang

    1999-08-20

    Photodissociation of water at a wavelength of 121.6 nanometers has been investigated by using the H-atom Rydberg tagging technique. A striking even-odd intensity oscillation was observed in the OH(X) product rotational distribution. Model calculations attribute this oscillation to an unusual dynamical interference brought about by two dissociation pathways that pass through dissimilar conical intersections of potential energy surfaces, but result in the same products. The interference pattern and the OH product rotational distribution are sensitive to the positions and energies of the conical intersections, one with the atoms collinear as H-OH and the other as H-HO. An accurate simulation of the observations would provide a detailed test of global H(2)O potential energy surfaces for the three (&Xtilde;/A/&Btilde;) contributing states. The interference observed from the two conical intersection pathways provides a chemical analog of Young's well-known double-slit experiment. PMID:10455048

  5. Dynamic Change of Water Quality in Hyporheic Zone at Water Curtain Cultivation Area, Cheongju, Korea

    Science.gov (United States)

    Moon, S. H.; Kim, Y.

    2015-12-01

    There has been recently growing numbers of facilities for water curtain cultivation of strawberry and lettuce in Korea. These areas are nearly all located in the fluvial deposits near streams which can replenish water resources into exhausted groundwater aquifers during peak season. The purpose of this study is on groundwater chemistry and the change in physical and chemical properties due to stream-groundwater exchange or mixing in the representative agricultural area among the Jurassic granitic terrain of Korea. In the study area, groundwater level continuously decreased from November through March due to intensive use of groundwater, which forced stream water into aquifer. After March, groundwater level was gradually recovered to the original state. To evaluate the extent and its variations of stream water mixing into aquifer, field parameters including T, pH, EC and DO values, concentrations of major ions and oxygen and hydrogen stable isotopic ratios were used. Field measurements and water sample collections were performed several times from 2012 to 2015 mainly during peak time of groundwater use. To compare the temporal variations and areal differences, 21 wells from four cross sections perpendicular to stream line were used. While water temperature, EC values and concentrations of Ca, Mg, Si, HCO3 showed roughly gradual increase from stream line to 150 m distance, pH and DO values showed reverse phenomenon. This can be used to evaluate the extent and limit of stream water introduction into aquifer. However, individual wells showed yearly variations in those parameters and this dynamic and unstable feature indicates that mixing intensity of stream water over groundwater in this hyporheic zone varied year by year according to amounts of groundwater use and decrease of groundwater level.

  6. Ionization dynamics of water dimer on ice surface

    Science.gov (United States)

    Tachikawa, Hiroto

    2016-05-01

    The solid surface provides an effective two-dimensional reaction field because the surface increases the encounter probability of bi-molecular collision reactions. Also, the solid surface stabilizes a reaction intermediate because the excess energy generated by the reaction dissipates into the bath modes of surface. The ice surface in the universe is one of the two dimensional reaction fields. However, it is still unknown how the ice surface affects to the reaction mechanism. In the present study, to elucidate the specific property of the ice surface reaction, ionization dynamics of water dimer adsorbed on the ice surface was theoretically investigated by means of direct ab-initio molecular dynamics (AIMD) method combined with ONIOM (our own n-layered integrated molecular orbital and molecular mechanics) technique, and the result was compared with that of gas phase reaction. It was found that a proton is transferred from H2O+ to H2O within the dimer and the intermediate complex H3O+(OH) is formed in both cases. However, the dynamic features were different from each other. The reaction rate of the proton transfer on the ice surface was three times faster than that in the gas phase. The intermediate complex H3O+(OH) was easily dissociated to H3O+ and OH radical on the ice surface, and the lifetime of the complex was significantly shorter than that of gas phase (100 fs vs. infinite). The reason why the ice surface accelerates the reaction was discussed in the present study.

  7. Reaction dynamics following electron capture of chlorofluorocarbon adsorbed on water cluster : a direct density functional theory molecular dynamics study

    OpenAIRE

    Tachikawa, Hiroto; ABE, Shigeaki

    2007-01-01

    The electron capture dynamics of halocarbon and its water complex have been investigated by means of the full dimensional direct density functional theory molecular dynamics method in order to shed light on the mechanism of electron capture of a halocarbon adsorbed on the ice surface. The CF2Cl2 molecule and a cyclic water trimer (H2O)3 were used as halocarbon and water cluster, respectively. The dynamics calculation of CF2Cl2 showed that both C–Cl bonds are largely elongated after the electr...

  8. A dynamic two-dimensional heterogeneous model for water gas shift reactors

    Energy Technology Data Exchange (ETDEWEB)

    Adams, Thomas A. II.; Barton, Paul I. [Massachusetts Institute of Technology, 77 Massachusetts Ave, Cambridge MA 02139 (United States)

    2009-11-15

    A dynamic, heterogeneous, two-dimensional model for packed-bed water gas shift reactors is presented. It can be applied to both high and low temperature shifts, and at scales ranging from industrial (for power plant applications) to small (such as automotive fuel cell applications). The model is suitable for any catalyst for which kinetic data are available, and shows excellent agreement with available experimental data for non-equilibrium conditions. The model is applied to an IGCC-TIGAS polygeneration plant to examine the dynamic behavior of the WGS units. The development of catalyst hot-spots is predicted during start-up or transition between steady states under certain conditions. (author)

  9. Single-cell dynamics of mast cell-CD4+ CD25+ regulatory T cell interactions.

    Science.gov (United States)

    Frossi, Barbara; D'Incà, Federica; Crivellato, Enrico; Sibilano, Riccardo; Gri, Giorgia; Mongillo, Marco; Danelli, Luca; Maggi, Laura; Pucillo, Carlo E

    2011-07-01

    The biological behavior of immune cells is determined by their intrinsic properties and interactions with other cell populations within their microenvironment. Several studies have confirmed the existence of tight spatial interactions between mast cells (MCs) and Tregs in different settings. For instance, we have recently identified the functional cross-talk between MCs and Tregs, through the OX40L-OX40 axis, as a new mechanism of reciprocal influence. However, there is scant information regarding the single-cell dynamics of this process. In this study, time-lapse video microscopy revealed direct interactions between Tregs and MCs in both murine and human cell co-cultures, resulting in the inhibition of the MC degranulation response. MCs incubated with WT, but not OX40-deficient, Tregs mediated numerous and long-lasting interactions and displayed different morphological features lacking the classical signs of exocytosis. MC degranulation and Ca2+ mobilization upon activation were inhibited by Tregs on a single-cell basis, without affecting overall cytokine secretion. Transmission electron microscopy showed ultrastructural evidence of vesicle-mediated secretion reconcilable with the morphological pattern of piecemeal degranulation. Our results suggest that MC morphological and functional changes following MC-Treg interactions can be ascribed to cell-cell contact and represent a transversal, non-species-specific mechanism of immune response regulation. Further research, looking at the molecular composition of this interaction will broaden our understanding of its contribution to immunity. PMID:21509780

  10. Photodesorption of water ice: a molecular dynamics study

    CERN Document Server

    Andersson, S

    2008-01-01

    Absorption of ultraviolet radiation by water ice coating interstellar grains can lead to dissociation and desorption of the ice molecules. These processes are thought to be important in the gas-grain chemistry in molecular clouds and protoplanetary disks, but very few quantitative studies exist. We compute the photodesorption efficiencies of amorphous water ice and elucidate the mechanisms by which desorption occurs. Classical molecular dynamics calculations were performed for a compact amorphous ice surface at 10 K thought to be representative of interstellar ice. Dissociation and desorption of H2O molecules in the top six monolayers are considered following absorption into the first excited electronic state with photons in the 1300-1500 Angstrom range. The trajectories of the H and OH photofragments are followed until they escape or become trapped in the ice. The probability for H2O desorption per absorbed UV photon is 0.5-1% in the top three monolayers, then decreases to 0.03% in the next two monolayers, a...

  11. Cytoarchitectonical dynamic of Sertoli cells in Melanorivulus punctatus (Cyprinodontiformes: Rivulidae).

    Science.gov (United States)

    Cassel, Mônica; Neves da Silva, Débora Fabiane; Ferreira, Adelina

    2013-02-01

    The Sertoli cell contributes to spermatogenesis acting in the differentiation of germ cells and being the only somatic cells present in the germinal compartment. So that spermatogenesis is primarily dependent of Sertoli-Sertoli and Sertoli-germ cell interactions once Sertoli cells provide critical factors necessary for a successful differentiation of germ cells to sperm. In teleost fish the cytoplasmic extensions of Sertoli cells support the cysts that remain closed until spermiogenesis. The number of Sertoli cells determines the testicular size, the number of testicular germ cells and the production capacity of spermatozoa. Our objective was to describe the morphology and the cytoarchitectonical dynamic of Sertoli cells in Melanorivulus punctatus, which were collected in the municipality of Chapada dos Guimarães, Mato Grosso, Brazil. The gonads were extracted and prepared according to histological routine for light microscopy and transmission electron microscopy. Sertoli cells have cytoplasmic extensions which provide the conformation of cysts in the interior of the lobes. These cells possess a polymorphic nucleus with a well-defined nuclear envelope and a prominent and eccentric nucleoli. Each cyst is sustained for more than one Sertoli cell and the cysts seem to share the Sertoli cells with each other regardless the stage of development of germ cells within these cysts. This disposal promotes a reticulated arrangement of Sertoli cells. The Sertoli cells lining the ducts assume rectangular shape with rounded nucleus. Thus, the morphological characteristics of Sertoli cells observed did not differ from what has been described for other teleosts. Despite the similarity in the morphology of these cells, we observed that its disposal in the extension of the gonad seems to differ from what is described for fish. The arrangement by which the cytoplasmic extensions of Sertoli cells connect the ends of lobes prevents the proliferation of spermatogonia on the lobe side

  12. Dynamic Modes of Red Blood Cells in Oscillatory Shear Flow

    OpenAIRE

    Noguchi, Hiroshi

    2009-01-01

    The dynamics of red blood cells (RBCs) in oscillatory shear flow was studied using differential equations of three variables: a shape parameter, the inclination angle $\\theta$, and phase angle $\\phi$ of the membrane rotation. In steady shear flow, three types of dynamics occur depending on the shear rate and viscosity ratio. i) tank-treading (TT): $\\phi$ rotates while the shape and $\\theta$ oscillate. ii) tumbling (TB): $\\theta$ rotates while the shape and $\\phi$ oscillate. iii) intermediate ...

  13. Dynamics of phytoplankton pigments in water and surface sediments of a large shallow lake

    Directory of Open Access Journals (Sweden)

    Ilmar Tõnno

    2011-06-01

    Full Text Available Our aim was to find out to which extent fossil phytoplankton pigments in the large shallow and turbid Lake Võrtsjärv carry information on the history of phytoplankton communities. For this purpose we examined how the changes in the pigment composition of surface sediments follow their changes in the water column. Depth-integrated lake water and surface sediment samples were collected weekly in May–October 2007. Considering cyanobacterial and diatom dominance in phytoplankton, we analysed fucoxanthin, diadinoxanthin and diatoxanthin as marker pigments for diatoms, zeaxanthin as a marker pigment for total cyanobacteria and canthaxanthin as a marker pigment for colonial cyanobacteria. Chlorophyll a and its derivative pheophytin a were applied as indicators for total phytoplankton. The dynamics of phytoplankton pigments in surface sediments generally did not follow their dynamics in the water column, possibly due to intensive resuspension and a high sedimentation rate in a large and shallow lake. It was noticed that the surface sediment carries information on pigment degradation intensity and on weight and size characteristics of phytoplankton cells, which affect their sinking and floating velocities. Higher pigment contents of sediment in spring were presumably caused by lower resuspension due to high water level and slower degradation in cold water. Pheophytin a and the marker pigments of cyanobacteria were found to be persistent against degradation in upper sediment layers, which makes them useful indicators for tracking the historical changes in phytoplankton communities also in a shallow lake. Sharp decrease in chemically unstable pigment contents between the sediment surface and deeper layers indicates that only the uppermost sediment surface is resuspended in Lake Võrtsjärv. The transformation of the diatom marker carotenoid diadinoxanthin to diatoxanthin was found to occur mainly in sediments and not in the water column, and the

  14. Rhizosphere water dynamics: role of exudates in mediating water retention and flow characteristics

    Science.gov (United States)

    Albalasmeh, Ammar; Ghezzehei, Teamrat

    2013-04-01

    In recent years, significant amount of literature showed that rhizosphere's physical and chemical properties markedly differ from those of the bulk soil. Plants invest large portion of their photosynthetic carbon in developing root architecture that optimally exploits water and nutrient distributions in the soil. There is indirect evidence suggesting that these exudates play a major role in altering the of the soil water retention properties. In this study, we investigated the role of root exudates on rhizosphere water dynamics using analog system. Glass beads were used to represent loose soil and dilute solutions of polygalacutronic acid (PGA) to mimic exudates (0, 1, 5, 15 and 29 g/L). The samples were subjected to periods of drying and subsequent equilibration. At each stage, the water potential was measured using WP4C Dewpoint PotentiaMeter. On the other hand, sand samples were saturated with PGA at the same concentration used to study the effect of exudates on water evaporation rate. The effect of root exudates on soil water retention can be attributed to at least two factors. The most widely speculated effect is through enhanced of soil aggregation. This effect is primarily due to capillary adhesion in fine pores within aggregates and is consistent with visual observation of pronounced aggregation in many rhizosphere soils. The second factor is related to osmotic effect of the exudate solution. Our observations show that the capillary effect is mostly limited to higher water potential regime (> -1 bar suction). Whereas the osmotic effect dominates in <- 1 bar suction. At the same time, the osmotic potential results from these organic exudates play an important role in reducing the evaporation rate. These results will provide direct quantitative evidence of how rhizosphere organic matter helps plant-soil relations.

  15. Senescent cells in growing tumors: population dynamics and cancer stem cells

    OpenAIRE

    C.A.M. La Porta; Zapperi, S.; Sethna, J. P.

    2012-01-01

    Author Summary It is commonly believed that cell senescence – the loss of replicative capacity of cells – acts as a barrier for tumor growth. Here we follow the evolution of senescence markers in melanoma cells and find that while most cancer cells eventually turn senescent, this is at root irrelevant for the long-term growth rate of a tumor. To demonstrate this, we construct a mathematical population dynamics model incorporating cancer stem cells which is able to reproduce quantitatively the...

  16. Neutron scattering reveals extremely slow cell water in a Dead Sea organism

    OpenAIRE

    Tehei, Moeava; Franzetti, Bruno; Wood, Kathleen; Gabel, Frank; Fabiani, Elisa; Jasnin, Marion; Zamponi, Michaela; Oesterhelt, Dieter; Zaccai, Giuseppe; Ginzburg, Margaret; Ginzburg, Ben-Zion

    2007-01-01

    Intracellular water dynamics in Haloarcula marismortui, an extremely halophilic organism originally isolated from the Dead Sea, was studied by neutron scattering. The water in centrifuged cell pellets was examined by means of two spectrometers, IN6 and IN16, sensitive to motions with time scales of 10 ps and 1 ns, respectively. From IN6 data, a translational diffusion constant of 1.3 × 10−5 cm2 s−1 was determined at 285 K. This value is close to that found previously for other cells and close...

  17. Observation of bubble formation in water during microwave irradiation by dynamic light scattering

    Science.gov (United States)

    Asakuma, Yusuke; Munenaga, Takuya; Nakata, Ryosuke

    2015-10-01

    A microwave reactor was designed for in situ observation of nano- and micro-bubbles, and size profiles during and after irradiation were measured with respect to irradiation power and time. Bubble formation in water during irradiation was observed even at temperatures below the boiling point of water. The maximum size strongly depended on radiation power and time, even at a given temperature. Nano-particles in the dispersion medium were found to play an important role in achieving more stable nucleation of bubbles around particles, and stable size distributions were obtained from clear autocorrelation by a dynamic light scattering system. Moreover, a combination of microwave induction heating and the addition of nano-particles to the dispersion medium can prevent heterogeneous nucleation of bubbles on the cell wall. Quantitative nano-bubble size profiles obtained by in situ observation provide useful information regarding microwave-based industrial processes for nano-particle production.

  18. Dynamic battery cell model and state of charge estimation

    Science.gov (United States)

    Wijewardana, S.; Vepa, R.; Shaheed, M. H.

    2016-03-01

    Mathematical modelling and the dynamic simulation of battery storage systems can be challenging and demanding due to the nonlinear nature of the battery chemistry. This paper introduces a new dynamic battery model, with application to state of charge estimation, considering all possible aspects of environmental conditions and variables. The aim of this paper is to present a suitable convenient, generic dynamic representation of rechargeable battery dynamics that can be used to model any Lithium-ion rechargeable battery. The proposed representation is used to develop a dynamic model considering the thermal balance of heat generation mechanism of the battery cell and the ambient temperature effect including other variables such as storage effects, cyclic charging, battery internal resistance, state of charge etc. The results of the simulations have been used to study the characteristics of a Lithium-ion battery and the proposed battery model is shown to produce responses within 98% of known experimental measurements.

  19. Online Soft Sensor of Humidity in PEM Fuel Cell Based on Dynamic Partial Least Squares

    OpenAIRE

    Rong Long; Qihong Chen; Liyan Zhang; Longhua Ma; Shuhai Quan

    2013-01-01

    Online monitoring humidity in the proton exchange membrane (PEM) fuel cell is an important issue in maintaining proper membrane humidity. The cost and size of existing sensors for monitoring humidity are prohibitive for online measurements. Online prediction of humidity using readily available measured data would be beneficial to water management. In this paper, a novel soft sensor method based on dynamic partial least squares (DPLS) regression is proposed and applied to humidity prediction i...

  20. Phosphorylation site dynamics of early T-cell receptor signaling

    DEFF Research Database (Denmark)

    Chylek, Lily A; Akimov, Vyacheslav; Dengjel, Jörn;

    2014-01-01

    systems-level understanding of how these components cooperate to control signaling dynamics, especially during the crucial first seconds of stimulation. Here, we used quantitative proteomics to characterize reshaping of the T-cell phosphoproteome in response to TCR/CD28 co-stimulation, and found that...... diverse dynamic patterns emerge within seconds. We detected phosphorylation dynamics as early as 5 s and observed widespread regulation of key TCR signaling proteins by 30 s. Development of a computational model pointed to the presence of novel regulatory mechanisms controlling phosphorylation of sites...

  1. Plastids: dynamic components of plant cell development

    Science.gov (United States)

    Guikema, J. A.; Gallegos, G. L.; Spooner, B. S. (Principal Investigator)

    1992-01-01

    The gravitropic bending of maize roots, as a response to reorientation of the root within a gravitational field, was examined for sensitivity to exogenous applications of the cytoskeletal inhibitor, cytochalasin D. Agar blocks were impregnated with this inhibitor, and were applied either to the root cap or to the zone of root cell elongation. Root growth was normal with either treatment, if the roots were not repositioned with respect to the gravitational vector. When untreated roots were placed in a horizontal position with respect to gravity, a 40 degree bending response was observed within one hour. This bending also occurred when cytochalasin D was applied at high concentrations to the zone of root cell elongation. However, when cytochalasin D above 40 micrograms/ml was applied to the root cap, roots lost the ability of directional reorientation within the gravitational field, causing a random bending.

  2. Colon stem cell and crypt dynamics exposed by cell lineage reconstruction.

    Directory of Open Access Journals (Sweden)

    Yitzhak Reizel

    2011-07-01

    Full Text Available Stem cell dynamics in vivo are often being studied by lineage tracing methods. Our laboratory has previously developed a retrospective method for reconstructing cell lineage trees from somatic mutations accumulated in microsatellites. This method was applied here to explore different aspects of stem cell dynamics in the mouse colon without the use of stem cell markers. We first demonstrated the reliability of our method for the study of stem cells by confirming previously established facts, and then we addressed open questions. Our findings confirmed that colon crypts are monoclonal and that, throughout adulthood, the process of monoclonal conversion plays a major role in the maintenance of crypts. The absence of immortal strand mechanism in crypts stem cells was validated by the age-dependent accumulation of microsatellite mutations. In addition, we confirmed the positive correlation between physical and lineage proximity of crypts, by showing that the colon is separated into small domains that share a common ancestor. We gained new data demonstrating that colon epithelium is clustered separately from hematopoietic and other cell types, indicating that the colon is constituted of few progenitors and ruling out significant renewal of colonic epithelium from hematopoietic cells during adulthood. Overall, our study demonstrates the reliability of cell lineage reconstruction for the study of stem cell dynamics, and it further addresses open questions in colon stem cells. In addition, this method can be applied to study stem cell dynamics in other systems.

  3. A quantitative and dynamic model for plant stem cell regulation.

    Directory of Open Access Journals (Sweden)

    Florian Geier

    Full Text Available Plants maintain pools of totipotent stem cells throughout their entire life. These stem cells are embedded within specialized tissues called meristems, which form the growing points of the organism. The shoot apical meristem of the reference plant Arabidopsis thaliana is subdivided into several distinct domains, which execute diverse biological functions, such as tissue organization, cell-proliferation and differentiation. The number of cells required for growth and organ formation changes over the course of a plants life, while the structure of the meristem remains remarkably constant. Thus, regulatory systems must be in place, which allow for an adaptation of cell proliferation within the shoot apical meristem, while maintaining the organization at the tissue level. To advance our understanding of this dynamic tissue behavior, we measured domain sizes as well as cell division rates of the shoot apical meristem under various environmental conditions, which cause adaptations in meristem size. Based on our results we developed a mathematical model to explain the observed changes by a cell pool size dependent regulation of cell proliferation and differentiation, which is able to correctly predict CLV3 and WUS over-expression phenotypes. While the model shows stem cell homeostasis under constant growth conditions, it predicts a variation in stem cell number under changing conditions. Consistent with our experimental data this behavior is correlated with variations in cell proliferation. Therefore, we investigate different signaling mechanisms, which could stabilize stem cell number despite variations in cell proliferation. Our results shed light onto the dynamic constraints of stem cell pool maintenance in the shoot apical meristem of Arabidopsis in different environmental conditions and developmental states.

  4. Effects of Water on Structure and Dynamics of Trehalose Glasses at Low Water Contents and its Relationship to Preservation Outcomes

    Science.gov (United States)

    Weng, Lindong; Ziaei, Shima; Elliott, Gloria D.

    2016-07-01

    Dry preservation of biologics in sugar glasses is regarded as a promising alternative to conventional cryopreservation. Evidence from various studies has suggested that there is a critical range of water content beyond which the viability of preserved biologics can be greatly compromised. In this study the viability of T-cells was determined as a function of end water content after microwave-assisted drying in trehalose solutions. Hydrogen-bonding and clustering phenomena in trehalose solutions of the same moisture content were also evaluated using molecular dynamics simulation. Post-rehydration viability decreased dramatically within the range of 0.1–1 gH2O/gdw. Molecular modeling revealed that as the water content approached 0.1 gH2O/gdw the matrix formed a large interconnected trehalose skeleton with a minimal number of bound water molecules scattered in the bulk. The diffusion coefficients of trehalose oxygen atoms most distant from the glycosidic linkage fluctuated around 7.5 × 10‑14 m2/s within the range of 0.02–0.1 gH2O/gdw and increased again to ~1.13 × 10‑13 m2/s at 0.01 gH2O/gdw and below due to the loss of water in the free volume between trehalose molecules. These insights can guide the optimal selection of final moisture contents to advance dry preservation methods.

  5. MODELING OF WATER DYNAMICS AND POLLUTANT SPREADING IN THE LUOMAHU RESERVOIR FOR WATER TRANSFER FORM SOUTH TO NORTH OF CHINA

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    Water quality is the key problem of the East-Line Project of Water Transfer from South to North China. In this paper, the principles of a 1D and 2D-integrated mathematical model for describing the dynamics of water in a flow-through river, canals and lakes was worked out. The numerical method and model algorithm were developed. The efficiency of the model was estimated by applying it to studying water dynamics in the Luomahu reservoir and simulating the spreading process of a polluted water mass and the evolution of the concentration. The results of calculations are used to assess water environmental quality and to manage water resource in the Luomahu reservoir and the Jinghang-Canal for the Project of Water Transfer from South to North China.

  6. Towards dynamic metabolic flux analysis in CHO cell cultures.

    Science.gov (United States)

    Ahn, Woo Suk; Antoniewicz, Maciek R

    2012-01-01

    Chinese hamster ovary (CHO) cells are the most widely used mammalian cell line for biopharmaceutical production, with a total global market approaching $100 billion per year. In the pharmaceutical industry CHO cells are grown in fed-batch culture, where cellular metabolism is characterized by high glucose and glutamine uptake rates combined with high rates of ammonium and lactate secretion. The metabolism of CHO cells changes dramatically during a fed-batch culture as the cells adapt to a changing environment and transition from exponential growth phase to stationary phase. Thus far, it has been challenging to study metabolic flux dynamics in CHO cell cultures using conventional metabolic flux analysis techniques that were developed for systems at metabolic steady state. In this paper we review progress on flux analysis in CHO cells and techniques for dynamic metabolic flux analysis. Application of these new tools may allow identification of intracellular metabolic bottlenecks at specific stages in CHO cell cultures and eventually lead to novel strategies for improving CHO cell metabolism and optimizing biopharmaceutical process performance. PMID:22102428

  7. Computational investigation of epithelial cell dynamic phenotype in vitro

    OpenAIRE

    Debnath Jayanta; Mostov Keith; Park Sunwoo; Kim Sean HJ; Hunt C Anthony

    2009-01-01

    Abstract Background When grown in three-dimensional (3D) cultures, epithelial cells typically form cystic organoids that recapitulate cardinal features of in vivo epithelial structures. Characterizing essential cell actions and their roles, which constitute the system's dynamic phenotype, is critical to gaining deeper insight into the cystogenesis phenomena. Methods Starting with an earlier in silico epithelial analogue (ISEA1) that validated for several Madin-Darby canine kidney (MDCK) epith...

  8. Alteration of mammalian cell metabolism by dynamic nutrient feeding

    OpenAIRE

    Zhou, Weichang; Rehm, Jutta; Europa, Anna; Hu, Wei-Shou

    1997-01-01

    The metabolism of hybridoma cells was controlled to reduce metabolic formation in fed-batch cultures by dynamically feeding a salt-free nutrient concentrate. For this purpose, on-line oxygen uptake rate (OUR) measurement was used to estimate the metabolic demand of hybridoma cells and to determine the feeding rate of a concentrated solution of salt-free DMEM/F12 medium supplemented with other medium components. The ratios among glucose, glutamine and other medium components in the feeding nut...

  9. Revealing the Dynamics of Thylakoid Membranes in Living Cyanobacterial Cells

    OpenAIRE

    Laura-Roxana Stingaciu; Hugh O’Neill; Michelle Liberton; Urban, Volker S.; Himadri B. Pakrasi; Michael Ohl

    2016-01-01

    Cyanobacteria are photosynthetic prokaryotes that make major contributions to the production of the oxygen in the Earth atmosphere. The photosynthetic machinery in cyanobacterial cells is housed in flattened membrane structures called thylakoids. The structural organization of cyanobacterial cells and the arrangement of the thylakoid membranes in response to environmental conditions have been widely investigated. However, there is limited knowledge about the internal dynamics of these membran...

  10. Horizontal soil water potential heterogeneity: simplifying approaches for crop water dynamics models

    Science.gov (United States)

    Couvreur, V.; Vanderborght, J.; Beff, L.; Javaux, M.

    2014-05-01

    use of 1-D spatial discretisation to represent soil-plant water dynamics is a worthy choice for densely seeded crops. For wide-row crops, e.g. maize, further theoretical developments that better account for horizontal SWP heterogeneity might be needed in order to properly predict soil-plant hydrodynamics in 1-D.

  11. Horizontal soil water potential heterogeneity: simplifying approaches for crop water dynamics models

    Directory of Open Access Journals (Sweden)

    V. Couvreur

    2014-01-01

    study confirms that the use of 1-D spatial discretisation to represent soil-plant water dynamics is a worthy choice for densely seeded crops. For wide-row crops, e.g. maize, further theoretical developments that better account for horizontal SWP heterogeneity might be needed in order to properly predict soil-plant hydrodynamics in 1-D.

  12. Continuous cell-to-cell mapping and dynamic PSA

    International Nuclear Information System (INIS)

    A current challenge in probabilistic safety analysis is the study of the dynamic behavior of systems. Several methods have been used, each one having its own drawbacks. The discrete Markovian approach (CCMT) especially suffers from modelling problems (e.g. introduction of control laws). A continuous Markovian approach (CCCMT) allows to get rid of such problems. The CCCMT is described in this paper and is applied to the well-known heated tank problem. Comparisons between CCCMT and CCMT are also given

  13. Single Cell Proteolytic Assays to Investigate Cancer Clonal Heterogeneity and Cell Dynamics Using an Efficient Cell Loading Scheme

    Science.gov (United States)

    Chen, Yu-Chih; Cheng, Yu-Heng; Ingram, Patrick; Yoon, Euisik

    2016-01-01

    Proteolytic degradation of the extracellular matrix (ECM) is critical in cancer invasion, and recent work suggests that heterogeneous cancer populations cooperate in this process. Despite the importance of cell heterogeneity, conventional proteolytic assays measure average activity, requiring thousands of cells and providing limited information about heterogeneity and dynamics. Here, we developed a microfluidic platform that provides high-efficiency cell loading and simple valveless isolation, so the proteolytic activity of a small sample (10–100 cells) can be easily characterized. Combined with a single cell derived (clonal) sphere formation platform, we have successfully demonstrated the importance of microenvironmental cues for proteolytic activity and also investigated the difference between clones. Furthermore, the platform allows monitoring single cells at multiple time points, unveiling different cancer cell line dynamics in proteolytic activity. The presented tool facilitates single cell proteolytic analysis using small samples, and our findings illuminate the heterogeneous and dynamic nature of proteolytic activity. PMID:27283981

  14. Single Cell Proteolytic Assays to Investigate Cancer Clonal Heterogeneity and Cell Dynamics Using an Efficient Cell Loading Scheme

    Science.gov (United States)

    Chen, Yu-Chih; Cheng, Yu-Heng; Ingram, Patrick; Yoon, Euisik

    2016-06-01

    Proteolytic degradation of the extracellular matrix (ECM) is critical in cancer invasion, and recent work suggests that heterogeneous cancer populations cooperate in this process. Despite the importance of cell heterogeneity, conventional proteolytic assays measure average activity, requiring thousands of cells and providing limited information about heterogeneity and dynamics. Here, we developed a microfluidic platform that provides high-efficiency cell loading and simple valveless isolation, so the proteolytic activity of a small sample (10–100 cells) can be easily characterized. Combined with a single cell derived (clonal) sphere formation platform, we have successfully demonstrated the importance of microenvironmental cues for proteolytic activity and also investigated the difference between clones. Furthermore, the platform allows monitoring single cells at multiple time points, unveiling different cancer cell line dynamics in proteolytic activity. The presented tool facilitates single cell proteolytic analysis using small samples, and our findings illuminate the heterogeneous and dynamic nature of proteolytic activity.

  15. Myosins and cell dynamics in cellular slime molds.

    Science.gov (United States)

    Yumura, Shigehiko; Uyeda, Taro Q P

    2003-01-01

    Myosin is a mechanochemical transducer and serves as a motor for various motile activities such as cell migration, cytokinesis, maintenance of cell shape, phagocytosis, and morphogenesis. Nonmuscle myosin in vivo does not either stay static at specific subcellular regions or construct highly organized structures, such as sarcomere in skeletal muscle cells. The cellular slime mold Dictyostelium discoideum is an ideal "model organism" for the investigation of cell movement and cytokinesis. The advantages of this organism prompted researchers to carry out pioneering cell biological, biochemical, and molecular genetic studies on myosin II, which resulted in elucidation of many fundamental features of function and regulation of this most abundant molecular motor. Furthermore, recent molecular biological research has revealed that many unconventional myosins play various functions in vivo. In this article, how myosins are organized and regulated in a dynamic manner in Dictyostelium cells is reviewed and discussed. PMID:12722951

  16. Dynamic simulation of a direct carbonate fuel cell power plant

    Energy Technology Data Exchange (ETDEWEB)

    Ernest, J.B. [Fluor Daniel, Inc., Irvine, CA (United States); Ghezel-Ayagh, H.; Kush, A.K. [Fuel Cell Engineering, Danbury, CT (United States)

    1996-12-31

    Fuel Cell Engineering Corporation (FCE) is commercializing a 2.85 MW Direct carbonate Fuel Cell (DFC) power plant. The commercialization sequence has already progressed through construction and operation of the first commercial-scale DFC power plant on a U.S. electric utility, the 2 MW Santa Clara Demonstration Project (SCDP), and the completion of the early phases of a Commercial Plant design. A 400 kW fuel cell stack Test Facility is being built at Energy Research Corporation (ERC), FCE`s parent company, which will be capable of testing commercial-sized fuel cell stacks in an integrated plant configuration. Fluor Daniel, Inc. provided engineering, procurement, and construction services for SCDP and has jointly developed the Commercial Plant design with FCE, focusing on the balance-of-plant (BOP) equipment outside of the fuel cell modules. This paper provides a brief orientation to the dynamic simulation of a fuel cell power plant and the benefits offered.

  17. Effects of hydrogen-bond environment on single particle and pair dynamics in liquid water

    Indian Academy of Sciences (India)

    Amalendu Chandra; Snehasis Chowdhuri

    2001-10-01

    We have performed molecular dynamics simulations of liquid water at 298 and 258 K to investigate the effects of hydrogen-bond environment on various single-particle and pair dynamical properties of water molecules at ambient and supercooled conditions. The water molecules are modelled by the extended simple point charge (SPC/E) model. We first calculate the distribution of hydrogen-bond environment in liquid water at both temperatures and then investigate how the selfdiffusion and orientational relaxation of a single water molecule and also the relative diffusion and relaxation of the hydrogen-bond of a water pair depend on the nature of the hydrogen-bond environment of the tagged molecules. We find that the various dynamical quantities depend significantly on the hydrogen-bond environment, especially at the supercooled temperature. The present study provides a molecular-level insight into the dynamics of liquid water under ambient and supercooled conditions.

  18. Simulating long-term carbon and water dynamics in northern peatlands (Invited)

    Science.gov (United States)

    Frolking, S. E.; Roulet, N. T.; Quillet, A.; Tuittila, E.; Bubier, J. L.

    2009-12-01

    We present a new model that simulates coupled carbon and water dynamics of northern peatlands at an annual time step over time scales of decades to millennia. The Holocene Peatland Model (HPM) simulates peatland carbon and water dynamics as the net consequence of several interacting processes: (1) above- and below-ground vegetation NPP and litter production for bryophytes and vascular plants; (2) aerobic and anaerobic litter/peat decomposition down the peat profile; (3) the dependence of peat physical and hydraulic properties on peat humification; and (4) peatland annual water balance, water table depth, and unsaturated zone water content. The model generates time series of vegetation, carbon and water dynamics over a 5000-10000 year simulation, and a ‘final state’ peat core that can be compared to contemporary peat core data. The sensitivities of peatland carbon and water dynamics to climate and climate variability and to succession rate are evaluated.

  19. The Environmental Effect on the Dynamical Behaviors of Single-Walled Carbon Nanotube in Water

    OpenAIRE

    Yan Yan; Weizhong Li; Wenquan Wang

    2014-01-01

    The paper investigates the dynamical behaviors of single-walled carbon nanotube (SWCNT) in water, focusing on the effect of external environment (i.e., water) on SWCNT. The SWCNT-water system comprises three constituent parts, that is, the SWCNT, the absorbed layer of water molecules, and the water flow around the water layer. The SWCNT and the absorbed layer of water are modeled as two-layer thin shells coupled via the interlayer vdW interaction, and the water surrounding the absorbed water ...

  20. A positive feedback cell signaling nucleation model of astrocyte dynamics

    Directory of Open Access Journals (Sweden)

    Gabriel A Silva

    2013-07-01

    Full Text Available We constructed a model of calcium signaling in astrocyte neural glial cells that incorporates a positive feedback nucleation mechanism, whereby small microdomain increases in local calcium can stochastically produce global cellular and intercellular network scale dynamics. The model is able to simultaneously capture dynamic spatial and temporal heterogeneities associated with intracellular calcium transients in individual cells and intercellular calcium waves (ICW in spatially realistic networks of astrocytes, i.e. networks where the positions of cells were taken from real in vitro experimental data of spontaneously forming sparse networks, as opposed to artificially constructed grid networks or other non-realistic geometries. This is the first work we are aware of where an intracellular model of calcium signaling that reproduces intracellular dynamics inherently accounts for intercellular network dynamics. These results suggest that a nucleation type mechanism should be further investigated experimentally in order to test its contribution to calcium signaling in astrocytes and in other cells more broadly. It may also be of interest in engineered neuromimetic network systems that attempt to emulate biological signaling and information processing properties in synthetic hardwired neuromorphometric circuits or coded algorithms.

  1. Real space Dynamical Super Cell Approximation for interacting disordered systems

    OpenAIRE

    Moradian, Rostam

    2004-01-01

    Effective medium super-cell approximation method which is introduced for disordered systems is extended to a general case of interacting disordered systems. We found that the dynamical cluster approximation (DCA) and also the non local coherent potential approximation (NLCPA) are two simple case of this technique. Whole equations of this formalism derived by using the effective medium theory in real space.

  2. Dynamic heterogeneity and DNA methylation in embryonic stem cells.

    KAUST Repository

    Singer, Zakary S

    2014-07-01

    Cell populations can be strikingly heterogeneous, composed of multiple cellular states, each exhibiting stochastic noise in its gene expression. A major challenge is to disentangle these two types of variability and to understand the dynamic processes and mechanisms that control them. Embryonic stem cells (ESCs) provide an ideal model system to address this issue because they exhibit heterogeneous and dynamic expression of functionally important regulatory factors. We analyzed gene expression in individual ESCs using single-molecule RNA-FISH and quantitative time-lapse movies. These data discriminated stochastic switching between two coherent (correlated) gene expression states and burst-like transcriptional noise. We further showed that the "2i" signaling pathway inhibitors modulate both types of variation. Finally, we found that DNA methylation plays a key role in maintaining these metastable states. Together, these results show how ESC gene expression states and dynamics arise from a combination of intrinsic noise, coherent cellular states, and epigenetic regulation.

  3. Dynamics of aluminum leaching from water purification sludge.

    Science.gov (United States)

    Cheng, Wen-Po; Fu, Chi-Hua; Chen, Ping-Hung; Yu, Ruey-Fang

    2012-05-30

    In this investigation, the shrinking core model is used to study the rate of aluminum salt leaching from water purification sludge (WPS). This model, which describes the aluminum leaching rate, can be developed to maximize the Al(III) recovering efficiency. Laboratory results indicate that when the mixing speed exceeds 80rpm, the effect of film diffusion control on the leaching process is greatly reduced, such that any further increase in the mixing speed does not affect the Al(III) leaching rate. Additionally, increasing the temperature or acid concentration improves Al(III) leaching rate. The laboratory data were verified by using the shrinking core model to confirm that the leaching of Al(III) from WPS is consistent with the inert-layer diffusion control model. This finding reveals that large amounts of SiO(2), Al(2)O(3) and other inert constituents will form an inter diffusion layer in the WPS and thus become the major limiting factors that control the Al(III) leaching process. The dynamic equation can be expressed as 1-3(1-x)(2/3)+2(1-x)=(2707.3 exp(-3887.6/T))t, in which the apparent activation energy and pre-exponential factors are 32.32 kJ/mol and 2707.3 min(-1), respectively, as determined by solving the Arrhenius equation. PMID:22459977

  4. A stochastic dynamic programming model for stream water quality management

    Indian Academy of Sciences (India)

    P P Mujumdar; Pavan Saxena

    2004-10-01

    This paper deals with development of a seasonal fraction-removal policy model for waste load allocation in streams addressing uncertainties due to randomness and fuzziness. A stochastic dynamic programming (SDP) model is developed to arrive at the steady-state seasonal fraction-removal policy. A fuzzy decision model (FDM) developed by us in an earlier study is used to compute the system performance measure required in the SDP model. The state of the system in a season is defined by streamflows at the headwaters during the season and the initial DO deficit at some pre-specified checkpoints. The random variation of streamflows is included in the SDP model through seasonal transitional probabilities. The decision vector consists of seasonal fraction-removal levels for the effluent dischargers. Uncertainty due to imprecision (fuzziness) associated with water quality goals is addressed using the concept of fuzzy decision. Responses of pollution control agencies to the resulting end-of-season DO deficit vector and that of dischargers to the fraction-removal levels are treated as fuzzy, and modelled with appropriate membership functions. Application of the model is illustrated with a case study of the Tungabhadra river in India.

  5. Stochastic dynamics of interacting haematopoietic stem cell niche lineages.

    Directory of Open Access Journals (Sweden)

    Tamás Székely

    2014-09-01

    Full Text Available Since we still know very little about stem cells in their natural environment, it is useful to explore their dynamics through modelling and simulation, as well as experimentally. Most models of stem cell systems are based on deterministic differential equations that ignore the natural heterogeneity of stem cell populations. This is not appropriate at the level of individual cells and niches, when randomness is more likely to affect dynamics. In this paper, we introduce a fast stochastic method for simulating a metapopulation of stem cell niche lineages, that is, many sub-populations that together form a heterogeneous metapopulation, over time. By selecting the common limiting timestep, our method ensures that the entire metapopulation is simulated synchronously. This is important, as it allows us to introduce interactions between separate niche lineages, which would otherwise be impossible. We expand our method to enable the coupling of many lineages into niche groups, where differentiated cells are pooled within each niche group. Using this method, we explore the dynamics of the haematopoietic system from a demand control system perspective. We find that coupling together niche lineages allows the organism to regulate blood cell numbers as closely as possible to the homeostatic optimum. Furthermore, coupled lineages respond better than uncoupled ones to random perturbations, here the loss of some myeloid cells. This could imply that it is advantageous for an organism to connect together its niche lineages into groups. Our results suggest that a potential fruitful empirical direction will be to understand how stem cell descendants communicate with the niche and how cancer may arise as a result of a failure of such communication.

  6. Molecular dynamics simulation of water between two charged layers of dipalmitoylphosphatidylserine

    NARCIS (Netherlands)

    Cascales, J.J.L.; Berendsen, H.J.C.; delaTorre, J.G.

    1996-01-01

    A molecular dynamics simulation of water between two charged layers of dipalmitoylphosphatidylserine in its liquid-crystalline state with atomic detail was carried out. From an analysis of a trajectory of 184 ps of length, we obtained information about the dynamics and structure of water between suc

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

    DEFF Research Database (Denmark)

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

    2007-01-01

    We have studied the dynamics of water molecules in six crystal structures of four human cytochromes P450, 2A6, 2C8, 2C9, and 3A4, with molecular dynamics simulations. In the crystal structures, only a few water molecules are seen and the reported sizes of the active-site cavity vary a lot. In the...

  8. Monitoring of chromosome dynamics of single yeast cells in a microfluidic platform with aperture cell traps.

    Science.gov (United States)

    Jin, Si Hyung; Jang, Sung-Chan; Lee, Byungjin; Jeong, Heon-Ho; Jeong, Seong-Geun; Lee, Sung Sik; Kim, Keun Pil; Lee, Chang-Soo

    2016-04-12

    Chromosome movement plays important roles in DNA replication, repair, genetic recombination, and epigenetic phenomena during mitosis and meiosis. In particular, chromosome movement in the nuclear space is essential for the reorganization of the nucleus. However, conventional methods for analyzing the chromosome movements in vivo have been limited by technical constraints of cell trapping, cell cultivation, oxygenation, and in situ imaging. Here, we present a simple microfluidic platform with aperture-based cell trapping arrays to monitor the chromosome dynamics in single living cells for a desired period of time. Under the optimized conditions, our microfluidic platform shows a single-cell trapping efficiency of 57%. This microfluidic approach enables in situ imaging of intracellular dynamics in living cells responding to variable input stimuli under the well-controlled microenvironment. As a validation of this microfluidic platform, we investigate the fundamental features of the dynamic cellular response of the individual cells treated with different stimuli and drug. We prove the basis for dynamic chromosome movement in single yeast cells to be the telomere and nuclear envelope ensembles that attach to and move in concert with nuclear actin cables. Therefore, these results illustrate the monitoring of cellular functions and obtaining of dynamic information at a high spatiotemporal resolution through the integration of a simple microfluidic platform. PMID:26980179

  9. Dynamic neural network controller model of PEM fuel cell system

    Energy Technology Data Exchange (ETDEWEB)

    Hatti, Mustapha [Nuclear Technologies Division, Nuclear Research Center of Birine, Ain Oussera, B.P 180, 17200 Djelfa (Algeria); Tioursi, Mustapha [Electrical Engineering Department, University of Sciences and Technology of Oran, B.P 1505, El M' Naouar, 31000 Oran (Algeria)

    2009-06-15

    This paper presents the artificial intelligence techniques to control a proton exchange membrane fuel cell system process, using particularly a methodology of dynamic neural network. In this work a dynamic neural network control model is obtained by introducing a delay line in the input of the neural network. A static production system including a PEMFC is subjected to variations of active and reactive power. Therefore the goal is to make the system follow these imposed variations. The simulation requires the modelling of the principal element (PEMFC) in dynamic mode. The simulation results demonstrate that the model-based dynamic neural network control scheme is appropriate for controlling, the stability of the identification and the tracking error were analyzed, and some reasons for the usefulness of this methodology are given. (author)

  10. Photon Counts Statistics in Leukocyte Cell Dynamics

    International Nuclear Information System (INIS)

    In the present experiment ultra-weak photon emission/chemiluminescence from isolated neutrophils was recorded. It is associated with the production of reactive oxygen species (ROS) in the 'respiratory burst' process which can be activated by PMA (Phorbol 12-Myristate 13-Acetate). Commonly, the reaction is demonstrated utilizing the enhancer luminol. However, with the use of highly sensitive photomultiplier equipment it is also recorded without enhancer. In that case, it can be hypothesized that photon count statistics may assist in understanding the underlying metabolic activity and cooperation of these cells. To study this hypothesis leukocytes were stimulated with PMA and increased photon signals were recorded in the quasi stable period utilizing Fano factor analysis at different window sizes. The Fano factor is defined by the variance over the mean of the number of photon within the observation time. The analysis demonstrated that the Fano factor of true signal and not of the surrogate signals obtained by random shuffling increases when the window size increased. It is concluded that photon count statistics, in particular Fano factor analysis, provides information regarding leukocyte interactions. It opens the perspective to utilize this analytical procedure in (in vivo) inflammation research. However, this needs further validation.

  11. Impact of Interfacial Water Transport in PEMFCs on Cell Performance

    International Nuclear Information System (INIS)

    Coupled cell performance evaluation, liquid water visualization by neutron radiography (NRG) and numerical modeling based on multiphase mixture (M2) model were performed with three types of GDMs: Micro Porous Layer (MPL) free; Carbon Paper (CP) with MPL; and CP free to investigate interfacial liquid water transport phenomena in PEMFCs and its effect on cell performance. The visualized results of MPL free GDM with different wettability of bi-polar plates (BPPs) showed hydrophilic BPP improved liquid water transport at the interface between CP and channel. Numerical modeling results indicated that this difference with BPP wettability was caused by the liquid water coverage difference on CP surface. Thus, controlling liquid water coverage is the one of the key strategies for improving cell performance. Additionally, liquid water distributions across the cell for three types of GDMs were compared and significant difference in liquid water content at the interface between Catalyst Layer (CL) and GDM was observed. Numerical modeling suggests this difference is influenced by the gap at the interface and that the MPL could minimize this effect. The CP free cell (i.e. only MPL) showed the best performance and the lowest liquid water content. There were multiple impacts of interfacial liquid water transport both at CL-GDM and GDM-channel interfaces. High hydrophobicity and fine structure of MPLs contributed to enhanced liquid water transport at GDM-channel interface and as a result reduced the liquid water coverage. At the same time, MPL improves contact at the CL-GDM interface in the same manner as seen in CP with MPL case. Thus, the CP free concept showed the best performance. It is suggested that the design of the interface between each component of the PEMFC has a great impact on cell performance and plays a significant role in achievement of high current density operation and cost reduction in FCEVs

  12. Unusual dynamic properties of water near the ice-binding plane of hyperactive antifreeze protein

    International Nuclear Information System (INIS)

    The dynamical properties of solvation water of hyperactive antifreeze protein from Choristoneura fumiferana (CfAFP) are analyzed and discussed in context of its antifreeze activity. The protein comprises of three well-defined planes and one of them binds to the surface of ice. The dynamical properties of solvation water around each of these planes were analyzed separately; the results are compared with the dynamical properties of solvation water of ice around its two crystallographic planes: basal and prism. Three main conclusions are inferred from our investigations. The first one is that the solvation shell of CfAFP does not seem to be particularly far-ranged, at least not beyond what is usually observed for proteins that do not interact with ice. Therefore, it does not appear to us that the antifreeze activity is enhanced by a long-ranged retardation of water mobility. Also the correlation between the collective mobility of water and the collective mobility of protein atoms highly resembles the one measured for the protein that does not interact with ice. Our second conclusion is that the dynamical properties of solvation water of CfAFP are non-uniform. The dynamics of solvation water of ice-binding plane is, in some respects, different from the dynamics of solvation water of the two remaining planes. The feature that distinguishes the dynamics of solvation water of the three planes is the activation energy of diffusion process. The third conclusion is that—from the three analyzed solvation shells of CfAFP—the dynamical properties of solvation water of the ice-binding plane resemble the most the properties of solvation water of ice; note, however, that these properties still clearly differ from the dynamic properties of solvation water of ice

  13. Unusual dynamic properties of water near the ice-binding plane of hyperactive antifreeze protein

    Energy Technology Data Exchange (ETDEWEB)

    Kuffel, Anna; Czapiewski, Dariusz; Zielkiewicz, Jan, E-mail: jaz@chem.pg.gda.pl [Department of Chemistry, Gdansk University of Technology, Narutowicza 11/12, 80–233 Gdansk (Poland)

    2015-10-07

    The dynamical properties of solvation water of hyperactive antifreeze protein from Choristoneura fumiferana (CfAFP) are analyzed and discussed in context of its antifreeze activity. The protein comprises of three well-defined planes and one of them binds to the surface of ice. The dynamical properties of solvation water around each of these planes were analyzed separately; the results are compared with the dynamical properties of solvation water of ice around its two crystallographic planes: basal and prism. Three main conclusions are inferred from our investigations. The first one is that the solvation shell of CfAFP does not seem to be particularly far-ranged, at least not beyond what is usually observed for proteins that do not interact with ice. Therefore, it does not appear to us that the antifreeze activity is enhanced by a long-ranged retardation of water mobility. Also the correlation between the collective mobility of water and the collective mobility of protein atoms highly resembles the one measured for the protein that does not interact with ice. Our second conclusion is that the dynamical properties of solvation water of CfAFP are non-uniform. The dynamics of solvation water of ice-binding plane is, in some respects, different from the dynamics of solvation water of the two remaining planes. The feature that distinguishes the dynamics of solvation water of the three planes is the activation energy of diffusion process. The third conclusion is that—from the three analyzed solvation shells of CfAFP—the dynamical properties of solvation water of the ice-binding plane resemble the most the properties of solvation water of ice; note, however, that these properties still clearly differ from the dynamic properties of solvation water of ice.

  14. Nonlinear Dynamic Theory of Acute Cell Injuries and Brain Ischemia

    Science.gov (United States)

    Taha, Doaa; Anggraini, Fika; Degracia, Donald; Huang, Zhi-Feng

    2015-03-01

    Cerebral ischemia in the form of stroke and cardiac arrest brain damage affect over 1 million people per year in the USA alone. In spite of close to 200 clinical trials and decades of research, there are no treatments to stop post-ischemic neuron death. We have argued that a major weakness of current brain ischemia research is lack of a deductive theoretical framework of acute cell injury to guide empirical studies. A previously published autonomous model based on the concept of nonlinear dynamic network was shown to capture important facets of cell injury, linking the concept of therapeutic to bistable dynamics. Here we present an improved, non-autonomous formulation of the nonlinear dynamic model of cell injury that allows multiple acute injuries over time, thereby allowing simulations of both therapeutic treatment and preconditioning. Our results are connected to the experimental data of gene expression and proteomics of neuron cells. Importantly, this new model may be construed as a novel approach to pharmacodynamics of acute cell injury. The model makes explicit that any pro-survival therapy is always a form of sub-lethal injury. This insight is expected to widely influence treatment of acute injury conditions that have defied successful treatment to date. This work is supported by NIH NINDS (NS081347) and Wayne State University President's Research Enhancement Award.

  15. Charge-Dependent Dynamics of Polyelectrolyte Dendrimer and Its Correlation with Invasive Water

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Wei-Ren [ORNL; Hong, Kunlun [ORNL; Li, Xin [ORNL; Liu, Emily [Rensselaer Polytechnic Institute (RPI); Liu, Yun [National Institute of Standards and Technology (NIST); Porcar, L. [National Institute of Standards and Technology (NIST); Smith, Gregory Scott [ORNL; Wu, Bin [ORNL; Mamontov, Eugene [ORNL; Egami, T. [University of Tennessee (UTK) and Oak Ridge National Laboratory (ORNL); Kolesnikov, Alexander I [ORNL; Diallo, Souleymane Omar [Oak Ridge National Laboratory (ORNL)

    2013-01-01

    Atomistic molecular dynamics (MD) simulations were carried out to investigate the local dynamics of polyelectrolyte dendrimers dissolved in deuterium oxide (D2O) and its dependence on molecular charge. Enhanced segmental dy-namics upon increase in molecular charge is observed, consistent with quasielastic neutron scattering (QENS) measurements. A strong coupling between the intra-dendrimer local hydration level and segmental dynamics is also revealed. Compelling evidence shows these findings originate from the electrostatic interaction between the hydrocarbon components of dendrimer and invasive water. This combined study provides fundamental insight into the dynamics of charged polyelectrolytes and the solvating water molecules.

  16. Coupling of the hydration water dynamics and the internal dynamics of actin detected by quasielastic neutron scattering

    International Nuclear Information System (INIS)

    Highlights: ► Quasielastic neutron scattering spectra of F-actin and G-actin were measured. ► Analysis of the samples in D2O and H2O provided the spectra of hydration water. ► The first layer hydration water around F-actin is less mobile than around G-actin. ► This difference in hydration water is in concert with the internal dynamics of actin. ► Water outside the first layer behaves bulk-like but influenced by the first layer. -- Abstract: In order to characterize dynamics of water molecules around F-actin and G-actin, quasielastic neutron scattering experiments were performed on powder samples of F-actin and G-actin, hydrated either with D2O or H2O, at hydration ratios of 0.4 and 1.0. By combined analysis of the quasielastic neutron scattering spectra, the parameter values characterizing the dynamics of the water molecules in the first hydration layer and those of the water molecules outside of the first layer were obtained. The translational diffusion coefficients (DT) of the hydration water in the first layer were found to be 1.2 × 10−5 cm2/s and 1.7 × 10−5 cm2/s for F-actin and G-actin, respectively, while that for bulk water was 2.8 × 10−5 cm2/s. The residence times were 6.6 ps and 5.0 ps for F-actin and G-actin, respectively, while that for bulk water was 0.62 ps. These differences between F-actin and G-actin, indicating that the hydration water around G-actin is more mobile than that around F-actin, are in concert with the results of the internal dynamics of F-actin and G-actin, showing that G-actin fluctuates more rapidly than F-actin. This implies that the dynamics of the hydration water is coupled to the internal dynamics of the actin molecules. The DT values of the water molecules outside of the first hydration layer were found to be similar to that of bulk water though the residence times are strongly affected by the first hydration layer. This supports the recent observation on intracellular water that shows bulk-like behavior

  17. A decision support tool for sustainable planning of urban water systems: presenting the Dynamic Urban Water Simulation Model.

    Science.gov (United States)

    Willuweit, Lars; O'Sullivan, John J

    2013-12-15

    Population growth, urbanisation and climate change represent significant pressures on urban water resources, requiring water managers to consider a wider array of management options that account for economic, social and environmental factors. The Dynamic Urban Water Simulation Model (DUWSiM) developed in this study links urban water balance concepts with the land use dynamics model MOLAND and the climate model LARS-WG, providing a platform for long term planning of urban water supply and water demand by analysing the effects of urbanisation scenarios and climatic changes on the urban water cycle. Based on potential urbanisation scenarios and their effects on a city's water cycle, DUWSiM provides the functionality for assessing the feasibility of centralised and decentralised water supply and water demand management options based on forecasted water demand, stormwater and wastewater generation, whole life cost and energy and potential for water recycling. DUWSiM has been tested using data from Dublin, the capital of Ireland, and it has been shown that the model is able to satisfactorily predict water demand and stormwater runoff. PMID:24183560

  18. The Dynamics of Interactions Among Immune and Glioblastoma Cells.

    Science.gov (United States)

    Eder, Katalin; Kalman, Bernadette

    2015-12-01

    Glioblastoma is the most common intracranial malignancy that constitutes about 50 % of all gliomas. Despite aggressive, multimodal therapy consisting of surgery, radiation, and chemotherapy, the outcome of patients with glioblastoma remains poor with 5-year survival rates of <10 %. Resistance to conventional therapies is most likely caused by several factors. Alterations in the functions of local immune mediators may represent a critical contributor to this resistance. The tumor microenvironment contains innate and adaptive immune cells in addition to the cancer cells and their surrounding stroma. These various cells communicate with each other by means of direct cell-cell contact or by soluble factors including cytokines and chemokines, and act in autocrine and paracrine manners to modulate tumor growth. There are dynamic interactions among the local immune elements and the tumor cells, where primarily the protective immune cells attempt to overcome the malignant cells. However, by developing somatic mutations and epigenetic modifications, the glioblastoma tumor cells acquire the capability of counteracting the local immune responses, and even exploit the immune cells and products for their own growth benefits. In this review, we survey those immune mechanisms that likely contribute to glioblastoma pathogenesis and may serve as a basis for novel treatment strategies. PMID:26224516

  19. Microenvironment-Centred Dynamics in Aggressive B-Cell Lymphomas

    Directory of Open Access Journals (Sweden)

    Matilde Cacciatore

    2012-01-01

    Full Text Available Aggressive B-cell lymphomas share high proliferative and invasive attitudes and dismal prognosis despite heterogeneous biological features. In the interchained sequence of events leading to cancer progression, neoplastic clone-intrinsic molecular events play a major role. Nevertheless, microenvironment-related cues have progressively come into focus as true determinants for this process. The cancer-associated microenvironment is a complex network of nonneoplastic immune and stromal cells embedded in extracellular components, giving rise to a multifarious crosstalk with neoplastic cells towards the induction of a supportive milieu. The immunological and stromal microenvironments have been classically regarded as essential partners of indolent lymphomas, while considered mainly negligible in the setting of aggressive B-cell lymphomas that, by their nature, are less reliant on external stimuli. By this paper we try to delineate the cardinal microenvironment-centred dynamics exerting an influence over lymphoid clone progression in aggressive B-cell lymphomas.

  20. Femtosecond vibrational dynamics in water nano-droplets

    NARCIS (Netherlands)

    Cringus, Gheorghe Dan

    2008-01-01

    Water is probably the most researched substance on Earth. The interest in water, and redominantly in liquid water, is due to its importance on both macro- and microscopic scales. Although people have been trying to understand water for centuries, this ubiquitous liquid is still surrounded by mystery

  1. Dynamic cell performance of kW-grade proton exchange membrane fuel cell stack with dead-ended anode

    International Nuclear Information System (INIS)

    Highlights: • A kW-grade fuel cell stack with anode dead-ended mode was examined. • The dead-ended anode is achieved by controlling the anode outlet solenoid valve. • Results indicated an optimal purge interval and duration for cell performance. - Abstract: This paper examines the dynamic cell performance of a kW-grade proton exchange membrane fuel cell stack with anode dead-ended mode fuel supply. A self-made kW-grade 40 cells stack with reaction area of 112.85 cm2 has been used in the experiment. A single-chip (DSPIC30F4011) is utilized for establishing a control circuit to monitor the voltage and current with constant-current loading. The stack temperature is controlled at a low-level temperature rise. To enhance the hydrogen utilization and reduce the water flooding in the fuel cell stack, the dead-ended anode operation is accomplished by controlling the open or close of the anode outlet solenoid valve. As the loading is heavy, the anode outlet solenoid valve is purged frequently to force the water to flow out. While a light load, the anode outlet solenoid valve is shut down for a period time for hydrogen saving. The solenoid valve is controlled to be opened, referred as purge interval, reaching the discharge amount for 1000 C, 1500 C, and 2000 C as parameter, respectively. The open period of solenoid valve, referred as purge duration, is set as 1 s, 3 s, and 5 s for this study. Experimental results indicate an optimal purge interval and duration for water management and cell performance of the fuel cell stack

  2. The dynamic relationship between property rights, water resource management and poverty in the Lake Victoria Basin.

    OpenAIRE

    Orindi, V.; Huggins, C.

    2005-01-01

    This review aims to synthesize information on the dynamic relationships between property rights to land and natural resources, water resource management and poverty in the Lake Victoria Basin of East Africa. It focuses on the way in which water management systems, under the conceptual umbrella of Integrated Water Resources Management (IWRM), address customary claims to land and water. The water sector in all the three countries is being reformed, decentralized and liberalized to improve effic...

  3. Microbial Species Diversity, Community Dynamics, and Metabolite Kinetics of Water Kefir Fermentation

    OpenAIRE

    Laureys, David; De Vuyst, Luc

    2014-01-01

    Water kefir is a sour, alcoholic, and fruity fermented beverage of which the fermentation is started with water kefir grains. These water kefir grains consist of polysaccharide and contain the microorganisms responsible for the water kefir fermentation. In this work, a water kefir fermentation process was followed as a function of time during 192 h to unravel the community dynamics, the species diversity, and the kinetics of substrate consumption and metabolite production. The majority of the...

  4. Transcriptome Dynamics of Pseudomonas putida KT2440 under Water Stress

    OpenAIRE

    Gülez, Gamze; Dechesne, Arnaud; Workman, Christopher T.; Smets, Barth F

    2012-01-01

    Water deprivation can be a major stressor to microbial life in surface and subsurface soil. In unsaturated soils, the matric potential (Ψm) is often the main component of the water potential, which measures the thermodynamic availability of water. A low matric potential usually translates into water forming thin liquid films in the soil pores. Little is known of how bacteria respond to such conditions, where, in addition to facing water deprivation that might impair their metabolism, they hav...

  5. Modelling water policies with sustainability constraints: a dynamic accounting analysis

    OpenAIRE

    Fabio Fiorillo; Antonio Palestrini; Paolo Polidori; Claudio Socci

    2006-01-01

    The EU Directive 2000/60/EC, also known as the “Framework directive in the field of water policy”, stresses the importance of water in human development processes and states that EU members should coordinate water policies towards a sustainable use of this resource; hence, water has a strategic role both for present and future generations and should be managed using a systemic approach. Sustainable policies for the management of water resources must also foresee the setting up of complex syst...

  6. Purinergic responses of chondrogenic stem cells to dynamic loading

    Directory of Open Access Journals (Sweden)

    Gađanski Ivana

    2013-01-01

    Full Text Available In habitually loaded tissues, dynamic loading can trigger ATP (adenosine 5’- triphosphate release to extracellular environment, and result in calcium signaling via ATP binding to purine P2 receptors1. In the current study we have compared purinergic responses (ATP release of two types of cells: bovine chondrocytes (bCHs and human mesenchymal stem cells (hMSC that were encapsulated in agarose and subjected to dynamic loading. Both cell types were cultured under chondrogenic conditions, and their responses to loading were evaluated by ATP release assay in combination with connexin (Cx-sensitive fluorescent dye (Lucifer Yellow - LY and a Cx-hemichannel blocker (Flufenamic acid - FFA. In response to dynamic loading, chondrogenic hMSCs released significantly higher amounts of ATP (5-fold in comparison to the bCHs early in culture (day 2. Triggering of LY uptake in the bCHs and hMSCs by dynamic loading implies opening of the Cx-hemichannels. However, the number of LY-positive cells in hMSC-constructs was 2.5-fold lower compared to the loaded bCH-constructs, suggesting utilization of additional mechanisms of ATP release. Cx-reactive sites were detected in both bCHs and hMSCs-constructs. FFA application led to reduced ATP release both in bCHs and hMSCs, which confirms the involvement of connexin hemichannels, with more prominent effects in bCHs than in hMSCs, further implying the existence of additional mechanism of ATP release in chondrogenic hMSCs. Taken together, these results indicate stronger purinergic response to dynamic loading of chondrogenic hMSCs than primary chondrocytes, by activation of connexin hemichannels and additional mechanisms of ATP release. [Projekat Ministrastva nauke Republike Srbije, ON174028 i br. III41007

  7. Modelling of water transport in the polymer electrolyte membrane of a fuel cell

    Czech Academy of Sciences Publication Activity Database

    Šimek, M.; Němec, Tomáš; Maršík, František

    Vol. 1. Liberec: Technical University of Liberec, 2010 - (Vít, T.; Dančová, P.), s. 670-686 ISBN 978-80-7372-670-6. [International Conference Experimental Fluid Mechanics 2010. Liberec (CZ), 24.11.2010-26.11.2010] R&D Projects: GA AV ČR(CZ) IAA200760801 Institutional research plan: CEZ:AV0Z20760514 Keywords : fuel cell * membrane water content * computational fluid dynamics Subject RIV: BJ - Thermodynamics

  8. Dynamics of water solutions of natural polysaccharides by fast field cycling nmr relaxometry

    Science.gov (United States)

    Prusova, Alena; Conte, Pellegrino; Kucerik, Jiri; de Pasquale, Claudio; Alonzo, Giuseppe

    2010-05-01

    Cryobiology studies the effect of low temperatures on living systems such as microorganisms and plants. In particular, plants growing in cold or frozen environments can survive such extreme conditions due to the cold hardening process. Hardening is a three step process during which, first, translocation of polysaccharides to the plant roots affects water structure in the cell-soil surface. For this reason, increase of cell-membrane permeability and resistance to temperatures from -5°C to -10°C is achieved. In a second step, chemical alteration of cell membrane arises and resistance to temperatures up to -20°C is obtained. The last hardening step consists in the vitrification of the plant tissues which allow plants to survive at temperatures as low as -50°C. Since polysaccharides play a very important role in the initial part of the cold hardening process, it is of paramount importance to study the effect of such natural biopolymers on water structure. Here, we present preliminary data obtained by fast field cycling NMR relaxometry on the effect of hyaluronan (an anionic, non-sulfated glycosaminoglycan) on water structure at different concentrations of the polysaccharide. Although hyaluronan is a polysaccharide found exceptionally in animal, human or bacterial bodies, in the present work it was used as a model "pilot" compound. In fact, it has an unique ability to hold water and it contains both polysaccharide and protein-like acetamido functionalities. For this reason, hyaluronan promotes the future research on other plant biopolymers such as, for instance, starch and other very specific proteins. Results revealed that different water-structure systems surround the molecule of hyaluronan in diluted and semidiluted systems. Namely, at the lowest hyaluronan concentration, three hydration shells can be recognized. The first hydration shell is made by bound water (BW) which is strongly fixed to the hyaluronan surface mainly through electrostatic interactions. A

  9. Cell fate reprogramming by control of intracellular network dynamics

    Science.gov (United States)

    Zanudo, Jorge G. T.; Albert, Reka

    Identifying control strategies for biological networks is paramount for practical applications that involve reprogramming a cell's fate, such as disease therapeutics and stem cell reprogramming. Although the topic of controlling the dynamics of a system has a long history in control theory, most of this work is not directly applicable to intracellular networks. Here we present a network control method that integrates the structural and functional information available for intracellular networks to predict control targets. Formulated in a logical dynamic scheme, our control method takes advantage of certain function-dependent network components and their relation to steady states in order to identify control targets, which are guaranteed to drive any initial state to the target state with 100% effectiveness and need to be applied only transiently for the system to reach and stay in the desired state. We illustrate our method's potential to find intervention targets for cancer treatment and cell differentiation by applying it to a leukemia signaling network and to the network controlling the differentiation of T cells. We find that the predicted control targets are effective in a broad dynamic framework. Moreover, several of the predicted interventions are supported by experiments. This work was supported by NSF Grant PHY 1205840.

  10. Quantitative analysis of impact measurements using dynamic load cells

    Directory of Open Access Journals (Sweden)

    Brent J. Maranzano

    2016-03-01

    Full Text Available A mathematical model is used to estimate material properties from a short duration transient impact force measured by dropping spheres onto rectangular coupons fixed to a dynamic load cell. The contact stress between the dynamic load cell surface and the projectile are modeled using Hertzian contact mechanics. Due to the short impact time relative to the load cell dynamics, an additional Kelvin–Voigt element is included in the model to account for the finite response time of the piezoelectric crystal. Calculations with and without the Kelvin–Voigt element are compared to experimental data collected from combinations of polymeric spheres and polymeric and metallic surfaces. The results illustrate that the inclusion of the Kelvin–Voigt element qualitatively captures the post impact resonance and non-linear behavior of the load cell signal and quantitatively improves the estimation of the Young's elastic modulus and Poisson's ratio. Mathematically, the additional KV element couples one additional differential equation to the Hertzian spring-dashpot equation. The model can be numerically integrated in seconds using standard numerical techniques allowing for its use as a rapid technique for the estimation of material properties.

  11. Evaluation of surface water dynamics for water-food security in seasonal wetlands, north-central Namibia

    OpenAIRE

    T. Hiyama; Suzuki, T.; Hanamura, M.; Mizuochi, H.; Kambatuku, J. R.; Niipele, J. N.; Fujioka, Y.; Ohta, T.; Iijima, M

    2014-01-01

    Agricultural use of wetlands is important for food security in various regions. However, land-use changes in wetland areas could alter the water cycle and the ecosystem. To conserve the water environments of wetlands, care is needed when introducing new cropping systems. This study is the first attempt to evaluate the water dynamics in the case of the introduction of rice-millet mixed-cropping systems to the Cuvelai system seasonal wetlands (CSSWs) in north-central Namibia. We first investiga...

  12. A Versatile Bioreactor for Dynamic Suspension Cell Culture. Application to the Culture of Cancer Cell Spheroids

    Science.gov (United States)

    Madeddu, Denise; Cerino, Giulia; Falco, Angela; Frati, Caterina; Gallo, Diego; Deriu, Marco A.; Falvo D’Urso Labate, Giuseppe; Quaini, Federico; Audenino, Alberto; Morbiducci, Umberto

    2016-01-01

    A versatile bioreactor suitable for dynamic suspension cell culture under tunable shear stress conditions has been developed and preliminarily tested culturing cancer cell spheroids. By adopting simple technological solutions and avoiding rotating components, the bioreactor exploits the laminar hydrodynamics establishing within the culture chamber enabling dynamic cell suspension in an environment favourable to mass transport, under a wide range of tunable shear stress conditions. The design phase of the device has been supported by multiphysics modelling and has provided a comprehensive analysis of the operating principles of the bioreactor. Moreover, an explanatory example is herein presented with multiphysics simulations used to set the proper bioreactor operating conditions for preliminary in vitro biological tests on a human lung carcinoma cell line. The biological results demonstrate that the ultralow shear dynamic suspension provided by the device is beneficial for culturing cancer cell spheroids. In comparison to the static suspension control, dynamic cell suspension preserves morphological features, promotes intercellular connection, increases spheroid size (2.4-fold increase) and number of cycling cells (1.58-fold increase), and reduces double strand DNA damage (1.5-fold reduction). It is envisioned that the versatility of this bioreactor could allow investigation and expansion of different cell types in the future. PMID:27144306

  13. A Versatile Bioreactor for Dynamic Suspension Cell Culture. Application to the Culture of Cancer Cell Spheroids.

    Science.gov (United States)

    Massai, Diana; Isu, Giuseppe; Madeddu, Denise; Cerino, Giulia; Falco, Angela; Frati, Caterina; Gallo, Diego; Deriu, Marco A; Falvo D'Urso Labate, Giuseppe; Quaini, Federico; Audenino, Alberto; Morbiducci, Umberto

    2016-01-01

    A versatile bioreactor suitable for dynamic suspension cell culture under tunable shear stress conditions has been developed and preliminarily tested culturing cancer cell spheroids. By adopting simple technological solutions and avoiding rotating components, the bioreactor exploits the laminar hydrodynamics establishing within the culture chamber enabling dynamic cell suspension in an environment favourable to mass transport, under a wide range of tunable shear stress conditions. The design phase of the device has been supported by multiphysics modelling and has provided a comprehensive analysis of the operating principles of the bioreactor. Moreover, an explanatory example is herein presented with multiphysics simulations used to set the proper bioreactor operating conditions for preliminary in vitro biological tests on a human lung carcinoma cell line. The biological results demonstrate that the ultralow shear dynamic suspension provided by the device is beneficial for culturing cancer cell spheroids. In comparison to the static suspension control, dynamic cell suspension preserves morphological features, promotes intercellular connection, increases spheroid size (2.4-fold increase) and number of cycling cells (1.58-fold increase), and reduces double strand DNA damage (1.5-fold reduction). It is envisioned that the versatility of this bioreactor could allow investigation and expansion of different cell types in the future. PMID:27144306

  14. Dynamics inside the cancer cell attractor reveal cell heterogeneity, limits of stability, and escape.

    Science.gov (United States)

    Li, Qin; Wennborg, Anders; Aurell, Erik; Dekel, Erez; Zou, Jie-Zhi; Xu, Yuting; Huang, Sui; Ernberg, Ingemar

    2016-03-01

    The observed intercellular heterogeneity within a clonal cell population can be mapped as dynamical states clustered around an attractor point in gene expression space, owing to a balance between homeostatic forces and stochastic fluctuations. These dynamics have led to the cancer cell attractor conceptual model, with implications for both carcinogenesis and new therapeutic concepts. Immortalized and malignant EBV-carrying B-cell lines were used to explore this model and characterize the detailed structure of cell attractors. Any subpopulation selected from a population of cells repopulated the whole original basin of attraction within days to weeks. Cells at the basin edges were unstable and prone to apoptosis. Cells continuously changed states within their own attractor, thus driving the repopulation, as shown by fluorescent dye tracing. Perturbations of key regulatory genes induced a jump to a nearby attractor. Using the Fokker-Planck equation, this cell population behavior could be described as two virtual, opposing influences on the cells: one attracting toward the center and the other promoting diffusion in state space (noise). Transcriptome analysis suggests that these forces result from high-dimensional dynamics of the gene regulatory network. We propose that they can be generalized to all cancer cell populations and represent intrinsic behaviors of tumors, offering a previously unidentified characteristic for studying cancer. PMID:26929366

  15. Dynamic observation of micronuclei and cell survival in human liver cancer cells irradiated by heavy ion

    International Nuclear Information System (INIS)

    The author reported dynamic changes of micronuclei and cell survival in human liver cancer cells SMMC-7721 irradiated by 25 MeV/u 40Ar14+. The results show: (1) Change rules of frequency of micronuclei induced by single irradiation and fractionation irradiation with culture time have not clear difference. (2) Irradiated (single, fractionation) liver cancer cells grow much slower than control and their survival number with culture time shows decay tendency. (3) Dynamic changes of the relationship between micronucleus frequency and cell survival number presents negative correlation. (4) For cells irradiated by dose of 0.68 Gy, 6.8 Gy and 68 Gy, frequency of micronuclei following culture 24 hours is lower than that following culture 96 hours. (5) Negative dependences of survival number of liver cancer cells for culture 24 hours and 48 hours on dose are demonstrated

  16. Electronic properties of semiconductor-water interfaces: Predictions from ab-initio molecular dynamics and many-body perturbation theory

    Science.gov (United States)

    Pham, Tuan Anh

    2015-03-01

    Photoelectrochemical cells offer a promising avenue for hydrogen production from water and sunlight. The efficiency of these devices depends on the electronic structure of the interface between the photoelectrode and liquid water, including the alignment between the semiconductor band edges and the water redox potential. In this talk, we will present the results of first principles calculations of semiconductor-water interfaces that are obtained with a combination of density functional theory (DFT)-based molecular dynamics simulations and many-body perturbation theory (MBPT). First, we will discuss the development of an MBPT approach that is aimed at improving the efficiency and accuracy of existing methodologies while still being applicable to complex heterogeneous interfaces consisting of hundreds of atoms. We will then present studies of the electronic structure of liquid water and aqueous solutions using MBPT, which represent an essential step in establishing a quantitative framework for computing the energy alignment at semiconductor-water interfaces. Finally, using a combination of DFT-based molecular dynamics simulations and MBPT, we will describe the relationship between interfacial structure, electronic properties of semiconductors and their reactivity in aqueous solutions through a number of examples, including functionalized Si surfaces and GaP/InP surfaces in contact with liquid water. T.A.P was supported by the U.S. Department of Energy at the Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344 and by the Lawrence Fellowship Program.

  17. Cell size dynamics and viability of cells exposed to hypotonic treatment and electroporation for electrofusion optimization:

    OpenAIRE

    Hudej, Rosana; Kandušer, Maša; Miklavčič, Damijan; Trontelj, Katja; Ušaj, Marko

    2009-01-01

    Background. Various electrofusion parameters have to be adjusted to obtain theoptimal electrofusion efficiency. Based on published data, good electrofusion conditions can be achieved with the hypotonic treatment. However, the duration of the hypotonic treatment before electroporation and buffer hypoosmolarity have to be adjusted in order to cause cell swelling, to avoid regulatory volume decrease and to preserve cell viability. The aims of our study were to determine cell size dynamics and vi...

  18. Cell size dynamics and viability of cells exposed to hypotonic treatment and electroporation for electrofusion optimization

    OpenAIRE

    Trontelj, Katja; Kandušer, Maša; Miklavčič, Damijan; Hudej, Rosana; Ušaj, Marko

    2015-01-01

    Background. Various electrofusion parameters have to be adjusted to obtain theoptimal electrofusion efficiency. Based on published data, good electrofusion conditions can be achieved with the hypotonic treatment. However, the duration of the hypotonic treatment before electroporation and buffer hypoosmolarity have to be adjusted in order to cause cell swelling, to avoid regulatory volume decrease and to preserve cell viability. The aims of our study were to determine cell size dynamics and vi...

  19. Stochastic and coherent dynamics of single and coupled beta cells

    DEFF Research Database (Denmark)

    burst period as function of an external applied stochastic term and use a technique for reducing the stochastic differential equations to ODEs for the average and higher order moments. The later method is approximate and we shall discuss the limits of validity. The individual beta cells are coupled...... phenomenon, modeled by a slow-fast nonlinear system of ordinary differential equations (ODEs). The single cell oscillations are complex as the dynamical behavior is a result of traversing a series of saddle node and homoclinic bifurcations, controlled by the slow variable. We shall present results on the...... beta cells in the simple one dimensional case and show how wave patterns can arise and propagate along the chain. These wave patterns can be blocked by inhomogeneous glucose concentration along the chain, and we shall show how the coupled cell model can be connected to the Fishers equation, which is...

  20. Dynamic Model of High Temperature PEM Fuel Cell Stack Temperature

    DEFF Research Database (Denmark)

    Andreasen, Søren Juhl; Kær, Søren Knudsen

    2007-01-01

    The present work involves the development of a model for predicting the dynamic temperature of a high temperature PEM (HTPEM) fuel cell stack. The model is developed to test different thermal control strategies before implementing them in the actual system. The test system consists of a prototype...... stack at a high stoichiometric air flow. This is possible because of the PBI fuel cell membranes used, and the very low pressure drop in the stack. The model consists of a discrete thermal model dividing the stack into three parts: inlet, middle and end and predicting the temperatures in these three...... parts, where also the temperatures are measured. The heat balance of the system involves a fuel cell model to describe the heat added by the fuel cells when a current is drawn. Furthermore the model also predicts the temperatures, when heating the stack with external heating elements for start-up, heat...

  1. Exploring neural cell dynamics with digital holographic microscopy

    KAUST Repository

    Marquet, Pierre

    2013-07-11

    In this review, we summarize how the new concept of digital optics applied to the field of holographic microscopy has allowed the development of a reliable and flexible digital holographic quantitative phase microscopy (DH-QPM) technique at the nanoscale particularly suitable for cell imaging. Particular emphasis is placed on the original biological ormation provided by the quantitative phase signal. We present the most relevant DH-QPM applications in the field of cell biology, including automated cell counts, recognition, classification, three-dimensional tracking, discrimination between physiological and pathophysiological states, and the study of cell membrane fluctuations at the nanoscale. In the last part, original results show how DH-QPM can address two important issues in the field of neurobiology, namely, multiple-site optical recording of neuronal activity and noninvasive visualization of dendritic spine dynamics resulting from a full digital holographic microscopy tomographic approach. Copyright © 2013 by Annual Reviews.

  2. Solid oxide electrolysis cell for decomposition of tritiated water

    International Nuclear Information System (INIS)

    The decomposition of tritiated water vapor with solid oxide electrolysis cell was proposed for the application to the D-T fusion reactor system. This method is essentially free from problems such as large tritium inventory, radiation damage, and generation of solid waste, so it is expected to be a promising one. Electrolysis of water vapor in argon carrier was performed using tube-type stabilized zirconia cell with porous platinum electrodes in the temperature range of 5000C to 9500C. High conversion ratio from water to hydrogen up to 99.9% was achieved. The characteristics of the cell is deduced from the Nernst's equation and conversion ratio is described as the function of the open circuit voltage. Experimental results agreed with the equation. Isotope effect in electrolysis is also discussed and experiments with heavy water were carried out. Obtained separation factor was slightly higher than the theoretical value

  3. Cell Stability Analysis of Conventional 6T Dynamic 8T SRAM Cell in 45NM Technology

    Directory of Open Access Journals (Sweden)

    K. Dhanumjaya

    2012-04-01

    Full Text Available A SRAM cell must meet requirements for operation in submicron/nano ranges. The scaling of CMOS technology has significant impact on SRAM cell -- random fluctuation of electrical characteristics and substantial leakage current. In this paper we present dynamic column based power supply 8 T SRAM cell and comparing the proposed SRAM cell with respect to conventional SRAM 6T in various aspects. To verify read stability and write ability analysis we use N-curve metric. Simulation results affirmed that proposed 8T SRAM cell achieved improved read stability, read current, and leakage current in 45nm Technology comparing with conventional 6T SRAM using cadence virtuoso tool.

  4. Growth dynamics of cancer cell colonies and their comparison with noncancerous cells

    Science.gov (United States)

    Huergo, M. A. C.; Pasquale, M. A.; González, P. H.; Bolzán, A. E.; Arvia, A. J.

    2012-01-01

    The two-dimensional (2D) growth dynamics of HeLa (cervix cancer) cell colonies was studied following both their growth front and the pattern morphology evolutions utilizing large population colonies exhibiting linearly and radially spreading fronts. In both cases, the colony profile fractal dimension was df=1.20±0.05 and the growth fronts displaced at the constant velocity 0.90±0.05 μm min-1. Colonies showed changes in both cell morphology and average size. As time increased, the formation of large cells at the colony front was observed. Accordingly, the heterogeneity of the colony increased and local driving forces that set in began to influence the dynamics of the colony front. The dynamic scaling analysis of rough colony fronts resulted in a roughness exponent α = 0.50±0.05, a growth exponent β = 0.32±0.04, and a dynamic exponent z=1.5±0.2. The validity of this set of scaling exponents extended from a lower cutoff lc≈60 μm upward, and the exponents agreed with those predicted by the standard Kardar-Parisi-Zhang continuous equation. HeLa data were compared with those previously reported for Vero cell colonies. The value of df and the Kardar-Parisi-Zhang-type 2D front growth dynamics were similar for colonies of both cell lines. This indicates that the cell colony growth dynamics is independent of the genetic background and the tumorigenic nature of the cells. However, one can distinguish some differences between both cell lines during the growth of colonies that may result from specific cooperative effects and the nature of each biosystem.

  5. Water and stress dynamics for North Carolina v. vinifera

    Science.gov (United States)

    As North Carolina wine grape (V. vinifera) production intensifies, the importance of water management must be addressed. Grape yield and composition, and consequently wine quality, are greatly influenced by the water regime under which the grapes were produced. Despite the importance of water manage...

  6. Water dynamics in hectorite clays: Influence of temperature studied by coupling neutron spin echo and molecular dynamics

    International Nuclear Information System (INIS)

    Within the wider context of water behavior in soils, and with a particular emphasis on clays surrounding underground radioactive waste packages, we present here the translational dynamics of water in clays in low hydrated states as studied by coupling molecular dynamics (MD) simulations and quasielastic neutron scattering experiments by neutron spin echo (NSE). A natural montmorillonite clay of interest is modeled by a synthetic clay which allows us to understand the determining parameters from MD simulations by comparison with the experimental values.We focus on temperatures between 300 and 350 K, i.e., the range relevant to the highlighted application. The activation energy Ea experimentally determined is 6.6 kJ/mol higher than that for bulk water. Simulations are in good agreement with experiments for the relevant set of conditions, and they give more insight into the origin of the observed dynamics. (authors)

  7. Application of quasi-elastic neutron scattering to dynamics study of confined water

    International Nuclear Information System (INIS)

    Background: Quasi-elastic neutron scattering (QENS) is an important experiment for dynamics study of confined water. It is significant to study the dynamics of confined water in cement paste. Purpose: In this paper, we have two aims. One is to present a reviewer of QENS study on dynamics of confined water in cement paste in recent years. The other is to illustrate the QENS application to the study on dynamics of confined water based on cement paste. Method: Relaxing cage model (RCM) is specially introduced for the analyses of QENS spectra. Results: Based on RCM, several parameters for describing the dynamics of confined water in cement paste, can be obtained from the analyses of QENS spectra: a fraction of mobile 'glassy' water molecules embedded in amorphous gel region surrounding the hydration products, 1-p, the capture time of confined water molecule in some place-τ0, the average translational relaxation time-<τ>, the self-diffusion coefficient-D, and a phenomenological shape parameter describing the uniform of amorphous in cement paste-β. Conclusion: All these provide a practical method for QENS study on dynamics of confined water in cement paste. (authors)

  8. Produced Water Treatment Using Microbial Fuel Cell Technology

    Energy Technology Data Exchange (ETDEWEB)

    Borole, A. P.; Campbell, R. [Campbell Applied Physics

    2011-05-20

    ORNL has developed a treatment for produced water using a combination of microbial fuel cells and electrosorption. A collaboration between Campbell Applied Physics and ORNL was initiated to further investigate development of the technology and apply it to treatment of field produced water. The project successfully demonstrated the potential of microbial fuel cells to generate electricity from organics in produced water. A steady voltage was continuously generated for several days using the system developed in this study. In addition to the extraction of electrical energy from the organic contaminants, use of the energy at the representative voltage was demonstrated for salts removal or desalination of the produced water. Thus, the technology has potential to remove organic as well as ionic contaminants with minimal energy input using this technology. This is a novel energy-efficient method to treat produced water. Funding to test the technology at larger scale is being pursued to enable application development.

  9. Dynamic properties of high structural integrity auxetic open cell foam

    Science.gov (United States)

    Scarpa, F.; Ciffo, L. G.; Yates, J. R.

    2004-02-01

    This paper illustrates various dynamic characteristics of open cell compliant polyurethane foam with auxetic (negative Poisson's ratio) behaviour. The foam is obtained from off-the-shelf open cell polyurethane grey foam with a manufacturing process based on mechanical deformation on a mould in a temperature-controlled oven. The Poisson's ratio is measured with an image processing technique based on edge detection with wavelet methods. Foam samples have been tested in a viscoelastic analyser tensile test machine to determine the Young's modulus and loss factor for small dynamic strains. The same samples have also been tested in an acoustic impedance tube to measure acoustic absorption and specific acoustic resistance and reactance with a transmissibility technique. Another set of tests has been set up on a cam plastometer machine for constant strain rate dynamic crushing analysis. All the tests have been carried out on auxetic and normal foam samples to provide a comparison between the two types of cellular solids. The results from the experimental tests are discussed and interpreted using microstructure models for cellular materials existing in the literature. The negative Poisson's ratio foam presented in this paper shows an overall superiority regarding damping and acoustic properties compared to the original conventional foam. Its dynamic crushing performance is also significantly superior to the normal foam, suggesting a possible use in structural integrity compliant elements.

  10. Single cell growth and gene expression dynamics in model organisms

    OpenAIRE

    Cookson, Natalie Anne

    2009-01-01

    The developing discipline of synthetic biology attempts to recreate in artificial systems the emergent properties found in natural biology. Progress in this field requires a thorough understanding of the basic cellular functions that underly complex biological networks. Here, we present several studies that use existing and novel methods to probe the dynamic behavior of the model organisms Saccharomyces cerevisiae and Escherichia coli at the single cell level. First, we develop a microfluidic...

  11. Dynamic electrical behavior of halide perovskite based solar cells

    OpenAIRE

    Nemnes, George Alexandru; Besleaga, Cristina; Tomulescu, Andrei Gabriel; Pintilie, Ioana; Pintilie, Lucian; Torfason, Kristinn; Manolescu, Andrei

    2016-01-01

    A dynamic electrical model is introduced to investigate the hysteretic effects in the I-V characteristics of perovskite based solar cells. By making a simple ansatz for the polarization relaxation, our model is able to reproduce qualitatively and quantitatively detailed features of measured I-V characteristics. Pre-poling effects are discussed, pointing out the differences between initially over- and under-polarized samples. In particular, the presence of the current over-shoot observed in th...

  12. Feedback Linearized Aircraft Control Using Dynamic Cell Structure

    Science.gov (United States)

    Jorgensen, C. C.

    1998-01-01

    A Dynamic Cell Structure (DCS ) Neural Network was developed which learns a topology representing network (TRN) of F-15 aircraft aerodynamic stability and control derivatives. The network is combined with a feedback linearized tracking controller to produce a robust control architecture capable of handling multiple accident and off-nominal flight scenarios. This paper describes network and its performance for accident scenarios including differential stabilator lock, soft sensor failure, control, stability derivative variation, and turbulence.

  13. Computational Systems Biology Analysis of Cell Reprogramming and Activation Dynamics

    OpenAIRE

    Fu, Yan

    2012-01-01

    In the past two decades, molecular cell biology has transitioned from a traditional descriptive science into a quantitative science that systematically measures cellular dynamics on different levels of genome, transcriptome and proteome. Along with this transition emerges the interdisciplinary field of systems biology, which aims to unravel complex interactions in biological systems through integrating experimental data into qualitative or quantitative models and computer simulations. In th...

  14. Dual interference channel quantitative phase microscopy of live cell dynamics

    OpenAIRE

    Shaked, Natan T.; Rinehart, Matthew T.; Wax, Adam

    2009-01-01

    We introduce and experimentally demonstrate a new fast and accurate method for quantitative imaging of the dynamics of live biological cells. Using a dual-channel interferometric setup, two phase-shifted interferograms of nearly-transparent biological samples are acquired in a single digital camera exposure, and digitally processed into the phase profile of the sample. Since two interferograms of the same sample are acquired simultaneously, most of the common phase noise is eliminated, enabli...

  15. Structure, dynamics and stability of water/scCO2/mineral interfaces from ab initio molecular dynamics simulations

    OpenAIRE

    Mal-Soon Lee; B. Peter McGrail; Roger Rousseau; Vassiliki-Alexandra Glezakou

    2015-01-01

    The boundary layer at solid-liquid interfaces is a unique reaction environment that poses significant scientific challenges to characterize and understand by experimentation alone. Using ab initio molecular dynamics (AIMD) methods, we report on the structure and dynamics of boundary layer formation, cation mobilization and carbonation under geologic carbon sequestration scenarios (T = 323 K and P = 90 bar) on a prototypical anorthite (001) surface. At low coverage, water film formation is ent...

  16. Deep water provenance and dynamics of the (de)glacial Atlantic meridional overturning circulation

    Science.gov (United States)

    Lippold, Jörg; Gutjahr, Marcus; Blaser, Patrick; Christner, Emanuel; de Carvalho Ferreira, Maria Luiza; Mulitza, Stefan; Christl, Marcus; Wombacher, Frank; Böhm, Evelyn; Antz, Benny; Cartapanis, Olivier; Vogel, Hendrik; Jaccard, Samuel L.

    2016-07-01

    Reconstructing past modes of ocean circulation is an essential task in paleoclimatology and paleoceanography. To this end, we combine two sedimentary proxies, Nd isotopes (εNd) and the 231Pa/230Th ratio, both of which are not directly involved in the global carbon cycle, but allow the reconstruction of water mass provenance and provide information about the past strength of overturning circulation, respectively. In this study, combined 231Pa/230Th and εNd down-core profiles from six Atlantic Ocean sediment cores are presented. The data set is complemented by the two available combined data sets from the literature. From this we derive a comprehensive picture of spatial and temporal patterns and the dynamic changes of the Atlantic Meridional Overturning Circulation over the past ∼25 ka. Our results provide evidence for a consistent pattern of glacial/stadial advances of Southern Sourced Water along with a northward circulation mode for all cores in the deeper (>3000 m) Atlantic. Results from shallower core sites support an active overturning cell of shoaled Northern Sourced Water during the LGM and the subsequent deglaciation. Furthermore, we report evidence for a short-lived period of intensified AMOC in the early Holocene.

  17. Dynamic Switch Between Two Adhesion Phenotypes in Colorectal Cancer Cells.

    Science.gov (United States)

    Geng, Yue; Chandrasekaran, Siddarth; Agastin, Sivaprakash; Li, Jiahe; King, Michael R

    2014-01-01

    The hematogenous metastatic cascade is mediated by the interaction of cancer cells and the endothelial cell lining of blood vessels. In this work, we examine the colon cancer cell line COLO 205, which grows simultaneously in both adherent and suspended states in culture and can serve as a good model for studying tumor heterogeneity. The two subpopulations of cells have different molecular characteristics despite being from the same parent cell line. We found that the ratio of adherent to suspended cells in culture is maintained at 7:3 (equilibrium ratio). The ratio was maintained even when we separate the two populations and culture them separately. After 8 h in culture the equilibrium was achieved only from either adherent or suspended population. The adherent cells were found to express less E-selectin binding glycans and demonstrated significantly weaker interaction with E-selectin under flow than the suspended cells. Manipulation of the epithelial-mesenchymal transition (EMT) markers β-catenin and E-cadherin expression, either by siRNA knockdown of β-catenin or incubation with E-cadherin antibody-coated microbeads, shifted the ratio of adherent to suspended cells to 9:1. Interestingly, human plasma supplemented media shifted the ratio of adherent to suspended cells in the opposite direction to 1:9, favoring the suspended state. The dynamic COLO 205 population switch presents unique differential phenotypes of their subpopulations and could serve as a good model for studying cell heterogeneity and the EMT process in vitro. PMID:24575161

  18. Photoelectrochemical decomposition of water utilizing monolithic tandem cells

    Energy Technology Data Exchange (ETDEWEB)

    Kocha, Shyam S.; Montgomery, Don; Peterson, Mark W.; Turner, John A. [National Renewable Energy Laboratory, Golden, CO (United States)

    1998-04-30

    Photovoltaic tandem cells consisting of a gallium indium phosphide (GaInP{sub 2}) homojunction grown epitaxially upon a gallium arsenide (GaAs) homojunction, with a GaAs tunnel-diode interconnection were utilized to photoelectrochemically decompose water in a 1 M sulfuric acid electrolyte solution. Using a sol-gel process, a platinum colloid in water was used to modify the illuminated front surface of the device to catalyze the water decomposition process. A unique feature of this device is that the hydrogen and oxygen are co-evolved from the illuminated surface. The exact mechanism of the water decomposition process is not fully understood at this time

  19. Stochastic Polynomial Dynamic Models of the Yeast Cell Cycle

    Science.gov (United States)

    Mitra, Indranil; Dimitrova, Elena; Jarrah, Abdul S.

    2010-03-01

    In the last decade a new holistic approach for tackling biological problems, systems biology, which takes into account the study of the interactions between the components of a biological system to predict function and behavior has emerged. The reverse-engineering of biochemical networks from experimental data have increasingly become important in systems biology. Based on Boolean networks, we propose a time-discrete stochastic framework for the reverse engineering of the yeast cell cycle regulatory network from experimental data. With a suitable choice of state set, we have used powerful tools from computational algebra, that underlie the reverse-engineering algorithm, avoiding costly enumeration strategies. Stochasticity is introduced by choosing at each update step a random coordinate function for each variable, chosen from a probability space of update functions. The algorithm is based on a combinatorial structure known as the Gr"obner fans of a polynomial ideal which identifies the underlying network structure and dynamics. The model depicts a correct dynamics of the yeast cell cycle network and reproduces the time sequence of expression patterns along the biological cell cycle. Our findings indicate that the methodolgy has high chance of success when applied to large and complex systems to determine the dynamical properties of corresponding networks.

  20. Factors Affecting Water Dynamics and Their Assessment in Agricultural Landscapes

    International Nuclear Information System (INIS)

    The intensification and extension of agriculture have contributed significantly to the global food production in the last five decades. However, intensification without due attention to the ecosystem services and sustainability of soil and water resources contributed to land and water quality degradation such as soil erosion, decreased soil fertility and quality, salinization and nutrient discharge to surface and ground waters. Land use change from forests to crop lands altered the vegetation pattern and hydrology of landscapes with increased nutrient discharge from crop lands to riverine environment. Global climate change will increase the amount of water required for agriculture in addition to water needed for further irrigation development causing water scarcity in many dry, arid and semi-arid regions. The water and nutrient use efficiencies of agricultural production systems are still below 40% in many regions across the globe. Nitrogen (N) and phosphorus (P) fertilizer use in agriculture have accelerated the cycling of these nutrients in the landscape and contributed to water quality degradation. Such nutrient pollution has a wide array of consequences including eutrophication of inland waters and marine ecosystems. While intensifying drought conditions, increasing water consumption and environmental pollution in many parts of the world threatens agricultural productivity and livelihood, these also provided opportunities for farmers to use improved land and water management technologies and practices to make agriculture resilient to external shocks

  1. Automated three-dimensional single cell phenotyping of spindle dynamics, cell shape, and volume

    CERN Document Server

    Plumb, Kemp; Pelletier, Vincent; Kilfoil, Maria L

    2015-01-01

    We present feature finding and tracking algorithms in 3D in living cells, and demonstrate their utility to measure metrics important in cell biological processes. We developed a computational imaging hybrid approach that combines automated three-dimensional tracking of point-like features with surface determination from which cell (or nuclear) volume, shape, and planes of interest can be extracted. After validation, we applied the technique to real space context-rich dynamics of the mitotic spindle, and cell volume and its relationship to spindle length, in dividing living cells. These methods are additionally useful for automated segregation of pre-anaphase and anaphase spindle populations in budding yeast. We found that genetic deletion of the yeast kinesin-5 mitotic motor cin8 leads to large mother and daughter cells that were indistinguishable based on size, and that in those cells the spindle length becomes uncorrelated with cell size. The technique can be used to visualize and quantify tracked feature c...

  2. The scale-free dynamics of eukaryotic cells.

    Directory of Open Access Journals (Sweden)

    Miguel A Aon

    Full Text Available Temporal organization of biological processes requires massively parallel processing on a synchronized time-base. We analyzed time-series data obtained from the bioenergetic oscillatory outputs of Saccharomyces cerevisiae and isolated cardiomyocytes utilizing Relative Dispersional (RDA and Power Spectral (PSA analyses. These analyses revealed broad frequency distributions and evidence for long-term memory in the observed dynamics. Moreover RDA and PSA showed that the bioenergetic dynamics in both systems show fractal scaling over at least 3 orders of magnitude, and that this scaling obeys an inverse power law. Therefore we conclude that in S. cerevisiae and cardiomyocytes the dynamics are scale-free in vivo. Applying RDA and PSA to data generated from an in silico model of mitochondrial function indicated that in yeast and cardiomyocytes the underlying mechanisms regulating the scale-free behavior are similar. We validated this finding in vivo using single cells, and attenuating the activity of the mitochondrial inner membrane anion channel with 4-chlorodiazepam to show that the oscillation of NAD(PH and reactive oxygen species (ROS can be abated in these two evolutionarily distant species. Taken together these data strongly support our hypothesis that the generation of ROS, coupled to redox cycling, driven by cytoplasmic and mitochondrial processes, are at the core of the observed rhythmicity and scale-free dynamics. We argue that the operation of scale-free bioenergetic dynamics plays a fundamental role to integrate cellular function, while providing a framework for robust, yet flexible, responses to the environment.

  3. A new model of long-term, coupled dynamics of carbon and water in northern peatlands

    Science.gov (United States)

    Frolking, S.; Roulet, N.

    2008-12-01

    We present a new model that simulates coupled carbon and water dynamics of northern peatlands at an annual time step over time scales of decades to millennia. The Holocene Peatland Model (HPM) simulates peatland carbon and water dynamics as the net consequence of several interacting processes: (1) above- and below-ground vegetation NPP and litter production for bryophytes, woody and herbaceous plants; (2) aerobic and anaerobic litter/peat decomposition down the peat profile; (3) the dependence of peat physical and hydraulic properties on peat composition and degree of humification; and (4) peatland annual water balance, water table depth, and unsaturated zone water content. In this initial analysis, a simulation of long- term peat accumulation is compared against peat core data from a northern peatland in North America. The sensitivity of peatland carbon and water dynamics to climate variability are explored.

  4. Global Dynamics of a Virus Dynamical Model with Cell-to-Cell Transmission and Cure Rate

    Directory of Open Access Journals (Sweden)

    Tongqian Zhang

    2015-01-01

    Full Text Available The cure effect of a virus model with both cell-to-cell transmission and cell-to-virus transmission is studied. By the method of next generation matrix, the basic reproduction number is obtained. The locally asymptotic stability of the virus-free equilibrium and the endemic equilibrium is considered by investigating the characteristic equation of the model. The globally asymptotic stability of the virus-free equilibrium is proved by constructing suitable Lyapunov function, and the sufficient condition for the globally asymptotic stability of the endemic equilibrium is obtained by constructing suitable Lyapunov function and using LaSalle invariance principal.

  5. DYNAMICS OF WATER CONSUMPTION CHANGES IN A TOURIST RESORT

    Directory of Open Access Journals (Sweden)

    Izabela Bartkowska

    2014-10-01

    Over 2011–2012 water extraction to the municipal water supply network was studied. The volume of water extracted every day was analyzed and the gathered volumes were analyzed statistically. The varying water extraction was also studied. The obtained results were presented in a graphic form. Basing on the descriptive stats and prepared diagrams certain general conclusions were drawn and the collected study figures and facts were summed up. This allowed to determine days of the highest and lowest water consumption. Also months of extreme water extraction and consumption were determined. The water extraction ranged from 1641 m3/24h to 2607 m3/24h, at an average value of 2077.4 m3/24h. Over the period under study the day of the largest water extraction and consumption was in July and the day of the lowest water extraction and consumption in December. During a week inhabitants used the highest water amount on Saturdays and the lowest on Sundays and other feast-days. Basing on the conducted measurements also the coefficient of water consumption per capita was determined. The fluctuation of this coefficient was identical as that for the water consumption. Within the period of study it ranged from 73.3 l/M 24h to 116.5 l/M 24h. The average value of the specific water consumption was 92.8 l/M 24h. For the sake of discussion the obtained results were compared with observations across the country.

  6. Dynamics of high Weber number drops impacting on hydrophobic surfaces with closed micro-cells.

    Science.gov (United States)

    Zhang, Rui; Hao, Pengfei; Zhang, Xiwen; He, Feng

    2016-06-29

    The impact dynamics and bouncing performance of high Weber number drops on hydrophobic surfaces with open and closed micro-cells are investigated. Central wetted rings are observed on both closed-cell and open-cell surfaces under high Weber number collisions, which are proposed to constitute the key element affecting the bouncing behaviour. It is found that the drops rebound on closed-cell surfaces where the central area is in the "hybrid wetting state" at high Weber numbers, while the drops adhere to the open-cell surfaces where the central region is in the Wenzel state. A theoretical model is developed to explain this interesting phenomenon, in which the liquid cannot reach the bottom of the closed-cell hydrophobic surfaces since the air stored in micro-cavities prevents the sliding motion of the liquid film and functions as a "gas spring" lifting the liquid lamella. This indicates that the hydrophobic surface with simple micro cavities can maintain the water-repellent characteristics under drop impacts at high Weber numbers. These findings are expected to be crucial to a fundamental understanding of the rapid collisions between drops and micro-structured surfaces, as well as a valuable strategy to guide the fabrication of novel super water-repellant and anti-icing surfaces. PMID:27306824

  7. A dynamic programming approach to water allocation for seasonally dry area, based on stochastic soil moisture

    Science.gov (United States)

    Lu, Z.; Porporato, A. M.

    2012-12-01

    seasonally dry areas, which are widely distributed in the world, are usually facing an intensive disparity between the lack of natural resource and the great demand of social development. In dry seasons of such areas, the distribution/allocation of water resource is an extremely critical and sensitive issue, and conflicts often occur due to lack of appropriate water allocation scheme. Among the many uses of water, the need of agricultural irrigation water is highly elastic, but this factor has not yet been made full use to free up water from agriculture use. The primary goal of this work is to design an optimal distribution scheme of water resource for dry seasons to maximize benefits from precious water resources, considering the high elasticity of agriculture water demand due to the dynamic of soil moisture affected by the uncertainty of precipitation and other factors like canopy interception. A dynamic programming model will be used to figure out an appropriate allocation of water resources among agricultural irrigation and other purposes like drinking water, industry, and hydropower, etc. In this dynamic programming model, we analytically quantify the dynamic of soil moisture in the agricultural fields by describing the interception with marked Poisson process and describing the rainfall depth with exponential distribution. Then, we figure out a water-saving irrigation scheme, which regulates the timetable and volumes of water in irrigation, in order to minimize irrigation water requirement under the premise of necessary crop yield (as a constraint condition). And then, in turn, we provide a scheme of water resource distribution/allocation among agriculture and other purposes, taking aim at maximizing benefits from precious water resources, or in other words, make best use of limited water resource.

  8. Molecular Dynamics Simulation of Diffusion Coefficients of Oxygen, Nitrogen and Sodium Chloride in Supercritical Water

    Institute of Scientific and Technical Information of China (English)

    肖吉; 陆九芳; 陈健; 李以圭

    2001-01-01

    Molecular dynamics simulation has been performed to determine the infinite-dilution diffusion coefficients of oxygen and nitrogen, and the diffusion coefficients of NaCl in supercritical water from 703.2- 763.2 K and 30-45 MPa.The results obtained show that the diffusion coefficients in supercritical water increase with temperature, while decreasing with pressure. Nevertheless, the diffusion coefficients in supercritical water are much larger than those in normal water.

  9. Crop-Diversification for Conservation of Water Resource and Agricultural Growth: A Comparative Dynamic Analysis

    OpenAIRE

    Joydeb Sasmal

    2013-01-01

    This article has addressed the problem of overexploitation of ground water for irrigation and built up a theoretical model to demonstrate how crop diversification in favour of water-saving crops can help conservation of water resource and agricultural growth. The comparative dynamic analysis on the optimal path of ground water stock has been done using variational differential equation. The qualitative results in Phase-Diagram show that if R&D expenditure is increased by the government or inp...

  10. Pressure-induced water transport in membrane channels studied by molecular dynamics.

    OpenAIRE

    Zhu, Fangqiang; Tajkhorshid, Emad; Schulten, Klaus

    2002-01-01

    A method is proposed to measure the water permeability of membrane channels by means of molecular dynamics simulations. By applying a constant force to the bulk water molecules and a counter force on the complementary system, a hydrostatic pressure difference across the membrane can be established, producing a net directional water flow. The hydraulic or osmotic permeability can then be determined by the ratio of the water flux and the pressure difference. The method is applied and tested on ...

  11. Dynamic Assessment of Water Quality Based on a Variable Fuzzy Pattern Recognition Model

    OpenAIRE

    Shiguo Xu; Tianxiang Wang; Suduan Hu

    2015-01-01

    Water quality assessment is an important foundation of water resource protection and is affected by many indicators. The dynamic and fuzzy changes of water quality lead to problems for proper assessment. This paper explores a method which is in accordance with the water quality changes. The proposed method is based on the variable fuzzy pattern recognition (VFPR) model and combines the analytic hierarchy process (AHP) model with the entropy weight (EW) method. The proposed method was applied ...

  12. Structural and dynamical properties of water on chemically modified surfaces: The role of the instantaneous surface

    Science.gov (United States)

    Bekele, Selemon; Tsige, Mesfin

    Surfaces of polymers such as atactic polystyrene (aPS) represent very good model systems for amorphous material surfaces. Such polymer surfaces are usually modified either chemically or physically for a wide range of applications that include friction, lubrication and adhesion. It is thus quite important to understand the structural and dynamical properties of liquids that come in contact with them to achieve the desired functional properties. Using molecular dynamics (MD) simulations, we investigate the structural and dynamical properties of water molecules in a slab of water in contact with atactic polystyrene surfaces of varying polarity. We find that the density of water molecules and the number distribution of hydrogen bonds as a function of distance relative to an instantaneous surface exhibit a structure indicative of a layering of water molecules near the water/PS interface. For the dynamics, we use time correlation functions of hydrogen bonds and the incoherent structure function for the water molecules. Our results indicate that the polarity of the surface dramatically affects the dynamics of the interfacial water molecules with the dynamics slowing down with increasing polarity. This work was supported by NSF Grant DMR1410290.

  13. Tracking the mechanical dynamics of human embryonic stem cell chromatin

    Directory of Open Access Journals (Sweden)

    Hinde Elizabeth

    2012-12-01

    Full Text Available Abstract Background A plastic chromatin structure has emerged as fundamental to the self-renewal and pluripotent capacity of embryonic stem (ES cells. Direct measurement of chromatin dynamics in vivo is, however, challenging as high spatiotemporal resolution is required. Here, we present a new tracking-based method which can detect high frequency chromatin movement and quantify the mechanical dynamics of chromatin in live cells. Results We use this method to study how the mechanical properties of chromatin movement in human embryonic stem cells (hESCs are modulated spatiotemporally during differentiation into cardiomyocytes (CM. Notably, we find that pluripotency is associated with a highly discrete, energy-dependent frequency of chromatin movement that we refer to as a ‘breathing’ state. We find that this ‘breathing’ state is strictly dependent on the metabolic state of the cell and is progressively silenced during differentiation. Conclusions We thus propose that the measured chromatin high frequency movements in hESCs may represent a hallmark of pluripotency and serve as a mechanism to maintain the genome in a transcriptionally accessible state. This is a result that could not have been observed without the high spatial and temporal resolution provided by this novel tracking method.

  14. 'Standpipes and beyond'-a universal water service dynamic

    OpenAIRE

    Esther Gerlach; Richard Franceys

    2010-01-01

    The failure of many developing countries water utilities to provide adequate services to low-income urban populations stands in marked contrast with calls for universal access to water services, often based on a concept of human rights. Much of the parallel, regulation oriented, 'universal service obligation' rhetoric not only ignores the origins and continuing evolution of the term but equally fails to consider the practical realities of achieving universality of networked urban water supply...

  15. Dynamic load balancing algorithm for molecular dynamics based on Voronoi cells domain decompositions

    Energy Technology Data Exchange (ETDEWEB)

    Fattebert, J.-L. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Richards, D.F. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Glosli, J.N. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)

    2012-12-01

    We present a new algorithm for automatic parallel load balancing in classical molecular dynamics. It assumes a spatial domain decomposition of particles into Voronoi cells. It is a gradient method which attempts to minimize a cost function by displacing Voronoi sites associated with each processor/sub-domain along steepest descent directions. Excellent load balance has been obtained for quasi-2D and 3D practical applications, with up to 440·106 particles on 65,536 MPI tasks.

  16. Development of some intestinal endocrine cell populations in water buffalo

    Directory of Open Access Journals (Sweden)

    L. Castaldo

    2010-02-01

    Full Text Available The occurrence and distribution of different endocrine cell types in the gastrointestinal tract of large and small domestic mammals have been extensively studied (Ceccarelli et al. 1995; Agungpriyono et al.2000. Some studies have been also carried out on the ontogeny of gut endocrine cells in mammals (Ono et al. 1994, and only few in ruminant. (Kitamura et al. 1985; Guilloteau et al. 1997. In order to complete a previous study regarding postnatal development of intestinal endocrine cells (Lucini et al. 1999, in this study we report the appearance and distribution of some endocrine cell types in the gut of water buffalo during foetal development.

  17. Dynamics of circulation of the waters around India

    Digital Repository Service at National Institute of Oceanography (India)

    Shetye, S.R.

    During the last decade the understanding of dynamics of the large-scale seasonal coastal currents around India has markedly improved. However, a number of major issues concerning circulation on the shelf and in the estuaries remain unresolved...

  18. Dynamic Enhanced Inter-Cell Interference Coordination for Realistic Networks

    DEFF Research Database (Denmark)

    Pedersen, Klaus I.; Alvarez, Beatriz Soret; Barcos, Sonia; Gerardino, Guillermo Andrés Pocovi; Wang, Hua

    2016-01-01

    Enhanced Inter-Cell Interference Coordination (eICIC) is a key ingredient to boost the performance of co-channel Heterogeneous Networks (HetNets). eICIC encompasses two main techniques: Almost Blank Subframes (ABS), during which the macro cell remains silent to reduce the interference, and biased...... user association to offload more users to the picocells. However, its application to realistic irregular deployments opens a number of research questions. In this paper, we investigate the operation of eICIC in a realistic deployment based on three-dimensional data from a dense urban European capital...... area. Rather than the classical semi-static and network-wise configuration, the importance of having highly dynamic and distributed mechanisms that are able to adapt to local environment conditions is revealed. We propose two promising cell association algorithms: one aiming at pure load balancing and...

  19. Water droplet accumulation and motion in PEM (Proton Exchange Membrane) fuel cell mini-channels

    International Nuclear Information System (INIS)

    Effective water management is one of the key strategies for improving low temperature PEM (Proton Exchange Membrane) fuel cell performance and durability. Phenomena such as membrane dehydration, catalyst layer flooding, mass transport and fluid flow regimes can be affected by the interaction, distribution and movement of water in flow plate channels. In this paper a literature review is completed in relation to PEM fuel cell water flooding. It is clear that droplet formation, movement and interaction with the GDL (Gas Diffusion Layer) have been studied extensively. However slug formation and droplet accumulation in the flow channels has not been analysed in detail. In this study, a CFD (Computational Fluid Dynamic) model and VOF (Volume of Fluid) method is used to simulate water droplet movement and slug formation in PEM fuel cell mini-channels. In addition, water slug visualisation is recorded in ex situ PEM fuel cell mini-channels. Observation and simulation results are discussed with relation to slug formation and the implications to PEM fuel cell performance. -- Highlights: ► Excess water in mini-channels from the collision and coalescence of droplets can directly form slugs in PEM fuel cells. ► Slugs can form at low flow rates so increasing the flow rate can reduce the size and frequency of slugs. ► One channel of a double serpentine mini-channel may become blocked due to the redistribution of airflow and pressure caused by slug formation. ► Correct GDL and mini-channel surface coatings are essential to reduce slug formation and stagnation. ► Having geometry changes (bends and steps) in the flow fields can disrupt slug movement and avoid channel blockages.

  20. Energetic and molecular water permeation mechanisms of the human red blood cell urea transporter B.

    Directory of Open Access Journals (Sweden)

    Slim Azouzi

    Full Text Available Urea transporter B (UT-B is a passive membrane channel that facilitates highly efficient permeation of urea. In red blood cells (RBC, while the major function of UT-B is to transport urea, it is assumed that this protein is able to conduct water. Here, we have revisited this last issue by studying RBCs and ghosts from human variants with defects of aquaporin 1 (AQP1 or UT-B. We found that UT-B's osmotic water unit permeability (pfunit is similar to that of AQP1. The determination of diffusional permeability coefficient (Pd allowed the calculation of the Pf/Pd ratio, which is consistent with a single-file water transport. Molecular dynamic simulations of water conduction through human UT-B confirmed the experimental finding. From these results, we propose an atomistic description of water-protein interactions involved in this permeation. Inside the UT-B pore, five water molecules were found to form a single-file and move rapidly along a channel by hydrogen bond exchange involving two critical threonines. We further show that the energy barrier for water located in the central region coincides with a water dipole reorientation, which can be related to the proton exclusion observed experimentally. In conclusion, our results indicate that UT-B should be considered as a new member of the water channel family.

  1. Dynamics of thraustochytrid protists in the water column of the Arabian Sea

    Digital Repository Service at National Institute of Oceanography (India)

    Raghukumar, S.; Ramaiah, N.; Raghukumar, C.

    Thraustochytrids, a group of osmoheterotrophic chromistan protists are ubiquitous in the sea. However, little is known of their ecological role, particularly in oceanic waters. To obtain in insight into their dynamics in this realm, thraustochytrids...

  2. Molecular Dynamics implementation of BN2D or 'Mercedes Benz' water model

    Science.gov (United States)

    Scukins, Arturs; Bardik, Vitaliy; Pavlov, Evgen; Nerukh, Dmitry

    2015-05-01

    Two-dimensional 'Mercedes Benz' (MB) or BN2D water model (Naim, 1971) is implemented in Molecular Dynamics. It is known that the MB model can capture abnormal properties of real water (high heat capacity, minima of pressure and isothermal compressibility, negative thermal expansion coefficient) (Silverstein et al., 1998). In this work formulas for calculating the thermodynamic, structural and dynamic properties in microcanonical (NVE) and isothermal-isobaric (NPT) ensembles for the model from Molecular Dynamics simulation are derived and verified against known Monte Carlo results. The convergence of the thermodynamic properties and the system's numerical stability are investigated. The results qualitatively reproduce the peculiarities of real water making the model a visually convenient tool that also requires less computational resources, thus allowing simulations of large (hydrodynamic scale) molecular systems. We provide the open source code written in C/C++ for the BN2D water model implementation using Molecular Dynamics.

  3. Computational investigation of epithelial cell dynamic phenotype in vitro

    Directory of Open Access Journals (Sweden)

    Debnath Jayanta

    2009-05-01

    Full Text Available Abstract Background When grown in three-dimensional (3D cultures, epithelial cells typically form cystic organoids that recapitulate cardinal features of in vivo epithelial structures. Characterizing essential cell actions and their roles, which constitute the system's dynamic phenotype, is critical to gaining deeper insight into the cystogenesis phenomena. Methods Starting with an earlier in silico epithelial analogue (ISEA1 that validated for several Madin-Darby canine kidney (MDCK epithelial cell culture attributes, we built a revised analogue (ISEA2 to increase overlap between analogue and cell culture traits. Both analogues used agent-based, discrete event methods. A set of axioms determined ISEA behaviors; together, they specified the analogue's operating principles. A new experimentation framework enabled tracking relative axiom use and roles during simulated cystogenesis along with establishment of the consequences of their disruption. Results ISEA2 consistently produced convex cystic structures in a simulated embedded culture. Axiom use measures provided detailed descriptions of the analogue's dynamic phenotype. Dysregulating key cell death and division axioms led to disorganized structures. Adhering to either axiom less than 80% of the time caused ISEA1 to form easily identified morphological changes. ISEA2 was more robust to identical dysregulation. Both dysregulated analogues exhibited characteristics that resembled those associated with an in vitro model of early glandular epithelial cancer. Conclusion We documented the causal chains of events, and their relative roles, responsible for simulated cystogenesis. The results stand as an early hypothesis–a theory–of how individual MDCK cell actions give rise to consistently roundish, cystic organoids.

  4. Sub-diffusion and population dynamics of water confined in soft environments

    Science.gov (United States)

    Hanot, Samuel; Lyonnard, Sandrine; Mossa, Stefano

    2016-02-01

    We have studied by using molecular dynamics computer simulations the dynamics of water confined in ionic surfactant phases, ranging from well ordered lamellar structures to micelles at low and high water loading, respectively. We have analysed in depth the main dynamical features in terms of mean-squared displacements and intermediate scattering functions, and found clear evidence of sub-diffusive behaviour. We have identified water molecules lying at the charged interface with the hydrophobic confining matrix as the main factor responsible for this unusual feature, and given a comprehensive picture of dynamics based on a very precise analysis of lifetimes at the interface. We conclude by providing, for the first time to our knowledge, a unique framework for rationalizing the existence of important dynamical heterogeneities in fluids adsorbed in soft confining environments.We have studied by using molecular dynamics computer simulations the dynamics of water confined in ionic surfactant phases, ranging from well ordered lamellar structures to micelles at low and high water loading, respectively. We have analysed in depth the main dynamical features in terms of mean-squared displacements and intermediate scattering functions, and found clear evidence of sub-diffusive behaviour. We have identified water molecules lying at the charged interface with the hydrophobic confining matrix as the main factor responsible for this unusual feature, and given a comprehensive picture of dynamics based on a very precise analysis of lifetimes at the interface. We conclude by providing, for the first time to our knowledge, a unique framework for rationalizing the existence of important dynamical heterogeneities in fluids adsorbed in soft confining environments. Electronic supplementary information (ESI) available. See DOI: 10.1039/C5NR05853H

  5. Molecular dynamics studies of water deposition on hematite surfaces

    Science.gov (United States)

    Kvamme, Bjørn; Kuznetsova, Tatiana; Haynes, Martin

    2012-12-01

    The interest in carbon dioxide for enhanced oil recovery is increasing proportional to the decrease in naturally driven oil production and also due to the increasing demand for reduced emission of carbon dioxide to the atmosphere. Transport of carbon dioxide in offshore pipelines involves high pressure and low temperatures which may lead to the formation of hydrate between residual water dissolved in carbon dioxide. The critical question is whether the water at some condition of temperature and pressure will drop out as liquid droplets or as water adsorbed on the surfaces of the pipeline and then subsequently form hydrates heterogeneously. In this work we have used the 6-311G basis set with B3LYP to estimate the charge distribution of different sizes of hematite crystals. The obtained surface charge distribution were kept unchanged while the inner charge distribution where scaled so as to result in an overall neutral crystal. These rust particles were embedded in water and chemical potential for adsorbed water molecules were estimated through thermodynamic integration and compared to similar estimates for same size water cluster. Estimated values of water chemical potentials indicate that it is thermodynamically favorable for water to adsorb on hematite, and that evaluation of potential carbon dioxide hydrate formation conditions and kinetics should be based this sequence of processes.

  6. Molecular Dynamics Simulations of Water Nanodroplets on Silica Surfaces

    DEFF Research Database (Denmark)

    Zambrano, Harvey A; Walther, Jens Honore; Jaffe, Richard L.

    2009-01-01

    Wetting is essential and ubiquitous in a variety of natural and technological processes.1,2,3 Silicon dioxides-water systems are abundant in nature and play fundamental roles in a vast variety of novel science and engineering activities such as silicon based devices, nanoscale lab on a chip systems...... amorphous silica-water systems....

  7. Short-Term Water Dynamics in Chihuahua City, Mexico

    OpenAIRE

    Thomas M Fullerton Jr; Ana Cecilia Nava

    2004-01-01

    Linear transfer ARIMA analysis of monthly per meter water consumption is conducted for Chihuahua City, Mexico. Sample data from January 1988 to December 2000 are analyzed. Time series utilized include water system revenue, climate, and industrial production data. Out-of-sample simulations are used to confirm the reliability of the in-sample estimation results.

  8. Arrangement and dynamics of water in natural zeolites

    International Nuclear Information System (INIS)

    Elastic, inelastic and quasielastic neutron scattering experiments are performed on natural zeolites. Hydrogen atoms at the water molecules could be located in the fibrous zeolites natrolite and edingtonite. Inelastic neutron spectra can be divided into translational (δE -5 cm sec-1 at T = 295 K for the full amount of water. (author) 6 refs., 4 figs., 1 tab

  9. Dynamic cell culture system: a new cell cultivation instrument for biological experiments in space

    Science.gov (United States)

    Gmunder, F. K.; Nordau, C. G.; Tschopp, A.; Huber, B.; Cogoli, A.

    1988-01-01

    The prototype of a miniaturized cell cultivation instrument for animal cell culture experiments aboard Spacelab is presented (Dynamic cell culture system: DCCS). The cell chamber is completely filled and has a working volume of 200 microliters. Medium exchange is achieved with a self-powered osmotic pump (flowrate 1 microliter h-1). The reservoir volume of culture medium is 230 microliters. The system is neither mechanically stirred nor equipped with sensors. Hamster kidney (Hak) cells growing on Cytodex 3 microcarriers were used to test the biological performance of the DCCS. Growth characteristics in the DCCS, as judged by maximal cell density, glucose consumption, lactic acid secretion and pH, were similar to those in cell culture tubes.

  10. Dynamic graphene filters for selective gas-water-oil separation

    Science.gov (United States)

    Bong, Jihye; Lim, Taekyung; Seo, Keumyoung; Kwon, Cho-Ah; Park, Ju Hyun; Kwak, Sang Kyu; Ju, Sanghyun

    2015-09-01

    Selective filtration of gas, water, and liquid or gaseous oil is essential to prevent possible environmental pollution and machine/facility malfunction in oil-based industries. Novel materials and structures able to selectively and efficiently filter liquid and vapor in various types of solutions are therefore in continuous demand. Here, we investigate selective gas-water-oil filtration using three-dimensional graphene structures. The proposed approach is based on the adjustable wettability of three-dimensional graphene foams. Three such structures are developed in this study; the first allows gas, oil, and water to pass, the second blocks water only, and the third is exclusively permeable to gas. In addition, the ability of three-dimensional graphene structures with a self-assembled monolayer to selectively filter oil is demonstrated. This methodology has numerous potential practical applications as gas, water, and/or oil filtration is an essential component of many industries.

  11. Specific Ions Modulate Diffusion Dynamics of Hydration Water on Lipid Membrane Surfaces

    OpenAIRE

    Song, Jinsuk; Franck, John; Pincus, Philip; Kim, Mahn Won; Han, Songi

    2014-01-01

    Effects of specific ions on the local translational diffusion of water near large hydrophilic lipid vesicle surfaces were measured by Overhauser dynamic nuclear polarization (ODNP). ODNP relies on an unpaired electron spin-containing probe located at molecular or surface sites to report on the dynamics of water protons within ∼10 Å from the spin probe, which give rise to spectral densities for electron–proton cross-relaxation processes in the 10 GHz regime. This pushes nuclear magnetic resona...

  12. Optimizing conjunctive use of surface water and groundwater resources with stochastic dynamic programming

    DEFF Research Database (Denmark)

    Davidsen, Claus; Liu, Suxia; Mo, Xinguo;

    2014-01-01

    customizable method. The method has been applied to the Ziya River basin, China. The basin is located on the North China Plain and is subject to severe water scarcity, which includes surface water droughts and groundwater over-pumping. The head-dependent groundwater pumping costs will enable assessment of the......Optimal management of conjunctive use of surface water and groundwater has been attempted with different algorithms in the literature. In this study, a hydro-economic modelling approach to optimize conjunctive use of scarce surface water and groundwater resources under uncertainty is presented. A...... stochastic dynamic programming (SDP) approach is used to minimize the basin-wide total costs arising from water allocations and water curtailments. Dynamic allocation problems with inclusion of groundwater resources proved to be more complex to solve with SDP than pure surface water allocation problems due...

  13. System dynamics model of Suzhou water resources carrying capacity and its application

    Directory of Open Access Journals (Sweden)

    Li CHENG

    2010-06-01

    Full Text Available A model of Suzhou water resources carrying capacity (WRCC was set up using the method of system dynamics (SD. In the model, three different water resources utilization programs were adopted: (1 continuity of existing water utilization, (2 water conservation/saving, and (3 water exploitation. The dynamic variation of the Suzhou WRCC was simulated with the supply-decided principle for the time period of 2001 to 2030, and the results were characterized based on socio-economic factors. The corresponding Suzhou WRCC values for several target years were calculated by the model. Based on these results, proper ways to improve the Suzhou WRCC are proposed. The model also produced an optimized plan, which can provide a scientific basis for the sustainable utilization of Suzhou water resources and for the coordinated development of the society, economy, and water resources.

  14. Computer simulation study of structure and dynamics of supercooled water in silica nanopores

    Science.gov (United States)

    Kuon, Nicholas; Ladanyi, Branka

    2014-03-01

    In narrow hydrophilic pores, interactions with pore walls and confinement dimensions allow water to remain liquid well below the normal freezing point. We investigate the properties of nanoconfined supercooled water by means of molecular simulation. The focus of our study is confinement in approximately cylindrical silica pores, with diameters in the 20-40 Å range, a model for MCM-41 materials. We use Gibbs-ensemble Monte Carlo method to determine water density in the pores in equilibrium with the bulk and molecular dynamics simulation to study the properties of confined water. We study the translational and rotational mobilities of molecules in different interfacial layers and the effects on water dynamics of interfacial hydrogen bonding. We make contact with quasi-elastic neutron scattering experiments on supercooled water in MCM-14 silica pores by calculating and analyzing self-intermediate scattering functions of water hydrogens. This research was supported by NSF grant number 1213682.

  15. Optical assessment of colored dissolved organic matter and its related parameters in dynamic coastal water systems

    Science.gov (United States)

    Shanmugam, Palanisamy; Varunan, Theenathayalan; Nagendra Jaiganesh, S. N.; Sahay, Arvind; Chauhan, Prakash

    2016-06-01

    Prediction of the curve of the absorption coefficient of colored dissolved organic matter (CDOM) and differentiation between marine and terrestrially derived CDOM pools in coastal environments are hampered by a high degree of variability in the composition and concentration of CDOM, uncertainties in retrieved remote sensing reflectance and the weak signal-to-noise ratio of space-borne instruments. In the present study, a hybrid model is presented along with empirical methods to remotely determine the amount and type of CDOM in coastal and inland water environments. A large set of in-situ data collected on several oceanographic cruises and field campaigns from different regional waters was used to develop empirical methods for studying the distribution and dynamics of CDOM, dissolved organic carbon (DOC) and salinity. Our validation analyses demonstrated that the hybrid model is a better descriptor of CDOM absorption spectra compared to the existing models. Additional spectral slope parameters included in the present model to differentiate between terrestrially derived and marine CDOM pools make a substantial improvement over those existing models. Empirical algorithms to derive CDOM, DOC and salinity from remote sensing reflectance data demonstrated success in retrieval of these products with significantly low mean relative percent differences from large in-situ measurements. The performance of these algorithms was further assessed using three hyperspectral HICO images acquired simultaneously with our field measurements in productive coastal and lagoon waters on the southeast part of India. The validation match-ups of CDOM and salinity showed good agreement between HICO retrievals and field observations. Further analyses of these data showed significant temporal changes in CDOM and phytoplankton absorption coefficients with a distinct phase shift between these two products. Healthy phytoplankton cells and macrophytes were recognized to directly contribute to the

  16. ELECTRICITY PRODUCTION FROM WASTE WATER USING MICROBIAL FUEL CELL

    OpenAIRE

    Mannarreddy Prabu; Munireddy Durgadevi; Manavalan Tamilvendan; Puthupattu Thangavelu Kalaichelvan; Venkatesan Kaviyarasan

    2012-01-01

    Microbial fuel cells (MFCs) an electricity producing device using waste-water treatment, biosensor, eco-friendly and low cost management of energy production. In this study, investigation power generation from waste water compared with their pure culture, mixed culture and different medium ingredients with microorganism. Enhance the power production with different ingredients like monosaccharide’s, nitrogen source and amino acids, these sources increasing the electron shuttle in the medium. G...

  17. Dynamics of Water Associated with Lithium Ions Distributed in Polyethylene Oxide.

    Science.gov (United States)

    Zhang, Zhe; Ohl, Michael; Diallo, Souleymane O; Jalarvo, Niina H; Hong, Kunlun; Han, Youngkyu; Smith, Gregory S; Do, Changwoo

    2015-11-01

    The dynamics of water in polyethylene oxide (PEO)/LiCl solution has been studied with quasielastic neutron scattering experiments and molecular dynamics (MD) simulations. Two different time scales of water diffusion representing interfacial water and bulk water dynamics have been identified. The measured diffusion coefficient of interfacial water remained 5-10 times smaller than that of bulk water, but both were slowed by approximately 50% in the presence of Li(+). Detailed analysis of MD trajectories suggests that Li(+) is favorably found at the surface of the hydration layer, and the probability to find the caged Li(+) configuration formed by the PEO is lower than for the noncaged Li(+)-PEO configuration. In both configurations, however, the slowing down of water molecules is driven by reorienting water molecules and creating water-Li(+) hydration complexes. Performing the MD simulation with different ions (Na(+) and K(+)) revealed that smaller ionic radius of the ions is a key factor in disrupting the formation of PEO cages by allowing spaces for water molecules to come in between the ion and PEO. PMID:26588420

  18. Dynamics of Water Associated with Lithium Ions Distributed in Polyethylene Oxide

    Science.gov (United States)

    Zhang, Zhe; Ohl, Michael; Diallo, Souleymane O.; Jalarvo, Niina H.; Hong, Kunlun; Han, Youngkyu; Smith, Gregory S.; Do, Changwoo

    2015-11-01

    The dynamics of water in polyethylene oxide (PEO)/LiCl solution has been studied with quasielastic neutron scattering experiments and molecular dynamics (MD) simulations. Two different time scales of water diffusion representing interfacial water and bulk water dynamics have been identified. The measured diffusion coefficient of interfacial water remained 5-10 times smaller than that of bulk water, but both were slowed by approximately 50% in the presence of Li+ . Detailed analysis of MD trajectories suggests that Li+ is favorably found at the surface of the hydration layer, and the probability to find the caged Li+ configuration formed by the PEO is lower than for the noncaged Li+-PEO configuration. In both configurations, however, the slowing down of water molecules is driven by reorienting water molecules and creating water-Li+ hydration complexes. Performing the MD simulation with different ions (Na+ and K+ ) revealed that smaller ionic radius of the ions is a key factor in disrupting the formation of PEO cages by allowing spaces for water molecules to come in between the ion and PEO.

  19. Comparison of Dynamic Visual Acuity between Water Polo Players and Sedentary Students

    Science.gov (United States)

    Quevedo-Junyent, Lluisa; Aznar-Casanova, Jose Antonio; Merindano-Encina, Dolores; Cardona, Genis; Sole-Forto, Joan

    2011-01-01

    In this study, we examined differences in dynamic visual acuity between elite and subelite water polo players and sedentary students. To measure dynamic visual acuity binocularly, we asked participants to indicate the orientation of a broken ring, similar to the Landolt C, which increased in size as it moved across a computer screen. Two different…

  20. Development of a dynamic model for cleaning ultra filtration membranes fouled by surface water

    NARCIS (Netherlands)

    Zondervan, Edwin; Betlem, Ben H.L.; Roffel, Brian

    2007-01-01

    In this paper, a dynamic model for cleaning ultra filtration membranes fouled by surface water is proposed. A model that captures the dynamics well is valuable for the optimization of the cleaning process. The proposed model is based on component balances and contains three parameters that can be de

  1. Dynamic modeling of a three-stage low-temperature ethanol reformer for fuel cell application

    Energy Technology Data Exchange (ETDEWEB)

    Garcia, Vanesa M.; Serra, Maria [Institut de Robotica i Informatica Industrial (CSIC-UPC), Llorens i Artigas 4-6, 08028 Barcelona (Spain); Lopez, Eduardo; Llorca, Jordi [Institut de Tecniques Energetiques, Universitat Politecnica de Catalunya, Diagonal 647, ed. ETSEIB, 08028 Barcelona (Spain)

    2009-07-01

    A low-temperature ethanol reformer based on a cobalt catalyst for the production of hydrogen has been designed aiming the feed of a fuel cell for an autonomous low-scale power production unit. The reformer comprises three stages: ethanol dehydrogenation to acetaldehyde and hydrogen over SnO{sub 2} followed by acetaldehyde steam reforming over Co(Fe)/ZnO catalyst and water gas shift reaction. Kinetic data have been obtained under different experimental conditions and a dynamic model has been developed for a tubular reformer loaded with catalytic monoliths for the production of the hydrogen required to feed a 1 kW PEMFC. (author)

  2. Dynamic modelling of a PV pumping system with special consideration on water demand

    International Nuclear Information System (INIS)

    Highlights: ► Evaluation of water demand and solar energy is essential for PV pumping system. ► The design for a PV water pumping system has been optimized based on dynamic simulations. ► It is important to conduct dynamic simulations to check the matching between water demand and water supply. ► AC pump driven by the fixed PV array is the most cost-effective solution. - Abstract: The exploitation of solar energy in remote areas through photovoltaic (PV) systems is an attractive solution for water pumping for irrigation systems. The design of a photovoltaic water pumping system (PVWPS) strictly depends on the estimation of the crop water requirements and land use since the water demand varies during the watering season and the solar irradiation changes time by time. It is of significance to conduct dynamic simulations in order to achieve the successful and optimal design. The aim of this paper is to develop a dynamic modelling tool for the design of a of photovoltaic water pumping system by combining the models of the water demand, the solar PV power and the pumping system, which can be used to validate the design procedure in terms of matching between water demand and water supply. Both alternate current (AC) and direct current (DC) pumps and both fixed and two-axis tracking PV array were analyzed. The tool has been applied in a case study. Results show that it has the ability to do rapid design and optimization of PV water pumping system by reducing the power peak and selecting the proper devices from both technical and economic viewpoints. Among the different alternatives considered in this study, the AC fixed system represented the best cost effective solution

  3. Dynamic monitoring of single cell lysis in an impedance-based microfluidic device.

    Science.gov (United States)

    Zhou, Ying; Basu, Srinjan; Laue, Ernest D; Seshia, Ashwin A

    2016-08-01

    A microfluidic device that is capable of trapping and sensing dynamic variations in the electrical properties of individual cells is demonstrated. The device is applied to the real-time recording of impedance measurements of mouse embryonic stem cells (mESCs) during the process of membrane lysis, with the resulting changes in the electrical properties of cells during this process being quantitatively tracked over time. It is observed that the impedance magnitude decreases dramatically after cell membrane lysis. A significant shift in the phase spectrum is also observed during the time course of this process. By fitting experimental data to physical models, the electrical parameters of cells can be extracted and parameter variations quantified during the process. In the cell lysis experiments, the equivalent conductivity of the cell membrane is found to increase significantly due to pore formation in the membrane during lysis. An increase in the specific capacitance of the membrane is also observed. On the other hand, the conductivity of the cytoplasm is observed to decrease, which may be explained the fact that excess water enters the cell through the gradual permeabilization of the membrane during lysis. Cells can be trapped in the device for periods up to several days, and their electrical response can be monitored by real-time impedance measurements in a label-free and non-invasive manner. Furthermore, due to the highly efficient single cell trapping capacity of the device, a number of cells can be trapped and held in separate wells for concurrent parallel experiments, allowing for the possibility of stepped parametric experiments and studying cell heterogeneity by combining measurements across the array. PMID:27299468

  4. Using stable isotopes of water to infer wetland hydrological dynamics

    OpenAIRE

    Clay, A.; Bradley, C.; Gerrard, A. J.; Leng, M. J.

    2002-01-01

    This paper considers the potential of oxygen and hydrogen isotope ratios to identify spatial and temporal changes in the water source of a lowland headwater wetland situated adjacent to the River Tern in Shropshire, UK. Stable isotope composition (d18O) of end-members varied between –7.5 and –8.0‰ for groundwater, –7.3 and –8.5‰ for river-water and –4.5 and –8.0‰ for precipitation. Water samples were extracted from six nests each comprising three porous cup samplers at depths of ...

  5. Using stable isotopes of water to infer wetland hydrological dynamics

    OpenAIRE

    Clay, A.; Bradley, C.; Gerrard, A. J.; Leng, M. J.

    2004-01-01

    This paper considers the potential of oxygen and hydrogen isotope ratios to identify spatial and temporal changes in the water source of a lowland headwater wetland situated adjacent to the River Tern in Shropshire, UK. Stable isotope composition (d18O) of end-members varied between –7.5 and –8.0‰ for groundwater, –7.3 and –8.5‰ for river-water and –4.5 and –8.0‰ for precipitation. Water samples were extracted from six nests each comprising three porous cup samplers at depths of 0.2 m, 0....

  6. Molecular Dynamics Simulations of Water Droplets On Hydrophilic Silica Surfaces

    DEFF Research Database (Denmark)

    Zambrano, Harvey A; Walther, Jens Honore; Jaffe, Richard L.

    2009-01-01

    Wetting is essential and ubiquitous in a variety of natural and technological processes. Silicon dioxides-water systems are abundant in nature and play fundamental roles in a vast variety of novel science and engineering activities such as silicon based devices, nanoscale lab on a chip systems and......, nanobubles have been observed and proposed as the origin of long range ``hydrophobic'' forces even for hydrophilic silica-water interfaces unusual phenomena related to nanobubbles have been observed. In this work we study the role of air on the wetting of amorphous silica-water systems. We conduct molecular...

  7. Effect of tritiated water on germ cells

    International Nuclear Information System (INIS)

    As part of a study investigating the biological effects of tritiated water (HTO), the relative biological effectiveness (RBE) of HTO was sought by comparison with the results of tritium simulation using Cs-137 and with the results of Co-60 gamma ray and fission neutron (Cf-252) irradiation, using as index the lethal effect on mouse newborn oocytes which are highly sensitive to radiation. As method, HTO was injected into the abdominal cavity of newborn ICR strain mice once on the 14th day after birth in a concentration of 46, 92, 184, or 276 μCi/10 g B.W. and the ovary was removed two weeks later (accumulated dose equivalent to 3.9, 7.7, 15.9, and 24.6 rad, respectively). The survival rates of premature oocytes in serial sections were calculated and compared with the results of tritium simulation using Cs-137 at the same dose rate. The results showed that the number of surviving oocytes decreased exponentially dependent on HTO and Cs-137 dose and gave 1.1 - 3.5 as the RBE of HTO to standard γ ray of Cs-137. As regards the results of irradiation with Co-60 (1 rad/min.) and Cf-252 (1 rad/min.) the lethal effect on oocytes was stronger in the order of Cf-252, HTO, Co-60, and Cs-137, and 1.6 - 2.4 was obtained as the RBE of Cf-252 to standard γ ray of Co-60. (author)

  8. Dynamic maintenance of stochastic molecular clusters on cell membranes

    Science.gov (United States)

    Mugler, Andrew; Wehrens, Martijn; Ten Wolde, Pieter Rein

    2015-03-01

    Clustering of molecules on cell membranes is a widely observed phenomenon. A key example is the oncoprotein Ras. Maintenance of Ras clusters has been linked to proper Ras signaling. Yet, the mechanism by which Ras clusters are maintained remains unclear. Recently it was discovered that activated Ras promotes further Ras activation. We show using particle-based simulation that this positive feedback link is sufficient to produce persistent clusters of active Ras molecules via a dynamic nucleation mechanism. The cluster statistics are consistent with experimental observations. Interestingly, our model does not support a Turing regime of macroscopic reaction-diffusion patterning. This means that the clustering we observe is a purely stochastic effect, arising from the coupling of the positive feedback network with the discrete nature of individual molecules. These findings underscore the importance of stochastic and dynamic properties of reaction diffusion systems for biological behavior.

  9. Analysis of the dynamics of a boiling water nuclear reactor

    International Nuclear Information System (INIS)

    The March-Leuba lineal reduced model is represented mathematically by a differential equations system, which corresponds to the direct transfer function, punctual kinetics approximation, neutron field dynamics, heat transfer in fuels, and channel dynamics approximation that relates the fuel temperature changes to the reactivity changes by vacuums. The model presents significant differences in one of the equation coefficients. The Pade order approximation used for the equation deduction for the channel has a different behavior to the exponential one for long periods of bubble residence. (Author)

  10. A population dynamics analysis of the interaction between adaptive regulatory T cells and antigen presenting cells.

    Directory of Open Access Journals (Sweden)

    David Fouchet

    Full Text Available BACKGROUND: Regulatory T cells are central actors in the maintenance of tolerance of self-antigens or allergens and in the regulation of the intensity of the immune response during infections by pathogens. An understanding of the network of the interaction between regulatory T cells, antigen presenting cells and effector T cells is starting to emerge. Dynamical systems analysis can help to understand the dynamical properties of an interaction network and can shed light on the different tasks that can be accomplished by a network. METHODOLOGY AND PRINCIPAL FINDINGS: We used a mathematical model to describe a interaction network of adaptive regulatory T cells, in which mature precursor T cells may differentiate into either adaptive regulatory T cells or effector T cells, depending on the activation state of the cell by which the antigen was presented. Using an equilibrium analysis of the mathematical model we show that, for some parameters, the network has two stable equilibrium states: one in which effector T cells are strongly regulated by regulatory T cells and another in which effector T cells are not regulated because the regulatory T cell population is vanishingly small. We then simulate different types of perturbations, such as the introduction of an antigen into a virgin system, and look at the state into which the system falls. We find that whether or not the interaction network switches from the regulated (tolerant state to the unregulated state depends on the strength of the antigenic stimulus and the state from which the network has been perturbed. CONCLUSION/SIGNIFICANCE: Our findings suggest that the interaction network studied in this paper plays an essential part in generating and maintaining tolerance against allergens and self-antigens.

  11. MEMS-based dynamic cell-to-cell culture platforms using electrochemical surface modifications

    International Nuclear Information System (INIS)

    MEMS-based biological platforms with the capability of both spatial placements and time releases of living cells for cell-to-cell culture experiments have been designed and demonstrated utilizing electrochemical surface modification effects. The spatial placement is accomplished by electrochemical surface modification of substrate surfaces to be either adhesive or non-adhesive for living cells. The time control is achieved by the electrical activation of the selective indium tin oxide co-culture electrode to allow the migration of living cells onto the electrode to start the cell-to-cell culture studies. Prototype devices have a three-electrode design with an electrode size of 50 × 50 µm2 and the separation gaps of 2 µm between them. An electrical voltage of −1.5 V has been used to activate the electrodes independently and sequentially to demonstrate the dynamic cell-to-cell culture experiments of NIH 3T3 fibroblast and Madin Darby canine kidney cells. As such, this MEMS platform could be a basic yet versatile tool to characterize transient cell-to-cell interactions

  12. Isomerization reaction dynamics and equilibrium at the liquid-vapor interface of water. A molecular-dynamics study

    Science.gov (United States)

    Benjamin, Ilan; Pohorille, Andrew

    1993-01-01

    The gauche-trans isomerization reaction of 1,2-dichloroethane at the liquid-vapor interface of water is studied using molecular-dynamics computer simulations. The solvent bulk and surface effects on the torsional potential of mean force and on barrier recrossing dynamics are computed. The isomerization reaction involves a large change in the electric dipole moment, and as a result the trans/gauche ratio is considerably affected by the transition from the bulk solvent to the surface. Reactive flux correlation function calculations of the reaction rate reveal that deviation from the transition-state theory due to barrier recrossing is greater at the surface than in the bulk water. This suggests that the system exhibits non-Rice-Ramsperger-Kassel-Marcus behavior due to the weak solvent-solute coupling at the water liquid-vapor interface.

  13. Using stable isotopes of water to infer wetland hydrological dynamics

    Science.gov (United States)

    Clay, A.; Bradley, C.; Gerrard, A. J.; Leng, M. J.

    This paper considers the potential of oxygen and hydrogen isotope ratios to identify spatial and temporal changes in the water source of a lowland headwater wetland situated adjacent to the River Tern in Shropshire, UK. Stable isotope composition (d18O) of end-members varied between -7.5 and -8.0‰ for groundwater, -7.3 and -8.5‰ for river-water and -4.5 and -8.0‰ for precipitation. Water samples were extracted from six nests each comprising three porous cup samplers at depths of 0.2 m, 0.5 m and 1.0 m between June 2000 and October 2001, and their isotope compositions determined. Groundwater appears to be the main source of water to the wetland, but stable isotope ratios enable seasonal variations in the contribution of precipitation to be determined, and indicate the extent of precipitation storage within the wetland.

  14. Dynamic graphene filters for selective gas-water-oil separation

    OpenAIRE

    Jihye Bong; Taekyung Lim; Keumyoung Seo; Cho-Ah Kwon; Ju Hyun Park; Sang Kyu Kwak; Sanghyun Ju

    2015-01-01

    Selective filtration of gas, water, and liquid or gaseous oil is essential to prevent possible environmental pollution and machine/facility malfunction in oil-based industries. Novel materials and structures able to selectively and efficiently filter liquid and vapor in various types of solutions are therefore in continuous demand. Here, we investigate selective gas-water-oil filtration using three-dimensional graphene structures. The proposed approach is based on the adjustable wettability o...

  15. Ibuprofen regulation of microtubule dynamics in cystic fibrosis epithelial cells.

    Science.gov (United States)

    Rymut, Sharon M; Kampman, Claire M; Corey, Deborah A; Endres, Tori; Cotton, Calvin U; Kelley, Thomas J

    2016-08-01

    High-dose ibuprofen, an effective anti-inflammatory therapy for the treatment of cystic fibrosis (CF), has been shown to preserve lung function in a pediatric population. Despite its efficacy, few patients receive ibuprofen treatment due to potential renal and gastrointestinal toxicity. The mechanism of ibuprofen efficacy is also unclear. We have previously demonstrated that CF microtubules are slower to reform after depolymerization compared with respective wild-type controls. Slower microtubule dynamics in CF cells are responsible for impaired intracellular transport and are related to inflammatory signaling. Here, it is identified that high-dose ibuprofen treatment in both CF cell models and primary CF nasal epithelial cells restores microtubule reformation rates to wild-type levels, as well as induce extension of microtubules to the cell periphery. Ibuprofen treatment also restores microtubule-dependent intracellular transport monitored by measuring intracellular cholesterol transport. These effects are specific to ibuprofen as other cyclooxygenase inhibitors have no effect on these measures. Effects of ibuprofen are mimicked by stimulation of AMPK and blocked by the AMPK inhibitor compound C. We conclude that high-dose ibuprofen treatment enhances microtubule formation in CF cells likely through an AMPK-related pathway. These findings define a potential mechanism to explain the efficacy of ibuprofen therapy in CF. PMID:27317686

  16. Dynamics of Tetrahymena macronuclear lamina during cell division

    Institute of Scientific and Technical Information of China (English)

    CHENBIN; ZHONGHEZHAI

    1994-01-01

    During mitosis,the nuclear lamina in higher eukaryotic cells undergoes a distinctly morphological change.It breaks down into lamin polymers or monomers at prophase.At telophase,the lamins reassemble around the condensed chromatin to form the layer of lamina.Using antiserum to mammalian lamins,we studied the dynamics of lamina during cell division in the macronuleus of Tetrahymena shanghaiensis,which divided in the way of amitosis.In contrast to those in higher animal cells,the typical perinuclear lamin distribution in the macronucleus persisted throughout the whole cell cycle.It was further found that in some synchronized cells,the lamin distribution bisplayed an unusual pattern consisting of a series of spots within the macronucleus.Using South-western hybridization,we found that the purified 66 KD lamin in Tetrahymena showed specific affinity with the telomere DNA sequence in the same species.Therefore,we propose that pattern of immunofluorescence may be due to the interaction of lamin protein with the nucleoli and the condensed chromatins in the macronucleus.

  17. Dynamic behavior of gasoline fuel cell electric vehicles

    Science.gov (United States)

    Mitchell, William; Bowers, Brian J.; Garnier, Christophe; Boudjemaa, Fabien

    As we begin the 21st century, society is continuing efforts towards finding clean power sources and alternative forms of energy. In the automotive sector, reduction of pollutants and greenhouse gas emissions from the power plant is one of the main objectives of car manufacturers and innovative technologies are under active consideration to achieve this goal. One technology that has been proposed and vigorously pursued in the past decade is the proton exchange membrane (PEM) fuel cell, an electrochemical device that reacts hydrogen with oxygen to produce water, electricity and heat. Since today there is no existing extensive hydrogen infrastructure and no commercially viable hydrogen storage technology for vehicles, there is a continuing debate as to how the hydrogen for these advanced vehicles will be supplied. In order to circumvent the above issues, power systems based on PEM fuel cells can employ an on-board fuel processor that has the ability to convert conventional fuels such as gasoline into hydrogen for the fuel cell. This option could thereby remove the fuel infrastructure and storage issues. However, for these fuel processor/fuel cell vehicles to be commercially successful, issues such as start time and transient response must be addressed. This paper discusses the role of transient response of the fuel processor power plant and how it relates to the battery sizing for a gasoline fuel cell vehicle. In addition, results of fuel processor testing from a current Renault/Nuvera Fuel Cells project are presented to show the progress in transient performance.

  18. Self-Regulating Water-Separator System for Fuel Cells

    Science.gov (United States)

    Vasquez, Arturo; McCurdy, Kerri; Bradley, Karla F.

    2007-01-01

    proposed system would perform multiple coordinated functions in regulating the pressure of the oxidant gas (usually, pure oxygen) flowing to a fuelcell stack and in removing excess product water that is generated in the normal fuel-cell operation. The system could function in the presence or absence of gravitation, and in any orientation in a gravitational field. Unlike some prior systems for removing product water, the proposed system would not depend on hydrophobicity or hydrophilicity of surfaces that are subject to fouling and, consequently, to gradual deterioration in performance. Also unlike some prior systems, the proposed system would not include actively controlled electric motors for pumping; instead, motive power for separation and pumping away of product water would be derived primarily from the oxidant flow and perhaps secondarily from the fuel flow. The net effect of these and other features would be to make the proposed system more reliable and safer, relative to the prior systems. The proposed system (see figure) would include a pressure regulator and sensor in the oxidant supply just upstream from an ejector reactant pump. The pressure of the oxidant supply would depend on the consumption flow. In one of two control subsystems, the pressure of oxidant flowing from the supply to the ejector would be sensed and used to control the speed of a set of a reciprocating constant-displacement pump so that the volumetric flow of nominally incompressible water away from the system would slightly exceed the rate at which water was produced by the fuel cell(s). The two-phase (gas/liquid water) outlet stream from the fuel cell(s) would enter the water separator, a turbinelike centrifugal separator machine driven primarily by the oxidant gas stream. A second control subsystem would utilize feedback derived from the compressibility of the outlet stream: As the separator was emptied of liquid water, the compressibility of the pumped stream would increase. The

  19. Molecular dynamics approach to water structure of HII mesophase of monoolein

    Science.gov (United States)

    Kolev, Vesselin; Ivanova, Anela; Madjarova, Galia; Aserin, Abraham; Garti, Nissim

    2012-02-01

    The goal of the present work is to study theoretically the structure of water inside the water cylinder of the inverse hexagonal mesophase (HII) of glyceryl monooleate (monoolein, GMO), using the method of molecular dynamics. To simplify the computational model, a fixed structure of the GMO tube is maintained. The non-standard cylindrical geometry of the system required the development and application of a novel method for obtaining the starting distribution of water molecules. A predictor-corrector schema is employed for generation of the initial density of water. Molecular dynamics calculations are performed at constant volume and temperature (NVT ensemble) with 1D periodic boundary conditions applied. During the simulations the lipid structure is kept fixed, while the dynamics of water is unrestrained. Distribution of hydrogen bonds and density as well as radial distribution of water molecules across the water cylinder show the presence of water structure deep in the cylinder (about 6 Å below the GMO heads). The obtained results may help understanding the role of water structure in the processes of insertion of external molecules inside the GMO/water system. The present work has a semi-quantitative character and it should be considered as the initial stage of more comprehensive future theoretical studies.

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2011-01-01

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

  1. Non-periodic molecular dynamics simulations of coarse grained lipid bilayer in water

    DEFF Research Database (Denmark)

    Kotsalis, E. M.; Hanasaki, I.; Walther, Jens Honore;

    2010-01-01

    We present a multiscale algorithm that couples coarse grained molecular dynamics (CGMD) with continuum solver. The coupling requires the imposition of non-periodic boundary conditions on the coarse grained Molecular Dynamics which, when not properly enforced, may result in spurious fluctuations of...... the material properties of the system represented by CGMD. In this paper we extend a control algorithm originally developed for atomistic simulations [3], to conduct simulations involving coarse grained water molecules without periodic boundary conditions. We demonstrate the applicability of our...... method in simulating more complex systems by performing a non-periodic Molecular Dynamics simulation of a DPPC lipid in liquid coarse grained water....

  2. A First Principles Molecular Dynamics Study Of Calcium Ion In Water

    Energy Technology Data Exchange (ETDEWEB)

    Lightstone, F; Schwegler, E; Allesch, M; Gygi, F; Galli, G

    2005-01-28

    In this work we report on Car-Parrinello simulations of the divalent calcium ion in water, aimed at understanding the structure of the hydration shell and at comparing theoretical results with a series of recent experiments. Our paper shows some of the progress in the investigation of aqueous solutions brought about by the advent of ab initio molecular dynamics and highlights the importance of accessing subtle details of ion-water interactions from first-principles. Calcium plays a vital role in many biological systems, including signal transduction, blood clotting and cell division. In particular, calcium ions are known to interact strongly with proteins as they tend to bind well to both negatively charged (e.g. in aspartate and glutamate) and uncharged oxygens (e.g. in main-chain carbonyls). The ability of calcium to coordinate multiple ligands (from 6 to 8 oxygen atoms) with an asymmetric coordination shell enables it to cross-link different segments of a protein and induce large conformational changes. The great biochemical importance of the calcium ion has led to a number of studies to determine its hydration shell and its preferred coordination number in water. Experimental studies have used a variety of techniques, including XRD, EXAFS, and neutron diffraction to elucidate the coordination of Ca{sup 2+} in water. The range of coordination numbers (n{sub C}) inferred by X-ray diffraction studies varies from 6 to 8, and is consistent with that reported in EXAFS experiments (8 and 7.2). A wider range of values (6 to 10) was found in early neutron diffraction studies, depending on concentration, while a more recent measurement by Badyal, et al. reports a value close to 7. In addition to experimental measurements, many theoretical studies have been carried out to investigate the solvation of Ca{sup 2+} in water and have also reported a wide range of coordination numbers. Most of the classical molecular dynamics (MD) and QM/MM simulations report n{sub C} in the

  3. 78 FR 34090 - New Hampshire Water Resources Board, Hydro Dynamics Corporation; Notice of Transfer of Exemption

    Science.gov (United States)

    2013-06-06

    ... From the Federal Register Online via the Government Publishing Office DEPARTMENT OF ENERGY Federal Energy Regulatory Commission New Hampshire Water Resources Board, Hydro Dynamics Corporation; Notice of Transfer of Exemption 1. By letter filed April 16, 2013, New Hampshire Water Resources Board...

  4. PREFACE: Dynamic crossover phenomena in water and other glass-forming liquids Dynamic crossover phenomena in water and other glass-forming liquids

    Science.gov (United States)

    Chen, Sow-Hsin; Baglioni, Piero

    2012-02-01

    This special section has been inspired by the workshop on Dynamic Crossover Phenomena in Water and Other Glass-Forming Liquids, held during November 11-13, 2010 at Pensione Bencistà, Fiesole, Italy, a well-preserved 14th century Italian villa tucked high in the hills overlooking Florence. The meeting, an assembly of world renowned scientists, was organized as a special occasion to celebrate the 75th birthday of Professor Sow-Hsin Chen of MIT, a pioneer in several aspects of complex fluids and soft matter physics. The workshop covered a large variety of experimental and theoretical research topics of current interest related to dynamic crossover phenomena in water and, more generally, in other glass-forming liquids. The 30 invited speakers/lecturers and approximately 60 participants were a select group of prominent physicists and chemists from the USA, Europe, Asia and Mexico, who are actively working in the field. Some highlights of this special issue include the following works. Professor Yamaguchi's group and their collaborators present a neutron spin echo study of the coherent intermediate scattering function of heavy water confined in cylindrical pores of MCM-41-C10 silica material in the temperature range 190-298 K. They clearly show that a fragile-to-strong (FTS) dynamic crossover occurs at about 225 K. They attribute the FTS dynamic crossover to the formation of a tetrahedral-like structure, which is preserved in the bulk-like water confined to the central part of the cylindrical pores. Mamontov and Kolesnikov et al study the collective excitations in an aqueous solution of lithium chloride over a temperature range of 205-270 K using neutron and x-ray Rayleigh-Brillouin (coherent) scattering. They detect both the low-frequency and the high-frequency sounds known to exist in pure bulk water above the melting temperature. They also perform neutron (incoherent) and x-ray (coherent) elastic intensity scan measurements. Clear evidence of the crossover in the

  5. How relevant is the interannual vegetation's dynamic in the water cycle at catchment scale?

    Science.gov (United States)

    Echeverría Martinez, Carlos Antonio; Ruiz-Pérez, Guiomar; Francés, Félix

    2016-04-01

    To effectively analyse a portion of the Earth's surface from a hydrological perspective, it is important to understand that water cycle and vegetation dynamics are strongly connected. Vegetation holds an important role in land surface water balance, in particular considering that vegetation physiology and spatial parameters are dynamic in time. A traditional hydrological model considerates vegetation as a static parameter through years, representing very well observed streamflow. Nowadays, the tendency is to include the vegetation as a state variable. In this way, we obtain a better simulation of both, blue water and green water, as well as the ratio between them. Applying the hydrological distributed model TETIS, this work presents the comparison of considering static vegetation or dynamics vegetation. The study catchment was characterized by a good availability of input data in the analysis period (from 1990 to 2011) and it is mainly covered by forested areas. The selected basin is the upper part of the Turia River, up to the Benageber Reservoir, analyzing if is relevant to use dynamics vegetation instead of static vegetation for the water resources evaluation in semiarid Mediterranean catchments. Both model variations were applied in three different scenarios: a dry year, a normal year and a wet year. In each scenario the model was applied considering both static vegetation and vegetation dynamics. At the catchment scale, considering vegetation as an stationary parameter both, green water and the ratio between blue and green water, were underestimated. Consequently, not considering the vegetation's dynamic in semiarid conditions can produce the underestimation of the amount of green water, which introduces a higher uncertainty in the resulting water balance in present conditions but also in future climate change scenarios.

  6. Resting stage cells of diatoms in deep waters in Kumano-

    OpenAIRE

    AKIRA, ISHIKAWA; Shingo, Kitami; Ken-Ichiro, Ishii; Toru, NAKAMURA; ICHIRO, IMAI

    2011-01-01

    The abundance and species composition of viable resting stage cells of diatoms were investigated in deep waters (200,500 and 1,000 m depths) collected at neighboring stations in Kumano-Nada, central part of Japan, in April, August and October 2006. Viable resting stage cells were enumerated by the modified extinction dilution method [most probable number (MPN) method] based on incubation. Resting stage cells were detected from all samples, except at 500 m depth in August, in a range of abunda...

  7. Dynamics of an electrochemical biosensor for the detection of toxic substances in water

    Science.gov (United States)

    Simon, Laurent; Ospina, Juan

    2016-05-01

    A proposed analytical method focuses on electrolyte transport to the electrode of an electrochemical cell. The recombinant Escherichia coli whole-cell biosensor detects toxicity in water based on a set of biochemical reactors. Previous contributions elucidated the kinetics of product formation and validated a mathematical model for its diffusion in the chamber. This work introduces an approach to investigate the dynamics of the probe using Laplace transforms and an effective time constant. The transfer function between the electrolyte production and the total current revealed a faster response for larger electrode radii. Both the first-order and effective time constants increased with the chamber height and radius. Separation of variables yields closed-form solutions and helps estimate the kinetics of p-aminophenol generation. When the bacteria were exposed to phenol concentrations of 1.6, 8.3 and 16 ppm, the corresponding overall rate constants were 5.11x10-7, 1.13x10-6 and 1.99x10-6 (product concentration unit/s2), respectively. In addition to parameter estimation, the method can be applied to perform sensitivity analysis and aid manufacturers in meeting design specifications of biosensors.

  8. Complex network analysis of phase dynamics underlying oil-water two-phase flows

    Science.gov (United States)

    Gao, Zhong-Ke; Zhang, Shan-Shan; Cai, Qing; Yang, Yu-Xuan; Jin, Ning-De

    2016-06-01

    Characterizing the complicated flow behaviors arising from high water cut and low velocity oil-water flows is an important problem of significant challenge. We design a high-speed cycle motivation conductance sensor and carry out experiments for measuring the local flow information from different oil-in-water flow patterns. We first use multivariate time-frequency analysis to probe the typical features of three flow patterns from the perspective of energy and frequency. Then we infer complex networks from multi-channel measurements in terms of phase lag index, aiming to uncovering the phase dynamics governing the transition and evolution of different oil-in-water flow patterns. In particular, we employ spectral radius and weighted clustering coefficient entropy to characterize the derived unweighted and weighted networks and the results indicate that our approach yields quantitative insights into the phase dynamics underlying the high water cut and low velocity oil-water flows.

  9. Pressure Dependence of the Dynamic Crossover Temperatures in Protein and its Hydration Water

    CERN Document Server

    Chu, Xiang-qiang; Kim, Chansoo; Fratini, Emiliano; Baglioni, Piero; Leao, Juscelino B; Chen, Sow-Hsin

    2008-01-01

    Recently we have shown experimental evidence for a fragile-to-strong dynamic crossover (FSC) phenomenon in hydration water around a globular protein (lysozyme) at ambient pressure. In this letter we show that when applying pressure to the protein-water system, the FSC crossover temperatures in hydration water of lysozyme tracks the similar Widom line emanating from the existence of a liquid-liquid critical point in a 1-D confined water (in MCM-41-S). The mean squared displacements (MSD) of hydrogen atoms in lysozyme and in its hydration water show a sudden change of slopes at the same characteristic temperature, which decreases with an increasing pressure. These results taken together give support of the idea that the dynamic crossover (or so-called glass transition) of the protein is a function of both temperature and pressure, following the FSC of its hydration water.

  10. Using stable isotopes of water to infer wetland hydrological dynamics

    Directory of Open Access Journals (Sweden)

    A. Clay

    2004-01-01

    Full Text Available This paper considers the potential of oxygen and hydrogen isotope ratios to identify spatial and temporal changes in the water source of a lowland headwater wetland situated adjacent to the River Tern in Shropshire, UK. Stable isotope composition (d18O of end-members varied between –7.5 and –8.0‰ for groundwater, –7.3 and –8.5‰ for river-water and –4.5 and –8.0‰ for precipitation. Water samples were extracted from six nests each comprising three porous cup samplers at depths of 0.2 m, 0.5 m and 1.0 m between June 2000 and October 2001, and their isotope compositions determined. Groundwater appears to be the main source of water to the wetland, but stable isotope ratios enable seasonal variations in the contribution of precipitation to be determined, and indicate the extent of precipitation storage within the wetland. Keywords: oxygen and hydrogen isotopes, water source, hydrodynamics, lowland wetland

  11. Experimental analysis of the dynamic behavior of a rotating disk submerged in water

    International Nuclear Information System (INIS)

    To study the dynamic behavior of turbine runners (natural frequencies and mode shapes) not only the added mass effect of still water has to be considered. Also the effect of rotation may not be neglected in the dynamic response. In the present study, the dynamic behavior of a rotating disk submerged in water is studied. For this purpose an experimental test rig has been developed. It consists of a rotating disk submerged in water that can be excited and its response can be measured from the rotating system by a slip ring system. For the excitation an impact device installed on the casing has been used. The response is measured with miniature accelerometers screwed on the disk. The influence of rotation on the dynamic response has been determined experimentally

  12. Analysis and numerical simulation of dynamic effect on rock under high pressure water jet

    Institute of Scientific and Technical Information of China (English)

    LI Xiao-hong; SI Hu; WANG Dan-dan

    2008-01-01

    Based on continuum mechanics and rock dynamics, analyzed the micro-structure damage of rock and the impulsive effect under high pressure water jet and developed the dynamic model. Further, on the assumption of that rock was homogeneous and isotropic, a computational model was established based on nonlinear finite element and Arbitrary Lagrangian-Eulerian(ALE) method. The dynamic effect impacted on rock under high pressure water jet was simulated by the dynamic contact method. The propagation of stress wave in rock was numerically simulated at different impacting velocity. The results show that the propagation velocity of stress wave is proportional to the impacting velocity of high pressure water jet. The faster the impacting velocity is, the quicker the comedown of stress wave.

  13. Dynamics and Synchrony of Pancreatic beta-cells and Islets

    DEFF Research Database (Denmark)

    Pedersen, Morten Gram

    2006-01-01

    Pancreatic beta-cells secrete insulin in response to raised glucose levels. Malfunctioning of this system plays an important role in the metabolic disease diabetes. The biological steps from glucose stimulus to the final release of insulin are incompletely understood, and a more complete...... description of these processes and their interactions would provide important input in the search for a better treatment of the disease. The thesis describes several aspects of mathematical modeling of beta-cells relevant for the understanding of glucose stimulated insulin secretion. It consists of an...... biological hypotheses. The subjects addressed are: Quasi-steady-state approximations of enzyme reactions, the effect of noise on bursting electrical behavior, exciation wave propagation in pancreatic islets, intra- and inter-islet synchronization and pulsatile insulin secretion, and mitochondrial dynamics....

  14. Modifying a dynamic global vegetation model for simulating large spatial scale land surface water balance

    Directory of Open Access Journals (Sweden)

    G. Tang

    2012-01-01

    Full Text Available Water balance models of simple structure are easier to grasp and more clearly connect cause and effect than models of complex structure. Such models are essential for studying large spatial scale land surface water balance in the context of climate and land cover change, both natural and anthropogenic. This study aims to (i develop a large spatial scale water balance model by modifying a dynamic global vegetation model (DGVM, and (ii test the model's performance in simulating actual evapotranspiration (ET, soil moisture and surface runoff for the coterminous United States (US. Toward these ends, we first introduced development of the "LPJ-Hydrology" (LH model by incorporating satellite-based land covers into the Lund-Potsdam-Jena (LPJ DGVM instead of dynamically simulating them. We then ran LH using historical (1982–2006 climate data and satellite-based land covers at 2.5 arc-min grid cells. The simulated ET, soil moisture and surface runoff were compared to existing sets of observed or simulated data for the US. The results indicated that LH captures well the variation of monthly actual ET (R2 = 0.61, p < 0.01 in the Everglades of Florida over the years 1996–2001. The modeled monthly soil moisture for Illinois of the US agrees well (R2 = 0.79, p < 0.01 with the observed over the years 1984–2001. The modeled monthly stream flow for most 12 major rivers in the US is consistent R2 > 0.46, p < 0.01; Nash-Sutcliffe Coefficients >0.52 with observed values over the years 1982–2006, respectively. The modeled spatial patterns of annual ET and surface runoff are in accordance with previously published data. Compared to its predecessor, LH simulates better monthly stream flow in winter and early spring by incorporating effects of solar radiation on snowmelt. Overall, this study proves the feasibility of incorporating satellite-based land-covers into a DGVM for simulating

  15. Dynamic modeling and controllability analysis of an ethanol reformer for fuel cell application

    Energy Technology Data Exchange (ETDEWEB)

    Garcia, Vanesa M.; Serra, Maria; Riera, Jordi [Institut de Robotica i Informatica Industrial (CSIC-UPC), Llorens i Artigas 4-6, 08028 Barcelona (Spain); Lopez, Eduardo [Institut de Tecniques Energetiques, Universitat Politecnica de Catalunya, Diagonal 647, ed. ETSEIB, 08028 Barcelona (Spain); Planta Piloto de Ingenieria Quimica (CONICET-UNS), Camino de la Carrindanga km7, 8000 Bahia Blanca (Argentina); Llorca, Jordi [Institut de Tecniques Energetiques, Universitat Politecnica de Catalunya, Diagonal 647, ed. ETSEIB, 08028 Barcelona (Spain)

    2010-09-15

    This work presents a controllability analysis of a low temperature ethanol reformer based on a cobalt catalyst for fuel cell application. The study is based on a non-linear dynamic model of a reformer which operates in three separate stages: ethanol dehydrogenation to acetaldehyde and hydrogen, acetaldehyde steam reforming, and water-gas-shift reaction. The controllability analysis is focused on the rapid dynamics due to mass balances and is based on a linearization of the complex non-linear model of the reformer. RGA, CN and MRI analysis tools are applied to the linear model suggesting that a good performance can be obtained with decentralized control for frequencies up to 0.1 rad s{sup -1}. (author)

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

    CERN Document Server

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

    2000-01-01

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

  17. Calculation of the coefficient and dynamics of water diffusion in graphite joints

    Institute of Scientific and Technical Information of China (English)

    WANG Jun; LIU Wen-bin

    2006-01-01

    The coefficient and dynamics of water diffusion in adhesive-graphite joints were calculated insitu with energy dispersive X-ray (EDX) analysis, a method that is significantly simpler than elemental analysis. Water diffusion coefficient and dynamics of adhesive-graphite joints treated by different surface treatment methods were also investigated. Calculation results indicated that the water diffusion rate in adhesive-graphite joints treated by sandpaper was higher than that treated by chemical oxidation or by silane couple agent. Also the durability of graphite joints treated by coupling agent is superior to that treated by chemical oxidation or sandpaper burnishing.

  18. Water Collective Dynamics in Whole Photosynthetic Green Algae as Affected by Protein Single Mutation.

    Science.gov (United States)

    Russo, Daniela; Rea, Giuseppina; Lambreva, Maya D; Haertlein, Michael; Moulin, Martine; De Francesco, Alessio; Campi, Gaetano

    2016-07-01

    In the context of the importance of water molecules for protein function/dynamics relationship, the role of water collective dynamics in Chlamydomonas green algae carrying both native and mutated photosynthetic proteins has been investigated by neutron Brillouin scattering spectroscopy. Results show that single point genetic mutation may notably affect collective density fluctuations in hydrating water providing important insight on the transmission of information possibly correlated to biological functionality. In particular, we highlight that the damping factor of the excitations is larger in the native compared to the mutant algae as a signature of a different plasticity and structure of the hydrogen bond network. PMID:27300078

  19. Molecular dynamics simulation studies on some topics of water molecules on hydrophobic surfaces

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    Molecular dynamics simulations have been used to study two topics of water molecules on hydrophobic surfaces. Some properties of the nanobubbles with different ingredients and behavior of single water chains in single-walled carbon nanochannels are exploited. Molecular simulations show that the density of the N2 and H2 are quite high, which is critical for the stability of the nanobubbles and may have potential applications, such as hydrogen storage, incorporated with recent experimental method to controllably produce hydrogen nanobubbles. The water molecules inside the nanochannel show an unexpected directed motion with long time period, which is indispensable in the future study of the dynamics of biological channels.

  20. Influence from sea water constituents on the efficiency of water electrolysis by PEM-cells

    DEFF Research Database (Denmark)

    Agersted, Karsten; Bentzen, Janet Jonna; Yde-Andersen, S.

    Among the sea-water specific impurities tested, magnesium has the most profound effect on PEM-cell degradation. Significant amounts of the cation was retrieved in the NAFION®-membrane structure after testing. Degradation was seen from a magnesium concentration as low as 3 10-7 mol/l, and increasing...... necessary to purify the feed water to ~1 μS/cm or even further while particularly focusing on the concentrations of polyvalent cations. e.g. magnesium....

  1. Understanding protein dynamical transition and protein-water interaction from dielectric relaxation calculations

    OpenAIRE

    Sirer, Irmak

    2006-01-01

    Dielectric properties of an aqueous lysozyme solution were calculated from 2 ns long MD simulations in the temperature range of 150-300 K and an 4 ns long simulation at 300 K. Static and frequency dependent dielectric constants of the system were calculated from auto- and cross-correlations of its three components (protein, water, ions). Cole-Cole plots for protein, water and the total solution were obtained. Emergence of an intense protein-water interaction above the dynamical transition bet...

  2. Water Scarcity in South Asia: A Dynamic Computable General Equilibrium Analysis

    OpenAIRE

    Narayanan, Badri G.; Taheripour, Farzad; Hertel, Thomas W.; Sahin, Sebnem; Escurra, Jorge J.

    2015-01-01

    The economy of South Asia faces serious challenges in water availability, which are expected to aggravate over the coming decades. In this context, we assess the long-run economy-wide impact of potential water scarcity in South Asia within a global context. This paper uses a dynamic Computable General Equilibrium (CGE) model, in tandem with an advanced comparative static CGE model, to examine the differences in economic growth possibilities in South Asia with and without water scarcity. Alter...

  3. Water Balance Dynamics of Cyprus - Actual State and Impacts of Climate Change

    OpenAIRE

    Dünkeloh, Armin

    2013-01-01

    A completely revised and enhanced version of the water balance model MODBIL of the regional water balance dynamics of Cyprus was developed for this study. The model is based on a physical, process-oriented, spatially distributed concept and is applied for the calculation of all important water balance components of the island for the time period of 1961-2004. The calibrated results are statistically analysed and visualised for the whole island area, and evaluated with respect to the renewabil...

  4. Effects of hydrogen bonding on supercooled liquid dynamics and the implications for supercooled water

    OpenAIRE

    Mattsson, Johan; Bergman, Rikard; Jacobsson, Per; Börjesson, Lars

    2008-01-01

    The supercooled state of bulk water is largely hidden by unavoidable crystallization, which creates an experimentally inaccessible temperature regime - a 'no man's land'. We address this and circumvent the crystallization problem by systematically studying the supercooled dynamics of hydrogen bonded oligomeric liquids (glycols), where water corresponds to the chain-ends alone. This novel approach permits a 'dilution of water' by altering the hydrogen bond concentration via variations in chain...

  5. Measurement of dynamic pressure and force effects of modulated water jet

    Czech Academy of Sciences Publication Activity Database

    Foldyna, Josef; Sitek, Libor; Jekl, Pavel; Švehla, B.

    Seoul: Korean Society of Water Jet Technology, 2002, s. 125-132. [Pacific Rim International Conference on Water Jetting Technology/7./. Jeju (KR), 27.10.2003-29.10.2003] R&D Projects: GA AV ČR(CZ) IAA2086001; GA ČR(CZ) GA105/03/0183 Institutional research plan: CEZ:AV0Z3086906 Keywords : modulated water jet * ultrasonic modulation Subject RIV: BK - Fluid Dynamics

  6. Single-particle dynamics of hydration water in protein

    International Nuclear Information System (INIS)

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

  7. Single-particle dynamics of hydration water in protein

    Energy Technology Data Exchange (ETDEWEB)

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

    1992-06-01

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

  8. Preliminary testing of an electrolysis cell for highly tritiated water

    International Nuclear Information System (INIS)

    In the framework of the European fusion technology programme, SCK/CEN (Mol, Belgium) has continued the development of an electrolysis cell for highly tritiated water. In the resulting original concept, the liquid inventory is limited to the vertical porous gas separator which is wetted by capillarity. Use is made of thermoelectric heat pumps to cool the cell down to about 80C. Intensive testing with light water has been performed successfully during more than 10,000 cumulated hours with mock-up cells, and during more than 6,000 cumulated hours with a prototype cell. These tests have demonstrated the robustness and the long-term reliability of the proposed system. Further experiments are going on with the aim to characterize the working of the capillary cell. In the same time, peripheral equipment such as demisters and cold traps are being tested. These devices are to be incorporated in a dedicated loop for testing with tritiated water at the nominal specific activity (-- 4.1019 Bq/m3)

  9. Sticky water surfaces: helix-coil transitions suppressed in a cell-penetrating peptide at the air-water interface.

    Science.gov (United States)

    Schach, Denise; Globisch, Christoph; Roeters, Steven J; Woutersen, Sander; Fuchs, Adrian; Weiss, Clemens K; Backus, Ellen H G; Landfester, Katharina; Bonn, Mischa; Peter, Christine; Weidner, Tobias

    2014-12-14

    GALA is a 30 amino acid synthetic peptide consisting of a Glu-Ala-Leu-Ala repeat and is known to undergo a reversible structural transition from a disordered to an α-helical structure when changing the pH from basic to acidic values. In its helical state GALA can insert into and disintegrate lipid membranes. This effect has generated much interest in GALA as a candidate for pH triggered, targeted drug delivery. GALA also serves as a well-defined model system to understand cell penetration mechanisms and protein folding triggered by external stimuli. Structural transitions of GALA in solution have been studied extensively. However, cell penetration is an interfacial effect and potential biomedical applications of GALA would involve a variety of surfaces, e.g., nanoparticles, lipid membranes, tubing, and liquid-gas interfaces. Despite the apparent importance of interfaces in the functioning of GALA, the effect of surfaces on the reversible folding of GALA has not yet been studied. Here, we use sum frequency generation vibrational spectroscopy (SFG) to probe the structural response of GALA at the air-water interface and IR spectroscopy to follow GALA folding in bulk solution. We combine the SFG data with molecular dynamics simulations to obtain a molecular-level picture of the interaction of GALA with the air-water interface. Surprisingly, while the fully reversible structural transition was observed in solution, at the water-air interface, a large fraction of the GALA population remained helical at high pH. This "stickiness" of the air-water interface can be explained by the stabilizing interactions of hydrophobic leucine and alanine side chains with the water surface. PMID:25494788

  10. Sticky water surfaces: Helix-coil transitions suppressed in a cell-penetrating peptide at the air-water interface

    Science.gov (United States)

    Schach, Denise; Globisch, Christoph; Roeters, Steven J.; Woutersen, Sander; Fuchs, Adrian; Weiss, Clemens K.; Backus, Ellen H. G.; Landfester, Katharina; Bonn, Mischa; Peter, Christine; Weidner, Tobias

    2014-12-01

    GALA is a 30 amino acid synthetic peptide consisting of a Glu-Ala-Leu-Ala repeat and is known to undergo a reversible structural transition from a disordered to an α-helical structure when changing the pH from basic to acidic values. In its helical state GALA can insert into and disintegrate lipid membranes. This effect has generated much interest in GALA as a candidate for pH triggered, targeted drug delivery. GALA also serves as a well-defined model system to understand cell penetration mechanisms and protein folding triggered by external stimuli. Structural transitions of GALA in solution have been studied extensively. However, cell penetration is an interfacial effect and potential biomedical applications of GALA would involve a variety of surfaces, e.g., nanoparticles, lipid membranes, tubing, and liquid-gas interfaces. Despite the apparent importance of interfaces in the functioning of GALA, the effect of surfaces on the reversible folding of GALA has not yet been studied. Here, we use sum frequency generation vibrational spectroscopy (SFG) to probe the structural response of GALA at the air-water interface and IR spectroscopy to follow GALA folding in bulk solution. We combine the SFG data with molecular dynamics simulations to obtain a molecular-level picture of the interaction of GALA with the air-water interface. Surprisingly, while the fully reversible structural transition was observed in solution, at the water-air interface, a large fraction of the GALA population remained helical at high pH. This "stickiness" of the air-water interface can be explained by the stabilizing interactions of hydrophobic leucine and alanine side chains with the water surface.

  11. In-situ measurement of the height of condensed water in steam pipes with dynamic flow

    Science.gov (United States)

    Lih, Shyh-Shiuh; Lee, Hyeong Jae; Bar-Cohen, Yoseph

    2016-04-01

    A method based on the use of enhanced filtered Hilbert envelope of the wave signal was developed in order to monitor the height of condensed water through the wall of steam pipes having dynamic flow conditions. A prototype testbed was designed and fabricated in this study to simulate the dynamic flow conditions including the air stream flowing above the water and bubble induced disturbance. A dual-transducer was used to perform the test as a basis for the multiple transducers system to facilitate the detectability and reliability for long term monitoring of the condensed water height in dynamic conditions. The results demonstrated that the method of measuring the water height using multiple-transducer system employing the developed novel signal processing technique is an efficient and accurate tool for practical applications.

  12. Molecular Dynamics Simulations of a Flexible Polyethylene: A Protein-Like Behaviour in a Water Solvent

    CERN Document Server

    Kretov, D A

    2005-01-01

    We used molecular dynamics (MD) simulations to study the density and the temperature behaviour of a flexible polyethylene (PE) subjected to various heating conditions and to investigate the PE chain conformational changes in a water solvent. First, we have considered the influence of the heating process on the final state of the polymeric system and the sensitivity of its thermodynamic characteristics (density, energy, etc.) for different heating regimes. For this purpose three different simulations were performed: fast, moderate, and slow heating. Second, we have investigated the PE chain conformational dynamics in water solvent for various simulation conditions and various configurations of the environment. From the obtained results we have got the pictures of the PE dynamical motions in water. We have observed a protein-like behaviour of the PE chain, like that of the DNA and the proteins in water, and have also estimated the rates of the conformational changes. For the MD simulations we used the optimized...

  13. Soil structure dynamics: Effects of management and water content

    OpenAIRE

    Munkholm, Lars J; Schjønning, Per; Elmholt, Susanne

    2002-01-01

    A review is given of the last 5 years research on soil structure dynamics carried out at the Danish Institute of Agricultural Sciences. The studies were initiated as part of a large programme focussing on the development of organic farming in Denmark. In organic farming a healthy and living soil is highly valued. Holistic thinking is also a key element in the organic farming concept. In order to integrate a holistic thinking in our soil structure research a multidisciplinary approach was adap...

  14. Uncertainty Analysis of Phytoplankton Dynamics in Coastal Waters

    OpenAIRE

    Niu, L.

    2015-01-01

    There is an increasing concern about the interactions between phytoplankton and coastal ecosystems, especially on the negative effects from coastal eutrophication and phytoplankton blooms. As the key indicator of the coastal ecosystem, phytoplankton plays an important role in the whole impact-effect chain. Primary production by phytoplankton forms the basic link in the food-chain. A lot of effort has been paid to the investigation of phytoplankton dynamics on the basis of literature surveys, ...

  15. Dynamics of Depletion and Replenishment of Water Storage in Stem and Roots of Black Spruce Measured by Dendrometers

    Science.gov (United States)

    Turcotte, Audrey; Rossi, Sergio; Deslauriers, Annie; Krause, Cornelia; Morin, Hubert

    2011-01-01

    In the short term, trees rely on the internal storage of water because it affects their ability to sustain photosynthesis and growth. However, water is not rapidly available for transpiration from all the compartments of the plant and the living tissues of the stem act as a buffer to preclude low water potentials during peaks of transpiration. In this paper, electronic dendrometers were used from mid-June to mid-September 2008 to compare the radius variations in stem and roots of black spruce [Picea mariana (Mill.) B.S.P.] in two sites of the boreal forest of Quebec, Canada, with different soil characteristics and water retention. The duration of the daily cycles was similar between sites and measurement heights but greater amplitudes of contraction and expansion were observed on the stem and in the site with the shallowest soil organic layer. The expansion phase had higher amplitudes and lasted longer than contraction. On average, the contraction phase occurred between 07:00 and 16:30 (legal time), while expansion lasted 14.5 h. The roots in the site with the deepest organic layer showed a wider variation in the onset of contraction, which could be as late as 13:00. The probability of observing the contraction phase depended on precipitation. With a precipitation 60% probability of observing contraction between 05:00 and 21:00, decreasing to 20% with precipitation >1.1 mm h−1. These findings demonstrated that the depth of the organic layer plays an important role in maintaining the internal water reserve of trees. The dynamics of water depletion and replenishment can modify the water potential of xylem and cell turgor during the enlargement phase, thus affecting radial growth. Changes in temperature and precipitation regime could influence the dynamics of internal water storage in trees growing on shallower and drier soils. PMID:22639583

  16. Optimizing basin-scale coupled water quantity and water quality management with stochastic dynamic programming

    DEFF Research Database (Denmark)

    Davidsen, Claus; Liu, Suxia; Mo, Xingguo;

    2015-01-01

    Few studies address water quality in hydro-economic models, which often focus primarily on optimal allocation of water quantities. Water quality and water quantity are closely coupled, and optimal management with focus solely on either quantity or quality may cause large costs in terms of the oth......-economic optimiza-tion model can be used to assess costs of meeting additional constraints such as minimum water qual-ity or to economically prioritize investments in waste water treatment facilities based on economic criteria....

  17. Several Dynamical Properties for a Nonlinear Shallow Water Equation

    Directory of Open Access Journals (Sweden)

    Ls Yong

    2014-01-01

    Full Text Available A nonlinear third order dispersive shallow water equation including the Degasperis-Procesi model is investigated. The existence of weak solutions for the equation is proved in the space L1(R∩BV (R under certain assumptions. The Oleinik type estimate and L2N(R  (N is a natural number estimate for the solution are obtained.

  18. Water dynamics in fresh and frozen yeasted dough.

    Science.gov (United States)

    Loveday, Simon M; Huang, Victor T; Reid, David S; Winger, Ray J

    2012-01-01

    Water is an integral part of wheat flour dough-the amount, physical state, and location of water are crucial to the formation of a dough that will hold gas and produce an open, aerated crumb structure in the final product. This has been understood for centuries by craft bakers, who were highly attuned to the "feel" of dough in their hands. In the 20th century, empirical instruments were invented that simulated part of the breadmaking process, and their limited predictive capacity made them valuable quality control tools. During the latter decades of the 20th century the cost and availability of advanced instrumental methods for characterizing foods improved dramatically, and facilitated a "fundamental science" approach to food research. The physicochemical mechanisms by which water exerts such a strong influence on the character of dough are now better understood. This review contrasts the empirical and fundamental view points, and summarizes recent knowledge about the roles of water in the manufacture of fresh and frozen yeasted dough. PMID:22369259

  19. Sox17-Mediated XEN Cell Conversion Identifies Dynamic Networks Controlling Cell-Fate Decisions in Embryo-Derived Stem Cells

    Directory of Open Access Journals (Sweden)

    Angela C.H. McDonald

    2014-10-01

    Full Text Available Little is known about the gene regulatory networks (GRNs distinguishing extraembryonic endoderm (ExEn stem (XEN cells from those that maintain the extensively characterized embryonic stem cell (ESC. An intriguing network candidate is Sox17, an essential transcription factor for XEN derivation and self-renewal. Here, we show that forced Sox17 expression drives ESCs toward ExEn, generating XEN cells that contribute to ExEn when placed back into early mouse embryos. Transient Sox17 expression is sufficient to drive this fate change during which time cells transit through distinct intermediate states prior to the generation of functional XEN-like cells. To orchestrate this conversion process, Sox17 acts in autoregulatory and feedforward network motifs, regulating dynamic GRNs directing cell fate. Sox17-mediated XEN conversion helps to explain the regulation of cell-fate changes and reveals GRNs regulating lineage decisions in the mouse embryo.

  20. Semiquantum molecular dynamics simulation of liquid water by time-dependent Hartree approach.

    Science.gov (United States)

    Kim, Hyeon-Deuk; Ando, Koji

    2009-08-14

    Semiquantum liquid water molecular dynamics simulation was developed using the time-dependent Hartree approach. The classical intra- and intermolecular potential functions of water were extended to describe the wave packet (WP) hydrogen atoms. The equations of motion with an extended phase space including auxiliary coordinates and momenta representing the hydrogen WP widths were derived and solved. The molecular dynamics simulation of semiquantum water demonstrated that the semiquantum hydrogen atoms make the liquid water less structured and the hydrogen bonds weakened. The poor structurization in liquid water was inferred from the increased mobility of a water molecule and the redshift of OH stretching frequency. The zero-point energy introduced by the semiquantum hydrogens enhances the anharmonic potential effects and contributes to the redshifted OH stretching vibration. We found a significant peak around 4400 cm(-1) in the absorption spectrum resulting from the energy exchange between the WP width dynamics and the coupling of the OH stretching mode and the rotational motion of each water. We proposed that a liquid free energy landscape is smoothed due to semiquantum hydrogen atoms, and influences the liquid structure and dynamics. PMID:19691391

  1. Modulation of dynamics and reactivity of water in reverse micelles of mixed surfactants.

    Science.gov (United States)

    Mitra, Rajib Kumar; Sinha, Sudarson Sekhar; Verma, Pramod Kumar; Pal, Samir Kumar

    2008-10-16

    In this contribution, we attempt to correlate the change in water dynamics in a reverse micellar (RM) core caused by the modification of the interface by mixing an anionic surfactant, sodium bis(2-ethylhexyl) sulfosuccinate (AOT), and a nonionic surfactant, tetraethylene glycol monododecyl ether (Brij-30), at different proportions, and its consequent effect on the reactivity of water, measured by monitoring the solvolysis reaction of benzoyl chloride (BzCl). The dimension of the RM droplets at different mixing ratios of AOT and Brij-30 (X(Brij-30)) has been measured using dynamic light scattering (DLS) technique. The physical properties of the RM water have been determined using Fourier transform infrared spectroscopy (FTIR) and compressibility studies, which show that with increasing X(Brij-30), the water properties tend toward that of bulk-like water. The solvation dynamics, probed by coumarin 500 dye, gets faster with X(Brij-30). The rotational anisotropy studies along with a wobbling-in-cone analysis show that the probe experiences less restriction at higher X(Brij-30). The kinetics of the water-mediated solvolysis also gets faster with X(Brij-30). The increased rate of solvolysis has been correlated with the accelerated solvation dynamics, which is another consequence of surfactant headgroup-water interaction. PMID:18808089

  2. Characterization of dynamic change of Fan-delta reservoir properties in water-drive development

    Energy Technology Data Exchange (ETDEWEB)

    Wu Shenghe; Xiong Qihua; Liu Yuhong [Univ. of Petroleum Changping, Beijing (China)

    1997-08-01

    Fan-delta reservoir in Huzhuangji oil field of east China, is a typical highly heterogeneous reservoir. The oil field has been developed by water-drive for 10 years, but the oil recovery is less than 12%, and water cut is over 90%, resulting from high heterogeneity and serious dynamic change of reservoir properties. This paper aims at the study of dynamic change of reservoir properties in water-drive development. Through quantitative imaging analysis and mercury injection analysis of cores from inspection wells, the dynamic change of reservoir pore structure in water-drive development was studied. The results show that the {open_quotes}large pore channels{close_quotes} develop in distributary channel sandstone and become larger in water-drive development, resulting in more serious pore heterogeneity. Through reservoir sensitivity experiments, the rock-fluid reaction in water-drive development is studied. The results show the permeability of some distal bar sandstone and deserted channel sandstone becomes lower due to swelling of I/S clay minerals in pore throats. OD the other hand, the permeability of distributary channel and mouth bar sandstone become larger because the authigenic Koalinites in pore throats are flushed away with the increase of flow rate of injection water. Well-logging analysis of flooded reservoirs are used to study the dynamic change of reservoir properties in various flow units. The distribution of remaining oil is closely related to the types and distribution of flow units.

  3. Revealing the Dynamics of Thylakoid Membranes in Living Cyanobacterial Cells

    Science.gov (United States)

    Stingaciu, Laura-Roxana; O'Neill, Hugh; Liberton, Michelle; Urban, Volker S.; Pakrasi, Himadri B.; Ohl, Michael

    2016-01-01

    Cyanobacteria are photosynthetic prokaryotes that make major contributions to the production of the oxygen in the Earth atmosphere. The photosynthetic machinery in cyanobacterial cells is housed in flattened membrane structures called thylakoids. The structural organization of cyanobacterial cells and the arrangement of the thylakoid membranes in response to environmental conditions have been widely investigated. However, there is limited knowledge about the internal dynamics of these membranes in terms of their flexibility and motion during the photosynthetic process. We present a direct observation of thylakoid membrane undulatory motion in vivo and show a connection between membrane mobility and photosynthetic activity. High-resolution inelastic neutron scattering experiments on the cyanobacterium Synechocystis sp. PCC 6803 assessed the flexibility of cyanobacterial thylakoid membrane sheets and the dependence of the membranes on illumination conditions. We observed softer thylakoid membranes in the dark that have three-to four fold excess mobility compared to membranes under high light conditions. Our analysis indicates that electron transfer between photosynthetic reaction centers and the associated electrochemical proton gradient across the thylakoid membrane result in a significant driving force for excess membrane dynamics. These observations provide a deeper understanding of the relationship between photosynthesis and cellular architecture.

  4. Graphene confinement effects on melting/freezing point and structure and dynamics behavior of water.

    Science.gov (United States)

    Foroutan, Masumeh; Fatemi, S Mahmood; Shokouh, F

    2016-05-01

    In this work, the melting/freezing point of confined water between two graphene sheets was calculated from the direct coexistence of the solid-liquid interface. Also, molecular dynamics simulation of confined liquid water-ice between two graphene sheets was applied. The phase transition temperature of the confined ice-water mixture was calculated as 240K that was 29K less than the non-confined ice-water system. In order to study the behavior of water molecules at different distances from the graphene sheets, 5 regions were provided using some imaginary planes, located between two graphene sheets. The obtained simulation results showed that water molecules located in the region near each graphene sheet with the thickness of 2nm had a different behavior from other water molecules located in other regions. The results demonstrated that water molecules in the vicinity of graphene sheets had more mean square displacements than those in the middle regions. PMID:27041448

  5. Specific ions modulate diffusion dynamics of hydration water on lipid membrane surfaces.

    Science.gov (United States)

    Song, Jinsuk; Franck, John; Pincus, Philip; Kim, Mahn Won; Han, Songi

    2014-02-12

    Effects of specific ions on the local translational diffusion of water near large hydrophilic lipid vesicle surfaces were measured by Overhauser dynamic nuclear polarization (ODNP). ODNP relies on an unpaired electron spin-containing probe located at molecular or surface sites to report on the dynamics of water protons within ~10 Å from the spin probe, which give rise to spectral densities for electron-proton cross-relaxation processes in the 10 GHz regime. This pushes nuclear magnetic resonance relaxometry to more than an order of magnitude higher frequencies than conventionally feasible, permitting the measurement of water moving with picosecond to subnanosecond correlation times. Diffusion of water within ~10 Å of, i.e., up to ~3 water layers around the spin probes located on hydrophilic lipid vesicle surfaces is ~5 times retarded compared to the bulk water translational diffusion. This directly reflects on the activation barrier for surface water diffusion, i.e., how tightly water is bound to the hydrophilic surface and surrounding waters. We find this value to be modulated by the presence of specific ions in solution, with its order following the known Hofmeister series. While a molecular description of how ions affect the hydration structure at the hydrophilic surface remains to be answered, the finding that Hofmeister ions directly modulate the surface water diffusivity implies that the strength of the hydrogen bond network of surface hydration water is directly modulated on hydrophilic surfaces. PMID:24456096

  6. Water supply dynamics and quality of alternative water sources in low-income areas of Lilongwe City, Malawi

    Science.gov (United States)

    Chidya, Russel C. G.; Mulwafu, Wapulumuka O.; Banda, Sembeyawo C. T.

    2016-06-01

    Recent studies in many developing countries have shown that Small Scale Independent Providers (SSIPs) in low-income areas (LIAs) are practical alternatives to water utilities. This study explored supply dynamics and quality of alternative water sources in four LIAs of Lilongwe City in Malawi using qualitative and quantitative methods. Household-level surveys (n = 120) and transect walks were employed to determine the socio-economic activities in the areas. One-on-one discussions were made with water source owners (SSIPs) (n = 24). Data on policy and institutional frameworks was collected through desktop study and Key Informant Interviews (n = 25). Quality of the water sources (shallow wells and boreholes) was determined by collecting grab samples (n = 24) in triplicate using 500 mL bottles. Selected physico-chemical and microbiological parameters were measured: pH, EC, TDS, turbidity, water temperature, salinity, K, Na, Ca, Mg, Cl-, F-, NO3-, alkalinity, water hardness, Fecal coliform (FC) and Faecal Streptococci (FS) bacteria. Water quality data was compared with Malawi Bureau of Standards (MBS) and World Health Organization (WHO) guidelines for drinking water. Shallow wells were reported (65%, n = 120) to be the main source of water for household use in all areas. Some policies like prohibition of boreholes and shallow wells in City locations were in conflict with other provisions of water supply, sanitation and housing. High levels of FC (0-2100 cfu/100 mL) and FS (0-1490 cfu/100 mL) at several sites (>90%, n = 24) suggest water contamination likely to impact on human health. This calls for upgrading and recognition of the water sources for improved water service delivery.

  7. Cell wall dynamics modulate acetic acid-induced apoptotic cell death of Saccharomyces cerevisiae

    Directory of Open Access Journals (Sweden)

    António Rego

    2014-08-01

    Full Text Available Acetic acid triggers apoptotic cell death in Saccharomyces cerevisiae, similar to mammalian apoptosis. To uncover novel regulators of this process, we analyzed whether impairing MAPK signaling affected acetic acid-induced apoptosis and found the mating-pheromone response and, especially, the cell wall integrity pathways were the major mediators, especially the latter, which we characterized further. Screening downstream effectors of this pathway, namely targets of the transcription factor Rlm1p, highlighted decreased cell wall remodeling as particularly important for acetic acid resistance. Modulation of cell surface dynamics therefore emerges as a powerful strategy to increase acetic acid resistance, with potential application in industrial fermentations using yeast, and in biomedicine to exploit the higher sensitivity of colorectal carcinoma cells to apoptosis induced by acetate produced by intestinal propionibacteria.

  8. Dynamics of two-dimensional monolayer water confined in hydrophobic and charged environments.

    Science.gov (United States)

    Kumar, Pradeep; Han, Sungho

    2012-09-21

    We perform molecular dynamics simulations to study the effect of charged surfaces on the intermediate and long time dynamics of water in nanoconfinements. Here, we use the transferable interaction potential with five points (TIP5P) model of a water molecule confined in both hydrophobic and charged surfaces. For a single molecular layer of water between the surfaces, we find that the temperature dependence of the lateral diffusion constant of water up to very high temperatures remains Arrhenius with a high activation energy. In case of charged surfaces, however, the dynamics of water in the intermediate time regime is drastically modified presumably due to the transient coupling of dipoles of water molecules with electric field fluctuations induced by charges on the confining surfaces. Specifically, the lateral mean square displacements display a distinct super-diffusive behavior at intermediate time scale, defined as the time scale between ballistic and diffusive regimes. This change in the intermediate time-scale dynamics in the charged confinement leads to the enhancement of long-time dynamics as reflected in increasing diffusion constant. We introduce a simple model for a possible explanation of the super-diffusive behavior and find it to be in good agreement with our simulation results. Furthermore, we find that confinement and the surface polarity enhance the low frequency vibration in confinement compared to bulk water. By introducing a new effective length scale of coupling between translational and orientational motions, we find that the length scale increases with the increasing strength of the surface polarity. Further, we calculate the correlation between the diffusion constant and the excess entropy and find a disordering effect of polar surfaces on the structure of water. Finally, we find that the empirical relation between the diffusion constant and the excess entropy holds for a monolayer of water in nanoconfinement. PMID:22998274

  9. Love and fear of water: Water dynamics around charged and apolar solutes

    NARCIS (Netherlands)

    S.T. van der Post

    2014-01-01

    Water molecules are deceptively simple considering their importance to many (biological) processes. The interesting properties of water and its role in these processes can be attributed to the ability of water molecules to form up to four hydrogen-bonds. This hydrogen-bond network is altered in the

  10. Dynamic modelling of water demand, water availability and adaptation strategies for power plants to global change

    International Nuclear Information System (INIS)

    According to the latest IPCC reports, the frequency of hot and dry periods will increase in many regions of the world in the future. For power plant operators, the increasing possibility of water shortages is an important challenge that they have to face. Shortages of electricity due to water shortages could have an influence on industries as well as on private households. Climate change impact analyses must analyse the climate effects on power plants and possible adaptation strategies for the power generation sector. Power plants have lifetimes of several decades. Their water demand changes with climate parameters in the short- and medium-term. In the long-term, the water demand will change as old units are phased out and new generating units appear in their place. In this paper, we describe the integration of functions for the calculation of the water demand of power plants into a water resources management model. Also included are both short-term reactive and long-term planned adaptation. This integration allows us to simulate the interconnection between the water demand of power plants and water resources management, i.e. water availability. Economic evaluation functions for water shortages are also integrated into the water resources management model. This coupled model enables us to analyse scenarios of socio-economic and climate change, as well as the effects of water management actions. (author)

  11. Nutrient dynamics in Amazon shelf waters: results from AMASSEDS

    Science.gov (United States)

    Demaster, David J.; Pope, Robert H.

    1996-03-01

    Four hydrographic cruises were conducted on the Amazon shelf as part of the AMASSEDS field program. During each cruise, approximately 55 stations were occupied and nutrients, as well as other hydrographic parameters, were measured. The results of this time series sampling program indicate that the nutrient concentrations in the riverine end-member (silicate = 144 μmol kg -1, phosphate = 0.7 μmol kg -1, nitrate = 16 μmol kg -1, ammonium = 0.4 μmol kg -1, and urea = 0.9 μmol kg -1) remain relatively constant, despite a two-fold seasonal variation in river water discharge rate. Of the major nutrients (nitrate, phosphate, ammonium and silicate), nitrate shows the greatest seasonal change in riverine end-member concentration with a high value (23 μmol kg -1) during the March cruise (rising river discharge) and a low value (12 μmol kg -1) during the November cruise (falling river discharge). Nitrate is the dominant nutrient form of inorganic nitrogen throughout most of the river/ocean mixing zone, however, in the outershelf area, where nitrate has been depleted by biological production, this nutrient occurs at concentrations comparable to the other nitrogen species (ammonium, nitrite and urea), which are at levels budget calculations have been used to establish the dominant external source of nutrients to the algal blooms occurring on the outer shelf. Based on flux core measurements, diffusive nutrient fluxes from Amazon shelf sediments are very low relative to riverine supply rates (silicate flux out = 1.3% of riverine flux, the nitrate plus ammonium flux is essentially zero, and the phosphate seabed flux shows removal of ˜2% of the riverine flux). Inventories of naturally occurring 210Pb were used to estimate the onshore flow of subsurface water onto the Amazon shelf. The radiochemical data indicate that the flux of water onto the shelf may be as much as five to ten times greater than the annual flow of the Amazon River. The nutrient flux from this shoreward

  12. Characterizing dynamic hysteresis and fractal statistics of chaotic two-phase flow and application to fuel cells

    Science.gov (United States)

    Burkholder, Michael B.; Litster, Shawn

    2016-05-01

    In this study, we analyze the stability of two-phase flow regimes and their transitions using chaotic and fractal statistics, and we report new measurements of dynamic two-phase pressure drop hysteresis that is related to flow regime stability and channel water content. Two-phase flow dynamics are relevant to a variety of real-world systems, and quantifying transient two-phase flow phenomena is important for efficient design. We recorded two-phase (air and water) pressure drops and flow images in a microchannel under both steady and transient conditions. Using Lyapunov exponents and Hurst exponents to characterize the steady-state pressure fluctuations, we develop a new, measurable regime identification criteria based on the dynamic stability of the two-phase pressure signal. We also applied a new experimental technique by continuously cycling the air flow rate to study dynamic hysteresis in two-phase pressure drops, which is separate from steady-state hysteresis and can be used to understand two-phase flow development time scales. Using recorded images of the two-phase flow, we show that the capacitive dynamic hysteresis is related to channel water content and flow regime stability. The mixed-wettability microchannel and in-channel water introduction used in this study simulate a polymer electrolyte fuel cell cathode air flow channel.

  13. Seasonal Dynamics of Water Use Strategy of Two Salix Shrubs in Alpine Sandy Land, Tibetan Plateau.

    Directory of Open Access Journals (Sweden)

    Yajuan Zhu

    Full Text Available Water is a limiting factor for plant growth and vegetation dynamics in alpine sandy land of the Tibetan Plateau, especially with the increasing frequency of extreme precipitation events and drought caused by climate change. Therefore, a relatively stable water source from either deeper soil profiles or ground water is necessary for plant growth. Understanding the water use strategy of dominant species in the alpine sandy land ecosystem is important for vegetative rehabilitation and ecological restoration. The stable isotope methodology of δD, δ18O, and δ13C was used to determine main water source and long-term water use efficiency of Salix psammophila and S. cheilophila, two dominant shrubs on interdune of alpine sandy land in northeastern Tibetan Plateau. The root systems of two Salix shrubs were investigated to determine their distribution pattern. The results showed that S. psammophila and S. cheilophila absorbed soil water at different soil depths or ground water in different seasons, depending on water availability and water use strategy. Salix psammophila used ground water during the growing season and relied on shallow soil water recharged by rain in summer. Salix cheilophila used ground water in spring and summer, but relied on shallow soil water recharged by rain in spring and deep soil water recharged by ground water in fall. The two shrubs had dimorphic root systems, which is coincident with their water use strategy. Higher biomass of fine roots in S. psammophila and longer fine roots in S. cheilophila facilitated to absorb water in deeper soil layers. The long-term water use efficiency of two Salix shrubs increased during the dry season in spring. The long-term water use efficiency was higher in S. psammophila than in S. cheilophila, as the former species is better adapted to semiarid climate of alpine sandy land.

  14. Seasonal Dynamics of Water Use Strategy of Two Salix Shrubs in Alpine Sandy Land, Tibetan Plateau.

    Science.gov (United States)

    Zhu, Yajuan; Wang, Guojie; Li, Renqiang

    2016-01-01

    Water is a limiting factor for plant growth and vegetation dynamics in alpine sandy land of the Tibetan Plateau, especially with the increasing frequency of extreme precipitation events and drought caused by climate change. Therefore, a relatively stable water source from either deeper soil profiles or ground water is necessary for plant growth. Understanding the water use strategy of dominant species in the alpine sandy land ecosystem is important for vegetative rehabilitation and ecological restoration. The stable isotope methodology of δD, δ18O, and δ13C was used to determine main water source and long-term water use efficiency of Salix psammophila and S. cheilophila, two dominant shrubs on interdune of alpine sandy land in northeastern Tibetan Plateau. The root systems of two Salix shrubs were investigated to determine their distribution pattern. The results showed that S. psammophila and S. cheilophila absorbed soil water at different soil depths or ground water in different seasons, depending on water availability and water use strategy. Salix psammophila used ground water during the growing season and relied on shallow soil water recharged by rain in summer. Salix cheilophila used ground water in spring and summer, but relied on shallow soil water recharged by rain in spring and deep soil water recharged by ground water in fall. The two shrubs had dimorphic root systems, which is coincident with their water use strategy. Higher biomass of fine roots in S. psammophila and longer fine roots in S. cheilophila facilitated to absorb water in deeper soil layers. The long-term water use efficiency of two Salix shrubs increased during the dry season in spring. The long-term water use efficiency was higher in S. psammophila than in S. cheilophila, as the former species is better adapted to semiarid climate of alpine sandy land. PMID:27243772

  15. Seasonal Dynamics of Water Use Strategy of Two Salix Shrubs in Alpine Sandy Land, Tibetan Plateau

    Science.gov (United States)

    Zhu, Yajuan; Wang, Guojie; Li, Renqiang

    2016-01-01

    Water is a limiting factor for plant growth and vegetation dynamics in alpine sandy land of the Tibetan Plateau, especially with the increasing frequency of extreme precipitation events and drought caused by climate change. Therefore, a relatively stable water source from either deeper soil profiles or ground water is necessary for plant growth. Understanding the water use strategy of dominant species in the alpine sandy land ecosystem is important for vegetative rehabilitation and ecological restoration. The stable isotope methodology of δD, δ18O, and δ13C was used to determine main water source and long-term water use efficiency of Salix psammophila and S. cheilophila, two dominant shrubs on interdune of alpine sandy land in northeastern Tibetan Plateau. The root systems of two Salix shrubs were investigated to determine their distribution pattern. The results showed that S. psammophila and S. cheilophila absorbed soil water at different soil depths or ground water in different seasons, depending on water availability and water use strategy. Salix psammophila used ground water during the growing season and relied on shallow soil water recharged by rain in summer. Salix cheilophila used ground water in spring and summer, but relied on shallow soil water recharged by rain in spring and deep soil water recharged by ground water in fall. The two shrubs had dimorphic root systems, which is coincident with their water use strategy. Higher biomass of fine roots in S. psammophila and longer fine roots in S. cheilophila facilitated to absorb water in deeper soil layers. The long-term water use efficiency of two Salix shrubs increased during the dry season in spring. The long-term water use efficiency was higher in S. psammophila than in S. cheilophila, as the former species is better adapted to semiarid climate of alpine sandy land. PMID:27243772

  16. A New Method for Water Desalination Using Microbial Desalination Cells

    KAUST Repository

    Cao, Xiaoxin

    2009-09-15

    Current water desalination techniques are energy intensive and some use membranes operated at high pressures. It is shownhere that water desalination can be accomplished without electrical energy input or high water pressure by using a source of organic matter as the fuel to desalinate water. A microbial fuel cell was modified by placing two membranes between the anode and cathode, creating a middle chamber for water desalination between the membranes. An anion exchange membrane was placed adjacent to the anode, and a cation exchange membrane was positioned next to the cathode. When current was produced by bacteria on the anode, ionic species in the middle chamber were transferred into the two electrode chambers, desalinating the water in the middle chamber. Proof-of-concept experiments for this approach, using what we call a microbial desalination cell (MDC), was demonstrated using water at different initial salt concentrations (5, 20, and 35 g/L) with acetate used as the substrate for the bacteria. The MDC produced a maximum of 2 W/m2 (31 W/m3) while at the same time removing about 90% of the salt in a single desalination cycle. As the salt was removed from the middle chamber the ohmic resistance of the MDC (measured using electrochemical impedance spectroscopy) increased from 25 Ω to 970 Ω at the end of the cycle. This increased resistance was reflected by a continuous decrease in the voltage produced over the cycle. These results demonstrate for the first time the possibility for a new method for water desalination and power production that uses only a source of biodegradable organic matter and bacteria. © 2009 American Chemical Society.

  17. Dynamics of Coalescence-Induced Jumping Water Droplets

    CERN Document Server

    Miljkovic, Nenad; Enright, Ryan; Wang, Evelyn N

    2013-01-01

    This fluid dynamics video shows the different interaction mechanisms of coalescence-induced droplet jumping during condensation on a nanostructured superhydrophobic surface. High speed imaging was used to show jumping behavior on superhydrophobic copper oxide and carbon nanotube surfaces. Videos demonstrating multi-jumping droplets, jumping droplet return to the surface, and droplet-droplet electrostatic repulsions were analyzed. Experiments using external electric fields in conjunction with high speed imaging in a custom built experimental chamber were used to show that all coalescence-induced jumping droplets on superhydrophobic surfaces become positively charged upon leaving the surface, which is detailed in the video.

  18. Research on Dispersed Oil Droplets Breakage and Emulsification in the Dynamic Oil and Water Hydrocyclone

    Directory of Open Access Journals (Sweden)

    Guangdong Guo

    2013-08-01

    Full Text Available Oil and water dynamic hydrocyclone is one type of facilities that separate two phases or multiple phases applied widely in the fields such as food processing, environmental protection, biological pharmacy, petroleum and chemistry. The dispersed oil droplets in the dynamic oil and water hydrocyclone were often broken into small drops by shear force, which decreased the separation efficiency of dynamic oil-water hydrocyclone greatly. To avoid the breakage of the oil droplets, the turbulence field and the velocity field of the dynamic hydrocyclone were studied by the software of Fluent to analyze the main reason that led to breakage of oil droplets. Results indicated that the deformation of oil droplets was caused by the viscous shear force; the breakage of oil droplets was caused by the Reynolds shear stress and the local pressure fluctuations. The main area that the drops were prone to breakup of the dynamic hydrocyclone is that the rotating grating nearby, the wall boundary layer of the drum and center axis of the drum. Finally, the breakage of oil droplets and emulsification of oil and water in the dynamic hydrocyclone were verified by the experiments.

  19. Replicator Dynamics of of Cancer Stem Cell; Selection in the Presence of Differentiation and Plasticity

    OpenAIRE

    Kaveh, Kamran; Kohandel, Mohammad; Sivaloganathan, Siv

    2014-01-01

    Stem cells have the potential to produce lineages of non-stem cell populations (differentiated cells) via a ubiquitous hierarchal division scheme. Differentiation of a stem cell into (partially) differentiated cells can happen either symmetrically or asymmetrically. The selection dynamics of a mutant cancer stem cell should be investigated in the light of a stem cell proliferation hierarchy and presence of a non-stem cell population. By constructing a three-compartment Moran-type model compos...

  20. Forest - water dynamics in a Mediterranean mountain environment.

    Science.gov (United States)

    Eliades, Marinos; Bruggeman, Adriana; Lange, Manfred; Camera, Corrado; Christou, Andreas

    2015-04-01

    In semi-arid Mediterranean mountain environments, the soil layer is very shallow or even absent due to the steep slopes. Soil moisture in these environments is limited, but still vegetation thrives. There is limited knowledge about where the vegetation extracts the water from, how much water it uses, and how it interacts with other processes in the hydrological cycle. The main objective of this study is to quantify the water balance components of a Pinus brutia forest at tree level, by measuring the tree transpiration and the redistribution of the water from trees to the soil and the bedrock fractures. The study area is located on a forested hill slope on the outside edge of Peristerona watershed in Cyprus. The site was mapped with the use of a total station and a differentially-corrected GPS, in order to create a high resolution DEM and soil depth map of the area. Soil depth was measured at a 1-m grid around the trees. Biometric measurements were taken from a total of 45 trees. Four trees were selected for monitoring. Six sap flow sensors are installed in the selected trees for measuring transpiration and reverse flows. Two trees have two sensors each to assess the variability. Four volumetric soil moisture sensors are installed around each tree at distances 1 m and 2 m away from the tree trunk. An additional fifth soil moisture sensor is installed in soil depths exceeding 20-cm depth. Four throughfall rain gauges were installed randomly around each tree to compute interception losses. Stemflow is measured by connecting an opened surface plastic tube collar at 1.6 m height around each tree trunk. The trunk surface gaps were filled with silicon glue in order to avoid any stemflow losses. The plastic collar is connected to a sealed surface rain gauge. A weather station monitors all meteorological variables on an hourly basis. Results showed a maximum sap flow volume of 77.9 L/d, from November to January. The sensors also measured a maximum negative flow of 7.9 L

  1. Dynamics of CO in Amorphous Water Ice Environments

    CERN Document Server

    Karssemeijer, L J; van Hemert, M C; van der Avoird, A; Allodi, M A; Blake, G A; Cuppen, H M

    2013-01-01

    The long-timescale behavior of adsorbed carbon monoxide on the surface of amorphous water ice is studied under dense cloud conditions by means of off-lattice, on-the-fly, kinetic Monte Carlo simula- tions. It is found that the CO mobility is strongly influenced by the morphology of the ice substrate. Nanopores on the surface provide strong binding sites which can effectively immobilize the adsorbates at low coverage. As the coverage increases, these strong binding sites are gradually occupied leav- ing a number of admolecules with the ability to diffuse over the surface. Binding energies, and the energy barrier for diffusion are extracted for various coverages. Additionally, the mobility of CO is determined from isothermal desorption experiments. Reasonable agreement on the diffusivity of CO is found with the simulations. Analysis of the 2152 cm$^{-1}$, polar CO band supports the computational findings that the pores in the water ice provide the strongest binding sites and dominate diffusion at low temperatur...

  2. A DYNAMIC ANALYSIS OF WATER SAVINGS FROM ADVANCED IRRIGATION TECHNOLOGY

    OpenAIRE

    Hornbaker, Robert H.; Mapp, Harry P., Jr.

    1988-01-01

    A computerized grain sorghum plant growth model is combined with recursive programming to analyze the potential irrigation water savings from adopting irrigation scheduling and low pressure center pivot irrigation technology. Results indicate that irrigation pumping can be reduced with increased yields and net returns by adopting low energy precision application (LEPA) irrigation systems. Variations in input and output prices affect optimal irrigation quantities for low pressure irrigation sy...

  3. Dynamics of supercooled water studied by neutron scattering

    International Nuclear Information System (INIS)

    Incoherent quasi-elastic and inelastic neutron scattering by water was performed in a temperature range extending to the supercooled state. The analysis of the quasi-elastic spectrum separates two main components and gives two characteristic times. Their temperature analysis justifies the use of the Jump Diffusion model and suggests a mechanism for the hydrogen bond breaking. The inelastic spectra extend until 600 MeV, i.e. covering the intramolecular vibration region showing, for the first time, the stretching band

  4. Time Resolved Broadband Terahertz Relaxation Dynamics of Electron in Water

    DEFF Research Database (Denmark)

    Wang, Tianwu; Iwaszczuk, Krzysztof; Cooke, David G.;

    We investigated the transient response of the solvated electron in water ejected by photodetachment from potassium ferrocyanide using time resolved terahertz spectroscopy (TSTS). Ultrabroadband THz transients are generated and detected by a two-color femtosecond-induced air plasma and air biased...... coherent detection, respectively. We find that the measured frequency dependent conductivity can be well described by a Drude-Smith model, supplemented by a Lorentz model oscillating near 5 THz....

  5. Mitochondrial dynamics and cell death in heart failure.

    Science.gov (United States)

    Marín-García, José; Akhmedov, Alexander T

    2016-03-01

    The highly regulated processes of mitochondrial fusion (joining), fission (division) and trafficking, collectively called mitochondrial dynamics, determine cell-type specific morphology, intracellular distribution and activity of these critical organelles. Mitochondria are critical for cardiac function, while their structural and functional abnormalities contribute to several common cardiovascular diseases, including heart failure (HF). The tightly balanced mitochondrial fusion and fission determine number, morphology and activity of these multifunctional organelles. Although the intracellular architecture of mature cardiomyocytes greatly restricts mitochondrial dynamics, this process occurs in the adult human heart. Fusion and fission modulate multiple mitochondrial functions, ranging from energy and reactive oxygen species production to Ca(2+) homeostasis and cell death, allowing the heart to respond properly to body demands. Tightly controlled balance between fusion and fission is of utmost importance in the high energy-demanding cardiomyocytes. A shift toward fission leads to mitochondrial fragmentation, while a shift toward fusion results in the formation of enlarged mitochondria and in the fusion of damaged mitochondria with healthy organelles. Mfn1, Mfn2 and OPA1 constitute the core machinery promoting mitochondrial fusion, whereas Drp1, Fis1, Mff and MiD49/51 are the core components of fission machinery. Growing evidence suggests that fusion/fission factors in adult cardiomyocytes play essential noncanonical roles in cardiac development, Ca(2+) signaling, mitochondrial quality control and cell death. Impairment of this complex circuit causes cardiomyocyte dysfunction and death contributing to heart injury culminating in HF. Pharmacological targeting of components of this intricate network may be a novel therapeutic modality for HF treatment. PMID:26872674

  6. An analytical model for predicting water table dynamics during drainage and evaporation

    Science.gov (United States)

    Cook, F. J.; Rassam, D. W.

    2002-06-01

    Water table dynamics in tile-drained fields have been thoroughly investigated by numerous researchers. Recent studies have highlighted the importance of incorporating the effects of evaporation into the design of such drainage systems. In tropical areas, evaporation plays a particularly crucial role in lowering the water table in finely textured soils. In this paper, water table dynamics are investigated for the case of coupled drainage and evaporation. A simple analytical model that determines the relative contribution of the drainage component to the draw down of the water table is proposed. The model's estimates compare reasonably well to field data, as well as those derived from numerical simulations conducted for various evaporation rates and soil types. When presented in a non-dimensional form, the model's results can provide a quick estimate of the relative contribution of drainage to lowering the water table, which is highly relevant to the hydrology of acid sulphate soils.

  7. Parameter optimization method for the water quality dynamic model based on data-driven theory.

    Science.gov (United States)

    Liang, Shuxiu; Han, Songlin; Sun, Zhaochen

    2015-09-15

    Parameter optimization is important for developing a water quality dynamic model. In this study, we applied data-driven method to select and optimize parameters for a complex three-dimensional water quality model. First, a data-driven model was developed to train the response relationship between phytoplankton and environmental factors based on the measured data. Second, an eight-variable water quality dynamic model was established and coupled to a physical model. Parameter sensitivity analysis was investigated by changing parameter values individually in an assigned range. The above results served as guidelines for the control parameter selection and the simulated result verification. Finally, using the data-driven model to approximate the computational water quality model, we employed the Particle Swarm Optimization (PSO) algorithm to optimize the control parameters. The optimization routines and results were analyzed and discussed based on the establishment of the water quality model in Xiangshan Bay (XSB). PMID:26277602

  8. Molecular Dynamics Study of Water Molecules in Interlayer of 14 ^|^Aring; Tobermorite

    KAUST Repository

    Yoon, Seyoon

    2013-01-01

    The molecular structure and dynamics of interlayer water of 14 Å tobermorite are investigated based on molecular dynamics (MD) simulations. Calculated structural parameters of the interlayer water configuration are in good agreement with current knowledge of the refined structure. The MD simulations provide detailed information on the position and mobility of the hydrogen and oxygen of interlayer water, as well as its self-diffusion coefficient, through the interlayer of 14 Å tobermorite. Comparison of the MD simulation results at 100 and 300 K demonstrates that water molecules in the interlayer maintain their structure but change their mobility. The dominant configuration and self-diffusion coefficient of interlayer water are obtained in this study. Copyright © 2013 Japan Concrete Institute.

  9. Dynamic Thermal Model And Control Of A Pem Fuel Cell System

    DEFF Research Database (Denmark)

    Liso, Vincenzo; Nielsen, Mads Pagh

    2013-01-01

    A lumped parameter dynamic model is developed for predicting the stack performance, temperatures of the exit reactant gases and coolant liquid outlet in a proton-exchange membrane fuel cell (PEMFC) system. The air compressor, humidifier and cooling heat exchanger models are integrated to study the...... fuel cell system. A PID temperature control is implemented to study the effect of stack temperature on settling times of other variables such as stack voltage, air flow rate, oxygen excess ratio and net power of the stack. The model allows an assessment of the effect of operating parameters (stack...... power output, cooling water flow rate, air flow rate, and environmental temperature) and parameter interactions on the system thermal performance. The model represents a useful tool to determine the operating temperatures of the various components of the thermal system, and thus to fully assess the...

  10. Structural Phase Transitions and Water Dynamics in Uranyl Fluoride Hydrates.

    Science.gov (United States)

    Miskowiec, Andrew; Kirkegaard, Marie C; Huq, Ashfia; Mamontov, Eugene; Herwig, Kenneth W; Trowbridge, Lee; Rondinone, Adam; Anderson, Brian

    2015-12-10

    We report a novel production method for uranium oxyfluoride [(UO2)7F14(H2O)7]·4H2O, referred to as structure D. Structure D is produced as a product of hydrating anhydrous uranyl fluoride, UO2F2, through the gas phase at ambient temperatures followed by desiccation by equilibration with a dry environment. We follow the structure of [(UO2)7F14(H2O)7]·4H2O through an intermediate, liquid-like phase, wherein the coordination number of the uranyl ion is reduced to 5 (from 6 in the anhydrous structure), and a water molecule binds as an equatorial ligand to the uranyl ion. Quasielastic neutron scattering results compare well with previous measurements of mineral hydrates. The two groups of structurally distinct water molecules in D perform restricted motion on a length scale commensurate with the O-H bond (r = 0.92 Å). The more tightly bound equatorial ligand waters rotate slower (Dr = 2.2 ps(-1)) than their hydrogen-bonded partners (Dr = 28.7 ps(-1)). PMID:26575434

  11. Proton Exchange Membrane Fuel Cell Design and Dynamic Modeling in MATLAB

    OpenAIRE

    S.V.T.Abirami; G.Samuel Muthura

    2015-01-01

    The alternatives to combustion engines in future will be fuel cells. The dynamic behavior of fuel cells for changing load conditions show poor voltage regulation. For improving the voltage regulation of PEM fuel cell, efficient control system should be designed. If the dynamic behavior of the fuel cell is known, the cost in designing the control system is greatly reduced .The behavior of the fuel cell for various load conditions and for changing pressure and temperature can be fou...

  12. Adaptation and dynamics of cat retinal ganglion cells.

    Science.gov (United States)

    Enroth-Cugell, C; Shapley, R M

    1973-09-01

    1. The impulse/quantum (I/Q) ratio was measured as a function of background illumination for rod-dominated, pure central, linear square-wave responses of retinal ganglion cells in the cat.2. The I/Q ratio was constant at low backgrounds (dark adapted state) and inversely proportional to the 0.9 power of the background at high backgrounds (the light adapted state). There was an abrupt transition from the dark-adapted state to the light-adapted state.3. It was possible to define the adaptation level at a particular background as the ratio (I/Q ratio at that background)/(dark adapted I/Q ratio).4. The time course of the square-wave response was correlated with the adaptation level. The response was sustained in the dark-adapted state, partially transient at the transition level, and progressively more transient the lower the impulse/quantum ratio of the ganglion cell became. This was true both for on-centre and off-centre cells.5. The frequency response of the central response mechanism at different adaptation levels was measured. It was a low-pass characteristic in the dark-adapted state and became progressively more of a bandpass characteristic as the cell became more light-adapted.6. The rapidity of onset of adaptation was measured with a time-varying adapting light. The impulse/quantum ratio is reset within 100 msec of the onset of the conditioning light, and is kept at the new value throughout the time the conditioning light is on.7. These results can be explained by a nonlinear feedback model. In the model, it is postulated that the exponential function of the horizontal cell potential controls transmission from rods to bipolars. This model has an abrupt transition from dark- to light-adapted states, and its response dynamics are correlated with adaptation level. PMID:4747229

  13. Water Usage for In-Situ Oil Shale Retorting – A Systems Dynamics Model

    Energy Technology Data Exchange (ETDEWEB)

    Earl D. Mattson; Larry Hull; Kara Cafferty

    2012-12-01

    A system dynamic model was construction to evaluate the water balance for in-situ oil shale conversion. The model is based on a systems dynamics approach and uses the Powersim Studio 9™ software package. Three phases of an insitu retort were consider; a construction phase primarily accounts for water needed for drilling and water produced during dewatering, an operation phase includes the production of water from the retorting process, and a remediation phase water to remove heat and solutes from the subsurface as well as return the ground surface to its natural state. Throughout these three phases, the water is consumed and produced. Consumption is account for through the drill process, dust control, returning the ground water to its initial level and make up water losses during the remedial flushing of the retort zone. Production of water is through the dewatering of the retort zone, and during chemical pyrolysis reaction of the kerogen conversion. The major water consumption was during the remediation of the insitu retorting zone.

  14. Spatial-Temporal Survey and Occupancy-Abundance Modeling To Predict Bacterial Community Dynamics in the Drinking Water Microbiome

    OpenAIRE

    Pinto, Ameet; Schroeder, Joanna; Lunn, Mary; Sloan, William; Raskin, Lutgarde

    2014-01-01

    ABSTRACT Bacterial communities migrate continuously from the drinking water treatment plant through the drinking water distribution system and into our built environment. Understanding bacterial dynamics in the distribution system is critical to ensuring that safe drinking water is being supplied to customers. We present a 15-month survey of bacterial community dynamics in the drinking water system of Ann Arbor, MI. By sampling the water leaving the treatment plant and at nine points in the d...

  15. Design of Compact Photoelectrochemical Cells for Water Splitting

    Directory of Open Access Journals (Sweden)

    Bosserez Tom

    2015-09-01

    Full Text Available Solar driven water splitting can be achieved by coupling electrolyzers with PhotoVoltaics (PV. Integration of both functions in a compact PhotoElectroChemical (PEC cell is an attractive option but presents significant scientific challenges. In this work, the design of single- and dual-compartment PEC cells for research purposes is discussed. The fabrication of separator-electrode assemblies is an important aspect, and upscaling of these architectures even to centimeter scale is not trivial. The layout of a new dual-compartment compact PEC cell with in-situ monitoring of pH, temperatures, and oxygen and hydrogen evolution for research purposes is presented. Finally, a prospect of future PEC cells for practical applications is presented.

  16. The influence of charge on the structure and dynamics of water encapsulated in reverse micelles.

    Science.gov (United States)

    Patra, Animesh; Luong, Trung Quan; Mitra, Rajib Kumar; Havenith, Martina

    2014-07-01

    Hydrogen-bonded structure and relaxation dynamics of water entrapped inside reverse micelles (RMs) composed of surfactants with different charged head groups: sodium bis(2-ethylhexyl) sulfosuccinate (AOT) (anionic), didodecyldimethylammonium bromide (DDAB) (cationic) and Igepal CO-520 (Igepal) (nonionic) in cyclohexane (Cy) have been studied as a function of hydration (defined by ). Sub-diffusive slow (sub-ns) relaxation dynamics of water has been measured by the time resolved fluorescence spectroscopy (TRFS) technique using two fluorophores, namely 8-anilino-1-naphthalenesulfonic acid (ANS) and coumarin-343 (C-343). The hydrogen bonded connectivity network of water confined in these RMs has been investigated by monitoring the hydrogen bond stretching and libration bands of water using far-infrared FTIR spectroscopy. In addition, the ultrafast collective relaxation dynamics of water inside these RMs has been determined by dielectric relaxation in the THz region (0.2-2.0 THz) using THz time domain spectroscopy (THz-TDS). While TRFS measurements establish the retardation of water dynamics for all the RM systems, FTIR and THz-TDS measurements provide with signature of charge specificity. PMID:24848870

  17. Water of Hydration Dynamics in Minerals Gypsum and Bassanite: Ultrafast 2D IR Spectroscopy of Rocks.

    Science.gov (United States)

    Yan, Chang; Nishida, Jun; Yuan, Rongfeng; Fayer, Michael D

    2016-08-01

    Water of hydration plays an important role in minerals, determining their crystal structures and physical properties. Here ultrafast nonlinear infrared (IR) techniques, two-dimensional infrared (2D IR) and polarization selective pump-probe (PSPP) spectroscopies, were used to measure the dynamics and disorder of water of hydration in two minerals, gypsum (CaSO4·2H2O) and bassanite (CaSO4·0.5H2O). 2D IR spectra revealed that water arrangement in freshly precipitated gypsum contained a small amount of inhomogeneity. Following annealing at 348 K, water molecules became highly ordered; the 2D IR spectrum became homogeneously broadened (motional narrowed). PSPP measurements observed only inertial orientational relaxation. In contrast, water in bassanite's tubular channels is dynamically disordered. 2D IR spectra showed a significant amount of inhomogeneous broadening caused by a range of water configurations. At 298 K, water dynamics cause spectral diffusion that sampled a portion of the inhomogeneous line width on the time scale of ∼30 ps, while the rest of inhomogeneity is static on the time scale of the measurements. At higher temperature, the dynamics become faster. Spectral diffusion accelerates, and a portion of the lower temperature spectral diffusion became motionally narrowed. At sufficiently high temperature, all of the dynamics that produced spectral diffusion at lower temperatures became motionally narrowed, and only homogeneous broadening and static inhomogeneity were observed. Water angular motions in bassanite exhibit temperature-dependent diffusive orientational relaxation in a restricted cone of angles. The experiments were made possible by eliminating the vast amount of scattered light produced by the granulated powder samples using phase cycling methods. PMID:27385320

  18. Radon exchange dynamics in a Karst system investigated by radon continuous measurements in water: First results

    International Nuclear Information System (INIS)

    In 2008 the underground Karst Laboratory of Bossea Cave started research on radon exchange dynamics between bedrock, cave waters (main collector and percolations) and indoor underground atmosphere. Radon air concentrations, normally high, increase more and more during the collector's floods. An explanation of this is a radon-water solubilisation process more effective in flood events, because of a greater rock-water contact surface. Radon is then carried by water into the cave and released into the air. To verify this, continuous measurements of radon concentration are needed not only in the air, but also in the waters of the cave. So a new device for continuous radon monitoring in water was tested, connected to the AlphaGuard radon monitor. For the first 6 months of 2010, for different sections of the cave, the correlations between radon in the air, radon in the waters and the collector's stream flow fluctuations were presented and discussed. (authors)

  19. Planning for Regional Water Resources in Northwest China Using a Dynamic Simulation Model

    Science.gov (United States)

    Chen, C.; Kalra, A.; Ahmad, S.

    2014-12-01

    Problem of water scarcity is prominent in northwest China due to its typical desert climate. Exceedence of sustainable yield of groundwater resources has resulted in groundwater depletion, which has raised a series of issues such as drying wells, increasing pumping costs and environmental damage. With a rapid agricultural and economic development, population increase has added extra stress on available water resources by increasing municipal, agricultural and industrial demands. This necessitates efficient water resources management strategies with better understanding of the causes of water stress and options for sustainable development of economy and management of environment. This study focuses on simulating the water supply and demand, under the influence of changing climate, for Shanshan County, located in northwest of China. A dynamic simulation model is developed using the modeling tool Stella for monthly water balance for the period ranging from 2000-2030. Different future water demand and supply scenarios are developed to represent: (1) base scenario- with current practices; (2) change of the primary water source; (3) improvement of irrigation efficiency; (4) reduction of irrigation area; and (5) reduction of industrial water demand. The results indicate that besides growing demand, the low water use efficiency and low level of water reuse are the primary concerns for water scarcity. Groundwater recharge and abstraction could be balanced by 2030, by reducing industrial demand by 50% and using high efficiency irrigation for agriculture. The model provided a better understanding of the effect of different policies and can help in identifying water resources management strategies.

  20. Molecular dynamics studies of pathways of water movement in cyanobacterial photosystem II

    Energy Technology Data Exchange (ETDEWEB)

    Gabdulkhakov, A. G., E-mail: azat@vega.protres.ru; Kljashtorny, V. G.; Dontsova, M. V. [Russian Academy of Sciences, Institute of Protein Research (Russian Federation)

    2015-01-15

    Photosystem II (PSII) catalyzes the light-induced generation of oxygen from water. The oxygen-evolving complex is buried deep in the protein on the lumenal side of PSII, and water molecules need to pass through protein subunits to reach the active site—the manganese cluster. Previous studies on the elucidation of water channels in PSII were based on an analysis of the cavities in the static PSII structure determined by X-ray diffraction. In the present study, we perform molecular dynamics simulations of the water movement in the transport system of PSII.

  1. Molecular dynamics studies of pathways of water movement in cyanobacterial photosystem II

    International Nuclear Information System (INIS)

    Photosystem II (PSII) catalyzes the light-induced generation of oxygen from water. The oxygen-evolving complex is buried deep in the protein on the lumenal side of PSII, and water molecules need to pass through protein subunits to reach the active site—the manganese cluster. Previous studies on the elucidation of water channels in PSII were based on an analysis of the cavities in the static PSII structure determined by X-ray diffraction. In the present study, we perform molecular dynamics simulations of the water movement in the transport system of PSII

  2. Optimizing basin-scale coupled water quantity and water quality man-agement with stochastic dynamic programming

    Science.gov (United States)

    Davidsen, Claus; Liu, Suxia; Mo, Xingguo; Engelund Holm, Peter; Trapp, Stefan; Rosbjerg, Dan; Bauer-Gottwein, Peter

    2015-04-01

    Few studies address water quality in hydro-economic models, which often focus primarily on optimal allocation of water quantities. Water quality and water quantity are closely coupled, and optimal management with focus solely on either quantity or quality may cause large costs in terms of the oth-er component. In this study, we couple water quality and water quantity in a joint hydro-economic catchment-scale optimization problem. Stochastic dynamic programming (SDP) is used to minimize the basin-wide total costs arising from water allocation, water curtailment and water treatment. The simple water quality module can handle conservative pollutants, first order depletion and non-linear reactions. For demonstration purposes, we model pollutant releases as biochemical oxygen demand (BOD) and use the Streeter-Phelps equation for oxygen deficit to compute the resulting min-imum dissolved oxygen concentrations. Inelastic water demands, fixed water allocation curtailment costs and fixed wastewater treatment costs (before and after use) are estimated for the water users (agriculture, industry and domestic). If the BOD concentration exceeds a given user pollution thresh-old, the user will need to pay for pre-treatment of the water before use. Similarly, treatment of the return flow can reduce the BOD load to the river. A traditional SDP approach is used to solve one-step-ahead sub-problems for all combinations of discrete reservoir storage, Markov Chain inflow clas-ses and monthly time steps. Pollution concentration nodes are introduced for each user group and untreated return flow from the users contribute to increased BOD concentrations in the river. The pollutant concentrations in each node depend on multiple decision variables (allocation and wastewater treatment) rendering the objective function non-linear. Therefore, the pollution concen-tration decisions are outsourced to a genetic algorithm, which calls a linear program to determine the remainder of the decision

  3. Population dynamics and exploitation of Metapenaeus affinis in Kuwaiti waters

    OpenAIRE

    Mohammed, H.M.

    1995-01-01

    Length-frequency data of Metapenaeus affinis collected from the trawl catches of R/V Bahith in Kuwaiti waters from 1985 to 1989 were combined with estimates of monthly total catch by the commercial and small-scale fleets operating in Kuwait, and analyzed using the Compleat ELEFAN software package. A major recruitment pulse of M. affinis occurs in spring and a minor one in autumn. Optimum relative yield per recruit (Y'/R) is obtained with the length-at-first capture (L sub(c)) of 24.4 cm CL fo...

  4. Dynamics of Nano-Confined Water under Pressure

    OpenAIRE

    Diallo, S. O.; Jazdzewska, M.; Palmer, J C; Mamontov, E.; Gubbins, K. E.; Sliwinska-Bartkowiak, M.

    2013-01-01

    We report a study of the effects of pressure on the diffusivity of water molecules confined in single- wall carbon nanotubes (SWNT) with average mean pore diameter of 16 Angstroms. The measurements were carried out using high-resolution neutron scattering, over the temperature range 220 < T < 260 K, and at two pressure conditions: ambient and elevated pressure. The high pressure data were collected at constant volume on cooling, with P varying from 1.92 kbar at temperature T = 260 K to 1.85 k...

  5. Dynamics simulation of the interaction between serine and water

    Science.gov (United States)

    Liu, Yang; Zhang, Peng; Lu, Ying-Bo; Han, Sheng-Hao; Yu, Hui

    2013-05-01

    Using the first principles density functional theory (DFT), we simulated the neutron scattering spectra of the hydration dynamics of serine. Experimental data analyses have shown that dissociative H2O molecules were more likely to form hydrogen bonds (H-bonds) with an -OH group in monohydrated serine and easily shift to a -NH_3 ^ + group at a higher hydration level [P. Zhang, Y. Zhang, S. H. Han, Q. W. Yan, R. C. Ford, and J. C. Li, J. Phys. Chem. A 110, 5000 (2006), 10.1021/jp0569741]. We set the 1:1 ratio hydrated compounds at the two positions and found that the H2O could be optimized to form H-bonds with -OH and -NH3+ separately. When the simulated phonon signals of the -OH…H2O and -NH3+…H2O combinations were summed on a 3:1 scale, the calculating spectra were in good agreement with the experimental results, especially for the peak at 423 cm-1 of the -OH…H2O combination and the peak at 367 cm-1 of the -NH3+…H2O combination, which mutually complemented the real spectrum. We confirm that H2O may break the intermolecular H-bonds of the interlaced binding -OH to form a new structure, and that with the skeleton deformation of serine, H2O forms stronger H-bonds more often with the -NH3+ side indicating the flexible dynamic mechanism of the serine hydration process.

  6. Molecular Dynamics Studies of Structure and Functions of Water-Membrane Interfaces

    Science.gov (United States)

    Pohorille, Andrew; Wilson, Michael A.; DeVincenzi, Donald L. (Technical Monitor)

    2001-01-01

    A large number of essential cellular processes occur at the interfaces between water and membranes. The selectivity and dynamics of these processes are largely determined by the structural and electrical properties of the water-membrane interface. We investigate these properties by the molecular dynamics method. Over the time scales of the simulations, the membrane undergoes fluctuations described by the capillary wave model. These fluctuations produce occasional thinning defects in the membrane which provide effective pathways for passive transport of ions and small molecules across the membrane. Ions moving through the membrane markedly disrupt its structure and allow for significant water penetration into the membrane interior. Selectivity of transport, with respect to ionic charge, is determined by the interfacial electrostatic potential. Many small molecules. of potential significance in catalysis, bioenergetics and pharmacology, are shown to bind to the interface. The energetics and dynamics of this process will be discussed.

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

    International Nuclear Information System (INIS)

    The dynamics of water in fresh and in rehydrated white bread is studied using quasielastic neutron scattering (QENS). A diffusion constant for water in fresh bread, without temperature gradients and with the use of a non-destructive technique, is presented here for the first time. The self-diffusion constant for fresh bread is estimated to be Ds = 3.8 x 10-10 m2 s-1 and the result agrees well with previous findings for similar systems. It is also suggested that water exhibits a faster dynamics than previously reported in the literature using equilibration of a hydration-level gradient monitored by vibrational spectroscopy. The temperature dependence of the dynamics of low hydration bread is also investigated for T = 280-350 K. The average relaxation time at constant momentum transfer (Q) shows an Arrhenius behavior in the temperature range investigated

  8. The hydrophobic effect: Molecular dynamics simulations of water confined between extended hydrophobic and hydrophilic surfaces

    DEFF Research Database (Denmark)

    Jensen, Morten Østergaard; Mouritsen, Ole G.; Peters, Günther H.J.

    2004-01-01

    Structural and dynamic properties of water confined between two parallel, extended, either hydrophobic or hydrophilic crystalline surfaces of n-alkane C36H74 or n-alcohol C35H71OH, are studied by molecular dynamics simulations. Electron density profiles, directly compared with corresponding...... experimental data from x-ray reflectivity measurements, reveal a uniform weak de-wetting characteristic for the extended hydrophobic surface, while the hydrophilic surface is weakly wetted. These microscopic data are consistent with macroscopic contact angle measurements. Specific water orientation is present...... at both surfaces. The ordering is characteristically different between the surfaces and of longer range at the hydrophilic surface. Furthermore, the dynamic properties of water are different at the two surfaces and different from the bulk behavior. In particular, at the hydrophobic surface, time...

  9. Dynamic modeling of stratification for chilled water storage tank

    International Nuclear Information System (INIS)

    Air conditioning of buildings can be costly and energy consuming. Application of thermal energy storage (TES) reduces cost and energy consumption. The efficiency of the overall operation is affected by storage tank sizing design, which affects thermal stratification of water during charging and discharging processes in TES system. In this study, numerical simulation is used to determine the relationship between tank size and good thermal stratification. Three dimensional simulations with different tank height-to-diameter ratio (HD) and inlet Reynolds number (Re) are investigated. The effect of the number of diffuser holes is also studied. For shallow tanks (low HD) simulations, no acceptable thermocline thickness can be seen for all Re experimented. Partial mixing is observed throughout the process. Medium HD tanks simulations show good thermocline behavior and clear distinction between warm and cold water can be seen. Finally, deep tanks (high HD) show less acceptable thermocline thickness as compared to that of medium HD tanks. From this study, doubling and halving the number of diffuser holes show no significant effect on the thermocline behavior

  10. Translational dynamics of water in a nanoporous layered silicate

    Science.gov (United States)

    Nair, Sankar; Chowdhuri, Zema; Peral, Inmaculada; Neumann, Dan A.; Dickinson, L. Charles; Tompsett, Geoffrey; Jeong, Hae-Kwon; Tsapatsis, Michael

    2005-03-01

    Neutron time-of-flight and backscattering spectroscopy have been used to study the translational diffusion of water molecules in the unusual layered material AMH-3, which consists of (zeolitelike) three-dimensionally nanoporous silicate layers spaced by (claylike) interlayer regions. The synthesis of AMH-3 and its characterization by Si29 NMR, Raman, and infrared spectroscopy, are described. An analysis of quasielastic neutron scattering (QENS) spectra using the random jump diffusion model reveals two translational diffusive motions clearly separated in time scales: a fast process ( Dtilde 10-9m2/s at 300 K), and a much slower process ( Dtilde 10-11m2/s at 300 K). Considering the structural model of AMH-3 and the transport properties extracted from the QENS data, it is suggested that the slower motion corresponds to diffusion by water molecules in the interlayer spaces whereas the fast process involves diffusion in the silicate layer. This first investigation of transport phenomena in nanoporous layered silicates like AMH-3 indicates that they have the potential to offer mass transport properties different from zeolite materials and layered clays.

  11. Dynamics of confined reactive water in smectite clay-zeolite composites

    International Nuclear Information System (INIS)

    The dynamics of water confined to mesoporous regions in minerals such as swelling clays and zeolites is fundamental to a wide range of resource management issues impacting many processes on a global scale, including radioactive waste containment, desalination, and enhanced oil recovery. Large-scale atomic models of freely diffusing multilayer smectite particles at low hydration confined in a silicalite cage are used to investigate water dynamics in the composite environment with the ReaxFF reactive force field over a temperature range of 300 647 K. The reactive capability of the force field enabled a range of relevant surface chemistry to emerge, including acid/base equilibria in the interlayer calcium hydrates and silanol formation on the edges of the clay and inner surface of the zeolite housing. After annealing, the resulting clay models exhibit both mono- and bilayer hydration structures. Clay surface hydration redistributed markedly and yielded to silicalite water loading. We find that the absolute rates and temperature dependence of water dynamics compare well to neutron scattering data and pulse field gradient measures from relevant samples of Ca-montmorillonite and silicalite, respectively. Within an atomistic, reactive context, our results distinguish water dynamics in the interlayer Ca(OH)2 nH2O environment from water flowing over the clay surface, and from water diffusing within silicalite. We find that the diffusion of water when complexed to Ca hydrates is considerably slower than freely diffusing water over the clay surface, and the reduced mobility is well described by a difference in the Arrhenius pre-exponential factor rather than a change in activation energy.

  12. Dynamics of confined reactive water in Smectic clay-zeolite composites

    International Nuclear Information System (INIS)

    The dynamics of water confined to mesoporous regions in minerals such as swelling clays and zeolites is fundamental to a wide range of resource management issues impacting many processes on a global scale, including radioactive waste containment, desalination, and enhanced oil recovery. Large-scale atomic models of freely diffusing multilayer smectite particles at low hydration confined in a silicalite cage are used to investigate water dynamics in the composite environment with the ReaxFF reactive force field over a temperature range of 300 647 K. The reactive capability of the force field enabled a range of relevant surface chemistry to emerge, including acid/base equilibria in the interlayer calcium hydrates and silanol formation on the edges of the clay and inner surface of the zeolite housing. After annealing, the resulting clay models exhibit both mono- and bilayer hydration structures. Clay surface hydration redistributed markedly and yielded to silicalite water loading. We find that the absolute rates and temperature dependence of water dynamics compare well to neutron scattering data and pulse field gradient measures from relevant samples of Ca-montmorillonite and silicalite, respectively. Within an atomistic, reactive context, our results distinguish water dynamics in the interlayer Ca(OH)2 nH2O environment from water flowing over the clay surface, and from water diffusing within silicalite. We find that the diffusion of water when complexed to Ca hydrates is considerably slower than freely diffusing water over the clay surface, and the reduced mobility is well described by a difference in the Arrhenius pre-exponential factor rather than a change in activation energy.

  13. Dynamic Assessment of Water Quality Based on a Variable Fuzzy Pattern Recognition Model

    Directory of Open Access Journals (Sweden)

    Shiguo Xu

    2015-02-01

    Full Text Available Water quality assessment is an important foundation of water resource protection and is affected by many indicators. The dynamic and fuzzy changes of water quality lead to problems for proper assessment. This paper explores a method which is in accordance with the water quality changes. The proposed method is based on the variable fuzzy pattern recognition (VFPR model and combines the analytic hierarchy process (AHP model with the entropy weight (EW method. The proposed method was applied to dynamically assess the water quality of Biliuhe Reservoir (Dailan, China. The results show that the water quality level is between levels 2 and 3 and worse in August or September, caused by the increasing water temperature and rainfall. Weights and methods are compared and random errors of the values of indicators are analyzed. It is concluded that the proposed method has advantages of dynamism, fuzzification and stability by considering the interval influence of multiple indicators and using the average level characteristic values of four models as results.

  14. Salt-Water Transport in Unsaturated Soils Under Crop Planting: Dynamics and Numerical Simulation

    Institute of Scientific and Technical Information of China (English)

    XU Li-Gang; YANG Jing-Song; ZHANG Qi; LIU Guang-Ming

    2005-01-01

    A laboratory salt-water dynamics experiment using unsaturated soils in packed silt loam and clay soil columns with different soil texture profiles and groundwater levels under crops were conducted to study the changes of salt-water dynamics induced by water uptake of crops and to propose the theoretical basis for the regulation and control of saltwater dynamics as well as to predict salinity levels. The HYDRUS 1D model was applied to simulate the one-dimensional movement of water and salt transport in the soil columns. The results showed that the salts mainly accumulated in the plow layer in the soil columns under crops. Soil water and salt both moved towards the plow layer due to soil water absorption by the crop root system. The salt contents in the column with lower groundwater were mostly greater than those with high groundwater. The water contents in the soil columns increased from top to the bottom due to plant root water uptake. The changes in groundwater level had little influence on water content of the root zone in the soil columns with crop planting. Comparison between the simulated and the determined values showed that model simulation results were ideal, so it is practicable to do numerical simulation of soil salt and water transport by the HYDRUS 1D model.Furthermore, if the actual movement of salt and water in fields is to be described in detail, much work needs to be done.The most important thing is to refine the parameters and select precise boundary conditions.

  15. Energy production from waste-water using microbial fuel cells

    International Nuclear Information System (INIS)

    Natural energy sources like fossil fuels are depleting due to increased human activities. Different types of alternatives are being explored to solve this problem with the consideration that they are sustainable. There are many environmental concerns connected with fossil fuel burning which after oxidation processes release greater amounts of carbon emissions in atmosphere. Now the trends are shifting towards exploiting renewable energy options, such as bioethanol, biodiesel, biohydrogen, biogas, and bioelectricity. Bioelectricity is harvested from organic substrates using Microbial Fuel Cells (MFC) that operate on oxidation reduction (redox) reactions. MFCs produce electricity in the presence of microorganisms from biodegradable substances. Waste-water contains enormous amount of organic matter that can be oxidized in MFC for electricity harvesting. In this review, the main focus is made on the applicability of microbial fuels cells for simultaneous waste-water treatment and electricity production. (author)

  16. The ultrafast reaction dynamics of hydrogen and interfacial structure of water on the Ru(001)-surface

    OpenAIRE

    Denzler, Daniel N.

    2003-01-01

    The goal of this work is to acquire detailed insight into the fundamental interaction mechanisms in surface chemistry and physics. Therefore the dynamic and static-structural properties of two prototypical adsorbate systems have been investigated: The ultrafast reaction dynamics of hydrogen on the Ru(001)-surface, and the interfacial structure of water on Ru(001). The investigation of the recombinative hydrogen formation according to Had+Had -> H2,gas was performed by irradiation...

  17. Polarizable molecular dynamics simulation of Zn(II) in water using the AMOEBA force field

    OpenAIRE

    Wu, Johnny C.; Piquemal, Jean-Philip; Chaudret, Robin; Reinhardt, Peter; Ren, Pengyu

    2010-01-01

    The hydration free energy, structure, and dynamics of the zinc divalent cation are studied using a polarizable force field in molecular dynamics simulations. Parameters for the Zn2+ are derived from gas-phase ab initio calculation of Zn2+-water dimer. The Thole-based dipole polarization is adjusted based on the Constrained Space Orbital Variations (CSOV) calculation while the Symmetry Adapted Perturbation Theory (SAPT) approach is also discussed. The vdW parameters of Zn2+ have been obtained ...

  18. A system dynamics computer model for long-term water quality planning

    OpenAIRE

    Smith, Edwin L.

    1985-01-01

    The objective of this study was to develop a comprehensive, basin-wide, water-quality-planning model using system dynamics methodology. Later, the model was to be interfaced with a more conventional system dynamics model: one simulating social, technological, economic, and political interactions. By doing so, it is envisioned that such management policies as zoning, abatement facilities, and best management practices may be simulated together.

  19. On the composition dependence of thermodynamic, dynamic and dielectric properties of water-methanol model mixtures. Molecular dynamics simulation results

    Directory of Open Access Journals (Sweden)

    E. Galicia-Andrés

    2015-12-01

    Full Text Available We have investigated thermodynamic and dynamic properties as well as the dielectric constant of water-methanol model mixtures in the entire range of composition by using constant pressure molecular dynamics simulations at ambient conditions. The SPC/E and TIP4P/Ew water models are used in combination with the OPLS united atom modelling for methanol. Changes of the average number of hydrogen bonds between particles of different species and of the fractions of differently bonded molecules are put in correspondence with the behavior of excess mixing volume and enthalpy, of self-diffusion coefficients and rotational relaxation times. From the detailed analyses of the results obtained in this work, we conclude that an improvement of the description of an ample set of properties of water-methanol mixtures can possibly be reached, if a more sophisticated, carefully parameterized, e.g., all atom, model for methanol is used. Moreover, exploration of parametrization of the methanol force field, with simultaneous application of different combination rules for methanol-water cross interactions, is required.

  20. Galectin-9: From cell biology to complex disease dynamics.

    Science.gov (United States)

    John, Sebastian; Mishra, Rashmi

    2016-09-01

    Galectins is a family of non-classically secreted, beta-galactoside-binding proteins that has recently received considerable attention in the spatio-temporal regulation of surface 'signal lattice' organization, membrane dynamics, cell-adhesion and disease therapeutics. Galectin-9 is a unique member of this family, with two non-homologous carbohydrate recognition domains joined by a linker peptide sequence of variable lengths, generating isoforms with distinct properties and functions in both physiological and pathological settings, such as during development, immune reaction, neoplastic transformations and metastasis. In this review, we summarize the latest knowledge on the structure, receptors, cellular targets, trafficking pathways and functional properties of galectin-9 and discuss how galectin-9-mediated signalling cascades can be exploited in cancers and immunotherapies. PMID:27581941

  1. Galectin-9: From cell biology to complex disease dynamics

    Indian Academy of Sciences (India)

    SEBASTIAN JOHN; RASHMI MISHRA

    2016-09-01

    Galectins is a family of non-classically secreted, β-galactoside-binding proteins that has recently received considerableattention in the spatio-temporal regulation of surface ‘signal lattice’ organization, membrane dynamics, cell-adhesionand disease therapeutics. Galectin-9 is a unique member of this family, with two non-homologous carbohydraterecognition domains joined by a linker peptide sequence of variable lengths, generating isoforms with distinctproperties and functions in both physiological and pathological settings, such as during development, immunereaction, neoplastic transformations and metastasis. In this review, we summarize the latest knowledge on thestructure, receptors, cellular targets, trafficking pathways and functional properties of galectin-9 and discuss howgalectin-9-mediated signalling cascades can be exploited in cancers and immunotherapies.

  2. Direct Adaptive Aircraft Control Using Dynamic Cell Structure Neural Networks

    Science.gov (United States)

    Jorgensen, Charles C.

    1997-01-01

    A Dynamic Cell Structure (DCS) Neural Network was developed which learns topology representing networks (TRNS) of F-15 aircraft aerodynamic stability and control derivatives. The network is integrated into a direct adaptive tracking controller. The combination produces a robust adaptive architecture capable of handling multiple accident and off- nominal flight scenarios. This paper describes the DCS network and modifications to the parameter estimation procedure. The work represents one step towards an integrated real-time reconfiguration control architecture for rapid prototyping of new aircraft designs. Performance was evaluated using three off-line benchmarks and on-line nonlinear Virtual Reality simulation. Flight control was evaluated under scenarios including differential stabilator lock, soft sensor failure, control and stability derivative variations, and air turbulence.

  3. Carrier injection dynamics in heterojunction solar cells with bipolar molecule

    Energy Technology Data Exchange (ETDEWEB)

    Takahashi, Yosuke; Yonezawa, Kouhei [Graduate School of Pure and Applied Science, University of Tsukuba, Tsukuba 305-8571 (Japan); Yasuda, Takeshi, E-mail: YASUDA.Takeshi@nims.go.jp, E-mail: moritomo.yutaka.gf@u.tsukuba.ac.jp [Photovoltaic Materials Unit, National Institute for Materials Science (NIMS), Tsukuba 305-0047 (Japan); Moritomo, Yutaka, E-mail: YASUDA.Takeshi@nims.go.jp, E-mail: moritomo.yutaka.gf@u.tsukuba.ac.jp [Graduate School of Pure and Applied Science, University of Tsukuba, Tsukuba 305-8571 (Japan); Center for Integrated Research in Fundamental Science and Engineering (CiRfSE), University of Tsukuba, Tsukuba 305-8571 (Japan)

    2015-03-23

    A boron subphthalocyanine chloride (SubPc) is a bipolar molecule and is used in hetero-junction organic solar cells. Here, we investigated the carrier injection dynamics from the donor α-sexithiophene (6T) or acceptor C{sub 60} layers to the bipolar SubPc layer by means of the femtosecond time-resolved spectroscopy. We observed gradual increase of the SubPc{sup –} (SubPc{sup +}) species within ≈300 ps. The increases are interpreted in terms of the exciton diffusion within the 6T (C{sub 60}) layer and subsequent electron (hole) injection at the interface. In 6T/SubPc heterojunction, the electron injection is observed even at 80 K. The robust electron injection is ascribed to the efficient charge separation within the 6T layer under photo exciation at 400 nm.

  4. Carrier injection dynamics in heterojunction solar cells with bipolar molecule

    International Nuclear Information System (INIS)

    A boron subphthalocyanine chloride (SubPc) is a bipolar molecule and is used in hetero-junction organic solar cells. Here, we investigated the carrier injection dynamics from the donor α-sexithiophene (6T) or acceptor C60 layers to the bipolar SubPc layer by means of the femtosecond time-resolved spectroscopy. We observed gradual increase of the SubPc– (SubPc+) species within ≈300 ps. The increases are interpreted in terms of the exciton diffusion within the 6T (C60) layer and subsequent electron (hole) injection at the interface. In 6T/SubPc heterojunction, the electron injection is observed even at 80 K. The robust electron injection is ascribed to the efficient charge separation within the 6T layer under photo exciation at 400 nm

  5. A DYNAMIC APPROACH TO CALCULATE SHADOW PRICES OF WATER RESOURCES FOR NINE MAJOR RIVERS IN CHINA

    Institute of Scientific and Technical Information of China (English)

    Jing HE; Xikang CHEN; Yong SHI

    2006-01-01

    China is experiencing from serious water issues. There are many differences among the Nine Major Rivers basins of China in the construction of dikes, reservoirs, floodgates, flood discharge projects, flood diversion projects, water ecological construction, water conservancy management, etc.The shadow prices of water resources for Nine Major Rivers can provide suggestions to the Chinese government. This article develops a dynamic shadow prices approach based on a multiperiod input-output optimizing model. Unlike previous approaches, the new model is based on the dynamic computable general equilibrium (DCGE) model to solve the problem of marginal long-term prices of water resources.First, definitions and algorithms of DCGE are elaborated. Second, the results of shadow prices of water resources for Nine Major Rivers in 1949-2050 in China using the National Water Conservancy input-holding-output table for Nine Major Rivers in 1999 are listed. A conclusion of this article is that the shadow prices of water resources for Nine Major Rivers are largely based on the extent of scarcity.Selling prices of water resources should be revised via the usage of parameters representing shadow prices.

  6. Combined Use of Neutron Thermalization and Electromagnetic Sensing in Assessing Soil Water Dynamics

    International Nuclear Information System (INIS)

    Agriculture is by far the largest consumer of available fresh water accounting for 70% of withdrawals worldwide. Meeting increased future demands for food and fibre will, by and large, need to be met by improving the efficient use of both irrigation and precipitation for crop production (FAO, 2002). Field research aimed at evaluating the efficiency of water use by crops invariably requires monitoring changes in soil water with time (e.g. Ibragimov et al., 2011). Such monitoring integrates the irrigation, precipitation, evapotranspiration and deep drainage history that affects the aggregate response of the system, which is manifested as soil water storage. These dynamic processes are important in evaluating the efficiency with which crop cultivars, irrigation strategies, cropping and tillage systems utilize available soil water for grain and biomass production. The neutron probe has been particularly effective in estimating soil water content because of its large measurement volume and linear response to changes in soil water (Hignett and Evett, 2002). However, neutron thermalization techniques suffer from poor spatial resolution which is problematic near the surface where there are steep soil water content gradients. Data acquisition at sub-daily intervals using the neutron probe is also impractical and restricts measurements to temporal resolutions that are unable to capture highly dynamic hydrological processes. When properly calibrated, automated soil water monitoring with proven electromagnetic (EM) sensors can facilitate measurements at short time scales associated with infiltration and evaporation processes near the surface.

  7. Documentation of INL’s In Situ Oil Shale Retorting Water Usage System Dynamics Model

    Energy Technology Data Exchange (ETDEWEB)

    Earl D Mattson; Larry Hull

    2012-12-01

    A system dynamic model was construction to evaluate the water balance for in-situ oil shale conversion. The model is based on a systems dynamics approach and uses the Powersim Studio 9™ software package. Three phases of an in situ retort were consider; a construction phase primarily accounts for water needed for drilling and water produced during dewatering, an operation phase includes the production of water from the retorting process, and a remediation phase water to remove heat and solutes from the subsurface as well as return the ground surface to its natural state. Throughout these three phases, the water is consumed and produced. Consumption is account for through the drill process, dust control, returning the ground water to its initial level and make up water losses during the remedial flushing of the retort zone. Production of water is through the dewatering of the retort zone, and during chemical pyrolysis reaction of the kerogen conversion. The document discusses each of the three phases used in the model.

  8. Modeling Water Management in Polymer-Electrolyte Fuel Cells

    Energy Technology Data Exchange (ETDEWEB)

    Department of Chemical Engineering, University of California, Berkeley; Weber, Adam; Weber, Adam Z.; Balliet, Ryan; Gunterman, Haluna P.; Newman, John

    2007-09-07

    Fuel cells may become the energy-delivery devices of the 21st century with realization of a carbon-neutral energy economy. Although there are many types of fuel cells, polymerelectrolyte fuel cells (PEFCs) are receiving the most attention for automotive and small stationary applications. In a PEFC, hydrogen and oxygen are combined electrochemically to produce water, electricity, and waste heat. During the operation of a PEFC, many interrelated and complex phenomena occur. These processes include mass and heat transfer, electrochemical reactions, and ionic and electronic transport. Most of these processes occur in the through-plane direction in what we term the PEFC sandwich as shown in Figure 1. This sandwich comprises multiple layers including diffusion media that can be composite structures containing a macroporous gas-diffusion layer (GDL) and microporous layer (MPL), catalyst layers (CLs), flow fields or bipolar plates, and a membrane. During operation fuel is fed into the anode flow field, moves through the diffusion medium, and reacts electrochemically at the anode CL to form hydrogen ions and electrons. The oxidant, usually oxygen in air, is fed into the cathode flow field, moves through the diffusion medium, and is electrochemically reduced at the cathode CL by combination with the generated protons and electrons. The water, either liquid or vapor, produced by the reduction of oxygen at the cathode exits the PEFC through either the cathode or anode flow field. The electrons generated at the anode pass through an external circuit and may be used to perform work before they are consumed at the cathode. The performance of a PEFC is most often reported in the form of a polarization curve, as shown in Figure 2. Roughly speaking, the polarization curve can be broken down into various regions. First, it should be noted that the equilibrium potential differs from the open-circuit voltage due mainly to hydrogen crossover through the membrane (i.e., a mixed potential

  9. Integrated Modeling and Design of Photoelectrochemical Water-Splitting Cells

    OpenAIRE

    Berger, Alan

    2014-01-01

    The photoelectrochemical production of fuels is an interesting research topic that aims to provide a low-cost method for storing solar energy. A one-dimensional model of a photoelectrochemical cell for solar water splitting has been developed, with applicability to both wired and wireless designs. The model of the light absorber handles electron and hole transport. The model of the electrolyte accounts for mass transport through regions of aqueous solution, including stagnant diffusion lay...

  10. Joint operation and dynamic control of flood limiting water levels for mixed cascade reservoir systems

    Science.gov (United States)

    Zhou, Yanlai; Guo, Shenglian; Liu, Pan; Xu, Chongyu

    2014-11-01

    Reservoirs are one of the most efficient infrastructures for integrated water resources development and management; and play a more and more important role in flood control and conservation. Dynamic control of the reservoir flood limiting water level (FLWL) is a valuable and effective approach to compromise the flood control, hydropower generation and comprehensive utilization of water resources of river basins during the flood season. The dynamic control models of FLWL for a single reservoir and cascade reservoirs have been extended for a mixed reservoir system in this paper. The proposed model consists of a dynamic control operation module for a single reservoir, a dynamic control operation module for cascade reservoirs, and a joint operation module for mixed cascade reservoir systems. The Three Gorges and Qingjiang cascade reservoirs in the Yangtze River basin of China are selected for a case study. Three-hour inflow data series for representative hydrological years are used to test the model. The results indicate that the proposed model can make an effective tradeoff between flood control and hydropower generation. Joint operation and dynamic control of FLWL can generate 26.4 × 108 kW h (3.47%) more hydropower for the mixed cascade reservoir systems and increase the water resource utilization rate by 3.72% for the Three Gorges reservoir and 2.42% for the Qingjiang cascade reservoirs without reducing originally designed flood prevention standards.

  11. Reconstructing dynamic molecular states from single-cell time series.

    Science.gov (United States)

    Huang, Lirong; Pauleve, Loic; Zechner, Christoph; Unger, Michael; Hansen, Anders S; Koeppl, Heinz

    2016-09-01

    The notion of state for a system is prevalent in the quantitative sciences and refers to the minimal system summary sufficient to describe the time evolution of the system in a self-consistent manner. This is a prerequisite for a principled understanding of the inner workings of a system. Owing to the complexity of intracellular processes, experimental techniques that can retrieve a sufficient summary are beyond our reach. For the case of stochastic biomolecular reaction networks, we show how to convert the partial state information accessible by experimental techniques into a full system state using mathematical analysis together with a computational model. This is intimately related to the notion of conditional Markov processes and we introduce the posterior master equation and derive novel approximations to the corresponding infinite-dimensional posterior moment dynamics. We exemplify this state reconstruction approach using both in silico data and single-cell data from two gene expression systems in Saccharomyces cerevisiae, where we reconstruct the dynamic promoter and mRNA states from noisy protein abundance measurements. PMID:27605167

  12. Dynamic simulation of a boiling water nuclear reactor

    International Nuclear Information System (INIS)

    For the application of modern control theory, specifically optimal control, to the boiling water reactor, it is necessary to have a linear model that is validated. The nonlinear model of the BWR derived on the basis of physical laws and empirical relations is linearized around an operating point and the model if verified against experimental results by simulating various tests such as the pressure transient test, change in power to recirculating pump etc. The transport delay occurring in the model is approximated by various representations and the results are compared with the exact delay representation. Validation such as discussed in the paper forms the basis for devising appropriate control strategies in the presence of disturbances. (author)

  13. Parameter identification in dynamical models of anaerobic waste water treatment.

    Science.gov (United States)

    Müller, T G; Noykova, N; Gyllenberg, M; Timmer, J

    2002-01-01

    Biochemical reactions can often be formulated mathematically as ordinary differential equations. In the process of modeling, the main questions that arise are concerned with structural identifiability, parameter estimation and practical identifiability. To clarify these questions and the methods how to solve them, we analyze two different second order models for anaerobic waste water treatment processes using two data sets obtained from different experimental setups. In both experiments only biogas production rate was measured which complicates the analysis considerably. We show that proving structural identifiability of the mathematical models with currently used methods fails. Therefore, we introduce a new, general method based on the asymptotic behavior of the maximum likelihood estimator to show local structural identifiability. For parameter estimation we use the multiple shooting approach which is described. Additionally we show that the Hessian matrix approach to compute confidence intervals fails in our examples while a method based on Monte Carlo Simulation works well. PMID:11965253

  14. Credibility theory based dynamic control bound optimization for reservoir flood limited water level

    Science.gov (United States)

    Jiang, Zhiqiang; Sun, Ping; Ji, Changming; Zhou, Jianzhong

    2015-10-01

    The dynamic control operation of reservoir flood limited water level (FLWL) can solve the contradictions between reservoir flood control and beneficial operation well, and it is an important measure to make sure the security of flood control and realize the flood utilization. The dynamic control bound of FLWL is a fundamental key element for implementing reservoir dynamic control operation. In order to optimize the dynamic control bound of FLWL by considering flood forecasting error, this paper took the forecasting error as a fuzzy variable, and described it with the emerging credibility theory in recent years. By combining the flood forecasting error quantitative model, a credibility-based fuzzy chance constrained model used to optimize the dynamic control bound was proposed in this paper, and fuzzy simulation technology was used to solve the model. The FENGTAN reservoir in China was selected as a case study, and the results show that, compared with the original operation water level, the initial operation water level (IOWL) of FENGTAN reservoir can be raised 4 m, 2 m and 5.5 m respectively in the three division stages of flood season, and without increasing flood control risk. In addition, the rationality and feasibility of the proposed forecasting error quantitative model and credibility-based dynamic control bound optimization model are verified by the calculation results of extreme risk theory.

  15. Dynamics of the Oxygen, Carbon Dioxide, and Water Interaction across the Insect Spiracle

    Directory of Open Access Journals (Sweden)

    S. M. Simelane

    2014-01-01

    Full Text Available This paper explores the dynamics of respiratory gases interactions which are accompanied by the loss of water through an insect’s spiracle. Here we investigate and analyze this interaction by deriving a system of ordinary differential equations for oxygen, carbon dioxide, and water vapor. The analysis is carried out in continuous time. The purpose of the research is to determine bounds for the gas volumes and to discuss the complexity and stability of the equilibria. Numerical simulations also demonstrate the dynamics of our model utilizing the new conditions for stability and instability.

  16. Wetting kinetics of water nano-droplet containing non-surfactant nanoparticles: A molecular dynamics study

    International Nuclear Information System (INIS)

    In this Letter, dynamic wetting of water nano-droplets containing non-surfactant gold nanoparticles on a gold substrate is examined via molecular dynamics simulations. The results show that the addition of non-surfactant nanoparticles hinders the nano-second droplet wetting process, attributed to the increases in both surface tension of the nanofluid and friction between nanofluid and substrate. The droplet wetting kinetics decreases with increasing nanoparticle loading and water-particle interaction energy. The observed wetting suppression and the absence of nanoparticle ordering near the contact line of nano-sized droplets differ from the wetting behaviors reported from nanofluid droplets of micron size or larger

  17. Wetting kinetics of water nano-droplet containing non-surfactant nanoparticles: A molecular dynamics study

    Energy Technology Data Exchange (ETDEWEB)

    Lu, Gui [Key Laboratory for Thermal Science and Power Engineering of MOE, Beijing Key Laboratory for CO2 Utilization and Reduction Technology, Tsinghua University, Beijing 100084 (China); Department of Mechanical Engineering and Mechanics, Drexel University, Philadelphia, Pennsylvania 19104 (United States); Hu, Han; Sun, Ying, E-mail: yyduan@tsinghua.edu.cn, E-mail: ysun@coe.drexel.edu [Department of Mechanical Engineering and Mechanics, Drexel University, Philadelphia, Pennsylvania 19104 (United States); Duan, Yuanyuan, E-mail: yyduan@tsinghua.edu.cn, E-mail: ysun@coe.drexel.edu [Key Laboratory for Thermal Science and Power Engineering of MOE, Beijing Key Laboratory for CO2 Utilization and Reduction Technology, Tsinghua University, Beijing 100084 (China)

    2013-12-16

    In this Letter, dynamic wetting of water nano-droplets containing non-surfactant gold nanoparticles on a gold substrate is examined via molecular dynamics simulations. The results show that the addition of non-surfactant nanoparticles hinders the nano-second droplet wetting process, attributed to the increases in both surface tension of the nanofluid and friction between nanofluid and substrate. The droplet wetting kinetics decreases with increasing nanoparticle loading and water-particle interaction energy. The observed wetting suppression and the absence of nanoparticle ordering near the contact line of nano-sized droplets differ from the wetting behaviors reported from nanofluid droplets of micron size or larger.

  18. Bulk volumetric liquid water content in a seasonal snowpack: modeling its dynamics in different climatic conditions

    Science.gov (United States)

    Avanzi, Francesco; Yamaguchi, Satoru; Hirashima, Hiroyuki; De Michele, Carlo

    2015-12-01

    We focus on the dynamics of volumetric liquid water content in seasonal snow covers. This is a key variable describing the fate of snowpacks during the melting season. However, its measurement and/or prediction by means of models at high spatial and temporal resolutions is still difficult due to both practical and theoretical reasons. To overcome these limitations in operational applications, we test the capability of a one-dimensional model to predict the dynamics of bulk volumetric liquid water content during a snow season. Multi-year data collected in three experimental sites in Japan are used as an evaluation. These sites are subjected to different climatic conditions. The model requires the calibration of one or two parameters, according to the degree of detail used. Either a simple temperature-index or a coupled melt-freeze temperature-index approach are considered to predict melting and/or melt-freeze dynamics of liquid water. Results show that, if melt-freeze dynamics are modeled, median absolute differences between data and predictions are consistently lower than 1 vol% at the sites where data of liquid water content are available. In addition, we find also that the model predicts correctly a dry condition in 80% of the observed cases at a site where calibration data are scarce. At the same site, observed isothermal conditions of the snow cover at 0 °C correspond to predictions of bulk volumetric liquid water content that are greater than 0.

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

    International Nuclear Information System (INIS)

    Fullerene C60 sub-colloidal particle with diameter ∼1 nm represents a boundary case between small and large hydrophobic solutes on the length scale of hydrophobic hydration. In the present paper, a molecular dynamics simulation is performed to investigate this complex phenomenon for bare C60 fullerene and its amphiphilic/charged derivatives, so called shape amphiphiles. Since most of the unique properties of water originate from the pattern of hydrogen bond network and its dynamics, spatial, and orientational aspects of water in solvation shells around the solute surface having hydrophilic and hydrophobic regions are analyzed. Dynamical properties such as translational-rotational mobility, reorientational correlation and occupation time correlation functions of water molecules, and diffusion coefficients are also calculated. Slower dynamics of solvent molecules—water retardation—in the vicinity of the solutes is observed. Both the topological properties of hydrogen bond pattern and the “dangling” –OH groups that represent surface defects in water network are monitored. The fraction of such defect structures is increased near the hydrophobic cap of fullerenes. Some “dry” regions of C60 are observed which can be considered as signatures of surface dewetting. In an effort to provide molecular level insight into the thermodynamics of hydration, the free energy of solvation is determined for a family of fullerene particles using thermodynamic integration technique

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2015-06-14

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