WorldWideScience

Sample records for dynamic membrane aeration

  1. Computational fluid dynamics simulations of membrane filtration process adapted for water treatment of aerated sewage lagoons.

    Science.gov (United States)

    Cano, Grégory; Mouahid, Adil; Carretier, Emilie; Guasp, Pascal; Dhaler, Didier; Castelas, Bernard; Moulin, Philippe

    2015-01-01

    The aim of this study is to apply the membrane bioreactor technology in an oxidation ditch in submerged conditions. This new wastewater filtration process will benefit rural areas (membranes developed without support are immersed in an aeration well and work in suction mode. The development of the membrane without support and more precisely the performance of spacers are approached by computational fluid dynamics in order to provide the best compromise between pressure drop/flow velocity and permeate flux. The numerical results on the layout and the membrane modules' geometry in the aeration well indicate that the optimal configuration is to install the membranes horizontally on three levels. Membranes should be connected to each other to a manifold providing a total membrane area of 18 m². Loss rate compared to the theoretical throughput is relatively low (less than 3%). Preliminary data obtained by modeling the lagoon provide access to its hydrodynamics, revealing that recirculation zones can be optimized by making changes in the operating conditions. The experimental validation of these results and taking into account the aeration in the numerical models are underway.

  2. Sequentially aerated membrane biofilm reactors for autotrophic nitrogen removal: microbial community composition and dynamics

    DEFF Research Database (Denmark)

    Pellicer i Nàcher, Carles; Franck, Stephanie; Gülay, Arda

    2014-01-01

    Membrane-aerated biofilm reactors performing autotrophic nitrogen removal can be successfully applied to treat concentrated nitrogen streams. However, their process performance is seriously hampered by the growth of nitrite oxidizing bacteria (NOB). In this work we document how sequential aeration...

  3. Sequentially aerated membrane biofilm reactors for autotrophic nitrogen removal: microbial community composition and dynamics

    DEFF Research Database (Denmark)

    Pellicer i Nàcher, Carles; Franck, Stephanie; Gülay, Arda

    2014-01-01

    Membrane-aerated biofilm reactors performing autotrophic nitrogen removal can be successfully applied to treat concentrated nitrogen streams. However, their process performance is seriously hampered by the growth of nitrite oxidizing bacteria (NOB). In this work we document how sequential aeration...... (rich in oxygen) and AnAOB in regions neighbouring the liquid phase. Both communities were separated by a transition region potentially populated by denitrifying heterotrophic bacteria. AOB and AnAOB bacterial groups were more abundant and diverse than NOB, and dominated by the r......-strategists Nitrosomonas europaea and Ca. Brocadia anammoxidans, respectively. Taken together, the present work presents tools to better engineer, monitor and control the microbial communities that support robust, sustainable and efficient nitrogen removal....

  4. Autotrophic Nitrogen Removal in a Membrane-Aerated Biofilm Reactor Under Continuous Aeration: A Demonstration

    DEFF Research Database (Denmark)

    Gilmore, Kevin R.; Terada, Akihiko; Smets, Barth F.

    2013-01-01

    This work describes the successful coupling of partial nitrification (nitritation) and anaerobic ammonium oxidation in a membrane-aerated biofilm reactor (MABR) with continuous aeration. Controlling the relative surface loadings of oxygen versus ammonium prevented complete nitrite oxidation and a...

  5. Biofilm formation on membranes used for membrane aerated biological reactors, under different stress conditions

    International Nuclear Information System (INIS)

    Andrade-Molinar, C.; Ballinas-Casarrubias, M. L.; Solis-Martinez, F. J.; Rivera-Chavira, B. E.; Cuevas-Rodirguez, G.; Nevarez-Moorillon, G. V.

    2009-01-01

    Bacterial biofilm play an important role in wastewater treatment processes, and have been optimized in the membrane aerated biofilm reactors (MABR). In MABR, a hydrophobic membrane is used as support for the formation of biofilm, and supplements enough aeration to assure an aerobic process. (Author)

  6. Membrane dynamics

    DEFF Research Database (Denmark)

    Bendix, Pól Martin

    2015-01-01

    Current topics include membrane-protein interactions with regard to membrane deformation or curvature sensing by BAR domains. Also, we study the dynamics of membrane tubes of both cells and simple model membrane tubes. Finally, we study membrane phase behavior which has important implications...... for the lateral organization of membranes as wells as for physical properties like bending, permeability and elasticity...

  7. Monitoring and modeling of nitrogen conversions in membrane-aerated biofilm reactors: Effects of intermittent aeration

    DEFF Research Database (Denmark)

    Ma, Yunjie

    Nitrogen can be removed from sewage by a variety of physicochemical and biological processes. Due to the high removal efficiency and relatively low costs, biological processes have been widely adopted for treating nitrogen-rich wastewaters. Among the biological technologies, biofilm processes show...... the membrane, whilst NH4+ is provid-ed from the bulk liquid phase. The counter substrate supply not only offers flexible aeration control, but also supports the development of a unique mi-crobial community and spatial structure inside the biofilm. In this study, lab-scale MABRs were operated under two types...... relevant biological N2O production pathways. Sensitive kinetic parameters were estimated with long-term bulk performance data. With the calibrated model, roles of HB and AnAOB were discussed and evaluated in mitigating N2O emissions in auto-trophic nitrogen removal MABRs. Moreover, I developed a 1-D...

  8. Optimizing aeration rates for minimizing membrane fouling and its effect on sludge characteristics in a moving bed membrane bioreactor

    International Nuclear Information System (INIS)

    Rahimi, Yousef; Torabian, Ali; Mehrdadi, Naser; Habibi-Rezaie, Mehran; Pezeshk, Hamid; Nabi-Bidhendi, Gholam-Reza

    2011-01-01

    Research highlights: → There is an optimum aeration rate in the MBMBR process compartments. → Optimum aeration rate maximizes nutrients removal. → Optimum aeration rate minimizes membrane fouling. → Both aeration rates in MBBR and membrane compartment can affect on membrane permeability. - Abstract: In MBR processes, sufficient aeration is necessary to maintain sustainable flux and to retard membrane fouling. Membrane permeability, sludge characteristics, nutrient removal and biomass growth at various air flow rates in the membrane and moving bed biofilm reactor (MBBR) compartments were studied in a pilot plant. The highest nitrogen and phosphorous removal rates were found at MBBR aeration rates of 151 and 85 L h -1 and a specific aeration demand per membrane area (SAD m ) of 1.2 and 0.4m air 3 m -2 h -1 , respectively. A linear correlation was found between the amount of attached biofilm and the nutrient removal rate. The aeration rate in the MBBR compartment and SAD m significantly influenced the sludge characteristics and membrane permeability. The optimum combination of the aeration rate in the MBBR compartment and SAD m were 151 L h -1 and 0.8-1.2m air 3 m membrane -2 h -1 , respectively.

  9. Optimizing aeration rates for minimizing membrane fouling and its effect on sludge characteristics in a moving bed membrane bioreactor

    Energy Technology Data Exchange (ETDEWEB)

    Rahimi, Yousef, E-mail: yrahimi@ut.ac.ir [Department of Civil and Environmental Engineering, Graduate Faculty of Environment, University of Tehran, No. 25 Qods St., Enghelab Ave., Tehran (Iran, Islamic Republic of); Torabian, Ali, E-mail: atorabi@ut.ac.ir [Department of Civil and Environmental Engineering, Graduate Faculty of Environment, University of Tehran, No. 25 Qods St., Enghelab Ave., Tehran (Iran, Islamic Republic of); Mehrdadi, Naser, E-mail: mehrdadi@ut.ac.ir [Department of Civil and Environmental Engineering, Graduate Faculty of Environment, University of Tehran, No. 25 Qods St., Enghelab Ave., Tehran (Iran, Islamic Republic of); Habibi-Rezaie, Mehran, E-mail: mhabibi@khayam.ut.ac.ir [Department of Biotechnology, Faculty of Biology, College of Science, University of Tehran, No. 25 Qods St., Enghelab Ave., Tehran (Iran, Islamic Republic of); Pezeshk, Hamid, E-mail: pezeshk@khayam.ut.ac.ir [Department of Statistics, Faculty of Mathematics and Computer, College of Science, University of Tehran, No. 25 Qods St., Enghelab Ave., Tehran (Iran, Islamic Republic of); Nabi-Bidhendi, Gholam-Reza, E-mail: ghhendi@ut.ac.ir [Department of Civil and Environmental Engineering, Graduate Faculty of Environment, University of Tehran, No. 25 Qods St., Enghelab Ave., Tehran (Iran, Islamic Republic of)

    2011-02-28

    Research highlights: {yields} There is an optimum aeration rate in the MBMBR process compartments. {yields} Optimum aeration rate maximizes nutrients removal. {yields} Optimum aeration rate minimizes membrane fouling. {yields} Both aeration rates in MBBR and membrane compartment can affect on membrane permeability. - Abstract: In MBR processes, sufficient aeration is necessary to maintain sustainable flux and to retard membrane fouling. Membrane permeability, sludge characteristics, nutrient removal and biomass growth at various air flow rates in the membrane and moving bed biofilm reactor (MBBR) compartments were studied in a pilot plant. The highest nitrogen and phosphorous removal rates were found at MBBR aeration rates of 151 and 85 L h{sup -1} and a specific aeration demand per membrane area (SAD{sub m}) of 1.2 and 0.4m{sub air}{sup 3} m{sup -2} h{sup -1}, respectively. A linear correlation was found between the amount of attached biofilm and the nutrient removal rate. The aeration rate in the MBBR compartment and SAD{sub m} significantly influenced the sludge characteristics and membrane permeability. The optimum combination of the aeration rate in the MBBR compartment and SAD{sub m} were 151 L h{sup -1} and 0.8-1.2m{sub air}{sup 3}m{sub membrane}{sup -2} h{sup -1}, respectively.

  10. Sequential Aeration of Membrane-Aerated Biofilm Reactors for High-Rate Autotrophic Nitrogen Removal: Experimental Demonstration

    DEFF Research Database (Denmark)

    Pellicer i Nàcher, Carles; Sun, Sheng-Peng; Lackner, Susanne

    2010-01-01

    One-stage autotrophic nitrogen (N) removal, requiring the simultaneous activity of aerobic and anaerobic ammonium oxidizing bacteria (AOB and AnAOB), can be obtained in spatially redox-stratified biofilms. However, previous experience with Membrane-Aerated Biofilm Reactors (MABRs) has revealed...... a difficulty in reducing the abundance and activity of nitrite oxidizing bacteria (NOB), which drastically lowers process efficiency. Here we show how sequential aeration is an effective strategy to attain autotrophic N removal in MABRs: Two separate MABRs, which displayed limited or no N removal under...... continuous aeration, could remove more than 5.5 g N/m2/day (at loads up to 8 g N/m2/day) by controlled variation of sequential aeration regimes. Daily averaged ratios of the surficial loads of O2 (oxygen) to NH4+ (ammonium) (LO2/LNH4) were close to 1.73 at this optimum. Real-time quantitative PCR based on 16...

  11. CFD simulation of fluid dynamic and biokinetic processes within activated sludge reactors under intermittent aeration regime.

    Science.gov (United States)

    Sánchez, F; Rey, H; Viedma, A; Nicolás-Pérez, F; Kaiser, A S; Martínez, M

    2018-08-01

    Due to the aeration system, biological reactors are the most energy-consuming facilities of convectional WWTPs. Many biological reactors work under intermittent aeration regime; the optimization of the aeration process (air diffuser layout, air flow rate per diffuser, aeration length …) is necessary to ensure an efficient performance; satisfying the effluent requirements with the minimum energy consumption. This work develops a CFD modelling of an activated sludge reactor (ASR) which works under intermittent aeration regime. The model considers the fluid dynamic and biological processes within the ASR. The biological simulation, which is transient, takes into account the intermittent aeration regime. The CFD modelling is employed for the selection of the aeration system of an ASR. Two different aeration configurations are simulated. The model evaluates the aeration power consumption necessary to satisfy the effluent requirements. An improvement of 2.8% in terms of energy consumption is achieved by modifying the air diffuser layout. An analysis of the influence of the air flow rate per diffuser on the ASR performance is carried out. The results show a reduction of 14.5% in the energy consumption of the aeration system when the air flow rate per diffuser is reduced. The model provides an insight into the aeration inefficiencies produced within ASRs. Copyright © 2018 Elsevier Ltd. All rights reserved.

  12. A Trade Study of Two Membrane-Aerated Biological Water Processors

    Science.gov (United States)

    Allada, Ram; Lange, Kevin; Vega. Leticia; Roberts, Michael S.; Jackson, Andrew; Anderson, Molly; Pickering, Karen

    2011-01-01

    Biologically based systems are under evaluation as primary water processors for next generation life support systems due to their low power requirements and their inherent regenerative nature. This paper will summarize the results of two recent studies involving membrane aerated biological water processors and present results of a trade study comparing the two systems with regards to waste stream composition, nutrient loading and system design. Results of optimal configurations will be presented.

  13. Intermittent Aeration Suppresses Nitrite-Oxidizing Bacteria in Membrane-Aerated Biofilms: A Model-Based Explanation

    DEFF Research Database (Denmark)

    Ma, Yunjie; Domingo Felez, Carlos; Plósz, Benedek G.

    2017-01-01

    . On the basis of dissolved oxygen (DO), ammonium, nitrite, and nitrate profiles within the biofilm and in the bulk, a 1-dimensional nitrifying biofilm model was developed and calibrated. The model was utilized to explore the potential mechanisms of NOB suppression associated with intermittent aeration...... nitritation, strategies to suppress nitrite-oxidizing bacteria (NOB) are needed, which are ideally grounded on an understanding of underlying mechanisms. In this study, a nitrifying MABR was operated under intermittent aeration. During eight months of operation, AOB dominated, while NOB were suppressed...... during intermittent aeration was mostly explained by periodic inhibition caused by free ammonia due to periodic transient pH upshifts. Dissolved oxygen limitation did not govern NOB suppression. Different intermittent aeration strategies were then evaluated for nitritation success in intermittently...

  14. Simultaneous nitrogen and organics removal using membrane aeration and effluent ultrafiltration in an anaerobic fluidized membrane bioreactor

    KAUST Repository

    Ye, Yaoli; Saikaly, Pascal; Logan, B.E.

    2017-01-01

    Dissolved methane and a lack of nutrient removal are two concerns for treatment of wastewater using anaerobic fluidized bed membrane bioreactors (AFMBRs). Membrane aerators were integrated into an AFMBR to form an Aeration membrane fluidized bed membrane bioreactor (AeMFMBR) capable of simultaneous removal of organic matter and ammonia without production of dissolved methane. Good effluent quality was obtained with no detectable suspended solids, 93±5% of chemical oxygen demand (COD) removal to 14±11 mg/L, and 74±8% of total ammonia (TA) removal to 12±3 mg-N/L for domestic wastewater (COD of 193±23 mg/L and TA of 49±5 mg-N/L) treatment. Nitrate and nitrite concentrations were always low (< 1 mg-N/L) during continuous flow treatment. Membrane fouling was well controlled by fluidization of the granular activated carbon (GAC) particles (transmembrane pressures maintained <3 kPa). Analysis of the microbial communities suggested that nitrogen removal was due to nitrification and denitrification based on the presence of microorganisms associated with these processes.

  15. Simultaneous nitrogen and organics removal using membrane aeration and effluent ultrafiltration in an anaerobic fluidized membrane bioreactor

    KAUST Repository

    Ye, Yaoli

    2017-08-03

    Dissolved methane and a lack of nutrient removal are two concerns for treatment of wastewater using anaerobic fluidized bed membrane bioreactors (AFMBRs). Membrane aerators were integrated into an AFMBR to form an Aeration membrane fluidized bed membrane bioreactor (AeMFMBR) capable of simultaneous removal of organic matter and ammonia without production of dissolved methane. Good effluent quality was obtained with no detectable suspended solids, 93±5% of chemical oxygen demand (COD) removal to 14±11 mg/L, and 74±8% of total ammonia (TA) removal to 12±3 mg-N/L for domestic wastewater (COD of 193±23 mg/L and TA of 49±5 mg-N/L) treatment. Nitrate and nitrite concentrations were always low (< 1 mg-N/L) during continuous flow treatment. Membrane fouling was well controlled by fluidization of the granular activated carbon (GAC) particles (transmembrane pressures maintained <3 kPa). Analysis of the microbial communities suggested that nitrogen removal was due to nitrification and denitrification based on the presence of microorganisms associated with these processes.

  16. Microbial activity catalyzes oxygen transfer in membrane-aerated nitritating biofilm reactors

    DEFF Research Database (Denmark)

    Pellicer i Nàcher, Carles; Domingo Felez, Carlos; Lackner, Susanne

    2013-01-01

    The remarkable oxygen transfer efficiencies attainable in membrane-aerated biofilm reactors (MABRs) are expected to favor their prompt industrial implementation. However, tests in clean water, currently used for the estimation of their oxygen transfer potential, lead to wrong estimates once biofilm...... is present, significantly complicating reactor modelling and control. This study shows for the first time the factors affecting oxygen mass transfer across membranes during clean water tests and reactor operation via undisturbed microelectrode inspection and bulk measurements. The mass transfer resistance...... of the liquid boundary layer developed at the membrane-liquid interface during clean water tests accounted for two thirds of the total mass transfer resistance, suggesting a strong underestimation of the oxygen transfer rates when it is absent (e.g. after biofilm growth). Reactor operation to attain partial...

  17. Microbial community stratification in Membrane-Aerated Biofilm Reactors for Completely Autotrophic Nitrogen Removal

    DEFF Research Database (Denmark)

    Pellicer i Nàcher, Carles; Ruscalleda, Maël; Terada, Akihiko

    of bacterial granules or biofilms. In this sense, completely autotrophic nitrogen removal from high ammonium strength wastewater was achieved in a Membrane-Aereated Biofilm Reactor (MABR) in a single step. Here, a biofilm containing nitrifiers (Aerobic Ammonium and Nitrite Oxidizing Bacteria, AOB and NOB......, respectively) and Anaerobic Ammonium Oxidizing Bacteria (AnAOB) is grown on bubbleless aeration membranes to remove ammonium. Since oxygen permeates through the membrane-biofilm interface while ammonium diffuses into the biofilm from the biofilm-liquid interface, oxygen gradients can be established across...... the biofilm, allowing nitrogen removal in a single reactor by simultaneous activity of the mentioned biocatalysts. This work consists on the analysis of the microbial community existing in two laboratory-scale reactors operated for more than 300 days, which removed up to 5.5 g-N/m2/day. The system contained...

  18. EXPERIMENTAL STUDY ON THE GAS-LIQUID FLOW IN THE MEMBRANE MICROPORE AERATION BIOREACTOR

    Directory of Open Access Journals (Sweden)

    DONG LIU

    2008-12-01

    Full Text Available Particle Image Velocimetry (PIV has been developed to measure the typical two-phase flow of various work conditions in Membrane Micropore Aeration Bioreactor (MMAB. The fluid phase is separated out using image processing techniques, which provides accurate measurements for the Bioreactor’s flow field, and makes it possible for quantitative analysis of the momentum exchange, heat exchange and the process of micro-admixture. The experimental method PIV used in this paper can preferably measure the complex flow in the reactor and initiates a new approach for the bioreactor design which mainly depends on experience at present.

  19. Membrane-aerated biofilm reactor for the removal of 1,2-dichloroethane by Pseudomonas sp strain DCA1

    NARCIS (Netherlands)

    Hage, J.C.; Houten, R.T.; Tramper, J.; Hartmans, S.

    2004-01-01

    A membrane-aerated biofilm reactor (MBR) with a biofilm of Pseudomonas sp. strain DCA1 was studied for the removal of 1,2-dichloroethane (DCA) from water. A hydrophobic membrane was used to create a barrier between the liquid and the gas phase. Inoculation of the MBR with cells of strain DCA1 grown

  20. Enhanced recovery of ammonia from swine manure anaerobic digester effluent using gas-permeable membranes and aeration

    Science.gov (United States)

    Atmospheric ammonia pollution from livestock wastes can be reduced using gas-permeable membrane technology by converting ammonia contained in the manure into ammonium salt for use in fertilizers. In this study, gas-permeable membrane technology was enhanced using aeration combined with nitrificatio...

  1. Effects of intermittent and continuous aeration on accelerative stabilization and microbial population dynamics in landfill bioreactors.

    Science.gov (United States)

    Sang, Nguyen Nhu; Soda, Satoshi; Inoue, Daisuke; Sei, Kazunari; Ike, Michihiko

    2009-10-01

    Performance and microbial population dynamics in landfill bioreactors were investigated in laboratory experiments. Three reactors were operated without aeration (control reactor, CR), with cyclic 6-h aeration and 6-h non-aeration (intermittently aerated reactor, IAR), and with continuous aeration (continuously aerated reactor, CAR). Each reactor was loaded with high-organic solid waste. The performance of IAR was highest among the reactors up to day 90. The respective solid weight, organic matter content, and waste volume on day 90 in the CR, IAR, and CAR were 50.9, 39.1, and 47.5%; 46.5, 29.3 and 35.0%; and 69, 38, and 53% of the initial values. Organic carbon and nitrogen compounds in leachate in the IAR and the CAR showed significant decreases in comparison to those in the CR. The most probable number (MPN) values of fungal 18S rDNA in the CAR and the IAR were higher than those in the CR. Terminal restriction fragment length polymorphism analysis showed that unique and diverse eubacterial and archaeal communities were formed in the IAR. The intermittent aeration strategy was favorable for initiation of solubilization of organic matter by the aerobic fungal populations and the reduction of the acid formation phase. Then the anaerobic H(2)-producing bacteria Clostridium became dominant in the IAR. Sulfate-reducing bacteria, which cannot use acetate/sulfate but which instead use various organics/sulfate as the electron donor/acceptor were also dominant in the IAR. Consequently, Methanosarcinales, which are acetate-utilizing methanogens, became the dominant archaea in the IAR, where high methane production was observed.

  2. Computational Fluid Dynamics Modelling of Hydraulics and Sedimentation in Process Reactors During Aeration Tank Settling

    DEFF Research Database (Denmark)

    Dam Jensen, Mette; Ingildsen, Pernille; Rasmussen, Michael R.

    2005-01-01

    Aeration Tank Settling is a control method alowing settling in the process tank during high hydraulic load. The control method is patented. Aeration Tank Settling has been applied in several waste water treatment plant's using present design of the process tanks. Some process tank designs have...... shown to be more effective than others. To improve the design of less effective plants Computational Fluid Dynamics (CFD) modelling of hydraulics and sedimentation has been applied. The paper discusses the results at one particular plant experiencing problems with partly short-circuiting of the inlet...

  3. An aerated and fluidized bed membrane bioreactor for effective wastewater treatment with low membrane fouling

    KAUST Repository

    Ye, Yaoli; Labarge, Nicole; Kashima, Hiroyuki; Kim, Kyoung Yeol; Hong, Pei-Ying; Saikaly, Pascal; Logan, Bruce E.

    2016-01-01

    Anaerobic fluidized bed membrane bioreactors (AFMBRs) use granular activated carbon (GAC) particles suspended by recirculation to effectively treat low strength wastewaters (∼100–200 mg L−1, chemical oxygen demand, COD), but the effluent can contain dissolved methane. An aerobic fluidized bed membrane bioreactor (AOFMBR) was developed to avoid methane production and the need for wastewater recirculation by using rising air bubbles to suspend GAC particles. The performance of the AOFMBR was compared to an AFMBR and a conventional aerobic membrane bioreactor (AeMBR) for domestic wastewater treatment over 130 d at ambient temperatures (fixed hydraulic retention time of 1.3 h). The effluent of the AOFMBR had a COD of 20 ± 8 mg L−1, and a turbidity of <0.2 NTU, for low-COD influent (153 ± 19 and 214 ± 27 mg L−1), similar to the AeMBR and AFMBR. For the high-COD influent (299 ± 24 mg L−1), higher effluent CODs were obtained for the AeMBR (38 ± 9 mg L−1) and AFMBR (51 ± 11 mg L−1) than the AOFMBR (26 ± 6 mg L−1). Transmembrane pressure of the AOFMBR increased at 0.04 kPa d−1, which was 20% less than the AeMBR and 57% less than the AFMBR, at the low influent COD. Scanning electron microscopy (SEM) analysis indicated a more uniform biofilm on the membrane in AOFMBR than that from the AeMBR biofilm, and no evidence of membrane damage. High similarity was found between communities in the suspended sludge in the AOFMBR and AeMBR (square-root transformed Bray–Curtis similarity, SRBCS, 0.69). Communities on the GAC and suspended sludge were dissimilar in the AOFMBR (SRBCS, 0.52), but clustered in the AFMBR (SRBCS, 0.63).

  4. An aerated and fluidized bed membrane bioreactor for effective wastewater treatment with low membrane fouling

    KAUST Repository

    Ye, Yaoli

    2016-09-24

    Anaerobic fluidized bed membrane bioreactors (AFMBRs) use granular activated carbon (GAC) particles suspended by recirculation to effectively treat low strength wastewaters (∼100–200 mg L−1, chemical oxygen demand, COD), but the effluent can contain dissolved methane. An aerobic fluidized bed membrane bioreactor (AOFMBR) was developed to avoid methane production and the need for wastewater recirculation by using rising air bubbles to suspend GAC particles. The performance of the AOFMBR was compared to an AFMBR and a conventional aerobic membrane bioreactor (AeMBR) for domestic wastewater treatment over 130 d at ambient temperatures (fixed hydraulic retention time of 1.3 h). The effluent of the AOFMBR had a COD of 20 ± 8 mg L−1, and a turbidity of <0.2 NTU, for low-COD influent (153 ± 19 and 214 ± 27 mg L−1), similar to the AeMBR and AFMBR. For the high-COD influent (299 ± 24 mg L−1), higher effluent CODs were obtained for the AeMBR (38 ± 9 mg L−1) and AFMBR (51 ± 11 mg L−1) than the AOFMBR (26 ± 6 mg L−1). Transmembrane pressure of the AOFMBR increased at 0.04 kPa d−1, which was 20% less than the AeMBR and 57% less than the AFMBR, at the low influent COD. Scanning electron microscopy (SEM) analysis indicated a more uniform biofilm on the membrane in AOFMBR than that from the AeMBR biofilm, and no evidence of membrane damage. High similarity was found between communities in the suspended sludge in the AOFMBR and AeMBR (square-root transformed Bray–Curtis similarity, SRBCS, 0.69). Communities on the GAC and suspended sludge were dissimilar in the AOFMBR (SRBCS, 0.52), but clustered in the AFMBR (SRBCS, 0.63).

  5. Rapid Startup and Loading of an Attached Growth, Simultaneous Nitrification/Denitrification Membrane Aerated Bioreactor

    Science.gov (United States)

    Meyer, Caitlin; Vega, Leticia

    2014-01-01

    The Membrane Aerated Bioreactor (MABR) is an attached-growth biological system for simultaneous nitrification and denitrification. This design is an innovative approach to common terrestrial wastewater treatments for nitrogen and carbon removal. Implementing a biologically-based water treatment system for long-duration human exploration is an attractive, low energy alternative to physiochemical processes. Two obstacles to implementing such a system are (1) the "start-up" duration from inoculation to steady-state operations and (2) the amount of surface area needed for the biological activity to occur. The Advanced Water Recovery Systems (AWRS) team at JSC explored these two issues through two tests; a rapid inoculation study and a wastewater loading study. Results from these tests demonstrate that the duration from inoculation to steady state can be reduced to two weeks and that the surface area to volume ratio baseline used in the Alternative Water Processor (AWP) test was higher than what was needed to remove the organic carbon and ammonium from the system.

  6. Computational fluid dynamics modelling of hydraulics and sedimentation in process reactors during aeration tank settling.

    Science.gov (United States)

    Jensen, M D; Ingildsen, P; Rasmussen, M R; Laursen, J

    2006-01-01

    Aeration tank settling is a control method allowing settling in the process tank during high hydraulic load. The control method is patented. Aeration tank settling has been applied in several waste water treatment plants using the present design of the process tanks. Some process tank designs have shown to be more effective than others. To improve the design of less effective plants, computational fluid dynamics (CFD) modelling of hydraulics and sedimentation has been applied. This paper discusses the results at one particular plant experiencing problems with partly short-circuiting of the inlet and outlet causing a disruption of the sludge blanket at the outlet and thereby reducing the retention of sludge in the process tank. The model has allowed us to establish a clear picture of the problems arising at the plant during aeration tank settling. Secondly, several process tank design changes have been suggested and tested by means of computational fluid dynamics modelling. The most promising design changes have been found and reported.

  7. Analysis of Process Gases and Trace Contaminants in Membrane-Aerated Gaseous Effluent Streams.

    Science.gov (United States)

    Coutts, Janelle L.; Lunn, Griffin Michael; Meyer, Caitlin E.

    2015-01-01

    In membrane-aerated biofilm reactors (MABRs), hollow fibers are used to supply oxygen to the biofilms and bulk fluid. A pressure and concentration gradient between the inner volume of the fibers and the reactor reservoir drives oxygen mass transport across the fibers toward the bulk solution, providing the fiber-adhered biofilm with oxygen. Conversely, bacterial metabolic gases from the bulk liquid, as well as from the biofilm, move opposite to the flow of oxygen, entering the hollow fiber and out of the reactor. Metabolic gases are excellent indicators of biofilm vitality, and can aid in microbial identification. Certain gases can be indicative of system perturbations and control anomalies, or potentially unwanted biological processes occurring within the reactor. In confined environments, such as those found during spaceflight, it is important to understand what compounds are being stripped from the reactor and potentially released into the crew cabin to determine the appropriateness or the requirement for additional mitigation factors. Reactor effluent gas analysis focused on samples provided from Kennedy Space Center's sub-scale MABRs, as well as Johnson Space Center's full-scale MABRs, using infrared spectroscopy and gas chromatography techniques. Process gases, such as carbon dioxide, oxygen, nitrogen, nitrogen dioxide, and nitrous oxide, were quantified to monitor reactor operations. Solid Phase Microextraction (SPME) GC-MS analysis was used to identify trace volatile compounds. Compounds of interest were subsequently quantified. Reactor supply air was examined to establish target compound baseline concentrations. Concentration levels were compared to average ISS concentration values and/or Spacecraft Maximum Allowable Concentration (SMAC) levels where appropriate. Based on a review of to-date results, current trace contaminant control systems (TCCS) currently on board the ISS should be able to handle the added load from bioreactor systems without the need

  8. Generalized chiral membrane dynamics

    International Nuclear Information System (INIS)

    Cordero, R.; Rojas, E.

    2003-01-01

    We develop the dynamics of the chiral superconducting membranes (with null current) in an alternative geometrical approach. Besides of this, we show the equivalence of the resulting description with the one known Dirac-Nambu-Goto (DNG) case. Integrability for chiral string model is obtained using a proposed light-cone gauge. In a similar way, domain walls are integrated by means of a simple Ansatz. (Author)

  9. Membrane-aerated biofilm reactor for the removal of 1,2-dichloroethane by Pseudomonas sp. strain DCA1.

    Science.gov (United States)

    Hage, J C; Van Houten, R T; Tramper, J; Hartmans, S

    2004-06-01

    A membrane-aerated biofilm reactor (MBR) with a biofilm of Pseudomonas sp. strain DCA1 was studied for the removal of 1,2-dichloroethane (DCA) from water. A hydrophobic membrane was used to create a barrier between the liquid and the gas phase. Inoculation of the MBR with cells of strain DCA1 grown in a continuous culture resulted in the formation of a stable and active DCA-degrading biofilm on the membrane. The maximum removal rate of the MBR was reached at a DCA concentration of approximately 80 micro M. Simulation of the DCA fluxes into the biofilm showed that the MBR performance at lower concentrations was limited by the DCA diffusion rate rather than by kinetic constraints of strain DCA1. Aerobic biodegradation of DCA present in anoxic water could be achieved by supplying oxygen solely from the gas phase to the biofilm grown on the liquid side of the membrane. As a result, direct aeration of the water, which leads to undesired coagulation of iron oxides, could be avoided.

  10. Rapid Start-up and Loading of an Attached Growth, Simultaneous Nitrification/Denitrification Membrane Aerated Bioreactor

    Science.gov (United States)

    Meyer, Caitlin E.; Pensinger, Stuart; Pickering, Karen D.; Barta, Daniel; Shull, Sarah A.; Vega, Letticia M.; Christenson, Dylan; Jackson, W. Andrew

    2015-01-01

    Membrane aerated bioreactors (MABR) are attached-growth biological systems used for simultaneous nitrification and denitrification to reclaim water from waste. This design is an innovative approach to common terrestrial wastewater treatments for nitrogen and carbon removal and implementing a biologically-based water treatment system for long-duration human exploration is an attractive, low energy alternative to physiochemical processes. Two obstacles to implementing such a system are (1) the "start-up" duration from inoculation to steady-state operations and (2) the amount of surface area needed for the biological activity to occur. The Advanced Water Recovery Systems (AWRS) team at JSC explored these two issues through two tests; a rapid inoculation study and a wastewater loading study. Results from these tests demonstrate that the duration from inoculation to steady state can be reduced to under two weeks, and that despite low ammonium removal rates, the MABRs are oversized.

  11. Model-based evaluation of the role of Anammox on nitric oxide and nitrous oxide productions in membrane aerated biofilm reactor

    DEFF Research Database (Denmark)

    Ni, Bing-Jie; Smets, Barth F.; Yuan, Zhiguo

    2013-01-01

    A multispecies one-dimensional biofilm model considering nitric oxide (NO) and nitrous oxide (N2O) productions for membrane aerated biofilm reactor (MABR) that remove nitrogen autotrophically through aerobic ammonia oxidation followed by Anammox is used to study the role of Anammox activity...... on the total nitrogen (TN) removal and the productions of NO and N2O. The model is applied to evaluate how periodic aeration as a control parameter reduces NO and N2O production but maintains high TN removal in MABR. The simulation results show over 3.5% of the removed TN could be attributed to NO and N2O...... production in MABR under the operational conditions optimal for TN removal (72%). An analysis of factors governing the Anammox activity in MABR shows that enhancing Anammox activity not only helps to achieve a high level of nitrogen removal but also reduces NO and N2O productions. Comparison of aeration...

  12. Energy Efficient Aeration in a Single Low Pressure Hollow Sheet Membrane Filtration Module

    DEFF Research Database (Denmark)

    Bentzen, Thomas Ruby; Ratkovich, Nicolas Rios; Rasmussen, Michael R.

    2011-01-01

    The main drawback of membrane bioreactors (MBR) systems is the fouling of the membrane, which is decreased and/or prevented through gas sparging. However, this practice is based on rules of thumb or a trial-and-error approaches which are tedious, very time-consuming, do not necessarily provide...... optimal fouling control and they are not energy efficient. Therefore, dedicated experiments are needed to fully understand the hydrodynamics of it. A hollow sheet (HS) MBR was studied. Experimental velocity measurements were made using micro-propellers and compared to CFD results. A good agreement between...... is homogeneously distributes over the predominant part of the membrane surface....

  13. Computational Fluid Dynamics Modelling of Hydraulics and Sedimentation in Process Reactors during Aeration Tank Settling

    DEFF Research Database (Denmark)

    Jensen, M.D.; Ingildsen, P.; Rasmussen, Michael R.

    2006-01-01

    Aeration tank settling is a control method allowing settling in the process tank during highhydraulic load. The control method is patented. Aeration tank settling has been applied in several wastewater treatment plants using the present design of the process tanks. Some process tank designs...... and outletcausing a disruption of the sludge blanket at the outlet and thereby reducing the retention of sludge in theprocess tank. The model has allowed us to establish a clear picture of the problems arising at the plantduring aeration tank settling. Secondly, several process tank design changes have been...

  14. Static and Dynamic Membrane Structures

    Directory of Open Access Journals (Sweden)

    Sergiu Ivanov

    2012-10-01

    Full Text Available While originally P systems were defined to contain multiset rewriting rules, it turned out that considering different types of rules may produce important results, such as increasing the computational power of the rules. This paper focuses on factoring out the concept of a membrane structure out of various P system models with the goal of providing useful formalisations. Both static and dynamic membrane structures are considered.

  15. Recovery of ammonia from swine manure using gas-permeable membranes: Effect of aeration

    Science.gov (United States)

    Gas-permeable membranes can recover ammonia from manure, reducing pollution whilst converting ammonia into ammonium salt fertilizer. The process involves manure pH control to increase ammonium (NH4) recovery rate that is normally carried out using an alkali. In this study a new strategy to avoid the...

  16. Start-up strategies of membrane-aerated biofilm reactor (MABR) for completely autotrophic nitrogen removal

    DEFF Research Database (Denmark)

    Sun, Sheng-Peng; Pellicer i Nàcher, Carles; Terada, Akihiko

    2009-01-01

    Completely autotrophic nitrogen removal, coupling aerobic and anaerobic ammonium oxidation, can be achieved via redox stratified biofilms growing on gas-permeable membranes. These sequential reactions are mediated by aerobic and anaerobic ammonium oxidizing bacteria (AOB and AnAOB). The major...

  17. Proteomics and the dynamic plasma membrane

    DEFF Research Database (Denmark)

    Sprenger, Richard R; Jensen, Ole Nørregaard

    2010-01-01

    plasma membrane is of particular interest, by not only serving as a barrier between the "cell interior" and the external environment, but moreover by organizing and clustering essential components to enable dynamic responses to internal and external stimuli. Defining and characterizing the dynamic plasma...... the challenges in functional proteomic studies of the plasma membrane. We review the recent progress in MS-based plasma membrane proteomics by presenting key examples from eukaryotic systems, including mammals, yeast and plants. We highlight the importance of enrichment and quantification technologies required...... for detailed functional and comparative analysis of the dynamic plasma membrane proteome....

  18. 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. Copyright © 2013 Elsevier Inc. All rights reserved.

  19. Dynamic membrane filtration in tangential flow

    International Nuclear Information System (INIS)

    Anon.

    1993-01-01

    Oil-containing waste water is produced in many cleaning processes and also on production of compressed air. Dynamic membrane filtration in the tangential flow mode has proved effective in the treatment of these stable emulsions. The possible applications of ceramic membrane filters are illustrated for a variety of examples. (orig.) [de

  20. Molecular dynamics simulation of a phospholipid membrane

    NARCIS (Netherlands)

    Egberts, Egbert; Marrink, Siewert-Jan; Berendsen, Herman J.C.

    We present the results of molecular dynamics (MD) simulations of a phospholipid membrane in water, including full atomic detail. The goal of the simulations was twofold: first we wanted to set up a simulation system which is able to reproduce experimental results and can serve as a model membrane in

  1. New jet-aeration system using 'Supercavitation'.

    Science.gov (United States)

    Schmid, Andreas

    2010-03-01

    A newly developed fine bubble aeration system, by which air is transferred under supercavitation conditions, shows a clearly better performance than traditional, well-known aerators that rely on the jet-pump principle and its performance can be compared to oxygen transfer rates achieved in membrane and foil plate aerators. A prototype supercavitation aerator installed at a sewage treatment plant revealed an air input rate, which was about one third lower than that of the jet-pump system, which it replaced. In spite of this low air input rate, the daily demand of pure oxygen for the additionally installed membrane aeration system went down by approximately 49%, from the original level of about 1,200 m(3)/day to about 600 m(3)/day-and this over a test period of more than 7 months. The observed high oxygen transfer rates cannot be explained by traditional mass transfer mechanisms. It is assumed that a large amount of water being transferred into the gas phase by supercavitation contacting directly oxygen also in the gas phase and thereby overcoming mass transfer hindrances which might be favoured by hydroxyl radicals. With this new aerator, during the first 3 months of test phase, already more than 10,000 Euros had been saved because of the reduced pure oxygen demand.

  2. Dynamic nuclear polarization methods in solids and solutions to explore membrane proteins and membrane systems.

    Science.gov (United States)

    Cheng, Chi-Yuan; Han, Songi

    2013-01-01

    Membrane proteins regulate vital cellular processes, including signaling, ion transport, and vesicular trafficking. Obtaining experimental access to their structures, conformational fluctuations, orientations, locations, and hydration in membrane environments, as well as the lipid membrane properties, is critical to understanding their functions. Dynamic nuclear polarization (DNP) of frozen solids can dramatically boost the sensitivity of current solid-state nuclear magnetic resonance tools to enhance access to membrane protein structures in native membrane environments. Overhauser DNP in the solution state can map out the local and site-specific hydration dynamics landscape of membrane proteins and lipid membranes, critically complementing the structural and dynamics information obtained by electron paramagnetic resonance spectroscopy. Here, we provide an overview of how DNP methods in solids and solutions can significantly increase our understanding of membrane protein structures, dynamics, functions, and hydration in complex biological membrane environments.

  3. Dilaton dynamics from production of tensionless membranes

    International Nuclear Information System (INIS)

    Cremonini, Sera; Watson, Scott

    2006-01-01

    In this paper we consider classical and quantum corrections to cosmological solutions of 11D supergravity (SUGRA) coming from dynamics of membrane states. We first consider the supermembrane spectrum following the approach of Russo and Tseytlin for consistent quantization. We calculate the production rate of Bogomol'nyi-Prasad-Sommerfield (BPS) membrane bound states in a cosmological background and find that such effects are generically suppressed by the Planck scale, as expected. However, for a modified brane spectrum possessing enhanced symmetry, production can be finite and significant. We stress that this effect could not be anticipated given only a knowledge of the low-energy effective theory. Once on shell, inclusion of these states leads to an attractive force pulling the dilaton towards a fixed point of S-duality, namely g s =1. Although the SUGRA description breaks down in this regime, inclusion of the enhanced states suggests that the center of M-theory moduli space is a dynamical attractor. Moreover, our results seem to suggest that string dynamics does indeed favor a vacuum near fixed points of duality

  4. Dynamic coating of mf/uf membranes for fouling mitigation

    KAUST Repository

    Tabatabai, S. Assiyeh Alizadeh

    2017-01-19

    A membrane system including an anti-fouling layer and a method of applying an anti-fouling layer to a membrane surface are provided. In an embodiment, the surface is a microfiltration (MF) or an ultrafiltration (UF) membrane surface. The anti-fouling layer can include a stimuli responsive layer and a dynamic protective layer applied over the stimuli responsive layer that can be a coating on a surface of the membrane. The stimuli responsive polymer layer can act as an adhesive prior to coating with the dynamic protective layer to aid in adhering the dynamic protective layer to the membrane surface. The dynamic protective layer can be formed by suitable nanoparticles that can prevent adhesion of foulants directly to the membrane surface. The stimuli responsive layer can be responsive to physio- chemical stimuli to cause a release of the stimuli responsive layer and the dynamic protective layer including foulants from the membrane.

  5. Solar powered dugout aeration

    International Nuclear Information System (INIS)

    Murrell, S.

    2001-10-01

    Pasture dugouts are a significant source of water for livestock on the Canadian Prairies and as such, must maintain the best water quality possible. Aeration improves the water quality and is part of a good management plan to reduce overall water treatment costs. Although dugouts can be aerated naturally through wind and wave action and photosynthesis, this generally aerates only the top portion of the dugout. Artificial aeration by air injection into the lowest point of the dugout ensures that the water is oxygenated throughout the entire dugout. Solar aeration can be used in remote areas where grid power is not practical. With solar powered aeration systems, solar panels are used to generate the electrical power needed to run the compressor while storing excess energy in batteries. A solar aeration system includes solar panels, deep cycle batteries to store excess power, a control board with a regulator, a compressor, a weighed feeder hose, and an air diffuser. This publication presented the design of a solar aeration system and its cost. 1 tab., 3 figs

  6. Dynamic Membrane Technology for Printing Wastewater Reuse

    Science.gov (United States)

    Liu, Lin; Lu, Xujie; Chen, Jihua

    As environmental regulations become rigid and the cost of freshwater increases, wastewater is considered as a major resource in China. The paper presented a study on the implementation of the advanced treatment process using dynamic membrane (DM) in reusing of printing wastewater. The DM was well formed by circulating 1.5g/L of PAC in 20 minutes, the trans-membrane pressure of 200 kPa and the cross-flow velocity of 0.75m/s. The printing effluents were treated in effluent treatment plants comprising a physicochemical option followed by biological process. The treated effluent contained chemical oxygen demand (COD), color and turbidity in the range of 45-60 mg/L, 0.030-0.045 (absorbance at 420 nm) and 3-5 NTU. The results showed that the COD, color and turbidity removal efficiencies of the DM permeate were 84%, 85% and 80%, respectively. The wastewater treated by DM was reused as process water and the final concentrated retentate could be discharged directly into sewage treatment works with no additional treatments. Cleaning and regeneration of DM were very convenient if necessary. The proper process was that the polluted DM was cleaned with tap water at high cross-flow velocity. When irreversible pollutants accumulate, it would be rinsed with chemicals tested and the membrane flux would be restored up to 95%. The result showed that DM was considered as a promising method for purification aimed at reuse of printing wastewater, resulting in direct environmental and economic benefits.

  7. Organization and Dynamics of Receptor Proteins in a Plasma Membrane.

    Science.gov (United States)

    Koldsø, Heidi; Sansom, Mark S P

    2015-11-25

    The interactions of membrane proteins are influenced by their lipid environment, with key lipid species able to regulate membrane protein function. Advances in high-resolution microscopy can reveal the organization and dynamics of proteins and lipids within living cells at resolutions membranes of in vivo-like complexity. We explore the dynamics of proteins and lipids in crowded and complex plasma membrane models, thereby closing the gap in length and complexity between computations and experiments. Our simulations provide insights into the mutual interplay between lipids and proteins in determining mesoscale (20-100 nm) fluctuations of the bilayer, and in enabling oligomerization and clustering of membrane proteins.

  8. Anaerobic dynamic membrane bioreactors for high strength wastewater treatment

    NARCIS (Netherlands)

    Ersahin, M.E.; Gimenez Garcia, J.B.; Ozgun, H.; Tao, Y.; Van Lier, J.B.

    2013-01-01

    A laboratory scale external anaerobic dynamic membrane bioreactor (AnDMBR) treating high strength wastewater was operated to assess the effect of gas sparging velocity and organic loading rate on removal efficiency and dynamic membrane (DM) filtration characteristics. An increase in gas sparging

  9. Dynamic Membrane Formation in Anaerobic Dynamic Membrane Bioreactors: Role of Extracellular Polymeric Substances.

    Directory of Open Access Journals (Sweden)

    Hongguang Yu

    Full Text Available Dynamic membrane (DM formation in dynamic membrane bioreactors plays an important role in achieving efficient solid-liquid separation. In order to study the contribution of extracellular polymeric substances (EPS to DM formation in anaerobic dynamic membrane bioreactor (AnDMBR processes, EPS extraction from and re-addition to bulk sludge were carried out in short-term filtration tests. DM formation behaviors could be well simulated by cake filtration model, and sludge with EPS re-addition showed the highest resistance coefficient, followed by sludge after EPS extraction. The DM layers exhibited a higher resistance and a lower porosity for the sludge sample after EPS extraction and for the sludge with EPS re-addition. Particle size of sludge flocs decreased after EPS extraction, and changed little with EPS re-addition, which was confirmed by interaction energy analysis. Further investigations by confocal laser scanning microscopy (CLSM analysis and batch tests suggested that the removal of in-situ EPS stimulated release of soluble EPS, and re-added EPS were present as soluble EPS rather than bound EPS, which thus improved the formation of DM. The present work revealed the role of EPS in anaerobic DM formation, and could facilitate the operation of AnDMBR processes.

  10. Application of dynamic membranes in anaerobic membranes in anaerobic membrane bioreactor systems

    NARCIS (Netherlands)

    Erşahin, M.E.

    2015-01-01

    Anaerobic membrane bioreactors (AnMBRs) physically ensure biomass retention by the application of a membrane filtration process. With growing application experiences from aerobic membrane bioreactors (MBRs), the combination of membrane and anaerobic processes has received much attention and become

  11. Membrane tension regulates clathrin-coated pit dynamics

    Science.gov (United States)

    Liu, Allen

    2014-03-01

    Intracellular organization depends on close communication between the extracellular environment and a network of cytoskeleton filaments. The interactions between cytoskeletal filaments and the plasma membrane lead to changes in membrane tension that in turns help regulate biological processes. Endocytosis is thought to be stimulated by low membrane tension and the removal of membrane increases membrane tension. While it is appreciated that the opposing effects of exocytosis and endocytosis have on keeping plasma membrane tension to a set point, it is not clear how membrane tension affects the dynamics of clathrin-coated pits (CCPs), the individual functional units of clathrin-mediated endocytosis. Furthermore, although it was recently shown that actin dynamics counteracts membrane tension during CCP formation, it is not clear what roles plasma membrane tension plays during CCP initiation. Based on the notion that plasma membrane tension is increased when the membrane area increases during cell spreading, we designed micro-patterned surfaces of different sizes to control the cell spreading sizes. Total internal reflection fluorescence microscopy of living cells and high content image analysis were used to quantify the dynamics of CCPs. We found that there is an increased proportion of CCPs with short (<20s) lifetime for cells on larger patterns. Interestingly, cells on larger patterns have higher CCP initiation density, an effect unexpected based on the conventional view of decreasing endocytosis with increasing membrane tension. Furthermore, by analyzing the intensity profiles of CCPs that were longer-lived, we found CCP intensity decreases with increasing cell size, indicating that the CCPs are smaller with increasing membrane tension. Finally, disruption of actin dynamics significantly increased the number of short-lived CCPs, but also decreased CCP initiation rate. Together, our study reveals new mechanistic insights into how plasma membrane tension regulates

  12. Mechanics and dynamics of triglyceride-phospholipid model membranes

    DEFF Research Database (Denmark)

    Pakkanen, Kirsi I.; Duelund, Lars; Qvortrup, Klaus

    2011-01-01

    We demonstrate here that triolein alters the mechanical properties of phospholipid membranes and induces extraordinary conformational dynamics. Triolein containing membranes exhibit fluctuations up to size range of 100µm and with the help of these are e.g. able to squeeze through narrow passages...... with larger lamellar distances observed in the TOPOPC membranes. These findings suggest repulsion between adjacent membranes. We provide a comprehensive discussion on the possible explanations for the observed mechanics and dynamics in the TOPOPC system and on their potential cellular implications....

  13. Hydrodynamic performance of a single-use aerated stirred bioreactor in animal cell culture: applications of tomography, dynamic gas disengagement (DGD), and CFD.

    Science.gov (United States)

    Kazemzadeh, Argang; Elias, Cynthia; Tamer, Melih; Ein-Mozaffari, Farhad

    2018-05-01

    The hydrodynamics of gas-liquid two-phase flow in a single-use bioreactor were investigated in detail both experimentally and numerically. Electrical resistance tomography (ERT) and dynamic gas disengagement (DGD) combined with computational fluid dynamics (CFD) were employed to assess the effect of the volumetric gas flow rate and impeller speed on the gas-liquid flow field, local and global gas holdup values, and Sauter mean bubble diameter. From the results obtained from DGD coupled with ERT, the bubble sizes were determined. The experimental data indicated that the total gas holdup values increased with increasing both the rotational speed of impeller and volumetric gas flow rate. Moreover, the analysis of the flow field generated inside the aerated stirred bioreactor was conducted using CFD results. Overall, a more uniform distribution of the gas holdup was obtained at impeller speeds ≥ 100 rpm for volumetric gas flow rates ≥ 1.6 × 10 -5  m 3 /s.

  14. Cardiolipin effects on membrane structure and dynamics.

    Science.gov (United States)

    Unsay, Joseph D; Cosentino, Katia; Subburaj, Yamunadevi; García-Sáez, Ana J

    2013-12-23

    Cardiolipin (CL) is a lipid with unique properties solely found in membranes generating electrochemical potential. It contains four acyl chains and tends to form nonlamellar structures, which are believed to play a key role in membrane structure and function. Indeed, CL alterations have been linked to disorders such as Barth syndrome and Parkinson's disease. However, the molecular effects of CL on membrane organization remain poorly understood. Here, we investigated the structure and physical properties of CL-containing membranes using confocal microscopy, fluorescence correlation spectroscopy, and atomic force microscopy. We found that the fluidity of the lipid bilayer increased and its mechanical stability decreased with CL concentration, indicating that CL decreases the packing of the membrane. Although the presence of up to 20% CL gave rise to flat, stable bilayers, the inclusion of 5% CL promoted the formation of flowerlike domains that grew with time. Surprisingly, we often observed two membrane-piercing events in atomic force spectroscopy experiments with CL-containing membranes. Similar behavior was observed with a lipid mixture mimicking the mitochondrial outer membrane composition. This suggests that CL promotes the formation of membrane areas with apposed double bilayers or nonlamellar structures, similar to those proposed for mitochondrial contact sites. All together, we show that CL induces membrane alterations that support the role of CL in facilitating bilayer structure remodeling, deformation, and permeabilization.

  15. Complex Dynamic Development of Poliovirus Membranous Replication Complexes

    Science.gov (United States)

    Nair, Vinod; Hansen, Bryan T.; Hoyt, Forrest H.; Fischer, Elizabeth R.; Ehrenfeld, Ellie

    2012-01-01

    Replication of all positive-strand RNA viruses is intimately associated with membranes. Here we utilize electron tomography and other methods to investigate the remodeling of membranes in poliovirus-infected cells. We found that the viral replication structures previously described as “vesicles” are in fact convoluted, branching chambers with complex and dynamic morphology. They are likely to originate from cis-Golgi membranes and are represented during the early stages of infection by single-walled connecting and branching tubular compartments. These early viral organelles gradually transform into double-membrane structures by extension of membranous walls and/or collapsing of the luminal cavity of the single-membrane structures. As the double-membrane regions develop, they enclose cytoplasmic material. At this stage, a continuous membranous structure may have double- and single-walled membrane morphology at adjacent cross-sections. In the late stages of the replication cycle, the structures are represented mostly by double-membrane vesicles. Viral replication proteins, double-stranded RNA species, and actively replicating RNA are associated with both double- and single-membrane structures. However, the exponential phase of viral RNA synthesis occurs when single-membrane formations are predominant in the cell. It has been shown previously that replication complexes of some other positive-strand RNA viruses form on membrane invaginations, which result from negative membrane curvature. Our data show that the remodeling of cellular membranes in poliovirus-infected cells produces structures with positive curvature of membranes. Thus, it is likely that there is a fundamental divergence in the requirements for the supporting cellular membrane-shaping machinery among different groups of positive-strand RNA viruses. PMID:22072780

  16. Single-particle tracking: applications to membrane dynamics.

    Science.gov (United States)

    Saxton, M J; Jacobson, K

    1997-01-01

    Measurements of trajectories of individual proteins or lipids in the plasma membrane of cells show a variety of types of motion. Brownian motion is observed, but many of the particles undergo non-Brownian motion, including directed motion, confined motion, and anomalous diffusion. The variety of motion leads to significant effects on the kinetics of reactions among membrane-bound species and requires a revision of existing views of membrane structure and dynamics.

  17. Hydrophilic Fe2O3 dynamic membrane mitigating fouling of support ceramic membrane in ultrafiltration of oil/water emulsion

    KAUST Repository

    Lu, Dongwei; Cheng, Wei; Zhang, Tao; Lu, Xinglin; Liu, Qianliang; Jiang, Jin; Ma, Jun

    2016-01-01

    Oil/water (O/W) emulsion is daily produced and difficult to be treated effectively. Ceramic membrane ultrafiltration is one of reliable processes for the treatment of O/W emulsion, yet still hindered by membrane fouling. In this study, two types of Fe2O3 dynamic membranes (i.e., pre-coated dynamic membrane and self-forming dynamic membrane) were prepared to mitigate the fouling of support ceramic membrane in O/W emulsion treatment. Pre-coated dynamic membrane (DM) significantly reduced the fouling of ceramic membrane (i.e., 10% increase of flux recovery rate), while self-forming dynamic membrane aggravated ceramic membrane fouling (i.e., 8.6% decrease of flux recovery rate) after four filtration cycles. A possible fouling mechanism was proposed to explain this phenomenon, which was then confirmed by optical images of fouled membranes and the analysis of COD rejection. In addition, the cleaning efficiency of composite membranes (i.e., Fe2O3 dynamic membrane and support ceramic membrane) was enhanced by substitution of alkalescent water backwash for deionized water backwash. The possible reason for this enhancement was also explained. Our result suggests that pre-coated Fe2O3 dynamic membrane with alkalescent water backwash can be a promising technology to reduce the fouling of ceramic membrane and enhance membrane cleaning efficiency in the treatment of oily wastewater.

  18. Hydrophilic Fe2O3 dynamic membrane mitigating fouling of support ceramic membrane in ultrafiltration of oil/water emulsion

    KAUST Repository

    Lu, Dongwei

    2016-03-17

    Oil/water (O/W) emulsion is daily produced and difficult to be treated effectively. Ceramic membrane ultrafiltration is one of reliable processes for the treatment of O/W emulsion, yet still hindered by membrane fouling. In this study, two types of Fe2O3 dynamic membranes (i.e., pre-coated dynamic membrane and self-forming dynamic membrane) were prepared to mitigate the fouling of support ceramic membrane in O/W emulsion treatment. Pre-coated dynamic membrane (DM) significantly reduced the fouling of ceramic membrane (i.e., 10% increase of flux recovery rate), while self-forming dynamic membrane aggravated ceramic membrane fouling (i.e., 8.6% decrease of flux recovery rate) after four filtration cycles. A possible fouling mechanism was proposed to explain this phenomenon, which was then confirmed by optical images of fouled membranes and the analysis of COD rejection. In addition, the cleaning efficiency of composite membranes (i.e., Fe2O3 dynamic membrane and support ceramic membrane) was enhanced by substitution of alkalescent water backwash for deionized water backwash. The possible reason for this enhancement was also explained. Our result suggests that pre-coated Fe2O3 dynamic membrane with alkalescent water backwash can be a promising technology to reduce the fouling of ceramic membrane and enhance membrane cleaning efficiency in the treatment of oily wastewater.

  19. The Cirque du Soleil of Golgi membrane dynamics.

    Science.gov (United States)

    Bankaitis, Vytas A

    2009-07-27

    The role of lipid metabolic enzymes in Golgi membrane remodeling is a subject of intense interest. Now, in this issue, Schmidt and Brown (2009. J. Cell Biol. doi:10.1083/jcb.200904147) report that lysophosphatidic acid-specific acyltransferase, LPAAT3, contributes to Golgi membrane dynamics by suppressing tubule formation.

  20. The Cirque du Soleil of Golgi membrane dynamics

    OpenAIRE

    Bankaitis, Vytas A.

    2009-01-01

    The role of lipid metabolic enzymes in Golgi membrane remodeling is a subject of intense interest. Now, in this issue, Schmidt and Brown (2009. J. Cell Biol. doi:10.1083/jcb.200904147) report that lysophosphatidic acid?specific acyltransferase, LPAAT3, contributes to Golgi membrane dynamics by suppressing tubule formation.

  1. Discriminating lysosomal membrane protein types using dynamic neural network.

    Science.gov (United States)

    Tripathi, Vijay; Gupta, Dwijendra Kumar

    2014-01-01

    This work presents a dynamic artificial neural network methodology, which classifies the proteins into their classes from their sequences alone: the lysosomal membrane protein classes and the various other membranes protein classes. In this paper, neural networks-based lysosomal-associated membrane protein type prediction system is proposed. Different protein sequence representations are fused to extract the features of a protein sequence, which includes seven feature sets; amino acid (AA) composition, sequence length, hydrophobic group, electronic group, sum of hydrophobicity, R-group, and dipeptide composition. To reduce the dimensionality of the large feature vector, we applied the principal component analysis. The probabilistic neural network, generalized regression neural network, and Elman regression neural network (RNN) are used as classifiers and compared with layer recurrent network (LRN), a dynamic network. The dynamic networks have memory, i.e. its output depends not only on the input but the previous outputs also. Thus, the accuracy of LRN classifier among all other artificial neural networks comes out to be the highest. The overall accuracy of jackknife cross-validation is 93.2% for the data-set. These predicted results suggest that the method can be effectively applied to discriminate lysosomal associated membrane proteins from other membrane proteins (Type-I, Outer membrane proteins, GPI-Anchored) and Globular proteins, and it also indicates that the protein sequence representation can better reflect the core feature of membrane proteins than the classical AA composition.

  2. Coupling of lipid membrane elasticity and in-plane dynamics

    Science.gov (United States)

    Tsang, Kuan-Yu; Lai, Yei-Chen; Chiang, Yun-Wei; Chen, Yi-Fan

    2017-07-01

    Biomembranes exhibit liquid and solid features concomitantly with their in-plane fluidity and elasticity tightly regulated by cells. Here, we present experimental evidence supporting the existence of the dynamics-elasticity correlations for lipid membranes and propose a mechanism involving molecular packing densities to explain them. This paper thereby unifies, at the molecular level, the aspects of the continuum mechanics long used to model the two membrane features. This ultimately may elucidate the universal physical principles governing the cellular phenomena involving biomembranes.

  3. Dynamic nanoplatforms in biosensor and membrane constitutional systems.

    Science.gov (United States)

    Mahon, Eugene; Aastrup, Teodor; Barboiu, Mihail

    2012-01-01

    Molecular recognition in biological systems occurs mainly at interfacial environments such as membrane surfaces, enzyme active sites, or the interior of the DNA double helix. At the cell membrane surface, carbohydrate-protein recognition principles apply to a range of specific non-covalent interactions including immune response, cell proliferation, adhesion and death, cell-cell interaction and communication. Protein-protein recognition meanwhile accounts for signalling processes and ion channel structure. In this chapter we aim to describe such constitutional dynamic interfaces for biosensing and membrane transport applications. Constitutionally adaptive interfaces may mimic the recognition capabilities intrinsic to natural recognition processes. We present some recent examples of 2D and 3D constructed sensors and membranes of this type and describe their sensing and transport capabilities.

  4. The ER in 3D: a multifunctional dynamic membrane network.

    Science.gov (United States)

    Friedman, Jonathan R; Voeltz, Gia K

    2011-12-01

    The endoplasmic reticulum (ER) is a large, singular, membrane-bound organelle that has an elaborate 3D structure with a diversity of structural domains. It contains regions that are flat and cisternal, ones that are highly curved and tubular, and others adapted to form contacts with nearly every other organelle and with the plasma membrane. The 3D structure of the ER is determined by both integral ER membrane proteins and by interactions with the cytoskeleton. In this review, we describe some of the factors that are known to regulate ER structure and discuss how this structural organization and the dynamic nature of the ER membrane network allow it to perform its many different functions. Copyright © 2011 Elsevier Ltd. All rights reserved.

  5. Organizing membrane-curving proteins: the emerging dynamical picture.

    Science.gov (United States)

    Simunovic, Mijo; Bassereau, Patricia; Voth, Gregory A

    2018-03-30

    Lipid membranes play key roles in cells, such as in trafficking, division, infection, remodeling of organelles, among others. The key step in all these processes is creating membrane curvature, typically under the control of many anchored, adhered or included proteins. However, it has become clear that the membrane itself can mediate the interactions among proteins to produce highly ordered assemblies. Computer simulations are ideally suited to investigate protein organization and the dynamics of membrane remodeling at near-micron scales, something that is extremely challenging to tackle experimentally. We review recent computational efforts in modeling protein-caused membrane deformation mechanisms, specifically focusing on coarse-grained simulations. We highlight work that exposed the membrane-mediated ordering of proteins into lines, meshwork, spirals and other assemblies, in what seems to be a very generic mechanism driven by a combination of short and long-ranged forces. Modulating the mechanical properties of membranes is an underexplored signaling mechanism in various processes deserving of more attention in the near future. Copyright © 2018 Elsevier Ltd. All rights reserved.

  6. Coordination of membrane and actin cytoskeleton dynamics during filopodia protrusion.

    Directory of Open Access Journals (Sweden)

    Changsong Yang

    2009-05-01

    Full Text Available Leading edge protrusion of migrating cells involves tightly coordinated changes in the plasma membrane and actin cytoskeleton. It remains unclear whether polymerizing actin filaments push and deform the membrane, or membrane deformation occurs independently and is subsequently stabilized by actin filaments. To address this question, we employed an ability of the membrane-binding I-BAR domain of IRSp53 to uncouple the membrane and actin dynamics and to induce filopodia in expressing cells. Using time-lapse imaging and electron microscopy of IRSp53-I-BAR-expressing B16F1 melanoma cells, we demonstrate that cells are not able to protrude or maintain durable long extensions without actin filaments in their interior, but I-BAR-dependent membrane deformation can create a small and transient space at filopodial tips that is subsequently filled with actin filaments. Moreover, the expressed I-BAR domain forms a submembranous coat that may structurally support these transient actin-free protrusions until they are further stabilized by the actin cytoskeleton. Actin filaments in the I-BAR-induced filopodia, in contrast to normal filopodia, do not have a uniform length, are less abundant, poorly bundled, and display erratic dynamics. Such unconventional structural organization and dynamics of actin in I-BAR-induced filopodia suggests that a typical bundle of parallel actin filaments is not necessary for generation and mechanical support of the highly asymmetric filopodial geometry. Together, our data suggest that actin filaments may not directly drive the protrusion, but only stabilize the space generated by the membrane deformation; yet, such stabilization is necessary for efficient protrusion.

  7. The kinetics of crossflow dynamic membrane bioreactor | Li | Water SA

    African Journals Online (AJOL)

    Crossflow dynamic membrane bioreactor (CDMBR) kinetics was investigated by treating caprolactam wastewater over a period of 180 d. The removal efficiencies of organic substances and nitrogen averaged over 99% and 80%, respectively. The observed sludge yield was only 0.14 g SS·g-1 COD·d-1 at an SRT of 30 d ...

  8. Dynamic modeling of ultrafiltration membranes for whey separation processes

    NARCIS (Netherlands)

    Saltik, M.B.; Ozkan, L.; Jacobs, M.; van der Padt, A.

    2017-01-01

    In this paper, we present a control relevant rigorous dynamic model for an ultrafiltration membrane unit in a whey separation process. The model consists of a set of differential algebraic equations and is developed for online model based applications such as model based control and process

  9. Dynamics of Born-Infeld membranes

    Energy Technology Data Exchange (ETDEWEB)

    Cordero, R [Departamento de Fisica, Escuela Superior de Fisica y Matematicas del I.P.N., Unidad Adolfo Lopez Mateos, Edificio 9, 07738 Mexico, D.F. (Mexico); Molgado, A [Facultad de Ciencias, Universidad de Colima, Bernal DIaz del Castillo 340, Col. Villas San Sebastian, Colima (Mexico); Rojas, E [Facultad de Fisica e Inteligencia Artificial, Universidad Veracruzana, 91000 Xalapa, Veracruz (Mexico)

    2007-11-15

    We present a geometrical inspired study of the dynamics of Dp-branes. We focus on the usual nonpolynomial Dirac-Born-Infeld action for the worldvolume swept out by the brane in its evolution in general background spacetimes. We emphasize the form of the resulting equations of motion which are quite simple and resemble Newton's second law, complemented with a conservation law for a worldvolume bicurrent.

  10. Dynamics of Born-Infeld membranes

    International Nuclear Information System (INIS)

    Cordero, R; Molgado, A; Rojas, E

    2007-01-01

    We present a geometrical inspired study of the dynamics of Dp-branes. We focus on the usual nonpolynomial Dirac-Born-Infeld action for the worldvolume swept out by the brane in its evolution in general background spacetimes. We emphasize the form of the resulting equations of motion which are quite simple and resemble Newton's second law, complemented with a conservation law for a worldvolume bicurrent

  11. Membrane recognition and dynamics of the RNA degradosome.

    Directory of Open Access Journals (Sweden)

    Henrik Strahl

    2015-02-01

    Full Text Available RNase E, which is the central component of the multienzyme RNA degradosome, serves as a scaffold for interaction with other enzymes involved in mRNA degradation including the DEAD-box RNA helicase RhlB. Epifluorescence microscopy under live cell conditions shows that RNase E and RhlB are membrane associated, but neither protein forms cytoskeletal-like structures as reported earlier by Taghbalout and Rothfield. We show that association of RhlB with the membrane depends on a direct protein interaction with RNase E, which is anchored to the inner cytoplasmic membrane through an MTS (Membrane Targeting Sequence. Molecular dynamics simulations show that the MTS interacts with the phospholipid bilayer by forming a stabilized amphipathic α-helix with the helical axis oriented parallel to the plane of the bilayer and hydrophobic side chains buried deep in the acyl core of the membrane. Based on the molecular dynamics simulations, we propose that the MTS freely diffuses in the membrane by a novel mechanism in which a large number of weak contacts are rapidly broken and reformed. TIRFm (Total Internal Reflection microscopy shows that RNase E in live cells rapidly diffuses over the entire inner membrane forming short-lived foci. Diffusion could be part of a scanning mechanism facilitating substrate recognition and cooperativity. Remarkably, RNase E foci disappear and the rate of RNase E diffusion increases with rifampicin treatment. Control experiments show that the effect of rifampicin is specific to RNase E and that the effect is not a secondary consequence of the shut off of E. coli transcription. We therefore interpret the effect of rifampicin as being due to the depletion of RNA substrates for degradation. We propose a model in which formation of foci and constraints on diffusion arise from the transient clustering of RNase E into cooperative degradation bodies.

  12. Dynamics of silver elution from functionalised antimicrobial nanofiltration membranes.

    Science.gov (United States)

    Choudhari, S; Habimana, O; Hannon, J; Allen, A; Cummins, E; Casey, E

    2017-07-01

    In an effort to mitigate biofouling on thin film composite membranes such as nanofiltration and reverse osmosis, a myriad of different surface modification strategies has been published. The use of silver nanoparticles (Ag-NPs) has emerged as being particularly promising. Nevertheless, the stability of these surface modifications is still poorly understood, particularly under permeate flux conditions. Leaching or elution of Ag-NPs from the membrane surface can not only affect the antimicrobial characteristics of the membrane, but could also potentially present an environmental liability when applied in industrial-scale systems. This study sought to investigate the dynamics of silver elution and the bactericidal effect of an Ag-NP functionalised NF270 membrane. Inductively coupled plasma-atomic emission spectroscopy was used to show that the bulk of leached silver occurred at the start of experimental runs, and was found to be independent of salt or permeate conditions used. Cumulative amounts of leached silver did, however, stabilise following the initial release, and were shown to have maintained the biocidal characteristics of the modified membrane, as observed by a higher fraction of structurally damaged Pseudomonas fluorescens cells. These results highlight the need to comprehensively assess the time-dependent nature of bactericidal membranes.

  13. A distributed dynamic model of a monolith hydrogen membrane reactor

    International Nuclear Information System (INIS)

    Michelsen, Finn Are; Wilhelmsen, Øivind; Zhao, Lei; Aasen, Knut Ingvar

    2013-01-01

    Highlights: ► We model a rigorous distributed dynamic model for a HMR unit. ► The model includes enough complexity for steady-state and dynamic analysis. ► Simulations show that the model is non-linear within the normal operating range. ► The model is useful for studying and handling disturbances such as inlet changes and membrane leakage. - Abstract: This paper describes a distributed mechanistic dynamic model of a hydrogen membrane reformer unit (HMR) used for methane steam reforming. The model is based on a square channel monolith structure concept, where air flows adjacent to a mix of natural gas and water distributed in a chess pattern of channels. Combustion of hydrogen gives energy to the endothermic steam reforming reactions. The model is used for both steady state and dynamic analyses. It therefore needs to be computationally attractive, but still include enough complexity to study the important steady state and dynamic features of the process. Steady-state analysis of the model gives optimum for the steam to carbon and steam to oxygen ratios, where the conversion of methane is 92% and the hydrogen used as energy for the endothermic reactions is 28% at the nominal optimum. The dynamic analysis shows that non-linear control schemes may be necessary for satisfactory control performance

  14. Dynamic complexity: plant receptor complexes at the plasma membrane.

    Science.gov (United States)

    Burkart, Rebecca C; Stahl, Yvonne

    2017-12-01

    Plant receptor complexes at the cell surface perceive many different external and internal signalling molecules and relay these signals into the cell to regulate development, growth and immunity. Recent progress in the analyses of receptor complexes using different live cell imaging approaches have shown that receptor complex formation and composition are dynamic and take place at specific microdomains at the plasma membrane. In this review we focus on three prominent examples of Arabidopsis thaliana receptor complexes and how their dynamic spatio-temporal distribution at the PM has been studied recently. We will elaborate on the newly emerging concept of plasma membrane microdomains as potential hubs for specific receptor complex assembly and signalling outputs. Copyright © 2017 Elsevier Ltd. All rights reserved.

  15. The dynamics of plant plasma membrane proteins: PINs and beyond.

    Science.gov (United States)

    Luschnig, Christian; Vert, Grégory

    2014-08-01

    Plants are permanently situated in a fixed location and thus are well adapted to sense and respond to environmental stimuli and developmental cues. At the cellular level, several of these responses require delicate adjustments that affect the activity and steady-state levels of plasma membrane proteins. These adjustments involve both vesicular transport to the plasma membrane and protein internalization via endocytic sorting. A substantial part of our current knowledge of plant plasma membrane protein sorting is based on studies of PIN-FORMED (PIN) auxin transport proteins, which are found at distinct plasma membrane domains and have been implicated in directional efflux of the plant hormone auxin. Here, we discuss the mechanisms involved in establishing such polar protein distributions, focusing on PINs and other key plant plasma membrane proteins, and we highlight the pathways that allow for dynamic adjustments in protein distribution and turnover, which together constitute a versatile framework that underlies the remarkable capabilities of plants to adjust growth and development in their ever-changing environment. © 2014. Published by The Company of Biologists Ltd.

  16. Membrane localization and dynamics of geranylgeranylated Rab5 hypervariable region.

    Science.gov (United States)

    Edler, Eileen; Schulze, Eric; Stein, Matthias

    2017-08-01

    The small GTPase Rab5 is a key regulator of endosomal trafficking processes and a marker for the early endosome. The C-terminal hypervariable region (HVR) of Rab5 is post-translationally modified at residues Cys 212 and Cys 213 to accommodate two geranylgeranyl anchors (C20 carbon chain length) in order to associate Rab5 with the membrane. The structural role of the HVR regarding protein-early endosome membrane recruitment is not resolved due to its high degree of flexibility and lack of crystallographic information. Here, full-atomistic and coarse-grained molecular dynamics simulations of the truncated Rab5 HVR 206-215 in three model membranes of increasing complexity (pure phospholipid bilayer, ternary membrane with cholesterol, six-component early endosome) were performed. Specific electrostatic interactions between the HVR 206-215 Arg 209 residue and the phosphate group of the inositol ring of PI(3)P were detected. This shows that PI(3)P acts as a first contact site of protein recruitment to the early endosome. The free energy change of HVR 206-215 extraction from the bilayer was largest for the physiological negatively charged membrane. 5μs coarse-grained simulations revealed an active recruitment of PI(3)P to the HVR 206-215 supporting the formation of Rab5- and PI(3)P enriched signaling platforms. Copyright © 2017 Elsevier B.V. All rights reserved.

  17. CFD model of an aerating hydrofoil

    International Nuclear Information System (INIS)

    Scott, D; Sabourin, M; Beaulieu, S; Papillon, B; Ellis, C

    2014-01-01

    Improving water quality in the tailrace below hydroelectric dams has become a priority in many river systems. In warm climates, water drawn by the turbine from deep in a reservoir can be deficient in dissolved oxygen (DO), a critical element in maintaining a healthy aquatic ecosystem. Many different solutions have been proposed in order to increase the DO levels in turbine discharge, including: turbine aeration systems (adding air to the water through either the turbine hub, the periphery or through distributed aeration in the runner blades); bubble diffusers in the reservoir or in the tailrace; aerating weirs downstream of the dams; and surface water pumps in the reservoir near the dam. There is a significant potential to increase the effectiveness of these solutions by improving the way that oxygen is introduced into the water; better distributions of bubbles will result in better oxygen transfer. In the present study, a two-phase Computational Fluid Dynamics model has been formulated using a commercial code to study the distribution of air downstream of a simple aerating hydrofoil. The two-phase model uses the Eulerian-Eulerian approach. Appropriate relations are used to model the interphase forces, including the Grace drag force model, the Favre averaged drag force and the Sato enhanced eddy viscosity. The model is validated using experimental results obtained in the water tunnel at the University of Minnesota's Saint Anthony Falls Laboratory. Results are obtained for water velocities between 5 and 10 m/s, air flow rates between 0.5 and 1.5 sL/min and for angles of attack between 0° and -8°. The results of this study show that the CFD model provides a good qualitative comparison to the experimental results by well predicting the wake location at the different flow rates and angles of attack used

  18. Spatiotemporal mapping of diffusion dynamics and organization in plasma membranes

    Science.gov (United States)

    Bag, Nirmalya; Ng, Xue Wen; Sankaran, Jagadish; Wohland, Thorsten

    2016-09-01

    Imaging fluorescence correlation spectroscopy (FCS) and the related FCS diffusion law have been applied in recent years to investigate the diffusion modes of lipids and proteins in membranes. These efforts have provided new insights into the membrane structure below the optical diffraction limit, new information on the existence of lipid domains, and on the influence of the cytoskeleton on membrane dynamics. However, there has been no systematic study to evaluate how domain size, domain density, and the probe partition coefficient affect the resulting imaging FCS diffusion law parameters. Here, we characterize the effects of these factors on the FCS diffusion law through simulations and experiments on lipid bilayers and live cells. By segmenting images into smaller 7  ×  7 pixel areas, we can evaluate the FCS diffusion law on areas smaller than 2 µm and thus provide detailed maps of information on the membrane structure and heterogeneity at this length scale. We support and extend this analysis by deriving a mathematical expression to calculate the mean squared displacement (MSDACF) from the autocorrelation function of imaging FCS, and demonstrate that the MSDACF plots depend on the existence of nanoscopic domains. Based on the results, we derive limits for the detection of domains depending on their size, density, and relative viscosity in comparison to the surroundings. Finally, we apply these measurements to bilayers and live cells using imaging total internal reflection FCS and single plane illumination microscopy FCS.

  19. Dynamics of fluid lines, sheets, filaments and membranes

    International Nuclear Information System (INIS)

    Coutris, N.

    1988-01-01

    We establish the dynamic equations of two types of fluid structures: 1) lines-filaments and 2) sheets-membranes. In the first part, we consider one-dimensional (line) and two-dimensional (sheet) fluid structures. The second part concerns the associated three- dimensional structures: filaments and membranes. In the third part, we establish the equations for thickened lines and thickened sheets. For that purpose, we introduce a thickness in the models of the first part. The fourth part concerns the thinning of the filament and the membrane. Then, by an asymptotic process, we deduce the corresponding equations from the equations of the second part in order to show the purely formal equivalence of the equations of the third and fourth parts. To obtain the equations, we make use of theorems whose proofs can be found in the appendices. The equations can be applied to many areas of interest: instabilities of liquid jets and liquid films, modelisation of interfaces between two different fluids as sheets or membranes, modelisation with the averaged equations over a cross section of single phase flows and two-phase flows in channels with a nonrectilinear axis such as bends or pump casings [fr

  20. Structure, Dynamics, and Phase Behavior of DOPC/DSPC Mixture Membrane Systems: Molecular Dynamics Simulation Studies

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Seonghan; Chang, Rakwoo [Kwangwoon University, Seoul (Korea, Republic of)

    2016-07-15

    Full atomistic molecular dynamics simulations have been performed for model mixture bilayer membrane systems consisting of 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC) and 1,2-distearoyl-sn-glycero-3-phosphocholine (DSPC) phospholipids to understand the effects of two essential parameters such as lipid composition and temperature on the structural, dynamical, and phase behavior of mixture membrane systems. Although pure DSPC membranes are in the gel-like (L{sub β}' or P{sub β}') phase at 323 K, raising the temperature by only 10 K or replacing 20% of DSPC lipids by DOPC lipids can change the gel-like phase into the completely liquid-crystalline phase (L{sub α}). This phase change is accompanied by dramatic change in both structural properties such as area per lipid, membrane thickness, deuterium order parameter, and tail angle distribution, and dynamics properties such as mobility map. We also observe that the full width at half-maximum (FWHM) data of tail angle distribution as well as area per lipid (or membrane thickness)can be used as order parameters for the membrane phase transition.

  1. Structure, Dynamics, and Phase Behavior of DOPC/DSPC Mixture Membrane Systems: Molecular Dynamics Simulation Studies

    International Nuclear Information System (INIS)

    Kim, Seonghan; Chang, Rakwoo

    2016-01-01

    Full atomistic molecular dynamics simulations have been performed for model mixture bilayer membrane systems consisting of 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC) and 1,2-distearoyl-sn-glycero-3-phosphocholine (DSPC) phospholipids to understand the effects of two essential parameters such as lipid composition and temperature on the structural, dynamical, and phase behavior of mixture membrane systems. Although pure DSPC membranes are in the gel-like (L_β' or P_β') phase at 323 K, raising the temperature by only 10 K or replacing 20% of DSPC lipids by DOPC lipids can change the gel-like phase into the completely liquid-crystalline phase (L_α). This phase change is accompanied by dramatic change in both structural properties such as area per lipid, membrane thickness, deuterium order parameter, and tail angle distribution, and dynamics properties such as mobility map. We also observe that the full width at half-maximum (FWHM) data of tail angle distribution as well as area per lipid (or membrane thickness)can be used as order parameters for the membrane phase transition.

  2. Deflector plants turbine aeration

    International Nuclear Information System (INIS)

    Miller, D.E.; Sheppard, A.R.; Widener, D.W.

    1991-01-01

    Water quality requirements have become a focal point in recent re-licensing of hydroelectric projects. The Federal Energy Regulatory Commission has significantly increased the relevance of license conditions to insure that turbine discharges meet state or other specific criteria for dissolved oxygen (D.O.). Due to naturally occurring depletion of D.O. at increased depths in large reservoirs, water withdrawn from this strata may result in unacceptably low levels of D.O. Different researchers have evaluated various methods of improving D.O. content in hydro turbine discharges, including; diffusers, weirs, oxygen injection, and variations of turbine venting. The authors describe an approach called deflector plate turbine aeration. This computer based, engineered approach allows systems to be evaluated, designed, and installed with predictable performance and costs. Many experts in this field now agree that, to the extent practical, turbine venting offers the most dependable, maintenance free, and cost effective solution to the low D.O. problem. The approach presented in this paper has resulted in proven results

  3. Dewatering of Chlorella pyrenoidosa using diatomite dynamic membrane: filtration performance, membrane fouling and cake behavior.

    Science.gov (United States)

    Zhang, Yalei; Zhao, Yangying; Chu, Huaqiang; Zhou, Xuefei; Dong, Bingzhi

    2014-01-01

    The diatomite dynamic membrane (DDM) was utilized to dewater Chlorella pyrenoidosa of 2 g dry weight/L under continuous-flow mode, whose ultimate algae concentration ranged from 43 g to 22 g dry weight/L of different culture time. The stable flux of DDM could reach 30 L/m(2) h over a 24 h operation time without backwash. Influences of extracellular organic matters (EOM) on filtration behavior and membrane fouling were studied. The DDM was divided into three sub-layers, the slime layer, the algae layer and the diatomite layer from the outside to the inside of the cake layer based on components and morphologies. It was found that EOM caused membrane fouling by accumulating in the slime and algae layers. The DDM intercepted polysaccharides, protein-like substances, humic-like substances and some low-MW organics. Proteins were indicated the major membrane foulants with increased protein/polysaccharide ratio from the slime layer to the diatomite layer as culture time increased. This method could be applied to subsequent treatment of microalgae coupling technology of wastewater treatment or microalgae harvesting for producing biofuel. Copyright © 2013 Elsevier B.V. All rights reserved.

  4. Dynamic analysis of magnetic nanoparticles crossing cell membrane

    Energy Technology Data Exchange (ETDEWEB)

    Pedram, Maysam Z. [Department of Mechanical Engineering, Sharif University of Tech., Azadi Ave., Tehran (Iran, Islamic Republic of); Shamloo, Amir, E-mail: shamloo@sharif.edu [Department of Mechanical Engineering, Sharif University of Tech., Azadi Ave., Tehran (Iran, Islamic Republic of); Ghafar-Zadeh, Ebrahim [Biologically-Inspired Sensors and Actuators Laboratory, Department of Electrical Engineering and Computer science, York University, Keel Street, Toronto (Canada); Alasty, Aria, E-mail: aalasti@sharif.edu [Department of Mechanical Engineering, Sharif University of Tech., Azadi Ave., Tehran (Iran, Islamic Republic of)

    2017-05-01

    Nowadays, nanoparticles (NPs) are used in a variety of biomedical applications including brain disease diagnostics and subsequent treatments. Among the various types of NPs, magnetic nanoparticles (MNPs) have been implemented by many research groups for an array of life science applications. In this paper, we studied MNPs controlled delivery into the endothelial cells using a magnetic field. Dynamics equations of MNPs were defined in the continuous domain using control theory methods and were applied to crossing the cell membrane. This study, dedicated to clinical and biomedical research applications, offers a guideline for the generation of a magnetic field required for the delivery of MNPs.

  5. Intermolecular detergent-membrane protein noes for the characterization of the dynamics of membrane protein-detergent complexes.

    Science.gov (United States)

    Eichmann, Cédric; Orts, Julien; Tzitzilonis, Christos; Vögeli, Beat; Smrt, Sean; Lorieau, Justin; Riek, Roland

    2014-12-11

    The interaction between membrane proteins and lipids or lipid mimetics such as detergents is key for the three-dimensional structure and dynamics of membrane proteins. In NMR-based structural studies of membrane proteins, qualitative analysis of intermolecular nuclear Overhauser enhancements (NOEs) or paramagnetic resonance enhancement are used in general to identify the transmembrane segments of a membrane protein. Here, we employed a quantitative characterization of intermolecular NOEs between (1)H of the detergent and (1)H(N) of (2)H-perdeuterated, (15)N-labeled α-helical membrane protein-detergent complexes following the exact NOE (eNOE) approach. Structural considerations suggest that these intermolecular NOEs should show a helical-wheel-type behavior along a transmembrane helix or a membrane-attached helix within a membrane protein as experimentally demonstrated for the complete influenza hemagglutinin fusion domain HAfp23. The partial absence of such a NOE pattern along the amino acid sequence as shown for a truncated variant of HAfp23 and for the Escherichia coli inner membrane protein YidH indicates the presence of large tertiary structure fluctuations such as an opening between helices or the presence of large rotational dynamics of the helices. Detergent-protein NOEs thus appear to be a straightforward probe for a qualitative characterization of structural and dynamical properties of membrane proteins embedded in detergent micelles.

  6. BSM-MBR: a benchmark simulation model to compare control and operational strategies for membrane bioreactors.

    Science.gov (United States)

    Maere, Thomas; Verrecht, Bart; Moerenhout, Stefanie; Judd, Simon; Nopens, Ingmar

    2011-03-01

    A benchmark simulation model for membrane bioreactors (BSM-MBR) was developed to evaluate operational and control strategies in terms of effluent quality and operational costs. The configuration of the existing BSM1 for conventional wastewater treatment plants was adapted using reactor volumes, pumped sludge flows and membrane filtration for the water-sludge separation. The BSM1 performance criteria were extended for an MBR taking into account additional pumping requirements for permeate production and aeration requirements for membrane fouling prevention. To incorporate the effects of elevated sludge concentrations on aeration efficiency and costs a dedicated aeration model was adopted. Steady-state and dynamic simulations revealed BSM-MBR, as expected, to out-perform BSM1 for effluent quality, mainly due to complete retention of solids and improved ammonium removal from extensive aeration combined with higher biomass levels. However, this was at the expense of significantly higher operational costs. A comparison with three large-scale MBRs showed BSM-MBR energy costs to be realistic. The membrane aeration costs for the open loop simulations were rather high, attributed to non-optimization of BSM-MBR. As proof of concept two closed loop simulations were run to demonstrate the usefulness of BSM-MBR for identifying control strategies to lower operational costs without compromising effluent quality. Copyright © 2011 Elsevier Ltd. All rights reserved.

  7. Visualizing functional motions of membrane transporters with molecular dynamics simulations.

    Science.gov (United States)

    Shaikh, Saher A; Li, Jing; Enkavi, Giray; Wen, Po-Chao; Huang, Zhijian; Tajkhorshid, Emad

    2013-01-29

    Computational modeling and molecular simulation techniques have become an integral part of modern molecular research. Various areas of molecular sciences continue to benefit from, indeed rely on, the unparalleled spatial and temporal resolutions offered by these technologies, to provide a more complete picture of the molecular problems at hand. Because of the continuous development of more efficient algorithms harvesting ever-expanding computational resources, and the emergence of more advanced and novel theories and methodologies, the scope of computational studies has expanded significantly over the past decade, now including much larger molecular systems and far more complex molecular phenomena. Among the various computer modeling techniques, the application of molecular dynamics (MD) simulation and related techniques has particularly drawn attention in biomolecular research, because of the ability of the method to describe the dynamical nature of the molecular systems and thereby to provide a more realistic representation, which is often needed for understanding fundamental molecular properties. The method has proven to be remarkably successful in capturing molecular events and structural transitions highly relevant to the function and/or physicochemical properties of biomolecular systems. Herein, after a brief introduction to the method of MD, we use a number of membrane transport proteins studied in our laboratory as examples to showcase the scope and applicability of the method and its power in characterizing molecular motions of various magnitudes and time scales that are involved in the function of this important class of membrane proteins.

  8. Dynamics of membrane nanotubes coated with I-BAR

    DEFF Research Database (Denmark)

    Farhangibarooji, Younes; Rørvig-Lund, Andreas; Semsey, Szabolcs

    2016-01-01

    Membrane deformation is a necessary step in a number of cellular processes such as filopodia and invadopodia formation and has been shown to involve membrane shaping proteins containing membrane binding domains from the IRSp53-MIM protein family. In reconstituted membranes the membrane shaping...

  9. Nanoscopic dynamics of bicontinous microemulsions: effect of membrane associated protein.

    Science.gov (United States)

    Sharma, V K; Hayes, Douglas G; Urban, Volker S; O'Neill, Hugh M; Tyagi, M; Mamontov, E

    2017-07-19

    Bicontinous microemulsions (BμE) generally consist of nanodomains formed by surfactant in a mixture of water and oil at nearly equal proportions and are potential candidates for the solubilization and purification of membrane proteins. Here we present the first time report of nanoscopic dynamics of surfactant monolayers within BμEs formed by the anionic surfactant sodium dodecyl sulfate (SDS) measured on the nanosecond to picosecond time scale using quasielastic neutron scattering (QENS). BμEs investigated herein consisted of middle phases isolated from Winsor-III microemulsion systems that were formed by mixing aqueous and oil solutions under optimal conditions. QENS data indicates that surfactants undergo two distinct motions, namely (i) lateral motion along the surface of the oil nanodomains and (ii) localized internal motion. Lateral motion can be described using a continuous diffusion model, from which the lateral diffusion coefficient is obtained. Internal motion of surfactant is described using a model which assumes that a fraction of the surfactants' hydrogens undergoes localized translational diffusion that could be considered confined within a spherical volume. The effect of cytochrome c, an archetypal membrane-associated protein known to strongly partition near the surfactant head groups in BμEs (a trend supported by small-angle X-ray scattering [SAXS] analysis), on the dynamics of BμE has also been investigated. QENS results demonstrated that cytochrome c significantly hindered both the lateral and the internal motions of surfactant. The lateral motion was more strongly affected: a reduction of the lateral diffusion coefficient by 33% was measured. This change is mainly attributable to the strong association of cytochrome c with oppositely charged SDS. In contrast, analysis of SAXS data suggested that thermal fluctuations (for a longer length and slower time scale compared to QENS) were increased upon incorporation of cytochrome c. This study

  10. Membrane dynamics in the intrinsic light-front coordinates

    International Nuclear Information System (INIS)

    Aragone, C.; Restuccia, A.; Torrealba, R.

    1991-01-01

    The authors study the dynamics of the membrane, using internal light-front (LF) coordinates. The set of constraints, although equivalent to the standard one, is different. The intrinsic LF gauge is defined. Four additional, alternative gauge-fixing conditions are analyzed. Two of them polynomialize the system, while the other two are convenient for studying the initial-value problem. In particular, one of them is also extrinsically (i.e., in the ambient space) light-front. In this gauge, the system is shown to be consistently reduced to attain a canonical form in terms of pure transverse variables. Two constraints on these variables still hold, clearly showing the presence, as they must, of D - 3 degrees of freedom. Finally, the initial-value problem in this intrinsic-extrinsic. LF gauge is solved. Although the paper is based on the first-order action, the LF-Hamiltonian approach is discussed too

  11. Insertion of Neurotransmitters into a Lipid Bilayer Membrane and Its Implication on Membrane Stability: A Molecular Dynamics Study.

    Science.gov (United States)

    Shen, Chun; Xue, Minmin; Qiu, Hu; Guo, Wanlin

    2017-03-17

    The signaling molecules in neurons, called neurotransmitters, play an essential role in the transportation of neural signals, during which the neurotransmitters interact with not only specific receptors, but also cytomembranes, such as synaptic vesicle membranes and postsynaptic membranes. Through extensive molecular dynamics simulations, the atomic-scale insertion dynamics of typical neurotransmitters, including methionine enkephalin (ME), leucine enkephalin (LE), dopamine (DA), acetylcholine (ACh), and aspartic acid (ASP), into lipid bilayers is investigated. The results show that the first three neurotransmitters (ME, LE, and DA) are able to diffuse freely into both 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) and 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphoethanolamine (POPE) membranes, and are guided by the aromatic residues Tyr and Phe. Only a limited number of these neurotransmitters are allowed to penetrate into the membrane, which suggests an intrinsic mechanism by which the membrane is protected from being destroyed by excessive inserted neurotransmitters. After spontaneous insertion, the neurotransmitters disturb the surrounding phospholipids in the membrane, as indicated by the altered distribution of components in lipid leaflets and the disordered lipid tails. In contrast, the last two neurotransmitters (ACh and ASP) cannot enter the membrane, but instead always diffuse freely in solution. These findings provide an understanding at the atomic level of how neurotransmitters interact with the surrounding cytomembrane, as well as their impact on membrane behavior. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  12. An NMR database for simulations of membrane dynamics.

    Science.gov (United States)

    Leftin, Avigdor; Brown, Michael F

    2011-03-01

    Computational methods are powerful in capturing the results of experimental studies in terms of force fields that both explain and predict biological structures. Validation of molecular simulations requires comparison with experimental data to test and confirm computational predictions. Here we report a comprehensive database of NMR results for membrane phospholipids with interpretations intended to be accessible by non-NMR specialists. Experimental ¹³C-¹H and ²H NMR segmental order parameters (S(CH) or S(CD)) and spin-lattice (Zeeman) relaxation times (T(1Z)) are summarized in convenient tabular form for various saturated, unsaturated, and biological membrane phospholipids. Segmental order parameters give direct information about bilayer structural properties, including the area per lipid and volumetric hydrocarbon thickness. In addition, relaxation rates provide complementary information about molecular dynamics. Particular attention is paid to the magnetic field dependence (frequency dispersion) of the NMR relaxation rates in terms of various simplified power laws. Model-free reduction of the T(1Z) studies in terms of a power-law formalism shows that the relaxation rates for saturated phosphatidylcholines follow a single frequency-dispersive trend within the MHz regime. We show how analytical models can guide the continued development of atomistic and coarse-grained force fields. Our interpretation suggests that lipid diffusion and collective order fluctuations are implicitly governed by the viscoelastic nature of the liquid-crystalline ensemble. Collective bilayer excitations are emergent over mesoscopic length scales that fall between the molecular and bilayer dimensions, and are important for lipid organization and lipid-protein interactions. Future conceptual advances and theoretical reductions will foster understanding of biomembrane structural dynamics through a synergy of NMR measurements and molecular simulations. Copyright © 2010 Elsevier B.V. All

  13. Dynamical and structural properties of lipid membranes in relation to liposomal drug delivery systems

    DEFF Research Database (Denmark)

    Jørgensen, Kent; Høyrup, Lise Pernille Kristine; Pedersen, Tina B.

    2001-01-01

    The structural and dynamical properties of DPPC liposomes containing lipopolymers (PEG-lipids) and charged DPPS lipids have been,studied in relation to the lipid membrane interaction of enzymes and peptides. The results suggest that both the lipid membrane structure and dynamics and in particular...

  14. Effect of acetone accumulation on structure and dynamics of lipid membranes studied by molecular dynamics simulations.

    Science.gov (United States)

    Posokhov, Yevgen O; Kyrychenko, Alexander

    2013-10-01

    The modulation of the properties and function of cell membranes by small volatile substances is important for many biomedical applications. Despite available experimental results, molecular mechanisms of action of inhalants and organic solvents, such as acetone, on lipid membranes remain not well understood. To gain a better understanding of how acetone interacts with membranes, we have performed a series of molecular dynamics (MD) simulations of a POPC bilayer in aqueous solution in the presence of acetone, whose concentration was varied from 2.8 to 11.2 mol%. The MD simulations of passive distribution of acetone between a bulk water phase and a lipid bilayer show that acetone favors partitioning into the water-free region of the bilayer, located near the carbonyl groups of the phospholipids and at the beginning of the hydrocarbon core of the lipid membrane. Using MD umbrella sampling, we found that the permeability barrier of ~0.5 kcal/mol exists for acetone partitioning into the membrane. In addition, a Gibbs free energy profile of the acetone penetration across a bilayer demonstrates a favorable potential energy well of -3.6 kcal/mol, located at 15-16Å from the bilayer center. The analysis of the structural and dynamics properties of the model membrane revealed that the POPC bilayer can tolerate the presence of acetone in the concentration range of 2.8-5.6 mol%. The accumulation of the higher acetone concentration of 11.2 mol% results, however, in drastic disordering of phospholipid packing and the increase in the membrane fluidity. The acetone molecules push the lipid heads apart and, hence, act as spacers in the headgroup region. This effect leads to the increase in the average headgroup area per molecule. In addition, the acyl tail region of the membrane also becomes less dense. We suggest, therefore, that the molecular mechanism of acetone action on the phospholipid bilayer has many common features with the effects of short chain alcohols, DMSO, and

  15. Management of microbial community composition, architecture and performance in autotrophic nitrogen removing bioreactors through aeration regimes

    DEFF Research Database (Denmark)

    Mutlu, A. Gizem

    to describe aggregation and architectural evolution in nitritation/anammox reactors, incorporating the possible influences of intermediates formed with intermittent aeration. Community analysis revealed an abundant fraction of heterotrophic types despite the absence of organic carbon in the feed. The aerobic...... and anaerobic ammonia oxidizing guilds were dominated by fast-growing Nitrosomonas spp. and Ca. Brocadia spp., while the nitrite oxidizing guild was dominated by high affinity Nitrospira spp. Emission of nitrous oxide (N2O) was evaluated from both reactors under dynamic aeration regimes. Contrary to the widely...... impacts could be isolated, increasing process understanding. It was demonstrated that aeration strategy can be used as a powerful tool to manipulate the microbial community composition, its architecture and reactor performance. We suggest operation via intermittent aeration with short aerated periods...

  16. The development of furrower model blade to paddlewheel aerator for improving aeration efficiency

    Science.gov (United States)

    Bahri, Samsul; Praeko Agus Setiawan, Radite; Hermawan, Wawan; Zairin Junior, Muhammad

    2018-05-01

    The successful of intensive aquaculture is strongly influenced by the ability of the farmers to overcome the deterioration of water quality. The problem is low dissolved oxygen through aeration process. The aerator device which widely used in pond farming is paddle wheel aerator because it is the best aerator in aeration mechanism and usable driven power. However, this aerator still has a low performance of aeration, so that the cost of aerator operational for aquaculture is still high. Up to now, the effort to improve the performance of aeration was made by two-dimensional blade design. Obviously, it does not provide the optimum result due to the power requirements for aeration is directly proportional to the increase of aeration rate. The aim of this research is to develop three-dimensional model furrowed blades. Design of Furrower model blades was 1.6 cm diameter hole, 45º of vertical angle blade position and 30º of the horizontal position. The optimum performance furrowed model blades operated on the submerged blade 9 cm with 567.54 Watt of electrical power consumption and 4.322 m3 of splash coverage volume. The standard efficiency aeration is 2.72 kg O2 kWh-1. The furrowed model blades can improve the aeration efficiency of paddlewheel aerator.

  17. Dynamic coating of mf/uf membranes for fouling mitigation

    KAUST Repository

    Tabatabai, S. Assiyeh Alizadeh; Leiknes, TorOve

    2017-01-01

    A membrane system including an anti-fouling layer and a method of applying an anti-fouling layer to a membrane surface are provided. In an embodiment, the surface is a microfiltration (MF) or an ultrafiltration (UF) membrane surface. The anti

  18. Pilot scale experiment with MBR operated in intermittent aeration condition: analysis of biological performance.

    Science.gov (United States)

    Capodici, M; Di Bella, G; Di Trapani, D; Torregrossa, M

    2015-02-01

    The effect of intermittent aeration (IA) on a MBR system was investigated. The study was aimed at analyzing different working conditions and the influence of different IA cycles on the biological performance of the MBR pilot plant, in terms of organic carbon and ammonium removal as well as extracellular polymeric substances (EPSs) production. The membrane modules were placed in a separate compartment, continuously aerated. This configuration allowed to disconnect from the filtration stage the biological phenomena occurring into the IA bioreactor. The observed results highlighted good efficiencies, in terms of organic carbon and ammonium removal. It was noticed a significant soluble microbial products (SMPs) release, likely related to the higher metabolic stress that anoxic conditions exerted on the biomass. However, the proposed configuration, with the membranes in a separate compartment, allowed to reduce the EPSs in the membrane tank even during the non-aerated phase, thus lowering fouling development. Copyright © 2014 Elsevier Ltd. All rights reserved.

  19. Models of dynamic extraction of lipid tethers from cell membranes

    International Nuclear Information System (INIS)

    Nowak, Sarah A; Chou, Tom

    2010-01-01

    When a ligand that is bound to an integral membrane receptor is pulled, the membrane and the underlying cytoskeleton can deform before either the membrane delaminates from the cytoskeleton or the ligand detaches from the receptor. If the membrane delaminates from the cytoskeleton, it may be further extruded and form a membrane tether. We develop a phenomenological model for this process by assuming that deformations obey Hooke's law up to a critical force at which the cell membrane locally detaches from the cytoskeleton and a membrane tether forms. We compute the probability of tether formation and show that tethers can be extruded only within an intermediate range of force loading rates and pulling velocities. The mean tether length that arises at the moment of ligand detachment is computed as are the force loading rates and pulling velocities that yield the longest tethers

  20. Design characteristics of Curved Blade Aerator w.r.t. aeration ...

    African Journals Online (AJOL)

    user

    To provide the required amount of oxygen, an aeration system is always ... and number of blades, depth of flow etc and physicochemical properties of the liquid. .... amounts to 29 cm with 12 blades (fiber strips) mounted on each aerator rotor.

  1. The ER in 3-D: a multifunctional dynamic membrane network

    OpenAIRE

    Friedman, Jonathan R.; Voeltz, Gia K.

    2011-01-01

    The endoplasmic reticulum (ER) is a large, singular, membrane-bound organelle that has an elaborate 3-D structure with a diversity of structural domains. It contains regions that are flat and cisternal, ones that are highly curved and tubular, and others adapted to form contact with nearly every other organelle and with the plasma membrane. ER 3-D structure is determined by both integral ER membrane proteins and by interactions with the cytoskeleton. Here, we describe some of the factors that...

  2. Dynamic shaping of cellular membranes by phospholipids and membrane-deforming proteins.

    Science.gov (United States)

    Suetsugu, Shiro; Kurisu, Shusaku; Takenawa, Tadaomi

    2014-10-01

    All cellular compartments are separated from the external environment by a membrane, which consists of a lipid bilayer. Subcellular structures, including clathrin-coated pits, caveolae, filopodia, lamellipodia, podosomes, and other intracellular membrane systems, are molded into their specific submicron-scale shapes through various mechanisms. Cells construct their micro-structures on plasma membrane and execute vital functions for life, such as cell migration, cell division, endocytosis, exocytosis, and cytoskeletal regulation. The plasma membrane, rich in anionic phospholipids, utilizes the electrostatic nature of the lipids, specifically the phosphoinositides, to form interactions with cytosolic proteins. These cytosolic proteins have three modes of interaction: 1) electrostatic interaction through unstructured polycationic regions, 2) through structured phosphoinositide-specific binding domains, and 3) through structured domains that bind the membrane without specificity for particular phospholipid. Among the structured domains, there are several that have membrane-deforming activity, which is essential for the formation of concave or convex membrane curvature. These domains include the amphipathic helix, which deforms the membrane by hemi-insertion of the helix with both hydrophobic and electrostatic interactions, and/or the BAR domain superfamily, known to use their positively charged, curved structural surface to deform membranes. Below the membrane, actin filaments support the micro-structures through interactions with several BAR proteins as well as other scaffold proteins, resulting in outward and inward membrane micro-structure formation. Here, we describe the characteristics of phospholipids, and the mechanisms utilized by phosphoinositides to regulate cellular events. We then summarize the precise mechanisms underlying the construction of membrane micro-structures and their involvements in physiological and pathological processes. Copyright © 2014 the

  3. Membrane Lipid Oscillation: An Emerging System of Molecular Dynamics in the Plant Membrane.

    Science.gov (United States)

    Nakamura, Yuki

    2018-03-01

    Biological rhythm represents a major biological process of living organisms. However, rhythmic oscillation of membrane lipid content is poorly described in plants. The development of lipidomic technology has led to the illustration of precise molecular profiles of membrane lipids under various growth conditions. Compared with conventional lipid signaling, which produces unpredictable lipid changes in response to ever-changing environmental conditions, lipid oscillation generates a fairly predictable lipid profile, adding a new layer of biological function to the membrane system and possible cross-talk with the other chronobiological processes. This mini review covers recent studies elucidating membrane lipid oscillation in plants.

  4. Quantitative Microscopic Analysis of Plasma Membrane Receptor Dynamics in Living Plant Cells.

    Science.gov (United States)

    Luo, Yu; Russinova, Eugenia

    2017-01-01

    Plasma membrane-localized receptors are essential for cellular communication and signal transduction. In Arabidopsis thaliana, BRASSINOSTEROID INSENSITIVE1 (BRI1) is one of the receptors that is activated by binding to its ligand, the brassinosteroid (BR) hormone, at the cell surface to regulate diverse plant developmental processes. The availability of BRI1 in the plasma membrane is related to its signaling output and is known to be controlled by the dynamic endomembrane trafficking. Advances in fluorescence labeling and confocal microscopy techniques enabled us to gain a better understanding of plasma membrane receptor dynamics in living cells. Here we describe different quantitative microscopy methods to monitor the relative steady-state levels of the BRI1 protein in the plasma membrane of root epidermal cells and its relative exocytosis and recycling rates. The methods can be applied also to analyze similar dynamics of other plasma membrane-localized receptors.

  5. Dynamics of membrane nanotubes coated with I-BAR

    Science.gov (United States)

    Barooji, Younes F.; Rørvig-Lund, Andreas; Semsey, Szabolcs; Reihani, S. Nader S.; Bendix, Poul M.

    2016-07-01

    Membrane deformation is a necessary step in a number of cellular processes such as filopodia and invadopodia formation and has been shown to involve membrane shaping proteins containing membrane binding domains from the IRSp53-MIM protein family. In reconstituted membranes the membrane shaping domains can efficiently deform negatively charged membranes into tubules without any other proteins present. Here, we show that the IM domain (also called I-BAR domain) from the protein ABBA, forms semi-flexible nanotubes protruding into Giant Unilamellar lipid Vesicles (GUVs). By simultaneous quantification of tube intensity and tubular shape we find both the diameter and stiffness of the nanotubes. I-BAR decorated tubes were quantified to have a diameter of ~50 nm and exhibit no stiffening relative to protein free tubes of the same diameter. At high protein density the tubes are immobile whereas at lower density the tubes diffuse freely on the surface of the GUV. Bleaching experiments of the fluorescently tagged I-BAR confirmed that the mobility of the tubes correlates with the mobility of the I-BAR on the GUV membrane. Finally, at low density of I-BAR the protein upconcentrates within tubes protruding into the GUVs. This implies that I-BAR exhibits strong preference for negatively curved membranes.

  6. Toward the Structure of Dynamic Membrane-Anchored Actin Networks

    Science.gov (United States)

    Weber, Igor

    2007-01-01

    In the cortex of a motile cell, membrane-anchored actin filaments assemble into structures of varying shape and function. Filopodia are distinguished by a core of bundled actin filaments within finger-like extensions of the membrane. In a recent paper by Medalia et al1 cryo-electron tomography has been used to reconstruct, from filopodia of Dictyostelium cells, the 3-dimensional organization of actin filaments in connection with the plasma membrane. A special arrangement of short filaments converging toward the filopod's tip has been called a “terminal cone”. In this region force is applied for protrusion of the membrane. Here we discuss actin organization in the filopodia of Dictyostelium in the light of current views on forces that are generated by polymerizing actin filaments, and on the resistance of membranes against deformation that counteracts these forces. PMID:19262130

  7. Changes in the anisotropy of oriented membrane dynamics induced by myelin basic protein

    Energy Technology Data Exchange (ETDEWEB)

    Natali, F. [OGG-INFM, Grenoble (France); Gliozzi, A.; Rolandi, R.; Relini, A. [Dipartimento di Fisica and Istituto Nazionale per la Fisica della Materia, Universita di Genova (Italy); Cavatorta, P.; Deriu, A. [Dipartimento di Fisica and Istituto Nazionale per la Fisica della Materia, Universita di Parma (Italy); Fasano, A. [Dipartimento di Biochimica e Biologia Molecolare, Universita di Bari (Italy); Riccio, P. [Dipartimento di Biologia D.B.A.F., Universita della Basilicata, Potenza (Italy)

    2002-07-01

    We report recent results showing the evidence of the effect induced by physiological amounts of myelin basic protein (MBP) on the dynamics of dimyristoyl L-a-phosphatidic acid (DMPA) membranes. Incoherent elastic neutron scattering scans, performed over a wide temperature range, have shown that the anisotropy of motions in oriented membranes is significantly enhanced by the presence of MBP. (orig.)

  8. A general theory of non-equilibrium dynamics of lipid-protein fluid membranes

    DEFF Research Database (Denmark)

    Lomholt, Michael Andersen; Hansen, Per Lyngs; Miao, L.

    2005-01-01

    We present a general and systematic theory of non-equilibrium dynamics of multi-component fluid membranes, in general, and membranes containing transmembrane proteins, in particular. Developed based on a minimal number of principles of statistical physics and designed to be a meso...

  9. On calculation of the electrostatic potential of a phosphatidylinositol phosphate-containing phosphatidylcholine lipid membrane accounting for membrane dynamics.

    Directory of Open Access Journals (Sweden)

    Jonathan C Fuller

    Full Text Available Many signaling events require the binding of cytoplasmic proteins to cell membranes by recognition of specific charged lipids, such as phosphoinositol-phosphates. As a model for a protein-membrane binding site, we consider one charged phosphoinositol phosphate (PtdIns(3P embedded in a phosphatidylcholine bilayer. As the protein-membrane binding is driven by electrostatic interactions, continuum solvent models require an accurate representation of the electrostatic potential of the phosphoinositol phosphate-containing membrane. We computed and analyzed the electrostatic potentials of snapshots taken at regular intervals from molecular dynamics simulations of the bilayer. We observe considerable variation in the electrostatic potential of the bilayer both along a single simulation and between simulations performed with the GAFF or CHARMM c36 force fields. However, we find that the choice of GAFF or CHARMM c36 parameters has little effect on the electrostatic potential of a given configuration of the bilayer with a PtdIns(3P embedded in it. From our results, we propose a remedian averaging method for calculating the electrostatic potential of a membrane system that is suitable for simulations of protein-membrane binding with a continuum solvent model.

  10. Effects of deformability and thermal motion of lipid membrane on electroporation: By molecular dynamics simulations

    KAUST Repository

    Sun, Sheng; Yin, Guangyao; Lee, Yi-Kuen; Wong, Joseph T.Y.; Zhang, Tong-Yi

    2011-01-01

    Effects of mechanical properties and thermal motion of POPE lipid membrane on electroporation were studied by molecular dynamics simulations. Among simulations in which specific atoms of lipids were artificially constrained at their equilibrium

  11. Development of a model for activated sludge aeration systems: linking air supply, distribution, and demand.

    Science.gov (United States)

    Schraa, Oliver; Rieger, Leiv; Alex, Jens

    2017-02-01

    During the design of a water resource recovery facility, it is becoming industry practice to use simulation software to assist with process design. Aeration is one of the key components of the activated sludge process, and is one of the most important aspects of modelling wastewater treatment systems. However, aeration systems are typically not modelled in detail in most wastewater treatment process modelling studies. A comprehensive dynamic aeration system model has been developed that captures both air supply and demand. The model includes sub-models for blowers, pipes, fittings, and valves. An extended diffuser model predicts both oxygen transfer efficiency within an aeration basin and pressure drop across the diffusers. The aeration system model allows engineers to analyse aeration systems as a whole to determine biological air requirements, blower performance, air distribution, control valve impacts, controller design and tuning, and energy costs. This enables engineers to trouble-shoot the entire aeration system including process, equipment and controls. It also allows much more realistic design of these highly complex systems.

  12. Concentration gradient driven molecular dynamics: a new method for simulations of membrane permeation and separation.

    Science.gov (United States)

    Ozcan, Aydin; Perego, Claudio; Salvalaglio, Matteo; Parrinello, Michele; Yazaydin, Ozgur

    2017-05-01

    In this study, we introduce a new non-equilibrium molecular dynamics simulation method to perform simulations of concentration driven membrane permeation processes. The methodology is based on the application of a non-conservative bias force controlling the concentration of species at the inlet and outlet of a membrane. We demonstrate our method for pure methane, ethane and ethylene permeation and for ethane/ethylene separation through a flexible ZIF-8 membrane. Results show that a stationary concentration gradient is maintained across the membrane, realistically simulating an out-of-equilibrium diffusive process, and the computed permeabilities and selectivity are in good agreement with experimental results.

  13. Exploring the Local Elastic Properties of Bilayer Membranes Using Molecular Dynamics Simulations

    DEFF Research Database (Denmark)

    Pieffet, Gilles; Botero, Alonso; Peters, Günther H.J.

    2014-01-01

    Membrane mechanical elastic properties regulate a variety of cellular processes involving local membrane deformation, such as ion channel function and vesicle fusion. In this work, we used molecular dynamics simulations to estimate the local elastic properties of a membrane. For this, we calculated...... the stretching process in molecular detail, allowing us to fit this profile to a previously proposed continuum elastic model. Through this approach, we calculated an effective membrane spring constant of 42 kJ-2.mol-1, which is in good agreement with the PMF calculation. Furthermore, the solvation energy we...

  14. Separation of Gas Mixtures by New Type of MembranesDynamic Liquid Membranes.

    Czech Academy of Sciences Publication Activity Database

    Setničková, Kateřina; Šíma, Vladimír; Petričkovič, Roman; Řezníčková Čermáková, Jiřina; Uchytil, Petr

    2016-01-01

    Roč. 160, FEB 29 (2016), s. 132-135 ISSN 1383-5866 Institutional support: RVO:67985858 Keywords : gas separation * liquid membrane * methane Subject RIV: CI - Industrial Chemistry, Chemical Engineering Impact factor: 3.359, year: 2016

  15. Microalgae fractionation using steam explosion, dynamic and tangential cross-flow membrane filtration.

    Science.gov (United States)

    Lorente, E; Hapońska, M; Clavero, E; Torras, C; Salvadó, J

    2017-08-01

    In this study, the microalga Nannochloropsis gaditana was subjected to acid catalysed steam explosion treatment and the resulting exploded material was subsequently fractionated to separate the different fractions (lipids, sugars and solids). Conventional and vibrational membrane setups were used with several polymeric commercial membranes. Two different routes were followed: 1) filtration+lipid solvent extraction and 2) lipid solvent extraction+filtration. Route 1 revealed to be much better since the used membrane for filtration was able to permeate the sugar aqueous phase and retained the fraction containing lipids; after this, an extraction required a much lower amount of solvent and a better recovering yield. Filtration allowed complete lipid rejection. Dynamic filtration improved permeability compared to the tangential cross-flow filtration. Best membrane performance was achieved using a 5000Da membrane with the dynamic system, obtaining a permeability of 6L/h/m 2 /bar. Copyright © 2017 Elsevier Ltd. All rights reserved.

  16. 3D-modelling of the thermal circumstances of a lake under artificial aeration

    Science.gov (United States)

    Tian, Xiaoqing; Pan, Huachen; Köngäs, Petrina; Horppila, Jukka

    2017-12-01

    A 3D-model was developed to study the effects of hypolimnetic aeration on the temperature profile of a thermally stratified Lake Vesijärvi (southern Finland). Aeration was conducted by pumping epilimnetic water through the thermocline to the hypolimnion without breaking the thermal stratification. The model used time transient equation based on Navier-Stokes equation. The model was fitted to the vertical temperature distribution and environmental parameters (wind, air temperature, and solar radiation) before the onset of aeration, and the model was used to predict the vertical temperature distribution 3 and 15 days after the onset of aeration (1 August and 22 August). The difference between the modelled and observed temperature was on average 0.6 °C. The average percentage model error was 4.0% on 1 August and 3.7% on 22 August. In the epilimnion, model accuracy depended on the difference between the observed temperature and boundary conditions. In the hypolimnion, the model residual decreased with increasing depth. On 1 August, the model predicted a homogenous temperature profile in the hypolimnion, while the observed temperature decreased moderately from the thermocline to the bottom. This was because the effect of sediment was not included in the model. On 22 August, the modelled and observed temperatures near the bottom were identical demonstrating that the heat transfer by the aerator masked the effect of sediment and that exclusion of sediment heat from the model does not cause considerable error unless very short-term effects of aeration are studied. In all, the model successfully described the effects of the aerator on the lake's temperature profile. The results confirmed the validity of the applied computational fluid dynamic in artificial aeration; based on the simulated results, the effect of aeration can be predicted.

  17. Design of high efficiency and energy saving aeration device for aquaculture

    Science.gov (United States)

    Liu, Sibo

    2017-03-01

    Energy efficient aeration device for aquaculture, in line with "by more than a generation, dynamic aeration" train of thought for technical design and improvement. Removable aeration terminal as the core, multi-level water to improve the method, the mobile fading pore aeration, intelligent mobile and open and close as the main function, aimed at solving the existing pond aeration efficiency, low energy consumption is high, the function of a single problem. From energy saving, efficiency, biological bacteria on the three directions, the aquaculture industry of energy conservation and emissions reduction. Device of the main advantages are: 1, original mobile fading aerator on the one hand, to expand the scope of work, playing a micro porous aeration of dissolved oxygen with high efficiency and to achieve "by more than a generation", on the other hand, through the sports equipment, stir the mixture of water, the water surface of photosynthesis of plants rich in dissolved oxygen input parts of the tank, compared to the stillness of the aerator can be more fully dissolved oxygen.2, through the opening of the pressure sensor indirect control device, can make the equipment timely and stop operation, convenient in use at the same time avoid the waste of energy.3, the biofilm suspension in aeration terminal, can be accomplished by nitration of microbial multi-level water improvement, still can make biofilm increase rate of netting in the movement process, the biological and mechanical aerobic promote each other, improve the efficiency of both. In addition, the device has small power consumption, low cost of characteristics. And have a certain degree of technical barriers, have their own intellectual property rights, and high degree of product market demand, easily accepted by customers, has a very high popularization value.

  18. Membrane Sculpting by F-BAR Domains Studied by Molecular Dynamics Simulations

    Science.gov (United States)

    Yu, Hang; Schulten, Klaus

    2013-01-01

    Interplay between cellular membranes and their peripheral proteins drives many processes in eukaryotic cells. Proteins of the Bin/Amphiphysin/Rvs (BAR) domain family, in particular, play a role in cellular morphogenesis, for example curving planar membranes into tubular membranes. However, it is still unclear how F-BAR domain proteins act on membranes. Electron microscopy revealed that, in vitro, F-BAR proteins form regular lattices on cylindrically deformed membrane surfaces. Using all-atom and coarse-grained (CG) molecular dynamics simulations, we show that such lattices, indeed, induce tubes of observed radii. A 250 ns all-atom simulation reveals that F-BAR domain curves membranes via the so-called scaffolding mechanism. Plasticity of the F-BAR domain permits conformational change in response to membrane interaction, via partial unwinding of the domains 3-helix bundle structure. A CG simulation covering more than 350 µs provides a dynamic picture of membrane tubulation by lattices of F-BAR domains. A series of CG simulations identified the optimal lattice type for membrane sculpting, which matches closely the lattices seen through cryo-electron microscopy. PMID:23382665

  19. Dynamic Response Analysis of Microflow Electrochemical Sensors with Two Types of Elastic Membrane

    Directory of Open Access Journals (Sweden)

    Qiuzhan Zhou

    2016-05-01

    Full Text Available The Molecular Electric Transducer (MET, widely applied for vibration measurement, has excellent sensitivity and dynamic response at low frequencies. The elastic membrane in the MET is a significant factor with an obvious effect on the performance of the MET in the low frequency domain and is the focus of this paper. In simulation experiments, the elastic membrane and the reaction cavity of the MET were analysed in a model based on the multiphysics finite element method. Meanwhile, the effects caused by the elastic membrane elements are verified in this paper. With the numerical simulation and practical experiments, a suitable elastic membrane can be designed for different cavity structures. Thus, the MET can exhibit the best dynamic response characteristics to measure the vibration signals. With the new method presented in this paper, it is possible to develop and optimize the characteristics of the MET effectively, and the dynamic characteristics of the MET can be improved in a thorough and systematic manner.

  20. Structure and Dynamic Properties of Membrane Proteins using NMR

    DEFF Research Database (Denmark)

    Rösner, Heike; Kragelund, Birthe

    2012-01-01

    conformational changes. Their structural and functional decoding is challenging and has imposed demanding experimental development. Solution nuclear magnetic resonance (NMR) spectroscopy is one of the techniques providing the capacity to make a significant difference in the deciphering of the membrane protein...... structure-function paradigm. The method has evolved dramatically during the last decade resulting in a plethora of new experiments leading to a significant increase in the scientific repertoire for studying membrane proteins. Besides solving the three-dimensional structures using state-of-the-art approaches......-populated states, this review seeks to introduce the vast possibilities solution NMR can offer to the study of membrane protein structure-function analyses with special focus on applicability. © 2012 American Physiological Society. Compr Physiol 2:1491-1539, 2012....

  1. Roles of membrane trafficking in plant cell wall dynamics

    Directory of Open Access Journals (Sweden)

    Kazuo eEbine

    2015-10-01

    Full Text Available The cell wall is one of the characteristic components of plant cells. The cell wall composition differs among cell types and is modified in response to various environmental conditions. To properly generate and modify the cell wall, many proteins are transported to the plasma membrane or extracellular space through membrane trafficking, which is one of the key protein transport mechanisms in eukaryotic cells. Given the diverse composition and functions of the cell wall in plants, the transport of the cell wall components and proteins that are involved in cell wall-related events could be specialized for each cell type, i.e., the machinery for cell wall biogenesis, modification, and maintenance could be transported via different trafficking pathways. In this review, we summarize the recent progress in the current understanding of the roles and mechanisms of membrane trafficking in plant cells and focus on the biogenesis and regulation of the cell wall.

  2. Dynamic potential and surface morphology study of sertraline membrane sensors

    Science.gov (United States)

    Khater, M.M.; Issa, Y.M.; Hassib, H.B.; Mohammed, S.H.

    2014-01-01

    New rapid, sensitive and simple electrometric method was developed to determine sertraline hydrochloride (Ser-Cl) in its pure raw material and pharmaceutical formulations. Membrane sensors based on heteropolyacids as ion associating material were prepared. Silicomolybdic acid (SMA), silicotungstic acid (STA) and phosphomolybdic acid (PMA) were used. The slope and limit of detection are 50.00, 60.00 and 53.24 mV/decade and 2.51, 5.62 and 4.85 μmol L−1 for Ser-ST, Ser-PM and Ser-SM membrane sensors, respectively. Linear range is 0.01–10.00 for the three sensors. These new sensors were used for the potentiometric titration of Ser-Cl using sodium tetraphenylborate as titrant. The surface morphologies of the prepared membranes with and without the modifier (ion-associate) were studied using scanning and atomic force microscopes. PMID:26257944

  3. 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

  4. Acoustic investigation of the aperture dynamics of an elastic membrane closing an overpressurized cylindrical cavity

    Science.gov (United States)

    Sánchez, Claudia; Vidal, Valérie; Melo, Francisco

    2015-08-01

    We report an experimental study of the acoustic signal produced by the rupture of an elastic membrane that initially closes a cylindrical overpressurized cavity. This configuration has been recently used as an experimental model system for the investigation of the acoustic emission from the bursting of elongated gas bubbles rising in a conduit. Here, we investigate the effect of the membrane rupture dynamics on the acoustic signal produced by the pressure release by changing the initial tension of the membrane. The initial overpressure in the cavity is fixed at a value such that the system remains in the linear acoustic regime. For large initial membrane deformation, the rupture time τ rup is small compared to the wave propagation time in the cavity and the pressure wave inside the conduit can be fully captured by the linear theory. For low membrane tension, a hole is pierced in the membrane but its rupture does not occur. For intermediate deformation, finally, the rupture progresses in two steps: first the membrane opens slowly; then, after reaching a critical size, the rupture accelerates. A transversal wave is excited along the membrane surface. The characteristic signature of each opening dynamics on the acoustic emission is described.

  5. Membrane dynamics and the regulation of epithelial cell polarity

    NARCIS (Netherlands)

    van der Wouden, JM; Maier, O; van IJzendoorn, SCD; Hoekstra, D

    2003-01-01

    Plasma membranes of epithelial cells consist of two domains, an apical and a basolateral domain, the surfaces of which differ in composition. The separation of these domains by a tight junction and the fact that specific transport pathways exist for intracellular communication between these domains

  6. Dynamic optimization of dead-end membrane filtration

    NARCIS (Netherlands)

    Blankert, B.; Betlem, Bernardus H.L.; Roffel, B.; Marquardt, Wolfgang; Pantelides, Costas

    2006-01-01

    An operating strategy aimed at minimizing the energy consumption during the filtration phase of dead-end membrane filtration has been formulated. A method allowing fast calculation of trajectories is used to allow incorporation in a hierarchical optimization scheme. The optimal trajectory can be

  7. Membrane recognition and dynamics of the RNA degradosome

    NARCIS (Netherlands)

    Strahl, H.; Turlan, C.; Khalid, S.; Bond, P.J.; Kebalo, J.M.; Peyron, P.; Poljak, L.; Bouvier, M.; Hamoen, L.; Luisi, B.F.; Carpousis, A.J.

    2015-01-01

    RNase E, which is the central component of the multienzyme RNA degradosome, serves as a scaffold for interaction with other enzymes involved in mRNA degradation including the DEAD-box RNA helicase RhlB. Epifluorescence microscopy under live cell conditions shows that RNase E and RhlB are membrane

  8. Study of Dynamic Membrane Behavior in Applied DC Electric Field

    Science.gov (United States)

    Dutta, Prashanta; Morshed, Adnan; Hossan, Mohammad

    2017-11-01

    Electrodeformation of vesicles can be used as a useful tool to understand the characteristics of biological soft matter, where vesicles immersed in a fluid medium are subjected to an applied electric field. The complex response of the vesicle membrane strongly depends on the conductivity of surrounding fluid, vesicle size and shape, and applied electric field We studied the electrodeformation of vesicles immersed in a fluid media under a short DC electric pulse. An immersed interface method is used to solve the electric field over the domain with conductive or non-conductive vesicles while an immersed boundary scheme is employed to solve fluid flow, fluid-solid interaction, membrane mechanics and vesicle movement. Force analysis on the membrane surface reveals almost linear relation with vesicle size, but highly nonlinear influence of applied field as well as the conductivity ratios inside and outside of the vesicle. Results also point towards an early linear deformation regime followed by an equilibrium stage for the membranes. Moreover, significant influence of the initial aspect ratio of the vesicle on the force distribution is observed across a range of conductivity ratios. Research reported in this publication was supported by the National Institute of General Medical Sciences of the National Institutes of Health under Award Number R01GM122081.

  9. Molecular assemblies and membrane domains in multivesicular endosome dynamics

    International Nuclear Information System (INIS)

    Falguieres, Thomas; Luyet, Pierre-Philippe; Gruenberg, Jean

    2009-01-01

    Along the degradation pathway, endosomes exhibit a characteristic multivesicular organization, resulting from the budding of vesicles into the endosomal lumen. After endocytosis and transport to early endosomes, activated signaling receptors are incorporated into these intralumenal vesicles through the action of the ESCRT machinery, a process that contributes to terminate signaling. Then, the vesicles and their protein cargo are further transported towards lysosomes for degradation. Evidence also shows that intralumenal vesicles can undergo 'back-fusion' with the late endosome limiting membrane, a route exploited by some pathogens and presumably followed by proteins and lipids that need to be recycled from within the endosomal lumen. This process depends on the late endosomal lipid lysobisphosphatidic acid and its putative effector Alix/AIP1, and is presumably coupled to the invagination of the endosomal limiting membrane at the molecular level via ESCRT proteins. In this review, we discuss the intra-endosomal transport routes in mammalian cells, and in particular the different mechanisms involved in membrane invagination, vesicle formation and fusion in a space inaccessible to proteins known to control intracellular membrane traffic.

  10. Transport dynamics in membranes of photosynthetic purple bacteria

    Science.gov (United States)

    Caycedo, Felipe; Rodriguez, Ferney; Quiroga, Luis; Fassioli, Francesca; Johnson, Neil

    2007-03-01

    Photo-Syntethic Unit (PSU) of purple bacteria is conformed by three basic constituents: Light Harvesting Complex 2 (LH2) antenna complexes, where chromophores are distributed in a ring in close contact with caroteniods with a function of collecting light; LH1s, ring shaped structures of chromophores which harvest and funnel excitations to the Reaction Centre (RC), where phtosynthesis takes place. Studies concerning a single PSU have been capable of reproducing experimental transfer times, but incapable of explaining the fact that architecture LH2-LH1-RC of phototosynthetic membranes changes as light intensity conditions vary. The organization of antenna complexes in the membranes that support PSU seems to have its own functionality. A hopping model where excitations are transferred within a membrane is used, and populations of RC, LH1 and LH2 are investigated. Different statistics concerning arrival times of excitations that excite a single PSU are considered and compared with the global model where coordinates of a great portion of a membrane are included. The model permits in a classical basis to understand which parameters make photosynthesis in purple bateria efficient and reliable.

  11. Dynamics of HIV-1 RNA Near the Plasma Membrane during Virus Assembly.

    Science.gov (United States)

    Sardo, Luca; Hatch, Steven C; Chen, Jianbo; Nikolaitchik, Olga; Burdick, Ryan C; Chen, De; Westlake, Christopher J; Lockett, Stephen; Pathak, Vinay K; Hu, Wei-Shau

    2015-11-01

    To increase our understanding of the events that lead to HIV-1 genome packaging, we examined the dynamics of viral RNA and Gag-RNA interactions near the plasma membrane by using total internal reflection fluorescence microscopy. We labeled HIV-1 RNA with a photoconvertible Eos protein via an RNA-binding protein that recognizes stem-loop sequences engineered into the viral genome. Near-UV light exposure causes an irreversible structural change in Eos and alters its emitted fluorescence from green to red. We studied the dynamics of HIV-1 RNA by photoconverting Eos near the plasma membrane, and we monitored the population of photoconverted red-Eos-labeled RNA signals over time. We found that in the absence of Gag, most of the HIV-1 RNAs stayed near the plasma membrane transiently, for a few minutes. The presence of Gag significantly increased the time that RNAs stayed near the plasma membrane: most of the RNAs were still detected after 30 min. We then quantified the proportion of HIV-1 RNAs near the plasma membrane that were packaged into assembling viral complexes. By tagging Gag with blue fluorescent protein, we observed that only a portion, ∼13 to 34%, of the HIV-1 RNAs that reached the membrane were recruited into assembling particles in an hour, and the frequency of HIV-1 RNA packaging varied with the Gag expression level. Our studies reveal the HIV-1 RNA dynamics on the plasma membrane and the efficiency of RNA recruitment and provide insights into the events leading to the generation of infectious HIV-1 virions. Nascent HIV-1 particles assemble on plasma membranes. During the assembly process, HIV-1 RNA genomes must be encapsidated into viral complexes to generate infectious particles. To gain insights into the RNA packaging and virus assembly mechanisms, we labeled and monitored the HIV-1 RNA signals near the plasma membrane. Our results showed that most of the HIV-1 RNAs stayed near the plasma membrane for only a few minutes in the absence of Gag, whereas

  12. Evaluation of the oleophilicity of different alkoxysilane modified ceramic membranes through wetting dynamic measurements

    Energy Technology Data Exchange (ETDEWEB)

    Gao, Nengwen, E-mail: nengwengao@cqut.edu.cn [State Key Laboratory of Materials-oriented Chemical Engineering, College of Chemistry and Chemical Engineering, Nanjing University of Technology, Nanjing 210009 (China); College of Chemistry and Chemical Engineering, Chongqing University of Technology, Chongqing 400050 (China); Ke, Wei [State Key Laboratory of Materials-oriented Chemical Engineering, College of Chemistry and Chemical Engineering, Nanjing University of Technology, Nanjing 210009 (China); Fan, Yiqun, E-mail: yiqunfan@njut.edu.cn [State Key Laboratory of Materials-oriented Chemical Engineering, College of Chemistry and Chemical Engineering, Nanjing University of Technology, Nanjing 210009 (China); Xu, Nanping [State Key Laboratory of Materials-oriented Chemical Engineering, College of Chemistry and Chemical Engineering, Nanjing University of Technology, Nanjing 210009 (China)

    2013-10-15

    Wettability has been recognized as one of the most important properties of porous materials for both fundamental and practical applications. In this study, the oleophilicity of Al{sub 2}O{sub 3} membranes modified by four alkoxysilanes with different length of alkyl group was investigated through oil wetting dynamic test. Fourier transform infrared spectroscopy (FTIR), thermogravimertric analysis (TGA), X-ray photoelectron spectroscopy (XPS), and scanning electron microscopy (SEM) were measured to confirm that ceramic membrane surfaces have been grafted with alkoxysilanes without changing the membrane morphology. A high speed video camera was used to record the spreading and imbibition process of oil on the modified membrane surface. The value of oil contact angle and its change during the wetting process were used to characterize the membrane oleophilicity. Characterization results showed that the oleophilicity of the modified membranes increased along with the increasing of the silane alkyl group. The influence of oleophilicity on the filtration performance of water-in-oil (W/O) emulsions was experimentally studied. A higher oil flux was obtained for membranes grafted with a longer alkyl group, indicating that increase oleophilicity can increase the membrane antifouling property. This work presents a valuable route to the surface oleophilicity control and testing of ceramic membranes in the filtration of non-polar organic solvents.

  13. Tunable hydrogen separation in porous graphene membrane: first-principle and molecular dynamic simulation.

    Science.gov (United States)

    Tao, Yehan; Xue, Qingzhong; Liu, Zilong; Shan, Meixia; Ling, Cuicui; Wu, Tiantian; Li, Xiaofang

    2014-06-11

    First-principle density functional theory (DFT) calculation and molecular dynamic (MD) simulation are employed to investigate the hydrogen purification performance of two-dimensional porous graphene material (PG-ESX). First, the pore size of PG-ES1 (3.2775 Å) is expected to show high selectivity of H2 by DFT calculation. Then MD simulations demonstrate the hydrogen purification process of the PG-ESX membrane. The results indicate that the selectivity of H2 over several other gas molecules that often accompany H2 in industrial steam methane reforming or dehydrogenation of alkanes (such as N2, CO, and CH4) is sensitive to the pore size of the membrane. PG-ES and PG-ES1 membranes both exhibit high selectivity for H2 over other gases, but the permeability of the PG-ES membrane is much lower than the PG-ES1 membrane because of the smaller pore size. The PG-ES2 membrane with bigger pores demonstrates low selectivity for H2 over other gases. Energy barrier and electron density have been used to explain the difference of selectivity and permeability of PG-ESX membranes by DFT calculations. The energy barrier for gas molecules passing through the membrane generally increase with the decreasing of pore sizes or increasing of molecule kinetic diameter, due to the different electron overlap between gas and a membrane. The PG-ES1 membrane is far superior to other carbon membranes and has great potential applications in hydrogen purification, energy clean combustion, and making new concept membrane for gas separation.

  14. Biological Membrane Ion Channels Dynamics, Structure, and Applications

    CERN Document Server

    Chung, Shin-Ho; Krishnamurthy, Vikram

    2007-01-01

    Ion channels are biological nanotubes that are formed by membrane proteins. Because ion channels regulate all electrical activities in living cells, understanding their mechanisms at a molecular level is a fundamental problem in biology. This book deals with recent breakthroughs in ion-channel research that have been brought about by the combined effort of experimental biophysicists and computational physicists, who together are beginning to unravel the story of these exquisitely designed biomolecules. With chapters by leading experts, the book is aimed at researchers in nanodevices and biosensors, as well as advanced undergraduate and graduate students in biology and the physical sciences. Key Features Presents the latest information on the molecular mechanisms of ion permeation through membrane ion channels Uses schematic diagrams to illustrate important concepts in biophysics Written by leading researchers in the area of ion channel investigations

  15. Electrokinetics of nanochannels and porous membranes with dynamic surface charges

    DEFF Research Database (Denmark)

    Andersen, Mathias Bækbo

    . Notably, we find that the conductance minimum is mainly caused by hydronium ions, and in our case almost exclusively due to carbonic acid generated from the dissolution of CO2 from the atmosphere. We carry out delicate experiments and measure the conductance of silica nanochannels as a function...... and consider strong out-of-equilibrium transport across the membrane. Our model predicts large pH variations in the electrodialysis system that in turn lowers the ion-selectivity of the membrane by protonation reactions. This opens up for significant over-limiting current. We use our model to investigate...... procedure that requires much attention to the comparability between the conditions in the model and in the experiment. Finally, we make a small digression and study induced-charge electro-osmosis (ICEO) and the validity of common EO slip formulae as a function of a finite Debye screening length...

  16. Description of the Gas Transport through Dynamic Liquid Membrane.

    Czech Academy of Sciences Publication Activity Database

    Uchytil, Petr; Setničková, Kateřina; Tseng, H.-H.; Šíma, Vladimír; Petričkovič, Roman

    2017-01-01

    Roč. 184, AUG 31 (2017), s. 152-157 ISSN 1383-5866 Grant - others:AV ČR(CZ) MOST-16-04 Program:Bilaterální spolupráce Institutional support: RVO:67985858 Keywords : gas separation * liquid membrane * solurion-diffusion model Subject RIV: CI - Industrial Chemistry, Chemical Engineering OBOR OECD: Chemical process engineering Impact factor: 3.359, year: 2016

  17. Multiscale molecular dynamics simulations of membrane remodeling by Bin/Amphiphysin/Rvs family proteins

    Science.gov (United States)

    Chun, Chan; Haohua, Wen; Lanyuan, Lu; Jun, Fan

    2016-01-01

    Membrane curvature is no longer thought of as a passive property of the membrane; rather, it is considered as an active, regulated state that serves various purposes in the cell such as between cells and organelle definition. While transport is usually mediated by tiny membrane bubbles known as vesicles or membrane tubules, such communication requires complex interplay between the lipid bilayers and cytosolic proteins such as members of the Bin/Amphiphysin/Rvs (BAR) superfamily of proteins. With rapid developments in novel experimental techniques, membrane remodeling has become a rapidly emerging new field in recent years. Molecular dynamics (MD) simulations are important tools for obtaining atomistic information regarding the structural and dynamic aspects of biological systems and for understanding the physics-related aspects. The availability of more sophisticated experimental data poses challenges to the theoretical community for developing novel theoretical and computational techniques that can be used to better interpret the experimental results to obtain further functional insights. In this review, we summarize the general mechanisms underlying membrane remodeling controlled or mediated by proteins. While studies combining experiments and molecular dynamics simulations recall existing mechanistic models, concurrently, they extend the role of different BAR domain proteins during membrane remodeling processes. We review these recent findings, focusing on how multiscale molecular dynamics simulations aid in understanding the physical basis of BAR domain proteins, as a representative of membrane-remodeling proteins. Project supported by the National Natural Science Foundation of China (Grant No. 21403182) and the Research Grants Council of Hong Kong, China (Grant No. CityU 21300014).

  18. Interferometric scattering (iSCAT) microscopy: studies of biological membrane dynamics

    Science.gov (United States)

    Reina, Francesco; Galiani, Silvia; Shrestha, Dilip; Sezgin, Erdinc; Lagerholm, B. Christoffer; Cole, Daniel; Kukura, Philipp; Eggeling, Christian

    2018-02-01

    The study of the organization and dynamics of molecules in model and cellular membranes is an important topic in contemporary biophysics. Imaging and single particle tracking in this particular field, however, proves particularly demanding, as it requires simultaneously high spatio-temporal resolution and high signal-to-noise ratios. A remedy to this challenge might be Interferometric Scattering (iSCAT) microscopy, due to its fast sampling rates, label-free imaging capabilities and, most importantly, tuneable signal level output. Here we report our recent advances in the imaging and molecular tracking on phase-separated model membrane systems and live-cell membranes using this technique.

  19. Dynamic nuclear polarization of membrane proteins: covalently bound spin-labels at protein–protein interfaces

    International Nuclear Information System (INIS)

    Wylie, Benjamin J.; Dzikovski, Boris G.; Pawsey, Shane; Caporini, Marc; Rosay, Melanie; Freed, Jack H.; McDermott, Ann E.

    2015-01-01

    We demonstrate that dynamic nuclear polarization of membrane proteins in lipid bilayers may be achieved using a novel polarizing agent: pairs of spin labels covalently bound to a protein of interest interacting at an intermolecular interaction surface. For gramicidin A, nitroxide tags attached to the N-terminal intermolecular interface region become proximal only when bimolecular channels forms in the membrane. We obtained signal enhancements of sixfold for the dimeric protein. The enhancement effect was comparable to that of a doubly tagged sample of gramicidin C, with intramolecular spin pairs. This approach could be a powerful and selective means for signal enhancement in membrane proteins, and for recognizing intermolecular interfaces

  20. Dynamics of the Fouling Layer Microbial Community in a Membrane Bioreactor

    DEFF Research Database (Denmark)

    Ziegler, Anja Sloth; McIlroy, Simon Jon; Larsen, Poul

    2016-01-01

    Membrane fouling presents the greatest challenge to the application of membrane bioreactor (MBR) technology. Formation of biofilms on the membrane surface is the suggested cause, yet little is known of the composition or dynamics of the microbial community responsible. To gain an insight...... of the fouling process, we concurrently investigated the communities of the biofilm, MBR bulk sludge, and the conventional activated sludge system used to seed the MBR system over several weeks from start-up. As the biofilm matured the initially abundant betaproteobacterial genera Limnohabitans, Hydrogenophaga...

  1. Characterization of Hydrophobic Interactions of Polymers with Water and Phospholipid Membranes Using Molecular Dynamics Simulations

    Science.gov (United States)

    Drenscko, Mihaela

    Polymers and lipid membranes are both essential soft materials. The structure and hydrophobicity/hydrophilicity of polymers, as well as the solvent they are embedded in, ultimately determines their size and shape. Understating the variation of shape of the polymer as well as its interactions with model biological membranes can assist in understanding the biocompatibility of the polymer itself. Computer simulations, in particular molecular dynamics, can aid in characterization of the interaction of polymers with solvent, as well as polymers with model membranes. In this thesis, molecular dynamics serve to describe polymer interactions with a solvent (water) and with a lipid membrane. To begin with, we characterize the hydrophobic collapse of single polystyrene chains in water using molecular dynamics simulations. Specifically, we calculate the potential of mean force for the collapse of a single polystyrene chain in water using metadynamics, comparing the results between all atomistic with coarse-grained molecular simulation. We next explore the scaling behavior of the collapsed globular shape at the minimum energy configuration, characterized by the radius of gyration, as a function of chain length. The exponent is close to one third, consistent with that predicted for a polymer chain in bad solvent. We also explore the scaling behavior of the Solvent Accessible Surface Area (SASA) as a function of chain length, finding a similar exponent for both all-atomistic and coarse-grained simulations. Furthermore, calculation of the local water density as a function of chain length near the minimum energy configuration suggests that intermediate chain lengths are more likely to form dewetted states, as compared to shorter or longer chain lengths. Next, in order to investigate the molecular interactions between single hydrophobic polymer chains and lipids in biological membranes and at lipid membrane/solvent interface, we perform a series of molecular dynamics simulations of

  2. Monitoring orientation and dynamics of membrane-bound melittin utilizing dansyl fluorescence.

    Science.gov (United States)

    Haldar, Sourav; Raghuraman, H; Chattopadhyay, Amitabha

    2008-11-06

    Melittin is a cationic hemolytic peptide isolated from the European honey bee, Apis mellifera. In spite of a number of studies, there is no consensus regarding the orientation of melittin in membranes. In this study, we used a melittin analogue that is covalently labeled at its amino terminal (Gly-1) with the environment-sensitive 1-dimethylamino-5-sulfonylnaphthalene (dansyl) group to obtain information regarding the orientation and dynamics of the amino terminal region of membrane-bound melittin. Our results show that the dansyl group in Dns-melittin exhibits red edge excitation shift in vesicles of 1,2-dioleoyl-sn-glycero-3-phosphocholine, implying its localization in a motionally restricted region of the membrane. This is further supported by wavelength-dependent anisotropy and lifetime changes and time-resolved emission spectra characterized by dynamic Stokes shift, which indicates relatively slow solvent relaxation in the excited state. Membrane penetration depth analysis using the parallax method shows that the dansyl group is localized at a depth of approximately 18 A from the center of the bilayer in membrane-bound Dns-melittin. Further analysis of dansyl and tryptophan depths in Dns-melittin shows that the tilt angle between the helix axis of membrane-bound melittin and the bilayer normal is approximately 70 degrees. Our results therefore suggest that melittin adopts a pseudoparallel orientation in DOPC membranes at low concentration.

  3. Molecular dynamics study of lipid bilayers modeling the plasma membranes of mouse hepatocytes and hepatomas.

    Science.gov (United States)

    Andoh, Yoshimichi; Aoki, Noriyuki; Okazaki, Susumu

    2016-02-28

    Molecular dynamics (MD) calculations of lipid bilayers modeling the plasma membranes of normal mouse hepatocytes and hepatomas in water have been performed under physiological isothermal-isobaric conditions (310.15 K and 1 atm). The changes in the membrane properties induced by hepatic canceration were investigated and were compared with previous MD calculations included in our previous study of the changes in membrane properties induced by murine thymic canceration. The calculated model membranes for normal hepatocytes and hepatomas comprised 23 and 24 kinds of lipids, respectively. These included phosphatidylcholine, phosphatidylethanolamine, phosphatidylserine, phosphatidylinositol, sphingomyelin, lysophospholipids, and cholesterol. We referred to previously published experimental values for the mole fraction of the lipids adopted in the present calculations. The calculated structural and dynamic properties of the membranes such as lateral structure, order parameters, lateral self-diffusion constants, and rotational correlation times all showed that hepatic canceration causes plasma membranes to become more ordered laterally and less fluid. Interestingly, this finding contrasts with the less ordered structure and increased fluidity of plasma membranes induced by thymic canceration observed in our previous MD study.

  4. Bicelles and Other Membrane Mimics: Comparison of Structure, Properties, and Dynamics from MD Simulations

    DEFF Research Database (Denmark)

    Vestergaard, Mikkel; Kraft, Johan Frederik; Vosegaard, Thomas

    2015-01-01

    present molecular dynamics simulations to elucidate structural and dynamic properties of small bicelles and compare them to a large alignable bicelle, a small nanodisc, and a lipid bilayer. Properties such as lipid packing and properties related to embedding both an α-helical peptide and a transmembrane...... protein are investigated. The small bicelles are found to be very dynamic and mainly assume a prolate shape substantiating that small bicelles cannot be regarded as well-defined disclike structures. However, addition of a peptide results in an increased tendency to form disc-shaped bicelles. The small......The increased interest in studying membrane proteins has led to the development of new membrane mimics such as bicelles and nanodiscs. However, only limited knowledge is available of how these membrane mimics are affected by embedded proteins and how well they mimic a lipid bilayer. Herein, we...

  5. Dynamics of epiretinal membrane removal off the retinal surface: a computer simulation project.

    Science.gov (United States)

    Dogramaci, Mahmut; Williamson, Tom H

    2013-09-01

    To use a computer simulation to discern the safest angle at which to peel epiretinal membranes. We used ANSYS V.14.1 software to analyse the dynamics involved in membrane removal off the retinal surface. The geometrical values were taken from optical coherence tomography of 30 eyes with epiretinal membranes. A range of Young's modulus values of 0.03, 0.01 and 0.09 MPa were assigned to the epiretinal membrane and to the retina separately. The ratio of maximum shear stress (MSS) recorded at the attachment pegs over that recorded at the membrane (P/E ratio) was determined at nine displacement angles (DA). Mean MSS values recorded at the attachment pegs, epiretinal membrane and retina were significantly different at 0.8668, 0.6091 and 0.0017 Pa consecutively (p<0.05). There was a significant negative linear correlation between DA and MSS recorded at the epiretinal membrane when the Young's modulus for the epiretinal membrane was higher than or equal to that for the attachment pegs and the retina. Nevertheless, there was a significant positive linear correlation between DA and P/E ratio when the Young's modulus for the epiretinal membrane was equal to or lower than that for the attachment pegs and the retina. Attachment pegs appear to be the most likely part to fail (tear) during removal procedures. Changing the direction at which the edge of the membrane is pulled can relocate the MSS within in the tissue complex. Safer and effective removal could be achieved by pulling epiretinal membranes onto themselves at 165° DA.

  6. Single Lipid Molecule Dynamics on Supported Lipid Bilayers with Membrane Curvature

    Directory of Open Access Journals (Sweden)

    Philip P. Cheney

    2017-03-01

    Full Text Available The plasma membrane is a highly compartmentalized, dynamic material and this organization is essential for a wide variety of cellular processes. Nanoscale domains allow proteins to organize for cell signaling, endo- and exocytosis, and other essential processes. Even in the absence of proteins, lipids have the ability to organize into domains as a result of a variety of chemical and physical interactions. One feature of membranes that affects lipid domain formation is membrane curvature. To directly test the role of curvature in lipid sorting, we measured the accumulation of two similar lipids, 1,2-Dihexadecanoyl-sn-glycero-3-phosphoethanolamine (DHPE and hexadecanoic acid (HDA, using a supported lipid bilayer that was assembled over a nanopatterned surface to obtain regions of membrane curvature. Both lipids studied contain 16 carbon, saturated tails and a head group tag for fluorescence microscopy measurements. The accumulation of lipids at curvatures ranging from 28 nm to 55 nm radii was measured and fluorescein labeled DHPE accumulated more than fluorescein labeled HDA at regions of membrane curvature. We then tested whether single biotinylated DHPE molecules sense curvature using single particle tracking methods. Similar to groups of fluorescein labeled DHPE accumulating at curvature, the dynamics of single molecules of biotinylated DHPE was also affected by membrane curvature and highly confined motion was observed.

  7. Dynamic, electronically switchable surfaces for membrane protein microarrays.

    Science.gov (United States)

    Tang, C S; Dusseiller, M; Makohliso, S; Heuschkel, M; Sharma, S; Keller, B; Vörös, J

    2006-02-01

    Microarray technology is a powerful tool that provides a high throughput of bioanalytical information within a single experiment. These miniaturized and parallelized binding assays are highly sensitive and have found widespread popularity especially during the genomic era. However, as drug diagnostics studies are often targeted at membrane proteins, the current arraying technologies are ill-equipped to handle the fragile nature of the protein molecules. In addition, to understand the complex structure and functions of proteins, different strategies to immobilize the probe molecules selectively onto a platform for protein microarray are required. We propose a novel approach to create a (membrane) protein microarray by using an indium tin oxide (ITO) microelectrode array with an electronic multiplexing capability. A polycationic, protein- and vesicle-resistant copolymer, poly(l-lysine)-grafted-poly(ethylene glycol) (PLL-g-PEG), is exposed to and adsorbed uniformly onto the microelectrode array, as a passivating adlayer. An electronic stimulation is then applied onto the individual ITO microelectrodes resulting in the localized release of the polymer thus revealing a bare ITO surface. Different polymer and biological moieties are specifically immobilized onto the activated ITO microelectrodes while the other regions remain protein-resistant as they are unaffected by the induced electrical potential. The desorption process of the PLL-g-PEG is observed to be highly selective, rapid, and reversible without compromising on the integrity and performance of the conductive ITO microelectrodes. As such, we have successfully created a stable and heterogeneous microarray of biomolecules by using selective electronic addressing on ITO microelectrodes. Both pharmaceutical diagnostics and biomedical technology are expected to benefit directly from this unique method.

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

    International Nuclear Information System (INIS)

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

    2016-01-01

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

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2016-04-14

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

  10. Membrane vesiculation induced by proteins of the dengue virus envelope studied by molecular dynamics simulations

    Science.gov (United States)

    de Oliveira dos Santos Soares, Ricardo; Oliveira Bortot, Leandro; van der Spoel, David; Caliri, Antonio

    2017-12-01

    Biological membranes are continuously remodeled in the cell by specific membrane-shaping machineries to form, for example, tubes and vesicles. We examine fundamental mechanisms involved in the vesiculation processes induced by a cluster of envelope (E) and membrane (M) proteins of the dengue virus (DENV) using molecular dynamics simulations and a coarse-grained model. We show that an arrangement of three E-M heterotetramers (EM3) works as a bending unit and an ordered cluster of five such units generates a closed vesicle, reminiscent of the virus budding process. In silico mutagenesis of two charged residues of the anchor helices of the envelope proteins of DENV shows that Arg-471 and Arg-60 are fundamental to produce bending stress on the membrane. The fine-tuning between the size of the EM3 unit and its specific bending action suggests this protein unit is an important factor in determining the viral particle size.

  11. AERATION OF THE ICE-COVERED WATER POOLS USING THE WAVE FLOW AERATOR

    Directory of Open Access Journals (Sweden)

    Solomin E.E

    2013-12-01

    Full Text Available This article describes the technical advantages and economic benefits of the ice-covered pool aeration plants consuming power from renewable energy sources. We made a comparative evaluation of the wave flow-aeration method and other methods of pool aeration. We showed the indexes and the characteristics of the wave flow-maker for aeration of ice-covered pools on the territory of Russia. We also made calculations of the economic benefits of aeration plants using the devices converting renewable energy. The project can be scaled and extended to the territory of the CIS, Europe, USA and Canada in the changing climate conditions and the variety of feed reservoirs around the world.

  12. Parametric Study of the Effect of Membrane Tension on Sunshield Dynamics

    Science.gov (United States)

    Ross, Brian; Johnston, John D.; Smith, James

    2002-01-01

    The NGST sunshield is a lightweight, flexible structure consisting of pretensioned membranes supported by deployable booms. The structural dynamic behavior of the sunshield must be well understood in order to predict its influence on observatory performance. A 1/10th scale model of the sunshield has been developed for ground testing to provide data to validate modeling techniques for thin film membrane structures. The validated models can then be used to predict the behaviour of the full scale sunshield. This paper summarizes the most recent tests performed on the 1/10th scale sunshield to study the effect of membrane preload on sunshield dynamics. Topics to be covered include the test setup, procedures, and a summary of results.

  13. Effect of Galactosylceramide on the Dynamics of Cholesterol-Rich Lipid Membranes

    DEFF Research Database (Denmark)

    Hall, A.; Rog, T.; Vattulainen, I.

    2011-01-01

    We use atom-scale molecular dynamics simulations to clarify the role of glycosphingolipids in the dynamics of cholesterol-rich lipid rafts. To this end, we consider lipid membranes that contain varying. amounts of galactosylceramide (GalCer), sphingomyelin, cholesterol, and phosphatidylcholine....... The results indicate that increasing the portion of GalCer molecules greatly slows down the lateral diffusion, Only 5-10 mol % of GalCer causes a decrease of almost an order of magnitude compared to corresponding membranes without GalCer. The slowing down is not related to interdigitation, which becomes...... weaker with increasing GalCer concentration. Instead, the decrease in diffusion is found to correlate with the increasing number of hydrogen bonds formed between GalCer and the phospholipid molecules, which is also observed to have other effects, such as to increase the friction between the membrane...

  14. Removal of radon by aeration: testing of various aeration techniques for small water works. For European Commission under Contract No FI4PCT960054 TENAWA project

    International Nuclear Information System (INIS)

    Salonen, L.; Mehtonen, J.; Turunen, H.; Mjoenes, L.; Hagberg, N.; Raff, O.

    2002-12-01

    Capability of various aeration techniques to remove radon from water in small waterworks was studied as a part of project (Treatment Techniques for Removing Natural Radionuclides from Drinking Water), which was carried out during 1997-1999 on a cost-shared basis (contract No. F14PCT960054) with The European Commission (CEC) under the supervision of the Directorate-General XII Radiation Protection Research Unit. In TENAWA project both laboratory and field experiments were performed in order to find reliable methods and equipment for removing natural radionuclides from ground water originating either from private wells or small waterworks. Because such techniques are more often needed in private households than at waterworks, the main emphasis of the research was aimed to solve the water treatment problems related to the private water supplies, especially bedrock wells. Radon was the most important radionuclide to be removed from water at waterworks whereas the removal of other radionuclides ( 234,238 U, 226,228 Ra, 210 Pb and 210 Po) was oft required from radonrich bedrock waters. The currently available methods and equipment were mainly tested during the field and laboratory experiments but the project was also aimed to find new materials, absorbents and membranes applicable for radionuclide removal from various types of ground waters (e.g. soft, hard, acidic). Because iron, manganese or organic occur in waters with radionuclides, their simultaneous removal was also studied. The project was divided into 13 work packages. In this report the results of the work package 2.2 are described. Elevated levels of radon and other natural radionuclides in European ground waters have been observed mainly in wide areas of the crystalline Scandinavian bedrock, especially in the granite rock areas of Finland and Sweden but also in more limited crystalline rock areas of Central and Southern Europe, Ukraine and Scotland. The radon removal efficiencies of different aeration methods

  15. Molecular Dynamics Simulations of Phospholipid Membranes and Their Interaction with Phospholipase A2

    NARCIS (Netherlands)

    Berendsen, Herman; Egberts, Bert; Marrink, Siewert; Ahlstroem, Peter; Pullman, Alberte; Jortner, Joshua; Pullman, Bernhard

    1992-01-01

    Molecular Dynamics computer simulations have been carried out both on simplified model systems of biological membranes and on di(palmitoyl)lecithin/water multibilayers. The results, which agree with experimental data on chain order parameters, show a considerable disorder with atomic distributions

  16. Dynamically formed hydrous zirconium (IV) oxide-polyelectrolyte membranes. III: Poly(acrylic acid) and substituted poly(acrylic acid) homo, co and terpolymer membranes

    International Nuclear Information System (INIS)

    Van Reenen, A.J.; Sanderson, R.D.

    1989-01-01

    A series of acrylic acid and substituted acrylic acid homo, co and terpolymers was synthesised. These polymers were used as polyelectrolytes in dynamically formed hydrous zirconium (iv) oxide-polyelectrolyte membranes. Substitution of the acrylic acid α-hydrogen was done to increase the number of carboxylic acid groups per monomer unit and to change the acid strength of acrylic acid carboxylic acid group. None of these changes improved the salt rejection of these membranes over that of commercially used poly(acrylic acid). Improvement in rejection was found when a hydrophobic comonomer, vinyl acetate, was used in conjunction with acrylic acid in a copolymer dynamic membrane. 16 refs., 6 figs., 1 tab

  17. Automated builder and database of protein/membrane complexes for molecular dynamics simulations.

    Directory of Open Access Journals (Sweden)

    Sunhwan Jo

    2007-09-01

    Full Text Available Molecular dynamics simulations of membrane proteins have provided deeper insights into their functions and interactions with surrounding environments at the atomic level. However, compared to solvation of globular proteins, building a realistic protein/membrane complex is still challenging and requires considerable experience with simulation software. Membrane Builder in the CHARMM-GUI website (http://www.charmm-gui.org helps users to build such a complex system using a web browser with a graphical user interface. Through a generalized and automated building process including system size determination as well as generation of lipid bilayer, pore water, bulk water, and ions, a realistic membrane system with virtually any kinds and shapes of membrane proteins can be generated in 5 minutes to 2 hours depending on the system size. Default values that were elaborated and tested extensively are given in each step to provide reasonable options and starting points for both non-expert and expert users. The efficacy of Membrane Builder is illustrated by its applications to 12 transmembrane and 3 interfacial membrane proteins, whose fully equilibrated systems with three different types of lipid molecules (DMPC, DPPC, and POPC and two types of system shapes (rectangular and hexagonal are freely available on the CHARMM-GUI website. One of the most significant advantages of using the web environment is that, if a problem is found, users can go back and re-generate the whole system again before quitting the browser. Therefore, Membrane Builder provides the intuitive and easy way to build and simulate the biologically important membrane system.

  18. Dynamics of the Glycophorin A Dimer in Membranes of Native-Like Composition Uncovered by Coarse-Grained Molecular Dynamics Simulations.

    Science.gov (United States)

    Flinner, Nadine; Schleiff, Enrico

    2015-01-01

    Membranes are central for cells as borders to the environment or intracellular organelle definition. They are composed of and harbor different molecules like various lipid species and sterols, and they are generally crowded with proteins. The membrane system is very dynamic and components show lateral, rotational and translational diffusion. The consequence of the latter is that phase separation can occur in membranes in vivo and in vitro. It was documented that molecular dynamics simulations of an idealized plasma membrane model result in formation of membrane areas where either saturated lipids and cholesterol (liquid-ordered character, Lo) or unsaturated lipids (liquid-disordered character, Ld) were enriched. Furthermore, current discussions favor the idea that proteins are sorted into the liquid-disordered phase of model membranes, but experimental support for the behavior of isolated proteins in native membranes is sparse. To gain insight into the protein behavior we built a model of the red blood cell membrane with integrated glycophorin A dimer. The sorting and the dynamics of the dimer were subsequently explored by coarse-grained molecular dynamics simulations. In addition, we inspected the impact of lipid head groups and the presence of cholesterol within the membrane on the dynamics of the dimer within the membrane. We observed that cholesterol is important for the formation of membrane areas with Lo and Ld character. Moreover, it is an important factor for the reproduction of the dynamic behavior of the protein found in its native environment. The protein dimer was exclusively sorted into the domain of Ld character in the model red blood cell plasma membrane. Therefore, we present structural information on the glycophorin A dimer distribution in the plasma membrane in the absence of other factors like e.g. lipid anchors in a coarse grain resolution.

  19. Dynamics of the Glycophorin A Dimer in Membranes of Native-Like Composition Uncovered by Coarse-Grained Molecular Dynamics Simulations.

    Directory of Open Access Journals (Sweden)

    Nadine Flinner

    Full Text Available Membranes are central for cells as borders to the environment or intracellular organelle definition. They are composed of and harbor different molecules like various lipid species and sterols, and they are generally crowded with proteins. The membrane system is very dynamic and components show lateral, rotational and translational diffusion. The consequence of the latter is that phase separation can occur in membranes in vivo and in vitro. It was documented that molecular dynamics simulations of an idealized plasma membrane model result in formation of membrane areas where either saturated lipids and cholesterol (liquid-ordered character, Lo or unsaturated lipids (liquid-disordered character, Ld were enriched. Furthermore, current discussions favor the idea that proteins are sorted into the liquid-disordered phase of model membranes, but experimental support for the behavior of isolated proteins in native membranes is sparse. To gain insight into the protein behavior we built a model of the red blood cell membrane with integrated glycophorin A dimer. The sorting and the dynamics of the dimer were subsequently explored by coarse-grained molecular dynamics simulations. In addition, we inspected the impact of lipid head groups and the presence of cholesterol within the membrane on the dynamics of the dimer within the membrane. We observed that cholesterol is important for the formation of membrane areas with Lo and Ld character. Moreover, it is an important factor for the reproduction of the dynamic behavior of the protein found in its native environment. The protein dimer was exclusively sorted into the domain of Ld character in the model red blood cell plasma membrane. Therefore, we present structural information on the glycophorin A dimer distribution in the plasma membrane in the absence of other factors like e.g. lipid anchors in a coarse grain resolution.

  20. Vacancy profile in reverse osmosis membranes studied by positron annihilation lifetime measurements and molecular dynamics simulations

    International Nuclear Information System (INIS)

    Shimazu, A; Shintani, T; Hirose, M; Goto, H; Suzuki, R; Kobayashi, Y

    2013-01-01

    The positron annihilation technique using a slow positron beam can be used for the study of the vacancy profiles in typical reverse osmosis (RO) membranes. In this study, the vacancy profile in the polyamide membrane that exhibits a high permselectivity between ions and water was studied using the positron annihilation technique and molecular dynamics simulations. Ortho-positronium (o-Ps) lifetimes in the surface region of the membranes were evaluated by using a slow positron beam. The diffusion behavior of Na + and water in the polyamides was simulated by molecular dynamics (MD) methods using the TSUBAME2 supercomputer at the Tokyo Institute of Technology and discussed with the vacancy profile probed by the o-Ps. The results suggested that the large hydration size of Na + compared to the vacancy size in the polyamides contributes to the increased diffusivity selectivity of water/Na + that is related to the NaCl desalination performance of the membrane. Both the hydration size of the ions and the vacancy size appeared to be significant parameters to discuss the diffusivity selectivity of water/ions in typical polyamide membranes.

  1. Some effects of aeration on anaerobic digestion

    Energy Technology Data Exchange (ETDEWEB)

    Bhywapathanapun, S

    1972-01-01

    The anaerobic digestion of meat works waste water is made possible by separating the sludge solids, after which necessary amounts of the concentrated sludge are returned to the digester. Sludge recirculation prolongs solid retention time in the digester. However, sludge separation by gravitational sedimentation is almost impossible because the sludge tends to rise with the continuous gassing. Therefore treatment of the sludge suspension prior to sedimentation is necessary for effective solid separation. The present study examined aeration degasification as a method for sludge suspension pretreatment and found that the rates of aeration of 0.75 to 1.0 VVM (0.12 to 0.16 cubic foot of air per gallon of mixed liquor per minute) were optimal for aeration degasification. The toxic effects on the anaerobic bacteria were small, daily gas production being reduced by only 5%.

  2. Structure and dynamics of cationic membrane peptides and proteins: Insights from solid-state NMR

    Science.gov (United States)

    Hong, Mei; Su, Yongchao

    2011-01-01

    Many membrane peptides and protein domains contain functionally important cationic Arg and Lys residues, whose insertion into the hydrophobic interior of the lipid bilayer encounters significant energy barriers. To understand how these cationic molecules overcome the free energy barrier to insert into the lipid membrane, we have used solid-state NMR spectroscopy to determine the membrane-bound topology of these peptides. A versatile array of solid-state NMR experiments now readily yields the conformation, dynamics, orientation, depth of insertion, and site-specific protein–lipid interactions of these molecules. We summarize key findings of several Arg-rich membrane peptides, including β-sheet antimicrobial peptides, unstructured cell-penetrating peptides, and the voltage-sensing helix of voltage-gated potassium channels. Our results indicate the central role of guanidinium-phosphate and guanidinium-water interactions in dictating the structural topology of these cationic molecules in the lipid membrane, which in turn account for the mechanisms of this functionally diverse class of membrane peptides. PMID:21344534

  3. Effects of deformability and thermal motion of lipid membrane on electroporation: By molecular dynamics simulations

    International Nuclear Information System (INIS)

    Sun, Sheng; Yin, Guangyao; Lee, Yi-Kuen; Wong, Joseph T.Y.; Zhang, Tong-Yi

    2011-01-01

    Research highlights: → MD simulations show that deformability and thermal motion of membrane affect electroporation. → Stiffer membrane inhibits electroporation and makes water penetrate from both sides. → Higher temperature accelerates electroporation. -- Abstract: Effects of mechanical properties and thermal motion of POPE lipid membrane on electroporation were studied by molecular dynamics simulations. Among simulations in which specific atoms of lipids were artificially constrained at their equilibrium positions using a spring with force constant of 2.0 kcal/(mol A 2 ) in the external electric field of 1.4 kcal/(mol A e), only constraint on lateral motions of lipid tails prohibited electroporation while non-tail parts had little effects. When force constant decreased to 0.2 kcal/(mol A 2 ) in the position constraints on lipid tails in the external electric field of 2.0 kcal/(mol A e), water molecules began to enter the membrane. Position constraints of lipid tails allow water to penetrate from both sides of membrane. Thermal motion of lipids can induce initial defects in the hydrophobic core of membrane, which are favorable nucleation sites for electroporation. Simulations at different temperatures revealed that as the temperature increases, the time taken to the initial pore formation will decrease.

  4. Plasma membrane organization and dynamics is probe and cell line dependent.

    Science.gov (United States)

    Huang, Shuangru; Lim, Shi Ying; Gupta, Anjali; Bag, Nirmalya; Wohland, Thorsten

    2017-09-01

    The action and interaction of membrane receptor proteins take place within the plasma membrane. The plasma membrane, however, is not a passive matrix. It rather takes an active role and regulates receptor distribution and function by its composition and the interaction of its lipid components with embedded and surrounding proteins. Furthermore, it is not a homogenous fluid but contains lipid and protein domains of various sizes and characteristic lifetimes which are important in regulating receptor function and signaling. The precise lateral organization of the plasma membrane, the differences between the inner and outer leaflet, and the influence of the cytoskeleton are still debated. Furthermore, there is a lack of comparisons of the organization and dynamics of the plasma membrane of different cell types. Therefore, we used four different specific membrane markers to test the lateral organization, the differences between the inner and outer membrane leaflet, and the influence of the cytoskeleton of up to five different cell lines, including Chinese hamster ovary (CHO-K1), Human cervical carcinoma (HeLa), neuroblastoma (SH-SY5Y), fibroblast (WI-38) and rat basophilic leukemia (RBL-2H3) cells by Imaging Total Internal Reflection (ITIR)-Fluorescence Correlation Spectroscopy (FCS). We measure diffusion in the temperature range of 298-310K to measure the Arrhenius activation energy (E Arr ) of diffusion and apply the FCS diffusion law to obtain information on the spatial organization of the probe molecules on the various cell membranes. Our results show clear differences of the FCS diffusion law and E Arr for the different probes in dependence of their localization. These differences are similar in the outer and inner leaflet of the membrane. However, these values can differ significantly between different cell lines raising the question how molecular plasma membrane events measured in different cell lines can be compared. This article is part of a Special Issue

  5. Bacterial subversion of host actin dynamics at the plasma membrane.

    Science.gov (United States)

    Carabeo, Rey

    2011-10-01

    Invasion of non-phagocytic cells by a number of bacterial pathogens involves the subversion of the actin cytoskeletal remodelling machinery to produce actin-rich cell surface projections designed to engulf the bacteria. The signalling that occurs to induce these actin-rich structures has considerable overlap among a diverse group of bacteria. The molecular organization within these structures act in concert to internalize the invading pathogen. This dynamic process could be subdivided into three acts - actin recruitment, engulfment, and finally, actin disassembly/internalization. This review will present the current state of knowledge of the molecular processes involved in each stage of bacterial invasion, and provide a perspective that highlights the temporal and spatial control of actin remodelling that occurs during bacterial invasion. © 2011 Blackwell Publishing Ltd.

  6. Parallel computing and molecular dynamics of biological membranes

    International Nuclear Information System (INIS)

    La Penna, G.; Letardi, S.; Minicozzi, V.; Morante, S.; Rossi, G.C.; Salina, G.

    1998-01-01

    In this talk I discuss the general question of the portability of molecular dynamics codes for diffusive systems on parallel computers of the APE family. The intrinsic single precision of the today available platforms does not seem to affect the numerical accuracy of the simulations, while the absence of integer addressing from CPU to individual nodes puts strong constraints on possible programming strategies. Liquids can be satisfactorily simulated using the ''systolic'' method. For more complex systems, like the biological ones at which we are ultimately interested in, the ''domain decomposition'' approach is best suited to beat the quadratic growth of the inter-molecular computational time with the number of atoms of the system. The promising perspectives of using this strategy for extensive simulations of lipid bilayers are briefly reviewed. (orig.)

  7. Super-resolution optical microscopy for studying membrane structure and dynamics.

    Science.gov (United States)

    Sezgin, Erdinc

    2017-07-12

    Investigation of cell membrane structure and dynamics requires high spatial and temporal resolution. The spatial resolution of conventional light microscopy is limited due to the diffraction of light. However, recent developments in microscopy enabled us to access the nano-scale regime spatially, thus to elucidate the nanoscopic structures in the cellular membranes. In this review, we will explain the resolution limit, address the working principles of the most commonly used super-resolution microscopy techniques and summarise their recent applications in the biomembrane field.

  8. Iron removal using an aerated granular filter

    Energy Technology Data Exchange (ETDEWEB)

    Cho, B.Y. [Dongguk University, Seoul (Republic of Korea). College of Engineering

    2005-10-01

    Laboratory scale experiments concerning iron removal from artificial raw water by an artificial filter using anthracite as filter media were conducted. The major findings were that iron oxidation and removal by an aerated filter is mainly a catalytic chemical reaction rather than a biological reaction. Further, iron removal does not perform effectively without aeration. Iron removal was very effective when the pH was weakly acidity. Iron oxide attached to the surface of the media is identified as ferrihydrite, which catalyzes the oxidation of iron as shown by Moessbauer spectra analysis.

  9. Shear reinforced beams in autoclaved aerated concrete

    DEFF Research Database (Denmark)

    Cornelius, Thomas

    2010-01-01

    Shear behaviour in concrete materials is very well documented, for normal density concrete materials. In this paper results of various tests on low density concrete materials like aerated autoclaved concrete (in the following denoted aircrete) will be presented and analyzed for different combinat....... Codes for designing prefabricated reinforced components of aircrete structures have adopted these recently developed approaches.......Shear behaviour in concrete materials is very well documented, for normal density concrete materials. In this paper results of various tests on low density concrete materials like aerated autoclaved concrete (in the following denoted aircrete) will be presented and analyzed for different...

  10. Acid mine water aeration and treatment system

    Science.gov (United States)

    Ackman, Terry E.; Place, John M.

    1987-01-01

    An in-line system is provided for treating acid mine drainage which basically comprises the combination of a jet pump (or pumps) and a static mixer. The jet pump entrains air into the acid waste water using a Venturi effect so as to provide aeration of the waste water while further aeration is provided by the helical vanes of the static mixer. A neutralizing agent is injected into the suction chamber of the jet pump and the static mixer is formed by plural sections offset by 90 degrees.

  11. Structural features and dynamic investigations of the membrane-bound cytochrome P450 17A1.

    Science.gov (United States)

    Cui, Ying-Lu; Xue, Qiao; Zheng, Qing-Chuan; Zhang, Ji-Long; Kong, Chui-Peng; Fan, Jing-Rong; Zhang, Hong-Xing

    2015-10-01

    Cytochrome P450 (CYP) 17A1 is a dual-function monooxygenase with a critical role in the synthesis of many human steroid hormones. The enzyme is an important target for treatment of breast and prostate cancers that proliferate in response to estrogens and androgens. Despite the crystallographic structures available for CYP17A1, no membrane-bound structural features of this enzyme at atomic level are available. Accumulating evidence has indicated that the interactions between bounded CYPs and membrane could contribute to the recruitment of lipophilic substrates. To this end, we have investigated the effects on structural characteristics in the presence of the membrane for CYP17A1. The MD simulation results demonstrate a spontaneous insertion process of the enzyme to the lipid. Two predominant modes of CYP17A1 in the membrane are captured, characterized by the depths of insertion and orientations of the enzyme to the membrane surface. The measured heme tilt angles show good consistence with experimental data, thereby verifying the validity of the structural models. Moreover, conformational changes induced by the membrane might have impact on the accessibility of the active site to lipophilic substrates. The dynamics of internal aromatic gate formed by Trp220 and Phe224 are suggested to regulate tunnel opening motions. The knowledge of the membrane binding characteristics could guide future experimental and computational works on membrane-bound CYPs so that various investigations of CYPs in their natural, lipid environment rather than in artificially solubilized forms may be achieved. Copyright © 2015. Published by Elsevier B.V.

  12. Dynamics of a bilayer membrane coupled to a two-dimensional cytoskeleton: Scale transfers of membrane deformations

    Science.gov (United States)

    Okamoto, Ryuichi; Komura, Shigeyuki; Fournier, Jean-Baptiste

    2017-07-01

    We theoretically investigate the dynamics of a floating lipid bilayer membrane coupled with a two-dimensional cytoskeleton network, taking into account explicitly the intermonolayer friction, the discrete lattice structure of the cytoskeleton, and its prestress. The lattice structure breaks lateral continuous translational symmetry and couples Fourier modes with different wave vectors. It is shown that within a short time interval a long-wavelength deformation excites a collection of modes with wavelengths shorter than the lattice spacing. These modes relax slowly with a common renormalized rate originating from the long-wavelength mode. As a result, and because of the prestress, the slowest relaxation is governed by the intermonolayer friction. Conversely, and most interestingly, forces applied at the scale of the cytoskeleton for a sufficiently long time can cooperatively excite large-scale modes.

  13. Analysis of direct contact membrane distillation based on a lumped-parameter dynamic predictive model

    KAUST Repository

    Karam, Ayman M.

    2016-10-03

    Membrane distillation (MD) is an emerging technology that has a great potential for sustainable water desalination. In order to pave the way for successful commercialization of MD-based water desalination techniques, adequate and accurate dynamical models of the process are essential. This paper presents the predictive capabilities of a lumped-parameter dynamic model for direct contact membrane distillation (DCMD) and discusses the results under wide range of steady-state and dynamic conditions. Unlike previous studies, the proposed model captures the time response of the spacial temperature distribution along the flow direction. It also directly solves for the local temperatures at the membrane interfaces, which allows to accurately model and calculate local flux values along with other intrinsic variables of great influence on the process, like the temperature polarization coefficient (TPC). The proposed model is based on energy and mass conservation principles and analogy between thermal and electrical systems. Experimental data was collected to validated the steady-state and dynamic responses of the model. The obtained results shows great agreement with the experimental data. The paper discusses the results of several simulations under various conditions to optimize the DCMD process efficiency and analyze its response. This demonstrates some potential applications of the proposed model to carry out scale up and design studies. © 2016

  14. Analysis of direct contact membrane distillation based on a lumped-parameter dynamic predictive model

    KAUST Repository

    Karam, Ayman M.; Alsaadi, Ahmad Salem; Ghaffour, NorEddine; Laleg-Kirati, Taous-Meriem

    2016-01-01

    Membrane distillation (MD) is an emerging technology that has a great potential for sustainable water desalination. In order to pave the way for successful commercialization of MD-based water desalination techniques, adequate and accurate dynamical models of the process are essential. This paper presents the predictive capabilities of a lumped-parameter dynamic model for direct contact membrane distillation (DCMD) and discusses the results under wide range of steady-state and dynamic conditions. Unlike previous studies, the proposed model captures the time response of the spacial temperature distribution along the flow direction. It also directly solves for the local temperatures at the membrane interfaces, which allows to accurately model and calculate local flux values along with other intrinsic variables of great influence on the process, like the temperature polarization coefficient (TPC). The proposed model is based on energy and mass conservation principles and analogy between thermal and electrical systems. Experimental data was collected to validated the steady-state and dynamic responses of the model. The obtained results shows great agreement with the experimental data. The paper discusses the results of several simulations under various conditions to optimize the DCMD process efficiency and analyze its response. This demonstrates some potential applications of the proposed model to carry out scale up and design studies. © 2016

  15. Dynamic molecular confinement in the plasma membrane by microdomains and the cytoskeleton meshwork.

    Science.gov (United States)

    Lenne, Pierre-François; Wawrezinieck, Laure; Conchonaud, Fabien; Wurtz, Olivier; Boned, Annie; Guo, Xiao-Jun; Rigneault, Hervé; He, Hai-Tao; Marguet, Didier

    2006-07-26

    It is by now widely recognized that cell membranes show complex patterns of lateral organization. Two mechanisms involving either a lipid-dependent (microdomain model) or cytoskeleton-based (meshwork model) process are thought to be responsible for these plasma membrane organizations. In the present study, fluorescence correlation spectroscopy measurements on various spatial scales were performed in order to directly identify and characterize these two processes in live cells with a high temporal resolution, without any loss of spatial information. Putative raft markers were found to be dynamically compartmented within tens of milliseconds into small microdomains (Ø confinement of the transferrin receptor protein. A free-like diffusion was observed when both the lipid-dependent and cytoskeleton-based organizations were disrupted, which suggests that these are two main compartmentalizing forces at work in the plasma membrane.

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

    DEFF Research Database (Denmark)

    Rønnest, A. K.; Peters, Günther H.J.; Hansen, Flemming Yssing

    2016-01-01

    Molecular dynamics simulations have been used to investigate the influence of the valency of counter-ions on the structure of freestanding bilayer membranes of the anionic 1,2-dimyristoyl-sn-glycero-3-phosphoglycerol (DMPG) lipid at 310 K and 1 atm. At this temperature, the membrane is in the fluid...... compared to experimental results and used to determine an average diffusion constant for all water molecules in the system. On extrapolating the diffusion constants inferred experimentally to a temperature of 310 K, reasonable agreement with the simulations is obtained. However, the experiments do not have...... the sensitivity to confirm the diffusion of a small component of water bound to the lipids as found in the simulations. In addition, the orientation of the dipole moment of the water molecules has been determined as a function of their depth in the membrane. Previous indirect estimates of the electrostatic...

  17. Effects of tailwater depth on spillway aeration

    African Journals Online (AJOL)

    2011-04-15

    Apr 15, 2011 ... Hydraulic structures such as spillways or weirs with their water-air controlling mechanisms are not only important for their structural properties but also for their effects on downstream ecology. Tailwater depth is an important factor affecting dissolved oxygen transfer and aeration rates of spillways. In this ...

  18. Plasma membrane factor XIIIA transglutaminase activity regulates osteoblast matrix secretion and deposition by affecting microtubule dynamics.

    Directory of Open Access Journals (Sweden)

    Hadil F Al-Jallad

    2011-01-01

    Full Text Available Transglutaminase activity, arising potentially from transglutaminase 2 (TG2 and Factor XIIIA (FXIIIA, has been linked to osteoblast differentiation where it is required for type I collagen and fibronectin matrix deposition. In this study we have used an irreversible TG-inhibitor to 'block -and-track' enzyme(s targeted during osteoblast differentiation. We show that the irreversible TG-inhibitor is highly potent in inhibiting osteoblast differentiation and mineralization and reduces secretion of both fibronectin and type I collagen and their release from the cell surface. Tracking of the dansyl probe by Western blotting and immunofluorescence microscopy demonstrated that the inhibitor targets plasma membrane-associated FXIIIA. TG2 appears not to contribute to crosslinking activity on the osteoblast surface. Inhibition of FXIIIA with NC9 resulted in defective secretory vesicle delivery to the plasma membrane which was attributable to a disorganized microtubule network and decreased microtubule association with the plasma membrane. NC9 inhibition of FXIIIA resulted in destabilization of microtubules as assessed by cellular Glu-tubulin levels. Furthermore, NC9 blocked modification of Glu-tubulin into 150 kDa high-molecular weight Glu-tubulin form which was specifically localized to the plasma membrane. FXIIIA enzyme and its crosslinking activity were colocalized with plasma membrane-associated tubulin, and thus, it appears that FXIIIA crosslinking activity is directed towards stabilizing the interaction of microtubules with the plasma membrane. Our work provides the first mechanistic cues as to how transglutaminase activity could affect protein secretion and matrix deposition in osteoblasts and suggests a novel function for plasma membrane FXIIIA in microtubule dynamics.

  19. Membrane dynamics of γ-secretase provides a molecular basis for Aβ binding and processing

    DEFF Research Database (Denmark)

    Somavarapu, Arun Kumar; Kepp, Kasper Planeta

    2017-01-01

    and explicit dynamics relevant to substrate processing remain unknown. We report a modeled structure utilizing the optimal multi-template information available, including loops and missing side chains, account of maturation cleavage, and explicit all-atom molecular dynamics in the membrane. We observe three...... interactions and induces shorter residence time and by inference releases Aβ peptides of longer lengths. Our simulations thus provide a molecular basis for substrate processing and changes in the Aβ42/Aβ40 ratio. Accordingly, selective binding to protect the semi-open “innocent” conformation provides......γ-secretase produces β-amyloid (Aβ) within its presenilin (PS1) subunit, mutations in which cause Alzheimer’s disease, and current therapies thus seek to modulate its activity. While the general structure is known from recent electron microscopy studies, direct loop- and membrane-interactions...

  20. Mitochondrial membranes with mono- and divalent salt: changes induced by salt ions on structure and dynamics

    DEFF Research Database (Denmark)

    Pöyry, Sanja; Róg, Tomasz; Karttunen, Mikko

    2009-01-01

    We employ atomistic simulations to consider how mono- (NaCl) and divalent (CaCl(2)) salt affects properties of inner and outer membranes of mitochondria. We find that the influence of salt on structural properties is rather minute, only weakly affecting lipid packing, conformational ordering......, and membrane electrostatic potential. The changes induced by salt are more prominent in dynamical properties related to ion binding and formation of ion-lipid complexes and lipid aggregates, as rotational diffusion of lipids is slowed down by ions, especially in the case of CaCl(2). In the same spirit, lateral...... diffusion of lipids is slowed down rather considerably for increasing concentration of CaCl(2). Both findings for dynamic properties can be traced to the binding of ions with lipid head groups and the related changes in interaction patterns in the headgroup region, where the binding of Na(+) and Ca(2+) ions...

  1. Comparison of Four Types of Membrane Bioreactor Systems in Terms of Shear Stress over the Membrane Surface using Computational Fluid Dynamics

    DEFF Research Database (Denmark)

    Ratkovich, Nicolas Rios; Bentzen, Thomas Ruby

    2013-01-01

    Membrane bioreactors (MBRs) have been used successfully in biological wastewater treatment to solve the perennial problem of effective solids–liquid separation. A common problem with MBR systems is clogging of the modules and fouling of the membrane, resulting in frequent cleaning and replacement...... and requires knowledge of the membrane fouling, hydrodynamics and biokinetics. Modern tools such as computational fluid dynamics (CFD) can be used to diagnose and understand the two-phase flow in an MBR. Four cases of different MBR configurations are presented in this work, using CFD as a tool to develop...

  2. Near-membrane dynamics and capture of TRPM8 channels within transient confinement domains.

    Directory of Open Access Journals (Sweden)

    Luis A Veliz

    Full Text Available BACKGROUND: The cold and menthol receptor, TRPM8, is a non-selective cation channel expressed in a subset of peripheral neurons that is responsible for neuronal detection of environmental cold stimuli. It was previously shown that members of the transient receptor potential (TRP family of ion channels are translocated toward the plasma membrane (PM in response to agonist stimulation. Because the spatial and temporal dynamics of cold receptor cell-surface residence may determine neuronal activity, we hypothesized that the movement of TRPM8 to and from the PM might be a regulated process. Single particle tracking (SPT is a useful tool for probing the organization and dynamics of protein constituents in the plasma membrane. METHODOLOGY/PRINCIPAL FINDINGS: We used SPT to study the receptor dynamics and describe membrane/near-membrane behavior of particles containing TRPM8-EGFP in transfected HEK-293T and F-11 cells. Cells were imaged using total internal reflection fluorescence (TIRF microscopy and the 2D and 3D trajectories of TRPM8 molecules were calculated by analyzing mean-square particle displacement against time. Four characteristic types of motion were observed: stationary mode, simple Brownian diffusion, directed motion, and confined diffusion. In the absence of cold or menthol to activate the channel, most TRPM8 particles move in network covering the PM, periodically lingering for 2-8 s in confined microdomains of about 800 nm radius. Removing cholesterol with methyl-beta-cyclodextrin (MβCD stabilizes TRPM8 motion in the PM and is correlated with larger TRPM8 current amplitude that results from an increase in the number of available channels without a change in open probability. CONCLUSIONS/SIGNIFICANCE: These results reveal a novel mechanism for regulating TRPM8 channel activity, and suggest that PM dynamics may play an important role in controlling electrical activity in cold-sensitive neurons.

  3. Dynamic Model of the High Temperature Proton Exchange Membrane Fuel Cell Stack Temperature

    DEFF Research Database (Denmark)

    Andreasen, Søren Juhl; Kær, Søren Knudsen

    2009-01-01

    The present work involves the development of a model for predicting the dynamic temperature of a high temperature proton exchange membrane (HTPEM) fuel cell stack. The model is developed to test different thermal control strategies before implementing them in the actual system. The test system co...... elements for start-up, heat conduction through stack insulation, cathode air convection, and heating of the inlet gases in the manifold. Various measurements are presented to validate the model predictions of the stack temperatures....

  4. PDMS/PVDF hybrid electrospun membrane with superhydrophobic property and drop impact dynamics for dyeing wastewater treatment using membrane distillation

    KAUST Repository

    An, Alicia Kyoungjin

    2016-10-21

    Fouling in membrane distillation (MD) results in an increase in operation costs and deterioration in a water quality. In this work, a poly(vinylidene fluoride-co-hexafluoropropene) (PVDF-HFP) electrospun (E-PH) membrane was fabricated by hybridizing polydimethylsiloxane (PDMS) polymeric microspheres with superhydrophobicity onto the E-PH membrane via electrospinning. The resulting hybrid PDMS with E-PH (E-PDMS) membrane showed a significant enhancement in surface hydrophobicity (contact angle, CA = 155.4°) and roughness (Ra = 1,285mm). The zeta potential of E-PDMS membrane surface showed a higher negative value than that of a commercial PVDF (C-PVDF) membrane. These properties of E-PDMS membrane provided an antifouling in treating of differently-charged dyes and generated a flake-like dye–dye (loosely bound foulant) structure on the membrane surface rather than in the membrane pores. This also led to a high productivity of E-PDMS membrane (34 Lm-2h-1, 50% higher than that of C-PVDF membrane) without fouling or wetting. In addition, complete color removal and pure water production were achieved during a long-term operation. An application of intermittent water flushing (WF) in direct contact MD (DCMD) operation led to a 99% CA recovery of E-PDMS membrane indicating its sustainability. Therefore, the E-PDMS membrane is a promising candidate for MD application in dyeing wastewater treatment.

  5. PDMS/PVDF hybrid electrospun membrane with superhydrophobic property and drop impact dynamics for dyeing wastewater treatment using membrane distillation

    KAUST Repository

    An, Alicia Kyoungjin; Guo, Jiaxin; Lee, Eui-Jong; Jeong, Sanghyun; Zhao, Yanhua; Wang, Zuankai; Leiknes, TorOve

    2016-01-01

    .4°) and roughness (Ra = 1,285mm). The zeta potential of E-PDMS membrane surface showed a higher negative value than that of a commercial PVDF (C-PVDF) membrane. These properties of E-PDMS membrane provided an antifouling in treating of differently-charged dyes

  6. Molecular dynamics study of lipid bilayers modeling the plasma membranes of normal murine thymocytes and leukemic GRSL cells.

    Science.gov (United States)

    Andoh, Yoshimichi; Okazaki, Susumu; Ueoka, Ryuichi

    2013-04-01

    Molecular dynamics (MD) calculations for the plasma membranes of normal murine thymocytes and thymus-derived leukemic GRSL cells in water have been performed under physiological isothermal-isobaric conditions (310.15K and 1 atm) to investigate changes in membrane properties induced by canceration. The model membranes used in our calculations for normal and leukemic thymocytes comprised 23 and 25 kinds of lipids, respectively, including phosphatidylcholine, phosphatidylethanolamine, phosphatidylserine, phosphatidylinositol, sphingomyelin, lysophospholipids, and cholesterol. The mole fractions of the lipids adopted here were based on previously published experimental values. Our calculations clearly showed that the membrane area was increased in leukemic cells, and that the isothermal area compressibility of the leukemic plasma membranes was double that of normal cells. The calculated membranes of leukemic cells were thus considerably bulkier and softer in the lateral direction compared with those of normal cells. The tilt angle of the cholesterol and the conformation of the phospholipid fatty acid tails both showed a lower level of order in leukemic cell membranes compared with normal cell membranes. The lateral radial distribution function of the lipids also showed a more disordered structure in leukemic cell membranes than in normal cell membranes. These observations all show that, for the present thymocytes, the lateral structure of the membrane is considerably disordered by canceration. Furthermore, the calculated lateral self-diffusion coefficient of the lipid molecules in leukemic cell membranes was almost double that in normal cell membranes. The calculated rotational and wobbling autocorrelation functions also indicated that the molecular motion of the lipids was enhanced in leukemic cell membranes. Thus, here we have demonstrated that the membranes of thymocyte leukemic cells are more disordered and more fluid than normal cell membranes. Copyright © 2013

  7. Dynamic solar-powered multi-stage direct contact membrane distillation system: Concept design, modeling and simulation

    KAUST Repository

    Lee, Jung Gil; Kim, Woo-Seung; Choi, June-Seok; Ghaffour, NorEddine; Kim, Young-Deuk

    2017-01-01

    This paper presents a theoretical analysis of the monthly average daily and hourly performances of a solar-powered multi-stage direct contact membrane distillation (SMDCMD) system with an energy recovery scheme and dynamic operating system. Mid

  8. Nonpolar interactions between trans-membrane helical EGF peptide and phosphatidylcholines, sphingomyelins and cholesterol. Molecular dynamics simulation studies

    NARCIS (Netherlands)

    Róg, T.; Murzyn, K.; Karttunen, M.E.J.; Pasenkiewicz-Gierula, M.

    2008-01-01

    A molecular dynamics simulation study of four lipid bilayers with inserted trans-membrane helical fragment of epithelial growth factor (EGF) receptor (EGF peptide) was performed. The lipid bilayers differ in their lipid composition and consist of (i) unsaturated phosphatidylcholine

  9. Structural and dynamical insights into the membrane-bound α-synuclein.

    Directory of Open Access Journals (Sweden)

    Neha Jain

    Full Text Available Membrane-induced disorder-to-helix transition of α-synuclein, a presynaptic protein, has been implicated in a number of important neuronal functions as well as in the etiology of Parkinson's disease. In order to obtain structural insights of membrane-bound α-synuclein at the residue-specific resolution, we took advantage of the fact that the protein is devoid of tryptophan and incorporated single tryptophan at various residue positions along the sequence. These tryptophans were used as site-specific markers to characterize the structural and dynamical aspects of α-synuclein on the negatively charged small unilamellar lipid vesicles. An array of site-specific fluorescence readouts, such as the spectral-shift, quenching efficiency and anisotropy, allowed us to discern various features of the conformational rearrangements occurring at different locations of α-synuclein on the lipid membrane. In order to define the spatial localization of various regions of the protein near the membrane surface, we utilized a unique and sensitive indicator, namely, red-edge excitation shift (REES, which originates when a fluorophore is located in a highly ordered micro-environment. The extent of REES observed at different residue positions allowed us to directly identify the residues that are localized at the membrane-water interface comprising a thin (∼ 15 Å layer of motionally restrained water molecules and enabled us to construct a dynamic hydration map of the protein. The combination of site-specific fluorescence readouts allowed us to unravel the intriguing molecular details of α-synuclein on the lipid membrane in a direct model-free fashion. Additionally, the combination of methodologies described here are capable of distinguishing subtle but important structural alterations of α-synuclein bound to different negatively charged lipids with varied head-group chemistry. We believe that the structural modulations of α-synuclein on the membrane could

  10. Dynamic behavior of ultra large graphene-based membranes using electrothermal transduction

    Science.gov (United States)

    Al-mashaal, A. K.; Wood, G. S.; Torin, A.; Mastropaolo, E.; Newton, M. J.; Cheung, R.

    2017-12-01

    This letter reports an experimental study of an electrothermal actuator made from an ultra-large graphene-based bilayer thin film with a diameter to thickness aspect ratio of ˜10 000. Suspended thin films consisting of multilayer graphene and 350-500 nm-thick Poly(methyl methacrylate) have been transferred over circular cavities with a diameter of 3.5 mm. The use of bilayer materials with different mechanical and thermal properties results in thin film structures that can be induced to vibrate mechanically under the electrothermal transduction mechanism. The dynamic response of the bilayer has been investigated electrothermally by driving the structures with a combination of alternating current and direct current actuation voltages ( Va c and Vd c) and characterizing their resonant frequencies. It has been found that the bilayer thin film structure behaves as a membrane. In addition, the actuation configurations affect not only the amplitude of vibration but also the tuning of the resonant frequency of the vibrating membranes. The existence of Joule heating-induced tension lowers the mechanical stiffness of the membrane and hence shifts the resonant frequency downwards by -108187 ppm. A resonant frequency of 3.26 kHz with a vibration amplitude of 4.34 nm has been achieved for 350 nm-thick membranes under actuation voltages of 1 V of Va c and 8 V of Vd c.

  11. Spike-threshold adaptation predicted by membrane potential dynamics in vivo.

    Directory of Open Access Journals (Sweden)

    Bertrand Fontaine

    2014-04-01

    Full Text Available Neurons encode information in sequences of spikes, which are triggered when their membrane potential crosses a threshold. In vivo, the spiking threshold displays large variability suggesting that threshold dynamics have a profound influence on how the combined input of a neuron is encoded in the spiking. Threshold variability could be explained by adaptation to the membrane potential. However, it could also be the case that most threshold variability reflects noise and processes other than threshold adaptation. Here, we investigated threshold variation in auditory neurons responses recorded in vivo in barn owls. We found that spike threshold is quantitatively predicted by a model in which the threshold adapts, tracking the membrane potential at a short timescale. As a result, in these neurons, slow voltage fluctuations do not contribute to spiking because they are filtered by threshold adaptation. More importantly, these neurons can only respond to input spikes arriving together on a millisecond timescale. These results demonstrate that fast adaptation to the membrane potential captures spike threshold variability in vivo.

  12. Effects of deformability and thermal motion of lipid membrane on electroporation: By molecular dynamics simulations

    KAUST Repository

    Sun, Sheng

    2011-01-01

    Effects of mechanical properties and thermal motion of POPE lipid membrane on electroporation were studied by molecular dynamics simulations. Among simulations in which specific atoms of lipids were artificially constrained at their equilibrium positions using a spring with force constant of 2.0kcal/(molÅ2) in the external electric field of 1.4kcal/(molÅe), only constraint on lateral motions of lipid tails prohibited electroporation while non-tail parts had little effects. When force constant decreased to 0.2kcal/(molÅ2) in the position constraints on lipid tails in the external electric field of 2.0kcal/(molÅe), water molecules began to enter the membrane. Position constraints of lipid tails allow water to penetrate from both sides of membrane. Thermal motion of lipids can induce initial defects in the hydrophobic core of membrane, which are favorable nucleation sites for electroporation. Simulations at different temperatures revealed that as the temperature increases, the time taken to the initial pore formation will decrease. © 2010 Elsevier Inc.

  13. Stable aerobic granules in continuous-flow bioreactor with self-forming dynamic membrane.

    Science.gov (United States)

    Liu, Hongbo; Li, Yajie; Yang, Changzhu; Pu, Wenhong; He, Liu; Bo, Fu

    2012-10-01

    A novel continuous-flow bioreactor with aerobic granular sludge and self-forming dynamic membrane (CGSFDMBR) was developed for efficient wastewater treatment. Under continuous-flow operation, aerobic granular sludge was successfully cultivated and characterized with small particle size of about 0.1-1.0mm, low settling velocity of about 15-25 m/h, loose structure and high water content of about 96-98%. To maintain the stability of aerobic granular sludge, strategies based on the differences of settling velocity and particle-size between granular and flocculent sludge were implemented. Moreover, in CGSFDMBR, membrane fouling was greatly relieved. Dynamic membrane was just cleaned once in more than 45 days' operation. CGSFDMBR presented good performance in treating septic tank wastewater, obtaining average COD, NH(4)(+)-N, TN and TP removal rates of 83.3%, 73.3%, 67.3% and 60%, respectively, which was more efficient than conventional bioreactors since that carbon, nitrogen and phosphorus were simultaneously removed in a single aerobic reactor. Copyright © 2012 Elsevier Ltd. All rights reserved.

  14. On the structure and dynamics of water associated with single-supported zwitterionic and anionic membranes

    DEFF Research Database (Denmark)

    Miskowiec, A.; Buck, Z. N.; Hansen, Flemming Yssing

    2017-01-01

    We have used high-resolution quasielastic neutron scattering (QENS) to investigate the dynamics of water molecules (time scale of motion similar to ∼10-11- 10-9 s) in proximity to single-supported bilayers of the zwitterionic lipid DMPC (1,2-dimyristoyl-sn-glycero-3-phosphorylcholine) and the ani......We have used high-resolution quasielastic neutron scattering (QENS) to investigate the dynamics of water molecules (time scale of motion similar to ∼10-11- 10-9 s) in proximity to single-supported bilayers of the zwitterionic lipid DMPC (1,2-dimyristoyl-sn-glycero-3-phosphorylcholine......) and the anionic lipid DMPG (1,2-dimyristoyl-sn-glycero-3-phosphoglycerol) in the temperature range 160-295 K. For both membranes, the temperature dependence of the intensity of neutrons scattered elastically and incoherently from these samples indicates a series of freezing/melting transitions...... the membrane and two types of confined water in closer proximity to the lipids. Specifically, we propose a water type termed "confined 2" located within and just above the lipid head groups of the membrane and confined 1 water that lies between the bulk-like and confined 2 water. Confined 1 water is only...

  15. An agar gel membrane-PDMS hybrid microfluidic device for long term single cell dynamic study.

    Science.gov (United States)

    Wong, Ieong; Atsumi, Shota; Huang, Wei-Chih; Wu, Tung-Yun; Hanai, Taizo; Lam, Miu-Ling; Tang, Ping; Yang, Jian; Liao, James C; Ho, Chih-Ming

    2010-10-21

    Significance of single cell measurements stems from the substantial temporal fluctuations and cell-cell variability possessed by individual cells. A major difficulty in monitoring surface non-adherent cells such as bacteria and yeast is that these cells tend to aggregate into clumps during growth, obstructing the tracking or identification of single-cells over long time periods. Here, we developed a microfluidic platform for long term single-cell tracking and cultivation with continuous media refreshing and dynamic chemical perturbation capability. The design highlights a simple device-assembly process between PDMS microchannel and agar membrane through conformal contact, and can be easily adapted by microbiologists for their routine laboratory use. The device confines cell growth in monolayer between an agar membrane and a glass surface. Efficient nutrient diffusion through the membrane and reliable temperature maintenance provide optimal growth condition for the cells, which exhibited fast exponential growth and constant distribution of cell sizes. More than 24 h of single-cell tracking was demonstrated on a transcription-metabolism integrated synthetic biological model, the gene-metabolic oscillator. Single cell morphology study under alcohol toxicity allowed us to discover and characterize cell filamentation exhibited by different E. coli isobutanol tolerant strains. We believe this novel device will bring new capabilities to quantitative microbiology, providing a versatile platform for single cell dynamic studies.

  16. Radon in water aeration system operational performance

    International Nuclear Information System (INIS)

    Lamarre, B.L.

    1990-01-01

    North East Environmental Products, Inc. is a manufacturer of residential scale aeration systems for removal of radon and volatile organic chemicals from private water supplies. This paper is a review of the operational history of residential scale point of entry (POE) radon aeration systems. Emphasis is placed on the difficulties and solutions encountered in actual installations caused by both mechanical difficulties and water quality parameters. A summary of radon reduction efficiency is presented for wells with radon concentrations from 21,000 to 2,600,000 pCi/L. A discussion of customer concerns and attitudes is presented along with other areas for further technical improvement. Training techniques for dealers and installers are also discussed. An update of the current status of the radon in water industry includes current sales volumes as compared to the potential market and an update on the radon in water MCL standard setting process from an industry perspective

  17. Dynamic analysis of CO₂ labeling and cell respiration using membrane-inlet mass spectrometry.

    Science.gov (United States)

    Yang, Tae Hoon

    2014-01-01

    Here, we introduce a mass spectrometry-based analytical method and relevant technical details for dynamic cell respiration and CO2 labeling analysis. Such measurements can be utilized as additional information and constraints for model-based (13)C metabolic flux analysis. Dissolved dynamics of oxygen consumption and CO2 mass isotopomer evolution from (13)C-labeled tracer substrates through different cellular processes can be precisely measured on-line using a miniaturized reactor system equipped with a membrane-inlet mass spectrometer. The corresponding specific rates of physiologically relevant gases and CO2 mass isotopomers can be quantified within a short-term range based on the liquid-phase dynamics of dissolved fermentation gases.

  18. Molecular dynamics simulations of Na+/Cl--dependent neurotransmitter transporters in a membrane-aqueous system

    DEFF Research Database (Denmark)

    Jørgensen, Anne Marie; Tagmose, L.; Jørgensen, A.M.M.

    2007-01-01

    We have performed molecular dynamics simulations of a homology model of the human serotonin transporter (hSERT) in a membrane environment and in complex with either the natural substrate S-HT or the selective serotonin reuptake inhibitor escitaloprom. We have also included a transporter homologue......, the Aquifex aeolicus leucine transporter (LeuT), in our study to evaluate the applicability of a simple and computationally attractive membrane system. Fluctuations in LeuT extracted from simulations are in good agreement with crystal logrophic B factors. Furthermore, key interactions identified in the X....... Specific interactions responsible for ligand recognition, are identified in the hSERT-5HT and hSERT-escitaloprom complexes. Our finding5 are in good agreement with predictions from mutagenesis studies....

  19. 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

  20. Energy transfer dynamics in an RC-LH1-PufX tubular photosynthetic membrane

    Energy Technology Data Exchange (ETDEWEB)

    Hsin, J; Sener, M; Schulten, K [Department of Physics and Beckman Institute, University of Illinois at Urbana-Champaign, Urbana (United States); Struempfer, J [Center for Biophysics and Computational Biology and Beckman Institute, University of Illinois at Urbana-Champaign, Urbana (United States); Qian, P; Hunter, C N, E-mail: kschulte@ks.uiuc.ed [Department of Molecular Biology and Biotechnology, University of Sheffield, Sheffield S10 2TN (United Kingdom)

    2010-08-15

    Light absorption and the subsequent transfer of excitation energy are the first two steps in the photosynthetic process, carried out by protein-bound pigments, mainly bacteriochlorophylls (BChls), in photosynthetic bacteria. BChls are anchored in light-harvesting (LH) complexes, such as light-harvesting complex I (LH1), which directly associates with the reaction center (RC), forming the RC-LH1 core complex. In Rhodobacter sphaeroides, RC-LH1 core complexes contain an additional protein, PufX, and assemble into dimeric RC-LH1-PufX core complexes. In the absence of LH complex II (LH2), the former complexes can aggregate into a helically ordered tubular photosynthetic membrane. We have examined the excitation transfer dynamics in a single RC-LH1-PufX core complex dimer using the hierarchical equations of motion for dissipative quantum dynamics that accurately, yet in a computationally costly manner, treat the coupling between BChls and their protein environment. A widely employed description, the generalized Foerster (GF) theory, was also used to calculate the transfer rates of the same excitonic system in order to verify the accuracy of this computationally cheap method. Additionally, in light of the structural uncertainties in the Rba. sphaeroides RC-LH1-PufX core complex, geometrical alterations were introduced into the BChl organization. It is shown that the energy transfer dynamics are not affected by the considered changes in the BChl organization and that the GF theory provides accurate transfer rates. An all-atom model for a tubular photosynthetic membrane is then constructed on the basis of electron microscopy data, and the overall energy transfer properties of this membrane are computed.

  1. Energy transfer dynamics in an RC-LH1-PufX tubular photosynthetic membrane

    International Nuclear Information System (INIS)

    Hsin, J; Sener, M; Schulten, K; Struempfer, J; Qian, P; Hunter, C N

    2010-01-01

    Light absorption and the subsequent transfer of excitation energy are the first two steps in the photosynthetic process, carried out by protein-bound pigments, mainly bacteriochlorophylls (BChls), in photosynthetic bacteria. BChls are anchored in light-harvesting (LH) complexes, such as light-harvesting complex I (LH1), which directly associates with the reaction center (RC), forming the RC-LH1 core complex. In Rhodobacter sphaeroides, RC-LH1 core complexes contain an additional protein, PufX, and assemble into dimeric RC-LH1-PufX core complexes. In the absence of LH complex II (LH2), the former complexes can aggregate into a helically ordered tubular photosynthetic membrane. We have examined the excitation transfer dynamics in a single RC-LH1-PufX core complex dimer using the hierarchical equations of motion for dissipative quantum dynamics that accurately, yet in a computationally costly manner, treat the coupling between BChls and their protein environment. A widely employed description, the generalized Foerster (GF) theory, was also used to calculate the transfer rates of the same excitonic system in order to verify the accuracy of this computationally cheap method. Additionally, in light of the structural uncertainties in the Rba. sphaeroides RC-LH1-PufX core complex, geometrical alterations were introduced into the BChl organization. It is shown that the energy transfer dynamics are not affected by the considered changes in the BChl organization and that the GF theory provides accurate transfer rates. An all-atom model for a tubular photosynthetic membrane is then constructed on the basis of electron microscopy data, and the overall energy transfer properties of this membrane are computed.

  2. Advanced Fluorescence Microscopy Approaches to Understand the Dynamic Organization of the Plasma Membrane in Eukaryotes

    DEFF Research Database (Denmark)

    Ziomkiewicz, Iwona

    signaling in plants. Furthermore, it was established that ENODL9 clustering affects the organization of the PM and distribution of other PM proteins. Analysis of the phenotype of mutant lines revealed that ENODL9 has an important role for plant development and the adaptation to osmotic stress. This resulted......The plasma membrane (PM) is a physical barrier that defines the boundaries of a cell. It not only isolates the cell interior from the environment, but also enables cell communication and a selective exchange of solutes. To serve those contrasting functions, the PM has a dynamic structure consisting...

  3. Dynamic Desorption of Adsorbing Species under Cross Membrane Pressure Difference: a New Defect Characterisation Approach in Zeolite Membranes

    Czech Academy of Sciences Publication Activity Database

    Prokopová, Olga; Kumakiri, I.; Kočiřík, Milan; Miachon, S.; Dalmon, J. A.

    2003-01-01

    Roč. 226, - (2003), s. 101-110 ISSN 0376-7388 R&D Projects: GA AV ČR IAA1040101; GA ČR GA104/01/0945 Institutional research plan: CEZ:AV0Z4040901 Keywords : zeolite membrane * membrane defect * desorption * water * n- butane Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 2.081, year: 2003

  4. Changes in the physical properties of the dynamic layer and its correlation with permeate quality in a self-forming dynamic membrane bioreactor.

    Science.gov (United States)

    Guan, Dao; Dai, Ji; Watanabe, Yoshimasa; Chen, Guanghao

    2018-09-01

    The self-forming dynamic membrane bioreactor (SFDMBR) is a biological wastewater treatment technology based on the conventional membrane bioreactor (MBR) with membrane material modification to a large pore size (30-100 μm). This modification requires a dynamic layer formed by activated sludge to provide effective filtration function for high-quality permeate production. The properties of the dynamic layer are therefore important for permeate quality in SFDMBRs. The interaction between the structure of the dynamic layer and the performance of SFDMBRs is little known but understandably complex. To elucidate the interaction, a lab-scale SFDMBR system coupled with a nylon woven mesh as the supporting material was operated. After development of a mature dynamic layer, excellent solid-liquid separation was achieved, as evidenced by a low permeate turbidity of less than 2 NTU. The permeate turbidity stayed below this level for nearly 80 days. In the fouling phase, the dynamic layer was compressed with an increase in the trans-membrane pressure and the quality of the permeate kept deteriorating until the turbidity exceeded 10 NTU. The investigation revealed that the majority of permeate particles were dissociated from the dynamic layer on the back surface of the supporting material, which is caused by the compression, breakdown, and dissociation of the dynamic layer. This phenomenon was observed directly in experiment instead of model prediction or conjecture for the first time. Copyright © 2018 Elsevier Ltd. All rights reserved.

  5. Anandamide-ceramide interactions in a membrane environment: Molecular dynamic simulations data.

    Science.gov (United States)

    Di Scala, Coralie; Mazzarino, Morgane; Yahi, Nouara; Varini, Karine; Garmy, Nicolas; Fantini, Jacques; Chahinian, Henri

    2017-10-01

    Anandamide is a lipid neurotransmitter that interacts with various plasma membrane lipids. The data here consists of molecular dynamics simulations of anandamide, C18-ceramide and cholesterol performed in vacuo and within a hydrated palmitoyl-oleoyl-phosphatidylcholine (POPC)/cholesterol membrane. Several models of anandamide/cholesterol and anandamide/ceramide complexes are presented. The energy of interaction and the nature of the intermolecular forces involved in each of these complexes are detailed. The impact of water molecules hydrating the POPC/cholesterol membrane for the stability of the anandamide/cholesterol and anandamide/ceramide complexes is also analyzed. From a total number of 1920 water molecules stochatiscally merged with the lipid matrix, 48 were eventually redistributed around the polar head groups of the anandamide/ceramide complex, whereas only 15 reached with the anandamide/cholesterol complex. The interpretation of this dataset is presented in the accompanying article "Ceramide binding to anandamide increases its half-life and potentiates its cytotoxicity in human neuroblastoma cells" [1].

  6. Interactions of Borneol with DPPC Phospholipid Membranes: A Molecular Dynamics Simulation Study

    Directory of Open Access Journals (Sweden)

    Qianqian Yin

    2014-11-01

    Full Text Available Borneol, known as a “guide” drug in traditional Chinese medicine, is widely used as a natural penetration enhancer in modern clinical applications. Despite a large number of experimental studies on borneol’s penetration enhancing effect, the molecular basis of its action on bio-membranes is still unclear. We carried out a series of coarse-grained molecular dynamics simulations with the borneol concentration ranging from 3.31% to 54.59% (v/v, lipid-free basis to study the interactions of borneol with aDPPC(1,2-dipalmitoylsn-glycero-3-phosphatidylcholine bilayer membrane, and the temperature effects were also considered. At concentrations below 21.89%, borneol’s presence only caused DPPC bilayer thinning and an increase in fluidity; A rise in temperature could promote the diffusing progress of borneol. When the concentration was 21.89% or above, inverted micelle-like structures were formed within the bilayer interior, which led to increased bilayer thickness, and an optimum temperature was found for the interaction of borneol with the DPPC bilayer membrane. These findings revealed that the choice of optimal concentration and temperature is critical for a given application in which borneol is used as a penetration enhancer. Our results not only clarify some molecular basis for borneol’s penetration enhancing effects, but also provide some guidance for the development and applications of new preparations containing borneol.

  7. Neutron scattering studies on protein dynamics using the human myelin peripheral membrane protein P2

    Directory of Open Access Journals (Sweden)

    Laulumaa Saara

    2015-01-01

    Full Text Available Myelin is a multilayered proteolipid membrane structure surrounding selected axons in the vertebrate nervous system, which allows the rapid saltatory conduction of nerve impulses. Deficits in myelin formation and maintenance may lead to chronic neurological disease. P2 is an abundant myelin protein from peripheral nerves, binding between two apposing lipid bilayers. We studied the dynamics of the human myelin protein P2 and its mutated P38G variant in hydrated powders using elastic incoherent neutron scattering. The local harmonic vibrations at low temperatures were very similar for both samples, but the mutant protein had increased flexibility and softness close to physiological temperatures. The results indicate that a drastic mutation of proline to glycine at a functional site can affect protein dynamics, and in the case of P2, they may explain functional differences between the two proteins.

  8. Protein-membrane interaction: effect of myelin basic protein on the dynamics of oriented lipids

    Energy Technology Data Exchange (ETDEWEB)

    Natali, F.; Relini, A.; Gliozzi, A.; Rolandi, R.; Cavatorta, P.; Deriu, A.; Fasano, A.; Riccio, P

    2003-08-01

    We have studied the effect of physiological amounts of myelin basic protein (MBP) on pure dimyristoyl L-{alpha}-phosphatidic acid (DMPA) oriented membranes. The investigation has been carried out using several complementary experimental methods to provide a detailed characterization of the proteo-lipid complexes. In particular, taking advantage of the power of the quasi-elastic neutron scattering (QENS) technique as optimal probe in biology, a significant effect is suggested to be induced by MBP on the anisotropy of lipid dynamics across the liquid-gel phase transition. Thus, the enhancement of the spatially restricted, vertical translation motion of DMPA is suggested to be the main responsible for the increased contribution of the out of plane lipid dynamics observed at 340 K.

  9. Neutron scattering studies on protein dynamics using the human myelin peripheral membrane protein P2

    Science.gov (United States)

    Laulumaa, Saara; Kursula, Petri; Natali, Francesca

    2015-01-01

    Myelin is a multilayered proteolipid membrane structure surrounding selected axons in the vertebrate nervous system, which allows the rapid saltatory conduction of nerve impulses. Deficits in myelin formation and maintenance may lead to chronic neurological disease. P2 is an abundant myelin protein from peripheral nerves, binding between two apposing lipid bilayers. We studied the dynamics of the human myelin protein P2 and its mutated P38G variant in hydrated powders using elastic incoherent neutron scattering. The local harmonic vibrations at low temperatures were very similar for both samples, but the mutant protein had increased flexibility and softness close to physiological temperatures. The results indicate that a drastic mutation of proline to glycine at a functional site can affect protein dynamics, and in the case of P2, they may explain functional differences between the two proteins.

  10. Dynamic simulation of pure hydrogen production via ethanol steam reforming in a catalytic membrane reactor

    International Nuclear Information System (INIS)

    Hedayati, Ali; Le Corre, Olivier; Lacarrière, Bruno; Llorca, Jordi

    2016-01-01

    Ethanol steam reforming (ESR) was performed over Pd-Rh/CeO 2 catalyst in a catalytic membrane reactor (CMR) as a reformer unit for production of fuel cell grade pure hydrogen. Experiments were performed at 923 K, 6–10 bar, and fuel flow rates of 50–200 μl/min using a mixture of ethanol and distilled water with steam to carbon ratio of 3. A static model for the catalytic zone was derived from the Arrhenius law to calculate the total molar production rates of ESR products, i.e. CO, CO 2 , CH 4 , H 2 , and H 2 O in the catalytic zone of the CMR (coefficient of determination R 2  = 0.993). The pure hydrogen production rate at steady state conditions was modeled by means of a static model based on the Sieverts' law. Finally, a dynamic model was developed under ideal gas law assumptions to simulate the dynamics of pure hydrogen production rate in the case of the fuel flow rate or the operating pressure set point adjustment (transient state) at isothermal conditions. The simulation of fuel flow rate change dynamics was more essential compared to the pressure change one, as the system responded much faster to such an adjustment. The results of the dynamic simulation fitted very well to the experimental values at P = 7–10 bar, which proved the robustness of the simulation based on the Sieverts' law. The simulation presented in this work is similar to the hydrogen flow rate adjustments needed to set the electrical load of a fuel cell, when fed online by the pure hydrogen generating reformer studied. - Highlights: • Ethanol steam reforming (ESR) experiments were performed in a Pd-Ag membrane reactor. • The model of the catalytic zone of the reactor was derived from the Arrhenius law. • The permeation zone (membrane) was modeled based on the Sieverts' law. • The Sieverts' law model showed good results for the range of P = 7–10 bar. • Pressure and fuel flow rate adjustments were considered for dynamic simulation.

  11. Differential dynamic and structural behavior of lipid-cholesterol domains in model membranes.

    Directory of Open Access Journals (Sweden)

    Luis F Aguilar

    Full Text Available Changes in the cholesterol (Chol content of biological membranes are known to alter the physicochemical properties of the lipid lamella and consequently the function of membrane-associated enzymes. To characterize these changes, we used steady-state and time resolved fluorescence spectroscopy and two photon-excitation microscopy techniques. The membrane systems were chosen according to the techniques that were used: large unilamellar vesicles (LUVs for cuvette and giant unilamellar vesicles (GUVs for microscopy measurements; they were prepared from dipalmitoyl phosphatidylcholine (DPPC and dioctadecyl phosphatidylcholine (DOPC in mixtures that are well known to form lipid domains. Two fluorescent probes, which insert into different regions of the bilayer, were selected: 1,6-diphenyl-1,3,5-hexatriene (DPH was located at the deep hydrophobic core of the acyl chain regions and 2-dimethylamino-6-lauroylnaphthalene (Laurdan at the hydrophilic-hydrophobic membrane interface. Our spectroscopy results show that (i the changes induced by cholesterol in the deep hydrophobic phospholipid acyl chain domain are different from the ones observed in the superficial region of the hydrophilic-hydrophobic interface, and these changes depend on the state of the lamella and (ii the incorporation of cholesterol into the lamella induces an increase in the orientation dynamics in the deep region of the phospholipid acyl chains with a corresponding decrease in the orientation at the region close to the polar lipid headgroups. The microscopy data from DOPC/DPPC/Chol GUVs using Laurdan generalized polarization (Laurdan GP suggest that a high cholesterol content in the bilayer weakens the stability of the water hydrogen bond network and hence the stability of the liquid-ordered phase (Lo.

  12. Membrane association and localization dynamics of the Ebola virus matrix protein VP40.

    Science.gov (United States)

    Gc, Jeevan B; Gerstman, Bernard S; Chapagain, Prem P

    2017-10-01

    The Ebola virus matrix protein VP40 is a major structural protein that provides the scaffolding for new Ebola virus particles. For this, VP40 is first trafficked to the lower leaflet of the plasma membrane (PM) in its dimeric form. Once associated with the PM, the VP40 dimers undergo structural rearrangements and oligomerize into hexamers and filaments that make up the virus matrix. Therefore, association of the VP40 dimers and their stabilization at the PM is a crucial step in the Ebola life-cycle. To understand the molecular details of the VP40 dimer-PM interactions, we investigated the dimer association with the inner leaflet of the PM using detailed all-atom molecular dynamics (MD) simulations. The formation of the dimer-PM complex is facilitated by the interactions of the VP40 lysine residues and the anionic lipids POPS, POPI, and PIP 2 in the PM. In contrast, the dimer fails to associate with a membrane without POPS, POPI, or PIP 2 lipids. We explored the mechanisms of the association and identified important residues and lipids involved in localization and stabilization of VP40 dimers at the PM. MD simulations elucidate the role of a C-terminal α-helix alignment parallel to the lipid bilayer surface as well as the creation of membrane defects that allow partial insertion of the hydrophobic residue V276 into the membrane to further stabilize the VP40 dimer-PM complex. Understanding the mechanisms of the VP40 dimer-PM association that facilitate oligomerization can be important for potentially targeting the VP40 for small molecules that can interfere with the virus life-cycle. Copyright © 2017 Elsevier B.V. All rights reserved.

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

    Directory of Open Access Journals (Sweden)

    Carles Calero

    2016-04-01

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

  14. Influence of attapulgite addition on the biological performance and microbial communities of submerged dynamic membrane bioreactor

    Directory of Open Access Journals (Sweden)

    Wensong Duan

    2017-12-01

    Full Text Available A submerged dynamic membrane bioreactor (sDMBR was developed to test the influence of attapulgite (AT addition on the treatment performances and the microbial community structure and function. The batch experimental results displayed the highest UV254 and dissolved organic carbon (DOC removal efficiencies with 5% AT/mixed liquid suspended solids addition dosage. The continuous sDMBR results showed that the removal efficiencies of chemical oxygen demand, NH4+-N, total nitrogen and total phosphorus significantly increased in the AT added sDMBR. Excitation emission matrix analysis demonstrated that the protein-like peaks and fulvic acid-like peaks were significantly decreased in both in the mixed liquid and the effluent of the AT added reactor. The obligate anaerobes were observed in the sDMBR with AT addition, such as Bacteroidetes and Gamma proteobacterium in the dynamic membrane, which played an important role in the process of sludge granulation. Bacterial community richness significantly increased after AT addition with predominated phyla of Proteobacteria and Bacteroidetes. Similarly, species abundance significantly increased in the AT added sDMBR. Further investigations with cluster proved that AT was a favorite biological carrier for the microbial ecology, which enriched microbial abundance and community diversity of the sDMBR.

  15. Bio-diatomite dynamic membrane reactor for micro-polluted surface water treatment.

    Science.gov (United States)

    Chu, Huaqiang; Cao, Dawen; Dong, Bingzhi; Qiang, Zhimin

    2010-03-01

    This work investigated the feasibility of treating micro-polluted surface water for drinking water production with a bio-diatomite dynamic membrane reactor (BDDMR) at lab-scale in continuous-flow mode. Results indicate that the BDDMR was effective in removing COD(Mn), DOC, UV(254), NH(3)-N and trihalomethanes' formation potential (THMFP) at a hydraulic retention time (HRT) of 3.5h due to its high concentrations of mixed liquor suspended solids (MLSS) and mixed liquor volatile suspended solids (MLVSS). The removal of pollutants was mainly ascribed to microbial degradation in BDDMR because the dynamic membrane alone was much less effective in pollutant removal. Though the diatomite particles (5-20microm) were much smaller in size than the aperture of the stainless steel support mesh (74microm), microorganisms and their extracellular polymer substances could bind these particles tightly to form bio-diatomite particles which were completely retained by the support mesh. The analysis of molecular weight (MW) distribution by gel permeation chromatography (GPC) shows that the BDDMR could effectively remove the hydrophilic fraction of dissolved organic materials present in the raw water. Copyright 2009 Elsevier Ltd. All rights reserved.

  16. Molecular dynamics simulation of radiation grafted FEP films as proton exchange membranes: Effects of the side chain length

    DEFF Research Database (Denmark)

    Li, Xue; Zhao, Yang; Li, Weiwei

    2017-01-01

    In order to study the microstructure of the prepared potential proton exchange membrane (PEM), molecular dynamics (MD) simulations were used to lucubrate the transport behavior of water molecules and hydronium ions inside the hydrated sulfonated styrene grafted fluorinated ethylene propylene (FEP...... whereas larger water clusters formed. The results of the mean square displacements (MSDs) show that the proton conductivities of the membranes with the proposed side chain lengths were about three fifths of the experimental data, of which the membrane with side chain length of 7 sulfonic styrene units...... was supposed to exhibit the highest proton conductivity, that is 115.69 mS cm-1. All of the supposed membrane models presented good proton conductivity that could definitely meet the application requirements of the proton exchange membranes. The MD simulations can provide an insight to the chain structure...

  17. Influence of myelin proteins on the structure and dynamics of a model membrane with emphasis on the low temperature regime

    Energy Technology Data Exchange (ETDEWEB)

    Knoll, W. [University Joseph Fourier, UFR PhiTEM, Grenoble (France); Institut Laue–Langevin, Grenoble (France); Peters, J. [University Joseph Fourier, UFR PhiTEM, Grenoble (France); Institut Laue–Langevin, Grenoble (France); Institut de Biologie Structurale, Grenoble (France); Kursula, P. [University of Oulu, Oulu (Finland); CSSB–HZI, DESY, Hamburg (Germany); Gerelli, Y. [Institut Laue–Langevin, Grenoble (France); Natali, F., E-mail: natali@ill.fr [Institut Laue–Langevin, Grenoble (France); CNR–IOM–OGG, c/o Institut Laue–Langevin, Grenoble (France)

    2014-11-28

    Myelin is an insulating, multi-lamellar membrane structure wrapped around selected nerve axons. Increasing the speed of nerve impulses, it is crucial for the proper functioning of the vertebrate nervous system. Human neurodegenerative diseases, such as multiple sclerosis, are linked to damage to the myelin sheath through demyelination. Myelin exhibits a well defined subset of myelin-specific proteins, whose influence on membrane dynamics, i.e., myelin flexibility and stability, has not yet been explored in detail. In a first paper [W. Knoll, J. Peters, P. Kursula, Y. Gerelli, J. Ollivier, B. Demé, M. Telling, E. Kemner, and F. Natali, Soft Matter 10, 519 (2014)] we were able to spotlight, through neutron scattering experiments, the role of peripheral nervous system myelin proteins on membrane stability at room temperature. In particular, the myelin basic protein and peripheral myelin protein 2 were found to synergistically influence the membrane structure while keeping almost unchanged the membrane mobility. Further insight is provided by this work, in which we particularly address the investigation of the membrane flexibility in the low temperature regime. We evidence a different behavior suggesting that the proton dynamics is reduced by the addition of the myelin basic protein accompanied by negligible membrane structural changes. Moreover, we address the importance of correct sample preparation and characterization for the success of the experiment and for the reliability of the obtained results.

  18. Spatiotemporal Aeration and Lung Injury Patterns Are Influenced by the First Inflation Strategy at Birth.

    Science.gov (United States)

    Tingay, David G; Rajapaksa, Anushi; Zonneveld, C Elroy; Black, Don; Perkins, Elizabeth J; Adler, Andy; Grychtol, Bartłomiej; Lavizzari, Anna; Frerichs, Inéz; Zahra, Valerie A; Davis, Peter G

    2016-02-01

    Ineffective aeration during the first inflations at birth creates regional aeration and ventilation defects, initiating injurious pathways. This study aimed to compare a sustained first inflation at birth or dynamic end-expiratory supported recruitment during tidal inflations against ventilation without intentional recruitment on gas exchange, lung mechanics, spatiotemporal regional aeration and tidal ventilation, and regional lung injury in preterm lambs. Lambs (127 ± 2 d gestation), instrumented at birth, were ventilated for 60 minutes from birth with either lung-protective positive pressure ventilation (control) or as per control after either an initial 30 seconds of 40 cm H2O sustained inflation (SI) or an initial stepwise end-expiratory pressure recruitment maneuver during tidal inflations (duration 180 s; open lung ventilation [OLV]). At study completion, molecular markers of lung injury were analyzed. The initial use of an OLV maneuver, but not SI, at birth resulted in improved lung compliance, oxygenation, end-expiratory lung volume, and reduced ventilatory needs compared with control, persisting throughout the study. These changes were due to more uniform inter- and intrasubject gravity-dependent spatiotemporal patterns of aeration (measured using electrical impedance tomography). Spatial distribution of tidal ventilation was more stable after either recruitment maneuver. All strategies caused regional lung injury patterns that mirrored associated regional volume states. Irrespective of strategy, spatiotemporal volume loss was consistently associated with up-regulation of early growth response-1 expression. Our results show that mechanical and molecular consequences of lung aeration at birth are not simply related to rapidity of fluid clearance; they are also related to spatiotemporal pressure-volume interactions within the lung during inflation and deflation.

  19. Numerical and experimental investigation of the self-inducing turbine aeration capacity

    International Nuclear Information System (INIS)

    Achouri, Ryma; Dhaouadi, Hatem; Mhiri, Hatem; Bournot, Philippe

    2014-01-01

    Highlights: • Numerical and experimental study of k L a coefficient of a self-inducing turbine. • Validation of experimental results. • Numerical study of k L a variation with the variation of impeller submersion and blade inclination. • Numerical study of the flow field and hydrodynamic parameters. - Abstract: Self-inducing turbines are a model of mixers that ensure the aeration of a fluid field without using a sparger and a surface aerator. Nevertheless, this type of turbines remain quite complicated in terms of behavior of the fluid within the tank, and its actual aeration capacity varies depending on the type of turbine used. The studied turbine is self-inducing and made of three blades and each blade contains five holes. In this work, we evaluated experimentally – using the technique of dynamic oxygenation and deoxygenating – the aeration capacity of our impeller by calculating the volumetric mass transfer coefficient k L a for various submergences and various inclination angles of the blade. This work was then validated by a numerical modeling using the commercial code Fluent, and the flow within the tank as well as the evolution of the hydrodynamic parameters was also studied. The simulation is steady state with a VOF multiphase model and the realizable k–ε turbulence model. We finally concluded that k L a decreases with the increase of the inclination angle and with the increase of the submergence of our turbine. We could also study the hydrodynamic parameters of the flow such as the power number, the aeration number and the shear rate

  20. Improved non-dimensional dynamic influence function method based on tow-domain method for vibration analysis of membranes

    Directory of Open Access Journals (Sweden)

    SW Kang

    2015-02-01

    Full Text Available This article introduces an improved non-dimensional dynamic influence function method using a sub-domain method for efficiently extracting the eigenvalues and mode shapes of concave membranes with arbitrary shapes. The non-dimensional dynamic influence function method (non-dimensional dynamic influence function method, which was developed by the authors in 1999, gives highly accurate eigenvalues for membranes, plates, and acoustic cavities, compared with the finite element method. However, it needs the inefficient procedure of calculating the singularity of a system matrix in the frequency range of interest for extracting eigenvalues and mode shapes. To overcome the inefficient procedure, this article proposes a practical approach to make the system matrix equation of the concave membrane of interest into a form of algebraic eigenvalue problem. It is shown by several case studies that the proposed method has a good convergence characteristics and yields very accurate eigenvalues, compared with an exact method and finite element method (ANSYS.

  1. Mechanisms for naphthalene removal during electrolytic aeration.

    Science.gov (United States)

    Goel, Ramesh K; Flora, Joseph R V; Ferry, John

    2003-02-01

    Batch tests were performed to investigate chemical and physical processes that may result during electrolytic aeration of a contaminated aquifer using naphthalene as a model contaminant. Naphthalene degradation of 58-66% took place electrolytically and occurred at the same rates at a pH of 4 and 7. 1,4-naphthoquinone was identified as a product of the electrolysis. Stripping due to gases produced at the electrodes did not result in any naphthalene loss. Hydrogen peroxide (which may be produced at the cathode) did not have any effect on naphthalene, but the addition of ferrous iron (which may be present in aquifers) resulted in 67-99% disappearance of naphthalene. Chlorine (which may be produced from the anodic oxidation of chloride) can effectively degrade naphthalene at pH of 4, but not at a pH of 7. Mono-, di- and poly chloronaphthalenes were identified as oxidation products. Ferric iron coagulation (due to the oxidation of ferrous iron) did not significantly contribute to naphthalene loss. Overall, electrolytic oxidation and chemical oxidation due to the electrolytic by-products formed are significant abiotic processes that could occur and should be accounted for if bioremediation of PAH-contaminated sites via electrolytic aeration is considered. Possible undesirable products such as chlorinated compounds may be formed when significant amounts of chlorides are present.

  2. Radionuclide migration test using undisturbed aerated soil

    International Nuclear Information System (INIS)

    Yamamoto, Tadatoshi; Ohtsuka, Yoshiro; Ogawa, Hiromichi; Wadachi, Yoshiki

    1988-01-01

    As one of the most important part of safety assessment on the shallow land disposal of lowlevel radioactive waste, the radionuclide migration was studied using undisturbed soil samples, in order to evaluate an exact radionuclide migration in an aerated soil layer. Soil samples used in the migration test were coastal sand and loamy soil which form typical surface soil layers in Japan. The aqueous solution containing 60 CoCl 2 , 85 SrCl 2 and 137 CsCl was fed into the soil column and concentration of each radionuclide both in effluent and in soil was measured. Large amount of radionuclides was adsorbed on the surface of soil column and small amount of radionuclides moved deep into the soil column. Difference in the radionuclide profile was observed in the low concentration portion particularly. It is that some fractions of 60 Co and 137 Cs are stable in non-ionic form and move downward through the soil column together with water. The radionuclide distribution in the surface of soil column can be fairly predicted with a conventional migration equation for ionic radionuclides. As a result of radionuclide adsorption, both aerated soil layers of coastal sand and loamy soil have large barrier ability on the radionuclide migration through the ground. (author)

  3. Oxidation of magnetite in aerated aqueous media

    International Nuclear Information System (INIS)

    Taylor, P.; Owen, D.G.

    1993-04-01

    Metastable equilibria involving phases less stable than hematite can be significantly more oxidizing than the calculated equilibrium between well-crystallized hematite and magnetite. In this report, generalized solubility and stability relationships between magnetite and Fe 2 O 3 .xH 2 O phases are derived to describe the metastable equilibria. Experiments with synthetic magnetite powders in aerated aqueous solutions show that crystalline hematite is formed within days at temperatures above 100 C in pure water or solutions containing anions (e.g., Cl - , SO 4 2 - , HCO 3 - ) that do not form very strong surface complexes with iron oxides. In the presence of dissolved phosphate or silica, however, the dissolution-precipitation route to hematite is strongly inhibited, and maghemite is a persistent metastable product. Thus, phosphate or silica are expected to delay the approach to magnetite-hematite equilibrium in aerated groundwaters conditioned by magnetite. These findings are presented in the context of nuclear fuel waste disposal. (author). 63 refs., 1 tab., 11 figs

  4. Molecular dynamics studies of simple membrane-water interfaces: Structure and functions in the beginnings of cellular life

    Science.gov (United States)

    Pohorille, Andrew; Wilson, Michael A.

    1995-01-01

    Molecular dynamics computer simulations of the structure and functions of a simple membrane are performed in order to examine whether membranes provide an environment capable of promoting protobiological evolution. Our model membrane is composed of glycerol 1-monooleate. It is found that the bilayer surface fluctuates in time and space, occasionally creating thinning defects in the membrane. These defects are essential for passive transport of simple ions across membranes because they reduce the Born barrier to this process by approximately 40%. Negative ions are transferred across the bilayer more readily than positive ions due to favorable interactions with the electric field at the membrane-water interface. Passive transport of neutral molecules is, in general, more complex than predicted by the solubility-diffusion model. In particular, molecules which exhibit sufficient hydrophilicity and lipophilicity concentrate near membrane surfaces and experience 'interfacial resistance' to transport. The membrane-water interface forms an environment suitable for heterogeneous catalysis. Several possible mechanisms leading to an increase of reaction rates at the interface are discussed. We conclude that vesicles have many properties that make them very good candidates for earliest protocells. Some potentially fruitful directions of experimental and theoretical research on this subject are proposed.

  5. Peptide insertion, positioning, and stabilization in a membrane: insight from an all-atom molecular dynamics simulation.

    Science.gov (United States)

    Babakhani, Arneh; Gorfe, Alemayehu A; Gullingsrud, Justin; Kim, Judy E; Andrew McCammon, J

    Peptide insertion, positioning, and stabilization in a model membrane are probed via an all-atom molecular dynamics (MD) simulation. One peptide (WL5) is simulated in each leaflet of a solvated dimyristoylglycero-3-phosphate (DMPC) membrane. Within the first 5 ns, the peptides spontaneously insert into the membrane and then stabilize during the remaining 70 ns of simulation time. In both leaflets, the peptides localize to the membrane interface, and this localization is attributed to the formation of peptide-lipid hydrogen bonds. We show that the single tryptophan residue in each peptide contributes significantly to these hydrogen bonds; specifically, the nitrogen heteroatom of the indole ring plays a critical role. The tilt angles of the indole rings relative to the membrane normal in the upper and lower leaflets are approximately 26 degrees and 54 degrees , respectively. The tilt angles of the entire peptide chain are 62 degrees and 74 degrees . The membrane induces conformations of the peptide that are characteristic of beta-sheets, and the peptide enhances the lipid ordering in the membrane. Finally, the diffusion rate of the peptides in the membrane plane is calculated (based on experimental peptide concentrations) to be approximately 6 A(2)/ns, thus suggesting a 500 ns time scale for intermolecular interactions.

  6. Enhancement of ultrasonic disintegration of sewage sludge by aeration.

    Science.gov (United States)

    Zhao, He; Zhang, Panyue; Zhang, Guangming; Cheng, Rong

    2016-04-01

    Sonication is an effective way for sludge disintegration, which can significantly improve the efficiency of anaerobic digestion to reduce and recycle use of sludge. But high energy consumption limits the wide application of sonication. In order to improve ultrasonic sludge disintegration efficiency and reduce energy consumption, aeration was introduced. Results showed that sludge disintegration efficiency was improved significantly by combining aeration with ultrasound. The aeration flow rate, gas bubble size, ultrasonic density and aeration timing had impacts on sludge disintegration efficiency. Aeration that used in later stage of ultrasonic irradiation with low aeration flow rate, small gas bubbles significantly improved ultrasonic disintegration sludge efficiency. At the optimal conditions of 0.4 W/mL ultrasonic irradiation density, 30 mL/min of aeration flow rate, 5 min of aeration in later stage and small gas bubbles, ultrasonic sludge disintegration efficiency was increased by 45% and one third of ultrasonic energy was saved. This approach will greatly benefit the application of ultrasonic sludge disintegration and strongly promote the treatment and recycle of wastewater sludge. Copyright © 2015. Published by Elsevier B.V.

  7. Influence of aeration and lighting on biomass production and protein ...

    African Journals Online (AJOL)

    The influence aeration and light intensity could have on biomass production and protein biosynthesis in a Spirulina sp. isolated from an oil-polluted brackish water marsh is examined. Biomass, proximal composition and amino acid composition obtained from aerated cultures of the organism were compared with ...

  8. 21 CFR 880.6100 - Ethylene oxide gas aerator cabinet.

    Science.gov (United States)

    2010-04-01

    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Ethylene oxide gas aerator cabinet. 880.6100... Miscellaneous Devices § 880.6100 Ethylene oxide gas aerator cabinet. (a) Identification. An ethyene oxide gas... required to remove residual ethylene oxide (ETO) from wrapped medical devices that have undergone ETO...

  9. Automatic Time Regulator for Switching on an Aeration Device for ...

    African Journals Online (AJOL)

    The need to aerate the pond at odd hours due to diurnal limit, save cost and human labor, necessitated the design of an automatic time regulator circuit, which controls the switching on and o of an aeration device at a pre determined and selected time interval (5mins., 10mins., 20mins., 30mins., and 40mins.) This design ...

  10. F-BAR family proteins, emerging regulators for cell membrane dynamic changes-from structure to human diseases.

    Science.gov (United States)

    Liu, Suxuan; Xiong, Xinyu; Zhao, Xianxian; Yang, Xiaofeng; Wang, Hong

    2015-05-09

    Eukaryotic cell membrane dynamics change in curvature during physiological and pathological processes. In the past ten years, a novel protein family, Fes/CIP4 homology-Bin/Amphiphysin/Rvs (F-BAR) domain proteins, has been identified to be the most important coordinators in membrane curvature regulation. The F-BAR domain family is a member of the Bin/Amphiphysin/Rvs (BAR) domain superfamily that is associated with dynamic changes in cell membrane. However, the molecular basis in membrane structure regulation and the biological functions of F-BAR protein are unclear. The pathophysiological role of F-BAR protein is unknown. This review summarizes the current understanding of structure and function in the BAR domain superfamily, classifies F-BAR family proteins into nine subfamilies based on domain structure, and characterizes F-BAR protein structure, domain interaction, and functional relevance. In general, F-BAR protein binds to cell membrane via F-BAR domain association with membrane phospholipids and initiates membrane curvature and scission via Src homology-3 (SH3) domain interaction with its partner proteins. This process causes membrane dynamic changes and leads to seven important cellular biological functions, which include endocytosis, phagocytosis, filopodium, lamellipodium, cytokinesis, adhesion, and podosome formation, via distinct signaling pathways determined by specific domain-binding partners. These cellular functions play important roles in many physiological and pathophysiological processes. We further summarize F-BAR protein expression and mutation changes observed in various diseases and developmental disorders. Considering the structure feature and functional implication of F-BAR proteins, we anticipate that F-BAR proteins modulate physiological and pathophysiological processes via transferring extracellular materials, regulating cell trafficking and mobility, presenting antigens, mediating extracellular matrix degradation, and transmitting

  11. Determination of Dynamics of Plant Plasma Membrane Proteins with Fluorescence Recovery and Raster Image Correlation Spectroscopy.

    Science.gov (United States)

    Laňková, Martina; Humpolíčková, Jana; Vosolsobě, Stanislav; Cit, Zdeněk; Lacek, Jozef; Čovan, Martin; Čovanová, Milada; Hof, Martin; Petrášek, Jan

    2016-04-01

    A number of fluorescence microscopy techniques are described to study dynamics of fluorescently labeled proteins, lipids, nucleic acids, and whole organelles. However, for studies of plant plasma membrane (PM) proteins, the number of these techniques is still limited because of the high complexity of processes that determine the dynamics of PM proteins and the existence of cell wall. Here, we report on the usage of raster image correlation spectroscopy (RICS) for studies of integral PM proteins in suspension-cultured tobacco cells and show its potential in comparison with the more widely used fluorescence recovery after photobleaching method. For RICS, a set of microscopy images is obtained by single-photon confocal laser scanning microscopy (CLSM). Fluorescence fluctuations are subsequently correlated between individual pixels and the information on protein mobility are extracted using a model that considers processes generating the fluctuations such as diffusion and chemical binding reactions. As we show here using an example of two integral PM transporters of the plant hormone auxin, RICS uncovered their distinct short-distance lateral mobility within the PM that is dependent on cytoskeleton and sterol composition of the PM. RICS, which is routinely accessible on modern CLSM instruments, thus represents a valuable approach for studies of dynamics of PM proteins in plants.

  12. Grey-box modelling of aeration tank settling.

    Science.gov (United States)

    Bechman, Henrik; Nielsen, Marinus K; Poulsen, Niels Kjølstad; Madsen, Henrik

    2002-04-01

    A model of the concentrations of suspended solids (SS) in the aeration tanks and in the effluent from these during Aeration tank settling (ATS) operation is established. The model is based on simple SS mass balances, a model of the sludge settling and a simple model of how the SS concentration in the effluent from the aeration tanks depends on the actual concentrations in the tanks and the sludge blanket depth. The model is formulated in continuous time by means of stochastic differential equations with discrete-time observations. The parameters of the model are estimated using a maximum likelihood method from data from an alternating BioDenipho waste water treatment plant (WWTP). The model is an important tool for analyzing ATS operation and for selecting the appropriate control actions during ATS, as the model can be used to predict the SS amounts in the aeration tanks as well as in the effluent from the aeration tanks.

  13. Automatic adjustment of cycle length and aeration time for improved nitrogen removal in an alternating activated sludge process

    DEFF Research Database (Denmark)

    Isaacs, Steven Howard

    1997-01-01

    The paper examines the nitrogen dynamics in the alternating BIODENITRO and BIODENIPHO processes with a focus on two control handles influencing now scheduling and aeration: the cycle length and the ammonia concentration at which a nitrifying period is terminated. A steady state analysis examining...

  14. Chemical crosslinking and mass spectrometry studies of the structure and dynamics of membrane proteins and receptors.

    Energy Technology Data Exchange (ETDEWEB)

    Haskins, William E.; Leavell, Michael D.; Lane, Pamela; Jacobsen, Richard B.; Hong, Joohee; Ayson, Marites J.; Wood, Nichole L.; Schoeniger, Joseph S.; Kruppa, Gary Hermann; Sale, Kenneth L.; Young, Malin M.; Novak, Petr

    2005-03-01

    Membrane proteins make up a diverse and important subset of proteins for which structural information is limited. In this study, chemical cross-linking and mass spectrometry were used to explore the structure of the G-protein-coupled photoreceptor bovine rhodopsin in the dark-state conformation. All experiments were performed in rod outer segment membranes using amino acid 'handles' in the native protein sequence and thus minimizing perturbations to the native protein structure. Cysteine and lysine residues were covalently cross-linked using commercially available reagents with a range of linker arm lengths. Following chemical digestion of cross-linked protein, cross-linked peptides were identified by accurate mass measurement using liquid chromatography-fourier transform mass spectrometry and an automated data analysis pipeline. Assignments were confirmed and, if necessary, resolved, by tandem MS. The relative reactivity of lysine residues participating in cross-links was evaluated by labeling with NHS-esters. A distinct pattern of cross-link formation within the C-terminal domain, and between loop I and the C-terminal domain, emerged. Theoretical distances based on cross-linking were compared to inter-atomic distances determined from the energy-minimized X-ray crystal structure and Monte Carlo conformational search procedures. In general, the observed cross-links can be explained by re-positioning participating side-chains without significantly altering backbone structure. One exception, between C3 16 and K325, requires backbone motion to bring the reactive atoms into sufficient proximity for cross-linking. Evidence from other studies suggests that residues around K325 for a region of high backbone mobility. These findings show that cross-linking studies can provide insight into the structural dynamics of membrane proteins in their native environment.

  15. Membrane topology and cellular dynamics of foot-and-mouth disease virus 3A protein.

    Directory of Open Access Journals (Sweden)

    Mónica González-Magaldi

    Full Text Available Foot-and-mouth disease virus non-structural protein 3A plays important roles in virus replication, virulence and host-range; nevertheless little is known on the interactions that this protein can establish with different cell components. In this work, we have performed in vivo dynamic studies from cells transiently expressing the green fluorescent protein (GFP fused to the complete 3A (GFP3A and versions including different 3A mutations. The results revealed the presence of a mobile fraction of GFP3A, which was found increased in most of the mutants analyzed, and the location of 3A in a continuous compartment in the cytoplasm. A dual behavior was also observed for GFP3A upon cell fractionation, being the protein equally recovered from the cytosolic and membrane fractions, a ratio that was also observed when the insoluble fraction was further fractioned, even in the presence of detergent. Similar results were observed in the fractionation of GFP3ABBB, a 3A protein precursor required for initiating RNA replication. A nonintegral membrane protein topology of FMDV 3A was supported by the lack of glycosylation of versions of 3A in which each of the protein termini was fused to a glycosylation acceptor tag, as well as by their accessibility to degradation by proteases. According to this model 3A would interact with membranes through its central hydrophobic region exposing its N- and C- termini to the cytosol, where interactions between viral and cellular proteins required for virus replication are expected to occur.

  16. Reactive molecular dynamic simulations on the gas separation performance of porous graphene membrane.

    Science.gov (United States)

    Esfandiarpoor, Somaye; Fazli, Mostafa; Ganji, Masoud Darvish

    2017-11-29

    The separation of gases molecules with similar diameter and shape is an important area of research. For example, the major challenge to set up sweeping carbon dioxide capture and storage (CCS) in power plants is the energy requisite to separate the CO 2 from flue gas. Porous graphene has been proposed as superior material for highly selective membranes for gas separation. Here we design some models of porous graphene with different sizes and shape as well as employ double layers porous graphene for efficient CO 2 /H 2 separation. The selectivity and permeability of gas molecules through various nanopores were investigated by using the reactive molecular dynamics simulation which considers the bond forming/breaking mechanism for all atoms. Furthermore, it uses a geometry-dependent charge calculation scheme that accounts appropriately for polarization effect which can play an important role in interacting systems. It was found that H-modified porous graphene membrane with pore diameter (short side) of about 3.75 Å has excellent selectivity for CO 2 /H 2 separation. The mechanism of gas penetration through the sub-nanometer pore was presented for the first time. The accuracy of MD simulation results validated by valuable DFT method. The present findings show that reactive MD simulation can propose an economical means of separating gases mixture.

  17. Monitoring single membrane protein dynamics in a liposome manipulated in solution by the ABELtrap

    Science.gov (United States)

    Rendler, T.; Renz, M.; Hammann, E.; Ernst, S.; Zarrabi, N.; Börsch, M.

    2011-02-01

    FoF1-ATP synthase is the essential membrane enzyme maintaining the cellular level of adenosine triphosphate (ATP) and comprises two rotary motors. We measure subunit rotation in FoF1-ATP synthase by intramolecular Foerster resonance energy transfer (FRET) between two fluorophores at the rotor and at the stator of the enzyme. Confocal FRET measurements of freely diffusing single enzymes in lipid vesicles are limited to hundreds of milliseconds by the transit times through the laser focus. We evaluate two different methods to trap the enzyme inside the confocal volume in order to extend the observation times. Monte Carlo simulations show that optical tweezers with low laser power are not suitable for lipid vesicles with a diameter of 130 nm. A. E. Cohen (Harvard) and W. E. Moerner (Stanford) have recently developed an Anti-Brownian electrokinetic trap (ABELtrap) which is capable to apparently immobilize single molecules, proteins, viruses or vesicles in solution. Trapping of fluorescent particles is achieved by applying a real time, position-dependent feedback to four electrodes in a microfluidic device. The standard deviation from a given target position in the ABELtrap is smaller than 200 nm. We develop a combination of the ABELtrap with confocal FRET measurements to monitor single membrane enzyme dynamics by FRET for more than 10 seconds in solution.

  18. Structural basis for plant plasma membrane protein dynamics and organization into functional nanodomains.

    Science.gov (United States)

    Gronnier, Julien; Crowet, Jean-Marc; Habenstein, Birgit; Nasir, Mehmet Nail; Bayle, Vincent; Hosy, Eric; Platre, Matthieu Pierre; Gouguet, Paul; Raffaele, Sylvain; Martinez, Denis; Grelard, Axelle; Loquet, Antoine; Simon-Plas, Françoise; Gerbeau-Pissot, Patricia; Der, Christophe; Bayer, Emmanuelle M; Jaillais, Yvon; Deleu, Magali; Germain, Véronique; Lins, Laurence; Mongrand, Sébastien

    2017-07-31

    Plasma Membrane is the primary structure for adjusting to ever changing conditions. PM sub-compartmentalization in domains is thought to orchestrate signaling. Yet, mechanisms governing membrane organization are mostly uncharacterized. The plant-specific REMORINs are proteins regulating hormonal crosstalk and host invasion. REMs are the best-characterized nanodomain markers via an uncharacterized moiety called REMORIN C-terminal Anchor. By coupling biophysical methods, super-resolution microscopy and physiology, we decipher an original mechanism regulating the dynamic and organization of nanodomains. We showed that targeting of REMORIN is independent of the COP-II-dependent secretory pathway and mediated by PI4P and sterol. REM-CA is an unconventional lipid-binding motif that confers nanodomain organization. Analyses of REM-CA mutants by single particle tracking demonstrate that mobility and supramolecular organization are critical for immunity. This study provides a unique mechanistic insight into how the tight control of spatial segregation is critical in the definition of PM domain necessary to support biological function.

  19. Salt-induced effects on natural and inverse DPPC lipid membranes: Molecular dynamics simulation.

    Science.gov (United States)

    Rezaei Sani, Seyed Mojtaba; Akhavan, Mojdeh; Jalili, Seifollah

    2018-08-01

    Molecular dynamics (MD) simulations of a dipalmitoylphosphatidylcholine (DPPC) bilayer and its neutral inverse-phosphocholine equivalent (DPCPe) were performed to find salt-induced effects on their surface structure and the nature of ion-lipid interactions. We found that the area per lipid is not considerably affected by the inversion, but the deuterium order parameter of carbon atoms in the region of carbonyl carbons changes dramatically. MD simulations indicate that Ca 2+ ions can bind to the surface of both DPPC and DPCPe membranes, but K + ions do not bind to them. In the case of Na + , however, the ions can bind to natural lipids but not to the inverse ones. Also, our results demonstrate that the hydration level of CPe bilayers is substantially lower than PC bilayers and the averaged orientation of water dipoles in the region of CPe headgroups is effectively inverted compared to PC lipids. This might be important in the interaction of the bilayer with its biological environment. Furthermore, it was found for the CPe bilayers that the enhanced peaks of the electrostatic potential profiles shift further away from the bilayer center relative to those of PC bilayers. This behavior makes the penetration of cations into the bilayer more difficult and possibly explains the experimentally observed enhanced release rates of anionic compounds in the CPe membrane. Copyright © 2018 Elsevier B.V. All rights reserved.

  20. Membrane Anchoring and Ion-Entry Dynamics in P-type ATPase Copper Transport

    DEFF Research Database (Denmark)

    Grønberg, Christina; Sitsel, Oleg; Lindahl, Erik

    2016-01-01

    Cu(+)-specific P-type ATPase membrane protein transporters regulate cellular copper levels. The lack of crystal structures in Cu(+)-binding states has limited our understanding of how ion entry and binding are achieved. Here, we characterize the molecular basis of Cu(+) entry using molecular-dynamics...... simulations, structural modeling, and in vitro and in vivo functional assays. Protein structural rearrangements resulting in the exposure of positive charges to bulk solvent rather than to lipid phosphates indicate a direct molecular role of the putative docking platform in Cu(+) delivery. Mutational analyses...... and simulations in the presence and absence of Cu(+) predict that the ion-entry path involves two ion-binding sites: one transient Met148-Cys382 site and one intramembranous site formed by trigonal coordination to Cys384, Asn689, and Met717. The results reconcile earlier biochemical and x-ray absorption data...

  1. Membrane viewpoint on black holes: Dynamical electromagnetic fields near the horizon

    International Nuclear Information System (INIS)

    Macdonald, D.A.; Suen, W.

    1985-01-01

    This paper is part of a series of papers with the aim of developing a complete self-consistent formalism for the treatment of electromagnetic and gravitational fields in the neighborhood of a black-hole horizon. In this membrane formalism, the horizon is treated as a closed two-dimensional membrane lying in a curved three-dimensional space, and endowed with familiar physical properties such as entropy and temperature, surface pressure and viscosity, and electrical conductivity, charge, and current. This paper develops the concept of the ''stretched horizon,'' which will be vital for both the electromagnetic and gravitational aspects of the formalism, and it presents several model problems illustrating the interaction of dynamical electromagnetic fields with stationary black-hole horizons: The field of a test charge in various states of motion outside the Schwarzschild horizon is analyzed in the near-horizon limit, where the spatial curvature may be ignored and the metric may be approximated by that of Rindler. This analysis elucidates the influence of the horizon on the shapes and motions of electric and magnetic field lines when external agents move the field lines in arbitrary manners. It also illustrates how the field lines interact with the horizon's charge and current to produce an exchange of energy and momentum between the external agent and the horizon. A numerical calculation of the dynamical relaxation of a magnetic field threading a Schwarzschild black hole is also presented, illustrating the ''cleaning'' of a complicated field structure by a black-hole horizon, and elucidating the constraints on the location of the stretched horizon

  2. Differential Effects of Cholesterol, Ergosterol and Lanosterol on a Dipalmitoyl Phosphatidylcholine (DPPC) membrane: A Molecular Dynamics Simulations Study

    Energy Technology Data Exchange (ETDEWEB)

    Cournia, Zoe [Yale University; Ullmann, G. Matthias [University of Bayreuth; Smith, Jeremy C [ORNL

    2007-02-01

    Lipid raft/domain formation may arise as a result of the effects of specific sterols on the physical properties of membranes. Here, using molecular dynamics simulation, we examine the effects of three closely-related sterols, ergosterol, cholesterol, and lanosterol, at a biologically relevant concentration (40 mol %) on the structural properties of a model dipalmitoyl phosphatidylcholine (DPPC) membrane at 309 and 323 K. All three sterols are found to order the DPPC acyl tails and condense the membrane relative to the DPPC liquid-phase membrane, but each one does this to a significantly different degree. The smooth {alpha}-face of ergosterol, together with the presence of tail unsaturation in this sterol, leads to closer interaction of ergosterol with the lipids and closer packing of the lipids with each other, so ergosterol has a higher condensing effect on the membrane, as reflected by the area per lipid. Moreover, ergosterol induces a higher proportion of trans lipid conformers, a thicker membrane, and higher lipid order parameters and is aligned more closely with the membrane normal. Ergosterol also positions itself closer to the bilayer/water interface. In contrast, the rough {alpha}-face of lanosterol leads to a less close interaction of the steroid ring system with the phospholipid acyl chains, and so lanosterol orders, straightens, and packs the lipid acyl chains less well and is less closely aligned with the membrane normal. Furthermore, lanosterol lies closer to the relatively disordered membrane center than do the other sterols. The behavior of cholesterol in all the above respects is intermediate between that of lanosterol and ergosterol. The findings here may explain why ergosterol is the most efficient of the three sterols at promoting the liquid-ordered phase and lipid domain formation and may also furnish part of the explanation as to why cholesterol is evolutionarily preferred over lanosterol in higher-vertebrate plasma membranes.

  3. Dynamic Modeling and Control of Distributed Heat Transfer Mechanisms: Application to a Membrane Distillation Module

    KAUST Repository

    Eleiwi, Fadi

    2015-12-01

    Sustainable desalination technologies are the smart solution for producing fresh water and preserve the environment and energy by using sustainable renewable energy sources. Membrane distillation (MD) is an emerging technology which can be driven by renewable energy. It is an innovative method for desalinating seawater and brackish water with high quality production, and the gratitude is to its interesting potentials. MD includes a transfer of water vapor from a feed solution to a permeate solution through a micro-porous hydrophobic membrane, rejecting other non-volatile constituents present in the influent water. The process is driven by the temperature difference along the membrane boundaries. Different control applications and supervision techniques would improve the performance and the efficiency of the MD process, however controlling the MD process requires comprehensive mathematical model for the distributed heat transfer mechanisms inside the process. Our objective is to propose a dynamic mathematical model that accounts for the time evolution of the involved heat transfer mechanisms in the process, and to be capable of hosting intermittent energy supplies, besides managing the production rate of the process, and optimizing its energy consumption. Therefore, we propose the 2D Advection-Diffusion Equation model to account for the heat diffusion and the heat convection mechanisms inside the process. Furthermore, experimental validations have proved high agreement between model simulations and experiments with less than 5% relative error. Enhancing the MD production is an anticipated goal, therefore, two main control strategies are proposed. Consequently, we propose a nonlinear controller for a semi-discretized version of the dynamic model to achieve an asymptotic tracking for a desired temperature difference. Similarly, an observer-based feedback control is used to track sufficient temperature difference for better productivity. The second control strategy

  4. Segregated phases in pulmonary surfactant membranes do not show coexistence of lipid populations with differentiated dynamic properties

    DEFF Research Database (Denmark)

    Bernardino de la Serna, Jorge; Orädd, Greger; Bagatolli, Luis

    2009-01-01

    surfactant membranes and membranes reconstituted from two surfactant hydrophobic fractions (i.e., all the lipids plus the hydrophobic proteins SP-B and SP-C, or only the total lipid fraction). These preparations show micrometer-sized fluid ordered/disordered phase coexistence, associated with a broad...... endothermic transition ending close to 37°C. However, both types of membrane exhibit uniform lipid mobility when analyzed by electron paramagnetic resonance with different spin-labeled phospholipids. A similar feature is observed with pulse-field gradient NMR experiments on oriented membranes reconstituted...... from the two types of surfactant hydrophobic extract. These latter results suggest that lipid dynamics are similar in the coexisting fluid phases observed by fluorescence microscopy. Additionally, it is found that surfactant proteins significantly reduce the average intramolecular lipid mobility...

  5. Aeration Strategies To Mitigate Nitrous Oxide Emissions from Single-Stage Nitritation/Anammox Reactors

    DEFF Research Database (Denmark)

    Domingo Felez, Carlos; Mutlu, A. Gizem; Jensen, Marlene Mark

    2014-01-01

    Autotrophic nitrogen removal is regarded as a resource efficient process to manage nitrogen-rich residual streams. However, nitrous oxide emissions of these processes are poorly documented and strategies to mitigate emissions unknown. In this study, two sequencing batch reactors performing single...... was noted when the duration of aeration was increased while decreasing air flow rate (10.9 +/- 3.2% Delta N2O/Delta TN). The extant ammonium oxidation activity (mgNH(4)(+)-N/gVSS.min) positively correlated with the specific N2O production rate (mgN(2)O-N/gVSS.min) of the systems. Operating under conditions......-stage nitritation/anammox were operated under different aeration strategies, gradually adjusted over six months. At constant but limiting oxygen loading, synthetic reject water was fed (0.75g-N/L.d) and high nitrogen removal efficiencies (83 +/- 5 and 88 +/- 2%) obtained. Dynamics of liquid phase nitrous (N2O...

  6. Interaction of the antimicrobial peptide polymyxin B1 with both membranes of E. coli: a molecular dynamics study.

    Directory of Open Access Journals (Sweden)

    Nils A Berglund

    2015-04-01

    Full Text Available Antimicrobial peptides are small, cationic proteins that can induce lysis of bacterial cells through interaction with their membranes. Different mechanisms for cell lysis have been proposed, but these models tend to neglect the role of the chemical composition of the membrane, which differs between bacterial species and can be heterogeneous even within a single cell. Moreover, the cell envelope of Gram-negative bacteria such as E. coli contains two membranes with differing compositions. To this end, we report the first molecular dynamics simulation study of the interaction of the antimicrobial peptide, polymyxin B1 with complex models of both the inner and outer membranes of E. coli. The results of >16 microseconds of simulation predict that polymyxin B1 is likely to interact with the membranes via distinct mechanisms. The lipopeptides aggregate in the lipopolysaccharide headgroup region of the outer membrane with limited tendency for insertion within the lipid A tails. In contrast, the lipopeptides readily insert into the inner membrane core, and the concomitant increased hydration may be responsible for bilayer destabilization and antimicrobial function. Given the urgent need to develop novel, potent antibiotics, the results presented here reveal key mechanistic details that may be exploited for future rational drug development.

  7. Molecular dynamics simulations on desulfurization of n-octane/thiophene mixture using silica filled polydimethylsiloxane nanocomposite membranes

    International Nuclear Information System (INIS)

    Shariatinia, Zahra; Jalali, Azin Mazloom; Taromi, Faramarz Afshar

    2016-01-01

    Molecular dynamics (MD) simulations were performed at 298.15 K and 1 atm in order to study microstructure and transport behaviors of polydimethylsiloxane (PDMS) membranes containing 0%–8% SiO 2 nanoparticles used for the separation of thiophene from n-octane. It was found that the fractional free volume (FFV) of 0% SiO 2 was the highest (47.24%) among five nanocomposite membranes and addition of 2%–8% silica nanoparticles led to dramatic decrease in the FFV of the cells. The x-ray diffraction (XRD) patterns of all membranes showed that they had a semi-crystalline structure containing a broad peak around 15°–18°. The radial distribution function (RDF) analysis proved that the smallest C(CH 2 -octane)–O(SiO 2 ), C(PDMS)–O(SiO 2 ) and H(thiophene)–O(SiO 2 ) distances were present in 4% SiO 2 membrane reflecting the silica–octane, silica–polymer and silica–thiophene interactions were the strongest in this membrane. The mean squared displacement (MSD) and diffusion coefficients of n-octane were both small in the 6% silica membrane but they were high for thiophene suggesting this membrane was the most suitable for the desulfurization process and separation of thiophene from n-octane. (paper)

  8. Membrane binding of an acyl-lactoferricin B antimicrobial peptide from solid-state NMR experiments and molecular dynamics simulations.

    Science.gov (United States)

    Romo, Tod D; Bradney, Laura A; Greathouse, Denise V; Grossfield, Alan

    2011-08-01

    One approach to the growing health problem of antibiotic resistant bacteria is the development of antimicrobial peptides (AMPs) as alternative treatments. The mechanism by which these AMPs selectively attack the bacterial membrane is not well understood, but is believed to depend on differences in membrane lipid composition. N-acylation of the small amidated hexapeptide, RRWQWR-NH(2) (LfB6), derived from the 25 amino acid bovine lactoferricin (LfB25) can be an effective means to improve its antimicrobial properties. Here, we investigate the interactions of C6-LfB6, N-acylated with a 6 carbon fatty acid, with model lipid bilayers with two distinct compositions: 3:1 POPE:POPG (negatively charged) and POPC (zwitterionic). Results from solid-state (2)H and (31)P NMR experiments are compared with those from an ensemble of all-atom molecular dynamic simulations running in aggregate more than 8.6ms. (2)H NMR spectra reveal no change in the lipid acyl chain order when C6-LfB6 is bound to the negatively charged membrane and only a slight decrease in order when it is bound to the zwitterionic membrane. (31)P NMR spectra show no significant perturbation of the phosphate head groups of either lipid system in the presence of C6-LfB6. Molecular dynamic simulations show that for the negatively charged membrane, the peptide's arginines drive the initial association with the membrane, followed by attachment of the tryptophans at the membrane-water interface, and finally by the insertion of the C6 tails deep into the bilayer. In contrast, the C6 tail leads the association with the zwitterionic membrane, with the tryptophans and arginines associating with the membrane-water interface in roughly the same amount of time. We find similar patterns in the order parameters from our simulations. Moreover, we find in the simulations that the C6 tail can insert 1-2Å more deeply into the zwitterionic membrane and can exist in a wider range of angles than in the negatively charged membrane. We

  9. Dynamic membrane interactions of antibacterial and antifungal biomolecules, and amyloid peptides, revealed by solid-state NMR spectroscopy.

    Science.gov (United States)

    Naito, Akira; Matsumori, Nobuaki; Ramamoorthy, Ayyalusamy

    2018-02-01

    A variety of biomolecules acting on the cell membrane folds into a biologically active structure in the membrane environment. It is, therefore, important to determine the structures and dynamics of such biomolecules in a membrane environment. While several biophysical techniques are used to obtain low-resolution information, solid-state NMR spectroscopy is one of the most powerful means for determining the structure and dynamics of membrane bound biomolecules such as antibacterial biomolecules and amyloidogenic proteins; unlike X-ray crystallography and solution NMR spectroscopy, applications of solid-state NMR spectroscopy are not limited by non-crystalline, non-soluble nature or molecular size of membrane-associated biomolecules. This review article focuses on the applications of solid-state NMR techniques to study a few selected antibacterial and amyloid peptides. Solid-state NMR studies revealing the membrane inserted bent α-helical structure associated with the hemolytic activity of bee venom melittin and the chemical shift oscillation analysis used to determine the transmembrane structure (with α-helix and 3 10 -helix in the N- and C-termini, respectively) of antibiotic peptide alamethicin are discussed in detail. Oligomerization of an amyloidogenic islet amyloid polypeptide (IAPP, or also known as amylin) resulting from its aggregation in a membrane environment, molecular interactions of the antifungal natural product amphotericin B with ergosterol in lipid bilayers, and the mechanism of lipid raft formation by sphingomyelin studied using solid state NMR methods are also discussed in this review article. This article is part of a Special Issue entitled "Biophysical Exploration of Dynamical Ordering of Biomolecular Systems" edited by Dr. Koichi Kato. Copyright © 2017 Elsevier B.V. All rights reserved.

  10. Impact of coagulant and flocculant addition to an anaerobic dynamic membrane bioreactor (AnDMBR) treating waste-activated sludge

    NARCIS (Netherlands)

    Kooijman, G.; Lopes, Wilton; Zhou, Z.; Guo, H.; de Kreuk, M.K.; Spanjers, H.L.F.M.; van Lier, J.B.

    2017-01-01

    In this work, we investigated the effects of flocculation aid (FA) addition to an anaerobic dynamic membrane bioreactor (AnDMBR) (7 L, 35°C) treating waste-activated sludge (WAS). The experiment consisted of three distinct periods. In period 1 (day 1–86), the reactor was operated as a

  11. Dynamic behavior of liquid water transport in a tapered channel of a proton exchange membrane fuel cell cathode

    NARCIS (Netherlands)

    Akhtar, N.; Kerkhof, P.J.A.M.

    2011-01-01

    A numerical model of a proton exchange membrane fuel cell (PEMFC) cathode with a tapered channel design has been developed in order to examine the dynamic behavior of liquid water transport. Three-dimensional, transient simulations employing the level-set method (available in COMSOL 3.5a, a

  12. Convergence of lateral dynamic measurements in the plasma membrane of live cells from single particle tracking and STED-FCS

    DEFF Research Database (Denmark)

    Lagerholm, B. Christoffer; Andrade, Débora M.; Clausen, Mathias P.

    2017-01-01

    Fluorescence correlation spectroscopy (FCS) in combination with the super-resolution imaging method STED (STED-FCS), and single-particle tracking (SPT) are able to directly probe the lateral dynamics of lipids and proteins in the plasma membrane of live cells at spatial scales much below the diff...

  13. Molecular, dynamic, and structural origin of inhomogeneous magnetization transfer in lipid membranes.

    Science.gov (United States)

    Swanson, Scott D; Malyarenko, Dariya I; Fabiilli, Mario L; Welsh, Robert C; Nielsen, Jon-Fredrik; Srinivasan, Ashok

    2017-03-01

    To elucidate the dynamic, structural, and molecular properties that create inhomogeneous magnetization transfer (ihMT) contrast. Amphiphilic lipids, lamellar phospholipids with cholesterol, and bovine spinal cord (BSC) specimens were examined along with nonlipid systems. Magnetization transfer (MT), enhanced MT (eMT, obtained with double-sided radiofrequency saturation), ihMT (MT - eMT), and dipolar relaxation, T 1D , were measured at 2.0 and 11.7 T. The amplitude of ihMT ratio (ihMTR) is positively correlated with T 1D values. Both ihMTR and T 1D increase with increasing temperature in BSC white matter and in phospholipids and decrease with temperature in other lipids. Changes in ihMTR with temperature arise primarily from alterations in MT rather than eMT. Spectral width of MT, eMT, and ihMT increases with increasing carbon chain length. Concerted motions of phospholipids in white matter decrease proton spin diffusion leading to increased proton T 1D times and increased ihMT amplitudes, consistent with decoupling of Zeeman and dipolar spin reservoirs. Molecular specificity and dynamic sensitivity of ihMT contrast make it a suitable candidate for probing myelin membrane disorders. Magn Reson Med 77:1318-1328, 2017. © 2016 International Society for Magnetic Resonance in Medicine. © 2016 International Society for Magnetic Resonance in Medicine.

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

    Directory of Open Access Journals (Sweden)

    Hong Sun

    2015-01-01

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

  15. Communication: Contrasting effects of glycerol and DMSO on lipid membrane surface hydration dynamics and forces

    Energy Technology Data Exchange (ETDEWEB)

    Schrader, Alex M. [Department of Chemical Engineering, University of California, Santa Barbara, California 93106 (United States); Cheng, Chi-Yuan [Department of Chemistry and Biochemistry, University of California, Santa Barbara, California 93106 (United States); Israelachvili, Jacob N. [Department of Chemical Engineering, University of California, Santa Barbara, California 93106 (United States); Department of Chemistry and Biochemistry, University of California, Santa Barbara, California 93106 (United States); Materials Department, University of California, Santa Barbara, California 93106 (United States); Han, Songi [Department of Chemical Engineering, University of California, Santa Barbara, California 93106 (United States); Department of Chemistry and Biochemistry, University of California, Santa Barbara, California 93106 (United States)

    2016-07-28

    Glycerol and dimethyl sulfoxide (DMSO) are commonly used cryoprotectants in cellular systems, but due to the challenges of measuring the properties of surface-bound solvent, fundamental questions remain regarding the concentration, interactions, and conformation of these solutes at lipid membrane surfaces. We measured the surface water diffusivity at gel-phase dipalmitoylphosphatidylcholine (DPPC) bilayer surfaces in aqueous solutions containing ≤7.5 mol. % of DMSO or glycerol using Overhauser dynamic nuclear polarization. We found that glycerol similarly affects the diffusivity of water near the bilayer surface and that in the bulk solution (within 20%), while DMSO substantially increases the diffusivity of surface water relative to bulk water. We compare these measurements of water dynamics with those of equilibrium forces between DPPC bilayers in the same solvent mixtures. DMSO greatly decreases the range and magnitude of the repulsive forces between the bilayers, whereas glycerol increases it. We propose that the differences in hydrogen bonding capability of the two solutes leads DMSO to dehydrate the lipid head groups, while glycerol affects surface hydration only as much as it affects the bulk water properties. The results suggest that the mechanism of the two most common cryoprotectants must be fundamentally different: in the case of DMSO by decoupling the solvent from the lipid surface, and in the case of glycerol by altering the hydrogen bond structure and intermolecular cohesion of the global solvent, as manifested by increased solvent viscosity.

  16. Characterization of Bifunctional Spin Labels for Investigating the Structural and Dynamic Properties of Membrane Proteins Using EPR Spectroscopy.

    Science.gov (United States)

    Sahu, Indra D; Craig, Andrew F; Dunagum, Megan M; McCarrick, Robert M; Lorigan, Gary A

    2017-10-05

    Site-directed spin labeling (SDSL) coupled with electron paramagnetic resonance (EPR) spectroscopy is a very powerful technique to study structural and dynamic properties of membrane proteins. The most widely used spin label is methanthiosulfonate (MTSL). However, the flexibility of this spin label introduces greater uncertainties in EPR measurements obtained for determining structures, side-chain dynamics, and backbone motion of membrane protein systems. Recently, a newer bifunctional spin label (BSL), 3,4-bis(methanethiosulfonylmethyl)-2,2,5,5-tetramethyl-2,5-dihydro-1H-pyrrol-1-yloxy, has been introduced to overcome the dynamic limitations associated with the MTSL spin label and has been invaluable in determining protein backbone dynamics and inter-residue distances due to its restricted internal motion and fewer size restrictions. While BSL has been successful in providing more accurate information about the structure and dynamics of several proteins, a detailed characterization of the spin label is still lacking. In this study, we characterized BSLs by performing CW-EPR spectral line shape analysis as a function of temperature on spin-labeled sites inside and outside of the membrane for the integral membrane protein KCNE1 in POPC/POPG lipid bilayers and POPC/POPG lipodisq nanoparticles. The experimental data revealed a powder pattern spectral line shape for all of the KCNE1-BSL samples at 296 K, suggesting the motion of BSLs approaches the rigid limit regime for these series of samples. BSLs were further utilized to report for the first time the distance measurement between two BSLs attached on an integral membrane protein KCNE1 in POPC/POPG lipid bilayers at room temperature using dipolar line broadening CW-EPR spectroscopy. The CW dipolar line broadening EPR data revealed a 15 ± 2 Å distance between doubly attached BSLs on KCNE1 (53/57-63/67) which is consistent with molecular dynamics modeling and the solution NMR structure of KCNE1 which yielded a

  17. Multilayer network representation of membrane potential and cytosolic calcium concentration dynamics in beta cells

    International Nuclear Information System (INIS)

    Gosak, Marko; Dolenšek, Jurij; Markovič, Rene; Slak Rupnik, Marjan; Marhl, Marko; Stožer, Andraž

    2015-01-01

    Highlights: • Physiological processes within and among pancreatic beta cells are very complex. • We analyze the simultaneous recordings of membrane potential and calcium dynamics. • We represent the interaction patterns among beta cells as a multilayer network. • The nature of the intracellular dynamics is found to rely on the network structure. - Abstract: Modern theory of networks has been recognized as a very successful methodological concept for the description and analysis of complex systems. However, some complex systems are more complex than others. For instance, several real-life systems are constituted by interdependent subsystems and their elements are subjected to different types of interactions that can also change with time. Recently, the multilayer network formalism has been proposed as a general theoretical framework for the description and analysis of such multi-dimensional complex systems and is acquiring more and more prominence in terms of a new research direction. In the present study, we use this methodology for the description of functional connectivity patterns and signal propagation between pancreatic beta cells in an islet of Langerhans at the levels of membrane potential (MP) and cytosolic calcium concentration ([Ca"2"+]_c) dynamics to study the extent of overlap in the two networks and to clarify whether time lags between the two signals in individual cells are in any way dependent on the role these cells play in the functional networks. The two corresponding network layers are constructed on the basis of signal directions and pairwise correlations, whereas the interlayer connections represent the time lag between both measured signals. Our results confirm our previous finding that both MP and [Ca"2"+]_c change spread across an islet in the form of a depolarization and a [Ca"2"+]_c wave, respectively. Both types of waves follow nearly the same path and the networks in both layers have a similar but not entirely the same structure

  18. Hydration dynamics of a lipid membrane: Hydrogen bond networks and lipid-lipid associations

    Science.gov (United States)

    Srivastava, Abhinav; Debnath, Ananya

    2018-03-01

    reveal that the slow relaxation rates of interfacial waters in the vicinity of lipids are originated from the chemical confinement of concerted hydrogen bond networks. The analysis suggests that the networks in the hydration layer of membranes dynamically facilitate the water mediated lipid-lipid associations which can provide insights on the thermodynamic stability of soft interfaces relevant to biological systems in the future.

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

    KAUST Repository

    Hussaini, I.S.; Wang, C.Y.

    2010-01-01

    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

  20. Dynamic activation of basilar membrane macrophages in response to chronic sensory cell degeneration in aging mouse cochleae.

    Science.gov (United States)

    Frye, Mitchell D; Yang, Weiping; Zhang, Celia; Xiong, Binbin; Hu, Bo Hua

    2017-02-01

    In the sensory epithelium, macrophages have been identified on the scala tympani side of the basilar membrane. These basilar membrane macrophages are the spatially closest immune cells to sensory cells and are able to directly respond to and influence sensory cell pathogenesis. While basilar membrane macrophages have been studied in acute cochlear stresses, their behavior in response to chronic sensory cell degeneration is largely unknown. Here we report a systematic observation of the variance in phenotypes, the changes in morphology and distribution of basilar membrane tissue macrophages in different age groups of C57BL/6J mice, a mouse model of age-related sensory cell degeneration. This study reveals that mature, fully differentiated tissue macrophages, not recently infiltrated monocytes, are the major macrophage population for immune responses to chronic sensory cell death. These macrophages display dynamic changes in their numbers and morphologies as age increases, and the changes are related to the phases of sensory cell degeneration. Notably, macrophage activation precedes sensory cell pathogenesis, and strong macrophage activity is maintained until sensory cell degradation is complete. Collectively, these findings suggest that mature tissue macrophages on the basilar membrane are a dynamic group of cells that are capable of vigorous adaptation to changes in the local sensory epithelium environment influenced by sensory cell status. Copyright © 2016 Elsevier B.V. All rights reserved.

  1. Membrane flux dynamics in the submerged ultrafiltration hybrid treatment process during particle and natural organic matter removal

    Institute of Scientific and Technical Information of China (English)

    Wei Zhang; Xiaojian Zhang; Yonghong Li; Jun Wang; Chao Chen

    2011-01-01

    Particles and natural organic matter (NOM) are two major concerns in surface water,which greatly influence the membrane filtration process.The objective of this article is to investigate the effect of particles,NOM and their interaction on the submerged ultrafiltration (UF) membrane flux under conditions of solo UF and coagulation and PAC adsorption as the pretreatment of UF.Particles,NOM and their mixture were spiked in tap water to simulate raw water.Exponential relationship,(JP/JP0 =axexp{-k[t-(n- 1)T]}),was developed to quantify the normalized membrane flux dynamics during the filtration period and fitted the results well.In this equation,coefficient a was determined by the value of Jp/Jp0 at the beginning of a filtration cycle,reflecting the flux recovery after backwashing,that is,the irreversible fouling.The coefficient k reflected the trend of flux dynamics.Integrated total permeability (ΣJp) in one filtration period could be used as a quantified indicator for comparison of different hybrid membrane processes or under different scenarios.According to the results,there was an additive effect on membrane flux by NOM and particles during solo UF process.This additive fouling could be alleviated by coagulation pretreatment since particles helped the formation of flocs with coagulant,which further delayed the decrease of membrane flux and benefited flux recovery by backwashing.The addition of PAC also increased membrane flux by adsorbing NOM and improved flux recovery through backwashing.

  2. In situ investigation of tubular microbial fuel cells deployed in an aeration tank at a municipal wastewater treatment plant.

    Science.gov (United States)

    Zhang, Fei; Ge, Zheng; Grimaud, Julien; Hurst, Jim; He, Zhen

    2013-05-01

    To examine the feasibility of integrating microbial fuel cells (MFCs) into an activated sludge process, three MFCs with different ion exchange membranes and/or cathode catalysts were installed in an aeration tank to treat primary effluent. Both contaminant treatment and electricity generation were studied during the operation for more than 400 days. The effects of membrane/catalysts on MFC performance were not observed, likely due to the low removal of chemical oxygen demand (COD) (tank, unless the key problems such as biofouling are solved. Copyright © 2013 Elsevier Ltd. All rights reserved.

  3. Dewaterability of sludge digested in extended aeration plants using ...

    African Journals Online (AJOL)

    STORAGESEVER

    2010-07-19

    Jul 19, 2010 ... extended aeration (EA) or anaerobic digestion were compared on full and lab scale sand drying ... Novak, 1999) and to the reduction of iron concentration in ... nutrient removal and provide semi-plug flow conditions to reduce.

  4. Aeration strategy for biofilm cultivation of the microalga Scenedesmus dimorphus.

    Science.gov (United States)

    Ji, Chunli; Wang, Junfeng; Liu, Tianzhong

    2015-10-01

    Biofilm cultivation of microalgae may be useful for biofuel production. However, many aspects for this cultivation method have not been well assessed. Accordingly, aeration strategy for biofilm cultivation of Scenedesmus dimorphus has been explored. Biomass, lipid and triacylglycerol (TAG) productivity in increased S. dimorphus as the CO2 concentration increased within 0.038-0.5% and kept constant with further increases. The biomass, lipid and TAG productivity increased with the speed increasing and an obvious threshold point was observed at 6.6 ml(-2) min(-1). The lipid and TAG content was unaffected by the aeration rate. Both the CO2 concentration as well as aeration speed affected the growth of S. dimorphus in biofilm cultivation. The optimized aeration strategy for biofilm cultivation was continuous air flow enriched with 1% CO2 (v/v) at 6.6 ml(-2) min(-1).

  5. The cytotoxic activity of miltefosine against Leishmania and macrophages is associated with dynamic changes in plasma membrane proteins.

    Science.gov (United States)

    Fernandes, Kelly Souza; de Souza, Paulo Eduardo Narcizo; Dorta, Miriam Leandro; Alonso, Antonio

    2017-01-01

    In this study, we combined electron paramagnetic resonance (EPR) spectroscopy with an analysis of biophysical cellular parameters to study the mechanisms underlying the in vitro anti-leishmanial activity of miltefosine (MT). A thiol-specific spin label attached to membrane-bound proteins of Leishmania amazonensis and peritoneal macrophages indicated that MT may bind to plasma membrane proteins in large quantities via a detergent-like action and cause structural changes associated with a marked increase in dynamics and exposure to an aqueous environment. EPR spectra of a spin-labeled stearic acid indicated strong interactions between the probe and membrane proteins and a marked increase in the membrane fluidity of MT-treated cells. The cytotoxicity of MT was found to depend on the cell concentration used in the assay. This dependence was described by an equation involving the 50% inhibitory concentrations of MT in the aqueous medium (c w50 ) and the cell membrane (c m50 ) and the membrane-aqueous medium partition coefficient of MT (K). With a c w50 of 8.7μM, macrophages were less sensitive to MT than amastigotes and promastigotes of Leishmania, which had c w50 values of 2.4-3.1μM. The estimated c m50 of MT for Leishmania was 1.8M, which appears sufficient to cause ruptures or formation of pores in the plasma membrane. Additionally, we demonstrated that the changes in the plasma membrane detected by EPR spectroscopy occurred at cytotoxic concentrations of MT, as assessed through in vitro assays. Copyright © 2016 Elsevier B.V. All rights reserved.

  6. Effect of Post-Infiltration Soil Aeration at Different Growth Stages on Growth and Fruit Quality of Drip-Irrigated Potted Tomato Plants (Solanum lycopersicum.

    Directory of Open Access Journals (Sweden)

    Yuan Li

    Full Text Available Soil hydraulic principles suggest that post-infiltration hypoxic conditions would be induced in the plant root-zone for drip-irrigated tomato production in small pots filled with natural soil. No previous study specifically examined the response of tomato plants (Solanum lycopersicum at different growth stages to low soil aeration under these conditions. A 2 × 6 factorial experiment was conducted to quantify effects of no post-infiltration soil aeration versus aeration during 5 different periods (namely 27-33, 34-57, 58-85, 86-99, and 27-99 days after sowing, on growth and fruit quality of potted single tomato plants that were sub-surface trickle-irrigated every 2 days at 2 levels. Soil was aerated by injecting 2.5 liters of air into each pot through the drip tubing immediately after irrigation. Results showed that post-infiltration aeration, especially during the fruit setting (34-57 DAS and enlargement (58-85 DAS growth stages, can positively influence the yield, root dry weight and activity, and the nutritional (soluble solids and vitamin C content, taste (titratable acidity, and market quality (shape and firmness of the tomato fruits. Interactions between irrigation level and post-infiltration aeration on some of these fruit quality parameters indicated a need for further study on the dynamic interplay of air and water in the root zone of the plants under the conditions of this experiment.

  7. Effect of Post-Infiltration Soil Aeration at Different Growth Stages on Growth and Fruit Quality of Drip-Irrigated Potted Tomato Plants (Solanum lycopersicum).

    Science.gov (United States)

    Li, Yuan; Jia, Zongxia; Niu, Wenquan; Wang, Jingwei; Zhang, Mingzhi

    2015-01-01

    Soil hydraulic principles suggest that post-infiltration hypoxic conditions would be induced in the plant root-zone for drip-irrigated tomato production in small pots filled with natural soil. No previous study specifically examined the response of tomato plants (Solanum lycopersicum) at different growth stages to low soil aeration under these conditions. A 2 × 6 factorial experiment was conducted to quantify effects of no post-infiltration soil aeration versus aeration during 5 different periods (namely 27-33, 34-57, 58-85, 86-99, and 27-99 days after sowing), on growth and fruit quality of potted single tomato plants that were sub-surface trickle-irrigated every 2 days at 2 levels. Soil was aerated by injecting 2.5 liters of air into each pot through the drip tubing immediately after irrigation. Results showed that post-infiltration aeration, especially during the fruit setting (34-57 DAS) and enlargement (58-85 DAS) growth stages, can positively influence the yield, root dry weight and activity, and the nutritional (soluble solids and vitamin C content), taste (titratable acidity), and market quality (shape and firmness) of the tomato fruits. Interactions between irrigation level and post-infiltration aeration on some of these fruit quality parameters indicated a need for further study on the dynamic interplay of air and water in the root zone of the plants under the conditions of this experiment.

  8. Sphingolipid topology and the dynamic organization and function of membrane proteins.

    Science.gov (United States)

    van Meer, Gerrit; Hoetzl, Sandra

    2010-05-03

    When acquiring internal membranes and vesicular transport, eukaryotic cells started to synthesize sphingolipids and sterols. The physical differences between these and the glycerophospholipids must have enabled the cells to segregate lipids in the membrane plane. Localizing this event to the Golgi then allowed them to create membranes of different lipid composition, notably a thin, flexible ER membrane, consisting of glycerolipids, and a sturdy plasma membrane containing at least 50% sphingolipids and sterols. Besides sorting membrane proteins, in the course of evolution the simple sphingolipids obtained key positions in cellular physiology by developing specific interactions with (membrane) proteins involved in the execution and control of signaling. The few signaling sphingolipids in mammals must provide basic transmission principles that evolution has built upon for organizing the specific regulatory pathways tuned to the needs of the different cell types in the body. Copyright 2009 Federation of European Biochemical Societies. Published by Elsevier B.V. All rights reserved.

  9. Study of test methods for radionuclide migration in aerated zone

    International Nuclear Information System (INIS)

    Li Shushen; Guo Zede; Wang Zhiming

    1993-01-01

    Aerated zone is an important natural barrier against transport of radionuclides released from disposal facilities of LLRW. This paper introduces study methods for radionuclide migration in aerated zone, including determination of water movement, laboratory simulation test, and field tracing test. For one purpose, results obtained with different methods are compared. These methods have been used in a five-year cooperative research project between CIRP and JAERI for an establishment of methodology for safety assessment on shallow land disposal of LLRW

  10. Groundwater Quality Improvement by Using Aeration and Filtration Methods

    OpenAIRE

    Nik N. Nik Daud; Nur H. Izehar; B. Yusuf; Thamer A. Mohamed; A. Ahsan

    2013-01-01

    An experiment was conducted using two aeration methods (water-into-air and air-into-water) and followed by filtration processes using manganese greensand material. The properties of groundwater such as pH, dissolved oxygen, turbidity and heavy metal concentration (iron and manganese) will be assessed. The objectives of this study are i) to determine the effective aeration method and ii) to assess the effectiveness of manganese greensand as filter media in removing iron an...

  11. Effect of aeration interval on oxygen consumption and GHG emission during pig manure composting.

    Science.gov (United States)

    Zeng, Jianfei; Yin, Hongjie; Shen, Xiuli; Liu, Ning; Ge, Jinyi; Han, Lujia; Huang, Guangqun

    2018-02-01

    To verify the optimal aeration interval for oxygen supply and consumption and investigate the effect of aeration interval on GHG emission, reactor-scale composting was conducted with different aeration intervals (0, 10, 30 and 50 min). Although O 2 was sufficiently supplied during aeration period, it could be consumed to  0.902), suggesting that lengthening the duration of aeration interval to some extent could effectively reduce GHG emission. Copyright © 2017 Elsevier Ltd. All rights reserved.

  12. Membrane potential dynamics of populations of cortical neurons during auditory streaming

    Science.gov (United States)

    Farley, Brandon J.

    2015-01-01

    How a mixture of acoustic sources is perceptually organized into discrete auditory objects remains unclear. One current hypothesis postulates that perceptual segregation of different sources is related to the spatiotemporal separation of cortical responses induced by each acoustic source or stream. In the present study, the dynamics of subthreshold membrane potential activity were measured across the entire tonotopic axis of the rodent primary auditory cortex during the auditory streaming paradigm using voltage-sensitive dye imaging. Consistent with the proposed hypothesis, we observed enhanced spatiotemporal segregation of cortical responses to alternating tone sequences as their frequency separation or presentation rate was increased, both manipulations known to promote stream segregation. However, across most streaming paradigm conditions tested, a substantial cortical region maintaining a response to both tones coexisted with more peripheral cortical regions responding more selectively to one of them. We propose that these coexisting subthreshold representation types could provide neural substrates to support the flexible switching between the integrated and segregated streaming percepts. PMID:26269558

  13. Dynamic modeling and experimental validation for direct contact membrane distillation (DCMD) process

    KAUST Repository

    Eleiwi, Fadi

    2016-02-01

    This work proposes a mathematical dynamic model for the direct contact membrane distillation (DCMD) process. The model is based on a 2D Advection–Diffusion Equation (ADE), which describes the heat and mass transfer mechanisms that take place inside the DCMD module. The model studies the behavior of the process in the time varying and the steady state phases, contributing to understanding the process performance, especially when it is driven by intermittent energy supply, such as the solar energy. The model is experimentally validated in the steady state phase, where the permeate flux is measured for different feed inlet temperatures and the maximum absolute error recorded is 2.78 °C. Moreover, experimental validation includes the time variation phase, where the feed inlet temperature ranges from 30 °C to 75 °C with 0.1 °C increment every 2min. The validation marks relative error to be less than 5%, which leads to a strong correlation between the model predictions and the experiments.

  14. Resonant responses and chaotic dynamics of composite laminated circular cylindrical shell with membranes

    Science.gov (United States)

    Zhang, W.; Liu, T.; Xi, A.; Wang, Y. N.

    2018-06-01

    This paper is focused on the resonant responses and chaotic dynamics of a composite laminated circular cylindrical shell with radially pre-stretched membranes at both ends and clamped along a generatrix. Based on the two-degree-of-freedom non-autonomous nonlinear equations of this system, the method of multiple scales is employed to obtain the four-dimensional nonlinear averaged equation. The resonant case considered here is the primary parametric resonance-1/2 subharmonic resonance and 1:1 internal resonance. Corresponding to several selected parameters, the frequency-response curves are obtained. From the numerical results, we find that the hardening-spring-type behaviors and jump phenomena are exhibited. The jump phenomena also occur in the amplitude curves of the temperature parameter excitation. Moreover, it is found that the temperature parameter excitation, the coupling degree of two order modes and the detuning parameters can effect the nonlinear oscillations of this system. The periodic and chaotic motions of the composite laminated circular cylindrical shell clamped along a generatrix are demonstrated by the bifurcation diagrams, the maximum Lyapunov exponents, the phase portraits, the waveforms, the power spectrums and the Poincaré map. The temperature parameter excitation shows that the Pomeau-Manneville type intermittent chaos occur under the certain initial conditions. It is also found that there exist the twin phenomena between the Pomeau-Manneville type intermittent chaos and the period-doubling bifurcation.

  15. Dynamic modeling and experimental validation for direct contact membrane distillation (DCMD) process

    KAUST Repository

    Eleiwi, Fadi; Ghaffour, NorEddine; Alsaadi, Ahmad Salem; Francis, Lijo; Laleg-Kirati, Taous-Meriem

    2016-01-01

    This work proposes a mathematical dynamic model for the direct contact membrane distillation (DCMD) process. The model is based on a 2D Advection–Diffusion Equation (ADE), which describes the heat and mass transfer mechanisms that take place inside the DCMD module. The model studies the behavior of the process in the time varying and the steady state phases, contributing to understanding the process performance, especially when it is driven by intermittent energy supply, such as the solar energy. The model is experimentally validated in the steady state phase, where the permeate flux is measured for different feed inlet temperatures and the maximum absolute error recorded is 2.78 °C. Moreover, experimental validation includes the time variation phase, where the feed inlet temperature ranges from 30 °C to 75 °C with 0.1 °C increment every 2min. The validation marks relative error to be less than 5%, which leads to a strong correlation between the model predictions and the experiments.

  16. Three-dimensional dynamic modelling of Polymer-Electrolyte-Membrane-Fuel-Cell-Systems; Dreidimensionale dynamische Modellierung und Berechnung von Polymer-Elektrolyt-Membran-Brennstoffzellen

    Energy Technology Data Exchange (ETDEWEB)

    Vath, Andreas

    2008-12-15

    This thesis deals with dynamic and multi-dimensional modelling of Polymer- Electrolyte-Membrane-Fuel-Cells (PEMFC). The developed models include all the different layers of the fuel cell e.g. flow field, gas diffusion layer, catalyst layer and membrane with their particular physical, chemical and electrical characteristics. The simulation results have been verified by detailed measurements performed at the research centre for hydrogen and solar energy in Ulm (ZSW Ulm). The developed three dimensional model describes the time- and spatial-dependent charge and mass transport in a fuel cell. Additionally, this model allows the analysis of critical operating conditions. For example, the current density distribution for different membranes is shown during insufficient humidification which results in local overstraining and degradation. The model also allows to analyse extreme critical operating conditions, e.g. short time breakdown of the humidification. Furthermore, the model shows the available potential of improvement opportunities in power density and efficiency of PEMFC due to optimisation of the gas diffusion layer, the catalyst and membrane. In the second part of the work the application of PEMFC systems for combined heat and power units is described by one-dimensional models for an electrical power range between 1 kW and 5 kW. This model contains the necessary components, e.g. gas processing, humidification, gas supply, fuel cell stack, heat storage, pumps, auxiliary burner, power inverter und additional aggregates. As a main result, it is possible to distinctly reduce the energy demand and the carbon dioxide exhaust for different load profiles. Today the costs for fuel cell systems are considerably higher than that of the conventional electrical energy supply. (orig.)

  17. Conformational study of bovine lactoferricin in membrane-micking conditions by molecular dynamics simulation and circular dichroism.

    Science.gov (United States)

    Daidone, Isabella; Magliano, Alessandro; Di Nola, Alfredo; Mignogna, Giuseppina; Clarkson, Matilda Manuela; Lizzi, Anna Rita; Oratore, Arduino; Mazza, Fernando

    2011-04-01

    Lactoferricins are potent antimicrobial peptides released by pepsin cleavage of Lactoferrins. Bovine Lactoferricin (LfcinB) has higher activity than the intact bovine Lactoferrin, and is the most active among the other Lactoferricins of human, murine and caprine origin. In the intact protein the fragment corresponding to LfcinB is in an helical conformation, while in water LfcinB adopts an amphipathic β-hairpin structure. However, whether any of these structural motifs is the antibacterial active conformation, i.e., the one interacting with bacterial membrane components, remains to be seen. Here we present Circular Dichroism (CD) spectra and Molecular Dynamics (MD) simulations indicating that in membrane-mimicking solvents the LfcinB adopts an amphipathic β-hairpin structure similar to that observed in water, but differing in the dynamic behavior of the side-chains of the two tryptophan residues. In the membrane-mimicking solvent these side-chains show a high propensity to point towards the hydrophobic environment, rather than being in the hydrophobic core as seen in water, while the backbone preserves the hairpin conformation as found in water. These results suggest that the tryptophans might act as anchors pulling the stable, solvent-invariant hairpin structure into the membrane.

  18. Oxygen enriched air using membrane for palm oil wastewater treatment

    Directory of Open Access Journals (Sweden)

    Ramlah Mohd Tajuddin

    2002-11-01

    Full Text Available A research aimed to explore new method of aeration using oxygen enriched air performance on BOD reduction of palm oil wastewater was conducted. The oxygen enriched air was obtained from an Oxygen Enriched System (OES developed using asymmetric polysulfone hollow fiber membrane with composition consisting of PSF: 22%, DMAc: 31.8%, THF: 31.8%, EtOH: 14.4%. Palm oil wastewater samples were taken from facultative pond effluent. These samples were tested for its initial biochemical oxygen demand (BOD, total suspended solids (TSS, pH, conductivity, turbidity, dissolved oxygen (DO, suspended solids (SS, and total dissolved solids (TDS before being subjected to two modes of aeration system, that is diffused air and oxygen enriched air. These water quality concentrations were tested for every 20 minutes for two-hour period during the aeration process. Results of BOD, TSS, pH, conductivity, DO, SS and TDS concentrations against time of samples from the two modes of aeration were then compared. It was found that DO concentration achieved in oxygen enriched air aeration was better than aeration using diffused air system. Aeration using OES improve the DO concentration in the wastewater and thus improve the BOD reduction and also influence other physical characteristics of wastewater. This phenomenon indicates the advantage of using air with higher oxygen concentration for wastewater aeration instead of diffused air system.

  19. Dynamic adsorption of mixtures of Rhodamine B, Pb (II), Cu (II) and Zn(II) ions on composites chitosan-silica-polyethylene glycol membrane

    Science.gov (United States)

    Mahatmanti, F. W.; Rengga, W. D. P.; Kusumastuti, E.; Nuryono

    2018-04-01

    The adsorption of a solution mixture of Rhodamine B, Pb (II), Cu (II) and Zn(II) was studied using dynamic methods employing chitosan-silica-polyethylene glycol (Ch/Si/P) composite membrane as an adsorptive membrane. The composite Ch/Si/P membrane was prepared by mixing a chitosan-based membrane with silica isolated from rice husk ash (ASP) and polyethylene glycol (PEG) as a plasticizer. The resultant composite membrane was a stronger and more flexible membrane than the original chitosan-based membrane as indicated by the maximum percentage of elongation (20.5 %) and minimum Young’s Modulus (80.5 MPa). The composite membrane also showed increased mechanical and hydrophilic properties compared to the chitosan membranes. The membrane was used as adsorption membrane for Pb (II), Cu (II), Cd (II) ions and Rhodamine B dyes in a dynamic system where the permeation and selectivity were determined. The permeation of the components was observed to be in the following order: Rhodamine B > Cd (II) > Pb (II) > Cu (II) whereas the selectivity was shown to decrease the order of Cu (II) > Pb (II) > Cd (II) > Rhodamine B.

  20. Characterization of Odorant Compounds from Mechanical Aerated Pile Composting and Static Aerated Pile Composting

    Directory of Open Access Journals (Sweden)

    Priyanka Kumari

    2016-04-01

    Full Text Available We studied airborne contaminants (airborne particulates and odorous compounds emitted from compost facilities in South Korea. There are primarily two different types of composting systems operating in Korean farms, namely mechanical aerated pile composting (MAPC and aerated static pile composting (SAPC. In this study, we analyzed various particulate matters (PM10, PM7, PM2.5, PM1, and total suspended particles, volatile organic compounds and ammonia, and correlated these airborne contaminants with microclimatic parameters, i.e., temperature and relative humidity. Most of the analyzed airborne particulates (PM7, PM2.5, and PM1 were detected in high concentration at SAPC facilities compered to MAPC; however these differences were statistically non-significant. Similarly, most of the odorants did not vary significantly between MAPC and SAPC facilities, except for dimethyl sulfide (DMS and skatole. DMS concentrations were significantly higher in MAPC facilities, whereas skatole concentrations were significantly higher in SAPC facilities. The microclimate variables also did not vary significantly between MAPC and SAPC facilities, and did not correlate significantly with most of the airborne particles and odorous compounds, suggesting that microclimate variables did not influence their emission from compost facilities. These findings provide insight into the airborne contaminants that are emitted from compost facilities and the two different types of composting agitation systems.

  1. Characterization of Odorant Compounds from Mechanical Aerated Pile Composting and Static Aerated Pile Composting.

    Science.gov (United States)

    Kumari, Priyanka; Lee, Joonhee; Choi, Hong-Lim

    2016-04-01

    We studied airborne contaminants (airborne particulates and odorous compounds) emitted from compost facilities in South Korea. There are primarily two different types of composting systems operating in Korean farms, namely mechanical aerated pile composting (MAPC) and aerated static pile composting (SAPC). In this study, we analyzed various particulate matters (PM10, PM7, PM2.5, PM1, and total suspended particles), volatile organic compounds and ammonia, and correlated these airborne contaminants with microclimatic parameters, i.e., temperature and relative humidity. Most of the analyzed airborne particulates (PM7, PM2.5, and PM1) were detected in high concentration at SAPC facilities compered to MAPC; however these differences were statistically non-significant. Similarly, most of the odorants did not vary significantly between MAPC and SAPC facilities, except for dimethyl sulfide (DMS) and skatole. DMS concentrations were significantly higher in MAPC facilities, whereas skatole concentrations were significantly higher in SAPC facilities. The microclimate variables also did not vary significantly between MAPC and SAPC facilities, and did not correlate significantly with most of the airborne particles and odorous compounds, suggesting that microclimate variables did not influence their emission from compost facilities. These findings provide insight into the airborne contaminants that are emitted from compost facilities and the two different types of composting agitation systems.

  2. Every day I'm rufflin': Calcium sensing and actin dynamics in the growth factor-independent membrane ruffling of professional phagocytes.

    Science.gov (United States)

    Schlam, Daniel; Canton, Johnathan

    2017-04-03

    Professional phagocytes continuously extend dynamic, actin-driven membrane protrusions. These protrusions, often referred to as membrane ruffles, serve a critical role in the essential phagocyte processes of macropinocytosis and phagocytosis. Small GTPases, such as RAC1/2, spatially and temporally regulate membrane ruffle formation. We have recently shown that extracellular calcium regulates the elaboration of membrane ruffles primarily through the synthesis of phosphatidic acid (PtdOH) at the plasma membrane. RAC1/2 guanine nucleotide exchange factors harbouring polybasic stretches are recruited by PtdOH to sites of ruffle formation. Here we discuss our findings and offer perspectives on how the regulation of dynamic actin structures at the plasma membrane by small GTPases is a critical component of phagocyte function.

  3. Toward the fourth dimension of membrane protein structure: insight into dynamics from spin-labeling EPR spectroscopy.

    Science.gov (United States)

    McHaourab, Hassane S; Steed, P Ryan; Kazmier, Kelli

    2011-11-09

    Trapping membrane proteins in the confines of a crystal lattice obscures dynamic modes essential for interconversion between multiple conformations in the functional cycle. Moreover, lattice forces could conspire with detergent solubilization to stabilize a minor conformer in an ensemble thus confounding mechanistic interpretation. Spin labeling in conjunction with electron paramagnetic resonance (EPR) spectroscopy offers an exquisite window into membrane protein dynamics in the native-like environment of a lipid bilayer. Systematic application of spin labeling and EPR identifies sequence-specific secondary structures, defines their topology and their packing in the tertiary fold. Long range distance measurements (60 Å-80 Å) between pairs of spin labels enable quantitative analysis of equilibrium dynamics and triggered conformational changes. This review highlights the contribution of spin labeling to bridging structure and mechanism. Efforts to develop methods for determining structures from EPR restraints and to increase sensitivity and throughput promise to expand spin labeling applications in membrane protein structural biology. Copyright © 2011 Elsevier Ltd. All rights reserved.

  4. Variable-angle epifluorescence microscopy characterizes protein dynamics in the vicinity of plasma membrane in plant cells.

    Science.gov (United States)

    Chen, Tong; Ji, Dongchao; Tian, Shiping

    2018-03-14

    The assembly of protein complexes and compositional lipid patterning act together to endow cells with the plasticity required to maintain compositional heterogeneity with respect to individual proteins. Hence, the applications for imaging protein localization and dynamics require high accuracy, particularly at high spatio-temporal level. We provided experimental data for the applications of Variable-Angle Epifluorescence Microscopy (VAEM) in dissecting protein dynamics in plant cells. The VAEM-based co-localization analysis took penetration depth and incident angle into consideration. Besides direct overlap of dual-color fluorescence signals, the co-localization analysis was carried out quantitatively in combination with the methodology for calculating puncta distance and protein proximity index. Besides, simultaneous VAEM tracking of cytoskeletal dynamics provided more insights into coordinated responses of actin filaments and microtubules. Moreover, lateral motility of membrane proteins was analyzed by calculating diffusion coefficients and kymograph analysis, which represented an alternative method for examining protein motility. The present study presented experimental evidence on illustrating the use of VAEM in tracking and dissecting protein dynamics, dissecting endosomal dynamics, cell structure assembly along with membrane microdomain and protein motility in intact plant cells.

  5. Reduced-Order Dynamic Modeling, Fouling Detection, and Optimal Control of Solar-Powered Direct Contact Membrane Distillation

    KAUST Repository

    Karam, Ayman M.

    2016-12-01

    Membrane Distillation (MD) is an emerging sustainable desalination technique. While MD has many advantages and can be powered by solar thermal energy, its main drawback is the low water production rate. However, the MD process has not been fully optimized in terms of its manipulated and controlled variables. This is largely due to the lack of adequate dynamic models to study and simulate the process. In addition, MD is prone to membrane fouling, which is a fault that degrades the performance of the MD process. This work has three contributions to address these challenges. First, we derive a mathematical model of Direct Contact Membrane Distillation (DCMD), which is the building block for the next parts. Then, the proposed model is extended to account for membrane fouling and an observer-based fouling detection method is developed. Finally, various control strategies are implemented to optimize the performance of the DCMD solar-powered process. In part one, a reduced-order dynamic model of DCMD is developed based on lumped capacitance method and electrical analogy to thermal systems. The result is an electrical equivalent thermal network to the DCMD process, which is modeled by a system of nonlinear differential algebraic equations (DAEs). This model predicts the water-vapor flux and the temperature distribution along the module length. Experimental data is collected to validate the steady-state and dynamic responses of the proposed model, with great agreement demonstrated in both. The second part proposes an extension of the model to account for membrane fouling. An adaptive observer for DAE systems is developed and convergence proof is presented. A method for membrane fouling detection is then proposed based on adaptive observers. Simulation results demonstrate the performance of the membrane fouling detection method. Finally, an optimization problem is formulated to maximize the process efficiency of a solar-powered DCMD. The adapted method is known as Extremum

  6. CFD Investigation of the effects of bubble aerator layouts on hydrodynamics of an activated sludge channel reactor.

    Science.gov (United States)

    Hreiz, Rainier; Potier, Olivier; Wicks, Jim; Commenge, Jean-Marc

    2018-03-08

    In this paper, computational fluid dynamics (CFD) simulations are employed to characterize the effects of bubble aerator layouts (i.e. spatial arrangement) on the hydrodynamics in activated sludge (AS) reactors. The first configuration considered is a channel reactor with aerators placed alongside one lateral wall, for which velocity measurements are available in literature. CFD results were in good agreement with experimental data, which proves that the model is sufficiently accurate and predictive. Accordingly, simulations and numerical residence time distribution tests were conducted for different aerator layouts to determine their effects on the reactor hydrodynamics. The results revealed that the flow characteristics are extremely sensitive to the aerators arrangement given the high gas flow rates used in AS processes. Among the layouts investigated, the one where diffusers are placed all over the reactor floor has led to the least dispersive flow, i.e. which characteristics best tend toward that of an ideal plug flow reactor. Indeed, this flow field presented the lowest average turbulent diffusion and the most uniform axial velocity and turbulence fields. Such a flow behaviour is expected to be highly beneficial for biological treatment since it reduces pollutant dilution by axial diffusion and limits raw wastewater channelling to the outlet.

  7. Dynamic behaviour of a flexible membrane tsunami Barrier with Dyneema®

    NARCIS (Netherlands)

    Hofland, B.; Marissen, R.; Bergsma, O.K.

    2016-01-01

    Proof-of-concept model tests on a novel self-deploying on-shore tsunami barrier were executed. The tsunami barrier consists of a membrane, floater and cables that are stored underground. Due to buoyancy the barrier self-deploys when struck by a tsunami. The membrane and cables consist of the strong,

  8. Dynamic hyperfiltration membranes for high-temperature spacecraft wash water recycle

    Science.gov (United States)

    Gaddis, J. L.; Brandon, C. A.

    1978-01-01

    The effect of operating parameters on the performance of the hyperfiltration membrane when operating on washwater was examined. The parameters were pressure, temperature, velocity, and concentration. Data taken included rejections of organic materials, ammonia, urea, and an assortment of ions. The membrane used was a dual layer, polyacrylic acid over zirconium oxide, deposited in situ on a porcelain ceramic substrate.

  9. Sphingolipid topology and the dynamic organization and function of membrane proteins

    NARCIS (Netherlands)

    van Meer, G.|info:eu-repo/dai/nl/068570368; Hoetzl, S.

    2010-01-01

    When acquiring internal membranes and vesicular transport, eukaryotic cells started to synthesize sphingolipids and sterols. The physical differences between these and the glycerophospholipids must have enabled the cells to segregate lipids in the membrane plane. Localizing this event to the Golgi

  10. Unmasking of spiral ganglion neuron firing dynamics by membrane potential and neurotrophin-3.

    Science.gov (United States)

    Crozier, Robert A; Davis, Robin L

    2014-07-16

    Type I spiral ganglion neurons have a unique role relative to other sensory afferents because, as a single population, they must convey the richness, complexity, and precision of auditory information as they shape signals transmitted to the brain. To understand better the sophistication of spiral ganglion response properties, we compared somatic whole-cell current-clamp recordings from basal and apical neurons obtained during the first 2 postnatal weeks from CBA/CaJ mice. We found that during this developmental time period neuron response properties changed from uniformly excitable to differentially plastic. Low-frequency, apical and high-frequency basal neurons at postnatal day 1 (P1)-P3 were predominantly slowly accommodating (SA), firing at low thresholds with little alteration in accommodation response mode induced by changes in resting membrane potential (RMP) or added neurotrophin-3 (NT-3). In contrast, P10-P14 apical and basal neurons were predominately rapidly accommodating (RA), had higher firing thresholds, and responded to elevation of RMP and added NT-3 by transitioning to the SA category without affecting the instantaneous firing rate. Therefore, older neurons appeared to be uniformly less excitable under baseline conditions yet displayed a previously unrecognized capacity to change response modes dynamically within a remarkably stable accommodation framework. Because the soma is interposed in the signal conduction pathway, these specializations can potentially lead to shaping and filtering of the transmitted signal. These results suggest that spiral ganglion neurons possess electrophysiological mechanisms that enable them to adapt their response properties to the characteristics of incoming stimuli and thus have the capacity to encode a wide spectrum of auditory information. Copyright © 2014 the authors 0270-6474/14/349688-15$15.00/0.

  11. Determination of re-aeration coefficients on high mountain rivers using nuclear techniques

    International Nuclear Information System (INIS)

    Fajardo, Marco

    2001-01-01

    The rivers Machangara and Guayllabamba in Quito, Ecuador, currently are highly polluted, mainly due to human and industrial residues from the city. The objective of this survey is to establish the dynamics of dissolved oxygen in these rivers using the Krypton 85 method to determine the re aeration coefficient in representative sectors of the rivers. In addition, conventional test tracers establish mean flow speed and flow longitudinal dispersion coefficients. The results of this study will be useful for future water quality modelling of these rivers, in order to define their behaviour and auto depurative capacity to treat sludge waters from Quito

  12. Dynamics of antifolate transport via the reduced folate carrier and the membrane folate receptor in murine leukaemia cells in vitro and in vivo

    NARCIS (Netherlands)

    Mauritz, Robert; Peters, Godefridus; Kathmann, Ietje; Teshale, Habte; Noordhuis, Paul; Comijn, Elizabeth; Pinedo, Herbert; Jansen, Gerrit

    Murine L1210 leukaemia cells expressing either the reduced folate carrier (RFC) or the membrane folate receptor (MFR) were studied in vitro and in vivo to assess the dynamics of membrane transport of two categories antifolates; folate-based inhibitors of dihydrofolate reductase (methotrexate,

  13. Convergence of lateral dynamic measurements in the plasma membrane of live cells from single particle tracking and STED-FCS

    International Nuclear Information System (INIS)

    Lagerholm, B Christoffer; Eggeling, Christian; Andrade, Débora M; Clausen, Mathias P

    2017-01-01

    Fluorescence correlation spectroscopy (FCS) in combination with the super-resolution imaging method STED (STED-FCS), and single-particle tracking (SPT) are able to directly probe the lateral dynamics of lipids and proteins in the plasma membrane of live cells at spatial scales much below the diffraction limit of conventional microscopy. However, a major disparity in interpretation of data from SPT and STED-FCS remains, namely the proposed existence of a very fast (unhindered) lateral diffusion coefficient, ⩾5 µ m 2 s −1 , in the plasma membrane of live cells at very short length scales, ≈⩽ 100 nm, and time scales, ≈1–10 ms. This fast diffusion coefficient has been advocated in several high-speed SPT studies, for lipids and membrane proteins alike, but the equivalent has not been detected in STED-FCS measurements. Resolving this ambiguity is important because the assessment of membrane dynamics currently relies heavily on SPT for the determination of heterogeneous diffusion. A possible systematic error in this approach would thus have vast implications in this field. To address this, we have re-visited the analysis procedure for SPT data with an emphasis on the measurement errors and the effect that these errors have on the measurement outputs. We subsequently demonstrate that STED-FCS and SPT data, following careful consideration of the experimental errors of the SPT data, converge to a common interpretation which for the case of a diffusing phospholipid analogue in the plasma membrane of live mouse embryo fibroblasts results in an unhindered, intra-compartment, diffusion coefficient of  ≈0.7–1.0 µ m 2 s −1 , and a compartment size of about 100–150 nm. (topical review)

  14. Interaction of monomeric Ebola VP40 protein with a plasma membrane: A coarse-grained molecular dynamics (CGMD) simulation study.

    Science.gov (United States)

    Mohamad Yusoff, Mohamad Ariff; Abdul Hamid, Azzmer Azzar; Mohammad Bunori, Noraslinda; Abd Halim, Khairul Bariyyah

    2018-06-01

    Ebola virus is a lipid-enveloped filamentous virus that affects human and non-human primates and consists of several types of protein: nucleoprotein, VP30, VP35, L protein, VP40, VP24, and transmembrane glycoprotein. Among the Ebola virus proteins, its matrix protein VP40 is abundantly expressed during infection and plays a number of critical roles in oligomerization, budding and egress from the host cell. VP40 exists predominantly as a monomer at the inner leaflet of the plasma membrane, and has been suggested to interact with negatively charged lipids such as phosphatidylinositol 4,5-bisphosphate (PIP 2 ) and phosphatidylserine (PS) via its cationic patch. The hydrophobic loop at the C-terminal domain has also been shown to be important in the interaction between the VP40 and the membrane. However, details of the molecular mechanisms underpinning their interactions are not fully understood. This study aimed at investigating the effects of mutation in the cationic patch and hydrophobic loop on the interaction between the VP40 monomer and the plasma membrane using coarse-grained molecular dynamics simulation (CGMD). Our simulations revealed that the interaction between VP40 and the plasma membrane is mediated by the cationic patch residues. This led to the clustering of PIP 2 around the protein in the inner leaflet as a result of interactions between some cationic residues including R52, K127, K221, K224, K225, K256, K270, K274, K275 and K279 and PIP 2 lipids via electrostatic interactions. Mutation of the cationic patch or hydrophobic loop amino acids caused the protein to bind at the inner leaflet of the plasma membrane in a different orientation, where no significant clustering of PIP 2 was observed around the mutated protein. This study provides basic understanding of the interaction of the VP40 monomer and its mutants with the plasma membrane. Copyright © 2018 Elsevier Inc. All rights reserved.

  15. PIV Study of Aeration Efficient of Stepped Spillway System

    Science.gov (United States)

    Abas, M. A.; Jamil, R.; Rozainy, M. R.; Zainol, M. A.; Adlan, M. N.; Keong, C. W.

    2017-06-01

    This paper investigates the three-dimensional (3D) simulation of Cascade aerator system using Lattice Boltzmann simulation and laboratory experiment was carried out to investigate the flow, aeration and cavitation in the spillway. Different configurations of stepped spillway are designed in this project in order to investigate the relationship between the configurations of stepped spillway and cavitation in the flow. The aeration in the stepped spillway will also be investigated. The experimental result will be compared with the simulated result at the end of this project. The figure of flow pattern at the 3rd step in simulation and experiment for Set 1 and Set 2 are look similar between LBM simulation and the experiment findings. This will provide a better understanding of the cavitation, aeration and flow in different configurations of the stepped spillway. In addition the occurrence of negative pressure region in the stepped spillway, increases the possibility of cavitation to occur. The cavitation will damage the structure of the stepped spillway. Furthermore, it also founds that increasing in barrier thickness of the stepped spillway will improve the aeration efficiency and reduce the cavitation in stepped spillway.

  16. Aerated drilling cutting transport analysis in geothermal well

    Science.gov (United States)

    Wakhyudin, Aris; Setiawan, Deni; Dwi Marjuan, Oscar

    2017-12-01

    Aeratad drilling widely used for geothermal drilling especially when drilled into predicted production zone. Aerated drilling give better performance on preventing lost circulation problem, improving rate of penetration, and avoiding drilling fluid invasion to productive zone. While well is drilled, cutting is produced and should be carried to surface by drilling fluid. Hole problem, especially pipe sticking will occur while the cutting is not lifted properly to surface. The problem will effect on drilling schedule; non-productive time finally result more cost to be spent. Geothermal formation has different characteristic comparing oil and gas formation. Geothermal mainly has igneous rock while oil and gas mostly sedimentary rock. In same depth, formation pressure in geothermal well commonly lower than oil and gas well while formation temperature geothermal well is higher. While aerated drilling is applied in geothermal well, Igneous rock density has higher density than sedimentary rock and aerated drilling fluid is lighter than water based mud hence minimum velocity requirement to transport cutting is larger than in oil/gas well drilling. Temperature and pressure also has impact on drilling fluid (aerated) density. High temperature in geothermal well decrease drilling fluid density hence the effect of pressure and temperature also considered. In this paper, Aerated drilling cutting transport performance on geothermal well will be analysed due to different rock and drilling fluid density. Additionally, temperature and pressure effect on drilling fluid density also presented to merge.

  17. Theoretical studies on membrane-based gas separation using computational fluid dynamics (CFD) of mass transfer

    International Nuclear Information System (INIS)

    Sohrabi, M.R.; Marjani, A.; Davallo, M.; Moradi, S.; Shirazian, S.

    2011-01-01

    A 2D mass transfer model was developed to study carbon dioxide removal by absorption in membrane contactors. The model predicts the steady state absorbent and carbon dioxide concentrations in the membrane by solving the conservation equations. The continuity equations for three sub domains of the membrane contactor involving the tube; membrane and shell were obtained and solved by finite element method (FEM). The model was based on 'non-wetted mode' in which the gas phase filled the membrane pores. Laminar parabolic velocity profile was used for the liquid flow in the tube side; whereas, the gas flow in the shell side was characterized by Happel's free surface model. Axial and radial diffusion transport inside the shell, through the membrane, and within the tube side of the contactor was considered in the mass transfer model. The predictions of percent CO/sub 2/ removal obtained by modeling were compared with the experimental values obtained from literature. They were the experimental results for CO/sub 2/ removal from CO/sub 2//N/sub 2/ gas mixture with amines aqueous solutions as the liquid solvent using polypropylene membrane contactor. The modeling predictions were in good agreement with the experimental values for different values of gas and liquid flow rates. (author)

  18. The influence of mesoscopic confinement on the dynamics of imidazolium-based room temperature ionic liquids in polyether sulfone membranes

    Science.gov (United States)

    Thomaz, Joseph E.; Bailey, Heather E.; Fayer, Michael D.

    2017-11-01

    The structural dynamics of a series of 1-alkyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (CnmimNTf2, n = 2, 4, 6, 10: ethyl—Emim; butyl—Bmim; hexyl—Hmim; decyl—Dmim) room temperature ionic liquids confined in the pores of polyether sulfone (PES 200) membranes with an average pore size of ˜350 nm and in the bulk liquids were studied. Time correlated single photon counting measurements of the fluorescence of the fluorophore coumarin 153 (C153) were used to observe the time-dependent Stokes shift (solvation dynamics). The solvation dynamics of C153 in the ionic liquids are multiexponential decays. The multiexponential functional form of the decays was confirmed as the slowest decay component of each bulk liquid matches the slowest component of the liquid dynamics measured by optical heterodyne-detected optical Kerr effect (OHD-OKE) experiments, which is single exponential. The fact that the slowest component of the Stokes shift matches the OHD-OKE data in all four liquids identifies this component of the solvation dynamics as arising from the complete structural randomization of the liquids. Although the pores in the PES membranes are large, confinement on the mesoscopic length scale results in substantial slowing of the dynamics, a factor of ˜4, for EmimNTf2, with the effect decreasing as the chain length increases. By DmimNTf2, the dynamics are virtually indistinguishable from those in the bulk liquid. The rotation relaxation of C153 in the four bulk liquids was also measured and showed strong coupling between the C153 probe and its environment.

  19. Bubbling jet characteristics in an aeration tank; Aeration sonai kiho funryu no ryudo kyodo

    Energy Technology Data Exchange (ETDEWEB)

    Kaji, M; Iguchi, M; Okita, K [Osaka University, Osaka (Japan). Faculty of Engineering; Nakatani, T [Kobe University, Kobe (Japan). Faculty of Engineering

    1996-11-25

    Laser Doppler velocimeter measurements were made to investigate bubbling jet characteristics in an aeration tank at a pressure of 200 kPa. The data were compared with previous measurements at atmospheric and reduced pressures. Bubble frequencies at the nozzle outlet were correlated with the mass flow rate of gas rather than the volumetric flow rate. In the far field where the buoyancy force of bubbles prevails, the axial and radial distributions of the mean velocity components, the r. m. s. values of turbulence components, the Reynolds shear stress and the skewness and flatness factors of the turbulence components obtained at an elevated pressure agreed well with those obtained at the atmospheric pressure for the same volumetric gas flow rate. Consequently, the liquid flow characteristics including the turbulence structure in the far field are not influenced by an increase in surface pressure as long as the volumetric gas flow rate is the same. 13 refs., 14 figs.

  20. Energy Consumption in Terms of Shear Stress for Two Types of Membrane Bioreactors used for Municipal Wastewater Treatment Processes

    DEFF Research Database (Denmark)

    Ratkovich, Nicolas Rios; Bentzen, Thomas Ruby; Rasmussen, Michael R.

    2012-01-01

    Two types of submerged membrane bioreactors (MBR): hollow fiber (HF) and hollow sheet (HS), have been studied and compared in terms of energy consumption and average shear stress over the membrane wall. The analysis of energy consumption was made using the correlation to determine the blower power...... of shear stress over the membrane surface was made using computational fluid dynamics (CFD) modelling. Experimental measurements for the HF MBR were compared with the CFD model and an error less that 8% was obtained. For the HS MBR, experimental measurements of velocity profiles were made and an error...... of 11% was found. This work uses an empirical relationship to determine the shear stress based on the ratio of aeration blower power to tank volume. This relationship is used in bubble column reactors and it is extrapolate to determine shear stress on MBR systems. This relationship proved...

  1. Integrating Solid-State NMR and Computational Modeling to Investigate the Structure and Dynamics of Membrane-Associated Ghrelin

    Science.gov (United States)

    Els-Heindl, Sylvia; Chollet, Constance; Scheidt, Holger A.; Beck-Sickinger, Annette G.; Meiler, Jens; Huster, Daniel

    2015-01-01

    The peptide hormone ghrelin activates the growth hormone secretagogue receptor 1a, also known as the ghrelin receptor. This 28-residue peptide is acylated at Ser3 and is the only peptide hormone in the human body that is lipid-modified by an octanoyl group. Little is known about the structure and dynamics of membrane-associated ghrelin. We carried out solid-state NMR studies of ghrelin in lipid vesicles, followed by computational modeling of the peptide using Rosetta. Isotropic chemical shift data of isotopically labeled ghrelin provide information about the peptide’s secondary structure. Spin diffusion experiments indicate that ghrelin binds to membranes via its lipidated Ser3. Further, Phe4, as well as electrostatics involving the peptide’s positively charged residues and lipid polar headgroups, contribute to the binding energy. Other than the lipid anchor, ghrelin is highly flexible and mobile at the membrane surface. This observation is supported by our predicted model ensemble, which is in good agreement with experimentally determined chemical shifts. In the final ensemble of models, residues 8–17 form an α-helix, while residues 21–23 and 26–27 often adopt a polyproline II helical conformation. These helices appear to assist the peptide in forming an amphipathic conformation so that it can bind to the membrane. PMID:25803439

  2. Integrating solid-state NMR and computational modeling to investigate the structure and dynamics of membrane-associated ghrelin.

    Directory of Open Access Journals (Sweden)

    Gerrit Vortmeier

    Full Text Available The peptide hormone ghrelin activates the growth hormone secretagogue receptor 1a, also known as the ghrelin receptor. This 28-residue peptide is acylated at Ser3 and is the only peptide hormone in the human body that is lipid-modified by an octanoyl group. Little is known about the structure and dynamics of membrane-associated ghrelin. We carried out solid-state NMR studies of ghrelin in lipid vesicles, followed by computational modeling of the peptide using Rosetta. Isotropic chemical shift data of isotopically labeled ghrelin provide information about the peptide's secondary structure. Spin diffusion experiments indicate that ghrelin binds to membranes via its lipidated Ser3. Further, Phe4, as well as electrostatics involving the peptide's positively charged residues and lipid polar headgroups, contribute to the binding energy. Other than the lipid anchor, ghrelin is highly flexible and mobile at the membrane surface. This observation is supported by our predicted model ensemble, which is in good agreement with experimentally determined chemical shifts. In the final ensemble of models, residues 8-17 form an α-helix, while residues 21-23 and 26-27 often adopt a polyproline II helical conformation. These helices appear to assist the peptide in forming an amphipathic conformation so that it can bind to the membrane.

  3. Single-cell analysis of pyroptosis dynamics reveals conserved GSDMD-mediated subcellular events that precede plasma membrane rupture.

    Science.gov (United States)

    de Vasconcelos, Nathalia M; Van Opdenbosch, Nina; Van Gorp, Hanne; Parthoens, Eef; Lamkanfi, Mohamed

    2018-04-17

    Pyroptosis is rapidly emerging as a mechanism of anti-microbial host defense, and of extracellular release of the inflammasome-dependent cytokines interleukin (IL)-1β and IL-18, which contributes to autoinflammatory pathology. Caspases 1, 4, 5 and 11 trigger this regulated form of necrosis by cleaving the pyroptosis effector gasdermin D (GSDMD), causing its pore-forming amino-terminal domain to oligomerize and perforate the plasma membrane. However, the subcellular events that precede pyroptotic cell lysis are ill defined. In this study, we triggered primary macrophages to undergo pyroptosis from three inflammasome types and recorded their dynamics and morphology using high-resolution live-cell spinning disk confocal laser microscopy. Based on quantitative analysis of single-cell subcellular events, we propose a model of pyroptotic cell disintegration that is initiated by opening of GSDMD-dependent ion channels or pores that are more restrictive than recently proposed GSDMD pores, followed by osmotic cell swelling, commitment of mitochondria and other membrane-bound organelles prior to sudden rupture of the plasma membrane and full permeability to intracellular proteins. This study provides a dynamic framework for understanding cellular changes that occur during pyroptosis, and charts a chronological sequence of GSDMD-mediated subcellular events that define pyroptotic cell death at the single-cell level.

  4. Impact of Coagulant and Flocculant Addition to an Anaerobic Dynamic Membrane Bioreactor (AnDMBR) Treating Waste-Activated Sludge.

    Science.gov (United States)

    Kooijman, Guido; Lopes, Wilton; Zhou, Zhongbo; Guo, Hongxiao; de Kreuk, Merle; Spanjers, Henri; van Lier, Jules

    2017-03-23

    In this work, we investigated the effects of flocculation aid (FA) addition to an anaerobic dynamic membrane bioreactor (AnDMBR) (7 L, 35 °C) treating waste-activated sludge (WAS). The experiment consisted of three distinct periods. In period 1 (day 1-86), the reactor was operated as a conventional anaerobic digester with a solids retention time (SRT) and hydraulic retention time (HRT) of 24 days. In period 2 (day 86-303), the HRT was lowered to 18 days with the application of a dynamic membrane while the SRT was kept the same. In period 3 (day 303-386), a cationic FA in combination with FeCl₃ was added. The additions led to a lower viscosity, which was expected to lead to an increased digestion performance. However, the FAs caused irreversible binding of the substrate, lowering the volatile solids destruction from 32% in period 2 to 24% in period 3. An accumulation of small particulates was observed in the sludge, lowering the average particle size by 50%. These particulates likely caused pore blocking in the cake layer, doubling the trans-membrane pressure. The methanogenic consortia were unaffected. Dosing coagulants and flocculants into an AnDMBR treating sludge leads to a decreased cake layer permeability and decreased sludge degradation.

  5. In-situ assessment of biofilm formation in submerged membrane system using optical coherence tomography and computational fluid dynamics

    KAUST Repository

    Fortunato, Luca

    2016-09-09

    This paper introduces a novel approach to study the biofouling development on gravity driven submerged membrane bioreactor (SMBR). The on-line monitoring of biofilm formation on a flat sheet membrane was conducted non-destructively using optical coherence tomography (OCT), allowing the in-situ investigation of the biofilm structure for 43 d. The OCT enabled to obtain a time-lapse of biofilm development on the membrane under the continuous operation. Acquired real-time information on the biofilm structure related to the change in the flux profile confirming the successful monitoring of the dynamic evolution of the biofouling layer. Four different phases were observed linking the permeate flux with the change of biofilm morphology. In particular, a stable flux of 2.1±0.1 L/m2 h was achieved with the achievement of steady biofilm morphology after 30 d of operation. Biofilm descriptors, such as thickness, biofilm area, macro-porosity and roughness (absolute and relative), were calculated for each OCT acquired scans. Interestingly, relative roughness was correlated with the flux decrease. Furthermore, the precise biofilm morphology obtained from the OCT scans was used in computational fluid dynamics (CFD) simulation to better understand the role of biofilm structure on the filtration mechanism. © 2016 Elsevier B.V.

  6. The dynamic interplay of plasma membrane domains and cortical microtubules in secondary cell wall patterning

    Directory of Open Access Journals (Sweden)

    Yoshihisa eOda

    2013-12-01

    Full Text Available Patterning of the cellulosic cell wall underlies the shape and function of plant cells. The cortical microtubule array plays a central role in the regulation of cell wall patterns. However, the regulatory mechanisms by which secondary cell wall patterns are established through cortical microtubules remain to be fully determined. Our recent study in xylem vessel cells revealed that a mutual inhibitory interaction between cortical microtubules and distinct plasma membrane domains leads to distinctive patterning in secondary cell walls. Our research revealed that the recycling of active and inactive ROP proteins by a specific GAP and GEF pair establishes distinct de novo plasma membrane domains. Active ROP recruits a plant-specific microtubule-associated protein, MIDD1, which mediates the mutual interaction between cortical microtubules and plasma membrane domains. In this mini review, we summarize recent research regarding secondary wall patterning, with a focus on the emerging interplay between plasma membrane domains and cortical microtubules through MIDD1 and ROP.

  7. Aspects concerning the quality of aeration for environmental friendly turbines

    Energy Technology Data Exchange (ETDEWEB)

    Bunea, F; Oprina, G [Hydrodynamics Department, National Institute for R and D in Electrical Engineering ICPE-CA, Splaiul Unirii, 313, Bucharest, 030138 (Romania); Houde, S; Ciocan, G D [Laboratoire de Machines Hydrauliques, Pavillon Adrien-Pouliot Universite Laval, 1065 rue de la medecine, Quebec G1V 0A6 (Canada); Baran, G; Pincovschi, I, E-mail: buneaflorentina@yahoo.co [Hydraulics, Hydraulic Machinery and Environmental Engineering Department, University Polytechnic of Bucharest, Splaiul Independentei, 313, Bucharest, 060042 (Romania)

    2010-08-15

    The hydro renewable energy provides a reliable power source; it does not pollute the air or land but affects the aquatic habitat due to low dissolved oxygen (DO) level in the water discharged from turbines. Hydro-turbines intake generally withdraws water from the bottom layer of the reservoirs with low DO level. In the different methods used for improving DO downstream the hydropower plants the volume of air is considered to be the main parameter of the injection. The energetic consumption is affected, in terms of loss of turbine efficiency due to air injection. The authors propose a study to show the importance of the quality of air injection, meaning bubble size, pressure loss on the aeration device etc. Different types of fine bubble aeration systems have been tested and compared. The capacity to predict the aeration by numerical simulation is analysed.

  8. Membrane composition and dynamics: a target of bioactive virgin olive oil constituents.

    Science.gov (United States)

    Lopez, Sergio; Bermudez, Beatriz; Montserrat-de la Paz, Sergio; Jaramillo, Sara; Varela, Lourdes M; Ortega-Gomez, Almudena; Abia, Rocio; Muriana, Francisco J G

    2014-06-01

    The endogenous synthesis of lipids, which requires suitable dietary raw materials, is critical for the formation of membrane bilayers. In eukaryotic cells, phospholipids are the predominant membrane lipids and consist of hydrophobic acyl chains attached to a hydrophilic head group. The relative balance between saturated, monounsaturated, and polyunsaturated acyl chains is required for the organization and normal function of membranes. Virgin olive oil is the richest natural dietary source of the monounsaturated lipid oleic acid and is one of the key components of the healthy Mediterranean diet. Virgin olive oil also contains a unique constellation of many other lipophilic and amphipathic constituents whose health benefits are still being discovered. The focus of this review is the latest evidence regarding the impact of oleic acid and the minor constituents of virgin olive oil on the arrangement and behavior of lipid bilayers. We highlight the relevance of these interactions to the potential use of virgin olive oil in preserving the functional properties of membranes to maintain health and in modulating membrane functions that can be altered in several pathologies. This article is part of a Special Issue entitled: Membrane Structure and Function: Relevance in the Cell's Physiology, Pathology and Therapy. Copyright © 2014 Elsevier B.V. All rights reserved.

  9. Studies of radon mitigation in well water by aeration

    International Nuclear Information System (INIS)

    Mafra, Karina Cristina; Paschuk, Sergei A.; Denyak, Valeriy; Reque, Marilson; Correa, Janine Nicolosi; Barbosa, Laercio

    2011-01-01

    The 222 Rn concentration in natural water in different countries usually is about few Bq/L and is the subject of the National legislation as well as International norms and recommendations. The United States Environmental Protection Agency (USEPA) established a limit of 11.1 Bq/L for the radon level in drinking water and this limit is considered as guideline in Canada and many countries of the European Union. This work presents the results of study of radon ( 222 Rn) concentration reduction in well water using the aeration process developed at the Laboratory of Applied Nuclear Physics of the Federal University of Technology (UTFPR). The water samples were collected from a well at Pinheirinho region of Curitiba in 2011. Experimental setup was based on the Radon Monitor (AlphaGUARD). The 222 Rn concentration was analyzed using the software DataEXPERT by Genitron Instruments, taking into account the volume of water sample, its temperature, atmospheric pressure and the total volume of the air in the vessels. Initial concentration of radon in water samples was 28,67 Bq/L which is bigger than maximum concentration recommended by USEPA. The mitigation was performed by means of diffusion aeration of water samples of 15L during the time interval of 24 hours following a period of 4 days. The efficiency of aeration mitigation was controlled by comparing the activity of radon in aerated water with reference water samples that were not aerated. Obtained results show very satisfactory decrease of 222 Rn activity in water samples even after few hours of intense aeration. (author)

  10. Influence of rotor circumference speed on flotation cell aeration

    Energy Technology Data Exchange (ETDEWEB)

    Dedek, F; Bortlik, V

    1978-01-01

    Laboratory test results of flotation experiments conducted in Czechoslovakia with the use of coal flotation particles <0.5 mm are presented. Three different cells and rotors were used, type MS, Denver, VRF 2 with various rotor diameters ranging from 40 mm to 95 mm. Nine tables show the results with varying flotation time, circumferenial velocity, flotation reagents and aeration. Test procedures are discussed; main results are that circumferenial velocity cannot be used as a decisive parameter for cell aeration and flotation efficiency, and that a direct transfer of parameters cannot be made to flotation cells with a different design and to larger industrial equipment. (4 refs.) (In German)

  11. Cholesterol depletion induces dynamic confinement of the G-protein coupled serotonin(1A) receptor in the plasma membrane of living cells.

    Science.gov (United States)

    Pucadyil, Thomas J; Chattopadhyay, Amitabha

    2007-03-01

    Cholesterol is an essential constituent of eukaryotic membranes and plays a crucial role in membrane organization, dynamics, function, and sorting. It is often found distributed non-randomly in domains or pools in biological and model membranes and is thought to contribute to a segregated distribution of membrane constituents. Signal transduction events mediated by seven transmembrane domain G-protein coupled receptors (GPCRs) are the primary means by which cells communicate with and respond to their external environment. We analyzed the role of cholesterol in the plasma membrane organization of the G-protein coupled serotonin(1A) receptor by fluorescence recovery after photobleaching (FRAP) measurements with varying bleach spot sizes. Our results show that lateral diffusion parameters of serotonin(1A) receptors in normal cells are consistent with models describing diffusion of molecules in a homogenous membrane. Interestingly, these characteristics are altered in cholesterol-depleted cells in a manner that is consistent with dynamic confinement of serotonin(1A) receptors in the plasma membrane. Importantly, analysis of ligand binding and downstream signaling of the serotonin(1A) receptor suggests that receptor function is affected in a significantly different manner when intact cells or isolated membranes are depleted of cholesterol. These results assume significance in the context of interpreting effects of cholesterol depletion on diffusion characteristics of membrane proteins in particular, and cholesterol-dependent cellular processes in general.

  12. Dynamic filtration and static adsorption of lead ions in aqueous solution by use of blended polysulfone membranes with nano size MCM-41 particles coated by polyaniline.

    Science.gov (United States)

    Toosi, Mohammad Reza; Emami, Mohammad Reza Sarmasti; Hajian, Sudeh

    2018-05-11

    MCM-41 mesopore was prepared by hydrothermal method and used for synthesis of polyaniline/MCM-41 nanocomposite via in situ polymerization. The nanocomposite was blended with polysulfone to prepare mixed matrix membrane in different content of nanocomposite by phase inversion method. Structural and surface properties of the samples were characterized by SEM, XRD, FTIR, AFM, TGA, BET, and zeta potential measurements. Effect of the nanocomposite content on the hydrophilicity, porosity, and permeability of the membrane was determined. Membrane performance was evaluated for removal of lead ions in dynamic filtration and static adsorption. The membranes were found as effective adsorptive filters for removal of lead ions via interactions between active sites of nanocomposite in membrane structure and lead ions during filtration. Results of batch experiments proved adsorptive mechanism of membranes for removal of lead ions with the maximum adsorption capacity of 19.6 mg/g.

  13. Single-molecule resolution of protein dynamics on polymeric membrane surfaces: the roles of spatial and population heterogeneity.

    Science.gov (United States)

    Langdon, Blake B; Mirhossaini, Roya B; Mabry, Joshua N; Sriram, Indira; Lajmi, Ajay; Zhang, Yanxia; Rojas, Orlando J; Schwartz, Daniel K

    2015-02-18

    Although polymeric membranes are widely used in the purification of protein pharmaceuticals, interactions between biomolecules and membrane surfaces can lead to reduced membrane performance and damage to the product. In this study, single-molecule fluorescence microscopy provided direct observation of bovine serum albumin (BSA) and human monoclonal antibody (IgG) dynamics at the interface between aqueous buffer and polymeric membrane materials including regenerated cellulose and unmodified poly(ether sulfone) (PES) blended with either polyvinylpyrrolidone (PVP), polyvinyl acetate-co-polyvinylpyrrolidone (PVAc-PVP), or polyethylene glycol methacrylate (PEGM) before casting. These polymer surfaces were compared with model surfaces composed of hydrophilic bare fused silica and hydrophobic trimethylsilane-coated fused silica. At extremely dilute protein concentrations (10(-3)-10(-7) mg/mL), protein surface exchange was highly dynamic with protein monomers desorbing from the surface within ∼1 s after adsorption. Protein oligomers (e.g., nonspecific dimers, trimers, or larger aggregates), although less common, remained on the surface for 5 times longer than monomers. Using newly developed super-resolution methods, we could localize adsorption sites with ∼50 nm resolution and quantify the spatial heterogeneity of the various surfaces. On a small anomalous subset of the adsorption sites, proteins adsorbed preferentially and tended to reside for significantly longer times (i.e., on "strong" sites). Proteins resided for shorter times overall on surfaces that were more homogeneous and exhibited fewer strong sites (e.g., PVAc-PVP/PES). We propose that strong surface sites may nucleate protein aggregation, initiated preferentially by protein oligomers, and accelerate ultrafiltration membrane fouling. At high protein concentrations (0.3-1.0 mg/mL), fewer strong adsorption sites were observed, and surface residence times were reduced. This suggests that at high concentrations

  14. Enhancing recovery of ammonia from swine manure anaerobic digester effluent using gas-permeable membrane technology.

    Science.gov (United States)

    Dube, P J; Vanotti, M B; Szogi, A A; García-González, M C

    2016-03-01

    Gas-permeable membrane technology is useful to recover ammonia from manure. In this study, the technology was enhanced using aeration instead of alkali chemicals to increase pH and the ammonium (NH4(+)) recovery rate. Digested effluents from covered anaerobic swine lagoons containing 1465-2097 mg NH4(+)-N L(-1) were treated using submerged membranes (0.13 cm(2) cm(-3)), low-rate aeration (120 mL air L-manure(-1) min(-1)) and nitrification inhibitor (22 mg L(-1)) to prevent nitrification. The experiment included a control without aeration. The pH of the manure with aeration rose from 8.6 to 9.2 while the manure without aeration decreased from 8.6 to 8.1. With aeration, 97-99% of the NH4(+) was removed in about 5 days of operation with 96-98% recovery efficiency. In contrast, without aeration it took 25 days to treat the NH4(+). Therefore, the recovery of NH4(+) was five times faster with the low-rate aeration treatment. This enhancement could reduce costs by 70%. Published by Elsevier Ltd.

  15. 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.

  16. The off-shell closed strings as the topological open membranes. Dynamical transmutation of world sheet dimension

    International Nuclear Information System (INIS)

    Kogan, Y.I.

    1989-05-01

    Using the connection between (2+1) Chern-Simons gauge theory and 2d Conformal Field Theory the on-shell string condition is obtained as a condition of full independence of interior of (2+1) world. The new method for off-shell continuation is considered based on the introduction of the Maxwell term in (2+1) theory. This leads to dynamical transmutation of world-sheet dimensions - the off-shell string becomes topological membrane (topological means that (2+1) theory has topological mass term). The dependence of parameters of (2+1) theory under the external fields is discussed. (author). 17 refs

  17. Colloid formation in groundwater by subsurface aeration: characterisation of the geo-colloids and their counterparts

    NARCIS (Netherlands)

    Wolthoorn, A.; Temminghoff, E.J.M.; Riemsdijk, van W.H.

    2004-01-01

    Subsurface aeration is used to oxidise Fe in situ in groundwater to make the water potable. In a groundwater system with pH > 7, subsurface aeration results in a non-mobile Fe precipitate and mobile Fe colloids. Since originally the goal of subsurface aeration is to remove Fe in situ, the

  18. Lateral Membrane Waves Constitute a Universal Dynamic Pattern of Motile Cells

    Science.gov (United States)

    Döbereiner, Hans-Günther; Dubin-Thaler, Benjamin J.; Hofman, Jake M.; Xenias, Harry S.; Sims, Tasha N.; Giannone, Grégory; Dustin, Michael L.; Wiggins, Chris H.; Sheetz, Michael P.

    2006-07-01

    We have monitored active movements of the cell circumference on specifically coated substrates for a variety of cells including mouse embryonic fibroblasts and T cells, as well as wing disk cells from fruit flies. Despite having different functions and being from multiple phyla, these cell types share a common spatiotemporal pattern in their normal membrane velocity; we show that protrusion and retraction events are organized in lateral waves along the cell membrane. These wave patterns indicate both spatial and temporal long-range periodic correlations of the actomyosin gel.

  19. Molecular dynamics simulations of the interactions of medicinal plant extracts and drugs with lipid bilayer membranes

    DEFF Research Database (Denmark)

    Kopec, Wojciech; Telenius, Jelena; Khandelia, Himanshu

    2013-01-01

    Several small drugs and medicinal plant extracts, such as the Indian spice extract curcumin, have a wide range of useful pharmacological properties that cannot be ascribed to binding to a single protein target alone. The lipid bilayer membrane is thought to mediate the effects of many such molecu......Several small drugs and medicinal plant extracts, such as the Indian spice extract curcumin, have a wide range of useful pharmacological properties that cannot be ascribed to binding to a single protein target alone. The lipid bilayer membrane is thought to mediate the effects of many...

  20. Micro-scale H2-CO2 dynamics in a hydrogenotrophic methanogenic membrane reactor

    DEFF Research Database (Denmark)

    Garcia-Robledo, Emilio; Ottosen, Lars Ditlev Mørck; Voigt, Niels Vinther

    2016-01-01

    Biogas production is a key factor in a sustainable energy supply. It is possible to get biogas with very high methane content if the biogas reactors are supplied with exogenous hydrogen, and one of the technologies for supplying hydrogen is through gas permeable membranes. In this study the activ......Biogas production is a key factor in a sustainable energy supply. It is possible to get biogas with very high methane content if the biogas reactors are supplied with exogenous hydrogen, and one of the technologies for supplying hydrogen is through gas permeable membranes. In this study...

  1. A hybrid total internal reflection fluorescence and optical tweezers microscope to study cell adhesion and membrane protein dynamics of single living cells

    NARCIS (Netherlands)

    Snijder-van As, M.I.; Rieger, B.; Joosten, B.; Subramaniam, Vinod; Figdor, Carl; Kanger, Johannes S.

    2009-01-01

    The dynamics of cell surface membrane proteins plays an important role in cell–cell interactions. The onset of the interaction is typically not precisely controlled by current techniques, making especially difficult the visualization of early-stage dynamics. We have developed a novel method where

  2. The impact of aeration on potato ( Solanum tuberosum L.) minituber ...

    African Journals Online (AJOL)

    Aeroponic systems are more effective than hydroponics for minituber production, as provided by the optimal system for root oxygenation. The study was conducted to improve conventional hydroponic systems by applying aeration so as to enhance potato minituber production yield via providing adequate oxygen in the root ...

  3. Dimensioning of aerated submerged fixed bed biofilm reactors ...

    African Journals Online (AJOL)

    The description of a biofilm mathematical model application for dimensioning an aerated fixed bed biofilm reactor (ASFBBR) for petrochemical wastewater polishing is presented. A simple one-dimensional model of biofilm, developed by P Harremöes, was chosen for this purpose. The model was calibrated and verified ...

  4. Tailwater concerns and the history of turbine aeration

    International Nuclear Information System (INIS)

    Bohac, C.E.; Ruane, R.J.

    1991-01-01

    All new proposals for hydropower development and many of the almost 300 hydroelectric projects which will be relicensed before 2000 will have to address the issue of minimum dissolved oxygen concentrations. This paper highlights some of the causes and concerns of low dissolved oxygen concentrations in releases from hydropower projects and describes the history of hydroturbine aeration for reaerating these releases

  5. Renewable energy for the aeration of wastewater ponds.

    Science.gov (United States)

    Hobus, I; Hegemann, W

    2003-01-01

    The application of a decentralised renewable energy supply for the aeration of wastewater ponds, and the influence of an unsteady oxygen supply on the specific conversion rate and biocoenose was investigated. With the discontinuous aeration the specific conversion rate is increased as compared to facultative ponds. The estimation of the microorganisms consortia was done with in situ hybridisation techniques. A significant shift in the bacteria population with the chosen specific probes for anaerobic, sulphate reducing and nitrifying bacteria could not be detected. Wastewater ponds have sufficient buffer volume to compensate for the fluctuating energy supply. But the efficiency of the energy supply of a photovoltaic plant decreases in shallow lakes (d photovoltaic and wind power plant, energy management, aeration system and wastewater pond, a simulation model was developed and tested. The application of renewable energy for the aeration of wastewater ponds is a useful alternative for the redevelopment of overloaded ponds as well as the construction of new wastewater ponds, especially in areas with an inadequate central electricity grid and a high availability of wind and solar energy.

  6. Passively Aerated Composting of Straw-Rich Organic Pig Manure

    NARCIS (Netherlands)

    Veeken, A.H.M.; Wilde, de V.; Szanto, G.; Hamelers, H.V.M.

    2002-01-01

    In this study pig manure from organic farming systems is composted with passive aeration. Effectiveness of the composting process strongly depended on the density of the compost. Best results were observed at a density of 700 kg/m3, where both aerobic degradation and drying were adequate and

  7. A review and investigations of some properties of foamed aerated ...

    African Journals Online (AJOL)

    The properties investigated on foamed aerated concrete having a designed density of 1600kg/m3 were: workability, density, compressive strength, tensile strength, and the water absorption capacity. The results showed that at the designed density adopted for this work, the material was workable and repeatable.

  8. Non-autoclaved aerated concrete with mineral additives

    Science.gov (United States)

    Il'ina, L. V.; Rakov, M. A.

    2016-01-01

    We investigated the effect of joint grinding of Portland cement clinker, silica and carbonate components and mineral additives to specific surface of 280 - 300 m2/kg on the properties (strength, average density and thermal conductivity) of non-autoclaved aerated concrete, and the porosity of the hardened cement paste produced from Portland cement clinker with mineral additives. The joint grinding of the Portland cement clinker with silica and carbonate components and mineral additives reduces the energy consumption of non-autoclaved aerated concrete production. The efficiency of mineral additives (diopside, wollastonite) is due to the closeness the composition, the type of chemical bonds, physical and chemical characteristics (specific enthalpy of formation, specific entropy) to anhydrous clinker minerals and their hydration products. Considering the influence of these additions on hydration of clinker minerals and formation of hardened cement paste structure, dispersed wollastonite and diopside should be used as mineral additives. The hardness and, consequently, the elastic modulus of diopside are higher than that of hardened cement paste. As a result, there is a redistribution of stresses in the hardened cement paste interporous partitions and hardening, both the partitions and aerated concrete on the whole. The mineral additives introduction allowed to obtain the non-autoclaved aerated concrete with average density 580 kg/m3, compressive strength of 3.3 MPa and thermal conductivity of 0.131 W/(m.°C).

  9. Modelling and test of aeration tank settling (ATS)

    DEFF Research Database (Denmark)

    Nielsen, M. K.; Bechmann, H.; Henze, Mogens

    2000-01-01

    The use of aeration tank settling during high hydraulic loads on large wastewater treatment plants has previously been demonstrated as a reliable technique and proven valuable. The paper proposes a simplified deterministic model to predict the efficiency of the method. It is shown...

  10. Dewaterability of sludge digested in extended aeration plants using ...

    African Journals Online (AJOL)

    Dewaterability of unconditioned sludge digested in full scale and lab scale experiments using either extended aeration (EA) or anaerobic digestion were compared on full and lab scale sand drying beds. Sludge digested in EA plants resulted in improvement in sludge dewaterability compared to sludge digested ...

  11. PROJECT OF COAGULANT DISPENSER IN PULVERIZATION AERATOR WITH WIND DRIVE

    Directory of Open Access Journals (Sweden)

    Ewa Osuch

    2017-09-01

    Full Text Available Lakes are one of most important freshwater ecosystems, playing significant role in functioning of nature and human economy. Swarzędzkie Lake is good example of ecosystem, which in last half-century was exposed to the influence of strong anthropopressure. Direct inflow of sewage with large number of biogens coming to the lake with water of inflows caused distinct disturbance of its functioning. In autumn 2011 restoration begined on Swarzędzkie Lake for reduction of lake trophy and improvement of water quality. For achieving better and quicker effect, simultaneously combination of some methods was applied, among others method of oxygenation of over-bottom water with help of pulverization aerator and method of precise inactivation of phosphorus in water depths. Characterization and analysis of improved coagulant dispenser applying active substance only during work of pulverization aerator is the aim of this thesis. Principle of dispenser work, its structure and location in pulverization aerator were explained. It was stated, that introduction to water a factor initiating process of phosphorus inactivation causes significant reduction of mineral phosphorus in water and size of coagulant dose correlates with intensity of work of pulverization aerator with wind drive.

  12. Characterization and behaviour of Autoclaved Aerated Concrete before Autoclaving

    NARCIS (Netherlands)

    Straub, Chr.; Florea, M.V.A.; Brouwers, H.J.H.; Schmidt, Wolfram; Msinjili, Nsesheye Susan

    In order to achieve a high quality Autoclaved Aerated Concrete (AAC) product, certain steps need to be ensured: the characterization of the raw materials, a proper mixing and correct slurry behaviour to achieve a good green body during green curing. In the current research the emphasis is on all of

  13. Investigation of flashing de-aeration with and without recirculation

    International Nuclear Information System (INIS)

    Kjellstroem, B.; Toecksberg, B.

    1977-06-01

    A series of experiments with flashing de-areation has been carried out at the institute of Thermal Energytechnology of the Royal Institute of Technology in Stockholm. The results of the experiments with flashing de-areation without recirculation of the condensate show very low contents of dissolved oxygen in the de-aerated water. The results indicate that the de-aeration process is independent of the pressure. De-aeration efficiencies over 99 percent were measured. The continued experiments with recirculation of the condensate show a considerably deteriorated de-aeration performance together with a marked pressure dependency. A simple theoretical model has been formulated which explains these results. Comparisons between the experimental data and calculations with this model indicate that a conservative estimation of the oxygen content of the outgoing water can be obtained if the oxygen content of the recirculated condensate is calculated for the partial pressure of noncondensible gases equal to the total pressure in the condensor. It seems also possible to estimate a lower limit for the oxygen content of the outgoing water. The range of oxygen content between those limits is about a factor of 10 for the conditions investigated. Further studies of the uptake of oxygen during condensation seem necessary if a more accurate prediction is desired

  14. Multi-scaled normal mode analysis method for dynamics simulation of protein-membrane complexes: A case study of potassium channel gating motion correlations

    Energy Technology Data Exchange (ETDEWEB)

    Wu, Xiaokun; Han, Min; Ming, Dengming, E-mail: dming@fudan.edu.cn [Department of Physiology and Biophysics, School of Life Sciences, Fudan University, Shanghai (China)

    2015-10-07

    Membrane proteins play critically important roles in many cellular activities such as ions and small molecule transportation, signal recognition, and transduction. In order to fulfill their functions, these proteins must be placed in different membrane environments and a variety of protein-lipid interactions may affect the behavior of these proteins. One of the key effects of protein-lipid interactions is their ability to change the dynamics status of membrane proteins, thus adjusting their functions. Here, we present a multi-scaled normal mode analysis (mNMA) method to study the dynamics perturbation to the membrane proteins imposed by lipid bi-layer membrane fluctuations. In mNMA, channel proteins are simulated at all-atom level while the membrane is described with a coarse-grained model. mNMA calculations clearly show that channel gating motion can tightly couple with a variety of membrane deformations, including bending and twisting. We then examined bi-channel systems where two channels were separated with different distances. From mNMA calculations, we observed both positive and negative gating correlations between two neighboring channels, and the correlation has a maximum as the channel center-to-center distance is close to 2.5 times of their diameter. This distance is larger than recently found maximum attraction distance between two proteins embedded in membrane which is 1.5 times of the protein size, indicating that membrane fluctuation might impose collective motions among proteins within a larger area. The hybrid resolution feature in mNMA provides atomic dynamics information for key components in the system without costing much computer resource. We expect it to be a conventional simulation tool for ordinary laboratories to study the dynamics of very complicated biological assemblies. The source code is available upon request to the authors.

  15. Porosimetric, Thermal and Strength Tests of Aerated and Nonaerated Concretes

    Science.gov (United States)

    Strzałkowski, Jarosław; Garbalińska, Halina

    2017-10-01

    The paper presents the results of porosimetry tests of lightweight concretes, obtained with three research methods. Impact of different porosity structures on the basic thermal and strength properties was also evaluated. Tests were performed, using the pressure gauge method on fresh concrete mixes, as well as using the mercury porosimetry test and optic RapidAir method on specimens prepared from mature composites. The study was conducted on lightweight concretes, based on expanded clay aggregate and fly ash aggregate, in two variants: with non-aerated and aerated cement matrix. In addition, two reference concretes, based on normal aggregate, were prepared, also in two variants of matrix aeration. Changes in thermal conductivity λ and volumetric specific heat cv throughout the first three months of curing of the concretes were examined. Additionally, tests for compressive strength on cubic samples were performed during the first three months of curing. It was found that the pressure gauge method, performed on a fresh mix, gave lowered values of porosity, compared to the other methods. The mercury porosity tests showed high sensitivity in evaluation of pores smaller than 30μm. Unfortunately, this technique is not suitable for analysing pores greater than 300μm. On the other hand, the optical method proves good in evaluation of large pores, greater than 300μm. The paper also presents results of correlation of individual methods of porosity testing. A consolidated graph of the pore structure, derived from both mercury and optical methods, was presented, too. For the all of six tested concretes, differential graphs of porosity, prepared with both methods, show a very broad convergence. The thermal test results indicate usefulness of aeration of the cement matrix of the composites based on lightweight aggregates for the further reduction of the thermal conductivity coefficient λ of the materials. The lowest values of the λ coefficient were obtained for the aerated

  16. Computational fluid dynamics simulations of flow and concentration polarization in forward osmosis membrane systems

    DEFF Research Database (Denmark)

    Gruber, M.F.; Johnson, C.J.; Tang, C.Y.

    2011-01-01

    is inspired by previously published CFD models for pressure-driven systems and the general analytical theory for flux modeling in asymmetric membranes. Simulations reveal a non-negligible external concentration polarization on the porous support, even when accounting for high cross-flow velocity and slip...

  17. Effect of heavy water on phospholipid membranes: experimental confirmation of molecular dynamics simulations

    Czech Academy of Sciences Publication Activity Database

    Beranová, Lenka; Humpolíčková, Jana; Sýkora, Jan; Benda, Aleš; Cwiklik, Lukasz; Jurkiewicz, Piotr; Gröbner, G.; Hof, Martin

    Roč. 14, č. 42 ( 2012 ), s. 14516-14522 ISSN 1463-9076 R&D Projects: GA AV ČR GEMEM/09/E006; GA ČR GBP208/12/G016 Institutional support: RVO:61388955 Keywords : phospholipid membranes * biophysics * physical chemistry Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 3.829, year: 2012

  18. Dipolar Relaxation Dynamics at the Active Site of an ATPase Regulated by Membrane Lateral Pressure

    Czech Academy of Sciences Publication Activity Database

    Fischermeier, E.; Pospíšil, Petr; Sayed, A.; Hof, Martin; Solioz, M.; Fahmy, K.

    2017-01-01

    Roč. 56, č. 5 (2017), s. 1269-1272 ISSN 1433-7851 R&D Projects: GA ČR(CZ) GBP208/12/G016 Institutional support: RVO:61388955 Keywords : fluorescence * ion pump * membrane proteins * nanodiscs * time-resolved emission Subject RIV: CF - Physical ; Theoretical Chemistry OBOR OECD: Physical chemistry Impact factor: 11.994, year: 2016

  19. Multi-response data treatment of dynamic and steady state permeation measurement on composite membrane

    Czech Academy of Sciences Publication Activity Database

    Fíla, V.; Bernauer, B.; Hrabánek, Pavel

    2006-01-01

    Roč. 200, 1-3 (2006), s. 120-121 ISSN 0011-9164 R&D Projects: GA AV ČR(CZ) 1QS401250509 Institutional research plan: CEZ:AV0Z40400503 Keywords : composite membrane * physical chemistry * Wicke-Kalenbach permeation Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 0.917, year: 2006

  20. Tellipsometry in Twente : Dynamics of Thin Film Membranes Under Applied Temperature Profiles

    NARCIS (Netherlands)

    Kappert, Emiel J.; Ogieglo, Wojciech; Raaijmakers, Michiel; Koziara, Beata; Wormeester, Herbert; Benes, Nieck E.

    2014-01-01

    We use in-situ ellipsometry to study the structural and chemical evolution of thin films as function of the temperature (‘Tellipsometry’). Particular focus is on organic, inorganic, and hybrid materials that are relevant to artificial membrane fabrication and operation. Our poster shows some

  1. Tellipsometry in Twente: Dynamics of Thin Film Membranes Under Applied Temperature Profiles

    OpenAIRE

    Kappert, Emiel J.; Ogieglo, Wojciech; Raaijmakers, Michiel; Koziara, Beata; Wormeester, Herbert; Benes, Nieck E.

    2014-01-01

    We use in-situ ellipsometry to study the structural and chemical evolution of thin films as function of the temperature (‘Tellipsometry’). Particular focus is on organic, inorganic, and hybrid materials that are relevant to artificial membrane fabrication and operation. Our poster shows some illustrative examples.

  2. Dynamic Simulation of a Proton Exchange Membrane Fuel Cell System For Automotive Applications

    DEFF Research Database (Denmark)

    Rabbani, Raja Abid; Rokni, Masoud

    2012-01-01

    parameters have been adjusted specifically for a 21.2 kW Ballard stack [1]. This model also incorporates the effects of water cross-over in the fuel cell membrane. Controls for temperatures, pressures, reactant stoichiometry and flows are implemented to simulate the system behaviour for different loads...

  3. Apoptotic Bax at Oxidatively Stressed Mitochondrial Membranes: Lipid Dynamics and Permeabilization

    Czech Academy of Sciences Publication Activity Database

    Dilgendein, A. P.; Pokorná, Šárka; Lidman, M.; Sparrman, T.; Šachl, Radek; Hof, Martin; Gröbner, G.

    2017-01-01

    Roč. 112, č. 10 (2017), s. 2147-2158 ISSN 0006-3495 R&D Projects: GA ČR(CZ) GBP208/12/G016 Institutional support: RVO:61388955 Keywords : LOW-FREQUENCY MOTION * OXIDIZED PHOSPHOLIPIDS * BILAYER-MEMBRANES Subject RIV: CF - Physical ; Theoretical Chemistry OBOR OECD: Physical chemistry Impact factor: 3.656, year: 2016

  4. Mitochondrial membranes with mono- and divalent salt: Changes induced by salt ions on structure and dynamics

    NARCIS (Netherlands)

    Pöyry, S.; Róg, T.; Karttunen, M.E.J.; Vattulainen, I.

    2009-01-01

    We employ atomistic simulations to consider how mono- (NaCl) and divalent (CaCl2) salt affects properties of inner and outer membranes of mitochondria. We find that the influence of salt on structural properties is rather minute, only weakly affecting lipid packing, conformational ordering, and

  5. Absorption and folding of melittin onto lipid bilayer membranes via unbiased atomic detail microsecond molecular dynamics simulation.

    Science.gov (United States)

    Chen, Charles H; Wiedman, Gregory; Khan, Ayesha; Ulmschneider, Martin B

    2014-09-01

    Unbiased molecular simulation is a powerful tool to study the atomic details driving functional structural changes or folding pathways of highly fluid systems, which present great challenges experimentally. Here we apply unbiased long-timescale molecular dynamics simulation to study the ab initio folding and partitioning of melittin, a template amphiphilic membrane active peptide. The simulations reveal that the peptide binds strongly to the lipid bilayer in an unstructured configuration. Interfacial folding results in a localized bilayer deformation. Akin to purely hydrophobic transmembrane segments the surface bound native helical conformer is highly resistant against thermal denaturation. Circular dichroism spectroscopy experiments confirm the strong binding and thermostability of the peptide. The study highlights the utility of molecular dynamics simulations for studying transient mechanisms in fluid lipid bilayer systems. This article is part of a Special Issue entitled: Interfacially Active Peptides and Proteins. Guest Editors: William C. Wimley and Kalina Hristova. Copyright © 2014. Published by Elsevier B.V.

  6. Alternative energy efficient membrane bioreactor using reciprocating submerged membrane.

    Science.gov (United States)

    Ho, J; Smith, S; Roh, H K

    2014-01-01

    A novel membrane bioreactor (MBR) pilot system, using membrane reciprocation instead of air scouring, was operated at constant high flux and daily fluctuating flux to demonstrate its application under peak and diurnal flow conditions. Low and stable transmembrane pressure was achieved at 40 l/m(2)/h (LMH) by use of repetitive membrane reciprocation. The results reveal that the inertial forces acting on the membrane fibers effectively propel foulants from the membrane surface. Reciprocation of the hollow fiber membrane is beneficial for the constant removal of solids that may build up on the membrane surface and inside the membrane bundle. The membrane reciprocation in the reciprocating MBR pilot consumed less energy than coarse air scouring used in conventional MBR systems. Specific energy consumption for the membrane reciprocation was 0.072 kWh/m(3) permeate produced at 40 LMH flux, which is 75% less than for a conventional air scouring system as reported in literature without consideration of energy consumption for biological aeration (0.29 kWh/m(3)). The daily fluctuating flux test confirmed that the membrane reciprocation is effective to handle fluctuating flux up to 50 LMH. The pilot-scale reciprocating MBR system successfully demonstrated that fouling can be controlled via 0.43 Hz membrane reciprocation with 44 mm or higher amplitude.

  7. Dynamic solar-powered multi-stage direct contact membrane distillation system: Concept design, modeling and simulation

    KAUST Repository

    Lee, Jung Gil

    2017-04-26

    This paper presents a theoretical analysis of the monthly average daily and hourly performances of a solar-powered multi-stage direct contact membrane distillation (SMDCMD) system with an energy recovery scheme and dynamic operating system. Mid-latitude meteorological data from Busan, Korea is employed, featuring large climate variation over the course of one year. The number of module stages used by the dynamic operating scheme changes dynamically based on the inlet feed temperature of the successive modules, which results in an improvement of the water production and thermal efficiency. The simulations of the SMDCMD system are carried out to investigate the spatial and temporal variations in the feed and permeate temperatures and permeate flux. The monthly average daily water production increases from 0.37m3/day to 0.4m3/day and thermal efficiency increases from 31% to 45% when comparing systems both without and with dynamic operation in December. The water production with respect to collector area ranged from 350m2 to 550m2 and the seawater storage tank volume ranged from 16m3 to 28.8m3, and the solar fraction at various desired feed temperatures from 50°C to 80°C have been investigated in October and December.

  8. Determination of the Orientation and Dynamics of Ergosterol in Model Membranes Using Uniform 13C Labeling and Dynamically Averaged 13C Chemical Shift Anisotropies as Experimental Restraints

    Science.gov (United States)

    Soubias, O.; Jolibois, F.; Massou, S.; Milon, A.; Réat, V.

    2005-01-01

    A new strategy was established to determine the average orientation and dynamics of ergosterol in dimyristoylphosphatidylcholine model membranes. It is based on the analysis of chemical shift anisotropies (CSAs) averaged by the molecular dynamics. Static 13C CSA tensors were computed by quantum chemistry, using the gauge-including atomic-orbital approach within Hartree-Fock theory. Uniformly 13C-labeled ergosterol was purified from Pichia pastoris cells grown on labeled methanol. After reconstitution into dimyristoylphosphatidylcholine lipids, the complete 1H and 13C assignment of ergosterol's resonances was performed using a combination of magic-angle spinning two-dimensional experiments. Dynamically averaged CSAs were determined by standard side-band intensity analysis for isolated 13C resonances (C3 and ethylenic carbons) and by off-magic-angle spinning experiments for other carbons. A set of 18 constraints was thus obtained, from which the sterol's molecular order parameter and average orientation could be precisely defined. The validity of using computed CSAs in this strategy was verified on cholesterol model systems. This new method allowed us to quantify ergosterol's dynamics at three molar ratios: 16 mol % (Ld phase), 30 mol % (Lo phase), and 23 mol % (mixed phases). Contrary to cholesterol, ergosterol's molecular diffusion axis makes an important angle (14°) with the inertial axis of the rigid four-ring system. PMID:15923221

  9. Molecular dynamics simulation studies of transmembrane transport of chemical components in Chinese herbs and the function of platycodin D in a biological membrane

    Directory of Open Access Journals (Sweden)

    Shufang Yang

    2017-04-01

    Conclusion: The Martini force field was successfully applied to the study of the interaction between herbal compounds and a biological membrane. By combining the dynamics equilibrium morphology, the distribution of drugs inside and outside the biomembrane, and the interaction sites of drugs on the DPPC bilayer, factors influencing transmembrane transport of drugs were elucidated and the function of platycodin D in a biological membrane was reproduced.

  10. Micro-scale H2-CO2 dynamics in a hydrogenotrophic methanogenic membrane reactor

    Directory of Open Access Journals (Sweden)

    Emilio Garcia-Robledo

    2016-08-01

    Full Text Available Biogas production is a key factor in a sustainable energy supply. It is possible to get biogas with very high methane content if the biogas reactors are supplied with exogenous hydrogen, and one of the technologies for supplying hydrogen is through gas permeable membranes. In this study the activity and stratification of hydrogen consumption above such a membrane was investigated by use of microsensors for hydrogen and pH. A hydrogenotrophic methanogenic community that was able to consume the hydrogen flux within 0.5 mm of the membrane with specific rates of up to 30 m3 H2 m-3 day-1 developed within 3 days in fresh manure and was already established at time zero when analyzing slurry from a biogas plant. The hydrogen consumption was dependent on a simultaneous carbon dioxide supply and was inhibited when carbon dioxide depletion elevated the pH to 9.2. The activity was only partially restored when the carbon dioxide supply was resumed. Bioreactors supplied with hydrogen gas should thus be carefully monitored and either have the hydrogen supply disrupted or be supplemented with carbon dioxide when the pH rises to values about 9.

  11. Effective pine bark composting with the Dome Aeration Technology

    International Nuclear Information System (INIS)

    Trois, Cristina; Polster, Andreas

    2007-01-01

    In South Africa garden refuse is primarily disposed of in domestic landfills. Due to the large quantities generated, any form of treatment would be beneficial for volume reduction, waste stabilization and resource recovery. Dome Aeration Technology (DAT) is an advanced process for aerobic biological degradation of garden refuse and general waste [Paar, S., Brummack, J., Gemende, B., 1999a. Advantages of dome aeration in mechanical-biological waste treatment. In: Proceedings of the 7th International Waste Management and Landfill Symposium, Cagliari, 4-8 October 1999; Paar, S., Brummack, J., Gemende, B., 1999b. Mechanical-biological waste stabilization by the dome aeration method. Environment Protection Engineering 25 (3/99). Mollekopf, N., Brummack, J., Paar, S., Vorster, K., 2002. Use of the Dome Aeration Technology for biochemical stabilization of waste prior to landfilling. In: Proceedings of the Wastecon 2002, Waste Congress and Exhibition, Durban, South Africa.]. It is a non-reactor open windrow composting process, with the main advantage being that the input material needs no periodic turning. A rotting time of only 3-4 months indicates the high efficiency. Additionally, the low capital/operational costs, low energy inputs and limited plant requirements provide potential for use in aerobic refuse stabilization. The innovation in the DAT process is the passive aeration achieved by thermally driven advection through open windrows caused by temperature differences between the degrading material and the outside environment. This paper investigates the application of Dome Aeration Technology to pine bark composting as part of an integrated waste management strategy. A full-scale field experiment was performed at the Bisasar Road Landfill Site in Durban to assess the influence of climate, waste composition and operational conditions on the process. A test windrow was constructed and measurements of temperature and airflow through the material were taken. The process

  12. The effect of airflow rates and aeration mode on the respiration activity of four organic wastes: Implications on the composting process.

    Science.gov (United States)

    Mejias, Laura; Komilis, Dimitrios; Gea, Teresa; Sánchez, Antoni

    2017-07-01

    The aim of this study was to assess the effect of the airflow and of the aeration mode on the composting process of non-urban organic wastes that are found in large quantities worldwide, namely: (i) a fresh, non-digested, sewage sludge (FSS), (ii) an anaerobically digested sewage sludge (ADSS), (iii) cow manure (CM) and (iv) pig sludge (PS). This assessment was done using respirometric indices. Two aeration modes were tested, namely: (a) a constant air flowrate set at three different initial fixed airflow rates, and (b) an oxygen uptake rate (OUR)-controlled airflow rate. The four wastes displayed the same behaviour namely a limited biological activity at low aeration, while, beyond a threshold value, the increase of the airflow did not significantly increase the dynamic respiration indices (DRI 1 max , DRI 24 max and AT 4 ). The threshold airflow rate varied among wastes and ranged from 42NL air kg -1 DMh -1 for CM and from 67 to 77NL air kg -1 DMh -1 for FSS, ADSS and PS. Comparing the two aeration modes tested (constant air flow, OUR controlled air flow), no statistically significant differences were calculated between the respiration activity indices obtained at those two aeration modes. The results can be considered representative for urban and non-urban organic wastes and establish a general procedure to measure the respiration activity without limitations by airflow. This will permit other researchers to provide consistent results during the measurement of the respiration activity. Results indicate that high airflows are not required to establish the maximum respiration activity. This can result in energy savings and the prevention of off-gas treatment problems due to the excessive aeration rate in full scale composting plants. Copyright © 2017 Elsevier Ltd. All rights reserved.

  13. PREPARATION OF ULTRA-LOW VOLUME WEIGHT AUTOCLAVED AERATED CONCRETE

    Directory of Open Access Journals (Sweden)

    Ondrej Koutny

    2016-12-01

    Full Text Available Autoclaved aerated concrete is a modern construction material that gains its popularity especially due to its thermal insulation performance resulting from low volume weight and porous structure with sufficient mechanical strength. Nowadays, there are attempts to use this material for thermal insulation purposes and to replace current systems, which have many disadvantages, mainly concerning durability. The key for improvement of thermal insulation properties is therefore obtaining a material based on autoclaved aerated concrete with extremely low volume weight (below 200 kg/m ³ ensuring good thermal isolation properties, but with sufficient mechanical properties to allow easy manipulation. This material can be prepared by foaming very fine powder materials such as silica fume or very finely ground sand. This paper deals with the possibilities of preparation and summarizes the basic requirements for successful preparation of such a material.

  14. Landfill aeration for emission control before and during landfill mining.

    Science.gov (United States)

    Raga, Roberto; Cossu, Raffaello; Heerenklage, Joern; Pivato, Alberto; Ritzkowski, Marco

    2015-12-01

    The landfill of Modena, in northern Italy, is now crossed by the new high velocity railway line connecting Milan and Bologna. Waste was completely removed from a part of the landfill and a trench for the train line was built. With the aim of facilitating excavation and further disposal of the material extracted, suitable measures were defined. In order to prevent undesired emissions into the excavation area, the aerobic in situ stabilisation by means of the Airflow technology took place before and during the Landfill Mining. Specific project features involved the pneumatic leachate extraction from the aeration wells (to keep the leachate table low inside the landfill and increase the volume of waste available for air migration) and the controlled moisture addition into a limited zone, for a preliminary evaluation of the effects on process enhancement. Waste and leachate were periodically sampled in the landfill during the aeration before the excavation, for quality assessment over time; the evolution of biogas composition in the landfill body and in the extraction system for different plant set-ups during the project was monitored, with specific focus on uncontrolled migration into the excavation area. Waste biological stability significantly increased during the aeration (waste respiration index dropped to 33% of the initial value after six months). Leachate head decreased from 4 to 1.5m; leachate recirculation tests proved the beneficial effects of moisture addition on temperature control, without hampering waste aerobization. Proper management of the aeration plant enabled the minimization of uncontrolled biogas emissions into the excavation area. Copyright © 2015 Elsevier Ltd. All rights reserved.

  15. MEMBRANE BIOREACTOR FOR TREATMENT OF RECALCITRANT WASTEWATERS

    Directory of Open Access Journals (Sweden)

    Suprihatin Suprihatin

    2012-02-01

    Full Text Available The low biodegradable wastewaters remain a challenge in wastewater treatment technology. The performance of membrane bioreactor systems with submerged hollow fiber micro- and ultrafiltration membrane modules were examined for purifying recalcitrant wastewaters of leachate of a municipal solid waste open dumping site and effluent of pulp and paper mill. The use of MF and UF membrane bioreactor systems showed an efficient treatment for both types wastewaters with COD reduction of 80-90%. The membrane process achieved the desirable effects of maintaining reasonably high biomass concentration and long sludge retention time, while producing a colloid or particle free effluent. For pulp and paper mill effluent a specific sludge production of 0.11 kg MLSS/kg COD removed was achieved. A permeate flux of about 5 L/m²h could be achieved with the submerged microfiltration membrane. Experiments using ultrafiltration membrane produced relatively low permeate fluxes of 2 L/m²h. By applying periodical backwash, the flux could be improved significantly. It was indicated that the particle or colloid deposition on membrane surface was suppressed by backwash, but reformation of deposit was not effectively be prevented by shear-rate effect of aeration. Particle and colloid started to accumulate soon after backwash. Construction of membrane module and operation mode played a critical role in achieving the effectiveness of aeration in minimizing deposit formation on the membrane surface.

  16. Laser-induced surface deformation microscope for the study of the dynamic viscoelasticity of plasma membrane in a living cell.

    Science.gov (United States)

    Morisaku, Toshinori; Yui, Hiroharu

    2018-05-15

    A laser-induced surface deformation (LISD) microscope is developed and applied to measurement of the dynamic relaxation responses of the plasma membrane in a living cell. A laser beam is tightly focused on an optional area of cell surface and the focused light induces microscopic deformation on the surface via radiation pressure. The LISD microscope not only allows non-contact and destruction-free measurement but provides power spectra of the surface responses depending on the frequency of the intensity of the laser beam. An optical system for the LISD is equipped via a microscope, allowing us to measure the relaxation responses in sub-cellular-sized regions of the plasma membrane. In addition, the forced oscillation caused by the radiation pressure for surface deformation extends the upper limit of the frequency range in the obtained power spectra to 106 Hz, which enables us to measure relaxation responses in local regions within the plasma membrane. From differences in power-law exponents at higher frequencies, it is realized that a cancerous cell obeys a weaker single power-law than a normal fibroblast cell. Furthermore, the power spectrum of a keratinocyte cell obeys a power-law with two exponents, indicating that alternative mechanical models to a conventional soft glassy rheology model (where single power-laws explain cells' responses below about 103 Hz) are needed for the understanding over a wider frequency range. The LISD microscope would contribute to investigation of microscopic cell rheology, which is important for clarifying the mechanisms of cell migration and tissue construction.

  17. Pyrene-Labeled Amphiphiles: Dynamic And Structural Probes Of Membranes And Lipoproteins

    Science.gov (United States)

    Pownall, Henry J.; Homan, Reynold; Massey, John B.

    1987-01-01

    Lipids and proteins are important functional and structural components of living organisms. Although proteins are frequently found as soluble components of plasma or the cell cytoplasm, many lipids are much less soluble and separate into complex assemblies that usually contain proteins. Cell membranes and plasma lipoproteins' are two important macro-molecular assemblies that contain both lipids and proteins. Cell membranes are composed of a variety of lipids and proteins that form an insoluble bilayer array that has relatively little curvature over distances of several nm. Plasma lipoproteins are different in that they are much smaller, water-soluble, and have highly curved surfaces. A model of a high density lipoprotein (HDL) is shown in Figure 1. This model (d - 10 nm) contains a surface of polar lipids and proteins that surrounds a small core of insoluble lipids, mostly triglycerides and cholesteryl esters. The low density (LDL) (d - 25 nm) and very low density (VLDL) (d 90 nm) lipoproteins have similar architectures, except the former has a cholesteryl ester core and the latter a core that is almost exclusively triglyceride (Figure 1). The surface proteins of HDL are amphiphilic and water soluble; the single protein of LDL is insoluble, whereas VLDL contains both soluble and insoluble proteins. The primary structures of all of these proteins are known.

  18. Molecular dynamics analysis of conformational change of paramyxovirus F protein during the initial steps of membrane fusion

    International Nuclear Information System (INIS)

    Martín-García, Fernando; Mendieta-Moreno, Jesús Ignacio; Mendieta, Jesús; Gómez-Puertas, Paulino

    2012-01-01

    Highlights: ► Initial conformational change of paramyxovirus F protein is caused only by mechanical forces. ► HRA region undergoes a structural change from a beta + alpha conformation to an extended coil and then to an all-alpha conformation. ► HRS domains of F protein form three single α-helices prior to generation of the coiled coil. -- Abstract: The fusion of paramyxovirus to the cell membrane is mediated by fusion protein (F protein) present in the virus envelope, which undergoes a dramatic conformational change during the process. Unlike hemagglutinin in orthomyxovirus, this change is not mediated by an alteration of environmental pH, and its cause remains unknown. Steered molecular dynamics analysis leads us to suggest that the conformational modification is mediated only by stretching mechanical forces once the transmembrane fusion peptide of the protein is anchored to the cell membrane. Such elongating forces will generate major secondary structure rearrangement in the heptad repeat A region of the F protein; from β-sheet conformation to an elongated coil and then spontaneously to an α-helix. In addition, it is proposed that the heptad repeat A region adopts a final three-helix coiled coil and that this structure appears after the formation of individual helices in each monomer.

  19. Polyhydroxyalkanoate synthesis by mixed microbial consortia cultured on fermented dairy manure: Effect of aeration on process rates/yields and the associated microbial ecology.

    Science.gov (United States)

    Coats, Erik R; Watson, Benjamin S; Brinkman, Cynthia K

    2016-12-01

    Polyhydroxyalkanoates (PHAs) are biodegradable polymers that can substitute for petroleum-based plastics in a variety of applications. One avenue to commercial PHA production involves coupling waste-based synthesis with the use of mixed microbial consortia (MMC). In this regard, production requires maximizing the enrichment of a MMC capable of feast-famine PHA synthesis, with the metabolic response induced through imposition of aerobic-dynamic feeding (ADF) conditions. However, the concept of PHA production in complex matrices remains unrefined; process operational improvements are needed, along with an enhanced understanding of the MMC. Research presented herein investigated the effect of aeration on feast-famine PHA synthesis, with four independent aeration state systems studied; MMC were fed volatile fatty acid (VFA)-rich fermented dairy manure. Regardless of the aeration state, all MMC exhibited a feast-famine response based on observed carbon cycling. Moreover, there was no statistical difference in PHA synthesis rates, with q PHA ranging from 0.10 to 0.19 CmmolPHA gVSS -1 min -1 ; VFA uptake rates exhibited similar statistical indifferences. PHA production assessments on the enriched MMC resulted in maximum intracellular concentrations ranging from 22.5 to 90.7% (mgPHA mgVSS -1 ); at maximum concentration, the mean hydroxyvalerate mol content was 73 ± 0.6%. While a typical feast-famine dissolved oxygen (DO) pattern was observed at maximum aeration, less resolution was observed at decreasing aeration rates, suggesting that DO may not be an optimal process monitoring parameter. At lower aeration states, nitrogen cycling patterns, supported by molecular investigations targeting AOBs and NOBs, indicate that NO 2 and NO 3 sustained feast-famine PHA synthesis. Next-generation sequencing analysis of the respective MMC revealed numerous and diverse genera exhibiting the potential to achieve PHA synthesis, suggesting functional redundancy embedded in the diverse

  20. Effect of process parameters on the dynamic behavior of polymer electrolyte membrane fuel cells for electric vehicle applications

    Directory of Open Access Journals (Sweden)

    A.A. Abd El Monem

    2014-03-01

    Full Text Available This paper presents a dynamic mathematical model for Polymer Electrolyte Membrane “PEM” fuel cell systems to be used for electric vehicle applications. The performance of the fuel cell, depending on the developed model and taking the double layer charging effect into account, is investigated with different process parameters to evaluate their effect on the unit behavior. Thus, it will be easy to develop suitable controllers to regulate the unit operation, which encourages the use of fuel cells especially with electric vehicles applications. The steady-state performance of the fuel cell is verified using a comparison with datasheet data and curves provided by the manufacturer. The results and conclusions introduced in this paper provide a base for further investigation of fuel cells-driven dc motors for electric vehicle.

  1. A moving boundary problem and orthogonal collocation in solving a dynamic liquid surfactant membrane model including osmosis and breakage

    Directory of Open Access Journals (Sweden)

    E.C. Biscaia Junior

    2001-06-01

    Full Text Available A dynamic kinetic-diffusive model for the extraction of metallic ions from aqueous liquors using liquid surfactant membranes is proposed. The model incorporates undesirable intrinsic phenomena such as swelling and breakage of the emulsion globules that have to be controlled during process operation. These phenomena change the spatial location of the chemical reaction during the course of extraction, resulting in a transient moving boundary problem. The orthogonal collocation method was used to transform the partial differential equations into an ordinary differential equation set that was solved by an implicit numerical routine. The model was found to be numerically stable and reliable in predicting the behaviour of zinc extraction with acidic extractant for long residence times.

  2. High-definition polymeric membranes: construction of 3D lithographed channel arrays through control of natural building blocks dynamics.

    Science.gov (United States)

    Speranza, Valentina; Trotta, Francesco; Drioli, Enrico; Gugliuzza, Annarosa

    2010-02-01

    The fabrication of well-defined interfaces is in high demand in many fields of biotechnologies. Here, high-definition membrane-like arrays are developed through the self-assembly of water droplets, which work as natural building blocks for the construction of ordered channels. Solution viscosity together with the dynamics of the water droplets can decide the final formation of three-dimensional well-ordered patterns resembling anodic structures, especially because solvents denser than water are used. Particularly, the polymer solution viscosity is demonstrated to be a powerful tool for control of the mobility of submerged droplets during the microfabrication process. The polymeric patterns are structured at very high levels of organization and exhibit well-established transport-surface property relationships, considered basics for any types of advanced biotechnologies.

  3. Gravity filtration performances of the bio-diatomite dynamic membrane reactor for slightly polluted surface water purification.

    Science.gov (United States)

    Chu, Huaqiang; Dong, Bingzhi; Zhang, Yalei; Zhou, Xuefei

    2012-01-01

    A bio-diatomite dynamic membrane (BDDM) reactor for surface water treatment under a water head of 30, 40, 50, 60 and 70 cm, respectively, was investigated, which was very effective for pollutants removal. The water head exerted strong influences on filtration flux of BDDM during the precoating process, as well as on the formation of BDDM and turbidity variations. A high filtration flux (approximately 200-300 L/m2 h) could be achieved in the long filtration times of BDDM with a stable effluent turbidity of approximately 0.11-0.25 NTU. The BDDM could remove particles larger than 25 μm completely. The adopted sintered diatomite mainly consisted of macro pores, which were beneficial for improving the filtration flux of BDDM. During the backwash stage, the BDDM could be removed completely by the air backwash.

  4. Spontaneous Vesicle Self-Assembly: A Mesoscopic View of Membrane Dynamics

    DEFF Research Database (Denmark)

    Shillcock, J. C.

    2012-01-01

    Amphiphilic vesicles are ubiquitous in living cells and industrially interesting as drug delivery vehicles. Vesicle self-assembly proceeds rapidly from nanometer to micrometer length scales and is too fast to image experimentally but too slow for molecular dynamics simulations. Here, we use...... parallel dissipative particle dynamics (DPD) to follow spontaneous vesicle self-assembly for up to 445 mu s with near-molecular resolution. The mean mass and radius of gyration of growing amphiphilic clusters obey power laws with exponents of 0.85 +/- 0.03 and 0.41 +/- 0.02, respectively. We show that DPD...... provides a computational window onto fluid dynamics on scales unreachable by other explicit-solvent simulations....

  5. Quantitative measurement of blood flow dynamics in chorioallantoic membrane of chicken embryo using laser Doppler anemometry

    Science.gov (United States)

    Borozdova, M. A.; Stiukhina, E. S.; Sdobnov, A. A.; Fedosov, I. V.; Postnov, D. E.; Tuchin, V. V.

    2016-04-01

    We report the results on in ovo application of developed Laser Doppler Anemometer (LDA) device. The chorioallantoic membrane (CAM) of 9-13 days chicken embryos was used as a biological model that allows an easy access to both arterial and venous vessels of different size. The key point of our study was to find out how the periodic and aperiodic pulsations of blood flow (which are inevitable in living organism) will affect the LDA functions and measuring capability. Specifically, we (i) developed the technique to extract and refine the pulse rhythm from the signal received from a vessel, and (ii) analyzed the changes in power spectra of LDA signal that are caused by heart beating and considerably complicate the reliable measurement of Doppler shift. Our main conclusion is that the algorithm of LDA data processing need to be improved, and this possibly can be done by counting the information on current phase of cardiac cycle.

  6. Interplay between membrane elasticity and active cytoskeleton forces regulates the aggregation dynamics of the immunological synapse

    Science.gov (United States)

    Dharan, Nadiv; Farago, Oded

    Adhesion between a T cell and an antigen presenting cell is achieved by TCR-pMHC and LFA1-ICAM1 protein complexes. These segregate to form a special pattern, known as the immunological synapse (IS), consisting of a central quasi-circular domain of TCR-pMHC bonds surrounded by a peripheral domain of LFA1-ICAM1 complexes. Insights gained from imaging studies had led to the conclusion that the formation of the central adhesion domain in the IS is driven by active (ATP-driven) mechanisms. Recent studies, however, suggested that passive (thermodynamic) mechanisms may also play an important role in this process. Here, we present a simple physical model, taking into account the membrane-mediated thermodynamic attraction between the TCR-pMHC bonds and the effective forces that they experience due to ATP-driven actin retrograde flow and transport by dynein motor proteins. Monte Carlo simulations of the model exhibit a good spatio-temporal agreement with the experimentally observed pattern evolution of the TCR-pMHC microclusters. The agreement is lost when one of the aggregation mechanisms is "muted", which helps to identify the respective roles in the process. We conclude that actin retrograde flow drives the centripetal motion of TCR-pMHC bonds, while the membrane-mediated interactions facilitate microcluster formation and growth. In the absence of dynein motors, the system evolves into a ring-shaped pattern, which highlights the role of dynein motors in the formation of the final concentric pattern. The interplay between the passive and active mechanisms regulates the rate of the accumulation process, which in the absence of one them proceeds either too quickly or slowly.

  7. Membrane Potential Dynamics of Spontaneous and Visually Evoked Gamma Activity in V1 of Awake Mice

    NARCIS (Netherlands)

    Perrenoud, Q.; Pennartz, C.M.A.; Gentet, L.J.

    2016-01-01

    Cortical gamma activity (30-80 Hz) is believed to play important functions in neural computation and arises from the interplay of parvalbumin-expressing interneurons (PV) and pyramidal cells (PYRs). However, the subthreshold dynamics underlying its emergence in the cortex of awake animals remain

  8. Effects of moderately enhanced levels of ozone on the acyl lipid composition and dynamical properties of plasma membranes isolated from garden pea (Pisum sativum)

    DEFF Research Database (Denmark)

    Hellgren, Lars; Sellden, G.; Sandelius, A.S.

    2001-01-01

    Plasma membranes were isolated from leaves of 16-day-old garden pea, Pisum sativum L., that had been grown in the absence or presence of 65 nl l(-1) ozone for 4 days prior to membrane isolation, Plasma membranes from ozone-fumigated plants contained significantly more acyl lipids per protein than....../stigmasterol and lipid/protein ratios, and suggesting that ozone-fumigated pea plants may be more susceptible to freezing injuries....... lipids, as well as in PC and PE, The amount of free sterols per protein was unaltered, but the percentage of campesterol increased, concomitant with a decrease in stigmasterol, The dynamical properties of the isolated plasma membranes were assessed using Laurdan fluorescence spectroscopy, which monitors...

  9. Insight into the adsorption profiles of the Saprolegnia monoica chitin synthase MIT domain on POPA and POPC membranes by molecular dynamics simulation studies.

    Science.gov (United States)

    Kuang, Guanglin; Liang, Lijun; Brown, Christian; Wang, Qi; Bulone, Vincent; Tu, Yaoquan

    2016-02-21

    The critical role of chitin synthases in oomycete hyphal tip growth has been established. A microtubule interacting and trafficking (MIT) domain was discovered in the chitin synthases of the oomycete model organism, Saprolegnia monoica. MIT domains have been identified in diverse proteins and may play a role in intracellular trafficking. The structure of the Saprolegnia monoica chitin synthase 1 (SmChs1) MIT domain has been recently determined by our group. However, although our in vitro assay identified increased strength in interactions between the MIT domain and phosphatidic acid (PA) relative to other phospholipids including phosphatidylcholine (PC), the mechanism used by the MIT domain remains unknown. In this work, the adsorption behavior of the SmChs1 MIT domain on POPA and POPC membranes was systematically investigated by molecular dynamics simulations. Our results indicate that the MIT domain can adsorb onto the tested membranes in varying orientations. Interestingly, due to the specific interactions between MIT residues and lipid molecules, the binding affinity to the POPA membrane is much higher than that to the POPC membrane. A binding hotspot, which is critical for the adsorption of the MIT domain onto the POPA membrane, was also identified. The lower binding affinity to the POPC membrane can be attributed to the self-saturated membrane surface, which is unfavorable for hydrogen-bond and electrostatic interactions. The present study provides insight into the adsorption profile of SmChs1 and additionally has the potential to improve our understanding of other proteins containing MIT domains.

  10. The effects of agitation and aeration on the production of gluconic acid by Aspergillus niger

    Energy Technology Data Exchange (ETDEWEB)

    Dronawat, S.N.; Svihla, C.K.; Hanley, T.R. [Univ. of Louisville, KY (United States)

    1995-12-31

    The effects of agitation and aeration in the production of gluconic acid by Aspergillus niger from a glucose medium were investigated. Experiments were conducted at aeration rates of 5.0 and 10.0 L/min. Four different agitation speeds were investigated for each aeration rate. Gluconic acid concentration and biomass concentration were analyzed, and the rate of consumption of substrate by A. niger was noted. The main purpose of this work was to find the optimal conditions of agitation and aeration for the growth of A. niger and production of gluconic acid in submerged culture in a batch fermentor at a bench-top scale. The oxygen-transfer rates at different agitation and aeration rates were calculated. The gluconic acid concentration and rate of growth of A. niger increased with increase in the agitation and aeration rates.

  11. Violent breaking wave impacts. Part 3. Effects of scale and aeration

    DEFF Research Database (Denmark)

    Bredmose, Henrik; Bullock, G. N.; Hogg, A. J.

    2015-01-01

    . The Bagnold-Mitsuyasu scaling law for the compression of an air pocket by a piston of incompressible water is rederived and generalised to 3D air pockets of arbitrary shape. Numerical results for wall pressure, force and impulse are then presented for a flip-through impact, a low-aeration impact and a high......The effects of scale and aeration on violent breaking wave impacts with trapped and entrained air are investigated both analytically and numerically. By dimensional analysis we show that the impact pressures for Froude scaled conditions prior to the impact depend on the scale and aeration level......-aeration impact, for nine scales and five levels of initial aeration. Two of these impact types trap a pocket of air at the wall. Among the findings of the paper is that for fixed initial aeration, impact pressures from the flip-through impact broadly follow Froude scaling. This is also the case for the two...

  12. Fast, Highly-Sensitive, and Wide-Dynamic-Range Interdigitated Capacitor Glucose Biosensor Using Solvatochromic Dye-Containing Sensing Membrane.

    Science.gov (United States)

    Khan, Md Rajibur Rahaman; Khalilian, Alireza; Kang, Shin-Won

    2016-02-20

    In this paper, we proposed an interdigitated capacitor (IDC)-based glucose biosensor to measure different concentrations of glucose from 1 μM to 1 M. We studied four different types of solvatochromic dyes: Auramine O, Nile red, Rhodamine B, and Reichardt's dye (R-dye). These dyes were individually incorporated into a polymer [polyvinyl chloride (PVC)] and N,N-Dimethylacetamide (DMAC) solution to make the respective dielectric/sensing materials. To the best of our knowledge, we report for the first time an IDC glucose biosensing system utilizing a solvatochromic-dye-containing sensing membrane. These four dielectric or sensing materials were individually placed into the interdigitated electrode (IDE) by spin coating to make four IDC glucose biosensing elements. The proposed IDC glucose biosensor has a high sensing ability over a wide dynamic range and its sensitivity was about 23.32 mV/decade. It also has fast response and recovery times of approximately 7 s and 5 s, respectively, excellent reproducibility with a standard deviation of approximately 0.023, highly stable sensing performance, and real-time monitoring capabilities. The proposed IDC glucose biosensor was compared with an IDC, potentiometric, FET, and fiber-optic glucose sensor with respect to response time, dynamic range width, sensitivity, and linearity. We observed that the designed IDC glucose biosensor offered excellent performance.

  13. Fast, Highly-Sensitive, and Wide-Dynamic-Range Interdigitated Capacitor Glucose Biosensor Using Solvatochromic Dye-Containing Sensing Membrane

    Directory of Open Access Journals (Sweden)

    Md. Rajibur Rahaman Khan

    2016-02-01

    Full Text Available In this paper, we proposed an interdigitated capacitor (IDC-based glucose biosensor to measure different concentrations of glucose from 1 μM to 1 M. We studied four different types of solvatochromic dyes: Auramine O, Nile red, Rhodamine B, and Reichardt’s dye (R-dye. These dyes were individually incorporated into a polymer [polyvinyl chloride (PVC] and N,N-Dimethylacetamide (DMAC solution to make the respective dielectric/sensing materials. To the best of our knowledge, we report for the first time an IDC glucose biosensing system utilizing a solvatochromic-dye-containing sensing membrane. These four dielectric or sensing materials were individually placed into the interdigitated electrode (IDE by spin coating to make four IDC glucose biosensing elements. The proposed IDC glucose biosensor has a high sensing ability over a wide dynamic range and its sensitivity was about 23.32 mV/decade. It also has fast response and recovery times of approximately 7 s and 5 s, respectively, excellent reproducibility with a standard deviation of approximately 0.023, highly stable sensing performance, and real-time monitoring capabilities. The proposed IDC glucose biosensor was compared with an IDC, potentiometric, FET, and fiber-optic glucose sensor with respect to response time, dynamic range width, sensitivity, and linearity. We observed that the designed IDC glucose biosensor offered excellent performance.

  14. Landfill aeration in the framework of a reclamation project in Northern Italy.

    Science.gov (United States)

    Raga, Roberto; Cossu, Raffaello

    2014-03-01

    In situ aeration by means of the Airflow technology was proposed for landfill conditioning before landfill mining in the framework of a reclamation project in Northern Italy. A 1-year aeration project was carried out on part of the landfill with the objective of evaluating the effectiveness of the Airflow technology for landfill aerobization, the evolution of waste biological stability during aeration and the effects on leachate and biogas quality and emissions. The main outcomes of the 1-year aeration project are presented in the paper. The beneficial effect of the aeration on waste biological stability was clear (63% reduction of the respiration index); however, the effectiveness of aeration on the lower part of the landfill is questionable, due to the limited potential for air migration into the leachate saturated layers. During the 1-year in situ aeration project approx. 275 MgC were discharged from the landfill body with the extracted gas, corresponding to 4.6 gC/kgDM. However, due to the presence of anaerobic niches in the aerated landfill, approx. 46% of this amount was extracted as CH4, which is higher than reported in other aeration projects. The O2 conversion quota was lower than reported in other similar projects, mainly due to the higher air flow rates applied. The results obtained enabled valuable recommendations to be made for the subsequent application of the Airflow technology to the whole landfill. Copyright © 2013 Elsevier Ltd. All rights reserved.

  15. Experimental silo-dryer-aerator for the storage of soybean grains

    Directory of Open Access Journals (Sweden)

    Paulo C. Coradi

    Full Text Available ABSTRACT This study aimed to verify the capacity of silo-dryer-aerator prototype equipment operating as a silo-storage-aerator for soybean quality analysis. Soybeans with water content of 17% (wet basis – w.b. were dried and stored in a silo-dryer-aerator system that was designed using a drying chamber, four independent storage cells, and a static capacity of 164 kg. Another batch of grains was stored in a silo-storage-aerator with a capacity of 1,200 kg. The experiment was set up in a completely randomized factorial 5 × 4 experimental design including five grain batches stored after being dried at 30, 40, and 50 °C (mixed grains were dried at three temperatures in the silo-dryer-aerator cells and one mixed grain batch stored in the silo-storage-aerator system under ambient air conditions for four storage times (zero, one, two, and three months. There was no difference between the grains stored in the silo-dryer-aerator and silo-storage-aerator at the end of the three-month storage in terms of the physico-chemical quality. The storage time associated with drying at 50 °C caused a reduction in the physical-chemical quality of the grains. The silo-dryer-aerator system was presented as a possible alternative to store soybean (Glycine max L. grains.

  16. Effect of influent aeration on removal of organic matter from coffee processing wastewater in constructed wetlands.

    Science.gov (United States)

    Rossmann, Maike; Matos, Antonio Teixeira; Abreu, Edgar Carneiro; Silva, Fabyano Fonseca; Borges, Alisson Carraro

    2013-10-15

    The aim of the present study was to evaluate the influence of aeration and vegetation on the removal of organic matter in coffee processing wastewater (CPW) treated in 4 constructed wetlands (CWs), characterized as follows: (i) ryegrass (Lolium multiflorum) cultivated system operating with an aerated influent; (ii) non-cultivated system operating with an aerated influent, (iii) ryegrass cultivated system operating with a non-aerated influent; and (iv) non-cultivated system operating with a non-aerated influent. The lowest average chemical oxygen demand (COD), biochemical oxygen demand (BOD) and total suspended solids (TSS) removal efficiencies of 87, 84 and 73%, respectively, were obtained in the ryegrass cultivated system operating with a non-aerated influent. However, ryegrass cultivation did not influence the removal efficiency of organic matter. Artificial aeration of the CPW, prior to its injection in the CW, did not improve the removal efficiencies of organic matter. On other hand it did contribute to increase the instantaneous rate at which the maximum COD removal efficiency was reached. Although aeration did not result in greater organic matter removal efficiencies, it is important to consider the benefits of aeration on the removal of the other compounds. Copyright © 2013 Elsevier Ltd. All rights reserved.

  17. Bioreactor tests preliminary to landfill in situ aeration: A case study

    Energy Technology Data Exchange (ETDEWEB)

    Raga, Roberto, E-mail: roberto.raga@unipd.it [ICEA Department, University of Padova. Via Marzolo, 9, 35131 Padova (Italy); Cossu, Raffaello [ICEA Department, University of Padova. Via Marzolo, 9, 35131 Padova (Italy)

    2013-04-15

    Highlights: ► Carbon and nitrogen mass balances in aerated landfill simulation reactors. ► Waste stabilization in aerated landfill simulation reactors. ► Effect of temperature on biodegradation processes in aerated landfills. - Abstract: Lab scale tests in bioreactor were carried out in the framework of the characterization studies of a landfill where in situ aeration (possibly followed by landfill mining) had been proposed as part of the novel waste management strategy in a region in northern Italy. The tests were run to monitor the effects produced by aerobic conditions at different temperatures on waste sampled at different depths in the landfill, with focus on the carbon and nitrogen conversion during aeration. Temperatures ranging from 35 to 45 °C were chosen, in order to evaluate possible inhibition of biodegradation processes (namely nitrification) at 45 °C in the landfill. The results obtained showed positive effects of the aeration on leachate quality and a significant reduction of waste biodegradability. Although a delay of biodegradation processes was observed in the reactor run at 45 °C, biodegradation rates increased after 2 months of aeration, providing very low values of the relevant parameters (as in the other aerated reactors) by the end of the study. Mass balances were carried out for TOC and N-NH{sub 4}{sup +}; the findings obtained were encouraging and provided evidence of the effectiveness of carbon and nitrogen conversion processes in the aerated landfill simulation reactors.

  18. DESAIN KONTROL AERATOR PADA INSTALASI PENGOLAHAN AIR LIMBAH SUWUNG DENGAN FUZZY LOGIC

    Directory of Open Access Journals (Sweden)

    I Made Mataram

    2010-12-01

    Full Text Available Limbah merupakan buangan yang dihasilkan dari suatu proses produksi baik industri maupun domestik (rumahtangga dan harus dikelola agar tidak menimbulkan pencemaran dan penurunan kualitas lingkungan. InstalasiPengolahan Air Limbah (IPAL merupakan suatu tempat pengolahan limbah yang bertempat di daerah Suwung.Pengolahan limbah cair dilakukan dengan menggunakan sistem kolam aerasi dan kolam sedimentasi.Pada proses aerasi yaitu proses reduksi BOD (Biological Oxygen Demand dan COD (Chemical OxygenDemand secara aerob digunakan aerator sebagai penghasil oksigen yaitu dengan cara menempatkan aerator didalam kolam aerasi sehingga menghasilkan oksigen berupa buih udara yang tercampur dengan air. Untuk IPALSuwung pengoperasian aerator masih dengan cara manual yaitu dioperasikan pada jam tertentu sehingga inputjumlah oksigen terkadang tidak sesuai dengan karakteristik input limbah yang diolah, maka diperlukan suatu sistemkontrol pengoperasian aerator yang dapat menghasilkan oksigen guna mereduksi COD secara tepat sesuai bakumutu limbahDalam penelitian ini dilakukan perencanaan desain kontrol pengoperasian aerator dengan fuzzy logic. Desainpengontrolan dengan menggunakan logika fuzzy pada pengoperasian aerator sudah dapat dibuat dan dapat bekerjasesuai dengan karateristik input/ouput limbah, ini terlihat dari lama operasi aerator yang bekerja sudah sesuaidengan input limbah. Penggunaan energi listrik dengan pengontrolan fuzzy pada pengoperasian aerator lebih rendahdibandingkan dengan penggunaan energi listrik pengoperasian secara manual, ini terlihat dari penggunaan energipengoperasian aerator manual dan fuzzy pada bulan Oktober 2010 yang memiliki selisih sebesar 6.693 kWh, bulanNovember 2010

  19. Composting of tobacco plant waste by manual turning and forced aeration system

    OpenAIRE

    Nonglak Saithep

    2009-01-01

    The efficiency of tobacco plant waste composting, by the manual turning and the forced aeration system, was compared. Tobacco plant waste, cow manure, urea fertiliser, and a compost inoculum mixture at a 100:10:0.2:0.01 ratio respectively, with 60% (w/v) moisture content, were set up in piling forms. The piles of the manual turning system were provided with turning aeration by hand at intervals of 7 days during the composting process. For the forced aeration system, each pile was aerated by a...

  20. Bioreactor tests preliminary to landfill in situ aeration: A case study

    International Nuclear Information System (INIS)

    Raga, Roberto; Cossu, Raffaello

    2013-01-01

    Highlights: ► Carbon and nitrogen mass balances in aerated landfill simulation reactors. ► Waste stabilization in aerated landfill simulation reactors. ► Effect of temperature on biodegradation processes in aerated landfills. - Abstract: Lab scale tests in bioreactor were carried out in the framework of the characterization studies of a landfill where in situ aeration (possibly followed by landfill mining) had been proposed as part of the novel waste management strategy in a region in northern Italy. The tests were run to monitor the effects produced by aerobic conditions at different temperatures on waste sampled at different depths in the landfill, with focus on the carbon and nitrogen conversion during aeration. Temperatures ranging from 35 to 45 °C were chosen, in order to evaluate possible inhibition of biodegradation processes (namely nitrification) at 45 °C in the landfill. The results obtained showed positive effects of the aeration on leachate quality and a significant reduction of waste biodegradability. Although a delay of biodegradation processes was observed in the reactor run at 45 °C, biodegradation rates increased after 2 months of aeration, providing very low values of the relevant parameters (as in the other aerated reactors) by the end of the study. Mass balances were carried out for TOC and N-NH 4 + ; the findings obtained were encouraging and provided evidence of the effectiveness of carbon and nitrogen conversion processes in the aerated landfill simulation reactors

  1. Monitoring transitory profiles of leachate humic substances in landfill aeration reactors in mesophilic and thermophilic conditions

    Energy Technology Data Exchange (ETDEWEB)

    Tong, Huanhuan [Residues and Resource Reclamation Centre, Nanyang Environment and Water Research Institute, Nanyang Technological University, 1 Cleantech Loop, CleanTech One, 637141 (Singapore); School of Civil and Environmental Engineering, Nanyang Technological University, 50 Nanyang Avenue, 639798 (Singapore); Yin, Ke; Ge, Liya; Giannis, Apostolos [Residues and Resource Reclamation Centre, Nanyang Environment and Water Research Institute, Nanyang Technological University, 1 Cleantech Loop, CleanTech One, 637141 (Singapore); Chuan, Valerie W.L. [School of Civil and Environmental Engineering, Nanyang Technological University, 50 Nanyang Avenue, 639798 (Singapore); Wang, Jing-Yuan, E-mail: JYWANG@ntu.edu.sg [Residues and Resource Reclamation Centre, Nanyang Environment and Water Research Institute, Nanyang Technological University, 1 Cleantech Loop, CleanTech One, 637141 (Singapore); School of Civil and Environmental Engineering, Nanyang Technological University, 50 Nanyang Avenue, 639798 (Singapore)

    2015-04-28

    Highlights: • Polymerization and condensation of humic substances (HS) were enhanced by aeration. • Carboxylic group was enriched in HS by aeration presenting improved hydrophilicity. • Mobility of humic acid, as a result was enhanced by aeration especially in young landfill. • Waste age plays an important role in leachate management during aeration. - Abstract: The presence of humic substances (HS) in landfill leachate is of great interest because of their structural stability and potential toxicity. This study examined the effects of temperature and waste age on the transformation of HS during in situ aeration of bioreactor landfills. By establishing aerobic conditions, dissolved organic carbon (DOC) rapidly accumulated in the bioreactor leachate. Fractional analysis showed that the elevated concentration of humic acids (HAs) was primarily responsible for the increment of leachate strength. Further structural characterization indicated that the molecular weight (MW) and aromacity of HS were enhanced by aeration in conjunction with thermophilic temperature. Interestingly, elevation of HAs concentration was not observed in the aeration reactor with a prolonged waste age, as the mobility of HAs was lowered by the high MW derived from extended waste age. Based on these results, aeration may be more favorable in aged landfills, since dissolution of HAs could be minimized by the evolution to larger MW compared to young landfills. Moreover, increased operation temperature during aeration likely offers benefits for the rapid maturation of HS.

  2. Nitrogen-removal performance and community structure of nitrifying bacteria under different aeration modes in an oxidation ditch.

    Science.gov (United States)

    Guo, Chang-Zi; Fu, Wei; Chen, Xue-Mei; Peng, Dang-Cong; Jin, Peng-Kang

    2013-07-01

    Oxidation-ditch operation modes were simulated using sequencing batch reactors (SBRs) with alternate stirring and aerating. The nitrogen-removal efficiencies and nitrifying characteristics of two aeration modes, point aeration and step aeration, were investigated. Under the same air-supply capacity, oxygen dissolved more efficiently in the system with point aeration, forming a larger aerobic zone. The nitrifying effects were similar in point aeration and step aeration, where the average removal efficiencies of NH4(+) N were 98% and 96%, respectively. When the proportion of anoxic and oxic zones was 1, the average removal efficiencies of total nitrogen (TN) were 45% and 66% under point aeration and step aeration, respectively. Step aeration was more beneficial to both anoxic denitrification and simultaneous nitrification and denitrification (SND). The maximum specific ammonia-uptake rates (AUR) of point aeration and step aeration were 4.7 and 4.9 mg NH4(+)/(gMLVSS h), respectively, while the maximum specific nitrite-uptake rates (NUR) of the two systems were 7.4 and 5.3 mg NO2(-)-N/(gMLVSS h), respectively. The proportions of ammonia-oxidizing bacteria (AOB) to all bacteria were 5.1% under point aeration and 7.0% under step aeration, and the proportions of nitrite-oxidizing bacteria (NOB) reached 6.5% and 9.0% under point and step aeration, respectively. The dominant genera of AOB and NOB were Nitrosococcus and Nitrospira, which accounted for 90% and 91%, respectively, under point aeration, and the diversity of nitrifying bacteria was lower than under step aeration. Point aeration was selective of nitrifying bacteria. The abundance of NOB was greater than that of AOB in both of the operation modes, and complete transformation of NH4(+) N to NO3(-)-N was observed without NO2(-)-N accumulation. Copyright © 2013 Elsevier Ltd. All rights reserved.

  3. Spatiotemporal dynamics of membrane remodeling and fusion proteins during endocytic transport.

    Science.gov (United States)

    Arlt, Henning; Auffarth, Kathrin; Kurre, Rainer; Lisse, Dominik; Piehler, Jacob; Ungermann, Christian

    2015-04-01

    Organelles of the endolysosomal system undergo multiple fission and fusion events to combine sorting of selected proteins to the vacuole with endosomal recycling. This sorting requires a consecutive remodeling of the organelle surface in the course of endosomal maturation. Here we dissect the remodeling and fusion machinery on endosomes during the process of endocytosis. We traced selected GFP-tagged endosomal proteins relative to exogenously added fluorescently labeled α-factor on its way from the plasma membrane to the vacuole. Our data reveal that the machinery of endosomal fusion and ESCRT proteins has similar temporal localization on endosomes, whereas they precede the retromer cargo recognition complex. Neither deletion of retromer nor the fusion machinery with the vacuole affects this maturation process, although the kinetics seems to be delayed due to ESCRT deletion. Of importance, in strains lacking the active Rab7-like Ypt7 or the vacuolar SNARE fusion machinery, α-factor still proceeds to late endosomes with the same kinetics. This indicates that endosomal maturation is mainly controlled by the early endosomal fusion and remodeling machinery but not the downstream Rab Ypt7 or the SNARE machinery. Our data thus provide important further understanding of endosomal biogenesis in the context of cargo sorting. © 2015 Arlt et al. This article is distributed by The American Society for Cell Biology under license from the author(s). Two months after publication it is available to the public under an Attribution–Noncommercial–Share Alike 3.0 Unported Creative Commons License (http://creativecommons.org/licenses/by-nc-sa/3.0).

  4. Localised electrochemical impedance measurements of a polymer electrolyte fuel cell using a reference electrode array to give cathode-specific measurements and examine membrane hydration dynamics

    Science.gov (United States)

    Engebretsen, Erik; Hinds, Gareth; Meyer, Quentin; Mason, Tom; Brightman, Edward; Castanheira, Luis; Shearing, Paul R.; Brett, Daniel J. L.

    2018-04-01

    Advances in bespoke diagnostic techniques for polymer electrolyte fuel cells continue to provide unique insight into the internal operation of these devices and lead to improved performance and durability. Localised measurements of current density have proven to be extremely useful in designing better fuel cells and identifying optimal operating strategies, with electrochemical impedance spectroscopy (EIS) now routinely used to deconvolute the various losses in fuel cells. Combining the two techniques provides another dimension of understanding, but until now each localised EIS has been based on 2-electrode measurements, composed of both the anode and cathode responses. This work shows that a reference electrode array can be used to give individual electrode-specific EIS responses, in this case the cathode is focused on to demonstrate the approach. In addition, membrane hydration dynamics are studied under current load steps from open circuit voltage. A three-stage process is identified associated with an initial rapid reduction in membrane resistance after 10 s of applying a current step, followed by a slower ramp to approximately steady state, which was achieved after ∼250 s. These results support previously published work that has looked at membrane swelling dynamics and reveal that membrane hydration/membrane resistance is highly heterogeneous.

  5. Control of membrane fouling during hyperhaline municipal wastewater treatment using a pilot-scale anoxic/aerobic-membrane bioreactor system

    Institute of Scientific and Technical Information of China (English)

    Jingmei Sun; Jiangxiu Rong; Lifeng Dai; Baoshan Liu; Wenting Zhu

    2011-01-01

    Membrane fouling limits the effects of long-term stable operation of membrane bioreactor (MBR).Control of membrane foulin can extend the membrane life and reduce water treatment cost effectively.A pilot scale anoxic/aerobic-membrane bioreactor (A/O MBR,40 L/hr) was used to treat the hyperhaline municipal sewage from a processing zone of Tianjin,China.Impact factors including mixed liquid sludge suspension (MLSS),sludge viscosity (μ),microorganisms,extracellular polymeric substances (EPS),aeration intensity and suction/suspended time on membrane fouling and pollution control were studied.The relationships among various factors associated with membrane fouling were analyzed.Results showed that there was a positive correlation among MLSS,sludge viscosity and trans-membrane pressure (TMP).Considering water treatment efficiency and stable operation of the membrane module,MLSS of 5 g/L was suggested for the process.There was a same trend among EPS,sludge viscosity and TMP.Numbers and species of microorganisms affected membrane fouling.Either too high or too low aeration intensity was not conducive to membrane fouling control.Aeration intensity of 1.0 m3/hr (gas/water ratio of 25:1) is suggested for the process.A long suction time caused a rapid increase in membrane resistance.However,long suspended time cannot prevent the increase of membrane resistance effectively even though a suspended time was necessary for scale off particles from the membrane surface.The suction/suspended time of 12 min/3 min was selected for the process.The interaction of various environmental factors and operation conditions must be considered synthetically.

  6. Research on the Efficiency of Drinking Water Aeration Systems

    Directory of Open Access Journals (Sweden)

    Andrius Styra

    2011-02-01

    Full Text Available A number of modern iron removal systems used in individual houses do not work properly. One of the reasons could be inappropriate work of the aeration system. Therefore, the aim of this research is to analyze three types of jet pumps used in individual houses in Lithuania and compare the amount of sucked oxygen with demand for dissolved oxygen the amount of which is calculated. When summarizing the results of research, it was discovered that the ejector worked unstable when flow was low, and therefore stable operation require additional pressure.Article in Lithuanian

  7. Determination of glucose exchange rates and permeability of erythrocyte membrane in preeclampsia and subsequent oxidative stress-related protein damage using dynamic-{sup 19}F-NMR

    Energy Technology Data Exchange (ETDEWEB)

    Dickinson, Elizabeth, E-mail: elizabeth.dickinson@york.ac.uk [University of York, Department of Chemistry (United Kingdom); Arnold, John R. P. [Selby College (United Kingdom); Fisher, Julie [University of Leeds, School of Chemistry (United Kingdom)

    2017-02-15

    The cause of the pregnancy condition preeclampsia (PE) is thought to be endothelial dysfunction caused by oxidative stress. As abnormal glucose tolerance has also been associated with PE, we use a fluorinated-mimic of this metabolite to establish whether any oxidative damage to lipids and proteins in the erythrocyte membrane has increased cell membrane permeability. Data were acquired using {sup 19}F Dynamic-NMR (DNMR) to measure exchange of 3-fluoro-3-deoxyglucose (3-FDG) across the membrane of erythrocytes from 10 pregnant women (5 healthy control women, and 5 from women suffering from PE). Magnetisation transfer was measured using the 1D selective inversion and 2D EXSY pulse sequences, over a range of time delays. Integrated intensities from these experiments were used in matrix diagonalisation to estimate the values of the rate constants of exchange and membrane permeability. No significant differences were observed for the rate of exchange of 3-FDG and membrane permeability between healthy pregnant women and those suffering from PE, leading us to conclude that no oxidative damage had occurred at this carrier-protein site in the membrane.

  8. Determination of glucose exchange rates and permeability of erythrocyte membrane in preeclampsia and subsequent oxidative stress-related protein damage using dynamic-"1"9F-NMR

    International Nuclear Information System (INIS)

    Dickinson, Elizabeth; Arnold, John R. P.; Fisher, Julie

    2017-01-01

    The cause of the pregnancy condition preeclampsia (PE) is thought to be endothelial dysfunction caused by oxidative stress. As abnormal glucose tolerance has also been associated with PE, we use a fluorinated-mimic of this metabolite to establish whether any oxidative damage to lipids and proteins in the erythrocyte membrane has increased cell membrane permeability. Data were acquired using "1"9F Dynamic-NMR (DNMR) to measure exchange of 3-fluoro-3-deoxyglucose (3-FDG) across the membrane of erythrocytes from 10 pregnant women (5 healthy control women, and 5 from women suffering from PE). Magnetisation transfer was measured using the 1D selective inversion and 2D EXSY pulse sequences, over a range of time delays. Integrated intensities from these experiments were used in matrix diagonalisation to estimate the values of the rate constants of exchange and membrane permeability. No significant differences were observed for the rate of exchange of 3-FDG and membrane permeability between healthy pregnant women and those suffering from PE, leading us to conclude that no oxidative damage had occurred at this carrier-protein site in the membrane.

  9. Polymer confined in membrane phases: influences on stability, structure and dynamics

    International Nuclear Information System (INIS)

    Javierre, Isabelle

    1999-01-01

    The addition of a hydrosoluble polymer to the different structures obtained with mixtures of water/surfactant/alcohol/oil alters the thermodynamic stability of microemulsion and lamellar phases. The reverse sponge phase disappears while one can observe the occurrence of a new phase, labelled L5, at intermediate polymer concentration. In polymer-'doped' solvent lamellar phase, the polymer induces an attractive contribution to the interaction between bilayers while in polymer-'doped' bilayers lamellar phase, the polymer increases the flexibility. The L5 phase exhibits symmetric sponge properties and furthermore presents very strong symmetry fluctuations. The relaxation of these fluctuations were experimentally evidenced for the first time. This unusual dynamic behaviour was confronted to the one of other sponge phases, in a large range of concentrations. (author) [fr

  10. Collagencin, an antibacterial peptide from fish collagen: Activity, structure and interaction dynamics with membrane

    International Nuclear Information System (INIS)

    Ennaas, Nadia; Hammami, Riadh; Gomaa, Ahmed; Bédard, François; Biron, Éric; Subirade, Muriel; Beaulieu, Lucie; Fliss, Ismail

    2016-01-01

    In this study, we first report characterization of collagencin, an antimicrobial peptide identified from fish collagen hydrolysate. The peptide completely inhibited the growth of Staphylococcus aureus at 1.88 mM. Although non-toxic up to 470 μM, collagencin was hemolytic at higher concentrations. The secondary structure of collagencin was mainly composed by β-sheet and β-turn as determined by CD measurements and molecular dynamics. The peptide is likely to form β-sheet structure under hydrophobic environments and interacts with both anionic (phosphatidylglycerol) and zwitterionic (phosphoethanolamine and phosphatidylcholine) lipids as shown with CD spectroscopy and molecular dynamics. The peptide formed several hydrogen bonds with both POPG and POPE lipids and remained at membrane–water interface, suggesting that collagencin antibacterial action follows a carpet mechanism. Collagenous fish wastes could be processed by enzymatic hydrolysis and transformed into products of high value having functional or biological properties. Marine collagens are a promising source of antimicrobial peptides with new implications in food safety and human health. - Highlights: • Collagencin, an antibacterial (G+ & G-) peptide identified from fish collagen hydrolysate. • The peptide completely inhibited the growth of S. aureus at 1.88 mM and non-toxic at 470 μM. • The secondary structure was mainly composed by β-sheet and turn as determined by CD and MD. • Collagencin interacts with both anionic and zwitterionic lipids as shown with CD and MD. • Collagencin antibacterial action probably follows a carpet mechanism.

  11. Collagencin, an antibacterial peptide from fish collagen: Activity, structure and interaction dynamics with membrane

    Energy Technology Data Exchange (ETDEWEB)

    Ennaas, Nadia [STELA Dairy Research Centre, Institute of Nutrition and Functional Foods, Université Laval, G1V 0A6 Québec, QC (Canada); Hammami, Riadh, E-mail: riadh.hammami@fsaa.ulaval.ca [STELA Dairy Research Centre, Institute of Nutrition and Functional Foods, Université Laval, G1V 0A6 Québec, QC (Canada); Gomaa, Ahmed [STELA Dairy Research Centre, Institute of Nutrition and Functional Foods, Université Laval, G1V 0A6 Québec, QC (Canada); Bédard, François; Biron, Éric [Faculty of Pharmacy, Université Laval and Laboratory of Medicinal Chemistry, CHU de Québec Research Centre, G1V 4G2 Québec, QC (Canada); Subirade, Muriel [STELA Dairy Research Centre, Institute of Nutrition and Functional Foods, Université Laval, G1V 0A6 Québec, QC (Canada); Beaulieu, Lucie, E-mail: lucie.beaulieu@fsaa.ulaval.ca [STELA Dairy Research Centre, Institute of Nutrition and Functional Foods, Université Laval, G1V 0A6 Québec, QC (Canada); Department of Biology, Chemistry and Geography, Université du Québec à Rimouski (UQAR), 300 Allée des Ursulines, Rimouski, QC G5L 3A1 (Canada); Fliss, Ismail, E-mail: ismail.fliss@fsaa.ulaval.ca [STELA Dairy Research Centre, Institute of Nutrition and Functional Foods, Université Laval, G1V 0A6 Québec, QC (Canada)

    2016-04-29

    In this study, we first report characterization of collagencin, an antimicrobial peptide identified from fish collagen hydrolysate. The peptide completely inhibited the growth of Staphylococcus aureus at 1.88 mM. Although non-toxic up to 470 μM, collagencin was hemolytic at higher concentrations. The secondary structure of collagencin was mainly composed by β-sheet and β-turn as determined by CD measurements and molecular dynamics. The peptide is likely to form β-sheet structure under hydrophobic environments and interacts with both anionic (phosphatidylglycerol) and zwitterionic (phosphoethanolamine and phosphatidylcholine) lipids as shown with CD spectroscopy and molecular dynamics. The peptide formed several hydrogen bonds with both POPG and POPE lipids and remained at membrane–water interface, suggesting that collagencin antibacterial action follows a carpet mechanism. Collagenous fish wastes could be processed by enzymatic hydrolysis and transformed into products of high value having functional or biological properties. Marine collagens are a promising source of antimicrobial peptides with new implications in food safety and human health. - Highlights: • Collagencin, an antibacterial (G+ & G-) peptide identified from fish collagen hydrolysate. • The peptide completely inhibited the growth of S. aureus at 1.88 mM and non-toxic at 470 μM. • The secondary structure was mainly composed by β-sheet and turn as determined by CD and MD. • Collagencin interacts with both anionic and zwitterionic lipids as shown with CD and MD. • Collagencin antibacterial action probably follows a carpet mechanism.

  12. Nonlinear empirical model of gas humidity-related voltage dynamics of a polymer-electrolyte-membrane fuel cell stack

    Science.gov (United States)

    Meiler, M.; Andre, D.; Schmid, O.; Hofer, E. P.

    Intelligent energy management is a cost-effective key path to realize efficient automotive drive trains [R. O'Hayre, S.W. Cha, W. Colella, F.B. Prinz. Fuel Cell Fundamentals, John Wiley & Sons, Hoboken, 2006]. To develop operating strategy in fuel cell drive trains, precise and computational efficient models of all system components, especially the fuel cell stack, are needed. Should these models further be used in diagnostic or control applications, then some major requirements must be fulfilled. First, the model must predict the mean fuel cell voltage very precisely in all possible operating conditions, even during transients. The model output should be as smooth as possible to support best efficient optimization strategies of the complete system. At least, the model must be computational efficient. For most applications, a difference between real fuel cell voltage and model output of less than 10 mV and 1000 calculations per second will be sufficient. In general, empirical models based on system identification offer a better accuracy and consume less calculation resources than detailed models derived from theoretical considerations [J. Larminie, A. Dicks. Fuel Cell Systems Explained, John Wiley & Sons, West Sussex, 2003]. In this contribution, the dynamic behaviour of the mean cell voltage of a polymer-electrolyte-membrane fuel cell (PEMFC) stack due to variations in humidity of cell's reactant gases is investigated. The validity of the overall model structure, a so-called general Hammerstein model (or Uryson model), was introduced recently in [M. Meiler, O. Schmid, M. Schudy, E.P. Hofer. Dynamic fuel cell stack model for real-time simulation based on system identification, J. Power Sources 176 (2007) 523-528]. Fuel cell mean voltage is calculated as the sum of a stationary and a dynamic voltage component. The stationary component of cell voltage is represented by a lookup-table and the dynamic voltage by a parallel placed, nonlinear transfer function. A

  13. Community structure, population dynamics and diversity of fungi in a full-scale membrane bioreactor (MBR) for urban wastewater treatment.

    Science.gov (United States)

    Maza-Márquez, P; Vilchez-Vargas, R; Kerckhof, F M; Aranda, E; González-López, J; Rodelas, B

    2016-11-15

    Community structure, population dynamics and diversity of fungi were monitored in a full-scale membrane bioreactor (MBR) operated throughout four experimental phases (Summer 2009, Autumn 2009, Summer 2010 and Winter, 2012) under different conditions, using the 18S-rRNA gene and the intergenic transcribed spacer (ITS2-region) as molecular markers, and a combination of temperature-gradient gel electrophoresis and 454-pyrosequencing. Both total and metabolically-active fungal populations were fingerprinted, by amplification of molecular markers from community DNA and retrotranscribed RNA, respectively. Fingerprinting and 454-pyrosequencing evidenced that the MBR sheltered a dynamic fungal community composed of a low number of species, in accordance with the knowledge of fungal diversity in freshwater environments, and displaying a medium-high level of functional organization with few numerically dominant phylotypes. Population shifts were experienced in strong correlation with the changes of environmental variables and operation parameters, with pH contributing the highest level of explanation. Phylotypes assigned to nine different fungal Phyla were detected, although the community was mainly composed of Ascomycota, Basidiomycota and Chytridiomycota/Blastocladiomycota. Prevailing fungal phylotypes were affiliated to Saccharomycetes and Chytridiomycetes/Blastocladiomycetes, which displayed antagonistic trends in their relative abundance throughout the experimental period. Fungi identified in the activated sludge were closely related to genera of relevance for the degradation of organic matter and trace-organic contaminants, as well as genera of dimorphic fungi potentially able to produce plant operational issues such as foaming or biofouling. Phylotypes closely related to genera of human and plant pathogenic fungi were also detected. Copyright © 2016 Elsevier Ltd. All rights reserved.

  14. Enhanced waste activated sludge digestion using a submerged anaerobic dynamic membrane bioreactor: performance, sludge characteristics and microbial community

    Science.gov (United States)

    Yu, Hongguang; Wang, Zhiwei; Wu, Zhichao; Zhu, Chaowei

    2016-02-01

    Anaerobic digestion (AD) plays an important role in waste activated sludge (WAS) treatment; however, conventional AD (CAD) process needs substantial improvements, especially for the treatment of WAS with low solids content and poor anaerobic biodegradability. Herein, we propose a submerged anaerobic dynamic membrane bioreactor (AnDMBR) for simultaneous WAS thickening and digestion without any pretreatment. During the long-term operation, the AnDMBR exhibited an enhanced sludge reduction and improved methane production over CAD process. Moreover, the biogas generated in the AnDMBR contained higher methane content than CAD process. Stable carbon isotopic signatures elucidated the occurrence of combined methanogenic pathways in the AnDMBR process, in which hydrogenotrophic methanogenic pathway made a larger contribution to the total methane production. It was also found that organic matter degradation was enhanced in the AnDMBR, thus providing more favorable substrates for microorganisms. Pyrosequencing revealed that Proteobacteria and Bacteroidetes were abundant in bacterial communities and Methanosarcina and Methanosaeta in archaeal communities, which played an important role in the AnDMBR system. This study shed light on the enhanced digestion of WAS using AnDMBR technology.

  15. Monitoring the bacterial community dynamics in a petroleum refinery wastewater membrane bioreactor fed with a high phenolic load.

    Science.gov (United States)

    Silva, Cynthia C; Viero, Aline F; Dias, Ana Carolina F; Andreote, Fernando D; Jesus, Ederson C; De Paula, Sergio O; Torres, Ana Paula R; Santiago, Vania M J; Oliveira, Valeria M

    2010-01-01

    The phenolic compounds are a major contaminant class often found in industrial wastewaters and the biological treatment is an alternative tool commonly employed for their removal. In this sense, monitoring microbial community dynamics is crucial for a successful wastewater treatment. This work aimed to monitor the structure and activity of the bacterial community during the operation of a laboratory-scale continuous submerged membrane bioreactor (SMBR), using PCR and RT-PCR followed by Denaturing Gradient Gel Electrophoresis (DGGE) and 16S rRNA libraries. Multivariate analyses carried out using DGGE profiles showed significant changes in the total and metabolically active dominant community members during the 4-week treatment period, explained mainly by phenol and ammonium input. Gene libraries were assembled using 16S rDNA and 16S rRNA PCR products from the fourth week of treatment. Sequencing and phylogenetic analyses of clones from 16S rDNA library revealed a high diversity of taxa for the total bacterial community, with predominance of Thauera genus (ca. 50%). On the other hand, a lower diversity was found for metabolically active bacteria, which were mostly represented by members of Betaproteobacteria (Thauera and Comamonas), suggesting that these groups have a relevant role in the phenol degradation during the final phase of the SMBR operation.

  16. Crystallization of the Membrane-Associated Annexin B1: Roles of Additive Screen, Dynamic Light Scattering, and Bioactivity Assay

    Energy Technology Data Exchange (ETDEWEB)

    Ding, F.; Xu, Y; Azzi, A; Zhu, D; Rehse, D; Chen, C; Sun, S; Lin, S

    2010-01-01

    Annexin B1 (AnxB1) is a calcium-dependent phospholipid binding protein from Taenia solium cysticercus and has been reported to possess anticoagulant activity, to inhibit phospholipase A{sub 2}, and to regulate membrane transport. Native AnxB1 and its selenomethionyl derivative have been overproduced in Escherichia coli and purified. The results of dynamic light scattering analysis showed that Hepes buffer combined with low concentration salts (NaCl or CaCl{sub 2}) was beneficial for preventing aggregation and for AnxB1 stabilization in the storage. After the additive screen, crystals have been yielded in the presence of guanidine hydrochloride (Gn-HCl). We determined that a low concentration of Gn-HCl significantly delayed clotting time and increased anticoagulant activity. Analysis of the crystal showed that in the presence of Gn-HCl, AnxB1 crystallizes in orthorhombic space group, which is modified from the cubic space group for crystals grown in the absence of Gn-HCl. A high quality data set (at 1.9 {angstrom}) has been collected successfully for crystals of L-selenomethionine labeled protein in the presence of Gn-HCl, to solve the structure with the single anomalous dispersion method (SAD). The unit cell parameters are a = 102.35 {angstrom}, b = 103.59 {angstrom}, c = 114.60 {angstrom}, {alpha} = {beta} = {gamma} = 90.00{sup o}.

  17. Dynamic environmental transmission electron microscopy observation of platinum electrode catalyst deactivation in a proton-exchange-membrane fuel cell.

    Science.gov (United States)

    Yoshida, Kenta; Xudong, Zhang; Bright, Alexander N; Saitoh, Koh; Tanaka, Nobuo

    2013-02-15

    Spherical-aberration-corrected environmental transmission electron microscopy (AC-ETEM) was applied to study the catalytic activity of platinum/amorphous carbon electrode catalysts in proton-exchange-membrane fuel cells (PEMFCs). These electrode catalysts were characterized in different atmospheres, such as hydrogen and air, and a conventional high vacuum of 10(-5) Pa. A high-speed charge coupled device camera was used to capture real-time movies to dynamically study the diffusion and reconstruction of nanoparticles with an information transfer down to 0.1 nm, a time resolution below 0.2 s and an acceleration voltage of 300 kV. With such high spatial and time resolution, AC-ETEM permits the visualization of surface-atom behaviour that dominates the coalescence and surface-reconstruction processes of the nanoparticles. To contribute to the development of robust PEMFC platinum/amorphous carbon electrode catalysts, the change in the specific surface area of platinum particles was evaluated in hydrogen and air atmospheres. The deactivation of such catalysts during cycle operation is a serious problem that must be resolved for the practical use of PEMFCs in real vehicles. In this paper, the mechanism for the deactivation of platinum/amorphous carbon electrode catalysts is discussed using the decay rate of the specific surface area of platinum particles, measured first in a vacuum and then in hydrogen and air atmospheres for comparison.

  18. Exploring a model of human chemokine receptor CCR2 in presence of TAK779: A membrane based molecular dynamics study

    Science.gov (United States)

    Balupuri, Anand; Sobhia, M. Elizabeth

    2014-04-01

    Chemokine receptor 2 (CCR2) is a G-protein coupled receptor (GPCR) and a crucial target for various inflammation-driven diseases. In the present study, molecular docking and molecular dynamics simulations were performed on a CCR2 homology model. This work includes the comparative MD simulations of uncomplexed and ‘antagonist-complexed’ CCR2 models. These simulations yield insights into the binding mechanism of antagonist TAK779 and improve the understanding of various structural changes induced by the ligand in the CCR2 protein. Here, one 20 ns MD simulation was carried out on the uncomplexed CCR2 model in lipid bilayer to explore the effects of lipid membrane on the protein. Another 20 ns MD simulation was performed under the similar conditions on the docked CCR2-TAK779 complex. An alteration in the position and orientation of the ligand in binding site was observed after the simulation. Examination of protein-ligand complex suggested that TAK779 produced a greater structural change on the TM-III, TM-IV, TM-V and TM-VI than TM-I, TM-II and TM-VII. Interaction networks involving the conserved residues of uncomplexed and ‘antagonist-complexed’ CCR2 models were also examined. The major difference was observed to be the role of conserved residues of the DRY motif of TM-III and the NPxxY motif of TM-VII of CCR2.

  19. Similarities and differences of serotonin and its precursors in their interactions with model membranes studied by molecular dynamics simulation

    Science.gov (United States)

    Wood, Irene; Martini, M. Florencia; Pickholz, Mónica

    2013-08-01

    In this work, we report a molecular dynamics (MD) simulations study of relevant biological molecules as serotonin (neutral and protonated) and its precursors, tryptophan and 5-hydroxy-tryptophan, in a fully hydrated bilayer of 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphatidyl-choline (POPC). The simulations were carried out at the fluid lamellar phase of POPC at constant pressure and temperature conditions. Two guest molecules of each type were initially placed at the water phase. We have analyzed, the main localization, preferential orientation and specific interactions of the guest molecules within the bilayer. During the simulation run, the four molecules were preferentially found at the water-lipid interphase. We found that the interactions that stabilized the systems are essentially hydrogen bonds, salt bridges and cation-π. None of the guest molecules have access to the hydrophobic region of the bilayer. Besides, zwitterionic molecules have access to the water phase, while protonated serotonin is anchored in the interphase. Even taking into account that these simulations were done using a model membrane, our results suggest that the studied molecules could not cross the blood brain barrier by diffusion. These results are in good agreement with works that show that serotonin and Trp do not cross the BBB by simple diffusion.

  20. New experimental set-up and procedure for analyzing the dynamics of permeation of H2(g) across Pd-based metallic membranes

    International Nuclear Information System (INIS)

    Decaux, C.; Millet, P.; Decaux, C.

    2006-01-01

    . Impedances of the sorbing (permeating) membrane materials are then calculated using the theory of linear and time-invariant systems, by numerically Fourier-transforming the discretely sampled pressure signals. Using appropriate initial and boundary conditions, it is shown that the rate constants of the two major steps of the sorption (permeation) mechanisms can be separately accessed, i.e. surface resistances related to hydrogen dissociation (upstream side) and recombination (downstream side) processes, and bulk diffusion impedance. This experimental equipment and this treatment procedure therefore provide a new tool for analyzing the dynamics of hydrogen permeation across metallic membranes. This tool can be used for diagnosis purposes and for optimizing the structure and composition of permeation membranes. Results obtained with Pd and Pd 77 Ag 23 foils are presented and discussed. (authors)

  1. Gas sorption and barrier properties of polymeric membranes from molecular dynamics and Monte Carlo simulations.

    Science.gov (United States)

    Cozmuta, Ioana; Blanco, Mario; Goddard, William A

    2007-03-29

    It is important for many industrial processes to design new materials with improved selective permeability properties. Besides diffusion, the molecule's solubility contributes largely to the overall permeation process. This study presents a method to calculate solubility coefficients of gases such as O2, H2O (vapor), N2, and CO2 in polymeric matrices from simulation methods (Molecular Dynamics and Monte Carlo) using first principle predictions. The generation and equilibration (annealing) of five polymer models (polypropylene, polyvinyl alcohol, polyvinyl dichloride, polyvinyl chloride-trifluoroethylene, and polyethylene terephtalate) are extensively described. For each polymer, the average density and Hansen solubilities over a set of ten samples compare well with experimental data. For polyethylene terephtalate, the average properties between a small (n = 10) and a large (n = 100) set are compared. Boltzmann averages and probability density distributions of binding and strain energies indicate that the smaller set is biased in sampling configurations with higher energies. However, the sample with the lowest cohesive energy density from the smaller set is representative of the average of the larger set. Density-wise, low molecular weight polymers tend to have on average lower densities. Infinite molecular weight samples do however provide a very good representation of the experimental density. Solubility constants calculated with two ensembles (grand canonical and Henry's constant) are equivalent within 20%. For each polymer sample, the solubility constant is then calculated using the faster (10x) Henry's constant ensemble (HCE) from 150 ps of NPT dynamics of the polymer matrix. The influence of various factors (bad contact fraction, number of iterations) on the accuracy of Henry's constant is discussed. To validate the calculations against experimental results, the solubilities of nitrogen and carbon dioxide in polypropylene are examined over a range of

  2. Passively Aerated Composting of Straw-Rich Pig Manure : Effect of Compost Bed Porosity

    NARCIS (Netherlands)

    Veeken, A.H.M.; Wilde, de V.; Hamelers, H.V.M.

    2002-01-01

    Straw-rich manure from organic pig farming systems can be composted in passively aerated systems as the high application of straw results in a compost bed with good structure and porosity. The passively aerated composting process was simulated in one-dimensional reactors of 2 m3 for straw-rich

  3. Water quality and bacteriology in an aquaculture facility equipped with a new aeration system

    Digital Repository Service at National Institute of Oceanography (India)

    Fernandes, S.O.; Kulkarni, S.S.; Shirodkar, R.R.; Karekar, S.V.; PraveenKumar, R.; Sreepada, R.A.; Vogelsang, C.; LokaBharathi, P.A.

    .J., & Reyes F L. de los. (2005). Effects of Aeration Cycles on Nitrifying Bacterial Populations and Nitrogen Removal in Intermittently Aerated Reactors. Applied and Environmental Microbiology, 71(12), 8565-8572. Li, Q., Chen, B., Qu, k., Yuan, Y., Li, J...

  4. Molecular dynamics simulations of outer-membrane protease T from E. coli based on a hybrid coarse-grained/atomistic potential

    International Nuclear Information System (INIS)

    Neri, Marilisa; Anselmi, Claudio; Carnevale, Vincenzo; Vargiu, Attilio V; Carloni, Paolo

    2006-01-01

    Outer-membrane proteases T (OmpT) are membrane enzymes used for defense by Gram-negative bacteria. Here we use hybrid molecular mechanics/coarse-grained simulations to investigate the role of large-scale motions of OmpT from Escherichia coli for its function. In this approach, the enzyme active site is treated at the all-atom level, whilst the rest of the protein is described at the coarse-grained level. Our calculations agree well with previously reported all-atom molecular dynamics simulations, suggesting that this approach is well suitable to investigate membrane proteins. In addition, our findings suggest that OmpT large-scale conformational fluctuations might play a role for its biological function, as found for another protease class, the aspartyl proteases

  5. Axionic membranes

    International Nuclear Information System (INIS)

    Aurilia, A.; Spallucci, E.

    1992-01-01

    A metal ring removed from a soap-water solution encloses a film of soap which can be mathematically described as a minimal surface having the ring as its only boundary. This is known to everybody. In this letter we suggest a relativistic extension of the above fluidodynamic system where the soap film is replaced by a Kalb-Ramand gauge potential B μν (x) and the ring by a closed string. The interaction between the B μν field and the string current excites a new configuration of the system consisting of a relativistic membrane bounded by the string. We call such a classical solution of the equation of motion an axionic membrane. As a dynamical system, the axionic membrane admits a Hamilton-Jacobi formulation which is an extension of the HJ theory of electromagnetic strings. (orig.)

  6. Structure and Orientation of Bovine Lactoferrampin in the Mimetic Bacterial Membrane as Revealed by Solid-State NMR and Molecular Dynamics Simulation

    Science.gov (United States)

    Tsutsumi, Atsushi; Javkhlantugs, Namsrai; Kira, Atsushi; Umeyama, Masako; Kawamura, Izuru; Nishimura, Katsuyuki; Ueda, Kazuyoshi; Naito, Akira

    2012-01-01

    Bovine lactoferrampin (LFampinB) is a newly discovered antimicrobial peptide found in the N1-domain of bovine lactoferrin (268–284), and consists of 17 amino-acid residues. It is important to determine the orientation and structure of LFampinB in bacterial membranes to reveal the antimicrobial mechanism. We therefore performed 13C and 31P NMR, 13C-31P rotational echo double resonance (REDOR), potassium ion-selective electrode, and quartz-crystal microbalance measurements for LFampinB with mimetic bacterial membrane and molecular-dynamics simulation in acidic membrane. 31P NMR results indicated that LFampinB caused a defect in mimetic bacterial membranes. Ion-selective electrode measurements showed that ion leakage occurred for the mimetic bacterial membrane containing cardiolipin. Quartz-crystal microbalance measurements revealed that LFampinB had greater affinity to acidic phospholipids than that to neutral phospholipids. 13C DD-MAS and static NMR spectra showed that LFampinB formed an α-helix in the N-terminus region and tilted 45° to the bilayer normal. REDOR dephasing patterns between carbonyl carbon nucleus in LFampinB and phosphorus nuclei in lipid phosphate groups were measured by 13C-31P REDOR and the results revealed that LFampinB is located in the interfacial region of the membrane. Molecular-dynamics simulation showed the tilt angle to be 42° and the rotation angle to be 92.5° for Leu3, which are in excellent agreement with the experimental values. PMID:23083717

  7. Accelerated anaerobic hydrolysis rates under a combination of intermittent aeration and anaerobic conditions

    DEFF Research Database (Denmark)

    Jensen, T. R.; Lastra Milone, T.; Petersen, G.

    2017-01-01

    Anaerobic hydrolysis in activated return sludge was investigated in laboratory scale experiments to find if intermittent aeration would accelerate anaerobic hydrolysis rates compared to anaerobic hydrolysis rates under strict anaerobic conditions. The intermittent reactors were set up in a 240 h...... for calculating hydrolysis rates based on soluble COD were compared. Two-way ANOVA with the Bonferroni post-test was performed in order to register any significant difference between reactors with intermittent aeration and strictly anaerobic conditions respectively. The experiment demonstrated a statistically...... significant difference in favor of the reactors with intermittent aeration showing a tendency towards accelerated anaerobic hydrolysis rates due to application of intermittent aeration. The conclusion of the work is thus that intermittent aeration applied in the activated return sludge process (ARP) can...

  8. Nitrous oxide emissions from an intermittent aeration activated sludge system of an urban wastewater treatment plant

    Directory of Open Access Journals (Sweden)

    William Z. de Mello

    2013-01-01

    Full Text Available This study investigated the emission of N2O during the sequential aerated (60-min and non-aerated (30-min stages of an intermittent aeration cycle in an activated sludge wastewater treatment plant (WWTP. N2O emission occurred during both stages; however, emission was much higher during aeration. Air stripping is the major factor controlling transfer of N2O from the sewage to the atmosphere. The N2O emissions exclusively from the aeration tank represented 0.10% of the influent total nitrogen load and the per capita emission factor was almost 3 times higher than that suggested by the IPCC for inventories of N2O emission from WWTPs.

  9. KSHV Entry and Trafficking in Target Cells—Hijacking of Cell Signal Pathways, Actin and Membrane Dynamics

    Directory of Open Access Journals (Sweden)

    Binod Kumar

    2016-11-01

    Full Text Available Kaposi’s sarcoma associated herpesvirus (KSHV is etiologically associated with human endothelial cell hyperplastic Kaposi’s sarcoma and B-cell primary effusion lymphoma. KSHV infection of adherent endothelial and fibroblast cells are used as in vitro models for infection and KSHV enters these cells by host membrane bleb and actin mediated macropinocytosis or clathrin endocytosis pathways, respectively. Infection in endothelial and fibroblast cells is initiated by the interactions between multiple viral envelope glycoproteins and cell surface associated heparan sulfate (HS, integrins (α3β1, αVβ3 and αVβ5, and EphA2 receptor tyrosine kinase (EphA2R. This review summarizes the accumulated studies demonstrating that KSHV manipulates the host signal pathways to enter and traffic in the cytoplasm of the target cells, to deliver the viral genome into the nucleus, and initiate viral gene expression. KSHV interactions with the cell surface receptors is the key platform for the manipulations of host signal pathways which results in the simultaneous induction of FAK, Src, PI3-K, Rho-GTPase, ROS, Dia-2, PKC ζ, c-Cbl, CIB1, Crk, p130Cas and GEF-C3G signal and adaptor molecules that play critical roles in the modulation of membrane and actin dynamics, and in the various steps of the early stages of infection such as entry and trafficking towards the nucleus. The Endosomal Sorting Complexes Required for Transport (ESCRT proteins are also recruited to assist in viral entry and trafficking. In addition, KSHV interactions with the cell surface receptors also induces the host transcription factors NF-κB, ERK1/2, and Nrf2 early during infection to initiate and modulate viral and host gene expression. Nuclear delivery of the viral dsDNA genome is immediately followed by the host innate responses such as the DNA damage response (DDR, inflammasome and interferon responses. Overall, these studies form the initial framework for further studies of

  10. Study on low intensity aeration oxygenation model and optimization for shallow water

    Science.gov (United States)

    Chen, Xiao; Ding, Zhibin; Ding, Jian; Wang, Yi

    2018-02-01

    Aeration/oxygenation is an effective measure to improve self-purification capacity in shallow water treatment while high energy consumption, high noise and expensive management refrain the development and the application of this process. Based on two-film theory, the theoretical model of the three-dimensional partial differential equation of aeration in shallow water is established. In order to simplify the equation, the basic assumptions of gas-liquid mass transfer in vertical direction and concentration diffusion in horizontal direction are proposed based on engineering practice and are tested by the simulation results of gas holdup which are obtained by simulating the gas-liquid two-phase flow in aeration tank under low-intensity condition. Based on the basic assumptions and the theory of shallow permeability, the model of three-dimensional partial differential equations is simplified and the calculation model of low-intensity aeration oxygenation is obtained. The model is verified through comparing the aeration experiment. Conclusions as follows: (1)The calculation model of gas-liquid mass transfer in vertical direction and concentration diffusion in horizontal direction can reflect the process of aeration well; (2) Under low-intensity conditions, the long-term aeration and oxygenation is theoretically feasible to enhance the self-purification capacity of water bodies; (3) In the case of the same total aeration intensity, the effect of multipoint distributed aeration on the diffusion of oxygen concentration in the horizontal direction is obvious; (4) In the shallow water treatment, reducing the volume of aeration equipment with the methods of miniaturization, array, low-intensity, mobilization to overcome the high energy consumption, large size, noise and other problems can provide a good reference.

  11. Molecular Dynamics Simulations Reveal the Conformational Flexibility of Lipid II and Its Loose Association with the Defensin Plectasin in the Staphylococcus aureus Membrane

    DEFF Research Database (Denmark)

    Witzke, Sarah; Petersen, Michael; Carpenter, Timothy S.

    2016-01-01

    dynamics simulation study of the conformational dynamics of Lipid II within a detailed model of the Staphylococcus aureus cell membrane. We show that Lipid II is able to adopt a range of conformations, even within the packed lipidic environment of the membrane. Our simulations also reveal dimerization...... the biosynthesis of the cell wall. Given the urgent need for development of novel antibiotics to counter the growing threat of bacterial infection resistance, it is imperative that a thorough molecular-level characterization of the molecules targeted by antibiotics be achieved. To this end, we present a molecular...... of Lipid II mediated by cations. In the presence of the defensin peptide plectasin, the conformational lability of Lipid II allows it to form loose complexes with the protein, via a number of different binding modes....

  12. Phospholipid fatty acids in mitochondria and microsomes of wheat and rice seedling roots during aeration and anaerobiosis

    International Nuclear Information System (INIS)

    Chirkova, T.V.; Sinyutina, N.F.; Blyudzin, Yu.A.; Barskii, I.E.; Smetannikova, S.V.

    1989-01-01

    Mitochondrial and microsomal fractions were isolated from the roots after residence of wheat and rice seedlings under conditions of aeration or anaerobiosis and used to determine the percentage ratio of phospholipid fatty acids (PFA), their content, and the rate of incorporation of [2- 14 C]-acetate into them. In rice mitochondria under anaerobic influence, the ratio of unsaturated to saturated PFA was higher than the level that occurred in the control plants and PFA content remained close to the control level throughout the entire course of exposure. On the other hand, these indices declined in wheat mitochondria and microsomes of both plants. Anoxia also powerfully inhibited incorporation of labelled acetate into PFA of both membrane fractions in wheat and rice seedlings alike. Probably indicating adaptive reorganizations in composition of the main groups of PFA and inhibition of their decomposition in rice mitochondria, the obtained data are discussed in relation to greater resistance to temporary anaerobiosis in rice as compared with wheat

  13. Nano- to microscale dynamics of P-selectin detachment from leukocyte interfaces. I. Membrane separation from the cytoskeleton

    DEFF Research Database (Denmark)

    Evans, Evan; Heinrich, Volkmar; Leung, Andrew

    2005-01-01

    to final detachment, the typical force history exhibited the following sequence of events: i), an initial linear-elastic displacement of the PMN surface, ii), an abrupt crossover to viscoplastic flow that signaled membrane separation from the interior cytoskeleton and the beginning of a membrane tether......, and iii), the final detachment from the probe tip by usually one precipitous step of P-selectin:PSGL-1 dissociation. In this first article I, we focus on the initial elastic response and its termination by membrane separation from the cytoskeleton, initiating tether formation. Quantifying membrane...

  14. Hydrodynamic effects of air sparging on hollow fiber membranes in a bubble column reactor.

    Science.gov (United States)

    Xia, Lijun; Law, Adrian Wing-Keung; Fane, Anthony G

    2013-07-01

    Air sparging is now a standard approach to reduce concentration polarization and fouling of membrane modules in membrane bioreactors (MBRs). The hydrodynamic shear stresses, bubble-induced turbulence and cross flows scour the membrane surfaces and help reduce the deposit of foulants onto the membrane surface. However, the detailed quantitative knowledge on the effect of air sparging remains lacking in the literature due to the complex hydrodynamics generated by the gas-liquid flows. To date, there is no valid model that describes the relationship between the membrane fouling performance and the flow hydrodynamics. The present study aims to examine the impact of hydrodynamics induced by air sparging on the membrane fouling mitigation in a quantitative manner. A modelled hollow fiber module was placed in a cylindrical bubble column reactor at different axial heights with the trans-membrane pressure (TMP) monitored under constant flux conditions. The configuration of bubble column without the membrane module immersed was identical to that studied by Gan et al. (2011) using Phase Doppler Anemometry (PDA), to ensure a good quantitative understanding of turbulent flow conditions along the column height. The experimental results showed that the meandering flow regime which exhibits high flow instability at the 0.3 m is more beneficial to fouling alleviation compared with the steady flow circulation regime at the 0.6 m. The filtration tests also confirmed the existence of an optimal superficial air velocity beyond which a further increase is of no significant benefit on the membrane fouling reduction. In addition, the alternate aeration provided by two air stones mounted at the opposite end of the diameter of the bubble column was also studied to investigate the associated flow dynamics and its influence on the membrane filtration performance. It was found that with a proper switching interval and membrane module orientation, the membrane fouling can be effectively

  15. Study on oxygen transfer by solid jet aerator with multiple openings

    Directory of Open Access Journals (Sweden)

    B.K. Shukla

    2018-04-01

    Full Text Available In the current study, two different sets of solid jet aerators having area of openings equal to 594.96 mm2 and 246.30 mm2 with rectangular nozzles having rounded ends were studied. Each set consisted of aerators having one, two, four and eight openings. The oxygenation performance of every model was studied for five different discharges of 1.11 l/s, 2.10 l/s, 2.96 l/s, 3.83 l/s and 4.69 l/s were studied. At low discharges, the aerator having lesser number of openings demonstrated more oxygen-transfer efficiency whereas at higher discharges, the aerator having more number of openings yielded more oxygenation-efficiency. Maximum value of oxygen-transfer efficiency of 21.53 kg-O2/kW-hr was obtained for the discharge of 1.11 l/s for single nozzle aerator; however the maximum oxygen-transfer factor of 2.0 × 10−2 s−1 was obtained at discharge of 4.69 l/s for aerator having eight numbers of openings having area of 594.96 mm2. On the other hand, maximum oxygen transfer efficiency of 10.93 kg-O2/kW-hr was demonstrated by aerator with single opening at a discharge of 1.11 l/s and maximum oxygen transfer factor of 7.83 × 10−3 s−1 was obtained from aerator with eight openings at a discharge of 4.69 l/s corresponding to set of aerators with area of openings equal to 246.30 mm2. Multiple non-linear regression modelling was applied to predict oxygen transfer of the aerators for different combinations of input parameters. At the end, the models were compared with conventional methods of aeration and were found to be competitive with traditional devices. Keywords: Plunging jet, Jet aerator, Oxygen transfer, Aeration, Dissolved oxygen

  16. Cracking in autoclaved aerated concrete: Experimental investigation and XFEM modeling

    International Nuclear Information System (INIS)

    Ferretti, D.; Michelini, E.; Rosati, G.

    2015-01-01

    The paper aims to investigate and model cracking development in beams and deep-beams made of autoclaved aerated concrete (AAC). Fracture mechanics of AAC has been first studied by performing three-point bending tests on beams, similar to those commonly used for ordinary concrete elements. In some of these tests, crack growth has been also monitored by using ESPI laser technique. In this way, it has been possible to calibrate the main parameters of a proper cohesive law by means of extended finite element inverse analysis. Subsequently, cracking tests have been also performed on deep-beams, whose behavior is more representative of full scale walls. To validate the proposed cohesive law, deep-beam experimental behavior has been finally simulated through XFEM

  17. Cracking in autoclaved aerated concrete: Experimental investigation and XFEM modeling

    Energy Technology Data Exchange (ETDEWEB)

    Ferretti, D., E-mail: daniele.ferretti@unipr.it [Department of Civil, Environmental, Land Management Engineering and Architecture, University of Parma, P.co Area delle Scienze 181/A, 43124 Parma (Italy); Michelini, E. [Department of Civil, Environmental, Land Management Engineering and Architecture, University of Parma, P.co Area delle Scienze 181/A, 43124 Parma (Italy); Rosati, G. [Department of Civil and Environmental Engineering, Politecnico di Milano, Piazza L. Da Vinci 32, 20133 Milano (Italy)

    2015-01-15

    The paper aims to investigate and model cracking development in beams and deep-beams made of autoclaved aerated concrete (AAC). Fracture mechanics of AAC has been first studied by performing three-point bending tests on beams, similar to those commonly used for ordinary concrete elements. In some of these tests, crack growth has been also monitored by using ESPI laser technique. In this way, it has been possible to calibrate the main parameters of a proper cohesive law by means of extended finite element inverse analysis. Subsequently, cracking tests have been also performed on deep-beams, whose behavior is more representative of full scale walls. To validate the proposed cohesive law, deep-beam experimental behavior has been finally simulated through XFEM.

  18. Thermal conductivity of newspaper sandwiched aerated lightweight concrete panel

    Energy Technology Data Exchange (ETDEWEB)

    Ng, Soon-Ching; Low, Kaw-Sai [Faculty of Engineering and Science, Universiti Tunku Abdul Rahman, Jalan Genting Kelang, Setapak, 53300 Kuala Lumpur, Wilayah Persekutuan (Malaysia)

    2010-12-15

    Investigation on the thermal conductivity of newspaper sandwiched aerated lightweight concrete (ALC) panels is the main purpose of this study. Various densities of ALC panels ranging from 1700, 1400 and 1100 kg/m{sup 3} with three different aerial intensities of newspaper sandwiched were produced. Investigation was limited to the effect of aerial intensity of newspaper sandwiched and the effect of density of ALC on thermal conductivity. It is found that the thermal conductivity of newspaper sandwiched ALC panels reduced remarkably compared to control ALC panels. The reduction was recorded at 18.0%, 21.8% and 20.7% correspond to densities of 1700, 1400 and 1100 kg/m{sup 3} with just a mere 0.05 g/cm{sup 2} aerial intensity of newspaper sandwiched. Newspaper sandwiched has a significant impact on the performance of thermal conductivity of ALC panels based on regression analysis. (author)

  19. Methane biofiltration using autoclaved aerated concrete as the carrier material.

    Science.gov (United States)

    Ganendra, Giovanni; Mercado-Garcia, Daniel; Hernandez-Sanabria, Emma; Boeckx, Pascal; Ho, Adrian; Boon, Nico

    2015-09-01

    The methane removal capacity of mixed methane-oxidizing bacteria (MOB) culture in a biofilter setup using autoclaved aerated concrete (AAC) as a highly porous carrier material was tested. Batch experiment was performed to optimize MOB immobilization on AAC specimens where optimum methane removal was obtained when calcium chloride was not added during bacterial inoculation step and 10-mm-thick AAC specimens were used. The immobilized MOB could remove methane at low concentration (~1000 ppmv) in a biofilter setup for 127 days at average removal efficiency (RE) of 28.7 %. Unlike a plug flow reactor, increasing the total volume of the filter by adding a biofilter in series did not result in higher total RE. MOB also exhibited a higher abundance at the bottom of the filter, in proximity with the methane gas inlet where a high methane concentration was found. Overall, an efficient methane biofilter performance could be obtained using AAC as the carrier material.

  20. Aeration-Controlled Formation of Acid in Heterolactic Fermentations

    DEFF Research Database (Denmark)

    Adler-Nissen, Jens

    1994-01-01

    fermentation processes should be analyzed as fed-batch fermentations with oxygen as the limiting substrate. Addition of fructose in limited amounts leads to the formation of one half mole of acetic acid for each mole fructose, thus offering an alternative mechanism for controlling acetic acid formation.......Controlled aeration of Leuconostoc mesenteroides was studied as a possible mechanism for control of the formation of acetic acid, a metabolite of major influence on the taste of lactic fermented foods. Fermentations were carried out in small scale in a medium in which growth was limited...... by the buffer capacity only. Ethanol and acetic acid formed during the fermentation were analyzed by rapid head space gas chromatography, and the ratio of the molar concentrations of these two volatiles quantitatively predicted the balance between the formation of acetic acid and lactic acid. The oxygen...

  1. Emissions of ammonia, carbon dioxide, and hydrogen sulfide from swine wastewater during and after acidification treatment: effect of pH, mixing and aeration

    DEFF Research Database (Denmark)

    Dai, Xiao-Rong; Blanes-Vidal, Victoria

    2013-01-01

    setup consisting of nine dynamic flux chambers. Three pH levels (pH = 6.0, pH = 5.8 and pH = 5.5), combined with short-term aeration and venting (with an inert gas) treatments were studied. Acidification reduced average NH(3) emissions from swine slurry stored after acidification treatment compared...... to emissions during storage of non-acidified slurry. The reduction were 50%, 62% and 77% when pH was reduce to 6.0, 5.8 and 5.5, respectively. However, it had no significant effect on average CO(2) and H(2)S emissions during storage of slurry after acidification. Aeration of the slurry for 30 min had no effect...

  2. Dynamic trafficking and delivery of connexons to the plasma membrane and accretion to gap junctions in living cells

    NARCIS (Netherlands)

    Lauf, Undine; Giepmans, Ben N G; Lopez, Patricia; Braconnot, Sebastien; Chen, Shu-Chih; Falk, Matthias M

    2002-01-01

    Certain membrane channels including acetylcholine receptors, gap junction (GJ) channels, and aquaporins arrange into large clusters in the plasma membrane (PM). However, how these channels are recruited to the clusters is unknown. To address this question, we have investigated delivery of GJ channel

  3. The Effect of Membrane Environment on Surfactant Protein C Stability Studied by Constant-pH Molecular Dynamics.

    Science.gov (United States)

    Carvalheda, Catarina A; Campos, Sara R R; Baptista, António M

    2015-10-26

    Pulmonary surfactant protein C (SP-C) is a small peptide with two covalently linked fatty acyl chains that plays a crucial role in the formation and stabilization of the pulmonary surfactant reservoirs during the compression and expansion steps of the respiratory cycle. Although its function is known to be tightly related to its highly hydrophobic character and key interactions maintained with specific lipid components, much is left to understand about its molecular mechanism of action. Also, although it adopts a mainly helical structure while associated with the membrane, factors as pH variation and deacylation have been shown to affect its stability and function. In this work, the conformational behavior of both the acylated and deacylated SP-C isoforms was studied in a DPPC bilayer under different pH conditions using constant-pH molecular dynamics simulations. Our findings show that both protein isoforms are remarkably stable over the studied pH range, even though the acylated isoform exhibits a labile helix-turn-helix motif rarely observed in the other isoform. We estimate similar tilt angles for the two isoforms over the studied pH range, with a generally higher degree of internalization of the basic N-terminal residues in the deacylated case, and observe and discuss some protonation-conformation coupling effects. Both isoforms establish contacts with the surrounding lipid molecules (preferentially with the sn-2 ester bonds) and have a local effect on the conformational behavior of the surrounding lipid molecules, the latter being more pronounced for acylated SP-C.

  4. Litter aeration and spread of Salmonella in broilers.

    Science.gov (United States)

    Bodí, Sara González; Garcia, Arantxa Villagra; García, Santiago Vega; Orenga, Clara Marín

    2013-08-01

    Litter quality in the poultry sector is one of the main parameters of health, productivity, and animal welfare. Therefore, innovative management methods have been developed to improve the quality of litter. One of them is litter aeration (LA) by tumbling. However, there is little information related to the effect of this technique on the spreading of pathogens of public health importance such as Salmonella. In this context, the objective of this study was to determine the epidemiology of Salmonella in poultry farms, when serial LA were implemented during the rearing cycle of broilers. For this purpose, an experimental broiler farm with 3 identical rooms was used in the study. Two rooms were assigned to the LA treatment, and the other one served as the control room. Environmental samples were taken in poultry houses after LA in 4 consecutive weeks at the end of the cycle. All samples collected were analyzed according to the standards of the International Organization for Standardization (ISO 6579:2002, Annex D). The results of this study showed that in the control and treated rooms, the percentage of positive samples for Salmonella decreased in the first 3 LA sessions (LA 1, LA 2, and LA 3). However, in the last LA session of rearing (LA 4), the percentage of positive samples increased from 8.2 to 33.2% in the control room instead the treated rooms where the positive samples decreased (P = 0.017). Thus, the aeration of the litter as litter management technique in poultry broiler production does not increase the shedding or the spread of Salmonella throughout broiler houses. In addition, it could be an effective technique to reduce the infective pressure of this bacterium in several areas of the farm or in certain moments of the rearing period with more risk of multiplication and spreading of Salmonella.

  5. The dynamics of the G protein-coupled neuropeptide Y2 receptor in monounsaturated membranes investigated by solid-state NMR spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Thomas, Lars; Kahr, Julian; Schmidt, Peter; Krug, Ulrike; Scheidt, Holger A.; Huster, Daniel, E-mail: daniel.huster@medizin.uni-leipzig.de [University of Leipzig, Institute of Medical Physics and Biophysics (Germany)

    2015-04-15

    In contrast to the static snapshots provided by protein crystallography, G protein-coupled receptors constitute a group of proteins with highly dynamic properties, which are required in the receptors’ function as signaling molecule. Here, the human neuropeptide Y2 receptor was reconstituted into a model membrane composed of monounsaturated phospholipids and solid-state NMR was used to characterize its dynamics. Qualitative static {sup 15}N NMR spectra and quantitative determination of {sup 1}H–{sup 13}C order parameters through measurement of the {sup 1}H–{sup 13}C dipolar couplings of the CH, CH{sub 2} and CH{sub 3} groups revealed axially symmetric motions of the whole molecule in the membrane and molecular fluctuations of varying amplitude from all molecular segments. The molecular order parameters (S{sub backbone} = 0.59–0.67, S{sub CH2} = 0.41–0.51 and S{sub CH3} = 0.22) obtained in directly polarized {sup 13}C NMR experiments demonstrate that the Y2 receptor is highly mobile in the native-like membrane. Interestingly, according to these results the receptor was found to be slightly more rigid in the membranes formed by the monounsaturated phospholipids than by saturated phospholipids as investigated previously. This could be caused by an increased chain length of the monounsaturated lipids, which may result in a higher helical content of the receptor. Furthermore, the incorporation of cholesterol, phosphatidylethanolamine, or negatively charged phosphatidylserine into the membrane did not have a significant influence on the molecular mobility of the Y2 receptor.

  6. A membrane stirrer for product recovery and substrate feeding.

    Science.gov (United States)

    Femmer, T; Carstensen, F; Wessling, M

    2015-02-01

    During fermentation processes, in situ product recovery (ISPR) using submerged membranes allows a continuous operation mode with effective product removal. Continuous recovery reduces product inhibition and organisms in the reactor are not exposed to changing reaction conditions. For an effective in situ product removal, submerged membrane systems should have a sufficient large membrane area and an anti-fouling concept integrated in a compact device for the limited space in a lab-scale bioreactor. We present a new membrane stirrer with integrated filtration membranes on the impeller blades as well as an integrated gassing concept in an all-in-one device. The stirrer is fabricated by rapid prototyping and is equipped with a commercial micromesh membrane. Filtration performance is tested using a yeast cell suspension with different stirring speeds and aeration fluxes. We reduce membrane fouling by backflushing through the membrane with the product stream. © 2014 Wiley Periodicals, Inc.

  7. Ammonia-based feedforward and feedback aeration control in activated sludge processes.

    Science.gov (United States)

    Rieger, Leiv; Jones, Richard M; Dold, Peter L; Bott, Charles B

    2014-01-01

    Aeration control at wastewater treatment plants based on ammonia as the controlled variable is applied for one of two reasons: (1) to reduce aeration costs, or (2) to reduce peaks in effluent ammonia. Aeration limitation has proven to result in significant energy savings, may reduce external carbon addition, and can improve denitrification and biological phosphorus (bio-P) performance. Ammonia control for limiting aeration has been based mainly on feedback control to constrain complete nitrification by maintaining approximately one to two milligrams of nitrogen per liter of ammonia in the effluent. Increased attention has been given to feedforward ammonia control, where aeration control is based on monitoring influent ammonia load. Typically, the intent is to anticipate the impact of sudden load changes, and thereby reduce effluent ammonia peaks. This paper evaluates the fundamentals of ammonia control with a primary focus on feedforward control concepts. A case study discussion is presented that reviews different ammonia-based control approaches. In most instances, feedback control meets the objectives for both aeration limitation and containment of effluent ammonia peaks. Feedforward control, applied specifically for switching aeration on or off in swing zones, can be beneficial when the plant encounters particularly unusual influent disturbances.

  8. Optimization of aeration for biodiesel production by Scenedesmus obliquus grown in municipal wastewater.

    Science.gov (United States)

    Han, Song-Fang; Jin, Wenbiao; Tu, Renjie; Abomohra, Abd El-Fatah; Wang, Zhi-Han

    2016-07-01

    Despite the significant breakthroughs in research on microalgae as a feedstock for biodiesel, its production cost is still much higher than that of fossil diesel. One possible solution to overcome this problem is to optimize algal growth and lipid production in wastewater. The present study examines the optimization of pretreatment of municipal wastewater and aeration conditions in order to enhance the lipid productivity of Scenedesmus obliquus. Results showed that no significant differences were recorded in lipid productivity of S. obliquus grown in primary settled or sterilized municipal wastewater; however, ultrasound pretreatment of wastewater significantly decreased the lipid production. Whereas, aeration rates of 0.2 vvm significantly increased lipid content by 51 %, with respect to the non-aerated culture, which resulted in maximum lipid productivity (32.5 mg L(-1) day(-1)). Furthermore, aeration enrichment by 2 % CO2 resulted in increase of lipid productivity by 46 % over the CO2 non-enriched aerated culture. Fatty acid profile showed that optimized aeration significantly enhanced monounsaturated fatty acid production, composed mainly of C18:1, by 1.8 times over the non-aerated S. obliquus culture with insignificant changes in polyunsaturated fatty acid proportion; suggesting better biodiesel characteristics for the optimized culture.

  9. Composting of tobacco plant waste by manual turning and forced aeration system

    Directory of Open Access Journals (Sweden)

    Nonglak Saithep

    2009-05-01

    Full Text Available The efficiency of tobacco plant waste composting, by the manual turning and the forced aeration system, was compared. Tobacco plant waste, cow manure, urea fertiliser, and a compost inoculum mixture at a 100:10:0.2:0.01 ratio respectively, with 60% (w/v moisture content, were set up in piling forms. The piles of the manual turning system were provided with turning aeration by hand at intervals of 7 days during the composting process. For the forced aeration system, each pile was aerated by a 3-HP air pump with a flow rate of 19 litres min-1 for 15 minutes every morning and evening. The completely randomised design of turned and force-aerated piles was performed in triplicate. The composting activity of both systems during the composting period was measured by several parameters: temperature, pH, moisture content, C/N ratio, growth of microorganisms, cellulase activity, and nicotine degradation in the set-up piles. Both systems had similar temperature, pH, and moisture content conditions in the piles during the composting process. However, the forced aeration system was more advantageous for the growth of mesophilic and thermophilic microorganisms, for cellulase activity from cellulase-producing microorganisms, and for nicotine degradation, when compared to the manual turning system. In conclusion, the forced aeration system was more efficient than the manual turning system in composting and is a viable alternative method for the composting process.

  10. Effects of Lys to Glu mutations in GsMTx4 on membrane binding, peptide orientation, and self-association propensity, as analyzed by molecular dynamics simulations.

    Science.gov (United States)

    Nishizawa, Kazuhisa; Nishizawa, Manami; Gnanasambandam, Radhakrishnan; Sachs, Frederick; Sukharev, Sergei I; Suchyna, Thomas M

    2015-11-01

    GsMTx4, a gating modifier peptide acting on cationic mechanosensitive channels, has a positive charge (+5e) due to six Lys residues. The peptide does not have a stereospecific binding site on the channel but acts from the boundary lipids within a Debye length of the pore probably by changing local stress. To gain insight into how these Lys residues interact with membranes, we performed molecular dynamics simulations of Lys to Glu mutants in parallel with our experimental work. In silico, K15E had higher affinity for 1-palmitoyl-2-oleoyl-glycero-3-phosphocholine bilayers than wild-type (WT) peptide or any other mutant tested, and showed deeper penetration than WT, a finding consistent with the experimental data. Experimentally, the inhibitory activities of K15E and K25E were most compromised, whereas K8E and K28E inhibitory activities remained similar to WT peptide. Binding of WT in an interfacial mode did not influence membrane thickness. With interfacial binding, the direction of the dipole moments of K15E and K25E was predicted to differ from WT, whereas those of K8E and K28E oriented similarly to that of WT. These results support a model in which binding of GsMTx4 to the membrane acts like an immersible wedge that serves as a membrane expansion buffer reducing local stress and thus inhibiting channel activity. In simulations, membrane-bound WT attracted other WT peptides to form aggregates. This may account for the positive cooperativity observed in the ion channel experiments. The Lys residues seem to fine-tune the depth of membrane binding, the tilt angle, and the dipole moments. Copyright © 2015 Elsevier B.V. All rights reserved.

  11. Measurement of the membrane dipole electric field in DMPC vesicles using vibrational shifts of p-cyanophenylalanine and molecular dynamics simulations.

    Science.gov (United States)

    Shrestha, Rebika; Cardenas, Alfredo E; Elber, Ron; Webb, Lauren J

    2015-02-19

    The magnitude of the membrane dipole field was measured using vibrational Stark effect (VSE) shifts of nitrile oscillators placed on the unnatural amino acid p-cyanophenylalanine (p-CN-Phe) added to a peptide sequence at four unique positions. These peptides, which were based on a repeating alanine-leucine motif, intercalated into small unilamellar DMPC vesicles which formed an α-helix as confirmed by circular dichroic (CD) spectroscopy. Molecular dynamics simulations of the membrane-intercalated helix containing two of the nitrile probes, one near the headgroup region of the lipid (αLAX(25)) and one buried in the interior of the bilayer (αLAX(16)), were used to examine the structure of the nitrile with respect to the membrane normal, the assumed direction of the dipole field, by quantifying both a small tilt of the helix in the bilayer and conformational rotation of the p-CN-Phe side chain at steady state. Vibrational absorption energies of the nitrile oscillator at each position showed a systematic blue shift as the nitrile was stepped toward the membrane interior; for several different concentrations of peptide, the absorption energy of the nitrile located in the middle of the bilayer was ∼3 cm(-1) greater than that of the nitrile closest to the surface of the membrane. Taken together, the measured VSE shifts and nitrile orientations within the membrane resulted in an absolute magnitude of 8-11 MV/cm for the dipole field, at the high end of the range of possible values that have been accumulated from a variety of indirect measurements. Implications for this are discussed.

  12. Dynamic bio-adhesion of polymer nanoparticles on MDCK epithelial cells and its impact on bio-membranes, endocytosis and paracytosis.

    Science.gov (United States)

    He, Bing; Yuan, Lan; Dai, Wenbing; Gao, Wei; Zhang, Hua; Wang, Xueqing; Fang, Weigang; Zhang, Qiang

    2016-03-21

    Nowadays, concern about the use of nanotechnology for biomedical application is unprecedentedly increasing. In fact, nanosystems applied for various potential clinical uses always have to cross the primary biological barrier consisting of epithelial cells. However, little is really known currently in terms of the influence of the dynamic bio-adhesion of nanosystems on bio-membranes as well as on endocytosis and transcytosis. This was investigated here using polymer nanoparticles (PNs) and MDCK epithelial cells as the models. Firstly, the adhesion of PNs on cell membranes was found to be time-dependent with a shift of both location and dispersion pattern, from the lateral adhesion of mainly mono-dispersed PNs initially to the apical coverage of the PN aggregate later. Then, it was interesting to observe in this study that the dynamic bio-adhesion of PNs only affected their endocytosis but not their transcytosis. It was important to find that the endocytosis of PNs was not a constant process. A GM1 dependent CDE (caveolae dependent endocytosis) pathway was dominant in the preliminary stage, followed by the co-existence of a CME (clathrin-mediated endocytosis) pathway for the PN aggregate at a later stage, in accordance with the adhesion features of PNs, suggesting the modification of PN adhesion patterns on the endocytosis pathways. Next, the PN adhesion was noticed to affect the structure of cell junctions, via altering the extra- and intra-cellular calcium levels, leading to the enhanced paracellular transport of small molecules, but not favorably enough for the obviously increased passing of PNs themselves. Finally, FRAP and other techniques all demonstrated the obvious impact of PN adhesion on the membrane confirmation, independent of the adhesion location and time, which might lower the threshold for the internalization of PNs, even their aggregates. Generally, these findings confirm that the transport pathway mechanism of PNs through epithelial cells is rather

  13. Dynamic bio-adhesion of polymer nanoparticles on MDCK epithelial cells and its impact on bio-membranes, endocytosis and paracytosis

    Science.gov (United States)

    He, Bing; Yuan, Lan; Dai, Wenbing; Gao, Wei; Zhang, Hua; Wang, Xueqing; Fang, Weigang; Zhang, Qiang

    2016-03-01

    Nowadays, concern about the use of nanotechnology for biomedical application is unprecedentedly increasing. In fact, nanosystems applied for various potential clinical uses always have to cross the primary biological barrier consisting of epithelial cells. However, little is really known currently in terms of the influence of the dynamic bio-adhesion of nanosystems on bio-membranes as well as on endocytosis and transcytosis. This was investigated here using polymer nanoparticles (PNs) and MDCK epithelial cells as the models. Firstly, the adhesion of PNs on cell membranes was found to be time-dependent with a shift of both location and dispersion pattern, from the lateral adhesion of mainly mono-dispersed PNs initially to the apical coverage of the PN aggregate later. Then, it was interesting to observe in this study that the dynamic bio-adhesion of PNs only affected their endocytosis but not their transcytosis. It was important to find that the endocytosis of PNs was not a constant process. A GM1 dependent CDE (caveolae dependent endocytosis) pathway was dominant in the preliminary stage, followed by the co-existence of a CME (clathrin-mediated endocytosis) pathway for the PN aggregate at a later stage, in accordance with the adhesion features of PNs, suggesting the modification of PN adhesion patterns on the endocytosis pathways. Next, the PN adhesion was noticed to affect the structure of cell junctions, via altering the extra- and intra-cellular calcium levels, leading to the enhanced paracellular transport of small molecules, but not favorably enough for the obviously increased passing of PNs themselves. Finally, FRAP and other techniques all demonstrated the obvious impact of PN adhesion on the membrane confirmation, independent of the adhesion location and time, which might lower the threshold for the internalization of PNs, even their aggregates. Generally, these findings confirm that the transport pathway mechanism of PNs through epithelial cells is rather

  14. EFFECT OF HYDRAULIC AND GEOMETRICAL PROPERTIES ON STEPPED CASCADE AERATION SYSTEM

    Directory of Open Access Journals (Sweden)

    VEDHACHALAM RATHINAKUMAR

    2017-03-01

    Full Text Available Stepped cascade aeration system is commonly used to aerate the water and wastewater to increase the dissolved oxygen during pre and post treatment process. In the present research, experiments were conducted to evaluate the performance of a rectangular Cascade Aeration System with varying flow rates, risers and tread by maintaining constant width of the channel using water collected from reverse osmosis plant. The experiments were carried out with four different risers such as 0.15 m, 0.18 m, 0.225 m and 0.30 m. Each rise was investigated with five different tread of 0.60 m, 0.55 m, 0.50 m, 0.45 m and 0.40 m. Comprehensive experimental investigations were carried out for different hydraulic loading rates of 0.005 to 0.035 m3/s/m2. Results obtained from the experiments reveals that increasing dimensionless discharges promotes more aeration, attains a maximum up to dimensionless discharge= 2.22 and beyond this there was a significant decrease in aeration. In addition, the increased in number of steps significantly enhances air entertainment and surface fall rate in the Stepped Cascade Aeration System. A regression equation was derived by keeping aeration efficiency as response with dimensionless discharge and oxygen saturation concentration as influencing parameters. The dimension less discharge is a function of critical depth of the rectangular channel and step height, whereas oxygen saturation concentration represents the ratio of oxygen deficit and oxygen saturation concentration. Based on the experimental results, the optimum design and/or results such as number of steps (12 numbers and hydraulic loading rate (0.025 m3/s/m2 with fixed tread width of 0.6 m were identified to achieve maximum aeration rate (0.5-0.60 in Aeration system.

  15. Molecular dynamics simulations of membrane deformation induced by amphiphilic helices of Epsin, Sar1p, and Arf1

    Science.gov (United States)

    Li, Zhen-Lu

    2018-03-01

    The N-terminal amphiphilic helices of proteins Epsin, Sar1p, and Arf1 play a critical role in initiating membrane deformation. The interactions of these amphiphilic helices with the lipid membranes are investigated in this study by combining the all-atom and coarse-grained simulations. In the all-atom simulations, the amphiphilic helices of Epsin and Sar1p are found to have a shallower insertion depth into the membrane than the amphiphilic helix of Arf1, but remarkably, the amphiphilic helices of Epsin and Sar1p induce higher asymmetry in the lipid packing between the two monolayers of the membrane. The insertion depth of amphiphilic helix into the membrane is determined not only by the overall hydrophobicity but also by the specific distributions of polar and non-polar residues along the helix. To directly compare their ability to deform the membrane, the coarse-grained simulations are performed to investigate the membrane deformation under the insertion of multiple helices. Project supported by the National Natural Science Foundation of China (Grant Nos. 91427302 and 11474155).

  16. Passive aeration composting of chicken litter: effects of aeration pipe orientation and perforation size on losses of compost elements.

    Science.gov (United States)

    Ogunwande, Gbolabo A; Osunade, James A

    2011-01-01

    A passive aeration composting study was undertaken to investigate the effects of aeration pipe orientation (PO) and perforation size (PS) on some physico-chemical properties of chicken litter (chicken manure + sawdust) during composting. The experimental set up was a two-factor completely randomised block design with two pipe orientations: horizontal (Ho) and vertical (Ve), and three perforation sizes: 15, 25 and 35 mm diameter. The properties monitored during composting were pile temperature, moisture content (MC), pH, electrical conductivity (EC), total carbon (C(T)), total nitrogen (N(T)) and total phosphorus (P(T)). Moisture level in the piles was periodically replenished to 60% for efficient microbial activities. The results of the study showed that optimum composting conditions (thermophilic temperatures and sanitation requirements) were attained in all the piles. During composting, both PO and PS significantly affected pile temperature, moisture level, pH, C(T) loss and P(T) gain. EC was only affected by PO while N(T) was affected by PS. Neither PO nor PS had a significant effect on the C:N ratio. A vertical pipe was effective for uniform air distribution, hence, uniform composting rate within the composting pile. The final values showed that PO of Ve and PS of 35 mm diameter resulted in the least loss in N(T). The PO of Ho was as effective as Ve in the conservation of C(T) and P(T). Similarly, the three PSs were equally effective in the conservation of C(T) and P(T). In conclusion, the combined effects of PO and PS showed that treatments Ve35 and Ve15 were the most effective in minimizing N(T) loss. Copyright © 2010 Elsevier Ltd. All rights reserved.

  17. Treatment Wetland Aeration without Electricity? Lessons Learned from the First Experiment Using a Wind-Driven Air Pump

    Directory of Open Access Journals (Sweden)

    Johannes Boog

    2016-11-01

    Full Text Available Aerated treatment wetlands have become an increasingly recognized technology for treating wastewaters from domestic and various industrial origins. To date, treatment wetland aeration is provided by air pumps which require access to the energy grid. The requirement for electricity increases the ecological footprint of an aerated wetland and limits the application of this technology to areas with centralized electrical infrastructure. Wind power offers another possibility as a driver for wetland aeration, but its use for this purpose has not yet been investigated. This paper reports the first experimental trial using a simple wind-driven air pump to replace the conventional electric air blowers of an aerated horizontal subsurface flow wetland. The wind-driven air pump was connected to a two-year old horizontal flow aerated wetland which had been in continuous (24 h aeration since startup. The wind-driven aeration system functioned, however it was not specifically adapted to wetland aeration. As a result, treatment performance decreased compared to prior continuous aeration. Inconsistent wind speed at the site may have resulted in insufficient pressure within the aeration manifold, resulting in insufficient air supply to the wetland. This paper discusses the lessons learned during the experiment.

  18. [Measurement and analysis of micropore aeration system's oxygenating ability under operation condition in waste water treatment plant].

    Science.gov (United States)

    Wu, Yuan-Yuan; Zhou, Xiao-Hong; Shi, Han-Chang; Qiu, Yong

    2013-01-01

    Using the aeration pool in the fourth-stage at Wuxi Lucun Waste Water Treatment Plant (WWTP) as experimental setup, off-gas method was selected to measure the oxygenating ability parameters of micropore aerators in a real WWTP operating condition and these values were compared with those in fresh water to evaluate the performance of the micropore aerators. Results showed that the micropore aerators which were distributed in different galleries of the aeration pool had significantly different oxygenating abilities under operation condition. The oxygenating ability of the micropore aerators distributed in the same gallery changed slightly during one day. Comparing with the oxygenating ability in fresh water, it decreased a lot in the real aeration pool, in more details, under the real WWTP operating condition, the values of oxygen transfer coefficient K(La) oxygenation capacity OC and oxygen utilization E(a) decreased by 43%, 57% and 76%, respectively.

  19. Structure and dynamics of alpha-tocopherol in model membranes and in solution: a broad-line and high-resolution NMR study

    International Nuclear Information System (INIS)

    Ekiel, I.H.; Hughes, L.; Burton, G.W.; Jovall, P.A.; Ingold, K.U.; Smith, I.C.

    1988-01-01

    Nuclear magnetic resonance has been applied to study the conformational dynamics of alpha-tocopherol (vitamin E) in solution and in model membranes. In nonviscous solution, 1 H nuclear magnetic resonance (NMR) showed that alpha-tocopherol is in rapid equilibrium between two or more puckered conformers of its heterocyclic ring. The most likely conformers to be so involved are the two half-chair forms. Deuterium NMR spectra of specifically deuteriated alpha-tocopherol in multilamellar dispersions of egg phosphatidylcholine, measured in the liquid-crystalline state, were characteristic of axially symmetric motional averaging. The orientation of the rotational axis within the molecular framework was determined. Studies on oriented multilamellar membranes revealed that this axis is perpendicular to the surface of the membrane. The profile of quadrupolar splittings along the hydrophobic tail does not have a plateau, in contrast to that of the fatty acyl chains of the membrane lipids. Longitudinal relaxation times (T1) were short. The presence of a minimum in their temperature dependence shows that molecular motion with an effective correlation time tau eff approximately equal to 3 X 10(-9)s is responsible for relaxation. However, the temperatures and absolute values of the minima depend on the position of the deuterium in the molecule, demonstrating that tau eff represents a complex blend of motions

  20. Membrane microdomains and the cytoskeleton constrain AtHIR1 dynamics and facilitate the formation of an AtHIR1-associated immune complex.

    Science.gov (United States)

    Lv, Xueqin; Jing, Yanping; Xiao, Jianwei; Zhang, Yongdeng; Zhu, Yingfang; Julian, Russell; Lin, Jinxing

    2017-04-01

    Arabidopsis hypersensitive-induced reaction (AtHIR) proteins function in plant innate immunity. However, the underlying mechanisms by which AtHIRs participate in plant immunity remain elusive. Here, using VA-TIRFM and FLIM-FRET, we revealed that AtHIR1 is present in membrane microdomains and co-localizes with the membrane microdomain marker REM1.3. Single-particle tracking analysis revealed that membrane microdomains and the cytoskeleton, especially microtubules, restrict the lateral mobility of AtHIR1 at the plasma membrane and facilitate its oligomerization. Furthermore, protein proximity index measurements, fluorescence cross-correlation spectroscopy, and biochemical experiments demonstrated that the formation of the AtHIR1 complex upon pathogen perception requires intact microdomains and cytoskeleton. Taken together, these findings suggest that microdomains and the cytoskeleton constrain AtHIR1 dynamics, promote AtHIR1 oligomerization, and increase the efficiency of the interactions of AtHIR1 with components of the AtHIR1 complex in response to pathogens, thus providing valuable insight into the mechanisms of defense-related responses in plants. © 2017 The Authors The Plant Journal © 2017 John Wiley & Sons Ltd.

  1. Sorption and permeation of gaseous molecules in amorphous and crystalline PPX C membranes: molecular dynamics and grand canonical Monte Carlo simulation studies

    International Nuclear Information System (INIS)

    Bian Liang; Shu Yuan-Jie; Wang Xin-Feng

    2012-01-01

    Amorphous and crystalline poly (chloro-p-xylylene) (PPX C) membranes are constructed by using a novel computational technique, that is, a combined method of NVT+NPT-molecular dynamics (MD) and gradually reducing the size (GRS) methods. The related free volumes are defined as homology clusters. Then the sorption and the permeation of gases in PPX C polymers are studied using grand canonical Monte Carlo (GCMC) and NVT-MD methods. The results show that the crystalline PPX C membranes provide smaller free volumes for absorbing or transferring gases relative to the amorphous PPX C area. The gas sorption in PPX C membranes mainly belongs to the physical one, and H bonds can appear obviously in the amorphous area. By cluster analyzing on the mean square displacement of gases, we find that gases walk along the x axis in the crystalline area and walk randomly in the amorphous area. The calculated permeability coefficients are close to the experimental data. (electromagnetism, optics, acoustics, heat transfer, classical mechanics, and fluid dynamics)

  2. Numerical simulation of physicochemical interactions between oxygen atom and phosphatidylcholine due to direct irradiation of atmospheric pressure nonequilibrium plasma to biological membrane with quantum mechanical molecular dynamics

    Science.gov (United States)

    Uchida, Satoshi; Yoshida, Taketo; Tochikubo, Fumiyoshi

    2017-10-01

    Plasma medicine is one of the most attractive applications using atmospheric pressure nonequilibrium plasma. With respect to direct contact of the discharge plasma with a biological membrane, reactive oxygen species play an important role in induction of medical effects. However, complicated interactions between the plasma radicals and membrane have not been understood well. In the present work, we simulated elemental processes at the first stage of physicochemical interactions between oxygen atom and phosphatidylcholine using the quantum mechanical molecular dynamics code in a general software AMBER. The change in the above processes was classified according to the incident energy of oxygen atom. At an energy of 1 eV, the abstraction of a hydrogen atom and recombination to phosphatidylcholine were simultaneously occurred in chemical attachment of incident oxygen atom. The exothermal energy of the reaction was about 80% of estimated one based on the bond energies of ethane. An oxygen atom over 10 eV separated phosphatidylcholine partially. The behaviour became increasingly similar to physical sputtering. The reaction probability of oxygen atom was remarkably high in comparison with that of hydrogen peroxide. These results suggest that we can uniformly estimate various physicochemical dynamics of reactive oxygen species against membrane lipids.

  3. 1H-detected MAS solid-state NMR experiments enable the simultaneous mapping of rigid and dynamic domains of membrane proteins

    Science.gov (United States)

    Gopinath, T.; Nelson, Sarah E. D.; Veglia, Gianluigi

    2017-12-01

    Magic angle spinning (MAS) solid-state NMR (ssNMR) spectroscopy is emerging as a unique method for the atomic resolution structure determination of native membrane proteins in lipid bilayers. Although 13C-detected ssNMR experiments continue to play a major role, recent technological developments have made it possible to carry out 1H-detected experiments, boosting both sensitivity and resolution. Here, we describe a new set of 1H-detected hybrid pulse sequences that combine through-bond and through-space correlation elements into single experiments, enabling the simultaneous detection of rigid and dynamic domains of membrane proteins. As proof-of-principle, we applied these new pulse sequences to the membrane protein phospholamban (PLN) reconstituted in lipid bilayers under moderate MAS conditions. The cross-polarization (CP) based elements enabled the detection of the relatively immobile residues of PLN in the transmembrane domain using through-space correlations; whereas the most dynamic region, which is in equilibrium between folded and unfolded states, was mapped by through-bond INEPT-based elements. These new 1H-detected experiments will enable one to detect not only the most populated (ground) states of biomacromolecules, but also sparsely populated high-energy (excited) states for a complete characterization of protein free energy landscapes.

  4. Properties of the Membrane Binding Component of Catechol-O-methyltransferase Revealed by Atomistic Molecular Dynamics Simulations

    DEFF Research Database (Denmark)

    Orlowski, A.; St-Pierre, J. F.; Magarkar, A.

    2011-01-01

    We used atomistic simulations to study the membrane-bound form of catechol-O-methyltransferase (MB-COMT). In particular we investigated the 26-residue transmembrane a-helical segment of MB-COMT together with the 24-residue fragment that links the transmembrane component to the main protein unit...... that was not included in our model. In numerous independent simulations we observed the formation of a salt bridge between ARC 27 and GLU40. The salt bridge closed the flexible loop that formed in the linker and kept it in the vicinity of the membrane-water interface. All simulations supported this conclusion...... that the linker has a clear affinity for the interface and preferentially arranges its residues to reside next to the membrane, without a tendency to relocate into the water phase. Furthermore, an extensive analysis of databases for sequences of membrane proteins that have a single transmembrane helical segment...

  5. Mechanisms of recognition and binding of α-TTP to the plasma membrane by multi-scale molecular dynamics simulations

    Directory of Open Access Journals (Sweden)

    Christos eLamprakis

    2015-07-01

    Full Text Available We used multiple sets of simulations both at the atomistic and coarse-grained level of resolution, to investigate interaction and binding of α-tochoperol transfer protein (α-TTP to phosphatidylinositol phosphate lipids (PIPs. Our calculations indicate that enrichment of membranes with such lipids facilitate membrane anchoring. Atomistic models suggest that PIP can be incorporated into the binding cavity of α-TTP and therefore confirm that such protein can work as lipid exchanger between the endosome and the plasma membrane. Comparison of the atomistic models of the α-TTP / PIPs complex with membrane-bound α-TTP revealed different roles for the various basic residues composing the basic patch that is key for the protein / ligand interaction. Such residues are of critical importance as several point mutations at their position lead to severe forms of ataxia with vitamin E deficiency (AVED phenotypes. Specifically, R221 is main residue responsible for the stabilisation of the complex. R68 and R192 exchange strong interactions in the protein or in the membrane complex only, suggesting that the two residues alternate contact formation, thus facilitating lipid flipping from the membrane into the protein cavity during the lipid exchange process. Finally, R59 shows weaker interactions with PIPs anyway with a clear preference for specific phosphorylation positions, hinting a role in early membrane selectivity for the protein. Altogether, our simulations reveal significant aspects at the atomistic scale of interactions of α-TTP with the plasma membrane and with PIP, providing clarifications on the mechanism of intracellular vitamin E trafficking and helping establishing the role of key residue for the functionality of α-TTP.

  6. Water droplet dynamic behavior during removal from a proton exchange membrane fuel cell gas diffusion layer by Lattice-Boltzmann method

    Energy Technology Data Exchange (ETDEWEB)

    Molaeimanesh, Golamreza; Akbari, Mohammad Hadi [Shiraz University, Shiraz (Iran, Islamic Republic of)

    2014-04-15

    A major challenge in the application of proton exchange membrane fuel cells (PEMFCs) is water management, with the flooding of electrodes as the main issue. The Lattice-Boltzmann method (LBM) is a relatively new technique that is superior in modeling the dynamic interface of multiphase fluid flow in complex microstructures such as non-homogeneous and anisotropic porous media of PEMFC electrodes. In this study, the dynamic behavior of a water droplet during removal from gas diffusion layer (GDL) of a PEMFC electrode with interdigitated flow field is simulated using LBM. The effects of GDL wettability and its spanwise and transverse gradients on the removal process are investigated. The results demonstrate great influence of wettability and its spanwise and transverse gradients on the dynamic behavior of droplets during the removal process. Although increasing the hydrophobicity of GDL results in better droplet removal, its increase beyond a critical value does not show a significant effect.

  7. Characterization and Modeling of Fundamental Parameters of a Membrane-Aerated Biological Reactor

    Data.gov (United States)

    National Aeronautics and Space Administration — Inherent in the expansion of human presence in space is the development of life support systems that are capable of meeting the demands of extended space habitation....

  8. Mixing characterisation of full-scale membrane bioreactors: CFD modelling with experimental validation.

    Science.gov (United States)

    Brannock, M; Wang, Y; Leslie, G

    2010-05-01

    Membrane Bioreactors (MBRs) have been successfully used in aerobic biological wastewater treatment to solve the perennial problem of effective solids-liquid separation. The optimisation of MBRs requires knowledge of the membrane fouling, biokinetics and mixing. However, research has mainly concentrated on the fouling and biokinetics (Ng and Kim, 2007). Current methods of design for a desired flow regime within MBRs are largely based on assumptions (e.g. complete mixing of tanks) and empirical techniques (e.g. specific mixing energy). However, it is difficult to predict how sludge rheology and vessel design in full-scale installations affects hydrodynamics, hence overall performance. Computational Fluid Dynamics (CFD) provides a method for prediction of how vessel features and mixing energy usage affect the hydrodynamics. In this study, a CFD model was developed which accounts for aeration, sludge rheology and geometry (i.e. bioreactor and membrane module). This MBR CFD model was then applied to two full-scale MBRs and was successfully validated against experimental results. The effect of sludge settling and rheology was found to have a minimal impact on the bulk mixing (i.e. the residence time distribution).

  9. How effective is aeration with vortex flow regulators? Pilot scale experiments

    Science.gov (United States)

    Wójtowicz, Patryk; Szlachta, Małgorzata

    2017-11-01

    Vortex flow regulators (VFR) are used in urban drainage systems as a replacement for traditional flow throttling devices. Vortex regulators are not only very efficient energy dissipators but also atomizers which are beneficial for sewer aeration. A deficit of dissolved oxygen can be a problem in both natural waters and sewerage. Hydrodynamic flow regulators can boost oxygen concentration preventing putrefaction and improving treatment of stormwater and wastewater. We were first to investigate the aeration efficiency of semi-commercial scale cylindrical vortex flow regulators to determine the potential of their application in environmental engineering and to propose modification to enhance the aeration capacity of basic designs. Different device geometries and arrangements of active outlets for both single and double discharge vortex regulators were tested in a recirculating system. In this study, we present a concise review of the current state of our extensive research on the aeration efficiency of vortex flow regulators and their application in sewerage systems.

  10. Nonlinear Modeling of Autoclaved Aerated Concrete Masonry Wall Strengthened using Ferrocement Sandwich Structure

    KAUST Repository

    M., Abdel-Mooty; M., El-Kashef; E., Fahmy; M., Abou-Zeid; M., Haroun

    2011-01-01

    Autoclaved Aerated Concrete (AAC) block are used mainly as non-load-bearing walls that provide heat insulation. This results in considerable saving in cooling energy particularly in hot desert environment with large variation of daily and seasonal

  11. Research About the Corosive Effects of FeCl3 in the Aeration Wastewater Basin

    Science.gov (United States)

    Panaitescu, C.; Petrescu, M. G.

    2018-01-01

    Biological aeration of industrial wastewater is a very impressive process in the treatment of wastewater. The involvement of chemical reagents in this process, however, implies the intensification of the corrosion processes due to both pollutants in the wastewater and the chemical reactions that occur when the coagulation / flocculation reagents are added. This paper explores the action of ferric chloride (FeCl3) on metallic parts in the aeration basin. The most affected structures are metal. At the classical basins the aeration systems were made of P295GH materials. The corrosion produced is uneven. The analysis of the high degree of corrosion was done according to the national and international standards. Finally, the paper supports the replacement of the existing aeration system with an anticorrosive material.

  12. Study on water infiltration in loess aerated zone at CIRP's field test site

    International Nuclear Information System (INIS)

    Du Zhongde; Zhao Yingjie; Ni Dongqi; Ma Binghui; Xu Zhaoyi; Tadao Tanaka; Masayuki Mukai

    2000-01-01

    Vertical joints and large pores existing uniquely in loess cause difference between loess and other homogenous soil media in water infiltration. Field test of water infiltration in loess aerated zone of and analysis with hydraulic theory of soil concludes that for the loess aerated zone of vertical joints existing in it makes little contribution to water infiltration under unsaturated condition, and large pores in the media would significantly retard water infiltration

  13. Low frequency aeration of pig slurry affects slurry characteristics and emissions of greenhouse gases and ammonia.

    Science.gov (United States)

    Calvet, Salvador; Hunt, John; Misselbrook, Tom H

    2017-07-01

    Low frequency aeration of slurries may reduce ammonia (NH 3 ) and methane (CH 4 ) emissions without increasing nitrous oxide (N 2 O) emissions. The aim of this study was to quantify this potential reduction and to establish the underlying mechanisms. A batch experiment was designed with 6 tanks with 1 m 3 of pig slurry each. After an initial phase of 7 days when none of the tanks were aerated, a second phase of 4 weeks subjected three of the tanks to aeration (2 min every 6 h, airflow 10 m 3  h -1 ), whereas the other three tanks remained as a control. A final phase of 9 days was established with no aeration in any tank. Emissions of NH 3 , CH 4 , carbon dioxide (CO 2 ) and N 2 O were measured. In the initial phase no differences in emissions were detected, but during the second phase aeration increased NH 3 emissions by 20% with respect to the controls (8.48 vs. 7.07 g m -3  [slurry] d -1 , P emissions were 40% lower in the aerated tanks (2.04 vs. 3.39 g m -3  [slurry] d -1 , P emissions remained after the aeration phase had finished. No effect was detected for CO 2 , and no relevant N 2 O emissions were detected during the experiment. Our results demonstrate that low frequency aeration of stored pig slurry increases slurry pH and increases NH 3 emissions.

  14. Integration of sand and membrane filtration systems for iron and pesticide removal without chemical addition

    DEFF Research Database (Denmark)

    Kowalski, Krysztof; Madsen, Henrik Tækker; Søgaard, Erik Gydesen

    2013-01-01

    the content of key foulants, the techniques can be used as a pre-treatment for nanofiltration and low pressure reverse osmosis that has proved to be capable of removing pesticides. It was found that a lower fouling potential could be obtained by using the membranes, but that sand filter was better at removing......Pilot plant investigations of sand and membrane filtration (MF/UF/NF/LPRO) have been performed to treat groundwater polluted with pesticides. The results show that simple treatment, with use of aeration and sand filtration or MF/UF membranes, does not remove pesticides. However, by reducing...... manganese and dissolved organic matter. The results indicate that combining aeration; sand filtration and membrane techniques might be a good option for pesticide removal without any addition of chemicals and minimized membrane maintenance....

  15. Quasi-three dimensional dynamic modeling of a proton exchange membrane fuel cell with consideration of two-phase water transport through a gas diffusion layer

    International Nuclear Information System (INIS)

    Kang, Sanggyu

    2015-01-01

    Water management is one of the challenging issues for low-temperature PEMFCs (proton exchange membrane fuel cells). When liquid water is formed at the GDL (gas diffusion layer), the pathway of reactant gas can be blocked, which inhibits the electrochemical reaction of PEMFC. Thus, liquid water transport through GDL is a critical factor determining the performance of a PEMFC. In present study, quasi-three dimensional dynamic modeling of PEMFC with consideration of two-phase water transport through GDL is developed. To investigate the distributions of PEMFC characteristics, including current density, species mole fraction, and membrane hydration, the PEMFC was discretized into twenty control volumes along the anode channel. To resolve the mass and energy conservation, the PEMFC is discretized into eleven and fifteen control volumes in the perpendicular direction, respectively. The dynamic variation of PEMFC characteristics of cell voltage, overvoltage of activation and ohmic, liquid water saturation through a GDL, and oxygen concentration were captured during transient behavior. - Highlights: • A quasi-three dimensional two-phase dynamic model of PEMFC is developed. • Presented model is validated by comparison with experimental data. • Two-phase model is compared with one-phase model at steady-states and transients.

  16. Intramolecular dynamics within the N-Cap-SH3-SH2 regulatory unit of the c-Abl tyrosine kinase reveal targeting to the cellular membrane.

    Science.gov (United States)

    de Oliveira, Guilherme A P; Pereira, Elen G; Ferretti, Giulia D S; Valente, Ana Paula; Cordeiro, Yraima; Silva, Jerson L

    2013-09-27

    c-Abl is a key regulator of cell signaling and is under strict control via intramolecular interactions. In this study, we address changes in the intramolecular dynamics coupling within the c-Abl regulatory unit by presenting its N-terminal segment (N-Cap) with an alternative function in the cell as c-Abl becomes activated. Using small angle x-ray scattering, nuclear magnetic resonance, and confocal microscopy, we demonstrate that the N-Cap and the Src homology (SH) 3 domain acquire μs-ms motions upon N-Cap association with the SH2-L domain, revealing a stabilizing synergy between these segments. The N-Cap-myristoyl tether likely triggers the protein to anchor to the membrane because of these flip-flop dynamics, which occur in the μs-ms time range. This segment not only presents the myristate during c-Abl inhibition but may also trigger protein localization inside the cell in a functional and stability-dependent mechanism that is lost in Bcr-Abl(+) cells, which underlie chronic myeloid leukemia. This loss of intramolecular dynamics and binding to the cellular membrane is a potential therapeutic target.

  17. Radioactivity in houses built of aerated concrete based on alum shale

    International Nuclear Information System (INIS)

    Swedjemark, G.A.

    1980-01-01

    The highest activities in commonly used Swedish building materials are found in aerated concrete based on alum shale. The enhanced activity level is due to the high content of radium-226. The average activity concentration of radium-226 varies between different producers of aerated concrete based on alum shale from 700 Bq kg - (20 pCi g - ) to 2 400 Bq kg - (65 pCi g - ). Houses built in the same way with the same amounts of aerated concrete can therefore have very different gamma levels and very different concentrations of radon in the air with the same air exchange rate. Aerated concrete based on alum shale was used as a building material in Sweden from 1930 to 1975. The average concentration of radon daughters found in houses built of aerated concrete based to a major extent on alum shale is about 100 bq/m 3 (2.7 pCi 1 - ). The highest radon concentrations have been found in houses built entirely of aerated concrete based on alum shale. A group of 9 houses with natural draught ventilation systems has been investigated with regard to the concentration of radon, the equilibrium equivalent concentration of radon (EEC) and the gamma dose rate. The air exchange rates varied between the houses from 0.21 to 0.43 h - and the radon concentration from 540 Bq m - (15 pCi 1 - ) to 1 160 Bq m - (31 pCi 1 - ). The values given are averages for each house. (author)

  18. Iodine-infused aeration for hull fouling prevention: a vessel-scale study.

    Science.gov (United States)

    Dickenson, Natasha C; Krumholz, Jason S; Hunsucker, Kelli Z; Radicone, Michael

    2017-11-01

    Biofouling is a significant economic and ecological problem, causing reduced vessel performance and increases in fuel consumption and emissions. Previous research has shown iodine vapor (I 2 )-infused aeration to be an environmentally friendly method for deterring the settlement of fouling organisms. An aeration system was deployed on a vessel with hull sections coated with two types of antifoulant coatings, Intersleek ® 1100 (fouling-release) and Interspeed ® BRA-640 (ablative copper biocide), as well as an inert epoxy barrier coating, to assess the effectiveness of aeration in conjunction with common marine coatings. I 2 -infused aeration resulted in consistent reductions of 80-90% in hard fouling across all three coatings. Additionally, aeration reduced the soft fouling rate by 45-70% when used in conjunction with both Intersleek ® and Interspeed ® BRA versus those coatings alone. The results of this study highlight the contribution of I 2 -infused aeration as a standalone mechanism for fouling prevention or as a complement to traditional antifouling coatings.

  19. Start-Up and Aeration Strategies for a Completely Autotrophic Nitrogen Removal Process in an SBR

    Directory of Open Access Journals (Sweden)

    Xiaoling Zhang

    2017-01-01

    Full Text Available The start-up and performance of the completely autotrophic nitrogen removal via nitrite (CANON process were examined in a sequencing batch reactor (SBR with intermittent aeration. Initially, partial nitrification was established, and then the DO concentration was lowered further, surplus water in the SBR with high nitrite was replaced with tap water, and continuous aeration mode was turned into intermittent aeration mode, while the removal of total nitrogen was still weak. However, the total nitrogen (TN removal efficiency and nitrogen removal loading reached 83.07% and 0.422 kgN/(m3·d, respectively, 14 days after inoculating 0.15 g of CANON biofilm biomass into the SBR. The aggregates formed in SBR were the mixture of activated sludge and granular sludge; the volume ratio of floc and granular sludge was 7 : 3. DNA analysis showed that Planctomycetes-like anammox bacteria and Nitrosomonas-like aerobic ammonium oxidization bacteria were dominant bacteria in the reactor. The influence of aeration strategies on CANON process was investigated using batch tests. The result showed that the strategy of alternating aeration (1 h and nonaeration (1 h was optimum, which can obtain almost the same TN removal efficiency as continuous aeration while reducing the energy consumption, inhibiting the activity of NOB, and enhancing the activity of AAOB.

  20. The aeration period of a model nuclear waste repository

    International Nuclear Information System (INIS)

    Sharland, S.M.; Tasker, P.W.

    1987-02-01

    We have constructed a model of the evolution of oxygen in a cement backfill which includes both its depletion through the canister corrosion reactions and its migration in the cement pores. The results indicate that the duration in which mild steel waste canisters may be subject to localised corrosion is very much shorter than the intended lifetime of the repository components, provided there is no external source of oxygen. For canisters spaced 1.2m apart, the model predicts a maximum aeration period of approximately 65 years, assuming high oxygen content and diffusivity in the backfill and low leakage current on the canisters (0.01 μA cm -2 ). In such a case a reducing environment is established throughout the backfill within this period. Under conditions of more restricted oxygen transport, reducing conditions are still established within a relatively short time in the immediate vicinity of the canisters, but the oxidation potential elsewhere in the backfill is then controlled by the uniform corrosion rate of the canisters. (author)

  1. Decentralized wastewater treatment using passively aerated biological filter.

    Science.gov (United States)

    Abou-Elela, Sohair I; Hellal, Mohamed S; Aly, Olfat H; Abo-Elenin, Salah A

    2017-10-13

    This study aimed to evaluate the efficiency of a novel pilot-scale passively aerated biological filter (PABF) as a low energy consumption system for the treatment of municipal wastewater. It consists of four similar compartments, each containing 40% of a non-woven polyester fabric as a bio-bed. The PABF was fed with primary treated wastewater under a hydraulic retention time (HRT) of 3.5 hr and a hydraulic loading rate of 5.5 m 2 /m 3 /d. The effect of media depth, HRT, dissolved oxygen (DO) and surface area of the media on the removal efficiency of pollutants was investigated. Results indicated that increasing media depth along the axis of the reactor and consequently increasing the HRT and DO resulted in great removal of different pollutants. A significant increase in the DO levels in the final effluent up to 6.7 mg/l resulted in good nitrification processes. Statistical analysis using SPSS showed that the reactor performance has significant removal efficiency (p filter systems.

  2. Comparative test on nuclide migration in aerated zone

    International Nuclear Information System (INIS)

    Li Shushen; Zhao Yingjie; Wu Qinghua; Wang Zhiming; Hao Janzhong; Ji Shaowei; Guo Liangtian; Guo Zhiming

    2002-01-01

    In order to study the influence of different tracer source layer material on nuclide migration behavior, the comparative test on stable elements Sr, Nd and Ce migration in aerated loess zone was carried out using loess and arenaceous quartz as the tracer source layer materials respectively. The test lasted 470 days. During the test, four times of sampling were done. The testing results indicate that under artificial sprinkling of 5 mm/h and 3 h/d, Nd and Ce not only in loess tracer source layer but also in arenaceous quartz tracer source layer did not obviously downwards migrated. Concentration peak of Sr for loess layer migrated down about 15 cm in 470 d (mass center moved down about 10 cm) but for arenaceous quartz layer the concentration peak of Sr did not obviously migrated down (mass center moved down about 2.7 cm). The test results show that very thin arenaceous quartz layer with thickness of 7 mm is also able to shield unsaturated water flow obviously. This is the main reason why the nuclides in arenaceous quartz layer migrate down slowly

  3. Mechanisms and methods for biofouling prevention via aeration

    Science.gov (United States)

    Dickenson, Natasha; Henoch, Charles; Belden, Jesse

    2013-11-01

    Biofouling is a major problem for the Navy and marine industries, with significant economic and ecological consequences. Specifically, biofouling on immersed hull surfaces generates increased drag and thus requires increased fuel consumption to maintain speed. Considerable effort has been spent developing techniques to prevent and control biofouling, but with limited success. Control methods that have proven to be effective are costly, time consuming, or negatively affect the environment. Recently, aeration via bubble injection along submerged surfaces has been shown to achieve long-lasting antifouling effects, and is the only effective non-toxic method available. An understanding of the basic mechanisms by which bubble-induced flow impedes biofouling is lacking, but is essential for the design of large-scale systems. We present results from an experimental investigation of several bubble induced flow fields over an inclined plate with simultaneous measurements of the fluid velocity and bubble characteristics using Digital article Image Velocimetry and high speed digital video. Trajectories of representative larval organisms are also resolved and linked with the flow field measurements to determine the mechanisms responsible for biofouling prevention.

  4. DECREASE OF SOLIDS IN GRAY WATER BY AERATION PROCESS

    Directory of Open Access Journals (Sweden)

    Gerardo Alonso Torres-Avalos

    2017-07-01

    Full Text Available The activated sludge process is a biological treatment consisting basically of agitation and aeration of a waste water mixture and a selected microorganisms sludge. The oxidation of organic matter was determined with several tests such as BOD5 (Biochemical Oxygen Demand, TSS (Total Sedimented Solids, SS (Sediment Solids, TDS (Total Dissolved Solids, FVS (fixed and volatile solids and finally a measurement of treated water turbidity. The results obtained for the reduction of the organic load during the first two days of treatment (samples 1, 2 and 3 are visible in each of the organic loading tests; during the last two days according to the samples 4 and 5 the solids showed an increase in organic load. The related organoleptic properties such as color showed a notable decrease. As for the tests performed at pH show a change, samples 1, 2 and 3 approaching a range where they are neutral and the last two samples (4 and 5 the pH has an elevation until it becomes alkaline. The efficiency of the method used for the treatment of residual water during the first days reduced the organic load with a variation of TS and TSS of 760, 569 ppm respectively. This is a viable alternative since this is a low cost method with short term results because organoleptic properties such as odor and color were lost during the first day of treatment.

  5. Evaluation of sequential aerated treatment of wastewater from hardboard mill

    Directory of Open Access Journals (Sweden)

    S. Videla

    1998-01-01

    Full Text Available Wastewater from a hardboard mill characterized by a high organic content (15-30 g/L COD was studied in a bench scale sequential aerated system in order to define a start up strategy. Inlet COD concentration varied from 0.5 to 25 g/L and the hydraulic retention time was maintained at 5 days. The sequential system proposed could reduce BOD, COD, TSS and phenol over 90% except when the inlet COD concentration was lower than 25 g/L.Água residual proveniente de uma indústria de tabuleiro de fibra dura caracterizada por ter um elevado conteúdo orgânico (15-30 g/L DQO foi estudada utilizando um sistema arejado seqüêncial de forma a definir uma estratégia de start up. A concentração de DQO na entrada do sistema variou na faixa de 0,5-25 g/L e o tempo de residência hidráulico foi mantido em 5 dias. O sistema seqüêncial proposto reduziu DBO, DQO, SST e fenol sobre 90% quando a concentração de DQO na entrada foi menor a 25 g/L.

  6. Hydroxyl radical induced degradation of salicylates in aerated aqueous solution

    International Nuclear Information System (INIS)

    Szabó, László; Tóth, Tünde; Homlok, Renáta; Rácz, Gergely; Takács, Erzsébet; Wojnárovits, László

    2014-01-01

    Ionizing radiation induced degradation of acetylsalicylic acid, its hydrolysis product salicylic acid and a salicylic acid derivative 5-sulpho-salicylic acid, was investigated in dilute aqueous solutions by UV–vis spectrophotometry, HPLC separation and diode-array or MS/MS detection, chemical oxygen demand, total organic carbon content and by Vibrio fischeri toxicity measurements. Hydroxyl radicals were shown to degrade these molecules readily, and first degradation products were hydroxylated derivatives in all cases. Due to the by-products, among them hydrogen peroxide, the toxicity first increased and then decreased with the absorbed dose. With prolonged irradiation complete mineralization was achieved. - Highlights: • In OH induced reactions of salicylates first products are hydroxylated derivatives. • With prolonged irradiation dihydroxy derivatives also form. • In aerated solutions the one-electron oxidant OH induces 3–4 oxidations. • Toxicity first increases and then decreases with dose mainly due to H 2 O 2 formation. • The toxicity in tap water is smaller than in pure water

  7. Use of dynamic light scattering and small-angle X-ray scattering to characterize new surfactants in solution conditions for membrane-protein crystallization

    Science.gov (United States)

    Dahani, Mohamed; Barret, Laurie-Anne; Raynal, Simon; Jungas, Colette; Pernot, Pétra; Polidori, Ange; Bonneté, Françoise

    2015-01-01

    The structural and interactive properties of two novel hemifluorinated surfactants, F2H9-β-M and F4H5-β-M, the syntheses of which were based on the structure and hydrophobicity of the well known dodecyl-β-maltoside (DD-β-M), are described. The shape of their micellar assemblies was characterized by small-angle X-ray scattering and their intermicellar inter­actions in crystallizing conditions were measured by dynamic light scattering. Such information is essential for surfactant phase-diagram determination and membrane-protein crystallization. PMID:26144228

  8. P2M2: Physical and physiological properties of membrane-aerated and membrane-supported biofilms

    DEFF Research Database (Denmark)

    Pellicer i Nàcher, Carles

    ) can enhance biofilm strength under certain conditions. Despite their crucial importance, there is currently no agreement within the scientific community on a protocol that optimizes EPS recovery from microbial samples without significantly compromising the viability of the embedded bacterial cells....... This behaviour was described with the addition of two terms (depending on system characteristics and reactor loading conditions) to existing model structures. In conclusion, we presented control strategies to engineer the microbial communities catalysing autotrophic nitrogen removal in MABRs, proposed methods...... to minimise the risk and effect of bacterial sloughing, and developed novel strategies to characterize, optimize, and better regulate oxygen transfer. Overall, the present work should serve to better design reactors supporting a cleaner, more robust, and cost-effective nitrogen removal. Furthermore, the large...

  9. An experimental study of the dynamic behavior of a 2 kW proton exchange membrane fuel cell stack under various loading conditions

    International Nuclear Information System (INIS)

    Jian, Qifei; Zhao, Yang; Wang, Haoting

    2015-01-01

    The dynamic behavior of the PEM (proton exchange membrane) fuel cell stack has great effect on the safety and effective operation of its applications. In this paper, a self-designed bulb-array is used to simulate the various loading conditions and study the dynamic behavior of a 2 kW PEM fuel cell stack. An evaluation index, including oscillation rate, pressure variation and dynamic resistance factor, is used to analyze the transient response of the PEM fuel cell stack. It is observed that the stack current increases about 8.6%, and the Oscillation rate decreases more rapidly after activation. In the step-up load stage, the oscillation rate and the dynamic resistance decrease more rapidly as the external load increases. Due to the periodic anodic purge process, a periodic voltage fluctuation can be seen. In addition, when the stack works in the open-loop state (working without the external load), the transient response of the stack current is significantly affected by the hydrogen humidity and the charge double-layer. - Highlights: • The working time of open-loop state significantly affects the transient response. • Oscillation rate decreases faster as the external load increases. • Dynamic resistance factor decreases as the external load increases. • The periodic anodic purge process leads to a slight periodic oscillation of voltage

  10. Influence of air scouring on the performance of a Self Forming Dynamic Membrane BioReactor (SFD MBR) for municipal wastewater treatment.

    Science.gov (United States)

    Salerno, Carlo; Vergine, Pompilio; Berardi, Giovanni; Pollice, Alfieri

    2017-01-01

    The Membrane BioReactor (MBR) is a well-established filtration-based technology for wastewater treatment. Despite the high quality of the effluent produced, one of the main drawbacks of the MBR is membrane fouling. In this context, a possible evolution towards systems having potentially lower installation and operating costs is the Self Forming Dynamic Membrane BioReactor (SFD MBR). Key of this technology is the self-formation of a biological filtering layer on a support of inert material. In this work, a lab-scale aerobic SFD MBR equipped with a nylon mesh was operated at approximately 95Lm -2 h -1 . Two mesh pore sizes (20 and 50μm) and three air scouring flow rates (150, 250, and 500mL air min -1 ) were tested at steady state. Under all the tested conditions, the SFD MBR effectively treated real municipal wastewater. The quality of the produced effluent increased for lower mesh size and lower air scouring intensity. Copyright © 2016 Elsevier Ltd. All rights reserved.

  11. In-situ assessment of biofilm formation in submerged membrane system using optical coherence tomography and computational fluid dynamics

    KAUST Repository

    Fortunato, Luca; Qamar, Adnan; Wang, Yiran; Jeong, Sanghyun; Leiknes, TorOve

    2016-01-01

    coherence tomography (OCT), allowing the in-situ investigation of the biofilm structure for 43 d. The OCT enabled to obtain a time-lapse of biofilm development on the membrane under the continuous operation. Acquired real-time information on the biofilm

  12. Investigation on flow pattern by submersible mechanical aerator aused in anaerobic-aerobic tank. Kenki koki ken'yo suichu aerator ni yoru sonai ryudo no chosa kensho

    Energy Technology Data Exchange (ETDEWEB)

    Ogasawara, M; Inoue, H; Kamei, T; Kato, N [Ebara Corp., Tokyo (Japan)

    1994-01-20

    As explained in the present report, flow pattern was verified in a submersible aerator tank for both anaerobic and aerobic wastewater treatment (submersible plant for the mechanical agitation and aeration). The verification was made in a water passage of the sewage treatment plant. The flowing was conditioned as per the measurement of both flow velocity and activated sludge concentration. The submersible aerator was installed so that balance might be kept in ventilating pressure between it and the diffusing plate. The flowing on the tank bottom was stabilized by installing a special guide at the outlet of aerator. The result was as follows: in both tanks during the anaerobic operation, the flow velocity was 0.15m/s as a whole and higher than the standard of 0.1m/s on the tank bottom. Under the tank top and at the middle of tank height, the flow velocity is lower than that on the tank bottom and the intake of dissolved oxygen is weak. In both tanks during the aerobic operation, the flow velocity as a whole is higher than that during the anaerobic operation. It is attributable to the airlift effect. The flow pattern during the aerobic operation is characterized by the flow which is generated, by airlift effect, under the tank top toward the wall. Then, that flow effectively works for the flowing on the tank bottom. Hardly dispersed, the pollutant concentration indicates that the flowing is sufficient in the tank. 4 refs., 6 figs., 3 tabs.

  13. Recovery of ammonia and production of high-grade phosphates from side-stream digester effluents using gas-permeable membranes

    Science.gov (United States)

    Phosphorus recovery was combined with ammonia recovery using gas-permeable membranes. In a first step, the ammonia and alkalinity were removed from municipal side-stream wastewater using low-rate aeration and a gas-permeable membrane manifold. In a second step, the phosphorus was removed using magne...

  14. The cytosolic domain of T-cell receptor ζ associates with membranes in a dynamic equilibrium and deeply penetrates the bilayer.

    Science.gov (United States)

    Zimmermann, Kerstin; Eells, Rebecca; Heinrich, Frank; Rintoul, Stefanie; Josey, Brian; Shekhar, Prabhanshu; Lösche, Mathias; Stern, Lawrence J

    2017-10-27

    Interactions between lipid bilayers and the membrane-proximal regions of membrane-associated proteins play important roles in regulating membrane protein structure and function. The T-cell antigen receptor is an assembly of eight single-pass membrane-spanning subunits on the surface of T lymphocytes that initiates cytosolic signaling cascades upon binding antigens presented by MHC-family proteins on antigen-presenting cells. Its ζ-subunit contains multiple cytosolic immunoreceptor tyrosine-based activation motifs involved in signal transduction, and this subunit by itself is sufficient to couple extracellular stimuli to intracellular signaling events. Interactions of the cytosolic domain of ζ (ζ cyt ) with acidic lipids have been implicated in the initiation and regulation of transmembrane signaling. ζ cyt is unstructured in solution. Interaction with acidic phospholipids induces structure, but its disposition when bound to lipid bilayers is controversial. Here, using surface plasmon resonance and neutron reflection, we characterized the interaction of ζ cyt with planar lipid bilayers containing mixtures of acidic and neutral lipids. We observed two binding modes of ζ cyt to the bilayers in dynamic equilibrium: one in which ζ cyt is peripherally associated with lipid headgroups and one in which it penetrates deeply into the bilayer. Such an equilibrium between the peripherally bound and embedded forms of ζ cyt apparently controls accessibility of the immunoreceptor tyrosine-based activation signal transduction pathway. Our results reconcile conflicting findings of the ζ structure reported in previous studies and provide a framework for understanding how lipid interactions regulate motifs to tyrosine kinases and may regulate the T-cell antigen receptor biological activities for this cell-surface receptor system.

  15. Ambient iron-mediated aeration (IMA) for water reuse.

    Science.gov (United States)

    Deng, Yang; Englehardt, James D; Abdul-Aziz, Samer; Bataille, Tristan; Cueto, Josenrique; De Leon, Omar; Wright, Mary E; Gardinali, Piero; Narayanan, Aarthi; Polar, Jose; Tomoyuki, Shibata

    2013-02-01

    Global water shortages caused by rapidly expanding population, escalating water consumption, and dwindling water reserves have rendered water reuse a strategically significant approach to meet current and future water demand. This study is the first to our knowledge to evaluate the technical feasibility of iron-mediated aeration (IMA), an innovative, potentially economical, holistic, oxidizing co-precipitation process operating at room temperature, atmospheric pressure, and neutral pH, for water reuse. In the IMA process, dissolved oxygen (O₂) was continuously activated by zero-valent iron (Fe⁰) to produce reactive oxygen species (ROS) at ambient pH, temperature, and pressure. Concurrently, iron sludge was generated as a result of iron corrosion. Bench-scale tests were conducted to study the performance of IMA for treatment of secondary effluent, natural surface water, and simulated contaminated water. The following removal efficiencies were achieved: 82.2% glyoxylic acid, ~100% formaldehyde as an oxidation product of glyoxylic acid, 94% of Ca²⁺ and associated alkalinity, 44% of chemical oxygen demand (COD), 26% of electrical conductivity (EC), 98% of di-n-butyl phthalate (DBP), 80% of 17β-estradiol (E2), 45% of total nitrogen (TN), 96% of total phosphorus (TP), 99.8% of total Cr, >90% of total Ni, 99% of color, 3.2 log removal of total coliform, and 2.4 log removal of E. Coli. Removal was attributed principally to chemical oxidation, precipitation, co-precipitation, coagulation, adsorption, and air stripping concurrently occurring during the IMA treatment. Results suggest that IMA is a promising treatment technology for water reuse. Copyright © 2012 Elsevier Ltd. All rights reserved.

  16. Effects of Agitation, Aeration and Temperature on Production of a Novel Glycoprotein GP-1 by Streptomyces kanasenisi ZX01 and Scale-Up Based on Volumetric Oxygen Transfer Coefficient

    Directory of Open Access Journals (Sweden)

    Yong Zhou

    2018-01-01

    Full Text Available The effects of temperature, agitation and aeration on glycoprotein GP-1 production by Streptomyces kanasenisi ZX01 in bench-scale fermentors were systematically investigated. The maximum final GP-1 production was achieved at an agitation speed of 200 rpm, aeration rate of 2.0 vvm and temperature of 30 °C. By using a dynamic gassing out method, the effects of agitation and aeration on volumetric oxygen transfer coefficient (kLa were also studied. The values of volumetric oxygen transfer coefficient in the logarithmic phase increased with increase of agitation speed (from 14.53 to 32.82 h−1 and aeration rate (from 13.21 to 22.43 h−1. In addition, a successful scale-up from bench-scale to pilot-scale was performed based on volumetric oxygen transfer coefficient, resulting in final GP-1 production of 3.92, 4.03, 3.82 and 4.20 mg/L in 5 L, 15 L, 70 L and 500 L fermentors, respectively. These results indicated that constant volumetric oxygen transfer coefficient was appropriate for the scale-up of batch fermentation of glycoprotein GP-1 by Streptomyces kanasenisi ZX01, and this scale-up strategy successfully achieved 100-fold scale-up from bench-scale to pilot-scale fermentor.

  17. Yields and Nutritional of Greenhouse Tomato in Response to Different Soil Aeration Volume at two depths of Subsurface drip irrigation

    Science.gov (United States)

    Li, Yuan; Niu, Wenquan; Dyck, Miles; Wang, Jingwei; Zou, Xiaoyang

    2016-01-01

    This study investigated the effects of 4 aeration levels (varied by injection of air to the soil through subsurface irrigation lines) at two subsurface irrigation line depths (15 and 40 cm) on plant growth, yield and nutritional quality of greenhouse tomato. In all experiments, fruit number, width and length, yield, vitamin C, lycopene and sugar/acid ratio of tomato markedly increased in response to the aeration treatments. Vitamin C, lycopene, and sugar/acid ratio increased by 41%, 2%, and 43%, respectively, in the 1.5 times standard aeration volume compared with the no-aeration treatment. An interaction between aeration level and depth of irrigation line was also observed with yield, fruit number, fruit length, vitamin C and sugar/acid ratio of greenhouse tomato increasing at each aeration level when irrigation lines were placed at 40 cm depth. However, when the irrigation lines were 15 cm deep, the trend of total fruit yields, fruit width, fruit length and sugar/acid ratio first increased and then decreased with increasing aeration level. Total soluble solids and titrable acid decreased with increasing aeration level both at 15 and 40 cm irrigation line placement. When all of the quality factors, yields and economic benefit are considered together, the combination of 40 cm line depth and “standard” aeration level was the optimum combination. PMID:27995970

  18. Impact of post-infiltration soil aeration at different growth stages of sub-surface trickle-irrigated tomato plants

    Science.gov (United States)

    Li, Yuan; Jia, Zong-xia; Niu, Wen-Quan; Wang, Jing-wei

    2016-07-01

    Sensitivity to low rhizosphere soil aeration may change over time and therefore plant response may also depend on different growth stages of a crop. This study quantified effects of soil aeration during 5 different periods, on growth and yield of trickle-irrigated potted single tomato plants. Irrigation levels were 0.6 to 0.7 (low level) or 0.7 to 0.8 (high level) of total water holding capacity of the pots. Soil was aerated by injecting 2.5 l of air into each pot through the drip tubing immediately after irrigation. Fresh fruit yield, above ground plant dry weight, plant height, and leaf area index response to these treatments were measured. For all these 4 response variables, means of post-infiltration aeration between 58 to 85 days after sowing were 13.4, 43.5, 13.7, and 37.7% higher than those for the non-aerated pots, respectively. The results indicated that: post-infiltration soil aeration can positively impact the yield and growth of sub-surface trickle-irrigated potted tomato plants; positive effects on plant growth can be obtained with aeration during the whole growth period or with aeration for partial periods; positive growth effects of partial periods of aeration appears to persist and result in yield benefit.

  19. Molecular dynamics simulations of cholesterol-rich membranes using a coarse-grained force field for cyclic alkanes

    Energy Technology Data Exchange (ETDEWEB)

    MacDermaid, Christopher M., E-mail: chris.macdermaid@temple.edu; Klein, Michael L.; Fiorin, Giacomo, E-mail: giacomo.fiorin@temple.edu [Institute for Computational Molecular Science, Temple University, 1925 North 12th Street, Philadelphia, Pennsylvania 19122-1801 (United States); Kashyap, Hemant K. [Department of Chemistry, Indian Institute of Technology Delhi, Hauz Khas, New Delhi 110016 (India); DeVane, Russell H. [Modeling and Simulation, Corporate Research and Development, The Procter and Gamble Company, West Chester, Ohio 45069 (United States); Shinoda, Wataru [Department of Applied Chemistry, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8603 (Japan); Klauda, Jeffery B. [Department of Chemical and Biomolecular Engineering, University of Maryland, College Park, Maryland 20742 (United States)

    2015-12-28

    The architecture of a biological membrane hinges upon the fundamental fact that its properties are determined by more than the sum of its individual components. Studies on model membranes have shown the need to characterize in molecular detail how properties such as thickness, fluidity, and macroscopic bending rigidity are regulated by the interactions between individual molecules in a non-trivial fashion. Simulation-based approaches are invaluable to this purpose but are typically limited to short sampling times and model systems that are often smaller than the required properties. To alleviate both limitations, the use of coarse-grained (CG) models is nowadays an established computational strategy. We here present a new CG force field for cholesterol, which was developed by using measured properties of small molecules, and can be used in combination with our previously developed force field for phospholipids. The new model performs with precision comparable to atomistic force fields in predicting the properties of cholesterol-rich phospholipid bilayers, including area per lipid, bilayer thickness, tail order parameter, increase in bending rigidity, and propensity to form liquid-ordered domains in ternary mixtures. We suggest the use of this model to quantify the impact of cholesterol on macroscopic properties and on microscopic phenomena involving localization and trafficking of lipids and proteins on cellular membranes.

  20. Corrosion behavior of electrodeposited Co-Fe alloys in aerated solutions

    Energy Technology Data Exchange (ETDEWEB)

    Chansena, A. [Research Unit on Corrosion, College of Data Storage Innovation, King Mongkut' s Institute of Technology Ladkrabang, Bangkok 10520 (Thailand); Sutthiruangwong, S., E-mail: sutha.su@kmitl.ac.th [Department of Chemistry, Faculty of Science, King Mongkut' s Institute of Technology Ladkrabang, Bangkok 10520 (Thailand); Research Unit on Corrosion, College of Data Storage Innovation, King Mongkut' s Institute of Technology Ladkrabang, Bangkok 10520 (Thailand)

    2017-05-01

    Co-Fe alloy is an important component for reader-writer in hard disk drive. The surface of the alloy is exposed to the environment both in gas phase and in liquid phase during manufacturing process. The study of corrosion behavior of Co-Fe alloys can provide useful fundamental data for reader-writer production planning especially when corrosion becomes a major problem. The corrosion study of electrodeposited Co-Fe alloys from cyclic galvanodynamic polarization was performed using potentiodynamic polarization technique. The composition of electrodeposited Co-Fe alloys was determined by X-ray fluorescence spectrometry. The patterns from X-ray diffractometer showed that the crystal structure of electrodeposited Co-Fe alloys was body-centered cubic. A vibrating sample magnetometer was used for magnetic measurements. The saturation magnetization (M{sub s}) was increased and the intrinsic coercivity (H{sub ci}) was decreased with increasing Fe content. The corrosion rate study was performed in aerated deionized water and aerated acidic solutions at pH 3, 4 and 5. The corrosion rate diagram for Co-Fe alloys was constructed. It was found that the corrosion rate of Co-Fe alloys was increased with increasing Fe content in both aerated deionized water and aerated acidic solutions. In aerated pH 3 solution, the Co-Fe alloy containing 78.8% Fe showed the highest corrosion rate of 7.7 mm yr{sup −1} with the highest M{sub s} of 32.0 A m{sup 2} kg{sup −1}. The corrosion rate of the alloy with 23.8% Fe was at 1.1 mm yr{sup −1} with M{sub s} of 1.2 A m{sup 2} kg{sup −1}. In aerated deionized water, the alloy with the highest Fe content of 78.5% still showed the highest corrosion rate of 0.0059 mm yr{sup −1} while the alloy with the lowest Fe content of 20.4% gave the lowest corrosion rate of 0.0045 mm yr{sup −1}. - Highlights: • The aeration during corrosion measurement simulates reader-writer head production environment. • The corrosion rate diagram for Co-Fe alloys

  1. SYSTEM OF PRECISE DOSING OF COAGULANT IN THE PULVERIZING AERATOR POWERED BY WIND USING FUZZY LOGIC

    Directory of Open Access Journals (Sweden)

    Andrzej Osuch

    2017-06-01

    Full Text Available One of the methods used to support land restoration lakes is the method of pulverizing aeration. Use of aerators powered exclusively by wind improves the condition of reservoirs, while not compromising the environment. The pulverizing aeration process drive is windy on the water aeration zone near bottom, while removing harmful gases anaerobic metabolism. Aerators of this type due to the unique method of operation also enable dosing of inactivation coagulants with oxygenated water to the depths of the lake. Mileage coagulant dosing can be made dependent on the speed of the wind, which has an impact on the performance of his work, because with the increase of wind speed dispensing valve coagulants should be stronger open. One of the methods for assessing the state of lakes is to measure water transparency. The softer visibility, the most likely state of the water is better. Dosage of coagulant so you can make the transparency of the water. Similarly, with increasing transparency water dispensing valve should be more covered up. Control of the drain valve dispenser coagulant can be simultaneously dependent on two factors. The study was designed method of control drain valve dispenser coagulant using fuzzy inference.

  2. Aerated biofilters with multiple-level air injection configurations to enhance biological treatment of methane emissions.

    Science.gov (United States)

    Farrokhzadeh, Hasti; Hettiaratchi, J Patrick A; Jayasinghe, Poornima; Kumar, Sunil

    2017-09-01

    Aiming to improve conventional methane biofilter performance, a multiple-level aeration biofilter design is proposed. Laboratory flow-through column experiments were conducted to evaluate three actively-aerated methane biofilter configurations. Columns were aerated at one, two, and three levels of the bed depth, with air introduced at flow rates calculated from methane oxidation reaction stoichiometry. Inlet methane loading rates were increased in five stages between 6 and 18mL/min. The effects of methane feeding rate, levels of aeration, and residence time on methane oxidation rates were determined. Samples collected after completion of flow-through experiments were used to determine methane oxidation kinetic parameters, V max , K m , and methanotrophic community distribution across biofilter columns. Results obtained from mixed variances analysis and response surfaces, as well as methanotrophic activity data, suggested that, biofilter column with two aeration levels has the most even performance over time, maintaining 85.1% average oxidation efficiency over 95days of experiments. Copyright © 2017 Elsevier Ltd. All rights reserved.

  3. Chemical Oxygen Demand abatement in sewage using Micro-Aeration Enhanced Ecological Floating Bed

    Science.gov (United States)

    Shi, Hongle; Zhou, Gaofeng; Liu, Yiqing; Tan, Jiancong; Fu, Yongsheng

    2018-02-01

    The traditional ecological floating bed combined with micro-aeration system and artificial medium was developed for the removal of contaminants and remediation of surface water. This micro-aeration enhanced ecological floating bed (MAEEFB) consisted of aeration unit, microbial processing unit and aquatic plant unit. Batch experiments were conducted in different operating conditions on the removal of chemical oxygen demand (COD) in the sewage using MAEEFB. The removal rate of COD by MAEEFB, enhanced ecological floating bed (EEFB) and traditional ecological floating bed (TEFB) in the same reaction conditions was 59.2%, 56.9% and 30.6%, respectively, indicating that the combination of micro-aeration system and artificial medium could enhance the removal efficiency of COD in TEFB. In MAEEFB, the aeration intensity should be designed reasonablely considering both treatment efficiency and operation cost. Only increasing the specific surface area of the packing cannot effectively improve the purification efficiency of water. Factors like packing material, ability of intercepting organics and complicated extent of microorganisms attaching on the packing should also be considered.

  4. Production of environmentally friendly aerated concrete with required construction and operational properties

    Directory of Open Access Journals (Sweden)

    Tkach Evgeniya

    2018-01-01

    Full Text Available The purpose of these studies is to justify the feasibility of recycling different types of industrial waste instead of conventional expensive raw materials in production of environmentally friendly aerated concrete with required construction and operational properties. The impact of wastes from various industries on the environmental condition of affected areas, as well as the results of their environmental assessment were analyzed to determine whether these wastes could be used in production of high-performance building materials. The assessment of industrial wastes in aerated concrete production suggests that industrial wastes of hazard class IV can be recycled to produce aerated concrete. An environmentally friendly method for large-scale waste recycling, including a two-step environmentally sustainable mechanism, was developed. The basic quality indicators of the modified aerated concrete proved that the environmental safety could be enhanced by strengthening the structure, increasing its uniformity and improving thermal insulation properties. The modified non-autoclaved aerated concrete products with improved physical and operational properties were developed. They have the following properties: density – D700; class of concrete – B3.5; thermal transmittance coefficient – 0.143 W/(m·°C; frost resistance – F75.

  5. Maximization of beta-galactosidase production: a simultaneous investigation of agitation and aeration effects.

    Science.gov (United States)

    Alves, Fernanda Germano; Filho, Francisco Maugeri; de Medeiros Burkert, Janaína Fernandes; Kalil, Susana Juliano

    2010-03-01

    In this work, the agitation and aeration effects in the maximization of the beta-galactosidase production from Kluyveromyces marxianus CCT 7082 were investigated simultaneously, in relation to the volumetric enzyme activity and the productivity, as well as the analysis of the lactose consumption and production of glucose, and galactose of this process. Agitation and aeration effects were studied in a 2 L batch stirred reactor. A central composite design (2(2) trials plus three central points) was carried out. Agitation speed varied from 200 to 500 rpm and aeration rate from 0.5 to 1.5 vvm. It has been shown in this study that the volumetric enzyme production was strongly influenced by mixing conditions, while aeration was shown to be less significant. Linear models for activity and productivity due to agitation and aeration were obtained. The favorable condition was 500 rpm and 1.5 vvm, which lead to the best production of 17 U mL(-1) for enzymatic activity, 1.2 U mL(-1) h(-1) for productivity in 14 h of process, a cellular concentration of 11 mg mL(-1), and a 167.2 h(-1) volumetric oxygen transfer coefficient.

  6. Nitrogen removal in the bioreactor landfill system with intermittent aeration at the top of landfilled waste

    International Nuclear Information System (INIS)

    He Ruo; Shen Dongsheng

    2006-01-01

    High ammonia concentration of recycled landfill leachate makes it very difficult to treat. In this work, a vertical aerobic/anoxic/anaerobic lab-scale bioreactor landfill system, which was constructed by intermittent aeration at the top of landfilled waste, as a bioreactor for in situ nitrogen removal was investigated during waste stabilization. Intermittent aeration at the top of landfilled waste might stimulate the growth of nitrifying bacteria and denitrifying bacteria in the top and middle layers of waste. The nitrifying bacteria population for the landfill bioreactor with intermittent aeration system reached between10 6 and 10 8 cells/dry g waste, although it decreased 2 orders of magnitude on day 30, due to the inhibitory effect of the acid environment and high organic matter in the landfilled waste. The denitrifying bacteria population increased by between 4 and 13 orders of magnitude compared with conventional anaerobic landfilled waste layers. Leachate NO 3 - -N concentration was very low in both two experimental landfill reactors. After 105 days operation, leachate NH 4 + -N and TN concentrations for the landfill reactor with intermittent aeration system dropped to 186 and 289 mg/l, respectively, while they were still kept above 1000 mg/l for the landfill reactor without intermittent aerobic system. In addition, there is an increase in the rate of waste stabilization as well as an increase of 12% in the total waste settlement for the landfill reactor with intermittent aeration system

  7. The dynamics of plasma membrane PtdIns(4,5)P(2) at fertilization of mouse eggs.

    Science.gov (United States)

    Halet, Guillaume; Tunwell, Richard; Balla, Tamas; Swann, Karl; Carroll, John

    2002-05-15

    A series of intracellular Ca2+ oscillations are responsible for triggering egg activation and cortical granule exocytosis at fertilization in mammals. These Ca2+ oscillations are generated by an increase in inositol 1,4,5-trisphosphate [Ins(1,4,5)P(3)], which results from the hydrolysis of phosphatidylinositol 4,5-bisphosphate [PtdIns(4,5)P(2)]. Using confocal imaging to simultaneously monitor Ca2+ and plasma membrane PtdIns(4,5)P(2) in single living mouse eggs we have sought to establish the relationship between the kinetics of PtdIns(4,5)P(2) metabolism and the Ca2+ oscillations at fertilization. We report that there is no detectable net loss of plasma membrane PtdIns(4,5)P(2) either during the latent period or during the subsequent Ca2+ oscillations. When phosphatidylinositol 4-kinase is inhibited with micromolar wortmannin a limited decrease in plasma membrane PtdIns(4,5)P(2) is detected in half the eggs studied. Although we were unable to detect a widespread loss of PtdIns(4,5)P(2), we found that fertilization triggers a net increase in plasma membrane PtdIns(4,5)P(2) that is localized to the vegetal cortex. The fertilization-induced increase in PtdIns(4,5)P(2) follows the increase in Ca2+, is blocked by Ca2+ buffers and can be mimicked, albeit with slower kinetics, by photoreleasing Ins(1,4,5)P(3). Inhibition of Ca2+-dependent exocytosis of cortical granules, without interfering with Ca2+ transients, inhibits the PtdIns(4,5)P(2) increase. The increase appears to be due to de novo synthesis since it is inhibited by micromolar wortmannin. Finally, there is no increase in PtdIns(4,5)P(2) in immature oocytes that are not competent to extrude cortical granules. These studies suggest that fertilization does not deplete plasma membrane PtdIns(4,5)P(2) and that one of the pathways for increasing PtdIns(4,5)P(2) at fertilization is invoked by exocytosis of cortical granules.

  8. Characterizing fluorescent dissolved organic matter in a membrane bioreactor via excitation-emission matrix combined with parallel factor analysis.

    Science.gov (United States)

    Maqbool, Tahir; Quang, Viet Ly; Cho, Jinwoo; Hur, Jin

    2016-06-01

    In this study, we successfully tracked the dynamic changes in different constitutes of bound extracellular polymeric substances (bEPS), soluble microbial products (SMP), and permeate during the operation of bench scale membrane bioreactors (MBRs) via fluorescence excitation-emission matrix (EEM) combined with parallel factor analysis (PARAFAC). Three fluorescent groups were identified, including two protein-like (tryptophan-like C1 and tyrosine-like C2) and one microbial humic-like components (C3). In bEPS, protein-like components were consistently more dominant than C3 during the MBR operation, while their relative abundance in SMP depended on aeration intensities. C1 of bEPS exhibited a linear correlation (R(2)=0.738; pbEPS amounts in sludge, and C2 was closely related to the stability of sludge. The protein-like components were more greatly responsible for membrane fouling. Our study suggests that EEM-PARAFAC can be a promising monitoring tool to provide further insight into process evaluation and membrane fouling during MBR operation. Copyright © 2016 Elsevier Ltd. All rights reserved.

  9. Radon removal equipment based on aeration: A literature study of tests performed in Sweden between 1981 and 1996

    International Nuclear Information System (INIS)

    Mjoenes, L.

    2000-02-01

    In Sweden some principles to reduce the radon concentration in drinking water were tested in the beginning of the 1980s. Spray aeration under atmospheric pressure, diffused bubble aeration, aeration in the pressure tank and different combinations of these principles were studied. Aeration in the drill hole and adsorption on granulated activated char-coal were also tested. The best results, about 70 % reduction, were obtained with aeration in the pressure tank with a spray system combined with diffused air bubbling. The Oerebro project in the beginning of the 1990s included on site testing of five different aeration solutions: Aeration in the drill hole, aeration in the storage tank, ejector aeration, shallow tray aeration and packed column aeration. The radon removal efficiency varied between 20 % and 99 %. In 1994 a study intended to test the radon removal capacity of different water treatment equipment was performed. Six units of radon separators were included but most of the tested equipment was installed for other water treatment purposes. The performed measurements showed that the only types of equipment that reduce the radon concentration efficiently are radon separators and reverse osmosis filters. The radon removal capacity of the radon separators varied between 23 % and 97 %. In 1996 the nine most common radon separators on the Swedish market were tested. The results showed that the tested radon removal equipment worked well, although the technical quality and chosen technical solutions were not always the best. The radon removal capacity of the units participating in this test was in most cases between 96 and 99 %. In some cases the capacity exceeded 99 %. In order to reach this radon removal capacity the water must be recirculated in a storage tank under atmospheric pressure

  10. Radon removal equipment based on aeration: A literature study of tests performed in Sweden between 1981 and 1996

    Energy Technology Data Exchange (ETDEWEB)

    Mjoenes, L

    2000-02-01

    In Sweden some principles to reduce the radon concentration in drinking water were tested in the beginning of the 1980s. Spray aeration under atmospheric pressure, diffused bubble aeration, aeration in the pressure tank and different combinations of these principles were studied. Aeration in the drill hole and adsorption on granulated activated char-coal were also tested. The best results, about 70 % reduction, were obtained with aeration in the pressure tank with a spray system combined with diffused air bubbling. The Oerebro project in the beginning of the 1990s included on site testing of five different aeration solutions: Aeration in the drill hole, aeration in the storage tank, ejector aeration, shallow tray aeration and packed column aeration. The radon removal efficiency varied between 20 % and 99 %. In 1994 a study intended to test the radon removal capacity of different water treatment equipment was performed. Six units of radon separators were included but most of the tested equipment was installed for other water treatment purposes. The performed measurements showed that the only types of equipment that reduce the radon concentration efficiently are radon separators and reverse osmosis filters. The radon removal capacity of the radon separators varied between 23 % and 97 %. In 1996 the nine most common radon separators on the Swedish market were tested. The results showed that the tested radon removal equipment worked well, although the technical quality and chosen technical solutions were not always the best. The radon removal capacity of the units participating in this test was in most cases between 96 and 99 %. In some cases the capacity exceeded 99 %. In order to reach this radon removal capacity the water must be recirculated in a storage tank under atmospheric pressure.

  11. Numerical Simulations of Two-Phase Flow in a Self-Aerated Flotation Machine and Kinetics Modeling

    KAUST Repository

    Fayed, Hassan E.; Ragab, Saad

    2015-01-01

    A new boundary condition treatment has been devised for two-phase flow numerical simulations in a self-aerated minerals flotation machine and applied to a Wemco 0.8 m3 pilot cell. Airflow rate is not specified a priori but is predicted by the simulations as well as power consumption. Time-dependent simulations of two-phase flow in flotation machines are essential to understanding flow behavior and physics in self-aerated machines such as the Wemco machines. In this paper, simulations have been conducted for three different uniform bubble sizes (db = 0.5, 0.7 and 1.0 mm) to study the effects of bubble size on air holdup and hydrodynamics in Wemco pilot cells. Moreover, a computational fluid dynamics (CFD)-based flotation model has been developed to predict the pulp recovery rate of minerals from a flotation cell for different bubble sizes, different particle sizes and particle size distribution. The model uses a first-order rate equation, where models for probabilities of collision, adhesion and stabilization and collisions frequency estimated by Zaitchik-2010 model are used for the calculation of rate constant. Spatial distributions of dissipation rate and air volume fraction (also called void fraction) determined by the two-phase simulations are the input for the flotation kinetics model. The average pulp recovery rate has been calculated locally for different uniform bubble and particle diameters. The CFD-based flotation kinetics model is also used to predict pulp recovery rate in the presence of particle size distribution. Particle number density pdf and the data generated for single particle size are used to compute the recovery rate for a specific mean particle diameter. Our computational model gives a figure of merit for the recovery rate of a flotation machine, and as such can be used to assess incremental design improvements as well as design of new machines.

  12. Numerical Simulations of Two-Phase Flow in a Self-Aerated Flotation Machine and Kinetics Modeling

    Directory of Open Access Journals (Sweden)

    Hassan Fayed

    2015-03-01

    Full Text Available A new boundary condition treatment has been devised for two-phase flow numerical simulations in a self-aerated minerals flotation machine and applied to a Wemco 0.8 m3 pilot cell. Airflow rate is not specified a priori but is predicted by the simulations as well as power consumption. Time-dependent simulations of two-phase flow in flotation machines are essential to understanding flow behavior and physics in self-aerated machines such as the Wemco machines. In this paper, simulations have been conducted for three different uniform bubble sizes (db = 0.5, 0.7 and 1.0 mm to study the effects of bubble size on air holdup and hydrodynamics in Wemco pilot cells. Moreover, a computational fluid dynamics (CFD-based flotation model has been developed to predict the pulp recovery rate of minerals from a flotation cell for different bubble sizes, different particle sizes and particle size distribution. The model uses a first-order rate equation, where models for probabilities of collision, adhesion and stabilization and collisions frequency estimated by Zaitchik-2010 model are used for the calculation of rate constant. Spatial distributions of dissipation rate and air volume fraction (also called void fraction determined by the two-phase simulations are the input for the flotation kinetics model. The average pulp recovery rate has been calculated locally for different uniform bubble and particle diameters. The CFD-based flotation kinetics model is also used to predict pulp recovery rate in the presence of particle size distribution. Particle number density pdf and the data generated for single particle size are used to compute the recovery rate for a specific mean particle diameter. Our computational model gives a figure of merit for the recovery rate of a flotation machine, and as such can be used to assess incremental design improvements as well as design of new machines.

  13. Numerical Simulations of Two-Phase Flow in a Self-Aerated Flotation Machine and Kinetics Modeling

    KAUST Repository

    Fayed, Hassan E.

    2015-03-30

    A new boundary condition treatment has been devised for two-phase flow numerical simulations in a self-aerated minerals flotation machine and applied to a Wemco 0.8 m3 pilot cell. Airflow rate is not specified a priori but is predicted by the simulations as well as power consumption. Time-dependent simulations of two-phase flow in flotation machines are essential to understanding flow behavior and physics in self-aerated machines such as the Wemco machines. In this paper, simulations have been conducted for three different uniform bubble sizes (db = 0.5, 0.7 and 1.0 mm) to study the effects of bubble size on air holdup and hydrodynamics in Wemco pilot cells. Moreover, a computational fluid dynamics (CFD)-based flotation model has been developed to predict the pulp recovery rate of minerals from a flotation cell for different bubble sizes, different particle sizes and particle size distribution. The model uses a first-order rate equation, where models for probabilities of collision, adhesion and stabilization and collisions frequency estimated by Zaitchik-2010 model are used for the calculation of rate constant. Spatial distributions of dissipation rate and air volume fraction (also called void fraction) determined by the two-phase simulations are the input for the flotation kinetics model. The average pulp recovery rate has been calculated locally for different uniform bubble and particle diameters. The CFD-based flotation kinetics model is also used to predict pulp recovery rate in the presence of particle size distribution. Particle number density pdf and the data generated for single particle size are used to compute the recovery rate for a specific mean particle diameter. Our computational model gives a figure of merit for the recovery rate of a flotation machine, and as such can be used to assess incremental design improvements as well as design of new machines.

  14. Single Molecule 3D Orientation in Time and Space: A 6D Dynamic Study on Fluorescently Labeled Lipid Membranes

    DEFF Research Database (Denmark)

    Börner, Richard; Ehrlich, Nicky; Hohlbein, Johannes

    2016-01-01

    Interactions between single molecules profoundly depend on their mutual three-dimensional orientation. Recently, we demonstrated a technique that allows for orientation determination of single dipole emitters using a polarization-resolved distribution of fluorescence into several detection channels...... interesting in non-isotropic environments such as lipid membranes, which are of great importance in biology. We used giant unilamellar vesicles (GUVs) labeled with fluorescent dyes down to a single molecule concentration as a model system for both, assessing the robustness of the orientation determination...

  15. Effects of amantadine on the dynamics of membrane-bound influenza A M2 transmembrane peptide studied by NMR relaxation

    Energy Technology Data Exchange (ETDEWEB)

    Cady, Sarah D.; Hong Mei [Iowa State University, Department of Chemistry (United States)], E-mail: mhong@iastate.edu

    2009-09-15

    The molecular motions of membrane proteins in liquid-crystalline lipid bilayers lie at the interface between motions in isotropic liquids and in solids. Specifically, membrane proteins can undergo whole-body uniaxial diffusion on the microsecond time scale. In this work, we investigate the {sup 1}H rotating-frame spin-lattice relaxation (T{sub 1{rho}}) caused by the uniaxial diffusion of the influenza A M2 transmembrane peptide (M2TMP), which forms a tetrameric proton channel in lipid bilayers. This uniaxial diffusion was proved before by {sup 2}H, {sup 15}N and {sup 13}C NMR lineshapes of M2TMP in DLPC bilayers. When bound to an inhibitor, amantadine, the protein exhibits significantly narrower linewidths at physiological temperature. We now investigate the origin of this line narrowing through temperature-dependent {sup 1}H T{sub 1{rho}} relaxation times in the absence and presence of amantadine. Analysis of the temperature dependence indicates that amantadine decreases the correlation time of motion from 2.8 {+-} 0.9 {mu}s for the apo peptide to 0.89 {+-} 0.41 {mu}s for the bound peptide at 313 K. Thus the line narrowing of the bound peptide is due to better avoidance of the NMR time scale and suppression of intermediate time scale broadening. The faster diffusion of the bound peptide is due to the higher attempt rate of motion, suggesting that amantadine creates better-packed and more cohesive helical bundles. Analysis of the temperature dependence of ln (T{sub 1{rho}}{sup -1}) indicates that the activation energy of motion increased from 14.0 {+-} 4.0 kJ/mol for the apo peptide to 23.3 {+-} 6.2 kJ/mol for the bound peptide. This higher activation energy indicates that excess amantadine outside the protein channel in the lipid bilayer increases the membrane viscosity. Thus, the protein-bound amantadine speeds up the diffusion of the helical bundles while the excess amantadine in the bilayer increases the membrane viscosity.

  16. Effect of aerated concrete blockwork joints on the heat transfer performance uniformity

    Science.gov (United States)

    Pukhkal, Viktor; Murgul, Vera

    2018-03-01

    Analysis of data on the effect of joints of the aerated concrete blocks on the heat transfer uniformity of exterior walls was carried out. It was concluded, that the values of the heat transfer performance uniformity factor in the literature sources were obtained for the regular fragment of a wall construction by approximate addition of thermal conductivities. Heat flow patterns for the aerated concrete exterior walls amid different values of the thermal conductivity factors and design ambient air temperature of -26 °C were calculated with the use of "ELCUT" software for modelling of thermal patterns by finite element method. There were defined the values for the heat transfer performance uniformity factor, reduced total thermal resistance and heat-flux density for the exterior walls. The calculated values of the heat transfer performance uniformity factors, as a function of the coefficient of thermal conductivity of aerated concrete blocks, differ from the known data by a more rigorous thermal and physical substantiation.

  17. [Research of aeration with bio-film technology to treat urban landscape water].

    Science.gov (United States)

    Song, Ying-Wei; Nie, Zhi-Dan; Nian, Yue-Gang; Huang, Min-Sheng; Huang, Jian-Jun; Yan, Hai-Hong; Zhang, Yang

    2008-01-01

    Research of the aeration with bio-film technology was carried out to treat scenic water of a sanatorium in Beijing. The aim of the research was improving the water habitat by increasing the transparency and reducing the concentration of N and P. The equipments were set in a 5,000 m2 water area, which combined the plug flow jet aerator with the elastic biological filler. The research indicated that the transparency increased from 25 cm to 120 cm by the technology. The removal efficiencies of NH4(+)-N, NO3(-)-N and TP were 86.6% , 90% and 73.3%, but there was only 22.4% for TN. The concentration of DO increased from 4.3 mg/L to 7 mg/L. In a word, the aeration with bio-film technology was an effective measure to improve the water habitat by increasing the transparency.

  18. Flexural Behaviour of Precast Aerated Concrete Panel (PACP with Added Fibrous Material: An Overview

    Directory of Open Access Journals (Sweden)

    Abdul Rahim Noor Hazlin

    2017-01-01

    Full Text Available The usage of precast aerated concrete panel as an IBS system has become the main alternative to conventional construction system. The usage of this panel system contributes to a sustainable and environmental friendly construction. This paper presents an overview of the precast aerated concrete panel with added fibrous material (PACP. PACP is fabricated from aerated foamed concrete with added Polypropylene fibers (PP. The influence of PP on the mechanical properties of PACP are studied and reviewed from previous research. The structural behaviour of precast concrete panel subjected to flexure load is also reviewed. It is found that PP has significant affects on the concrete mixture’s compressive stregth, tensile strength and flexural strength. It is also found that PP manage to control the crack propagation in the concrete panel.

  19. Thermal Response Of An Aerated Concrete Wall With Micro-Encapsulated Phase Change Material

    Science.gov (United States)

    Halúzová, Dušana

    2015-06-01

    For many years Phase Change Materials (PCM) have attracted attention due to their ability to store large amounts of thermal energy. This property makes them a candidate for the use of passive heat storage. In many applications, they are used to avoid the overheating of the temperature of an indoor environment. This paper describes the behavior of phase change materials that are inbuilt in aerated concrete blocks. Two building samples of an aerated concrete wall were measured in laboratory equipment called "twin-boxes". The first box consists of a traditional aerated concrete wall; the second one has additional PCM micro-encapsulated in the wall. The heat flux through the wall was measured and compared to simulation results modeled in the ESP-r program. This experimental measurement provides a foundation for a model that can be used to analyze further building constructions.

  20. Influence of agitation speeds and aeration rates on the Xylanase activity of Aspergillus niger SS7

    Directory of Open Access Journals (Sweden)

    Yasser Bakri

    2011-08-01

    Full Text Available In this study, the effect of agitation and aeration rates on xylanase activity of Aspergillus niger SS7 in 3-litre stirred tank bioreactor was investigated. The agitation rates tested were 100, 200 and 300 rpm at each airflow rates of 0.5, 1.0 and 1.5 vvm. The maximum xylanase activity in mono- agitator system was at the agitation speed of 200 rpm and aeration rate of 1.0 vvm. In bi-agitator system, at low agitation speed (100 rpm, the xylanase activity was enhanced by 13% compared to mono- agitator system for an aeration rate of 1.0 vvm. Xylanase productivity in continuous culture was higher by approximately 3.5 times than in batch culture.