Nonlinear electro-mechanobiological behavior of cell membrane during electroporation

KAUST Repository

Deng, Peigang

2012-01-01

A nonlinear electroporation (EP) model is proposed to study the electro-mechanobiological behavior of cell membrane during EP, by taking the nonlinear large deformation of the membrane into account. The proposed model predicts the critical transmembrane potential and the activation energy for EP, the equilibrium pore size, and the resealing process of the pore. Single-cell EP experiments using a micro EP chip were conducted on chicken red blood cells at different temperatures to determine the activation energy and the critical transmembrane potential for EP. The experimental results are in good agreement with the theoretical predictions. © 2012 American Institute of Physics.

Behavior of Reinforced Concrete Membrane Elements Subjected to Bidirectional Shear Loads

OpenAIRE

Labib, M.; Moslehy, Y.; Ayoub, A.

2013-01-01

The shear design and behavior of a typical membrane reinforced concrete (RC) element has been extensively studied in the past several decades. Such design requires knowledge of the constitutive behavior of RC elements subjected to a shear stress acting along its plane (in-plane shear). These constitutive models were accurately derived from experimental test data on representative RC panel elements. The true behavior of many large, complex structures, however, involves interaction between the ...

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.

Pore-level determination of spectral reflection behaviors of high-porosity metal foam sheets

Science.gov (United States)

Li, Yang; Xia, Xin-Lin; Ai, Qing; Sun, Chuang; Tan, He-Ping

2018-03-01

Open cell metal foams are currently attracting attention and their radiative behaviors are of primary importance in high temperature applications. The spectral reflection behaviors of high-porosity metal foam sheets, bidirectional reflectance distribution function (BRDF) and directional-hemispherical reflectivity were numerically investigated. A set of realistic nickel foams with porosity from 0.87 to 0.97 and pore density from 10 to 40 pores per inch were tomographied to obtain their 3-D digital cell network. A Monte Carlo ray-tracing method was employed in order to compute the pore-level radiative transfer inside the network within the limit of geometrical optics. The apparent reflection behaviors and their dependency on the textural parameters and strut optical properties were comprehensively computed and analysed. The results show a backward scattering of the reflected energy at the foam sheet surface. Except in the cases of large incident angles, an energy peak is located almost along the incident direction and increases with increasing incident angles. Through an analytical relation established, the directional-hemispherical reflectivity can be related directly to the porosity of the foam sheet and to the complex refractive index of the solid phase as well as the specularity parameter which characterizes the local reflection model. The computations show that a linear decrease in normal-hemispherical reflectivity occurs with increasing porosity. The rate of this decrease is directly proportional to the strut normal reflectivity. In addition, the hemispherical reflectivity increases as a power function of the incident angle cosine.

Preparation, Characterization and Permeation Behavior of Poly(methyl acrylate-Poly(dimethyl siloxane-Poly(methyl acrylate Block Copolymer/Poly(vinyl acetate Blend Membranes

Directory of Open Access Journals (Sweden)

Mohammad Ali Semsarzadeh

2015-03-01

Full Text Available Structure of polymeric materials is of the most important factors in determination of the characteristics and properties of the membranes. Various research and developments on polymeric membranes confirm the direct correlation between structure-properties of polymeric membranes. In this research, the structural outcome of poly(methyl acrylate-poly(dimethyl siloxane-poly(methyl acrylate/poly(vinyl acetate blend membranes and its relationship with gas permeation behavior of the blends were investigated. The flexible block copolymer of poly(methyl acrylate-poly(dimethyl siloxane-poly(methyl acrylate (PMA-PDMS-PMA was synthesized via atom transfer radical polymerization. Morphology and chemical structure of the synthesized block copolymer was investigated by Fourier transform infrared spectroscopy, proton nuclear magnetic resonance, gel permeation chromatography, X-ray diffraction analysis, differential scanning calorimetry and scanning electron microscopy. Blend membranes of PMA-PDMS-PMA and poly(vinyl acetate (PVAc were prepared by solution casting method in different compositions. By adding poly(vinyl acetate to PMA-PDMS-PMA block copolymer, the selectivity of the membranes for carbon dioxide/methane pair gases were increased by 55%. Fractional free volume (an indication of chain packing efficiency in blend membranes and dielectric constant (an indication of the molar volume and molar polarization of the blend membranes were obtained as the factors reflected the microstructural effect of PMA-PDMS-PMA and PVAc blend membranes. The efforts were directed toward expressing more precise structure-properties relationship of PMA-PDMS-PMA/PVAc blend membranes. The experimental permeability values of the blend membranes reported in this research were compared with the modified logarithmic model. The modified logarithmic model was evaluated for other blend membranes.

Filtration behavior of casein glycomacropeptide (CGMP) in an enzymatic membrane reactor: fouling control by membrane selection and threshold flux operation

DEFF Research Database (Denmark)

Luo, Jianquan; Morthensen, Sofie Thage; Meyer, Anne S.

2014-01-01

. In this study, the filtration performance and fouling behavior during ultrafiltration (UF) of CGMP for the enzymatic production of 3′-sialyllactose were investigated. A 5kDa regenerated cellulose membrane with high anti-fouling performance, could retain CGMP well, permeate 3′-sialyllactose, and was found...... to be the most suitable membrane for this application. Low pH increased CGMP retention but produced more fouling. Higher agitation and lower CGMP concentration induced larger permeate flux and higher CGMP retention. Adsorption fouling and pore blocking by CGMP in/on membranes could be controlled by selecting...... a highly hydrophilic membrane with appropriate pore size. Operating under threshold flux could minimize the concentration polarization and cake/gel/scaling layers, but might not avoid irreversible fouling caused by adsorption and pore blocking. The effects of membrane properties, pH, agitation and CGMP...

The Development and Validation of an In Vitro Airway Model to Assess Realistic Airway Deposition and Drug Permeation Behavior of Orally Inhaled Products Across Synthetic Membranes.

Science.gov (United States)

Huynh, Bao K; Traini, Daniela; Farkas, Dale R; Longest, P Worth; Hindle, Michael; Young, Paul M

2018-04-01

Current in vitro approaches to assess lung deposition, dissolution, and cellular transport behavior of orally inhaled products (OIPs) have relied on compendial impactors to collect drug particles that are likely to deposit in the airway; however, the main drawback with this approach is that these impactors do not reflect the airway and may not necessarily represent drug deposition behavior in vivo. The aim of this article is to describe the development and method validation of a novel hybrid in vitro approach to assess drug deposition and permeation behavior in a more representative airway model. The medium-sized Virginia Commonwealth University (VCU) mouth-throat (MT) and tracheal-bronchial (TB) realistic upper airway models were used in this study as representative models of the upper airway. The TB model was modified to accommodate two Snapwell ® inserts above the first TB airway bifurcation region to collect deposited nebulized ciprofloxacin-hydrochloride (CIP-HCL) droplets as a model drug aerosol system. Permeation characteristics of deposited nebulized CIP-HCL droplets were assessed across different synthetic membranes using the Snapwell test system. The Snapwell test system demonstrated reproducible and discriminatory drug permeation profiles for already dissolved and nebulized CIP-HCL droplets through a range of synthetic permeable membranes under different test conditions. The rate and extent of drug permeation depended on the permeable membrane material used, presence of a stirrer in the receptor compartment, and, most importantly, the drug collection method. This novel hybrid in vitro approach, which incorporates a modified version of a realistic upper airway model, coupled with the Snapwell test system holds great potential to evaluate postairway deposition characteristics, such as drug permeation and particle dissolution behavior of OIPs. Future studies will expand this approach using a cell culture-based setup instead of synthetic membranes, within a

Ozone mass transfer behaviors on physical and chemical absorption for hollow fiber membrane contactors.

Science.gov (United States)

Zhang, Yong; Li, Kuiling; Wang, Jun; Hou, Deyin; Liu, Huijuan

2017-09-01

To understand the mass transfer behaviors in hollow fiber membrane contactors, ozone fluxes affected by various conditions and membranes were investigated. For physical absorption, mass transfer rate increased with liquid velocity and the ozone concentration in the gas. Gas flow rate was little affected when the velocity was larger than the critical value, which was 6.1 × 10 -3 m/s in this study. For chemical absorption, the flux was determined by the reaction rate between ozone and the absorbent. Therefore, concentration, species, and pH affected the mass transfer process markedly. For different absorbents, the order of mass transfer rate was the same as the reaction rate constant, which was phenol, sodium nitrite, hydrogen peroxide, and oxalate. Five hydrophobic membranes with various properties were employed and the mass transfer behavior can be described by the Graetz-Lévèque equation for the physical absorption process. The results showed the process was controlled by liquid film and the gas phase conditions, and membrane properties did not affect the ozone flux. For the chemical absorption, gas film, membrane and liquid film affected the mass transfer together, and none of them were negligible.

Heterogeneous structure and its effect on properties and electrochemical behavior of ion-exchange membrane

Science.gov (United States)

Ariono, D.; Khoiruddin; Subagjo; Wenten, I. G.

2017-02-01

Generally, commercially available ion-exchange membrane (IEM) can be classified into homogeneous and heterogeneous membranes. The classification is based on degree of heterogeneity in membrane structure. It is well known that the heterogeneity greatly affects the properties of IEM, such as conductivity, permselectivity, chemical and mechanical stability. The heterogeneity also influences ionic and electrical current transfer behavior of IEM-based processes during their operation. Therefore, understanding the role of heterogeneity in IEM properties is important to provide preliminary information on their operability and applicability. In this paper, the heterogeneity and its effect on IEM properties are reviewed. Some models for describing the heterogeneity of IEM and methods for characterizing the degree of heterogeneity are discussed. In addition, the influence of heterogeneity on the performance of IEM-based processes and their electrochemical behavior are described.

The relationship between lateral differences in tympanic membrane temperature and behavioral impulsivity.

Science.gov (United States)

Helton, William S

2010-11-01

In this study lateral differences in tympanic membrane temperature (T(Ty)) were explored as a correlate of either impulsive or cautious responding in Go-No-Go tasks. Thirty-two women and men performed two sustained attention to response tasks (Go-No-Go tasks). Those with warmer right in comparison to left tympanic membranes were more cautious, and those with warmer left in comparison to right tympanic membranes were more impulsive. This finding is in line with previous research and theory indicating a hemispheric bias for active and passive behavior. T(Ty) may be a useful addition to the techniques employed by neuropsychologists. Copyright 2010 Elsevier Inc. All rights reserved.

Stretched membrane heliostats: design and structural analysis of reflectance module and support of a heliostats of 9 m. diaform and 60 m''3 of reflectance surface

International Nuclear Information System (INIS)

Figarola Torres, J. M.

1993-01-01

After having designed and built at CIEMAT a first prototype of a Btretched membrane heliostats of 3 m. diameter, the design and the structural analysis of the different components included in the reflectance module and support of another heliostats, this one of 9 m. diameter and 60 m2. of reflectance surface, are shown In this report. This last heliostats will be mounted on a pedestal and its driving device at the Solar Platform of Almeria. In order to optimize design and performance, the structural analysis of its basic components has been analyzed with the finite elements program ANSYS. The following elements have been subject to analysis: the membrane and their ring supports, stretching system and the structural support. A similar scheme to the one applied to the previous prototype has been used on the focus control system. That includes a linear transducer, a variable frequency and a fan. Finally it has to be pointed out that substantial improvements have been achieved with respect to the first prototype concerning design and cost. (Author) 5 refs

Collective cell behavior on basement membranes floating in space

Science.gov (United States)

Ellison, Sarah; Bhattacharjee, Tapomoy; Morley, Cameron; Sawyer, W.; Angelini, Thomas

The basement membrane is an essential part of the polarity of endothelial and epithelial tissues. In tissue culture and organ-on-chip devices, monolayer polarity can be established by coating flat surfaces with extracellular matrix proteins and tuning the trans-substrate permeability. In epithelial 3D culture, spheroids spontaneously establish inside-out polarity, morphing into hollow shell-like structures called acini, generating their own basement membrane on the inner radius of the shell. However, 3D culture approaches generally lack the high degree of control provided by the 2D culture plate or organ-on-chip devices, making it difficult to create more faithful in vitro tissue models with complex surface curvature and morphology. Here we present a method for 3D printing complex basement membranes covered in cells. We 3D print collagen-I and Matrigel into a 3D growth medium made from jammed microgels. This soft, yielding material allows extracellular matrix to be formed as complex surfaces and shapes, floating in space. We then distribute MCF10A epithelial cells across the polymerized surface. We envision employing this strategy to study 3D collective cell behavior in numerous model tissue layers, beyond this simple epithelial model.

Organic fouling behavior of superhydrophilic polyvinylidene fluoride (PVDF) ultrafiltration membranes functionalized with surface-tailored nanoparticles: Implications for organic fouling in membrane bioreactors

KAUST Repository

Liang, Shuai; Qi, Genggeng; Xiao, Kang; Sun, Jianyu; Giannelis, Emmanuel P.; Huang, Xia; Elimelech, Menachem

2014-01-01

This study systematically investigates the organic fouling behavior of a superhydrophilic polyvinylidene fluoride (PVDF) ultrafiltration membrane functionalized via post-fabrication tethering of surface-tailored silica nanoparticles to poly

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...

A Dynamic Object Behavior Model and Implementation Based on Computational Reflection

Institute of Scientific and Technical Information of China (English)

HE Cheng-wan; HE Fei; HE Ke-qing

2005-01-01

A dynamic object behavior model based on computational reflection is proposed. This model consists of function level and meta level, the meta objects in meta level manage the base objects and behaviors in function level, including dynamic binding and unbinding of base object and behavior.We implement this model with RoleJava Language, which is our self linguistic extension of the Java Language. Meta Objects are generated automatically at compile-time, this makes the reflecton mechanism transparent to programmers. Finally an example applying this model to a banking system is presented.

On-site Determination of Trace Arsenic by Reflection-Absorption Colorimetry of Molybdenum Blue Collected on a Membrane Filter.

Science.gov (United States)

Hasegawa, Yuya; Suzuki, Yasutada; Kawakubo, Susumu

2017-01-01

An on-site determination method for trace arsenic has been developed by collecting it as molybdenum blue (MB) in the presence of tetradecyldimethylbenzylammonium chloride on a mixed cellulose ester membrane filter and by measuring reflection absorbance (RA) of MB on the filter using a laboratory-made palm-top size reflection-absorbance colorimeter with a red light-emitting diode. The value of RA was proportional to the amount of arsenic up to 0.5 μg with a detection limit of 0.01 μg. The proposed method was successfully applied to soil extract and hot-spring water samples.

Enhancement of electron flux by means of diamond membrane

International Nuclear Information System (INIS)

Gavrilov, S.A.; Il'ichev, Eh.A.; Poltoratskij, Eh.A.; Rychkov, G.S.; Dzbanovskij, N.N.; Minakov, P.V.; Suetin, N.V.

2004-01-01

One investigates into secondary electron emission (SEE) from diamond films made in the form of 2.5-5 μm thickness membranes. SEE is investigated under two modes: the reflection and the streaming ones. SEE coefficient is evaluated on the basis of analysis of behavior of 0.1-30 keV energy electrons in solid material. It is shown that in case of reflection the SEE coefficient may be over 100 at energies equal to 3 keV, while in case of streaming it does not exceed 5 even at 30 keV energy values [ru

Teacher Perceptions of the Classroom Behavior of Reflective and Impulsive Children

Science.gov (United States)

McKinney, James D.

1975-01-01

Four second-grade teachers completed the Classroom Behavior Inventory for every student in their class (N=101). Subjects were classified as either reflective (N=32) or impulsive (N=32) by using the Matching Familiar Figures Test (MFF). (Author)

Allowing for Reflection Time does not Change Behavior in Dictator and Cheating Games

DEFF Research Database (Denmark)

Andersen, Steffen; Gneezy, Uri; Kajackaite, Agne

2018-01-01

Reaction time, usually measured in seconds, has been shown to be correlated with decisions in experimental games. In this paper, we study how allowing for a full day of “reflection time” alters behavior. We compare behavior in dictator and cheating games when participants make immediate choices...

Effect of copper (II) ion against elongation behavior of amyloid {beta} fibrils on liposome membranes

Energy Technology Data Exchange (ETDEWEB)

Shimanouchi, T.; Onishi, R.; Kitaura, N.; Umakoshi, H.; Kuboi, R. [Division of Chemical Engineering, Graduate School of Engineering Science, Osaka University, 1-3 Machikaneyama-cho, Toyonaka, Osaka (Japan)

2012-01-15

The fibril growth behavior of amyloid {beta} protein (A{beta}) on cell membranes is relating to the progression of Alzheimer's disease. This growth behavior of A{beta} fibrils is sensitively affected by the metal ions, neurotransmitters, or bioreactive substrate. The inhibitory effect of those materials was quantitatively estimated from the viewpoints of ''crystal growth''. In a bulk aqueous solution, copper (II) ion showed the strong inhibitory effect on the growth of A{beta} fibrils. Meanwhile, the addition of a closed-phospholipid bilayer membrane (liposome) could reduce the above inhibitory effect of copper (II) ion. (copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

Effects of Phase Separation Behavior on Morphology and Performance of Polycarbonate Membranes

Science.gov (United States)

Idris, Alamin; Man, Zakaria; Maulud, Abdulhalim S.; Khan, Muhammad Saad

2017-01-01

The phase separation behavior of bisphenol-A-polycarbonate (PC), dissolved in N-methyl-2-pyrrolidone and dichloromethane solvents in coagulant water, was studied by the cloud point method. The respective cloud point data were determined by titration against water at room temperature and the characteristic binodal curves for the ternary systems were plotted. Further, the physical properties such as viscosity, refractive index, and density of the solution were measured. The critical polymer concentrations were determined from the viscosity measurements. PC/NMP and PC/DCM membranes were fabricated by the dry-wet phase inversion technique and characterized for their morphology, structure, and thermal stability using field emission scanning electron microscopy, Fourier transform infrared spectroscopy, and thermogravimetric analysis, respectively. The membranes’ performances were tested for their permeance to CO2, CH4, and N2 gases at 24 ± 0.5 °C with varying feed pressures from 2 to 10 bar. The PC/DCM membranes appeared to be asymmetric dense membrane types with appreciable thermal stability, whereas the PC/NMP membranes were observed to be asymmetric with porous structures exhibiting 4.18% and 9.17% decrease in the initial and maximum degradation temperatures, respectively. The ideal CO2/N2 and CO2/CH4 selectivities of the PC/NMP membrane decreased with the increase in feed pressures, while for the PC/DCM membrane, the average ideal CO2/N2 and CO2/CH4 selectivities were found to be 25.1 ± 0.8 and 21.1 ± 0.6, respectively. Therefore, the PC/DCM membranes with dense morphologies are appropriate for gas separation applications. PMID:28379173

Effects of Phase Separation Behavior on Morphology and Performance of Polycarbonate Membranes

Directory of Open Access Journals (Sweden)

Alamin Idris

2017-04-01

Full Text Available The phase separation behavior of bisphenol-A-polycarbonate (PC, dissolved in N-methyl-2-pyrrolidone and dichloromethane solvents in coagulant water, was studied by the cloud point method. The respective cloud point data were determined by titration against water at room temperature and the characteristic binodal curves for the ternary systems were plotted. Further, the physical properties such as viscosity, refractive index, and density of the solution were measured. The critical polymer concentrations were determined from the viscosity measurements. PC/NMP and PC/DCM membranes were fabricated by the dry-wet phase inversion technique and characterized for their morphology, structure, and thermal stability using field emission scanning electron microscopy, Fourier transform infrared spectroscopy, and thermogravimetric analysis, respectively. The membranes’ performances were tested for their permeance to CO2, CH4, and N2 gases at 24 ± 0.5 °C with varying feed pressures from 2 to 10 bar. The PC/DCM membranes appeared to be asymmetric dense membrane types with appreciable thermal stability, whereas the PC/NMP membranes were observed to be asymmetric with porous structures exhibiting 4.18% and 9.17% decrease in the initial and maximum degradation temperatures, respectively. The ideal CO2/N2 and CO2/CH4 selectivities of the PC/NMP membrane decreased with the increase in feed pressures, while for the PC/DCM membrane, the average ideal CO2/N2 and CO2/CH4 selectivities were found to be 25.1 ± 0.8 and 21.1 ± 0.6, respectively. Therefore, the PC/DCM membranes with dense morphologies are appropriate for gas separation applications.

A synergetic analysis method for antifouling behavior investigation on PES ultrafiltration membrane with self-assembled TiO2 nanoparticles.

Science.gov (United States)

Li, Xin; Li, Jiansheng; Fang, Xiaofeng; Bakzhan, Kariboz; Wang, Lianjun; Van der Bruggen, Bart

2016-05-01

Fouling of ultrafiltration (UF) membranes is a major impediment for their use in drinking water production. Mixed matrix membranes (MMMs) may have great opportunities in dealing with this challenge due to their hierarchical structures and multiple functionalities. In this study, a synergetic analysis method based on intermolecular adhesion force measurement and fouling process simulation was applied to investigate the fouling mechanism of polyethersulfone (PES) UF membranes containing in situ self-assembled TiO2 nanoparticles (NPs). The fouling resistance behavior and antifouling mechanism of the newly developed composite membranes were investigated with sodium alginate (SA), bovine serum albumin (BSA) and humic acid (HA) as model organic foulants. An improved antifouling effect was conspicuously observed for the composite membranes, expressed by a lower flux decline and significantly better cleaning efficiency. A strong correlation between the self-assembled structure of TiO2 NPs and the antifouling behavior of the composite membrane was observed. A lower magnitude and a narrower distribution of adhesion forces for the composite membrane suggest the effective suppression of foulants adsorption on the clean or fouled membrane. The simulation analysis indicates that the main fouling mechanism was standard blocking and cake filtration, further confirming the superiority of the NPs self-assembled structure in mitigating membrane fouling. This dual analysis method may provide a promising technological support for the application of modified UF membranes with self-assembled NPs in drinking water production. Copyright © 2016 Elsevier Inc. All rights reserved.

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.

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.

Dietary fatty acids alter blood pressure, behavior and brain membrane composition of hypertensive rats

NARCIS (Netherlands)

de Wilde, MC; Hogyes, E; Kiliaan, AJ; Farkas, T; Luiten, PGM; Farkas, E; Wilde, Martijn C. de; Hőgyes, Endre; Kiliaan, Amanda J.

2003-01-01

The beneficial effect of dietary n-3 polyunsaturated fatty acids (PUFAs) on developing hypertension has been repeatedly demonstrated. However. related changes in brain membrane composition and its cognitive correlates have remained unclear. Our study aimed at a comprehensive analysis of behavior and

Superhydrophilic Thin-Film Composite Forward Osmosis Membranes for Organic Fouling Control: Fouling Behavior and Antifouling Mechanisms

KAUST Repository

Tiraferri, Alberto

2012-10-16

This study investigates the fouling behavior and fouling resistance of superhydrophilic thin-film composite forward osmosis membranes functionalized with surface-tailored nanoparticles. Fouling experiments in both forward osmosis and reverse osmosis modes are performed with three model organic foulants: alginate, bovine serum albumin, and Suwannee river natural organic matter. A solution comprising monovalent and divalent salts is employed to simulate the solution chemistry of typical wastewater effluents. Reduced fouling is consistently observed for the superhydrophilic membranes compared to control thin-film composite polyamide membranes, in both reverse and forward osmosis modes. The fouling resistance and cleaning efficiency of the functionalized membranes is particularly outstanding in forward osmosis mode where the driving force for water flux is an osmotic pressure difference. To understand the mechanism of fouling, the intermolecular interactions between the foulants and the membrane surface are analyzed by direct force measurement using atomic force microscopy. Lower adhesion forces are observed for the superhydrophilic membranes compared to the control thin-film composite polyamide membranes. The magnitude and distribution of adhesion forces for the different membrane surfaces suggest that the antifouling properties of the superhydrophilic membranes originate from the barrier provided by the tightly bound hydration layer at their surface, as well as from the neutralization of the native carboxyl groups of thin-film composite polyamide membranes. © 2012 American Chemical Society.

Superhydrophilic thin-film composite forward osmosis membranes for organic fouling control: fouling behavior and antifouling mechanisms.

Science.gov (United States)

Tiraferri, Alberto; Kang, Yan; Giannelis, Emmanuel P; Elimelech, Menachem

2012-10-16

This study investigates the fouling behavior and fouling resistance of superhydrophilic thin-film composite forward osmosis membranes functionalized with surface-tailored nanoparticles. Fouling experiments in both forward osmosis and reverse osmosis modes are performed with three model organic foulants: alginate, bovine serum albumin, and Suwannee river natural organic matter. A solution comprising monovalent and divalent salts is employed to simulate the solution chemistry of typical wastewater effluents. Reduced fouling is consistently observed for the superhydrophilic membranes compared to control thin-film composite polyamide membranes, in both reverse and forward osmosis modes. The fouling resistance and cleaning efficiency of the functionalized membranes is particularly outstanding in forward osmosis mode where the driving force for water flux is an osmotic pressure difference. To understand the mechanism of fouling, the intermolecular interactions between the foulants and the membrane surface are analyzed by direct force measurement using atomic force microscopy. Lower adhesion forces are observed for the superhydrophilic membranes compared to the control thin-film composite polyamide membranes. The magnitude and distribution of adhesion forces for the different membrane surfaces suggest that the antifouling properties of the superhydrophilic membranes originate from the barrier provided by the tightly bound hydration layer at their surface, as well as from the neutralization of the native carboxyl groups of thin-film composite polyamide membranes.

The Consumer Behavior Challenge: Designing an Assignment to Motivate Student Reflection and Self-Growth

Science.gov (United States)

Gravois, Renée; Lopez, Tará Burnthorne; Budden, Michael C.

2017-01-01

The tension caused by change pushes students to reflect on their new situation, examine preconceived ideas, and synthesize new with existing knowledge. In the Consumer Behavior Challenge, students are challenged to step outside of their comfort zone by changing a behavior or trying something new for a period of time. Through guided reflection…

Experimental and analytical analysis of polarization and water transport behaviors of hydrogen alkaline membrane fuel cell

Science.gov (United States)

Huo, Sen; Zhou, Jiaxun; Wang, Tianyou; Chen, Rui; Jiao, Kui

2018-04-01

Experimental test and analytical modeling are conducted to investigate the operating behavior of an alkaline electrolyte membrane (AEM) fuel cell fed by H2/air (or O2) and explore the effect of various operating pressures on the water transfer mechanism. According to the experimental test, the cell performance is greatly improved through increasing the operating pressure gradient from anode to cathode which leads to significant liquid water permeation through the membrane. The high frequency resistance of the A901 alkaline membrane is observed to be relatively stable as the operating pressure varies based on the electrochemical impedance spectroscopy (EIS) method. Correspondingly, based on the modeling prediction, the averaged water content in the membrane electrode assembly (MEA) does not change too much which leads to the weak variation of membrane ohmic resistance. This reveals that the performance enhancement should give the credit to better electro-chemical reaction kinetics for both the anode and cathode, also prone by the EIS results. The reversion of water back diffusion direction across the membrane is also observed through analytical solution.

Single Molecule Kinetics of ENTH Binding to Lipid Membranes

Energy Technology Data Exchange (ETDEWEB)

Rozovsky, Sharon [Univ. of Delaware, Newark, DE (United States); Forstner, Martin B. [Syracuse Univ., NY (United States); Sondermann, Holger [Cornell Univ., Ithaca, NY (United States); Groves, Jay T. [Univ. of California, Berkeley, CA (United States); Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)

2012-04-03

Transient recruitment of proteins to membranes is a fundamental mechanism by which the cell exerts spatial and temporal control over proteins’ localization and interactions. Thus, the specificity and the kinetics of peripheral proteins’ membrane residence are an attribute of their function. In this article, we describe the membrane interactions of the interfacial epsin N-terminal homology (ENTH) domain with its target lipid phosphatidylinositol (4,5)-bisphosphate (PtdIns(4,5)P₂). The direct visualization and quantification of interactions of single ENTH molecules with supported lipid bilayers is achieved using total internal reflection fluorescence microscopy (TIRFM) with a time resolution of 13 ms. This enables the recording of the kinetic behavior of ENTH interacting with membranes with physiologically relevant concentrations of PtdIns(4,5)P₂ despite the low effective binding affinity. Subsequent single fluorophore tracking permits us to build up distributions of residence times and to measure ENTH dissociation rates as a function of membrane composition. In addition, due to the high time resolution, we are able to resolve details of the motion of ENTH associated with a simple, homogeneous membrane. In this case ENTH’s diffusive transport appears to be the result of at least three different diffusion processes.

Variable-angle total internal reflection fluorescence microscopy of intact cells of Arabidopsis thaliana

Directory of Open Access Journals (Sweden)

Kim Myung K

2011-09-01

Full Text Available Abstract Background Total internal reflection fluorescence microscopy (TIRFM is a powerful tool for observing fluorescently labeled molecules on the plasma membrane surface of animal cells. However, the utility of TIRFM in plant cell studies has been limited by the fact that plants have cell walls, thick peripheral layers surrounding the plasma membrane. Recently, a new technique known as variable-angle epifluorescence microscopy (VAEM was developed to circumvent this problem. However, the lack of a detailed analysis of the optical principles underlying VAEM has limited its applications in plant-cell biology. Results Here, we present theoretical and experimental evidence supporting the use of variable-angle TIRFM in observations of intact plant cells. We show that when total internal reflection occurs at the cell wall/cytosol interface with an appropriate angle of incidence, an evanescent wave field of constant depth is produced inside the cytosol. Results of experimental TIRFM observations of the dynamic behaviors of phototropin 1 (a membrane receptor protein and clathrin light chain (a vesicle coat protein support our theoretical analysis. Conclusions These findings demonstrate that variable-angle TIRFM is appropriate for quantitative live imaging of cells in intact tissues of Arabidopsis thaliana.

REFLECTIVE FUNCTIONING AND PERSONALITY ORGANIZATION: ASSOCIATIONS WITH NEGATIVE MATERNAL BEHAVIORS.

Science.gov (United States)

Ensink, Karin; Rousseau, Marie-Eve; Biberdzic, Marko; Bégin, Michaël; Normandin, Lina

2017-05-01

The aim of this study was to examine whether mothers who manifest insensitive and disconnected behaviors in interaction with their infants differ in terms of maternal reflective functioning (RF), personality organization, and histories of abuse. A total of 86 mother-infant dyads, 28 of them with histories of abuse, participated in the study. RF was assessed with the Adult Attachment Interview (C. George, N. Kaplan, & M. Main, 1985), and personality organization was assessed with the self-report Inventory of Personality Organization (M.F. Lenzenweger, J.F. Clarkin, O.F. Kernberg, & P.A. Foelsh, 2001; L. Normandin et al., 2002), before the birth of the baby. Maternal behaviors were assessed using the Disconnected and Extremely Insensitive Parenting measure when the infants were 15 to 18 months old. The results of multivariate analyses of covariance indicate that both RF and personality organization were associated with disconnected and extremely insensitive maternal behaviors. Mothers classified as presenting intrusive/aggressive behaviors had significantly lower RF as well as significantly more difficulties in personality organization, including reality testing, identity, and defense mechanisms. Withdrawn and disconnected maternal behaviors were associated with the combination of difficulties in mentalization and personality organization rather than difficulties in one specific area. In sum, the study provides new evidence regarding the importance of a mentalizing stance about early attachment relationships for the modulation of maternal behaviors, especially intrusive/aggressive behaviors. © 2017 Michigan Association for Infant Mental Health.

Functional connectivity experiments reflect routine movement behavior of a tropical hummingbird species.

Science.gov (United States)

Volpe, Noelia L; Hadley, Adam S; Robinson, W Douglas; Betts, Matthew G

Translocation experiments, in which researchers displace animals and then monitor their movements to return home, are commonly used as tools to assess functional connectivity of fragmented landscapes. Such experiments are purported to have important advantages of being time efficient and of standardizing “motivation” to move across individuals. Yet, we lack tests of whether movement behavior of translocated birds reflects natural behavior of unmanipulated birds. We compared the routine movement behavior of a tropical hummingbird, the Green Hermit (Phaethornis guy), to that of experimentally translocated individuals. We tested for differences in site selection patterns during movement at two spatial scales (point and path levels). We also compared movement rates between treatments. Behaviors documented during translocation experiments reflected those observed during routine movements. At the point level, both translocated and non-translocated birds showed similar levels of preference for mature tropical forest. At the path level, step selection functions showed both translocated and non-translocated hummingbirds avoiding movement across non-forested matrix and selecting streams as movement corridors. Movement rates were generally higher during translocation experiments. However, the negative influence of forest cover on movement rates was proportionately similar in translocation and routine movement treatments. We report the first evidence showing that movement behavior of birds during translocation experiments is similar to their natural movement behavior. Therefore, translocation experiments may be reliable tools to address effects of landscape structure on animal movement. We observed consistent selection of landscape elements between translocated and non-translocated birds, indicating that both routine and translocation movement studies lead to similar conclusions regarding the effect of landscape structure and forest composition on functional connectivity

Erythrocytes Membrane Alterations Reflecting Liver Damage in CCl₄-Induced Cirrhotic Rats: The Ameliorative Effect of Naltrexone

Directory of Open Access Journals (Sweden)

Fatemeh Sarhadi Kholari

2016-11-01

Full Text Available Cirrhosis is the consequence of chronic liver disease. Deleterious effects of oxidative stress on hepatocytes may be reflected in the erythrocyte membrane. Naltrexone (NTX has been shown to attenuate hepatocellular injury in fibrotic animal models. The aim of this study was to investigate the progressive effect of CCl4 on the liver and whether the improvement of liver cirrhosis can be monitored through alterations in the erythrocyte membrane. In this study, 84 male Wistar rats were divided into 4 groups and received reagents (i.p. as follows: 1- CCl₄, 2- NTX + CCl₄, 3- Mineral Oil (M, and 4- NTX + M. After 2, 6 and 8 weeks, the blood and liver tissue samples were collected. Plasma enzyme activities, the content of erythrocyte GSH and some membrane compositions, including protein carbonyl, protein sulfhydryl, and malondialdehyde were assessed. After 6 and 8 weeks, plasma enzyme activities and the content of protein carbonyl were higher in CCl4 group significantly, as compared to other groups (P<0.001. NTX significantly diminished protein carbonyl and plasma enzyme activities (P<0.001. GSH did not change until the 6th week. However, CCl4+NTX increased it significantly as compared to CCl₄ group (P<0.05. Protein sulfhydryl showed changes in NTX+CCl₄ group which indicated a significant increase in protein sulfhydryl content in a 6th week compared to CCl4 group (P<0.05. MDA did not show any significant alteration. CCl₄-induced cirrhosis is accompanied by increased content of oxidative stress markers, especially protein carbonyl of RBC membrane and plasma enzyme activities. This study shows that the progression of liver cirrhosis and the ameliorative effect of NTX can be followed through alterations of these markers.

Penguin eggshell membranes reflect homogeneity of mercury in the marine food web surrounding the Antarctic Peninsula

International Nuclear Information System (INIS)

Brasso, Rebecka L.; Polito, Michael J.; Lynch, Heather J.; Naveen, R.; Emslie, Steven D.

2012-01-01

Remote regions such as the Antarctic have become increasingly important for investigations into far-reaching anthropogenic impacts on the environment, most recently in regard to the global mercury cycle. Spatial patterns of mercury availability in four regions of the Antarctic Peninsula were investigated using three species of sympatrically breeding Pygoscelis penguins as biomonitors. Eggshells with intact membranes from Adélie, Gentoo, and Chinstrap penguins were collected at 24 breeding colonies in the South Orkney Islands, South Shetland Islands, eastern Antarctic Peninsula, and western Antarctic Peninsula during the 2006/2007 austral summer. In addition, we compared eggshell membrane mercury concentrations with eggshell stable isotope values (δ 15 N and δ 13 C) to determine if species-specific trophic or foraging habitat preferences influenced female mercury exposure prior to breeding. With few exceptions, mercury concentrations were found to be fairly homogeneous throughout the Antarctic Peninsula suggesting little spatial variation in the risk of exposure to dietary mercury in this food web. Mercury concentrations in Gentoo and Adélie penguins were similar while Chinstrap penguins tended to have higher eggshell membrane mercury concentrations than their congeners. However, inter and intra-specific differences in eggshell membrane mercury concentration were not related to eggshell δ 15 N or δ 13 C values, a likely result of all three species foraging at similar trophic positions. The lack of regional-scale differences in mercury availability in this marine ecosystem may be a reflection of generally uniform atmospheric deposition and upwelling of regionally homogeneous deep water rather than from geographically distinct point sources. -- Highlights: ► We examined regional patterns of mercury availability in the Antarctic Peninsula. ► Three species of Pygoscelis penguins were used as biomonitors. ► Chinstrap penguins tended to have higher mercury

[Adsorption characteristics of proteins on membrane surface and effect of protein solution environment on permeation behavior of berberine].

Science.gov (United States)

Li, Yi-Qun; Xu, Li; Zhu, Hua-Xu; Tang, Zhi-Shu; Li, Bo; Pan, Yong-Lan; Yao, Wei-Wei; Fu, Ting-Ming; Guo, Li-Wei

2017-10-01

In order to explore the adsorption characteristics of proteins on the membrane surface and the effect of protein solution environment on the permeation behavior of berberine, berberine and proteins were used as the research object to prepare simulated solution. Low field NMR, static adsorption experiment and membrane separation experiment were used to study the interaction between the proteins and ceramic membrane or between the proteins and berberine. The static adsorption capacity of proteins, membrane relative flux, rejection rate of proteins, transmittance rate of berberine and the adsorption rate of proteins and berberine were used as the evaluation index. Meanwhile, the membrane resistance distribution, the particle size distribution and the scanning electron microscope (SEM) were determined to investigate the adsorption characteristics of proteins on ceramic membrane and the effect on membrane separation process of berberine. The results showed that the ceramic membrane could adsorb the proteins and the adsorption model was consistent with Langmuir adsorption model. In simulating the membrane separation process, proteins were the main factor to cause membrane fouling. However, when the concentration of proteins was 1 g•L⁻¹, the proteins had no significant effect on membrane separation process of berberine. Copyright© by the Chinese Pharmaceutical Association.

Enriched glucose and dextrin mannitol-based media modulates fibroblast behavior on bacterial cellulose membranes

Energy Technology Data Exchange (ETDEWEB)

Stumpf, Taisa R.; Pértile, Renata A.N. [Integrated Technologies Laboratory, Department of Chemical and Food Engineering (Brazil); Rambo, Carlos R., E-mail: rambo@intelab.ufsc.br [Department of Electrical Engineering, Federal University of Santa Catarina, Florianópolis 88040-900 (Brazil); Porto, Luismar M. [Integrated Technologies Laboratory, Department of Chemical and Food Engineering (Brazil)

2013-12-01

Bacterial cellulose (BC) produced by Gluconacetobacter hansenii is a suitable biopolymer for biomedical applications. In order to modulate the properties of BC and expand its use as substrate for tissue engineering mainly in the form of biomembranes, glucose or dextrin were added into a BC fermentation mannitol-based medium (BCGl and BCDe, respectively) under static culture conditions. SEM images showed effects on fiber density and porosity on both sides of the BC membranes. Both enriched media decreased the BET surface area, water holding capacity, and rehydration rate. Fourier transform infrared (attenuated total reflectance mode) spectroscopy (FTIR-ATR) analysis revealed no change in the chemical structure of BC. L929 fibroblast cells were seeded on all BC-based membranes and evaluated in aspects of cell adhesion, proliferation and morphology. BCG1 membranes showed the highest biological performance and hold promise for the use in tissue engineering applications. - Highlights: • Glucose and dextrin were used to modify culture media for BC production. • Microarchitecture of BC was different depending on the enriching agent. • Fibroblasts adhered on the surface of BC modified microarchitectures. • Fibroblasts adhered on glucose modified BC exhibited healthy cell morphology.

Enriched glucose and dextrin mannitol-based media modulates fibroblast behavior on bacterial cellulose membranes

International Nuclear Information System (INIS)

Stumpf, Taisa R.; Pértile, Renata A.N.; Rambo, Carlos R.; Porto, Luismar M.

2013-01-01

Bacterial cellulose (BC) produced by Gluconacetobacter hansenii is a suitable biopolymer for biomedical applications. In order to modulate the properties of BC and expand its use as substrate for tissue engineering mainly in the form of biomembranes, glucose or dextrin were added into a BC fermentation mannitol-based medium (BCGl and BCDe, respectively) under static culture conditions. SEM images showed effects on fiber density and porosity on both sides of the BC membranes. Both enriched media decreased the BET surface area, water holding capacity, and rehydration rate. Fourier transform infrared (attenuated total reflectance mode) spectroscopy (FTIR-ATR) analysis revealed no change in the chemical structure of BC. L929 fibroblast cells were seeded on all BC-based membranes and evaluated in aspects of cell adhesion, proliferation and morphology. BCG1 membranes showed the highest biological performance and hold promise for the use in tissue engineering applications. - Highlights: • Glucose and dextrin were used to modify culture media for BC production. • Microarchitecture of BC was different depending on the enriching agent. • Fibroblasts adhered on the surface of BC modified microarchitectures. • Fibroblasts adhered on glucose modified BC exhibited healthy cell morphology

Materials Genomics Screens for Adaptive Ion Transport Behavior by Redox-Switchable Microporous Polymer Membranes in Lithium-Sulfur Batteries.

Science.gov (United States)

Ward, Ashleigh L; Doris, Sean E; Li, Longjun; Hughes, Mark A; Qu, Xiaohui; Persson, Kristin A; Helms, Brett A

2017-05-24

Selective ion transport across membranes is critical to the performance of many electrochemical energy storage devices. While design strategies enabling ion-selective transport are well-established, enhancements in membrane selectivity are made at the expense of ionic conductivity. To design membranes with both high selectivity and high ionic conductivity, there are cues to follow from biological systems, where regulated transport of ions across membranes is achieved by transmembrane proteins. The transport functions of these proteins are sensitive to their environment: physical or chemical perturbations to that environment are met with an adaptive response. Here we advance an analogous strategy for achieving adaptive ion transport in microporous polymer membranes. Along the polymer backbone are placed redox-active switches that are activated in situ, at a prescribed electrochemical potential, by the device's active materials when they enter the membrane's pore. This transformation has little influence on the membrane's ionic conductivity; however, the active-material blocking ability of the membrane is enhanced. We show that when used in lithium-sulfur batteries, these membranes offer markedly improved capacity, efficiency, and cycle-life by sequestering polysulfides in the cathode. The origins and implications of this behavior are explored in detail and point to new opportunities for responsive membranes in battery technology development.

Protein-centric N-glycoproteomics analysis of membrane and plasma membrane proteins.

Science.gov (United States)

Sun, Bingyun; Hood, Leroy

2014-06-06

The advent of proteomics technology has transformed our understanding of biological membranes. The challenges for studying membrane proteins have inspired the development of many analytical and bioanalytical tools, and the techniques of glycoproteomics have emerged as an effective means to enrich and characterize membrane and plasma-membrane proteomes. This Review summarizes the development of various glycoproteomics techniques to overcome the hurdles formed by the unique structures and behaviors of membrane proteins with a focus on N-glycoproteomics. Example contributions of N-glycoproteomics to the understanding of membrane biology are provided, and the areas that require future technical breakthroughs are discussed.

Evaluation of the release behavior of the dexamethasone embedded in polycarbonate polyurethane membranes: an in vitro study

International Nuclear Information System (INIS)

Kim, Dong Hyun; Kang, Sung Gwon; Lee, Chul Gab; Park, Sang Soo; Lee, Don Haeng; Lee, Gyu Baek; Song, Ho Young

2003-01-01

To evaluate the release behavior of dexamethasone embedded in a polycarbonate polyurethane membrane. Both water-soluble and water-insoluble dexamethasone were tested, and the release behavior of five water-insoluble dexamethasone films of different thickness (78 to 211 μm) was also evaluated. The amount of dexamethasone used was 10% of the total weight of the polyurethan film mass. Each film was placed in a centrifuge tube containing 25 ml of 0.1-M neutral phosphate buffer, and the tubes were placed in a shaking incubator to quantify the amount of drug released into the buffer, absorption spectroscopy (λ max=242 nm) was employed. In the test involving water-soluble dexamethasone, 60%, of the drug was released during the first two hours of the study. Films containing water-insoluble dexamethasone, on the other hand, released 40%, 60% and 75% of the dexamethasone in one, three and seven days, respectively. Both types of film maintained low-dose drug release for 28 days. When release behavior was compared between water-insoluble films of different thickness, thicker film showed less initial burst and more sustained release. Dexamethasone release behavior varies according to drug solubility and membrane thickness, and may thus be conrolled

On the freezing behavior and diffusion of water in proximity to single-supported zwitterionic and anionic bilayer lipid membranes

DEFF Research Database (Denmark)

Miskowiec, A.; Buck, Z. N.; Brown, M. C.

2014-01-01

We compare the freezing/melting behavior of water hydrating single-supported bilayers of a zwitterionic lipid DMPC with that of an anionic lipid DMPG. For both membranes, the temperature dependence of the elastically scattered neutron intensity indicates distinct water types undergoing...... translational diffusion: bulk-like water probably located above the membrane and two types of confined water closer to the lipid head groups. The membranes differ in the greater width of the water freezing transition near the anionic DMPG bilayer compared to zwitterionic DMPC as well as in the abruptness...

Behavior as a Reflection of Man’s Moral and Aesthetic Nature

Directory of Open Access Journals (Sweden)

Botakoz A. Zhekibaeva

2013-01-01

Full Text Available The article studies crucial problem of moral and aesthetic nature of an individual, which is considered as a problem of dialectical, contradictory relation of consciousness, its spiritual content and actual behavioral manifestations by psychological and educational literature. Man’s moral and aesthetic nature is revealed on the basis of study of scientific works by Russian and foreign scientists. It is a social and natural integrity, an organic and indissoluble unity of moral, aesthetic, corporal, aesthetic and external artistic and expressive nature. The article justifies the idea that behavior, reflecting the moral and aesthetic nature of personality is indicator of his/her moral and aesthetic development, maturity of moral qualities, educated aesthetic perception, subtle emotional reactions on moral and aesthetic manifestations and their keen perception

Development of III-Sb metamorphic DBR membranes on InP for vertical cavity laser applications

Science.gov (United States)

Addamane, S. J.; Mansoori, A.; Renteria, E. J.; Dawson, N.; Shima, D. M.; Rotter, T. J.; Hains, C. P.; Dawson, L. R.; Balakrishnan, G.

2016-04-01

Sb-based metamorphic DBR membranes are developed for InP-based vertical cavity laser applications. The reflectivity of the metamorphic DBR membrane is compared to the reflectivity of a lattice-matched DBR to characterize the optical quality of the DBR membrane. The metamorphic interface between InP and the III-antimonides is found to degrade the reflectivity of the DBR. Therefore, the growth temperature for the metamorphic DBR is optimized in order to obtain highly reflective (>99.8%) III-Sb thin-film membranes.

Membrane interaction of retroviral Gag proteins

Directory of Open Access Journals (Sweden)

Robert Alfred Dick

2014-04-01

Full Text Available Assembly of an infectious retroviral particle relies on multimerization of the Gag polyprotein at the inner leaflet of the plasma membrane. The three domains of Gag common to all retroviruses-- MA, CA, and NC-- provide the signals for membrane binding, assembly, and viral RNA packaging, respectively. These signals do not function independently of one another. For example, Gag multimerization enhances membrane binding and is more efficient when NC is interacting with RNA. MA binding to the plasma membrane is governed by several principles, including electrostatics, recognition of specific lipid head groups, hydrophobic interactions, and membrane order. HIV-1 uses many of these principles while Rous sarcoma virus (RSV appears to use fewer. This review describes the principles that govern Gag interactions with membranes, focusing on RSV and HIV-1 Gag. The review also defines lipid and membrane behavior, and discusses the complexities in determining how lipid and membrane behavior impact Gag membrane binding.

Materials Genomics Screens for Adaptive Ion Transport Behavior by Redox-Switchable Microporous Polymer Membranes in Lithium–Sulfur Batteries

Science.gov (United States)

2017-01-01

Selective ion transport across membranes is critical to the performance of many electrochemical energy storage devices. While design strategies enabling ion-selective transport are well-established, enhancements in membrane selectivity are made at the expense of ionic conductivity. To design membranes with both high selectivity and high ionic conductivity, there are cues to follow from biological systems, where regulated transport of ions across membranes is achieved by transmembrane proteins. The transport functions of these proteins are sensitive to their environment: physical or chemical perturbations to that environment are met with an adaptive response. Here we advance an analogous strategy for achieving adaptive ion transport in microporous polymer membranes. Along the polymer backbone are placed redox-active switches that are activated in situ, at a prescribed electrochemical potential, by the device’s active materials when they enter the membrane’s pore. This transformation has little influence on the membrane’s ionic conductivity; however, the active-material blocking ability of the membrane is enhanced. We show that when used in lithium–sulfur batteries, these membranes offer markedly improved capacity, efficiency, and cycle-life by sequestering polysulfides in the cathode. The origins and implications of this behavior are explored in detail and point to new opportunities for responsive membranes in battery technology development. PMID:28573201

Penguin eggshell membranes reflect homogeneity of mercury in the marine food web surrounding the Antarctic Peninsula

Energy Technology Data Exchange (ETDEWEB)

Brasso, Rebecka L., E-mail: rlb1196@uncw.edu [University of North Carolina Wilmington, Department of Biology and Marine Biology, 601 South College Road, Wilmington, NC 28403 (United States); Polito, Michael J. [University of North Carolina Wilmington, Department of Biology and Marine Biology, 601 South College Road, Wilmington, NC 28403 (United States); Lynch, Heather J. [Ecology and Evolution Department, 640 Life Sciences Bldg., Stony Brook University, Stony Brook, NY 11794 (United States); Naveen, R. [Oceanites Inc., PO Box 15259, Chevy Chase, MD 20825 (United States); Emslie, Steven D. [University of North Carolina Wilmington, Department of Biology and Marine Biology, 601 South College Road, Wilmington, NC 28403 (United States)

2012-11-15

Remote regions such as the Antarctic have become increasingly important for investigations into far-reaching anthropogenic impacts on the environment, most recently in regard to the global mercury cycle. Spatial patterns of mercury availability in four regions of the Antarctic Peninsula were investigated using three species of sympatrically breeding Pygoscelis penguins as biomonitors. Eggshells with intact membranes from Adelie, Gentoo, and Chinstrap penguins were collected at 24 breeding colonies in the South Orkney Islands, South Shetland Islands, eastern Antarctic Peninsula, and western Antarctic Peninsula during the 2006/2007 austral summer. In addition, we compared eggshell membrane mercury concentrations with eggshell stable isotope values ({delta}{sup 15}N and {delta}{sup 13}C) to determine if species-specific trophic or foraging habitat preferences influenced female mercury exposure prior to breeding. With few exceptions, mercury concentrations were found to be fairly homogeneous throughout the Antarctic Peninsula suggesting little spatial variation in the risk of exposure to dietary mercury in this food web. Mercury concentrations in Gentoo and Adelie penguins were similar while Chinstrap penguins tended to have higher eggshell membrane mercury concentrations than their congeners. However, inter and intra-specific differences in eggshell membrane mercury concentration were not related to eggshell {delta}{sup 15}N or {delta}{sup 13}C values, a likely result of all three species foraging at similar trophic positions. The lack of regional-scale differences in mercury availability in this marine ecosystem may be a reflection of generally uniform atmospheric deposition and upwelling of regionally homogeneous deep water rather than from geographically distinct point sources. -- Highlights: Black-Right-Pointing-Pointer We examined regional patterns of mercury availability in the Antarctic Peninsula. Black-Right-Pointing-Pointer Three species of Pygoscelis

Parental Reflective Functioning Moderates the Relationship between Difficult Temperament in Infancy and Behavior Problems in Toddlerhood

Science.gov (United States)

Wong, Kristyn; Stacks, Ann M.; Rosenblum, Katherine L.; Muzik, Maria

2017-01-01

This study assessed the links between infant negative affect, parental reflective functioning (RF), and toddler behavior problems in a sample of 84 women and their infants. Mothers provided self-report demographic data and completed the Infant Behavior Questionnaire-Revised during a home visit when the infant was 7 months old. They also completed…

Improved surface property of PVDF membrane with amphiphilic zwitterionic copolymer as membrane additive

Energy Technology Data Exchange (ETDEWEB)

Li Jianhua, E-mail: jhli_2005@163.com [Institute of Biomedical and Pharmaceutical Technology and College of Chemistry and Chemical Engineering, Fuzhou University, Fuzhou 350001 (China); Li Mizi; Miao Jing; Wang Jiabin; Shao Xisheng [Institute of Biomedical and Pharmaceutical Technology and College of Chemistry and Chemical Engineering, Fuzhou University, Fuzhou 350001 (China); Zhang Qiqing, E-mail: zhangqiq@126.com [Institute of Biomedical and Pharmaceutical Technology and College of Chemistry and Chemical Engineering, Fuzhou University, Fuzhou 350001 (China) and Institute of Biomedical Engineering, Chinese Academy of Medical Science, Peking Union Medical College, Tianjin 300192 (China)

2012-06-15

An attempt to improve hydrophilicity and anti-fouling properties of PVDF membranes, a novel amphiphilic zwitterionic copolymer poly(vinylidene fluoride)-graft-poly(sulfobetaine methacrylate) (PVDF-g-PSBMA) was firstly synthesized by atom transfer radical polymerization (ATRP) and used as amphiphilic copolymer additive in the preparation of PVDF membranes. The PVDF-g-PSBMA/PVDF blend membranes were prepared by immersion precipitation process. Fourier transform infrared attenuated reflection spectroscopy (FTIR-ATR) and X-ray photoelectronic spectroscopy (XPS) measurements confirmed that PSBMA brushes from amphiphilic additives were preferentially segregated to membrane-coagulant interface during membrane formation. The morphology of membranes was characterized by scanning electron microscopy (SEM). Water contact angle measurements showed that the surface hydrophilicity of PVDF membranes was improved significantly with the increasing of amphiphilic copolymer PVDF-g-PSBMA in cast solution. Protein static adsorption experiment and dynamic fouling resistance experiment revealed that the surface enrichment of PSBMA brush endowed PVDF blend membrane great improvement of surface anti-fouling ability.

Improved surface property of PVDF membrane with amphiphilic zwitterionic copolymer as membrane additive

International Nuclear Information System (INIS)

Li Jianhua; Li Mizi; Miao Jing; Wang Jiabin; Shao Xisheng; Zhang Qiqing

2012-01-01

An attempt to improve hydrophilicity and anti-fouling properties of PVDF membranes, a novel amphiphilic zwitterionic copolymer poly(vinylidene fluoride)-graft-poly(sulfobetaine methacrylate) (PVDF-g-PSBMA) was firstly synthesized by atom transfer radical polymerization (ATRP) and used as amphiphilic copolymer additive in the preparation of PVDF membranes. The PVDF-g-PSBMA/PVDF blend membranes were prepared by immersion precipitation process. Fourier transform infrared attenuated reflection spectroscopy (FTIR-ATR) and X-ray photoelectronic spectroscopy (XPS) measurements confirmed that PSBMA brushes from amphiphilic additives were preferentially segregated to membrane-coagulant interface during membrane formation. The morphology of membranes was characterized by scanning electron microscopy (SEM). Water contact angle measurements showed that the surface hydrophilicity of PVDF membranes was improved significantly with the increasing of amphiphilic copolymer PVDF-g-PSBMA in cast solution. Protein static adsorption experiment and dynamic fouling resistance experiment revealed that the surface enrichment of PSBMA brush endowed PVDF blend membrane great improvement of surface anti-fouling ability.

Membrane-initiated non-genomic signaling by estrogens in the hypothalamus: cross-talk with glucocorticoids with implications for behavior

Directory of Open Access Journals (Sweden)

Jennifer eRainville

2015-02-01

Full Text Available The estrogen receptor (ER and glucocorticoid receptor (GR are members of the nuclear receptor superfamily that can signal using both non-genomic and genomic transcriptional modes. Though genomic modes of signaling have been well characterized and several behaviors attributed to this signaling mechanism, the physiological significance of non-genomic modes of signaling has not been well understood. This has partly been due to the controversy regarding the identity of the membrane ER (mER or membrane GR (mGR that may mediate rapid, non-genomic signaling and the downstream signaling cascades that may result as a consequence of steroid ligands binding the mER or the mGR. Both estrogens and glucocorticoids exert a number of actions on the hypothalamus, including feedback. This review focuses on the various candidates for the mER or mGR in the hypothalamus and the contribution of non-genomic signaling to classical hypothalamically-driven behaviors and changes in neuronal morphology. It also attempts to categorize some of the possible functions of non-genomic signaling at both the cellular level and at the organismal level that are relevant for behavior, including some behaviors that are regulated by both estrogens and glucocorticoids in a potentially synergistic manner. Lastly, it attempts to show that steroid signaling via non-genomic modes may provide the organism with rapid behavioral responses to stimuli.

Mixed gas plasticization phenomena in asymmetric membranes

NARCIS (Netherlands)

Visser, Tymen

2006-01-01

This thesis describes the thorough investigation of mixed gas transport behavior of asymmetric membranes in the separation of feed streams containing plasticizing gases in order to gain more insights into the complicated behavior of plasticization. To successfully employ gas separation membranes in

Regulation of adhesion behavior of murine macrophage using supported lipid membranes displaying tunable mannose domains

International Nuclear Information System (INIS)

Kaindl, T; Oelke, J; Kaufmann, S; Tanaka, M; Pasc, A; Konovalov, O V; Funari, S S; Engel, U; Wixforth, A

2010-01-01

Highly uniform, strongly correlated domains of synthetically designed lipids can be incorporated into supported lipid membranes. The systematic characterization of membranes displaying a variety of domains revealed that the equilibrium size of domains significantly depends on the length of fluorocarbon chains, which can be quantitatively interpreted within the framework of an equivalent dipole model. A mono-dispersive, narrow size distribution of the domains enables us to treat the inter-domain correlations as two-dimensional colloidal crystallization and calculate the potentials of mean force. The obtained results demonstrated that both size and inter-domain correlation can precisely be controlled by the molecular structures. By coupling α-D-mannose to lipid head groups, we studied the adhesion behavior of the murine macrophage (J774A.1) on supported membranes. Specific adhesion and spreading of macrophages showed a clear dependence on the density of functional lipids. The obtained results suggest that such synthetic lipid domains can be used as a defined platform to study how cells sense the size and distribution of functional molecules during adhesion and spreading.

Binge drinking, reflection impulsivity, and unplanned sexual behavior: impaired decision-making in young social drinkers.

Science.gov (United States)

Townshend, Julia M; Kambouropoulos, Nicolas; Griffin, Alison; Hunt, Frances J; Milani, Raffaella M

2014-04-01

The repeated pattern of heavy intoxication followed by withdrawal from alcohol (i.e., "binge drinking") has been found to have substantial adverse effects on prefrontal neural systems associated with decision-making and impulse control. Repeated binge drinking has been linked to risky and unplanned sexual behavior; however few studies have examined the role of impulsivity and related cognitive processes in understanding this association. The aim of this study was to examine the relationship between binge drinking, "reflection impulsivity" (deficits in gathering and evaluating information during decision-making), alcohol-related expectancies, and unplanned sexual behavior in a sample of young social drinkers. Ninety-two university students completed the alcohol use questionnaire (AUQ) to measure alcohol intake and binge drinking. Two groups (low-binge and high-binge) were generated from the AUQ data. The Information Sampling Task (IST) was used to measure reflection impulsivity; the Alcohol Expectancy Questionnaire (AEQ) for alcohol outcome expectancies; and an unplanned sexual behavior questionnaire, which asked about the number of unplanned sexual events. When compared to the low-binge drinking group, the high-binge drinkers had significantly more unplanned sexual encounters and were impaired on the IST, reflection-impulsivity task. They scored higher on the alcohol expectancy factors of sociability, risk and aggression, negative self-perception, and in particular liquid courage. In a regression analysis, number of unplanned sexual encounters, binge drinking score, and liquid courage were all significantly related. These results support the role of binge drinking in reduced impulse control and decision-making deficits. The findings indicate that high-binge drinkers demonstrate impairments on an impulse control task similar to that observed in dependent samples and this may be a factor in understanding the negative behavioral consequences associated with excessive

Styrene-Based Copolymer for Polymer Membrane Modifications

OpenAIRE

Harsha Srivastava; Harshad Lade; Diby Paul; G. Arthanareeswaran; Ji Hyang Kweon

2016-01-01

Poly(vinylidene fluoride) (PVDF) was modified with a styrene-based copolymer. The crystalline behavior, phase, thermal stability, and surface morphology of the modified membranes were analyzed. The membrane surface roughness showed a strong dependence on the styrene-acrylonitrile content and was reduced to 34% for a PVDF/styrene-acrylonitrile blend membrane with a 40/60 ratio. The thermal and crystalline behavior confirmed the blend miscibility of both polymers. It was observed in X-ray diffr...

Lignin-based membranes for electrolyte transference

Energy Technology Data Exchange (ETDEWEB)

Zhang, Xiao; Garcia-Valls, Ricard [Departament d' Enginyeria Quimica, Escola Tecnica Superior d' Enginyeria Quimica, Universitat Rovira i Virgili, Av. Paisos Catalans 26, 43007 Tarragona (Spain); Benavente, Juana [Department of Applied Fisics, Faculty of Science, University of Malaga, Malaga (Spain)

2005-08-18

Homogeneous PSf-LS membranes are formed by incorporating Lignosulfonate (LS) into the Polysulfone (PSf) network. LS obtained from sulfite pulping process contains sulfonic acid groups that will act as proton transport media. PSf-LS membranes were characterized by reflectance Infrared and scanning electron microscopy. LS showed significant influence on membrane morphology. Higher LS concentration caused a decrease in macrovoid formation and induced larger pores. Precipitation temperature was investigated as influencing parameter. Proton fluxes through PSf-LS membranes were measured by transport experiments. Impedance analysis confirmed that PSf-LS membranes possess ion conductivity. The selected PSf-LS membranes exhibited high selectivity for proton over methanol, which indicates their potential applicability in direct methanol fuel cell (DMFC). (author)

Behavior of the P1.HTR mastocytoma cell line implanted in the chorioallantoic membrane of chick embryos

Directory of Open Access Journals (Sweden)

S.F. Avram

2013-01-01

Full Text Available The P1.HTR cell line includes highly transfectable cells derived from P815 mastocytoma cells originating from mouse breast tissue. Despite its widespread use in immunogenic studies, no data are available about the behavior of P1.HTR cells in the chick embryo chorioallantoic membrane model. The objective of the present investigation was to study the effects of P1.HTR cells implanted on the chorioallantoic membrane of chick embryos. We inoculated P1.HTR cells into the previously prepared chick embryo chorioallantoic membrane and observed the early and late effects of these cells by stereomicroscopy, histochemistry and immunohistochemistry. A highly angiotropic and angiogenic effect occurred early after inoculation and a tumorigenic potential with the development of mastocytoma keeping well mast cells immunophenotype was detected later during the development. The P1.HTR mastocytoma cell line is a good tool for the development of the chick embryo chorioallantoic membrane mastocytoma model and also for other studies concerning the involvement of blood vessels. The chick embryo chorioallantoic membrane model of mastocytoma retains the mast cell immunophenotype under experimental conditions and could be used as an experimental tool for in vivo preliminary testing of antitumor and antivascular drugs.

Study on the Fouling Behavior of Polyethylene and Silica Nanoparticles Mixed Matrix Membranes in Filtration of Humic Acid Solution

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Ali Akbari

2016-09-01

Full Text Available Because most contaminants in water create strong interactions with hydrophobic surfaces, there are usually problems such as flux decline and pore blocking in polyethylene (PE membranes due to irreversible adsorption of foulants on their intrinsic hydrophobic surface. Therefore, in this work, attempts were made to improve the properties of PE membranes in terms of water flux and membrane fouling resistance by dispersion of silica nanoparticles (NPs. First, NPs were synthesized by sol-gel method at two concentrations of ammonia (0.5 and 1 mol/L. The synthesized NPs with smaller size were used to fabricate the mixed matrix PE membranes containing 0, 0.5, 1 and 2 wt% NPs. FE-SEM and EDX analyses were employed to evaluate the morphology and structure of the fabricated membranes and confirmed the presence of NPs in the membranes matrix. The results of pure water flux test revealed that the membrane containing 1 wt% NPs displayed the maximum flux of 30 L/m2.h. Furthermore, the performance and fouling behaviors of membranes during filtration of humic acid solution, one of the most important contaminants of water resources, were studied using a classical fouling model. Fouling mechanism analysis showed that for neat and NPs-embedded membranes containing 0.5 and 2 wt% NPs, the best fit of the data was obtained by cake layer formation as well as the intermediate blocking mechanisms. However, the best fit of the experimental data of NPs-embedded membrane containing 1 wt% occurred with only cake layer formation mechanism. The investigation on membrane fouling resistance showed that 1 wt% NPs-embedded membrane displayed 58% maximum flux recovery and 52% reversibility to total fouling ratio, respectively.

Study of the Mechanical Behavior of a Hyperelastic Membrane

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Bourbaba Houaria

2014-04-01

Full Text Available The benefits in emloying plastics material in microfluidic devices manufactures are extremely attractive that include reduced cost and simplified manufacturing procedures, particularly when compared to silicon. An additional benefit is the wide range of available plastic materials which allow the manufacturer to choose materials' properties suitable for their specific application. The Polydimethylsiloxane is commonly used in a wide range of microfluidic applications due to its flexibility and low cost. In addition the properties of the Polymethyl methacrylate such as the low cost, high transparency, and good chemical properties are needed in microfluidics applications. In this paper, we have used Finit Elements method to simulate the mechanical behavior of Polydimethylsiloxane and Polymethylmethacrylate using hyper elastic and linear elastic model. Sevral parameters have been studied; such as, thickness and number of mesh in order to optimize the dimension of the membrane. Also, we have studied the impact of the mesh form on the membrane’s displacement.

Pervaporation and sorption behavior of zeolite-filled polyethylene glycol hybrid membranes for the removal of thiophene species.

Science.gov (United States)

Lin, Ligang; Zhang, Yuzhong; Li, Hong

2010-10-01

Polyethylene glycol (PEG)-CuY zeolite hybrid membranes were prepared for sulfur removal from gasoline feed. The sorption and diffusion behavior of typical gasoline components through the hybrid membranes has been investigated by systematic studies of dynamic sorption curves. Influencing factors including feed temperature, permeate pressure, and zeolite content in the membranes on membrane performance have been evaluated. Immersion experiments results showed the preferential sorption of thiophene, which is key in fulfilling the separation of thiophene/hydrocarbon mixtures. The sorption, diffusion, and permeation coefficients of gasoline components in filled membranes are higher than those in unfilled membranes. Pervaporation (PV) and gas chromatography (GC) experiments results corresponded to the discussions on dynamic sorption curves. PV experiments showed that lower permeate pressure meant higher separation performance. The optimum temperature occurred at 383K, and an Arrhenius relationship existed between permeation flux and operating temperature. The CuY zeolite filling led to a significant increase of flux since the porous zeolite provides for more diffusion for small molecules in mixed matrix membranes. The sulfur enrichment factor increased first and then decreased with the increasing zeolite content, which was attributed to the combined influence of complexation force between CuY and thiophenes as well as the trade-off phenomenon between flux and selectivity. At 9 wt% CuY content, a higher permeation flux (3.19 kg/(m(2) h)) and sulfur enrichment factor (2.95) were obtained with 1190 microg/g sulfur content level in gasoline feed. Copyright 2010 Elsevier Inc. All rights reserved.

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

Effect of membrane and through-wall bending stresses on fatigue crack growth behavior and coolant leakage velocity

International Nuclear Information System (INIS)

Yoo, Yeon-Sik

2003-11-01

This study clarified the effect of a membrane and a through-wall bending stresses on fatigue crack growth behavior and coolant leakage velocity due to irregularity of crack surface. Each stress component relates to fatigue crack growth behavior directly in general and thus the wild-used K I solutions are anticipated to give good evaluation results on it. Meanwhile, it is necessary to notify that surface irregularity for coolant leakage assessment is made by stress history in nature. Surface irregularity is known to be largely classified into the following two aspects: surface roughness due to continuous crack opening and closure behavior and surface turnover due to cyclic bending stress dominance. Therefore, the deterministic parameters on resistance of coolant leakage by surface irregularity are considered to be not only stress history but crack opening behavior. (author)

Contact behavior modelling and its size effect on proton exchange membrane fuel cell

Science.gov (United States)

Qiu, Diankai; Peng, Linfa; Yi, Peiyun; Lai, Xinmin; Janßen, Holger; Lehnert, Werner

2017-10-01

Contact behavior between the gas diffusion layer (GDL) and bipolar plate (BPP) is of significant importance for proton exchange membrane fuel cells. Most current studies on contact behavior utilize experiments and finite element modelling and focus on fuel cells with graphite BPPs, which lead to high costs and huge computational requirements. The objective of this work is to build a more effective analytical method for contact behavior in fuel cells and investigate the size effect resulting from configuration alteration of channel and rib (channel/rib). Firstly, a mathematical description of channel/rib geometry is outlined in accordance with the fabrication of metallic BPP. Based on the interface deformation characteristic and Winkler surface model, contact pressure between BPP and GDL is then calculated to predict contact resistance and GDL porosity as evaluative parameters of contact behavior. Then, experiments on BPP fabrication and contact resistance measurement are conducted to validate the model. The measured results demonstrate an obvious dependence on channel/rib size. Feasibility of the model used in graphite fuel cells is also discussed. Finally, size factor is proposed for evaluating the rule of size effect. Significant increase occurs in contact resistance and porosity for higher size factor, in which channel/rib width decrease.

Comparison of biofouling mechanisms between cellulose triacetate (CTA) and thin-film composite (TFC) polyamide forward osmosis membranes in osmotic membrane bioreactors.

Science.gov (United States)

Wang, Xinhua; Zhao, Yanxiao; Yuan, Bo; Wang, Zhiwei; Li, Xiufen; Ren, Yueping

2016-02-01

There are two types of popular forward osmosis (FO) membrane materials applied for researches on FO process, cellulose triacetate (CTA) and thin film composite (TFC) polyamide. However, performance and fouling mechanisms of commercial TFC FO membrane in osmotic membrane bioreactors (OMBRs) are still unknown. In current study, its biofouling behaviors in OMBRs were investigated and further compared to the CTA FO membrane. The results indicated that β-D-glucopyranose polysaccharides and microorganisms accounted for approximately 77% of total biovolume on the CTA FO membrane while β-D-glucopyranose polysaccharides (biovolume ratio of 81.1%) were the only dominant biofoulants on the TFC FO membrane. The analyses on the biofouling structure implied that a tighter biofouling layer with a larger biovolume was formed on the CTA FO membrane. The differences in biofouling behaviors including biofoulants composition and biofouling structure between CTA and TFC FO membranes were attributed to different membrane surface properties. Copyright © 2015 Elsevier Ltd. All rights reserved.

A Triadic Reflective-Impulsive-Interoceptive Awareness Model of General and Impulsive Information System Use: Behavioral Tests of Neuro-Cognitive Theory.

Science.gov (United States)

Turel, Ofir; Bechara, Antoine

2016-01-01

This study examines a behavioral tripartite model developed in the field of addiction, and applies it here to understanding general and impulsive information technology use. It suggests that technology use is driven by two information-processing brain systems: reflective and impulsive, and that their effects on use are modulated by interoceptive awareness processes. The resultant reflective-impulsive-interoceptive awareness model is tested in two behavioral studies. Both studies employ SEM techniques to time-lagged self-report data from n 1 = 300 and n 2 = 369 social networking site users. Study 1 demonstrated that temptations augment the effect of habit on technology use, and reduce the effect of satisfaction on use. Study 2 showed that temptations strengthen the effect of habit on impulsive technology use, and weaken the effect of behavioral expectations on impulsive technology use. Hence, the results consistently support the notion that information technology users' behaviors are influenced by reflective and impulsive information processing systems; and that the equilibrium of these systems is determined, at least in part, by one's temptations. These results can serve as a basis for understanding the etiology of modern day addictions.

Monitoring Protein Fouling on Polymeric Membranes Using Ultrasonic Frequency-Domain Reflectometry

Directory of Open Access Journals (Sweden)

Robin Fong

2011-08-01

Full Text Available Novel signal-processing protocols were used to extend the in situ sensitivity of ultrasonic frequency-domain reflectometry (UFDR for real-time monitoring of microfiltration (MF membrane fouling during protein purification. Different commercial membrane materials, with a nominal pore size of 0.2 µm, were challenged using bovine serum albumin (BSA and amylase as model proteins. Fouling induced by these proteins was observed in flat-sheet membrane filtration cells operating in a laminar cross-flow regime. The detection of membrane-associated proteins using UFDR was determined by applying rigorous statistical methodology to reflection spectra of ultrasonic signals obtained during membrane fouling. Data suggest that the total power reflected from membrane surfaces changes in response to protein fouling at concentrations as low as 14 μg/cm2, and results indicate that ultrasonic spectra can be leveraged to detect and monitor protein fouling on commercial MF membranes.

Modification of Salmonella Lipopolysaccharides Prevents the Outer Membrane Penetration of Novobiocin

Energy Technology Data Exchange (ETDEWEB)

Nobre, Thatyane M.; Martynowycz, Michael W.; Andreev, Konstantin; Kuzmenko, Ivan; Nikaido, Hiroshi; Gidalevitz, David

2015-12-01

Small hydrophilic antibiotics traverse the outer membrane of Gram-negative bacteria through porin channels. Large lipophilic agents traverse the outer membrane through its bilayer, containing a majority of lipopolysaccharides in its outer leaflet. Genes controlled by the two-component regulatory system PhoPQ modify lipopolysaccharides. We isolate lipopolysaccharides from isogenic mutants of Salmonella sp., one lacking the modification, the other fully modified. These lipopolysaccharides were reconstituted asmonolayers at the air-water interface, and their properties, aswell as their interaction with a large lipophilic drug, novobiocin, was studied. X-ray reflectivity showed that the drug penetrated the monolayer of the unmodified lipopolysaccharides reaching the hydrophobic region,butwas prevented fromthis penetration intothemodified lipopolysaccharides.Results correlatewith behavior of bacterial cells, which become resistant to antibiotics after PhoPQ-regulated modifications. Grazing incidence x-ray diffraction showed that novobiocin produced a striking increase in crystalline coherence length, and the size of the near-crystalline domains.

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)

Using Audience Response Systems to Encourage Student Engagement and Reflection on Ethical Orientation and Behavior

Science.gov (United States)

Micheletto, Melinda J.

2011-01-01

The purpose of this study was to use an audience response system (ARS) to engage students in classroom discussions concerning sensitive and controversial topics (e.g., business ethics), assess student's ethical orientation and conduct in unethical behaviors, and encourage reflection on their personal level of ethicality. Students used ARS devices…

Sensitive determination of trace mercury by UV-visible diffuse reflectance spectroscopy after complexation and membrane filtration-enrichment.

Science.gov (United States)

Yin, Changhai; Iqbal, Jibran; Hu, Huilian; Liu, Bingxiang; Zhang, Lei; Zhu, Bilin; Du, Yiping

2012-09-30

A simple, sensitive and selective solid phase reflectometry method is proposed for the determination of trace mercury in aqueous samples. The complexation reagent dithizone was firstly injected into the properly buffered solution with vigorous stirring, which started a simultaneous formation of nanoparticles suspension of dithizone and its complexation reaction with the mercury(II) ions to make Hg-dithizone nanoparticles. After a definite time, the mixture was filtered with membrane, and then quantified directly on the surface of the membrane by using integrating sphere accessory of the UV-visible spectrophotometer. The quantitative analysis was carried out at a wavelength of 485 nm since it yielded the largest difference in diffuse reflectance spectra before and after reaction with mercury(II).A good linear correlation in the range of 0.2-4.0 μg/L with a squared correlation coefficient (R(2)) of 0.9944 and a detection limit of 0.12 μg/L were obtained. The accuracy of the method was evaluated by the analysis of spiked mercury(II) concentrations determined using this method along with those determined by the atomic fluorescence mercury vapourmeter and the results obtained were in good agreement. The proposed method was applied to the determination of mercury in tap water and river water samples with the recovery in an acceptable range (95.7-105.3%). Copyright © 2012 Elsevier B.V. All rights reserved.

Formation of oriented membrane multilayers of Na/K-ATPase

International Nuclear Information System (INIS)

Pachence, J.M.; Knott, R.; Edelman, I.S.; Schoenborn, B.P.; Wallace, B.A.

1982-01-01

The isolated membrane-bound enzyme retains its ouabain-sensitive ATP hydrolysis activity, and produces ATP-dependent Na + and K + fluxes when incorporated into phospholipid vesicles. The ultimate goal of this work is to determine its low resolution structure using both X-ray and neutron diffraction. A number of methods were used to impart lamellar stacking order to highly purified pig Na/K-ATPase membranes. Upon partial dehydration, x-ray diffraction from Na/K-ATPase membrane multilayers at 98% relative humidity yielded discrete reflections of 118 A periodicity, diffracting to 1/14.8 A -1 , additionally, continuous diffraction to 1/10 A -1 was obtained. Subjecting the membrane multilayers to high magnetic fields improved the quality of the lamellar diffraction dramatically. Neutron diffraction studies of the partially dehydrated Na/K-ATPase membrane multilayers detected a mosaic spread of 2 0 when the samples were subjected to a magnetic field of 5 Tesla perpendicular to the membrane surface; the reflections were narrower than the camera line width; hence, the lattice disorder has also decreased significantly, although only four orders were measured

Homosexual Behavior in Female Mountain Gorillas: Reflection of Dominance, Affiliation, Reconciliation or Arousal?

Directory of Open Access Journals (Sweden)

Cyril C Grueter

Full Text Available Humans are unique among primates for not only engaging in same-sex sexual acts, but also forming homosexual pair bonds. To shed light on the evolutionary origins of homosexuality, data on the occurrence and contexts of same-sex behavior from nonhuman primates may be of particular significance. Homosexual behavior involving females is poorly researched in most primate taxa, exceptions being Japanese macaques, rhesus macaques, Hanuman langurs and bonobos. We present data on homosexual behavior in female mountain gorillas in the Virunga Volcanoes (Rwanda and test four functional hypotheses, namely reconciliation, affiliation, dominance expression and sexual arousal. Homosexual interactions between females involved both ventro-dorsal and ventro-ventral copulations accompanied by vocalizations and courtship displays. The only sociosexual hypothesis that received partial empirical support is the social status hypothesis, i.e., that mounting reaffirms the dominance hierarchy. There is also some limited evidence that same-sex behavior reflects an overall state of arousal or is triggered via a 'pornographic' effect. An adaptive function of female homosexual behavior is not readily apparent, and we tentatively conclude (until a more rigorous test becomes available that it may simply be related to sexual gratification or that it is an evolutionary by-product of an adaptation.

Homosexual Behavior in Female Mountain Gorillas: Reflection of Dominance, Affiliation, Reconciliation or Arousal?

Science.gov (United States)

Grueter, Cyril C; Stoinski, Tara S

2016-01-01

Humans are unique among primates for not only engaging in same-sex sexual acts, but also forming homosexual pair bonds. To shed light on the evolutionary origins of homosexuality, data on the occurrence and contexts of same-sex behavior from nonhuman primates may be of particular significance. Homosexual behavior involving females is poorly researched in most primate taxa, exceptions being Japanese macaques, rhesus macaques, Hanuman langurs and bonobos. We present data on homosexual behavior in female mountain gorillas in the Virunga Volcanoes (Rwanda) and test four functional hypotheses, namely reconciliation, affiliation, dominance expression and sexual arousal. Homosexual interactions between females involved both ventro-dorsal and ventro-ventral copulations accompanied by vocalizations and courtship displays. The only sociosexual hypothesis that received partial empirical support is the social status hypothesis, i.e., that mounting reaffirms the dominance hierarchy. There is also some limited evidence that same-sex behavior reflects an overall state of arousal or is triggered via a 'pornographic' effect. An adaptive function of female homosexual behavior is not readily apparent, and we tentatively conclude (until a more rigorous test becomes available) that it may simply be related to sexual gratification or that it is an evolutionary by-product of an adaptation.

Quantification of functional groups and modeling of their ionization behavior in the active layer of FT30 reverse osmosis membrane.

Science.gov (United States)

Coronell, Orlando; Mariñas, Benito J; Zhang, Xijing; Cahill, David G

2008-07-15

A new experimental approach was developed to measure the concentration of charged functional groups (FGs) in the active layer of thin-film composite reverse osmosis (RO) and nanofiltration (NF) membranes as a function of solution pH. FT30 RO membrane, with a fully aromatic polyamide (PA) active layer sandwiched between a polysulfone support and a coating layer, was used. The experiments consisted of saturating charged FGs with heavy ion probes, and determining the ion probe concentration by Rutherford backscattering spectrometry (RBS). Deprotonated carboxylic groups were saturated with Ag+, and protonated amine groups with W04(2-). The ionization behavior of carboxylic and amine groups was modeled based on acid-base equilibrium theory. While the ionization behavior of amine groups was satisfactorily described by one dissociation constant (pKa = 4.74), two pKa values (5.23 and 8.97) were necessary to describe the titration curve of carboxylic groups. These results were consistent with the bimodal pore size distribution (PSD) of FT30 active layer reported in the literature. The calculated total concentrations of carboxylic and amine groups in the active layer of the FT30 RO membrane studied were 0.432 and 0.036 M, respectively, and the isoelectric point (IEP) was 4.7. The total concentration of carboxylic and amine groups revealed that the degree of cross-linking of the PA active layer of the FT30 RO membrane studied was 94%.

[Determination of Trace Lead in Water by UV-Visible Diffuse Reflectance Spectroscopy Combined with Surfactant and Membrane Filtration-Enrichment].

Science.gov (United States)

Zhang, Xiao-fang; Zhu, Bi-lin; Li, Wei; Wang, Lei; Zhang, Lei; Wu, Ting; Du, Yi-ping

2015-07-01

In this paper, a method of determination of trace lead in water by UV-Visible diffuse reflectance spectroscopy combined with surfactant and membrane filtration enrichment was proposed. In the NH3 x H2O-NH4Cl buffer solution with pH 8.5, the lead(II) ion would react with dithizone to form the red complex under vigorous stirring, which is hydrophobic and can be enriched by the mixed cellulose ester membrane. In addition, the nonionic surfactant Polyoxyethylene lauryl ether (Brij-30) was added into the solution to improve the enrichment efficiency, then visible diffuse reflectance spectra of the membrane were measured directly after the membrane were naturally dried. We also optimized the reaction conditions which may affect the complexation reaction process, such as type of surfactants, the concentration of the surfactant, the reaction acidity, the concentration of dithizone as well as the reaction time. The research results show that under the optimum conditions, a good linear correlation between absorbance at 485 nm and concentration of lead in the range of 5.0-100.0 microg x L(-1) was obtained with a squared correlation coefficient (R2) of 0.9906, and the detection limit was estimated accordingly to be 2.88 microg x L(-1). To determine real water sample, the interference from some potential coexisting ions was also studied at the optimal conditions when the concentration of lead (II) ion standard solution was fixed to 20 microg x L(-1). The results indicate that the following ions cannot interfere in the determination of lead with the proposed method: 500 times of the K+, Na+, Ca2+, Mg2+, NH4+, NO3-, Cl-, CH3COO-, SO4(2-); 10 times of the Al3+ (using 10% NaF as a masking reagent to avoid the interference); 10 times of the Fe3+ (using 10% NaF and 10% sodium potassium tartrate as masking reagents); 10 times of Hg2+ or Zn2+ (using 10% NaSCN and 10% potassium sodium tartrate as masking reagents); the same amount of Cd2+, Cu2+. The proposed method was applied to the

Functionalized nanoparticle interactions with polymeric membranes.

Science.gov (United States)

Ladner, D A; Steele, M; Weir, A; Hristovski, K; Westerhoff, P

2012-04-15

A series of experiments was performed to measure the retention of a class of functionalized nanoparticles (NPs) on porous (microfiltration and ultrafiltration) membranes. The findings impact engineered water and wastewater treatment using membrane technology, characterization and analytical schemes for NP detection, and the use of NPs in waste treatment scenarios. The NPs studied were composed of silver, titanium dioxide, and gold; had organic coatings to yield either positive or negative surface charge; and were between 2 and 10nm in diameter. NP solutions were applied to polymeric membranes composed of different materials and pore sizes (ranging from ≈ 2 nm [3 kDa molecular weight cutoff] to 0.2 μm). Greater than 99% rejection was observed of positively charged NPs by negatively charged membranes even though pore diameters were up to 20 times the NP diameter; thus, sorption caused rejection. Negatively charged NPs were less well rejected, but behavior was dependent not only on surface functionality but on NP core material (Ag, TiO(2), or Au). NP rejection depended more upon NP properties than membrane properties; all of the negatively charged polymeric membranes behaved similarly. The NP-membrane interaction behavior fell into four categories, which are defined and described here. Copyright © 2011 Elsevier B.V. All rights reserved.

Enzyme immobilization by fouling in ultrafiltration membranes: Impact of membrane configuration and type on flux behavior and biocatalytic conversion efficacy

DEFF Research Database (Denmark)

Luo, Jianquan; Meyer, Anne S.; Jonsson, Gunnar Eigil

2014-01-01

Enzyme-immobilization in membranes accomplished by fostering membrane fouling was evaluated. Four different membrane configurations and five membranes were compared for immobilization of alcohol dehydrogenase (ADH) in terms of enzyme loading, permeate flux and final biocatalytic conversion...... and PLGC regenerated cellulose membranes. With these two highly hydrophilic membranes, the ADH enzyme activity was fully retained even after 24h of storage of the membrane. Filtration blocking and resistance models were used to analyze the fouling/immobilization mechanisms and give explanations...... for the different results. The work confirms that fouling-induced enzyme immobilization is a promising option for enhancing biocatalytic productivity, and highlights the significance of the membrane type and configuration for optimal performance....

Thermomechanical Response of Self-Assembled Nanoparticle Membranes

Energy Technology Data Exchange (ETDEWEB)

Wang, Yifan [Department; James; Chan, Henry [Center; Narayanan, Badri [Center; McBride, Sean P. [Department; Sankaranarayanan, Subramanian K. R. S. [Center; Lin, Xiao-Min [Center; Jaeger, Heinrich M. [Department; James

2017-07-21

Monolayers composed of colloidal nanoparticles, with a thickness of less than 10 nm, have remarkable mechanical moduli and can suspend over micrometer-sized holes to form free-standing membranes. In this paper, we discuss experiment's and coarse-grained molecular dynamics simulations characterizing the thermomechanical properties of these self-assembled nanoparticle membranes. These membranes remain strong and resilient up to temperatures much higher than previous simulation predictions and exhibit an unexpected hysteretic behavior during the first heating cooling cycle. We show this hysteretic behavior can be explained by an asymmetric ligand configuration from the self assembly process and can be controlled by changing the ligand coverage or cross-linking the ligand molecules. Finally, we show the screening effect of water molecules on the ligand interactions can strongly affect the moduli and thermomechanical behavior.

Functional polyelectrolyte multilayer membranes for water purification applications

International Nuclear Information System (INIS)

Tripathi, Bijay P.; Dubey, Nidhi C.; Stamm, M.

2013-01-01

Highlights: ► LBL film on the surface and in to the pores was prepared via flow through method. ► The membranes showed high rejection of Congo Red with sufficiently high flux. ► High antifouling ability in terms of both organic and bio fouling was observed. -- Abstract: A diverse set of supported multilayer assemblies with controllable surface charge, hydrophilicity, and permeability to water and solute was fabricated by pressure driven permeation of poly(sodium 4-styrenesulfonate) (PSS) and poly(diallyldimethylammonium chloride) (PDDA) solution through poly(ethylene terephthalate) (PET) track-etched membranes. The polyelectrolyte multilayer fabrication was confirmed by means of FTIR, SEM, AFM, ellipsometry, zetapotential, and contact angle characterization. The prepared membranes were characterized in terms of their pure water permeability, flux recovery, and resistance to organic and biofouling properties. The antifouling behavior of the membranes was assessed in terms of protein adsorption and antibacterial behavior. Finally, the membranes were tested for rejection of selected water soluble dyes to establish their usefulness for organic contaminant removal from water. The membranes were highly selective and capable of nearly complete rejection of congo red with sufficiently high fluxes. The feasibility of regenerating the prepared membranes fouled by protein was also demonstrated and good flux recovery was obtained. In summary, the multilayer approach to surface and pore modification was shown to enable the design of membranes with the unique combination of desirable separation characteristics, regenerability of the separation layer, and antifouling behavior

Functional polyelectrolyte multilayer membranes for water purification applications

Energy Technology Data Exchange (ETDEWEB)

Tripathi, Bijay P., E-mail: bijayptripathi@yahoo.com [Department of Nanostructured Materials, Leibniz Institute of Polymer Research Dresden, Hohe Str. 6, 01069 Dresden (Germany); Dubey, Nidhi C. [Department of Nanostructured Materials, Leibniz Institute of Polymer Research Dresden, Hohe Str. 6, 01069 Dresden (Germany); Technische Universität Dresden, Department of Chemistry, 01069 Dresden (Germany); Stamm, M., E-mail: stamm@ipfdd.de [Department of Nanostructured Materials, Leibniz Institute of Polymer Research Dresden, Hohe Str. 6, 01069 Dresden (Germany); Technische Universität Dresden, Department of Chemistry, 01069 Dresden (Germany)

2013-05-15

Highlights: ► LBL film on the surface and in to the pores was prepared via flow through method. ► The membranes showed high rejection of Congo Red with sufficiently high flux. ► High antifouling ability in terms of both organic and bio fouling was observed. -- Abstract: A diverse set of supported multilayer assemblies with controllable surface charge, hydrophilicity, and permeability to water and solute was fabricated by pressure driven permeation of poly(sodium 4-styrenesulfonate) (PSS) and poly(diallyldimethylammonium chloride) (PDDA) solution through poly(ethylene terephthalate) (PET) track-etched membranes. The polyelectrolyte multilayer fabrication was confirmed by means of FTIR, SEM, AFM, ellipsometry, zetapotential, and contact angle characterization. The prepared membranes were characterized in terms of their pure water permeability, flux recovery, and resistance to organic and biofouling properties. The antifouling behavior of the membranes was assessed in terms of protein adsorption and antibacterial behavior. Finally, the membranes were tested for rejection of selected water soluble dyes to establish their usefulness for organic contaminant removal from water. The membranes were highly selective and capable of nearly complete rejection of congo red with sufficiently high fluxes. The feasibility of regenerating the prepared membranes fouled by protein was also demonstrated and good flux recovery was obtained. In summary, the multilayer approach to surface and pore modification was shown to enable the design of membranes with the unique combination of desirable separation characteristics, regenerability of the separation layer, and antifouling behavior.

Spatial behavior reflects the mental disorder in OCD patients with and without comorbid schizophrenia.

Science.gov (United States)

Gershoni, Anat; Hermesh, Haggai; Fineberg, Naomi A; Eilam, David

2014-02-01

Resolving the entangled nosological dilemma of whether obsessive-compulsive disorder (OCD) with and without schizophrenia (schizo-OCD and OCD, respectively) are two independent entities or whether schizo-OCD is a combined product of its parent disorders. Studying motor activity in OCD and in schizo-OCD patients. Performance of the patients was compared with the performance of the same motor task by a matching control individual. Behavior in both schizo-OCD and OCD patients differed from controls in the excessive repetition and addition of acts, thus validating an identical OC facet. However, there was a significant difference in spatial behavior. Schizo-OCD patients traveled over a greater area with less focused activity as typical to schizophrenia patients and in contrast to OCD patients, who were more focused and traveled less in a confined area. While schizo-OCD and OCD patients share most of the OC ritualistic attributes, they differ in the greater spread of activity in schizo-OCD, which is related to schizophrenia disorder. It is suggested that the finding on difference in spatial behavior is a reflection of the mental differences between OCD and schizophrenia. In other words, this could be an overt and observable manifestation of the mental state, and therefore may facilitate the nosology of OC spectrum disorders and OCD. It seems as if both the OCD patients' focus on specific thoughts, and the contrasting wandering thoughts of schizophrenia patients, are reflected in the focused activity of the former and wandering from one place to the next of the latter.

Human Lipoproteins at Model Cell Membranes

DEFF Research Database (Denmark)

Browning, K L; Lind, T K; Maric, S

2017-01-01

High and low density lipoproteins (HDL and LDL) are thought to play vital roles in the onset and development of atherosclerosis; the biggest killer in the western world. Key issues of initial lipoprotein (LP) interactions at cellular membranes need to be addressed including LP deposition and lipid...... exchange. Here we present a protocol for monitoring the in situ kinetics of lipoprotein deposition and lipid exchange/removal at model cellular membranes using the non-invasive, surface sensitive methods of neutron reflection and quartz crystal microbalance with dissipation. For neutron reflection, lipid...... support the notion of HDL acting as the 'good' cholesterol, removing lipid material from lipid-loaded cells, whereas LDL acts as the 'bad' cholesterol, depositing lipid material into the vascular wall....

Reflectance Modeling

Science.gov (United States)

Smith, J. A.; Cooper, K.; Randolph, M.

1984-01-01

A classical description of the one dimensional radiative transfer treatment of vegetation canopies was completed and the results were tested against measured prairie (blue grama) and agricultural canopies (soybean). Phase functions are calculated in terms of directly measurable biophysical characteristics of the canopy medium. While the phase functions tend to exhibit backscattering anisotropy, their exact behavior is somewhat more complex and wavelength dependent. A Monte Carlo model was developed that treats soil surfaces with large periodic variations in three dimensions. A photon-ray tracing technology is used. Currently, the rough soil surface is described by analytic functions and appropriate geometric calculations performed. A bidirectional reflectance distribution function is calculated and, hence, available for other atmospheric or canopy reflectance models as a lower boundary condition. This technique is used together with an adding model to calculate several cases where Lambertian leaves possessing anisotropic leaf angle distributions yield non-Lambertian reflectance; similar behavior is exhibited for simulated soil surfaces.

[Self-reflection, interpersonal behavior and psychoanalytic ethics].

Science.gov (United States)

Bürgy, M

1997-05-01

In the middle ages, ethical practice included a metaphysical theory of value. In comparison with that, self-reflection and interpersonality should be described as principles of more individual ethics and proceeding from philosophy to psychoanalysis in modern times. Drawing a borderline between human philosophy and metaphysies, Kant defined his so-called categorial imperative as a basic phenomenon of human reciprocity. Ethical relationship to another person, however, requires realization of one's own self, i.e. self-reflection. Hegel's subsequent association of intersubjectivity and selfreflection supplied the basis for Sarte's constitution of consciousness: Existence as existing for the good of the fellow-being. Self-reflection, basing on the sight of one's own self by the other person, leads to Sartre's concept of existential psychoanalysis and to his understanding of ethics. His concept illustrates the decline of significance of philosophy for the analysis of human relationship. Habermas describes self-reflection and interpersonality as fundamental principles of the psychoanalytic therapy and its ethical demands. With the historical concept of the super-ego, Freud established therapeutical one-sidedness and abstinence from ethics; however, as therapeutical interrelationship continued to intensity, ethics of depth psychology also began to develop. This ethical demand was not expressly formulated within the context of psychoanalysis, with the exception of jung and his epigones. Nevertheless, psychoanalytic interaction implies the development of self-reflection, which definitely represents a step forward in the sense of "ethical enlightenment" represented by Kant.

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

An adhesion-based method for plasma membrane isolation: evaluating cholesterol extraction from cells and their membranes.

Science.gov (United States)

Bezrukov, Ludmila; Blank, Paul S; Polozov, Ivan V; Zimmerberg, Joshua

2009-11-15

A method to isolate large quantities of directly accessible plasma membrane from attached cells is presented. The method is based on the adhesion of cells to an adsorbed layer of polylysine on glass plates, followed by hypotonic lysis with ice-cold distilled water and subsequent washing steps. Optimal conditions for coating glass plates and time for cell attachment were established. No additional chemical or mechanical treatments were used. Contamination of the isolated plasma membrane by cell organelles was less than 5%. The method uses inexpensive, commercially available polylysine and reusable glass plates. Plasma membrane preparations can be made in 15 min. Using this method, we determined that methyl-beta-cyclodextrin differentially extracts cholesterol from fibroblast cells and their plasma membranes and that these differences are temperature dependent. Determination of the cholesterol/phospholipid ratio from intact cells does not reflect methyl-beta-cyclodextrin plasma membrane extraction properties.

Impulsive approach tendencies towards physical activity and sedentary behaviors, but not reflective intentions, prospectively predict non-exercise activity thermogenesis.

Science.gov (United States)

Cheval, Boris; Sarrazin, Philippe; Pelletier, Luc

2014-01-01

Understanding the determinants of non-exercise activity thermogenesis (NEAT) is crucial, given its extensive health benefits. Some scholars have assumed that a proneness to react differently to environmental cues promoting sedentary versus active behaviors could be responsible for inter-individual differences in NEAT. In line with this reflection and grounded on the Reflective-Impulsive Model, we test the assumption that impulsive processes related to sedentary and physical activity behaviors can prospectively predict NEAT, operationalized as spontaneous effort exerted to maintain low intensity muscle contractions within the release phases of an intermittent maximal isometric contraction task. Participants (n = 91) completed a questionnaire assessing their intentions to adopt physical activity behaviors and a manikin task to assess impulsive approach tendencies towards physical activity behaviors (IAPA) and sedentary behaviors (IASB). Participants were then instructed to perform a maximal handgrip strength task and an intermittent maximal isometric contraction task. As hypothesized, multilevel regression analyses revealed that spontaneous effort was (a) positively predicted by IAPA, (b) negatively predicted by IASB, and (c) was not predicted by physical activity intentions, after controlling for some confounding variables such as age, sex, usual PA level and average force provided during the maximal-contraction phases of the task. These effects remained constant throughout all the phases of the task. This study demonstrated that impulsive processes may play a unique role in predicting spontaneous physical activity behaviors. Theoretically, this finding reinforces the utility of a motivational approach based on dual-process models to explain inter-individual differences in NEAT. Implications for health behavior theories and behavior change interventions are outlined.

Influence of membrane composition on its flexibility

International Nuclear Information System (INIS)

Gerbelli, B.B.; Teixeira da Silva, E.R.; Oliveira, C.L.P.; Oliveira, E.A.

2012-01-01

Full text: Lamellar phases and vesicles composed of lipids have been used as model systems to investigate biological process related to cell membrane as well as promising carriers for drugs and gene therapy. The composition of the membrane determines its three dimensional shape and its properties such as rigidity and compressibility which play an important role on membrane fusion, protein adhesion, interactions between proteins, etc. We present systematic study of a lamellar system composed mainly of lecithin which is a biocompatible phospholipid and simusol, which is a mixture of fatty acids that acts as a cosurfactant introducing flexibility to the membrane. Using X ray scattering we determine the lamellar periodicity as a function of the hydration for different formulations of the membrane; ranging from 100 % to 50 % mass fraction of lecithin. The X-ray spectra are fitted using a 4 Gaussian model [1]that allows us to determine the lamellar periodicity and the Caille parameter [2]. The ideal swelling law relating the membrane volume fraction (φ m ) to the lamellar periodicity (D) is given by φ m =δ m /D, where δ m is the thickness membrane, however, when steric interactions are dominant with respect to electrostatic and van der Waals interactions, deviations from this behavior are expected [3]. We present experimental data illustrating the swelling behavior for the membrane compositions and the respective behavior of the hydration limit, membrane Luzzati [4], of the Caille parameter and qualitative interpretation of the interaction forces the systems studying the parameter membrane square amplitude fluctuation[5]. [1] Private communication with Prof. Dr. Cristiano Luis Pinto de Oliveira. [2] Caille A. et all, Acad. Sci. Paris B274 (1972) 891. [3] E. Kurtisovski et all, PRL 98, 258103 (2007). [4] Nagle et all, Curr Opin Struct Biol. 2000 Aug;10(4):474-80. [5] H. I. Petrache. Structure and interactions of fluid phospholipids bilayers measured by high resolution

Influence of membrane composition on its flexibility

Energy Technology Data Exchange (ETDEWEB)

Gerbelli, B.B.; Teixeira da Silva, E.R.; Oliveira, C.L.P.; Oliveira, E.A. [Universidade de Sao Paulo (USP), SP (Brazil)

2012-07-01

Full text: Lamellar phases and vesicles composed of lipids have been used as model systems to investigate biological process related to cell membrane as well as promising carriers for drugs and gene therapy. The composition of the membrane determines its three dimensional shape and its properties such as rigidity and compressibility which play an important role on membrane fusion, protein adhesion, interactions between proteins, etc. We present systematic study of a lamellar system composed mainly of lecithin which is a biocompatible phospholipid and simusol, which is a mixture of fatty acids that acts as a cosurfactant introducing flexibility to the membrane. Using X ray scattering we determine the lamellar periodicity as a function of the hydration for different formulations of the membrane; ranging from 100 % to 50 % mass fraction of lecithin. The X-ray spectra are fitted using a 4 Gaussian model [1]that allows us to determine the lamellar periodicity and the Caille parameter [2]. The ideal swelling law relating the membrane volume fraction ({phi}{sub m}) to the lamellar periodicity (D) is given by {phi}{sub m} ={delta}{sub m}/D, where {delta}{sub m} is the thickness membrane, however, when steric interactions are dominant with respect to electrostatic and van der Waals interactions, deviations from this behavior are expected [3]. We present experimental data illustrating the swelling behavior for the membrane compositions and the respective behavior of the hydration limit, membrane Luzzati [4], of the Caille parameter and qualitative interpretation of the interaction forces the systems studying the parameter membrane square amplitude fluctuation[5]. [1] Private communication with Prof. Dr. Cristiano Luis Pinto de Oliveira. [2] Caille A. et all, Acad. Sci. Paris B274 (1972) 891. [3] E. Kurtisovski et all, PRL 98, 258103 (2007). [4] Nagle et all, Curr Opin Struct Biol. 2000 Aug;10(4):474-80. [5] H. I. Petrache. Structure and interactions of fluid phospholipids

Fouling behaviors of polybenzimidazole (PBI)-polyhedral oligomeric silsesquioxane (POSS)/polyacrylonitrile (PAN) hollow fiber membranes for engineering osmosis processes

KAUST Repository

Chen, Sicong; Fu, Xiuzhu; Chung, Neal Tai-Shung

2014-01-01

This paper investigated the individual effects of reverse salt flux and permeate flux on fouling behaviors of as-spun and annealed polybenzimidazole (PBI)-polyhedral oligomeric silsesquioxane (POSS)/polyacrylonitrile (PAN) hollow fiber membranes under forward osmosis (FO) and pressure retarded osmosis (PRO) processes. Two types of membrane fouling had been studied; namely, inorganic fouling (CaSO4·2H2O gypsum scaling) during FO operations and organic fouling (sodium alginate fouling) during PRO operations. It is found that gypsum scaling on the membrane surface may be inhibited and even eliminated with an increase in reverse MgCl2 flux due to competitive formations of MgSO4° and CaSO4·2H2O. In contrast, the increase of reverse NaCl flux exhibits a slight enhancement on alginate fouling in both FO and PRO processes. Comparing to the reverse salt flux, the permeate flux always plays a dominant role in fouling. Therefore, lesser fouling has been observed on the membrane surface under the pressurized PRO process than FO process because the reduced initial flux mitigates the fouling phenomena more significantly than the enhancement caused by an increase in reverse NaCl flux. © 2013 Elsevier B.V.

Fouling behaviors of polybenzimidazole (PBI)-polyhedral oligomeric silsesquioxane (POSS)/polyacrylonitrile (PAN) hollow fiber membranes for engineering osmosis processes

KAUST Repository

Chen, Sicong

2014-02-01

This paper investigated the individual effects of reverse salt flux and permeate flux on fouling behaviors of as-spun and annealed polybenzimidazole (PBI)-polyhedral oligomeric silsesquioxane (POSS)/polyacrylonitrile (PAN) hollow fiber membranes under forward osmosis (FO) and pressure retarded osmosis (PRO) processes. Two types of membrane fouling had been studied; namely, inorganic fouling (CaSO4·2H2O gypsum scaling) during FO operations and organic fouling (sodium alginate fouling) during PRO operations. It is found that gypsum scaling on the membrane surface may be inhibited and even eliminated with an increase in reverse MgCl2 flux due to competitive formations of MgSO4° and CaSO4·2H2O. In contrast, the increase of reverse NaCl flux exhibits a slight enhancement on alginate fouling in both FO and PRO processes. Comparing to the reverse salt flux, the permeate flux always plays a dominant role in fouling. Therefore, lesser fouling has been observed on the membrane surface under the pressurized PRO process than FO process because the reduced initial flux mitigates the fouling phenomena more significantly than the enhancement caused by an increase in reverse NaCl flux. © 2013 Elsevier B.V.

Mechanics of Lipid Bilayer Membranes

Science.gov (United States)

Powers, Thomas R.

All cells have membranes. The plasma membrane encapsulates the cell's interior, acting as a barrier against the outside world. In cells with nuclei (eukaryotic cells), membranes also form internal compartments (organelles) which carry out specialized tasks, such as protein modification and sorting in the case of the Golgi apparatus, and ATP production in the case of mitochondria. The main components of membranes are lipids and proteins. The proteins can be channels, carriers, receptors, catalysts, signaling molecules, or structural elements, and typically contribute a substantial fraction of the total membrane dry weight. The equilibrium properties of pure lipid membranes are relatively well-understood, and will be the main focus of this article. The framework of elasticity theory and statistical mechanics that we will develop will serve as the foundation for understanding biological phenomena such as the nonequilibrium behavior of membranes laden with ion pumps, the role of membrane elasticity in ion channel gating, and the dynamics of vesicle fission and fusion. Understanding the mechanics of lipid membranes is also important for drug encapsulation and delivery.

Determine equilibrium dissociation constant of drug-membrane receptor affinity using the cell membrane chromatography relative standard method.

Science.gov (United States)

Ma, Weina; Yang, Liu; Lv, Yanni; Fu, Jia; Zhang, Yanmin; He, Langchong

2017-06-23

The equilibrium dissociation constant (K D ) of drug-membrane receptor affinity is the basic parameter that reflects the strength of interaction. The cell membrane chromatography (CMC) method is an effective technique to study the characteristics of drug-membrane receptor affinity. In this study, the K D value of CMC relative standard method for the determination of drug-membrane receptor affinity was established to analyze the relative K D values of drugs binding to the membrane receptors (Epidermal growth factor receptor and angiotensin II receptor). The K D values obtained by the CMC relative standard method had a strong correlation with those obtained by the frontal analysis method. Additionally, the K D values obtained by CMC relative standard method correlated with pharmacological activity of the drug being evaluated. The CMC relative standard method is a convenient and effective method to evaluate drug-membrane receptor affinity. Copyright © 2017 Elsevier B.V. All rights reserved.

Rapid Preparation of a Plasma Membrane Fraction: Western Blot Detection of Translocated Glucose Transporter 4 from Plasma Membrane of Muscle and Adipose Cells and Tissues.

Science.gov (United States)

Yamamoto, Norio; Yamashita, Yoko; Yoshioka, Yasukiyo; Nishiumi, Shin; Ashida, Hitoshi

2016-08-01

Membrane proteins account for 70% to 80% of all pharmaceutical targets, indicating their clinical relevance and underscoring the importance of identifying differentially expressed membrane proteins that reflect distinct disease properties. The translocation of proteins from the bulk of the cytosol to the plasma membrane is a critical step in the transfer of information from membrane-embedded receptors or transporters to the cell interior. To understand how membrane proteins work, it is important to separate the membrane fraction of cells. This unit provides a protocol for rapidly obtaining plasma membrane fractions for western blot analysis. © 2016 by John Wiley & Sons, Inc. Copyright © 2016 John Wiley & Sons, Inc.

Tandem Facial Amphiphiles for Membrane Protein Stabilization

DEFF Research Database (Denmark)

Chae, Pil Seok; Gotfryd, Kamil; Pacyna, Jennifer

2010-01-01

We describe a new type of synthetic amphiphile that is intended to support biochemical characterization of intrinsic membrane proteins. Members of this new family displayed favorable behavior with four of five membrane proteins tested, and these amphiphiles formed relatively small micelles....

Synthesis and membrane behavior of a new class of unnatural phospholipid analogs useful as phospholipase A2 degradable liposomal drug carriers

DEFF Research Database (Denmark)

Andresen, Thomas Lars; Jørgensen, Kent

2005-01-01

A new and unnatural type of lipid analogs with the phosphocholine and phosphoglycerol head groups linked to the C-2 position of the glycerol moiety have been synthesized and the thermodynamic lipid membrane behavior has been investigated using differential scanning calorimetry. From the heat capa...

Neuronal Differentiation Modulated by Polymeric Membrane Properties.

Science.gov (United States)

Morelli, Sabrina; Piscioneri, Antonella; Drioli, Enrico; De Bartolo, Loredana

2017-01-01

In this study, different collagen-blend membranes were successfully constructed by blending collagen with chitosan (CHT) or poly(lactic-co-glycolic acid) (PLGA) to enhance their properties and thus create new biofunctional materials with great potential use for neuronal tissue engineering and regeneration. Collagen blending strongly affected membrane properties in the following ways: (i) it improved the surface hydrophilicity of both pure CHT and PLGA membranes, (ii) it reduced the stiffness of CHT membranes, but (iii) it did not modify the good mechanical properties of PLGA membranes. Then, we investigated the effect of the different collagen concentrations on the neuronal behavior of the membranes developed. Morphological observations, immunocytochemistry, and morphometric measures demonstrated that the membranes developed, especially CHT/Col30, PLGA, and PLGA/Col1, provided suitable microenvironments for neuronal growth owing to their enhanced properties. The most consistent neuronal differentiation was obtained in neurons cultured on PLGA-based membranes, where a well-developed neuronal network was achieved due to their improved mechanical properties. Our findings suggest that tensile strength and elongation at break are key material parameters that have potential influence on both axonal elongation and neuronal structure and organization, which are of fundamental importance for the maintenance of efficient neuronal growth. Hence, our study has provided new insights regarding the effects of membrane mechanical properties on neuronal behavior, and thus it may help to design and improve novel instructive biomaterials for neuronal tissue engineering. © 2017 S. Karger AG, Basel.

Constitutive Behavior of Reinforced Concrete Membrane Elements under Tri-directional Shear

Science.gov (United States)

Labib, Moheb

The two-dimensional behavior of typical reinforced concrete (RC) structures has been extensively studied in the past several decades by investigating the constitutive behavior of full-scale reinforced concrete elements subjected to a bi-axial state of stress. In order to understand the true behavior of many large complex structures, the goal of this investigation is to develop new constitutive relationships for RC elements subjected to tri-directional shear stresses. Recently, additional out-of-plane jacks were installed on the panel tester at University of Houston so that concrete elements could be subjected to tri-directional shear stresses. This upgrade makes the panel tester the only one of its kind in the US that is capable of applying such combinations of stresses on full-scale reinforced concrete elements. This dissertation presents the details of the mounting and installation of the additional hydraulic jacks on the universal panel tester. The experimental program includes a series of seven reinforced concrete elements subjected to different combinations of in-plane and out-of-plane shear stresses. Increasing the applied out-of-plane shear stresses reduced the membrane shear strength of the elements. The effect of applying out-of-plane shear stresses on the in-plane shear strength was represented by modifying the softening coefficient in the compression stress strain curve of concrete struts. The modified model was able to capture the behavior and the ultimate capacity of the tested elements. The effect of the in-plane shear reinforcement ratio on the interaction between in-plane and out-of-plane shear stresses was evaluated. The model was implemented in the Finite Element package FEAP and was used to predict the ultimate capacity of many structures subjected to a combination of in-plane and out-of-plane shear stresses. The results of the analytical model were used to develop simplified design equations for members subjected to bi-directional shear loads

Impulsive approach tendencies towards physical activity and sedentary behaviors, but not reflective intentions, prospectively predict non-exercise activity thermogenesis.

Directory of Open Access Journals (Sweden)

Boris Cheval

Full Text Available Understanding the determinants of non-exercise activity thermogenesis (NEAT is crucial, given its extensive health benefits. Some scholars have assumed that a proneness to react differently to environmental cues promoting sedentary versus active behaviors could be responsible for inter-individual differences in NEAT. In line with this reflection and grounded on the Reflective-Impulsive Model, we test the assumption that impulsive processes related to sedentary and physical activity behaviors can prospectively predict NEAT, operationalized as spontaneous effort exerted to maintain low intensity muscle contractions within the release phases of an intermittent maximal isometric contraction task. Participants (n = 91 completed a questionnaire assessing their intentions to adopt physical activity behaviors and a manikin task to assess impulsive approach tendencies towards physical activity behaviors (IAPA and sedentary behaviors (IASB. Participants were then instructed to perform a maximal handgrip strength task and an intermittent maximal isometric contraction task. As hypothesized, multilevel regression analyses revealed that spontaneous effort was (a positively predicted by IAPA, (b negatively predicted by IASB, and (c was not predicted by physical activity intentions, after controlling for some confounding variables such as age, sex, usual PA level and average force provided during the maximal-contraction phases of the task. These effects remained constant throughout all the phases of the task. This study demonstrated that impulsive processes may play a unique role in predicting spontaneous physical activity behaviors. Theoretically, this finding reinforces the utility of a motivational approach based on dual-process models to explain inter-individual differences in NEAT. Implications for health behavior theories and behavior change interventions are outlined.

Pyrolytic carbon membranes containing silica: morphological approach on gas transport behavior

Science.gov (United States)

Park, Ho Bum; Lee, Sun Yong; Lee, Young Moo

2005-04-01

Pyrolytic carbon membrane containing silica (C-SiO 2) is a new-class material for gas separation, and in the present work we will deal with it in view of the morphological changes arising from the difference in the molecular structure of the polymeric precursors. The silica embedded carbon membranes were fabricated by a predetermined pyrolysis step using imide-siloxane copolymers (PISs) that was synthesized from benzophenone tetracarboxylic dianhydrides (BTDA), 4,4'-oxydianiline (ODA), and amine-terminated polydimethylsiloxane (PDMS). To induce different morphologies at the same chemical composition, the copolymers were prepared using one-step (preferentially a random segmented copolymer) sand two-step polymerization (a block segmented copolymer) methods. The polymeric precursors and their pyrolytic C-SiO 2 membranes were analyzed using thermal analysis, atomic force microscopy, and transmission electron microscopy, etc. It was found that the C-SiO 2 membrane derived from the random PIS copolymer showed a micro-structure containing small well-dispersed silica domains, whereas the C-SiO 2 membrane from the block PIS copolymer exhibited a micro-structure containing large silica domains in the continuous carbon matrix. Eventually, the gas transport through these C-SiO 2 membranes was significantly affected by the morphological changes of the polymeric precursors.

Measuring shape fluctuations in biological membranes

International Nuclear Information System (INIS)

Monzel, C; Sengupta, K

2016-01-01

Shape fluctuations of lipid membranes have intrigued cell biologists and physicists alike. In the cellular context, their origin—thermal or active—and their physiological significance are open questions. These small incessant displacements, also called membrane undulations, have mostly been studied in model membranes and membranes of simple cells like erythrocytes. Thermal fluctuations of such membranes have been very well described both theoretically and experimentally; active fluctuations are a topic of current interest. Experimentally, membrane fluctuations are not easy to measure, the main challenge being to develop techniques which are capable of measuring very small displacements at very high speed, and preferably over a large area and long time. Scattering techniques have given access to fluctuations in membrane stacks and a variety of optical microscopy based techniques have been devised to study membrane fluctuations of unilamellar vesicles, erythrocytes and other cells. Among them are flicker spectroscopy, dynamic light scattering, diffraction phase microscopy and reflection interference contrast microscopy. Each of these techniques has its advantages and limitations. Here we review the basic principles of the major experimental techniques used to measure bending or shape fluctuations of biomembranes. We report seminal results obtained with each technique and highlight how these studies furthered our understanding of physical properties of membranes and their interactions. We also discuss suggested role of membrane fluctuations in different biological processes. (topical review)

Dependence of Shear and Concentration on Fouling in a Membrane Bioreactor with Rotating Membrane Discs

DEFF Research Database (Denmark)

Jørgensen, Mads Koustrup; Pedersen, Malene Thostrup; Christensen, Morten Lykkegaard

2014-01-01

Rotating ceramic membrane discs were fouled with lab-scale membrane bioreactors (MBR) sludge. Sludge filtrations were performed at varying rotation speeds and in different concentric rings of the membranes on different sludge concentrations. Data showed that the back transport expressed by limiting...... flux increased with rotation speed and distance from membrane center as an effect of shear. Further, the limiting flux decreased with increasing sludge concentration. A model was developed to link the sludge concentration and shear stress to the limiting flux. The model was able to simulate the effect...... of shear stress and sludge concentration on the limiting flux. The model was developed by calculating the shear rate at laminar flow regime at different rotation speeds and radii on the membrane. Furthermore, through the shear rate and shear stress, the non-Newtonian behavior of MBR sludge was addressed...

Reflections on "Verbal Behavior" at 60

Science.gov (United States)

Schlinger, Henry D., Jr.

2017-01-01

In the present essay, commemorating the 60th anniversary of the publication of B. F. Skinner's "Verbal Behavior", I stand by and defend the judgment I expressed in my article "The Long Goodbye: Why B. F. Skinner's 'Verbal Behavior' Is Alive and Well on the 50th Anniversary of Its Publication" (2008c)--that Skinner's…

Guiding Moral Behavior through a Reflective Learning Practice

Science.gov (United States)

Hedberg, Patricia R.

2017-01-01

Reflective learning practice embedded across the business curriculum is a powerful way to equip students with intentionally formed moral habits of the mind and heart. This article explores why and how to apply reflective learning to the teaching of business ethics. To act with integrity in complicated work organizations, students need skills and…

Microbial transformation of biomacromolecules in a membrane bioreactor: implications for membrane fouling investigation.

Directory of Open Access Journals (Sweden)

Zhongbo Zhou

Full Text Available BACKGROUND: The complex characteristics and unclear biological fate of biomacromolecules (BMM, including colloidal and soluble microbial products (SMP, extracellular polymeric substances (EPS and membrane surface foulants (MSF, are crucial factors that limit our understanding of membrane fouling in membrane bioreactors (MBRs. FINDINGS: In this study, the microbial transformation of BMM was investigated in a lab-scale MBR by well-controlled bioassay tests. The results of experimental measurements and mathematical modeling show that SMP, EPS, and MSF had different biodegradation behaviors and kinetic models. Based on the multi-exponential G models, SMP were mainly composed of slowly biodegradable polysaccharides (PS, proteins (PN, and non-biodegradable humic substances (HS. In contrast, EPS contained a large number of readily biodegradable PN, slowly biodegradable PS and HS. MSF were dominated by slowly biodegradable PS, which had a degradation rate constant similar to that of SMP-PS, while degradation behaviors of MSF-PN and MSF-HS were much more similar to those of EPS-PN and EPS-HS, respectively. In addition, the large-molecular weight (MW compounds (>100 kDa in BMM were found to have a faster microbial transformation rate compared to the small-MW compounds (<5 kDa. The parallel factor (PARAFAC modeling of three-dimensional fluorescence excitation-emission matrix (EEM spectra showed that the tryptophan-like PN were one of the major fractions in the BMM and they were more readily biodegradable than the HS. Besides microbial mineralization, humification and hydrolysis could be viewed as two important biotransformation mechanisms of large-MW compounds during the biodegradation process. SIGNIFICANCE: The results of this work can aid in tracking the origin of membrane foulants from the perspective of the biotransformation behaviors of SMP, EPS, and MSF.

Interaction of Defensins with Model Cell Membranes

Science.gov (United States)

Sanders, Lori K.; Schmidt, Nathan W.; Yang, Lihua; Mishra, Abhijit; Gordon, Vernita D.; Selsted, Michael E.; Wong, Gerard C. L.

2009-03-01

Antimicrobial peptides (AMPs) comprise a key component of innate immunity for a wide range of multicellular organisms. For many AMPs, activity comes from their ability to selectively disrupt and lyse bacterial cell membranes. There are a number of proposed models for this action, but the detailed molecular mechanism of selective membrane permeation remains unclear. Theta defensins are circularized peptides with a high degree of selectivity. We investigate the interaction of model bacterial and eukaryotic cell membranes with theta defensins RTD-1, BTD-7, and compare them to protegrin PG-1, a prototypical AMP, using synchrotron small angle x-ray scattering (SAXS). The relationship between membrane composition and peptide induced changes in membrane curvature and topology is examined. By comparing the membrane phase behavior induced by these different peptides we will discuss the importance of amino acid composition and placement on membrane rearrangement.

Bifurcation behavior during the hydrogen production in two compatible configurations of a novel circulating fluidized bed membrane reformer

International Nuclear Information System (INIS)

Chen, Z.; Elnashaie, S.S.

2004-01-01

'Full text:' Multiplicity of steady states (Static Bifurcation Behavior, SBB) in a novel Circulating Fluidized Bed (CFB) membrane reformer for the efficient production of hydrogen by steam reforming of heptane (model component of heavy hydrocarbons and renewable bio-oils) is investigated. The present paper highlights the practical implications of this phenomenon on the behavior of this novel reformer with special focusing on hydrogen production. Two configurations are considered and compared. One is with the catalyst regeneration before the gas-solid separation and the other one is with the catalyst regeneration after the gas-solid separation. Multiplicity of the steady states prevails over a number of design and operating parameters with important impact on the reformer performance. The basis of process evaluation is focused on the net hydrogen production. The dependence of the behavior of this autothermal CFB is shown to be quite complex and defy the simple logic of non-autothermal processes. The unit can be a very efficient hydrogen producer provided its bifurcation behavior is well understood and correctly exploited. (author)

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.

Fatty acid profiles from the plasma membrane and detergent resistant membranes of two plant species.

Science.gov (United States)

Carmona-Salazar, Laura; El Hafidi, Mohammed; Gutiérrez-Nájera, Nora; Noyola-Martínez, Liliana; González-Solís, Ariadna; Gavilanes-Ruíz, Marina

2015-01-01

It is essential to establish the composition of the plant plasma membrane in order to understand its organization and behavior under continually changing environments. Knowledge of the lipid phase, in particular the fatty acid (FA) complex repertoire, is important since FAs determine many of the physical-chemical membrane properties. FAs are constituents of the membrane glycerolipid and sphingolipid backbones and can also be linked to some sterols. In addition, FAs are components of complex lipids that can constitute membrane micro-domains, and the use of detergent-resistant membranes is a common approach to study their composition. The diversity and cellular allocation of the membrane lipids containing FAs are very diverse and the approaches to analyze them provide only general information. In this work, a detailed FA analysis was performed using highly purified plasma membranes from bean leaves and germinating maize embryos and their respective detergent-resistant membrane preparations. The analyses showed the presence of a significant amount of very long chain FAs (containing 28C, 30C and 32C), in both plasma membrane preparations from bean and maize, that have not been previously reported. Herein is demonstrated that a significant enrichment of very long chain saturated FAs and saturated FAs can occur in detergent-resistant membrane preparations, as compared to the plasma membranes from both plant species. Considering that a thorough analysis of FAs is rarely performed in purified plasma membranes and detergent-resistant membranes, this work provides qualitative and quantitative evidence on the contributions of the length and saturation of FAs to the organization of the plant plasma membrane and detergent-resistant membranes. Copyright © 2014 Elsevier Ltd. All rights reserved.

Plasma deposited fluorinated films on porous membranes

Energy Technology Data Exchange (ETDEWEB)

Gancarz, Irena [Department of Polymer and Carbon Materials, Wrocław University of Technology, 50-370 Wrocław (Poland); Bryjak, Marek, E-mail: marek.bryjak@pwr.edu.pl [Department of Polymer and Carbon Materials, Wrocław University of Technology, 50-370 Wrocław (Poland); Kujawski, Jan; Wolska, Joanna [Department of Polymer and Carbon Materials, Wrocław University of Technology, 50-370 Wrocław (Poland); Kujawa, Joanna; Kujawski, Wojciech [Nicolaus Copernicus University, Faculty of Chemistry, 7 Gagarina St., 87-100 Torun (Poland)

2015-02-01

75 KHz plasma was used to modify track etched poly(ethylene terephthalate) membranes and deposit on them flouropolymers. Two fluorine bearing monomers were used: perflourohexane and hexafluorobenzene. The modified surfaces were analyzed by means of attenuated total reflection infra-red spectroscopy, X-ray photoelectron spectroscopy, scanning electron microscopy, atomic force microscopy and wettability. It was detected that hexaflourobenxene deposited to the larger extent than perflourohaxane did. The roughness of surfaces decreased when more fluoropolymer was deposited. The hydrophobic character of surface slightly disappeared during 20-days storage of hexaflourobenzene modified membrane. Perfluorohexane modified membrane did not change its character within 120 days after modification. It was expected that this phenomenon resulted from post-reactions of oxygen with radicals in polymer deposits. The obtained membranes could be used for membrane distillation of juices. - Highlights: • Plasma deposited hydrophobic layer of flouropolymers. • Deposition degree affects the surface properties. • Hydrohilization of surface due to reaction of oxygen with entrapped radicals. • Possibility to use modified porous membrane for water distillation and apple juice concentration.

[Formation of purple membranes during salt bacteria cultivation].

Science.gov (United States)

Chekulaeva, L N; Korolev, Iu N; Telegin, N L; Rikhireva, G T

1975-01-01

Experiments have been carried out on cultivation of halophile with probe selection in the interval of 1--2 hours to record the spectra of repeated disturbed completed inner reflection. Periodicity in the changes of spectral characteristics of the culture with the interval of 20--24 hours is revealed. A clearly expressed dichroism of the amid II band of the membrane complex is found, the absence of this dichroism in the protein isolated from the membrane complex is stated. It is suggested that dichroism revealed is a specific feature of the presence of purpuric membranes in the cells. Spontaneous plane orientation of protein macromolecules in purpuric membranes is established. The level of dichroism of amid II band is shown to depend on fermentation conditions of salt bacteria.

Observing Engineering Student Teams from the Organization Behavior Perspective Using Linguistic Analysis of Student Reflections and Focus Group Interviews

Science.gov (United States)

Kearney, Kerri S.; Damron, Rebecca; Sohoni, Sohum

2015-01-01

This paper investigates group/team development in computer engineering courses at a University in the Central USA from the perspective of organization behavior theory, specifically Tuckman's model of the stages of group development. The investigation, conducted through linguistic analysis of student reflection essays, and through focus group…

TEMPERATURE DEPENDENT PHASE BEHAVIOR AND PROTEIN PARTITIONING IN GIANT PLASMA MEMBRANE VESICLES

OpenAIRE

Johnson, SA; Stinson, BM; Go, M; Carmona, LM; Reminick, JI; Fang, X; Baumgart, T

2010-01-01

Liquid-ordered (Lo) and liquid-disordered (Ld) phase coexistence has been suggested to partition the plasma membrane of biological cells into lateral compartments, allowing for enrichment or depletion of functionally relevant molecules. This dynamic partitioning might be involved in fine-tuning cellular signaling fidelity through coupling to the plasma membrane protein and lipid composition. In earlier work, giant plasma membrane vesicles, obtained by chemically induced blebbing from cultured...

Glucose-neopentyl glycol (GNG) amphiphiles for membrane protein study

DEFF Research Database (Denmark)

Chae, Pil Seok; Rana, Rohini R; Gotfryd, Kamil

2013-01-01

The development of a new class of surfactants for membrane protein manipulation, "GNG amphiphiles", is reported. These amphiphiles display promising behavior for membrane proteins, as demonstrated recently by the high resolution structure of a sodium-pumping pyrophosphatase reported by Kellosalo ...

“Where Does the Circle End?”: Representation as a Critical Aspect of Reflection in Teaching Social and Behavioral Sciences in Medicine

Science.gov (United States)

Devlin, Michael J.; Richards, Boyd F.; Cunningham, Hetty; Desai, Urmi; Lewis, Owen; Mutnick, Andrew; Nidiry, Mary Anne J.; Saha, Prantik; Charon, Rita

2014-01-01

Objective This paper describes a reflective learning program within a larger curriculum on behavioral and social science that makes use of close reading, written representation of experience, discussion, and textual response. This response may in turn lead to further reflection, representation, and response in a circular pattern. A unique feature of this program is that it pays attention to the representation itself as the pivotal activity within reflective learning. Using the narrative methods that are the hallmark of this program, faculty writings were analyzed to characterize the essential benefits that derive from these practices. Methods In the context of a faculty development seminar on the teaching of behavioral and social sciences in medical curricula, a group of fifteen faculty members wrote brief narratives of reflective learning experiences in which they had made use of the methods described above. Their responses were submitted to iterative close reading and discussion, and potential themes were identified. Results Four themes emerged: writing as attention to self, writing as attention to other, writing as reader/writer contract, and writing as discovery. In each instance, writing provides a new or deepened perspective, and in each case the dividends for the writer are amplified by the narrative skills of those who read, listen, and respond. Conclusions The narrative pedagogy described and modeled herein provides a potentially promising approach to teaching the social, cultural, behavioral, and interpersonal aspects of medical education and practice. Future research will deepen our understanding of the benefits and limitations of this pedagogy and expand our appreciation of its applications. PMID:25272952

Differential natural organic matter fouling of ceramic versus polymeric ultrafiltration membranes.

Science.gov (United States)

Lee, Seung-Jin; Kim, Jae-Hong

2014-01-01

Ceramic ultrafiltration membranes has drawn increasing attention in drinking water treatment sectors as an alternative to traditional polymeric counterparts, yet only limited information has been made available about the characteristics of ceramic membrane fouling by natural organic matter. The effects of solution chemistry including ionic strength, divalent ion concentration and pH on the flux behavior were comparatively evaluated for ceramic and polymeric ultrafiltration of synthetic water containing model natural organic matter. Filtration characteristics were further probed via resistance-in-series model analysis, fouling visualization using quantum dots, batch adsorption test, contact angle measurement, solute-membrane surface adhesion force measurement, and quantitative comparison of fouling characteristics between ceramic and polymeric membranes. The results collectively suggested that the effects of solution chemistry on fouling behavior of ceramic membranes were generally similar to polymeric counterparts in terms of trends, while the extent varied significantly depending on water quality parameters. Lower fouling tendency and enhanced cleaning efficiency were observed with the ceramic membrane, further promoting the potential for ceramic membrane application to surface water treatment. Copyright © 2013 Elsevier Ltd. All rights reserved.

Imaging height fluctuations in free-standing graphene membranes

Science.gov (United States)

Dorsey, Kyle; Miskin, Marc; Barnard, Arthur; Rose, Peter; Cohen, Itai; McEuen, Paul

We present a technique based on multi-wavelength interference microscopy to measure the heights of observed ripples in free-standing graphene membranes. Graphene membranes released from a transparent substrate produce interference fringes when viewed in the reflection mode of an inverted microscope(Blees et. al. Nature 524 (7564): 204-207 (2015)). The fringes correspond to corrugation of the membrane as it floats near an interface. A single set of fringes is insufficient to uniquely determine the height profile, as a given fringe spacing can correspond to an increase or decrease in height by λ / 2 . Imaging at multiple wavelengths resolves the ambiguities in phase, and enables unique determination of the height profile of the membrane (Schilling et. al.Phys. Rev. E, 69:021901, 2004). We utilize this technique to map out the height fluctuations in free-standing graphene membranes to answer questions about fundamental mechanical properties of two-dimensional materials.

The effects of a shared, Intranet science learning environment on the academic behaviors of problem-solving and metacognitive reflection

Science.gov (United States)

Parker, Mary Jo

This study investigated the effects of a shared, Intranet science environment on the academic behaviors of problem-solving and metacognitive reflection. Seventy-eight subjects included 9th and 10th grade male and female biology students. A quasi-experimental design with pre- and post-test data collection and randomization occurring through assignment of biology classes to traditional or shared, Intranet learning groups was employed. Pilot, web-based distance education software (CourseInfo) created the Intranet learning environment. A modified ecology curriculum provided contextualization and content for traditional and shared learning environments. The effect of this environment on problem-solving, was measured using the standardized Watson-Glaser Critical Thinking Appraisal test. Metacognitive reflection, was measured in three ways: (a) number of concepts used, (b) number of concept links noted, and (c) number of concept nodes noted. Visual learning software, Inspiration, generated concept maps. Secondary research questions evaluated the pilot CourseInfo software for (a) tracked user movement, (b) discussion forum findings, and (c) difficulties experienced using CourseInfo software. Analysis of problem-solving group means reached no levels of significance resulting from the shared, Intranet environment. Paired t-Test of individual differences in problem-solving reached levels of significance. Analysis of metacognitive reflection by number of concepts reached levels of significance. Metacognitive reflection by number of concept links noted also reach significance. No significance was found for metacognitive reflection by number of concept nodes. No gender differences in problem-solving ability and metacognitive reflection emerged. Lack of gender differences in the shared, Intranet environment strongly suggests an equalizing effect due to the cooperative, collaborative nature of Intranet environments. Such environments appeal to, and rank high with, the female

In situ temperature tunable pores of shape memory polyurethane membranes

International Nuclear Information System (INIS)

Ahn, Joon-Sung; Yu, Woong-Ryeol; Youk, Ji Ho; Ryu, Hee Youk

2011-01-01

Conventional shape memory polymers, such as shape memory polyurethanes (SMPU), can exhibit net two-way shape memory behavior (2WSM), i.e., upon heating and subsequent cooling, their macroscopic shapes change reversibly under an applied bias load. This paper is aimed at reporting similar 2WSM behavior, especially by focusing on the size of nanopores/micropores in SMPU membranes, i.e., the size of the pores can be reversibly changed by up to about 300 nm upon repeated heating and cooling. The SMPU membranes were prepared by electrospinning and elongated at temperatures higher than the transition temperature of the SMPU. Under the constant stress, the size change of the pores in the membranes was measured by applying cyclic temperature change. It was observed that the pore size changed from 150 to 440 nm according to the temperature change, demonstrating that the SMPU membrane can be utilized as a smart membrane to selectively separate substances according to their sizes by just controlling temperature

A Fluid Membrane-Based Soluble Ligand Display System for Live CellAssays

Energy Technology Data Exchange (ETDEWEB)

Nam, Jwa-Min; Nair, Pradeep N.; Neve, Richard M.; Gray, Joe W.; Groves, Jay T.

2005-10-14

Cell communication modulates numerous biological processes including proliferation, apoptosis, motility, invasion and differentiation. Correspondingly, there has been significant interest in the development of surface display strategies for the presentation of signaling molecules to living cells. This effort has primarily focused on naturally surface-bound ligands, such as extracellular matrix components and cell membranes. Soluble ligands (e.g. growth factors and cytokines) play an important role in intercellular communications, and their display in a surface-bound format would be of great utility in the design of array-based live cell assays. Recently, several cell microarray systems that display cDNA, RNAi, or small molecules in a surface array format were proven to be useful in accelerating high-throughput functional genetic studies and screening therapeutic agents. These surface display methods provide a flexible platform for the systematic, combinatorial investigation of genes and small molecules affecting cellular processes and phenotypes of interest. In an analogous sense, it would be an important advance if one could display soluble signaling ligands in a surface assay format that allows for systematic, patterned presentation of soluble ligands to live cells. Such a technique would make it possible to examine cellular phenotypes of interest in a parallel format with soluble signaling ligands as one of the display parameters. Herein we report a ligand-modified fluid supported lipid bilayer (SLB) assay system that can be used to functionally display soluble ligands to cells in situ (Figure 1A). By displaying soluble ligands on a SLB surface, both solution behavior (the ability to become locally enriched by reaction-diffusion processes) and solid behavior (the ability to control the spatial location of the ligands in an open system) could be combined. The method reported herein benefits from the naturally fluid state of the supported membrane, which allows

Limiting hydrophobic behavior and reflectance response of dragonfly and damselfly wings

Science.gov (United States)

Aideo, Swati Nawami; Mohanta, Dambarudhar

2016-11-01

In this work, through water contact angle (CA) measurements, we explore hydrophobic behavior of different parts of the hind wings of a dragonfly, Gynacantha Dravida and of a damselfly, Pseudagrion Microcephalum. As we move from the basal to distal region, the contact angle (θ) was found to vary in the range of 120-136° for both the species. Moreover, the wing of the dragonfly was seen to be more hydrophobic than that of the damselfly one. An attempt has also been made to link roughness factor (rφ) and solid-water fraction (φ) through the simplified Wenzel and Cassie-Baxter models. We noticed that, rφ and φ tend to follow a linear relation that gives rφ = 1.47 in the limit, Δθ segment was believed to be stronger than that of the basal part, the edge parts of the dragonfly and damselfly wings exhibited exponential associated growing trends with increasing wavelength. The relative reflectance response, corresponding to ∼494 nm and 370 nm peaks, gets nearly doubled for the edge specimen as compared to the distal and basal parts. The edge- specimen, which comprises of rectangular shaped, periodic microstructures, displayed carotenoid based two broad peak maxima at ∼422 nm and ∼494 nm. The surface roughness which arises through the distribution of oblate-shaped nano-fibrils is believed to be the basis of sub-surface volume scattering. Interrelating nanostructure surface roughness based wettability and reflectance characteristics would provide new insights on structure-property relationship in naturally available soft matter systems including templates of biological origin.

Erythrocyte Membrane Failure by Electromechanical Stress

Directory of Open Access Journals (Sweden)

E Du

2018-01-01

Full Text Available We envision that electrodeformation of biological cells through dielectrophoresis as a new technique to elucidate the mechanistic details underlying membrane failure by electrical and mechanical stresses. Here we demonstrate the full control of cellular uniaxial deformation and tensile recovery in biological cells via amplitude-modified electric field at radio frequency by an interdigitated electrode array in microfluidics. Transient creep and cyclic experiments were performed on individually tracked human erythrocytes. Observations of the viscoelastic-to-viscoplastic deformation behavior and the localized plastic deformations in erythrocyte membranes suggest that electromechanical stress results in irreversible membrane failure. Examples of membrane failure can be separated into different groups according to the loading scenarios: mechanical stiffening, physical damage, morphological transformation from discocyte to echinocyte, and whole cell lysis. These results show that this technique can be potentially utilized to explore membrane failure in erythrocytes affected by other pathophysiological processes.

Stretched membrane heliostats: design and structural analysis of reflectance module and support of a heliostats of 9 m. diaform and 60 m''3 of reflectance surface; Diseno y analisis estructural del modulo reflectante y estructura soporte de un heliostato de 9 m. de diametro y 60 m2 de superficie reflectante

Energy Technology Data Exchange (ETDEWEB)

Figarola Torres, J M

1993-07-01

After having designed and built at CIEMAT a first prototype of a Btretched membrane heliostats of 3 m. diameter, the design and the structural analysis of the different components included in the reflectance module and support of another heliostats, this one of 9 m. diameter and 60 m2. of reflectance surface, are shown In this report. This last heliostats will be mounted on a pedestal and its driving device at the Solar Platform of Almeria. In order to optimize design and performance, the structural analysis of its basic components has been analyzed with the finite elements program ANSYS. The following elements have been subject to analysis: the membrane and their ring supports, stretching system and the structural support. A similar scheme to the one applied to the previous prototype has been used on the focus control system. That includes a linear transducer, a variable frequency and a fan. Finally it has to be pointed out that substantial improvements have been achieved with respect to the first prototype concerning design and cost. (Author) 5 refs.

Characterization, optical properties and laser ablation behavior of epoxy resin coatings reinforced with high reflectivity ceramic particles

Science.gov (United States)

Li, Wenzhi; Kong, Jing; Wu, Taotao; Gao, Lihong; Ma, Zhuang; Liu, Yanbo; Wang, Fuchi; Wei, Chenghua; Wang, Lijun

2018-04-01

Thermal damage induced by high power energy, especially high power laser, significantly affects the lifetime and performance of equipment. High-reflectance coating/film has attracted considerable attention due to its good performance in the damage protection. Preparing a high-reflectance coating with high reaction endothermal enthalpy will effectively consume a large amount of incident energy and in turn protect the substrate from thermal damage. In this study, a low temperature process was used to prepare coatings onto substrate with complex shape and avoid thermal effect during molding. An advanced high reflection ceramic powder, La1‑xSrxTiO3+δ , was added in the epoxy adhesive matrix to improve the reflectivity of coating. The optical properties and laser ablation behaviors of coatings with different ceramic additive ratio of La1‑xSrxTiO3+δ and modified epoxy-La1‑xSrxTiO3+δ with ammonium polyphosphate coatings were investigated, respectively. We found that the reflectivity of coatings is extremely high due to mixed high-reflection La1‑xSrxTiO3+δ particles, up to 96% at 1070 nm, which can significantly improve the laser resistance. In addition, the ammonium polyphosphate modifies the residual carbon structure of epoxy resin from discontinuous fine particles structure to continuous and porous structure, which greatly enhances the thermal-insulation property of coating. Furthermore, the laser ablation threshold is improved obviously, which is from 800 W cm‑2 to 1000 W cm‑2.

Fouling behavior of poly(ether)sulfone ultrafiltration membrane during concentration of whey proteins: Effect of hydrophilic modification using atmospheric pressure argon jet plasma.

Science.gov (United States)

Damar Huner, Irem; Gulec, Haci Ali

2017-12-01

The aim of the study was to investigate the effects of hydrophilic surface modification via atmospheric pressure jet plasma (ApJPls) on the fouling propensity of polyethersulfone (PES) ultrafiltration (UF) membranes during concentration of whey proteins. The distance from nozzle to substrate surface of 30mm and the exposure period of 5 times were determined as the most effective parameters enabling an increase in ΔG iwi value of the plain membrane from (-) 14.92±0.89mJ/m 2 to (+) 17.57±0.67mJ/m 2 . Maximum hydrophilicity and minimum surface roughness achieved by argon plasma action resulted in better antifouling behavior, while the hydraulic permeability and the initial permeate flux were decreased sharply due to the plasma-induced surface cross-linking. A quite steady state flux was obtained throughout the UF with the ApJPls modified PES membrane. The contribution of R frev to R t , which was 94% for the UF through the plain membrane, decreased to 43% after the plasma treatment. The overall results of this study highlighted the ApJPls modification decreased the fouling propensity of PES membrane without affecting the original protein rejection capability and improved the recovery of initial permeate flux after chemical cleaning. Copyright © 2017 Elsevier B.V. All rights reserved.

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.

Atomic force microscopy analysis of synthetic membranes applied in release studies

Energy Technology Data Exchange (ETDEWEB)

Olejnik, Anna, E-mail: annamar@amu.edu.pl; Nowak, Izabela

2015-11-15

Graphical abstract: - Highlights: • We compare eight synthetic membranes by atomic force microscopy. • We predict the behavior of membranes in the release experiments. • The polymeric synthetic membranes varied in shape and size. • We detect substructures in pores of cellulose esters and nylon membranes. • Substructures limit the release rate of active compound. - Abstract: Synthetic membranes are commonly used in drug release studies and are applied mostly in quality control. They contain pores through which the drug can be diffused directly into the receptor fluid. Investigation of synthetic membranes permits determination of their structure and characterization of their properties. We suggest that the preliminary characterization of the membranes can be relevant to the interpretation of the release results. The aim of this study was to compare eight synthetic membranes by using atomic force microscopy in order to predict and understand their behavior in the release experiments. The results proved that polytetrafluoroethylene membrane was not suitable for the release study of tetrapeptide due to its hydrophobic nature, thickness and the specific structure with high trapezoid shaped blocks. The additional substructures in pores of mixed cellulose esters and nylon membranes detected by AFM influenced the diffusion rate of the active compound. These findings indicate that the selection of the membrane for the release studies should be performed cautiously by taking into consideration the membrane properties and by analyzing them prior the experiment.

Atomic force microscopy analysis of synthetic membranes applied in release studies

International Nuclear Information System (INIS)

Olejnik, Anna; Nowak, Izabela

2015-01-01

Graphical abstract: - Highlights: • We compare eight synthetic membranes by atomic force microscopy. • We predict the behavior of membranes in the release experiments. • The polymeric synthetic membranes varied in shape and size. • We detect substructures in pores of cellulose esters and nylon membranes. • Substructures limit the release rate of active compound. - Abstract: Synthetic membranes are commonly used in drug release studies and are applied mostly in quality control. They contain pores through which the drug can be diffused directly into the receptor fluid. Investigation of synthetic membranes permits determination of their structure and characterization of their properties. We suggest that the preliminary characterization of the membranes can be relevant to the interpretation of the release results. The aim of this study was to compare eight synthetic membranes by using atomic force microscopy in order to predict and understand their behavior in the release experiments. The results proved that polytetrafluoroethylene membrane was not suitable for the release study of tetrapeptide due to its hydrophobic nature, thickness and the specific structure with high trapezoid shaped blocks. The additional substructures in pores of mixed cellulose esters and nylon membranes detected by AFM influenced the diffusion rate of the active compound. These findings indicate that the selection of the membrane for the release studies should be performed cautiously by taking into consideration the membrane properties and by analyzing them prior the experiment.

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.

Behavior of 4-Hydroxynonenal in Phospholipid Membranes

Czech Academy of Sciences Publication Activity Database

Vazdar, Mario; Jurkiewicz, Piotr; Hof, Martin; Jungwirth, Pavel; Cwiklik, Lukasz

2012-01-01

Roč. 116, č. 22 (2012), s. 6411-6415 ISSN 1520-6106 R&D Projects: GA ČR GA203/08/0114; GA ČR GAP208/10/0376; GA MŠk LH12001; GA AV ČR GEMEM/09/E006 Institutional research plan: CEZ:AV0Z40550506; CEZ:AV0Z40400503 Keywords : fluorescence spectroscopy * molecular dynamics * membrane s * 4-hydroxynonenal Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 3.607, year: 2012

Investigation of Filtration Membranes from the Dairy Protein Industry for Residual Fouling Using Infrared Spectroscopy and Chemometrics

DEFF Research Database (Denmark)

Jensen, Jannie Krog

the reversible fouling can be removed/cleaned. The aim of this thesis is to investigate the residual fouling that is deposited on ultrafiltration and microfiltration membranes after usage. The membrane surfaces are investigated using infrared spectroscopy with an attenuated reflectance sampling unit...... and this is thesis work highlights the strengths and weaknesses of using infrared spectroscopy to investigate residual fouling on membranes and in particular the challenges with the infrared penetration depth when layering in the samples occurs. Real size production membrane cartridges at different stages of use...... microfiltration membrane cartridges were investigated with Attenuated- Total-Reflection Fourier-Transform-Infrared (ATR FT-IR) to map the residual fouling on both types of cartridges. The height of the characteristic amide peaks from proteins were used to determine the relative concentrations. The first...

Glucose-neopentyl glycol (GNG) amphiphiles for membrane protein study.

Science.gov (United States)

Chae, Pil Seok; Rana, Rohini R; Gotfryd, Kamil; Rasmussen, Søren G F; Kruse, Andrew C; Cho, Kyung Ho; Capaldi, Stefano; Carlsson, Emil; Kobilka, Brian; Loland, Claus J; Gether, Ulrik; Banerjee, Surajit; Byrne, Bernadette; Lee, John K; Gellman, Samuel H

2013-03-21

The development of a new class of surfactants for membrane protein manipulation, "GNG amphiphiles", is reported. These amphiphiles display promising behavior for membrane proteins, as demonstrated recently by the high resolution structure of a sodium-pumping pyrophosphatase reported by Kellosalo et al. (Science, 2012, 337, 473).

Generation of membrane potential beyond the conceptual range of Donnan theory and Goldman-Hodgkin-Katz equation.

Science.gov (United States)

Tamagawa, Hirohisa; Ikeda, Kota

2017-09-01

Donnan theory and Goldman-Hodgkin-Katz equation (GHK eq.) state that the nonzero membrane potential is generated by the asymmetric ion distribution between two solutions separated by a semipermeable membrane and/or by the continuous ion transport across the semipermeable membrane. However, there have been a number of reports of the membrane potential generation behaviors in conflict with those theories. The authors of this paper performed the experimental and theoretical investigation of membrane potential and found that (1) Donnan theory is valid only when the macroscopic electroneutrality is sufficed and (2) Potential behavior across a certain type of membrane appears to be inexplicable on the concept of GHK eq. Consequently, the authors derived a conclusion that the existing theories have some limitations for predicting the membrane potential behavior and we need to find a theory to overcome those limitations. The authors suggest that the ion adsorption theory named Ling's adsorption theory, which attributes the membrane potential generation to the mobile ion adsorption onto the adsorption sites, could overcome those problems.

Sulfonated hydrocarbon graft architectures for cation exchange membranes

DEFF Research Database (Denmark)

Nielsen, Mads Møller; Jankova Atanasova, Katja; Hvilsted, Søren

2013-01-01

A synthetic strategy to hydrocarbon graft architectures prepared from a commercial polysulfone and aimed as ion exchange membrane material is proposed. Polystyrene is grafted from a polysulfone macroinitiator by atom transfer radical polymerization, and subsequently sulfonated with acetyl sulfate...... to various degrees. Series of grafting densities and graft lengths are prepared, and membranes are solvent cast from DMSO. The membrane properties in aqueous environments are evaluated from their water swelling behavior, and their thermal properties and stability are investigated by thermogravimetric...

Transport Properties, Mechanical Behavior, Thermal and Chemical Resistance of Asymmetric Flat Sheet Membrane Prepared from PSf/PVDF Blended Membrane on Gauze Supporting Layer

Directory of Open Access Journals (Sweden)

Nita Kusumawati

2018-05-01

Full Text Available Asymmetric polysulfone (PSf membrane is prepared using phase inversion method and blending with polyvinylidene fluoride (PVDF on the gauze solid support. Casting solution composition optimization has been done to get PSf/PVDF membrane with best characteristics and permeability. The result shows that blending on PSf with PVDF polymer using phase inversion method has been very helpful in creating an asymmetric porous membrane. Increased level of PVDF in casting solution has increased the formation of asymmetry structure and corresponding flux membrane. The result from thermal test using Differential Scanning Calorimetry (DSC-Thermal Gravimetric Analysis (TGA shows the resistance of the membrane to temperature 460 °C. Membrane resistance against acid looks from undetectable changes on infrared spectra after immersion process in H2SO4 6–98 v/v%. While membrane color changes from white to brownish and black is detected after the immersion process in sodium hydroxide (NaOH 0.15–80 w/v%.

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

Real and virtual worlds alike: Adolescents' psychopathology is reflected in their videogame virtual behaviors.

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Segev, Aviv; Gabay-Weschler, Hila; Naar, Yossi; Maoz, Hagai; Bloch, Yuval

2017-01-01

Current research refers to videogames as a constant variable. However, games today are designed to be highly interactive and versatile: two players may be using the same videogame, but as a result of different using patterns, the game will not necessarily encompass the same content and gameplay. The current study examined the possible relationship between psychopathology and in-game playing patterns. We hypothesized that adolescents would play videogames differently, in a manner that would reflect their particular psychopathologies. We examined 47 male adolescents from three diagnostic groups: those suffering from externalizing psychopathologies, internalizing psychopathologies and controls. We performed a high-resolution examination of their gameplay, using in-game quantitative statistics mechanisms of two fundamentally different games, a structured racing game and an unstructured adventure game. While there was no difference in the groups' using patterns of the structured game, there was a high variability between the groups' using patterns when they were using a non-structured game. These findings suggest that virtual behavior in unstructured games is reflective of adolescent-players psychopathology, and might shed light on an unexplored facet of videogames research. Possible implications are discussed.

Differences in the Aspect Ratio of Gold Nanorods that Induce Defects in Cell Membrane Models.

Science.gov (United States)

Lins, Paula M P; Marangoni, Valéria S; Uehara, Thiers M; Miranda, Paulo B; Zucolotto, Valtencir; Cancino-Bernardi, Juliana

2017-12-19

Understanding the interactions between biomolecules and nanomaterials is of great importance for many areas of nanomedicine and bioapplications. Although studies in this area have been performed, the interactions between cell membranes and nanoparticles are not fully understood. Here, we investigate the interactions that occur between the Langmuir monolayers of dipalmitoylphosphatidyl glycerol (DPPG) and dipalmitoylphosphatidyl choline (DPPC) with gold nanorods (NR)-with three aspect ratios-and gold nanoparticles. Our results showed that the aspect ratio of the NRs influenced the interactions with both monolayers, which suggest that the physical morphology and electrostatic forces govern the interactions in the DPPG-NR system, whereas the van der Waals interactions are predominant in the DPPC-NR systems. Size influences the expansion isotherms in both systems, but the lipid tails remain conformationally ordered upon expansion, which suggests phase separation between the lipids and nanomaterials at the interface. The coexistence of lipid and NP regions affects the elasticity of the monolayer. When there is coexistence between two phases, the elasticity does not reflect the lipid packaging state but depends on the elasticity of the NP islands. Therefore, the results corroborate that nanomaterials influence the packing and the phase behavior of the mimetic cell membranes. For this reason, developing a methodology to understand the membrane-nanomaterial interactions is of great importance.

Zwitterionic materials for antifouling membrane surface construction.

Science.gov (United States)

He, Mingrui; Gao, Kang; Zhou, Linjie; Jiao, Zhiwei; Wu, Mengyuan; Cao, Jialin; You, Xinda; Cai, Ziyi; Su, Yanlei; Jiang, Zhongyi

2016-08-01

Membrane separation processes are often perplexed by severe and ubiquitous membrane fouling. Zwitterionic materials, keeping electric neutrality with equivalent positive and negative charged groups, are well known for their superior antifouling properties and have been broadly utilized to construct antifouling surfaces for medical devices, biosensors and marine coatings applications. In recent years, zwitterionic materials have been more and more frequently utilized for constructing antifouling membrane surfaces. In this review, the antifouling mechanisms of zwitterionic materials as well as their biomimetic prototypes in cell membranes will be discussed, followed by the survey of common approaches to incorporate zwitterionic materials onto membrane surfaces including surface grafting, surface segregation, biomimetic adhesion, surface coating and so on. The potential applications of these antifouling membranes are also embedded. Finally, we will present a brief perspective on the future development of zwitterionic materials modified antifouling membranes. Membrane fouling is a severe problem hampering the application of membrane separation technology. The properties of membrane surfaces play a critical role in membrane fouling and antifouling behavior/performance. Antifouling membrane surface construction has evolved as a hot research issue for the development of membrane processes. Zwitterionic modification of membrane surfaces has been recognized as an effective strategy to resist membrane fouling. This review summarizes the antifouling mechanisms of zwitterionic materials inspired by cell membranes as well as the popular approaches to incorporate them onto membrane surfaces. It can help form a comprehensive knowledge about the principles and methods of modifying membrane surfaces with zwitterionic materials. Finally, we propose the possible future research directions of zwitterionic materials modified antifouling membranes. Copyright © 2016 Acta Materialia Inc

Decreasing Off-Task Behavior through a Dot/Point Reward System and Portfolio Reflection with Second, Fifth, and Sixth Graders

Science.gov (United States)

Butera, Lisa M.; Giacone, Maria V.; Wagner, Kelly A.

2008-01-01

The purpose of this action research project report was to decrease off-task behavior through a dot/point reward system and portfolio reflections. Students involved in this research were in second, fifth, and sixth grade. There were a total of 85 student participants and 35 teacher participants. The dates of this research began on September 4, 2007…

Nano-swimmers in biological membranes and propulsion hydrodynamics in two dimensions.

Science.gov (United States)

Huang, Mu-Jie; Chen, Hsuan-Yi; Mikhailov, Alexander S

2012-11-01

Active protein inclusions in biological membranes can represent nano-swimmers and propel themselves in lipid bilayers. A simple model of an active inclusion with three particles (domains) connected by variable elastic links is considered. First, the membrane is modeled as a two-dimensional viscous fluid and propulsion behavior in two dimensions is examined. After that, an example of a microscopic dynamical simulation is presented, where the lipid bilayer structure of the membrane is resolved and the solvent effects are included by multiparticle collision dynamics. Statistical analysis of data reveals ballistic motion of the swimmer, in contrast to the classical diffusion behavior found in the absence of active transitions between the states.

Transport of Carbon Dioxide through a Biomimetic Membrane

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Efstathios Matsaridis

2011-01-01

Full Text Available Biomimetic membranes (BMM based on polymer filters impregnated with lipids or their analogues are widely applied in numerous areas of physics, biology, and medicine. In this paper we report the design and testing of an electrochemical system, which allows the investigation of CO2 transport through natural membranes such as alveoli barrier membrane system and also can be applied for solid-state measurements. The experimental setup comprises a specially designed two-compartment cell with BMM connected with an electrochemical workstation placed in a Faraday cage, two PH meters, and a nondispersive infrared gas analyzer. We prove, experimentally, that the CO2 transport through the natural membranes under different conditions depends on pH and displays a similar behavior as natural membranes. The influence of different drugs on the CO2 transport process through such membranes is discussed.

Determination of acoustic properties of thin polymer films utilizing the frequency dependence of the reflection coefficient of ultrasound.

Science.gov (United States)

Tohmyoh, Hironori; Sakamoto, Yuhei

2015-11-01

This paper reports on a technique to measure the acoustic properties of a thin polymer film utilizing the frequency dependence of the reflection coefficient of ultrasound reflected back from a system comprising a reflection plate, the film, and a material that covers the film. The frequency components of the echo reflected from the back of the plate, where the film is attached, take their minimum values at the resonant frequency, and from these frequency characteristics, the acoustic impedance, sound velocity, and the density of the film can be determined. We applied this technique to characterize an ion exchange membrane, which has high water absorbability, and successfully determined the acoustic properties of the membrane without getting it wet.

Stretched membrane heliostats: design and structural analysis of reflectance module and support of a heliostats of 9 m. diaform and 60 m''3 of reflectance surface; Diseno y analisis estructural del modulo reflectante y estructura soporte de un heliostato de 9 m. de diametro y 60 m2 de superficie reflectante

Energy Technology Data Exchange (ETDEWEB)

Figarola Torres, J. M.

1993-07-01

After having designed and built at CIEMAT a first prototype of a Btretched membrane heliostats of 3 m. diameter, the design and the structural analysis of the different components included in the reflectance module and support of another heliostats, this one of 9 m. diameter and 60 m2. of reflectance surface, are shown In this report. This last heliostats will be mounted on a pedestal and its driving device at the Solar Platform of Almeria. In order to optimize design and performance, the structural analysis of its basic components has been analyzed with the finite elements program ANSYS. The following elements have been subject to analysis: the membrane and their ring supports, stretching system and the structural support. A similar scheme to the one applied to the previous prototype has been used on the focus control system. That includes a linear transducer, a variable frequency and a fan. Finally it has to be pointed out that substantial improvements have been achieved with respect to the first prototype concerning design and cost. (Author) 5 refs.

Antibacterial Membrane with a Bone-Like Structure for Guided Bone Regeneration

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YuYuan Zhang

2015-01-01

Full Text Available An antibacterial membrane with a bone-like structure was developed for guided bone regeneration (GBR by mineralising acellular bovine pericardium (ABP and loading it with the antibiotic minocycline. The bovine pericardium (BP membrane was processed using physical and chemical methods to remove the cellular components and obtain ABP membranes. Then, the ABP membranes were biomimetically mineralised using a calcium phosphate-loaded agarose hydrogel system aided by electrophoresis. Minocycline was adsorbed to the mineralised ABP membrane, and the release profile in vitro was studied. The membranes were characterised through scanning electron microscopy, diffuse reflectance-Fourier transform infrared spectroscopy, and X-ray diffraction. Results showed that the ABP membrane had an asymmetric structure with a layer of densely arranged and irregularly aligned collagen fibrils. Collagen fibrils were calcified with the formation of intrafibrillar and interfibrillar hydroxyapatites similar to the bone structure. Minocycline was incorporated into the mineralised collagen membrane and could be released in vitro. This process endowed the membrane with an antibacterial property. This novel composite membrane offers promising applications in bioactive GBR.

Basement Membrane Type IV Collagen and Laminin: An Overview of Their Biology and Value as Fibrosis Biomarkers of Liver Disease.

Science.gov (United States)

Mak, Ki M; Mei, Rena

2017-08-01

Basement membranes provide structural support to epithelium, endothelium, muscles, fat cells, Schwann cells, and axons. Basement membranes are multifunctional: they modulate cellular behavior, regulate organogenesis, promote tissue repair, form a barrier to filtration and tumor metastasis, bind growth factors, and mediate angiogenesis. All basement membranes contain type IV collagen (Col IV), laminin, nidogen, and perlecan. Col IV and laminin self-assemble into two independent supramolecular networks that are linked to nidogen and perlecan to form a morphological discernable basement membrane/basal lamina. The triple helical region, 7S domain and NCI domain of Col IV, laminin and laminin fragment P1 have been evaluated as noninvasive fibrosis biomarkers of alcoholic liver disease, viral hepatitis, and nonalcoholic fatty liver disease. Elevated serum Col IV and laminin are related to degrees of fibrosis and severity of hepatitis, and may reflect hepatic basement membrane metabolism. But the serum assays have not been linked to disclosing the anatomical sites and lobular distribution of perisinusoidal basement membrane formation in the liver. Hepatic sinusoids normally lack a basement membrane, although Col IV is a normal matrix component of the space of Disse. In liver disease, laminin deposits in the space of Disse and codistributes with Col IV, forming a perisinusoidal basement membrane. Concomitantly, the sinusoidal endothelium loses its fenestrae and is transformed into vascular type endothelium. These changes lead to capillarization of hepatic sinusoids, a significant pathology that impairs hepatic function. Accordingly, codistribution of Col IV and laminin serves as histochemical marker of perisinusoidal basement membrane formation in liver disease. Anat Rec, 300:1371-1390, 2017. © 2017 Wiley Periodicals, Inc. © 2017 Wiley Periodicals, Inc.

On the study of catalytic membrane reactor for water detritiation: Modeling approach

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Liger, Karine, E-mail: karine.liger@cea.fr [CEA, DEN, DTN/SMTA/LIPC Cadarache, Saint Paul-lez-Durance F-13108 (France); Mascarade, Jérémy [CEA, DEN, DTN/SMTA/LIPC Cadarache, Saint Paul-lez-Durance F-13108 (France); Joulia, Xavier; Meyer, Xuan-Mi [Université de Toulouse, INPT, UPS, Laboratoire de Génie Chimique, 4, Allée Emile Monso, Toulouse F-31030 (France); CNRS, Laboratoire de Génie Chimique, Toulouse F-31030 (France); Troulay, Michèle; Perrais, Christophe [CEA, DEN, DTN/SMTA/LIPC Cadarache, Saint Paul-lez-Durance F-13108 (France)

2016-11-01

Highlights: • Experimental results for the conversion of tritiated water (using deuterium as a simulant of tritium) by means of a catalytic membrane reactor in view of tritium recovery. • Phenomenological 2D model to represent catalytic membrane reactor behavior including the determination of the compositions of gaseous effluents. • Good agreement between the simulation results and experimental measurements performed on the dedicated facility. • Explanation of the unexpected behavior of the catalytic membrane reactor by the modeling results and in particular the gas composition estimation. - Abstract: In the framework of tritium recovery from tritiated water, efficiency of packed bed membrane reactors have been successfully demonstrated. Thanks to protium isotope swamping, tritium bonded water can be recovered under the valuable Q{sub 2} form (Q = H, D or T) by means of isotope exchange reactions occurring on catalyst surface. The use of permselective Pd-based membrane allows withdrawal of reactions products all along the reactor, and thus limits reverse reaction rate to the benefit of the direct one (shift effect). The reactions kinetics, which are still little known or unknown, are generally assumed to be largely greater than the permeation ones so that thermodynamic equilibriums of isotope exchange reactions are generally assumed. This paper proposes a new phenomenological 2D model to represent catalytic membrane reactor behavior with the determination of gas effluents compositions. A good agreement was obtained between the simulation results and experimental measurements performed on a dedicated facility. Furthermore, the gas composition estimation permits to interpret unexpected behavior of the catalytic membrane reactor. In the next future, further sensitivity analysis will be performed to determine the limits of the model and a kinetics study will be conducted to assess the thermodynamic equilibrium of reactions.

On the study of catalytic membrane reactor for water detritiation: Modeling approach

International Nuclear Information System (INIS)

Liger, Karine; Mascarade, Jérémy; Joulia, Xavier; Meyer, Xuan-Mi; Troulay, Michèle; Perrais, Christophe

2016-01-01

Highlights: • Experimental results for the conversion of tritiated water (using deuterium as a simulant of tritium) by means of a catalytic membrane reactor in view of tritium recovery. • Phenomenological 2D model to represent catalytic membrane reactor behavior including the determination of the compositions of gaseous effluents. • Good agreement between the simulation results and experimental measurements performed on the dedicated facility. • Explanation of the unexpected behavior of the catalytic membrane reactor by the modeling results and in particular the gas composition estimation. - Abstract: In the framework of tritium recovery from tritiated water, efficiency of packed bed membrane reactors have been successfully demonstrated. Thanks to protium isotope swamping, tritium bonded water can be recovered under the valuable Q_2 form (Q = H, D or T) by means of isotope exchange reactions occurring on catalyst surface. The use of permselective Pd-based membrane allows withdrawal of reactions products all along the reactor, and thus limits reverse reaction rate to the benefit of the direct one (shift effect). The reactions kinetics, which are still little known or unknown, are generally assumed to be largely greater than the permeation ones so that thermodynamic equilibriums of isotope exchange reactions are generally assumed. This paper proposes a new phenomenological 2D model to represent catalytic membrane reactor behavior with the determination of gas effluents compositions. A good agreement was obtained between the simulation results and experimental measurements performed on a dedicated facility. Furthermore, the gas composition estimation permits to interpret unexpected behavior of the catalytic membrane reactor. In the next future, further sensitivity analysis will be performed to determine the limits of the model and a kinetics study will be conducted to assess the thermodynamic equilibrium of reactions.

The State of Water in Proton Conducting Membranes

Energy Technology Data Exchange (ETDEWEB)

Allcock, Harry R.; Benesi, Alan; Macdonald, Digby D.

2010-08-27

The research carried out under grant No. DE-FG02-07ER46371, "The State of Water in Proton Conducting Membranes", during the period June 1, 2008 - May 31, 2010 was comprised of three related parts. These are: 1. An examination of the state of water in classical proton conduction membranes with the use of deuterium T1 NMR spectroscopy (Allcock and Benesi groups). 2. A dielectric relaxation examination of the behavior of water in classical ionomer membranes (Macdonald program). 3. Attempts to synthesize new proton-conduction polymers and membranes derived from the polyphosphazene system. (Allcock program) All three are closely related, crucial aspects of the design and development of new and improved polymer electrolyte fuel cell membranes on which the future of fuel cell technology for portable applications depends.

Oxygen Transport Membranes

Energy Technology Data Exchange (ETDEWEB)

S. Bandopadhyay

2008-08-30

The focus of this research was to develop new membrane materials by synthesizing different compounds and determining their defect structures, crystallographic structures and electrical properties. In addition to measuring electrical conductivity, oxygen vacancy concentration was also evaluated using thermogravimetry, Neutron diffraction and Moessbauer Spectroscopy. The reducing conditions (CO{sub 2}/CO/H{sub 2} gas mixtures with steam) as encountered in a reactor environment can be expected to have significant influence on the mechanical properties of the oxides membranes. Various La based materials with and without Ti were selected as candidate membrane materials for OTM. The maximum electrical conductivity of LSF in air as a function of temperature was achieved at < 600 C and depends on the concentration of Sr (acceptor dopant). Oxygen occupancy in LSF was estimated using Neutron diffractometry and Moessbauer Spectroscopy by measuring magnetic moment changes depending on the Fe{sup 3+} and Fe{sup 4+} ratio. After extensive studies of candidate materials, lanthanum ferrites (LSF and LSFT) were selected as the favored materials for the oxygen transport membrane (OTM). LSF is a very good material for an OTM because of its high electronic and oxygen ionic conductivity if long term stability and mechanical strength are improved. LSFT not only exhibits p-type behavior in the high oxygen activity regime, but also has n-type conduction in reducing atmospheres. Higher concentrations of oxygen vacancies in the low oxygen activity regime may improve the performance of LSFT as an OTM. The hole concentration is related to the difference in the acceptor and donor concentration by the relation p = [Sr'{sub La}]-[Ti{sm_bullet}{sub Fe}]. The chemical formulation predicts that the hole concentration is, p = 0.8-0.45 or 0.35. Experimental measurements indicated that p is about {approx} 0.35. The activation energy of conduction is 0.2 eV which implies that LSCF conducts via the

Single cell adhesion strength assessed with variable-angle total internal reflection fluorescence microscopy

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Marcelina Cardoso Dos Santos

2017-06-01

Full Text Available We propose a new strategy to evaluate adhesion strength at the single cell level. This approach involves variable-angle total internal reflection fluorescence microscopy to monitor in real time the topography of cell membranes, i.e. a map of the membrane/substrate separation distance. According to the Boltzmann distribution, both potential energy profile and dissociation energy related to the interactions between the cell membrane and the substrate were determined from the membrane topography. We have highlighted on glass substrates coated with poly-L-lysine and fibronectin, that the dissociation energy is a reliable parameter to quantify the adhesion strength of MDA-MB-231 motile cells.

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.

Do Scaffolding Tools Improve Reflective Writing in Professional Portfolios? A Content Analysis of Reflective Writing in an Advanced Preparation Program

Science.gov (United States)

Houston, Cynthia R.

2016-01-01

Reflective practice is an important skill that teachers must develop to be able to assess the effectiveness of their teaching and modify their instructional behavior. In many education programs reflective narratives, which are often part of teaching portfolios, are intended to assess students' abilities in these areas. Research on reflectivity in…

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.

Effects of semen preservation on boar spermatozoa head membranes.

Science.gov (United States)

Buhr, M M; Canvin, A T; Bailey, J L

1989-08-01

Head plasma membranes were isolated from the sperm-rich fraction of boar semen and from sperm-rich semen that had been subjected to three commercial preservation processes: Extended for fresh insemination (extended), prepared for freezing but not frozen (cooled), and stored frozen for 3-5 weeks (frozen-thawed). Fluorescence polarization was used to determine fluidity of the membranes of all samples for 160 min at 25 degrees C and also for membranes from the sperm-rich and extended semen during cooling and reheating (25 to 5 to 40 degrees C, 0.4 degrees C/min). Head plasma membranes from extended semen were initially more fluid than from other sources (P less than 0.05). Fluidity of head membranes from all sources decreased at 25 degrees C, but the rate of decrease was significantly lower for membranes from cooled and lower again for membranes from frozen-thawed semen. Cooling to 5 degrees C reduced the rate of fluidity change for plasma membranes from the sperm-rich fraction, while heating over 30 degrees C caused a significantly greater decrease. The presence of Ca++ (10 mM) lowered the fluidity of the head plasma membranes from sperm-rich and extended semen over time at 25 degrees C but did not affect the membranes from the cooled or frozen-thawed semen. The change in head plasma membrane fluidity at 25 degrees C may reflect the dynamic nature of spermatozoa membranes prior to fertilization. Extenders, preservation processes and temperature changes have a strong influence on head plasma membrane fluidity and therefore the molecular organization of this membrane.

Young-Adult Male Rats’ Vulnerability to Chronic Mild Stress Is Reflected by Anxious-Like instead of Depressive-Like Behaviors

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Herrera-Pérez José Jaime

2016-01-01

Full Text Available In a previous study, we found that chronic mild stress (CMS paradigm did not induce anhedonia in young-adult male rats but it reduced their body weight gain. These contrasting results encouraged us to explore other indicators of animal’s vulnerability to stress such as anxious-like behaviors, since stress is an etiologic factor also for anxiety. Thus, in this study, we evaluated the vulnerability of these animals to CMS using behavioral tests of depression or anxiety and measuring serum corticosterone. Male Wistar rats were exposed to four weeks of CMS; the animals’ body weight and sucrose preference (indicator of anhedonia were assessed after three weeks, and, after the fourth week, some animals were evaluated in a behavioral battery (elevated plus maze, defensive burying behavior, and forced swimming tests; meanwhile, others were used to measure serum corticosterone. We found that CMS (1 did not affect sucrose preference, immobility behavior in the forced swimming test, or serum corticosterone; (2 decreased body weight gain; and (3 increased the rat’s entries into closed arms of the plus maze and the cumulative burying behavior. These data indicate that young male rats’ vulnerability to CMS is reflected as poor body weight gain and anxious-like instead of depressive-like behaviors.

Distributed microscopic actuation analysis of paraboloidal membrane shells of different geometric parameters

Science.gov (United States)

Yue, Honghao; Lu, Yifan; Deng, Zongquan; Tzou, Hornsen

2018-03-01

Paraboloidal membrane shells of revolution are commonly used as key components for advanced aerospace structures and aviation mechanical systems. Due to their high flexibility and low damping property, active vibration control is of significant importance for these in-orbit membrane structures. To explore the dynamic control behavior of space flexible paraboloidal membrane shells, precision distributed actuation and control effectiveness of free-floating paraboloidal membrane shells with piezoelectric actuators are investigated. Governing equations of the shell structronic system are presented first. Then, distributed control forces and control actions are formulated. A transverse mode shape function of the paraboloidal shell based on the membrane approximation theory and specified boundary condition is assumed in the modal control force analysis. The actuator induced modal control forces on the paraboloidal shell are derived. The expressions of microscopic local modal control forces are obtained by shrinking the actuator area into infinitesimal and the four control components are investigated respectively to predict the spatial microscopic actuation behavior. Geometric parameter (height-radius ratio and shell thickness) effects on the modal actuation behavior are explored when evaluating the micro-control efficiency. Four different cases are discussed and the results reveal the fact that shallow (e.g., antennas/reflectors) and deep (e.g., rocket/missile fairing) paraboloidal shells exhibit totally different modal actuation behaviors due to their curvature differences. Analytical results in this paper can serve as guidelines for optimal actuator placement for vibration control of different paraboloidal structures.

Lipopolysaccharide Membranes and Membrane Proteins of Pseudomonas aeruginosa Studied by Computer Simulation

Energy Technology Data Exchange (ETDEWEB)

Straatsma, TP

2006-12-01

Pseudomonas aeruginosa is a ubiquitous environmental Gram-negative bacterium with high metabolic versatility and an exceptional ability to adapt to a wide range of ecological environments, including soil, marches, coastal habitats, plant and animal tissues. Gram-negative microbes are characterized by the asymmetric lipopolysaccharide outer membrane, the study of which is important for a number of applications. The adhesion to mineral surfaces plays a central role in characterizing their contribution to the fate of contaminants in complex environmental systems by effecting microbial transport through soils, respiration redox chemistry, and ion mobility. Another important application stems from the fact that it is also a major opportunistic human pathogen that can result in life-threatening infections in many immunocompromised patients, such as lung infections in children with cystic fibrosis, bacteraemia in burn victims, urinary-tract infections in catheterized patients, hospital-acquired pneumonia in patients on respirators, infections in cancer patients receiving chemotherapy, and keratitis and corneal ulcers in users of extended-wear soft contact lenses. The inherent resistance against antibiotics which has been linked with the specific interactions in the outer membrane of P. aeruginosa makes these infections difficult to treat. Developments in simulation methodologies as well as computer hardware have enabled the molecular simulation of biological systems of increasing size and with increasing accuracy, providing detail that is difficult or impossible to obtain experimentally. Computer simulation studies contribute to our understanding of the behavior of proteins, protein-protein and protein-DNA complexes. In recent years, a number of research groups have made significant progress in applying these methods to the study of biological membranes. However, these applications have been focused exclusively on lipid bilayer membranes and on membrane proteins in lipid

Comprehensive in silico prediction and analysis of chlamydial outer membrane proteins reflects evolution and life style of the Chlamydiae

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Myers Garry

2009-12-01

Full Text Available Abstract Background Chlamydiae are obligate intracellular bacteria comprising some of the most important bacterial pathogens of animals and humans. Although chlamydial outer membrane proteins play a key role for attachment to and entry into host cells, only few have been described so far. We developed a comprehensive, multiphasic in silico approach, including the calculation of clusters of orthologues, to predict outer membrane proteins using conservative criteria. We tested this approach using Escherichia coli (positive control and Bacillus subtilis (negative control, and applied it to five chlamydial species; Chlamydia trachomatis, Chlamydia muridarum, Chlamydia (a.k.a. Chlamydophila pneumoniae, Chlamydia (a.k.a. Chlamydophila caviae, and Protochlamydia amoebophila. Results In total, 312 chlamydial outer membrane proteins and lipoproteins in 88 orthologous clusters were identified, including 238 proteins not previously recognized to be located in the outer membrane. Analysis of their taxonomic distribution revealed an evolutionary conservation among Chlamydiae, Verrucomicrobia, Lentisphaerae and Planctomycetes as well as lifestyle-dependent conservation of the chlamydial outer membrane protein composition. Conclusion This analysis suggested a correlation between the outer membrane protein composition and the host range of chlamydiae and revealed a common set of outer membrane proteins shared by these intracellular bacteria. The collection of predicted chlamydial outer membrane proteins is available at the online database pCOMP http://www.microbial-ecology.net/pcomp and might provide future guidance in the quest for anti-chlamydial vaccines.

How synthetic membrane systems contribute to the understanding of lipid-driven endocytosis.

Science.gov (United States)

Schubert, Thomas; Römer, Winfried

2015-11-01

Synthetic membrane systems, such as giant unilamellar vesicles and solid supported lipid bilayers, have widened our understanding of biological processes occurring at or through membranes. Artificial systems are particularly suited to study the inherent properties of membranes with regard to their components and characteristics. This review critically reflects the emerging molecular mechanism of lipid-driven endocytosis and the impact of model membrane systems in elucidating the complex interplay of biomolecules within this process. Lipid receptor clustering induced by binding of several toxins, viruses and bacteria to the plasma membrane leads to local membrane bending and formation of tubular membrane invaginations. Here, lipid shape, and protein structure and valency are the essential parameters in membrane deformation. Combining observations of complex cellular processes and their reconstitution on minimal systems seems to be a promising future approach to resolve basic underlying mechanisms. This article is part of a Special Issue entitled: Mechanobiology. Copyright © 2015 Elsevier B.V. All rights reserved.

Magnetic apatite for structural insights on the plasma membrane

International Nuclear Information System (INIS)

Stanca, Sarmiza E; Müller, Robert; Dellith, Jan; Deckert, Volker; Krafft, Christoph; Popp, Jürgen; Fritzsche, Wolfgang; Nietzsche, Sandor; Stöckel, Stephan; Biskup, Christoph

2015-01-01

The iron oxide-hydroxyapatite (FeOxHA) nanoparticles reported here differ from those reported before by their advantage of homogeneity and simple preparation; moreover, the presence of carboxymethyldextran (CMD), together with hydroxyapatite (HA), allows access to the cellular membrane, which makes our magnetic apatite unique. These nanoparticles combine magnetic behavior, Raman label ability and the property of interaction with the cellular membrane; they therefore represent an interesting material for structural differentiation of the cell membrane. It was observed by Raman spectroscopy, scanning electron microscopy (SEM) and fluorescence microscopy that FeOxHA adheres to the plasma membrane and does not penetrate the membrane. These insights make the nanoparticles a promising material for magnetic cell sorting, e.g. in microfluidic device applications. (paper)

Magnetic apatite for structural insights on the plasma membrane

Science.gov (United States)

Stanca, Sarmiza E.; Müller, Robert; Dellith, Jan; Nietzsche, Sandor; Stöckel, Stephan; Biskup, Christoph; Deckert, Volker; Krafft, Christoph; Popp, Jürgen; Fritzsche, Wolfgang

2015-01-01

The iron oxide-hydroxyapatite (FeOxHA) nanoparticles reported here differ from those reported before by their advantage of homogeneity and simple preparation; moreover, the presence of carboxymethyldextran (CMD), together with hydroxyapatite (HA), allows access to the cellular membrane, which makes our magnetic apatite unique. These nanoparticles combine magnetic behavior, Raman label ability and the property of interaction with the cellular membrane; they therefore represent an interesting material for structural differentiation of the cell membrane. It was observed by Raman spectroscopy, scanning electron microscopy (SEM) and fluorescence microscopy that FeOxHA adheres to the plasma membrane and does not penetrate the membrane. These insights make the nanoparticles a promising material for magnetic cell sorting, e.g. in microfluidic device applications.

Wastewater treatment with ion-exchange chitin membrane

International Nuclear Information System (INIS)

Paulenova, A.; Fjeld, R. A.; Visacky, V.

2001-01-01

Chitin, poly(N-acetyl-D glucosamine) and chitosan, its deacetylated derivates have recently obtained attention as bio-sorbents, because they shown a great ability to accumulate heavy metals and other pollutants. It was found that recovery of metals is strongly affected by pH. At low acidic pH range 4-5 chitin membrane exhibits better selectivity for lead than for cadmium or zinc. Sorption preference for metals decreases in the order: Pb > Cd > Zn. For uranium, as well for strontium was observed significant increase of recovery at decrease of pH to slightly acidic, close to neutral value. It was shown that chemical behavior of chitin membrane is excellent; ion-exchange nature of chitin was not changed during chitin membrane manufacturing process. Using of chitin membrane instead of chitin flake column brings significant increasing of driving force of the separation process, limited in the case of column experimental design by diffusion coefficient, while in the case of membrane process only by mass transfer coefficient. (authors)

Theoretical design strategies of bipolar membrane fuel cell with enhanced self-humidification behavior

Science.gov (United States)

Li, Qiushi; Gong, Jian; Peng, Sikan; Lu, Shanfu; Sui, Pang-Chieh; Djilali, Ned; Xiang, Yan

2016-03-01

The bipolar membrane fuel cells (BPMFCs), which have a unique acid-alkaline jointed membrane electrode assembly (MEA) structure, have demonstrated their great potential for self-humidification during operation. Although the self-humidification ability of such bipolar membranes (BPMs) has recently been validated by a one-dimensional BPM model, the transport mechanism and the formation of self-humidification in the MEAs are not well understood. In the present study, a two-dimensional cross-channel MEA model is developed to elucidate the mechanisms and enhancement of water transport on self-humidification with comprehensive consideration of the three electrochemical reaction zones. The water-formation interface model has been successfully investigated by theoretical and experimental interface reaction kinetics, streamlines of water flux present the formation process and mechanism of self-humidification. A critical current (voltage) value, beyond which self-humidification is initiated, is identified. It is also found that such critical current (voltage) can be adjusted by changing the membrane thickness and the water uptake property of the ionomer. It is concluded that fabricating BPMs with proper membrane thickness and water uptake property are effective strategies to enhance the water management and cell performance in BPMFCs.

Ion Transport through Diffusion Layer Controlled by Charge Mosaic Membrane

Directory of Open Access Journals (Sweden)

Akira Yamauchi

2012-01-01

Full Text Available The kinetic transport behaviors in near interface of the membranes were studied using commercial anion and cation exchange membrane and charge mosaic membrane. Current-voltage curve gave the limiting current density that indicates the ceiling of conventional flux. From chronopotentiometry above the limiting current density, the transition time was estimated. The thickness of boundary layer was derived with conjunction with the conventional limiting current density and the transition time from steady state flux. On the other hand, the charge mosaic membrane was introduced in order to examine the ion transport on the membrane surface in detail. The concentration profile was discussed by the kinetic transport number with regard to the water dissociation (splitting on the membrane surface.

Block copolymer/homopolymer dual-layer hollow fiber membranes

KAUST Repository

Hilke, Roland

2014-12-01

We manufactured the first time block copolymer dual-layer hollow fiber membranes and dual layer flat sheet membranes manufactured by double solution casting and phase inversion in water. The support porous layer was based on polystyrene and the selective layer with isopores was formed by micelle assembly of polystyrene-. b-poly-4-vinyl pyridine. The dual layers had an excellent interfacial adhesion and pore interconnectivity. The dual membranes showed pH response behavior like single layer block copolymer membranes with a low flux for pH values less than 3, a fast increase between pH4 and pH6 and a constant high flux level for pH values above 7. The dry/wet spinning process was optimized to produce dual layer hollow fiber membranes with polystyrene internal support layer and a shell block copolymer selective layer.

The tension of framed membranes from computer simulations

DEFF Research Database (Denmark)

Hamkens, Daniel; Jeppesen, Claus; Ipsen, John H.

2018-01-01

the membranes display power-law characteristics for the equation of state, while higher tension levels includes both an extended linear (elastic) as well as a highly non-linear stretching regime. For semi-flexible membranes a transition from extended to buckled conformations takes place at negative frame......Abstract.: We have analyzed the behavior of a randomly triangulated, self-avoiding surface model of a flexible, fluid membrane subject to a circular boundary by Wang-Landau Monte Carlo computer simulation techniques. The dependence of the canonical free energy and frame tension on the frame area...... is obtained for flexible membranes. It is shown that for low bending rigidities the framed membrane is only stable above a threshold tension, suggesting a discontinuous transition from the collapsed (branched polymer) state to a finite tension extended state. In a tension range above this threshold tension...

Deformation analysis of a film-overlapped micro-pump membrane structure

International Nuclear Information System (INIS)

Lee, Fu-Shin; Wang, Pi-Wen; Chen, Chih-Hsiung

2008-01-01

A novel approach is developed to study a film-overlapped membrane structure. Meanwhile, the established model is employed to design the micro-pump membrane structure and to evaluate its pumping efficiency. Two-dimensional coupling effects between the overlapping actuator films and the deformable membrane are thoroughly investigated, including the influences on the membrane from the overlapping films' elongation effects, Poisson's ratio effects and shear strain effects. Overall deformations and interactions for the three-layer membrane structures are accurately calculated through exercising the developed model, in contrast to what difficulties are usually encountered in carrying out FEM methods with very thin elements meshed for the actuator films. Furthermore, this study demonstrates that the high stiffness of the actuating metal films needs to be reflected in the equivalent stiffness of the membrane structures, especially when the sizes of the actuator films become compatible with the sizes of the membranes. Hence, the optimal micro-pumping efficiency of a membrane structure is acquired upon exercising the developed model, and larger sizes of the actuating films do not definitely obtain larger pumping efficiencies for the electromagnetically actuated micro-pumps

Protein adsorption capability on polyurethane and modified-polyurethane membrane for periodontal guided tissue regeneration applications

Energy Technology Data Exchange (ETDEWEB)

Sheikh, Zeeshan [Matrix Dynamics Group, Faculty of Dentistry, University of Toronto, Fitzgerald Building, 150 College Street, Toronto, ON M5S 3E2 (Canada); School of Engineering and Materials Science, Queen Mary, University of London, Mile End Rd, London, E1 4NS (United Kingdom); Khan, Abdul Samad, E-mail: draskhan@ciitlahore.edu.pk [Interdisciplinary Research Centre in Biomedical Materials, COMSATS Institute of Information Technology, Lahore 54000 (Pakistan); Roohpour, Nima [Oral Care R& D, GSK St., Georges Ave., Weybridge KT13 8PA (United Kingdom); Glogauer, Michael [Matrix Dynamics Group, Faculty of Dentistry, University of Toronto, Fitzgerald Building, 150 College Street, Toronto, ON M5S 3E2 (Canada); Rehman, Ihtesham u [Department of Materials Science and Engineering, The Kroto Research Institute, North Campus, University of Sheffield, Broad Lane, Sheffield S3 7HQ (United Kingdom)

2016-11-01

Periodontal disease if left untreated can result in creation of defects within the alveolar ridge. Barrier membranes are frequently used with or without bone replacement graft materials for achieving periodontal guided tissue regeneration (GTR). Surface properties of barrier membranes play a vital role in their functionality and clinical success. In this study polyetherurethane (PEU) membranes were synthesized by using 4,4′-methylene-diphenyl diisocyanate (MDI), polytetramethylene oxide (PTMO) and 1,4-butane diol (BDO) as a chain extender via solution polymerization. Hydroxyl terminated polydimethylsiloxane (PDMS) due to having inherent surface orientation towards air was used for surface modification of PEU on one side of the membranes. This resulting membranes had one surface being PEU and the other being PDMS coated PEU. The prepared membranes were treated with solutions of bovine serum albumin (BSA) in de-ionized water at 37 °C at a pH of 7.2. The surface protein adsorptive potential of PEU membranes was observed using Attenuated Total Reflectance Fourier Transform Infrared Spectroscopy (ATR-FTIR), Raman spectroscopy and Confocal Raman spectroscopy. The contact angle measurement, tensile strength and modulus of prepared membranes were also evaluated. PEU membrane (89.86 ± 1.62°) exhibited less hydrophobic behavior than PEU-PDMS (105.87 ± 3.16°). The ultimate tensile strength and elastic modulus of PEU (27 ± 1 MPa and 14 ± 2 MPa) and PEU-PDMS (8 ± 1 MPa and 26 ± 1 MPa) membranes was in required range. The spectral analysis revealed adsorption of BSA proteins on the surface of non PDMS coated PEU surface. The PDMS modified PEU membranes demonstrated a lack of BSA adsorption. The non PDMS coated side of the membrane which adsorbs proteins could potentially be used facing towards the defect attracting growth factors for periodontal tissue regeneration. Whereas, the PDMS coated side could serve as an occlusive barrier for preventing gingival epithelial

Protein adsorption capability on polyurethane and modified-polyurethane membrane for periodontal guided tissue regeneration applications

International Nuclear Information System (INIS)

Sheikh, Zeeshan; Khan, Abdul Samad; Roohpour, Nima; Glogauer, Michael; Rehman, Ihtesham u

2016-01-01

Periodontal disease if left untreated can result in creation of defects within the alveolar ridge. Barrier membranes are frequently used with or without bone replacement graft materials for achieving periodontal guided tissue regeneration (GTR). Surface properties of barrier membranes play a vital role in their functionality and clinical success. In this study polyetherurethane (PEU) membranes were synthesized by using 4,4′-methylene-diphenyl diisocyanate (MDI), polytetramethylene oxide (PTMO) and 1,4-butane diol (BDO) as a chain extender via solution polymerization. Hydroxyl terminated polydimethylsiloxane (PDMS) due to having inherent surface orientation towards air was used for surface modification of PEU on one side of the membranes. This resulting membranes had one surface being PEU and the other being PDMS coated PEU. The prepared membranes were treated with solutions of bovine serum albumin (BSA) in de-ionized water at 37 °C at a pH of 7.2. The surface protein adsorptive potential of PEU membranes was observed using Attenuated Total Reflectance Fourier Transform Infrared Spectroscopy (ATR-FTIR), Raman spectroscopy and Confocal Raman spectroscopy. The contact angle measurement, tensile strength and modulus of prepared membranes were also evaluated. PEU membrane (89.86 ± 1.62°) exhibited less hydrophobic behavior than PEU-PDMS (105.87 ± 3.16°). The ultimate tensile strength and elastic modulus of PEU (27 ± 1 MPa and 14 ± 2 MPa) and PEU-PDMS (8 ± 1 MPa and 26 ± 1 MPa) membranes was in required range. The spectral analysis revealed adsorption of BSA proteins on the surface of non PDMS coated PEU surface. The PDMS modified PEU membranes demonstrated a lack of BSA adsorption. The non PDMS coated side of the membrane which adsorbs proteins could potentially be used facing towards the defect attracting growth factors for periodontal tissue regeneration. Whereas, the PDMS coated side could serve as an occlusive barrier for preventing gingival epithelial

Benefits of transformational behaviors for leaders: A daily investigation of leader behaviors and need fulfillment.

Science.gov (United States)

Lanaj, Klodiana; Johnson, Russell E; Lee, Stephanie M

2016-02-01

Although a large body of work has examined the benefits of transformational leadership, this work has predominantly focused on recipients of such behaviors. Recent research and theory, however, suggest that there are also benefits for those performing behaviors reflective of transformational leadership. Across 2 experience-sampling studies, we investigate the effects of such behaviors on actors' daily affective states. Drawing from affective events theory and self-determination theory we hypothesize and find that engaging in behaviors reflective of transformational leadership is associated with improvement in actors' daily affect, more so than engaging in behaviors reflective of transactional, consideration, initiating structure, and participative leadership. Behaviors reflective of transformational leadership improved actors' affect in part by fulfilling their daily needs. Furthermore, extraversion and neuroticism moderated these effects such that extraverts benefitted less whereas neurotics benefitted more from these behaviors in terms of affective changes. We consider the theoretical and practical implications of these findings and offer directions for future research. (c) 2016 APA, all rights reserved).

Natural organic matter interactions with polyamide and polysulfone membranes: Formation of conditioning film

KAUST Repository

Gutierrez, Leonardo; Aubry, Cyril; Valladares Linares, Rodrigo; Croue, Jean-Philippe

2015-01-01

A conditioning film changes the physicochemical properties of the membrane surface and strongly affects subsequent fouling behavior. Results from this Atomic Force Microscopy study indicate that Natural Organic Matter (NOM) characteristics, membrane

The Comparative Study on Vapor-Polymerization and Pressure-dependent Conductance Behavior in Polypyrrole-hybridized Membranes

Energy Technology Data Exchange (ETDEWEB)

Hanif, Zahid; Lee, Seyeong; Arsalani, Nasir; Geckeler, Kurt E.; Hong, Sukwon; Yoon, Myung-Han [Gwangju Institute of Science and Technology, Gwangju (Korea, Republic of)

2016-02-15

In this study, commercially available cellulose membranes were hybridized with conjugated polymer via vapor-phase polymerization using pyrrole and iron chloride as a monomer and oxidant, respectively. The iron (III) chloride layer dip-coated on the hydrophilic cell ulose surface oxidized the vaporized pyrrole monomer leading to the polypyrrole-cellulose hybrid membrane. The conductivity of hybrid membrane was optimized by varying the oxidant concentration and the monomer vapor exposure time. The various surface characterizations of polypyrrole-cellulose hybrid membrane show that the conductive polypyrrole layer was uniformly deposited onto the surface of cellulose fibrous networks unlike the polypyrrole-nylonhybrid membrane prepared in the similar way. The polypyrrole-incorporated cellulose networks exhibits steeper electrical conductance increase over the vertical pressure than its nylon counterpart. Our result suggests that the polypyrrole-cellulose hybrid membrane can be applicable for a disposable high-load pressure sensor.

The Comparative Study on Vapor-Polymerization and Pressure-dependent Conductance Behavior in Polypyrrole-hybridized Membranes

International Nuclear Information System (INIS)

Hanif, Zahid; Lee, Seyeong; Arsalani, Nasir; Geckeler, Kurt E.; Hong, Sukwon; Yoon, Myung-Han

2016-01-01

In this study, commercially available cellulose membranes were hybridized with conjugated polymer via vapor-phase polymerization using pyrrole and iron chloride as a monomer and oxidant, respectively. The iron (III) chloride layer dip-coated on the hydrophilic cell ulose surface oxidized the vaporized pyrrole monomer leading to the polypyrrole-cellulose hybrid membrane. The conductivity of hybrid membrane was optimized by varying the oxidant concentration and the monomer vapor exposure time. The various surface characterizations of polypyrrole-cellulose hybrid membrane show that the conductive polypyrrole layer was uniformly deposited onto the surface of cellulose fibrous networks unlike the polypyrrole-nylonhybrid membrane prepared in the similar way. The polypyrrole-incorporated cellulose networks exhibits steeper electrical conductance increase over the vertical pressure than its nylon counterpart. Our result suggests that the polypyrrole-cellulose hybrid membrane can be applicable for a disposable high-load pressure sensor.

Altered Behavioral and Autonomic Pain Responses in Alzheimer’s Disease Are Associated with Dysfunctional Affective, Self-Reflective and Salience Network Resting-State Connectivity

Directory of Open Access Journals (Sweden)

Paul A. Beach

2017-09-01

Full Text Available While pain behaviors are increased in Alzheimer’s disease (AD patients compared to healthy seniors (HS across multiple disease stages, autonomic responses are reduced with advancing AD. To better understand the neural mechanisms underlying these phenomena, we undertook a controlled cross-sectional study examining behavioral (Pain Assessment in Advanced Dementia, PAINAD scores and autonomic (heart rate, HR pain responses in 24 HS and 20 AD subjects using acute pressure stimuli. Resting-state fMRI was utilized to investigate how group connectivity differences were related to altered pain responses. Pain behaviors (slope of PAINAD score change and mean PAINAD score were increased in patients vs. controls. Autonomic measures (HR change intercept and mean HR change were reduced in severe vs. mildly affected AD patients. Group functional connectivity differences associated with greater pain behavior reactivity in patients included: connectivity within a temporal limbic network (TLN and between the TLN and ventromedial prefrontal cortex (vmPFC; between default mode network (DMN subcomponents; between the DMN and ventral salience network (vSN. Reduced HR responses within the AD group were associated with connectivity changes within the DMN and vSN—specifically the precuneus and vmPFC. Discriminant classification indicated HR-related connectivity within the vSN to the vmPFC best distinguished AD severity. Thus, altered behavioral and autonomic pain responses in AD reflects dysfunction of networks and structures subserving affective, self-reflective, salience and autonomic regulation.

Gene expression during zombie ant biting behavior reflects the complexity underlying fungal parasitic behavioral manipulation

NARCIS (Netherlands)

de Bekker, Charissa; Ohm, Robin A; Loreto, Raquel G; Sebastian, Aswathy; Albert, Istvan; Merrow, Martha; Brachmann, Andreas; Hughes, David P

2015-01-01

BACKGROUND: Adaptive manipulation of animal behavior by parasites functions to increase parasite transmission through changes in host behavior. These changes can range from slight alterations in existing behaviors of the host to the establishment of wholly novel behaviors. The biting behavior

Quantum statistical mechanics of nonrelativistic membranes: crumpling transition at finite temperature

Science.gov (United States)

Borelli, M. E. S.; Kleinert, H.; Schakel, Adriaan M. J.

2000-03-01

The effect of quantum fluctuations on a nearly flat, nonrelativistic two-dimensional membrane with extrinsic curvature stiffness and tension is investigated. The renormalization group analysis is carried out in first-order perturbative theory. In contrast to thermal fluctuations, which soften the membrane at large scales and turn it into a crumpled surface, quantum fluctuations are found to stiffen the membrane, so that it exhibits a Hausdorff dimension equal to two. The large-scale behavior of the membrane is further studied at finite temperature, where a nontrivial fixed point is found, signaling a crumpling transition.

Ligand and membrane-binding behavior of the phosphatidylinositol transfer proteins PITPα and PITPβ.

Science.gov (United States)

Baptist, Matilda; Panagabko, Candace; Cockcroft, Shamshad; Atkinson, Jeffrey

2016-12-01

Phosphatidylinositol transfer proteins (PITPs) are believed to be lipid transfer proteins because of their ability to transfer either phosphatidylinositol (PI) or phosphatidylcholine (PC) between membrane compartments, in vitro. However, the detailed mechanism of this transfer process is not fully established. To further understand the transfer mechanism of PITPs we examined the interaction of PITPs with membranes using dual polarization interferometry (DPI), which measures protein binding affinity on a flat immobilized lipid surface. In addition, a fluorescence resonance energy transfer (FRET)-based assay was also employed to monitor how quickly PITPs transfer their ligands to lipid vesicles. DPI analysis revealed that PITPβ had a higher affinity to membranes compared with PITPα. Furthermore, the FRET-based transfer assay revealed that PITPβ has a higher ligand transfer rate compared with PITPα. However, both PITPα and PITPβ demonstrated a preference for highly curved membrane surfaces during ligand transfer. In other words, ligand transfer rate was higher when the accepting vesicles were highly curved.

Super-Resolution Microscopy: Shedding Light on the Cellular Plasma Membrane.

Science.gov (United States)

Stone, Matthew B; Shelby, Sarah A; Veatch, Sarah L

2017-06-14

Lipids and the membranes they form are fundamental building blocks of cellular life, and their geometry and chemical properties distinguish membranes from other cellular environments. Collective processes occurring within membranes strongly impact cellular behavior and biochemistry, and understanding these processes presents unique challenges due to the often complex and myriad interactions between membrane components. Super-resolution microscopy offers a significant gain in resolution over traditional optical microscopy, enabling the localization of individual molecules even in densely labeled samples and in cellular and tissue environments. These microscopy techniques have been used to examine the organization and dynamics of plasma membrane components, providing insight into the fundamental interactions that determine membrane functions. Here, we broadly introduce the structure and organization of the mammalian plasma membrane and review recent applications of super-resolution microscopy to the study of membranes. We then highlight some inherent challenges faced when using super-resolution microscopy to study membranes, and we discuss recent technical advancements that promise further improvements to super-resolution microscopy and its application to the plasma membrane.

Behavior of nafion membrane at elevated temperature and pressure

Czech Academy of Sciences Publication Activity Database

Paidar, M.; Mališ, J.; Bouzek, K.; Žitka, Jan

2010-01-01

Roč. 14, 1-3 (2010), s. 106-111 ISSN 1944-3994. [PERMEA 2009. Prague, 07.06.2009-11.06.2009] EU Projects: European Commission(XE) 212903 - WELTEMP Institutional research plan: CEZ:AV0Z40500505 Keywords : polymer electrolyte * perfluorosulfonic acid * membrane conductivity Subject RIV: CD - Macromolecular Chemistry Impact factor: 0.752, year: 2010

Separation of Peptides with Forward Osmosis Biomimetic Membranes

Science.gov (United States)

Bajraktari, Niada; Madsen, Henrik T.; Gruber, Mathias F.; Truelsen, Sigurd; Jensen, Elzbieta L.; Jensen, Henrik; Hélix-Nielsen, Claus

2016-01-01

Forward osmosis (FO) membranes have gained interest in several disciplines for the rejection and concentration of various molecules. One application area for FO membranes that is becoming increasingly popular is the use of the membranes to concentrate or dilute high value compound solutions such as pharmaceuticals. It is crucial in such settings to control the transport over the membrane to avoid losses of valuable compounds, but little is known about the rejection and transport mechanisms of larger biomolecules with often flexible conformations. In this study, transport of two chemically similar peptides with molecular weight (Mw) of 375 and 692 Da across a thin film composite Aquaporin Inside™ Membrane (AIM) FO membrane was investigated. Despite the relative large size, both peptides were able to permeate the dense active layer of the AIM membrane and the transport mechanism was determined to be diffusion-based. Interestingly, the membrane permeability increased 3.65 times for the 692 Da peptide (1.39 × 10−12 m2·s−1) compared to the 375 Da peptide (0.38 × 10−12 m2·s−1). This increase thus occurs for an 85% increase in Mw but only for a 34% increase in peptide radius of gyration (Rg) as determined from molecular dynamics (MD) simulations. This suggests that Rg is a strong influencing factor for membrane permeability. Thus, an increased Rg reflects the larger peptide chains ability to sample a larger conformational space when interacting with the nanostructured active layer increasing the likelihood for permeation. PMID:27854275

Plasma-polymerized alkaline anion-exchange membrane: Synthesis and structure characterization

International Nuclear Information System (INIS)

Hu Jue; Meng Yuedong; Zhang Chengxu; Fang Shidong

2011-01-01

After-glow discharge plasma polymerization was developed for alkaline anion-exchange membranes synthesis using vinylbenzyl chloride as monomer. X-ray photoelectron spectroscopy and attenuated total reflection Fourier transform infrared spectroscopy were used to characterize the chemical structure properties of plasma-polymerized membranes. Ion-exchange capacities of quaternized poly(vinylbenzyl chloride) (QPVBC) membranes were measured to evaluate their capability of hydroxyl ion transport. A mechanism of plasma polymerization using VBC as monomer that accounts for the competitive effects of free radicals polymerization and plasma ablation in the plasma polymerization process was proposed. Our results indicate that plasma discharge power influences the contents of functional groups and the structure of the plasma polymer membranes, which attribute to the coactions of polymerization and ablation. The properties of uniform morphology, good adhesion to the substrate, high thermal stability and satisfying anion conduction level suggest the potential application of QPVBC membrane deposited at discharge power of 20 W in alkaline direct methanol fuel cells.

Surface interactions and fouling properties of Micrococcus luteus with microfiltration membranes.

Science.gov (United States)

Feng, Lei; Li, Xiufen; Song, Ping; Du, Guocheng; Chen, Jian

2011-11-01

This study was conducted to investigate microbial adhesion of Micrococcus luteus to polypropylene (PP) and polyvinylidene fluoride (PVDF) membranes in relation to the variation of the interfacial energies in the membrane-bacteria systems, for revealing effects of short-range surface interactions on filtration behavior. Both the membranes and M. luteus showed typical strong electron donors and hydrophilic properties. The AB component was dominant in the interfacial energies of the two membrane-bacteria systems. M. luteus presented larger negative U(mlb)(XDLVO) to the PP membrane than to the PVDF membrane. The adhesion experiments also proved that M. luteus had higher adhesion percentage to the PP membrane. This study demonstrated that the adhesion potentials of M. luteus to the PP and PVDF membranes might be explained in terms of bacterium, membrane, and intervening medium surface properties, which are mainly determined by the interfacial energies in the systems according to the XDLVO theory.

Rubber particle proteins, HbREF and HbSRPP, show different interactions with model membranes.

Science.gov (United States)

Berthelot, Karine; Lecomte, Sophie; Estevez, Yannick; Zhendre, Vanessa; Henry, Sarah; Thévenot, Julie; Dufourc, Erick J; Alves, Isabel D; Peruch, Frédéric

2014-01-01

The biomembrane surrounding rubber particles from the hevea latex is well known for its content of numerous allergen proteins. HbREF (Hevb1) and HbSRPP (Hevb3) are major components, linked on rubber particles, and they have been shown to be involved in rubber synthesis or quality (mass regulation), but their exact function is still to be determined. In this study we highlighted the different modes of interactions of both recombinant proteins with various membrane models (lipid monolayers, liposomes or supported bilayers, and multilamellar vesicles) to mimic the latex particle membrane. We combined various biophysical methods (polarization-modulation-infrared reflection-adsorption spectroscopy (PM-IRRAS)/ellipsometry, attenuated-total reflectance Fourier-transform infrared (ATR-FTIR), solid-state nuclear magnetic resonance (NMR), plasmon waveguide resonance (PWR), fluorescence spectroscopy) to elucidate their interactions. Small rubber particle protein (SRPP) shows less affinity than rubber elongation factor (REF) for the membranes but displays a kind of "covering" effect on the lipid headgroups without disturbing the membrane integrity. Its structure is conserved in the presence of lipids. Contrarily, REF demonstrates higher membrane affinity with changes in its aggregation properties, the amyloid nature of REF, which we previously reported, is not favored in the presence of lipids. REF binds and inserts into membranes. The membrane integrity is highly perturbed, and we suspect that REF is even able to remove lipids from the membrane leading to the formation of mixed micelles. These two homologous proteins show affinity to all membrane models tested but neatly differ in their interacting features. This could imply differential roles on the surface of rubber particles. © 2013.

Glucose-Neopentyl Glycol (GNG) Amphiphiles for Membrane Protein Solubilization, Stabilization and Crystallization

OpenAIRE

Chae, Pil Seok; Rana, Rohini R.; Gotfryd, Kamil; Rasmussen, Søren G. F.; Kruse, Andrew C.; Cho, Kyung Ho; Capaldi, Stefano; Carlsson, Emil; Kobilka, Brian; Loland, Claus J.; Gether, Ulrik; Banerjee, Surajit; Byrne, Bernadette; Lee, John K.; Gellman, Samuel H.

2013-01-01

The development of a new class of surfactants for membrane protein manipulation, “GNG amphiphiles”, is reported. These amphiphiles display promising behavior for membrane proteins, as demonstrated recently by the high resolution structure of a sodium-pumping pyrophosphatase reported by Kellosalo et al.

Ciprofloxacin release using natural rubber latex membranes as carrier.

Science.gov (United States)

Dias Murbach, Heitor; Jaques Ogawa, Guilherme; Azevedo Borges, Felipe; Romeiro Miranda, Matheus Carlos; Lopes, Rute; Roberto de Barros, Natan; Guedes Mazalli, Alexandre Vinicius; Gonçalves da Silva, Rosângela; Ferreira Cinman, José Luiz; de Camargo Drago, Bruno; Donizetti Herculano, Rondinelli

2014-01-01

Natural rubber latex (NRL) from Hevea brasiliensis is easily manipulated, low cost, is of can stimulate natural angiogenesis and cellular adhesion, is a biocompatible, material and presents high mechanical resistance. Ciprofloxacin (CIP) is a synthetic antibiotic (fluoroquinolone) used in the treatment of infection at external fixation screws sites and remote infections, and this use is increasingly frequent in medical practice. The aim of this study was to develop a novel sustained delivery system for CIP based on NRL membranes and to study its delivery system behavior. CIP was found to be adsorbed on the NRL membrane, according to results of energy dispersive X-ray spectroscopy. Results show that the membrane can release CIP for up to 59.08% in 312 hours and the mechanism is due to super case II (non-Fickian). The kinetics of the drug release could be fitted with double exponential function X-ray diffraction and Fourier transform infrared (FTIR) spectroscopy shows some interaction by hydrogen bound, which influences its mechanical behavior.

Long-Time Plasma Membrane Imaging Based on a Two-Step Synergistic Cell Surface Modification Strategy.

Science.gov (United States)

Jia, Hao-Ran; Wang, Hong-Yin; Yu, Zhi-Wu; Chen, Zhan; Wu, Fu-Gen

2016-03-16

Long-time stable plasma membrane imaging is difficult due to the fast cellular internalization of fluorescent dyes and the quick detachment of the dyes from the membrane. In this study, we developed a two-step synergistic cell surface modification and labeling strategy to realize long-time plasma membrane imaging. Initially, a multisite plasma membrane anchoring reagent, glycol chitosan-10% PEG2000 cholesterol-10% biotin (abbreviated as "GC-Chol-Biotin"), was incubated with cells to modify the plasma membranes with biotin groups with the assistance of the membrane anchoring ability of cholesterol moieties. Fluorescein isothiocyanate (FITC)-conjugated avidin was then introduced to achieve the fluorescence-labeled plasma membranes based on the supramolecular recognition between biotin and avidin. This strategy achieved stable plasma membrane imaging for up to 8 h without substantial internalization of the dyes, and avoided the quick fluorescence loss caused by the detachment of dyes from plasma membranes. We have also demonstrated that the imaging performance of our staining strategy far surpassed that of current commercial plasma membrane imaging reagents such as DiD and CellMask. Furthermore, the photodynamic damage of plasma membranes caused by a photosensitizer, Chlorin e6 (Ce6), was tracked in real time for 5 h during continuous laser irradiation. Plasma membrane behaviors including cell shrinkage, membrane blebbing, and plasma membrane vesiculation could be dynamically recorded. Therefore, the imaging strategy developed in this work may provide a novel platform to investigate plasma membrane behaviors over a relatively long time period.

Weak glycolipid binding of a microdomain-tracer peptide correlates with aggregation and slow diffusion on cell membranes.

Directory of Open Access Journals (Sweden)

Tim Lauterbach

Full Text Available Organized assembly or aggregation of sphingolipid-binding ligands, such as certain toxins and pathogens, has been suggested to increase binding affinity of the ligand to the cell membrane and cause membrane reorganization or distortion. Here we show that the diffusion behavior of the fluorescently tagged sphingolipid-interacting peptide probe SBD (Sphingolipid Binding Domain is altered by modifications in the construction of the peptide sequence that both result in a reduction in binding to ganglioside-containing supported lipid membranes, and at the same time increase aggregation on the cell plasma membrane, but that do not change relative amounts of secondary structural features. We tested the effects of modifying the overall charge and construction of the SBD probe on its binding and diffusion behavior, by Surface Plasmon Resonance (SPR; Biacore analysis on lipid surfaces, and by Fluorescence Correlation Spectroscopy (FCS on live cells, respectively. SBD binds preferentially to membranes containing the highly sialylated gangliosides GT1b and GD1a. However, simple charge interactions of the peptide with the negative ganglioside do not appear to be a critical determinant of binding. Rather, an aggregation-suppressing amino acid composition and linker between the fluorophore and the peptide are required for optimum binding of the SBD to ganglioside-containing supported lipid bilayer surfaces, as well as for interaction with the membrane. Interestingly, the strength of interactions with ganglioside-containing artificial membranes is mirrored in the diffusion behavior by FCS on cell membranes, with stronger binders displaying similar characteristic diffusion profiles. Our findings indicate that for aggregation-prone peptides, aggregation occurs upon contact with the cell membrane, and rather than giving a stronger interaction with the membrane, aggregation is accompanied by weaker binding and complex diffusion profiles indicative of heterogeneous

Fouling distribution in forward osmosis membrane process.

Science.gov (United States)

Lee, Junseok; Kim, Bongchul; Hong, Seungkwan

2014-06-01

Fouling behavior along the length of membrane module was systematically investigated by performing simple modeling and lab-scale experiments of forward osmosis (FO) membrane process. The flux distribution model developed in this study showed a good agreement with experimental results, validating the robustness of the model. This model demonstrated, as expected, that the permeate flux decreased along the membrane channel due to decreasing osmotic pressure differential across the FO membrane. A series of fouling experiments were conducted under the draw and feed solutions at various recoveries simulated by the model. The simulated fouling experiments revealed that higher organic (alginate) fouling and thus more flux decline were observed at the last section of a membrane channel, as foulants in feed solution became more concentrated. Furthermore, the water flux in FO process declined more severely as the recovery increased due to more foulants transported to membrane surface with elevated solute concentrations at higher recovery, which created favorable solution environments for organic adsorption. The fouling reversibility also decreased at the last section of the membrane channel, suggesting that fouling distribution on FO membrane along the module should be carefully examined to improve overall cleaning efficiency. Lastly, it was found that such fouling distribution observed with co-current flow operation became less pronounced in counter-current flow operation of FO membrane process. Copyright © 2014 The Research Centre for Eco-Environmental Sciences, Chinese Academy of Sciences. Published by Elsevier B.V. All rights reserved.

[Does a lateral gradient of membrane potential on the plasma membrane of growing pollen tube of germinating pollen grain exist?].

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Andreev, I M

2011-01-01

The data presented in the article by Breigina et al. (2009) "Changes in the membrane potential during pollen grain germination and pollen tube growth" (Tsitologiya. 51 (10): 815-823) and concerning the measurement of electric membrane potential (Delta Psi) on the plasma membrane of growing pollen tube of germinating pollen grain with the use of fluorescent potential-sensitive dye, di-4-ANEPPS, were critically analyzed in order to clarify whether a lateral gradient of Delta Psi on this membrane indeed exists. This analysis showed that the main conclusion of the authors of the above article on the existence of polar distribution of Delta Psi along the pollen tube plasma membrane is not in accordance with a number of known peculiarities of di-4-ANEPPS behavior in biological membranes and requires a significant revision. The findings in question reported by the authors, in my opinion, might be interpreted as evidence for the presence on the plasma membrane of growing pollen tube not only the membrane potential Delta Psi but also lateral gradient of so called intra-membrane dipole potential. Based on the comments made, another interpretation of the experimental results described by Breigina et al. has been offered. In addition, some drawbacks in the methodology used by the authors for measurement of Delta Psi with other fluorescent potential-sensitive dye, DiBAC3(3), are also shortly considered.

GABA-B receptor activation and conflict behavior

International Nuclear Information System (INIS)

Ketelaars, C.E.J.; Bollen, E.L.; Rigter, H.; Bruinvels, J.

1988-01-01

Baclofen and oxazepam enhance extinction of conflict behavior in the Geller-Seifter test while baclofen and diazepam release punished behavior in Vogel's conflict test. In order to investigate the possibility that the effect of the selective GABA-B receptor agonist baclofen is mediated indirectly via the GABA-A/benzodiazepine receptor complex, the effect of pretreatment of rats with baclofen on [ 3 H]-diazepam binding to washed and unwashed cortical and cerebellar membranes of rats has been studied. Baclofen pretreatment increase Bmax in washed cerebellar membranes when bicuculline was present in the incubation mixture. No effect was seen in cortical membranes. The present results render it unlikely that the effect of baclofen on extinction of conflict behavior and punished drinking is mediated via the GABA-A/benzodiazepine receptor complex. 50 references, 1 figure, 4 tables

Anti-fouling behavior of hyperbranched polyglycerol-grafted poly(ether sulfone) hollow fiber membranes for osmotic power generation.

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Li, Xue; Cai, Tao; Chung, Tai-Shung

2014-08-19

To sustain high performance of osmotic power generation by pressure-retarded osmosis (PRO) processes, fouling on PRO membranes must be mitigated. This is especially true for the porous support of PRO membranes because its porous structure is very prone to fouling by feeding river water. For the first time, we have successfully designed antifouling PRO thin-film composite (TFC) membranes by synthesizing a dendritic hydrophilic polymer with well-controlled grafting sites, hyperbranched polyglycerol (HPG), and then grafting it on poly(ether sulfone) (PES) hollow fiber membrane supports. Compared to the pristine PES membranes, polydopamine modified membranes, and conventional poly(ethylene glycol) (PEG)-grafted membranes, the HPG grafted membranes show much superior fouling resistance against bovine serum albumin (BSA) adsorption, E. coli adhesion, and S. aureus attachment. In high-pressure PRO tests, the PES TFC membranes are badly fouled by model protein foulants, causing a water flux decline of 31%. In comparison, the PES TFC membrane grafted by HPG not only has an inherently higher water flux and a higher power density but also exhibits better flux recovery up to 94% after cleaning and hydraulic pressure impulsion. Clearly, by grafting the properly designed dendritic polymers to the membrane support, one may substantially sustain PRO hollow fiber membranes for power generation.

Molecular Origin of Model Membrane Bending Rigidity

International Nuclear Information System (INIS)

Kurtisovski, Erol; Taulier, Nicolas; Waks, Marcel; Ober, Raymond; Urbach, Wladimir

2007-01-01

The behavior of the bending modulus κ of bilayers in lamellar phases was studied by Small Angle X-ray Scattering technique for various nonionic C i E j surfactants. The bilayers are either unswollen and dispersed in water or swollen by water and dispersed in dodecane. For unswollen bilayers, the values of κ decrease with both an increase in the area per surfactant molecule and in the polar head length. They increase when the aliphatic chain length increases at constant area per surfactant molecule. Whereas for water-swollen membranes, the values of κ decrease as the content of water increases converging to the value of the single monolayer bending modulus. Such a behavior results from the decoupling of the fluctuations of the two surfactant membrane monolayers. Our results emphasize the determinant contribution of the surfactant conformation to κ

Sulfur removal from fuel using zeolites/polyimide mixed matrix membrane adsorbents

International Nuclear Information System (INIS)

Lin, Ligang; Wang, Andong; Dong, Meimei; Zhang, Yuzhong; He, Benqiao; Li, Hong

2012-01-01

Graphical abstract: Membrane adsorption process is proposed for sulfur removal. Three-dimensional network structure is key to fulfill adsorption function of MMMs, which adsorption/desorption behavior is markedly related with binding force with sulfur molecules. Highlights: ► Membrane adsorption process is proposed for sulfur removal. ► Three-dimensional network structure of MMMs is key to fulfill adsorption function. ► Adsorption/desorption behavior is markedly related with binding force. - Abstract: A novel membrane adsorption process was proposed for the sulfur removal from fuels. The mixed matrix membranes (MMMs) adsorbents composed of polyimide (PI) and various Y zeolites were prepared. By the detailed characterization of FT-IR, morphology, thermal and mechanical properties of MMMs adsorbents, combining the adsorption and desorption behavior research, the process–structure–function relationship was discussed. Field-emission scanning electron microscope (FESEM) images show that the functional particles are incorporated into the three-dimensional network structure. MMMs adsorbents with 40% of zeolites content possess better physical properties, which was confirmed by mechanical strength and thermo stability analysis. Influence factors including post-treatment, content of incorporated zeolites, adsorption time, temperature, initial sulfur concentration as well as sulfur species on the adsorption performance of MMMs adsorbents have been evaluated. At 4 wt.% zeolites content, adsorption capacity for NaY/PI, AgY/PI and CeY/PI MMMs adsorbents come to 2.0, 7.5 and 7.9 mg S/g, respectively. And the regeneration results suggest that the corresponding spent membranes can recover about 98%, 90% and 70% of the desulfurization capacity, respectively. The distinct adsorption and desorption behavior of MMMs adsorbents with various functional zeolites was markedly related with their various binding force and binding mode with sulfur compounds.

Conformationally Preorganized Diastereomeric Norbornane-Based Maltosides for Membrane Protein Study

DEFF Research Database (Denmark)

Das, Manabendra; Du, Yang; Ribeiro, Orquidea

2017-01-01

were generally better at stabilizing membrane proteins than short alkyl chain agents. Furthermore, use of one well-behaving NBM enabled us to attain a marked stabilization and clear visualization of a challenging membrane protein complex using electron microscopy. Thus, this study not only describes......Detergents are essential tools for functional and structural studies of membrane proteins. However, conventional detergents are limited in their scope and utility, particularly for eukaryotic membrane proteins. Thus, there are major efforts to develop new amphipathic agents with enhanced properties....... Here, a novel class of diastereomeric agents with a preorganized conformation, designated norbornane-based maltosides (NBMs), were prepared and evaluated for their ability to solubilize and stabilize membrane proteins. Representative NBMs displayed enhanced behaviors compared to n...

Controlled release of mitomycin C from PHEMAH-Cu(II) cryogel membranes.

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Bakhshpour, Monireh; Yavuz, Handan; Denizli, Adil

2018-02-19

Molecular imprinting technique was used for the preparation of antibiotic and anti-neoplastic chemotherapy drug (mitomycin C) imprinted cryogel membranes (MMC-ICM). The membranes were synthezied by using metal ion coordination interactions with N-methacryloyl-(l)-histidine methyl ester (MAH) functional monomer and template molecules (i.e. MMC). The 2-hydroxyethyl methacrylate (HEMA) monomer and methylene bisacrylamide (MBAAm) crosslinker were used for the preparation of mitomycin C imprinted cryogel membranes by radical suspension polymerization technique. The imprinted cryogel membranes were characterized by scanning electron microscopy (SEM), Brunauer-Emmett-Teller (BET), Fourier transform infrared spectroscopy-attenuated total reflectance (FTIR-ATR) and swelling degree measurements. Cytotoxicity of MMC-ICMs was investigated using mouse fibroblast cell line L929. Time-dependent release of MMC was demonstrated within 150 h from cryogel membranes. Cryogels demonstrated very high MMC loading efficiency (70-80%) and sustained MMC release over hours.

Removal properties of human enteric viruses in a pilot-scale membrane bioreactor (MBR) process.

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Miura, Takayuki; Okabe, Satoshi; Nakahara, Yoshihito; Sano, Daisuke

2015-05-15

In order to evaluate removal properties of human enteric viruses from wastewater by a membrane bioreactor (MBR), influent, anoxic and oxic mixed liquor, and membrane effluent samples were collected in a pilot-scale anoxic-oxic MBR process for 16 months, and concentrations of enteroviruses, norovirus GII, and sapoviruses were determined by real-time PCR using murine norovirus as a process control. Mixed liquor samples were separated into liquid and solid phases by centrifugation, and viruses in the bulk solution and those associated with mixed liquor suspended solids (MLSS) were quantified. Enteroviruses, norovirus GII, and sapoviruses were detected in the influent throughout the sampling period (geometrical mean, 4.0, 3.1, and 4.4 log copies/mL, respectively). Enterovirus concentrations in the solid phase of mixed liquor were generally lower than those in the liquid phase, and the mean log reduction value between influent and anoxic mixed liquor was 0.40 log units. In contrast, norovirus GII and sapovirus concentrations in the solid phase were equal to or higher than those in the liquid phase, and higher log reduction values (1.3 and 1.1 log units, respectively) were observed between influent and anoxic mixed liquor. This suggested that enteroviruses were less associated with MLSS than norovirus GII and sapoviruses, resulting in lower enterovirus removal in the activated sludge process. Enteroviruses and norovirus GII were detected in the MBR effluent but sapoviruses were not in any effluent samples. When MLSS concentration was reduced to 50-60% of a normal operation level, passages of enteroviruses and norovirus GII through a PVDF microfiltration membrane were observed. Since rejection of viruses by the membrane was not related to trans-membrane pressure which was monitored as a parameter of membrane fouling, the results indicated that adsorption to MLSS plays an important role in virus removal by an MBR, and removal properties vary by viruses reflecting different

The utility of vignettes to stimulate reflection on professionalism: theory and practice.

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Bernabeo, E C; Holmboe, E S; Ross, K; Chesluk, B; Ginsburg, S

2013-08-01

Professionalism remains a substantive theme in medical literature. There is an emerging emphasis on sociological and complex adaptive systems perspectives that refocuses attention from just the individual role to working within one's system to enact professionalism in practice. Reflecting on responses to professional dilemmas may be one method to help practicing physicians identify both internal and external factors contributing to (un) professional behavior. We present a rationale and theoretical framework that supports and guides a reflective approach to the self assessment of professionalism. Guided by principles grounded in this theoretical framework, we developed and piloted a set of vignettes on professionally challenging situations, designed to stimulate reflection in practicing physicians. Findings show that participants found the vignettes to be authentic and typical, and reported the group experience as facilitative around discussions of professional ambiguity. Providing an opportunity for physicians to reflect on professional behavior in an open and safe forum may be a practical way to guide physicians to assess themselves on professional behavior and engage with the complexities of their work. The finding that the focus groups led to reflection at a group level suggests that effective reflection on professional behavior may require a socially interactive process. Emphasizing both the behaviors and the internal and external context in which they occur can thus be viewed as critically important for understanding professionalism in practicing physicians.

Glucose-Neopentyl Glycol (GNG) Amphiphiles for Membrane Protein Solubilization, Stabilization and Crystallization

Science.gov (United States)

Rana, Rohini R.; Gotfryd, Kamil; Rasmussen, Søren G. F.; Kruse, Andrew C.; Cho, Kyung Ho; Capaldi, Stefano; Carlsson, Emil; Kobilka, Brian; Loland, Claus J.; Gether, Ulrik; Banerjee, Surajit

2012-01-01

The development of a new class of surfactants for membrane protein manipulation, “GNG amphiphiles”, is reported. These amphiphiles display promising behavior for membrane proteins, as demonstrated recently by the high resolution structure of a sodium-pumping pyrophosphatase reported by Kellosalo et al. PMID:23165475

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

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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.

RETENTION OF HUMIC ACID FROM WATER BY NANOFILTRATION MEMBRANE AND INFLUENCE OF SOLUTION CHEMISTRY ON MEMBRANE PERFORMANCE

Directory of Open Access Journals (Sweden)

M. A. Zazouli, S. Nasseri, A. H. Mahvi, M. Gholami, A. R. Mesdaghinia, M. Younesian

2008-01-01

Full Text Available The objectives of this research were to investigate the rejection efficiency of salt and hydrophobic fraction of natural organic matter, to study the flux decline behavior with a spiral wound nanofiltration membrane, and also to survey the influence of water chemistry on membrane performance. Experiments were conducted using a cross flow pilot-scale membrane unit with a full circulation mode. Humic acid was used as hydrophobic organic matter and NaCl as background electrolyte. Results showed that flux reduction increased with increasing ionic strength and humic acid concentration, and with lower pH. The rejection efficiency of organic and salt decreased with the decrease in pH and increase in ionic strength, because of osmotic pressure increase, leading to permeate flux decline and decrease in salt rejection. In addition, the improved salt rejection was likely due to Donnan exclusion by humic material close to membrane surfaces. The average rejection efficiency of humic acid and salt ranged between 91.2%-95.25% and 63.6%-80%, respectively. Dissolved organic carbon concentration was less than 0.57mg/L in permeate for all experiments. With increasing organic concentration, the charge of the membrane surface has become more negative due to the adsorption of organic foulants on the membrane surface, and thus increased the electrostatic repulsion. However, the increasing surface charge had the potential to result in a larger molecular weight cut-off of a fouled membrane due to membrane swelling which can lead to lower rejection solutes. Therefore, results of this study indicated that membrane fouling may significantly affect the rejection of organic and ion solute.

Exploring the Spatiotemporal Organization of Membrane Proteins in Living Plant Cells.

Science.gov (United States)

Wang, Li; Xue, Yiqun; Xing, Jingjing; Song, Kai; Lin, Jinxing

2018-04-29

Plasma membrane proteins have important roles in transport and signal transduction. Deciphering the spatiotemporal organization of these proteins provides crucial information for elucidating the links between the behaviors of different molecules. However, monitoring membrane proteins without disrupting their membrane environment remains difficult. Over the past decade, many studies have developed single-molecule techniques, opening avenues for probing the stoichiometry and interactions of membrane proteins in their native environment by providing nanometer-scale spatial information and nanosecond-scale temporal information. In this review, we assess recent progress in the development of labeling and imaging technology for membrane protein analysis. We focus in particular on several single-molecule techniques for quantifying the dynamics and assembly of membrane proteins. Finally, we provide examples of how these new techniques are advancing our understanding of the complex biological functions of membrane proteins.

Absence of first-order unbinding transitions of fluid and polymerized membranes

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Grotehans, Stefan; Lipowsky, Reinhard

1990-01-01

Unbinding transitions of fluid and polymerized membranes are studied by renormalization-group (RG) methods. Two different RG schemes are used and found to give rather consistent results. The fixed-point structure of both RG's exhibits a complex behavior as a function of the decay exponent tau for the fluctuation-induced interaction of the membranes. For tau greater than tau(S2) interacting membranes can undergo first-order transitions even in the strong-fluctuation regime. These estimates for tau(S2) imply, however, that both fluid and polymerized membranes unbind in a continuous way in the absence of lateral tension.

Materials dependence of mixed gas plasticization behavior in asymmetric membranes

NARCIS (Netherlands)

Visser, Tymen; Masetto, N.; Wessling, Matthias

2007-01-01

The mass transport of asymmetric membranes for the separation of carbon dioxide/methane mixtures is determined by competitive sorption and plasticization. With increasing feed pressure in mixed gas experiments, the selectivity decreases due to both effects. Distinction whether one or the other

Direct visualization of membrane architecture of myelinating cells in transgenic mice expressing membrane-anchored EGFP.

Science.gov (United States)

Deng, Yaqi; Kim, BongWoo; He, Xuelian; Kim, Sunja; Lu, Changqing; Wang, Haibo; Cho, Ssang-Goo; Hou, Yiping; Li, Jianrong; Zhao, Xianghui; Lu, Q Richard

2014-04-01

Myelinogenesis is a complex process that involves substantial and dynamic changes in plasma membrane architecture and myelin interaction with axons. Highly ramified processes of oligodendrocytes in the central nervous system (CNS) make axonal contact and then extrapolate to wrap around axons and form multilayer compact myelin sheathes. Currently, the mechanisms governing myelin sheath assembly and axon selection by myelinating cells are not fully understood. Here, we generated a transgenic mouse line expressing the membrane-anchored green fluorescent protein (mEGFP) in myelinating cells, which allow live imaging of details of myelinogenesis and cellular behaviors in the nervous systems. mEGFP expression is driven by the promoter of 2'-3'-cyclic nucleotide 3'-phosphodiesterase (CNP) that is expressed in the myelinating cell lineage. Robust mEGFP signals appear in the membrane processes of oligodendrocytes in the CNS and Schwann cells in the peripheral nervous system (PNS), wherein mEGFP expression defines the inner layers of myelin sheaths and Schmidt-Lanterman incisures in adult sciatic nerves. In addition, mEGFP expression can be used to track the extent of remyelination after demyelinating injury in a toxin-induced demyelination animal model. Taken together, the membrane-anchored mEGFP expression in the new transgenic line would facilitate direct visualization of dynamic myelin membrane formation and assembly during development and process remodeling during remyelination after various demyelinating injuries.

Sodium ion conducting polymer electrolyte membrane prepared by phase inversion technique

Science.gov (United States)

Harshlata, Mishra, Kuldeep; Rai, D. K.

2018-04-01

A mechanically stable porous polymer membrane of Poly(vinylidene fluoride-hexafluoropropylene) has been prepared by phase inversion technique using steam as a non-solvent. The membrane possesses semicrystalline network with enhanced amorphicity as observed by X-ray diffraction. The membrane has been soaked in an electrolyte solution of 0.5M NaPF6 in Ethylene Carbonate/Propylene Carbonate (1:1) to obtain the gel polymer electrolyte. The porosity and electrolyte uptake of the membrane have been found to be 67% and 220% respectively. The room temperature ionic conductivity of the membrane has been obtained as ˜ 0.3 mS cm-1. The conductivity follows Arrhenius behavior with temperature and gives activation energy as 0.8 eV. The membrane has been found to possess significantly large electrochemical stability window of 5.0 V.

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.

REFLECTIONS ON BEHAVIORAL CRISES PREVENTION AND INTERVENTION IN SPECIAL EDUCATION SCHOOLS IN THE UNITED STATES

Directory of Open Access Journals (Sweden)

Roland PAULAUSKAS

2011-04-01

Full Text Available The development of civilization made crises an inseparable part of our lives. Crises manifest themselves in almost all social areas and organizations, including educational institutions. The goals of the article are to present a theoretical model of normal, deviant and antisocial behaviors, and discuss the psycho-social characteristics of emotionally disturbed adolescents situated in a residential special education school in the United States. The article also gives an analysis of their most prevalent behavioral crises, escalation stages, as well as nonviolent crisis prevention and intervention strategies. The methods that were used include scientific literature review, analysis of statistical information supplied from different government sources, review and analysis of student records, as well as the author’s analytical reflections in working with emotionally disturbed youngsters in residential special education schools in the United States.The results of the study indicate that scientists from different fields use different terminology to describe socially nonconforming behaviors. The author presents a theoretical model of normal, deviant and antisocial behavior that could enhance better understanding and identification of high risk situations and conduct leading to serious crises. The analysis of student records revealed that most of the adolescents situated in special education residential schools are diagnosed with a number of mental health problems. This suggests that the currently prevailing care and education paradigm in the special education residential schools should shift to a more comprehensive treatment paradigm. The article also discusses the pros and cons of nonviolent crisis intervention. It is the author’s opinion that all special education schools serving children with emotional disorders should adopt one of the nonviolent crisis intervention models and develop and implement crisis management policies, plans and procedures.

Phosphoric acid distribution in the membrane electrode assembly of high temperature proton exchange membrane fuel cells

International Nuclear Information System (INIS)

Kwon, Kyungjung; Park, Jung Ock; Yoo, Duck Young; Yi, Jung S.

2009-01-01

The ionomer content in electrode is one of the most important parameters for the high performance of fuel cells. The high temperature PEMFC based on phosphoric acid (PA)-doped polymer membrane with unhumidified reactant gases has a difficulty in controlling the liquid state PA ionomer content in electrode. To evaluate the PA content in electrode, the three techniques of cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and acid-base titration (ABT) are carried out in situ or ex situ. The properties of membrane electrode assembly (MEA) such as electrochemical surface area (ESA), ohmic resistance, charge transfer resistance, double layer capacitance and the amount of PA in MEA components (anode, cathode and membrane) are extracted by each technique. Ex situ CV with the usage of dry gases has a limitation in assessing the reliable ESA of unhumidified PEMFC. While in situ EIS presents some informative values of resistance and capacitance for understanding the PA distribution in MEA, its sensitivity to the PA content in MEA components needs to be higher for detecting a subtle change in PA distribution. Ex situ ABT supplies a clear PA distribution in MEA at room temperature but does not seem to reflect the operating state well at high temperatures. However, it can be used as a detection tool for the loss of the initial acid content in membrane during a long-term MEA durability study.

Phosphoric acid distribution in the membrane electrode assembly of high temperature proton exchange membrane fuel cells

Energy Technology Data Exchange (ETDEWEB)

Kwon, Kyungjung [Fuel Cell Group, Energy Lab, SAIT, Samsung Electronics Co., Ltd., San 14-1, Nongseo-dong, Giheung-gu, Yongin-si, Gyeonggi-do, 446-712 (Korea, Republic of)], E-mail: kfromberk@gmail.com; Park, Jung Ock; Yoo, Duck Young; Yi, Jung S. [Fuel Cell Group, Energy Lab, SAIT, Samsung Electronics Co., Ltd., San 14-1, Nongseo-dong, Giheung-gu, Yongin-si, Gyeonggi-do, 446-712 (Korea, Republic of)

2009-11-01

The ionomer content in electrode is one of the most important parameters for the high performance of fuel cells. The high temperature PEMFC based on phosphoric acid (PA)-doped polymer membrane with unhumidified reactant gases has a difficulty in controlling the liquid state PA ionomer content in electrode. To evaluate the PA content in electrode, the three techniques of cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and acid-base titration (ABT) are carried out in situ or ex situ. The properties of membrane electrode assembly (MEA) such as electrochemical surface area (ESA), ohmic resistance, charge transfer resistance, double layer capacitance and the amount of PA in MEA components (anode, cathode and membrane) are extracted by each technique. Ex situ CV with the usage of dry gases has a limitation in assessing the reliable ESA of unhumidified PEMFC. While in situ EIS presents some informative values of resistance and capacitance for understanding the PA distribution in MEA, its sensitivity to the PA content in MEA components needs to be higher for detecting a subtle change in PA distribution. Ex situ ABT supplies a clear PA distribution in MEA at room temperature but does not seem to reflect the operating state well at high temperatures. However, it can be used as a detection tool for the loss of the initial acid content in membrane during a long-term MEA durability study.

Membrane fusion-competent virus-like proteoliposomes and proteinaceous supported bilayers made directly from cell plasma membranes.

Science.gov (United States)

Costello, Deirdre A; Hsia, Chih-Yun; Millet, Jean K; Porri, Teresa; Daniel, Susan

2013-05-28

Virus-like particles are useful materials for studying virus-host interactions in a safe manner. However, the standard production of pseudovirus based on the vesicular stomatitis virus (VSV) backbone is an intricate procedure that requires trained laboratory personnel. In this work, a new strategy for creating virus-like proteoliposomes (VLPLs) and virus-like supported bilayers (VLSBs) is presented. This strategy uses a cell blebbing technique to induce the formation of nanoscale vesicles from the plasma membrane of BHK cells expressing the hemagglutinin (HA) fusion protein of influenza X-31. These vesicles and supported bilayers contain HA and are used to carry out single particle membrane fusion events, monitored using total internal reflection fluorescence microscopy. The results of these studies show that the VLPLs and VLSBs contain HA proteins that are fully competent to carry out membrane fusion, including the formation of a fusion pore and the release of fluorophores loaded into vesicles. This new strategy for creating spherical and planar geometry virus-like membranes has many potential applications. VLPLs could be used to study fusion proteins of virulent viruses in a safe manner, or they could be used as therapeutic delivery particles to transport beneficial proteins coexpressed in the cells to a target cell. VLSBs could facilitate high throughput screening of antiviral drugs or pathogen-host cell interactions.

Conditions that Stabilize Membrane Domains Also Antagonize n-Alcohol Anesthesia

Science.gov (United States)

Machta, Benjamin B.; Gray, Ellyn; Nouri, Mariam; McCarthy, Nicola L. C.; Gray, Erin M.; Miller, Ann L.; Brooks, Nicholas J.; Veatch, Sarah L.

2016-08-01

Diverse molecules induce general anesthesia with potency strongly correlated both with their hydrophobicity and their effects on certain ion channels. We recently observed that several n-alcohol anesthetics inhibit heterogeneity in plasma membrane derived vesicles by lowering the critical temperature ($T_c$) for phase separation. Here we exploit conditions that stabilize membrane heterogeneity to further test the correlation between the anesthetic potency of n-alcohols and effects on $T_c$. First we show that hexadecanol acts oppositely to n-alcohol anesthetics on membrane mixing and antagonizes ethanol induced anesthesia in a tadpole behavioral assay. Second, we show that two previously described `intoxication reversers' raise $T_c$ and counter ethanol's effects in vesicles, mimicking the findings of previous electrophysiological and behavioral measurements. Third, we find that hydrostatic pressure, long known to reverse anesthesia, also raises $T_c$ in vesicles with a magnitude that counters the effect of butanol at relevant concentrations and pressures. Taken together, these results demonstrate that $\\Delta T_c$ predicts anesthetic potency for n-alcohols better than hydrophobicity in a range of contexts, supporting a mechanistic role for membrane heterogeneity in general anesthesia.

Domains of increased thickness in microvillar membranes of the small intestinal enterocyte

DEFF Research Database (Denmark)

Kunding, Andreas H; Christensen, Sune M; Danielsen, E Michael

2010-01-01

The apical surface of the enterocyte is sculpted into a dense array of cylindrical microvillar protrusions by supporting actin filaments. Membrane microdomains (rafts) enriched in cholesterol and glycosphingolipids comprise roughly 50% of the microvillar membrane and play a vital role in orchestr......The apical surface of the enterocyte is sculpted into a dense array of cylindrical microvillar protrusions by supporting actin filaments. Membrane microdomains (rafts) enriched in cholesterol and glycosphingolipids comprise roughly 50% of the microvillar membrane and play a vital role...... in orchestrating absorptive/digestive action of dietary nutrients at this important cellular interface. Increased membrane thickness is believed to be a morphological characteristic of rafts. Thus, we investigated whether the high contents of lipid rafts in the microvillar membrane is reflected in local variations...... was clearly monophasic. The encountered domains of increased thickness (DITs) occupied 48% of the microvillar membrane and from the data we estimated the area of a single DIT to have a lower limit of 600 nm(2). In other experiments we mapped the organization of biochemically defined lipid rafts by immunogold...

Biofouling investigation in membrane filtration systems using Optical Coherence Tomography (OCT)

KAUST Repository

Fortunato, Luca

2017-10-01

Biofouling represents the main problem in membrane filtration systems. Biofouling arises when the biomass growth negatively impacts the membrane performance parameters (i.e. flux decrease and feed channel pressure drop). Most of the available techniques for characterization of biofouling involve membrane autopsies, providing information ex-situ destructively at the end of the process. OCT, is non-invasive imaging technique, able to acquire scans in-situ and non-destructively. The objective of this study was to evaluate the suitability of OCT as in-situ and non-destructive tool to gain a better understanding of biofouling behavior in membrane filtration systems. The OCT was employed to study the fouling behavior in two different membrane configurations: (i) submerged flat sheet membrane and (ii) spacer filled channel. Through the on-line acquisition of OCT scans and the study of the biomass morphology, it was possible to relate the impact of the fouling on the membrane performance. The on-line monitoring of biofilm formation on a flat sheet membrane was conducted in a gravity-driven submerged membrane bioreactor (SMBR) for 43 d. Four different phases were observed linking the variations in permeate flux with changes in biofilm morphology. Furthermore, the biofilm morphology was used in computational fluid dynamics (CFD) simulation to better understand the role of biofilm structure on the filtration mechanisms. The time-resolved OCT analysis was employed to study the biofouling development at the early stage. Membrane coverage and average biofouling layer thickness were found to be linearly correlated with the permeate flux pattern. An integrated characterization methodology was employed to characterize the fouling on a flat sheet membrane, involving the use of OCT as first step followed by membrane autopsies, revealing the presence of a homogeneous layer on the surface. In a spacer filled channel a 3D OCT time series analysis of biomass development under

Tuning of Block Copolymer Membrane Morphology through Water Induced Phase Inversion Technique

KAUST Repository

Madhavan, Poornima

2016-06-01

Isoporous membranes are attractive for the regulation and detection of transport at the molecular level. A well-defined asymmetric membranes from diblock copolymers with an ordered nanoporous membrane morphologies were fabricated by the combination of block copolymer self-assembly and non-solvent-induced phase separation (NIPS) technique. This is a straightforward and fast one step procedure to develop integrally anisotropic (“asymmetric”) membranes having isoporous top selective layer. Membranes prepared via this method exhibit an anisotropic cross section with a thin separation layer supported from underneath a macroporous support. These membrane poses cylindrical pore structure with ordered nanopores across the entire membrane surfaces with pore size in the range from 20 to 40 nm. Tuning the pore morphology of the block copolymer membranes before and after fabrication are of great interest. In this thesis, we first investigated the pore morphology tuning of asymmetric block copolymer membrane by complexing with small organic molecules. We found that the occurrence of hydrogen-bond formation between PS-b-P4VP block copolymer and –OH/ –COOH functionalized organic molecules significantly tunes the pore morphology of asymmetric nanoporous membranes. In addition, we studied the complexation behavior of ionic liquids with PS-b-P4VP block copolymer in solutions and investigated their effect on final membrane morphology during the non-solvent induced phase separation process. We found that non-protic ionic liquids facilitate the formation of hexagonal nanoporous block copolymer structure, while protic ionic liquids led to a lamella-structured membrane. Secondly, we demonstrated the catalytic activity of the gold nanoparticle-enhanced hollow fiber membranes by the reduction of nitrophenol. Also, we systematically investigated the pore morphology of isoporous PS-b-P4VP using 3D imaging technique. Thirdly, we developed well-distributed silver nanoparticles on the

Membrane-lipid therapy: A historical perspective of membrane-targeted therapies - From lipid bilayer structure to the pathophysiological regulation of cells.

Science.gov (United States)

Escribá, Pablo V

2017-09-01

Our current understanding of membrane lipid composition, structure and functions has led to the investigation of their role in cell signaling, both in healthy and pathological cells. As a consequence, therapies based on the regulation of membrane lipid composition and structure have been recently developed. This novel field, known as Membrane Lipid Therapy, is growing and evolving rapidly, providing treatments that are now in use or that are being studied for their application to oncological disorders, Alzheimer's disease, spinal cord injury, stroke, diabetes, obesity, and neuropathic pain. This field has arisen from relevant discoveries on the behavior of membranes in recent decades, and it paves the way to adopt new approaches in modern pharmacology and nutrition. This innovative area will promote further investigation into membranes and the development of new therapies with molecules that target the cell membrane. Due to the prominent roles of membranes in the cells' physiology and the paucity of therapeutic approaches based on the regulation of the lipids they contain, it is expected that membrane lipid therapy will provide new treatments for numerous pathologies. The first on-purpose rationally designed molecule in this field, minerval, is currently being tested in clinical trials and it is expected to enter the market around 2020. However, it seems feasible that during the next few decades other membrane regulators will also be marketed for the treatment of human pathologies. This article is part of a Special Issue entitled: Membrane Lipid Therapy: Drugs Targeting Biomembranes edited by Pablo V. Escribá. Copyright © 2017. Published by Elsevier B.V.

Retention behavior of flavonoids on immobilized artificial membrane chromatography and correlation with cell-based permeability.

Science.gov (United States)

Tsopelas, Fotios; Tsagkrasouli, Maria; Poursanidis, Pavlos; Pitsaki, Maria; Vasios, George; Danias, Panagiotis; Panderi, Irene; Tsantili-Kakoulidou, Anna; Giaginis, Constantinos

2018-03-01

The aim of the study was to investigate the immobilized artificial membrane (IAM) retention mechanism for a set of flavonoids and to evaluate the potential of IAM chromatography to model Caco-2 permeability. For this purpose, the retention behavior of 41 flavonoid analogs on two IAM stationary phases, IAM.PC.MG and IAM.PC.DD2, was investigated. Correlations between retention factors, logk w(IAM) and octanol-water partitioning (logP) were established and the role of hydroxyl groups of flavonoids to the underlying retention mechanism was explored. IAM retention and logP values were used to establish sound linear models with Caco-2 permeability (logP app ) taken from the literature. Both stepwise regression and multivariate analysis confirmed the contribution of hydrogen bond descriptors, as additional parameters in the either logk w(IAM) or logP models. Retention factors on both IAM stationary phases showed comparable performance with n-octanol-water partitioning towards Caco-2 permeability. Copyright © 2017 John Wiley & Sons, Ltd.

Enhancement of growth and osteogenic differentiation of MC3T3-E1 cells via facile surface functionalization of polylactide membrane with chitooligosaccharide based on polydopamine adhesive coating

International Nuclear Information System (INIS)

Li, Huihua; Luo, Chuang; Luo, Binghong; Wen, Wei; Wang, Xiaoying; Ding, Shan; Zhou, Changren

2016-01-01

Graphical abstract: - Highlights: • COS was conveniently immobilized on PDLLA membrane based on PDOPA adhesive layer. • The hydrophilicity of PDLLA membrane was improved by modified with PDOPA and COS. • COS-functionalized PDLLA membrane is favorable to cell adhesion and proliferation. • COS-coated PDLLA membrane notably promote osteogenic differentiation of MC3T3-E1. - Abstract: To develop a chitooligosaccharide(COS)-functionalized poly(D,L-lactide) (PDLLA) membrane to enhance growth and osteogenic differentiation of MC3T3-E1 cells, firstly a thin polydopamine (PDOPA) layer was adhered to the PDLLA membrane via the self-polymerization and strong adhesion behavior of dopamine. Subsequently, COS was immobilized covalently on the resultant PDLLA/PDOPA composite membrane by coupling with PDOPA active coating. The successful immobilization of the PDOPA and COS was confirmed by attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy and X-ray photoelectron spectroscopy (XPS). Scanning electronic microscopy (SEM) and atomic force microscopy (AFM) results indicated that the surface topography and roughness of the membranes were changed, and the root mean square increased from 0.613 nm to 6.96 and 7.12 nm, respectively after coating PDOPA and COS. Water contact angle and surface energy measurements revealed that the membrane hydrophilicity was remarkably improved by surface modification. In vitro cells culture results revealed that the PDOPA- and COS-functionalized surfaces showed a significant increase in MC3T3-E1 cells adhesion, proliferation, osteogenic differentiation and alkaline phosphate activity compared to the pristine PDLLA substrate. Furthermore the COS-functionalized PDLLA membrane was more effectively at enhancing osteoblast activity than the PDOPA-functionalized PDLLA membrane.

Pore channel surface modification for enhancing anti-fouling membrane distillation

Science.gov (United States)

Qiu, Haoran; Peng, Yuelian; Ge, Lei; Villacorta Hernandez, Byron; Zhu, Zhonghua

2018-06-01

Membrane surface modification by forming a functional layer is an effective way to improve the anti-fouling properties of membranes; however, the additional layer and the potential blockage of bulk pores may increase the mass transfer resistance and reduce the permeability. In this study, we applied a novel method of preparing anti-fouling membranes for membrane distillation by dispersing graphene oxide (GO) on the channel surface of polyvinylidene fluoride membranes. The surface morphology and properties were characterized by scanning electron microscopy, atomic force microscope, and Fourier transform infrared spectrometry. Compared to the membrane surface modification by nanoparticles (e.g. SiO2), GO was mainly located on the pore surface of the membrane bulk, rather than being formed as an individual layer onto the membrane surface. The performance was evaluated via a direct-contact membrane distillation process with anionic and cationic surfactants as the foulants, separately. Compared to the pristine PVDF membrane, the anti-fouling behavior and distillate flux of the GO-modified membranes were improved, especially when using the anionic surfactant as the foulant. The enhanced anti-fouling performance can be attributed to the oxygen containing functional groups in GO and the healing of the membrane pore defects. This method may provide an effective route to manipulate membrane pore surface properties for anti-fouling separation without increasing mass transfer resistance.

Expansion of thermodynamic model of solute permeation through reverse osmosis membrane

International Nuclear Information System (INIS)

Nishimaki, Kenzo; Koyama, Akio

1994-01-01

Many studies have been performed on permeation mechanism of solute and solvent in membrane separation process like reverse osmosis or ultrafiltration, and several models of solute/solvent permeation through membrane are proposed. Among these models, Kedem and Katchalsky, based on the theory of thermodynamics of irreversible processes, formulated the one-solute permeation process in their mathematical model, which treats membrane as a black box, not giving consideration to membrane structure and to interaction between membrane material and permeates, viz. solute and solvent. According to this theory, the driving force of solute/solvent permeation through membrane is the difference of their chemical potential between both sides of membrane, and the linear phenomenological equation is applied to describing the relation between driving force and flux of solute/solvent. This equation can be applied to the irreversible process only when the process is almost in equilibrium. This condition is supposed to be satisfied in the solute/solvent permeation process through compact membrane with fine pores like reverse osmosis membrane. When reverse osmosis is applied to treatment process for liquid waste, which usually contains a lot of solutes as contaminants, we can not predict the behavior of contaminants by the above one-solute process model. In the case of multi-solutes permeation process for liquid waste, the number of parameter in thermodynamic model increases rapidly with the number of solute, because of coupling phenomenon among solutes. In this study, we expanded the above thermodynamic model to multi-solute process applying operational calculus to the differential equations which describe the irreversible process of the system, and expressed concisely solute concentration vector as a matrix product. In this way, we predict the behavior of solutes in multi-solutes process, using values of parameters obtained in two-solutes process. (author)

Ultrastructural analysis of nanoparticles and ions released in periprosthetic membranes.

Science.gov (United States)

Sabbatini, Maurizio; Gatti, Giorgio; Renò, Filippo; Bosetti, Michela; Marchese, Leonardo; Cannas, Mario

2014-12-30

The distribution and relationship of hydroxyapatite debris, nanometric organic and metal wear particles and metal ions on periimplant interface membranes following aseptic and septic arthroplastic loosening were investigated. Scanning electron microscopy and X-ray spectroscopic analysis were used to analyze debris and ion distribution. Hydroxyapatite debris appeared with different morphology in a particular distribution among several membranes. These differences may reflect the occurrence of different friction forces taking place between prosthesis and bone interface in the several types of prostheses studied. Metal wear particles were detected in greater numbers in membranes from noncemented prostheses compared with those from cemented ones. In contrast, more organic particles were present in membrane from cemented prosthesis. No differences were observed between aseptic and septic membranes. Our findings support the need to evaluate the occurrence of friction forces that periprosthetic bone debris production may induce to exacerbate cellular reactivity. Furthermore, cellular engulfment of debris and the high level of different ions released indicate the occurrence of a toxic environment that may induce failure of any reparative pathways.

Membrane Protein Mobility and Orientation Preserved in Supported Bilayers Created Directly from Cell Plasma Membrane Blebs.

Science.gov (United States)

Richards, Mark J; Hsia, Chih-Yun; Singh, Rohit R; Haider, Huma; Kumpf, Julia; Kawate, Toshimitsu; Daniel, Susan

2016-03-29

Membrane protein interactions with lipids are crucial for their native biological behavior, yet traditional characterization methods are often carried out on purified protein in the absence of lipids. We present a simple method to transfer membrane proteins expressed in mammalian cells to an assay-friendly, cushioned, supported lipid bilayer platform using cell blebs as an intermediate. Cell blebs, expressing either GPI-linked yellow fluorescent proteins or neon-green fused transmembrane P2X2 receptors, were induced to rupture on glass surfaces using PEGylated lipid vesicles, which resulted in planar supported membranes with over 50% mobility for multipass transmembrane proteins and over 90% for GPI-linked proteins. Fluorescent proteins were tracked, and their diffusion in supported bilayers characterized, using single molecule tracking and moment scaling spectrum (MSS) analysis. Diffusion was characterized for individual proteins as either free or confined, revealing details of the local lipid membrane heterogeneity surrounding the protein. A particularly useful result of our bilayer formation process is the protein orientation in the supported planar bilayer. For both the GPI-linked and transmembrane proteins used here, an enzymatic assay revealed that protein orientation in the planar bilayer results in the extracellular domains facing toward the bulk, and that the dominant mode of bleb rupture is via the "parachute" mechanism. Mobility, orientation, and preservation of the native lipid environment of the proteins using cell blebs offers advantages over proteoliposome reconstitution or disrupted cell membrane preparations, which necessarily result in significant scrambling of protein orientation and typically immobilized membrane proteins in SLBs. The bleb-based bilayer platform presented here is an important step toward integrating membrane proteomic studies on chip, especially for future studies aimed at understanding fundamental effects of lipid interactions

Transmembrane protein diffusion in gel-supported dual-leaflet membranes.

Science.gov (United States)

Wang, Chih-Ying; Hill, Reghan J

2014-11-18

Tools to measure transmembrane-protein diffusion in lipid bilayer membranes have advanced in recent decades, providing a need for predictive theoretical models that account for interleaflet leaflet friction on tracer mobility. Here we address the fully three-dimensional flows driven by a (nonprotruding) transmembrane protein embedded in a dual-leaflet membrane that is supported above and below by soft porous supports (e.g., hydrogel or extracellular matrix), each of which has a prescribed permeability and solvent viscosity. For asymmetric configurations, i.e., supports with contrasting permeability, as realized for cells in contact with hydrogel scaffolds or culture media, the diffusion coefficient can reflect interleaflet friction. Reasonable approximations, for sufficiently large tracers on low-permeability supports, are furnished by a recent phenomenological theory from the literature. Interpreting literature data, albeit for hard-supported membranes, provides a theoretical basis for the phenomenological Stokes drag law as well as strengthening assertions that nonhydrodynamic interactions are important in supported bilayer systems, possibly leading to overestimates of the membrane/leaflet viscosity. Our theory provides a theoretical foundation for future experimental studies of tracer diffusion in gel-supported membranes.

Membrane fouling of forward osmosis (FO) membrane for municipal wastewater treatment: A comparison between direct FO and OMBR.

Science.gov (United States)

Sun, Yan; Tian, Jiayu; Zhao, Zhiwei; Shi, Wenxin; Liu, Dongmei; Cui, Fuyi

2016-11-01

In this work, membrane fouling behavior in a direct forward osmosis (FO) and an osmotic membrane bioreactor (OMBR) for municipal wastewater treatment was systematically investigated and compared. During the long-term operation, much severer flux decline was observed for the direct FO than that for the OMBR. The cake layer was found to be much thicker, together with large amounts of microorganisms growing on the membrane surface in direct FO. Interestingly, no obvious attachment of microorganisms on the membrane surface was observed in the OMBR. The fourier transform infrared spectroscopy (FTIR) and excitation emission matrices (EEM) analyses showed the polysaccharides and proteins were the dominant organic foulants in the fouling layer, and the quantity of the organic substances was also higher in direct FO than that in OMBR. Energy-dispersive X-ray (EDX) results indicated the main inorganic elements in the fouling layer were Ca, Mg, Fe and P, all of which exhibited higher relative percentages in direct FO than that in OMBR. The occurrence of higher contents of microorganisms, organic foulants and inorganic elements in the cake layer caused a higher filtration resistance for the FO membrane in the direct FO. Although more severe membrane fouling was identified in direct FO, the hydraulic and chemical cleaning was more effective on recovering the water permeability of the membrane in direct FO than that in OMBR. Copyright © 2016 Elsevier Ltd. All rights reserved.

Ankylosing Spondylitis: a Reflection and a Question

Directory of Open Access Journals (Sweden)

Annia Deysi Hernández Martín

2014-07-01

Full Text Available Ankylosing spondylitis is a chronic inflammatory disease that affects the synovial membrane, joint entheses and para-articular structures of the spine, including the sacroiliac joints and limbs. We present a case of ankylosing spondylitis that had evolved for 12 years despite the relatively early diagnosis and treatment, showing flexion deformity and limitation of spinal movements. On radiological examination an early evolution to ankylosis was observed, which motivated us to make a reflection and a question.

Interplay of mycolic acids, antimycobacterial compounds and pulmonary surfactant membrane: a biophysical approach to disease.

Science.gov (United States)

Pinheiro, Marina; Giner-Casares, Juan J; Lúcio, Marlene; Caio, João M; Moiteiro, Cristina; Lima, José L F C; Reis, Salette; Camacho, Luis

2013-02-01

This work focuses on the interaction of mycolic acids (MAs) and two antimycobacterial compounds (Rifabutin and N'-acetyl-Rifabutin) at the pulmonary membrane level to convey a biophysical perspective of their role in disease. For this purpose, accurate biophysical techniques (Langmuir isotherms, Brewster angle microscopy, and polarization-modulation infrared reflection spectroscopy) and lipid model systems were used to mimic biomembranes: MAs mimic bacterial lipids of the Mycobacterium tuberculosis (MTb) membrane, whereas Curosurf® was used as the human pulmonary surfactant (PS) membrane model. The results obtained show that high quantities of MAs are responsible for significant changes on PS biophysical properties. At the dynamic inspiratory surface tension, high amounts of MAs decrease the order of the lipid monolayer, which appears to be a concentration dependent effect. These results suggest that the amount of MAs might play a critical role in the initial access of the bacteria to their targets. Both molecules also interact with the PS monolayer at the dynamic inspiratory surface. However, in the presence of higher amounts of MAs, both compounds improve the phospholipid packing and, therefore, the order of the lipid surfactant monolayer. In summary, this work discloses the putative protective effects of antimycobacterial compounds against the MAs induced biophysical impairment of PS lipid monolayers. These protective effects are most of the times overlooked, but can constitute an additional therapeutic value in the treatment of pulmonary tuberculosis (Tb) and may provide significant insights for the design of new and more efficient anti-Tb drugs based on their behavior as membrane ordering agents. Copyright © 2012 Elsevier B.V. All rights reserved.

The Role of Membrane Curvature in Nanoscale Topography-Induced Intracellular Signaling.

Science.gov (United States)

Lou, Hsin-Ya; Zhao, Wenting; Zeng, Yongpeng; Cui, Bianxiao

2018-05-15

Over the past decade, there has been growing interest in developing biosensors and devices with nanoscale and vertical topography. Vertical nanostructures induce spontaneous cell engulfment, which enhances the cell-probe coupling efficiency and the sensitivity of biosensors. Although local membranes in contact with the nanostructures are found to be fully fluidic for lipid and membrane protein diffusions, cells appear to actively sense and respond to the surface topography presented by vertical nanostructures. For future development of biodevices, it is important to understand how cells interact with these nanostructures and how their presence modulates cellular function and activities. How cells recognize nanoscale surface topography has been an area of active research for two decades before the recent biosensor works. Extensive studies show that surface topographies in the range of tens to hundreds of nanometers can significantly affect cell functions, behaviors, and ultimately the cell fate. For example, titanium implants having rough surfaces are better for osteoblast attachment and host-implant integration than those with smooth surfaces. At the cellular level, nanoscale surface topography has been shown by a large number of studies to modulate cell attachment, activity, and differentiation. However, a mechanistic understanding of how cells interact and respond to nanoscale topographic features is still lacking. In this Account, we focus on some recent studies that support a new mechanism that local membrane curvature induced by nanoscale topography directly acts as a biochemical signal to induce intracellular signaling, which we refer to as the curvature hypothesis. The curvature hypothesis proposes that some intracellular proteins can recognize membrane curvatures of a certain range at the cell-to-material interface. These proteins then recruit and activate downstream components to modulate cell signaling and behavior. We discuss current technologies

Study of Membrane Reflector Technology

Science.gov (United States)

Knapp, K.; Hedgepeth, J.

1979-01-01

Very large reflective surfaces are required by future spacecraft for such purposes as solar energy collection, antenna surfaces, thermal control, attitude and orbit control with solar pressure, and solar sailing. The performance benefits in large membrane reflector systems, which may be derived from an advancement of this film and related structures technology, are identified and qualified. The results of the study are reported and summarized. Detailed technical discussions of various aspects of the study are included in several separate technical notes which are referenced.

Micropore and nanopore fabrication in hollow antiresonant reflecting optical waveguides.

Science.gov (United States)

Holmes, Matthew R; Shang, Tao; Hawkins, Aaron R; Rudenko, Mikhail; Measor, Philip; Schmidt, Holger

2010-01-01

We demonstrate the fabrication of micropore and nanopore features in hollow antiresonant reflecting optical waveguides to create an electrical and optical analysis platform that can size select and detect a single nanoparticle. Micropores (4 μm diameter) are reactive-ion etched through the top SiO(2) and SiN layers of the waveguides, leaving a thin SiN membrane above the hollow core. Nanopores are formed in the SiN membranes using a focused ion-beam etch process that provides control over the pore size. Openings as small as 20 nm in diameter are created. Optical loss measurements indicate that micropores did not significantly alter the loss along the waveguide.

FROM THE BEHAVIORAL ANALYSIS TO POST-BEHAVIORALISM: HISTORY OF PARADIGM

Directory of Open Access Journals (Sweden)

M. I. Bogachev

2017-01-01

Full Text Available Article is devoted to the review of formation and decline of behavioralism paradigm in political science. The author begins the analysis with critical consideration of the scientific concepts preceding emergence of modernist empiricism within which there is a behavioral analysis. Further the researcher traces formation behaviorism in the social disciplines: formation model in psychology, release of the theory out of limits of pure psychology and transferring ideas in sociology and political science. The author analyzes inquiries to the scientific theory by behavioralism. He opens the principles of behavioralism as paradigm in political science. The author presents the conceptual and contextual factors promoting recession of popularity behavioralism in political science and submits methodological restrictions approach. The author states the main claims of critics to this research approach and explains the reasons decline this paradigm. At the same time the methodological reflection of behavioralism which has followed recession of his popularity is reflected in work. The author opens the principles of the new methodological direction – post-behavioralism and the position of modern representatives of the behavioral analysis.

Properties of Plasma Membrane from Pea Root Seedlings under Altered Gravity

Science.gov (United States)

Klymchuk, D.; Baranenko, V.; Vorobyova, T. V.; Kurylenko, I.; Chyzhykova, O.; Dubovoy, V.

In this study, the properties of pea (Pisum sativum L.) plasma membrane were examined to determine how the membrane structure and functions are regulated in response to clinorotation (2 rev/min) conditions. Membrane preparations enriched by plasma membrane vesicles were obtained by aqueous two-phase partitioning from 6-day seedling roots. The specific characteristics of H^+-ATPase, lípid composition and peroxidation intensity as well as fluidity of lipid bilayer were analysed. ATP hydrolytic activity was inhibited by ortovanadate and was insensitive to aside and nitrate in sealed plasma membrane vesicles isolated from both clinorotated and control seedlings. Plasma membrane vesicles from clinorotated seedlings in comparison to controls were characterised by increase in the total lipid/protein ratio, ATP hydrolytic activity and intensifying of lipid peroxidation. Sitosterol and campesterol were the predominant free sterol species. Clinorotated seedlings contained a slightly higher level of unsaturated fatty acid than controls. Plasma membrane vesicles were labelled with pyrene and fluorescence originating from monomeric (I_M) molecules and excimeric (I_E) aggregates were measured. The calculated I_E/I_M values were higher in clinorotated seedlings compared with controls reflecting the reduction in membrane microviscosity. The involvement of the changes in plasma membrane lipid content and composition, fluidity and H^+-ATPase activity in response of pea seedlings to altered gravity is discussed.

A study of the anti-reflection efficiency of natural nano-arrays of varying sizes

International Nuclear Information System (INIS)

Sun Mingxia; Liang Aiping; Zheng Yongmei; Watson, Gregory S; Watson, Jolanta A

2011-01-01

The dependence of optical reflectivity and wettability on the surface topography of 32 species of cicada wing membranes has been investigated using UV-visible spectrophotometry, contact angle measurements and environmental scanning electron microscopy. The nanoscale hexagonally close packed protrusions have been shown to exhibit an anti-reflection and in some cases an anti-wetting function. The parameters of the structures were measured to be 77-148 nm in diameter, 44-117 nm in spacing and 159-481 nm in height. The transmittance spectrum and static contact angles were measured. At a wavelength range of 500-2500 nm, only minor differences in the anti-reflection performance were observed for each cicada species ascribed to the mechanism of impedance matching between cuticle and air. The transmittance properties of cicada wings were altered successfully through the scanning probe microscope-based manipulation by reducing the protrusion height via the contact mode. A near linear dependence was found between a decrease in protuberance height and a resulting increase in reflectance intensity. A diversity of wettability was observed with contact angles varying from 56.5 0 to 146.0 0 . Both effects of anti-reflection and wettability are dependent on the height of protrusions. The anti-reflection is insensitive when the wavelength is larger than the lateral feature size of the nanostructure. The stronger hydrophobic properties are generally associated with a larger diameter, closer spacing and greater height of protrusions when the wing membrane is intact.

High-performance polyamide thin-film composite nanofiltration membrane: Role of thermal treatment

Science.gov (United States)

Liu, Baicang; Wang, Shuai; Zhao, Pingju; Liang, Heng; Zhang, Wen; Crittenden, John

2018-03-01

Nanofiltration (NF) membranes have many excellent applications (e.g., removing multivalent ions and pretreating water before reverse osmosis, RO), but their relatively high cost limits their application. Especially in recent years, researchers have paid substantial attention to reducing the cost of NF membranes. In this paper, high-performance NF membranes were fabricated using interfacial polymerization (IP) methods. The polymer concentration, IP solution concentration, and thermal treatment conditions were varied. The synthesized membranes were characterized using scanning electron microscopy (SEM), atomic force microscopy (AFM), a contact angle goniometer, X-ray photoelectron spectroscopy (XPS), attenuated total reflectance fourier transform infrared (ATR-FTIR) spectroscopy, and performance tests. The results show that water flux was significantly improved using a hot-water thermal treatment method. Our fabricated thermal-treated NF membrane had an approximately 15% higher water permeability with a value of 13.6 L/(m2 h bar) than that of the commercially available GE HL membrane with a value of 11.8 L/(m2 h bar). Our membranes had the same MgSO4 rejection as that of the GE HL membrane. We found that the thermal treatment causes the NF membrane surface to be smoother and have a high crosslinking degree.

Membranes, methods of making membranes, and methods of separating gases using membranes

Science.gov (United States)

Ho, W. S. Winston

2012-10-02

Membranes, methods of making membranes, and methods of separating gases using membranes are provided. The membranes can include at least one hydrophilic polymer, at least one cross-linking agent, at least one base, and at least one amino compound. The methods of separating gases using membranes can include contacting a gas stream containing at least one of CO.sub.2, H.sub.2S, and HCl with one side of a nonporous and at least one of CO.sub.2, H.sub.2S, and HCl selectively permeable membrane such that at least one of CO.sub.2, H.sub.2S, and HCl is selectively transported through the membrane.

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.

Fluorescent probes for detecting cholesterol-rich ordered membrane microdomains: entangled relationships between structural analogies in the membrane and functional homologies in the cell

Directory of Open Access Journals (Sweden)

Gérald Gaibelet

2017-02-01

Full Text Available This review addresses the question of fluorescent detection of ordered membrane (micro domains in living (cultured cells, with a “practical” point of view since the situation is much more complicated than for studying model membranes. We first briefly recall the bases of model membrane structural organization involving liquid-ordered and -disordered phases, and the main features of their counterparts in cell membranes that are the various microdomains. We then emphasize the utility of the fluorescent probes derived from cholesterol, and delineate the respective advantages, limitations and drawbacks of the existing ones. In particular, besides their intra-membrane behavior, their relevant characteristics should integrate their different cellular fates for membrane turn-over, trafficking and metabolism, in order to evaluate and improve their efficiency for in-situ probing membrane microdomains in the cell physiology context. Finally, at the present stage, it appears that Bdp-Chol and Pyr-met-Chol display well complementary properties, allowing to use them in combination to improve the reliability of the current experimental approaches. But the field is still open, and there remains much work to perform in this research area.

Reactive Membrane Barriers for Containment of Subsurface Contamination

Energy Technology Data Exchange (ETDEWEB)

William A. Arnold; Edward L. Cussler

2007-02-26

The overall goal of this project was to develop reactive membrane barriers--a new and flexible technique to contain and stabilize subsurface contaminants. Polymer membranes will leak once a contaminant is able to diffuse through the membrane. By incorporating a reactive material in the polymer, however, the contaminant is degraded or immobilized within the membrane. These processes increase the time for contaminants to breakthrough the barrier (i.e. the lag time) and can dramatically extend barrier lifetimes. In this work, reactive barrier membranes containing zero-valent iron (Fe{sup 0}) or crystalline silicotitanate (CST) were developed to prevent the migration of chlorinated solvents and cesium-137, respectively. These studies were complemented by the development of models quantifying the leakage/kill time of reactive membranes and describing the behavior of products produced via the reactions within the membranes. First, poly(vinyl alcohol) (PVA) membranes containing Fe{sup 0} and CST were prepared and tested. Although PVA is not useful in practical applications, it allows experiments to be performed rapidly and the results to be compared to theory. For copper ions (Cu{sup 2+}) and carbon tetrachloride, the barrier was effective, increasing the time to breakthrough over 300 times. Even better performance was expected, and the percentage of the iron used in the reaction with the contaminants was determined. For cesium, the CST laden membranes increased lag times more than 30 times, and performed better than theoretical predictions. A modified theory was developed for ion exchangers in reactive membranes to explain this result. With the PVA membranes, the effect of a groundwater matrix on barrier performance was tested. Using Hanford groundwater, the performance of Fe{sup 0} barriers decreased compared to solutions containing a pH buffer and high levels of chloride (both of which promote iron reactivity). For the CST bearing membrane, performance improved by a

Reactive Membrane Barriers for Containment of Subsurface Contamination

International Nuclear Information System (INIS)

William A. Arnold; Edward L. Cussler

2007-01-01

The overall goal of this project was to develop reactive membrane barriers--a new and flexible technique to contain and stabilize subsurface contaminants. Polymer membranes will leak once a contaminant is able to diffuse through the membrane. By incorporating a reactive material in the polymer, however, the contaminant is degraded or immobilized within the membrane. These processes increase the time for contaminants to breakthrough the barrier (i.e. the lag time) and can dramatically extend barrier lifetimes. In this work, reactive barrier membranes containing zero-valent iron (Fe 0 ) or crystalline silicotitanate (CST) were developed to prevent the migration of chlorinated solvents and cesium-137, respectively. These studies were complemented by the development of models quantifying the leakage/kill time of reactive membranes and describing the behavior of products produced via the reactions within the membranes. First, poly(vinyl alcohol) (PVA) membranes containing Fe 0 and CST were prepared and tested. Although PVA is not useful in practical applications, it allows experiments to be performed rapidly and the results to be compared to theory. For copper ions (Cu 2+ ) and carbon tetrachloride, the barrier was effective, increasing the time to breakthrough over 300 times. Even better performance was expected, and the percentage of the iron used in the reaction with the contaminants was determined. For cesium, the CST laden membranes increased lag times more than 30 times, and performed better than theoretical predictions. A modified theory was developed for ion exchangers in reactive membranes to explain this result. With the PVA membranes, the effect of a groundwater matrix on barrier performance was tested. Using Hanford groundwater, the performance of Fe 0 barriers decreased compared to solutions containing a pH buffer and high levels of chloride (both of which promote iron reactivity). For the CST bearing membrane, performance improved by a factor of three when

Membrane Cholesterol Modulates Superwarfarin Toxicity

Energy Technology Data Exchange (ETDEWEB)

Marangoni, M. Natalia; Martynowycz, Michael W.; Kuzmenko, Ivan; Braun, David; Polak, Paul E.; Weinberg, Guy; Rubinstein, Israel; Gidalevitz, David; Feinstein, Douglas L.

2016-04-26

Superwarfarins are modified analogs of warfarin with additional lipophilic aromatic rings, up to 100-fold greater potency, and longer biological half-lives. We hypothesized that increased hydrophobicity allowed interactions with amphiphilic membranes and modulation of biological responses. We find that superwarfarins brodifacoum and difenacoum increase lactate production and cell death in neuroblastoma cells. In contrast, neither causes changes in glioma cells that have higher cholesterol content. After choleterol depletion, lactate production was increased and cell viability was reduced. Drug-membrane interactions were examined by surface X-ray scattering using Langmuir monolayers of dipalmitoylphosphatidylcholine and/or cholesterol. Specular X-ray reflectivity data revealed that superwarfarins, but not warfarin, intercalate between dipalmitoylphosphatidylcholine molecules, whereas grazing incidence X-ray diffraction demonstrated changes in lateral crystalline order of the film. Neither agent showed significant interactions with monolayers containing >20% cholesterol. These findings demonstrate an affinity of superwarfarins to biomembranes and suggest that cellular responses to these agents are regulated by cholesterol content.

Toluene impurity effects on CO2 separation using a hollow fiber membrane for natural gas

KAUST Repository

Omole, Imona C.

2011-03-01

The performance of defect-free cross-linkable polyimide asymmetric hollow fiber membranes was characterized using an aggressive feed stream containing up to 1000ppm toluene. The membrane was shown to be stable against toluene-induced plasticization compared with analogs made from Matrimid®, a commercial polyimide. Permeation and sorption analysis suggest that the introduction of toluene vapors in the feed subjects the membrane to antiplasticization, as the permeance decreases significantly (to less than 30%) under the most aggressive conditions tested. Separation efficiencies reflected by permselectivities were less affected. The effect of the toluene on the membrane was shown to be reversible when the toluene was removed. © 2010 Elsevier B.V.

Toluene impurity effects on CO2 separation using a hollow fiber membrane for natural gas

KAUST Repository

Omole, Imona C.; Bhandari, Dhaval A.; Miller, Stephen J.; Koros, William J.

2011-01-01

The performance of defect-free cross-linkable polyimide asymmetric hollow fiber membranes was characterized using an aggressive feed stream containing up to 1000ppm toluene. The membrane was shown to be stable against toluene-induced plasticization compared with analogs made from Matrimid®, a commercial polyimide. Permeation and sorption analysis suggest that the introduction of toluene vapors in the feed subjects the membrane to antiplasticization, as the permeance decreases significantly (to less than 30%) under the most aggressive conditions tested. Separation efficiencies reflected by permselectivities were less affected. The effect of the toluene on the membrane was shown to be reversible when the toluene was removed. © 2010 Elsevier B.V.

Proteomic response of Bacillus subtilis to lantibiotics reflects differences in interaction with the cytoplasmic membrane

NARCIS (Netherlands)

Wenzel, M.; Kohl, B.; Münch, D.; Raatschen, N.; Albada, H.B.; Hamoen, L.; Metzler-Nolte, N.; Sahl, H.G.; Bandow, J.E.

2012-01-01

Mersacidin, gallidermin, and nisin are lantibiotics, antimicrobial peptides containing lanthionine. They show potent antibacterial activity. All three interfere with cell wall biosynthesis by binding lipid II, but they display different levels of interaction with the cytoplasmic membrane. On one end

Measuring the composition-curvature coupling in binary lipid membranes by computer simulations

International Nuclear Information System (INIS)

Barragán Vidal, I. A.; Müller, M.; Rosetti, C. M.; Pastorino, C.

2014-01-01

The coupling between local composition fluctuations in binary lipid membranes and curvature affects the lateral membrane structure. We propose an efficient method to compute the composition-curvature coupling in molecular simulations and apply it to two coarse-grained membrane models—a minimal, implicit-solvent model and the MARTINI model. Both the weak-curvature behavior that is typical for thermal fluctuations of planar bilayer membranes as well as the strong-curvature regime corresponding to narrow cylindrical membrane tubes are studied by molecular dynamics simulation. The simulation results are analyzed by using a phenomenological model of the thermodynamics of curved, mixed bilayer membranes that accounts for the change of the monolayer area upon bending. Additionally the role of thermodynamic characteristics such as the incompatibility between the two lipid species and asymmetry of composition are investigated

Measuring the composition-curvature coupling in binary lipid membranes by computer simulations

Energy Technology Data Exchange (ETDEWEB)

Barragán Vidal, I. A., E-mail: vidal@theorie.physik.uni-goettingen.de; Müller, M., E-mail: mmueller@theorie.physik.uni-goettingen.de [Institut für Theoretische Physik, Georg-August-Universität, Friedrich-Hund-Platz 1, 37077 Göttingen (Germany); Rosetti, C. M., E-mail: carla@dqb.fcq.unc.edu.ar [Centro de Investigaciones en Química Biológica de Córdoba, Departamento de Química Biológica, Facultad de Ciencias Químicas, Universidad Nacional de Córdoba, Ciudad Universitaria, Córdoba (Argentina); Pastorino, C., E-mail: pastor@cnea.gov.ar [Departamento de Física de la Materia Condensada, Centro Atómico Constituyentes, CNEA/CONICET, Av. Gral. Paz 1499, 1650 Pcia. de Buenos Aires (Argentina)

2014-11-21

The coupling between local composition fluctuations in binary lipid membranes and curvature affects the lateral membrane structure. We propose an efficient method to compute the composition-curvature coupling in molecular simulations and apply it to two coarse-grained membrane models—a minimal, implicit-solvent model and the MARTINI model. Both the weak-curvature behavior that is typical for thermal fluctuations of planar bilayer membranes as well as the strong-curvature regime corresponding to narrow cylindrical membrane tubes are studied by molecular dynamics simulation. The simulation results are analyzed by using a phenomenological model of the thermodynamics of curved, mixed bilayer membranes that accounts for the change of the monolayer area upon bending. Additionally the role of thermodynamic characteristics such as the incompatibility between the two lipid species and asymmetry of composition are investigated.

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.

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

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.

Studies on improved integrated membrane-based chromatographic process for bioseparation

Science.gov (United States)

Xu, Yanke

To improve protein separation and purification directly from a fermentation broth, a novel membrane filtration-cum-chromatography device configuration having a relatively impermeable coated zone near the hollow fiber module outlet has been developed. The integrated membrane filtration-cum-chromatography unit packed with chromatographic beads on the shell side of the hollow fiber unit enjoys the advantages of both membrane filtration and chromatography; it allows one to load the chromatographic media directly from the fermentation broth or lysate and separate the adsorbed proteins through the subsequent elution step in a cyclic process. Interfacial polymerization was carried out to coat the bottom section of the hollow fiber membrane while leaving the rest of the hollow fiber membrane unaffected. Myoglobin (Mb), bovine serum albumin (BSA) and a-lactalbumin (a-LA) were used as model proteins in binary mixtures. Separation behaviors of binary protein mixtures were studied in devices using either an ultrafiltration (UF) membrane or a microfiltration (MF) membrane. Experimental results show that the breakthrough time and the protein loading capacities were dramatically improved after coating in both UF and MF modules. For a synthetic yeast fermentation broth feed, the Mb and a-LA elution profiles for the four consecutive cyclic runs were almost superimposable. Due to the lower transmembrane flux in this device plus the periodical washing-elution during the chromatographic separation, fouling was not a problem as it is in conventional microfiltration. A mathematical model describing the hydrodynamic and protein loading behaviors of the integrated device using UF membrane with a coated zone was developed. The simulation results for the breakthrough agree well with the experimental breakthrough curves. The optimal length of the coated zone was obtained from the simulation. A theoretical analysis of the protein mass transfer was performed using a diffusion-convection model

The Comparative Study of Morals and Democracy and Their Effect on the Behavioral Reflections of Khawaja Nasir Al-Din Tusi and John Dewey

Science.gov (United States)

Mirzaei, Khalil; Golestani, Sayyed Hashem; Vaezi, Sayyed Hossain

2016-01-01

This study was aimed at comparatively analyzing morals and democracy from John Dewey and Khawaja Nasir al-Din Tusi's viewpoint. It also sought the effect of the two philosophers' viewpoint about morals and democracy and behavioral reflections. The purpose of this study was also to become familiar with the effect of morals and democracy on…

How Culture Influences Teacher Self-Reflective Problem Solving Behavior and Self-Efficacy: Experiences of White Female Teachers Working through Relationship with Black Students in a Mid-Western American City

Science.gov (United States)

Tolson, Bonnie Lynn

2013-01-01

Teachers make a difference. White female middle-class teachers represent 84 percent of Americas' teachers. How does culture influence the self-reflective problem-solving behaviors of urban teachers? Urban schools fail youth by opening the doors for a mass exodus. The problem solving behavior of urban teachers may contribute to the student exodus…

Membrane Modeling, Simulation and Optimization for Propylene/Propane Separation

KAUST Repository

Alshehri, Ali

2015-06-01

, product purity and the recovery ratio. These findings were utilized to develop simple and accurate empirical correlations to predict the attainability behavior in real membranes, which showed good agreement with experimental and simulation results for various applications. Furthermore, the attainability of the most promising two and three-stage membrane systems are discussed by considering the complete well mixed assumption. The same behaviors that describe single-stage attainability are also recognized for multiple-stages. This discussion leads to a major discovery regarding the nature of the relationship between the attainability parameters in a multiple-stage membrane system with that of a single-stage system. Study of the economics of the multiple-stage membrane process for propylene/propane separation identifies the technology as a potential alternative to the conventional distillation process, even at the existing membrane performance, but conditionally at low to moderate membrane cost and sufficient durability. To study the energy efficiency of membrane retrofitting to an existing distillation process, a shortcut method was developed to calculate the minimum practical separation energy (MPSE) of the membrane and distillation processes. It was discovered that the MPSE of the hybrid system is only determined by the membrane selectivity and the applied transmembrane pressure ratio in three stages. At the first stage, when selectivity is low, the membrane process is not competitive to the distillation process. At the second medium selectivity stage, the membrane/distillation hybrid system can help to reduce the energy consumption; the higher the membrane selectivity the lower the energy requirement. The energy conservation is further improved as the pressure ratio increases. At the third stage, when both the selectivity and pressure ratio are high, the hybrid system will change to a single-stage membrane unit, resulting in a significant reduction in energy consumption

A cell-free assay to determine the stoichiometry of plasma membrane proteins.

Science.gov (United States)

Trigo, Cesar; Vivar, Juan P; Gonzalez, Carlos B; Brauchi, Sebastian

2013-04-01

Plasma membrane receptors, transporters, and ion channel molecules are often found as oligomeric structures that participate in signaling cascades essential for cell survival. Different states of protein oligomerization may play a role in functional control and allosteric regulation. Stochastic GFP-photobleaching (SGP) has emerged as an affordable and simple method to determine the stoichiometry of proteins at the plasma membrane. This non-invasive optical approach can be useful for total internal reflection of fluorescence microscopy (TIRFM), where signal-to-noise ratio is very high at the plasma membrane. Here, we report an alternative methodology implemented on a standard laser scanning confocal microscope (LSCM). The simplicity of our method will allow for its implementation in any epifluorescence microscope of choice.

Ethical reflection and psychotherapy.

Science.gov (United States)

Vyskocilová, Jana; Prasko, Jan

2013-01-01

Theories of ethics and ethical reflection may be applied to both theory and practice in psychotherapy. There is a natural affinity between ethics and psychotherapy. Psychotherapy practice is concerned with human problems, dilemmas and emotions related to both one's own and other people's values. Ethics is also concerned with dilemmas in human thinking and with how these dilemmas reflect other individuals' values. Philosophical reflection itself is not a sufficient basis for the ethics of psychotherapy but it may aid in exploring attitudes related to psychotherapy, psychiatry and health care. PubMed, Web of Science and Scopus databases were searched for articles containing the keywords "psychotherapy", "ethics", "therapeutic relationship" and "supervision". The search was conducted by repeating the terms in various combinations without language or time restrictions. Also included were data from monographs cited in reviews. The resulting text is a review with conclusions concerning ethical aspects of psychotherapy. The ability to behave altruistically, sense for justice and reciprocity and mutual help are likely to be genetically determined as dispositions to be later developed by upbringing or to be formed or deformed by upbringing. Early experiences lead to formation of ethical attitudes which are internalized and then applied to both one's own and other people's behavior. Altruistic behavior has a strong impact on an individual's health and its acceptance may positively influence the pathophysiological mechanisms underlying numerous diseases. Ethical theory and reflection, however, may be applied to both theory and practice of psychotherapy in a conscious, targeted and thoughtful manner. In everyday practice, psychotherapists and organizations must necessarily deal with conscious conflicts between therapeutic possibilities, clients' wishes, their own as well as clients' ideas and the real world. Understanding one's own motives in therapy is one of the aims of a

Nuclide separation modeling through reverse osmosis membranes in radioactive liquid waste

Directory of Open Access Journals (Sweden)

Byung-Sik Lee

2015-12-01

Full Text Available The aim of this work is to investigate the transport mechanism of radioactive nuclides through the reverse osmosis (RO membrane and to estimate its effectiveness for nuclide separation from radioactive liquid waste. An analytical model is developed to simulate the RO separation, and a series of experiments are set up to confirm its estimated separation behavior. The model is based on the extended Nernst–Plank equation, which handles the convective flux, diffusive flux, and electromigration flux under electroneutrality and zero electric current conditions. The distribution coefficient which arises due to ion interactions with the membrane material and the electric potential jump at the membrane interface are included as boundary conditions in solving the equation. A high Peclet approximation is adopted to simplify the calculation, but the effect of concentration polarization is included for a more accurate prediction of separation. Cobalt and cesium are specifically selected for the experiments in order to check the separation mechanism from liquid waste composed of various radioactive nuclides and nonradioactive substances, and the results are compared with the estimated cobalt and cesium rejections of the RO membrane using the model. Experimental and calculated results are shown to be in excellent agreement. The proposed model will be very useful for the prediction of separation behavior of various radioactive nuclides by the RO membrane.

Nuclide separation modeling through reverse osmosis membranes in radioactive liquid waste

Energy Technology Data Exchange (ETDEWEB)

Lee, Byung Sik [KEPCO Engineering and Construction, Gimcheon (Korea, Republic of)

2015-12-15

The aim of this work is to investigate the transport mechanism of radioactive nuclides through the reverse osmosis (RO) membrane and to estimate its effectiveness for nuclide separation from radioactive liquid waste. An analytical model is developed to simulate the RO separation, and a series of experiments are set up to confirm its estimated separation behavior. The model is based on the extended Nernst-Plank equation, which handles the convective flux, diffusive flux, and electromigration flux under electroneutrality and zero electric current conditions. The distribution coefficient which arises due to ion interactions with the membrane material and the electric potential jump at the membrane interface are included as boundary conditions in solving the equation. A high Peclet approximation is adopted to simplify the calculation, but the effect of concentration polarization is included for a more accurate prediction of separation. Cobalt and cesium are specifically selected for the experiments in order to check the separation mechanism from liquid waste composed of various radioactive nuclides and nonradioactive substances, and the results are compared with the estimated cobalt and cesium rejections of the RO membrane using the model. Experimental and calculated results are shown to be in excellent agreement. The proposed model will be very useful for the prediction of separation behavior of various radioactive nuclides by the RO membrane.

Removal of 125I from radioactive experimental waste with an anion exchange paper membrane

International Nuclear Information System (INIS)

Inoue, Hiroyoshi; Kagoshima, Mayumi

2000-01-01

The behavior of radioactive iodide and chloride ions through an anion exchange paper membrane to remove 125 I from radioactive experimental waste has been studied with nonequilibrium thermodynamic analyses. Anion exchange paper membrane was found to be electroconductively more permeable to iodide ion than to chloride ion. The iodide ion bound more strongly to the anion exchange site within a membrane phase than the chloride ion by more than twice. The results suggested that an anion exchange paper membrane was appropriate for the filtration removal system

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.

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.

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.

Monitoring voltage-sensitive membrane impedance change using radio frequency interrogation.

Science.gov (United States)

Dharia, Sameera; Rabbitt, Richard D

2010-01-01

Here we present a new technique to monitor dynamic conformational changes in voltage-sensitive membrane-bound proteins using radio frequency (RF) impedance measurements. Xenopus oocytes were transfected to express ShakerB-IR K(+) ion channels, and step changes in membrane potential were applied using two-electrode voltage clamp (TEVC). Simultaneously, bipolar extracellular electrodes were used to measure the RF electrical impedance across the cell (300 kHz - 1 MHz). RF current will either pass through the media, around the cell, or displace charge across the cell membrane. The change in displacement current in the cell membrane during voltage clamp resulted in measurable RF impedance change. RF impedance change during DC membrane depolarization was significantly greater in ShakerB-IR expressing oocytes than in endogenous controls at 300 kHz, 500 kHz and, to a lesser extent, 1 MHz. Since the RF were too high to modulate ShakerB-IR protein conformational state (e.g. open channel probability), impedance changes are interpreted as reflections of voltage-dependent protein conformation and associated biophysics such as ion-channel dipole interactions, fluctuations in bound water, or charged lipid head-group rotations.

Analysis of protein interactions at native chloroplast membranes by ellipsometry.

Directory of Open Access Journals (Sweden)

Verena Kriechbaumer

Full Text Available Membrane bound receptors play vital roles in cell signaling, and are the target for many drugs, yet their interactions with ligands are difficult to study by conventional techniques due to the technical difficulty of monitoring these interactions in lipid environments. In particular, the ability to analyse the behaviour of membrane proteins in their native membrane environment is limited. Here, we have developed a quantitative approach to detect specific interactions between low-abundance chaperone receptors within native chloroplast membranes and their soluble chaperone partners. Langmuir-Schaefer film deposition was used to deposit native chloroplasts onto gold-coated glass slides, and interactions between the molecular chaperones Hsp70 and Hsp90 and their receptors in the chloroplast membranes were detected and quantified by total internal reflection ellipsometry (TIRE. We show that native chloroplast membranes deposited on gold-coated glass slides using Langmuir-Schaefer films retain functional receptors capable of binding chaperones with high specificity and affinity. Taking into account the low chaperone receptor abundance in native membranes, these binding properties are consistent with data generated using soluble forms of the chloroplast chaperone receptors, OEP61 and Toc64. Therefore, we conclude that chloroplasts have the capacity to selectively bind chaperones, consistent with the notion that chaperones play an important role in protein targeting to chloroplasts. Importantly, this method of monitoring by TIRE does not require any protein labelling. This novel combination of techniques should be applicable to a wide variety of membranes and membrane protein receptors, thus presenting the opportunity to quantify protein interactions involved in fundamental cellular processes, and to screen for drugs that target membrane proteins.

Profiling the outer membrane proteome during growth and development of the social bacterium Myxococcus xanthus by selective biotinylation and analyses of outer membrane vesicles.

Science.gov (United States)

Kahnt, Jörg; Aguiluz, Kryssia; Koch, Jürgen; Treuner-Lange, Anke; Konovalova, Anna; Huntley, Stuart; Hoppert, Michael; Søgaard-Andersen, Lotte; Hedderich, Reiner

2010-10-01

Social behavior in the bacterium Myxococcus xanthus relies on contact-dependent activities involving cell-cell and cell-substratum interactions. To identify outer membrane proteins that have a role in these activities, we profiled the outer membrane proteome of growing and starving cells using two strategies. First, outer membrane proteins were enriched by biotinylation of intact cells using the reagent NHS (N-hydroxysuccinimide)-PEO(12) (polyethylene oxide)-biotin with subsequent membrane solubilization and affinity chromatography. Second, the proteome of outer membrane vesicles (OMV) was determined. Comparisons of detected proteins show that these methods have different detection profiles and together provide a comprehensive view of the outer membrane proteome. From 362 proteins identified, 274 (76%) were cell envelope proteins including 64 integral outer membrane proteins and 85 lipoproteins. The majority of these proteins were of unknown function. Among integral outer membrane proteins with homologues of known function, TonB-dependent transporters comprise the largest group. Our data suggest novel functions for these transporters. Among lipoproteins with homologues of known function, proteins with hydrolytic functions comprise the largest group. The luminal load of OMV was enriched for proteins with hydrolytic functions. Our data suggest that OMV have functions in predation and possibly in transfer of intercellular signaling molecules between cells.

Shaping of parabolic cylindrical membrane reflectors for the Dart Precision Test Bed

Science.gov (United States)

Morgan, R.; Agnes, Gregory S.; Dragovan, M.; Barber, D.; Marcin, M.; White, C.; Dooley, J.; Hatheway, A.

2004-01-01

The DART is a new telescope architecture consisting of a single aperture formed from two cylindrical parabolic reflectors. The system is ideally suited to using tensioned membranes for the reflective surfaces, owing to the zero Gaussian curvature of a cylindrical parabola. In this paper, we present experimental measurements for shaping the membranes by using curved boundary elements to achieve coarse shaping, and a pair of precision rails shaped by moments and forces at the ends, and lightly pushed into the surface, to provide fine shape control.

CO2-Switchable Membranes Prepared by Immobilization of CO2-Breathing Microgels.

Science.gov (United States)

Zhang, Qi; Wang, Zhenwu; Lei, Lei; Tang, Jun; Wang, Jianli; Zhu, Shiping

2017-12-20

Herein, we report the development of a novel CO 2 -responsive membrane system through immobilization of CO 2 -responsive microgels into commercially available microfiltration membranes using a method of dynamic adsorption. The microgels, prepared from soap-free emulsion polymerization of CO 2 -responsive monomer 2-(diethylamino)ethyl methacrylate (DEA), can be reversibly expanded and shrunken upon CO 2 /N 2 alternation. When incorporated into the membranes, this switching behavior was preserved and further led to transformation between microfiltration and ultrafiltration membranes, as indicated from the dramatic changes on water flux and BSA rejection results. This CO 2 -regulated performance switching of membranes was caused by the changes of water transportation channel, as revealed from the dynamic water contact angle tests and SEM observation. This work represents a simple yet versatile strategy for making CO 2 -responsive membranes.

SINTESIS MEMBRAN NATA ALOE VERA-ETILENDIAMIN DAN KARAKTERISASINYA

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EB Susatyo

2014-06-01

showed a different behavior in terms of mechanical properties and structure. The membrane of pure nata had strong mechanical properties, while the membrane of activated nata tended to be fragile, while the nata-en membrane was loamy. The infrared spectra of the three types of membranes (from pure nata, activated nata , and nata-en generally did not change significantly, there was only a shift of the wavelength of each membrane. Based on the infrared spectra, it can be seen that each membrane has a hydroxyl group, but there was widened absorption for each membrane. Alkyl and carboxyl groups are still visible, although the activated nata membrane absorption is reduced, while in the nata-en membrane it was founded a new peak that indicated the presence of amine groups. This proves that there has been a bond between nata with ethylenediamine.

Smart membranes for monitoring membrane based desalination processes

KAUST Repository

Laleg-Kirati, Taous-Meriem

2017-10-12

Various examples are related to smart membranes for monitoring membrane based process such as, e.g., membrane distillation processes. In one example, a membrane, includes a porous surface and a plurality of sensors (e.g., temperature, flow and/or impedance sensors) mounted on the porous surface. In another example, a membrane distillation (MD) process includes the membrane. Processing circuitry can be configured to monitor outputs of the plurality of sensors. The monitored outputs can be used to determine membrane degradation, membrane fouling, or to provide an indication of membrane replacement or cleaning. The sensors can also provide temperatures or temperature differentials across the porous surface, which can be used to improve modeling or control the MD process.

Improved antifouling properties of polymer membranes using a ‘layer-by-layer’ mediated method

KAUST Repository

Chen, Lin

2013-01-01

Polymeric reverse osmosis membranes were modified with antifouling polymer brushes through a \\'layer by layer\\' (LBL) mediated method. Based on pure physical electrostatic interaction, the attachment of LBL films did not alter separation performance of the membranes. In addition, the incorporation of an LBL film also helped to amplify the number of potential reaction sites on the membrane surfaces for attachment of antifouling polymer brushes, which were then attached to the surface. Attachment of the brushes included two different approaches, grafting to and grafting from. Attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR), X-ray photoelectron spectroscopy (XPS) and water contact angle measurements showed successful growth of the LBL films and subsequently the polymer brushes. Using this method to modify reverse osmosis membranes, preliminary performance testing showed the antifouling properties of the as-modified membranes were much better than the virgin membrane with no significant loss in water flux and salt rejection. © 2013 The Royal Society of Chemistry.

Attainability and minimum energy of multiple-stage cascade membrane Systems

KAUST Repository

Alshehri, Ali

2015-08-12

Process design and simulation of multi-stage membrane systems have been widely studied in many gas separation systems. However, general guidelines have not been developed yet for the attainability and the minimum energy consumption of a multi-stage membrane system. Such information is important for conceptual process design and thus it is the topic of this work. Using a well-mixed membrane model, it was determined that the attainability curve of multi-stage systems is defined by the pressure ratio and membrane selectivity. Using the constant recycle ratio scheme, the recycle ratio can shift the attainability behavior between single-stage and multi-stage membrane systems. When the recycle ratio is zero, all of the multi-stage membrane processes will decay to a single-stage membrane process. When the recycle ratio approaches infinity, the required selectivity and pressure ratio reach their absolute minimum values, which have a simple relationship with that of a single-stage membrane process, as follows: View the MathML sourceSn=S1, View the MathML sourceγn=γ1, where n is the number of stages. The minimum energy consumption of a multi-stage membrane process is primarily determined by the membrane selectivity and recycle ratio. A low recycle ratio can significantly reduce the required membrane selectivity without substantial energy penalty. The energy envelope curve can provide a guideline from an energy perspective to determine the minimum required membrane selectivity in membrane process designs to compete with conventional separation processes, such as distillation.

Recent advances on polymeric membranes for membrane reactors

KAUST Repository

Buonomenna, M. G.; Choi, Seung Hak

2012-01-01

. The successful use of membranes in membrane reactors is primary the result of two developments concerning: (i) membrane materials and (ii) membrane structures. The selection of a suited material and preparation technique depends on the application the membrane

Application of thin film cellulose composite membrane for dye wastewater reuse

KAUST Repository

Puspasari, Tiara

2016-09-22

The use of low cost membranes with high salt/dye selectivity and high flux is ideal for an economic and eco-friendly treatment of dye wastewater. Here, regenerated cellulose membranes prepared from trimethylsilyl cellulose are studied for treating artificial dye effluents. In the experiments using a feed containing Congo Red and high NaCl concentration, the membrane featured impressive dye removal with zero salt rejection combined with high flux. More interestingly, the membrane reached as much as 600 LMH flux at 80 °C and 4 bar while maintaining high dye rejection close to 98%. In prolonged experiments up to 75 h the membrane exhibited good antifouling behavior with nearly 100% flux recovery. This study may provide a promising alternative of dye effluent treatment where high amounts of monovalent salts are present. © 2016

Effect of process parameters on the dynamic behavior of polymer electrolyte membrane fuel cells for electric vehicle applications

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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.

Reduced Graphene Oxide Membranes: Applications in Fog Collection and Water Purification

KAUST Repository

Tang, Bo

2017-05-01

Reduced graphene oxide (rGO) has attracted considerable interest recently as the low cost and chemical stable derivative of pristine graphene with application in many applications such as energy storage, water purification and electronic devices. This dissertation thoroughly investigated stacked rGO membrane fabrication process by vacuum-driven filtration, discovered asymmetry of the two surfaces of the rGO membrane, explored application perspectives of the asymmetric rGO membrane in fog collection and microstructure patterning, and disclosed membrane compaction issue during water filtration and species rejection. In more details, this dissertation revealed that, with suitable pore size, the filtration membrane substrate would leave its physical imprint on the bottom surface of the rGO membrane in the form of surface microstructures, which result in asymmetric dynamic water wettability properties of the two surfaces of the rGO membrane. The asymmetric wettability of the rGO membrane would lead to contrasting fog harvesting behavior of its two surfaces. The physical imprint mechanism was further extended to engineering pre-designed patterns selectively on the bottom surface of the rGO membrane. This dissertation, for the first time, reported the water flux and rejection kinetics, which was related to the compaction of the rGO membrane under pressure in the process of water filtration.

Hemocompatible polyethersulfone/polyurethane composite membrane for high-performance antifouling and antithrombotic dialyzer.

Science.gov (United States)

Yin, Zehua; Cheng, Chong; Qin, Hui; Nie, Chuanxiong; He, Chao; Zhao, Changsheng

2015-01-01

Researches on blood purification membranes are fuelled by diverse clinical needs, such as hemodialysis, hemodiafiltration, hemofiltration, plasmapheresis, and plasma collection. To approach high-performance dialyzer, the integrated antifouling and antithrombotic properties are highly necessary for the design/modification of advanced artificial membranes. In this study, we propose and demonstrate that the physical blend of triblock polyurethane (PU) and polyethersulfone (PES) may advance the performance of hemodialysis membranes with greatly enhanced blood compatibility. It was found that the triblock PU could be blended with PES at high ratio owing to their excellent miscibility. The surfaces of the PES/PU composite membranes were characterized using attenuated total reflectance-Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, water contact angle measurement, and surface ζ-potentials. The results indicated that the membrane surfaces were assembled with hydrophilic segregation layer owing to the migration of amphiphilic PU segments during membrane preparation, which might confer the composite membranes with superior hemocompatibility. The cross-section scanning electron microscopy images of the composite membranes exhibited structure transformation from finger-like structure to sponge-like structure, which indicated that the composite membrane had tunable porosity and permeability. The further ultrafiltration experiments indicated that the composite membranes showed increased permeability and excellent antifouling ability. The blood compatibility observation indicated that PES/PU composite membranes owned decreased protein adsorption, suppressed platelet adhesion, and prolonged plasma recalcification time. These results indicated that the PES/PU composite membranes exhibited enhanced antifouling and antithrombotic properties than the pristine PES membrane. The strategy may forward the fabrication of blood compatible composite membranes for

Recent advances on polymeric membranes for membrane reactors

KAUST Repository

Buonomenna, M. G.

2012-06-24

Membrane reactors are generally applied in high temperature reactions (>400 °C). In the field of fine chemical synthesis, however, much milder conditions are generally applicable and polymeric membranes were applied without their damage. The successful use of membranes in membrane reactors is primary the result of two developments concerning: (i) membrane materials and (ii) membrane structures. The selection of a suited material and preparation technique depends on the application the membrane is to be used in. In this chapter a review of up to date literature about polymers and configuration catalyst/ membranes used in some recent polymeric membrane reactors is given. The new emerging concept of polymeric microcapsules as catalytic microreactors has been proposed. © 2012 Bentham Science Publishers. All rights reserved.

THE COLLOIDAL BEHAVIOR OF EDESTIN

Science.gov (United States)

Hitchcock, David I.

1922-01-01

1. It has been shown by titration experiments that the globulin edestin behaves like an amphoteric electrolyte, reacting stoichiometrically with acids and bases. 2. The potential difference developed between a solution of edestin chloride or acetate separated by a collodion membrane from an acid solution free from protein was found to be influenced by salt concentration and hydrogen ion concentration in the way predicted by Donnan's theory of membrane equilibrium. 3. The osmotic pressure of such edestin-acid salt solutions was found to be influenced by salt concentration and by hydrogen ion concentration in the same way as is the potential difference. 4. The colloidal behavior of edestin is thus completely analogous to that observed by Loeb with gelatin, casein, and egg albumin, and may be explained by Loeb's theory of colloidal behavior, which is based on the idea that proteins react stoichiometrically as amphoteric electrolytes and on Donnan's theory of membrane equilibrium. PMID:19871959

Behavior of a New Elastomeric material used as polyolefinic geo membrane in waterproofing; Comportamiento de un nuevo material elastomerico utilizado como geomembrana poliolefinica en impermeabilizacion

Energy Technology Data Exchange (ETDEWEB)

Blanco, M.; Aguilar, E.; Vara, T. A; Soriano, J.; Garcia, F.; Castillo, F.

2011-07-01

Two decades ago that Balsas de Tenerife (BALTEN) and the Centro de Estudios y Experimentacion de Obras Publicas (CEDEX), in its experimental field of the south of the Tenerife Island have installed a series of materials to known their behaviour over time. These products among which was placed over a dozen years ago, on an elastomeric polyolefin. This work presents the performance of this synthetic geo membrane, focusing on the evolution in the time of the tensile properties static puncture, low temperature folding, dynamic impact, joint strength (shear and peeling test), optical microscopy of reflection nd scanning electron microscopy. (Author) 11 refs.

Surface characterization of hemodialysis membranes based on streaming potential measurements.

Science.gov (United States)

Werner, C; Jacobasch, H J; Reichelt, G

1995-01-01

Hemodialysis membranes made from cellulose (CUPROPHAN, HEMOPHAN) and sulfonated polyethersulfone (SPES) were characterized using the streaming potential technique to determine the zeta potential at their interfaces against well-defined aqueous solutions of varied pH and potassium chloride concentrations. Streaming potential measurements enable distinction between different membrane materials. In addition to parameters of the electrochemical double layer at membrane interfaces, thermodynamic characteristics of adsorption of different solved species were evaluated. For that aim a description of double layer formation as suggested by Börner and Jacobasch (in: Electrokinetic Phenomena, p. 231. Institut für Technologie der Polymere, Dresden (1989)) was applied which is based on the generally accepted model of the electrochemical double layer according to Stern (Z. Elektrochemie 30, 508 (1924)) and Grahame (Chem. Rev. 41, 441 (1947)). The membranes investigated show different surface acidic/basic and polar/nonpolar behavior. Furthermore, alterations of membrane interfaces through adsorption processes of components of biologically relevant solutions were shown to be detectable by streaming potential measurements.

Regulation of multispanning membrane protein topology via post-translational annealing.

Science.gov (United States)

Van Lehn, Reid C; Zhang, Bin; Miller, Thomas F

2015-09-26

The canonical mechanism for multispanning membrane protein topogenesis suggests that protein topology is established during cotranslational membrane integration. However, this mechanism is inconsistent with the behavior of EmrE, a dual-topology protein for which the mutation of positively charged loop residues, even close to the C-terminus, leads to dramatic shifts in its topology. We use coarse-grained simulations to investigate the Sec-facilitated membrane integration of EmrE and its mutants on realistic biological timescales. This work reveals a mechanism for regulating membrane-protein topogenesis, in which initially misintegrated configurations of the proteins undergo post-translational annealing to reach fully integrated multispanning topologies. The energetic barriers associated with this post-translational annealing process enforce kinetic pathways that dictate the topology of the fully integrated proteins. The proposed mechanism agrees well with the experimentally observed features of EmrE topogenesis and provides a range of experimentally testable predictions regarding the effect of translocon mutations on membrane protein topogenesis.

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.

The role of membrane microdomains in transmembrane signaling through the epithelial glycoprotein Gp140/CDCP1

Science.gov (United States)

Alvares, Stacy M.; Dunn, Clarence A.; Brown, Tod A.; Wayner, Elizabeth E.; Carter, William G.

2008-01-01

Cell adhesion to the extracellular matrix (ECM) via integrin adhesion receptors initiates signaling cascades leading to changes in cell behavior. While integrin clustering is necessary to initiate cell attachment to the matrix, additional membrane components are necessary to mediate the transmembrane signals and the cell adhesion response that alter downstream cell behavior. Many of these signaling components reside in glycosphingolipid-rich and cholesterol-rich membrane domains such as Tetraspanin Enriched Microdomains (TEMs)/Glycosynapse 3 and Detergent-Resistant Microdomains (DRMs), also known as lipid rafts. In the following article, we will review examples of how components in these membrane microdomains modulate integrin adhesion after initial attachment to the ECM. Additionally, we will present data on a novel adhesion-responsive transmembrane glycoprotein Gp140/CUB Domain Containing Protein 1, which clusters in epithelial cell-cell contacts. Gp140 can then be phosphorylated by Src Family Kinases at tyrosine 734 in response to outside-in signals- possibly through interactions involving the extracellular CUB domains. Data presented here suggests that outside-in signals through Gp140 in cell-cell contacts assemble membrane clusters that associate with membrane microdomains to recruit and activate SFKs. Active SFKs then mediate phosphorylation of Gp140, SFK and PKCδ with Gp140 acting as a transmembrane scaffold for these kinases. We propose that the clustering of Gp140 and signaling components in membrane microdomains in cell-cell contacts contributes to changes in cell behavior. PMID:18269919

Selectivity of Direct Methanol Fuel Cell Membranes

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Antonino S. Aricò

2015-11-01

Full Text Available Sulfonic acid-functionalized polymer electrolyte membranes alternative to Nafion® were developed. These were hydrocarbon systems, such as blend sulfonated polyetheretherketone (s-PEEK, new generation perfluorosulfonic acid (PFSA systems, and composite zirconium phosphate–PFSA polymers. The membranes varied in terms of composition, equivalent weight, thickness, and filler and were investigated with regard to their methanol permeation characteristics and proton conductivity for application in direct methanol fuel cells. The behavior of the membrane electrode assemblies (MEA was investigated in fuel cell with the aim to individuate a correlation between membrane characteristics and their performance in a direct methanol fuel cell (DMFC. The power density of the DMFC at 60 °C increased according to a square root-like function of the membrane selectivity. This was defined as the reciprocal of the product between area specific resistance and crossover. The power density achieved at 60 °C for the most promising s-PEEK-based membrane-electrode assembly (MEA was higher than the benchmark Nafion® 115-based MEA (77 mW·cm−2 vs. 64 mW·cm−2. This result was due to a lower methanol crossover (47 mA·cm−2 equivalent current density for s-PEEK vs. 120 mA·cm−2 for Nafion® 115 at 60 °C as recorded at OCV with 2 M methanol and a suitable area specific resistance (0.15 Ohm cm2 for s-PEEK vs. 0.22 Ohm cm2 for Nafion® 115.

Selectivity of Direct Methanol Fuel Cell Membranes.

Science.gov (United States)

Aricò, Antonino S; Sebastian, David; Schuster, Michael; Bauer, Bernd; D'Urso, Claudia; Lufrano, Francesco; Baglio, Vincenzo

2015-11-24

Sulfonic acid-functionalized polymer electrolyte membranes alternative to Nafion(®) were developed. These were hydrocarbon systems, such as blend sulfonated polyetheretherketone (s-PEEK), new generation perfluorosulfonic acid (PFSA) systems, and composite zirconium phosphate-PFSA polymers. The membranes varied in terms of composition, equivalent weight, thickness, and filler and were investigated with regard to their methanol permeation characteristics and proton conductivity for application in direct methanol fuel cells. The behavior of the membrane electrode assemblies (MEA) was investigated in fuel cell with the aim to individuate a correlation between membrane characteristics and their performance in a direct methanol fuel cell (DMFC). The power density of the DMFC at 60 °C increased according to a square root-like function of the membrane selectivity. This was defined as the reciprocal of the product between area specific resistance and crossover. The power density achieved at 60 °C for the most promising s-PEEK-based membrane-electrode assembly (MEA) was higher than the benchmark Nafion(®) 115-based MEA (77 mW·cm(-2) vs. 64 mW·cm(-2)). This result was due to a lower methanol crossover (47 mA·cm(-2) equivalent current density for s-PEEK vs. 120 mA·cm(-2) for Nafion(®) 115 at 60 °C as recorded at OCV with 2 M methanol) and a suitable area specific resistance (0.15 Ohm cm² for s-PEEK vs. 0.22 Ohm cm² for Nafion(®) 115).

Gas transport behavior of mixed-matrix membranes composed of silica nanoparticles in a polymer of intrinsic microporosity (PIM-1)

KAUST Repository

Ahn, Juhyeon; Chung, Wookjin; Pinnau, Ingo; Song, Jingshe; Du, Naiying; Robertson, Gilles P.; Guiver, Michael D.

2010-01-01

Recently, high-free volume, glassy ladder-type polymers, referred to as polymers of intrinsic microporosity (PIM), have been developed and their reported gas transport performance exceeded the Robeson upper bound trade-off for O2/N2 and CO2/CH4. The present work reports the gas transport behavior of PIM-1/silica nanocomposite membranes. The changes in free volume, as well as the presence and volume of the void cavities, were investigated by analyzing the density, thermal stability, and nano-structural morphology. The enhancement in gas permeability (e.g., He, H2, O2, N2, and CO2) with increasing filler content shows that the trend is related to the true silica volume and void volume fraction. Crown Copyright © 2009.

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

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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.

Surface modification of poly(vinylidene fluoride) membrane with hydrophilic and anti-fouling performance via a two-step polymerization

Energy Technology Data Exchange (ETDEWEB)

Chen, Gui-E; Sun, Li; Huang, Hui-Hong; Liu, Yan-Jun [Shanghai Institute of Technology, Shanghai (China); Xu, Zhen-Liang; Yang, Hu [East China University of Science and Technology, Shanghai (China)

2015-12-15

The surface modification of poly (vinylidene fluoride) (PVDF) membrane was performed via a two-step polymerization reactions. Poly (acrylic acid) (PAAc) was first grafted onto the membrane surface for the preparation of PVDF-g-PAAc membrane, and then poly (ethylene glycol) 200 (PEG 200) was immobilized on the membrane surface by the esterification reaction for the fabrication of PVDF-g-PEGA membrane. Attenuated total reflectance (ATR) FTIR, X-ray photoelectron spectroscopy (XPS), scanning electron microscope (SEM), and protein adsorption, water flux, water content and dynamic contact angle were conducted to characterize the structures and performance of the resultant PVDF membranes. The experimental results showed that the adsorption of bovine serum albumin (BSA) on the PVDF-g-PEGA membrane decreased about 80% when the grafting ratio reached to 15 wt%, compared with the pristine PVDF membrane. Moreover, the water contact angle of the membrane dropped to 60.5o, while the membrane pore sizes remained little changed.

Membrane pumping technology, helium and hydrogen isotopes separation in the fusion hydrogen

International Nuclear Information System (INIS)

Pigarov, A.Yu.; Pistunovich, V.I.; Busnyuk, A.O.

1994-01-01

A gas pumping system for the ITER, improved by implementation of superpermeable membranes for selective hydrogen isotope exhaust, is considered. The study of the pumping capability of a niobium membrane for a hydrogen-helium mixture has been fulfilled. The membrane superpermeability can be only realized for atomic hydrogen. Helium does not pass through the membrane, and its presence does not affect the hydrogen pumping. A detailed Monte Carlo simulation of gas behavior for the experimental facility has been done. The probability of permeation for a hydrogen atom for one collision with the membrane is ∼0.1; the same probability of molecule permeation is ∼10 -5 . The probability for atomization, i.e. re-emission of an atomizer is ∼0.2; the probability of recombination of an atom is ∼0.2

Solvent accessible surface area (ASA) of simulated phospholipid membranes

DEFF Research Database (Denmark)

Tuchsen, E.; Jensen, Morten Østergaard; Westh, P.

2003-01-01

The membrane-solvent interface has been investigated through calculations of the solvent accessible surface area (ASA) for simulated membranes of DPPC and POPE. For DPPC at 52 degreesC we found an ASA of 126 +/- 8 Angstrom(2) per lipid molecule, equivalent to twice the projected lateral area......, even the most exposed parts of the PC head-group show average ASAs of less than half of its maximal or 'fully hydrated' value. The average ASA of a simulated POPE membrane was 96 +/- 7 Angstrom(2) per lipid. The smaller value than for DPPC reflects much lower ASA of the ammonium ion, which is partially...... compensated by increased exposure of the ethylene and phosphate moieties. The ASA of the polar moieties Of (PO4, NH3 and COO) constitutes 65% of the total accessible area for POPE, making this interface more polar than that of DPPC. It is suggested that ASA information can be valuable in attempts...

Functionalized membranes for environmental remediation and selective separation

Science.gov (United States)

Xiao, Li

Membrane process including microfiltration (MF), ultrafiltration (UF), nanofiltration (NF) and reverse osmosis (RO) have provided numerous successful applications ranging from drinking water purification, wastewater treatment, to material recovery. The addition of functional moiety in the membranes pores allows such membranes to be used in challenging areas including tunable separations, toxic metal capture, and catalysis. In this work, polyvinylidene fluoride (PVDF) MF membrane was functionalized with temperature responsive (poly(N-isopropylacrylamide), PNIPAAm) and pH responsive (polyacrylic acid, PAA) polymers. It's revealed that the permeation of various molecules (water, salt and dextran) through the membrane can be thermally or pH controlled. The introduction of PAA as a polyelectrolyte offers an excellent platform for the immobilization of metal nanoparticles (NPs) applied for degradation of toxic chlorinated organics with significantly increased longevity and stability. The advantage of using temperature and pH responsive polymers/hydrogels also includes the high reactivity and effectiveness in dechlorination. Further advancement on the PVDF functionalization involved the alkaline treatment to create partially defluorinated membrane (Def-PVDF) with conjugated double bounds allowing for the covalent attachment of different polymers. The PAA-Def-PVDF membrane shows pH responsive behavior on both the hydraulic permeability and solute retention. The sponge-like PVDF (SPVDF) membranes by phase inversion were developed through casting PVDF solution on polyester backing. The SPVDF membrane was demonstrated to have 4 times more surface area than commercial PVDF MF membrane, allowing for enhanced nanoparticles loading for chloro-organics degradation. The advanced functionalization method and process were also validated to be able to be scaled-up through the evaluation of full-scale functionalized membrane provided by Ultura Inc. California, USA. Nanofiltration (NF

Effects of Lateral and Terminal Chains of X-Shaped Bolapolyphiles with Oligo(phenylene ethynylene Cores on Self-Assembly Behavior. Part 2: Domain Formation by Self-Assembly in Lipid Bilayer Membranes

Directory of Open Access Journals (Sweden)

Stefan Werner

2017-09-01

Full Text Available Supramolecular self-assembly of membrane constituents within a phospholipid bilayer creates complex functional platforms in biological cells that operate in intracellular signaling, trafficking and membrane remodeling. Synthetic polyphilic compounds of macromolecular or small size can be incorporated into artificial phospholipid bilayers. Featuring three or four moieties of different philicities, they reach beyond ordinary amphiphilicity and open up avenues to new functions and interaction concepts. Here, we have incorporated a series of X-shaped bolapolyphiles into DPPC (1,2-dipalmitoyl-sn-glycero-3-phosphocholine bilayers of giant unilamellar vesicles. The bolapolyphiles consist of a rod-like oligo(phenylene ethynylene (OPE core, hydrophilic glycerol-based headgroups with or without oligo(ethylene oxide expansions at both ends and two lateral alkyl chains attached near the center of the OPE core. In the absence of DPPC and water, the compounds showed thermotropic liquid-crystalline behavior with a transition between polyphilic and amphiphilic assembly (see part 1 in this issue. In DPPC membranes, various trends in the domain morphologies were observed upon structure variations, which entailed branched alkyl chains of various sizes, alkyl chain semiperfluorination and size expansion of the headgroups. Observed effects on domain morphology are interpreted in the context of the bulk behavior (part 1 and of a model that was previously developed based on spectroscopic and physicochemical data.

Assessing the removal of organic micro-pollutants from anaerobic membrane bioreactor effluent by fertilizer-drawn forward osmosis

KAUST Repository

Kim, Youngjin; Li, Sheng; Chekli, Laura; Woo, Yun Chul; Wei, Chunhai; Phuntsho, Sherub; Ghaffour, NorEddine; Leiknes, TorOve; Shon, Ho Kyong

2017-01-01

In this study, the behavior of organic micro-pollutants (OMPs) transport including membrane fouling was assessed in fertilizer-drawn forward osmosis (FDFO) during treatment of the anaerobic membrane bioreactor (AnMBR) effluent. The flux decline

Extracellular membrane vesicles in blood products-biology and clinical relevance

Directory of Open Access Journals (Sweden)

Emilija Krstova Krajnc

2016-01-01

Full Text Available Extracellular membrane vesicles are fragments shed from plasma membranes off all cell types that are undergoing apoptosis or are being subjected to various types of stimulation or stress.  Even in the process of programmed cell death (apoptosis, cell fall apart of varying size vesicles. They expose phosphatidylserine (PS on the outer leaflet of their membrane, and bear surface membrane antigens reflecting their cellular origin. Extracellular membrane vesicles have been isolated from many types of biological fluids, including serum, cerebrospinal fluid, urine, saliva, tears and conditioned culture medium. Flow cytometry is one of the many different methodological approaches that have been used to analyze EMVs. The method attempts to characterize the EMVs cellular origin, size, population, number, and structure. EMVs are present and accumulate in blood products (erythrocytes, platelets as well as in fresh frozen plasma during storage. The aim of this review is to highlight the importance of extracellular vesicles as a cell-to-cell communication system and the role in the pathogenesis of different diseases. Special emphasis will be given to the implication of extracellular membrane vesicles in blood products and their clinical relevance. Although our understanding of the role of  EMVs in disease is far from comprehensive, they display promise as biomarkers for different diseases in the future and also as a marker of quality and safety in the quality control of blood products.

Nanofiltration and nanostructured membranes--should they be considered nanotechnology or not?

Science.gov (United States)

Mueller, Nicole C; van der Bruggen, Bart; Keuter, Volkmar; Luis, Patricia; Melin, Thomas; Pronk, Wouter; Reisewitz, Robert; Rickerby, David; Rios, Gilbert M; Wennekes, Wilco; Nowack, Bernd

2012-04-15

Nanofiltration is frequently associated with nanotechnology - obviously because of its name. However, the term "nano" in nanofiltration refers - according to the definition of the International Union of Pure and Applied Chemistry (IUPAC) - to the size of the particles rejected and not to a nanostructure as defined by the International Organisation of Standardisation (ISO) in the membrane. Evidently, the approach to standardisation of materials differs significantly between membrane technology and nanotechnology which leads to considerable confusion and inconsistent use of the terminology. There are membranes that can be unambiguously attributed to both membrane technology and nanotechnology such as those that are functionalized with nanoparticles, while the classification of hitherto considered to be conventional membranes as nanostructured material is questionable. A driving force behind the efforts to define nanomaterials is not least the urgent need for the regulation of the use of nanomaterials. Since risk estimation is the basis for nanotechnology legislation, the risk associated with nanomaterials should also be reflected in the underlying standards and definitions. This paper discusses the impacts of the recent attempts to define nanomaterials on membrane terminology in the light of risk estimations and the need for regulation. Copyright © 2011 Elsevier B.V. All rights reserved.

Membrane fouling mechanism of biofilm-membrane bioreactor (BF-MBR): Pore blocking model and membrane cleaning.

Science.gov (United States)

Zheng, Yi; Zhang, Wenxiang; Tang, Bing; Ding, Jie; Zheng, Yi; Zhang, Zhien

2018-02-01

Biofilm membrane bioreactor (BF-MBR) is considered as an important wastewater treatment technology that incorporates advantages of both biofilm and MBR process, as well as can alleviate membrane fouling, with respect to the conventional activated sludge MBR. But, to be efficient, it necessitates the establishment of proper methods for the assessment of membrane fouling. Four Hermia membrane blocking models were adopted to quantify and evaluate the membrane fouling of BF-MBR. The experiments were conducted with various operational conditions, including membrane types, agitation speeds and transmembrane pressure (TMP). Good agreement between cake formation model and experimental data was found, confirming the validity of the Hermia models for assessing the membrane fouling of BF-MBR and that cake layer deposits on membrane. Moreover, the influences of membrane types, agitation speeds and transmembrane pressure on the Hermia pore blocking coefficient of cake layer were investigated. In addition, the permeability recovery after membrane cleaning at various operational conditions was studied. This work confirms that, unlike conventional activated sludge MBR, BF-MBR possesses a low degree of membrane fouling and a higher membrane permeability recovery after cleaning. Copyright © 2017 Elsevier Ltd. All rights reserved.

Membrane recognition and dynamics of the RNA degradosome.

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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.

Desolventizing of soybean oil/azeotrope mixtures using ceramic membranes.

Science.gov (United States)

de Melo, Jonas R M; Tiggeman, Lidia; Rezzadori, Katia; Steffens, Juliana; Palliga, Marshall; Oliveira, J Vladimir; Di Luccio, Marco; Tres, Marcus V

2017-08-01

This work investigates the use of ceramic membranes with different molecular weight cut-offs (MWCOs: 5, 10 and 20 kDa) to desolventize azeotropic solvent mixtures (ethanol/n-hexane and isopropyl alcohol/n-hexane) from soybean oil/azeotrope micelles. Results show that a decrease in the MWCO of a membrane and an increase in the solvent mass ratio in the mixture resulted in a significant reduction in the permeate flux. The 20 kDa membrane presented the highest permeate flux, 80 and 60 kg/m 2 h for the soybean oil/n-hexane/isopropyl alcohol and soybean oil/n-hexane/ethanol azeotropes, respectively, for an oil to solvent ratio of 1:3 (w/w). The highest oil retention was found using the n-hexane/isopropyl alcohol azeotrope, around 25% in the membrane with the lowest MWCO, that is, 5 kDa. It is shown that the azeotropic mixtures provided intermediate characteristics compared to the original pure solvent behavior.

Separation Process by Porous Membranes: A Numerical Investigation

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Acto de Lima Cunha

2014-07-01

Full Text Available A major problem associated with the membrane separation processes is the permeate flux drop, limiting the widespread of industrial application of this process. This occurs due to the accumulation of solute concentration near the membrane surface. An exact quantification of the concentration polarization as a function of process conditions is essential to estimate the system performance satisfactorily. In this sense, this work aims to predict the behavior of the concentration polarization boundary layer along the length of a permeable tubular membrane, over various operation conditions. The numerical solution of the Navier-Stokes equation, coupled to Darcy's and mass transfer equations, is obtained by the commercial software ANSYS CFX 12, considering a two-dimensional computational domain. The study evaluates the effects of axial Reynolds and Schmidt numbers on the concentration polarization boundary layer thickness during the cross-flow filtration process. Numerical results have shown that the mathematical model is able to predict the formation and growth of the concentration polarization boundary layer along the length of the tubular membrane.

Secure base scripts are associated with maternal parenting behavior across contexts and reflective functioning among trauma-exposed mothers.

Science.gov (United States)

Huth-Bocks, Alissa C; Muzik, Maria; Beeghly, Marjorie; Earls, Lauren; Stacks, Ann M

2014-01-01

There is growing evidence that "secure-base scripts" are an important part of the cognitive underpinnings of internal working models of attachment. Recent research in middle class samples has shown that secure-base scripts are linked to maternal attachment-oriented behavior and child outcomes. However, little is known about the correlates of secure base scripts in higher-risk samples. Participants in the current study included 115 mothers who were oversampled for childhood maltreatment and their infants. Results revealed that a higher level of secure base scriptedness was significantly related to more positive and less negative maternal parenting in both unstructured free play and structured teaching contexts, and to higher reflective functioning scores on the Parent Development Interview-Revised Short Form. Associations with parent-child secure base scripts, specifically, indicate some level of relationship-specificity in attachment scripts. Many, but not all, significant associations remained after controlling for family income and maternal age. Findings suggest that assessing secure base scripts among mothers known to be at risk for parenting difficulties may be important for interventions aimed at altering problematic parental representations and caregiving behavior.

Direct quantification of negatively charged functional groups on membrane surfaces

KAUST Repository

Tiraferri, Alberto

2012-02-01

Surface charge plays an important role in membrane-based separations of particulates, macromolecules, and dissolved ionic species. In this study, we present two experimental methods to determine the concentration of negatively charged functional groups at the surface of dense polymeric membranes. Both techniques consist of associating the membrane surface moieties with chemical probes, followed by quantification of the bound probes. Uranyl acetate and toluidine blue O dye, which interact with the membrane functional groups via complexation and electrostatic interaction, respectively, were used as probes. The amount of associated probes was quantified using liquid scintillation counting for uranium atoms and visible light spectroscopy for the toluidine blue dye. The techniques were validated using self-assembled monolayers of alkanethiols with known amounts of charged moieties. The surface density of negatively charged functional groups of hand-cast thin-film composite polyamide membranes, as well as commercial cellulose triacetate and polyamide membranes, was quantified under various conditions. Using both techniques, we measured a negatively charged functional group density of 20-30nm -2 for the hand-cast thin-film composite membranes. The ionization behavior of the membrane functional groups, determined from measurements with toluidine blue at varying pH, was consistent with published data for thin-film composite polyamide membranes. Similarly, the measured charge densities on commercial membranes were in general agreement with previous investigations. The relative simplicity of the two methods makes them a useful tool for quantifying the surface charge concentration of a variety of surfaces, including separation membranes. © 2011 Elsevier B.V.

Computational Design of Multi-component Bio-Inspired Bilayer Membranes

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Evan Koufos

2014-04-01

Full Text Available Our investigation is motivated by the need to design bilayer membranes with tunable interfacial and mechanical properties for use in a range of applications, such as targeted drug delivery, sensing and imaging. We draw inspiration from biological cell membranes and focus on their principal constituents. In this paper, we present our results on the role of molecular architecture on the interfacial, structural and dynamical properties of bio-inspired membranes. We focus on four lipid architectures with variations in the head group shape and the hydrocarbon tail length. Each lipid species is composed of a hydrophilic head group and two hydrophobic tails. In addition, we study a model of the Cholesterol molecule to understand the interfacial properties of a bilayer membrane composed of rigid, single-tail molecular species. We demonstrate the properties of the bilayer membranes to be determined by the molecular architecture and rigidity of the constituent species. Finally, we demonstrate the formation of a stable mixed bilayer membrane composed of Cholesterol and one of the phospholipid species. Our approach can be adopted to design multi-component bilayer membranes with tunable interfacial and mechanical properties. We use a Molecular Dynamics-based mesoscopic simulation technique called Dissipative Particle Dynamics that resolves the molecular details of the components through soft-sphere coarse-grained models and reproduces the hydrodynamic behavior of the system over extended time scales.

Thermomechanical characterization of a membrane deformable mirror

International Nuclear Information System (INIS)

Morse, Kathleen A.; McHugh, Stuart L.; Fixler, Jeff

2008-01-01

A membrane deformable mirror has been investigated for its potential use in high-energy laser systems. Experiments were performed in which the deformable mirror was heated with a 1 kW incandescent lamp and the thermal profile, the wavefront aberrations, and the mechanical displacement of the membrane were measured. A finite element model was also developed. The wavefront characterization experiments showed that the wavefront degraded with heating. Above a temperature of 35 deg. C, the wavefront characterization experiments indicated a dramatic increase in the high-order wavefront modes before the optical beam became immeasurable in the sensors. The mechanical displacement data of the membrane mirror showed that during heating, the membrane initially deflected towards the heat source and then deflected away from the heat source. Finite element analysis (FEA) predicted a similar displacement behavior as shown by the mechanical displacement data but over a shorter time scale and a larger magnitude. The mechanical displacement data also showed that the magnitude of membrane displacement increased with the experiments that involved higher temperatures. Above a temperature of 35 deg. C, the displacement data showed that random deflections as a function of time developed and that the magnitude of these deflections increased with increased temperature. We concluded that convection, not captured in the FEA, likely played a dominant role in mirror deformation at temperatures above 35 deg. C

MODIFICATION OF ERYTHROCYTE MEMBRANE PROTEINS WITH POLYETHYLENE GLYCOL 1500

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N. G. Zemlianskykh

2016-10-01

Full Text Available The aim of the work was to study the effect of polyethylene glycol PEG-1500 on the Ca2+-ATPase activity and changes in CD44 surface marker expression in human erythrocyte membranes. Determination of the Ca2+-ATPase activity was carried out in sealed erythrocyte ghosts by the level of accumulation of inorganic phosphorus. Changes in the expression of CD44 and amount of CD44+-erythrocytes were evaluated by flow cytometry. The inhibition of Ca2+-ATPase activity and a reduction in the level of CD44 expression and also the decrease in the amount CD44+-cells were found, reflecting a fairly complex restructuring in the membrane-cytoskeleton complex of erythrocytes under the influence of PEG-1500. Effect of PEG-1500 on the surface CD44 marker could be mediated by modification of proteins of membrane-cytoskeleton complex, as indicated by accelerated loss of CD44 in erythrocyte membranes after application of protein cross-linking reagent diamide. Reduced activity of Ca2+-ATPase activity may contribute to the increase in intracellular Ca2+ level and thus leads to a modification of interactions of integral proteins with cytoskeletal components that eventually could result in membrane vesiculation and decreasing in expression of the CD44 marker, which is dynamically linked to the cytoskeleton.

Development of advanced membrane process for treatment of radioactive liquid wastes

International Nuclear Information System (INIS)

Lee, Kune Woo; Choi, W. K.; Lee, J. W.; Jung, G. H.

2002-01-01

The followings were studied through the project entitled 'Development of advanced membrane process for treatment of radioactive liquid wastes'. 1. Surface modification technique of microfiltration membrane. Microporous hydrophobic polypropylene(PP) membrane were modified by radiation-induced grafting using hydrophilic monomers such as arylic acid(AAc), 2-hydroxyethyl methacrylate(HEMA) and styrenesulfonic acid(SSS). The effect of grafting conditions was investigated. Also, copolymeric condition of AAc and EGDMA for nylon membrane was studied. The structure of grafted PP membrane was examined by using FTIR-ATR spectroscopy, SEM and contact angle. The grafted membrane was characterized by measureing the water flux, the ion exchange capacity or the binding capacity of the metal ions. A study on the permeation behavior of simulated waste water containing oil emulsion and characterization of membrane fouling was carried out in the crossflow membrane filtration process using capillary type PP microfiltration membrane modified by radiation induced grafting of HEMA. The effects of various operating parameters were investigated. 2. Electrofiltration Technology. In this section, the process conditions for fouling prevention of membrane by evaluating the effects of operational parameters such as external electric field strength, crossflow velocity, transmembrane pressure, etc. on the permeate flux in electrofiltration were established and the process applicability for oil emulsion wastes containing surfactant using parallel plate type electrofiltration module was evaluated

Development of advanced membrane process for treatment of radioactive liquid wastes

Energy Technology Data Exchange (ETDEWEB)

Lee, Kune Woo; Choi, W. K.; Lee, J. W.; Jung, G. H

2002-01-01

The followings were studied through the project entitled 'Development of advanced membrane process for treatment of radioactive liquid wastes'. 1. Surface modification technique of microfiltration membrane. Microporous hydrophobic polypropylene(PP) membrane were modified by radiation-induced grafting using hydrophilic monomers such as arylic acid(AAc), 2-hydroxyethyl methacrylate(HEMA) and styrenesulfonic acid(SSS). The effect of grafting conditions was investigated. Also, copolymeric condition of AAc and EGDMA for nylon membrane was studied. The structure of grafted PP membrane was examined by using FTIR-ATR spectroscopy, SEM and contact angle. The grafted membrane was characterized by measureing the water flux, the ion exchange capacity or the binding capacity of the metal ions. A study on the permeation behavior of simulated waste water containing oil emulsion and characterization of membrane fouling was carried out in the crossflow membrane filtration process using capillary type PP microfiltration membrane modified by radiation induced grafting of HEMA. The effects of various operating parameters were investigated. 2. Electrofiltration Technology. In this section, the process conditions for fouling prevention of membrane by evaluating the effects of operational parameters such as external electric field strength, crossflow velocity, transmembrane pressure, etc. on the permeate flux in electrofiltration were established and the process applicability for oil emulsion wastes containing surfactant using parallel plate type electrofiltration module was evaluated.

Inverse colloidal crystal membranes for hydrophobic interaction membrane chromatography.

Science.gov (United States)

Vu, Anh T; Wang, Xinying; Wickramasinghe, S Ranil; Yu, Bing; Yuan, Hua; Cong, Hailin; Luo, Yongli; Tang, Jianguo

2015-08-01

Hydrophobic interaction membrane chromatography has gained interest due to its excellent performance in the purification of humanized monoclonal antibodies. The membrane material used in hydrophobic interaction membrane chromatography has typically been commercially available polyvinylidene fluoride. In this contribution, newly developed inverse colloidal crystal membranes that have uniform pores, high porosity and, therefore, high surface area for protein binding are used as hydrophobic interaction membrane chromatography membranes for humanized monoclonal antibody immunoglobulin G purification. The capacity of the inverse colloidal crystal membranes developed here is up to ten times greater than commercially available polyvinylidene fluoride membranes with a similar pore size. This work highlights the importance of developing uniform pore size high porosity membranes in order to maximize the capacity of hydrophobic interaction membrane chromatography. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Membrane fluidization by alcohols inhibits DesK-DesR signalling in Bacillus subtilis.

Science.gov (United States)

Vaňousová, Kateřina; Beranová, Jana; Fišer, Radovan; Jemioła-Rzemińska, Malgorzata; Matyska Lišková, Petra; Cybulski, Larisa; Strzałka, Kazimierz; Konopásek, Ivo

2018-03-01

After cold shock, the Bacillus subtilis desaturase Des introduces double bonds into the fatty acids of existing membrane phospholipids. The synthesis of Des is regulated exclusively by the two-component system DesK/DesR; DesK serves as a sensor of the state of the membrane and triggers Des synthesis after a decrease in membrane fluidity. The aim of our work is to investigate the biophysical changes in the membrane that are able to affect the DesK signalling state. Using linear alcohols (ethanol, propanol, butanol, hexanol, octanol) and benzyl alcohol, we were able to suppress Des synthesis after a temperature downshift. The changes in the biophysical properties of the membrane caused by alcohol addition were followed using membrane fluorescent probes and differential scanning calorimetry. We found that the membrane fluidization induced by alcohols was reflected in an increased hydration at the lipid-water interface. This is associated with a decrease in DesK activity. The addition of alcohol mimics a temperature increase, which can be measured isothermically by fluorescence anisotropy. The effect of alcohols on the membrane periphery is in line with the concept of the mechanism by which two hydrophilic motifs located at opposite ends of the transmembrane region of DesK, which work as a molecular caliper, sense temperature-dependent variations in membrane properties. Copyright © 2017 Elsevier B.V. All rights reserved.

Micro-friction behavior of amorphous carbon films on porous AAO membrane synthesized by the pyrolysis of polyethleneglycol 400

International Nuclear Information System (INIS)

Tu, J.P.; Jiang, C.X.; Guo, S.Y.; Fu, M.F.

2005-01-01

The amorphous carbon films with different degrees of graphitization were synthesized by the pyrolysis of polyethleneglycol 400 infiltrated in the nano-sized pores of anodic aluminum oxide (AAO) membrane. The morphology and microstructure of the carbon films were characterized by scanning electron microscopy, X-ray diffraction and Raman spectroscopy. The micro-friction behavior of the amorphous carbon films sliding against GCr15 steel in ambient air was investigated using a ball-on-disk tester at an applied load of 980 mN and a sliding velocity of 0.2 m s -1 . The graphitization degree in the carbon films had effect on the micro-friction properties. In comparison, the amorphous carbon film with high graphitization degree showed low friction coefficient and high wear resistance. An efficient approach was brought for enhancing the friction performance of aluminum

Micro-friction behavior of amorphous carbon films on porous AAO membrane synthesized by the pyrolysis of polyethleneglycol 400

Energy Technology Data Exchange (ETDEWEB)

Tu, J P [Department of Materials Science and Engineering, Zhejiang University, Hangzhou 310027 (China); Jiang, C X [Department of Materials Science and Engineering, Zhejiang University, Hangzhou 310027 (China); Department of Mechanical and Electronic Engineering, Nanchang University, Nanchang 330029 (China); Guo, S Y [Department of Mechanical Engineering, Zhejiang Sci-Tech University, Hangzhou 310033 (China); Fu, M F [Department of Mechanical and Electronic Engineering, Nanchang University, Nanchang 330029 (China)

2005-05-25

The amorphous carbon films with different degrees of graphitization were synthesized by the pyrolysis of polyethleneglycol 400 infiltrated in the nano-sized pores of anodic aluminum oxide (AAO) membrane. The morphology and microstructure of the carbon films were characterized by scanning electron microscopy, X-ray diffraction and Raman spectroscopy. The micro-friction behavior of the amorphous carbon films sliding against GCr15 steel in ambient air was investigated using a ball-on-disk tester at an applied load of 980 mN and a sliding velocity of 0.2 m s{sup -1}. The graphitization degree in the carbon films had effect on the micro-friction properties. In comparison, the amorphous carbon film with high graphitization degree showed low friction coefficient and high wear resistance. An efficient approach was brought for enhancing the friction performance of aluminum.

RESEARCH ON REDUCING PREMATURITY RUPTURE OF MEMBRANE

Directory of Open Access Journals (Sweden)

Maria URSACHI (BOLOTA

2016-12-01

-term (3 days and distance (2 years interventional methods applied; clinical investigation of complications arising post intervention; studying behavior synthetic amnion. Conclusions: The cause of PRAS is multifactorial. Traditionally, fetal membrane rupture has been attributed to increased physical stress, which weakens the membranes. At the molecular level PRAS is the result of reducing collagen synthesis, alteration of the structure of collagen to accelerate degradation. In addition, these biochemical changes can be amplified and biophysical stress today. The priorities of this research include elucidation of the normal biological process of fetal membranes, including extracellular matrix remodeling, apoptosis.

Polyurethane membranes for surgical gown applications

Science.gov (United States)

Ukpabi, Pauline Ozoemena

The Occupational Safety and Health Administration (OSHA) recently issued a directive requiring all employers to supply personnel protective equipment to employees who are at risk of exposure to blood or other potentially infectious body fluids. For the healthcare worker, a wide variety of surgical gowns is available commercially but there are concerns over their barrier effectiveness and/or wearer comfort. To successfully create a barrier fabric which combines resistance to fluid penetration with comfort, a complete understanding of the relationship between membrane structure and functional properties is required. In this study, we investigated the surface properties of hydrophilicity and hydrophobicity in polyurethane membranes intended for use in surgical gowns. The polyurethane membranes were grafted with side chains of varying lengths, polyethylene glycol (PEG) being used for the hydrophilic modifications and perfluoroalkyl compounds (a monofunctional acid and a difunctional amino alcohol) for the hydrophobic modifications. The hydrophilic treatment was intended to improve the comfort properties of monolithic membranes without adversely affecting their barrier properties. The hydrophobic treatment, on the other hand, was intended to improve the fluid repellency and hence barrier properties of microporous membranes without adversely affecting their comfort properties. Reflection infrared spectroscopy showed that fluorine was successfully grafted onto the polyurethane backbone during the hydrophobic modification, but was not sensitive enough to detect PEG grafting in leached polyethylene glycol-treated polyurethanes. X-ray photoelectron spectroscopy showed that the perfluoroalkylated polyurethanes contained up to 40% fluorine on their surfaces and the PEG-treated polyurethanes showed an increase in their C-O content over the unmodified polyurethane. Scanning electron microscopy not only showed that perfluoroalkylation yielded polyurethane membranes with very

Smart membranes for monitoring membrane based desalination processes

KAUST Repository

Laleg-Kirati, Taous-Meriem; Karam, Ayman M.

2017-01-01

Various examples are related to smart membranes for monitoring membrane based process such as, e.g., membrane distillation processes. In one example, a membrane, includes a porous surface and a plurality of sensors (e.g., temperature, flow and

Analysis of flux reduction behaviors of PRO hollow fiber membranes: Experiments, mechanisms, and implications

KAUST Repository

Xiong, Jun Ying

2016-01-15

Pressure retarded osmosis (PRO) is a promising technology to harvest renewable osmotic energy using a semipermeable membrane. However, a significant flux reduction has been always observed that severely shrinks the harvestable power to a level only marginally higher or even lower than the economically feasible value. This work focuses on the elucidation of various underlying mechanisms responsible for the flux reduction. First, both inner-selective and outer-selective thin film composite (TFC) hollow fiber membranes are employed to examine how the fundamental internal factors (such as the surface salinity of the selective layer at the feed side (CF,m) and its components) interact with one another under the fixed bulk salinity gradient, resulting in various behaviours of external performance indexes such as water flux, reverse salt flux, and power density. Then, the research is extended to investigate the effects of the growing bulk feed salinity due to the accumulated reverse salt flux along PRO modules. Finally, the insights obtained from the prior two stationary conditions are combined with the advanced nucleation theory to elucidate the dynamic scaling process by visualizing how the multiple fundamental factors (such as local supersaturation, nucleation rate and nuclei size) evolve and interplay with one another in various membrane regimes during the whole scaling process. To our best knowledge, it is the first time that the advanced nucleation theory is applied to study the PRO scaling kinetics in order to provide subtle and clear pictures of the events occurring inside the membrane. This study may provide useful insights to design more suitable TFC hollow fiber membranes and to operate them with enhanced water flux so that the PRO process may become more promising in the near future.

Biomimetic membranes and methods of making biomimetic membranes

Science.gov (United States)

Rempe, Susan; Brinker, Jeffrey C.; Rogers, David Michael; Jiang, Ying-Bing; Yang, Shaorong

2016-11-08

The present disclosure is directed to biomimetic membranes and methods of manufacturing such membranes that include structural features that mimic the structures of cellular membrane channels and produce membrane designs capable of high selectivity and high permeability or adsorptivity. The membrane structure, material and chemistry can be selected to perform liquid separations, gas separation and capture, ion transport and adsorption for a variety of applications.

FOULING CHARACTERIZATION OF MEMBRANE CONTACTORS USED FOR THE RECOVERY AND CONCENTRATION OF AMMONIA FROM UNDIGESTED PIG SLURRY

DEFF Research Database (Denmark)

Zarebska, Agata; Norddahl, Birgir; Christensen, Knud Villy

2012-01-01

The main obstacle impeding implementation of membrane contactors for the recovery and concentration of ammonia from swine manure is the phenomena of membrane fouling. Fouling is defined as the accumulation of suspended or dissolved substances on the membrane surface and/or within its pores. Due...... to the different types of fouling which can occur in a membrane system, characterization of fouling is a complex problem. Fouling intensity, morphology and composition of fouling layers has been determined using Scanning Electron Microscopy, X-ray Energy Dispersive Spectrometry and Attenuated Total Reflectance...... Infrared Spectrometry. Based on the analysis of fouled membranes, it is concluded that membrane fouling is dominated by organic fouling in combination with biofouling mainly due to adsorption and deposition of undegraded organic matter. The average fouling layer thickness was estimated to 127.4 μm after...

Gel layer formation on membranes in Membrane Bioreactors

NARCIS (Netherlands)

Van den Brink, P.F.H.

2014-01-01

The widespread application of membrane bioreactors (MBRs) for municipal wastewater treatment is hampered by membrane fouling. Fouling increases energy demand, reduces process performance and creates the need for more frequent (chemical) membrane cleaning or replacement. Membrane fouling in MBRs is

Membranes: A Variety of Energy Landscapes for Many Transfer Opportunities.

Science.gov (United States)

Bacchin, Patrice

2018-02-22

A membrane can be represented by an energy landscape that solutes or colloids must cross. A model accounting for the momentum and the mass balances in the membrane energy landscape establishes a new way of writing for the Darcy law. The counter-pressure in the Darcy law is no longer written as the result of an osmotic pressure difference but rather as a function of colloid-membrane interactions. The ability of the model to describe the physics of the filtration is discussed in detail. This model is solved in a simplified energy landscape to derive analytical relationships that describe the selectivity and the counter-pressure from ab initio operating conditions. The model shows that the stiffness of the energy landscape has an impact on the process efficiency: a gradual increase in interactions (such as with hourglass pore shape) can reduce the separation energetic cost. It allows the introduction of a new paradigm to increase membrane efficiency: the accumulation that is inherent to the separation must be distributed across the membrane. Asymmetric interactions thus lead to direction-dependent transfer properties and the membrane exhibits diode behavior. These new transfer opportunities are discussed.

Species Uptake and Mass Transport in Membranes for Vanadium Redox Flow Batteries

International Nuclear Information System (INIS)

Elgammal, Ramez A.; Tang, Zhijiang; Sun, Che-Nan; Lawton, Jamie; Zawodzinski, Thomas A.

2017-01-01

In this contribution, we provide a synthesis of results to date describing uptake and mass transport of water, vanadium species and protons in Nafion membranes for use as separators in VRFBs. Resistance issues as well as species cross-over are important contributors to performance loss in VRFBs. After a brief discussion of our state-of-the-art cell performance, we consider the uptake and transport of various species through a number of membrane materials. We draw together numerous previous studies and augment them with new data to provide a summary of our present state of understanding of the experimental facts regarding membrane behavior.

Preparation and performance of porous phase change polyethylene glycol/polyurethane membrane

International Nuclear Information System (INIS)

Ke Guizhen; Xie Huifang; Ruan Ruping; Yu Weidong

2010-01-01

Based on the theory of clotty porous phase change materials, the porous membrane was prepared with the blend of polyurethane (PU) and two polyethylene glycol (PEG) systems. Studied by scanning electron microscope (SEM), Fourier transform infrared (FT-IR), wide angle X-ray diffraction (WAXD), differential scanning calorimetry (DSC) and thermo-gravimetric (TG) tests, the morphology structure, chemical composition, crystalline morphology, phase change behaviors and thermal stability of porous phase change membrane were investigated. The results showed that the PU/PEG membrane had obvious porous structural feature, suitable transition temperature and high transition enthalpy. It is a flexible membrane with good energy storage function. When it is between solid and liquid transfer state in microcosms, the membrane can still keep solid shape in macroscopic state at high temperature during phase transition processing. It means that porous membrane PCM can be regarded as functional polymer. This method solved the problem of low working materials content in phase change textile. It succeeded in introducing the porous technology into functional textile's formation, and developed a new way to improve the phase change enthalpy largely for adjustable textile.

Natural organic matter interactions with polyamide and polysulfone membranes: Formation of conditioning film

KAUST Repository

Gutierrez, Leonardo

2015-03-31

A conditioning film changes the physicochemical properties of the membrane surface and strongly affects subsequent fouling behavior. Results from this Atomic Force Microscopy study indicate that Natural Organic Matter (NOM) characteristics, membrane surface properties, and solution chemistry are fundamental during conditioning film formation. Repulsive forces were observed between HUM (humic-NOM) and Polyamide (PA) or Polysulfone (PS) membranes during approach in Na+ and Ca2+ solutions. However, repulsive and attractive forces were randomly recorded during BIOP (biopolymer-NOM) approach to both membranes, possibly caused by low electrostatic repulsion, hydrogen bonding, and presence of chemically/physically heterogeneous regions on membrane surfaces. During retracting, Ca2+ ions increased HUM adhesion to PA and PS membrane, indicating cation bridging/complexation as dominant interacting mechanism for this isolate. BIOP adsorption on PS and PA membrane was stronger than HUM under similar solution conditions, where hydrogen bonding would play an important role. Additionally, irrespective of solution conditions, higher adhesion energy was recorded on PS than on PA membrane for both NOM isolates, indicating membrane hydrophobicity as an important interacting factor. Results from this research will advance our understanding of conditioning film formation for NOM isolates and membranes of different physicochemical characteristics.

Modification of Polyamide-Urethane (PAUt Thin Film Composite Membrane for Improving the Reverse Osmosis Performance

Directory of Open Access Journals (Sweden)

Li-Fen Liu

2018-03-01

Full Text Available In the current study, the poly (amide-urethane (PAUt membranes were successfully fabricated by interfacial polymerization of m-phenylenediamine (MPD and 5-choroformyloxyisophaloyl chloride (CFIC on the polysulfone substrates. Two modification methods based on layer-by-layer assembly were applied to modify the PAUt membrane surface to achieve antifouling property: 1. Chitosan (CS was directly self-assembled on the PAUt membrane (i.e., PAUt-CS; and 2. polydimethyl diallyl ammonium chloride (PDDA, polystyrene sulfonate (PSS, and CS were successively self-assembled on the membrane surface (i.e., PAUt-PDDA/PSS/CS. The resultant membranes were symmetrically characterized by Attenuated Total Reflection Fourier Transform Infrared Spectroscopy (ATR-FTIR, X-ray Photoelectron Spectroscopy (XPS, Scanning Electron Microscopy (SEM, Atomic Force Microscopy (AFM and Contact Angle Meter (CAM, respectively. The results indicated that the modified membranes had much smoother and more hydrophilic surfaces as compared to the nascent PAUt membrane. Meanwhile, the modified membranes exhibited better reverse osmosis performance in terms of water permeability and salt rejection. After the modified membranes were fouled by lake water, the PAUt-PDDA/PSS/CS membrane presented the best antifouling performance among the three types of membranes. Combining the reverse osmosis performance with the anti-fouling property obviously, the PAUt-PDDA/PSS/CS membrane behaved as a promising candidate to be used in real applications.

Interactions of sugar-based bolaamphiphiles with biomimetic systems of plasma membranes.

Science.gov (United States)

Nasir, Mehmet Nail; Crowet, Jean-Marc; Lins, Laurence; Obounou Akong, Firmin; Haudrechy, Arnaud; Bouquillon, Sandrine; Deleu, Magali

2016-11-01

Glycolipids constitute a class of molecules with various biological activities. Among them, sugar-based bolaamphiphiles characterized by their biocompatibility, biodegradability and lower toxicity, became interesting for the development of efficient and low cost lipid-based drug delivery systems. Their activity seems to be closely related to their interactions with the lipid components of the plasma membrane of target cells. Despite many works devoted to the chemical synthesis and characterization of sugar-based bolaamphiphiles, their interactions with plasma membrane have not been completely elucidated. In this work, two sugar-based bolaamphiphiles differing only at the level of their sugar residues were chemically synthetized. Their interactions with membranes have been investigated using model membranes containing or not sterol and with in silico approaches. Our findings indicate that the nature of sugar residues has no significant influence for their membrane interacting properties, while the presence of sterol attenuates the interactions of both bolaamphiphiles with the membrane systems. The understanding of this distinct behavior of bolaamphiphiles towards sterol-containing membrane systems could be useful for their applications as drug delivery systems. Copyright © 2016. Published by Elsevier B.V.

Fostering students' reflection about bias in healthcare: cognitive dissonance and the role of personal and normative standards.

Science.gov (United States)

Hernandez, Rachael A; Haidet, Paul; Gill, Anne C; Teal, Cayla R

2013-04-01

To reduce cognitive dissonance about one's beliefs or behavior, individuals may compare their behavior to personal and/or normative standards. The details of this reflection process are unclear. We examined how medical students compare their behavior or beliefs to standards in discussions about implicit bias, and explored if and how different reflective pathways (preserving vs. reconciling) are associated with each standard. Third-year students engaged in a small-group discussion about bias. Some students and group facilitators also participated in a debriefing about the experience. Using qualitative methods, the transcripts from these 11 sessions were analyzed for evidence of student comparison to a standard and of reflection pathways. Of 557 text units, 75.8% could be coded with a standard and/or a path of reflection. Students referenced personal and normative standards about equally, and preserved or reconciled existing beliefs about equally. Uses of normative standards were associated with preservation-type reflection, and uses of personal standards with reconciliation-type reflection. Normative expectations of physicians are sometimes used to provoke students' consideration of implicit biases about patients. To encourage critical reflection and reconciliation of biased beliefs or behavior, educators should frame reflective activities as a personal exercise rather than as a requirement.

Effect of phospholipid composition and phase on nanodisc films at the solid-liquid interface as studied by neutron reflectivity

DEFF Research Database (Denmark)

Wadsäter, Maria Helena; Barker, Robert; Mortensen, Kell

2013-01-01

of the cell membrane and can act as a nanometer-sized container for functional single membrane proteins. In this study, we present a general nanodisc-based system, intended for structural and functional studies of membrane proteins. In this method, the nanodiscs are aligned at a solid surface, providing...... the ability to determine the average structure of the film along an axis perpendicular to the interface as measured by neutron reflectivity. The nanodisc film was optimized in terms of nanodisc coverage, reduced film roughness, and stability for time-consuming studies. This was achieved by a systematic...

Recent Advances in the Fabrication of Membranes Containing “Ion Pairs” for Nanofiltration Processes

Directory of Open Access Journals (Sweden)

Yan-Li Ji

2017-12-01

Full Text Available In the face of serious environmental pollution and water scarcity problems, the membrane separation technique, especially high efficiency, low energy consumption, and environmental friendly nanofiltration, has been quickly developed. Separation membranes with high permeability, good selectivity, and strong antifouling properties are critical for water treatment and green chemical processing. In recent years, researchers have paid more and more attention to the development of high performance nanofiltration membranes containing “ion pairs”. In this review, the effects of “ion pairs” characteristics, such as the super-hydrophilicity, controllable charge character, and antifouling property, on nanofiltration performances are discussed. A systematic survey was carried out on the various approaches and multiple regulation factors in the fabrication of polyelectrolyte complex membranes, zwitterionic membranes, and charged mosaic membranes, respectively. The mass transport behavior and antifouling mechanism of the membranes with “ion pairs” are also discussed. Finally, we present a brief perspective on the future development of advanced nanofiltration membranes with “ion pairs”.

Electric field-induced reorganization of two-component supported bilayer membranes.

Science.gov (United States)

Groves, J T; Boxer, S G; McConnell, H M

1997-12-09

Application of electric fields tangent to the plane of a confined patch of fluid bilayer membrane can create lateral concentration gradients of the lipids. A thermodynamic model of this steady-state behavior is developed for binary systems and tested with experiments in supported lipid bilayers. The model uses Flory's approximation for the entropy of mixing and allows for effects arising when the components have different molecular areas. In the special case of equal area molecules the concentration gradient reduces to a Fermi-Dirac distribution. The theory is extended to include effects from charged molecules in the membrane. Calculations show that surface charge on the supporting substrate substantially screens electrostatic interactions within the membrane. It also is shown that concentration profiles can be affected by other intermolecular interactions such as clustering. Qualitative agreement with this prediction is provided by comparing phosphatidylserine- and cardiolipin-containing membranes.

Flux Enhancement in Membrane Distillation Using Nanofiber Membranes

Directory of Open Access Journals (Sweden)

T. Jiříček

2016-01-01

Full Text Available Membrane distillation (MD is an emerging separation technology, whose largest application potential lies in the desalination of highly concentrated solutions, which are out of the scope of reverse osmosis. Despite many attractive features, this technology is still awaiting large industrial application. The main reason is the lack of commercially available membranes with fluxes comparable to reverse osmosis. MD is a thermal separation process driven by a partial vapour pressure difference. Flux, distillate purity, and thermal efficiency are always in conflict, all three being strictly connected with pore size, membrane hydrophobicity, and thickness. The world has not seen the ideal membrane yet, but nanofibers may offer a solution to these contradictory requirements. Membranes of electrospun PVDF were tested under various conditions on a direct contact (DCMD unit, in order to determine the optimum conditions for maximum flux. In addition, their performance was compared to commonly available PTFE, PE, and PES membranes. It was confirmed that thinner membranes have higher fluxes and a lower distillate purity and also higher energy losses via conduction across the membrane. As both mass and heat transfer are connected, it is best to develop new membranes with a target application in mind, for the specific membrane module and operational conditions.

Membrane fusion and inverted phases

International Nuclear Information System (INIS)

Ellens, H.; Siegel, D.P.; Alford, D.; Yeagle, P.L.; Boni, L.; Lis, L.J.; Quinn, P.J.; Bentz, J.

1989-01-01

We have found a correlation between liposome fusion kinetics and lipid phase behavior for several inverted phase forming lipids. N-Methylated dioleoylphosphatidylethanolamine (DOPE-Me), or mixtures of dioleoylphosphatidylethanolamine (DOPE) and dioleoylphosphatidylcholine (DOPC), will form an inverted hexagonal phase (HII) at high temperatures (above TH), a lamellar phase (L alpha) at low temperatures, and an isotropic/inverted cubic phase at intermediate temperatures, which is defined by the appearance of narrow isotropic 31 P NMR resonances. The phase behavior has been verified by using high-sensitivity DSC, 31 P NMR, freeze-fracture electron microscopy, and X-ray diffraction. The temperature range over which the narrow isotropic resonances occur is defined as delta TI, and the range ends at TH. Extruded liposomes (approximately 0.2 microns in diameter) composed of these lipids show fusion and leakage kinetics which are strongly correlated with the temperatures of these phase transitions. At temperatures below delta TI, where the lipid phase is L alpha, there is little or no fusion, i.e., mixing of aqueous contents, or leakage. However, as the temperature reaches delta TI, there is a rapid increase in both fusion and leakage rates. At temperatures above TH, the liposomes show aggregation-dependent lysis, as the rapid formation of HII phase precursors disrupts the membranes. We show that the correspondence between the fusion and leakage kinetics and the observed phase behavior is easily rationalized in terms of a recent kinetic theory of L alpha/inverted phase transitions. In particular, it is likely that membrane fusion and the L alpha/inverted cubic phase transition proceed via a common set of intermembrane intermediates

Formation of complexes between functionalized chitosan membranes and copper: A study by angle resolved XPS

Energy Technology Data Exchange (ETDEWEB)

Jurado-López, Belén [Departamento de Química Inorgánica, Facultad de Ciencias, Universidad de Málaga, 29071 Málaga (Spain); Vieira, Rodrigo Silveira [Chemical Engineering Department, Universidade Federal do Ceará, UFC, 60455-760 Fortaleza, CE (Brazil); Rabelo, Rodrigo Balloni; Beppu, Marisa Masumi [School of Chemical Engineering, University of Campinas, UNICAMP, P.O. Box 6066, 13081-970 Campinas, SP (Brazil); Casado, Juan [Departamento de Química-Física, Facultad de Ciencias, Universidad de Málaga, 29071 Málaga (Spain); Rodríguez-Castellón, Enrique, E-mail: castellon@uma.es [Departamento de Química Inorgánica, Facultad de Ciencias, Universidad de Málaga, 29071 Málaga (Spain)

2017-01-01

Chitosan is a biopolymer with potential applications in various fields. Recently, it has been used for heavy metals removal like copper, due to the presence of amino and hydroxyl groups in its structure. Chitosan membranes were crosslinked with epichlorohydrin and bisoxirano and functionalized with chelating agents, such as iminodiacetic acid, aspartic acid and tris-(2-amino-ethyl) polyamine. These membranes were used for copper adsorption and the formed complexes were characterized. Thermal and crystalline properties of chitosan membranes were studied by TG-DCS and X-ray diffraction. Raman, XPS and FT-IR data confirmed that copper is linked to the modified chitosan membranes by the amino groups. The oxidation state of copper-chitosan membranes were also studied by angle resolved XPS, and by UV–Vis diffuse reflectance spectroscopy. - Highlights: • Chitosan membranes were crosslinked with epichlorohydrin and bisoxirano and functionalized with chelating agents. • The chelating agent were iminodiacetic acid, aspartic acid and tris-(2-amino-ethyl) polyamine. • The functionalized membranes were used for copper adsorption and studied by ARXPS, Raman, TG-DCS, FT-IR and XRD. • Spectroscopic data confirmed that copper is linked to the modified chitosan membranes by the amino groups.

Fabrication of electrospun nanofibrous membranes for membrane distillation application

KAUST Repository

Francis, Lijo

2013-02-01

Nanofibrous membranes of Matrimid have been successfully fabricated using an electrospinning technique under optimized conditions. Nanofibrous membranes are found to be highly hydrophobic with a high water contact angle of 130°. Field emission scanning electron microscopy and pore size distribution analysis revealed the big pore size structure of electrospun membranes to be greater than 2 μm and the pore size distribution is found to be narrow. Flat sheet Matrimid membranes were fabricated via casting followed by phase inversion. The morphology, pore size distribution, and water contact angle were measured and compared with the electrospun membranes. Both membranes fabricated by electrospinning and phase inversion techniques were tested in a direct contact membrane distillation process. Electrospun membranes showed high water vapor flux of 56 kg/m2-h, which is very high compared to the casted membrane as well as most of the fabricated and commercially available highly hydrophobic membranes. ©2013 Desalination Publications.

High temperature transport properties of polyphosphazene membranes for direct methanol fuel cells

Energy Technology Data Exchange (ETDEWEB)

Xiangyang Zhou; Chalkova, E. [Pennsylvania State University (United States). The Energy Institute; Weston, J.; Lvov, S.N. [Pennsylvania State University (United States). The Energy Institute; Pennsylvania State University (United States). Department of Energy and Geo-Environment Engineering; Hofmann, M.A.; Ambler, C.M.; Allcock, H.R. [Pennsylvania State University (United States). Department of Chemistry

2003-06-30

Experimental methods for studying the conductivity and methanol permeability of proton conductive polymers over a wide range of temperatures have been developed. The proton conductivity and methanol permeability of several polymer electrolyte membranes including sulfonated and phosphonated poly[(aryloxy)phosphazenes] was determined at temperatures up to 120 {sup o}C. Nafion 117 membranes were tested using the same methods in order to determine the reliability of the methods. Although the conductivities of the polyphosphazene membranes were either similar to or lower than that of the Nafion 117 membranes, they continue to hold promise for fuel cell applications. We observed similar activation energies of proton conduction for Nafion 117, and for sulfonated and phosphonated polyphosphazene membranes. However, the methanol permeability of a sulfonated membrane was about 8 times lower than that of the Nafion 117 membrane at room temperature although the values were comparable at 120 {sup o}C. The permeability of a phosphonated phosphazene derivative was about 40 times lower than that of the Nafion 117 membrane at room temperature and about 9 times lower at 120 {sup o}C. This is a significant improvement over the behavior of Nafion 117. (author)

High temperature transport properties of polyphosphazene membranes for direct methanol fuel cells

Energy Technology Data Exchange (ETDEWEB)

Zhou Xiangyang; Weston, Jamie; Chalkova, Elena; Hofmann, Michael A.; Ambler, Catherine M.; Allcock, Harry R.; Lvov, Serguei N

2003-06-30

Experimental methods for studying the conductivity and methanol permeability of proton conductive polymers over a wide range of temperatures have been developed. The proton conductivity and methanol permeability of several polymer electrolyte membranes including sulfonated and phosphonated poly[(aryloxy)phosphazenes] was determined at temperatures up to 120 deg. C. Nafion 117 membranes were tested using the same methods in order to determine the reliability of the methods. Although the conductivities of the polyphosphazene membranes were either similar to or lower than that of the Nafion 117 membranes, they continue to hold promise for fuel cell applications. We observed similar activation energies of proton conduction for Nafion 117, and for sulfonated and phosphonated polyphosphazene membranes. However, the methanol permeability of a sulfonated membrane was about 8 times lower than that of the Nafion 117 membrane at room temperature although the values were comparable at 120 deg. C. The permeability of a phosphonated phosphazene derivative was about 40 times lower than that of the Nafion 117 membrane at room temperature and about 9 times lower at 120 deg. C. This is a significant improvement over the behavior of Nafion 117.

High temperature transport properties of polyphosphazene membranes for direct methanol fuel cells

International Nuclear Information System (INIS)

Zhou Xiangyang; Weston, Jamie; Chalkova, Elena; Hofmann, Michael A.; Ambler, Catherine M.; Allcock, Harry R.; Lvov, Serguei N.

2003-01-01

Experimental methods for studying the conductivity and methanol permeability of proton conductive polymers over a wide range of temperatures have been developed. The proton conductivity and methanol permeability of several polymer electrolyte membranes including sulfonated and phosphonated poly[(aryloxy)phosphazenes] was determined at temperatures up to 120 deg. C. Nafion 117 membranes were tested using the same methods in order to determine the reliability of the methods. Although the conductivities of the polyphosphazene membranes were either similar to or lower than that of the Nafion 117 membranes, they continue to hold promise for fuel cell applications. We observed similar activation energies of proton conduction for Nafion 117, and for sulfonated and phosphonated polyphosphazene membranes. However, the methanol permeability of a sulfonated membrane was about 8 times lower than that of the Nafion 117 membrane at room temperature although the values were comparable at 120 deg. C. The permeability of a phosphonated phosphazene derivative was about 40 times lower than that of the Nafion 117 membrane at room temperature and about 9 times lower at 120 deg. C. This is a significant improvement over the behavior of Nafion 117

Asymmetric PDLLA membranes containing Bioglass(R) for guided tissue regeneration: characterization and in vitro biological behavior

NARCIS (Netherlands)

Leal, A.I.; Caridade, S.G.; Ma, J.; Yu, N.; Gomes, M.; Reis, R.L.; Jansen, J.A.; Walboomers, X.F.; Mano, J.F.

2013-01-01

OBJECTIVE: In the treatment of periodontal defects, composite membranes might be applied to protect the injured area and simultaneously stimulate tissue regeneration. This work describes the development and characterization of poly(d,l-lactic acid)/Bioglass(R) (PDLLA/BG) composite membranes with

Identification of membrane-associated proteins with pathogenic potential expressed by Corynebacterium pseudotuberculosis grown in animal serum.

Science.gov (United States)

Raynal, José Tadeu; Bastos, Bruno Lopes; Vilas-Boas, Priscilla Carolinne Bagano; Sousa, Thiago de Jesus; Costa-Silva, Marcos; de Sá, Maria da Conceição Aquino; Portela, Ricardo Wagner; Moura-Costa, Lília Ferreira; Azevedo, Vasco; Meyer, Roberto

2018-01-25

Previous works defining antigens that might be used as vaccine targets against Corynebacterium pseudotuberculosis, which is the causative agent of sheep and goat caseous lymphadenitis, have focused on secreted proteins produced in a chemically defined culture media. Considering that such antigens might not reflect the repertoire of proteins expressed during infection conditions, this experiment aimed to investigate the membrane-associated proteins with pathogenic potential expressed by C. pseudotuberculosis grown directly in animal serum. Its membrane-associated proteins have been extracted using an organic solvent enrichment methodology, followed by LC-MS/MS and bioinformatics analysis for protein identification and classification. The results revealed 22 membrane-associated proteins characterized as potentially pathogenic. An interaction network analysis indicated that the four potentially pathogenic proteins ciuA, fagA, OppA4 and OppCD were biologically connected within two distinct network pathways, which were both associated with the ABC Transporters KEGG pathway. These results suggest that C. pseudotuberculosis pathogenesis might be associated with the transport and uptake of nutrients; other seven identified potentially pathogenic membrane proteins also suggest that pathogenesis might involve events of bacterial resistance and adhesion. The proteins herein reported potentially reflect part of the protein repertoire expressed during real infection conditions and might be tested as vaccine antigens.

Development of PVDF Membrane Nanocomposites via Various Functionalization Approaches for Environmental Applications

Directory of Open Access Journals (Sweden)

Douglas M. Davenport

2016-01-01

Full Text Available Membranes are finding wide applications in various fields spanning biological, water, and energy areas. Synthesis of membranes to provide tunable flux, metal sorption, and catalysis has been done through pore functionalization of microfiltration (MF type membranes with responsive behavior. This methodology provides an opportunity to improve synthetic membrane performance via polymer fabrication and surface modification. By optimizing the polymer coagulation conditions in phase inversion fabrication, spongy polyvinylidene fluoride (PVDF membranes with high porosity and large internal pore volume were created in lab and full scale. This robust membrane shows a promising mechanical strength as well as high capacity for loading of adsorptive and catalytic materials. By applying surface modification techniques, synthetic membranes with different functionality (carboxyl, amine, and nanoparticle-based were obtained. These functionalities provide an opportunity to fine-tune the membrane surface properties such as charge and reactivity. The incorporation of stimuli-responsive acrylic polymers (polyacrylic acid or sodium polyacrylate in membrane pores also results in tunable pore size and ion-exchange capacity. This provides the added benefits of adjustable membrane permeability and metal capture efficiency. The equilibrium and dynamic binding capacity of these functionalized spongy membranes were studied via calcium ion-exchange. Iron/palladium catalytic nanoparticles were immobilized in the polymer matrix in order to perform the challenging degradation of the environmental pollutant trichloroethylene (TCE.

Regulation of Expressive Behavior as Reflecting Affect Socialization.

Science.gov (United States)

Saarni, Carolyn

Regulated expressiveness (the modification of expressive behavior) is a complex phenomenon. Accomplished basically in four ways, regulated expressiveness has developmental dimensions, motivational precursors, and cognitive antecedents, including perspective-taking ability and the growth of self-awareness. Ability to regulate expressiveness appears…

Interplay of electrostatics and lipid packing determines the binding of charged polymer coated nanoparticles to model membranes.

Science.gov (United States)

Biswas, Nupur; Bhattacharya, Rupak; Saha, Arindam; Jana, Nikhil R; Basu, Jaydeep K

2015-10-07

Understanding of nanoparticle-membrane interactions is useful for various applications of nanoparticles like drug delivery and imaging. Here we report on the studies of interaction between hydrophilic charged polymer coated semiconductor quantum dot nanoparticles with model lipid membranes. Atomic force microscopy and X-ray reflectivity measurements suggest that cationic nanoparticles bind and penetrate bilayers of zwitterionic lipids. Penetration and binding depend on the extent of lipid packing and result in the disruption of the lipid bilayer accompanied by enhanced lipid diffusion. On the other hand, anionic nanoparticles show minimal membrane binding although, curiously, their interaction leads to reduction in lipid diffusivity. It is suggested that the enhanced binding of cationic QDs at higher lipid packing can be understood in terms of the effective surface potential of the bilayers which is tunable through membrane lipid packing. Our results bring forth the subtle interplay of membrane lipid packing and electrostatics which determine nanoparticle binding and penetration of model membranes with further implications for real cell membranes.

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.

Covalent attachment of phospholipid analogous polymers to modify a polymeric membrane surface: a novel approach.

Science.gov (United States)

Xu, Zhi-Kang; Dai, Qing-Wen; Wu, Jian; Huang, Xiao-Jun; Yang, Qian

2004-02-17

A novel method for the surface modification of a microporous polypropylene membrane by tethering phospholipid analogous polymers (PAPs) is given, which includes the photoinduced graft polymerization of N,N-dimethylaminoethyl methacrylate (DMAEMA) and the ring-opening reaction of grafted poly-(DMAEMA) with 2-alkyloxy-2-oxo-1,3,2-dioxaphospholanes. Five 2-alkyloxy-2-oxo-1,3,2-dioxaphospholanes, containing octyloxy, dodecyloxy, tetradecyloxy, hexadecyloxy, and octadecyloxy groups in the molecular structure, were used to fabricate the PAP-modified polypropylene membranes. The attenuated total reflectance FT-IR spectra of the original, poly(DMAEMA)-grafted, and PAP-modified membranes confirmed the chemical changes on the membrane surface. Scanning electron microscope pictures showed that, compared with the original membrane, the surface porosities ofpoly(DMAEMA)-grafted and PAP-modified membranes were somewhat reduced. Water contact angles measured by the sessile drop method on PAP-modified membranes were slightly lower than that on the original polypropylene membrane, but higher than those on poly(DMAEMA)-grafted membranes with the exception of octyloxy-containing PAP-modified membranes. However, BSA adsorption experiments indicated that the five PAP-modified membranes had a much better protein-resistant property than the original polypropylene membrane and the poly(DMAEMA)-grafted membranes. For hexadecyloxy- and octadecyloxy-containing PAP-modified membranes, almost no protein adsorption was observed when the grafting degree was above 6 wt %. It was also found that the platelet adhesion was remarkably suppressed on the PAP-modified membranes. All these results demonstrate that the described approach is an effective way to improve the surface biocompatibility for polymeric membranes.

Effects of physical and chemical aspects on membrane fouling and cleaning using interfacial free energy analysis in forward osmosis.

Science.gov (United States)

Zhang, Wanzhu; Dong, Bingzhi

2018-05-20

Natural organic matter (NOM) in micro-polluted water purification using membranes is a critical issue to handle. Understanding the fouling mechanism in the forward osmosis (FO) process, particularly identifying the predominant factor that controls membrane fouling, could have significant effects on exerting the advantages of FO technique. Cellulose triacetate no-woven (CTA-NW) membrane is applied to experiments with a high removal efficiency (> 99%) for the model foulant. Tannic acid (TA) is used as a surrogate foulant for NOM in the membrane fouling process, thus enabling the analysis of the effects of physical and chemical aspects of water flux, retention, and adsorption. The membrane fouling behavior is affected mainly by the combined effects of the osmotic dragging force and the interaction of the pH in the working solution, foulants, and calcium ions, as demonstrated by the water flux loss and the changes of membrane retention and adsorption. The fouled CTA-NW membrane (in PRO mode) could be flux-recovered by > 85% through physical cleaning methods. The interfacial free energy analysis theory was used to analyze the membrane fouling behavior with calculating the interfacial cohesion and adhesion free energies. The cohesion free energy refers to the deposition of foulants (TA or TA combined with calcium ions) on a fouled membrane. In addition, the adhesion free energy could be used to evaluate the interaction between foulants and a clean membrane.

Fiber optic sensor based on reflectivity configurations to detect heart rate

Science.gov (United States)

Yunianto, M.; Marzuki, A.; Riyatun, R.; Lestari, D.

2016-11-01

Research of optical fiber-based heart rate detection sensor has been conducted using the reflection configurationon the thorax motion modified. Optical fiber used in this research was Plastic Optical Fiber (POF) with a diameter of 0.5. Optical fiber system is made with two pieces of fiber, the first fiber is to serve as a transmitter transmitting light from the source to the reflector membrane, the second fiber serves as a receiver. One of the endsfrom the two fibersis pressed and positioned perpendicular of reflector membrane which is placed on the surface of the chest. The sensor works on the principle of intensity changes captured by the receiver fiber when the reflector membrane gets the vibe from the heart. The light source used is in the form of Light Emitting Diode (LED) and Light Dependent Resistor (LDR) as a light sensor. Variations are performed on the reflector membrane diameter. The light intensity received by the detector increases along with the increasing width of the reflector membrane diameter. The results show that this sensor can detect the harmonic peak at a frequency of 1.5 Hz; 7.5 Hz; 10.5 Hz; and 22.5 Hz in a healthy human heart with an average value of Beat Per Minute (BPM) by 78 times, a prototype sensor that is made can work and function properly.

Membrane order in the plasma membrane and endocytic recycling compartment.

Science.gov (United States)

Iaea, David B; Maxfield, Frederick R

2017-01-01

The cholesterol content of membranes plays an important role in organizing membranes for signal transduction and protein trafficking as well as in modulating the biophysical properties of membranes. While the properties of model or isolated membranes have been extensively studied, there has been little evaluation of internal membranes in living cells. Here, we use a Nile Red based probe, NR12S, and ratiometric live cell imaging, to analyze the membrane order of the plasma membrane and endocytic recycling compartment. We find that after a brief incubation to allow endocytosis, NR12S is distributed between the plasma membrane and the endocytic recycling compartment. The NR12S reports that the endocytic recycling compartment is more highly ordered than the plasma membrane. We also find that the plasma membrane and the endocytic recycling compartment are differentially affected by altering cellular cholesterol levels. The membrane order of the plasma membrane, but not the endocytic recycling compartment, is altered significantly when cellular cholesterol content is increased or decreased by 20%. These results demonstrate that changes in cellular cholesterol differentially alter membrane order within different organelles.

Electromechanical performance analysis of inflated dielectric elastomer membrane for micro pump applications

Science.gov (United States)

Saini, Abhishek; Ahmad, Dilshad; Patra, Karali

2016-04-01

Dielectric elastomers have received a great deal of attention recently as potential materials for many new types of sensors, actuators and future energy generators. When subjected to high electric field, dielectric elastomer membrane sandwiched between compliant electrodes undergoes large deformation with a fast response speed. Moreover, dielectric elastomers have high specific energy density, toughness, flexibility and shape processability. Therefore, dielectric elastomer membranes have gained importance to be applied as micro pumps for microfluidics and biomedical applications. This work intends to extend the electromechanical performance analysis of inflated dielectric elastomer membranes to be applied as micro pumps. Mechanical burst test and cyclic tests were performed to investigate the mechanical breakdown and hysteresis loss of the dielectric membrane, respectively. Varying high electric field was applied on the inflated membrane under different static pressure to determine the electromechanical behavior and nonplanar actuation of the membrane. These tests were repeated for membranes with different pre-stretch values. Results show that pre-stretching improves the electromechanical performance of the inflated membrane. The present work will help to select suitable parameters for designing micro pumps using dielectric elastomer membrane. However this material lacks durability in operation.This issue also needs to be investigated further for realizing practical micro pumps.

Reconstitution of high-affinity opioid agonist binding in brain membranes

Energy Technology Data Exchange (ETDEWEB)

Remmers, A.E.; Medzihradsky, F. (Univ. of Michigan Medical School, Ann Arbor (United States))

1991-03-15

In synaptosomal membranes from rat brain cortex, the {mu} selective agonist ({sup 3}H)dihydromorphine in the absence of sodium, and the nonselective antagonist ({sup 3}H)naltrexone in the presence of sodium, bound to two populations of opioid receptor sites with K{sub d} values of 0.69 and 8.7 nM for dihydromorphine, and 0.34 and 5.5 nM for naltrexone. The addition of 5 {mu}M guanosine 5{prime}-({gamma}-thio)triphosphate (GTP({gamma}S)) strongly reduced high-affinity agonist but not antagonist binding. Exposure of the membranes to high pH reduced the number of GTP({gamma}-{sup 35}S) binding sites by 90% and low K{sub m}, opioid-sensitive GTPase activity by 95%. In these membranes, high-affinity agonist binding was abolished and modulation of residual binding by GTP({gamma}S) was diminished. Alkali treatment of the glioma cell membranes prior to fusion inhibited most of the low K{sub m} GTPase activity and prevented the reconstitution of agonist binding. The results show that high-affinity opioid agonist binding reflects the ligand-occupied receptor - guanine nucleotide binding protein complex.

Effect of titanium dioxide (TiO2) on largely improving solar reflectance and cooling property of high density polyethylene (HDPE) by influencing its crystallization behavior

International Nuclear Information System (INIS)

Wang, Shichao; Zhang, Jun

2014-01-01

Highlights: • HDPE/TiO 2 composites have more perfect crystal structure. • Refractive index is the key factor affecting the final solar reflectance. • HDPE/TiO 2 composites can achieve high solar reflectance. • The real cooling property is in accordance with solar reflectance. - Abstract: In this study, the different crystal forms of titanium dioxide (TiO 2 ) were added into high density polyethylene (HDPE) to fabricate cool material. Crystal structure, crystallization behavior, crystal morphology were investigated by wide angle X-ray diffraction (WAXD), differential scanning calorimetry (DSC) and polarized optical microscope (POM). Scanning electron microscope (SEM) was applied to observe dispersion of TiO 2 particles in the HDPE matrix and the cross section morphology. The solar reflectance and actual cooling property were evaluated by UV–Vis–NIR spectrometer and a self-designed device. By adding TiO 2 particles into HDPE matrix, the polymer chain could crystallize into more perfect and thermal stable lamella. The presence of TiO 2 particles dramatically increased the number of nucleation site therefore decreased the crystal size. The subsequent solar reflectance was related to the degree of crystallinity, the spherulite size of HDPE, refractive index, and distribution of TiO 2 particles in HDPE matrix. It was found the rutile TiO 2 could largely improve the total solar reflectance from 28.2% to 51.1%. Finally, the temperature test showed that the composites had excellent cooling property, which was in accordance with solar reflectance result

Structure and organization of nanosized-inclusion-containing bilayer membranes

Science.gov (United States)

Ren, Chun-Lai; Ma, Yu-Qiang

2009-07-01

Based on a considerable amount of experimental evidence for lateral organization of lipid membranes which share astonishingly similar features in the presence of different inclusions, we use a hybrid self-consistent field theory (SCFT)/density-functional theory (DFT) approach to deal with bilayer membranes embedded by nanosized inclusions and explain experimental findings. Here, the hydrophobic inclusions are simple models of hydrophobic drugs or other nanoparticles for biomedical applications. It is found that lipid/inclusion-rich domains are formed at moderate inclusion concentrations and disappear with the increase in the concentration of inclusions. At high inclusion content, chaining of inclusions occurs due to the effective depletion attraction between inclusions mediated by lipids. Meanwhile, the increase in the concentration of inclusions can also cause thickening of the membrane and the distribution of inclusions undergoes a layering transition from one-layer structure located in the bilayer midplane to two-layer structure arranged into the two leaflets of a bilayer. Our theoretical predictions address the complex interactions between membranes and inclusions suggesting a unifying mechanism which reflects the competition between the conformational entropy of lipids favoring the formation of lipid- and inclusion-rich domains in lipids and the steric repulsion of inclusions leading to the uniform dispersion.

Effect of crosslinking on the physico-chemical properties of radiation grafted PEM fuel cell membranes

International Nuclear Information System (INIS)

Mohamed Mahmoud Nasef; Hamdani Saidi

2006-01-01

The effect of crosslinking on the physico-chemical properties of radiation grafted proton conducting membranes (PFA-g-PSSA) was investigated. The membranes were prepared by radiation induced grafting of styrene/divinylbenzene (DVB) mixtures onto poly (tetrafluoroethylene-co-perfluorovinyl either) (PFA) films followed by sulfonation reactions. The variation of DVB content in the grafting mixture was in the range of 1-4 vol %. The equivalent weight, swelling, behavior and the proton conductivity of crosslinked membranes having equal degrees of grafting prepared found to be dependent predominantly on the level of crosslinking. The obtained membranes were found to posses a good combination of physico-chemical properties that is matching the commercial Nation 117 membranes

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.

Distributed sensing signal analysis of deformable plate/membrane mirrors

Science.gov (United States)

Lu, Yifan; Yue, Honghao; Deng, Zongquan; Tzou, Hornsen

2017-11-01

Deformable optical mirrors usually play key roles in aerospace and optical structural systems applied to space telescopes, radars, solar collectors, communication antennas, etc. Limited by the payload capacity of current launch vehicles, the deformable mirrors should be lightweight and are generally made of ultra-thin plates or even membranes. These plate/membrane mirrors are susceptible to external excitations and this may lead to surface inaccuracy and jeopardize relevant working performance. In order to investigate the modal vibration characteristics of the mirror, a piezoelectric layer is fully laminated on its non-reflective side to serve as sensors. The piezoelectric layer is segmented into infinitesimal elements so that microscopic distributed sensing signals can be explored. In this paper, the deformable mirror is modeled as a pre-tensioned plate and membrane respectively and sensing signal distributions of the two models are compared. Different pre-tensioning forces are also applied to reveal the tension effects on the mode shape and sensing signals of the mirror. Analytical results in this study could be used as guideline of optimal sensor/actuator placement for deformable space mirrors.

Axon-glia interaction and membrane traffic in myelin formation

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Robin eWhite

2014-01-01

Full Text Available In vertebrate nervous systems myelination of neuronal axons has evolved to increase conduction velocity of electrical impulses with minimal space and energy requirements. Myelin is formed by specialised glial cells which ensheath axons with a lipid-rich insulating membrane. Myelination is a multi-step process initiated by axon-glia recognition triggering glial polarisation followed by targeted myelin membrane expansion and compaction. Thereby, a myelin sheath of complex subdomain structure is established. Continuous communication between neurons and glial cells is essential for myelin maintenance and axonal integrity. A diverse group of diseases, from multiple sclerosis to schizophrenia, have been linked to malfunction of myelinating cells reflecting the physiological importance of the axon-glial unit. This review describes the mechanisms of axonal signal integration by oligodendrocytes emphasising the central role of the Src-family kinase Fyn during CNS myelination. Furthermore, we discuss myelin membrane trafficking with particular focus on endocytic recycling and the control of PLP (proteolipid protein transport by SNARE proteins. Finally, PLP mistrafficking is considered in the context of myelin diseases.

Determinants of nursing competence of nursing students in Taiwan: the role of self-reflection and insight.

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Eng, Cheng-Joo; Pai, Hsiang-Chu

2015-03-01

A nursing practicum course is critical to strengthening the nursing competence of nursing students. Research has found that practice stress and coping behaviors can have either a negative or positive influence on the learning and practice performance of nursing students. Nevertheless, there are few evidence-based studies related to the relationship between self-reflection and insight and nursing competence in Taiwanese nursing students. To test the determinants and the effect of self-reflection and insight on nursing competence in nursing students during the first 2 months of their practice experience. Cross-sectional and correlational research designs were employed. From September to November 2013, a total of 312 nursing students at a junior college in southern Taiwan served as participants in this study. Four questionnaires were used to collect data: Self-reflection and Insight Scale (SRIS), Perceived Stress Scale (PSS), Coping Behavior Inventory (CBI), and Holistic Nursing Competence Scale (HNCS). The research model was evaluated through structural equation modeling (SEM), with the use of the partial least squares (PLS) method. Results indicated that self-reflection and insight, practice stress, and practice coping behavior were statistically significantly associated with nursing competence. In addition, self-reflection and insight were significantly and positively associated with practice coping behavior and negatively associated with practice stress. Students' coping behavior partially mediates the effect of self-reflection and stress on nursing competence. Overall, these variables explained 39.4% of the variance in these students' nursing competence. Self-reflection and insight affected nursing competence during the practice period. These variables have not only had a direct influence on nursing competence but also an indirect effect through the mediating effect of coping behavior and stress. Copyright © 2014 Elsevier Ltd. All rights reserved.

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

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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

Testing of a 7-tube palladium membrane reactor for potential use in TEP

International Nuclear Information System (INIS)

Carlson, Bryan J.; Trujillo, Stephen; Willms, R. Scott

2010-01-01

A Palladium Membrane Reactor (PMR) consists of a palladium/silver membrane permeator filled with catalyst (catalyst may be inside or outside the membrane tubes). The PMR is designed to recover tritium from the methane, water, and other impurities present in fusion reactor effluent. A key feature of a PMR is that the total hydrogen isotope content of a stream is significantly reduced as (1) methane-steam reforming and/or water-gas shift reactions proceed on the catalyst bed and (2) hydrogen isotopes are removed via permeation through the membrane. With a PMR design matched to processing requirements, nearly complete hydrogen isotope removals can be achieved. A 3-tube PMR study was recently completed. From the results presented in this study, it was possible to conclude that a PMR is appropriate for TEP, perforated metal tube protectors function well, platinum on aluminum (PtA) catalyst performs the best, conditioning with air is probably required to properly condition the Pd/Ag tubes, and that CO/CO 2 ratios maybe an indicator of coking. The 3-tube PMR had a permeator membrane area of 0.0247 m 2 and a catalyst volume to membrane area ratio of 4.63 cc/cm 2 (with the catalyst on the outside of the membrane tubes and the catalyst only covering the membrane tube length). A PMR for TEP will require a larger membrane area (perhaps 0.35 m 2 ). With this in mind, an intermediate sized PMR was constructed. This PMR has 7 permeator tubes and a total membrane area of 0.0851 m 2 . The catalyst volume to membrane area ratio for the 7-tube PMR was 5.18 cc/cm 2 . The total membrane area of the 7-tube PMR (0.0851 m 2 ) is 3.45 times larger than total membrane area of the 3-tube PMR (0.0247 m 2 ). The following objectives were identified for the 7-tube PMR tests: (1) Refine test measurements, especially humidity and flow; (2) Refine maintenance procedures for Pd/Ag tube conditioning; (3) Evaluate baseline PMR operating conditions; (4) Determine PMR scaling method; (5) Evaluate PMR

Molecular analysis of interactions between dendrimers and asymmetric membranes at different transport stages.

Science.gov (United States)

He, XiaoCong; Qu, ZhiGuo; Xu, Feng; Lin, Min; Wang, JiuLing; Shi, XingHua; Lu, TianJian

2014-01-07

Studying dendrimer-biomembrane interactions is important for understanding drug and gene delivery. In this study, coarse-grained molecular dynamics simulations were performed to investigate the behaviors of polyamidoamine (PAMAM) dendrimers (G4 and G5) as they interacted with asymmetric membranes from different sides of the bilayer, thus mimicking different dendrimer transport stages. The G4 dendrimer could insert into the membrane during an equilibrated state, and the G5 dendrimer could induce pore formation in the membrane when the dendrimers interacted with the outer side (outer interactions) of an asymmetric membrane [with 10% dipalmitoyl phosphatidylserine (DPPS) in the inner leaflet of the membrane]. During the interaction with the inner side of the asymmetric membrane (inner interactions), the G4 and G5 dendrimers only adsorbed onto the membrane. As the membrane asymmetry increased (e.g., increased DPPS percentage in the inner leaflet of the membrane), the G4 and G5 dendrimers penetrated deeper into the membrane during the outer interactions and the G4 and G5 dendrimers were adsorbed more tightly onto the membrane for the inner interactions. When the DPPS content reached 50%, the G4 dendrimer could completely penetrate through the membrane from the outer side to the inner side. Our study provides molecular understanding and reference information about different dendrimer transport stages during drug and gene delivery.

Receptor-mediated endocytosis generates nanomechanical force reflective of ligand identity and cellular property.

Science.gov (United States)

Zhang, Xiao; Ren, Juan; Wang, Jingren; Li, Shixie; Zou, Qingze; Gao, Nan

2018-08-01

Whether environmental (thermal, chemical, and nutrient) signals generate quantifiable, nanoscale, mechanophysical changes in the cellular plasma membrane has not been well elucidated. Assessment of such mechanophysical properties of plasma membrane may shed lights on fundamental cellular process. Atomic force microscopic (AFM) measurement of the mechanical properties of live cells was hampered by the difficulty in accounting for the effects of the cantilever motion and the associated hydrodynamic force on the mechanical measurement. These challenges have been addressed in our recently developed control-based AFM nanomechanical measurement protocol, which enables a fast, noninvasive, broadband measurement of the real-time changes in plasma membrane elasticity in live cells. Here we show using this newly developed AFM platform that the plasma membrane of live mammalian cells exhibits a constant and quantifiable nanomechanical property, the membrane elasticity. This mechanical property sensitively changes in response to environmental factors, such as the thermal, chemical, and growth factor stimuli. We demonstrate that different chemical inhibitors of endocytosis elicit distinct changes in plasma membrane elastic modulus reflecting their specific molecular actions on the lipid configuration or the endocytic machinery. Interestingly, two different growth factors, EGF and Wnt3a, elicited distinct elastic force profiles revealed by AFM at the plasma membrane during receptor-mediated endocytosis. By applying this platform to genetically modified cells, we uncovered a previously unknown contribution of Cdc42, a key component of the cellular trafficking network, to EGF-stimulated endocytosis at plasma membrane. Together, this nanomechanical AFM study establishes an important foundation that is expandable and adaptable for investigation of cellular membrane evolution in response to various key extracellular signals. © 2017 Wiley Periodicals, Inc.

Giant plasma membrane vesicles: models for understanding membrane organization.

Science.gov (United States)

Levental, Kandice R; Levental, Ilya

2015-01-01

The organization of eukaryotic membranes into functional domains continues to fascinate and puzzle cell biologists and biophysicists. The lipid raft hypothesis proposes that collective lipid interactions compartmentalize the membrane into coexisting liquid domains that are central to membrane physiology. This hypothesis has proven controversial because such structures cannot be directly visualized in live cells by light microscopy. The recent observations of liquid-liquid phase separation in biological membranes are an important validation of the raft hypothesis and enable application of the experimental toolbox of membrane physics to a biologically complex phase-separated membrane. This review addresses the role of giant plasma membrane vesicles (GPMVs) in refining the raft hypothesis and expands on the application of GPMVs as an experimental model to answer some of key outstanding problems in membrane biology. Copyright © 2015 Elsevier Inc. All rights reserved.

How patient-selected colors for removable appliances are reflected in electronically tracked compliance (wear times and wear behavior).

Science.gov (United States)

Schott, Timm C; Menne, Dieter

2018-03-27

A broad spectrum of colors for removable appliances, intended to optimize acceptance of treatment and patient cooperation, have been available on the dental market for years. This is the first study to analyze how patient-selected colors are reflected in wear times and wear behavior of removable appliances. The study included 117 children (55 girls and 62 boys) who were treated with active removable plate or functional appliances. All patients were offered to choose from 11 different colors, which were pooled into six groups (black, blue, green, yellow, pink, red) for analysis, or to combine any two to four colors ("multicolored" group) for their appliances. All appliances featured a built-in microsensor (TheraMon; MC Technology, Hargelsberg, Austria) for objective wear-time tracking. Differences between wear times were analyzed using pairwise t tests and Tukey correction. The longest median wear times were recorded in the blue and green groups (≈11 h/d) and the shortest ones in the red and pink groups (≈9 h/d), but they were not significantly influenced by the patient-selected colors. The median wear times involved an age-related decrease by 0.56 h/y that was statistically significant ( P = .00005). No gender-specific patterns of wear behavior were observed. Patient-selected colors for removable appliances can presumably improve acceptance of treatment, but they are not associated with statistically significant improvements in wear time or wear behavior.

Domain 4 (D4) of Perfringolysin O to Visualize Cholesterol in Cellular Membranes-The Update.

Science.gov (United States)

Maekawa, Masashi

2017-03-03

The cellular membrane of eukaryotes consists of phospholipids, sphingolipids, cholesterol and membrane proteins. Among them, cholesterol is crucial for various cellular events (e.g., signaling, viral/bacterial infection, and membrane trafficking) in addition to its essential role as an ingredient of steroid hormones, vitamin D, and bile acids. From a micro-perspective, at the plasma membrane, recent emerging evidence strongly suggests the existence of lipid nanodomains formed with cholesterol and phospholipids (e.g., sphingomyelin, phosphatidylserine). Thus, it is important to elucidate how cholesterol behaves in membranes and how the behavior of cholesterol is regulated at the molecular level. To elucidate the complexed characteristics of cholesterol in cellular membranes, a couple of useful biosensors that enable us to visualize cholesterol in cellular membranes have been recently developed by utilizing domain 4 (D4) of Perfringolysin O (PFO, theta toxin), a cholesterol-binding toxin. This review highlights the current progress on development of novel cholesterol biosensors that uncover new insights of cholesterol in cellular membranes.

Membrane distillation of industrial cooling tower blowdown water

Directory of Open Access Journals (Sweden)

N.E. Koeman-Stein

2016-06-01

Full Text Available The potential of membrane distillation for desalination of cooling tower blowdown water (CTBD is investigated. Technical feasibility is tested on laboratory and pilot scale using real cooling tower blowdown water from Dow Benelux in Terneuzen (Netherlands. Two types of membranes, polytetrafluorethylene and polyethylene showed good performance regarding distillate quality and fouling behavior. Concentrating CTBD by a factor 4.5 while maintaining a flux of around 2 l/m2*h was possible with a water recovery of 78% available for reuse. Higher concentration factors lead to severe decrease in flux which was caused by scaling. Membrane distillation could use the thermal energy that would otherwise be discharged of in a cooling tower and function as a heat exchanger. This reduces the need for cooling capacity and could lead to a total reduction of 37% water intake for make-up water, as well as reduced energy and chemicals demands and greenhouse gas emissions.

Membrane interactions of ionic liquids and imidazolium salts.

Science.gov (United States)

Wang, Da; Galla, Hans-Joachim; Drücker, Patrick

2018-06-01

Room-temperature ionic liquids (RTILs) have attracted considerable attention in recent years due to their versatile properties such as negligible volatility, inflammability, high extractive selectivity and thermal stability. In general, RTILs are organic salts with a melting point below ~100 °C determined by the asymmetry of at least one of their ions. Due to their amphiphilic character, strong interactions with biological materials can be expected. However, rising attention has appeared towards their similarity and interaction with biomolecules. By employing structural modifications, the biochemical properties of RTILs can be designed to mimic lipid structures and to tune their hydrophobicity towards a lipophilic behavior. This is evident for the interaction with lipid-membranes where some of these compounds present membrane-disturbing effects or cellular toxicity. Moreover, they can form micelles or lipid-like bilayer structures by themselves. Both aspects, cellular effects and membrane-forming capacities, of a novel class of lipophilic imidazolium salts will be discussed.

Membrane selectivity and disordering mechanism of antimicrobial peptide protegrin-1

Science.gov (United States)

Ishitsuka, Yuji

Protegrin-1 (PG-1) is a beta-sheet antimicrobial peptide (AMP), a class of peptides innate to various organisms and functions as a defense agent against harmful microorganisms by means of membrane disordering. Characteristic chemical and structural properties of AMPs allow selective interaction against invaders' cell membranes. Despite their enormous biomedical potential, progress towards developing them into therapeutic agents has been hampered by a lack of insight into their mechanism of action. AMP insertion assays using Langmuir monolayers reveal that both electrostatic properties of the lipid head group as well as the packing density of the lipid tail group play important roles in determining the membrane selectivity of AMPs. These results help elucidate how the AMP selectively targets the cell membrane of microorganisms over the cell membrane of the host. In addition, these results also explain the higher hemolytic ability of PG-1 against human red blood cells (RBCs) compared to the hemolytic ability of PG-1 against sheep and pig RBCs. Synchrotron X-ray reflectivity shows that PG-1 penetrates into the lipid layer. Grazing incidence X-ray diffraction and fluorescence microscopy indicate that the insertion of PG-1 disorders tail group packing. Membrane selectivity and insertion location information of AMPs with different primary sequence and secondary structure have been obtained by using a truncated version of PG-1: PC-17, and an alpha-helical AMP, LL-37, respectively. The similarity of the membrane disordering process across these various peptides motivated us to test the membrane disordering effect of molecules designed to mimic these peptides. Peptide-mimics based on meta-phenylene ethynylenes demonstrate similar membrane disordering effects, showing that the potency of AMPs is derived from their overall chemical and structural properties, rather than exact peptide sequence. Atomic force microscopy (AFM) was used to directly image first, the PG-1

Interaction between lipid monolayers and poloxamer 188: An X-ray reflectivity and diffraction study

DEFF Research Database (Denmark)

Wu, G.H.; Majewski, J.; Ege, C.

2005-01-01

The mechanism by which poloxamer 188 (P188) seals a damaged cell membrane is examined using the lipid monolayer as a model system. X-ray reflectivity and grazing-incidence x-ray diffraction results show that at low nominal lipid density, P188, by physically occupying the available area and phase ...

Parametric study of hydrogen production from ethanol steam reforming in a membrane microreactor

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M. de-Souza

2013-06-01

Full Text Available Microreactors are miniaturized chemical reaction systems, which contain reaction channels with characteristic dimensions in the range of 10-500 µm. One possible application for microreactors is the conversion of ethanol to hydrogen used in fuel cells to generate electricity. In this paper a rigorous isothermal, steady-state two-dimensional model was developed to simulate the behavior of a membrane microreactor based on the hydrogen yield from ethanol steam reforming. Furthermore, this membrane microreactor is compared to a membraneless microreactor. A potential advantage of the membrane microreactor is the fact that both ethanol steam reforming and the separation of hydrogen by a permselective membrane occur in one single microdevice. The simulation results for steam reforming yields are in agreement with experimental data found in the literature. The results show that the membrane microreactorpermits a hydrogen yield of up to 0.833 which is more than twice that generated by the membraneless reactor. More than 80% of the generated hydrogen permeates through the membrane and, due to its high selectivity, the membrane microreactor delivers high-purity hydrogen to the fuel cell.

Structure and physical properties of bio membranes and model membranes

International Nuclear Information System (INIS)

Tibor Hianik

2006-01-01

Bio membranes belong to the most important structures of the cell and the cell organelles. They play not only structural role of the barrier separating the external and internal part of the membrane but contain also various functional molecules, like receptors, ionic channels, carriers and enzymes. The cell membrane also preserves non-equilibrium state in a cell which is crucial for maintaining its excitability and other signaling functions. The growing interest to the bio membranes is also due to their unique physical properties. From physical point of view the bio membranes, that are composed of lipid bilayer into which are incorporated integral proteins and on their surface are anchored peripheral proteins and polysaccharides, represent liquid s crystal of smectic type. The bio membranes are characterized by anisotropy of structural and physical properties. The complex structure of bio membranes makes the study of their physical properties rather difficult. Therefore several model systems that mimic the structure of bio membranes were developed. Among them the lipid monolayers at an air-water interphase, bilayer lipid membranes, supported bilayer lipid membranes and liposomes are most known. This work is focused on the introduction into the physical word of the bio membranes and their models. After introduction to the membrane structure and the history of its establishment, the physical properties of the bio membranes and their models are stepwise presented. The most focus is on the properties of lipid monolayers, bilayer lipid membranes, supported bilayer lipid membranes and liposomes that were most detailed studied. This lecture has tutorial character that may be useful for undergraduate and graduate students in the area of biophysics, biochemistry, molecular biology and bioengineering, however it contains also original work of the author and his co-worker and PhD students, that may be useful also for specialists working in the field of bio membranes and model

Thermotropic and Barotropic Phase Behavior of Phosphatidylcholine Bilayers

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Nobutake Tamai

2013-01-01

Full Text Available Bilayers formed by phospholipids are frequently used as model biological membranes in various life science studies. A characteristic feature of phospholipid bilayers is to undergo a structural change called a phase transition in response to environmental changes of their surroundings. In this review, we focus our attention on phase transitions of some major phospholipids contained in biological membranes, phosphatidylcholines (PCs, depending on temperature and pressure. Bilayers of dipalmitoylphosphatidylcholine (DPPC, which is the most representative lipid in model membrane studies, will first be explained. Then, the bilayer phase behavior of various kinds of PCs with different molecular structures is revealed from the temperature–pressure phase diagrams, and the difference in phase stability among these PC bilayers is discussed in connection with the molecular structure of the PC molecules. Furthermore, the solvent effect on the phase behavior is also described briefly.

Determination of membrane behaviour during transport of pollutants n clay barriers

International Nuclear Information System (INIS)

Musso, M.; Pejon, O.

2010-01-01

The study of the transport of contaminants in clay barriers had a extensive development in environmental geotechnics. The most studied transport processes are solutes by advection - dispersion and diffusion generated by hydraulic and chemical gradients respectively. Greater attention should be given to the chemical - osmotic flow and behavior membrane clay barriers, since in one case the water molecules move through the existence of a chemical gradient and on the other the means totally or partially inhibits the passage of solutes. The team developed to measure these processes was constructed based on items international literature and performance was verified using two types of materials KCl solution . One material is a bentonite geocomposite (Geosynthetic Clay Liner GCL ) similar to that used by other researchers. The other material is a soil barrier compacted clay (Compacted Clay Liner CCL) Fm. Corumbataí (Permian), belonging to the Paraná basin in the state of Sao Paulo, Brazil . The results show the proper performance of the equipment built . Osmotic pressure generation and membrane performance was verified for both samples. Further corroborated influence of the type of clay mineral in the osmotic pressure generated value and membrane behavior

β-arrestin regulates estradiol membrane-initiated signaling in hypothalamic neurons.

Directory of Open Access Journals (Sweden)

Angela M Wong

Full Text Available Estradiol (E2 action in the nervous system is the result of both direct nuclear and membrane-initiated signaling (EMS. E2 regulates membrane estrogen receptor-α (ERα levels through opposing mechanisms of EMS-mediated trafficking and internalization. While ß-arrestin-mediated mERα internalization has been described in the cortex, a role of ß-arrestin in EMS, which underlies multiple physiological processes, remains undefined. In the arcuate nucleus of the hypothalamus (ARH, membrane-initiated E2 signaling modulates lordosis behavior, a measure of female sexually receptivity. To better understand EMS and regulation of ERα membrane levels, we examined the role of ß-arrestin, a molecule associated with internalization following agonist stimulation. In the present study, we used an immortalized neuronal cell line derived from embryonic hypothalamic neurons, the N-38 line, to examine whether ß-arrestins mediate internalization of mERα. β-arrestin-1 (Arrb1 was found in the ARH and in N-38 neurons. In vitro, E2 increased trafficking and internalization of full-length ERα and ERαΔ4, an alternatively spliced isoform of ERα, which predominates in the membrane. Treatment with E2 also increased phosphorylation of extracellular-signal regulated kinases 1/2 (ERK1/2 in N-38 neurons. Arrb1 siRNA knockdown prevented E2-induced ERαΔ4 internalization and ERK1/2 phosphorylation. In vivo, microinfusions of Arrb1 antisense oligodeoxynucleotides (ODN into female rat ARH knocked down Arrb1 and prevented estradiol benzoate-induced lordosis behavior compared with nonsense scrambled ODN (lordosis quotient: 3 ± 2.1 vs. 85.0 ± 6.0; p < 0.0001. These results indicate a role for Arrb1 in both EMS and internalization of mERα, which are required for the E2-induction of female sexual receptivity.

Why Do Fast-Growing Bacteria Enter Overflow Metabolism? Testing the Membrane Real Estate Hypothesis.

Science.gov (United States)

Szenk, Mariola; Dill, Ken A; de Graff, Adam M R

2017-08-23

Bacteria and other cells show a puzzling behavior. At high growth rates, E. coli switch from respiration (which is ATP-efficient) to using fermentation for additional ATP (which is inefficient). This overflow metabolism results in a several-fold decrease in ATP produced per glucose molecule provided as food. By integrating diverse types of experimental data into a simple biophysical model, we give evidence that this onset is the result of the membrane real estate hypothesis: Fast growth drives cells to be bigger, reducing their surface-to-volume ratios. This decreases the membrane area available for respiratory proteins despite growing demand, causing increased crowding. Only when respiratory proteins reach their crowding limit does the cell activate fermentation, since fermentation allows faster ATP production per unit membrane area. Surface limitation thus creates a Pareto trade-off between membrane efficiency and ATP yield that links metabolic choice to the size and shape of a bacterial cell. By exploring the predictions that emerge from this trade-off, we show how consideration of molecular structures, energetics, rates, and equilibria can provide important insight into cellular behavior. Copyright © 2017 Elsevier Inc. All rights reserved.

Grafting of glycidyl methacrylate/styrene onto polyvinyldine fluoride membranes for proton exchange fuel cell

International Nuclear Information System (INIS)

Abdel-Hady, E.E.; El-Toony, M.M.; Abdel-Hamed, M.O.

2013-01-01

Simultaneous gamma irradiation was used effectively for grafting facilitation of glycidyl methacrylate (GMA) and styrene (Sty) onto polyvinylidine fluoride (PVDF). Grafting percent was 122 when monomers ratio are 30% Sty and 70% GMA at 20 KGy gamma irradiation dose. Characterization of the membrane was performed using FT-IR, ion exchange capacity (IEC), water uptake. Mechanical behavior such as tensile strength was studied while morphological structure of the membrane was carried out by scan electron microscope (SEM). The membrane with degree of grafting 122% showed higher IEC (1.2 m mol/cm) than those of Nafion membrane with corresponding proton conductivity of 5.7 × 10 −2 S/cm similar to it. Operating the fuel cell unit showed higher voltage of the prepared membranes than that of Nafion 211. The prepared membranes stability for 300 h work approved their applicability from the cost benefit point of view

Polyurethane Nanofiber Membranes for Waste Water Treatment by Membrane Distillation

Directory of Open Access Journals (Sweden)

T. Jiříček

2017-01-01

Full Text Available Self-sustained electrospun polyurethane nanofiber membranes were manufactured and tested on a direct-contact membrane distillation unit in an effort to find the optimum membrane thickness to maximize flux rate and minimize heat losses across the membrane. Also salt retention and flux at high salinities up to 100 g kg−1 were evaluated. Even though the complex structure of nanofiber layers has extreme specific surface and porosity, membrane performance was surprisingly predictable; the highest flux was achieved with the thinnest membranes and the best energy efficiency was achieved with the thickest membranes. All membranes had salt retention above 99%. Nanotechnology offers the potential to find modern solutions for desalination of waste waters, by introducing new materials with revolutionary properties, but new membranes must be developed according to the target application.

Reflecting reflection in supervision

DEFF Research Database (Denmark)

Lystbæk, Christian Tang

associated with reflection and an exploration of alternative conceptions that view reflection within the context of settings which have a more group- and team-based orientation. Drawing on an action research project on health care supervision, the paper questions whether we should reject earlier views...... of reflection, rehabilitate them in order to capture broader connotations or move to new ways of regarding reflection that are more in keeping with not only reflective but also emotive, normative and formative views on supervision. The paper presents a critical perspective on supervision that challenge...... the current reflective paradigm I supervision and relate this to emotive, normative and formative views supervision. The paper is relevant for Nordic educational research into the supervision and guidance...

Evolution of a Rippled Membrane during Phospholipase A2 Hydrolysis Studied by Time-Resolved AFM

DEFF Research Database (Denmark)

Leidy, Chad; Mouritsen, Ole G.; Jørgensen, Kent

2004-01-01

The sensitivity of phospholipase A2 (PLA2) for lipid membrane curvature is explored by monitoring, through time-resolved atomic force microscopy, the hydrolysis of supported double bilayers in the ripple phase. The ripple phase presents a corrugated morphology. PLA2 is shown to have higher activity...... toward the ripple phase compared to the gel phase in 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) membranes, indicating its preference for this highly curved membrane morphology. Hydrolysis of the stable and metastable ripple structures is monitored for equimolar DMPC/1,2-distearoyl- sn-glycero-3....... This is reflected in an increase in ripple spacing, followed by a sudden flattening of the lipid membrane during hydrolysis. Hydrolysis of the ripple phase results in anisotropic holes running parallel to the ripples, suggesting that the ripple phase has strip regions of higher sensitivity to enzymatic attack. Bulk...

Direct Numerical Simulations of Concentration and Temperature Polarization in Direct Contact Membrane Distillation

Science.gov (United States)

Lou, Jincheng; Tilton, Nils

2017-11-01

Membrane distillation (MD) is a method of desalination with boundary layers that are challenging to simulate. MD is a thermal process in which warm feed and cool distilled water flow on opposite sides of a hydrophobic membrane. The temperature difference causes water to evaporate from the feed, travel through the membrane, and condense in the distillate. Two challenges to MD are temperature and concentration polarization. Temperature polarization represents a reduction in the transmembrane temperature difference due to heat transfer through the membrane. Concentration polarization describes the accumulation of solutes near the membrane. These phenomena reduce filtration and lead to membrane fouling. They are difficult to simulate due to the coupling between the velocity, temperature, and concentration fields on the membrane. Unsteady regimes are particularly challenging because noise at the outlets can pollute the near-membrane flow fields. We present the development of a finite-volume method for the simulation of fluid flow, heat, and mass transport in MD systems. Using the method, we perform a parametric study of the polarization boundary layers, and show that the concentration boundary layer shows self-similar behavior that satisfies power laws for the downstream growth. Funded by the U.S. Bureau of Reclamation.

Optimization of design parameters for bulk micromachined silicon membranes for piezoresistive pressure sensing application

International Nuclear Information System (INIS)

Belwanshi, Vinod; Topkar, Anita

2016-01-01

Finite element analysis study has been carried out to optimize the design parameters for bulk micro-machined silicon membranes for piezoresistive pressure sensing applications. The design is targeted for measurement of pressure up to 200 bar for nuclear reactor applications. The mechanical behavior of bulk micro-machined silicon membranes in terms of deflection and stress generation has been simulated. Based on the simulation results, optimization of the membrane design parameters in terms of length, width and thickness has been carried out. Subsequent to optimization of membrane geometrical parameters, the dimensions and location of the high stress concentration region for implantation of piezoresistors have been obtained for sensing of pressure using piezoresistive sensing technique.

Optimization of design parameters for bulk micromachined silicon membranes for piezoresistive pressure sensing application

Science.gov (United States)

Belwanshi, Vinod; Topkar, Anita

2016-05-01

Finite element analysis study has been carried out to optimize the design parameters for bulk micro-machined silicon membranes for piezoresistive pressure sensing applications. The design is targeted for measurement of pressure up to 200 bar for nuclear reactor applications. The mechanical behavior of bulk micro-machined silicon membranes in terms of deflection and stress generation has been simulated. Based on the simulation results, optimization of the membrane design parameters in terms of length, width and thickness has been carried out. Subsequent to optimization of membrane geometrical parameters, the dimensions and location of the high stress concentration region for implantation of piezoresistors have been obtained for sensing of pressure using piezoresistive sensing technique.

Fouling in Membrane Distillation, Osmotic Distillation and Osmotic Membrane Distillation

Directory of Open Access Journals (Sweden)

Mourad Laqbaqbi

2017-03-01

Full Text Available Various membrane separation processes are being used for seawater desalination and treatment of wastewaters in order to deal with the worldwide water shortage problem. Different types of membranes of distinct morphologies, structures and physico-chemical characteristics are employed. Among the considered membrane technologies, membrane distillation (MD, osmotic distillation (OD and osmotic membrane distillation (OMD use porous and hydrophobic membranes for production of distilled water and/or concentration of wastewaters for recovery and recycling of valuable compounds. However, the efficiency of these technologies is hampered by fouling phenomena. This refers to the accumulation of organic/inorganic deposits including biological matter on the membrane surface and/or in the membrane pores. Fouling in MD, OD and OMD differs from that observed in electric and pressure-driven membrane processes such electrodialysis (ED, membrane capacitive deionization (MCD, reverse osmosis (RO, nanofiltration (NF, ultrafiltration (UF, microfiltration (MF, etc. Other than pore blockage, fouling in MD, OD and OMD increases the risk of membrane pores wetting and reduces therefore the quantity and quality of the produced water or the concentration efficiency of the process. This review deals with the observed fouling phenomena in MD, OD and OMD. It highlights different detected fouling types (organic fouling, inorganic fouling and biofouling, fouling characterization techniques as well as various methods of fouling reduction including pretreatment, membrane modification, membrane cleaning and antiscalants application.

Measuring and manipulating audiences : A personal reflection

NARCIS (Netherlands)

Bulterman, Dick C A

2016-01-01

Understanding the emotional reactions of audiences to a wide range of content types is an important area of research. In this article, I provide a personal reflection on various approaches to modeling, quantifying and understanding audience behavior based on a broad range of evaluation techniques.

Ultra-thin Oxide Membranes: Synthesis and Carrier Transport

Science.gov (United States)

Sim, Jai Sung

-stoichiometry. Temperature dependence of the electrical resistivity of the nanowall showed semiconducting behavior with an activation energy different from that of TiO2 single crystals and was attributed to formation of TinO2n-1 phases after FIB processing. The CeO2 study involved high temperature conductivity studies on substrate-free self-supported nano-crystalline ceria membranes up to 800 K. Increasing conductivity with oxygen partial pressure directly opposing the behavior of thin film devices 'clamped' by substrate has been observed. This illustrate that the relaxed nature of free standing membranes, and increased surface to volume ratio enables more sensitive electrical response to oxygen adsorption which could have implications for their use in oxygen storage devices, solid oxide fuel cells, and chemical sensors. The work in this thesis advances the understanding of materials in freestanding membrane form and advances fabrication techniques that have not been explored before, having implications for sensors, actuators, SOFC, memristors, and physics of quasi-2D materials.

Enzymatic degradation behavior and cytocompatibility of silk fibroin-starch-chitosan conjugate membranes

Energy Technology Data Exchange (ETDEWEB)

Baran, Erkan T., E-mail: erkantur@metu.edu.tr; Tuzlakoglu, Kadriye, E-mail: kadriye@dep.uminho.pt; Mano, Joao F., E-mail: jmano@dep.uminho.pt; Reis, Rui L., E-mail: rgreis@dep.uminho.pt

2012-08-01

The objective of this study was to investigate the influence of silk fibroin and oxidized starch conjugation on the enzymatic degradation behavior and the cytocompatability of chitosan based biomaterials. The tensile stress of conjugate membranes, which was at 50 Megapascal (MPa) for the lowest fibroin and starch composition (10 weight percent (wt.%)), was decreased significantly with the increased content of fibroin and starch. The weight loss of conjugates in {alpha}-amylase was more notable when the starch concentration was the highest at 30 wt.%. The conjugates were resistant to the degradation by protease and lysozyme except for the conjugates with the lowest starch concentration. After 10 days of cell culture, the proliferation of osteoblast-like cells (SaOS-2) was stimulated significantly by higher fibroin compositions and the DNA synthesis on the conjugate with the highest fibroin (30 wt.%) was about two times more compared to the native chitosan. The light microscopy and the image analysis results showed that the cell area and the lengths were decreased significantly with higher fibroin/chitosan ratio. The study proved that the conjugation of fibroin and starch with the chitosan based biomaterials by the use of non-toxic reductive alkylation crosslinking significantly improved the cytocompatibility and modulated the biodegradation, respectively. - Highlights: Black-Right-Pointing-Pointer Silk fibroin, starch and chitosan conjugates were prepared by reductive alkylation. Black-Right-Pointing-Pointer The enzymatic biodegradation and the cytocompatibility of conjugates were tested. Black-Right-Pointing-Pointer The conjugate with 30% starch composition was degraded by {alpha}-amylase significantly. Black-Right-Pointing-Pointer Higher starch composition in conjugates prevented protease and lysozyme degradation. Black-Right-Pointing-Pointer Fibroin incorporation effectively increased the cell proliferation of conjugates.

Impact of two different saponins on the organization of model lipid membranes.

Science.gov (United States)

Korchowiec, Beata; Gorczyca, Marcelina; Wojszko, Kamila; Janikowska, Maria; Henry, Max; Rogalska, Ewa

2015-10-01

Saponins, naturally occurring plant compounds are known for their biological and pharmacological activity. This activity is strongly related to the amphiphilic character of saponins that allows them to aggregate in aqueous solution and interact with membrane components. In this work, Langmuir monolayer techniques combined with polarization modulation infrared reflection-absorption spectroscopy (PM-IRRAS) and Brewster angle microscopy were used to study the interaction of selected saponins with lipid model membranes. Two structurally different saponins were used: digitonin and a commercial Merck Saponin. Membranes of different composition, namely, cholesterol, 1,2-dipalmitoyl-sn-glycero-3-phosphocholine or 1,2-dipalmitoyl-sn-glycero-3-phospho-rac-(1-glycerol) were formed at the air/water and air/saponin solution interfaces. The saponin-lipid interaction was characterized by changes in surface pressure, surface potential, surface morphology and PM-IRRAS signal. Both saponins interact with model membranes and change the physical state of membranes by perturbing the lipid acyl chain orientation. The changes in membrane fluidity were more significant upon the interaction with Merck Saponin. A higher affinity of saponins for cholesterol than phosphatidylglycerols was observed. Moreover, our results indicate that digitonin interacts strongly with cholesterol and solubilize the cholesterol monolayer at higher surface pressures. It was shown, that digitonin easily penetrate to the cholesterol monolayer and forms a hydrogen bond with the hydroxyl groups. These findings might be useful in further understanding of the saponin action at the membrane interface and of the mechanism of membrane lysis. Copyright © 2015 Elsevier B.V. All rights reserved.

Reading Poetry for Critical Reflection on Consumer Behavior

Science.gov (United States)

Scimone, Anthony J.

2010-01-01

Like many other dimensions of everyday life, people's need to satisfy themselves with stuff derives from deep impulses and responds to both obvious and subtle images. Ultimately, it isn't the commodities people buy so much as the behaviors they exhibit that are worth critical examination. What better way, then, to understand this phenomenon than…

Flow and fouling in membrane filters: Effects of membrane morphology

Science.gov (United States)

Sanaei, Pejman; Cummings, Linda J.

2015-11-01

Membrane filters are widely-used in microfiltration applications. Many types of filter membranes are produced commercially, for different filtration applications, but broadly speaking the requirements are to achieve fine control of separation, with low power consumption. The answer to this problem might seem obvious: select the membrane with the largest pore size and void fraction consistent with the separation requirements. However, membrane fouling (an inevitable consequence of successful filtration) is a complicated process, which depends on many parameters other than membrane pore size and void fraction; and which itself greatly affects the filtration process and membrane functionality. In this work we formulate mathematical models that can (i) account for the membrane internal morphology (internal structure, pore size & shape, etc.); (ii) fouling of membranes with specific morphology; and (iii) make some predictions as to what type of membrane morphology might offer optimum filtration performance.

Proteolysis inside the membrane is a rate-governed reaction not driven by substrate affinity.

Science.gov (United States)

Dickey, Seth W; Baker, Rosanna P; Cho, Sangwoo; Urban, Siniša

2013-12-05

Enzymatic cleavage of transmembrane anchors to release proteins from the membrane controls diverse signaling pathways and is implicated in more than a dozen diseases. How catalysis works within the viscous, water-excluding, two-dimensional membrane is unknown. We developed an inducible reconstitution system to interrogate rhomboid proteolysis quantitatively within the membrane in real time. Remarkably, rhomboid proteases displayed no physiological affinity for substrates (K(d) ~190 μM/0.1 mol%). Instead, ~10,000-fold differences in proteolytic efficiency with substrate mutants and diverse rhomboid proteases were reflected in k(cat) values alone. Analysis of gate-open mutant and solvent isotope effects revealed that substrate gating, not hydrolysis, is rate limiting. Ultimately, a single proteolytic event within the membrane normally takes minutes. Rhomboid intramembrane proteolysis is thus a slow, kinetically controlled reaction not driven by transmembrane protein-protein affinity. These properties are unlike those of other studied proteases or membrane proteins but are strikingly reminiscent of one subset of DNA-repair enzymes, raising important mechanistic and drug-design implications. Copyright © 2013 Elsevier Inc. All rights reserved.

Fluorescence interference contrast based approach to study real time interaction of melittin with plasma membranes

Science.gov (United States)

Gupta, Sharad; Gui, Dong; Zandi, Roya; Gill, Sarjeet; Mohideen, Umar

2014-03-01

Melittin is an anti-bacterial and hemolytic toxic peptide found in bee venom. Cell lysis behavior of peptides has been widely investigated, but the exact interaction mechanism of lytic peptides with lipid membranes and its constituents has not been understood completely. In this paper we study the melittin interaction with lipid plasma membranes in real time using non-invasive and non-contact fluorescence interference contrast microscopy (FLIC). Particularly the interaction of melittin with plasma membranes was studied in a controlled molecular environment, where these plasma membrane were composed of saturated lipid, 1,2-diphytanoyl-sn-glycero-3-phosphocholine (DPhPC) and unsaturated lipid, 1,2-dioleoyl-sn-glycero-3-phosphocholine(DOPC) with and without cholesterol. We found out that melittin starts to form nanometer size pores in the plasma membranes shortly after interacting with membranes. But the addition of cholesterol in plasma membrane slows down the pore formation process. Our results show that inclusion of cholesterol to the plasma membranes make them more resilient towards pore formation and lysis of membrane.

Surface modification of seawater desalination reverse osmosis membranes: Characterization studies & performance evaluation

KAUST Repository

Matin, Asif

2014-06-01

In this work we report surface modification of commercial reverse osmosis membranes by depositing ultrathin copolymer coatings, which could potentially enhance the biofouling resistance of RO membranes. Hydrophilic monomer hydroxyethyl methacrylate (HEMA) and a hydrophobic monomer, perfluorodecyl acrylate (PFDA) were copolymerized directly on the active layer of commercial aromatic polyamide reverse osmosis (RO) membranes using an initiated Chemical Vapor Deposition (iCVD) technique. Attenuated total reflective Fourier transform infrared spectra (ATR-FTIR) verified the successful modification of the membrane surfaces as a new FTIR adsorption band around 1730cm-1 corresponding to carbonyl groups in the copolymer film appeared after the deposition. X-ray Photoelectron spectroscopy (XPS) analysis also confirmed the presence of the copolymer film on the membrane surface by showing strong fluorine peaks emanating from the fluorinated alkyl side chains of the PFA molecules. Contact angle measurements with deionized water showed the modified membrane surfaces to be initially very hydrophobic but quickly assumed a hydrophilic character within few minutes. Atomic Force Microscopy (AFM) revealed that the deposited films were smooth and conformal as the surface topology of the underlying membrane surface remained virtually unchanged after the deposition. FESEM images of the top surface also showed that the typical ridge-and-valley structure associated with polyamide remained intact after the deposition. Short-term permeation tests using DI water and 2000ppm NaCl water showed that the deposited copolymer coatings had negligible effect on permeate water flux and salt rejection. © 2013 Elsevier B.V.

Reduced Graphene Oxide Membranes: Applications in Fog Collection and Water Purification

KAUST Repository

Tang, Bo

2017-01-01

fog harvesting behavior of its two surfaces. The physical imprint mechanism was further extended to engineering pre-designed patterns selectively on the bottom surface of the rGO membrane. This dissertation, for the first time, reported the water flux

Tailored adhesion behavior of polyelectrolyte thin films deposited on plasma-treated poly(dimethylsiloxane) for functionalized membranes

Energy Technology Data Exchange (ETDEWEB)

Bassil, Joelle, E-mail: joelle.bassil@univ-lorraine.fr [Institut Jean Lamour (IJL), UMR CNRS 7198, Université de Lorraine, Parc de Saurupt CS50840, 54011 Nancy (France); Alem, Halima, E-mail: halima.alem@univ-lorraine.fr [Institut Jean Lamour (IJL), UMR CNRS 7198, Université de Lorraine, Parc de Saurupt CS50840, 54011 Nancy (France); Henrion, Gérard, E-mail: gerard.henrion@univ-lorraine.fr [Institut Jean Lamour (IJL), UMR CNRS 7198, Université de Lorraine, Parc de Saurupt CS50840, 54011 Nancy (France); Roizard, Denis, E-mail: denis.roizard@univ-lorraine.fr [Laboratoire Réactions et Génie des Procédés (LRGP), UMR CNRS 7274, ENSIC, Université de Lorraine, 1 rue Grandville, 54011 Nancy (France)

2016-04-30

Graphical abstract: - Highlights: • The surface of PDMS membrane was first modified by Ar/O{sub 2} plasma to increase its surface energy. • Subsequently, a homogeneous multilayer of the well-known couple of polyelectrolyte PDADMAC/PSS was deposited on the plasma treated PDMS. • The relation between the parameters of the modification processes and the morphology, wettability, structure and adhesion of the polyelectrolytes layers based PDMS membranes is investigated and enlightened. - Abstract: Completely homogenous films formed via the layer-by-layer assembly of poly(diallyldimethylammonium chloride) (PDADMAC) and the poly(styrene sulfonate) were successfully obtained on plasma-treated poly(dimethylsiloxane) (PDMS) substrates. To modify the hydrophobicity of the PDMS surface, a cold plasma treatment was previously applied to the membrane, which led to the creation of hydrophilic groups on the surface of the membrane. PDMS wettability and surface morphology were successfully correlated with the plasma parameters. A combination of contact angle measurements, scanning electron microscopy (SEM) and atomic force microscopy (AFM) analysis was used to demonstrate that homogeneous and hydrophilic surfaces could be achieved on PDMS cold-plasma-treated membranes. The stability of the assembled PEL layer on the PDMS was evaluated using a combination of pull-off testing and X-ray photoelectron spectroscopy (XPS), which confirmed the relevance of a plasma pre-treatment as the adhesion of the polyelectrolyte multilayers was greatly enhanced when the deposition was completed on an activated PDMS surface at 80 W for 5 min.

Magnetic field effects on electric behavior of [Fe(CN6]3− at bare and membrane-coated electrodes

Directory of Open Access Journals (Sweden)

Govindachetty Saravanan, Katsuhiko Fujio and Sumio Ozeki

2008-01-01

Full Text Available The cyclic voltammetric behavior of [Fe(CN6]3− was investigated under homogeneous magnetic fields perpendicular to the electrode surface in order to determine the effects of magnetic fields on the distribution of an Fe2+/Fe3+ redox couple. The cathodic current was enhanced much more than the anodic current by a homogeneous magnetic field, suggesting that the concentration gradient of paramagnetic [Fe(CN6]3− and diamagnetic [Fe(CN6]4− formed at an electrode surface may also contribute to the asymmetric current. The apparent diffusion coefficient of the redox couple increased by over 30% in both cathodic and anodic processes upon applying a magnetic field. For a gold electrode coated with dioctadecyldimethylammonium, the application of a magnetic field perpendicular to the surface increased the peak-to-peak separation, and enhanced the asymmetric current. It is inferred that the application of a magnetic field promotes the electron-tunneling process by tilting chain molecules in the barrier membrane.