Showing papers on "Membrane published in 2001"
TL;DR: In this paper, the authors explain the transport properties and the swelling behaviour of NAFION and different sulfonated polyetherketones in terms of distinct differences on the microstructures and in the p K a of the acidic functional groups.
2,755 citations
TL;DR: It is shown that mouse Apg12-Apg5 conjugate localizes to the isolation membranes in mouse embryonic stem cells, and the covalent modification of Apg5 with Apg 12 is not required for its membrane targeting, but is essential for involvement of ApG5 in elongation of the isolation membrane.
Abstract: In macroautophagy, cytoplasmic components are delivered to lysosomes for degradation via autophagosomes that are formed by closure of cup-shaped isolation membranes. However, how the isolation membranes are formed is poorly understood. We recently found in yeast that a novel ubiquitin-like system, the Apg12-Apg5 conjugation system, is essential for autophagy. Here we show that mouse Apg12-Apg5 conjugate localizes to the isolation membranes in mouse embryonic stem cells. Using green fluorescent protein–tagged Apg5, we revealed that the cup-shaped isolation membrane is developed from a small crescent-shaped compartment. Apg5 localizes on the isolation membrane throughout its elongation process. To examine the role of Apg5, we generated Apg5-deficient embryonic stem cells, which showed defects in autophagosome formation. The covalent modification of Apg5 with Apg12 is not required for its membrane targeting, but is essential for involvement of Apg5 in elongation of the isolation membranes. We also show that Apg12-Apg5 is required for targeting of a mammalian Aut7/Apg8 homologue, LC3, to the isolation membranes. These results suggest that the Apg12-Apg5 conjugate plays essential roles in isolation membrane development.
1,372 citations
TL;DR: In this article, the most influential membrane properties governing colloidal fouling rate of reverse osmosis (RO) and nanofiltration (NF) membranes were identified for physical surface morphology, surface chemical properties, surface zeta potential, and specific surface chemical structure.
1,110 citations
TL;DR: In this article, an overview of the membrane development for proton-conductive polymer (composite) membranes for the application membrane fuel cells, focusing on the membrane developments in this field performed at ICVT.
1,006 citations
TL;DR: In this paper, the various factors influencing electrospun nonwoven fibrous membrane structure and transport properties are discussed, as well as the application of elastomeric membranes for protective clothing applications.
852 citations
TL;DR: In this paper, the authors give a brief outline of the field that has emerged on the basis of theoretical models on porous as well as non-porous membranes, and discuss mainly the solution cast polymeric membranes.
667 citations
TL;DR: In this paper, a systematic investigation of the conductivity of Nafion 117 and sulfonated polyether ether ketone (S-PEEK) membranes was performed as a function of relative humidity (rh) in a wide range of temperature (80-160°C).
603 citations
TL;DR: Track membrane (TM) technology is an example of industrial application of track etching technique as discussed by the authors, and it has been used in many applications, such as process filtration, cell culture, and laboratory filtering.
593 citations
TL;DR: In this article, the first large-scale NaA zeolite membrane plant was put into industrial operation and the successful fabrication of the plant and the high level of PV properties of the module were discussed.
586 citations
TL;DR: A review of the development of carbon membranes in the last 30 years and a clear future direction in research for carbon membrane can be found in this article, where carbon membranes can be divided into four major configurations: flat sheet, membrane supported on tube, capillary, and hollow fiber.
582 citations
TL;DR: In this paper, the authors report approaches to the development of high temperature membranes for proton exchange membrane fuel cells; composite perfluorinated sulfonic acid membranes were prepared to improve water retention, and non-aqueous proton conducting membrane was prepared to circumvent the loss of water.
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09 Jul 2001
TL;DR: In this article, the state-of-the-art of Pervaporation processes in the chemical industry is described. But, as discussed in Section 2.1, it is based on the separation of organic molecules from gas streams by means of Membranes.
Abstract: List of Contributors. MEMBRANE MATERIALS AND MEMBRANE PREPARATION. Introduction. Membrane Market. Membrane Preparation. Presently Available Membranes for Liquid Separation. Surface Modification of Membranes. Gas Separation with Membranes. CURRENT APPLICATIONS AND PERSPECTIVES. The Separation of Organic Vapors from Gas Streams by Means of Membranes (K. Ohlrogge & K. St?rken). Gas Separation Membrane Applications (D. Stookey). State-of-Art of Pervaporation Processes in the Chemical Industry (H. Br?schke). Nanofiltration of Charged Organic Molecules in Aqueous and Non-aqueous Solvents: Separation Results and Mechanisms (J. Hestekin, et al.). Industrial Membrane Reactors (M. Kemmere & J. Keurentjes). Electromembrane Processes (T. Davis, et al.). Membrane Technology in the Chemical Industry: Future Directions (R. Baker). Subject Index.
TL;DR: In this paper, a one-dimensional non-isothermal model of a proton exchange membrane (PEM) fuel cell has been developed to investigate the effect of various design and operating conditions on the cell performance, thermal response and water management.
TL;DR: In this article, a series of sequenced sulfonated naphthalenic polyimides with improved solubility were prepared by polycondensation in m-cresol using aromatic diamines containing phenylether bonds and/or bulky groups.
TL;DR: In this article, the preparation, characterization, properties and applications of polypyrrole (PPY) are reviewed in detail according to the synthetic methods and their applications, and effects of various parameters such as doping anions, additives, and oxidant, on the PPY properties are also concerned.
Abstract: Polypyrrole (PPY) is one of the most promising materials for multifunctionalized applications. Preparation, characterization, properties and applications of PPYs are reviewed in this paper. In addition, the PPY composites are described in detail according to the synthetic methods and their applications. At the same time, effects of various parameters such as doping anions, additives, and oxidant, on the PPY properties are also concerned. The PPY films and membranes used for ion exchange, pervaporation, and gas separation are mentioned. In this review, ion exchange membranes are highlighted. Moreover, the further investigation of PPY composite membranes for oxygen enrichment is predicted. A total of 117 references are cited.
TL;DR: In this article, the authors discuss two different membrane reactor concepts which both rely on supported palladium, on the one hand as a permselective membrane material, and on the other hand as base component of a membrane-type hydrogenation catalyst.
Abstract: Membrane reactors applied to catalytic reactions are currently being studied in many places world-wide. Significant developments in membrane science and the vision of process intensification by multifunctional reactors have stimulated a lot of academic and industrial research, which is impressively demonstrated by more than 100 scientific papers on catalytic membrane reactors being published per year. Palladium as a noble metal with exceptional hydrogen permeation properties and, at the same time, broad applicability as a catalyst, first of all for hydrogenation, is part of many of these developments. This paper discusses two different membrane reactor concepts which both rely on supported palladium, on the one hand as a permselective membrane material, and on the other hand as base component of a membrane-type hydrogenation catalyst. Dense palladium composite membranes can be used for hydrogen separation from packed-bed catalysts in gas-phase hydrocarbon dehydrogenation reactions. Mesoporous membranes containing dispersed bimetallic Pd/X-clusters can be employed as so-called catalytic diffusers for liquid-phase hydrogenation, e.g. of nitrate and nitrite in water. The principles of both concepts are introduced, recently obtained experimental data are evaluated in connection with literature results, and the perspectives for further development are highlighted.
TL;DR: The N-terminal domain of the influenza hemagglutinin is deduced to be a kinked, predominantly helical amphipathic structure that could perturb lipid packing and facilitate lipid mixing between juxtaposed membranes.
Abstract: The N-terminal domain of the influenza hemagglutinin (HA) is the only portion of the molecule that inserts deeply into membranes of infected cells to mediate the viral and the host cell membrane fusion. This domain constitutes an autonomous folding unit in the membrane, causes hemolysis of red blood cells and catalyzes lipid exchange between juxtaposed membranes in a pH-dependent manner. Combining NMR structures determined at pHs 7.4 and 5 with EPR distance constraints, we have deduced the structures of the N-terminal domain of HA in the lipid bilayer. At both pHs, the domain is a kinked, predominantly helical amphipathic structure. At the fusogenic pH 5, however, the domain has a sharper bend, an additional 3(10)-helix and a twist, resulting in the repositioning of Glu 15 and Asp 19 relative to that at the nonfusogenic pH 7.4. Rotation of these charged residues out of the membrane plane creates a hydrophobic pocket that allows a deeper insertion of the fusion domain into the core of the lipid bilayer. Such an insertion mode could perturb lipid packing and facilitate lipid mixing between juxtaposed membranes.
TL;DR: The use of grafting material in combination with collagen membranes seems to improve clinical outcomes for furcation, but not intrabony, defects when compared to the use of membranes alone, and the properties that make collagen membranes attractive for use in regenerative therapy will be addressed.
Abstract: Collagen materials have been utilized in medicine and dentistry because of their proven biocompatability and capability of promoting wound healing. For guided tissue regeneration (GTR) procedures, collagen membranes have been shown to be comparable to non-absorbable membranes with regard to probing depth reduction, clinical attachment gain, and percent of bone fill. Although these membranes are absorbable, collagen membranes have been demonstrated to prevent epithelial down-growth along the root surfaces during the early phase of wound healing. The use of grafting material in combination with collagen membranes seems to improve clinical outcomes for furcation, but not intrabony, defects when compared to the use of membranes alone. Recently, collagen materials have also been applied in guided bone regeneration (GBR) and root coverage procedures with comparable success rates to non-absorbable expanded polytetrafluoroethylene (ePTFE) membranes and conventional subepithelial connective tissue grafts, respectively. Long-term clinical trials are still needed to further evaluate the benefits of collagen membranes in periodontal and peri-implant defects. This article will review the rationale for each indication and its related literature, both in vitro and in vivo studies. The properties that make collagen membranes attractive for use in regenerative therapy will be addressed. In addition, varieties of cross-linking techniques utilized to retard the degradation rate of collagen membranes will be discussed.
TL;DR: X-ray photoelectron spectroscopy demonstrated quantitatively that a considerable amount of the adsorbed particles were tightly self-assembled at the expense of the initial loss of those that were loosely bound, and became stabilized even after exposure to the various washing and harsh RO operating conditions.
Abstract: Hybrid organic/inorganic reverse osmosis (RO) membranes composed of aromatic polyamide thin films underneath titanium dioxide (TiO2) nanosized particles have been fabricated by a self-assembly process, aiming at breakthrough of biofouling problems. First, positively charged particles of the colloidal TiO2 were synthesized by a sol−gel process, and the diameter of the resulting particles in acidic aqueous solution was estimated to be ≈2 nm by analyzing the UV−visible absorption characteristics with a quantum mechanical model developed by Brus. Transmission electron microscopy (TEM) further confirmed the formation of the quantum-sized TiO2 particles (∼10 nm or less). The TiO2 particles appeared to exist in the crystallographic form of anatase as observed with the X-ray diffraction (XRD) pattern in comparison with those of commercial 100% rutile and commercial 70:30% anatase-to-rutile mixture. The hybrid thin-film-composite (TFC) aromatic polyamide membranes were prepared by self-assembly of the TiO2 nanopar...
TL;DR: It is proposed that these rates of mechanochemical processes, such as endocytosis, membrane extension and membrane resealing after cell wounding, are also controlled physically, through an apparently continuous adhesion between plasma membrane lipids and cytoskeletal proteins.
Abstract: The rates of mechanochemical processes, such as endocytosis, membrane extension and membrane resealing after cell wounding, are known to be controlled biochemically, through interaction with regulatory proteins. Here, I propose that these rates are also controlled physically, through an apparently continuous adhesion between plasma membrane lipids and cytoskeletal proteins.
TL;DR: The fouling mechanism controlling the flux decline involved the combined effects of adsorptive and colloidal fouling by the hydrophilic neutral fraction in the internal pore structure of the membrane.
TL;DR: Overall, whereas all studied cationic antimicrobial peptides interacted with membranes, they were quite heterogeneous in their impact on these membranes.
TL;DR: In this paper, the organic-inorganic hybrid of poly(amide-6-b-ethylene oxide) (PEBAX ® ) and silica were prepared via in situ polymerization of tetraethoxysilane (TEOS) using the sol-gel process and their gas transport properties were studied.
TL;DR: Localization studies with GFP-tagged binding domains and antibodies provide new views of the non-uniform, dynamic distribution of PI(4,5)P(2) in membranes and its organization in raft-like domains.
TL;DR: A novel mechanism for proton leakage through lipid bilayers is proposed and a structure-function rationale for distinguishing the structures of the phytosterols as inhibitors of proton leaks from that of cholesterol which is proposed to inhibit leaks of Na(+).
TL;DR: In this article, a polymer electrolyte membrane fuel cell based on polybenzimidazole (PBI) membranes has been prepared and H3PO4-doped in a doping range from 300 to 1600 mol %.
Abstract: A polymer electrolyte membrane fuel cell operational at temperatures around 150–200 °C is desirable for fast electrode kinetics and high tolerance to fuel impurities For this purpose polybenzimidazole (PBI) membranes have been prepared and H3PO4-doped in a doping range from 300 to 1600 mol % Physiochemical properties of the membrane electrolyte have been investigated by measurements of water uptake, acid doping level, electric conductivity, mechanical strength and water drag coefficient Electrical conductivity is found to be insensitive to humidity but dependent on the acid doping level At 160 °C a conductivity as high as 013 S cm−1 is obtained for membranes of high doping levels Mechanical strength measurements show, however, that a high acid doping level results in poor mechanical properties At operational temperatures up to 190 °C, fuel cells based on this polymer membrane have been tested with both hydrogen and hydrogen containing carbon monoxide
TL;DR: The present and future membrane market is assessed and new developments and future research needs are discussed in this article, where fundamental aspects of membranes and membrane processes are discussed, as well as technically and economically effective applications.
Abstract: During the last 35 years membranes have evolved from a laboratory tool to industrial products with significant technical and commercial impact. Today, membranes are used for desalination of sea and brackish water and for treating industrial effluents. They are efficient tools for the concentration and purification of food and pharmaceutical products and the production of base chemicals. Furthermore, membranes are key components in artificial organs, drug delivery devices, and energy conversion systems. In combination with conventional techniques membranes often provide cleaner and more energy-efficient production routes for high-quality products. Fundamental aspects of membranes and membrane processes are discussed, as well as technically and economically effective applications. The present and future membrane market is assessed and new developments and future research needs are discussed.
TL;DR: In this paper, a phenomenological description of proton conductance in polymer electrolyte membranes is provided, based on contemporary views of the proton transfer processes in condensed media and a model for heterogeneous polymers.
Abstract: We provide a phenomenological description of proton conductance in polymer electrolyte membranes, based on contemporary views of proton transfer processes in condensed media and a model for heterogeneous polymer electrolyte membrane structure. The description combines the proton transfer events in a single pore with the total pore-network performance and, thereby, relates structural and kinetic characteristics of the membrane. The theory addresses specific experimentally studied issues such as the effect of the density of proton localization sites (equivalent weight) of the membrane material and the water content of the pores. The effect of the average distance between the sulfonate groups, which changes during membrane swelling, is analyzed in particular, and the factors which determine the temperature dependence of the macroscopic membrane conductance are disclosed. Numerical estimates of the specific membrane conductivity obtained from the theory agree very well with typical experimental data, thereby confirming the appropriateness of the theoretical concepts. Moreover, the versatility of the models offers a useful and transparent frame for combining the analysis of both experimental data and the results of molecular dynamics simulations.
TL;DR: Results show that zinc can protect membranes from iron-initiated lipid oxidation by occupying negatively charged sites with potential iron binding capacity, and suggests that zinc is a pivotal component of the antioxidant defense network that protects membranes from oxidation.
TL;DR: It is shown that cross-linking, a process known to be important for certain cell-signaling processes, can selectively translocate molecules to liquid-ordered domains, and that domain formation and disruption critically depends on the cholesterol density.
Abstract: As shown earlier, raft-like domains resembling those thought to be present in natural cell membranes can be formed in supported planar lipid monolayers. These liquid-ordered domains coexist with a liquid-disordered phase and form in monolayers prepared both from synthetic lipid mixtures and lipid extracts of the brush border membrane of mouse kidney cells. The domains are detergent-resistant and are highly enriched in the glycosphingolipid GM1. In this work, the properties of these raft-like domains are further explored and compared with properties thought to be central to raft function in plasma membranes. First, it is shown that domain formation and disruption critically depends on the cholesterol density and can be controlled reversibly by treating the monolayers with the cholesterol-sequestering reagent methyl-β-cyclodextrin. Second, the glycosylphosphatidylinositol-anchored cell-surface protein Thy-1 significantly partitions into the raft-like domains. The extent of this partitioning is reduced when the monolayers contain GM1, indicating that different molecules can compete for domain occupation. Third, the partitioning of a saturated phospholipid analog into the raft phase is dramatically increased (15% to 65%) after cross-linking with antibodies, whereas the distribution of a doubly unsaturated phospholipid analog is not significantly affected by cross-linking (≈10%). This result demonstrates that cross-linking, a process known to be important for certain cell-signaling processes, can selectively translocate molecules to liquid-ordered domains.