http://www.mdpi.com/journal/membranes Latest open access articles published in Membranes at http://www.mdpi.com/journal/membranes http://www.mdpi.com/2077-0375/2/2/216 Lithium-air (Li-air) batteries have a much higher theoretical energy density than conventional lithium batteries and other metal air batteries, so they are being developed for applications that require long life. Water vapor from air must be prevented from corroding the lithium (Li) metal negative electrode during discharge under ambient conditions, i.e., in humid air. One method of protecting the Li metal from corrosion is to use an oxygen selective membrane (OSM) that allows oxygen into the cell while stopping or slowing the ingress of water vapor. The desired properties and some potential materials for OSMs for Li-air batteries are discussed and the literature is reviewed. http://www.mdpi.com/2077-0375/2/2/216 Fri, 11 May 2012 00:00:00 CEST Membranes 2012-05-11 2 2 Review 216 227 2077-0375 Oxygen Selective Membranes for Li-Air (O2) Batteries 2012-05-11 doi: 10.3390/membranes2020216 Owen Crowther Mark Salomon http://www.mdpi.com/2077-0375/2/2/214 We would like to request a correction to the author listing. The following changes should be made in respect to the original publication of this article [1]. [...] http://www.mdpi.com/2077-0375/2/2/214 Wed, 02 May 2012 00:00:00 CEST Membranes 2012-05-02 2 2 Correction 214 215 2077-0375 Correction: Self-Assembling Peptide Surfactants A6K and A6D Adopt a-Helical Structures Useful for Membrane Protein Stabilization. Membranes 2011, 1, 314-326 2012-05-02 doi: 10.3390/membranes2020214 Kamila Oglęcka Furen Zhuang Charlotte A. E. Hauser http://www.mdpi.com/2077-0375/2/2/198 Immobilization of enzymes is one of the most promising methods in enzyme performance enhancement, including stability, recovery, and reusability. However, investigation of suitable solid support in enzyme immobilization is still a scientific challenge. Polyethersulfone (PES) and aminated PES (PES–NH2) were successfully synthesized as novel materials for immobilization. Membranes with various pore sizes (from 10–600 nm) based on synthesized PES and PES–NH2 polymers were successfully fabricated to be applied as bioreactors to increase the immobilized lipase performances. The influence of pore sizes, concentration of additives, and the functional groups that are attached on the PES backbone on enzyme loading and enzyme activity was studied. The largest enzyme loading was obtained by Mucor miehei lipase immobilized onto a PES–NH2 membrane composed of 10% of PES–NH2, 8% of dibutyl phthalate (DBP), and 5% of polyethylene glycol (PEG) (872.62  µg/cm2). Hydrolytic activity of the immobilized lipases indicated that the activities of biocatalysts are not significantly decreased by immobilization. From the reusability test, the lipase immobilized onto PES–NH2 showed a better constancy than the lipase immobilized onto PES (the percent recovery of the activity of the lipases immobilized onto PES–NH2 and PES are 97.16% and 95.37%, respectively), which indicates that this novel material has the potential to be developed as a bioreactor for enzymatic reactions. http://www.mdpi.com/2077-0375/2/2/198 Thu, 12 Apr 2012 00:00:00 CEST Membranes 2012-04-12 2 2 Article 198 213 2077-0375 Immobilization of Mucor miehei Lipase onto Macroporous Aminated Polyethersulfone Membrane for Enzymatic Reactions 2012-04-12 doi: 10.3390/membranes2020198 Nurrahmi Handayani Katja Loos Deana Wahyuningrum Buchari Muhammad Ali Zulfikar http://www.mdpi.com/2077-0375/2/1/134 In recent years, stimuli responsive materials have gained significant attention in membrane separation processes due to their ability to change specific properties in response to small external stimuli, such as light, pH, temperature, ionic strength, pressure, magnetic field, antigen, chemical composition, and so on. In this review, we briefly report recent progresses in light-driven materials and membranes. Photo-switching mechanisms, valved-membrane fabrication and light-driven properties are examined. Advances and perspectives of light responsive polymer membranes in biotechnology, chemistry and biology areas are discussed. http://www.mdpi.com/2077-0375/2/1/134 Fri, 02 Mar 2012 00:00:00 CET Membranes 2012-03-02 2 1 Review 134 197 2077-0375 Light Responsive Polymer Membranes: A Review 2012-03-02 doi: 10.3390/membranes2010134 Fiore Pasquale Nicoletta Daniela Cupelli Patrizia Formoso Giovanni De Filpo Valentina Colella Annarosa Gugliuzza http://www.mdpi.com/2077-0375/2/1/118 During the vesicular trafficking process, cellular membranes undergo dynamic morphological changes, in particular at the vesicle generation and fusion steps. Changes in membrane shape are regulated by small GTPases, coat proteins and other accessory proteins, such as BAR domain-containing proteins. In addition, membrane deformation entails changes in the lipid composition as well as asymmetric distribution of lipids over the two leaflets of the membrane bilayer. Given that P4-ATPases, which catalyze unidirectional flipping of lipid molecules from the exoplasmic to the cytoplasmic leaflets of the bilayer, are crucial for the trafficking of proteins in the secretory and endocytic pathways, changes in the lipid composition are involved in the vesicular trafficking process. Membrane remodeling is under complex regulation that involves the composition and distribution of lipids as well as assembly of proteins. http://www.mdpi.com/2077-0375/2/1/118 Wed, 29 Feb 2012 00:00:00 CET Membranes 2012-02-29 2 1 Review 118 133 2077-0375 Mechanisms of Membrane Curvature Generation in Membrane Traffic 2012-02-29 doi: 10.3390/membranes2010118 Hye-Won Shin Hiroyuki Takatsu Kazuhisa Nakayama http://www.mdpi.com/2077-0375/2/1/91 Eukaryotic cells have complicated membrane systems. The outermost plasma membrane contains various substructures, such as invaginations and protrusions, which are involved in endocytosis and cell migration. Moreover, the intracellular membrane compartments, such as autophagosomes and endosomes, are essential for cellular viability. The Bin-Amphiphysin-Rvs167 (BAR) domain superfamily proteins are important players in membrane remodeling through their structurally determined membrane binding surfaces. A variety of BAR domain superfamily proteins exist, and each family member appears to be involved in the formation of certain subcellular structures or intracellular membrane compartments. Most of the BAR domain superfamily proteins contain SH3 domains, which bind to the membrane scission molecule, dynamin, as well as the actin regulatory WASP/WAVE proteins and several signal transduction molecules, providing possible links between the membrane and the cytoskeleton or other machineries. In this review, we summarize the current information about each BAR superfamily protein with an SH3 domain(s). The involvement of BAR domain superfamily proteins in various diseases is also discussed. http://www.mdpi.com/2077-0375/2/1/91 Mon, 27 Feb 2012 00:00:00 CET Membranes 2012-02-27 2 1 Review 91 117 2077-0375 The BAR Domain Superfamily Proteins from Subcellular Structures to Human Diseases 2012-02-27 doi: 10.3390/membranes2010091 Fatemeh Safari Shiro Suetsugu http://www.mdpi.com/2077-0375/2/1/70 This paper reviews major research and development issues relating to hydrogels as scaffolds for tissue engineering, the article starts with a brief introduction of tissue engineering and hydrogels as extracellular matrix mimics, followed by a description of the various types of hydrogels and preparation methods, before a discussion of the physical and chemical properties that are important to their application. There follows a short comment on the trends of future research and development. Throughout the discussion there is an emphasis on the genetic understanding of bone tissue engineering application. http://www.mdpi.com/2077-0375/2/1/70 Tue, 14 Feb 2012 00:00:00 CET Membranes 2012-02-14 2 1 Review 70 90 2077-0375 Development of Hydrogels and Biomimetic Regulators as Tissue Engineering Scaffolds 2012-02-14 doi: 10.3390/membranes2010070 Junbin Shi Malcolm M. Q. Xing Wen Zhong http://www.mdpi.com/2077-0375/2/1/40 Hydrogel materials consisting of water-swollen polymer networks exhibit a large number of specific properties highly attractive for a variety of optical biosensor applications. This properties profile embraces the aqueous swelling medium as the basis of biocompatibility, non-fouling behavior, and being not cell toxic, while providing high optical quality and transparency. The present review focuses on some of the most interesting aspects of surface-attached hydrogel films as active binding matrices in optical biosensors based on surface plasmon resonance and optical waveguide mode spectroscopy. In particular, the chemical nature, specific properties, and applications of such hydrogel surface architectures for highly sensitive affinity biosensors based on evanescent wave optics are discussed. The specific class of responsive hydrogel systems, which can change their physical state in response to externally applied stimuli, have found large interest as sophisticated materials that provide a complex behavior to hydrogel-based sensing devices. http://www.mdpi.com/2077-0375/2/1/40 Wed, 08 Feb 2012 00:00:00 CET Membranes 2012-02-08 2 1 Review 40 69 2077-0375 Thin Hydrogel Films for Optical Biosensor Applications 2012-02-08 doi: 10.3390/membranes2010040 Anca Mateescu Yi Wang Jakub Dostalek Ulrich Jonas http://www.mdpi.com/2077-0375/2/1/16 This overview aims to summarize the existing potential of “Ionogels” as a platform to develop stimuli responsive materials. Ionogels are a class of materials that contain an Ionic Liquid (IL) confined within a polymer matrix. Recently defined as “a solid interconnected network spreading throughout a liquid phase”, the ionogel therefore combines the properties of both its solid and liquid components. ILs are low melting salts that exist as liquids composed entirely of cations and anions at or around 100 °C. Important physical properties of these liquids such as viscosity, density, melting point and conductivity can be altered to suit a purpose by choice of the cation/anion. Here we provide an overview to highlight the literature thus far, detailing the encapsulation of IL and responsive materials within these polymeric structures. Exciting applications in the areas of optical and electrochemical sensing, solid state electrolytes and actuating materials shall be discussed. http://www.mdpi.com/2077-0375/2/1/16 Tue, 07 Feb 2012 00:00:00 CET Membranes 2012-02-07 2 1 Review 16 39 2077-0375 Stimuli Responsive Ionogels for Sensing Applications—An Overview 2012-02-07 doi: 10.3390/membranes2010016 Andrew Kavanagh Robert Byrne Dermot Diamond Kevin J. Fraser http://www.mdpi.com/2077-0375/2/1/1 With the objective of making advancements in the area of pro-thrombotic microparticle characterization in cardiovascular biology, we present a novel method to separate blood circulating microparticles using a membrane-based, nanopore filtration system. In this qualitative study, electron microscopy observations of these pro-thrombotic mouse microparticles, as well as mouse platelets and leukocytes obtained using a mouse inferior vena cava ligation model of deep-vein thrombosis are presented. In particular, we present mouse microparticle morphology and microstructure using SEM and TEM indicating that they appear to be mostly spherical with diameters in the 100 to 350 nm range. The nanopore filtration technique presented is focused on the development of novel methodologies to isolate and characterize blood circulating microparticles that can be used in conjunction with other methodologies. We believe that determination of microparticle size and structure is a critical step for the development of reliable assays with clinical or research application in thrombosis and it will contribute to the field of nanomedicine in thrombosis. http://www.mdpi.com/2077-0375/2/1/1 Tue, 27 Dec 2011 00:00:00 CET Membranes 2011-12-27 2 1 Article 1 15 2077-0375 Physical Characterization of Mouse Deep Vein Thrombosis Derived Microparticles by Differential Filtration with Nanopore Filters 2011-12-27 doi: 10.3390/membranes2010001 Antonio Peramo Jose A. Diaz http://www.mdpi.com/2077-0375/1/4/394 Studies on the budding yeast Saccharomyces cerevisiae have revealed that fungal plasma membranes are organized into different subdomains. One new domain termed MCC/eisosomes consists of stable punctate patches that are distinct from lipid rafts. The MCC/eisosome domains correspond to furrows in the plasma membrane that are about 300 nm long and 50 nm deep. The MCC portion includes integral membrane proteins, such as the tetraspanners Sur7 and Nce102. The adjacent eisosome includes proteins that are peripherally associated with the membrane, including the BAR domains proteins Pil1 and Lsp1 that are thought to promote membrane curvature. Genetic analysis of the MCC/eisosome components indicates these domains broadly affect overall plasma membrane organization. The mechanisms regulating the formation of MCC/eisosomes in model organisms will be reviewed as well as the role of these plasma membrane domains in fungal pathogenesis and response to antifungal drugs. http://www.mdpi.com/2077-0375/1/4/394 Tue, 13 Dec 2011 00:00:00 CET Membranes 2011-12-13 1 4 Review 394 411 2077-0375 Membrane Compartment Occupied by Can1 (MCC) and Eisosome Subdomains of the Fungal Plasma Membrane 2011-12-13 doi: 10.3390/membranes1040394 Lois M. Douglas Hong X. Wang Lifang Li James B. Konopka http://www.mdpi.com/2077-0375/1/4/354 A large number of RING finger (RNF) proteins are present in eukaryotic cells and the majority of them are believed to act as E3 ubiquitin ligases. In humans, 49 RNF proteins are predicted to contain transmembrane domains, several of which are specifically localized to membrane compartments in the secretory and endocytic pathways, as well as to mitochondria and peroxisomes. They are thought to be molecular regulators of the organization and integrity of the functions and dynamic architecture of cellular membrane and membranous organelles. Emerging evidence has suggested that transmembrane RNF proteins control the stability, trafficking and activity of proteins that are involved in many aspects of cellular and physiological processes. This review summarizes the current knowledge of mammalian transmembrane RNF proteins, focusing on their roles and significance. http://www.mdpi.com/2077-0375/1/4/354 Fri, 09 Dec 2011 00:00:00 CET Membranes 2011-12-09 1 4 Review 354 393 2077-0375 The Role of the Transmembrane RING Finger Proteins in Cellular and Organelle Function 2011-12-09 doi: 10.3390/membranes1040354 Nobuhiro Nakamura http://www.mdpi.com/2077-0375/1/4/345 Electroformation of cell-sized lipid membrane vesicles (giant vesicles, GVs), from egg yolk phosphatidylcholine, was examined varying the shape of the counter electrode. Instead of a planar ITO (indium tin oxide) electrode commonly used, platinum wire mesh was employed as a counter electrode facing lipid deposit on a planar formation electrode. The modification did not significantly alter GV formation, and many GVs of 30–50 µm, some as large as 100 µm, formed as with the standard setup, indicating that a counter electrode does not have to be a complete plane. When the counter electrode was reduced to a set of two parallel platinum wires, GV formation deteriorated. Some GVs formed, but only in close proximity to the counter electrode. Lower electric voltage with this setup no longer yielded GVs. Instead, a large onion-like multilamellar structure was observed. The deteriorated GV formation and the formation of a multilamellar structure seemed to indicate the weakened effect of the electric field on lipid deposit due to insufficient coverage with a small counter electrode. Irregular membranous objects formed by spontaneous swelling of lipid without electric voltage gradually turned into multilamellar structure upon following application of voltage. No particular enhancement of GV formation was observed when lipid deposit on a wire formation electrode was used in combination with a large planar counter electrode. http://www.mdpi.com/2077-0375/1/4/345 Thu, 24 Nov 2011 00:00:00 CET Membranes 2011-11-24 1 4 Technical Note 345 353 2077-0375 Effect of Counter Electrode in Electroformation of Giant Vesicles 2011-11-24 doi: 10.3390/membranes1040345 Yukihisa Okumura Shuuhei Oana http://www.mdpi.com/2077-0375/1/4/327 Sea-food processing wastes and underutilized species of fish are a potential source of functional and bioactive compounds. A large number of bioactive substances can be produced through enzyme-mediated hydrolysis. Suitable enzymes and the appropriate bioreactor system are needed to incubate the waste materials. Membrane separation is a useful technique to extract, concentrate, separate or fractionate the compounds. The use of membrane bioreactors to integrate a reaction vessel with a membrane separation unit is emerging as a beneficial method for producing bioactive materials such as peptides, chitooligosaccharides and polyunsaturated fatty acids from diverse seafood-related wastes. These bioactive compounds from membrane bioreactor technology show diverse biological activities such as antihypertensive, antimicrobial, antitumor, anticoagulant, antioxidant and radical scavenging properties. This review discusses the application of membrane bioreactor technology for the production of value-added functional materials from sea-food processing wastes and their biological activities in relation to health benefits. http://www.mdpi.com/2077-0375/1/4/327 Tue, 25 Oct 2011 00:00:00 CEST Membranes 2011-10-25 1 4 Review 327 344 2077-0375 Membrane Bioreactor Technology for the Development of Functional Materials from Sea-Food Processing Wastes and Their Potential Health Benefits 2011-10-25 doi: 10.3390/membranes1040327 Se-Kwon Kim Mahinda Senevirathne http://www.mdpi.com/2077-0375/1/4/314 Elucidation of membrane protein structures have been greatly hampered by difficulties in producing adequately large quantities of the functional protein and stabilizing them. A6D and A6K are promising solutions to the problem and have recently been used for the rapid production of membrane-bound G protein-coupled receptors (GPCRs). We propose that despite their short lengths, these peptides can adopt α-helical structures through interactions with micelles formed by the peptides themselves. These α-helices are then able to stabilize α-helical motifs which many membrane proteins contain. We also show that A6D and A6K can form β-sheets and appear as weak hydrogels at sufficiently high concentrations. Furthermore, A6D and A6K together in sodium dodecyl sulfate (SDS) can form expected β-sheet structures via a surprising α-helical intermediate. http://www.mdpi.com/2077-0375/1/4/314 Fri, 21 Oct 2011 00:00:00 CEST Membranes 2011-10-21 1 4 Article 314 326 2077-0375 Self-Assembling Peptide Surfactants A6K and A6D Adopt a-Helical Structures Useful for Membrane Protein Stabilization 2011-10-21 doi: 10.3390/membranes1040314 Furen Zhuang Kamila Oglęcka Charlotte A. E. Hauser http://www.mdpi.com/2077-0375/1/4/299 Hollow fiber liquid phase micro-extraction (LPME) of linear alkylbenzene sulfonates (LAS) from aqueous samples was studied. Ion pair extraction of C10, C11, C12 and C13 homologues was facilitated with trihexylamine as ion-pairing agent, using di-n-hexylether as solvent for the supported liquid membrane (SLM). Effects of extraction time, acceptor buffer concentration, stirring speed, sample volume, NaCl and humic acids were studied. At 10–50 µg L−1 linear R2-coefficients were 0.99 for C10 and C11 and 0.96 for C12. RSD was typically ~15%. Three observations were especially made. Firstly, LPME for these analytes was unusually slow with maximum enrichment observed after 15–24 h (depending on sample volume). Secondly, the enrichment depended on LAS sample concentration with 35–150 times enrichment below ~150 µg L−1 and 1850–4400 times enrichment at 1 mg L−1. Thirdly, lower homologues were enriched more than higher homologues at low sample concentrations, with reversed conditions at higher concentrations. These observations may be due to the fact that LAS and the amine counter ion themselves influence the mass transfer at the water-SLM interface. The observations on LPME of LAS may aid in LPME application to other compounds with surfactant properties or in surfactant enhanced membrane extraction of other compounds. http://www.mdpi.com/2077-0375/1/4/299 Thu, 13 Oct 2011 00:00:00 CEST Membranes 2011-10-13 1 4 Article 299 313 2077-0375 Liquid Phase Micro-Extraction of Linear Alkylbenzene Sulfonate Anionic Surfactants in Aqueous Samples 2011-10-13 doi: 10.3390/membranes1040299 Niklas Larsson Paulina Otrembska Mercedes Villar Jan Åke Jönsson http://www.mdpi.com/2077-0375/1/4/275 Silk fibroin has attracted great interest in tissue engineering because of its outstanding biocompatibility, biodegradability and minimal inflammatory reaction. In this study, two kinds of biocomposites based on regenerated silk fibroin are fabricated by electrospinning and post-treatment processes, respectively. Firstly, regenerated silk fibroin/tetramethoxysilane (TMOS) hybrid nanofibers with high hydrophilicity are prepared, which is superior for fibroblast attachment. The electrospinning process causes adjacent fibers to ‘weld’ at contact points, which can be proved by scanning electron microscope (SEM). The water contact angle of silk/tetramethoxysilane (TMOS) composites shows a sharper decrease than pure regenerated silk fibroin nanofiber, which has a great effect on the early stage of cell attachment behavior. Secondly, a novel tissue engineering scaffold material based on electrospun silk fibroin/nano-hydroxyapatite (nHA) biocomposites is prepared by means of an effective calcium and phosphate (Ca–P) alternate soaking method. nHA is successfully produced on regenerated silk fibroin nanofiber within several min without any pre-treatments. The osteoblastic activities of this novel nanofibrous biocomposites are also investigated by employing osteoblastic-like MC3T3-E1 cell line. The cell functionality such as alkaline phosphatase (ALP) activity is ameliorated on mineralized silk nanofibers. All these results indicate that this silk/nHA biocomposite scaffold material may be a promising biomaterial for bone tissue engineering. http://www.mdpi.com/2077-0375/1/4/275 Mon, 10 Oct 2011 00:00:00 CEST Membranes 2011-10-10 1 4 Article 275 298 2077-0375 Fabrication and Biocompatibility of Electrospun Silk Biocomposites 2011-10-10 doi: 10.3390/membranes1040275 Kai Wei Byoung-Suhk Kim Ick-Soo Kim http://www.mdpi.com/2077-0375/1/4/265 Cell-sized lipid bilayer membrane vesicles (giant vesicles, GVs) or semi-vesicles were formed from egg yolk phosphatidylcholine on a platinum electrode under applied electric voltage by electroformation. Micromanipulation of the semi-vesicle by first pressing its membrane with a glass microneedle and then withdrawing the needle left a GV in the interior of the vesicle. During the process, an aqueous solution of Ficoll that filled the needle was introduced into the newly formed inner vesicle and remained encapsulated. Approximately 50% of attempted micromanipulation resulted in the formation of an inner daughter vesicle, “microvesiculation”. By repeating the microvesiculation process, multiple inner GVs could be formed in a single parent semi-vesicle. A semi-vesicle with inner GVs could be detached from the electrode by scraping with a microneedle, yielding an oligovesicular vesicle (OVV) with desired inner aqueous contents. Microvesiculation of a GV held on the tip of a glass micropipette was also possible, and this also produced an OVV. Breaking the membrane of the parent semi-vesicle by micromanipulation with a glass needle after microvesiculation, released the inner GVs. This protocol may be used for controlled formation of GVs with desired contents. http://www.mdpi.com/2077-0375/1/4/265 Mon, 26 Sep 2011 00:00:00 CEST Membranes 2011-09-26 1 4 Article 265 274 2077-0375 Formation of Oligovesicular Vesicles by Micromanipulation 2011-09-26 doi: 10.3390/membranes1040265 Yukihisa Okumura Tohru Ohmiya Toshiki Yamazaki http://www.mdpi.com/2077-0375/1/3/249 Electrospinning is a versatile method for forming continuous thin fibers based on an electrohydrodynamic process. This method has the following advantages: (i) the ability to produce thin fibers with diameters in the micrometer and nanometer ranges; (ii) one-step forming of the two- or three-dimensional nanofiber network assemblies (nanofibrous membranes); and (iii) applicability for a broad spectrum of molecules, such as synthetic and biological polymers and polymerless sol-gel systems. Electrospun nanofibrous membranes have received significant attention in terms of their practical applications. The major advantages of nanofibers or nanofibrous membranes are the functionalities based on their nanoscaled-size, highly specific surface area, and highly molecular orientation. These functionalities of the nanofibrous membranes can be controlled by their fiber diameter, surface chemistry and topology, and internal structure of the nanofibers. This report focuses on our studies and describes fundamental aspects and applications of electrospun nanofibrous membranes. http://www.mdpi.com/2077-0375/1/3/249 Fri, 26 Aug 2011 00:00:00 CEST Membranes 2011-08-26 1 3 Review 249 264 2077-0375 Functionality in Electrospun Nanofibrous Membranes Based on Fiber’s Size, Surface Area, and Molecular Orientation 2011-08-26 doi: 10.3390/membranes1030249 Hidetoshi Matsumoto Akihiko Tanioka http://www.mdpi.com/2077-0375/1/3/232 In recent decades, engineered membranes have become a viable separation technology for a wide range of applications in environmental, food and biomedical fields. Membranes are now competitive compared to conventional techniques such as adsorption, ion exchangers and sand filters. The main advantage of membrane technology is the fact that it works without the addition of any chemicals, with relatively high efficiency and low energy consumption with well arranged process conductions. Hence they are widely utilized in biotechnology, food and drink manufacturing, air filtration and medical uses such as dialysis for kidney failure patients. Membranes from nanofibrous materials possess high surface area to volume ratio, fine tunable pore sizes and their ease of preparation prompted both industry and academic researchers to study their use in many applications. In this paper, modern concepts and current research progress on various nanofibrous membranes, such as water and air filtration media, are presented. http://www.mdpi.com/2077-0375/1/3/232 Mon, 22 Aug 2011 00:00:00 CEST Membranes 2011-08-22 1 3 Review 232 248 2077-0375 Recent Trends in Nanofibrous Membranes and Their Suitability for Air and Water Filtrations 2011-08-22 doi: 10.3390/membranes1030232 Ramalingam Balamurugan Subramanian Sundarrajan Seeram Ramakrishna http://www.mdpi.com/2077-0375/1/3/217 Nickel (II) preconcentration and speciation analysis using a hollow fiber supported liquid membrane (HFSLM) device was studied. A counterflow of protons coupled to complexation with formate provided the driving force of the process, while Kelex 100 was employed as carrier. The influence of variables related to module configuration (acceptor pH and carrier concentration) and to the sample properties (donor pH) on the preconcentration factor, E, was simultaneously studied and optimized using a 3 factor Doehlert matrix response surface methodology. The effect of metal concentration was studied as well. Preconcentration factors as high as 4240 were observed  depending on the values of the different variables. The effects of the presence of inorganic anions (NO2-, SO42-, Cl-, NO3-, CO32-, CN-) and dissolved organic matter (DOM) in the form of humic acids were additionally considered in order to carry out a speciation analysis study. Nickel preconcentration was observed to be independent of both effects, except when cyanide was present in the donor phase. A characterization of the transport regime was performed through the analysis of the dependence of E on the temperature. E increases with the increase in temperature according to the equation E(K) = -8617.3 + 30.5T with an activation energy of 56.7 kJ mol-1 suggesting a kinetic-controlled regime. Sample depletion ranged from 12 to 1.2% depending on the volume of the donor phase (100 to 1000 mL, respectively). http://www.mdpi.com/2077-0375/1/3/217 Thu, 18 Aug 2011 00:00:00 CEST Membranes 2011-08-18 1 3 Article 217 231 2077-0375 Nickel (II) Preconcentration and Speciation Analysis During Transport from Aqueous Solutions Using a Hollow-fiber Permeation Liquid Membrane (HFPLM) Device 2011-08-18 doi: 10.3390/membranes1030217 Ana Nelly Bautista-Flores Eduardo Rodríguez De San Miguel Josefina de Gyves Jan Åke Jönsson http://www.mdpi.com/2077-0375/1/3/195 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. http://www.mdpi.com/2077-0375/1/3/195 Wed, 10 Aug 2011 00:00:00 CEST Membranes 2011-08-10 1 3 Article 195 216 2077-0375 Monitoring Protein Fouling on Polymeric Membranes Using Ultrasonic Frequency-Domain Reflectometry 2011-08-10 doi: 10.3390/membranes1030195 Elmira Kujundzic Alan R. Greenberg Robin Fong Mark Hernandez http://www.mdpi.com/2077-0375/1/3/184 Electroformation of cell-sized lipid membrane vesicles (giant vesicles, GVs) from egg yolk phosphatidylcholine under applied electric voltage was examined on a substrate of a polymer mesh placed between two planar indium tin oxide coated glass electrodes. Under appropriate conditions, GVs were formed in good yield on meshes of various polymer materials, namely, hydrophobic poly(propylene), poly(ethylene terephthalate), a carbon fiber/nylon composite, and relatively hydrophilic nylon. Arranging threads in a mesh structure with appropriate openings improved GV formation compared to simply increasing the number of threads. For optimal electroformation of GVs, the size and shape of a mesh opening were crucial. With a too large opening, GV formation deteriorated. When the sides of an opening were partially missing, GV formation did not occur efficiently. With an adequate opening, a deposited lipid solution could fill the opening, and a relatively uniform lipid deposit formed on the surface of threads after evaporation of the solvent. This could supply a sufficient amount of lipids to the opening and also prevent a lipid deposit from becoming too thick for electroformation. As a result, good GV formation was often observed in openings filled with swelled lipid. http://www.mdpi.com/2077-0375/1/3/184 Fri, 15 Jul 2011 00:00:00 CEST Membranes 2011-07-15 1 3 Article 184 194 2077-0375 Electroformation of Giant Vesicles on a Polymer Mesh 2011-07-15 doi: 10.3390/membranes1030184 Yukihisa Okumura Takuya Sugiyama http://www.mdpi.com/2077-0375/1/3/162 A frontier to be conquered in the field of membrane technology is related to the very limited scientific base for the rational and task-specific design of membranes. This is especially true for nanofiltration membranes with properties that are based on several solute-membrane interaction mechanisms. “Thinking in terms of Structure-Activity-Relationships” (T-SAR) is a methodology which applies a systematic analysis of a chemical entity based on its structural formula. However, the analysis become more complex with increasing size of the molecules considered. In this study, T-SAR was combined with classical membrane characterization methods, resulting in a new methodology which allowed us not only to explain membrane characteristics, but also provides evidence for the importance of the chemical structure for separation performance. We demonstrate an application of the combined approach and its potential to discover stereochemistry, molecular interaction potentials, and reactivity of two FilmTec nanofiltration membranes (NF-90 and NF-270). Based on these results, it was possible to predict both properties and performance in the recovery of hydrophobic ionic liquids from aqueous solution. http://www.mdpi.com/2077-0375/1/3/162 Fri, 15 Jul 2011 00:00:00 CEST Membranes 2011-07-15 1 3 Article 162 183 2077-0375 Thinking in Terms of Structure-Activity-Relationships (T-SAR): A Tool to Better Understand Nanofiltration Membranes 2011-07-15 doi: 10.3390/membranes1030162 José F. Fernández Bernd Jastorff Reinhold Störmann Stefan Stolte Jorg Thöming http://www.mdpi.com/2077-0375/1/3/149 The objective of the study was to compare the antioxidant activity of two distinct hydrolysates and their peptide fractions prepared by ultrafiltration (UF) using membranes with molecular weight cut-off of 5 and 1 kDa. The hydrolysates were a delipidated egg yolk protein concentrate (EYP) intensively hydrolyzed with a combination of two bacterial proteases, and a phosphoproteins (PPP) extract partially hydrolyzed with trypsin. Antioxidant activity, as determined by the oxygen radical absorbance capacity (ORAC) assay, was low for EYP and PPP hydrolysates with values of 613.1 and 489.2 µM TE×g−1 protein, respectively. UF-fractionation of EYP hydrolysate increased slightly the antioxidant activity in permeate fractions (720.5–867.8 µM TE×g−1 protein). However, ORAC values were increased by more than 3-fold in UF-fractions prepared from PPP hydrolysate, which were enriched in peptides with molecular weight lower than 5 kDa. These UF-fractions were characterized by their lower N/P atomic ratio and higher phosphorus content compared to the same UF-fractions obtained from EYP-TH. They also contained high amounts of His, Met, Leu, and Phe, which are recognized as antioxidant amino acids, but also high content in Lys and Arg which both represent target amino acids of trypsin used for the hydrolysis of PPP. http://www.mdpi.com/2077-0375/1/3/149 Wed, 06 Jul 2011 00:00:00 CEST Membranes 2011-07-06 1 3 Article 149 161 2077-0375 Comparative Composition and Antioxidant Activity of Peptide Fractions Obtained by Ultrafiltration of Egg Yolk Protein Enzymatic Hydrolysates 2011-07-06 doi: 10.3390/membranes1030149 Bertrand P. Chay Pak Ting Yoshinori Mine Lekh R. Juneja Tsutomu Okubo Sylvie F. Gauthier Yves Pouliot http://www.mdpi.com/2077-0375/1/2/132 Electrochemical impedance spectroscopy (EIS) has been used to estimate the non-frequency dependent (static) dielectric constants of base polymers such as poly(vinyl chloride) (PVC), cellulose triacetate (CTA) and polystyrene (PS). Polymer inclusion membranes (PIMs) containing different amounts of PVC or CTA, along with the room temperature ionic liquid Aliquat 336 and plasticizers such as trisbutoxyethyl phosphate (TBEP), dioctyl sebecate (DOS) and 2-nitrophenyloctyl ether (NPOE) have been investigated. In this study, the complex and abstract method of EIS has been applied in a simple and easy to use way, so as to make the method accessible to membrane scientists and engineers who may not possess the detailed knowledge of electrochemistry and interfacial science needed for a rigorous interpretation of EIS results. The EIS data reported herein are internally consistent with a percolation threshold in the dielectric constant at high concentrations of Aliquat 336, which illustrates the suitability of the EIS technique since membrane percolation with ion exchangers is a well-known phenomenon. http://www.mdpi.com/2077-0375/1/2/132 Thu, 23 Jun 2011 00:00:00 CEST Membranes 2011-06-23 1 2 Article 132 148 2077-0375 Electrochemical Impedance Spectroscopy—A Simple Method for the Characterization of Polymer Inclusion Membranes Containing Aliquat 336 2011-06-23 doi: 10.3390/membranes1020132 Michelle O’Rourke Noel Duffy Roland De Marco Ian Potter http://www.mdpi.com/2077-0375/1/2/119 Sintered stainless steel (SSS) microfiltration membranes, which served as electrode directly, were used for the experiment of separating Alamin, a calcium salt and protein containing particles, found in dairy processing. Fouling and cleaning of the SSS membranes under the application of an external electric field were studied. The imposed electric field was found, diverging the pH of permeate and retentate. This in turn altered the solubility of the calcium salt and impacted the performance of electro microfiltration membrane. Using electric field as an enhanced cleaning-in-place (CIP) method in back flushing SSS membrane was also studied. http://www.mdpi.com/2077-0375/1/2/119 Mon, 30 May 2011 00:00:00 CEST Membranes 2011-05-30 1 2 Article 119 131 2077-0375 Experimental Study of Fouling and Cleaning of Sintered Stainless Steel Membrane in Electro-Microfiltration of Calcium Salt Particles 2011-05-30 doi: 10.3390/membranes1020119 Frank G. F. Qin John Mawson Xin An Zeng http://www.mdpi.com/2077-0375/1/2/109 Electroformation of cell-sized lipid membrane vesicles (giant vesicles, GVs) from egg yolk phosphatidylcholine was examined using a poly(ethylene terephthalate) sheet coated with indium tin oxide (ITO-PET) as the electrode material. With sinusoidal ac voltage, GV formation occurred in a similar manner to that on an ITO-glass electrode widely used in electroformation. Difference in the specific electrical resistance of ITO-PET did not significantly affect electroformation. The present results indicate that ITO-PET may be used as more flexible and less expensive electrode material in electroformation. In order to obtain insights into electroformation, other electric voltage forms, static dc and dc pulses, were also tested in place of commonly used sinusoidal ac. Under the present conditions, the best GV formation was observed with dc pulses of negative polarity. The result with static dc demonstrated that the mechanical vibration of swelling lipid seen with sinusoidal ac voltage was not essential for GV formation. On the positive electrode, the electroswelling of lipid mainly yielded non-spherical membranous objects. Pre-application of positive dc voltage on lipid hindered GV formation in electroswelling of the lipid with ac. http://www.mdpi.com/2077-0375/1/2/109 Thu, 26 May 2011 00:00:00 CEST Membranes 2011-05-26 1 2 Article 109 118 2077-0375 Electroformation of Giant Vesicles on Indium Tin Oxide (ITO)-Coated Poly(ethylene terephthalate) (PET) Electrodes 2011-05-26 doi: 10.3390/membranes1020109 Yukihisa Okumura Yuuichi Iwata http://www.mdpi.com/2077-0375/1/2/98 Biodegradable polymers have attracted much attention from an environmental point of view. Optically pure lactic acid that can be prepared by fermentation is one of the important raw materials for biodegradable polymer. The separation and purification of lactic acid from the fermentation broth are the major portions of the production costs. We proposed the application of supported ionic liquid membranes to recovering lactic acid. In this paper, the effect of ionic liquids, such as Aliquat 336, CYPHOS IL-101, CYPHOS IL-102, CYPHOS IL-104, CYPHOS IL-109 and CYPHOS IL-111 on the lactic acid permeation have been studied. Aliquat 336, CYPHOS IL-101 and CYPHOS IL-102 were found to be the best membrane solvents as far as membrane stability and permeation of lactic acid are concerned. CYPHOS IL-109 and CYPHOS IL-111 were found to be unsuitable, as they leak out from the pores of the supported liquid membrane (SLM), thereby allowing free transport of lactic acid as well as hydrochloric acid. CYPHOS IL-102 was found to be the most adequate (Permeation rate = 60.41%) among these ionic liquids as far as the separation of lactic acid is concerned. The permeation mechanisms, by which ionic liquid-water complexes act as the carrier of lactate and hydrochloric acid, were proposed. The experimental permeation results have been obtained as opposed to the expected values from the solution-diffusion mechanism. http://www.mdpi.com/2077-0375/1/2/98 Fri, 13 May 2011 00:00:00 CEST Membranes 2011-05-13 1 2 Article 98 108 2077-0375 Effect of Ammonium- and Phosphonium-Based Ionic Liquids on the Separation of Lactic Acid by Supported Ionic Liquid Membranes (SILMs) 2011-05-13 doi: 10.3390/membranes1020098 Michiaki Matsumoto Abhishek Panigrahi Yuuki Murakami Kazuo Kondo http://www.mdpi.com/2077-0375/1/2/91 Several microscopic and scattering techniques at different observation scales (from atomic to macroscopic) were used to characterize both surface and bulk properties of four new flat-sheet polyethersulfone (PES) membranes (10, 30, 100 and 300 kDa) and new 100 kDa hollow fibers (PVDF). Scanning Electron Microscopy (SEM) with “in lens” detection was used to obtain information on the pore sizes of the skin layers at the atomic scale. White Light Interferometry (WLI) and Atomic Force Microscopy (AFM) using different scales (for WLI: windows: 900 × 900 µm2 and 360 × 360 µm2; number of points: 1024; for AFM: windows: 50 × 50 µm2 and 5 × 5 µm2; number of points: 512) showed that the membrane roughness increases markedly with the observation scale and that there is a continuity between the different scan sizes for the determination of the RMS roughness. High angular resolution ellipsometric measurements were used to obtain the signature of each cut-off and the origin of the scattering was identified as coming from the membrane bulk. http://www.mdpi.com/2077-0375/1/2/91 Wed, 13 Apr 2011 00:00:00 CEST Membranes 2011-04-13 1 2 Article 91 97 2077-0375 Membrane Characterization by Microscopic and Scattering Methods: Multiscale Structure 2011-04-13 doi: 10.3390/membranes1020091 Rahma Tamime Yvan Wyart Laure Siozade Isabelle Baudin Carole Deumie Karl Glucina Philippe Moulin http://www.mdpi.com/2077-0375/1/1/80 Petroleum transformation industries have applied membrane processes for solvent and hydrocarbon recovery as an economic alternative to reduce their emissions and reuse evaporated components. Separation of the volatile organic compounds (VOCs) (toluene-propylene-butadiene) from air was performed using a poly dimethyl siloxane (PDMS)/α-alumina membrane. The experimental set-up followed the constant pressure/variable flow set-up and was operated at ~21 °C. The membrane is held in a stainless steel module and has a separation area of 55 × 10−4 m². Feed stream was set to atmospheric pressure and permeate side to vacuum between 3 and 5 mbar. To determine the performance of the module, the removed fraction of VOC was analyzed by Gas Chromatography/Flame Ionization Detector (GC/FID). The separation of the binary, ternary and quaternary hydrocarbon mixtures from air was performed at different flow rates and more especially at low concentrations. The permeate flux, permeance, enrichment factor, separation efficiency and the recovery extent of the membrane were determined as a function of these operating conditions. The permeability coefficients and the permeate flux through the composite PDMS-alumina membrane follow the order given by the Hildebrand parameter: toluene > 1,3-butadiene > propylene. The simulated data for the binary VOC/air mixtures showed fairly good agreement with the experimental results in the case of 1,3-butadiene and propylene. The discrepancies observed for toluene permeation could be minimized by taking into account the effects of the porous support and an influence of the concentration polarization. Finally, the installation of a 0.02 m2 membrane module would reduce 95% of the VOC content introduced at real concentration conditions used in the oil industry. http://www.mdpi.com/2077-0375/1/1/80 Thu, 03 Mar 2011 00:00:00 CET Membranes 2011-03-03 1 1 Article 80 90 2077-0375 Volatile Organic Compound (VOC) Removal by Vapor Permeation at Low VOC Concentrations: Laboratory Scale Results and Modeling for Scale Up 2011-03-03 doi: 10.3390/membranes1010080 Georgette Rebollar-Perez Emilie Carretier Nicolas Lesage Philippe Moulin http://www.mdpi.com/2077-0375/1/1/70 The use of membrane reactors for enzymatic and co-factor regenerating reactions offers versatile advantages such as higher conversion rates and space-time-yields and is therefore often applied in industry. However, currently available screening and kinetics characterization systems are based on batch and fed-batch operated reactors and were developed for whole cell biotransformations rather than for enzymatic catalysis. Therefore, the data obtained from such systems has only limited transferability for continuous membrane reactors. The aim of this study is to evaluate and to improve a novel screening and characterization system based on the membrane reactor concept using the enzymatic hydrolysis of cellulose as a model reaction. Important aspects for the applicability of the developed system such as long-term stability and reproducibility of continuous experiments were very high. The concept used for flow control and fouling suppression allowed control of the residence time with a high degree of precision (±1% accuracy) in a long-term study (>100 h). http://www.mdpi.com/2077-0375/1/1/70 Fri, 25 Feb 2011 00:00:00 CET Membranes 2011-02-25 1 1 Article 70 79 2077-0375 Continuous Membrane-Based Screening System for Biocatalysis 2011-02-25 doi: 10.3390/membranes1010070 Evgenij Lyagin Anja Drews Subhamoy Bhattacharya Matthias Kraume http://www.mdpi.com/2077-0375/1/1/59 Downward and upward ultrafiltration (UF) was performed using the suspensions of nanosized colloidal silica with different particle diameters and their filtration rates were compared. In downward UF, the filtration rate decreases as the particle diameter decreases because the specific filtration resistance of the filter cake becomes significantly higher. In contrast, the filtration rate in upward UF increases with the decrease in the particle diameter because the filter cake consisting of small particles is exfoliated much more easily under the influence of gravity than that of large ones. In order to evaluate the characteristics of the filter cake exfoliation, the steady filtration rate in the upward mode was measured. The steady filtration rate has a tendency to decrease with particle concentration as well as mean particle diameter. Therefore, when the small particles are added into a given concentration of large particle suspension, the mean particle diameter decreases and the total particle concentration increases due to the dosage of small particles. This results in a maximum of the steady filtration rate at a certain dosage of small particles. Moreover, an estimation equation was proposed for predicting the steady filtration rate in upward UF of colloidal silica suspensions with various mean particle diameters and total particle concentrations. http://www.mdpi.com/2077-0375/1/1/59 Thu, 20 Jan 2011 00:00:00 CET Membranes 2011-01-20 1 1 Article 59 69 2077-0375 Characteristics of Filter Cake Exfoliation in Upward Ultrafiltration of Nanoparticle Suspensions 2011-01-20 doi: 10.3390/membranes1010059 Yasuhito Mukai Aya Nishio http://www.mdpi.com/2077-0375/1/1/48 Membrane distillation (MD) was applied for the concentration of a range of dairy streams, such as whole milk, skim milk and whey. MD of a pure lactose solution was also investigated. Direct contact MD (DCMD) mode experiments were carried out in continuous concentration mode, keeping the warm feed/retentate and cold permeate stream temperatures at 54 °C and 5 °C respectively. Performance in terms of flux and retention was assessed. The flux was found to decrease with an increase of dry-matter concentration in the feed. Retention of dissolved solids was found to be close to 100% and independent of the dry-matter concentration in the feed. Fourier Transform Infrared Spectroscopy (FTIR) of the fouled membranes confirms organics being present in the fouling layer. http://www.mdpi.com/2077-0375/1/1/48 Tue, 04 Jan 2011 00:00:00 CET Membranes 2011-01-04 1 1 Article 48 58 2077-0375 Direct Contact Membrane Distillation of Dairy Process Streams 2011-01-04 doi: 10.3390/membranes1010048 Angela Hausmann Peter Sanciolo Todor Vasiljevic Elankovan Ponnampalam Nohemi Quispe-Chavez Mike Weeks Mikel Duke http://www.mdpi.com/2077-0375/1/1/37 Carbon nanotubes are attractive approach for designing of new membranes for advanced molecular separation because of their unique transport properties and ability to mimic biological protein channels. In this work the synthetic approach for fabrication of carbon nanotubes (CNTs) composite membranes is presented. The method is based on growth of multi walled carbon nanotubes (MWCNT) using chemical vapour deposition (CVD) on the template of nanoporous alumina (PA) membranes. The influence of experimental conditions including carbon precursor, temperature, deposition time, and PA template on CNT growth process and quality of fabricated membranes was investigated. The synthesis of CNT/PA composites with controllable nanotube dimensions such as diameters (30–150 nm), and thickness (5–100 µm), was demonstrated. The chemical composition and morphological characteristics of fabricated CNT/PA composite membranes were investigated by various characterisation techniques including scanning electron microscopy (SEM), energy-dispersive x-ray spectroscopy (EDXS), high resolution transmission electron microscopy (HRTEM) and x-ray diffraction (XRD). Transport properties of prepared membranes were explored by diffusion of dye (Rose Bengal) used as model of hydrophilic transport molecule. http://www.mdpi.com/2077-0375/1/1/37 Mon, 27 Dec 2010 00:00:00 CET Membranes 2010-12-27 1 1 Article 37 47 2077-0375 Synthesis of Carbon Nanotube (CNT) Composite Membranes 2010-12-27 doi: 10.3390/membranes1010037 Tariq Altalhi Milena Ginic-Markovic Ninghui Han Stephen Clarke Dusan Losic http://www.mdpi.com/2077-0375/1/1/25 Membranes are crucial in modern industry and both new technologies and materials need to be designed to achieve higher selectivity and performance. Exotic materials such as nanoparticles offer promising perspectives, and combining both their very high specific surface area and the possibility to incorporate them into macrostructures have already shown to substantially increase the membrane performance. In this paper we report on the fabrication and engineering of metal-reinforced carbon nanotube (CNT) Bucky-Paper (BP) composites with tuneable porosity and surface pore size. A BP is an entangled mesh non-woven like structure of nanotubes. Pure CNT BPs present both very high porosity (>90%) and specific surface area (>400 m2/g). Furthermore, their pore size is generally between 20–50 nm making them promising candidates for various membrane and separation applications. Both electro-plating and electroless plating techniques were used to plate different series of BPs and offered various degrees of success. Here we will report mainly on electroless plated gold/CNT composites. The benefit of this method resides in the versatility of the plating and the opportunity to tune both average pore size and porosity of the structure with a high degree of reproducibility. The CNT BPs were first oxidized by short UV/O3 treatment, followed by successive immersion in different plating solutions. The morphology and properties of these samples has been investigated and their performance in air permeation and gas adsorption will be reported. http://www.mdpi.com/2077-0375/1/1/25 Tue, 21 Dec 2010 00:00:00 CET Membranes 2010-12-21 1 1 Article 25 36 2077-0375 Control of Porosity and Pore Size of Metal Reinforced Carbon Nanotube Membranes 2010-12-21 doi: 10.3390/membranes1010025 Ludovic Dumee Leonora Velleman Kallista Sears Matthew Hill Jurg Schutz Niall Finn Mikel Duke Stephen Gray http://www.mdpi.com/2077-0375/1/1/13 Cross-flow ultrafiltration of macromolecular solutions in a module with microchannels is expected to have the advantages of fast diffusion from the membrane surface and a high ratio of membrane surface area to feed liquid volume. Cross-flow ultrafiltration modules with microchannels are expected to be used for separation and refining and as membrane reactors in microchemical processes. Though these modules can be applied as a separator connected with a micro-channel reactor or a membrane reactor, there have been few papers on their performance. The purpose of this study was to clarify the relationship between operational conditions and performance of cross-flow ultrafiltration devices with microchannels. In this study, Poly Vinyl Pyrrolidone (PVP) aqueous solution was used as a model solute of macromolecules such as enzymes. Cross-flow ultrafiltration experiments were carried out under constant pressure conditions, varying other operational conditions. The permeate flux decreased in the beginning of each experiment. After enough time passed, the permeate flux reached a constant value. The performance of the module was discussed based on the constant values of the flux. It was observed that the permeate flux increased with increasing transmembrane pressure (TMP) and feed flow rate, and decreased with an increase of feed liquid concentration. A model of the transport phenomena in the feed liquid side channel and the permeation through the membrane was developed based on the concentration and velocity distributions in the feed side channel. The experimental results were compared with those based on the model and the performance of the ultrafiltration module is discussed. http://www.mdpi.com/2077-0375/1/1/13 Thu, 16 Dec 2010 00:00:00 CET Membranes 2010-12-16 1 1 Article 13 24 2077-0375 A Model for Transport Phenomena in a Cross-Flow Ultrafiltration Module with Microchannels 2010-12-16 doi: 10.3390/membranes1010013 Aiko Nishimoto Shiro Yoshikawa Shinichi Ookawara http://www.mdpi.com/2077-0375/1/1/3 In this study, a chitosan substrate was modified by simulated body fluid (SBF) treatment, in which the effect of the chosen crosslinking agent was investigated. Two crosslinking agents, glutaraldehyde (GA) and sodium tripolyphosphate (TPP), were used before the SBF process. By using TPP as the crosslinking agent, the Ca/P ratio and the degree of crystallinity were very close to the natural bone matrix. On the contrary, the substrate properties were very different from natural bone when the crosslinking agent GA was used. The results indicate that the produced substrates were  biomimetic when the TPP was applied. On the SBF-modified chitosan substrates with TPP crosslinking, the cultured osteoblastic cells expressed better proliferation, mitochondria activity and differentiation ability. The chitosan crosslinked using TPP was a good template in the SBF process, which resulted in a highly biomimetic layer. This biomimetic substrate possesses excellent biocompatibility and osteoconduction ability, promising high potential in the promotion of bone tissue engineering. http://www.mdpi.com/2077-0375/1/1/3 Wed, 15 Dec 2010 00:00:00 CET Membranes 2010-12-15 1 1 Article 3 12 2077-0375 The Fabrication of Biomimetic Chitosan Scaffolds by Using SBF Treatment with Different Crosslinking Agents 2010-12-15 doi: 10.3390/membranes1010003 Chung-Tun Liao Ming-Hua Ho http://www.mdpi.com/2077-0375/1/1/1 Membrane separation, from its infancy as a predominantly laboratory technique in the middle of the last century, has advanced with remarkable speed and now underpins a range of mature industrial technologies. [...] http://www.mdpi.com/2077-0375/1/1/1 Sun, 12 Dec 2010 00:00:00 CET Membranes 2010-12-12 1 1 Editorial 1 2 2077-0375 Welcome to Membranes — A New Open Access Journal on Membrane Separation and Technology 2010-12-12 doi: 10.3390/membranes1010001 Spas D. Kolev