Home About us Contact
|
Home About us Contact | ||
|
|
||
Membrane Used (membrane + used)
Selected AbstractsMembrane bioreactors: overview of the effects of module geometry on mixing energyASIA-PACIFIC JOURNAL OF CHEMICAL ENGINEERING, Issue 3 2009Yuan Wang Abstract Membranes used in municipal membrane bioreactor (MBR) plants can be configured as flat sheet (FS) membranes or hollow fibre (HF) membranes. The HFs can be mounted either horizontally or vertically. The membranes can be immersed in their own vessel or within the aerobic vessel. These various configurations combine to give a unique reactor design. Current methods of design assume the mixing characteristics (e.g. each reactor vessel is completely mixed); hence the energy necessary to achieve complete mixing cannot be optimised. This paper presents an overview of mixing studies undertaken by the authors' research group on pilot- and full-scale MBRs through residence time distribution (RTD) analysis and computational fluid dynamics (CFD) modelling. The drawbacks of current technique for the sizing of MBRs (e.g. compartmental modelling) are highlighted. The use of CFD as a design tool to evaluate the mixing and energy of MBRs with different configurations (e.g. HF vs FS, inside submerged vs outside submerged) is presented. The MBR CFD model was validated using field-measured RTD data and compared with compartmental model. Results from mixing studies suggest that HF membranes are more energy efficient in terms of creating completely mixed conditions than the FS membranes. Copyright © 2009 Curtin University of Technology and John Wiley & Sons, Ltd. [source] Skin Repair Using a Porcine Collagen I/III Membrane,Vascularization and Epithelization PropertiesDERMATOLOGIC SURGERY, Issue 6 2010FALK WEHRHAN MD BACKGROUND Collagen membranes have been developed to overcome the problem of limited availability of skin grafts. Vascularization and restricted functional epithelization limit the success of bioartificial constructs. OBJECTIVE To compare the vascularization, epithelization, and integration of a porcine collagen I/III membrane with that of split-thickness skin grafts on skin wounds. MATERIALS AND METHODS In 21 adult pigs, full-thickness skin defects on the rear side of the ear healed by split-thickness skin grafting, by covering with the membrane, or by free granulation. Skin samples on postoperative days 1, 3, 7, 14, 21, and 28 were evaluated histologically (hematoxylin-eosin, Sirius Red) and using immunohistochemistry (cytokeratin 5/6, transforming growth factor beta receptor (TGF,R-III) and immunoblot (TGF,1,3, Smad2/3). Epithelial thickness and TGF,R-III-positive capillary area were quantitatively assessed. RESULTS Epithelization and vascularization in the membrane group were not significantly different from in the group treated with a split-thickness skin graft. Free granulation showed significantly slower epithelization and vascularization (p<.05). TGF,1 and Smad2/3 complex expression were high during free granulation. Matrix was distinguishable until day 7. CONCLUSIONS This membrane serves as a suitable full-thickness dermal substitute, because the membrane is vascularized faster than free granulation tissue and enables early epithelization. Geistlich Biomaterials (Wolhusen, Switzerland) provided the collagen membrane used in this study [source] Determination of the operational pH value of a buffering membrane by an isoelectric trapping separation of a carrier ampholyte mixtureELECTROPHORESIS, Issue 5 2008Robert Y. North Abstract The operational pH value of a buffering membrane used in an isoelectric trapping separation is determined by installing the membrane as the separation membrane into a multicompartmental electrolyzer operated in the two-separation compartment configuration. A 3 Effect of addition of organic microspheres on proton conductivity property of sulfonated poly(arylene ether sulfone) membraneJOURNAL OF APPLIED POLYMER SCIENCE, Issue 6 2008Cui Liang Abstract Sulfonated poly(arylene ether sulfone) (SPAES)/polystyrene(PS) and SPAES/polystyrene sulfonic acid (PSSA) composite membranes were studied for a proton-exchange membrane used in a fuel cell. PS microspheres were synthesized by emulsion polymerization. PSSA microspheres with 5.3 mmol/g ion-exchange capacity (IEC) were prepared by sulfonation of PS microspheres. The composite membranes were prepared by solution casting. SPAES/PSSA composite membranes showed higher proton conductivity than a SPAES membrane because of the IEC improved by adding PSSA. Although the addition of PSSA also brought about the increase of a methanol permeability, the proton/methanol selectivity defined as the ratio of the proton conductivity to the methanol permeability was improved at low humidity by adding 5 wt % of PSSA microspheres. Differential scanning calorimetry results indicated that the amount of free water varied in the cases of the addition of the two kinds of organic microspheres. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 [source] The Effect of Preparation Procedures on the Morphology of Melanin from the Ink Sac of Sepia officinalisPIGMENT CELL & MELANOMA RESEARCH, Issue 1 2003Yan Liu The structure of melanin extracted from the ink sac of the cuttlefish Sepia officinalis was examined for different methods of isolation and purification of the pigment. Scanning electron microscopy (SEM) images of Sepia eumelanin prepared by different procedures establish that multi-,m-sized aggregates reported by previous workers are generated by their sample preparation, and that the dominant constituents of Sepia melanin are ,150 nm spherical granules. Brunauer-Emmett-Teller (BET) measurements reveal that Sepia eumelanin from Sigma (prepared by spray drying the pigment) has a surface area of 14.3 m2/g. Pigment extracted directly from the fresh ink sac and then freeze-dried has a surface area of 21.5 m2/g, while CO2 -supercritically dried has a surface area of 37.5 m2/g. This is consistent with SEM images showing that the process of freeze-drying produces aggregates, but to a lesser extent than spray drying. Supercritical drying of the sample produces suspensions of the individual ,150 nm granule, which is more reflective of the natural pigment. Brunauer-Emmett-Teller surface area analysis and Barrett-Joyner-Halenda (BJH) pore volume analysis indicate that the surface of the granules is not smooth and the interior of the granules is not porous, but rather the aggregates of granules are porous. Ultra-high resolution SEM and atomic force microscopy (AFM) images show the granules are easily deformed and are comprised of smaller constituents. De-aggregation of the granules by sonication and ultra-filtration reveal a range of structures depending on the pore size of the membrane used. The implications of these results on quantifying photochemical properties and kinetic reaction rate constants of melanin are discussed. [source] Influence of Different Hemodialysis Membranes on Red Blood Cell Susceptibility to Oxidative StressARTIFICIAL ORGANS, Issue 1 2000Leonardo Lucchi Abstract: Oxidative stress is crucial in red blood cell (RBC) damage induced by activated neutrophils in in vitro experiments. The aim of the study was to evaluate whether the bioincompatibility phenomena occurring during hemodialysis (HD) (where neutrophil activation with increased free radical production is well documented) may have detrimental effects on RBC. We evaluated RBC susceptibility to oxidative stress before and after HD in 15 patients using Cuprophan, cellulose triacetate, and polysulfone membrane. RBC were incubated with t-butyl hydroperoxide as an oxidizing agent both in the presence and in the absence of the catalase inhibitor sodium azide. The level of malonaldehyde (MDA), a product of lipid peroxidation, was measured at 0, 5, 10, 15, and 30 min of incubation. When Cuprophan membrane was used, the MDA production was significantly higher after HD, indicating an increased susceptibility to oxidative stress in comparison to pre-HD. The addition of sodium azide enhanced this phenomenon. Both cellulose triacetate and polysulfone membranes did not significantly influence RBC susceptibility to oxidative stress. Neither the level of RBC reduced glutathione nor the RBC glutathione redox ratio changed significantly during HD with any of the membranes used. The RBC susceptibility to oxidative stress was influenced in different ways according to the dialysis membrane used, being increased only when using the more bioincompatible membrane Cuprophan, where neutrophil activation with increased free radical production is well documented. The alterations found in this study might contribute to the reduced RBC longevity of HD patients where a bioincompatible membrane is used. [source] Spongy Polyethersulfone Membrane for Hepatocyte Cultivation: Studies on Human Hepatoma C3A CellsARTIFICIAL ORGANS, Issue 9 2008Andrzej Kinasiewicz Abstract:, There are different types of membranes used for hepatocyte cultivation. In our studies, spongy polyethersulfone (PES) membranes were examined as a support for hepatic cell cultivation in vitro. The extended surface of the membranes allows to introduce a high cell number especially in three-dimensional gel structure. Scanning electron microscopy analysis indicated that C3A cells used in our experiments grew well on PES membranes forming microvilli characteristic for normal hepatocytes. Analysis of cell viability proved that spongy PES membrane is well tolerated by J774 macrophages and did not stimulate nitric oxide synthesis. Bile canalicular structures were observed in fluorescence microscopy after F-actin staining with tetramethyl rhodamine iso-thiocyanate (TRITC)-phalloidin. The C3A cells showed high affinity to the PES membranes and adhered to almost 90% during the initial 24 h of incubation. Albumin production increased during static culture from the value of 805.2 ± 284.4 (ng/24 h/initial 106 cells) during the first days, to 2017.6 ± 505.9 (ng/24 h/initial 106 cells) after 10 days of culture. In conclusion, the spongy PES membranes can be used as scaffold for hepatocyte cultivation, especially for the creation of three-dimensional environments. [source] Influence of Different Hemodialysis Membranes on Red Blood Cell Susceptibility to Oxidative StressARTIFICIAL ORGANS, Issue 1 2000Leonardo Lucchi Abstract: Oxidative stress is crucial in red blood cell (RBC) damage induced by activated neutrophils in in vitro experiments. The aim of the study was to evaluate whether the bioincompatibility phenomena occurring during hemodialysis (HD) (where neutrophil activation with increased free radical production is well documented) may have detrimental effects on RBC. We evaluated RBC susceptibility to oxidative stress before and after HD in 15 patients using Cuprophan, cellulose triacetate, and polysulfone membrane. RBC were incubated with t-butyl hydroperoxide as an oxidizing agent both in the presence and in the absence of the catalase inhibitor sodium azide. The level of malonaldehyde (MDA), a product of lipid peroxidation, was measured at 0, 5, 10, 15, and 30 min of incubation. When Cuprophan membrane was used, the MDA production was significantly higher after HD, indicating an increased susceptibility to oxidative stress in comparison to pre-HD. The addition of sodium azide enhanced this phenomenon. Both cellulose triacetate and polysulfone membranes did not significantly influence RBC susceptibility to oxidative stress. Neither the level of RBC reduced glutathione nor the RBC glutathione redox ratio changed significantly during HD with any of the membranes used. The RBC susceptibility to oxidative stress was influenced in different ways according to the dialysis membrane used, being increased only when using the more bioincompatible membrane Cuprophan, where neutrophil activation with increased free radical production is well documented. The alterations found in this study might contribute to the reduced RBC longevity of HD patients where a bioincompatible membrane is used. [source]
| | ||||||||||||