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Membrane Method (membrane + method)
Selected AbstractsInvestigation of a Novel Catalyst Coated Membrane Method to Prepare Low-Platinum-Loading Membrane Electrode Assemblies for PEMFCsFUEL CELLS, Issue 2 2009X. Leimin Abstract In this work, a novel catalyst coated membrane (CCM) approach,a catalyst-sprayed membrane under irradiation (CSMUI),was developed to prepare MEAs for proton exchange membrane fuel cell (PEMFC) application. Catalyst ink was sprayed directly onto the membrane and an infrared light was used simultaneously to evaporate the solvents. The resultant MEAs prepared by this method yielded very high performance. Based on this approach, the preparation of low-platinum-content MEAs was investigated. It was found that for the anode, even if the platinum loading was decreased from 0.2 to 0.03,mg,cm,2, only a very small performance decrease was observed; for the cathode, when the platinum loading was decreased from 0.3 to 0.15,mg,cm,2, just a 5% decrease was detected at 0.7,V, but a 35% decrease was observed when the loading was decreased from 0.15 to 0.06,mg,cm,2. These results indicate that this approach is much better than the catalyst coated gas diffusion layer (GDL) method, especially for the preparation of low-platinum-content MEAs. SEM and EIS measurements indicated ample interfacial contact between the catalyst layer and the membrane. [source] Estimation of Ion-Pairing Constants in Plasticized Poly(vinyl chloride) Membranes Using Segmented Sandwich Membranes TechniqueELECTROANALYSIS, Issue 17-18 2009Vladimir Abstract Segmented sandwich membrane method was used to determine ion-pairing constants for four cationic sites: tris-(2,3,4-dodecyloxy)benzenetrimethylammonium, tris-(2,3,4-dodecyloxy)benzenedimethyloctylammonium, tris-(2,3,4-dodecyloxy)benzenemethyldioctylammonium, and dimethyldioctadecylammonium with chloride, bromide, nitrate, benzene sulfonate, trichloroacetate, thiocyanate, perchlorate and picrate, as well as ion-pairing constants for two anionic sites: tetraphenylborate and tris-(2,3,4-octyloxy)benzenesulfonate with dimedrol, quinine, anapriline, and amantadine cations in poly(vinyl chloride) membranes plasticized with 2-nitrophenyl octyl ether. Ion association constants of anions with quaternary ammonium sites regularly increase from picrate to chloride along with reduction of the anion radius and with improvement of site exchanger center steric accessibility. Ion association constants of amine cations with tris-(2,3,4-octyloxy)benzenesulfonate are several orders higher than those with tetraphenylborate and regularly increase from tertiary amine to primary one. [source] Development of a Novel Automatic Potentiometric System for Determination of Selenium and Its Application in Pharmaceutical Formulations and Anodic SlimeELECTROANALYSIS, Issue 9 2008Ayman Abstract Poly(vinyl chloride) polymeric membrane sensors containing Sn(IV) phthalocyanine dichloride (SnPC) and Co(II) phthalocyanine (CoPC) as novel electroactive materials dispersed in o -nitrophenyl octylether (o -NPOE) as a plasticizer are examined potentiometrically with respect to their response toward selenite (SeO32,) ions. Fast Nernstian response for SeO32, ions over the concentration ranges 7.0×10,6,1.0×10,3 and 8.0×10,6,1.0×10,3 mol L,l at pH,3.5,8.5 with lower detection limit of 5.0×10,6 and 8.0×10,6 mol L,1 and calibration slopes of ,25.4 and ,29.7,mV decade,1 are obtained with SnPC and CoPC based membrane sensors, respectively. The proposed sensors reveals by the modified separate solution method (MSSM) a good selectivity over different anions which differ significantly from the classical Hofmeister series. A segmented sandwich membrane method is used to determine complex formation constants of the ionophores in situe in the solvent polymeric sensing membranes. Membrane incorporating CoPC in a tubular flow detector is used in a two channels flow injection set up for continuous monitoring of selenite at a frequency of ca. 50 samples h,1. Direct determination of selenium in pharmaceutical formulations and anodic slime gives results in good agreement with data obtained using standard ICP method. [source] Numeric Simulation of Ion-Site Association Effects in Ion-Selective Electrode ResponseELECTROANALYSIS, Issue 15-16 2003Konstantin Abstract Effects in ion-selective electrode response and selectivity, caused by ion-site association in membranes are studied by means of numeric simulations based on a generalized model, which does not rely on a certain degree of the dissociation of electrolytes in membranes. The variability of the experimental values of the potentiometric selectivity coefficients is considered in view of the association in membranes. The reasons why the "dissociation approach" often fits experimental data are also discussed. A novel version of segmented sandwich membrane method is proposed for direct potentiometric measurements of ion-site association constants in membranes, and preliminary experimental results are presented. [source] Preparation and evaluation of poly-butylcyanoacrylate nanoparticles for oral delivery of thymopentinJOURNAL OF PHARMACEUTICAL SCIENCES, Issue 6 2008Weiling He Abstract Thymopentin (Tp5) was loaded in poly-butylcyanoacrylate (PBCA) nanoparticles (NP) in order to enhance the oral bioavailability of Tp5. PBCA-Tp5-NP was prepared by nanoprecipitation methods. Dialyzing membrane method was employed to examine the in vitro release of PBCA-Tp5-NP in PBS, and Tp5 samples in the release medium were detected by HPLC. The cell proliferation test (3H-thymidine) was conducted to verify the PBCA-Tp5-NP bioactivity in vitro. The pharmacodynamical studies were performed on preimmunoinhibited rats and in flow cytometer. The size and the entrapment efficiency of PBCA-Tp5-NP were 178,±,39 nm and 92.21,±,1.08%, respectively. In vitro release data show that less than 60% Tp5 was released from lyophilized PBCA-Tp5-NP while 80% Tp5 was released from the colloidal PBCA-Tp5-NPs in 48 h. The proliferation test showed that PBCA-Tp5-NP had the similar effect as Tp5. The in vivo data showed that oral PBCA-Tp5-NPs had similar function as what intravenous Tp5 did. The oral bioavailability of Tp5 could be enhanced by PBCA nanoparticles. PBCA-Tp5-NP had the property of sustained-release and the efficacy of Tp5 was not changed after formulation. © 2007 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 97:2249,2258, 2008 [source] ADAMTS13 cleavage efficiency is altered by mutagenic and, to a lesser extent, polymorphic sequence changes in the A1 and A2 domains of von Willebrand factorBRITISH JOURNAL OF HAEMATOLOGY, Issue 4 2008Cynthia M. Pruss Summary The multimeric plasma protein von Willebrand factor (VWF) is regulated in size by its protease, ADAMTS13 (a disintegrin and metalloproteinase with thrombospondin type 1 motif, member 13). Y1605-M1606 cleavage site mutations and single nucleotide polymorphisms (SNPs) in the VWF A1 and A2 domains were examined for alteration in ADAMTS13-mediated cleavage of VWF. Recombinant human full-length VWF (rVWF) was digested with recombinant human ADAMTS13 (rADAMTS13) using a dialysis membrane method with 1·5 mol/l urea, and analyzed via multimer migration distance. The glutathione- S -transferase (GST) and histidine-tagged construct, E1554-R1668 of VWF (VWF115) was assayed via enzyme-linked immunosorbent assay: VWF115 was bound to anti-GST coated plates, digested with rADAMTS13, and intact VWF115 detected via horseradish peroxidase-labelled anti-histidine tag antibody. All alterations examined in the Y1605-M1606 cleavage site greatly reduced the cleavability of VWF by ADAMTS13 in the rVWF assay. Greatest cleavage resistance in both assays was observed in Y1605A/M1606A. In contrast, Y1605H and M1606L show a loss of cleavability only in the rVWF assay, suggesting that an aromatic ring at 1605 is critical for ADAMTS13 recognition. Additionally, under our rVWF assay conditions, the G1643S polymorphism showed increased cleavage, suggesting a Type 2A VWD phenotype, while D1472H, Q1571H and P1601T showed slightly decreased ADAMTS13 cleavage. Our two complementary assay conditions show that A-domain changes in VWF alter ADAMTS13-mediated proteolysis. [source] | ||||||||||