56 research outputs found

    Coating of Nafion Membranes with Polyelectrolyte Multilayers to Achieve High Monovalent/Divalent Cation Electrodialysis Selectivities

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    Electrodialysis (ED) membranes typically exhibit modest selectivities between monovalent and divalent ions. This paper reports a dramatic enhancement of the monovalent/divalent cation selectivities of Nafion 115 membranes through coating with multilayer poly­(4-styrenesulfonate) (PSS)/protonated poly­(allylamine) (PAH) films. Remarkably, K<sup>+</sup>/Mg<sup>2+</sup> ED selectivities reach values >1000, and similar monovalent/divalent cation selectivities occur with feed solutions containing K<sup>+</sup> and Ca<sup>2+</sup>. For comparison, the corresponding K<sup>+</sup>/Mg<sup>2+</sup> selectivity of bare Nafion 115 is only 1.8 ± 0.1. However, with 0.01 M KNO<sub>3</sub> and 0.01 M Mg­(NO<sub>3</sub>)<sub>2</sub> in the source phase, as the applied current density increases from 1.27 to 2.54 mA cm<sup>–2</sup>, the K<sup>+</sup>/Mg<sup>2+</sup> selectivities of coated membranes decrease from >1000 to 22. Water-splitting at strongly overlimiting current densities may lead to a local pH increase close to the membrane surface and alter film permeability or allow passage of Mg­(OH)<sub><i>x</i></sub> species to decrease selectivity. When the source phase contains 0.1 M KNO<sub>3</sub> and 0.1 M Mg­(NO<sub>3</sub>)<sub>2</sub>, the K<sup>+</sup> transference number approaches unity and the K<sup>+</sup>/Mg<sup>2+</sup> selectivity is >20 000, presumably because the applied current is below the limiting value for K<sup>+</sup> and H<sup>+</sup> transport is negligible at this high K<sup>+</sup> concentration. The high selectivities of these membranes may enable electrodialysis applications such as purification of salts that contain divalent or trivalent ions

    MOESM1 of Genetic polymorphisms in the circumsporozoite protein of Plasmodium malariae show a geographical bias

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    Additional file 1. Frequency distribution of the NAAG tetrapeptide repeat unit in the central repeat region of pmcsp. (a) Frequency distribution of the repeat unit in isolates collected from Thailand, Myanmar, Kenya, and Cameroon. (b) Frequency distribution of the repeat unit in isolates collected from Asia and Africa. X-axis represents the number of repeat units, and Y-axis indicates the number of samples corresponding to each repeat unit

    MOESM2 of Genetic polymorphisms in the circumsporozoite protein of Plasmodium malariae show a geographical bias

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    Additional file 2. Frequency distribution of the NDAG tetrapeptide repeat unit in the central repeat region of pmcsp. (a) Frequency distribution of the repeat unit in isolates collected from Thailand, Myanmar, Kenya, and Cameroon. (b) Frequency distribution of the repeat unit in isolates collected from Asia and Africa

    Multifactorial Optimizations for Directing Endothelial Fate from Stem Cells

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    <div><p>Embryonic stem cells (ESC) and induced pluripotent stem (iPS) cells are attractive in vitro models of vascular development, therapeutic angiogenesis, and tissue engineering. However, distinct ESC and iPS cell lines respond differentially to the same microenvironmental factors. Developing improved/optimized differentiation methodologies tailored/applicable in a number of distinct iPS and ESC lines remains a challenge in the field. Currently published methods for deriving endothelial cells (EC) robustly generate high numbers of endothlelial progenitor cells (EPC) within a week, but their maturation to definitive EC is much more difficult, taking up to 2 months and requiring additional purification. Therefore, we set out to examine combinations/levels of putative EC induction factors—utilizing our stage-specific chemically-defined derivation methodology in 4 ESC lines including: kinetics, cell seeding density, matrix signaling, as well as medium treatment with vascular endothelial growth factor (VEGF), and basic fibroblast growth factor (bFGF). The results indicate that temporal development in both early and late stages is the most significant factor generating the desired cells. The generation of early Flk-1<sup>+</sup>/KDR<sup>+</sup> vascular progenitor cells (VPC) from pluripotent ESC is directed predominantly by high cell seeding density and matrix signaling from fibronectin, while VEGF supplementation was NOT statistically significant in more than one cell line, especially with fibronectin matrix which sequesters autocrine VEGF production by the differentiating stem cells. Although some groups have shown that the GSK3-kinase inhibitor (CHIR) can facilitate EPC fate, it hindered the generation of KDR+ cells in our preoptimized medium formulations. The methods summarized here significantly increased the production of mature vascular endothelial (VE)-cadherin+ EC, with up to 93% and 57% purity from mouse and human ESC, respectively, before VE-cadherin+ EC purification.</p></div
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