990 research outputs found

    Morphology of supported polymer electrolyte ultra-thin films: a numerical study

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    Morphology of polymer electrolytes membranes (PEM), e.g., Nafion, inside PEM fuel cell catalyst layers has significant impact on the electrochemical activity and transport phenomena that determine cell performance. In those regions, Nafion can be found as an ultra-thin film, coating the catalyst and the catalyst support surfaces. The impact of the hydrophilic/hydrophobic character of these surfaces on the structural formation of the films has not been sufficiently explored yet. Here, we report about Molecular Dynamics simulation investigation of the substrate effects on the ionomer ultra-thin film morphology at different hydration levels. We use a mean-field-like model we introduced in previous publications for the interaction of the hydrated Nafion ionomer with a substrate, characterized by a tunable degree of hydrophilicity. We show that the affinity of the substrate with water plays a crucial role in the molecular rearrangement of the ionomer film, resulting in completely different morphologies. Detailed structural description in different regions of the film shows evidences of strongly heterogeneous behavior. A qualitative discussion of the implications of our observations on the PEMFC catalyst layer performance is finally proposed

    Estimativa da diversidade genética entre genótipos de sorgo sacarino baseando-se em caracteres agroindustriais.

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    O sorgo sacarino (Sorghum bicolor) se trata de uma planta que apresenta elevada produção de biomassa, porte alto e colmos suculentos com elevados teores de açúcares fermentescíveis no caldo. Estudos sobre diversidade genética são utilizados com frequência proporcionando a seleção dos melhores indivíduos, em busca do aumento da freqüência de alelos favoráveis. O objetivo deste trabalho foi avaliar a existência da variabilidade genética entre acessos e caracterizar a divergência genética entre genótipos de sorgo sacarino pertencentes ao programa de melhoramento do Centro Nacional de Pesquisa Milho e Sorgo (CNPMS), baseado-se em caracteres agroindustriais. O experimento foi conduzido no Centro Nacional de Pesquisa Milho e Sorgo (CNPMS), situado na cidade de Sete Lagoas, MG. Foram avaliados um total de 40 genótipos de sorgo sacarino. Os dados foram submetidos à análise de variância. Para o estudo da divergência genética entre os genótipos foi estimada a distância generalizada de Mahalanobis, obtidas a partir dos dados padronizados e posterior agrupamento utilizando o método hierárquico de ligação média entre grupos (UPGMA). Os resultados obtidos nos 40 acessos de sorgo sacarino do Centro Nacional de Milho e Sorgo evidenciam a existência da variabilidade genética

    Crystalline Assemblies and Densest Packings of a Family of Truncated Tetrahedra and the Role of Directional Entropic Forces

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    Polyhedra and their arrangements have intrigued humankind since the ancient Greeks and are today important motifs in condensed matter, with application to many classes of liquids and solids. Yet, little is known about the thermodynamically stable phases of polyhedrally-shaped building blocks, such as faceted nanoparticles and colloids. Although hard particles are known to organize due to entropy alone, and some unusual phases are reported in the literature, the role of entropic forces in connection with polyhedral shape is not well understood. Here, we study thermodynamic self-assembly of a family of truncated tetrahedra and report several atomic crystal isostructures, including diamond, {\beta}-tin, and high- pressure lithium, as the polyhedron shape varies from tetrahedral to octahedral. We compare our findings with the densest packings of the truncated tetrahedron family obtained by numerical compression and report a new space filling polyhedron, which has been overlooked in previous searches. Interestingly, the self-assembled structures differ from the densest packings. We show that the self-assembled crystal structures can be understood as a tendency for polyhedra to maximize face-to-face alignment, which can be generalized as directional entropic forces.Comment: Article + supplementary information. 23 pages, 10 figures, 2 table

    Mindfulness based interventions in multiple sclerosis: a systematic review

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    <b>Background</b> Multiple sclerosis (MS) is a stressful condition; depression, anxiety, pain and fatigue are all common problems. Mindfulness based interventions (MBIs) mitigate stress and prevent relapse in depression and are increasingly being used in healthcare. However, there are currently no systematic reviews of MBIs in people with MS. This review aims to evaluate the effectiveness of MBIs in people with MS.<p></p> <b>Methods</b> Systematic searches were carried out in seven major databases, using both subject headings and key words. Papers were screened, data extracted, quality appraised, and analysed by two reviewers independently, using predefined criteria. Study quality was assessed using the Cochrane Collaboration risk of bias tool. Perceived stress was the primary outcome. Secondary outcomes include mental health, physical health, quality of life, and health service utilisation. Statistical meta-analysis was not possible. Disagreements were adjudicated by a third party reviewer.<p></p> <b>Results</b> Three studies (n = 183 participants) were included in the final analysis. The studies were undertaken in Wales (n = 16, randomised controlled trial - (RCT)), Switzerland (n = 150, RCT), and the United States (n = 17, controlled trial). 146 (80%) participants were female; mean age (SD) was 48.6 (9.4) years. Relapsing remitting MS was the main diagnostic category (n = 123, 67%); 43 (26%) had secondary progressive disease; and the remainder were unspecified. MBIs lasted 6–8 weeks; attrition rates were variable (5-43%); all employed pre- post- measures; two had longer follow up; one at 3, and one at 6 months. Socio-economic status of participants was not made explicit; health service utilisation and costs were not reported. No study reported on perceived stress. All studies reported quality of life (QOL), mental health (anxiety and depression), physical (fatigue, standing balance, pain), and psychosocial measures. Statistically significant beneficial effects relating to QOL, mental health, and selected physical health measures were sustained at 3- and 6- month follow up.<p></p> <b>Conclusion</b> From the limited data available, MBIs may benefit some MS patients in terms of QOL, mental health, and some physical health measures. Further studies are needed to clarify how MBIs might best serve the MS population.<p></p&gt

    Bradykinin Release Avoids High Molecular Weight Kininogen Endocytosis

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    Human H-kininogen (120 kDa) plays a role in many pathophysiological processes and interacts with the cell surface through protein receptors and proteoglycans, which mediate H-kininogen endocytosis. in the present work we demonstrate that H-kininogen containing bradykinin domain is internalized and different endogenous kininogenases are present in CHO-K1 cells. We used CHO-K1 (wild type) and CHO-745 (mutant deficient in proteoglycans biosynthesis) cell lines. H-kininogen endocytosis was studied using confocal microscopy, and its hydrolysis by cell lysate fraction was determined by immunoblotting. Bradykinin release was also measured by radioimmunoassay. H-kininogen interaction with the cell surface of CHO-745 cells resulted in bradykinin release by serine proteases. in CHO-K1 cells, which produce heparan and chondroitin sulfate proteoglycans, internalization of H-kininogen through its bradykinin domain can occur on lipid raft domains/caveolae. Nevertheless bradykinin-free H-kininogen was not internalized by CHO-K1 cells. the H-kininogen present in acidic endosomal vesicles in CHO-K1 was approximately 10-fold higher than the levels in CHO-745. CHO-K1 lysate fractions were assayed at pH 5.5 and intact H-kininogen was totally hydrolyzed into a 62 kDa fragment. By contrast, at an assay pH 7.4, the remained fragments were 115 kDa, 83 kDa, 62 kDa and 48 kDa in size. the anti-pain-Sepharose chromatography separated endogenous kininogenases from CHO-K1 lysate fraction. No difference was detected in the assays at pH 5.5 or 7.4, but the proteins in the fraction bound to the resin released bradykinin from H-kininogen. However, the proteins in the unbound fraction cleaved intact H-kininogen at other sites but did not release bradykinin. H-kininogen can interact with extravascular cells, and is internalized dependent on its bradykinin domain and cell surface proteoglycans. After internalization, H-kininogen is proteolytically processed by intracellular kininogenases. the present data also demonstrates that serine or cysteine proteases in lipid raft domains/caveolae on the CHO cell can hydrolyze H-kininogen, thus releasing kinins.Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)Fundacao de Apoio a Universidade Federal de São Paulo-FAP/UNIFESPUniversidade Federal de São Paulo UNIFESP, Escola Paulista Med, Dept Bioquim, São Paulo, SP, BrazilUniv Anhanguera São Paulo UNIAN SP, Programa Biomat, São Paulo, SP, BrazilUniv Anhanguera São Paulo UNIAN SP, Programa Biotecnol, São Paulo, SP, BrazilUniversidade Federal de São Paulo UNIFESP, Escola Paulista Med, Dept Biofis, São Paulo, SP, BrazilUniversidade Federal de São Paulo UNIFESP, Escola Paulista Med, Dept Bioquim, São Paulo, SP, BrazilUniversidade Federal de São Paulo UNIFESP, Escola Paulista Med, Dept Biofis, São Paulo, SP, BrazilCNPq: CNPq 472403/2007-9FAPESP: FAPESP 13/05822-9FAPESP: FAPESP 2012/50219-6Web of Scienc

    [validation Of The Brazilian Version Of Mini-test Casi-s].

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    To determine CASI-S accuracy in the diagnosis of dementia. The Cognitive Abilities Screening Instrument - Short Form (CASI-S) was applied in 43 Alzheimer's disease (AD) patients and 74 normal controls. AD diagnosis was based on DSM-IV, NINCDS-ADRDA, and CAMDEX. CASI-S includes: registration, temporal orientation, verbal fluency (4-legged animals in 30s), and recall (3 words). Its maximum score is 33 points. A copy of 2 pentagons was added. ROC curve showed an accuracy of 0.87, with standard error of 0.032, and 95% confidence intervall between 0.795 and 0.925. The cut-off score for cognitive deficit was 23, with sensitivity of 76.7%, specificity 86.5%, positive likelihood ratio (LR) 5.68, and negative LR 0.27. The cut-off score for subjects 70 years or older was 20, with sensitivity of 71.4% and specificity 97.1%. CASI-S is a practical test, with high specificity, particularly in individuals above 70 years of age. The adding of the drawing test did not improve its accuracy.63416-2
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