1,729 research outputs found

    Recovering S1S^1-invariant metrics on S2S^2 from the equivariant spectrum

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    We prove an inverse spectral result for S1S^1-invariant metrics on S2S^2 based on the so-called asymptotic equivariant spectrum. This is roughly the spectrum together with large weights of the S1S^1 action on the eigenspaces. Our result generalizes an inverse spectral result of the first and last named authors, together with Victor Guillemin, concerning S1S^1-invariant metrics on S2S^2 which are invariant under the antipodal map. We use higher order terms in the asymptotic expansion of a natural spectral measure associated with the Laplacian and the S1S^1 action.Comment: 16 pages; minor revisions throughout following comments from referee

    Hearing Delzant polytopes from the equivariant spectrum

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    Let M^{2n} be a symplectic toric manifold with a fixed T^n-action and with a toric K\"ahler metric g. Abreu asked whether the spectrum of the Laplace operator Δg\Delta_g on C(M)\mathcal{C}^\infty(M) determines the moment polytope of M, and hence by Delzant's theorem determines M up to symplectomorphism. We report on some progress made on an equivariant version of this conjecture. If the moment polygon of M^4 is generic and does not have too many pairs of parallel sides, the so-called equivariant spectrum of M and the spectrum of its associated real manifold M_R determine its polygon, up to translation and a small number of choices. For M of arbitrary even dimension and with integer cohomology class, the equivariant spectrum of the Laplacian acting on sections of a naturally associated line bundle determines the moment polytope of M.Comment: 23 pages, 9 figures; v2 is published versio

    Multiband tunneling in trilayer graphene

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    The electronic tunneling properties of the two stable forms of trilayer graphene (TLG), rhombohedral ABC and Bernal ABA, are examined for pn and pnp junctions as realized by using a single gate (SG) or a double gate (DG). For the rhombohedral form, due to the chirality of the electrons, the Klein paradox is found at normal incidence for SG devices while at high energy interband scattering between additional propagation modes can occur. The electrons in Bernal ABA TLG can have a monolayer- or bilayer-like character when incident on a SG device. Using a DG however both propagation modes will couple by breaking the mirror symmetry of the system which induces intermode scattering and resonances that depend on the width of the DG pnp junction. For ABC TLG the DG opens up a band gap which suppresses Klein tunneling. The DG induces also an unexpected asymmetry in the tunneling angle for single valley electrons

    Fingolimod Treatment Modulates PPARγ and CD36 Gene Expression in Women with Multiple Sclerosis

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    Fingolimod is an oral immunomodulatory drug used in the treatment of multiple sclerosis (MS) that may change lipid metabolism. Peroxisome proliferator-activated receptors (PPAR) are transcription factors that regulate lipoprotein metabolism and immune functions and have been implicated in the pathophysiology of MS. CD36 is a scavenger receptor whose transcription is PPAR regulated. The objective of this study was to evaluate whether fingolimod treatment modifies PPAR and CD36 gene expression as part of its action mechanisms. Serum lipoprotein profiles and PPAR and CD36 gene expression levels in peripheral leukocytes were analysed in 17 female MS patients before and at 6 and 12 months after fingolimod treatment initiation. Clinical data during the follow-up period of treatment were obtained. We found that fingolimod treatment increased HDL-Cholesterol and Apolipoprotein E levels and leukocyte PPARγ and CD36 gene expression. No correlations were found between lipid levels and variations in PPARγ and CD36 gene expression. PPARγ and CD36 variations were significantly correlated during therapy and in patients free of relapse and stable disease. Our results suggest that PPARγ and CD36-mediated processes may contribute to the mechanisms of action of fingolimod in MS. Further studies are required to explore the relation of the PPARγ/CD36 pathway to the clinical efficacy of the drug and its involvement in the pathogenesis of the disease.info:eu-repo/semantics/publishedVersio

    Flexão simples : análise comparativa REBAP vs. EC2

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    O Eurocódigo 2 recomenda a utilização de relações tensões-extensões de cálculo quer para o betão quer para o aço, diferentes das propostas pelo REBAP. Com o objectivo de analisar a influência desta alteração normativa no dimensionamento à flexão simples de secções rectangulares, efectuou-se um estudo comparativo em termos de grandezas adimensionais. Na comunicação descreve-se o estudo efectuado, assim como, as principais conclusões obtidas

    Flexão composta : análise comparativa REBAP vs. EC2

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    No contexto actual nacional, o dimensionamento de estruturas de betão armado tem sido maioritariamente efectuado em conformidade com a norma nacional, o Regulamento de Estruturas de Betão Armado e Pré Esforçado (REBAP). Com a aprovação, no passado recente, do Eurocódigo 2 (EC2) a nível europeu, antevê-se que em breve lhe seja atribuído o estatuto de norma nacional, através da publicação de um texto idêntico. Em termos gerais o EC2, quando comparado com o REBAP, apresenta diferenças consideráveis na forma e no conteúdo que se repercutem no dimensionamento das estruturas de betão armado. Perante este cenário torna se imperioso efectuar estudos comparativos entre as duas normas aos mais diferentes níveis. O caso particular do dimensionamento à flexão ao nível da secção transversal em elementos estruturais lineares, que tem por base a hipótese de Navier Bernoulli (secções planas antes e após a deformação), recorre a leis tensões extensões de cálculo dos materiais intervenientes: o betão e o aço. As propostas do REBAP e do EC2 para definir estas leis são ligeiramente diferentes. Em trabalhos anteriores demonstrou se que as diferenças obtidas no dimensionamento de secções rectangulares à flexão simples adoptando as duas regulamentações (REBAP e EC2) são marginais. No presente trabalho pretende se avaliar a mesma diferença, mas desta feita para o caso em que o elemento estrutural se encontra sujeito a flexão composta. Deste modo, o objectivo é o de analisar a influência das diferenças que existem entre o REBAP e o EC2 ao nível dos diagramas tensões extensões de cálculo para os materiais betão e aço, no dimensionamento de secções rectangulares à flexão composta. No presente trabalho descreve se o estudo comparativo efectuado, assim como as principais conclusões obtidas

    New biodegradable polylactide material with antimicrobial properties

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    This study aimed to investigate the bactericidal, fungicidal and non-phytotoxic properties of vapor permeable polylactide films containing five different concentrations (in the range of 0.2–1.0%) of thiabendazole. All films showed bactericidal properties on Staphylococcus aureus and Escherichia coli. Thiabendazole introduced into polylactide affected the antifungal activity of the materials containing 0.8 and 1.0% thiabendazole. The films containing thiabendazole were characterized by increased permeability. The vapor permeability of the film increased with the increase of the biocide content in the composites. The new materials had no a negative effect on the growth and development of monocotyledonous and dicotyledonous plants. It has been shown that the presence of thiabendazole increases the water vapor permeability of polylactide films. The obtained materials are biodegradable and can be used in horticulture and agriculture to protect plants against pathogens. The use of films with biocide properties will reduce the use of plant protection products. This is particularly important due to the need to protect biodiversity in the ecosystem of agricultural soils

    Social policies and emotions in Latin America: A theoretical approach to their analysis

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    This article aims at making a conceptual analysis of the links between social policies, emotions and World Images. It tries to frame the theoretical and epistemic plots of subjacent assumptions that involve (and activate) State interventions on "the social". The following is the argumentative strategy that has been chosen: firstly, we will account for the links between social policies and the capitalist regime of accumulation; secondly, we will explain the proposed theoretical links between World Image and policies of emotions; thirdly, we will offer some arguments which show the analytical richness of linking social policies and policies of emotions through the concept of World Image; fourthly, as an example, we will frame the massiveness of social policies as a World Image that transmits emotionalities linked to the reproduction of the regime of accumulation. Lastly, as a conclusion, we ask and warn about some components of social policies which make them stand as tools for coloniality

    Utilization of Estremoz marbles sawing sludge in ceramic industry – Preliminary Approach

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    Portugal is in forefront of world marble production, the marble quarries and processing industries in Estremoz region has an important role in economic life. The amount of waste produced by this activity is massive and cause several problems. The aim of this study is to investigate the suitability and the effect of Estremoz marble sawing sludge in mixtures with clay to ceramic industry. Another main concern is the manufacture of environmental friend ceramics. Plasticity behavior of clay mixtures with 2.5, 5, 10, 15 and 20wt% of marble powder were evaluated. The incorporation of waste reduces the liquid limit and plastic index of pastes. Clay bodies were molded by uniaxial pressure and fired at maximum temperature of 950ºC. The results reveal that the addiction of marble powder increases the water absorption, apparent porosity while the bulk density decreases. Due to their influence in the melted phase an improvement in mechanical strength characteristics was registered, namely in rupture modulus. This preliminary study shows that the use such mixtures are promising in term of ceramics technological properties. Keywords: Estremoz marbles, clay, reuse, ceramics
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