11,566 research outputs found

    Accelerating Cold Dark Matter Cosmology (ΩΛ0\Omega_{\Lambda}\equiv 0)

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    A new kind of accelerating flat model with no dark energy that is fully dominated by cold dark matter (CDM) is investigated. The number of CDM particles is not conserved and the present accelerating stage is a consequence of the negative pressure describing the irreversible process of gravitational particle creation. A related work involving accelerating CDM cosmology has been discussed before the SNe observations [Lima, Abramo & Germano, Phys. Rev. D53, 4287 (1996)]. However, in order to have a transition from a decelerating to an accelerating regime at low redshifts, the matter creation rate proposed here includes a constant term of the order of the Hubble parameter. In this case, H0H_0 does not need to be small in order to solve the age problem and the transition happens even if the matter creation is negligible during the radiation and part of the matter dominated phase. Therefore, instead of the vacuum dominance at redshifts of the order of a few, the present accelerating stage in this sort of Einstein-de Sitter CDM cosmology is a consequence of the gravitational particle creation process. As an extra bonus, in the present scenario does not exist the coincidence problem that plagues models with dominance of dark energy. The model is able to harmonize a CDM picture with the present age of the universe, the latest measurements of the Hubble parameter and the Supernovae observations.Comment: 9 pages, 6 figures, typos corrected, references added, discussion in Appendix B extende

    Nanostructured 3D Constructs Based on Chitosan and Chondroitin Sulphate Multilayers for Cartilage Tissue Engineering

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    Nanostructured three-dimensional constructs combining layer-by-layer technology (LbL) and template leaching were processed and evaluated as possible support structures for cartilage tissue engineering. Multilayered constructs were formed by depositing the polyelectrolytes chitosan (CHT) and chondroitin sulphate (CS) on either bidimensional glass surfaces or 3D packet of paraffin spheres. 2D CHT/CS multi-layered constructs proved to support the attachment and proliferation of bovine chondrocytes (BCH). The technology was transposed to 3D level and CHT/CS multi-layered hierarchical scaffolds were retrieved after paraffin leaching. The obtained nanostructured 3D constructs had a high porosity and water uptake capacity of about 300%. Dynamical mechanical analysis (DMA) showed the viscoelastic nature of the scaffolds. Cellular tests were performed with the culture of BCH and multipotent bone marrow derived stromal cells (hMSCs) up to 21 days in chondrogenic differentiation media. Together with scanning electronic microscopy analysis, viability tests and DNA quantification, our results clearly showed that cells attached, proliferated and were metabolically active over the entire scaffold. Cartilaginous extracellular matrix (ECM) formation was further assessed and results showed that GAG secretion occurred indicating the maintenance of the chondrogenic phenotype and the chondrogenic differentiation of hMSCs

    Prata Ken: cultivar de bananeira resistente à sigatoka-negra, para o Estado do Amazonas.

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    Com base em avaliações realizadas durante dois ciclos produtivos em Manaus, onde a sigatoka-negra está presente, foi selecionada a cultivar Prata Ken para recomendação aos produtores amazonenses. Características e recomendações da cultivar. Espaçamento e densidade populacional. Adubação. Adubação de cobertura/planta.bitstream/item/26001/1/ComTec10.pd

    Serological detection of antibodies against Paracoccidioides brasiliensis in dogs with leishmaniasis

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    The aim of this study was to detect antibodies against Paracoccidioides brasiliensis in dogs seropositive and seronegative for leishmaniasis. Sera from 836 dogs (449 positive and 387 negative to leishmaniasis) were analysed by ELISA and the immunodiffusion test using gp43 and exoantigen, respectively. The analysis of the 836 serum samples by ELISA and the immunodiffusion test showed a positivity of 67.8 % and 7.3%, respectively, for P. brasiliensis infection. The dogs positive to leishmaniasis showed a higher reactivity to gp43 (79.9%) and exoantigen (12.7%) than the negative ones (54.0% and 1.0%, respectively). The higher reactivity to P. brasiliensis antigens may be due to cross-reactivity or a co-infection of dogs by Leishmania and P. brasiliensis. The lower correlation (0.187) observed between reactivity to gp43 and Leishmania antigen reinforces the latter hypothesis

    BRS Requinte: nova cultivar de feijoeiro comum de tipo de grão carioca com retardamento do escurecimento do grão.

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    A cultivar BRS Requinte originou-se do cruzamento Carioca MG // POT 94 / AN910523, realizado pela Embrapa Arroz e Feijão.bitstream/CNPAF/21540/1/comt_65.pd

    BRS Campeiro: nova cultivar de feijoeiro comum de grão preto, indicada para o Sul do Brasil.

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    A cultivar BRS Campeiro originou-se de um programa de indução de mutação visando alterar a cor do tegumento da cultivar Corrente, desenvolvida pela Embrapa Arroz e Feijão.bitstream/CNPAF/21537/1/comt_62.pd
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