33,609 research outputs found

    Flag-Dipole Spinor Fields in ESK Gravities

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    We consider the Riemann-Cartan geometry as a basis for the Einstein-Sciama-Kibble theory coupled to spinor fields: we focus on f(R)f(R) and conformal gravities, regarding the flag-dipole spinor fields, type-(4) spinor fields under the Lounesto classification. We study such theories in specific cases given for instance by cosmological scenarios: we find that in such background the Dirac equation admits solutions that are not Dirac spinor fields, but in fact the aforementioned flag-dipoles ones. These solutions are important from a theoretical perspective, as they evince that spinor fields are not necessarily determined by their dynamics, but also a discussion on their structural (algebraic) properties must be carried off. Furthermore, the phenomenological point of view is shown to be also relevant, since for isotropic Universes they circumvent the question whether spinor fields do undergo the Cosmological Principle.Comment: 18 pages, improved versio

    Seismic vulnerability assessment of the old city centre of Seixal, Portugal

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    The seismic vulnerability assessment of old traditional masonry building stocks, in a seismic risk mitigation perspective, is truly essential not only for buildings with recognized historical and patrimonial value, but also, in relation to regular buildings. In this sense, this paper approaches the issue of the seismic vulnerability assessment of masonry buildings through the application of a simplified methodology to building stock of the old city centre of Seixal, Portugal. This methodology is based on a vulnerability index, suitable in the evaluation of damage and in the creation of large scale loss scenarios (economical and human). Over 500 buildings were evaluated in accordance with the referred methodology and the results obtained were then integrated into a Geographical Information System tool. The integration of this kind of vulnerability and loss results into a GIS tool allows that city councils or regional authorities make their decisions based on a global view of the site under analysis, which led to more accurate and faster decisions either in terms of risk mitigation strategies or rehabilitation plans. This tool can also assumes great importance in the construction of safety and rescue plans

    Vulnerability assessment of urban building stock: a hierarchic approach

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    In the last decades the evaluation of the seismic risk are of rising concern, considered essential in the activity and definition of strategy planning and urban management. The evaluation of the seismic vulnerability of the existent building stock in the perspective of the seismic risk mitigation should not be placed only in relation to the isolated buildings of relevant historical and cultural importance, but also, in relation to the agglomerate of buildings in urban centres. The chronological construction process frequently results in characteristic heterogeneity of masonry and wall connection quality. In addition, buildings do not constitute independent units given that they share the mid-walls with adjacent buildings and the façade walls are aligned. This way, as post-seismic observations proved, buildings do not have an independent structural behaviour, but they interact amongst themselves, mainly for horizontal actions and so the structural performance should be studied at the level of the aggregate and not only for each isolated building. In most cases, for masonry structures there is no need for sophisticated dynamic analyses for seismic resistance verification or vulnerability assessment. This is even more relevant when an assessment at the level of a city centre is pursued. In this work, the results of evaluation of the vulnerability will be presented in accordance to three proposed methodologies based on a vulnerability index that consequently allows the evaluation of damage and creation of loss scenarios (economical and human) not only at the level of the building and its façade walls but also at the level of the aggregates. It will be discussed and evaluated the application of the referred methodologies and its integration in an SIG platform

    Dynamical Lorentz and CPT symmetry breaking in a 4D four-fermion model

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    In a 4D chiral Thirring model we analyse the possibility that radiative corrections may produce spontaneous breaking of Lorentz and CPT symmetry. By studying the effective potential, we verified that the chiral current ψˉγμγ5ψ\bar\psi\gamma^{\mu} \gamma_5 \psi may assume a nonzero vacuum expectation value which triggers the Lorentz and CPT violations. Furthermore, by making fluctuations on the minimum of the potential we dynamically induce a bumblebee like model containing a Chern-Simons term.Comment: Small modifications in the text and new references added, 12 pages, 4 figures, revtex4. To appear in Phys. Rev.

    On the radiative corrections in the Horava-Lifshitz z=2 QED

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    We calculate one-loop contributions to the two and three point spinor-vector functions in z=2 Horava-Lifshitz QED. This allows us to obtain the anomalous magnetic moment.Comment: 10 pages, minor correction

    Identificação molecular de Pseudallescheria boydii em palma de óleo.

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    A cultura da palma de óleo (Elaeis guineensis Jacq.) vem se expandindo rapidamente no Estado do Pará. Durante os testes de investigação da principal doença da cultura, o amarelecimento fatal, verificou-se a presença de alguns fungos provenientes de plantas doentes e sem sintoma. Assim, o presente trabalho teve o objetivo de identificar uma dessas espécies de fungos por meio do PCR seguido do sequenciamento nucleotídico. Para isso, tecidos do interior do estipe e raízes foram plaqueados em meio ágar-água, e posteriormente, os fungos foram repicados para meio BDA. As placas contendo a espécie selecionada foram mantidas a temperatura ambiente. Após 10 dias, o fungo teve seu DNA extraído para realização do PCR utilizando os primers ITS4 e ITS5. Os produtos do PCR foram sequenciados e avaliados via programas Blast e Clustalw, onde se verificou identidade de 98 a 100% com vários acessos de Pseudallescheria boydii, inclusive aqueles que têm efeito fungistático contra fungos fitopatogênicos. Os isolados foram mantidos na micoteca do Laboratório de Fitopatologia da Embrapa Amazônia Oriental e estão sendo estudados quanto ao seu potencial uso no controle biológico de fungos fitopatogênicos. Este foi o primeiro relato de P. boydii em palma

    Slavnov-Taylor identities for noncommutative QED4_4

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    In this work we present an analysis of the one-loop Slavnov-Taylor identities in noncommutative QED4_4. The vectorial fermion-photon and the triple photon vertex functions were studied, with the conclusion that no anomalies arise.Comment: 24 pages, revtex4, v2: typos correcte
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