2,669 research outputs found

    Self-Forces on Electric and Magnetic Linear Sources in the Space-Time of a Cosmic String

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    In this paper we calculate the magnetic and electric self-forces, induced by the conical structure of a cosmic string space-time, on a long straight wire which presents either a constant current or a linear charge density. We also show how these self-forces are related by a Lorentz tranformation and, in this way, explain what two different inertial observers detect in their respective frames.Comment: 10 pages, LaTeX, to be published in Phys. Rev. D

    The self-energy of a charged particle in the presence of a topological defect distribution

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    In this work we study a charged particle in the presence of both a continuous distribution of disclinations and a continuous distribution of edge dislocations in the framework of the geometrical theory of defects. We obtain the self-energy for a single charge both in the internal and external regions of either distribution. For both distributions the result outside the defect distribution is the self-energy that a single charge experiments in the presence of a single defect.Comment: 12 pages, Revtex4, two figures,to appear in Int. Joun. Mod. Phys.

    Validation of the Lower Tagus Valley velocity and structural model using ambient noise broadband measurements

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    Along his history the Lower Tagus Valley (LTV) region was shaken by several earthquakes, some of them were produced in large ruptures of offshore structures located southwest of the Portuguese coastline, among these we the Lisbon earthquake of 1 November 1755; other moderates earthquakes were produced by local sources such as the 1344, 1531 and the 1909 Benavente earthquake. In order to promote an improved assessment of the seismic hazard in this region, we propose the introduction of realistic methods on the prediction of ground motion produced by moderate to large earthquakes in LTV. This process involves the establishment of a structural 3D model based on all the available geophysical and geotechnical data on the area (seismic, gravimetric, deep wells and geological outcrops) and the determination of wave propagation from a finite difference method: by applying the E3D program [1,2]. To confirm this model we use broadband ambient noise measurements collected in two profiles with azimuth perpendicular to the basin axis and we applied the horizontal to vertical (H/V) spectral ratio method [3] to the recordings in order to estimate the amplification of the basin. The H/V curves obtained reveals the existence of two low frequency peaks centered on 0.2 a 1 Hz frequencies[4]. These peaks are strongly related with the thickness of Cenozoic and alluvial sediments. By inversion of the H/V curve, we obtain a more detailed velocity model for the region where the profile were determined, which is in good agreement with borehole data and other results obtained with magnetic and seismic reflection methods

    Marcos de formação/transformação da Região Metropolitana de Campinas à luz da história territorial paulista: séculos XVII-XX.

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    O território de São Paulo contém, em seu interior, diferentes paisagens culturais; paisagens que, formadas no curso do tempo, sofreram transformações profundas nos últimos séculos frente aos processos acelerados de substituição da cobertura vegetal pela produção diversificada de gêneros, criação e agricultura de exportação; pela entrada massiva de grupos populacionais procedentes das mais variadas regiões do Brasil e do mundo (cerca de 70 grupos étnicos); pela intensidade da urbanização (entre os séculos XIX e XX); pela complexificação dos sistemas de escoamento (estradas tropeiras, linhas férreas, estradas de rodagem, aviação), entre outros, que permitiram a então Capitania, depois Província e atual Estado vencer a Serra do Mar (que a mantivera isolada da dinâmica colonial ao longo dos séculos XVI a XVIII) e estabelecer vínculos comerciais e produtivos entre as regiões mais interiorizadas e o litoral. Particularmente, nos últimos cento e sessenta anos, a intensidade e força de certos processos, em grande medida externos ao território paulista, se revelaram capazes de apagar (nos limites entre dizimar e incorporar) a presença milenar de populações indígenas, ao mesmo tempo em que diluir marcas centenárias de constituição cultural original (indígenas e européias) para dar lugar a paisagens plenamente alteradas em suas bases econômicas, sociais, culturais e políticas originais. A expressão ?paulista?, utilizada para caracterizar um povo diferente pelos hábitos, língua, costumes e formas de vida mestiça, passou em pouco tempo a designar uma população disforme pelos tantos aspectos culturais, vínculos e motivações agora associadas ao capital transnacional. No estudo da Região Metropolitana de Campinas encontramos testemunhos das diferentes paisagens

    Predictors of hotel clients’ satisfaction in the Cape Verde Islands

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    Tourism has been fundamental for countries’ economic development, and Africa is the destination with the biggest tourism growth potential. Using 1414 travelers’ online reviews collected from TripAdvisor, the present work aims to understand which variables predict the satisfaction of Cape Verde’s hotel clients. Satisfaction was analyzed using sentiment analysis and ANOVA to predict the effect of the gathered variables on clients’ satisfaction. Results indicate that 90% of the clients revealed positive satisfaction and that nationality, date of stay, and previous traveler experiences affect satisfaction. Contrarily to our predictions, there is no statistically significant evidence that gender influences satisfaction. The findings of this study will help hotel marketing managers to align their strategies accordingly and meet their clients’ expectations.info:eu-repo/semantics/publishedVersio

    Gravitational Geometric Phase in the Presence of Torsion

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    We investigate the relativistic and non-relativistic quantum dynamics of a neutral spin-1/2 particle submitted an external electromagnetic field in the presence of a cosmic dislocation. We analyze the explicit contribution of the torsion in the geometric phase acquired in the dynamic of this neutral spinorial particle. We discuss the influence of the torsion in the relativistic geometric phase. Using the Foldy-Wouthuysen approximation, the non-relativistic quantum dynamics are studied and the influence of the torsion in the Aharonov-Casher and He-McKellar-Wilkens effects are discussed.Comment: 14 pages, no figur

    Landau Analog Levels for Dipoles in the Noncommutative Space and Phase Space

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    In the present contribution we investigate the Landau analog energy quantization for neutral particles, that possesses a nonzero permanent magnetic and electric dipole moments, in the presence of an homogeneous electric and magnetic external fields in the context of the noncommutative quantum mechanics. Also, we analyze the Landau--Aharonov--Casher and Landau--He--McKellar--Wilkens quantization due to noncommutative quantum dynamics of magnetic and electric dipoles in the presence of an external electric and magnetic fields and the energy spectrum and the eigenfunctions are obtained. Furthermore, we have analyzed Landau quantization analogs in the noncommutative phase space, and we obtain also the energy spectrum and the eigenfunctions in this context.Comment: 20 pages, references adde

    Contributo para o estudo das plantas vasculares endémicas da Ilha das Flores (Açores).

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    IV Expedição Científica do Departamento de Biologia – Flores 1989.Conforme mostra MALATO-BELIZ (1988), o número de taxa vasculares endémicos nas ilhas dos Açores varia entre um máximo de 62 taxa (ilha de S. Miguel) e um mínimo de 11 taxa endémicos na ilha Graciosa. A pequena ilha das Flores com 51 taxa endémicos ultrapassa claramente neste particular as ilhas Graciosa (11), S. Maria (35) e Corvo (37) e quase iguala em número de espécies endémicas ilhas bastante maiores como a Terceira (55) e o Faial (55). Não admira pois que em termos da relação "nº taxa endémicos/unidade de superfície (Km2)" a ilha das Flores com 0,357 end./Km2, apenas seja ultrapassada por S. Maria (0,360 end./ Km2) e pelo Corvo (2,126 end./Km2), 0 valor médio para o arquipélago situa-se apenas nos 0,184 end./Km2. A explicação para esta relativa riqueza em espécies endémicas da ilha das Flores fica sem dúvida a dever-se à grande diversidade de biótopos que ela possui e à existência de algumas manchas vegetais menos alteradas pelo homem
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