20,764 research outputs found

    Developing a site-conditions map for seismic hazard Assessment in Portugal

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    The evaluation of site effects on a broad scale is a critical issue for seismic hazard and risk assessment, land use planning and emergency planning. As characterization of site conditions based on the shear-wave velocity has become increasingly important, several methods have been proposed in the literature to estimate its average over the first thirty meters (Vs30) from more extensively available data. These methods include correlations with geologic-geographic defined units and topographic slope. In this paper we present the first steps towards the development of a site–conditions map for Portugal, based on a regional database of shear-wave velocity data, together with geological, geographic, and lithological information. We computed Vs30 for each database site and classified it according to the corresponding geological-lithological information using maps at the smallest scale available (usually 1:50000). We evaluated the consistency of Vs30 values within generalized-geological classes, and assessed the performance of expedient methodologies proposed in the literature

    Vanishing Viscosity Limits and Boundary Layers for Circularly Symmetric 2D Flows

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    We continue the work of Lopes Filho, Mazzucato and Nussenzveig Lopes [LMN], on the vanishing viscosity limit of circularly symmetric viscous flow in a disk with rotating boundary, shown there to converge to the inviscid limit in L2L^2-norm as long as the prescribed angular velocity α(t)\alpha(t) of the boundary has bounded total variation. Here we establish convergence in stronger L2L^2 and LpL^p-Sobolev spaces, allow for more singular angular velocities α\alpha, and address the issue of analyzing the behavior of the boundary layer. This includes an analysis of concentration of vorticity in the vanishing viscosity limit. We also consider such flows on an annulus, whose two boundary components rotate independently. [LMN] Lopes Filho, M. C., Mazzucato, A. L. and Nussenzveig Lopes, H. J., Vanishing viscosity limit for incompressible flow inside a rotating circle, preprint 2006

    Experimental determination of the non-extensive entropic parameter qq

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    We show how to extract the qq parameter from experimental data, considering an inhomogeneous magnetic system composed by many Maxwell-Boltzmann homogeneous parts, which after integration over the whole system recover the Tsallis non-extensivity. Analyzing the cluster distribution of La0.7_{0.7}Sr0.3_{0.3}MnO3_{3} manganite, obtained through scanning tunnelling spectroscopy, we measure the qq parameter and predict the bulk magnetization with good accuracy. The connection between the Griffiths phase and non-extensivity is also considered. We conclude that the entropic parameter embodies information about the dynamics, the key role to describe complex systems.Comment: Submitted to Phys. Rev. Let

    GeMs/GSAOI observations of La Serena 94: an old and far open cluster inside the solar circle

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    Physical properties were derived for the candidate open cluster La Serena 94, recently unveiled by the VVV collaboration. Thanks to the exquisite angular resolution provided by GeMS/GSAOI, we could characterize this system in detail, for the first time, with deep photometry in JHKs_{s} - bands. Decontaminated JHKs_{s} diagrams reach about 5 mag below the cluster turnoff in H. The locus of red clump giants in the colour - colour diagram, together with an extinction law, was used to obtain an average extinction of AV=14.18±0.71A_V =14.18 \pm 0.71. The same stars were considered as standard - candles to derive the cluster distance, 8.5±1.08.5 \pm 1.0 kpc. Isochrones were matched to the cluster colour - magnitude diagrams to determine its age, logt(yr)=9.12±0.06\log{t(yr)}=9.12\pm 0.06, and metallicity, Z=0.02±0.01Z=0.02\pm0.01. A core radius of rc=0.51±0.04r_{c}=0.51\pm 0.04 pc was found by fitting King models to the radial density profile. By adding up the visible stellar mass to an extrapolated mass function, the cluster mass was estimated as M=(2.65±0.57)×103M=(2.65\pm0.57) \times 10^3 M_{\odot}, consistent with an integrated magnitude of MK=5.82±0.16M_{K}=-5.82\pm0.16 and a tidal radius of rt=17.2±2.1r_{t}=17.2\pm2.1 pc. The overall characteristics of La Serena 94 confirm that it is an old open cluster located in the Crux spiral arm towards the fourth Galactic quadrant and distant 7.30±0.497.30\pm 0.49 kpc from the Galactic centre. The cluster distorted structure, mass segregation and age indicate that it is a dynamically evolved stellar system.Comment: 16 pages, 24 figures, 2 Tables, accepted by MNRAS; corrected typo

    Stellar parameters for stars of the CoRoT exoplanet field

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    Aims:To support the computation and evolutionary interpretation of periods associated with the rotational modulation, oscillations, and variability of stars located in the CoRoT fields, we are conducting a spectroscopic survey for stars located in the fields already observed by the satellite. These observations allow us to compute physical and chemical parameters for our stellar sample. Method: Using spectroscopic observations obtained with UVES/VLT and Hydra/Blanco, and based on standard analysis techniques, we computed physical and chemical parameters (TeffT_{\rm{eff}}, log(g)\log \,(g), [Fe/H]\rm{[Fe/H]}, vmicv_{\rm{mic}}, vradv_{\rm{rad}}, vsin(i)v \sin \,(i), and A(Li)A(\rm{Li})) for a large sample of CoRoT targets. Results: We provide physical and chemical parameters for a sample comprised of 138 CoRoT targets. Our analysis shows the stars in our sample are located in different evolutionary stages, ranging from the main sequence to the red giant branch, and range in spectral type from F to K. The physical and chemical properties for the stellar sample are in agreement with typical values reported for FGK stars. However, we report three stars presenting abnormal lithium behavior in the CoRoT fields. These parameters allow us to properly characterize the intrinsic properties of the stars in these fields. Our results reveal important differences in the distributions of metallicity, TeffT_{\rm eff}, and evolutionary status for stars belonging to different CoRoT fields, in agreement with results obtained independently from ground-based photometric surveys. Conclusions: Our spectroscopic catalog, by providing much-needed spectroscopic information for a large sample of CoRoT targets, will be of key importance for the successful accomplishment of several different programs related to the CoRoT mission, thus it will help further boost the scientific return associated with this space mission.Comment: 43 pages, 17 figures, accepted for publication in A&

    Determinação da Carga Alergénica (Ole e1) Presente no Ar Atmosférico na Região de Évora: Correlação com o conteúdo polínico de Olea

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    Introdução: Em Portugal, o pólen da oliveira (Olea europaea) constitui uma das fontes mais relevantes de aero-alergénios, sendo uma causa frequente de polinose na região Mediterrânica, onde o Ole e 1 é um alergeno major. Apesar de se julgar apenas associado aos grãos de pólen, desconhece-se a variabilidade inter-anual da carga alergénica do pólen e ainda existe alguma controvérsia sobre a forma como este aeroalergeno se distribui no ar atmosférico. Objectivo: Este trabalho teve como objectivos: i) determinar a fracção dos bioaerossóis mais rica em Ole e 1; ii) avaliar a correlação dos conteúdos diários de pólen e aeroalergeno no ar atmosférico; iii) avaliar variação anual da carga alergénica do pólen. Métodos: Os aeroalergenos foram captados utilizando um colector de impacto CHEMVOL equipado com dois filtros com capacidade para reter partículas de diferentes dimensões: PM>10µm e 10µm>PM>2,5µm. Após 24h os filtros foram retirados, a fracção proteica foi extraída e os alergenos quantificados por ELISA. Simultaneamente o pólen foi monitorizado pela tecnologia padrão utilizando um colector volumétrico Burkard 7-Day Recording Volumetric Spore Trap. Os colectores foram ambos colocados numa mesma plataforma a 17m de altura, e a ≈3-4m um do outro. Resultados: Entre 2009 e 2011, registou-se uma variação inter-anual quer do perfil quer da duração da época polínica (39, 47 e 45 dias, respectivamente). O conteúdo polínico total no ar atmosférico também foi variável no intervalo de 7240 a 12524 grãos/m3. Mais de 90% do alergeno foi encontrado na fracção de bioaerossóis de PM>10µm. O conteúdo em Ole e 1 foi directamente proporcional ao número de grãos de pólen no ar atmosférico, tendo-se encontrado uma correlação positiva entre os valores diários dos dois parâmetros. Comparando as épocas estudadas, os conteúdos totais de Ole e1 e de pólen não foram proporcionais, tendo-se observado que a carga alergénica por grão de pólen variou mais de 3x. Conclusões: Estes resultados sugerem que o Ole e 1 está preferencialmente associado aos grãos de pólen. Os conteúdos em pólen e Ole e 1 variaram inter-anualmente, tendo a carga alergénica dos grãos de pólen sido diferente. Este trabalho poderá assim contribuir para o desenvolvimento de um indicador que permita melhorar a previsão do risco de exposição a aeroalergenos. Agradecimentos: Este foi realizado no âmbito do projecto europeu HIALINE (Executive Agency for Health and Consumers, grant agreement No 2008 11 07)
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