519 research outputs found
Slowly Rotating Anisotropic Neutron Stars in General Relativity and Scalar-Tensor Theory
Some models (such as the Skyrme model, a low-energy effective field theory
for QCD) suggest that the high-density matter prevailing in neutron star
interiors may be significantly anisotropic. Anisotropy is known to affect the
bulk properties of nonrotating neutron stars in General Relativity. In this
paper we study the effects of anisotropy on slowly rotating stars in General
Relativity. We also consider one of the most popular extensions of Einstein's
theory, namely scalar-tensor theories allowing for spontaneous scalarization (a
phase transition similar to spontaneous magnetization in ferromagnetic
materials). Anisotropy affects the moment of inertia of neutron stars (a
quantity that could potentially be measured in binary pulsar systems) in both
theories. We find that the effects of scalarization increase (decrease) when
the tangential pressure is bigger (smaller) than the radial pressure, and we
present a simple criterion to determine the onset of scalarization by
linearizing the scalar-field equation. Our calculations suggest that binary
pulsar observations may constrain the degree of anisotropy or even, more
optimistically, provide evidence for anisotropy in neutron star cores.Comment: 19 pages, 7 figures, 1 table. Matches version in press in CQG. Fixed
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Análisis de la cuota del mercado turístico en Portugal
El presente trabajo presenta un estudio dónde se procuró evaluar el desempeño y la competitividad de los
destinos turísticos en Portugal. La evaluación se realizó bajo un instrumento de análisis, Análisis de la Cuota de
Mercado, propuesto por Faulkner. Del análisis efectuado se concluyó, con respecto a la evolución de los destinos
turísticos, que las Islas de Madeira y Azores pueden clasificarse como regiones de éxito o mercados en
crecimiento con las carteras de mercados menos concentradas. Los destinos turísticos Lisboa y Vale do Tejo y
Algarve representan mercados maduros al situarse en la región de incertidumbre. Por último, los destinos Norte,
Centro y Alentejo pueden considerarse mercados en declive con una elevada dependencia del mercado de origen
Europa Meridional. Se concluye aún, que los destinos turísticos presentaran desempeños distintos entre si, es
decir, en el período analizado se observaran alteraciones en la competitividad turística en los destinos en estudio.O presente trabalho apresenta um estudo onde se procurou avaliar o desempenho e a competitividade dos
destinos turísticos em Portugal. Para tal, aplicou-se um instrumento de análise, Análise da Quota de Mercado,
proposto por Faulkner. Da análise efectuada concluiu-se, quanto à evolução dos destinos turísticos, que as Ilhas
da Madeira e Azores podem classificar-se como regiões de êxito ou mercados em crescimentos registando as
carteiras de mercados menos concentradas. Os destinos turísticos Lisboa y Vale do Tejo e o Algarve representam
mercados maduros ao se situarem na região de incerteza. Por último, os destinos turísticos Norte, Centro e
Alentejo podem considerar-se mercados em declínio obtendo uma elevada dependência em relação à origem
Europa Meridional. Concluiu-se ainda, que os destinos turísticos apresentaram desempenhos distintos entre si,
ou seja, no período analisado observaram-se alterações na competitividade turística dos destinos em estudo
Temporal evolution of roughness development on polymer surfaces exposed to non-thermal plasma
Brazilian agencies: CNPq and CAPES/PRINTUFSC, 2019Processes such as ablation, erosion and corrosion generally create roughness patterns on solid surfaces. Despite the randomness of this phenomenon, some patterns can be described mathematically by studying statistically the mechanisms behind them. This paper reports an experimental study on the temporal evolution of the roughness development of polymer surfaces exposed to argon non-thermal plasma under reduced pressure of 5 mbar and 65 W of applied power. The substrates studied were polypropylene, high density polyethylene, polyamide-6 and poly(ether ether)ketone. The mean roughness data as well as the saturation roughness values showed differences between polyolefin and polymers containing heteroatoms and notably the dependence of the etching on the packing density of the polymer chains. The plasma-etched surfaces were described statistically as self-affine surfaces using scaling law analysis, exhibiting roughness exponents of α ca.0.73 ± 0.2 and growth exponents of β ca. 1.0 ± 0.1. The roughness increases and decreases successively during treatment although presenting a general linear behavior in a non-monotonous way, as a function of time. The models for the shadowing and redistribution of active species can be complemented with the transient crosslinking model of the observed flattening stages.publishersversionpublishe
Flexural behaviour of hybrid FRC-GFRP/PUR sandwich panels
The present work has been developed in the scope of the research project ‘‘Easyfloor – Development of composite sandwich panels for building floor rehabilitation”. This project aims at developing a hybrid sandwich panel, constituting an alternative construction system to conventional floor solutions, mainly for buildings rehabilitation. The developed hybrid sandwich panel is composed of a top face layer of steel fibre reinforced self-compacting concrete (FRC), a core of polyurethane (PUR) closed-cell foam and a bottom face sheet and lateral webs of glass fibre reinforced polymer (GFRP). The composite (GFRP/PUR) is manufactured by pultrusion, and its cross-section includes a sheet of GFRP between the FRC and PUR. After the production of the composite part, fresh FRC is poured onto the FRP component to materialize the top face of the panel. Full-scale tests on the developed sandwich panels have been carried out to characterize their flexural behaviour. The experimental programme included flexural tests i) on single supported panels, ii) on two panels side adhesively bonded and iii) on single panels with different connection solutions to walls. The present work includes a detailed description of the developed panels and of the experimental programme. It also presents and discusses the relevant results. The observed performance of the tested specimens is critically analysed.FCT - Fundação para a Ciência e a Tecnologia (SFRH/BSAB/150266/2019
Instabilities in neutrino-plasma density waves
One examines the interaction and possible resonances between supernova
neutrinos and electron plasma waves. The neutrino phase space distribution and
its boundary regions are analyzed in detail. It is shown that the boundary
regions are too wide to produce non-linear resonant effects. The growth or
damping rates induced by neutrinos are always proportional to the neutrino flux
and .Comment: 9 pages, a few words modified to match PRD publicatio
Power Law Scaling for a System of Interacting Units with Complex Internal Structure
We study the dynamics of a system composed of interacting units each with a
complex internal structure comprising many subunits. We consider the case in
which each subunit grows in a multiplicative manner. We propose a model for
such systems in which the interaction among the units is treated in a mean
field approximation and the interaction among subunits is nonlinear. To test
the model, we identify a large data base spanning 20 years, and find that the
model correctly predicts a variety of empirical results.Comment: 4 pages with 4 postscript figures (uses Revtex 3.1, Latex2e,
multicol.sty, epsf.sty and rotate.sty). Submitted to PR
Optimizing Electroactive Organisms: The Effect of Orthologous Proteins
publishersversionpublishe
The African hind's (Cephalopholis taeniops, serranidae) use of artificial reefs off Sal Island (Cape Verde): a preliminary study based on acoustic telemetry
The African hind Cephalopholis taeniops (Valenciennes, 1828) is one of the most important commercial demersal species caught in the Cape Verde archipelago. The species is closely associated with hard substrate and is one of the main attractions for SCUBA divers. In January 2006 a former Soviet fishing vessel - the Kwarcit - was sunk off Santa Maria Bay (Sal Island). Young C. taeniops are commonly observed in this artificial reef (AR). In order to investigate the species' use of the AR, 4 specimens were captured and surgically implanted underwater with Vemco brand acoustic transmitters. The fish were monitored daily with an active telemetry receiver for one week after release. Simultaneously, an array of 3 passive VR2 / VR2W receivers was set for 63 days, registering data that allowed an analysis of spatial, daily and short term temporal activity patterns. The results showed site fidelity to the AR, with no migrations to the nearby natural reef. The method used allowed to register a consistent higher activity during daytime and a preference for the area opposite the dominant current
Universality Classes for Interface Growth with Quenched Disorder
We present numerical evidence that there are two distinct universality
classes characterizing driven interface roughening in the presence of quenched
disorder. The evidence is based on the behavior of , the coefficient
of the nonlinear term in the growth equation. Specifically, for three of the
models studied, at the depinning transition, while
for the two other models, .Comment: 11 pages and 3 figures (upon request), REVTeX 3.0, (submitted to PRL
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