Vacuum Polarization by a Magnetic Flux Tube at Finite Temperature in the Cosmic String Spacetime

In this paper we analyse the effect produced by the temperature in the vacuum polarization associated with charged massless scalar field in the presence of magnetic flux tube in the cosmic string spacetime. Three different configurations of magnetic fields are taken into account: $(i)$ a homogeneous field inside the tube, $(ii)$ a field proportional to $1/r$ and $(iii)$ a cylindrical shell with $\delta$-function. In these three cases, the axis of the infinitely long tube of radius $R$ coincides with the cosmic string. Because the complexity of this analysis in the region inside the tube, we consider the thermal effect in the region outside. In order to develop this analysis, we construct the thermal Green function associated with this system for the three above mentioned situations considering points in the region outside the tube. We explicitly calculate in the high-temperature limit, the thermal average of the field square and the energy-momentum tensor.Comment: 16 pages, 1 figur

A semiquantitative approach to the impurity-band-related transport properties of GaMnAs nanolayers

We investigate the spin-polarized transport of GaMnAs nanolayers in which a ferromagnetic order exists below a certain transition temperature. Our calculation for the self-averaged resistivity takes into account the existence of an impurity band determining the extended ("metallic" transport) or localized (hopping by thermal excitation) nature of the states at and near the Fermi level. Magnetic order and resistivity are inter-related due to the influence of the spin polarization of the impurity band and the effect of the Zeeman splitting on the mobility edge. We obtain, for a given range of Mn concentration and carrier density, a "metallic" behavior in which the transport by extended carriers dominates at low temperature, and is dominated by the thermally excited localized carriers near and above the transition temperature. This gives rise to a conspicuous hump of the resistivity which has been experimentally observed and brings light onto the relationship between transport and magnetic properties of this material

On the nature of the spin-polarized hole states in a quasi-two-dimensional GaMnAs ferromagnetic layer

A self-consistent calculation of the density of states and the spectral density function is performed in a two-dimensional spin-polarized hole system based on a multiple-scattering approximation. Using parameters corresponding to GaMnAs thin layers, a wide range of Mn concentrations and hole densities have been explored to understand the nature, localized or extended, of the spin-polarized holes at the Fermi level for several values of the average magnetization of the Mn ystem. We show that, for a certain interval of Mn and hole densities, an increase on the magnetic order of the Mn ions come together with a change of the nature of the states at the Fermi level. This fact provides a delocalization of spin-polarized extended states anti-aligned to the average Mn magnetization, and a higher spin-polarization of the hole gas. These results are consistent with the occurrence of ferromagnetism with relatively high transition temperatures observed in some thin film samples and multilayered structures of this material.Comment: 3 page

Exploring dynamic lighting, colour and form with smart textiles

This paper addresses an ongoing research, aiming at the development of smart textiles that transform the incident light that passes through them – light transmittance – to design dynamic light without acting upon the light source. A colour and shape change prototype was developed with the objective of studying textile changes in time; to explore temperature as a dynamic variable through electrical activation of the smart materials and conductive threads integrated in the textile substrate; and to analyse the relation between textile chromic and morphologic behaviour in interaction with light. Based on the experiments conducted, results have highlighted some considerations of the dynamic parameters involved in the behaviour of thermo-responsive textiles and demonstrated design possibilities to create interactive lighting scenarios.This work is supported by FEDER funds through the Operational Programme for Competitiveness Factors – COMPETE and National Funds through FCT – Foundation for Science and Technology within the scope of the projects SFRH/BD/87196/2012, POCI-01-0145-FEDER-007136 and UID/CTM/00264. The authors also like to acknowledge Smart Textiles Design Lab for the support on the prototype development.info:eu-repo/semantics/publishedVersio

When subjective social status matters: moderating effects in the association between victimization and mental health

Social status is found to interfere with health outcomes after adverse life experiences. Evidence suggests the importance of subjective social status (SSS), above and beyond objective status. This study tests the moderating role of SSS in the association between victimization and mental health, considering the effect of distinct forms of victimization, clinical symptoms and psychological well-being. A sample of 300 adults completed self-reported questionnaires. Results revealed that greater psychological victimization was associated with lower self-acceptance and autonomy, and greater sexual victimization was associated with lower autonomy, particularly when participants reported lower SSS. Implications for intervention with victims are discussed.info:eu-repo/semantics/acceptedVersio

The frequency and nature of `cloud-cloud collisions' in galaxies

We investigate cloud-cloud collisions, and GMC evolution, in hydrodynamic simulations of isolated galaxies. The simulations include heating and cooling of the ISM, self--gravity and stellar feedback. Over timescales $<5$ Myr most clouds undergo no change, and mergers and splits are found to be typically two body processes, but evolution over longer timescales is more complex and involves a greater fraction of intercloud material. We find that mergers, or collisions, occur every 8-10 Myr (1/15th of an orbit) in a simulation with spiral arms, and once every 28 Myr (1/5th of an orbit) with no imposed spiral arms. Both figures are higher than expected from analytic estimates, as clouds are not uniformly distributed in the galaxy. Thus clouds can be expected to undergo between zero and a few collisions over their lifetime. We present specific examples of cloud--cloud interactions in our results, including synthetic CO maps. We would expect cloud--cloud interactions to be observable, but find they appear to have little or no impact on the ISM. Due to a combination of the clouds' typical geometries, and moderate velocity dispersions, cloud--cloud interactions often better resemble a smaller cloud nudging a larger cloud. Our findings are consistent with the view that spiral arms make little difference to overall star formation rates in galaxies, and we see no evidence that collisions likely produce massive clusters. However, to confirm the outcome of such massive cloud collisions we ideally need higher resolution simulations.Comment: 13 pages, 15 figures, accepted for publication in MNRA

Efeito das condições de extração no rendimento e qualidade do leite de castanha-do-Brasil despeliculada.

Autoria: FERBERG [i.e. FELBERG], I