12,346 research outputs found
Gauge Fluctuations in Superconducting Films
In this paper we consider a superconducting film modeled by the
Ginzburg-Landau model, confined between two parallel planes a distance
apart from one another. Our approach is based on the Gaussian effective
potential in the transverse unitarity gauge, which allows to treat gauge
contributions in a compact form. Using techniques from dimensional and
-function regularizations, modified by the confinement conditions, we
investigate the critical temperature as a function of the film thickness .
The contributions from the scalar self-interaction and from the gauge
fluctuations are clearly identified. The model suggests the existence of a
minimal critical thickness below which superconductivity is suppressed.Comment: 6 pages Revtex, no figure
Bar pattern speed evolution over the last 7 Gyr
The tumbling pattern of a bar is the main parameter characterising its
dynamics. From numerical simulations, its evolution since bar formation is
tightly linked to the dark halo in which the bar is formed through dynamical
friction and angular momentum exchange. Observational measurements of the bar
pattern speed with redshift can restrict models of galaxy formation and bar
evolution. We aim to determine, for the first time, the bar pattern speed
evolution with redshift based on morphological measurements. We have selected a
sample of 44 low inclination ringed galaxies from the SDSS and COSMOS surveys
covering the redshift range 0 <z< 0.8 to investigate the evolution of the bar
pattern speed. We have derived morphological ratios between the deprojected
outer ring radius (R_{ring}) and the bar size (R_{bar}). This quantity is
related to the parameter {\cal R}=R_{CR}/R_{bar} used for classifiying bars in
slow and fast rotators, and allow us to investigate possible differences with
redshift. We obtain a similar distribution of at all redshifts. We do not
find any systematic effect that could be forcing this result. The results
obtained here are compatible with both, the bulk of the bar population (~70%)
being fast-rotators and no evolution of the pattern speed with redshift. We
argue that if bars are long-lasting structures, the results presented here
imply that there has not been a substantial angular momentum exchange between
the bar and halo, as predicted by numerical simulations. In consequence, this
might imply that the discs of these high surface-brightness galaxies are
maximal.Comment: Accepted for publication in A&
Triplectic Gauge Fixing for N=1 Super Yang-Mills Theory
The Sp(2)-gauge fixing of N = 1 super-Yang-Mills theory is considered here.
We thereby apply the triplectic scheme, where two classes of gauge-fixing
bosons are introduced. The first one depends only on the gauge field, whereas
the second boson depends on this gauge field and also on a pair of Majorana
fermions. In this sense, we build up the BRST extended (BRST plus antiBRST)
algebras for the model, for which the nilpotency relations,
s^2_1=s^2_2=s_1s_2+s_2s_1=0, hold.Comment: 10 pages, no figures, latex forma
Deep spectroscopic luminosity function of Abell 85: no evidence for a steep upturn of the faint-end slope
We present a new deep determination of the spectroscopic LF within the virial
radius of the nearby and massive Abell\,85 (A85) cluster down to the dwarf
regime (M* + 6) using VLT/VIMOS spectra for galaxies with m mag and mag arcsec. The
resulting LF from 438 cluster members is best modelled by a double Schechter
function due to the presence of a statistically significant upturn at the
faint-end. The amplitude of this upturn (),
however, is much smaller than that of the SDSS composite photometric cluster LF
by Popesso et al. 2006, -2. The faint-end slope of the LF in
A85 is consistent, within the uncertainties, with that of the field. The red
galaxy population dominates the LF at low luminosities, and is the main
responsible for the upturn. The fact that the slopes of the spectroscopic LFs
in the field and in a cluster as massive as A85 are similar suggests that the
cluster environment does not play a major role in determining the abundance of
low-mass galaxies.Comment: 6 pages, 4 figures, accepted at MNRAS lette
Triplectic Quantization of W2 gravity
The role of one loop order corrections in the triplectic quantization is
discussed in the case of W2 theory. This model illustrates the presence of
anomalies and Wess Zumino terms in this quantization scheme where extended BRST
invariance is represented in a completely anticanonical form.Comment: 10 pages, no figure
Equipamentos alternativos na obtenção de farinha de resíduos de tambaqui (Colossoma macropomum).
O tambaqui (Colossoma macropomum) é o segundo maior peixe de escama da América, superado apenas pelo pirarucu. Nativo da bacia Amazônica, atualmente vem ganhando destaque na aquicultura familiar da Região Norte, como no Estado do Pará, onde seu consumo vem aumentando gradativamente, principalmente na forma de filés. No entanto, o processo de filetamento de pescado gera um volume de resíduos superior a 50%, que pode se tornar um importante poluente se não tiver um manuseio adequado. Estes resíduos possuem alto teor de proteína e de outros nutrientes que tem grande demanda em outros setores, como na elaboração de farinhas para ração animal, por exemplo. Contudo, as instalações iniciais para o processamento de farinhas é um tanto quanto oneroso. O objetivo deste foi, através da adaptação de utensílios e equipamentos, elaborar um processo em escala piloto para aproveitamento de resíduos de tambaqui que pode ser realizado por pequenos e médios produtores, para produção de farinha e consequente incorporação em suas rações. Com teor de 8% de lipídios e 61% de proteína, o produto elaborado em pequena escala enquadrouse nos padrões de farinhas da RIISPOA e ANFAR
Short term effects of irradiance on the growth of Pterocladiella capillacea (Gelidiales, Rhodophyta)
Pterocladiella capillacea has been economically exploited for agar extraction in the Azores for many years. Harvesting dropped to a full stop in the early 1990s due to a population collapse, but restarted in 2013. Since then it has been intensively harvested and overexploitation must be prevented, with both sustainable harvesting and effective cultivation practices. This study represents the first attempt to determine optimal conditions for P. capillacea production in the Azores, and evaluates its vegetative growth in two experiments using von Stosch’s medium designed to test entire thallus and tips portions response to different irradiances (30, 70 and 150 μmol photons m¯² s¯¹). The best relative growth rate (RGR) was recorded at 150 μmol photons m¯² s¯¹ for the entire thalli and tips after two-weeks and three-weeks, respectively, indicating that an acclimation period is necessary to assure the growth of this alga under experimental conditions. Higher RGR was obtained at higher irradiance (3.98 ± 2.10% fm day¯¹), but overall, growth rates were low or negative. Epiphytes were a serious problem towards the end of the entire thallus experiments, where Feldmannia irregularis proliferate at all irradiances. Future cultivation approaches complemented with other relevant environmental factors (e.g. pH, photoperiod, salinity), are recommended.FCT – Fundação para a Ciência e Tecnologia projects UID/BIA/00329/2013, 2015 - 2018 and UID/BIA/00329/2019, CIRN (Centro de Investigação de Recursos Naturais, University of the Azores), and CIIMAR (Interdisciplinary Centre of Marine and Environmental Research, Porto, Portugal). RFP was supported by a doctoral grant M3.1.2/F/024/2011, Fundo Regional para a Ciência e Tecnologia.info:eu-repo/semantics/publishedVersio
Mapeamento da distribuição da temperatura em sistema de aquecimento para aves.
Projeto: 02.10.06.002
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