Nonlinear elastic polymers in random flow

Polymer stretching in random smooth flows is investigated within the framework of the FENE dumbbell model. The advecting flow is Gaussian and short-correlated in time. The stationary probability density function of polymer extension is derived exactly. The characteristic time needed for the system to attain the stationary regime is computed as a function of the Weissenberg number and the maximum length of polymers. The transient relaxation to the stationary regime is predicted to be exceptionally slow in the proximity of the coil-stretch transition.Comment: 10 pages, to be published in J. Fluid Mec

Starburst and AGN activity in ultraluminous infrared galaxies

(Abridged) We examine the power source of 41 local Ultraluminous Infrared Galaxies using archival infrared and optical photometry. We fit the observed Spectral Energy Distributions (SEDs) with starburst and AGN components; each component being drawn from a family of templates. We find all of the sample require a starburst, whereas only half require an AGN. In 90% of the sample the starburst provides over half the IR emission, with a mean fractional luminosity of 82%. When combined with other galaxy samples we find that starburst and AGN luminosities correlate over 6 decades in IR luminosity suggesting that a common factor governs both luminosities, plausibly the gas masses in the nuclear regions. We find that the mid-IR 7.7 micron line-continuum ratio is no indication of the starburst luminosity, or the fractional AGN luminosity, and therefore that this ratio is not a reliable diagnostic of the power source in ULIRGs. We propose that the scatter in the radio-IR correlation in ULIRGs is due to a skewed starburst IMF and/or relic relativistic electrons from a previous starburst, rather than contamination from an obscured AGN. We show that most ULIRGs undergo multiple starbursts during their lifetime, and by inference that mergers between more than two galaxies may be common amongst ULIRGs. Our results support the evolutionary model for ULIRGs proposed by Farrah et al 2001, where they can follow many different evolutionary paths of starburst and AGN activity in transforming merging spiral galaxies into elliptical galaxies, but that most do not go through an optical QSO phase. The lower level of AGN activity in our local sample than in z~1 HLIRGs implies that the two samples are distinct populations. We postulate that different galaxy formation processes at high-z are responsible for this difference.Comment: 24 pages, 8 figures. Accepted for publication in MNRA

Constructing networks of defects with scalar fields

We propose a new way to build networks of defects. The idea takes advantage of the deformation procedure recently employed to describe defect structures, which we use to construct networks, spread from small rudimentary networks that appear in simple models of scalar fields.Comment: 5 pages, 4 figures, version with new title, motivations and references, to appear in PL

Microlens Parallaxes with SIRTF

The Space Infrared Telescope Facility (SIRTF) will drift away from the Earth at about 0.1 AU/yr. Microlensing events will therefore have different characteristics as seen from the satellite and the Earth. From the difference, it is possible in principle to measure v-tilde, the transverse velocity of the lens projected onto the observer plane. Since v-tilde has very different values for different populations (disk, halo, Large Magellanic Cloud), such measurements could help identify the location, and hence the nature, of the lenses. I show that the method previously developed by Gould for measuring such satellite parallaxes fails completely in the case of SIRTF: it is overwhelmed by degeneracies which arise from fact that the Earth and satellite observations are in different band passes. I develop a new method which allows for observations in different band passes and yet removes all degeneracies. The method combines a purely ground-based measurement of the "parallax asymmetry" with a measurement of the delay between the time the event peaks at the Earth and satellite. In effect, the parallax asymmetry determines the component of v-tilde in the Earth-Sun direction, while the delay time measures the component of v-tilde in the direction of the Earth's orbit.Comment: 21 pages plus 3 figure

Evolution of the far-infrared luminosity functions in the Spitzer Wide-area Infrared Extragalactic Legacy Survey

We present new observational determination of the evolution of the rest-frame 70 and 160 micron and total infrared (TIR) galaxy luminosity functions (LFs) using 70 micron data from the Spitzer Wide-area Infrared Extragalactic Legacy Survey (SWIRE). The LFs were constructed for sources with spectroscopic redshifts only in the XMM-LSS and Lockman Hole fields from the SWIRE photometric redshift catalogue. The 70 micron and TIR LFs were constructed in the redshift range 0<z<1.2 and the 160 micron LF was constructed in the redshift range 0<z<0.5 using a parametric Bayesian and the vmax methods. We assume in our models, that the faint-end power-law index of the LF does not evolve with redshifts. We find the the double power-law model is a better representation of the IR LF than the more commonly used power-law and Gaussian model. We model the evolution of the FIR LFs as a function of redshift where where the characteristic luminosity, $L^\ast$ evolve as \propto(1+z)^{\alpha_\textsc{l}}. The rest-frame 70 micron LF shows a strong luminosity evolution out to z=1.2 with alpha_l=3.41^{+0.18}_{-0.25}. The rest-frame 160 micron LF also showed rapid luminosity evolution with alpha_l=5.53^{+0.28}_{-0.23} out to z=0.5. The rate of evolution in luminosity is consistent with values estimated from previous studies using data from IRAS, ISO and Spitzer. The TIR LF evolves in luminosity with alpha_l=3.82^{+0.28}_{-0.16} which is in agreement with previous results from Spitzer 24 micron which find strong luminosity evolution. By integrating the LF we calculated the co-moving IR luminosity density out to z=1.2, which confirm the rapid evolution in number density of LIRGs and ULIRGs which contribute ~68^{+10}_{-07} % to the co-moving star formation rate density at z=1.2. Our results based on 70 micron data confirms that the bulk of the star formation at z=1 takes place in dust obscured objects.Comment: 17 pages, 14 figure

SDSSJ143244.91+301435.3 at VLBI: a compact radio galaxy in a narrow-line Seyfert 1

We present VLBI observations, carried out with the European Very Long Baseline Interferometry Network (EVN), of SDSSJ143244.91+301435.3, a radio-loud narrow-line Seyfert 1 (RLNLS1) characterized by a steep radio spectrum. The source, compact at Very Large Array (VLA) resolution, is resolved on the milliarcsec scale, showing a central region plus two extended structures. The relatively high brightness temperature of all components (5x10^6-1.3x10^8 K) supports the hypothesis that the radio emission is non-thermal and likely produced by a relativistic jet and/or small radio lobes. The observed radio morphology, the lack of a significant core and the presence of a low frequency (230 MHz) spectral turnover are reminiscent of the Compact Steep Spectrum sources (CSS). However, the linear size of the source (~0.5kpc) measured from the EVN map is lower than the value predicted using the turnover/size relation valid for CSS sources (~6kpc). This discrepancy can be explained by an additional component not detected in our observations, accounting for about a quarter of the total source flux density, combined to projection effects. The low core-dominance of the source (CD<0.29) confirms that SDSSJ143244.91+301435.3 is not a blazar, i.e. the relativistic jet is not pointing towards the observer. This supports the idea that SDSSJ143244.91+301435.3 may belong to the "parent population" of flat-spectrum RLNLS1 and favours the hypothesis of a direct link between RLNLS1 and compact, possibly young, radio galaxies.Comment: 8 pages, 3 figures, accepted for publication in MNRA

Aplicación del método Delphi para la inclusión de las externalidades en análisis de seguridad y de salud laboral

Organizations should regularly conduct an assessment of their occupational hazards in order to design and implement preventive measures that are necessary and sufficient to deal with the level of risk, the costs of prevention and the safety at levels considered acceptable by the organization. Furthermore, the selection of measures to be implemented in an organization should take into account both internal and external costs. Externalities are of great importance in terms of the costs of accidents at work; nevertheless, they are not often properly addressed by the organizations. In this paper we describe an application of the Delphi method to understand how externalities can be included in Occupational Safety and Health.Las organizaciones deben realizar periódicamente una evaluación de sus riesgos laborales con el fin de diseñar y poner en práctica medidas preventivas que sean necesarias y suficientes para mantener e l nivel de riesgo, los costos de la prevención y la seguridad en los niveles considerados aceptables por la organización. Por otra parte, la selección de las medidas a aplicar en una organización debe tener en cuenta tanto los costes internos como externos. Las externalidades son de gran importancia en términos de los costos de los accidentes de trabajo; sin embargo, a menudo no se tratan adecuadamente por las organizaciones. En este artículo se describe una aplicación del método Delphi para entender cómo los factores externos pueden ser incluidos en la Seguridad y Salud Laboral.The authors would like to acknowledge all the experts who have participated in the Delphi panel. The authors also acknowledge the anonymous reviewers who helped to improve the overall quality of the current manuscript. This study was financially supported by FCT-Fundação para a Ciência e Tecnologia of Portugal, under the project ID/CEC/00319/2013

Fused Filament Fabrication over fabrics: experiments and applications

The focus of this paper is to explore the use of Fused Filament Fabrication technology, a material extrusion additive manufacturing technology, by depositing melted Polilactic Acid (PLA) over a substrate – fabric - instead of on an empty building tray. The textile’s composition, nozzle and building plate temperature, printed PLA thickness and printed geometry have been considered as variables that could influence the structural and adhesion properties on this study so, therefor, were took into consideration and tested throughout the printing process through specimens printed with different combined parameters. The aim of this exploration process was developing an experimental procedure to study the limitations and capabilities of this printing technology over textiles, and which different variables’ combination would contribute to a better overall result in the development of a self-supporting textile based structural model, that could be apply in different contexts without the need of any extra external support. Results showed that PLA adherence to the fabric is correlated with nozzle/building plate temperature and printing thickness: higher temperature and thickness provide higher adherence. The weave of the textile didn´t reflect on better results but the polyester felt fabric exhibit maximum adherence with printed PLA in all sets of temperatures. In addition, geometries with reinforcement lines along the fabric stress direction provided better structural results. These results enable new application possibilities for the FFF technology combined in fabrics such as in interior, fashion and shoe ware design.publishe

Fiscal sustainability analysis: the case of PALOP economies

The Global Financial Crisis has typically led to a significant widening of fiscal positions (i.e., higher budget deficits and public debt). We address the sustainability of public finances in Portuguese-speaking African countries (PALOP), through adequate econometric testing. Our findings for the period 1975-2015 suggest that most of the PALOP have compromised the sustainability of their corresponding fiscal positions, leading these economies to be set on unsustainable public finance trajectories.info:eu-repo/semantics/publishedVersio

Hemoglobin genotype has minimal influence on the physiological response of juvenile atlantic cod (Gadus morhua) to environmental challenges

Hemoglobin (Hb) polymorphism in cod is associated with temperature‐related differences in biogeographical distribution, and several authors have suggested that functional characteristics of the various hemoglobin isoforms (HbIs) directly influence phenotypic traits such as growth rate. However, no study has directly examined whether Hb genotype translates into physiological differences at the whole animal level. Thus, we generated a family of juvenile Atlantic cod consisting of all three main Hb genotypes (HbI‐1/1, HbI‐2/2, and HbI‐1/2) by crossing a single pair of heterozygous parents, and we compared their metabolic and cortisol responses to an acute thermal challenge (10&deg;C to their critical thermal maximum [CTM] or 22&deg;C, respectively) and tolerance of graded hypoxia. There were no differences in routine metabolism (at 10&deg;C), maximum metabolic rate, metabolic scope, CTM (overall mean 22.9&deg; &plusmn; 0.2&deg;C), or resting and poststress plasma cortisol levels among Hb genotypes. Further, although the HbI‐1/1 fish grew more (by 15%&ndash;30% during the first 9 mo) when reared at 10&deg; &plusmn; 1&deg;C and had a slightly enhanced hypoxia tolerance at 10&deg;C (e.g., the critical O2 levels for HbI‐1/1, HbI‐2/2, and HbI‐1/2 cod were 35.56% &plusmn; 1.24%, and 40.20% &plusmn; 1.99% air saturation, respectively), these results are contradictory to expectations based on HbI functional properties. Thus, our findings (1) do not support previous assumptions that growth rate differences among cod Hb genotypes result from a more efficient use of the oxygen supply&mdash;that is, reduced standard metabolic rates and/or increased metabolic capacity&mdash;and (2) suggest that in juvenile cod, there is no selective advantage to having a particular Hb genotype with regards to the capacity to withstand ecologically relevant environmental challenges.<br /