Radio emission of SN1993J. The complete picture: II. Simultaneous fit of expansion and radio light curves

We report on a simultaneous modelling of the expansion and radio light curves of SN1993J. We have developed a simulation code capable of generating synthetic expansion and radio light curves of supernovae by taking into consideration the evolution of the expanding shock, magnetic fields, and relativistic electrons, as well as the finite sensitivity of the interferometric arrays used in the observations. Our software successfully fits all the available radio data of SN 1993J with an standard emission model for supernovae extended with some physical considerations, as an evolution in the opacity of the ejecta material, a radial drop of the magnetic fields inside the radiating region, and a changing radial density profile of the circumstellar medium beyond day 3100 after explosion.Comment: 12 pages, 12 figures, accepted for publication in A&

Absolute kinematics of radio source components in the complete S5 polar cap sample. III. First wide-field high-precision astrometry at 15.4 GHz

We report on the first wide-field, high-precision astrometric analysis of the 13 extragalactic radio sources of the complete S5 polar cap sample at 15.4 GHz. We describe new algorithms developed to enable the use of differenced phase delays in wide-field astrometric observations and discuss the impact of using differenced phase delays on the precision of the wide-field astrometric analysis. From this global fit, we obtained estimates of the relative source positions with precisions ranging from 14 to 200 $\mu$as at 15.4 GHz, depending on the angular separation of the sources (from $\sim$1.6 to $\sim$20.8 degrees). These precisions are $\sim$10 times higher than the achievable precisions using the phase-reference mapping technique.Comment: 9 pages, 7 figure

Integration of statistics and food process engineering: Assessing the uncertainty of thermal processing and shelf-life estimations

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Public and private sector wages interactions in a general equilibrium model

This paper develops a dynamic general equilibrium model in which the public and the private sector interact in the labor market. Previous studies that analyze the labor market effects of public sector employment and wages have mostly assumed exogenous rules for public wage and public employment. We show that theories that equalize wages with marginal products in the private sector can rationalize the interaction of public and private sector wages when extended to accommodate a non-trivial government sector/public sector union that endogenously determines public employment and wages. Our model suggests a positive correlation between public and private sector wages. Any increase in tax revenues, coupled with the existence of a positive public-private sector wage gap, makes working in the public sector an attractive option. Thus, a positive neutral productivity shock increases public and private sector wages. More interestingly, even a private-sector specific productivity shock spills-over to the public sector, increasing public wages. These facts lend some support to the wage leading role of the private sector. Nevertheless, at the same time, a positive shock to public sector wages would lead to an increase in private sector wages, via the flow of workers from the private to the public sector. JEL Classification: C32, J30, J51, J52, E62, E63, H50Labor market, public employment, public wages, Trade Unions

Solitary-wave vortices in quadratic nonlinear media

We find families of vortex solitary waves in bulk quadratic nonlinear media under conditions for second-harmonic generation. We show that the vortex solitary waves are azimuthally unstable and that they decay into sets of stable spatial solitons. We calculate the growth rates of the azimuthal perturbations and show how those affect the pattern of output light. © 1998 Optical Society of AmericaPeer ReviewedPostprint (published version

8.4GHz VLBI observations of SN2004et in NGC6946

We report on 8.4GHz Very Long Baseline Interferometry (VLBI) observations of the type II-P supernova SN2004et in the spiral galaxy NGC 6946, made on 20 February 2005 (151 days after explosion). The Very Large Array (VLA) flux density was 1.23$\pm$0.07 mJy, corresponding to an isotropic luminosity at 8.4GHz of (4.45$\pm$0.3)$\times10^{25}$ erg s$^{-1}$ Hz$^{-1}$ and a brightness temperature of (1.3$\pm$0.3)$\times10^{8}$ K. We also provide an improved source position, accurate to about 0.5 mas in each coordinate. The VLBI image shows a clear asymmetry. From model fitting of the size of the radio emission, we estimate a minimum expansion velocity of 15,700$\pm$2,000 km s$^{-1}$. This velocity is more than twice the expected mean expansion velocity estimated from a synchrotron self-absorbed emission model, thus suggesting that synchrotron self-absorption is not relevant for this supernova. With the benefit of an optical spectrum obtained 12 days after explosion, we favor an emission model which consists of two hot spots on an underlying expanding shell of width comparable to that of SN 1993J.Comment: Accepted for publication in A&A (22/05/07

Spatial wave intensity correlations in quasi-one-dimensional wires

Spatial intensity correlations between waves transmitted through random media are analyzed within the framework of the random matrix theory of transport. Assuming that the statistical distribution of transfer matrices is isotropic, we found that the spatial correlation function can be expressed as the sum of three terms, with distinctive spatial dependences. This result coincides with the one obtained in the diffusive regime from perturbative calculations, but holds all the way from quasi-ballistic transport to localization. While correlations are positive in the diffusive regime, we predict a transition to negative correlations as the length of the system decreases.Comment: 10 pages, 3 figures. Submitted to Physical Review Letter

Existence and uniqueness of limit cycles for generalized -Laplacian Liénard equations

Agraïments: The first author is also supported by a PNPD/CAPES grant. The third author is supported by FQM-1861 (Junta de Andalucía) grants.The Liénard equation x'' + f(x)x' + g(x) = 0 appears as a model in many problems of science and engineering. Since the first half of the 20th century, many papers have appeared providing existence and uniqueness conditions for limit cycles of Li'enard equations. In this paper we extend some of these results for the case of the generalized ϕ-Laplacian Liénard equation, (ϕ(x'))' + f(x)ψ(x') + g(x) = 0. This generalization appears when derivations of the equation different from the classical one are considered. In particular, the relativistic van der Pol equation, [x'/p1 − (x'/c)2]'+ µ(x2 − 1)x' + x = 0, has a unique periodic orbit when µ 6= 0