Analytical and numerical investigation of mixed-type functional differential equations

NOTICE: this is the author’s version of a work that was accepted for publication in Journal of computational and applied mathematics. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document. Changes may have been made to this work since it was submitted for publication. A definitive version was subsequently published in Journal of computational and applied mathematics, 234 (2010), doi: 10.1016/j.cam.2010.01.028This journal article is concerned with the approximate solution of a linear non-autonomous functional differential equation, with both advanced and delayed arguments

Scene-adapted plug-and-play algorithm with convergence guarantees

Recent frameworks, such as the so-called plug-and-play, allow us to leverage the developments in image denoising to tackle other, and more involved, problems in image processing. As the name suggests, state-of-the-art denoisers are plugged into an iterative algorithm that alternates between a denoising step and the inversion of the observation operator. While these tools offer flexibility, the convergence of the resulting algorithm may be difficult to analyse. In this paper, we plug a state-of-the-art denoiser, based on a Gaussian mixture model, in the iterations of an alternating direction method of multipliers and prove the algorithm is guaranteed to converge. Moreover, we build upon the concept of scene-adapted priors where we learn a model targeted to a specific scene being imaged, and apply the proposed method to address the hyperspectral sharpening problem

Detection of the compressed primary stellar wind in eta Carinae

A series of three HST/STIS spectroscopic mappings, spaced approximately one year apart, reveal three partial arcs in [Fe II] and [Ni II] emissions moving outward from eta Carinae. We identify these arcs with the shell-like structures, seen in the 3D hydrodynamical simulations, formed by compression of the primary wind by the secondary wind during periastron passages.Comment: Accepted for publication in the Astrophysical Journal Letter

Unplugging the Universe: the neglected electromagnetic consequence of decoupling

This letter concentrates on the non-equilibrium evolution of magnetic field structures at the onset of recombination, when the charged particle current densities decay as neutrals are formed. We consider the effect that a decaying magnetic flux has on the acceleration of particles via the transient induced electric field. Since the residual charged-particle number density is small as a result of decoupling, we shall consider the magnetic and electric fields essentially to be imposed, neglecting the feedback from any minority accelerated population. We find that the electromagnetic treatment of this phase transition can produce energetic electrons scattered throughout the Universe. Such particles could have a significant effect on cosmic evolution in several ways: (i) their presence could delay the effective end of the recombination era; (ii) they could give rise to plasma concentrations that could enhance early gravitational collapse of matter by opposing cosmic expansion to a greater degree than neutral matter could; (iii) they could continue to be accelerated, and become the seed for reionisation at the later epoch $z \approx 10$.Comment: 4 pages, no figure

On the changes in the physical properties of the ionized region around the Weigelt structures in Eta Carinae over the 5.54-yr spectroscopic cycle

We present HST/STIS observations and analysis of two prominent nebular structures around the central source of Eta Carinae, the knots C and D. The former is brighter than the latter for emission lines from intermediate or high ionization potential ions. The brightness of lines from intermediate and high ionization potential ions significantly decreases at phases around periastron. We do not see conspicuous changes in the brightness of lines from low ionization potential (<13.6 eV) that the total extinction towards the Weigelt structures is that the total extinction towards the Weigelt structures is AsubV =2/0. that the total extinction towards the Weigelt structures is AV = 2.0. Weigelt C and D are characterized by an electron density of that the total extinction towards the Weigelt structures is AV = 2.0. Weigelt C and D are characterized by an electron density of 10exp6.9 cm-3 that does not significantly change throughout the orbital cycle. The electron temperature varies from 5500 K (around periastron) to 7200 K (around apastron). The relative changes in the brightness of He I lines are well reproduced by the variations in the electron temperature alone. We found that, at phases around periastron, the electron temperature seems to be higher for Weigelt C than that of D. The Weigelt structures are located close to the Homunculus equatorial plane, at a distance of about 1240 AU from the central source. From the analysis of proper motion and age, the Weigelt complex can be associated with the equatorial structure called the Butterfly Nebula surrounding the central binary system.Comment: 19 pages, 18 figure

DIGESTIBILIDAD DE LA MATERIA SECA DE HENO DE MANÍ RIZOMA PERENNE (A GLABRATA) COSECHADO EN EL TRÓPICO CARIBEÑO

The in vitro true dry matter digestibility (IVTDMD) of rhizoma perennial peanut (RPP) forage was evaluated in trials at Lajas (PI no. 276233, 262826, 262833, 262839, and cvs Florigraze and Arbrook) and Juana Díaz (PI no. 276233, 262839, and cv Florigraze), Puerto Rico. At both sites, the forage was cut at six-, nine-, and 12-wk harvest intervals (HI) in each of the four seasons of the year. The digestibility of the forage was not influenced by genotype. Mean IVTDMD across HI and season of growth was 64.3 and 62.5% in the Lajas and Juana Díaz trials, respectively. The IVTDMD decreased in a quadratic manner (P &lt; 0.01) as HI increased from six to 12 weeks. The digestibility of forage harvested at six and nine weeks was similar, with a relative decline of 6.6 and 10.6% as HI increased from nine to 12 weeks in Lajas and Juana Díaz, respectively. Season of growth influenced IVTDMD (P &lt; 0.01). In both trials, the highest digestibility was obtained in forage grown in summer. The effect of season of growth on IVTDMD was greatest in forage harvested at 12 weeks, and least in forage harvested at six weeks. The high digestibility reported among genotypes evaluated suggests they are a viable alternative for the production of high quality hay in the Caribbean tropics. La digestibilidad verdadera de la materia seca in vitro (DVMSIV) del maní rizoma perenne (MRP) fue evaluada en Lajas (núm. Pl 276233, 262826, 262833, 262839 y los cvs Florigraze y Arbrook) y Juana Díaz (núm. PI 276233, 262839 y el cv Florigraze). En ambas localidades, el forraje se cortó a intervalos de seis, nueve y 12 semanas en cada una de las cuatro estaciones del año. La DVMSIV del forraje no fue afectada por el genotipo del MRP evaluado. Las medias fueron 64.3 y 62.5% para los MRP evaluados en Lajas y Juana Díaz, respectivamente. A medida que se alargó el intervalo de corte de seis a 12 semanas la DVMSIV se redujo (P &lt; 0.01) en una forma cuadrática. En ambos estudios, la digestibilidad del forraje cosechado a las seis y nueve semanas fue similar; al aumentar de nueve a 12 semanas hubo una reducción relativa en la DVMSIV de 6.6 y 10.6% en Lajas y Juana Díaz, respectivamente. La estación de crecimiento afectó (P &lt; 0.01) la DVMSIV. El forraje cosechado durante el verano tuvo la digestibilidad más alta en ambas localidades. El efecto de la estación de crecimiento fue mayor en el forraje cosechado a un intervalo de 12 semanas y menor en el forraje cosechado a las seis semanas de crecimiento. La alta digestibilidad de los genotipos evaluados sugiere que el MRP es una alternativa viable para la producción de heno de alta calidad en el trópico caribeño