A tabu search heuristic for the Equitable Coloring Problem

The Equitable Coloring Problem is a variant of the Graph Coloring Problem where the sizes of two arbitrary color classes differ in at most one unit. This additional condition, called equity constraints, arises naturally in several applications. Due to the hardness of the problem, current exact algorithms can not solve large-sized instances. Such instances must be addressed only via heuristic methods. In this paper we present a tabu search heuristic for the Equitable Coloring Problem. This algorithm is an adaptation of the dynamic TabuCol version of Galinier and Hao. In order to satisfy equity constraints, new local search criteria are given. Computational experiments are carried out in order to find the best combination of parameters involved in the dynamic tenure of the heuristic. Finally, we show the good performance of our heuristic over known benchmark instances

Free Form of the Foldy-Wouthuysen Transformation in External Electromagnetic Fields

We derive the exact Foldy-Wouthuysen transformation for Dirac fermions in a time independent external electromagnetic field in the basis of the Ritus eigenfunctions, namely the eigenfunctions of the operator $(\gamma \cdot \Pi)^2$, with $\Pi^\mu = p^\mu - e A^\mu$. In this basis, the transformation acquires a free form involving the dynamical quantum numbers induced by the field.Comment: 8 pages. Accepted in J. Phys. A: Math. and Theo. (Fast Track Communication

Spatial Modulation of linear and quadratic susceptibilities in Lithium Niobate crystals by using femtosecond laser pulses

In this work we present the spatial control of the linear susceptibility (χ1) in Lithium Niobate crystals by means of infrared (800 nm) femtosecond interaction. Diffraction gratings have been performed on the surface (relief) and inside (phase) of these samples by femtosecond laser writing. Also we have performed a spatial control of the quadratic susceptibility (χ 2 ) by direct writing of a pattern of ferroelectric domains on the surface of z cut substrates by using the second harmonic femtosecond pulses (400 nm). Finally, efficient photonic devices for second harmonic generation via quasi phase matching could be obtained following the experimental procedure presented in this work

Inhomogeneous Universe Models with Varying Cosmological Term

The evolution of a class of inhomogeneous spherically symmetric universe models possessing a varying cosmological term and a material fluid, with an adiabatic index either constant or not, is studied.Comment: 11 pages Latex. No figures. To be published in the GRG Journa

Pharmacological treatment of obesity

El tratamiento de la obesidad, estará basado siempre en dos pilares fundamentales, dieta y ejercicio. No obstante, en determinados casos puede estar indicado un tratamiento farmacológico adicional. Se revisan los posibles tratamientos en función del lugar de actuación, de acuerdo al mismo esquema que sigue el alimento en el organismo, esto es: ingesta, absorción, metabolismo y excreción. De esta forma, se repasan los anorexígenos, que actúan sobre la ingesta; los distintos tipos de fibras e inhibidores que actúan en la absorción; y en los fármacos que actúan sobre el metabolismo, se describe la línea de investigación que actualmente se encuentra abierta sobre fármacos estimuladores α,β-selectivos, como el futuro en el tratamiento de la obesidad.The treatrnent of the obesity will be based always in two fundamentals points: diet, and exercise. Although, in sorne cases it could be indicated an aditional pharmacologic treatment. Possibles treatments depending of the actuation place, according to the same scheme that food follows in the organism, have been revised. This is: intake, absorption, metabolism and excretion. In this way, the anorexigenics which act on the intake are revised; the different kind of fibres and inhibitors which act in the absorption; and in drugs which act on the metabolism, the investigation way that actually is open about specific α,β-adrenoceptor agonist like the future in the obesity treatment, is described