Dyakonons in hyperbolic metamaterials

We have analyzed surface-wave propagation that takes place at the boundary between an isotropic medium and a semi-infinite metal-dielectric periodic medium cut normally to the layers. In the range of frequencies where the periodic medium shows hyperbolic space dispersion, hybridization of surface waves (dyakonons) occurs. At low to moderate frequencies, dyakonons enable tighter confinement near the interface in comparison with pure SPPs. On the other hand, a distinct regime governs dispersion of dyakonons at higher frequencies.

Engineered surface waves in hyperbolic metamaterials

We analyzed surface-wave propagation that takes place at the boundary between a semi-infinite dielectric and a multilayered metamaterial, the latter with indefinite permittivity and cut normally to the layers. Known hyperbolization of the dispersion curve is discussed within distinct spectral regimes, including the role of the surrounding material. Hybridization of surface waves enable tighter confinement near the interface in comparison with pure-TM surface-plasmon polaritons. We demonstrate that the effective-medium approach deviates severely in practical implementations. By using the finite-element method, we predict the existence of long-range oblique surface waves.

A new code for the Hall-driven magnetic evolution of neutron stars

Over the past decade, the numerical modeling of the magnetic field evolution in astrophysical scenarios has become an increasingly important field. In the crystallized crust of neutron stars the evolution of the magnetic field is governed by the Hall induction equation. In this equation the relative contribution of the two terms (Hall term and Ohmic dissipation) varies depending on the local conditions of temperature and magnetic field strength. This results in the transition from the purely parabolic character of the equations to the hyperbolic regime as the magnetic Reynolds number increases, which presents severe numerical problems. Up to now, most attempts to study this problem were based on spectral methods, but they failed in representing the transition to large magnetic Reynolds numbers. We present a new code based on upwind finite differences techniques that can handle situations with arbitrary low magnetic diffusivity and it is suitable for studying the formation of sharp current sheets during the evolution. The code is thoroughly tested in different limits and used to illustrate the evolution of the crustal magnetic field in a neutron star in some representative cases. Our code, coupled to cooling codes, can be used to perform long-term simulations of the magneto-thermal evolution of neutron stars.

Difference schemes for numerical solutions of lagging models of heat conduction

Non-Fourier models of heat conduction are increasingly being considered in the modeling of microscale heat transfer in engineering and biomedical heat transfer problems. The dual-phase-lagging model, incorporating time lags in the heat flux and the temperature gradient, and some of its particular cases and approximations, result in heat conduction modeling equations in the form of delayed or hyperbolic partial differential equations. In this work, the application of difference schemes for the numerical solution of lagging models of heat conduction is considered. Numerical schemes for some DPL approximations are developed, characterizing their properties of convergence and stability. Examples of numerical computations are included.

Propagation of Dyakonon Wave-Packets at the Boundary of Metallodielectric Lattices

We rigorously analyze the propagation of localized surface waves that takes place at the boundary between a semi-infinite layered metal-dielectric (MD) nanostructure cut normally to the layers and a isotropic medium. It is demonstrated that Dyakonov-like surface waves (also coined dyakonons) with hybrid polarization may propagate in a wide angular range. As a consequence, dyakonon-based wave-packets (DWPs) may feature sub-wavelength beamwidths. Due to the hyperbolic-dispersion regime in plasmonic crystals, supported DWPs are still in the canalization regime. The apparent quadratic beam spreading, however, is driven by dissipation effects in metal.

Nuevos horizontes en materia de viajes combinados

Los viajes combinados han ocupado tradicionalmente un lugar destacado dentro de la amplia gama de servicios ofrecidos por los operadores turísticos. Por ello, el Consejo de la Unión Europea adoptó en 1990 la Directiva 90/314/CEE, de 13 de junio, relativa a los viajes combinados, las vacaciones combinadas y los circuitos combinados, con el fin de eliminar, o cuanto menos mitigar, la especial situación de indefensión en que se encontraba aquél que los contrataba. Desde la aprobación de esta Directiva han pasado casi veinticinco años y ante el surgimiento de problemas derivados de la aparición de nuevos modelos de negocio y formas de contratación de los servicios turísticos que ni siquiera se plantearon en aquel momento, se ha hecho necesaria la revisión de una normativa a todas luces obsoleta e incapaz de proteger adecuadamente a los usuarios de estos servicios. Así, el 9 de julio de 2013 la Comisión Europea aprobó la Propuesta de Directiva del Parlamento Europeo y del Consejo relativa a los viajes combinados y los servicios asistidos de viaje, por la que se modifican el Reglamento (CE) nº 2006/2004 y la Directiva 2011/83/UE y por la que se deroga la Directiva 90/314/CEE. El objetivo de este trabajo se centra en analizar las modificaciones propuestas por la C C omisión respecto al ámbito de aplicación de la Directiva 90/314/CEE y su posible repercusión en las legislaciones internas, sobre todo teniendo en cuenta el enfoque de armonización máxima que se pretende dar al nuevo texto.