Losses for microwave transmission in metamaterials for producing left-handed materials: The strip wires

This paper shows that the effective dielectric permitivity for the metamaterials used so far to obtain left-handed materials, with strip wires 0.003cm thick, is dominated by the imaginary part at 10.6- 11.5 GHz frequencies, where the band pass filter is, and therefore there is not propagation and the wave is inhomogeneous inside the medium. This is shown from finite-differences time-domain calculations using the real permitivity values for the Cu wires. For thicker wires the losses are reduced and the negative part of the permitivity dominates. As the thickness of the wires is critical for the realization of a good transparent left- handed material we propose that the strip wires should have thickness of 0.07-0.1cm and the split ring resonators 0.015-0.03c

Optical forces on small particles from partially coherent light

We put forward a theory on the optical force exerted upon a dipolar particle by a stationary and ergodic partially coherent light field. We show through a rigorous analysis that the ensemble averaged electromagnetic force is given in terms of a partial gradient of the space variable diagonal elements of the coherence tensor. Further, by following this result we characterize the conservative and non-conservative components of this force. In addition, we establish the propagation law for the optical force in terms of the coherence function of light at a diffraction plane. This permits us to evaluate the effect of the degree of coherence on the force components by using the archetypical configuration of Young's two apertures diffraction pattern, so often employed to characterize coherence of waves

S-Duality for Linearized Gravity

We develope the analogue of S-duality for linearized gravity in (3+1)-dimensions. Our basic idea is to consider the self-dual (anti-self-dual) curvature tensor for linearized gravity in the context of the Macdowell-Mansouri formalism. We find that the strong-weak coupling duality for linearized gravity is an exact symmetry and implies small-large duality for the cosmological constant.Comment: 18 pages, Latex, to be published in Phys. Lett.

Theory of Electromagnetic Wave Transmission through Metallic Gratings of Subwavelength Slits

We present FDTD calculations for transmission of light and other electromagnetic waves through periodic arrays of slits in a metallic slab. The results show resonant, frequency dependent, transmittance peaks for subwavelength widths of the slits which can be up to a factor of ten with respect to those out of resonance. Although our conclusions agree with previous work by Lezec and Thio as regards both the magnitude of the enhancement and the lack of contribution of surface plasmon polaritons of the metal surface to this effect, we derive an interpretation from a theory that deals with emerging beam- Rayleigh anomalies of the grating, and with Fabry-Perot resonances of the perforated slab considered as an effective medium.Comment: 12 pages 3 figure

The same and the contrary. Construction of a paradox in the Visitors Center of the Swiss National Park by Valerio Olgiati

[EN] Making a riddle is to establish an estrangement to solve. Its time tends to be a closed time, finished, complete. Anyway, if the riddle eludes the solution, its value will stay in the permanency of the paradox. Its time will be an open time, in a continuous course. The Visitors Center of Zemez is a perpetual estrangement: the outside and the inside are the same and the contrary at the same time. The contrary because the symmetrical and stable exterior don’t make us predict the labyrinthine inside. The same because there is continuity and a simple and complete unity between the inside and the outside achieved by the use of a single monolithic and unifying constructive system: walls and frameworks of white reinforced concrete. This article will describe how, with the use of this material, the construction of a radical and authentic estrangement is expected.[ES] Construir un acertijo es establecer un extrañamiento a resolver. Su tiempo tiende a ser un tiempo cerrado, acabado, completo. Ahora bien, si el acertijo elude la solución, su valor residirá en la permanencia de la paradoja. Su tiempo será un tiempo abierto, en continua circulación. El Centro de Visitantes de Zernez es un extrañamiento perpetuo: el exterior y el interior son a la vez lo mismo y lo contrario. Lo contrario porque el exterior simétrico y estable no nos hace predecir su laberíntico interior. Lo mismo porque existe una continuidad y una unidad simple y total entre el dentro y el fuera conseguida por la utilización de un único sistema constructivo monolítico e integrador: muros y forjados de hormigón armado blanco. El presente escrito describe cómo con la utilización de este material se pretende la construcción de un extrañamiento radical y auténtico.Nieto García, JÁ. (2014). Lo mismo y lo contrario Construcción de una paradoja en el Centro de Visitantes del Parque Nacional Suizo de Valerio Olgiati. EN BLANCO. Revista de Arquitectura. 6(16):87-93. doi:10.4995/eb.2014.5813SWORD8793616CORTÁZAR, Julio. "Después del almuerzo" en: Final de juego, Buenos Aires, Editorial Sudamericana, 1964, 194 p

El voluntariado corporativo. Un modelo de responsabilidad empresarial para el desarrollo social

Corporate or business volunteerism is the best manifestation of the exercise of the social responsibility in the organizations when they want to implement its social action programs for the development. Free and voluntary collaboration of the employees of an organization, performing activities aimed at improving the welfare of other people or social groups must respond to a proper planning in order to optimize the effectiveness of their efforts. At the same time, volunteering is a key business for the improvement of relations between the company and its internal stakeholders, promoting integration, cohesion and motivation of its employees, and so it should be strategically designed to achieve these purposes.El voluntariado empresarial, denominado también corporativo, constituye la mejor manifestación del ejercicio de la responsabilidad social de las organizaciones al poner en práctica sus programas de acción social para el desarrollo. La colaboración voluntaria y libre de las personas vinculadas laboralmente a una organización, realizando actividades destinadas a la mejora del bienestar de otras personas o grupos sociales, debe responder a una adecuada planificación con el objetivo de optimizar la eficacia de sus esfuerzos. Al mismo tiempo, el voluntariado empresarial es un instrumento fundamental para la mejora de las relaciones entre la empresa y sus públicos internos, propiciando la integración, la cohesión y la motivación de sus empleados, y como tal debe ser estratégicamente diseñado para el cumplimiento de estos fines.L’entreprise volontaire, appelée également entreprise est la meilleure manifestation de l’exercice de la responsabilité sociale des organisations, de mettre en pratique leur action sociale pour les programmes de développement. Les volontaires de collaboration gratuits sont des personnes professionnellement liées à une organisation, qui mènent des activités visant à l’amélioration du bien-être des autres personnes ou de groupes sociaux, et dont la contratation doit répondre à une planification appropriée dans le but d’optimiser l’efficacité de leurs efforts. Au même temps, le bénévolat corporatif est un instrument essentiel pour l’amélioration des relations entre la compagnie et son public interne, pour favoriser l’intégration, la cohésion et la motivation de ses employés et comme telle, il doit être stratégiquement conçu pour ces fins