Casimir force calculations near the insulator-conductor transition in gold thin films

We present theoretical calculations of the Casimir force for Au thin films near the insulator-conductor transition that has been observed experimentally. The dielectric function of the Au thin films is described by the Drude-Smith model. The parameters needed to model the dielectric function such as the relaxation time, plasma frequency and the backscattering constant depend on the thickness of the film. The Casimir force decreases as the film thickness decreases until it reaches a minimum after which the force increases again. The minimum of the force coincides with the critical film thickness where a percolation conductor-insulator occurs.Comment: 5 figures, 1 tabl

Optimizing the G/T ratio of the DSS-13 34-meter beam-waveguide antenna

Calculations using Physical Optics computer software were done to optimize the gain-to-noise-temperature (G/T) ratio of Deep Space Station (DSS)-13, the Deep Space Network's (DSN's) 34-m beam-waveguide antenna, at X-band for operation with the ultra-low-noise amplifier maser system. A better G/T value was obtained by using a 24.2-dB far-field-gain smooth-wall dual-mode horn than by using the standard X-band 22.5-dB-gain corrugated horn

MHD simulations of coronal supra-arcade downflows including anisotropic thermal conduction

Coronal supra-arcade downflows (SADs) are observed as dark trails descending towards hot turbulent fan shaped regions. Due to the large temperature values, and gradients in these fan regions the thermal conduction should be very efficient. While several models have been proposed to explain the triggering and the evolution of SADs, none of these scenarios address a systematic consideration of thermal conduction. Thus, we accomplish this task numerically simulating the evolution of SADs within this framework. That is, SADs are conceived as voided (subdense) cavities formed by non-linear waves triggered by downflowing bursty localized reconnection events in a perturbed hot fan. We generate a properly turbulent fan, obtained by a stirring force that permits control of the energy and vorticity input in the medium where SADs develop. We include anisotropic thermal conduction and consider plasma properties consistent with observations. Our aim is to study if it is possible to prevent SADs to vanish by thermal diffusion. We find that this will be the case, depending on the turbulence parameters. In particular, if the magnetic field lines are able to envelope the voided cavities, thermally isolating them from the hot environment. Velocity shear perturbations that are able to generate instabilities of the Kelvin-Helmholtz type help to produce magnetic islands, extending the life-time of SADs

Van der Waals torque induced by external magnetic fields

We present a method for inducing and controlling van der Waals torques between two parallel slabs using a constant magnetic field. The torque is calculated using the Barash theory of dispersive torques. In III-IV semiconductors such as $InSb$, the effect of an external magnetic field is to induce an optical anisotropy, in an otherwise isotropic material, that will in turn induce a torque. The calculations of the torque are done in the Voigt configuration, with the magnetic field parallel to the surface of the slabs. As a case study we consider a slab made of calcite and a second slab made of $InSb$. In the absence of magnetic field there is no torque. As the magnetic field increases, the optical anisotropy of $InSb$ increases and the torque becomes different from zero, increasing with the magnetic field. The resulting torque is of the same order of magnitude as that calculated using permanent anisotropic materials when the magnetic fields is close to 1 T.Comment: to appear in Journal of Applied Physic

The Rise and Fall of Income Inequality in Mexico: 1989-2010

Inequality in Mexico rose between 1989 and 1994 and declined between 1994 and 2010. We examine the role of market forces (demand and supply of labour by skill), institutional factors (minimum wages and unionization rate), and public policy (cash transfers) in explaining changes in inequality. We apply the ‘re-centered influence function’ method to decompose changes in hourly wages into characteristics and returns. The main driver is changes in returns. Returns rose (1989-1994) due to institutional factors and labor demand. Returns declined (1994-2006) due to changes in supply and --to a lesser extent--in demand; institutional factors were not relevant. Government transfers contributed to the decline in inequality, especially after 2000.inequality, wages, disposable income, labor markets, Mexico

Reduction of the Casimir force using aerogels

By using silicon oxide based aerogels we show numerically that the Casimir force can be reduced several orders of magnitude, making its effect negligible in nanodevices. This decrease in the Casimir force is also present even when the aerogels are deposited on metallic substrates. To calculate the Casimir force we model the dielectric function of silicon oxide aerogels using an effective medium dielectric function such as the Clausius-Mossotti approximation. The results show that both the porosity of the aerogel and its thickness can be use as control parameters to reduce the magnitude of the Casimir force.Comment: to appear J. Appl. Phy

Presentación del proyecto «Léxico Neológico Orteguiano»

La conciencia neológica de José Ortega y Gasset y su advertencia por parte de la crítica especializada me ha llevado a aproximarme a este aspecto de la creación del filósofo español y a emprender la tarea de detectar, clasificar y analizar sus acuñaciones léxicas. El proyecto está ahora en su ecuador, pues se han vaciado los neologismos de los cuatro primeros tomos de sus Obras completas (2004-10). Es decir: he barrido la producción orteguiana desde sus comienzos (1902) hasta el año 1931 y se han defendido sendos trabajos de fin de máster correspondientes a los neologismos de 1939 y 1940. En definitiva, treinta y un años de los cincuenta y tres que comprenden toda su obra ya han sido analizados, de manera que puede decirse que el proyecto ha alcanzado una fase en la cual se pueden adelantar resultados, a mi juicio, relevantes. Por lo pronto, he de decir que, hasta la fecha, el corpus neológico orteguiano obtenido es de 221 unidades léxicas. Pero esto no es todo. El proyecto está sirviendo, además, para obtener una serie de beneficios colaterales: por ejemplo, la función orteguiana como reactivador de unidades léxicas, más que su creador (por lo que se van a descartar algunas creaciones que los especialistas dan como suyas pero que no pueden considerarse como tales); o la constatación de la autoría orteguiana de textos sin su firma, de erratas graves o de lecturas inciertas o dudosas, gracias a determinadas ocurrencias léxicas; o la adscripción orteguiana a determinadas corrientes de innovación léxica, que se remontan hasta el siglo XIV (por lo que el trabajo está sirviendo también para la constatación de determinados neologismos en autores que van del Prerrenacimiento hasta la Generación del 98). Como conclusión sucinta, puede confirmarse con mi trabajo el deseo, por parte de Ortega y Gasset, de confeccionar un vocabulario personal conforme a los mecanismos propios que le brindan las lenguas: intra-, pero también interlingüísticos.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

La labor lexicográfica de Esteban de Terreros

Mis reflexiones sobre la labor lexicográfica de Esteban de Terreros pretenden dar cuenta, desde una nueva perspectiva, de la importancia del autor y su obra: (1) las cualidades de Terreros como lexicógrafo; (2) la superación del modelo del Diccionario de autoridades (1726-39); y (3) la concepción integral de su obra.Esteban de Terreros-en lan lexikografikoari buruzko gogoeta hauek egilearen eta obraren garrantziaz ohartaraztea dute helburu: (1) lexikografo gisa Terrerosek zituen dohainak; (2) Diccionario de autoridades delako eredua gainditzea (1726-39); eta (3) haren obraren kontzepzio osoa.Mes réflexions sur le travail lexicographique d'Esteban de Terreros tentent de rendre compte, à partir d'une nouvelle perspective, de l'importance de l'auteur et de son oeuvre : (1) les qualités de Terreros comme lexicographe ; (2) le surpassement du modèle du Diccionario de autoridades (1726-39) ; et (3) la conception intégrale de son oeuvre.My reflections on the lexicographic work by Esteban de Terreros pretendsto explain, from a new perspective, the importance of the author and his work: (1)Terreros' qualities as a lexicographer; (2) the overcoming of the model of Dictionary of authorities (1726-39); and (3) the integral conception of his work

3D MHD simulation of polarized emission in SN 1006

We use three dimensional magnetohydrodynamic (MHD) simulations to model the supernova remnant SN 1006. From our numerical results, we have carried out a polarization study, obtaining synthetic maps of the polarized intensity, the Stokes parameter $Q$, and the polar-referenced angle, which can be compared with observational results. Synthetic maps were computed considering two possible particle acceleration mechanisms: quasi-parallel and quasi-perpendicular. The comparison of synthetic maps of the Stokes parameter $Q$ maps with observations proves to be a valuable tool to discern unambiguously which mechanism is taking place in the remnant of SN 1006, giving strong support to the quasi-parallel model.Comment: 6 pages, 4 figures, accepted by MNRA