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.

Exact and analytic-numerical solutions of lagging models of heat transfer in a semi-infinite medium

Different non-Fourier models of heat conduction have been considered in recent years, in a growing area of applications, to model microscale and ultrafast, transient, nonequilibrium responses in heat and mass transfer. In this work, using Fourier transforms, we obtain exact solutions for different lagging models of heat conduction in a semi-infinite domain, which allow the construction of analytic-numerical solutions with prescribed accuracy. Examples of numerical computations, comparing the properties of the models considered, are presented.

Ultrasonic and X-ray computed tomography characterization of progressive fracture damage in low-porous carbonate rocks

This paper studies the fracturing process in low-porous rocks during uniaxial compressive tests considering the original defects and the new mechanical cracks in the material. For this purpose, five different kinds of rocks have been chosen with carbonate mineralogy and low porosity (lower than 2%). The characterization of the fracture damage is carried out using three different techniques: ultrasounds, mercury porosimetry and X-ray computed tomography. The proposed methodology allows quantifying the evolution of the porous system as well as studying the location of new cracks in the rock samples. Intercrystalline porosity (the smallest pores with pore radius < 1 μm) shows a limited development during loading, disappearing rapidly from the porosimetry curves and it is directly related to the initial plastic behaviour in the stress–strain patterns. However, the biggest pores (corresponding to the cracks) suffer a continuous enlargement until the unstable propagation of fractures. The measured crack initiation stress varies between 0.25 σp and 0.50 σp for marbles and between 0.50 σp and 0.85 σp for micrite limestone. The unstable propagation of cracks is assumed to occur very close to the peak strength. Crack propagation through the sample is completely independent of pre-existing defects (porous bands, stylolites, fractures and veins). The ultrasonic response in the time-domain is less sensitive to the fracture damage than the frequency-domain. P-wave velocity increases during loading test until the beginning of the unstable crack propagation. This increase is higher for marbles (between 15% and 30% from initial vp values) and lower for micrite limestones (between 5% and 10%). When the mechanical cracks propagate unstably, the velocity stops to increase and decreases only when rock damage is very high. Frequency analysis of the ultrasonic signals shows clear changes during the loading process. The spectrum of treated waveforms shows two main frequency peaks centred at low (~ 20 kHz) and high (~ 35 kHz) values. When new fractures appear and grow the amplitude of the high-frequency peak decreases, while that of the low-frequency peak increases. Besides, a slight frequency shift is observed towards higher frequencies.

Oblique surface waves at an interface between a metal–dielectric superlattice and an isotropic dielectric

We investigate the existence and dispersion characteristics of surface waves that propagate at an interface between a metal–dielectric superlattice and an isotropic dielectric. Within the long-wavelength limit, when the effective-medium (EM) approximation is valid, the superlattice behaves like a uniaxial plasmonic crystal with the main optical axes perpendicular to the metal–dielectric interfaces. We demonstrate that if such a semi-infinite plasmonic crystal is cut normally to the layer interfaces and brought into contact with a semi-infinite dielectric, a new type of surface mode can appear. Such modes can propagate obliquely to the optical axes if favorable conditions regarding the thickness of the layers and the dielectric permittivities of the constituent materials are met. We show that losses within the metallic layers can be substantially reduced by making the layers sufficiently thin. At the same time, a dramatic enlargement of the range of angles for oblique propagation of the new surface modes is observed. This can lead, however, to field non-locality and consequently to failure of the EM approximation.

Las Reales viruelas, muerte e inoculación en la Corte española

Durante el siglo XVIII, la viruela alcanzó su máxima expresión como enfermedad devastadora, y se convirtió en la primera causa de mortalidad infantil. En su deambular como azote mundial, diezmaba la población afectando a todas las clases sociales. Las monarquías europeas sufrieron la virulencia de la enfermedad, y se produjeron cambios notables en el devenir de las casas reales por el fallecimiento de reyes o príncipes herederos. La introducción de la inoculación como remedio preventivo contra la viruela fue apoyada por las monarquías, pero no se aplicó de manera sistemática, lo que redujo su impacto en las estadísticas de mortalidad. Revisamos los efectos de la viruela en la Corte española, enfermedad que llevó a la extinción de la Casa de Austria y afectó también a los borbones; de manera tardía, estos aceptaron la inoculación y contribuyeron a la propagación de la vacuna.

Una propuesta fallida para propagar la vacuna contra la viruela en Hispanoamérica (1802)

Tras la inicial propagación del método jenneriano por Inglaterra y el resto del continente europeo, se mostró un gran interés por difundirlo hacia Oriente y América. En el caso de España, los focos epidémicos que estaban ocurriendo en los territorios de ultramar movieron a las autoridades de los distintos virreinatos a solicitar a la Corona que enviara cuanto antes el nuevo remedio. La monarquía borbónica, que había introducido las expediciones científicas como elemento de progreso y dominio, aprobó el proyecto conocido como “Real Expedición Filantrópica de la Vacuna”, que partió hacia América al mando de Balmis en 1803. Relatamos una propuesta inédita anterior a esa, en la que un desconocido cirujano, Rafael de Malaguilla, se ofreció para llevar a cabo una iniciativa similar.