Exception for the zero-forward-scattering theory

Studies on single scattering of electromagnetic waves by magnetic particles were reported in the 1980s by Kerker et al. [J. Opt. Soc. Am. 73, 765 (1983)] . They obtained that very small spherical particles with electric permittivity and magnetic permeability values such that ε=(4−μ)/(2μ+1) do not produce forward scattering. We show here that this condition contains an interesting exception at ( ε=−2 , μ=−2 ) when electric and magnetic resonances are present and around which the scattered field distribution is computed and described showing a polarization-insensitive behavior at the point ( ε=−2 , μ=−2 )

Identificación de áreas desertificadas y preservadas en una unidad de conservación en el Estado de Paraíba - Brasil

The objective of this study is to identify and analyse the main characteristics of areas potentially degraded by desertification and of preserved areas using the Soil Surface Moisture Index (SSMI), alongside the Land Surface Temperature (LST) and Normalized Difference Vegetation Index (NDVI). The study is based on a set of points obtained in the field and from the RGB false colour image for the Environmental Protection Areas (EPA) of the Cariri, in the semi-arid region of Paraíba, using a space-time cross-section covering both rainy and dry periods. The results showed that at all points in Desertified Areas, the main characteristics were a low SSMI, high LST and low NDVI in both periods. The Preserved Areas, on the other hand, presented a high SSMI, moderate LST and high NDVI in the rainy period, with the same characteristics repeated in the dry period for SSMI and NDVI, but with a low LST. Timely identification of these characteristics, both in areas degraded by desertification and in better preserved areas, can provide useful information for future decisions relating to the physical and territorial management of the Conservation Unit.El objetivo de este estudio fue identificar y analizar las principales características de áreas potencialmente degradadas por desertificación y de áreas preservadas. Para ello se utilizaron el Índice de Humedad Superficial del Suelo (IHSS), junto con la Temperatura de la Superficie de la Tierra (TS) y el Índice de Vegetación de Diferencia Normalizada (IVDN). El estudio está basado en un conjunto de puntos obtenidos en el campo y en la composición de la imagen de falso color RGB para el Área de Protección Ambiental (APA) del Carirí, en la región semiárida de Paraíba, utilizando un corte espacio-temporal que abarca la estación lluviosa y seca. Los resultados mostraron que en todos los puntos de las Áreas Desertificadas las principales características fueron el IHSS bajo, TS alto y IVDN bajo en ambos períodos. Las Áreas Preservadas, por su parte, presentaron IHSS alto, TS moderado e IVDN alto en la época de lluvias, con las mismas características repetidas en el periodo seco para IHSS y IVDN, pero con TS bajo. La identificación puntual de estas características, tanto en áreas degradadas por desertificación como en las más conservadas, puede aportar información útil para la toma de decisiones futuras relacionadas con la gestión territorial y física de la Unidad de Conservación

A model of Mira's cometary head/tail entering the Local Bubble

We model the cometary structure around Mira as the interaction of an AGB wind from Mira A, and a streaming environment. Our simulations introduce the following new element: we assume that after 200 kyr of evolution in a dense environment Mira entered the Local Bubble (low density coronal gas). As Mira enters the bubble, the head of the comet expands quite rapidly, while the tail remains well collimated for a 100 kyr timescale. The result is a broad-head/narrow-tail structure that resembles the observed morphology of Mira's comet. The simulations were carried out with our new adaptive grid code WALICXE, which is described in detail.Comment: 12 pages, 8 figures (4 in color). Accepted for publication in The Astrophysical Journa

Decentralized Self-adaptation in Large-scale Distributed Systems

The evolution of technology is leading to a world where computational systems are made of a huge number of components spread over a logical network: these components operate in a highly dynamic and unpredictable environment, joining or leaving the system and creating connections between them at runtime. This scenario poses new challenges to software engineers that have to design and implement such complex systems. We want to address this problem, designing and developing an infrastructure, GRU, that uses self-adaptive decentralized techniques to manage large-scale distributed systems. GRU will help developers to focus on the functional part of their application instead of the needed self-adaptive infrastructure. We aim to evaluate our project with concrete case studies, providing evidence on the validity of our approach, and with the feedback provided by developers that will test our system. We believe this approach can contribute to fill the gap between the theoretical study of self-adaptive systems and their application in a production context

Yukawa hierarchies at the point of E8E_8 in F-theory

We analyse the structure of Yukawa couplings in local SU(5) F-theory models with $E_8$ enhancement. In this setting the $E_8$ symmetry is broken down to SU(5) by a 7-brane configuration described by T-branes, all the Yukawa couplings are generated in the vicinity of a point and only one family of quarks and leptons is massive at tree-level. The other two families obtain their masses when non-perturbative effects are taken into account, being hierarchically lighter than the third family. However, and contrary to previous results, we find that this hierarchy of fermion masses is not always appropriate to reproduce measured data. We find instead that different T-brane configurations breaking $E_8$ to SU(5) give rise to distinct hierarchical patterns for the holomorphic Yukawa couplings. Only some of these patterns allow to fit the observed fermion masses with reasonable local model parameter values, adding further constraints to the construction of F-theory GUTs. We consider an $E_8$ model where such appropriate hierarchy is realised and compute its physical Yukawas, showing that realistic charged fermions masses can indeed be obtained in this case.Comment: 46 pages + appendices, 5 figures. v2, added references and typos corrected, version accepted on JHEP. v3, typos correcte

Light scattering by an array of electric and magnetic nanoparticles

Light scattering by an array of alternating electric and magnetic nanoparticles is analyzed in detailed. Specific geometrical conditions are derived, where such an array behaves like double-negative particles, leading to a suppression of the backscattered intensity. This effect is very robust and could be used to produce double-negative metamaterials using single-negative components

Open string wavefunctions in flux compactifications

We consider compactifications of type I supergravity on manifolds with SU(3) structure, in the presence of RR fluxes and magnetized D9-branes, and analyze the generalized Dirac and Laplace-Beltrami operators associated to the D9-brane worldvolume fields. These compactifications are T-dual to standard type IIB toroidal orientifolds with NSNS and RR 3-form fluxes and D3/D7 branes. By using techniques of representation theory and harmonic analysis, the spectrum of open string wavefunctions can be computed for Lie groups and their quotients, as we illustrate with explicit twisted tori examples. We find a correspondence between irreducible unitary representations of the Kaloper-Myers algebra and families of Kaluza-Klein excitations. We perform the computation of 2- and 3-point couplings for matter fields in the above flux compactifications, and compare our results with those of 4d effective supergravity.Comment: 89 pages, 4 figures. v3: more typos corrected, version published in JHE

The Socio-Environmental Survey: a tool for an integrated study of protected areas. The case of Sierra Sur de Sevilla and Sierra de Cádiz

La declaración de Espacios Naturales Protegidos ha producido con frecuencia conflictos con las poblaciones locales en la gestión de la conservación de la naturaleza. En respuesta a esta realidad han surgido nuevos métodos y estrategias que buscan una mejor integración de la componente social en las áreas protegidas. Este artículo presenta los resultados de una Encuesta Socio-Ambiental (ESA) realizada durante la elaboración de una propuesta de Espacio Natural Protegido para la Red de Espacios Naturales Protegidos de Andalucía en la campiña agrícola del Subbético, entre las provincias de Sevilla y Cádiz (sur de España). A partir de los datos obtenidos se propone y discute la aplicación de la figura de Paisaje Protegido (tipo Categoría V de UICN) asociada a un modelo de gestión participativa abierta.The declaration of Protected Areas has frequently led to conflicts with local populations because of nature conservation management. In response to this reality new methods and strategies are emerging that are looking for a better integration of the social component in Protected Areas. This article shows the results of a Socio-Environmental Survey (SES) conducted during the elaboration of a Protected Area proposal for the Andalusian Protected Areas Network in the Subbetic agricultural “campiña”, between Seville and Cádiz provinces (Southern Spain). Based on the data obtained, the application of the Protected Landscape figure (type Category V of IUCN) associated to an open participatory management model is proposed and discussed