Phase-change metasurfaces for dyamic beam steering and beam shaping in the infrared

This is the author accepted manuscript. The final version is available from the publisher via the DOI in this recordWe present novel phase-change material based metasurfaces for dynamic, recnofigurable and efficient wavefront shaping in the infrared spectrum. Dynamic control and reconfigurability was obtained by incorporating an ultra-thin layer of the widely-used phase change material Ge2Sb2Te5. Our approach exploits hybrid dielectic/plasmonic resonances to achieve local (subwavelength) phase control of light with low losses. A full 2π optical phase coverage was achieved with this approach, which allows for a wide flexibility in terms of realizable designs. To illustrate this concept, dynamic beam steering devices and reconfigurable planar focusing mirrors (both operating at optical telecommunications wavelengths) and their performance investigated. Absolute efficiencies up to 65% are achieved, significantly higher than the efficiencies of more commonly reported plasmonic-based phase-change metasurfaces.CDW acknowledges funding via the US Naval Research Laboratories ONRG programme (#N62909-16-1-2174) and the EPSRC ChAMP and WAFT grants (EP/M015130/1 and EP/M015173/1). CRdeG acknowledges funding via the EPSRC CDT in Metamaterials (EP/L015331/1). CRdeG Acknowledges Joaquin Faneca-Ruedas and Dr Anna Baldycheva

Nota corta. Detección mediante PCR multiplex y caracterización de cepas no toxigénicas de Pseudomonas syringae pv. phaseolicola de distintas zonas de España

The efficient control of halo blight, caused by Pseudomonas syringae pv. phaseolicola, is primarily based on the use of pathogen-free seed. Detection of the pathogen in seeds is currently carried out with high-sensitive methods based on the detection by PCR of genes involved in the biosynthesis of phaseolotoxin, which was believed to be produced by all strains of the pathogen with epidemiological importance. However, field epidemics of halo blight in the county of Castilla y León, Spain, are often associated to nontoxigenic isolates of P. syringae pv. phaseolicola, which cannot be detected using current molecular and serological methods. The results presented in this work show the existence of nontoxigenic isolates of P. syringae pv. phaseolicola in areas other than Castilla y León, indicating the need to establish a reliable methodology for seed certification. A simple two-step methodology is presented with the aim to identify both types of isolates that is based on a multiplex enrichment PCR of seed soakates and on pathogenicity assays.El control eficiente de la grasa de la judía causada por Pseudomonas syringae pv. phaseolicola se basa principalmente en la utilización de semilla libre del patógeno. La detección del patógeno en semilla se efectúa mediante métodos altamente sensibles basados en la detección por PCR de los genes responsables de la biosíntesis de la faseolotoxina, la cual, hasta ahora, se consideraba que era sintetizada por todas las cepas del patógeno con importancia epidemiológica. Sin embargo, en la Comunidad de Castilla y León, España, las epidemias de grasa de la judía en campo se asocian frecuentemente con cepas no toxigénicas de P. syringae pv. phaseolicola, que no pueden ser detectadas con los métodos moleculares y serológicos actuales. Los resultados presentados en este trabajo demuestran la existencia de aislados no toxigénicos de P. syringae pv. phaseolicola en zonas distintas de Castilla y León, lo que implica la necesidad de establecer una metodología fiable para la certificación de semillas de judía. Con este propósito, se presenta un sencillo protocolo en dos fases que permite la identificación de los dos tipos de aislados, y que se basa en una PCR multiplex con enriquecimiento a partir de extractos de semilla y en ensayos de patogenicidad

Arsenic, fluoride and other trace elements in the Argentina Pampean plain

The contents of arsenic (As), fluoride (F) and other trace elements (B, Cd, Cr, Cu, Fe, Mn, Ni, Pb, V, Zn, Ba, Si and Sr) have been determined in groundwater samples from the Langueyú creek basin, in the Argentina Pampean plain. This research aims to establish the baseline concentration and geographical distribution of trace elements in this basin. This aim has particular interest to public health in the city of Tandil where groundwater is the principal source of water for human supply. The baseline concentrations of elements in the Langueyú creek basin are in good agreement with published data from other locations of the Pampean aquifer. The arsenic limit of 10mg/l, established as provisional limit by the World Health Organization (WHO), was exceeded in 78% of the sampled wells, with As concentration increasing in the direction of groundwater flow. Concentrations of B, Cd, Cu, Cr, Fe, Mn, Ni, Pb and Zn regulated by the Argentinian Food Code (CAA) do not exceed the maximum limit for drinking water, although concentrations of Ni, Zn or Pb peaked up at some wells, probably due to pipeline corrosion. The strong correlation observed between As, F, V, Cr and B has been related to their anionic character at the groundwater natural alkaline pH that is likely associated with similar mobilization (adsorption/desorption) processes. Worst consequences for human health have arisen in areas with the highest arsenic concentration in drinking water. The conclusions of this study contribute to understand the provenance and mobilization processes of some trace elements in groundwater. It enables the decision making regarding the public health priorities and the technological treatments of water resources in urban and rural areas

Caracterización fisicoquímica de las aguas superficiales en la cuenca del Arroyo del Fuerte, Tandil

Fil: Cifuentes, M.. Universidad Nacional del Centro de la Provincia de Buenos Aires. Facultad de Ciencias Humanas. Centro de Investigaciones y Estudios Ambientales; ArgentinaFil: Gabellone, Néstor A.. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. Instituto de Limnología Dr. Raúl Ringuelet; ArgentinaFil: Ruiz de Galarreta, Alejandro. Universidad Nacional del Centro de la Provincia de Buenos Aires. Facultad de Ciencias Humanas. Centro de Investigaciones y Estudios Ambientales; Argentin

All-dielectric hybrid silicon/Ge2Sb2Te5 optical metasurfaces for tunable and switchable light control in the near infrared

This is the final version.We report a novel reconfigurable metasurface based on the combination of all-dielectric arrays of silicon meta-atoms, with deeply subwavelength (< λ0/150) Ge2Sb2Te5 layers. Our approach allows to selectively and individually control electric and magnetic resonances.Engineering and Physical Sciences Research Council (EPSRC

Lens numerical aperture control with phase-change metasurfaces

This is the author accepted manuscript.The control of lens numerical aperture has many applications, including photography, imaging, and laser processing. Here we introduce active control of numerical aperture via a focusing phase-change meta-mirror. This can potentially operate at high speed in a low cost, light and compact format. We demonstrate designs for both infrared (3000 nm) and visible (632.8 nm) wavelengths.Engineering and Physical Sciences Research Council (EPSRC)Atomic Weapons Establishment (AWE

Optical and Thermal Design and Analysis of Phase-Change Metalenses for Active Numerical Aperture Control

This is the final version. Available on open access from MDPI via the DOI in this recordThe control of a lens's numerical aperture has potential applications in areas such as photography and imaging, displays, sensing, laser processing and even laser-implosion fusion. In such fields, the ability to control lens properties dynamically is of much interest, and active meta-lenses of various kinds are under investigation due to their modulation speed and compactness. However, as of yet, meta-lenses that explicitly offer dynamic control of a lens's numerical aperture have received little attention. Here, we design and simulate active meta-lenses (specifically, focusing meta-mirrors) using chalcogenide phase-change materials to provide such control. We show that, operating at a wavelength of 3000 nm, our devices can change the numerical aperture by up to a factor of 1.85 and operate at optical intensities of the order of 1.2 × 109 Wm-2. Furthermore, we show the scalability of our design towards shorter wavelengths (visible spectrum), where we demonstrate a change in NA by a factor of 1.92.Engineering and Physical Sciences Research Council (EPSRC)Margarita Salas fellowshi

Remote Thermal Sources for Switching Phase-Change Material-Based Metasurfaces

This is the final version.Atomic Weapons Establishment (AWE) plcEngineering and Physical Sciences Research Council (EPSRC

Switching of Phase-Change Optical Metasurfaces via Remote Thermal Sources

This is the final version.Atomic Weapons Establishment (AWE) plcEngineering and Physical Sciences Research Council (EPSRC