Reconfigurable phase-change optical metasurfaces: novel design concepts to practicable devices

Optical metasurfaces have been proven to be capable of controlling amplitude, phase and polarization of optical beams without the need of bulky geometries, making them really attractive for the development of compact photonic devices. Recently, their combination with chalcogenide phase-change materials (traditionally employed in non-volatile optical and electrical memories), whose refractive index can be reversibly and repeatedly controlled, has been proposed to yield low power consumption tunable metasurfaces having several functionalities in a single device. However, despite phase-change memories are commercially available since various decades now, the unification of phase-change materials with metasurfaces towards real life applications is becoming a formidable task, mainly due to the several engineering branches involved in this technology, which sometimes compromise each other in a non-trivial way. This includes thermo/optical, thermo/electric, and chemical incompatibilities which are typically not taken into account by researchers working in the field, resulting in devices having exciting reconfigurable properties, but at the same time, lack of practicability. This thesis is therefore dedicated to the development of novel phase-change metasurface architectures which could partially or totally address such engineering problems. Particular emphasis has been put in the realization of reconfigurable metasurfaces for active wavefront control, as such a functionality remains relatively unexplored. The first part of this thesis focuses in the first experimental demonstration of active, reconfigurable non-mechanical beam steering devices working the near-infrared. This was achieved via integration of ultra-thin films of chalcogenide phase-change materials (in this case, the widely employed alloy Ge2Sb2Te5) within the body of a dielectric spacer in a plasmonic metal/insulator/metal metasurface architecture. Active, and optically reversible beam steering between two different angles with efficiencies up to 40% were demonstrated. The second part of this work shows the work carried out in metal-free metasurfaces as a way to manipulate optical beams with high efficiency in both transmission and/or reflection. This was achieved via combination of all-dielectric silicon nanocylinders with deeply-subwavelenght sized Ge2Sb2Te5 inclusions. By strategic placement of the phase-change inclusions in the regions of high electric field density, independent and active control of the metasuface resonances is demonstrated, with modulations depths as high as 70% and 65% in reflection and transmission respectively. Multilevel, and fully reversible optically-induced switching of the phasechange layer is also reported, with up to 11 levels of tunability over 8 switching cycles. Finally, the last section of this thesis introduces the concept of hybrid dielectric/plasmonic phase-change metasurfaces having key functional benefits when compared to both purely dielectric and plasmonic approaches. The proposed architectures showed great versatility in terms of both active amplitude and phase control, offering the possibility of designing devices for different purposes (i.e. such as active absorbers/modulators or beam steerers with enhanced efficiency) employing the same unit-cell configuration with minor geometry re-optimizations. Initial device experimental demonstrations of such an approach are discussed, as well as their potential in terms of delivering in-situ electrical switching capabilities using a metallic ground plane as a resistive heater.Engineering and Physical Sciences Research Council (EPSRC

La comunicación pública de la ciencia en Argentina: los casos de "El Gato y La Caja" y "CONICET Dialoga"

Abstract This article is based on the results of an investigation that explored how the media CONICET Dialoga and El Gato y La Caja communicate on Facebook from the perspective of Public Communication of Science Studies. In this framework, the use of new narratives and communicative interactivity are considered as structural factors for this process. The publications that the media shared in the social network during two weeks of November 2018 were analyzed. The results revealed the use of multimedia resources as part of their communicative strategy, an incipient use of hypertextuality to share science communication with the masses, and an uneven level in the possibilities of participation that they established with their audience. The conclusions show that although both media share the ways they communicate, which are in the line of the postulates of Public Communication of Science, CONICET Dialoga is the one which is aligned with the cognitive deficit model, while El Gato y La Caja presents a proposal related to the contextual ethnographic model.El presente artículo recupera los resultados de una investigación que abordó los modos en que los medios CONICET Dialoga y El Gato y la Caja comunican en Facebook desde la perspectiva de la Comunicación Pública de la Ciencia (CPC). En este marco, se considera el uso de nuevas narrativas y la interactividad comunicativa como factores estructurales de dicho proceso. Se analizaron las publicaciones que los medios compartieron en la red social durante dos semanas de noviembre del año 2018. Los resultados revelaron la presencia de recursos multimedia como parte de la estrategia comunicativa, un incipiente uso de la hipertextualidad para abrir la comunicación de la ciencia al público masivo y una dispar utilización de las posibilidades de participación que establecieron con sus públicos. Se concluye que si bien ambos medios comparten sus formas de comunicar con características que los alinean con los postulados de la CPC, CONICET Dialoga es el medio que se ajusta al modelo de déficit cognitivo, mientras que El Gato y La Caja presenta una propuesta alineada con el modelo etnográfico contextual.Abstract This article is based on the results of an investigation that explored how the media CONICET Dialoga and El Gato y La Caja communicate on Facebook from the perspective of Public Communication of Science Studies. In this framework, the use of new narratives and communicative interactivity are considered as structural factors for this process. The publications that the media shared in the social network during two weeks of November 2018 were analyzed. The results revealed the use of multimedia resources as part of their communicative strategy, an incipient use of hypertextuality to share science communication with the masses, and an uneven level in the possibilities of participation that they established with their audience. The conclusions show that although both media share the ways they communicate, which are in the line of the postulates of Public Communication of Science, CONICET Dialoga is the one which is aligned with the cognitive deficit model, while El Gato y La Caja presents a proposal related to the contextual ethnographic model

Análisis, síntesis y diseño de un motor de combustión interna alternativo radial

Resumen El presente proyecto tiene como objetivo analizar el mecanismo principal del MCIA (motor de combustión interna alternativo) radial y desarrollar un modelo en 3 dimensiones mediante software CAD, más concretamente, mediante CATIA V5. Asimismo, el modelo desarrollado será examinado con ANSYS, un programa de análisis por el método de elementos finitos (MEF), capaz de simular el comportamiento cinemático y dinámico del mecanismo. Dicho estudio servirá para evaluar el mecanismo diseñado en base a las tensiones obtenidas como resultado.Abstract This Project has the aim of analyzing the main mechanism of the radial AICE (alternative internal combustion engine) and developing a 3-dimension model through CAD software, specifically, through CATIA V5. Likewise, the model developed will be assessed with ANSYS, a program which analyzes by means of the finite element method (FEM), capable of simulating the kinematic and dynamic behaviour of the device. This survey will be used to evaluate the designed mechanism based on the stress obtained as a result.Laburpena Proiektu honek BEMA (barne errekuntzako motore alternativo) erradialaren mekanismo printzipala aztertzea eta 3 dimentsioko eredu bat CAD softwarearen laguntzaz, zehazki CATIA V5-ren laguntzaz, garatzea du helburu. Halaber, garatutako eredua ANSYS-ren bidez aztertuko da, elementu finituen metodoa (EFM) erabiltzen duen programa, mekanismoaren jokabide zinematiko eta dinamikoa simulatzeko gai dena. Azterketa hau erabilgarria izango da diseinatutuako mekanismoa ebaluatzeko emandako tentsioen emaitzetan oinarrituta

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

A validated finite element analysis procedure for porous structures

Cellular materials are gaining interest thanks to developments in additive manufacturing. Whilst Finite Element Analysis (FEA) is commonly used to obtain the mechanical behaviour of these structures, different modelling and simulation methodologies are followed in literature. Consequently, there is not a clear procedure to accurately evaluate the mechanical properties of porous structures. This study presents a method to perform FEA of lattice structures with accurate results. All inputs required to simulate compression testing of lattices in FEA were investigated, these included the modelling type, element size, number of unit cells required, boundary conditions and the material model. The effect of these variables on the modulus and yield strength of a lattice structure was studied. Lattices with two unit cell structures, varying unit cell sizes and relative densities were additively manufactured in stainless steel, compression tested and compared to FE simulations. The material model for the FE simulations was obtained from tensile testing individual micro-struts of varying diameters. FE simulation results were in good agreement with the experimental results with an average error for the modulus and yield strength of ~10% and 17% respectively. The methodology presented should provide a foundation to accelerate development and adoption of these structures

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

Assessment of hydrochemical characteristics of the Langueyú creek basin applying multivariate statistical analysis

This work aimed to analyze a hydrochemical dataset of Langueyú creek basin (Buenos Aires, Argentina) applying two multivariate statistical analysis methodologies: cluster analysis and main component analysis. In the basin is settled the Tandil city, which relies on groundwater for different purposes (drinking, industry, agriculture, etc.). This is why it is considered essential to a thorough understanding of hydrochemical characteristics. Phreatic levels were measured and groundwatersamples were taken with a quaterly frecuency in a monitoring net of thirty wells. Physicochemical parameters, conductivity, pH, major ions and nitrate, were determined. The results of cluster and main component analysis showed that it is possible to separate two groups of samples: One group is composed of samples located in the recharge zone and the proximal foothill (elevation 150 m.a.s.l); and a second group is composed of samples that are located to the NE. It was concluded that two processes are determinants to define hydrochemical characteristics of the study area: a) the salts acquisition during the way through the porous medium, which begins with the dissolution of carbonates, due to the acidity acquired by the reaction with CO2 during its infiltration through the unsaturated zone, and b) calcium-sodium exchange combined with the retention of potassium in clays. Multivariate statistical analysis has proved to be a useful tool for interpreting hydrochemical results and the validation of the hydrogeological conceptual model.Este trabajo tuvo como objetivo analizar un conjunto de datos hidroquímicos de la cuenca del arroyo Langueyú (Buenos Aires, Argentina) aplicando dos metodologías de análisis estadístico multivariado: análisis de conglomerados y de componentes principales. En la cuenca se asienta la ciudad de Tandil, que depende del agua subterránea para diferentes fines (consumo humano, industria, agricultura, etc.). Es por esto que se considera indispensable un conocimiento profundo de sus características hidroquímicas. Se midieron los niveles freáticos y se tomaron muestras de agua con una frecuencia cuatrimestral en una red de monitoreo de treinta pozos. Se determinaron los parámetros físico-químicos, conductividad, pH, iones mayoritarios y nitrato. Los resultados de los análisis de conglomerados y componentes principales mostraron que es posible separar dos grupos de muestras: Un grupo se compone de las ubicadas en la zona de recarga y piedemonte proximal (elevación 150 msnm); y otro grupo se compone de las muestras ubicadas hacia el NE. Se concluyó que los dos procesos determinantes para definir las características hidroquímicas son: a) la adquisición de sales en el recorrido por el medio poroso, que comienza con la disolución de carbonatos, debido a la acidez adquirida por la reacción con CO2 durante su infiltración a través de la zona no saturada, y b) el intercambio iónico calcio-sodio, combinado con la retención de potasio en las arcillas. El análisis estadístico multivariado ha demostrado ser una herramienta útil para interpretar resultados hidroquímicos y para la validación del modelo hidrogeológico conceptual.Fil: Barranquero, Rosario Soledad. Universidad Nacional del Centro de la Provincia de Buenos Aires. Facultad de Ciencias Humanas. Departamento de Ciencias Ambientales. Centro de Investigacion y Estudios Ambientales; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Tandil; ArgentinaFil: Varni, Marcelo. Universidad Nacional del Centro de la Provincia de Buenos Aires. Rectorado. Instituto de Hidrología de Llanuras - Sede Azul; ArgentinaFil: Ruiz de Galarreta, Alejandro. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas; ArgentinaFil: Quiroga, Miguel. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas; Argentina. Universidad Nacional del Centro de la Provincia de Buenos Aires; ArgentinaFil: Landa, Roberto. Universidad Nacional del Centro de la Provincia de Buenos Aires; Argentin

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

Ekonomia Ekologikoaren eta Ekonomia Sozial eta Solidarioaren arteko hurbilketa. Agenda bateratu baterako elementuak

Geroz eta ageriagoa den ingurumen-iraunkortasunaren inguruko krisiak etorkizun zehaztugabea planteatzen du geure gizarteetan. Horrenbestez, ekonomia neoklasikoari eta ka-pitalismoari lotutako proposamenen porrota ageria denean, premia handia dago ingurumenak planteatzen dituen erronkei erantzuna emango dioten bestelako proposamenak eskaintzeko. Artikulu honen bitartez, ekonomia heterodoxoen artean aurkitu ditzakegun Ekonomia Ekolo-gikoa eta Ekonomia Sozial eta Solidarioaren arteko harremanetan sakondu nahi da. Izan ere, hauen arteko hurbilketa batek ingurumen eta gizarte krisiei erantzuteko konbergitu dezakete. Horretarako, ohiko ekonomiak erabiltzen duen ikuspegi analitikotik aldenduta, eta naturarekiko eta gizartearekiko bestelako harremanak planteatzen dituzten bi eredu hauen arteko batera-garritasun, desadostasun eta adostasunetan arakatu da, agenda partekatua aurrera eramatea ahalbidetzen dieten elementuak aztertzeko.; The increasingly crisis of environmental sustainability presents an uncertain future for our societies. Therefore, when the neoclassical economy and capitalist proposals fails, there is a great need to offer other proposals that respond to the challenges posed by the en-vironment. This article aims to delve into the relations between the Ecological Economy and the Social and Solidarity Economy that we can find among the heterodox economies. In fact, an approach between them can converge to respond to both, environmental and social crises. To that end, far from the analytical approach used by the dominant economy, have been ana-lyzed the converging elements, disagreements and points of agreement between these two models. Keeping in mind that both pose a different relation with nature and society, in order to explore elements that allow to advance in the shared agenda

Microbiota contaminante en agua de tambos-queserías de tipo familiar

La Cuenca Lechera Mar y Sierras, Argentina, posee una larga trayectoria en la producción de leche y subproductos con un importante crecimiento en la elaboración de quesos en los últimos años. Muchas son empresas de tipo familiar que procesan la leche y elaboran quesos en el mismo establecimiento, donde también viven, y generalmente no cuentan con agua de red para las maniobras de producción y consumo.El objetivo de este trabajo fue analizar la calidad bacteriológica del agua proveniente del recurso hídrico subterráneo y de su distribución en establecimientos de tipo familiar. Se tomaron 52 muestras incluyendo agua de las perforaciones de abastecimiento (18), de uso en tambo (14) y quesería (20) de 5 establecimientos visitados en distintas épocas del año. Se determinaron según normas internacionales estandarizadas APHA: recuento de bacterias mesófilas viables, coliformes totales, coliformes termotolerantes, presencia de Escherichia coli, Pseudomonas aeruginosa, enterococos, esporas de clostridios sulfito reductores, Salmonella spp y Shigella spp.Todos los establecimientos presentaron, en al menos uno de los muestreos, alguna muestra no apta de acuerdo a los criterios de agua potable de Código Alimentario Argentino (CAA). En total se observó que 33% de las muestras de pozo sobrepasaron los límites de indicadores de calidad higiénica (mesófilos y coliformes totales), 35,7% y 45% de las muestras de tambo y queserías, respectivamente, presentaron recuentos de coliformes totales elevados. En algunas de esas muestras se detectó además la presencia de Escherichia coli, Pseudomonas aeruginosa, enterococos, esporas de clostridios sulfito reductores o Salmonella spp. Por otro lado, 6 muestras aptas según los criterios de CAA resultaron positivas para enterococos o clostridios sulfito reductores.Los altos recuentos de indicadores de calidad higiénica y la presencia de bacterias indicadoras de contaminación fecal reflejan condiciones constructivas deficientes y problemas en localizaciones de los pozos en algunos de los establecimientos, como también fallas de higiene. Los resultados destacan la necesidad de un mayor conocimiento de la hidrogeología del lugar y de la infraestructura del acceso y manejo del agua, así como de implementar sistemas de desinfección y controles periódicos incluyendo la evaluación de bacterias más resistentes a las características de la producción.Fil: Tabera, Anahi. Universidad Nacional del Centro de la Provincia de Buenos Aires. Facultad de Ciencias Veterinarias; ArgentinaFil: Ruiz de Galarreta, Alejandro. Universidad Nacional del Centro de la Provincia de Buenos Aires. Facultad de Ciencias Humanas. Departamento de Ciencias Ambientales. Centro de Investigación y Estudios Ambientales; ArgentinaFil: Krüger, Alejandra. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tandil. Centro de Investigación Veterinaria de Tandil. Universidad Nacional del Centro de la Provincia de Buenos Aires. Centro de Investigación Veterinaria de Tandil. Provincia de Buenos Aires. Gobernación. Comision de Investigaciones Científicas. Centro de Investigación Veterinaria de Tandil; ArgentinaXXIV Congreso Latinoamericano de Microbiología; XL Congreso Chileno de Microbiología; II Reunión Anual de la Asociación Chilena de Inmunología y IX Reunión de la Sociedad Latinoamericana de Tuberculosis y otras MicobacteriosisSantiago de ChileChileAsociación Latinoamericana de Microbiologí