Computationally efficient analysis of extraordinary optical transmission through infinite and truncated subwavelength hole arrays

The authors present a computationally efficient technique for the analysis of extraordinary transmission through both infinite and truncated periodic arrays of slots in perfect conductor screens of negligible thickness. An integral equation is obtained for the tangential electric field in the slots both in the infinite case and in the truncated case. The unknown functions are expressed as linear combinations of known basis functions, and the unknown weight coefficients are determined by means of Galerkin's method. The coefficients of Galerkin's matrix are obtained in the spatial domain in terms of double finite integrals containing the Green's functions (which, in the infinite case, is efficiently computed by means of Ewald's method) times cross-correlations between both the basis functions and their divergences. The computation in the spatial domain is an efficient alternative to the direct computation in the spectral domain since this latter approach involves the determination of either slowly convergent double infinite summations (infinite case) or slowly convergent double infinite integrals (truncated case). The results obtained are validated by means of commercial software, and it is found that the integral equation technique presented in this paper is at least two orders of magnitude faster than commercial software for a similar accuracy. It is also shown that the phenomena related to periodicity such as extraordinary transmission and Wood's anomaly start to appear in the truncated case for arrays with more than 100 (10×10) slots

Potato virus X (PVX) elimination as short and long term effects of hydrogen peroxide and salicylic acid is differentially mediated by oxidative stress in synergism with thermotherapy

Articulo científico indezadoAbstract Short and long term effects of hydrogen peroxide (H2O2) and salicylic acid (SA) were examined in: thermotolerance, virus X (PVX)-free microplants obtained by in vitro thermotherapy, catalase activity (CAT) and H2O2 concentration. Short term effects (STE) were tested as follows: (a) nodal explants were cultivated 30 d on MS medium containing SA 10−5 or 10−6 M; and (b) nodal explants were waterlogged for 1 h in 1 or 5 mMH2O2 solution and subsequently cultured in MS for 30 d. Long term effects were tested as follows (LTE): the experimental regime was identical to STE but SA and H2O2 treated plants were subcultured for an additional 30 d period onMS. All treatments were followed by thermotherapy (32–42 C) for 35 d. Results showed SA and H2O2 induced thermotolerance during thermotherapy. The percentage of PVX-free plants obtained in H2O2 was significantly higher than in SA in STE and LTE by 3-and 4 fold respectively. CAT activity was differentially mediated by SA and H2O2.This research was supported by a grant from Recursos Fiscales, INIFAP

Disorder Effects in One-Dimensionally Periodic Extraordinary Transmission Structures

Extraordinary transmission structures show promising capabilities for highly selective filters in both frequency and angle of incidence. However, their realistic response once manufacturing limitations are taken into account remains unexplored. In this manuscript, we explore a novel degree of freedom: disorder. We expand on previously developed highly efficient method of moment (MoM) implementations to study the effects on the transmission properties of large but finite chains of slots due to different families of disorder: lateral and vertical displacements as well as scatterer manipulation (modifying sizes and rotation angles), showing their effects on the transmission spectrum.Ministerio de Ciencia e Innovación PID2020-116739GB-I0

Engineering Casimir interactions with epsilon-near-zero materials

In this paper, we theoretically demonstrate the tunability of the Casimir force both in sign and magnitude between parallel plates coated with dispersive materials. We show that this force, existing between uncharged plates, can be tuned by carefully choosing the value of the plasma frequency (i.e., the epsilon-near-zero frequency) of the coating in the neighborhood of the resonance frequency of the cavity. The coating layer enables a continuous variation of the force between four limiting values when a coating is placed on each plate. We explore the consequences of such variation when pairs of electric and magnetic conductors (i.e., low and high impedance surfaces) are used as substrates on either side, showing that this continuous variation results in changes in the sign of the force, leading to both stable and unstable conditions, which could find interesting potential applications in nanomechanics, including nanoparticle tweezing.Defense Advanced Research Program Agency (DARPA) HR00112090084MCIN/AEI/10.13039/501100011033 PID2020-116739GB-I0

Extraordinary Transmission and Radiation from Finite by Infinite Arrays of Slots

In this communication an efficient method of moments (MoM) code is used for the analysis of the extraordinary transmission (EOT) through a periodic array of rectangular slots in a conducting screen, in the case where the number of slots is finite in one direction and infinite in the orthogonal direction. The slots can be arbitrarily rotated within the periodic unit cell. Once the magnetic current density on the slots is obtained by means of MoM, both the transmission coefficient and the far-field radiated by the array of slots are computed. The onset of EOT turns out to be strongly dependent on the orientation of the slots with respect to the direction in which the array is infinite. If the slots are perpendicular to this direction, EOT appears for a single infinite chain of slots. However, tens of parallel chains of slots are required to reproduce the EOT response when the slots are aligned along the parallel chains direction. The obtained radiation patterns show the excitation of grating lobes as the number of slots grow in the direction where the arrays are finite.Engineering and Physical Sciences Research Council (EPSRC) U.K EP/L015331/1Junta de Andalucía P12-TIC-1435Ministerio de Economía, Industria y Competitividad TEC2017-84724-

Mimicking glide-symmetry dispersion with coupled slot metasurfaces (article)

This is the author accepted manuscript. The final version is available from AIP Publishing via the DOI in this record.The dataset associated with this article is in ORE at http://hdl.handle.net/10871/29285In this Letter we demonstrate that the dispersion properties associated with glide symmetry can be achieved in systems that only possess reflection symmetry by balancing the influence of two sub-lattices. We apply this approach to a pair of coupled slots cut into an infinite perfectly conducting plane. Each slot is notched on either edge, with the complete two-slot system having only mirror symmetry. By modifying the relative size of the notches on either side of the slots, we show that a linear dispersion relation with a degeneracy with non-zero group velocity at the Brillouin zone boundary can be achieved. These properties, until now, only found in systems with glide symmetry are numerically and experimentally validated. We also show that these results can be used for the design of ultra-wideband one-dimensional leaky wave antennas in coplanar waveguide technology.The authors wish to acknowledge financial support from the Engineering and Physical Sciences Research Council (EPSRC) of the United Kingdom, via the EPSRC Centre for Doctoral Training in Metamaterials (Grant No. EP/L015331/1)

Effective-periodicity effects in Fibonacci slot arrays

In this Letter, the transmission properties of a nonperiodic array of slots arranged in the form of a Fibonacci sequence are investigated. By arranging the slots in this manner, an additional periodicity can be utilized, resulting in corresponding resonance features in the transmitted signal. By investigating the transmission response of a perforated metallic sheet over a broad frequency range (6–40 GHz), it is shown that this simple one-dimensional chain supports two periodicities, one due to the regular periodic separation and one due to average spacing—which is related to the golden ratio. This response replicates the resonant behavior of a two-dimensional periodic array with a single nonperiodic array also creating new families of diffraction lobes in the far-field region.MCIN/AEI/10.13039/501100011033 PID2020-116739GB-I00EPSRC EP/R004781/1EPSRC EP/L015331/

Estrategias de enseñanza utilizadas por el equipo docente y estrategias de aprendizaje aplicadas por la madre menor de edad privada de libertad del Centro de Formación Juvenil Zurquí para favorecer sus habilidades académicas

Metodología cualitativaLa educación es un derecho inmerso a lo largo de la historia de vida, sea en la etapa de la niñez, adolescencia o adultez. Y en nuestro país es inalienable. Desde la óptica de Derechos Humanos, las personas privadas de libertad también tienen derecho a la educación en igualdad de oportunidades. En el año 2015 ingresa al Centro de Formación Juvenil Zurquí la primera mujer, menor de edad en estado de embarazo, por lo que no contaba con la infraestructura necesaria para albergar a esta joven madre y fue hasta el 2017 que tanto el Ministerio de Justicia y Paz como la empresa privada unieron esfuerzos para brindar lo necesario a la población gestante. Los objetivos de este estudio se centran en las estrategias de cómo aprende la mujer madre menor de edad privada de libertad, así como las estrategias de enseñanza que emplea el grupo de docentes, para estimular el aprendizaje del Centro de Formación Juvenil Zurquí. Se enmarca dentro de un diseño cualitativo, con un enfoque de caso instrumental, basado en la descripción y análisis de estrategias de enseñanza utilizadas por el equipo docente y estrategias de aprendizaje aplicadas por la madre menor de edad privada de libertad, como objeto de estudio. Se utilizó una guía de entrevista dirigida a docentes y otra a la madre, así como una guía de observación para obtener información y conocer aspectos dentro del contexto de aula en el Centro de Formación Juvenil Zurquí. Como parte de los principales hallazgos tenemos: La estudiante pone en práctica algunas estrategias, como lectura de la materia vista en clase y subrayado de contenidos. El tiempo es aprovechable cuando la estudiante está en el centro educativo, ya que en la casa cuna no cuenta con tutores y debe cumplir con obligaciones de madre. El Limitado acceso a útiles escolares y recursos tecnológicos, restringe el uso de estrategias y técnicas de estudio e investigación que la joven pueda utilizar. El proceso educativo no se ve afectado durante el período pre ni postnatal, por los docentes adecuan la materia para la estudiante y ella muestra motivación extrínseca para salir adelante por su hijo y un mejor futuro económico para ambos. El grupo docente estructura grupos multinivel donde los contenidos son adaptados a las competencias curriculares de cada estudiante. El espacio físico y recursos didácticos de baja tecnología de las aulas es adecuado, pero no es aprovechado al máximo. A pesar de los recursos limitados tanto humanos como económicos, se brinda respuesta a las necesidades educativas de cada estudiante.UCR::Vicerrectoría de Docencia::Ciencias Sociales::Facultad de Educación::Escuela de Orientación y Educación Especia

Assessment of major depressive disorder model in rat

El trastorno depresivo mayor (MDD) es una enfermedad caracterizada por la presencia de dos o más episodios depresivos consecutivos, es un factor de riesgo para cometer suicidio. La mayoría de las terapias antidepresivas se basan en el mantenimiento de la serotonina (5-HT) en la hendidura sináptica. El modelo debulbectomía olfatoria bilateral (OBX) tiene características similares al trastorno depresivo humano. El objetivo de este trabajo es caracterizar a la bulbectomía olfatoria como un modelo de depresión en ratas. Los resultados obtenidos muestran cambios fisiológicos y conductuales que son comparables a la depresión humana, las ratas bulbectomizadas disminuyeron de peso comparadas con los grupos control y cirugía sin extracción, la presencia de la hiperactividad es reducida después de 21 días de tratamiento con antidepresivos, la respuesta alterada a los estímulos adversos y la disminución del acicalamiento puede ser comparado con síntomas de depresión en humanos.Major depressive disorder (MDD) is a disease characterized by the presence of two or more depressive episodes. It is a risk factor to commit suicide. The most common antidepressant therapies are based on maintaining serotonin (5-HT) in the synaptic cleft. The bilateral olfactory bulbectomy (OBX) in rat model have characteristics similar to human depressive disorder. The aim of this work is to characterize olfactory bulbectomy as a depressive major model in rats. These results show physiological and behavioral changes that are comparable to human depression; bulbectomized rats have decreased weight compared to control and surgery without extraction groups, the presence of hyperactivity is reduced after 21 days of treatment with antidepressants (SSRI), altered response to adverse stimuli and a decrease of grooming can be equated a symptom of depression in humans

Development and Validation of a Questionnaire on Motivation for Cooperative Playful Learning Strategies

Playful learning strategies, such as educational gamification, game-based learning, and escape rooms are increasingly being incorporated into the university education system. In this study, it aims to develop and validate an instrument to analyze motivation regarding the use of playful learning strategies in university students. A total of 450 university students aged between 18 and 55 (Mean = 22.72; Standard Deviation = 5.01) were part of the sample, with whom playful strategies were implemented during the 2019/2020 school year. The results obtained in the confirmatory factor analysis indicate that the questionnaire on motivation for playful learning strategies has adequate psychometric properties to assess the motivation and perception of student learning in the implementation of ludic strategies in the classroom in the Spanish university context