Modeling and Analysis of Composite Antenna Superstrates Consisting on Grids of Loaded Wires

We study the characteristics and radiation mechanism of antenna superstrates based on closely located periodical grids of loaded wires. An explicit analytical method based on the local field approach is used to study the reflection and transmission properties of such superstrates. It is shown that as a result of proper impedance loading there exists a rather wide frequency band over which currents induced to the grids cancel each other, leading to a wide transmission maximum. In this regime radiation is produced by the magnetic dipole moments created by circulating out-of-phase currents flowing in the grids. An impedance matrix representation is derived for the superstrates, and the analytical results are validated using full-wave simulations. As a practical application example we study numerically the radiation characteristics of dipole antennas illuminating finite-size superstrates.Comment: 9 pages, 11 figures. In the second version we have clarified the analysis related to the prototype, and re-desinged the prototype antenn

Desempeño docente y gestión escolar en una institución educativa pública de la Ugel 02 - Lima 2022

La investigación considera el estudio de la mediación pedagógica de los docentes en su desempeño favorable mediante el uso de estrategias metodológicas, estrategias de evaluación y recursos que éste utilice en el aprendizaje para mejorar el sistema educativo y como base la gestión escolar en el marco social, político y económico; por lo que el objetivo de estudio es determinar la relación entre el desempeño docente y la gestión escolar en una institución educativa pública de la UGEL 02 - Lima 2022. El trabajo de investigación tiene un enfoque cuantitativo de nivel descriptivo correlacional, el diseño de investigación es no experimental, se trabajó con una muestra censal de 83 docentes y con dos instrumentos validados. Para procesar la información se utilizó el Software estadístico SPSS V26. Los resultados estadísticos, al concluir los objetivos de la investigación, facilitaron las siguientes conclusiones: el desempeño docente, con respecto a la gestión estratégica, administrativa, pedagógica y comunitaria guarda una relación moderada directa y positiva (promedio 0,35); y la relación entre las variables desempeño docente y la gestión escolar tiene una relación moderada directa y positiva (0,37); por lo que consideramos que el proceso de cambio es lento entre estas dos variables

On the Definition of Effective Permittivity and Permeability For Thin Composite Layers

The problem of definition of effective material parameters (permittivity and permeability) for composite layers containing only one-two parallel arrays of complex-shaped inclusions is discussed. Such structures are of high importance for the design of novel metamaterials, where the realizable layers quite often have only one or two layers of particles across the sample thickness. Effective parameters which describe the averaged induced polarizations are introduced. As an explicit example, we develop an analytical model suitable for calculation of the effective material parameters $\epsilon_{\rm{eff}}$ and $\mu_{\rm{eff}}$ for double arrays of electrically small electrically polarizable scatterers. Electric and magnetic dipole moments induced in the structure and the corresponding reflection and transmission coefficients are calculated using the local field approach for the normal plane-wave incidence, and effective parameters are introduced through the averaged fields and polarizations. In the absence of losses both material parameters are purely real and satisfy the Kramers-Kronig relations and the second law of thermodynamics. We compare the analytical results to the simulated and experimental results available in the literature. The physical meaning of the introduced parameters is discussed in detail.Comment: 6 pages, 5 figure

A Focusing Metamaterial Based Wollaston Prism

By using existing metal mesh technology we propose a new lens design that behaves in a similar way to a Wollaston Prism. That is, a device that separates out the two linear polarised states of the incident field and then focuses them separately on same focal plane. The design is an evolution of an existing GRIN lens based on the same technology. The proposed lens design has a diameter of 75mm while only being 2mm thick. This will focus two beams at a distance of 250mm with a separation of 10mm, over the frequency range of 100-200GHZ. Such a device would be useful where space and weight are an issue and would allow the use of incoherent detectors

Cloning and expression analysis of hemoglobin genes from maize (\u3ci\u3eZea mays\u3c/i\u3e ssp. \u3ci\u3emays\u3c/i\u3e) and teosinte (\u3ci\u3eZea mays\u3c/i\u3e ssp. \u3ci\u3eparviglumis\u3c/i\u3e)

With the exception of barley and rice, little is known about the existence of hemoglobins (Hbs) in cereals. This work reports the cloning and analysis of hb genes from maize (Zea mays ssp. mays) and teosinte (Zea mays ssp. parviglumis). Coding sequences of maize and teosinte hb genes (hbm and hbt, respectively) are highly similar to each other and are interrupted by three introns located at identical positions as other plant hb genes. Sequences of predicted Hbm and Hbt proteins are identical. The hydropathic profile of Hbm and Hbt is highly similar to that of rice Hb1, suggesting that Hbm, Hbt and Hb1 have the same tertiary structure and biochemical properties. Expression analysis showed that low levels of Hb transcripts, but considerable levels of Hb proteins exist in maize embryonic organs. No Hb transcripts and proteins were detected in teosinte embryonic organs. Low levels of Hb proteins, but no Hb transcripts, were detected in maize and teosinte vegetative organs. These observations suggest that the regulation of hb genes is different in maize and teosinte embryonic organs, and that the expression of hb genes is down- or up-regulated in maize and teosinte, respectively, from germination to vegetative growing

Cloning and expression analysis of hemoglobin genes from maize (\u3ci\u3eZea mays\u3c/i\u3e ssp. \u3ci\u3emays\u3c/i\u3e) and teosinte (\u3ci\u3eZea mays\u3c/i\u3e ssp. \u3ci\u3eparviglumis\u3c/i\u3e)

With the exception of barley and rice, little is known about the existence of hemoglobins (Hbs) in cereals. This work reports the cloning and analysis of hb genes from maize (Zea mays ssp. mays) and teosinte (Zea mays ssp. parviglumis). Coding sequences of maize and teosinte hb genes (hbm and hbt, respectively) are highly similar to each other and are interrupted by three introns located at identical positions as other plant hb genes. Sequences of predicted Hbm and Hbt proteins are identical. The hydropathic profile of Hbm and Hbt is highly similar to that of rice Hb1, suggesting that Hbm, Hbt and Hb1 have the same tertiary structure and biochemical properties. Expression analysis showed that low levels of Hb transcripts, but considerable levels of Hb proteins exist in maize embryonic organs. No Hb transcripts and proteins were detected in teosinte embryonic organs. Low levels of Hb proteins, but no Hb transcripts, were detected in maize and teosinte vegetative organs. These observations suggest that the regulation of hb genes is different in maize and teosinte embryonic organs, and that the expression of hb genes is down- or up-regulated in maize and teosinte, respectively, from germination to vegetative growing

Thermographic imaging: assessment of drought and heat tolerance in Spanish germplasm of Brachypodium distachyon.

The annual grass Brachypodium distachyon has been recently recognized as the model plant for functional genomics of temperate grasses, including cereals of economic relevance like wheat and barley. Sixty-two lines of B. distachyon were assessed for response to drought stress and heat tolerance. All these lines, except the reference genotype BD21, derive from specimens collected in 32 distinct locations of the Iberian Peninsula, covering a wide range of geo- climatic conditions. Sixteen lines of Brachypodium hybridum, an allotetraploid closely related to B. distachyon were used as reference of abiotic-stress well-adapted genotypes. Drought tolerance was assessed in a green-house trial. At the rosette-stage, no irrigation was applied to treated plants whereas their replicates at the control were maintained well watered during all the experiment. Thermographic images of treated and control plants were taken after 2 and 3 weeks of drought treatment, when stressed plants showed medium and extreme wilting symptoms. The mean leaf temperature of stressed (LTs) and control (LTc) plants was estimated based upon thermographic records from selected pixels (183 per image) that strictly correspond to leaf tissue. The response to drought was based on the analysis of two parameters: LTs and the thermal difference (TD) between stressed and control plants (LTs – LTc). The response to heat stress was based on LTc. Comparison of the mean values of these parameters showed that: 1) Genotypes better adapted to drought (B. hybridum lines) presented a higher LTs and TD than B. distachyon lines. 2) Under high temperature conditions, watered plants of B. hybridum lines maintained lower LTc than those of B. distachyon. Those results suggest that in these species adaptation to drought is linked to a more efficient stomata regulation: under water stress stomata are closed, increasing foliar temperature but also water use efficiency by reducing transpiration. With high temperature and water availability the results are less definite, but still seems that opening stomata allow plants to increase transpiration and therefore to diminish foliar temperature

Engagement y satisfacción laboral en trabajadores administrativos de una empresa minera de Lima – 2022

En la investigación se desarrolló como principal objetivo establecer en modo de correlación las variables Engagement y Satisfaccion Laboral en trabajadores administrativos de una empresa minera, Lima 2022. El presente estudio fue de tipo básico, correlacional, descriptivo, transversal y de diseño no experimental. La población estuvo conformada por 187 trabajadores administrativos, de la cual se obtuvo una muestra de 126 trabajadores mediante un muestreo no probabilístico, En este trabajo los instrumentos aplicados fueron UWES-17 y SL- SPC con el propósito calcular la relación entre Engagement y satisfaccion laboral respectivamente. Los principales resultados muestran que las variables Engagement y Satisfacción Laboral en trabajadores en una empresa de Lima tienen una relación significativa. Esto se corrobora debido a que la significancia (p- valor=0.000) es menor a 5%, también se observó que esta relación es directa debido a que el coeficiente de correlación de Spearman (Rho) resulto ser 0.475. Por lo tanto se concluyo que a mayor satisfacción laboral mayor nivel de Engagement, lo que quiere decir que mientras un trabajador mantenga una relación afectiva acorde a sus expectativas hacia su centro laboral mayor será la conexión emocional – cognitiva con las actividades de su labor capaz de enfrentar las demandas laborales

Resonant meta-surface superstrate for single and multifrequency dipole antenna arrays

The design of a multifrequency dipole antenna array based on a resonant meta-surface superstrate is proposed. The behavior of a single element that is closely placed to a meta-surface is experimentally investigated. The proposed meta-surface is based on resonating unit cells formed by capacitively loaded strips and split ring resonators. By tuning a dipole antenna to the pass band of the meta-surface, the physical area is effectively illuminated enhancing the radiation performance. The gain, radiation efficiency and effective area values of the whole configuration are compared to the ones obtained with a single dipole without superstrate. Radiation efficiency values for the proposed configuration of more than 80% and gain values of more than 4.5 1 dB are obtained. Based on this configuration, simulated results of a multifrequency antenna array are presented. Distinctive features of this configuration are high isolation between elements (20 dB for a distance of lambda0/4), and low back radiation

Use of thermographic imaging to screen for drought-tolerant genotypes in Brachypodium distachyon

Thermal imaging has been used to evaluate the response to drought and warm temperatures in a collection of Brachypodium distachyon lines adapted to varied environmental conditions. Thermographic records were able to separate lines from contrasting rainfall regimes. Genotypes from dryer environments showed warmer leaves under water deficit, which suggested that decreased evapotranspiration was related to a more intense stomatal closure. When irrigated and under high temperature conditions, drought-adapted lines showed cooler leaves than lines from wetter zones. The consistent, inverse thermographic response of lines to water stress and heat validates the reliability of this method to assess drought tolerance in this model cereal. It additionally supports the hypothesis that stomatal-based mechanisms are involved in natural variation for drought tolerance in Brachypodium. The study further suggests that these mechanisms are not constitutive but likely related to a more efficient closing response to avoid dehydration in adapted genotypes. Higher leaf temperature under water deficit seems a dependable criterion of drought tolerance, not only in B. distachyon but also in the main cereal crops and related grasses where thermography can facilitate high-throughput preliminary screening of tolerant materials