Un contaminante químico desde el principio hasta el final

Accésit 2021[ES] De manera general, al ingresar en la Universidad de León, los estudiantes del Grado de C.C. Ambientales se muestran desmotivados en las asignaturas de Química, puesto que muchos de ellos las consideran difíciles de entender y poco interesantes para su futuro laboral. Debido a este desinterés, los resultados académicos obtenidos en estas materias son pobres. Sin embargo, la Química subyace tras la totalidad de los fenómenos ambientales, por lo que su estudio es, a todas luces, necesario. Asimismo, se considera que las metodologías didácticas activas constituyen una de las herramientas más adecuadas para lograr mejores resulta-dos académicos. Por ello, se plantea desarrollar la experiencia docente titulada Un contaminante químico desde el principio hasta el final

Numerical evaluation of the Green's functions for arbitrarily shaped cylindrical enclosures and their optimization by a new spatial images method

IIn this paper, a spatial image technique is used to efficiently calculate the mixed potential Green’s functions associated with electric sources, when they are placed inside arbitrarily shaped cylindrical cavities. The technique is based on placing electric dipole images and charges outside the cavity region. Their strength and orientation are thencalculated by imposing the appropriate boundary conditions for the fields at discrete points on the metallic wall. A method for the assessment of the potentials accuracy is proposed, and several optimization techniques are presented. Three cavities are analyzed to demonstrate the usefulness of the techniques. The cutoff frequencies and potentials patterns are compared to those obtained by a standard finite elements technique, showing excellent agreement. Finally, a band-pass filter based on coupled lines is analyzed, demonstrating the practical value of the technique.This work has been developed with support from the Spanish National Project (CICYT) with reference TEC2004-04313-C02-02/TCM, and the Regional Seneca Project with reference 02972/PI/0

Speciation of organoarsenicals in aqueous solutions by Raman spectrometry and quantum chemical calculations

.Knowledge about the existence and stability of different species of organoarsenicals in solution is of the most significant interest for fields so different as chemical, environmental, biological, toxicological and forensic. This work provides a comparative evaluation of the Raman spectra of four organoarsenicals (o-arsanilic acid, p-arsanilic acid, roxarsone and cacodylic acid) in aqueous solutions under acidic, neutral and alkaline conditions. Speciation of some of these organoarsenicals is possible by Raman spectrometry at different selected pHs. Further, we examine the proficiency of computational chemistry to obtain the theoretical Raman spectra of the four organoarsenicals compounds. To this end, we employ a computational protocol that includes explicit water molecules and conformational sampling, finding that the calculated organoarsenicals spectra agree reasonably well with those experimentally obtained in an aqueous solution in the whole pH range covered. Finally, we highlight the effectiveness of quantum chemical calculations to identify organoarsenicals in an aqueous solution.S

El Aprendizaje Basado en Problemas como herramienta para el estudio de los fenómenos geológicos

Para suscitar interés y motivar al alumnado de 4º de ESO de la materia de Biología y Geología, se ha diseñado una experiencia de enseñanza-aprendizaje fundamentada en una metodología de Aprendizaje Basado en Problemas (ABP). En este ABP se estudian las relaciones que existen, de manera no siempre evidente, entre los fenómenos geológicos y sus consecuencias biológicas, así como los procesos de causa-efecto presentes en la naturaleza. De este modo, se pretende mejorar el pensamiento crítico y abstracto de los estudiantes. La evaluación de esta buena práctica se ha realizado mediante una matriz de rúbrica, elaborada por el profesor y entregada previamente a los alumnos. Además, se ha incluido un cuestionario de evaluación de la actividad por parte de los estudiantes, resultando muy bien valorada por los mismos

New models involving quantum chemical parameters for assessing the chromatographic retention process

.Knowledge about the theoretical relationship between the analyte properties and the critical chromatographic parameters is mandatory for a better interpretation of the separation mechanism and a more leisurely development of quantitative studies. In a preliminary stage of this work, we introduce the Gumbel distribution, the extreme value distribution type-I widely used in other fields, as a novel tool for modelling the chromatographic peak shape. Further, we develop mathematical models to evaluate the effect of the experimental variables and various quantum parameters on the chromatographic indices, such as the retention time, capacity factor, asymmetry factor, tailing factor and number of theoretical plates. Finally, we propose a mechanistic behaviour for the chromatographic separation process based on the structure-retention relationship of fifteen selected drugs involving several molecular quantum parametersS

Fast and efficient calculation of the multilayered shielded green's functions employing neural networks

In this paper, neural networks are used to efficiently calculate the multilayered media boxed Green’s functions needed in integral equation (IE) formulations. The analysis of complex multilayered shielded circuits is computationally time consuming, due to the need to calculate the multilayered-media boxed Green’s functions. Using neural networks as radial basis function networks, the boxed Green’s functions can be calculated quickly, thus greatly reducing the computational time associated with the analysis of practical circuits. Once the neural network is trained with a known set of pairs of inputs and outputs, new outputs are quickly calculated, thus increasing the efficiency of the IE method

Analysis of Thick Wire Antennas Using a Novel and Simple Kernel Treatment

This paper presents novel aspects concerning the analysis of thick-wire antennas. The analysis is carried out using an integral equation (IE) technique, in which the kernel is treated with a novel numerical-integration procedure. A comparison with other techniques are included, showing the advantages of the newly proposed method. The novel treatment of the kernel requires the efficient extraction of the singularities. For this purpose, two different techniques are presented, and their advantages and drawbacks are discussed. Using the procedure proposed, complex thick wire antennas with rotational symmetry are analyzed. A combined antenna composed of cylindrical and conical sections is studied. The results show that the new techniques derived are efficient and lead to accurate results

Novel implementation of transversal filters in multilayered microstrip technology

This paper presents novel and compact implementations of bandpass filters using transversal topologies. The structures presented implement diferent transfer functions of order three in multilayered microstrip technology. In order to allow for easy implementation of the required coupling, multilayered broadside configurations are proposed. We demonstrate that with the proposed configurations, both dualband and quasi-elliptic responses can be easily synthesized, by only changing the sign of certain entries in the coupling matrix. To easily adjust the sign of the coupling, novel resonators are proposed, including simple half-wavelength transmission line resonators, meander line resonators and shortcircuited resonators. Experimental validations for both prototypes are presented, demonstrating the validity and usefulness of the proposed con gurations.The authors thank Ministerio de Educacion y Ciencia of Spain, which has supported this work with the Project TEC2007-67630-C03/TCM

A neural-network method for the analysis of multilayered shielded microwave circuits

In this paper, a neural-network-based method for the analysis of practical multilayered shielded microwave circuits is presented. Using this idea, a radial basis function neural network (RBFNN) is trained to approximate the space-domain multilayered media boxed Green’s functions used in the integral-equation (IE) method. Once the RBFNN has been trained, the outputs of the neural network (NN) replace the exact Green’s functions, during the numerical solution of the IE. The computation of the RBFNN output values is very fast in comparison with the numerical methods used to calculate the exact Green’s functions. This paper describes two novel strategies for efficiently training the RBFNN. In the first strategy, the input space of the RBFNN is divided into several spatial and frequency regions. The spatial subdivision is extended for the first time to both observation and source regions. In addition, the subdivision of the observation points regions is applied in a novel manner to the whole cross section of the metallic box. The second strategy combines the above region subdivision with an adaptive selection of the neurons variances in each region. The accuracy and the computational gain achieved with the NN method proposed makes possible the implementation of computer-aided-design tools that can be used for the analysis and design of integrated shielded microwave circuits (e.g., monolithic microwave integrated circuit devices) on a real-time basis

Estudio bibliométrico de la presencia de plomo en el medio ambiente

[ES] El plomo es un metal pesado altamente tóxico que puede producir gran cantidad de efectos adversos sobre la salud humana y el medio ambiente, dependiendo de la concentración en la que se encuentre. Los objetivos de este trabajo son: realizar estudios bibliométricos referidos a compartimentos ambientales en los que se encuentra el plomo, fuentes antropogénicas de emisión, métodos de análisis y determinación y métodos de eliminación, y determinar cuál es la base de datos que aporta un mayor número de publicaciones a los estudios realizados. Los compartimentos ambientales en los que se ha estudiado mayormente el plomo son el agua y el suelo; la fuente de emisión antropogénica más común es la minería; el método de análisis y determinación más estudiado la Espectrometría de Masas con fuente de Plasma de Acoplamiento Inductivo (ICP-MS) y el método de eliminación más empleado es el de adsorción. Se observó que la plataforma WOS aporta un mayor número de publicaciones que Scopus en los estudios realizados