Un estudio del uso de modelos moleculares en la didáctica del enlace covalente en bachillerato

Algunos de los conceptos complejos trabajados desde las asignaturas de ciencias requieren un alto nivel de abstracción para su comprensión, lo que supone una dificultad para su aprendizaje. El empleo de imágenes y modelos en 3-Dimensiones puede ser una herramienta útil para mejorar el proceso de aprendizaje de estos conceptos. En este estudio analizamos el efecto del uso de modelos moleculares en el aprendizaje del enlace covalente con alumnos de bachillerato. Se ha observado que las calificaciones obtenidas por los alumnos no se corresponden con el grado de comprensión de los conceptos, dándose el caso de que estudiantes con altas calificaciones tienen dificultades a la hora de emplear la teoría de enlace de valencia (TEV) para relacionar hibridación de orbitales atómicos con forma de las moléculas. Así mismo se ha demostrado que, tras las sesiones con modelos moleculares, los estudiantes han mejorado su capacidad de realizar representaciones geométricas de diferentes moléculas, lo que sugiere que, en el contexto analizado, el empleo de este tipo de herramienta docente en la didáctica del enlace covalente repercute positivamente en el aprendizaje

Controlling eutrophication by means of water recirculation: an optimal control perspective

In this work, the artificial recirculation of water is presented and analyzed, from the perspective of the optimal control of partial differential equations, as a tool to prevent eutrophication effects in large waterbodies. A novel formulation of the environmental problem, based on the coupling of nonlinear models for hydrodynamics, water temperature and concentrations of the different species involved in the eutrophication processes, is introduced. After a complete and rigorous analysis of the existence of optimal solutions, a full numerical algorithm for their computation is proposed. Finally, some numerical results for a realistic scenario are shown, in order to prove the efficiency of our approach.Xunta de Galicia | Ref. ED431C 2019/02Agencia Estatal de Investigación | Ref. MTM2016-75140-

A study of the use of molecular models in the teaching of covalent-bond in high school

Esther Cascarosa Salillas. Universidad de ZaragozaFrancisco J. Fernández-Álvarez. Universidad de ZaragozaFrancisco J. Santiago. IES Pablo Serrano, ZaragozaRecepción: 22.06.2018 | Aceptado: 15.09.2018Correspondencia a través de ORCID: Esther Cascarosa - 0000-0002-3696-7673Algunos de los conceptos complejos trabajados desde las asignaturas de ciencias requieren un alto nivel de abstracción para su comprensión, lo que supone una dificultad para su aprendizaje. El empleo de imágenes y modelos en 3-Dimensiones puede ser una herramienta útil para mejorar el proceso de aprendizaje de estos conceptos. En este estudio analizamos el efecto del uso de modelos moleculares en el aprendizaje del enlace covalente con alumnos de bachillerato. Se ha observado que las calificaciones obtenidas por los alumnos no se corresponden con el grado de comprensión de los conceptos, dándose el caso de que estudiantes con altas calificaciones tienen dificultades a la hora de emplear la teoría de enlace de valencia (TEV) para relacionar hibridación de orbitales atómicos con forma de las moléculas. Así mismo se ha demostrado que, tras las sesiones con modelos moleculares, los estudiantes han mejorado su capacidad de realizar representaciones geométricas de diferentes moléculas, lo que sugiere que, en el contexto analizado, el empleo de este tipo de herramienta docente en la didáctica del enlace covalente repercute positivamente en el aprendizaje.Abstract: Science subjects contain complex and abstract concepts. Thus, the use of certain tools such as images or 3-D models could be useful and motivating tools to improve the teaching learning process. For this reason, this study is therefore aimed at analysing student’s understanding of covalent-bond concepts after the management of molecular models to improve the understanding of the same. Student’s showed great results but these were not related to a proper understanding of them but to the fact of using molecular models since students improved their geometric abilities to represent molecules. As a result, students proved the effectiveness of these aforementioned models in the teaching of the covalent-bond, in the analysed context.Universidad de Granada. Departamento de Psicología Social. Proyecto de Innovación Docente ReiDoCre

Un estudio del uso de modelos moleculares en la didáctica del enlace covalente en bachillerato.

Algunos de los conceptos complejos trabajados desde las asignaturas de ciencias requieren un alto nivel de abstracción para su comprensión, lo que supone una dificultad para su aprendizaje. El empleo de imágenes y modelos en 3 - Dimensiones puede ser una herramienta útil para mejorar el proceso de aprendizaje de estos conceptos. En este estudio analizamos el efecto del uso de modelo s moleculares en el aprendizaje del enlace covalente con alumnos de bachillerato. Se ha observado que las calificaciones obtenidas por los alumnos no se corresponden con el grado de comprensión de los conceptos, dándose el caso de que estudiantes con altas calificaciones tienen dificultades a la hora de emplear la teoría de enlace de valencia (TEV) para relacionar hibridación de orbitales atómicos con forma de las moléculas. Así mismo se ha demostrado que, tras las sesiones con modelos moleculares, los estu diantes han mejorado su capacidad de realizar representaciones geométricas de diferentes moléculas, lo que sugiere que, en el contexto analizado, el empleo de este tipo de herramienta docente en la didáctica del enlace covalente repercute positivamente en el aprendizaje. Science subjects contain complex and abstract concepts. Thus, the use of certain tools such as images or 3-D models could be useful and motivating tools to improve the teaching learning process. For this reason, this study is therefore aimed at analysing students understanding of covalent-bond concepts after the management of molecular models to improve the understanding of the same. Student's showed great results but these were not related to a proper understanding of them but to the fact of using molecular models since students improved their geometric abilities to represent molecules. As a result, students proved the effectiveness of these aforementioned models in the teaching of the covalent-bond, in the analysed context

On Estimating the Headcount Index by Using the Logistic Regression Estimator

The problem of estimating a proportion has important applications in the field of economics, and in general, in many areas such as social sciences. A common application in economics is the estimation of the headcount index. In this paper, we define the general headcount index as a proportion. Furthermore, we introduce a new quantitative method for estimating the headcount index. In particular, we suggest to use the logistic regression estimator for the problem of estimating the headcount index. Assuming a real data set, results derived from Monte Carlo simulation studies indicate that the logistic regression estimator can be more accurate than the traditional estimator of the headcount index

An alternative mechanistic paradigm for the β-Z hydrosilylation of terminal alkynes: The role of acetone as a silane shuttle

The β-Z selectivity in the hydrosilylation of terminal alkynes has been hitherto explained by introduction of isomerisation steps in classical mechanisms. DFT calculations and experimental observations on the system [M(I)2{κ-C,C,O,O-(bis-NHC)}]BF4 (M=Ir (3 a), Rh (3 b); bis-NHC=methylenebis(N-2-methoxyethyl)imidazole-2-ylidene) support a new mechanism, alternative to classical postulations, based on an outer-sphere model. Heterolytic splitting of the silane molecule by the metal centre and acetone (solvent) affords a metal hydride and the oxocarbenium ion [R 3Si - O(CH3)2]+, which reacts with the corresponding alkyne in solution to give the silylation product [R 3Si - CHï£C - R]+. Thus, acetone acts as a silane shuttle by transferring the silyl moiety from the silane to the alkyne. Finally, nucleophilic attack of the hydrido ligand over [R3Si - CHï£C - R]+ affords selectively the β-(Z)- vinylsilane. The β-Z selectivity is explained on the grounds of the steric interaction between the silyl moiety and the ligand system resulting from the geometry of the approach that leads to β-(E)-vinylsilanes. Silanes catch the shuttle: An outer-sphere mechanism that explains the β-Z hydrosilylation of terminal alkynes based on the role of acetone as a silane shuttle is disclosed. Heterolytic splitting of the silane molecule by the metal centre and acetone affords a metal hydride and the oxocarbenium ion [R 3Si - O(CH3)2]+, which reacts with the alkyne in solution to give the silylation product [R3Si - CHï£C - R]+ (see figure). © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.This work was supported by the Spanish Ministry of Economy and Competitiveness (MINECO/FEDER) (CONSOLIDER INGENIO-2010, CTQ2011-27593 projects, and “Ramón y Cajal” (P.J.S.M.) and “Juan de la Cierva” (M.I.) programmes) and the DGA/FSE (E07).Peer Reviewe

Analysis of the Genetic Parameters for Dairy Linear Appraisal and Zoometric Traits: A Tool to Enhance the Applicability of Murciano-Granadina Goats Major Areas Evaluation System

Selection for zoometrics defines individuals’ productive longevity, endurance, enhanced productive abilities and consequently, their long-term profitability. When zoometric analysis is aimed at large highly selected populations or in those at different levels of selection, linear appraisal systems (LAS) provide a timely response. This study estimates genetic and phenotypic parameters for zoometric/LAS traits in Murciano-Granadina goats, estimating genetic and phenotypic correlations among all traits, and determining whether major area selection would be appropriate or if adaptability strategies may need to be followed. Heritability estimates for the zoometric/LAS traits were low to high, ranging from 0.09 to 0.43, and the accuracy of estimation has improved after decades, rendering standard errors negligible. Scale inversion of specific traits may need to be performed before major areas selection strategies are implemented. Genetic and phenotypic correlations suggests that negative selection against thicker bones and higher rear insertion heights indirectly results in the optimization of selection practices in the rest of the traits, especially those in the structure, capacity and mammary system major areas. The integration and implementation of the strategies proposed within the Murciano-Granadina breeding program maximizes selection opportunities and the sustainable international competitiveness of the Murciano-Granadina goat in the dairy goat breed panorama

Optimization and Validation of a Linear Appraisal Scoring System for Milk Production-Linked Zoometric Traits in Murciano-Granadina Dairy Goats and Bucks

Implementing linear appraisal systems (LAS) may reduce time, personnel and resource costs when performing large-scale zoometric collection. However, optimizing complex zoometric variable panels and validating the resulting reduced outputs may still be necessary. The lack of cross-validation may result in the loss of accuracy and value of the practices implemented. Special attention should be paid when zoometric panels are connected to economically-relevant traits such as dairy performance. This methodological proposal aims to optimize and validate LAS in opposition to the traditional measuring protocols routinely implemented in Murciano-Granadina goats. The sample comprises 41,323 LAS and traditional measuring records from 22,727 herdbook-registered primipara does, 17,111 multipara does and 1485 bucks. Each record includes information on 17 linear traits for primipara/multipara does and 10 traits for bucks. All zoometric parameters are scored on a nine-point scale. Cronbach’s alpha values suggest a high internal consistency of the optimized variable panels. Model fit, variability explanation power and predictive power (mean square error (MSE), Akaike (AIC)/corrected Akaike (AICc) and Bayesian information criteria (BIC), respectively) suggest the model comprising zoometric LAS scores performs better than traditional zoometry. Optimized reduced models are able to capture variability for dairy-related zoometric traits without noticeable detrimental effects on model validity properties