Critical issues in the determination of the bentonite cation exchange capacity

The swelling pressure and transport properties of bentonites are controlled by the electric charge density of solid particles, which is commonly estimated from the laboratory measurement of the cation exchange capacity (CEC). However, the standard ammonium displacement method for CEC determination does not take into account the fabric changes that occur in bentonites under exposure to high salt concentration solutions. A series of laboratory tests was conducted to assess the relevance of such a critical issue, by varying the concentration of the extracting KCl solution with respect to that of the standard test. The obtained results show that the release of the adsorbed ammonium cations depends on the bentonite fabric, which is controlled by the KCl concentration. As a consequence, the ammonium displacement method may provide an unrepresentative estimate of the CEC of bentonites. The methylene blue titration method, despite its apparently more limited accuracy, instead seems to provide a more reliable estimation of the CEC, as the bentonite fabric is maintained dispersed during the test

Implementation and Assessment Methodologies of Teachers' Training Courses for STEM Activities

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Modalidades de cursado virtual en la universidad y rendimiento académico de los alumnos

El presente trabajo tiene como principal objetivo analizar la relación entre las modalidades de estudio virtual, la participación de los estudiantes en la Plataforma Tecnológica en una universidad privada argentina y el rendimiento académico de los mismos en las distintas evaluaciones previstas para la obtención de la regularidad o la promoción durante el cursado de diversas carreras. Este análisis se ha hecho en el marco de un proyecto inscripto en la Red Ilumno (Gómez, 2014). La pregunta principal pretende abordar los trayectos de aprendizaje que hacen los alumnos en la utilización de los objetos de aprendizaje como lecturas, videos, autoevaluaciones, chat, foros, wikis, trabajos prácticos; dispuestos en las plataformas virtuales. Los objetivos generales que orientan el trabajo son describir y analizar las características de los trayectos que los estudiantes desarrollan en la plataforma tecnológica y la relación entre los distintos perfiles de recorrido y el rendimiento académico que presentan los alumnos. Para ello se tiene previsto la administración de encuestas, entrevistas y seguimiento de los intercambios virtuales en la Plataforma, trabajo complementario del análisis que se presenta en esta ocasión. Entonces el objetivo de lo transmitido en esta ponencia se orienta a establecer relaciones entre los usos de los recursos dispuestos en la Plataforma Tecnológica y el rendimiento académico de los estudiantes e indagar si existe una diferencia en dicho rendimiento, según calificaciones alcanzadas en las instancias evaluativas, en relación a las modalidades de cursado e-learning y b- learning. El enfoque de investigación ha sido cuantitativo tomando los datos desde las cifras arrojadas por la Plataforma Tecnológica. En líneas generales ha quedado demostrado que los estudiantes que cursan en b-learning, la cual es una modalidad combinada, alcanzan mejores calificaciones y obtienen en mayor número la promoción de las asignaturas que quienes cursan en una modalidad totalmente virtual como es la e-learning. Por otra parte, son recursos más significativos en función de las evaluaciones, las lecturas y las autoevaluaciones de lecturas tanto para la realización de los trabajos prácticos como las evaluaciones parciales. Tienen menores impactos los foros, videos y autoevaluaciones de videos. Los trabajos prácticos impactan en el nivel de rendimiento de las evaluaciones parciales.Eje: Tecnología en EducaciónRed de Universidades con Carreras en Informática (RedUNCI

Motives to use Facebook and problematic Facebook use in adolescents

Background and aims There is a growing body of evidence suggesting that problematic Facebook use (PFU) is an emerging problem, particularly among adolescents. Although a number of motivations explaining why people engage in frequent Facebook use have been identified, less is known about the specific psychological needs underlying PFU. The aim of this study is to test a model designed to assess the unique contribution of psychological motives for using Facebook to the different PFU dimensions in a sample of adolescents. Methods A total of 864 Italian adolescents participated in the study. Multivariate multiple regression was run to test whether the four motives were differently associated with problematic dimensions. Results The results showed that the two motives with negative valence (coping and conformity) were significantly linked to the five dimensions of PFU, whereas the two motives with positive valence (enhancement and social) appeared to be weaker predictors for three out of these five dimensions. Discussion and conclusion In conclusion, psychological motives for using Facebook appeared to significantly contribute to explaining PFU among adolescents, and should be considered by researchers and educational practitioners

Motives to use Facebook and problematic Facebook use in adolescents

Background and aims There is a growing body of evidence suggesting that problematic Facebook use (PFU) is an emerging problem, particularly among adolescents. Although a number of motivations explaining why people engage in frequent Facebook use have been identified, less is known about the specific psychological needs underlying PFU. The aim of this study is to test a model designed to assess the unique contribution of psychological motives for using Facebook to the different PFU dimensions in a sample of adolescents. Methods A total of 864 Italian adolescents participated in the study. Multivariate multiple regression was run to test whether the four motives were differently associated with problematic dimensions. Results The results showed that the two motives with negative valence (coping and conformity) were significantly linked to the five dimensions of PFU, whereas the two motives with positive valence (enhancement and social) appeared to be weaker predictors for three out of these five dimensions. Discussion and conclusion In conclusion, psychological motives for using Facebook appeared to significantly contribute to explaining PFU among adolescents, and should be considered by researchers and educational practitioners

Exploring hypotheses of the actions of TGF-beta 1 in epidermal wound healing using a 3D computational multiscale model of the human epidermis

In vivo and in vitro studies give a paradoxical picture of the actions of the key regulatory factor TGF-beta 1 in epidermal wound healing with it stimulating migration of keratinocytes but also inhibiting their proliferation. To try to reconcile these into an easily visualized 3D model of wound healing amenable for experimentation by cell biologists, a multiscale model of the formation of a 3D skin epithelium was established with TGF-beta 1 literature-derived rule sets and equations embedded within it. At the cellular level, an agent-based bottom-up model that focuses on individual interacting units ( keratinocytes) was used. This was based on literature-derived rules governing keratinocyte behavior and keratinocyte/ECM interactions. The selection of these rule sets is described in detail in this paper. The agent-based model was then linked with a subcellular model of TGF-beta 1 production and its action on keratinocytes simulated with a complex pathway simulator. This multiscale model can be run at a cellular level only or at a combined cellular/subcellular level. It was then initially challenged ( by wounding) to investigate the behavior of keratinocytes in wound healing at the cellular level. To investigate the possible actions of TGF-beta 1, several hypotheses were then explored by deliberately manipulating some of these rule sets at subcellular levels. This exercise readily eliminated some hypotheses and identified a sequence of spatial-temporal actions of TGF-beta 1 for normal successful wound healing in an easy-to-follow 3D model. We suggest this multiscale model offers a valuable, easy-to-visualize aid to our understanding of the actions of this key regulator in wound healing, and provides a model that can now be used to explore pathologies of wound healing