This study describes and analyzes the design, development, application and evaluation of a new pe... more This study describes and analyzes the design, development, application and evaluation of a new pedagogical methodology based on interactive games for mobile devices (PDAs). The methodology is oriented to developing problem-solving skills in science classes for 8 th graders, by including pre-classroom activities with the teacher, classroom activities, and a central activity using an interactive game for a mobile device. The core problem they had to solve through the game consisted in preserving and evolving different biological species from the animal kingdom, in an unknown and varying environment, by modifying some key factors for evolution of the species. The study was implemented in two main stages: a guided visit to a zoo observing animals directly, and a simulation game that takes place in the school during four weeks. Results show highly motivated learners with a fast adoption of mobile devices, fully engaged in a learning task without external control.
The aim of the present thesis was to better understand the physiological role of the phytohormone... more The aim of the present thesis was to better understand the physiological role of the phytohormones jasmonates (JAs) and abscisic acid (ABA) during fruit ripening in prospect of a possible field application of JAs and ABA to improve fruit yield and quality. In particular, the effects of exogenous application of these substances at different fruit developmental stages and under different experimental conditions were evaluated. Some aspects of the water relations upon ABA treatment were also analysed. Three fruit species, peach (Prunus persica L. Batsch), golden (Actinidia chinensis) and green kiwifruit (Actinidia deliciosa), and several of their cvs, were used for the trials. Different experimental models were adopted: fruits in planta, detached fruit, detached branches with fruit, girdled branches and micropropagated plants. The work was structured into four sets of experiments as follows: (i) Pre-harvest methyl jasmonate (MJ) application was performed at S3/S4 transition under field...
It is argued that today is an information driven society. Being able to engage digital informatio... more It is argued that today is an information driven society. Being able to engage digital information abilities to solve an information interaction activity within digital environments is key for social participation, equality and for bridging socio-economic and cultural gaps. Developing these abilities within school classrooms has become a priority. However, research suggest that a majority of students can only complete basic and explicit information-gathering and management tasks within digital environments. Literature constantly holds that students’ expressed experiences of information interaction activities are key for developing digital information abilities. Notwithstanding, there are still important gaps within our understanding of students’ expressed experiences of them. To address such gaps we employ phenomenography to study Chile’s Secondary Technical and Vocational Education and Training students’ expressed experiences of information interaction abilities; a group that has likewise been overlooked. By means of purposeful sampling, a total of 24 students participated in the study. Focusing on both the out-of and in-school settings, findings suggest that the apparent clear-cut division between the out-of and in-school experiencing seems not to be as pristine as some might suggest. Findings also indicate that specialty courses, as they are currently designed, might not be favorable for developing digital information abilities as well as pointing towards the importance of situating students’ expressed experiences within wider discourses surrounding digital ability development.
Emotions and reflection are critical in teachers’ work. Still, there is no agreement in how these... more Emotions and reflection are critical in teachers’ work. Still, there is no agreement in how these elements connect in assessing past experiences to redesign teaching practices. In this qualitative study, we interviewed six (n = 6) Chilean preservice teachers four times each to analyse what they learn about becoming an educator by reflecting upon four emotions (anger, sadness, pride, and enjoyment). We found that teachers post-hoc reflection upon such emotions provides candidates with information to develop a sense of positional adjustment to overcome emergent difficulties at schools, reach a delimitation between the private and working world, identify teaching enhancement opportunities, and plan the incorporation of strategies in future actions. We also propose a model that coordinates suppressive and generative candidates’ responses after reflecting upon their emotions. In addition, candidates perceive themselves to be unequipped to deal with their own and external emotions effectively. We suggest that emotional training should be considered as an explicit component of teacher education in Latin America. (co-authored with Alvaro Salinas)
Este artículo busca responder a las preguntas por cuán reflexivos son los estudiantes de pedagogí... more Este artículo busca responder a las preguntas por cuán reflexivos son los estudiantes de pedagogía al finalizar su formación de pregrado y qué oportunidades ofrecen los documentos que ellos deben elaborar durante su práctica profesional final, para desarrollar esta reflexión docente. Se aplicaron dos rúbricas a 50 documentos elaborados por estudiantes de seis programas de formación de profesores en Chile. Los resultados muestran que el foco de la reflexión en los documentos analizados se concentra en sólo algunas dimensiones y deja fuera otras que son importantes, tales como la reflexión sobre los propios aprendizajes de los estudiantes. Asimismo, los resultados del análisis muestran, en general, una baja reflexión docente, y diferencias entre los programas analizados. Estas diferencias se relacionarían con la especificidad y orientación que se plantea a los estudiantes sobre lo que se espera de ellos en cada sección del documento elaborado. This article seeks to determine how reflexive students of pedagogy are upon completing their undergraduate training, and what opportunities are offered by the documents they must prepare during their final professional practice, to develop this teaching reflection. Two rubrics were applied to 50 documents prepared by students in six teachers' training programs in Chile. The results show that the reflective approach of the documents analyzed concentrates only on some dimensions, and leaves out other important ones, such as reflection on the students' own lessons learned. Furthermore, the results of the analysis show, in general, a low level of reflective teaching, and differences between the programs analyzed. These differences were related to the specific and orientation students express regarding what is expected of them in each section of the prepared document.
Magis, Revista Internacional de Investigación en Educación
Este artículo describe la frecuencia con la cual estudiantes de pedagogía realizan prácticas refl... more Este artículo describe la frecuencia con la cual estudiantes de pedagogía realizan prácticas reflexivas, y analiza factores que pueden explicar esta frecuencia. Para ello se empleó una perspectiva cuantitativa que incluyó una encuesta a una muestra de 650 estudiantes de 134 programas de formación de profesores en Chile. Los resultados muestran que los factores más importantes para explicar la práctica reflexiva se relacionan con el supervisor. Los factores relacionados con los compañeros de estudio y con la discusión sobre la profesión docente contribuyen menos a la práctica reflexiva.
RESUMEN La práctica reflexiva ha recibido un creciente interés de parte de la investigación y de ... more RESUMEN La práctica reflexiva ha recibido un creciente interés de parte de la investigación y de la formación docente a nivel internacional. Sin embargo, hay poco acuerdo sobre qué es y cómo medirla. Este artículo se propone validar un instrumento cuantitativo en español, para medir la práctica reflexiva en estudiantes de pedagogía. Para ello se aplicó la traducción de la escala de reflexividad elaborada por Larrivee, a una muestra probabilística de 489 estudiantes de pedagogía en Chile. El análisis de datos incluyó análisis factorial exploratorio y confirmatorio y el cálculo de la confiabilidad de la escala. La escala resultante está compuesta por 20 ítems agrupados en tres dimensiones distintas (reflexión superficial, pedagógica y crítica), con buenos indicadores de confiabilidad. El trabajo contribuye a definir operacionalmente el concepto de práctica reflexiva y ofrece la posibilidad de medir el constructo. Al finalizar, se discuten limitaciones y proyecciones de este trabajo. Palabras clave: formación de profesores, reflexión, validación de escala, práctica reflexiva.
Abstract The study presented in this paper consisted in defining a Teaching in a Digital Environm... more Abstract The study presented in this paper consisted in defining a Teaching in a Digital Environment (TIDE) capacity construct and developing a performance-based test to measure Chilean teachers' ability to teach students how to solve information and communication tasks in a digital environment. The test was applied to a sample of 828 in-service teachers in Chile, together with a characterization questionnaire. Results showed that very few Chilean teachers mastered all the tasks and that only one third were able to provide students with orientations in solving information and communication tasks, revealing that the majority are not playing a mediation role in a digital environment. In relation to explaining variables, science and younger teachers with more years of teaching experience performed better in the test. Nevertheless the low explanation provided by the variables included suggests that variables that have previously accounted for teachers ICT integration are not as good in predicting TIDE capacity. This shows the relevance of developing mixed methods research that together with quantitative data provides qualitative data to help explain this capacity in greater depth.
The microstructure of low-alloy multiphase transformation-induced plasticity (TRIP) steels consis... more The microstructure of low-alloy multiphase transformation-induced plasticity (TRIP) steels consists of ferrite, bainite, and metastable retained austenite, which can be transformed into martensite by plastic deformation. In some cases, residual martensite can be present in the initial microstructure. The mechanical behavior of these steels depends on the interaction between the intrinsic characteristics of the existing phases and the austenite stability. Due to these factors, the definition of their true stress-strain flow law is complex. This work presents the mechanical characterization of a phenomenological constitutive stress-strain flow law based on the Bouquerel et al. model, as evaluated for three TRIP steels of the same composition but undergoing different heat treatments. Morphological aspects of the existing phases, austenite stability, and suitable mixture laws between phases are considered. The model is found to accurately reproduce a true stress-strain flow law obtained...
Magis, Revista Internacional de Investigación en Educación, 2019
Este artículo describe la frecuencia con la cual estudiantes de pedagogía realizan prácticas refl... more Este artículo describe la frecuencia con la cual estudiantes de pedagogía realizan prácticas reflexivas, y analiza factores que pueden explicar esta frecuencia. Para ello se empleó una perspectiva cuantitativa que incluyó una encuesta a una muestra de 650 estudiantes de 134 programas de formación de profesores en Chile. Los resultados muestran que los factores más importantes para explicar la práctica reflexiva se relacionan con el supervisor. Los factores relacionados con los compañeros de estudio y con la discusión sobre la profesión docente contribuyen menos a la práctica reflexiva.
Revista Perspectivas: Notas sobre intervención y acción social
En este texto se presenta una mirada a la educación y al sistema escolar desde la diversidad y la... more En este texto se presenta una mirada a la educación y al sistema escolar desde la diversidad y la singularidad de las experiencias de los jóvenes, a partir de algunas conclusiones extraídas de una investigación llevada a cabo por el CIDE en los años 94 y 95, sobre "Las Prácticas Culturales de los Jóvenes Secundarios". La metodología de investigación consistió básicamente en la realización de entrevistas en profundidad y en el desarrollo de una encuesta masiva. ¿Cuáles son las interpelaciones que surgen de las experiencias y de la subjetividad de los jóvenes hacia la escuela, en particular en términos de equidad del sistema y de relevancia de los modelos culturales escolares? ¿Cuáles son las pistas que permiten una redefinicióin de las tareas, estructuras y modelos de la escuela en relación al sistema social y cultural y a las aspiraciones de los sujetos? El artículo que presentamos a continuacion pretende contribuir a la dilucidación de estas y otras interrogantes respecto...
The effect that the microstructure exerts on the Transformation-Induced Plasticity (TRIP) phenome... more The effect that the microstructure exerts on the Transformation-Induced Plasticity (TRIP) phenomenon and on the mechanical properties in a multiphase steel was studied. Samples of an initially cold-rolled ferrite-pearlite steel underwent different intercritical annealing treatments at 750 • C until equal fractions of austenite/ferrite were reached; the intercritical treatment was followed by isothermal bainitic treatments before cooling the samples to room temperature. Samples in the first treatment were heated directly to the intercritical temperature, whereas other samples were heated to either 900 • C or 1100 • C to obtain a fully homogenized, single-phase austenitic microstructure before performing the intercritical treatment. The high-temperature homogenization of austenite resulted in a decrease in its stability, so a considerable austenite fraction transformed into martensite by cooling to room temperature after the bainitic heat treatment. Most of the retained austenite transformed during the tensile tests, and, consequently, the previously homogenized steels showed the highest Ultimate Tensile Strength (UTS). In turn, the steel with a ferritic-pearlitic initial microstructure exhibited higher ductility than the other steels and texture components that favor forming processes.
This study describes the level of adoption of information and communication technologies in teach... more This study describes the level of adoption of information and communication technologies in teaching in three Latin American countries. It also analyzes factors that affect the process by which teachers incorporate these technologies into their classrooms. In order to do so, an online survey was conducted with 89 teachers. The results show that most of the teachers rated themselves at the highest levels of technology adoption. However, the analysis reveals differences between countries associated with individual-type factors, such as the perception of ICT’s contribution to teaching and learning, and the training and knowledge teachers have in this realm. By contrast, the professional culture was not correlated to these differences, and the various actors with which teachers interact, such as the education ministry and school administration, displayed a non-linear relationship with technology adoption. This suggests the need for a better understanding of the complex relationship between the culture, the various actors involved, and the degree to which teachers adopt technology in education.
Resumo: Los indicadores de maduración esquelética han sido utilizados con el fin de aproximarse a... more Resumo: Los indicadores de maduración esquelética han sido utilizados con el fin de aproximarse al momento en que puede presentarse el inicio del acelere del crecimiento prepuberal en el niño y de esta forma aprovechar ese potencial de crecimiento en el ...
La confesion es una declaracion de voluntad hecha por una persona, que puede serle desfavorable, ... more La confesion es una declaracion de voluntad hecha por una persona, que puede serle desfavorable, total o parcialmente, debe ser declaracion de parte, personal, tener por objeto hechos personales del confesante, favorables a la parte contraria, con signifi cacion probatoria, voluntaria, expresa y terminante, seria, con capacidad juridica del confesante y no como resultado de metodos violentos o artificiales. En Derecho Tributario esta determinada por los Articulos 747, 748 y 749 del Estatuto Tributario. Los Articulos 29 y 33 de la Constitucion consagran los derechos a la presuncion de inocencia y a la no autoincriminacion. Tales derechos deben operar en materia tributaria. Asi mismo el de in dubio pro reo se extiende a toda disciplina sancionadora. El debido proceso administrativo garantiza que los actos de la administracion se ajusten al ordenamiento juridico. El derecho de defensa regula el esquema sancionatorio de la administracion publica, se prohiben las sanciones objetivas o de plano y se proscribe cualquier arbitrariedad y se exige acatar el debido proceso, por lo que la confesion presunta aplicada en materia tributaria es una sancion de plano, que en nuestra opinion se aparta del ordenamiento constitucional y de estos principios. La Corte Constitucional, entre otras Sentencias con las C-422 de 2002 y C-258 de 2011, extiende el debido proceso a todo tipo de actuacion judicial o administrativa. De manera, que ante la obligacion de los contribuyentes de presentar su denuncio rentistico la administracion tiene la carga de la prueba y no debe trasladarla al contribuyente, salvo lo dispuesto expresamente por el legislador en los Articulos 786 a 791 del Estatuto Tributario.
ABSTRACT The hospital environment is particularly susceptible to contamination by bacterial patho... more ABSTRACT The hospital environment is particularly susceptible to contamination by bacterial pathogens that grow on surfaces as biofilms. An increased risk of disease may be a direct consequence of their formation. Understanding bacterial adhesion to surfaces could be of special interest in order to avoid biofilm formation. In this work, aluminum alloy plates were modified by coating them with organosilanes via the sol-gel process in order to get surfaces with different points of zero charge (PZCs). These coatings were homogeneous, with smooth surface and reduced metal corrosion. These modified surfaces were investigated to elucidate their effects on bacterial retention at two different times of a strain of Pseudomonas aeruginosa at different pHs. Bacterial retention revealed significant differences between the coated surfaces. Surfaces with low PZC showed a low bacterial retention due to electrostatic repulsion. On the other hand, surfaces with high PZC presented a distinct behavior: bacterial retention increased with pH due to the image charge generated in the metal surfaces. According to these results, when biofilm formation is undesired, the use of low PZC surfaces is the best choice since they showed low attachment efficiency in bacterial retention.
This study describes and analyzes the design, development, application and evaluation of a new pe... more This study describes and analyzes the design, development, application and evaluation of a new pedagogical methodology based on interactive games for mobile devices (PDAs). The methodology is oriented to developing problem-solving skills in science classes for 8 th graders, by including pre-classroom activities with the teacher, classroom activities, and a central activity using an interactive game for a mobile device. The core problem they had to solve through the game consisted in preserving and evolving different biological species from the animal kingdom, in an unknown and varying environment, by modifying some key factors for evolution of the species. The study was implemented in two main stages: a guided visit to a zoo observing animals directly, and a simulation game that takes place in the school during four weeks. Results show highly motivated learners with a fast adoption of mobile devices, fully engaged in a learning task without external control.
The aim of the present thesis was to better understand the physiological role of the phytohormone... more The aim of the present thesis was to better understand the physiological role of the phytohormones jasmonates (JAs) and abscisic acid (ABA) during fruit ripening in prospect of a possible field application of JAs and ABA to improve fruit yield and quality. In particular, the effects of exogenous application of these substances at different fruit developmental stages and under different experimental conditions were evaluated. Some aspects of the water relations upon ABA treatment were also analysed. Three fruit species, peach (Prunus persica L. Batsch), golden (Actinidia chinensis) and green kiwifruit (Actinidia deliciosa), and several of their cvs, were used for the trials. Different experimental models were adopted: fruits in planta, detached fruit, detached branches with fruit, girdled branches and micropropagated plants. The work was structured into four sets of experiments as follows: (i) Pre-harvest methyl jasmonate (MJ) application was performed at S3/S4 transition under field...
It is argued that today is an information driven society. Being able to engage digital informatio... more It is argued that today is an information driven society. Being able to engage digital information abilities to solve an information interaction activity within digital environments is key for social participation, equality and for bridging socio-economic and cultural gaps. Developing these abilities within school classrooms has become a priority. However, research suggest that a majority of students can only complete basic and explicit information-gathering and management tasks within digital environments. Literature constantly holds that students’ expressed experiences of information interaction activities are key for developing digital information abilities. Notwithstanding, there are still important gaps within our understanding of students’ expressed experiences of them. To address such gaps we employ phenomenography to study Chile’s Secondary Technical and Vocational Education and Training students’ expressed experiences of information interaction abilities; a group that has likewise been overlooked. By means of purposeful sampling, a total of 24 students participated in the study. Focusing on both the out-of and in-school settings, findings suggest that the apparent clear-cut division between the out-of and in-school experiencing seems not to be as pristine as some might suggest. Findings also indicate that specialty courses, as they are currently designed, might not be favorable for developing digital information abilities as well as pointing towards the importance of situating students’ expressed experiences within wider discourses surrounding digital ability development.
Emotions and reflection are critical in teachers’ work. Still, there is no agreement in how these... more Emotions and reflection are critical in teachers’ work. Still, there is no agreement in how these elements connect in assessing past experiences to redesign teaching practices. In this qualitative study, we interviewed six (n = 6) Chilean preservice teachers four times each to analyse what they learn about becoming an educator by reflecting upon four emotions (anger, sadness, pride, and enjoyment). We found that teachers post-hoc reflection upon such emotions provides candidates with information to develop a sense of positional adjustment to overcome emergent difficulties at schools, reach a delimitation between the private and working world, identify teaching enhancement opportunities, and plan the incorporation of strategies in future actions. We also propose a model that coordinates suppressive and generative candidates’ responses after reflecting upon their emotions. In addition, candidates perceive themselves to be unequipped to deal with their own and external emotions effectively. We suggest that emotional training should be considered as an explicit component of teacher education in Latin America. (co-authored with Alvaro Salinas)
Este artículo busca responder a las preguntas por cuán reflexivos son los estudiantes de pedagogí... more Este artículo busca responder a las preguntas por cuán reflexivos son los estudiantes de pedagogía al finalizar su formación de pregrado y qué oportunidades ofrecen los documentos que ellos deben elaborar durante su práctica profesional final, para desarrollar esta reflexión docente. Se aplicaron dos rúbricas a 50 documentos elaborados por estudiantes de seis programas de formación de profesores en Chile. Los resultados muestran que el foco de la reflexión en los documentos analizados se concentra en sólo algunas dimensiones y deja fuera otras que son importantes, tales como la reflexión sobre los propios aprendizajes de los estudiantes. Asimismo, los resultados del análisis muestran, en general, una baja reflexión docente, y diferencias entre los programas analizados. Estas diferencias se relacionarían con la especificidad y orientación que se plantea a los estudiantes sobre lo que se espera de ellos en cada sección del documento elaborado. This article seeks to determine how reflexive students of pedagogy are upon completing their undergraduate training, and what opportunities are offered by the documents they must prepare during their final professional practice, to develop this teaching reflection. Two rubrics were applied to 50 documents prepared by students in six teachers' training programs in Chile. The results show that the reflective approach of the documents analyzed concentrates only on some dimensions, and leaves out other important ones, such as reflection on the students' own lessons learned. Furthermore, the results of the analysis show, in general, a low level of reflective teaching, and differences between the programs analyzed. These differences were related to the specific and orientation students express regarding what is expected of them in each section of the prepared document.
Magis, Revista Internacional de Investigación en Educación
Este artículo describe la frecuencia con la cual estudiantes de pedagogía realizan prácticas refl... more Este artículo describe la frecuencia con la cual estudiantes de pedagogía realizan prácticas reflexivas, y analiza factores que pueden explicar esta frecuencia. Para ello se empleó una perspectiva cuantitativa que incluyó una encuesta a una muestra de 650 estudiantes de 134 programas de formación de profesores en Chile. Los resultados muestran que los factores más importantes para explicar la práctica reflexiva se relacionan con el supervisor. Los factores relacionados con los compañeros de estudio y con la discusión sobre la profesión docente contribuyen menos a la práctica reflexiva.
RESUMEN La práctica reflexiva ha recibido un creciente interés de parte de la investigación y de ... more RESUMEN La práctica reflexiva ha recibido un creciente interés de parte de la investigación y de la formación docente a nivel internacional. Sin embargo, hay poco acuerdo sobre qué es y cómo medirla. Este artículo se propone validar un instrumento cuantitativo en español, para medir la práctica reflexiva en estudiantes de pedagogía. Para ello se aplicó la traducción de la escala de reflexividad elaborada por Larrivee, a una muestra probabilística de 489 estudiantes de pedagogía en Chile. El análisis de datos incluyó análisis factorial exploratorio y confirmatorio y el cálculo de la confiabilidad de la escala. La escala resultante está compuesta por 20 ítems agrupados en tres dimensiones distintas (reflexión superficial, pedagógica y crítica), con buenos indicadores de confiabilidad. El trabajo contribuye a definir operacionalmente el concepto de práctica reflexiva y ofrece la posibilidad de medir el constructo. Al finalizar, se discuten limitaciones y proyecciones de este trabajo. Palabras clave: formación de profesores, reflexión, validación de escala, práctica reflexiva.
Abstract The study presented in this paper consisted in defining a Teaching in a Digital Environm... more Abstract The study presented in this paper consisted in defining a Teaching in a Digital Environment (TIDE) capacity construct and developing a performance-based test to measure Chilean teachers' ability to teach students how to solve information and communication tasks in a digital environment. The test was applied to a sample of 828 in-service teachers in Chile, together with a characterization questionnaire. Results showed that very few Chilean teachers mastered all the tasks and that only one third were able to provide students with orientations in solving information and communication tasks, revealing that the majority are not playing a mediation role in a digital environment. In relation to explaining variables, science and younger teachers with more years of teaching experience performed better in the test. Nevertheless the low explanation provided by the variables included suggests that variables that have previously accounted for teachers ICT integration are not as good in predicting TIDE capacity. This shows the relevance of developing mixed methods research that together with quantitative data provides qualitative data to help explain this capacity in greater depth.
The microstructure of low-alloy multiphase transformation-induced plasticity (TRIP) steels consis... more The microstructure of low-alloy multiphase transformation-induced plasticity (TRIP) steels consists of ferrite, bainite, and metastable retained austenite, which can be transformed into martensite by plastic deformation. In some cases, residual martensite can be present in the initial microstructure. The mechanical behavior of these steels depends on the interaction between the intrinsic characteristics of the existing phases and the austenite stability. Due to these factors, the definition of their true stress-strain flow law is complex. This work presents the mechanical characterization of a phenomenological constitutive stress-strain flow law based on the Bouquerel et al. model, as evaluated for three TRIP steels of the same composition but undergoing different heat treatments. Morphological aspects of the existing phases, austenite stability, and suitable mixture laws between phases are considered. The model is found to accurately reproduce a true stress-strain flow law obtained...
Magis, Revista Internacional de Investigación en Educación, 2019
Este artículo describe la frecuencia con la cual estudiantes de pedagogía realizan prácticas refl... more Este artículo describe la frecuencia con la cual estudiantes de pedagogía realizan prácticas reflexivas, y analiza factores que pueden explicar esta frecuencia. Para ello se empleó una perspectiva cuantitativa que incluyó una encuesta a una muestra de 650 estudiantes de 134 programas de formación de profesores en Chile. Los resultados muestran que los factores más importantes para explicar la práctica reflexiva se relacionan con el supervisor. Los factores relacionados con los compañeros de estudio y con la discusión sobre la profesión docente contribuyen menos a la práctica reflexiva.
Revista Perspectivas: Notas sobre intervención y acción social
En este texto se presenta una mirada a la educación y al sistema escolar desde la diversidad y la... more En este texto se presenta una mirada a la educación y al sistema escolar desde la diversidad y la singularidad de las experiencias de los jóvenes, a partir de algunas conclusiones extraídas de una investigación llevada a cabo por el CIDE en los años 94 y 95, sobre "Las Prácticas Culturales de los Jóvenes Secundarios". La metodología de investigación consistió básicamente en la realización de entrevistas en profundidad y en el desarrollo de una encuesta masiva. ¿Cuáles son las interpelaciones que surgen de las experiencias y de la subjetividad de los jóvenes hacia la escuela, en particular en términos de equidad del sistema y de relevancia de los modelos culturales escolares? ¿Cuáles son las pistas que permiten una redefinicióin de las tareas, estructuras y modelos de la escuela en relación al sistema social y cultural y a las aspiraciones de los sujetos? El artículo que presentamos a continuacion pretende contribuir a la dilucidación de estas y otras interrogantes respecto...
The effect that the microstructure exerts on the Transformation-Induced Plasticity (TRIP) phenome... more The effect that the microstructure exerts on the Transformation-Induced Plasticity (TRIP) phenomenon and on the mechanical properties in a multiphase steel was studied. Samples of an initially cold-rolled ferrite-pearlite steel underwent different intercritical annealing treatments at 750 • C until equal fractions of austenite/ferrite were reached; the intercritical treatment was followed by isothermal bainitic treatments before cooling the samples to room temperature. Samples in the first treatment were heated directly to the intercritical temperature, whereas other samples were heated to either 900 • C or 1100 • C to obtain a fully homogenized, single-phase austenitic microstructure before performing the intercritical treatment. The high-temperature homogenization of austenite resulted in a decrease in its stability, so a considerable austenite fraction transformed into martensite by cooling to room temperature after the bainitic heat treatment. Most of the retained austenite transformed during the tensile tests, and, consequently, the previously homogenized steels showed the highest Ultimate Tensile Strength (UTS). In turn, the steel with a ferritic-pearlitic initial microstructure exhibited higher ductility than the other steels and texture components that favor forming processes.
This study describes the level of adoption of information and communication technologies in teach... more This study describes the level of adoption of information and communication technologies in teaching in three Latin American countries. It also analyzes factors that affect the process by which teachers incorporate these technologies into their classrooms. In order to do so, an online survey was conducted with 89 teachers. The results show that most of the teachers rated themselves at the highest levels of technology adoption. However, the analysis reveals differences between countries associated with individual-type factors, such as the perception of ICT’s contribution to teaching and learning, and the training and knowledge teachers have in this realm. By contrast, the professional culture was not correlated to these differences, and the various actors with which teachers interact, such as the education ministry and school administration, displayed a non-linear relationship with technology adoption. This suggests the need for a better understanding of the complex relationship between the culture, the various actors involved, and the degree to which teachers adopt technology in education.
Resumo: Los indicadores de maduración esquelética han sido utilizados con el fin de aproximarse a... more Resumo: Los indicadores de maduración esquelética han sido utilizados con el fin de aproximarse al momento en que puede presentarse el inicio del acelere del crecimiento prepuberal en el niño y de esta forma aprovechar ese potencial de crecimiento en el ...
La confesion es una declaracion de voluntad hecha por una persona, que puede serle desfavorable, ... more La confesion es una declaracion de voluntad hecha por una persona, que puede serle desfavorable, total o parcialmente, debe ser declaracion de parte, personal, tener por objeto hechos personales del confesante, favorables a la parte contraria, con signifi cacion probatoria, voluntaria, expresa y terminante, seria, con capacidad juridica del confesante y no como resultado de metodos violentos o artificiales. En Derecho Tributario esta determinada por los Articulos 747, 748 y 749 del Estatuto Tributario. Los Articulos 29 y 33 de la Constitucion consagran los derechos a la presuncion de inocencia y a la no autoincriminacion. Tales derechos deben operar en materia tributaria. Asi mismo el de in dubio pro reo se extiende a toda disciplina sancionadora. El debido proceso administrativo garantiza que los actos de la administracion se ajusten al ordenamiento juridico. El derecho de defensa regula el esquema sancionatorio de la administracion publica, se prohiben las sanciones objetivas o de plano y se proscribe cualquier arbitrariedad y se exige acatar el debido proceso, por lo que la confesion presunta aplicada en materia tributaria es una sancion de plano, que en nuestra opinion se aparta del ordenamiento constitucional y de estos principios. La Corte Constitucional, entre otras Sentencias con las C-422 de 2002 y C-258 de 2011, extiende el debido proceso a todo tipo de actuacion judicial o administrativa. De manera, que ante la obligacion de los contribuyentes de presentar su denuncio rentistico la administracion tiene la carga de la prueba y no debe trasladarla al contribuyente, salvo lo dispuesto expresamente por el legislador en los Articulos 786 a 791 del Estatuto Tributario.
ABSTRACT The hospital environment is particularly susceptible to contamination by bacterial patho... more ABSTRACT The hospital environment is particularly susceptible to contamination by bacterial pathogens that grow on surfaces as biofilms. An increased risk of disease may be a direct consequence of their formation. Understanding bacterial adhesion to surfaces could be of special interest in order to avoid biofilm formation. In this work, aluminum alloy plates were modified by coating them with organosilanes via the sol-gel process in order to get surfaces with different points of zero charge (PZCs). These coatings were homogeneous, with smooth surface and reduced metal corrosion. These modified surfaces were investigated to elucidate their effects on bacterial retention at two different times of a strain of Pseudomonas aeruginosa at different pHs. Bacterial retention revealed significant differences between the coated surfaces. Surfaces with low PZC showed a low bacterial retention due to electrostatic repulsion. On the other hand, surfaces with high PZC presented a distinct behavior: bacterial retention increased with pH due to the image charge generated in the metal surfaces. According to these results, when biofilm formation is undesired, the use of low PZC surfaces is the best choice since they showed low attachment efficiency in bacterial retention.
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Papers by Alvaro Salinas