El papel del péndulo en la construcción del paradigma newtoniano

This paper shows the important role of one of the most common instruments, the pendulum, in the construction of the newtonian paradigm. From the analysis of some interesting applications carried out by the greatest scientists of that time, we conclude that the appropriate use of the pendulum in the classroom can be an easy way to introduce historical and epistemological evolution of basic physical concepts

Transferencia inter-dominios en resolución de problemas : una propuesta instruccional basada en el proceso de «traducción algebraica»

Understanding a science and math word problem means constructing mental representations at different levels of abstraction. Secondary students have dificulties solving algebraic word problems due to the transition from the concrete representation to the mathematic representation. In order to facilitate the «algebraic translation» of the problems, we adapt a «rule to put a problem into equations» by Puig (1998) and insert it in an experimental methodology devoted to improving the inter-domain transfer in science. Results show the power of the instructional methodology to overcome most of the students’ dificulties, no matters their average academic performance.Comprender un problema con enunciado en ciencias y matemáticas implica construir representaciones mentales en diferentes niveles de abstracción. Las dificultades que los estudiantes de secundaria tienen a la hora de resolver problemas algebraicos con enunciado parecen originarse en la transición entre la representación concreta y la representación matemática de los problemas. Para facilitar este proceso llamado «traducción algebraica del problema», se adapta una «regla para poner un problema en ecuaciones» propuesta por Puig (1998) y se integra en una metodología experimental en la que se busca mejorar la transferencia inter-dominios en ciencias. Los resultados muestran la potencia de la propuesta para superar gran parte de los obstáculos que los estudiantes de estos niveles tienen, con independencia de su rendimiento académico global

Creativity, metacognition, and self-efficacy in error detection in worked-out problem examples.

La utilización de problemas verbales totalmente resueltos es práctica habitual en las aulas de ciencias de la educación secundaria. Dada la escasez de estudios sobre la detección de errores en problemas resueltos de ciencias, los objetivos de esta investigación se centraron en la habilidad de detectar errores en problemas resueltos y en los efectos sobre esta habilidad de la creatividad científica, las destrezas metacognitivas, la autoeficacia en el aprendizaje las ciencias, el nivel académico y el género. Para ello, se llevó a cabo una investigación cuantitativa ex post facto de carácter transversal. Participaron 139 estudiantes (74 mujeres y 65 hombres) de 3º y 4º de Educación Secundaria Obligatoria (ESO) , y 1º de Bachillerato (14-17 años). A todos ellos se les administró un cuestionario sobre destrezas metacognitivas y autoeficacia, otro cuestionario sobre creatividad científica, y una prueba de detección de errores en dos problemas verbales resueltos. Los análisis de correlaciones, de regresión múltiple y de mediación sugieren que: a) la capacidad de detección de errores fue baja en general; b) las variables que más influyeron en la variabilidad en la detección de errores en los problemas fueron el nivel académico, la autoeficacia y la creatividad científica; y c) la autoeficacia ejerció un papel de mediadora entre las destrezas metacognitivas y la detección de errores, lo que evidenció el efecto indirecto de las destrezas metacognitivas sobre la detección de errores en los problemas.The use of word problem worked-out examples is a common practice in secondary school science classrooms. Given the paucity of studies on ability to detect errors in worked-out science problem examples, the goals of this research focused on this ability and the effects of scientific creativity, metacognitive skills, science learning self-efficacy, grade level, and gender on it. A quantitative ex post facto cross-sectional research was conducted. A total of 139 students (74 girls and 65 boys) from three different grades of Spanish secondary education (9th, 10th, and 11th grades, between 14 and 17 years old) participated. An error detection task in two worked-out problem exemples with embedded errors, a questionnaire on metacognitive skills and science learning self-efficacy, and a questionnaire on scientific creativity, were administered to participants. Correlation, multiple regression, and mediation analyses suggest that: a) error detection ability was low overall; b) the variables that most influenced error detection in worked-out problem examples were grade level, science learning self-efficacy, and scientific creativity; and c) self-efficacy played the role of mediator between metacognitive skills and error detection, which showed the indirect effect of metacognitive skills on error detection in worked out problem examples

Influence of metal organic chemical vapour deposition growth conditions on vibrational and luminescent properties of ZnO nanorods

Producción CientíficaA detailed optical characterization by means of micro Raman and cathodoluminescence spectroscopy of catalyst-free ZnO nanorods grown by atmospheric-metal organic chemical vapour deposition has been carried out. This characterization has allowed correlating the growth conditions, in particular the precursors partial-pressures and growth time, with the optical properties of nanorods. It has been shown that a high Zn supersaturation can favor the incorporation of nonradiative recombination centers, which can tentatively be associated with ZnI-related defects. Characterization of individual nanorods has evidenced that ZnI-related defects have a tendency to accumulate in the tip part of the nanorods, which present dark cathodoluminescence contrast with respect to the nanorods bottom. The effect of a ZnO buffer layer on the properties of the nanorods has been also investigated, showing that the buffer layer improves the luminescence efficiency of the ZnO nanorods, revealing a significant reduction of the concentration of nonradiative recombination centers.Ministerio de Ciencia e Innovación (Projects MAT2007-66129, MAT-2010-20441-C02, MAT-2010-16116, and TEC2011-28076-C02-02)Generalitat Valenciana (Prometeo/2011-035 and ISIC/2012/008, Institute of Nanotechnologies for Clean Energies

ZnMgO-based UV photodiodes: a comparison of films grown by spray pyrolysis and MBE

Detecting the UV part of the spectrum is fundamental for a wide range of applications where ZnMgO has the potential to play a central role. The shortest achievable wavelength is a function of the Mg content in the films, which in turn is dependent on the growth technique. Moreover, increasing Mg contents lead to an electrical compensation of the films, which directly affects the responsivity of the photodetectors. In addition, the metal-semiconductor interface and the presence of grain boundaries have a direct impact on the responsivity through different gain mechanisms. In this work, we review the development of ZnMgO UV Schottky photodiodes using molecular beam epitaxy and spray pyrolysis, and we analyze and compare the physical mechanisms underlying the photodetector behavior. © (2016) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only

Biological Convergence of Cancer Signatures

Gene expression profiling has identified cancer prognostic and predictive signatures with superior performance to conventional histopathological or clinical parameters. Consequently, signatures are being incorporated into clinical practice and will soon influence everyday decisions in oncology. However, the slight overlap in the gene identity between signatures for the same cancer type or condition raises questions about their biological and clinical implications. To clarify these issues, better understanding of the molecular properties and possible interactions underlying apparently dissimilar signatures is needed. Here, we evaluated whether the signatures of 24 independent studies are related at the genome, transcriptome or proteome levels. Significant associations were consistently observed across these molecular layers, which suggest the existence of a common cancer cell phenotype. Convergence on cell proliferation and death supports the pivotal involvement of these processes in prognosis, metastasis and treatment response. In addition, functional and molecular associations were identified with the immune response in different cancer types and conditions that complement the contribution of cell proliferation and death. Examination of additional, independent, cancer datasets corroborated our observations. This study proposes a comprehensive strategy for interpreting cancer signatures that reveals common design principles and systems-level properties

El Conocimiento Didáctico del Contenido en ciencias: estado de la cuestión

This paper gives a descriptive overview of the literature related to Pedagogical Content Knowledge - PCK - in the sciences. It is expected that this review can contribute to a better understanding of PCK, pointing out what has been investigated about this concept. Specifically, we analyze: a) how PCK is defined, what are its main features and how it has been appropriated by teachers; b) the relationship between PCK, knowledge of the contents to be taught and students learning; c) how PCK was actually used in teachers' training and teachers' evaluation; and, d) the scientific areas in which PCK has been studied. It concludes that PCK is an essential tool for improving the quality of teacher training

Errores conceptuales en el estudio del equilibrio químico: nuevas aportaciones relacionadas con la incorrecta aplicación del principio de Le Chatelier

The limited usefulness of the Le Chatelier's principle and its vague and ambiguous formulation may be some of the sources of misconceptions in chemical equilibrium. To diagnose misconceptions a written test was administered to 170 first-year students. Responses revealed that mistakes emerged tl~rougha: ) misapplication and misunderstanding of the Le Chatelier's principle; b) utilization of rote-learning recall and algorithmic procedures; c) incorrect control of the variables involved and limited use of the chemical equilibriuni law; d) lack of mastery of the principles of chemical equilibrium and difficulty in transfering them to new situations