Conocimientos puestos en juego por futuros profesores de matemáticas cuando justifican la selección de tareas

En algunos planes de formación de profesores, el profesor aprende a manejar herramientas conceptuales y metodológicas para elaborar propuestas docentes. En este artículo, identificamos los tres tipos de conocimiento que los futuros profesores que participaron en un plan de formación de ese tipo utilizaron cuando justificaron su propuesta docente: uno relacionado con las herramientas, otro con elementos transversales del plan de formación y un tercer tipo de conocimiento ajeno al plan de formación. Constatamos que el conocimiento relacionado con las herramientas es dominante, se entremezcla con los otros dos tipos de conocimiento y se enuncia de forma ajena a la propia matemática

Argumentos que utilizan los futuros profesores cuando seleccionan tareas matemáticas

En algunos planes de formación de profesores de matemáticas se proporciona al profesor herramientas conceptuales y metodológicas, que llamaremos organizadores del currículo, para que analice y seleccione tareas matemáticas. En este artículo, analizamos los argumentos que emplean futuros profesores en un plan de formación de ese tipo cuando seleccionan tareas. Encontramos que sus argumentos hacen referencia a tres tipos de conocimiento: uno directamente relacionado con los organizadores, otro relacionado con elementos transversales incluidos en el plan de formación y un tercero ajeno al plan. Analizando esta clasificación, encontramos que hay un desarrollo muy desigual de los distintos organizadores, que los argumentos relacionados con los organizadores son dominantes pero se entremezclan con los demás y que, aún cuando se refieren a tareas matemáticas concretas, con frecuencia se enuncian en términos generales ajenos a la tarea analizada

Crystallization and preliminary X-ray diffraction analysis of the N-terminal domain of Paenibacillus barcinonensis xylanase 10C containing the CBM22-1-CBM22-2 tandem

© 2015 International Union of Crystallography. A construct containing the CBM22-1-CBM22-2 tandem forming the N-terminal domain of Paenibacillus barcinonensis xylanase 10C (Xyn10C) has been purified and crystallized. A xylan-binding function and an affinity for mixed β-1,3/β-1,4 glucans have previously been demonstrated for some members of the CBM22 family. The sequence of the tandem is homologous to the N-terminal domains found in several thermophilic enzymes. Crystals of this tandem were grown by the streak-seeding method after a long optimization strategy. The structure has been determined by molecular replacement to a resolution of 2.43Å and refinement is under way. This study represents the first structure containing two contiguous CBM22 modules, which will contribute to a better understanding of the role that this multiplicity plays in fine-tuning substrate affinity.Peer Reviewe

Generalized continuum model for the analysis of nonlinear vibrations of taut strings with microstructure

Classical continuum models are unable to capture the response of a microstructured solid when the scale effect is relevant. In vibration analysis, this limitation appears when the solid undergoes vibrations of wavelength that approaches the characteristic length of the microstructure. A discrete model may be formulated to account for this effect, but this comes at the expenses of high computational costs. For example, scale effects are relevant in strings employed in sensing applications which often rely on information gathered in the nonlinear dynamic regime. In this work, we study the dynamic behavior of a taut string modeled as a lattice of particles linked to first neighbors by linear springs. We develop an inertia-gradient generalized continuum model of the chain, which undergoes nonlinear vibrations. Unlike the corresponding classical continuum model, enrichment of the kinetic energy density with the characteristic length of the microstructure permits the model to capture short-wavelength vibrations. Comparison of the response predicted by the continuum models highlights that the generalized model provides better estimations of the dynamic response of the considered microstructured string in the nonlinear regime and at short wavelengths.Program during academic year 2017-18. This work was supported by the Ministerio de Economía y Competitividad de España (grant numbers DPI2014-57989-P and BES-2015-073720).Publicad

Localización neuroeléctrica de procesos cognitivos

Recording techniques of electrical cerebral activity with surface electrodes are shown and supported as a valid choice of a physiological study of the cognitive function of the human brain. Likewise, we describe the techniques of topographical representation of neuroelectrical potentials, as well as the current source density analysis and the localization of cerebral generators by evoked potentials. We conclude that it is possible to determine the localization of active cortical zones during perception, motor and cognitive processes, starting from a limited number of physiological hypotheses, in relation to the electrical behaviour of the cortical neurons and according to an electrical model of the head.Se presentan y defienden las técnicas de registro de la actividad eléctrica cerebral con electrodos de superficie como una alternativa válida para el estudio fisiológico de la función cognitiva del cerebro humano. Asimismo, se describen las técnicas de representación topográfica de potencial neuroeléctrico, así como las de análisis de densidad de corriente y de localización de generadores cerebrales de potenciales evocados. Se concluye que es posible determinar la localización de zonas corticales activas durante procesos de percepción, motores y cognitivos, partiendo de un número limitado de hipótesis fisiológicas, en relación al comportamiento eléctrico de las neuronas corticales y según un modelo eléctrico de la cabeza.DGICYT TM90-15

Crystallization and preliminary X-ray diffraction analysis of the N-terminal domain of Paenibacillus barcinonensis xylanase 10C containing the CBM22-1-CBM22-2 tandem

A construct containing the CBM22-1-CBM22-2 tandem forming the N-terminal domain of Paenibacillus barcinonensis xylanase 10C (Xyn10C) has been purified and crystallized. A xylan-binding function and an affinity for mixed [beta]-1,3/[beta]-1,4 glucans have previously been demonstrated for some members of the CBM22 family. The sequence of the tandem is homologous to the N-terminal domains found in several thermophilic enzymes. Crystals of this tandem were grown by the streak-seeding method after a long optimization strategy. The structure has been determined by molecular replacement to a resolution of 2.43 Å and refinement is under way. This study represents the first structure containing two contiguous CBM22 modules, which will contribute to a better understanding of the role that this multiplicity plays in fine-tuning substrate affinit

Preface: Earth Observation for Integrated Water and Basin Management: Challenges for adaptation to a changing environment

Integrated river basin management involves a sound knowledge of water and land interactions, and impacts from and feedbacks to human activity. Remote sensing has been an efficient and increasingly promising means of gathering direct information of the Earth surface, as well as information on water and energy fluxes. The recent generation of high-resolution sensors offers a huge potential for monitoring, assessing, and modelling our changing environment in a context of uncertainty about how future climate conditions will affect the current water resource and basin management framework. Moreover, large amounts of data are now available posing a challenging opportunity to the scientific community for both exploring and transforming these data into readily usable information products for different end-users in our societies

Optimising an outdoor membrane photobioreactor for tertiary sewage treatment

The operation of an outdoor membrane photobioreactor plant which treated the effluent of an anaerobic membrane bioreactor was optimised. Biomass retention times of 4.5, 6, and 9 days were tested. At a biomass retention time of 4.5 days, maximum nitrogen recovery rate:light irradiance ratios, photosynthetic efficiencies and carbon biofixations of 51.7 ± 14.3 mg N·mol−1, 4.4 ± 1.6% and 0.50 ± 0.05 kg CO2·m3influent, respectively, were attained. Minimum membrane fouling rates were achieved when operating at the shortest biomass retention time because of the lower solid concentration and the negligible amount of cyanobacteria and protozoa. Hydraulic retention times of 3.5, 2, and 1.5 days were tested at the optimum biomass retention times of 4.5 days under non-nutrient limited conditions, showing no significant differences in the nutrient recovery rates, photosynthetic efficiencies and membrane fouling rates. However, nitrogen recovery rate:light irradiance ratios and photosynthetic efficiency significantly decreased when hydraulic retention time was further shortened to 1 day, probably due to a rise in the substrate turbidity which reduced the light availability in the culture. Optimal carbon biofixations and theoretical energy recoveries from the biomass were obtained at hydraulic retention time of 3.5 days, which accounted for 0.55 ± 0.05 kg CO2·m−3influent and 0.443 ± 0.103 kWh·m−3influent, respectively