Una propuesta didáctica para la enseñanza de la regla de los signos para la multiplicación

En nuestro trabajo de investigación nos centramos en la regla de los signos para la operación de multiplicación y nuestro interés se enfoca en generar una propuesta didáctica orientada a provocar un espacio de análisis y reflexión que permita a los escolares esclarecer las reglas de los signos para la multiplicación. Nuestro diseño contempla la naturaleza histórica y epistemológica de las reglas de los signos para multiplicación; y considera un enfoque centrado en el alumno; es decir; el escolar como agente activo; tomando en cuenta una estructura didáctica, epistemológica y cognitiva; enmarcada en la ingeniería didáctica como metodología

An in situ Electrochemical Study of Electrodeposited Nickel and Nickel-Yttrium Oxide Composite Using Scanning Electrochemical Microscopy

Electrodeposited nickel and nickel-yttrium oxide composite samples were studied in situ using scanning electrochemical microscopy (SECM). The monitored probe currents in phosphate-citrate buffer (pH 4.2) in the presence or absence of Ru(NH3)63+ as an oxidizing mediator near the Ni surface show that the SECM is a useful tool for study of the electrochemical activity of heterogeneous metal surface at micrometer scales. The SECM ultramicroelectrode probe tip provides information about the shape, activity and location of particles, such as Y2O3 introduced (co-deposited) in the Ni-matrix of the composite. Experiments show that the Ni-matrix in the composite coating is more active than the pure Ni-coating. This fact is expected, because of texture changes in the Ni structure upon introduction (by co-deposition) of Y2O3 particles. In the absence of mediator in the solution, the electrochemical activity of heterogeneous metal surface at a micro-level is investigated by using O2 concentration changes. The rate of reaction for O2 reduction was found to locally vary at electrodes floating at the open-circuit potential (o.c.p) when compared to an electrode potentiostatically polarized at a more positive potential than the o.c.p. This behavior suggests that local anode and cathode regions are being observed at the o.c.p. sample

Fast-Scan Cyclic Voltammetry - Scanning Electrochemical Microscopy

The use of fast scan cyclic voltammetry (FSCV) to generate images in scanning electrochemical microscopy is demonstrated. In the FSCV-SECM method a cyclic voltammogram is acquired at each grid point of the scanned area. Thus, each point in the SECM image is a data array rather than a single value. This provides a significant increase in the amount of data collected per scan and provides the ability to make images of multiple analytes per scan. In addition, the use of cyclic voltammetry allows images based on adsorptive as well as diffusional processes. In this paper, we describe the FSCV-SECM experiment and equipment, we show that FSCV-SECM can resolve multiple chemical species in a single scan, and we demonstrate that cathodic-stripping voltammetry can be used to image the concentration profiles of halide ions

The Activity of Silicon Carbide Particles in Al-Based Metal Matrix Composites Revealed by Scanning Electrochemical Microscopy

Scanning electrochemical microscopy (SECM) is used to image variations in electrochemical activity over the surface of an aluminum-based metal matrix composite (MMC) in contact with buffered or unbuffered neutral solutions. The composite consists of an Al - 13.5% Si - 9% Mg alloy matrix and reinforcing silicon carbide particles (SiCp). Feedback mode SECM imaging using ferrocenemethanol as a redox mediator in 0.1 M NaCl solution and in buffer solution (pH 6.8) revealed that the SiC particles are electrochemically active. The data suggest that the electronic conductivity at these sites is higher than that of the Al2O3 film covering the alloy matrix surface. The reduction of dissolved oxygen on the silicon carbide particles was investigated by in situ SECM images of samples and current vs. tip-substrate distance curves. The results with samples of SiCp/Al composites immersed in distilled water alone or in either 0.1 M NaCl or boric acid/borax buffer containing ferrocenemethanol as mediator demonstrate that the silicon carbide particles are conductive and act as local cathodes for the reduction of oxygen

Como lograr que los alumnos de segundo grado le den un enfoque comunicativo y funcional a la escritura

Licenciatura en Educación Primari

¿Es posible promover el manejo forestal sin consecuencias importantes para la diversidad de especies?: el caso del ejido Coapilla, Chiapas

Campeche,Chetumal,San Cristóbal,Tapachula,Villahermos

Videojuego para el repaso de fracciones “Tséem Took y la princesa de Uxmal Versión 1.1”

Se expone el diseño de un videojuego didáctico conformado de varias actividades, con el propósito de que los estudiantes de primaria, en especial los educandos de sexto grado, refuercen el estudio de la noción de fracción. Este juego es creado considerando un avatar, cuya acción de movimiento para el usuario es en tercera persona. Los escenarios son creados por herramientas de modelado en 2D, 3D y exportado a un formato que entienda el motor de juegos XNA.A videogame with several activities for students in the primary level is proposed. Our objective is to help students of the sixth year in the learning of the math fractions. The videogame is supported by a didactic analysis. The videogame includes an avatar who is manipulated by the user in the third person view. Virtual scene considers different types of 2D and 3D objects and it was developed using the XNA game engine.Facultad de Informátic