Extending the Coordination of Cognitive and Social Perspectives

Cognitive analyses are typically used to study individuals, whereas social analyses are typically used to study groups. In this article, I make a distinction between what one is looking with?one’s theoretical lens?and what one is looking at?e.g., an individual or a group?. By emphasizing the former, I discuss social analyses of individuals and cognitive analyses of groups, additional analyses that can enhance mathematics education research. I give examples of each and raise questions about the appropriateness of such analyses

An approach to the design of mathematical task sequences: Conceptual learning as abstraction

This paper describes an emerging approach to the design of task sequences and the theory that undergirds it. The approach aims at promoting particular mathematical concepts, understood as the result of reflective abstraction. Central to this approach is the identification of available student activities from which students can abstract the intended ideas. The approach differs from approaches in which learning to solve the problem posed is the intended learning. The paper illustrates the approach through data from a teaching experiment on division of fractions

Current-driven magnetization decrease in single crystalline ferromagnetic manganese oxide

The electrical and magnetic response to a bias current has been investigated in a singlecrystalline ferromagnetic manganese oxide $\Pr_{0.8}$Ca$_{0.2}$MnO$_3$ . A significant decrease of the magnetization is observed at the same threshold current where a non-linearity of V-I characteristics appears. Such a behavior cannot be understood in the framework of the filamentary picture usually invoked for the non linearity of the other manganese oxides. Instead, an analogy with spintronic features might be useful and experimental signatures seem to be in agreement with excitations of spin waves by an electric current. This provides an example of a bulk system in which the spin polarized current induces a macroscopic change in the magnetization.Comment: 3 pages, 4 figure

Localized exciton-polariton modes in dye-doped nanospheres: a quantum approach

We model a dye-doped polymeric nanosphere as an ensemble of quantum emitters and use it to investigate the localized exciton-polaritons supported by such a nanosphere. By determining the time evolution of the density matrix of the collective system, we explore how an incident laser field may cause transient optical field enhancement close to the surface of such nanoparticles. Our results provide further evidence that excitonic materials can be used to good effect in nanophotonics.Comment: 16 pages, 4 figure

Extensión de la coordinación de las perspectivas cognitiva y social

Cognitive analyses are typically used to study individuals, whereas social analyses are typically used to study groups. In this article, I make a distinction between what one is looking with -one’s theoretical lens-and what one is looking at -e.g., an individual or a group-. By emphasizing the former, I discuss social analyses of individuals and cognitive analyses of groups, additional analyses that can enhance mathematics education research. I give examples of each and raise questions about the appropriateness of such analyses.Los análisis cognitivos se usan típicamente para estudiar individuos mientras que los análisis sociales se usan normalmente para estudiar grupos. En este artículo, distingo entre lo que se usa para mirar -el lente teórico propio- y lo que se mira -por ejemplo, un individuo o un grupo-. Enfatizando lo primero, discuto los análisis sociales de individuos y los análisis cognitivos de grupos sociales, análisis adicionales que pueden enriquecer la investigación en educación matemática. Presento ejemplos de cada uno de ellos y planteo preguntas respecto de la conveniencia de estos análisis

Una aproximación al diseño de secuencias de tareas matemáticas: aprendizaje conceptual como abstracción

This paper describes an emerging approach to the design of task sequences and the theory that undergirds it. The approach aims at promoting particular mathematical concepts, understood as the result of reflective abstraction. Central to this approach is the identification of available student activities from which students can abstract the intended ideas. The approach differs from approaches in which learning to solve the problem posed is the intended learning. The paper illustrates the approach through data from a teaching experiment on division of fractions.Este artículo describe una aproximación emergente al diseño de secuencias de tareas y la teoría que la sustenta. La aproximación pretende promover conceptos matemáticos concretos como resultado de una abstracción reflexiva. Es central en esta aproximación la identificación de actividades disponibles para los estudiantes con las que puedan abstraer las ideas pretendidas. La aproximación difiere de aquellas en las que el aprendizaje para resolver problemas es el aprendizaje que se pretende. El artículo ilustra la aproximación a través de datos de un experimento de enseñanza sobre la división de fracciones.This research was supported by the National Science Foundation (REC0450663 and DRL-1020154). The opinions expressed do not necessarily reflect the views of the foundation

An approach to the design of mathematical task sequences: Conceptual learning as abstraction

This paper describes an emerging approach to the design of task sequences and the theory that undergirds it. The approach aims at promoting particular mathematical concepts, understood as the result of reflective abstraction. Central to this approach is the identification of available student activities from which students can abstract the intended ideas. The approach differs from approaches in which learning to solve the problem posed is the intended learning. The paper illustrates the approach through data from a teaching experiment on division of fractions. Una aproximación al diseño de secuencias de tareas matemáticas: aprendizaje conceptual como abstracción Este artículo describe una aproximación emergente al diseño de secuencias de tareas y la teoría que la sustenta. La aproximación pretende promover conceptos matemáticos concretos como resultado de una abstracción reflexiva. Es central en esta aproximación la identificación de actividades disponibles para los estudiantes con las que puedan abstraer las ideas pretendidas. La aproximación difiere de aquellas en las que el aprendizaje para resolver problemas es el aprendizaje que se pretende. El artículo ilustra la aproximación a través de datos de un experimento de enseñanza sobre la división de fracciones.Handle: http://hdl.handle.net/10481/41628WOS-ESC

Effect of magnetic field and temperature on the ferroelectric loop in MnWO4

The ferroelectric properties of MnWO4 single crystal have been investigated. Despite a relatively low remanent polarization, we show that the sample is ferroelectric. The shape of the ferroelectric loop of MnWO4 strongly depends on magnetic field and temperature. While its dependence does not directly correlate with the magnetocapacitance effect before the paraelectric transition, the effect of magnetic field on the ferroelectric polarization loop supports magnetoelectric coupling.Comment: 3 pages, 4 figures, first report on ferroelectric loop in MnWO

Towards a standardised line list for G191-B2B, and other DA type objects

We present a comprehensive analysis of the far UV spectrum of G191-B2B over the range of 900-1700{\AA} using co-added data from the FUSE and STIS archives. While previous identifications made by Holberg et al. (2003) are reaffirmed in this work, it is found that many previously unidentified lines can now be attributed to Fe, Ni, and a few lighter metals. Future work includes extending this detailed analysis to a wider range of DA objects, in the expectation that a more complete analysis of their atmospheres can be realised.Comment: 4 pages, 2 figures, 1 table: To appear in the proceedings of the "18th European White Dwarf Workshop" in Krakow, Poland, 201