Ring-Pattern Dynamics in Smectic-C* and Smectic-C_A* Freely Suspended Liquid Crystal Films

Ring patterns of concentric 2pi-solitons in molecular orientation, form in freely suspended chiral smectic-C films in response to an in-plane rotating electric field. We present measurements of the zero-field relaxation of ring patterns and of the driven dynamics of ring formation under conditions of synchronous winding, and a simple model which enables their quantitative description in low polarization DOBAMBC. In smectic C_A* TFMHPOBC we observe an odd-even layer number effect, with odd number layer films exhibiting order of magnitude slower relaxation rates than even layer films. We show that this rate difference is due to much larger spontaneous polarization in odd number layer films.Comment: 4 RevTeX pgs, 4 eps figures, submitted to Phys. Rev. Let

The French Didactic Tradition in Mathematics

This chapter presents the French didactic tradition. It first describes theemergence and development of this tradition according to four key features (role ofmathematics and mathematicians, role of theories, role of design of teaching andlearning environments, and role of empirical research), and illustrates it through two case studies respectively devoted to research carried out within this traditionon algebra and on line symmetry-reflection. It then questions the influence of thistradition through the contributions of four researchers from Germany, Italy, Mexicoand Tunisia, before ending with a short epilogue

Using tasks to explore teacher knowledge in situation-specific contexts

This article was published in the journal, Journal of Mathematics Teacher Education [© Springer] and the original publication is available at www.springerlink.comResearch often reports an overt discrepancy between theoretically/out-of context expressed teacher beliefs about mathematics and pedagogy and actual practice. In order to explore teacher knowledge in situation-specific contexts we have engaged mathematics teachers with classroom scenarios (Tasks) which: are hypothetical but grounded on learning and teaching issues that previous research and experience have highlighted as seminal; are likely to occur in actual practice; have purpose and utility; and, can be used both in (pre- and in-service) teacher education and research through generating access to teachers’ views and intended practices. The Tasks have the following structure: reflecting upon the learning objectives within a mathematical problem (and solving it); examining a flawed (fictional) student solution; and, describing, in writing, feedback to the student. Here we draw on the written responses to one Task (which involved reflecting on solutions of x+x−1=0 of 53 Greek in-service mathematics teachers in order to demonstrate the range of teacher knowledge (mathematical, didactical and pedagogical) that engagement with these tasks allows us to explore

Roteiros de aprendizagem a partir da transposição didática reflexiva

Este artigo busca socializar o produto da dissertação de mestrado profissional em Ensino de Matemática. Apresentamos roteiros de aprendizagem como uma possibilidade educacional para que professores de matemática do Ensino Médio possam aplicá-los de modo a desenvolver a matemática a partir de dados reais. Os roteiros foram adaptados de trabalhos oriundos do Projeto de Iniciação Científica do IFC - Campus Rio do Sul. A pesquisa foi embasada na teoria da Transposição Didática e na Educação Matemática Crítica. Essa abordagem foi denominada de Transposição Didática Reflexiva, com o intuito de unir as duas teorias num processo em que o saber a ser ensinado seja adaptado de forma a provocar reflexões, instituindo um cenário para investigação que propicie a participação do aluno no processo, provoque discussões e tomada de decisão, de modo a instigar o sujeito a ser transformador de sua própria realidade. De modo particular, o artigo apresenta, em linhas gerais, um dos roteiros detalhados na dissertação, aplicado em uma turma do IFC - Campus Rio do Sul

Coalescence in the 1D Cahn-Hilliard model

We present an approximate analytical solution of the Cahn-Hilliard equation describing the coalescence during a first order phase transition. We have identified all the intermediate profiles, stationary solutions of the noiseless Cahn-Hilliard equation. Using properties of the soliton lattices, periodic solutions of the Ginzburg-Landau equation, we have construct a family of ansatz describing continuously the processus of destabilization and period doubling predicted in Langer's self similar scenario

O Fenômeno Didático Institucional da Rigidez e a Atomização das Organizações Matemáticas Escolares

Nesta investigação estudamos um fenômeno didático complexo que se manifesta na desconexão dos conteúdos matemáticos que constituem o programa oficial do ensino secundário/médio e que está fortemente relacionado com a rigidez e a atomização da Matemática escolar. Para tal estudo utilizamos as ferramentas teóricas e metodológicas que nos proporciona a Teoria Antropológica do Didático (TAD) cujo objeto primário de investigação é a análise da atividade matemática escolar institucional. Assim, realizamos estudos exploratórios nos manuais escolares de Matemática do ensino secundário de Portugal e da Espanha, contrastando e comprovando cinco conjeturas relacionadas, por exemplo, com a ausência de questionamento e justificação das técnicas utilizadas. Concluimos que nestes países as praxeologias matemáticas apresentam-se desarticuladas, rígidas,e, consequentemente, surgem isoladas atividades de modelagem matemática nas instituições escolares

Conceptually driven and visually rich tasks in texts and teaching practice: the case of infinite series

The study we report here examines parts of what Chevallard calls the institutional dimension of the students’ learning experience of a relatively under-researched, yet crucial, concept in Analysis, the concept of infinite series. In particular, we examine how the concept is introduced to students in texts and in teaching practice. To this purpose, we employ Duval's Theory of Registers of Semiotic Representation towards the analysis of 22 texts used in Canada and UK post-compulsory courses. We also draw on interviews with in-service teachers and university lecturers in order to discuss briefly teaching practice and some of their teaching suggestions. Our analysis of the texts highlights that the presentation of the concept is largely a-historical, with few graphical representations, few opportunities to work across different registers (algebraic, graphical, verbal), few applications or intra-mathematical references to the concept's significance and few conceptually driven tasks that go beyond practising with the application of convergence tests and prepare students for the complex topics in which the concept of series is implicated. Our preliminary analysis of the teacher interviews suggests that pedagogical practice often reflects the tendencies in the texts. Furthermore, the interviews with the university lecturers point at the pedagogical potential of: illustrative examples and evocative visual representations in teaching; and, student engagement with systematic guesswork and writing explanatory accounts of their choices and applications of convergence tests

Developing critical analysis of explanations in physics teachers: Which direction to take?

International audienc

european didactic traditions in mathematics aspects and examples from four selected cases

In this paper, we report on the presentations and activities from the strand on "European Didactic Traditions" during the Thematic Afternoon at ICME-13. The focal point of the first hour of this afternoon were four key features that were identified as common in all European traditions and the second and third hours were devoted to the presentation of concrete examples from four specific traditions, organised in four parallel sessions