Dualidade onda-partícula: uma sequência didática para o ensino médio com foco em atividades investigativas

Há algumas décadas, o ensino de tópicos relacionados com a Física Moderna e Contemporânea no Ensino Médio tinha um papel secundário e muitas vezes era simplesmente deixado de lado. Entretanto, atualmente vivemos em um mundo cada vez mais globalizado onde as informações circulam com grande velocidade e os avanços científicos e tecnológicos estão cada vez mais presentes em nosso cotidiano. Desta forma, os conteúdos relacionados com a Física Moderna e Contemporânea passaram a ter uma importância que talvez antes não existisse, e o ensino deste conteúdo no Ensino Médio passou a ter um caráter obrigatório. Neste contexto, apresentamos neste trabalho uma proposta para o Ensino do conteúdo Dualidade Onda-Partícula em uma perspectiva investigativa. Com base nessa perspectiva construímos uma sequência de ensino, composta de textos de apoio conceitual, atividades e roteiros de demonstrações experimentais. A metodologia utilizada é baseada em atividades investigativas. Para subsidiar nossa análise, os dados foram processados por meio de aplicação de questionário, gravações das aulas e de um diário de campo. A sequência foi aplicada no primeiro semestre de 2018, em uma turma, com 35 alunos, do segundo ano do Ensino Médio da Escola Estadual de Ensino Fundamental e Médio Aflordízio Carvalho da Silva, situada em Vitória, Espírito Santo (ES). A pesquisa de natureza quali-quanti, teve como principal objetivo analisar a aprendizagem dos conteúdos conceituais dos estudantes. De acordo com os resultados obtidos é possível perceber como as atividades desenvolvidas durante a intervenção possuem potencial para favorecer a aprendizagem conceitual

Optimal Taylor-Couette flow: Radius ratio dependence

Taylor-Couette flow with independently rotating inner (i) and outer (o) cylinders is explored numerically and experimentally to determine the effects of the radius ratio {\eta} on the system response. Numerical simulations reach Reynolds numbers of up to Re_i=9.5 x 10^3 and Re_o=5x10^3, corresponding to Taylor numbers of up to Ta=10^8 for four different radius ratios {\eta}=r_i/r_o between 0.5 and 0.909. The experiments, performed in the Twente Turbulent Taylor-Couette (T^3C) setup, reach Reynolds numbers of up to Re_i=2x10^6$ and Re_o=1.5x10^6, corresponding to Ta=5x10^{12} for {\eta}=0.714-0.909. Effective scaling laws for the torque J^{\omega}(Ta) are found, which for sufficiently large driving Ta are independent of the radius ratio {\eta}. As previously reported for {\eta}=0.714, optimum transport at a non-zero Rossby number Ro=r_i|{\omega}_i-{\omega}_o|/[2(r_o-r_i){\omega}_o] is found in both experiments and numerics. Ro_opt is found to depend on the radius ratio and the driving of the system. At a driving in the range between {Ta\sim3\cdot10^8} and {Ta\sim10^{10}}, Ro_opt saturates to an asymptotic {\eta}-dependent value. Theoretical predictions for the asymptotic value of Ro_{opt} are compared to the experimental results, and found to differ notably. Furthermore, the local angular velocity profiles from experiments and numerics are compared, and a link between a flat bulk profile and optimum transport for all radius ratios is reported.Comment: Submitted to JFM, 28 pages, 17 figure

Investigation of low latitude scintillations in Brazil within the cigala project

Ionospheric scintillations are fluctuations in the phase and amplitude of the signals from GNSS satellites occurring when they cross regions of electron density irregularities in the ionosphere. Such disturbances can cause serious degradation on GNSS system performance, including integrity, accuracy and availability. The two indices internationally adopted to characterize ionospheric scintillations are: the amplitude scintillation index, S4, which is the standard deviation of the received power normalized by its mean value, and the phase scintillation index, σΦ, which is the standard deviation of the de-trended carrier phase. At low latitudes scintillations occur very frequently and can be intense. This is because the low latitudes show a characteristic feature of the plasma density, known as the equatorial anomaly, EA, for which a plasma density enhancement is produced and seen as crests on either side of the magnetic equator. It is a region in which the electron density is considerably high and inhomogeneous, producing ionospheric irregularities causing scintillations. The upcoming solar maximum, which is expected to reach its peak around May 2013, occurs at a time when our reliance on high-precision GNSS (such as GPS, GLONASS and the forthcoming GALILEO) has reached unprecedented proportions. Understanding and monitoring of scintillations are essential, so that warnings and forecast information can be made available to GNSS end users, either for global system or local augmentation network administrators in order to guarantee the necessary levels of accuracy, integrity and availability of high precision and/or safety-of-life applications. Especially when facing severe geospatial perturbations, receiver-level mitigations are also needed to minimize adverse effects on satellite signals tracking availability and accuracy. In this context, the challenge of the CIGALA (Concept for Ionospheric scintillation mitiGAtion for professional GNSS in Latin America) project, co-funded by the European GNSS Agency (GSA) through the European 7th Framework Program, is to understand the causes of ionospheric disturbances and model their effects in order to develop novel counter-measure techniques to be implemented in professional multi-frequency GNSS receivers. This paper describes the scientific advancements made within the project to understand and characterize ionospheric scintillation in Brazil by means of historical and new datasets

Application of Synchrotron Radiation-Based Micro-Analysis on Cadmium Yellows in Pablo Picasso's Femme

The cultural heritage community is increasingly exploring synchrotron radiation (SR) based techniques for the study of art and archaeological objects. When considering heterogeneous and complex micro-samples, such as those from paintings, the combination of different SR X-ray techniques is often exploited to overcome the intrinsic limitations and sensitivity of the single technique. Less frequently, SR X-ray analyses are combined with SR micro-photoluminescence or micro-Fourier Transform Infrared spectroscopy, which provide complementary information on the molecular composition, offering a unique integrated analysis approach. Although the spatial correlation between the maps obtained with different techniques is not straightforward due to the different volumes probed by each method, the combination of the information provides a greater understanding and insight into the paint chemistry. In this work, we discuss the advantages and disadvantages of the combination of X-ray techniques and SR-based photoluminescence through the study of two paint micro-samples taken from Pablo Picasso's Femme (1907). The painting contains two cadmium yellow paints (based on CdS): one relatively intact and one visibly degraded. SR micro-analyses demonstrated that the two Cd-yellow paints differ in terms of structure, chemical composition, and photoluminescence properties. In particular, on the basis of the combination of different SR measurements, we hypothesize that the degraded yellow is based on nanocrystalline CdS with high presence of Cd(OH)Cl. These two characteristics have enhanced the reactivity of the paint and strongly influenced its stability