Alem-Mar Bernardes Goncalves

In this manuscript, we introduce a novel device that computes the magnetic field along the path as a function of the path. This device, comprising 3D-printed parts: a magnetometer and a wheel with an optical encoder connected to a microcontroller that sends data to a computer wirelessly, offers a unique approach to verifying Ampere’s Law. By moving the device in a closed loop, with and without a wire carrying current, the magnetic field can be graphed as a function of position, providing a fresh perspective on this fundamental law.

Linear air tracks are essential experimental tools used in undergraduate laboratory courses. They facilitate the exploration of kinematic and dynamic topics in a frictionless environment. While commercial air track systems require significant investment, affordable alternatives are valuable for making such apparatuses accessible to high schools and universities. We test and compare a low-cost air track made from medium density fibreboard (MDF) wood as a possible alternative. In this manuscript, we performed new experiments on the uniformly accelerated motion of a glider in an inclined plane to compare the friction of the MDF air track with that of a commercial one. We tested the built and commercial gliders and air tracks for angles of 1, 2, and 5 degrees. Our findings revealed that the friction was about 10 − 4 for all setups analysed. We also observed the influence of air drag on the glider’s movement and attempted to quantify it using the quadratic velocity air drag model. Overall, the results indicate only a slight difference between the MDF air track and the commercial version, suggesting that the MDF air track is a viable and cost-effective alternative to commercial systems.

Objective: To evaluate the effect of toothpastes with active principles based on calcium and phosphate on human dental enamel submitted to the erosion cycle. Material and Methods: Enamel fragments were divided into 6 groups (n=10): Control (CTRL), Bianco pro-clinical (BIAN), Biomin F (BIOM), Biorepair (BIOR), Restore (REST), and Sensodyne Repair & Protect (SENS). The erosion/toothpaste cycle consisted of 90 seconds in 0.1% citric acid, followed by a two-minute immersion in toothpaste slurry. Four cycles/day were conducted over 5 days, with toothpaste used in the 1st and 4th cycles. The relative surface microhardness (rSMH) and roughness by Atomic Force Microscopy (AFM) data were obtained and analyzed by one-way ANOVA, Tukey test, and Student’s t-test (α = 0.05). Results: All groups exhibited reduced microhardness and increased roughness compared to baseline (p < 0.005). Toothpastes improved microhardness versus the control, with BIOM and BIOR showing the highest values. While REST showed no dental erosion control, with a pronounced increase in surface roughness, the other toothpastes varied in effectiveness, with BIOM performing best. The AFM images showed similarities between the REST and CTRL groups (exposed area) and between the control and cycle-exposed areas in the BIOM group. Conclusion: The toothpastes had variable effects on enamel erosion control, with the best performance observed in the BIOM and BIOR groups.

Este artigo propõe um produto educacional como proposta para introduzir o conceito de meia-vida no processo de decaimento radioativo, tema de difícil compreensão para estudantes da Educação Básica devido à sua natureza abstrata e a impossibilidade de realização de experimentos práticos em sala de aula. Para superar essas limitações, desenvolvemos uma proposta de produto educacional baseada em simulação, utilizando poliedros como representação de átomos instáveis em processo de decaimento. Essa metodologia busca tornar o conceito de meia-vida mais tangível e acessível aos estudantes, promovendo uma compreensão prática e visual da probabilidade de decaimento radioativo e estimulando o aprendizado por meio da mobilização de invariantes operatórios. A proposta também explora o potencial dos poliedros como recurso didático para responder à seguinte questão de pesquisa: “o uso de simulações com poliedros contribui para uma compreensão mais profunda dos conceitos de meia-vida e decaimento radioativo entre estudantes da Educação Básica?". O trabalho foi implementado em uma turma de primeiro ano do ensino médio de uma escola pública estadual. Os resultados indicam que a simulação com poliedros se mostrou capaz de abordar temas complexos como a radioatividade. Além disso, observamos que o uso dos poliedros mobilizou invariantes operatórios, auxiliando na construção de significados para esses conceitos. A atividade também gerou maior engajamento e participação dos estudantes, demonstrando que a simulação é uma proposta enriquecedora para o ensino de temas abstratos em Física na Educação Básica.

We present here a board game that introduces the concept of a radioactive decay chain. The game explores the four natural decay series, permitting students to i We present here a board game that introduces the concept of a radioactive decay chain. The game explores the four natural decay series, permitting students to i

In this manuscript, we present a homemade linear air track made of wood and plastic by laser cutting and 3D printing. It can be used for physics experiments on kinematics and dynamics. To exemplify its use, we perform position measurements as a function of time for the gliders moving in the inclined track. The experiment shows the uniformly accelerated motion as expected, and permitted us to verify the low friction coefficient of the air track.

Materials produced through equal channel angular extrusion (ECAE) may offer enhanced mechanical properties over classic thermomechanical processing like extrusion or rolling. Conventional techniques such as electron backscatter diffraction (EBSD) may be insufficient to properly characterize the microstructure of these materials. Darkfield (DF) transmission electron microscopy (TEM), on the other hand, may lead to erroneous conclusions with respect to grain size. In this work, zirconium was submitted to ECAE deformation through four passes in the Bc route at 350 °C. The microstructure was evaluated through FEG-SEM/EBSD (field emission gun–scanning electron microscopy), DF TEM, and ACOM/TEM (automated crystal orientation mapping in TEM). EBSD revealed that the microstructure was heterogeneous with a few large grains surrounded by a fine submicrometric structure, which was only partially resolved through this technique. The fine structure was, however, described through ACOM/TEM. DF TEM was revealed to be somewhat unreliable when the same region was evaluated through ACOM/TEM. Therefore, a combination of techniques seems to be required for proper characterization.

Using a 3D-printed device, an Arduino board, and a force sensor, we measured the force interaction as a function of the distance in an apparatus-like ‘magnetic tractor beam’. This apparatus has been designed to demonstrate the nature of the chemical bond. The magnet configuration is such that the interaction follows a potential analogous to that described by Leonardo–Jones for a chemical bond. This similarity can be applied to demonstrate chemical bonds in teaching science.

O avanço das tecnologias nas últimas décadas tem feito com que os aparatos tecnológicos se tornem cada vez mais presentes na sociedade. Dentre os diversos dispositivos presentes no mundo contemporâneo, o GPS (Global Positioning System) se apresenta como um recurso de extrema importância em áreas como a aviação e o transporte de mercadorias. Esse dispositivo possui fortes bases na teoria da relatividade restrita, devido à diferença de velocidade entre os satélites em órbita e os receptores localizados na superfície terrestre, ocasionando em uma dilatação temporal. Este trabalho desenvolveu um produto tecnológico, de cunho pedagógico, utilizando a Aprendizagem Baseada em Projetos (ABP) como referencial metodológico, com o objetivo de responder a seguinte questão de pesquisa: Quais invariantes operatórios relacionados à Teoria da Relatividade Restrita podem ser mobilizados por meio de uma atividade investigativa, tendo a aprendizagem baseada em projetos como referencial metodológico? Para análise dos dados, utilizamos a Teoria dos Campos Conceituais (TCC) desenvolvida por Gerard Vergnaud. A pesquisa foi implementada em uma turma de terceiro ano do ensino médio com um grupo de 20 estudantes em uma escola pública. Os resultados demonstram que, aliado à metodologia da ABP, o produto tecnológico se apresentou como um recurso pedagógico significativo, mobilizando diversos grupos de invariantes operatórios, alguns explícitos, outros implícitos, indo assim ao encontro da TCC, possibilitando uma demonstração dos efeitos relativísticos no cotidiano. Por fim, acreditamos que esta pesquisa venha favorecer a prática pedagógica do professor e o processo de aprendizagem dos estudantes.

A miniaturized and low-cost electrochemical 3D-printed system for rapid and accurate quantification of ethanol content in ethanol fuel using electrochemical impedance spectroscopy (EIS) was developed. The monolithic design of the system incorporates insulating thermoplastic electrode separators, with only the cover being mobile, allowing for easy assembly and handling. The portable device, measuring approximately 26 × 24 mm, has a maximum capacity of 1 mL, making it suitable for lab-on-a-chip and portable analysis. By utilizing the dielectric constant of ethanol and ethanol fuel mixtures with water, the miniaturized EIS cell quantifies ethanol content effectively. To validate its performance, we compared measurements from four gas stations with a digital densimeter, and the values obtained from the proposed system matched perfectly. Our miniaturized and low-cost electrochemical 3D-printed device can be printed and assembled in two hours, offering a cost-effective solution for fast and precise ethanol quantification. Its versatility, affordability, and compatibility with lab-on-a-chip platforms make it easily applicable, including for fuel quality control and on-site analysis in remote locations.