Neste trabalho apresentamos uma experiência simples de condução térmica usando sensores de temperatura digitais com tecnologia one-wire(um-fio) associados a uma placa Arduino para controle e aquisição de dados. Os sensores utilizados são acessóveis e podem ser facilmente encontrados no mercado nacional. O modelo experimental reproduz uma experiência clássica de condução térmica usada comumente em livros didáticos de física para apresentar e discutir a lei de Fourier da condução térmica. Os resultados se mostraram suficientemente sensíveis para revelar uma distribuição não linear de temperaturas numa situação em que condições de contorno pouco realistas, e comumente aplicadas à lei de Fourier nos livros didáticos, resulta num comportamento linear.

We present in this work a simple experiment of thermal conduction using digital temperature sensors with one-wire technology associated with an Arduino board to control and data acquisition. The sensors used are affordable and can be easily found in the country market. The experimental model reproduces a classic experiment of thermal conduction commonly used in textbooks of physics to present and discuss the Fourier law of heat conduction. The results were sufficiently sensitive to reveal a nonlinear temperature distribution in a situation where unrealistic boundary conditions, usually applied to the Fourier law in textbooks, results in linear behavior.

Apresentamos uma montagem experimental simples para o estudo da maré atmosférica, baseada no uso da placa Arduino Uno. Com essa montagem, o professor de física no Ensino Médio poderá apresentar para seus alunos as oscilações barométricas, um efeito fundamentalmente de origem térmica devido ao aquecimento da atmosfera produzido pela radiação solar. Apresentamos também uma comparação entre a maré atmosférica e o efeito gravitacional da maré oceânica, destacando as diferenças entre os dois fenômenos.

We present a simple experimental apparatus for studying the atmospheric tide based on the use of Arduino Uno board. With this apparatus, the physics teacher in high school can present to your students barometric oscillations, an effect mainly of thermal origin, due to the warming of the atmosphere produced by solar radiation. We also present a comparison between atmospheric tide and the gravitational effect of ocean tide, with emphasis on the differences between the two phenomena.

The objective of this study was to investigate how mechanical surface treatments performed for removal of excess of molten glass, influence the fracture toughness of a dental zirconia toughened alumina (In-Ceram® Zirconia). Infiltrated ZTA disks were submitted to three different surface treatments (grinding, sandblasting and grinding + sandblasting + annealing). Fracture toughness was accessed through indentation strength test (IS). X ray diffraction was used to investigate the metastability of tetragonal zirconia particles under all treatments proposed. Kruskall-Wallis non-parametrical test and Weibull statistics were used to analyze the results. Grinding (group 1) introduced defects which decreased the fracture toughness and reliability, presenting the lowest K IC. On the other hand, grinding followed by sandblasting and annealing (group 3) presented the highest K IC. Sandblasting (group 2) presented the highest reliability but lower K IC compared to group 3.

The main objective of this study was to evaluate the influence of mechanical surface treatments for excess glass removal on the fracture toughness of a glass infiltrated zirconia toughened alumina "GI-ZTA" disks (In-Ceram® Zirconia). The GI-ZTA disks were submitted to three different mechanical surface treatments after glass infiltration (grinding, sandblasting and grinding/sandblasting/annealing). Fracture toughness was evaluated through indentation fracture (IF) test. Reliability of tests results was accessed through Weibull statistics. Results: Indentation fracture tests (IF) of GI-ZTA disks have shown that grinding was the surface treatment that presented the lowest K Ic and reliability. An annealing treatment after grinding and sandblasting promoted an increase in K Ic, mainly due to monoclinic-tetragonal reverse transformation recovering the tetragonal zirconia lost during the different mechanical surface treatments. The highest K Ic values were observed after sandblasting and grinding/sandblasting/annealing. Significance: The proposed mechanical surface treatments played an important role on the metastability of tetragonal zirconia and strongly influenced the mechanical performance of GI-ZTA. Kruskhall-Wallis test indicated that K Ic values of the three mechanical surface treatments were statistically distinct.

The structure of ammonium azide (NH4)N3 was (re-)deter-minated ab initio from x-ray powder diffraction experiment using synchrotron radiation. We tried to detail and comment the different steps involved in the structure determination. The compound crysta-llize in the orthorhombic Pmna space group (no.53) with a = 8.937(1) Å, b = 3.8070(5) Å, c = 8.664(1) Å, V = 294.79(7) Å3; Z = 4. It was possible to locate and refine the hydrogen coordinates, in two diffe-rent approaches, and to establish the H-bonds. The final structural parameters are in good agreement with previous results based on three-dimensional neutron diffraction.

La estructura de la azida de amonio (NH4)N3 fue redeterminada mediante ab-initio a partir de los datos de difracción de rayos X empleando eadiación de sincrotrón. El compuesto cristaliza en el grupo espacial Pmna (no.53) con a = 8.937(1) Å, b = 3.8070(5) Å, c = 8.664(1) Å, V = 294.79(7) Å3; Z = 4. Fue posible localizar y refinar las coordenadas de hidrógeno, en dos aproximaciones diferentes, y establecer las uniones de hidrógeno. Los parámetros finales de la estructura están en buena concordancia con resultados previos basados en el análisis de la difracción tridimensional de neutrones.