Abstract The objective of this work was to evaluate the mechanical properties of porous alumina ceramics, using the rice husk as a porogenic element. The rice husk was milled and graded in two granulometry, <65 μm and 65-150 μm, and added in a high purity calcined alumina in the proportion of 5, 15 and 30 wt%. The samples were pressed by uniaxial pressing and sintered at 1450 ºC for 1 h. Sintered density, total porosity, Young’s modulus, modulus of rupture, and compressive strength were evaluated. Samples were also prepared without the addition of rice husk (RH) in order to compare the properties. Porous ceramics with total porosity ranging from 24% to 54% were produced, and with the composition of 5% RH 65-150 μm, a high porosity value was obtained for a lower loss in mechanical properties.

Em geral, o ensino de óptica no nível médio está concentrado na óptica geométrica. Apesar de ser um modelo de sucesso para explicar fenômenos como reflexão e refração da luz, ele não aborda satisfatoriamente a discussão sobre a natureza ondulatória da luz, além de não explicar fenômenos como difração e interferência. Neste trabalho propomos um experimento simples e de baixo custo para discutir a natureza ondulatória da luz e o limite em que a óptica geométrica é válida. A proposta constitui também um dispositivo para realização de medidas de objetos cuja dimensão seja da ordem do comprimento de onda da luz.

In general, optics teaching at high school level focus on geometric optics. This is a successful model to explain reflection and refraction of light. However, it is not appropriate to discuss the wave nature of light, and to explain diffraction and interference, for example. In this work, we propose a simple experiment, of low cost, to discuss the wave nature of light and the limit in which the geometric optics is valid. Our proposal also provides a device to perform measurements of objects whose dimension is of the order of the wavelength of light.

The experiment was carried out to verify if total cholesterol, HDL-cholesterol and triacylglicerol plasma levels are affected when laying hens are fed rations containing different dietary oil sources. One hundred sixty 50 week-old hens, assigned to four treatments with five replicates using 8 hens per replicate were used. The experimental period was of 84 days divided in 3 cycles of 28 days each. In the last day of each cycle, blood samples of 2 hens per replicate were randomly choose and blood samples were collected. On the other hand, blood was also collected at 7 am, 11 am and 3 pm aiming to study the daily changes of these lipids. Blood lipid parameters were not affected by different dietary oil sources (p > 0.05); however, HDL-cholesterol did change during the day, giving evidence that this lipid is indeed involved in the egg yolk formation.