Programa de Pos graduacao em

Brasília de Minas, Brazil

Programa de Pos graduacao em

Brasília de Minas, Brazil
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Thome R.G.,Federal University of Minas Gerais | Domingos F.F.T.,Federal University of Minas Gerais | Santos H.B,Federal University of Säo João del Rei | Martinelli P.M.,Federal University of Minas Gerais | And 3 more authors.
Tissue and Cell | Year: 2012

Aiming to better understand folliculogenesis, this study evaluated cell death and proliferation of ovarian cells, besides cathepsin-D expression in Prochilodus argenteus captured in two sites of the São Francisco River downstream from the Três Marias Dam, Brazil. In the site immediately following the Dam (S1), low levels of dissolved oxygen were registered in the rainy period. The water temperature was higher in the São Francisco River immediately after the confluence with the Abaeté River (S2), regardless of the period. In S1, the ovaries showed smaller oocytes, high caspase-3 enzymatic activity and apoptosis, lower cells in proliferation and GSI, as well as a lesser quantity of cathepsin-D when compared to females captured from S2. Regarding relative frequency of ovarian structures, in the dry period, only oogonia and perinucleolar oocytes were found in fish ovaries from both sites. On the other hand, in the rainy period, the relative frequency of oogonia and perinucleolar oocytes decreased and the vitellogenic oocytes increased in S2. Postovulatory follicles were observed only in S2, whereas atretic follicles occurred at a higher frequency in S1. Our results showed that apoptosis, cell proliferation and cathepsina-D evaluation can be used as biomarkers of environmental impact. © 2011 Elsevier Ltd.

Medeiros S.G.,Programa de Pos Graduacao Em | Dutra R.P.S.,Programa de Pos Graduacao Em | Grilo J.P.F.,University of Aveiro | Martinelli A.E.,Programa de Pos Graduacao Em | And 2 more authors.
Ceramica | Year: 2016

This work aimed to evaluate the effects of processing on microstructure and properties of alumina-mullite composites via reactive sintering of a mixture of kaolinite clay and aluminum hydroxide. Cylindrical pellets were pressed at 40 MPa and sintered between 1300 and 1600 °C. The technological properties were determined as a function of sintering temperature. The evaluation of crystalline phases and microstructure was performed by X-ray diffraction and electron microscopy. Structural results indicate the attainment of mullite and alumina at 1300 °C. Apparent porosity below 0.8% and flexural strength higher than 40 MPa were obtained for sintering temperatures above 1450 °C. A flexural strength as high as 70 MPa was obtained after sintering at 1600 °C. This study demonstrates the possibility of preparing low cost alumina-mullite composites with technological properties compatible with those of ceramics produced by companies with large operations in the international market of refractory products.

High emissivity coatings have been used in industrial applications over 40 years with the goal of reducing the thermal losses in heating processes. By applying a high emissivity coating on the internal surface of a kiln lining, it is possible to increase the efficiency in heat exchange between the atmosphere and the walls, reducing the heat loss and also the fuel consumption. In general ceramic compounds such as cerium oxide, boron carbide, silicon boride, molybdenum silicide or chromium oxide are used as emissivity agents to obtain the desired thermo-optical properties in coatings. However, such compounds often prevent their application due to its high commercial value or its scarcity. In this context, this study aimed to evaluate the effects of iron chromite, an abundant mineral oxide and affordable commercial value in its use as emissivity agent in high emissivity refractory coatings. Through an indirect method of measuring emissivity, different coatings compositions with and without the addition of iron chromite were evaluated, in a comparative manner, aiming its application as coatings for refractory and insulation linings of industrial heating furnaces. With iron chromite additions of 7.5%, there was almost 8% increase in the emissivity of the coatings, suggesting their potential for this application.

Santos M.N.,Federal University of Ouro Preto | Rocha P.A.S.,Federal University of Säo João del Rei | da Silva A.R.D.,Programa de Pos Graduacao em | da Mota Silveira R.A.,Programa de Pos Graduacao em
Revista Escola de Minas | Year: 2012

In this work, a hybrid finite element that incorporates in its formulation the second-order effect, material yielding and connection flexibility effects are presented to study the behavior of plane steel frames. In fact, it is the classic beam-column finite element that presents, at its ends, pairs of springs arranged in sequence. One of the springs is represented in the mathematical formulation of this element by the parameter Sc, which defines the joint stiffness of the members; the other spring, whose rigidity is simulated by the parameter Ss, evaluates the plastification of the cross section. The element stiffness matrix incorporates these three mentioned nonlinear effects. Therefore, the aim of this work is to investigate the computer efficiency of this hybrid finite element in the isolated and combined simulation of these nonlinear effects. Initially, equilibrium and stability of classic structural problems with high nonlinear behavior and critical points in the equilibrium paths are studied. Semi-rigid structural systems with initial geometric imperfections are also evaluated. Later, the hybrid element is tested in the inelastic analysis of plane steel frames based on refined plastic-hinge method. Through these examples, it was possible to validate and verify the use of the proposed hybrid finite element in the numerical modeling of various nonlinear structural problems in civil engineering.

Barros J.D.,Programa de Pos Graduacao em | De Oliveira Junior J.J.,Federal University of Rio Grande do Norte | Da Silva S.G.,Programa de Pos Graduacao em | De Farias R.F.,Campus Universitario
Journal of Microwaves and Optoelectronics | Year: 2011

In this work, the electrical signals obtained by application of microwaves in chemical and bone tissues are analyzed and classified using techniques of signal processing and pattern recognition. For this, Wavelet Transform is applied as a method to extract relevant features of signal and KNN is used as a classification technique. The results showed that microwave signals can be analyzed using Wavelet Transform, which can be used to reconstruct the signals with minimal error rate and KNN showed satisfactory results. © 2011 SBMO/SBMag.

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