Cubic approximation for the transverse displacement in BEM for elastic plates analysis

This work presents an application for the plate analysis formulation by BEM where 3 boundary equations are used, written for the transverse displacement w and the normal and tangential derivatives partial derivativew/partial derivativen and partial derivativew/partial derivatives. In this extension, the transverse displacement w is approximated by a cubic polynomial and, as a consequence, partial derivativew/partial derivatives has a quadratic approximation. This alternative BEM formulation improves the analysis of thin plates, when compared to the formulation using the linear approximation for the displacements, mainly in the obtaining of the bending moments at the boundary of the plate. The implementation of this proposal to the computational codes is simple. (C) 2004 Published by Elsevier Ltd.

Elastic modulus and hardness of CaTiO3, CaCu3Ti4O12 and CaTiO3/CaCu3Ti4O12 mixture

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Elastic scattering and the proton form factor

We use the QCD pomeron model proposed by Landshoff and Nachtmann to compute the differential and the total cross-sections for pp scattering in order to discuss a QCD-based approach to the proton form factor. This model is quite dependent on the experimental electromagnetic form factor, and it is not totally clear why this form factor gives good results even at moderate transferred momentum. We exchange the electromagnetic form factor by the asymptotic QCD proton form factor determined by Brodsky and Lepage (BL) plus a prescription for its low energy behavior dictated by the existence of a dynamically generated gluon mass. We fit the data with this QCD inspired form factor and a value for the dynamical gluon mass consistent with the ones determined in the literature. Our results also provide a determination of the proton wave function at the origin, which appears in the BL form factor.

Comparative Study of the Mechanical Resistance of 2 Separate Plates and 2 Overlaid Plates Used in the Fixation of the Mandibular Condyle: An In Vitro Study

Purpose: The objective of this study was to carry out a comparative evaluation of the mechanical resistance of 2 rigid internal fixation techniques for fractures of the mandibular condyle using miniplates.Materials and Methods: Fort), polyurethane resin replicas of human hemimandibles were used. The hemimandibles were sectioned to simulate a high subcondylar fracture and then stabilized with 2 fixing techniques using 2.0-mm system plates and screws. The fixation techniques were 2 separate 4-hole plates with 8 screws, and 2 overlaid 4-hole plates with 4 screws. Each system was submitted to load tests, with the application of the load in mediolateral and anteroposterior directions in an Instron 4411 universal assay machine (Instron, Norwood, MA).Results: Load values and peak displacement were measured. Means and standard deviations were evaluated by analysis of variance (P < .05) and Tukey tests, in which it was verified that the anteroposterior peak load value was affected by the arrangement of the plates on the models, although no differences were observed between the groups for the mediolateral peak load. The arrangement of the plates did not have any influence on peak displacement. Similarly, the final value of the mediolateral load was not affected by the arrangement of the plates on the model.Conclusion: The experimental model with 2 separate plates was statistically superior to the model with 2 overlaid plates only in relation to anteroposterior peak load. Despite showing superiority in mediolateral peak load and peak displacement, there was no statistical difference between the groups for these parameters. (C) 2009 American Association of Oral and Maxillofacial Surgeons

Biomechanical Study in Polyurethane Mandibles of Different Metal Plates and Internal Fixation Techniques, Employed in Mandibular Angle Fractures

The aim of this study was to perform a physicochemical and morphological characterization and compare the mechanical behavior of an experimental Ti-Mo alloy to the analogous metallic Ti-based fixation system, for mandibular angle fractures. Twenty-eight polyurethane mandibles were uniformly sectioned on the left angle. These were divided into 4 groups: group Eng 1P, one 2.0-mm plate and 4 screws 6 mm long; group Eng 2P, two 2.0-mm plates, the first fixed with 4 screws 6 mm long and the second with 4 screws 12 mm long. The same groups were created for the Ti-15Mo alloy. Each group was subjected to linear vertical loading at the first molar on the plated side in a mechanical testing unit. Means and standard deviations were compared with respect to statistical significance using ANOVA. The chemical composition of the Ti-15Mo alloy was close to the nominal value. The mapping of Mo and Ti showed a homogeneous distribution. SEM of the screw revealed machining debris. For the plates, only the cpTi plate undergoes a surface treatment. The metallographic analysis reveals granular microstructure, from the thermomechanical trials. A statistically significant difference was found (P < 0.05) when the comparison between both internal fixation techniques was performed. The 2P technique showed better mechanical behavior than 1P.

First-principles simulation of elastic constants and electronic properties of GaN

The electronic and structural properties and elastic constants of the wurtzite phase of GaN, was investigated by computer simulation at Density Functional Theory level, with B3LYP and B3PW hybrid functional. The electronic properties were investigated through the analysis of the band structures and density of states, and the mechanical properties were studied through the calculus of the elastic constants: C11, C33, C44, C12, and C13. The results show that the maximum of the valence band and the minimum of the conduction band are both located at the Γ point, indicating that GaN is a direct band gap semiconductor. The following constants were obtained for B3LYP and B3PW (in brackets): C11 = 366.9 [372.4], C33 = 390.9 [393.4], C44 = 99.1 [96.9], C12 = 143.6 [155.2], and C13 = 107.6 [121.4].

Differential and partial cross sections of elastic and inelastic positronium-helium-atom scattering

Scattering of positronium (Ps) by a helium atom has been investigated in a three-Ps-state coupled-channel model including Ps(1s,2s,2p) states using a recently proposed time-reversal-symmetric regularized electron-exchange model potential. Specifically, we report results of differential cross sections for elastic scattering and target-elastic Ps excitations. We also present results for total and different partial cross sections and compare them with experiment and other calculations.

Fluorescence and confocal laser scanning microscopy imaging of elastic fibers in hematoxylin-eosin stained sections

We have studied the possibility of associating fluorescence microscopy and hematoxylin-eosin staining for the identification of elastic fibers in elastin-rich tissues. Elastic fibers and elastic laminae were consistently identified by the proposed procedure, which revealed itself to be easy and useful for the determination of such structures and their distribution. The fluorescence properties of stained elastic fibers are due to eosin staining as revealed by fluorescence analysis of the dye in solution, with no or only minor contribution by the elastin autofluorescence. The main advantage of this technique resides in the possibility of studying the distribution of elastic fibers in file material without further sectioning and staining. The use of the confocal laser scanning microscope greatly improved the resolution and selectivity of imaging elastic fibers in different tissues. The determination of the three-dimensional distribution and structure of elastic fiber and laminae using the confocal laser scanning microscope was evaluated and also produced excellent results.

Hardness and elastic modulus of carbon-germanium alloys

This work reports on the mechanical properties of germanium-rich amorphous carbon-germanium alloys prepared by RF sputtering of a germanium/graphite target under an argon/hydrogen atmosphere. Nano-hardness, elastic modulus and stress were investigated as a function of the carbon content. The stress, which is reduced by the incorporation of carbon, was related to the film structure and to the difference in the Ge-Ge and Ge-C bond length. Contrary to what was expected, the hardness and elastic modulus of the alloys are lower than the corresponding values for pure amorphous hydrogenated germanium film, which in turn has both properties also smaller than those of crystalline germanium. These properties are analyzed in terms of the structural properties of the films. (C) 2001 Elsevier B.V. B.V All rights reserved.

Morphology of collagen fibers and elastic system fibers in actinic cheilitis

Background: Actinic cheilitis (AC) is a premalignant condition intimately related to exposure of the lips to sun rays. Aim: The objective of this study was to evaluate the elastic and collagen fibers in the lamina propria of AC. The degree of epithelial atypia was correlated with the quantity of elastic and collagen fibers. Materials and Methods: Fifty-one cases were investigated. One slide was stained with hematoxylin-eosin for the evaluation of atypia, the second was stained with Weigert′s resorcin-fuchsin for the assessment of elastic fibers, and the third slide was stained with Mallory′s trichrome for the analysis of collagen fibers. Results: Ordinal logistic regression analysis revealed a significant correlation between the presence of atypia and collagen fibers (P<0.05). Conclusions: It was concluded that there seems to be a reduction in the quantity of collagen fibers in cases of moderate and severe atypia. No correlation was observed between the degradation of elastic system fibers and the grade of dysplasia.

Dynamic stationary response of reinforced plates by the boundary element method

A direct version of the boundary element method (BEM) is developed to model the stationary dynamic response of reinforced plate structures, such as reinforced panels in buildings, automobiles, and airplanes. The dynamic stationary fundamental solutions of thin plates and plane stress state are used to transform the governing partial differential equations into boundary integral equations (BIEs). Two sets of uncoupled BIEs are formulated, respectively, for the in-plane state ( membrane) and for the out-of-plane state ( bending). These uncoupled systems are joined to formamacro-element, in which membrane and bending effects are present. The association of these macro-elements is able to simulate thin-walled structures, including reinforced plate structures. In the present formulation, the BIE is discretized by continuous and/or discontinuous linear elements. Four displacement integral equations are written for every boundary node. Modal data, that is, natural frequencies and the corresponding mode shapes of reinforced plates, are obtained from information contained in the frequency response functions (FRFs). A specific example is presented to illustrate the versatility of the proposed methodology. Different configurations of the reinforcements are used to simulate simply supported and clamped boundary conditions for the plate structures. The procedure is validated by comparison with results determined by the finite element method (FEM).

Isolation of brucella spp from milk of brucellosis positive cows in São Paulo and Minas Gerais states

A brucelose é uma zoonose crônica de importância para a Saúde Pública. Considerando o pequeno número de dados brasileiros sobre a sua presença em leite cru e derivados não-pasteurizados, estudamos a presença de brucelas em leite de animais sorologicamente positivos. A soroaglutinação rápida (SAR), a soroaglutinação lenta (SAL) e a soroaglutinação lenta com tratamento do soro com 2-mercaptoetanol foram utilizados para identificar os animais positivos nas propriedades estudadas. Amostras diárias de 300 ml de leite foram colhidas por três dias de todos os quartos mamários produtivos (75 ml/teto). As amostras eram misturadas e centrifugadas. Parte do sedimento e do sobrenadante foi inoculada em meios de Farrel e Brodie-Sinton (BS) suplementados com agentes antimicrobianos. As placas e tubos foram cultivados por sete dias a 37ºC, em microaerofilia. As colônias suspeitas no meio BS foram imediatamente repicadas para ágar-Brucella, e cultivadas sob a mesma condição. Os microrganismos isolados foram submetidos a procedimentos de identificação, incluindo a coloração de Gram, requerimento de CO2, produção de H2S, atividade da urease e crescimento na presença de tionina e fucsina. Das 49 amostras examinadas, isolou-se Brucella abortus de 15 (30,61%). Os biótipos isolados foram: biótipo 1 em uma amostra (2,04%), biótipo 2 em oito (16,32%) e biótipo 3 em seis amostras (12,25%)

Mechanical properties and dimensional effects of ZnO- and SnO(2)-based varistors

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Influence of strains and defects on ferroelectric and dielectric properties of thin-film barium-strontium titanates

Pristine, W and Mn 1% doped Ba(0.6)Sr(0.4)TiO(3) epitaxial thin films grown on the LaAlO(3) substrate were deposited by pulsed laser deposition (PLD). Dielectric and ferroelectric properties were determined by the capacitance measurements and X-ray diffraction was used to determine both residual elastic strains and defect-related inhomogeneous strains-by analyzing diffraction line shifts and line broadening, respectively. We found that both elastic and inhomogeneous strains are affected by doping. This strain correlates with the change in Curie-Weiss temperature and can qualitatively explain changes in dielectric loss. To explain the experimental findings, we model the dielectric and ferroelectric properties of interest in the framework of the Landau-Ginzburg-Devonshire thermodynamic theory. As expected, an, elastic-strain contribution due to the epilayer-substrate misfit has an important influence on the free-energy. However, additional terms that correspond to the defect-related inhomogeneous strain had to be introduced to fully explain the measurements.

Biocompatibility of denture base acrylic resins evaluated M culture of L929 cells. Effect of polymerisation cycle and postpoymerisation treatments

Objective: the purpose of this study was to evaluate the effect of two post-polymerisation treatments and different cycles of polymerisation on the cytotoxicity of two denture base resins.Materials and methods: the resins tested were Lucitone 550 and QC 20. Discs of resins were fabricated following the manufacturer's instructions. Lucitone 550 was processed by long cycle or short cycle. The resin QC 20 was processed by reverse cycle or normal cycle. The specimens were divided into groups: (i) post-polymerised in microwave for 3 min at 500 W; (ii) post-polymerised in water-bath at 55 degrees C for 60 min and (iii) without post-polymerisation. Eluates were prepared by placing three discs into a sterile glass vial with 9 ml of Eagle's medium and incubated at 37 degrees C for 24 hours. L929 cells were seeded into 96 3 well culture plates and DNA synthesis was assessed by H-thymidine incorporation assay.Results: the results were submitted to two-way ANOVA and Tukey HSD test. QC 20 specimens polymerised by the normal cycle and submitted to microwave post-polymerisation were graded as moderately cytotoxic. Similar results were observed for Lucitone 550 processed by long cycle without post-polymerisation. The other experimental groups were graded as not cytotoxic. After water-bath post-polymerisation, specimens of Lucitone 550 processed by long cycle produced significantly lower inhibition of DNA synthesis than the other groups.Conclusion: the long cycle increased the cytotoxicity of Lucitone 550 and water-bath post-polymerisation reduced the cytotoxicity of Lucitone 550 processed by long cycle.