A Decomposition and Noise Removal Method Combining Diffusion Equation and Wave Atoms for Textured Images

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

Study of stress distribution with finite element method in a root with prefabricated threaded split shaft post - Part I

A finite element analysis was carried out to study the role of prefabricated threaded split shaft post (Flexi-Post) on dentinal stress in pulpless tooth. Three dimensional plane strain model of mesio-distal section of a human maxillary central incisor without restoration was analysed with the MSC/NASTRAN (MacNeal/ Schwendler) general purpose finite analysis program was executed on a microcomputer. The model as discretized into 48.954 axisymmetric finite elements defined by 10.355 nodes. Each element was assigned unique elastic properties to represent the materials modeled. Homogeneity, isotropy and linear elasticity were assume for all material. A simulation of static load of 100N was applied to the incisal edge of the post; vertical. Maximal principal stresses and von Mises equivalent stress were calculated. Using the element analysis model employed in this study, the following can be concluded concerning threaded split shaft post (Flexi-Post): Maximum principal stresses in dentin were located at cervical place and at the post apex. The apical threads of the post not redirecting stresses away from the root.

A square-wave voltammetric method for analysing the colour marker quinizarine in petrol and diesel fuels

This work presents an electroanalytical method based on square-wave voltammetry (SWV) for the determination of quinizarine (QNZ) in a mixture of Britton-Robinson buffer 0.08 mol L-1 with 30% of acetonitrile. The QNZ was oxidized at glassy carbon electrode in and the well-defined peak at +0.45 V vs. Ag/AgCl can be used for its determination as colour marker in fuel samples. All parameters were optimized and analytical curves can be constructed for QNZ concentrations ranging from 2.0 x 10(-6) mol L-1 to 1.4 x 10(-5) mol L-1, using f = 60 Hz and E-sw = 25 mV. The method offers a limit detection of 4.12 x 10(-7) mol L-1 and a standard deviation of 4.5% when six measurements of 1.25 x 10(-5) mol L-1 are compared. The method was successfully applied for determining QNZ in gasoline and diesel oil and the obtained results showed good agreement with those reported previously. (c) 2006 Elsevier Ltd. All rights reserved.

Evaluating the residual stress in PbTiO3 thin films prepared by a polymeric chemical method

We report a study of residual stress in PbTiO3 (PT) thin films prepared on Si substrates by a polymeric chemical method. The E(1TO) frequency was used to evaluate the residual stress through an empirical equation available for bulk PT. We find that the residual stress in PT films increases as the film thickness decreases and conclude that it originates essentially from the contributions of extrinsic and intrinsic factors. Polarized Raman experiments showed that the PT films prepared by a polymeric chemical method are somewhat a-domain (polar axis c parallel to the substrate) oriented.

Application of acoustoelasticity to measure the stress generated by milling in ASTM A36 steel plates

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Circulating leukocyte heat shock protein 70 (HSP70) and oxidative stress markers in rats after a bout of exhaustive exercise

A novel method to measure oxidative stress resulting from exhaustive exercise in rats is presented. In this new procedure we evaluated the erythrocyte antioxidant enzymes, catalase ( CAT) and glutathione reductase (GR), the plasma oxidative attack markers, reactive carbonyl derivatives (RCD) and thiobarbituric reactive substances (TBARS). Muscular tissue damage was evaluated by monitoring plasma creatine kinase (CK) and plasma taurine ( Tau) concentrations. Also, we monitored total sulphydryl groups (TSG) and uric acid (UA), and the level of the 70 kDa heat shock protein (HSP70) in leukocytes as a marker of oxidative stress. In the study we found a correspondence between erythrocyte CAT and GR activities and leukocyte HSP70 levels, principally 3 h after the acute exercise, and this suggested an integrated mechanism of antioxidant defense. The increase in levels of plasma Tau was coincident with the increasing plasma levels of CK and TBARS, principally after two hours of exercise. Thus tissue damage occurred before the expression of any anti-oxidant system markers and the monitoring of Tau, CK or TBARS may be important for the estimation of oxidative stress during exhaustive exercise. Furthermore, the integrated analyses could be of value in a clinical setting to quantify the extent of oxidative stress risk and reduce the need to perform muscle biopsies as a tool of clinical evaluation.

Development of a Validated Stability-Indicating LC Assay and Stress Degradation Studies of Linezolid in Tablets

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

Direct observation of oxidative stress on the cell wall of Saccharomyces cerevisiae strains with atomic force microscopy

We imaged pores on the surface of the cell wall of three different industrial strains of Saccharomyces cerevisiae using atomic force microscopy. The pores could be enlarged using 10 mM diamide, an SH residue oxidant that attacks surface proteins. We found that two strains showed signs of oxidative damage via changes in density and diameter of the surface pores. We found that the German strain was resistant to diamide induced oxidative damage, even when the concentration of the oxidant was increased to 50 mM. The normal pore size found on the cell walls of American strains had diameters of about 200nm. Under conditions of oxidative stress the diameters changed to 400nm.This method may prove to be a useful rapid screening process (45-60 min) to determine which strains are oxidative resistant, as well as being able to screen for groups of yeast that are sensitive to oxidative stress. This rapid screening tool may have direct applications in molecular biology (transference of the genes to inside of living cells) and biotechnology (biotransformations reactions to produce chiral synthons in organic chemistry.

Incommensurate spin-density-wave and metal-insulator transition in the one-dimensional periodic Anderson model

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

Finite-Element Analysis of Stress on Dental Implant Prosthesis

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

An evaluation of shot peening, residual stress and stress relaxation on the fatigue life of AISI 4340 steel

Shot peening is a method widely used to improve the fatigue strength of materials. through the creation of a compressive residual stress field (CRSF) in their surface layers. In the present research the gain in fatigue life of AISI 4340 steel, Used in landing gear. is evaluated under four Shot peening conditions. Rotating bending fatigue tests were conducted and the CRSF was measured by an X-ray tensometry prior and during fatigue tests. It was observed that relaxation of the CRSF occurred due to the fatigue process. In addition, the fractured fatigue specimens were investigated using a scanning electron microscope in order to obtain information about the crack initiation points. The evaluation of fatigue life, relaxation of CRSF and crack sources are discussed. (C) 2002 Elsevier B.V. Ltd. All rights reserved.

A high dynamic range method for the direct readout of a dynamic phase change in homodyne interferometers

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

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).

Influence of Cusp Inclination on Stress Distribution in Implant-Supported Prostheses. A Three-Dimensional Finite Element Analysis

Purpose: The aim of this study was to assess the influence of cusp inclination on stress distribution in implant-supported prostheses by 3D finite element method.Materials and Methods: Three-dimensional models were created to simulate a mandibular bone section with an implant (3.75 mm diameter x 10 mm length) and crown by means of a 3D scanner and 3D CAD software. A screw-retained single crown was simulated using three cusp inclinations (10 degrees, 20 degrees, 30 degrees). The 3D models (model 10d, model 20d, and model 30d) were transferred to the finite element program NeiNastran 9.0 to generate a mesh and perform the stress analysis. An oblique load of 200 N was applied on the internal vestibular face of the metal ceramic crown.Results: The results were visualized by means of von Mises stress maps. Maximum stress concentration was located at the point of application. The implant showed higher stress values in model 30d (160.68 MPa). Cortical bone showed higher stress values in model 10d (28.23 MPa).Conclusion: Stresses on the implant and implant/abutment interface increased with increasing cusp inclination, and stresses on the cortical bone decreased with increasing cusp inclination.

Photoelastic Stress Analysis in Screwed and Cemented Implant-Supported Dentures With External Hexagon Implants

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