An alternative finite element formulation for determination of streamlines in two-dimensional problems

It is well known that the numerical solutions of incompressible viscous flows are of great importance in Fluid Dynamics. The graphics output capabilities of their computational codes have revolutionized the communication of ideas to the non-specialist public. In general those codes include, in their hydrodynamic features, the visualization of flow streamlines - essentially a form of contour plot showing the line patterns of the flow - and the magnitudes and orientations of their velocity vectors. However, the standard finite element formulation to compute streamlines suffers from the disadvantage of requiring the determination of boundary integrals, leading to cumbersome implementations at the construction of the finite element code. In this article, we introduce an efficient way - via an alternative variational formulation - to determine the streamlines for fluid flows, which does not need the computation of contour integrals. In order to illustrate the good performance of the alternative formulation proposed, we capture the streamlines of three viscous models: Stokes, Navier-Stokes and Viscoelastic flows.

Development of a three-dimensional nonlinear viscoelastic constitutive model of solid propellant

A three dimensional nonlinear viscoelastic constitutive model for the solid propellant is developed. In their earlier work, the authors have developed an isotropic constitutive model and verified it for one dimensional case. In the present work, the validity of the model is extended to three-dimensional cases. Large deformation, dewetting and cyclic loading effects are treated as the main sources of nonlinear behavior of the solid propellant. Viscoelastic dewetting criteria is used and the softening of the solid propellant due to dewetting is treated by the modulus decrease. The nonlinearities during cyclic loading are accounted for by the functions of the octahedral shear strain measure. The constitutive equation is implemented into a finite element code for the analysis of propellant grains. A commercial finite element package ‘ABAQUS’ is used for the analysis and the model is introduced into the code through a user subroutine. The model is evaluated with different loading conditions and the predicted values are in good agreement with the measured ones. The resulting model applied to analyze a solid propellant grain for the thermal cycling load.

Comparison between one-dimensional uncoupled and convection-conduction conjugated approaches in finned surface heat transfer

This work studies the forced convection problem in internal flow between concentric annular ducts, with radial fins at the internal tube surface. The finned surface heat transfer is analyzed by two different approaches. In the first one, it is assumed one-dimensional heat conduction along the internal tube wall and fins, with the convection heat transfer coefficient being a known parameter, determined by an uncoupled solution. In the other way, named conjugated approach, the mathematical model (continuity, momentum, energy and K-epsilon equations) applied to tube annuli problem was numerically solved using finite element technique in a coupled formulation. At first time, a comparison was made between results obtained for the conjugated problem and experimental data, showing good agreement. Then, the temperature profiles under these two approaches were compared to each other to analyze the validity of the one-dimensional classical formulation that has been utilized in the heat exchanger design.

Comparative analysis of two-dimensional electrophoresis maps (2-DE) of Helicobacter pylori from Brazilian patients with chronic gastritis and duodenal ulcer: a preliminary report

Helicobacter pylori is a bacterium recognized as the major cause of peptic ulcer and chronic gastritis. Recently, a proteome-based approach was developed to investigate pathogenic factors related to H. pylori. In this preliminary study, H. pylori strains were isolated from gastric biopsies of patients with chronic gastritis and duodenal ulcers. A partial proteomic analysis of H. pylori strains was performed by bacterial lyses and proteins were separated by two-dimensional gel electrophoresis (2-DE). A comparative analysis was performed to verify a differential protein expression between these two 2-DE maps. These data should be useful to clarify the role of different proteins related to bacterial pathogenesis. This study will be completed using a larger number of samples and protein identification of H. pylori by MALDI-TOF mass spectrometry.

Immunoblotting analyses using two-dimensional gel electrophoresis of Trypanosoma cruzi excreted-secreted antigens

Trypanosoma cruzi trypomastigotes excrete-secrete a complex mixture of antigenic molecules. This antigenic mixture denominated trypomastigote excreted-secreted antigens contains a 150-160 kDa band that shows excellent performance in Chagas' disease diagnosis by immunoblotting. The present study partially characterized by two-dimensional gel electrophoresis the immunoreactivity against the 150-160kDa protein using sera samples from chagasic patients in different phases of the disease. Trypomastigote excreted-secreted antigen preparations were subjected to high-resolution two-dimensional (2D) gel electrophoresis followed by immunoblotting with sera from chagasic and non-chagasic patients. The 150-160kDa protein presented four isoforms with isoelectric focusing ranging from 6.2 to 6.7. The four isoforms were recognized by IgM from acute phase and IgG from chronic phase sera of chagasic patients. The 150-160kDa isoform with IF of approximately 6.4 became the immunodominant spot with the progression of the disease. No cross-reactivity was observed with non-chagasic or patients infected with Leishmania sp. In this study we provide basic knowledge that supports the validation of trypomastigote excreted-secreted antigens for serological diagnosis of Chagas' disease.

VARIAÇÃO DIMENSIONAL DOS ELEMENTOS XILEMÂTICOS EM DUAS ESPÉCIES MADEIREIRAS DA AMAZÔNIA

Árvores de Saccoglotis guianensis Benth e Andira parviflora Ducke com aproximadamente 26 metros de altura foram seccionadas em sete partes para estudo das dimensões de fibras e dos elementos de vasos. No sentido radial ambas espécies mostraram um aumento no comprimento de fibras com algumas irregularidades da medula para o câmbio bem como fibras mais curtas no topo do tronco. Neste existe um maior número de vasos por milímetro quadrado. É discutido a influência de reguladores de crescimento no número de elementos de vasos. Existe uma diminuição no comprimento das fibras e elementos de vasos em direção ao topo depois de terem alcançado valores máximos numa determinada altura, e um decrescimo irregular na largura desses elementos da base para o topo das árvores. No sentido radial ambas espécies mostraram um pequeno aumento na largura das fibras e elementos de vasos. Estes e as fibras são menores nos galhos, e onde o número de elementos de vasos é maior para as duas espécies. A razão W/C utilizada como uma estimativa da razão do volume da parede celular para o volume da celula diminui da medula em direção ao câmbio. São apresentados 10 gráficos e uma tabela é discutido os fatores que podem influenciar na variação dos elementos ao longo da árvore.

Dynamic three-dimensional reconstruction of the heart by transesophageal echocardiography

OBJECTIVE: To evaluate echocardiography accuracy in performing and obtaining images for dynamical three-dimensional (3D) reconstruction. METHODS: Three-dimensional (3D) image reconstruction was obtained in 20 consecutive patients who underwent transesophageal echocardiography. A multiplanar 5 MHz transducer was used for 3D reconstruction. RESULTS: Twenty patients were studied consecutively. The following cardiac diseases were present: valvar prostheses-6 (2 mitral, 2 aortic and 2 mitral and aortic); mitral valve prolapse- 3; mitral and aortic disease - 2; aortic valve disease- 5; congenital heart disease- 3 (2 atrial septal defect- ASD - and 1 transposition of the great arteries -TGA); arteriovenous fistula- 1. In 7 patients, color Doppler was also obtained and used for 3D flow reconstruction. Twenty five cardiac structures were acquired and 60 reconstructions generated (28 of mitral valves, 14 of aortic valves, 4 of mitral prostheses, 7 of aortic prostheses and 7 of the ASD). Fifty five of 60 (91.6%) reconstructions were considered of good quality by 2 independent observers. The 11 reconstructed mitral valves/prostheses and the 2 reconstructed ASDs provided more anatomical information than two dimensional echocardiography (2DE) alone. CONCLUSION: 3D echocardiography using a transesophageal transducer is a feasible technique, which improves detection of anatomical details of cardiac structures, particularly of the mitral valve and atrial septum.

On the presence of hepatic stellate cells in portal spaces

Previous studies in mice with hypervitaminosis A have demonstrated that fat-storing cells (hepatic stellate cells-HSCs) participate in schistosomal granuloma fibrogenesis. The origin of such cells in portal areas, away from the Disse spaces, was herein investigated. HSCs were identified in frozen sections of the liver by means of Sudan III staining. They appeared as red-stained cells disposed along the sinusoids of normal mice, but were never found within portal spaces. However, in the chronically inflamed portal spaces of Capillaria hepatica-infected mice, Sudan III-positive cells were frequently present among leukocytes and fibroblast-like cells. Thus, there are no resident HSCs in portal spaces, but their presence there in chronic inflammatory processes indicates that they are able to migrate from peri-sinusoidal areas in order to reach the portal areas.