Stability of finite difference schemes for complex diffusion processes

In this paper we present a rigorous proof for the stability of a class of finite difference schemes applied to nonlinear complex diffusion equations. Complex diffusion is a common and broadly used denoising procedure in image processing. To illustrate the theoretical results we present some numerical examples based on an explicit scheme applied to a nonlinear equation in the context of image denoising.FCT PTDC/SAU-ENB/111139/200

Avaliação do impacto resultante da integração em larga escala de unidades de microgeração nas redes de distribuição de média e baixa tensão

Documento confidencial. Não pode ser disponibilizado para consultaTese de mestrado integrado. Engenharia Electrotécnica e de Computadores (Major Energia). Faculdade de Engenharia. Universidade do Porto. 201

Improved adaptive complex diffusion despeckling filter

Despeckling optical coherence tomograms from the human retina is a fundamental step to a better diagnosis or as a preprocessing stage for retinal layer segmentation. Both of these applications are particularly important in monitoring the progression of retinal disorders. In this study we propose a new formulation for a well-known nonlinear complex diffusion filter. A regularization factor is now made to be dependent on data, and the process itself is now an adaptive one. Experimental results making use of synthetic data show the good performance of the proposed formulation by achieving better quantitative results and increasing computation speed.Fundação para a Ciência e TecnologiaFEDERPrograma COMPET

Ocular fundus Imaging: from structure to function

Imaging the ocular fundus, namely the retina, to detect and/or monitor changes over time from the healthy condition is of fundamental importance to assess onset and disease progression and is a valuable tool to understand the basic mechanisms of ocular diseases. Current trends point to the need for less or non-invasive approaches, to the need for detailed (higher spatial and temporal resolution) imaging systems and to the quantification as opposed to qualitative classification of any findings. In this work we present a snapshot of our research by presenting two examples of technical development aiming to obtain structural and function information from the human retina, in vivo, using non-invasive techniques, namely optical coherence tomography imaging. Based on our experience and developed work, we are now starting to bridge the gap to brain imaging as the eye is only the starting point of vision.FCTFEDERProgram COMPET

Numerical solution of time-dependent Maxwell’s equations for modeling scattered electromagnetic wave’s propagation

We present the discontinuous Galerkin method combined with a low-storage Runge-Kutta method as an accurate and efficient way to numerically solve the time-dependent Maxwell’s equations. We investigate the numerical scheme in the context of modeling scattered electromagnetic wave’s propagation through human eye’s structures

Guinea grass and its effects on the initial growth of Eucalyptus 7 urograndis clones

Esta pesquisa teve o objetivo de avaliar o efeito da conviv\ueancia de capim-coloni\ue3o sobre o crescimento inicial de plantas de clones de eucalipto. Foram instalados dois ensaios com mudas de clones de eucalipto e de capim-coloni\ue3o, que cresceram em parcelas delimitadas lateralmente por paredes de alvenaria preenchidas com terra. O primeiro ensaio obedeceu ao delineamento experimental inteiramente casualizado, com tr\ueas repeti\ue7\uf5es, e tratamentos em esquema fatorial 5 x 2 (cinco clones de eucalipto, e a aus\ueancia ou presen\ue7a de duas plantas de capim-coloni\ue3o plantadas a 10 cm da muda de eucalipto). O segundo ensaio foi semelhante ao primeiro, por\ue9m, com apenas tr\ueas clones de eucalipto, cinco repeti\ue7\uf5es, e tratamentos em esquema fatorial 3 x 2 (tr\ueas clones de eucalipto e a aus\ueancia ou presen\ue7a de capim-coloni\ue3o). Os clones de eucalipto n\ue3o afetaram de modo diferenciado o crescimento de capim-coloni\ue3o, sendo que aqueles que conviveram com a planta daninha n\ue3o apresentaram diferen\ue7a no seu desenvolvimento, igualando-os quando sob competi\ue7\ue3o. As caracter\uedsticas dos clones de eucalipto mais sens\uedveis \ue0 conviv\ueancia com capim-coloni\ue3o foram: \ue1rea foliar, mat\ue9ria seca de folhas e caule. O clone 3 foi o que se mostrou mais sens\uedvel \ue0 conviv\ueancia com capim-coloni\ue3o e o clone 1 mais tolerante, por\ue9m todos os clones estudados tiveram influ\ueancia negativa da conviv\ueancia com capim-coloni\ue3o.This study aimed to evaluate the guinea grass effect ( Panicum maximum ) on the initial growth of different Eucalyptus 7 urograndis clones. Two assays were established with eucalyptus clones and guinea grass seedlings. The plants were grown in plots with cement borders filled with soil. Each plot received a eucalyptus seedling. The first assay had a completely randomized experimental design, with three replications, and treatments in a 5x2 factorial scheme (five eucalyptus clones and the absence or presence of two guinea grass plants at 10 cm distance from eucalyptus seedling). The second assay was similar to the first, however with three eucalyptus clones. The experimental design was completely randomized, with five replications, and a 3x2 factorial scheme (three eucalyptus clones and the absence or presence of two guinea grass plants). The presence of eucalyptus clones did not affect guinea grass development. The eucalyptus clones that coexisted with guinea grass plants did not show differences in their development, making the clones equal when under competition. The most susceptible characteristics of eucalyptus clones to guinea grass were foliar area, shoot and stem dry matter. Clone 3 showed the most sensitivity to guinea grass, and clone 1 was the most tolerant, but all clones studied suffered a negative interference from guinea grass

Variation between Pathological Measurement and Endoscopically Estimated Size of Colonic Polyps

Background and Aims: Accurate determination of colonic polyp size is vital to an appropriate surveillance. The main aim of this study was to evaluate variation between the polyp size reported by the endoscopist and its pathological measurement. Methods: A retrospective analysis of all colonic adenomatous polyps resected in a 12-month period was performed at our center. Endoscopic and pathological size for each polyp were compared, and overestimation rates, underestimation rates, and endoscopic-pathological variation (EPV) were calculated. Results: Among the 573 polyps that were included, the mean endoscopic and pathological sizes were 8.00 and 6.66 mm, respectively. The most frequent error, in 62.1%, was overestimation by the colonoscopist. Overestimation and EPV were associated with resection technique (higher in endoscopic mucosal resection and smaller with biopsy forceps) and colonoscopist. They were not associated with years of experience in colonoscopy. Overestimation was more frequent in larger polyps. Conclusions: Our study shows significant discordance between endoscopic and pathological size of colonic polyps with a clear tendency for endoscopic overestimation. Larger polyps are more difficult to accurately assess than smaller ones. This propensity for error was not related to colonoscopist’s years of experience and seems to be an individual tendency

Vitamin D nutritional status and vitamin D regulated antimicrobial peptides in serum and pleural fluid of patients with infectious and noninfectious pleural effusions

Background: Vitamin D and vitamin D dependent antimicrobial peptides such as Cathelicidin (LL-37) and ?-defensin 2 have an important role in innate and adaptative immunity, but their role in pleural effusions has not been studied before. Methods: Serum and pleural fluid samples from 152 patients with pleural effusion were collected, corresponding to 45 transudates and 107 exudates, 51 infectious effusions (14 complicated and 37 non-complicated), 44 congestive heart failure effusions and 38 malignant effusions. The levels of 25 OH-vitamin D, 1,25-(OH)2-vitamin D, Vitamin D Binding Protein (VDBP), LL-37 and ?-defensin 2, both in serum and pleural fluid were evaluated in this prospective study. Differences between groups were analysed using unpaired t tests or Mann?Whitney tests. Correlations between data sets were examined using Pearson correlation coefficient or Spearman rank correlation coefficient. Diagnostic accuracy was estimated using ROC curve analysis. Results: Low serum 25 OH vitamin D levels were found in all groups. Infectious effusions (IE) had higher serum and pleural fluid LL-37 levels compared to congestive heart failure or malignant effusions. Among IE, complicated had higher serum and pleural fluid LL-37 levels, and lower serum ?-defensin-2 levels. Positive correlations were found between serum 25 OH-vitamin D levels and serum or pleural 1,25-(OH)2-vitamin D levels, and between 1,25-(OH) 2-vitamin D and LL-37 serum. Diagnostic accuracy of the different molecules was moderate at best. Conclusions: Hypovitaminosis D is highly prevalent in pleural effusions. LL-37 is produced intrapleurally in IE. This production is higher in complicated IE. No evidence of pleural production of ?-defensin 2 was found in any of the groups. Diagnostic accuracy of the different molecules is at the best moderate for discriminating different types of effusions

Stability of finite difference schemes for complex diffusion processes

Complex diffusion is a common and broadly used denoising procedure in image processing. The method is based on an explicit finite difference scheme applied to a diffusion equation with a proper complex diffusion parameter in order to preserve edges and the main features of the image, while eliminating noise. In this paper we present a rigorous proof for the stability condition of complex diffusion finite difference scheme