Restauration d'image de contours incomplets par modelisation par champs de Markov

Dans ce rapport, nous presentons un algorithme permettant de restaurer des images de contours incomplets. Nous utilisons une modelisation markovienne et des distributions de Gibbs. Pour ce faire, certains criteres a optimiser sont determines afin de completer les parties manquantes. La mise en oeuvre de methodes deterministes("Iterated Conditional Mode") ou stochastiques (echantillonneur de Gibbs) de relaxation permet d'aboutir a une configuration stable dans laquelle les contours sont completes. Notre travail consiste a modifier un algorithme propose par J.L. Marroquin en 1989 et a l'etendre dans le but de traiter des images bruitees et de scenes reelles. Pour illustrer cette methode, nous presentons des resultats sur plusieurs types d'images: des images synthetiques bruitees et des images reelles(images d'interieur, images satellite: SPOT)

A Markovian Model For Contour Grouping

In order to interpret and analyse a scene, determining the contours is a fundamental step. Classical methods of contour extration do not always allow the detection of all the controus. We notice, for exemple, that the contours obtained by a Canny-Deriche filter have some gaps, especially at corners or at T-junctions. In short, the boundaries which are detected are not always closed. In this report, we present an algorith that restores incomplete contours. We model the image by Markov Random Fields and we define the Gibbs Distribution associated with it. In order to complete the contours, several criteria are defined and introduced in an energy function, which has to be optimized. The deterministic ICM "Iterated Conditional Mode" relaxation algorithm is implemented to minimize this energy function. The result is a contour image consisting of closed contours. This method has been tested on different images which present different types of difficulties (indoors, outdoors, satellite (SPOT), industrial and medical images)

Modélisation markovienne pour le groupement de contours avec une coopération contours-régions

Dans ce rapport, nous présentons un nouveau modèle markovien pour la restauration de contours incomplets en utilisant une coopération contours-régions. A partir de l'image originale des niveaux de gris, les contours correspondent aux discontinuités de l'intensité lumineuse. Ils sont fréquemment détectés à l'aide d'un filtrage de Canny-Deriche, suivi de la suppression des non-maxima locaux et d'un seuillage par hystérésys. Les contours sont biens localisés mais présentent parfois certaines interruptions, notamment aux niveaux des «coins» et des «jonctions en T». Pour les compléter, nous conservons comme données initiales ces contours et des régions informations sur les régions définies à partir d'un algorithme «fusion-éclatement». Cet algorithme de prolongation des lignes de contours a pour contrainte de ne pas prolonger un contour dans une zone homogène. Pour ce faire, nous définissons des critères à minimiser afin de compléter les parties manquantes, et nous les insérons dans une nouvelle fonction d'énergie. De plus, nous déterminons des contraintes sur les constantes incluses dans la fonction d'énergie. C'est à l'aide de la méthode des «boites qualitatives» que nous justifions le choix de ces constantes.\  Pour optimiser cette fonction, nous mettons en oeuvre des méthodes stochastique ou déterministe, qui permettent d'aboutir à une configuration stable dans laquelle les contours sont complétés. Cette méthode a été testée sur différentes images et permet d'obtenir des résultats de bonne qualité

The potential therapeutic use of cord blood in autologous transplants or in special patients: a review and update

Umbilical Cord Blood is a rich source of hematopoietic stem cells widely used as a substitute of bone marrow (BM) in transplants. Cells from umbilical cord blood present advantages over BM cells, mainly as they are younger and a have higher proliferative rate. Besides hematopoietic stem cells, umbilical cord blood contains endothelial and mesenchymal progenitor cells, suggesting their possible application in cell therapy protocols for different tissues. In this paper, we discuss the importance of autologous umbilical cord blood storage and the research on stem cell transplantation for degenerative diseases.O sangue de cordão umbilical e placentário (SCUP) é uma rica fonte de células-tronco (CT) hematopoéticas e é amplamente utilizado como substituto da medula óssea em casos de transplante. As células do SCUP possuem vantagens sobre as células da medula óssea (MO), principalmente por serem mais jovens e apresentarem maior taxa proliferativa. Além dos progenitores hematopoéticos, o sangue de cordão umbilical contém progenitores endoteliais e mesenquimais, sugerindo sua possível aplicação nos novos protocolos de terapia celular para diferentes tecidos. Na presente revisão, discutimos a importância do armazenamento do sangue de cordão umbilical autólogo e as pesquisas desenvolvidas para a sua aplicação em doenças degenerativas.Cryopraxis Criobiologia LtdaUniversidade Federal de São Paulo (UNIFESP), Escola Paulista de Medicina (EPM)Instituto de Traumato-ortopediaSanta Casa de São PauloHospital Samaritano de São PauloUFRJ HUCFFHospital Central do ExércitoUFRJ IPPMGUFRJCollege of Medicine Department of Neurosurgery Center of Excellence for Aging & Brain RepairUNIFESP, EPMSciEL

The Raman optical activity of β-D-xylose: where experiment and theory meet

Besides its applications in bioenergy and biosynthesis, β-D-xylose is a very simple monosaccharide that exhibits relatively high rigidity. As such, it provides the best basis to study the impact of different solvation shell radii on the computation of its Raman optical activity (ROA) spectrum. Indeed, this chiroptical spectroscopic technique provides exquisite sensitivity to stereochemistry, and benefits much from theoretical support for interpretation. Our simulation approach combines density functional theory (DFT) and molecular dynamics (MD) in order to efficiently account for the crucial hydration effects in the simulation of carbohydrates and their spectroscopic response predictions. Excellent agreement between the simulated spectrum and the experiment was obtained with a solvation radius of 10 Å. Vibrational bands have been resolved from the computed ROA data, and compared with previous results on different monosaccharides in order to identify specific structure–spectrum relationships and to investigate the effect of the solvation environment on the conformational dynamics of small sugars. From the comparison with ROA analytical results, a shortcoming of the classical force field used for the MD simulations has been identified and overcome, again highlighting the complementary role of experiment and theory in the structural characterisation of complex biomolecules. Indeed, due to unphysical puckering, a spurious ring conformation initially led to erroneous conformer ratios, which are used as weights for the averaging of the spectral average, and only by removing this contribution was near perfect comparison between theory and experiment achieved

Calculation of Raman optical activity spectra for vibrational analysis

By looking back on the history of Raman Optical Activity (ROA), the present article shows that the success of this analytical technique was for a long time hindered, paradoxically, by the deep level of detail and wealth of structural information it can provide. Basic principles of the underlying theory are discussed, to illustrate the technique's sensitivity due to its physical origins in the delicate response of molecular vibrations to electromagnetic properties. Following a short review of significant advances in the application of ROA by UK researchers, we dedicate two extensive sections to the technical and theoretical difficulties that were overcome to eventually provide predictive power to computational simulations in terms of ROA spectral calculation. In the last sections, we focus on a new modelling strategy that has been successful in coping with the dramatic impact of solvent effects on ROA analyses. This work emphasises the role of complementarity between experiment and theory for analysing the conformations and dynamics of biomolecules, so providing new perspectives for methodological improvements and molecular modelling development. For the latter, an example of a next-generation force-field for more accurate simulations and analysis of molecular behaviour is presented. By improving the accuracy of computational modelling, the analytical capabilities of ROA spectroscopy will be further developed so generating new insights into the complex behaviour of molecules