Sainte Térèse

Copia digital. Valladolid : Junta de Castilla y León. Consejería de Cultura y Turismo, 201

Extended Czjzek model applied to NMR parameter distributions in sodium metaphosphate glass

The Extended Czjzek Model (ECM) is applied to the distribution of NMR parameters of a simple glass model (sodium metaphosphate, $\mathrm{NaPO_3}$) obtained by Molecular Dynamics (MD) simulations. Accurate NMR tensors, Electric Field Gradient (EFG) and Chemical Shift Anisotropy (CSA), are calculated from Density Functional Theory (DFT) within the well-established PAW/GIPAW framework. Theoretical results are compared to experimental high-resolution solid-state NMR data and are used to validate the considered structural model. The distributions of the calculated coupling constant $C_Q\propto |V_{zz}|$ and of the asymmetry parameter $\eta_Q$ that characterize the quadrupolar interaction are discussed in terms of structural considerations with the help of a simple point charge model. Finally, the ECM analysis is shown to be relevant for studying the distribution of CSA tensor parameters and gives new insight into the structural characterization of disordered systems by solid-state NMR.Comment: 17 pages, 12 figures to be published in J. Phys.: Condens. Matte

Electrophysiologic characteristics of cells spanning the left ventricular wall of human heart: Evidence for presence of M cells

Objectives.The present work was designed to provide an initial characterization of M cells in the normal human heart.Background.Recent studies have uncovered a unique population of cells in the midmyocardial region of the canine ventricle. These cells, named M cells, were found to possess electrophysiologic features and a pharmacologic responsiveness different from those of other myocardial cells. Although well characterized in the dog, their presence or absence in the human heart is unknown.Methods.Standard microelectrode techniques were used to map slices of ventricular free wall obtained from normal human hearts (n = 4). Preparations were paced at cycle lengths ranging from 1 to 10 s.Results.We identified three cell subtypes: endocardial, subepicardial (M cells) and epicardial cells. The principal features differentiating M cells from the other cell subtypes were their longer action potential duration, more accentuated action potential duration rate relations and greater maximal rate of increase in action potential upstroke (Vmax). Our findings suggest that M cells represent ∼ 30% of the cellular mass of the left ventricular wall. Concordance between changes in their repolarization and changes in QTU interval provide support for the role of M cells in the generation of the electrocardiographic (ECG) U wave.Conclusions.This study provides evidence for the existence of M cells in the human heart that contribute to heterogeneity of repolarization within the ventricular wall. Our findings provide strong support for the hypothesis that M cells contribute importantly to the manifestation of the U wave on the ECG

A Simulation Model for the Evaluation of the Electrical Power Potential Harnessed by a Marine Current Turbine in the Raz de Sein

This work is supported by Brest Métropole Océane (BMO) and the European Social Fund (ESF). It is done within the framework of the Marine Renewable Energy Commission of the Brittany Maritime Cluster (Pôle Mer Bretagne).International audienceThis paper deals with the development of a Matlab-Simulink model of a marine current turbine system through the modeling of the resource and the rotor. The purposes of the simulation model are two: performances and dynamic loads evaluation in different operating conditions and control system development for turbine operation based on pitch and speed control. In this case, it is necessary to find a compromise between the simulation model accuracy and the control loop computational speed. The Blade Element Momentum (BEM) approach is then used for the turbine modeling. As the developed simulation model is intended to be used as a sizing and site evaluation tool for current turbine installations, it has been applied to evaluate the extractable power from the Raz de Sein (Brittany, France). Indeed, tidal current data from the Raz de Sein are used to run the simulation model over various flow regimes and yield the power capture with time

Impact of carbonation on unsaturated water transport properties of cement-based materials

International audienceIn unsaturated conditions, the durability of concrete structures is strongly dependent on the evolution of the amount of free water within concrete porosity. Reliable durability assessment of concrete structures in relation to their environment thus requires accurate unsaturated water transport description as well as reliable input data. The effect of carbonation on water transport remains poorly studied and data are lacking. It was then the purpose of this article to acquire all the data needed to describe unsaturated water transport in carbonated cementitious materials (porosity, water retention and unsaturated permeability). Four hardened pastes made with four different binders were carbonated at 3% CO2 to ensure representativeness with natural carbonation. Beyond the modification of the water retention curve and porosity clogging, significant microcracking due to carbonation shrinkage was observed. The consequence on permeability highlighted a competition between porosity clogging and microcracking that was dependent on the initial mineralogical composition

The Ẓufār painted Inscriptions in Oman: Epigraphy and New Technologies

We propose here a standardised protocol to record and trace painted inscriptions, in order to minimise personal biases. DStretch®, a plug-in for ImageJ© specifically designed for the enhancement of digital images, allows reproducible and operator-independent results, improving objectivity in documenting rock art sites in remote and harsh environments. We provide two examples of its application to Ẓufār sites in Oman, and compare our results with previously published tracings. The improvement is so good that we envisage to apply the same method to a number of other sites, with a view to a reappraisal of the corpus of painted inscriptions of Ẓufār.Wetensch. publicati

Guides optiques infrarouges pour la détection du CO2

session affiches A7 " Instrumentation, Caractérisation et Capteurs " [A7.1]National audienceL'équipe Verres et Céramiques développe des fibres optiques originales qui sont à la base de la réalisation de capteur optique opérant dans l'infrarouge. L'intérêt et le potentiel de ces capteurs ont été démontrés dans des domaines variés, notamment en biologie et en médecine. L'objet de ce travail consiste à exploiter ce savoir faire pour réaliser des guides optiques permettant la détection et le monitoring du CO2. Des premiers résultats ont été obtenus en transmission classique entre deux fibres infrarouges. Ils ont montré qu'il est possible de détecter jusqu'à 0.5% de CO2. L'objectif actuel est d'améliorer la sensibilité de détection au dioxyde de carbone par une augmentation de la surface de contact gaz-fibre, en utilisant des fibres microstructurées. Une autre voie consiste à fabriquer des guides planaires qui nous permettent d'envisager, à terme, la réalisation de micro-composants optiques en verre de chalcogénure avec une robustesse et une compacité accrue

Severe hepatic sinusoidal obstruction associated with oxaliplatin-based chemotherapy in patients with metastatic colorectal cancer

Background: In advanced metastatic colorectal adenocarcinoma, the addition of a neo-adjuvant systemic treatment to surgery might translate into a survival advantage, although this is yet to be confirmed by ongoing randomized trials. The objective of this study was to assess the effects of preoperative systemic chemotherapy on the morphology of non-tumoral liver. Patients and methods: A large series of surgically resected liver metastases (n = 153) was selected. Light microscopy, electron microscopy, and immunohistochemistry using antibodies against endothelial cells (CD31) and hepatic stellate cells (α-SM actin, CRBP-1) were performed to identify sinusoidal wall integrity. Results: We found that 44 (51%) of the 87 post-chemotherapic liver resection specimens had sinusoidal dilatation and hemorrhage, related to rupture of the sinusoidal barrier. In contrast, the 66 livers treated by surgery alone remained normal. In 21 out of the 44 post-chemotherapy patients (48%), perisinusoidal and veno-occlusive fibrosis also developed. Sinusoidal injury persisted several months after end of chemotherapy, and fibrosis may progress. Development of lesions was strongly correlated to the use of oxaliplatin; 34 out of 43 patients (78%) treated with this drug showed striking sinusoidal alterations. Conclusions: Systemic neo-adjuvant chemotherapy in metastatic colorectal cancer frequently causes morphological lesions involving hepatic microvasculature. Sinusoidal obstruction, complicated by perisinusoidal fibrosis and veno-occlusive lesion of the non-tumoral liver revealed by this study, should be included in the list of the adverse side-effects of colorectal systemic chemotherapy, in particular related to the use of oxaliplati

First Principles NMR Study of Fluorapatite under Pressure

NMR is the technique of election to probe the local properties of materials. Herein we present the results of density functional theory (DFT) \textit{ab initio} calculations of the NMR parameters for fluorapatite (FAp), a calcium orthophosphate mineral belonging to the apatite family, by using the GIPAW method [Pickard and Mauri, 2001]. Understanding the local effects of pressure on apatites is particularly relevant because of their important role in many solid state and biomedical applications. Apatites are open structures, which can undergo complex anisotropic deformations, and the response of NMR can elucidate the microscopic changes induced by an applied pressure. The computed NMR parameters proved to be in good agreement with the available experimental data. The structural evaluation of the material behavior under hydrostatic pressure (from --5 to +100 kbar) indicated a shrinkage of the diameter of the apatitic channel, and a strong correlation between NMR shielding and pressure, proving the sensitivity of this technique to even small changes in the chemical environment around the nuclei. This theoretical approach allows the exploration of all the different nuclei composing the material, thus providing a very useful guidance in the interpretation of experimental results, particularly valuable for the more challenging nuclei such as $^{43}$Ca and $^{17}$O.Comment: 8 pages, 2 figures, 3 table