Études numériques de la diffusion couplée d'oxygène, glucose et d'acide lactique dans le disque intervertébral

Revue de la littérature -- Anatomie du disque intervertebral -- Objectifs et description de la thèse -- Analysis of non linear coupled diffusion of oxygen and lactic acid in intervertebral discs -- Computation of coupled diffusion of oxygen, glucose and lactic acid in an intervertebral disc -- Investigation of solute concentrations in a 3D model intervertebral disc -- Discussion générale

Leaping the hurdles in developing regenerative treatments for the intervertebral disc from preclinical to clinical

Chronic back and neck pain is a prevalent disability, often caused by degeneration of the intervertebral disc. Because current treatments for this condition are less than satisfactory, a great deal of effort is being applied to develop new solutions, including regenerative strategies. However, the path from initial promising idea to clinical use is frought with many hurdles to overcome. Many of the keys to success are not necessarily linked to science or innovation. Successful translation to clinic will also rely on planning and awareness of the hurdles. It will be essential to plan your entire path to clinic from the outset and to do this with a multidisciplinary team. Take advise early on regulatory aspects and focus on generating the proof required to satisfy regulatory approval. Scientific demonstration and societal benefits are important, but translation cannot occur without involving commercial parties, which are instrumental to support expensive clinical trials. This will only be possible when intellectual property can be protected sufficiently to support a business model. In this manner, commercial, societal, medical, and scientific partners can work together to ultimately improve patient health. Based on literature surveys and experiences of the co‐authors, this opinion paper presents this pathway, highlights the most prominent issues and hopefully will aid in your own transational endeavors

Representing Imprecise Time Intervals in OWL 2

International audienceRepresenting and reasoning on imprecise temporal information is a common requirement in the field of Semantic Web. Many works exist to represent and reason on precise temporal information in OWL; however, to the best of our knowledge, none of these works is devoted to imprecise temporal time intervals. To address this problem, we propose two approaches: a crisp-based approach and a fuzzy-based approach. (1) The first approach uses only crisp standards and tools and is modelled in OWL 2. We extend the 4D-fluents model, with new crisp components, to represent imprecise time intervals and qualitative crisp interval relations. Then, we extend the Allen’s interval algebra to compare imprecise time intervals in a crisp way and inferences are done via a set of SWRL rules. (2) The second approach is based on fuzzy sets theory and fuzzy tools and is modelled in Fuzzy-OWL 2. The 4D-fluents approach is extended, with new fuzzy components, in order to represent imprecise time intervals and qualitative fuzzy interval relations. The Allen’s interval algebra is extended in order to compare imprecise time intervals in a fuzzy gradual personalized way. Inferences are done via a set of Mamdani IF-THEN rules

Desalination by Membrane Distillation

At present, around 25% of water desalination processes are based on distillation. Similar to classical distillation, membrane distillation is a phased-change process in which a hydrophobic membrane separates two phases. Membrane distillation is considered an emerging player in the desalination, food processing and water treatment market. Due to its high salt rejection, less fouling propensity, operating at moderate temperature and pressure, membrane distillation is considered as a future sustainable desalination technology. The distillation process is quite well known in desalination. However, membrane distillation emerged a few decades ago, and a thorough understanding is needed to adapt this technique in the near future. This review chapter introduces the classical distillation and membrane distillation as an emerging technology in the desalination arena. Heat and mass transfer and thermodynamics in membrane distillation, characteristics of the performance metrics of membrane distillation are also described. Finally, the performance evaluation of MD is presented. The possibility of using low-grade heat in membrane distillation allows it to integrate directly to solar energy and industrial waste heat

Fabrication of flexible silicon nanowires by self-assembled metal assisted chemical etching for surface enhanced Raman spectroscopy

A homogenous array of flexible gold coated silicon nanowires was fabricated by the combination of nano spheres lithography and metal assisted chemical etching to obtain highly effective Surface Enhanced Raman Spectroscopy (SERS) substrates. 3D nanostructures with different aspect ratios and well-defined geometries were produced by adjusting the fabrication parameters in order to select the best configuration for SERS analysis. The optimum flexible nanowires with an aspect ratio of 1 : 10 can self-close driven by the microcapillary force under exposure to liquid and trap the molecules at their metallic coated ``fingertips'', thus generating hot spots with ultrahigh field enhancement. The performance of these SERS substrates was evaluated using melamine as the analyte probe with various concentrations from the millimolar to the picomolar range. Flexible gold coated SiNWs demonstrated high uniformity of the Raman signal over large area with a variability of only 10% and high sensitivity with a limit of detection of 3.20 x 10(-7) mg L-1 (picomolar) which promotes its application in several fields such food safety, diagnostic and pharmaceutical. Such an approach represents a low-cost alternative to the traditional nanofabrication processes to obtain well ordered silicon nanostructures, offering multiple degrees of freedom in the design of different geometries such as inter-wire distance, density of the wires on the surface as well as their length, thus showing a great potential for the fabrication of SERS substrates

The Effect of Sustained Compression on Oxygen Metabolic Transport in the Intervertebral Disc Decreases with Degenerative Changes

Intervertebral disc metabolic transport is essential to the functional spine and provides the cells with the nutrients necessary to tissue maintenance. Disc degenerative changes alter the tissue mechanics, but interactions between mechanical loading and disc transport are still an open issue. A poromechanical finite element model of the human disc was coupled with oxygen and lactate transport models. Deformations and fluid flow were linked to transport predictions by including strain-dependent diffusion and advection. The two solute transport models were also coupled to account for cell metabolism. With this approach, the relevance of metabolic and mechano-transport couplings were assessed in the healthy disc under loading-recovery daily compression. Disc height, cell density and material degenerative changes were parametrically simulated to study their influence on the calculated solute concentrations. The effects of load frequency and amplitude were also studied in the healthy disc by considering short periods of cyclic compression. Results indicate that external loads influence the oxygen and lactate regional distributions within the disc when large volume changes modify diffusion distances and diffusivities, especially when healthy disc properties are simulated. Advection was negligible under both sustained and cyclic compression. Simulating degeneration, mechanical changes inhibited the mechanical effect on transport while disc height, fluid content, nucleus pressure and overall cell density reductions affected significantly transport predictions. For the healthy disc, nutrient concentration patterns depended mostly on the time of sustained compression and recovery. The relevant effect of cell density on the metabolic transport indicates the disturbance of cell number as a possible onset for disc degeneration via alteration of the metabolic balance. Results also suggest that healthy disc properties have a positive effect of loading on metabolic transport. Such relation, relevant to the maintenance of the tissue functional composition, would therefore link disc function with disc nutrition

Boundary element simulation of void formation in fibrous reinforcements based on the Stokes–Darcy formulation

The Boundary Element Method (BEM) is applied for the solution of the problem of void formation in fibrous reinforcements used in composite materials. Stokes and Darcy formulations for the channel and porous medium are considered, including three main differences with most of the previous models reported in the literature that deal with this type of problem: the consideration of the general form of the Beavers–Joseph slip condition instead of the Saffman simplification, the calculation of the flow direction-dependent capillary pressure in the porous medium without experimental factors and the consideration of the surface traction effects in the channel fluid front. An analytical solution of a simple problem is presented to assess the accuracy and convergence of the BEM solution, obtaining good agreement between the results. In order to evaluate the main differences between the Stokes–Darcy formulation and a dual-scale permeability Darcy approach, a problem of constant pressure filling is considered, showing significant differences in the evolution of the flow field as: filling times, shape of the moving fluid front and size and shape of the formed voids. Finally, several simulations at constant flow rate are carried out to analyze the influence of the capillary number, tow porosity, width of transverse tow, fluid penetrability and RUC porosity on the size, shape and location of the void. In general, the void size and shape are influenced by the considered parameters, but the void location is not

Génération automatique des requêtes de médiation dans un environnement hétérogène

Nowadays, mediation systems are widely used. However, their implementation raises several problems, especially the definition of mediation queries when there is a high number of sources, and an important amount of metadata. The heterogeneity of the data sources makes this problem even more complex.We propose in this thesis an approach to automatically generate the mediation queries in a relational context. Our algorithm produces a set of possible mediation queries given the description of a set of heterogeneous and distributed data sources. We have developed a tool to automatically generate mediation queries in a heterogeneous context. We provide some performance evaluations to test the scalability of our tool, and to show its usability for systems of different size.Les systèmes de médiation sont aujourd'hui largement développés et connus. Cependant, leur mise en œuvre pose un certain nombre de problèmes, en particulier la définition de requêtes de médiation en présence d'un grand nombre de sources de données, et d'un volume important de méta-données les décrivant. Ce problème est d'autant plus complexe que les sources sont hétérogènes.Face a cette problématique, nous proposons dans cette thèse pour le contexte relationnel, une approche de génération automatique de requêtes de médiation. A partir de la description d'un ensemble de sources de données distribuées et hétérogènes et de méta-données, notre algorithme produit un ensemble de requêtes de médiation possibles. Nous avons développé un outil qui permet de générer automatiquement des requêtes de médiation dans un environnement hétérogène. Notre objectif principal étant de fournir à l'utilisateur un outil adapté aux petits et grands systèmes, nous avons réalisé une série de tests d'évaluation des performances pour mesurer son passage à l'échelle. Ces tests montrent la faisabilité de notre approche

Préservation du patrimoine colonial habitat du 19ème 20ème siècle : présentation d'un guide technique de réhabilitation

181 f. : ill. ; 30 cm (+CD-Rom)Le patrimoine architectural du 19éme et 20éme siècle dit colonial, mal connu et non reconnu, occupe aujourd'hui une place importante dans le parc national du logement. Il est clair que sa mise à l'écart ne pourra que renforcer sa dégradation et par conséquent la perte des valeurs qu’il représente. Il est important de souligner que l'ensemble de ce parc immobilier, représentant un patrimoine d'une valeur inestimable, se trouve actuellement dans un état de dégradation alarmant nécessitant une intervention (réhabilitation, restauration...) urgente de la part des pouvoirs publics. Cet état vétuste de ce cadre bâti est essentiellement dû à l'action conjuguée de plusieurs facteurs parmi lesquels on peut citer l'action du milieu environnemental, les secousses sismiques, l'absence d'entretien, les contraintes sociales (densité d'occupation), l'inexistence d'instruments adaptés pour mener des opérations de réhabilitation et de conservation, entre autre un guide technique de réhabilitation. Les quelques travaux d'entretient, menés jusque là, se concentrent généralement sur des opérations de badigeonnages des façades dissimulant à cet effet les véritables pathologies que connaît ce patrimoine. L’objectif principal de notre travail de recherche consiste à présenter un guide technique de réhabilitation du parc bâti (habitat) de la période coloniale du 19ème 20ème. Intervenir sur un édifice patrimonial revient impérativement aux étapes du diagnostic et de l’intervention, la connaissance et la maitrise des différentes typologies est alors principalement nécessaire. Le repérage des différentes typologies et pathologies s’est effectué non seulement sur la base d’un travail documentaire, qui s’est basé sur la revue Chantier et différents guides de réhabilitation, mais essentiellement sur un travail de terrain, à travers les différents sites où des opérations de réhabilitation, de restauration ou de démolition ont été entreprises. La maitrise des typologies et pathologies s’avère primordiale pour la présentation de remèdes et de solutions de réhabilitation. Mots- clés : Habitat, patrimoine architectural, colonial, typologies structurelles, pathologies, diagnostic, réhabilitation, guide technique