On surface electropolishing for the development of metallic stents

Les maladies cardiovasculaires sont responsables d'environ le tiers de tous les cas de décès au Canada. L'une des solutions utilisées pour résoudre ce problème consiste à utiliser un dispositif métallique constitué d'un maillage ayant une forme d’un filet et appelé stent. Les stents sont de petits dispositifs implantés dans des vaisseaux sanguins rétrécis pour rétablir la circulation sanguine et éviter une crise cardiaque ou un accident vasculaire cérébral et pour traiter les anévrismes du cerveau. Un contrôle précis de la surface de ces stents est nécessaire pour assurer la compatibilité de l'alliage choisi avec le milieu biologique dont il va être en contact avec. Les stents métalliques doivent satisfaire à des conditions précises définies en fonction de leur application finale. Ils doivent respecter des exigences strictes en termes de propriétés mécaniques, d'interaction électrochimique (corrosion) et de cytocompatibilité. Les alliages suivants sont traditionnellement utilisés dans les applications biomédicales et plus précisément pour les applications cardiovasculaires: l'alliage AISI316L est considéré comme une référence dans ce domaine, mais l'alliage L605, un alliage à base de Cobalt, prend de plus en plus d'importance grâce à ses propriétés mécaniques élevées (haute ductilité et haute résistance à la traction) et résistance élevée à la corrosion. L'utilisation d'alliages de titane est la nouvelle frontière pour les biomatériaux dans les applications cardiovasculaires, il est considéré comme un nouveau candidat potentiel pour les stents cardiovasculaires. Les alliages de titane présentent une combinaison unique de haute résistance et de grande ductilité (résistance à la traction et déformation uniforme supérieures à 1000 MPa et 30% respectivement). L’électropolissage est une étape de prétraitement appliquée à ces alliages métalliques pour obtenir des surfaces chimiquement homogènes, recouvertes d'une couche d'oxyde uniforme et amorphe, généralement de rugosité très lisse. Ce processus permet non seulement de contrôler les propriétés physiques de la surface, mais également celles chimiques. Le processus d'électropolissage comporte certaines variables, telles que le courant, la tension, la solution électrolytique et la température de l'électrolyte. En les contrôlant, il est possible de comprendre et d'améliorer les propriétés de la surface. Le but de ce projet est d’étudier les effets des différents variables d’électropolissage (courant, tension, solution électrolytique) sur les caractéristiques / propriétés de surface (morphologie, composition chimique et mouillabilité) des alliages utilisés pour la fabrication de stents.Cardiovascular diseases (CVD) are responsible for about one-third of all death cases in Canada. One of the solutions used to solve this problem is using a metallic device made of a mesh and called a stent. Stents are small devices that are implanted in narrowed blood vessels to restore blood flow and to avoid a heart attack or stroke and to treat brain aneurysms. An accurate surface control is needed to assure the cytocompatibility of the chosen alloy with its biologic environment. Metallic stents must satisfy precise conditions defined according to their final application. They need to respect strict requirements, in terms of mechanical properties, electrochemical interaction (corrosion) and cytocompatibility. The following alloys are traditionally used in biomedical applications and more precisely for cardiovascular applications: the alloy AISI316L is considered a reference in this field, but the alloy L605, a Co-based material, is gaining more and more importance, due to its high mechanical properties (high ductility and high ultimate tensile strength) and high corrosion resistance. The use of Titanium alloys is the new frontier for biomaterials in cardiovascular applications, it is considered as a new potential candidate for cardiovascular stents. Titanium alloys, shows a unique combination of high strength and high ductility (ultimate tensile strength and uniform deformation higher than 1000 MPa and 30%, respectively). Electropolishing is a pre-treatment step applied to these alloys to obtain chemically homogeneous surfaces, covered with a uniform and amorphous oxide layer, generally with a very smooth roughness. This process not only makes it possible to control the physical properties of the surface, but also the chemical ones. The electropolishing process has some changeable variables, such as current, voltage, electrolytic solution and temperature of electrolyte. By controlling them, it is possible to understand and improve the surface properties. This work is aimed at studying the effects of electropolishing changeable variables (current, voltage, electrolytic solution) on surface characteristics/properties (morphology, chemical composition and wettability) of those alloys used for the manufacture of stents

Investigating technologies and techniques for flood monitoring and detecting

The need for a flood alerting and forecasting system is becoming ever more critical, especially given the effects of increasing severe weather over the last ten years. Flash floods, particularly, are deadly because of the short time period in which they develop, as well as the difficulty in predicting their occurrence. Consequently, floods have become recognized as the most fatal natural disaster in the United States. Recent developments in artificial intelligence (AI) and machine Learning (ML) algorithms are promising for overcoming related issues by providing data driven solutions for more reliable and efficient forecasting. The study reported in this thesis first explored market-available, industrial-based flood monitoring and alerting systems developed and deployed by several private companies and federal agencies. Weather conditions that accompany flash flood events were then analyzed as first steps in building an ML flood forecasting model. Weather attributes were analyzed both statistically and visually to uncover their importance for modeling. Subsequently, common ML classification techniques were compared with a variety of neural network architectures to determine the best model for forecasting flooding. Modeling results showed that a one-hour forecast XGBoost ensemble model outperformed others, with an 85% accuracy for forecasting a flood event and a 92% AUC score. This thesis introduces a novel approach for evaluating non-contact flood detection technologies. An open-channel testbed was designed and constructed, and several non-contact water level and velocity technologies were evaluated under various conditions. Results showed that market available radar technology delivered the most accurate readings with an MAE score of approximately 2 cm and MAE of 0.1 m/s

Platelets in the Newborn

Platelets were first described in the mid-nineteenth century. Since then, their roles were identified in hemostasis and thrombosis, inflammation, leukocyte interactions, angiogenesis, and cancer growth. But there is little information about such platelet functions in the newborn. Several studies highlighted some platelet differences between newborns and adults. Yet, in spite of these differences, healthy newborns appear to be adequately protected. A number of factors, however, were reported to negatively affect neonatal platelets. These include maternal hypertensive disorders or infections, neonatal asphyxia or respiratory distress, therapies such as ampicillin or indomethacin, and treatment modalities such as ventilators, nitric oxide, or extracorporeal membrane oxygenation (ECMO). Their effects on newborn platelets are usually transitory, lasting from several hours to a few days or weeks. If these effects are well characterized, they could serve as reporters for diagnosis and monitoring during therapy. Careful studies of neonatal platelets are needed to improve the understanding of basic physiology and pathophysiology in this cohort and to identify possible targets for intervention and therapy

Contribution a l'etude de la diffusion multiple des electrons dans des objets polycristallins : (energie comprise entre 0,3 et 3 MeV)

SIGLECNRS T Bordereau / INIST-CNRS - Institut de l'Information Scientifique et TechniqueFRFranc

Etude de la transmission et de la rétrodiffusion d'électrons d'énergie 0,05 à 3 MeV dans le domaine de la diffusion multiple

A knowledge of the motion of electrons in matter is of fundamental importance, particularly in scanning microscopy, in microanalysis and in space physics. We present our experimental results for monoenergetic electrons incident normal to polycrystalline targets under multiple scattering conditions. The measurement give information concerning the transmission and backscattering coefficients, the angular distributions and the path-length inside the specimen. We give analytic expressions that describe the experimental results accurately over a very wide range of energies (0.05-3 MeV).Le comportement des électrons dans la matière est d'un intérêt fondamental, notamment en microscopie à balayage, en microanalyse et en physique spatiale. Nous présentons dans cet article l'ensemble de nos résultats expérimentaux dans le domaine de la diffusion multiple pour un faisceau d'électrons monocinétiques tombant normalement sur des cibles polycristallines. Les mesures sont relatives aux coefficients de transmission et de rétrodiffusion, aux distributions angulaires, ainsi qu'au parcours entier des électrons dans la matière. Nous donnons des relations analytiques qui permettent de retrouver avec précision les résultats expérimentaux dans un vaste domaine énergétique (0,05 à 3 MeV)

Flood Monitoring and Prediction System Development [cover title]

ODOT SPR Item Number 2314The first half of this report details the design of a flooding emulation system to evaluate LiDAR-, radar-, and ultrasonic-based devices for monitoring water level rise and measure water flow speed. The second half of the report describes the incorporation of NOAA data with data collected at ODOT weather station to predict the potential of flooding