Non-contact, single-sided access ultrasonic guided waves for the assessment of materials mechanical properties

Abstract: Research about material characterization without contact has been carried out by many authors using immersion or laser-based ultrasonic techniques. Immersion techniques however imply that the material is not water sensitive and that the sample fits within the immersion tank. Therefore, it is important to develop a characterization process that is suitable for all types of materials, and ideally not requiring access to both sides of the tested specimen, as this is often not possible in industrial context.Résumé de la communication présentée lors du congrès international tenu conjointement par Canadian Society for Mechanical Engineering (CSME) et Computational Fluid Dynamics Society of Canada (CFD Canada), à l’Université de Sherbrooke (Québec), du 28 au 31 mai 2023

Mapping the energy and diffusion landscapes of membrane proteins at the cell surface using high-density single-molecule imaging and Bayesian inference: application to the multi-scale dynamics of glycine receptors in the neuronal membrane

Protein mobility is conventionally analyzed in terms of an effective diffusion. Yet, this description often fails to properly distinguish and evaluate the physical parameters (such as the membrane friction) and the biochemical interactions governing the motion. Here, we present a method combining high-density single-molecule imaging and statistical inference to separately map the diffusion and energy landscapes of membrane proteins across the cell surface at ~100 nm resolution (with acquisition of a few minutes). When applying these analytical tools to glycine neurotransmitter receptors (GlyRs) at inhibitory synapses, we find that gephyrin scaffolds act as shallow energy traps (~3 kBT) for GlyRs, with a depth modulated by the biochemical properties of the receptor-gephyrin interaction loop. In turn, the inferred maps can be used to simulate the dynamics of proteins in the membrane, from the level of individual receptors to that of the population, and thereby, to model the stochastic fluctuations of physiological parameters (such as the number of receptors at synapses). Overall, our approach provides a powerful and comprehensive framework with which to analyze biochemical interactions in living cells and to decipher the multi-scale dynamics of biomolecules in complex cellular environments.Comment: 23 pages, 4 figure

Influence of a pulsed laser regime on surface finish induced by thedirect metal deposition process on a Ti64 alloy

tThe direct metal deposition (DMD) laser technique is a free-form metal deposition process, which allowsgenerating a prototype or small series of near net-shape structures. Despite numerous advantages, oneof the most critical issues of the technique is that produced pieces have a deleterious surface finish whichrequires post machining steps. Following recent investigations where the use of laser pulses instead of acontinuous regime was successful to obtain smoother DMD structures, this paper relates investigationson the influence of a pulsed laser regime on the surface finish induced by DMD on a widely used titaniumalloy (Ti64). Findings confirm that using high mean powers improves surface finish but also indicate aspecific effect of the laser operating mode: using a quasi-continuous pulsed mode instead of fully-cw laserheating is an efficient way for surface finish improvement. For similar average powers, the use of a pulsedmode with large duty cycles is clearly shown to provide smoothening effects. The formation of larger andstable melt pools having less pronounced lateral curvatures, and the reduction of thermal gradients andMarangoni flow in the external side of the fusion zone were assumed to be the main reasons for surfacefinish improvement. Additional results indicate that combining the benefits from a pulsed regime and auniform laser irradiation does not provide further reduction of surface roughness

Influence of various process conditions on surface finishes induced by the direct metal deposition laser technique on a Ti–6Al–4V alloy

The direct metal deposition (DMD) with laser is a free-form metal deposition process for manufacturing dense pieces, which allows generating a prototype or small series of near net-shape structures. One of the most critical issues is that produced pieces have a deleterious surface finish which systematically requires post machining steps. This problem has never been fully addressed before. The present work describes investigations on the DMD process, using an Yb-YAG disk laser, and a widely used titanium alloy (Ti–6Al–4V) to understand the influence of the main process parameters on the surface finish quality. The focus of our work was: (1) to understand the physical mechanisms responsible for deleterious surface finishes, (2) to propose different experimental solutions for improving surface finish. In order to understand the physical mechanisms responsible for deleterious surface finishes, we have carried out: (1) a precise characterization of the laser beam and the powder stream; (2) a large number of multi-layered walls using different process parameters (P(W), V(m/min), Dm (g/min), Gaussian or uniform beam distribution); (3) a real time fast camera analysis of melt pool dynamics and melt-pool – powder stream coupling; (4) a characterization of wall morphologies versus process parameters using 2D and 3D profilometry. The results confirm that surface degradation depends on two distinct aspects: the sticking of nonmelted or partially melted particles on the free surfaces, and the formation of menisci with more or less pronounced curvature radii. Among other aspects, a reduction of layer thickness and an increase of melt-pool volumes to favor re-melting processes are shown to have a beneficial effect on roughness parameters. Last, a simple analytical model was proposed to correlate melt-pool geometries to resulting surface finishes

Seismic and aseismic deformation along the East African Rift System from a reanalysis of the GPS velocity field of Africa

International audienceThe improvement of the geodetic coverage within the African Plate over the last decade together with an extended GPS position time-series allows improved accuracy in determining the velocity field than prior geodetic studies. Using this new velocity field of the whole African continent, the best model proposed here remains consistent with previous studies including the existence of two small plates along the East African Rift System (EARS, Victoria and Rovuma).We focus specifically on the velocities along this plate boundary by estimating both the geodetic and the seismic moment rate.Whereas we use a scalar form of the Kostrov relation to calculate the geodetic moment rate, the seismic moment rate is obtained by integrating the cumulative truncated Gutenberg-Richter earthquake distribution of local events in the 39-yr-long worldwide catalogue, using a maximum likelihood method. This statistical method allows us to take into account the probable incompleteness of the existing catalogue and to assume the seismic moment rate calculated from this short catalogue to be representative of the long-term seismic deformation. The comparison of geodetic and seismic energy release sheds light on the variations of mechanical behaviour related to intracontinental extension along the EARS. The southward increase, observed along the rift, of the proportion of geodetic moment seismically accommodated suggests a significant control of the thermal structure associated with different states of rifting evolution

Conception d'un BioMicroRobot autonome

Cet article présente les avancements technologiques pour la conception théorique et pratique d'une architecture élémentaire et minimale d'un BioMicroRobot (BMR) hexapode autonome. L'autonomie minimale dépend du système de gestion des événements globaux, régionaux et locaux. Cette gestion est avant tout perçue par deux types de récepteurs : les extérocepteurs internes (vision) et ceux externes (système de repérage et de détection de l'environnement). La planification des événements dans un environnement confiné repose sur un système complexe qui incorpore un microcontrôleur d'architecture RISC, un système de propulsion bio-inspiré indépendant qui agit comme un pilote, un système d'alimentation et de communication et finalement un détecteur de proximité qui agit à titre d'extérocepteurs internes. L'avant dernière section présente un procédé de fabrication de la structure complète du BMR qui peut supporter une hiérarchie hybride à deux niveaux avec la logique floue

Discerning differences: Ion beam analysis of ancient faience from Naukratis and Rhodes

Faience technology was known in Egypt since the Predynastic Period and practiced for a period also in Bronze Age Greece, but, having been lost, was reintroduced to the Greek world only in the first half of the first millennium BC. The Greek island of Rhodes and the Greek-Egyptian trade harbour of Naukratis in the Nile Delta are suspected to be key centres of early Greek-style faience production, exporting amulets and vessels across the Mediterranean region. Yet the nature and scale of their production and their role in technology transfer, vis-à-vis Egyptian and Levantine/Phoenician production, remain little understood. The main aim of this study was to discover whether it is possible to define chemical characteristics for the faience produced and found at Naukratis, and to use this data to differentiate between artefacts produced here and elsewhere.A programme of ion beam (PIXE and PIGE) analysis was conducted under the CHARISMA transnational access scheme, known to be a suitable tool for studying ancient vitreous artefacts as it provides a non-destructive means of obtaining precise and accurate quantitative compositional data. Both the internal body of damaged objects as well as the outer glaze layer were analysed, of which only the latter are discussed here. The results of this study indicate that the faience found at both Naukratis and on Rhodes is compositionally similar. However, some small differences were found in the raw materials used in its production which may help us to better characterise the production of different faience manufacturing centres.La technique de la faïence, connue en Égypte depuis la période prédynastique et utilisée également pendant un certain temps en Grèce à l’âge du Bronze, s’est perdue ensuite. Elle ne fut réintroduite dans le monde grec que vers la première moitié du Ier millénaire av. J.-C. On pense que l’île grecque de Rhodes et le port marchand gréco-égyptien de Naucratis dans le delta du Nil furent de grands foyers de production de faïences, exportant des amulettes et des vases dans tout le pourtour méditerranéen. Cependant, la nature et l’ampleur de leur production restent mal connues, de même que leur rôle dans la diffusion des techniques de fabrication en Égypte et au Levant/Phénicie. Cette recherche avait pour principal objectif de savoir s’il était possible de déterminer les caractéristiques chimiques des faïences fabriquées et découvertes à Naucratis, afin de mieux discerner les différences entre les objets produits sur ce site et ailleurs.Nous avons pu conduire des analyses par faisceaux d’ions (méthodes PIXE et PIGE) dans le cadre du programme européen CHARISMA d’accès transnational, offrant un outil adapté à l’étude des objets antiques vitrifiés, car c’est un moyen non-destructeur de recueillir des données quantitatives précises et fiables sur la composition des matériaux. Nous avons analysé aussi bien la pâte, à l’intérieur d’objets abîmés, que la glaçure extérieure, et c’est cette dernière qui est décrite ici. Les résultats de notre étude font apparaître une composition similaire pour les faïences découvertes à Naucratis et à Rhodes. Quelques petites variations découvertes dans les matières premières employées pourraient faciliter la caractérisation des faïences fabriquées dans les différents foyers de production

Angiotensin II Infusion Induces Marked Diaphragmatic Skeletal Muscle Atrophy

Advanced congestive heart failure (CHF) and chronic kidney disease (CKD) are characterized by increased angiotensin II (Ang II) levels and are often accompanied by significant skeletal muscle wasting that negatively impacts mortality and morbidity. Both CHF and CKD patients have respiratory muscle dysfunction, however the potential effects of Ang II on respiratory muscles are unknown. We investigated the effects of Ang II on diaphragm muscle in FVB mice. Ang II induced significant diaphragm muscle wasting (18.7±1.6% decrease in weight at one week) and reduction in fiber cross-sectional area. Expression of the E3 ubiquitin ligases atrogin-1 and muscle ring finger-1 (MuRF-1) and of the pro-apoptotic factor BAX was increased after 24 h of Ang II infusion (4.4±0.3 fold, 3.1±0.5 fold and 1.6±0.2 fold, respectively, compared to sham infused control) suggesting increased muscle protein degradation and apoptosis. In Ang II infused animals, there was significant regeneration of injured diaphragm muscles at 7 days as indicated by an increase in the number of myofibers with centralized nuclei and high expression of embryonic myosin heavy chain (E-MyHC, 11.2±3.3 fold increase) and of the satellite cell marker M-cadherin (59.2±22.2% increase). Furthermore, there was an increase in expression of insulin-like growth factor-1 (IGF-1, 1.8±0.3 fold increase) in Ang II infused diaphragm, suggesting the involvement of IGF-1 in diaphragm muscle regeneration. Bone-marrow transplantation experiments indicated that although there was recruitment of bone-marrow derived cells to the injured diaphragm in Ang II infused mice (267.0±74.6% increase), those cells did not express markers of muscle stem cells or regenerating myofibers. In conclusion, Ang II causes marked diaphragm muscle wasting, which may be important for the pathophysiology of respiratory muscle dysfunction and cachexia in conditions such as CHF and CKD

Stratégies innovatrices pour le contrôle actif vibratoire du rayonnement acoustique de structures planes

Un ensemble de stratégies est présenté dans le cadre de cette étude afin de permettre le contrôle actif vibratoire du rayonnement acoustique de structures planes à partir de mesures de déformation. L'utilisation de capteurs à fibres optiques de type Fabry-Perot est validée en contrôle actif. De tels capteurs et de telles stratégies s'adaptent bien au développement de matériaux intelligents puisqu'ils permettent l'intégration des capteurs et actionneurs à l'intérieur même des structures. Deux approches sont définies afin d'évaluer la puissance acoustique rayonnée par des structures planes à partir de mesures de déformation. La première approche est basée sur le calcul de la puissance acoustique effective, soit par la reconstruction du champ de déplacement à partir du champ de déformation ou soit à partir d'une reformulation de l'intégrale de rayonnement. La seconde approche optimise le calcul de la première en utilisant une transformée en ondelettes du champ de déplacement pour estimer la puissance acoustique rayonnée. Ces approches sont validées par simulation numérique et il est montré qu'une bonne représentation de la puissance est obtenue lorsqu'un nombre suffisant de capteurs est utilisé. Les approches proposées sont mises en forme dans un schéma de contrôle actif optimal puis validées par simulation numérique. En plus de révéler de bonnes performances de contrôle, ces simulations permettent d'évaluer l'effet de plusieurs paramètres sur les stratégies de contrôle. La validation expérimentale des approches est réalisée à l'aide d'une poutre simplement supportée et instrumentée de capteurs et d'actionneurs. Un système de contrôle actif adapté aux stratégies et aux capteurs est mis en oeuvre. L'utilisation des capteurs optiques est alors validée dans le cadre de ces stratégies. Les résultats de contrôle permettent d'identifier les mécanismes des différentes approches et de comparer les performances du contrôleur en temps réel avec celles obtenues en contrôle optimal. Des limitations apparaissent alors dans la mise en oeuvre des stratégies. Il est montré que les stratégies d'optimisation par l'estimation de la puissance acoustique rayonnée fournissent de bonnes performances tout en permettant une adaptation plus rapide de l'algorithme de contrôle aux statistiques variables du signal