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National audience; Knowledge of human’s force capacities enables the design of physical Human-Robot Interaction (pHRI) workspaces. As measuring force capacities for all postures is time consuming, predicting force capacities from a subset of measurements performed in a limited number of postures is crucial. The force capacities can be described as a convex polytope by means of a personalized musculoskeletal (MSK) model (Skuric et al. 2022). However, the tuning of a MSK model is difficult due to the high number of parameters. Thanks to its constraint-free nature on the optimization function, a genetic algorithm is implemented to find a MSK model parameter set, which fits and predicts force polytopes.

International audience; On-chip study of blood flow has emerged as a powerful tool to assess the contribution of each component of blood to its overall function. Blood has indeed many functions, from gas and nutrient transport to immune response and thermal regulation. Red blood cells play a central role therein, in particular through their specific mechanical properties, that directly influence pressure regulation, oxygen perfusion, or platelet and white cells segregation towards endothelial walls. As the bloom of in-vitro studies has led to the apparition of various storage and sample preparation protocols, we address the question of the robustness of the results involving cell mechanical behavior against this diversity. The effects of three conservation media (EDTA, citrate and glucose-albumin-sodium-phosphate) and storage time on the red blood cell mechanical behavior are assessed under different flow conditions: cell deformability by ektacytometry, shape recovery of cells flowing out of a microfluidic constriction, and cell flipping dynamics under shear flow. The impact of buffer solutions (phosphate-buffered saline and density-matched suspension using iodixanol/Optiprep) are also studied by investigating individual cell flipping dynamics, relative viscosity of cell suspensions and cell structuration under Poiseuille flow. Our results reveal that storing blood samples up to seven days after withdrawal and suspending them in adequate density-matched buffer solutions has in most experiments a moderate effect on the overall mechanical response, with a possible rapid evolution in the first three days after sample collection. SIGNIFICANCE Blood is in intimate contact with all organs in the body, supplying oxygen, nutrients and drugs while removing waste. It carries cells involved in immune response, wound repair and tumor dissemination. Blood is easily collected, revealing the presence of disease through biomarker analysis. It is storable and transfusable. Thus, blood is the subject of many in-vitro studies for research and medical purposes. Guidelines associated to sample preparation or storage conditions have been established, but these may affect its mechanical behavior. In this collaborative study, we provide new guidelines to minimize the impact of specific experimental requirements (e.g. density matching, blood freshness) by focusing on the single or collective motion of red blood cells in a large range of flow conditions.

International audience; Background: Mucus is known to play a pathogenic role in muco-obstructive lung diseases, but little is known about the determinants of mucus rheology. The purpose of this study is to determine which sputum components influence sputum rheology in patients with muco-obstructive lung diseases.Methods: We performed a cross sectional prospective cohort study. Spontaneous sputum was collected from consecutive patients with muco-obstructive lung diseases. Sputum rheology was assessed using the Rheomuco® rheometer (Rheonova, Grenoble); the elastic modulus G′, viscous modulus G″, and the critical stress threshold σc were recorded. Key quantitative and qualitative biological sputum components were determined by cytology, nucleic acid amplification tests and mass spectrometry.Results: 48 patients were included from January to August 2019. Among them, 10 had asthma, 14 COPD and 24 non-CF bronchiectasis (NCFB). The critical stress threshold σc predicted a sputum eosinophilia superior to 1.25% with 89.19% accuracy (AUC = 0.8762). G′ and G″ are positively correlated with MUC5AC protein concentration ((rho = 0.361; P = .013) and (rho = 0.335; P = .021), respectively). σc was positively correlated with sputum eosinophilia (rho = 0.394; P = .012), MUC5B (rho = 0.552; P < .001) and total protein (rho = 0.490; P < .001) concentrations. G′ and G″ were significantly higher in asthma patients (G’ = 14.49[7.18–25.26]Pa, G’‘ = 3.0[2.16–5.38]Pa) compared to COPD (G’ = 5.01[2.94–6.48]Pa, P = .010; G’‘ = 1.45[1.16–1.94]Pa, P = .006) and to NCFB (G’ = 4.99[1.49–10.49]Pa, P = .003; G’’ = 1.46[0.71–2.47]Pa, P = .002).Conclusion: In muco-obstructive lung diseases, rheology predicts sputum eosinophilia and is correlated with mucin concentrations, regardless of the underlying disease.Clinical trial registration: (registrar, website, and registration number), where applicable NCT04081740.

Passive acoustic monitoring can be an effective method for monitoring species, allowing the assembly of large audio datasets, removing logistical constraints in data collection and reducing anthropogenic monitoring disturbances. However, the analysis of large acoustic datasets is challenging and fully automated machine learning processes are rarely developed or implemented in ecological field studies. One of the greatest uncertainties hindering the development of these methods is spatial generalisability—can an algorithm trained on data from one place be used elsewhere?We demonstrate that heterogeneity of error across space is a problem that could go undetected using common classification accuracy metrics. Second, we develop a method to assess the extent of heterogeneity of error in a random forest classification model for six Amazonian bird species. Finally, we propose two complementary ways to reduce heterogeneity of error, by (i) accounting for it in the thresholding process and (ii) using a secondary classifier that uses contextual data.We found that using a thresholding approach that accounted for heterogeneity of precision error reduced the coefficient of variation of the precision score from a mean of 0.61 ± 0.17 (SD) to 0.41 ± 0.25 in comparison to the initial classification with threshold selection based on F-score. The use of a secondary, contextual classification with thresholding selection accounting for heterogeneity of precision reduced it further still, to 0.16 ± 0.13, and was significantly lower than the initial classification in all but one species. Mean average precision scores increased, from 0.66 ± 0.4 for the initial classification, to 0.95 ± 0.19, a significant improvement for all species.We recommend assessing—and if necessary correcting for—heterogeneity of precision error when using automated classification on acoustic data to quantify species presence as a function of an environmental, spatial or temporal predictor variable.

The Extra-Cellular-Matrix (ECM) is a complex interconnected 3D network that provides structural support for the cells and tissues and defines organ architecture key for their healthy functioning. However, the intimate mechanisms by which ECM acquire their 3D architecture are still largely unknown. In this paper, we address this question by means of a 3D individual based model of interacting fibers able to spontaneously crosslink or unlink to each other and align at the crosslinks. We show that such systems are able to spontaneously generate different types of architectures. We provide a thorough analysis of the emerging structures by an exhaustive parametric analysis and the use of appropriate visualization tools and quantifiers in 3D. The most striking result is that the emergence of ordered structures can be fully explained by a single emerging variable : the proportion of crosslinks in the network. This simple variable becomes an important putative target to control and predict the structuring of biological tissues, to suggest possible new therapeutic strategies to restore tissue functions after disruption, and to help in the development of collagen-based scaffolds for tissue engineering. Moreover, the model reveals that the emergence of architecture is a spatially homogeneous process following a unique evolutionary path, and highlights the essential role of dynamical crosslinking in tissue structuring., Comment: 28 pages, 12 figures, 2 tables

Wood characteristics of trees grown in agroforestry systems are little studied, even if growth conditions are different from conventional stands. This work aimed to determine the impact of the agroforestry system on the heartwood formation process of hybrid walnut (Juglans regia × nigra) trees, especially the resulting extractive contents. Ethanol and water extractions were successively performed on wood samples taken across the diameter of the trunk of agroforestry (AF) and forest (FC) walnut trees to get the radial distribution of the extractive contents. All the samples were analyzed by NIR-spectroscopy and NIR-hyperspectral imaging. Statistical discriminant models were developed to classify the samples from both different forestry systems, according to their chemical composition. The results indicated no significant differences between the values of extractive contents of AF and FC walnut woods, whatever the radial position. At the intra-tree scale, the quantity of extractives does not increase significantly with the radial position. However, partial least squares-discriminant analysis (PLS-DA) regression models, developed with NIRS measurements, showed that significant chemical differences exist between AF and FC trees, especially for extractives composition and lignin content. This allowed to classify wood specimens from both forestry systems. These results were confirmed by hyperspectral camera analyses.

The drying of human whole blood pools has been studied experimentally to improve the understanding of drops and pools of human whole blood. Here blood is assimilated to a complex fluid made of several bio-colloids. The blood pools were created inside a glove box under controlled conditions. We performed experiments at temperatures of 21 °C, 29 °C, and 37 °C, and relative humidity ranging from 20 % to 70 %. The air inside the glove box was still, and the evaporation process was mainly purely diffusive. A human blood diffusion coefficient of (1.08 ± 0.02) × 10 −9 m 2 /s was obtained. This value is in agreement with literature values for polymers and colloidal films. Moreover, we elaborated an updated model using Page's model to describe the drying kinetics of human blood pools. The effect of the surface area of pools was considered using a diffusive characteristics time. These findings are of interest for biomedical and forensic applications.

International audience; Underground nuclear explosions generate non-isothermal two-phase flow, heat and mass transfer, and tracer transport through fractured porous media. The governing equations of these coupled phenomena on the Darcy scale are presented and the corresponding numerical code is briefly described. Two configurations are considered. In the first one, the damaged zone generated by the explosion is replaced by equivalent macroscopic boundary conditions at the bottom of the medium. Vapor condensation at distance from this zone plays a crucial role and slows down the tracer transport to the ground surface, while the presence of hot liquid water and of hot rubble particles in it accelerates it. In the second configuration, the damaged zone itself is treated as a porous medium with specific properties and is integrated in the simulation domain. Several regions can be distinguished with different properties, such as the chimney, the cavity, the solidified magma, the fractured porous medium, and the intact porous medium. Phase change, heat transfer and tracer transport can be detailed in these regions and at the boundaries between them. Among the most important conclusions, the role of phase change, of the thermal properties and therefore of the temperature, is pointed out.

International audience; Objective: The main goal of the athletes who undergo anterior cruciate ligament reconstruction (ACLR) surgery is a successful return-to-sport. At this stage, identifying muscular deficits becomes important. Hence, in this study, three discriminative features based on surface electromyographic signals (sEMG) acquired in a dynamic protocol are introduced to assess the damping ability and interpret activation patterns in lower-limb muscles of ACLR athletes. Methods: The features include the median frequency of the power spectrum density (PSD), the relative percentage of the equivalent damping or equivalent stiffness derived from the median frequency, and the energy of the signals in the time-frequency plane of the pseudo-Wigner-Ville distribution (PWVD). To evaluate the features, 11 healthy and 11 ACLR athletes (6 months post-reconstruction surgery) were recruited to acquire the sEMG signals from the medial and the lateral parts of the hamstrings, quadriceps, and gastrocnemius muscles in pre- and post-fatigue single-leg landings. Results: A significant damping deficiency is observed in the hamstring muscles of ACLR athletes by evaluating the proposed features. This deficiency indicates that more attention should be paid to this muscle of ACLR athletes in pre-return-to-sport rehabilitations. Conclusion: The quality of electromyography-based pre-return-to-sport assessments on ACLR subjects depends on the sEMG acquisition protocol, as well as the type and nature of the extracted features. Hence, combinatorial application of both energy-based features (derived from the PWVD) and power-based features (derived from the PSD) could facilitate the assessment process by providing additional biomechanical information regarding the behavior of the muscles surrounding the knee.

Motion capture is traditionally performed with marker-based systems. However, these solutions are hardly compatible with on-field sports analysis, and markerless alternatives are being explored. One of the most promising prospects lies at the intersection of machine learning for 2D pose estimation, computer vision for 3D reconstruction from multiple video sources, and biomechanics for constraining 3D coordinates to an anatomically consistent model. We released Pose2Sim, an open-source package striving to answer these needs in a user-friendly way. OpenPose 2D keypoint coordinates are robustly triangulated, and serve as input for a full-body OpenSim inverse kinematics procedure. Pose2Sim robustness has been evaluated for people entering and exiting the field of view, degraded image quality, calibration errors, and decreased number of cameras. Its accuracy has also been assessed and deemed sufficient for walking, running, and ergometer cycling analysis. In the context of a competition, using lightweight and wireless action cameras is convenient. We tested such hardware on boxing sequences and proposed post-calibration and post-synchronization procedures. Finally, capturing both the athlete and their equipment can be valuable. We studied the kinematics of both a pilot and his bike in a BMX race by training a DeepLabCut bike model, triangulated and mapped on a custom-articulated OpenSim model. This work brings out interesting new perspectives for the analysis of sports movement.; La capture de mouvement est traditionnellement effectuée à l’aide de marqueurs réfléchissants placés sur la peau. Cependant, ces méthodes ne conviennent pas à l'analyse contextuelle du sport sur le terrain, et des alternatives sans marqueur sont étudiées. L’une des perspectives les plus prometteuses à ce sujet se situe à l’intersection de l’apprentissage machine pour l’estimation de pose 2D, de la vision par ordinateur pour la reconstruction 3D à partir de plusieurs sources vidéo, et de la biomécanique pour contraindre les coordonnées 3D à un modèle anatomiquement cohérent. Nous avons proposé Pose2Sim, un package open-source et simple d’utilisation visant à répondre à ces besoins. Les détections 2D d’OpenPose sont triangulées de manière robuste, et transmises à OpenSim pour une cinématique inverse corps complet. La robustesse de Pose2Sim a été estimée face à des personnes "parasites" entrant le champ de vision, à une qualité d’image dégradée, à des erreurs de calibration, et à un nombre de caméras réduit. Son exactitude a également été évaluée, et jugée satisfaisante pour l’analyse de la marche, de la course, et du cyclisme. Dans un contexte de compétition, il peut être utile d'employer des caméras légères et sans fil de type GoPro. Nous avons testé ce matériel sur des séquences de boxe, et proposé des procédures de post-calibration et de post-synchronisation. Enfin, capturer à la fois l’athlète et son équipement serait intéressant. Nous avons calculé la cinématique d’un pilote de BMX avec son vélo, en entraînant un modèle DeepLabCut pour le vélo, triangulé et appliqué sur un modèle poly-articulé OpenSim. L’ensemble de ces résultats apporte des perspectives novatrices pour l’analyse du mouvement sportif.

International audience; On a curved surface, epithelial cells can adapt to geometric constraints by tilting and by exchanging their neighbors from apical to basal sides, known as an apicobasal T1 (AB-T1) transition. The relationship between cell tilt, AB-T1 transitions, and tissue curvature still lacks a unified understanding. Here, we propose a general framework for cell packing in curved environments and explain the formation of AB-T1 transitions under different conditions. We find that steep curvature gradients can lead to cell tilting and induce AB-T1 transitions. Conversely, large curvature anisotropy can drive AB-T1 transitions by hydrostatic pressure. The two mechanisms compete to determine the impact of tissue geometry and mechanics on optimized cell rearrangements in 3D.

The location of the instantaneous centre of rotation (ICR) of a lumbar unit has a considerable clinical importance as a spinal health estimator. Consequently, many studies have been conducted to measure or estimate the ICR during rotations in the three anatomical planes; however the results reported are widely scattered. Even if some inter-subjects variability is to be expected, such inconsistencies are likely explained by the differences in methods and experiments. Therefore, in this paper we seek to model three behaviours of the ICR during lateral bending and axial rotation based on results published in the literature. In order to assess the metabolic and mechanical sensibility to the assumption made on the ICR kinematics, we used a previously validated three dimensional non-linear poroelastic model of a porcine intervertebral disc to simulate physiological lateral and axial rotations. The impact of the geometry was also briefly investigated by considering a 11$$^\circ$$ ∘ wedge angle. From our simulations, it appears that the hypothesis made on the ICR location does not significantly affect the critical nutrients concentrations but gives disparate predictions of the intradiscal pressure at the centre of the disc (variation up to 0.7 MPa) and of the displacement fields (variation up to 0.4 mm). On the contrary, the wedge angle does not influence the estimated intradiscal pressure but leads to minimal oxygen concentration decreased up to 33% and increased maximal lactate concentration up to 13%. While we can not settle on which definition of the ICR is more accurate, this work suggests that patient-specific modeling of the ICR is required and brings new insights that can be useful for the development of new tools or the design of surgical material such as total lumbar disc prostheses.

International audience; Biological cells can actively tune their intracellular architecture according to their overall shape. Here we explore the rheological implication of such coupling in a minimal model of a dense cellular material where each cell exerts an active mechanical stress along its axis of elongation. Increasing the active stress amplitude leads to several transitions. An initially hexagonal crystal motif is first destabilized into a solid with anisotropic cells whose shear modulus eventually vanishes at a first critical activity. Increasing activity beyond this first critical value, we find a re-entrant transition to a regime with finite hexatic order and finite shear modulus, in which cells arrange according to a rhombile pattern with periodically arranged rosette structures. The shear modulus vanishes again at a third threshold beyond which spontaneous tissue flows and topological defects of the nematic cell shape field arise. Flow and stress fields around the defects agree with active nematic theory, with either contractile or extensile signs, as also observed in several epithelial tissue experiments.

In the first chapter of this manuscript, my previous research projects are firstly synthesized. Based on the current context of musculoskeletal disorders which are considered as a critical public health issue, a conceptual five-step model for physical ergonomics is introduced (Model, Sensor, Analysis, Assessment, Intervention). This model serves as a basis for the first part of my previous research projects dedicated to physical ergonomic assessment using on-body sensors (electrogoniometers, inertial measurement units, etc.). As this assessment is also feasible in real-time, the second part of my previous research is submitted, by focusing on the use of continuous sensorial feedback, so called biofeedback, for human motion optimization. In a third part, the ergonomic intervention is presented in terms of physical assistance, by considering exoskeletons as a promising solution to prevent musculoskeletal disorders. The analysis of human-exoskeleton interactions thus allows to limit current issues and extents related to the use of these disposals. In the second chapter of this manuscript, the five-step model for physical ergonomics permits to lay the foundation of my future research projects. These projects are including investigations on new methodologies for characterizing human motion, e.g. mecanomyography and embedded force sensors, both in sport and occupational environments. Developing methodologies for assessing passive exoskeletons in the field is also explored, as well as the improvement of human-exoskeleton interactions, which will allow forward definition of bioinspired control laws for active exoskeletons. These future projects are based on collaborations with both academic and professional partners. Finally, the last chapter of this manuscript summarizes my academic activities and responsibilities, both at scientific level through publications and research grants, and pedagogical level through education initiatives and innovative pedagogical projects that have been funded.

This work aims to model the mechanical processes used by tree branches to control their posture despite their increasing weight loading. The two known options for a branch to maintain its orientation are the asymmetry of maturation stress, including reaction wood formation, and eccentric radial growth. Both options can be observed in nature and influence the stress distribution developed in the branch each year. This so-called "growth stress" reflects the mechanical state of the branch. In this work, a growth stress model was developed at the cross-section level in order to quantify and study the bio-mechanical impact of each process. For illustration, this model was applied to branches of two 50-year-old trees, one softwood Pinus pinaster and one hardwood Prunus avium (wild cherry tree), both simulated with the AmapSim discrete element software. For the wild cherry tree, the computed ouputs highlighted that the eccentricity of radial growth seems to be as efficient as the formation of reaction wood to maintain the postural control despite the increasing gravity. For the pine tree, eccentric radial growth appears to be less efficient than the formation of reaction wood. But although it does not necessarily act as a relevant lever for postural control, it greatly modifies the profile pattern of mechanical stress and could provide mechanical safety of the branch. This work opens experimental perspectives to understand the biomechanical processes involved in the formation of branches and their mechanical safety.

International audience

International audience; We report on a systematic numerical exploration of the vesicle dynamics in a channel, which is a model of red blood cells in microcirculation. We find a spontaneous transition, called swirling, from straight motion with axisymmetric shape to a motion along a helix with a stationary deformed shape that rolls on itself and spins around the flow direction. We also report on a planar oscillatory motion of the mass center, called three-dimensional snaking for which the shape deforms periodically. Both emerge from supercritical pitchfork bifurcation with the same threshold. The universality of these oscillatory dynamics emerges from Hopf bifurcations with two order parameters. These two oscillatory dynamics are put in the context of vesicle shape and dynamics in the parameter space of reduced volume v, capillary number, and confinement. Phase diagrams are established for v = 0.95, v = 0.9, and v = 0.85 showing that oscillatory dynamics appears if the vesicle is sufficiently deflated. Stationary shapes (parachute/bullet/peanut, croissant, and slipper) are fixed points, while swirling and snaking are characterized by two limit cycles.

International audience; Lateral epicondylitis, also known as tennis elbow, is a major health issue among tennis players. This musculo-skeletal disorder affects hand extensor tendons, results in substantial pain and impairments for sporting and everyday activities and requires several weeks of recovery. Unfortunately, prevention remains limited by the lack of data regarding biomechanical risk factors, especially because in vivo evaluation of hand tendon forces remains challenging. Electromyography-informed musculo-skeletal modeling is a noninvasive approach to provide physiological estimation of tendon forces based on motion capture and electromyography but was never applied to study hand tendon loading during tennis playing. The objective of this study was to develop such electromyography-informed musculo-skeletal model to provide new insight into hand tendon loading in tennis players. The model was tested with three-dimensional kinematics and electromyography data of two players performing forehand drives at two-shot speeds and with three rackets. Muscle forces increased with shot speed but were moderately affected by racket properties. Wrist prime extensors withstood the highest forces, but their relative implication compared to flexors depended on the player-specific grip force and racket motion strategy. When normalizing wrist extensor forces by shot speed and grip strength, up to threefold differences were observed between players, suggesting that gesture technique, for example, grip position or joint motion coordination, could play a role in the overloading of wrist extensor tendons. This study provided a new methodology for in situ analysis of hand biomechanical loadings during tennis gesture and shed a new light on lateral epicondylitis risk factors.

The aims of the present study were to characterize the mechanical output of final road sprints of an elite sprinter during international competitions in relation to his power-velocity-endurance characteristics, and to investigate the relationship between this sprint performance and the power produced during preceding phases of the race. The sprinter performed a set of short and long sprints (5 to 15 s) on a cycle ergometer to determine his maximal power-velocity-endurance profile. Based on eleven races, the distribution of power throughout each race, peak and mean power (Ppeak and Pmean ) and associated pedalling rates (vPpeak and vPmean ) during the final sprint were analyzed. The power-velocity-endurance profile of the sprinter indicated that his mean maximal power and corresponding optimal pedalling rate ranged from 20.1 W.kg-1 (124 rpm) for a 1-s sprint to 15.2 W.kg-1 (112 rpm) for 20 s. Race data showed that final road sprints were mainly performed on the ascending limb of the power-velocity relationship (vPpeak , 104±8 and vPmean , 101±8 rpm). Additionally, Ppeak and Pmean were lower than the theoretical maximal power determined from the power-velocity-endurance profile (10.4±7.0% and 11.2±9.2%, respectively), which highlighted a significant state of fatigue induced by the race. Finally, sprint power exhibited a high variability between races and was strongly related to the level of power produced during the last minute before the sprint. These findings show the importance of considering both the power-velocity-endurance qualities and the power demand of the last lead-up phase before the sprint in order to optimize final sprint performance.

Quasi-static ultrasound elastography is a medical imaging technique dedicated to the mechanical characterization of biological tissues. This technique uses, for diagnosis, criteria mainly derived from the axial strain, which is the most accurately estimated component. However, imaging the strain tensor would be of interest, not only for a better evaluation of the tissue response to compression, but also for the implementation of reconstruction methods to access to the mechanical properties of the examined tissues.In this PhD work, two research axes were developed to analyze the elastic properties of biological tissues. The first axis focused on the development of a regularization method in order to smooth the displacement fields and to obtain less noisy, and thus usable, strain images. The results on numerical simulations, phantoms and breast tissues showed the strong contribution of this method, when facing complex and noisy data, especially for the lateral components of displacement and strain. Moreover, the proposed approach allowed to obtain shear strain images and rotation elastograms on which shear/rotation patterns were clearly detectable around the inclusions/lesions. The second research axis focused on the development of a method using the virtual work principle to reconstruct the spatial distribution of the Young's modulus within linear, elastic and isotropic media. This method requires the knowledge of the displacement/strain fields and the applied force. To overcome the lack of 3D ultrasound data, the reconstruction of the elastic modulus has been studied under the assumptions of plane stresses and plane strains. The results on numerical simulations and phantoms showed an accurate reconstruction of the Young's modulus mapping, in terms of region localization, shape and size. The modulus values are correctly estimated when the assumptions introduced in the method are respected. On the other hand, when the assumptions are no longer satisfied, a decrease in elastic contrast is observed. Nevertheless, the regions with distinct elastic properties in a medium remain clearly visible, both in simulations and in phantom data. Finally, the results on breast tissues indicate a stiffer region in agreement with the position of the lesion observable on the ultrasound imaging. These different results are promising and particularly interesting for a more complete analysis of biological tissues in quasi-static ultrasound elastography., L'élastographie ultrasonore quasi-statique est une technique d'imagerie médicale dédiée à la caractérisation mécanique des tissus biologiques. Cette technique utilise pour le diagnostic des critères issus principalement des images de la déformation axiale, qui est la composante estimée avec le plus de précision. Néanmoins, une imagerie complète du tenseur de déformation serait intéressante, non seulement pour une meilleure évaluation de la réponse du tissu à la compression, mais aussi et surtout pour la mise en œuvre de méthodes de reconstruction permettant d'accéder aux propriétés mécaniques des tissus imagés.Dans ces travaux de thèse, deux axes de recherche ont été développés afin de permettre une analyse des propriétés élastiques des tissus biologiques. Le premier axe a porté sur le développement d'une méthode de régularisation afin de lisser les champs de déplacement et d'obtenir des images de déformation moins bruitées, et donc exploitables. Les résultats sur des simulations numériques, des fantômes et des tissus mammaires in vivo, ont montré la forte contribution de cette méthode face à des données complexes et bruitées, notamment pour les composantes latérales du déplacement et de la déformation. De plus, l'approche proposée a permis d'obtenir des images de déformation en cisaillement et des élastogrammes de rotation sur lesquels des motifs de cisaillement/rotation étaient clairement détectables autour des inclusions/lésions. Le deuxième axe de recherche a été centré sur le développement d'une méthode utilisant le principe des travaux virtuels pour reconstruire la distribution spatiale du module d'Young au sein de milieux élastiques, linéaires et isotropes. Cette méthode nécessite de connaitre au préalable les champs de déplacement/déformation ainsi que la force appliquée. Pour pallier le manque de données 3D en échographie, la reconstruction du module élastique a été étudiée sous les hypothèses des contraintes et déformations planes. Les résultats sur simulations numériques et fantômes ont montré une reconstruction précise de la cartographie du module d'Young, en termes de localisation des régions, de leur forme et de leur taille. Les valeurs de module sont correctement estimées lorsque les hypothèses introduites dans la méthode sont respectées. En revanche, lorsque les hypothèses ne sont plus satisfaites, une diminution du contraste élastique est observée. Néanmoins les régions aux propriétés élastiques distinctes dans un milieu restent clairement visibles, que ce soit en simulations ou pour les données de fantômes. Enfin, les résultats sur tissus mammaires indiquent une région plus rigide en accord avec la position de la lésion observable à l'échographie. Ces différents résultats sont prometteurs et particulièrement intéressants pour une analyse plus complète des tissus biologiques en élastographie ultrasonore quasi-statique.

International audience

International audience; L’étude et la modélisation des interactions entre piétons et usagers de fauteuil roulant électrique (FRE) est un enjeu majeur pour le développement d’assistance à la conduite de tels fauteuils, notamment pour suivre l’intention de déplacement de l’usager tout en évitant une collision avec un piéton à proximité. Pour mieux comprendre les intentions et les distances de proximité piéton-FRE lors de déplacement en groupe, nous avons demandé à un usager de FRE de rejoindre un groupe de deux piétons, marchant côte à côte. Les marcheurs se déplaçaient d’un point de départ à un point d’arrivée situé en face à 20m. Le participant en FRE arrivait perpendiculairement à la trajectoire des marcheurs. Ils devaient alors tous les trois rejoindre ensemble le point d’arrivée. 9 participants marchant (8 hommes, 1 femme, 27ans) et 3 usagers de FRE (3 hommes, 43 ans) ont participé à cette étude. 2 des usagers de FRE étaient ergothérapeutes, 1 avaient une paralysie cérébrale. Trois sessions incluant 1 usager de FRE et 3 marcheurs ont été réalisées. Chaque paire de marcheurs a réalisé 10 essais, pour un total de 20 essais par marcheur et 30 essais pour l’usager en FRE. L’analyse en cours porte sur les adaptations de mouvement de la personne en FRE et des piétons ainsi que leurs positions relatives. Il s’agit alors d’étudier le comportement d’interaction qui permet aux marcheurs et à l’usager de FRE de former un groupe, les distances de proximité ainsi que de potentielles asymétries marcheur-marcheur et marcheur usager de FRE.

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Background: Direct dental restoration implies a drying of the dentin substrate. This drying may induce significant strain in the dentin, affecting the bonding efficiency of the restoration. Objective: We measure the dilatation of dentine under changes of relative humidity as well as the impact of humidity on dentin elastic properties. This investigates the role of relative humidity variation during dental surgery on restoration lifetime. Methods: We have coupled an environmental chamber to control both temperature and humidity on the sample, with an optical microscope to measure precisely the strain on the sample surface, after a quantification of the measurement noise. This set-up is used on carefully prepared samples placed on a compression device to measure the elastic parameters. Results: Dentin dilates when the relative humidity increases, with a coefficient of hygroscopic expansion of typically 6.10-3 %.(%RH)-1. This dilatation occurs in about ten minutes. Young modulus and Poisson's ratio are not modified by the variation of relative humidity. Conclusions: Hygroscopic expansion is an order of magnitude larger than thermal expansion during dental surgery: around 0.3% with respect to 0.03%. These levels are low with respect to dental rupture, but may induce a significant decrease of the life-expectancy of a restoration.

One of the major issues in the computational mechanics is to take into account the geometrical complexity. To overcome this difficulty and to avoid the expensive mesh generation, geometrically unfitted methods, i.e. the numerical methods using the simple computational meshes that do not fit the boundary of the domain, and/or the internal interfaces, have been widely developed. In the present work, we investigate the performances of an unfitted method called $\phi$-FEM that converges optimally and uses classical finite element spaces so that it can be easily implemented using general FEM libraries. The main idea is to take into account the geometry thanks to a level set function describing the boundary or the interface. Up to now, the $\phi$-FEM approach has been proposed, tested and substantiated mathematically only in some simplest settings: Poisson equation with Dirichlet/Neumann/Robin boundary conditions. Our goal here is to demonstrate its applicability to some more sophisticated governing equations arising in the computational mechanics. We consider the linear elasticity equations accompanied by either pure Dirichlet boundary conditions or by the mixed ones (Dirichlet and Neumann boundary conditions co-existing on parts of the boundary), an interface problem (linear elasticity with material coefficients abruptly changing over an internal interface), a model of elastic structures with cracks, and finally the heat equation. In all these settings, we derive an appropriate variant of $\phi$-FEM and then illustrate it by numerical tests on manufactured solutions. We also compare the accuracy and efficiency of $\phi$-FEM with those of the standard fitted FEM on the meshes of similar size, revealing the substantial gains that can be achieved by $\phi$-FEM in both the accuracy and the computational time.

International audience; The goal of this thesis is to develop musculoskeletal-based models of upper limb force capacities that can be personalized to an individual. Such models are needed for physical Robot interaction (phRI) to provide the right assistance given the knowledge of human capacities. Other applications include exoskeleton design and computer aided ergonomics. For a specific static posture of the upper limb, the force capacities can be represented by a convex polytope called the force feasible set which describes the maximal forces which can be applied tothe environment or resisted in any task space direction. This set can be either measured via a force sensor or computed considering a musculoskeletal model (MSK) representative of the subject’s upper limb. However, in practice, it is impossible to obtain the true MSK model of a subject due to the wide intra-variability of its parameters, the important number of parameters to tune and inter-variability between subjects. This thesis focuses on creating personalized musculoskeletal models able to reproduce the experimental force feasible sets of an individual in various postures. Current research on scaling musculoskeletal models allows us to obtain a solid candidate to describe the bone and joint structure, using motion capture. There is still a need to find good candidates for his muscle structure. The current work of this thesis is to use an artificial intelligence approach via evolutionary algorithms to retrieve muscle configurations among which the simulated forces feasible sets fit the measured ones.

Recent evidence suggests that during volitional stepping older adults control whole-body angular momentum (H) less effectively than younger adults, which may impose a greater challenge for balance control during this task in the elderly. This study investigated the influence of aging on the segment angular momenta and their contributions to H during stepping. Eighteen old and 15 young healthy adults were instructed to perform a series of stepping at two speed conditions: preferred and as fast as possible. Full-body kinematics were recorded to compute angular momenta of the trunk, arms and legs and their contributions to total absolute H on the entire stepping movement. Results indicated that older adults exhibited larger angular momenta of the trunk and legs in the sagittal plane, which contributed to a higher sagittal plane H range during stepping compared to young adults. Results also revealed that older adults had a greater trunk contribution and lower leg contribution to total absolute H in the sagittal plane compared to young adults, even though there was no difference in the other two planes. These results stress that age-related changes in H control during stepping arise as a result of changes in trunk and leg rotational dynamics.

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International audience; In this paper, we propose a blueprint of a new deep network unfolding a baseline quantum mechanics-based adaptive denoising scheme (De-QuIP). Relying on the theory of quantum many-body physics, the De-QuIP architecture incorporates local patch similarity measures through a term akin to interaction in quantum physics. Our proposed deep network embeds both quantum interactions and other quantum concepts, mainly the Hamiltonian operator. The integration of these quantum tools brings a nonlocal structure to the proposed deep network that harnesses the power of the convolutional layers to enhance the adaptability of the model. Thus, recasting De-QuIP in the framework of a deep learning network while preserving the essence of the baseline structure is the main contribution of this work. Experiments conducted on the Gaussian denoising problem, chosen here for illustration purpose, over a large sample set demonstrate start-of-the-art performance of the proposed deep network, dubbed as Deep-De-QuIP hereafter. Based on the properties of De-QuIP, its intrinsic adaptive structure, Deep-De-QuIP network could be easily extended to other noise models.

International audience; The purpose of this study is to optimize the design of racing wheelchairs to improve the performances of the athletes. The design of manual wheelchair allows athletes to express their full potential. Two models have then been created. The first one to compute the optimal position of the shoulder of the athlete relatively to the wheelchair to obtain the maximal wheelchair speed for long distance races. The second one was designed to represent the 100 m race and to optimize the pelvis position of the athlete on the wheelchair to reduce the time to reach 100 m. Our model quantified the maximal speed reached by the wheelchair to 32 km/h and the optimal time to 14.35 s. To obtain these performances, the athlete would be in a lying position, with the vertical position of the pelvis centre close to the vertical position of the shoulder. The second program also returned the optimal speed curve of the wheelchair during the 100 m race. The coaches could then use the optimal acceleration curve found in this study to match the acceleration of the wheelchair of their athlete.

International audience; Root mechanical traits, including tensile strength (Tr), tensile strain (εr), modulus of elasticity (Er) and tensile toughness (Wr), play a key role in plant functioning (e.g., anchorage and stem stability). Yet, their variability and their relationships with other root traits are poorly known. Here, we characterize Tr, εr, Er and Wr at both intra-and interspecific levels and examine how they covary with other root traits related to root economics space (RES). We used twelve herbaceous species from contrasting taxonomical families grown in controlled plein-air conditions. For each species, we excavated root systems and measured morphological and chemical traits and mechanical traits at two locations (proximal versus distal) for two root types (absorptive versus transport roots). Transport roots tended to show higher mechanical trait values than absorptive roots, especially for εr, while the location where the root was sampled showed a limited effect on root mechanics. The five monocots (Poaceae species) had higher mechanical traits than the seven dicots (including five Fabaceae species) except for Er. Root mechanical traits covaried positively and were strongly positively correlated with specific root length, i.e., a trait related to soil exploration strategy, and negatively with root diameter and root tissue density, i.e. a trait related to root life span. We demonstrate the important role of species category and root type in governing mechanical trait variation at both intra-and inter-specific levels. Our results can be regarded as the first evidence of the link between root mechanical robustness and the RES through a strong association with the 'do-it-yourself' soil exploration strategy.

International audience; Two-dimensional deep-learning pose estimation algorithms can suffer from biases in joint pose localizations, which are reflected in triangulated coordinates, and then in 3D joint angle estimation. Pose2Sim, our robust markerless kinematics workflow, comes with a physically consistent OpenSim skeletal model, meant to mitigate these errors. Its accuracy was concurrently validated against a reference marker-based method. Lower-limb joint angles were estimated over three tasks (walking, running, and cycling) performed multiple times by one participant. When averaged over all joint angles, the coefficient of multiple correlation (CMC) remained above 0.9 in the sagittal plane, except for the hip in running, which suffered from a systematic 15° offset (CMC = 0.65), and for the ankle in cycling, which was partially occluded (CMC = 0.75). When averaged over all joint angles and all degrees of freedom, mean errors were 3.0°, 4.1°, and 4.0°, in walking, running, and cycling, respectively; and range of motion errors were 2.7°, 2.3°, and 4.3°, respectively. Given the magnitude of error traditionally reported in joint angles computed from a marker-based optoelectronic system, Pose2Sim is deemed accurate enough for the analysis of lower-body kinematics in walking, cycling, and running.

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Two third of manual wheelchair (MWC) users report suffering or having suffered from shoulder pain or injury [1]. To favour the understanding of these disorders, it is crucial to quantify the shoulder kinematics and kinetics during MWC locomotion [2]. However, soft tissue artefacts (STA) are particularly present at the scapula, making it difficult to accurately track the bone motion [3], motivating researchers to propose compensation methods based on acromion or scapula spine marker clusters and a calibration pose [4]. Apart from invasive or irradiative methods, the reference method to localize the scapula bone is based on external palpation generally through the use of a scapula palpator (SP) [5]. In this study, we propose to compare the scapula kinematics reconstructed from a cluster with STA compensation based on one or two calibration static poses during the push phase with the reference method using a SP. ANR-19-CE19-0007

International audience; Introduction:Marker-based kinematics is hardly compatible with sports movement analysis, especially because it hinders natural movement. Hence, deep-learning based markerless solutions are being developed, such as Pose2Sim [1]. Sports in competition may also be subject to setup constraints, preventing the use of heavy equipment and installation. The use of lightweight action cameras, with post-calibration and post-synchronization, can be pertinent in this context. This study aimed at investigating the accuracy of the Pose2Sim pipeline in such suboptimal conditions. We assessed the measures of key performance indicators in boxing, which involves swift and 3-dimensional full-body movements.Methods:One male elite boxer performed 6 repetitions of a boxing sequence composed of 3 punches (jab, high hook, low hook). His 3D motion was captured both with a marker-based protocol, and with a light-weight markerless one. The latter involved 8 GoPro cameras, which were post-calibrated based on the dimensions of the boxing ring, and post-synchronized based on time-lagged correlations of 2D keypoints speeds between paired cameras. The markerless kinematic analysis was then performed with Pose2Sim. Both protocols used the same OpenSim [2] model to optimize inverse kinematics. Displacement of lead foot, pelvis, lead fist, and velocity of lead fist were analyzed for the jab. Rotation of rear foot, pelvis, displacement of rear fist, and velocity of rear fist were analyzed for the hooks. Waveform similarity was assessed with the inter-protocol coefficient of multiple correlation [3]. Time and magnitude of peaks were also compared.Results:Results from the marker-based and markerless approaches demonstrated excellent waveform similarity (CMC>0.94), and times-to-peak exhibited intervals of under one frame (i.e., 17 ms). Magnitudes-at-peak were very close for displacements (below 6 cm), but not for fist velocity on jab (1.2m/s difference) nor for rotations on hooks (up to 20° difference, e.g. for pelvis rotation).Conclusion:Despite the use of action cameras, and of suboptimal calibration and synchronization procedures, our lightweight markerless protocol gives satisfying results for the analysis of key performance indicators in boxing, especially for limb displacements. Nevertheless, results should be taken with caution for velocity and for rotation measurements. Such a light-weight markerless protocol could be useful in situations where more accurate marker-based approaches are not conceivable, such as sports competitions.

International audience; In this study, we propose to use MR-Acoustic Radiation Force Imaging (MR-ARFI) as a transient elastography method to estimate the viscoelasticity and the anisotropy of an ultrasound absorbing medium.Methods: MR-ARFI1 uses the acoustic radiation force induced by a focused ultrasound beam to generate a remote micrometric displacement (push) at the ultrasonic focal region. This push results in the propagation of a transient shear wave of velocity cs that is encoded in the MRI phase signal by a motionsensitized sequence synchronized to the push. The resulting MR-ARFI phase profile depicts the ARFI spot, whose size increases with tissue stiffness. A previous quantitative MR-ARFI method2 has been proposed that allows estimating the local shear modulus μ of the medium around the focal spot, through the identification of the MR-ARFI profile. However, that work was limited to isotropic media, and the viscoelastic relaxation time τ was fixedarbitrarily. In this work, we propose to estimate τ following the approach published by Kaye et al.3 and Dadakova et al.4, which consists in fitting the phase signal at the focal spot for different temporal synchronization steps. Process is also extended to tissue anisotropy estimation, by performing individual fits on each radial profile extracted from the MR-ARFI phase image (Fig. A). The method is first validated on a homogeneous phantom calibrated for elastography (CIRS, USA; datasheet μref = 5.9 kPa ± 5%). Second, changes in biomechanical properties are estimated before and after a HIFU thermal ablation in ex vivo calf muscle tissue.Results: In the CIRS phantom, the value determined for τ is 3.3 ms at the focal spot. Using our MR-ARFI model, the polar representation of μ is isotropic, with an average value of 7.9 kPa ± 3% (Fig. B). In the calf tissue, τ decreases from 7.5 ms pre-HIFU to 4.5 ms post-HIFU, while μ globally decreases (Fig. C) suggesting that the meat softens as a result of heating. Figure C shows the shear modulus angular distribution both pre- and post-heating in calf tissues that appear to be highly anisotropic. The acquisition time for polar map of μ was 4 s, corresponding to the acquisitionof 2 MR images with opposite motion sensitivity polarities.Discussion: Quantitative MR-ARFI with viscoelastic model and anisotropic analysis provides shear modulus in the same range as μref in the CIRS phantom. After the HIFU experiment, cutting the calf tissue revealed a very irregular fiber orientation, consistent with the anisotropy observed with MR-ARFI. The maximum temperature rise reached in this experiment was 50 ºC, which results in meat tenderization, as already reported in the literature.Conclusion: The proposed method allows for local, quantitative, and direction-dependent viscoelasticity measurements around the focal spot. Its ability to provide polar maps of μ makes it a promising method to gain insights into biological tissue mechanical properties. The modification of τ found with HIFU heating calls for a further refined modeling of viscoelasticity to extend the method to the monitoring of HIFU ablations.

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International audience; Under natural conditions, plants are subjected to mechanical stresses and potentially show a response at a distance from the site of stimulation suggesting the transfer of information. The nature of the information vector remains unknown to date. The propagation of an electrical signal following the bending of the poplar stem was studied by extracellular electrophysiology measurements. This study revealed the propagation of a graded potential (GP), an electrical response with original characteristics that dierentiate it from an action potential (AP) and its electrotonic propagation, leading to the idea of another mode of propagation and to the hypothesis of a hydroelectric coupling. In order to determine whether the PG is likely to trigger a biological response, various RNA seq experiments were undertaken. The results revealed a signicant transcriptional response at a distance from the solicited area, dependent on the passage of a PG.

Background: The aim of this study was to evaluate the aortic diameter and volume during the first year after a type A repair to predict the long-term prognosis of a residual aortic dissection (RAD). Methods: All patients treated in our center for an acute type A dissection with a RAD and follow-up > 3 years were included. We defined two groups: group 1 with dissection-related events (defined as an aneurysmal evolution, distal reintervention, or aortic-related death) and group 2 without dissection-related events. The aortic diameters and volume analysis were evaluated on three postoperative CT scans: pre-discharge (T1), 3–6 months (T2) and 1 year (T3). Results: Between 2009 and 2016, 54 patients were included. Following a mean follow-up of 75.4 months (SD 31.5), the rate of dissection-related events was 62.9% (34/54). The total aortic diameters of the descending thoracic aorta were greater in group 1 at T1, T2 and T3, with greater diameters in the FL (p < 0.01). The aortic diameter evolution at 3 months was not predictive of long-term dissection-related events. The total thoracic aortic volume was significantly greater in group 1 at T1 (p < 0.01), T2 (p < 0.01), and T3 (p < 0.01). At 3 months, the increase in the FL volume was significantly greater in group 1 (p < 0.01) and was predictive for long-term dissection-related events. Conclusion: This study shows that an initial CT scan volume analysis coupled with another at 3 months is predictive for the long-term evolution in a RAD. Based on this finding, more aggressive treatment could be given at an earlier stage.

International audience; Frost hardiness is the main factor affecting plant species distribution at high latitudes and altitudes. The main effects of freeze-thaw cycles on trees are damages to living cells, as well as the formation of gas embolism in xylem vessels. Frost effect on trees is also quantified through changes in branch diameter.In order to resorb embolism, some species (walnut, maple, birch, etc.) exhibit an increase in xylem sap pressure during successive freeze-thaw cycles. The modelling of such phenomenon is very challenging due to its multi-physics and multi-scale nature. In this work, we present a numerical model coupling heat transfer, phase change, water and osmotic fluxes, taking into consideration different cell types within walnut branch tissues. We show how diameter and pressure variations are inter-related, and we validate the model against experimental results from the literature. We eventually show how this work can be adapted in order to explore inter-species differences.

International audience; Rubber trees (Hevea brasiliensis) are grown on about 15 million hectares of plantations in tropical plantations, producing 13 million tons of rubber per year of industry (IRSG statistics 2020). However, during their economic life on the plantation, rubber trees appear to be very susceptible to wind damages in general and trunk breakage in particular. The main hypothesis is that bleeding could affect the capacity of the tree to produce wood and increase its trunk diameter and thus, its mechanical rigidity. According to reports from growers and breeders, there is inter-clonal variability in the susceptibility of trees to breakage. This suggests the possibility to select rubber tree clones that would be less susceptible to wind breakage. Biomechanical analysis of the risk of tree breakage involves i) morphological and geometrical parameters, linked to the tree's architecture (size of the crown, tapering of the trunk, etc.); ii) the mechanical properties of the wood formed in the trunk, particularly its elastic modulus and resistance to breakage. Here, we focus on two rubber tree clones well-known to show contrasted sensitivity to wind breakage; one being considered as "weak" and the other as "resistant". Standing tree bending tests were carried out to the trunk breaking point in two plantation plots (Ivory Coast) to assess the resistance to breakage of each clone. Figure 1 shows the principle of a standing tree bending test and Figure 2 shows an example of a fracture surface. The results obtained during a field tests campaign in 2022 will arebe presented and discussed.

International audience; This work aims to model the consequences of different strategies used by tree branches to ensure a given posture. If tree branches were simple beams, they would collapse under their weight. Of course, branches have the ability to control their orientation, and thus compensate for the effect of gravity, which increases every year by the way of the primary and secondary growths that espectively increase the length and diameter of the organ. The two known strategies of the branch to straighten itself are the asymetry of maturation stress, including reaction wood formation, and eccentric growth. Both strategies are generally observed simultaneously in nature and influence the stress distribution developed in the branch each year. This so-called growth stress reflects the mechanical state of the branch. In this work, a growth stress model was developed at the cross-section level in order to quantify the biomechanical impact of each strategy. To provide realistic input to the model, branch profiles were modelled using the growth simulation software AMAP Sim. These modelling results provided different loading laws that evolved with space and time. Fordifferent types of branches, the impact of the two postural control strategies was then examined. In a final step, a profiling of the branch at different points of its final shape allowed to follow the evolution of the stress distribution along the branch. Figure 1 illustrates the approach. On the left, the main axis of a maritime pine branch Pinus Pinae is shown at different stages of development. On the right, the stress profile in a section at the branch insertion is proposed. In this case, the eccentricity is zero, so the branch must produce reaction wood (compression wood for a softwood) to maintain its posture. This is shown by the compressive stress in the lower section of the branch.

International audience; Purpose: Immune checkpoint blocker (ICB) associated myocarditis (ICB-myocar-ditis) may present similarly and/or overlap with other cardiac pathology including acute cor-onary syndrome presenting a challenge for prompt clinical diagnosis.Methods: An international registry was used to retrospectively identify cases of ICB-myocarditis. Presence of coronary artery disease (CAD) was defined as coronary artery steno-sis >70% in patients undergoing coronary angiogram.Results: Among 261 patients with clinically suspected ICB-myocarditis who underwent a coro-nary angiography, CAD was present in 59/261 patients (22.6%). Coronary revascularization was performed during the index hospitalisation in 19/59 (32.2%) patients. Patients undergoing coro-nary revascularization less frequently received steroids administration within 24 h of admission compared to the other groups (p = 0.029). Myocarditis-related 90-day mortality was 9/17 (52.7%) in the revascularised cohort, compared to 5/31 (16.1%) in those not revascularized and 25/156 (16.0%) in those without CAD (p = 0.001). Immune-related adverse event-related 90-day mortality was 9/17 (52.7%) in the revascularized cohort, compared to 6/31 (19.4%) in those not revascularized and 31/156 (19.9%) in no CAD groups (p = 0.007). All-cause 90-day mortality was 11/17 (64.7%) in the revascularized cohort, compared to 13/31 (41.9%) in no revas-cularization and 60/158 (38.0%) in no CAD groups (p = 0.10). After adjustment of age and sex, coronary revascularization remained associated with ICB-myocarditis-related death at 90 days (hazard ratio [HR] = 4.03, 95% confidence interval [CI] 1.84-8.84, p < 0.001) and was margin-ally associated with all-cause death (HR = 1.88, 95% CI, 0.98-3.61, p = 0.057).Conclusion: CAD may exist concomitantly with ICB-myocarditis and may portend a poorer outcome when revascularization is performed. This is potentially mediated through delayed diag-nosis and treatment or more severe presentation of ICB-myocarditis.

International audience; Stiffness plays a central action in plant cell extension. Here, we present a protocol to detect changes in stiffness on the external epidermal cell wall of living plant roots using atomic force microscopy (AFM). We provide generalized instructions for collecting force-distance curves and analysis of stiffness using contact-based mechanical model. With this protocol, and some initial training in AFM, a user is able to perform indentation experiments on 4-and 5-day-old Arabidopsis thaliana and determine stiffness properties.

International audience; While cementless implants are now widely used clinically, implant debonding still occur and is difficult to anticipate. Assessing the biomechanical strength of the bone-implant interface can help improving the understanding of osseointegration phenomena and thus preventing surgical failures. A dedicated and standardized implant model was considered. The samples were tested using a mode III cleavage device to assess the mechanical strength of the bone-implant interface by combining experimental and numerical approaches. Four rough (Sa = 24.5 µm) osseointegrated coin-shaped implants were left in sheep cortical bone during 15 weeks of healing time. Each sample was experimentally rotated at 0.03°/sec until complete rupture of the interface. The maximum values of the torque were comprised between 0.48 and 0.72 N.m, while a significant increase of the normal force from 7-12 N to 31-43 N was observed during the bone-implant interface debonding, suggesting the generation of bone debris at the bone-implant interface. The experimental results were compared to an isogeometric finite element model describing the adhesion and debonding phenomena through a modified Coulomb's law, based on a varying friction coefficient to represent the transition from an unbroken to a broken bone-implant interface. A good agreement was found between numerical and experimental torques, with numerical friction coefficients decreasing from 8.93 to 1.23 during the bone-implant interface rupture, which constitutes a validation of this model to simulate the debonding of an osseointegrated bone-implant interface subjected to torsion.

Studies have demonstrated that hurricanes can drive selection in Neotropical anoles. In a recent study, it was shown that post-hurricane survivors showed longer toepad areas and, surprisingly, shorter femurs. 2. One potential explanation for the reduction in femur length is that increased drag on individuals with longer femurs causes them to be blown off their perch. Consequently, lizards with shorter femora might survive better in hurricanes. 3. To gain insight into the form-function relationships of drag reduction in perched lizards exposed to high-velocity winds, we quantified drag forces on Anolis lizard models in realistic grasping positions using computational fluid dynamics. 4. We showed that overall drag, as well as the relatively high drag at the hindlimbs strongly increase with the distance of the pelvic region from the perch. As optimal postures to resist sustained arboreal pulling involve extended limbs, longer hindlimbs increase the chance of having the limbs and pelvic region positioned outside the zone in which efficient shielding from the wind by the perch occurs. 5. Our study underlines the complexity of performance trade-offs on the evolution of limb morphology in arboreal lizards, and emphasizes the importance of generally ignored functions such as aerodynamic drag reduction in arboreal ecosystems.

Tumor progression and metastatic dissemination are driven by cell-intrinsic and biomechanical cues that favor the growth of life-threatening secondary tumors. We recently identified pro-metastatic vascular regions with blood flow profiles that are permissive for the arrest of circulating tumor cells. We have further established that such flow profiles also control endothelial remodeling, which favors extravasation of arrested CTCs. Yet, how shear forces control endothelial remodeling is unknown. In the present work, we aimed at dissecting the cellular and molecular mechanisms driving blood flow-dependent endothelial remodeling. Transcriptomic analysis of endothelial cells revealed that blood flow enhanced VEGFR signaling, among others. Using a combination of in vitro microfluidics and intravital imaging in zebrafish embryos, we now demonstrate that the early flow-driven endothelial response can be prevented upon specific inhibition of VEGFR tyrosine kinase and subsequent signaling. Inhibitory targeting of VEGFRs reduced endothelial remodeling and subsequent metastatic extravasation. These results confirm the importance of VEGFR-dependent endothelial remodeling as a driving force of CTC extravasation and metastatic dissemination. Furthermore, the present work suggests that therapies targeting endothelial remodeling might be a relevant clinical strategy in order to impede metastatic progression.