Birth and death processes with neutral mutations

In this paper, we review recent results of ours concerning branching processes with general lifetimes and neutral mutations, under the infinitely many alleles model, where mutations can occur either at birth of individuals or at a constant rate during their lives. In both models, we study the allelic partition of the population at time t. We give closed formulae for the expected frequency spectrum at t and prove pathwise convergence to an explicit limit, as t goes to infinity, of the relative numbers of types younger than some given age and carried by a given number of individuals (small families). We also provide convergences in distribution of the sizes or ages of the largest families and of the oldest families. In the case of exponential lifetimes, population dynamics are given by linear birth and death processes, and we can most of the time provide general formulations of our results unifying both models.Comment: 20 pages, 2 figure

Strong fluid–solid interactions with segregated CFD solvers

Purpose: A fluid-structure coupling partitioned scheme involving rigid bodies supported by spring-damper systems is presented. This scheme can be used with already existing fluid flow solvers without the need to modify them. Design/methodology/approach: The scheme is based on a modified Broyden method. It solves the equations of solid body motion in which the external forces coming from the flow are provided by a segregated flow solver used as a black box. The whole scheme is implicit. Findings: The proposed partitioned method is stable even in the ultimate case of very strong fluid-solid interactions involving a massless cylinder oscillating with no structural damping. The overhead associated with the coupling scheme represents an execution time increase by a factor of about 2 to 5, depending on the context. The scheme also has the advantage of being able to incorporate turbulence modeling directly through the flow solver. It has been tested successfully with URANS simulations without wall law, thus involving thin high aspect-ratio cells near the wall. Originality/value: Such problems are known to be very difficult to solve and previous studies usually rely on monolithic approaches. To the authors’ knowledge, this is the first time a partitioned scheme is used to solve fluid-solid interactions involving massless component

Nouvelle approche de modélisation de la branche de magnétisation pour la simulation des transitoires électromagnétiques

Trajectoires du phénomène d'hystérésis avec saturation -- Modèle de Preisach -- Modèle de Stoner et Wolhfarth -- Modèle de Jiles et Atherton -- Revue des modèles numériques actuels -- Modèle type 96 -- Modèle type 92 -- Modèle de Preisach modifié -- Modèle de MATLAB/Power system blockset -- Modèle de résistance de magnétisation instantannée -- Nouveau modèle -- Boucle majeure -- Boucles mineures -- Courbe de première magnétisation -- Contexte de programmation -- Domaine du temps -- Domaine fréquentiel et régime permanent -- Initialisation -- Gestion de la pile des extrema -- Méthode de modification d'estimation de flux -- Méthode de la bissection et oscillations numériques -- Méthode d'itération panique -- Régresseur non-linéaire -- Scénarios de simulation

Transformer Modeling for Low-And Mid-Frequency Electromagnetic Transients Simulation

RÉSUMÉ Dans cette thèse, de nouveaux modèles de transformateurs pour les transitoires électromagnétiques à basse fréquence ont été développés pour les appareils cuirassés. Ces modèles utilisent l'approche des inductances de fuite couplées, qui a l'avantage de ne pas nécessiter l'emploi d'enroulements fictifs pour connecter le modèle de fuite à un modèle topologique du noyau, tout en arrivant au même résultat en court-circuit que le modèle BCTRAN (matrice d'admittance indéfinie).Afin d'accroître le raffinement des modèles, il est proposé de partitionner les enroulements en bobines (agencement d'un ou de plusieurs tours de l'enroulement complet). Cependant, les mesures en court-circuit entre les bobines ne sont jamais disponibles, car on ne peut pas avoir accès à chaque bobine séparément en pratique. Pour combler cette lacune, une nouvelle méthode analytique basée sur la méthode des images a été développée, ce qui permet le calcul des inductances de court-circuit en 2-D entre des conducteurs de section rectangulaire. Les résultats de la nouvelle méthode convergent vers ceux obtenus par la méthode des éléments finis en 2-D. De plus, l'hypothèse que le champ de fuite est approximativement 2-D pour les transformateurs cuirassés a été validée à l'aide d'une simulation en 3-D avec un modèle plus complet de transformateur, incluant la cuve et les écrans magnétiques. Le produit de cette nouvelle méthode pour calculer les inductances de court-circuit entre les bobines a été utilisé pour calculer les inductances propres et mutuelles du modèle d'inductances de fuite couplées. Les résultats montrent, d'une part, que l'inductance de court-circuit totale des enroulements correspond bien aux mesures expérimentales et d'autre part, que le modèle d'inductances de fuite couplées donne des résultats identiques en court-circuit au modèle BCTRAN.En général, les inductances de fuite dans les modèles de transformateurs sont calculées à partir des essais en court-circuit et la branche de magnétisation est calculée à partir des essais à vide. De plus, on suppose généralement que les fuites sont négligeables pour le transformateur à vide et que le courant de magnétisation est infime pendant un court-circuit. Bien que l'hypothèse de perméabilité infinie soit valable pendant un court-circuit, car la force magnétomotrice dans le noyau est négligeable, on ne peut en dire autant de l'hypothèse selon laquelle les fuites sont négligeables à vide. En fait, le noyau ferromagnétique du transformateur commence à saturer à vide et une partie du flux magnétique fuit à l'extérieur du noyau. Pour prendre cela en compte, une méthode analytique novatrice est proposée dans cette thèse, qui permet d'enlever la contribution des flux de fuite lors des essais à vide afin de calculer correctement les branches de magnétisation des modèles proposés.Cependant, il doit être souligné que les courants de Foucault ont été négligés lors du développement de la nouvelle méthode analytique pour calculer les inductances de court-circuit (comme pour les autres méthodes analytiques).----------ABSTRACT In this work, new models are developed for single-phase and three-phase shell-type transformers for the simulation of low-frequency transients, with the use of the coupled leakage model. This approach has the advantage that it avoids the use of fictitious windings to connect the leakage model to a topological core model, while giving the same response in short-circuit as the indefinite admittance matrix (BCTRAN) model. To further increase the model sophistication, it is proposed to divide windings into coils in the new models. However, short-circuit measurements between coils are never available. Therefore, a novel analytical method is elaborated for this purpose, which allows the calculation in 2-D of short-circuit inductances between coils of rectangular cross-section. The results of this new method are in agreement with the results obtained from the finite element method in 2-D. Furthermore, the assumption that the leakage field is approximately 2-D in shell-type transformers is validated with a 3-D simulation.The outcome of this method is used to calculate the self and mutual inductances between the coils of the coupled leakage model and the results are showing good correspondence with terminal short-circuit measurements.Typically, leakage inductances in transformers are calculated from short-circuit measurements and the magnetizing branch is calculated from no-load measurements, assuming that leakages are unimportant for the unloaded transformer and that magnetizing current is negligible during a short-circuit. While the core is assumed to have an infinite permeability to calculate short-circuit inductances, and it is a reasonable assumption since the core's magnetomotive force is negligible during a short-circuit, the same reasoning does not necessarily hold true for leakage fluxes in no-load conditions. This is because the core starts to saturate when the transformer is unloaded. To take this into account, a new analytical method is developed in this dissertation, which removes the contributions of leakage fluxes to properly calculate the magnetizing branches of the new models. However, in the new analytical method for calculating short-circuit inductances (as with other analytical methods), eddy-current losses are neglected. Similarly, winding losses are omitted in the coupled leakage model and in the new analytical method to remove leakage fluxes to calculate core parameters from no-load tests. These losses will be taken into account in future work. Both transformer models presented in this dissertation are based on the classical hypothesis that flux can be discretized into flux tubes, which is also the assumption used in a category of models called topological models. Even though these models are physically-based, there exist many topological models for a given transformer geometry

BriFiSeg: a deep learning-based method for semantic and instance segmentation of nuclei in brightfield images

Generally, microscopy image analysis in biology relies on the segmentation of individual nuclei, using a dedicated stained image, to identify individual cells. However stained nuclei have drawbacks like the need for sample preparation, and specific equipment on the microscope but most importantly, and as it is in most cases, the nuclear stain is not relevant to the biological questions of interest but is solely used for the segmentation task. In this study, we used non-stained brightfield images for nuclei segmentation with the advantage that they can be acquired on any microscope from both live or fixed samples and do not necessitate specific sample preparation. Nuclei semantic segmentation from brightfield images was obtained, on four distinct cell lines with U-Net-based architectures. We tested systematically deep pre-trained encoders to identify the best performing in combination with the different neural network architectures used. Additionally, two distinct and effective strategies were employed for instance segmentation, followed by thorough instance evaluation. We obtained effective semantic and instance segmentation of nuclei in brightfield images from standard test sets as well as from very diverse biological contexts triggered upon treatment with various small molecule inhibitor. The code used in this study was made public to allow further use by the community

Intégration de relevés topographiques et de mesures GPS en mode cinématique pour l’analyse des performances de cyclistes sur piste.

Habituellement, lors des entraînements sportifs traditionnels, on ne mesure que des temps de passage à certains endroits le long du parcours ne permettant que de calculer des vitesses moyennes. Les analyses subséquentes ne tiennent ni compte de la trajectoire réelle de l’athlète ni de la topographie du parcours. Il est donc impossible de localiser l’endroit exact où l’athlète a perdu de la vitesse et d’en expliquer rationnellement la cause. Avec l’avancement technologique dans le domaine du positionnement par satellites GPS, il existe des récepteurs permettant de déterminer des positions à une précision centimétrique à une cadence élevée (10 Hz ou mieux), et ce en temps réel. Dans cet article, les mesures de performances de cyclistes obtenues par méthodes GPS sont intégrées à des données physiologiques et à des images vidéo. De plus, le relevé topographique du vélodrome a permis de construire un modèle numérique de terrain (MNT) de celui-ci.Usually, during traditional sport training one only records split times at certain points over a course which just allows to calculate average speeds. Subsequent analyses do not consider the real trajectory of the athlete and the topography of the course. It is therefore impossible to precisely locate where and/or when an athlete has lost speed. Advances in Global Positioning System (GPS) technology have led to receivers allowing for the calculation of positions, in real-time, with centimeter level accuracy at a high sampling rate (10 Hz or better). In this paper, the cyclists’ performances as monitored by GPS are integrated with video images and heart beat recording. A GPS topographical survey has also allowed to construct a Digital Terrain Model (DTM) of the velodrome

Reflection matrix approach for quantitative imaging of scattering media

We present a physically intuitive matrix approach for wave imaging and characterization in scattering media. The experimental proof-of-concept is performed with ultrasonic waves, but this approach can be applied to any field of wave physics for which multi-element technology is available. The concept is that focused beamforming enables the synthesis, in transmit and receive, of an array of virtual transducers which map the entire medium to be imaged. The inter-element responses of this virtual array form a focused reflection matrix from which spatial maps of various characteristics of the propagating wave can be retrieved. Here we demonstrate: (i) a local focusing criterion that enables the image quality and the wave velocity to be evaluated everywhere inside the medium, including in random speckle, and (ii) an highly resolved spatial mapping of the prevalence of multiple scattering, which constitutes a new and unique contrast for ultrasonic imaging. The approach is demonstrated for a controllable phantom system, and for in vivo imaging of the human abdomen. More generally, this matrix approach opens an original and powerful route for quantitative imaging in wave physics.Comment: 18 pages, 6 figure

Paroles de Bernard Lambert : un paysan révolutionnaire

Le texte publié est la transcription des paroles prononcées par Bernard Lambert le 4 mai 1981 au séminaire « Luttes dans et pour l'espace rural » de Françoise Bourquelot et Nicole Mathieu à l'EHESS. Un récit de trente ans d'histoire du syndicalisme paysan, qui montre une pensée d'avant-garde, une ouverture sur les problèmes internationaux, une capacité de se projeter dans l'avenir. A former union member testimony and commitment The history of French farmers' unions since thirty years is related by Bernard LAMBERT (1931-1984), a long-time trade unionist, founder member of the union « Paysans travailleurs » and author of the book entitled Les paysans dans la lutte des classes (1970). Bernard LAMBERT's talk to a seminar held in Paris on May 4th 1981 at the EHESS, reveals, through debates put back in their context, his avant-garde ideas, his concern for international problems and his will to anticipate the future

Simulated In-home Teletreatment for Anomia

This pilot study explored the feasibility of in-home teletreatment for patients with post-stroke anomia. Three participants over 65 years of age suffering from post-stroke anomia were treated in this pre/post-intervention case study. They received 12 speech therapy teletreatments (two sessions/week for 6 weeks) aimed at improving confrontation naming skills. Half of the failed items from a set of 120 preselected stimuli were trained during treatment (Block A-trained stimuli) while the other half served as controls (Block B-untrained stimuli). Variables measured were: 1) efficacy of treatment (performance on Block-A vs. Block B Stimuli), and 2) participants’ satisfaction with teletreatment (using a French adaptation of the Telemedicine satisfaction questionnaire). All participants showed clinically relevant improvement on confrontation naming of trained items and less improvement for untrained items. The researchers also obtained high satisfaction scores on the questionnaire (above 57/60). This pilot study supports the feasibility of speech therapy teletreatments applied to neurological language disorders

Sexual dimorphism in the walrus mandible: comparative description and geometric morphometrics

peer reviewedThe modern walrus Odobenus rosmarus is characterized by marked sexual dimorphism, related to its polygynous behavior and the aggressive competition between males during the breeding season. Previous studies treated skeletal sexual dimorphism in walruses either qualitatively or with basic quantitative measurements. The present study combines a detailed qualitative comparison of male and female walrus mandibles with quantitative two-dimensional geometric morphometrics analysis (principal component analysis, Procrustes ANOVA and a linear discriminant analysis). In addition to identifying previously recognized sexually dimorphic features (e.g., convexity of the anterior margin of the mandible in adult males), our study finds new morphological differences between males and females, such as a relative dorsal expansion of the anterior part of the mandible and an accentuated concavity between the dorsal margin and the coronoid process in adult males. Both our qualitative comparisons and quantitative analyses demonstrate that sexual dimorphism as expressed in the mandible of extant walruses is statistically significant and that (variation in) mandibular morphology can be used as tool to attribute sex with a good degree of accuracy to isolated mandibles or skeletons lacking the cranium. Sexual dimorphism in walruses is directly related to their sexual behavior, characterized as aggressive in males and linked to a polygynous reproduction system. Indeed, the difference in size of the tusks between males and females but also the use of these during intraspecific fights, can reasonably account for this great mandibular morphological disparity between adult males and females, but also among different ontogenetic stages. Finally, the results obtained in the present study may serve as a starting point for assessing sexual dimorphism more in-depth and studying inter- and intraspecific variation in the mandibles of fossil walruses by identifying quantified size and shape mandibular features