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Tuning bubble coalescence rates over orders of magnitude in liquid mixtures of simple surface rheology : experiments and theory
No full textThe coalescence time of bubbles in a liquid depends both on the nature of the liquid, which determines the molecular interactions between the gas/liquid interfaces and their surface rheology, and on the geometry, prescribed by the curvature of the bubbles. Coalescence is well described in pure liquids that have no interfacial rheology and in which the interactions are attractive. In contrast, the mechanisms are poorly understood in more complex liquids in which coalescence times are orders of magnitudes larger than in pure liquids and are unpredictable. To provide insight on these mechanisms, we use model systems that are binary mixtures of miscible oils. In these liquids, interfaces have purely attractive molecular interactions and the surface rheology simply reduces to a well-described surface elasticity, which can be controlled by the composition of the mixture. We measure the coalescence rate by forming periodic trains of bubbles in millifluidic tubes whose radius varies over 1.5 decade. We report coalescence times spanning more than three decades and, for a given composition, varying according to a power law with curvature, with an exponent larger than that reported in pure liquids. The experimental behavior is in excellent agreement with a numerical resolution of the coupled thermodynamical and hydrodynamical equations, performed in the simple geometry of a suspended liquid film. Our results clearly reveal the effects of both geometry and surface elasticity and show, for the first time, how the coalescence time of bubbles in liquid mixtures can be predicted quantitatively
« Les vertus improbables d’un corpus vain : les romans roses des années 1920-1930 »
No full textInternational audienc
Assessing nonlinear effects in high-power optical amplifiers for WDM FSO communications up to 200 Gbps per channel
No full textInternational audienceHigh power generation is an enabling technology for high capacity Free Space Optical feeder links. In this paper, we review recent results obtained over several measurement campaigns. We point out the different types of nonlinearities and their impact on the transmissions for different modulation formats. We then focus on the effects of four wave mixing on wavelength division multiplexing transmissions and we present a method to estimate receiver sensitivity penalties.
À propos de l’occupation ancienne du littoral de la Manche : les vestiges du plateau de Ver-Meuvaines (Calvados), du Bronze final au Bas-Empire
No full textInternational audienceThe excavations carried out in Ver-sur-Mer in 2019, in the area of the British Normandy Memorial dedicated to the memory of the Commonwealth soldiers killed during the landing and the Battle of Normandy, have seen the discovery of a set of remains ranging from the Late Bronze Age to the Lower Roman Empire. These remains are located at the top of the plateau of Ver-Meuvaines, which overlooks the coast as well as a vast prehistoric bog, the Quintefeuille Forest, where many witnesses of human contact with the coastline have been collected, from Prehistory to Late Antiquity. The Late Bronze Age settlement consists of a circular building, the second discovered during the archaeological works before the construction of the memorial. It was succeeded by a U-shaped enclosure, open to the east, and doubled to the west by a ditch that connects it to the south with another enclosure, spotted in aerial survey. The U-shaped enclosure houses six buildings, including five granaries and a possible dwelling, eight silos, as well as some stone quarries, dating from Hallstatt D/La Tène A. In the bordering ditch, that and seems older (Hallstatt C), was found a set of salt brickworks. The third occupation highlighted dates back to Roman Antiquity and brings together a set of stone quarries along a way, dated from the 2nd-3rd Centuries AD, an isolated well and a cremation tomb from the 3rd Century, as well as two women burials, probably relatives, buried side by side facing the sea, during the 4th Century. All these remains are associated with occupations that cover the entire extent of the coastal plateau, as well as various elements of material culture testifying to the relations maintained by their occupants with the coast: hunting and fishing practices, salt production, livestock farming. These data highlight a mixed economy based on the combination of land and coastal resources and are part of the long history of people living by the Channel.Les fouilles menées à Ver-sur-Mer en 2019, dans l’emprise du British Normandy Memorial dédié à la mémoire des soldats du Commonwealth tombés lors du débarquement et de la bataille de Normandie, ont vu la mise au jour d’un ensemble de vestiges allant de la fin de l’âge du Bronze au Bas-Empire romain. Ces vestiges s’inscrivent au sommet du plateau de Ver-Meuvaines qui surplombe la côte ainsi qu’une vaste tourbière préhistorique, la forêt de Quintefeuille, où ont été recueillis de nombreux témoins de la fréquentation humaine du littoral, de la préhistoire à la fin de l’Antiquité. L’occupation du Bronze final consiste en un édifice circulaire, un second a été mis au jour sur le plateau au cours des travaux préalables au mémorial. Lui a succédé un enclos ouvert à l’est et doublé à l’ouest par un fossé qui le relie au sud à un autre enclos, repéré en prospection aérienne. L’enclos en U abrite six bâtiments, dont cinq greniers et une possible habitation, huit silos, ainsi que quelques carrières de pierre, datés du Hallstatt D/La Tène ancienne. Le fossé qui le borde a livré quant à lui un lot de briquetage salicole et semble un peu plus ancien (Hallstatt C). La troisième occupation mise en évidence remonte à l’Antiquité et réunit un ensemble de carrières de pierre le long du chemin, datées des iie-iiie s. apr. J.-C., un puits isolé et une tombe à incinération du iiie s., ainsi que deux inhumations de femmes, probablement parentes, enterrées côte à côte face à la mer, au ive s. Tous ces vestiges sont associés à des occupations qui couvrent toute l’étendue du plateau littoral, ainsi qu’à divers éléments de culture matérielle témoignant des relations entretenues par leurs occupants avec le littoral : pratiques cynégétiques et halieutiques, production de sel, élevage. Ces données mettent en lumière une économie fondée sur la mixité des ressources de la terre ferme et du trait de côte, et s’inscrivent dans la longue histoire des populations riveraines de la Manche
Le site de la « Rue de la Missionnaire » : première attestation d’une occupation domestique de l’âge du Bronze à l’Île d’Yeu (Vendée)
No full textNational audienceThe excavation of La Missionnaire, located in the central part of Île d’Yeu (Vendée), has provided insight of a Bronze Age domestic occupation. This settlement comprises two ditches and a possible building with five postholes. Radiocarbon analysis highlights two chronological phases, spanning from the Early Bronze Age to the beginning of the Middle Bronze Age. However, the small surface area of the excavation and the poor preservation of the archaeological remains hinders a detailed analysis of the site. Nevertheless, unpublished lithic and pottery assemblages underscore the domestic nature of the occupation.La fouille du site de la Missionnaire a permis d’appréhender une occupation domestique datée de l’âge du Bronze au centre de l’île d’Yeu (Vendée). Celle-ci se caractérise par la présence de deux fossés et d’un éventuel bâtiment composé de cinq trous de poteau conservés. Les datations par le radiocarbone ont permis de déceler deux phases dans cette occupation, s’échelonnant entre l’âge du Bronze ancien et le début de l’âge du Bronze moyen. La fenêtre réduite de l’opération ainsi que la faible conservation des vestiges ne permettent cependant pas de caractériser précisément cet habitat. L’aspect domestique est tout de même visible au travers de l’étude des corpus inédits du mobilier lithique et céramique
Façades monumentales en pierre ou en terre des mégalithes sur les rivages atlantiques de l’Europe : serions-nous passés à côté de quelque chose d’important ?
No full textNational audienceIt is widely agreed that the megalithic monuments of Great Britain, Ireland and western France are furnished very often with an impressive stone façade, in contrast to those of the Iberian peninsula. In the eastern part of Britain, other monuments take the form of mounds of earth with edges marked by timber fences or turf walling, as are also found in the Channel Islands, in Normandy, and in Charente. The role that may have been played by structures of unbaked earth as an alternative constructional technique should also be considered. That would modify our view of the external elevation of certain of these monuments, and of the phasing that is proposed, and perhaps even our understanding of the use of the associated burial spaces. Recent work such as that undertaken in Galicia or in the Asturias in Spain contributes evidence relevant to this issue. Beyond these specific examples, the aim of this article is to lay the foundations for research at the scale of the European Atlantic façade.On partira du constat généralement admis que les monuments mégalithiques de Grande-Bretagne, d’Irlande et de l’Ouest de la France disposent très souvent d’une imposante façade en pierre, contrairement à ceux de la péninsule Ibérique. Dans la partie est des îles Britanniques, d’autres monuments correspondent à des accumulations de terre délimitées par des parois en bois ou construites en mottes de gazon, comme également dans les îles Anglo-Normandes, en Normandie, ou en Charente. On peut toutefois s’interroger sur l’existence de bâtis en terre crue comme technique de construction alternative, ce qui pourrait modifier notre perception de l’élévation de certains de ces monuments, mais aussi parfois jusqu’aux phasages proposés, voire notre compréhension du mode de fonctionnement des espaces sépulcraux afférents. De récents travaux, comme en Galice ou dans les Asturies, en Espagne, viennent concrétiser ce questionnement. Au-delà de ces quelques exemples, l’objet de cet article sera donc de poser les premières bases d’une problématique à l’échelle de la façade atlantique de l’Europe
Vers une édition sémantique de vidéos volumétriques: segmentation 4D basée Gaussian Splatting et moyens d’évaluation
No full textVolumetric video enables dynamic 3D representations of real-world scenes, supporting free-viewpoint exploration and natural 6 Degrees of Freedom (6 DoF) navigation. To achieve truly immersive interaction, semantic segmentation is essential for object-level understanding. While recent novel view synthesis methods, such as Neural Radiance Fields (NeRF) and 3D Gaussian Splatting (3DGS), have advanced 3D reconstruction and static scene segmentation, semantic segmentation in 4D dynamic scenes remains relatively underexplored. Key difficulties include maintaining semantic consistency across space and time, as well as the lack of richly annotated multi-view datasets for dynamic environments. This thesis addresses this gap by introducing MUVOD, a multi-view video object segmentation dataset featuring 17 real-world scenarios with 4D-consistent object masks for 459 instances across 73 categories. A benchmark is established for evaluating 4D segmentation methods. Furthermore, we propose a novel 4D segmentation approach based on 3DGS, extending static object segmentation to dynamic scenes by incorporating a learnable Object Identity Encoding into the reconstruction pipeline. The method supports photorealistic RGB and mask rendering at arbitrary viewpoints and timepoints, offering an efficient and portable solution for 4D scene understanding and editing.La vidéo volumétrique permet des représentations 3D dynamiques de scènes réelles, offrant une exploration multi-vues et une navigation naturelle en six degrés de liberté (6 DoF). Pour une interaction véritablement immersive, la segmentation sémantique est essentielle afin de permettre une compréhension des objets au niveau individuel. Bien que les méthodes récentes de synthèse de vues nouvelles, telles que les Neural Radiance Fields (NeRF) et le 3D Gaussian Splatting (3DGS), aient considérablement fait progresser la reconstruction 3D et la segmentation de scènes statiques, la segmentation sémantique dans des scènes dynamiques 4D reste relativement peu explorée. Les principaux défis incluent le maintien de la cohérence sémantique dans l’espace et le temps, ainsi que le manque de jeux de données multi-vues richement annotés pour les environnements dynamiques. Cette thèse répond à ces limitations en introduisant MUVOD, un jeu de données de segmentation d’objets en vidéo multi-vues, couvrant 17 scènes réelles avec des masques 4D cohérents pour 459 instances réparties sur 73 catégories. Un benchmark est proposé pour l’évaluation des méthodes de segmentation 4D. Nous proposons également une nouvelle approche de segmentation 4D fondée sur 3DGS, qui étend la segmentation d’objets statiques aux scènes dynamiques en intégrant un vecteur d’identité d’objet apprenable dans le pipeline de reconstruction. Cette méthode permet le rendu photoréaliste en RGB ainsi que la génération de masques d’objets à n’importe quel point de vue et instant temporel, offrant ainsi une solution efficace et portable pour la compréhension et l’édition de scènes 4D
Dating C/S Structures in Syntectonic Granites by In Situ Rb‐Sr Analyses on Muscovite
No full textInternational audienceThe interplay of crystallisation, deformation and fluid–rock interactions makes deciphering geochronological information complex in syntectonic granites. In this study, we apply in situ Rb‐Sr analyses to selected samples from the Questembert Variscan syntectonic granite in Western France, which was emplaced along the South Armorican Shear Zone as indicated by widespread C/S structures. The results show that the Rb‐Sr system in muscovite records about 25–30 Ma of geological activity, from crystallisation of the granite at ca . 320–315 Ma, recorded by muscovite porphyroclasts, to late‐stage permeation of small quantities of fluids along pre‐existing shear planes at 290 Ma that triggered localised recrystallization of fine‐grained muscovite during the waning stages of regional deformation. These results, thus, show that microscale in situ Rb‐Sr analyses allow recognising discrete events long after the main phase of crystallisation of the granite, emphasising the need for careful petrographic analysis to inform interpretation of geochronological data
Image processing reveals the robustness of vision transformers against adversarial attacks
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Pelvic organ prolapse is highly prevalent in women with spina bifida
No full textInternational audienceIntroduction: Women with spina bifida often experience neurological impairments leading to pelvic organ dysfunction, including difficulties with bladder and bowel emptying that necessitate frequent Valsalva manoeuvres. These factors, combined with pelvic floor weakness, may increase the risk of pelvic organ prolapse (POP). This study aimed to assess the prevalence of POP in women with spina bifida, identify associated risk factors and evaluate outcomes of surgical management.Methods: We retrospectively analysed a prospectively maintained database of women with spina bifida seen at a French referral centre from 2007 to 2024. Age under 18 and congenital perineal abnormality were exclusion criteria. The primary outcome was the presence of POP grade 2 or higher (Baden-Walker classification). Secondary outcomes included symptomatic POP requiring surgery, recurrence after surgery, use of vaginal pessaries and related symptoms.Results: POP grade ≥2 was present in 14.8% of patients. Women with POP were older (median 44 vs. 31 years; p < 0.0001) and more frequently parous (58.5% vs. 18.3%; p < 0.0001), although 41.5% of POP cases occurred in nulliparous women. Apical prolapse was predominant (64.3%). Among 11 patients who underwent POP surgery, 54.5% experienced recurrence. Multivariate analysis identified parity (OR 5.33; p = 0.005) and lower maximum urethral closure pressure (OR 0.97; p = 0.02) as independent risk factors.Conclusions: POP is highly prevalent in young adult women with spina bifida, including many nulliparous patients. The parity status and a low maximum urethral closure pressure could be associated with an increased risk of POP in this population. High recurrence after surgery highlights the need for information, routine screening and tailored management in this population