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Analyse numérique de l'interaction entre une chambre de combustion rotative à détonation et une turbine axiale
No full textA Rotating Detonation Combustor (RDC), where one or several detonation waves are rotating around a typically annular combustion chamber, may be an alternative combustion technology for gas turbines, with perspectives of reducing fuel consumption, increasing thermal efficiency and reducing emissions. Among numerous additional challenges, thepossibly detrimental interaction of the unsteady, high-enthalpy combustor exhaust gas with the downstream located axial turbine is a largely unresolved issue. To facilitate this coupling, installing an ejector between RDC and turbine is a viable option. In the current work, three separate ejector configurations are investigated using a Large-Eddy Simulation(LES), Reynolds-Averaged Navier-Stokes (RANS) simulations and 1D modeling, and the potential for integration with an RDC is evaluated. The analysis revealed that both the internal flow field and the design requirements are considerably different between a conventional ejector and an ejector coupled to an RDC. The study showed that integrating an ejector with an RDC renders the exhaust gas much more admissible for turbine entry by reducing fluctuations, mean velocity and mean temperature. Nevertheless, the presence of the ejector in the thermodynamic cycle led to performance penalties, compared to a reference cycle without an ejector present. The ejector entrainment ratio was determined as a crucial parameter controlling both dampening characteristics and global cycle performance: Small values provided for high cycle efficiency but low dampening (and vice versa). A detailed analysis of local entropy generation in the ejector showed that under RDC-representative conditions, thermal losses show the highest contribution, followed by viscous dissipation losses. The majority of losses concentrated in the shear layer between the RDC exhaust gas and the entrained secondary flow. Based on a design study using steady RANS, a preliminary set of design guidelines could be established for an annular ejector coupled to an RDC. The work showed that a minimal secondary flow passage, and a relatively long constant-area mixing chamber are beneficial. In addition, it was asserted that 1D and RANS modeling are useful in preliminary design, but that an unsteady approach such as LES is necessary afterwards to capture the essential flow physics. The presented work showed both a methodology to evaluate integrated ejector performance, and a possible final annular ejector that can be readily coupled to an RDC.Une chambre de combustion à détonation rotative (RDC), dans laquelle une ou plusieurs ondes de détonation tournent autour d’une chambre de combustion annulaire, peut constituer une technologie de combustion alternative pour les turbines à gaz, avec des perspectives de réduction de la consommation de carburant et de réduction des émissions. Parmi de nombreux défis, l’interaction potentiellement négative des gaz d’échappement instationnaires et à haute enthalpie de la chambre de combustion avec la turbine axiale située en aval est un problème en grande partie non résolu. Pour faciliter ce couplage, l’installation d’un éjecteur entre le RDC et la turbine axiale est une option. Dans le travail actuel, trois configurations d’éjecteurs sont étudiées à l’aide d’une simulation aux grandes échelles (LES), de simulations Reynolds-Averaged Navier-Stokes (RANS) et d’une modélisation 1D, et le potentiel d’intégration avec un RDC est évalué. L’analyse a révélé que la physique interne et les exigences de conception sont considérablement différents entre un éjecteur conventionnel et un éjecteur intégré avec un RDC. L’étude a montré que l’intégration d’un éjecteur avec un RDC rend les gaz d’échappement plus admissibles à l’entrée de la turbine en réduisant les fluctuations, la vitesse moyenne et la température moyenne. Néanmoins, la présence de l’éjecteur dans le cycle thermodynamique entraîne des pénalités de performances, par rapport à un cycle de référence sans présence d’éjecteur. Le rapport d’entraînement a été déterminé comme un paramètre contrôlant à la fois les caractéristiques d’amortissement et les performances globales du cycle : de petites valeurs permettent une efficacité de cycle élevée mais un faible amortissement (et vice versa). Une analyse détaillée de la génération d’entropie locale dans l’éjecteur a montré que dans des conditions représentatives du RDC, les pertes thermiques présentent la contribution la plus élevée, suivies par les pertes par dissipation visqueuse. La majorité des pertes se sont concentrées dans la couche de cisaillement entre les gaz d’échappement RDC et le flux secondaire entraîné. Sur la base d’une étude de conception utilisant RANS, certaines lignes directrices de conception pourraient être établis pour un éjecteur annulaire couplé à un RDC. Les travaux ont montré qu’un passage d’écoulement secondaire minimal et une chambre de mélange à section constante relativement longue sont bénéfiques. En outre, il a été affirmé que les modélisations 1D et RANS sont utiles dans la conception préliminaire, mais qu’une approche instationnaire telle que LES est nécessaire par la suite pour capturer la physique essentielle de l’écoulement
Sex-specific benefits of a combined supplementation of B vitamins, nicotinamide riboside, folate and cobalamin, in a murine model of heart failure
No full textInternational audienceDespite a substantial therapeutic arsenal to treat patients affected by heart failure (HF), no treatment specifically targets alterations of cardiac energy metabolism described in HF. Based on the results of previous studies demonstrating the cardiac preventive effects of B vitamins when introduced before inducing cardiac pressure overload in mice, we investigated the efficacy of a diet supplemented with a B vitamin cocktail (B3, B9 and B12 (3VitB)) to restore energy metabolism and improve cardiac function in an animal model of established HF. Four weeks after transverse aortic constriction (TAC) induction, male and female mice were treated with 3VitB. 3VitB increased life expectancy and reduced the TAC-induced alterations of cardiac parameters in males. Although these effects on survival and cardiac function were less clear in females due to their higher resistance to TAC, the 3VitB cocktail was beneficial in females as 8 weeks of treatment improved physical capacities and led to milder cardiomyocyte stress-induced hypertrophy in similar ways to those observed in males. In both sexes, 3VitB protected cardiac mitochondrial oxidative capacities, at least by supporting the process of mitochondrial biogenesis. Interestingly, our results revealed sex-specificities not only in response to cardiac pressure overload but also in response to 3VitB treatment. Overall, this study demonstrated the efficacy of 3VitB to preserved cardiac function and energy metabolism in an established HF model, especially in males that are more sensitive to cardiac pressure overload. This confers credit to vitamin supplementations and to metabolic therapy as new strategies to treat HF
Guidelines for Lyme borreliosis: clinical manifestations
No full textInternational audienceLyme borreliosis (LB) is a tick-borne zoonosis caused by spirochetes belonging to the Borrelia burgdorferi sensu lato (Bb sl) complex. In Europe, multiple pathogenic species-including B. afzelii, B. garinii, and B. burgdorferi sensu stricto-are responsible for a wide diversity of clinical manifestations. The disease may present in various stages-localized, early disseminated, or late disseminated-depending on the time elapsed since the tick bite and the organs involved, such as the skin, joints, or nervous system.Erythema migrans (EM) is the most frequent clinical presentation, accounting for approximately 80% of LB cases in France. It is an early localized form, characterized by a painless, centrifugally expanding erythematous lesion centered on the tick-bite site, typically appearing 3 to 30 days post-exposure and resolving within 15 days under antibiotic therapy. Neuroborreliosis (NBL), most commonly associated with B. garinii, occurs in approximately 6-15% of French cases. It represents a disseminated form, often presenting as meningoradiculitis or peripheral facial palsy, with generally favorable outcomes under antibiotic treatment, although persistent post-infectious symptoms may occur.These guidelines address the full clinical spectrum of LB, from common manifestations such as EM to rare complications involving cardiac or ophthalmological systems. They also encompass atypical presentations not specifically linked to LB and provide specific recommendations for special populations, including pregnant women and immunocompromised patients. The current section summarizes the principal clinical features of LB and supports the rationale underlying recent diagnostic and therapeutic recommendations
Punctured tubular neighborhoods and stable homotopy at infinity
No full textIn this revised version (August 2025), we add a survey of \infty-categorical (co)limits and a replacement lemma for higher functoriality (Lem. 1.4.5), a framework for explicit models of punctured tubular neighborhoods (§3.4), and a new theory of orientation classes for line bundles and Thom spaces of virtual bundles over singular curves (§5.1, 5.2). Building on this, we make explicit the normalization of the resulting isomorphisms, reformulate our main theorem (Th. 5.3.3) to incorporate orientation classes, and show how these choices yield quadratic Mumford matrices computed via Smith form over the Grothendieck-Witt ring of the base field. The appendices are expanded to give a better account of the notion of orientation classes, and to describe trace computations on Chow-Witt groups over possibly non-perfect fields. We warmly thank the referee for insightful comments that motivated us to make our approach much more precise and comprehensive
Combattre les biofilms inter-règnes à l’aide de composésisolés de la plante invasive Ludwigia grandiflora et de ses champignons endophytes
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Lignaggio e vassallaggio nella Chanson de Guillaume, l’auxilium per la battaglia
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Les effets de la responsabilité subjective des sujets privés de liberté en Argentine : approches théorique et psychopathologique
No full textWhat link can be observed between the law and the statements made by the inmate during this meeting with the clinical psychologist in the prison environment? The behaviour of inmates raises questions when they break the codes that establish order in a given society. Our society in the 21st century is particularly virulent and lacks clear boundaries. This society, filled with objects and new technologies, creates more distant social ties. The effects: subjects without a compass, without boundaries, expressing themselves with words that are both empty and dense, and with complete literalness. To understand these effects, we will briefly discuss the history of the Penal Code in our country, Argentina, and then we will enter a high-security prison. We will listen to the words of the subjects through clinical excerpts, develop concepts and conduct an in-depth analysis from a psychoanalytical perspective. Our conceptual compass, that of subjective responsibility in relation to subjective truth, will enable us to stay on course throughout this study. The subject of our research invites us to focus on the grey areas of this encounter between the individual and collective spheres. The response we receive is that of subjects deprived of freedom who have cut themselves off from the chains of subjective imprisonment, suffering according to their family history but in close relationship with the current world that tends to dehumanise them.Quel lien peut-on observer entre la loi juridique et la prise de parole du sujet incarcéré lors de cette rencontre entre le sujet et le.la psychologue clinicien.ne dans le milieu carcéral ? Les effets des sujets incarcérés nous interrogent dès lors qu'ils transgressent les codes permettant d’établir un ordre dans une société donnée. La nôtre, dans ce XXIe siècle, est particulièrement virulente et sans limites claires. Cette société comblée d’objets et de nouvelles technologies crée des liens sociaux plus distants. Les effets : des sujets sans boussole, sans limite contenante, s’exprimant avec une parole à la fois vide et dense, et dans une littéralité pleine et entière. Pour comprendre ces effets, nous aborderons succinctement l’histoire du Code pénal dans notre pays, l’Argentine, puis nous entrerons dans une prison de haute sécurité. Nous écouterons la parole des sujets à travers des extraits cliniques, nous déploierons des concepts et nous mènerons une analyse approfondie depuis la psychanalyse. Notre boussole conceptuelle, celle de la responsabilité subjective en lien avec la vérité subjective, nous permettra de garder le cap tout au long de cette étude. Le sujet de notre recherche nous invite à mettre l’accent sur les zones d’ombre de cette rencontre entre les champs individuel et collectif. La réponse que nous accueillons est celle de sujets privés de liberté qui se sont coupés des chaînes d’un emprisonnement subjectif, souffrant selon leur roman familial mais en étroite relation avec ce monde actuel qui tend à les déshumaniser
Quantifying grain boundary deformation mechanisms in small-grained metals
No full textInternational audienceDislocations are the crystalline defects responsible for the mechanical properties of conventional metals and alloys. When they become scarce or constrained, such as in nanocrystals 1 , grain boundarybased mechanisms may compensate and lead to permanent deformation 2,3 . Shear-migration coupling is thought to be the most efficient of these processes 4,5 , but despite an intense research activity, no consensus has emerged to quantify the possible shear produced by a migrating grain boundary 6 . Here we show experimentally that in small-grained polycrystals, this shear does not depend on the grain boundary misorientation and that its efficiency remains low. These findings support a novel conception of grain boundaries, that may not be regarded as crystalline defects carrying an intrinsic "coupling factor" 7 (similarly to the Burgers vector of a dislocation) but rather as specific lattices containing peculiar defects, known as disconnections, that will in turn govern the properties, at least mechanical, of grain boundaries. They also confirm that polycrystals can plastically deform without dislocations but less effectively, providing a potential path to explain the poor ductility of nanocrystalline metals at low and room temperature
Nicolas Legros de la Neuville (1764–1844), the Inventor of the ‘fixateur’
No full textInternational audienceIn April 1822, the French Minister of State for the Interior granted a patent for the manufacture of fixateurs, a mechanism for stabilising the tuning pegs of plucked and bowed stringed instruments to prevent them from slipping under the tension of the strings, a device found in only a handful of guitars of the period, several of which were made by the famous French guitar maker Pierre René Lacote (1785–1871). Although briefly mentioned in several modern sources, this device, halfway between the traditional system of wooden tuning pegs and modern worm gear tuners, has not been the subject of any study, nor has its inventor, Nicolas Legros de la Neuville (1764–1844), one of the many minor music theory instructors and guitar teachers who lived in Paris at the time of La Guitaromanie. Therefore, in order to shed more light on Legros de la Neuville and his invention, the fixateur, this article will provide details on his life and works, as well as on the functioning and significance of this mechanism