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GW241011 and GW241110: Exploring Binary Formation and Fundamental Physics with Asymmetric, High-spin Black Hole Coalescences
No full textInternational audienceWe report the observation of gravitational waves from two binary black hole coalescences during the fourth observing run of the LIGO–Virgo–KAGRA detector network, GW241011 and GW241110. The sources of these two signals are characterized by rapid and precisely measured primary spins, nonnegligible spin–orbit misalignment, and unequal mass ratios between their constituent black holes. These properties are characteristic of binaries in which the more massive object was itself formed from a previous binary black hole merger and suggest that the sources of GW241011 and GW241110 may have formed in dense stellar environments in which repeated mergers can take place. As the third-loudest gravitational-wave event published to date, with a median network signal-to-noise ratio of 36.0, GW241011 furthermore yields stringent constraints on the Kerr nature of black holes, the multipolar structure of gravitational-wave generation, and the existence of ultralight bosons within the mass range 10–10 eV
Bridging the gap: oxygen and nutrient budgets in the Loire estuary using a benthic-pelagic box model
No full textInternational audienceIn hypoxic estuaries, sediment feedback is clearly a key factor in nutrient and oxygen cycling, favouring nutrient enrichment and oxygen depletion in the water column. It is crucial to understand these mechanisms to implement effective management strategies for these coastal systems. In this study, a coupled benthic-pelagic box model was developed to assess the impact of sediment and water column processes on nutrient and dissolved oxygen stocks in a hypoxic estuary. The model integrates physical and biogeochemical processes, focusing on the sediment-water column interaction during two contrasting hydrological contexts sampled in 2021: a winter flood and a summer low discharge period. The model reproduces the main processes well, despite some discrepancies with the observed data due to the underlying assumptions, which are discussed. The winter flood caused substantial erosion of upstream sediments, resulting in a strong redox gradient and high sediment-water exchange. The short residence time of the water prevented solutes accumulation, minimising their influence on oxygen and nutrient stocks. In summer, under low flow conditions, benthic recycling to the water column is intensified, resulting in an increase in ammonium concentration of up to 91%, compared to 67% from pelagic processes. In contrast, phosphate release remains modest (around 4%), particularly from the sediments underneath the Turbidity Maximum Zone (TMZ), where benthic exchange is limited by the presence of an oxide-rich sediment layer that acts as a barrier. However, phosphate availability in summer is primarily driven by pelagic desorption from suspended particles, notably in the TMZ. The results clearly highlight a decoupling between nitrogen and phosphorus recycling, which is promoting nitrogen enrichment and potentially favouring harmful algal blooms and hypoxia. The proposed simplified modelling approach is a crucial step in identifying the estuarine processes controlling oxygen and nutrient dynamics and can be easily applied to any estuary
Approcher les futurs urbains par le récit
No full textInternational audienceApprocher les futurs urbains par le récit Laurent Matthey et Luca Piddiu, avec les étudiants de l'atelier « Imagination des futurs et méthodes créatives». Le récit est de plus en plus utilisé comme instrument de prospective territoriale. À partir d'un atelier d'étudiants dans la région genevoise, cet article s'intéresse à la manière dont la fiction permet de tester des modèles d'organisation spatiale. De la prévision à la prospective, renouveler la planification par le récit. Qu'on la conçoive comme une tentative d'organisation, de régulation ou d'anticipation, la planification territoriale est inextricablement liée à la question du futur souhaité par une collectivité donnée. Si elle est encore souvent abordée d'un point de vue prévisionniste, cette question tend à s'ouvrir à des processus plus participatifs, qui prennent en considération la diversité des mondes possibles. Des démarches tendent ainsi à se développer à différentes étapes de la fabrique des plans, pour mettre en dialogue des visions alternatives d'un devenir collectif. On y mobilise des méthodes classiques (analyse temporelle, diagnostic du présent, identification des signaux faibles, scénarios, stratégies d'action…) ou émergentes (retroprospective [backcasting], design fiction, fictions exploratoires…) tirées de la boîte à outils de la prospective territoriale. Les approches par le récit prennent une importance notable dans ce contexte. Sans doute parce que le récit est paré de vertus innombrables. Il renforcerait l'engagement des parties prenantes dans la décision. Il affinerait la perception sensible des mondes à venir. Il faciliterait enfin l'imagination et permettrait de penser l'inconcevable (Matthey, Gaberell et Cogato Lanza 2025). Il est toutefois souvent difficile d'identifier ce dont le récit est précisément le nom. Certains usages semblent en effet en faire le synonyme d'imaginaire, d'autres l'identifient à une vision collective, d'autres enfin le renvoient à l'idée d'une histoire suffisamment forte pour mobiliser un large public. Si cette polysémie participe sans doute de son attrait, une définition minimale pourrait toutefois permettre de mieux identifier les différentes opérations symboliques
Promoting a master plan by encouraging participation: On the culture of convergence in urban planning
No full textInternational audienceThe aim of this contribution is to help develop a new model of the use of storytelling in planning. To this end, it draws on media studies research as well as literary studies that examine so-called transmedia storytelling devices. The authors use this method to examine the communication strategy around the 2030 Cantonal Master Plan of the Republic and Canton of Geneva (Switzerland). This communication strategy, which attempts to construct the reception of development projects, mobilizes practical regimes that can strengthen the engagement of different audiences with the process of giving narrative form to future urban developments. Communication and public participation in an urban project tend to hybridize, thereby complexifying debates on the use of storytelling in planning, which often contrast its educational use (explain projects to the general public) with its manipulative use (make projects desirable so they may be accepted). By conducting an analysis through the prism of transmedia storytelling, we can simultaneously consider these two aspects of communication in planning
Impact de l’alimentation périnatale déséquilibrée sur le remodelage de l’axe intestin-cerveau
No full textFollowing an initial research path focused on dopaminergic mechanisms and synaptic plasticity in Parkinson’s disease, I shifted my work upon joining INRAE to study the gut-brain axis and the impact of perinatal nutrition on brain development. My research first addressed the remodeling of reward circuits following an unbalanced maternal diet, in which I identified long-lasting dysfunctions in the dopaminergic system and disruptions of energy homeostasis. I then conducted a mechanistic study on the role of cholecystokinin (CCK), specifically the blockade of the CCK2 receptor in the striatum, to understand how this neuropeptide modulates synaptic plasticity and motivational behaviors.Finally, through a one-year research mission in the United States, I acquired advanced tools (chemogenetics, targeted tracing, FosTRAP2) to better decipher the interactions between the gut, the vagus nerve, and cerebral circuits. These approaches have been crucial for securing strategic funding (ORION, ANR GARpe, Microconnect), thereby reinforcing my national and international standing. Alongside my research activities, I have integrated two PhD students in co-supervision since joining INRAE, and a third thesis has recently begun under the GARpe and ORION projects, illustrating both my commitment to training early-career scientists and the evolving dynamic of my research themes.Après un parcours initial consacré aux mécanismes dopaminergiques et à la plasticité synaptique dans la maladie de Parkinson, j’ai réorienté mes recherches, lors de mon recrutement à INRAE, vers l’étude de l’axe intestin-cerveau et l’influence de la nutrition périnatale sur le développement cérébral. Mes travaux ont porté d’abord sur le remodelage des circuits de la récompense consécutif à une alimentation maternelle déséquilibrée, où j’ai mis en évidence un dysfonctionnement durable du système dopaminergique et une altération de l’homéostasie énergétique. J’ai ensuite entrepris une étude mécaniste du rôle de la cholécystokinine (CCK), notamment via une inhibition du récepteur CCK2 dans le striatum, pour comprendre comment ce neuropeptide modulait la plasticité synaptique et les comportementsmotivationnels. Enfin, grâce à une mission de recherche d’un an aux États-Unis, j’ai acquis des compétences et des outils de pointe (chémogénétique, traçages spécifiques, FosTRAP2) pour mieux décrypter les interactions entre l’intestin, le nerf vague et les circuits cérébraux. Ces approches ont été déterminantes pour l’obtention de financements stratégiques (ORION, ANR GARpe, Microconnect), me permettant de consolider mon positionnement national et international. Parallèlement à mes activités de recherche, j’ai intégré dans ce travail deux doctorants en co-encadrement depuis mon arrivée à INRAE, et une troisième thèse vient de débuter dans le cadre des projets GARpe et ORION, illustrant à la fois mon engagement dans la formation de jeunes chercheurs et la dynamique de mes thématiques de recherche
Stochastic programming for the design and configuration planning of reconfigurable assembly lines under demand uncertainty
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On-the-fly adaptive sampling strategy for data-driven computational mechanics: Applications to computational homogenisation
No full textInternational audienceTo overcome well-known drawbacks of classical phenomenological constitutive modelling of non-linear heterogeneous materials, a popular approach is the so-called computational homogenisation (CH), which relies on a combined description of constitutive behaviours and spatial morphology of smaller scales constituents. Their computational implementation usually encompasses two-level finite element numerical models (FE2), which quickly leads to prohibitive computational costs, even for problems with a modest number of degrees of freedom. A popular strategy in the literature to alleviate such computational burden is to use machine learning-based surrogate constitutive models, although fundamental drawbacks such as the absence of interpretability, limited extrapolation capability, and limited mathematical analysis, are still present. On the other hand, the so-called (model-free) data-driven computational mechanics (DDCM) paradigm Kirchdoerfer and Ortiz (2016) proposes the direct integration of ``experimental data'', completely bypassing the need for explicit constitutive laws. The main goal of this work is to show how the DDCM approach can be used in synergy with CH to bypass fully-coupled multiscale computations. A naive approach to using multiscale constitutive behaviour along with DDCM is the offline construction of a database via CH by assuming some sampling of the strain-space. This approach has little interest since the region of the strain-space covered during a simulation is problem-dependent. During the iterations of the DDCM solver, a finite set of strain-stress pairs is used as input, while another set, comprising mechanically admissible states, is dynamically generated. Such a scenario naturally unveils the most relevant goal-oriented phase-space instances to guide a material dataset enrichment iterative procedure, bridging DDCM and CH towards computationally effective two-scale simulations. On the other hand, the performance is limited if the quality of the mechanically admissible states is low, particularly when the material dataset is not insufficiently dense. To address these challenges, we propose meaningful ranking scores alongside numerical techniques to enhance the DDCM solver in sparse data scenarios. As result, we show through meaningful numerical examples that the proposed framework results in significant computational savings if compared to standard FE2
The R2D3 approach towards fast quantitative NMR: maintaining accuracy and reducing the experimental time
No full textInternational audienceThe R2D3 approach can drastically decrease the experimental time while retaining the key aspects of a quantitative experiment. A high time gain factor can be achieved, close to that of INEPT and without its drawbacks
Experimental setup development for CeO2 normal spectral emissivity measurement at high temperature
No full textInternational audienceCeO2 emissivity knowledge with its temperature is primordial for solar fuel production workframe. Indeed, it plays a crucial role in the ceramic architecture optimisation in order to increase its efficiency. An experimental setup using radiometric method has been developped to allow normal spectral emissivity measurement from 400 to 7500 cm−1(i.e. from 1,33 to 20 µm) and from 400 to 1244°C is presented in this work. It has been validated with SiC, from which the radiative behaviour is well known, and then has been used for CeO2 ceramic characterization