HAL-MINES ParisTech
Not a member yet
27348 research outputs found
Sort by
Low temperature brine formation by serpentinization on asteroid (162173) Ryugu
No full textInternational audienceSecondary mineral prevalence in Ryugu samples, similar to primitive carbonaceous-Ivuna type (CI) chondrites, suggests that aqueous alteration was a key factor in its formation. However, this general consensus masks our limited understanding of the specific mechanisms and environmental conditions involved in water-rock interactions on primitive asteroids. Highresolution cathodoluminescence (CL) analysis of the ubiquitous dolomite crystals in Ryugu samples reveals concentric epitaxial overgrowths with varying levels of Mn 2+ -activated luminescence. CL panchromatic images and spectral deconvolution provide compelling evidence for the evolution of aqueous fluids toward highly saturated brines. Given the close association of dolomite with widespread intergrowths of serpentine and saponite in the matrix, we propose that brine formation occurs as a byproduct of serpentinization. Unlike large-scale evaporation or freezing, this process can locally cause the hydrothermal fluid to dry out, significantly increasing its salinity over time. This leads to the sporadic precipitation of an evaporite mineral sequence, with dolomite forming at an early stage. This serpentinizationdriven brine formation model offers a convincing alternative to a purely prograde alteration history for Ryugu. It may also provide a better explanation for the alteration processes of Bennu and other CI chondrite parent bodies
Comment je fais… un cerclage cervical définitif par voie laparoscopique
No full textInternational audienceNo abstract availabl
Uncertainty Quantification of Spline Predictors on Compact Riemannian Manifolds
No full textTo predict smooth physical phenomena from observations, spline interpolation provides an interpretable framework by minimizing an energy functional associated with the Laplacian operator. This work proposes a methodology to construct a spline predictor on a compact Riemannian manifold, while quantifying the uncertainty inherent in the classical deterministic solution. Our approach leverages the equivalence between spline interpolation and universal kriging with a specific covariance kernel. By adopting a Gaussian random field framework, we generate stochastic simulations that reflect prediction uncertainty. However, on compact manifolds, the covariance kernel depends on the generally unknown spectrum of the Laplace-Beltrami operator. To address this, we introduce a finite element approximation based on a triangulation of the manifold. This leads to the use of intrinsic Gaussian Markov Random Fields (GMRF) and allows for the incorporation of anisotropies through local modifications of the Riemannian metric. The method is validated using a temperature study on a sphere, where the operator's spectrum is known, and is further extended to a test case on a cylindrical surface
Impact of the representation of water transfer in the unsaturated zone on water flux in a ecohydrological critical zone model.
No full textOZCARInternational audienceAn increasing number of critical zone models are seeking to capture hydrological dynamics in an integrative fashion, reconciling water dynamics at multiple scales, and capture reciprocal linkage with plant dynamics. EcH2O-iso (Kuppel et al., 2018) is such a numerical tool, where a process based, fully distributed formulation has been balanced with computational efficiency using a simplified formulation of subsurface water dynamics: three layers where top-layer infiltration is described using the Green-Ampt approach, while vertical water travel to deeper layers is gravity-driven, all using a saturation dependent hydraulic conductivity. This approach is sequential within grid cells and along the lateral drainage network, providing a fast, robust, and stable water budget. While this formulation has been successful in capturing ecohydrological dynamics (including that of isotopes tracers) in a variety of critical zone settings, gravity-driven percolation has failed to reproduce finer dynamics in some critical zone observatories displaying arid conditions and thick vadose zone (several tens of meters). In this work, we add the possibility of considering a vertical dynamical water fluxes exchange between the layers using the Richards equation. The simulations are performed on a single pixel in order to focus on the importance of the subsurface water flux dynamics on the vertical axis only. The implementation of the Richards equation is based on the numerical resolution of Ross (2003). The resolution makes use of the Kirchhoff transform to increase the speed and the stability of the solution. The Brooks and Corey retention curve parameters are used for the resolution as it is in the original EcH2O-iso model. The resolution of Ross (2003) is also usable for heterogeneous soils and provides a solution for the advection-dispersion equation for solute transport. The latter features paves the way for future work, including the tracer module implemented isotopy tracking in EcH2O-iso. The fact that both the original (sequential) and current (dynamical) vertical routines are available as options in the same critical model allows for a direct benchmarking of performances and computing in a flexible comparison of the consequences of such different approaches of the subsurface flux modelling. We first validated the implementation of unsaturated zone representation thanks to standard 1D benchmarks. The impact of the new vertical routing scheme in EcH2O-iso is then evaluated in a deeply weathered profile in a dry tropical forest where a calibration of hydrodynamic parameters had been previously carried out with the sequential routing version of the model. Finally, at the same site, the newly-implement dynamical approach is used to perform a sensitivity analysis and a calibration of the parameters over a large number of simulations, and compared again to the performances of the sequential-base model.ReferencesKuppel, S. et al : EcH2O-iso 1.0: water isotopes and age tracking in a process-based, distributed ecohydrological model, Geosci. Model Dev., 2018.Ross, P. J.: Modeling soil water and solute transport - Fast, simplified numerical solutions, Agronomy Journal, 2003
Assessing long-term variability in daily river water temperature in the Seine Basin, including the Paris metropolitan area
No full textInternational audienceSurface water temperature (SWT) is a key factor of aquatic ecosystem balance but also of domestic,industrial and agricultural water uses, particularly in densely populated regions with intense humanactivities. SWT is affected by multiple drivers, including meteorological conditions (e.g. airtemperature, precipitation, solar radiation, wind speed) and anthropogenic activities (e.g. wastewatertreatment plant effluents, nuclear reactor cooling, datacenter cooling, and urban cooling systems).These drivers exhibit strong spatial and temporal variability. Consequently, SWT exhibits pronouncedvariability at short-term (e.g. day-to-day) timescales, influencing the structure of aquatic communities(Bonacina et al., 2023) and human uses, such as energy production (Du et al., 2026), as well as atlong-term timescales, particularly since the Industrial Revolution, in response to ongoing globalchange. Characterizing these dynamics at the scale of large river basins is essential for understandingclimate-change impacts, assessing risks of critical thermal thresholds, and informing adaptive waterand energy resources management strategies. Conducting such characterization is particularlychallenging in the Seine River Basin (France), a 76,238 km² basin that includes the Paris metropolitanarea, hosts 17 million inhabitants, and faces competing water and energy uses. This study aimed tocharacterize long-term daily river water temperature dynamics across the Seine River Basin from1958 to 2025. Continuous daily SWT time series from 1958 to 2025 were reconstructed at nearly 80monitoring stations using an LSTM model. The time series were subsequently analysed with respectto critical thermal thresholds identified for different water uses (drinking water supply, industrialcooling, irrigation, and ecosystem preservation), in order to assess the risks of reaching or exceedingthese thresholds during the study period. This approach enables the analysis of long-term thermaltrends and paves the way for identifying adaptation levers supporting sustainable, multi-use water-resource management
Integrating Transient Hydrogeology Models for Enhanced Interpretation of Geophysical Data in the Vadose Zone
No full textInternational audienceQuantifying water and heat fluxes at the interface between surface water (SW), groundwater (GW), and the vadose zone (VZ) is critical for sustainable water and energy resource management under global change. Direct field measurements are challenging because SW–GW exchanges depend on initial and boundary conditions and the spatial distribution of hydrofacies, which are often poorly constrained. Usually, these fluxes are estimated by calibrating models using classical data like hydraulic heads and river discharge. But it is well known that these data did not get enough information to constrain these fluxes. To overcome the lack of direct in situ data, de Marsily et al., (2005) and Schilling et al., (2019) suggested to couple the classical observations with unconventional data such as the geophysical surveys, for instance successfully applied in the context of SW-GW exchanges by Dangeard et al., (2021). Binley et al., (2015), in their comprehensive review, highlighted the robustness of geophysical methods for imaging subsurface structures and estimating saturation profiles, reinforcing their role as essential tools for characterizing vadose zone processes.This study develops a transient, process-based hydrogeophysical forward model that integrates hydrological and geophysical processes. The geophysical methods used in this study are electrical resistivity tomography (ERT), seismic methods, and heat tracing, applied as complementary approaches to characterize vadose zone dynamics and link hydrological processes to geophysical data. The hydrological model (Rivière et al., 2020) rigorously solves Richards’ equation coupled with heat transport—simulating variably saturated water and thermal fluxes in porous media under transient conditions—and was validated with experimental and field data to explore the variability of saturated flow and heat fluxes. The seismic model, based on Solazzi et al., (2021) uses the Hertz-Mindlin contact theory combined with the Biot-Gassmann model and simulates the influence of capillary suction with a transient method. The electrical model uses the Waxman-Smits petrophysical law to quantify electrical conductivity of the soil. The outputs of the hydrological model are coupled with geophysical forward models to compute synthetic geophysical models (P and S wave velocity, electrical resistivity) and associated data (more particularly surface wave phase velocity, apparent electrical resistivity); as well as heat tracing signals). The synthetic case considered in this study is a 1D soil column, subjected to seasonal variations in precipitation and temperature, to analyze the resulting dynamics and their geophysical data.Testing this integrated model under typical spring conditions in the Paris Basin demonstrates:The added value of transient modeling for interpreting geophysical data. Sensitivity of seismic and electrical responses to soil saturation and pressure changes, even without water table fluctuations. The influence of past infiltration events on geophysical survey interpretation. This approach provides new insights into VZ functioning and strengthens the link between hydrological processes and geophysical signatures, paving the way for improved characterization of subsurface dynamics under global changes
From one-off collaboration to embedded practices: Accounting for diversity in Small and Medium Enterprises’ university–industry collaborative research trajectories
No full textInternational audienceSmall and medium-sized enterprises (SMEs), despite their importance for innovation and economic growth, remain underrepresented in Open Innovation (OI) activities with universities, particularly in the form of university–industry collaborations (UIC). Prior research mainly focuses on large firms or analyzes UIC at the level of individual projects, leaving the firm-level dynamics of SMEs’ sustained engagement in collaborative research underexplored. This study adopts an evolutionary perspective to examine how SMEs initiate, structure, and institutionalize collaborative research with universities. Drawing on a longitudinal multiple-case analysis of 21 French SMEs engaged in repeated UICs. Based on 32 semi-structured interviews and 83 secondary data sources, we reconstruct firms’ engagement trajectories across multiple collaborative research initiatives. Using an inductive process approach, we identify three interrelated phases: preconditions, in which organizational transitions, sectoral needs and CEO exposure to scientific networks shape latent research orientations; formalization, characterized by the adoption of standardized collaboration instruments and explicit research roles; and institutionalization/transformation, where collaborative research becomes embedded in organizational routines, exceeding initial expectations and occasionally becoming a component of the client relationship.By shifting the focus from individual projects to firm-level trajectories, this study contributes a process model of SMEs’ sustainable engagement in UIC and offers insights for managers and policymakers seeking to foster durable collaborative research strategies
Paying for Training to Make Training Pay Off: EvidenceFrom France
No full textInternational audienceThis paper investigates the impact of increased financial compensation during training on jobseekers' labor market outcomes. We exploit a reform implemented in France in May 2021 that raised training allowances exclusively for non- recipients of unemployment benefits. Using administrative longitudinal data, we compare the trajectories of trainees affected and unaffected by the reform. Our empirical strategy combines a synthetic triple- difference estimator with an event- study framework. We find no evidence that the reform increased employment rates within 24 months of training entry, but it did enhance job quality, improving both stability and alignment with the training field
Modelling of solar plant operating loss for preventive maintenance scheduling optimization
No full textInternational audienceModelling of solar plant operating loss for preventive maintenance scheduling optimizatio
Santé mentale en tension Enjeux épistémologiques, politiques et cliniques d’un espace fragmenté
No full textInternational audienceObjectivesMental health has emerged as a major policy issue at the crossroads of health, political, and ethical concerns. Declared a “national cause” in 2025 and 2026, it is receiving renewed attention while the associated theoretical paradigms and public programs are the subject of intense debate. In this context, an interdisciplinary workshop entitled “Mental Health Policies: Pluralistic Concepts and Perspectives” was held in June of 2025. The event aimed to foster dialogue between researchers, clinicians, and institutional actors regarding the tensions that structure the mental health landscape.Materials and methodsWe report the discussions that took place during this workshop based on an inductive analysis of the exchanges using Braun and Clarke's (2006) method. The corpus, consisting of all interactions, was coded into more than 1700 segments grouped into thematic axes, then manually refined.ResultsFirst, the lack of collective representation of care providers appears to be a persistent consequence of a fragmented health care organization. Care delivery modes and patient populations vary greatly, and the different paths (private practice, community-based care, academic–hospital settings, etc.) often operate in silos. While this diversity reflects initiative and innovation, it does not uphold an unified voice. Second, paradigmatic reframing is considered necessary, integrating prevention, diagnosis, and care. New tools make it possible to articulate biological, clinical, social, or linguistic data without imposing a single overarching model. The objective is to create transparent, interoperable and inclusive methodologies between biomedical, psychodynamic, and social approaches to strengthen user involvement. . Third, in a context of budgetary constraint, it is also crucial to re-allocate funding toward what is most useful for care. This requires identifying financing mechanisms that promote good practices through appropriate incentives and support the many teams engaged in experimentation and evaluation.DiscussionThis workshop shed light on the major forces at play: an acknowledged plurality of approaches, constructive disagreements over evidence-based models, and a shared commitment to tying together the complexity of clinical situations and organizational structures. Its main contribution lies in bringing into dialogue worlds that rarely meet : clinical practice, social sciences, and institutions. The exchanges showed how these perspectives can enrich one another when they are articulated together.ConclusionOur team effort is expected to grow through further meetings , particularly on: (i) research policy issues in mental health (data and commons); (ii) the role of care providers, users, and caregivers in decision-making processes; and (iii) the financing of psychiatry (allocated budgets and psychotherapy coverage).ObjectifsLa santé mentale s’impose comme un enjeu sociétal majeur à la croisée de préoccupations sanitaires, politiques et éthiques. Déclarée « grande cause nationale » en 2025 et 2026, elle fait l’objet d’une attention renouvelée alors que les paradigmes théoriques et les politiques publiques qui s’y rattachent se trouvent au cœur de vifs débats. Dans ce contexte a été organisée en juin 2025 une journée d’étude interdisciplinaire intitulée « Politiques de santé mentale : concepts et perspectives pluriels », rencontre visant à faire dialoguer chercheurs, cliniciens et acteurs institutionnels autour des tensions qui structurent l’espace de la santé mentale.Matériels et méthodesNous restituons les propos tenus dans le cadre de cette journée à partir d’une analyse inductive fondée sur la méthode de Braun et Clarke (2006). Le corpus constitué de l’intégralité des échanges a été codé en plus de 1700 segments regroupés en axes thématiques, avant d’être manuellement retravaillé.RésultatsPrimo, le défaut de représentation des acteurs du soin apparaît le produit persistant de l’organisation du système de santé. Les contextes d’exercice et patientèles divergent, les circuits (libéral, secteur, hospitalo-universitaire, etc.) fonctionnent souvent en silos. Cette diversité, signe d’initiative, a pour revers une dilution du message collectif. Secondo, un refondement paradigmatique est jugé nécessaire, intégrant prévention, diagnostic et soins. De nouveaux outils peuvent articuler données biologiques, cliniques, sociales ou linguistiques, sans imposer un modèle unique. Il s’agit de créer des espaces de partage entre approches biomédicales, psychodynamiques et sociales, de renforcer la participation des usagers, et de s’appuyer sur des méthodologies transparentes, interopérables et inclusives. Tertio, dans un contexte de restriction budgétaire, il semble prioritaire de rediriger les fonds vers ce qui est utile aux soins. Il s’agit d’identifier des modes de financement qui soutiennent les bonnes pratiques, les nombreuses équipes qui expérimentent et évaluent.DiscussionCette journée d’étude a permis de rendre visibles les lignes de force à l’œuvre : une pluralité d’approches assumée, des désaccords argumentés sur les cadres de preuve, ainsi que la volonté partagée de tenir ensemble la complexité des situations cliniques et des organisations. L’apport principal tient à la mise en relation de mondes qui dialoguent rarement dans le même temps : clinique, sciences sociales, et institutions. Les échanges ont montré comment ces registres peuvent s’enrichir mutuellement lorsqu’ils sont articulés.ConclusionNotre collectif est amené à se densifier et de nouveaux temps d’échanges sont prévus, notamment sur : (i) les thématiques des politiques de recherche en santé mentale (données et communs) ; (ii) la place des soignants, des usagers et des aidants dans les processus décisionnaires ; (iii) le financement de la psychiatrie (budgets alloués et remboursement des psychothérapies)