Portail HAL UPEC
Not a member yet
55480 research outputs found
Sort by
Unraveling the non-equilibrium chemistry of the temperate sub-Neptune K2-18 b
No full textInternational audienceContext. The search for habitable Earth-like exoplanets can present significant observational challenges, due to their small size and faint signals. M-dwarf stars provide an opportunity to detect and characterize smaller planets, particularly sub-Neptunes, which are among the most common exoplanetary types. K2-18 b, a temperate sub-Neptune in the habitable zone of an M-dwarf star, has been studied using HST and JWST, revealing an H 2 -rich atmosphere with detected CH 4 and possible CO 2 . However, previous debates on atmospheric composition emphasize the importance of non-equilibrium chemistry models. These models are crucial for interpreting exoplanetary atmospheres, and for constraining key parameters such as metallicity, C/O ratio, and vertical mixing (K zz ).Aims. This study aims to comprehensively explore the parameter space of metallicity, C/O, and K zz for K2-18 b using the nonequilibrium chemical model FRECKLL in conjunction with JWST observational data. By refining these constraints, we seek to improve our understanding of the planet's atmospheric composition and to detect minor species in a temperate sub-Neptune within the habitable zone of an M-dwarf star. Methods. Our approach involves running non-equilibrium chemical models across a three-dimensional parameter space (metallicity, C/O, and K zz ), generating the corresponding theoretical spectra, and comparing these spectra to JWST observational data to refine atmospheric constraints. This approach assumes a fixed P-T profile, which is sufficient to capture first-order chemical trends, though it introduces some uncertainty in the derived values. Results. We retrieved a best-fit atmospheric model for K2-18 b favoring high metallicity (266 +291 -104 at 2σ) and a high C/O value (C/O ≥ 2.1 at 2σ). CH 4 is robustly detected (log 10 [CH 4 ] = -0.3 +0.1 -1.7 at 1 mbar), while CO 2 and other species remain uncertain due to observational noise and spectral overlap. The K zz has no significant impact on the fit and remains unconstrained. Non-equilibrium models exceed 4σ confidence over a flat-line, which validates the presence of atmospheric features. Several minor species may exist at ppm levels, though their features are likely masked by dominant species. Conclusions. We used non-equilibrium chemical models and JWST data to investigate the atmosphere of K2-18 b, revealing a high metallicity, a high C/O, and complex chemical composition. While CH 4 is robustly detected, CO 2 remains uncertain, and minor species (e.g., H 2 O and NH 3 ) are likely present. A lower limit on C/O is constrained, though no upper limit is established. The high C/O also suggests a higher probability of aerosol formation. Our findings highlight the limitations of traditional retrievals with constant abundances and the importance of non-equilibrium models with combining exploration on a large range of metallicity and C/O values. Although equilibrium models can reproduce the data, physical conditions indicate that the atmosphere is in a non-equilibrium state, highlighting the limited constraints from current observations and the pressing need for improved data. Future observations with JWST NIRSpec G395H and ELT/ANDES will be key to refining atmospheric constraints and probing potential habitability
Optimal Margins in Demands–Resources Fit and Student Engagement
No full textInternational audienceA long-standing view in stress and motivation research is that strong resources can offset the strain of high demands—a “buffering” process thought to sustain engagement (students’ dedication, absorption, and vigor in learning) under pressure. Yet this account rarely considers how engagement varies across the full set of demand–resource combinations, whether balanced or imbalanced, and whether both are at high or low levels. Drawing on person–environment fit perspectives, we analyzed three independent datasets spanning middle school to higher education (N = 423, 587, 734) using cubic response surface analysis to examine how a key demand (study workload) and key resources (teacher, peer, and parental support; self-efficacy) jointly shape engagement. Across contexts, engagement was highest when resources outweighed demands, consistent with protective effects. However, when demands and resources were in balance, engagement often peaked at moderate to moderately high intensity, then declined once both were high. This decline is consistent with protective inhibition, a self-regulatory process in which the behavioral system reduces sustained effort to prevent overstrain, even when resources are still available. This pattern affected up to one-fifth of students, challenging the notion that high levels of resources indefinitely counteract high demands. These findings identify intensity thresholds in demand–resource alignment that can limit or boost engagement, highlighting the value of calibrating, not simply increasing, resources in high-demand settings
How to identify factors influencing mode choice behaviors within a heterogeneous metropolitan area? A novel approach midway between data science and econometrics
No full textInternational audienceEstimating factors influencing mode choice behaviors has posed a significant challenge for decision makers. In this paper, we propose a three-step method to estimate mode choice between public transportation and private vehicles within a heterogeneous metropolitan area. First, we implement a deep learning model, Altaïr, capable of inferring travel times and travel flows by leveraging multi-source input data (Step 1). To identify homogeneous sub-regions regarding mode choice behaviors, two data clustering models are performed: k-means and a Gaussian Mixture Model (GMM, Step 2). The GMM reveals three spatial clusters based on the relationships between relative travel times and relative travel flows in public transportation and private vehicles. Moreover, an econometric model (robust ordinary least squares) is employed to identify additional explanatory variables, including sociodemographic features and location variables (Step 3). This hybrid method is currently employed in the Paris metropolitan area (France). At the metropolitan level, we find that competitive travel times in public transportation lead to higher ridership. Conversely, when the time ratio exceeds approximately 3.5–4, public transportation use becomes negligible in comparison to private vehicles. This hybrid method allows for precise, interpretable prediction of mode choice between public transportation and private vehicles. The method's results are close to those of the regional Household Travel Surveys (HTS), as shown in a validation analysis. The design ensures the transferability of the method to any metropolitan area, including areas with incomplete data
Édito du dossier thématique : Autour des campagnes, XVIIe-XXe siècles
No full textInternational audienc
The Lived Experience of Patients Diagnosed with Vitiligo and a Preliminary Conceptual Disease Model: Insights from Patients, Patient Advocates, and Clinicians
No full textInternational audienceIntroductionPatients with vitiligo experience high disease and psychosocial burden, and dissatisfaction with current treatment options, highlighting a need to understand the disease from a patient perspective. This study gathered insights from key opinion leaders (KOLs) and patient advocates on a conceptual disease model of vitiligo and gained patient perspectives through qualitative interviews on the disease burden and concepts important to patients with nonsegmental vitiligo (NSV), and what degree and anatomical location of repigmentation may constitute a meaningful change with treatment.MethodsThis cross-sectional, observational study involved virtual, semi-structured, qualitative interviews with expert KOLs treating patients with vitiligo, patient advocates, and patients diagnosed with NSV.ResultsPatient advocates (n = 5) and KOLs (n = 6) felt that the conceptual disease model comprehensively captured the signs, symptoms, and impact of vitiligo, and had minor changes including reordering symptoms. Of 22 patients interviewed, most experienced depigmentation on their arms, trunk, hands, feet; and 86.4% had vitiligo on their face. The most frequently reported sign or symptom was increased sensitivity to the sun (82%). Patients reported that vitiligo broadly impacts many facets of life, most commonly emotional well-being (82%). Patients reported that perceived treatment success is driven by the extent of vitiligo repigmentation, especially on the face and hands, and would consider 20–25% repigmentation a meaningful improvement.ConclusionThis study provides insight into the lived experience of patients with NSV, and alignment from patient advocates and KOLs on the conceptual disease model of vitiligo. The findings increase our understanding and inform vitiligo clinical studies
La RSE maîtriser - Comprendre - Agir
No full textInternational audienceFaced with the rapid rise of Corporate Social Responsibility (CSR) as a strategic priority, a paradox persists: its implementation often remains confused, fragmented, and difficult to operationalize.This book responds to two essential observations. On the one hand, the lack of knowledge about the genealogy of CSR and the multiple schools of thought that have shaped it leads to a disparity of definitions, undermining its credibility. On the other hand, its multidisciplinary nature—spanning management, law, sociology, marketing, and environmental sciences—makes its translation into concrete and effective actions particularly complex.Designed as a practical and educational guide, this book targets a broad audience: students, managers, trainers, and professionals engaged in implementing CSR approaches. Far from pursuing over-specialization, it offers a balanced, generalist training, enabling readers to navigate between understanding strategic issues and operational deployment.Structured into three parts, the book first explores the historical and conceptual foundations of CSR, then provides tools and methodologies for its implementation within a rigorous normative framework. Finally, it invites readers to test and deepen their knowledge through a series of practical exercises: review questions, multiple-choice tests, and mini-cases inspired by real situations.An indispensable resource for anyone wishing to clarify, structure, and optimize their commitment to a meaningful and future-oriented endeavor.Face à l’essor fulgurant de la responsabilité sociétale des entreprises (RSE) comme priorité stratégique, un paradoxe demeure : sa mise en œuvre reste confuse, fragmentée et difficile à opérationnaliser. Cet ouvrage répond à deux constats : d’une part, la méconnaissance de la généalogie et des courants de pensée de la RSE fragilise sa crédibilité ; d’autre part, sa dimension pluridisciplinaire – management, droit, sociologie, marketing, sciences de l’environnement – complexifie son application concrète. Conçu comme un guide pratique et pédagogique, il s’adresse à un large public : étudiants, cadres, formateurs et professionnels. Loin de l’ultra-spécialisation, il propose une formation généraliste et équilibrée, articulant compréhension stratégique et déploiement opérationnel. Structuré en trois parties, il expose les fondements de la RSE, fournit des outils et méthodes pour sa mise en œuvre, puis offre des exercices pratiques (questions, QCM, mini-cas). Un outil indispensable pour clarifier, structurer et renforcer toute démarche RSE
Pour une histoire des désescalades énergétiques
No full textInternational audienceThere is no consensus in the social sciences on the terms used to describe the transition from a world with high environmental impacts based on resource extraction and stock energies, to a world that is less threatened by multiple risks over the long term. Sustainable development, sobriety and transition have been or are still being debated, particularly in history. This article proposes a new approach to these issues, based on the notion of energy de-escalation. It explores the interest of a notion that insists on the process itself, on its difficulty and its incarnation, while also describing the final horizon, of lower energy and power consumption.Les termes employés pour décrire le passage d’un monde aux forts impacts environnementaux fondé sur l’extraction de ressources et les énergies de stock vers un monde susceptible de s’inscrire dans un temps long moins menacé par de multiples risques ne font pas consensus dans les sciences sociales. Développement durable, sobriété ou transition ont fait ou font encore débat, notamment en histoire. Cet article propose une nouvelle façon d’entrer sur ces questions à partir de la notion de désescalade énergétique. Il explore l’intérêt d’une notion qui insiste sur le processus lui-même, sur sa difficulté et son incarnation, tout en décrivant également l’horizon final, d’une moindre consommation énergétique et de puissance
Glofitamab in refractory or relapsed diffuse large B cell lymphoma after failing CAR-T cell therapy: a phase 2 LYSA study
No full textInternational audiencePersons with diffuse large B cell lymphoma (DLBCL) refractory or in first progression/relapsed (R/R) after chimeric antigen receptor T (CAR-T) cell therapy exhibit dramatic outcomes. We enrolled such persons in a phase 2 single-arm, nonblinded trial ( NCT04703686 ) to evaluate the efficacy and safety of glofitamab, a CD20-CD3 T cell-engaging bispecific antibody, using a short ramp-up regimen to reach full dose within 1 week. A total of 46 participants received at least one glofitamab infusion following obinutuzumab (anti-CD20 monoclonal antibody) pretreatment. The primary endpoint was overall survival (OS). Secondary endpoints included independent-assessed best overall metabolic response rate (OMRR) and complete metabolic response rate (CMRR), progression-free survival (PFS), duration of response, safety and tolerability and health-related quality of life. After a median follow-up of 15.3 months (95% confidence interval (CI), 10.1-17.7), the primary endpoint was met, achieving a median OS of 14.7 months (90% CI, 8.8-not reached). The best OMRR was 76.1%. The best CMRR was 45.7%. The median PFS was 3.8 months (95% CI, 2.4-19.6). Despite the shortened setup dosing, no excess cytokine release syndrome or neurotoxicity events were observed (grade ≥ 3, 0% for both). In conclusion, glofitamab improved OS in participants with R/R DLBCL after CAR-T cell therapy, with a favorable safety profile
Size effects of rarefied gas flows in nanochannels by simulations based on statistical surrogate model for atomistic collisions
No full textInternational audienceIn this paper, the problem of helium gas transport in graphene nanochannels is investigated by a multilevel approach coupling surrogate modeling and Monte Carlo simulations. Under the rarefaction condition, the Knudsen diffusion is the dominant gas flow regime, characterized by gas-wall collisions. Furthermore, at low temperatures, helium gas atoms can be adsorbed on the surface and move like Brownian particles. To address the problem, the collision data between gas atoms and wall surfaces in equilibrium state are first generated by Molecular Dynamics simulations. A general statistical surrogate model based on polynomial chaos expansion accounting for adsorption and surface diffusion is constructed. The model exploits the Langevin dynamics analogy to satisfy physical constraints on the velocity distribution, the decaying time dependent velocity correlation and time dependent displacement behavior. The trained model is then used in Monte Carlo simulations to compute various transport quantities in long nanochannels. Numerical results from the Monte Carlo study show that the approach can capture the size effect on the diffusion coefficient and transmission probability. Without being limited to helium and graphene, the developed method can be applied to any gas and solid couple and the problem of construction of kinetic boundary conditions
Women directors on traditionally male-dominated stock exchange boards: can they make a difference?
No full textInternational audienceStock exchanges are regulated markets that promote sustainable business practices, including encouraging board gender diversity among listed companies. However, despite their essential role in advancing gender diversity at board level across companies, it is surprising that little research has investigated their internal efforts in implementing such practices. To fill this gap, we examine exchanges’ board gender diversity using a unique firm-level panel dataset comprising 22 equity stock exchanges representing 53 percent of the World Federation of Exchanges’ total market capitalization covering 1995 to 2019. We find that board gender diversity increased and, drawing on resource dependence theory, we also examine its impact on performance. We find that the effect is positive, especially when women have competencies better adapted to the new exchanges’ business environment −business administration, international, and regulatory background- and when the CEO is a woman since she may legitimize those women’s contributions and enable their impact on performance