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Face à la "professionnalisation ségrégative". Les tactiques des apprentis du supérieur
No full textInternational audienc
The impact of dynamic ambidexterity on the performance of organizations: evidence from corporate venture capital investing in North America
No full textCNRS 2, HCERES A, ABS 3International audienceThe purpose of this paper is to study the evolution of corporate investors’ exploitation-exploration allocations and their long-term performance outcomes. The sample consists of 243 North American firms pursuing corporate venture capital (CVC) investments from 1993 to 2017. The results show that dynamic sequential ambidexterity promotes higher firm performance than balanced or simultaneous forms of ambidexterity. Alternating pursuit of exploitation and exploration characterized by a regular frequency of change over time enhances corporate investors’ financial performance. The results suggest that CVC firms develop additional expertise in pursuing both exploitation and exploration activities over time which helps to enhance their performance. The findings also show that in times of crisis, the combined use of both exploration and exploitation in CVC investments enables firms to enhance their financial performance. The results are robust to alternative measures of financial performance and to endogeneity concerns. This paper provides insights to policymakers and managers of firms that are investing in CVC activities
Déploiement des solutions fondées sur la nature en milieu urbain : performance thermique et faisabilité urbaine à toutes les échelles
No full textRapid urbanisation rate and the modification of surface properties have altered energy balance and wind dynamics within the cities. This has modified locate climate, enhancing the Urban Heat Island (UHI). This phenomenon creates elevated temperatures are experienced in dense areas, mainly at night. Likewise, climate change could induce intensity and frequency of extreme events (such as heatwaves) are higher, becoming the UHI a challenge and threat of urban resilience. Nature-Based Solution (NBS), such as green roof, have appeared as a strategy for mitigation of elevated temperatures, because of the effect of evapotranspiration (ET) from vegetation. Nevertheless, the performance of NBS to cooling the air and its variability across different temporal and spatial scales are still unclear. As well, conditions that can influence their implementation in complex urban environments are unstudied.In this context, this thesis focuses on the evaluation of elements than could influence their installation across scales. First, campaigns of measure of the ET process were carried out in the Blue Green Wave (BGW), a green roof located in Bienvenüe building in front of the Ecole des Ponts ParisTech, in the Cité Descartes (eastern of Paris). The thermal and physical performance of the BGW was characterised through three different methods: the surface energy balance (SEB), the evapotranspiration chamber and the water balance during dry conditions. Differences in the three methods of measure were observed and the errors causing these were discussed. A sensitivity analysis served to determine principal variables affecting SEB estimations and make recommendations for further campaigns of measure.Second, the fractal geometry was used to analyse the complexity and heterogeneity of the spatial distribution in the case study of Est-Ensemble (eastern of Paris), and to develop a multiscale scenario of NBS deployment. More specifically, fractal dimension helped to analyse the hierarchical organisation of the built-up structure and NBS across different scales. These properties served in the multiscale scenario to reconcile the built-up structure with the NBS, by installing NBS of different sizes in the spaces not occupied by the buildings (lacunas) but over the fractal structure of buildings too.Finally, in order to improve the understanding of thermal flux variability measured in the BGW, statistical multiscale data analysis was used. The preliminary results demonstrated than air temperature and structure parameter of refraction index of air (〖C_n〗^2), impacting ET, exhibit a scaling behaviour affecting by intermittency, a commonly observed feature of turbulent flows. In addition, results suggested the need to investigate the additional meteorological parameters affecting turbulent activity in the BGW, such as wind speedL’urbanisation rapide et la modification des propriétés de surface ont modifié le bilan énergétique et la dynamique du vent dans les villes. Cela a engendré la modification du climat local, favorisant l'îlot de chaleur urbain (ICU). Ce phénomène crée des augmentations des températures importantes dans les aires plus denses, notamment dans la nuit. De plus, dans le contexte du changement climatique, l’intensité et occurrence des événements extrêmes (comme les vagues de chaleur) pourrait être plus élevée, ce qui fait de l'ICU une difficulté majeure pour la résilience urbaine. Les Solutions fondées sur la Nature (SFN), telles que les toits verts, sont apparues comme une stratégie d'atténuation des températures élevées, en raison de l'effet de l'évapotranspiration (ET) de la végétation. Néanmoins, la performance du SFN pour refroidir l'air et sa variabilité à différentes échelles temporelles et spatiales n’est toujours pas claire. De plus, les conditions qui peuvent influencer leur mise en œuvre dans des environnements urbains complexes n'ont pas été étudiées.Dans ce contexte, cette thèse s'intéresse à l'évaluation d'éléments susceptibles d'influencer la mise en place de SFN à travers les échelles. Dans un premier temps, des campagnes de mesure du procédé ET ont été réalisées dans le Blue Green Wave (BGW), un toit vert situé dans le bâtiment Bienvenüe, placée en face de l'Ecole des Ponts ParisTech, dans la Cité Descartes (est de Paris). Les performances thermiques et physiques de la BGW ont été caractérisées par trois méthodes différentes : le bilan énergétique de surface (SEB), la chambre d'évapotranspiration et le bilan hydrique en conditions sèches. Des différences dans les trois méthodes de mesure ont été observées et les erreurs à l'origine de celles-ci ont été discutées. Une analyse de sensibilité a permis de déterminer les principales variables affectant les estimations de SEB et de formuler des recommandations pour d'autres campagnes de mesure.Dans un second temps, la complexité et l'hétérogénéité de l'organisation spatiale d'un territoire où les SFN seraient implantées, a été étudiée à travers la géométrie fractale. Plus précisément, la dimension fractale a permis d'analyser l'organisation hiérarchique de la structure urbaine, et des primitives fractales ont été utilisées pour développer un scénario multi-échelles de déploiement des SFN avec une étude de cas dans Est-Ensemble (est de Paris). A partir de l'organisation fractale des SFN, le scénario multiéchelle a réconcilié la structure bâtie avec les SFN, en installant des SFN de différentes tailles dans les espaces non occupés par les bâtiments (lacunes) mais également sur la structure fractale des bâtiments. Enfin, afin d'améliorer la compréhension de la variabilité des flux thermiques mesurés dans le BGW, une analyse statistique multiéchelle des données a été utilisée. Les résultats préliminaires ont démontré que la température de l'air et le paramètre de structure de l'indice de réfraction de l'air (〖C_n〗^2), lesquels impactent le flux d’ET, présentent un comportement multiéchelle affectant par l’intermittence, une caractéristique couramment observée des écoulements turbulents. En outre, les résultats suggèrent la nécessité d'étudier les paramètres météorologiques supplémentaires affectant l'activité turbulente dans la BGW, tels que la vitesse du vent
Screening quaternary Heusler by machine learning for application in thermoelectricity
No full textInternational audienceHeusler alloys, full and half-, thanks to their high versatility of compositions as well as their very interesting properties, are good candidates for thermoelectric applications. In the Heusler family, quaternary alloys also exist and allow to further increase the chemical diversity and so one to achieve more complex properties. However, due to the high number of combinations, traditional screening methods are not effective to target relevant compounds. To accelerate this research, it is advantageous to use machine learning methods. In our project, we are looking for new promising quaternary Heusler compounds screened within a dataset of 24 selected elements. First, a database of calculated thermodynamic, electronic and magnetic properties, obtain from DFT calculations (Density Functional Theory) on binary and ternary compounds was constructed. Then, a supervised learning with the neural network model was built to predict the enthalpy of formation and the density of state at the Fermi level (metallic or semiconductor character) of quaternary Heusler compounds. Our model presents comparable or superior performance than the state of art and allow to identify promising compounds among the 24^4 possible configurations of our dataset
Modeling and simulation of hypervelocity impact of drops and sprays on liquid or solid surfaces
No full textInternational audienc
Three-Year Outcomes in Kidney Transplant Recipients Switched From Calcineurin Inhibitor-Based Regimens to Belatacept as a Rescue Therapy
No full textInternational audienceBackground: The long-term benefits of conversion from calcineurin inhibitors (CNIs) to belatacept in kidney transplant recipients (KTr) are poorly documented .Methods: A single-center retrospective work to study first-time CNI to belatacept conversion as a rescue therapy [eGFR <30 ml/min/1.73 m 2 , chronic histological lesions, or CNI-induced thrombotic microangiopathy (TMA)]. Patient and kidney allograft survivals, eGFR, severe adverse events, donor-specific antibodies (DSA), and histological data were recorded over 36 months after conversion.Results: We included N = 115 KTr. The leading cause for switching was chronic histological lesions with non-optimal eGFR (56.5%). Three years after conversion, patient, and death-censored kidney allograft survivals were 88% and 92%, respectively, eGFR increased significantly from 31.5 ± 17.5 to 36.7 ± 15.7 ml/min/1.73 m 2 ( p < 0.01), the rejection rate was 10.4%, OI incidence was 5.2 (2.9–7.6) per 100 person-years. Older age was associated with death, eGFR was not associated with death nor allograft loss. No patient developed dn DSA at M36 after conversion. CNI-induced TMA disappeared in all cases without eculizumab use. Microvascular inflammation and chronic lesions remained stable.Conclusion: Post-KT conversion from CNIs to belatacept, as rescue therapy, is safe and beneficial irrespective of the switch timing and could represent a good compromise facing organ shortage. Age and eGFR at conversion should be considered in the decision whether to switch
Externalities from urban renewal: evidence from a French program
No full textInternational audienceWe contribute to the evaluation of urban renewal policies based on a large-scale program launched in France in 2004. Using an estimator aimed at avoiding bias in the estimation of treatment effects that are heterogeneous across treatment groups or time periods, and complementing its results with a more precise double fixed effects difference-indifferences estimator, we find no significant aggregate impact of the program on housing prices. We identify four dampening factors that can explain this lack of aggregate impact: a sometimes insufficient level of funding per neighborhood, a stigma effect in the most deprived neighborhoods, the isolation of some neighborhoods located far from city centers, and the concentration of the program's funding on types of operations associated with small impacts on housing prices
Tour d'horizon de la contamination en débris plastiques des compartiments environnementaux
No full textConférence plénière invitéeNational audienc
Temporal trends in calls for suicide attempts to poison control centers in France during the COVID-19 pandemic: a nationwide study
No full textInternational audienceConcerns have been raised about early vs. later impacts of the COVID-19 pandemic on suicidal behavior. However, data remain sparse to date. We investigated all calls for intentional drug or other toxic ingestions to the eight Poison Control Centers in France between 1st January 2018 and 31st May 2022. Data were extracted from the French National Database of Poisonings. Calls during the study period were analyzed using time trends and time series analyses with SARIMA models (based on the first two years). Breakpoints were determined using Chow test. These analyses were performed together with examination of age groups (<= 11, 12-24, 25-64, >= 65 years) and gender effects when possible. Over the studied period, 66,589 calls for suicide attempts were received. Overall, there was a downward trend from 2018, which slowed down in October 2019 and was followed by an increase from November 2020. Number of calls observed during the COVID period were above what was expected. However, important differences were found according to age and gender. The increase in calls from mid-2020 was particularly observed in young females, while middle-aged adults showed a persisting decrease. An increase in older-aged people was observed from mid-2019 and persisted during the pandemic. The pandemic may therefore have exacerbated a pre-existing fragile situation in adolescents and old-aged people. This study emphasizes the rapidly evolving situation regarding suicidal behaviour during the pandemic, the possibility of age and gender differences in impact, and the value of having access to real-time information to monitor suicidal acts