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L’influence des syndicats depuis les années 1950 en France. De nouveaux éclairages à partir de données quantitatives
No full textThis article uses multiple sources of quantitative data to trace the evolution of trade union influence in France since the 1950s. On the one hand, we put into perspective explanations of the decline in union membership in the 1980s due to socioeconomic changes or generational renewal. On the other hand, we qualify the idea of a linear decline by highlighting other factors that drive the unions' capacity for mobilization, linked to the economic, social, and political context.Cet article restitue, à partir de multiples sources de données quantitatives, l’évolution de l’influence des syndicats en France depuis les années 1950. Nous relativisons d’une part les explications de la désyndicalisation des années 1980 par des transformations socioéconomiques ou par un renouvellement générationnel. Nous nuançons d’autre part l’idée d’un déclin linéaire, en faisant apparaître d'autres ressorts de la capacité de mobilisation des syndicats, liés au contexte économique, social et politique
Recycling flax fibre composites by using a chemical solvolysis process in near- and supercritical conditions: linking fibre integrity to micro-mechanical performance
No full textAccords "Elsevier-Couperin"International audienceThe growing demand for bio-based composites has intensified the need for efficient recycling strategies that preserve fibre integrity and reduce environmental impact. In this study, unidirectional flax-reinforced composites with epoxy and poly-amide 11 (PA 11) matrices are manufactured and subsequently recycled using a solvolysis-recycling based process under near- and supercritical conditions in a semi-continuous flow reactor. A water/ethanol mixture (50/50 in mol) is employed as solvent at 250°C and 300°C under 250 bar. The recovered flax fibres are characterised using scanning electron microscopy (SEM), nanoindentation (NI) and atomic force microscopy (AFM). Mechanical tests on the original composites demonstrate tensile properties consistent with the best values reported in the literature, supported by low porosity levels (∼2%). After solvolysis, flax fibres recovered from PA 11 composites exhibit clean surfaces, preserved cell wall organisation, and nano-mechanical properties close to virgin fibres. In contrast, fibres from epoxy composites experience substantial degradation, especially at 300°C, with pronounced ultrastructural damage and a 65.8% reduction in indentation modulus. AFM confirms localised degradation patterns and lumen-driven damage pathways. These results highlight the superior recyclability of Flax – PA 11 systems and the intrinsic limitations of Flax – Epoxy composites for fibre-preserving solvolysis. Overall, the study provides composite manufacturers and recyclers with new insights into fibre-scale degradation mechanisms and supports the development of more circular, eco-efficient bio-composite architectures.</p
Reassessing the benefits of European integration and the European Union's ability to achieve strategic autonomy
No full textEuropean integration is now faced with the question of strategic autonomy. Against this backdrop, this paper has three objectives. First, it uses disaggregated trade data and established empirical methods to assess the benefits of European integration on trade among the members of the European Union (EU) as well as on trade between EU members and non-member countries, including non-members that are part of the Single Market. Second, it evaluates the costs of EU strategic autonomy -implying not trading with "riskier" partners. Third, it asks whether deeper integration within the EU can alleviate these costs. The paper shows that the gains from European integration are substantial, albeit heterogeneous across Member States, non-members, and sectors, and that the costs of strategic autonomy can be offset by deeper, but comparatively more modest, integration efforts within the European Union
Water vapour isotope anomalies during an atmospheric river event at Dome C, East Antarctica
No full textInternational audienceAbstract. From 19 to 23 December 2018, an atmospheric river sourced in the Atlantic hit the French–Italian Concordia station, located at Dome C, East Antarctic Plateau, 3233 m above sea level (a.s.l.). It induced a significant surface warming (+18 °C in 3 d), combined with high specific humidity (3-fold increase in 3 d) and a strong isotopic anomaly in water vapour (+17 ‰ for δ18O). The isotopic composition of water vapour monitored during the event may be explained by the isotopic signature of long-range water transport, and by local moisture uptake during the event. In this study, we used continuous meteorological and isotopic water vapour observations, together with the atmospheric general circulation model LMDZ6iso, to describe this event and quantify the influence of each of these processes. The presence of mixed-phase clouds during the event induced a significant increase in downward long wave radiation, leading to high surface temperature and resulting in high turbulent mixing in the boundary layer. Although surface fluxes are underestimated in LMDZ6iso, near-surface temperature and specific humidity are well represented. The surface vapour δ18O is accurately simulated during the event, despite an overestimated amplitude in the diurnal cycle outside of the event. Using the LMDZ6iso simulation, we perform a surface water vapour mass budget by decomposing total specific humidity into contributions from individual processes. Our analysis demonstrates that surface sublimation, which becomes significantly stronger during the event compared to typical diurnal cycles, emerges as the dominant driver of the vapour δ18O signal at the peak of the event, accounting for approximately 70 % of the total contribution. The second largest contribution comes from moisture input via large-scale advection associated with the atmospheric river, accounting for approximately 30 % of the total. Consequently, our results reveal that the isotopic signal monitored in water vapour during this atmospheric river event reflects both long-range moisture advection and interactions between the boundary layer and the snowpack. Only specific meteorological conditions driven by a pronounced moisture intrusion can explain these strong interactions. Given the marked imprint of air–snow exchanges on the vapour isotopic signal, improving the representation of local processes in climate models could substantially improve the simulation of the isotopic signal over Antarctica and provide valuable insight into moisture uptake processes
De-risking renewable investments: Internalizing the risks and quantifying the impact of de-risking instruments
No full textInternational audienceMobilizing sufficient investment for renewable energy is critical to achieving global climate goals, yet high financing costs – primarily driven by risk perceptions – continue to hinder the deployment of variable renewables that are capital intensive, especially in emerging economies. This study comprehensively assesses the risks affecting renewable investments, categorizing them into political, economic, transformation, resource, curtailment, and technological risks. We then map these risk categories to targeted de-risking instruments, including guarantee schemes, regulatory measures, and economic incentives. Building on an extended Capital Asset Pricing Model (CAPM), we develop and calibrate a novel cost of capital model that internalizes individual risk elements and the effect of de-risking tools across a global dataset.Our results show that, without de-risking, the cost of capital can exceed 16 % for solar PV and wind projects in high-risk countries, compared to below 6 % in advanced markets. De-risking instruments – such as political risk guarantees and tax incentives – can reduce the project cost of capital by up to 5 percentage points, leading to a 30 %–35 % reduction in the levelized cost of energy. These findings highlight the critical role of tailored de-risking strategies in accelerating clean energy transitions and offer actionable insights for policymakers and investors
Building localized and generic scenarios for sea and river dikes based on their socio-ecological footprint
No full textInternational audienceIn light of climate change and a new regulatory context, the DIGUES research program is exploring the potential futures of French dikes up to 2050. An interdisciplinary, forward-looking approach has been applied to consider the socio-ecological footprint of the ways in which dikes evolve. It brings together social and environmental sciences with stakeholder participation to build localized and generic scenarios. This approach offers an alternative to technical approaches based solely on sea or river defense, as it puts forward a method that links the physical dynamics of the environment to social and organizational issues and variables. The pathways presented (dikes maintained in their current state, reinforced, lowered, or moved back) therefore position the future of dikes in terms of continuity or transformative strategies in a context where territories take on greater responsibility in the face of climate change. In diking strategies, local public action is still driven by territorial goals and should consider more environmental dynamics. Developing territorial projects that include social and ecological elements helps to promote transformative strategies
Search for decays at the LHCb experiment with Run 2 data
No full textInternational audienceA search for the lepton-flavour-violating decay is carried out using data collected by the LHCb experiment between 2016 and 2018 in proton-proton collisions at the LHC at a centre-of-mass energy of 13 TeV, corresponding to an integrated luminosity of 5.4 fb. An upper limit of is set at the 90% (95%) confidence level on the branching fraction of the decay
Observation of the decay
No full textInternational audienceThe first observation of the decay is reported using proton-proton collision data recorded with the LHCb detector corresponding to an integrated luminosity of . The decay mode is observed for the first time, with a significance of . Its branching fraction is measured relative to the decay mode \begin{align*} \frac{\cal{BF}(χ_{c1}(3872)\rightarrow J\mskip -3mu/\mskip -2muψμ^+μ^-)}{\cal{BF}(χ_{c1}(3872)\rightarrow J\mskip -3mu/\mskip -2muψπ^+π^-)} = \left(1.64\pm 0.32\pm 0.05\right)\times10^{-3}, \end{align*} where the first uncertainty includes both statistical contributions and systematic contributions which are uncorrelated between data-taking periods, and the second represents the systematic contributions that are correlated between data-taking periods
Search for heavy long-lived charged particles with level-1 trigger scouting data from proton-proton collisions at = 13.6 TeV
No full textInternational audienceA search for heavy long-lived charged particles at the LHC is presented. Particles interacting with the CMS muon detector across several bunch crossings are searched for using a data sample of proton-proton collisions at = 13.6 TeV collected with the CMS detector in 2024, corresponding to an integrated luminosity of 3.7 fb. This is the first search relying on the novel level-1 trigger scouting data set collected without any trigger selection, allowing correlations between bunch crossings to be analyzed. The results are interpreted as upper limits on the cross sections of several benchmark processes with pair production of heavy long-lived charged particles. Upper limits on the fiducial cross section of a heavy long-lived charged particle with 500 GeV and 0.83 are also set in different ranges of . This analysis is a crucial proof of concept for the level-1 trigger data scouting system and complements existing searches for heavy long-lived charged particles by extending the sensitivity to lower values
A robust computational framework for the mixture-energy-consistent six-equation two-phase model with instantaneous mechanical relaxation terms
No full textWe present a robust computational framework for the numerical solution of a hyperbolic 6-equation single-velocity two-phase system. The system's main interest is that, when combined with instantaneous mechanical relaxation, it recovers the solution of the 5-equation model of Kapila. Several numerical methods based on this strategy have been developed over the years. However, neither the 5- nor 6-equation model admits a complete set of jump conditions because they involve non-conservative products. Different discretizations of these terms in the 6-equation model exist. The precise impact of these discretizations on the numerical solutions of the 5-equation model, in particular for shocks, is still an open question to which this work provides new insights. We consider the phasic total energies as prognostic variables to naturally enforce discrete conservation of total energy and compare the accuracy and robustness of different discretizations for the hyperbolic operator. Namely, we discuss the construction of an HLLC approximate Riemann solver in relation to jump conditions. We then compare an HLLC wave-propagation scheme which includes the non-conservative terms, with Rusanov and HLLC solvers for the conservative part in combination with suitable approaches for the non-conservative terms. We show that some approaches for the discretization of non-conservative terms fit within the framework of path-conservative schemes for hyperbolic problems. We then analyze the use of various numerical strategies on several relevant test cases, showing both the impact of the theoretical shortcomings of the models as well as the importance of the choice of a robust framework for the global numerical strategy