HAL Portal de Univ. Gustave Eiffel
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The Birth of Green Chemistry: A Political History
No full textInternational audienceFew authors have investigated the origins of green chemistry (GC). Most literature relies on a narrative of its birth at the US Environmental Protection Agency in the 1990s through the original work by Paul Anastas and John Warner and the successful networking and institutionalizing activities that followed. However, this perspective has two drawbacks: it fails to consider the Environmental Protection Agency’s (EPA) political background (without which individual action would not have been possible), and it highlights a contradiction between the revolutionary theoretical message of the founders of GC and their strategy of promotion, which is uncritical of “brown” chemistry and excludes participation by civil society and the public. I argue that GC is not only the success of enthusiastic individuals who took advantage of existing political resources to promote a new vision of greening research and innovation but is also an expression of major political changes and a tool for managing chemical risks at the EPA in the 1990s. Using the concept of “design,” I argue that GC is a tool illustrating the EPA’s comanagement approach with the regulated industry. The paper sheds light on how authorities react to the difficulties of regulating chemical risks
Reducing Emissions in Road Transport: A Multi-Class Traffic Assignment and Speed Control Study
No full textInternational audienceThe transportation sector accounts for 23% of global energy-related CO2 emissions, with road vehicles contributing 70\% of these emissions. Traffic Assignment (TA) models are essential for optimizing traffic flow, reducing congestion, and consequently lowering emissions from this sector. This study proposes a traffic management strategy aimed at reducing carbon emissions through speed limit controls in multi-modal freeway networks. We propose a method that solves the network User Equilibrium (UE) problem while optimizing carbon emissions by adjusting speed limits. By focusing on multi-modal traffic management and calculating carbon abatement curves, this approach provides practical tools for traffic authorities to design effective policies. The proposed methodology is applied to a realistic case study of a freeway network in Tilburg, The Netherlands. Numerical experiments are conducted under various scenarios, analyzing the impact of different objective functions and constraints on traffic flow, emissions, and travel time. The results show that incorporating speed controls and allowing flexibility in route choices through Bounded Rationality User Equilibrium (BRUE) significantly reduces emissions and total travel costs compared to traditional UE models. Specifically, the proposed method can reduce overall emissions by up to 19.5\% compared to the most optimized traditional UE models. These findings offer valuable insights for policymakers aiming to create eco-friendly and economically viable traffic management strategies
Entropy-based burn in time analysis and ranking for (A)MCMC algorithms in high dimension
No full textInternational audienceMany recent and often (Adaptive) Markov Chain Monte Carlo (A)MCMC methods are associated in practice to unknown rates of convergence. We propose a simulation-based methodology to estimate and compare MCMC’s performance in terms of shortest burn in time, using a Kullback divergence criterion requiring an estimate of the entropy of the algorithm densities at each iteration, computed from iid simulated chains. In previous works, we proved some consistency results in MCMC setup for an entropy estimate based on Monte Carlo integration of a kernel density estimate proposed by [18], and we investigate an alternative Nearest Neighbor (NN) entropy estimate from [24]. This estimate has been used mostly in univariate situations until recently when entropy estimation in higher dimensions has been considered in other fields like neuroscience or system biology. Unfortunately, in higher dimensions, both estimators converge slowly with a noticeable bias. The present work goes several steps further, with bias reduction and automatic (A)MCMC burn in time analysis in mind. First, for bias reduction, we apply in our situation a “crossed NN-type” nonparametric estimate of the Kullback divergence between two densities, based on iid samples from each, introduced by [39, 40]. We prove the consistency of these entropy estimates under recent uniform control conditions, for the successive densities of a generic class of MCMC algorithm to which most of the methods proposed in the recent literature belong. Secondly, we propose an original solution based on a PCA for reducing relevant dimension and bias in even higher dimensions whenever PCA is efficient. Our algorithms for MCMC simulation and entropy estimation are progressively added to the R package EntropyMCMC taking advantage of recent advances in high performance (parallel) computing
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Droit(s) et Territoire(s) – Regards croisés des sciences juridiques et territoriales
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Conformational fluxionality of long-chain alkene clusters in the gas phase evidenced from a combined experimental and theoretical approach
No full textInternational audienceClusters bound by weak, non-covalent forces, such as van der Waals interactions and hydrogen bonds, are ubiquitous in dilute media ranging from aerosols to molecular fluids and biological structures, their interest being not only fundamental as in astrochemistry but also more applied as in organic electronics. Neutral clusters of up to six 1-hexene molecules produced by supersonic expansion of a gas mixture were ionized, mass selected, and spectroscopically characterized using synchrotron-based VUV photoelectron photoion coincidence technique. Ionization energies inferred from these measurements show decreasing trends as the cluster size increases, by about 0.5 eV over the range of 1–6 molecules. Dedicated theoretical DFT-based calculations were performed to unravel the possible structures of these clusters and determine their vertical and adiabatic ionization energies. Our computational search for stable structures considered the possible chirality effects associated with most conformers of the monomer having enantiomers, in an approach with a broad structural sampling employing classical force fields followed by systematic re-optimization using an efficient quantum chemical method. Vertical and adiabatic ionization energies obtained using wavefunction-based methods exhibit significant dispersion due to conformational flexibility already in the monomer, but these effects are magnified in clusters due to their fluxionality at the experimental temperature of about 130 K. Overall, the trends obtained for the calculated vertical ionization energies agree well with the measured data and suggest that possible chiral recognition effects that could stabilize specific structures are likely to be hampered under the present experimental conditions
Monitoring plastic debris in urban stormwater: fluxes and management issues
No full textInternational audienceSewage systems may be the preferred pathways for plastic debris from urban areas to the natural environment during wet periods. Some French local authorities are trying to prevent this leakage into the environment by equipping combined sewer (mixed of stormwater and wastewater) or stormwater outfalls (separate sewer systems) with nets. More than a curative solution, these devices represent a unique opportunity to monitoring urban litter, including plastic debris, as close as possible to their source of emission, i.e., urban areas. Since 2020, nets are being (or have been) in used in French cities. In several cities, anthropogenic litter from the nets was collected, washed, air dried and sorted according to the J-list classification (Fleet et al., 2021), which is the updated European classification first developed for marine and riverine litter (MSFD Technical Subgroup on Marine Litter, 2013). Results show that urban waters are a major source of macroplastics for rivers, with mass flows per capita within the orders of magnitude of those estimated in French rivers (1-10 g/cap/yr). In addition, mass flows and items categories differ relative to the type of sewage systems, land use and local specificities. In combined sewer, wipes are by far the main waste found in nets often followed by tobacco-related products and sweet wrappers from roadways. In stormwater run-off, tobacco-related products and sweet wrappers are the main categories by numb, but bottles (in metal, glass and plastic) rank TOP 5 by mass. Acquiring those data is a very harsh task and a dedicated technical platform is under development to extend monitoring at the national level (or beyond) over the long term.
Multifractal analysis based on the weak scaling exponent and applications to MEG recordings in neuroscience
No full textWe develop the mathematical properties of a multifractal analysis of data based on the weak scaling exponent. The advantage of this analysis is that it does not require any a priori global regularity assumption on the analyzed signal, in contrast with the previously used Hölder or p-exponents. As an illustration, we show that this technique allows one to perform a multifractal analysis of MEG signals, which records electromagnetic brain activity, that was not theoretically valid using the formerly introduced methods based on Hölder or p-exponents
Empirical risk minimization algorithm for multiclass classification of S.D.E. paths
No full textWe address the multiclass classification problem for stochastic diffusion paths, assuming that the classes are distinguished by their drift functions, while the diffusion coefficient remains common across all classes. In this setting, we propose a classification algorithm that relies on the minimization of the L 2 risk. We establish rates of convergence for the resulting predictor. Notably, we introduce a margin assumption under which we show that our procedure can achieve fast rates of convergence. Finally, a simulation study highlights the numerical performance of our classification algorithm
Comparable outcomes between cruciate‐substituting and posterior‐stabilized inserts in robotic total knee arthroplasty under the functional alignment principles
No full textInternational audienceAbstract Purpose Functional alignment (FA) has emerged as a personalized strategy in total knee arthroplasty (TKA) to optimize outcomes by accounting for patient‐specific anatomical and soft tissue characteristics. Limited evidence exists on how polyethylene insert type, specifically cruciate‐substituting (CS) versus posterior‐stabilized (PS), impacts clinical outcomes and complications in this context. Methods This retrospective comparative study included 329 patients who underwent robotic‐assisted TKA with FA principles with a minimum 2‐year follow‐up. Patients were divided into two groups: CS or PS implants. CS inserts were selected for patients with an intact posterior cruciate ligament (PCL), while PS inserts were used in cases of PCL insufficiency or significant flexion contractures. Preoperative and post‐operative outcomes, including Knee Society Scores (KSS), Forgotten Joint Scores (FJS), range of motion (ROM) and complications, were assessed. Implant survivorship was analyzed using the Kaplan–Meier method. Results At a median follow‐up of 36 months, no significant differences were observed between CS and PS groups in KSS (knee: p = 0.45; function: p = 0.4), FJS ( p = 0.7) or ROM (median flexion: 130° in both groups, p = 0.52). Specific complications included intraoperative lateral condyle fractures in the PS group and femoral component revisions due to instability in the CS group. The overall complication rates and implant survivorship were comparable ( p = 0.55 and p = 0.85, respectively). Conclusion This study is the first to evaluate polyethylene insert type in FA and demonstrates that both CS and PS inserts provide comparable outcomes and safety profiles in robotic‐assisted TKA. These findings underscore the importance of patient‐specific implant selection, with further research needed to assess long‐term results. Level of Evidence Level III