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Combustion of NH3/CH4 mixtures in a swirl burner: Study of non-premixed flames with radial fuel injection
No full textInternational audienceThe transition to renewable energy is essential in addressing climate change. While natural gas plays a significant role in this transition, it still produces CO2 emissions. Ammonia (NH3) is being investigated as a promising alternative fuel. However, ammonia combustion presents several technical challenges, such as low flame velocity, limited calorific value, difficulties with flame stabilization, and high NOx emissions. This study examines the impact of ammonia addition to methane, equivalence ratio, and swirl number on pollutant emissions (NO, CO, CH4, and CO2), exhaust gas temperature, and flame stability. Experiments are carried out using a swirl burner with a radial fuel injection in a 1-meter high combustion chamber. The burner consists of two concentric tubes, with the inner tube supplying fuel and the outer tube supplying air. The fuel is injected radially through eight holes at the burner exit. The ammonia fraction ranges from 0 to 100 %, the equivalence ratio from 0.8 to 1.0, and the swirl number from 0.8 to 1.4, with a constant flame power of 10 kW. Emissions of NO, CO, CH4, and CO2 are measured in the dry exhaust gases using a multi-gas analyzer, inside chamber temperatures are measured and the flame structure is analyzed via OH* and NH2* chemiluminescence and velocity measurements by LDA technique. The results show that both the swirl number and equivalence ratio significantly alter flame geometry, affecting combustion zones and flame height. Axial velocity measurements indicate that the recirculation zone shrinks with ammonia addition, while a high swirl number increases axial velocity, promoting ammonia combustion and upstream flame propagation. Up to 30 % ammonia, the flame remains stable, but higher ammonia levels lead to fluctuations in stabilization. High ammonia content in the fuel mixture results in reductions of NO, CO, and CO2 emissions, though there is a potential increase in unburned gases. As expected, the inside chamber temperatures decrease as the ammonia fraction increases
The effect of articulatory rehearsal on dual-retrieval processes in semantically related list recall: A comparison between 8- and 10-year-old children and young adults
No full textInternational audienceWhen asked to remember a list of items for later testing, we often repeat earlier items to ourselves as later items are presented. This process, called “rehearsal,” develops during childhood. The present study examined the role of rehearsal in recalling lists of semantically related words and used the dual-retrieval model to pinpoint the retrieval processes modified by rehearsal in children and adults. Thirty-one children (Mage = 8.8 years, SD = 0.5, 12 females and 19 males) and 29 adults (Mage = 20.5 years, SD = 2.7, 23 females and 6 males) performed a complex span task consisting of maintaining words to be recalled later in immediate and delayed tests, while performing a concurrent task. The difficulty of the task was adjusted according to each participant’s abilities. Participants performed the task either silently, which allowed them to use rehearsal, or under articulatory suppression, which reduced rehearsal opportunities. The results showed that, although adults had a higher rate of correct recall, children benefited from rehearsal opportunities for both immediate and delayed correct recall. There were also fewer semantic errors in both age groups when rehearsal could be used. The dual-retrieval model revealed that rehearsal fosters direct access to verbatim memory and reconstruction based on gist memory. Finally, the difference in correct recall and direct access between the two age groups decreased when rehearsal could be used. These findings suggest that, although rehearsal is more effective for adults, children benefit more from it for correct recall and direct access to verbatim traces
Les caddies de la colère. La grande grève des employé.e.es de l'hypermarché Mammouth Alma (Rennes, 1975)
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Seasonal divergence in the sensitivity of carbon and water fluxes to climate variability in terrestrial ecosystems
No full textInternational audienceUnderstanding vegetation sensitivity to hydroclimate factors, especially how carbon and water cycles respond toclimate change, is crucial for assessing ecosystem vulnerability. However, the seasonal sensitivity of carbon andwater fluxes to temperature, radiation, soil water content, and vapor pressure deficit across diverse biomes andclimates remains unclear. Here, we use 196 eddy covariance observations from sensor networks distributedglobally, along with daily estimates from Earth System Models (ESMs), to quantify the seasonal sensitivity ofdaily gross primary productivity (GPP), ecosystem respiration (RE), net ecosystem productivity (NEP), andevapotranspiration (ET) to various hydroclimate factors. Our ridge regression analysis reveals seasonal variationsin the sensitivity of carbon and water fluxes to hydroclimate factors across globally distributed flux sites. GPPand NEP are most sensitive to air temperature (TA) in spring, but to radiation (RAD) in summer, autumn andwinter. RE consistently exhibits positive sensitivity to TA across all seasons, while ET shows the highest sensi-tivity to RAD throughout the year. Although energy-related factors like TA and RAD dominate the influence oncarbon and water fluxes at sub-seasonal scales, soil water content (SWC) and vapor pressure deficit (VPD)become increasingly important during summer, particularly in drylands. At sites with long-term measurements,we identified a significant upward trend in the sensitivity of summer GPP to SWC with 0.005 ± 0.002 per year,suggesting that terrestrial ecosystems are becoming more constrained by water stress during summer. Comparedto observations, ESMs generally overestimate the sensitivity of GPP to SWC and VPD, while underestimate thesensitivity to RAD and TA during summer. Our findings enhanced the understanding of the seasonal response ofecosystem carbon and water cycles to hydroclimate factors, offering insights into ecosystem function underfuture climate change
Efficient and Scalable Search for Statistics
No full textInternational audienceInformed public debate needs high-quality data. In this context, high-quality statistical data sources are a valuable category of reference information based on which a claim can be checked. To facilitate the work of journalists or other fact-checkers, users’ questions about a specific claim should be automatically answered based on statistical tables. This task is complicated by the large number, size, and variety of statistical datasets.We introduce the statistical table discovery problem (STD, in short), which aims, given a natural language question and a set of statistic datasets (multidimensional tables), to find the tables most relevant for the question. We then describe STAR, an algorithm for solving the STD problem. Unlike existing table discovery (TD) solutions aimed at relational tables, STAR is devised specifically for multidimensional ones. Further, STAR treats the space and time dimensions of statistical datasets separately. We experimentally show that these features, together, make STAR outperform state-of-the-art TD systems adapted to the STD problem, in terms of scalability, search quality, preprocessing and question answering time
"Saisir l’expérience étudiante du racisme et des discriminations à l’université. Enjeux de caractérisation et d’interprétation des faits dans l’enquête Acadiscri"
No full textInternational audienceÀ partir des données recueillies dans le cadre de l’enquête Acadiscri, qui place la focale sur l’expérience des personnes, cet article s’intéresse au racisme et aux discriminations raciales vécus par les étudiant·es dans le contexte universitaire. Montrant la prégnance de ces phénomènes dans l’enseignement supérieur, il souligne en particulier la fréquence des micro-agressions raciales et leur caractère répété. Mais contrairement à l’hypothèse d’un racisme essentiellement voilé ou implicite dans le cadre universitaire, l’enquête révèle aussi l’existence de manifestations ouvertes de racisme. Le texte analyse ensuite le rôle joué par les trajectoires expérientielles et par la politisation des étudiant·es dans la conscientisation du racisme, tout comme l’importance du contexte de ces interactions disqualifiantes, qui viennent contredire les croyances égalitaires investies dans l'institution universitaire
Process evaluation of a school-based vaccination intervention to improve HPV vaccine coverage: A mixed-method study embedded in the French PrevHPV cluster randomized controlled trial
No full textInternational audienceBackgroundHuman papillomavirus vaccine coverage (HPV VC) remains suboptimal in many countries. French authorities launched the PrevHPV research program, which included a cluster randomized controlled trial (cRCT) to evaluate the effectiveness of an ‘at-school vaccination’ intervention. Within this trial, we conducted a process evaluation of this intervention, specifically analyzing (i) its implementation, (ii) its mechanisms of impact, and (iii) the contextual factors influencing implementation (facilitators/barriers).MethodWe conducted a mixed-method study embedded in the PrevHPV cRCT (April 2021–April 2022). ‘At-school vaccination’ consisted of vaccination day(s) on school premises where mobile vaccination teams (MVTs) initiated HPV vaccination free of charge for eligible adolescents (i.e., non-vaccinated adolescents aged 11+). Quantitative data were collected through activity reports and self-administered questionnaires of adolescents and school staff. Qualitative data collected through six focus groups with school staff and MVTs were analyzed using thematic analysis.ResultsOf the 31 schools (14,772 adolescents) randomized to implement ‘at-school vaccination’, 12 (39 %) dropped out. Among the participating schools, analysis of implementation showed that 17 % of adolescents returned valid consent forms, of whom 89 % initiated vaccination. MVTs played a central role in implementing vaccination day(s), supported by several school staff (e.g., school nurses, education assistants). Regarding mechanisms of impacts, satisfaction with the vaccination days was high among adolescents and school staff. The intervention generated both positive and negative group effects among adolescents. Contextual factors that facilitated implementation included the preparation of a list of adolescents to be vaccinated and the availability and motivation of school staff. The main barriers related to the management of consent forms and missing health records.ConclusionWe formulated recommendations for implementing at-school vaccination, which may be particularly helpful for the French school HPV vaccination campaigns that were scaled up nationally in 2023. We also discussed potential macro-level improvement strategies, involving modifications to the legislative framework
Advanced integrated human in vitro approach to explore gut-brain barrier interactions with gut microbiota metabolites and pesticides
No full textInternational audienceThe gut microbiota (GM) plays a central role in host barrier homeostasis. Alterations in GM due to chronic dietary pesticide residues can have far-reaching consequences on human health. Although in vitro models are increasingly used to study organophosphate effects, especially Chlorpyrifos (CPF), accurately modeling complex GM-host interactions remains challenging. Here we investigated how CPF-altered GM metabolites influence epithelial and brain barrier integrity. An integrated human-relevant in vitro approach combining three complementary models: the Simulator of the Human Intestinal Microbial Ecosystem (SHIME®) under control and CPF-exposed conditions to evaluate both short-term and long-term effects (15 and 30 days), a Caco-2-based intestinal barrier (IB) and a blood-brain barrier (BBB) co-culture. Two parallel experimental setups (SHIME-IB and SHIME-BBB) were developed: SHIME®-derived microbial metabolites and pesticide residues supernatants were directly applied to each barrier model for 24 h. Confocal imaging revealed discontinuous localization of tight junction proteins (occludin, claudin-5 and ZO-1) without concomitant increase in FITC-dextran apparent permeability or overt cytotoxicity. This structural disorganization occurred despite unchanged transcriptional expression of tight junctions, except for a significant reduction of CLDN5 mRNA in the BBB at CPF15, suggesting early molecular signals. In contrast, we showed a selective decrease in P-GP (P-glycoprotein) expression in both barriers, confirmed at the protein level. Concurrently, IL-8 (Interleukin-8) secretion increased markedly in IB, particularly at CPF15, highlighting its potential as an early biomarker chemokine-driven inflammatory activation. This integrated approach provides an ethical model to study environmental contaminants' effects on human barriers, revealing microbiota-mediated disruption by CPF
Coupling of electrochemical systems with nature-based solution for wastewater treatment: A comprehensive review to evaluate the synergy, efficacy and applicability
No full textInternational audienceThis paper critically reviews for the first time electrochemical-assisted nature-based solution (NBS) systems applied for wastewater treatment. Such coupling could be a more sustainable response to address the water issues through the Sustainable Development Goals (SDGs) from the United Nations. Eight electrochemical/NBS systems combinations have been identified in the literature: (i) electro-coagulation (EC)/electro-oxidation (EO)-constructed wetland (CW), (ii) microbial fuel cell (MFC)-CW, (iii) bio-electrochemical system (BES)-CW, (iv) electrokinetic (EK)-phytoremediation (PR), (v) MFC/EC-vermi filtration (VF), (vi) electro-Fenton (EF)-algal pond (AP), (vii) electrochemical disinfection (ED)/ICME-soil infiltration, and (viii) SI/green wall (GW). The main principles, mechanisms and parameters have been critically reviewed, as well as the synergies gained through such coupling. Still, challenges remained to be solved. The matrix effect during electrochemical treatment could induce toxicity of the treated solution before NBS remediation, which remained underexplored. In addition, the mechanisms involved in the NBS systems are still not fully clarified, meaning that the process control is not easy to implement due to difficulties in getting predictive modelling. A few recommendations concern the need to develop suitable electrochemical designs, such as microfluidic devices, particularly adapted to low-conductivity effluent to avoid the addition of supporting electrolyte. Future work should experimentally validate low-energy electrosorption-based processes in combination with NBS
Framework for real-time multimodal container transport risk management
No full textInternational audienceIn the current context of globalization, multimodal container transport plays an important role in the efficiency and effectiveness of the supply chain. Indeed, containerization induces high productivity during port handling and a reduction of transport costs thanks to groupage. It also ensures the integrity and security of the goods transported. Nevertheless, the large number of stakeholders involved in the container transport process makes it extremely complex and leads to a loss of visibility and traceability during the transit of goods. In addition, the transit process is very often subject to random events that lead to delivery delays and increased transport costs. Considering all these difficulties, this work proposes a system for real-time detection of random events that may disrupt the multimodal transport of containers. In this paper we show how by relying on container traceability/visibility data, textual data and on natural language processing techniques, our system can detect in real time random events that may disrupt the transport flow. We describe the different modules and models that make up our system and then show its performance through a real use case. This work focuses on decision support for the activities of the stakeholders involved in the multimodal transport chain (exporters, consignees, carriers, shipping companies, etc.). The research is conducted in collaboration with an industrial partner (Traxens), who develops a real-time tracking solution for containers