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Combinatoire des algèbres de descentes et revêtements de graphes
No full textWe give a direct combinatorial proof that the product of two descent classes in a symmetric group is a sum of descent classes. The proof is based on the fact that the group product gives a covering map when descent classes are endowed with the graph structure coming from the weak order. The main geometric argument is valid for any Coxeter group, even infinite ones for which the descent algebra does not exist.On donne une preuve combinatoire directe du fait que le produit de deux classes de descentes du groupe symétrique est une somme de classes de descentes. La preuve repose sur un argument géométrique de théorie des graphes, valable dans le cadre général des groupes de Coxeter
Spatial Equity in Urban Mobility: A PCA-Based Analysis of Multimodal Accessibility in Caen, France
No full textInternational audienceThis study analyzes the spatial accessibility of key services in Caen, France, focusing on how different transport modes (car, bicycle, and public transit) influence access to essential services across the urban and suburban landscape. Indeed, the introduction of traffic restrictions in towns with low emission zones encourages a detailed study, on a fine spatial scale, of the differences in accessibility between different modes of transport, for different services and for different journey times. Using spatial analysis techniques, we examine accessibility patterns in relation to services such as shops, healthcare, education, and tourism, highlighting significant disparities between transport modes. The findings reveal that car travel provides the highest accessibility across all service categories, particularly for healthcare and recreational services, while bicycle and public transit accessibility is more limited, especially in peripheral areas. A Principal Component Analysis (PCA) synthesizes the multimodal accessibility data, and hierarchical clustering identifies distinct patterns of accessibility using different transport modes across the city. The study further explores temporal trends in accessibility, showing how different modes perform over varying travel times. Based on these findings, we propose targeted policy interventions aimed at improving public transit, enhancing cycling infrastructure, decentralizing essential services, and promoting mixed-use urban development. Future research directions include examining socio-economic disparities, the impact of emerging mobility technologies, and the environmental implications of accessibility patterns. This research provides valuable insights for urban planners seeking to improve mobility equity and sustainability in urban areas
De One Health aux territoires de Santé : vers une approche interdisciplinaire de la santé animale ancrée dans les enjeux des territoires
No full texthttps://www.youtube.com/watch?v=jAg86SUQ-akInternational audienceDe One Health aux territoires de Santé : vers une approche interdisciplinaire de la santé animale ancrée dans les enjeux des territoires
One-dimensional numerical modelling of long-term thermo-mechanical behaviour of energy pile in clay
No full textInternational audienceOne-dimensional numerical modelling of long-term thermo-mechanical behaviour of energy pile in cla
Communicating the risk of erosion: the effects of map-based communication on risk perception and affect
No full textInternational audienceThis study firstly aims to understand the impacts of map representations of coastal erosion on risk perception and affects of lay citizens. Secondly, it aims to study the effect of differing design of cartographic features on observation and interpretation of the message conveyed by different maps. Seven maps were presented to the participants (N = 50), varying according endogenous (abstraction, regalian cartridge) and exogenous characteristics (background, colours). A questionnaire interrogated risk perception and affect before and after observation, while eye-tracking data were recorded during the observation of each map. This experiment shows that communicating erosion risk by maps reduces perceived knowledge of risk but also reduces fear of the risk. The abstraction level significantly impacts observation patterns: correlation maps seem to guide visual attention in a more relevant way and to convey the message more clearly and effectively than other types of maps. But there is no influence of the other characteristics even if interviews show that colours seem to influence the message interpretatio
Reassessing air pollution exposure: How daily mobility and activities shape individual risk in greater Paris
No full textInternational audienceUnderstanding individual exposure to air pollution is essential for tackling environmental inequalities and informing public policies aimed at reducing disparities. Traditional approaches often focus on residential locations, but exposure is intrinsically linked to daily mobility, activities and socio-economic profiles. This study presents new results based on a dynamic exposure modelling approach that takes these dimensions into account, offering a more realistic assessment of air pollution risk. By integrating high-resolution air quality data with detailed information on individual mobility, activities and socio-economic characteristics, we quantify the exposure of 400,000 individuals in the Île-de-France region. Our approach takes into account all the environments that individuals visit during the day and the time spent in each of them, going beyond static exposure assessments based on residential location. We compare this dynamic model with traditional exposure calculations, revealing significant differences in the spatial distributions of PM10 and NO2 exposure. Our analysis highlights how mobility patterns and daily activities contribute to total exposure, demonstrating that place of residence is only one part of reality. For example, commuting, workplaces and leisure activities play a key role in determining individual exposure levels. The results of our study show that dynamic exposure calculation provides a better understanding of exposure factors and offers a framework for understanding environmental inequalities. By shifting the focus from home-based to person-based exposure, our approach makes it possible to identify levers for action to reduce disparities and support targeted public health action. Our study redefines the way in which we assess the risks associated with air pollution, by highlighting the need to take into account mobility behaviour and individual trajectories
The changing tracks of land value capture in constrained policy contexts; A comparison of London’s Crossrail and Grand Paris Express
No full textInternational audienceLand value capture is often vaunted as having significant potential to fund public infrastructure, including mega transport projects like urban metro railway schemes. Yet land value capture is frequently challenging to operationalise and project promotors can be reluctant to use it to finance schemes. This article explores why and how land value capture came to be deployed in financing two major contemporary comparable urban railway developments: Grand Paris Express (France) and Crossrail (London, UK). We adopt an institutional perspective which seeks to understand how the dynamic relationships between different institutional bodies shaped the decision to use land value capture and the design of the resulting mechanisms employed by focusing on the political economy, planning regime and taxation regime of each project. We critically discuss the merits of using land value capture in funding these projects by considering why and how actors came to develop instruments that when not seen in isolation, make a meaningful contribution to the overall funding mechanisms employed
Spinal cord morphology and PKD2L1+ cells distribution: effects of age, sex, and spinal segment in mice
No full textInternational audienceIntroduction: Morphometrical studies of the mouse spinal cord are often limited to one age or sex, restricting our understanding of anatomical variability. This study provides a detailed analysis of the spinal cord in mice, examining the effects of age, sex, and spinal region, along with the distribution of PKD2L1-positive (PKD2L1 + ) cells along the rostro-caudal axis.Methods: Using 811 transverse sections from a total of 18 3- and 8-week-old mice, DAPI immunofluorescence and confocal imaging, 14 dimensions of gray matter (GM), white matter (WM), and the central canal (CC) were assessed using landmarks positioning and segmentation methods.Results: Age was the most influential factor: between 3- and 8- weeks-old, the spinal cord showed reduced rostro-caudal length ( p = 2.49e-04), smaller ventral GM horns ( p < 0.005), deeper ventral commissures ( p = 5.58e-13), and an increase in CC area (from 1925.58 ± 630.16 μm 2 to 2199.50 ± 569.44 μm 2 ). Looking at sex-related differences, females showed higher variability across several parameters, with subtle differences in GM organization ( p < 0.05) and CC morphology (mean area = 2146.39 ± 632.91 μm 2 in females vs. 1998.36 ± 589.85 μm 2 in males). Along the rostro-caudal axis, WM size, as well as GM dorsal and ventral horn dimensions, differed significantly across spinal segments ( p < 0.005). CC position also shifted dorsally in cervical and lumbar regions depending on age and sex ( p < 0.005). PKD2L1 + cells were mainly clustered near the CC, with over 46% located proximally. The highest densities (>300 cells/segment) were found in lumbar and lower thoracic regions. Discussion These results indicate progressive structural changes during development, including reorganization of cells and CC architecture stabilization. The distribution of PKD2L1 + cells is consistent with their proposed role as cerebrospinal fluid-contacting neurons potentially involved in sensing fluid composition and modulating locomotor control. Their increased presence in caudal segments suggests functional specialization in different spinal regions Conclusion: This work provides detailed, segment-specific anatomical data crucial for developing accurate and physiological numerical models. Adding age and sex differences emphasizes the need to reflect biological variability in simulations. Additionally, the mapping of PKD2L1 + neurons offers valuable insight into their spatial organization and potential involvement in sensory processing, locomotor function, and neurological or developmental disorders
Contester les projets olympiques en Seine-Saint-Denis.Une coproduction des connaissances face à l’urbanisme événementiel ?
No full textInternational audienceSince 2017, in Seine-Saint-Denis (France), the Comité de Vigilance JO 2024 has been mobilizing residents, associations, and researchers to challenge the urban projects linked to the Paris 2024 Olympic and Paralympic Games. Faced with the transformations imposed by this event-driven urban planning, the collective has been developing forms of counter-expertise with residents and citizens, such as territorial analysis, pleas, and alternative projects. The aim was to document the social and environmental effects of these developments and to call for local needs to be better taken into account. This paper explores the processes of co-production of knowledge between residents, activists, professionals, and researchers, aimed at building an audible and credible alternative account of the Olympic projects, informing public opinion, and challenging public and private organizations. By exploring the epistemic dimension of this mobilization, the objective of this research is to understand how collective knowledge, rooted in local experience, can influence the urban fabric in the context of mega-events and strengthen people’s ability to cope with current socio-spatial and environmental challenges.Depuis 2017, le Comité de vigilance JO 2024 à Saint-Denis mobilise habitant·es, associations et chercheur·es pour contester les projets urbains liés aux Jeux olympiques et paralympiques de Paris 2024. Face aux transformations imposées par cet urbanisme événementiel, le collectif élabore des contre-expertises habitantes et citoyennes – diagnostics, plaidoyers et projets alternatifs – pour documenter les effets sociaux et environnementaux de ces aménagements et demander une meilleure prise en compte des besoins locaux. Cet article analyse le processus de coproduction des savoirs entre habitant·es, militant·es, professionnel·les et chercheur·es visant à construire un récit alternatif audible et crédible des projets olympiques, à informer l’opinion publique et à interpeller les institutions. En explorant la dimension épistémique de cette mobilisation, il s’agit de comprendre comment des savoirs collectifs, ancrés dans l’expérience locale, peuvent influencer la fabrique urbaine dans un contexte de méga-événements et renforcer la capacité des populations à faire face aux défis socio-spatiaux et environnementaux actuels
