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Evaluating and Understanding the Geocoding of City Directories of Paris (1787-1914): Data-Driven Geography of Urban Sprawl and Densification
No full textInternational audienceAs in other western cities, the fast-paced urban, industrial, and commercial sprawl of Paris during the 19th century provided the backdrop and driving force for the publishing phenomenon of trade directories. We show how these collections of millions of nominative entries associated with addresses can be turned into a serial dataset whose massive, fine-grained, and geolocated nature opens up new possibilities for quantitative and multi-scale analyses of the dynamics at play during one of the most dramatic socio-spatial transformations of the city. We highlight the methodological conditions of such data-driven analyses and emphasize the importance of understanding source effects. The findings underscore the significance of data science in critically evaluating digital sources and adhering to best practices in the production of large historical datasets
Ordre normatif et désordre contractuel
No full textInternational audienceÀ propos de l'arrêt de la Cour de cassation du 8 octobre 202
Johann Heinrich Lambert's memoir ``Theorie der Parallellinien": A review with commentary
No full textWe review the memoir \emph{heorie der Parallellinien} by Johann Heinrich Lambert, written in 1766. Lambert, a victim of the prejudices of his time, conceived this memoir as an attempt to prove the so-called parallel postulate of Euclid's \emph{Elements}, and consequently, the non-existence of the geometry that we now call hyperbolic geometry. In fact, by developing the foundations of a geometry obtained by replacing the parallel postulate with its negation while keeping Euclid's other postulates unchanged, Lambert was hoping to arrive at a contradiction. Of course, he failed in his endeavor, but these attempts at proving the parallel postulate implicitly contain, without Lambert having foreseen it, fundamental results of hyperbolic geometry, the discovery of which, by Lobachevsky, Bolyai and Gauss, was not to take place until the following century. Thus, Lambert's memoir (which he did not intend to publish but which was eventually published in 1895) constitutes one of the founding texts of non-Euclidean geometry. Spherical geometry is one of the three geometries of constant curvature, the other two being Euclidean geometry and hyperbolic geometry. In this sense, along with hyperbolic geometry, spherical geometry constitutes one of the two non-Euclidean geometries. In fact, Lambert, like Lobachevsky and others after him, understood the deep relationships between the three geometries: Euclidean, spherical, and hyperbolic, in particular the formal and the more profound analogies between the trigonometric formulae, the properties of birectangular isosceles quadrilaterals and of trirectangular quadrilaterals, the monotonicity properties (which can be formulated in terms of convexity properties) which hold in opposite senses in spherical and hyperbolic geometry which at some points he calls a sphere of imaginary radius.It is for these reasons that we decided to include in this volume, dedicated to spherical geometry, a chapter on this important memoir by Lambert, trying to highlight its most important ideas.This paper will appear as a chapter in the book ``Spherical Geometry in the Eighteenth Century I: Euler, Lagrange and Lambert", ed. R. Caddeo and A. Papadopoulos, Springer Nature Switzerland, 2026
Food formulation: rheological and tribological determinants of oral processing and flavor perception
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A pyronin-based “covalent-assembly” fluorescent probe for sensitive detection of cyanide in pure aqueous media and real water samples
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Interdiction des paiements. Frais de déplacements professionnels
No full textInternational audience(Soc. 6 mai 2025, no 20-11.889, F-D, AGS et a. c/ M.F. et a., RPC 2025. Comm. 93, note C. Lebel
A critical role of heterotrophic bacteria in early diagenesis of carbonates through exopolymer degradation and calcium release.
No full textInternational audienceThe degradation of exopolymeric substances (EPS) by heterotrophic bacteria, concomitant release of calcium ions and precipitation of carbonates were studied in a temperate mountain lake, Lac d'Ilay, Jura France. Phytoplankton blooms in this lake produced large amounts of exopolymeric substances (EPS; 1.8–3.0 mg L −1 ), probably inhibiting CaCO 3 precipitation by binding Ca 2+ as shown by the saturation index of calcite and aragonite remaining well below 1. EPS settled to the sediments, where additional polymeric substances were produced by the benthic community. The total amount of EPS decreased downcore from ca 50 μg/g dry sediment near the surface to ca 1.5 μg/g dry sediment at the bottom (120 cm depth). A decrease in acidity, protein and sugar content, and calcium‐binding capacity of EPS with depth coincided with active calcite precipitation. Aerobic and anaerobic EPS‐degrading heterotrophic enrichments were obtained from the top, middle and bottom of the core. Doubling times of aerobic cultures from the top were six times shorter than those of cultures obtained from the bottom of the core, but anaerobic growth rates were similar across all enrichments. Aerobic turnover rates of organic compounds decreased by a factor of 4–5 from top to bottom; anaerobic rates were similar at all depths, except for the turnover of polymers, which was negligible at the surface compared to rates at the middle and bottom. All enrichments released calcium when grown on EPS. Growth on calcium‐saturated EPS in anaerobic cultures obtained from the bottom of the core was the slowest, but still released 26% of the Ca in 20 days. This release during EPS degradation explained an increase in free calcium ions with depth reported in a previous study and may account for a large fraction of the carbonate mud. This suggests that sediments should be considered as an important source of biogenic carbonates
: Suivi qualitatif du recours au Contrat d’engagement jeune
No full textLe Contrat d’engagement jeune (CEJ), initié en mars 2022, s’adresse aux jeunes de 16 à 25 ans en difficulté d’insertion sociale et professionnelle. Mis en œuvre par les Missions locales et par France Travail, il combine un accompagnement « intensif » par une conseillère et une allocation mensuelle, conditionnés à la réalisation de 15 à 20 heures d’activités hebdomadaires. Il a fait l’objet d’une enquête sociologique, dont les résultats et analyses font l’objet de ce rapport, menée entre octobre 2023 et mai 2025. Elle repose sur 223 entretiens et 74 séquences d’observation dans onze territoires aux caractéristiques variées. Elle explore les usages du CEJ, le travail des conseillères, et les effets du dispositif sur les structures du service public de l’emploi.Succédant à la Garantie jeunes dans un contexte post-Covid marqué par une précarité juvénile et des débats sur l’ouverture du RSA aux moins de 25 ans, le CEJ est présenté comme plus « intensif » que les dispositifs lui préexistant. Il introduit une obligation inédite de « 15 à 20 heures d’activités » hebdomadaires, censée responsabiliser les jeunes et répondre aux critiques d’« assistanat ». Il est mis en œuvre par les Missions locales et France Travail. Son déploiement contribue aussi à réorganiser les politiques d’insertion : les Missions locales, historiquement en charge de ce public, l’ont perçu comme une mise en concurrence avec France Travail.Le CEJ a accéléré des transformations déjà engagées dans les Missions locales : intensification des tâches administratives, montée en puissance du management, rationalisation et division horizontale du travail. Les conseillères, majoritairement des femmes issues des classes populaires ou moyennes, revendiquent une « fibre sociale », et investissent l’écoute et le soutien relationnel dans leur relation avec les jeunes. Elles valorisent le lien de confiance qu’elles nouent avec eux et elles, et dénoncent la surcharge administrative et parfois les tensions liées au contrôle des activités. Elles jugent le CEJ de manière ambivalente en ce que d’une part, il permet de renforcer le travail relationnel, en raison de l’intensité des rencontres qu’il suppose et de sa logique contractuelle, mais que d’autre part, il génère une surcharge de travail administrative décrite comme un facteur majeur d’empêchement du travail.Les bénéficiaires du CEJ sont majoritairement issu·es des classes populaires précarisées, cumulant souvent instabilité économique, sociale, scolaire et psychique. Ils décrivent un rapport à l’école et au marché du travail marqué par des orientations subies, des emplois précaires et des expériences dévalorisantes. Au regard de leurs conditions de vie et de leurs projets, le CEJ est un soutien important, traduit par une aide financière et l’accompagnement d’une conseillère, mais il reste temporaire et apporte rarement une réponse structurelle à leurs difficultés.Enfin, le CEJ poursuit une logique d’adaptation des jeunes aux opportunités locales de travail ou de formation. L’exigence des « 15 à 20 heures d’activités » est son innovation majeure, mais son interprétation varie selon les territoires et les conseillères, alimentant des jugements normatifs sur la légitimité des activités. L’allocation, à la fois ressource vitale et objet de contrôle moral, cristallise les tensions entre aide sociale et contrepartie. Le CEJ semble ainsi illustrer une tendance au renforcement du contrôle et de la responsabilisation, déséquilibrant le principe des droits et devoirs dans les politiques d’insertion
Pigment‐Macromolecule Complexes Isolation from Sea Urchin Biomineral Waste for Coloring Materials
No full textInternational audienceThe production and widespread use of synthetic pigments and dyes have significant environmental and health impacts. Despite this, synthetic colorants remain dominant due to their wide color range, high stability, strong tinting power, and lower cost compared to natural alternatives. Therefore, to offer sustainable and competitive substitutes, eco‐friendly methods for producing bio‐based pigments with similar performance are essential. Herein, a methodology has been developed to extract the entire colored organic fraction occluded within seashell biomineral waste, which comprises pigments and pigment‐macromolecule complexes. This process involves an optimized cleaning procedure of the biomineral soft tissues, a tailored biochemical extraction, and detailed characterization of the extracted fraction. Applied to sea urchin skeletons, this method successfully isolates polyhydroxylated naphthoquinone (PHNQ)‐macromolecule complexes. These complexes show superior pH stability in purple hues compared to free PHNQ, which shifts from red to purple in basic conditions. Notably, the approach enhances colorant yield by up to five times. These results, together with mineral pigment synthesis and fabric dyeing assays performed with the extracted colored organic fraction, contribute to a better understanding of the origin of color in biominerals and reveal the versatility of these natural pigments for environmentally friendly coloring of both organic and inorganic materials