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Modélisation de la mobilité quotidienne et reconstitution des trajectoires spatiotemporelles
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Production collaborative de capsules vidéo en mathématiques, dans une perspective inclusive
No full textInternational audienceThis contribution analyzes the organization and functioning of a multidisciplinary and multi-category team working on the design of video capsules for deaf students. It examines how each member contributed, according to their skills and area of expertise, to the design of these resources from an inclusive perspective.Cette contribution analyse l'organisation et le fonctionnement d'une équipe pluridisciplinaire et pluricatégorielle qui oeuvre pour la conception de capsules vidéos pour les élèves sourds. . Il s’agit d’étudier de quelles manières chacun a contribué, selon ses compétences et son champ d'expertise, à la conception de ces ressources dans une perspective inclusive
Shapley value to rank vulnerabilities on attack graphs: Applications to cyberdeception
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Minimum time problem for the double integrator with a loss-of-control region
No full textInternational audienceIn this paper we address the minimum time problem for the double integrator, but here, in contrast with the classical version of this problem, the control is constrained to remain constant as long as the state belongs to a given region of the state space called loss-of-control region. This situation prevents switches from occurring in the loss-of-control region and, therefore, a new analysis has to be performed. For this purpose we prove an appropriate version of the Pontryagin maximum principle in which the necessary conditions comprise two key components. The first is an averaged Hamiltonian gradient condition to determine the optimal constant values of the control in the loss-of-control region. The second is, similarly to hybrid maximum principles found in the literature, that the costate admits discontinuity jumps at the interface between the loss-of-control region and its complement. We then highlight the theoretical use of these necessary conditions by solving analytically the minimum time problem for the double integrator with an illustrative loss-of-control region (precisely, the left vertical half-space). New behaviors are observed such as the lack of dynamic programming principle, of feedback expression and of saturation of the control constraint set. Finally we further illustrate these aspects by solving numerically the same minimum time problem for the double integrator but with two other illustrative loss-of-control regions (first a sloped half-space, then a disk)
Quand Érec rencontre Erec(k). Réflexions croisées sur l’édition et l’interprétation des romans deChrétien de Troyes et de Hartmann von Aue
No full textInternational audienceHartmanns von Aue Erec, die deutschsprachige Übertragung des ersten Artusromans Chrétiens de Troyes Érec et Énide, ist ein paradigmatisches Beispiel für die intensive Zirkulation von Erzählstoffen im westeuropäischen Kulturraum des Mittelalters. Aus unterschiedlichen Gründen hat für beide Romane jeweils eine Handschrift (Paris, BnF fr. 794 und Wien, ÖNB, Cod. Ser. nova 2663) eine zentrale Rolle in der editorischen und kritischen Tradition gespielt. Vorliegender Beitrag zieht eine vergleichende Bilanz der Editionsgeschichte beider Texte, der damit verbundenen Debatten sowie ihrer Folgen für die Interpretation der Texte und die Erfassung beider Autorfiguren. Aus den gekreuzten Blicken geht hervor, wie produktiv eine komparatistische Perspektive sein kann, welche die Transformationen der Texte sowohl durch ihre Überlieferung als auch durch die Editionspraxis mit einbezieht.La traduction-réécriture en langue allemande, par Hartmann von Aue à la fin du XIIe siècle, du premier roman composé par Chrétien de Troyes, Érec et Énide, est un exemple bien connu de l’intense circulation de la matière narrative dans l’espace occidental médiéval. Pour chacun des textes, un manuscrit a joué un rôle central dans les traditions éditoriale et critique (Paris, BnF fr. 794 pour le texte de Chrétien, Wien, ÖNB, Cod. Ser. nova 2663 pour celui de Hartmann). Le présent article dresse un bilan de l’histoire des éditions des deux romans, des débats auxquels elles ont donné lieu et de leurs conséquences sur l’interprétation des textes et la perception de leurs auteurs. Ce bilan croisé vise à mettre en valeur l’intérêt, pour la démarche comparatiste, de tenir compte des particularités de la tradition textuelle et de l’influence des pratiques des éditeurs modernes
Combined effects of soil multi‐contamination by metals and metalloids and drought slow down the ecological restoration of a Mediterranean scrubland
No full textInternational audienceIn Mediterranean ecosystems, soil contamination by metals and metalloids and drought represent major abiotic stresses whose combined effects on plant communities remain poorly understood, hindering effective ecological restoration practices. Here we evaluated the responses of plant community and species to combined stresses during a 4-year ecological restoration operation in Mediterranean scrubland. We conducted monthly monitoring of plant communities across 20 restoration plots, analyzing taxonomic and phylogenetic diversity attributes alongside soil contamination levels and drought indices using mixed-effects and hurdle models. Our results highlight that both stresses combined reduced taxonomic diversity and the diversity of distant lineages within the plant community by exerting a strong environmental filtering on species. Synergistic effects revealed that species richness decreased more strongly under high drought at low contamination levels than at high contamination levels, suggesting prior selection for tolerant species. Annual species were primarily impacted by drought through stress-avoidance strategies, while perennial species were more affected by metal and metalloid contamination despite their stress-tolerance mechanisms. Our findings highlight the importance of considering combined stress effects in restoration planning and identify phylogenetic diversity as a powerful criterion for species selection. Several perennial species, particularly Coronilla juncea, showed high tolerance and restoration potential for metal and metalloid-contaminated Mediterranean ecosystems facing increasing drought under climate change
The role of tropical forest fragment vegetation in maintaining arthropod diversity and spillover to adjacent sugarcane fields
No full textInternational audienceAbstract The degradation of forests in tropical agricultural landscapes has reduced biodiversity and may negatively affect ecosystem services. However, the role of forest fragments in the provision of ecosystem services for agroecosystems, such as biological control, is still not well understood. This study analyses the relationship between tree diversity and arthropod communities in forest fragments and adjacent sugarcane fields around Jaboticabal (São Paulo, Brazil) to evaluate the benefits of preserving Atlantic Forest fragments. We tested the hypotheses: (1) arthropod diversity and the abundance of key functional groups in forest fragments are favoured by tree diversity, (2) diversity and abundance of these functional groups in sugarcane fields depend on adjacent forests and (3) the insect community composition of forest fragments and sugarcane fields is similar due to spillover effects. Arthropods were sampled in 10 forest fragments over 2 years (2020 and 2022) using traps (Malaise, yellow pan) and direct tree sampling. We identified arthropods to morphospecies (2020) and family level (2022) and associated families to functional groups. We found that the quality of forest fragments, particularly tree species richness, was positively related to forest arthropod richness and frequency (occupied samples) of functional groups involved in ecosystem services such as predators, but also of phytophagous insects. There was also a strong positive correlation between insect family richness and functional groups of forest fragments and adjacent sugarcane fields, indicating potential spillover and spatial connectivity between habitats. Although insect community composition was significantly different between forest fragments and sugarcane fields, NMDS ordination revealed partial overlap of family communities, suggesting many shared taxa in both habitats. This study highlights the importance of diverse forest fragments in preserving insect biodiversity and related ecosystem services in tropical agricultural landscapes and advocates for the conservation and restoration of these habitats. However, the benefits in terms of crop damage reduction and yields remain to be confirmed.A degradação de florestas em paisagens agrícolas tropicais reduziu a biodiversidade e pode afetar negativamente os serviços ecossistémicos. No entanto, o papel dos fragmentos florestais na prestação de serviços ecossistémicos para agroecossistemas, como o controle biológico, ainda não é bem compreendido. Este estudo analisa a relação entre a diversidade de árvores e as comunidades de artrópodes em fragmentos florestais e canaviais adjacentes na região de Jaboticabal (São Paulo, Brasil), para avaliar os benefícios da preservação de fragmentos da Mata Atlântica. Testamos as hipóteses: (1) a diversidade de artrópodes e a abundância de grupos funcionais‐chave são favorecidas pela diversidade de árvores; (2) a diversidade e a abundância desses grupos funcionais em canaviais dependem das florestas adjacentes; e (3) a composição da comunidade de insetos em fragmentos florestais e canaviais é semelhante devido aos efeitos de transbordamento. Artrópodes foram amostrados em dez fragmentos florestais em dois anos (2020 e 2022) usando armadilhas (Malaise e Bandeja amarela) e amostragem direta em árvores. Identificamos artrópodes em nível de morfoespécie (2020) e família (2022), e associamos famílias a grupos funcionais. Constatamos que a qualidade dos fragmentos florestais, particularmente a riqueza de árvores, apresentou correlação positiva com a riqueza de artrópodes florestais e a frequência (amostras ocupadas) de grupos funcionais envolvidos em serviços ecossistêmicos, como predadores, mas também de insetos fitófagos. Houve também uma forte correlação positiva entre a riqueza de famílias de insetos e os grupos funcionais de fragmentos florestais e canaviais adjacentes, indicando potencial transbordamento e conectividade espacial entre habitats. Embora a composição da comunidade de insetos tenha sido significativamente diferente entre fragmentos florestais e canaviais, a ordenação NMDS revelou sobreposição parcial das comunidades familiares, sugerindo muitos táxons compartilhados em ambos os habitats. Este estudo destaca a importância dos fragmentos florestais na preservação da biodiversidade de insetos e dos serviços ecossistêmicos relacionados em paisagens agrícolas tropicais e defende a conservação e a restauração desses habitats. No entanto, os benefícios em termos de redução de danos às culturas e aumento da produtividade ainda precisam ser confirmados
Les défis olympiques de la luge : relations institutionnelles, représentativité internationale et standardisation des infrastructures (1964-2026)
No full textInternational audienceCe chapitre explore l’histoire olympique de la luge de course, entre 1964 et 2026. Discipline sportive au passé foisonnant quoique méconnu, la luge accède au milieu du XXe siècle aux honneurs olympiques pour ne plus quitter le programme de l’évènement quadriennal d’hiver. Restent des défis de taille pour asseoir sa place dans le microcosme olympique, parmi lesquels les relations institutionnelles entre la Fédération internationale de luge (FIL) et le CIO ; la question de la représentativité internationale de ce sport ; ou encore les évolutions techniques relatives à la confection des pistes dédiées (et bientôt « combinées » avec les pratiques du bobsleigh et du skeleton). En se reposant sur les archives du Centre d’études olympiques de Lausanne, l’analyse montre le chemin parcouru par le sport de luge jusqu’au cœur des Jeux d’hiver et du Mouvement olympique
Behavioral and functional responses of Hormogaster samnitica to different organic amendments
No full textInternational audienceThe decline of soil organic matter in Mediterranean agroecosystems, coupled with the underutilization of crop residues, calls for sustainable strategies that enhance soil health while valorizing local organic resources. This study investigates the behavioral and functional responses of Hormogaster samnitica, a large-bodied, endogeic earthworm, to four organic amendments derived from agricultural residues: vine pruning compost (PRUN), vine pruning compost with a commercial accelerator (COMM), vine pruning compost inoculated with Indigenous Microorganisms (INDG), and vermicompost from spent coffee grounds (VERM). The experiment was conducted in laboratory mesocosms using repacked soil columns. Earthworms were introduced at three body size classes (“big”, “medium” and “small”), and their impact on soil porosity and infiltration was assessed via X-ray tomography and infiltration tests. Results showed that body size significantly affected earthworm activity, with larger individuals creating wider and deeper burrows and markedly increasing water infiltration. Among treatments, COMM significantly enhanced macroporosity in the amended soil layer and induced a marked shift in the vertical distribution of macropores. However, despite increased porosity, compost-based amendments generally reduced infiltration rates compared to the CTRL. VERM showed limited effects on both bioturbation and infiltration. A two-choice preference test revealed that H. samnitica exhibited weak substrate preferences, while the more generalist Aporrectodea caliginosa clearly favored compost-based treatments over VERM and CTRL. Overall, these findings highlight the importance of considering species-specific traits and amendment properties when evaluating the ecological impact of organic inputs, and support the use of compost as a biostimulant for soil fauna and structure enhancement in Mediterranean systems
Entre Néron et les Flaviens : les pestilences à Rome et dans l'empire
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