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Optimization of the representation of results in interval arithmetic
No full textInterval arithmetic enables rigorous bounding of rounding errors, but standard representations require storing two floating-point numbers per interval, which increases memory costs and data transfer in large-scale computations. We propose a compressed interval representation inspired by the FP-ANR format, encoding both the center and the radius within a single floating-point word while preserving the strict inclusion of the original interval. We present an efficient algorithm to convert center-radius intervals into this format with minimal over-approximation. Its applications to the interval matrix product and the interval Newton method demonstrate the practical benefits of this representation. Additionally, the proposed approach enables the integration of mixed-precision computations, paving the way for scalable and memory-efficient interval arithmetic in scientific computing
Columbia supercontinent remnants in the Tuareg Shield (Iforas, Mali)
No full textInternational audienceThe Iforas Granulitic Unit (Tuareg Shield), east of the West African Craton, is a key place to help reconstructing the Columbia supercontinent evolution. In this area, the emplacement of magmatic protoliths is constrained at c. 2.05–2.06 Ga and the production of the magmas involved recycling of a Paleoproterozoic to Archean crustal component (up to 3.0 Ga). For the first time, this study emphasizes two distinct Paleoproterozoic granulitic events. The first one occurs at ca. 2.0 Ga and was followed by a second event of very-high temperature (up to 920°C) at ca. 1.89 Ga. Rocks from the Iforas Granulitic Unit subsequently remained at high temperature (≥500°C) for a protracted period of c. 150 Myrs and record multiple phases of accessory mineral growth, dissolution and recrystallisation. This is illustrated by U-Pb monazite ages, peaking at 1780–1760 Ma, reflecting fluid driven replacement reactions as documented by apatite / allanite coronas around monazite. Cooling of the granulites, down to c. 500°C, occurred in the range 1720–1700 Ma (apatite and rutile ages). The chronology of the magmatic/metamorphic events is consistent with a collisional setting involving a micro-continental block consisting of the Iforas / In Ouzzal granulitic units sandwiched between the West African Craton and an eastern landmass which may be the Saharan metacraton. This study has major consequences for global reconstructions of the Columbia supercontinent as it demonstrates that, at c. 1.8 Ga, this microcontinent fits as a continuation of the Khondalite Belt or Trans North China Belt of the North China Crato
Processus ponctuels à deux phases partiellement observés
No full textInternational audienceIn this paper, a two-phase spatio-temporal point process (STPP) defined on a countable metric space and characterized by a conditional intensity function is introduced. In the first phase, the process is memoryless, generating completely random point patterns. In the second phase, the location and occurrence time of each event depend on the spatial configuration of previous events, thereby inducing spatio-temporal correlation. Theoretical results that characterize the distributional properties of the process are established, enabling both efficient numerical simulation and Bayesian inference. A statistical inference framework is developed, for the setting in which the STPP is observed at discrete calendar dates while the spatial locations of events are recorded, their exact occurrence times are unobserved, i.e., interval-censored. This partial observation scheme commonly arises in ecological and epidemiological applications, such as the monitoring of plant disease or insect pest spread across a spatial grid over time. The methodology is illustrated through an analysis of the spatio-temporal spread of sugarcane yellow leaf virus (SCYLV) in an initially disease-free sugarcane plot in Guadeloupe, FrenchWest Indies.Dans cet article, nous introduisons un processus ponctuel spatio-temporel (STPP) à 2 phases, défini sur un espace métrique dénombrable et caractérisé par une fonction d'intensité conditionnelle. Dans la première phase, le processus est sans mémoire et génère des configurations ponctuelles totalement aléatoires. Dans la seconde phase, l'emplacement et le moment d'occurrence de chaque événement dépendent de la configuration spatiale des événements précédents, induisant ainsi une corrélation spatio-temporelle. Des résultats théoriques caractérisant les propriétés de distribution du processus sont établis, permettant à la fois une simulation numérique efficace et une inférence bayésienne. Un cadre d'inférence statistique est développé pour le cas où le STPP est observé à des dates calendaires discrètes tandis que les emplacements spatiaux des événements sont enregistrés, mais que leurs instants d'occurrence exacts ne sont pas observés, c'est-à-dire qu'ils sont censurés par intervalle. Ce schéma d'observation partielle se rencontre couramment dans les applications écologiques et épidémiologiques, telles que la surveillance des maladies des plantes ou de la propagation des insectes nuisibles sur une grille spatiale au fil du temps. La méthodologie est illustrée par une analyse de la propagation spatio-temporelle du virus de la jaunisse de la canne à sucre (SCYLV) dans une parcelle de canne à sucre initialement saine en Guadeloupe, dans les Antilles françaises
(Un)Making mess at Europe's data borders: Order, control, critique
No full textInternational audienceCritical border and migration studies have shown that border practices are often messy, ambiguous, improvised and uncertain, while datafication has amplified messiness and its effects on migrants. Describing ‘mess’ at borders has been a critical intervention against the myth of order, homogeneity, predictability, clarity or efficiency. Yet, ‘mess’ can also open spaces for agency and resisting data borders. What do these ambiguities mean for the critical potential of diagnosing mess? Drawing on research we have conducted in border zones in France, Italy, Germany and Spain, we show that the critical potential of mess cannot be gauged through the binary of mess/order. We argue that we need to introduce a third term – control – to understand the critical potential of mess. To do so, we first unpack three dimensions of ‘mess’ – spatial, temporal and material – to situate it in relation to diagnoses of failure, friction, improvisation and non-knowledge in bordering practices. Second, we raise questions about the limits that the co-constitution of mess/order entails for critical research on data borders. Third, we show how control transforms the binary of mess/order into a question about ‘kinds of mess’
Resource landscape shapes the composition and stability of the human vaginal microbiota
No full textInternational audienceThe vaginal microbiota is associated with the health of women and newborns alike. Despite its comparatively simple composition relative to other human microbiota systems, the mechanisms underpinning the dynamics and stability of vaginal microbial communities remain elusive. A crucial, yet so far underexplored, aspect of vaginal microbiota ecology is the role played by nutritional resources. Glycogen and its derivatives, produced by vaginal epithelia, are accessible to all bacterial constituents of the microbiota. Concurrently, free sialic acid and fucose offer supplementary nutritional resources to bacterial strains capable of cleaving them from glycans, which are structurally integral to mucus. Notably, bacteria adept at sialic acid exploitation are often correlated with adverse clinical outcomes and are frequently implicated in bacterial vaginosis (BV). In this study, we introduce a novel mathematical model tailored to human vaginal microbiota dynamics to explore the interactions between bacteria and their respective nutritional landscape. Our resource-based model examines the impact of the relative availability of glycogen derivatives (accessible to all bacterial species) and sialic acid (exclusive to some BV-associated bacteria) on the composition of the vaginal microbiota. Our findings elucidate that the success of BV-associated bacteria is intricately linked to their exclusive access to specific nutritional resources. This private access fortifies communities dominated by BV-associated bacteria, rendering them resilient to compositional transitions. We empirically corroborate our model prediction with longitudinal clinical data on microbiota composition and previously unpublished metabolomic profiles obtained from a North American cohort. The insights gleaned from this study shed light on potential pathways for BV prevention and treatment
An Integrative Approach With Cytogenetic and Molecular Data of the Leaf‐Cutting Ant Acromyrmex hystrix (Latreille, 1802) Highlights a Notably Derived Karyotype in the Genus
No full textInternational audienceFungus‐growing ants are a peculiar ant group that cultivates fungi for food. Within this group, the so‐called leaf‐cutting ants ( Atta Fabricius, 1804, Acromyrmex Mayr, 1865 and Amoimyrmex Cristiano et al. 2020) hold significant ecological and economic importance. Previous studies have highlighted conserved chromosome numbers with 2 n = 22 in Atta and Amoimyrmex , and 2 n = 38 in Acromyrmex , with the single exception of the social parasite Acromyrmex ameliae De Souza et al. 2007, with 2 n = 36, as a result of Robertsonian fusion. Although Acromyrmex hystrix (Latreille, 1802) is the type species of Acromyrmex , it is one of the least‐known species of this genus. In this study, we described its karyotype and inferred the phylogenetic relationships within Acromyrmex . A distinct chromosome number was detected for the species, with 2 n = 28 chromosomes and a karyotypic formula of 10m + 16sm + 2st. Our phylogenetic reconstruction revealed Ac. hystrix constituted a separate clade within Acromyrmex . This karyotype is derived within Acromyrmex , with a chromosome number reduction from 2 n = 38 to 28. Cytogenetic and molecular data revealed the evolutionary divergence of Ac. hystrix within Acromyrmex . Although leaf‐cutting ants are among the most studied ants, many gaps remain in our understanding of these insects. The inclusion of additional species in the molecular phylogeny, coupled with chromosomal information, could provide insights into the evolution of Acromyrmex
Une histoire des sports olympiques d'hiver
No full textInternational audienceConsidérés aujourd’hui comme l’un des évènements sportifs internationaux majeurs, les Jeux olympiques d’hiver ont connu une émergence contrastée et un développement contesté, depuis la question de l’existence même des JO d’hiver, à laquelle les pays nordiques s’opposèrent longtemps, jusqu’à celle de la présence de nouveaux sports, qui frappe régulièrement à la porte des Jeux. Dépendants des contraintes spatiales pour glisser ou patiner, les Jeux olympiques d’hiver vont être confrontés à une série de défis qui vont fréquemment remettre en question leur existence comme leur sens. L’internationalisation réduite des pays concernés, la faiblesse du nombre de pratiquants comme le périmètre réduit de ces sports, le changement climatique ou la concurrence de nouvelles activités sont quelques-uns des défis qui se sont présentés aux JO d’hiver, amenant à des transformations significatives. Réunissant les meilleurs spécialistes internationaux de chaque sport, l’ouvrage témoigne d'une volonté d’offrir au lecteur français un panorama, discipline par discipline, qui dépasse la simple compétition pour questionner le contexte politique, économique, culturel et social. Il conduit à étudier le processus d’ olympisation des sports concernés et les conséquences quant à leurs formats, leurs modalités de pratiques, comme leur reconnaissance. Cet ouvrage propose en définitive un siècle d'histoire des sports olympiques d’hiver au prisme de l’histoire du monde, à travers 15 articles sur chacune des disciplines au programme de Milan-Cortina 2026
Mathématiques et contextes : regards croisés
No full textInternational audienceIn France, mathematics occupies a central place in the education system, and French excellence in fundamental mathematical research is internationally recognized. However, the performance of French students in this discipline remains below international standards, particularly in the overseas territories. These gaps can be explained by structural and ideological obstacles specific to overseas France, inherited from the colonial situation and perpetuated in the postcolonial context, but also by the persistence of an "indifferent to differences" approach within the republican educational system. It is precisely these extracurricular dynamics that most often generate difficulties in the transmission of mathematical knowledge and that continue to have a significant impact on the quality of learning for students in the overseas territories, associating this discipline with a world of values, a horizon of ambitions, and a great deal of prejudice. This collaborative work aims to present the most current research in the field of mathematics education: research inspired by a contextual approach, studying educational practices and systems, as well as the perceptions and experiences of teachers and learners in France's overseas territories, in order to describe and analyze the complex relationships between contexts and teaching methodologies and to identify avenues for action, epistemological reflections, and methodological proposals. With a preface by Antoine Delcroix. Contributors: Manuel Garçon, Mickaëlle Ramassamy, Cyrille Guieu, Maurizio Alì, Céline Guilmois, Eléda Robo, Frédéric Anciaux, Laurence Cabanel, Line Numa-Bocage, Mélissa Arneton, Sandrine Méjias, Rachel Pheulpin.En France, les mathématiques occupent une place centrale dans le système éducatif et l’excellence française dans la recherche fondamentale en mathématique est reconnue au niveau international. Cependant, les résultats des élèves français dans cette discipline restent en deçà des standards internationaux, notamment dans de les territoires ultramarins. Ces écarts peuvent être expliqués par des obstacles structurels et idéologiques propres à la France d’Outre-mer, hérités de la situation coloniale et perpétués dans le contexte postcolonial, mais aussi par la persistance d’une approche « indifférente aux différences » dans l’offre éducative républicaine. Ce sont justement ces dynamiques extra-scolaires qui génèrent le plus souvent des difficultés dans le processus de transmission du savoir mathématique et qui continuent d’exercer un impact certain sur la qualité des apprentissages des élèves et étudiants de l’Outre-mer, en associant cette discipline à un univers de valeurs, un horizon d’ambitions et beaucoup de préjugés.Cet ouvrage collectif a l’ambition de présenter les travaux de recherche les plus actuels dans le domaine de la didactique des mathématiques : des travaux qui, inspirés par une approche contextuelle, étudient les pratiques et les dispositifs éducatifs mais aussi les représentations et le vécu des enseignants et des apprenants ultramarins afin de décrire et analyser les liens très complexes qu’entretiennent les contextes et les didactiques pour dégager des pistes d’actions, des réflexions épistémologiques et des propositions méthodologiques.Avec une préface d'Antoine Delcroix.Contributeurs: Manuel Garçon , Mickaëlle Ramassamy , Cyrille Guieu , Maurizio Alì , Céline Guilmois , Eléda Robo , Frédéric Anciaux , Laurence Cabanel , Line Numa-Bocage , Mélissa Arneton , Sandrine Méjias , Rachel Pheulpin