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Matching collapse and expansion across Matter Trapping surfaces in inhomogeneous CDM models
No full textInternational audienceIn the present work we examine the MTS, for the restriction to spherical dust plus , proving that it actually is a characteristic surface of the Cauchy problem (generated by its characteristic curves), which opens the possibility for infinite solutions. This translate as the MTS being a boundary between arbitrarily independent solutions, reminiscent of the Birkhoff theorem effects. This property is illustrated with combinations of 3 examples containing MTSs and (CDM, Schwarzschild-de Sitter, Lemaître-Tolman-Bondi-de Sitter: LTBdS -- i.e. the inhomogeneous, spherically symmetric CDM). The LTBdS model presents a static, stable MTS for the first time
Why methane surged in the atmosphere during the early 2020s
No full textInternational audienceThe atmospheric methane (CH 4 ) growth rate surged after 2019, peaking at 16.2 parts per billion per year (ppb year −1 ) in 2020 before declining to 8.6 ppb year −1 in 2023. Using multiple atmospheric inversions constrained by observation- and model-based prescribed hydroxyl radical (OH) fields and CH 4 atmospheric data, we show that a drop of OH radicals in 2020–2021, followed by recovery in 2022–2023, accounted for 83% of year-on-year variations in the CH 4 growth rate, the rest being explained by wetland and inland water emissions, which increased between 2019 and 2020–2022 [+8.6 ± 2.6 teragrams of CH 4 per year (TgCH 4 year −1 )] and then decreased between 2022 and 2023 (−9.9 ± 3.3 TgCH 4 year −1 ). Most emission changes from 2019 to 2023 occurred in northern tropical wetlands in Africa and Asia, whereas South American wetlands emissions declined and Arctic emissions increased after 2019
Long-term growth and persistence of granitic inselbergs in a semi-arid cratonic landscape
No full textInternational audienceGranitic inselbergs are enduring landforms that punctuate planation surfaces in tectonically stable settings, yet the mechanisms and timescales of their persistence remain debated. Here, we present a multi-nuclide cosmogenic dataset ( 10Be, 26Al, 21Ne) from bedrock, fluvial sediments, and planation surfaces in the semi-arid Central Ceará Domain, northeastern Brazil, to quantify denudation rates and reconstruct the long-term dynamics of residual relief formation. This triple-nuclide approach enables independent validation of denudation contrasts and long-term exposure histories, providing quantitative constraints on inselberg evolution that a single-nuclide approach could not resolve. Bedrock denudation rates (1-4 m Myr^ -1 ) are systematically lower than basin-wide rates (8-14 m Myr^ -1 ), revealing a regional pattern of vertical differential denudation. When combined with summit elevations and surface exposure ages of up to 5 Myr, these contrasts suggest that cumulative relief growth has been operating over timescales of tens of millions of years (1-57 Myr). Morphological and structural observations further indicate localized mass wasting and heterogeneous erosion styles, modulated by rock fabric and joint density. Cosmogenic nuclide inventories in detrital sediments reveal partial reworking from older sediment stocks, including surface pebbles with exposure ages up to 5 Myr, which record multi-stage of burial and re-exposure histories and reflect episodic remobilization in low-connectivity, semi-arid catchments. Rather than static relicts of ancient surfaces, inselbergs in this cratonic setting emerge as dynamic landforms actively sustained by slow but persistent differential denudation. These results provide new constraints on long-term cratonic landscape evolution and underscore the interplay between lithological resistance, structural inheritance, and sediment transfer processes in sustaining topographic relief. They also call for a critical reassessment of classical inselberg models, suggesting that hybrid mechanisms, rather than single-process paradigms, more accurately capture the complexity of residual landform development in cratonic interiors
Rare interspecific hybridisation between sympatric African four-striped mice, and indications of fine-scale intraspecific spatial structure related to social factors
No full textInternational audienceSpatial and social population structures can influence intra- and interspecific genetic processes. We investigated the spatial and social genetic structure of two sister species and evaluated whether there was evidence of hybridisation between them at a microgeographic scale, in syntopy. Our study models were Rhabdomys bechuanae (Rbech) and Rhabdomys dilectus dilectus (Rdil). We generated population genetic data using microsatellite markers and cross-referenced some of these results with published behavioural data from a prior study, reanalysed here. We compared genetic diversity and gene flow both in sympatry and allopatry, we tested for hybridisation between the sister species in sympatry and assessed the relationship between kinship and fine-scale spatial and social organisation. Genetic diversity was high within all populations of the two species. Population genetic substructure was more pronounced in Rbech than in Rdil, consistent with stronger group cohesion reported for Rbech. STRUCTURE and NEWHYBRIDS analyses suggested that sympatric individuals, 5% in Rbech, and 2% in Rdil, might have hybrid ancestry. Our results indicate social fences may limit gene flow within and between species. Further, limited hybridisation suggests that, despite syntopy, only rare events of hybridisation may occur, possibly at phases of density troughs and/or that F1 hybrids have a relatively low fitness
Experimental evolution of Plasmodium yoelii in single and helminth-coinfected mice.
No full textInternational audienceBackground Coinfection has the potential to affect key traits describing the infection dynamics, the severity of the disease and in fine parasite fitness. However, despite its pervasiveness, experimental work investigating how parasites adapt to the conditions provided by a coinfected host is mostly missing. Methods We adopted an experimental evolution approach to investigate if coinfection with the nematode Heligmosomoides polygyrus (Hp) affected the infection dynamics and virulence of the murine malaria parasite Plasmodium yoelii (Py). To this purpose, lines of Py were passaged either in single infected hosts (SI-lines) or in hosts that had been previously infected with Hp (COI-lines). After five and seven passages, the infection dynamics and virulence of evolved lines were compared to the ancestral Py population during single infection trials. COI-lines were also used to infect hosts during coinfection trials, allowing us to compare within-host Py replication when the environment during the evaluation trials matched the environment experienced during the passages and when the two environments were mismatched. Results We found that serial passages increased parasitemia and Py virulence, due to the competitive advantage of genotypes with the fastest replication rate, but SI-lines and COI-lines had relatively similar replication rate and virulence. Hosts infected with evolved lines of Py were also less tolerant (steeper slope between red blood cell counts and parasitemia) but there was no difference between SI-lines and COI-lines. Finally, we found that when COI-lines were used during single infection trials (mismatched environments), they had a slower early replication rate compared to matched-environment trials. Conclusions We did not find strong evidence supporting a divergence between the virulence of SI-lines and COI-lines, possibly due to the cost of virulence paid by COI-lines. However, Py rapidly adapted to the environmental conditions provided by single infected or coinfected hosts, as shown by the slower replication rate found in mismatched-environment trials
Chemin d’impact du LLUNAM : cadre de référence pour investiguer, concevoir, expérimenter et évaluer ensemble des Solutions fondées sur la Nature sur l’aire urbaine de Montpellier
No full textRapport d’ateliers multi-acteur∙ricesCe rapport présente le chemin d’impact du living lab LLUNAM, dédié au déploiement des Solutions fondées sur la Nature sur l’aire urbaine de Montpellier. Ce chemin d’impact a été co-construit en mobilisant la démarche de planification stratégique ASIRPA lors d’ateliers multi-acteur∙rices. Cette démarche vise à expliciter collectivement les impacts souhaités au long terme, les changements nécessaires pour y contribuer et les stratégies transformatrices à mettre en œuvre pour les générer.Le document articule un diagnostic partagé des enjeux socio-environnementaux du territoire, une vision à l'horizon 2050 d’une métropole fondée sur la nature, ainsi que l’identification de voies de changement structurantes. Celles-ci intègrent des dimensions de gouvernance, de production et partage de connaissances, d’(inter)médiation, de participation citoyenne, de cadre réglementaire et de transformation des pratiques professionnelles.Conçu comme un outil opérationnel et stratégique, ce rapport a vocation à servir de guide de pilotage pour investiguer, concevoir, expérimenter et évaluer, avec les acteur∙rices du territoire, des Solutions fondées sur la Nature. Il peut ainsi être mobilisé comme cadre de référence par les porteur∙euses de projets qui souhaitent situer leurs initiatives dans le champ d’action du living lab LLUNAM
Self-Portrait of the Focusing Process in Speckle: II. Gouy Phase Shift for Defocus Correction and Pixel Depth Reassignment
No full textThis is the second article in a series of three dealing with the exploitation of speckle for aberration correction and reverberation compensation in reflection imaging. When probing heterogeneous media with waves, we have to cope with multi-scale fluctuations of the wave velocity. On the one hand, short-scale heterogeneities induce back-scattered echoes whose random interference generate a speckle pattern on the beamformed image. On the other hand, large-scale fluctuations of the wave-velocity can distort the focused wave-fronts, resulting in aberrations on the same image. In this paper, we show how the self-portrait of the wave evolves as a function of the speed-of-sound model. Strikingly, a Gouy phase shift is observed when the speed-of-sound model is optimal. This particularly sensitive feature enables: (i) an optimization of the speed-of-sound model for each pixel of the image; (ii) a local and fine compensation of defocus across the field-of-view, thereby compensating for most aberrations in the image. Experiment in a tissue-mimicking phantom and numerical simulations are first presented to validate our method. It is then applied to in-vivo liver data of a difficult-to-image patient. The speed-of-sound optimization allows an axial compensation of aberrations and a depth-reassignment of each singly-scattered echo to the actual position of the associated scatterer. As distance measurement is often critical for diagnosis, such a wave speed optimization can be crucial for ultrasound but also for any other imaging methods based on the principle of echo-location
ACTB deletions or single-nucleotide loss-of-function variants: expansion and further delineation of the phenotype and review of the literature
No full textInternational audienceBackground Pathogenic gain-of-function or dominant-negative effect missense variations in ACTB are associated with a neurodevelopmental disorder characterised by intellectual disability (ID), seizures, sensorineural hearing loss, cerebral, renal and ocular abnormalities and dysmorphic features (Baraitser-Winter cerebrofrontofacial syndrome). ACTB encodes beta-actin, a highly conserved protein involved in cell motility, structure and integrity. Deletions including ACTB, and, more rarely, single-nucleotide loss-of-function variants in ACTB have been described in patients with a distinct phenotype including developmental delay, ID, microcephaly, growth restriction, cardiac and renal abnormalities and dysmorphic features. Methods We collected 14 individuals and 1 fetus carrying a heterozygous deletion including ACTB , and 4 individuals with a heterozygous truncating variant. Genotypic and phenotypic data were analysed. Furthermore, a comprehensive review of all cases reported to date was also undertaken. Results Twelve out of 17 individuals presented with ID, and 3 out of 17 with learning disabilities. Speech delay and behavioural abnormalities were observed in 15 out of 17 and 12 out of 17 individuals, respectively, motor delay in 9 out of 17 and growth restriction in 9 out of 18. Most of the individuals (13/18) had recognisable dysmorphic features. 11 anomalies were de novo, except for 1 deletion inherited from the mother. The size of the deletion varied from 125 kb to 1.6 Mb and could result from a fork stalling and template switching. Conclusion This study allowed us to better characterise the phenotype associated with the haploinsufficiency of ACTB, underlying the high prevalence of neurodevelopmental disorders (ID, speech and motor delay, behavioural abnormalities) and growth restriction in this recognisable syndrome
La Planète Revisitée des îles de GuadeloupeProgramme d’exploration de la faune et de la flore terrestre et marine sur les îles des Saintes, Marie Galante et La DésiradeRapport intermédiaire 2025
No full textRight to stay? Long-run experimental evidence on land formalization and widows’ tenure security in Benin
No full textInternational audienceIn many parts of the world, women’s land rights remain informal, leaving widows – especially those without a male heir – at high risk of losing access to their land and homes when their husbands die. We study whether large-scale land formalization programs can improve widows’ tenure security, using data from a randomized controlled trial in rural Benin. Four years after the intervention, widows in villages with land formalization were significantly more likely to remain in their homes, with the strongest effects among those without a male heir. We identify two key mechanisms: increased community recognition of women’s land rights and greater decision-making power over land resources. These findings highlight the potential of land formalization to strengthen women’s tenure security and promote their long-term economic stability in similar settings