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Building a coherent chronological framework for ice cores, marine sediment cores and speleothems over the last 640 000 years
No full textInternational audienceQuantifying the phase relationships between changes in orbital forcing and internal climate responses, such as changes in atmospheric greenhouse gas concentrations and global sea level, during past glacial Terminations is challenging. This is partly due to the lack of precise dating for climate archives beyond the range of radiocarbon dating. It is also challenging to build a coherent temporal framework that allows the sequence of events to be determined across multiple paleorecords from different types of archives. In this study, we present a methodology for establishing a coherent chronology covering the last 640 000 years, by integrating a selection of ice cores, sediment cores, and speleothems using the Bayesian dating model Paleochrono-1.1. Various sensitivity tests were conducted to explore the impact of climate alignment assumptions, the associated chronological uncertainties, and the assumptions related to the sedimentation scenario of the archives. These tests allow us to quantify uncertainty windows for the temporal offset between changes in atmospheric CO 2 and in δ 18 O benthic at the onset of six of the last seven glacial Terminations. With this approach, we provide uncertainties on this phasing from a minimum of 0.6 ka for Termination I, and up to 3.4 ka for Termination VI, compared with more than 4 ka of uncertainty previously
Assessment of ex vivo antimalarial drug efficacy in African Plasmodium falciparum parasite isolates, 2016–2023: a genotype–phenotype association study
No full textInternational audienceBackground: Given the altered responses to both artemisinins and lumefantrine in Eastern Africa, monitoring antimalarial drug resistance in all African countries is paramount.Methods: We measured the susceptibility to six antimalarials using ex vivo growth inhibition assays (IC50) for a total of 805 Plasmodium falciparum isolates obtained from travellers returning to France (2016-2023), mainly from West and Central Africa. Isolates were sequenced using molecular inversion probes (MIPs) targeting forty-three genes across the parasite genome, of which nineteen are drug resistance genes.Findings: Ex vivo susceptibility of all assessed antimalarial compounds was consistent with their potent activity. The median IC50 values for the six drugs were 1.1 nM [IQR: 0.8-1.7] for DHA, 16.7 nM [9.9-27.4] for LMF, 29.5 nM [19.1-45.5] for MFQ, 23.4 nM [17.1-39.0] for MDAQ, 26.7 nM [18.0-41.2] for CQ, and 18.5 nM [15.1-24.3] for PPQ. Only four isolates carried a validated pfkelch13 mutation. Multiple mutations in pfcrt and one in pfmdr1 (Asn86Tyr) were significantly associated with altered susceptibility to multiple drugs, and their frequencies decreased over time. Pfcrt and pfmdr1 mutations altered susceptibility to lumefantrine and mefloquine in an additive manner, with the wild-type haplotype (pfcrt K76-pfmdr1 N86) exhibiting the lowest susceptibility.Interpretation: Our study on P. falciparum isolates from West and Central Africa indicates a low frequency of molecular markers associated with artemisinin resistance and a modest but significant decrease (1.6-2.3X) in the frequency of multidrug resistance markers. These genotypic changes likely mark parasite adaptation to sustained drug pressure and call for intensifying the monitoring of antimalarial drug resistance in Africa
Phase transitions and chemical segregation in Ge-rich GST based phase change memory cells
No full textInternational audienceIn this work, a detailed chemical and crystallographic analysis of basic logic and a few selected intermediate RESET states of Ge-rich Ge-Sb-Te-based (GST) phase-change memories (PCM) is presented, with a particular focus on the understanding of the microscopic mechanisms underlying their electrical characteristics. We demonstrate that Ge-rich GST-based PCM store the information not only in their crystalline or amorphous phase, as in conventional PCM based on Ge 2 Sb 2 Te 5 , but also in their active material stoichiometries: the amorphous phase is characterized by a Ge-rich composition, guaranteeing automotive-compliant retention, while the crystalline phase shows a composite structure, made of cubic GST and rhombohedral Sb grains, the latter mostly found close to the heater. This switching of composition explains the high temperature retention capability of Ge-rich GST cells and their preserved good functionality in the high conductive state. Analysis of intermediate RESET states unveils the microscopic details of these physical and chemical transitions, giving insights on the physical origin of the electrical characteristics of Ge-rich GST-based PCM
Mid- to Late-Holocene branched GDGT-based air temperatures from a crater lake in Cameroon (Central Africa)
No full textInternational audienceAfrican low-latitude regions tend to be underrepresented in global continental temperature reconstructions, limiting both our understanding and the reliability of predictions of past and future changes in temperature and precipitation in those parts of the world. The lack of continuous sedimentary archives and quantitative temperature proxies further complicates this issue, especially outside Eastern Africa. Here, we use data collected in Cameroon lakes to assess branched glycerol dialkyl glycerol tetraether (brGDGT)-based temperature proxies and examine potential confounding variables impacting temperature reconstructions. By analyzing GDGT distributions in soil watershed, water column, and surface sediment samples from a total of 11 Cameroon lakes, we could verify that the degree of methylation of brGDGTs (through the MBT ' 5Me) can serve as a reliable indicator for reconstructing mean annual air temperatures. Additionally, we could confirm that surface water conductivity represents a controlling factor for the brGDGT assemblage in surface sediments of crater lakes. Moreover, we provide the first reconstruction of Mid-to Late-Holocene GDGT-based air temperatures for a crater lake in Cameroon (Central Africa), revealing a temperature decrease of 2.5 degrees C over the last 7000 years, which agrees with recently published records for East Africa but exceeds current model predictions. These discrepancies highlight the need for additional studies to focus on this geographically underrepresented area
A coral microatoll record of sea-level rise, interseismic deformation, and El Niño in La Union, Philippines since 1906 CE
No full textInternational audienceRelative sea level (RSL) along western Luzon is influenced by climate change, tectonic deformation, and the El Nino-Southern Oscillation. Long, high-resolution records of past changes in sea level and land level are crucial to distinguish these contributions for forecasting future RSL or identifying tectonic hazards. Coral microatolls are invaluable proxies for reconstructing RSL, but their interpretation relies on understanding how short-and longterm changes are recorded in the coral skeleton. We analyzed growth bands from 1906 to 2018 CE of a Porites microatoll from Balaoan, La Union, Philippines, using X-rays of vertical cross sections. The microatoll's surface morphology, annual banding, and growth history reveal RSL rise during its lifetime punctuated by 17 diedowns. Coral diedowns generally coincide with low water near the site, often resulting from El Nino events. Excluding eroded sections, 10 of the 11 strongest El Ninos since 1918 produced a diedown. Similarly, excluding a diedown caused by the coral tilting, 10 of the 12 preserved diedowns exceeding 3 mm in amplitude occurred during strong El Ninos. Between 1948 and 2018 CE, RSL rose at 1.3 +/- 1.8 mm/yr (2 sigma). Comparing sea-level rates from satellite altimetry and RSL from the coral, we estimate vertical land motion at-0.1 +/- 12.1 mm/yr between 1995 and 2018 CE. The indicative meaning at Balaoan, defined as the relationship between local water levels and the highest level of growth of a coral microatoll before its most recent diedown, is estimated at 31.5 +/- 10.0 cm (2 sigma) above lowest astronomical tide
Influence of local topographic structures on the atmospheric mechanisms related to the Andean-Amazon rainiest zone
No full textInternational audienceThe Andes-Amazon transition region features critically important ecological services on the local, regional and global scales. This region is among the rainiest zones in the world, with rainfall rates of up to 7000 mm/year. However, the physical mechanisms leading to the existence of these "precipitation hotspots" remain poorly known. Here, we attempt to disentangle the controlling atmospheric mechanisms exerted by local topographic structures that started to uplift about 5-10 million years ago in response to the Nazca Ridge subduction, in the vicinity of the Quincemil hotspot, the most intense of them. We first use the Weather Research and Forecasting model to conduct sensitivity tests to planetary boundary layer parameterizations at 5 km horizontal grid spacing during the austral summer of 2012-13. After finding the most suitable configuration in terms of the diurnal cycle of rainfall intensity and extent, we further perform topographic sensitivity tests by reducing the Fitzcarrald Arch lowlands and, on top of it, by removing the Camisea mountain. The Fitzcarrald Arch deflects moisture flux towards Quincemil, while the Camisea mountain induces local vortical circulations that increase moisture transport, convergence and rainfall over Quincemil, ultimately controlling its location and intensity by up to 40 %. When reducing the height of the Andes in half, we find that it sustains the development of precipitation hotspots, accounting for up to 60 % of rainfall, by providing a mechanical forcing to increase regional-scale moisture fluxes. Such mechanisms dominate during nighttime, when rainfall peaks in the region, and might explain the existence of the rainiest zone in the Andes-Amazon transition
Climat urbain et impact sanitaire de la chaleur à Échirolles et Grenoble: Rapport final du projet CASSANDRE, ADEME
No full textThe CASSANDRE project aims to characterize heat extremes at fine spatial and temporal scales and to assess their health impacts, particularly among vulnerable populations in the Grenoble metropolitan area. Conducted in close partnership with the municipalities of Grenoble and Échirolles, the project addresses their adaptation needs in the face of climate change and adopts an interdisciplinary approach combining climatology, epidemiology, data science, and geo-governance.The first objective focused on characterizing the urban heat island (UHI) through an adapted and refined Local Climate Zone (LCZ) typology, improving meteorological and climatological knowledge of heat extremes associated with specific weathertypes and integrating biometeorological indicators. The dense intra-urban network of meteorological sensors deployed since 2019 was supplemented by additional climatic datasets (Météo-France, ERA5). The second objective evaluated the relevance of available health indicators and analyzed socio-spatial vulnerability to heat, particularly among elderly populations and very young children. The latter was investigated using a locally developed and unique neonatal database. The third objective, carried out in close collaboration with local authorities, produced decision-support, training, and communication toolsaimed at protecting populations and promoting adaptation to urban thermal stress.The CASSANDRE project has enhanced the understanding of Grenoble’s urban climate and its heat islands. The intensity of the Urban Heat Island (UHI) ranges from +1 to +4.7 °C, depending on urban morphology, season and vegetation cover.Heatwaves, increasingly frequent and occurring earlier in the season, intensify tropical nights. The local climate is likely shifting toward a humid subtropical type with hot summers (Cfb → Cfa). Cross-analysis of climatic and social data shows thatheat exposure and social disadvantage do not always overlap: Dense, highly mineralized areas are warmer but are home to populations with greater adaptability, while more vegetated yet socially deprived neighborhoods remain vulnerable. Prenatalexposure to heat during mid-pregnancy is associated with reduced birth weight. These findings inform local adaptation strategies focused on urban greening, soil de-impermeabilization, and coordinated heat crisis managementLe projet CASSANDRE vise à caractériser les extrêmes de chaleur à des échelles spatio-temporelles fines et à évaluer leurs impacts sanitaires, en particulier sur les populations vulnérables du territoire grenoblois. Conduit en partenariat étroit avec les collectivités de Grenoble et Échirolles, il répond à leurs besoins d’adaptation face au réchauffement climatique et mobilise une approche interdisciplinaire croisant climatologie, épidémiologie, sciences des données et géogouvernance.Dans un premier temps, le projet a permis de caractériser l’îlot de chaleur urbain (ICU) à partir d’une typologie urbaine des Zones Climatiques Locales (LCZ pour Local Climate Zone) adaptée et affinée. Il a également contribué à améliorer les connaissances météo-climatiques sur les extrêmes de chaleur, en lien avec les types de temps et les indicateurs biométéorologiques. Le dense réseau intra-urbain de capteurs météorologiques déployé depuis 2019 a été complété par d’autres sources de données (Météo-France, ERA5). Ensuite, les travaux ont permis d’évaluer la pertinence des indicateurs sanitaires disponibles et d’analyser la vulnérabilité socio-spatiale à la chaleur, en particulier celle des populations âgées et de la toute petite enfance, étudiée à partir d’une base de données néonatales originale développée localement. Enfin, le projet, conduit en lien étroit avec les collectivités, a abouti à la production d’outils d’aide à la décision, de formation et de communication pour la protection des populations dans une perspective d’adaptation au stress thermique urbain.Le projet CASSANDRE a amélioré la compréhension du climat urbain grenoblois et de ses îlots de chaleur. L’intensité de l’ICU varie de +1 à +4,7°C selon la morphologie urbaine, la saison et la végétation. Les vagues de chaleur, plus longues et précoces, amplifient les nuits tropicales. Le climat local risque d’évoluer vers un type subtropical humide à été chaud (Cfb → Cfa). Le croisement des données révèle que chaleur et défaveur sociale ne coïncident pas toujours : les zones denses et minérales sont plus chaudes mais concernent des populations faisant preuve d’une meilleure capacité d’adaptation, tandis que les quartiers défavorisés, plus verts, sont socialement plus vulnérables. L’exposition prénatale à la chaleur en milieu de grossesse réduit le poids à la naissance. Ces résultats doivent contribuer à guider les politiques locales d’adaptation et plaident en faveur d’actions de végétalisation, de dés-imperméabilisation et d’une gestion coordonnée des crises
Tailoring the dynamics of Al metal–organic framework nanocrystals: from rigid nanoparticles to flexible nanowires
No full textInternational audienceHere we describe the synthesis of a series of 1D anisotropic Al metal–organic framework (i.e., DUT-5(Al)) nanostructures differing in their crystal dimensions and aspect ratios. By using graphene oxide (GO) nanoscrolls as structure-directing agents, we synthesized monodisperse DUT-5(Al) nanowires (NWs) that are >6 μm in length. Shorter DUT-5(Al) nanorods (∼50 nm) and polydisperse samples with broader size distributions were prepared without GO. Remarkably, these nanostructures also differed by their dynamic properties upon the adsorption of guest molecules. While DUT-5(Al) nanorods exhibited a rigid large pore (lp) phase, it was revealed that DUT-5(Al) NWs could present a gating behavior characterized by a structural transition from a disordered narrow pore (np) phase to the lp phase upon adsorption. The structure of DUT-5(Al) NWs and their guest-responsive structural flexibility were fully characterized by coupling high-resolution TEM, 3D electron diffraction, high-resolution synchrotron PXRD and PDF, adsorption isotherms, and in situ PXRD. To the best of our knowledge, this study delivers an unprecedented design of flexible DUT-5(Al) NWs, revising the conventional view of this MOF as a rigid porous material. Moreover, this demonstrates that tuning the aspect ratio of MOF particles can influence their structural flexibility
Les Styloleptus du « groupe posticalis » des Petites Antilles et de Trinidad (Coleoptera Cerambycidae)
No full textInternational audienceStyloleptus of the "posticalis group" from the Lesser Antilles and Trinidad (Coleoptera Cerambycidae). Using recent material and specimens from the National museum of natural history (Paris), we have re-examined the taxonomic status of Styloleptus populations in the Lesser Antilles: Styloleptus inermis (F., 1801) and S. posticalis (Gahan, 1895) sensu lato. Morphology and DNA barcoding (CO1) demonstrate that Styloleptus bonfilsi Villiers, 1980 is a valid species (status revalidated), which is endemic to the hygrophilous forests of Guadeloupe and Dominica. Styloleptus posticalis is reported for the first time from Trinidad; it is a widespread and fairly variable species, whose DNA barcode diverges slightly between islands. DNA barcodes are provided for the different taxa and islands. Illustrations and a table of distinctive characters are also provided.À partir de matériel récent et des types présents au Muséum national d'Histoire naturelle (Paris), nous avons ré-examiné le statut taxonomique des populations de Styloleptus des Petites Antilles : Styloleptus inermis (F., 1801) et S. posticalis (Gahan, 1895) sensu lato. La morphologie et le code-barres ADN (CO1) démontrent que Styloleptus bonfilsi Villiers, 1980 est une espèce valide (statut revalidé), endémique des forêts hygrophiles de Guadeloupe et Dominique. Styloleptus posticalis est signalé pour la première fois de Trinidad ; c'est une espèce répandue et assez variable, dont le code-barres ADN diverge légèrement en fonction des îles. Des codes-barres ADN sont rendus disponibles pour les différents taxons et îles. Des illustrations et un tableau des caractères distinctifs sont fournis
Multicenter performance evaluation of the "quanty TOXO (RH region)" kit (Clonit) for molecular diagnosis of toxoplasmosis
No full textInternational audienceThe diagnosis of congenital toxoplasmosis or disseminated toxoplasmosis in immunocompromised patients nowadays relies on molecular tools, in particular real-time PCR. There are many reagents on the market, and their evaluation by independent experts provides valuable information to medical biologists who are looking for a high-performance kit among the different references. Under the aegis of the French National Reference Center for Toxoplasmosis, we report here a multicenter evaluation of the analytical and clinical performances of the "quanty TOXO (RH region)" PCR assay manufactured by Clonit. The kit showed good analytical performance, as indicated by the results of serial dilution tests and external quality control samples. PCR efficiencies varied from 95% to 105%; linearity zone extended over four log units (R² >0.99), and limit of detection varied from <1 parasite/mL to between 1 and 5 parasites/mL, i.e., from <0.08 parasite/PCR to between 0.2 and 1 parasite/PCR, depending on the center. Based on 141 cryopreserved DNAs from a large range of clinical specimens, we determined a clinical sensitivity of 94.7% (71/75; 95% confidence interval [CI]: 87.1%-97.9%) and a clinical specificity of 100% (66/66; 95% CI: 94.5%-100%). Four false negative results were detected despite amplification carried out in duplicate. Overall, the "quanty TOXO (RH region)" PCR assay demonstrated satisfactory analytical and clinical performances for the diagnosis of toxoplasmosis, even using extraction and amplification techniques or biological matrices not validated by the manufacturer.IMPORTANCEDue to its speed and accuracy, PCR is now the gold standard for diagnosing congenital and disseminated toxoplasmosis. High-performance molecular testing is essential, especially for immunocompromised patients and congenital infections, to initiate early treatment. This diagnostic approach increasingly relies on commercial assays. However, commercially available kits do not guarantee performance. In this study, conducted by the French National Reference Center for Toxoplasmosis, we performed an independent multicenter evaluation of the "quanty TOXO (RH region)" PCR assay manufactured by Clonit. Our results showed that this kit delivered satisfactory results for routine diagnostic use. However, among the 141 clinical samples tested, four false negative results were noted, corresponding to specimens with low parasitic load