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Bathymetry mapping using the high resolution VENμS satellite: an easy-to-transfer estimation over Glorioso Islands
No full textInternational audienceAccurate global bathymetry mapping underpins natural hazard prediction or marine habitat management. However approximately 80% of the seafloor remains unmapped. Traditional waterborne (multi-/single-beam sonar) and airborne (lidar, spectral inversion) methods provide high precision and complementary coverage but are constrained in cost, accessibility, and temporal resolution. Spaceborne approaches, leveraging high- to very high-resolution multispectral and lidar sensors, increasingly enable shallow-water bathymetry retrieval at regional to global scales. This study investigates the potential of the VENμS mission for deriving shallow bathymetry over Glorioso Archipelago (Indian Ocean). VENμS superspectral imagery (12 bands, 4 m resolution, daily revisit) was collected in 2022 and attempted to predict ~83,000 lidar illuminations acquired in 2009. Three predictor series were investigated: surface reflectance, ln-transformed surface reflectance, and band ratios of ln-transformed surface reflectance. Nine depth ranges, from 0 to -45 m, were modeled using stepwise three-factor linear regressions, with performance assessed across calibration, validation, and test subsets. Results indicate excellent performance with ln-transformed surface reflectance achieving the highest predictive skill. The [0; -10 m] interval was optimal, with R2test reaching 0.93 using blue, green, and yellow-2 bands, even if the [0; -30 m] range was satisfactorily modelled (R2test = 0.78). VENμS-derived bathymetry maps show strong concordance with lidar to ~5 m depth, though increasing divergence suggests potential sediment redistribution over the 13-year period. These findings demonstrate that simple, transferable linear models applied to VENμS imagery can yield accurate, scalable shallow-water bathymetry, highlighting the mission’s value for cost-effective coastal mapping and supporting global seabed initiatives such as Seabed 2030
Le champ géomagnétique et la dynamique du noyau de la Terre
No full textLe champ magnétique de la Terre est un objet fascinant observé avec grand intérêt depuis plusieurs siècles, et une source d'informations unique sur la structure, l'histoire et la dynamique de notre planète. Cet article présente un panorama des observations géomagnétiques, de la théorie de la dynamique du noyau Terrestre, de la géodynamo convective, ainsi que des étapes clés franchies par les simulations numériques. Si le mystère de la géodynamo a pu susciter des débats intenses depuis le début du siècle dernier, les deux dernières décennies ont vu une accélération remarquable des progrès réalisés par la communauté scientifique, portée en particulier par l'essor rapide de la simulation numérique. Une stratégie cohérente a en effet émergé pour que cette simulation puisse rendre compte de l'extrême disparité d'échelles d'espace et de temps intervenant dans la physique du noyau. La combinaison des données géomagnétiques et des modèles dynamiques a de plus permis d'augmenter notre connaissance de la structure et des propriétés physiques internes de notre planète, et fournit aujourd'hui un outil utile de prédiction à destination des activités technologiques humaines
Extraction de valeurs minutes depuis les magnétogrammes histrorique sur papier
No full textInternational audienceIn the past, the variations of the Earth magnetic field were recorded on paper magnetograms. A manual process was needed to produce tables of hourly values, that today are included in digital databases and allow to study the evolution of the magnetic field over several decades. To enhance the exploitation of these paper data, we developed a software to extract magnetic time series with a higher sampling rate. The resolution of the paper record depends strongly on technology evolutions through the 20th century and the sensitivity on the type of mechanical-optical system used. For this study we focus on the years 1957 and 1958, the strongest solar maximum of the last century and present data from three observatories managed by French institutes: Chambon-la-forêt (CLF) in France, M'Bour (MBO) in Senegal and Bangui (BNG) in Central Africa, where La Cour magnetometers were deployed. We present data from some of the major magnetic storms
Evidence of high genetic differentiation driven by limited gene flow in a lower canopy African tropical rainforest tree species, Coula edulis Baill. (Coulaceae)
No full textEthical approval: Samples from Cameroon (Mbalmayo, Bidem) were collected with a research permit granted by MINRESI (000102/MINRESI/B00/C00/C10/C13). In Gabon, a research permit was granted by CENAREST (n◦AR0034/19/MESRSTT/CENAREST/CG/CST/ CSAR). In Liberia, authorization was granted by the FDA (ref: MD/04/2016/-2).International audienceBackgroundThe distribution of intra-speci c genetic diversity in tropical African forest tree species often reveals discontinuities in the form of genetic clusters distributed in parapatry or allopatry. To date, most population genetic studies have focused on canopy trees with potentially high gene dispersal capacities.In contrast, few studies have examined lower canopy tree species, whose more limited gene dispersal may exacerbate genetic discontinuities. In this study, we used nuclear microsatellites (SSRs) to characterize the genetic structure of populations of Coula edulis Baill., a lower canopy species commonly known as "African walnut", exploited for its edible seeds. ResultsAcross its distribution range, we detected one genetic cluster in Upper Guinea (UG) and six in Lower Guinea (LG). High levels of genetic differentiation (F ST = 0.39 to 0.59) were found between UG and LG, while differentiation within LG varied widely (F ST = 0.08 to 0.50). Genetic discontinuities associated to high differentiation and a phylogeographic signal (R ST, F ST ) suggest ancient divergence, possibly driven by population fragmentation during historical climatic uctuations, while those associated with limited differentiation may re ect more recent divergence and/or genetic homogenization effect due to ongoing gene ow. Genetic diversity within LG clusters was highly variable (H e = 0.40-0.71), with evidence of a founder or bottleneck effect observed in the southeastern Cameroon cluster, resulting in reduced diversity of a relict population. The UG population also showed low diversity (H e = 0.38), likely attributable to a historical bottleneck. Morphometric analyses of herbarium specimens revealed some differentiation between LG and UG populations, questioning the taxonomic status of the taxon. ConclusionsOur results suggest that, given the limited gene dispersal observed in C. edulis, the observed genetic discontinuities are expected to persist over extended timescales and provide baseline information for the conservation and potential domestication of the species' genetic resources.</div
A fermented functional food enriched in phytosterol and carotenoids improves lipid profile and insulin resistance and restores vitamin A status in high-fat diet-induced metabolic syndrome rats
No full textInternational audienceTackling metabolic syndrome (MetS) using functional fermented food has recently attracted much attention. A vegetable-fermented maize - and fruit-based probiotic functional food (maize 5% and fruits 30%) was previously designed, which was enriched in papaya/melon carotenoids and dispersible phytosterols to obtain a cholesterol-lowering effect. The aim of this work was to investigate the effect of this new functional food on an HFD (high-fat diet)-induced MetS rat model focusing on lipid and glucose metabolic disorders and considering vitamin A status. Male Sprague-Dawley rats (n = 36) were randomly divided into 4 groups (n = 9): a control group (C); an HFD group; and two HFD groups receiving 1.44 g per rat per day of the functional fermented food during the three months of the experiment following a preventive (HFD-P) or a curative (HFD-C) mode. The intake of the functional food decreased the adipose tissue amount by 1.5 times in preventive and curative mode groups and restored their LDL cholesterol and triglyceride levels to C level. The area of hepatic lipid droplets was reduced in both HFD-P and HFD-C groups compared with HFD group, which was associated with a reduction in inflammation and lipid oxidation. Both the HFD-P and HFD-C groups alleviated HFD-induced insulin resistance, as evidenced by the return of fasting insulin levels and the HOMA-IR index to control levels. However, only the HFD-C group improved the glucose tolerance test and skeletal muscle insulin sensitivity. Notably, alteration in vitamin A status in HFD rats was restored with HFD-C and HFD-P. Altogether, these results support the potential of this nutritional strategy to prevent MetS
Crazy : Unifying Memory and CPU Management Subsystems
No full textInternational audienceMemory management (MM) and scheduling are two core components of the operating system (OS) that are traditionally studied and implemented separately, resulting in doubled development and maintenance efforts for kernel developers. In this work, we identify the conceptual similarities between these two subsystems and propose their unification under a generalized resource mapping framework called Crazy.To validate this approach, we developed a prototype, CrazyOS, by merging two semi-microkernels for MM and CPU management. We then implemented several policies atop CrazyOS, including the sophisticated Completely Fair Scheduler (CFS)
Production, emploi et recyclage des métaux ferreux. Penser les analogues expérimentaux à partir du site médiéval du Castel-Miner, Ariège
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Deciphering HIV vaccine-induced Antibody response according to ethnicity
No full textInternational audienceOBJECTIVE: One recurrent question is whether an HIV-1 preventive vaccine requires adaptation to geographic and/or ethnicity background. A recent attempt to improve the Thai RV144 vaccine efficacy in South Africa resulted in non-efficacy. The potential reasons for this disappointing outcome are probably multifactorial; the role of ethnicity could not be investigated given the trials' demographics. DESIGN: To assess the role of ethnicity in the immune responses induced in HIV vaccine trials, we considered the HVTN 204 vaccine trial, which was conducted in the USA and South Africa. METHODS: Univariate and multivariate analysis of antibody responses were conducted to assess ethnicity, geographic location, Fc-receptor polymorphism, sex at birth, age and geographic location. RESULTS: We found that Black South Africans displayed higher total Immunoglobulins compared to White Americans. Noteworthy, Black South Africans showed lower HIV-specific binding IgG following vaccination. As they also showed lower background at baseline, differences between ethnic groups were narrowed after baseline background subtraction, referred to as delta values for the vaccine response outcome. CONCLUSIONS: The observed modifications of HIV-specific Ab immune responses to the HVTN 204 vaccine according to genetic, geographic location and ethnic background warrants further investigation. Additional studies of immunological differences, especially with vaccine platforms inducing high HIV-specific antibodies that correlate with vaccine efficacy may help decipher the impact of ethnicity on HIV-vaccine efficacy
Etiologic Diagnosis of Neuropathies Based on First‐Line Screening of TTR Gene Mutations
No full textInternational audienceABSTRACT Background Hereditary amyloid transthyretin (ATTRv) is caused by TTR gene mutations, which lead to multisystem amyloid deposits. A misdiagnosis is common, which delays treatment. We assessed the prevalence of TTR mutations in patients with neuropathy of unknown cause at the first stage of assessment. Methods This prospective study, conducted in western France, assessed patients with neuropathy aged 18–90 years. We excluded individuals with known causes or prior screening of TTR mutations. Genetic analyses of TTR mutations were done using Sanger sequencing. Clinical, biochemical, and electrophysiological data were collected. Statistical analyses estimated the prevalence of TTR amyloidosis in this cohort. Results Among 400 patients, four (1%) were identified as having a heterozygous TTR mutation. The mean age of these patients with a TTR mutation was 75 years, with a mean duration of neuropathy of 2.5 years. The initial symptoms varied, with one patient experiencing mixed sensory impairment, another with motor and sensory issues, one with purely motor symptoms, and one with small‐fiber sensory impairment. Notably, none had cardiological or renal impairments, and all exhibited sensorimotor neuropathy upon electromyography. Three patients had an axonal profile, and one showed demyelinating neuropathy, which highlighted the diagnostic challenges. Interpretation We identified a 1% prevalence of TTR mutations, which is lower than that reported previously, and highlights the influence of selective inclusion criteria on such estimates. Our data emphasize the need for early detection because patients frequently lack red‐flag symptoms. Ultimately, early screening allows for prompt management and minimizes long‐term complications in individuals with unexplained neuropathy. Trial Registration: ClinicalTrials.Gov Identifier: NCT03190577