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Post-exploitation fate of alluvial goldmines in the Amazon: soil erosion, metal(loid) remobilisation and evolution of ecological functions during restoration
No full textInternational audienceArtisanal and small-scale gold mining is responsible for deforestation and habitat degradation in Amazonian ecosystems due to soil reworking and increased turbidity in surrounding rivers. In French Guiana, legal mines are required to perform rehabilitation after gold extraction. To assess the successfulness of this rehabilitation, the temporal evolution of particles and metal(loid)s (mercury, lead, arsenic) export was measured, as well as several parameters linked to soil functions (soil carbon and nitrogen, microbial diversity, enzymatic activities). Results show a rapid decrease in particle export (i.e., 3-fold reduction within the first 8 months, and up to 2000-fold reduction after 4 years), linked to an increase in spontaneous colonisation by herbaceous plants. This decrease in particle export induced an efficient decrease in metal(loid)s (Hg, Pb, As) export predominantly associated to the particulate fraction. The parameters associated with ecological functions did not show any significant increase within 5 years after rehabilitation, possibly due to depletion of nitrogen stocks by the herbaceous growth inducing a competition for resources with soil microbial communities. Microbial communities on the mining site displayed significant evolutions during the 5 years after restoration, with no visible convergence with forest-soil communities, but underlining the adaptability to climatic conditions and a changing environment. These results highlight that current rehabilitation practices are efficient in limiting particle and major contaminants export while more attention needs to be addressed to the recovery of soil functions and biological activitie
How to constrain long-term laterite formation using a multi-isotopic approach (Cr, Fe, Li).
No full textInternational audienc
Theoretical proposal for a unified Bayesian model of adaptation in non-interactive and interactive speech production
No full textInternational audienceIn the scientific study of speech production, as well as in speech and language therapy, a variety of experimental paradigms and tasks resulting in plasticity and adaptation of the system are used. However, existing computational models accounting for adaptation appear segregated: feedback effects during non-interactive, altered speech are mostly accounted for by speech production models, whereas accommodation effects during interactive speech are mostly accounted for by speech perception models. In this paper, we consider COSMO, a previous unified Bayesian framework of speech perception and speech production, as the basis for a theoretical proposal and Bayesian model of adaptation effects. We show how these effects in both non-interactive and interactive speech production experiments could be described in this framework, thanks for its ability to separate knowledge and representations from their involvement during speech tasks
Sulfamethazine biodegradation in sediments is driven by chronic exposure concentrations
No full textInternational audienceSulfonamide antibiotics like sulfamethazine (SMZ) can accumulate in river surface sediments and promote the development of sulfonamide-degrading microorganisms. However, it remains unclear whether the capacity of natural microbial communities to biodegrade sulfonamide is significantly stimulated above specific exposure thresholds. To investigate this, we performed a 47-day microcosm study in laboratory channels, exposing natural sediment communities to six SMZ concentrations (from C0 to C5) using an exponential dose–response design with a maximal nominal concentration of 10 mg.kg−1 DW. At the end of the experiment, 14C-SMZ mineralization kinetics revealed a strong microbial adaptation to SMZ biodegradation at the two highest concentrations tested. Indeed, percentage mineralization was about 50 % in treatment C4 and 62 % in treatment C5 but remained lower than 2 % in all other treatments (C0 to C3). The relative abundance of sadA genes increased in C4 and C5, suggesting sadA as a key functional gene controlling potential to biodegrade SMZ within the community. The adaptation to biodegradation of SMZ was associated with changes in microbial community structure, diversity and composition. Cyanobacteria and Bacteroidota were the phyla most negatively affected by treatments C4 and C5 whereas the relative abundance of Proteobacteria increased, suggesting that at least some of the bacteria involved in SMZ biodegradation belonged to this class. Changes in diversity and the increase in the biodegradation potential of SMZ had no influence on the community tolerance to this pharmaceutical, as assessed through short-term toxicity tests on β-glucosidase activity
Modeling teleseismic P wave interference from distant oceanic sources for upper mantle reflection imaging.
No full textInternational audienceAt regional scale, P waves reflected on mantle discontinuities extracted by stacking seismic noise analysis are observed in cross-correlation functions (Poli et al., 2012). Under specific noise field condition, Pedersen et al. (2022), significantly improved the SNR of Pv410p and Pv660p. Initially it was assumed that the waves extracted reflected, albeit in a non perfect wave, the so-called Green's function. However, as the noise field is not perfectly distributed, the full Green's function is not retrieved, and details on these reflected wave properties (constituents in the CC, amplitudes, time bias, ...) remain unknown. We here show which major coherent phases interact to reconstruct Pv410p and Pv660p, and give a way to analyze bias between the observed cross-correlation and the Green's function, both in terms of time delays and relative amplitudes. These waves stem from long-range mantle phases that interact in the correlation function to enhance short-range reflections. We also simulated cross-correlation functions using very distant sources, ranging from a single point to realistic ocean models. The complexity of the wave field, which introduces cross terms into the correlation function, converges better when the source is extended. Our results demonstrate how to correct the simple modeling of these waves in order to obtain a detailed characterization of the observables in the noise cross-correlation. This opens up the possibility of using body-wave retrieval to obtain an accurate picture of mantle discontinuities and to constrain their compositions and temperatures using forward modeling and thermophysics
Neurodevelopmental Vulnerability in Alzheimer's Disease and Frontotemporal Dementia
No full textInternational audienceBackground Neurodevelopmental disorders (NDDs) may influence the course of Alzheimer's disease (AD) and frontotemporal dementia (FTD). However, prior studies have focused on specific pairs of NDDs and variants of AD/FTD. Adopting a dimensional approach to NDDs and considering the heterogeneity of AD/FTD, we investigated the association between a neurodevelopmental vulnerability (DV) and the clinical presentation and age at onset of AD/FTD. Methods We prospectively and consecutively recruited 84 AD/FTD participants and 41 matched controls. AD/FTD participants were classified into typical (amnestic AD, behavioral FTD) and atypical (primary progressive aphasia, frontal and posterior variants of AD, right temporal variant of FTD, amnestic FTD) presentations. Participants underwent a neuropsychological assessment and answered a novel questionnaire on NDDs symptoms. Using k‐means clustering based on the questionnaire, participants were assigned to a DV+ (with neurodevelopmental vulnerability) or a DV− (without) cluster. This data‐driven approach enabled an unbiased classification of individuals with a DV, beyond traditional diagnostic labels. Results DV frequencies did not differ between the AD/FTD (18%) and control (15%) χ 2 = 0.205; p = 0.651); and between typical (21%) and atypical (11%) subgroups (Fisher's test, p = 0.184). However, in DV+ patients, symptom onset occurred 8.0 years earlier than in DV− patients (95% CI [−14, −3.0]; p = 0.005), with a median onset age of 58 years (IQR: 15). Conclusions A DV could favor early‐onset AD/FTD, but may not affect susceptibility to typical and atypical variants of AD/FTD. The underlying neurophysiological processes involved require future investigation, with implications for precision medicine and individualized treatment strategies. Study Registration Numbers RnIPH 2023‐71 and Research Ethics Committee file No. 2023_765
Waviness and self-sustained turbulence in plane Couette-Poiseuille flow
No full textDirect numerical simulations of a Couette-Poiseuille flow were performed near the transition to turbulence to investigate the nonlinear relationship between streak waviness and rolls. This relationship is a key step in Waleffe's model for a self-sustaining process (SSP). Simulations were conducted for Reynolds numbers ranging from 500 to 940, and a range of initial perturbation amplitudes were used. In these simulations, the streaks, rolls, and streak waviness initially increase. The optimal time for this growth is close to the linear transient growth period for small perturbations, but much shorter for large, highly nonlinear perturbations. For higher Reynolds numbers and large initial perturbations, the velocity field reaches a turbulent steady state, whereas it relaxes to a laminar state in other cases. The main result is that the waviness of the streaks is a quadratic function of the rolls, provided that its value is sufficiently large.Direct numerical simulations of a Couette-Poiseuille flow were performed near the transition to turbulence to investigate the nonlinear relationship between streak waviness and rolls. This relationship is a key step in Waleffe's model for a self-sustaining process (SSP). Simulations were conducted for Reynolds numbers ranging from 500 to 940, and a range of initial perturbation amplitudes were used. In these simulations, the streaks, rolls, and streak waviness initially increase. The optimal time for this growth is close to the linear transient growth period for small perturbations, but much shorter for large, highly nonlinear perturbations. For higher Reynolds numbers and large initial perturbations, the velocity field reaches a turbulent steady state, whereas it relaxes to a laminar state in other cases. The main result is that the waviness of the streaks is a quadratic function of the rolls, provided that its value is sufficiently large
Quantitative structural geology in the deep ocean using photogrammetry: Implications for the polyphased tectonic evolution of the Buteur Ridge, French Guiana
No full textInternational audienceThe Buteur Ridge is a 7 km-long and 6 km-wide relief on the eastern rifted margin of the Demerara Plateau, offshore French Guiana. This margin was formed during the Lower Cretaceous. In early 2023, the oceanographic cruise DIADEM used a manned deep submersible (Nautile) to sample and directly observe the eastern flank of this 3750 m-deep ridge.This study presents a new underwater photogrammetric method developed from the Nautile video records. This method incorporates both camera and submarine movements to produce photogrammetric 3D models of the seafloor below decimetre scale. The presented underwater photogrammetric method can be used for both past and future video records, as long as both underwater device and camera movements are recorded.The data obtained from the 3D reconstructions allow to reconstruct detailed stratigraphic and structural framework of the Buteur Ridge. The eastern flank of the Buteur Ridge is entirely composed of sedimentary layers. Structural analysis at bed scale suggests prograding structures likely associated with a N-S-directed paleocurrent. At ridge scale, structural analysis combined with seismic observations suggests that the Buteur Ridge is the result of a polyphased tectonic evolution. We highlight that Cretaceous tilted blocks, bounded by east-dipping faults, are overlapped by a post-rift unit. The syn-rift units are in contact with the east-dipping post-rift unit by a post-rift unconformity. Subsequent tilt and fault reactivation offset both the post-rift unconformity and the post-rift unit, resulting in the present relief of the Buteur Ridge
Motion processing in visual cortex of maculopathy patients
No full textInternational audiencePrevious studies on animal models suggested that visual areas involved in motion processing could undergo important cortical reorganizations following retinal damages. This could have major implications for patients suffering from macular degeneration (MD), one leading cause of vision loss. Here, we performed fMRI recordings in a group of maculopathy patients (N=7, 3 women, including individuals suffering from age-related macular degeneration or from Stargardt’s Disease) and a control group to characterize the motion processing cortical network in MD patients and determine whether this network is modified following the onset of the scotoma. We used an experimental protocol based on random-dot kinematograms (RDKs) classically employed to characterize motion-selective areas in the brain. To ensure that the visual information processed by the two groups was equivalent, the visual field in each control participant was masked using an artificial scotoma directly derived from clinical measurements in their paired patient. We found that in MD patients, translational motion elicited significant and robust activations in a restricted cortical network which included the human V5/MT+ complex (hMT+), areas V3A and V6, and a portion of primary visual areas (V1, V2 and V3) connected to peripheral vision. Importantly, the same patterns of responses were also observed in control participants. Moreover, the extent and strength of activation within these motion-selective areas did not differ significantly between the two groups. Altogether, these results suggest that in humans, the motion-selective network does not undergo significant large-scale cortical reorganizations following the onset of MD
Polarized-boson pairs at NLO in the SMEFT
No full textInternational audienceWe present a computation of diboson production in the channel at the Large Hadron Collider (LHC), incorporating leptonic decays of the gauge bosons and considering intermediate gauge bosons with definite polarization states. The analysis includes contributions from the Standard Model effective field theory (SMEFT) and is carried out at next-to-leading order accuracy in QCD, matched to a parton-shower simulation. Our implementation allows for the selection of specific helicity configurations, both in the Standard Model and in the presence of dimension-six operators inducing anomalous triple-gauge-boson couplings. This work provides a key ingredient for both polarization-template and quantum-tomography analyses of diboson systems at the LHC within the SMEFT framework