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Effects of lateral hydrological connectivity on the taxonomic and functional structure of fish communities in Saône river floodplains (France): implications for non‐native species distribution.
No full textInternational audienceLarge alluvial plain rivers provide a complex mosaic of freshwater habitats characterised by a lateral hydrological connectivity (LHC) gradient between the main channel and floodplains. This connectivity plays a key role in structuring aquatic communities, influencing species distribution, diversity, and ecosystem processes. The aims of our study were to assess the effects of the LHC gradient on both fish taxonomic and functional diversity, and to characterise the effects of this connectivity on the distribution of non‐native species. Community data were gathered through electrofishing at five sites in the main channel of the Saône River (France), and in four permanently (parapotamic) and four occasionally (plesiopotamic) connected oxbows. Functional diversity was investigated using a trait‐based approach as surrogates of ecosystem processes. A total of 28 fish species were identified, including 14 non‐native species. Our results show that main channel and plesiopotamic oxbows exhibited distinct compositional and structural patterns of fish communities, while parapotamic oxbows displayed an intermediate composition and community structure. Taxonomic and functional diversity decreased along the lateral continuum from the main channel to plesiopotamic waterbodies. In contrast, while non‐native species richness was similar between the main channel and floodplains, their densities were higher in floodplain oxbows. These findings highlight the prominent role of hydrological connectivity in sustaining both taxonomic and functional diversity in riverine ecosystems. Fish community variations between habitats may be explained by physical changes resulting from reduced connectivity, primarily characterised by a loss of depth and surface area, which in turn affect a broad spectrum of abiotic and biotic factors. High densities of non‐native species in lentic environments like oxbows can be attributed to specific abiotic conditions (e.g., hypoxia, rapid temperature fluctuations and eutrophication) and the greater tolerance and plasticity of non‐native species compared to native species. Additionally, the absence of predators reduces top‐down control and intensifies competition with native species for resources. Conservation and management strategies should prioritise preserving and restoring connectivity to support native fish communities, limit the dominance of non‐native species, and maintain the ecological integrity of freshwater ecosystems
A reversed latitudinal ocean oxygen gradient in the Proterozoic
No full textInternational audienceMajor changes in the oxygenation of the atmosphere and ocean have been suggested to trigger the taxonomic diversification and ecological expansion of complex life, including animals, during the Neoproterozoic–Palaeozoic transition. However, testing this hypothesis is hampered by the paucity of quantitative constraints on the oceanic oxygen availability at that time. Here we show how the spatial pattern of I/Ca ratios in marine carbonates—a proxy for dissolved oxygen in the local upper ocean—provides a fingerprint of the oxygenation state of Earth’s surface. Spatial analyses on published I/Ca ratios spanning the past 2,000 million years show that the latitudinal gradient of oxygen concentrations in the upper ocean was reversed in the Proterozoic eon relative to the modern pattern of decreasing oxygen concentrations from the mid-latitudes to the Equator. Using an Earth system model, we identify that the Proterozoic I/Ca latitudinal pattern is associated with a biosphere-controlled distribution of oxygen in the upper ocean at a low atmospheric oxygen level, and the transition to a modern pattern in the I/Ca proxy may correspond to a threshold of around 1% of today’s atmospheric oxygen concentration
Comment est mesurée l'audience des syndicats français dans le secteur privé ?
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Dyadic Ru-based nanomaterials for visible light-driven photocatalytic hydrogen evolution
No full textInternational audienceVisible light-driven water splitting is an appealing strategy to store renewable energy in the chemical bonds of molecular hydrogen. In this regard, the development of photocatalytic architectures where charge transfer and recombination can be controlled represents a key challenge. The surface functionalization of Ru/RuO 2 nanoparticles (NPs) with the [Ru(2,2′-bpy) 2 (qpy)](PF 6 ) 2 photosensitizer (PS), yielding PS-NPs "dyadic" hybrid nanomaterials, represents a promising strategy. Four HER photocatalysts with different PS:NPs ratios are synthesized and thoroughly characterized by analytical and spectroscopic techniques. X-ray photoelectron spectroscopy (XPS) reveals the covalent binding of the PS to the NPs surface. Analysis of the photocatalytic performance in aqueous triethanolamine (TEOA) shows that the activation of the nanocatalyst (RuO 2 reduction) and the hydrogen evolution rate improves when the PS loading increases. Under visible-light irradiation, the nanomaterials with higher PS loading show sustained production of hydrogen for at least 80 h. The morphological and compositional evolution of the hybrid nanomaterials under photocatalytic conditions is studied and correlated with hydrogen production rates over time, pointing to a sequential leaching of PS from the nanomaterials surface. Additionally, photophysical experiments allow attaining an insight into the photochemical mechanism, which involves oxidative quenching with a fast electron injection, but also fast back electron transfer.</div
Application of perturbation theory to finding vibrational frequencies of a spheroid
No full textInternational audienceWe apply perturbation theory of boundary conditions, originally developed by A.B. Migdal and independently by S.A. Moszkowski for deformed atomic nuclei, to finding eigenfrequencies of Raman-active spheroidal modes of a spheroid from these of a sphere and compare the outcomes with the results of numerical calculations for CdSe and silver nanoparticles. The modes are characterized by the total angular momentum and are five-fold degenerate for a sphere but split into three distinct modes, characterized by the absolute value of the total angular momentum projection onto the spheroidal axis, in case of a spheroid. The perturbation method works well in case of the rigid boundary conditions, with the displacement field set to zero at the boundary, and accurately predicts the splittings when the spheroidal shape is close to a sphere, but fails in case of the stress-free boundary conditions
Prevalence of Vision Loss in High-Income Countries and in Eastern and Central Europe in 2020: Magnitude and Temporal Trends
No full textInternational audiencePurposeTo estimate the prevalence of vision loss for 2020 in high-income countries (HICs) and Central/Eastern Europe and analyse evolving trends since 1990.MethodsBased on a systematic review of medical literature, prevalence of blindness, moderate and severe vision impairment (MSVI), mild vision impairment (VI), moderate VI and presbyopia were estimated for 1990, 2000, 2010, and 2020.ResultsThe study included 68 population-based studies. In the whole study region, the age-standardized prevalence (all ages) of blindness, MSVI, moderate VI, severe VI, mild VI, and presbyopia-related VI was 0.17% (95% CI:0.15–0.19), 2.27% (2.05–2.49), 2.06% (1.84–2.29), 0.21% (0.18–0.23), 1.79% (1.62–1.99), and 2.61% (1.88–3.48) respectively, with slightly higher rates for women than men. The prevalence rates were higher in Central/Eastern Europe than in the HIC, and lower than the global rates. Stratified between Australasia, high-income Asia Pacific region, high‐income North America, Western Europe, Central Europe, and Eastern Europe, the age-standardized prevalence of blindness changed between 2000 and 2020 for men aged 50+ years by −7.95% (−8.11/−7.78), −14.51% (−14.64/−14.38), +13.18% (+13.00/+13.36), −12.07% (−12.23/−11.91), −14.39% (−14.54/−14.23), and −23.59% (−23.72/−23.46), respectively, without significant sex-related differences. Highest increase was in high‐income North America (+13.18% (+13.00/+13.36)) and most marked reduction in Eastern Europe (−23.59% (−23.72/−23.46)). Estimated blind individuals were stratified as follows: Australasia, 68,866 (54,913–84,527), high-income Asia Pacific region, 535,124 (439,912–640,330), high‐income North America, 711,990 (575,977–867,402), Western Europe, 1,533,752 (1,218,371–1,898,343), Central Europe, 327,352 (264,513–398,083) and Eastern Europe, 789,618 (663,130–923,121).ConclusionsAge-standardized prevalence of blindness and MSVI have further decreased in HIC and Eastern/Central Europe (except for high‐income North America with an increase)
Predicting climate impacts on health at subseasonal-to-seasonal timescales.
No full textInternational audienceThe potential to use subseasonal-to-seasonal (S2S) prediction systems for outcomes in health is presented, using four case studies of malaria, dengue, heat waves, and meningococcal meningitis. While promising, many such applications are currently in the demonstration phase, and examples of operationalizing S2S-based early warning systems, fully integrated with decision support, have yet to emerge. Potential reasons for this operationalization bottleneck are discussed, which include restrictions on open access to health and climate data, the unfulfilled requirement for training in the use of such systems, and the mismatch between the prediction paradigm and the decision entry points in health-planning systems. The S2S project, sponsored by the World Meteorological Organization, may help to demonstrate the potential application of climate information, but the lack of real-time access inhibits the operationalization of evaluated systems. It is recommended that partnership platforms, established through the Global Framework for Climate Services and related mechanisms, enable the climate and health academic and operational communities to work together on real-time provision and assessment of health early warning systems. This is particularly important in developing countries where climate-driven health outcomes can be severe
Disillusions and paradoxes of the massification of education in France
No full textInternational audienceBased on an analysis of French educational policies since the 1950s, this paper assesses their global impact and their unexpected effects upon individuals and society, concerning students’ learning, access to the labour market, and some attitudes and behaviours, notably civic ones. It shows that from an academic point of view, the lengthening of schooling does not increase pupils’ level as much as the multiplication of diplomas would suggest, nor reduce social inequalities. Moreover, when entering the job market, competition is harsher and the least qualified face more and more difficulties, and develop a resentment that feeds populism. These global unintended effects lead us to question the paradox of the French education system and the meritocratic equality of opportunities it is supposed to implement
Spatio-temporal thermalization and adiabatic cooling of guided light waves
No full textInternational audienceWe propose and theoretically characterize three-dimensional spatio-temporal thermalization ofa continuous-wave classical light beam propagating along a multi-mode optical waveguide. By combining a non-equilibrium kinetic approach based on the wave turbulence theory and numerical simulations of the field equations, we anticipate that thermalizing scattering events are dramatically accelerated by the combination of strong transverse confinement with the continuous nature of the temporal degrees of freedom. In connection with the blackbody catastrophe, the thermalization of the classical field in the continuous temporal direction provides a novel intrinsic mechanism for adiabatic cooling and spatial beam condensation. This process of adiabatic cooling is distinct from other mechanisms of thermalization and provides new insights into the dynamics of far-from-equilibrium closed systems and their route to thermalization
Integration DeepLabv3+ applied to RGB images and vegetation indices for nitrogen status in cereal–legume intercropping system
No full textInternational audienceThis study presents a low-cost, non-invasive approach to monitor the nitrogen status of Triticale in a Triticale–Faba bean intercropping system, an agroecological strategy to avoid chemical nitrogen inputs, using consumer-grade smartphone RGB images and deep learning. Three smartphones (Samsung Galaxy A12, Xiaomi Redmi Note 4, and Redmi Note 11) were used to capture canopy images. A DeepLabV3+ model with a ResNet-50 backbone was trained to semantically segment Triticale pixels from mixed canopies. Training the model on patch-based image subsets, rather than full images, substantially enhanced segmentation accuracy (mIoU = 90.64%). The normalized Dark Green Color Index (nDGCI) derived from segmented images at the canopy scale, was evaluated as a proxy for nitrogen status against normalized SPAD (nSPAD) measurements, a tedious leaf scale method. Strong linear relationships were observed between nDGCI and nSPAD (pooled correlation across optical devices of R² ≈ 0.60 and optical device-specific ranging from R² = 0.69 to 0.87). Statistical analyses highlighted significant effects of cropping modality, phenological stage, and device on both indices, but the method reliably distinguished between nitrogen treatments. Device-specific calibration effectively corrected offsets, validating the feasibility of smartphone-based AI for detailed monitoring in intercropped systems. This approach offers a practical cost-effective alternative to conventional tools enabling precision agriculture in agroecological contexts