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Diffuse gamma-ray and neutrino emission from the Milky Way and the local knee in the cosmic ray spectrum
No full textInternational audienceThe LHAASO observatory has recently measured details of the cosmic-ray (CR) spectrum in the knee region (1 -- 10 PeV) with unprecedented precision, including its average CR mass composition and the spectrum of the proton component. We use these precision measurements, combined with direct measurements of CRs by space-based detectors, to derive predictions for the spectrum of diffuse gamma-ray and neutrino emission from the interstellar medium under the assumption that the CR spectrum is universal throughout the Milky Way. We compare these predictions with the Fermi-LAT and LHAASO measurements of the diffuse gamma-ray flux from inner and outer Galactic Plane regions and with estimates of the neutrino flux based on the IceCube data for the same Galactic Plane regions. We notice that the model predictions exceed LHAASO gamma-ray measurements at energies above 100 TeV. This excess can be interpreted within a CR knee model assuming a "local PeV CR bubble''. Within this model, we infer the extension of the local PeV CR bubble of 1.5 +/- 0.3 kpc in the direction of the inner Galaxy and of 0.7+/-0.3 kpc toward the outer Galaxy
Biogeochemical processes driving the fate of arsenic in phytostabilised mine tailings based on a metric-scale experiment
No full textInternational audienceSecuring mine tailings represents a major environmental challenge. Metal mines frequently produce solid wastes containing iron (Fe) and sulphur (S), often associated with the toxic metalloid arsenic (As). Phytostabilisation often appears as a suitable option to decrease contamination due to erosion, at a moderate cost. However, side effects linked to this remediation technique like the rise of As and metals mobility along the soil-groundwater continuum are not fully understand, preventing its deployment by site managers. A two-year pilot experiment at a metric scale was performed in order to reproduce the soil-groundwater continuum in a remediated tailing. A stainless-steel column was filled with 1200 kg of fine tailings from an old tin (Sn) mine. The column experiment was divided in two layers: unsaturated zone (UZN) in the upper part and below a saturated zone (SZ). Transient boundary conditions were applied to the top of the pilot implying periodic watering (close to site rainfall), controlled temperature and surface lighting (day/night cycles). Controlled outlet discharge was set at the bottom. Baseline monitoring of the bare tailing was performed during 6 months then assisted phytostabilisation was started by amending the half part of the UZN with limestone and compost and seeded with Festuca rubra. Porewater and solid samples were sampled monthly and every 6 months, respectively.The As concentration in tailings porewater during baseline period was about 50 µg.L-1. The following redox sequence has been monitored in SZ layer: denitrification, ferric iron reduction and reduction of AsV into AsIII. These two last microbially-mediated redox reactions played a key role in As mobility by inducing dissolution of As-bearing iron oxides and increasing As solubility, respectively. Immediately after starting of phytostabilisation, the porewater AsV concentration rose in the first centimetres of the UZN layer. The As plume then spread progressively in the deeper part. This light housing experimental dataset will be used to calibrate and validate a reactive transport model (RTM) explicitly integrating microbially-mediated reactions related to As, Fe and S metabolisms. This RTM outputs will be used to help the operational management of former mining sites to design efficient phytostabilisation framework for old tailings dump
Bacteria with antibacterial activities isolated from Magallana gigas microbiota as potential probiotics against Vibrio aestuarianus infections in oyster farming
No full textInternational audienceIntroduction: Oyster farming is a significant industry worldwide, but it is threatened by various diseases such as Pacific Oyster Mortality Syndrome and vibriosis. V. aestuarianus is one of the major causes of mortality for market-size oysters, resulting in significant economic losses for oyster farmers. Among the various control methods developed, probiotics appear to be a promising approach. More specifically, the use of the antibacterial activity of bacteria from the natural microbiota of the oyster Magallana gigas appears to be a sustainable solution against V. aestuarianus infections.Results: Our study investigated the probiotic potential of bacteria isolated from the microbiota of M. gigas oysters. We screened a collection of 334 bacteria against eight target pathogens, including V. aestuarianus, and identified 78 bacteria with antibacterial activity for which eight retained this activity in their culture supernatants. Five strains were selected for further testing and exposed to oysters prior to V. aestuarianus infection. Our results show that four strains significantly reduced oyster mortality, with a maximum reduction of 70 %. In addition, changes in oyster microbiota composition were observed following exposure, but the administered bacteria were not detected in the microbiota.Conclusion: Our findings demonstrate the potential of oyster microbiota-derived bacteria as probiotics for disease control in oyster farming. This approach could provide a sustainable and environmentally friendly solution for the oyster farming industry. Further research is needed to understand the underlying mechanisms and to develop effective probiotic-based strategies for preventing V. aestuarianus infection
Reconstructing the trophic structure of Maastrichtian elasmobranch communities in Morocco using calcium isotopes
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Generation of sub-daily precipitation time series anywhere in Switzerland by mapping the parameters of GWEX-MRC, an at-site weather generator
No full textInternational audienceStudy Region Switzerland Study Focus Stochastic weather generators (WGENs) are a common tool for generating long precipitation scenarios, also needed at ungauged sites. This study evaluates different methods for obtaining the parameters of a hybrid at-site WGEN at any location within the study area. The hybrid GWEX-MRC model is composed of GWEX, a daily WGEN, and MRC, a disaggregation model based on multiplicative random cascades. Two approaches are considered for obtaining parameter maps. The first approach applies classical spatial interpolation techniques, kriging and thin-plate splines, to parameter estimates derived from rain gauge data. The second approach uses CombiPrecip, an hourly gridded precipitation product from MeteoSwiss, to estimate parameters at grid scale. New Hydrological Insights for the Region We find that the parameters of GWEX-MRC can be interpolated with satisfactory results across Switzerland. Among interpolation techniques, kriging with elevation as an external drift performs best for GWEX, while thin-plate spline with elevation gives better results for MRC. The comparison of the two approaches, interpolation of site-based estimates and direct parameter estimation using CombiPrecip, showed comparable or slightly different performance depending on the precipitation statistic and season. These findings reveal the feasibility of both approaches and provide insights into their relative strengths and limitations. In addition, this study demonstrates that long precipitation scenarios can be reliably generated throughout Switzerland, which can later be used to feed a hydrological model
Pourquoi choisir un niveau marin extrême «unique » ne fonctionne pas à l’île d’Yeu : quelle méthode pour l’évaluation des risques à l’île d’Yeu (085) ?
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A Comprehensive study of time delay between optical/near-infrared and X-ray emissions in black hole X-ray binaries
No full textInternational audienceWe conducted a comprehensive study of daily delays using multi-wavelength data from a sample of well-studied black hole X-ray binaries, specifically focusing on the sources GX 339-4, 4U 1543-47, and XTE J1550-564. The Interpolated-Correlation Function method was employed to investigate the temporal relationship between the X-ray (Compton component) and optical-infrared (OIR) emissions. Our results show that during the rising hard state, the Compton emission consistently lags behind OIR emission for several days. In contrast, during the decaying hard state, the OIR emission lags behind the Compton emission by approximately 6 to 35 days. This measurement can potentially be used in models of accretion physics and disk instability. We explore the underlying mechanisms responsible for these time delays, highlighting the critical role of viscous heating in the accretion disk in generating OIR luminosity for these sources. The observed time delays during both the rising and decaying hard states are well explained by the disk instability model
Comprehensive Physicochemical and Biological Analysis of Hydroxyapatite/Dextran Powders before and after Immersion in Kokubo Solution
No full textInternational audienceUnderstanding the behavior of biomaterials under physiological conditions is essential for the development of new materials for implants and bone regeneration. This study addresses the critical need to evaluate how exposure to simulated body fluid (SBF) affects hydroxyapatite (HAp) and dextran-coated hydroxyapatite (HApDx) nanoparticles, which are widely considered for biomedical applications due to their bioactivity and biocompatibility. Structural, morphological, and surface property changes induced by SBF immersion were systematically investigated for the first time using advanced characterization techniques, such as X-ray diffraction (XRD), scanning electron microscopy (SEM), atomic force microscopy (AFM), Fourier transform infrared spectroscopy (FTIR), FT-Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), and fractal and Minkowski functional analyses. The results revealed that SBF immersion significantly influenced both HAp and HApDx, leading to reduced crystallite sizes, surface smoothening, and enhanced structural homogeneity. FTIR and FT-Raman spectra indicated subtle structural modifications, while SEM and AFM analyses confirmed the formation of a biomimetic apatite layer and a decrease in surface roughness. These changes are indicative of improved bioactivity, suggesting enhanced potential for osteoconductivity and cellular interaction. Biological evaluations using MG63 osteoblast-like cells demonstrated favorable cell viability and adhesion across 24, 48, and 72 h, particularly for the samples immersed in SBF. AFM further confirmed that surface modifications supported the cell attachment and proliferation. Overall, our findings underscore the importance of SBF exposure in enhancing the physicochemical and biological performance of HAp-based materials, reinforcing their promise for biomedical applications
Hydraulic stability and wave overtopping characteristics of Tblock™ armour units on a 3V:4H slope
No full text( IF 5.5; Q1)International audienceTblock™ is a newly developed single-layer regularly placed interlocking concrete block that has been designed to work on breakwaters and revetments. Physical model tests were conducted to assess the hydraulic stability and overtopping of the armour layer under a wide range of wave steepness on a 3V:4H slope. Based on 51 stability tests, it was observed that the stability of the Tblock™ armour layer decreases as wave steepness increases. This pattern resembles the behavior of Tetrapod and Cube armour layers. Furthermore, an extreme case of brittle destruction was observed, where the failure occurred rapidly after the extraction of the first unit. When compared with other interlocking armour units, Tblock™ demonstrated higher stability number (Ns) across a wide range of wave steepness. Based on 27 tests, overtopping performance was unsatisfactory, with a roughness coefficient (γf) of 0.73. Moreover, it was confirmed that increasing wave steepness also reduces the roughness effect of the armour layer. The reflection coefficient was found to be comparable to that of other concrete armour units
Construction, experimental study and mathematical modelling of the solar dryer for tropical woods species under the dry month of Maroua (Cameroon)
No full textInternational audienceThe aim is to present both experimental and theoretical data useful in the modelling, optimization and industrial scaling up of the drying of three common kinds of wood with 0.003 m thick in the solar dryer and open sun drying. The results showed that for forced convection drying mode, the three wood's average initial moisture contents of 0.6696 ± 0.061577 kg/kg were reduced to an average moisture content of 0.08 kg/kg in 7–12 days while it was 6–12 days using natural convection mode. This translated to a 29.41 to 50 % time reduction when compared to open sun drying. The estimated moisture diffusivity ranged from 1.86025 × 10−9 m2/s to 1.84603 × 10−9 m2/s in forced convention mode while it was 7.6817 × 10−10 m2/s to 1.83034 × 10−9 m2/s in natural convention mode. Similarly, the value of estimated moisture diffusivity ranged from 1.36783 × 10−9 m2/s to 1.95254 × 10−9 m2/s for open sun drying. The calculated average values of the mass transfer coefficient were 5.8 × 10−6 m/s, and 5.15 × 10−6 m/s for forced and natural convection respectively while the heat transfer coefficient were 12.992 W/m2·K and 11.777 W/m2·K for the same case scenario. Theoretical modelling of the drying kinetics showed the good results with a maximum error of about 3%