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Development of Ag-Added InSn Solders for ReBCO Joints
No full textInternational audienceThis study explores ternary Ag-added InSn solders to develop low-resistance, reliable, and mechanically robust joints between YBCO tapes, an essential requirement for superconducting magnets, including the magnets in the fusion industry. To investigate the impact of Ag addition to the widely used SnIn solder, several solders were made by adding small amounts of Ag (1-5wt.% ) to the eutectic In-Sn solder. Lap joints were fabricated between YBCO tapes using these solders and were characterized for electrical resistivity, microstructure, and mechanical properties. According to the results, Ag addition changes the solder bulk structure with minimum impact on the interface and mainly dissolves in the In-rich phase of the solder. The joints made with Ag-added solders show significantly higher mechanical strength and ductility, with fracture shifting from the joint to the tape outside the joint region, and reasonably low electrical resistance. The optimized 5wt.% Ag addition to the binary In-Sn solder showed the best compromised joining performance as a result of a homogenous joint microstructure, offering a promising approach towards more reliable joints for superconducting magnet applications
Type II hot corrosion of the polycrystalline nickelbased superalloy AD730 in presence of Na 2 SO 4 and Na2SO4 -MgSO4 deposits
No full textInternational audienceThe type II corrosion resistance of AD730 was studied at 650 °C and 700 °C in air + 400 ppm SO2 (g), in the presence of Na2SO4 and Na2SO4-MgSO4 deposits. At 650°C, the pit-like attacks were of similar depth for both salts and less severe than those observed at 700°C. Although the sulfate mixture (Na2SO4-MgSO4) was liquid at 700°C from the beginning of the exposure, it proved to be less aggressive than Na2SO4. Wavelength dispersive spectrometry characterization of the pits revealed the systematic stratification of the oxides from the alloy-corrosion products interface toward the corrosion products-gas interface across the pit corrosion products, i.e. the establishment of a gradient of oxygen ions activity. High resolution transmission electron microscopy highlighted a high level of porosity, sulfur enrichment as well as the presence of the WS2 sulfide, with an anisotropic bidimensional structure, located at the alloy-oxide interface. Sulfation tests carried out on nickel oxide and cobalt oxide in the presence of Na2SO4 and Na2SO4-MgSO4 showed little sulfation with the magnesium-containing salt, thus demonstrating how MgSO4 contributes to limit the corrosion at 700°C. The results demonstrated that the severe hot corrosion attacks are not only related to the formation of a liquid phase, but also to its chemical composition
Focus sur l'exécution provisoire d'une décision de justice
No full textInternational audienceComment un ancien président de la République jugé coupable d’association de malfaiteurs dans l’affaire dite du « financement libyen de la campagne présidentielle de 2007 » peut-il être incarcéré puis libéré trois semaines plus tard ? Autrement dit, quel est l’effet de l’appel sur l’exécution d’une décision de justice de premier degré ? Et en quoi consiste le mandat de dépôt différé qui a été décerné puis levé ? Focus sur l'exécution provisoire d'une décision de justice
pH Sensitivity of the SERF1a Conformational Ensemble
No full textInternational audienceThe MOAG-4/SERF class of proteins is a positive regulator of the aggregate formation of amyloid proteins that play an important role in the origin of numerous age-related diseases. In this class of proteins, previous structural studies showed that SERF1a is a very flexible protein, containing at least one α-helical region. The present work proposes the first description of the conformational space of SERF1a at two pH values (6 and 6.8) using nuclear magnetic resonance (NMR) and small-angle X-ray scattering (SAXS). SERF1a NMR conformations have been generated using the CYANA-FLYA procedure as well as the TAiBP (Threading-Augmented interval Branch-and-Prune) procedure, based on the systematic enumeration of protein conformations within an original distance geometry scheme. The generated conformations were filtered using Pepsi-SAXS by fitting small-angle X-ray experiments based on size exclusion chromatography (SEC-SAXS). At pH 6.8, a good fit of the SEC-SAXS curves was obtained for the CYANA and TAiBP NMR conformations, while at pH 6, analysis of the NMR conformations and the SEC-SAXS curves indicated that there could be a conformational exchange between a compact conformation displaying long-range nuclear Overhauser effects (NOEs) between residues LYS-13 and THR-32, and slightly more extended conformations. The shortening of the C-terminal α-helix, as well as the destabilization of the N-terminal α-helix at acidic pH, may be related to the physiological function of SERF1a in the nucleoli. Interestingly, the N-terminal region of SERF1a displays numerous possible binding pockets, particularly in the region interacting with α-synuclein, detected by chemical shift perturbations. In general, the TAiBP procedure allows for a more expanded exploration of the SERF1a conformational space as well as for a description of the internal dynamics of SERF1a in agreement with NMR relaxation and with predictions from the protein primary sequence
Trait-dependent declines of threatened endemic trees following plant invasion on a tropical oceanic island
No full textInternational audienceBiological invasions are a leading cause of the ongoing biodiversity crisis, and particularly so on islands. However, the role of invasive alien plants (IAPs) as a driver of native plant declines and extinctions remains unclear. The inherently slow and gradual nature of plant extinctions, especially that of long-lived woody species, could be a reason. Here, we examined temporal trends in subpopulations of 28 threatened endemic tree (TET) taxa. We questioned the frequency with which they decline in association with IAPs on Reunion Island (South-West Indian Ocean), and asked whether the most susceptible TET taxa exhibit characteristics that could reveal the underlying ecological mechanisms. We resurveyed 182 historically described subpopulations and tested whether observed trends of juvenile and adult TETs correlate with the abundance in IAPs using path analyses, while distinguishing TET taxa with respect to their leaf–height–seed characteristics and extinction risk. The trend of adult TETs was not affected by IAPs but that of juvenile TETs was negatively correlated with the abundance of IAPs in the understory layer. This was particularly the case for TET taxa with conservative resource-use strategies (low specific leaf area or low maximum height), whose juveniles might be particularly susceptible to competition with IAPs, but not for TET taxa with large seeds, whose metabolic reserves make seedlings more likely to attain a critical size. These findings suggest that IAPs can significantly contribute to the extinction dynamics of trees, primarily by limiting regeneration through competitive exclusion, and that their impacts vary depending on the traits of the affected taxa
Metal-free visible-light carbonylation of alkyl iodides to amides <i>via</i> consecutive photoinduced electron transfer
No full textInternational audienceA visible-light-driven, metal-free carbonylation of unactivated alkyl iodides is reported, enabling the directsynthesis of 35 structurally diverse amides in good to excellent yields. The reaction shows broad functional-group tolerance toward both amines and alkyl iodides, including bioisosteric motifs and complex naturalproduct derivatives, underscoring its potential for late-stage functionalization. Mechanistic investigationscombining flash photolysis, spectroelectrochemistry, irradiated thin-layer cyclic voltammetry, and EPRspectroscopy reveal a consecutive photoinduced electron transfer (ConPET) mechanism that divergesfrom conventional single-photon photoredox catalysis. DFT calculations elucidate the key radicalcarbonylation steps governing reactivity and selectivity. This sustainable and operationally simple methodoffers a transition-metal-free approach to carbonylation, expanding the toolbox for highly reducingtransformations under mild conditions
Understory plant indicator values poorly perform at monitoring temporal changes in French forest soil chemical properties
No full textInternational audienceUnderstory plant communities are widely used to infer soil conditions through species indicator values (IVs), scores reflecting species’ ecological preferences for factors such as soil acidity, moisture, or nutrient levels. While their reliability to describe soil conditions along spatial gradients is well established, their ability to capture temporal changes in soil chemistry remains largely untested at both temporal and geographical scales. We combined 26 years of vegetation monitoring with two French national soil surveys (1993–1997; 2007–2012) across 102 permanent forest plots to assess the reliability of community soil indices (CSIs) as bioindicators of soil pH, carbon-to-nitrogen ratio (C/N), and extractable phosphorus. CSIs were computed by averaging species IVs for each plot and survey. Temporal dynamics of measured soil properties and CSIs were analyzed using mixed-effects models at the national scale, while local trends were estimated separately for each plot to directly compare measured and vegetation-inferred changes. CSIs showed strong spatial correlations with measured pH and C/N, but weaker relationships for phosphorus. In contrast, no significant coupling was found between temporal changes in CSIs and measured soil parameters, with frequent mismatches in both direction and magnitude at the plot level. Measured soil dynamics were mainly driven by initial edaphic conditions and stand age, whereas CSI dynamics responded primarily to canopy openness and anthropogenic disturbances such tree harvesting. These findings confirm the value of IVs for spatial bioindication but highlight their limited sensitivity for detecting long-term soil changes, especially where soil changes remain modest
Photodynamic ablation of floating lung cancer cells using PVA and TPGS emulsified PLGA nanoparticles loaded with pyropheophorbide-a
No full textInternational audienceMetastasis or the spread of cancer cells to other tissues is a hallmark that leads to the majority of cancer-related deaths worldwide. When metastasizing cancer cells invade into the bloodstream, they become floating cells, also known as circulating tumor cells (CTCs), which can lead to the development of metastasis-associated multidrug resistance in advanced cancer patients. Eradication of CTCs has received much attention as a strategy for preventing metastasis. Photodynamic therapy (PDT) has attracted growing interest as a minimally invasive approach for cancer treatment. Pyropheophorbide-a (PPa) is photosensitizer with advantages of relatively high wavelength absorption and high extinction coefficient; however, it has limited PDT therapeutic benefits due to poor solubility. This work aimed to employ PDT for killing CTCs by utilizing PVA and TPGS coated PLGA nanoparticles, loaded with PPa. The PPa-entrapped PLGA nanoparticles (PPa-NPs) exhibited a spherical morphology under TEM with an average size of 124.9 ± 2.3 nm and a zeta potential value of −32.0 ± 1.4 mV. The PPa-NPs enhanced singlet oxygen generation in water upon light activation. PPa-NPs successfully delivered PPa into A549 floating cells under CTC-mimicking conditions, with 21-fold increase in intracellular PPa accumulation when compared to free PPa treatment. After red light excitation, intracellular ROS level was elevated in PPa-NPs treated floating cells, in a dose-dependent manner, and correlated with photocytotoxic effect of PPa-NPs in the floating cells. Our results demonstrate that PVA and TPGS stabilized PLGA NPs efficiently preserved the photophysical properties of PPa for eradicating CTCs by PDT with red light activation
Climate shocks and banking sector stability: Evidence from El Niño southern oscillation
No full textInternational audienceThis study introduces a novel ex ante approach to assess the short-term impact of climate shocks on banking sector stability by examining the effect of El Niño Southern Oscillation (ENSO) on banking sector distance-to-default. Using dynamic panel data econometric modeling, we investigate the macroeconomic implications of ENSO-induced climate shocks, such as El Niño and La Niña events, on banking sector stability in 51 countries across three regions particularly exposed to the consequences of ENSO oscillations (East Asia and Pacific, Latin America and the Caribbean, and Sub-Saharan Africa) during the period 2000–2020. Our findings show that the adverse effects of these climate shocks on banking sector stability are unevenly distributed among countries, with more pronounced and robust adverse effects of El Niño events in the short-term, particularly in Latin America and the Caribbean and, to a lesser extent, Sub-Saharan Africa. We also document the short-term adverse effects of La Niña events for Latin American and the Caribbean countries. Further estimates suggest that the increase in non-performing loans is a key transmission channel linking El Niño events to banking sector stability. As global warming should intensify the frequency and magnitude of ENSO's cyclical pattern, these findings can help estimate the potential adverse effects of climate change-related natural disasters on banking sector stability and inform future mitigation and adaptation policies
Microstructure optimization by combinatorial approach applied to Duplex Medium Manganese steels
No full textInternational audienceThis study introduces a novel combinatorial approach for optimizing the microstructure of duplex medium-manganese (Mn) steels by coupling a controlled thermal gradient with in situ high-energy X-ray diffraction (HEXRD) during intercritical annealing. A temperature gradient (680–720 °C) across a single sample enables real-time monitoring of phase transformations over a broad thermal range in one experiment. Compared to isothermal trials, this method offers high-resolution insight into austenite formation kinetics and phase stability, enabling accurate identification of the optimal temperature window for maximizing retained austenite. The results reveal a narrow optimal range (∼700–710 °C) where retained austenite fractions exceed 30 %, surpassing values from traditional methods. Post-mortem Electron Backscatter Diffraction (EBSD) analysis showed the spatial distribution of stabilized austenite, highlighting the complementary roles of in situ and ex situ characterization. This work demonstrates the potential of gradient-based combinatorial metallurgy to accelerate process optimization and support the design of high-performance third-generation advanced high-strength steels