HAL Portal UPPA (University of Pau and the Pays de l'Adour)
Not a member yet
42255 research outputs found
Sort by
Hybrid photonics for overcoming the limitations of silicon (Conference Presentation)
No full textInternational audienceSilicon photonics has emerged as a promising platform to address future challenges in many applications, including data communications, sensing, and optical communications, among others. However, the properties of silicon alone are not enough to overcome key limitations related to speed, power consumption, and scalability. In particular, silicon exhibits strong two-photon absorption (TPA) at telecom wavelengths and is centrosymmetric, which limits the use of its nonlinear optical properties, such as the Kerr and Pockels effects. To address these challenges, new strategies have focused on integrating novel materials into the silicon photonics platform. The presentation will explore recent developments in materials with optical properties that complement those of silicon and silicon nitride. It will also highlight the integration of crystalline oxides including Lithium Niobate and doped zirconia (ZrO₂), in silicon photonics platform
Development of on-site sampling and analysis methods for accurate isotopic underground gas storage monitoring
No full textInternational audienceIn the context of the energy transition favoring decarbonized gas energies, underground natural gas storage sites are required to receive new effluents known as “renewable gases”, including hydrogen and biomethane. This involves the development of appropriate sampling and analysis methodologies for the effective monitoring of gas storage infrastructures. Such methodologies must be secure, robust, and tailored to the specific application, considering several factors such as ease of use, industrial field conditions, and the long-term sustainability of the analytical chain.Our aim was to develop robust analytical methods, from sampling to analysis, for monitoring natural gas and other gaseous effluents stored or about to be stored, as well as those likely to be generated in the underground gas storage aquifer ‘UGS – A’. In order to provide tools to ensure the integrity of underground gas storage facilities and highlighting the phenomena occurring there. Several on-site sampling and laboratory isotopic analysis methods have been developed and validated for alkanes and others gaseous chemical compounds.Two sampling systems have been evaluated. The first system is a direct gas sampler using vacuum-sealed vials, compatible with high- and low-pressure gas sources, including gas from tubing head and annular spaces. The second system involves preconcentration and uses adsorbent tubes to capture specific trace compounds. Both systems have been tested for reproducibility on reference gas standard and actual natural gas samples to verify the accuracy of δ13C and δ2H isotopic measurements of alkanes (C1-C6) and to investigate any potential fractionation occurring during the sampling process. The methods developed were applied to samples from multiple gas wells as part of a comprehensive ‘UGS-A’ monitoring study conducted at two gas reservoirs, demonstrating high measurement efficiency
Cross-kingdom microbial interactions drive arsenic detoxification and functional stabilization in century-old mine tailings
No full textLiu, Jian-Li Yao, Jun Bashir, Safdar Duran, Robert eng Netherlands 2025/10/22 J Hazard Mater. 2025 Oct 19;499:140190. doi: 10.1016/j.jhazmat.2025.140190.Legacy gold mine tailings pose persistent environmental risks due to sustained metal(loid) mobilization under acidic andoligotrophic conditions. This study investigated microbial community dynamics in 130-year-old tailings, comparing surface (0-10 cm) and subsurface (50-100 cm) layers. The tailings exhibited acidic conditions and nutrient oligotrophic, with elevated iron and arsenic concentrations. While mineralogical analysis identified quartz and lead arsenate (PbAs(2)O(6)) as dominant phases. Bacterial diversity decreased significantly with depth and community structure was depth-stratified, whereas fungal communities showed structural stability despite variations in richness. pH emerged as the primary factor influencing both bacterial and fungal community assembly, with metal(loid) concentrations also contributing to taxonomic distribution. Keystone taxa exhibited genetic potential for carbon fixation, phosphorus solubilization, and arsenic detoxification, with cross-domain co-occurrence suggesting functional complementarity. This study elucidates the microbial mechanisms underpining arsenic stabilization and nutrient cycling in century-old mine tailings, providing a foundation for targeted bioremediation strategies
Vertical forest strata position and niche shifts between juvenile and adult spiders
No full textInternational audienceFunctional trait analyses have become a vital part of ecological and evolutionary research in recent years. Nevertheless, this progress highlights the persistent and significant gaps in our knowledge of species traits, a limitation known as the Raunkiæran shortfall. For spiders, the difficulty in properly identifying immature specimens has often contributed to discarding the contribution of these lifestages to intraspecific functional variability and community structure. Species microhabitat preferences along the vertical gradient in forest biomes are amongst the traits frequently unknown for spider juveniles, despite their relevance for multiple aspects of spiders' ecology. To bridge this knowledge gap, in this study, we used spider community data collected from the native forests on two islands belonging to the Azores Archipelago, a well-characterized and species-poor system ideal for trait-focused studies. Our goals were to compare the mean verticality and vertical range of adult and juvenile spiders belonging to different hunting guilds (hunters and web weavers) and ballooning propensity (frequent, occasional and rare ballooners). We did this using two-sample paired Wilcoxon signed rank tests and Kruskal–Wallis tests, followed by Dunn’s tests to check for differences in the variation of adult and juvenile verticality from species belonging to different functional groups. Across 22 species sampled at 16 sites on two islands, adult and juvenile spiders did not differ in their mean vertical position within the forest strata. Unexpectedly, however, adults occupied a significantly broader vertical range than juveniles, indicating greater habitat flexibility than anticipated. The pattern observed for vertical range remained when looking at the two hunting guilds considered (hunters and web-weavers), although, in the case of hunters, adults tended to have lower mean verticality than juveniles. Finally, for the three categories of ballooning propensity (frequent, occasional and rare), we observed that juveniles of rare ballooners had higher mean verticality, while, for all categories, these tended to have lower values of vertical range. Our findings show the importance of including juveniles in microhabitat studies, as well as how this seems to vary across functional groups. It is hoped that this study will serve as a valuable baseline to future research aiming to better incorporate immature life stages in spider community ecology, particularly as new standardised methodologies are developed to reliably associate juveniles with their adult forms
Reactivity of Petrobactin and Its Sulfonated Derivatives with Iron and Their Determination by Isotopic Saturation Fast Size-Exclusion Chromatography–Inductively Coupled Plasma Mass Spectrometry (ICP-MS)
No full textPré-dépôt HAL IPREM via X2HalInternational audiencePetrobactin is a bis-catechol siderophore, synthesized by Marinobacter nauticus (formerly Marinobacter hydrocarbonoclasticus), an important oil-degrading bacterium that proliferates in oil-polluted marine ecosystems. The complexes formed by petrobactin and its sulfonated derivatives with iron were, for the first time, chromatographically separated and identified by mass spectrometry. Conditions for the separation of the iron complexes using reversed-phase HPLC and size-exclusion LC were optimized. A method for quantifying petrobactin and its sulfonated derivatives has been developed. The analytical procedure is based on the saturation of the apo form of the siderophore with isotopically enriched iron, followed by its separation by ultraperformance size-exclusion chromatography with ICP-MS detection. The method is characterized by a detection limit of 0.03 ± 0.01 and 0.02 ± 0.01 μmol L-1, for petrobactin and sulfonated derivatives, respectively. Conditions of the formation of iron complexes were discussed in terms of iron source and pH. The complexation reaction was the fastest when iron was supplied as citrate or malate and when it occurred at pH 8. The monosulfonated derivative bound iron significantly faster than petrobactin itself, unlike the disulfonated derivative
Collaboration is our most powerful resistance in an increasingly fragmented world: Science is the light that reveals the unity beneath our differences
No full textInternational audienc
Bridged diheteroaryl-vinylene scaffolds as novel non-fullerene acceptors: a theoretical approach
No full textInternational audienceVinylene-bridged heteroaryl NFAs were computationally designed and evaluated across six key parameters against Y6. Several candidates show strong electronic and photophysical properties, highlighting promise for next-generation organic electronics
UV-photoelectron spectroscopy and MS-CASPT2/CASSCF study of the thermolysis of azidoethyl-methyl sulfide: Characterization and mechanism of the formation of S- methy l-N- sulfenylethanimine
No full textInternational audienceThe thermal decomposition of azidoethyl methyl sulfide was studied by real-time UV-photoelectron spectroscopy (UV-PES) at temperatures ranging from 773 to 1023 K. Different ionization energies were obtained using density functional theory calculations to assign UV-PES spectra. The complete active space self-consistent field and multistate second-order perturbation methods were used to predict the formation of different species present in the thermal decomposition process. N2 and S-methyl-N-sulfenylethanimine are generated at 773 K. The first step of the reaction is the dissociation of the molecule into nitrene and nitrogen. The spin state (singlet or triplet) of nitrene formed in the first step of the reaction is temperature-dependent. At low temperatures (T ≤ 650 K), both states are formed with almost the same probability; in contrast, at high temperatures (T ≥ 1000 K), singlet nitrene is the majority intermediate. From this singlet nitrene, three stable reaction products were detected in the experiments: an imine derivative, a four-member cyclic derivative, and a sulfenyl derivative
