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Robustness of Constraint Automata for Description Logics with Concrete Domains
No full textInternational audienceDecidability or complexity issues about the consistency problem for description logics with concrete domains have already been analysed with tableaux-based or type elimination methods. Concrete domains in ontologies are essential to consider concrete objects and predefined relations. In this work, we expose an automata-based approach leading to the optimal upper bound ExpTime, that is designed by enriching the transitions with symbolic constraints. We show that the nonemptiness problem for such automata belongs to ExpTime if the concrete domains satisfy a few simple properties. Then, we provide a reduction from the consistency problem for ontologies, yielding ExpTime-membership. Thanks to the expressivity of constraint automata, the results are extended to additional ingredients such as inverse roles, functional role names and constraint assertions, while maintaining ExpTime-membership, which illustrates the robustness of the approach.Decidability or complexity issues about the consistency problem for description logics with concrete domains have already been analysed with tableaux-based or type elimination methods. Concrete domains in ontologies are essential to consider concrete objects and predefined relations. In this work, we expose an automata-based approach leading to the optimal upper bound ExpTime, that is designed by enriching the transitions with symbolic constraints. We show that the nonemptiness problem for such automata belongs to ExpTime if the concrete domains satisfy a few simple properties. Then, we provide a reduction from the consistency problem for ontologies, yielding ExpTime-membership. Thanks to the expressivity of constraint automata, the results are extended to additional ingredients such as inverse roles, functional role names and constraint assertions, while maintaining ExpTime-membership, which illustrates the robustness of the approach
A relaxation scheme for the equations of isentropic gas dynamics on a network with jump transmission conditions
No full textInternational audienceIn this paper we propose a new numerical scheme of relaxation type to approximate the Euler equations of isentropic gas dynamics on the arcs of a network. At the junction mass conservation and a jump transmission condition on the density are given, and a new solver is introduced to deal with both subsonic and supersonic cases. Consistency properties of the solver are proven and numerical tests are displayed to show its good performance also with respect to other possible solvers
Panorama rapide de l’actualité « Numérique » du 4 février 2025 au 11 février 2026
No full textSommaire :DonnéesLa CJUE confirme la justiciabilité des décisions contraignantes de l’EDPB : CJUE, 10 février 2026, aff. C97/23 P L’expérimentation de la vidéosurveillance algorithmique est prolongée : Projet de loi, modifié par l’Assemblée nationale, relative à l’organisation des jeux Olympiques et Paralympiques de 2030, n° 278. Intelligence artificielleL’IA générative, accélérateur de cyberattaques ? L’avertissement officiel : Agence de cybersécurité, « L’IA générative face aux attaques informatiques, synthèse 2025, publié le 4 février 2026.PlateformesJeux à objets numériques monétisables : l’expérimentation encadrée d’un nouveau modèle hybride : Décret n° 2026-60 du 4 février 2026 relatif à l’expérimentation des jeux à objets numériques monétisables, NOR : CPPB2516565D. JORF n° 0031 du 6 février 2026DSA : TikTok visé par des conclusions préliminaires pour design addictif de la Commission : Les conclusions préliminaires présentées le 6 février.Transparence et pluralisme : la Commission éclaire l’application de l’article 18 du règlement EMFA : Commission, Lignes directrices au titre de l’article 18 du règlement européen sur la liberté des médias (EMFA), 6 février 2026
Possible favored great oxidation event scenario on exoplanets around M-stars with the example of TRAPPIST-1e
No full textInternational audienceThe Great Oxidation Event (GOE), which marked the transition from an anoxic to an oxygenated atmosphere, occurred 2.4 billion years ago on Earth, several hundreds of millions of years after the emergence of oxygenic photosynthesis. This long delay implies that specific conditions in terms of biomass productivity and burial were necessary to trigger the GOE. It could be a limiting factor for the development of oxygenated atmospheres on inhabited exoplanets. In this study, we explore the specificities of a terrestrial planet in the habitable zone of an M dwarf for a GOE. Using a 1D coupled photochemical-climate model, we simulate the atmospheric evolution of TRAPPIST-1e, an Earth-like exoplanet, exploring the effect of oxygen sources (biotic or abiotic). Our results show that the stellar energy distribution promotes O[Formula: see text] production at lower O[Formula: see text] concentrations compared to Earth, and the ozone layer on TRAPPIST-1e forms more efficiently. This lowers the threshold for atmospheric oxidation, suggesting that the GOE on TRAPPIST-1e would occur quickly after the rise of oxygenic photosynthesis, up to 1Gyrs earlier than on Earth, and would reach O[Formula: see text] enabling oxygenic respiration and thus the development of animals. We may question whether this is a general behavior around several M-stars. Furthermore, we discuss how the overproduction of ozone could make O[Formula: see text] detection possible using the James Webb Space Telescope, providing a potential method to observe oxygenation signatures on exoplanets in the near future. Previous studies predicted that for an Earth-like atmosphere O[Formula: see text] would require over 150 transits for detection, but our results show that significantly fewer transits could be needed
Stoichiometry-driven tuning of hole conductivity in MOCVD-grown β-Ga2O3 on r-sapphire substrates
No full textInternational audienceβ-Ga2O3 is a promising ultra-wide bandgap semiconductor for next-generation power and optoelectronic devices, but achieving stable p-type conductivity remains a major challenge with limited understanding of native point defects engineering. In this work, we report a systematic study on the influence of Ga and O flow rate during MOCVD growth on the structural and electrical properties of undoped β-Ga2O3 epilayers. Two sets of samples were grown: (i) varying oxygen content to span O/Ga ≈ 180-2700 at fixed Ga content, and (ii) varying gallium content at fixed O/Ga = 1600.Structural characterization using out-of-plane and in-plane high resolution X-ray diffraction, Raman spectroscopy, and scanning electron microscopy revealed a strong correlation between growth conditions and film microstructure. Increasing O/Ga flow ratio improves grain alignment, reduces lattice disorder. Hall effect measurements show the semi-insulating p-type conductivity in all samples, with enhancement of native p-type conductivity in oxygen-rich conditions, increasing the hole concentration from 6.0×10 13 to 1.7×10 15 cm -3 at 800 K. Interestingly, the improvement in hole mobility correlates with the increasing in Ga content (up to 18.5 cm 2 /V•s) at higher growth rate and improved grain alignment. These results demonstrate that reproducible control of stoichiometry and microstructure of β-Ga2O3 thin films grown by MOCVD provides a possibility to tune native-defect concentrations, thus electrical properties of material
Upland Methane Sinks Under Climate Change: Global Patterns, Drivers and Trends
No full textInternational audienceABSTRACT Well‐aerated upland soils serve as a crucial biological sink for atmospheric methane (CH 4 ), playing a key role in mitigating climate change. However, current understanding of how this CH 4 sink responds to global climate change remains limited. To address this, we integrated 1092 observational data points to construct a dataset covering multiple global change factors and used meta‐analysis to quantify the response mechanisms of the upland CH 4 sink. Results show that warming, reduced precipitation, and elevated carbon dioxide concentrations significantly strengthened the CH 4 sink, while increased precipitation and nitrogen addition weakened it. Interactive effects were also observed: low‐level nitrogen deposition acted antagonistically with increased precipitation, but synergistically with warming. We subsequently optimized a CH 4 oxidation model to explore the global distribution patterns and future trends under different climate scenarios. The current global upland soil CH 4 sink is estimated at approximately 37 Tg year −1 and generally shows an increasing temporal trend. Spatially, the sink exhibits heterogeneity: a greater extent of desert areas in the Northern Hemisphere leads to a lower CH 4 sink per unit area compared to the Southern Hemisphere. Future spatiotemporal trends of the soil CH 4 sink will depend on the climate pathway. Under the Shared Socioeconomic Pathway (SSP) 1–2.6 scenario, the CH 4 sink declines over time, whereas under SSP5‐8.5, it follows a unimodal trajectory. Variations in the soil CH 4 sink also differ across regions. These changes are primarily associated with atmospheric CH 4 concentrations under different climate pathways, as well as alterations in soil temperature and moisture resulting from various climate change drivers. These findings underscore the importance of the upland CH 4 sink in the global CH 4 cycle and significantly advance our understanding of its response mechanisms to climate change
Estimation of CO2 fluxes in the cities of Zurich and Paris using the ICON-ART CTDAS inverse modelling framework
No full textInternational audienceObservation-based estimation of urban CO2 emissions can help cities track their pathway to net zero emissions, a goal many cities worldwide have adopted. While mesoscale atmospheric transport models are an effective component in inversion systems estimating country-level emissions, their use in urban-scale inversions presents a significant challenge. Here, we present one-year flux inversion results with the mesoscale ICON-ART atmospheric transport model for two cities with contrasting size and topographic complexity: Zurich and Paris. Inversions were performed with an ensemble square root filter, assimilating observations from a dense rooftop CO2 sensor network in Zurich and from a tall tower network in Paris. The inversion framework optimized gridded anthropogenic and biospheric fluxes, along with background mole fractions from eight inflow regions. Prior anthropogenic emissions were based on detailed inventories provided by local authorities. In Zurich, the inversion resulted in a posterior annual anthropogenic emission of 1012.3±38.8 kt yr−1, representing approximately a 30 % reduction compared to the prior, with the most significant decreases during winter periods of elevated ambient temperatures. In contrast, the posterior fluxes in Paris remained close to the prior, with an annual emission of 3580.0±101.9 kt yr−1, which is 7 % higher than the prior. This comparison highlights the influence of city-specific factors – such as topography, city size, and observational network – on the inversion system performance. Furthermore, our findings demonstrate the potential of mesoscale models to refine urban emission estimates, offering valuable insights for policymakers and researchers working to improve emission inventories and advance urban climate strategies
Selective Disruption of Plasmodium falciparum mitochondrial DNA via G-Quadruplex-Binding Ligand RHPS4 Provides a Novel Antimalarial Strategy
No full textInternational audienceABSTRACT Malaria caused by Plasmodium falciparum remains a major health threat, killing over 600,000 people annually. The spread of resistance to all major antimalarials, including artemisinins, highlights the urgent need for new drugs with distinct mechanisms of action. Here we show that the G-quadruplex ligand RHPS4, an acridine derivative, displays strong antiplasmodial activity against both drug-sensitive and -resistant P. falciparum strains and clinical isolates. RHPS4 primarily targets the trophozoite stage and induces major mitochondrial alterations, including reduction of mitochondrial DNA (mtDNA) and transcriptional dysfunctions. Bioinformatic analyses identified at least eight putative G4-forming sequences within the parasite’s mtDNA. Biophysical studies confirmed G4 folding of at least one sequence and its interaction with RHPS4. These findings indicate that RHPS4 disrupts P. falciparum mitochondrial metabolism through G4 stabilization, leading to parasite death, and establish mtDNA G4 structures as novel therapeutic targets for antimalarial development