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A parsimonious tail compliant multiscale statistical model for aggregated rainfall
No full textInternational audienceModeling rainfall intensity distributions across aggregation scales (from sub-hourly to weekly) is essential for hydrological risk analysis and IDF curves. Aggregation naturally imposes mathematical constraints: return levels must be ordered by time scale, as daily accumulations necessarily exceed sub-daily ones. From a statistical perspective, each aggregation step should ideally not require additional parameters, yet parsimonious models describing the full distribution remain scarce, as most literature focuses on seasonal block maxima. In this study, we propose a parsimonious framework to model all rainfall intensities (low to large) across scales. We utilize the Extended Generalized Pareto Distribution (EGPD), which aligns with extreme value theory for both tails while remaining flexible for the bulk of the distribution. We establish a general result on the behavior of EGPD variables under various aggregation procedures. To overcome the difficulty of direct likelihood inference, we link the EGPD class to Poisson compound sums. This allows the use of the Panjer algorithm for efficient composite likelihood evaluation. Our approach ensures that return levels do not cross across scales and enables estimation for return periods below annual or seasonal levels. We demonstrate the method using sub-hourly series from six French stations with diverse climates. Only eight parameters are needed per station to capture scales from six minutes to three days. IDF curves above and below the annual scale are provided
Combining the second data release of the European Pulsar Timing Array with low-frequency pulsar data
No full textInternational audienceLow-frequency radio data improve the sensitivity of pulsar timing arrays (PTAs) to propagation effects such as dispersion measure (DM) variations, enabling better noise characterization essential for detecting the stochastic gravitational wave background (GWB). We combined LOFAR (100-200 MHz) and NenuFAR (30-90 MHz) observations with the recent European and Indian PTA release (DR2new+) into a new dataset, DR2low, spanning ~11 years for 12 pulsars. DR2low allows updated noise models, increasing PTA sensitivity to the GWB. Using Libstempo and Enterprise, we applied standard noise models including red noise (RN) and time-variable DM (DMv) as power laws, and performed Bayesian model selection over RN, DMv, and an additional chromatic noise term (CN4). Compared to DR2new+, DR2low improves DM constraints and separates DM and RN contributions. We found that the RN is required in the final model for 10 out of 12 pulsars, compared to only 5 in the DR2new+ dataset. The improved sensitivity to plasma effects provided by DR2low also favors the identification of significant CN4 in eight pulsars, while none showed such evidence in DR2new+. The analysis also reveals unmodelled solar wind effects, particularly near solar conjunction, with residual delays absorbed into the DM component, highlighting the importance of accurately modelling the solar wind in PTA datasets
1D linear stability analysis based on an adjusted correction factor for dynamic expansion: Application to plates and rods
No full textInternational audienceThis work investigates the onset and development of plastic strain localization during the dynamic expansion of metallic shells. The multiple necking and fragmentation scenario are here viewed as originating from the development of geometrical perturbations (i.e., surface roughness), whose time evolution plays a critical role for the late free flight of fragments. Based on the extended 1DXLSA (One-Dimensional eXtended Linear Stability Analysis) model of Xavier et al. (2021), and using the 2DXLSA of Xavier et al. (2020) and FEM calculations as references, we propose an adjustment of the stress approximation in the neck section to better capture the onset of multiple necking in cylindrical (plate) and ring (round bar) geometries. A modified Bridgman correction factor is then introduced, which highlights the limitations of the previous 1DXLSA study. A good agreement in terms of time evolution of the perturbations is obtained between Finite element simulations, two-dimensional linear stability approach and the new 1D model
Holographic shear correlators at low temperatures, and quantum
No full textInternational audienceThe strongly-coupled 3-dimensional theory, holographically dual to black branes at fixed chemical potential \muext and temperature is considered in AdS Einstein-Maxwell theory. The retarded Green's functions at frequency is calculated using holography in the regime ω, T \ll \muext but otherwise arbitrary. When the transverse space has finite volume, there is a non-zero energy scale , scaling as for large , below which quantum-gravitational corrections due to the fluctuations of the nearly-gapless Schwarzian modes become important. Such corrections to the retarded Green's function are calculated at different relative values of , , and . The limit is used to define the shear viscosity . As the temperature is lowered below , quantum corrections are found to increase the value of with respect to its semiclassical value. The quantum-corrected result for diverges as at , in accord with corresponding results for the absorption cross section. The quantum result for the ratio , where is the entropy density, dips below the semiclassical limit of when , then turns back to increase towards lower temperatures, and finally diverges at temperatures much below
The Lucie-7B LLM and the Lucie Training Dataset: Open resources for multilingual language generation
No full textWe present both the Lucie Training Dataset and the Lucie-7B foundation model. The Lucie Training Dataset is a multilingual collection of textual corpora centered around French and designed to offset anglo-centric biases found in many datasets for large language model pretraining. Its French data is pulled not only from traditional web sources, but also from French cultural heritage documents, filling an important gap in modern datasets. Beyond French, which makes up the largest share of the data, we added documents to support several other European languages, including English, Spanish, German, and Italian. Apart from its value as a resource for French language and culture, an important feature of this dataset is that it prioritizes data rights by minimizing copyrighted material. In addition, building on the philosophy of past open projects, it is redistributed in the form used for training and its processing is described on Hugging Face and GitHub. The Lucie-7B foundation model is trained on equal amounts of data in French and English -- roughly 33% each -- in an effort to better represent cultural aspects of French-speaking communities. We also describe two instruction fine-tuned models, Lucie-7B-Instruct-v1.1 and Lucie-7B-Instruct-human-data, which we release as demonstrations of Lucie-7B in use. These models achieve promising results compared to state-of-the-art models, demonstrating that an open approach prioritizing data rights can still deliver strong performance. We see these models as an initial step toward developing more performant, aligned models in the near future. Model weights for Lucie-7B and the Lucie instruct models, along with intermediate checkpoints for the former, are published on Hugging Face, while model training and data preparation code is available on GitHub. This makes Lucie-7B one of the first OSI compliant language models according to the new OSI definition
Scalable model development of carbon photosynthetic assimilation and partitioning in a green microalga during nitrogen starvation
No full textInternational audienceLipid accumulation in green microalgae is induced by stresses (e.g. nitrogen starvation) which compromise photosynthetic activity resulting in significantly lower biomass productivity than under nutrient replete conditions. While algae photosynthetic growth has been well characterized and modelled under nutrient replete conditions, the loss of photosynthetic activity during nitrogen starvation lacks specific studies to determine suitable parameterisation. The loss of photosynthetic activity of the lipid-accumulating microalgae Chlorella vulgaris NIES 227 was studied under varying light intensities during nitrogen starvation. Partition of assimilated carbon between the different macromolecules pools (carbohydrates, lipids, and proteins) was concomitantly monitored. The results showed that the decrease of photosynthetic activity correlated well to the increase of cell C:N ratio = 0,883, =65) enabling to develop a model of microalgae growth and carbon partition under nitrogen starvation. Biomass dry-weight increase could be predicted with good accuracy ( = 0,940, = 66), as total lipid and carbohydrate production could also be predicted with fair accuracy (=0,841 and 0,618 respectively). The present study henceforth showed that modelling microalgae productivity based on photosynthetic activity inferred from local light intensity, as done in scalable models under nutrient replete conditions, may be extended to nitrogen starvation conditions and enabled the prediction of lipids and carbohydrates productivity. The model proposed should thus prove useful in optimizing photobioreactors design for the production of important energetic molecules based on light distribution knowledge
The food grade bacterium Lactobacillus helveticus VEL12193 promotes autophagy by releasing membrane vesicles
No full textInternational audienceThe food grade bacterium Lactobacillus helveticus VEL12193 promotes autophagy by</div
Many-body Quantum Score: a scalable benchmark for digital and analog quantum processors and first test on a commercial neutral atom device
No full textWe propose the Many-body Quantum Score (MBQS), a practical and scalable application level benchmark protocol designed to evaluate the capabilities of quantum processing units (QPUs)—both gate-based and analog—for simulating many-body quantum dynamics. MBQS quantifies performance by identifying the maximum number of qubits with which a QPU can reliably reproduce correlation functions of the transverse-field Ising model following a specific quantum quench. This paper presents the MBQS protocol and highlights its design principles, supported by analytical insights, classical simulations, and experimental data. It also displays results obtained with Ruby, an analogQPU based on Rydberg atoms developed by the Pasqal company. These findings demonstrateMBQS’s potential as a robust and informative tool for benchmarking near-term quantum devices for many-body physics
Development of an actively cooled radio-frequency test bench for the ITER ICRF windows
No full text25th Topical Conference on Radio-Frequency Power in Plasmas (RFPPC2025) from May, 19 to May, 22, 2025 in the castle "Schloss Hohenkammer", GermanyInternational audienceRadio-Frequency (RF) windows (or feedthroughs) are under development for the ITER Ion Cyclotron Range of Frequencies (ICRF) system (40-55 MHz). To test these first of a kind RF window units, an actively cooled radio-frequency coaxial resonator was designed and is currently under construction at CEA/IRFM. This testbed is specified to reach 50 kV peak maximum voltage or 2.5 kA peak maximum current at the middle of the test articles in continuous-wave operation (3600 s RF pulses with a ¼ duty cycle). The operating frequency of the resonator is set to 55 MHz. The conditions of the tests are 0.6 MPa (absolute, dry air) at one side of the RF windows, vacuum (10 -4 Pa) environment at the other side of the front window and 0.3 MPa (absolute, dry air) at the rear window. These conditions are representative of the current ITER ICRF environment: the vacuum side simulates the torus vacuum inside the tokamak, and the pressurized side mimics the gas conditions within the transmission lines connecting the RF generators to the antenna. Since it is not possible to maximise both voltage and current at a given position of a resonator, two resonator configurations are foreseen, for each of the front and rear windows (hence 4 different configurations). Each of the front and rear windows will be tested at maximum voltage and maximum current. The test bench was designed to be modular, allowing the positioning of either the rear of the front windows for voltage or current RF test, hence leading to cost reduction. This paper is a description of the RF design, the mechanical design, and a rough description of the ongoing manufacturing phase
Mapping the neutron flux in the cavity of the CROCUS zero-power reactor with 3 He position-sensitive detectors
No full textInternational audienceThis work presents the results of a preliminary investigation of the neutron distribution in the CROCUS zeropower reactor cavity, i.e., the internal space located between the reactor vessel and the concrete shielding, using a 3 He position-sensitive proportional counter. This detector enables the determination of the neutron interaction position along the active volume, allowing for the reconstruction of the spatial distribution of thermal neutrons. The objective of this study is to provide experimental data on the evolution, both in shape and magnitude, of the neutron flux in the surrounding region of the reactor, characterizing the spatial variations with increasing distance from the core center. Measurements are performed in two regions of the cavity: the upper part, extending from the fuel to the reactor ceiling, and the lateral side, spanning from the vessel wall to the cavity boundary