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Remote Sensing Data Assimilation With a Chained Hydrologic‐Hydraulic Model for Flood Forecasting
No full textInternational audienceEffective flood risk management requires reliable forecasts with extended lead times to enable the implementation of cost‐effective and timely measures. In this study, we present a chained hydrologic‐hydraulic modeling framework designed for effective near‐real‐time flood forecasting. The system integrates runoff predictions from a large‐scale hydrologic model (ISBA‐CTRIP) as inputs into high‐resolution, local hydrodynamic models (TELEMAC‐2D) to forecast water levels and flood extents. To improve the forecast accuracy, an Ensemble Kalman Filter is employed to reduce uncertainties in hydrological forcing and friction parameters by jointly assimilating in situ water level measurements and satellite‐derived flood maps. Such a data assimilation framework operates in a real‐time forecasting configuration, consisting of a reanalysis phase having an assimilation window up to the current time, followed by a forecast phase from the current time to the expected lead time. Three forecasting strategies were evaluated: (a) using CTRIP‐predicted runoff for both reanalysis and forecast phases, (b) using observed discharge for reanalysis and CTRIP runoff for forecast, and (c) using observed discharge for reanalysis and keeping a constant discharge during the forecast. Results show that using observed discharge during reanalysis combined with CTRIP‐predicted runoff for forecasting yields the most consistent performance. However, for all three strategies, forecast accuracy declines with longer lead times, especially when errors in the CTRIP forcings are non‐stationary. This work highlights the potential for hydrologic model, despite their inherent imperfections, to serve as effective inputs for local hydraulic models, enabling near‐real‐time flood forecasting through the assimilation of in situ and remote sensing data
Iterative confidence-based pseudo-labeling for semi-supervised lung cancer segmentation under annotation scarcity
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Study of Decay Shape Factors in First-Forbidden Transitions with for Reactor Antineutrino Spectra Predictions
No full textInternational audienceThe electron spectra of the decays of Rb and Cs, key contributors to the reactor antineutrino spectrum, were measured at the IGISOL facility using radioactive beams of high isotopic purity. The shapes of the measured spectra were compared with various shape models, including first-forbidden correction factors for ground-state to ground-state transitions. Comparisons with previous experimental results are also provided. The shapes of the newly measured spectra are well reproduced employing feedings extracted from total absorption gamma spectroscopy measurements
Etude de la survie des microorganismes collectés par des filtres de centrales de traitement d'air
No full textInternational audienceSampling microbial aerosols may be difficult due to their low concentration. Air handling unit (AHU) filters, which accumulate these bioaerosols with large volumes of treated air, represent an alternative for studying the airborne microbiota in buildings. However, the survival of microorganisms on these filters remains poorly understood. This study proposes to analyze the viability within a microbial community on an AHU filter in the presence of model dust (corn starch powder). During a one-year study and under real-world conditions (full-scale AHU model), the survival and evolution of three model microorganisms were monitored: Aspergillus niger (spores), Bacillus subtilis (in spore form), and Staphylococcus epidermidis (in vegetative form), using agar culture and molecular biology methods. The results show that spore-forming microorganisms accumulate and are able to grow on the filter, even when exposed to high air velocity. This growth is accompanied by an increase in the water content of the filter and is followed by a mortality phase (decrease in culture counts). The microorganisms in vegetative form are rapidly lysed and their DNA degraded. In conclusion, microbial growth is possible on the surface of AHU filters and depends heavily on the amount of water available and the nature of the microorganisms. The identification of microorganisms in filter samples, by culture or molecular biology, is strongly influenced by the nature of the microorganisms, as well as the humidity and temperature in the AHU.L'échantillonnage des aérosols microbiens peut-être difficile dans l'air en raison de leur faible concentration. Les filtres de centrales de traitement d'air (CTA), qui accumulent ces bioaérosols du fait des grands volumes d'air traités, représentent une alternative pour l'étude du microbiote aérien des bâtiments. Cependant, la survie des microorganismes sur ces filtres reste mal comprise. Cette étude propose d'analyser la viabilité au sein d'une communauté microbienne sur un filtre de CTA en présence d'une poussière modèle (poudre d'amidon de maïs). Pendant un an et en conditions réalistes (modèle de CTA à échelle 1), la survie et l'évolution de trois microorganismes modèles ont été suivies : Aspergillus niger (spores), Bacillus subtilis (sous forme sporulée) et Staphylococcus epidermidis (sous forme végétative), en utilisant la culture sur milieu gélosé et des méthodes de biologie moléculaire. Les résultats montrent que les microorganismes sporulés s'accumulent et sont capables de croître sur le filtre, même lorsqu'ils sont exposés à une vitesse d'air élevée. Cette croissance est concomitante à une augmentation de la teneur en eau du filtre et du gâteau de filtration et est suivie d'une phase de mortalité (diminution des dénombrements par culture). En revanche, les microorganismes sous forme végétative sont rapidement lysés et leur ADN dégradé. En conclusion, la croissance microbienne est possible à la surface des filtres de CTA et dépend fortement de la quantité d'eau disponible ainsi que de la nature des microorganismes. L'identification des microorganismes dans les échantillons de filtre, qu'elle soit par culture ou par biologie moléculaire, est donc fortement influencée par la nature des microorganismes, ainsi que l'humidité et la température dans la CTA
GWTC-4.0: Updating the Gravitational-Wave Transient Catalog with Observations from the First Part of the Fourth LIGO-Virgo-KAGRA Observing Run
No full textInternational audienceVersion 4.0 of the Gravitational-Wave Transient Catalog (GWTC-4.0) adds new candidates detected by the LIGO, Virgo, and KAGRA observatories through the first part of the fourth observing run (O4a: 2023 May 24 15:00:00 to 2024 January 16 16:00:00 UTC) and a preceding engineering run. In this new data, we find 128 new compact binary coalescence candidates that are identified by at least one of our search algorithms with a probability of astrophysical origin and that are not vetoed during event validation. We also provide detailed source property measurements for 86 of these that have a false alarm rate < 1 \rm{yr}^{-1}. Based on the inferred component masses, these new candidates are consistent with signals from binary black holes and neutron star-black hole binaries (GW230518_125908 and GW230529_181500). Median inferred component masses of binary black holes in the catalog now range from (GW230627_015337) to (GW231123_135430), while GW231123_135430 was probably produced by the most massive binary observed in the catalog. For the first time we have discovered binary black hole signals with network signal-to-noise ratio exceeding 30, GW230814_230901 and GW231226_01520, enabling high-fidelity studies of the waveforms and astrophysical properties of these systems. Combined with the 90 candidates included in GWTC-3.0, the catalog now contains 218 candidates with and not otherwise vetoed, doubling the size of the catalog and further opening our view of the gravitational-wave Universe
Thermal production of hard and soft axions
No full textInternational audienceThe axion is of particular phenomenological interest: not only does it solve the strong CP problem of QCD, but it is also a compelling candidate for light dark matter (DM). Ultra-relativistic/"hot" axions, produced in the early Universe by interacting with the Standard Model (SM) plasma, can also constitute dark radiation (DR): a measurable contribution to the energy density of the Universe characterized by the "effective number of neutrinos" Neff. More precise measurements of Neff by the Simons Observatory are on the way; as they can be used to constrain the parameter space of axion theories, a renewed look at computations of thermal axion production is in order.A proper computation of the thermal axion production rate should account for the collective effects of the medium, as they cure would-be divergences caused by soft particle exchange. Various computation schemes exist to do this: in this talk I will discuss three of them, their issues and how the theory uncertainty they induce on the rate is carried over to determinations of Neff. A specific, longstanding issue is (unphysical) production rate negativity at soft axion momenta. Along with already published results for computation schemes that alleviate the negativity issue, I will also discuss new leading-order (LO) results obtained by my collaborators and I at soft axion momenta. Those results open the possiblity for a matching with future classical lattice gauge theory (CLGT) results at nonzero axion momenta, allowing for precise results for the axion rate on a wide momentum range. Finally, I will review the updated results for the axion contribution to Neff and the associated theory uncertainty.This talk is based on 2404.06113 (by J. Ghiglieri and I) and 2601.08221 (by J. Ghiglieri, M. Laine, G.S.S. Sakoda and I)
Hadron Physics Opportunities at FAIR
No full textInternational audienceThis White Paper outlines a coordinated, decade-spanning programme of hadron and QCD studies anchored at the GSI/FAIR accelerator complex. Profiting from intense deuteron, proton and pion beams coupled with high-rate capable detectors and an international theory effort, the initiative addresses fundamental questions related to the strong interaction featuring confinement and dynamical mass generation. This includes our understanding of hadron-hadron interactions and the composition of hadrons through mapping the baryon and meson spectra, including exotic states, and quantifying hadron structure. This interdisciplinary research connects topics in the fields of nuclear, heavy-ion, and (nuclear) astro (particle) physics, linking, for example, terrestrial data to constraints on neutron star structure. A phased roadmap with SIS100 accelerator start-up and envisaged detector upgrades will yield precision cross sections, transition form factors, in-medium spectral functions, and validated theory inputs. Synergies with external programmes at international accelerator facilities worldwide are anticipated. The programme is expected to deliver decisive advances in our understanding of non-perturbative (strong) QCD and astrophysics, and high-rate detector and data-science technology
Model-independent searches of new physics in DARWIN with a semi-supervised deep learning pipeline
No full textInternational audienceWe present a novel deep learning pipeline to perform a model-independent, likelihood-free search for anomalous (i.e., non-background) events in the proposed next generation multi-ton scale liquid Xenon-based direct detection experiment, DARWIN. We train an anomaly detector comprising a variational autoencoder and a classifier on extensive, high-dimensional simulated detector response data and construct a one-dimensional anomaly score optimised to reject the background only hypothesis in the presence of an excess of non-background-like events. We benchmark the procedure with a sensitivity study that determines its power to reject the background-only hypothesis in the presence of an injected WIMP dark matter signal, outperforming the classical, likelihood-based background rejection test. We show that our neural networks learn relevant energy features of the events from low-level, high-dimensional detector outputs, without the need to compress this data into lower-dimensional observables, thus reducing computational effort and information loss. For the future, our approach lays the foundation for an efficient end-to-end pipeline that eliminates the need for many of the corrections and cuts that are traditionally part of the analysis chain, with the potential of achieving higher accuracy and significant reduction of analysis time
Feature Degradation for Frugality: A Case Study of Overleaf Application
No full textInternational audienceThe increasing energy consumption of Information and Communication Technologies (ICT) contributes significantly to global greenhouse gas emissions, requiring strategies for energy reduction. Techniques such as Diagonal Scaling and Brownout, originally proposed for managing peak loads through the degradation of quality of service, also present a promising opportunity for energy savings. However, a lack of case studies applying these techniques to real-world, production-grade applications persists. This paper presents a case study that applies feature degradation to the widely adopted, open-source Overleaf LaTeX editor, built on a microservices architecture, to reduce its energy consumption. First, an energy profile of all major services under load was conducted on the Grid'5000 testbed. This profiling identified the LaTeX compilation process as the primary energy consumer, responsible for approximately 90% of the application's total energy use. Focusing on this service, the energy savings achieved by enabling Overleaf's "fast mode", a compilation setting that reduces processing load, were then evaluated. Experimental results across various load levels demonstrate that activating this mode reduces the energy consumed per compilation request by 4% to 15%. Finally, strategies to mitigate the potential rebound effect through the integration of behavioural and economic approaches into software design are discussed.</div