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Holocene climatic changes in the Kerguelen archipelago (South Indian Ocean) based on marine and lacustrine palaeoclimatic archives
No full textInternational audienceClimatic variability in the Southern Hemisphere is largely controlled by the latitudinal position of the Southern Hemisphere Westerly Winds (SHW), whose migration influences precipitation, temperature, and Antarctic upwelling. This study presents the results of analyses of two lacustrine sediment cores from Lake Armor, located on the subantarctic Kerguelen Islands (49 • 15′S, 69 • 10′E), within the SHW belt. Lipid biomarkers (Glycerol Dialkyl Glycerol Tetraethers, n-alkanes, and their hydrogen isotopes) were used to reconstruct mean annual air temperature above freezing (MAF) and humidity conditions. These records are compared with a high-resolution diatom-based summer sea surface temperature (SST) reconstruction from marine core MD11-3353, situated 150 km southwest of Lake Armor. In the late glacial and Early Holocene, our results reveal a period of warm air temperature, comparable to current values and very warm sea surface temperature, 5°C above the current values. Around 9000 cal a BP, an abrupt transition occurred, marked by a cooling of 5°C in SST and 1.5°C in MAF, interpreted as a northward migration of the SHW and associated oceanic fronts. The Mid-to-Late Holocene period is characterized by pronounced MAF variability, including a notably warm interval between 3000 and 2000 cal a BP, when n-alkane dD suggests the prevalence of wetter conditions. Since ~250 cal a BP, a southward migration of the SHW has produced a 2.5°C rise in MAF. Our findings are overall consistent with previous studies from the Indian Ocean, but permit us to go a step further as by comparing SSTs and air temperatures. This suggests that SST is not a reliable predictor of air temperature on the Kerguelen Islands, particularly during the Early Holocene. We hence argue that Kerguelen air temperature is predominantly controlled by the position of westerly winds, as an indicator of reorganisations in air mass trajectories
TGCAT — A Tool to Analyse the Content of Sea Level Data Portals
No full textInternational audienceThe volume of tide gauge data available to the sea level community has grown substantially, with information distributed across numerous global, national, and institutional data centres. As a result, the main challenge is no longer accessing data, but identifying the most relevant dataset for a given application. Currently, more than 15 global data centres provide sea level information, each tailored to different users and use cases (e.g., real‐time monitoring, delayed‐mode analysis, monthly means). For users unfamiliar with tide gauge data, selecting the appropriate source can be difficult. Tide Gauge CATalog (TGCAT) is a software tool developed to address this challenge. It helps users discover where specific tide gauge data are available and assists data providers and centres in identifying inconsistencies, such as misreferenced stations or discrepancies in metadata. TGCAT collects metadata from global and national sea level data centres to produce intercomparable catalogues. It also allows visualisation of data availability timelines across multiple sources. Written entirely in Python and linked to an online dashboard ( www.sonel.org/tgcat ), TGCAT is designed as an open, community‐based platform. Its goal is to improve data discoverability, support better referencing practices, and help users navigate the complex landscape of tide gauge data portals
Electron paramagnetic resonance (EPR) spin trapping applied to Chardonnay wines: impact of phenolic content and ethanol
No full textInternational audienceChemical oxidation is the main cause of damage during the bottle aging of white wines. It is due to Fenton-type reaction mechanisms, i.e., a radical oxidation cascade which leads to the formation of 1-hydroxyethyl radicals (1-HER) from ethanol. An optimized electron paramagnetic resonance (EPR) approach, using the Fenton reaction and N-tert-Butyl-α-(4-pyridyl-1-oxide) nitrone as spin trap, was used to study the formation kinetic of 1-HER. Important parameters of the reaction were identified and optimized, i.e., temperature, dissolved oxygen and free bisulfite content. We found that acetaldehyde removed bisulfite without artifacts on 1-HER kinetics, making the protocol suitable for routine laboratory analysis. We then validated the log-normal model to describe the complex formation/degradation kinetic of 1-HER and used it to rank 69 Chardonnay wines in four categories. Low levels of phenolic acid, in particular the cinnamic acids such as caftaric acid, seemed to correspond to a specific formation kinetic of 1-HER (high level produced slowly). In addition, ethanol concentration (0-100 % vol.) greatly impacted its formation kinetics, whereas it had non-significant effect within the white wine range (12-15 % vol.). These results demonstrate that the response of white wines to radical oxidation in controlled and tuned conditions is a promising approach to evaluate aging potential and suggest that maturity level might modulate the 1-HER formation in Chardonnay wines.</div
On the Kantorovich contraction of Markov semigroups
No full textThis paper develops a novel operator theoretic framework to study the contraction properties of Markov semigroups with respect to a general class of Kantorovich semi-distances, which notably includes Wasserstein distances. The rather simple contraction cost framework developed in this article, which combines standard Lyapunov techniques with local contraction conditions, helps to unifying and simplifying many arguments in the stability of Markov semigroups, as well as to improve upon some existing results. Our results can be applied to both discrete time and continuous time Markov semigroups, and we illustrate their wide applicability in the context of (i) Markov transitions on models with boundary states, including bounded domains with entrance boundaries, (ii) operator products of a Markov kernel and its adjoint, including two-block-type Gibbs samplers, (iii) iterated random functions and (iv) diffusion models, including overdampted Langevin diffusion with convex at infinity potentials
Local climate change action plans in France: between formal compliance and grassroots appropriation
No full textInternational audienc
Characterization of a radiation detector based on opaque water-based liquid scintillator
No full textInternational audienceWe present the characterization of a novel radiation detector based on an opaque water-based liquid scintillator. Opaque scintillators, also known as LiquidO, are made to be highly scattering, such that the scintillation light is effectively confined, and read out through wavelength-shifting fibers. The 1-liter, 32-channel prototype demonstrates the capability for both spectroscopy and topological reconstruction of point-like events. The design, construction, and evaluation of the detector are described, including modeling of the scintillation liquid optical properties and the detector's response to gamma rays of several energies. A mean position reconstruction error of 4.4 mm for 1.6 MeV-equivalent events and 7.4 mm for 0.8 MeV-equivalent events is demonstrated using a simple reconstruction approach analogous to center-of-mass
First simultaneous measurement of the gamma-ray and neutron emission probabilities in inverse kinematics at a heavy-ion storage ring
No full textInternational audienceThe probabilities for gamma-ray and particle emission as a function of the excitation energy of a decaying nucleus are valuable observables for constraining the ingredients of the models that describe the de-excitation of nuclei near the particle emission threshold. These models are essential in nuclear astrophysics and applications. In this work, we have for the first time simultaneously measured the gamma-ray and neutron emission probabilities of 208Pb. The measurement was performed in inverse kinematics at the Experimental Storage Ring (ESR) of the GSI/FAIR facility, where a 208Pb beam interacted through the 208Pb(p,p') reaction with a hydrogen gas jet target. Instead of detecting the gamma-rays and neutrons emitted by 208Pb, we detected the heavy beam-like residues produced after gamma and neutron emission. These heavy residues were fully separated by a dipole magnet of the ESR and were detected with outstanding efficiencies. The comparison of the measured probabilities with model calculations has allowed us to test different descriptions of the gamma-ray strength function and the nuclear level density available in the literature
Supernova Pointing Capabilities of DUNE
No full textInternational audienceThe determination of the direction of a stellar core collapse via its neutrino emission is crucial for the identification of the progenitor for a multimessenger follow-up. A highly effective method of reconstructing supernova directions within the Deep Underground Neutrino Experiment (DUNE) is introduced. The supernova neutrino pointing resolution is studied by simulating and reconstructing electron-neutrino charged-current absorption on Ar and elastic scattering of neutrinos on electrons. Procedures to reconstruct individual interactions, including a newly developed technique called ``brems flipping'', as well as the burst direction from an ensemble of interactions are described. Performance of the burst direction reconstruction is evaluated for supernovae happening at a distance of 10 kpc for a specific supernova burst flux model. The pointing resolution is found to be 3.4 degrees at 68% coverage for a perfect interaction-channel classification and a fiducial mass of 40 kton, and 6.6 degrees for a 10 kton fiducial mass respectively. Assuming a 4% rate of charged-current interactions being misidentified as elastic scattering, DUNE's burst pointing resolution is found to be 4.3 degrees (8.7 degrees) at 68% coverage
Accuracy, consistency, and contextual understanding of large language models in restorative dentistry and endodontics
No full textInternational audienceObjective: This study aimed to evaluate and compare the performance of several large language models (LLMs) in the context of restorative dentistry and endodontics, focusing on their accuracy, consistency, and contextual understanding. Methods: The dataset was extracted from the national educational archives of the Colle`ge National des Enseignants en Odontologie Conservatrice (CNEOC) and includes all chapters from the reference manual for dental residency applicants. Multiple-choice questions (MCQs) were selected following a review by three independent academic experts. Four LLMs were assessed: ChatGPT-3.5, ChatGPT-4 (OpenAI), Claude-3 (Anthropic), and Mistral 7B (Mistral AI). Model accuracy was determined by comparing responses with expert-provided answers. Consistency was measured through robustness (the ability to provide identical responses to paraphrased questions) and repeatability (the ability to provide identical responses to the same question). Contextual understanding was evaluated based on the model's ability to categorise questions correctly and infer terms from definitions. Additionally, accuracy was reassessed after providing the LLMs with the relevant full course chapter. Results: A total of 517 MCQs and 539 definitions were included. ChatGPT-4 and Claude-3 demonstrated significantly higher accuracy and repeatability than Mistral 7B, with ChatGPT-4 showing the greater robustness. Advanced LLMs displayed high accuracy in presenting dental content, although performance varied on closely related concepts. Supplying course chapters generally improved response accuracy, though inconsistently across topics. Conclusion: Even the most advanced LLMs, such as ChatGPT-4 and Claude 3, achieve moderate performance and require cautious use due to inconsistencies in robustness. Future studies should focus on integrating validated content and refining prompt engineering to enhance the educational and clinical utility of LLMs. Clinical Significance: The findings underscore the potential of advanced LLMs and context-based prompting in restorative dentistry and endodontics
Toward perioperative, numerically assisted irreversible electroporation for hepatocellular carcinoma: clinical outcomes informed by numerical simulations
No full textInternational audienceObjectives Numerical evaluation of irreversible electroporation (IRE) holds significant potential to assist practitioners in planning and guiding these complex procedures. We aimed to establish a correlation between the results of retrospective numerical simulations of IRE and clinical outcomes in the treatment of hepatocellular carcinoma (HCC). Materials and methods IRE procedures conducted at our center for HCCs < 5 cm were reconstructed. Per-procedural imaging was used to generate a 3D geometric model of the tumor and its surroundings. The spatial coordinates of electrodes and treatment parameters were used to retrospectively simulate the EF using the static linear model. The proportion of tumor volume encompassed by 3D mappings of different EF magnitudes was correlated with clinical efficacy using a logistic regression algorithm. Results 31 IRE procedures were included. HCCs had a median diameter of 20 mm (range: 7-45 mm). At 1 month, 29/ 31 tumors (93.5%) showed complete ablation, but 10 of these recurred later (median delay: 7 months). The percentages of tumor coverage by EF isolines were significantly lower in the 12 cases of local IRE failure compared to the 19 cases of IRE success: 97.7% vs. 100% at 300 V/cm (p < 0.001); 89.7% vs. 100% at 400 V/cm (p < 0.001) and 82.8% vs. 95.4% at 500 V/cm (p < 0.01) with 400 V/cm being the most discriminative threshold dose (ROC-AUC: 0.904). Tumor coverage < 95% by the 400 V/cm isoline was associated with IRE failure (2-year incidence: 89% vs. 21.7%, p < 0.0001). Conclusion Numerical simulations of IRE correlate with local treatment outcomes. This study suggests that, in HCC, inadequate tumor coverage by the 400 V/cm isoline predicts and localizes recurrence. Key PointsQuestion Can the clinical outcomes of irreversible electroporation for hepatocellular carcinoma be predicted using numerical simulation of the electric field (EF) distribution? Findings Inadequate tumor coverage by simulated EF maps predicts and localizes recurrence, with 400 V/cm being the most discriminative isodose threshold (ROC-AUC > 0.9). Clinical relevance Numerical simulations of the electric field correlate with local treatment outcomes of irreversible electroporation for hepatocellular carcinoma within a computational framework compatible with clinical use. Real-time identification of insufficient tumor coverage can enable operators to adapt and optimize treatment delivery.</div