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Dephasing of islet building between leeward and windward reef-rim sides, Bora Bora Island, Society Archipelago, central South Pacific
No full textInternational audienceDefining the timing and accretional mode of low-lying, reef-rim islets over the recent past is a prerequisite for better understanding their future dynamical behaviour in response to rapid rise in sea level and increasing storminess. In high island settings where reliefs locally act as protection against meteorological hazards, establishing the level of vulnerability in the face of global warming remains an important issue. At Bora Bora, a high volcanic island (French Polynesia), internal lithostratigraphy of two selected islets - Motu Tevairoa, leeward, west-north-western side; Motu Tofari, windward, east-north-eastern side - from the barrier-reef rim was reconstructed from four excavated cross-sections. Motu Tevairoa exhibits at the ocean-facing shoreline, pebble- and sand-supported facies abruptly grading into sand-dominated facies inwards. Motu Tofari is dominated by boulder-pebble facies along the oceanic border. U/Th dating was conducted from a collection of 48 coral clasts, in order to reconstruct the timing of islet building. Motu Tevairoa appears to have started to develop by about 2300-2200 cal yr BP from a central islet depocentre laterally extending over time. At the ocean-facing settings, deposition was initiated by about 1600 cal yr BP. By contrast, on Motu Tofari, deposition along the oceanic shoreline, occurred as soon as 3100 cal yr BP. A time lag of approximately 1000 years seems to separate islet accretion between the windward and leeward sides. This strongly suggests that winter storms in the southern hemisphere and those generated from an easterly direction in the northern hemisphere, mid latitudes have played a major role in periodically supplying the north-eastern rim in coral detritus while the western side was occasionally nourished by distant-source swells derived from the north-western sectors. In both settings, the main phases of islet building occurred during the late Holocene sea-level drop. This questions the ability of islets at Bora Bora to adapt to a rapid rise in sea level in the near future
A slot-based energy storage decision-making approach for optimal Off-Grid telecommunication operator
No full textPreprint version at arXiv:2412.01731 Accepted journal version at https://authors.elsevier.com/a/1lU75VwcQvf4yInternational audienceThis paper proposes a slot-based energy storage approach for decision-making in the context of an Off-Grid telecommunication operator. We consider network systems powered by solar panels, where harvest energy is stored in a battery that can also be sold when fully charged. To reflect real-world conditions, we account for non-stationary energy arrivals and service demands that depend on the time of day, as well as the failure states of PV panel. The network operator we model faces two conflicting objectives: maintaining the operation of its infrastructure and selling (or supplying to other networks) surplus energy from fully charged batteries. To address these challenges, we developed a slot-based Markov Decision Process (MDP) model that incorporates positive rewards for energy sales, as well as penalties for energy loss and battery depletion. This slot-based MDP follows a specific structure we have previously proven to be efficient in terms of computational performance and accuracy. From this model, we derive the optimal policy that balances these conflicting objectives and maximizes the average reward function. Additionally, we present results comparing different cities and months, which the operator can consider when deploying its infrastructure to maximize rewards based on location-specific energy availability and seasonal variations. Experimental results show that our proposed algorithm outperforms classical methods in large-scale scenarios. While Relative Value Iteration algorithm remains competitive on smaller instances, its convergence time increases significantly under strict precision requirements (e.g., Ɛ < 10^{-10}). In contrast, our method maintains both speed and robustness, solving MDPs with up to 2.10^5 states and 100 actions in under one hour, whereas standard approaches exceed 10^4 seconds
Cuspidal -modular representations of distinguished by a Galois involution
No full text42 pagesInternational audienceLet be a quadratic extension of non-Archimedean locally compact fields of residual characteristic with Galois automorphism , and let be an algebraically closed field of characteristic . We reduce the classification of -distinguished cuspidal -representations of to the level setting. Moreover, under a parity condition, we give necessary conditions for a -selfdual cuspidal -representation to be distinguished. Finally, we classify the distinguished cuspidal -representations of having a distinguished cuspidal lift to
Homocitrulline is Associated with Cardiovascular Outcomes in Non-Dialysis Patients with CKD
No full textInternational audienceBackground Protein carbamylation contributes to an increase in the cardiovascular risk in certain patient populations (e.g. in patients with chronic kidney disease (CKD) because of elevated urea concentrations). Homocitrulline (HCit) is a biomarker of overall protein carbamylation. In a study of a large cohort of non-dialysis patients with a confirmed diagnosis of CKD and an estimated glomerular filtration rate (eGFR) <60mL/min/1.73m 2 , we sought to determine whether the serum HCit concentration was associated with adverse cardiovascular outcomes and all-cause mortality. Methods CKD-REIN is a prospective cohort of CKD patients with an eGFR<60mL/min/1.73m 2 . The baseline serum HCit concentration was centrally measured. The 2,195 patients included in the analysis were divided into tertiles (T) groups according to the baseline HCit concentration (T1<292, T2=[292–429], and T3≥430 µmol/mol lysine). Adjusted Cox proportional hazards models were used to estimate hazard ratios (HRs) for the first major adverse cardiovascular event (MACE) and death before kidney replacement therapy (KRT). Results Among the 2,195 included patients, the median age was 68, and the mean eGFR was 34.6 mL/min/1.73m 2 . The median [IQR] serum HCit was 352[266–481] µmol/mol lysine. The HCit concentration was correlated with the eGFR (r=-0.57) and the urea concentrations (r=0.73). In an adjusted linear regression model, the HCit concentration was independently and positively associated with age, eGFR decrease, urea, anemia, baseline prescription of diuretics, and negatively associated with male sex and an elevated urinary albumin-to-creatinine ratio. The adjusted HR[95%CI] for MACEs as a function of the baseline HCit concentration was 1.32[0.96–1.84] for T2 and 1.63[1.16–2.30] for T3, compared to T1. The risk of death before KRT as a function of the baseline serum HCit concentration was 2.09[1.45–3.03] for T3 and 1.48[1.04–2.11] for T2, compared to T1. Conclusions Our analysis of a large cohort of patients with CKD demonstrated that the serum HCit concentration was associated with a greater likelihood of a MACE and death. To confirm causality, further studies of therapeutic interventions for preventing or reducing carbamylation are now warranted
Super‐reduced Polyoxometalates in Aqueous Solution: Historical Perspectives and Current Challenges
No full textInternational audiencePolyoxometalates (POMs) represent a versatile class of molecular metal oxides often described as “electron reservoir” or “electron sponge” due to their remarkable ability to store and transfer electrons. These properties make them highly attractive for applications in electrochemical‐energy storage systems, such as batteries or supercapacitors. This contribution reports the historical milestones and modern advancements of the super‐reduced POMs in aqueous solution, focusing on systems constructed from molybdenum and tungsten centers. Particular attention is given to the pioneering work of Souchay and his students, who, between the 1960s and 1980s, published a series of articles (originally in French) that highlighted the exceptional super‐reducibility of Keggin‐type POMs. The aim of this work is to guide researchers interested in using POMs for electrochemical energy storage applications, and to identify future challenges in the chemistry of super‐reduced POMs
Decatungstate-Based Ionic Liquid Highly Active Under Mild Conditions for Upgrading Recalcitrant Humins from Biorefineries
No full textInternational audienceAmong all the materials resulting from the recovery of biomass, humin co-products are produced today on a large scale, particularly in the sugar industry and biorefineries. Humins formation, with typical yields between 10 and 50 wt %, significantly reduces the efficiency and economic viability of the processes. With their complex structure, their low solubility and their low reactivity, their valorization constitutes a real challenge. This paper aims to establish the proof-of -concept for the transformation of recalcitrant humins into high value-added biobased products using polyoxometalate-based ionic liquids (POM-ILs) under "mild" conditions. In this contribution the POM-IL (P6,6,6,14)4[W10O32] is used in the presence of H2O2, at atmospheric pressure and 90°C for just one hour.This system proved to be a powerful oxidizing catalyst for extensive depolymerization of humins and their valorization into platform molecules. Under these conditions, the humin powder underwent an almost complete oxidative dissolution in the 94-99 % yield range, leading to the formation of various carboxylic acids of industrial interest and sugars.</p
Prediction of incidence of hypertension in France and associated factors: results from the CONSTANCES cohort
No full textInternational audienceEstimating hypertension incidence and improving screening in general population could enhance blood pressure control and decrease cardiometabolic risks. Identifying those likely to develop hypertension is essential. Our study focused on predicting onset hypertension and its incidence based on initial characteristics. Methods: We utilized data from the French prospective CONSTANCES cohort, including volunteers assessed twice over 5 years up to 31 December 2019, who were initially free from hypertension. Hypertension was defined as having a SBP at least 140 mmHg or DBP at least 90 mmHg during the second checkup or if antihypertensive medication was prescribed. We calculated annual incidence rates among subgroups and used machine learning models to identify predictors of hypertension. The impact of changes in BMI was analyzed using logistic regression. Results: Of the 11 112 participants (average age 47.5 ± 12 years), 1929 (17.4%) developed hypertension within an average of 5.2 years, with 383 on medication. The incidence rate was 3.4 new cases per 100 person-years, rising with age and consistently higher in men (4.3 vs. 2.8). A blood pressure (BP) threshold of 130 mmHg predicted 70% of new cases. One-point BMI reduction significantly reduced hypertension risk by 16%, regardless of initial BMI and SBP levels. Conclusion: The study reports a notable hypertension incidence of 3.4 new cases per 100 person-years, particularly among those with SBP over 130 mmHg, highlighting the need for regular screening. Early diagnosis and control can mitigate hypertension's adverse effects, emphasizing the crucial role of preventive measures like BMI reduction
emIAM v1.0: an emulator for integrated assessment models using marginal abatement cost curves
No full textInternational audienceWe developed an emulator for integrated assessment models (emIAM) based on a marginal abatement cost (MAC) curve approach. Drawing on the output of IAMs in the Exploring National and Global Actions to reduce Greenhouse gas Emissions (ENGAGE) Scenario Explorer and the GET model, we derived an extensive array of MAC curves, encompassing 10 IAMs, at the global and regional levels for 10 regions; three gases (CO 2 , CH 4 , and N 2 O); eight portfolios of available mitigation technologies; and two emission sources. We tested the performance of emIAM by coupling it with the simple climate model ACC2 (ACC2-emIAM). Our analysis showed that the optimizing climate-economy model ACC2-emIAM adequately reproduced a majority of the original IAM emission outcomes under similar conditions. This can facilitate systematic exploration of IAMs with small computational resources. emIAM holds the potential to enhance the capabilities of simple climate models as a tool for calculating cost-effective pathways directly aligned with temperature targets.</div