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Cost-utility analysis of a web-based interactive patient education platform: evidence from a randomized clinical trial for end-stage renal disease patients
No full textInternational audienceObjectives: Chronic kidney disease and its most severe complication, end-stage renal disease (ESRD), represents an estimated financial burden of €4.4 billion in 2021 in France. Therapeutic patient education (TPE) improves ESRD management and health outcomes. This study explored whether providing access to an interactive web-based TPE platform with community features was cost-effective.Methods: A within-trial cost-utility analysis was carried out over an 18 months horizon, using data from the PIC-R (Plateforme Interactive Communautaire—dialyse et transplantation Rénale) trial. ESRD or post-transplant patients were randomized 1:1:1 to a control group with no specific TPE program (Control), an intervention group with online TPE (e-TPE) and an intervention group with online TPE coupled with community features such as a patient forum and a chatroom with both patients and health care professionals (e-TPE + chat). The outcome measure was the cost per quality-adjusted life-year (QALY) and per year of full capability (YFC). Both intention-to-treat (ITT) and per protocol (PP) analyses were conducted, and missing data were handled using multiple imputation and selection models. Sensitivity analyses were performed.Results: Among the 815 patients assessed for eligibility across 12 French centres, a total of 549 patients were included in the economic analysis: 186 in the Control group, 189 in the e-TPE group and 174 in the e-TPE + chat group. The e-TPE group demonstrated cost savings and slightly higher QALYs compared to the control group, making e-TPE dominant. Conversely, the e-TPE + chat intervention resulted in higher costs without substantial effectiveness gains, making it not cost-effective.Conclusions: e-TPE was deemed cost-effective for ESRD patients, while e-TPE + chat was not. Web-based platforms improve ESRD management when targeted to likely users
Templex for Lagrangian dynamics in the Southwestern Atlantic
No full textInternational audienceThis work presents the first application of the templex approach to observational datasets, using Lagrangian trajectories obtained from satellite altimetry in the ocean. The templex is a recent topological construct that extends classical ideas from template theory to higher-dimensional systems. Unlike other methods in Topological Data Analysis, which lack flow information, a templex encodes both the structure of phase space through a BraMAH cell complex and the organization of flow cycles upon it through a directed graph defined on its highest-dimensional cells. As shown in earlier works, the description of flows in phase space indirectly enables a description of fluid flows in physical space, since particles sharing the same dynamics are known to move coherently. Particle sets in the Southwestern Atlantic Ocean are analyzed, revealing that the Lagrangian finite-time dynamics in this region can be related to those produced by a nonautonomous meandering jet model. We distinguished non-mixing (regular) islands from the chaotic sea. The results are also compared to those obtained from metric methods describing material transport in fluid flows and to the spatial organization of chlorophyll-a concentration. The seasonal variability of chaotic dynamics is also discussed
Atmospheric Turbulence in the Upper Troposphere and Lower Stratosphere From Airborne Observations During the DCOTSS Field Campaign
No full textInternational audienceTurbulence in the upper troposphere and lower stratosphere (UTLS) plays an important role in total energy dissipation and in the transport and mixing of heat, momentum, and atmospheric constituents while also posing significant hazards to aviation. In this study, we leverage high-altitude in situ observations from the NASA Dynamics and Chemistry of the Summer Stratosphere (DCOTSS) field campaign—including data acquired near convection and at altitudes rarely covered by commercial aircraft—to investigate turbulence and its potential link to UTLS composition. We find that strong turbulence occurs frequently within 2 km above the tropopause, which corresponds to 1–2 km above deep convective cloud tops, particularly within moist convective plumes characterized by enhanced water vapor. The occurrence of strong turbulence increases with proximity to convection with elevated frequencies persisting out to 100 km from convective cores. In particular, enhanced turbulence potential occurs near UTLS convective outflows, which is supported by favorable environmental factors such as strong vertical wind shear, flow deformation, and large divergence tendencies. Furthermore, although turbulence intensity and water vapor are generally weakly correlated, positive correlations occur more frequently near the tropopause and under strong vertical wind shear, suggesting that turbulent mixing may contribute to localized stratospheric moistening under certain atmospheric conditions. The findings demonstrate the utility of high-altitude in situ observations for advancing our understanding of UTLS turbulence and its influence on atmospheric composition, with implications not only for climate but also for future high-altitude aviation applications
δ 13 C carbon isotopic composition of CO 2 in the atmosphere by Lidar. A preliminary study with a CDIAL system at 2-µm
No full textInternational audienceOur understanding of the global carbon cycle needs for new observations of CO2 concentration at different space and time scales but also would benefit from observations of additional tracers of intra-atmospheric or surface-atmosphere exchanges to characterize sources and sinks. Lidar is a well-known promising technology for this research as it can provide, at the same time, structure of the atmosphere, dynamics and composition of several trace gas concentration. In this framework, a coherent differential absorption lidar (CDIAL) has been developed at LMD to measure simultaneously and separately 12CO2 and 13CO2 isotopic composition of CO2 in the atmosphere. It also provides the wind speed along the line of sight of the laser with an additional Doppler ability. This paper investigates the methodology of three wavelengths DIAL in the spectral domain of 2-µm to obtain range-resolved CO2 isotopic ratio δ13C. The set-up of the lidar as well as the signal processing is described in details. First atmospheric measurements along three days are achieved in the surface layer above the suburban area of Ecole Polytechnique campus, Palaiseau, France. Typical performances of the instrument (median values along 70 h of measurement) with 10 min of time averaging show: (1) a precision around 0.6 % for 1.2 km range resolution for 12CO2 mixing ratio (2) a precision around 3.2 % for 1.6 km range resolution for 13CO2 mixing ratio. In situ co-located gas analyser measurements are used to correct for biases that are explained neither by the spectroscopic database accuracy nor the signal processing and will need further investigation. Nevertheless, this preliminary study enables to make a useful state of the art for current lidar ability to provide δ13C measurements in the atmosphere with respect to geophysical expected anomalies and to predict the necessary performances of a future optimized instrument
Avis du conseil scientifique du comité de bassin Seine-Normandie sur le projet de mise à grand gabarit de la liaison fluviale entre Bray-sur-Seineet Nogent-sur-Seine
No full textCet avis du conseil scientifique porte sur le projet de mise à grand gabarit de la liaison fluviale entre Bray-sur-Seine et Nogent-sur-Seine, visant à permettre la circulation de péniches de 2500t (alors que des péniches de 600 t peuvent déjà naviguer), ce qui implique d’aménager un tronçon sur 28,5 km.Il apparaît clairement, d’après les éléments du projet, les avis de l’Autorité environnementale et de l’OFB et la contre-expertise du Secrétaire général pour l’investissement, que ce projet ne répond pas aux ambitions de la Stratégie d’adaptation du bassin au changement climatique, et contribue à amplifier les dommages et risques vis-à-vis des milieux aquatiques, sans que les bénéfices en termes d’atténuation soient tangibles. Il implique notamment de détruire une des plus importantes zones humides de l’hexagone et zone d’expansion naturelle des crues de la Seine, et impacte directement le lit de la Seine, la nappe alluviale ainsi que leurs interactions
Débris plastiques sur les berges de Seine – Dynamiques de stockage, remobilisation et fragmentation
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Three Worlds in One: Venus as a Natural Laboratory for the Effect of Rotation Period on Atmospheric Circulation
No full textInternational audienceBecause of its rotation period of 243 days, Venus is considered a slowly rotating planet. However, its persistent superrotating atmospheric jets, which increase in speed from surface to cloud tops, effectively set a faster rotation speed than the surface rotation. Using the Venus Planetary Climate Model and wind measurements taken by the Pioneer Venus entry probes, we show that the Rossby radius of deformation of the atmosphere varies with height. The atmosphere falls into three circulation regimes: (1) from the surface to 20 km, the Rossby radius of deformation exceeds the planetary radius and no Rossby waves form; (2) from 20 to 50 km, the tropical Rossby radius becomes smaller than the planetary radius, and a circulation regime characterized by a superrotating equatorial jet and mid-latitude Rossby gyres appears; (3) from 50 to 70 km, the extratropical Rossby radius becomes smaller than the planetary radius, the jet develops mid-latitude maxima, and the Rossby gyres shift to high latitudes. Studies of exoplanetary circulation regimes as a function of rotation period have repeatedly shown a similar progression. While observing the circulations of exoplanets to confirm these predictions is not currently possible, the presence of different circulation regimes on Venus and their dependence on altitude could be tested by observing campaigns. Such evidence would be the first observational support for the theory connecting differences in planetary rotation periods to circulation regime transitions and would ground predictions of exoplanet circulations in a validated framework
Gradient Flows of Potential Energies in the Geometry of Sinkhorn Divergences
No full textWe analyze the gradient flow of a potential energy in the space of probability measures when we substitute the optimal transport geometry with a geometry based on Sinkhorn divergences, a debiased version of entropic optimal transport. This gradient flow appears formally as the limit of the minimizing movement scheme, a.k.a. JKO scheme, when the squared Wasserstein distance is substituted by the Sinkhorn divergence. We prove well-posedness and stability of the flow, and that, in the long term, the energy always converges to its minimal value. The analysis is based on a change of variable to study the flow in a Reproducing Kernel Hilbert Space, in which the evolution is no longer a gradient flow but described by a monotone operator. Under a restrictive assumption we prove the convergence of our modified JKO scheme towards this flow as the time step vanishes. We also provide numerical illustrations of the intriguing properties of this newly defined gradient flow
Bubbles and Crashes with Partially Sophisticated Investors
No full textInternational audienceWe analyze bubbles and crashes in a model in which some investors are partially sophisticated. While the expectations of such investors are endogenously determined in equilibrium, these are based on a coarse understanding of the market dynamics. We highlight how such investors may endogenously switch from euphoria to panic and how this may lead to equilibrium bubbles and crashes even in a purely speculative market in which information is complete and it is commonly understood that the bubble cannot grow forever. We also show how this setting can match stylized empirical facts, and we investigate whether bubbles may last longer when the share of fully rational traders increases
Pressure-Liquefied Ammonia Jet Dispersion: Multi-Model Intercomparison Using Desert Tortoise and FLADIS Field Data
No full textInternational audienceThis paper presents the findings of an international model inter-comparison exercise that was undertaken in the period 2021-2024 to assess the performance of atmospheric dispersion models for simulating releases of pressure-liquefied ammonia. The exercise used data from ammonia field trialsdating from the 1980s and 1990s: the Desert Tortoise and the FLADIS trials. Concentration data from two arcs of sensors in the Desert Tortoise trials and three arcs of sensors in the FLADIS trials were used. Twenty-one independent modelling teams from North America and Europe participated in the exercise and provided in total twenty-seven sets of results from a range of different models, including empirically-based nomograms, integral, Gaussian puff, Lagrangian particle, and Computational Fluid Dynamics (CFD) models. The work is novel in presenting the results from such a large cohort of models,examining specifically the dispersion behaviour of ammonia. This is particularly relevant at the current time, given the growing international interest in using ammonia as a clean energy vector and shipping fuel.The study found that the agreement between model predictions and measurements (as determined by performance measures such as geometric mean bias and geometric variance) varied between different models. At any downwind distance, the range in predicted plume arc-max concentrations spanned arange of up to one or two orders of magnitude about the measurements. Several modelling teams used the same models and, in most cases, their predictions differed. Given appropriate inputs, most models generally predicted concentrations that agreed with the data within commonly-used model acceptance criteria. There was no single class of model that provided superior predictions to others; predictions from several empirically-based nomograms, integral, Gaussian puff, Lagrangian particle, and CFD models were all in close agreement with the data (as defined by the model acceptance criteria).The findings of the exercise are being used to help plan a programme of future ammonia experiments in the USA, called the Jack Rabbit III trials. The results are also useful for assessing the performance of models that may be applied to assess risks at ammonia facilities, and for emergency planning and response