HAL-Université de Bretagne Occidentale
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Nephrectomy in autosomal dominant polycystic kidney disease: a consensus statement of the ERA Genes & Kidney Working Group
No full textInternational audienceA substantial number of patients with autosomal dominant polycystic kidney disease (ADPKD) undergo a nephrectomy, especially in workup for a kidney transplantation. Currently, there is no evidence-based algorithm to guide clinicians about which patients should undergo nephrectomy, the optimal timing of this procedure, or the preferred surgical technique. This systematic review-based</div
Mapping Soil Moisture Using Drones: Challenges and Opportunities
No full textInternational audienceDroughts are becoming more frequent, severe, and impactful across the globe. Agroecosystems, which are human-made ecosystems with high water demand that provide essential ecosystem services, are vulnerable to extreme droughts. Although water use efficiency in agriculture has increased in rec ent decades, drought management should be based on long-term, proactive strategies rather than crisis management. The AgrHyS network of sites in French Brittany collects high-resolution soil moisture data from agronomic stations and catchments to improve understanding of temporal soil moisture dynamics and enhance water use efficiency. Frequent mapping of soil moisture and plant water stress is crucial for assessing water stress risk in the context of global warming. Although satellite remote sensing provides reliable, periodic global data on surface soil moisture, it does so at a very coarse spatial resolution. The intrinsic spatial heterogeneity of surface soil moisture requires a higher spatial resolution in order to address upcoming challenges on a local scale. Drones are an excellent tool for upscaling point measurements to catchment level using different onboard cameras. In this study, we evaluated the potential of multispectral images, thermal images and LiDAR data captured in several concurrent drone flights for high-resolution mapping of soil moisture spatial variability, using in situ point measurements of soil water content and plant water stress in both agricultural areas and natural ecosystems. Statistical models were fitted to map soil water content in two areas: a natural marshland and a grassland-covered agricultural field. Our results demonstrate the statistical significance of topography, land surface temperature and red band reflectance in the natural area for retrieving soil water content. In contrast, the grasslands were best predicted by the transformed normalised difference vegetation index (TNDVI)
Optimization and Multi-Model Approaches for Maximizing Ship Decarbonization
No full textInternational audienceAligned with the International Maritime Organization's (IMO) aim to lower greenhouse gas emissions, the use of Wind-Assisted Ship Propulsion (WASP) in maritime transport is gaining increased attention. The study and optimization of WASP remain challenging due to complex physics and the high number of parameters involved. This includes interactions between aerodynamics, hydrodynamics, and structural dynamics, which require advanced multi-physics modeling. Additionally, numerous factors must be optimized, from design and control parameters to route selection, all within the variable maritime environment. Addressing these challenges demands multi-model approaches and multi-criteria optimization methods to maximize energy efficiency effectively. In this context, the laboratories of Ecole Navale, IFREMER, ENSM, and ENSTA Bretagne are collaborating on several research projects, with a selection of two thematic studies presented here.The first study is carried out as part of the SHIVA and SAWASP projects, jointly led by Ecole Navale, IFREMER and ENSTA Bretagne. The goal of these projects is to optimize the hydrodynamic performance of innovative, fully electric, Vertical-Axis Propellers (VAPs) and their optimal use in conjunction with a wind-assisted ships. To achieve this, the SHIVA project implements a multi-criteria optimization of the propeller blade-pitching laws, utilizing multi-fidelity numerical and experimental surrogate models. These optimizations enable the determination of a set of optimal pitch laws for different operating points of the propeller. In the SAWASP project, a 6-meter wind-assisted ship equipped with VAPs is developed to study the optimal aerodynamic-hydrodynamic coupling. In particular, the energy gains from using VAPs as the main propulsion system, generating a lateral anti-drift force, are studied. The use of Reinforcement Learning (RL) methods to maintain optimal ship operation performance at sea, as an uncertain environment, is also part of this project.The second study is conducted within the framework of the SOMOS project, jointly managed by ENSM and ENSTA Bretagne. The project's goal is to create and validate a set of numerical tools, that allow for rapid and precise assessment of the energy efficiency of wind-assisted ships. For the purposes of this study, a modular and comprehensive ship motion solver is formulated as an optimal control optimization problem, to evaluate, compare, and optimize energy performance. Such an approach is very complex to implement and, depending on the fidelity-level used, may require very high modeling costs. This is why most research efforts focus on specific aspects of the broader problem, often overlooking the coupling of maritime routing, ship motion analysis, and the optimization of control parameters along the planned sea route. The present work provides an innovative approach for the calculation of optimized trajectories for wind-assisted ship, by both considering the ship's maneuvering capabilities and the optimization of ship control and/or design parameters. In contrast to conventional routing methods, the proposed approach achieves high computational efficiency and relies on direct multiple shooting methods to determine optimal ship control parameters (RPM, rudder angle, etc.) and design variables (rotor Flettner or sail positioning, rudder area, etc.) along the sea route, satisfying the constraints of complying with the ship's equations of motion
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Phénomènes radiatifs et aérauliques en milieu urbain : comment la géomatique contribue à améliorer leur connaissance et leur prévision ?
No full textInternational audienceThe shape of a city, along with the layout of its streets, buildings, and green spaces, can significantly influence the flow of wind through open spaces and the amount of solar radiation received by various surfaces. Wind patterns and solar radiation directly impact urban overheating and the dispersion of pollutants, thereby affecting the quality of the urban environment and the comfort of its residents. The development of geomatics-based models that directly correlate characteristics of the built environment with wind and sunlight fields can aid in informing political decision-making. The aim of this article is to highlight the relationships between the calculation of specific physical variables and geomatics methods, to describe experiments in modeling the radiative and aeraulic physics of urban areas within the context of GIS, and to identify some of the scientific and technical challenges that remain in this field.La forme de la ville, l’agencement de ses rues, de ses bâtiments et de ses espaces verts peuvent modifier significativement la circulation du vent dans l’espace ouvert et la quantité de rayonnement solaire reçue par les bâtiments et les surfaces. Le vent et le rayonnement affectent directement la surchauffe urbaine et la dispersion des polluants en ville, et par conséquent la qualité de l’environnement urbain et le confort des habitants. Développer, dans le contexte de la géomatique, des modèles qui permettent de relier directement des caractéristiques de l’environnement construit à des champs de vents ou d’ensoleillement permet d’éclairer la décision politique. Cet article vise à mettre en évidence les relations entre le calcul de certaines variables physiques et des méthodes de géomatique, à décrire des expériences de modélisation de la physique radiative et aéraulique de la ville dans le contexte du SIG, et également à relever certains verrous scientifiques ou techniques qui subsistent dans le domaine
SFI Smart Ocean dataset for underwater acoustic communications (SODAC)
No full textInternational audienceUnderwater acoustic data communication is an enabling technology for operations such as environmental monitoring, exploitation of ocean resources, and autonomous inspection of offshore infrastructure. The only viable technique for subsea telemetry over longer distances is by encoding the information in sound waves. However, the influence of the ocean environment on sound propagation can be harsh, resulting in a poor performance of protocols designed for terrestrial radio-frequency communications. This justifies active research on physical-layer algorithms and network protocols that are robust to acoustic propagation in the oceans. Factors that hamper progress are the lack of accepted standard test channels and hard-to-obtain field data. A majority of academic institutions cannot afford at-sea experimentation, resorting to simplified channel models to test new protocols. To make field data accessible to a wider audience, this article presents a dataset of hydrophone recordings of communication and channel probe waveforms collected in an enclosed fjord environment. The SFI Smart Ocean Dataset for Acoustic Communications (SODAC) allows users to test communication algorithms on in situ data, with opportunities to publish reproducible results that set a realistic benchmark for other researchers
Atosan, a new exopolysaccharide secreted by a Vibrio alginolyticus strain isolated from a deep-sea hydrothermal vent environment
No full textInternational audienceBacteria are able to colonize various environments, even the most hostile ones, due to their ability to synthesize an extracellular protective matrix. Bacteria isolated from deep-sea hydrothermal vent environments have been identified as very effective producers of polysaccharide-rich matrix. In particular, exopolysaccharides (EPS) synthesized by Vibrio marine species have shown to be composed of uronic acid and hexosamine residues, similarly to glycosaminoglycans, components of mammalian tissues. In the present study, the fine structure of a new high-molecular weight EPS, named atosan, secreted by the deep-sea hydrothermal vent bacterium Vibrio alginolyticus AT1219 strain, was determined. A complementary analytical approach, including Nuclear Magnetic Resonance spectroscopy and mass spectrometry was applied to elucidate the repeating unit of the polysaccharide. A linear pentasaccharide with a unique monosaccharide sequence: [→3)-α-d-Galp-(1→3)-β-d-GalpA-(1→3)-β-d-GlcpNAc-(1→4)-α-d-GalpNAc-(1→4)-β-d-GlcpA-(1→] was described. In parallel, the genome sequence was investigated to get insight into the genetic mechanisms of atosan biosynthesis. Amongst eight clusters assigned to carbohydrate biosynthesis, three of them were closely related to the biosynthesis of the extracellular polysaccharide. Determination of the fine structure of atosan is a prerequisite step to better understand the relationship between its structure and resulting functional properties
Near Steady Late Pleistocene Tropical Denudation Rates in SW Madagascar
No full textInternational audienceDenudation is a key parameter controlling the evolution of the Earth's surface, the production of soils, the stability of relief, or the long‐term evolution of climate. Climate fluctuations conversely have a strong impact on denudation, but these complex feedback mechanisms are still under‐constrained. To better predict future changes that will affect our habitat and understand the links between climate and denudation, precise quantification of paleo‐denudation rates is required. In this work, we measure cosmogenic radionuclides (10Be) in turbidites of a well‐dated marine sedimentary core recovered in the Mozambique Channel to provide a 900‐ka long near‐continuous record of paleo‐denudation rates over the 100‐ka climatic cycles. Neodymium isotopes and heavy mineral analysis were used to provide constraints on the provenance of terrigenous sediments exported from Madagascar to the studied site and show that temporal variations in sediment provenance are limited and decoupled from climatic cyclicity. Our 10Be‐based paleo‐denudation rates are in the same order as modern rates, ranging from 17.4 ± 5.8 mm/ka to 73.9 ± 29.4 mm/ka (1 standard deviation), and do not show major variations through the Middle and Late Pleistocene. Importantly, we did not identify a systematic significant impact of glacial/interglacial cyclicity on denudation rates. Denudation of this subtropical island may instead have been controlled by variability of monsoon intensity associated with shifts in the Inter Tropical Convergence Zone, but this interpretation remains speculative at this stage as it cannot be recorded within the resolution of cosmogenic‐derived denudation rates
