HAL-Université de Bretagne Occidentale
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Four contemporary problems in extreme value analysis
No full textThis article gives a summary of recent results on extreme value analysis that were presented at the Journées MAS 2024 in Poitiers. We first set the general background and motivation for these results, and we then discuss partial solutions to four contemporary problems in extreme value analysis: the construction of bias-reduced estimators of the Expected Shortfall (or Tail-Valueat-Risk) at extreme levels, extremal regression and inference in the presence of dependent data, multivariate inference about extreme quantiles using an analogue of the classical ANOVA method in regression, and improved estimation of tail risk measures using nonparametric resampling of multivariate Generalized Pareto distributions
The concept of 'nature-based solutions' applied to urban coastal risks: A bibliometric and content analysis review
No full textInternational audienceNature-based solutions (NBS) are increasingly proposed as a response to the growing vulnerability of coastal areas to the risks of coastal erosion and flooding. These solutions rely on the functioning of ecosystems to mitigate the effects of coastal hazards. However, the ability of ecosystems to act as buffer zones is being compromised due to increasing urbanization in coastal areas. The implementation of NBS in urbanized coastal areas is becoming a major challenge for our societies, as coastal cities densely concentrate populations and valuable assets. This study has two main objectives: (1) to provide a structured overview of current NBS research and (2) to explore whether and how NBS are utilized in urban coastal risk management. A critical review of the literature serves as a foundation for understanding how NBS is conceptualized, identifies the factors contributing to the ambiguity of the term, and proposes five key elements for defining NBS. A systematic review of 3384 publications from Scopus shows that coastal issues represent a secondary focus in NBS research (14%). Coastal NBS studies primarily address coastal erosion and flooding exacerbated by sea level rise through natural coastal ecosystems. While urban issues related to climate change are at the heart of NBS research, the urban dimension has very little connection with coastal NBS. This article highlights the need for a multifaceted response to manage coastal risks in coastal cities, combining hard and soft engineering (hybrid solutions), inshore and offshore NBS, coastal and stormwater NBS, and regulating urbanization in flood-prone areas. The application of NBS in coastal risk management calls for incorporating natural coastline dynamics into land-use planning and rethinking our fixed modes of coastal occupation. This article provides keys to understanding the concept of NBS to facilitate its integration into coastal risk management plans
Novel settlement substrates for European flat oyster (Ostrea edulis) restoration
No full textInternational audienceThe flat oyster Ostrea edulis L., once common in the North Sea, declined rapidly due to intensive fisheries in the late 19th century and disease outbreaks at the beginning of the 20th century and is now listed as 'threatened' or 'declining,' with restoration of oyster beds now included in European directives and national plans. For oyster restoration, availability of suitable substrate is required to ensure successful settlement of oyster larvae. Off-shore windfarms are good candidates for restoration as bottom disturbance is not allowed and hard substrate is present in the form of so-called scour protection. This can provide settlement substrate for oyster larvae. In addition to the rock material that currently makes up the scour protection, studies focus on finding alternative and moldable materials that stimulate settlement. The aim of this study was to identify flat oyster larvae settlement preferences for different substrate materials. Oyster settlement on conventional scour protection rock (granite and eclogite), and currently used sandstone and concrete were compared to new types of scour protection rock (marble and limestone). In addition, three new substrates were included in the tests: a coating based on fine ground oyster shells (BESE-reef paste), substrate made of sandy dredged sediment (Geowall) and a bioinspired glue that binds crushed oyster shell fragments together (SeaCrete). Flat oyster larvae were exposed to the substrates in two hatchery experiments as well as under realistic, challenging field conditions. Flat oyster larvae settled on all substrates, with the lowest spat density on eclogite, granite and Geowall and the highest spat density on the two novel substrates SeaCrete and BESE-reef paste. These results promise to enhance native European oyster bed restoration with limited environmental impact as the novel substrates have low CO2 footprints and make use of wasted shells from the seafood industry
Ensemble Filter on dynamically driven RKHS: Application to a Multilayer Quasi-Geostrophic ocean model
No full textEstimating the ocean’s dynamic state, particularly at the mesoscale, is challenging due to the non-linear nature of ocean processes. Traditional data assimilation methods like optimal interpolation (OI) and four-dimensional variational assimilation (4D-Var) improve ocean state estimates but face trade-offs: OI is computationally efficient but struggles with small-scale features, while 4D-Var is more accurate but computationally demanding. Ensemble methods offer a compromise, with ensemble Kalman filters assuming Gaussianity and particle filters limited by high-dimensional systems.This article introduces a novel ensemble filter using a Reproducing Kernel Hilbert Spaces (RKHS) framework, embedding observables in time-evolving RKHSs to relax Gaussianity assumptions and provide computational efficiency comparable to 3D-Var while addressing 4D-Var problems. A key innovation is a tiled assimilation approach that enhances the ensemble's physical properties over time. Applied to a quasi-geostrophic model of the North Atlantic with synthetic sea surface height (SSH) data, this RKHS-based filter accurately assimilates observations with non-Gaussian noise, improving both the accuracy and efficiency of ocean state estimations in complex systems
Chélateurs azamacrocycliques de cations métalliques : exemples d’applications en biologie
No full textInternational audienc
Defining motility: the uses, operationalisations and limits of a concept
No full textInternational audienceThe aim of this review is to examine the definition and use of the concept of motility. Based on published and unpublished literature in the humanities and social sciences to date, the PRISMA method has been used. The Google Scholar electronic database was consulted in French and English. This concept has been the subject of empirical research and theoretical criticism. Among the 60 references selected, the literature reveals changes in the definition of motility and criticisms of the scope and measurement of the concept. Motility corresponds to an entity’s ability to move from one place to another within a social and spatial space. It can be used to study motivations for travel and inequalities in mobility, depending on socio-demographic conditions and context. This concept is widely applied to qualitative studies, and less so to quantitative ones. Its definition has been enriched between 2002 and the present day. Its three-dimensional composition (access, skills, appropriation) remains the subject of consensus, although there are divergences between the theory and its operationalisation. Other questions about the link between mobility and motility remain unanswered. Finally, control plays a key role in motility, while influencing mobility choices and experiences with predictive potential for daily mobility
APLOSE: A web-based annotation platform for underwater passive acoustic monitoring
No full textInternational audienceEmerging detection and classification algorithms based on deep learning models require manageable large-scale manual annotations of ground truth data. To date, the challenge of creating large and accurate annotated datasets of underwater sounds has been a major obstacle to the development of robust recognition algorithms. APLOSE (Annotation PLatform for Ocean Sound Explorers) is an open-source, web-based tool which facilitates collaborative annotation campaigns in underwater acoustics. The platform was used to carry out research projects on inter-annotator variability, to build training and testing data sets for detection algorithms and to perform bioacoustics analysis on noisy datasets. In the future, it will enable the creation of high-quality reference datasets to test and train the new detection and classification algorithms
Open vs. Robot-Assisted Artificial Urinary Sphincter Implantation in Women with Stress Urinary Incontinence: A Multicenter Comparative Study
No full textInternational audienceBackground: The artificial urinary sphincter has been an effective treatment for stress urinary incontinence caused by intrinsic sphincter deficiency in women. However, the use of this device has been limited by the technical difficulties and risks associated with the open implantation procedure. Preliminary studies using robotic techniques have shown promising results, but only one small study has compared robotic to open procedures. This study aims to compare the outcomes of robotic and open artificial urinary sphincter implantation in women with stress urinary incontinence due to intrinsic sphincter deficiency in a large multicenter cohort. Methods: Data were collected retrospectively from female patients who underwent open or robot-assisted artificial urinary sphincter implantation from 2006 to 2020 at 12 urology departments. The primary outcome was the rate of complications within 30 days after surgery, graded using the Clavien-Dindo Classification. Perioperative and functional outcomes were compared between the two groups. Results: A total of 135 patients were included, with 71 in the robotic group and 64 in the open group. The open group had a higher rate of intraoperative complications (27.4% vs. 12.7%; p = 0.03) and postoperative complications (46.8% vs. 15.5%; p < 0.0001). More patients in the robotic group achieved full continence (83.3% vs. 62.3%; p = 0.01). The open group had higher explantation (27.4% vs. 1.4%; p < 0.0001) and revision rates (17.5% vs. 5.6%; p = 0.02). The estimated 1-year explantation-free survival rate was higher in the robotic group. (98.6% vs. 78.3%; p = 0.001). Conclusions: Robot-assisted implantation may reduce perioperative morbidity and improve functional outcomes compared to open implantation in women with stress urinary incontinence
Frictional dissipation of incident waves over a spatially varying rough barrier reef in Mayotte, Indian Ocean
No full textInternational audienceCoral reefs serve as a highly effective natural barrier against incom ing ocean waves. However, climate change and human induced degradations are threatening reefs, reducing their capacity to protect coastal populations by di minishing the frictional processes that dissipate wave energy. The most common approach to represent wave energy dissipation through bottom friction relies on the estimation of a representative roughness length, whose definition on coral environments remains to be elucidated. As a consequence, a generic parametrization for friction processes on coral reef systems is still lacking. In this study, high resolution hydrodynamical and topographical data collected at the South West barrier reef of Mayotte, Indian Ocean, were used to perform an estimation of wave friction. The hydraulic roughness estimated across the reef varies spatially, and attempts are made to connect this information with the diverse bed morphologies observed in the field
