HAL-Université de Bretagne Occidentale
Not a member yet
75442 research outputs found
Sort by
What Can Be Recovered Under Sparse Adversarial Corruption? Assumption-Free Theory for Linear Measurements
No full textLet A in R^{m x n} be an arbitrary, known matrix and e a q-sparse adversarial vector. Given y = A x* + e and q, we seek the smallestt robust solution set containing x* that is uniformly recoverable from y without knowing e. While exact recovery of x* via strong (and often impractical) structural assumptions on A or x* (e.g., restricted isometry, sparsity) is well studied, recoverability for arbitrary A and x* remains open. Our main result shows that the best that smallest robust solution set is x* + ker(U), where U is the unique projection matrix onto the intersection of rowspaces of all possible submatrices of A obtained by deleting 2q rows. Moreover, we prove that every x that minimizes the l_0-norm of y - A x lies in x* + ker(U), which then gives a constructive approach to recover this set
How the Covid-19 pandemic has changed the behaviour of consumers of fisheries and aquaculture products (FAP) in France
No full textInternational audienceA year after the pandemic, we surveyed 1268 French FAP consumers in April 2021 to evaluate if the crisis had led to more sustainable consumption patterns by giving priority to fresh seafood from local circuits. We also match those results with a study prior to the Covid-19 to estimate the impact of the crisis on the perception of FAP. For more than 50% of consumers, the Covid-19 crisis did not lead to change in their FAP consumption and we found a very small proportion of consumers who increased their purchases of fresh FAP and favoured short channels during and after the Covid-19 crisis. We demonstrate that pre-Covid-19 characteristics and attitudes are important explanatory factors for behaviour during the crisis. Big consumers of fresh FAP and consumers with a positive image of the health benefits of seafood were more likely to have increased their consumption of fresh FAP. Similarly, people who were used to consuming FAP away from home instead consumed FAP at home during the crisis and after. The results also suggest that consumers tended to perceive FAP as more expensive after the Covid-19, a major obstacle to the emergence of more sustainable consumption behaviour in this sector
Retour aux sources : (re)lire La Queste del saint Graal en contexte manuscrit
No full textInternational audienc
Landscape features and urban heat island: episodic analyses during the dry season in a city of the Pre-Amazon region of Mato Grosso (Brazil).
No full textInternational audienceThis study aims to analyze the urban heat island in the city of Sinop (State of Mato Grosso, Brazil), based on three characteristic episodes of the dry season. The analysis focuses on the spatialization of temperature and the intensity of the phenomenon, as well as its association with landscape features.Methodology: The analysis of the urban heat island was grounded in the Urban Climate System and the technicalmethodological framework for investigating the phenomenon in medium and small-sized cities. Urban and rural landscape aspects were examined based on the adaptation of Local Climate Zones and the measurement of nighttime air temperature through mobile transects and fixed points. The data were processed and analyzed using statistical association techniques and multicriteria linear regression modeling, in order to predict the spatial distribution of air temperature and the intensity of the heat island.Findings: The analyses highlight the influence of landscape features, physical elements, and urban spatial organization on temperature distribution and the formation of the heat island. They reinforce the mitigating role of vegetation and the greater heating in densely built areas, and also point to the influence of seasonality and regional atmospheric conditions on local thermal variation
Unraveling the Spatial Variability of Fossil Coral Reef Morphology on Aruba and the Implications for Paleo Sea Level Estimates
No full textInternational audienceThe morphology of a coral reef terrace (CRT) is a key parameter in the interpretation and quantification of past sea‐level changes, but it is directly influenced by local morphodynamic and hydrodynamic conditions. Spatial differences in terrace morphology may therefore result in over‐ or underestimation of paleorelative sea levels and their associated uncertainties. To investigate this, we integrate high‐precision field surveys from the island of Aruba (Leeward Antilles, Caribbean Sea) with a stratigraphic forward model (DionisosFlow®) to quantify the intra‐island variability of the Quaternary coral reef sequence. We establish that a possible slight North‐South tectonic tilt of the island may drive differences in the elevation of CRTs and the number of emerged fossil coral reefs imprinted on the coastal landscape. However, terrace geometry is primarily defined by the basement slope and wave exposure. All together, our results show that even small‐scale environmental and hydrodynamic variability can introduce meter‐scale errors in sea‐level reconstructions derived from CRTs
Delivery assist catheters for mechanical thrombectomy: a systematic review
No full textInternational audienceIntroduction: Mechanical thrombectomy for acute ischemic stroke is often limited by the tortuous anatomy and the ‘ledge effect’ caused at the junction of a large-bore aspiration catheter and smaller inner devices. Novel delivery assist catheters with smooth tapered distal tips have been developed to facilitate the navigation of aspiration or microcatheters to the clot. Methods: We performed a PRISMA-guided systematic review of these tapered delivery assist catheters, analyzing their design, regulatory status, and all available evidence on technical performance, clinical outcomes, and safety. A comprehensive literature search (through July 2025) was conducted for studies and reports on the above devices. Results: A total of 18 reports met the inclusion criteria, covering 7 distinct assist catheters. All devices share a common design of a variably stiff, single-lumen catheter with an atraumatic tapered distal segment that minimizes the gap between the inner device and the outer aspiration catheter. Use of these catheters enabled successful trackability and clot engagement in >90% of cases across most series, often without a guidewire, and with low complication rates. Conclusions: Tapered delivery assist catheters represent an innovation in thrombectomy. Ongoing studies and broader adoption will further clarify their impact on procedural efficiency and patient outcomes