Population genomics of a critically endangered data-deficient elasmobranch, the blue skate Dipturus batis

Doctoral thesis (PhD) - Nord University, 2021publishedVersio

RT-SLAM: A Generic and Real-Time Visual SLAM Implementation

This article presents a new open-source C++ implementation to solve the SLAM problem, which is focused on genericity, versatility and high execution speed. It is based on an original object oriented architecture, that allows the combination of numerous sensors and landmark types, and the integration of various approaches proposed in the literature. The system capacities are illustrated by the presentation of an inertial/vision SLAM approach, for which several improvements over existing methods have been introduced, and that copes with very high dynamic motions. Results with a hand-held camera are presented.Comment: 10 page

Relaxation of Loaded ESCRT-III Spiral Springs Drives Membrane Deformation

International audienceESCRT-III is required for lipid membrane remodeling in many cellular processes, from abscission to viral budding and multi-vesicular body biogenesis. However, how ESCRT-III polymerization generates membrane curvature remains debated. Here, we show that Snf7, the main component of ESCRT-III, polymerizes into spirals at the surface of lipid bilayers. When covering the entire membrane surface, these spirals stopped growing when densely packed: they had a polygonal shape, suggesting that lateral compression could deform them. We reasoned that Snf7 spirals could function as spiral springs. By measuring the polymerization energy and the rigidity of Snf7 filaments, we showed that they were deformed while growing in a confined area. Furthermore, we observed that the elastic expansion of compressed Snf7 spirals generated an area difference between the two sides of the membrane and thus curvature. This spring-like activity underlies the driving force by which ESCRT-III could mediate membrane deformation and fission

On-the-fly Auditory Masking for Scalable VOIP Bridges

International audienceEndpoints or conference servers of current audio-conferencing solutions use all the audio frames they receive in order to mix them into one final aggregate stream. However, at each time-instant, some of this content may not be audible due to auditory masking. Hence, sending corresponding frames through the network leads to a loss of bandwidth, while decoding them for mixing or spatial audio processing leads to increased processor load. In this paper, we propose a solution based on an efficient on-the-fly auditory masking evaluation. Our technique allows prioritizing audio frames in order to select only those audible for each connected client. We present results of quality tests showing the transparency of the algorithm. We describe its integration in a France Telecom audio conference server. Tests in a 3D game environment with spatialized chat capabilities show a 70% average reduction in required bandwidth, demonstrating the efficiency of our method

Using CamiTK for rapid prototyping of interactive Computer Assisted Medical Intervention applications

Computer Assisted Medical Intervention (CAMI hereafter) is a complex multi-disciplinary field. CAMI research requires the collaboration of experts in several fields as diverse as medicine, computer science, mathematics, instrumentation, signal processing, mechanics, modeling, automatics, optics, etc

Thermodynamic evidence of giant salt deposit formation by serpentinization: an alternative mechanism to solar evaporation

International audienceThe evaporation of seawater in arid climates is currently the main accepted driving mechanism for the formation of ancient and recent salt deposits in shallow basins. However, the deposition of huge amounts of marine salts, including the formation of tens of metres of highly soluble types (tachyhydrite and bischofite) during the Aptian in the South Atlantic and during the Messinian Salinity Crisis, are inconsistent with the wet and warm palaeoclimate conditions reconstructed for these periods. Recently, a debate has been developed that opposes the classic model of evaporite deposition and argues for the generation of salt by serpentinization. The products of the latter process can be called "dehydratites". The associated geochemical processes involve the consumption of massive amounts of pure water, leading to the production of concentrated brines. Here, we investigate thermodynamic calculations that account for high salinities and the production of soluble salts and MgCl2-rich brines through sub-seafloor serpentinization processes. Our results indicate that salt and brine formation occurs during serpentinization and that the brine composition and salt assemblages are dependent on the temperature and CO2 partial pressure. Our findings help explain the presence and sustainability of highly soluble salts that appear inconsistent with reconstructed climatic conditions and demonstrate that the presence of highly soluble salts probably has implications for global tectonics and palaeoclimate reconstructions

Evaluating the suitability of close-kin mark-recapture as a demographic modelling tool for a critically endangered elasmobranch population

Estimating the demographic parameters of contemporary populations is essential to the success of elasmobranch conservation programmes, and to understanding their recent evolutionary history. For benthic elasmobranchs such as skates, traditional fisheries-independent approaches are often unsuitable as the data may be subject to various sources of bias, whilst low recapture rates can render mark-recapture programmes ineffectual. Close-kin mark-recapture (CKMR), a novel demographic modelling approach based on the genetic identification of close relatives within a sample, represents a promising alternative approach as it does not require physical recaptures. We evaluated the suitability of CKMR as a demographic modelling tool for the critically endangered blue skate (Dipturus batis) in the Celtic Sea using samples collected during fisheries-dependent trammel-net surveys that ran from 2011 to 2017. We identified three full-sibling and 16 half-sibling pairs among 662 skates, which were genotyped across 6291 genome-wide single nucleotide polymorphisms, 15 of which were cross-cohort half-sibling pairs that were included in a CKMR model. Despite limitations owing to a lack of validated life-history trait parameters for the species, we produced the first estimates of adult breeding abundance, population growth rate, and annual adult survival rate for D. batis in the Celtic Sea. The results were compared to estimates of genetic diversity, effective population size (Ne), and to catch per unit effort estimates from the trammel-net survey. Although each method was characterized by wide uncertainty bounds, together they suggested a stable population size across the time-series. Recommendations for the implementation of CKMR as a conservation tool for data-limited elasmobranchs are discussed. In addition, the spatio-temporal distribution of the 19 sibling pairs revealed a pattern of site fidelity in D. batis, and supported field observations suggesting an area of critical habitat that could qualify for protection might occur near the Isles of Scilly.publishedVersio

Temporary organizational forms and coopetition in cycling: What makes a breakaway successful in the Tour de France?

Purpose: In road cycling races, one of riders’ main objectives is to win stages, which most often requires breaking away from the pack of riders. What is it that makes a breakaway succeed, i.e. enable one of its members to win the stage? Design/methodology/approach: Descriptive statistics were computed and a logit model of breakaway success was estimated, based on a new kind of statistical data describing the development of each of the 268 breakaways that occurred in the 76 regular stages of the Tour de France 2013 to 2016. Findings: Breakaway success partly depends on the physics of cycling: breakaways are more successful when the stage is hilly or in mountain than flat. In addition, the likelihood of breakaway success depends on strategic moves such as attack timing and the percentage of riders with a teammate in the breakaway. Research limitations/implications: Understanding why certain breakaways succeed and others do not is useful to comprehend cycling performance and to help coopetitive temporary organizational forms such as breakaways optimize their strategic behavior. A limitation is the focus on the Tour de France only. Originality/value: The present study adds to the literature on temporary organizational forms, coopetition and cycling performance by analyzing within-stage data in cycling and, as such, enabling to capture its strategic dimension