HAL Université de Savoie
Not a member yet
59053 research outputs found
Sort by
Magnetotactic bacteria affiliated with diverse <i>Pseudomonadota</i> families biomineralize intracellular Ca-carbonate
No full textInternational audienceIntracellular calcium carbonate formation has long been associated with a single genus of giant Gammaproteobacteria, Achromatium. However, this biomineralization has recently received increasing attention after being observed in photosynthetic Cyanobacteriota and in two families of magnetotactic bacteria affiliated with the Alphaproteobacteria. In the latter group, bacteria form not only intracellular amorphous calcium carbonates into large inclusions that are refringent under the light microscope, but also intracellular ferrimagnetic crystals into organelles called magnetosomes. Here new observations suggest that magnetotactic bacteria previously identified in the sediments and water column of Lake Pavin (France) were only a small fraction of the diversity of bacteria producing intracellular amorphous calcium carbonates. To explore this diversity further, we conducted a comprehensive investigation of magnetotactic populations with refractive granules using a combination of environmental microbiology, genomic and mineralogy approaches on cells sorted by micromanipulation. Several species belonging to divergent genera of two Pseudomonadota classes were identified and characterized. Scanning transmission electron microscopy coupled with energy-dispersive X-ray spectrometry support that all these species indeed form intracellular amorphous calcium carbonates. Cryo soft X-ray tomography experiments conducted on ice-vitrified cells, enabled 3D investigation of inclusions volume, which was found to occupy 44-68% of the cell volume. Metabolic network modeling highlighted different metabolic abilities of Alpha-and Gammaproteobacteria, including methylotrophy and CO 2 fixation via the reverse Krebs cycle or the Calvin-Benson-Bassham cycle. Overall, this study strengthens a convergent evolution scenario for intracellular carbonatogenesis in Bacteria, and further supports that it is promoted by the fixation of CO 2 in anoxic environments.</div
Agriculture and plant management from lowland to foothills in semi-arid Central Asia. Archaeobotanical study of Bronze and Iron Age sites in southern Uzbekistan
No full textInternational audienc
Remediation of soil subjected to suffusion using fine injection techniquescombined experimental and numerical insights
No full textThe phenomenon of suffusion, commonly observed in gap-graded soils, involves the detachment and transport of the finest grains under internal fluid flow through porous media. This can lead to significant loss of fines, potentially causing mechanical instabilities in the material and posing a risk of catastrophic failure in hydraulic structures. To mitigate this risk, a novel approach is investigated by introducing fines into loose skeleton composed of coarse sand grains. This study aims to: (1) examine the infiltration process of fines injection; (2) evaluate its effectiveness from point of view of the mechanical behavior of the suffused sample using both numerical and experimental methods. For the first objective, both experimental and numerical results show that the distribution of injected fine grains decay exponentially along the infiltration depth, allowing a straightforward characterization of the infiltration process via the mean infiltration distance L 0 . A micro-mechanically based probabilistic model is put forward to interpret L 0 from the pore/constriction size distribution of the coarse sand column (matrix) across a board range of size ratios R (D 15 /d) between fine and coarse grains. Regarding the second objective, the mechanical properties of the soil before and after fines injection are analyzed using constant-volume triaxial tests. The role of a small amount of injected fines on macroscopic material properties, such as contractive behaviors and liquefaction resistance, is evaluated from both numerical and experimental aspects. The findings reveal the beneficial role of the fine grains inclusion in delaying/preventing the development of plastic strain in the coarse grain skeleton, thus enhancing the overall loose material stability
Influence of mindfulness and coping flexibility in the early phases of burnout development in intensive care unit healthcare workers during the COVID-19 pandemic
No full textInternational audienceBackgroundCaregivers in intensive care units are exposed to high levels of stress, which were exacerbated during the COVID-19 pandemic, increasing the incidence of stress-related disorders, including burnout. MethodsWe evaluated the influence of mindfulness and coping flexibility in the early days of burnout development in a prospective study of 50 military caregivers working in a mobile resuscitation unit during the COVID-19 pandemic. We visited the participants at the end of deployment (day 0; D0) and three weeks later (D21). On D0, the participants completed questionnaires assessing mindfulness (Freiburg Mindfulness Inventory; FMI), coping flexibility (Flexcop), and burnout (Burnout Measure, Short Version; BMS). Subjective sleep symptoms were also assessed to evaluate their relationship with burnout. The BMS was repeated on D21. ResultsFour short-term burnout evolutions were observed: (i) "healthy" on D0 and D21;(ii) "exhausted," healthy on D0 and burnout on D21; (iii) "resilient," burnout on D0 and healthy on D21; and (iv) "burnout" on D0 and D21. Compared with healthy participants on D0, only resilient participants had lower FMI (η2 = 0.22; p = 0.032).Exhausted participants had more difficulty waking, and burnout participants had higher daytime fatigue than healthy participants. FMI scores on D0 negatively correlated with BMS scores on D21 (r = -0.40 r 2 = 0.16 p = 0.009) for the entire population, and also after excluding burnout status at D0 (r = -0.41 r 2 = 0.17 p = 0.02).Flexcop scores on D0 did not correlate with BMS scores on D21. ConclusionsThis study underlines the importance of mindfulness in the early days of burnout onset, and suggests considering its reinforcement for prevention of burnout and its measurement as a potential biomarker of burnout risk.</div
Effects of Dribbling Constraints on Sprint Acceleration Performance According to Maturity Status in Handball Players
No full textInternational audienceAbstract Sudlow, A, Pommerell, F, Galantine, P, Del Sordo, G, Boyas, S, Rahmani, A, Robichon, J, Samozino, P, Duché, P, and Peyrot, N. Effects of dribbling constraints on sprint acceleration performance according to maturity status in handball players. J Strength Cond Res XX(X): 000–000, 2025—The aim was to determine the effects of dribbling and maturation in handball players on sprinting horizontal force production capacities. One hundred sixteen male handball players participated (10–39 years). Split times and continuous velocity-time data were collected using a radar in sprinting and dribbling conditions. Samozino's method was applied to obtain horizontal force-velocity relationship parameters (Pmax, F 0 , v 0 , S FV ) and technical variables (RFmax, D RF ). Somatic maturity was determined from peak height velocity (PHV). Statistical significance for all tests was set at an alpha level p < 0.05. Interaction effects were observed for split times revealing that, at all distances, each maturity group decreased in performance when dribbling and that maturation effects persisted in both conditions ( p < 0.05, d = 0.33–3.83). No interaction effects were observed for any of the mechanical outputs but decreases in all outputs were observed in the dribbling condition, all maturity groups combined ( p < 0.002, d = 0.36–0.90). Greater relative change in performance was observed for Pre-PHV vs. Post-PHV and Adults at almost all distances ( p < 0.05, d = 0.59–0.93). No effects of maturation were observed for any of the mechanical outputs. Dribbling in handball has effects on horizontal force capacities with reductions in Pmax primarily due to greater losses in v 0 than F 0 , suggesting that improvement in dribbling proficiency leads to smaller decreases in propulsive force production capacities
Recognition of Pieces of Arithmetic Hyperplanes Using the Stern–Brocot Tree
No full textInternational audienceThe classical problem of discrete structure recognition is revisited in this paper. We focus on pieces of naive lines and, more generally, naive arithmetic hyperplanes, and present a new approach to recognising these discrete structures based on the Stern-Brocot tree. The algorithm for pieces of lines in dimension 2 proposes an alternative method to the state of the art, retaining linear complexity and incrementality for the segments. While most of the concepts can be generalised to planes in dimension 3 and hyperplanes in higher dimensions, certain points in the management of the descent in the Stern-Brocot tree merit further study. The proposed algorithm calculates separating chords characterising the membership of planes to cones generated by the branch of the Stern-Brocot tree. This generalisation shows the close link between arithmetic hyperplanes and the generalised Stern-Brocot tree and opens up interesting prospects for recognising pieces of arithmetic hyperplanes. Finally, we propose a geometric interpretation of separating chords and an interpretation of plane probing algorithms in the Stern-Brocot tree, showing both the links and the differences with our approach
Delivering Sustainability Through Ecosystem Innovation: A Multilevel Framework for Sustainability Transition
No full textInternational audiencehttps://doi.org/10.37725/mgmt.2025.1371
Long-term changes of zooplankton in alpine lakes result from a combination of local and global threats
No full textInternational audienceLakes located above treeline or alpine ones offer valuable opportunities to assess the effects of natural and human-induced influences, ranging from local to global scales. Further, there is a growing concern about several local threats jeopardizing the ecological integrity of these ecosystems. Zooplankton communities, which essentially comprise the entire pelagic consumer compartment in naturally fishless alpine lakes, can indicate ecosystem changes. Here, we analysed 643 zooplankton samples from 101 lakes and ponds in the Western Alps, collected over 19 years (2006-2024). Community data-taxa and functional groups-were examined to evaluate zooplankton responses to local natural and anthropogenic factors and to detect long-term changes linked to broader regional or global trends. Long-term trends showed declines in cold stenothermal taxa and groups, which are consistent with the effects of climate warming. Despite most lakes being located within protected areas, about half were affected by local anthropogenic factors such as fish introduction and hydroelectric exploitation. Our findings highlight that a critical component of aquatic ecosystems underwent significant taxonomic and functional composition shifts over time, likely due to a combination of climate change and widespread fish introductions. The study emphasises the need for conservation measures and actions to safeguard still pristine alpine lakes and recover impacted ones to enhance mountain aquatic biota resilience to projected global changes
Assigning taxonomy and traits to DNA sequences of river diatoms in a region with limited taxonomic knowledge using the updated and annotated reference library Diat.barcode
No full textSupplementary materialhttps://www.limnology-journal.org/articles/limn/olm/2025/01/limn250020/limn250020.htmlInternational audienceWe present a new version of a barcoding reference library dedicated to diatoms, Diat.barcode v12, with newly published sequences, annotated with ecological, and biological traits (size class, life forms, ecological guilds, etc ) and curated by a college of experts. Diat.barcode incorporates rbcL data on all diatoms, though freshwater taxa are better represented. We used this library in two different areas, one where the taxonomic coverage of the library was good (mainland France) and another where it was poor (French Guyana) with about 320 diatom samples collected for river monitoring across both regions. We show that a direct bioinformatic assignment of environmental sequences to traits (ecological guilds, habitats, morphology) has great potential in French Guyana where species knowledge is poor and therefore the proportion of assigned environmental sequences is much lower (12.8%) than trait assignation (30%). We used co-correspondence analyses to show that, unlike mainland France where all species and trait assignation datasets were significantly correlated, in French Guyana only 7 out of 13 trait categories showed a significant correlation. This indicates a significant loss of ecological information through species assignment in French Guyana. Consequently, directly assigning environmental sequences to traits can be useful and provide more ecological information in regions with poor taxonomic knowledge because of the many rbcL sequences without taxonomic assignations
Can genetic diversity in microalgae species be explained by climate: an overview of metabarcoding with diatoms
No full textInternational audienceDiatoms, a diverse and abundant group of microalgae, play a crucial role in the functioning of rivers, and are widely used as indicators of ecological quality. This microalgae group has an intraspecific genetic diversity that is poorly understood on a global scale. We examined their genetic diversity using metabarcoding data from Nordic to Equatorial rivers (n = 1103 samples). Notably, 61% of genetic variants were endemic to a single climate zone, including 33% from the Equatorial zone. Looking at the genetic diversity within species, one third of the species showed geographic pattern between climate zones and the phylogenetic structure of their communities indicated that they were shaped by environmental filtering. Another third showed no geographic pattern, and their communities were in majority shaped by neutral processes. A final group was between these two situations. Interestingly, no geographic pattern was observed within the same climate zones, even in regions over 10 000 km apart. We conclude that the numerous species showing allopatric diversification between climate zones, would deserve to be separated into new species to improve diatom-based biomonitoring tools. For future studies, expanding geographical sampling coverage, together with using multi-markers or metagenomes approaches would enable to go beyond these results