Portail HAL-PSL
Not a member yet
293219 research outputs found
Sort by
Aubigné-Racan (Sarthe, Pays de la Loire). Le site antique de Cherré et son environnement de la Protohistoire au début du Moyen Âge: Rapport d'activités scientifiques 2025
No full textMorphological Development and Evolution of Barchanoid Dunes on the Cap Ferret Coastal Spit
No full textInternational audienceBarchans are crescent-shaped dunes with their convex side facing the wind and their horns pointing downwind, commonly observed in deserts but also in coastal environments. This study investigates the dune field of the Cap Ferret Spit (5-km wide, 23-km long; Atlantic Coast, SW France) including of series of barchanoids dunes, currently stabilized by forest cover. The aims are to classify each dune into distinct typologies and characterize their morphology in order to analyze their evolution. LiDAR-based analysis identified four distinct barchanoid dune types. Moreover, it revealed superimposed bedforms on the dunes, including draping and oscillating patterns, reflecting the influence of consistent wind regimes during dune development and migration. This study proposes an evolutionary sequence in which proto-barchans evolve into barchanoid ridges and eventually as mature isolated barchans. These findings provide insight into the geomorphological evolution of barchanoid dunes in a coastal context, and particularly their migration pattern on a coastal spit syste
CHIME/Slow overview and pilot survey: A new backend to search for second-duration radio transients with the CHIME telescope
No full textInternational audienceWe present an overview of CHIME/Slow, a real-time transient search backend under development to search for second-duration radio transients using the CHIME telescope, and results obtained from a pilot survey carried out using the prototype version of the search pipeline. The prototype CHIME/Slow pipeline was tested on archival data obtained in December 2022, January 2023 and February 2023 with a total on-sky time of 17 days with an instantaneous Field of View (FoV) of 13 deg . In this pilot survey, we detected nine bursts, one from a new non-repeating source and eight from the known hyperactive repeating source FRB 20220912A. Out of these nine bursts, two bursts from the repeater were not detected by CHIME/FRB, while the non-repeater was detected in the side-lobe of a beam in the CHIME/FRB exhibiting shorter pulse width and narrower bandwidth compared to the CHIME/Slow detection. Here we report properties of the bursts, discuss the sensitivity and completeness of the current version of the CHIME/Slow pipeline, and outline future development to improve its performance. Finally, based on these results, we report the all-sky rate (95% credible region) of radio transients with pulse widths between 16 ms to 5 s, fluence above 5 Jy ms and observing frequency of 600 MHz to be between 184 and 4556 bursts sky day
Palestine ! Résistances ici et ailleurs
No full textIn this article, the editors articulate the positioning they have adopted for this issue, whose contributions were assembled while war and genocide were unfolding in Palestine. They subsequently examine the imageries of struggle and the major sequences of resistance that have punctuated the Palestinian people’s historical struggle, which, in their view, constitute an indispensable historical framework for reading this issue. In light of these orientations, the introduction synthetically presents the arguments of the various articles assembled here. The initial contributions describe the struggles of Palestinians in Palestine and in the diaspora, including through artistic creation; others attest to the diversity of forms and expressions that support for the Palestinian cause assumes across various countries globally.Résister, y compris à l’impuissance. Ce numéro réunit des œuvres d’artistes gazaouis et des textes de chercheur·es, issus de travaux de terrain. Ceux-ci éclairent la diversité des résistances et des imaginaires de lutte qui s’engagent pour l’existence de la Palestine et du peuple palestinien là et ailleurs, depuis les ruines de Gaza, les rues, les stades de foot, les instances internationales ou les réseaux sociaux, en France, en Israël, en Afrique du Sud… Face à une nouvelle guerre coloniale qui redistribue la géopolitique mondiale, il est exclu de se taire, indispensable de rendre intelligible et crucial de continuer à débattre et se projeter
Fluorine-stabilized β-nickel hydroxides: composition, structural features, and electrochemical properties
No full text"ADC - Accord Couperin / American Chemical Society (2024-2026)"International audienceMost commercial Ni-based alkaline batteries use β-Ni(OH)2 as the cathode material. These batteries are particularly attractive due to the use of low-cost materials and nonflammable aqueous electrolytes, which enhance safety and recyclability. However, these electrodes suffer from structural instability during charge–discharge cycles caused by phase transitions between β-Ni(OH)2/β-NiOOH and α-Ni(OH)2/γ-NiOOH redox couples, leading to capacity fading over time. Therefore, stabilizing the β polymorph remains a significant challenge. In this study, nickel hydroxyfluorides (Ni(OH)2–xFx) were synthesized using microwave-assisted hydrothermal routes. It was possible to increase the fluorine content up to 0.48 while maintaining the β-Ni(OH)2 structural type. Powder X-ray diffraction and vibrational spectroscopy (FTIR, Raman) revealed substantial structural variations with fluorine incorporation. The highly electronegative fluorine plays a crucial role in enhancing both intraslab interactions, by increasing lattice rigidity, and interslab interactions, by affecting the level of the O–H bonds and H–H electrostatic repulsion. UV–vis–NIR spectroscopy confirmed the increased bond ionicity of the fluorinated samples, evidenced by an optical bandgap opening, a decrease of crystal field stabilization energy, and a slight increase of the Racah parameter. Thermogravimetric analysis showed a gradual increase in the decomposition temperature with higher fluorine content. Interestingly, the thermal decomposition of nickel hydroxyfluorides resulted in a novel synthesis method for nickel oxyfluorides (Ni1–(y/2) □y/2O1–yFy), stabilizing nickel vacancies. Galvanostatic cycling tests indicated a significant capacity decrease in the fluorine-containing samples. To further understand the mechanisms behind the reduced electrochemical performance, chemical oxidation tests were conducted. These tests demonstrated the inability of the fluorinated samples to be oxidized, suggesting that the high electronegativity of fluorine prevents nickel oxidation.</p
Le pythagorisme comme clé de lecture de l’hypogée de la Porta Maggiore : essai de bilan critique
No full textInternational audienc
Incorporation of Ruthenium Polypyridyl Complexes into DNA Oligonucleotides by Copper-Free Click Chemistry
No full textInternational audienceAlternative methods for the preparation of naïve libraries for SELEX experiments are in dire need, particularly when hydrophobic, bulky, and complex modification patterns are considered. Here, we explore first steps towards the preparation of libraries equipped with ruthenium polypyridyl complexes using Strain-Promoted Azide-Alkyne Cycloaddition (SPAAC) reactions. We demonstrated that dsDNA products can be efficiently equipped with dibenzocyclooctyne (DIBAC) moieties using a suitable modified nucleoside triphosphate and PEX reactions or PCR. The resulting dsDNA products can then be further modified using SPAAC and ruthenium polypyridyl complexes equipped with azide moieties, permitting the installation of >10 complexes. Finally, dsDNA can be efficiently converted into the corresponding modified ssDNA using magnetoseparation. These results offer the possibility of producing longer oligonucleotides equipped with complex modification patterns and open the way to SPAACclick-SELEX methodologie
« Ce qu’il y a de bien avec le changement climatique… »
No full textInternational audienceUn documentaire récent entend brosser une image désirable de la France de 2100 à +4°C pour contrer le pessimisme ambiant. Résultat: une France rance, qui a renoncé à l'atténuation, à la justice sociale et même au bon sens. Une tribune collective rétablit les faits scientifiques sur la dévastation du système Terre et remet la question politique au premier plan
Managed re-alignment: a multifaceted approach in ecological restoration of coastal floodplains
No full textInternational audienceLow-lying coasts in Europe share a long history of land reclamation enabled by flood defences, which radically transformed natural coastal processes and buffers. Traditional coastal adaptation, by raising dykes, is increasingly challenged due to environmental and sustainability issues in light of wetland loss and the climate crisis. Managed re-alignment (MR) departs from “hold the line” coastal defence approaches by encouraging the planned removal or relocation of coastal defence lines and the incorporation of softer, nature-based flood protection. MR implies substantial changes in landscape and land use and has significant local socio-environmental implications. Despite complex conceptual, technical, ecological, political and social challenges, this approach has received increased attention in northwest Europe as a key method towards the ecological restoration of coastal floodplains. In this article, we review: (1) how MR terminology varies according to disciplinary focus, public perception and regional preferences; (2) how emerging hybrid flood defence approaches contribute to restore foreshore environments; (3) how to engage local communities in co-designing MR projects while appropriately acknowledging, valuing and compensating impacts at community level. Finally, we draw lessons learnt from past experience and highlight critical questions at scientific, political and management levels. Managed re-alignment (MR) has been applied in Europe since the 1960s for coastal restoration. Restored areas nevertheless are far from compensating historical wetland losses. Hybrid designs foster a shift towards nature-based coastal adaptation and protection systems. MR supports rethinking spatial planning and advancing integrated coastal zone management. Local engagement is crucial for effective MR planning and better chances of successful outcomes