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Critical Majorana fermion at a topological quantum Hall bilayer transition
No full textInternational audienceQuantum Hall bilayers are a uniquely tunable platform that can realize continuous transitions between distinct topological phases of matter. One prominent example is the transition between the Halperin state and the Moore--Read Pfaffian, long predicted to host a critical theory of Majorana fermions but so far not verified in unbiased microscopic simulations. Using the fuzzy sphere regularization, we identify the low-energy spectrum at this transition with the 3D gauged Majorana conformal field theory. We show that the transition is driven by the closing of the neutral fermion gap, and we directly extract the operator content in both integer and half-integer spin sectors. Our results resolve the long-standing question of the nature of a topological phase transition in a setting relevant to quantum Hall experiments, while also providing the first realization of a fermionic theory on the fuzzy sphere, previously limited to bosonic theories
A narrative review of the impact of anthropogenic light and noise on owls
No full textInternational audienceToday, owls are exposed to increasingly brightly lit nights and noisy environments because of human activities. To understand the impacts of artificial light at night (ALAN) and anthropogenic noise we performed an evidence synthesis. We searched four literature databases and Google Scholar and we collected 39 relevant articles (1945-2024) providing 125 cases (64 on light pollution and 61 on noise pollution), targeting 25 species (c. 10% of owl species). We found harmful effects of both sensory pollutants on several outcomes. First, ALAN tends to reduce acoustic communication and to be associated with a lower occurrence of owl species, although it is difficult to confirm whether ALAN leads to silent or absent owls. Moreover, ALAN disturbs owl-prey interactions. Although light probably improves owl vision, the light-avoidance behaviour of small mammals could result in poorer hunting success of owls feeding on mammals. Conversely, ALAN enhances food provisioning and even breeding of owls feeding on insects that are attracted by light, to the detriment of these prey populations. Second, human-induced noise clearly tends to reduce owl vocalization, yet that vocalization may be essential to communication between individuals. The ability of owls to detect prey (hunting success) is also reduced under noise exposure (even at low amplitude), probably as the result of masking and distraction. Studies also demonstrate that anthropogenic noise can cause physiological and behavioural stress and disturbance to owls. Such adverse effects may contribute to declines in reproduction and occurrence of owls observed in noisy areas. As a result, we recommend reduction of both sensory stressors as much as possible, for owls and for ecosystem stability, for example by maintaining and restoring quiet and dark areas. We also recommend more consideration of owls in sensory ecology research to fill knowledge gaps.De nos jours, les rapaces nocturnes sont exposés à des nuits de plus en plus lumineuses et à un environnement de plus en plus bruyant en raison des activités humaines. Pour comprendre l'impact potentiel de la lumière artificielle nocturne et du bruit anthropique, nous avons réalisé une revue de littérature. Nous avons interrogé 4 bases de données bibliographiques et Google scholar et nous avons collecté 39 articles pertinents (1945–2024) fournissant respectivement 125 cas (64 sur la pollution lumineuse et 61 sur la pollution sonore), ciblant en tout 25 espèces (~10% des Strigiformes ). Nous avons trouvé plusieurs effets néfastes des pollutions lumineuse et sonore. Tout d'abord, la lumière artificielle tend à diminuer la communication acoustique et est associée à une occurrence plus faible, bien qu'il soit difficile de confirmer si les chouettes sont plus silencieuses ou absentes. Il est indéniable que l'éclairage nocturne perturbe les interactions entre les rapaces nocturnes et leurs proies, ce qui peut expliquer en partie cette situation pour les espèces qui se nourrissent de rongeurs, selon les effets documentés de la luminosité de la lune: alors que la lumière améliore la vision des chouettes/hiboux, le comportement d'évitement de la lumière des petits mammifères pourrait entraîner un moins bon succès de chasse. Inversement, l'éclairage artificiel améliore l'approvisionnement en nourriture et même la reproduction des chouettes insectivores, probablement au détriment des populations de proies attirées par la lumière. Deuxièmement, les sons artificiels tendent clairement à diminuer la vocalisation des chouettes, pourtant essentielle à la communication (par exemple entre partenaires). La capacité des Strigiformes à détecter leurs proies (succès de chasse) est également réduite en cas d'exposition au bruit (même à faible amplitude), sûrement par un effet de masquage et de distraction. Les données démontrent également que le bruit anthropique provoque du stress et des perturbations, tant au niveau physiologique que comportemental. Ces effets négatifs peuvent être responsables de la tendance à la baisse de la reproduction et de l'occurrence des rapaces nocturnes qui est également observée dans les zones bruyantes. Par conséquent, nous recommandons de réduire autant que possible les deux facteurs de stress sensoriel—pour les chouettes/hiboux et pour la stabilité des écosystèmes—par exemple en maintenant et en rétablissant des zones calmes et sombres. Nous demandons également que les Strigiformes soient davantage pris en compte dans la recherche en écologie sensorielle afin de combler les lacunes en matière de connaissances
Polymer Vesicle Microreactors Produced using Permeable Polymer Blocks: Circumventing Complex Functionality to Impart Membrane Permeability
No full textInternational audienceThe use of giant vesicles as microreactors presents a novel approach to control biochemical reactions in confined spaces, offering advantages such as compartmentalization, tunable permeability, and potential for biomimetic applications. These constructs can serve as versatile platforms for catalysis, drug delivery, and synthetic biology by providing confined environments that mimic natural cellular compartments. We have successfully produced microvesicles (also referred to as giant vesicles) by means of the simple double emulsification method using five amphiphilic block copolymers comprising poly(ethylene oxide) (PEO) as hydrophilic segment and five disparate hydrophobic blocks: poly(caprolactone) (PCL), poly(methyl methacrylate) (PMMA), poly(lactic acid) (PLA), poly [2-(diisopropylamino)ethyl methacrylate] (PDPA), and poly[2-(heptamethyleneimino)ethyl methacrylate] (PHIA). The last two blocks are pH-responsive (PDPA, PHIA), while the first ones are not (PCL, PMMA, PLA). The resulting vesicles have average size ranging from 2.9 to 9.3 µm, with the pHresponsive vesicles exhibiting larger diameters, likely due to partial protonation of the hydrophobic blocks. The formation of the giant vesicles was confirmed via optical and fluorescence microscopy using Nile red as a hydrophobic marker. The ability of the vesicles to encapsulate larger molecules was demonstrated by loading Alexa-labeled bovine serum albumin (BSA-Alexa). In the step further, the potential of these vesicles as microreactors was explored by encapsulating horseradish peroxidase enzyme (HRP) and evaluating the catalytic oxidation of o-dianisidine in the presence of hydrogen peroxide (H₂O₂), a reaction catalyzed by the HRP enzyme. The experimental evidences highlight that the pH-responsive vesicles are permeable to the reactants, as evidenced by colored product formation, whereas the permeability of the nonresponsive assemblies is reported to be negligible. Truly, the non-responsive vesicles exhibited particularly low permeability, even at the pH where the catalytic activity of the enzyme is optimized. These findings highlight the potential of pH-responsive vesicles for controlled molecular transport and catalytic applications, paving the way for their use in biocatalysis as microreactors
Marine Model Organisms for Mechanobiology Studies
No full textInternational audienceMarine invertebrate species have been used as model organisms in evo-devo studies for over a century. These species provided a great advantage in seminal microscopic studies because of the large size of their eggs and embryos and the easy accessibility to the first embryological processes afforded by their external fertilization and development. This review provides a historical perspective on the use of marine invertebrates—including echinoderms, ascidians, and spiralians—in the study of embryo mechanics. Here, we highlight the key contributions of marine invertebrates to the understanding of cortical and cytoplasmic mechanics, the implementation of early cleavage patterns, and tissue mechanics. We also examine the emergence of different blastula shapes in metazoans and focus on the clear dichotomy between compact and hollow embryos, suggesting a canalization of a compact embryo shape in taxa that display invariant cleavage patterns such as nematodes, spiralians, and ascidians.With recent advances in high-resolution imaging, computational modeling, and the development of modern genetic and genomic tools, marine invertebrate model organisms continue to be at the forefront of evolutionary developmental biology and mechanobiology. Their contribution to these fields not only provides invaluable insights into the fundamental principles of morphogenesis but also offers an ideal comparative framework that allows the exploration of the evolution of mechanical and biological processes across metazoans
Ultramafic float rocks at Jezero crater (Mars): excavation of lower crustal rocks or mantle peridotites by impact cratering?
No full textInternational audienceBased on observation and data from meteorites and in situ scientific missions, experiments as well as models, the Martian mantle is assumed to share some compositional and mineralogical affinity with the terrestrial mantle. However, there might be subtle differences like the Martian mantle being more ferroan. Yet, we do not have any direct analysis of a Martian mantle rock to confirm this assumption. NASA’s Perseverance rover found olivine-rich boulder-sized float rocks on the upper Jezero fan (Mars). These boulders have an ultramafic composition and their mineralogy is dominantly composed of Fo73±3 olivine with high-Mg orthopyroxene, Cr-rich Ti-Fe oxides and minor plagioclase and high-Ca pyroxene. Microtextural and petrological analysis reveals that these minerals crystallized at equilibrium. In addition, these boulders are different from all the bedrocks analyzed by Perseverance along its traverse which are crustal igneous rocks and sediments. Comparing our data to Martian meteorites and available Mars bulk silicate models (BSM), we discuss that these boulders could represent primitive melts and/or lower crustal material, and we specifically hypothesize that they could be mantle peridotites. We propose that these putative mantle rocks could have been excavated by the succession of impacts from the shallow mantle or lower crust in the Isidis region where Jezero crater is located. These olivine-rich boulders could thereby constitute the first direct analysis of a Martian mantle rock
Core stability in additively separable hedonic games of low treewidth
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Accords commerciaux et pêche durable
No full textInternational audienceThis study examines the impact of trade agreements and their specific provisions on the sustainability of marine fisheries resources. Using global data on the Mean Trophic Level (MTL) between 1950 and 2018 and a comprehensive dataset of environmental provisions from trade agreements signed between 1947 and 2018, we estimate the impact on the MTL of signing (i) a free trade agreement and (ii) a free trade agreement including fishery-related provisions. To address potential endogeneity problems associated with fisheries-related provisions, we use a difference-in-differences (DID) propensity score matching method. Our results show that while trade agreements tend to negatively impact the MTL, including fisheries-related provisions offsets this negative impact among signatory countries. By examining the potential mechanisms underlying this result, we are able to temper the optimistic findings in the existing literature on the beneficial environmental outcomes of environmental provisions. Our findings suggest that these provisions do not foster the adoption of more effective resource management practices. Instead, they appear to reduce trade opportunities, which is contrary to the objective of trade creation in trade agreements.Cette étude examine l'impact des accords commerciaux et de leurs dispositions spécifiques sur la durabilité des ressources halieutiques marines. À partir de données mondiales sur le niveau trophique moyen (MTL) entre 1950 et 2018 et d'un ensemble complet de données sur les dispositions environnementales des accords commerciaux signés entre 1947 et 2018, nous estimons l'impact sur le MTL de la signature (i) d'un accord de libre-échange et (ii) d'un accord de libre-échange comprenant des dispositions relatives à la pêche. Pour remédier aux problèmes d'endogénéité potentiels liés aux dispositions relatives à la pêche, nous utilisons une méthode d'appariement des scores de propension à la différence dans les différences (DID). Nos résultats montrent que si les accords commerciaux ont tendance à avoir un impact négatif sur le MTL, l'inclusion de dispositions relatives à la pêche compense cet impact négatif parmi les pays signataires. En examinant les mécanismes potentiels qui sous-tendent ce résultat, nous sommes en mesure de tempérer les conclusions optimistes de la littérature existante sur les effets bénéfiques des dispositions environnementales. Nos conclusions suggèrent que ces dispositions ne favorisent pas l'adoption de pratiques de gestion des ressources plus efficaces. Au contraire, elles semblent réduire les opportunités commerciales, ce qui est contraire à l'objectif de création d'échanges commerciaux dans les accords commerciaux
Dislocation evolution and redistribution during stress relaxation in single crystal AD730TM after prior plastic strain at 700 °C
No full textInternational audienceUnderstanding dislocation evolution during viscoplastic deformation is essential to accurately predict high-temperature superalloy behavior. While creep and monotonic deformation are well studied, the evolution of the dislocation substructures during stress relaxation, particularly following prior plastic straining, remains unclear. This study investigates a single crystal γ/γ' AD730TM superalloy deformed at 700 °C, focusing on dislocation evolution and redistribution. Transmission electron microscopy reveals that stacking faults formed during plastic straining progressively disappear during relaxation, suggesting thermally activated mechanisms such as dislocation re-association and recovery. After re-association, perfect dislocations spread into the matrix, forming a homogeneous dislocation network. These microstructural evolutions are believed to underlie the macroscopic stress relaxation behavior, which exhibits two regimes in the Norton diagram: an initial high-stress exponent regime linked to rapid dislocation rearrangement, followed by a low-stress exponent regime associated with broader dislocation activity
Optimizing the Viability of Interacting Systems with Evolutionary Algorithms
No full textInternational audienceViability theory studies the behavior of dynamical systems, with the aim of keeping them viable, or in other terms, keep their trajectories within desired constraints in the state space. Finding strategies to keep a dynamical system viable is already a challenge for optimization algorithms, but this task becomes even harder for multi-agent systems, where agents’ individual decision can influence the dynamics of the whole system. In this paper, we consider a multi-agent dynamic system and introduce an evolutionary approach for optimizing agents’ interaction behaviour, delimited by some a priori agreements, in the form of a set of commitments, with the objective of keeping the system viable. This approach is tested on the case-study of a collective project grouping several agritouristic activities on a shared place. Experimental results show that it is possible to find a set of agents’ commitments that can maintain system viability, supporting the proposed framework’s effectiveness
