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Fonctions de distribution de paires d'un gaz superfluide de fermions de spin 1/2 en interaction de contact dans la théorie BCS dépendant du temps linéarisée
No full textFinal version, in English (58 pages) and in French (58 pages) ; to appear in Comptes Rendus PhysiqueInternational audienceWe show that the minimal mean-field theory to use for calculating the pair distribution functions of a spatially homogeneous, unpolarized spin-1/2 superfluid Fermi gas is not the ordinary static BCS theory, but the linearized time-dependent BCS theory implemented via the fluctuation-dissipation theorem. Indeed, the former completely ignores the acoustic excitation branch - the phonons - of the superfluid, while the latter explicitly takes it into account, as well as the quantum fluctuations induced by the broken-pair continuum. Unlike the first, the second theory (i) reflects the effect of these collective excitations on the system's equation of state, including at zero temperature, (ii) allows the function to go at sufficiently large distances strictly below its asymptotic value where is the gas density, as expected according to the quantum hydrodynamics of Landau and Khalatnikov at low temperatures, and (iii) predicts in the function at short distances subdominant contributions in 3D and in 2D, alongside the dominant contributions in 3D and in 2D already present in static BCS theory but with a lower coefficient. This discussion is relevant to the recent theoretical work of Obeso-Jureidini and Romero-Rochin, and to the ongoing experiments on cold atomic gases at ENS and MIT.Nous montrons que la théorie de champ moyen minimale à utiliser pour le calcul des fonctions de distribution de paires d'un gaz superfluide de fermions de spin spatialement homogène non polarisé n'est pas la théorie BCS statique ordinaire, mais la théorie BCS dépendant du temps linéarisée, mise en œuvre par le truchement du théorème de fluctuation-dissipation. En effet, la première ignore totalement la branche d'excitation acoustique - les phonons - du superfluide, alors que la seconde en tient compte explicitement, ainsi que des fluctuations quantiques induites par le continuum de paires brisées. Contrairement à la première, la seconde théorie (i) répercute l'effet de ces excitations collectives sur l'équation d'état du système, y compris à température nulle, (ii) permet à la fonction de descendre à distance assez grande strictement en dessous de sa valeur asymptotique où est la densité du gaz, comme il se doit d'après l'hydrodynamique quantique de Landau et Khalatnikov à basse température, et (iii) prédit dans la fonction à courte distance des contributions sous-dominantes en à 3D et en à 2D, à côté des contributions dominantes en à 3D et en à 2D déjà présentes dans la théorie BCS statique mais avec un coefficient plus faible. Cette discussion est pertinente pour les travaux théoriques récents d'Obeso-Jureidini et de Romero-Rochin, et pour les expériences en cours sur les gaz d'atomes froids à l'ENS et au MIT
Inconsistance spatiale : L’influence du lieu sur le tri des déchets ménagers
No full textInternational audienceL’économie circulaire accorde une place centrale au recyclage, qui implique la mise en œuvre généralisée du tri des déchets ménagers dans les espaces privés, semi-publics et publics. La littérature existante a largement étudié les antécédents psychologiques et contextuels du comportement de tri, mais en se focalisant principalement sur un lieu spécifique, sans considérer que le lieu de tri pourrait modérer l’influence de ces antécédents. Pour examiner cette question de recherche, nous développons un modèle dual du comportement de tri des déchets, fondé sur une intégration des cadres TPB (Theory of Planned Behavior) et NAM (Norm Activation Model). Pour le tester, nous avons collecté des données déclaratives sur les pratiques de tri de 296 étudiants français dans trois lieux successifs (domicile, université et trajet vers l’université), que nous avons analysées à l’aide d’équations structurelles (PLS-SEM). Bien que les routes psychologique et contextuelle influencent toutes deux le tri, leur importance relative varie selon les lieux. De plus, à l’université et sur le trajet vers l’université, la route contextuelle influence la route psychologique. Ces résultats éclairent les raisons pour lesquelles le comportement de tri des déchets ménagers peut être inconsistant selon les lieux, et invitent les chercheurs à répliquer les modèles de comportements pro-environnementaux dans tous les contextes pertinents avant de formuler des recommandations de politiques publiques visant à les promouvoir
A spectral induced polarization instrument using square-wave current injection to track critical zone processes: application to long-term monitoring of a wetland
No full textInternational audienceIn the last two decades, the improvement of both instruments and theory, as well as the broadened scope of applications, led to a spectacular development of the use of induced polarization. In particular, the richness of complex conductivity spectra is driving the scientific community towards vast deployment of this measurement method often referred to as spectral induced polarization (SIP). In this contribution, we describe an innovative multichannel instrument that we develop for fast monitoring of critical zone processes. The spectral content of a signal with line spectrum resulting from square-wave current is exploited by injecting successively three square-wave currents with periods of 1, 10 and 100 s, covering the frequency range of 10−2 to 102 Hz in less than 4 min. One data set consists of eight successive current injections at different depths. For each current injection, the electrical potential is simultaneously measured at seven dipoles. The time-series are recorded with a 2 kHz sampling rate, allowing to calculate by Fourier transform the amplitude and phase spectra up to 1 kHz for each quadrupole. The complex conductivity data was validated by a comparison with the commercial SIP-Fuchs instrument, despite a significant discrepancy below 0.1 Hz which may be due to a worse signal-to-noise ratio at low frequencies. The prototype version of the instrument has been installed in 2018 at a wetland at Ploemeur-Guidel hydrogeological observatory to monitor reactive processes with high spatial resolution across the top metre of soil. The instrumental device, controlled by a Gantner data acquisition system connected to a solar panel, is fully autonomous and consumes little energy. Acquisitions are made several times a day and recorded on a SD card. Seven-year continuous monitoring highlights significant temporal variations of both subsurface resistivity and phase angle. The absence of correlation between resistivity and phase variations in the continuously saturated soil thickness highlights the potential of the system to monitor and separate different types of dynamics processes, such as groundwater/surface water mixing and mineral precipitation/dissolution
Comparative Toxicity of Bordeaux Mixture by Ingestion and Cuticular Contact Under Climate Change Conditions on <i>Trichogramma cordubensis</i>
No full textInternational audienceIn the face of environmental contamination to copper, mainly resulting from frequent copper-based fungicide applications, it is crucial to understand the side effects of these pesticides on non-target organisms to favor sustainable pest management. Pest natural enemies are indeed severely exposed to copper fungicides through external physical contact and by ingestion. In this study, we assessed the effects of Bordeaux mixture applications on the longevity of the biological control agent Trichogramma cordubensis (Vargas and Cabello, 1985) (Hymenoptera: Trichogrammatidae). The first set of experiments aimed to evaluate the effective doses of Bordeaux mixture contamination by using eight doses from 0 g.L -1 to 160 g.L -1 . When ingesting honey contaminated with Bordeaux mixture the longevity of T. cordubensis was strongly reduced. Conversely, cuticular contact with Bordeaux mixture, without ingestion, had no effect on T. cordubensis longevity. The second set of experiments examined how the effects of Bordeaux mixture on T. cordubensis longevity were modulated by global warming conditions, under two fluctuating climatic regimes simulating current and future conditions in Burgundy, France. These experiments used effective doses obtained after the first experiments. Similarly to the first experiments, Bordeaux mixture ingestion led to strongly reduced longevity, whereas cuticular contact had no effects on T. cordubensis longevity. Warming conditions reduced T. cordubensis longevity by 36% after both ingestion and cuticular contact with Bordeaux mixture, with no statistical interaction with Bordeaux mixture. Ingesting Bordeaux mixture was considered to be slightly to moderately harmful, significantly reducing the longevity from 40% to 81% with increasing concentrations, whereas cuticular contact with Bordeaux mixture was harmless to T. cordubensis. This study sheds new light on the side effects of metal-based fungicides on natural enemies and their subsequent effects on biocontrol programs. It suggests that increasing temperatures should have deleterious effects on Trichogramma species, regardless of fungicide contamination by Bordeaux mixture
SIRT1 mediates brain metabolic and developmental consequences of methionine synthase deficiency in inborn errors of cobalamin metabolism
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Targeting Expanded CUG and CTG Repeats as a Therapeutic Approach for Myotonic Dystrophy Type 1 (DM1)
No full textInternational audienceMyotonic dystrophy type 1 (DM1) is caused by expanded CTG repeats, d(CTG) exp , transcribed into toxic r(CUG) exp RNA repeats that sequester splicing regulator MBNL1, leading to its loss‐of‐function. An emerging therapeutic strategy toward DM1 treatment relies on the inhibition of MBNL1 sequestration by using small molecules, oligomers, peptides, engineered proteins, or synthetic oligonucleotides that interact with CUG repeats at the RNA level and/or CTG repeats at the DNA level. This review covers ∼18 years of research in the field of CUG and CTG ligands that were identified or rationally designed as DM1 drug candidates, with an emphasis on their chemical structures, molecular design, RNA‐ or DNA‐binding modes, in vitro affinities and specificities, molecular mechanisms of action, and biological activity in DM1 models
In pursuit of security : armed conflict and support for democracy in Mali
No full text4 : otherThis paper studies how armed conflict affects public attitudes to democracy. We analyze the role of both experience and fear of violence in support for basic democratic principles andpreference for democratic rule in Mali, a country torn by a multi-dimensional conflict since 2012. We combine event location data with sub-nationally representative household surveydata including first-hand add-on survey modules on governance, peace and security collected yearly from 2014 to 2019. On the one hand, we find that exposure to violence has a smallnegative to zero effect on attitudes to democracy. Our results are robust to recent event-study approaches as well as to selection into migration. Behind the null effect of violence lieheterogeneities based on the identity of the armed group involved. On the other hand, fear of conflict has strong negative impacts on the public's commitment to democratic values andsupport for democracy. Greater support for military rule from fearful individuals is driven by those living in areas not affected by the conflict. In conflict-free areas, citizens are willingto forgo certain freedoms in pursuit of greater security
Two new species of Caloptilia (Lepidoptera, Gracillariidae) from New Caledonia inducing galls on Glochidion billardierei (Phyllanthaceae) and redescription of C. xanthopharella (Meyrick, 1880)
No full textInternational audienceNew Caledonia is a biodiversity hotspot with high levels of micro-endemism, yet its gracillariid fauna remains poorly documented. Here, two new species of Caloptilia Hübner, 1825 (Gracillariidae) are described from Glochidion J.R.Forst. & G.Forst. (Phyllanthaceae) host plants in Parc des Grandes Fougères, New Caledonia: Caloptilia augeas Guiguet, Lopez-Vaamonde, van Nieukerken & Ohshima, sp. nov ., and Caloptilia ceryneia Guiguet, Lopez-Vaamonde, van Nieukerken & Ohshima, sp. nov . Both species induce leaf galls on Glochidion billardierei Baill., co-occurring on the same host species, sometimes even on the same leaf. They exhibit distinct wing patterns, but very similar male and female genitalia, and DNA barcoding supports their status as separate species. These findings provide evidence for potential within-host sympatric speciation, as documented in other gall-inducing insects. The larval biology of C. augeas and C. ceryneia reveals a unique frass disposal behaviour, whereby waste is excreted through a hole and the aperture is subsequently sealed—an adaptation not previously reported in gall-inducing Lepidoptera. Our findings double the known number of gall-inducing species in Gracillariidae, highlighting that this life history strategy may be more common than currently appreciated. We also provide new information on distribution and host plants of Caloptilia xanthopharella (Meyrick, 1880), a leaf roller found on the same host plant, G. billardierei . These findings mark the first records of the subfamily Gracillariinae in New Caledonia. This study underscores the underexplored diversity of New Caledonian gracillariids and emphasises the conservation value of Parc des Grandes Fougères. Further surveys in the Indo-Pacific region may reveal additional yet undescribed Caloptilia species associated with Phyllanthaceae and help clarify the evolutionary mechanisms underpinning their diversification
Le mystère des pépites vertes (enfin résolu!) – A la source des matières colorantes des sites paléolithiques de la vallée de l’Ardèche
No full textNational audienceLes opérations archéologiques menées dans la vallée de l’Ardèche et du Chassezac ont livré un corpus remarquable de matières colorantes. Parmi elles, plusieurs fragments à inclusions vertes ont été identifiés à la grotte aux Points (30), à l’abri des Pêcheurs (07) et au Mas d’Aiguillon (07). Des matériaux similaires, mais sans inclusions, proviennent d’Huchard et de la Baume d’Oulen (07). L’étude pétrographique révèle une matrice argilo-ferrugineuse fine, associant hématite en feuillets et aluminosilicates, témoignant d’une origine probablement hydrothermale.Ces caractéristiques suggèrent qu’une stratégie de sélection a guidée la collecte des matières colorantes.Deux approches complémentaires ont été menées : la première, analytique (microscopie, Raman, DRX), pour déterminer la nature minéralogique des inclusions vertes ; la seconde, dans le cadre du PCR Pigmentothèque, pour rechercher des affleurements compatibles. Les prospections de 2024 ont abouti à la découverte, d’un affleurement présentant toutes les caractéristiques pétrographiques recherchées : matrice argilo-ferrugineuse et… pépites vertes
Possibilities, challenges, and limitations of dinosaur eggshells LA-ICP-MS U-Pb dating based on samples from Provence (Upper Cretaceous, France)
No full textObtaining accurate chronostratigraphic constraints on continental deposits is challenging, necessitating innovative dating approaches. Here, we investigate the feasibility of Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICP-MS) U-Pb dating of dinosaur eggshell fragments from the Late Cretaceous of Provence, France. Preliminary optical, Scanning Electron Microscopy (SEM), and cathodoluminescence (CL) analyses were critical for identifying zones of optimal preservation and mitigating potential diagenetic contamination. Results from two samples attributed to Megaloolithus mamillare and Cairanoolithus dughii yielded ages of 68.1 ± 4.7 Ma and 68.7 ± 10.2 Ma, respectively, broadly consistent with regional stratigraphic markers. Element mapping reveals significant spatial variation in U and Pb concentrations within individual eggshells, with zones of high contamination contrasting with well-preserved cores. The data highlight the crucial role of diagenesis and organic matter in influencing U-Pb system behavior, although it appears to be limited to early diagenesis. While LA-ICP-MS U-Pb dating of dinosaur eggshells presents substantial challenges, this study demonstrates its potential with careful sample selection and nuanced interpretation, paving the way for further refinement and broader application