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Search for planetary-mass ultra-compact binaries using data from the first part of the LIGO--Virgo--KAGRA fourth observing run
No full textInternational audienceWe present a search for gravitational waves from inspiraling, planetary-mass ultra-compact binaries using data from the first part of the fourth observing run of LIGO, Virgo and KAGRA. Finding no evidence of such systems, we determine the maximum distance reach for such objects and their merger rate densities, independently of how they could have formed. Then, we identify classes of primordial black-hole mass distributions for which these rate limits can be translated into relevant constraints on the mass distribution of primordial black holes, assuming that they compose all of dark matter, in the mass range . Our constraints are consistent with existing microlensing results in the planetary-mass range, and provide a complementary probe to sub-solar mass objects
Verres aluminoborosilicatés dopés au bismuth synthétisés sous haute pression : rôle du bismuth sur la solubilité de l'iode
No full textInternational audienceBismuth-aluminoborosilicate glasses have gained interest as a possible matrix for nuclear waste immobilisation, as bismuth-based sorbents have enhanced affinity for volatile radioisotopes removal. Conjointly, it has been recently demonstrated that using high-pressure conditions is an interesting tool to improve volatile elements retention during glass synthesis. This study tries to combine these two fields showing significant improvement in 129-iodine incorporation into the structure of Bi-bearing glasses synthesised under high-pressure conditions (1 GPa and 1250°C) by comparison with Bi-free glasses or Bi-containing glasses obtained at ambient pressure. Two series of glasses have been investigated in the SiO2-Al2O3-B2O3-Na2O-CaO-Bi2O3 system, either with high (~13 mol.% Al2O3) or low (~5mol.% Al2O3) Al2O3 and Bi2O3 content ranging from 0.5 to 16 mol.%. We show that I incorporation increases with increasing Bi2O3 and can reach up to 2.8 mol.%, which is much higher than Bi-free comparable glasses synthesised under the same conditions. The 11 B NMR analysis demonstrated a drastic decrease in the proportion of tetrahedral BO4 with increasing Bi2O3 content regardless of the alumina content. 27 Al displayed a large majority of IV Al, with a steady increase of CN Al for the Al-rich series, and nearly constant CN Al for the Al-poor series as we increase Bi2O3 content. O 1s XPS spectra demonstrates a clear change towards a general depolymerisation of the glass structure with increasing Bi2O3 content. It confirms the network-modifier role of Bi 3+ in such a glass system and explains the increase in I content. This work paves the way for new glass composition to be synthesised using high-pressure to address the worldwide issue of the volatile nuclear wastes.Les verres à base aluminoborosilicatés dopés en bismuth ont suscité un intérêt croissant en tant que matrice potentielle pour l'immobilisation des déchets nucléaires, notamment car les sorbants à base de bismuth présentent une affinité accrue pour l'adsorption des radio-isotopes volatils. Parallèlement, il a récemment été démontré que l'utilisation de conditions de haute pression constituait un outil intéressant pour améliorer la rétention des éléments volatils lors de la synthèse du verre. Cette étude tente de combiner ces deux domaines en montrant une amélioration significative de l'incorporation de l'iode dans la structure des verres contenant du Bi; synthétisés dans des conditions de haute pression (1 GPa et 1250 °C) par rapport aux verres sans Bi ou aux verres contenant du Bi obtenus à pression ambiante. Deux séries de verres ont été étudiées dans un système a base silicaté, avec une teneur élevée (~13 mol.% Al2O3) ou faible (~5mol.% Al2O3) en Al2O3 et une teneur en Bi2O3 comprise entre 0,5 et 16 mol.%. Nous montrons que l'incorporation d'I augmente avec l'augmentation de Bi2O3 et peut atteindre jusqu'à 2,8 mol.%, ce qui est beaucoup plus élevé que les verres comparables sans Bi synthétisés dans les mêmes conditions. L'analyse RMN 11B a démontré une diminution drastique de la proportion de BO4 tétraédrique avec l'augmentation de la teneur en Bi2O3, quelle que soit la teneur en alumine. Le 27Al a montré une grande majorité d'Al IV, avec une augmentation régulière de CN Al pour la série riche en Al, et un CN Al presque constant pour la série pauvre en Al à mesure que nous augmentons la teneur en Bi2O3. Les spectres XPS O 1s montrent un changement clair vers une dépolymérisation générale de la structure du verre avec l'augmentation de la teneur en Bi2O3 . Cela confirme le rôle de modificateur de réseau du Bi 3+ dans un tel système de verre et explique l'augmentation de la teneur en I. Ces travaux ouvrent la voie à la synthèse d'une nouvelle composition de verre à haute pression pour répondre au problème mondial des déchets nucléaires volatils
Site-specific attachment of a H2-evolving artificial metalloenzyme onto carbon nanotubes via electrografting of a protected thiophenolate diazonium salt
No full textInternational audienceThe development of efficient and stable electrodes for hydrogen evolution is a key challenge in the field of artificial enzymes and bioelectrocatalysis. We report the tuning of an artificial metalloenzyme–electrode interface using a covalent near-monolayered thiophenolate functionalisation of multiwalled carbon nanotubes (MWCNT). To this end, we synthesized, characterized, and electrografted 4-diazophenyl disulfide bis(tetrafluoroborate) to the surface of carbon-nanotube electrodes. A subsequent deprotection step yields highly functionalized thiophenolate-modified CNTs, which were employed for the immobilization of ferrocene derivatives and rubredoxins either via disulfide or thiolene formation. Introduction of a surface-accessible cysteine residue via site-directed mutagenesis of rubredoxin – followed by Fe-to-Ni metal substitution – affords the site-specific immobilization of this H2-evolving artificial metalloenzyme, which delivers up to 4 mA cm−2 at 800 mV overpotential
Interactions between ionizing radiation and Vairimorpha (Nosema) ceranae on the honeybee, Apis mellifera L.
No full textInternational audienceThe global decline of honeybee colonies represents a major ecological concern, primarily attributed to simultaneous exposure to multiple stressors. These include biotic pressures, such as parasitic infections, and abiotic pressures, such as exposure to ionizing radiation, which remains poorly understood. Assessing their combined effects provides novel insights into how biological and radiological stressors interact within the organism. Here, we investigated the individual and combined effects of Vairimorpha ceranae (formerly Nosema ceranae) infection and chronic gamma irradiation (14 µGy/h or 14 × 10³ µGy/h) on honeybee health. Measurements included survival, syrup consumption, spore load, and biomarkers related to energy metabolism, antioxidant defenses, immunity, detoxification, and neural enzyme activity. Two successive experiments, conducted at different collection periods, allowed us to account for biological variability between bee cohorts. Infection by V. ceranae caused high mortality and major impairments in metabolic, antioxidant, and immune functions. Ionizing radiation induced more moderate effects, characterized by redox imbalance and reduced detoxification capacity, which varied with dose rate. Under combined exposure, the two stressors produced mainly antagonistic interactions affecting antioxidant, immune, and detoxification systems. However, a synergistic effect was observed on ATP production, suggesting an energetic compensation mechanism. These findings highlight complex physiological disturbances, revealing the multifactorial vulnerability of honeybees and emphasizing the need to integrate interactions between multiple stressors and natural biological variability into ecotoxicological assessments
On modeling quantum point contacts in quantum Hall systems
No full textQuantum point contacts (QPC) are a key instrument in investigating the physics of edge excitations in the quantum Hall effect. However, at not-so-high bias voltage values, the predictions of the conventional point QPC model often deviate from the experimental data both in the integer and (more prominently) in the fractional quantum Hall regime. One of the possible explanations for such behaviors is the dependence of the tunneling between the edges on energy, an effect not present in the conventional model. Here we introduce two models that take QPC spatial extension into account: wide-QPC model that accounts for the distance along which the edges are in contact; long-QPC model accounts for the fact that the tunneling amplitude originates from a finite bulk gap and a finite distance between the two edges. We investigate the predictions of these two models in the integer quantum Hall regime for the energy dependence of the tunneling amplitude. We find that these two models predict opposite dependences: the amplitude decreasing or increasing away from the Fermi level. We thus elucidate the effect of the QPC geometry on the energy dependence of the tunneling amplitude and investigate its implications for transport observables
Polyselenylsulfides as neglected central intermediates in Selenium cycling
No full textInternational audienceSelenium (Se) is an essential yet toxic trace element with one of the narrowest nutritional optimums of all elements. The speciation of Se significantly influences its mobility, bioavailability, bioaccumulation, and toxicity. Se cycling in the environment has been generally understood as a sequence of bidirectional redox processes of Se species. Elemental Se (Se0) is considered a central species that is thermodynamically favoured in the redox conditions found in most environments. The identification of a novel group of dissolved species, polyselenylsulfides (with the general formula SexSy2-), is reported in this work. These species form upon the reaction of Se0 with sulfide. Using derivatisation and ultrahigh-performance liquid chromatography electrospray ionisation quadrupole time-of-flight mass spectrometry (UHPLC–ESI–qTOF–MS), polysulfides (Sx2-, x = 2–6), selenide (Se2-), polyselenides (Sex2-, x = 2–3), and previously undetected polyselenylsulfides (SeS2-, SeS22-, Se2S2-, and SeS32-) were detected. The reaction was spontaneous and proceeded rapidly at alkaline pH (completed within <24 h). A slower and incomplete reaction was observed at circumneutral pH. The fast and spontaneous reaction down to circumneutral pH suggests the ubiquitous importance of polyselenylsulfides in sulfidic environments and calls for revising the environmental fate of Se. The existence of polyselenylsulfides challenges the traditional 'selenocentric' view, which focuses on specific, bidirectional redox reactions involving Se species only. Moreover, the perception of Se0 as a terminal, insoluble species in many anoxic environments is questioned. Adoption of a "chalcogenic perspective" is proposed, wherein the Se and sulfur (S) cycles are closely interconnected, and the fate of Se is governed by the presence of sulfide
Log-time algorithms for exact stochastic simulation of fully-connected reaction networks using low-rank decomposition and rejection sampling
No full textInternational audienceWe show how to adapt and modify the \gls{ssa}, also known as the Lanore-Gillespie algorithm, to exactly and efficiently simulate a chemical reaction network following rate equations for large dense systems, bypassing the quadratic time and space complexity of the original algorithm, by combining a low-rank decomposition of the upper bound of the propensity matrix with rejection sampling to significantly reduce the time and memory manipulation costs of the reaction priority queues. The resulting algorithms exhibit logarithmic-time and linear-space complexity, which allows us to reach physical times and system sizes that were unattainable for previous simulations (deterministic or stochastic) due to a substantial speed-up of several orders of magnitude compared to the \gls{ssa}, along with considerably less memory consumption than any previous methods. As a physical application, we simulate the time evolution of solute precipitation in a FeCu alloy under thermal ageing. The resulting temporal evolution of the distribution and cluster size of Cu precipitates also matches very well with small-angle neutron scattering experiments
Robust estimation with latin hypercube sampling: a central limit theorem for Z-estimators
No full textLatin hypercube sampling (LHS) is a widely used stratified sampling method in computer experiments. In this work, we extend the existing convergence results for the sample mean under LHS to the broader class of -estimators, estimators defined as the zeros of a sample mean function. We derive the asymptotic variance of these estimators and demonstrate that it is smaller when using LHS compared to traditional independent and identically distributed (i.i.d.) sampling. Furthermore, we establish a Central Limit Theorem for -estimators under LHS, providing a theoretical foundation for its improved efficiency
The way forward for assessing the human health safety of cosmetics in the EU: Proceedings of Workshop 2
No full textInternational audienceAbstractUnder the European Cosmetic Regulation, safety assessments of cosmetics and their ingredients must be conducted without the use of animals. This regulatory requirement poses a number of challenges, as validated alternative methods are only available for some of the toxicological endpoints that are typically considered in standard human health risk assessments. Despite significant progress since the ban in 2013, particularly in the development of New Approach Methodologies (NAMs) for local and acute toxicity, and for mutagenicity/genotoxicity, there remains an urgent need for non-animal test methods to assess systemic toxicity, which often becomes evident after repeated or long-term exposure. Currently, no validated animal-free alternatives are available for assessing sub-acute, sub-chronic and chronic toxicity, carcinogenicity, developmental/reproductive toxicity, or for a major part of toxicokinetics. In response to these challenges, the Methodology Working Group of the Scientific Committee on Consumer Safety organised a dedicated workshop in December 2024 to discuss advances in the application of Next Generation Risk Assessment (NGRA) as a strategic animal-free approach for the safety assessment of cosmetic ingredients. The workshop focused on a number of important key issues for the practical application of NAMs and NGRA, their regulatory acceptance and identification of possible (partial) solutions to overcome existing limitations
Forecasting Primordial Non-Gaussianity from UNIONS Lyman-Break Galaxies and Planck CMB lensing
No full textInternational audiencePrimordial non-Gaussianities (PNGs), characterized by , provide a powerful window into the physics of inflation. Cross-correlating high-redshift tracer samples with the CMB lensing potential offers a particularly robust probe of PNGs, mitigating imaging systematics that typically affect large-scale measurements from tracer auto-spectra. In this context, UNIONS enables the selection of -dropout high-redshift Lyman-Break Galaxies (LBGs). We perform a MCMC-based forecast to estimate the uncertainties on and on a galaxy bias parameter, which captures our uncertainty in the tracer bias. From the angular cross-power spectrum between LBGs and Planck CMB lensing, we forecast for an idealized photometric sample of LBGs selected with a Random Forest classification algorithm from UNIONS-like imaging, with a resulting surface density of deg. This precision can be improved to after spectroscopic follow-up with DESI, during its next phase starting in 2029, DESI-II. We test a more realistic -dropout LBG selection using early UNIONS data, which yields a denser sample of objects at deg. From this sample, covering a larger footprint and expected to have a higher large-scale galaxy bias, we forecast , with similar precision achievable after DESI spectroscopic follow-up. In addition, we perform preliminary validation of the redshift distribution using the clustering-redshift method with DESI DR1 data, confirming the calibration from deep, small-area photometric fields. However, accounting for uncertainties in the clustering-redshift distribution significantly degrades the constraining power