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Standard Sirens in 2040s: Probing the Cosmic Expansion History with Gravitational Waves and Spectroscopic Galaxy Surveys
No full textInternational audienceGravitational waves (GWs) from compact binary coalescences have matured into a robust cosmological probe, providing self-calibrated luminosity distance measurements independent of any cosmic distance ladder, hence the term "standard sirens". The binary neutron star merger GW170817 delivered the first such measurement of the Hubble constant, demonstrating that GWs offer a path to precision cosmology with systematics orthogonal to standard cosmological probes. To convert GW distances into cosmological parameters, redshift information is essential. To maximize the scientific potential, the redshift must be obtained from individual galaxies, either by identifying electromagnetic counterparts of GW events (bright sirens) or by statistically associating potential hosts within the GW localization volume (dark sirens). The precision of these redshifts sets the achievable accuracy. Forecasts show that photometric uncertainties degrade cosmological constraints by up to an order of magnitude compared to spectroscopic ones. Wide-field, high-multiplex spectroscopic facilities will therefore be an essential infrastructure for GW cosmology in the 2040s
Beyond Stage IV: Quasar and Galaxy Clustering and the Fundamental Physics of the 2040s
No full textInternational audienceStage IV galaxy surveys (DESI, 4MOST, MOONS, Euclid) are establishing precision constraints on cosmological parameters through baryon acoustic oscillations and redshift-space distortions, yet fundamental questions on neutrino masses, inflationary physics, and the nature of gravity remain beyond their reach. We present a science case for next-generation wide-field spectroscopic surveys targeting with simultaneous observations of thousands of galaxies, quasars, and emission-line galaxies. Such surveys would deliver transformative advances: (i) cosmological constraints on absolute neutrino masses (), three times more stringent than Stage IV, enabling resolution of the neutrino mass hierarchy; (ii) detection of primordial non-Gaussianity at the level of , probing multi-field inflation; (iii) measurements of structure growth spanning cosmic time to constrain dark energy and test gravitational modifications. Achieving these goals requires revolutionary advances in spectroscopic multiplexing ( simultaneous spectra), sub- redshift precision at scale, and field-level inference techniques exploiting higher-order clustering statistics. We demonstrate that the proposed Wide-field Spectroscopic Telescope concept provides a technically feasible and scientifically compelling path to unlock the physics of neutrinos, inflation, and gravity that will remain inaccessible to Stage IV surveys
Freins d'accès aux services de santé en Polynésie française : approche qualitative
No full textInternational audienceIntroduction : L’accessibilité des services biomédicaux constitue un défi complexe en Polynésie française. La configuration territoriale en de multiples îles dispersées et la centralisation des filières spécialisées à Tahiti voire en dehors du territoire impliquent des mobilités parfois contraignantes pour les usagers et propices aux inégalités d’accès. But de l’étude : À partir d’une recherche qualitative et inductive centrée sur l’expérience ordinaire des usagers, l’article identifie différents facteurs contraignant l’accès aux services biomédicaux dans ce contexte.Résultats : L’approche qualitative et inductive constitue une entrée particulièrement pertinente pour comprendre le point de vue des usagers en matière d’accessibilité des services de santé et identifier la pluralité des facteurs pouvant contraindre l’accès à ces services. L’éloignement du domicile, parfois prolongé ou répété, implique des coûts et des contraintes multiples. Les usagers mobilisent des ressources privées (relations familiales, capital économique) pour pallier ces contraintes, couvrir les besoins non pris en charge par le système de protection sociale et accéder aux services des filières spécialisées. Les usagers les moins dotés en ressources économiques et sociales peuvent renoncer aux services biomédicaux en raison de l'absence de solutions d’hébergement sur le lieu de prise en charge ou des coûts trop élevés impliqués par leur séjour. Les relations familiales, toutefois ambivalentes, peuvent également être un motif d’empêchement d’accès aux soins (mésententes ; obligations). Conclusions : Les ressources économiques et les relations familiales constituent des déterminants de l’accès aux soins et services biomédicaux en Polynésie française, pouvant conduire les usagers à renoncer à une prise en charge
Formation dynamics of an ethylene carbonate-derived solid–electrolyte-interphase in commercial Li-ion batteries
No full textInternational audienceThe importance of the solid–electrolyte-interphase (SEI) is well-established in lithium-ion (Li-ion) batteries, but the technical story behind its formation remains incomplete. Current research has largely focused on the nature of the deposited layer, while the formation dynamics, particularly those occurring in the solution phase, remain elusive. Here, by employing operando infrared fiber evanescent wave spectroscopy (IR-FEWS) to conduct real-time monitoring of the chemical dynamics of ethylene carbonate-based electrolytes and graphite anodes, we reveal that the assembly of the SEI layer follows a classical heterogeneous nucleation and growth process under appropriate kinetic constraints. Our findings, supported by various other in situ/ex situ techniques, show that during charging, the newly generated species (e.g. lithium ethylene dicarbonate (LEDC) and Li2CO3), that are destined for the SEI, can also diffuse away from the graphite–electrolyte interface into the electrolyte. The deposition of the species occurs via a heterogeneous nucleation process with the low-solubility inorganic species (e.g. Li2CO3) preferentially nucleating on the graphite surface, followed by more-soluble organic species (e.g. LEDC). Limiting diffusion to promote the deposition is crucial for facilitating efficient SEI formation with competitive deposition kinetics depending not only on the charging rate and temperature, but also the electrolyte quantity. When the formation parameter-space is intentionally modified by employing a high current pulse during initial charging followed immediately by an ageing step, a more stable SEI with lower resistance is developed, leading to longer lifetimes for the Li-ion pouch cells prepared with this new protocol. Collectively, these findings deepen our mechanistic understanding of SEI formation from the “solution” phase perspective and offer an enriched framework for defining initial charging protocols for battery manufacturing
Motor complications and postural abnormalities interplay in Parkinson's disease
No full textInternational audienceBackground: Postural abnormalities (PA) and motor complications (MCs, including motor fluctuations - MFs- and levodopa-induced dyskinesia - LIDs) are hallmark of Parkinson's disease (PD) progression, yet their relationship remains poorly understood.Objective: To investigate the association between PA and MCs, motor symptoms, and non-motor symptoms (NMS) in patients with PD, and to assess whether PA influences the development of MCs over time.Methods: Data of the prospective NS-Park cohort (27 French PD Expert Centers) were analysed. PA was defined by a score ≥2 on item 3.13 of the MDS-UPDRS-III. Associations between PA and MCs, as well as with other motor symptoms and NMS, were assessed using logistic regression models. We used interval censoring survival models to assess the associations between PA at inclusion and the incidence of MCs. Analyses were adjusted for sex, age, disease duration, dopaminergic dose, and disease severity.Results: Among 13,037 included PD patients (58.7 % male, median age at diagnosis 61 years), 724 (5.6 %) presented with PA. Patients with PA had longer disease duration, higher disease severity, and higher dopaminergic treatment. PA exhibited a higher prevalence of troublesome MFs (OR: 5.96; 95 % CI: 4.25-8.32) and LIDs (OR: 2.81; 95 % CI: 1.79-4.30), while associations with milder MCs were inconsistent. However, PA was not significantly associated with the development of MCs during follow-up.Conclusions: PA are associated with more frequent severe MCs, and a higher burden of motor and NMS, making patient care particularly challenging
Camera calibration of the first Large-Sized Telescope of the Cherenkov Telescope Array Observatory
No full textInternational audienceThe Cherenkov Telescope Array Observatory (CTAO), a forthcoming very-high-energy gamma-ray facility, will use the Imaging Atmospheric Cherenkov Technique (IACT) to achieve unprecedented energy and angular resolution from 20 GeV to 300 TeV. Large-Sized Telescopes (LSTs) are crucial for the low-energy range. This paper details the calibration tools and methods developed for the first LST (LST-1) to ensure the precise conversion of photomultiplier tube signals and accurate photon timing, vital for the reconstruction of extensive air showers. This framework supports LST-1’s early science and will be applied to future LSTs
Culturable macroplastic-associated potential human pathogens in coral reef lagoons, Madagascar
No full textInternational audiencePotentially human pathogenic bacteria (PHPBs) have been detected in plastic-associated marine microbiomes, primarily through DNA-based methods. However, data on their culturability and concentrations on plastics remain limited, yet are essential to assess actual health risks. To address this gap, 70 floating macroplastic and 20 seawater samples were collected from two human-impacted reef lagoons in southwestern Madagascar (Atsimo-Andrefana region). PHPBs were cultured from their microbiomes using selective media and quantified. Macroplastics were predominantly polypropylene (34 %) and polyamide (31 %). In increasing order of concentration, four culturable PHPBs, Staphylococcus aureus, Escherichia coli, Enterococcus faecalis, and Vibrio Harveyi clade species, were identified on both macroplastics and in seawater, across all sites and polymer types. Notably, 52 % of macroplastic samples harbored two PHPB species simultaneously, while only 7 % were PHPB-free. Concentrations of all PHPBs were consistently and significantly higher on macroplastics than in seawater, regardless of the measurement unit or polymer type, with the Vibrio Harveyi clade being the most abundant. No significant correlations were observed among PHPB species concentrations, suggesting limited interaction and independent colonization. These findings indicate that floating macroplastics may serve as reservoirs and fomites for viable PHPBs. However, their potential impacts on ecosystems and human health should be interpreted cautiously. We emphasize the need to contextualize PHPB concentration data by considering factors such as exposure pathways, environmental persistence, and bacterial virulence, rather than relying solely on concentration-based comparisons, which may lead to misinterpretation
Token positional games
No full textThe classical Maker-Breaker positional game is played on a board which is a hypergraph H, with two players, Maker and Breaker, alternately claiming vertices of H until all the vertices are claimed. When the game ends, Maker wins if she has claimed all the vertices of some edge of H; otherwise, Breaker wins. Playing this game in real life can be done by placing tokens on the vertices of the board. In this paper, we study the unfortunate case in which one or both players do not have enough tokens to cover all the vertices and, as such, will have to move their tokens around at some point instead of placing new ones. There may be a bias, in that Maker and Breaker do not necessarily have the same amount of tokens. The present paper initiates the study of this generalization of positional games, called token positional games.A particularly interesting case is when Maker has a winning strategy in the classical game: what is the lowest number of tokens with which she still wins against Breaker's unlimited stock? We notably show that, for k-uniform hypergraphs on an arbitrarily large number n of vertices, this number equals k if k ∈ {2, 3} but can vary from k to Ω(n) if k ≥ 4. From an algorithmic point of view, PSPACE-hardness in general is inherited from classical positional games, but we get a polynomial-time algorithm to solve the case where Breaker only has one token. We also establish EXPTIME-completeness for a "token sliding" variation of the game.</div
A Constructive Method to Minimize the Index of Coincidence under Marginal Constraints
No full textWe consider the problem of minimizing the index of coincidence of a joint distribution under fixed marginal constraints. This objective is motivated by several applications in information theory, where the index of coincidence naturally arises.A closed-form solution is known when the marginals satisfy a strong feasibility condition, but this condition is rarely met in practice. We first show that the measure of the set of marginals for which condition applies vanishes as the dimension grows.We then characterize the structure of the optimal coupling in the general case, proving that it exhibits a monotone staircase of zero entries. Based on this structure, we propose an explicit iterative construction and prove that it converges in finitely many steps to a minimizer.Main result of the paper is a complete constructive solution of index-of-coincidence minimization
Which signal(s) can we retrieve from a phylogenomic analysis of a plant syngameon
No full textInternational audienceA syngameon is a multispecies interbreeding network —that is, a group of otherwise distinct species linked by limited gene exchange. Although the term was coined a century ago, the value of this framework in understanding the diversity of organisms, such as oaks, pines, and eucalyptus, has only recently been recognized.Armeria (Plumbaginaceae) is a diploid plant genus of mostly Mediterranean perennial herbs, and is a syngameon based on abundant independent evidence. It ranks third among genera with the most endemic species in the Iberian Peninsula.To build an evolutionary framework for Armeria, which remained elusive using Sanger sequencing technology-based analyses, we have initiated a project in which we will use a targeted high-throughput sequencing approach with a custom-designed bait kit, combined with genome skimming (HybSeq). Due to the interbreeding nature of this network, a relevant question is which signals —taxonomic, geographic, or mixed— we will be able to recover, and in which regions and lineages. We hypothesize that a geographic signal will be strong in highly diverse regions, such as the Iberian Peninsula. We anticipate a contrasting scenario for the distinct A. maritima group, which spans the largest range across several continents but co-occurs with few or no other congeners. Phylogenomic analysis of the entire genus will be complemented by phylogeographic approaches for two groups: the A. maritima group and the A. villosa group. The latter consists of a species that underwent adaptive introgression from several congeners in different parts of its range, resembling the relative old compilospecies concept