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Measurements of quasar proximity zones with the Lyman- forest of DESI Y1 quasars
No full textInternational audienceThe intergalactic medium (IGM) around quasars is shaped by their dense environments and by their excess ionizing radiation, forming a "quasar proximity zone" whose size and anisotropy depend on the quasar's halo mass, luminosity, age, and radiation geometry. Using over 10,000 quasar pairs from the Dark Energy Spectroscopic Instrument (DESI) Year 1 data, with projected comoving separations , we investigate how the proximity zone of foreground quasars at affects Lyman-alpha absorption in their background quasars. The large DESI sample enables unprecedented precision in measuring this "transverse proximity" effect, allowing a detailed investigation of the signal's dependence on the projected separation of quasar pairs and the luminosity of the foreground quasar. We find that enhanced gas clustering near quasars dominates over their ionizing effect, leading to stronger absorption on neighboring sightlines. Under the assumption that quasar ionizing luminosity is isotropic and steady, we infer the IGM overdensity profile in the vicinity of quasars, finding overdensities as high as at comoving distance from the most luminous systems. Surprisingly, however, we find no significant dependence of the proximity profile on the luminosity of the foreground quasar. This lack of luminosity dependence could reflect a cancellation between higher ionizing flux and higher gas overdensity, or it could indicate that quasar emission is highly time variable or anisotropic, so that the observed luminosity does not trace the ionizing flux on nearby sightlines
Search for ttbar resonances in final states with exactly one or two leptons using 140 fb of pp collision data at TeV with the ATLAS experiment
No full textInternational audienceA search for heavy spin-1 and spin-2 resonances decaying into a top-antitop-quark pair has been performed with 140 fb of proton-proton collision data collected by the ATLAS experiment at the Large Hadron Collider at a centre-of-mass energy of TeV. Final states with either exactly one electron or muon, or exactly two leptons (, or ), large missing transverse momentum, and two jets, at least one of which must be identified as likely containing a b-hadron decay, are considered. The search targets resonances with both narrow and broad widths relative to the detector resolution, and with masses in the range of 0.4-5.0 TeV. No significant deviation from the Standard Model prediction is observed. Exclusion limits are set on the production cross-section times branching ratio for hypothetical bosons, Kaluza-Klein gravitons, and Kaluza-Klein gluons that decay into top-quark pairs
Constraining primordial non-Gaussianity from DESI DR1 quasars and Planck PR4 CMB Lensing
No full textInternational audienceWe present the first measurement of local-type primordial non-Gaussianity from the cross-correlation between million spectroscopically confirmed quasars from the first data release (DR1) of the Dark Energy Spectroscopic Instrument (DESI) and the Planck PR4 CMB lensing reconstructions. The analysis is performed in three tomographic redshift bins covering , covering a sky fraction of . We adopt a catalog-based pseudo- estimator and apply linear imaging weights validated on noiseless mocks. Compared to previous analyses using photometric quasar samples, our results benefit from the high purity of the DESI spectroscopic sample, the reduced noise of PR4 lensing, and the absence of excess large-scale power in the spectroscopic quasar auto-correlation. Fitting simultaneously for the non-Gaussianity parameter and the linear bias amplitude in each redshift bin, we obtain for a response parameter , and for . These results improve the constraints on by compared to the previous analysis based on the Legacy Imaging Survey DR9. Our results demonstrate the statistical power of DESI quasars for probing inflationary physics, and highlight the promise of future DESI data releases
Assessment of the tritium analysis performance of a nonylphenol-ethoxylate-free liquid scintillator by interlaboratory comparison
No full textInternational audienceWith a view to using liquid scintillators compliant with the REACH (Registration, Evaluation, Authorisation and Restriction of Chemicals) regulations, some laboratories have expressed an interest in testing the ProSafe LT+ , a liquid scintillator without nonylphenol-ethoxylates (NPE). In order to evaluate the impact of using this new liquid on the analysis results, the CETAMA consortium organised two interlaboratory comparisons. Two ranges of tritium activity were selected to meet the needs of environmental and waste monitoring. 23 laboratories took part in these exercises, comparing results obtained with Prosafe LT+ to those obtained with NPE-containing liquid scinitllators. From the results it was seen that the background and the background noise obtained with the nonylphenol-ethoxylates-free liquid scintillator are not significantly different from that of the usual liquid scintillator, whether for the waste or environmental domain, over short (15 min) or long (200 min) counting times. Furthermore, the decision threshold and the detection limit values estimated with ProSafe LT+ were no different from those of usual scintillators. However, for the measurement of samples, and particularly for samples with a tritium activity above 15 Bq/kg, the ProSafe LT+ presented a reduced measurement quality compared to the nonylphenol-ethoxylates-containing LS i.e. the measurement uncertainty obtained with ProSafe LT+ is systematically higher. In light of the results obtained through this study, the authors recommend the use of the ProSafe LT+ with the proviso that the deterioration in measurement uncertainty be taken into account and found to be compatible with a laboratory’s individual needs
Numerical simulation of band gap characteristics of periodic curved stiffened plates considering fluid-structure interaction
No full textInternational audienceCurved stiffened plates are frequently subjected to vibration challenges during their application in marine and underwater engineering structures. Traditional vibration mitigation strategies, such as increasing structural stiffness or incorporating high-damping materials, often lead to increased design complexity. In this study, a novel vibration reduction approach is proposed by designing periodic structures with appropriately arranged curved stiffeners. This approach leverages the unique band gap characteristics of periodic structures for vibration attenuation. A numerical framework is established for band gap analysis of arbitrarily curved stiffened plates, incorporating fluid-structure interaction (FSI) effects. Specifically, the constitutive model of the curved stiffened plate is derived using the Mindlin plate theory and Timoshenko beam theory. The fluid-structure interaction is modeled via the added mass method, and periodic boundary conditions are applied to both the plate and the fluid domains based on Bloch's theorem. Numerical validation confirms the accuracy of the modal analysis for curved stiffened plates. The importance of properly arranging curved stiffeners was demonstrated through time-domain dynamic analyses of several finite structures, which also confirmed the effectiveness of the band gap. The influence of the fluid environment on the system's band gap characteristics was thoroughly examined. Particular attention was given to how the amplitude, wavelength, and structural parameters of sinusoidal stiffeners affect the band gap, as well as the anisotropic propagation of elastic waves in sinusoidal stiffened plates. The results indicate that specific stiffener designs play a critical role in tuning band gap properties and enhancing structural vibration performance, offering valuable insights for vibration reduction in fluid-structure coupled curved stiffened plate applications
Boucler la boucle du parcours de Morris
No full textInternational audienceL'algorithme de Morris parcourt un arbre mutable en temps linéaire et en espace constant. L'arbre est modifié au cours de l'itération, mais restauré au fur et à mesure. Nous en proposons une preuve avec Creusot, un outil de vérification déductive de programme Rust
Sputtered species during ion irradiation of adenine: Implications for Titan's atmospheric chemistry
No full textCassini-Huygens detected complex molecules exceeding several thousand atomic mass units in Titan's atmosphere as well as energetic O+, OH+ and H2O+ ions in Saturn's magnetosphere. The heavy molecules are suggested to be nitrogenous polycyclic aromatic hydrocarbons (PANH). The energetic ions are thought to penetrate into Titan's atmosphere, potentially modifying the structure and chemistry of these macromolecules. This study investigates the composition of chemical species sputtered into the gas-phase once energetic ions impact said macromolecules. We have irradiated thin film samples of adenine (C5H5N5), a heterocyclic aromatic, at the HUN-REN Institute for Nuclear Research (ATOMKI) in Debrecen, Hungary. The experiments varied key parameters such as ion type (Neq+, Oq+, OHq+ and H2Oq+), energies (10 and 20 keV), temperatures (150 and 300 K) and fluences (up to 2 × 1015 ions . cm-2). In-situ quadrupole mass spectrometry measured the residual gas of the experimental chamber, analysing the material that was sputtered into the gas phase during irradiation. The deconvolution of these mass spectra was done using a Monte-Carlo approach, revealing a plethora of compounds including HCN, N2, C2N2, C2H3N, C3HN, CH2N2, NH3, C2H2 and CH4. Larger species like C5H5N5, C4H4N4 and C3H3N3 were only detected at the on-set of the irradiation. The sputtering of hydrocarbons and nitriles highlights a potential feedback mechanism in Titan's atmosphere. The direct formation of CO and CO2 from PANH irradiation appears unlikely
L’avenir de la coopération au développement : vers un monde post-APD ?
No full textInternational audienceNone of the Sustainable Development Goals will be met by 2030: persistent poverty, growing inequalities and inadequate financial resources attest to this collective failure. Even as ODA declines, the costs of eradicating extreme poverty remain within reach. The emergence of a ‘post-ODA world’ reveals a crisis of purpose, two competing visions of what is needed: ‘improve’ the aid architecture we have or ‘reinvent’ it, breaking with the colonial or hierarchical underpinnings. Western NGOs, faced with a double imperative – decolonial and environmental - must re-think their economic models, power structures and partnerships to contribute to a new order of international cooperationEn 2030, aucun Objectif de développement durable ne sera atteint : la pauvreté persistante, les inégalités accrues et le financement insuffisant marquent cet échec collectif. Alors que l’Aide publique au développement (APD) décline, les coûts de l’éradication de l’extrême pauvreté demeurent accessibles. L’émergence d’un « monde post-APD » révèle une crise de finalité où s’affrontent deux visions : « améliorer » l’existant ou « réinventer » l’architecture du développement en rompant avec ses logiques coloniales et hiérarchiques. Confrontées à une double injonction décoloniale et environnementale, les ONG occidentales doivent repenser les modèles économiques, les structures de pouvoir et les partenariats afin de contribuer à un nouvel ordre de coopération international
Bayesian network-informed conditional random forests for probabilistic multisite downscaling of precipitation occurrence
No full textInternational audienceThis work introduces Bayesian network-informed conditional random forests (BNICRF): a novel multiresponse classification method for downscaling the joint probability distribution of precipitation occurrence at multiple geographical locations from large-scale reanalysis predictors. BNICRFs combine a Bayesian network to model spatial dependencies and a set of random forests to predict local precipitation from large-scale inputs. Extending prior studies on Bayesian networks and random forests in climate downscaling, this method is validated under the experimental framework of the COST action VALUE (the largest, most exhaustive intercomparison study of statistical downscaling methods to date). Results demonstrate that BNICRFs effectively capture spatial relationships while maintaining single-site predictive performance comparable to single-site random forests and a well-performing generalized linear model in VALUE. Additionally, BNICRFs outperform a robust multisite approach proposed in Chandler (2020) in predictive capability while matching spatial performance. Incorporating temporal structures further enables BNICRFs to generate temporarily and spatially realistic precipitation occurrence fields
PanGBank: a database of pangenome graphs for comparative microbial genomics
No full textInternational audiencePangenome analysis provides crucial insights into microbial diversity, evolution, and adaptation. However, publicly available downloadable pangenome resources to support such studies are currently lacking. In this context, we present PanGBank, a comprehensive database compiling pangenome collections constructed with the PPanGGOLiN software suite .PanGBank currently provides pangenomes for 3,873 prokaryotic species represented by ≥15 genomes, built through a reproducible NextFlow pipeline. The resource includes a RESTful API for programmatic access and a user-friendly web interface (https://pangbank.genoscope.cns.fr) for intuitive exploration by non-developer researchers. As of today, PanGBank comprises two pangenome collections built from genomes (originating from RefSeq and GenBank) of the GTDB taxonomic database (release R10-RS220) (2) ensuring broad coverage of microbial diversity.PanGBank provides a scalable and updatable platform for pangenome exploration across microbial clades. By offering multiple curated pangenome collections, it fills a critical gap in the field and paves the way for broader, collaborative, and data-driven microbial genomics research. As a use case, PanGBank and the new features introduced in PPanGGOLiN version 2 are being applied to explore antibiotic resistance in Acinetobacter baumannii from a pangenome perspective