Exploring nuclear structure with multiparticle azimuthal correlations at the LHC

International audienceUnderstanding nuclear structure provides essential insights into the properties of atomic nuclei. In this paper, details of the nuclear structure of $^{\rm 129}$Xe, such as the quadrupole deformation and the nuclear diffuseness, are studied by extensive measurements of anisotropic-flow-related observables in Xe$-$Xe collisions at a center-of-mass energy per nucleon pair $\sqrt{s_{\rm NN}} = 5.44$ TeV with the ALICE detector at the LHC. The results are compared with those from Pb$-$Pb collisions at $\sqrt{s_{\rm NN}} = 5.02$ TeV for a baseline, given that the $^{\rm 208}$Pb nucleus is not deformed. Furthermore, comprehensive comparisons are performed with a state-of-the-art hybrid model using IP-Glasma+MUSIC+UrQMD. It is found that among various IP-Glasma+MUSIC+UrQMD calculations with different values of nuclear parameters, the one using a nuclear diffuseness parameter of $a_0=0.492$ and a nuclear quadrupole deformation parameter of $\beta_2=0.207$ provides a better description of the presented flow measurements. These studies represent an important step towards a thorough exploration of the imaging power of nuclear collisions at ultrarelativistic energy and the search for the imprint of nuclear structure on various flow observables in heavy-ion collisions at the LHC. The findings demonstrate the potential of nuclear structure studies at the TeV energy scale and highlight that the LHC experiments can complement existing low-energy experiments on nuclear structure studies

Real-bogus scores for active anomaly detection

International audienceIn the task of anomaly detection in modern time-domain photometric surveys, the primary goal is to identify astrophysically interesting, rare, and unusual objects among a large volume of data. Unfortunately, artifacts -- such as plane or satellite tracks, bad columns on CCDs, and ghosts -- often constitute significant contaminants in results from anomaly detection analysis. In such contexts, the Active Anomaly Discovery (AAD) algorithm allows tailoring the output of anomaly detection pipelines according to what the expert judges to be scientifically interesting. We demonstrate how the introduction real-bogus scores, obtained from a machine learning classifier, improves the results from AAD. Using labeled data from the SNAD ZTF knowledge database, we train four real-bogus classifiers: XGBoost, CatBoost, Random Forest, and Extremely Randomized Trees. All the models perform real-bogus classification with similar effectiveness, achieving ROC-AUC scores ranging from 0.93 to 0.95. Consequently, we select the Random Forest model as the main model due to its simplicity and interpretability. The Random Forest classifier is applied to 67 million light curves from ZTF DR17. The output real-bogus score is used as an additional feature for two anomaly detection algorithms: static Isolation Forest and AAD. While results from Isolation Forest remained unchanged, the number of artifacts detected by the active approach decreases significantly with the inclusion of the real-bogus score, from 27 to 3 out of 100. We conclude that incorporating the real-bogus classifier result as an additional feature in the active anomaly detection pipeline significantly reduces the number of artifacts in the outputs, thereby increasing the incidence of astrophysically interesting objects presented to human experts

Improved Degradation of Phenanthrene in Soil Washing Eluent byPhoto-Fenton Like Process with Citric Acid

International audienceHerein, improved degradation of phenanthrene (PHE), one of the common polycyclic aromatic hydrocarbons (PAHs), was explored in a citric acid (CA) photo-Fenton like system under UVB irradiation. Degradation of PHE in soil washing (SW) eluent by the nonionic surfactant Tween 80 (TW80) using Fe(III)-CA complex was compared with other iron complexes showing a faster degradation with a rate constant of 3.07 × 10−2 min−1. The stability as well as photochemical transformation of Fe(III)-CA under UVB radiation was evaluated, followed by comparison of PHE oxidation with traditional Fenton or Fenton like process. Fe(III)-CA complex was found to be stable in dark but quickly photo dissociated under irradiation. The system using Fe(III)-CA was proved oxidizing PHE more efficiently than traditional Fenton reaction with a rate constant of 3.92 × 10−3min−1 and Fe(II)-CA involved system with a rate constant of 1.74 × 10−2 min−1. A two-stage pattern of PHE decay was observed in the UVB/H2O2/Fe(III)-CA system. The effects of operational factors including Fe(III)-CA dosage, Fe(III)/CA ratio, H2O2 and TW80 dosage on PHE degradation were explored. The checked parameters exhibited different influence on PHE degradation. This work provided a cost-effective strategy for remediating soil pollutants in SW effluent with the presence of surfactant

Les processus d’acclimatation des arbres face aux stress mécaniques : la gravité et le vent

International audienc

Understanding complex volcanic hydrosystems using a multi-tracer approach

International audienceClimate change affects groundwater availability and residence times, necessitating a thorough understanding of aquifer characteristics to define sustainable yields, particularly in regions where water is heavily exploited. This study focuses on the Volvic volcanic aquifer (Chaîne des Puys, France), where groundwater recharge has decreased due to climate change, raising concerns about water use sustainability. To address these challenges, this work proposes a multi-tracer approach, based on hydrogeological monitoring, including the estimation of groundwater ages, major elements chemistry and water stable isotopes to better characterise this resource decrease and more peculiarly its origin and its impact on the environment that has never been addressed. Relative fractions of ancient and modern water contributions (up to 20 %) to the aquifer have been thus estimated as well as the apparent ages of groundwaters (34 years). We highlight the complementarity of tracers used, allowing a better definition of recharge sources and transit times of groundwaters within the aquifer. These results led to the proposal of a hydrogeological conceptual model, highlighting a bi-modal recharge, distinguishing between a long-term recharge upon 30 years, supplemented by a recent component (≃ 1 year) related to annual precipitation. This study provides valuable information on groundwater circulation and the response of volcanic aquifers systems to climate change, while highlighting the importance of assessing residence times. By addressing the challenges posed by systems with contrasting permeability and recharge gradients, it improves understanding of volcanic hydrology and provides a basis for the development of (numerical) hydrological models to assess the impacts of global change

Techniques d’identification microbienne

MasterDescription de l'ensemble des techniques d'analyse microbienne, leur intérêts, limites et choix en fonction des besoins et du type d'échantillons.Focus particulier sur l'outil Maldi TOF, principe, protocole, intérêts et limite

Who Pays Whom? Anonymous EMV-Compliant Contactless Payments

International audienceEMV is the de-facto worldwide payment system used by Mastercard, Visa, American Express, and such. In-shop EMV contactless payments are not anonymous or private: the payers’ long-term identification data leaks to Merchants or even to observers. Anti-Money Laundering (AML), Know Your Customer (KYC) and Strong Customer Authentication (SCA) are payment regulations protecting us from illegal activities, but –in so doing– contribute chiefly to this lack of privacy in EMV payments. Threading the tightrope of AML, KYC and SCA regulations, we provide two privacy-enhancing, EMV-compatible, law-abiding and practicable contactless-payments protocols: PrivBank and PrivProxy. We do not use privacy-enhancing technology, like homomorphic encryption, that would break backwards-compatibility with current EMV, but rather we do privacy by engineering design, adhering to the existing EMV infrastructure, as is. So, PrivBank and PrivProxy provably achieve strong notions of payers and merchant privacy, anonymity and unlinkability as seen in e-cash or shopping vouchers, whilst being implementable in EMV as it stands

Causalités

National audienc

Bases de physiologie végétale et flux de sèves

National audienceLes bases physiologiques pour comprendre la nature des sèves d'un arbre, leur fabrication et leur circulation