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Effects of the built-in electric field on free and bound excitons in a polar GaN/AlGaN/GaN based heterostructure
No full textInternational audienceLow-temperature luminescence spectra reveal the presence of two independant populations of GaN excitons within a GaN/AlGaN/GaN/Al2O3 heterostructure in which a thick (1.5 µm) AlGaN layer separates a thin (150 nm) top GaN layer and a thick (3.5 µm) bottom GaN layer grown on sapphire. The presence of these two spectrally-distinct families of excitons in each GaN layer of the heterostructure is demonstrated using three different experimental methods: (i) low-power µ-photoluminescence (µPL) using laser excitation sources with wavelengths above and below the AlGaN bandgap, (ii) µPL as a function of optically injected free carrier density, and (iii) quantitative numerical simulation of the µ-Reflectivity (µR). One major impact of the built-in electric field is the reduction of the excitonic lifetime in the GaN surface layer, which transitions from less than 10 ps in the presence of the built-in electric field to the bulk lifetime (90 ps) when the field is screened. This increase in the excitonic lifetime is related to the modification of the band structure in the presence of optically injected free carriers. The effect of these lifetime variations on the luminescence spectra is analyzed. Lastly, we provide an estimate of the Mott density in GaN as nMott = 4 × 10 17 cm -3 at 130 K, consistent with values reported in the literature and accounting for the free carrier density required to screen the electric field
Equilibrium and Love, Self and Others: Simone de Beauvoir in Dialogue with Kierkegaard
No full textInternational audienceThis chapter proposes a fresh perspective on the ways in which Simone de Beauvoir’s philosophy can be drawn into dialogue with Kierkegaard’s, giving voice to the depth and originality of Beauvoir’s own thought and contributions to the development of existential philosophy. Drawing on the early writings of Beauvoir from the Cahiers de jeunesse, written before Beauvoir’s encounter with either Kierkegaard’s works or with Jean-Paul Sartre, it retraces two themes central to Beauvoir’s early thought and their later development throughout her oeuvre: equilibrium and love, and their relation to understanding of self and others. Tracing these themes back to Beauvoir’s early writings provides evidence that rather than a direct influence on existentialist concepts, Beauvoir’s encounter with Kierkegaard is better understood as an encounter with a partner in dialogue, enabling Beauvoir to work out many of the philosophical intuitions she had already begun developing in her youth. These themes, which are also central to Kierkegaard’s philosophy, serve to guide a comparative reading of the resonances to be found between Beauvoir’s thought and Kierkegaard’s. They offer a means of re-reading Kierkegaard through the lens of Beauvoir’s concepts, which can also serve to offer new perspectives on Kierkegaard’s thought and its social and ethical implications
Perioperative antimicrobial prophylaxis and surgical site infection prevention, what clinicians and researchers must know
No full textInternational audienceSurgical site infections (SSIs) are among the most common healthcare-associated infections, leading to increased morbidity, prolonged hospital stays, and significant healthcare costs. Surgical antimicrobial prophylaxis (SAP) is a critical strategy for SSI prevention, yet its effectiveness is threatened by antimicrobial resistance and variability in clinical practice.This narrative review provides an evidence-based update on the pathophysiology of SSIs, highlighting the interplay between endogenous microbiota, surgical stress, and perioperative factors such as hypoxia, immune modulation, and microbiome disruption. The current state-of-the-art in SAP is reviewed, including antibiotic selection, timing, dosing, intraoperative redosing, and the avoidance of unnecessary postoperative administration.Key intra- and postoperative measures to reduce the risk of SSI are covered, including glycaemic control, body temperature management, goal-directed fluid therapy, and skin antisepsis. A critical appraisal of the supporting evidence is included, with emphasis on areas of ongoing debate.The final section outlines future research priorities: optimizing dosing in obese patients, evaluating continuous infusion, tailoring prophylaxis to surgical site and microbiome, and addressing the management of patients colonized with multidrug-resistant organisms. Non-antibiotic strategies and rapid diagnostic tests are also discussed as promising avenues to enhance precision in infection prevention.By integrating current knowledge with emerging perspectives, this review aims to support the refinement of SSI prevention strategies and contribute to antimicrobial stewardship in modern surgical practice
Diagnosis and management of patients with Crohn’s disease. Position paper from the GETAID
No full textInternational audienceThe therapeutic arsenal for treating Crohn's disease has grown rapidly, expanding to include advanced therapies with various modes of action. Over the last two decades, physicians and patients have significantly improved the treatment of Crohn's disease, setting ambitious goals. In 2024, French clinical guidelines were established through a validated process involving the adaptation of international gastroenterology societies' clinical guidelines and French consensus meetings. The French guidelines aimed to ensure the applicability of new approaches in France, taking into account specific restrictions on drug authorization and reimbursement. This position statement outlines the specificity of the French guidelines compared to other international recommendations
IMRED, ICMJE/COPE, EQUATOR : cadres et normes de publication des recherches originales en santé publique
No full textNational audienceThis article presents a structured reflection on the standards and frameworks governing the publication of original research, focusing on the biomedical field, and more specifically, on public health. It draws on Le Moigne’s general systems theory and its systemic triangulation, which analyzes complex objects (in this case, the publication system) through three complementary poles: ontological (what it is), functional (what it does), and genetic (how it evolves). These three dimensions help illuminate the main normative frameworks of publication: (i) the IMRAD structure (Introduction, Methods, Results, and Discussion), which illustrates the ontological pole by ensuring the clarity and replicability of scientific results; (ii) the recommendations of the International Committee of Medical Journal Editors (ICMJE) and the Committee on Publication Ethics (COPE), which provide functional and ethical guidance for the writing and submission of articles, including the roles and responsibilities of authors and contributors; and (iii) the guidelines of the EQUATOR network (Enhancing the QUAlity and Transparency Of health Research), which influence both the writing of articles and the design of studies themselves (genetic pole).The analysis offers perspectives to incorporate Le Moigne’s teleological pole, which questions the very purpose of the scientific publication system and its alignment with major societal challenges. Together, these evolving frameworks interact and continuously develop to promote scientific publications that are not only clear and well-structured but also rigorous in both methodological and ethical terms, while opening space for reflection on the place and role of science in our societies.Cet article propose une réflexion structurée sur les normes et cadres qui régissent la publication de recherches originales, en se concentrant sur le domaine biomédical et plus particulièrement sur la santé publique. Il s’appuie sur la théorie du système général de Le Moigne et sa triangulation systémique, qui analyse les objets complexes (ici, le système de publication) à travers trois pôles complémentaires : ontologique (ce que c’est), fonctionnel (ce que cela fait) et génétique (comment cela évolue). Ces trois dimensions permettent d’éclairer les grands cadres normatifs de la publication : (i) la structure IMRED (Introduction, Méthodes, Résultats et Discussion), qui illustre le pôle ontologique en assurant la lisibilité et la réplicabilité des résultats scientifiques ; (ii) les recommandations du Comité international des éditeurs de revues médicales (ICMJE) et du Comité d’éthique de la publication (COPE), qui fournissent des repères fonctionnels et éthiques pour la rédaction et la soumission des articles, intégrant notamment les rôles et responsabilités des auteurs et contributeurs ; (iii) les lignes directrices du réseau EQUATOR (Enhancing the QUAlity and Transparency Of health Research), qui influencent à la fois la rédaction des articles et la conception même des recherches (pôle génétique).L’analyse énonce des perspectives afin d’intégrer le pôle téléologique de Le Moigne, qui interroge la finalité même du système de publication scientifique et sa cohérence avec les grands enjeux sociétaux. Ensemble, ces cadres évolutifs interagissent et évoluent constamment pour tendre vers des publications scientifiques non seulement claires et bien structurées, mais aussi rigoureuses sur les plans méthodologiques et éthiques, tout en ouvrant un espace de réflexion sur la place et le rôle de la science dans nos sociétés
Les eaux de surface dans le changement climatique : effets des sécheresses sur la (photo)chimie des cours d'eau alpins
No full textThe term “alpine” has two quite different meanings. When the word is capitalized, Alpine streams refer to running waters of the Alps, at any elevation. When not capitalized, alpine streams refer to running waters of the alpine zone above the tree line, anywhere in the world. In this PhD thesis, the first context was adopted. The work described in the following sections sought to examine, at least in part, the effects of climate change-related drought conditions on the chemistry of streams born from and flowing through the Italian Alps. A sampling campaign was carried out on three streams of the Piemonte region, Italy, through the whole year 2022, which has been defined as one of the worst ever experienced by Alpine water courses. The analysis of nutrient concentrations downstream of the wastewater treatment plants operating on the rivers allowed to get insights into the impacts of their effluents on the final receiving basins under drought conditions. The streams displayed some shared features, e.g. higher nutrient concentrations downstream, most marked in the lowest flows months. For the Stura di Lanzo, the Principal Component Analysis (PCA) showed some interesting negative correlations between the chemical variables and the flow regimes. Moreover, correlations with the ecological and microbiological variables in the same conditions were looked for. The hydrological and chemical parameters measured on one of the streams were used to model the photochemistry transformation of three common pollutants (acetaminophen, diclofenac and naproxen) under the same water scarcity conditions. The modelling highlighted how the chemical and hydrological conditions determined by the drought in 2022 actually shaped the photochemical transformation of the pollutants (e.g. the increased nitrate, nitrite and organic carbon concentrations during low flows enhanced the photodegradation by •OH and 3CDOM* downstream of the WWTP, whereas shallower and slower waters led to an increased direct photolysis). An enhanced photochemical transformation rate under drought conditions, however, does not necessarily lead to a sufficient removal of the compounds before they reach the sea.Besides this, the photochemistry of a pool of pharmaceuticals (chlorpromazine, lamotrigine and tiapride) traced by UHPLC-HRMS-QTOF in the sampled river waters was studied. Direct photolysis and indirect photochemistry were described, transformation products formed by photolysis identified and the second order reaction rate constants measured through nanosecond Laser Flash Photolysis. The effects of both 2022 drought and varying DOC, NO3− and water depth on the behavior of the three molecules were then investigated by photochemical modelling.In the last part of the work, the focus was shifted towards sustainable methods for the removal of contaminants from wastewaters, to prevent them from reaching the natural environment. The efficiency of ZVI-Fenton process at pH 4 in eliminating a selection of CECs and bacteria from secondary municipal wastewater was assessed and compared to the results obtained with the same method at different pH values. The tested treatment was proven to be rather effective in the degradation of both the contaminants (ibuprofen, cefazolin and sulfamethoxazole) and the microorganisms, but at the same time the results call for further studies to overcome the main issues related to the pH limitations.Le terme « Alpin » a deux significations très différentes. Lorsque le mot prend une majuscule, les cours d'eau Alpins désignent les eaux courantes des Alpes, quelle que soit l'altitude. Sans majuscule, les cours d'eau alpins désignent les eaux courantes de la zone alpine au-dessus de la limite des arbres, partout dans le monde. Dans cette thèse de doctorat, le premier contexte a été adopté. Les travaux décrits dans les sections suivantes visaient à examiner, au moins en partie, les effets des conditions de sécheresse liées au changement climatique sur la chimie des cours d'eau qui naissent et traversent les Alpes italiennes. Une campagne d'échantillonnage a été menée sur trois cours d'eau de la région du Piémont, en Italie, tout au long de l'année 2022, qui a été définie comme l'une des pires jamais vécues par les cours d'eau Alpins. L'analyse des concentrations de nutriments en downstream des stations d'épuration des eaux usées opérant sur les rivières a permis de mieux comprendre l'impact de leurs effluents sur les bassins récepteurs finaux dans des conditions de sécheresse. Les cours d'eau présentaient certaines caractéristiques communes, par exemple des concentrations de nutriments plus élevées en aval, plus marquées au cours des mois où les flux sont les plus faibles. Pour la Stura di Lanzo, l'analyse en composantes principales (ACP) a montré des corrélations négatives intéressantes entre les variables chimiques et les régimes d'écoulement. En outre, des corrélations avec les variables écologiques et microbiologiques dans les mêmes conditions ont été recherchées. Les paramètres hydrologiques et chimiques mesurés sur l'un des cours d'eau ont été utilisés pour modéliser la transformation photochimique de trois polluants courants (acétaminophène, diclofénac et naproxène) dans les mêmes conditions de pénurie d'eau. La modélisation a mis en évidence la façon dont les conditions chimiques et hydrologiques déterminées par la sécheresse de 2022 ont effectivement façonné la transformation photochimique des polluants (par exemple, l'augmentation des concentrations de nitrate, de nitrite et de carbone organique pendant les faibles débits a renforcé la photodégradation par le radical hydroxyle et l'état excité triplet de la matière organique chromophore en aval de la STEP, tandis que les eaux moins profondes et plus lentes ont conduit à une photolyse directe plus élevée). Un rate de transformation photochimique accru dans des conditions de sécheresse ne conduit cependant pas nécessairement à une élimination suffisante des composés avant qu'ils n'atteignent la mer. En outre, la photochimie d'un pool de produits pharmaceutiques (chlorpromazine, lamotrigine et tiapride) suivis par UHPLC-HRMS-QTOF dans les eaux fluviales prélevées a été étudiée. La photolyse directe et la photochimie indirecte ont été décrites, les produits de transformation formés par photolyse ont été identifiés et les constantes de vitesse de réaction du second ordre ont été mesurées par la technique de nanosecond Laser Flash Photolysis (LFP). Les effets de la sécheresse de 2022 et de la variation du carbone organique dissous, des nitrates et de la profondeur de l'eau sur le comportement des trois molécules ont ensuite été étudiés par modélisation photochimique. Dans la dernière partie du travail, l'accent a été mis sur les méthodes soutenables pour l'élimination des contaminants des eaux usées. L'efficacité du traitement ZVI-Fenton à pH 4 dans l'élimination d'une sélection de contaminants émergents et de bactéries des eaux usées municipales secondaires a été évaluée et comparée aux résultats obtenus avec la même méthode à différentes valeurs de pH. Le traitement testé s'est montré assez efficace dans la dégradation des contaminants (ibuprofène, céfazoline et sulfaméthoxazole) et des micro-organismes, mais en même temps, les résultats nécessitent d'autres études pour surmonter les principaux problèmes liés aux limitations du pH
Measurement of the Higgs boson production in association with top quarks in multilepton final states in collisions at TeV with the ATLAS detector
No full textInternational audienceA measurement of the associated production of a top-quark pair with the Higgs boson () in multilepton final states is presented. The analysis is based on a data sample of proton-proton collisions at TeV recorded with the ATLAS detector at the CERN Large Hadron Collider and corresponding to an integrated luminosity of 140 fb. Six final states defined by the number and flavour of reconstructed charged leptons are combined in a simultaneous likelihood fit to extract the signal and constrain the most relevant backgrounds. The measured cross-section normalised to Standard Model (SM) prediction is . This result corresponds to an observed (expected) significance of 3.3 (5.3). Additionally, two other fits are used to measure the cross-section differentially in bins of the Higgs boson transverse momentum in the simplified template cross-section framework, and to extract the associated production cross-section of a single top-quark with the Higgs boson () together with the one. The structure of the top quark-Higgs boson Yukawa coupling is probed through analysis of and events. The results are compatible with the SM hypothesis, and values of the mixing angle between -even and -odd top-Higgs Yukawa couplings of are excluded at 68 confidence level
Multi-kingdom microbial assemblage modulates its metabolism under contrasted cloud conditions: Microbial metabolism in cloud conditions
No full textInternational audienceAbstract Microorganisms maintain metabolic activity in clouds, with recognized impacts on the chemistry of small organic compounds, radicals and their precursors. However, how microbial activity is modulated by cloud environmental variables remains unknown. Here we explored the metabolic response of an assemblage of representative microbial isolates from cloud water, composed of a basidiomycetous yeast (Dioszegia hungarica) and three bacterial strains (Rhodococcus enclensis, Pseudomonas syringae and P. graminis), in synthetic cloud water exposed to contrasted conditions of temperature (5°C vs 17°C), light (dark vs artificial solar light) and oxidants (0 μM vs 250 μM H2O2), to mimic typical cloud conditions during winter night (WN) and summer day (SD). Metabolomics and metatranscriptomics allowed the identification of 25 differentially abundant metabolites and 218 differentially expressed genes (DEGs). Both SD metabolomes and metatranscriptomes suggested active mitochondria-driven energy production, with fungal DEGs involved in fatty acids biosynthesis and succinate assimilation, and 3 differentially abundant acylcarnitines that support fatty acid transport into the mitochondrion for oxidative phosphorylation. In contrast, bacteria displayed DEGs for cell division arrest and components of ROS scavenging systems. Under the WN condition, both bacteria and yeast exhibited a similar prosperous state with DEGs encoding translation, protein repair and turnover, as well as cell cycle related functions. Thus, eukaryotes and prokaryotes may engage in distinct strategies to survive in clouds, depending on environmental conditions. This study consolidates our understanding of microbial roles and interactions in cloud water, paving the way for deeper insights into the chemistry of atmospheric systems
Optimal Smoothed Analysis of the Simplex Method
No full textInternational audienceSmoothed analysis is a method for analyzing the performance of algorithms, used especially for those algorithms whose running time in practice is significantly better than what can be proven through worst-case analysis. Spielman and Teng (STOC '01) introduced the smoothed analysis framework of algorithm analysis and applied it to the simplex method. Given an arbitrary linear program with variables and inequality constraints, Spielman and Teng proved that the simplex method runs in time , where σ> 0 is the standard deviation of Gaussian distributed noise added to the original LP data. Spielman and Teng's result was simplified and strengthened over a series of works, with the current strongest upper bound being pivot steps due to Huiberts, Lee and Zhang (STOC '23). We prove that there exists a simplex method whose smoothed complexity is upper bounded by pivot steps. Furthermore, we prove a matching high-probability lower bound of on the combinatorial diameter of the feasible polyhedron after smoothing, on instances using inequality constraints. This lower bound indicates that our algorithm has optimal noise dependence among all simplex methods, up to polylogarithmic factors
Éducation Physique et Sportive : construction d'une discipline scolaire
No full textLa construction de l'Éducation Physique et Sportive en temps que discipline scolaire ne va pas de soi. Des politiques publiques du sport à celles de la santé, l'EPS est au croisement de prérogatives et d'enjeux variés, auxquels les enseignantes et enseignants doivent s'adapter. Comment l'EPS trouve sa place en temps que discipline au sein du système scolaire français ?Claire Ravez, chargée d’étude au sein de l’équipe Veille et Analyse de l’Institut français de l’Éducation (ENS de Lyon) a publié ce mois-ci un numéro d’une Édurevue, une synthèse approfondie, sur l’Education Physique et Sportive, intitulée « L'EPS : de ses buts à ses terrains». Avec Laurent Dastugue, maître de conférence au laboratoire ACTÉ (Activité, Connaissance,Transmission et Éducation) à l’Université Clermont Auvergne, mais aussi formateur à l’INSPE et ancien professeur d'EPS dans le second degré, ils reviennent pour nous, sur le plateau d'Iféquoi, sur les enjeux et la construction disciplinaire de l'Éducation Physique et Sportive.Quelle est l'histoire de la discipline dans le système scolaire Français ? De l'apprentissage de la pratique à l'apprentissage de l'enseignement : quel mouvement l'enseignant·e d'EPS doit effectuer ? Quelle place de la pratique sportive en STAPS ? Quels enjeux pour l'EPS en terme de Santé ? Comment l’EPS s’inscrit-elle dans le socle commun ? Autant de questions auxquelles répondent ce mois-ci nos deux invité·es