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La Loire en crue : dynamiques hydrogéomorphologiques et réponses des sociétés riveraines depuis l'époque médiévale (Loire nivernaise et bourbonnaise)
No full textThe Loire River is the longuest one in France, with a watershed covering a fifth of the metropolitan territory. However, knowledge of its past floods remains very poorly known. In response, the aim of this thesis is to study the hydrogeomorphological activity fluctuation of the Loire River on the one hand, and on the other hand to study the responses of riparian societies to this activity between Digoin and Nevers over the last millennium. This thesis is based on an interdisciplinary approach and two axes. The first is to reconstruct the past hydrological activity of the Loire River based on documentary and sedimentary archives over the last millennium. An unpublished chronology of 781 Loire floods has been reconstructed from 1380 to 2023. The intensity of each event has been determined and we identified 10 periodes of hight hydrological activity and 8 of low activity by using flood indice. The stratigraphic study of the Loire River paleochannels sedimentary fill reveals a hydrosedimentary history linked to past climatic fluctuations: the Medieval Climatic Optimum period (10th-13th c.) is characterized by a relative quietness of this activity, much more intense thereafter during the Little Ice Age (14th-19th c.). Paleochannel stratigraphy has also revealed the passage of numerous floods, probably the most intense. This exclusive signature of extreme events can be explained by the very low level of fine sediment transport on the Loire, and the consequent scarcity of deposits on the proximal and distal plains. This configuration has been exacerbated over the last few centuries by human impacts. The second axis focuses on the Loire River riparian societies responses to its hydrogeomorphological activity. The Nevers and Decize urban communities managing the Loire riverbed as early as the 14th c. in order to reduce their vulnerability to the flooding and wandering. The timing of these engeneering workings does not seem to correspond to the different hydrological activity periods. But some events affected these societies, in particular those of 1586, 1789 and 1790. The study of old maps and Lidar DTM shows that riparian societies in a rural context also adapted to the river's constraints. While engeneering working are present on the rivers banks of Nevers and Decize from the 14th c., their number increased in rural areas and extended to the entire study area from the mid-18th c., mainly to serve the needs of navigation. The sedimentary and hydrogeomorphological consequences can be observed from the mid-18th c. We observed an important incision of the alluvial floor from the 18th c. to the present day. The combination of the effets of engeneering working, incision and a general reduction in hydrological activity from the mid-XXth c., has led to a sharp contraction of the active band.La Loire est le fleuve le plus long de France avec un bassin versant dont la surface constitue un cinquième du territoire français métropolitain. Pour autant, la connaissance relative aux crues passées de la Loire demeure très lacunaire. En réponse, cette thèse consiste à renseigner avec précision les fluctuations de l’activité hydrogéomorphologique de la Loire au cours du dernier millénaire. Il s’agit également d’étudier les réponses des sociétés riveraines à cette activité entre Digoin et Nevers. La réalisation de ces objectifs repose sur une approche interdisciplinaire articulée autour de deux axes. Le premier vise à reconstituer l’activité hydrogéomorphologique passée de la Loire au cours du dernier millénaire à partir des archives documentaires et sédimentaires. Une chronologie inédite de 781 crues de la Loire a été reconstituée de 1380 à 2023. La détermination de l’intensité de chaque évènement et l’utilisation d’indices de crue ont permis de caractériser dix périodes de forte et huit de faible activité hydrologique. L’étude stratigraphique des remblaiements sédimentaires des paléochenaux de la Loire témoigne d’une histoire hydrosédimentaire liée aux fluctuations climatiques passées : la période de l’Optimum Climatique Médiéval (Xe – XIIIe s.) se caractérise par une activité plutôt calme, bien plus intense par la suite au cours du Petit Âge Glaciaire (XIVe – XIXe s.). La stratigraphie des paléochenaux a également permis la détection du passage de nombreuses crues, probablement les plus intenses. Cette signature exclusive des évènements extrêmes s’explique par un transport sédimentaire fin très faible sur la Loire limitant, voire excluant, des dépôts en plaine proximale et distale. Cette configuration a été aggravée au cours des derniers siècles par l’aménagement du fleuve et l’incision du plancher alluvial. Le second axe vise à étudier les réponses des sociétés riveraines de la Loire vis-à-vis de son activité hydrogéomorphologique. Les communautés urbaines de Nevers et Decize aménagèrent le lit de la Loire dès le XIVe s. afin de limiter la vulnérabilité de leurs ponts face aux crues, mais aussi et surtout aux migrations de la Loire. Si la temporalité des aménagements ne semble pas répondre aux différentes périodes d’activité hydrologique, certains évènements marquèrent tout de même ces sociétés, en particulier ceux de 1586, 1789 et 1790. En contexte rural, l’étude des cartes anciennes et du MNT Lidar témoigne d’une adaptation des sociétés riveraines aux contraintes fluviales. Si les berges de Nevers et Decize sont fortement aménagées dès le XIVe s., l’aménagement général du lit de la Loire s’étend en contexte rural et ne s’accélère véritablement qu’à partir du milieu du XVIIIe s., principalement pour servir les besoins de la navigation. Les conséquences sédimentaires et hydrogéomorphologiques des aménagements sont enregistrées dès le milieu du XVIIIe s. Celui-ci entraîne une très forte incision du plancher alluvial du XVIIIe s. à nos jours. La combinaison de l’effet des aménagements, de l’incision et de la diminution générale de l’activité hydrologique à partir du milieu du XXe s., provoque une très forte contraction de la bande active
Rates of convergence of a binary classification procedure for time-homogeneous S.D.E paths
No full textIn the context of binary classification of trajectories generated by time-homogeneous stochasticdifferential equations, we consider a mixture model of two diffusion processes characterized bya stochastic differential equation whose drift coefficient depends on the class or label, which ismodeled as a discrete random variable taking two possible values, and whose diffusion coefficient is independent of the class. We assume that the drift and diffusion coefficients are unknown as well as the law of the discrete random variable that models the class. In this paper, we study the minimax convergence rate of the resulting nonparametric plug-in classifier under different sets of assumptions on the mixture model considered. As the plug-in classifier is based on nonparametric estimators of the coefficients of the mixture model, we also provide a minimax convergence rate of the risk of estimation of the drift coefficients on the real line.Dans le contexte de la classification binaire de trajectoires générées par des équations différentielles stochastiques homogènes en temps, nous considérons un modèle de mélange de deux processus de diffusion caractérisés par une équation différentielle stochastique dont le coefficient de dérive dépend de la classe, laquelle est modélisée par une variable aléatoire discrète à valeurs dans {0,1}, et dont le coefficient de diffusion est indépendant de la classe. Nous supposons que les coefficients de dérive et de diffusion sont inconnus aussi bien que la loi discrète de la variable aléatoire qui modélise la classe. Dans cet article, nous étudions la vitesse minimax de convergence de la procédure de classification non-paramétrique de type plug-in qui en résulte, sous un ensemble d'hypothèses sur le modèle de mélange considéré. Comme le classifier plug-in est basé sur les estimateurs non-paramétriques des coefficients du modèle de mélange de diffusions, nous établissons également une vitesse minimax du risque d'estimation des coefficients de dérive sur R
Investigating the Photochemical Properties of Cytosine and Thymine Under Mars-Like Conditions: Effect of UV Radiation and Calcium Perchlorate
No full textInternational audienceMars missions actively search for organic matter as potential biosignatures. Yet harsh conditions at the surface, including unfiltered ultraviolet (UV) light above 190 nm and oxidizing agents such as perchlorates, challenge the preservation of compounds relevant to astrobiology, such as nucleobases. Since current instruments primarily analyze samples from the uppermost surface layer, understanding the stability of organic matter under Mars-like surface conditions is essential. Nucleobases have interesting photochemical properties, as they can dimerize under UV light. Previous work showed that UV exposure of uracil under Mars-like conditions rapidly leads to more photostable dimers, with an enhanced photodecomposition yield when perchlorates are present. Additional chemical groups, including alkyne (C≡C) and nitrile (C≡N), emerge in the presence of calcium perchlorate and indicate novel photoproducts. The present work investigates the evolution of two other pyrimidine nucleobases, cytosine and thymine, in simulated UV martian conditions with and without calcium perchlorate. Infrared spectroscopy monitoring of the sample throughout the duration of the experiment showed that cytosine and thymine both form photoproducts under UV light, likely dimers for thymine. Moreover, both molecules seem to interact spontaneously with calcium perchlorates prior to any UV exposure, to form either a complex with cytosine or a change in the crystalline phase with thymine
On weak compactness and uniform regularity in Lipschitz free spaces
No full textWe analyze the properties of weakly compact sets in Lipschitz free spaces. Prior research has established that, for a complete metric space M , weakly precompact sets in the Lipschitz free space F (M ) are tight. In this paper, we prove that these sets actually exhibit a stronger property, which we call uniform regularity. However, this condition alone is not sufficient to characterize weakly compact sets, except in the case of scattered metric spaces. On the other hand, if T is an R-tree, we leverage Godard's isometry between F (T ) and L 1 (λ T ) to obtain an intrinsic characterization of weakly compact sets in F (T ). This approach allows us to identify conditions that may describe weak compactness across a wider range of spaces. In particular, we provide a characterization of norm-compactness in terms of sums of "large molecules", while we show that sums of "small molecules" contain an ℓ 1 -basis
An explicit exotic representation of a rank-one simple Lie group via convex bodies
No full textIn \cite{DP}, Delzant and Py showed that there exist continuous irreducible isometric actions of \psl on the infinite-dimensional hyperbolic space \H^\infty. Such continuous irreducible actions do not exist on the hyperbolic spaces \H^n when n>2 and their associated embeddings \H^2 \to \H^\infty given by the orbit maps were later called \emph{exotic} by Monod and Py in \cite{MP}. In this article, we produce a continuous and irreducible representation of \psl\to \Isom(\H^\infty) using the hyperbolic model for convex bodies introduced in \cite{DF}. This yields a convex cocompact \psl-action on the infinite-dimensional hyperbolic space \H^\infty, of which the compact quotient over the minimal \psl-invariant convex set is homeomorphic to the 2-dimensional oriented Banach--Mazur compactum. Moreover, we study the geometry of one of its orbit maps and compute the Hausdorff dimension of the limit set of this representation
Real-world patterns of treatment intensity and prognostic model performance in older AML: Insights from the french ALFA-PPP cohort
No full textInternational audienceBackground: In older patients (pts) with newly diagnosed (ND) acute myeloid leukemia (AML), treatment options have expanded significantly. While intensive chemotherapy (ICT) remains the standard of care for fit pts, venetoclax (VEN)-based low-intensity therapies (LIT) are increasingly used. Despite existing guidelines, the choice between ICT and LIT varies in real-life practice. Advances in understanding the prognostic role of disease genetics have led to risk models for pts receiving LIT, mostly validated in clinical trials. Their relevance in unselected real-world populations, however, remains uncertain. In this study, we analyzed patterns of treatment intensity and evaluated the performance of LIT risk models in a real-world cohort of older pts with ND-AML. Methods: We analyzed data from the ND-AML cohort of the prospective ALFA-PPP study (NCT04777916), initiated in 2022 to collect real-life clinical and biological data from 29 centers. Centralized genomic (50-gene NGS) and MRD assessments were planned for all pts. We report findings from the first 652 pts aged ≥60 years enrolled between April 2022 and June 2025. In those treated with LIT, we assessed the prognostic value of the 4-gene molecular risk signature (mPRS, PMID: 38113472), the ELN-2024 classification (PMID: 39133932), and the refined ELN (rELN)-2024 model (PMID: 39486083). Results: Among 652 pts, 315 were female and 337 male (median age 71y [60–94]; ECOG 0–2/3–4: 625/27; HCT-CI 0–2/≥3: 401/251). AML was de novo in 442 pts (68%), therapy-related in 105 (16%), post-MDS in 70 (11%), and post-MPN in 35 (5%). Among 591 evaluable pts, NPM1, FLT3, IDH1/2, sAML-like mutations (PMID: 35767897), and MR cytogenetic abnormalities were seen in 25%, 21%, 21%, 58%, and 28%, respectively. Of 652 pts, 346 (53%) received ICT (7+3 based regimen: n=187; CPX-351: n=80; other: n=7) and 306 (47%) VEN-based LIT (VEN+azacitidine: n=305; VEN+LDAC: n=1). ICT was used in 89%, 78%, 60%, and 8% of pts aged 60–65, 65–70, 70–75, and >75y, respectively. According to investigators, main reasons for choosing LIT were advanced age (n=253, 83%), comorbidities (n=79, 26%), and AML features (n=74, 24%). Analysis showed that LIT use was independently associated with older age (p<.001), ECOG>2 (p=0.02), HCT-CI≥3 (p<.001), post-MDS (p=0.001), post-MPN (p<.001), sAML-like mutations (p<.001), MR karyotype (p<.001), and TP53 mutations (p<.001). With median follow-up of 15.3m (IQR 7.2–23.8), 12-month OS was 73% (95% CI, 68–79) with ICT vs 46% (95% CI, 40–52) with LIT. Among 288 LIT pts with genetic data (129 female [45%], 159 male [55%]; median age, 77 years [60–94]; ECOG 0–2/3–4: 270/18; HCT-CI 0–2/≥3: 152/136), the mPRS classified 139 (48%) pts as favorable risk, 77 (27%) as intermediate risk, and 72 (25%) as adverse risk. According to ELN-2024, 148 (51%) pts were categorized as favorable, 79 (27%) as intermediate, and 61 (21%) as adverse. The rELN-2024 model reclassified 58 pts (20%) as favorable, 133 (46%) as intermediate, and 97 (34%) as adverse. Median OS was 10.1 months (95% CI, 7.7–12.0). Median OS by mPRS was 13.7 months (95% CI, 11.7–18.9), 10.0 (6.5–13.9), and 4.8 (3.5–7.4) for favorable, intermediate, and adverse-risk pts, respectively. According to ELN-2024, median OS was 13.1 months (11.7–15.5), 10.0 (6.5–13.9), and 4.3 (3.0–7.4), while for rELN-2024, it was 31.0 months (14.2–NA), 11.5 (8.9–14.8), and 4.4 (3.3–7.2), for the favorable, intermediate, and adverse risk group, respectively. Discriminative performance for OS showed a Harrell's c-index of 0.64 (95% CI, 0.58–0.70) for mPRS, 0.64 (0.58–0.70) for ELN-2024, and 0.70 (0.64–0.76) for rELN-2024. Compared to ELN-2024, mPRS showed no significant difference in discriminative ability (pairwise C-index difference via non-parametric bootstrap: ΔC-index = –0.01 [95% CI, –0.02–0.01]; p=0.49). rELN-2024 significantly outperformed both mPRS (ΔC-index = +0.06 [95% CI, 0.02–0.10]; p<.01) and ELN-2024 (ΔC-index = +0.06 [95% CI, 0.02–0.10]; p<.01). Conclusions: In this real-world cohort of ND-AML pts aged ≥60 years, both ICT and VEN-based LIT were commonly administered, with treatment choice guided by patient- and disease-related factors. ICT was associated with encouraging OS outcomes in older selected pts. Among the prognostic models evaluated in the LIT group, the rELN-2024 showed superior discriminative performance compared to mPRS and ELN-2024, most notably by better identifying favorable-risk pts with substantially prolonged OS
Le devenir des murettes anti‑crues en Île‑de‑France
No full textInternational audienceL'article interroge les ouvrages de défense contre l'inondation des quartiers riverains de la Seine que sont les « murettes anti‑crue » de la métropole francilienne, dans le nouveauréférentiel de l’action publique qui cherche davantage à réduire la vulnérabilitéou à favoriser la résilience des territoires exposés aux inondations. Quel futur imaginer pour ces digues, dont une majorité d’entre nous ignore la fonction de défense contre les inondations ? Quels scénarios peut‑on imaginer et quelles places ces murettes peuvent‑elles plausiblement occuper dans les politiques de protection de la métropole parisienne contre les inondations
An Instrumented Hammer to Detect the Rupture of the Pterygoid Plates
No full textInternational audienceCraniofacial osteotomies involving pterygomaxillary disjunction are common procedures in maxillofacial surgery. Surgeons still rely on their proprioception to determine when to stop impacting the osteotome, which is important to avoid complications such as dental damage and bleeding. Our group has developed a technique consisting in using an instrumented hammer that can provide information on the mechanical properties of the tissue located around the osteotome tip. The aim of this study is to determine whether a mallet instrumented with a force sensor can be used to predict the crossing of the osteotome through the pterygoid plates. Methods 31 osteotomies were carried out in 16 lamb skulls. For each impact, the force signal obtained was analysed using a dedicated signal processing technique. A prediction algorithm based on an SVM classifier and a cost matrix was applied to the database. Results We showed that the device could always detect the crossing of the osteotome, sometimes before its occurrence. The prediction accuracy of the device was 94.7%. The method seemed to be sensitive to the thickness of the plate and to crack apparition and propagation. Conclusion These results pave the way for the development of a per-operative decision support system in maxillofacial surgery
Spectral optical properties of soot: laboratory investigation of propane flame particles and their link to composition
No full textInternational audienceSoot aerosol generated from the incomplete combustion of biomass and fossil fuels is a major light-absorber; however its spectral optical properties for varying black carbon (BC) and brown carbon (BrC) content remain uncertain. In this study, soot aerosols with varying maturity and composition, i.e. elemental-to-total-carbon ratio (EC/TC), have been studied systematically in a large simulation chamber to determine their mass absorption, scattering, and extinction cross sections (MAC, MSC, MEC); single-scattering albedo (SSA); and absorption and scattering Ångström exponents (AAE, SAE). The MAC, MEC, SSA, and AAE show a variability between the different types of soot with varying EC/TC ratios. The MAC (MEC) at 550 nm increases for increasing EC/TC, with values of 1.0 (1.4) m2 g−1 for EC/TC = 0.0 (BrC-dominated soot) and 4.6 (5.1) m2 g−1 for EC/TC = 0.79 (BC-dominated soot). The AAE and SSA (550 nm) decrease from 3.79 and 0.29 (EC/TC = 0.0) to 1.27 and 0.10 (EC/TC = 0.79). Combining present results for soot from propane combustion with literature data for flame soot from diverse fuels supports a generalised exponential relationship between particle EC/TC and its MAC and AAE values (MAC550=(1.3±0.05) e(1.8±0.1)(EC/TC); AAE=(0.73±0.12)+(3.29±0.12) e-(2.32±0.30)(EC/TC), which represents the optical continuum of spectral absorption for soot with varying maturity. From this, it is possible to extrapolate a MAC of 7.9 and 1.3 m2 g−1 (550 nm) and an AAE (375–870 nm) of 1.05 and 4.02 for pure EC (BC-like) and pure OC (BrC-like) soot. The established relationship can provide a useful parameterisation for models to estimate the absorption from combustion aerosols and their BC and BrC contributions
Etats de santé ressentis des étudiant-e-s. Différenciations géographiques, dynamiques spatio-temporelles
No full textInternational audienceCe chapitre analyse l'état de santé ressenti des étudiant-e-s à travers une approche géographique et temporelle. A partir des enquêtes CDV 2010-2023, les autrices et auteurs identifient les facteurs sociaux associés aux écarts de santé perçus (genre, origine sociale, filière d'inscription) et soulignent les disparités territoriales, en particulier la situation préoccupante des étudiant-e-s des DROM-COM et de certaines zones franciliennes