HAL-ENS-LYON
Not a member yet
104280 research outputs found
Sort by
Modeling reactions at the solid/liquid interface: Polyols at the γ-Al2O3 /water interface
No full textInternational audienc
The MeerKAT Absorption Line Survey (MALS) data release 3: Cold atomic gas associated with the Milky Way
No full textInternational audienceAims . We present results of a blind search for Galactic H I 21-cm absorption lines toward 19 130 radio sources brighter than 1 mJy at 1.4 GHz, using 390 pointings of the MeerKAT Absorption Line Survey (MALS), each pointing centered on a source brighter than 200 mJy. The spectral resolution, the median spatial resolution, and the median 3 σ optical depth sensitivity ( τ 3 σ ) are 5.5 km s −1 , ~ 9″, and 0.381, respectively. We used the spectra of the central sources and the other off-axis radio sources within the telescope pointings to constrain the properties of H I gas in the local interstellar medium (LISM) of the Galaxy. Methods . Through an automated procedure, we detected 3640 H I absorption features over ~800 deg 2 . This represents the largest Galactic H I absorption line catalog to date. We used H I 21-cm emission line measurements from HI4PI, an all sky single-dish survey, and far-infrared maps from COBE/DIRBE and IRAS/ISSA in addition to the Gaussian decomposition of the HI4PI into cold (CNM), lukewarm (LNM), and warm (WNM) neutral medium phases for our analyses. Results . We find a strong linear correlation with a coefficient of 0.84 between the H I 21-cm emission line column densities ( N HI ) and the visual extinction ( A V ) measured toward the pointing center, along with the confinement of the absorption features to a narrow range in radial velocities (−25< v LSR [km s −1 ]<+25). This implies that the detected absorption lines form a homogeneous sample of H I clouds in the LISM. For central sight lines (median τ 3 σ =0.008), the detection rate is 82±5%. All the central MALS sight lines with H I absorption have N HI (CNM) + N HI (LNM) ≥ N HI (WNM). The H I 21-cm absorption optical depth is linearly correlated to N HI and A V , with a correlation coefficient in excess of 0.8 up to N HI ≃ 2 · 10 21 cm −2 or, equivalently, A V ≃ 1 mag. Above this threshold, A V traces the total hydrogen content, and consequently, A V and the single-dish N HI scale, differently. The slopes of N HI distributions of central sight lines with H I 21-cm absorption detections and non-detection differ at >2 σ . A similar difference is observed for H 2 detections and non-detections in damped Lyman-alpha systems at z ≳1.8, implying that turbulence-driven WNM-to-CNM conversion is the common governing factor for the presence of H I 21-cm and H 2 absorption. Through a comparison of central and off-axis absorption features, we find the optical depth variations (Δ τ ) to be higher for pointings centered on regions with a higher N HI and CNM fraction. However, no such dependence is observed for the covering fraction of the absorbing structures over 0.1–10 pc. The slope (2.327 ± 0.153) of root mean square (rms) fluctuations in optical depth variations in the quiescent gas associated with LISM is shallower than the earlier measurements in the disk. The densities (20–30 cm −3 ) inferred from |Δ τ | at the median separation (1.5 pc) of the sample are typical of the CNM values. The negligible (median ~0 km s −1 ) velocity shifts between central and off-axis absorbers are in line with the hypothesis that the CNM/LNM clouds freeze out of the extended WNM phase
Commission Femmes et Astronomie de la SF2A : Women participation in french astronomy 2025
No full textInternational audienceThe Commission Femmes et Astronomie of the French Astronomical Society, has conducted a statistical study aimed at mapping the current presence of women in French professional astronomy and establishing a baseline for tracking its evolution over time. This study follows an initial survey carried out in 2021, which covered eight astronomy and astrophysics institutes (1,060 employees). This year, the scope was expanded to 11 institutes, bringing together a total of 1,525 employees, including PhD students, postdoctoral researchers, academics, as well as technical and administrative staff, representing about 57% of the whole French community. We examined how the proportion of women varies according to career stage, level of responsibility, job security, and income. The results are compared to the 2021-2022 survey and appear to illustrate the well-known "leaky pipeline", with one of the main bottlenecks being access to permanent positions. The study shows that the proportion of women consistently declines with increasing job security, career seniority, qualification level, and salary
Hard Questions in Soft Matter: A Personal Journey Through Accademic Science
No full textInternational audienceHello, my name is Thomas Gibaud and I am an invited professor from the Physics Laboratory at ENS de Lyon, France . I’m an experimental physicist, and my passion is soft matter— materials like colloids, gels, and other soft solids that behave in fascinating and often surprising ways. What intrigues me most about gels is that they seem so ordinary at first glance — think of everyday materials like ketchup, foam, or shower gel. And yet, their mechanical properties can be tuned and transformed using external forces such as shear or even high-power ultrasound. To explore this, I combine microscopy and scattering techniques to probe their structure, with rheology to measure how they respond mechanically. My goal is to connect what we see on the microscopic scale with the way these materials behave in our hands. My research began from a purely fundamental curiosity [1-3], but I soon discovered that it also opens the door to real-world applications: making suspensions easier to transport [4,5] or stimuli responsive gels [6,7], with potential to improving materials for 3D printing. More recently, I stepped into a completely different domain. In collaboration with a chiropractor, I applied rheology to model the mechanical properties of tendons, particularly the fascia lata [8]. Together, we developed new methods to quantify their behavior and design better rehabilitation strategies — whether for recovery after an accident, for athletes, or to support healthy aging. In this seminar, I’d like to take you on a journey through my scientific path: why I chose to dive into soft matter, how I eventually secured an academic position, how I design my research questions, and the many collaborations that shape my work. I’ll also share how I’ve learned to navigate — and even enjoy — the challenges of research, from highly technical experiments in large falicities (Synchrotron ESRF, Grenoble, France) to spending a sabbatical year in Guimarães with my family.[1] Gibaud T. Filamentous phages as building blocks for reconfigurable and hierarchical self-assembly. Journal of Physics: Condensed Matter 29, 493003 (2017).[2] Balchunas A., Jia L. L., Zakhary M. J., Robaszewski J., Gibaud T., Dogic Z., Pelcovits R. A., Powers T. R. Force induced formation of twisted chiral ribbons. Physical Review Letters 125, 018002 (2020).[3] Gibaud T., Constantin D. Direct Liquid to Crystal Transition in a Quasi-Two-Dimensional Colloidal Membrane. The Journal of Physical Chemistry Letters 9, 4302 (2018).[4] Bauland J., Bouthier L. V., Poulesquen A., Gibaud T. Attractive carbon black dispersions: structural and mechanical responses to shear. Journal of Rheology 68, 429 (2024).[5] Gibaud T., Dagès N., Lidon P., Jung G., Ahouré L. C., Sztucki M., Poulesquen A., Hengl N., Pignon F., Manneville S. Rheo-acoustic gels: Tuning mechanical and flow properties of colloidal gels with ultrasonic vibrations. Physical Review X 10, 011028 (2020).[6] Dagès N., Lidon P., Jung G., Pignon F., Manneville S., Gibaud T. Mechanics and structure of carbon black gels under high-power ultrasound. Journal of Rheology 65, 477 (2021).[7] Dagès N., Bouthier L. V., Matthews L., Manneville S., Divoux T., Poulesquen A., Gibaud T. Interpenetration of fractal clusters drives elasticity in colloidal gels formed upon flow cessation. Soft Matter 18, 6645 (2022).[8] Germain F., Gibaud T. In vivo measurements of fascia lata mechanics combined to a memory fiber–recruitment–viscoelastic modeling approach. Submitted (2025)
Monogamy of entanglement between cones
No full textInternational audienceA separable quantum state shared between parties and can be symmetrically extended to a quantum state shared between party and parties for every . Quantum states that are not separable, i.e., entangled, do not have this property. This phenomenon is known as "monogamy of entanglement". We show that monogamy is not only a feature of quantum theory, but that it characterizes the minimal tensor product of general pairs of convex cones and : The elements of the minimal tensor product are precisely the tensors that can be symmetrically extended to elements in the maximal tensor product for every . Equivalently, the minimal tensor product of two cones is the intersection of the nested sets of -extendible tensors. It is a natural question when the minimal tensor product coincides with the set of -extendible tensors for some finite . We show that this is universally the case for every cone if and only if is a polyhedral cone with a base given by a product of simplices. Our proof makes use of a new characterization of products of simplices up to affine equivalence that we believe is of independent interest
Co-designing a shared digital decision aid for HPV vaccination in French general practice
No full textInternational audienceBackground: Human papillomavirus (HPV) is responsible for the most common sexually transmitted infection in the world and persistent infection of oncogenic types is associated with an increased risk of cancers. This infection could be prevented by vaccination. However, in a time of vaccine hesitancy, the decision to get vaccinated or to have a child vaccinated is the result of a complex process and decision aids are tools that may be of help in this context.Objective: The aim of this article is to present the development of a shared decision aid for HPV vaccination in France, destined to be used during general practice consultations.Methods: In order to develop the shared decision aid, we followed the steps recommended by the International Patient Decision Aids Standard (IPDAS), i.e. scoping and defining the objectives, assembling the steering group, designing (carrying out two focus groups and a narrative review of the literature) and testing in a alpha test phase (carrying out three focus groups and 11 individual interviews). The tool was co-constructed with adolescents, parents and general practitioners.Results: We created an online shared decision aid which included the definition of HPV, epidemiological data, the mode of contamination, the different locations of the disease, the development of cancer, the importance of Pap smears, the effectiveness of the vaccination as well as the possible side effects. The various focus groups as well as individual interviews made it possible to determine the values and expectations of patients and physicians thus improving the decision aid. This development also made it possible to confirm an existing need for this type of tool for both patients and physicians.Conclusions: We have developed a shared decision aid that could help general practitioners communicate about HPV vaccination and get more patients vaccinated. The impact of its use during the consultation will be evaluated on criteria such as the resolution of the decision-making conflict and ultimately on the vaccination coverage, as part of the PrevHPV study
From layer-cake models to complex subsurface structures: a flexible transdimensional inversion approach
No full textInternational audienceWe present a transdimensional inversion to quantify stratigraphic and petrophysical uncertainties in 2D stratified subsurface models. The objective is to infer the number and position of geological units and their associated properties during inversion. The transdimensional framework relies on a reversible jump Markov chain Monte Carlo (RJMCMC) sampler, which provides self-adaptive capabilities for the parameterization to evolve with the data, and converge to parsimonious posterior solutions. These solutions balance model complexity with the information provided by diverse datasets, such as well logs, seismic surveys, and well tests, which can be integrated within a joint inversion framework. Nevertheless, parameterizations must be carefully defined, as ensuring a small number of parameters is required to maintain reasonable computational times. In this talk, we present an overview of the different geometrical and petrophysical parameterizations that can be used for this purpose. Starting from the classical 1D "layer-cake" model with piecewise constant properties, often employed in geophysics, we progressively introduce more complex parameterizations which better approach the complexity of subsurface layers. These include inclined layers, anticlines, synclines, faulted structures, and lateral variability. By moving towards increasingly realistic parameterizations, the methodology aims to improve the estimation of stratified properties while accounting for structural and stratigraphic variability. Synthetic and real-world applications with various data types will be briefly presented to demonstrate the ability of the sampler to recover coherent results when the parameterization and the noise model are appropriately defined. Overall, this approach provides a unified and adaptable framework for geomodeling, paving the way for improved subsurface characterization and uncertainty quantification in 3D
Sensitivity to climate and vegetation dynamics of a peatland record from central Cameroon during the African Humid Period
No full textInternational audienceSignificant climatic and vegetation changes have occurred in tropical Africa over the Holocene, especially duringthe African Humid Period (AHP). However, the complexity of interpreting and comparing several proxies from diverse sites complicates the characterization and differentiation of climatic and environmental changes at local, regional and global scales. This study investigates a 6-m peat core from the Ngaoundaba maar volcanic crater (Northeastern Cameroon, later simply called Ngaoundaba), spanning the last 10 ka using pollen analysis and a large panel of lipid biomarkers. We produce new high-resolution, continuous, multiproxy records of vegetation, temperature, and precipitation spanning most of the Holocene. All of these proxies indicate a substantial transition approximately 5.7–5.6 ka cal BP, which is supported by cluster analyses and marks the end of the AHP. A shift from an open-water to a vegetated peatland, the disappearance of some wooded species, and the expansion of grass and sedge pollen all indicate significant local and regional changes. The gradual terrestrialization of peat surfaces also had an impact on lipid biomarker proxies. An unusual extensive variation in hydrogen isotopic composition (D/H) of long-chain n-alkanes during the Holocene, in contrast to other records from West and Central Africa, may be attributed to the increased contribution from local wetland plants, including sedges and grasses, which thrive in peat water that is more D-enriched than rainwater, peat water being the water accumulating in the wetland. Likewise, temperature variations reconstructed using bacterial branched glycerol dialkyl glycerol tetraethers (brGDGTs) are influenced by confounding factors, like changes in peat pH or moisture levels, which may be constrained using our multiproxy methodology. The temperature record from Ngaoundaba indicates a slight increase in temperature during the mid-Holocene relative to pre-industrial levels. The Ngaoundaba peat deposit documents a massive and abrupt shift in vegetation at the end of the AHP, linked with changes in precipitation amount and/or seasonality, which also significantly affected the peat microbial community. The Ngaoundaba peat record, because of its high sensitivity to climatic and environmental changes, is a crucial new source for understanding the end of the African Humid Period in Western Central Africa
Context specific challenges of the WHO infection prevention and control core components in the Faranah Region: a mixed methods approach
No full textInternational audienceInfection prevention and control (IPC) programs have been reported to reduce healthcare associated infections by up to 70%. These rates vary globally, with scare data suggesting that the highest prevalence occurs in the African region exceeding 50% in Guinea. The Infection Prevention and Control Assessment Framework facilitates the evaluation of WHO guidelines on core components of infection prevention and control programs.Using this framework, selected healthcare facilities in Faranah, Guinea were evaluated ahead of an implementation of a training of trainer's program. Between May 2023 and March 2024, in a mixed method approach, the core components of 25 healthcare facilities were assessed in conjunction with an evaluation of 17 trainer's knowledge and perception on hand hygiene through standardized tools.Findings were further triangulated through a deductive analysis consisting of participant observations and semi structured interviews. The overall median of the Infection Prevention and Control Assessment Framework score in the region was basic (242.5, IQR 172.5 -342.5). Lowest scores were reported for IPC education, whereas IPC guidelines and healthcare associated infection surveillance received high scores. Rural healthcare centers had the lowest score (210.0, IQR 157.5 -265.0), confirmed by qualitative assessment indicating a lack of allocated budget in these facilities in addition to generally observed patient and staff overload. Participant observation found that while healthcare associated infection surveillance scored highly and IPC guidelines were displayed on posters; their practical application was rare. This was triangulated with healthcare workers selfreporting hand hygiene compliance of up to 90% whereby demonstrating considerable gaps in knowledge of WHO hand hygiene standards.Our study provides detailed understanding of a resource limited setting and highlights the importance of continuous IPC training together with behavior changes and the improvement of healthcare associated infection surveillance. In settings where a majority reside in rural areas, appointed health centers must be paid special attention to as they may often be underserved.Finally, infrastructural challenges such as the allocation of budget, patient and staff overload need to be addressed in order to improve the health and safety of patients and healthcare workers
Apprendre en lisant : traces et récits de lecture en langue étrangère au XVIIe
No full textInternational audienceAu XVIIe siècle, en Europe, bon nombre d’outils didactiques, qu’il s’agisse de méthodes, de dialogues ou de grammaires, insèrent des références littéraires ou s’inspirent de mises en forme littéraires, dramatiques ou poétiques pour nourrir, faciliter et rendre agréable l’apprentissage d’une langue étrangère. Ainsi en est-il de Francisco Trenado qui, dans son Arte muy curiosa por la qual se enseña muy de rayz, el entender, y hablar la Lengua Italiana (Medina del Campo, 1596), invite à lire sa grammaire en regard de sa traduction du Canzionere de Pétrarque,« pues hablandola y leyéndola, se aprende qualquiera lengua » (« car en parlant et en lisant, on apprend n’importe quelle langue »). En nous fondant sur un corpus de grammaires, méthodes, et dialogues didactiques, ainsi que sur des récits de voyage racontant l’apprentissage d’une langue étrangère par la lecture (Madame d’Aulnoy et l’Abbé de Choisy en particulier), nous analysons, dans cette communication, les représentations de la réception d’œuvres en langue étrangère en vue de l’apprentissage. Nous interrogeons également les reconfigurations du champ littéraire et éditorial du fait de ce goût pour le livre étranger. C’est alors un rapport à la lecture, considérée comme une véritable immersion dans un monde – culturel comme linguistique – qui se fait jour