Archive ouverte HAL de CY Cergy Paris Université
Not a member yet
38365 research outputs found
Sort by
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
Utiliser la métalangue grammaticale lors des échanges langagiers à visée réflexive en 2ème primaire (CE1) : une mission impossible?
No full textInternational audienc
Development and preclinical evaluation of a dual therapeutic platform for skin applications
No full textInternational audienceIntroductionSkin disorders, such as chronic wounds, atopic dermatitis or psoriasis, are often associated with oxidative stress and bacterial infections, which contribute to impaired healing and disease progression. The combined challenge of oxidative stress and infection, along with the increasing prevalence of multidrug-resistant pathogens, underscores the urgent need for innovative dual-targeted therapies. This work presents the development of a platform integrating an elastomeric scaffold filled with an alginate hydrogel incorporating two Staphylococcus aureus bacteriophages (ISP & GRCS) and curcumin-loaded nanostructured lipid carriers (CUR-NLCs) for antioxidant properties. This multifunctional approach is designed to address both infection and oxidative stress.Materials and MethodsThe elastomeric poly(glycerol sebacate) (PGS) scaffold was fabricated using a salt-leaching technique. Alginate formulations loaded with CUR-NLCs and bacteriophages (ISP and GRCS) were gelled in situ within the scaffold’s cavities. The resulting platform was mechanically and morphologically characterized by compressive strength tests and scanning electron microscopy (SEM). The release of curcumin and active bacteriophages was determined by spectrophotometry and double agar overlay assay respectively. Preclinical evaluation included an MTS assay on human fibroblasts (BJ) and human keratinocytes (HEKn), along with histological analysis using a reconstructed human epidermis model (SkinEthic RHE). Antibacterial and antioxidant activity were performed by CFU counting and ABTS assay respectively.ResultsPGS scaffolds were successfully filled with alginate formulations without compromising the lytic activity of bacteriophages, with loading efficiency superior to 80%. Furthermore, hydrogel formation within the scaffold’s pores was confirmed by SEM. The final platform, incorporating CUR-NLC and bacteriophages, exhibited good elasticity recovery and Young’s modulus comparable to human skin. Furthermore, sustained release of active phages was observed, with concentrations exceeding 60 % (< 10⁹ PFU/mL) after 72 hours. Cytotoxicity assays confirmed the absence of toxicity in human skin fibroblasts (BJ) and keratinocytes (HEKn). Biocompatibility was further assessed using a reconstructed human epidermis model (SkinEthic RHE) to evaluate potential skin irritation and effects on epidermal metabolic activity and barrier integrity. Finally, the platform’s therapeutic efficacy was evaluated by studying its antibiofilm activity against methicillin-resistant Staphylococcus aureus strains and antioxidant activity.DiscussionThe successful incorporation of the alginate hydrogel with bioactive agents within PGS scaffolds highlights the platform’s versatility. Its preserved structural integrity, favorable mechanical properties, and demonstrated biocompatibility further confirming its suitability for skin applications. Further studies are needed to fully explore its dual therapeutic potential.ConclusionsThe developed bifunctional platform stands out by integrating both properties into a single system, compared to conventional treatments. It represents a promising approach as a novel adjuvant therapy for the treatment of skin disorders by simultaneously targeting bacterial infections and inflammation. Its ability to sustain the release of bioactive agents while maintaining biocompatibility makes it a potential candidate for advanced wound care applications. Future in vivo studies are necessary to confirm its therapeutic benefits and evaluate its long-term stability
Influence of the Forgetting Factor in the Recursive Least Squares RLS Algorithm on the Quality and Precision of the Identified Parameters in a DC Corona Discharge
No full textInternational audienc
A beamforming frequency to mitigate the beamsquint effect in sub-THz
No full textInternational audienceIn this paper, we propose to adapt the beamforming frequency for ultra massive multiple-input multipleoutput uniform linear arrays allowing a maximum array gain while minimizing the angle deviation induced by the beamsquint effect. This original adapted frequency deviates from the center frequency fc. It paves the way for the beamforming frequency to be a degree of freedom. Our simulations show that the proposed analytical solution is close to the optimal numerical solution with less computational complexity
On Sibuya trees and forests
No full textInternational audienceWe show that the Sibuya distribution and its non-critical relatives arerelevant in the context of the recursive generation of both simply generatedand increasing critical trees' and forests' progenies. A special class ofgeneralized Stirling numbers are at the heart of the analysis of the inducedoccupancy distributions. Asymptotic aspects of large forests are addressed
Trabajo matemático en Álgebra Lineal. Una transición a través de paradigmas
No full textResearch on the teaching and learning of linear algebra has been ongoing for several decades, but it has recently been renewed in the context of non-routine tasks and technological ecosystems, including artificial intelligence. This article analyzes two key transitions: (a) from school-level geometry and algebra to linear algebra, and (b) between different paradigms of linear algebra. We propose a fundamental situation in which the goal is to find the vertices of a polygon given its midpoints. This problem can be modeled using systems of linear equations that may have a unique solution, infinitely many, or none. The situation was divided into three tasks and implemented in three universities in the Valparaíso region that train future mathematics teachers. Forty pre-service teachers participated. Data collected included audio recordings, screen captures, and written productions. The analysis was conducted using the categories of the Mathematical Working Space and the paradigms of linear algebra. Results show that most students were able to transition from geometry to linear algebra, mainly within the first paradigm. The mathematical work was predominantly semiotic and instrumental, but a gradual increase in discursive work was observed all along the didactical situation. Various digital tools were used—mainly GeoGebra and MatrixCalculator, with some use of Wolfram Alpha and ChatGPT—serving to both find algebraic solutions and validate them geometrically. The findings suggest that a long sequence of several open tasks involving domain changes and diverse technologies can support the introduction of linear algebra in teacher education.La investigación sobre la enseñanza y el aprendizaje del álgebra lineal se ha desarrollado durante varias décadas, pero recientemente ha cobrado nuevo impulso en el contexto de tareas no rutinarias y ecosistemas tecnológicos, incluida la inteligencia artificial. Este artículo analiza dos transiciones clave: (a) desde la geometría y el álgebra escolar hacia el álgebra lineal, y (b) entre diferentes paradigmas del álgebra lineal. Proponemos una situación fundamental cuyo objetivo es encontrar los vértices de un polígono dados sus puntos medios. Este problema puede modelarse mediante sistemas de ecuaciones lineales que pueden tener una solución única, infinitas soluciones o ninguna. La situación se dividió en tres tareas y se implementó en tres universidades de la región de Valparaíso que forman futuros profesores de matemáticas. Participaron cuarenta profesores en formación inicial. Los datos recogidos incluyeron grabaciones de audio, capturas de pantalla y producciones escritas. El análisis se realizó utilizando las categorías del Espacio de Trabajo Matemático y los paradigmas del álgebra lineal. Los resultados muestran que la mayoría de los estudiantes logró transitar desde la geometría al álgebra lineal, principalmente dentro del primer paradigma. El trabajo matemático fue predominantemente instrumental e instrumental, pero se observó un aumento progresivo del trabajo discursivo a lo largo de la situación didáctica. Se utilizaron diversos artefactos digitales —principalmente GeoGebra y MatrixCalculator, con algún uso de Wolfram Alpha y ChatGPT— que sirvieron tanto para encontrar soluciones algebraicas como para validarlas geométricamente. Los hallazgos sugieren que una secuencia prolongada de varias tareas abiertas, que involucren cambios de dominio y tecnologías diversas, puede apoyar la introducción del álgebra lineal en la formación de profesores.</p
Unique and nonunique minimizing travelling waves for some Ginzburg–Landau type equations
No full textInternational audienceThis is a summary of an upcoming work in collaboration with Mihai Maris. We study the Schrödinger equation with a nonzero condition at infinity for some nonlinearities, for which the existence of travelling waves has been proven in [22] as solutions of a minimization problem. We show that for some of them, we do not have uniqueness of this minimizer, and we study how these travelling changes when we change the speed and/or the nonlinearity. We also discuss some examples where we have the uniqueness of travelling waves that are solutions to minimisation problems, as well as questions related to the stability of these objects