Archive ouverte de Centrale Lyon
Not a member yet
32420 research outputs found
Sort by
A deterministic particle approximation for a fourth-order equation
No full textWe provide a deterministic particle approximation to a fourth order equation withapplications in cell-cell adhesion. In order to do that, first we show that the equation can beasymptotically obtained as a limit from a class of well-posed nonlocal partial differential equations.These latter have the advantage that the particles’ empirical measure naturally satisfies the equation. Afterwards, we obtain stability of the 2-Wasserstein gradient flow of this family of nonlocalequations that we use in order to recover a deterministic particle approximation of the fourth orderequation. Up to our knowledge, in this manuscript we derive the first deterministic particle approximation for a fourth-order partial differential equation. Finally, we give some numerical simulationsof the model at the particles level
Grafixer: Enabling User-Centric Repairs for Property Graphs
No full textInternational audienceWe introduce Grafixer, an innovative interactive tool that enables human-in-the-loop repair of property graphs. By leveraging user expertise, Grafixer allows collaborative identification and correction of data inconsistencies while ensuring an efficient repair process. Users can upload property graph datasets and define constraints using Cypher, a widely adopted query language. The system efficiently manages overlapping data violations, ensuring that multiple users can work simultaneously on independent repairs without conflicts. Additionally, Grafixer provides an interactive dashboard that allows administrators to monitor real-time statistics, track progress, and oversee the repair process. In our demo, we showcase the complete repair workflow from both the administrator's and users' perspectives. Administrators can configure the repair process, monitor ongoing corrections, and assess the overall status of the graph. Meanwhile, users engage in the repair process by reviewing violations, proposing corrections, and contributing to improving data quality through an intuitive and guided interface
Analysis of Robustness of 650 V GaN HEMT under Repetitive Short-Circuits
No full text#12International audienceShort-circuit studies for Power GaN HEMT initiated in 2013, remain limited and primarily focus ondestructive tests. Rather than carrying out destructive short-circuits, which would make it much more difficult toanalyse the component once it has been destroyed, it has been decided to carry out repetitive, non-destructiveshort-circuits. Successive short-circuits, interspersed with electrical characterizations, help identify degradationand failure mechanisms. Two suppliers of 650 V GaN components, with normally-on and normally-off types, weretested. Despite efforts to minimize loop inductance, initial tests failed, requiring bench optimization and SPICEsimulations. Multiple test bench versions were developed. Drifts in parameters were observed and supplierdifferences influenced stability and robustness, leading to hypotheses explaining these discrepancie
Raman and photoluminescence characterization of β-Ga2O3 for power electronic application
No full textInternational audienc
Macrophage polarization determines inflammation amplification and resolution
No full textSterile inflammation is a form of pathogen-free inflammation caused by non-infectious stimuli, such as injury, toxins, or cell stress. It serves to protect tissues, promote repair, and restore homeostasis. Like other forms of inflammation, sterile inflammation has three distinct stages: initiation, amplification, and resolution. The transition between the last two phases is particularly important for restoring tissue balance. If this process is disrupted, it can lead to the development of chronic inflammation and various diseases. Although the exact mechanisms that control this transition in the process of sterile inflammation are not fully understood, they remain a key area of research.In this work, we develop a mathematical model to explore the interplay between pro- and anti-inflammatory mediators in the process of sterile inflammation. The model consists of an integro-differential reaction-diffusion system that captures the spatial and temporal evolution of inflammation within tissue and blood. Specifically, the model tracks the concentrations of seventeen key-players involved in the inflammatory response, including circulating macrophages, DAMPs, RAMPs, inflammatory cytokines, and tissue-resident macrophages (TRMs). We focus on the role of macrophage polarization in determining the outcome of sterile inflammation, whether it leads to resolution or chronicity. According to this model, the anti-inflammatory processes, namely the inhibition in polarization of M1-type macrophages, can lead to the resolution of inflammation
Gd<sup>3+</sup>-Doped Biocompatible Fluorinated Carbon Dots for Bimodal Bioimaging Applications
No full textInternational audienceFluorinated carbon dots (FCDs) represent a promising class of nanomaterials for biomedical applications owing to their biocompatibility, high fluorescence, and chemical stability. In this work, we report for the first time the synthesis and systematic investigation of Gd3+-doped FCDs (Gd-FCDs) obtained via a solvothermal route using urea, anhydrous citric acid, 3-(trifluoromethyl) aniline and Gadolinium (III) chloride hexahydrate. By incorporating paramagnetic Gd3+ ions into fluorinated fluorescent carbon dots, we aimed to create multifunctional nanoprobes capable of simultaneous fluorescence and magnetic resonance imaging (MRI). Comprehensive characterization demonstrated that Gd 3+ doping significantly altered the structural and optical properties of FCDs. While pristine FCDs were ultrasmall (2-8 nm), Gd-FCDs exhibited larger sizes (40-80 nm) due to ion-induced aggregation. During the synthesis process Gd3+-ions are efficient positively charged centers stimulating formation of FCDs around them, resulting in bigger final complexes. Zeta potentials of FCDs and Gd-FCDs are -27.8 mV and -1.5 mV, respectively. UV-Vis and fluorescence analyses revealed changes in electronic transitions and reduced fluorescence intensity, consistent with the introduction of nonradiative pathways by Gd 3+ ions. Time-resolved fluorescence studies further confirmed modified exciton dynamics. Importantly, proton relaxation measurements showed drastic reductions in both T1 and T2 relaxation times for Gd-FCDs in the concentration range 0.015 -4 g/L, highlighting their strong MRI contrast capability across different magnetic field strengths. Cell toxicity measurements on 3T3-L1 biological cells show that all the FCDs revealed no toxicity against cells, indicating their complete biological compatibility at the concentration levels between 0.175 and 0.334 mg/mL. Its efficiently penetrate into cell nuclei, enabling robust fluorescent cell labeling across the visible spectrum
Extremal functions for twisted sharp Sobolev inequalities with lower order remainder terms
No full textInternational audienc
Differentially private and decentralized randomized power method
No full textThe randomized power method has gained significant interest due to its simplicity and efficient handling of large-scale spectral analysis and recommendation tasks. However, its application to large datasets containing personal information (e.g., web interactions, search history, personal tastes) raises critical privacy problems. This paper addresses these issues by proposing enhanced privacy-preserving variants of the method. First, we propose a variant that reduces the amount of the noise required in current techniques to achieve Differential Privacy (DP). More precisely, we refine the privacy analysis so that the Gaussian noise variance no longer grows linearly with the target rank, achieving the same (ε, δ)-DP guarantees with strictly less noise. Second, we adapt our method to a decentralized framework in which data is distributed among multiple users. The decentralized protocol strengthens privacy guarantees with no accuracy penalty and a low computational and communication overhead. Our results include the provision of tighter convergence bounds for both the centralized and decentralized versions, and an empirical comparison with previous work using real recommendation datasets
Li-Yau-Hamilton Inequality on the JKO Scheme for the Granular-Medium Equation
No full textWe establish a version of the Li-Yau-Hamilton inequality for the Granular-Medium equation on the torus, both at the PDE level and for its time-discrete approximation given by the JKO scheme. We then apply this estimate to derive further quantitative results for the continuous and discrete JKO flows, including Lipschitz and bounds, as well as a quantitative Harnack inequality. Finally, we use the regularity provided by this estimate to show that the JKO scheme for the Fokker-Planck equation converges in L^2_{\mathrm{loc}((0, +∞); H^2 (\mathbb{T}^d ))</div
A tool for visual analysis and photo-realistic rendering of forest landscape model simulations
No full textInternational audienceSimulation outputs from Forest Landscape Models are complex, and tools for their visualanalysis and effective communication are often limited. In this paper, we present EcoViz, anovel, open-source visualization platform designed to complement existing forest models byproviding advanced 3D visualization capabilities. EcoViz facilitates the exploration ofsimulation results through two primary modes: symbolic rendering, designed for analyticaltasks, such as pattern recognition and model evaluation, and photorealistic rendering,leveraging physically-based rendering (Mitsuba 3) and a custom library of European 3D treemodels for communication purposes.The platform imports data in a typical model output format (e.g., spatially explicit individualtree or cohort data) and employs a temporally coherent sampling technique to visualizeindividual trees derived from cell-based density maps. Key features include: interactive side-by-side comparison of different simulation scenarios or time points, with synchronizednavigation (viewpoint, timeline, transects), a mini-map overview, timeline controls with linkedecological metric graphs, and transect analysis tools. Developed using C++/Qt/OpenGL,EcoViz is cross-platform.The practical application of EcoViz is demonstrated by visualizing simulations ofBerchtesgaden National Park under baseline and climate change scenarios exported fromthe iLand forest landscape model. This case study showcases the utility of EcoViz forcomparative scenario analysis across spatial scales and how it aids model evaluationthrough visual inspection. While symbolic views support detailed analysis, the photorealisticoutput offers a compelling tool for science communication with diverse audiences, includingscientific peers, forest managers, and the public