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Effect of hydrogenation on type II silicon clathrate films
No full textInternational audienceIn this study we investigate for the first time the effect of hydrogenation on the properties of type II silicon clathrate films (SiCL). These clathrates are an alternative form of silicon based on a cage structure. It can be either emptied or filled with sodium atoms, leading to a metallic or semiconducting behavior with a tunable direct bandgap of 1.6-1.8 eV. There are a wide range of potential applications for such materials such as in electronics, optoelectronics, photovoltaics, batteries, spintronics or hydrogen (H) storage. However, the role of H in such materials remains largely unexplored and is not well understood experimentally. In this work, we hydrogenate the clathrates films using a H plasma with a substrate temperature of 400 • C. We evaluate the H content in the films by Time-of-Flight Secondary Ion Mass Spectrometry and Elastic Recoil Detection Analysis. The latter indicates a SiH 0.006 molar concentration before and SiH 0.070 after hydrogenation. Such a H content within the SiCL films is too low for practical hydrogen storage applications. Nevertheless, the incorporated H plays the role of dopant, leading to a reduction in the work function by around 0.3 eV. This demonstrates that even a modest hydrogen uptake can significantly enhance the electronic properties of silicon clathrates
Investigating Experimental Short Term Imprint Dynamics in Ferroelectric Hafnium Oxide Through Phase‐Field Modeling
No full textInternational audienceAbstract Ferroelectric imprint in Hf 0.5 Zr 0.5 O 2 (HZO) polycrystalline thin films poses severe reliability challenges to ferroelectric devices, with its underlying mechanisms still under debate. In this study, a novel 3D phase‐field modeling framework is presented to investigate the time‐dependent imprint phenomenon in HZO thin films. The phase‐field model incorporates charge injection and electron tunneling within the polycrystalline phase‐field structure, effectively reproducing key experimental trends, including polarization‐voltage curve shifts with increasing pause time, together with the recovery process achieved through field cycling. Through comprehensive analysis, the framework contributes to elucidating the complex interplay between the interfacial dielectric layer and electron detrapping mechanisms, which are critical in shaping ferroelectric imprint behavior. These findings enhance the understanding of imprint mechanisms in polycrystalline hafnium oxide and provide strategic insights for improving the performance and long‐term reliability of HZO‐based ferroelectric devices
Terrain descriptors for landscape synthesis, analysis and simulation
No full textInternational audienceSynthetic landscape generation is an active research area within Computer Graphics. Algorithms for terrain synthesis and ecosystem simulations often rely on simple descriptors such as slope, light accessibility, and drainage area. Typically, the results are assessed from a perceptual standpoint, focusing primarily on visual plausibility. Other fields, such as Geomorphology and Earth Sciences, have already proposed several analytical descriptors to measure various terrain properties. This work aims to bridge the gap between these disciplines and Computer Graphics. We provide a comprehensive review of commonly used terrain metrics that may be relevant for landscape synthesis, analysis, or simulations. Additionally, we compare the approaches used in Computer Graphics to see if these metrics, or similar ones, have already been introduced. Moreover, we report feedback from a preliminary study conducted with a group of artists to evaluate the potential applications of previously unused metrics. By implementing all these metrics, we enable performance comparisons. Together with the provided correlation matrix, this helps identify instances where a simpler and faster metric can serve as a proxy for a more computationally intensive one
Uncovering candidate Nanog-Helper genes in early mouse embryo differentiation using differential entropy and network inference
No full textInternational audienceIn the preimplantation mammalian embryo, stochastic cell-to-cell expression heterogeneity is followed by signal reinforcement to initiate the specification of Inner Cell Mass (ICM) cells into Epiblast (Epi). The expression of NANOG, the key transcription factor for the Epi fate, is necessary but not sufficient: coincident expression of other factors is required. To identify possible Nanog-helper genes, we analyzed gene expression variability in five time-stamped single-cell transcriptomic datasets using differential entropy, a quantitative measure of cell-to-cell heterogeneity. The entropy of Nanog displays a peak-shaped temporal pattern from the 16-cell to the 64-cell stage, consistent with its key role in Epi specification. By estimating the entropy profiles of the 21 genes common to all five datasets, we identified three genes - Pecam1, Sox2, and Hnf4a - whose variability in expression patterns mirrors that of Nanog. We further performed gene regulatory network inference using CARDAMOM, an algorithm that exploits temporal dynamics and transcriptional bursting. The results revealed that these three genes exhibit reciprocal activation with Nanog at the 32-cell stage. This regulatory motif reinforces fate-switching decisions and co-expression states. Our innovative analysis of single-cell transcriptomic data thus uncovers a likely role for Pecam1, Sox2, and Hnf4a as key genes that, when coincidentally expressed with Nanog, initiate ICM differentiation
Improving reproducibility in bioinformatics workflows with BioFlow-Model
No full textInternational audienceScientific workflows are crucial for managing data, but they do not fully comply with FAIR principles yet. To improve the sharing and reuse of workflow, recent models enable the representation of traces from scientific workflow executions. However they still lack of detailed or unambiguous information. In this paper, we present BioFlow-Model, a model for improving reproducibility and querying of scientific workflows. It extends existing models when possible and provide new concepts where needed. We have also proposed mappings with existing models to increase interoperability
Mobile Learning and Effects in Higher Education: A Systematic Review
No full textInternational audienceThis publication is the result of research presented at a conference jointly organized by the UNESCO Chair of the University of Strasbourg and the Computer Science Center (CUI) of the University of Geneva
Longitudinal Modularity, a Modularity for Link Streams
No full textInternational audienceTemporal networks are commonly used to model real-life phenomena. When these phenomena represent interactions and are captured at a fine-grained temporal resolution, they are modeled as link streams. Community detection is an essential network analysis task. Although many methods exist for static networks, and some methods have been developed for temporal networks represented as sequences of snapshots, few works can handle link streams. This article introduces the first adaptation of the well-known Modularity quality function to link streams. Unlike existing methods, it is independent of the time scale of analysis. After introducing the quality function, and its relation to existing static and dynamic definitions of Modularity, we show experimentally its relevance for dynamic community evaluation
A generic query-modify framework for volumetric mesh processing
No full textInternational audienceWe introduce a query-modify framework for automating volumetric mesh processing. Our method enables flexible and efficient modifications of geometric structures composed of multiple volumes with minimal user-implemented code. Modifications are provided as rules consisting of a query mesh and a target mesh representing structural information to be extracted and replaced. The rules enable both localized queries to be matched with a portion of an input mesh and targeted modifications on the matched portion of the input mesh. Our approach generalizes standard mesh manipulations and adapts to various applications, including geometric modeling, remeshing, and topology-aware transformations. We showcase our framework on several use cases, including the first complete implementation of a tetrahedral recombination method based on 171 cases, exhaustively classifying all possible recombinations. Our framework allows for arbitrarily connected collections of volumes as queries, enabling automated and application-driven mesh modifications
On the Rayleigh-Bénard convection problem for rotating fluids
No full textIn contrast with a large variety of conventional models of thermally driven fluids, we show that the standard Oberbeck-Boussinesq approximation cannot be obtained as a singular limit of the Navier-Stokes-Fourier system in the rotational coordinate system, with the buoyancy force proportional to the sum of the gravitational and centrifugal forces multiplied by the temperature variation