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Maurice is not dead! Une introduction à l'étude des conflictualités rurales
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Characterization of interstellar carbon dust analogues synthesized by dielectric barrier discharge and evolution after irradiation with 3 MeV H+
No full textInternational audience‘Fluffy’ hydrogenated amorphous carbon (a-C:H) was synthesized using a dielectric barrier discharge plasma, driven by nanosecond high voltage pulses at 1 kHz frequency in a helium–butane mixture. The a-C:H samples were characterized by scanning and transmission electron microscopy, laser-assisted and secondary ion mass spectrometry, and Raman and Fourier-transform infrared spectroscopy. We find that a-C:H samples exhibit infrared absorption features in good agreement with those observed for carbonaceous dust in IRAS 08572 + 3915 galaxy. We discuss their nano- to microscale structure and derive their hydrogen to carbon (H/C) ratios from the results obtained by three distinct experimental characterization techniques. Relying on the average H/C value determined by mass spectrometry and Raman spectroscopy, we can then constrain the absorption strengths values to those best corresponding to our dust analogue, and calculate the H/C ratio from the infrared spectra. Altogether, we find that our dust analogue consists of a dominant hydrogen-rich aliphatic network, with small, isolated, aromatic regions. The a-C:H dust analogue was then irradiated with 3 MeV H+ and subsequently analysed ex situ. Morphological and chemical changes, including the evolution of H/C, CH2/CH3, and sp2/sp3 ratios, were observed with increasing proton fluence, indicating dehydrogenation and graphitization. Proton bombardment shifted the initial location of a-C:H in the hydrocarbon ternary phase diagram toward the central region defined by IRAS 08572 + 3915 observations. The decay of the 3.4 m band with proton fluence was used to calculate CH destruction cross-sections, results consistent with a direct effect of cosmic rays on the disappearance of the 3.4 m band
Synthesis of polysaccharide-based block copolymers obtained by click chemistry from opened β-cyclodextrin and growth polymerization
No full textInternational audienceThe synthesis of well-defined oligosaccharides via cyclodextrin (CD) ring opening is an efficient method for obtaining tailored monomers, which are then suitable for further polymerization. Starting from benzoylated β-CD, which contains seven glucose units, pure difunctionalized benzoylated heptaoses were synthesized. This approach produced heptaoligosaccharides with either azide (A) or propargyl (B) as reactive groups at the reducing and non-reducing ends with a yield between 81 and 96 %, and corresponding to α,ω-diazidoheptaose, α,ω-dipropargylheptaose, and ω-azido-α-propargylheptaose for the AA, BB, and AB monomers, respectively. A highly efficient deprotection process provided access to difunctionalized linear and polar heptasaccharides with high purity (87–99 %). The newly synthesized oligosaccharidic blocks were then polymerized via copper-catalyzed 1,3-dipolar cycloaddition leading to seven original and distinct polymers. These include unprotected (AA-BB or AB-AB) or benzoylated (AB-AB) homo- and hetero-copolymers, as well as hydrophobic blocks randomly distributed with hydrophilic ones (AB-AB) or alternating unprotected-benzoylated blocks (AA-BB). Two additional polymers were obtained by quaternization of triazole rings. Characterization by SEC, TGA, XRD, NMR, and MALDI-TOF MS revealed that a mixture of polymers containing 1–34 blocks could be obtained, with a degree of polymerization ranging from 126 to 238 sugar units and moderate to excellent yields (30–85 %)
Evaluation and comparison of analytical methods for monitoring polymer depolymerization: application to poly(bisphenol A carbonate) methanolysis
No full textInternational audiencePolymer depolymerization after use represents a significant challenge to reduce both the environmental impact of plastic pollution and the utilization of non-sustainable raw materials. Recently, there has been a demand to form a coherent strategy for the analysis of polymer degradation, of which, some approaches have been observed to be used inappropriately or incompletely. This article proposes an analysis strategy for monitoring the depolymerization of poly(bisphenol-A carbonate) (PBPAC), using methanolysis as a model method. It is based on five analytical methods, which our study attempts to combine and compare according to their ideal use case: size exclusion chromatography (SEC), high-performance liquid chromatography (HPLC) and Fouriertransform infrared (FT-IR), nuclear magnetic resonance (NMR) and Matrix Assisted Laser Desorption Ionization -Time of Flight spectroscopy (MALDI-TOF). This strategy allows both a qualitative approach, where the depolymerization products can be identified and a quantitative one, where the percentage of polymer degradation can be determined, together with the detection limit of each associated technique (i.e. 0.06 %, 20 %, 10 %, 8 % and 0.5 % for SEC, HPLC, FT-IR, NMR and MALDI-TOF respectively). As a result, the range of applications for each analytical method is assessed, and a guide to determine the minimum methods to be used to qualify and quantify degradation is proposed, in relation to the progress of degradation and the yields obtained. This has enabled us to characterize and propose a new quantitative FT-IR-based methodology, compatible with high-throughput screening, to study the degradation of PBPAC, allowing for quantification of degradation from 10 % onwards
Modeling of Streamer in Gas by FEM and Semi-Lagrangian Method
No full textInternational audienceDetermining the likelihood of occurrence, growth and extinction of partial discharges between two conductors is a key point when designing electrical devices such as transformers, electrical machines or busbars. The continuity equations governing both time-and position-dependence of charged particle densities allows to build the most comprehensive model of partial discharge development in gas. Known in the literature as fluid model, plasma model or even electrohydrodynamic model, it consists of set of drift-diffusionreaction type equations strongly coupled to Poisson's equation that still remains challenging to solve by means of FEM due to numerical instability. This paper deals with the modeling of spatio-temporal growth of partial discharge inside gas solved by means of FEM and stabilized by means of a semi-Lagrangian method
Les fonctionnaires et la liberté d'expression à la lumière du loyalisme
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L'évaluation par capacités afin d'arrêter de (dé-)compenser
No full textInternational audienceA method for evaluating and monitoring students’ learning outcomes, is based on the definition of capabilities within each teaching unit, but above all on their connection via a graph for an entire course. If a capability is a pedagogical objective of a specific course, it is based on prerequisites, sometimes from other courses, other teaching units, or even previous training courses. These scientific links are used to build the graph. Each teacher has access at all times to the skills validated by each student, so that he or she can adapt the support provided. This approach, which is explained in this article, does not conflict with the classic creation of grades, always used in France to create averages and compensations between courses, much to the benefit of students. Unfortunately, however, they can sometimes lead to desesperate the teacher who sees that students have not mastered the prerequisites of his or her teaching, or worse, to a deep sadness that could lead to decompensation.Une méthode d’évaluation et de suivi des étudiant-e-s au plus proche de leurs acquis est basée sur la définition de capacités au sein de chaque enseignement, mais surtout de leur connexion via un graphe pour toute une formation. Si une capacité est un objectif pédagogique d’un enseignement spécifique, elle s’appuie sur des prérequis, parfois d’autres matières, d’autres unités d’enseignement, ou même de formations antérieures. Ces liens scientifiques servent à construire le graphe. Chaque enseignant-e a accès à tout instant aux capacités validées par chaque étudiant-e afin d’adapter son accompagnement. Cette démarche, explicitée au sein de cet article, n’est pas contradictoire à la création classique de note pour une matière. Les notes sont utilisées en faisant des moyennes et des compensations entre matières pour le plus grand bonheur des étudiant-e-s. Hélas, elles amènent parfois l’enseignant-e qui constate que des étudiant-e-s ne maîtrisent pas les prérequis de son enseignement, à perdre espoir, voir à une tristesse profonde qui risque de mener à une décompensation
Nanosized LaAl<sub>(1-x)</sub>Fe<sub>x</sub>O<sub>3</sub> oxides: characterization, optical and sono-photocatalytic applications
No full textInternational audienceAbstract The LaAl1-xFexO3 oxides (with x = 0, 0.05, 0.10 and 0.15) have successfully synthetized by the citrate-based Sol–Gel route. X-ray diffraction analysis confirms the preservation of the rhombohedral structure (as pristine-LaAlO3) with a linear increase of the lattice parameters according to the x value. The broadening of diffraction lines was indicated the nanometric nature of the synthetized oxides and the crystallites size was determined using the Scherrer equation. Additionally, the Diffuse Reflectance Spectroscopy revealed a modification of absorption properties for the iron-based compounds, suggesting their potential as effective photocatalysts under visible light. The photogenerated current was also exhibited an enhanced efficiency in the separation of electron–hole pairs for higher Fe3+ ions substitution rates. The variation in current density follows a power-law relationship with light power density and a wavelength-dependent study demonstrated that compounds containing iron show significantly more effective absorption in the blue spectral region. Based on these findings, the photocatalytic properties were further investigated. For the unsubstituted LaAlO3 (LA Sample), low photocatalytic activity, achieving only 10% of degradation within 30 min under visible light irradiation was observed. For substituted oxides with x = 0.05 (LAF1), 0.10 (LAF2) and 0.15 (LAF3) a higher photocatalytic activity (65%, 72%, and 81% of degradation in 30 min, respectively) and a pseudo-first order kinetic has been highlighted. Further, coupling photocatalysis with ultrasound to achieve sonophotocatalysis have shown a significant increase in carbofuran degradation rates after 30 min compared to classical photocatalysis (i.e., 20%, 86%, 91%, and 99% of degradation for LA, LAF1, LAF2 and LAF3 samples, respectively). The kinetics studies showed 0.0064, 0.0322, 0.0418, and 0.0502 min−1 rate for LA, LAF1, LAF2 and LAF3 samples, respectively. A study carried out according to pollutant concentration and to the pH showed an optimal efficiency of 99% for LAF3 sample under the following conditions: 30 min, 50 ppm (carbofuran concentration) at pH = 6. Further, the mechanism was explored and tests in presence of scavengers were indicated that the holes (h+ ) and superoxide radicals (O2•– ) are the main reactive species for degradation of carbofuran
Uncertainty in quantitative bipolar argumentation frameworks
No full textInternational audienceOnline deliberation platforms allow people to exchange their opinions around a specified issue and to vote on these opinions in order to reach a collective decision. Argumentation allows to structure and analyse user input for these platforms. A debate can be represented by a quantitative bipolar argumentation framework where votes on each argument of the debate are aggregated into an initial weight. One of the main challenges these platforms face is sparse voting i.e. participants vote on a few number of arguments, leading to an imbalance of the number of votes between the arguments. In this paper, we propose a methodology that handles sparse voting in online debates, by introducing imprecise quantitative bipolar argumentation frameworks that incorporate uncertainty on the initial weights. Specifically, we leverage votes on arguments to initialize weight intervals that represent the uncertainty on the initial weights, using the imprecise Dirichlet model. We use four state-of-the-art bipolar gradual semantics to generate a final acceptability interval on each argument and we introduce several properties to study the effect of these semantics on the uncertainty on each argument's final evaluation. Our methodology allows for a more robust representation of argument strength in the presence of limited data
The role of oxygen vacancies on the hydrodeoxygenation of lignin-derived compounds over Pd/SiCeO<sub>2</sub> catalysts
No full textInternational audienceThis work studies the effect of oxygen vacancies in a silica-doped ceria support on the mechanism of HDO reaction of phenol, m-cresol, xylenol and anisole over Pd-based catalysts. Increasing the silica content increased the density of oxygen vacancies due to the decrease in the CeO2 crystallite size. The addition of silica also promoted the reaction rate for HDO of phenolic compounds, whereas the rate for HDO of anisole remained approximately constant. These results revealed that the oxygen vacancies promoted the cleavage of the C-OH bond of phenolic molecules. Moreover, the presence of an electron donor on the aromatic ring reduces the energy barrier necessary for the cleavage of the Carom – OH bond. In the case of anisole, this molecule adsorbs on the Ce cations close to the metallic particles and then, the variation of the concentration of oxygen vacancies does not affect the rate of HD