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H-atom loss and migration in hydrogen-rich peptide cation radicals: The role of chemical environment
No full textInternational audienceHydrogen-atom loss and intramolecular hydrogen-atom migration in peptide radical and cation radical were investigated by quantum chemical calculations for models that include zero to three hydrogen bonds with the ammonium groups. Five different DFT functionals have been checked to study the geometry relaxation and fragmentation processes after electron attachment to peptide cations. The structural changes associated with the geometry relaxation are shown to be dependent on the level of calculation. Furthermore, comparison with CCSD(T) calculations indicates that an adequate description of the electronic state of the reduced protonated peptide is not a sufficient prerequisite to provide accurate energy barrier. Calculating fragmentation reactions of hydrogen-rich peptide cation radicals is pointed out to be a challenging task as none of the DFT functionals are fully effective to describe the whole process. M06-2X is an adequate choice if it provides the correct ground state, otherwise LC-BLYP should be chosen.The electron attachment site and the electron affinity value are highly sensitive to the number of hydrogen bonds with the ammonium group. An ammonium cation with zero, one, and, to a smaller extent, two hydrogen bonds easily captures an incoming electron and subsequently undergoes an H-atom loss process rather than a proton coupled electron transfer. This suggests an explanation for the low amount of c and z fragments observed upon ECD for small protonated peptides, where the ammonium groups cannot be highly intramolecularly “solvated”
Tableau sequences, open diagrams, and Baxter families
No full textWalks on Young's lattice of integer partitions encode many objects of algebraic and combina-torial interest. Chen et al. established connections between such walks and arc diagrams. We show that walks that start at ∅, end at a row shape, and only visit partitions of bounded height are in bijection with a new type of arc diagram – open diagrams. Remarkably two subclasses of open diagrams are equinumerous with well known objects: standard Young tableaux of bounded height, and Baxter permutations. We give an explicit combinatorial bijection in the former case
Optimization of Picrosirius red staining protocol to determine collagen fiber orientations in vaginal and uterine cervical tissues by Mueller polarized microscopy
No full textInternational audiencePolarized microscopy provides unique information on anisotropic samples. In its most complete implementation, namely Mueller microscopy, this technique is well suited for the visualization of fibrillar proteins orientations, with collagen in the first place. However, the intrinsic optical anisotropy of unstained tissues has to be enhanced by Picrosirius Red (PR) staining to enable Mueller measurements. In this work, we compared the orientation mapping provided by Mueller and second harmonic generation (SHG) microscopies on PR stained samples of vaginal and uterine cervix tissues. SHG is a multiphoton technique that is highly specific to fibrillar collagen, and was taken as the gold standard for its visualization. We showed that Mueller microscopy can be safely used to determine collagen orientation in PR stained cervical tissue. In contrast, in vaginal samples, Mueller microscopy revealed orientations not only of collagen but also of other anisotropic structures. Thus PR is not fully specific to collagen, which necessitates comparison to SHG microscopy in every type of tissue. In addition to this study of PR specificity, we determined the optimal values of the staining parameters. We found that staining times of 5min, and sample thicknesses of 5 mu m were sufficient in cervical and vaginal tissues. Microsc. Res. Tech. 78:723-730, 2015. (c) 2015 Wiley Periodicals, Inc
A flexible route to substituted hydroxy-cyclopentanones from cyclobutanones
No full textInternational audienceAcetonyl radicals derived from TBS-protected 1-(alpha-xanthylacetyl)-1-cyclobutanes readily undergo addition to unactivated alkenes. Deprotection of the resulting adducts with Et4NF/THF and exposure to silica gel cause ring expansion to give substituted hydroxycyclopentanones. Products of addition to ally! cyanide also underwent beta-elimination of the xanthate when treated with Et4NF/THF. (C) 2015 Elsevier Ltd. All rights reserved
Ultra-short laser induced electron excitation/relaxation kinetics
No full textInternational audienceLaser-induced electronic excitation, absorption and relaxation are the key issues in ultra-short laser interactions with dielectric materials. To numerically analyze these processes, several approaches are typically used. First, several detailed non-equilibrium models are based on a system of the detailed kinetic Boltzmann equations. Then, Fokker-Planck equations are also used. Finally, much more simplified rate equations are typically used in engineering modelling [1,2]. These models require additional sub-models to account for photo-ionization, electron-impact ionization, defect formation, recombination and other relaxation processes. In these sub-models, many parameters are rather unknown and are calculated based on additional considerations. One of such parameters is electron collision frequency [1-3], which was found to be crucial in determination of laser absorption and hence of laser damage.Boltzmann-based calculations are performed including all possible collisional processes. As a result, electron energy distributions are obtained allowing a better analysis of ultra-short laser interactions. The results reveal an effect of the laser-field on collision frequencies resulting in smaller free-carriers absorption than the one predicted by commonly used rate-equation models. Both electron-electron and electron-phonon relaxation are then examined, and the mean energy density of the electron sub-system is investigated as a function of laser fluence and pulse duration. Because efficient bond breaking requires energy, these calculations provide the required thresholds [4]. The dependency of the calculated damage threshold on laser pulse duration is compared with the available experimental data. The developed model is useful for many laser applications including high precision in laser treatment, laser-assisted atomic probe analysis, and for the development of new powerful laser systems.References[1] B. Chimier, O. Utéza, N. Sanner, M. Sentis, T. Itina, P. Lassonde, F. Légaré, F. Vidal, and J. C. Kieffer. "Damage and ablation thresholds of fused-silica in femtosecond regime." Physical Review B 84 (9), 094104, (2011).[2]T.E. Itina, N.S. Shcheblanov, N. Electronic excitation in femtosecond laser interactions with wide-band-gap materials. Applied Physics A, 98(4), 769-775 (2010).[3] C. Xie, V. Jukna, C. Milián, R. Giust, I. Ouadghiri-Idrissi, T. Itina, J. M. Dudley, A. Couairon, F. Courvoisier. "Tubular filamentation for laser material processing. Scientific reports, 5 (2015).[4] N. S. Shcheblanov, T. E. Itina, Appl. Phys. Femtosecond laser interactions with dielectric materials: insights of a detailed modeling of electronic excitation and relaxation processes, Appl. Phys. A, 110(3), 579-583 (2013)
Stabilité des solitons de l'équation de Landau-Lifshitz à anisotropie planaire
No full textSéminaire Laurent Schwartz - EDP et applicationsCet exposé présente plusieurs résultats récents quant à la stabilité des solitons sombres de l'équation de Landau-Lifshitz à anisotropie planaire, en particulier, quant à la stabilité orbitale des trains (bien préparés) de solitons gris et à la stabilité asymptotique de ces mêmes solitons
Réconcilier l'économie normative et l'économie comportementale
No full textThe aim of this thesis is to address from a methodological, philosophical and theoretical perspective the problem of how to reconcile normative and behavioural economics — the “reconciliation problem”. The first part develops a methodological assessment of behavioural welfare economics (and more specifically of libertarian paternalism), which currently constitutes the most accepted approach to deal with the reconciliation problem. We argue that behavioural welfare economics is in the direct continuation of neoclassical welfare economics, and that its conception of individual behaviour is tightly connected to Pareto’s reductionist model of the Homo economicus. It is assumed that an individual can be defined by “true” preferences — distinct from her revealed preferences — and that those preferences are consistent and context-independent. The satisfaction ofthose true preferences is taken as the normative criterion. The existence of true preferences requires accepting that people have access to a latent mode of reasoning able to generate consistent and context-independent preferences, and to treat individual decision-making as if it was the result of an optimisation problem faced by an inner rational agent trapped in an outer psychological shell. We argue on the contrary that we cannot defineunambiguously such true preferences. We then argue that the normative challenge raised by behavioural economics is that individuals may lack of autonomy: rather than focusing on the satisfaction of one’s preferences, we argue that what matters is the ability to choose one’s own preferences. Since we suggest that the difficulties of behavioural welfare economics are related to its commitment to an implausible model of individual preferences, we provide in the second part of the thesis a model of preferences compatible with our methodological analysis: we take Bacharach’s variable frame theory as the primitive of our analysis, and build a model of endogenous preferences, in which individuals can choose tosome extent their own preferences. The main contributions of this model are that (i) it does not require the existence of latent true preferences, and (ii) the individuals are allowed to team reason. We assume that collective preferences are strategically chosen, and show that team reasoners tend to be aggressive (cooperative) with other teams in submodular (supermodular) games. We finally show that team reasoning can be empirically justified as an ecologically rational heuristic.L’objet de cette thèse est d’offrir une analyse tant méthodologique que philosophique et théorique du “problème de réconciliation”, i.e. des implications normatives des résultats de l’économie comportementale. La première partie vise à dresser une analyse méthodologique de l’économie du bien-être comportementale (et en particulier du paternalisme libertarien), qui constitue actuellement la principale approche pour traiter le problème de réconciliation. Nous montrons que l’économie du bien-être comportementale est dans la directe lignée de l’économie du bien-être néoclassique, et que le modèle de comportement individuel sur lequel elle repose est étroitement lié au réductionnisme du modèle de l’Homo economicus développé par Pareto. Il est supposé qu’un individu peut être défini par ses “vraies” préférences, distinctes de ses préférences révélées, et que ces préférences sont cohérentes et stables. Le critère normatif retenu est alors la satisfaction de ces vraies préférences. L’existence de telles vraies préférences requiert l’existence d’un mode de raisonnement latent chez les individus susceptible de générer despréférences cohérentes et stables, et ainsi représente le raisonnement individuel comme un problème d’optimisation pour un agent rationnel intérieur, séparé du monde par une enveloppe psychologique externe. Nous montrons qu’il n’est pas possible de définir de façon non ambiguë ce que seraient de telles vraies préférences. Nous suggérons ensuite que le problème normatif soulevé par les résultats de l’économie comportementale est que les individus sont susceptibles de manquer d’autonomie: au lieu de se concentrer sur la satisfaction de ses préférences, nous proposons comme critère normatif la capacité de choisir ses propres préférences. Dans la mesure où les difficultés de l’économie du bien-être comportementale sont liées à son modèle de préférences sous-jacent, nous proposons dans la seconde partie de cette thèse un modèle de préférences compatible avec notre analyse: nous prenons comme primitive de notre analyse la variable frame theoryproposée par Bacharach, et développons un modèle de préférences endogènes, dans lequel les individus peuvent choisir dans une certaine mesure leurs propres préférences. Les principales contributions de ce modèle sont (i) l’absence de référence à une notion de vraiespréférences sous-jacentes, et (ii) la possibilité de modéliser des phénomènes d’intentionnalité collective (team reasoning). Nous supposons que les préférences collectives des individus sont le résultat d’un choix stratégique, et montrons que les individus tendent à être volontairement agressif (coopératif) avec les autres groupes d’individus dans le cadre de jeux sous-modulaires (super-modulaires). Nous montrons également que le team reasoning peut être justifié empiriquement comme une heuristique écologiquement rationnelle
Phaseless inverse scattering in the one-dimensional case
No full textInternational audienceWe consider the one-dimensional Schrödinger equation with a potential satisfying the standard assumptions of the inverse scattering theory and supported on the half-line x ≥ 0. For this equation at fixed positive energy we give explicit formulas for finding the full complex valued reflection coefficient to the left from appropriate phaseless scattering data measured on the left, i.e. for x < 0. Using these formulas and known inverse scattering results we obtain global uniqueness and reconstruction results for phaseless inverse scattering in dimension d = 1
Searches for supersymmetry using the MT2 variable in hadronic events produced in pp collisions at 8 TeV
No full textsee paper for full list of authorsInternational audienceSearches for supersymmetry (SUSY) are performed using a sample of hadronic events produced in 8 TeV pp collisions at the CERN LHC. The searches are based on the MT2 variable, which is a measure of the transverse momentum imbalance in an event. The data were collected with the CMS detector and correspond to an integrated luminosity of 19.5 inverse femtobarns. Two related searches are performed. The first is an inclusive search based on signal regions defined by the value of the MT2 variable, the hadronic energy in the event, the jet multiplicity, and the number of jets identified as originating from bottom quarks. The second is a search for a mass peak corresponding to a Higgs boson decaying to a bottom quark-antiquark pair, where the Higgs boson is produced as a decay product of a SUSY particle. For both searches, the principal backgrounds are evaluated with data control samples. No significant excess over the expected number of background events is observed, and exclusion limits on various SUSY models are derived
Compressed Sensing Performance of Random Bernoulli Matrices with High Compression Ratio
No full textInternational audienceThis paper studies the sensing performance of random Bernoulli matrices with column size n much larger than row size m. It is observed that as the compression ratio n/m increases, this kind of matrices tends to present a performance floor regarding the guaranteed signal sparsity. The performance floor is effectively estimated with the formula 1 2 (πm/2 + 1). To the best of our knowledge, it is the first time in compressed sensing, a theoretical estimation is successfully proposed to reflect the real performance