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Far infrared spectra of solid state l-serine, l-threonine, l-cysteine, and l-methionine in different protonation states
No full textInternational audienceIn this study, experimental far infrared measurements of L-serine, L-threonine, L-cysteine, and L-methionine are presented showing the spectra for the 1.0-13.0 pH range. In parallel, solid state DFT calculations were performed on the amino acid zwitterions in the crystalline form. We focused on the lowest frequency far infrared normal modes, which required the most precision and convergence of the calculations. Analysis of the computational results, which included the potential energy distribution of the vibrational modes, permitted a detailed and almost complete assignment of the experimental spectrum. In addition to characteristic signals of the two main acid-base couples, CO2H/CO2- and NH3+/NH2, specific side chain contributions for these amino acids, including CCO and CCS vibrational modes were analyzed. This study is in line with the growing application of FIR measurements to biomolecules. (c) 2015 Elsevier B.V. All rights reserved
Nanosensors for embedded monitoring of construction materials: the '2D conformable' route
No full textNICOM 5 - Fifth International Symposium on Nanotechnology in Construction, CHICAGO, ETATS-UNIS, 24-/05/2015 - 26/05/2015We propose an approach to embedded monitoring of construction materials relying on 2D, conformable architectures that are expected to be lower cost and more robust than their 3D counterparts. In this article, we present two examples: a RFID-enabled carbon nanotube strain sensor on plastic for microcrack monitoring in concrete and a nanoparticle-asphalt sandwich for weigh-in-motion applications
A high resolution study of the Martian water cycle with a global climate model
No full textInternational audienceThe martian water cycle's main source is the northern polar cap. Running high resolution models, up to 360° per 180°, help better resolve this ice cap, and better mimic the gradual retreat of the seasonal cap. Atmospheric circulation is also better resolved. Water vapor advection and the subsequent formation of clouds quite differ when we compare these brand new high resolution simulations and the usual lower resolution ones at 64 per 48 grid points
Configuration Tracking for Mechanical Systems by Kinematic Reduction and Fast Oscillating Controls
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Further remarks on Markus-Yamabe instability for time-varying delay differential equations
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A three-dimensional map of tidal dissipation over abyssal hills
No full textInternational audienceThe breaking of internal tides is believed to provide a large part of the power needed to mix the abyssal ocean and sustain the meridional overturning circulation. Both the fraction of internal tide energy that is dissipated locally and the resulting vertical mixing distribution are crucial for the ocean state, but remain poorly quantified. Here we present a first worldwide estimate of mixing due to internal tides generated at small-scale abyssal hills. Our estimate is based on linear wave theory, a nonlinear parameterization for wave breaking and uses quasi-global small-scale abyssal hill bathymetry, stratification, and tidal data. We show that a large fraction of abyssal-hill generated internal tide energy is locally dissipated over mid-ocean ridges in the Southern Hemisphere. Significant dissipation occurs above ridge crests, and, upon rescaling by the local stratification, follows a monotonic exponential decay with height off the bottom, with a nonuniform decay scale. We however show that a substantial part of the dissipation occurs over the smoother flanks of mid-ocean ridges, and exhibits a middepth maximum due to the interplay of wave amplitude with stratification. We link the three-dimensional map of dissipation to abyssal hills characteristics, ocean stratification, and tidal forcing, and discuss its potential implementation in time-evolving parameterizations for global climate models. Current tidal parameterizations only account for waves generated at large-scale satellite-resolved bathymetry. Our results suggest that the presence of small-scale, mostly unresolved abyssal hills could significantly enhance the spatial inhomogeneity of tidal mixing, particularly above mid-ocean ridges in the Southern Hemisphere
Focused labeled proof systems for modal logic
No full textInternational audienceFocused proofs are sequent calculus proofs that group inference rules into alternating positive and negative phases. These phases can then be used to define macro-level inference rules from Gentzen's original and tiny introduction and structural rules. We show here that the inference rules of labeled proof systems for modal logics can similarly be described as pairs of such phases within the LKF focused proof system for first-order classical logic. We consider the system G3K of Negri for the modal logic K and define a translation from labeled modal formulas into first-order polarized formulas and show a strict correspondence between derivations in the two systems, i.e., each rule application in G3K corresponds to a bipole—a pair of a positive and a negative phases—in LKF. Since geometric axioms (when properly polarized) induce bipoles, this strong correspondence holds for all modal logics whose Kripke frames are characterized by geometric properties. We extend these results to present a focused labeled proof system for this same class of modal logics and show its soundness and completeness. The resulting proof system allows one to define a rich set of normal forms of modal logic proofs
Activitée de marché et réactivité du prix à travers les échelles
No full textThis thesis tackles several issues raised by the multi-scale properties of financial data. Itconsists of four connected parts which can however be read independently.In the first part, we introduce the Rough Fractional Stochastic Volatility (RFSV) model. In thisframework, the logarithm of the volatility is a fractional Ornstein-Uhlenbeck process with longmean reversion time scale and small Hurst index. We show that this model reproduces numer-ous stylized facts of financial data such as implied volatility properties, the autocorrelationstructure and the regularity of the volatility. In particular, the RFSV sheds some new light onthe supposed long memory property of volatility.The second part deals with the long-time behavior of Hawkes and autoregressive processeswhich are nearly unstable, that is whose kernels have a norm close to one. We show that inthe case where the kernel has a light tail, nearly unstable Hawkes processes asymptoticallybehaves as integrated Cox-Ingersoll-Ross (CIR) processes. In the case where it has a powerlaw shape, depending on the power law exponent, the limiting process asymptotically exhibitseither long memory or a rough behavior. This enables us to use the modeling of the order flowas a Hawkes process to obtain a microstructural foundation of the rough nature of volatility.Similar results are obtained for autoregressive processes.In the third part of this thesis, we propose two estimation procedures for the kernels of Hawkesprocesses. These algorithms are in particular relevant to the case of slowly decreasing Hawkeskernels which corresponds to what is observed on financial data. The first method relies on theinversion of the Wiener-Hopf equation while the second is based on a likelihood maximizationvia a stochastic gradient ascent.Finally, we are interested in deriving, under very general assumptions, consequences of marketefficiency on the structure of price impact. We prove the existence of a model independent fairprice with respect to which the average ex post gain of limit orders must be equal to zero. Wefinally show that, under a few additional assumptions, price impact must be proportional tothe market anticipation of the order flow imbalance.Cette thèse traite plusieurs problèmes posés par le caractère multi-échelle des données fi-nancières. Elle est composée de quatre parties interconnectées pouvant néanmoins être luesindépendamment.On introduit dans la première partie le modèle RFSV à volatilité rugueuse. Dans ce modèle, lelogarithme de la volatilité est modélisé par un processus d’Ornstein-Uhlenbeck fractionnaire àtemps de retour à la moyenne long et exposant de Hurst petit. Nous montrons que ce modèlepermet de reproduire le comportement de la surface de volatilité ainsi que de nombreux faitsstylisés statistiques tels que la structure d’autocorrélation et la régularité de la volatilité. Enparticulier, nous semblons montrer que, contrairement à l’idée communément admise, celle-cine présente pas de longue mémoire en loi de puissance.La deuxième partie porte sur le comportement en temps long des processus de Hawkes etdes processus autorégressifs quasi instables, c’est-à-dire dont le noyau a une norme prochede un. Nous montrons que dans le cas où le noyau est à queue fine, les processus de Hawkesquasi instables se comportent asymptotiquement comme des processus de Cox-Ingersoll-Rossintégrés. Dans le cas où le noyau est en loi de puissance, en fonction de son exposant, ladistribution limite est un processus à longue mémoire ou un processus C 1 à derivée rugueuse.En modélisant le flux d’ordres par un processus de Hawkes, ce résultat nous permet d’établirdes fondements microstructurels à l’irrégularité de la volatilité évoquée dans la première partie.Nous obtenons des résultats similaires pour les processus autorégressifs.Dans la troisième partie de cette thèse, nous proposons deux procédures statistiques permettantd’estimer les noyaux de processus de Hawkes. Nous adaptons ces algorithmes au cas où lesnoyaux sont à décroissance lente, situation observée sur les données. La première procédurese fonde sur l’inversion de l’équation de Wiener-Hopf tandis que la deuxiéme consiste en unemaximisation de la vraisemblance par descente de gradient stochastique.Enfin, dans la dernière partie de cette thèse, nous nous intéressons, sous des hypothèses lesplus générales possible, aux conséquences de l’efficience du prix sur la structure de l’impactde marché. Nous obtenons l’existence d’un prix efficient par rapport auquel le gain ex postdes ordres limites doit être nul. Finalement, nous montrons que si l’impact permanent desmétaordres est linéaire en leur volume, les fluctuations de prix doivent être proportionnellesaux variations de l’anticipation par le marché du déséquilibre de volume
The Martian ionosphere: comparison of a global climate model with MARSIS data
No full textInternational audienceWe present here the comparison of the electron den- sity profiles predicted by a 3D global climate model (GCM), the Mars GCM developed at the Laboratoire de Météorologie Dynamique (LMD-MGCM) [4], with the measurements from the instrument MARSIS on board Mars Express [5]. The observations were ob- tained during 5 Martian Years (MY), from MY27 to MY31 (mid 2005-end of 2013). The model was run using the observed day-to-day variability of the UV solar flux and of the dust load during that period. We focus the comparison on two parameters: the electron density at the main peak, and the altitude of the peak. Special attention will be paid to the variability of these two parameters with different geophysical parameters (latitude, SZA, ...), which can provide interesting in- formation about the neutral upper atmosphere of Mars and its interaction with the UV solar radiation
