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Laser Induced Breakdown Spectroscopy (LIBS) offers possibility for fast de- tection of sample composition without its preparation. For this reason it is attractive anywhere where the fast detection and no sample preparation are needed. As in many other branches the technical and scientific progress im- proves and spreads the possibilities of LIBS based devices and laboratory appa- ratuses. The time-resolved spectroscopy is allowed by spectrograph equipped with fast camera, broadband spectra can be acquired in single exposition by broadband spectrometers. Smaller and lighter laser sources together with com- pact spectrometers can be implemented to portable device and can be used out of laboratory. Computers offer quick data processing. The device named ChemCam installed on the NASA's next Mars rover, curiosity, is good exam- ple of high technology application in LIBS. However, there are still challenges and we hope that this work will be fruitful for anyone who is interested in the LIBS. The project of presented thesis was performed as a joint supervision project between the Department of Experimental Physics at Comenius University in Bratislava and Laboratiore Interdisciplinaire Carnot de Bourgogne at Univer- sit ́e de Bourgogne in Dijon. The aim of the project was to join experience from both laboratories, experience in laser constructions from Dijon and experience with spectroscopy from Bratislava. The both are essential for LIBS. In Bratislava the work was coordinated by prof.Pavel Veis and it was fo- cused on LIBS under the laboratory conditions. The time-resolved broadband spectrometry was used in the research. In order to achieve required spectra, the spectral response of the optical system was determined which was later used for the corrections. The research of self-absorption phenomena started in the last period with aim to use this effect, usually considered as negative, for the composition determination. In Dijon the work was supervised by Dr. Olivier Musset and directed toward development of LIBS device which could be used out of laboratory. The small 6 7 laser which was previously developed in the laboratory was implemented in the device. The development was successfully finished and testing process began in the last period of the thesis. The geological samples have been used for the testing process which was performed in deep cooperation with geologists. The first chapter comprises a brief introduction to LIBS. It is divided into some parts about laser induced plasma, laser induced breakdown and evolution of the plasma after breakdown. The section dealing with local thermodynamic equilibrium is also included. The section describes importance of LTE and the possibilities to determine this state. The second chapter is dedicated to the developed portable LIBS device. In the introduction, different type of LIBS devices are presented with their possibilities. Then the portable device developed in Dijon is described part by part with brief characteristic of developed software. The device possibilities and limits are sketched in the last section of the chapter with respect to results obtained in the testing process. The third chapter deals with capabilities of LIBS apparatus which was set up in the laboratory. The process of spectral response measurement and its results are presented and consequently used in next sections in process of plasma parameters determination. The composition of used samples are determined by using of calibration free method with aim to choose proper location in the plasma for which results are the most representative. The last chapter includes introduction to the subject of self-absorption phenomena. The simple model and basic theory are presented with suggestion how to use the phenomena in positive way. The simple experiment and its results are presented at the end of the chapter together with discussion about the possibilities and perspectives of the suggested method.
This review summarizes the state of the art in the synthesis of well-defined glycopolymers by Reversible-Deactivation Radical Polymerization (RDRP) from its inception in 1998 until August 2012. Glycopolymers architectures have been successfully synthesized with four major RDRP techniques: Nitroxide-mediated radical polymerization (NMP), cyanoxyl-mediated radical polymerization (CMRP), atom transfer radical polymerization (ATRP) and reversible addition-fragmentation chain transfer (RAFT) polymerization. Over 140 publications were analyzed and their results summarized according to the technique used and the type of monomer(s) and carbohydrates involved. Particular emphasis was placed on the experimental conditions used, the structure obtained (comonomer distribution, topology), the degree of control achieved and the (potential) applications sought. A list of representative examples for each polymerization process can be found in tables placed at the beginning of each section covering a particular RDRP technique.
1,6-Bis(1-imidazolyl)-2,4-hexadiyne (1) and1,6-bis(1-benzimidazolyl)-2,4-hexadiyne (5) have beenpreparedby a novel method that consists in refluxing excess imidazole and benzimidazole with 2,4-hexadiyne-1,6-diol bis(p-toluenesulfonate),pTS (3). This procedure is a viable alternative to the widely used Hay coupling protocol in case the target diyne possesses substituents capable of deactivating the copper catalyst by complexation. Diyne1crystallizes as a hydrate,1?H2O(2). For this compound, water is essential toachieve a crystalline material, and attempts to obtain crystals without included solvent were unsuccessful. In the structure of2, the organic fragments organize around the water molecule and interact with it through a dense network of hydrogen bonds. The CMC-CMC moieties are not oriented suitably for topochemical polymerization, and when trying to alter the organizationof the crystal by heating so as to induce polymerization, water is lost in an abrupt fashion that leads to instantaneous decomposition into polyaromatic-like species. Similar results were observed when water was removedin vacuo at room temperature. The benzimidazole-containing compound can be crystallized with water molecules (4)orwithout(5). X-ray crystallography shows that the structure of 5is organized by numerous C-H...N, C-H...p,andimidazolyl...imidazolyl p-p interactions. The diacetylene molecules almost have the right arrangement for topochemical polymerization, withpossibly reactingCMC-CMC fragments not beingparallel, a rare situation indiacetylene chemistry. Yet, experiments showthat topochemical polymerizationdoes not occur. Incorporationofwater in the lattice of5leads toa solvate that is topochemically reactive. Unlike2, however, water molecules in 4are not isolated but are organized as ribbons. Spectroscopic characterization of the polymer of4indicates that it is a blue phase polymer, with water coordinated to it. This study shows that it is possible to use water, and more generally solvent molecules, to transform a nonreactive diacetylene into a reactive one, even though this approach is less predictable than the cocrystal approach developed by Fowler, Lauher, and Goroff. The solvate approach is simple to implement, quite versatile because of the large rangeof solvents available, andonedoes not face theproblemof having to remove the host in case one needs to recover the polymer. Previous studies describing a similar approach are scarce.
We present a mathematical study of the order book as a multidimensional continuous- time Markov chain where the order flow is modeled by independent Poisson processes. Our aim is to bridge the gap between the microscopic description of price formation (agent- based modeling), and the Stochastic Differential Equations approach used classically to describe price evolution at macroscopic time scales. To do this, we rely on the theory of infinitesimal generators and Foster-Lyapunov stability criteria for Markov chains. We motivate our approach using an elementary example where the spread is kept constant ("perfect market making"). Then we compute the infinitesimal generator associated with the order book in a general setting, and link the price dynamics to the instantaneous state of the order book. In the last section, we prove that the order book is ergodic - in particular it has a stationary distribution - that it converges to its stationary state exponentially fast, and that the large-scale limit of the price process is a Brownian motion.
In this paper, we consider a discrete time economy where we assume that the short term interest rate follows a quadratic term structure of a regime switching asset process. The possible non-linear structure and the fact that the interest rate can have different economic or financial trends justify the interest of Regime Switching Quadratic Term Structure Model (RS-QTSM). Indeed, this regime switching process depends on the values of a Markov chain with a time dependent transition probability matrix which can well captures the different states (regimes) of the economy. We prove that under this modelling that the conditional zero coupon bond price admits also a quadratic term structure. Moreover, the stochastic coefficients which appear in this decomposition satisfy an explicit system of coupled stochastic backward recursions.
In this note, we cast a Hawkes process-based order book model into a markovian setting and; using techniques from the theory of Markov chains and stochastic stability, show that the order book is stable and leads to a diffusive price limit at large time scales.
Ambient energy harvesting also known as energy scavenging is the process where energy is obtained from the environment, converted, and stored to power small devices such as wireless sensors. We present a variant of EDF scheduling algorithm called EH-EDF (Energy Harvesting-Earliest Deadline First). Decisions are taken at run-time without having prior knowledge about the future energy production and task characteristics. We gauge the performance of EH-EDF by means of simulations in order to show its benefits .W eevaluat ean dcompar esevera lvariant so fEH-ED Fi nterm so fpercentag eo ffeasibl etas ksets .Metric ssuc ha saverage length of the idle times are also considered. Simulations tend to demonstrate that no online scheduler can reach optimality in a real-time energy harvesting environment.
In this paper, we investigate the behaviors of the Belief Propagation algorithm considered as a dynamic system. In the context of LDPC (Low Den- sity Parity-Check) codes, we use the noise power of the transmission channel as a potentiometer to evaluate the different motions that the BP can follow. The computations of dynamic quantifiers as the bifurcation diagram, the Lyapunov ex- ponent and the reconstructed trajectory enable to bring out four main behaviors. In addition, we propose a novel measure that is the hyperspheres method, which provides the knowledge of the time evolution of the attractor size. The information collected from these different quantifiers helps to better understand the BP evolu- tion and to focus on the noise power values for which the BP suffers from chaos.
We give three new algorithms to solve the "isomorphism of polynomial" problem, which was underlying the hardness of recovering the secret-key in some multivariate trapdoor one-way functions. In this problem, the adversary is given two quadratic functions, with the promise that they are equal up to linear changes of coordinates. Her objective is to compute these changes of coordinates, a task which is known to be harder than Graph-Isomorphism. Our new algorithm build on previous work in a novel way. Exploiting the birthday paradox, we break instances of the problem in time q^(2n/3) (rigorously) and q^(n/2) (heuristically), where q^n is the time needed to invert the quadratic trapdoor function by exhaustive search. These results are obtained by turning the algebraic problem into a combinatorial one, namely that of recovering partial information on an isomorphism between two exponentially large graphs. These graphs, derived from the quadratic functions, are new tools in multivariate cryptanalysis.
In this paper, we investigate the behaviors of the Belief Propagation algorithm considered as a dynamic system. In the context of LDPC (Low Den- sity Parity-Check) codes, we use the noise power of the transmission channel as a potentiometer to evaluate the different motions that the BP can follow. The computations of dynamic quantifiers as the bifurcation diagram, the Lyapunov ex- ponent and the reconstructed trajectory enable to bring out four main behaviors. In addition, we propose a novel measure that is the hyperspheres method, which provides the knowledge of the time evolution of the attractor size. The information collected from these different quantifiers helps to better understand the BP evolu- tion and to focus on the noise power values for which the BP suffers from chaos.
We consider a nonrelativistic charged particle in a 1D moving potential well. This quantum system is subject to a control, which is the acceleration of the well. It is represented by a wave function solution of a Schrödinger equation, the position of the well together with its velocity. We prove the following controllability result for this bilinear control system: given an initial condition close enough to an eigenstate and a target close enough to another eigenstate, the wave function can be moved exactly from the first one to the second one in finite time. Moreover, we can control the position and the velocity of the well. Our proof uses moment theory, a Nash-Moser implicit function theorem, the return method and expansion to the second order.
In this short course we are going to review some of the main existing Eulerian approaches to the numerical simulation of the full water wave problem. More specifically, the lectures willl cover the boundary integral equation method, higher order spectral method, Dirichlet-to-Neumann operator approach and, finally, the conformal mapping technique. The advantages and shortcomings of different methods will be discussed as well. The course does not assume any particular knowledge in hydrodynamics. It is therefore suitable for researchers and graduate students in applied mathematics and related fields.
Le but de cette étude est de caractériser les propriétés radiatives d'un milieu poreux fortement hétérogène et anisotrope. Une approche statistique a été adoptée afin de déterminer les fonctions de distribution cumulée d'extinction, d'absorption et de diffusion ainsi que les fonctions de phase de diffusion à partir de la morphologie du milieu et de ses caractéristiques locales. La caractérisation complète a permis de montrer qu'au voisinage des parois, la loi de Beer n'est pas vérifiée. Une expression simple de la fonction de phase a été numériquement démontrée.
The plasma-spraying process generates materials with typical, porous and complex, microstructures. Inspired by Dielectric Multilayer Mirrors (DMMs), thermal sprayed media may be used in the field of optics, particularly for making scattering and reflecting coatings suitable for a large range of wavelengths. In fact, pores inside plasma sprayed matrix create numerous optical index discontinuities, similarly to the gaps created in DMMs, in order to obtain high reflectivity. The porosity of coatings microstructure can be customized by selection of plasma sprayed process parameters. This study aimed to optimize scattering and reflectance properties in porous alumina by the control of spray parameters resulting in the optimized porosity. A self-supporting bi-layer with a diffuse reflectance over 90% over a large band of wavelengths was obtained. The first layer (micro-structured), which is thick enough to support the free standing, was prepared by atmospheric plasma spraying (APS). The second layer (nanostructured) was manufactured by suspension plasma spraying (SPS) over the first layer in order to enhance the reflectance at short wavelengths.
In this short course we are going to review some of the main existing Eulerian approaches to the numerical simulation of the full water wave problem. More specifically, the lectures willl cover the boundary integral equation method, higher order spectral method, Dirichlet-to-Neumann operator approach and, finally, the conformal mapping technique. The advantages and shortcomings of different methods will be discussed as well. The course does not assume any particular knowledge in hydrodynamics. It is therefore suitable for researchers and graduate students in applied mathematics and related fields.
Climate variability and climate change induce important intra- and inter-annual variability of precipitation that significantly alters the hydrologic cycle. The surface water budgets and the plant or ecosystem water use efficiency (WUE) are in turn modified. Obtaining greater insight into how climatic variability and agricultural practices affect water budgets and regarding their components in croplands is, thus, important for adapting crop management and limiting water losses. Therefore, the principal objectives of this study are: (1) to assess the contribution of different components to the agro-ecosystem water budget and (2) to evaluate how agricultural practices and climate modify the components of the surface water budget. To achieve these goals, we tested a new method for partitioning evapotranspiration (ETR), measured by means of an eddy-covariance method, into soil evaporation (E) and plant transpiration (TR) based on marginal distribution sampling (MDS). The partitioning method proposed requires continuous flux recording and measurements of soil temperature and humidity close to the surface, global radiation above the canopy and assessment of leaf area index dynamics. This method is well suited for crops because it requires a dataset including long bare-soil periods alternating with vegetated periods for accurate partitioning estimation. We compared these estimations with calibrated simulations of the ICARE-SVAT double source mechanistic model. The results showed good agreement between the two partitioning methods, demonstrating that MDS is a convenient, simple and robust tool for estimating E with reasonable associated uncertainties. During the growing season, the proportion of E in ETR was approximately one-third and varied mainly with crop leaf area. When calculated on an annual time scale, the proportion of E in ETR reached more than 50%, depending on the crop leaf area and on the duration and distribution of bare soil within the year.
The tectonosedimentary development of the South Atlantic is compared with the Central Atlantic margins, which are associated with major episodes of magmatism during the Mesozoic continental break-up. Subsequently, the Cenozoic break-up in the North Atlantic led to the formation of the volcanic Norwegian-Greenland conjugate margins. The DSDP boreholes in the magma-poor Iberian-Newfoundland margins have confirmed the occurrence of exhumed mantle at the ocean - continent transition. This possibility has been suggested for the South Atlantic margins, but still lacks confirmation from drilling. The Red Sea and the Gulf of Aden may be considered as natural laboratories to study the break- up processes and formation of divergent continental margins. Using key geological and geophysi- cal data, we compare some of the structures observed in incipient stages of basin formation between the African and the Arabian plates with the structures observed in older sedimentary basins associated with the Gondwana break-up. We also analyse deep seismic reflection profiles and potential field data at the continent-ocean boundary of these conjugate margins, using palin- spastic reconstructions to define the corresponding seismic pairs. We conclude that the Red Sea and the Gulf of Aden display remarkable differences to the Iberian-Newfoundland margins, and notable similarities with the South Atlantic margins.
We analyse P-wave receiver functions across the western Gulf of Aden and southern Red Sea continental margins in Western Yemen to constrain crustal thickness, internal crustal structure and the bulk seismic velocity characteristics in order to address the role of magmatism, faulting and mechanical crustal thinning during continental breakup. We analyse teleseismic data from 21 stations forming the temporary Young Conjugate Margins Laboratory (YOCMAL) network together with GFZ and Yemeni permanent stations. Analysis of computed receiver functions shows that (1) the thickness of unextended crust on the Yemen plateau is ∼35km; (2) this thins to ∼22km in coastal areas and reaches less than 14km on the Red Sea coast, where presence of a high-velocity lower crust is evident. The average Vp/Vs ratio for the western Yemen Plateau is 1.79, increasing to ∼1.92 near the Red Sea coast and decreasing to 1.68 for those stations located on or near the granitic rocks. Thinning of the crust, and by inference extension, occurs over a ∼130-km-wide transition zone from the Red Sea and Gulf of Aden coasts to the edges of the Yemen plateau. Thinning of continental crust is particularly localized in a <30-km-wide zone near the coastline, spatially co-incident with addition of magmatic underplate to the lower crust, above which on the surface we observe the presence of seaward dipping reflectors (SDRs) and thickened Oligo-Miocene syn-rift basaltic flows. Our results strongly suggest the presence of high-velocity mafic intrusions in the lower crust, which are likely either synrift magmatic intrusion into continental lower crust or alternatively depleted upper mantle underplated to the base of the crust during the eruption of the SDRs. Our results also point towards a regional breakup history in which the onset of rifting was synchronous along the western Gulf of Aden and southern Red Sea volcanic margins followed by a second phase of extension along the Red Sea margin.
An efficient numerical method to compute solitary wave solutions to the free surface Euler equations is reported. It is based on the conformal mapping technique combined with an efficient Fourier pseudo-spectral method. The resulting nonlinear equation is solved via the Petviashvili iterative scheme. The computational results are compared to some existing approaches, such as the Tanaka method and Fenton's high-order asymptotic expansion. Several important integral quantities are numerically computed for a large range of amplitudes. The integral representation of the velocity and acceleration fields in the bulk of the fluid is also provided.
An improved Lozi function with alternate coefficients has been proposed. The modifications in the model allow to remove the holes in the attractor which are not desirable, but appeared in the previous Lozi function; in this way, an everywhere dense attractor can be obtained. Moreover, the strong sensitivity to the type of binarisation (conversion of real values to 0 and 1) has been demonstrated; this conversion to binary numbers is instrumental to apply the NIST tests for randomness. The results have been validated and compared via NIST tests, for the different methods of quantization. Finally, is has been verfied that the multi-random properties of the output signal have been improved thanks to the following strategies : under-sampling of the output signal, and the system order increasing. Keywords. Nonlinear dynamical system, ring-coupled map, Lozi function, NIST tests, discrete-time map, dense chaotic attractor, pseudo random number generator 1 I
The extreme characteristics of long wave run-up are studied in this paper. First we give a brief overview of the existing theory which is mainly based on the hodograph transformation (Carrier & Greenspan, 1958). Then, using numerical simulations, we build on the work of Stefanakis et al. (2011) for an infinite sloping beach and we find that resonant run-up amplification of monochromatic waves is robust to spectral perturbations of the incoming wave and resonant regimes do exist for certain values of the frequency. In the setting of a finite beach attached to a constant depth region, resonance can only be observed when the incoming wavelength is larger than the distance from the undisturbed shoreline to the seaward boundary. Wavefront steepness is also found to play a role in wave run-up, with steeper waves reaching higher run-up values.
Fifty years ago, FitzHugh introduced a phase portrait that became famous for a twofold reason: it captured in a physiological way the qualitative behavior of Hodgkin-Huxley model and it revealed the power of simple dynamical models to unfold complex firing patterns. To date, in spite of the enormous progresses in qualitative and quantitative neural modeling, this phase portrait has remained a core picture of neuronal excitability. Yet, a major difference between the neurophysiology of 1961 and of 2011 is the recognition of the prominent role of calcium channels in firing mechanisms. We show that including this extra current in Hodgkin-Huxley dynamics leads to a revision of FitzHugh-Nagumo phase portrait that affects in a fundamental way the reduced modeling of neural excitability. The revisited model considerably enlarges the modeling power of the original one. In particular, it captures essential electrophysiological signatures that otherwise require non-physiological alteration or considerable complexification of the classical model. As a basic illustration, the new model is shown to highlight a core dynamical mechanism by which calcium channels control the two distinct firing modes of thalamocortical neurons.
This paper studies the excitability properties of a generalized FitzHugh-Nagumo model. The model differs from the classical FitzHugh-Nagumo model in that it accounts for the effect of cooperative gating variables such as activation of calcium currents. Excitability is explored by unfolding a pitchfork bifurcation that is shown to organize five different types of excitability. In addition to the three classical types of neuronal excitability, two novel types are described and distinctly associated to the presence of cooperative variables.
Les tâches d'empan de mémoire de travail sont des tâches dans lesquelles des items doivent être maintenus en mémoire à court terme pendant qu'un traitement concurrent est effectué. Le but de la présente étude était de déterminer si, comme le soutient le modèle de partage temporel des ressources (Barrouillet, Bernardin, & Camos, 2004), les traitements gênent le maintien parce que les deux composantes entrent en compétition pour des processus communs ou plus simplement parce que les stratégies de maintien des items à rappeler sont perturbées par l'intrusion de l'information à traiter simultanément. Quatre-vingt sujets adultes étaient soumis à une tâche d'empan où ils devaient maintenir des lettres en même temps qu'ils devaient juger soit de la parité soit de la position spatiale de nombre présentés successivement à l'écran. Par ailleurs, ces nombres apparaissaient à un rythme régulier et donc prévisible ou bien aléatoire. Conformément à nos attentes, et contrairement à l'hypothèse d'une perturbation des stratégies de maintien, les jugements de parité qui nécessitent des récupérations en mémoire entraînaient de plus faibles empans que la tâche spatiale qui ne requiert qu'une sélection de réponse alors que le rythme de réalisation de la tâche secondaire n'avait pas d'effet sur les empans.
La contamination de l'air par les produits phytosanitaires peut induire des risques importants pour la santé humaine. Les techniques de pulvérisation induisent une contamination de l'air, notamment en production fruitière. En 2001, des expérimentations ont montré des niveaux importants de contamination en aval d'une parcelle de vigne pendant et après la période de pulvérisation. A l'échelle de l'homme l'exposition est toutefois difficile à mesurer à cause de la grande variabilité spatio-temporelle de la contamination. Pour pallier cette difficulté, les travaux de recherche portent sur le couplage de données de simulation et de mesure pour évaluer avec précision la qualité de l'air. Les expérimentation sont conduite en laboratoire ou dans les champs. L'objectif est de développer des méthodologies d'échantillonnage et d'analyse adaptées à la protection de populations afin d'améliorer les méthodes de pulavrisation. / Air contamination by Plant Protection Products (PPPs) carries significant risks for human health. Crop protection spraying induces air contamination, mainly in fruit production. In 2001, observations showed important transfers during and after spraying (direct losses vs. volatilization from soil and crop), downwind a productive vineyard. At the human scale the resulting exposure is difficult to measure because the PPPS concentration vary greatly in space and time. In consequence, researches are focused on coupling simulation tools and data to estimate properly the air contamination. Experimentations are conducted at fieldscale and labscale. The objective is to improve the methodology on air sampling and to develop analysis tools dedicated to population protection and spraying optimisation recommendation.
Marine Synechococcus undergo a wide range of environmental stressors, especially high and variable irradiance, which may induce oxidative stress through the generation of reactive oxygen species (ROS). While light and ROS could act synergistically on the impairment of photosynthesis, inducing photodamage and inhibiting photosystem II repair, acclimation to high irradiance is also thought to confer resistance to other stressors. To identify the respective roles of light and ROS in the photoinhibition process and detect a possible light-driven tolerance to oxidative stress, we compared the photophysiological and transcriptomic responses of Synechococcus sp. WH7803 acclimated to low light (LL) or high light (HL) to oxidative stress, induced by hydrogen peroxide (H₂O₂) or methylviologen. While photosynthetic activity was much more affected in HL than in LL cells, only HL cells were able to recover growth and photosynthesis after the addition of 25 μM H₂O₂. Depending upon light conditions and H₂O₂ concentration, the latter oxidizing agent induced photosystem II inactivation through both direct damage to the reaction centers and inhibition of its repair cycle. Although the global transcriptome response appeared similar in LL and HL cells, some processes were specifically induced in HL cells that seemingly helped them withstand oxidative stress, including enhancement of photoprotection and ROS detoxification, repair of ROS-driven damage, and regulation of redox state. Detection of putative LexA binding sites allowed the identification of the putative LexA regulon, which was down-regulated in HL compared with LL cells but up-regulated by oxidative stress under both growth irradiances.
Chaque année du début du prin - temps jusqu'aux premiers jours de l'automne, des milliards d'abeilles sortent de leurs ruches et partent visiter les fleurs des paysages environnants. Elles y trouvent nectars et pollens, éléments essentiels à la base de leur alimentation. C'est par cette intense activité de butinage que l'abeille domestique participe activement à la pollinisation des plantes sauvages et cultivées. Son influence directe sur la qualité et la quantité des récoltes ainsi que sur le maintien de la biodiversité florale est aujourd'hui largement validée et souligne le rôle prépondérant des abeilles (sauvages et domestiques) dans le fonctionnement des écosystèmes. En France, les abeilles domestiques, Apis mellifera (Hymenoptera: Apidae), sont l'outil de travail d'environ 70 000 apiculteurs professionnels et amateurs qui tirent bénéfice des labeurs de cet hyménoptère (environ 20 000 tonnes de miel récoltées en France en 2009).
Ce modeste article vise à donner quelques pistes pour la recherche diachronique du verbe basque. Il s'inscrit dans le cadre d'un projet de recherche de thèse de doctorat, et loin de prétendre donner la clé de l'évolution du verbe basque, il espère offrir quelques remarques de morphologie et syntaxe qui selon nous ont leur importance au moment de faire l'histoire des formes verbales. Les verbes périphrastiques ont attiré l'attention de nombreux bascologues. Tout d'abord Lafon (1943) consacra le deuxième tome de sa thèse aux formes périphrastiques des textes du XVIème siècle. Après lui, d'autres comme Yrizar en ont répertorié les quelques nuances morphologiques et les nombreuses nuances phonétiques que l'on retrouve d'un dialecte à l'autre. Dans ce court article nous n'entendons pas traiter la composition phonétique des formes périphrastiques, mais plutôt leur structure morpho-syntaxique. Pour cela, nous allons étudier les trois périphrases principales des XVIème et XVIIème siècles, à savoir, (i) racine verbale + auxiliaires *edin, *ezan, *iro, egin, (ii) nom verbal à l'inessif + auxiliaires izan, *edun, (iii) participe + auxiliaires izan, *edun; et les classer selon leurs structure, emploi(s), niveau de grammaticalisation à cette époque. Comme nous le verrons, il a souvent été pensé que la périphrase verbale du basque est attribuable au contact avec les langues romanes. Après l'étude de chacune de ces trois périphrases, nous verrons que parmi elles, seule une, a des parallèles dans ces langues, et que les deux autres semblent être issues d'une évolution interne au basque. Nous tenterons enfin de proposer une chronologie relative de ces périphrases, mais aussi de celles-ci par rapport aux formes simples, ou fortes.
Les récents épisodes de turbulence financière sont venus remettre en cause la précision des mesures classiques de risque pour évaluer les risques extrêmes. Ces mesures de risques, telles que la VaR, sont devenues incontournables dans la gestion des risques et l'allocation d'actifs (Basak et Shapiro [2001] ; Monfort [2008]). Nous estimons le risque de modèle des mesures de risque et nous évaluons son impact sur l'allocation d'actifs optimale à différents horizons. Nos résultats montrent, sur des données longues américaines, une relation en U-inversé entre notre mesure du risque de modèle sur les VaR historiques et l'horizon de l'agent représentatif, qui impacte sensiblement son allocation optimale.
Nous décrivons une méthode pour comparer des techniques de diagnostic des connaissances en fonction de leur impact sur les prises de décision de l'EIAH. À partir de traces d'apprenants, nous utilisons une méthode de classification automatique pour prédire le résultat (succès ou échec) d'une aide donnée par l'EIAH, en prenant en considération des informations sur l'apprenant, la tâche et l'état des connaissances de l'apprenant. Il en résulte une stratégie d'aide apprise automatiquement et permettant de sélectionner dans une situation donnée l'aide ayant la probabilité la plus élevée de succès. Le moyen usuel mais coûteux d'évaluer une telle stratégie d'aide est de l'implémenter et de la tester sur de nouveaux apprenants, ce qui nécessite du temps et des moyens. Nous utilisons plutôt des données déjà collectées, où les aides sont données aléatoirement aux apprenants, pour simuler l'impact d'une stratégie d'aide. Nous comparons ensuite différentes stratégies d'aide basées sur différentes techniques de diagnostic. Nous avons testé notre méthode en utilisant les données du Reading Tutor (projet LISTEN), destiné à l'apprentissage de la lecture. Nous rapportons la précision de la prédiction de quatre techniques de diagnostic en validation croisée, puis comparons l'impact des stratégies d'aide basées sur ces techniques. Notre méthode fournit une métrique pour comparer différentes techniques de diagnostic fondées sur leur utilité pour les prises de décision de l'EIAH.
Le but de cette étude est de caractériser les propriétés radiatives d'un milieu poreux fortement hétérogène et anisotrope. Une approche statistique a été adoptée afin de déterminer les fonctions de distribution cumulée d'extinction, d'absorption et de diffusion ainsi que les fonctions de phase de diffusion à partir de la morphologie du milieu et de ses caractéristiques locales. La caractérisation complète a permis de montrer qu'au voisinage des parois, la loi de Beer n'est pas vérifiée. Une expression simple de la fonction de phase a été numériquement démontrée.
The plasma-spraying process generates materials with typical, porous and complex, microstructures. Inspired by Dielectric Multilayer Mirrors (DMMs), thermal sprayed media may be used in the field of optics, particularly for making scattering and reflecting coatings suitable for a large range of wavelengths. In fact, pores inside plasma sprayed matrix create numerous optical index discontinuities, similarly to the gaps created in DMMs, in order to obtain high reflectivity. The porosity of coatings microstructure can be customized by selection of plasma sprayed process parameters. This study aimed to optimize scattering and reflectance properties in porous alumina by the control of spray parameters resulting in the optimized porosity. A self-supporting bi-layer with a diffuse reflectance over 90% over a large band of wavelengths was obtained. The first layer (micro-structured), which is thick enough to support the free standing, was prepared by atmospheric plasma spraying (APS). The second layer (nanostructured) was manufactured by suspension plasma spraying (SPS) over the first layer in order to enhance the reflectance at short wavelengths.
Dans cet article, nous présentons un quadrupleur de fréquences à 110 GHz conçu et développé en technologie SiGe:C BiCMOS 130 nm. Le circuit est conçu pour un système d'imagerie basé sur un radar à ondes continues modulées (FMCW) en bande-F et emploie une cascade de deux cellules de Gilbert avec des charges réactives réalisées avec des lignes de transmission TFML (thin-film microstrip line). Le signal d'entrée différentiel, qui est utilisé pour la validation du quadrupleur, est généré en utilisant un balun actif avec un amplificateur-limiteur différentiel. Le signal différentiel à la sortie du quadrupleur est relié via un câblage par fil avec un balun passif réalisé à l'aide des lignes de transmission. Les résultats des mesures d'un circuit prototype ont permis de prouver que cette approche de la génération des fréquences des ondes millimétriques peut offrir une bande fonctionnelle allant jusqu'à 25 GHz avec une puissance de sortie de 0 dBm.
Background
n.a
N(6)-threonylcarbamoyladenosine (t(6)A) is a modified nucleotide found in all transfer RNAs (tRNAs) decoding codons starting with adenosine. Its role is to facilitate codon-anticodon pairing and to prevent frameshifting during protein synthesis. Genetic studies demonstrated that two universal proteins, Kae1/YgjD and Sua5/YrdC, are necessary for t(6)A synthesis in Saccharomyces cerevisiae and Escherichia coli. In Archaea and Eukarya, Kae1 is part of a conserved protein complex named kinase, endopeptidase and other proteins of small size (KEOPS), together with three proteins that have no bacterial homologues. Here, we reconstituted for the first time an in vitro system for t(6)A modification in Archaea and Eukarya, using purified KEOPS and Sua5. We demonstrated binding of tRNAs to archaeal KEOPS and detected two distinct adenosine triphosphate (ATP)-dependent steps occurring in the course of the synthesis. Our data, together with recent reconstitution of an in vitro bacterial system, indicated that t(6)A cannot be catalysed by Sua5/YrdC and Kae1/YgjD alone but requires accessory proteins that are not universal. Remarkably, we observed interdomain complementation when bacterial, archaeal and eukaryotic proteins were combined in vitro, suggesting a conserved catalytic mechanism for the biosynthesis of t(6)A in nature. These findings shed light on the reaction mechanism of t(6)A synthesis and evolution of molecular systems that promote translation fidelity in present-day cells.
In approachability with full monitoring there are two types of conditions that are known to be equivalent for convex sets: a primal and a dual condition. The primal one is of the form: a set C is approachable if and only all containing half-spaces are approachable in the one-shot game; while the dual one is of the form: a convex set C is approachable if and only if it intersects all payoff sets of a certain form. We consider approachability in games with partial monitoring. In previous works (Perchet 2011; Mannor et al. 2011) we provided a dual characterization of approachable convex sets; we also exhibited efficient strategies in the case where C is a polytope. In this paper we provide primal conditions on a convex set to be approachable with partial monitoring. They depend on a modified reward function and lead to approachability strategies, based on modified payoff functions, that proceed by projections similarly to Blackwell's (1956) strategy; this is in contrast with previously studied strategies in this context that relied mostly on the signaling structure and aimed at estimating well the distributions of the signals received. Our results generalize classical results by Kohlberg 1975 (see also Mertens et al. 1994) and apply to games with arbitrary signaling structure as well as to arbitrary convex sets.
Présentation du calcul de la distance intertextuelle et de deux méthodes de classification (classification hiérarchique ascendante, analyse arborée). Caractérisation du vocabulaire spécifique des différentes classes. Application à un groupe d'entretiens sur le confort électrique.
We consider supervised learning problems within the positive-definite kernel framework, such as kernel ridge regression, kernel logistic regression or the support vector machine. With kernels leading to infinite-dimensional feature spaces, a common practical limiting difficulty is the necessity of computing the kernel matrix, which most frequently leads to algorithms with running time at least quadratic in the number of observations n, i.e., O(n^2). Low-rank approximations of the kernel matrix are often considered as they allow the reduction of running time complexities to O(p^2 n), where p is the rank of the approximation. The practicality of such methods thus depends on the required rank p. In this paper, we show that in the context of kernel ridge regression, for approximations based on a random subset of columns of the original kernel matrix, the rank p may be chosen to be linear in the degrees of freedom associated with the problem, a quantity which is classically used in the statistical analysis of such methods, and is often seen as the implicit number of parameters of non-parametric estimators. This result enables simple algorithms that have sub-quadratic running time complexity, but provably exhibit the same predictive performance than existing algorithms, for any given problem instance, and not only for worst-case situations.
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