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We present the magnetic properties of silica-supported metal (Fe,catalyst) nanoparticles synthesized by precipitation of metal nitrate in ammonia-based medium. Our goal is the study of possible metal-support interactions in the nanoporous catalyst. The temperature dependence of the magnetization for all samples display spin-glass like behavior below c.a. 11-12 K, with clear Curie-Weiss dependence in the high-temperature regime. Spin-glass-like behavior was inferred from dynamic AC susceptibility data after analyzing the frequency-dependence of the in-phase component χ'(f) by the expression W = ΔTf/[Tf Δlog(f)] = 3.0 × 10−3. We found that the magnetic behavior of the catalyst is drastically affected by the existence of interactions between the metal and the support.
TiO2 thin films were grown by pulsed laser deposition on a wide variety of oxide single-crystal substrates and characterized in detail by four-circle X-ray diffraction. Films grown at 873 K on (100)-oriented SrTiO3 and LaAlO3 were (001)-oriented anatase, while on (100) MgO they were (100)-oriented. On (110) SrTiO3 and MgO, (102) anatase was observed. On M-plane and R-plane sapphire, (001)- and (101)-oriented rutile films were obtained, respectively. On C-plane sapphire, the coexistence of (001) anatase, (112) anatase and (100) rutile was found; increasing the deposition temperature tended to increase the rutile proportion. Similarly, films grown at 973 K on (100) and (110) MgO showed the emergence, besides anatase, of (110) rutile. All these films were epitaxically grown, as shown by ' scans and/or pole figures, and the various observed orientations were explained on the basis of misfit considerations and interface arrangement.
Covalent embedding of a (eta(6)-arene) ruthenium(II) complex into the protein papain gives rise to a metalloenzyme displaying a catalytic efficiency for a Lewis acid-mediated catalysed Diels-Alder reaction enhanced by two orders of magnitude in water.
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.
Human brain networks have topological properties in common with many other complex systems, prompting the following question: what aspects of brain network organization are critical for distinctive functional properties of the brain, such as consciousness? To address this question, we used graph theoretical methods to explore brain network topology in resting state functional MRI data acquired from 17 patients with severely impaired consciousness and 20 healthy volunteers. We found that many global network properties were conserved in comatose patients. Specifically, there was no significant abnormality of global efficiency, clustering, small-worldness, modularity, or degree distribution in the patient group. However, in every patient, we found evidence for a radical reorganization of high degree or highly efficient "hub" nodes. Cortical regions that were hubs of healthy brain networks had typically become nonhubs of comatose brain networks and vice versa. These results indicate that global topological properties of complex brain networks may be homeostatically conserved under extremely different clinical conditions and that consciousness likely depends on the anatomical location of hub nodes in human brain networks.
The introduction of distance learning does not only bring a wider audience, but also much more diversity among the learners: first, because it can be integrated more easily into a Life-long Learning strategy; secondly, because the learners are not restricted to a sing le area and thus learners from different countries and with different cultures follow the curriculum. We have observed this in various DL diplomas in which we participate. In this article, we will shed some light on the difficulties and challenges arising from these multi-cultural settings. Based on our research work, we would like to insist on two particular points which are the necessity to adapt the pedagogical settings (e.g. pedagogical scenarios) according to the learners' behaviour to overcome unforeseen problems due to cultural differences and the importance of considering mobile technologies to overcome limited access to the technology in developing countries and to ensure continuous interaction among learners and with tutors.
User needs are expanding and becoming more and more complex with the emergence of newly adopted technologies. As a result, the convergence of smart devices, having the capability to communicate as well as sharing information and ensuring user need satisfaction, leads to profoundly change the way we interact with our environment. They should provide an adaptive assistance in both reactive and proactive mode and new communication methods focused on multimodal and multichannel interfaces. However, most of existing context-aware systems have extremely tight coupling between applications' semantic and sensor's details. So, the objective of our research is to implement an approach which can support the ability to reuse sensors and to evolve existing applications to use new context types. In this paper, we illustrate our approach for proactive intelligent assistance and we describe our architecture based on three principal layers. These layers are designed in order to build applications which can increase the welfare of the user situated in intelligent environment.
Human brain networks have topological properties in common with many other complex systems, prompting the following question: what aspects of brain network organization are critical for distinctive functional properties of the brain, such as consciousness? To address this question, we used graph theoretical methods to explore brain network topology in resting state functional MRI data acquired from 17 patients with severely impaired consciousness and 20 healthy volunteers. We found that many global network properties were conserved in comatose patients. Specifically, there was no significant abnormality of global efficiency, clustering, small-worldness, modularity, or degree distribution in the patient group. However, in every patient, we found evidence for a radical reorganization of high degree or highly efficient "hub" nodes. Cortical regions that were hubs of healthy brain networks had typically become nonhubs of comatose brain networks and vice versa. These results indicate that global topological properties of complex brain networks may be homeostatically conserved under extremely different clinical conditions and that consciousness likely depends on the anatomical location of hub nodes in human brain networks.
Acoustic imaging is a standard technique for mapping positions and powers of acoustic sources using microphone arrays, which often causes an ill-posed inverse problem. In this article, we firstly improve the forward model of acoustic power propagation by considering background noises at the sensor array, and the propagation uncertainty caused by wind tunnel effect. We then propose a robust super-resolution approach via sparsity constraint for the acoustic imaging in strong background noises. The sparsity parameter is adaptively derived from the sparse distribution of source powers. The proposed approach can jointly reconstruct source powers and positions, as well as the background noise power. Our approach is compared with the conventional beamforming, deconvolution and sparse regularization methods by simulated, real data and hybrid data respectively. It is feasible to apply our approach for mapping complex monopole sources using the 2D non-uniform microphone array in wind tunnel tests.
The European Earth observation programme GMES (Global Monitoring for Environment and Security) aims at providing environmental information to support policymakers, public authorities and both public and commercial users. A systematic monitoring and forecasting of the state of the Earth's subsystems is currently under development. Six thematic areas are developed: marine, land, atmosphere, emergency, security and climate change. A land monitoring service, a marine monitoring service and an atmosphere monitoring service will contribute directly to the monitoring of climate change and to the assessment of mitigation and adaptation policies. Additional GMES services will address respectively emergency response and security-related aspects. The pre-operational atmosphere service of GMES is currently provided through the FP7 project MACC (Monitoring Atmospheric Composition and Climate). MACC combines state-of-the-art atmospheric modelling with Earth observation data to provide information services covering European Air Quality, Global Atmospheric Composition, Climate, and UV and Solar Energy. Within the radiation subproject (MACC-RAD) existing historical and daily updated databases for monitoring incoming surface solar irradiance are further developed. The service will meet the needs of European and national policy development and the requirements of (commercial) downstream services (e.g. planning, monitoring, efficiency improvements, integration into energy supply grids). The SOLEMI service (operated by MACC partner DLR) and the SoDa service (operated by MACC partner ARMINES and its subsidiary Transvalor) have been specifically developed in several national, European and ESA projects to fulfil the requirements for long-term databases and NRT services. On its transition process from the precursor services SoDa and SOLEMI the following User's Guide intends to summarize existing knowledge, which has been published only in a scattered manner. Part A 'Users' Expectations' describes the communities of users, their expectations and gives an overview of the compliance of the MACC RAD service with those. In Part B 'Creating Databases', the current databases HelioClim and SOLEMI as well as the methods used to convert satellite images into solar surface irradiance are presented. The quality of the retrieved irradiances is discussed. An overview of the operations and workflow is presented for the creation, updating and monitoring of these databases. Part C 'Delivering products' is devoted to the supply of products. The core products are defined. The future MACC-RAD Service is described and a prototype is presented. It is intended to update this User's Guide regularly following the realisation of the MACC RAD service line.
Chelonanthus alatus is a bat-pollinated, pioneer Gentianaceae that clusters in patches where still-standing, dried-out stems are interspersed among live individuals. Flowers bear circum-floral nectaries (CFNs) that are attractive to ants, and seed dispersal is both barochorous and anemochorous. Although, in this study, live individuals never sheltered ant colonies, dried-out hollow stems--that can remain standing for 2 years--did. Workers from species nesting in dried-out stems as well as from ground-nesting species exploited the CFNs of live C. alatus individuals in the same patches during the daytime, but were absent at night (when bat pollination occurs) on 60.5% of the plants. By visiting the CFNs, the ants indirectly protect the flowers--but not the plant foliage--from herbivorous insects. We show that this protection is provided mostly by species nesting in dried-out stems, predominantly Pseudomyrmex gracilis. That dried-out stems remain standing for years and are regularly replaced results in an opportunistic, but stable association where colonies are sheltered by one generation of dead C. alatus while the live individuals nearby, belonging to the next generation, provide them with nectar; in turn, the ants protect their flowers from herbivores. We suggest that the investment in wood by C. alatus individuals permitting still-standing, dried-out stems to shelter ant colonies constitutes an extended phenotype because foraging workers protect the flowers of live individuals in the same patch. Also, through this process these dried-out stems indirectly favor the reproduction (and so the fitness) of the next generation including both their own offspring and that of their siblings, all adding up to a potential case of inclusive fitness in plants.
Establishing a direct link between climate change and fluctuations in animal populations through long-term monitoring is difficult given the paucity of baseline data. We hypothesized that social wasps are sensitive to climatic variations, and thus studied the impact of ENSO events on social wasp populations in French Guiana. We noted that during the 2000 La Niña year there was a 77.1% decrease in their nest abundance along ca. 5 km of forest edges, and that 70.5% of the species were no longer present. Two simultaneous 13-year surveys (1997-2009) confirmed the decrease in social wasps during La Niña years (2000 and 2006), while an increase occurred during the 2009 El Niño year. A 30-year weather survey showed that these phenomena corresponded to particularly high levels of rainfall, and that temperature, humidity and global solar radiation were correlated with rainfall. Using the Self-Organizing Map algorithm, we show that heavy rainfall during an entire rainy season has a negative impact on social wasps. Strong contrasts in rainfall between the dry season and the short rainy season exacerbate this effect. Social wasp populations never recovered to their pre-2000 levels. This is probably because these conditions occurred over four years; heavy rainfall during the major rainy seasons during four other years also had a detrimental effect. On the contrary, low levels of rainfall during the major rainy season in 2009 spurred an increase in social wasp populations. We conclude that recent climatic changes have likely resulted in fewer social wasp colonies because they have lowered the wasps' resistance to parasitoids and pathogens. These results imply that Neotropical social wasps can be regarded as bio-indicators because they highlight the impact of climatic changes not yet perceptible in plants and other animals.
Here we show that Daceton armigerum, an arboreal myrmicine ant whose workers are equipped with hypertrophied trap-jaw mandibles, is characterized by a set of unexpected biological traits including colony size, aggressiveness, trophobiosis and hunting behavior. The size of one colony has been evaluated at ca. 952,000 individuals. Intra- and interspecific aggressiveness were tested and an equiprobable null model used to show how D. armigerum colonies react vis-à-vis other arboreal ant species with large colonies; it happens that D. armigerum can share trees with certain of these species. As they hunt by sight, workers occupy their hunting areas only during the daytime, but stay on chemical trails between nests at night so that the center of their home range is occupied 24 hours a day. Workers tend different Hemiptera taxa (i.e., Coccidae, Pseudococcidae, Membracidae and Aethalionidae). Through group-hunting, short-range recruitment and spread-eagling prey, workers can capture a wide range of prey (up to 94.12 times the mean weight of foraging workers).
The introduction of distance learning does not only bring a wider audience, but also much more diversity among the learners: first, because it can be integrated more easily into a Life-long Learning strategy; secondly, because the learners are not restricted to a sing le area and thus learners from different countries and with different cultures follow the curriculum. We have observed this in various DL diplomas in which we participate. In this article, we will shed some light on the difficulties and challenges arising from these multi-cultural settings. Based on our research work, we would like to insist on two particular points which are the necessity to adapt the pedagogical settings (e.g. pedagogical scenarios) according to the learners' behaviour to overcome unforeseen problems due to cultural differences and the importance of considering mobile technologies to overcome limited access to the technology in developing countries and to ensure continuous interaction among learners and with tutors.
Nous construisons une analyse des dispositifs identitaires contemporains (dont les réseaux socionumériques) sur plusieurs niveaux : au niveau informatique (modèle conceptuel clôturant représentations sociales et sociabilités) ; au niveau microsocial (négociation des singularités subjectives et ancrage des normes sociales) ; au niveau économique (stratégies hégémoniques et partenariat avec les industries culturelles) ; au niveau sociopolitique (expérimentation de postures individuelles sur la base d'expériences affectives et dans un cercle privé rendant possible l'engagement dans les processus délibératifs constituant le sens commun). Pour appréhender ces enjeux, nous avons mis en œuvre une méthodologie immersive et multi-située en compagnie d'une population composée de figures du sujet contemporain : des apprentis en BTS dans le secteur du Tertiaire, soumis à un complexe de contraintes, et engagés au niveau personnel et socioprofessionnel dans divers dispositifs identitaires. Il ressort de ces analyses plusieurs propositions théoriques, dont celle du cadre privatif présenté comme ensemble de contraintes identitaires définies ou négociées par les interactants et resitué au niveau informatique (ingénierie de la vie privée médiatisée), microsocial (veille mutuelle), économique (modèle socioéconomique du salon), sociopolitique (espace anecdotique), et méthodologique (immersion auprès des usagers).
Cette thèse propose une évaluation du contenu environnemental des relations économiques entre le Japon et la Chine, en se basant sur l'analyse de trois canaux de transfert de technologies vertes. Afin de déterminer des dynamiques de diffusion de technologies environnementales (amélioration de l'efficacité énergétique, récupération des polluants, dépollution ou exploitation de sources d'énergie renouvelables), la démonstration s'est concentrée sur trois vecteurs particuliers : les flux commerciaux, les familles internationales de brevets et les Mécanismes pour un Développement Propre (MDP) du Protocole de Kyoto. L'analyse des flux commerciaux depuis le Japon vers la Chine révèle que les importations chinoises de biens environnementaux, de biens d'équipement et de biens de haute technologie sont des canaux de diffusion technologique. En particulier, les estimations économétriques montrent que les importations de biens de haute technologie affectent négativement l'intensité énergétique et carbonique du PIB chinois. L'analyse des données sur les familles internationales de brevets souligne que les technologies facilitant la diminution des niveaux de pollution atmosphérique dominent les transferts du Japon vers la Chine. Enfin, des transferts de connaissances et d'équipements environnementaux apparaissent également dans le cadre des projets MDP financés par des firmes nippones et implantés en Chine. L'analyse empirique de ces MDP fait apparaître que des plans de formation sont mis en œuvre parallèlement à la transmission d'équipements environnementaux, sachant que les transferts apparaissent principalement dans le cadre de projets hydrauliques et éoliens. L'analyse révèle bien que la densité des relations économiques entre le Japon et la Chine s'accompagne de la diffusion de technologies environnementales. L'écart de développement entre le Japon et la Chine ainsi que la présence de capacités d'absorption sur le territoire chinois favorisent la diffusion technologique au travers des flux économiques. L'impact positif de ces flux sur la qualité de l'environnement chinois est renforcé par les incitations gouvernementales aux transferts de technologies ainsi que les législations chinoises sur l'orientation géographique et sectorielle des investissements.
Human brain networks have topological properties in common with many other complex systems, prompting the following question: what aspects of brain network organization are critical for distinctive functional properties of the brain, such as consciousness? To address this question, we used graph theoretical methods to explore brain network topology in resting state functional MRI data acquired from 17 patients with severely impaired consciousness and 20 healthy volunteers. We found that many global network properties were conserved in comatose patients. Specifically, there was no significant abnormality of global efficiency, clustering, small-worldness, modularity, or degree distribution in the patient group. However, in every patient, we found evidence for a radical reorganization of high degree or highly efficient "hub" nodes. Cortical regions that were hubs of healthy brain networks had typically become nonhubs of comatose brain networks and vice versa. These results indicate that global topological properties of complex brain networks may be homeostatically conserved under extremely different clinical conditions and that consciousness likely depends on the anatomical location of hub nodes in human brain networks.
Cet article présente d'abord un rappel des connaissances actuelles concernant l'acquisition des connaissances orthographiques lexicales. Une recherche expérimentale d'auto-apprentissage est ensuite présentée, dans laquelle l'influence du traitement visuel sur les acquisitions orthographiques a été étudiée. Pendant la phase d'apprentissage, certains items étaient présentés de façon à permettre un traitement visuel simultané de toutes les lettres du mot (c.-à-d. un traitement visuel "mot entier"), d'autres pas. Les résultats montrent que, au delà du décodage, le traitement visuel simultané de toutes les lettres d'un mot lu favorise l'acquisition de l'orthographe spécifique de ce même mot.
Cet article rend compte de l'état des connaissances en ce qui concerne les facteurs cognitifs impliqués dans l'acquisition des connaissances orthographiques lexicales. Il traite dans une première partie des données mettant en évidence la relation entre les capacités de lecture et l'acquisition des connaissances orthographiques. Une seconde partie expose les raisons pour lesquelles cette mise en évidence ne permet pas de comprendre pleinement les mécanismes d'acquisition de l'orthographe. Enfin, la troisième partie rend compte des connaissances acquises récemment concernant l'implication d'autres facteurs que le décodage dans cet apprentissage.
We propose in this paper a new generative model for graphs that uses a latent space approach to explain timestamped interactions. The model is designed to provide global estimates of activity dates in historical networks where only the interaction dates between agents are known with reasonable precision. Experimental results show that the model provides better results than local averages in dense enough networks
We present a non parametric bayesian inference strategy to automatically infer the number of classes during the clustering process of a discrete valued random network. Our methodology is related to the Dirichlet process mixture models and inference is performed using a Blocked Gibbs sampling procedure. Using simulated data, we show that our approach improves over competitive variational inference clustering methods.
We present a new primal-dual splitting algorithm for structured monotone inclusions in Hilbert spaces and analyze its asymptotic behavior. A novelty of our framework, which is motivated by image recovery applications, is to consider inclusions that combine a variety of monotonicity-preserving operations such as sums, linear compositions, parallel sums, and a new notion of parallel composition. The special case of minimization problems is studied in detail, and applications to signal recovery are discussed. Numerical simulations are provided to illustrate the implementation of the algorithm.
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.
We propose a probabilistic model for a system at a threshold of instability. The distribution of residence times below the threshold that characterizes the properties of the system is studied analytically in various cases.
In this paper, the asymptotic first order analysis, both mathematical and numerical, of two structures bonded together is presented. Two cases are considered, the gluing of an elastic structure with a rigid body and the gluing of two elastic structures. The glue is supposed to be elastic and to have its stiffness of the same order than those of the elastic structures. An original numerical method is developed to solve the mechanical problem of stiff interface at order 1, based on the Nitsche's method. Several numerical examples are provided to show the efficiency of both the analytical approximation and the numerical method.
We invoke some ideas from finite geometry to map bijectively 135 heptads of mutually commuting three-qubit observables into 135 symmetric four-qubit ones. After labeling the elements of the former set in terms of a seven-dimensional Clifford algebra, we present the bijective map and most pronounced actions of the associated symplectic group on both sets in explicit forms. This formalism is then employed to shed novel light on recently-discovered structural and cardinality properties of an aggregate of three-qubit Mermin's ''magic'' pentagrams. Moreover, some intriguing connections with the so-called black-hole--qubit correspondence are also pointed out.
This paper surveys the theoretical and empirical relationship between economic growth and financial systems. Firstly, the existence of financial systems has a positive effect on growth because it increases the insurance against the illiquidity of real investment, the diversification of technological risk and the informations on investment projects. But informational asymmetries creates market imperfections which decreases economic growth. The costs and benefits for fostering growth of financial intermediation versus financial markets are also investigated, in particular, for their ability to control investment projects and to avoid a potential bias for short term projects. Finally, the econometric evaluations of the relationship between growth and finance are presented.
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.
The European Earth observation programme GMES (Global Monitoring for Environment and Security) aims at providing environmental information to support policymakers, public authorities and both public and commercial users. A systematic monitoring and forecasting of the state of the Earth's subsystems is currently under development. Six thematic areas are developed: marine, land, atmosphere, emergency, security and climate change. A land monitoring service, a marine monitoring service and an atmosphere monitoring service will contribute directly to the monitoring of climate change and to the assessment of mitigation and adaptation policies. Additional GMES services will address respectively emergency response and security-related aspects. The pre-operational atmosphere service of GMES is currently provided through the FP7 project MACC (Monitoring Atmospheric Composition and Climate). MACC combines state-of-the-art atmospheric modelling with Earth observation data to provide information services covering European Air Quality, Global Atmospheric Composition, Climate, and UV and Solar Energy. Within the radiation subproject (MACC-RAD) existing historical and daily updated databases for monitoring incoming surface solar irradiance are further developed. The service will meet the needs of European and national policy development and the requirements of (commercial) downstream services (e.g. planning, monitoring, efficiency improvements, integration into energy supply grids). The SOLEMI service (operated by MACC partner DLR) and the SoDa service (operated by MACC partner ARMINES and its subsidiary Transvalor) have been specifically developed in several national, European and ESA projects to fulfil the requirements for long-term databases and NRT services. On its transition process from the precursor services SoDa and SOLEMI the following User's Guide intends to summarize existing knowledge, which has been published only in a scattered manner. Part A 'Users' Expectations' describes the communities of users, their expectations and gives an overview of the compliance of the MACC RAD service with those. In Part B 'Creating Databases', the current databases HelioClim and SOLEMI as well as the methods used to convert satellite images into solar surface irradiance are presented. The quality of the retrieved irradiances is discussed. An overview of the operations and workflow is presented for the creation, updating and monitoring of these databases. Part C 'Delivering products' is devoted to the supply of products. The core products are defined. The future MACC-RAD Service is described and a prototype is presented. It is intended to update this User's Guide regularly following the realisation of the MACC RAD service line.
De nombreux indicateurs climatiques et expériences de modélisation montrent l'influence des paramètres de l'orbite terrestre sur les variations passées des systèmes de mousson en Asie et en Afrique. En particulier, les moussons sont amplifiées au début de l'Holocène, période de maximum d'insolation au sommet de l'atmosphère pendant l'été boréal. Ce travail s'intéresse aux variations des systèmes de mousson du Sahel, d'Inde et d'Asie du sud-est au début de l'Holocène (9.5 ka BP) et à l'Holocène moyen (6 ka BP) à l'aide du modèle couplé IPSL-CM4. Il met en évidence l'effet de la précession des équinoxes et de l'influence de diverses rétroactions du climat sur la saisonnalité et les variations relatives de ces trois systèmes de mousson au cours de l'Holocène. Ainsi l'amplitude et la phase des mécanismes de réponse aux variations d'insolation diffèrent entre la mousson indienne et la mousson africaine. La thèse aborde aussi le possible rôle de téléconnections entre les systèmes de mousson et les moyennes latitudes. Des expériences de sensibilité à la calotte résiduelle au début de l'Holocène et à l'impact du flux d'eau douce lié à la fonte des calottes en Atlantique Nord montrent des réponses différentes des systèmes asiatiques et africains à ces forçages. Pour compléter ces expériences, la réponse des moussons à un flux d'eau douce en Atlantique Nord est comparée pour plusieurs périodes climatiquespassées (Eémien, dernier maximum glaciaire et Holocène), présente et future. Les résultats des simulations à l'Holocène et au dernier maximum glaciaire sont mis en regard d'enregistrements paléoclimatiques océaniques prélevés dans l'Océan Indien.
L'écoulement et le transport dans les milieux hétérogènes a principalement lieu dans des chenaux d'écoulement préférentiels. Il est donc crucial d'y caractériser au mieux les processus de transport. Pourtant, les techniques actuelles ne permettent pas de décrire le transport à l'échelle d'un site par les équations valides à l'échelle hydrodynamique, il est donc nécessaire d'effectuer un changement d'échelle pour décrire le transport à une échelle où la complexité du milieu n'apparaît plus directement. Les principaux objectifs de cette thèse ont été de caractériser l'impact à l'échelle du chenal de deux effets négligés dans la plupart des études hydrogéologiques. (i) Le premier survient lorsque la présence du soluté modifie significativement la masse volumique du fluide. Ce contraste densitaire modifie le chemin emprunté par le nuage de soluté. Dans un chenal horizontal lisse, le régime pré-asymptotique de dispersion est modifié et le nuage de soluté subit un retard. (ii) L'autre effet classiquement négligé survient lorsque l'écoulement est rapide (ou la viscosité du fluide faible). Les effets inertiels qui entrent alors en jeu sont étudiés dans un chenal d'ouverture variable et périodique. Des zones de recirculation apparaissent dans les cavités. Un soluté peut y pénétrer par diffusion et y rester piégé durant un temps long, tandis que l'écoulement principal est réduit à un chenal central d'ouverture moins hétérogène. (iii) Enfin, la combinaison des effets (i) et (ii) est abordée. Chacune des trois études est menée à l'échelle hydrodynamique en fonction du nombre de Reynolds, du nombre de Péclet et d'un nombre adimensionnel quantifiant l'impact du contraste densitaire.
We propose in this paper a new generative model for graphs that uses a latent space approach to explain timestamped interactions. The model is designed to provide global estimates of activity dates in historical networks where only the interaction dates between agents are known with reasonable precision. Experimental results show that the model provides better results than local averages in dense enough networks
We present a non parametric bayesian inference strategy to automatically infer the number of classes during the clustering process of a discrete valued random network. Our methodology is related to the Dirichlet process mixture models and inference is performed using a Blocked Gibbs sampling procedure. Using simulated data, we show that our approach improves over competitive variational inference clustering methods.
In the literature, there have been several papers about unbiased estimation in presence of censoring. In this work, we generalise the doubly robust unbiased transformation with censoring proposed by Rubin and Van der Laan and Suzukawa. We show it is the uniformly minimum variance unbiased transformation with censoring. The new more general transformation we obtain is also doubly robust and asymptotically normal.
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