Les ondes de type choeur sont parmi les ondes électromagnétiques les plus intenses observées dans la magnétosphère interne de la Terre, et jouent un rôle crucial dans la dynamique des ceintures de radiation terrestres qui est un enjeu majeur de la météorologie de l’espace. Elles sont en effet responsables de l’accélération et la perte des électrons énergétiques qui peuplent notamment la ceinture externe. Or, les satellites ne peuvent couvrir entièrement la magnétosphère interne, et les données de ces ondes sont pauvres dans certaines régions. Le but de cette thèse est donc de pouvoir compléter les données satellites par le biais des simulations numériques, en déterminant les distributions statistiques des ondes de type choeur dans la magnétosphère interne. Pour cela, un code dit de traçage de rayons a été développé, incluant un modèle réaliste de magnétosphère interne. La propagation des ondes choeur par le biais de ce code est d’abord décrite dans ce travail, mettant notamment l’accent sur l’importance de l’angle azimutal des ondes. Puis, en utilisant la base de données de trajectoires réalisée pour des paramètres typiques des choeurs sources, la reconstruction des distributions statistiques mesurées par Cluster est présentée. Il est ainsi démontré l’invalidité, aux moyennes et hautes latitudes, de l’approximation quasi-longitudinale utilisée dans de nombreux calculs de la dynamique des ceintures de radiation. En se basant sur ces distributions réalistes d’angles normaux, mais aussi d’amplitude des ondes, il est ensuite démontré l’importante différence obtenue sur les pertes d’électrons énergétiques. Par la suite, la précision de nos simulations numériques pour l’étude des ondes choeurs réfléchies dans la magnétosphère est mise en évidence, ainsi que leur importance étant donné le peu d’observations. Nos simulations indiquent notamment que les tons descendants d’ondes choeur peuvent provenir de la réflexion magnétosphérique de tons montants. / Chorus type whistler waves are one of the most intense electromagnetic waves observed in the Earth’s inner magnetosphere, and play a crucial role in the dynamics of radiation belts which is a critical issue in space weather. They are indeed responsible for acceleration and loss of the energetic electron population that shape the outer belt. As spacecraft trajectories cannot entirely cover the inner magnetosphere, satellite measurements are poor in some regions. The aim of this thesis is thus to be able to complete observational data making use of numerical simulations, by determining the statistical distributions of chorus waves in the inner magnetosphere. In order to achieve this aim, a ray tracing code has been developed, including a realistic model of the inner magnetosphere. First, wave propagation by means of this program is described in this work, emphasizing notably the significance of wave azimuthal angle. Then, making use of the trajectory database computed for typical source chorus parameters, the reconstruction of statistical distributions recorded on Cluster spacecraft is presented. It is thereby demonstrated that quasi-longitudinal approximation, used in numerous simulations of radiation belts dynamics, is no longer valid at medium and high latitudes. Taking these realistic distributions as a basis, it is then demonstrated the major discrepancy obtained for energetic electrons losses. Subsequently, the accuracy of our numerical simulations for the study of magnetospherically reflected chorus waves is highlighted, as well as their importance due to the lack of observational data. Our simulations notably indicate that falling tone chorus emissions can originate from the magnetospheric reflection of rising tone elements.

Fostering identification with Europe among citizens could legitimise European integration. Whether such an identity exists, however, remains an on-going debate among scholars. This research returns to the foundations of how a European identity is constructed, transmitted and transformed. It explores narratives of European identity in a carefully chosen context - European Schools for children of EU officials - where identification with Europe should mirror official EU visions. A qualitative content analysis explores narrations of 101 students collected during interviews and focus groups across three schools, and analyses documents and interviews with EU officials, school directors and teachers. This analysis reveals a descriptive puzzle: official EU and European School propositions of (multi-) national narratives differ markedly from teachers' and students' conceptions of cosmopolitan and transnational identities. The EU constructs an out-group of its own nationalist past and non-EU citizens. On the other hand, students construct an explicitly European in-group, but differentiate themselves from more national and less mobile lifestyles. This disparity, in turn, reveals a causal puzzle about how differences in narratives emerge. I use process tracing to elucidate the relationship between European schooling and students' identification with Europe. The results show a distorted transmission where broader EU goals are elaborated and transformed by teachers and further fuelled by interactions amongst students with similarly mobile and multilingual backgrounds. I develop a dual mechanism to understand how the varieties of identification with Europe develop: the concept of "doing Europe" explains how students nourish a transnational social network; "telling Europe", on the other hand, considers students' exposure to European symbols and stories in school and both national and anti-nationalist narratives provided by teachers and peers. Together, this leads to a transformed but ultimately European in-group understanding. Overall, this project underlines the complexity of identity construction, given that top-down transmission gets altered even in this favourable case. Specifically, it informs future research on European identity by detailing peculiar narratives and offering a causal approach to how these narratives emerge.

Cellular checkpoints are typically considered to both facilitate the ordered execution of the cell cycle and to act as a barrier to oncogene driven cell cycles and the transmission of unresolved genetic lesions from one phase to the next. Furthermore, these mechanisms are also believed to underpin the responses of cells, both in normal and cancerous tissues, to those therapies that either directly or indirectly generate DNA damage. In recent studies however, it has become clear these checkpoints permit the passage of significant genomic aberrations into subsequent cell cycle phases and even descendant cells, and that heterogeneous responses are apparent amongst genetically identical cells. The consequences of this checkpoint ‘negligence’ remain relatively uncharacterised despite the importance of checkpoints in current models for how genomic instability is avoided in the face of ubiquitous DNA damage. Unresolved DNA damage is presumably inherited by subsequent cell cycle phases and descendant cells yet characterisation of the consequences of this has been relatively limited to date. I therefore utilised microscopy-based lineage tracing of cells expressing genetically encoded fluorescent sensors, particularly the Fluorescent Ubiquitination-based Cell Cycle Indicator (FUCCI) probes (Sakaue-Sawano et al., 2008), with semi-automated image analysis to characterise the response of single cells and their descendants to DNA lesions across multiple cell cycle generations. This approach, complemented by generational tracing by flow cytometry, permitted me to characterise the timing of cell fate determination in treated and descendant cells, the non-genetic heterogeneity in checkpoint responses and overall lineage behaviour, correlations between cells (similarly to Sandler et al., 2015) and cell cycle timing dependencies in the response to DNA damaging agents. With these single cell analytical approaches I show that the consequences of DNA damage on descendant cell fate is dramatic, suggesting checkpoint mechanisms may have consequences and even cooperate across phases and generations. U2OS cell lineages traced for three generations following the induction of DNA damage in the form of strand breaks showed greatly induced cell death in the daughters and granddaughters of DNA damaged cells, termed delayed death. Furthermore, lineage behaviour was characterised as highly heterogeneous in when and whether cell death occurred. Complementary flow cytometric approaches validated the findings in U2OS cells and suggested HeLa cells may show similar behaviour. These findings indicate that checkpoint models need to incorporate multigenerational behaviour in order to better describe the response of cells to DNA damage. Understanding the processes governing cell fate determination in descendant cells will impact upon our understanding of the development of genomic instability during carcinogenesis and how DNA-damaging chemotherapeutics drive cells to ‘quit’ the cell cycle.

No description available.

Placé à la frontière entre l'informatique graphique et la physique, le rendu d'image physiquement réaliste est un domaine qui tente de créer des images en simulant le comportement optique des matériaux. Les applications sont multiples : restauration virtuelle d'oeuvre du patrimoine, simulation d'effets optiques, rendu industriel pour la conception, voire même, conception assistée par ordinateur de la couleur. Cette thèse présente les travaux réalisés au cours du projet Virtuelium, un logiciel de rendu d'image physiquement réaliste dont la quatrième version a été développée dans le cadre de cette thèse. Elle en présente les principes et méthodologies utilisés pour les mesures et la validation des résultats. Nous présentons aussi plusieurs travaux réalisés durant cette thèse avec cet outil : de la restauration virtuelle à la bio-photonique sans oublier un aperçu de rendu de "matériaux à effet", pour des applications industrielles (peintures, encres, cosmétiques, etc.). / Laying between computer graphics and physics, the rendering of physically based images is a domain that attempt to create images by simulating the optical behaviour of materials interacting with light (either natural or not). There are several applications : virtual restoration of cultural heritage artefacts, simulation of optical effects, industrial rendering for design and even computer-aided design of colour. This thesis presents the works realised within Virtuelium project framework, a physically based rendering software. The fourth version was developed during this thesis. Here will be presented the principles and methodologies involved for the measurements and the validation of the obtained results. We present also several works that have been done during that thesis using Virtuelium: from virtual restoration to bio-photonics, including an overview of iridescent pigments rendered for an industrial purpose.

abstract: Embedded assessment constantly updates a model of the student as the student works on instructional tasks. Accurate embedded assessment allows students, instructors and instructional systems to make informed decisions without requiring the student to stop instruction and take a test. This thesis describes the development and comparison of several student models for Dragoon, an intelligent tutoring system. All the models were instances of Bayesian Knowledge Tracing, a standard method. Several methods of parameterization and calibration were explored using two recently developed toolkits, FAST and BNT-SM that replaces constant-valued parameters with logistic regressions. The evaluation was done by calculating the fit of the models to data from human subjects and by assessing the accuracy of their assessment of simulated students. The student models created using node properties as subskills were superior to coarse-grained, skill-only models. Adding this extra level of representation to emission parameters was superior to adding it to transmission parameters. Adding difficulty parameters did not improve fit, contrary to standard practice in psychometrics. / Dissertation/Thesis / Masters Thesis Computer Science 2015

abstract: EMBRACE (Enhanced Moved By Reading to Accelerate Comprehension in English) is an IPad application that uses the Moved By Reading strategy to help improve the reading comprehension skills of bilingual (Spanish speaking) English Language Learners (ELLs). In EMBRACE, students read the text of a story and then move images corresponding to the text that they read. According to the embodied cognition theory, this grounds reading comprehension in physical experiences and thus is more engaging. In this thesis, I used the log data from 20 students in grades 2-5 to design a skill model for a student using EMBRACE. A skill model is the set of knowledge components that a student needs to master in order to comprehend the text in EMBRACE. A good skill model will improve understanding of the mistakes students make and thus aid in the design of useful feedback for the student.. In this context, the skill model consists of vocabulary and syntax associated with the steps that students performed. I mapped each step in EMBRACE to one or more skills (vocabulary and syntax) from the model. After every step, the skill level is updated in the model. Thus, if a student answered the previous step incorrectly, the corresponding skills are decremented and if the student answered the previous question correctly, the corresponding skills are incremented, through the Bayesian Knowledge Tracing algorithm. I then correlated the students’ predicted scores (computed from their skill levels) to their posttest scores. I evaluated the students’ predicted scores (computed from their skill levels) by comparing them to their posttest scores. The two sets of scores were not highly correlated, but the results gave insights into potential improvements that could be made to the system with respect to user interaction, posttest scores and modeling algorithm. / Dissertation/Thesis / Masters Thesis Computer Science 2016

abstract: Political and economic competition, so goes the broad argument, reduce corruption because competition increases the cost of actors to engage in corrupt practices. It increases the risk of exposure, provides non-corrupt alternatives for consumers, and introduces non-corrupt practices into the political and economic domains. Why then, has corruption persisted in the Central Eastern European countries decades after the introduction of political and economic competition in the early 1990s? This dissertation asks how and why the emergence of competition in the political and economic domains leads to a transformation of the patterns of corruption. I define corruption as an act involving a public official who violates the norms or regulations of their office, receives some compensation in return, and thus harms the public interest. I argue that under conditions of a communist past and high levels of uncertainty, the simultaneous emergence of political and economic competition transforms the opportunity structures of actors to engage in corruption. The resulting constellation of powerful incentives for and weak constraints against corruption encourages political and economic actors to enter into corrupt state-business relationships. Finally, the resource distribution between the actors in the corrupt state-business relationship determines the type of corruption that emerges—legal corruption, local capture, or covert political financing. To test the causal mechanism, I employ intensive process-tracing of the micro-causal mechanisms of eleven corruption cases in Poland and Hungary. Using paired comparisons of cases from the same business sector but at different points in time, the dissertation examines how corruption patterns transformed over time in Poland and Hungary. The dissertation shows that the emergence of political and economic competition changes the opportunity structures of actors in favor of corruption. Moreover, the new constellation of incentives and constraints encourages political and economic actors to establish corrupt state-business relationships. Crucially, I find that the resource distribution within these corrupt relationships determines the type of corruption emerges—local capture where both sides have concentrated resources that balance each other out, legal corruption when a strong economic actor confronts a fragmented political actor, and covert political financing when a weak economic actor faces a strong political actor. / Dissertation/Thesis / Doctoral Dissertation Political Science 2018

While exact methods, such as DDA or T-matrix, can be applied to particles withsizes comparable to the wavelength, computational demands mean that they are size limited. For particles much larger than the wavelength, the Geometric Optics approximation can be employed, but in doing so wave effects, such as interference and diffraction, are ignored. In between these two size extremes there exists a need for computational techniques which are capable of handling the wide array of ice crystal shapes and sizes that are observed in cirrus clouds. The Beam Tracing model developed within this project meets these criteria. It combines aspects of geometric optics and physical optics. Beam propagation is handled by Snell's law and the law of reflection. A beam is divided into reflected and transmitted components each time a crystal facet is illuminated. If the incident beam illuminates multiple facets it is split, with a new beam being formed for each illuminated facet. The phase-dependent electric field amplitude of the beams is known from their ampli- tude (Jones) matrices. These are modified by transmission and reflection matrices, whose elements are Fresnel amplitude coefficients, each time a beam intersects a crystal facet. Phase tracing is carried out for each beam by considering the path that its 'centre ray' would have taken. The local near-field is then mapped, via a surface integral formulation of a vector Kirchhoff diffraction approximation, to the far-field. Once in the far-field the four elements of the amplitude matrix are trans- formed into the sixteen elements of the scattering matrix via known relations. The model is discussed in depth, with details given on its implementation. The physical basis of the model is given through a discussion of Ray Tracing and how this leads to the notion of Beam Tracing. The beam splitting algorithm is described for convex particles followed by the necessary adaptations for concave and/or ab- sorbing particles. Once geometric aspects have been established details are given as to how physical properties of beams are traced including: amplitude, phase and power. How diffraction is implemented in the model is given along with a review of existing diffraction implementations. Comparisons are given, first against a modified Ray Tracing code to validate the geometric optics aspects of the model. Then, specific examples are given for the cases of transparent, pristine, smooth hexagonal columns of four different sizes and orientations; a highly absorbing, pristine, smooth hexagonal column and a highly absorbing, indented, smooth hexagonal column. Analysis of two-dimensional and one-dimensional intensity distributions and degree of linear polarisation results are given for each case and compared with results acquired through use of the Amster- dam Discrete-Dipole Approximation (ADDA) code; with good agreement observed. To the author's best knowledge, the Beam Tracer developed here is unique in its ability to handle concave particles; particles with complex structures and the man- ner in which beams are divided into sub-beams of quasi-constant intensity when propagating in an absorbing medium. One of the model's potential applications is to create a database of known particle scattering patterns, for use in aiding particle classification from images taken by the Small Ice Detector (SID) in-situ probe. An example of creating such a database for hexagonal columns is given.

Le concept de processeur multicœurs constitue le facteur dominant pour offrir des hautes performances aux applications parallèles. Afin de développer des applications parallèles capable de tirer profit de ces plate-formes, les développeurs doivent prendre en compte plusieurs aspects, allant de l'architecture aux caractéristiques propres à l'application. Dans ce contexte, la Mémoire Transactionnelle (Transactional Memory – TM) apparaît comme une alternative intéressante à la synchronisation basée sur les verrous pour ces plates-formes. Elle permet aux programmeurs d'écrire du code parallèle encapsulé dans des transactions, offrant des garanties comme l'atomicité et l'isolement. Lors de l'exécution, les opérations sont exécutées spéculativement et les conflits sont résolus par ré-exécution des transactions en conflit. Bien que le modèle de TM ait pour but de simplifier la programmation concurrente, les meilleures performances ne pourront être obtenues que si l'exécutif est capable de s'adapter aux caractéristiques des applications et de la plate-forme. Les contributions de cette thèse concernent l'analyse et l'amélioration des performances des applications basées sur la Mémoire Transactionnelle Logicielle (Software Transactional Memory – STM) pour des plates-formes multicœurs. Dans un premier temps, nous montrons que le modèle de TM et ses performances sont difficiles à analyser. Pour s'attaquer à ce problème, nous proposons un mécanisme de traçage générique et portable qui permet de récupérer des événements spécifiques à la TM afin de mieux analyser les performances des applications. Par exemple, les données tracées peuvent être utilisées pour détecter si l'application présente des points de contention ou si cette contention est répartie sur toute l'exécution. Notre approche peut être utilisée sur différentes applications et systèmes STM sans modifier leurs codes sources. Ensuite, nous abordons l'amélioration des performances des applications sur des plate-formes multicœurs. Nous soulignons que le placement des threads (thread mapping) est très important et peut améliorer considérablement les performances globales obtenues. Pour faire face à la grande diversité des applications, des systèmes STM et des plates-formes, nous proposons une approche basée sur l'Apprentissage Automatique (Machine Learning) pour prédire automatiquement les stratégies de placement de threads appropriées pour les applications de TM. Au cours d'une phase d'apprentissage préliminaire, nous construisons les profiles des applications s'exécutant sur différents systèmes STM pour obtenir un prédicteur. Nous utilisons ensuite ce prédicteur pour placer les threads de façon statique ou dynamique dans un système STM récent. Finalement, nous effectuons une évaluation expérimentale et nous montrons que l'approche statique est suffisamment précise et améliore les performances d'un ensemble d'applications d'un maximum de 18%. En ce qui concerne l'approche dynamique, nous montrons que l'on peut détecter des changements de phase d'exécution des applications composées des diverses charges de travail, en prévoyant une stratégie de placement appropriée pour chaque phase. Sur ces applications, nous avons obtenu des améliorations de performances d'un maximum de 31% par rapport à la meilleure stratégie statique. / Multicore processors are now a mainstream approach to deliver higher performance to parallel applications. In order to develop efficient parallel applications for those platforms, developers must take care of several aspects, ranging from the architectural to the application level. In this context, Transactional Memory (TM) appears as a programmer friendly alternative to traditional lock-based concurrency for those platforms. It allows programmers to write parallel code as transactions, which are guaranteed to execute atomically and in isolation regardless of eventual data races. At runtime, transactions are executed speculatively and conflicts are solved by re-executing conflicting transactions. Although TM intends to simplify concurrent programming, the best performance can only be obtained if the underlying runtime system matches the application and platform characteristics. The contributions of this thesis concern the analysis and improvement of the performance of TM applications based on Software Transactional Memory (STM) on multicore platforms. Firstly, we show that the TM model makes the performance analysis of TM applications a daunting task. To tackle this problem, we propose a generic and portable tracing mechanism that gathers specific TM events, allowing us to better understand the performances obtained. The traced data can be used, for instance, to discover if the TM application presents points of contention or if the contention is spread out over the whole execution. Our tracing mechanism can be used with different TM applications and STM systems without any changes in their original source codes. Secondly, we address the performance improvement of TM applications on multicores. We point out that thread mapping is very important for TM applications and it can considerably improve the global performances achieved. To deal with the large diversity of TM applications, STM systems and multicore platforms, we propose an approach based on Machine Learning to automatically predict suitable thread mapping strategies for TM applications. During a prior learning phase, we profile several TM applications running on different STM systems to construct a predictor. We then use the predictor to perform static or dynamic thread mapping in a state-of-the-art STM system, making it transparent to the users. Finally, we perform an experimental evaluation and we show that the static approach is fairly accurate and can improve the performance of a set of TM applications by up to 18%. Concerning the dynamic approach, we show that it can detect different phase changes during the execution of TM applications composed of diverse workloads, predicting thread mappings adapted for each phase. On those applications, we achieve performance improvements of up to 31% in comparison to the best static strategy.