The Dutung-Thaktote extensional fault zone and nappe structures documented by illite crystallinity and clay-mineral paragenesis in the Tethys Himalaya between Spiti river and Tso Morari, NW India

Numerous measurements by XRD of the Scherrer width at half-peak height (001 reflection of illite), coupled with analyses of clay-size assemblages, provide evidence for strong variations in the conditions of low temperature metamorphism in the Tethyan Himalaya metasediments between the Spiti river and the Tso Morari. Three sectors can be distinguished along the Spiti river-Tso Morari transect. In the SW, the Takling and Parang La area is characterised by a metamorphism around anchizone-epizone boundary conditions. Further north, in the Dutung area, the metamorphic grade abruptly decreases to weak diagenesis, with the presence of mixed-layered clay phases. At the end of the profile towards the NE, a progressive metamorphic increase up to greenschist facies is recorded, marked by the appearance of biotite and chloritoid. The combination of these data with the structural. observations permits to propose that a nappe stack has been crosscut by the younger Dutung-Thaktote extensional fault zone (DTFZ). The change in metamorphism across this zone helps to assess the displacements which occurred during synorogenic extension. In the SW and NE parts of the studied transect, a burial of 12 km has been estimated, assuming a geothermal gradient of 25 degrees C/km. In the SW part, this burial is due to the juxtaposition of the Shikar Beh and Mata nappes and in the NE part, solely to burial beneath the Mata nappe. In the central part of the profile, the effect of the DTFZ is to bring down diagenetic sediments in-between the two aforesaid metamorphic zones. The offset along the Dutung-Thaktote normal faults is estimated at 16 km.

Structural, metamorphic and geochronological relations between the Zanskar Shear Zone and the Miyar Shear Zone (NW Indian Himalaya): Evidence for two distinct tectonic structures and implications for the evolution of the High Himalayan Crystalline of Zanskar

The geologic structures and metamorphic zonation of the northwestern Indian Himalaya contrast significantly with those in the central and eastern parts of the range, where the high-grade metamorphic rocks of the High Himalayan Crystalline (HHC) thrust southward over the weakly metamorphosed sediments of the Lesser Himalaya along the Main Central Thrust (MCT). Indeed, the hanging wall of the MCT in the NW Himalaya mainly consists of the greenschist facies metasediments of the Chamba zone, whereas HHC high-grade rocks are exposed more internally in the range as a large-scale dome called the Gianbul dome. This Gianbul dome is bounded by two oppositely directed shear zones, the NE-dipping Zanskar Shear Zone (ZSZ) on the northern flank and the SW-dipping Miyar Shear Zone (MSZ) on the southern limb. Current models for the emplacement of the HHC in NW India as a dome structure differ mainly in terms of the roles played by both the ZSZ and the MSZ during the tectonothermal evolution of the HHC. In both the channel flow model and wedge extrusion model, the ZSZ acts as a backstop normal fault along which the high-grade metamorphic rocks of the HHC of Zanskar are exhumed. In contrast, the recently proposed tectonic wedging model argues that the ZSZ and the MSZ correspond to one single detachment system that operates as a subhorizontal backthrust off of the MCT. Thus, the kinematic evolution of the two shear zones, the ZSZ and the MSZ, and their structural, metamorphic and chronological relations appear to be diagnostic features for discriminating the different models. In this paper, structural, metamorphic and geochronological data demonstrate that the MSZ and the ZSZ experienced two distinct kinematic evolutions. As such, the data presented in this paper rule out the hypothesis that the MSZ and the ZSZ constitute one single detachment system, as postulated by the tectonic wedging model. Structural, metamorphic and geochronological data are used to present an alternative tectonic model for the large-scale doming in the NW Indian Himalaya involving early NE-directed tectonics, weakness in the upper crust, reduced erosion at the orogenic front and rapid exhumation along both the ZSZ and the MSZ.

Tapping the innovation potential of corporate engagement with stakeholders

Summary This dissertation explores how stakeholder dialogue influences corporate processes, and speculates about the potential of this phenomenon - particularly with actors, like non-governmental organizations (NGOs) and other representatives of civil society, which have received growing attention against a backdrop of increasing globalisation and which have often been cast in an adversarial light by firms - as a source of teaming and a spark for innovation in the firm. The study is set within the context of the introduction of genetically-modified organisms (GMOs) in Europe. Its significance lies in the fact that scientific developments and new technologies are being generated at an unprecedented rate in an era where civil society is becoming more informed, more reflexive, and more active in facilitating or blocking such new developments, which could have the potential to trigger widespread changes in economies, attitudes, and lifestyles, and address global problems like poverty, hunger, climate change, and environmental degradation. In the 1990s, companies using biotechnology to develop and offer novel products began to experience increasing pressure from civil society to disclose information about the risks associated with the use of biotechnology and GMOs, in particular. Although no harmful effects for humans or the environment have been factually demonstrated even to date (2008), this technology remains highly-contested and its introduction in Europe catalysed major companies to invest significant financial and human resources in stakeholder dialogue. A relatively new phenomenon at the time, with little theoretical backing, dialogue was seen to reflect a move towards greater engagement with stakeholders, commonly defined as those "individuals or groups with which. business interacts who have a 'stake', or vested interest in the firm" (Carroll, 1993:22) with whom firms are seen to be inextricably embedded (Andriof & Waddock, 2002). Regarding the organisation of this dissertation, Chapter 1 (Introduction) describes the context of the study, elaborates its significance for academics and business practitioners as an empirical work embedded in a sector at the heart of the debate on corporate social responsibility (CSR). Chapter 2 (Literature Review) traces the roots and evolution of CSR, drawing on Stakeholder Theory, Institutional Theory, Resource Dependence Theory, and Organisational Learning to establish what has already been developed in the literature regarding the stakeholder concept, motivations for engagement with stakeholders, the corporate response to external constituencies, and outcomes for the firm in terms of organisational learning and change. I used this review of the literature to guide my inquiry and to develop the key constructs through which I viewed the empirical data that was gathered. In this respect, concepts related to how the firm views itself (as a victim, follower, leader), how stakeholders are viewed (as a source of pressure and/or threat; as an asset: current and future), corporate responses (in the form of buffering, bridging, boundary redefinition), and types of organisational teaming (single-loop, double-loop, triple-loop) and change (first order, second order, third order) were particularly important in building the key constructs of the conceptual model that emerged from the analysis of the data. Chapter 3 (Methodology) describes the methodology that was used to conduct the study, affirms the appropriateness of the case study method in addressing the research question, and describes the procedures for collecting and analysing the data. Data collection took place in two phases -extending from August 1999 to October 2000, and from May to December 2001, which functioned as `snapshots' in time of the three companies under study. The data was systematically analysed and coded using ATLAS/ti, a qualitative data analysis tool, which enabled me to sort, organise, and reduce the data into a manageable form. Chapter 4 (Data Analysis) contains the three cases that were developed (anonymised as Pioneer, Helvetica, and Viking). Each case is presented in its entirety (constituting a `within case' analysis), followed by a 'cross-case' analysis, backed up by extensive verbatim evidence. Chapter 5 presents the research findings, outlines the study's limitations, describes managerial implications, and offers suggestions for where more research could elaborate the conceptual model developed through this study, as well as suggestions for additional research in areas where managerial implications were outlined. References and Appendices are included at the end. This dissertation results in the construction and description of a conceptual model, grounded in the empirical data and tied to existing literature, which portrays a set of elements and relationships deemed important for understanding the impact of stakeholder engagement for firms in terms of organisational learning and change. This model suggests that corporate perceptions about the nature of stakeholder influence the perceived value of stakeholder contributions. When stakeholders are primarily viewed as a source of pressure or threat, firms tend to adopt a reactive/defensive posture in an effort to manage stakeholders and protect the firm from sources of outside pressure -behaviour consistent with Resource Dependence Theory, which suggests that firms try to get control over extemal threats by focussing on the relevant stakeholders on whom they depend for critical resources, and try to reverse the control potentially exerted by extemal constituencies by trying to influence and manipulate these valuable stakeholders. In situations where stakeholders are viewed as a current strategic asset, firms tend to adopt a proactive/offensive posture in an effort to tap stakeholder contributions and connect the organisation to its environment - behaviour consistent with Institutional Theory, which suggests that firms try to ensure the continuing license to operate by internalising external expectations. In instances where stakeholders are viewed as a source of future value, firms tend to adopt an interactive/innovative posture in an effort to reduce or widen the embedded system and bring stakeholders into systems of innovation and feedback -behaviour consistent with the literature on Organisational Learning, which suggests that firms can learn how to optimize their performance as they develop systems and structures that are more adaptable and responsive to change The conceptual model moreover suggests that the perceived value of stakeholder contribution drives corporate aims for engagement, which can be usefully categorised as dialogue intentions spanning a continuum running from low-level to high-level to very-high level. This study suggests that activities aimed at disarming critical stakeholders (`manipulation') providing guidance and correcting misinformation (`education'), being transparent about corporate activities and policies (`information'), alleviating stakeholder concerns (`placation'), and accessing stakeholder opinion ('consultation') represent low-level dialogue intentions and are experienced by stakeholders as asymmetrical, persuasive, compliance-gaining activities that are not in line with `true' dialogue. This study also finds evidence that activities aimed at redistributing power ('partnership'), involving stakeholders in internal corporate processes (`participation'), and demonstrating corporate responsibility (`stewardship') reflect high-level dialogue intentions. This study additionally finds evidence that building and sustaining high-quality, trusted relationships which can meaningfully influence organisational policies incline a firm towards the type of interactive, proactive processes that underpin the development of sustainable corporate strategies. Dialogue intentions are related to type of corporate response: low-level intentions can lead to buffering strategies; high-level intentions can underpin bridging strategies; very high-level intentions can incline a firm towards boundary redefinition. The nature of corporate response (which encapsulates a firm's posture towards stakeholders, demonstrated by the level of dialogue intention and the firm's strategy for dealing with stakeholders) favours the type of learning and change experienced by the organisation. This study indicates that buffering strategies, where the firm attempts to protect itself against external influences and cant' out its existing strategy, typically lead to single-loop learning, whereby the firm teams how to perform better within its existing paradigm and at most, improves the performance of the established system - an outcome associated with first-order change. Bridging responses, where the firm adapts organisational activities to meet external expectations, typically leads a firm to acquire new behavioural capacities characteristic of double-loop learning, whereby insights and understanding are uncovered that are fundamentally different from existing knowledge and where stakeholders are brought into problem-solving conversations that enable them to influence corporate decision-making to address shortcomings in the system - an outcome associated with second-order change. Boundary redefinition suggests that the firm engages in triple-loop learning, where the firm changes relations with stakeholders in profound ways, considers problems from a whole-system perspective, examining the deep structures that sustain the system, producing innovation to address chronic problems and develop new opportunities - an outcome associated with third-order change. This study supports earlier theoretical and empirical studies {e.g. Weick's (1979, 1985) work on self-enactment; Maitlis & Lawrence's (2007) and Maitlis' (2005) work and Weick et al's (2005) work on sensegiving and sensemaking in organisations; Brickson's (2005, 2007) and Scott & Lane's (2000) work on organisational identity orientation}, which indicate that corporate self-perception is a key underlying factor driving the dynamics of organisational teaming and change. Such theorizing has important implications for managerial practice; namely, that a company which perceives itself as a 'victim' may be highly inclined to view stakeholders as a source of negative influence, and would therefore be potentially unable to benefit from the positive influence of engagement. Such a selfperception can blind the firm from seeing stakeholders in a more positive, contributing light, which suggests that such firms may not be inclined to embrace external sources of innovation and teaming, as they are focussed on protecting the firm against disturbing environmental influences (through buffering), and remain more likely to perform better within an existing paradigm (single-loop teaming). By contrast, a company that perceives itself as a 'leader' may be highly inclined to view stakeholders as a source of positive influence. On the downside, such a firm might have difficulty distinguishing when stakeholder contributions are less pertinent as it is deliberately more open to elements in operating environment (including stakeholders) as potential sources of learning and change, as the firm is oriented towards creating space for fundamental change (through boundary redefinition), opening issues to entirely new ways of thinking and addressing issues from whole-system perspective. A significant implication of this study is that potentially only those companies who see themselves as a leader are ultimately able to tap the innovation potential of stakeholder dialogue.

Projets de coopération universitaire : l'émergence de nouvelles structures de gouvernance

Depuis le début des années quatre-vingt-dix, le modèle classique de l'université est fortement remis en question: pénétration accrue des acteurs privés, attentes de la société civile, contractualisation et «horizontalisation» des relations, etc. L'université bouge et doit s'adapter à un environnement en mutation. En Suisse, les projets de coopération inter universités semblent être une des réponses privilégiées par les acteurs dominants du système pour faire face à ces changements. Toutefois, la mise en place de nouveaux arrangements institutionnels notamment sous la forme de réseaux d'enseignement et de recherche ne va pas sans soulever de nombreuses interrogations. Premièrement, et notamment du fait de bases légales peu développées, les collaborations institutionnalisées n'ont pas toutes la même configuration. Nous devons donc nous questionner sur les formes concrètes prises par ces réseaux d'enseignement et de recherche et sur les raisons qui ont conduit à l'adoption d'un type particulier de structure de coopération. Ensuite, comme ces structures ne viennent pas remplacer, mais plutôt se superposer à celles préexistantes, il convient de comprendre la redistribution du pouvoir au sein de formes institutionnelles complexes. Plus précisément, l'analyse de la nouvelle répartition des compétences entre les institutions hiérarchiques (les universités) et les coopérations (réseaux) en particulier sous l'angle de l'autonomie dont ces dernières disposent, se révèle être un angle d'approche fructueux. Finalement, la question de l'évaluation de ces nouvelles formes de gouvernance va se poser. Outre les formes prises par ces structures, une discussion doit être menée autour des limites démocratiques de cette nouvelle forme du secteur public. Ce working paper présente dans un premier temps quelques facteurs qui ont contraints les universités à une remise en cause de leurs structures de gouvernance. Il introduit ensuite quelques éléments théoriques faisant référence aux théories portant sur les réseaux et plus particulièrement à l'approche institutionnelle de ceux-ci. La troisième partie de ce papier présente brièvement les structures de gouvernance du système universitaire helvétique ainsi que les récentes pressions au changement ayant favorisé la mise en place de ces réseaux. Finalement, la quatrième partie étudie, au travers de six cas de coopérations inter-universitaires suisses, la forme prise par ces réseaux, essentiellement sous l'angle de leur degré d'autonomie.

Acute pulmonary toxicity following occupational exposure to a floor stain protector in the building industry in Switzerland.

BACKGROUND: Waterproofing agents are widely applied to leather and textile garments; they are also used as floor stain protectors by professionals. Acute respiratory injury is described in three cases of young healthy adults following occupational inhalation of a new waterproofing formulation containing an acrylate fluoropolymer. Within 1 or 2 h after exposure they developed a rapidly progressive dyspnoea; two of them had hypoxaemia and flu-like reactions. All patients improved with supportive treatment in a few days. The mechanism of toxicity is still under investigation, but experimental data suggest the role of this new acrylate fluoropolymer. CONCLUSION: Tilers should be warned against spraying floor stain repellents; there is also a need to make consumers aware that the spraying of waterproofing agents in a closed environment and concomitant smoking should be avoided.

Bunch frequency multiplication by RF injection into an isochronous ring

La collaboration CLIC (Compact LInear Collider, collisionneur linéaire compact) étudie la possibilité de réaliser un collisionneur électron-positon linéaire à haute énergie (3 TeV dans le centre de masse) et haute luminosité (1034 cm-2s-1), pour la recherche en physique des particules. Le projet CLIC se fonde sur l'utilisation de cavités accélératrices à haute fréquence (30 GHz). La puissance nécessaire à ces cavités est fournie par un faisceau d'électrons de basse énergie et de haute intensité, appelé faisceau de puissance, circulant parallèlement à l'accélérateur linéaire principal (procédé appelé « Accélération à Double Faisceau »). Dans ce schéma, un des principaux défis est la réalisation du faisceau de puissance, qui est d'abord généré dans un complexe accélérateur à basse fréquence, puis transformé pour obtenir une structure temporelle à haute fréquence nécessaire à l'alimentation des cavités accélératrices de l'accélérateur linéaire principal. La structure temporelle à haute fréquence des paquets d'électrons est obtenue par le procédé de multiplication de fréquence, dont la manipulation principale consiste à faire circuler le faisceau d'électrons dans un anneau isochrone en utilisant des déflecteurs radio-fréquence (déflecteurs RF) pour injecter et combiner les paquets d'électrons. Cependant, ce type de manipulation n'a jamais été réalisé auparavant et la première phase de la troisième installation de test pour CLIC (CLIC Test Facility 3 ou CTF3) a pour but la démonstration à faible charge du procédé de multiplication de fréquence par injection RF dans un anneau isochrone. Cette expérience, qui a été réalisée avec succès au CERN au cours de l'année 2002 en utilisant une version modifiée du pré-injecteur du grand collisionneur électron-positon LEP (Large Electron Positron), est le sujet central de ce rapport. L'expérience de combinaison des paquets d'électrons consiste à accélérer cinq impulsions dont les paquets d'électrons sont espacés de 10 cm, puis à les combiner dans un anneau isochrone pour obtenir une seule impulsion dont les paquets d'électrons sont espacés de 2 cm, multipliant ainsi la fréquence des paquets d'électrons, ainsi que la charge par impulsion, par cinq. Cette combinaison est réalisée au moyen de structures RF résonnantes sur un mode déflecteur, qui créent dans l'anneau une déformation locale et dépendante du temps de l'orbite du faisceau. Ce mécanisme impose plusieurs contraintes de dynamique de faisceau comme l'isochronicité, ainsi que des tolérances spécifiques sur les paquets d'électrons, qui sont définies dans ce rapport. Les études pour la conception de la Phase Préliminaire du CTF3 sont détaillées, en particulier le nouveau procédé d'injection avec les déflecteurs RF. Les tests de haute puissance réalisés sur ces cavités déflectrices avant leur installation dans l'anneau sont également décrits. L'activité de mise en fonctionnement de l'expérience est présentée en comparant les mesures faites avec le faisceau aux simulations et calculs théoriques. Finalement, les expériences de multiplication de fréquence des paquets d'électrons sont décrites et analysées. On montre qu'une très bonne efficacité de combinaison est possible après optimisation des paramètres de l'injection et des déflecteurs RF. En plus de l'expérience acquise sur l'utilisation de ces déflecteurs, des conclusions importantes pour les futures activités CTF3 et CLIC sont tirées de cette première démonstration de la multiplication de fréquence des paquets d'électrons par injection RF dans un anneau isochrone.<br/><br/>The Compact LInear Collider (CLIC) collaboration studies the possibility of building a multi-TeV (3 TeV centre-of-mass), high-luminosity (1034 cm-2s-1) electron-positron collider for particle physics. The CLIC scheme is based on high-frequency (30 GHz) linear accelerators powered by a low-energy, high-intensity drive beam running parallel to the main linear accelerators (Two-Beam Acceleration concept). One of the main challenges to realize this scheme is to generate the drive beam in a low-frequency accelerator and to achieve the required high-frequency bunch structure needed for the final acceleration. In order to provide bunch frequency multiplication, the main manipulation consists in sending the beam through an isochronous combiner ring using radio-frequency (RF) deflectors to inject and combine electron bunches. However, such a scheme has never been used before, and the first stage of the CLIC Test Facility 3 (CTF3) project aims at a low-charge demonstration of the bunch frequency multiplication by RF injection into an isochronous ring. This proof-of-principle experiment, which was successfully performed at CERN in 2002 using a modified version of the LEP (Large Electron Positron) pre-injector complex, is the central subject of this report. The bunch combination experiment consists in accelerating in a linear accelerator five pulses in which the electron bunches are spaced by 10 cm, and combining them in an isochronous ring to obtain one pulse in which the electron bunches are spaced by 2 cm, thus achieving a bunch frequency multiplication of a factor five, and increasing the charge per pulse by a factor five. The combination is done by means of RF deflecting cavities that create a time-dependent bump inside the ring, thus allowing the interleaving of the bunches of the five pulses. This process imposes several beam dynamics constraints, such as isochronicity, and specific tolerances on the electron bunches that are defined in this report. The design studies of the CTF3 Preliminary Phase are detailed, with emphasis on the novel injection process using RF deflectors. The high power tests performed on the RF deflectors prior to their installation in the ring are also reported. The commissioning activity is presented by comparing beam measurements to model simulations and theoretical expectations. Eventually, the bunch frequency multiplication experiments are described and analysed. It is shown that the process of bunch frequency multiplication is feasible with a very good efficiency after a careful optimisation of the injection and RF deflector parameters. In addition to the experience acquired in the operation of these RF deflectors, important conclusions for future CTF3 and CLIC activities are drawn from this first demonstration of the bunch frequency multiplication by RF injection into an isochronous ring.<br/><br/>La collaboration CLIC (Compact LInear Collider, collisionneur linéaire compact) étudie la possibilité de réaliser un collisionneur électron-positon linéaire à haute énergie (3 TeV) pour la recherche en physique des particules. Le projet CLIC se fonde sur l'utilisation de cavités accélératrices à haute fréquence (30 GHz). La puissance nécessaire à ces cavités est fournie par un faisceau d'électrons de basse énergie et de haut courant, appelé faisceau de puissance, circulant parallèlement à l'accélérateur linéaire principal (procédé appelé « Accélération à Double Faisceau »). Dans ce schéma, un des principaux défis est la réalisation du faisceau de puissance, qui est d'abord généré dans un complexe accélérateur à basse fréquence, puis transformé pour obtenir une structure temporelle à haute fréquence nécessaire à l'alimentation des cavités accélératrices de l'accélérateur linéaire principal. La structure temporelle à haute fréquence des paquets d'électrons est obtenue par le procédé de multiplication de fréquence, dont la manipulation principale consiste à faire circuler le faisceau d'électrons dans un anneau isochrone en utilisant des déflecteurs radio-fréquence (déflecteurs RF) pour injecter et combiner les paquets d'électrons. Cependant, ce type de manipulation n'a jamais été réalisé auparavant et la première phase de la troisième installation de test pour CLIC (CLIC Test Facility 3 ou CTF3) a pour but la démonstration à faible charge du procédé de multiplication de fréquence par injection RF dans un anneau isochrone. L'expérience consiste à accélérer cinq impulsions, puis à les combiner dans un anneau isochrone pour obtenir une seule impulsion dans laquelle la fréquence des paquets d'électrons et le courant sont multipliés par cinq. Cette combinaison est réalisée au moyen de structures déflectrices RF qui créent dans l'anneau une déformation locale et dépendante du temps de la trajectoire du faisceau. Les résultats de cette expérience, qui a été réalisée avec succès au CERN au cours de l?année 2002 en utilisant une version modifiée du pré-injecteur du grand collisionneur électron-positon LEP (Large Electron Positon), sont présentés en détail.

Artificial evolution on network structures : how time and space influence dynamics

Abstract The main objective of this work is to show how the choice of the temporal dimension and of the spatial structure of the population influences an artificial evolutionary process. In the field of Artificial Evolution we can observe a common trend in synchronously evolv¬ing panmictic populations, i.e., populations in which any individual can be recombined with any other individual. Already in the '90s, the works of Spiessens and Manderick, Sarma and De Jong, and Gorges-Schleuter have pointed out that, if a population is struc¬tured according to a mono- or bi-dimensional regular lattice, the evolutionary process shows a different dynamic with respect to the panmictic case. In particular, Sarma and De Jong have studied the selection pressure (i.e., the diffusion of a best individual when the only selection operator is active) induced by a regular bi-dimensional structure of the population, proposing a logistic modeling of the selection pressure curves. This model supposes that the diffusion of a best individual in a population follows an exponential law. We show that such a model is inadequate to describe the process, since the growth speed must be quadratic or sub-quadratic in the case of a bi-dimensional regular lattice. New linear and sub-quadratic models are proposed for modeling the selection pressure curves in, respectively, mono- and bi-dimensional regu¬lar structures. These models are extended to describe the process when asynchronous evolutions are employed. Different dynamics of the populations imply different search strategies of the resulting algorithm, when the evolutionary process is used to solve optimisation problems. A benchmark of both discrete and continuous test problems is used to study the search characteristics of the different topologies and updates of the populations. In the last decade, the pioneering studies of Watts and Strogatz have shown that most real networks, both in the biological and sociological worlds as well as in man-made structures, have mathematical properties that set them apart from regular and random structures. In particular, they introduced the concepts of small-world graphs, and they showed that this new family of structures has interesting computing capabilities. Populations structured according to these new topologies are proposed, and their evolutionary dynamics are studied and modeled. We also propose asynchronous evolutions for these structures, and the resulting evolutionary behaviors are investigated. Many man-made networks have grown, and are still growing incrementally, and explanations have been proposed for their actual shape, such as Albert and Barabasi's preferential attachment growth rule. However, many actual networks seem to have undergone some kind of Darwinian variation and selection. Thus, how these networks might have come to be selected is an interesting yet unanswered question. In the last part of this work, we show how a simple evolutionary algorithm can enable the emrgence o these kinds of structures for two prototypical problems of the automata networks world, the majority classification and the synchronisation problems. Synopsis L'objectif principal de ce travail est de montrer l'influence du choix de la dimension temporelle et de la structure spatiale d'une population sur un processus évolutionnaire artificiel. Dans le domaine de l'Evolution Artificielle on peut observer une tendence à évoluer d'une façon synchrone des populations panmictiques, où chaque individu peut être récombiné avec tout autre individu dans la population. Déjà dans les année '90, Spiessens et Manderick, Sarma et De Jong, et Gorges-Schleuter ont observé que, si une population possède une structure régulière mono- ou bi-dimensionnelle, le processus évolutionnaire montre une dynamique différente de celle d'une population panmictique. En particulier, Sarma et De Jong ont étudié la pression de sélection (c-à-d la diffusion d'un individu optimal quand seul l'opérateur de sélection est actif) induite par une structure régulière bi-dimensionnelle de la population, proposant une modélisation logistique des courbes de pression de sélection. Ce modèle suppose que la diffusion d'un individu optimal suit une loi exponentielle. On montre que ce modèle est inadéquat pour décrire ce phénomène, étant donné que la vitesse de croissance doit obéir à une loi quadratique ou sous-quadratique dans le cas d'une structure régulière bi-dimensionnelle. De nouveaux modèles linéaires et sous-quadratique sont proposés pour des structures mono- et bi-dimensionnelles. Ces modèles sont étendus pour décrire des processus évolutionnaires asynchrones. Différentes dynamiques de la population impliquent strategies différentes de recherche de l'algorithme résultant lorsque le processus évolutionnaire est utilisé pour résoudre des problèmes d'optimisation. Un ensemble de problèmes discrets et continus est utilisé pour étudier les charactéristiques de recherche des différentes topologies et mises à jour des populations. Ces dernières années, les études de Watts et Strogatz ont montré que beaucoup de réseaux, aussi bien dans les mondes biologiques et sociologiques que dans les structures produites par l'homme, ont des propriétés mathématiques qui les séparent à la fois des structures régulières et des structures aléatoires. En particulier, ils ont introduit la notion de graphe sm,all-world et ont montré que cette nouvelle famille de structures possède des intéressantes propriétés dynamiques. Des populations ayant ces nouvelles topologies sont proposés, et leurs dynamiques évolutionnaires sont étudiées et modélisées. Pour des populations ayant ces structures, des méthodes d'évolution asynchrone sont proposées, et la dynamique résultante est étudiée. Beaucoup de réseaux produits par l'homme se sont formés d'une façon incrémentale, et des explications pour leur forme actuelle ont été proposées, comme le preferential attachment de Albert et Barabàsi. Toutefois, beaucoup de réseaux existants doivent être le produit d'un processus de variation et sélection darwiniennes. Ainsi, la façon dont ces structures ont pu être sélectionnées est une question intéressante restée sans réponse. Dans la dernière partie de ce travail, on montre comment un simple processus évolutif artificiel permet à ce type de topologies d'émerger dans le cas de deux problèmes prototypiques des réseaux d'automates, les tâches de densité et de synchronisation.

Quadrant/octant sequencing and the role of coherent structures in bed load sediment entrainment

To permit the tracking of turbulent flow structures in an Eulerian frame from single-point measurements, we make use of a generalization of conventional two-dimensional quadrant analysis to three-dimensional octants. We characterize flow structures using the sequences of these octants and show how significance may be attached to particular sequences using statistical mull models. We analyze an example experiment and show how a particular dominant flow structure can be identified from the conditional probability of octant sequences. The frequency of this structure corresponds to the dominant peak in the velocity spectra and exerts a high proportion of the total shear stress. We link this structure explicitly to the propensity for sediment entrainment and show that greater insight into sediment entrainment can be obtained by disaggregating those octants that occur within the identified macroturbulence structure from those that do not. Hence, this work goes beyond critiques of Reynolds stress approaches to bed load entrainment that highlight the importance of outward interactions, to identifying and prioritizing the quadrants/octants that define particular flow structures. Key Points <list list-type=''bulleted'' id=''jgrf20196-list-0001''> <list-item id=''jgrf20196-li-0001''>A new method for analysing single point velocity data is presented <list-item id=''jgrf20196-li-0002''>Flow structures are identified by a sequence of flow states (termed octants) <list-item id=''jgrf20196-li-0003''>The identified structure exerts high stresses and causes bed-load entrainment