In seismology, an important goal is to attain a better understanding of the earthquake process. In this study of the physics of aftershock generation, I couple statistical analysis with modelling of physical processes in the postseismic period. I present a theoretical formulation for the distribution of interevent times for aftershock sequences obeying the empirically well established Omori law. As opposed to claims by other authors, this work demonstrates that the duration of the time interval between two successive earthquakes cannot be used to identify whether or not they belong to the same aftershock sequence or occur as a result of the same underlying process. This implies that a proper understanding of earthquake interevent time distributions is necessary before conclusions regarding the physics of the earthquake process are drawn. In a discussion of self-organised criticality (SOC) in relation to empirical laws in seismology, I find that Omori's law for aftershocks cannot be used as evidence for the theory of SOC. Instead, I consider that the occurrence of aftershocks in accordance with Omori's law is a result of a physical process that can be modelled and understood. I analyse characteristic features in the spatiotemporal distribution of aftershocks in the south Iceland seismic zone, following the two M6.5 June 2000 earthquakes and a M4.5 earthquake in September, 1999. These features include an initially constant aftershock rate, whose duration is larger following a larger main shock, and a subsequent power law decay that is interrupted by distinct and temporary deviations in terms of rate increases and decreases. Based on pore pressure diffusion modelling, I interpret these features in terms of main shock initiated diffusion processes. I conclude that thorough data analysis and physics-based modelling are essential components in attempts to improve our understanding of processes governing the occurrence of earthquakes.

Service integration is central to current government strategy for promoting positive outcomes for young people with educational and additional needs, yet evidence to support the efficacy of this strategy remains elusive. A review of the literature finds that many of the facilitators of successful multi-agency working are at the intra-group level. These barriers and facilitating factors are organised into an Eco-systemic Model of Multi-Agency Working (EMMA) which addresses leadership processes, group-level interactions and problem-solving processes. The first stage of the study generates data for intervention materials to be used in the second stage. This is achieved by comparing the purposes and practices of each group at different systemic levels. This stage of the study also provides baseline questionnaire data for the second stage of the study. Consideration is given to the sources of conflict within each group, the strategies used to resolve these conflicts and the levels of hierarchical and systemic thinking within the participating multi-agency groups. The resulting analysis is found to fit well within the EMMA model and the distinctiveness of each of the systemic levels as well as their interdependence is discussed. Suggestions are made for improved multi-agency practices and new directions for the educational psychologist in facilitating improved practice are explored. Paper II Abstract In the first phase of this two-stage study, self-organised learning principles were proposed as a useful knowledge base upon which to draw when facilitating change in multi-agency groups. In this second phase, this hypothesis is put to the test. Data from the first phase is used in combination with wider research findings to design feedback materials for participating groups. Evidence gathered from ensuing meeting transcripts, interviews and questionnaire data is compared with baseline data gathered in the first phase to assess the impact of this intervention on group functioning. Evidence is presented of improved clarity of purpose, improved group functioning and early signs of improved outcomes, though results are highly variable between groups. Different levels of group functioning were found to be inter-dependent, lending support to an eco-systemic model of multi-agency working. Trait-based models of leadership and conflict resolution are challenged. It is argued that improving outcomes for young people is dependent upon the healthy functioning of multi-agency groups and that investing resources in reflective learning in multi-agency groups is a worthwhile step towards securing better outcomes for young people.

Ce travail de thèse ce focalise sur la croissance et la caractérisation de Nanofils (NFs) et de Microfils (µFs) de GaN. L'élaboration de telles structures est obtenue par épitaxie en phase vapeur d'organométalliques à partir de deux stratégies de croissances: l'une dite auto-organisée, réalisée sur substrat saphir, l'autre appelée sélective ou localisée, obtenue sur template GaN de polarité Ga. Quelque soit la stratégie employée, nous montrons que la croissance de structures verticales suivant l'axe c requièrent l'utilisation d'un flux de NH3 et d'un rapport V/III faible, lorsque nous les comparons avec les valeurs utilisées pour la réalisation de couches planaires de GaN. Les paramètres et les étapes de croissances ayant une influence sur le rapport d'aspect (hauteur/diamètre) sont étudiées et mises en évidence pour chacune des stratégies employées. Par ailleurs, les mécanismes de croissance ainsi que les propriétés structurales et optiques de ces objets sont caractérisés par MEB, MET, CL et µPL. En particulier, les expériences réalisées sur les µFs auto-organisés permettent d'observer et d'expliquer l'origine de la double polarité, de mettre en lueur la différence d'incorporation de dopants/d'impuretés entre les domaines Ga et N, d'identifier la présence de deux sections de propriétés électriques et optiques différentes, et de révéler la présence de deux types de résonances optiques: des Modes de galerie et des Modes de Fabry-Perot. D'autres part, nous étudions la courbure des dislocations vers les surfaces libres des NFs localisés et µFs auto-organisés, et pointons la présence de fautes d'empilement basales dans des régions de faibles dimensions. / This work focus on growth and characterization of GaN Nanowires (NWs) and Microwires (µWs). Such structures are obtained by Metal Organic Vapor Phase Epitaxy with two growth strategies: one called self-organized which is realized on sapphire, and the other named selective area growth which is obtained on a GaN Ga-polar template. Whatever the growth strategies employed, vertical growth of structures along the c axis requires the use of a low NH3 flux and V/III ratio, when they are compared with values used for planar growth of GaN. The influence of growth parameters and growth steps on aspect ratio (height/diameter) are studied and highlight for each growth strategies employed. Beside, growth mechanisms and structural and optical properties of such objects are characterized by SEM, TEM, CL and µPL. In particular, experiments realized on self-organized µWs enable us to observe and explain the origin of the double polarity, to highlight the dopants/impurities incorporation difference between Ga and N-domain, to identify two sections with differences in electrical and optical properties, and to reveal the presence of two types of optical resonances, identify as Whispering Gallery Modes and Fabry-Perot Modes. On the other hand, we study the bending of dislocations on free walls of localized NWs and self-organized µWs, and pointed out the presence of basal stacking faults in regions of small dimensions.

Viele Industrieunternehmen sind auf der Suche nach neuen Strategien für eine zukunftssichernde Produktentwicklung. Die Gründe dafür sind in den Herausforderungen zu suchen, die häufig in schnelle Änderungen von Kundenwünschen, der Verbreitung moderner Informations- und Kommunikationstechnologien, kürzeren Technologielebenszyklen, Forderungen nach ökologischer Nachhaltigkeit wie auch in der weiteren zunehmenden Vernetzung der Wirtschaft zu suchen. Die heutige Entwicklungsumgebung in Unternehmen, mit meist starren Abteilungsstrukturen, wenig Kommunikation mit den Kunden und zwischen den Abteilungen im Unternehmen sowie der Auslieferung eines auf einem einmal erstellen Lastenheft basierenden Produkten wird den Anforderungen nicht mehr gerecht. In diesem Zusammenhang rücken agile Vorgehensweisen gepaart mit additiven Fertigungsverfahren für physische Produkte in den Fokus der Entwicklung.