This current study empirically tested elements of Ehlers and Clark's (2000) cognitive model of Posttraumatic Stress Disorder (PTSD) symptom maintenance using path analysis and structural equation modeling (SEM). Ehlers and Clark's model suggests that a reciprocal relationship between cognitive appraisals of the traumatic event and characteristics of the trauma memory maintain symptoms by increasing one's sense of current threat. Participants in the current study were 405 undergraduates at a Midwestern university who each reported having experienced at least one traumatic event during his/her lifetime. Path analysis was utilized to examine the possibility that one's posttraumatic cognitions may mediate the relationship between the centrality of the traumatic event to one's sense of self and one's current level of PTSD symptoms. The reverse mediation was also tested for each of the PTSD symptom clusters. Results indicate that both event centrality and posttraumatic cognitions are unique and independent predictors of current symptom level. SEM procedures were used to examine possible mediation as well as to test a reciprocal relationship between these predictors. Results are generally consistent with those from the path analysis although additional research is necessary before any firm conclusions can be stated. Overall, the results of this study support aspects of the cognitive model of PTSD; cognitive appraisals of the self and memory characteristics of the event were highly related to levels of distress. However, the current study suggests that overly integrated trauma memories lead to greater distress and not poorly integrated ones as suggested by Ehlers and Clark. The relationship between trauma memories and PTSD is in need of further study as is the role of memory and cognitions in the temporal development of PTSD.

Sub-Riemannian geometry is the natural setting for studying dynamical systems, as noise often has a lower dimension than the dynamics it enters. This makes sub-Riemannian geometry an important field of study. In this thesis, we analysis some of the aspects of sub-Riemannian diffusion processes on manifolds. We first focus on studying the small-time asymptotics of sub-Riemannian diffusion bridges. After giving an overview of recent work by Bailleul, Mesnager and Norris on small-time fluctuations for the bridge of a sub-Riemannian diffusion, we show, by providing a specific example, that, unlike in the Riemannian case, small-time fluctuations for sub-Riemannian diffusion bridges can exhibit exotic behaviours, that is, qualitatively different behaviours compared to Brownian bridges. We further extend the analysis by Bailleul, Mesnager and Norris of small-time fluctuations for sub-Riemannian diffusion bridges, which assumes the initial and final positions to lie outside the sub-Riemannian cut locus, to the diagonal and describe the asymptotics of sub-Riemannian diffusion loops. We show that, in a suitable chart and after a suitable rescaling, the small-time diffusion loop measures have a non-degenerate limit, which we identify explicitly in terms of a certain local limit operator. Our analysis also allows us to determine the loop asymptotics under the scaling used to obtain a small-time Gaussian limit for the sub-Riemannian diffusion bridge measures by Bailleul, Mesnager and Norris. In general, these asymptotics are now degenerate and need no longer be Gaussian. We close by reporting on work in progress which aims to understand the behaviour of Brownian motion conditioned to have vanishing $N$th truncated signature in the limit as $N$ tends to infinity. So far, it has led to an analytic proof of the stand-alone result that a Brownian bridge in $\mathbb{R}^d$ from $0$ to $0$ in time $1$ is more likely to stay inside a box centred at the origin than any other Brownian bridge in time $1$.

La dernière décennie a vu l'exploitation d’application d’inspection automatique dans plusieurs domaines grâce à l’avancé des capteurs de vision et des méthodes d’analyse de texture et de segmentation d’images. Cependant, la nature difficile des images de chaussées (fortement texturée), la petite taille des défauts (fissures) conduisent au constat que l’inspection dans ce domaine est réalisée manuellement. Chaque année, en France, des opérateurs doivent visualiser des milliers de kilomètres d'images de route pour y relever des dégradations. Cette façon de faire est couteuse, lente et a un résultat plutôt subjectif. L’objectif de ce travail de thèse est de développer une méthode permettant la détection et la classification des fissures automatiquement sur ces images de chaussées. Le coeur de la thèse est une nouvelle méthode de segmentation, la Free Form Anisotropy (FFA). D'une part, elle permet de prendre en compte simultanément les attributs concernant la forme et l’intensité des pixels d’une fissure pour la détection. D’autre part, une nouvelle modélisation est utilisée en recherchant des chemins minima dans des graphes (images) afin de trouver la forme de la fissure dès qu'elle est présente dans l’image. Après la segmentation, l’extraction et la classification de défauts sont réalisées par une transformée de Hough et par le calcul de l’orientation locale des pixels. Les résultats expérimentaux ont été obtenus à partir de plusieurs bases d’images et compares avec des méthodes existantes. / These last decades have seen application of automatic inspection in many fields thanks to advanced vision sensors and image analysis methods. However, the difficult nature of pavement images, the small size of defects (cracks) lead to the fact that inspection in this area is done mostly manually. Each year in France, operator must view images of thousands kilometers of roads to detect these degradations. This method is expensive, slow and has a rather subjective result. The objective of this thesis is to develop a method for the detection and the classification of cracks on these pavement images automatically. In this thesis, a new method of segmentation has been developed: the Free Form Anisotropy (FFA). On one hand, this method allows to take into account both the features concerning form and intensity of cracks, for the detection. On the other hand, a new model is used to search minimum paths in graphs (images). This minimum path follows crack form when crack is present. After segmentation, extraction and classification of defects are performed by the Standard Hough Transform and by calculating local orientation of pixels. Experimental results have been obtained from different image databases and compared with other existing methods.

Sharp-wave ripples (SWR) generated in the CA3 subregion of the hippocampus (HC) during rest and sleep appear to coordinate memory consolidation to the neocortex (NC) by (1) reactivating small subsets of neurons (i.e. cell-assemblies) that encode recent waking experience and (2) propagating this information through the hippocampal formation. Although CA3 self-organizes SWRs in the absence of extrinsic inputs, cortical input to the HC conveyed by perforant path (PP) may influence SWR initiation nevertheless. Still, direct evidence that PP synaptic excitation can elicit SWRs is lacking, and it is unclear how this influence might compete or interact with self-organizing mechanisms. This dissertation tested the hypothesis that CA3's SWR pattern generator would self-organize its activity in the absence of PP input, but readily entrain to such input when present. Spontaneous SWRs (sSWR) occurred in slices prepared from the ventral portion of the mouse HC. Low-intensity electrical stimulation of PP afferents evoked short-latency field EPSPs in CA3 that were often followed by precisely timed evoked SWRs (eSWR). The network and single-cell characteristics of sSWRs and eSWRs were indistinguishable, indicative of a common patter generator. PP stimuli that followed sSWRs too closely usually failed to elicit eSWRs. Using a custom MATLAB/Simulink application to control PP stimulus timing during the ~250 ms sSWR refractory period revealed a statistically significant effect of stimulus delay (25, 50, 100, and 200 ms) on eSWR incidence, reaching a value of 0.72 (95% CI = [0.61, 0.81]) 200 ms after sSWR onset. In contrast, sSWR incidence at this time was much lower (95% CI = [0.015, 0.049]). Lesions targeting the direct PP input to CA3 substantially reduced eSWR incidence. In intact slices, eSWRs were readily evoked by stimulating the medial entorhinal cortex (MEC). In summary, PP input to CA3 from the MEC can initiate SWRs at times when self-organizing mechanisms generally cannot. Assuming sSWRs convey information to the NC, the ensuing refractory period might provide an opportunity for cortical feedback to reinforce the recently engaged cell-assembly. In the absence of such feedback, CA3 could revert to its default mode of self-organized replay.

The Casimir effect refers to the primarily attractive force between material bodies due to quantum fluctuations in the electromagnetic field. The Casimir effect is difficult to calculate in general, since it is sensitive to the exact shapes of the bodies and involves contributions from all frequencies. As a result, calculating the Casimir effect between general bodies usually requires a numerical approach. The worldline method computes Casimir energies by creating an ensemble of space-time paths corresponding to a virtual particle interacting with the bodies. This method was originally developed for a scalar fields coupled to an idealized background potential, rather than the vector electromagnetic field interacting with media. This thesis presents work on extending the worldline method to account for the material properties of the interacting bodies, and the polarizations of electromagnetism. This thesis starts by covering background material on path integrals, and quantizing the electromagnetic field in media. The electromagnetic field is decomposed in terms of two scalar fields for planar bodies, where these scalar fields correspond to the transverse-electric and transverse-magnetic polarizations of the electromagnetic field. The worldline path integrals are developed for both polarizations, and solved analytically. Next, numerical methods are developed and tested in the context of planar bodies. The starting positions, and scale of the paths, and shape of the paths are sampled via Monte Carlo methods. The transverse-magnetic path integral also requires specialized methods for estimating derivatives, and path construction. The analytical and numerical results for both worldline path integrals are in agreement with known solutions. Finally, specialized methods are developed for computing derivatives of the worldline Casimir-energy path integrals, allowing for efficient numerical computations of Casimir forces and torques.

Made available in DSpace on 2014-06-11T19:35:19Z (GMT). No. of bitstreams: 0 Previous issue date: 2011-04-15Bitstream added on 2014-06-13T19:24:55Z : No. of bitstreams: 1 lopes_al_dr_arafcl.pdf: 735527 bytes, checksum: 7abbf5aff44c84f06e921ddc6a20f181 (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / O objetivo do trabalho é analisar como o governo de Hugo Chávez se propôs a refundação do Estado venezuelano, através de um processo de elaboração de uma nova constituição e com base numa retórica nacionalista e bolivariana, que pretendia transformar radicalmente a estrutura econômica, mas acabou sendo limitado pela força da permanência do legado institucional do país construído sobre a dependência do petróleo e a lógica rentista. Para tanto, nos utilizamos de autores que trabalham com a dimensão institucional do desenvolvimento econômico e se preocupam em explicar porque diante de condições materiais parecidas ocorrem resultados bastante diferenciados no que se refere ao nível de desenvolvimento econômico alcançado. A resposta estaria nas trajetórias distintas de construção institucional, já que há arranjos que incentivam os atores a produzir e inovar, enquanto outros estimulam ações improdutivas e parasitárias. Nesse sentido procuramos mostrar que as instituições construídas ao longo do tempo na Venezuela, essencialmente, incentivaram a lógica rentista entre os atores sociais, dos empresários aos sindicatos. Para isso nos utilizamos dos conceitos de lock in e, principalmente, de path dependence que nos permitem qualificar a dimensão histórica do problema, mostrando como ao longo do tempo os atores adotaram estratégias e ações que se reforçaram e bloquearam qualquer mudança, já que os setores com maior poder de barganha dificultaram qualquer alteração nos arranjos existentes na medida em que foram favorecidos por eles. Inclusive, a principal fonte de path dependence são os rendimentos crescentes dos arranjos existentes, o que, no caso da Venezuela, torna muito difícil qualquer alteração no modelo rentista. O trabalho procura mostrar que, mesmo com Chávez que propõe um socialismo sob base rentista, ou seja, mantém o modelo ainda... / The purpose of this work is to analyze how the government of Hugo Chávez has proposed to overhaul the Venezuelan State, through a process of drafting a new constitution and based upon a nationalistic and Bolivarian rhetoric, which sought to radically transform the economic structure, but was limited by the strength of the permanence of the institutional legacy of the country which, in turn, was built up on the oil dependence and on a rentier logic basis. For this, we recur to authors that work with the institutional dimension of economic development and care in explaining why in the face of similar material conditions, distinct results regarding the level of accomplished economic development are achieved. The answer would lie in different paths of institutional construction, as there are arrangements that encourage the actors to produce and innovate, while others stimulate unproductive and predatory actions. We try to show that the institutions built over time in Venezuela, basically encouraged the rentier logic among the social actors, from the entrepreneurs to the work unions. For this we use the concept of lock-in, and especially the concept of path dependence. Both allow us to classify the historical dimension of the problem, showing how actors have continuously adopted strategies and actions which reinforced and blocked any possibility of changes, since the sectors with greater bargaining power hampered any modification in existing arrangements as they were benefited by them. Also the main source of path dependence are increasing returns of existing arrangements, which in the case of Venezuela, make any change in the rentier model rather difficult. This work shows that, even taking into account that Chávez proposes a rentier-based socialism, what means the model is kept even though nationalized, it still repeats what was done in previous decades, albeit with a social... (Complete abstract click electronic access below)

Made available in DSpace on 2014-06-11T19:24:17Z (GMT). No. of bitstreams: 0 Previous issue date: 2009-11-27Bitstream added on 2014-06-13T20:31:26Z : No. of bitstreams: 1 bezerra_cm_me_arafcl.pdf: 411923 bytes, checksum: 3d944238095336e490c57b13d9229122 (MD5) / Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / O objetivo deste trabalho é analisar como o processo de inovações tecnológicas é tratado pela Teoria dos Sistemas Complexos. A abordagem neoclássica tradicional, ao partir de pressupostos bastante restritivos sobre os agentes e os mercados, não é capaz de fornecer explicações plausíveis aos vários problemas econômicos da vida real. Ao desconsiderar a dinâmica dos fenômenos econômicos, essa abordagem foi incapaz de incorporar os aspectos do processo de inovação e mudança tecnológica. A abordagem evolucionária, nesse sentido, ao considerar a racionalidade limitada, incerteza e heterogeneidade presente em ambientes que exibem inovação, foi capaz de fornecer um tratamento mais próximo da realidade. A inovação é, então, entendida como uma mudança descontínua que altera as condições estruturais gerando desenvolvimento, progresso e evolução no sistema. Já abordagem dos sistemas complexos, ao apresentar um arcabouço não reducionista e que se fundamenta sobre uma perspectiva evolucionária e sistêmica, concebe a economia como um sistema composto por agentes heterogêneos que interagem entre si. Apesar do ambiente de incerteza nas decisões tomadas, os agentes procuram se adaptar às informações recebidas do meio e se auto-organizarem gerando com isso novos padrões de auto-ordenamento e estruturas emergentes. A modelagem, nesse sentido, tem por principal objetivo descobrir as propriedades emergentes resultantes da interação entre os agentes no sistema. Por fim chega-se a conclusão de que as inovações tecnológicas apresentaram resultados mais satisfatórios e mais condizentes quando analisadas dentro dessa perspectiva agent-based. / The purpose of this dissertation is to discuss how processes of technological innovation are analyzed by Complex Systems Theory. Traditional neoclassical approach is unable to provide plausible explanations of a number of real world economic issues, as it starts from very restrictive assumptions on agents and markets. By neglecting economic phenomena dynamics, it has been unable of comprehend some aspects of innovation and technical change processes under its purview. Evolutionary economics, by taking issues such as bounded rationality, uncertainty and heterogeneity in environments with innovation, has been better positioned to afford a closer-to-reality treatment. In this approach, innovation is seen as a disruptive change that alters the system’s structural conditions, generating development, progress, and evolution. Accordingly, the complex systems approach, by furnishing a non-reductionist framework and in being supported on an evolutionary and systemic perspective, conceives the economy as a system composed by interactions among heterogeneous agents. Nevertheless uncertainty in the decision-making process, yet the agents endeavors to adapt to information coming from the environment and to self-organize. In doing so, they generate new patterns of self-ordained emerging structures. Modeling techniques, in this sense, aim primarily to uncover emerging properties resulting from agents’ interaction in the system. The main conclusion is that technological innovations are more successfully and more cogently described when analyzed from this agent-based perspective.

In the work of the Control Engineering research group of the Department of Computer Science, Electrical and Space Engineering, Signals and systems at Luleå University of Technology a need had arisen for a path planning algorithm. The ongoing research with Unmanned Aerial Vehicles(UAVs) had so far been done with any complicated paths being created manually with waypoints set by the uses. To remove this labourious part of the experimental process a path should be generated automatically by simply providing a program with the position of the UAV, the goal to which the user wants it to move, as well as information about the UAV's surroundings in the form of a 3D map.In addition to simply finding an available path through a  3D environment the path should also be adapted to the risks that the physical environment poses to a flying robot. This was achieved by adapting a previously developed algorithm, which did the simple path planning task well, by adding a penalty weight to areas near obstacles, pushing the generated path away from them.The planner was developed working with the OctoMap map system which represents the physical world by segmenting it into cubes of either open or occupied space. The open segments of these maps could then be used as vertices of a graph that the planning algorithm could traverse.The algorithm itself was written in C++ as a node of the Robot Operating System(ROS) software framework to allow it to smoothly interact with previously developed software used by the Control Engineering Robotics Group.The program was tested by simulations where the path planner ROS node was sent maps as well as UAV position and intended goal. These simulations provided valid paths, with the performance of the algorithm as well as the quality of the paths being evaluated for varying configurations of the planners parameters.The planner works well in simulation and is deemed ready for use in practical experiments.

How new regional growth paths emerge and what policy concepts are most adequate for nurturing their evolution constitute recurring themes in regional innovation and development studies. New industrial paths are often portrayed as the result of market-driven processes and Schumpeterian entrepreneurial efforts. This view goes along with a neoliberal policy approach that restricts the role of public interventions to setting up a suitable regulatory frame and supporting an entrepreneurial climate. The theoretical underpinnings and policy perspectives of this approach have been challenged by the innovation system literature, which offers a systemic view on the rise of new growth paths and advocates a more proactive role of public policy. This paper investigates the role of policy models beyond these traditional ones. We contrast different variants of systemic and multi-scalar policy concepts for new regional industrial path development. Our literature-based study shows that more recent models go beyond new path development and growth per se, paying more attention to the direction of innovation and change, and to policy approaches for achieving more sustainable forms of development. We scrutinize the theoretical and empirical bases of these new policy models and discuss why they are superior to neoliberal and older systemic ones.

>Magister Scientiae - MSc / This paper focuses on the newly revived interest to model free approach in finance. Instead of postulating some probability measure it emerges in a form of an outer-measure. We review the behavior of a market stock price and the stochastic assumptions imposed to the stock price when deriving the Black-Scholes formula in the classical case. Without any stochastic assumptions we derive the Black-Scholes formula using a model free approach. We do this by means of protocols that describe the market/game. We prove a statement that prices a European option in continuous time.