Decentralized Clearing in Financial Networks

We consider a situation in which agents have mutual claims on each other, summarized in a liability matrix. Agents' assets might be insufficient to satisfy their liabilities leading to defaults. In case of default, bankruptcy rules are used to specify the way agents are going to be rationed. A clearing payment matrix is a payment matrix consistent with the prevailing bankruptcy rules that satisfies limited liability and priority of creditors. Since clearing payment matrices and the corresponding values of equity are not uniquely determined, we provide bounds on the possible levels equity can take. Unlike the existing literature, which studies centralized clearing procedures, we introduce a large class of decentralized clearing processes. We show the convergence of any such process in finitely many iterations to the least clearing payment matrix. When the unit of account is sufficiently small, all decentralized clearing processes lead essentially to the same value of equity as a centralized clearing procedure. As a policy implication, it is not necessary to collect and process all the sensitive data of all the agents simultaneously and run a centralized clearing procedure.

Adaptive Sampling with Mobile Sensor Networks

Mobile sensor networks have unique advantages compared with wireless sensor networks. The mobility enables mobile sensors to flexibly reconfigure themselves to meet sensing requirements. In this dissertation, an adaptive sampling method for mobile sensor networks is presented. Based on the consideration of sensing resource constraints, computing abilities, and onboard energy limitations, the adaptive sampling method follows a down sampling scheme, which could reduce the total number of measurements, and lower sampling cost. Compressive sensing is a recently developed down sampling method, using a small number of randomly distributed measurements for signal reconstruction. However, original signals cannot be reconstructed using condensed measurements, as addressed by Shannon Sampling Theory. Measurements have to be processed under a sparse domain, and convex optimization methods should be applied to reconstruct original signals. Restricted isometry property would guarantee signals can be recovered with little information loss. While compressive sensing could effectively lower sampling cost, signal reconstruction is still a great research challenge. Compressive sensing always collects random measurements, whose information amount cannot be determined in prior. If each measurement is optimized as the most informative measurement, the reconstruction performance can perform much better. Based on the above consideration, this dissertation is focusing on an adaptive sampling approach, which could find the most informative measurements in unknown environments and reconstruct original signals. With mobile sensors, measurements are collect sequentially, giving the chance to uniquely optimize each of them. When mobile sensors are about to collect a new measurement from the surrounding environments, existing information is shared among networked sensors so that each sensor would have a global view of the entire environment. Shared information is analyzed under Haar Wavelet domain, under which most nature signals appear sparse, to infer a model of the environments. The most informative measurements can be determined by optimizing model parameters. As a result, all the measurements collected by the mobile sensor network are the most informative measurements given existing information, and a perfect reconstruction would be expected. To present the adaptive sampling method, a series of research issues will be addressed, including measurement evaluation and collection, mobile network establishment, data fusion, sensor motion, signal reconstruction, etc. Two dimensional scalar field will be reconstructed using the method proposed. Both single mobile sensors and mobile sensor networks will be deployed in the environment, and reconstruction performance of both will be compared.In addition, a particular mobile sensor, a quadrotor UAV is developed, so that the adaptive sampling method can be used in three dimensional scenarios.

The Planned and the Emergent: An Alternative Model of Learning and Literacy

Within academic institutions, writing centers are uniquely situated, socially rich sites for exploring learning and literacy. I examine the work of the Michigan Tech Writing Center's UN 1002 World Cultures study teams primarily because student participants and Writing Center coaches are actively engaged in structuring their own learning and meaning-making processes. My research reveals that learning is closely linked to identity formation and leading the teams is an important component of the coaches' educational experiences. I argue that supporting this type of learning requires an expanded understanding of literacy and significant changes to how learning environments are conceptualized and developed. This ethnographic study draws on data collected from recordings and observations of one semester of team sessions, my own experiences as a team coach and UN 1002 teaching assistant, and interviews with Center coaches prior to their graduation. I argue that traditional forms of assessment and analysis emerging from individualized instruction models of learning cannot fully account for the dense configurations of social interactions identified in the Center's program. Instead, I view the Center as an open system and employ social theories of learning and literacy to uncover how the negotiation of meaning in one context influences and is influenced by structures and interactions within as well as beyond its boundaries. I focus on the program design, its enaction in practice, and how engagement in this type of writing center work influences coaches' learning trajectories. I conclude that, viewed as participation in a community of practice, the learning theory informing the program design supports identity formation —a key aspect of learning as argued by Etienne Wenger (1998). The findings of this study challenge misconceptions of peer learning both in writing centers and higher education that relegate peer tutoring to the role of support for individualized models of learning. Instead, this dissertation calls for consideration of new designs that incorporate peer learning as an integral component. Designing learning contexts that cultivate and support the formation of new identities is complex, involves a flexible and opportunistic design structure, and requires the availability of multiple forms of participation and connections across contexts.

L’étiologie des différences individuelles dans le contrôle de soi à la petite enfance : une étude des facteurs génétiques et environnementaux

Contexte et objectifs. Le contrôle de soi serait, selon Gottfredson et Hirschi (1990), le meilleur prédicteur de la délinquance. Il serait déterminé, selon les auteurs, exclusivement par les facteurs environnementaux (compétences parentales, surveillance et punition) et ce, avant l'âge de sept ans. Il ne serait pas question des facteurs génétiques dans l'étiologie du contrôle de soi. Or, plusieurs études récentes menées à l'adolescence et à l'âge adulte avancent que le contrôle de soi serait d'origine partiellement génétique. Deux objectifs seront poursuivis. D'abord, considérant que le contrôle de soi, tel que décrit par Gottfredson et Hirschi (1990), n'ait jamais été étudié spécifiquement à la petite enfance, il a été nécessaire d'opérationnaliser le construit à la petite enfance à partir des informations existantes sur le contrôle de soi. Ensuite, il s'agira d'estimer l’influence relative des facteurs génétiques et environnementaux sur le contrôle de soi à 18, 30 et 48 mois. Méthodologie. En tout, 672 familles de jumeaux monozygotes ou dizygotes de la grande région métropolitaine de Montréal ont pris part à l'Étude des jumeaux nouveau-nés du Québec. Les items utilisés proviennent du Child Behavior Checklist (Achenbach, 1994) et ont été obtenus via les parents des jumeaux. La zygotie a été évaluée à l’aide du Zygosity Questionnaire for Young Twins (Goldsmith, 1991) et le sexe a été déterminé par les assistants de recherché. Trois temps de mesures furent étudiés : 18 mois (n = 664), 30 mois (n = 617) et 48 mois (n = 531). Résultats. Les résultats des analyses factorielles confirmatoires suggèrent par le biais des estimés qu'il soit possible de générer un facteur du contrôle de soi à la petite enfance à partir des indicateurs sélectionnés et que ceux-ci se regroupent sous l'égide d'un seul facteur. Les résultats concernant l’étiologie montrent que les différences individuelles observées seraient, majoritairement influencées par les facteurs génétiques (additifs ou de dominance) suivis par les environnements uniques. Conclusion. Les résultats suggèrent que les facteurs génétiques jouent un rôle important dans l’étiologie des différences individuelles dans le contrôle de soi tôt dans le développement alors que les environnements communs ne seraient pas impliqués. Les résultats sont compatibles avec les études menées à l'adolescence et à l'âge adulte et sont en contradiction avec les postulats de Gottfredson et Hirschi (1990).

Investigating the Role of PDE4D1/2 in Vascular Smooth Muscle Cell Desensitization

Thesis (Master, Biochemistry) -- Queen's University, 2016-10-14 02:44:01.604

ROLE OF THE FRONTAL EYE FIELD, SUPERIOR COLLICULUS, AND BASAL GANGLIA IN FLEXIBLE SACCADE BEHAVIOR

A distributed network of cortical and subcortical brain regions mediates the control of voluntary behavior, but it is unclear how this complex system may flexibly shift between different behavioral events. This thesis describes the neurophysiological changes in several key nuclei across the brain during flexible behavior, using saccadic eye movements in rhesus macaque monkeys. We examined five nuclei critical for saccade initiation and modulation: the frontal eye field (FEF) in the cerebral cortex, the subthalamic nucleus (STN), caudate nucleus (CD), and substantia nigra pars reticulata (SNr) in the basal ganglia (BG), and the superior colliculus (SC) in the midbrain. The first study tested whether a ‘threshold’ theory of how neuronal activity cues saccade initiation is consistent with the flexible control of behavior. The theory suggests there is a fixed level of FEF and SC neuronal activation at which saccades are initiated. Our results provide strong evidence against a fixed saccade threshold in either structure during flexible behavior, and indicate that threshold variability might depend on the level of inhibitory signals applied to the FEF or SC. The next two studies investigated the BG network as a likely candidate to modulate a saccade initiation mechanism, based on strong inhibitory output signals from the BG to the FEF and SC. We investigated the STN and CD (BG input), and the SNr (BG oculomotor output) to examine changes across the BG network. This revealed robust task-contingent shifts in BG signaling (Chapter 3), which uniquely impacted saccade initiation according to behavioral condition (Chapters 3 and 4). The thesis concludes with a published short review of the mechanistic effects of BG deep brain stimulation (Chapter 5), and a general discussion including proof of concept saccade behavioral changes in an MPTP-induced Parkinsonian model (Chapter 6). The studies presented here demonstrate that the conditions for saccade initiation by the FEF and SC vary according to behavioral condition, while simultaneously, large-scale task dependent shifts occur in BG signaling consistent with the observed modulation of FEF and SC activity. Taken together, these describe a mechanistic framework by which the cortico-BG loop may contribute to the flexible control of behavior.

CLASHES IN CONFINEMENT: MEN’S GENDERED EXPERIENCES WITH CONFLICT IN CANADIAN PRISONS

This dissertation presents the results of in-depth qualitative interviews with twenty-three formerly imprisoned men regarding their lived experience with prison conflict and the pain of incarceration. The results suggest that prison is a gendered ‘total institution’ (Goffman 1961). The pains that men experience in prison are uniquely gendered in that the deprivations imposed by incarceration– deprivation of autonomy, liberty, goods and services, heterosexual sex, and security (Sykes 1958) – in the reverse, define idealized masculinity as it is currently socially constructed: self-reliance, independence, toughness or invulnerability, material and economic success, and heterosexual prowess. From these shared deprivations emerges a gendered code of conduct that perpetuates a hierarchy among incarcerated men by constructing violent masculinity as a subcultural norm. The results suggest that the gender code in prison represents a set of rules that create opportunities for men to police each other’s gender performance and make claims to masculine statuses. Because status is inextricably tied to survival in this context, many men feel pressured to perform violent masculinities in prison despite privately subscribing to a non-violent sense of self-concept. The results suggest that violence is an expressive and instrumental resource for men in prison. A gender theory of prison violence, methodological findings, theoretical implications, ethical considerations and the short and long term aftermath of violent prison conflict are discussed.

Practical, appropriate, empirically-validated guidelines for designing educational games

There has recently been a great deal of interest in the potential of computer games to function as innovative educational tools. However, there is very little evidence of games fulfilling that potential. Indeed, the process of merging the disparate goals of education and games design appears problematic, and there are currently no practical guidelines for how to do so in a coherent manner. In this paper, we describe the successful, empirically validated teaching methods developed by behavioural psychologists and point out how they are uniquely suited to take advantage of the benefits that games offer to education. We conclude by proposing some practical steps for designing educational games, based on the techniques of Applied Behaviour Analysis. It is intended that this paper can both focus educational games designers on the features of games that are genuinely useful for education, and also introduce a successful form of teaching that this audience may not yet be familiar with.

Convergence time to equilibrium distributions of autonomous and periodic non-autonomous graphs

We present some estimates of the time of convergence to the equilibrium distribution in autonomous and periodic non-autonomous graphs, with ergodic stochastic adjacency matrices, using the eigenvalues of these matrices. On this way we generalize previous results from several authors, that only considered reversible matrices.