Thesis (Ph. D.)--Miami University, Dept. of Psychology, 2007. / Title from second page of PDF document. Includes bibliographical references (p. 155-160).

La perception visuelle de l’espace est largement déterminée par les capacités visuelles des individus. Cependant, la recherche sur l’influence de variables dites non visuelles semble indiquer une importance déterminante des dimensions corporelle et émotionnelle sur la perception visuelle. Dans cette thèse, nous nous sommes intéressés à la perception des distances et avons tenté de comprendre en quoi nos perceptions pouvaient refléter la nature de nos interactions sensorimotrices avec notre environnement. Dans une première étude nous avons montré que des contraintes d’actions, tel que le coût énergétique, générées par les dispositions de l’environnement, pouvaient avoir une influence sur la perception de distances allocentriques. Dans une seconde étude, nous avons tenté de mettre en évidence le rôle du processus d’intégration sensorimotrice dans des tâches d’évaluation de distances, ainsi que de comprendre l’influence des modalités non visuelles, telles que l’audition et la motricité, dans ce même type de tâche. Enfin, dans une troisième étude, nous nous sommes intéressés au concept de fluence – i.e., information métacognitive renseignant le système sur la qualité de ses interactions dans son environnement – et proposons l’idée selon laquelle ce signal contenu dans le flux perceptif permettrait d’expliquer différentes variations perceptives liées aux contraintes de nos actions. Finalement, cette thèse défend une approche unifiée de la perception, selon laquelle la limite entre les concepts d’action et de perception devrait être repensée afin de rendre compte de la nature sensorimotrice de nos connaissances. / Visual perception of space is mainly known as depending upon one’s vision capacity. However, research about the influence of non-visual variables seems to indicate that the body also plays an important role in visual perception. In this Ph.D. thesis, we support the idea that distance perception has to be studied as a function of the sensorimotor interactions between the individuals and their environment. In the first study, we showed that action constraints in the environment such as energetic cost could influence allocentric distance perception. In the second study, we focused on the role of the sensorimotor integration process in distance perception tasks, as well as the influence of non-visual variables such as audition and motor activity. In the third study, we investigated the phenomenology of perception, and more precisely in the relative fluency of motor activity. In other words, we focused here on the metacognitive feedback that emerges from the quality of the interactions with the environment. We highlighted that such a metacognitive signal could explain the influence of action constraints on distance perception. Finally, this work provides strong supports to the idea of an integrative approach of perception according to which the theoretical boundary between perception and action is questioned by the sensorimotor nature of our knowledge.

Établir une théorie de gravité quantique qui décrit de manière cohérente les propriétés quantiques de la matière et de l'espace-temps est l'un des défis majeurs de la physique théorique. Malgré plusieurs décennies de recherches, de nombreux problèmes conceptuels et techniques doivent encore être résolus. L'étude de modèles simplifiés donne des idées de résolution. La première partie de la thèse traite de la gravité quantique bidimensionnelle. À deux dimensions, la gravité quantique est beaucoup mieux comprise et de nombreux calculs peuvent être faits exactement. Si la gravité quantique bidimensionnelle a été largement étudiée quand elle est couplée à de la matière conforme, le cas de la matière non-conforme était très peu connu jusque récemment. Nous calculons d'abord l'action gravitationnelle pour un champ scalaire massif sur une surface de Riemann avec bords puis pour un fermion de Majorana massif sur une variété compacte. Ce dernier cas correspond à une CFT perturbée par une perturbation conforme et est d'ordinaire étudié grâce à l'ansatz de DDK, mais les résultats sont différents. Finalement, on calcule le spectre de l'action de Mabuchi dans l'approximation du minisuperespace. La seconde partie étudie les propriétés thermales des trous noirs dans le contexte de la correspondance AdS/CFT. On construit un modèle de mécanique quantique fondé sur les principes holographiques pour simuler la dynamique des trous noirs quantiques. Ce modèle permet d'obtenir des résultats numériques exacts. / Finding a theory of quantum gravity describing in a consistent way the quantum properties of matter and spacetime geometry is one of the greatest challenges of modern theoretical physics. However after several decades of research, many conceptual and technical issues are still to be resolved. Insights on these questions can be given by simplified toy models that allow for exact computations. The first part of the thesis deals with two-dimensional quantum gravity. In two dimensions quantum gravity is much better understood and many computations can be carried out exactly. Whereas two-dimensional quantum gravity coupled to conformal matter has been widely studied and is now well understood, much less was known until recently when matter is non-conformal. First we compute the gravitational action for a massive scalar field on a Riemann surface with boundaries and then for a massive Majorana fermion on a manifold without boundary. The latter case corresponds to a CFT perturbed by a conformal perturbation and is usually tackled through the DDK ansatz, but the results do not seem to match. Finally we give a minisuperspace computation of the spectrum of the Mabuchi action, a functional that appears in the gravitational action for a massive scalar field. In the second part we focus on black hole thermal behaviour which provides a lot of insight of how a theory of quantum gravity should look like. In the context of string theory the AdS/CFT correspondence provides powerful tools for understanding the microscopic origin of black holes thermodynamics. We construct a quantum mechanical toy model based on holographic principles to study the dynamics of quantum black holes.

This thesis examines how communication technology is used for creating a democratic and committed participation within collective action organizations (CAOs). This is achieved by illuminating how organizations' structure and culture relate to their communication. It’s done by in-depth interviews with network-based movements and association-based organizations, and analyses of their digital newsletters. The analysis is based on affordance-driven theory, capturing the interaction between organizations and their digital platforms. The focus lies on how internal democracy and collective action are afforded or constrained to some degrees. Degrees of deliberation for creating common ground and active participation are made visible by using the concept of communicative action. Theories within social movement studies, such as collective action, broaden the understanding of how the perception of digital tools shapes and is shaped by their structure and culture. The results show that the usage and coordination of communication channels is essential for the practice of internal democracy in everyday work, beyond annual meetings and board meetings. Independent chat-based platforms enable an increased control of conversations, cooperation and coordination, while information overload and effective decision- making processes can hinder democratic participation. Commercial social media platforms such as Facebook enables new flows of engagement and connectivity but constrains coordination and control of the framing process within Facebook groups. Additionally, unpredictable algorithms and advertising policy on Facebook makes it difficult to reach out. Overall, the study suggests a broadened view of communication, where communication and usage of digital media should not be considered as instrumental entities. Rather, it is strongly related to how channels are being coordinated, how organizations are organized and the view of participation. Formal structures can both hinder and enable increased communicative action that contributes to democratic participation.

Published Article / Magnesium is the second most abundant intracellular cation with many control and regulatory functions. It regulates energy production and utilization and modulates activity of membrane ionic channels. Magnesium has direct control effects on cardiac myocyte ion channels making it useful in certain arrhythmias. Calcium is responsible for pacemaker excitation and for excitation-contraction coupling in myocytes but increased intracellular calcium produces early and late afterdepolarisations initiating arrhythmias. Magnesium regulates calcium channel activity preventing raised intracellular levels. Potassium channel activity is enhanced by magnesium hyperpolarizing the cell reducing arrhythmia generation. Magnesium is effective against long QT Torsade de Pointes. In rapid atrial fibrillation magnesium produces rate control slowing AV nodal conduction. Magnesium prevents digitalis toxicity due to associated hypomagnesemia.

No description available.

This thesis investigated the effects of intergroup contact on different types of collective action tendencies among advantaged and disadvantaged groups. Studies 1 and 2 tested the simultaneous effects of intergroup contact and established predictors of collective action on collective action tendencies and ingroup and outgroup oriented policies among Blacks and Whites in South Africa, and compared the effects of intergroup contact and social identity on collective action tendencies via relative deprivation and group efficacy. The findings revealed that while social identity was positively associated with collective action tendencies, both directly and indirectly, effects of contact were negative and indirect via relative deprivation and group efficacy. Studies 3 and 4 investigated the effects of contact and social identity on collective action tendencies via perceived threats. Using data from Turkish and Kurdish groups in Turkey, I found that social identity predicted collective action tendencies positively, both directly and indirectly, while it predicted outgroup attitudes negatively and indirectly via perceived threats. Intergroup contact, on the other hand, predicted outgroup attitudes positively, both directly and indirectly, and collective action tendencies negatively via perceived threats. In Study 5, intergroup contact was positively associated, both directly and indirectly, via perspective taking and collective guilt, associated with outgroup oriented collective action tendencies. In Study 6, the effect of social identity on ingroup oriented collective action was positive and direct. Intergroup contact with the weaker minority group, on the other hand, was positively associated with outgroup oriented collective action tendencies via perspective taking. Additionally, intergroup contact with the majority outgroup moderated this relationship. When participants reported more contact with the majority group, intergroup contact with the weaker minority was not associated with outgroup oriented collective action tendencies. However, when the participants reported less contact with the majority group, intergroup contact positively predicted outgroup oriented collective action tendencies. Finally, Study 7 investigated the effects of two different dimensions of contact, contact with the majority and minority on collective action, via outgroup attitudes, dual-identification, and common ingroup identity in a three wave longitudinal design (N=610) among Turkish Cypriots in northern Cyprus. While the results did not support findings from the previous studies on the so-called paradoxical effects of contact on collective action tendencies, they revealed a robust negative reciprocal relationship between outgroup attitudes toward Greek Cypriots and collective action tendencies.

published_or_final_version / abstract / Zoology / Master / Master of Philosophy

Collecting and annotating videos of realistic human actions is tedious, yet critical for training action recognition systems. We propose a method to actively request the most useful video annotations among a large set of unlabeled videos. Predicting the utility of annotating unlabeled video is not trivial, since any given clip may contain multiple actions of interest, and it need not be trimmed to temporal regions of interest. To deal with this problem, we propose a detection-based active learner to train action category models. We develop a voting-based framework to localize likely intervals of interest in an unlabeled clip, and use them to estimate the total reduction in uncertainty that annotating that clip would yield. On three datasets, we show our approach can learn accurate action detectors more efficiently than alternative active learning strategies that fail to accommodate the "untrimmed" nature of real video data. / text

Modular reinforcement learning is an approach to resolve the curse of dimensionality problem in traditional reinforcement learning. We design and implement a modular reinforcement learning algorithm, which is based on three major components: Markov decision process decomposition, module training, and global action selection. We define and formalize module class and module instance concepts in decomposition step. Under our framework of decomposition, we train each modules efficiently using SARSA($\lambda$) algorithm. Then we design, implement, test, and compare three action selection algorithms based on different heuristics: Module Combination, Module Selection, and Module Voting. For last two algorithms, we propose a method to calculate module weights efficiently, by using standard deviation of Q-values of each module. We show that Module Combination and Module Voting algorithms produce satisfactory performance in our test domain. / text