The basolateral complex of the amygdala (BLA) is a key component of the neuronal circuitry underlying the acquisition and the extinction of Pavlovian conditioned fear. The present series of experiments examined the role of neuronal activity and NMDA receptors (NMDAr) activation in the BLA on learning and relearning context conditioned fear and its extinction. Disruption of neuronal activity in the BLA prevented the acquisition of fear responses to a novel, a moderately familiar or a highly familiar context. It also prevented the reacquisition of fear responses to a conditioned or an extinguished context. Local blockade of NMDAr containing the NR2B subunit prior to training extinction or re-extinction impaired the short- and long-term loss of fear responses. In contrast, a similar blockade subsequent to training extinction or re-extinction left the long-term loss of fear responses unaffected. Disruption of neuronal activity in the BLA prior to training extinction and re-extinction depressed fear responses. It impaired the long-term loss of fear produced by extinction training but spared and even facilitated the long-loss of fear produced by re-extinction training when extinction had already been learned. The exact same outcome was observed when neuronal activity in the BLA was disrupted subsequent to training extinction and re-extinction. These findings suggest that the BLA is critical for both learning and relearning context conditioned fear. In contrast, the BLA is necessary for learning but not relearning extinction of conditioned fear. This implies that once extinction has been learned, others structures support the retrieval and the expression of extinction memory. This is consistent with current neural model of extinction that involves interactions between several neural substrates including the BLA and the medial prefrontal cortex.

The experiments reported in this thesis studied the mechanisms of expression of overexpectation of conditioned fear, as measured by freezing. In Stage I, rats were conditioned to fear a tone and a flashing light conditioned stimulus (CS) through pairings with a 0.5 mA, 1 s shock. In Stage II, overexpectation was trained by the reinforcement of a compound of these CSs with a shock of the same magnitude. Two compound ?? shock pairings produced an overexpectation effect, as measured by freezing to presentations of the tone alone, while further Stage II training caused over-training of overexpectation. Expression of the overexpectation effect produced by two compound ?? shock pairings could be prevented by pre-test injection of the benzodiazepine partial inverse agonist FG7142. This effect was dose-dependent and not due to state-dependent memory. Control experiments suggested that it was also not due to any general effect of FG7142 on the Pavlovian freezing response. Freezing to a tone that had been conditioned, but not subjected to any decremental training procedures, was unaffected by administration of FG7142 before either the conditioning or test session. FG7142 also did not affect freezing to a tone that had been subjected to an associative blocking procedure. The hypothesis that overexpectation of conditioned fear may be context-dependent was also tested. However, renewal was not observed. Rats that received Stage II training in a context distinct from the Stage I training context showed equivalent expression of overexpectation regardless of whether testing was conducted in the Stage I or Stage II training context. These results are consistent with the hypothesis that overexpectation, like extinction, leads to the imposition of a GABAA receptor-mediated mask on the fear CR. Moreover, they suggest that this masking of fear is the specific consequence of negative predictive error.

The nineteenth century discourse of extinction – a consensus of thought primarily based upon the assumption that ‘savage’ races would be displaced by the arrival of European civilisation – provided the intellectual foundation for policies which resulted in Aboriginal dispossession, internment, and death in Tasmania. For a long time, the Aboriginal Tasmanians were thought to have been annihilated. However, this claim is now understood to be fanciful. Aboriginality is no longer defined as a racial category but rather as an identity that has its basis in community. Nevertheless, extinction discourse continues to shape the features of modern literature about Tasmania. The first chapter of this dissertation will examine how extinction discourse was imagined in the nineteenth century and will trace the parallels that contemporary fiction about contact history shares with it. The novels examined include Doctor Wooreddy’s Prescription for Enduring the Ending of the World by Mudrooroo, The Savage Crows by Robert Drewe, Manganinnie by Beth Roberts, and Wanting by Richard Flanagan. The extinctionist elements in these novels include a tendency to euglogise about the ‘lost race’ and a reliance on the trope of the last man or woman. The second chapter of the dissertation will examine novels that attempt to construct a representation of Aboriginality without reference to extinction. These texts subvert and ironise extinction discourse as a way of breaking the discursive continuities with colonialism and establishing a more nuanced view of Aboriginal identity in a post-colonial context. Novels analysed here include Drift by Brian Castro, Elysium by Robert Edric, and English Passengers by Matthew Kneale. / However, in attempting to arrive at new understandings about Aboriginality, non-Aboriginal authors are hindered by the epistemological difficulties of knowing and representing the Other. In particular, they seem unable to extricate themselves from the binaries of colonialism.

Après avoir rappelé quelques définitions et résultats concernant<br />l'atténuation du flux lumineux d'une source éloignée due à la poussière dans notre Galaxie et dans des galaxies proches (phénomène physique appelé « extinction »), nous décrivons brièvement le phénomène de mirage gravitationnel ainsi que les<br />processus physiques pouvant affecter la photométrie observée des images multiples d'un quasar distant.<br /><br />Nous présentons ensuite une méthode originale pour estimer le décalage vers le rouge (le « redshift ») du déflecteur (la « galaxie lentille ») d'un mirage gravitationnel. Cette méthode se base sur les effets causés par l'extinction de la lumière par la poussière interstellaire au sein de la lentille.<br /><br />Après une présentation de la méthode et quelques considérations<br />préalables, des simulations numériques sont effectuées pour tester<br />la méthode et calculer sa précision. La méthode est ensuite appliquée à des données réelles.<br /><br />Par la suite, nous tentons d'extraire la loi d'extinction de la galaxie lentille à partir des spectres des images multiples de la source d'arrière-plan.<br /><br />Enfin, nous utilisons la technique de l'analyse en composantes principales pour classifier une loi d'extinction parmi une collection de lois d'extinction connues. À nouveau, après une rapide présentation de l'analyse en composantes principales et de son application aux lois d'extinction, des simulations numériques sont utilisées pour évaluer la fiabilité de la méthode, laquelle est également appliquée à un cas réel.

Les parallaxes trigonométriques du satellite Hipparcos vont considérablement modifier de nombreux domaines de l'Astronomie. Leur précision annoncée (un facteur 5 par rapport à celles obtenues au sol) et leur nombre (100 000...) méritent une étude approfondie des erreurs externes et des éventuels effets systématiques. Après avoir décrit un modèle empirique à trois dimensions de l'absorption interstellaire qui nous a permis d'estimer la couleur d'une grande partie des étoiles du Catalogue d'Entrée d'Hipparcos, nous montrons, à l'aide des données préliminaires obtenues par le satellite, la qualité du Catalogue d'Entrée. Tirant parti des nombreuses données (au sol ou provenant d'Hipparcos) et des calibrations photométriques et spectroscopiques, cette thèse a également pour objet de mettre au point différentes méthodes qui permettront de valider statistiquement les futures parallaxes d'Hipparcos. Ces méthodes, utilisant notamment l'estimation conditionnelle pour étudier les différents biais des données, sont appliquées en détail aux parallaxes préliminaires obtenues avec un an de mission, et permettent de dégager des perspectives pour les calibrations des magnitudes absolues. Enfin, à l'aide d'analyses multivariées de données du Catalogue d'Entrée, une étude cinématique des étoiles A du voisinage solaire montre que le temps de mélange des vitesses spatiales est supérieur à deux années galactiques.

Light scattering and surface Plasmon calculations were done on a variety of novel geometries using the DDSCAT software package, which simulates the scattering of objects using the discrete dipole approximation method. Calculations were done on core shell nanoparticles consisting of a silver shell and a TiO2 core in order to determine changes in the extinction spectrum and the near field patterns. Several geometries were tested, including spheres, cylinders, and hexagons, each of varying size and number. It was determined that when geometries were coupled together, there was significant near field enhancement where the geometries were in contact. This enhancement along with the increase in extinction in the visible region of the light spectrum makes these nanoparticles idea for solar cell technology, where they would increase efficiency.

No description available.

We use the elitist and extinction policies to improve the simple genetic algorithm in this study. We expect that the search technique can avoid falling into the local maximum due to the premature convergence, and the chance of finding the near-optimal parameter in the larger searching space could be obviously increased. The accelerometer is then taken as the sensor for output measurement, and the designed controller is implemented to actively suppress the vibration of the plain that is due to the excitation effect of the high-speed and precision positioning of the linear motor. From the computer simulations and the experimented results, it is obvious that the near-optimal controller designed by using genetic approach with elitist and extinction can improve the effect of vibration suppression; the settling time is also decrease. For the vibration suppressions of high-speed precision positioning problems, the results are satisfactory in the cases of short, middle and long distance.

In this study, visibility observation, aerosol sampling, statistical analysis and model regression were conducted to investigate the influence of suspended particle characteristics and pollution sources on visibility and extinction coefficient in Koahsiung metropolitan area. The scene monitored by a digital camera was then proceeded by digital image processing and were then compared with observed atmospheric visibility observation. Meteorological parameters of various weather patterns (including relative humidity, wind direction, wind speed and mixing height ) played important roles on the reduction of visibility in metropolitan area. Synoptic charts were collected over the 1992-1999 period to analyze their influence on ambient air quality. This study revealed that high PM10 concentration and unhealthful PSI index occurred at weather patterns of high pressure outflow style I and circus-sluice of high pressure outflow¡C Regular visibility was observed during the period of November 1998- April 2000. The highest visibility was above 20 km while the lowest visibility was loss than 1 km in Koahsiung metropolitan area. The observed visibility was mainly distribution over the 2-6 km. The visibility below 6 km were about 61.88% of total observation days and poor visibility was usually occurred in winter. Besides, intensive visibility observation was conducted in January and March, 2000. Visibility was observed hourly at Kaohsiung Meteorological Station and Fa-Shin Temple, respectively. Suspended particles were continuously sampled for five hours at Chien-Chen, Sen-Min and Chien-Gin ambient air quality stations. These measurements were conducted to investigate the influence of chemical and physical properties of suspended particle and meteorological parameters on visibility and extinction coefficient in Koahsiung metropolitan area. Receptor model was applied to understand the emission sources of fine particles (PM2.5) and investigate the influence of emission sources on visual air quality. In addition, the determination of visibility by imagine processing was discussed. Visibility observation was coincided with scene monitoring in order to clarify the relationship between image processing and observed visibility. A illumination eigenvalue calculated by picture transfer software was used to correlate with observed visibility. This study revealed that, illumination eigenvalue and observed visibility had strong negative correlation (R=-0.9079) at effective visual range of 5-10 km. Results form single-factor analysis indicated that no significant variation of aerosol particle concentration was observed at three ambient air quality stations. A bi-mode size distribution of aerosol particles was observed for most stations in Koahsiung metropolitan area. The peak aerodynamic diameter of fine and coarse particles was observed at 0.56-1.0

Thesis (Ph. D.)--Oregon State University, 2010. / Printout. Includes bibliographical references (leaves 155-180). Also available on the World Wide Web.