Impulsivity and stress are two of the most important determinants of drug addiction in that both factors predict the initiation and maintenance of drug use, as well as relapse to drug taking following abstinence. Despite this combined influence, the interaction between stress and impulsivity has never been examined systematically in animal models of addiction. The objective of the current study is to examine the role of acute stress on two different measures of impulsivity in rats: the Go/No-go test measures motor impulsivity, and the Delayed Reinforcement Paradigm measures cognitive impulsivity. To determine whether a 1 hr restraint stress is physiologically stressful, blood samples from rats in Experiment 1 were taken at 5 different sampling points: baseline (0 min), reactivity (15 and 60 min) and recovery (100 and 180 min). In Experiments 2 and 3, rats were tested in either the Go/No-go test or the Delayed Reinforcement test immediately following 1 hr of restraint stress. Results from Experiment 1 show that 1 hr of restraint stress increased plasma corticosterone concentrations at 15 min and 60 min; corticosterone concentrations returned to baseline levels by 100 min. Following stress, the percentage of Go interval responding was not altered during Go/No-go testing (Experiment 2), nor were there changes in the indifference point values during Delayed Reinforcement testing (Experiment 3). These results suggest that 1 hr of acute stress does not increase either motor or cognitive impulsivity, and stress may influence addiction via mechanisms that are independent of impulsivity. / Thesis (Master, Psychology) -- Queen's University, 2009-08-24 15:17:00.597

The Winnipeg River Drainage Basin (WRDB), located in the boreal forest region of Canada, is a pivotal region of focus for the assessment of water availability to determine susceptibility to drought in the past. To date, there have been relatively few paleolimnological studies focusing on how lake levels have changed in the past and whether these changes have been synchronous in the WRDB. This study investigates temporal patterns in effective moisture from Little Raleigh Lake over the last two millennia. Analyses are based on diatoms from two near-shore sediment cores from different locations and water depth in Little Raleigh Lake. Changes in diatom assemblages are used to reconstruct quantitative estimates of effective moisture in the past through the calibration of a diatom-inferred depth model developed from diatom assemblages in surficial sediments along a depth transect in Little Raleigh Lake. Declines of ~1-3m occurred during the late Holocene, with prolonged periods of aridity consistent with the timing of the Medieval Climate Anamoly (~950-1250AD) and the Little Ice Age (~1650-1750AD). The nearshore core retrieved closer to the present-day ecotone between the benthic and planktonic diatom assemblages was more sensitive to tracking water level changes in the lake than the deeper core. Conditions during the last two millennia can be used for the assessment of water availability in the past, and may offer insight on future conditions under increasing temperatures. / Thesis (Master, Biology) -- Queen's University, 2011-07-29 17:09:49.155

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No description available.

No description available.

Unsaturated swelling clays are used in engineered barriers for waste disposal facilities due to their self-sealing ability and low hydraulic conductivity. The characterization of unsaturated clay behaviour is required for design of these barriers. In recent years, several small-scale laboratory and full-scale field tests have been conducted to characterize the mechanical and hydraulic behaviour of the unsaturated swelling clay. This focus of the present study is towards the development of constitutive models to simulate hydraulic and mechanical behaviour of precompacted unsaturated swelling clay, called the bentonite-sand buffer (BSB) material. Development, calibration, implementation, and application of the proposed constitutive models form the scope of the study. The results of laboratory triaxial tests with controlled suction and suction measurements are used to calibrate the constitutive models presented. An algorithm, called the PEM (Parameter Evaluation Method), which is useful to estimate constitutive model parameters and evaluate the performance of constitutive models is proposed. This algorithm has been used to estimate the parameters of two elasto-plastic constitutive models (i.e., the BBM (Alonso et al. 1990) and the BGM (Blatz and Graham 2003)) based on the laboratory tests results on the BSB material. New 3-dimensional porosity-dependent permeability model (kwn) and water retention surface (WRS) are developed in this study. The mathematical formulations of these models using parameters calibrated with laboratory tests conducted on the BSB material are provided. Implementation algorithms of the BBM, the BGM, the kwn, and the WRS in 2-phase flow hydraulic-mechanical (H-M) analysis using a 2D-finite difference method are also provided . Three combinations of hydraulic and mechanical constitutive models (linear elastic model, BGM, vanGenuchten (1980) and kwn models) are used to simulate small-scale infiltration processes in the BSB material. Two types of tests, constant volume (CV) and constant mean stress (CMS) tests are simulated using 2D-finite difference H-M analysis. The full-scale isothermal test (ITT) of AECL is modelled using 3 combinations of H-M constitutive models. The ITT experiment comprises of buffer, rock, and concrete materials. The selected combinations of H-M constitutive models are used in three types of analyses: buffer-only (BO); buffer-rock with 20x30m domain (BR); and time-dependent boundary conditions (BCt). The results of the study show that the applications of the elasto-plastic mechanical constitutive models and porosity-dependent permeability (kwn) model are improvements over existing constitutive models to model this class of problem. The rock properties and applied boundary conditions are significant in modelling the ITT experiment. The application of the time-dependent boundary condition can reduce the uncertainty of the rock properties and boundary conditions within the rock, so that it improves the model ability to simulate the hydraulic-mechanical behaviour of unsaturated swelling clay.

In this thesis, we investigate the impact of channels that have a bursty nature in a cognitive radio network scenario. Our goal is to design a general channel usage model that can handle bursty primary user channel usage. The proposed model describes idle periods with a discrete platoon arrival process and describes busy periods with a discrete phase type distribution. The performance of the proposed model is compared with two more traditionally encountered channel usage models in three different secondary user access schemes. First, we design a reactive access scheme to show the poor performance results an in- vestigator can potentially obtain when ignoring bursty data traffic. We have also analyzed two proactive secondary network access schemes. Numerical results show that the achiev- able utilization and interference probability of the network are affected when traditional channel models are used in a bursty PU channel.

The New Zealand Black (NZB) mouse chromosome 13 (c13) is linked to development of autoimmunity. B6 mice containing a portion of NZBc13 (B6.NZBc13 (c13)) develop a lupus phenotype that includes: autoantibody production, increased B and T cell activation, and marginal zone B cell and myeloid dendritic cell expansions. c13 mice have a B cell intrinsic dsRNA-sensing defect, leading to increased TLR3 expression and survival. The role of the aberrant dsRNA sensing in the generation of the c13 autoimmune phenotype was assessed by generating c13 mice with TLR3 knocked out (c13.TLR3KO). Marginal zone B cell expansion and B cell activation were attenuated in c13.TLR3KO mice, but other cellular phenotypes were not affected. Autoantibody production was partially reduced. These results indicate that altered dsRNA-sensing contribute to a portion of the altered cellular phenotypes in c13 mice, but that other susceptibility loci in the c13 interval are required for full development of autoimmunity.

The buoyancy-driven air flow and the associated energy transfer within a half-scale stairwell model have been investigated experimentally and theoretically. The experimental work comprised the larger part of the investigation. The stairwell model consisted of a lower and an upper compartment connected through the stairway. The recirculation of air was maintained by a continuous supply of heat in the lower compartment. Two different cases, referred to as closed and open non-sloping ceiling stairwells, were considered. In the former, the stairwell formed a closed system, and in the latter situation the air was allowed to enter and leave the stairwell through small openings in the lower and upper compartments, a situation which may arise in practice due to the presence of cracks. The experimental work provided detailed measurements of the velocity and temperature within the stairwell model. Hot-wire anemometers of a temperature-compensated type were used to measure the velocities, and the air temperatures were measured using platinum resistance probes. These measurements, supported by flow visualisation using smoke, provided a detailed description of the flow field. Due to the symmetry condition which existed in the stairwell, the measurements were carried out in only one-half of the stairwell. The results for both closed and open cases include the velocity and temperature profiles at the throat area (minimum area between the stairway and the lower compartment ceiling) for various distances from the side wall, mean temperatures in the upper and the lower compartments, volume and mass flows up and down the stairwell. The effect of the heat input rate on these parameters is also included. The results also include the heat losses through various surfaces bounding the system, heat and mass transfer through the stairwell joints and inlet and outlet openings, and the wall temperatures. The theoretical work was concerned with a numerical prediction of turbulent flow in two-dimensions. The k-c turbulence model, with the buoyancy terms included, was adopted. The governing equations for mass, momentum, energy and those of the turbulence model were solved using a finite-volume method. The model incorporates the SIMPLE algorithm for the derivation of pressure. The wall-function method was used for the treatment of the flow near the walls. The hybrid discretisation scheme was adopted. The predicted f low pattern was in good agreement with the pattern established by experiment. The proportion of the heat loss from the upper compartment was also in good agreement with the experiment. The maximum velocities in the throat area were underpredicted. The discrepancy between the prediction and experiment is believed to arise from shortcomings of the turbulence model, the treatment of the near-wall flow and the two-dimensionality of the numerical model.

Despite recognition that wellbeing and academic achievement are compatible educational goals, few education systems have clearly established how wellbeing can be meaningfully and purposefully implemented in educational experiences. The overarching aims of this thesis were to examine the relationships between wellbeing and senior secondary educational experiences, to develop a conceptual framework based on an extensive, multi-disciplinary literature review, to refine the framework through document analysis and experimental study, and to propose a model of student wellbeing that could support both researchers in the development of indicators to monitor student wellbeing and educators seeking to plan for and assess wellbeing-enhancing educational experiences. Implications for the use of the Student Wellbeing Model for the design and review of educational experiences at the classroom level are discussed.