THE TRANSPORT OF HEAT BY FLOWING GROUNDWATER IN A DISCRETE FRACTURE

In typical theoretical or experimental studies of heat migration in discrete fractures, conduction and thermal dispersion are commonly neglected from the fracture heat transport equation, assuming heat conduction into the matrix is predominant. In this study analytical and numerical models are used to investigate the significance of conduction and thermal dispersion in the plane of the fracture for a point and line sources geometries. The analytical models account for advective, conductive and dispersive heat transport in both the longitudinal and transverse directions in the fracture. The heat transport in the fracture is coupled with a matrix equation in which heat is conducted in the direction perpendicular to the fracture. In the numerical model, the governing heat transport processes are the same as the analytical models; however, the matrix conduction is considered in both longitudinal and transverse directions. Firstly, we demonstrate that longitudinal conduction and dispersion are critical processes that affect heat transport in fractured rock environments, especially for small apertures (eg. 100 μm or less), high flow rate conditions (eg. velocity greater than 50 m/day) and early time (eg. less than 10 days). Secondly, transverse thermal dispersion in the fracture plane is also observed to be an important transport process leading to retardation of the migrating heat front particularly at late time (eg. after 40 days of hot water injection). Solutions which neglect dispersion in the transverse direction underestimate the locations of heat fronts at late time. Finally, this study also suggests that the geometry of the heat sources has significant effects on the heat transport in the system. For example, the effects of dispersion in the fracture are observed to decrease when the width of the heat source expands.

Analysis of Hyporheic Flow Induced by a Bar in a Gravel Stream: an Experimental Study

Thesis (Master, Civil Engineering) -- Queen's University, 2016-06-01 00:03:02.939

Challenges, Strengths and Opportunities Related to Implementing Comprehensive Evidence-Based Guidelines on Breast Cancer Survivorship Care by Primary Care Physicians and Nurse Practitioners in Southeastern Ontario

Background Many breast cancer survivors continue to have a broad range of physical and psychosocial problems after breast cancer treatment. As cancer centres move forward with earlier discharge of stable breast cancer survivors to primary care follow-up it is important that comprehensive evidence-based breast cancer survivorship care is implemented to effectively address these needs. Research suggests primary care providers are willing to provide breast cancer survivorship care but many lack the knowledge and confidence to provide evidence-based care. Purpose The overall purpose of this thesis was to determine the challenges, strengths and opportunities related to implementing comprehensive evidence-based breast cancer survivorship guidelines by primary care physicians and nurse practitioners in southeastern Ontario. Methods This mixed-methods research was conducted in three phases: (1) synthesis and appraisal of clinical practice guidelines relevant to provision of breast cancer survivorship care within the primary care practice setting; (2) a brief quantitative survey of primary care providers to determine actual practices related to provision of evidence-based breast cancer survivorship care; and (3) individual interviews with primary care providers about the challenges, strengths and opportunities related to provision of comprehensive evidence-based breast cancer survivorship care. Results and Conclusions In the first phase, a comprehensive clinical practice framework was created to guide provision of breast cancer survivorship care and consisted of a one-page checklist outlining breast cancer survivorship issues relevant to primary care, a three-page summary of key recommendations, and a one-page list of guideline sources. The second phase identified several knowledge and practice gaps, and it was determined that guideline implementation rates were higher for recommendations related to prevention and surveillance aspects of survivorship care and lowest related to screening for and management of long-term effects. The third phase identified three major challenges to providing breast cancer survivorship care: inconsistent educational preparation, provider anxieties, and primary care burden; and three major strengths or opportunities to facilitate implementation of survivorship care guidelines: tools and technology, empowering survivors, and optimizing nursing roles. A better understanding of these challenges, strengths and opportunities will inform development of targeted knowledge translation interventions to provide support and education to primary care providers.

Regulation of electrical transmission by protein kinase C in Aplysia bag cell neurons

Electrical synapses are composed of gap junctions, made from paired hemi-channels that allow for the transfer of current from one neuron to another. Gap junctions mediate electrical transmission in neurons, where they synchronize spiking and promote rapid transmission, thereby influencing the coordination, pattern, and frequency of firing. In the marine snail, Aplysia calfornica, two clusters of neuroendocrine bag cell neurons use electrical synapses to synchronize a 30-min burst of action potentials, known as the afterdischarge, which releases egg-laying hormone and induces reproduction. In culture, paired bag cell neurons present a junctional conductance that is non-rectifying and largely voltage-independent. During the afterdischarge, PKC is activated, which is known to increase voltage-gated Ca2+ current; yet, little is understood as to how this pathway impacts electrical transmission. The transfer of presynaptic spike-like waveforms (generated in voltage-clamp) to the postsynaptic cell (measured in current-clamp) was monitored with or without PKC activation. It was found that pretreatment with the PKC activator, phorbol-12-myristate-13-acetate (PMA), enhanced junctional conductance between bag cell neurons. Furthermore, in control, presynaptic action potential waveforms mainly evoked postsynaptic electrotonic potentials at both -60 and -40 mV. However, with PKC activation the presynaptic stimulus consistently elicited postsynaptic action potentials from resting potentials of -40 mV, and would occasionally result in firing from repetitive input at -60 mV. Moreover, to assess whether this enhanced electrical transmission genuinely reflects a greater junctional conductance or a change in postsynaptic responsiveness, a fast-phase junctional-like current was applied to single bag cell neurons. Neurons in PMA always fired action potentials in response to current injection as opposed to control, which were less likely to spike. This outcome did not change when the junctional-like current was artificially enhanced in control conditions. Also, in response to fast- and slow-phase electrotonic potential (ETP) waveforms, Ca2+ current was markedly larger in single PMA-treated neurons. These findings suggest that PKC activation may contribute to afterdischarge fidelity by recruiting postsynaptic Ca2+ current to promote synchronous network firing. Finally, Aplysia gap junction genes (innexins) were transfected into mouse N2A cells and characterized. This revealed a biophysical and pharmacological profile similar to native gap junctions.