published_or_final_version / Medicine / Master / Master of Research in Medicine

Lead and lead-tin solder were widely used in premise plumbing in North America until the 1980’s. Although this soldering practice has reduced significantly, lead release from older premise plumbing remains a concern. Utilities often use corrosion inhibitors to protect the piping in the distribution system and reduce lead release in premise plumbing. This study compares sodium silicates and phosphates as corrosion inhibitors for lead release in low alkalinity water. The study was carried out at the J.D. Kline Water Treatment Plant in Halifax, Nova Scotia, Canada. The experimental design compared sodium silicates (concentration of 18mg/L) and zinc orthophosphate (concentration of 0.8mg/L) as corrosion inhibitors at a pH of 7.3 for three disinfectant treatment groups (high chloramines (3mg/L), low chloramines (1mg/L), and chlorine (1mg/L)).

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The electrical heterogeneity of the heart has been recognized as an important feature of normal cardiac function. In cardiac myocytes, considerable electrophysiological differences in sodium channel currents have been reported between the atria and the ventricle. Although, these differences have been primarily attributed to heterogeneous populations of Na+ channel isoforms within cardiac tissue, the link between these electrophysiological differences and certain cardiac pathologies has been loosely studied. We sought to further elucidate the electrophysiological differences between the atria and the ventricle by characterizing INa in both cell types. For these studies we had initially predicted the atria to contain a greater density of TTX-sensitive Na+ channel isoforms compared to that of the ventricle. We used two well-known Na+ channel blockers: lidocaine (100 μM, 30 μM, 10 μM) and tetrodotoxin (TTX; 10 nM, 30 nM). In addition, we also applied hydrogen peroxide (H2O2; 100 μM, 30 μM, 10 μM) to atrial myocytes, which served as our pathological model for reactive oxygen species (ROS). When we applied lidocaine to cardiac myocytes, we observed an overall mixed response in both cell types. Specifically, we noted the most significant differences (p < 0.05) in peak INa, shifts in steady-state inactivation, and impaired recovery from fast inactivation in the presence of 100 μM lidocaine. Given the non-uniform responses to lidocaine, our results support the theory that tissue specific populations of Na+ channel isoforms exist within cardiac myocytes. In order to further elucidate the electrophysiological differences between the ventricle and the atria, we applied TTX, which is selective for TTX-sensitive Na+ currents. Our results indicated no overall significant differences between the ventricle and the atria, suggesting that the population of TTX-sensitive Na+ channel isoforms within the atria specifically, may not be pharmacologically detectable. Finally, our results also demonstrated that the atria are sensitive to ROS, where H2O2 significantly prolonged the action potential duration (APD) in atrial myocytes. Our results also suggest that, in addition to INa, other ion channels may be mediating a component of the H2O2-induced prolongation of the APD in adult rat atrial myocytes. / Thesis (Master, Physiology) -- Queen's University, 2010-08-27 10:04:19.043

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In this thesis an attempt has been made to try to dissect out the relative importance of atrial natriuretic peptides (ANP) and the renin-angiotensin-aldosterone system in the control of sodium balance in normal man. At the same time the thesis examines the relevance of ANP in the pathophysiology of essential hypertension and cardiac transplantation and the potential therapeutic value of manipulating the ANP system. The studies described in this thesis were important in suggesting a dominant role of suppression of the renin-angiotensin-aldosterone system in permitting excretion of short term increases in intravenous or oral sodium intake. The permissive effects of suppression of angiotensin II or aldosterone for the excretion of an intravenous sodium load showed clear time differences, with suppression of angiotensin II important immediately but the response to suppression of aldosterone delayed. In contrast, there appears to be only a transient role for changes in circulating levels of ANP in the response to an intravenous sodium load and little evidence that changes in ANP release are important in responding to acute increases in dietary sodium intake in normal subjects. However, the sensing mechanism for ANP release is clearly activated by sustained changes in dietary sodium intake. Studies of prolonged dietary sodium alteration in normal subjects clear evidence for a role of ANP in the medium term regulation of sodium balance and further dietary studies suggested an important role for the ANP system in pathophysiology in essential hypertension and in cardiac transplant recipients.

This thesis studies the effects of Na diffusion in Cu(In,Ga)Se2 (CIGS) solar cells,caused by electrical Potential Induced Degradation (PID) and how to prevent it. Thiswas done by subjecting CIGS solar cells a temperature of 850C and an electrical biasfrom the backside of the glass substrate to the Mo back contact of the CIGS cell.When the bias was negative at the back contact the Na diffused in to the CIGS(degradation) and when it was positive the ions diffused out again (recovery). TheCIGS samples were electrically characterized with IV- and EQE-measurements duringthese conditions and compositional depth profiling was used to track the Nadistribution.This study showed that during degradation Na seemed to accumulate in the interfacesbetween the different layers in the CIGS cell. The buffer and window layers arestrongly affected by Na diffusion. Zn(O,S) buffer layer showed a clear difference inrecovery behavior compared to CdS buffer layer. The introduction of an Al2O3barrier layer between the CIGS and Mo back contact increased the degradation timefrom 50 h to 160 h. During this study it was also found that in some cases the CIGSsolar cells efficiency could be improved by degrading the cells and then recoveringthem, in the best case from 13% average energy efficiency to 15% efficiency.