The effects of developmental lead (Pb2+) exposure on the anxiolytic-like effect of diazepam (5.0 mg/kg IP) and 8-OH-DPAT (0.3 mg/ kg IP) were studied. Wistar dams were exposed to 250 ppm lead acetate in drinking water during pregnancy. Control rats were derived from dams that consumed tap water, and had no exposure to Pb2+ afterwards. Male offspring were tested at the age of 12 weeks. We studied the anxiolytic-like effect of diazepam and 8-OH-DPAT in an elevated plus maze device and the Vogel conflict test. Diazepam in doses of 5.0 mg/kg IP significantly increased the percentage of time spent on open arms in control rats being without effect in Pb2+-exposed animals. 8-OH-DPAT 0.3 mg/kg IP increased the percentage of time spent on open arms in both experimental groups (control and Pb2+ but the anxiolytic-like effect was much more pronounced in Pb2+-intoxicated animals. The benzodiazepine anxiolytic diazepam produced a significant effect in the Vogel conflict test in control rats. A 5.0 mg/kg dose of those drugs caused a significant increase in the number of electric shocks rats received. In the ontogenetically Pb2+-exposed rats diazepam also augmented the number of shocks accepted, but this effect was much less pronounced than in control animals. Conversely, 8-OH-DPAT at doses of 0.3 mg/kg IP was without effect in both tested groups as far as the anticonflict effect is concerned. The results of the present report demonstrated that exposure to Pb2+ during pregnancy induced hypersensitivity to 5-HT1A agonist mediated anxiolytic-like effect but attenuated that of benzodiazepine (diazepam).

Pacemaker implantation can be associated with several complications, including myocardial perforation with or without pericardial effusion, venous thrombosis, vegetations of the tricuspid valve (TV) or pacing lead, and tricuspid regurgitation (TR). The TR is thought to be derived from deformity or perforation of the TV by the pacing lead or secondary to atrioventricular discordance with asynchronous ventricular pacing. Severe TR can be deleterious to the patient because it raises the central venous pressure by increasing the right sided preload. Chronically, the increase in right sided blood volume can result in an increase in the right atrial pressure leading to a decrease in venous return and low cardiac output. Severe TR from leaflet adhesion to the pacemaker lead has not been reported before. With the aging of the population and the expanding use of pacemakers and implantable cardioverter defibrillators (ICD) in clinical practice, this complication may be seen more frequently. We present a patient diagnosed with severe TR, years after his pacemaker implantation. His TR was thought to be caused by adhesion of the tricuspid valve to his pacemaker lead.

Using data from the Third National Health and Nutrition Examination Survey, we assessed measures of puberty in U.S. girls in relation to blood lead levels to determine whether sexual maturation may be affected by current environmental lead exposure. The study sample included 1,706 girls 8-16 years old with pubic hair and breast development information; 1,235 girls 10-16 years old supplied information on menarche. Blood lead concentrations (range = 0.7-21.7 pg/dL) were categorized into three levels: 0.7-2.0, 2.1-4.9, and 5.0-21.7 μg/dL. Sexual maturation markers included self-reported attainment of menarche and physician determined Tanner stage 2 pubic hair and breast development. Girls who had not reached menarche or stage 2 pubic hair had higher blood lead levels than did girls who had. For example, among girls in the three levels of blood lead described above, the unweighted percentages of 10-year-olds who had attained Tanner stage 2 pubic hair were 60.0, 51.2, and 44.4%, respectively, and for girls 12 years old who reported reaching menarche, the values were 68.0, 44.3, and 38.5%, respectively. The negative relation of blood lead levels with attainment of menarche or stage 2 pubic hair remained significant in logistic regression even after adjustment for race/ethnicity, age, family size, residence in metropolitan area, poverty income ratio, and body mass index. In conclusion, higher blood lead levels were significantly associated with delayed attainment of menarche and pubic hair among U.S. girls, but not with breast development.

Many secondary schools in Utah have adopted the Project Lead the Way (PLTW) pre-engineering program. Little research has been conducted in Utah to show how successful these programs are or what factors are perceived to contribute to that success. This research is about defining PLTW program success and identifying factors perceived to improve success. This was accomplished by interviewing career and technical education directors in Utah who have the PLTW program in their districts. Questionnaires were also developed to question PLTW teachers, school administrators, and counselors with PLTW in their schools about factors that might contribute to PLTW program success. A successful PLTW program in Utah was found to be a program that was perceived to meet the goals of implementation, had the ability to attract adequate student enrollment, and was perceived to promote scholarly student achievement. It was found that successful PLTW programs (a) utilize dynamic teachers taking advantage of teacher professional development, (b) capitalize on student interest in the subject and differentiate learning models and environments, (c) utilize a collaborative effort between schools, industry, and community, (d) advertise class offerings and program benefits so students can make wise class choices during registration, and (e) make sure resources and facilities are available for all the curriculum requirements.

Ferroelectric random access memories (FRAM) are considered as future memories due to high speed, low cost, low power, excellent radiation hardness, nonvolatility, and good compatibility with the existing integrated circuit (IC) technology. The non-volatile FRAM devices are divided into two categories, based on reading technique: destructive readout (DRO) FRAM and non-destructive readout (NDRO) FRAM. Lead zirconate titanate (PZT) is recently considered as one of the most promising materials for DRO FRAM devices due to its excellent ferroelectric properties. There are remarkable advances in the applications of PZT thin films, but the direct integration into high density CMOS devices is restricted by high processing temperatures. Hence, it is desirable to lower processing temperature and develop novel high temperature electrode-barrier layers for achieving high density DRO FRAM devices. The NDRO FRAM devices have been developed mainly using metal-ferroelectric-semiconductor (MFS) and metal-ferroelectric-metal-insulator-semiconductor (MFMIS) structure. This devices use the remanent polarization of ferroelectric films to control the surface conductivity of a silicon substrate. The problem of the NDRO FRAM is that the actual electric field applied to ferroelectric films is very small compared to the external electric field, because of the large depolarization field in the MFS structure and the high capacitance ratio of ferroelectric capacitor and SiO2 capacitor in series in the MFMIS structure. Since the typical ferroelectric films show very high dielectric constant over 400, it is desired to develop ferroelectric films with low dielectric constant and low coercive electric field. This research is primarily focused on developing low temperature processing and high temperature electrode-barrier layers for DRO FRAM application, and exploiting novel ferroelectric materials for NDRO FRAM application. The low temperature processing was achieved by a novel sol-gel processing, which takes advantage of in-situ electrode template layer, rapid heating-treatment without pyrolysis step, and molecularly modified precursors. The PZT films with various composition were also investigated as a function of Ti content. In order to study the integration issues for these PZT films, a substrate was constructed as Pt/TiN/TiSi₂/poly-Si, which represents a scheme of capacitor in high density DRO FRAM devices. The ferroelectric films were incorporated into the substrate, and their ferroelectric properties were investigated as a function of annealing temperature. Excellent ferroelectric properties were observed for the thin films processed at a low temperature of 500 °C as contacting between top Pt and bottom polysilicon. The other approach we have taken to overcome the integration problems in high density DRO FRAM devices is to develop high temperature electrode barrier layers. In this research, Pt/IrO2/Ir hybrid layers were prepared on poly-Si substrate as high temperature electrode-barriers. The PZT films fabricated on the Pt/IrO₂/Ir/poly-Si substrates exhibited good ferroelectric properties and outstanding fatigue properties after high temperature processing. It was observed from Auger electron spectroscopy (AES) profiles that the hybrid oxide electrode minimized fatigue problem by reducing the oxygen vacancies entrapment at the electrode/ferroelectric interfaces. This results indicated that Pt/IrO₂/Ir high temperature electrode-barrier layers promise to solve major problems of PZT integration into high density DRO memory devices. For the NDRO FRAM devices, Sr₂Nb₂O₇ and La₂Ti₂O₇ thin films were prepared on Pt-coated silicon, Si(100), and Pt/IrO₂/SiO₂/Si substrates by metalorganic deposition (MOD) technique. The Sr₂Nb₂O₇ and La₂Ti₂O₇ thin films showed the dielectric constant values of 48 and 46, respectively. However, no ferroelectricity was observed at room temperature, which might be attributed to extremely small grains. Extensive studies on preparation and properties of Sr₂(Ta_1-xNb_x)O₇ (STN) both in bulk and thin film form were carried out as a function of composition. The STN films exhibited small dielectric constant of around 46, irrespective of the composition. / Ph. D.

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Thirty years since the removal of lead from gasoline, lead still poses a health risk. Children are most at-risk for adverse health outcomes caused by lead toxicity due to both behavioural (e.g., hand-to-mouth behaviour) and physiological differences (i.e., increased intake of lead by body weight, higher uptake rate and a higher vulnerability to the effects of lead) compared to adults (Yeoh et al., 2009). As a result, governments must identify children that may be at-risk of lead poisoning and develop practical methods to mitigate lead exposure. Before a government can develop a policy to help mitigate exposure of lead for children, we need to understand the spatial distribution of lead within the city. A popular spatial model used within air pollution research may allow more accurate, and more localized predictions than the most common interpolation method, kriging. Land use regression (LUR) is a technique leveraging multiple predictor variables to help estimate the spatial distribution of the dependent variable. By using historical sources of lead, LUR can be used to model soil lead levels (SLL) with localized variation. Unfortunately, spurious relationships can be the basis of a LUR model, which may lead to an overfitted spatial model resulting in a model with little generalizability and questionable ability to estimate the dependent variable at unobserved locations. Ultimately, Empirical Bayesian Kriging may be the best option for soil contamination research due to its ability to provide a smoothed prediction surface and its dependence on the spatial structure of the data to provide estimations. The benefit to society and the return on investment (ROI) is often the justification for lead remediation. Gould (2009) estimates a $17 to $221 ROI for every dollar spent on lead hazard control. One of the main components of this estimate of ROI comes from the decrease in intelligence quotient (IQ) that a child may experience as a consequence of lead toxicity. There are three main ways that a decrease in IQ can negatively impact the economy, (i) lower potential lifetime earnings, (ii) reduced tax revenues, and (iii) higher spending on special education (Gould, 2009). Since IQ has such a significant role in the ROI estimates, chapter 3 seeks to achieve a greater understanding of the relationship between blood lead levels (BLLs) and IQ. The loss of IQ points for an increase in blood lead concentration proposed by Lanphear et al. (2005) and referenced by Gould (2009) is significantly higher than what we found in our meta-analysis. Thus, the projected ROI proposed by Gould (2009) may be much lower than previously calculated. In the final chapter, the cost associated with permanent lead abatement is investigated based on ROI projections as a case study in Hamilton, Ontario. We show that, in most cases, permanent lead remediation is far too expensive for a municipal government. Furthermore, the capital initially invested may not be distributed back into the local economy, as the ROI suggests. We suggest that municipal governments make decisions based on need, rather than basing remediation decisions on ROI projections. Furthermore, we recommend the use of hazard quotient maps to help justify lead remediation as a more accurate representation of potential lead toxicity, instead of only looking at SLL exceedances across the city. / Dissertation / Doctor of Philosophy (PhD)

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