Background: The causes of childhood brain tumors (CBT) are essentially unknown. Exposure to extremely low frequency magnetic fields (ELF-MF) (3-3000Hz) is an ubiquitous part of modern life. However, very few studies have investigated the possible effect of maternal occupational ELF-MF exposure on CBT and the available findings are inconsistent across studies. / Methods: We examined the role of maternal occupational exposure to ELF-MF shortly before and during pregnancy on the incidence of childhood brain tumors. A total of 548 incident cases and 760 healthy controls recruited between 1980 and 2002 from two Canadian provinces (Quebec and Ontario) were included and their mothers were interviewed. Tumors were classified as astroglial tumors, primitive neuroectodermal tumors (PNET), and other gliomas. Quantitative occupational ELF-MF exposure in microtesla units was estimated using individual exposure estimations or a job exposure matrix. We used three metrics to analyze exposure: cumulative, average, and maximum level attained. / Results: Using the average exposure metric measured before conception, an increased risk was observed for astroglial tumors (OR=1.5, and 95% CI=1.0-2.4). During the entire pregnancy period, a significantly increased risk was observed for astroglial tumors as well as for all childhood brain tumors with the average metric (OR=1.6, 95% CI=1.1-2.5 and OR=1.5; 95% CI=1.1-2.2, respectively). Based on job titles, a two-fold risk increase was observed for astroglial tumors (OR=2.3, 95% CI=0.8-6.3) and for all childhood brain tumors (OR=2.3, 95% CI=1.0-5.4) among sewing machine operators. / Conclusion: Results are suggestive of a possible association between maternal occupational ELF-MF exposure and certain brain tumors in their offspring. / Keywords: brain tumors, occupational exposures, maternal exposures, magnetic fields, childhood cancer, job exposure matrix

Diseases that affect dairy cattle have serious economic and animal welfare implications. The inclusion of immune response (IR) traits in breeding indices has been suggested to improve inherent animal health, and decrease the use of antimicrobials. The objectives of this research were to (1) evaluate cell-mediated (CMIR) and antibody-mediated immune responses (AMIR) on 680 Holstein cows from 58 herds across Canada, (2) estimate genetic parameters of these traits (3) examine the associations with routinely evaluated traits as well as the incidence of mastitis, (4) evaluate the correlation of natural and specific antibody and (5) perform a genome-wide association study (GWAS) to determine genetic markers associated with high or low IR. In collaboration with the Canadian Bovine Mastitis Research Network cows were immunized with both a type 1 and type 2 test antigen to stimulate CMIR and AMIR, respectively. A cutaneous delayed-type hypersensitivity test to the type 1 test antigen was used as an indicator of CMIR, and serum antibody (IgG1 and IgG2) to the type 2 test antigen as an indicator of AMIR. IR phenotypes varied significantly by cow, herd and region in Canada. Heritability estimates were moderate, 0.19 for CMIR and 0.16-0.43 for AMIR depending on time in the immunization protocol and antibody isotype. Beneficial associations between AMIR and some reproductive traits were found. Using estimated breeding values, cows were classified as high, average or low responders. High AMIR cows had significantly lower incidence rates of clinical mastitis compared to average and low cows. No difference was found when cows were classified based on CMIR. Natural antibody was not genetically correlated with specific antibody nor was it associated with mastitis. The GWAS found 198 genetic markers significantly associated with AMIR, with the majority on chromosome 23 where the major histocompatability complex is located. Other significant genes involved in IR include those associated with the complement system, interleukin 17 and tumor necrosis factor. This research confirms the benefit of identifying high IR cows and gives a glimpse of current IR profiles in Canadian Holsteins. This was the first GWAS for IR traits in dairy cattle and suggests it may be possible to include IR traits in genomic selection indices. / This research was financed by grants to B.A. Mallard from National Sciences and Engineering Research Council of Canada, Alberta Milk, Dairy Farmers of New Brunswick, Nova Scotia, Ontario and Prince Edward Island, Novalait Inc., Dairy Farmers of Canada, DairyGen council of Canadian Dairy Network, Agriculture and Agri-Food Canada, Public Health Agency of Canada, Technology PEI Inc., Université de Montréal and University of Prince Edward Island through the Canadian Bovine Mastitis Research Network. Kathleen Adele Thompson Crispi was funded by the Dairy Farmers of Ontario Doctoral Research Assistantship.

Pressure tubes pick up hydrogen while they are in service within CANDU reactors. Sufficiently high hydrogen concentration can lead to hydride precipitation during reactor shutdown/repair at flaws, resulting in the potential for eventual rupture of the pressure tubes by a process called Delayed Hydride Cracking (DHC). The threshold stress intensity factor (KIH) below which the cracks will not grow by delayed hydride cracking of Zr-2.5Nb micro pressure tubes (MPTs) has been determined using a load increasing mode (LIM) method at different temperatures. MPTs have been used to allow easy study of the impact of properties like texture and grain size on DHC. Previous studies on MPTs have focused on creep and effects of stress on hydride orientation; here the use of MPTs for DHC studies is confirmed for the first time. Micro pressure tube samples were hydrided to a target hydrogen content of 100 ppm using an electrolytic method. For DHC testing, 3 mm thick half ring samples were cut out from the tubes using Electrical Discharge Machining (EDM) with a notch at the center. A sharp notch with a root radius of 15 µm was introduced by broaching to facilitate crack initiation. The direct current potential drop method was used to monitor crack growth during the DHC tests. For the temperature range tested the threshold stress intensity factors for the micro pressure tube used were found to be 6.5-10.5 MPa.m1/2 with the value increasing with increasing temperature. The average DHC velocities obtained for the three different test temperatures 180, 230 and 250oC were 2.64, 10.87 and 8.45 x 10-8 m/s, respectively. The DHC data obtained from the MPTs are comparable to the data published in the literature for full sized CANDU pressure tubes. / Thesis (Master, Mechanical and Materials Engineering) -- Queen's University, 2009-04-24 12:55:36.917

<p>The aim of this study was to identify factors associated with reporting incidents of sexual violence after seventy-two hours at the sexual assault service centre in Newcastle, KwaZulu-Natal. This descriptive study was based on retrospective analysis of 534 medical records of victims of sexual violence at the Newcastle hospital between 2005 and 2009. A data collection sheet was designed to extract information from three sources namely: the victims‟ hospital files, J88 forms and specific hospital forms that were completed for sexual assault victims. The collected data were entered into and processed for analysis using EPI INFO statistical package. Frequencies, means and standard deviations were calculated for the data set. Test of significance was also done using the Chi-square test and presented using odds ratios with 95% CI and p-value of &lt / 0.05. The victims‟ age range was 2-81years (mean= 18.84, &sigma / =13.25). Approximately 87% were female and 59.4% of the victims were aged 0-17 years. One in five victims (19.7%) was HIV positive, and most (74.4%) reported rape with vaginal penetration. Fifty-nine percent reported within 72 hours of being assaulted. The most common reason for delayed reporting (21.5%) was fear of the perpetrator. Most of the sexual assaults were committed by male (96%) and single perpetrator (90%). Nearly a third (32.4%) of the sexual violence occurred within intimate relationships and more than two-thirds (68%) knew the perpetrators. In all, 35% sustained injuries during the assault and a third (34.5%) reported the use of weapons during the assault. Nearly half of the victims (48.7%) were referred to hospital by their relatives who also accompanied them to the facility (42.1%). Of the 198 victims that were offered post-exposure prophylaxis (PEP), 87% collected the full 28-day course.</p>

Environmental and genetic factors contribute to the development of schizophrenia. For example, epidemiological evidence has linked infections during pregnancy with increased incidence of schizophrenia in the adult offspring. At the same time mutation to DISC1, a protein involved in neurone migration and synaptic plasticity, is an important genetic risk for the disorder. Accordingly, the aim of this project was to determine if these environmental and genetic influences converge along a common pathogenic pathway leading to schizophrenia. Using a model of prenatal infection by bacterial endotoxin in rodents, we demonstrated a 50% reduction in DISC1 protein expression in the hippocampus and cortex of juvenile offspring. In addition, we found a significant induction of prostaglandins (final mediators of the inflammatory process) in the fetal brain while many cytokines remained unaltered. Taken together our results identify prostaglandins as potential mediators of the teratogenic effects of prenatal infection and show that prenatal infection itself can affect systems related to genetic risk factors for schizophrenia, in this case DISC1.

Photon upconversion by sensitized triplet–triplet annihilation (UC-STTA) is a photophysical process that facilitates the conversion of two low-energy photons into a single high-energy photon. A low-energy photon is absorbed by a sensitizer molecule that produces a triplet excited state which is transferred to an emitter molecule. When two emitter triplet states encounter each other, TTA can take place to produce a singlet excited state which decays by emission of a high-energy (upconverted) photon. While traditional single-threshold dye-sensitized solar cells (DSSCs) have a maximum efficiency limit of ca. 30%, it has been predicted theoretically that implementation of UC-STTA in DSSCs could increase that efficiency to more than 40%. A possible way to implement UC-STTA into DSSCs, would be to replace the standard sensi- tized nanostructured TiO2 photoanodes by upconverting ones loaded with emitter molecules. Following TTA, the excited emitter molecule would be quenched by injection of a high-energy electron into the conduction band of the TiO2. To explore the practical aspects of this strategy for a highly efficient DSSC, in this thesis UC-STTA is studied in model systems based on nanostructured ZrO2 films. These ZrO2 films are a good proxy for the TiO2 films used in DSSCs, and allow for relatively easy optimization and study of UC-STTA by allowing measurements of the upconverted photons without the complications of electron injection into the film. Herein it is experimentally proven that UC-STTA is viable on nanostructured metal oxide films under non-coherent irradiation with intensities comparable to sunlight. Two different system architectures are studied, differing in the position of the molecular components involved in the UC-STTA mechanism. Both architectures have the emitter molecules adsorbed onto the ZrO2 surface, but the sensitizers are positioned either in solution around the nanostructure, or co-adsorbed with the emitters onto the ZrO2 surface. A set of challenges in the study and optimization of the UC-STTA process is identified for each type of system. Proposals are also given for how to further improve the understanding and UC-STTA optimization of these systems toward application in DSSCs to overcome the present solar energy conversion efficiency limit.

This dissertation consists of three independent essays in Macroeconomics. The first essay studies whether efficiency can be improved by introducing government-issued illiquid bonds to an economy where money is the only asset and essential. In contrast with perfectly liquid bonds, illiquid bonds can increase societal welfare in two ways: First, allocating consumption goods among heterogeneous agents more efficiently; second, stimulating consumption and output level by loosening the liquidity constraints of households. More importantly, since societal welfare is elevated persistently when the inflation rates range from a level slightly above Friedman Rule to an upper bound, this essay provides an insight into the essentiality of illiquid bonds. The second essay provides a novel propagation mechanism of productivity shocks to explain an empirical fact: The response curve of output to a positive productivity shock reaches its peak up to eight quarters after the shock. Using a micro-founded monetary search model and focusing on agents’ decisions on establishing long-term trading relationships in the goods market, I show that when a positive shock takes place in the economy, marginal agents break down previous trading relationships and explore better matching opportunities. As a result, shortly after the shock, the average productivity level of transactions increases, but the total number of transactions decreases. The calibrated model shows that the latter effect dominates, resulting a slightly decrease of aggregate output after a positive productivity shock. The search friction, together with the monetary channel, gives rise to a delayed output response at the aggregate level. The third essay develops a general equilibrium theory of household formation – i.e., marriage – following Coase’s theory of firm formation. Individuals in the model consume both market-and home-produced commodities, and home production is facilitated through marriage. Market frictions, including taxation, search and bargaining problems, increase marriage rates when home and market goods are substitutes. In particular, inflation, as a tax on market activity, makes household production and hence marriage more attractive, as long as singles use cash more than married individuals, which is supported by data. The prediction that inflation and other taxes affect household formation is also supported by evidence.

This dissertation consists of three independent essays in Macroeconomics. The first essay studies whether efficiency can be improved by introducing government-issued illiquid bonds to an economy where money is the only asset and essential. In contrast with perfectly liquid bonds, illiquid bonds can increase societal welfare in two ways: First, allocating consumption goods among heterogeneous agents more efficiently; second, stimulating consumption and output level by loosening the liquidity constraints of households. More importantly, since societal welfare is elevated persistently when the inflation rates range from a level slightly above Friedman Rule to an upper bound, this essay provides an insight into the essentiality of illiquid bonds. The second essay provides a novel propagation mechanism of productivity shocks to explain an empirical fact: The response curve of output to a positive productivity shock reaches its peak up to eight quarters after the shock. Using a micro-founded monetary search model and focusing on agents’ decisions on establishing long-term trading relationships in the goods market, I show that when a positive shock takes place in the economy, marginal agents break down previous trading relationships and explore better matching opportunities. As a result, shortly after the shock, the average productivity level of transactions increases, but the total number of transactions decreases. The calibrated model shows that the latter effect dominates, resulting a slightly decrease of aggregate output after a positive productivity shock. The search friction, together with the monetary channel, gives rise to a delayed output response at the aggregate level. The third essay develops a general equilibrium theory of household formation – i.e., marriage – following Coase’s theory of firm formation. Individuals in the model consume both market-and home-produced commodities, and home production is facilitated through marriage. Market frictions, including taxation, search and bargaining problems, increase marriage rates when home and market goods are substitutes. In particular, inflation, as a tax on market activity, makes household production and hence marriage more attractive, as long as singles use cash more than married individuals, which is supported by data. The prediction that inflation and other taxes affect household formation is also supported by evidence.

The demand for wireless data services has been dramatically growing over the last decade. This growth has been accompanied by a significant increase in the number of users sharing the same wireless medium, and as a result, interference management has become a hot topic of research in recent years. In this dissertation, we investigate feedback and transmitter cooperation as two closely related tools to manage the interference and achieve high data rates in several wireless networks, focusing on additive white Gaussian noise (AWGN) interference, X, and broadcast channels. We start by a one-to-many network, namely, the three-user multiple-input multiple-output (MIMO) Gaussian broadcast channel, where we assume that the transmitter obtains the channel state information (CSI) through feedback links after a finite delay. We also assume that the feedback delay is greater than the channel coherence time, and thus, the CSI expires prior to being exploited by the transmitter for its current transmission. Nevertheless, we show that this delayed CSI at the transmitter (delayed CSIT) can help the transmitter to achieve significantly higher data rates compared to having no CSI. We indeed show that delayed CSIT increases the channel degrees of freedom (DoF), which is translated to an unbounded increase in capacity with increasing signal-to-noise-ratio (SNR). For the symmetric case, i.e. with the same number of antennas at each receiver, we propose different transmission schemes whose achievable DoFs meet the upper bound for a wide range of transmit-receive antenna ratios. Also, for the general non-symmetric case, we propose transmission schemes that characterize the DoF region for certain classes of antenna configurations. Subsequently, we investigate channels with distributed transmitters, namely, Gaussian single-input single-output (SISO) K-user interference channel and 2×K X channel under the delayed CSIT assumption. In these channels, in major contrast to the broadcast channel, each transmitter has access only to its own messages. We propose novel multiphase transmission schemes wherein the transmitters collaboratively align the past interference at appropriate receivers using the knowledge of past CSI. Our achievable DoFs are greater than one (which is the channel DoF without CSIT), and strictly increasing in K. Our results are yet the best available reported DoFs for these channels with delayed CSIT. Furthermore, we consider the K-user r-cyclic interference channel, where each transmitter causes interference on only r receivers in a cyclic manner. By developing a new upper bound, we show that this channel has K/r DoF with no CSIT. Moreover, by generalizing our multiphase transmission ideas, we show that, for r=3, this channel can achieve strictly greater than K/3 DoF with delayed CSIT. Next, we add the capability of simultaneous transmission and reception, i.e. full-duplex operation, to the transmitters, and investigate its impact on the DoF of the SISO Gaussian K-user interference and M×K X channel under the delayed CSIT assumption. By proposing new cooperation/alignment techniques, we show that the full-duplex transmitter cooperation can potentially yield DoF gains in both channels with delayed CSIT. This is in sharp contrast to the previous results on these channels indicating the inability of full-duplex transmitter cooperation to increase the channel DoF with either perfect instantaneous CSIT or no CSIT. With the recent technological advances in implementation of full-duplex communication, it is expected to play a crucial role in the future wireless systems. Finally, we consider the Gaussian K-user interference and K×K X channel with output feedback, wherein each transmitter causally accesses the output of its paired receiver. First, using the output feedback and under no CSIT assumption, we show that both channels can achieve DoF values greater than one, strictly increasing in K, and approaching the limiting value of 2 as K→∞. Then, we develop transmission schemes for the same channels with both output feedback and delayed CSIT, known as Shannon feedback. Our achievable DoFs with Shannon feedback are greater than those with the output feedback for almost all values of K.

In an attempt to reduce costs and improve customer satisfaction, manufacturers have been adopting strategies such as Delayed Product Differentiation (DPD) while managing broader product lines. In this study, first a general framework on DPD is formed in the light of basic articles in the literature. The vanilla box assembly process which is a special form of modular design type of DPD is modeled and analyzed. In the vanilla box assembly process, inventory is stored in a special form of semi-finished products, called vanilla boxes, that can serve more than one final product. We model the vanilla box assembly process considering the costs of inventory and unsatisfied demand under the capacity limitations, stochastic demand and bill of material requirements. We formulate the model as an extensive form of stochastic integer program in which stochastic demand is modeled using a set of demand scenarios each of which is assigned a probability of occurrence. The model is solved as a standard integer programming model that minimizes the expected value of the objective function. The impact of product demand scenarios, common component levels, shortage penalty cost to holding cost ratio levels and capacity restrictions on the total cost and fill rates is studied. We compare the performance of vanilla box assembly process to assemble-to-order process and provide insights on their performances. Computational results indicate that the vanilla box assembly process is a promising alternative to the assemble-to-order process in most of the problem instances.