M.Sc.

The serial interval (SI), defined as the symptom time between an infector and an infectee, is widely used to better understand transmission patterns of an infectious disease. Estimating the SI for tuberculosis (TB) is complicated by the slow progression from asymptomatic infection to active, symptomatic disease, and the fact that there is only a 5-10% lifetime risk of developing active TB disease. Furthermore, the time of symptom onset for infectors and infectees is rarely observed accurately. In this dissertation, we first conduct a systematic literature review to demonstrate the limited methods currently available to estimate the serial interval for TB as well as the few estimates that have been published. Secondly, under the assumption of an ideal scenario where all SIs are observed with precision, we evaluate the effect of prior information on estimating the SI in a Bayesian framework. Thirdly, we apply cure models, proposed by Boag in 1949, to estimate the SI for TB in a Bayesian framework. We show that the cure models perform better in the presence of credible prior information on the proportion of the study population that develop active TB disease, and should be chosen over traditional survival models which assume that all of the study population will eventually have the event of interest—active TB disease. Next, we modify the method by Reich et al. in 2009 by using a Riemann sum to approximate the likelihood function that involves a double integral. In doing so, we are able to reduce the computing time of the approximation method by around 50%. We are also able to relax the assumption of uniformity on the censoring intervals. We show that when using weights that are consistent with the underlying skewness of the intervals, the proposed approaches consistently produce more accurate estimates than the existing approaches. We provide SI estimates for TB using empirical datasets from Brazil and USA/Canada.

No description available.

The purpose of this paper is to define and investigate some of the properties of chains. Particular attention is given to a natural topology for chains, called the interval topology, and how the chain properties and topological properties of chains affect each other.

Class of 2007 Abstract / Objectives: To create a nomogram that can accurately predict dosing intervals for aminoglycoside dosing in neonates based on one concentration measurement. Methods: Pooled pharmacokinetic data from previous studies were used (n=341) to create a nomogram that would accurately predict dosing intervals for aminoglycosides. The population value for volume of distribution (0.45 L/kg) was used to formulate a nomogram to select a dosing interval for neonates that would achieve a trough concentration of < 0.5 mg/L one hour prior to the next scheduled dose. The fixed dose of 4 mg/kg was used to simulate concentration elimination profiles all neonates in the study group. The data from the study group elimination profile was then compared against the nomogram and evaluated for the number of correct dosing intervals the nomogram predicted from hour 6 to 22 at 1 hour intervals. The trough concentration cutoff was < 0.5 mg/L with neonates not achieving this concentration prior to the next dose to be deemed dosed incorrectly. The nomogram was considered to have failed at any time point where the nomogram indicated an interval that would not have achieved the desired trough concentration of < 0.5 mg/L or if the interval chosen by the nomogram was longer then necessary. Results: The simulated data from the test group showed that from 15 to 21 hours post infusion 81.0 to 92.1% of neonates had the correct interval predicted by the nomogram. Greater accuracy was achieved the longer time that elapsed before a concentration is drawn, with the greatest accuracy (92.1%) at 21 hours post infusion. However, this was close to the next dose recommending a concentration draw time at 18 hours post infusion to maximize the combination of accuracy and time remaining before the next scheduled dose. This gives the lab time to report the concentration before the next dose is scheduled and achieves an accuracy rate of 87.6%. Conclusions: The use of this nomogram is a valid tool to predict dosing intervals for aminoglycosides in neonates and can aid in saving hospital resources by needing only one concentration measurement to determine dosing interval.

M.Sc.

No description available.

The reproductive biology of a pride of lions (Panthera leo) was studied on the 8500 ha Karongwe Game Reserve from 1999 to 2005. Over this period, the pride consisted of between four and 11 lions with a paired coalition of adult males during the first three years and a single adult male for the next three years.We recorded shorter than normal interbirth intervals, high birth rates of 1.3 cubs/lioness/year, very high cub survival rates, and subadults leaving the pride at young ages. This translated into substantially faster growth rates than are typical in large lion populations in ecologically similar circumstances such as Kruger National Park, but are similar to those of lions in Serengeti National Park. These demographic characteristics were probably induced initially by a lack of intense intraspecific competition and high prey availability, but population stability was maintained through the removal of young subadults by management. Interestingly, variability in conception rates between lionesses resulted in lower growth rates than have been found in other similar reintroduced lion populations. These demographic traits characterize many of the small reintroduced lion populations, and call for appropriate management to avoid the consequences of high predator densities.

Introduction: People with asthma suffer from lower fitness levels when compared to their peers. The abnormal respiratory response to exercise, known as exercise induced bronchoconstriction (EIB), in the majority of people with asthma is a barrier to improving fitness levels. EIB severity can be increased with airway inflammation, which can be measured by exhaled nitric oxide (eNO). One exercise protocol, high intensity interval exercise (HIIE), may decrease the risk of developing EIB in people with asthma. HIIE warm up studies have demonstrated that HIIE is feasible and reduces the incidence of EIB in subsequent exercise bouts. HIIE may be ideal for people with asthma because it can decrease the duration of high ventilation that can trigger EIB, and improve their fitness levels. The purpose of this study is to compare the acute respiratory effects of traditional constant workrate exercise to a novel HIIE protocol in adults with asthma. Methods: 5 females and 2 males with asthma were recruited to perform two randomly assigned exercise protocols: HIIE (30 seconds of 140% the peak workrate and 90 seconds at 20%) and constant workrate exercise (CWR) (60% peak workrate). Workrates were determined by a peak cardiopulmonary exercise test. Measures of pulmonary function and airway inflammation were done pre and post exercise protocols. During exercise protocols, operational lung volumes, heart rate, rating of perceived exertion (RPE) was obtained. Results: FEV1 decreased significantly in both exercise protocols (HIIE 3.91± 0.65 to 3.33 ± 0.61 vs. CWR 3.90 ±0.50 to 3.09 ± 0.63). eNO measurements decreased after both exercise protocols (HIIE 40.4± 34.8 vs. CWR 42.1 ± 36.3. Conclusion: FEV1 and eNO findings are similar in HIIE and CWR exercise in adults with asthma, therefore, the novel HIIE is a feasible exercise protocol to help improve fitness levels of adults with asthma.

Thesis (Ph.D.)--York University, 2007. Graduate Programme in Mathematics and Statistics. / Typescript. Includes bibliographical references (leaves 109-110). Also available on the Internet. MODE OF ACCESS via web browser by entering the following URL: http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&res_dat=xri:pqdiss&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&rft_dat=xri:pqdiss:NR32041