Thesis (Ph. D.)--University of Washington, 2000. / Vita. Includes bibliographical references (p. 243-256).

Thesis (Ph. D.)--University of Chicago, Department of Astronomy and Astrophysics, 2001. / Includes bibliographical references. Also available on the Internet.

Thesis (Ph.D.)--Brown University, 2008. / Vita. Advisor : Ian Dell'Antonio. Includes bibliographical references (leaves 122-124).

Thesis (Ph. D.)--University of Chicago, Dept. of Physics, August 2003. / Includes bibliographical references. Also available on the Internet.

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This dissertation focuses on determining the properties of the environments and the line-of-sight mass distributions for a sample of strong gravitational lenses as well as establishing their effects on the observed lens properties and the Hubble constant.Strong gravitational lenses ought to be able to provide important constraints for cosmology, however the lack of understanding of their large--scale environments has hindered their use. Here, we present a spectroscopic survey of the environments and lines of sight of 28 strong galaxy--mass lenses. We determine redshifts for 9698 galaxies in the fields of these lenses and identify 163 structures with at least five members in 26 fields. We find that 12 of 26 lenses are group members. Six of these groups are newly discovered. Overall, between 38--67% of lenses are in groups, and in 8--31% of the lenses the group makes a significant contribution to the lens potential. Line-of-sight structures are present in virtually every lens field, and in 19% of lenses the structures appear to be a significant perturbation to the lens potential. We consider the effect of the environment on H0 derived from gravitational lenses. We find that, when the environment is ignored, lenses in groups predict a systematically higher value of H0, inconsistent at the 1 sigma level with H0 derived from isolated lenses. Correcting for the environment and line of sight structures brings the two values into agreement and lowers the combined value (H=66-3.2+3.4). Without correction for the environment, the H0 values from strong lenses should be considered a strict upper limit. We explore the correlation between the observed lens properties and external perturbations from the observational perspective. We find that four-image lenses are statistically more likely to be in groups than two-image lenses. Furthermore, the distributions of convergences are statistically different for quads and doubles. This finding strongly supports the idea that the high quad-to-double ratios are at least partially due to the effect of the environment. We also examine the connections between flux anomalies and environment and the correlations between image separations and convergence. We find no significant links due to the limitations of our sample.

Aim: The aim of this study was to establish normal values for Schirmer tear test (version 2) and tear break up time (TBUT) in a South African young adult Black population. Method: Following ethical approval by the biomedical research and ethics committee, KwaZulu-Natal, participants were recruited from the city of Durban in South Africa via personal invitations, poster advertisements and University of KwaZulu-Natal optometry clinic clients. McMonnies questionnaire for dry eye diagnosis was administered and those who failed were excluded from the main study. Two hundred (100 males and 100 females) participants who met the inclusion criteria were included in the study. Following a slit lamp examination of the eye, the Schirmer test was administered and the following day, the TBUT was measured. A re-test version of the two procedures were conducted one week after, at about the same time of the day for each subject. Results: The participants were aged 18-30 years, mean = 20.77 ± 2.29 years. The mean Schirmer test values for all participants (N = 200; 400 eyes) was 15.96 ± 6.86mm. The values for the males and females (200 eyes each) were 16.34 ± 6.93mm and 15.58 ± 6.81mm respectively. The mean TBUT (400 eyes) was 7.18 ± 1.89 secs. The mean values for the males and females (200 eyes each) were 6.90 ± 1.88 secs and 7.32 ± 1.67 secs respectively. A strong positive correlation (r = 0.895) and (r = 0.914) respectively was found between the right and left eyes in the two tests. Conclusion: Generally, the mean values found in this study for the Schirmer test are similar to those that have been reported in the literature. However, values for TBUT differ from the values that have been previously reported, being higher in some instances and lower in others. These findings have implications for dry eye diagnosis and also contact lens practice in South Africa. / Thesis (M.Optom.)-University of KwaZulu-Natal, Westville, 2012.