published_or_final_version / Community Medicine / Master / Master of Public Health

published_or_final_version / Chemistry / Master / Master of Philosophy

A subaperture configuration to test aspheric optical components or systems is developed. The method developed has potential for testing rotationally symmetric aspheres without the use of null lenses. The aperture is divided into annular subaperture regions and an interferometer is refocused for each region to reduce the fringe density. Essential mathematical treatments involving annular subapertures, such as annular Zernike polynomials, are provided in detail. Numerical and experimental validations of the algorithm are described. Tolerance analyses on subaperture measurements are given. Computer programs were written to link the subaperture Zernike coefficients and to determine the full-aperture Zernike coefficients.

Conventional imaging techniques for cancer detection have difficulty finding small, deep tumors. Single-detector radiation probes have been developed to search for deep lesions in a patient who has been given a tumor-seeking radiopharmaceutical. These probes perform poorly, however, when the background activity in the patient varies greatly from site to site. We have developed a surgical dual-detector probe that solves the problem of background activity variation, by simultaneously monitoring counts from a region of interest and counts from adjacent normal tissue. A comparison of counts from the detectors can reveal the class of tissue, tumor or normal, in the region of interest. In this dissertation we apply methods from statistical decision theory and derive a suitable comparison of counts to help us decide whether a tumor is present in the region of interest. We use the Hotelling trace criterion with a few assumptions to find a linear discriminant function, which can be reduced to a normalized subtraction of the counts for large background count-rate variations. If area under the ROC curve is our figure of merit, the likelihood ratio is the optimum discriminant. We model likelihood functions of the data given the "tumor" and "no-tumor" hypotheses, and calculate the likelihood ratio. Using a spatial response map of the dual probe, a computer torso phantom, and estimates of activity distribution, we simulate a surgical staging procedure to test the dual probe and the discriminant functions. Results of the simulations show that the dual probe effectively solves the problem of background activity variations when used with any of the discriminant functions derived in this dissertation.

A brief study of the imagery of the bilateral symmetric optical system is presented. This study has been developed with a theoretical structure similar to that of the rotationally symmetric optical system and can be considered a generalization. It provides a simple, clear understanding of the main features of the imagery of the optical systems under consideration. and gives useful design insight. Some design examples are provided that illustrate the use and value of the theory developed.

The problem of using a computer to control the figuring of an optical surface is investigated. By assuming a linear, shift invariant figuring process, the amount of material removed during each figuring run can be computed. This is done by convolving a tool removal profile with a dwell function that describes the amount of time the figuring tool spends in each area element on the surface. Four methods of computing a dwell function that will best remove the figure errors are described. The advantages of making surface figure measurements using direct wavefront measurement techniques over the interferogram analysis methods used in previous computer controlled figuring machines are also discussed. The design and construction of a computer controlled optical figuring machine is then reviewed. The machine uses a computer controlled heterodyne interferometer to provide optical testing data on the surface being polished. Two microcomputers are used to analyze the test data and run the machine. Optical figuring is performed by scanning a polishing head with a known removal function over the surface at a rate derived from the surface errors. The operation of the software that computes the run path data and controls the machine hardware is outlined. The performance of each of the machine components is evaluated by comparing the behavior predicted by theory to the measured behavior. Initially, the accuracy of the interferometer is measured. The interferometer is then used to determine the performance of the polishing head by measuring the tool removal function. It is then shown that the machine can be run so that a predictable amount of material is removed from the surface. Finally, the feedback loop is closed and surface figure data from the interferometer is used to correctly polish the central region of a 16 inch diameter mirror. It is shown that the surface figure can be predicted with good accuracy over the entire surface. This work concludes with recommendations for improving the machine hardware and for improving the figuring performance near the edge of the surface being polished.

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No description available.

No research has been performed comparing percent body fat measurements using dual energy x-ray absorptiometry (DEXA) and air plethysmography after weight loss. The purpose of this investigation was to compare body composition assessments using the Bod Pod® Body Composition System (BP) and the DEXA ProdigyTM before and after an 8-week weight loss diet and exercise program. Based on prior comparison studies, it was hypothesized that percent fat values would be significantly lower using the BP compared to the DEXA before and after weight loss. Also since both methods have been shown to be reliable, it was hypothesized that the BP and DEXA would detect similar changes in percent fat in response to a weight-loss intervention. Twelve women (42 ± 8 yrs) and ten men (40 + 11 yrs) had their percent body fat estimated using the BP and whole body DEXA ProdigyTM scanner. A similar significant (P < 0.05) decrease in percent body fat was observed using the BP and DEXA ProdigyTM (-2.2% and -1.8%, respectively) after weight loss. Percent body fat using the BP was significantly lower than the DEXA ProdigyTM before (36 ± 10.7% and 38.1 ± 9.4%, respectively) and after (33.8 ± 10.8% and 36.3 + 10.6%, respectively) the weight loss program. Significant Pearson correlation coefficients between the DEXA ProdigyTM and the BP were noted pre (r = 0.975) and post (r = 0.968) weight loss. These data indicate the BP provides significantly lower absolute %fat values within a range of body fat levels (20-56%) when compared to the DEXA. However, the BP and DEXA detect similar changes in %fat, fatfree mass, and fat mass from weight loss in men and women. Also, the BP consistently overestimated fat-free mass and underestimated %fat and fat mass compared to values obtained from DEXA. / School of Physical Education