AIM: The primary purpose of this thesis was to evaluate the pattern of changes to accommodation and phoria when pre-presbyopic individuals perform near work for 20 minutes with +2D lenses. In addition, the thesis also investigates the effect of the accommodative vergence cross-link (AV/A) and age on binocular adaptation to addition lenses. METHODS: Accommodation was measured using the PowerRefractor (Multichannel Systems, Germany) and phoria was measured using the modified Thorington Technique. Twenty four pre-presbyopic and emmetropic individuals (11 adults and 13 children) participated in the study. All participants fixated a near target at a distance of 33 cm for 20 minutes with +2D (lens condition) and without (no lens condition) +2D addition lenses. Binocular and monocular changes in accommodation and near phoria were measured at the outset and at 3, 6, 9, 15 and 20 minute intervals. RESULTS: Effect of +2D lenses on accommodation and phoria: The emmetropic adult participants exhibited lag of accommodation under the no lens condition (binocular: 0.51 ± 0.12D; monocular: 0.64 ± 0.15D) that were eliminated (under monocular viewing) and reversed (exceeded demand by 0.51 ± 0.11 D under binocular viewing condition) with the addition of +2D lenses. The near phoria showed a significant increase towards exophoria by 6 ± 0.56 ∆D upon introduction of +2D lenses. Sustained near viewing with +2 D lenses resulted in significant reduction of the binocular focus alone (not monocular focus) after 3 minutes of binocular viewing (magnitude of reduction: 0.24D; P<0.01). The exophoria also showed a concomitant reduction after 3 minutes of fixation at the near task (Magnitude of reduction: 3.6 ± 0.6 ∆D; P<0.001). The magnitude and rate of vergence adaptation, determined using an exponential function, was found to be 4.6 ± 0.21 ∆D and 2.12 minutes respectively for the emmetropic adult participants. Effect of age on vergence adaptation: A pattern of significant reduction in phoria and binocular focus similar to the adult participants was observed in young children. Analysis of the vergence adaptation curves in the two age groups did not show any significant difference in both the magnitude as well as the rate of phoria adaptation within the age range tested (Magnitude of adaptation - Adults: 4.65 ∆D; Children: 4.51 ∆D; P > 0.05; Time constants -Adults: 2.12 minutes: Children: 1.53 minutes, P > 0.05). Effect of AV/A ratio on vergence adaptation: The stimulus (St-AV/A) and the response AV/A (R-AV/A) ratios were determined and the participants were divided into two groups (low and high AV/A ratio) under both the conditions. The result indicated that, under both testing conditions (stimulus and response AV/A), the individuals with higher AV/A ratios demonstrated greater magnitudes of vergence adaptation than those individuals with lower ratios (Magnitude of adaptation: Low St-AV/A = 4.12 ∆D; Low R-AV/A= 4.25∆D; High St-AV/A = 4.88 ∆D; High R-AV/A = 4.65∆D; P<0.05) CONCLUSIONS: Introduction of near addition lenses initiated an increase in exophoria and convergence driven accommodation. Vergence adaptation occurred after 3 minutes of binocular viewing thus reducing exophoria and convergence driven accommodation. The magnitude and completeness of phoria adaptation were seen to depend on an individuals AV/A ratio with greater magnitude and incomplete adaptation observed in participants with higher AV/A ratios. Age, within the limits of the study did not appear to influence phoria adaptation with near addition lenses.

In this Medical Physics M.Sc. project, a near-infrared (NIR) fluorescence imaging system was built for in-vivo diagnosis and evaluation of pigmented skin abnormalities and diseases. Light coming from a 785 nm diode laser is coupled into a ring light guide to uniformly illuminate the skin surface with a field-of-view (FOV) of 25 mm diameter. The diffuse reflectance and emitted fluorescence photons are collected by an NIR-sensitive CCD camera, with computer-controlled filter switch to select between reflectance mode and fluorescence mode. Both reflectance and fluorescence images of skin disorders were obtained with an exposure time of 2 seconds. The results show that cutaneous melanin in pigmented skin disorders emits higher NIR autofluorescence (AF) than surrounding normal tissue. This finding challanged the conventional concept that melanin is a non-fluorescence substance. The developed NIR autofluorescence imaging method also provided a new and direct way to characterize cutaneous melanin and can potentially be used for evaluation and diagnosis of pigmented skin diseases and skin cancers, such as melanoma.

In this Medical Physics M.Sc. project, a near-infrared (NIR) fluorescence imaging system was built for in-vivo diagnosis and evaluation of pigmented skin abnormalities and diseases. Light coming from a 785 nm diode laser is coupled into a ring light guide to uniformly illuminate the skin surface with a field-of-view (FOV) of 25 mm diameter. The diffuse reflectance and emitted fluorescence photons are collected by an NIR-sensitive CCD camera, with computer-controlled filter switch to select between reflectance mode and fluorescence mode. Both reflectance and fluorescence images of skin disorders were obtained with an exposure time of 2 seconds. The results show that cutaneous melanin in pigmented skin disorders emits higher NIR autofluorescence (AF) than surrounding normal tissue. This finding challanged the conventional concept that melanin is a non-fluorescence substance. The developed NIR autofluorescence imaging method also provided a new and direct way to characterize cutaneous melanin and can potentially be used for evaluation and diagnosis of pigmented skin diseases and skin cancers, such as melanoma.

This thesis will focus on spherical near-field antenna measurements and the methods developed or modified for the work of this thesis to estimate the uncertainty in a particular far-field radiation pattern. We will discuss the need for error assessment in spherical near-field antenna measurements. A procedure will be proposed that, in an automated fashion, can be used to determine the overall uncertainty in the measured far-field radiation pattern of a particular antenna. This overall uncertainty will be the result of a combination of several known sources of error common to SNF measurements. This procedure will consist of several standard SNF measurements, some newly developed tests, and several stages of post-processing of the measured data. The automated procedure will be tested on four antennas of various operating frequencies and directivities to verify its functionality. Finally, total uncertainty data will be presented to the reader in several formats.

Near-duplicate documents can adversely affect the efficiency and effectiveness of search engines. Due to the pairwise nature of the comparisons required for near-duplicate detection, this process is extremely costly in terms of the time and processing power it requires. Despite the ubiquitous presence of near-duplicate detection algorithms in commercial search engines, their application and impact in research environments is not fully explored. The implementation of near-duplicate detection algorithms forces trade-offs between efficiency and effectiveness, entailing careful testing and measurement to ensure acceptable performance. In this thesis, we describe and evaluate a scalable implementation of a near-duplicate detection algorithm, based on standard shingling techniques, running under a MapReduce framework. We explore two different shingle sampling techniques and analyze their impact on the near-duplicate document detection process. In addition, we investigate the prevalence of near-duplicate documents in the runs submitted to the adhoc task of TREC 2009 web track.

Three studies utilizing a single group of growing beef steers were conducted to ascertain the effects of tick stress on cattle and to evaluate the use of bio-forensic techniques of detection. Steers (n = 28, 194 ± 3.0 kg) were randomly assigned to one of four treatments in a 2 x 2 factorial arrangement: moderate (14.0 ± 1.0% CP, 60 ± 1.5% TDN) versus low (7.0 ± 1.0% CP, 58 ± 1.5% TDN) plane of nutrition, and control (no tick) versus tick treatment (300 pair of adult (Amblyomma americanum) per treated animal). Steers were individually fed experimental diets ad libitum for 35 days prior to and 21 days following the start of tick infestation (day 0), with peak tick feeding occurring 10 to 14 days post tick infestation. In study 1, blood was sampled on day -7, 0, 7, 8, 9, 10, 11, 13, 17 and 21, and plasma analyzed for metabolic and endocrine indicators. Within the low plane of nutrition, IGF-1 (ng/ml) was greater in control (P < 0.05) than in the tick treated (139.57 ± 9.3 vs 111.4 ± 9.3) group. Within the moderate plane of nutrition, tick treated cattle had higher (P < 0.05) plasma cortisol than nontreated. In study 2, fecal samples were analyzed for metabolic, endocrine and immunologic indicators. Fecal cortisol was the only constituent measured that was affected by treatment and not by plane of nutrition. The highest average daily fecal cortisol observed was for day 13, during peak tick feeding and after six days of repeated blood sampling. In study 3, near infrared spectra were obtained in the 1100-2498 nm range. Spectra were assembled into groups by plane of nutrition, treatment, and by plane of nutrition by treatment. Periods of 7 ± 1 days correspond to significant delineations in the tick feeding cycle. There were differences in pre-infestation versus infestation fecal spectra within the tick treated groups in both the moderate and low planes of nutrition. These differences can not be wholly attributed to tick treatment, but may have also been affected by blood sampling stress.

Current orbital solutions for 99942 Apophis predict a close approach to the Earth in April 2029. The parameters of that approach affect the future trajectory of Apophis, potentially leading to an impact in 2036, 2056, 2068, etc. The dynamic model used for this prediction does not account for non-gravitational perturbations including solar pressure and the Yarkovsky effect. Estimates of the displacement due to these perturbations range from -1500 to 1500km by 2029, comparable to 7? uncertainty in orbital solution. Uncertainties in physical characteristics stem from a lack of direct observations and a shortage of empirical data on similar objects. These perturbations, which stem from interactions with solar radiation, are directly related to the albedo of Apophis? surface. By modifying the average albedo of Apophis by 0.5%, between 4 and 15m of displacement can be effected between 2023 and 2029, rendering this method capable of avoiding all near-nominal solution keyholes. This modification is obtained by the deposition of electrostatically charged particles. These particles are charged via tribo-electrification and cure on the surface of Apophis creating a 30 micron thick layer of material with desired properties. This study found that a change in average albedo would nominally require 160kg of polytetrafluoroethylene (PTFE) to increase by 0.5% or 290kg of PTFE to decrease by 0.5%. The Apophis Exploration and Mitigation mission concept both improves accuracy of nongravitational perturbation models and delivers the albedo modification mechanism to Apophis, launching in 2021 and modifying albedo in 2023.

Neuroscientists have uncovered much about the dorsal and ventral visual object processing pathways. However, little is understood about the functional development of these pathways in human infants. Behavioral data has shown that as early as 2.5 months, infants are sensitive to spatiotemporal information for object individuation in occlusion events. This study used Near Infrared Spectroscopy to assess neural activation (as evidenced by an increase in HbO2) in four areas of the pathways: primary visual cortex (O1), posterior parietal cortex (P3), lateral occipital (T5), and inferior temporal (T3) in awake human infants aged 5.5 months while they view either a spatiotemporaldiscontinuity event or a control event. Three major predictions were made: 1) since the events contain visually distinct objects, there should be significant neural activation in O1 to both events, 2) if the dorsal route mediates the processing of spatiotemporal discontinuities, then there should also be a significant increase in P3 in response to the spatiotemporal-discontinuity event but not to the control event, and 3) activation present in T3 and T5 should not vary by condition if the ventral pathway is not responsible for the processing of spatiotemporal discontinuities. Results supported all three predictions.

With the improvement of biological techniques, the amount of biosequences data, such as DNA, RNA and protein sequences, are growing explosively. It is almost impossible to handle such huge amount of data purely by manpower. Thus the requirement of the great computing power is essential. There are some ways to treat biosequence data, finding identical biosequences, searching similar biosequences, or mining the signature of biosequences. All of these are based on the same problems, the biosequence alignment problems. In this dissertation, we shall study the biosequence alignment problems to raise the biological meaning of the optimal or near-optimal alignments since the biologists and computer scientists sometimes argue the biological meaning of the mathematically optimal alignment obtained based on some scoring functions. We first study the methods to improve the optimal alignment of two given biosequences. Since usually the optimal alignment is not unique, there should exist the best one among the optimal alignments, and we try to extract this by defining some other criteria to judge the goodness of the alignments when the traditional methods cannot decide which is the better one. Two algorithms are proposed for solving the newly defined biosequence alignment problems, the smoothest optimal alignment and the most conserved optimal alignment problems. Some other criteria are also discussed since most of them can be solved in a similar way. Then we notice that the most biologically meaningful alignment may not be the optimal one since there is no perfect scoring matrix. We address our candidates in those near-optimal alignments, and present a tracing marking function to get all near-optimal alignments and use the criterion "the most conserved" to filter it, which is named as the near-optimal block alignment (NBA) problem. Finally, as everybody knows that existing scoring matrices are not perfect at all, we try to figure out how we choose the winner when multiple scoring matrices are applied. We define some reasonable schemes to decide the winner alignment. In this dissertation, we solve and discuss the algorithms for near-optimal alignment problems on biosequences. In the future, we would like to do some experiments to support or reject these concepts.

Thesis (M.A.)--University of Oregon, 2000. / Typescript. Includes vita and abstract. Includes bibliographical references (leaves 204-206).