Thesis (M. App. Sc.)--University of Queensland, 2001. / Includes bibliographical references.

Thesis (Ph. D.)--Lehigh University, 2002. / Includes vita. Includes bibliographical references (leaves 164-175).

Thesis (Ph. D.)--University of Michigan. / Cover title. "Reprinted from the Botanical gazette, 50:257-284, no. 4, October, 1910."

Thesis (Ph. D.)--University of Missouri-Columbia, 1998. / Typescript. Vita. Includes bibliographical references (leaves 84-85). Also available on the Internet.

Lost circulation and wellbore failure are common problems in the petroleum industry and they increase drilling costs dramatically. Casing drilling in depleted zones helps reduce drilling costs and problems related to lost circulation and wellbore failure. Thus, casing drilling is an important technology to minimize or eliminate conventional drilling problems in depleted zones. This thesis is focused on a study of smear effect in casing drilling in depleted formations. It is based on information about casing drilling and a commercial computer software ABAQUS. The smearing mechanism of drilling solids into the wellbore wall and the effects of parameters that affect the stress distribution around the wellbore wall are studied. Moreover, multiple wellbore cracks are studied to determine their effects on hoop stress distribution and all the results are given at the results chapter of this study. All the discussions about the changing parameters are given in results section. In conclusion, the smear effect in casing drilling can significantly improve hoop stresses around the wellbore and lost circulation problems can be minimized by using casing as a drilling string. These models can be used as a basic tool to understand smear effects in casing drilling in depleted formations. / text

The primary purpose of this study was to examine if the coupling effect could be overcome in a bimanual isometric tracking task, using methods similar to those of the Kovacs et al. team in previous bimanual kinematic research. Thirty right-handed participants, with a mean age 22.5 (SD 3.5) years, free from any neurological disorder or physical ailment, were randomly assigned to one of three groups that differed in percent of feedback provided during the practice trials (100%, 50% or 0%). The participants then performed a bimanual isometric manipulation tracking task that was a 2:1 rhythm (backwards C shape) scaled to 30% maximum voluntary contraction (MVC). Participants performed five blocks of five trials with the feedback schedule assigned to their group, rested for 30 minutes, then performed a retention task. Significant differences (p<.05) in Root Mean Square Error (RMSE) occurred between the 100% group and both the 50% and 0% groups during the practice blocks. Significant differences (p<.05) also occurred between the 50% group and the 100% and 0% group for the first four practice blocks. Though differences occurred between the groups during the practice trials, no differences occurred between the groups during the retention block. These findings support the position that the coupling effect in bimanual isometric manipulation tasks is very strong and cannot be as easily overcome as it is in kinematic bimanual task. This may be due to the feedback systems used in isometric conditions versus kinematic tasks (i.e. force and pressure sensation vs. position and motion proprioception). / text

Background: University administrator physical activity (PA) attitudes and actions may play an important role in student fitness promotion on campus but have been given little attention. Guided by the Theory of Planned Behavior (TPB), this study explored the relationships of factors that influence Chinese university administrator PA behaviors. Methods: A survey was designed to collect information regarding participants’ PA behaviors, intentions, perceived health, body mass index (BMI) and common demographic factors. A total of 474 Chinese university administrators participated in this study with 443 completed surveys. Path analysis was used to test the predictive and mediational role of the aforementioned variables on total PA. Results: Results revealed a good model fit. Attitudes mediated the effects of BMI and perceived health on total PA; subjective norms and self-efficacy had significant direct effects and mediated the effects of satisfaction and attitudes on total PA. The effects of intentions on total PA were not significant. Conclusions: Chinese university administrator PA behaviors were significantly influenced by attitudes, subjective norms, self-efficacy, BMI, perceived health and satisfaction with exercise facilities. The non-significant effects of intention on PA participation were not expected. More studies on university administrator’s PA are needed in the future. / text

published_or_final_version / Dentistry / Doctoral / Doctor of Philosophy

published_or_final_version / Dental Materials Science / Master / Master of Science in Dental Materials Science

Predators can affect prey by increasing their mortality, or may reduce the fitness of prey which modify their behaviours in response to predation risks (i.e. risk effects). Non-lethal effects of predators on prey behaviours are still poorly understood, although they may have cascading effects through food webs. This thesis examined the effect of habitat structure and symbiotic associations on the interaction between predatory fish and three rhynchocinetid shrimps: Rhynchocinetes typus in temperate rocky reefs in Chile, R. brucei in tropical rocky reefs in Hong Kong and Cinetorhynchus hendersoni in coral reefs in Malaysia. Underwater observations in Chile revealed that R. typus was rarely found on substrata with simple structure where refuges were scarce or lacking, but the effect of substratum complexity on their abundance was weak, probably because low fish abundance (and hence predation risk) did not affect survival probability below a critical threshold of refuge availability. This was in accordance with the observation that shrimp and fish abundance were negatively correlated in managed areas where fishing was limited, but not in open-access areas, were fish were less abundant. In addition, shrimps tended to form large aggregations in large shelters that offered limited protection against predators. Overall, direct effects of predation on shrimp densities and population structure were weak in Chile, whereas indirect effects on shrimp distribution within reefs appear to have been mediated through behavioural responses. Shrimp and other small decapods often associate with invertebrate hosts in order to gain protection from predators. In Hong Kong, where prolonged overexploitation of large predatory fishes has resulted in dominance of small fishes, R. brucei uses two alternative hosts: an urchin (Diadema setosum) and an anemone (Entacmaea quadricolor). Underwater surveys revealed that shrimps were rarely found outside crevices and holes unless associated with anemones and urchins. Experiments in the laboratory confirmed that, when given a choice, shrimps avoided open areas and associated with anemones and urchins which protected them against fish. Shrimps also imprinted upon the host species with which they were associated when collected from the field, and selected that host when given a choice. In Malaysia, where fish were more abundant than in Chile or Hong Kong, predation risks on C. hendersoni were high during the day, and shrimps exhibited nocturnal activity seemingly to reduce predation risk. Shrimps preferred only the most complex substrata, which provided the best protection against predators, while substrata with simple structure and few refuges were avoided. Tethering experiments and field observations confirmed that diel behaviour and substratum selection were driven by predation risk. Differences in fish abundance and diversity at the three study sites resulted in varying predation risks that influenced activity patterns and habitat choice by reef shrimps. These behavioural responses of prey to predation risks and their interactions with habitat structure have important implications for predicting how human disturbances, such as overfishing or habitat degradation, may disrupt predator-prey interactions and modify food webs. / published_or_final_version / Biological Sciences / Doctoral / Doctor of Philosophy