Philosophiae Doctor - PhD / The fluoride release and chemical adherence to tooth structure remain the most desirable features of glass ionomer restorative cements (GICs). Although the physical properties for multi-surface restorations are well-defined, even with the introduction of newer GICs not all demands have been met. Yet, increased use of GICs will only be possible if clinicians change their perceptions of the low survival rate of GICs. The lower clinical success rate of GICs is partly due to the marginal integrity and wear over time, which has often been recorded in the literature as restoration failure. The current, well-established restorative options for the primary dentition are Resin Modified Glass Ionomers (RMGICs) and Compomer resins. There is a paradigm shift towards materials that are more biologically favourable. Areas of research for dental materials include antibacterial properties in conjunction with ion release to maintain healthy restored teeth. If a GIC can provide adequate physical properties with the inclusion of the aforementioned features, GICs might become a more viable permanent restorative solution.

Graduation date: 2000

Managing cattle to disseminate seeds of desirable plants, or alternatively, to restrict weed seed contamination on rangelands is of interest to managers. Four experiments were conducted to determine effects of ruminant digestion on germination of ingested seeds. A number of plant species representing a variety of seed size and seed coat hardness were subjected to in vitro digestion. Experiment one was conducted to determine effect of varying lengths of digestion time on seed germination. Seed germination varied by plant species in response to length of digestion. Germination of large soft-coated seeds, such as bluebunch wheatgrass (Agropyron spicatum (Pursh) Scribn. & Smith Goldar) and basin wildrye (Elymus cinereus Scribn & Merril Magnar), was reduced to 0%. Smaller grass seeds, such as Sherman big bluegrass (Poa secunda Presl. Sherman), survived but germination declined following 24-hour, 48-hour, and 72-hour digestion. Experiment two examined effect of different stages of ruminant digestion on seed germination. The combination of Stage I (rumen-simulated digestion) and Stage II (abomasal-simulated digestion) resulted in greatest seed mortality. Two water treatments were included to evaluate the effects of high temperatures (39��C), moisture uptake, and lack of oxygen. Water + O��� and Water + CO��� reduced germination, however not as much as Stage I and Stage II treatments. The third experiment determined effects of diet quality on seed germination. Seeds digested in rumen fluid collected from steers fed a 72% corn concentrate diet resulted in 0% germination for all species. Grass seed germination was low for seeds digested in rumen fluid collected from steers fed a forage diet. Whitetop (Cardaria draba (L.) Hand.) germination was 24% and 28% for 35-hour and 59-hour roughage treatment, respectively, and germination was 0% for 35-hour and 59-hour concentrate treatments. Germination of water-only treatments for most species was reduced in comparison to the control treatment, but was greater than remaining treatments. Experiment four evaluated germination of seeds exposed to in situ versus in vitro digestion. In situ digestion resulted in lower seed germination than in vitro digestion for all species examined. Large, soft grass seeds may not be suitable candidates for reseeding rangelands. However, it is important for managers to recognize that cattle may distribute viable weed seeds in feces. Confining cattle or supplementing with high concentrate diets may help prevent spread of weedy species. / Graduation date: 1997

Agents with differential constraints, although common in the real world, pose a particular difficulty for motion planning algorithms. Methods for solving such problems are still relatively slow and inefficient. In particular, current motion planners generally can neither "see" the world around them, nor generalize from experience. That is, their reliance on collision tests as the only means of sensing the environment yields a tactile, myopic perception of the world. Such short-sightedness greatly limits any potential for detection, learning, or reasoning about frequently encountered situations. In result these methods solve each problem in exactly the same way, whether the first or the hundredth time they attempt it, each time none the wiser. The key component of this thesis proposes a general approach for motion planning in which local sensory information, in conjunction with prior accumulated experience, are exploited to improve planner performance. The approach relies on learning viability models for the agent's "perceptual space", and the use thereof to direct planning effort. In addition, a method is presented for improving runtimes of the RRT motion planning algorithm in heavily constrained search-spaces, a common feature for agents with differential constraints. Finally, the thesis explores the use of viability models for maintaing safe operation of user-controlled agents, a related application which could be harnessed to yield additional, more "natural" experience data for further improving motion planning.

Agents with differential constraints, although common in the real world, pose a particular difficulty for motion planning algorithms. Methods for solving such problems are still relatively slow and inefficient. In particular, current motion planners generally can neither "see" the world around them, nor generalize from experience. That is, their reliance on collision tests as the only means of sensing the environment yields a tactile, myopic perception of the world. Such short-sightedness greatly limits any potential for detection, learning, or reasoning about frequently encountered situations. In result these methods solve each problem in exactly the same way, whether the first or the hundredth time they attempt it, each time none the wiser. The key component of this thesis proposes a general approach for motion planning in which local sensory information, in conjunction with prior accumulated experience, are exploited to improve planner performance. The approach relies on learning viability models for the agent's "perceptual space", and the use thereof to direct planning effort. In addition, a method is presented for improving runtimes of the RRT motion planning algorithm in heavily constrained search-spaces, a common feature for agents with differential constraints. Finally, the thesis explores the use of viability models for maintaing safe operation of user-controlled agents, a related application which could be harnessed to yield additional, more "natural" experience data for further improving motion planning.

As fish cell cultures continue to be explored as alternatives to whole fish for evaluating the toxicity of environment chemicals, technical issues have emerged that influence results and thus need to be understood and standardized. These include carrier solvents, dosing protocols, exposure vessel, exposure media, viability endpoints, and cell lines. Some of these factors have been explored in this thesis for eight reactive contaminants exhibiting varied physicochemical properties using the rainbow trout cell lines RTgill-W1 and RTL-W1. Sodium dodecyl sulphate (SDS) was used as a reference (control) chemical. Cell viability was evaluated with alamar Blue, carboxyfluoroscein diacetate acetoxymethyl ester and neutral red as measures respectively of metabolic activity, plasma membrane integrity, and lysosomal function. Experimental in vitro EC50 values were compared to 1) pre-existing in vivo LC50s from the fathead minnow database and 2) pre-existing in vitro EC50s from the Halle database. Results point to good in vitro/in vivo correlations for menadione, dichlorophene, hexachlorophene, and acrolein. Poor correlations were observed for allyl alcohol, 4-fluoroaniline, acetaldehyde, and 2,3-dimethyl-1,3-butadiene due to a combination of solubility and volatility problems. Overall, the results suggest that the impact of different technical approaches on the evaluation of acute toxicity in vitro depends very much on the chemical class being investigated and less on the characteristics of the cell line. The in vitro cytotoxicity of reactive chemicals is challenging due to the nature of the chemicals’ physicochemical properties. Further improving the in vitro toxicity of reactive chemicals is a prerequisite for the ultimate goal of using fish cell cultures as acceptable, standard alternatives to the use of fish acute lethality assays.

As fish cell cultures continue to be explored as alternatives to whole fish for evaluating the toxicity of environment chemicals, technical issues have emerged that influence results and thus need to be understood and standardized. These include carrier solvents, dosing protocols, exposure vessel, exposure media, viability endpoints, and cell lines. Some of these factors have been explored in this thesis for eight reactive contaminants exhibiting varied physicochemical properties using the rainbow trout cell lines RTgill-W1 and RTL-W1. Sodium dodecyl sulphate (SDS) was used as a reference (control) chemical. Cell viability was evaluated with alamar Blue, carboxyfluoroscein diacetate acetoxymethyl ester and neutral red as measures respectively of metabolic activity, plasma membrane integrity, and lysosomal function. Experimental in vitro EC50 values were compared to 1) pre-existing in vivo LC50s from the fathead minnow database and 2) pre-existing in vitro EC50s from the Halle database. Results point to good in vitro/in vivo correlations for menadione, dichlorophene, hexachlorophene, and acrolein. Poor correlations were observed for allyl alcohol, 4-fluoroaniline, acetaldehyde, and 2,3-dimethyl-1,3-butadiene due to a combination of solubility and volatility problems. Overall, the results suggest that the impact of different technical approaches on the evaluation of acute toxicity in vitro depends very much on the chemical class being investigated and less on the characteristics of the cell line. The in vitro cytotoxicity of reactive chemicals is challenging due to the nature of the chemicals’ physicochemical properties. Further improving the in vitro toxicity of reactive chemicals is a prerequisite for the ultimate goal of using fish cell cultures as acceptable, standard alternatives to the use of fish acute lethality assays.

Originally described from the Asian honey bee, Apis cerana, the microsporidian Nosema ceranae is an obligate, intracellular parasite that has recently been discovered infecting the western honey bee, Apis mellifera. More research on the biology of N. ceranae as well as on the impact it may have on A. mellifera is greatly needed. However, conducting studies on N. ceranae is not only dependent on seasonal availability of Nosema spores, but also on reliable methods for determining spore viability. This study presents the results of using cryogenics to provide long term storage of viable N. ceranae spores and a differential staining procedure that details how to use bright field microscopy with the fluorescent viability dye, propidium iodide (PI), and the fluorescent stain, 4', 6-diamidino-2-phenylindole (DAPI) to differentiate viable and nonviable spores. Using these methods, it was found that freezing N. ceranae at -70 °C in 10% glycerol yielded the lowest mean rate of spore mortality after thawing (24.2% ± 2.2).

Seeds of wild rice (Zizania palustris var. interior) have been reported to show highest survival when dehydrated at 25 QC. It has also been reported that axis cells sustained least damage at this drying temperature. In the present study, a linear relationship between drying rate and dehydration temperature was established. Whereas highest positive tetrazolium staining and lowest leakage were recorded for seeds that were dehydrated at 25 QC, maximum germination was recorded for seeds dried at 20 QC. A proportion of seeds showed the presence of glasses, irrespective of the dehydration temperatures used. Parameters of the glass to liquid transition, however, correlated with neither water content nor sugar profiles. The ratio of raffinose to sucrose was similar among all the treatments. A hydroperoxide test revealed a linear relationship between peroxide levels and temperature of drying although the levels of fatty acids were not correlated with hydroperoxide levels. Butanal levels and total aldehydes evolved, on the other hand, showed a high negative correlation with peroxide levels. Electron microscopy showed that the variability and relative abundance of peripheral membrane complexes (PMCs) was the highest for cells of embryonic axes dehydrated at 25 QC and the lowest for embryonic axes of seeds dried at 10 QC. Furthermore, intramembrane particles (IMPs) were evenly distributed in cells of axes dried at 25 or 37 QC. In contrast, membranes of cells of axes dehydrated at 10 QC showed large IMP-free areas. The relative abundance of IMPs was the highest for cells of embryonic axes dried at 25 QC, and the lowest for cells of axes dehydrated at 10 QC. From these observations, it is suggested that membrane phase transition, with the concomitant elimination of proteins, accompanies dehydration of Z. paluslris seeds at 10 QC, whereas at 37 QC peroxidation may predominate. / Thesis (M.Sc.)-University of Natal, Durban, 1996.

Thesis (Ph.D.)--Bowling Green State University, 2007. / Document formatted into pages; contains xii, 121 p. : maps. Includes bibliographical references.