INTRODUCTION: The demand for healthcare services is expected to increase significantly faster than the rate of growth of healthcare providers in the United States. One method for meeting the demand is the utilization of physician assistants in the management of patient care. Medical doctors and residents have traditionally provided radiation oncology patient care. It was not until recently that the use of physician assistants in radiation oncology became common practice. However, the most effective utilization of physician assistants in radiation oncology has not been fully elucidated at this time. REVIEW OF THE LITERATURE: The demand for radiation oncology services is expected to increase in part because people are living longer; there is increased cancer survivorship, and better treatment modalities. Physician assistants are capable of providing high quality patient care comparable to medical doctors and improving patient satisfaction. The need for Physician assistants in radiation oncology is expected to increase significantly by 2020. Effective models of team-based care are becoming increasingly important as the demand for radiation oncology services increases. PAs can be used in a variety of different models including shared, independent, and mixed models of team-based care. The utilization of physician assistants in radiation oncology is maximized when physician assistants provide care that otherwise could only be performed by a medical doctor. For example, when radiation oncology centers use a mixed model of team-based medicine, the practice can bill services provided by a physician assistant at 100% of the medical doctor service fee rate thus maximizing the cost effectiveness of physician assistants. METHODS: This study is aimed at determining the statistical difference in terms of new patient and established patient visits within an academic medical center radiation oncology unit before and after the addition of a physician assistant. A pre- and post-physician assistant analysis of new and established patient visits will be analyzed using a paired T-test. CONCLUSION: This study is unique in that it is focusing on a single radiation oncology center. A significant limitation of the study will be the small, single center, sample size. However, the results of this study can be used in the future as a reference for the expected impact of a physician assistant on a radiation oncology center.

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This thesis addresses health-policy relevant questions regarding quantity and quality of service delivery in primary healthcare using health administrative data from the province of Ontario. It is comprised of four chapters that explore the following questions: (1) What is the impact of switching from an enhanced fee-for-service (EFFS) payment model to a blended capitation payment model on the specialist referral rates of primary care physicians? (2) What are the rates of inappropriate laboratory testing in the province of Ontario? (3) What are the costs and determinants (physician and practice characteristics) of these inappropriate tests? (4) What is the impact of primary care payment structure on the quantity (number and cost) and the quality (appropriateness) of clinical laboratory testing? Fee-for-service (FFS) payment systems give physicians an incentive to treat patients on the margin of being referred, whereas in capitation systems physicians do not have a financial incentive to treat such marginal patients. Chapter 1 empirically examines how these two payment systems affect referral rates. The results show an increase in specialist visits upon a switch from an EFFS model to a blended capitation model when the physician is listed as the referring physician in the data, but no change in total specialist visits for these physicians’ patients. This change is not observed immediately upon switching payment models. Physicians paid by blended capitation who practice in an interdisciplinary health team have fewer specialist visits per rostered patient compared to EFFS physicians, despite an increase in their patients’ specialist visits after joining the interdisciplinary team. Using a definition of inappropriateness that quantifies ordering clinical laboratory tests too often or too soon following a previous test, Chapter 2 examines the rates of inappropriate laboratory testing for nine selected analytes in Ontario. The chapter finds that the percentage of inappropriate tests ranges from 6% to 20%. Moreover, between 60% and 85% of the time, the physician ordering an inappropriate test is the same physician who ordered the previous test. The findings also show that specialists are more likely than primary care physicians to order repeat tests too soon. Chapter 3 examines the costs and determinants associated with the rates of inappropriate laboratory utilization. The associated costs of inappropriate/redundant laboratory testing for the selected analytes ranges between 6 – 20% of the total cost of each test. Statistical analyses of the association of physician and practice characteristics with inappropriate testing are done using a logit model. Conditional upon the variables within the model, male physicians, physicians trained outside of Canada, older physicians, and a younger patient population are all shown to be associated with less inappropriate testing. Primary care physicians in group practices and in payment models with pay-for-performance (P4P) incentives are less likely to order inappropriate tests and specialist physicians are twice as likely to order inappropriately compared to FFS primary care physicians. Differences in physician, practice and patient characteristics, however, explain only a small amount of the variation in inappropriate utilization. Chapter 4 examines how physicians’ laboratory test ordering patterns change following a switch from an FFS payment model enhanced with P4P to a blended capitation payment model, and the differences in ordering patterns between traditional staffing and interdisciplinary teams within the blended capitation model. Using a propensity score weighted fixed-effects specification to address selection, the chapter estimates that a mandatory switch to capitation would lead to an average of 3% fewer laboratory requisitions per patient. Patients’ laboratory utilization also becomes more concentrated with the rostering physician. More importantly, using diabetes-related laboratory tests as a case study, physicians order 3% fewer inappropriate/redundant tests after joining the blended model and 9% fewer if they joined an interdisciplinary care team within the blended model. / Thesis / Doctor of Philosophy (PhD)

Temperate grasslands and the services they provide are threatened with severe degradation from human-driven land use changes. Among the worst affected services is pollinator support with grassland degradation contributing to the global decline in insect abundance due to habitat loss and a lack of floral resources. This has prompted conservation organizations to support pollinator conservation on working landscapes by increasing floral resources, but gaps remain in the consistent establishment of native forbs in intensively managed agricultural areas. We evaluated factors that influence native forb establishment during seed-based enrichment planting of tall fescue-dominated cattle pastures in two separate experiments: one testing a range of site preparation treatments with different seasons of sowing and comparing their effects on tall fescue suppression and seeded native plant establishment and the other investigating the effects of seed rate and pre-seeding cold stratification on native forb establishment on separate plots. For the site preparation experiment, we observed a mean target plant density of 0.12 target plants per m2 (SD = 0.247) The greatest target plant stem density (P < 0.0001) and species richness (P < 0.001) was in plots treated with a 2% glyphosate solution and sown with native seeds in early summer with the next five best treatments composed solely of fall sown replicates. For the seed and stratification experiment, we observed a mean target plant density of 88 target plants per m2 (SD = 73.9). Higher seeding resulted in greater target plant abundance in plots (P < 0.0001) with a seed rate of 56 kg/ha-1 resulting in almost three times as many target plants compared to 2.24 kg/ha-1. Pre-seeding stratification resulted in an increase in target plant abundance (P < 0.01). Target species richness was consistent between treatment levels. Results suggest that native forb establishment can be enhance by eliminating pasture grasses prior to seeding and the use of high seeding rates sown in the fall or using stratified seed. / Master of Science / Temperate grasslands and the services they provide are threatened with severe degradation from human-driven land use changes. Among the worst affected services is pollinator support with grassland degradation contributing to the global decline in insect abundance due to habitat loss and a lack of floral resources. To reverse this decline, conservation groups are encouraging the use of native plants throughout the landscape especially on farms and ranches to provide more resources for insect pollinators. One exciting opportunity exists in planting wildflowers into tall fescue-dominated cattle pastures that occupy millions of hectares of land in the Southeastern United States to provide food for pollinating insects. However little information exists on how to successfully establish wildflowers as much expertise is based on work done in the tallgrass prairie region of the Midwest. This study's goal was to investigate what control wildflower establishment by evaluating the success of an existing establishment experiment testing several site preparation techniques and different sowing seasons. A separate experiment was set up looking at the effect different seed rate and cold moist stratification had on establishment success of wildflowers. For the site preparation experiment, establishment was low for all treatments with a mean target plant density of 0.12 target plant per m2 (SD = 0.247). Summer sown 2% glyphosate had the highest wildflower richness and abundance at 0.35 target plants per m2 (SD = 0.247) and fall sown treatments were found to have higher sown wildflower abundance and richness than summer sown treatments. For the seed and stratification experiment, we observed a mean target plant density of 88 target plants per m2 (SD = 73.9). Target plant abundance did change between treatment levels with the highest and second highest seed levels yielding nearly three times and twice as many sown wildflowers as the lowest treatment respectively. Stratification resulted in an increase in sown wildflower abundance and sown wildflower richness did not differ significantly between treatment levels. Results suggest that native forb establishment can be enhance by eliminating pasture grasses prior to seeding and the use of high seeding rates sown in the fall using stratified seed.

Evaluation of the data from the series of batch experiments has led to the following conclusions: 1. Currently used methods of quantifying oxygen uptake rate, especially for batch reactors, yield values of oxygen utilization considerably lower than those predicted by mass balance considerations for these three wastes. In the face of Blok's published data indicating much better results with a short run reactor, it must be assumed that the length of run selected was at least partially responsible. 2. While quantitatively unsatisfactory, the methods for determining oxygen uptake used in these experiments seem to be of some use as monitors of biological systems. Changes in slope of the oxygen utilization curve were found to be more apparent at lower loadings. / Master of Science

The southern pine beetle (SPB) poses a significant threat to pine forests of the southeastern US. Pre-commercial thinning (PCT) is a commonly used silvicultural practice to mitigate and prevent SPB spread in young southern pine stands. Typically, PCT represents an added management cost to landowners and thinned material is not utilized for forest products. Increased demand for woody biomass energy may provide landowners and harvesting contractors an opportunity to utilize PCT residues as a woody biomass energy feedstock, which may wholly or partially offset PCT costs. However, little information is available regarding harvestable biomass quantities in PCT stands and few studies have assessed harvesting productivity and costs in very young pine stands. To develop estimates of biomass abundance in PCT candidate stands, loblolly pine (Pinus taeda) stands aging 5 to 12-years old, and enrolled in the Virginia Department of Forestry Pine Bark Beetle Prevention Program (VDOF PBBPP), were inventoried across the Piedmont and Coastal Plain regions of Virginia. To attain productivity and cost estimates of utilizing small-diameter stems for woody biomass energy, a biomass harvesting case study was then conducted on a 15-year old loblolly pine stand. Results of the inventory and case study indicate that stands at the upper age limit for the PCT program may contain harvestable quantities of biomass (39.63 green tons/acre), although high harvesting costs ($23.46/green ton) relative to regional delivered biomass prices may limit the economic feasibility of utilizing PCT biomass for energy. / Master of Science