Browsing by Author "Thompson, William"
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Item Chronic toxicity of perfluoroheptanoic acid (PFHpA) and perfluorooctanoic acid (PFOA) to northern bobwhite (Colinus virginianus)(2018-08) Thompson, William; Anderson, Todd A.; Jackson, Andrew W.; Crago, JordanThis project’s primary objective was to characterize any adverse impacts of two perfluoroalkyl acids (PFAAs) to birds, with growth, development, and survival as the primary endpoints. PFAAs are a class of persistent, anthropogenic pollutants used in a wide variety of products for their non-reactivity, including in aqueous firefighting foam (AFFF). This study evaluated if chronic exposure at environmentally relevant concentrations could alter the health and reproductive fitness of adult birds and any negative impacts in ovo exposure may have on their offspring through maternal deposition into eggs. Secondary endpoints included examining how much accumulation of the target chemical occurs in liver tissue and how the body burden of PFOA and PFHpA, the two target PFAAs of this study, are altered by egg deposition. Furthermore, this project attempted to assess how much of the target chemical was present in egg yolk and how much juvenile quail retain after one month of growth. Chronic toxicity of the two target compounds was tested using Northern Bobwhite (Colinus virginianus) as the model species. Adult birds were exposed to drinking water containing nominal concentrations of 20 ng/mL, 1 ng/mL, and 0.1 ng/mL of the target chemical over the course of study (90 days). Juvenile bobwhite offspring were assessed for 30 days to determine any potential fitness effects from in ovo exposure. Residue analysis was conducted on adult and juvenile liver tissue as well as on eggs. Neither PFHpA or PFOA reduced hatching success, reproduction, or adult or juvenile Northern bobwhite survival at 1.860 or 1.745 µg/kg/day, respectively. However, it did appear that chromic ingestion of PFOA (1.745 µg PFOA/kg/day) may significantly increase weight of hatchling birds after one week, an effect observed in other vertebrates. Furthermore, residue analysis confirmed that female birds do reduce their body burden of both PFOA and PFHpA through deposition to eggs. In addition, some non-significant patterns of liver damage were identified in adult birds following chronic exposure.Item Estimation of Lower-body Kinetics from Loading Profile and Kinematics Alone, Without Measured Ground Reaction Forces(48th International Conference on Environmental Systems, 2018-07-08) Thompson, William; Huffman, R. Kenneth; Gallo, Christopher; Dewitt, John; Humphreys, B. T.; Godfrey, Aaron; Frenkel, David; Lewandowski, BethBiomechanical models of human motion can estimate kinetic outcomes, such as joint moments, joint forces, and muscle forces. Typically, one performs an inverse dynamics (ID) analysis to compute joint moments from the kinematics and measured external forces. Sometimes it is impractical to measure ground reaction forces and moments (GRF&M). We devised an empirical method for performing ID analysis of resistance exercises without measured GRF&M. The method solves the multibody dynamics equations of motion with four key assumptions about the GRF&M that reduce the number of unknowns. The assumptions are 1) negligible ground reaction moments, 2) fixed lateral/medial location of the center of pressure (COP), 3) equal fore/aft location of the COP between the feet, and 4) constant angle of the GRF vector relative to vertical in the frontal plane. We used evaluation trials from a prototype exercise countermeasure device to test this approach. Four participants performed squat and deadlift exercises at various loads. We compared results from traditional ID analysis to results without measured GRF&M using our method. We found that joint moment trajectories in the sagittal plane were similarly shaped between the two methods, and the amount of root mean squared error (RMSE), measured by difference in joint moment impulse, was typically under 15% (except for deadlift at the knee, <50%). Non-sagittal joint moment trajectories, which are much lower in overall magnitude, were not always similarly shaped between the two methods. Non-sagittal moments displayed much higher RMSE, with values ranging from 50-1000%. These findings were further supported by validation metrics (Sprague and Geers’ P and M metrics, Pearson’s r correlation coefficient). Based on these findings, we concluded that useful kinetic results are obtained from ID analysis of squat and deadlift exercises, even without measuring GRF&M, as long as the outcomes of interest lie in the sagittal plane.