Forests play an important role in mitigating climate change. It can not only provide carbon sequestration in standing forests and long-life forest products, but can also reduce carbon release by bioenergy’s substitution of fossil fuel. Therefore, a comprehensive impact from forest carbon on landowners’ forest management decisions should be analyzed when considering those uncertainties in carbon life cycle. The first part of the dissertation is a meta-analysis review, in which important factors that can influence the estimation of harvesting rotations under carbon sequestration are summarized and analyzed. It concludes that some issues as natural disturbances and forest bioenergy deserve more attentions, which are addressed in the following two chapters. The second part adopts a revised Faustmann model to assess the relation between wildfire risk and prescribed fire under four assumed carbon policy scenarios. It arrives at the conclusion that penalty on carbon release in prescribed fire may reduce carbon sequestration in standing forests and make forest landowners to take the risk of loss in wildfire. Thus, a carbon policy with such a regulation should be adopted with caution. The third part investigates the probable influence brought by wood-based biofuel of stochastic prices with a Monte Carlo method. The results demonstrate that the assumption of double stochastic prices leads to earlier harvesting when comparing to constant price scenario or stochastic price assumption of only timber. The stochasticity of energy price may benefit landowners but also introduce uncertainties into their revenue. It also reduces sequestered carbon in standing forests and long-life forest products, which should be paid more attention when a general point of view on forest carbon is the concern. This project is informative for landowners who are facing new opportunities and challenges in forest management and is also helpful for carbon policy makers when dealing with forest carbon dilemmas of prescribed fire and bioenergy.

In 2010, comet 103P/Hartley 2 was observed pre- and post-perihelion using the George and Cynthia Mitchell Integral Field Spectrometer on the 2.7-m telescope at McDonald Observatory in Texas. Data for gaseous radicals C2, C3, CH, CN, and NH2 were collected over six nights from 15 July to 10 November. The spectral data were used to create coma maps for each of the observed species, and the maps were processed using radial and azimuthal mean division techniques to create enhanced images of the coma, revealing subtle morphological features. 340 enhanced coma images were created for each observation and species. Visual inspection reveals that the coma is heterogeneous between the five detected radicals, and statistical analyses verify this result. To compliment the ongoing investigation of Hartley 2 as studied by the EPOXI flyby mission, findings from other researchers (Belton et al., 2012; Syal et al., 2012; and Thomas et al., 2012) are used to characterize the nucleus spin state and identify dust jet locations on the nucleus. With rotational period measurements from EPOXI, dust jet vectors on the nucleus surface are rotated to relevant observation times in November to compare the computed jet directions with the radical densities in the coma. Dust jet sites on the smaller nucleus lobe show a stronger correlation with high radical concentrations than the dust sites on the larger nucleus lobe. Production rates for potential parentage of radical species are calculated using the radial outflow Haser model (Haser, 1957), which are compared to mixing ratios relative to water from separate campaigns to constrain parentage. NH3 is likely the sole producer of NH2, whereas CN may be produced from a combination of HCN, C2N2, and CH3CN. Traditional parentage of C2, C3, and CH do not yield acceptable fits or suitable mixing ratios with the Haser model, and it is possible that extended coma ices having relatively short scale lengths greatly contribute to production of these radicals. These results provide further evidence that the Hartley 2 nucleus is heterogeneous in composition, and the rotational analysis indicates that specific jet sites are correlated with certain radical species.

Field and greenhouse studies were conducted during 2004 through 2006 at the Rodney R. Foil Plant Science Research Center, Starkville, MS. Six sorghum and soybean rotation treatments were tested to determine their effect on plant pathogen, insect, and nematode diversity and density levels. Treatments included 1) continuous sorghum, 2) continuous soybean, 3) sorghum-soybean-sorghum rotation, 4) soybean-sorghum-soybean rotation, 5) sorghum-soybean-soybean rotation, and 6) soybean-sorghum-sorghum rotation. Several nematode and insect species were identified during the study, but were always below economic thresholds. Six insect species were identified on soybean during each growing season and used as the indicator species for this study. The most prevalent were threecornered alfalfa hopper (Spissistilus festinus (Say) and bean leaf beetle (Cerotoma trifurcata (Forester). Sorghum webworm (Nola sorghiella Riley) and corn earworm (Helicoverpa zea (Boddie) were the most common insects on sorghum panicles. Rotations did not affect the diversity or density levels of the indicator soybean or sorghum insects during the three year study. Plant disease levels during the investigation showed variable results. Three foliar fungal pathogens including Diaporthe phaseolorum (Cooke & Ellis) Sacc. var. meridionalis, Septoria glycines Hemmi, and Cercospora sojina Hara on soybean, and Gloeocercospora sorghi D. Brain & Edgerton ex Deighton on sorghum were observed. The only virus disease on soybean was bean pod mottle, but levels were not affected by the rotations during the study. Zonate spot caused by G. sorghi was the most prevalent foliar sorghum disease, but was not affected by the rotations. Six frequently isolated fungal pathogens from either soybean or sorghum roots included Macrophomina phaseolina (Tassi) G. Goidanich, Rhizoctonia solani Kühn, D. phaseolorum, Aspergillus spp., Trichoderma spp and Fusarium spp. Aflatoxin contamination of sorghum seed was low (<20 ppb) the first two years of the study, but was high (790 ppb) in 2006. Significantly greater soybean and sorghum yields were obtained from rotated systems compared to monoculture systems in 2005. In a greenhouse test, M. phaseolina infection of soybean led to significantly greater root disease ratings, lower plant height and dry weight than the untreated control. Sorghum plant growth was not affected by M. phaseolina and R. solani.

No / Background - Although there is a wealth of research into the kinematic coupling between the foot and shank, it remains unclear whether the relationship is stable across speed and mode of gait. The aim of this study was to determine whether the coupling relationship between the forefoot, rearfoot and shank differed between walking and running, and across different running speeds. Methods Twelve subjects walked/ran barefoot over-ground at one walking and three running speeds. The shank, rearfoot and forefoot were modelled as rigid segments and three-dimensional joint kinematics were determined using a seven camera ProReflex system. Coupling between the forefoot, rearfoot and shank was assessed using cross-correlation and vector coding techniques. Findings Cross-correlation of rearfoot eversion/inversion with shank internal/external rotation was lower in walking (r=0.49) compared to running (r>0.95). This was also the case between rearfoot frontal plane and forefoot sagittal plane motion (walking, r=¿0.80; running, r=¿0.96). Rearfoot frontal plane and forefoot transverse plane cross-correlation was high in both running and walking (r>0.90), but there was little evidence of any coupling between rearfoot frontal plane and forefoot frontal plane motion in any condition. No differences in cross-correlations were found between the three running speeds. Interpretation Kinematic coupling between the forefoot, rearfoot and shank was weak during walking relative to running. In particular, the low cross-correlation between rearfoot eversion/inversion and shank internal/external rotation during walking implies the two motions are not rigidly linked, as has been assumed in previous injury models.

Seismic isolation is a method of earthquake resistant design which has been proven to effectively reduce the damaging effects of earthquakes on buildings as well as the contents within them. However, traditional implementation of an isolation system tends to be expensive. For new construction, rigid diaphragms above and below the isolation layer and construction of a seismic gap contribute to expenses, while retrofit applications also require excavation beneath the building and may need extensive foundation work. To mitigate these major costs bearings may be placed on the tops of columns, forgoing the construction of a seismic gap, additional rigid diaphragm, and foundation work. However, columns under the isolation layer may be flexible, changing the bearing end conditions traditionally assumed. To investigate the effects of flexible end conditions on elastomeric bearings, an analytical model that accounts for translation and rotation of both endplates was developed based on Haringx's theory. The derivation accounts for compressibility of the rubber and results in a simple stiffness matrix. To evaluate the model, an experimental program testing column-bearing subassemblies under quasi-static cyclic conditions was conducted. Experimental findings show that flexible end conditions can significantly reduce the lateral stiffness of elastomeric bearings. Simulations with the theoretical model compare well under small deformations, but elastic softening of the moment-rotation relationship causes theoretical results to diverge from experimental with larger endplate rotations. The effectiveness of column-top isolation as a retrofit strategy was investigated through nonlinear time history analyses of a moment resisting frame designed to the 1965 National Building Code of Canada and retrofitted with column-top isolation. The frame was simulated under ground motions representative of current hazards and showed that the retrofit resulted in significant reductions in interstory drifts and floor accelerations. Yielding was observed throughout the original frame under maximum considered earthquakes, while the retrofit frame remained elastic. / Thesis / Master of Applied Science (MASc)

Soil-borne oomycetes include plant pathogens that cause substantial losses in the agricultural sector. To better manage this important group of pathogens, it is critical to understand how they respond to common agricultural practices, such as tillage and crop rotation. Here, a long-term field experiment with a split-plot design with tillage as the main plot factor (conventional tillage [CT] vs. no till [NT], 2 levels) and rotation as the subplot factor (monocultures of soybean, corn, or wheat, and corn-soybean-wheat rotation, 4 levels) was sampled. Post-harvest oomycete communities were characterized over three consecutive years (2016-2018) by metabarcoding the Internal Transcribed Spacer 1 (ITS1) region of soil DNA extracts. The community contained 292 Amplicon Sequence Variants (ASVs) and was dominated by Globisporangium spp. (85.1% in abundance, 203 ASV) and Pythium spp. (10.4%, 51 ASV). NT decreased diversity and community compositional structure heterogeneity, while crop rotation only affected the community structure under CT. Soil and crop health represented by soybean seedling vitality was lowest in soils under CT cultivating soybean or corn, while grain yield of the three crops responded differently to tillage and crop rotation regimes. The interaction effects of tillage and rotation on most oomycetes species accentuated the complexity of managing these pathogens.

This research aims to investigate whether expertise, specifically martial arts expertise, is transferrable across domains, which would indicate spatial skills in one task can also apply to a seemingly unrelated one. In this study, reaction time during a mental rotation task was compared between experts and novices. Participants were shown two images and had to decide if the images were the same or mirror reflections. The images were comprised of Shepard-Metzler blocks, people in martial arts poses, and people in neutral poses. The results suggest expertise is not transferable across domains. While experts outperformed novices with some of the martial arts stimuli, there was not a significant difference with the neutral poses. Novices performed better than experts with the Shepard-Metzler blocks. This suggests experts may have embodied some of the stimuli to facilitate faster reaction times. Further research must be conducted to investigate if any type of expertise is transferable across domains, which could assist in the development of employee training programs, and to validate the human figures used as stimuli.

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Work-related musculoskeletal disorders (WMSDs) remain a substantial problem in the workplace. Rotation, in which workers are rotated between tasks, is widely used as an administrative control, as it is considered to reduce WMSD risk through reducing physical exposures and increasing exposure variation. However, despite its widespread use, there is limited evidence that rotating between tasks is effective in reducing the risk of WMSDs. Inconsistencies in measured outcomes of rotation may be attributed to the variety of parameters involved in determining rotation schedules, including which tasks to include in a schedule, the rate at which workers rotate, and the order in which tasks are performed. This research assessed the effects of rotation, specifically focusing on rotation frequency and task order, on muscle fatigue and performance when included tasks loaded the same muscle group. Twelve participants completed six experimental sessions in each of three studies, during which repetitive tasks were performed for one hour either with or without rotation. Each study simulated a different task, including static shoulder abduction, box lifting, and a light assembly task. Rotation occurred between lower and higher exertion levels, and each rotation schedule varied in both rotation frequency (rotating every 15 minutes vs. 30 minutes) and task order (starting with the lower vs. higher intensity task). Muscle fatigue was assessed through several measures, including electromyography, and ratings of perceived discomfort. Performance was assessed through the accuracy of shoulder moment output, the accuracy of box placement, or the speed of assembly completion. As expected, rotation was effective in reducing fatigue compared to higher intensity tasks with no rotation, although it increased fatigue compared to the lower intensity with no rotation. While effects of rotation frequency and task order were seen on some measures, results across all three studies did not indicate consistent effects of either rotation frequency or task order on fatigue or performance. As such, the practical relevance of these rotation parameters and the likely impacts of rotation are not yet clear, and further assessments are needed. Such assessments should ideally involve longer durations, field studies, and/or more direct measures of injury or injury risk. / Ph. D.