Radiotherapy aims to strike a tumour with high accuracy, but anatomic changes and internal organ motion introduce uncertainties and therefore large margins are conventionally used to compensate for this. The MR-Linac will enable target tracking prior to and during treatment which will make daily adjustments of a treatment plan possible. But a motion tracking of the target requires fast 3D imaging and image processing which are currently not viable with sufficiently low latency. In this project a method to estimate the motion of a target by using a parameterized motion model created prior to treatment and a stream of 2D images acquired during treatment was studied. The motion model had been parameterized by using principal component analysis (PCA). The 2D images were aligned to the corresponding images in the motion model through deformable image registration which resulted in a deformation field. Then new parameters (eigenmode weights) of the motion model were calculated by taking the projection of the deformation field on a vector space spanned by the eigenmodes of the PCA motion model. An estimation of the motion was then created by applying the new weights to the PCA motion model. The results were evaluated by visual comparison and with quantitative metrics such as the Dice similarity coefficient. The method was applied to data from 9 volunteers and the results confirmed that the proposed method can estimate the motion of a target and indicated that it is most suitable for volunteers with large intra-fraction motion. The results also showed that the temporal resolution of the motion model can be increased by using 2D images of lower spatial resolution. The created motion model can be used for many clinical applications like retrospectively calculating the accumulated doses in the tumour and the organs-at-risk and potentially could be used for real-time target tracking.

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This dissertation focuses on the non local continuum peridynamics model for the mechanics of materials, related constitutive models, its connections to molecular dynamics and classical elasticity, and its multiscale and multimodel capabilities. A more generalized role is defined for influence functions in the state-based peridynamic model which allows for the strength of non local interactions to be modulated. This enables the connection between different peridynamic constitutive models, establishing a hierarchy that reveals that some models are special cases of others. Furthermore, this allows for the modulation of the strength of non local interactions, even for a fixed radius of interactions between material points in the peridynamics model. The multiscale aspect of peridynamics is demonstrated through its connections to molecular dynamics. Using higher-order gradient models, it is shown that peridynamics can be viewed as an up-scaling of molecular dynamics, preserving the relevant dynamics under appropriate choices of length scales. The state-based peridynamic model is shown to be appropriate for the description of multiscale and multimodel systems. A formulation for nonlocal interface problems involving scalar fields is presented, and derivations of non local transmission conditions are derived. Specializations that describe local, non local, and local/non local transmission conditions are considered. Moreover, the convergence of the non local transmission conditions to their classical local counterparts is shown. In all cases, results are illustrated by numerical experiments. / A Dissertation submitted to the Department of Scientific Computing in partial fulfillment of the requirements for the degree of Doctor of Philosophy. / Degree Awarded: Fall Semester, 2010. / Date of Defense: July 20, 2010. / Interface Problems, Upscaling, Continuum Mechanics, Peridynamics, Multiscale, Nonlocality / Includes bibliographical references. / Max Gunzburger, Professor Directing Thesis; Per Arne Rikvold, University Representative; Anter El-Azab, Committee Member; Janet Peterson, Committee Member; Sachin Shanbhag, Committee Member; Richard B. Lehoucq, Committee Member; Michael L. Parks, Committee Member.

Graduation date: 1999

The purpose of this research was to use whitebark pine trees at three major sites in western Montana to: (1) determine tree species response to climate, (2) reconstruct past climate conditions, (3) determine the effects of climate shifts on treeline, and (4) reconstruct fire history from fire-scar data. I collected samples from whitebark pine and subalpine fir and from remnant whitebark pine in the western Beaverhead-Deerlodge and Lolo National Forests. In the climate response analysis, the Palmer Drought Severity Index (PDSI) had the highest correlations with whitebark pine growth. The strongest relationship occurred in the previous year’s June and July. Precipitation in the previous year’s May and June was also positively related to growth. I reconstructed the previous year’s June and July PDSI at all sites using a transfer function with tree-ring indices as the independent variable. The most intense drought year since 728 occurred in 1468. The reconstruction showed no evidence of a shift in the intensity and duration of wet and drought periods between the Medieval Warm Period and Little Ice Age. To evaluate possible effects of increased global temperatures since the beginning of the 19th century on tree growth at high-elevation sites in western Montana, I established plots at 10 sites. I examined the establishment dates of all stems in each plot. Additionally, I examined the spatial relationships with establishment dates using a nearest neighbor statistic. Movement of treeline upslope was seen at the lower and upper elevation plots, while the mid-elevation plots remained stable. The greatest degree of movement (150 m) at treeline occurred in the 1980s. Fire frequency and fire seasonality varied over time, reflecting the influence of climatic conditions. I collected 26 fire-scarred samples from a single site in the Gravely Range. The reconstruction of fire history revealed that fire was most frequent at the Gravely Range site during the Medieval Warm Period, but became less frequent during the Little Ice Age. Fire could possible play a role in the stand dynamics of the whitebark pine/subalpine fir ecosystem and limit the recruitment of whitebark pine.

The purpose of this dissertation research was to investigate the extent of natural and anthropogenic impacts on declining whitebark pine communities. My research used dendroecology to study multicentury changes in these threatened communities to assess current and past forest dynamics and the overlapping effects of white pine blister rust, mountain pine beetle, and climate change in the northern Rocky Mountains. I created whitebark pine (host) and subalpine fir (nonhost) chronologies and collected species composition, stand structure, and forest health data in sites along a latitudinal transect through the Rocky Mountains in western Montana. The standstructure data indicate over 70% of whitebark pines at all sites are declining or dead. The high mortality of whitebark pines was caused by the overlapping effects of past (1880s, 1920s, and 1970s) and current mountain pine beetle outbreaks, and more recently by white pine blister rust infection. Whitebark pine populations, in the majority of our sites, are being successionally replaced by subalpine fir, grand fir, and Engelmann spruce in all levels of the forest strata (trees, saplings, and seedlings). Shade-tolerant trees began establishing between 150 and 300 years ago at all sites, a finding that suggests 20th century fire suppression is not responsible for the successional replacement of whitebark pine forests. Whitebark pine and subalpine fir growth respond strongly to drought and precipitation. This indicates wet conditions from precipitation and snowpack melt in the previous summer enhance tree growth during the following growing season. My climate reconstruction results support other climate reconstructions, east of the Continental Divide, that found precipitation and Palmer Drought Severity Index (PDSI) have more of an influence on subalpine forest growth than temperature. The reconstruction data contribute an important high-elevation component to existing drought reconstructions from lower elevations in the northern Rocky Mountains. Whitebark pine communities should continue to be monitored as continued periods of drought will likely make whitebark pines more susceptible to mountain pine beetle attack and weaken their resistance to white pine blister rust infection.

This dissertation examines the links between culture and tradition. It argues that traditions are influenced by the underlying cultural foundations from which they develop. It also argues that as traits diffuse between cultures, they do not do so “as is” but are interpreted by the recipient culture group and altered by their cultural beliefs. Because of the alterations that occur, the diffusion event is not a one-directional incident. The alteration of the trait causes the original exporter to evaluate the changes made, thereby altering the source culture’s opinion of the recipient group. The dissertation uses a three-stage model to examine the above arguments by using the diffusion of the National Hockey League (NHL) into the South during the 1990s as a data source. The first stage of the model investigates the place of hockey in southern sport culture prior to the NHL’s arrival, the Precondition. The second stage examines how hockey culture developed between the arrival of each southern franchise and the Lockout lost season of 2004-05. The final stage compares the cultural underpinnings of southern hockey to general southern sport culture and hockey’s hearth culture. This dissertation found that southern hockey’s cultural foundations lie in general southern culture and not with hockey’s hearth culture. This finding supports the notion that diffusion events do not occur as direct exchanges of cultural traits but rather diffused traits are altered to fit into existing cultural frameworks. This finding led to an alteration in the original model, with the concept of a “cultural filter” being added. Key Words: Tradition, culture, South, hockey

Previous theories of immigrant integration indicate that spatial propinquity is a necessary ingredient for a cohesive ethnic community. Wilbur Zelinsky’s heterolocalism theory suggests this is no longer the case in today’s world where technology has drastically reduced the friction of distance in human interaction. This thesis uses a mixture of quantitative and qualitative techniques to test heterolocalism’s applicability to emergent Latino communities in the Southeastern United States. The results of this research generally support Zelinsky’s theory that a growing number of ethnic communities are socially but not spatially cohesive.

Homebuilt aircraft have a high accident rate during the flight test period, particularly during their first and second flights. For the 2002-2004 period, over 1.0% of homebuilt aircraft were involved in an accident on their first flight, and 3.3% were involved in accidents in the first 40 hours of operation. Untrained, low time in aircraft type amateur flight test participants, unorthodox flight test procedures, and lack of clear guidance as to who should and how to conduct safe and effective flight test lead to unsafe conditions and the accident statistics support this hypothesis. In the accidents analyzed, lack of experience was specifically cited by the NTSB as a causal factor in 15.6% of the accidents. Poor decision-making was also a common thread, with 15.6% involving faulty decision-making by the pilot-builder. Shappell and Wiegmann’s Human Factors Analysis and Classification System (HFACS) is applied to interpret the statistics and the model is applied to the current state of homebuilt flight test in comparison to professional flight test. Detailed comparison is made between amateur and professional flight test practices and case studies are provided to support the analysis. The author proposes that ideally, flight test is left to trained professionals. The training, experience, and support structure of professional testers and their organizations can effectively mitigate the lack of time in type and training characteristic of the typical homebuilt flight tester. Accepting that this is not always practical in the homebuilt flight test world, it is recommended that professional practices be applied to amateur flight testing. Furthermore, it is suggested that the guidance available to amateur flight testers be improved and that regulations require that the homebuilder meet with an FAA-designated engineering representative regarding the conduct of flight test.

Previous theories of immigrant integration indicate that spatial propinquity is a necessary ingredient for a cohesive ethnic community. Wilbur Zelinsky’s heterolocalism theory suggests this is no longer the case in today’s world where technology has drastically reduced the friction of distance in human interaction. This thesis uses a mixture of quantitative and qualitative techniques to test heterolocalism’s applicability to emergent Latino communities in the Southeastern United States. The results of this research generally support Zelinsky’s theory that a growing number of ethnic communities are socially but not spatially cohesive.