published_or_final_version / abstract / toc / Surgery / Doctoral / Doctor of Philosophy

<p>Previous studies of agricultural conditions in the Mekong Delta (MD) have identified soil compaction as an obstacle to sustainable production. A conceptual model for soil formation was presented to demonstrate the link between soil hydrology and plant response. Detailed studies of soil moisture dynamics in agricultural fields were conducted using a dynamic process-orientated model. Pressure head and water flow were simulated for three selected sites during a year for which empirical data were available. Daily meteorological data were used as dynamic input and measured pressure head was used to estimate parameter values that satisfied various acceptance criteria. The Generalised Likelihood Uncertainty Estimation (GLUE) approach was applied for calibration procedures with 10,000 runs, each run using random values within the chosen range of parameter values. To evaluate model performance and uncertainty estimation, re-sampling was carried out using coefficient of determination (R2) and mean error (ME) as the criteria. Correlations between parameters and R2 (and ME) and among parameters were also considered to analyse the relationship of the selected parameter set in response to increases/decreases in the acceptable simulations. The method was successful for two of the three sites, with many accepted simulations. For these sites, the uncertainty was reduced and it was possible to quantify the importance of the different parameters.</p><p> </p>

As a result of medical advancement and cultural patterns of Western society, traumatic head injury is increasingly a problem for the injured, their families, medical and social services professionals, and the community at large. Head trauma is remarkable because of the complex nature of the residual disabilities which include long lasting cognitive and emotional problems, social isolation, and family disruption. The purpose of this study was to re-examine the phenomenon of recovery after mild to moderate head injury using an ethnographic research approach. The data were based on the experiences of 21 disabled and their families in the community setting. The disabled represented a range of stages of recovery and severity of disability. The data was collected using three field work strategies: extensive semi-structured interviews, participant observation, and non-academic document review. After collection the data was subjected to thematic and content analysis, that resulted in the selection of themes that characterized the experiences for the head injured and their families. The themes for the head injured informants were: dead days, loneliness, and forgetting. The family members' experiences were represented in the themes: responsibility, vulnerability, tough love, gender differences, and reactions to the experience. Next the data were interpreted using five theoretical concepts from cultural anthropology: liminality, personhood, social labelling, sick role and double bind. In addition, the reflexive influence of the investigator on the research process was addressed. The trustworthiness of the ethnography was assessed in terms of credibility, transferability, dependability and confirmability. Several variables were found to be important to the long term outcome of head injury. These variables were: family directed therapy, double bind communication patterns, and lifelong recovery. Two other factors were found to be critical for the recovery of the head injured. These were economic disincentives to the return to employment and the importance of the social and family environment. In the final section the research and policy implications of the study were discussed in relation to management and service provisions.

Several research groups have applied elevated hydrostatic pressure to ONH astrocytes cultured on a rigid substrate as an in vitro model for glaucoma. These studies have shown significant biological effects and this hydrostatic pressure model is now becoming generally accepted in the ophthalmic community. However, since the applied pressures were modest the finding of significant biological effects due to pressure alone is surprising. We hypothesized that the application of hydrostatic pressure as described in these studies also altered gas tensions in the culture media. Our goal was to design equipment and carry out experiments to separate the biologic effects of pressure from those of hypoxia on cultured astrocytes. We designed equipment and carried out experiments to subject cultures of DITNC1 astrocytes to the four combinations of two levels of each parameter. We explored the morphology and migration rates of astrocytes, but observed no significant change in any of these properties.

Glaucoma is a common cause of blindness worldwide, yet the etiology of the disease is unclear. A leading hypothesis is that elevated intraocular pressure (IOP) affects the biomechanical environment within the tissues of the optic nerve head (ONH), and that the altered biomechanical environment contributes to optic nerve damage and consequent loss of vision. The biomechanical environment of the ONH is strongly dependent on the biomechanical properties of sclera, particularly scleral stiffness. However there is significant variability in reported stiffness data for human sclera. Therefore, our research goal was to measure the stiffness of human sclera and incorporate this information into finite element models of the human eye to characterize and quantify the biomechanical environment within and around the optic nerve head region at different IOP levels. Human sclera adjacent to the optic nerve head showed highly nonlinear, nearly isotropic and heterogeneous stiffness which was found to be substantially lower than that previously assumed, particularly at lower levels of IOP. The products c*c1 and c*c2, measures of stiffness in the latitudinal and longitudinal directions from the Fung constitutive model, were 2.9 ± 2.0 MPa and 2.8 ± 1.9 MPa, respectively, and were not significantly different (two-sided t-test; p = 0.795). Scleral stiffness was not statistically different between left and right eyes of an individual (p = 0.952) and amongst the quadrants of an eye (p = 0.412 and p = 0.456 in latitudinal and longitudinal directions, respectively). Three stress-strain relationships consistent with the 5th, 50th and 95th percentiles of the measured scleral stiffness distribution were selected as representatives of compliant, median and stiff scleral properties and were implemented in a generic finite element model of the eye using a hyperelastic five-parameter Mooney-Rivlin material model. Models were solved for IOPs of 15, 25 and 50 mmHg. The magnitudes of strains at the optic nerve head region were substantial at even the lowest applied IOP (15 mmHg) and increased at elevated IOPs (e.g. the third principal strain in the compliant model reached as much as 5.25% in the lamina cribrosa at 15mmHg and 8.84% in the lamina cribrosa at 50 mmHg). Scleras that are “weak”, but still within the physiologic range, are predicted to lead to appreciably increased optic nerve head strains and could represent a risk factor for glaucomatous optic neuropathy. As IOP increased from 15 to 50 mmHg, principal strains in the model with a compliant sclera increased at a lower rate than in the model with a stiff sclera. We quantified the biomechanical environment within and around the optic nerve head region using a range of experimentally measured mechanical properties of sclera and at different IOPs. We showed that IOP-related strains within optic nerve head tissues can reach potentially biologically significant levels (capable of inducing a range of effects in glial cells) even at average levels of IOP and for typical human scleral biomechanical properties.

The goal of this thesis was to evaluate the cost-effectiveness of implantable Doppler technology (IDT) used to monitor free tissue transfer (FTT) procedures in the treatment of cancer of the upper aerodigestive tract (UADT). First, a systematic review of the literature on the effectiveness of traditional and IDT monitoring techniques was performed. Second, a utility survey using a time trade-off technique was created and administered. The results from this survey were used to establish utility values for health states common in patients undergoing FTT procedures. Third, a cost study using the microcosting data available through the Ottawa Hospital was performed. Finally, a decision analytic model was created and an economic evaluation from the payer perspective was completed. A probabilistic sensitivity analysis (PSA) and a value of information analysis (VOI) were performed. The thesis found that the currently available evidence supports IDT as a cost-effective intervention. Further research should be directed towards determining the effectiveness of both traditional and IDT monitoring.

Adolescence is a risk period for offending and head injury (HI), with rates of HI in young offender populations frequently exceeding those in the community. Poor parenting practices have been associated with increased risk of offending and development of reactive and proactive aggression. Preliminary research suggests HI may discriminate offender profiles within young offenders, but the influence of HI on offending alongside parenting and aggression is less well known. This study explored the relationships between parenting practices, reactive and proactive aggression, HI and offending in a sample of male young offenders from a Young Offender Institute (n=98) using self report data. A history of at least one HI was reported by 73.5%, with 61.1% reporting a knock out from their worst HI. Poor supervision emerged as a key predictor: predicting knock out history, indicators of offending and reactive and proactive aggression. Repeated HI was predictive of reactive aggression and a knock out history predicted earlier age of first offence. The impact of HI on outcomes via neuropsychological sequelea or as a “marker” for contextual risk factors such as poor supervision and reactive aggression are examined. Clinical implications for young offenders are discussed.

Virtual Reality är ett media med gamla rötter, men samtidigt en ny teknologi för allmänheten. Ett av problemen med VR är att det kan frammana visst obehag då det brukas, så kallad simulatorsjuka (Kennedy m.fl., 1993), vilket forskare studerar i syftet att förstå hur det undviks. I denna undersökning har en artefakt tagits fram i form av en spelprototyp, av slaget 2,5D-side-scrollingspel till VR, och använts för att studera uppkomsten av simulatorsjuka. Artefakten använder en head-mounted display för att uppnå VR. Tre testpersoner deltog i undersökningen, och för att mäta symptomen användes ett beprövat frågeformulär samt kvalitativa intervjuer. Data visar på att en tidigare hypotes om intryckskonflikt (Kolasinski, 1995, s.7) är inkorrekt, samt att konventionella orienteringsmekaniker har vissa fördelar. För framtida studier bör simulatorsjuka undersökas från fler vinklar och/eller med ett större urval av testpersoner.

Background In the treatment of head and neck cancers (HNCs), radiotherapy (RT) has the advantage of organ preservation compared to surgery. However, treatment toxicities associated with RT can affect important functions for everyday life, both in the acute and late stage. RT to macroscopic tumour in HNC is commonly combined with elective RT to cervical lymph nodes at risk of microscopic involvement. The resulting risk reduction of the elective treatment based on dose-volume parameters is sparsely evaluated. So is the relationship between the elective treatment and treatment toxicity. The present thesis addresses these aspects. A strategy aimed at improving the outcome of RT is accelerated fractionation (AF). AF strives to shorten total treatment time to minimise proliferation of the tumour tissue during the RT period. We have investigated the impact of AF on both disease control and toxicity. Methods In the ARTSCAN study, 750 patients with localised HNC were randomised between AF (68 Gy in 4.5 weeks) and conventional fractionation (CF) (68 Gy in 7 weeks). The elective treatment volume was prescribed 46 Gy with CF in both treatment arms. The thesis is based on four individual papers, investigating the issues above in the whole study population or in sub-populations. Results No difference in disease control or late toxicity between CF and AF was observed at five years. However, there was an increased acute toxicity with AF. Weight loss was associated with treatment volume, independent of tumour stage. The elective treatment volume was found to be an independent risk factor for late aspiration, as well as mean dose to the pharyngeal constrictor muscles, neck dissection, and age at randomisation. There was a significant risk reduction for node relapses in volumes treated to an elective dose. Only a relapse in volumes treated to &gt;60 Gy affected the survival. Conclusion The present thesis questions the benefit of AF in definitive RT as well as extensive elective treatment of the cervical nodes.

This exploratory study examined the effectiveness of child teacher relationship training (CTRT) with at-risk preschool children exhibiting disruptive behavior. The participants included a total of 23 Head Start teachers and their aides, and children identified by their teachers as exhibiting clinical or borderline levels of externalizing behavior problems. Teacher participants included 22 females and 1 male; demographics were reported as 56% Hispanic ethnicity, 17% Black American, and 22% European American. Child participants included 15 males and 5 females; demographics were reported as 60% Hispanic, 30% Black American, and 10% European American. A 2 by 3 (Group x Repeated Measures) split plot ANOVA was used to analyze the data. According to teacher reports using the Teacher Report Form (C-TRF) and blinded raters’ reports using the Direct Observation Form (DOF) to assess disruptive behaviors, children whose teachers received the CTRT intervention demonstrated statistically significant decreases (p < .05) in externalizing behaviors on the C-TRF and total problems on the DOF from pre- to mid- to post-test, compared to children whose teachers participated in the active control group. The CTRT intervention demonstrated large treatment effects on both measures (C-TRF: ?p2 =.173; DOF: ?p2=.164) when compared to CD, revealing the practical significance of the findings on reducing disruptive behaviors. According to independent raters on the DOF, 90% of children receiving the CTRT intervention moved from clinical levels of behavioral concern to more normative levels of functioning following treatment, establishing the clinical significance of CTRT as an early mental health intervention for preschool children in Head start exhibiting disruptive behavior.