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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
411

Total knee replacement serious game for surgical education and training

Cowan, Brent B. D. 01 August 2012 (has links)
Traditionally, orthopaedic surgical training has primarily taken place in the operating room. Given the growing trend of decreasing resident work hours in North America and globally due to political mandate, training time in the operating room has generally been decreased. This has led to less operative exposure, teaching, and feedback for orthopaedic surgery residents. To solve this problem, a 3D serious game that was designed for the purpose of training orthopaedic surgery residents the steps comprising the total knee replacement procedure. Real-time, 3D graphical and sound rendering technologies are employed to provide sensory realism ensuring that the knowledge gained within the serious game can be more easily recalled and applied a real world scenario. A usability study to address user perceptions of the game’s ease of use, and the potential for learning and engagement was conducted. Results indicate that the serious game is easy to use, intuitive, and stimulating. / UOIT
412

Does hormone replacement therapy benefit cognition in elderly, postmenopausal women : a true or mistaken association?

Winquist, Brandace 18 December 2003
Hormone replacement therapy (HRT) has been studied as a protective factor for cognitive decline and dementia. However, study findings have been inconsistent. Variation in study findings may be due to differences in study designs, small sample size, exposure ascertainment, diagnostic procedures, and inclusion of relevant risk and confounding factors. Moreover, there may be significant differences between the characteristics of women choosing to use HRT and those opting not to use the therapy. Using a large-scale, population-based, cohort study, we examined the relationship between HRT and cognition while paying particular attention to moderating and confounding factors. The main outcomes of interest were to assess differences in risk for cognitive impairments and dementia between HRT user and never user groups; examine HRTs impact on age of onset of dementia; and explore the relationship between duration of HRT and cognitive decline. Logistic regression and Cox Proportional Hazards models were used to test HRT as a predictor for cognitive impairments, Alzheimers disease and vascular dementia, as well as to assess the effect of duration. Linear regression was used to consider the putative relationship between age at onset of dementia and HRT status. HRT use was found to be a statistically significant predictor for Alzheimers disease and vascular dementia. Overall, HRT use did not significantly predict for milder cognitive impairments, although significant interaction effects indicate that HRT may be protective at least for specific sub-groups of women. No durational effect was found for any of the outcomes. Neither did HRT appear to predict for age at onset of dementia. Notably, a large proportion of women in the current study reported using estrogen-only hormone supplements, and therefore generalizations regarding the findings are likely limited to estrogen-only preparations, not combination estrogen-progestin therapies. These findings must be considered within the context of the other known and potential risks and benefits that HRT may afford.
413

Does hormone replacement therapy benefit cognition in elderly, postmenopausal women : a true or mistaken association?

Winquist, Brandace 18 December 2003 (has links)
Hormone replacement therapy (HRT) has been studied as a protective factor for cognitive decline and dementia. However, study findings have been inconsistent. Variation in study findings may be due to differences in study designs, small sample size, exposure ascertainment, diagnostic procedures, and inclusion of relevant risk and confounding factors. Moreover, there may be significant differences between the characteristics of women choosing to use HRT and those opting not to use the therapy. Using a large-scale, population-based, cohort study, we examined the relationship between HRT and cognition while paying particular attention to moderating and confounding factors. The main outcomes of interest were to assess differences in risk for cognitive impairments and dementia between HRT user and never user groups; examine HRTs impact on age of onset of dementia; and explore the relationship between duration of HRT and cognitive decline. Logistic regression and Cox Proportional Hazards models were used to test HRT as a predictor for cognitive impairments, Alzheimers disease and vascular dementia, as well as to assess the effect of duration. Linear regression was used to consider the putative relationship between age at onset of dementia and HRT status. HRT use was found to be a statistically significant predictor for Alzheimers disease and vascular dementia. Overall, HRT use did not significantly predict for milder cognitive impairments, although significant interaction effects indicate that HRT may be protective at least for specific sub-groups of women. No durational effect was found for any of the outcomes. Neither did HRT appear to predict for age at onset of dementia. Notably, a large proportion of women in the current study reported using estrogen-only hormone supplements, and therefore generalizations regarding the findings are likely limited to estrogen-only preparations, not combination estrogen-progestin therapies. These findings must be considered within the context of the other known and potential risks and benefits that HRT may afford.
414

The Stable American Mind: Understanding Attitudes Towards Government and Taxes, 1990-2011

Eldred, Christopher P. 01 January 2011 (has links)
As the federal government seeks ways to stimulate our economy and reduce our national debt, understanding public attitudes on the role and size of government and the taxes that support it is important. This thesis evaluates how US public opinion towards government and taxes has changed from 1990 to the present, and analyzes several potential causes for changes that have occurred. It is intended to be an update of William G. Mayer’s 1992 book entitled The Changing American Mind, which analyzed changing public opinion from 1960-1988. In following his analysis, the causes I have analyzed are generational replacement, fiscal and economic indicator data, and important political events. Through and examination of public polling data from the last twenty years, I have concluded that attitudes fluctuated relatively mildly on these issues since 1990. My analysis reveals that generational replacement exerted little influence on opinions. However, analysis also reveals that major changes in fiscal and economic indicator data and various major policy initiatives induced the greatest swings in public opinion of the last two decades. I believe that these changes reflect that American aggregate opinion remains constructed on a post-Ronald Reagan ideological foundation, whose features include an inherent suspicion of government and resistance to taxes. Understanding this is crucial to understanding the nation’s political trajectory.
415

Models of interference in monocultures and mixtures of wheat (Triticum aestivum L.) and quackgrass (Elytrigia repens (L.) Nevski.).

Wilcox, Douglas Howard 21 January 2009 (has links)
Quackgrass is the most serious perennial grassy weed of wheat in Manitoba. Field experiments and surveys investigating the nature and extent of interference in monocultures and mixtures of quackgrass and wheat were conducted over the years 1987 to 1989 at Portage La Prairie, Manitoba, Canada. Intraspecific and interspecific interference between spring wheat and quackgrass was investigated in the field using an additive series design consisting of five replacement series proportions at total stand densities of 75, 150, and 300 plants sqM. A revised synthetic no-interaction analysis determined that wheat was superior to quackgrass in both intraspecific and interpecific interference and that niche dedifferentiation was large. Quackgrass reproductive variable were less sensitive to interspecific interference than were vegetative variables. Surveys of commercial fields of spring wheat infested with quackgrass were conducted using a dynamic stratified random sampling design in which systematic samples were taken at approximately 30, 60 and 93 days after planting. Wheat yield loss, as a percentage of weed-free yield, (Yw%) was related to spring quackgrass shoot counts/m-2 (Qs) by a rectangular hyperbolic model of the form Yw% = 98.7(1-0.433(Qs)/100(1+(0.433(Qs)/193.7))). Wheat kernel weight was the wheat yield component most influenced by quackgrass infestation. In quackgrass populations the majority of new rhizome production occurred during wheat senescence and biomass partitioning to heads increased as quackgrass infestation increased. Allometric models of the relationship between quackgrass parts were site specific and generally became more accurate the later the sampling date. A set of models relating spring quackgrass infestation to yield losses in hard red spring wheat, flax, and polish canola were combined with allometric models in a multi-year spreadsheet (Lotus 1-2-3, v 3.1) model. Simulations run using the multi-year model demonstrated the potential of a spreadsheet model of assisting in weed control decisions. / October 1995
416

Wear and Boundary Lubrication in Modular Total Knee Replacements

Brandt, Jan-Mels 25 January 2008 (has links)
Wear of the polyethylene (PE) bearing surface and wear particle-induced osteolysis (bone resorption) can lead to failure of modular total knee replacements and make expensive revision surgery necessary. Gamma-in-air sterilization of the PE insert and having a modular tibial component are both risk factors for excessive backside wear that contribute to osteolysis and implant failure. The overall wear (backside and topside) of modular total knee replacements has been subjected to considerable research in order to avoid such implant failure. The investigations reported in the present thesis evaluated both the clinical and in vitro wear performance of modular total knee replacements. The clinical investigations included damage assessment of retrieved PE inserts. A semi-quantitative grading method was developed and used to assess backside surface damage on 52 PE inserts retrieved from contemporary total knee replacement surgeries. Statistical analyses, such as univariate and multiple linear regression analysis, were performed to identify factors that influence backside damage including implant design features and patient characteristics. The damage features on the retrieved tibial PE inserts were also assessed with surface characterization techniques, such as scanning electron microscopy, energy dispersive X-ray analysis, and surface profilometry. To reduce surface damage and thus wear, PE inserts should be either gas-plasma or ethylene-oxide sterilized, used with polished tibial trays and held in place with a partial-peripheral locking mechanism. Synovial fluid samples were aspirated from a total of twenty patients and some basic biochemical analyses were performed. The total protein concentration, protein constituent fractions, the level of osmolality, and trace element concentrations were measured and compared with the same characteristics of four serum lubricants that were frequently used in simulator wear testing to mimic synovial fluid. In vitro investigations were conducted to explore the effects of some major constituents of the serum lubricants on the wear rate using a knee simulator apparatus. Increased protein constituent degradation led to increased wear. Such findings suggested that a protein layer acted as a boundary lubricant to protect the PE surfaces of knee implants. The protein constituent fractions of alpha calf serum (ACS) were similar to those measured for synovial fluid. These ACS lubricants were used in further wear studies in which hyaluronic acid (HA) and phosphate buffer solution (PBS) were successively added. The PBS was used in place of the distilled water to generate a serum lubricant with a clinically relevant level of osmolality. The thermal stability of the ACS lubricants and synovial fluid were measured. The thermal stability of the ACS lubricant that contained HA and PBS was about the same as that of human synovial fluid. The simulator wear rate of PE was significantly influenced by both HA and PBS. In further investigations, sodium azide, which has been used to inhibit microbial growth in simulator wear testing, was shown to be highly ineffective. Microbial contamination was recognized and the organism responsible was identified using standard microbiological methods. The use of an antibiotic-antimycotic mixture as the microbial inhibitor in the ACS + PBS + HA lubricant created a sterile environment and thus very clinically relevant environment for wear testing. The content of this thesis represents a comprehensive data collection on retrieval analysis and lubricant-specific knee simulator wear testing of modular total knee replacements. A more clinically relevant lubricant composition for simulator wear testing was proposed (U.S. patent Serial number 60/899,894; pending since February 9th, 2007) that improved upon the current guideline from the International Standards Organization for knee simulator wear testing. The present thesis should serve as a guide for the surgeon, researcher and the implant manufacturer to evaluate retrieved implant components and to select lubricant additives for wear testing that closely mimics the in vivo wear conditions.
417

Motivation är nyckeln till förändring : En studie om ungdomars upplevelse av behandlingsmetoden Aggression Replacement Training

Danielsson, Åsa, Olsson, Farida January 2010 (has links)
Sedan 1990-talet har behandlingsmetoden Aggression Replacement Training (ART) fått ett stort genomslag i Sverige och metoden används såväl inom socialtjänstens öppenvård som inom kriminalvården, samt på många av Statens institutioners ungdomshem. ART tycks idag vara en av de mest spridda manualbaserade behandlingsmetoderna (Kaunitz & Strandberg, 2009, s. 37). Mot bakgrund av metodens omfattande tillämpning inom dessa områden, ansåg vi att det fanns skäl till att undersöka hur ungdomar som genomgått ART träning upplevde metoden. Detta är också syftet med denna studie. Då vi har förstått att det finns få svenska kvalitativa studier om ungdomars erfarenheter av ART, menar vi att det är av intresse att i föreliggande studie belysa denna fråga.Vi valde därför att genomföra en kvalitativ undersökning, varvid vi intervjuade sex stycken ungdomar som samtliga har haft problem med ett antisocialt beteende och kriminalitet. I syfte att analysera vår empiri har vi utkristalliserat följande fem teman: motivation, gruppens betydelse, användbara kunskaper, övning ger färdighet och faktorer som påverkar. Vår studie visar bland annat att ungdomarnas aggressiva och destruktiva beteende genom åren har belönats och förstärkts, vilket vi anser kan vara en förklaring till varför dessa beteenden hos ungdomarna har vidmakthållits. Vi har också sett att ungdomarnas motivation till att förändra sina destruktiva beteenden tycks vara avgörande för att ungdomarna skall vilja ta till sig de verktyg som ART tillhandahåller. Vidare kan vi konstatera att ART gruppens sammansättning och atmosfären i gruppen är viktig för att ART deltagarna skall kunna ge sig hän i träningen, och därmed få en större behållning av behandlingsmetoden. Vi har förstått att de kunskaper som ungdomarna har förvärvat genom ART, riskerar att försvinna då missbruk finns med i bilden. Då den unge eventuellt har en komplex problematik, anser vi att andra behandlingsprogram utöver, eller i kombination med ART, kan vara verkningsfulla.
418

Wear and Boundary Lubrication in Modular Total Knee Replacements

Brandt, Jan-Mels 25 January 2008 (has links)
Wear of the polyethylene (PE) bearing surface and wear particle-induced osteolysis (bone resorption) can lead to failure of modular total knee replacements and make expensive revision surgery necessary. Gamma-in-air sterilization of the PE insert and having a modular tibial component are both risk factors for excessive backside wear that contribute to osteolysis and implant failure. The overall wear (backside and topside) of modular total knee replacements has been subjected to considerable research in order to avoid such implant failure. The investigations reported in the present thesis evaluated both the clinical and in vitro wear performance of modular total knee replacements. The clinical investigations included damage assessment of retrieved PE inserts. A semi-quantitative grading method was developed and used to assess backside surface damage on 52 PE inserts retrieved from contemporary total knee replacement surgeries. Statistical analyses, such as univariate and multiple linear regression analysis, were performed to identify factors that influence backside damage including implant design features and patient characteristics. The damage features on the retrieved tibial PE inserts were also assessed with surface characterization techniques, such as scanning electron microscopy, energy dispersive X-ray analysis, and surface profilometry. To reduce surface damage and thus wear, PE inserts should be either gas-plasma or ethylene-oxide sterilized, used with polished tibial trays and held in place with a partial-peripheral locking mechanism. Synovial fluid samples were aspirated from a total of twenty patients and some basic biochemical analyses were performed. The total protein concentration, protein constituent fractions, the level of osmolality, and trace element concentrations were measured and compared with the same characteristics of four serum lubricants that were frequently used in simulator wear testing to mimic synovial fluid. In vitro investigations were conducted to explore the effects of some major constituents of the serum lubricants on the wear rate using a knee simulator apparatus. Increased protein constituent degradation led to increased wear. Such findings suggested that a protein layer acted as a boundary lubricant to protect the PE surfaces of knee implants. The protein constituent fractions of alpha calf serum (ACS) were similar to those measured for synovial fluid. These ACS lubricants were used in further wear studies in which hyaluronic acid (HA) and phosphate buffer solution (PBS) were successively added. The PBS was used in place of the distilled water to generate a serum lubricant with a clinically relevant level of osmolality. The thermal stability of the ACS lubricants and synovial fluid were measured. The thermal stability of the ACS lubricant that contained HA and PBS was about the same as that of human synovial fluid. The simulator wear rate of PE was significantly influenced by both HA and PBS. In further investigations, sodium azide, which has been used to inhibit microbial growth in simulator wear testing, was shown to be highly ineffective. Microbial contamination was recognized and the organism responsible was identified using standard microbiological methods. The use of an antibiotic-antimycotic mixture as the microbial inhibitor in the ACS + PBS + HA lubricant created a sterile environment and thus very clinically relevant environment for wear testing. The content of this thesis represents a comprehensive data collection on retrieval analysis and lubricant-specific knee simulator wear testing of modular total knee replacements. A more clinically relevant lubricant composition for simulator wear testing was proposed (U.S. patent Serial number 60/899,894; pending since February 9th, 2007) that improved upon the current guideline from the International Standards Organization for knee simulator wear testing. The present thesis should serve as a guide for the surgeon, researcher and the implant manufacturer to evaluate retrieved implant components and to select lubricant additives for wear testing that closely mimics the in vivo wear conditions.
419

Cervical Total Level Arthroplasty System With PEEK All-Polymer Articulations

Langohr, Gordon Daniel George January 2011 (has links)
The cervical spine must provide structural support for the head, allow large range of motion and protect both the spinal cord and branching nerves. There are two types of spinal joints: the intervertebral discs which are flexible connections and the facets, which are articulating synovial joints. Both types degenerate with age. Current surgical treatments include spinal fusion and articulating disc replacement implants. If both disc and facet joints are degenerated, fusion is the only option. In spinal fusion, the disc is removed and the adjacent vertebrae are fused which causes abnormally high stress levels in adjacent discs. In disc replacement, an articulating device is inserted to restore intervertebral motion and mimic healthy spinal kinematics. Disc arthroplasty does not significantly increase adjacent level stress but the lack of rotational constraint causes increased facet contact pressures. Thus, there is a need for a cervical total level arthroplasty system (CTLAS) that has a disc implant specifically designed to preserve the facet joints and implants for facet arthroplasty that can act independently or in-unison with the disc replacement. The conceptual design of a CTLAS implant system was proposed that would replace the disc and the facet joints. To facilitate medical imaging, PEEK (polyetheretherkeytone) was selected as the structural and bearing material. In the present thesis, multi-station pin-on-plate wear testing was initiated for pairs of unfilled (OPT) and carbon-fiber-reinforced (CFR) PEEK. Wear is important in arthroplasty implant design because wear particles can cause osteolysis leading to loosening. A variety of experiments were performed to investigate the effects of load, contact geometry and lubricant composition on wear. CFR PEEK was found to have much lower and more predictable wear than OPT PEEK in the present experiments. The wear of OPT PEEK pairs showed sensitivity to lubricant protein concentration. The coefficient of friction during testing was found to be quite high (up to 0.5), which might have clinical implications. Also, some subsurface fatigue was found, exposing carbon fibers of CFR PEEK. This remains a concern for its long-term application. Further wear testing is recommended using actual implants in a spine wear simulator.
420

Dopaminergic contributions to distance estimation in Parkinson’s disease: A sensory-perceptual deficit?

Ehgoetz Martens, Kaylena 10 1900 (has links)
Recent research has found that perceptual deficits exist in Parkinson’s disease (PD), yet the link between perception and movement impairments is not well understood. Inaccurate estimation of distance has the potential to be an underlying cause of movement impairments. Alternatively, those with PD may not be able to perceive their own movements accurately. The main objective of this thesis was to evaluate (1) whether distance estimation is influenced by static perception compared to perception during movement in PD, (2) how visual motion processing contributes to distance estimation during movement, and (3) how dopaminergic medication contributes to these distance estimation deficits. Thirty-seven participants (19 individuals with PD, 18 age-matched healthy control participants (HC) estimated distance to a remembered target in a total of 48 trials, in 4 randomized blocks. Estimation conditions included: (i) no motion: participants pointed with a laser, (ii) motion: participants walked to the estimated position, (iii) visual motion (wheelchair): participants were pushed in a wheelchair while they gave their estimate, (iv) visual motion (VR): participants completed their distance estimate while seated and viewed themselves (as if they were walking) in VR. PD patients completed this protocol twice; once OFF and once ON dopaminergic medication. Participants were matched for age, distance acuity, Modified Mini Mental State Exam (3MS), spatial working memory and motor planning ability. In Study 1 (no motion vs. motion), individuals with PD and healthy control participants did not differ in judgment accuracy during the no motion condition. However, those with PD did have greater amounts of error compared to healthy control participants while estimating distance during the motion condition. Similarly, those with PD significantly underestimated the target position compared to healthy control participants during the motion condition only. Individuals with PD demonstrated greater variability overall. In Study 2, error did not differ between PD and HC groups during visual motion perception (wheelchair). Interestingly, the HC group tended to perform significantly worse than those with PD in the VR condition. Overall, across both studies there was no significant influence of dopaminergic medication in any of the conditions. Individuals with PD demonstrated distance estimation deficits only when required to move through their environment. In contrast to estimations made with movement, neither static estimation nor estimations made with visual motion revealed significant differences between the two groups. Thus perceptual estimation deficits appear to occur only during movement, which may be suggestive of an underlying sensory processing deficit which leads to a problem integrating vision and self-motion information.

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