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Chen H.-M.,UWO | Goela A.,UWO | Goela A.,University of London | Garvin G.J.,UWO | And 3 more authors.
Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics) | Year: 2010

This study investigates a new parameterization of deformation fields for image registration. Instead of standard displacements, this parameterization describes a deformation field with its transformation Jacobian and curl of end velocity field. It has two important features which make it appealing to image registration: 1) it relaxes the need of an explicit regularization term and the corresponding ad hoc weight in the cost functional; 2) explicit constraints on transformation Jacobian such as topology preserving and incompressibility constraints are straightforward to impose in a unified framework. In addition, this parameterization naturally describes a deformation field in terms of radial and rotational components, making it especially suited for processing cardiac data. We formulate diffeomorphic image registration as a constrained optimization problem which we solve with a step-then-correct strategy. The effectiveness of the algorithm is demonstrated with several examples and a comprehensive evaluation of myocardial delineation over 120 short-axis cardiac cine MRIs acquired from 20 subjects. It shows competitive performance in comparison to two recent segmentation based approaches. © 2010 Springer-Verlag.


Dixon J.,University of Waterloo | Luginaah I.N.,UWO | Mkandawire P.,Carleton University
Journal of Health Care for the Poor and Underserved | Year: 2014

This article addresses the implications of the mandatory delay in coverage for individuals residing in the Upper West Region (UWR) of Ghana who have dropped out of the National Health Insurance Scheme (NHIS) but later attempt to reenroll. Using data collected in 2011 in Ghana's UWR, we use a negative log-log model (n=1,584) to compare those who remain enrolled in the scheme with those who have dropped out. Women with unreliable incomes, who reported being food-insecure and those living with young children were more likely to drop out (OR range: 1.22-1.79, p<.05). Men, in contrast, were 50% more likely to drop out of the NHIS for being unsatisfied with services provided (OR range: 1.25-1.62, p<.01). Contrary to the original mandate of the NHIS, our study reveals clear gender differences in the factors contributing to dropouts, pointing to a bias in the impact of the block-out policy that is penalizing women for being poor. © Meharry Medical College.


Soliman A.M.,University of Western Ontario | Nehdi M.L.,UWO
ACI Materials Journal | Year: 2011

This study pioneers the concept of self-accelerated concrete. The effect of adding partially hydrated cementitious materials (premade or from returned/unused concrete) on the setting and hardening process of reactive powder concrete (RPC) cured at various temperatures was investigated. The partially hydrated cementitious materials (PHCMs) were added at rates of 25, 33, and 50% of the overall batch weight. Similar mixtures incorporating chloridebased accelerating admixtures (CAs) and nonchloride-based accelerating admixtures (NCAs) were also tested for comparison. The results indicate that the added PHCMs alert the hydration kinetics and act as a setting and hardening accelerator. Mixtures incorporating PHCMs showed comparable or higher early-age compressive strengths than those of both the control mixture and mixtures incorporating accelerating admixtures. Microstructure analyses indicate that the addition of PHCMs enhances the nucleation and renews the formation process of calcium silicate hydrates (CSHs) through diminishing the protective layer formed around anhydrated tricalcium silicate (C3S) during the pre-induction period. Therefore, using PHCMs paves the way for self-accelerated concrete without the need for accelerating admixtures, providing a safe and cost-effective method for precast and cast-in-place concrete. Using leftover and unused concrete in this process enhances the sustainability of concrete and minimizes disposal in ready mixed concrete operations. © 2011, American Concrete Institute. All rights reserved.


Azimian H.,Lawson Health Research Institute | Azimian H.,University of Western Ontario | Patel R.V.,CSTAR | Naish M.D.,UWO | Kiaii B.,CSTAR
Proceedings - IEEE International Conference on Robotics and Automation | Year: 2011

In this paper, robust preoperative planning of RAMICS is formulated. The intent of the proposed planning framework is to improve surgical outcomes by contemplating the intraoperative conditions of the surgical procedure and the geometry of the patient's thoracic anatomy. This includes improvements in target reachability, instrument dexterity for critical surgical tasks, surgical task feasibility and visibility. Given the patient's preoperative computed tomography images of the chest, the planning framework aims to determine the optimal location of the access ports on the ribcage, along with the optimal pose of the robotic arms relative to the patient's anatomy. To minimize susceptibility of the results to intraop-erative geometric uncertainty, the planning is formulated as a Generalized Semi-Infinite Program (GSIP) with a convex lower level problem and a multi-criteria objective function. By solving the GSIP, tolerable geometric uncertainty within the task space is increased by eliminating the likelihood of collisions and joint limit violation in a neighborhood of the surgical target. © 2011 IEEE.


Petrella R.J.,University of Western Ontario | Lattanzio C.N.,UWO | Shapiro S.,UWO | Overend T.,UWO
Canadian Family Physician | Year: 2010

OBJECTIVE: To determine the effects of adding stages of change-based counseling to an exercise prescription for older, sedentary adults in family practice. DESIGN: The Step Test Exercise Prescription Stages of change counseling study was a 12-month cluster randomized trial. SETTING: Forty family practices in 4 regions of Canada. PARTICIPANTS: Healthy, community-dwelling men (48%) and women (52%) with a mean (SD) age of 64.9 (7.1) years (range 55 to 85 years). There were a total of 193 participants in the intervention group and 167 in the control group. INTERVENTION: Intervention physicians were trained to deliver a tailored exercise prescription and a transtheoretical behaviour change counseling program. Control physicians were trained to deliver the exercise prescription alone. MAIN OUTCOME MEASURES: Predicted cardiorespiratory fitness, measured by predicted maximal oxygen consumption (pVO2max), and energy expenditure, measured by 7-day physical activity recall. RESULTS: Mean increase in pVO2max was significant for both the intervention (3.02 [95% confidence interval 2.40 to 3.65] mL/kg/min) and control (2.21 [95% confidence interval 1.27 to 3.15] mL/kg/min) groups at 12 months (P < .001); however, there was no difference between groups. Women in the intervention group improved their fitness significantly more than women in the control group did (3.20 vs 1.23 mL/kg/min). The intervention group had a 4-mm Hg reduction in systolic blood pressure, while the control group's mean reduction was 0.4 mm Hg (P < .001). The mean (SD) energy expended significantly increased and was higher in the intervention group than in the control group (69.06 [169.87] kcal/d vs -6.96 [157.06] kcal/d, P < .006). Practice setting characteristics did not significantly affect the primary outcomes. CONCLUSION: The Step Test Exercise Prescription Stages of change exercise and behavioural intervention improved fitness and activity and lowered systolic blood pressure across a range of Canadian practices, but this was not significantly different from the control group, which received only the exercise prescription. Women in the intervention group showed higher levels of fitness than women in the control group did; men in both groups showed similar improvement.


Guha T.K.,UWO | Kopp G.A.,UWO
12th Americas Conference on Wind Engineering 2013, ACWE 2013: Wind Effects on Structures, Communities, and Energy Generation | Year: 2013

A combined load sharing, nail-slip model to predict the failure of roof-to-wall toenail connections in residential wood-frame buildings is presented. The model, in which the roof elements are idealized as an equivalent 2-D beam, uses piece-wise linear load-displacement curves to describe the progressive nail withdrawal observed in experiments, and combines it with elastic beam theory to characterize load sharing through the roof elements and the overall failure of such connections. The model demonstrates its capability in effectively capturing the damage progression due to load duration and load sharing effects exhibited by a system of interconnected roof-to-wall-connections by predicting the connection responses that reasonably match with the outcomes of controlled load sharing experiments. The validated model, subjected to fluctuating wind loads obtained from design storms of different durations, is further used to develop fragility curves of connection damage/failures. In particular, the effect of different storm durations with the same peak load as well as different peak loads proportional to the duration are investigated.


Chen H.M.,UWO
Medical image computing and computer-assisted intervention : MICCAI ... International Conference on Medical Image Computing and Computer-Assisted Intervention | Year: 2010

This study investigates a new parameterization of deformation fields for image registration. Instead of standard displacements, this parameterization describes a deformation field with its transformation Jacobian and curl of end velocity field. It has two important features which make it appealing to image registration: 1) it relaxes the need of an explicit regularization term and the corresponding ad hoc weight in the cost functional; 2) explicit constraints on transformation Jacobian such as topology preserving and incompressibility constraints are straightforward to impose in a unified framework. In addition, this parameterization naturally describes a deformation field in terms of radial and rotational components, making it especially suited for processing cardiac data. We formulate diffeomorphic image registration as a constrained optimization problem which we solve with a step-then-correct strategy. The effectiveness of the algorithm is demonstrated with several examples and a comprehensive evaluation of myocardial delineation over 120 short-axis cardiac cine MRIs acquired from 20 subjects. It shows competitive performance in comparison to two recent segmentation based approaches.


Uchiteleva E.,UWO | Primak S.,UWO
Eurasip Journal on Wireless Communications and Networking | Year: 2014

Abstract: In this paper, we use a set of modulated discrete prolate spheroidal sequences (MDPSS) to represent a band-limited channel in the scenario with scattering from one or more clusters which can be used in both vehicle-to-infrastructure (V2I) or vehicle-to-vehicle (V2V) communication cases. Then we evaluate the performance of 2×1 space-time transmit diversity (STTD) system with Alamouti coding and imperfect channel estimation at the receiver. We consider examples of different scattering environments which represent vehicular communication in urban areas, derive expressions for autocorrelation function of channel gains and verify it by simulation. Scattering effect on estimation quality of the system is examined in terms of minimum mean square error (MMSE) and bit error rate (BER). © 2014, Uchiteleva and Primak; licensee Springer.


Al-Aama T.,UWO | Brymer C.,UWO | Gutmanis I.,UWO | Gutmanis I.,Lawson Health Research Institute | And 3 more authors.
International Journal of Geriatric Psychiatry | Year: 2011

Background Disturbance in the metabolism of tryptophan and tryptophan-derived compounds (e.g., melatonin) may have a role in the pathogenesis of delirium. Objective To evaluate the efficacy of low dose exogenous melatonin in decreasing delirium. Design A randomized, double-blinded, placebo-controlled study. Setting An Internal Medicine service in a tertiary care centre in London, Ontario, Canada. Participants 145 individuals aged 65 years or over admitted through the emergency department to a medical unit in a tertiary care hospital. Intervention Patients were randomized to receive either 0.5 mg of melatonin or placebo every night for 14 days or until discharge. Measurements The primary outcome was the occurrence of delirium as determined by Confusion Assessment Method (CAM) criteria. Results Of a total of 145 individuals (mean age (standard deviation): 84.5 (6.1) years) 72 were randomly assigned to the melatonin group and 73 to the placebo group. Melatonin was associated with a lower risk of delirium (12.0% vs. 31.0%, p = 0.014), with an odds ratio (OR), adjusted for dementia and co-morbidities of 0.19 (95% confidence intervals (CI): 0.06-0.62). Results were not different when patients with prevalent delirium were excluded. Limitation An intention to treat analysis was not possible due to loss to follow-up. Conclusion Exogenous low dose melatonin administered nightly to elderly patients admitted to acute care may represent a potential protective agent against delirium. Copyright © 2010 John Wiley & Sons, Ltd.


Abbas S.,University of Engineering and Technology Lahore | Soliman A.M.,UWO | Nehdi M.L.,UWO
ACI Materials Journal | Year: 2014

Steel corrosion induces distress in concrete structures, resulting in the cracking and spalling of the concrete cover, which accelerates further damage. Chloride ions (Cl-) and carbonation are the primary causes of steel corrosion in concrete. This study investigates the effects of Cl- in precast concrete tunnel lining (PCTL) segments through conducting various tests on cylindrical cores extracted from conventional reinforced concrete (RC) and steel fiber-reinforced concrete (SFRC) segments. The full-scale PCTL segments were fabricated and cured at an industrial precast plant. Experimental results show that the external specimens (extrados and intrados faces) of both the RC and SFRC PCTL segments exhibited lower Cl- penetration due to surface treatment using a cement slurry. The Cl- diffusion coefficient was a function of the exposure period and concentration of the salt solution for both the RC and SFRC segments. SFRC PCTL segments better resisted the ingress of Cl- than control RC segments due to a barrier effect induced by steel fibers (SF), which helped inhibiting the penetration of Cl- into the hardened concrete. This study demonstrates the potential of SFRC as a more durable alternative for precast segmental tunnel linings compared to conventional RC. © 2014, American Concrete Institute.

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