University of Waterloo
http://hdl.handle.net/10012/1
The University of Waterloo institution-wide UWSpace community.2017-06-27T20:56:25ZCase Studies with Mathematical Modeling of Free-radical Multi-component Bulk/Solution Polymerizations:Part 2
http://hdl.handle.net/10012/12040
Case Studies with Mathematical Modeling of Free-radical Multi-component Bulk/Solution Polymerizations:Part 2
Dorschner, David; Jung, Woosung; Riahinezhad, Marzieh; Duever, Thomas; Penlidis, Alexander
In Part 2 of this series of two extensive overviews of multi-component polymerization case studies, we
again present mathematical modeling results with experimental confirmations. Part 2 represents a
refinement and expansion of the detailed and extensive mathematical model presented in Part 1 for freeradical,
bulk and/or solution multi-component polymerizations. The expansion is mainly with respect to
depropagation, thus making the model more fluent at elevated polymerization temperatures and, in
parallel, with additional features as backbiting (with systems involving butyl acrylate). The model
considers up to six monomers (unique in the literature), for either batch or semi-batch reactor modes. As
the simulator database contains several monomers, initiators, solvents, chain transfer agents and
inhibitors, all tested over a wide range of polymerization conditions, from data in both academic and
industrial laboratories, several hundred combinations of ingredients can be modeled. The many outputs
generated by the model include conversion, molecular weight, polymer composition, branching
indicators, sequence length, as well as many other polymerization characteristics related to both
production rate and polymer quality. Although the only literature data found to date contain a maximum
of four monomers, model predictions for homo-, co-, ter- and tetra-polymerizations show reasonable
agreement against the data at both regular and elevated temperatures. With these expansions, this model
is directed towards becoming a complete free-radical polymerization tool for training and educational
uses both in industry and academia.
This is an Accepted Manuscript of an article published by Taylor & Francis in Journal of Macromolecular Science, Part A on April 27, 2017, available online: http://dx.doi.org/10.1080/10601325.2017.1312678
2017-01-01T00:00:00ZAnalytic Combinatorics in Several Variables: Effective Asymptotics and Lattice Path Enumeration
http://hdl.handle.net/10012/12039
Analytic Combinatorics in Several Variables: Effective Asymptotics and Lattice Path Enumeration
Melczer, Stephen
The field of analytic combinatorics, which studies the asymptotic behaviour of sequences through analytic properties of their generating functions, has led to the development of deep and powerful tools with applications across mathematics and the natural sciences. In addition to the now classical univariate theory, recent work in the study of analytic combinatorics in several variables (ACSV) has shown how to derive asymptotics for the coefficients of certain D-finite functions represented by diagonals of multivariate rational functions. This thesis examines the methods of ACSV from a computer algebra viewpoint, developing rigorous algorithms and giving the first complexity results in this area under conditions which are broadly satisfied. Furthermore, this thesis gives several new applications of ACSV to the enumeration of lattice walks restricted to certain regions. In addition to proving several open conjectures on the asymptotics of such walks, a detailed study of lattice walk models with weighted steps is undertaken.
2017-06-26T00:00:00ZCost Effectiveness Analysis of Riluzole for ALS in Ontario Home Care Setting
http://hdl.handle.net/10012/12038
Cost Effectiveness Analysis of Riluzole for ALS in Ontario Home Care Setting
Kim, Yong-Jin
Objective: To identify the factors associated with the prescription of riluzole and assess its cost-effectiveness for patients diagnosed with Amyotrophic Lateral Sclerosis (ALS) in long stay home care in Ontario, Canada.
Method: A retrospective cohort study was conducted using the Ontario Association of Community Care Access Centres – Home Care (OACCAC-HC) data. Assessment records of ALS patients admitted into home care between April 1st, 2005 and March 31st, 2013, who had information on whether or not they used riluzole, were reviewed. Univariate and multiple logistic regressions analysis were used to identify the predictors influencing the receipt of riluzole. Variables included in the analyses were chosen in correlation to the prognostic factors identified in the literature review. For the cost-effectiveness analysis, cost data were obtained from relevant literatures and published information on Canadian Institute for Health Information Patient Cost Estimator accounting for the cost of administration of riluzole, standard supportive home care services, and cost-savings from delay in hospitalization. Effectiveness was measured using time to discharge from home care due to death, placement into long-term care, and hospitalization, controlling for potential confounding variables using propensity score stratification. The incremental cost-effectiveness ratio was calculated based on time spent in different states and the associated utility scores using the stratified population and expressed as cost per life-year gained and quality-adjusted life-year gained. Sensitivity analyses included one-way deterministic sensitivity analysis to investigate the change in ICER due to variations in specific input parameters. Scenario analyses were developed to depict the ICERs in best and worst case scenarios.
Resuts: The total study population comprised of 1,351 patients diagnosed with ALS, of which 1,277 patients had information on the use of riluzole. In the multiple logistic regression analysis, older age, moderate – moderate severe impairment in cognitive functions, not being married and geographical locations across LHINs (Champlain, Erie St. Clair, Hamilton Niagara Haldimand Brant, Mississauga Halton, North East, South East, and South West) decreased the likelihood of riluzole prescription. Primary analysis showed that treatment with riluzole was associated with prolonged survival in home care [HR = 0.86; 95% confidence interval: 0.745 – 0.99; p=0.046]. Survival gain associated with riluzole was 1.5 months, while the incremental cost was approximately $5,000 per patient. Thus, the incremental cost-effectiveness ratio of riluzole versus standard supportive home care services was $41,128.85 per life-year gained or $55,579.53 per quality-adjusted life-year gained. One-way deterministic sensitivity analysis suggested an ICER ranging from $50,000 – 78,000 per QALY, while scenario analyses depicting best and worst case scenarios suggested an ICERs of $29,890.36 per QALY and $106,641.52 per QALY.
Conclusion: Patient characteristics such as age, cognitive score, geographical location and marital status markedly influenced drug utilization of riluzole. In addition, the findings of this study indicate that riluzole has a borderline or unfavorable cost-effectiveness for patients diagnosed with ALS in home care setting.
2017-06-23T00:00:00ZHigh Aspect Ratio Polystyrene Structure and Nano-gap Electrode Fabrication Using Electron Beam Lithography
http://hdl.handle.net/10012/12037
High Aspect Ratio Polystyrene Structure and Nano-gap Electrode Fabrication Using Electron Beam Lithography
Azibi, Azizah
Nanotechnology has experienced a rapid growth over the past decade, thanks to the development of nanofabrication technologies needed to fabricate nano-devices. The key technique for nanofabrication is nano-lithography. Among the various lithography methods, electron beam lithography (EBL) is the most popular one for R&D and prototyping. EBL uses a focused electron beam to expose a polymer material called resist, such that it undergoes chemical reaction to render it soluble (positive resist) or insoluble (negative resist) by developer. One particular challenge for EBL is the fabrication of high aspect ratio (structure height over width or diameter) nano-structures, which often suffers from pattern collapse caused by capillary force during rinsing liquid drying. In this study we report a novel approach to tackle this issue to a certain degree. We form an array of thin “ceiling” on top of the tall resist structures (here an array of pillar) to “hold” them together and thus reduce the structure collapse. Meanwhile, development can still be completed by optimizing the size of the ceiling patches such that developer has enough time to enter and dissolve the unexposed negative resist under the ceiling. The “ceiling” can be formed by low-energy electron beam exposure that will cross-link only the upper portion of the thick resist; whereas the tall resist structure is exposed at high energy having deep penetration depth. Pattern collapse or detachment was greatly reduced by using our technique, though some degree of structure deformation was found after development. Using high aspect ratio resist structures, it is possible to fabricate high aspect ratio functional materials such as silicon.
2017-06-22T00:00:00Z