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Articles 1 - 20 of 20
Full-Text Articles in Physical Sciences and Mathematics
Anisotropic Kernel Smoothing For Change-Point Data With An Analysis Of Fire Spread Rate Variability, John Ronald James Thompson
Anisotropic Kernel Smoothing For Change-Point Data With An Analysis Of Fire Spread Rate Variability, John Ronald James Thompson
Electronic Thesis and Dissertation Repository
Wildland fires are natural disturbances that enable the renewal of forests. However, these fires also place public safety and property at risk. Understanding forest fire spread in any region of Canada is critical to promoting forest health, and protecting human life and infrastructure. In 2014, Ontario updated its Wildland Fire Management Strategy, moving away from ``zone-based" decision making to ``appropriate response" decision making. This new strategy calls for an assessment of the risks and benefits of every wildland fire reported in the province. My research places the emphasis on the knowledge and understanding of fire spread rates and their variabilities. …
Bias Assessment And Reduction In Kernel Smoothing, Wenkai Ma
Bias Assessment And Reduction In Kernel Smoothing, Wenkai Ma
Electronic Thesis and Dissertation Repository
When performing local polynomial regression (LPR) with kernel smoothing, the choice of the smoothing parameter, or bandwidth, is critical. The performance of the method is often evaluated using the Mean Square Error (MSE). Bias and variance are two components of MSE. Kernel methods are known to exhibit varying degrees of bias. Boundary effects and data sparsity issues are two potential problems to watch for. There is a need for a tool to visually assess the potential bias when applying kernel smooths to a given scatterplot of data. In this dissertation, we propose pointwise confidence intervals for bias and demonstrate a …
Trends In Obesity And Multimorbidity In Canada., Michael Lebenbaum, Gregory S Zaric, Amardeep Thind, Sisira Sarma
Trends In Obesity And Multimorbidity In Canada., Michael Lebenbaum, Gregory S Zaric, Amardeep Thind, Sisira Sarma
Epidemiology and Biostatistics Publications
Very few studies have examined trends in multimorbidity over time and even fewer have examined trends over time across different body mass index (BMI) groups. Given a general decline in death rates but increased cardiovascular risk factors among individuals with obesity, the trend in the association between obesity and multimorbidity is hypothesized to be increasing over time. The data for our study came from the 1996-97 National Population Health Survey and the 2005 and 2012-13 Canadian Community Health Surveys (N = 277,366 across all 3 surveys). We examined trends in the association between BMI groups and multimorbidity using a logistic …
Substance Use Patterns Among Women Living With Hiv Compared With The General Female Population Of Canada, Mostafa Shokoohi, Greta R Bauer, Angela Kaida, Ashley Lacombe-Duncan, Mina Kazemi, Brenda Gagnier, Alexandra De Pokomandy, Mona Loutfy
Substance Use Patterns Among Women Living With Hiv Compared With The General Female Population Of Canada, Mostafa Shokoohi, Greta R Bauer, Angela Kaida, Ashley Lacombe-Duncan, Mina Kazemi, Brenda Gagnier, Alexandra De Pokomandy, Mona Loutfy
Epidemiology and Biostatistics Publications
BACKGROUND: HIV infection and substance use synergistically impact health outcomes of people with HIV. In this study, we assessed the prevalence of substance use among women living with HIV (WLWH) and compared them with expected values from general data.
METHODS: Cigarette smoking, frequency of alcohol consumption, last-month non-prescribed cannabis use (vs. last-year use), and last 3 months regular (≥once/week) and occasional (
RESULTS: Compared to expected estimates from general population women, a higher proportion of WLWH reported daily cigarette smoking (SPD: 26.8% [95% CI: 23.9, 29.7]), smoking ≥20 cigarettes/day (SPD: 11.6% [9.8, 13.6]), regular non-prescribed cannabis use (SPD: 8.0% [4.1, …
Family Physician Remuneration Schemes And Specialist Referrals: Quasi-Experimental Evidence From Ontario, Canada., Sisira Sarma, Nirav Mehta, Rose Anne Devlin, Koffi Ahoto Kpelitse, Lihua Li
Family Physician Remuneration Schemes And Specialist Referrals: Quasi-Experimental Evidence From Ontario, Canada., Sisira Sarma, Nirav Mehta, Rose Anne Devlin, Koffi Ahoto Kpelitse, Lihua Li
Epidemiology and Biostatistics Publications
Understanding how family physicians respond to incentives from remuneration schemes is a central theme in the literature. One understudied aspect is referrals to specialists. Although the theoretical literature has suggested that capitation increases referrals to specialists, the empirical evidence is mixed. We push forward the empirical research on this question by studying family physicians who switched from blended fee-for-service to blended capitation in Ontario, Canada. Using several health administrative databases from 2005 to 2013, we rely on inverse probability weighting with fixed-effects regression models to account for observed and unobserved differences between the switchers and nonswitchers. Switching from blended fee-for-service …
Statistical Tools For Assessment Of Spatial Properties Of Mutations Observed Under The Microarray Platform, Bin Luo
Electronic Thesis and Dissertation Repository
Mutations are alterations of the DNA nucleotide sequence of the genome. Analyses of spatial properties of mutations are critical for understanding certain mutational mechanisms relevant to genetic disease, diversity, and evolution. The studies in this thesis focus on two types of mutations: point mutations, i.e., single nucleotide polymorphism (SNP) genotype differences, and mutations in segments, i.e., copy number variations (CNVs). The microarray platform, such as the Mouse Diversity Genotyping Array (MDGA), detects these mutations genome-wide with lower cost compared to whole genome sequencing, and thus is considered for suitability as a screening tool for large populations. Yet it provides observation …
Statistical Modeling Of Co2 Flux Data, Fang He
Statistical Modeling Of Co2 Flux Data, Fang He
Electronic Thesis and Dissertation Repository
Carbon dioxide (CO2) flux is important for agriculture and carbon cycle studies. Only a small proportion of the land is currently covered by proper equipment to directly collect CO2 flux data. The CO2 flux data has an obvious annual cycle with the phase changing from year to year. How to build a model to estimate the annual effect and seasonal dynamics is a challenging task. With the help of the Moderate Resolution Imaging Spectroradiometer (MODIS) which is carried by NASA satellites, corresponding data, such as normalized difference vegetation index (NDVI), is freely available from NASA. Our goals are modeling the …
Effectiveness Of 4-Aminopyridine For The Management Of Spasticity In Spinal Cord Injury: A Systematic Review, Joshua Weiner, Jane Hsieh, Amanda Mcintyre, Robert Teasell
Effectiveness Of 4-Aminopyridine For The Management Of Spasticity In Spinal Cord Injury: A Systematic Review, Joshua Weiner, Jane Hsieh, Amanda Mcintyre, Robert Teasell
Epidemiology and Biostatistics Publications
Background: Spasticity is a common secondary complication of spinal cord injury (SCI), which can severely impact functional independence and quality of life. 4-Aminopyridine (4-AP) is a potassium channel blocker that has been studied as an intervention for spasticity in individuals with SCI. Objective: To conduct a systematic review of the available evidence regarding the effectiveness of 4-AP for the management of spasticity in individuals with SCI. Methods: A comprehensive literature search was conducted on five electronic databases for articles published in English up to January 2017. Studies were included if (1) the sample size was three or more subjects, (2) …
The Periglacial Landscape Of Mars: Insight Into The 'Decameter-Scale Rimmed Depressions' In Utopia Planitia, Arya Bina
Electronic Thesis and Dissertation Repository
Currently, Mars appears to be in a ‘frozen’ and ‘dry’ state, with the clear majority of the planet’s surface maintaining year-round sub-zero temperatures. However, the discovery of features consistent with landforms found in periglacial environments on Earth, suggests a climate history for Mars that may have involved freeze and thaw cycles. Such landforms include hummocky, polygonised, scalloped, and pitted terrains, as well as ice-rich deposits and gullies, along the mid- to high-latitude bands, typically with no lower than 20o N/S. The detection of near-surface and surface ice via the Phoenix lander, excavation of ice via recent impact cratering activity as …
The Statistical Exploration In The $G$-Expectation Framework: The Pseudo Simulation And Estimation Of Variance Uncertainty, Yifan Li
Electronic Thesis and Dissertation Repository
The $G$-expectation framework, motivated by problems with \emph{uncertainty}, is a new generalization of the classical probability framework. Similar to the Choquet expectation, the $G$-expectation can be represented as the supremum of a class of linear expectations. In the past two decades, it has developed into a complete stochastic structure connected with a large family of nonlinear PDEs. Nonetheless, to apply it to real-world problems with uncertainty, it is fundamentally necessary to build up the associated statistical methodology.
This thesis explores the \emph{computation, simulation, and estimation} of the $G$-normal distribution (a typical distribution with variance uncertainty) by constructing a new substructure …
Stochastic Modelling Of Implied Correlation Index And Herd Behavior Index. Evidence, Properties And Pricing., Lin Fang
Electronic Thesis and Dissertation Repository
In this work, we provide the definition, study properties, and craft new stochastic models for two dependence indices: the implied correlation index and the herd behavior index (HIX). In particular, we model and price financial derivatives on the basic implied correlation index (CIX) as reported by CBOE. Our analysis is the first revealing the presence of heteroscedasticity in the time series of CIX leading to two Correlation Stochastic Volatility (CSV) models. We describe properties of CSV models and use discretization methods for their simulation. A partial estimation methodology is implemented on CBOE S& P 500 CIX historical data treating the …
A Mapping Review Of Randomized Controlled Trials In The Spinal Cord Injury Research Literature, Amanda Mcintyre, Brooke Benton, Shannon Janzen, Jerome Iruthayarajah, Joshua Weiner, Janice J. Eng, Robert Teasell, Spinal Cord Injury Research Evidence Team
A Mapping Review Of Randomized Controlled Trials In The Spinal Cord Injury Research Literature, Amanda Mcintyre, Brooke Benton, Shannon Janzen, Jerome Iruthayarajah, Joshua Weiner, Janice J. Eng, Robert Teasell, Spinal Cord Injury Research Evidence Team
Epidemiology and Biostatistics Publications
Study design
Mapping Review.
Objective
The objective of this study was to map out and characterize the quantity and quality of all published spinal cord injury (SCI) randomized controlled trials (RCTs) with respect to number, sample size, and methodological quality between January 1970 and December 2016.
Setting
Not applicable.
Methods
A literature search of multiple research databases was conducted. Studies adhering to the following criteria were included: the research design was an RCT; written in English; participants were >18 years; and the sample was >50% SCI. Data were extracted pertaining to author(s), year of publication, country of origin, initial and …
Analysis Challenges For High Dimensional Data, Bangxin Zhao
Analysis Challenges For High Dimensional Data, Bangxin Zhao
Electronic Thesis and Dissertation Repository
In this thesis, we propose new methodologies targeting the areas of high-dimensional variable screening, influence measure and post-selection inference. We propose a new estimator for the correlation between the response and high-dimensional predictor variables, and based on the estimator we develop a new screening technique termed Dynamic Tilted Current Correlation Screening (DTCCS) for high dimensional variables screening. DTCCS is capable of picking up the relevant predictor variables within a finite number of steps. The DTCCS method takes the popular used sure independent screening (SIS) method and the high-dimensional ordinary least squares projection (HOLP) approach as its special cases.
Two methods …
Statistical Applications In Healthcare Systems, Maryam Mojalal
Statistical Applications In Healthcare Systems, Maryam Mojalal
Electronic Thesis and Dissertation Repository
This thesis consists of three contributing manuscripts related to waiting times with possible applications in health care. The first manuscript is inspired by a practical problem related to decision making in an emergency department (ED). As short-run predictions of ED censuses are particularly important for efficient allocation and management of ED resources we model ED changes and present estimations for short term (hourly) ED censuses at each time point. We present a Markov-chain based algorithm to make census predictions in near future.
Considering the variation in arrival pattern and service requirements, we apply and compare three models which best describe …
Computational Modelling Of Human Transcriptional Regulation By An Information Theory-Based Approach, Ruipeng Lu
Computational Modelling Of Human Transcriptional Regulation By An Information Theory-Based Approach, Ruipeng Lu
Electronic Thesis and Dissertation Repository
ChIP-seq experiments can identify the genome-wide binding site motifs of a transcription factor (TF) and determine its sequence specificity. Multiple algorithms were developed to derive TF binding site (TFBS) motifs from ChIP-seq data, including the entropy minimization-based Bipad that can derive both contiguous and bipartite motifs. Prior studies applying these algorithms to ChIP-seq data only analyzed a small number of top peaks with the highest signal strengths, biasing their resultant position weight matrices (PWMs) towards consensus-like, strong binding sites; nor did they derive bipartite motifs, disabling the accurate modelling of binding behavior of dimeric TFs.
This thesis presents a novel …
Advances In Semi-Nonparametric Density Estimation And Shrinkage Regression, Hossein Zareamoghaddam
Advances In Semi-Nonparametric Density Estimation And Shrinkage Regression, Hossein Zareamoghaddam
Electronic Thesis and Dissertation Repository
This thesis advocates the use of shrinkage and penalty techniques for estimating the parameters of a regression model that comprises both parametric and nonparametric components and develops semi-nonparametric density estimation methodologies that are applicable in a regression context.
First, a moment-based approach whereby a univariate or bivariate density function is approximated by means of a suitable initial density function that is adjusted by a linear combination of orthogonal polynomials is introduced. Such adjustments are shown to be mathematically equivalent to making use of standard polynomials in one or two variables. Once extended to apply to density estimation, in which case …
Tinnitus And Dysfunctional Interactions Between Distributed Resting State Networks, Sivayini Kandeepan
Tinnitus And Dysfunctional Interactions Between Distributed Resting State Networks, Sivayini Kandeepan
Western Research Forum
It is known that peripheral lesions in the cochlea or the auditory nerve produce dysfunctional input to central auditory structures and induce changes in the auditory system causing tinnitus. Recently, it has been proposed that the unified percept of tinnitus could be considered as an emergent property of multiple overlapping dynamic brain networks, each encoding a specific tinnitus characteristic.
The aim of our study was to investigate the neuronal activation patterns associated with specific clinical tinnitus characteristics using fMRI. We hypothesize that tinnitus clinical characteristics could be associated with specific resting-state activity and connectivity patterns and that this could be …
Modelling The Common Risk Among Equities Using A New Time Series Model, Jingjia Chu
Modelling The Common Risk Among Equities Using A New Time Series Model, Jingjia Chu
Electronic Thesis and Dissertation Repository
A new additive structure of multivariate GARCH model is proposed where the dynamic changes of the conditional correlation between the stocks are aggregated by the common risk term. The observable sequence is divided into two parts, a common risk term and an individual risk term, both following a GARCH type structure. The conditional volatility of each stock will be the sum of these two conditional variance terms. All the conditional volatility of the stock can shoot up together because a sudden peak of the common volatility is a sign of the system shock.
We provide sufficient conditions for strict stationarity …
Some Applications Of Higher-Order Hidden Markov Models In The Exotic Commodity Markets, Heng Xiong
Some Applications Of Higher-Order Hidden Markov Models In The Exotic Commodity Markets, Heng Xiong
Electronic Thesis and Dissertation Repository
The liberalisation of regional and global commodity markets over the last several decades resulted in certain commodity price behaviours that require new modelling and estimation approaches. Such new approaches have important implications to the valuation and utilisation of commodity derivatives. Derivatives are becoming increasingly crucial for market participants in hedging their exposure to volatile price swings and in managing risks associated with derivative trading. The modelling of commodity-based variables is an integral part of risk management and optimal-investment strategies for commodity-linked portfolios. The characteristics of commodity price evolution cannot be captured sufficiently by one-state driven models even with the inclusion …
Advances In The Modeling Of Heavy-Tailed Distributions, Sang Jin Kang
Advances In The Modeling Of Heavy-Tailed Distributions, Sang Jin Kang
Electronic Thesis and Dissertation Repository
Several advances are proposed in connection with the approximation and estimation of heavy-tailed distributions, some of which also apply to other types of distributions. It is first explained that on initially applying the Esscher transform to heavy-tailed density functions such as the Pareto, Student-t and Cauchy densities, one can utilize a moment-based technique whereby the tilted density functions are expressed as the product of a base density function and a polynomial adjustment. Alternatively, density approximants can be secured by appropriately truncating the distributions or mapping them onto compact supports. The validity of these approaches is corroborated by simulation studies. …