LIAM Distinguished Lectures and Seminars

Estimating reproduction numbers using nucleotide sequence data by the "Bayesian evolutionary analysis by sampling trees"(BEAST)

Abstract: Bayesian phylogenetic methods are commonly used for rapidly mutated viruses, which can affect reconstructed tree structure, to infer epidemiological processes from genetic data. Here I will introduce basic of the Bayesian theorem with BEAST briefly and Birth-death(BD) model which make the BEAST available to estimate reproduction number. After the introduction, I will show examples of its application to real sequence data, pandemic(H1N1) 2009 in Argentina and Hepatitis C virus(HCV) in Egypt.

Dr. Kiyeon Kim
Visitor Scholar
York University

Date: Nov 28, 2017
Time: 10:00-11:00 AM
Location: Kinsmen 286

 

Study on data mining method of gene transcriptome in tuberculosis

Abstract: This study will utilize the characteristics of transcriptome data related with TB, through significant analysis, association rule analysis, multi-level genetic model and dynamic time warping model to discover more key host gene associated with tuberculosis and their categories; to research the spatial correlation of all kinds of key genes and their roles in the formation of tuberculosis; to analysis dynamic changes of gene transcription on different time scales and the transcription rules in various conditions; to predict the potential expressions of pathogenic genes.       

Dr. Xu Zhang
Post-doctoral Fellow
York University

Date: Nov 21, 2017
Time: 10:00-11:00 AM
Location: Kinsmen 286

LIAM-PHAC symposium on LIAM-ADERSIM Agent-based Simulator for the Gastro-intestinal Pathway of L. monocytogenes

Date: November 17, 2017
Time: 10:00 A.M to 12:00 P.M
Location: Kinsmen 286

Agent-Based model development for with-in host dynamics of L. monocytogenes

Abstract: The case fatality and illness rates associated with L. monocytogenes remain unchanged over the decades despite the significant efforts and control protocol obtained by private and public sectors.In order to demonstrate the human gastro-intestinal pathway of L. monocytogenes, we develop an agent based model. I will demonstrate the impact of food intake pattern, stomach pH variation and storage condition on the survival of L. monocytogenes in the stomach. The model will also illustrate the role of immune potential to prevent intestinal infections.      

Dr. Ashrafur Rahman
Post-doctoral Fellow
York University

Date: Nov 14, 2017
Time: 10:00-11:00 AM
Location: Kaneff Tower

Sleep Duration and Chronic Condition Among Canadian Adults: Do Mental Illness Play a Mediating Role?

Abstract: Chronic condition has been major contributors to reduced quality of life, loss of productivity, and increased hospitalization and health care costs as well as premature death in Canada.For better chronic condition prevention, this large-scale study was designed to explore the potential association of sleep duration with chronic condition and mediation by mental illness. We obtained data from the 2011-2012 Canadian Community Health Survey. A total of 40,614 participants aged 18 years or older from four provinces (Nova Scotia, Quebec, Manitoba, and Alberta) that participated in the sleep survey module were selected for the study. Logistic regressions were performed to assess the mediation of mental illness on the association between sleep duration and chronic condition. The age- and sex- standardized prevalence of any chronic condition in four provinces of Canada was 54.5%. Compared to those sleep 7 to < 9 h, participants in both short (< 5 h, and 5 to < 7 h) and long (9 to < 11 h, and ≥ 11 h) sleep duration reported a higher prevalence of any chronic condition. After adjusting for all potential confounders, the “U-shaped” association between sleep duration and any chronic condition persisted. Following the criteria of examining mediating effects, mental illness was found significantly mediated the relationships between sleep duration and any chronic condition(all Sobel P< 0.001). However, the mediated effect size of mental illness was obviously higher in long sleep duration (32.8% and 33.4%) than short sleep duration (14.0% and 9.5%). Sleep duration had U-shaped relationships with the presence of chronic condition. Mental illness play a mediating role on the relationships between sleep duration and chronic condition, especially in long sleep duration.

Dr. Haijiang Dai
Post-doctoral Fellow
York University

 

Date: Nov 7, 2017
Time: 10:00-11:00 AM
Location: Kaneff Tower

 

Understanding the dynamics of West Nile Virus in Emilia-Romagna, Italy

Abstract:  West Nile Virus (WNV) has been identified for the first time in Italy in 1998, and more continuously since 2008 with a total of 173 neurological human cases between 2008 and 2015. Still the circulation of the virus appears to have been episodic with most cases concentrated in a few years and a few hotspots shifting in different years.  The region Emilia Romagna, which is one of the most affected areas, has set up since 2009 a systematic program of mosquito and corvids (known to be among the most competent bird species for WNV) trapping and testing. Data collected through this program have been analysed through a mathematical model in order to understand the main drivers of the observed dynamics. The analysis has mainly been based on an SIR (for competent birds)-SI (mosquitoes) model, with an environmentally driven population model, validated on independent data, for mosquito dynamics, and a simple population model for bird dynamics, in which the free parameters  were the mosquito biting rate  and the host-vector ratio. Our results showed that simplest models with constant mosquito feeding behaviours are incompatible with the observed seasonal patterns of infected mosquitoes and birds. On the other hand, including a seasonal shift in mosquito feeding behaviour makes model outputs much more consistent with observed data. Our findings can be of particular interest for public health policy makers, as they provide important insights on WNV dynamics in order to improve surveillance, and risk assessment of WNV in the area.

Marco Tosato
PhD Candidate
York University

 

Date: Oct 24, 2017
Time: 10:00-11:00 AM
Location: Kaneff Tower

pH dependent C. jejuni thermal inactivation models and application to poultry scalding

Abstract: Campylobacter jejuni related outbreaks and prevalence on retail poultry products pose threats to public health and cause financial burden worldwide. To resolve these problems, it is imperative to take a closer look at poultry processing practices and standards. Using available data (D-values) on the thermal inactivation of C. jejuni we develop a comprehensive inactivation model, taking into account the variation of strain-specific heat resistance, experimental method, and suspension pH. Utilizing our C. jejuni thermal inactivation model, we study the poultry scalding process. We present a mechanistic model of bacteria transfer and inactivation during a typical immersion scald
in a high-speed industrial plant. Integration of our 
C. jejuni inactivation model into the scalding model culminates in validation against industrial processing data. In particular, we successfully predict bacteria concentrations in the scald water and link key factors such as scald water pH and temperature to cross-contamination and overall microbiological quality of carcasses. Furthermore, we demonstrate the applicability of our inactivation model for scalding operations at seven Canadian poultry plants. In addition to providing recommendations for best-practice and a review of scalding research, our work is intended to act as a modular foundation for further research in the interest of public health and financial well-being. 

Zack McCarthy
PhD Candidate
York University

Date: Oct 24, 2017
Time: 10:00-11:00 AM
Location: CB 126

Lone star tick and its dynamics

Jemisa Sadiku , Zilong Song,
PhD Candidate
York University

Date: Oct 10, 2017
Time: 10:00-11:00 AM
Location: CB 126

Effect of Host Resistance on Tick Population Dynamics  

Abstract: The purpose of this model is to demonstrate the tick population dynamics when we consider bitten host with resistance. The reason why we consider such observation it's because there is evidence of tick's population size to be reduced if they are biting hosts with resistance.The reaction of sensitized host when a tick starts feeding is very different from that of susceptible 'naive' host. For instance, the feeding site of sensitized host is characterized by erythema and also by intra-epidermal vesicles packed with basophils which will result in immediate death of the tick. On the other hand susceptible hosts have very little and slow reaction to the tick feeding site allowing the tick to fully finish the feeding process and hence to achieve the disease transmission to the host. 

In addition, we will observe how the values of parameters are correlated with tick's population dynamics and also observe if these biological factor are supported by the mathematical model.
 

Jemisa Sadiku (Joint work with Mahnaz Alavinejad),
PhD Candidate
York University

Date: Oct 3, 2017
Time: 10:00-11:00 AM
Location: CB 126

Bayesian Inference of Multiple Gaussian Graphical Models

Abstract: I will present a Bayesian approach to inference of multiple networks that has been proposed by Stingo et al. (JASA, 2015). The Bayesian approach readily allows the incorporation of crucial features into a model, including sharing of graph structure across related sample groups and providing a means for obtaining a measure of relative network similarity across groups. The approach also provides the the ability to include prior knowledge of edge-specific interactions and to encourage the degree of similarity to an established network. I will give a brief background on Bayesian inference and graphical modeling of network data and then describe the model specification, including the choice of prior distributions in the model by Stingo et al. I will present the numerical methods used for posterior inference and model selection and conclude with simulation results and an application of the methods to modeling protein networks.

Chris Prashad
PhD Candidate
York University

Date: June 19, 2017
Time: 3:00 PM – 4:00 PM
Location: CB 126

Please note Distinguished Lectures are in RED.

LIAM symposium on Infection Dynamics Modelling and Informatics

Date: May 8, 2017
Time: 1:30 P.M to 4:30 P.M
Location: CB 126


DISTINGUISHED LECTURE: Diffusive Host-Pathogen System with Different Dispersal Rates and Spatial Heterogeneity

Xingfu Zou
Professor
University of Western, Ontario

Abstract: We will demonstrate some recent results on a diffusive host-pathogen model with spatially heterogeneous parameters and distinct dispersal rates for the susceptible and infected hosts. In addition to global existence of solution, existence of a global attractor, we also discuss the threshold dynamics in terms of the basic reproduction number R_0 which is identified as the spectral radius of a linear operator in the appropriate functions space. When R_0>1, the solution of the model is uniformly persistent and there exists a positive steady state. In the latter case, we also explore the asymptotic profiles of the endemic steady state as the dispersal rate of the susceptible or infected hosts approaches zero. The results reveal some differences between the roles that the dispersion of susceptible and infectious hosts can play.

Date: April 24, 2017
Time: 2:30 P.M to 3:30 P.M
Location: CB 126

A Model of Chikungunya Transmission with Virus Mutation

Xiaomei Feng
Lecturer of Applied Mathematics
Yuncheng University, China

Date: April 17, 2017
Time: 12:30 PM – 1:30 PM
Location: CB 126

Population Dynamics and Genetic Studies of Sex-Determining Alleles in Honey Bees

Abstract:Crossing of different races of honeybees has become a common practice in these days. But many breeders fear that no pure races will be available in future to conserve the local honeybee ecotypes. Therefore population genetic studies are necessary to establish the expected viability of brood in such populations. Allele frequencies are responsible for viability and is used to characterize the genetic diversity in population. In this talk I will present some work of Jerzy Woyke, ''Population Genetic Studies on Sex Alleles in Honey Bee Using the example of the Kangroo Island Bee Sanctuary'', Journal of Apicultural Research 15(3/4), 1976, in which he formulated and analyzed the mathematical models and analytical expression for calculating the frequencies of sex alleles in subsequent generations and two sexes of honeybees. Also, I will discuss some mathematical theories of the population dynamics of the sex determining alleles in honeybees, developed by ShozoYokoyama and Mastoshi Nei, ''Population Dynamics of Sex-Determining Alleles in Honey Bees and Self-Incompatibility Alleles in Plants'', Genetics 91(3), 1978, where they proved that in an infinitely large populations with n number of alleles, the equilibrium frequency of sex alleles is 1/n and the asymptotic rate of approach to this equilibrium is 2/3n per generation.

Bushra Majeed
M.A Student
York University

Date: April 3, 2017
Time: 12:30 PM – 1:30 PM
Location: CB 126

Network of neurons with delayed feedback and dynamic memory enhancement.

Abstract:Delayed negative feedback, coupled with absolute refractory period, can generated a large amount of stable periodic orbits for associate memory storage and retrieval.

Dr. Jianhong Wu
University Distinguished Research Professor
Canada Research Chair in Industrial and Applied Mathematics
Laboratory for Industrial and Applied Mathematics (LIAM)
Department of Mathematics and Statistics
York University, Toronto, Canada

Date: March 20, 2017
Time: 12:30 PM – 1:30 PM
Location: CB 126

Complementary Sex Determination Substantially Increases Extinction Proneness of Haplodiploid Populations

Abstract: Haplodiploid insects such as ants, bees, and wasps are very important components of terrestrial ecosystems, and their conservation is essential for economic as well as ecological reasons. The conservation genetics of haplodiploids has received very little attention. Haplodiploidy is the property of hymenoptera due to complementary sex determination. In this unique system females develop from the fertilized egg while haploid males are produced from unfertilized egg, however diploid male are also produced but homozygous at the sex-determining locus. In this talk, I will present the work of Amro Zayed and Laurence Packer in which they discussed that the complementary sex determination mechanism in hymenoptera through homozygosity, leading to the production of more sterile and inviable diploid males, due to which haplodiploids are substantially more, rather than less, prone to extinction. Some results on the base of stochastic modelling will also be provided to see the effect of diploid male production (DMP) on the extinction dynamics of haplodiploid populations.

Bushra Majeed
M.A Student
York University

Date: January 30, 2017
Time: 12:30 PM – 1:30 PM
Location: CB 126

Modelling the Evolution of Influenza towards to its Prediction

Abstract: The transmission dynamics of infectious disease is non-linear, since the expected number of transmission events is proportional to the number of both susceptibles and invectives. Mathematical modelling has been playing a key role in understanding and predicting the transmission dynamics. An important disease which is difficult to understand and predict is Influenza. The difficulty in predicting influenza dynamics arises from i). the host of influenza is not only human, the most strains causing pandemic come from the non-human population, but the field data of non-human cases is not enough for predicting the invasion dynamics of influenza from non-human hosts; ii) Even in human population influenza virus evolves quickly and the efficacy of vaccine wanes quickly, so modelling the evolution of influenza in human population is challenging; iii) The transmission probability of influenza is changing
over time, it correlates with the absolute humidity and so the model coefficients in the nonlinear term is a function of time. In this talk, I will introduce some progress how mathematical modelling contributes to the understanding the transmission dynamics of influenza, especially for ii) and iii).

Dr. Ryosuke Omori
Assistant Professor
Research Centre for Zoonosis Control, Hokkaido University, Japan

Date: January 09, 2017
Time: 2:30 PM – 5:30 PM
Location: North Ross 201

Descriptive versus mechanistic dose-response modeling of L. monocytogenes infection in human population

Abstract: Dose-response relationship of L. monocytogenes infection is fundamental in evalution of risk analysis. Descriptive models (exponential, log-logistic and betarpoisson) describing the dose-response relationships have been widely used in L. monocytogenes outbreaks. These models, unfortunately, lack the insights of host-pathogen interaction that drive the response outcomes. Recently, we have developed a mechanistic model to account for the host-pathogen interaction in mouth to gut pathway that provides a mechanistic basis of dose-response relationship for L. monocytogenes infection. Our current study looks into the differences and similarities of two modeling approaches. In particular, we identify the key parameters and their relative ranges that differentiate the models in L. monocytogenes outbreak to human population.

Dr. Ashrafur Rahman
Post-doctoral fellow

Date: December 15, 2016
Time: 10:30 am to 11:30 am
Location: CB 126

The Lyapunov's functions of some epidemic models of control with vaccine: Case of Tuberculosis and Polio.

Abstract: For the TB, the spread dynamics of the tuberculosis through mathematical models that incorporates both latent and clinical stages has been proposed by HONGBIN GUO and MICHAEL Y. LI.
In this work, we modified the precedent model and we add a strategy of control with vaccine. Then we calculated the basic reproduction number (R0). If R0 ≤ 1, the TB always dies out, otherwise the tuberculosis becomes endemic. The global stability of endemic equilibrium is established through direct Lyapunov and Lasalle Methods. We confirmed our analytics results through numerical simulations.
Talking about Polio, because of the lack of treatment of that disease, the only mean of prevention is immunization through live oral polio vaccine (OPV) or/and inactivated polio vaccine ( IPV).
Poliomyelitis is a very contagious viral infection caused by poliovirus. Children are principally targeted.
In this paper, we assessed the impact of vaccination in the control of spread of poliomyelitis. We used the deterministic SVEIR model of infectious disease transmission (Susceptible-Vaccinated-Latent-Infectious-Removed), where vaccinated individuals are also susceptible even in a lesser degree.
Using Lyapunov-Lasalle methods, we proved the global asymptotic stability of the unique endemic equilibrium whenever Rvac > 1. Some numerical simulations based on poliomyelitis data from Cameroon, conducted us to approve analytic results and demonstrated the importance of vaccinate coverage when it comes to controlling the spread of that disease.
In terms of perspectives, a study related to Polio, of multi group cases with migration between compartments of the same epidemic status is to be issue.

Dr Léontine NKAMBA
Senior Lecturer
University of Yaounde
Higher Teacher Training College
Department of Mathematics

Date: December 8, 2016
Time: 10:30 am to 11:30 am
Location: CB 126

Does two lags really make a trouble for stability analysis?

Seminar Notes

Dr. Jianhong Wu
University Distinguished Research Professor
Canada Research Chair in Industrial and Applied Mathematics
Laboratory for Industrial and Applied Mathematics (LIAM)
Department of Mathematics and Statistics
York University, Toronto, Canada

Date: December 1, 2016
Time: 10:30 am to 11:30 am
Location: CB 126

Investigating the optimal dengue vaccination to mitigate Zika cases

Biao Tang
Visiting PhD Candidate
Xi’an Jiaotong University, China,
York Univerisy and Fields Institution, Toronto, Canada

Abstract: This is a follow-up study of our previous model on implication of dengue vaccination for Zika outbreak, in which we found that due to the antibody-dependent enhancement, vaccinated individuals with antibody against dengue could have higher chance to be contaminated by Zikavirus, thus dengue vaccination could induce more Zika cases. In this study, we perform numerical experiments to seek the optimal dengue vaccination ratio that could benefit the control of both diseases. Ultimately, we aim to provide vaccination guidelines for dengue prevalent regions to reduce local Zika cases.

Date: November 17, 2016
Time: 10:30 to 11:30 am
Location: CB 126

Basic Introduction of LDA Topic Model on Text Mining

Bowen Sun
Master of Science Candidate
Simon Fraser University, British Columbia, Canada.

Abstract: In machine learning and natural language processing, a topic model is a type of statistical model for discovering the abstract ‘topics’ that occur in a collection of documents. Intuitively, given a document is about some topic, the occurrence of some particular words is expected to be more or less frequent. Thus, the topic model is very useful in the content exploration or key point extraction from large document corpora. In this presentation, I will give an introduction of some basic process in text mining and the LDA topic model theory

Date: November 10, 2016
Time: 10:30 to 11:30 am
Location: CB 126

Modelling antibody enhancement and its consequence for integrated vector borne disease control

Biao Tang
Visiting PhD Candidate
Xi’an Jiaotong University, China,
York Univerisy and Fields Institution, Toronto, Canada

Abstract: We present our recent work on modelling co-infection of diseases sharing the same vector, and the consequence of antibody enhancement for integrated intervention including vaccination, using dengue and Zika as references. This is based on joint work with Yanni Xiao and Jianhong Wu.

Date: October 13, 2016
Time: 10:30 to 11:30 am
Location: CB 126

 DISTINGUISHED LECTURE: Novel Principles and Approaches of Bioinformation Acquisition at the Nanoscale and Molecular Level

Kemin Wang

Professor
Hunan University, China

Abstract: This talk gives a systematic review of the pioneering research in bioinformation acquisition at the nanoscale and molecular level, developed at the Key Laboratory for Bio-Nanotechnology and Molecular Engineering of Hunan Province. It focuses on challenges of this development for bioinformatics and complex data analytics.

Date: October 11, 2016
Time: 11:30 to 12:30 am
Location: CB 126

Mathematical modelling of cross-diffusion in biofilms

Kazi Rahman
Post-doctoral Fellow
York University and Ryerson University
Toronto, Canada

Abstract: We propose a deterministic continuum model for mixed culture biofilms where movement of one species is affected by the presence of the other. Two derivations of this new model are presented. One derivation is based on the continuous time, discrete space master equation and the other one is based on the equations of conservation of mass and momentum. Starting from both viewpoints, we derive the same dual-species diffusion-reaction model for biofilms that comprises three non-standard diffusion effects: (i) degeneracy as the local biomass density vanishes, (ii) a super-diffusion singularity as the local biomass density approaches its a priori known maximum, and (iii) non-linear cross-diffusion. (i) describes the finite speed of propagation of the biofilm/water interface, (ii) describes volume filling effects, and (iii) describes the mixing of both biomass species. We present a numerical method for this highly nonlinear PDE model of biofilm that can tackle these three nonlinear diffusion effects. To investigate the effect of the new model feature, we study the role of the cross-diffusion terms in numerical simulations of three biofilm models: competition, allelopathy, and a mixed system formed by anaerobic and an anaerobic species. In all three systems we observe that accounting for cross-diffusion affects local biofilm structure, in particular the relative local distribution of biomass, but it does not affect overall lumped quantities such as the total amount of biomass in the system. As an application, our highly nonlinear density dependent cross-diffusion model is used in order to incorporate an experimental observation in models of disinfection of microbial biofilms. An extended reaction kinetics based on carbon consumption during disinfection is introduced. Our simulations show that the extended model captures the experimental observation, and suggest that the consumption of carbon substrates during inactivation due to antibiotics helps biofilms to survive and re-grow. Finally, as an extension of dual-species model, a generalized cross-diffusion model of k interacting species is derived considering the continuous time and discrete space master equation passing to the continuous limit. Moreover, a criterion for preserving the positivity of the solution of this type of generalized cross-diffusion model is presented.

Date: October 6, 2016
Time: 10:30 to 11:30 am
Location: CB 126

Neural Dynamics and Optimization of Online Advertising Systems

Yong Yang
PhD Candidate
York University
Toronto, Canada

Abstract: Real time Bidding (RTB) is a relatively new advertising technology that allows online advertising to be purchased and served on the fly. RTB ingests and distributes impressions from thousands of parameters simultaneously. Infersystems is an algorithm provider whose technologies apply nonparametric statistics to improve the performance of both Demand Side Platforms (DSPs) and Supply Side Platforms (SSPs). InferSystems generates media buying and optimization rules to minimize the cost per action (CPA) and cost per click (CPC) of a digital advertising campaign. These results are accomplished by using InferSystems proprietary, predictive analytic and decision engine (i.e., Infer Engine) that is able to predict super rare events from sparse data. Based on a variety of data training techniques, the Infer Engine automatically outputs a decision table of media buying rules. Buying rules are the number of combinations of parameters, such as country, banner code, banner position, landing url and bidding time. When users access the web page, all user information is uploaded to the web server. Infer Engine attempts to match impressions and the rules in the decision table. These generated media buying rules are able to predict which impressions are the most likely ones to be the clicked advertisements. As time goes by, these buying rules will fail to work and hence we expect to see a dramatic drop in the number of impressions if these buying rules are not revised / replaced. The objective of this thesis is two folds: to predict click impression dynamics, and to quantify the effectiveness of media buying rules and the decay of these rules. The model proposed is similar to, but different from, the classical epidemiological models for infectious diseases, this is due to the similarity between the considered click impression dynamics and the disease infection exposure dynamics.

Date: September 22, 2016
Time: 10:30 to 11:30 am
Location: CB 126

LIAM Initiatives during 2016-2017

Dr. Jianhong Wu
University Distinguished Research Professor
Canada Research Chair in Industrial and Applied Mathematics
Laboratory for Industrial and Applied Mathematics (LIAM)
Department of Mathematics and Statistics
York University, Toronto, Canada

Date: September 16, 2016
Time: 11:30 am to 12:30 pm
Location: CB 126

Neural Network Based Approach for Subspace Clustering of High Dimensional Data

Bowen Sun
Visiting M.Sc. Student
Simon Fraser University
Vancouver, Canada

Abstract: We are living in a data/information driven society, and every aspect of our life greatly depends on our ability to collect, analyze and understand large sets of data and information. These large data sets with high dimensions arise naturally from a variety of fields, such as bioinformatics, text mining. And the traditional clustering algorithms can’t work effectively for these types of data because of the well- known problem, the curse of dimensionality. In this talk, I am going to introduce a neural network architecture, PART developed by Professor Wu and his LIAM team, which is based on the ART developed by Carpenter and Grossberg. I will also discuss the algorithm for clustering high dimensional data sets.

Date: April 22, 2016
Time: 11:30 am to 12:30 pm
Location: CB 126

Mathematical Solutions of Pharmacokinetic Models When Nonlinearity Is An Issue

Xiaotian Wu
Visiting Professor
University of Montreal
Montreal, Canada

Abstract: Analytical solutions of pharmacokinetic models are appealing since they provide a clear and direct way to reveal the relationship between different model components, and greatly improve the process of drug development and drug design. In this talk, I will present mathematical solutions, including time-course of drug concentration and estimation of key pharmacokinetics parameters, of some pharmacokinetic models where nonlinear elimination is an important factor for some drug disposition, typically hormone drugs such as granulocyte colony-stimulating factor (G-CSF). This is a joint work with Professors Fahima Nekka and Jun Li at Université de Montréal.

Date: April 8, 2016
Time: 11:30 am to 12:30 pm
Location: CB 126

Predictive Modelling of Health Clusters for Chronic Disease Management

Yawen Xu
Postdoctoral fellow
York University and Manifolds Data Mining Inc.
Toronto, Canada

Abstract: Join Yawen Xu, York University, and Ted Hains & Zhen Mei, Manifold Data Mining Inc. lecture on health clusters of patients with chronic diseases, particularly diabetes and heart diseases. They will introduce a predictive modelling technique for classifying a patient into clusters, based on their demographics, mental health and stress, health outcomes, social connection, motivation and lifestyles.

Date: April 1, 2016
Time: 2:30 pm to 4:30 pm
Location: York Lanes Room 280N

Mathematical Modeling of Infectious Diseases From the Pre-Vaccine to Vaccine Era

Felicia Maria G. Magpantay
Assistant Professor
University of Manitoba
Manitoba, Canada

Abstract: The dynamics of vaccine-preventable diseases depend on the underlying disease process and the nature of the vaccine. In this talk I will discuss imperfect vaccines and the epidemiological consequences of different modes of vaccine failure. In particular, I will focus on the dynamics during the transition from the pre-vaccine to vaccine era and some new methodologies for dealing with incomplete data during this period.

I will also present an application to pertussis, a childhood disease that was once considered a candidate for eradication. This highly infectious disease is still a significant cause of child mortality in the world, and has been reemerging in some countries that maintain high vaccination coverage (e.g. USA, UK). Recent events have highlighted how much we still do not know about the mechanics of this disease and the type of immunity rendered by infection and vaccination. I will discuss some of the progress we have made in fitting a general stochastic model of pertussis, and the ideas behind the likelihood-based statistical inference methods (trajectory matching and iterated filtering) used to estimate the vaccine parameters.

Date: March 28, 2016
Time: 2:00 pm to 3:00 pm
Location: CB 126

Self-Excited Vibrations in Damped Wave Equations

Nemanja Kosovalic
Assistant Professor
University of South Alabama
Alabama, United States

Abstract: Over the last fifty years much work has been devoted to the study of forced vibrations in damped wave equations. From the mechanical point of view, external forcing is the simplest way of putting energy back into the system to balance out the friction, which results in a global time periodic solution whose amplitude does not decay. Another way of putting energy back into the system results from the presence of a restoring force with time delay. This leads to 'self-excited' vibrations. We discuss some aspects of self-excited vibrations for damped wave equations.

Date: March 18, 2016
Time: 11:30 am to 12:30 pm
Location: CB 126

The Evolution of Antimicrobial De-escalation: Part II

Lindsey Falk
Masters of Public Health (Epidemiology) Candidate
University of Toronto
Toronto, Canada

Abstract: Antibiotic resistance is a prominent issue in healthcare and there is a need to identify strategies that reduce resistance to broad spectrum antibiotics without compromising patient outcomes. This talk builds on a previous seminar given by Xi Huo and Josie Hughes, where a transmission model of P. aeruginosa in an intensive care unit (ICU) was presented to explore the evolutionary and ecologic impacts of antimicrobial de-escalation. De-escalation is a treatment strategy that aims to preserve the efficacy of broad spectrum antibiotics by switching patients to narrower agents. Although it has been applied widely in ICUs, the impacts are poorly understood. I will present the results from the model, which compares the de-escalation strategy to usual care under two different de-escalation approaches. As the mathematical model has previously been discussed, the focus will be on the clinical and public health implications of the model.

Date: March 11, 2016
Time: 11:30 am to 12:30 pm
Location: CB 126

Mathematical Modeling of With-In Host Dynamics of Listeria monocytogenes

Ashrafur Rahman
Postdoctoral Fellow
York University
Toronto, Canada

Abstract: Listeriosis is a potential food-borne disease caused by L. monocytogenes. The disease is an important public health problem as it poses a severe risk to certain populations including pregnant women, older adults, and individuals with a weakened immune systems. An individual can be infected with L. monocytogenes after consuming contaminated food. The bacteria can colonize in the intestines and reach the liver, spleen and placenta via the blood and lymphatic vessels. In this talk, I will outline modeling approaches of the Listeria invasion into the gut and its translocation at different organs. I will highlight the role of the immune responses and the inoculation doses that determine the difference of infection, and characterize the critical transition of listeriosis from mild to severe. This is based on joint work with D. Munther, J. Wu and a team of scientists from the Public Health Agency of Canada.

Date: March 4, 2016
Time: 11:30 am to 12:30 pm
Location: CB 126

Existence and Uniqueness of Mild and Strict Solutions for Abstract Differential Equations with State Dependent Delay

Michelle Pierri
Professor
São Paulo University
São Paulo, Brazil

Abstract: The theory of differential equations with delay is one of many important branches of the theory of differential questions. Recently, a new class of delay equations with a state-dependent delay (SDD) has attracted much attention of researchers. The study of ordinary and partial differential equations with state dependent delay differ from the case of ordinary and partial differential equations with constant or time-dependent delays. In this talk, we present some results related the existence of mild and strict solutions for abstract differential equations with state dependent delay. Our main result is concerning the existence of alpha-Holder strict solutions for this class of problems.

Date: February 26, 2016
Time: 11:30 am to 12:30 pm
Location: CB 126

Population Dynamics of Borrelia burgdorferi in Lyme disease

Jemisa Sadiku
PhD Candidate
Department of Mathematics and Statistics, York University
Toronto, Canada

Abstract: Many chronic inflammatory diseases are known to be caused by persistent bacterial or viral infections. A well-studied example is the tick-borne infection by the gram-negative spirochaetes of the genus Borrelia in humans and other mammals. It causes severe symptoms of chronic inflammation and subsequent tissue damage (Lyme Disease), particularly in large joints and the central nervous system, but also in the heart and other tissues of untreated patients. Although killed efficiently by human phagocytic cells in vitro, Borrelia exhibits a remarkably high infectivity in mice and men. In experimentally infected mice, the first immune response almost clears the infection. However, approximately 1 week post infection, the bacterial population recovers and reaches an even larger size before entering the chronic phase. We discussed a mathematical model (Binder et al., Frontiers in Microbiology, 2012) that describes the bacterial growth and the immune response against Borrelia burgdorferi in the C3H mouse strain that has been established as an experimental model for Lyme disease. The peculiar dynamics of the infection excludes two possible mechanistic explanations for the regrowth of the almost cleared bacteria. Neither the hypothesis of bacterial dissemination to different tissues nor a limitation of phagocytic capacity were compatible with experiment. The mathematical model predicts that Borrelia recovers from the strong initial immune response by the regrowth of an immune-resistant sub-population of the bacteria. The chronic phase appears as an equilibration of bacterial growth and adaptive immunity. This result has major implications for the development of the chronic phase of Borrelia infections as well as on potential protective clinical interventions.

Date: February 19, 2016
Time: 11:30 am to 12:30 pm
Location: CB 126

Research on Key Technologues to Quantify, Simulate, and Standardize Acupuncture Manipulations

Yine He
Faculty
Shanghai University of Traditional Chinese Medicine
Shanghai, China

Abstract: In this talk, I will introduce the basic concepts of acupuncture and how it can be applied to heal some diseases in China. I will talk about our project and the problems we encountered during clinical activities and research work. The project was based on previous studies on acupuncture techniques and we wanted to improve the hardware devices for parameter acquisition. We improved the software by quantifying parameters, taking videos, and collecting commentary of expert acupuncturists. Afterwards, we established an integrated database of acupuncture specialists and their manipulations. To this database, we applied data mining technologies to analyze the data, extracted common characteristics, and established a mathematical model which describes the features of good acupuncture manipulations. Finally, we applied simulation technologies to have established an experimental research platform based on the mathematical model. The platform can be used to collect and analyze data, and to simulate excellent acupuncture manipulations.

Date: February 5, 2016
Time: 11:30 am to 12:30 pm
Location: CB 126

Modelling the Post-Treatment Control of HIV Infection Using a Within-Host Model with Latent Reservoir and Immune Impairment

Shaoli Wang
Lecturer
School of Mathematics and Statistics, Henan University
Henan, China

Abstract: I will give a simplified within-host model with latent reservoir and immune impairment to explain the post-treatment immune control by exploring the bistability of the model. Mathematically, we show if the basic infection reproductive number, R_{0}, is less than one, the uninfected equilibrium of the proposed model is globally asymptotically stable, which means that the virus will die out. If R_{0} is greater than one, we can obtain two additional thresholds: the post-treatment immune control threshold and the elite control threshold. If the proliferation rate of CTLs is less than the post-treatment immune control threshold, the positive equilibria does not exist, the immune free equilibrium is stable, and the system will have virus rebound. If the proliferation rate of CTLs is within the bistable interval (between the two additional thresholds) and the initial virus population is low, then the system will be under post-treatment immune control. While the proliferation rate of CTLs is greater than the elite control threshold, the positive immune equilibrium is stable, the immune free equilibrium is unstable, and the system will be under elite control.

Date: January 29, 2016
Time: 11:30 am to 12:30 pm
Location: CB 126

Existence and Uniqueness of Solutions for Abstract Neutral Equations with State Dependent Delay

Eduardo Hernández
Professor
São Paulo University
São Paulo, Brazil

Abstract: In this seminar we present some results on the existence and uniqueness of strict solutions for a class of abstract neutral equations with state dependent delay with applications to partial neutral functional differential equations.

Date: January 22, 2016
Time: 11:30 am to 12:30 pm
Location: CB 126

Local Bifurcation Theory for Some Nonreversible Wave Equations

Nemanja Kosovalic
Assistant Professor
University of South Alabama
Alabama, United States

Abstract: Over the last fifty years a huge effort has been devoted to the study of the local bifurcation of periodic and quasi-periodic
solutions for reversible wave equations. Despite this effort, there are gaps in what is currently known about the nonreversible counterpart. Nonreversible wave equations generally include wave equations having either time delay or damping terms. We discuss some results in this direction and some open problems. This work presented is collaborative work with Dr. Brian Pigott and Dr. Chris Lin.

Date: December 21, 2015
Time: 11:30 am to 12:30 pm
Location: CB 126

The Evolutionary Ecology of Antimicrobial Descalation

Josie Hughes
Post-doctoral Fellow
Mount Sinai Hospital

Xi Huo
Post-doctoral Fellow
York University and Ryerson University

Abstract: We model the transmission of P. aeruginosa in intensive care units (ICUs) with deescalation as the major antibiotic treatment strategy. That is, empirical therapy is initiated when a patient is infected with P. aeruginosa, right after the laboratory test results become available, the definitive therapy will be de-escalated - the broad-spectrum antibiotic for empirical therapy is switched to a narrow-spectrum antibiotic if possible. De-escalation is a treatment strategy that have been applied widely in ICUs, with the aim of reducing the risk of super-infection and preserve the efficacy of broad spectrum drugs. It has been considered as a potential way of reducing antibiotic use and antimicrobial resistance in ICUs. This is a project of the Development of an Antimicrobial Resistance Diversity Index (ARDI) led by Prof. Jianhong Wu.

Date: December 11, 2015
Time: 11:30 am to 12:30 pm
Location: CB 126

Flocking, Flocking Bifurcation and Flocking Switches in a Two-Agent Flock with Processing Delay

Xiao Wang
Professor
College of Science, National University for Defense Technology
Changsha, China

Abstract: Necessary and sufficient conditions are established for a two-agent flock model with processing delay to admit a time-asymptotic flocking. The results provide a relation based on which proper initial positions and velocities can be selected to form a flocking with predetermined position displacement distance. It is shown that the processing delay can terminate a flocking, can induce a flocking and can lead to a flocking bifurcation resulting a periodic flocking. It is also shown that the processing delay can induce flocking switches in the sense that as the processing delay varies, the flocking may follow a switching pattern as no flocking-flocking-periodic flocking-flocking-divergence.

Date: November 27, 2015
Time: 11:30 am to 12:30 pm
Location: CB 126

Multiple-Platform Data Integration Method with Applications to Combined Analysis of Microarray and Proteomic Data

Yawen Xu
Postdoctoral Fellow
Department of Mathematics and Statistics, York University
Toronto, Canada

Abstract: It’s desirable in genomic studies to select biomarkers that differentiate between normal and diseased populations based on related data sets from different platforms. Most recently developed integration methods focus on correlation analyses between gene and protein expression profiles. These methods select biomarkers with concordant behavior but do not directly select differentially expressed biomarkers. Other methods combine statistical evidence in terms of ranks and p-values, but they don't account for the dependency relationships among the data across platforms. We propose an integration method to perform hypothesis testing and biomarkers selection based on multi-platform data sets observed from normal and diseased populations.

Date: November 13, 2015
Time: 11:30 am to 12:30 pm
Location: CB 126

Stability or Instability of Switched Systems with Time-Delay Using Fast and Random Switches

Yao Guo
Postdoctoral Fellow
Department of Mathematics and Statistics
Toronto, Canada

Abstract: This talk first presents examples that systems even with time delays switching among stable subsystems can be destabilized by fast switches. To illustrate this phenomenon, we introduce a prototype model which includes a linear random switched system with time-delay, and theoretically establish conditions under which the switched system can still be either unstable or stable by using certain sets of switches. Standard tools of stochastic theory are utilized in theoretical arguments, including Doob’s Optimal Stopping Theorem. In addition, we explain intuitively how this phenomenon happens and provide numerical simulations to reinforce our theoretical results.

Date: October 9, 2015
Time: 11:30 am to 12:30 pm
Location: Ross N638

Bistability in Ideological Conflict

Shaoli Wang
Henan University
Henan, China

Abstract: In this talk, we analyze the dynamics of the ideological model provided by Marvel et al. [1]. We show that bistability appears when the constant fraction of zealots, p, is less than a critical value p=pc. In this case, when a subpopulation crosses certain boundaries, its stable equilibrium switches accordingly. We also prove that in the case of p=pc, a saddle-node bifurcation replaces the bistability, and leaves a unique stable equilibrium, which means the entire population reaches a consensus. Simulations show that a system with two zealots, p1 and p2, is bistable with strictly positive equilibrium.

Date: September 30, 2015
Time: 2:30 pm to 3:30 pm
Location: TEL 5021A

DISTINGUISHED LECTURE: Transmission Dynamics and Final Epidemic Size of Ebola Virus Disease Outbreaks with Varying
Interventions

Gergely Röst
Professor
University of Szeged
Szeged, Hungary

Abstract: The 2014 Ebola Virus Disease (EVD) outbreak in West Africa was the largest and longest ever reported since the first identification of this disease. We propose a compartmental mode for EVD dynamics, including virus transmission in the community, at hospitals, and at funerals. Using time-dependent parameters, we incorporate the increasing intensity of intervention efforts. Fitting the system to the early phase of the 2014 West Africa Ebola outbreak, we estimate the basic reproduction number as 1.44. We derive a final size relation which allows us to forecast the total number of cases during the outbreak when effective interventions are in place. Our model predictions show that, as long as cases are reported in any country, intervention strategies cannot be dismissed. Since the main driver in the current slowdown of the epidemic is not the depletion of susceptibles, future waves of infection might be possible, if control measures or population behavior are relaxed. By comparing model output to real data, we show that the model can provide very accurate predictions even when intervention parameters are time-varying.

Date: September 30, 2015
Time: 3:30 pm to 4:00 pm
Location: TEL 5021A

DISTINGUISHED LECTURE: Traveling Waves in Isothermal Diffusion Systems: Existence, Stability and Oscillations

Yuanwei Qi
University of Central Florida
Florida, USA

Abstract: In this talk I shall present some of the most recent results my and collaborators and I have proved in the last a few years. In particular, we show a promising model proposed by a leading world authority in chemical engineering, Prof. Gary of U. Cambridge, FRS, has very rich structures and the analytic study proves to be far more challenge than the old model.

Date: September 30, 2015
Time: 4:00 pm to 4:30 pm
Location: TEL 5021A

Some Points on Traveling Wave Front of Reaction-Diffusion Systems with Delay: The Threshold Dynamics

Ruili Feng
PhD candidate, University of Science and Technology of China

Abstract:

Date: September 18, 2015
Time: 11:30 am to 12:00 pm
Location: Ross N638

Building an Assessment Model for a Movie Quality Rating

Yong Yang

Abstract: SINA weibo (新浪微博)and Film and state administration of press, publication, radio, film and Television of The people's republic of china(国家广电总局) propose a project on movie quality rating assessment. SINA Weibo is one of the most popular Chinese microblogging website in china. SINA team wants to build a model for the movie quality rating .Based on this project, I will introduce a dataset and propose a method. Any suggestions or methods are welcome.

Date: September 18, 2015
Time: 12:00 pm to 12:30 pm
Location: Ross N638

Consensus and Clustering of Linear Leader-Following System with Delay

Yicheng Liu
Associate Professor
College of Science, National University of Defense Technology
Changsha, China

Abstract: Two or more groups with different initial opinion values would develop into a common consensus if there are special communications and interactions between groups. What adjacent structures within groups make them reaching a consensus is an important issue. In this talk, we present an opinion consensus and clustering problem between two groups, say leader group and following group. The evolution of opinions is described as a normalized continuous dynamical system involving a distributed delay. With hypothesis that the normal Laplacian matrix has a semisimple zero eigenvalue, we find that the coupled system reaches an unconditional consensus if and only if the multiplicity of zero is 1, and reaches a conditional consensus if the coupled structure is multipartite. Also, we will mention the relationship between consensus value of coupled group and consensus values of each group. An analytic consensus value formula is deduced by using the eigenvector analysis method. In results, we find the consensus value falls into the interval of leader’s and following’s consensus values. Meanwhile, the influence strength between groups has sensitively affected consensus value of the coupled system.

Date: September 11, 2015
Time: 11:30 am to 12:30 pm
Location: Ross N638

DISTINGUISHED LECTURE: Mad Cow Disease: How Collaboration Between Biologists and Mathematicians Lead to a New Discovery About Prion Formation

Laurent Pujo-Manjouet
Associate Professor
Université Clude Bernard
Lyon, France

Abstract: In a previous work by Alvarez-Martinez et al. (2011), the authors pointed out some fallacies in the mainstream interpretation of the prion amyloid formation. It appeared necessary to propose an original hypothesis able to reconcile the in vitro data with the predictions of a mathematical model describing the problem. During this talk, I will introduce a model developed accordingly with the hypothesis that an intermediate on-pathway leads to the conformation of the prion protein into an amyloid competent isoform thanks to a structure, called micelles, formed from hydrodynamic interaction. I will also compare data to the prediction of our model and propose a new hypothesis for the formation of infectious prion amyloids.

Date: September 1st, 2015
Time: 2:30 pm to 3:30 pm
Location: Ross N940

DISTINGUISHED LECTURE: The Information System Approach Towards Big Data Processing and Analysis

Weidong Bao
Professor
College of Information System and Management, National University of Defense Technology
Changsha, China

Jiuyang Tang
Professor
College of Information System and Management, National University of Defense Technology
Changsha, China

Yaohong Zhang
Associate Professor
College of Information System and Management, National University of Defense Technology
Changsha, China

Zhimeng Li
Associate Professor
College of Information System and Management, National University of Defense Technology
Changsha, China

Abstract: A group of four scientists from the College of Information System and Management (CISM) at the National University of Defense Technology (NUDT) will introduce their recent research findings and the training and research capacity at NUDT, to furtheren exploration of collaborative opportunities between LIAM and CISM. They share common research interest in the discipline of Management Science and Engineering (MSE), and their research expertise in the fields of information system approach towards big data and cloud computing includes supporting information technologies; data analytics and design technologies; methodologies for information system management; and information systems analytics and design for special applications. The group will discuss their perspective on potential collaboration with LIAM and York’s ADERSIM group in crisis management using big data and cloud computing based simulation.

Date: August 21, 2015
Time: 10:30 am to 11:30 pm
Location: Ross N638