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UBC Math Dept
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Mathematical Biology and related seminars

October, 2018
Wednesday,
October 17
Hisashi Ohtsuki -- 3:00 pm in ESB 4127
Dept of Evolutionary Studies of Biosystems, The Graduate University for Advanced Studies (SOKENDAI)
Allele frequency spectrum in a cancer cell population
Abstract
A traditional population-genetics approach studies geneaologies in a population of a fixed size, which forms the basis of several spectral theories of finite samples. In contrast, a population of tumor cells typically experiences an exponential growth phase in its initial progression, which is far from constant population size. In this work, I develop two different numerical procedures, one of which is based on forward-in-time and the other is based on backward-in-time treatment, to derive allele frequency spectrum in such exponentially growing cancer cell populations. We find significance bias toward singletons both analytically and numerically, which reflects the fact that most observed mutations have recent origins in a growing population.
Comment:This work was done in collaboration with Prof. Hideki Innan
Wednesday,
October 24
Caroline Colijn -- 3:00 pm in ESB 4127
SFU
Connecting genomic data with vaccine design through modelling
Abstract
While vaccines are available and are effective in protecting against colonisation and disease with Streptococcus pneumoniae, their effectiveness is limited by strain (serotype) replacement following widespread vaccination. Understanding the post-vaccination balance of serotypes would present the opportunity to achieve a final population composed of the most benign (non-invasive) strains. However, the complex ecology of the pneumococcus makes it difficult to predict the post-vaccination balance of strains. Recently, Corander et al proposed that there is widespread apparent negative frequency-dependent selection (NFDS) in the pneumococcus (Corander et al 2017 Nat. Ecol. Evol.). Here, we use this principle to develop a deterministic model of pneumococcal strain dynamics, and use the model to make predictions about the ecological response of the pneumococcal population to new candidate vaccine strategies. We find that we can identify formulations that out-perform existing formulations in the model. Furthermore, it is possible to obtain a final model population that scores as well as the currently used formulation, using a vaccine strategy with fewer serotypes -- these formulations would be much less costly to produce than current vaccines. We suggest that this approach could provide a template for principled vaccine design based on global surveillance data and genomics. This is joint work with N. Croucher.
Comment:Dr. Colijn is a new C150 Chair holder at SFU, and is just recently arrived in BC.
Wednesday,
October 31
Gerardo Ortigoza -- 3:00 pm in ESB 4127
Universidad Veracruzana Mexico
Mathematical modeling and simulation of the Chikungunya spread in Veracruz Mexico
Abstract
Chikungunya is a viral disease transmitted to humans by infected mosquitoes: Aedes aegypti and Aedes albopictus. It causes fever and severe joint pain. Other symptoms include muscle pain, headache, nausea, fatigue and rash. Joint pain is often debilitating and can vary in duration. Some of the main mathematical methods to simulate Chikungunya spread are set as ordinary differential equations over compartmental models, SEIR for host and sei for vectors. We propose a spatio-temporal description of chikungunya spread using a cellular automata over unstructured triangular meshes.
Comment:Prof. Ortigoza is a sabbatical visitor in the Department of Mathematics, hosted by Prof Fred Bruer
November, 2018
Wednesday,
November 14
Geoff Wasteneys -- 3:00 pm in ESB 4127
Dept of Botany, UBC
Mechanisms modulating developmental transitions in plants
Abstract
Geoff plans to talk about the transition from proliferation to differentiation, which is work following up on the paper that his group recently published in Current Biology. See: https://phys.org/news/2018-08-secrets.html
Wednesday,
November 21
Simon van Vliet -- 3:00 pm in ESB 4127
UBC
Wednesday,
November 28
Sarafa Iyaniwura -- 3:00 pm in ESB 4127
Department of Mathematics, UBC
Instability triggered by a single defective cell among a group of cells in a two-dimensional domain
Abstract
We formulated and analyzed a class of coupled cell-bulk PDE-ODE model for describing communication between localized spatially segregated dynamically active signallying compartments of common small radius, which are coupled through a passive bulk diffusion in a two-dimensional domain. Each of these cells secret some chemical into the medium, and can also sense the concentration of this chemical around their boundary, which in turn leads to the activation of signaling pathways within the cells that enable them adjust their intracellular dynamics. In the limit where the bulk diffusion coefficient is asymptotically large, the method of matched asymptotic expansions is used to reduce the coupled PDE-ODE model into a system of ODEs. This system further studied to investigate the existence of instability through Hopf bifurcation that is triggered by a single defective cell among a group of identical cells. Furthermore, we studied the effect of the effective area of the domain on the synchronization of the intracellular dynamics of the cell.
December, 2018
Monday,
December 3
Alex Mogilner -- 4:00 pm in TBA
NYU (Courant Institute)
Self-polarization, rapid migration and turning of motile cells
Abstract
Cell migration is a fundamentally important phenomenon underlying wound healing, tissue development, immune response and cancer metastasis. Understanding basic physics of the cell migration presented a great challenge until, in the last three decades, a combination of biological, biophysical and mathematical approaches shed light on basic mechanisms of the cell migration. I will describe models, based on nonlinear partial differential equations and free boundary problems, which predicted that individual cells do not linger in a symmetric stationary state for too long, but rather spontaneously break symmetry and initiate motility. The cells can either crawl straight, or turn, depending on mechanical parameters. I will show how experimental data supported the models, and I will also review current computational challenges.
This seminar is part of the IAM Colloquium Series.
Comment:This lecture is part of the IAM Distinguished Alumni Series
February, 2019
Wednesday,
February 6
Joy Richman -- 3:00 pm in ESB 4127
Dept of Dentistry, UBC
Coordination of mesenchymal cell movements is required for facial morphogenesis
Abstract
TBA
March, 2019
Monday,
March 11
Paul Kulesa -- 3:00 pm in TBA
Srowers Medical Institute
TBA
This seminar is part of the IAM Colloquium Series.
Comment:Distinguished IAM Colloquium

Seminar series sponsored by PIMS.

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