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 Events
Tommi Muller
UBC
Wed 21 Feb 2018, 3:15pm
Mathematical Biology Seminar
ESB 4127
Embarrassingly Parallel, Infinite Chains: Reducing computational complexity to analyze T immune cell membrane receptor kinetics and generalizing the Hidden Markov Model
ESB 4127
Wed 21 Feb 2018, 3:15pm-4:15pm

Abstract

The dynamics of the T immune cell membrane and the motion of its surface-bound receptors can be analyzed using a sophisticated microscopy technique called Total Internal Reflection Fluorescence Microscopy (TIRF), where receptors can be tagged with light-emitting particles that are illuminated by a laser. Methods in probability and numerical analysis, such as the Finite-State Hidden Markov Model and the Metropolis-Hastings algorithm, were applied to the trajectories of the receptors from the microscopy images using single-particle tracking to estimate parameters such the diffusivity and Markov state transition probabilities of the receptors. This, however, is very computationally expensive, taking days on a supercomputer for the data analysis to complete. There is also another issue involving the Finite-State Hidden Markov Model: Before applying the model, the user must first choose and fix the number of states to model in the system. This is a significant limitation as it disables the model from adjusting to new data and it increases the possibility of over/under-fitting data and cherry-picking data. In this presentation, we will explore TIRF, the Metropolis-Hastings Algorithm, and an approach to reduce computation time: an Embarrassingly Parallel Monte Carlo Markov Chain (MCMC) heuristic. We will also discuss the potential of using the newly developed Infinite Hidden Markov Model, which aims to overcome the limitation of fixing a finite number of states by allowing an arbitrary number of states to dynamically model data, chosen from an infinite-sized state space.
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University of Bristol
Mon 26 Feb 2018, 3:00pm
Discrete Math Seminar
MATX 1101
Incidences in arbitrary fields
MATX 1101
Mon 26 Feb 2018, 3:00pm-4:00pm

Abstract

The Szemerédi-Trotter theorem gives a sharp upper bound on the maximum number of incidences between any finite sets of points and lines living in the real plane; this has also been extended to the complex plane. We can also ask for such an incidence bound over arbitrary fields. I will talk about two results in this direction in work joint with Frank de Zeeuw. The study of incidence bounds over the reals has found many applications in additive combinatorics; in arbitrary fields this utility remains true, and I shall present some of these applications. 

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School of Interactive Computing College of Computing GeorgiaTech
Mon 26 Feb 2018, 3:00pm SPECIAL
Institute of Applied Mathematics
ESB 2012
Optimizing physical contacts for locomotion and manipulation: turning the challenges of contacts into solutions.
ESB 2012
Mon 26 Feb 2018, 3:00pm-4:00pm

Abstract

 

Note for Attendees

Reception before the talk in ESB 4133 (the PIMS lounge). This talk is in the IAM/PIMS distinguished speaker series. 
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SFU
Mon 26 Feb 2018, 4:00pm SPECIAL
Algebraic Geometry Seminar
MATX 1118
Fujita's Freeness Conjecture for Complexity-One T-Varieties
MATX 1118
Mon 26 Feb 2018, 4:00pm-5:00pm

Abstract

 Fujita famously conjectured that for a $d$-dimensional smooth
projective variety $X$ with ample divisor $H$, $mH+K_X$ is basepoint
free whenever $m\geq d+1$. I will discuss recent joint work with Klaus
Altmann in which we show this conjecture is true whenever $X$ admits
an effective action by a torus of dimension $d-1$.
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