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Practical Inference Methods for Mechanistic Modelling of Biological Systems
Pascal

Variational Inference for Markov Jump Processes

author: Guido Sanguinetti, University of Sheffield

Description

Markov jump processes (MJPs) underpin our understanding of many important systems in science and technology. They provide a rigorous probabilistic framework to model the joint dynamics of groups (species) of interacting individuals, with applications ranging from information packets in a telecommunications network to epidemiology and population levels in the environment. These processes are usually non-linear and highly coupled, giving rise to non-trivial steady states (often referred to as emerging properties). Unfortunately, this also means that exact statistical inference is unfeasible and approximations must be made in the analysis of these systems. A traditional approach, which has been very successful throughout the past century, is to ignore the discrete nature of the processes and to approximate the stochastic process with a deterministic process whose behaviour is described by a system of non-linear, coupled ODEs. This approximation relies on the stochastic fluctuations being negligible compared to the average population counts. There are many important situations where this assumption is untenable: for example, stochastic fluctuations are reputed to be responsible for a number of important biological phenomena, from cell differentiation to pathogen virulence. Researchers are now able to obtain accurate estimates of the number of macromolecules of a certain species within a cell, prompting a need for practical statistical tools to handle discrete data.

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Slides
0:00 Variational inference for Markov jump processes
0:18 Talk plan
0:42 - Questions
2:11 Relevance to life sciences
4:09 Mathematical notation
5:28 Master equation
7:12 Variational inference
7:48 KL divergence between MJPs
8:47 Continuous limit
9:24 Posterior processes
10:25 Mean-field approximation
11:54 Constraints
12:47 Functional derivatives
13:29 Backward equation
14:15 Including observations
14:20 Functional derivatives
14:32 Backward equation
14:38 Including observations
15:26 Algorithm: Approximating the posterior (E-step)
15:48 Functional derivatives
15:54 Algorithm: Approximating the posterior (E-step)
16:46 Parameter estimation (M-step)
17:12 Application: Lotka-Volterra
18:18 Results: Lotka-Volterra
19:25 Parameter estimates
20:08 Application: Gene auto-regulation
21:06 Parameter estimation
21:28 Identifiability of critical parameter
22:09 Autoregulatory network: Results
22:56 Conclusions
24:03 Future work

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Reviews and comments:

Comment1 Sakura, March 24, 2008 at 5:42 a.m.:

Its very nice. I do more understand what MPJs is. Thank you very much.


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