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Events

• Oct

  15

  Appl Math: Trevor GrandPre on "Model-free Inference from Time-series Data"

  McCormick-Engineering Sciences and Applied Mathematics (ESAM)

  11:15 AM M416, Technological Institute

  EVENT DETAILS

  Title: Model-free Inference from Time-series Data

  Speaker: Trevor GrandPre, Princeton University

  Abstract: Drawing inferences from experimental data often involves imposing models, which can lead to inaccurate conclusions. Theory sometimes points to quantities that are significant independent of the underlying mechanisms, but making accurate model-free estimates of these quantities can be hard because finite data generates systematic errors. I present two cases where we develop new methods to address and correct these errors: (1) extracting long-term population growth from single-cell lineage data and (2) estimating the evidence for the arrow of time in patterns of neural activity. For population growth, key observables are the number of divisions and generation times along a lineage for a fixed time. Simple growth rate estimators suffer from finite-time bias at short times. This bias scales inversely with time and can be corrected. At longer times, rare events introduce a linearization bias, causing an abrupt phase transition explained by a simple model of disordered systems. Our approach yields accurate estimates provided the lineage counts and lengths stay below the critical point, allowing inference of how mutations and physiological variations impact fitness. In the case of neural activity, the relevant observables are the moments of activity and the waiting times between these moments. Estimating the irreversibility—quantified by the Kullback-Leibler divergence between the distribution of forward and backward trajectories—faces similar biases. Finding the systematic dependence of these biases on sample size allows for accurate estimates, including detecting systems that obey detailed balance, and opens a path to exploring how the brain represents the arrow of time. Generally, this new understanding of how model-free estimators rely on a complex order of limits of the amount of data and the length of each sample may allow quantitative understanding of other relevant processes such as gene regulation, cell-cycle dynamics, and signal transduction.

  Zoom: https://northwestern.zoom.us/j/92938364014

  Special Note: This colloquium is co-sponsored by the Chemical and Biological Engineering department in McCormick

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  TIME Tuesday, October 15, 2024 at 11:15 AM - 12:15 PM

  LOCATION M416, Technological Institute    map it

  ADD TO CALENDAR

  CONTACT Ted Shaeffer    ted.shaeffer@northwestern.edu EMAIL

  CALENDAR McCormick-Engineering Sciences and Applied Mathematics (ESAM)

• Mar

  11

  Appl Math: Vaseem Shaik on "Active Particles in Inhomogeneous Environments"

  McCormick-Engineering Sciences and Applied Mathematics (ESAM)

  11:15 AM M416, Technological Institute

  EVENT DETAILS

  Title: Active Particles in Inhomogeneous Environments

  Speaker: Vaseem Shaik, Northwestern University

  Abstract: Active particles are entities, either living (like microorganisms, birds, and humans) or non-living (like nanorobots), that convert stored energy into directed motion. A suspension of these particles is called active matter. They often navigate through inhomogeneous environments such as gradients in heat, light, nutrients, or fluid properties like viscosity and density, exhibiting directed motion known as taxis (e.g., chemotaxis, phototaxis, gravitaxis). This summary focuses on μm - mm-sized particles swimming in fluids with mechanical property gradients, like viscosity, elasticity, and density. It discusses phenomena like viscotaxis (response to viscosity gradients), behavior similar to light refraction in viscosity gradients (described by a Snell’s like law), durotaxis (response to elasticity gradients), and densitaxis (response to density gradients), with implications for plankton migration. The study also covers particle-induced mixing and the influence of noise, exploring how these inhomogeneities can control active matter in confined environments.

  Zoom: https://northwestern.zoom.us/j/96970714028

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  To subscribe to the Applied Mathematics Colloquia List send a message to LISTSERV@LISTSERV.IT.NORTHWESTERN.EDU with the command:

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  more less

  TIME Tuesday, March 11, 2025 at 11:15 AM - 12:15 PM

  LOCATION M416, Technological Institute    map it

  ADD TO CALENDAR

  CONTACT Ted Shaeffer    ted.shaeffer@northwestern.edu EMAIL

  CALENDAR McCormick-Engineering Sciences and Applied Mathematics (ESAM)

• Mar

  15

  Winter Classes End

  University Academic Calendar

  All Day

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  Winter Classes End

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  TIME Saturday, March 15, 2025

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  CONTACT Office of the Registrar    nu-registrar@northwestern.edu EMAIL

  CALENDAR University Academic Calendar

• Mar

  17

  Winter exams begin

  University Academic Calendar

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  Winter exams begin

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  TIME Monday, March 17, 2025

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  CONTACT Office of the Registrar    nu-registrar@northwestern.edu EMAIL

  CALENDAR University Academic Calendar

• Mar

  22

  Spring Break Begins

  University Academic Calendar

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  Spring Break Begins

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  TIME Saturday, March 22, 2025

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  CONTACT Office of the Registrar    nu-registrar@northwestern.edu EMAIL

  CALENDAR University Academic Calendar

• Mar

  31

  Spring Break Ends

  University Academic Calendar

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  Spring Break Ends

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  TIME Monday, March 31, 2025

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  CONTACT Office of the Registrar    nu-registrar@northwestern.edu EMAIL

  CALENDAR University Academic Calendar

• Apr

  1

  Spring Classes Begin - Northwestern Monday: Classes scheduled to meet on Mondays meet on this day.

  University Academic Calendar

  All Day

  EVENT DETAILS

  Spring Classes Begin - Northwestern Monday: Classes scheduled to meet on Mondays meet on this day.

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  TIME Tuesday, April 1, 2025

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  CONTACT Office of the Registrar    nu-registrar@northwestern.edu EMAIL

  CALENDAR University Academic Calendar

• Apr

  8

  Appl Math: Brennan Sprinkle on "Title TBA"

  McCormick-Engineering Sciences and Applied Mathematics (ESAM)

  11:15 AM M416, Technological Institute

  EVENT DETAILS

  Title: TBA

  Speaker: Brennan Sprinkle, Colorado School of Mines

  Abstract: TBA

  Zoom: TBA

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  To subscribe to the Applied Mathematics Colloquia List send a message to LISTSERV@LISTSERV.IT.NORTHWESTERN.EDU with the command:

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  more less

  TIME Tuesday, April 8, 2025 at 11:15 AM - 12:15 PM

  LOCATION M416, Technological Institute    map it

  ADD TO CALENDAR

  CONTACT Ted Shaeffer    ted.shaeffer@northwestern.edu EMAIL

  CALENDAR McCormick-Engineering Sciences and Applied Mathematics (ESAM)