**Seminars and Colloquiums**

for the week of February 29, 2016

for the week of February 29, 2016

*SPEAKER:*

Jim Conant, UTK, Monday

Dr. Cory Merow, Ecology and Evolutionary Biology, Univ. of Connecticut, Monday

Dr. Tian Hon, Mathematics Univ. of California, Irvine, Tuesday

Kai Kang, UTK, Tuesday

Richard Schugart, Western Kentucky University, NIMBioS, Thursday

Ryan Loga, Joshua Mike, Kevin Sonnanburg, UTK, Thursday

Elias Wegert, TU Bergakademie Freiberg, Thursday

David Krieg, Freiberg, Germany, Friday

Tea Time - Cancelled

**Monday, February 29th**

TOPOLOGY AND GEOMETRY SEMINAR

TITLE: Cochran’s Invariants and Some Four Dimensional Topology

SPEAKER: Jim Conant, UTK

TIME: 2:30pm – 3:20pm

ROOM: Ayres 113

In the 1980s Tim Cochran defined a sequence of invariants of 2 component links generalizing the classical Sato-Levine invariant. We will discuss recent joint work with Rob Schneiderman and Peter Teichner, where we show that these invariants give obstructions to a link in S3 bounding a certain king of 2-complex into the 4-ball. One goal of the talk is to help develop the audience’s intuition about four dimensional space.

EEB/NIMBIOS SPATIAL BIOLOGY SEMINAR

TITLE: Making the most of imperfect data: Inferring mechanism by linking regional forecasts to population and
community dynamics in a changing world

SPEAKER: Dr. Cory Merow, Ecology and Evolutionary Biology, Univ. of Connecticut

TIME: 4:30pm-5:30pm

ROOM: Alumni Memorial Building, Room 27

Forecasting ecological responses to dynamic, often noanalogue, environments will be key to mitigating global change. The societal demand for management strategies challenges ecologists to forecast systems lacking critical data. In this talk, I will provide an overview of my approach to making the best of imperfect data to develop mechanistic forecasts of population, community and ecosystem responses to climate change, disturbance, and nonnative species.

** Tuesday, March 1st **

BCMB/NIMBIOS SPECIAL SEMINAR

TITLE: Mathematical models for understanding phenotypic heterogeneity and pasticity of living cells.

SPEAKER: Dr. Tian Hon, Mathematics Univ. of California, Irvine

TIME: 10am – 11:15am

ROOM: TBD, ccrawley@nimbios.org

The development and function of tissues in multicellular organisms rely on specialization of cellular phenotypes. This phenotypic heterogeneity needs to be generated via cell differentiation and maintained in a highly regulated manner. In addition, the dynamic nature of many biological processes, such as tissue regeneration and immune responses, often entails phenotypic plasticity of cells, also known as transdiferentiation. The complexity of these processes requires quantitative modeling for interactions among molecular species and cellular components, relating dynamic features of the intrinsic design of the cells to the behaviors of the cells and tissues. In this talk, I will discuss role of models in understanding heterogeneity and plasticity of cells using two biological systems that I recently studied: 1) the heterogeneous differentiation of CD4+ T cells and 2) the multi-step epithelial-to-mesenchymal (EMT) transitions. Computational analysis of the models have led to several new discoveries, elucidation of intriguing and perplexing observations, and testable predictions. In particular, our modeling study delineates critical roles of interconnected feedback loops in producing multiple intermediate states during phenotypic transitions and the importance of these multistep transitions.

STOCHASTICS SEMINAR

TITLE: Introduction to Sequential Monte Carlo filters

SPEAKER: Kai Kang, UTK

TIME: 2:10pm – 3:25pm

ROOM: Ayres 114

Optimal filtering problem is a recurrent theme in signal processing and many other research fields. However, the optimal filter does not admit a closed form expression in most situations. Sequential Monte Carlo (SMC) filters are a set of simulation-based methods designed to solve the optimal filtering problem numerically. In this talk, I will present the framework of SMC filter and its asymptotic behavior. The topic is accessible to any graduate student with basic probability knowledge.

**Thursday, March 3rd **

DIFFERENTIAL EQUATIONS SEMINAR

TITLE: Differential-Equation Models in Wound Healing

SPEAKER: Richard Schugart, Western Kentucky University, NIMBioS

TIME: 2:10pm - 3:25pm

ROOM: Ayres 113

In this talk, I will present multiple wound-healing problems. The first problem uses optimal control theory to analyze the treatment of a bacterial infection in a wound with oxygen therapy. Two types of oxygen therapies (hyperbaric and topical) will be presented and preliminary results will be presented. The second problem uses patient data to formulate a mathematical model for proteolytic enzyme interactions and their effects on the healing response of a wound. Curve fitting of the model and sensitivity analyses will be presented with some interesting results when comparing different sensitivity analyses. Extensions of both problems will also be discussed.

GRADUATE STUDENT SEMINAR

TITLE: GS Seminar Spotlight on Geometry, Analysis, and PDEs

SPEAKER: Ryan Loga, Joshua Mike, Kevin Sonnanburg, UTK

TIME: 3:40pm-4:30pm

ROOM: Ayres G004

In the third installment of the GS Seminar Spotlight Series, we take a look at UTK Analysis, PDEs, and Geometry. We have yet another excellent panel who will share their experiences picking out classes; taking prelims; choosing an advisor; and much more! Plus, they will field any questions that you may have about moving into one of these areas during your time as a graduate student at UTK.

JUNIOR COLLOQUIUM

TITLE: Exploring Complex Functions Using Phase Plots

SPEAKER: Elias Wegert, TU Bergakademie Freiberg

TIME: 3:40pm - 4:35pm

ROOM: Ayres 405

Graphical visualization of functions is one of the most powerful tools in (applied) mathematics. While pictorial representations of real functions are widely used for centuries, representations of complex (analytic) functions are not so common. As a counterpart of the traditional ``analytic landscapes'', the talk promotes special color-representations, so-called “phase plots'', depicting a function f directly on its domain by color-coding the argument (or phase) of f.

Phase plots are like fingerprints: though part of the information (the modulus) is neglected, meromorphic functions can be uniquely reconstructed from their phase plots up to a positive constant factor. Moreover, several modifications allow one to incorporate additional information.

In the talk we explain how basic properties of a function can be recovered from its phase plot, show images of special functions, and present applications in teaching and research: the argument principle and its extension, universality of the Riemann zeta function, and the discovery of a stochastic periodicity in its phase plot.

**Friday, March 4th **

ANALYSIS SEMINAR

TITLE: Incompressibility, Rigidity and Uniqueness

SPEAKER: David Krieg, Freiberg, Germany

TIME: 2:30pm - 3:20pm

ROOM: Ayres 121

Abstract: We will discuss circle packings filling Jordan domains under several normalizations. To begin with, three boundary points are associated with three boundary circles, which have to be touched in a generalized sense. This leads to an incompressibility property and eventually to uniqueness. Afterwards the concept of crosscuts is introduced, which leads to a rigidity statement for circle packings with respect to maximal crosscuts. At last I investigate the behavior of circle packings, where a boundary and an interior point are associated with a boundary and an interior circle, respectively. A uniqueness result for this kind of normalization is proved by combining the rigidity and incompressibility properties found before.

*If you are interested in giving or arranging a talk for one of our seminars or colloquiums, please review our calendar. *

*If you have questions, or a date you would like to confirm, please contact colloquium AT math DOT utk DOT edu *

**Past notices:**