Please note special time.

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Grace Yeom will be defending her thesis, titled Temperature-Dependent Photoluminescence: Properties of Carbon Nanodots Derived from Polyethylene Glycol.

Faculty Advisor:  Dr. Doo Young Kim

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Dawn Kato will be defending her dissertation, titled Applications of Gas Chromatography/Mass Spectrometry and Capillary Electrophoresis for the Analysis of Lignocellulosic Biomass.

Faculty Advisor:  Dr. Bert Lynn

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Rahul Butala will be defending his dissertation: Salen Aluminum Compounds in the Dealkylation and Detection of Organophosphates.

Faculty Advisor:  Dr. David Atwood

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Warintra Pitsawong will be defending her dissertation: Bases for Breadth--Insights into how the Mechanism and Dynamics of Nitroreductase can Explain this Enzyme's Broad Substrate Repertoire.

Faculty Advisor:  Dr. Anne-Frances Miller

Title:  Conditions for the toric homogenous Markov Chain models to have square-free quadratic Groebner basis

Abstract:  Discrete time Markov chains are often used in statistical models to fit the observed data from a random physical process. Sometimes, in order to simplify the model, it is convenient to consider time-homogeneous Markov chains, where the transition probabilities do not depend on the time.  While under the time-homogeneous Markov chain model it is assumed that the row sums of the transition probabilities are equal to one, under the the toric homogeneous Markov chain (THMC) model the parameters are free and the row sums of the transition probabilities are not restricted.

In this talk we consider a Markov basis and a Groebner basis for the toric ideal associate with the design matrix (configuration) defined by THMC model with the state space with $m$ states where $m \geq 2$ and we study when THMC with $m$ states have a square-free quadratic Groebner basis.  One such example is the embedded discrete Markov chain for the Kimura three parameter model. This is joint work with Abraham Martin del Campo and Akimichi Takemura.

Departmental Tea hosted by the Gradaute Student Council.  All are welcome to come and mingle over coffee, tea, and cookies!

Title:  An introduction to operads

Abstract:  Operads first arose in the 60's and 70's for the study of loop spaces, but there was a large resurgence of interest in the 90's once connections with Koszul duality, moduli spaces, and representation theory were realized. I will discuss the definition and familiar examples in both topology and algebra. We will see Stasheff polyhedra in the context of loop spaces as well as examples related to moduli spaces.

Title:  Derangements, discrete Morse theory, and the homology of the boolean complex

Abstract:  The boolean complex is a construction associated to finite simple graphs. We summarize a matching which shows that this complex is homotopy equivalent to a wedge of spheres, and the number of these spheres is related to the boolean number, a graph invariant. To better understand this structure, we use a correspondence between derangements and basis elements and compute the homology of the boolean complex for several specific examples. A basic knowledge of discrete Morse theory may be helpful but is not necessary.

Pizza at 4:00 p.m., talk at 4:15 p.m.

Title:  Bouquet algebra of toric ideals

Abstract: To any integer matrix A one can associate a toric ideal I_A, whose sets of generators are basic objects in discrete linear optimization, statistics, and graph/hypergraph sampling algorithms. The basic algebraic problem is that of implicitization: given the matrix A, find a set of generators with some given property (minimal, Groebner, Graver, etc.). Then there is a related problem of complexity: how complicated can these generators be? In general, it is known that Graver bases are much more complicated than minimal generators. But there are some classical families of toric ideals where these sets actually agree, providing very nice results on complexity and sharp degree bounds.

This talk is about combinatorial signatures of generating sets of I_A. For the special case when A is a 0/1 matrix, bicolored hypergraphs give the answer. It turns out that such hypergraphs give an intuition for constructing basic building blocks for the general case too. Namely, we introduce the bouquet graph and bouquet ideal of the toric ideal I_A, whose structure determines the Graver basis. This, in turn, leads to a complete characterization of toric ideas for which the following sets are equal: the Graver basis, the universal Groebner basis, any reduced Groebner basis and any minimal generating set. This generalizes many of the classical examples.