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Colloquia

Professor Alan Rendall 9/29/2015

Sustained oscillations in phosphorylation cascades

Date: 9/29/2015
Time: 3:30PM-4:30PM
Place: 315 Armstrong Hall

Alan Rendall

Abstract:Signalling networks are sets of chemical reactions used to transmit information
in living cells. One pattern frequently encountered in this context is that of a
phosphorylation cascade, where phosphate groups are added to proteins in
successive stages. In this talk I report on work with Juliette Hell on the existence
of periodic solutions in systems of ODE modelling a key example of
a cascade of this type, the MAP kinase cascade. The mathematical tools used
for this are bifurcation theory and geometric singular perturbation theory.
I will also describe the relation of these results to the idea that oscillations
are often related to negative feedback loops, where the feedback may arise
in an implicit way due to sequestration effects.

Date, Location: 
2015-09-29

Professor Martha Alibali 9/28/2015

Defining and Measuring Conceptual Knowledge of Mathematics

Date: 9/28/2015
Time: 3:30PM-4:30PM
Place: 121 Armstrong Hall

Martha Alibali

Abstract:Both researchers and educators recognize the importance of conceptual knowledge in mathematics. However, it has proven difficult to identify and measure conceptual knowledge in many mathematical domains. This talk provides an overview of research on conceptual knowledge in the literature on mathematical thinking. I discuss (1) how conceptual knowledge is defined in the mathematical thinking literature, broadly speaking, and (2) how conceptual knowledge is defined, operationalized, and measured in three specific mathematical domains: equivalence, cardinality, and inversion. This review uncovers several shortcomings in this body of literature, most notably a lack of consistency in definitions of conceptual knowledge and a lack of alignment between definitions and measures. To address these issues, I propose a general framework that divides conceptual knowledge into two facets: knowledge of general principles and knowledge of the principles underlying procedures.

Date, Location: 
2015-09-28

Professor Bing Wei 9/25/2015

Hamiltonian properties, branch number and k-tree related graphs

Date: 9/25/2015
Time: 3:30PM-4:30PM
Place: 315 Armstrong Hall

Bing Wei

Abstract: Download Here

Date, Location: 
2015-09-25

Professor Suohai Fan 8/13/2015

On $r$-hued colorings
of graphs

Date: 8/13/2015
Time: 2:30PM-3:20PM
Place: 315 Armstrong Hall

Suohai Fan

Abstract:For integers $k, r > 0$, a $(k, r )$-coloring of a graph $G$
is a proper $k$-coloring $c$ such that for any vertex $v$ with degree
$d(v)$, $v$ is adjacent to at least
min$\{d(v),r\}$ different colors. Such coloring is also called as an $r$-hued
coloring. The {\it $r$-hued chromatic number} of $G$, $\chi_{r}(G)$, is the least integer
$k$ such that a $(k, r )$-coloring of $G$ exists. In this talk, we will present some
of the progresses in this area.

Date, Location: 
2015-08-13

Michael Wester 4/29/2015

Determining the Parameters in Spatially Resolved Models of the
Motion of Proteins in the Membranes of Stimulated Cells

Date: 4/29/2015
Time: 3:30PM-4:30PM
Place: 315 Armstrong Hall

Michael Wester

Abstract: We show how to compute a dimerization rate from stimulated cell diffusion
data which can be used in a spatially resolved stochastic simulator to
accurately reproduce the data. For our data and for strong stimuli,
the time dependent diffusion coefficient rapidly transitions from the
diffusion constant for unstimulated cells to a significantly smaller
value. The diffusion data is generated using sparse labeling with
quantum dots which allows us to analyze using a non-spatial system
of two linear differential equations. We then use a closely related
system of two non-spatial nonlinear differential equations to compute a
spatially resolved reaction rate to use in our simulation code. Using
these reaction rates we successfully reproduce the biological data.
The framework developed here can be extended to analyze other time
dependent diffusion data.

Date, Location: 
2015-04-29

John Thompson 4/15/2015

Investigating student understanding and application of mathematics needed in physics: Definite integrals and the Fundamental Theorem of Calculus

Date: 4/15/2015
Time: 4:30PM-5:30PM
Place: 422 Armstrong Hall

John Thompson

Abstract: Learning physics concepts often requires the ability to interpret and manipulate the underlying mathematical representations and formalism (e.g., equations, graphs, and diagrams). Physics students are expected to be able to apply mathematics concepts to find connections between various physical quantities that are related via derivatives and/or integrals. Our own research into student conceptual understanding of physics has led us to investigate how students think about and use prerequisite, relevant mathematics, especially calculus, to solve physics problems. This is a rapidly growing research area in physics education.
Based on responses to questions administered in thermodynamics, we developed or adapted questions related to definite integrals and the Fundamental Theorem of Calculus (FTC), specifically with graphical representations, that are relevant in physics contexts, including some integrals that result in a negative quantity. Questions were administered in written form and in individual interviews; some questions had parallel versions in both mathematics and physics. Eye-tracking experiments provided additional information on visual attention during problem solving. Our findings are consistent with much of the literature in undergraduate mathematics education; we also have identified new difficulties and reasoning in students’ responses to the given problems.

Date, Location: 
2015-04-15

Gexin Yu 4/13/2015

On path cover of
regular graphs

Date: 4/13/2015
Time: 3:30PM-4:30PM
Place: 315 Armstrong Hall

Gexin Yu

Abstract: A path cover of a graph is a set of disjoint paths so that every vertex in the graph is contained in one of the paths. The path cover number p(G) of graph G is the cardinality of a path cover with minimum number of paths. Reed conjectured that a 2-connected 3-regular graph has path cover number at most $\lceil n/10\rceil$. In this paper, we confirm this conjecture.

Date, Location: 
2015-04-13

Xiangwen Li 4/13/2015

Forbidden graphs and
group connectivity

Date: 4/13/2015
Time: 4:30PM-5:30PM
Place: 315 Armstrong Hall

Xiangwen Li

Abstract: Here

Date, Location: 
2015-04-13

Arthur T. Benjamin 4/9/2015

Combinatorial Trigonometry (and a method to DIE for)

Date: 4/9/2015
Time: 2:30PM-3:30PM
Place: 315 Armstrong Hall

Arthur T. Benjamin

Abstract: Many trigonometric identities, including the Pythagorean theorem, have combinatorial proofs. Furthermore, some combinatorial problems have trigonometric solutions. All of these problems can be reduced to alternating sums, and are attacked by a technique we call D.I.E.
(Description, Involution, Exception). This technique offers new insights to identities involving binomial coefficients, Fibonacci numbers, derangements, and Chebyshev polynomials.

Date, Location: 
2015-04-09

Guantao Chen 3/6/2015

Lovasz-Plummer Conjecture on Spanning Halin Subgraphs

Date: 3/6/2015
Time: 3:30PM-4:30PM
Place: 315 Armstrong Hall

Guantao Chen

Abstract: Here

Date, Location: 
2015-03-06

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