CS/Math Seminar
Speakers
The CS/Math Seminar for Spring 2008 will be held during the free period (from about 12:10pm to about 1:10pm) on Wednesdays in Room BSB 336 unless otherwise announced. Please send email to Dr. Rajiv Gandhi (rajivg at camden dot rutgers dot edu) to be included in the seminar announcements mailing list. He will be coordinating the seminars during this academic year.
The tentative schedule for the talks is listed below. Titles/abstracts of talks will be posted as they become available.
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Raja Jothi (Jan 31, 2008): Science Lecture Hall at 12:30pm-1:20pm
Regulatory proteins within a hierarchical framework have distinct dynamic properties
This talk will be co-hosted with the Computational and Integrative Biology Seminar; please note the location/time of the talk.
Abstract: Topological properties of social and biological networks have revealed general principles of complex systems. Though recent studies on transcription networks have shown that regulatory proteins could be grouped into layers within a hierarchical framework, the dynamic properties of proteins within and across the layers have not been investigated. Here, we present a novel graph-theoretical algorithm, based on topological sort, to elucidate hierarchical structures in directed networks. We use it to identify three mutually exclusive layers of regulatory proteins - initiators, propagators and effectors - in the yeast transcriptional regulatory program. Overlaying diverse genome-scale datasets on the hierarchical structure reveals the presence of unique dynamic properties characterizing regulatory proteins within each layer.
In particular, we show that initiators are present in higher abundance and have a much longer protein half-life but have comparable transcript degradation rates with propagators and effectors. This suggests that post-transcriptional regulation of propagators and effectors is more important than transcriptional regulation. In addition, we find that initiators are significantly noisier than propagators and effectors. This would mean that noisy expression of initiators allows at least few members in a population to readily respond to changes in the environment. At the same time, low noise in effectors and propagators would ensure fidelity in signaling and regulation of relevant target genes. Taken together our findings suggest that regulatory proteins within the hierarchical structure have dynamic properties that are coherent within a layer and distinct across layers, thus making the network more robust and adaptable in a population. Our findings have direct implications in synthetic biology experiments aimed at engineering regulatory networks to control distinct phenotypic outcomes.
Dr. Jothi is affiliated with the National Heart Lung and Blood Institute (NHLBI), National Institutes of Health (NIH) -
Bradford Greening
Wed, Feb. 13, 2008Proofs that Really Count: The Art of Combinatorial Proof
Abstract: We will present elegant proofs of several identities on numbers that arise frequently in Mathematics such as Binomial Coefficients and Fibonacci Numbers. The proofs use elementary counting techniques as opposed to more traditional methods of proof.
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Howard Jacobowitz, Dept. of Mathematics
Thursday, Feb 28, 2008Meromorphic function and holomorphic line bundles
Abstract: I would like to outline the proof of a classic theorem of C.L.Siegel which asserts that for a compact complex manifold the transcendence degree of the field of meromorphic functions is less than or equal to the dimension of the manifold. The proof relies on an upper estimate for the number of sections of a holomorphic line bundle.
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Jean-Camille Birget
Thursday, March 12, 2008Bijective circuits and R. Thompson groups
Abstract: We define bijective circuits, and motivate them; in particular, any circuit can be simulated in some sense by a bijective circuit. We look at connections between bijective circuits and subgroups of the Thompson group V. We give some coNP-completeness and #P-completeness results for problems about the Thompson group.
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Suneeta Ramaswami
Thu. March 27Guard Placement for Wireless Localization
Abstract: I will discuss the wireless localization problem: Place a set of fixed localizers (guards) in the plane so as to enable mobile communication devices to prove that they are inside a secure region, defined as the interior of a simple polygon P. The guards are equipped with directional transmitters that can broadcast a key within a fixed angular range. A point determines if it is inside P from a monotone boolean formula on the keys, using AND and OR operations only. The goal is to minimize the number of guards. I will discuss a paper that establishes an upper bound of (n-2) for the number of guards required to localize a simple n-sided polygon (Eppstein, Goodrich, and Satchinava, ACM Symp. on Computational Geometry '07). A straightforward lower bound of (n/2) was also shown in that paper. Time permitting, I will discuss an improved lower bound.
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Kerri Hansen
Wed. April 2nd.Exploring Public Key Cryptography
Abstract: I will cover the following topics, in order: Diffie-Hellman Key Exchange,(The Diffie Hellman Problem and the Discrete Logarithm Problem: How the two are essentially equivalent), The Discrete Logarithm, ElGamal Cryptosystem, and Elliptic Curves. I am providing a worked example for the Diffie-Hellman Key Exchange and for the ElGamal Cryptosystem. Because there is not enough time, I am simply introducing implementing ElGamal on Elliptic Curves. If there is time, I will also introduce the Digital Signature Algorithm and the Elliptic Curve Digital Signature Algorithm.
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Daniel Cranston - DIMACS, Rutgers University and Bell Labs
Wed. April 9thDischarging And Reducibility: An Introduction By Example
Abstract: Many coloring results and structural results on graphs are proved using a pair of techniques called reducibility and discharging. The most well-known such result is the 4-Color Theorem. More generally, to prove a hypothetical Theorem A for planar graphs, our proof has two phases: a discharging phase and a reducibility phase. In the discharging phase, we prove that every planar graph must contain at least one subgraph from a specified list. The name discharging comes from the fact that we assign a charge (an integer) to each vertex so the sum of the charges is negative; we move the charge around (discharge it) so that only vertices appearing in one of the specified subgraphs have negative charge. In the reducibility phase, we prove that any minimal counterexample to Theorem A cannot contain any subgraph in the specified list. This implies that there is no counterexample to Theorem A, and hence, the theorem is true.
In this talk, we illustrate the techniques of discharging and reducibility by proving the following theorem: The vertices of a planar graph of girth at least 14 can be partitioned into two subsets I and F such that G[F] is a forest and I is a 2-independent set, that is: any two vertices in I are distance more than 2 apart in G. This structural theorem has applications to star coloring; a star coloring is a proper coloring such that the union of any two color classes induces a forest of disjoint stars.
This is joint work with Craig Timmons and Andre Kundgen, both of California State, San Marcos. -
Deepak Kumar
Professor of Computer Science, Bryn Mawr College
Wed. April 16The Context of Computing Education
Abstract: Computing has brought about significant changes in the way we look at the world in all disciplines and walks of life. Perhaps the most dramatic change witnessed in the past decade has been the context of computing: there has been an enormous increase in the access to computers among postsecondary students. Consequently the pressure to improve and innovate computing education has never been greater. In this presentation I will motivate the need for innovation from the perspective of the current context of computing education. I will also highlight some promising approaches being developed that impact the way we teach, design curricula, and to attract a wider, more diverse student body into computing.