Colloquium Abstracts
Fall 2009- Summer 2010
Friday, November 6, 2009
Alain Arneodo
Laboratoire Joliot Curie et Laboratoire de Physique, Ecole Normale Supérieure de Lyon 46 Allée d'Italie, 69364 Lyon Cedex 07, France
What is the Role of "JUNK DNA"
Lecture at 2:10 pm, 101 Neville Hall
What is the role of 95% of the human genome that does not code for proteins? Recent technical progress in live cell imaging have confirmed that the structure and dynamics of chromatin play an essential role in regulating many biological processes, such as gene activity, DNA replication, recombination and DNA damage repair. In the first part of this talk, we use the space-scale decomposition provided by the continuous wavelet transform (WT) to characterize the scale invariance properties of genomic sequences. We show the existence of long-range correlations (LRC) over distances up to 20 -30 kbp. To understand to which extent the observed LRCs could influence the compaction and accessibility of genomic information in the cells, we perform a fractal analysis of DNA structural profiles, e.g., DNA bending profiles based on nucleosome positioning data. In the second part of this talk, we investigate the thermodynamical properties of 2D elastic chains submitted locally to mechanical/topological constraint as loops. We show that a possible key to understanding this is that the LRC structural disorder induced by the sequence may favor the autonomous formation of small (few hundreds bp) DNA loops and, in turn, the propensity of eukaryotic DNA to interact with histones to form nucleosomes. We further compare the model predictions to genome-scale nucleosome positioning data recently obtained by Yuan et al. for S. cerevisiae chromosome III (Science 309, 2005). The statistical analysis of the experimental profile of nucleosome occupancy displays striking similarities to the energy landscape of nucleosome formation computed from the sequence.including the nucleosome-free regions observed at gene promoters These results constitute a first experimental evidence of the influence of LRCs on the nucleosomal organisation. The third part of this talk is devoted to the recent experimental observation of LRC in the 2D equilibrium conformations of eukaryotic DNA by AFM visualization techniques.
Thursday, November 5, 2009 - Mathematics "Career Day" Lecture
Leigh Snowden, National Security Agency
Mathematics at the National Security Agency
Lecture at 3:10 pm
In her talk she will mention how she came to work as NSA, the different kinds of work mathematicians do there, including a brief description of public key cryptography, and the different summer programs and entry-level programs for mathematicians.
Tuesday, October 20, 2009 - Mathematics "Career Day" Lecture
Marylou Murphy, FSA MAAA, Vice-President & Actuary, Unum Group
Paul Correia, ASA, Associate Actuary, Unum Group
Actuarial Opportunities
Lecture at 2:10 pm, 100 Neville Hall
Marylou Murphy and Paul Correia from Unum will discuss career opportunities in the actuarial profession. Marylou will describe the role actuaries play and the skill sets needed to excel. In addition, she will discuss opportunities at Unum, a leading provider of employee benefits and the market leader in providing disability and long term care insurance in the U.S.
Paul Correia will then describe his experiences to date in the career path and how his educational background has helped him succeed.
Thursday, Oct. 08, 2009
3:10pm, 108 Neville Hall
Tasneem Zaihra, University of New Brunswick
Variance function in semi-parametric analysis of count data
(Refreshments at 2:30pm, 108 Neville Hall)
The purpose of this paper is to determine an appropriate variance function (mean- variance relationship) which can be used in the semi-parametric analysis of over- dispersed count data (for example, for the analysis of count data by extended quasi- likelihood and double extended quasi-likelihood). We use hypothesis testing approach through a broader class of models and data analytic approach. The models considered are the three parameter negative binomial distribution and the extended quasi-likelihood. Wide analysis involving tests, data analysis and simulations indicate that the three parameter generalized negative binomial distribution does not improve in fit to count data over the simpler negative binomial distribution. Further data analysis and simulations using the extended quasi-likelihood indicate that the negative binomial variance function µ + cµ2 is preferable over a simpler variance function c3 µ2 for data with small mean and small over-dispersion. Otherwise c3 µ2 is a preferable variance function over the negative binomial variance function.
