Brown University Center for Statistical Sciences Seminar
Johns Hopkins University, Bloomberg School of Public Health, Biostatistics Department | |
*Lectureship Series on Statistical Genetics and Bioinformatics
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Abstract: Giovanni Parmigiani, Elizabeth Garrett, Ramaswamy Anbazhagan, and Edward Gabrielson, The Department of Pathology and the Sidney Kimmel Comprehensive Cancer Center at Johns Hopkins University School of Medicine, Baltimore, MD.
Several recent studies have sought to refine the classification of lung cancer through gene expression profiling, using various gene microarray platforms. To initiate the process of cross- validating and integrating the results of these types of studies, we developed statistical approaches that allow overall assessments of profile similarities, as well as comparisons of individual genes for association with outcomes. Our analysis focused on three projects that analyzed gene expression in a wide range of lung cancer histologic types, using cDNA and oligonucleotide array platforms. In the context of these studies we will present practical statistical approaches for integrating expression information across studies. We first compared the data from these studies for consistency of co-expression relationships among pairs of genes, to identify genes that are consistently measured across platforms. We then compared studies for associations of specific genes to outcomes, extending traditional meta-analysis tools. We finally investigated consistency of unsupervised classifications across studies.
Center for Fluid Mechanics Seminar and The Fluids, Thermal and Chemical Processes Group of The Divison of Engineering
Abstract: The design of underwater vehicles operating in the surf zone or other high-energy environments is likely to have viable biomimetic solutions. The flapping fin is capable of producing high instantaneous forces, giving fish the ability to turn and accelerate rapidly. Additionally, the lateral line, an array of nerves running the length of the body, enables fish to sense the flow characteristics in their environment, aiding obstacle entrainment, schooling, rheotaxis, and prey detection. The ability to sense the changing flows in the environment and then use that information with high control authority would better enable an autonomous vehicle to survive and maneuver in dangerous currents. As an initial foray into the sensory and control methods that could be used by a biomimetic vehicle, we studied energy extraction through synchronization with an incoming cylinder wake with both live fish and mechanical flapping foils.
Rainbow trout voluntarily synchronize their motions to cylinder wakes in both frequency and phase. The oscillating flows in the wake create a beneficial angle-of-attack across the trout's tail, enabling the fish to passively hold position in the stream. These effects were studied with live and euthanized fish as well as with a mechanical flapping foil moving both passively and actively within the cylinder wake. These results are applicable for reducing energy expenditure in vehicles holding position in currents containing large-scale turbulence as well as for lightweight power generators in streams.
Joint Computer Science and Applied Math Pattern Theory Seminar
Abstract: Spectral clustering methods, i.e methods that use eigenvectors of a suitably chosen matrix to partition the data, have recently become popular. This talk will analyze from a novel perspective why spectral clustering works. In particular, we show that spectral algorithms work in a wider and more interesting range of cases than it is generally believed. In the vicinity of some special points called perfect, spectral clustering optimizes simultaneously two criteria: a dissimilarity measure akin to the isoperimetric number (that we call the multiway normalized cut) and a cluster coherence measure (that we callthe gap).
Based on these results, we demonstrate that several popular clustering algorithms are equivalent near perfect points, we propose new methods for selecting the number of clusters and show their superior performance in experiments.
Joint work with: Jianbo Shi, Deepak Verma, Liang Xu
Host: Professor Thomas Hofmann
Brown Analysis Seminar
Joint Applied Mathematics and TCASCV Colloquium
Thanksgiving Lecture
182 George Street, Room 110 |
Abstract: In the hands of Newton and Leibniz, calculus was a theory that involved geometrical figures. These formed a part of the reasoning. There followed thereupon a gradual decline of the image in mathematics in favor of the symbolic, and by the early 20th century, the image was all but dead. Why? Computer graphics has to some extent restored the image to its former prominence in mathematics and promises in the future to be an uneasy partner with the symbolic.
Scientific Computing Seminar
University of North Carolina at Charlotte | |
Abstract: In this talk, we will present recent results on modeling of the optical coupling of whispering gallery modes (WGM) between microcavity resonators. WGM are special evanscent modes inside microcylinders or microshperes with large Q factor, which are being considered for photonic waveguide or sensor applications. We will present simulation results based on discontinuous spectral methods for the coupled microcylinders and study the dependence of coupling on the separation or size variation of the microcylinders.
Special Scientific Computing Seminar
The University of Tokyo | |
Abstract: Direct numerical simulation of a turbulent channel flow at Re_tau = 1160 was made in order to examine the relationship between the near-wall quasi- streamwise vortices (QSVs) and the large-scale outer-layer structures. This simulation was carried out with the Earth Simulator, which is the fastest super computer in the world. The visualized flow field and the statistics suggest that not only the QSVs but also edges of the large-scale structres appear near the wall (y^+ ~30). Away from the wall, the low/high-speed large-scale structures prevail, and the QSVs are clustered preferably in the low-speed ones. The contribution of the large-scale structures to the Reynolds stress is much larger than that of the clustering QSVs in the outer layer. These large-scale structures seem to have an autonomous cycle that does not depend on the near-wall coherent structures.
PDE Seminar
Abstract: The talk will be concerned with feedback strategies for non-cooperative differential games. In the case of Nash equilibrium solutions, it is well known that the value functions satisfy a system of Hamilton-Jacobi equation. If the system is hyperbolic, in one space dimension one can apply the theory of conservation laws, and show that a small BV solution of the P.D.E. yield a Nash equilibrium solution of the differential game. In several space dimensions, the system of H-J equations is generically not hyperbolic and the Cauchy problem is not well posed. To recover some stability, we consider semi-cooperative strategies, seeking a Pareto optimum instead of a Nash equilibrium. In this case, the corresponding H-J system turns out to be always weakly hyperbolic.
Department of Mathematics Colloquium
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