Brown University Center for Statistical Sciences Seminar
Abstract: We consider the choice of an optimal sample size for multiple comparison problems. The motivating application is the choice of the number of microarray experiments to be carried out when learning about differential gene expression. However, the appoach is valid in any application that involves multiple comparison in a large number of hypothesis tests.
We discuss two decision problems in the context of this setup, the sample size selection and the decision about the multiple comparisons. The focus of the discussion is on the sample size selection. For the multiple comparison we assume an approach as in Genovese and Wasserman (2002), based on controlling posterior expected false discovery rate (FDR). For the sample size selection we adopt a decision theoretic solution, using expected false negative rate (FNR) as decision criterion, combined with a power analysis as sensitivity diagnostic. Posterior expected FDR and marginal FNR are computed with respect to an assumed parametric probability model. In our implementation we use a version of the model proposed in Newton et al. (2001). But the discussion is independent of the chosen probability model. The approach is valid for any model that includes positive prior probabilities for the null hypotheses in the multiple comparisons, and that allows efficient marginal and posterior simulation. Posterior and marginal simulation can be done by dependent Markov chain Monte Carlo simulation.
*Peter Mueller, Giovanni Parmigiani, Christian Robert,
Judith Rousseau
**Sponsored by the C.V. Starr Foundation Lectureship Fund
***Co Sponsored by The Center for Genetics and Genomics
Brown University Joint Materials/Solid Mechanics Seminar Series
Department of Mechanical, Aerospace & Nuclear Engineering, Rensselaer Polytechnic Institute, Troy, NY | |
Abstract: During thin film deposition, both kinetics and mechanics interact with the texture and morphology of the thin film. Understanding the interaction mechanisms will facilitate the design of various nanostructures on the surface and in the bulk of thin films. Combining atomistic simulations and magnetron sputtering experiments, we have recently revealed several new mechanisms of the texture and morphology evolution. In this talk, I will focus on two sets of results. First, I will present two new kinetic barriers, facet-facet and step-facet barriers: the concept, the numerical determination and the experimental validation. Then, I will turn to the self-organization of alternating textures: its realization, mechanics-driven mechanism, and potential applications.
Center for Fluid Mechanics Seminar
Department of Electrical Engineering and Computer Science | |
Abstract: Continuum electromechanics of ferrohydrodynamic interactions in magnetic liquids (ferrofluids) and electrohydrodynamic interactions between charged and polarizable dielectric liquids will be described with video presentations of simple experiments. With a brief presentation of magnetic fluid science and technology representative magnetic fluid phenomena include: ferrofluid rise due to magnetization force; ferrohydrodynamic spike and labyrinth instabilities; stabilization of the Saffman-Taylor pusher fluid fingering instability where a less viscous fluid pushes a more viscous fluid; and ferrofluid spiral patterns, flows, and abrupt transitions from a continuous to discrete phase in rotating magnetic fields. Analogous electrohydrodynamic presentations include: Coulombic force on a surface within a more conducting liquid (von Quicke's rotor); spontaneous high voltage generation from self-excited electrostatic induction machines (Lord Kelvin's dynamo using falling water droplets); interfacial fluid convection cells driven by interfacial surface charge; fluid rise due to electrical polarization forces; electrostatic control of fluid jet profiles; electric field stabilization of the Rayleigh-Taylor instability of a more dense fluid over a less fluid; and dielectric fluid labyrinth instability. Magnetic fluid analysis will also be presented for plane Poiseuille/Couette flow in alternating and rotating magnetic fields to demonstrate and explain "negative viscosity" phenomena. Confirming torque measurements using a Couette viscometer will be compared to the theory. Magnetic fluid bells, chains, and sheet flows will also be shown as a function of magnetic field strength and direction.
Brown Analysis Seminar
Scientific Computing Seminar
University of California, Davis | |
Abstract: Traditionally, high order Godunov-type central schemes employ local polynomial reconstructions. These reconstructions avoid transfer of information across discontinuities through nonlinear limiters which act as local edge detectors. Here we introduce an adaptive method which employ global edge detection to ensure that information is extracted in the direction of smoothness while maintaining computational stability. Additionally, the global edge detection substantially reduces the computational cost. The reconstruction incorporates the largest symmetric stencil possible without crossing discontinuities. Consequently, the spatial order of accuracy is proportional to the number of cells to the nearest discontinuity, reaching exponential order at the interior of regions of smoothness.
This research was conducted jointly with Eitan Tadmor.
PDE Seminar
Abstract: The relativistic Landau-Maxwell system is the most fundamental and complete model for describing the dynamics of a dilute collisional plasma in which particles interact through Coulombic collisions and through their self-consistent electromagnetic field. We construct the first global in time classical solutions. Our solutions are constructed in a periodic box and near the relativistic Maxwellian, the Juttner solution.
Department of Mathematics Colloquium
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