Brown University Graduate School Dissertation Defense
Brown University Center for Statistical Sciences Seminar
Abstract: Of concern to pharmaceutical companies is a perceived trend on the part of regulatory agencies to require that, in a confirmatory clinical trial, significance be achieved for all of "p" endpoints, where p>1. This is a delicate testing problem; the null and alternative hypotheses are defined by "non-standard" partitions of the parameter space. This talk examines some new results in this area which pertain to the intersection-union and likelihood ratio tests. We give a simple expression for the p-value, and a computable lower bound for the power.
It is also shown that the "multiple endpoints" testing problem is equivalent, in a QT study (Q and T are two points on an ECG) to testing whether a drug is non-inferior to placebo. Finally, we outline a procedure that may be used to construct an approximate confidence interval for the "true" maximum difference in QT between drug and placebo.
Brown University,
Joint Materials/Solid Mechanics Seminar Series
University of Michigan, Ann Arbor | |
Abstract:
Advancing technologies demand solid structures
of ever-decreasing length scales. During fabrication
and use of these structures, atoms are mobile by diffusion
or other mass transport processes. The structures
may change configurations over time. Experimental evidence
has accumulated in recent years that nanoscale structures
can self-assemble, leading to ordered nanophase patterns
in polymers and other materials. In a structure, collective
actions of photons, electrons and ions contribute to the free
energy. When the configuration of the structure changes,
the free energy also changes. This free energy change
defines a thermodynamic force which, in its turn, motivates
the configuration change of the structure. The effects of such
forces may be negligible in macrostructures, but significant
in nanostructures. Insight into these forces becomes
increasingly valuable as the structures of technological
interest miniaturize. This talk presents some of our recent
work on self-organized nanostructures and guided self-assembly.
Examples include self-organized nanophase patterns on solid
surfaces, guided assembly by surface chemistry and strain field,
organized nanovoids and nanobubbles in a solid, patterning
multilayer of molecules via dipole interaction, electric field
induced ordered polymer nanostructures and tuning of
nanoparticles in polymer nanocomposites. We have developed a
thermodynamic framework to study the remarkable phenomena.
Large-scale simulations have been developed to simulate the
process of formation and evolution of nanostructures. The
simulations reveal remarkably rich dynamics and suggest a
significant degree of experimental control in growing
ordered nanoscale structures.
Note: There will be a dinner following the seminar.
Please contact Ms. Pat Capece at x3-1501 if you plan to attend.
Special Applied Mathematics Colloquium
Center for Scienfific Computation and Mathematical Modeling (CSCAMM) Department of Mathematics and Institute for Physical Science & Technology University of Maryland, College Park | |
Abstract: I will present a novel representation of general images which are decomposed into hierarchical scales of edges. The starting point is a variational decomposition of an image, f = u_{0}+v_{0}, where [u_{0},v_{0}], is the minimizer of the interpolation functional, J(f,c_{0})=\inf _{u+v=f} {\parallel u \parallel_{BV}+c_{0} (\parellel v \parellel _{L^{2})^{2}}. Such minimizers are standard tools for denoising, deblurring, compression, ... of images. Here, u_{0} should capture `essential features' of f, to be separated from the spurious components in v_{0}, and c_{0} is a fixed threshold which dictates separation of scales. To proceed, we iterate the refinement step [u_{j}+1,v_{j}+1] =\arg\inf J(v_{j}c_{0}2^{j}), leading to the hierarchical decomposition, f=\Sigma_{j=0}^{k} u_{j}+ v_{k}. The resulting hierarchical decomposition, f ~ \Sigma _{j} u_{j}, is essentially nonlinear. The questions of convergence, energy decomposition, localization and adaptivity are discussed. The decomposition is constructed by numerical solution of successive Euler-Lagrange equations. Numerical results illustrate applications to synthetic and real images (both greyscale and colored images).
Brown University Graduate School Dissertation Defense
Special LCDS/PDE Seminar
Brown Analysis Seminar
Brown University Graduate School Dissertation Defense
Brown University Graduate School Dissertation Defense
Brown University Graduate School Dissertation Defense
Brown University Graduate School Dissertation Defense Information
Scientific Computing Seminar
Center for Biophysical Modeling and Simulation and Department of Chemistry, University of Utah, Salt Lake City, Utah | |
Abstract: A new methodology for coarse-graining condensed phase and biomolecular systems will be described. The approach provides a multiscale connection between atomistic molecular dynamics and reduced coarse-grained models, the latter being more appropriate for the mesoscopic scale. Applications of the resulting approach will be given for liquids, lipid bilayers, and peptides, as well as for larger protein complexes such as actin filaments. The issue of modeling correct dynamics in coarse-grained simulations will also be addressed if time allows.
Center for Computational Molecular Biology Seminar
Johns Hopkins University, Applied Physics Laboratory | |
Abstract: Since the sequencing of the human genome in 2000, over 25 large eukaryotic genomes have been assembled. Many of these species are closely related to humans, ranging in evolutionary distance from 5 million (chimpanzee) to 400 million (fish) years. In the current post-genomic era, much of the focus of genomic research has shifted to comparative genomics, the study of the similarities and differences between the entire genomes of related species.
Comparative genomics can not only shed light on the evolutionary relationships among species, but also be used as a tool to annotate genes on newly sequenced genomes by projecting known gene locations from similar species.
Visualizing comparative genomics data presents a challenge due to the complexity, range of scale, and discontinuities in the differences between genomes. These can vary in size from single nucleotide polymorphisms to rearrangements of major portions of entire chromosomes. In this talk, we will present some of the techniques we have developed and experimented with to visualize comparative genomic data at Applied Biosystems Corporation, and discuss their implementation in a visualization tool we have developed called Atavist.
Biography: Dr. Turner is a Senior Computer Scientist at Johns Hopkins University Applied Physics Laboratory. His research interests include bioinformatics visualization, interactive 2D and 3D graphics, object-oriented software design and 3D character animation. Before working at APL, he was a member of the Informatics Research group at Applied Biosystems and technical lead for development of the Celera Genome Browser at Celera Genomics.
Participating Departments: Applied Mathematics, Computer Science, Ecology and Evolutionary Biology, Molecular Biology, Cell Biology and Biochemistry, and Molecular Pharmacology, Physiology and Biotechnology
PDE Seminar
Abstract: Liouville's equation---which comes up in conformal geometry in particular---is formally the Euler-Lagrange equation of a functional E. However, if u is the maximal solution, E(u) is infinite. We present a renormalized variational characterization of u in a Sobolev space, leading to a new a priori bound.
The construction relies on the detailed asymptotics of u at the boundary provided by the method of Fuchsian Reduction (FR). It leads to a new inequality which contains both Hardy's and Trudinger's inequalities.
Other applications of FR, and the main difficulties in the proofs will be briefly outlined.
Department of Mathematics Colloquium
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