Events Archive

Jan
16
2013
Rotation Rate of Rods in Turbulence
PLEASE NOTE: This is a WEBINAR The transport of particulate material by fluid flow is a problem with far reaching applications. Isotropic particles that are very small and neutrally buoyant behave as Lagrangian tracers and move with the local fluid velocity. However, particles that are large or density mismatched compared to the fluid have different dynamics from the local fluid. The rotational dynamics of anisotropic particles is different from spherical tracers and this fascinating problem is central for many applications ranging from cellulose fibers in paper making to dynamics of ice...
Jan
15
2013
Understanding and Engineering Dynamics and Variability in Gene Regulation and Beyond
I will discuss three examples describing the utility of understanding and/or exploiting both epigenetic and genetic variability in populations of yeast cells. First, I describe an unappreciated and dominant role for cell-cycle phase on transcriptional variability and dynamics. We show that for a model “noisy” gene in S. cerevisiae, the common view that large variability observed in mRNA numbers is due to a transcriptional bursting, where a promoter undergoes random and intermittent periods of active transcription, is incomplete and possibly...
Jan
14
2013
Using Growth and Folding to Shape Elastic Sheets
Despite their everyday familiarity, thin sheets (paper, plastic, fabric, etc.) display remarkable and complex behaviors that still challenge theoretical description. The intricate coupling between the geometry of surfaces and the elasticity of a thin sheet necessarily leads to the formation of singularities, nonlinear elasticity, and geometric frustration. Nevertheless, multicellular organisms - like you - develop their three dimensional structures in part by exploiting these elastic phenomena. These considerations have led to new theoretical and experimental tools to shape elastic sheets into...
Dec
11
2012
New signaling pathway in muscle: X-ROS
X-ROS signaling is a novel redox signaling pathway that links mechanical stress to changes in [Ca2+]i.  This pathway is activated rapidly and locally within a muscle cell under physiological conditions, but can also contribute to Ca2+-dependent arrhythmia in heart and to the dystrophic phenotype in heart and skeletal muscle 1, 2.  Upon physiologic cellular stretch, microtubules serve as mechanotransducers to activate NADPH oxidase 2 (NOX2) in the transverse tubules and sarcolemmal membranes to produce reactive oxygen species (ROS).  In heart, the ROS acts locally to activate ryanodine receptor Ca2+...
Dec
10
2012
Ultra-High Energy Cosmic Rays from Blazars
Blazar astronomy is rapidly progressing thanks in large part to the successes of the Fermi Gamma-ray Space Telescope and the ground-based gamma-ray telescopes. More than 1000 active galaxies have been detected at GeV energies, and nearly 50 at Very-High Energies (VHE,  > 100 GeV). We can now explore multiwavelength and multi-messenger connections in unprecedented detail, and derive the astroparticle implications of those results. In this presentation, leptonic and hadronic spectral modeling of blazars is reviewed with the intent of identifying ultra-high energy cosmic rays (UHECRs) in  the spectral energy...
Dec
10
2012
Numerical solutions to the optimal stabilization Hamilton-Jacobi PDE in control theory
PLEASE NOTE: This is a WEBINAR A problem of practical interest in control theory is to stabilize a nonlinear dynamical system through the action of a feedback control.  The stabilization problem can be embedded as an optimal control problem leading one to solve a Hamilton-Jacobi (HJ) PDE.  The associated HJ equation is a first order nonlinear singular PDE and, under suitable conditions, can be solved locally using power series methods.  In this talk, I will present a numerical method that extends the domain of...
Dec
10
2012
A New Physiological Boundary Condition for Hemodynamics
PLEASE NOTE: This is a WEBINAR Accurate modeling of blood flow provides insights into arterial stent design, surgical planning, and analysis of stroke risk. Unfortunately, fully detailed modeling of the cardiovascular system is computationally impossible due to the enormous number of blood vessels in the body.  Instead, a common technique is to choose a small subset of arteries to model in detail while accounting for the "un-modeled" parts of the cardiovascular system through boundary conditions.  A popular tactic for deriving such a boundary condition is to...
Dec
06
2012
The Co-Evolution of Galaxies and Black Holes: A Local Perspective
I will summarize our current understanding on the relation between the evolution of black holes and galaxies in the local universe. I will show that the growth of supermassive black holes as traced by optically luminous active galactic nuclei is strongly linked to the on-going formation of stars in the bulge component of galaxies. It is likely that this co-evolution is driven by the accretion and radial transport of cold gas, but major mergers of galaxies are not the primary mechanism for doing this. I will show that the fuel source for the black hole growth may be mass loss from intermediate mass stars and that the black hole growth may be limited in part by feedback from supernovae...
Dec
04
2012
Electromechanical Pumping in the Embryonic Tubular Heart
Recent advancements in computational fluid dynamics have enabled researchers to efficiently explore problems that involve moving elastic boundaries immersed in fluids for problems such as cardiac fluid dynamics, fish swimming, and the movement of bacteria. These...
Dec
04
2012
Hamiltonian reductions in plasma physics
Given the complexity of the dynamics of a plasma, reductions are needed. The Hamiltonian framework offers various ways to carry out such reductions. I will introduce some of these methods by considering in particular the example of gyrokinetics, which is a kinetic model for plasmas in a strong magnetic field.

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