Events Archive

Jan
31
2013
Detonating Superbursts on Neutron Starts: from a Shocking Start to a Long Tail
Superbursts are the most powerful repeating thermonuclear flashes observed from accreting neutron stars. Runaway thermonuclear burning of carbon ignites deep in the star's envelope. Close to the crust, superbursts are sensitive to the ill-understood nuclear physics processes in dense neutron-rich matter. We present the latest numerical simulations of carbon burning. Comparing the tail of the simulated lightcurve to observations constrains the depth of carbon ignition, whereas the start exhibits the signs of a shock caused by detonation. Recently increasing observational evidence points at interaction between X-ray bursts and the accretion disk. As the most powerful X-ray bursts,...
Jan
31
2013
Interchanging the Roles of Light and Matter
Atom interferometers that use pulses of light for coherent control of matter-wave interference can be used for wide ranging studies of light-matter interactions and for realizing precision measurements in atomic physics. We describe an echo type interferometer that utilizes a relatively simple setup to manipulate laser-cooled Rb atoms in a single ground state manifold. We review progress toward a precise determination of the atomic fine structure constant and gravitational acceleration. *Work supported by CFI, OIT, OCE, NSERC and York University
Jan
30
2013
Direct Determination of Time Varying Flow Structures
PLEASE NOTE: This is a WEBINAR Scientists for years have been trying to better understand the mechanisms that are responsible for transport and mixing in fluid flow.  Mixing is important as it is used in everything from food preparation to energy production to biomedical devices, and is seen in both single and multiphase environments.  While mixing applications are wide ranging, a complete and proper understanding of mixing and transport mechanisms is still lacking....
Jan
29
2013
Biofilms Suck and Epithelial Cells Blow: Forces in Multi-cellular Systems
Multicellular behavior in bacterial biofilms is intimately tied to the production of an extracellular polysaccharide (EPS) matrix that encases the cells and provides physical integrity to the colony as a whole.  As a colony grows from a few cells into a biofilm, a sudden increase in EPS production generates osmotic stresses that cause the biofilm to expand. Moreover, EPS production is triggered by a nutrient depletion gradient that develops in the biofilm due to diffusive mass transport limitations. These polymer physics based biofilm behaviors...
Jan
29
2013
Localized patterns and traveling waves in reaction-diffusion systems
PLEASE NOTE: This is a WEBINAR Two topics in pattern formation for reaction-diffusion equations will be addressed in this talk.  In the first, I will discuss the existence proof for stationary localized spots in the planar and the three-dimensional Swift--Hohenberg equation using geometric blow-up techniques. The spots have a much larger amplitude than that expected from a formal scaling in the far field. One advantage of the...
Jan
28
2013
"How Do Chipper, Kobe, Serena and Rory Do It? What Physics Has to Say About Achievements in Sports"
A great part of physics deals with motion, and the essence of sports is the human body in motion.  The components of the human body that produce motion, namely the skeletal muscles and bones, and the sports equipment itself are bound by the laws of physics.  Aspects of various sports, including baseball, basketball, karate, figure skating, golf, tennis, long jump, and more, will be examined using introductory-level physics.  We will also discuss whether we have reached our limits in human performance in certain sports.  All who appreciate the workings of the human body and the...
Jan
24
2013
The Dark and the Light: Black Holes, Dark Halos, and their Influence on Galaxy Evolution
Supermassive black holes are amazingly exotic and yet ubiquitous objects, residing in the centers of essentially all stellar bulges in galaxies. Recent years have seen remarkable advances in our understanding of how these black holes form and grow over cosmic time, and how energy released by active galactic nuclei (AGN) connects the growth of black holes to their host galaxies and large-scale structures. I will review some recent work that explores these connections, with a focus on statistical studies of AGN clustering and the links between black hole growth and and star formation. I will highlight some new insights into how and when AGN "feedback" is important for galaxy...
Jan
23
2013
Transitions in turbulent Plane Couette Flow with Rotation
PLEASE NOTE: This is a WEBINAR The interplay of shearing and rotational forces in fluids  significantly affects the transport properties of turbulent fluids  such as the heat flux in rotating convection and the angular momentum  flux in a fluid annulus between differentially rotating cylinders. A  numerical investigation was undertaken to study the role of these  forces using plane Couette flow subject to rotation about an axis  perpendicular to both wall-normal and streamwise directions. Using a  set of progressively...
Jan
17
2013
Explorations of Spin-Nematic Dynamics in a Spin-1 BEC: Squeezing, Non-Gaussian Distributions, and Stabilization
Current study in quantum dynamical evolution of complex systems investigates quantum systems characterized by fluctuations and quantum correlations.  Spin-1 condensates are predicted to generate non-classical states with quantum correlations, specifically squeezed states in the early low depletion limit and highly non-Gaussian distributions in the long term beyond the low depletion limit.  These states are created due to the quantum fluctuations about an unstable equilibrium in the spin-nematic subspaces to which the system is initialized.  In this talk I will discuss the...
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...

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