Events Archive

Oct
31
2011
Winner of the Nobel Prize in Physics in 2007, Fert speaks about his work in spintronics.
Oct
31
2011
Albert Fert, Nobel Prize in Physics 2007 Joint colloquium between the School of Physics and MRSEC Spintronics exploits the influence of the electron spin orientation on electronic transport. It is mainly known for the “giant magnetoresistance” (GMR) and the large increase of the hard disc capacity obtained with read heads based on the GMR, but it has...
Oct
28
2011
A quantum computer uses superposition states to accomplish tasks (e.g., database search and factoring of integers) more efficiently than any known classical computing strategy. In conventional registers for quantum information processing, quantum bits are associated with individual two-level quantum systems. Separate addressing and interaction with these systems permit one-bit gates, while an interaction between systems is neededto accomplish two-bit gates. The seminar will review recent theoretical proposals to implement quantum computing in collective excitation degrees of freedom in ensembles ofidentical quantum systems. In these proposals one does not address...
Oct
26
2011
Computational models of the Earth system lie at the heart of modern climate science. Concerns about their predictions have been illegitimately used to undercut the case that the climate is changing and this has put dynamical modelling in an awkward position. I will discuss ways that we, as a community, can contribute by highlighting some of the major outstanding questions that drive climate science, and I will outline their mathematical dimensions. I will put a particular focus on the issue of simultaneously handling the information coming from data and models, and argue that this balancing act will impact the way in...
Oct
25
2011
At the small scale of a cell swimming in water, inertial effects are unimportant. Therefore, the motion of the fluid is governed by Stokes equations, which are linear. Nevertheless, there are many situations in which nonlinear effects are important. In this talk I will describe two such situations. The first is swimming in a viscoelastic material, which is motivated by the fact that many microorganisms move in non-Newtonian media such as mucus. I will present a simple model that shows how fading memory affects swimming speed. We will also present experimental results for a helix swimming in a viscoelastic fluid. The second situation I will consider is the...
Oct
19
2011
Neutron stars are observed to rotate as fast as 716 Hz. Astrophysicists believe that they are spun-up by accretion of matter and angular momentum in binary star systems. However, the "r-mode" instability of rotating neutron stars, which is driven by gravitational radiation reaction, appears to prevent spin up via accretion to rotation frequencies above about 350 Hz.
Oct
13
2011
We all know that modern science is undergoing a profound transformation as it aims to tackle the complex problems of the 21st Century.  It isbecoming highly collaborative; problems as diverse as climate change, renewable energy, or the origin of gamma-ray bursts require understandingprocesses that no single group or community alone has the skills to address. At the same time, after centuries of little change, compute, data, and network environments have grown by 9-12 orders of magnitude in the last few decades.  Moreover, science is not only compute-intensive but is dominated now by data-intensive methods.  This dramatic change in the culture and methodology of...
Oct
07
2011
In the framework of the Fitzhugh-Nagumo kinetics and the oscillatory recovery in excitable media, we present a new type of meandering of the spiral waves, which leads to spiral break up and spatiotemporal chaos. The tip of the spiral follows an outward spiral-like trajectory and the spiral core expands in time. This type of destabilization of simple rotation is attributed to the effects of curvature and the wave-fronts interactions in the case of oscillatory damped recovery to the rest state. This model offers a new route to and caricature for cardiac fibrillation, and when we apply the feedback resonant drift method, for defibrillation all wave activity gets eliminated at the...

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