Fluctuations in Dynamical Systems Far From Equilibrium

The workshop will bring together people from applied mathematics, dynamical systems, condensed matter physics and statistical physics. The theme are fluctuations far from equilibrium, particularly in stochastic dynamics. A focus will be on so-called fluctuation relations, which generalize the second law of thermodynamics to small systems. They have been found to be generally valid very far from equilibrium. This active, recent topic of research will be discussed both from a theoretical and from an experimental point of view. Cross-links to large deviation theory and to anomalous stochastic processes will be explored.

Programme

11.30 - 12.30 Ian Ford, UCL: A rough guide to fluctuation relations

14.00 - 15.00 David Carberry, University of Bristol: Fluctuation Relations: Experimental Demonstrations

15.00 - 16.00 Adrian Baule, QMUL: Exact relations in non-equilibrium statistical mechanics

16.30 - 17.30  Nicholas Watkins, Cambridge, UK: Anomalous Diffusion, Anomalous Time Series, and the models that describe them

All talks will be held in seminar room M103 (first floor) of the Department of Mathematics at Queen Mary University of London.

For more information contact Prof Ferruccio Renzoni

Paper in Journal of Quantitative Spectroscopy and Radiative Transfer

Our paper Evanescent wave optical trapping and transport of micro- and nanoparticles on tapered optical fibers has been published online in the Journal of Quantitative Spectrocopy and Radiative Transfer doi: 10.1016/j.jqsrt.2012.06.005.

From the abstract: We investigate the manipulation of microscopic and nanoscopic particles using the evanescent optical field surrounding an optical fiber that is tapered to a micron-scale diameter, and propose that this scheme could be used to discriminate between, and thereby sort, metallic nanoparticles. First we show experimentally the concept of the transport of micron-sized spheres along a tapered fiber and measure the particle velocity. Having demonstrated the principle we then consider theoretically the application to the optical trapping and guiding of metallic nanoparticles, where the presence of a plasmon resonance is used to enhance optical forces. We show that the dynamics of the nanoparticles trapped by the evanescent field can be controlled by the state of polarization of the fiber mode, and by using more than one wavelength differently detuned from the nanoparticle plasmon resonance. Such a scheme could potentially be used for selectively trapping and transporting nano- or microscopic material from a polydisperse suspension.

Visit by Sile Nic Chormaic's Group

On Thursday 3 May we were visited by members of Sile Nic Chormaic's Group from University College Cork who were in London en route from Ireland to Japan.  Our groups collaborate on the Nanofibre Optical Interfaces for Ion Atoms and Molecules (NOIs) project.  Some pictures of the group were taken by Dr VB Tiwari (UC Cork & Raja Ramanna Centre for Advanced Technology, Indore).

New Group Members

Chris Fury has joined the UCL Optical Tweezers Group from April 2012 to study for a PhD.  Chris gained a degree in Physics from Exeter University, followed by an MSc in Fusion Energy from York University, which included a research project at the Central Laser Facility at the Rutherford Appleton Lab.

Chris joins the group to work at the National Physical Laboratory on the NPL/UCL optical and acoustic microbubble trapping project.

Physics Department Annual Review

The UCL Department of Physics & Astronomy Annual Review 2011-12 has been published.  In this year's review Phil is featured in the 'Academic showcase' section.

Royal Society Summer Exhibition 2012

The UCL/NPL microbubble trapping project will have a stand at the Royal Society Summer Exhibition 2012, called 'Pop! The sound of bubbles'.  This stand will be run by many of the scientists involved in the project including Gianluca Memoli, Eleanor Stride, Caroline Harfield & Louise Wright.  The exhibition runs from 03-08 July 2012 at the Royal Society.
Our display will feature the science of microbubble trapping as well as many other everyday applications of microbubble technology (including some that might surprise you!).
You can follow the sound of bubbles blog for the latest updates on our project, or the Summer Science 2012 twitter @summerscience for more about the exhibition.

David Carberry visit and seminar

David Carberry (Bristol University) is visiting and giving the AMOP Physics seminar on Wednesday 22 February.  David works on optical micromanipulation techniques and recently demonstrated a multi-point holographic optical tweezers controlled through an iPad.  The abstract for his seminar is below:

Title:  Non-spherical optically trapped probes: Design, control and applications
Abstract: Non-spherical probe particles have a number of advantages over microspheres: rotational motion may be monitored and controlled, the trapping points may be removed from the probe’s tip, and the tip can be more accurately positioned than a microsphere of equivalent radius.

We demonstrate a range of non-spherical probes, and discuss how they may be tailored to specific applications. We consider how probe geometry affects the region of space the tip explores – the ‘tip thermal volume’, and the relaxation times of this motion¹. By independently position-clamping translational and rotational modes in different ways, we are able to further control the shape of the tip thermal volume, and dramatically improve the position resolution of the probe, with no reduction in force sensitivity².

Using holographic optical tweezers combined with stereomicroscopy, we can both control and track the motion of our non-spherical probes in all three dimensions. Finally, we demonstrate the use of our probes to image surfaces in 3D³, and measure force and torque interactions with biological specimens. 

  

1. S.H. Simpson and S. Hanna. ‘Thermal Motion of a holographically trapped SPM-like probe’. Nanotechnology, 20 395710 (2009)
2. D.B. Phillips et al. ‘Position clamping of optically trapped microscopic non-spherical probes’. Optics Express, 19 20622 (2011)
3. D.B. Phillips et al. ‘Surface imaging using holographic optical tweezers’. Nanotechnology, 22 285503 (2011)