Small stuff

New Grants

HiPED Project, MBDA, Dr Kevin Ronald, 01/10/09 - 31/05/11, Award Value: £192,000.00, FEC Value: £192,245.00

Extreme Light Infrastructure (ELI), STFC - UK Research Council, Professor Dino Jaroszynski, 01/04/2008 - 31/03/2011, FEC: £194,662.00, Award Value: £70,000.00

LASERLAB, EC - FP7, Professor Dino Jaroszynski, 01/03/2009 - 29/02/2012, FEC: £447,108.00, Award Value: £194,566.03

CORNER, EC - FP7, Dr Shashank Virmani, 01/11/2009 - 30/06/2011, FEC: £40,529.00, Award Value: £10,936.00

LASSIE, EC - FP7, Dr Helen Fraser, 01/02/10 - 31/01/14, FEC: £540,678.00, Award Value: £329,607

IOP Select

A publication by Strathclyde researcher Shashank Virmani and collaborator Martin Plenio ('Upper bounds on fault tolerance thresholds of noisy Clifford-based quantum computers' New J. Phys. 12 033012 (2010)), has been selected for IOP Select, a showcase for papers appearing in journals published by the Institute of Physics that are deemed to be especially novel or significant.

[SV]

Editors' choice

A paper Universal nonexponential relaxation: Complex dynamics in simple liquids was the 3rd most downloaded paper of J. Chem. Phys. in December 2009. Subsequently, it was selected JChemPhys editors’ choice as one of the most innovative and influential articles in the field of Chemical Physics in 2009.

It describes ultrafast spectrosocopy experiments on liquid argon, krypton, and xenon that show that the atomic relaxation dynamics is much more complicated than expected. Instead of the expected exponential relaxation, a stretched exponential is seen. This behaviour is essentially identical to that in liquid water, which throws up questions about the (un)importance of hydrogen bonds in cage breakup and diffusion in liquid water.

[KW]

Century-old problem of optical momentum resolved

It has been known since Einstein’s pioneering work that the momentum of a photon is Planck’s constant divided by its wavelength (h/λ).  But what happens to this momentum when the light enters a transparent medium like glass?  Surprisingly, there are two very credible answers to this seemingly innocent question.  According to Minkowski’s theory, published in 1908, the density of optical momentum is DxB so that the momentum of a photon inside the medium exceeds its value in free space by a factor of the refractive index (nh/λ).  It is easy to see that this must be true, of course, because this is precisely the factor by which the wavelength of the light decreases on entering the medium.  Just one year later, in 1909, Abraham proposed that the momentum density should in fact be ExH/c² so that the momentum of a photon is less than its value in free space by a factor of the refractive index (h/(nλ)).  We can understand this reduction simply as a manifestation of the fact that the photon carries the same energy as in free space but at a speed that is reduced by the refractive index.

Extremely powerful and simple arguments have been put forward in support of both momenta and the experimental situation is also confusing with experiments reported supporting both momenta.  Put simply, to question the Abraham form for the momentum would put into doubt the relativistic equivalence of mass and energy and Newton’s first law of motion.  To question the Minowski form, however, is to cast doubt of the Heisenberg uncertainty principle and also on the Doppler shift.

Recent work at Strathclyde has demonstrated that both momenta are indeed correct but that one, the Abraham momentum is the “kinetic momentum” while the Minkowski form is the “canonical momentum”.  This separation tells us to expect that the mechanical or particle properties of light are associated with the Abraham momentum while its wave properties are associated with the Minkowski form.  This not only tells us why there have to be two momenta but also which one will manifest itself in any given experimental situation.

The work was reported in Physical Review Letters and in the issue of Philosphical Transaction of the Royal Society A to mark the 350th Anniversary of the Royal Society. It has been reported in Science and in Physics World.

[SB]

SUPA International Advisory Committee

The SUPA International Advisory Committee met recently in Glasgow with representatives of SUPA and the Scottish Funding Council to review the health of Scottish physics. The department was represented by HoD David Birch, presently Acting SUPA CEO, and Rob Martin, Condensed Matter and Materials Physics theme Leader. The day proved to be very constructive and helpful to SUPA's strategic planning as it moves forward with the £48M SUPA2 investment.

[DJSB]

LIBRA Project Open Day at the Royal Society London

The LIBRA (Laser Induced Beams of Radiation and Applications) project is a £4.8M Basic Technology project funded by EPSRC, with the objectives to develop short pulse, high power laser-plasma sources of high energy ions and other radiation, and the technology to generate these radiation pulses at high repetition rates (few Hz).  

On the 10th February the LIBRA consortium hosted an Open Day at the Royal Society in London to demonstrate progress made to date in the four-year project, which has now reached the half-way point. The event was well attended and a number of presentations were made on key topics of the project. Professor Paul Bolton from the Photo-Medical Research Centre in Japan gave a keynote talk on international efforts in the development of laser-driven ion sources and potential medical applications. Researchers from Strathclyde presented progress made in Strathclyde-led project work packages, including first measurements of ion acceleration using the new Astra-Gemini laser at the Rutherford Appleton Laboratory. A paper on this work by David Carroll et al will appear shortly in the New Journal of Physics.

For more information please contact Dr. Paul McKenna

[DC & PM]

Photophysics for Healthcare

Research in the Photophysics Group in collaboration with Kings College London School of Medicine has recently made promising progress on one of the great healthcare challenges of the 21st century, namely non-invasive sensing of blood glucose for diabetes management.  Diabetes is a global epidemic with nearly 4 million people dying from it each year. There is estimated to be 250 million people worldwide suffering from the disease, a figure expected to rise to 380 million by 2025. In the UK there are 3 million cases at a prevalence of around 2,000 per week. This represents 10% of the healthcare costs of many nations including the UK.  The key to better patient care of this incurable disease is to establish normal blood glucose levels as regularly as possible.  Non-invasive blood glucose measurement is the crucial step that has so far proved elusive with intermittent finger pricks still having to be used to monitor blood glucose. Continuous methods with potential and tested so far, such as enzyme electrodes, have proved to be unreliable and, being invasive, receive poor patient compliance. The Strathclyde – Kings College approach is to use the fluorescence decay of an encapsulated probe molecule inserted as a smart tattoo or optical fibre in the subcutaneous tissue and measured using an optical fibre-coupled pocket size fluorometer.

Fluorescence of microcapsules in the absence (left) and presence (right) of glucose. The microcapsules were fabricated using a Badan labelled and genetically modified glucose binding protein adsorbed on a CaCO3 template and encapsulated using alternating nano-layers of poly-L-lysine and heparin.

Using fluorescence decay as a measurement in medical sensing has the advantages of high sensitivity, accurate calibration and independence from both probe concentration fluctuations and background interference. As part of the £5M EPSRC/SFC Science and Innovation Award in Nanometrology led by David Birch, the Kings College team led by Professor John Pickup have successfully achieved layer-by-layer encapsulation of a glucose binding protein (GBP) labelled with the environmentally sensitive dye Badan. The Badan-GBP sensor shows a remarkable increase in its fluorescence intensity and decay time in the presence of glucose over the relevant metabolic glucose range of 5 – 30 mM. As glucose binds the protein closes and the dye is shielded from the higher polarity of water and its fluorescence intensity increases by as much as 300%. Olaf Rolinski performed the first decay time measurements on this system in buffer order to demonstrate its feasibility and these initial results have since been reproduced in plasma and recently published in Biosensors & Bioelectronics (Saxl et al 24, 3229-3234, 2009) with the next stages of the research set to include medical trials. 

[DJSB]