2,455 research outputs found
Reflection-less device allows electromagnetic warp drive
One of the striking properties of artificially structured materials is the
negative refraction, an optical feature that known natural materials do not
exhibit. Here, we propose a simple design, composed of two parallel layers of
materials with different refraction indices , that constructs perfect
reflection-less devices. The electromagnetic waves can tunnel from one layer to
the other, a feature that resembles a truncation of the physical space leading
to an electromagnetic warp drive. Since the refractive indices do not require
any large values, this method demonstrates for the first time the practical
feasibility of guiding electromagnetic fields in complete absence of reflection
phenomena and without degradation of transmission efficiency at all.Comment: 8 pages, 7 figure
Polarized Helium to Image the Lung
The main findings of the european PHIL project (Polarised Helium to Image the
Lung) are reported. State of the art optical pumping techniques for polarising
^3He gas are described. MRI methodological improvements allow dynamical
ventilation images with a good resolution, ultimately limited by gas diffusion.
Diffusion imaging appears as a robust method of lung diagnosis. A discussion of
the potential advantage of low field MRI is presented. Selected PHIL results
for emphysema are given, with the perspectives that this joint work opens up
for the future of respiratory medicine.Comment: To be published in Proc. ICAP 2004 (19th Int. Conf. on Atomic
Physics, Rio, July 26-30 2004
Inversible Max-Plus Algebras and Integrable systems
We present an extended version of max-plus algebra which includes the inverse
operator of "max". This algebra enables us to ultra-discretize the system
including subtractions and obtain new ultra-discrete equations. The known
ultra-discrete equations can also be recovered by this construction.Comment: 21 page
Two pion electroproduction
We have extended a model for the reaction to virtual
photons and selected the diagrams which have a in the final state. The
agreement found with the and reactions is good. The sensitivity of the results to
transition form factors is also studied. The present reaction,
selecting a particular final state, is an extra test for models of the
amplitude.Comment: 4 pages, 2 figures, Talk given at Meson 2000 Workshop, Krakow,
Poland, 19-23 May 200
NMR Time Reversal Experiments in Highly Polarised Liquid 3He-4He Mixtures
Long-range magnetic interactions in highly magnetised liquids
(laser-polarised 3He-4He dilute mixtures at 1 K in our experiment) introduce a
significant non-linear and non-local contribution to the evolution of nuclear
magnetisation that leads to instabilities during free precession. We recently
demonstrated that a multi-echo NMR sequence, based on the magic sandwich pulse
scheme developed for solid-state NMR, can be used to stabilise the
magnetisation against the effect of distant dipolar fields. Here, we report
investigations of echo attenuation in an applied field gradient that show the
potential of this NMR sequence for spin diffusion measurements at high
magnetisation densities.Comment: Accepted for publication in the Journal of Low Temperature Physic
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