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Review of the measurements of the strong coupling constant at LEP 2
Since 1995, LEP has steadily increased the center of mass energy of the
colliding beams, from the M_Z resonance to 133, 161 and 172 GeV. New
measurements of the strong coupling constant, alpha_s, at these energies have
been performed by the LEP experiments, L3, ALEPH, OPAL and DELPHI. In this
article, the new results are summarized, and combined with the previous LEP
measurement of alpha_s(M_Z) in order to obtain an updated LEP average of
alpha_s(M_Z) = 0.120 +- 0.005.Comment: 5-6 pages, 3 figures. Talk given at the DIS 97 conference, Chicago,
April 1997.Replacement: update figure 1. Also available here
http://hep.ph.liv.ac.uk/~martis
Entropy Production in Relativistic Binary Mixtures
In this paper we calculate the entropy production of a relativistic binary
mixture of inert dilute gases using kinetic theory. For this purpose we use the
covariant form of Boltzmann's equation which, when suitably transformed, yields
a formal expression for such quantity. Its physical meaning is extracted when
the distribution function is expanded in the gradients using the well-known
Chapman-Enskog method. Retaining the terms to first order, consistently with
Linear Irreversible Thermodynamics we show that indeed, the entropy production
can be expressed as a bilinear form of products between the fluxes and their
corresponding forces. The implications of this result are thoroughly discussed
Light Collimation and Focussing by a Thin Flat Metallic Slab
We present experimental and theoretical work showing that a flat metallic
slab can collimate and focus light impinging on the slab from a punctual
source. The effect is optimised when the radiation is around the bulk, not at
the surface, plasma frequency. And the smaller the imaginary part of the
permittivity is, the better the collimation. Experiments for Ag in the visible
as well as calculations are presented. We also discuss the interesting case of
the Aluminium whose imaginary part of the permittivity is very small at the
plasma frequency in UV radiation. Generalization to other materials and
radiations are also discussed.Comment: 6 pages, 3 figures. To be published on Optics Lette
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