Infrared (IR) gas sensors are a minority of the general gas-sensing instrument market. They compete with devices based upon gas interaction with surfaces such as electrochemical sensors. They di¬er in that IR devices are selective, can`fail to safety' and are potentially intrinsically safe. However, they tend to be more expensive, using existing technology. We may expect that in due course the impact of all solid-state semiconductor mid-IR technology should revolutionize this situation and lead to signi cant growth in IR gas sensing.

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A plasma confined by an externally applied curved magnetic field will show an accelerated motion ('drift') to the region of weaker field. This motion is analysed in three different ways, In the first description the magnetohydrodynamic equation of motion is used, with the only assumption that no appreciable transverse accelerations are present. Secondly, the well-known microscopic picture (charge separation leading to E/B drift) is analysed for a ,!3 < 1 plasma with the guiding centre approximation. In the third model the change in the total energy of the system caused by a small outward displacement is considered. I n all models the outward acceleration is found to be uR = 2k(T, + ZT,)/Rml where R is the radius of curvature of the field. The energy for the outward motion is partly supplied by the primary circuit and partly by an expansion of the plasma.

We construct a kink solution on a non-BPS D-brane using Berkovits' formulation of superstring field theory in the level truncation scheme. The tension of the kink reproduces 95% of the expected BPS D-brane tension. We also find a lump-like solution which is interpreted as a kink-antikink pair, and investigate some of its properties. These results may be considered as successful tests of Berkovits' superstring field theory combined with the modified level truncation scheme.