The electrical conductivity of heavily doped polyacetylene, (CH)", has been measured from room temperature down to 0.4 mK and in magnetic fields from 0 to 290 Oe. Below 30 mK the resistance increases logarithmically with decreasing temperature, and decreases roughly logarithmically with increasing magnetic field. The results are compared to recent localization and interaction models of electron transport in systems of reduced dimensionality.Linear polyacetylene is the simplest conjugated polymer, consisting of a chain of carbon atoms, along which m electrons overlap and form a quasi-onedimensional energy band. Interest in this semiconducting polymer has been stimulated by the successful demonstration of doping; the room-temperature electrical conductivity of (CH)" films can be varied over 12 orders of magnitude. The qualitative
Texture transitions in superfluid 3 He-A are produced by a moving bellows system controlling mass flow. These texture changes are caused by the competition of magnetic, flow, and gradient energies. We have located the boundary of a region of stability with v* s II / IIH. This boundary may be related to theoretical predictions of a transition to helical textures, but there is substantial disagreement with the theory over the maximum magnitude of the superfluid velocity in what we interpret as uniform textures. PACS numbers: 67.50.Fi, 43.35. + d, 47.20. + m Textures in superfluid 3 He are a striking manifestation of the symmetry of the order parameter. To date, however, only a few relatively simple textures have been studied. We report here the first measurements on nontrivial dynamic textures in the A phase which are produced in a controlled fashion and which exhibit great sensitivity to the effect of superfluid flow. We have located a boundary between the uniform texture and a complex texture by varying the magnetic field while maintaining a constant mass flow.
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