The experimental observation of a phase transition between two uniaxial nematic liquid-crystalline phases is reported. High-resolution x-ray scattering and ac calorimetric studies on binary mixtures of octyl- and decyloxyphenyl-nitrobenzoyloxy benzoates show evidence of a first-order transition between two nematic phases with different types of short-range smectic order. This transition is observed in the vicinity of the termination of the smectic-Ad-smectic-A1 phase boundary, in accordance with theoretical predictions.
The melting of lipid-based microcylinders (tubules) has been investigated for systems with single and multiple bilayer walls using high field, magnetic birefringence, and precision microcalorimetry. The pretransitional behavior of both the magnetic birefringence and the specific heat is very different in tubules with a single bilayer wall from that of tubules with multiple bilayers.