On the basis of linear hydrodynamics, we analyze the trajectory of particle-hedgehog systems, attracted by a -1/2 disclination (defect line) in a nematic liquid crystal. We show that, as with the interactions between like-particles, the interaction between a particle and a disclination has an electrostatic analogue, the splay replacing the electric field, except for the symmetry properties. The disclination thus attracts the beads along nonradial tracks and in a self-assembling process, or template mechanism, may build a microscopic necklace with them.

Conoscopic observations have been made on a mixture of potassium laurate, 1-decanol, and D2O in the discotic-uniaxial, biaxial, and cylindric-uniaxial nematic phases. The differences between the principal refractive indices have been measured, leading to a complete determination of the tensor order parameter in all the three phases. In the biaxial phase, the symmetric invariants of the order parameter are found to have a linear dependence on temperature, in good agreement with the prediction of the mean-field model.