Colloidal Liquid Crystals Confined to Synthetic Tactoids

When a liquid crystal forming particles are confined to a spatial volume with dimensions comparable to that of their own size, they face a complex trade-off between their global tendency to align and the local constraints imposed by the boundary conditions. This interplay may lead to a non-trivial orientational patterns that strongly depend on the geometry of the confining volume. This novel regime of liquid crystalline behavior can be probed with colloidal particles that are macro-aggregates of biomolecules. Here we study director fields of filamentous fd-viruses in quasi-2D lens-shaped chambers that mimic the shape of tactoids, the nematic droplets that form during isotropic-nematic phase separation. By varying the size and aspect ratio of the chambers we force these particles into confinements that vary from circular to extremely spindle-like shapes and observe the director field using fluorescence microscopy. In the resulting phase diagram, next to configurations predicted earlier for 3D tactoids, we find a number of novel configurations. Using Monte Carlo Simulations, we show that these novel states are metastable, yet long-lived. Their multiplicity can be explained by the co-existence of multiple dynamic relaxation pathways leading to the final stable states.

“Not Everything That Shakes Is a Seizure”: Making the Determination of Test Article–Induced Convulsions in Toxicology Studies

Spontaneous unexpected events occasionally develop during the course of rodent preclinical toxicology studies. The presentation of serious adverse events on animal studies may require notification of these events to the Food and Drug Administration if the events are most likely the direct result of test article administration. Classical conditioning of emotional responses may occur over the course of a repeat-dose study and clinical observation calls of “convulsions” are reported to the study director and/or staff veterinarians. In the current heightened environment of most research laboratories related to general animal welfare issues, it is imperative to have an action plan that will help to elucidate the potential origins of these motor events. We provide 10 factors that should be considered to help the study director determine the most likely cause of these motor attacks as being organic or psychogenic in origin.