Role of surfactant in the stability of liquid crystal-based nanocolloids.

We examine the dependence of liquid crystalline nanocolloid formation and stability on surfactant. Nanocolloids composed of polymerizable liquid crystal mesogens and cross-linking agents and capped with either ionic or nonionic surfactants are prepared via the miniemulsion technique. Colloids synthesized with anionic surfactant were stable and displayed 2D hexagonal packing when deposited via slow vertical pulling of the silicon substrate from an aqueous suspension. Liquid crystal nanocolloids stabilized with the nonionic, polar polymer polyvinyl alcohol (PVA) were stable in aqueous environments but coalesced upon drying to form relatively large, well-defined crystal-like structures with uniform birefringence. SEM images reveal that the coalesced structures have mesalike features. Polarized light, atomic force, and polarized Raman microscopy of these structures indicate that the liquid crystal molecules are arranged with their long molecular axis slightly tilted with respect to the surface normal. A mechanism is proposed to explain the formation of the mesalike structures from the nanocolloids. These studies provide fundamental insight into the incorporation and stabilization of polymerizable liquid crystal molecules into nanovolumes and open up opportunities for the incorporation of functionality and anisotropy into isotropically shaped nanocolloids.

A comparison of email versus letter threat contacts toward members of the United States Congress.

To better understand inappropriate correspondence sent to public officials, 301 letter cases and 99 email cases were randomly selected from the United States Capitol Police investigative case files and compared. Results indicate that letter writers were significantly more likely than emailers to exhibit indicators of serious mental illness (SMI), engage in target dispersion, use multiple methods of contact, and make a problematic approach toward their target. Emailers were significantly more likely than letter writers to focus on government concerns, use obscene language, and display disorganization in their writing. Also, letter writers tended to be significantly older, have more criminal history, and write longer communications. A multivariate model found that disorganization, SMI symptoms, problematic physical approach, and target dispersion significantly differentiated between the correspondence groups. The group differences illuminated by this study reveal that letter writers are engaging in behavior that is higher risk for problematic approach than are emailers.