Order calamities

Liquid crystals may be divided into two broad categories, thermotropic and lyotropic, according to the principal means of breaking down the complete order of the soHd state. Thermotropic Hquid crystals result from the melting of mesogenic soHds due to an increase in temperature. Both pure substances and mixtures form thermotropic Hquid crystals. In order for a mixture to be a thermotropic Hquid crystal, the different components must be completely miscible. Table 1 contains a few examples of the many Hquid crystal forming compounds (2). Much more is known about calamitic (rod-Hke) Hquid crystals then discotic (disk-like) Hquid crystals, since the latter were discovered only recendy. Therefore, most of this section deals exclusively with calamities, with brief coverage of discotics at the end. 

Flexocoefficients have also been obtained from the threshold voltages and wave numbers of electric field-induced flexoelectric instabilities (which are discussed in more detaii in Chapter 4 by Buka et al. ) for ClPbislOBB and for the molecule 4-((3-(4-(4-(decyloxy) benzoyloxy)benzoyloxy) phenylimino) methyl)-3-hydroxyphenyl 4-(6-(4 -cyanobiphenyl-4-yloxy)hexyloxy) benzoate (BCCB), which is a dimer composed of a calamitic and a BC molecule. In both cases the flexocoefficients were found to have the same order as that of calamities. 

Complex reactive transport models are integrated with geophysical information systems appHed to radionuclides. The behavior of Sr, Co, Ru, and can be used for breakthrough proposes. Short pulses (of 1-28 days) with 100% activity can be chosen as input signal in order to simulate a calamity at the recharge facilities. 

The nematic phase of nonlinear mesogens may be biaxial - a translationally disordered fluid phase with two directors n and o specifying the orientational order (Fig. 5.3). Biaxial order in a nematic is predicted to occur [29] if the shape anisotropy of the idealized molecule (discoid) representing the nonlinear meso-gen is appropriately intermediate between the prolate shape of calamities and the oblate shape of discotics. Discoid-shaped mesogens lend themselves to a variety of stratified phases. Ferroelectric (Sapp) and antiferroelectric (Sapa) layer motifs in the normal smectic phases of discoid-shaped mesogens are readily envisioned (Fig. 5.4), but less obvious is the possibility of generating chiral supramolecular structures from such achiral discoid-shaped mesogens (Fig. 5.5) [30]. 

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