Unaligned Samples

An aligned monodomain of a nematic liquid crystal is characterized by a single director n. However, in imperfectly aligned or unaligned samples the director varies tlirough space. The appropriate tensor order parameter to describe the director field is then... 

The quadrupole splitting, Ai q of 117.8 kHz observed for the oriented block of [2,2- H2]Gly labeled silk fibroin fiber is the same as the value in the spectrum of an unaligned sample as shown in Fig. 23.9(B). Therefore, if the latter quadrupole splitting is used to provide a value of the proportionality constant, (3/4)e qQ/h, which describes the relationship between the quadrupole splitting and the angle CD (the angle of the C H bond vector of Gly relative to the fiber axis) > CD is calculated as 90°. By taking into account an... 

The solid-state NMR spectrum of an oriented block of the [3,3,3- HsjAla labeled silk fibroin fiber was also observed. The quadrupole splitting, Avq, is 39.8 kHz and is the same as the value in the spectrum of the unaligned sample. This is the same as the case of the [2,2- H2]Gly labeled silk fibroin fiber. The smaller value of the quadrupole splitting for the Ala site indicates the presence of three-fold fast rotation about the Ca-C/3 axis [50, 72]. This... 

A normal, unaligned sample of a nematic material does not usually have a director that points in the same direction in all regions of the sample. The director changes throughout the sample and at positions where the director abmptly changes direction, no specific... 

Ferroelectric chiral smectic C phases lack inversion symmetry, and are distinguished by spontaneous helicoidal electric polarization, The first experiment to measure SHG from ferroelectric liquid crystals was carried out [89] on unaligned samples under a dc electric field. Phase-matched SHG in ferroelectric liquid crystals has been carried out by using an electric field to unwind the helix [90]. Mechanical deformations in chiral smectic C elastomers have been shown to give rise to SHG [91]. A great deal of work has been carried out recently in studying SHG in ferroelectric liquid crys-... 

The columnar phases of metallomesogens have the electrical properties of molecular semiconductors [77-84]. Figure 22 presents the Arrhenius plots of the a.c. conductivity (copper phthalocyanines (13) determined by Van der Pol et al. [83]. The conductivity increases with increasing temperature. The activation energy is approximately 0.5-0.6 eV at 175 °C for the compounds 13 with R=0C8H 7 and OC12H25. 

Figure 22. Arrhenius plots of the electrical conductivity (o) of unaligned samples of copper phlhalocy-anines(13). Data points (A) R=H ( ) R=OCHgH,7 ( ) R=OCi2H25. a slight increase in the conductivity is observed for the last compound at the transition from the mesophase to the crystalline phase (indicated by the arrow). (From Van der Pol et al. [83], reproduced by permission of Taylor and Francis Ltd.).

Figure 23. Temperature dependence of the d.c. conductivity (

The helical structure of F-actin itself. This information is not ideally obtained in an unaligned sample aligned scattering techniques would be preferred in this case. 

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