Defect Textures

The main quality attributes of fruits are appearance (colour, size, shape, lack of defects), texture and flavour (ripeness). Consumer satisfaction, however, relates... 

Parolari, G., Virgili, R., and Schivazzappa, C. (1994). Relationship between cathepsin B activity and compositional parameters in dry-cured hams of normal and defective texture. Meat Set 38, 117-122. 

Walker, L. Wagner, N. Rheology of region I flow in a lyotropic liquid-crystal polymer the effects of defect texture. J. Rheol. 1994, 38 (5), 1525-1547. 

Fig. 49 The homeotropic and rectilinear defect textures of the hexagonal columnar phase of supermolecule 43 (xlOO)...

The mesophase defect textures exhibited by 47 were typical of those normally found for a chiral nematic phase, except they were only revealed upon annealing, which is probably a function of the viscosity of the material. Thus the sample was annealed just below the clearing point. After 24 h, large areas of the preparation evolved to show fingerprint defects and the Grandjean plane... 

Plate 1. The defect texture of the TGBA phase, under crossed polars, formed on coohng from the isotropic hquid (xlOO). The textures show both platelets and Grandjean planar regions (associated with a helical macrostructure)... 

The formation of the TGBA phase from the isotropic liquid can also be observed in free standing films. The defects formed in this case tend to be filamentary in nature, see Plate 8. Such a texture is not normally seen in free standing films of other liquid crystals, and therefore the presence of this defect texture is diagnostic for the characterization of TGB phases. In addition to the observation of such filamentary textures in free standing films, filaments were also observed embedded in homeotropically aligned smectic A phases, see Plate 9. 

POM), the Schlieren and homeotropic defect textures of the nematic phase, and the focal conic and homeotropic defect textures of the smectic A phase could be observed (Fig. 4.3). In addition, the parallel and perpendicular dielectric permittivities of mixtures of the GNPs dispersed in host nematic LCs were determined by using one-cell method , which was reported by Clark et al. [47 9]. 

Fig. 4.3 a, b Homeotropic and schlieren textures of the nematic phase of 8CB containing 5 wt% 1 coated GNPs. c Sheared nematic texture near to the edge of the cover slip, d Focal-conic defect texture of the smectic A phase. Magnification xlOO [46], Copyright from Wiley-VCH 2011... 

Cubic phases (Cub) are mesophases of cubic symmetry (Diele, 2002). Because of their high symmetry, their physical properties are no Imiger anisotropic. No defect texture is observed by polarizing optical microscopy (POM vide infra) and the image between crossed polarizers remains black. The cubic mesophases are very viscous and often their formation kinetics is very slow. Although cubic mesophases are very common for lyotropic LCs, where a cubic phase is possible between any pair of phases, there are only relatively few examples of cubic mesophases in thermotropic LCs. Whereas a cubic mesophase can be relatively easily detected when it is present between two anisotmpic mesophases, it is difficult to observe the formation of the cubic phase when it is formed by cooling an isotropic liquid. In this case, a deformatirMi of air bubbles in the melt is observed, as well as a sharp increase in the viscosity of the liquid. 

The identification of hexagonal columnar phases is relatively straight-forward. The defect textures seen in the microscope at 100 x magnification show fan-like domains, however, they lack elliptical and hyperbolic disclinations that are present for lamellar phases, see Fig. 19. 

The current-potential characteristics (Fig. 9.20), which are the most indicative for practical fuel cell performance, were also investigated to select the optimal and the most advantageous catalyst support from nanotubular material. It is clearly seen that KOH-activated nanotubes with a defected texture, enriched in oxygen and aggravated conductivity, show the worse characteristic, whereas graphitized NTs have the best performance. However, templated nanotubes show definitively better performance than raw catalj ic nanotubes, most probably due to the wide central canal that accelerates diffusion of reagents as well as oxidation products. 

L. M. Walker, W. A. Kernick, and N. J. Wagner, In situ analysis of the defect texture in liquid crystal polymer solutions under shear. Macromolecules 30,508-514 (1997). 

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