Longitudinal Morphology

As-spun synthetic fibers are typically straight. However, some synthetic fibers possess a wavy, undulating stractuie, which is called crimp. Crimped fibers can be produced by different methods. The most straightforward method is to introduce crimp by thermomechanical means. In this method, straight fibers are mechanically deformed into a crimped structure, followed by heat setting. 

An alternative approach is to produce self-crimped fibers by using the bicomponent fiber structures discussed in section 3.5.1. The two components in the fibers can be different polymers or the same polymer but with different average molecular weights, different molecular weight distributions, different additives, or other structural differences. The key to introduce self-crimp is to design stmc-tural asymmetry across the fiber cross-section. 

and Kudo, Y, High-Speed Melt Spinning of Bicomponent Fibers Mechanism of Fiber Structure Development in Polyfethylene tere-phthalate)/Propylene System , Journal of Applied Polymer Science, 62, 1913-1924, 1996. 

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Some of the longitudinal morphologies that can be developed in manufactured fibers. 

In hardwoods, morphological structural elements in longitudinal series comprise the segmented structure termed vessel . Vessels, which are exposed in transverse section, constitute about 10-46% of the stem volume in deciduous hardwoods and are cells of relatively large diameters (50-300 p.m). Vessels have in short the appearance of open vertical tubes within the wood structure because their end walls have partially dissolved. By comparison, the hardwood vessel diameter can be as much a 10 times the diameter of a softwood fiber. 

The first vector lists the relevant ecological domains of the river system the hydrological character the longitudinal, vertical and lateral connectivity aspects of sediment transport and morphology landscape features and biotopes as well as relevant aspects of aquatic ecosystems. 

The question that we need to ask ourselves is whether the longitudinal dispersion can be predicted accurately for these rivers. Equation (6.35), which predicts that >l/(m+/i) = constant, is shown in Table 6.4 to have a large range of constants, probably because of the variations in cross section and morphology seen in natural streams. Fisher (1973) observed that this constant seemed to depend on mean surface width, W, and substituted W for h in the numerator of equation (6.34) to develop the following empirical equation to characterize longitudinal dispersion coefficient in rivers ... 

Researchers have been dogged by the inability to delineate between myoactivity and neuroactivity, mainly because the isolation of individual tissues by dissection is extremely difficult. This obstruction precipitated the development of methods to generate dispersed muscle fibres, and these preparations provided the first visual information on individual muscle fibres and/or muscle fibre bundles three morphologically distinct fibre types were recorded from Schistosoma mansoni, frayed, spindle-shaped and crescent-shaped fibres (Day et al., 1993). Although the location of all three fibre types within the worm is not clear, it has been suggested that the frayed fibres originate from the longitudinal muscle layer. 

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