Fibril distribution

Although there is a strong molecular and nanoscopic driving force behind our understanding of the functionality of collagen fibrillar structures, the mesoscopic and macroscopic properties of the tissue are where the structural integrity manifests itself. One of the differences in mechanical resistive properties between tissues such as skin and tendon is the feltwork nature of fibril distribution in skin. This allows resistance to strain to occur within a two-dimensional plane. In contrast, tendon is required (normally) to resist strain only along its axis. 

Another possibility for the presence of inaccessible surfeces is distortions within the fibril, interior surfeces. Some mechanical treatment of wood fibers shows a strong impact on CP/MAS spectra (22). Distortions of the cellulose I structure within the fibril, distributed along the fibril, may also constitute zones of geometrical discontinuities. 

Lyocell fibers consist entirely of cellulose. One fiber is composed of uniformly thick fibrils distributed over the whole cross section. This structure is another difference from the traditional fibers from regenerated cellulose, which is usually characterized by a core-sheath structure. The evolution of this fibrillar structure can be explained by the rapid segregation processes occurring during the regeneration of the cellulose from the spinning solution. This structure (Fig. 2.30) imparts the particular properties of the lyocell fiber. 

The paste-extmsion process includes the incorporation of ca 16—25 wt % of the lubricant (usually a petroleum fraction) the mixture is roUed to obtain uniform lubricant distribution. This wetted powder is shaped into a preform at low pressure (2.0—7.8 MPa or 19—77 atm) which is pushed through a die mounted in the extmder at ambient temperature. The shear stress exerted on the powder during extmsion confers longitudinal strength to the polymer by fibrillation. The lubricant is evaporated and the extmdate is sintered at ca 380°C. 

The formation of a fibrillar structure in TLCP blends makes the mechanical properties of this kind of composites similar to those of conventional fiber reinforced thermoplastics [11,26]. However, because the molecular orientation and fibrillation of TLCPs are generally flow-induced, the formation, distribution, and alignment of these droplets and fibers are considerably more processing-dependent. We do not know ... 

In all cases of the processing conditions, TLCP domains were well dispersed and deformed to droplets in the core layer, but there was only a narrow distribution of their aspect ratio (about Hd 6) and less orientation. In both transition and skin layers, the domains were also well dispersed, but more oriented and fibrillated in the flow direction. From this reason, we give the distribution of aspect ratio Ud) and fiber number (N) versus fiber length class in Fig. 22, only for skin and transition layers, respectively. 

Vaughan L et al (1988) D-periodic distribution of collagen type IX along cartilage fibrils. J Cell Biol 106(3) 991-997... 

For the transformation of the macrocomposite model to a molecular composite model for the ultimate strength of the fibre the following assumptions are made (1) the rods in the macrocomposite are replaced by the parallel-oriented polymer chains or by larger entities like bundles of chains forming fibrils and (2) the function of the matrix in the composite, in particular the rod-matrix interface, is taken over by the intermolecular bonds between the chains or fibrils. In order to evaluate the effect of the chain length distribution on the ultimate strength the monodisperse distribution, the Flory distribution, the half-Gauss and the uniform distribution are considered. 

The structural model of GebeF and its recent overhaul by Schmidt-Rohr o show no indicahon of hydrophobic pores these models correspond to hydrated cylindrical fibrils or water-containing inverted cylinders with rather uniform distribution of charged surface groups at polymer-water interfaces. 

Dhein S, Poeppel P, Kriisemann K, Gottwald M Changes in connexin 43 distribution after 24 hours of atrial fibrillation. Proc Intern Gap Junction Conference, Key Largo, 1997a pp 51. 

Amyloid fibrils formed from a-synuclein have been found in Lewy bodies of patients with Parkinson s disease.64 Spin labels were introduced at 36 positions between amino acid 5 and 136 of a-synuclein. Distributions of interspin distances between the same labels on neighboring chains were determined by analysis of CW line-shapes in solution. For the fibrils analysis of the percent of molecules with distances <15 A, 15-20 A, and > 20 A revealed a highly ordered and specifically folded core region of 70 amino acids ( residues 34 to 101). In contrast, the N terminus region is structurally heterogeneous and the C terminus appears to be completely unfolded. 

With the methods discussed in Chapter 6.5. we are able to produce small polymer particles from solutions of polymers in compressed gases [52,53], First results indicate that, depending on the process conditions and the nozzle design, a wide variety of spherical particles, small fibrils, or longer fibres can be obtained. Sometimes the particle-size distribution obtained is very uniform, in other cases, a wide variety of sizes is obtained. In some cases, the monomer was used as solvent for the equivalent polymer. The particles, fibrils, etc., obtained may be used for direct spray-coating of surfaces but they also offer new opportunities as raw materials in their own right. New products are underway that are based on such technologies. 

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