Fibrils orientation

The isotropic microhardness properties of dentin contrast markedly with the anisotropic microhardness properties of various types of bone [64]. Microhardness is strongly dependent on crystal orientation, and less dependent on fibril orientation. Wang and Weiner [33] therefore proposed that the isotropy arises from a combination of structural features related to crystal orientation. The crystal layers in adjacent fibrils within the same bundle, are not aligned... 

Fig. 4 Description of a craze (a) with a Dugdale zone, and the local analysis (b) as a long strip representing the anisotropic craze structure made of main fibrils oriented along direction 2, connected with lateral cross-tie fibrils along direction 1...

Figure 13. Cell wall schematic diagram showing S , S2, arid S3 of secondary wall, primary wall, and their fibril orientations 6 with respect to...

These are covered with a sheath of para-crystaUine polyglucosan material surrounded by hemicellulose [29]. In most natural fibers, these micro-fibrils orient themselves at an angle to the fiber axis called the micro-fibril angle. The ultimate mechanical properties of natural fibers are found to be dependent on the microfibrillar angle. Gassan et al. have performed calculations on the elastic properties of natural fibers [30]. 

Oyler and Tycko have demonstrated that absolute, molecular-level structural information can be obtained from solid state NMR measurements on partially oriented amyloid fibrils.In particular, it has been shown that the direction of the fibril axis relative to a carbonyl CSA tensor can be determined from MAS sideband patterns in C NMR spectra of fibrils deposited on planar substrates. Deposition of fibrils on a planar substrate creates a highly anisotropic distribution of fibril orientations (hence, CSA tensor orientations) with most fibrils lying in the substrate plane. The anisotropic orientational distribution gives rise to distorted spinning sideband patterns in MAS spectra from which the fibril axis direction can be inferred. 

Fig. 8.10 A schematic diagram of the cylindrical fibrils oriented normal to a craze plane. For clarity the craze region is shown at (a) and the fibrils within it at (b). (Adapted by permission of Marcel Dekker Inc.)...

The fibril orientation in Figure 6 indicates that they were formed from material piled up in front of stylus due to plowing. Since this material is anchored to the sides of the wear tracl it becomes stretched and oriented into long fibrils. These fibrils make a large contribution to the lateral force exerted on the stylus. The high strength of oriented polyethylene ensures that failure initiates in the relatively unoriented material where the fibril is anchored to the side of the wear track. One end of the fibril is essentially tom from fhe matrix. Catastrophic fibril failure produces a large, rapid drop in lateral force and allows the stylus to junq> forward. This results in the sharp current spike coincident with the load (bop. 

Carboxymethyl Cellulose (CMC) -In vivo cellulose ribbon formation prevented normal fasciation of fibril bundles into a typical ribbon -Thinner ribbon width and smaller crystallite fibril size -Aggregates and pellicle show birefringence, and contain crossed, superimposed layers of cellulose fibrils oriented in parallel -Less resistant to stress... 

Several layers have to be distinguished in the wall thickness, not only by the macromolecular composition but also by the microflbril orientation, i.e., the angle between the fibril orientation and the longitudinal axis of the cell. Between two adjacent cells lies a highly lignified region called middle lamella. Both middle lamella and adjoining primary walls are sometimes referred to as compound middle lamella. The secondary cell wall is laid down after cell extension is... 

Figure 22 Model of mineralized collagen fibril orientation within lamellae and relative to the osteon axis. Redrawn, based on Wagermaier, W. Gupta, H. S. Gourrier, A. etal. Biointerphases2006, 1,1-5 and modified.

Figure 3. Temperature dependence of spacing of (002) in cellulose crystallite and the half value angle of (002) representing cellulose fibril orientation. 0, spacing of (002) , the half value angle of (002).

Band (d) at ca. 125 C comes from the deformation in the fibril orientation by the disorder in its conformation close to the surface of the cellular parts. 

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