53 layer fibril orientations

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... 

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... 

The waU of a cellulose fiber in turn exhibits a complex, laminar structure, wherein each layer consists of smaller, unidirectional fibers, or microfibrils, in the range of 5 to 50 run wide, and anywhere from 100 run to several microns long, depending on the source [33]. Each layer of microfibrils varies with respect to fibril orientation (microfibril angle). Microfibrils in turn have a composite stracture, consisting of slender cellulose crystallites, or whiskers, with diameters on the order of 5 run, which are threaded together and embedded in the microfibrils between amorphous regions of cellulose and hemicellulose [34]. Hence, cellulose can be viewed as a composite material from the nanoscale perspective (whiskers in microfibrils), the microscopic perspective (microfibrils in fibers), and the macroscopic perspective (fibers in wood). 

Figure 11.14. SEM micrographs of PP/PIDT MFCs (a) uniaxial cryofracture surface, (b) area showing excellent fibril orientation, (c) crossply cryofracture surface showing interface between plies and a thin layer (arrow) of neat PP, (d) area with fibrils running transversely, (e) random cryofracture surface with a large area aligned parallel with sample, (f) change in orientation between the upper left and the center [111]...

The dominating S2-layer contains the cellulose micro fibrils orientated under an acute angle toward the fiber axis. Such orientation of the microfibrils imparts to natural cellulose fibers increased mechanical properties. The microfibrils of the cell wall consist of elementary nanofibrils, and each such fibril is built of ordered nanocrystallites and low ordered non-crystalline (amorphous] domains statistically alternated along the fibril. The early investigations supposed the presence in various cellulose samples of elementary nanofibrils having a constant lateral size of 3.5 nm (Manley, 1964 Muhlenthaler, 1969]. However, recent... 

Although the osteon has been the subject of numerous studies for decades, its detailed stracture is still a matter of dispute. It is understood that the lamellar arrangement is a midtilayer stracture where each fibrous layer is oriented in a different direction. The correlation of the mineralized fibril stracture to the lamellar mechanical properties over entire osteons is not yet fully understood. 

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. 

Figure 2 The lamellar substructure of a fibril. (a) Reciprocal positions of crystalline lamellae as a result of fiber annealing. (b) The situation after relaxation of stress affecting TTM. ai.2 - average angle of orientation of TTM CL - crystalline lamellae CB - crystalline blocks (crystallites) mF -border of microfibrils and F - fibril. In order to simplify it was assumed that (1) there are the taut tie molecules (TTM) only in the separating layers, (2) the axis of the fibril is parallel to the fiber axis.

Benzene-ring orientation 100 Boundary layer 151 Broad line NMR 197 Buckling of fibrils 140... 

The major component of the framework is a-chitin [16,18]. All we know about its structural motif at the nanometer level is that the chitin chains of the whole tooth do have a preferred orientation. In another phylum (the Crustacea), chitin frameworks are organized into layers, in which the fibrils of each layer have a preferred orientation. These have been compared to liquid crystals [19]. The orientation direction changes from layer to layer, usually by discrete angles and in one direction. Thus a plywood-like structure is formed. 

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