Structural heterogeneity

One of the primary tasks in connection with the use of AE method is to identify defects by the AE parameters. For identification of nature of the destruction centre in the polymeric composites it is necessary to consider the peculiarities of their heterogeneous structure, that is presence of at least two different components (filler and connector), and also boundary transitional layers. 

The ideas developed in this chapter are descriptive of shock waves in fluids. Solids have many significant features that distinguish them from liquids and gases, such as shear strength, polymorphic phase transformations, heterogeneous structure, anisotropy, and viscoplastic behavior. The influences of these special properties of solids on shock compression are the topics of several of the other chapters, and for the most part are ignored in this introduction to the basic principles of shock compression. 

In general, the water uptake of D films tended to be higher than that of / films, but a more significant difference was shown by microhardness measurements. The results obtained with all three vehicles showed that the D areas were significantly softer than the / areas and that the distribution of the hardness values corresponded to that of the resistances. It was concluded that these films have a very heterogeneous structure and that / and D areas are brought about by differences in crosslinking density within the film. 

It appears that during the drying of paint or varnish films the presence of solvent molecules interferes with the process of cross-linking consequently the films have a heterogeneous structure and films of improved protective quality arise when solvents are eliminated. 

Mixing is the key step whose results affect all the processing Flow properties reflect the heterogeneous structure ... 

As discussed above, lipid membranes are dynamic structures with heterogeneous structure involving different lipid domains. The coexistence of different kinds of domains implies that boundaries must exist. The appearance of leaky interfacial regions, or defects, has been suggested to play a role in abrupt changes in solute permeabilities in the two-phase coexistence regions [91,92]. 

If an inert good solvent is used in solution polymerization, the gel thus obtained will have a supercoiled (expanded) structure (Gel B). Gel B swells in good solvents much more than Gel A which is synthesized in bulk. If the amount of the crosslinking divinyl monomer in the reaction mixture is increased while the amount of solvent remains constant, highly crosslinked networks are formed that cannot absorb all solvent molecules present in the reaction mixture and a heterogeneous structure results (Gel C). A part of the solvent separates from the gel phase during polymerization and the formed Gel C consists of two continuous phases, a gel and a solvent phase. If the amount of solvent is further increased, a... 

Figure 5.4 Electron micrograph showing demixing of D-Glu-12 helices from L-Man-8 tubules to form heterogeneous structures (bar = 500 nm). Reprinted with permission from Ref. 31. Copyright 1990 by the American Chemical Society.

Asakura, T., Yao, J. M., Yamane, T., Umemura, K., and Ultrich, A. S. (2002b). Heterogeneous structure of silk fibres from Bombyx mod resolved by C-13 solid-state NMR spectroscopy./. Am. Chem. Soc. 124, 8794-8795. 

Fujiki, T., Concept of Secondary Heterogeneous Structure of Long-Chain Branched Poiyethyiene, /. Appl. Polym. Set, 15, 47 (1971)... 

Plant cell walls are complex, heterogeneous structures composed mainly of polymers, such as cellulose, hemicelluloses, and lignins. In spite of several decades of research, cell wall assembly and the biosynthesis and ultimate biodegradative pathways of individual polymers are still far from being fully understood. One simple example will suffice Even today, no enzyme capable of catalyzing cellulose formation in vitro has been obtained. 

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