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Gelation is an efficient way to fabricate fibrous protein materials. Briefly, it is an aggregation process where protein molecules assembly from a random structure into an organized structure such as nanofibrillar networks. According to their mechanisms, the fibrous proteins gelation can be classified into physical gelation and chemical gelation. The physical gelation is formed by the conformational transformation of fibroin proteins, which can be triggered by temperature, concentration, pH, or shear force. On the other hand, the chemical gelation is to cross-link fibrous proteins through chemical and/or enzymatic reactions. In this chapter, we summarize the protocols for preparing fibrous protein hydrogels, including both physical and chemical methods. The mechanisms of these gelation methods are also highlighted.

The nonlinear parameter N (phase shift parameter) of a medium is considered to be related closely to the state of tissue at both levels of molecules and cells1),2),3),4). Hence, it is expected as one of the most significant promising new parameters for detection of disease such as cancer at their very early stages. As a concrete method the system which uses the pumping wave to give pressure variation and the probing ultrasonic waves to detect the resulting phase shift has been developed2).

In an earlier article (Weaire, 1985), one of the present authors reviewed some of the ideas and methods which have been aimed at the understanding of the random structure of amorphous solids and analogous two- dimensional structures, such as that of the 2d soap froth. The enigmatic title “The constraint of discord” was taken from a nineteenth century reference.