Surface structure yield stress

In conclusion to this section let us discuss the problem of interaction between a dispersion medium and filler. It was noted above that by varying intermoecular interaction on the filler s surface the yield stress may be varied over a wide range as a measure of strength of the structure being formed. 

Fry (11,12) has conducted two studies on the effects of wall shear on the endothelial lining of the aortic wall. He found that the endothelial cells on the vessel wall could be damaged at wall-shear stresses of about 400 dynes/cm and could be eroded off the vessel wall at shear stresses of about 950 dynes/cm. He observed that when the endothelial surface was exposed to shearing stresses above some critical value (400 dynes/cm2) the cells began to suffer structural and chemical changes. The critical stress is known as the "yielding" stress. 

Variously structured nickel films also produced some very peculiar product distributions," as they did with ethane at 393-433 K on (111) and (100) oriented films gave propane-r/g and (usually) -d2 as the major products, but randomly orientated but sintered film at 400-435 K yielded propane-di and -d%, and an unsintered film at 273 K gave only the -d isomer. These results closely resemble those obtained with ethane, and lend stress to the importance of surface structure in deciding what intermediates are formed and how they react. The absence of results for single crystal surfaces of nickel is sorely felt. 

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