Defect rates, acceleration

Qualitative examples abound. Perfect crystals of sodium carbonate, sulfate, or phosphate may be kept for years without efflorescing, although if scratched, they begin to do so immediately. Too strongly heated or burned lime or plaster of Paris takes up the first traces of water only with difficulty. Reactions of this type tend to be autocat-alytic. The initial rate is slow, due to the absence of the necessary linear interface, but the rate accelerates as more and more product is formed. See Refs. 147-153 for other examples. Ruckenstein [154] has discussed a kinetic model based on nucleation theory. There is certainly evidence that patches of product may be present, as in the oxidation of Mo(lOO) surfaces [155], and that surface defects are important [156]. There may be catalysis thus reaction VII-27 is catalyzed by water vapor [157]. A topotactic reaction is one where the product or products retain the external crystalline shape of the reactant crystal [158]. More often, however, there is a complicated morphology with pitting, cracking, and pore formation, as with calcium carbonate [159]. 

On the other hand, when the deposit is less noble than the substrate (Fig. 12.13(b)), the simation reverses. If there is a defect, the coating becomes the anode while the exposed substrate is cathodically protected. Because the surface of the coating largely exceeds that of the defect, the acceleration of the corrosion rate of the coating due to... 

Figure 5. Effect of ion bombardment on the decay rate of a 1-D grating of period 17 pm on An (100) at 993C. The ion damage greatly accelerates the decay either by formation of surface defects or by removing the impurities. Similar effects are produced by oxygen exposure. The ordinate is proportional to the grating amplitude.

A serious complication of HIV infection is HIV-associated thrombocytopenia, This results from immune-mediated platelet destruction and decreased or defective platelet production due to infection of megakaryocytes with HIV-1 (211). HIV-related thrombocytopenia may be associated with an accelerated progression to AIDS and decreased survival rates. Hence management of thrombocytopenia in AIDS patient is crucial to prevent severe complications, Severe bleeding complications in HIV-infected hemophilia patients treated with protease inhibitors... 

If export competence is associated with a loosely folded precursor, then parameters that accelerate folding or stabilize folded states should impede export. This relationship has also been explored in E. coli using a DHFR fusion protein. At low levels of synthesis, a hybrid protein consisting of the signal peptide and the first 153 amino acid residues of OmpA joined to DHFR is efficiently secreted. However, addition of trimethoprim imparts a kinetic defect in the secretion rate of the hybrid protein. The effect of trimethoprim is dependent on the presence of a full length, presumably active, DHFR moiety, indicating that secretion in vivo is inhibited by stabilization of the native DHFR structure (FreudI et ai, 1988). 

---