Protection mechanism migration

Renger G and Wolff C (1977) Further evidence for dissipative energy migration via triplet states in photosynthesis. The protective mechanism of carotenoids in Rhodopseudomonas spheroides chromatophores. Biochim Biophys Acta 460 47-... 

A reduction in stabilizer concentration can take place in pipes as a protection mechanism against oxidation, migration, and extraction by water. The concentration profile of PE-MD pipe exposed to water internally and to air externally becomes asymmetric due to exposure. Figure 5.262 left. Maximum concentration shifts toward the pipe outer wall, because stabilizer reduction caused by extraction is higher on the inner pipe wall than reduction caused by oxidation on the outer pipe wall. If the same pipe is loaded both internally and externally by air, the concentration profile remains symmetric. Figure 5.262 right. A PB pipe exhibits a symmetric profile even under internal load by water and external load by air however, stabilizer concentration also decreases [191]. 

This interpretation of the experimental data is supported by the differences observed in the deactivation patterns and carbon contents after test, since one notorious effect of Hjp is the capacity to diminish the deactivation caused by coke deposition on the active sites [21,22]. This is supposed to be due to a reaction with the coke precursors, very likely a hydrogenolysis. In pure silica-aluminas, where no source of spillover is present, no special protection against deactivation should be observed. Indeed, the silica-aluminas lose most of their activity (about 80%) before reaching the steady-state and present the highest carbon contents after catalytic test. On the other hand, in the case of the mechanical mixtures, where spillover hydrogen is continuously produced by the CoMo/Si02 phase and can migrate to the silica-alumina surface, the predicted protection effect is noticed. The relative losses of activity are much lower... 

Where it is possible for flammable or toxic gas or vapor released within a hazardous area to migrate to the inlets for HVAC systems serving nonhazardous enclosed areas such as control rooms, detection systems should be installed in those HVAC inlets or connecting ductwork. Detection should be provided in HVAC system intakes if the building, room, or enclosure served is not electrically classified and a flammable (or toxic) gas or vapor could feasibly be drawn into the area, either by mechanical ventilation systems or by differential pressures. The detection system should alarm and automatically shutdown the HVAC to prevent gas or vapor concentration in the protected space from reaching the flammable or toxic range. 

Of all the commercially available organic and inorganic polymeric materials, RTV silicone elastomer has proved to he one of the most effective encapsulants used for mechanical and moisture protection of the Integrated Circuitry (1C) devices. A general overview of the RTV silicone elastomer and its commercial preparation and cure mechanism are described. Improved electrical performance of the RTV silicone encapsulant, by immobilizing the contaminant ions, such as Na, K" , Cl , with the addition of the heterocyclic poly-ethers as the contaminant ion scavengers seems to have a potential application as the contaminant ionic migration preventor in the electronic applications. 

There is no stable entity Al2+(aq) to compare with Fe2+(aq) consequently, the mechanism that causes rust to be nonprotective because of migration of Fe2+(aq) through the water before precipitation as FeO(OH) does not apply to aluminum, on which Al(OH)3 or AIO(OH) forms, at once, on the anodic site. Conversely, removal of the protective aluminum oxide film cannot occur by the reductive dissolution mechanism described for iron. 

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