H absorption promoters

ASB purely surface efiects can exist in the steady state [53,61,62,113]. This conclusion can be extended to all the HER mechanisms where one step is in quasiequilibrium. This analysis, which can also be performed by a thermodynamic treatment in expressing equalities of chemical potentials for hydrogen in the different phases, disagrees with the conclusions of a thermodynamic treatment of poison effects proposed by other authors, suggesting that a blocking effect may induce H absorption promotion in this case [101],... 

Mechanisms of Action of H Absorption Promoters 2.7.1 Conditions for H Absorption Promotion... 

The preceding analysis provides no explanation for ASB promoting effects on H absorption observed in cases where the HER is not controlled by a coupled Volmer-Tafel mechanism, for example, on noble metals such as Pt and Pd [77,78,108,122]. On these metals, the electroadsorption step in the HER is in quasiequilibrium at low cathodic overpotentials (chemical combination being the rate-determining step) when the overpotential increases, it becomes coupled to the electrocombination step [129]. So H absorption promotion by ASB on these metals can be explained only if the surface-bulk transfer step is not in equilibrium, that is. Equations 2.12a and 2.38 do not apply, at least on the clean surface, and the ASB increases the kinetics of this step [60,68]. 

Significance interpretation activities, EIA, 10 236, 10 240t Si-H absorption, 20 14 Si-hybrid sealants, 22 38-40, 48t Silages, 20 863 Silane(s), 13 612, 22 489, 547 adhesion of sealant, 22 34 adhesion-promoting, 22 41 chemical vapor deposition precursor, 5 805t... 

Nishihata, T., and J.H. Rytting. 1997. Absorption-promoting adjuvants Enhancing action on rectal absorption. Adv Drug Deliv Rev 28 205. 

Sasaki, H., et al. 1995. Ocular permeability of FITC-dextran with absorption promoter for ocular delivery of peptide drug. J Drug Target 3 129. 

Sasaki, H., Igarashi,Y.,Nagano,T., Nishida, K., and Nakamura, J. (1995), Different effects of absorption promoters on corneal and conjunctival penetration of ophthalmic beta-blockers, Pharm. Res., 12(8), 1146-1150. 

Yamamoto, A., T. Morita, M. Hashida, and H. Sezaki. 1992. Effect of absorption promoters on the nasal absorption of drugs with various molecular weights. Int. J. Pharm. 93 91-99. 

Okabe, H., Obata, Y, Takayama, K., and Nagai, T. (1990). Percutaneous absorption promoting effect and skin irritancy of monocyclic monoterpenes. Drug. Des. Deliv, 6 229-238. 

Murakami, T., Yata, N., Tamauchi, H., Kamada, A. (1982). Studies of absorption promoters for rectal delivery preparations. II. A possible mechanism of promoting efficacy of enamine derivatives in rectal absorption, 30(2), 659-665. 

Kaji, Y., Uekama, K., Yoshikawa, H., Takada, K. and Muranishi, S., Selective transfer of 1-hexylcarbamoyl-5-fluorouracil into lymphatics by combination of cyclodextrin polymer complexation and absorption promoter in the rat, Int. J. Pharm., 24, 79-89 (1985). 

Katsuma, M., Watanabe, S., Kawai, H., Takemura, S., Sako, K. (2006). Effects of absorption promoters on insulin absorption through colon-targeted delivery. International Journal of... 

As a conclusion, the promoting effects of adsorption site blockers on H entry can be understood not by considering the effective diminution of 0 the overall coverage of OPD H (determined by integration of adsorption pseudocapacitance vs. potential curves [117-119]), but by considering the variation of x the local OPD H coverage in the sites not blocked [obtained by normahzation of 0 or from the Tafel and permeation slopes (see Tables 1 and 2)]. If the surfece-bulk transfer step is in equilibrium, a significant increase of the bulk H eoncentration can be induced by ASB surface effects only for the HER mechanism where the steps of electroadsorption and chemical combination are coupled. This analysis provides a quantitative explanation of the effects of promotion of H absorption into iron and ferrous alloys. 

The preceding analysis provides no explanation for ASB promoting effects on H absorption observed in cases where the HER is not controlled by a coupled Volmer-Tafel mechanism, e.g., on noble metals such as Pt and Pd [73,74,101,113]. On... 

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