Potential attenuation

No exact mathematical analysis of potential attenuation for all structures has yet been developed. Some indicative analysis has been achieved for a buried pipelinewhich is perhaps the simplest case. 

For the same arrangement of the topmost layer, the same surface atomic density, and the same surface composition (100% Pt), but a difference in electronic structure = 0.33 eV), the ORR is enhanced by factor of 10 on Pt(lll)-skin relative to Pt(l 11). The rationale for this unprecedented increase in catalytic activity can be found in Fig. 3.4a, which shows that at the same potential attenuated sub-... 

Contents indude performance review of modem mine waste management, management requirements, prediction of add generation potential, attenuation of chemical constituents, finer system design, closure, ground water monitoring, and economic impacts. 

Based on the calponin expression pattern and nucleotide sequence differences it has been established that three genes generate the calponin variants [122,125,128]. Miano and Olson [127] reported that hi calponin transcription begins at two dosely located initiation sites in the promoter. This is probably due to the absence of either a TATAA box or an initiator consensus element, which makes this promoter quite unique compared to those discussed above. In addition, transient transfection assay shows that this promoter is active in cell lines that do not express the endogeneous hi calponin gene. The presence of an upstream polypurine sequence in the promoter might potentially attenuate the level of transcription and, thus, hamper or exclude hi calponin in non-SMC cells [127]. 

P. Pierson, K.P. Bethune, W.H. Hartt, P. Anathakrishnan, A new equation for potential attenuation and anode current output projection for cathodicaUy polarized marine pipelines and risers. Corrosion 56 (2000) 350-360. 

Nonclinical research is also of interest in this domain. Arsenic trioxide (ATO) is efficacious in the treatment of patients with acute promyelocytic leukemia but is associated with cardiotoxicity. It has previously been documented that morphine has antioxidant, antiapoptotic, and cytoprotective properties and is able to attenuate cytotoxicity. Therefore, Amini-Khoei and colleagues (2016) employed cardiomyo-cytes to investigate the potential attenuation of ATO-induced cardiotoxicity by morphine. The authors reported that morphine attenuated ATO-induced cytotoxicity and suggested that morphine may have protective properties when the drug is used in humans as an oncologic agent. 

The potential attenuation (fluctuation of potential) in an impressed-current system has a detrimental effect on conx)sion prevention of a metallic structure containing defects. For instance, a coated pipeline buried in soil is subjected to experience current leakage due to coating defects known as holidays. 

The potential attenuation (profile) based on this model is shown in Figure 8.11 along with the ideal protective area for cathodic protection. The protective points are located at a distance y between the anode and the pipeline stmcture. This potential attenuation indicates that the potential falls off from the center of the disk implying that the electric field has an outward conponent in the plane of the disk. The solid line is for the coated steel pipeline, while the dashed line is for possible nonlinear potential distribution of a bare steel pipeline. 

Figure 8.11 Schematic potential attenuation (potential profile) along the y-direction for one drainage point.

Despite the several mathematical models being developed for describing corrosion problems and their solutions, each model has its own degree of accuracy, which depends on the chosen variables and conditions, and numerical method for determining relevant parameters that describe a particular corrosion phenomenon. Comprehensive reviews of models for describing a particular problem, such as crevice cathodic protection, pitting growth rate, current and potential attenuation are available in the literature [2,3,18,25-32]. 

In addition, the phenomenon of potential attenuation has been theoretically included as a cmde approximation as predicted by the Charge Disk and Uhlig models. Both models exhibit similar potential profiles. RnaUy, sets of formulae used in cathodic protection are given as mathematical recipes for practical purposes in the field of corrosion prevention. 

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