Resistance elements, bulk

In order to illustrate the principal elements of the model, a simple electrical scheme is shown in Figure 6. The bulk of the specimen is taken to be purely resistive. The bulk resistance Rg is in series with a contact impedance. The latter is depicted as a resistance R parallel with a contact capacitance C. A further elaboration is necessary before undertaking the task of identifying... 

Fig. 6.1 Symbolic equivalent circuit of an electrode wire heated and polarised inside solutioiL Resistor and capacitor symbols drawn stand for elements of differential size Cdl double layer capacity elements along the wire length, Zf faradaic impedance elements, Rsoi solution resistance elements inside bulk solution. REF symbolises the reference and counter electrodes in common, and POL the polarisation and current measuring circuit From [3], with permissirm...

In moderately resistive samples with ionic conduction migration process controls the bulk-media conduction and the bulk resistance exceed the bulk capacitive impedance only at the highest frequencies. In practically all "real life" systems there is at least some "lossy path" through a bulk-media resistance RguLK in parallel with the Cg, resulting in predominant conduction through a resistive element at the frequencies where > Rg. The... 

Figure 11-lOA [75, 76] shows the Nyquist spectra at +1.00 V at TiOj electrodes in solution containing electroactive [Fe(CN)ions (pH 4.7) with and without the addition of HSA into the bulk solution. In the absence of the protein, the equivalent circuit used to fit the experimental data is reduced to a typical Randles circuit containing Warburg diffusion and [Fe(CN) ] charge-transfer resistance elements in parallel with a double-layer capacitance (Figure 11-lOA). In the presence of a full protein layer, additional processes related... 

Subsequently, at higher frequencies the current would propagate outward and come across the bulk medium, which can be represented by a parallel combination of a resistive extracellular fluid and cell membranes. As was discussed above in Sectionll-2, the "bulk"-solution current at high frequencies can be conducted along two pathways, either around or between cells in extracellular media or through and across cells (intracellular). The extracellular medium is assumed to be principally resistive and is represented by a purely resistive element (Rg )- densities, there are sufficient numbers of... 

Because a length of metal associated with the connector contact is ordinarily in the path between the contact end to which a wire is terminated and the contact interface, its resistance (bulk resistance) must be added to contact resistance when considering the connector as a circuit element. This overall resistance is sometimes erroneously called contact resistance. 

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