Reverse-field polarity power supply

The need for a reverse-field polarity power supply is at least two-fold 1) It permit a complete spectral analysis of the substance under study. By reversing field polarity, the substance zones can be run forward and backward in front of the detector as many times as needed. Incremental changes as small as 1- or 2-nm in wavelength can be used to maximize instrumental sensitivity, thus allowing coverage of the entire spectral range. In fact, this feature provides the same functions as a diode array detector, albeit somewhat slower. Proteins and peptides have almost identical spectral characteristics, however, when other functional groups are attached to it, is possible to observe more than one maximal absorbance peak. For example,... 

An example of such a series of transient experiments for a sample of paper without conductive additives (softwood Kraft pulp, 450 CSF, 80 g/m2 basis weight, Sample 1), is shown in Fig. 16. This series of transient currents represents the electric field dependence of charge transport associated with mobile ions within the water associated with the fibrous network of the papor. The initial transient current, labeled (a), corresponds to the first application of an electric field (E = 2.5 x 103 Volts/cm) to the new sample. After reversing the polarity of the power supply an electric field of the same magnitude is applied to the sample which leads to the transient current shown by label (b) in Fig. 16. (N.B. the scale of the ordinate is different for... 

Fig. 16 (a)). Again reversing the polarity of the voltage and maintaining the same value of the electric field leads to the transient current labeled (c). Subsequent experiments, where the magnitude of the electric field was monotonically increased but where the polarity of the power supply was first positive and then negative, results in the transient current pairs (d) and (e), (f) and (g), and (h) and (i), respectively. 

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