Electric potential, generation

Figure 3.7 shows the simultaneous measurement of the time courses of the electric potential across the interface and the interfacial tension at a chemical oscillation induced at the W/NB interface by successive introduction of SDS into the water phase. Clearly, the interfacial tension and the electric potential changed simultaneously. No change in the interfacial tension was observed before the first electric potential generation. This result indicated that the electric potential was induced not by desorption of the surfactants from the interface, but by their sudden and corrective adsorption onto the interface. The absolute value of the electric potential at the peaks was almost constant at about 200 mV under our experimental conditions. In contrast, the baseline of the electric potential gradually increased. Corresponding to the increase of the electric potential, a... 

This topic is included in order to contribute brief details of the principles involved in the quantitative analysis of amino acids and of some oligopeptides in aqueous solutions. The simple equipment needed so that an electrical response owing to the presence of these compounds will be generated and measured is based on particular enzyme-catalysed reactions. These create net changes of electrical potential generated in various ways from the reaction products that are created and the magnitude of the electrical response is proportional to the concentration of the amino acid or peptide. 

The electrical potential generated between membrane and solution phases, the Donnan potential, is derived from Eqs. (2.17) and (2.18),... 

T. Sata, Properties of ion-exchange membranes combined anisotropically with conducting polymers. 2. Relation of electrical potential generation to preparation conditions of composite membranes, Chem. Mater. 1991, 3, 838-843. 

T. Sata, Properties of composite membranes prepared from ion exchange membranes and conducting polymers. II. Electrical potential generation from cell composed of a cation exchange membrane-polypyrrole composite membrane and ferric ion form cation exchange membrane, J. Membr. Sci., 1993, 82, 247-253. 

Dose/response curves were developed from traces such as shown in Figure 3B for dinoseb. For comparative purposes, the concentration of compound required to increase the rate of ferricyanide reduction to twice that of the no-herbicide control rate are shown in the last column of Table VI. Uncouplers such as FCCP accelerate the rate of ferricyanide reduction, presumably by shuttling protons across the membrane in response to the electrical potential generated by the reduction of ferricyanide by ferrocene (28). In this study, FCCP was the most effective compound. The two phenolic herbicides (dinoseb and ioxynil) were more active than propanil and chlorpropham. Among the carbanilates, 3-CHPC and... 

Like the EEG, the EMG is a summation of cellular activity however, the EMG is primarily a result of the firing of muscle cells. If many muscle cells fire simultaneously (as happens when a muscle contracts), the electrical potentials generated near the surface of the skin will reflect that muscular activity. In practice, a very fine electrode is inserted into the muscle to stimulate a specific region. A second electrode or set of electrodes can then detect the resultant muscle activity. The EMG, then, is used primarily to detect abnormalities in muscle excitation. 

Piezoelectric, in which periodic changes in physical size of certain crystals (such as quartz, tourmaline, and zinc oxide) due to applied electric potential generates mechanical vibrations, which are propagated as sound waves. Used in the range fi om 20 kHz to 10 GHz. 

The zeta potential (Q depends on the surface charge that appears at the interface of a liquid-solid pair when the two are brought into direct contact. The zeta potential represents the electric potential generated as a consequence of this electric surface charge. The zeta potential is normally treated as being invariant with respect to temperature, but recent experiments have suggested that this is not always accurate. It is important to have a precise estimate of because calculation of electroosmotic flow velocity in a microchannel (using the Smoluchowski equation) depends directly upon this value. 

The second technique, known as electro-osmosis, causes a fluid in contact with a stationary charged surface to move in response to an applied electric field. The third technique, which can be regarded as the converse of electro-osmosis, is known as the streaming potential technique. The streaming potential involves the measurement of the electric potential generated when a liquid is forced under pressure to move in contact with a stationary charged surface. Finally, the sedimentation potential technique is a method that is, in a way, the converse of electrophoresis. A sedimentation potential arises across the suspension when charged particles settle in a stationary liquid. Adamson (29) explained the basic principles of these electrokinetic techniques in a nutshell as shown in Table 2. 

The electrical potential generated by eye movement, called electrooculography (EOG), is also recorded in the EEG system. It is acquired through a pair of active and reference bipolar electrodes, plugged into a bipolar polygraphic EEG channel where the EOG signal is ampMed and digitized. 

The four possible types of electrokinetic phenomena are streaming (current) potential (electric potential generated by fluid movement relative to another phase), sedimentation potential or Dorn phenomenon or Dom effect (due to dispersed particles motion relative to the fluid caused by sedimentation) and electrophoresis and electro-osmosis (movement of two phases is caused by an external potential difference). 

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