Current oscillation characterization

Fig. 4 [7, 8], At anodic potentials near J the electrode behavior is characterized by an exponential dependence of current on potential and by the uneven dissolution of silicon surface leading to the formation of porous silicon (PS) [9]. The values of the characteristic currents J to J4 are a function of electrolyte composition but are largely independent of doping. At potentials more positive than the second plateau current J4, current oscillation may occur [8]. The surface resulting from dissolution at potentials higher than the second peak is brightly smooth, while that produced between the first and second peak is relatively less smooth [10].

Finke, A., P. Poizot, C. Guery, and J.M. Tarascon, Characterization and Id reactivity ofelec-trodeposited copper—tin nanoalloys prepared under spontaneous current oscillations. Journal of the Electrochemical Society, 2005. 152(12) pp. A2364—A2368... 

The cone-jet mode at the spray capillary tip described and illustrated in Figures 1.1 and 1.3a is only one of the many possible ES modes. For a qualitative description of this and other modes, see Cloupeau [13a-c]. More recent studies by Vertes and coworkers [15] using fast time-lapse imaging of the Taylor cone provide details on the evolution of the Taylor cone into a cone jet and pulsations of the jet. These pulsations lead to spray current oscillations. The current oscillations are easy to determine with conventional equipment and can be used as a guide for finding conditions that stabilize the jet and improve signal-to-noise ratios of the mass spectra. The cone-jet mode is the most used and best characterized mode in the electrospray literature [12, 13]. 

The examples we saw are for L C circuits supplied from a direct current source. What happens when an L C circuit is excited by an alternating current source Once again, oscillatory response will be present. The oscillatory waveform superimposes on the fundamental waveform until the damping forces sufficiently attenuate the oscillations. At this point, the system returns to normal operation. In a power system characterized by low resistance and high values of L and C, the effects would be more damaging than if the system were to have high resistance and low L and C because the natural frequencies are high when the values of L and C are low. The... 

Roe, M.W., Worley, J.F., Qian, E, Tamarina, N., Mittal, A.A., Dralyuk, E, Blair, N.T., Mertz, R.J., Philipson, L.H., and Dukes, I.D. 1998. Characterization of a Ca2+ release-activated nonselective cation current regulating membrane potential and [Ca2+]i oscillations in h ansgenically derived b-cells. JBiol Chem 273, 10402-10410. 

The physical meaning of the real and of the imaginary parts of % is the following. Re % is proportional to the dissipated energy in the system — the heat produced per period of the field oscillation is eqnal to 1/2 Re %. On the other hand, the phase-lag of the current (with respect to the applied field) is characterized by the phase angle. 

Otterstedt et a/.also studied waves in the oscillatory regime during Co dissolution. The oscillations possess a relaxationhke character, which is typical for oscillations between the active and the passive state of metal dissolution reactions. They are characterized by long, quasi-stationary periods of vanishing current density, followed by a sharp... 

Roe, M.W., et al.. Characterization of a Ca release-activated nonselective cation current regulating membrane potential and [Ca ]i oscillations in transgenically derived beta-cells. J Biol Chem, 1998 273(17) 10402-10410. 

In a Curie-point pyrolyzer, an oscillating current is induced into the pyrolysis filament by means of a high-frequency coil. It is essential that this induction coil be powerful enough to permit heating the wire to its specific Curie-point temperature quickly. In such systems, the filament temperature is said to be self-limiting, since the final or pyrolysis temperature is selected by the composition of the wire itself, and not by some selection made in the electronics of the instrument. Properly powered, a Curie-point system can heat a filament to pyrolysis temperature in milliseconds. Providing that wires of the same alloy composition are used each time, the final temperature is well characterized and reproducible. 

Fourier transform (FT) analyzers. The FT instruments have the highest available resolution. Currently there are two types, the orbitraps and the ion cyclotron resonance (ICR) systans. Mass resolution in orbitraps can reach 250,000, while ICR systems can have resolutions of >3,000,000. In these analyzers ions oscillate/rotate within a cell and are detected by recording the electrical current that the passage of ions induces in the snrfaces of the cell. The resolution attainable is inversely proportional to both the mass of the analyte ion and the time required to acquire the data. A consequence of this proportionality is that the highest resolutions cannot be obtained on the chromatographic timescale where mnltiple spectra must be collected to enable the characterization of peaks that are only a few seconds wide. LIT/FT combinations are the most common form of MS/MS systems that ntilize orbitrap and ICR analyzers (Sections 2.3.4 and 23122). 

Chronopotentiometry scans for three different concentrations of HCHO helped to characterize behavior of IPMC in HCHO solution. For all cases, the oscillations started at about 7 mA/cm (further noted as threshold current) with a constant value of 0.11-0.13 Hz up to the current density of 14mA/cm. After further increasing the current, in IMHCHO, the frequency decreases as shown in Fig. 3.20. In 2 M HCHO, the frequency maintains a constant valne regardless of higher current density, and in 3 M HCHO... 

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