Anodic first pulses

Tunable electrodes will be the way of the future. Using electrodes with multiple contacts through which electric fields in the tissue space can be shaped will enable purveyors of neural prostheses to electronically adjust or improve the efficacy without physically moving the electrode relative to the target tissue. These techniques, field steering, will likely utilize both anodic and cathodic first pulse paradigms. 

Xenia Beebe et al. evaluated the maximum charge injection capacity of activated iridium wire electrodes in bicarbonate buffered saline as 2.1 m C/cm and l.OmC/cm for anodic-first and cathodic-first, 0.2ms charge balanced biphasic current pulses, respectively [1]. Bicarbonate buffered saline has a pH between 7.35 and 7.45 (similar to the human blood plasma) and is comparable to PBS with a pH value of 7.4. The counter electrode was an iridium foil. The reference electrode was a saturated calomel electrode. Cyclic voltammetry at lOOmV/s revealed a water window of -0.6 V +0.8 V, the same as versus Ag AgCl. 

Vacuum arc can also be initiated by pulsed laser, as shown in Fig. 4 [15,16]. The target material is first vaporized into plasma by pulsed laser, and vacuum arc is subsequently initiated and more plasma is generated under the function of the electric field between the anode and the cathode (target). Since the arc is controllable, the surface quality might be evi-... 

Three types of measurements were performed in this study. First, photodissociation cross sections were measured, in which the total photofragment yield was measured as a function of dissociation photon energy. In these experiments, the electron signal generated by the microchannel plates is collected with a flat metal anode, so that only the total charge per laser pulse is measured. The beam block is 3 mm wide for these measurements. 

Ion Chambers How can we use this primary ionization to produce a detectable signal The first class of devices to be discussed is the pulse-type ion chambers. A sketch of such a device (a parallel-plate ion chamber) is shown in Figure 18.1. Note that one electrode has been connected to the negative terminal of the voltage source, making it the cathode, while the other electrode acts as the anode. 

From Eqs. (4.68)-(4.70), it is clear that the anodic normalized limiting currents (corresponding to e 2 —> oo) obtained for planar and spherical electrodes have an identical expression, and are only dependent on the ratio between the time lengths of the first and second potential pulse, r, and r2,... 

Nearly any type of cell (prokaryotic or eukaryotic) can be transformed by the technique of electroporation. Protoplasts are first prepared by enzymatic or chemical disruption of the host-cell membrane polysaccharides. Next, the recombinant vector is introduced to the protoplast suspension residing in a very low ionic strength buffer (or distilled water). This DNA-protoplast suspension is then subjected to one or several 250-V pulses delivered from a cathode and anode placed directly into the solution. This applied voltage gradient will cause a certain population of the cells (—1010 per... 

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