1) Electrical Stimulation (20 points): Determining the \"optimal\" parameters fo
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Question
1) Electrical Stimulation (20 points): Determining the "optimal" parameters for electrical stimulation is a challenging task. For the following three sets of parameters, explain what each option stands for and under which circumstances you would choose one over the other a) Cathodic vs anodic(5 points) b) Monopolar vs bipolar (5 points) c) Monophasic vs biphasic (5 points) d) Assume that the impedance of your stimulation electrode is suddenly doubled. If you are delivering your stimulus as current pulses, what danger this change could bring? (5 points)Explanation / Answer
A. To keep the chemistry of these two processes straight, first consider the metal part you are coating. In cathodic electrocoat, the part is the cathode and in anodic electrocoat, the part is the anode. Follow the four E’s of the electrocoat process to keep track of the major process steps: electrolysis, electrophoresis, electrodeposition and electroendosmosis.
Electrodeposition coatings are initiated by the electrolysis of water, which makes the current flow possible and starts the process. The reduction of water occurs at the cathode and the oxidation of water occurs at the anode.
Cathodic Case (Reduction of water at the negative charged part): 2H2O(l) + 2e? ? H2(g) + 2OH?(aq)
Anodic Case (Oxidation of water at the positive charged part): 2H2O(l) ? O2(g) + 4H+(aq) + 4e?
In cathodic electrocoating, the part has a negative charge to which positively charged polymer is attracted, a movement called electrophoresis. The anodic case is similar, but the polymer has a negative charge and the part has a positive charge.
The electrodeposition coating occurs directly at the part, which is initiated by the oxidation or reduction reactions of water at the part. In cathodic electrocoat, hydroxide is produced at the part, which neutralizes the salting acid of the positively charged polymer and the polymer coating is deposited onto the part. It is important to note that, in this electrodeposition process, there is no oxidation or reduction of the polymeric coating—only a change in the solubility that results in the coating being deposited onto the part. In anodic electrocoat, the hydron, produced by the oxidation of water, neutralizes the base of negatively charged polymer.
Following the deposition of the polymeric coatings, the water moves away from the part—termed electroendosmosis—and the part is insulated and deposition is completed. Insulation is the major factor to limit the film thickness of the final coating. You can use steel and aluminum in both processes.
Remember that, in anodic electrocoat, since the oxidation occurs at the part, many metals can be oxidized in this process. This can contribute to weaker corrosion resistance, so special consideration needs to be given for the quality of corrosion protection that is needed for the application. The use of cathodic electrocoat is very common in automotive applications, for example, when strong corrosion resistance is essential. Special pretreatment may be required if you use aluminum and steel in the same cathodic bath.
B)
Materials and Methods
A total of 137 patients with benign prostatic hyperplasia (mean age 67 years, range 47 to 91) were prospectively randomly assigned to undergo monopolar (67) or bipolar (70) transurethral resection of the prostate. Patient characteristics of the 2 groups were similar. Hemoglobin (as a marker of blood loss) was measured preoperatively and perioperatively. I-PSS, I-PSS-QoL score, maximal flow rate and post-void residual urine volume were assessed preoperatively and 3 and 12 months postoperatively. Duration of surgery, indwelling catheter use and hospitalization were also documented, as were postoperative clot retention requiring removal by catheterization or surgery, and rates of bladder neck and/or urethral strictures.
Results
No significant perioperative differences were found in duration of surgery, catheterization or hospitalization, or in blood loss or rates of blood transfusion and transurethral resection syndrome. Postoperatively there were no significant differences in I-PSS or I-PSS-QoL scores, or rates of rehospitalization, clot retention, blood transfusions, reoperation or urethral strictures. However, bladder neck stricture occurred significantly more often in the bipolar group (8.5% vs 0%, p = 0.02). The 3 and 12-month followup showed significant and equal improvement in micturition in the 2 groups.
Conclusions
Bipolar and monopolar transurethral resection of the prostate are effective and safe techniques for the surgical treatment of benign prostatic hyperplasia. The only significant difference between them was a significantly higher rate of bladder neck strictures with bipolar resection of the prostate.
C)The key difference between monophasic and biphasic defibrillator is that the monophasic defibrillator is a type of defibrillation waveform where a shock is delivered to the heart from one vector as shown below. Whereas, in biphasic defibrillation, shock is delivered to the heart via two vectors. In other words, monophasic shock is given in only one direction from one electrode to the other. In a biphasic shock, the initial direction of shock is reversed by changing the polarity of the electrodes in the latter part of the shock being delivered.
D)the impedance of your stimulation electrode is suddenly doubled. The current will be decreases.
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