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Ionization Chamber Instrumentation
Published in Arash Darafsheh, Radiation Therapy Dosimetry: A Practical Handbook, 2021
Larry A. DeWerd, Blake R. Smith
Properly defined voltage requires an indication of the magnitude and the polarity. In the United States, 300 V is the typical high-voltage bias magnitude. In Figure 2.2, the guard (and collector) is +300 V with respect to the outer shell. This perspective is commonly referred to as the “collecting electrode potential.” Some electrometer manufacturers reverse the reference point, indicating the outer shell potential with respect to the guard. This perspective is commonly referred to as the “thimble bias.” Thus, the thimble bias shown in Figure 2.2 is −300 V. The high-voltage bias configuration in Figure 2.2 will produce a negative charge collection. Unfortunately, the manufacturers do not always label the bias polarity selector switch to indicate whether it is the collecting electrode potential or thimble bias. There may even be inconsistency between models from a particular manufacturer. In addition, some electrometer models display the opposite polarity of the measured charge or current. Generally, the high-voltage bias is measured at the input connector and reported as the guard voltage with respect to the outer shell for each corresponding bias selector setting of the electrometer.
Technetium-Labeled Compounds
Published in Garimella V. S. Rayudu, Lelio G. Colombetti, Radiotracers for Medical Applications, 2019
Suresh C. Srivastava, Powell Richards
Direct coulometric reduction of pertechnetate has been studied by a number of workers.41, 43, 44, 55, 62, 76, 80 Use of acidic media, in particular those containing phosphate or polyphosphate, has been shown to provide more reliable data which could be suitable for analytical purposes. Coulometry as a means to determine Polarographic n values has been questioned by Munze,75 and others. Some typical results on the controlled potential coulometric measurements of the number of electrons transferred are described in Table 4. In acidic or phosphate buffered solutions, in general, n has a value of 4. Depending upon the potential used, n in basic solution is observed to be 3 or 4. Munze75 attributed the discrepancy between his Polarographic and coulometric data to the slow one-electron step in the coulometric measurements, which is not fast enough to be determined polarographically. Sensitivity of the n values to the electrode potential is another problem in coulometry of pertechnetate solutions. It is thus difficult at times to directly correlate the coulometric data with Polarographic results. Significant reliability of the coulometric data could, however, result from several procedural modifications.47
The Special Position of 99mTc in Nuclear Medicine
Published in Frank Helus, Lelio G. Colombetti, Radionuclides Production, 2019
Significant use has also been made of electrochemical reactions of 99mTc. Benjamin96 pioneered the technique of labeling human serum albumin with technetium by electrolysis in a cell containing a zirconium anode. Conflicting theories97,98 have been put forward to explain the mechanism of the reaction; the weight of the evidence appears to support the more familiar concept of chelation by the ligand after the pertchnetate has been reduced to a lower oxidation state. The chelation of 99mTc via electrolysis using tin electrodes99–101 has been attributed to the same mechanism. More recent work by Russell and Majerik102 has shown that provided the electrode potential is controlled within certain limits and in the presence of a chelating agent, 99mTc can also be reduced at inert electrodes.
Erosive potential of ice tea beverages and kombuchas
Published in Acta Odontologica Scandinavica, 2023
Elisa Lind, Hilma Mähönen, Rose-Marie Latonen, Lippo Lassila, Marja Pöllänen, Vuokko Loimaranta, Merja Laine
The fluoride content was measured with a Thermo Scientific Orion Fluoride Selective Electrode at RT. The samples contained equal volumes of TISAB solution and tea beverage. TISAB solution was prepared by mixing 500 ml deionized water (resistivity 18 MΩ·cm), 57 ml acetic acid and 58 g NaCl (AnalaR NORMAPUR) with a magnetic stirrer. Thereafter, 5 M NaOH was added until the pH of the solution was 5.02 and water was added until the volume was 1000 ml. The pH was measured with an Orion™ Triode™ 3-in-1 pH/ATC Probe connected to a Thermo Scientific Orion Star A111 benchtop pH meter. Calibration was made by using 0.05, 0.1, 5, 50 and 100 ppm fluoride dilutions. The results were calculated using a Nernst equation. E = measured electrode potential;E0= the potential of the reference electrode;S = slope;A = activity level of fluoride.
Probing the correlation between corrosion resistance and biofouling of thermally sprayed metallic substrata in the field
Published in Biofouling, 2022
Pedro A. Vinagre, Johan B. Lindén, Enara Mardaras, Emiliano Pinori, Johan Svenson
Electrochemical tests were performed by using an Autolab PGSTAT 302 N potentiostat. A conventional three-electrode cell was used, where the working electrode was the specimen under study; saturated Ag/AgCl was the reference electrode, and a platinum wire was the counter-electrode. A solution of ocean water prepared according to ASTM D1141 (ASTM D1141-98 2021) was used as electrolyte. The contact area was ∼ 1.2 cm2. The tests were carried out at room temperature in triplicate. During the polarization test, the electrode potential was scanned at a rate of 0.167 mV s−1 from an initial potential of −0.3 V (with reference to the open circuit potential), to a potential at which the specimen reached a current density of 0.25 mA cm−2. The corrosion current density values were obtained by the Tafel extrapolation method.
Using hydrogen peroxide to prevent antibody disulfide bond reduction during manufacturing process
Published in mAbs, 2018
Cheng Du, Yunping Huang, Ameya Borwankar, Zhijun Tan, Anthony Cura, Joon Chong Yee, Nripen Singh, Richard Ludwig, Michael Borys, Sanchayita Ghose, Nesredin Mussa, Zheng Jian Li
Since the disulfide bond reduction is a redox reaction, it is possible to use redox indicators as a simple, rapid and robust way to replace the DTNB test and to forecast the potential risk of LMW formation during harvest and recovery. A redox indicator undergoes a definite color change at a specific electrode potential in a similar way as pH indicators undergo a color change at a specific pH. To find the appropriate redox indicator, an array of commercially available redox indicators were tested, and several were identified as the best potential candidates that can be used in biologics manufacturing process.