| Summary: | 碩士 === 國立中正大學 === 機械工程所 === 95 === This research investigates experimentally the effect and optimization of thermal control factors on freezing injury in FaDu nasopharyngeal carcinoma cells by Taguchi method. Freeze/thaw experiments based on the L8(27) two-level orthogonal array of the Taguchi method are conducted to determine the statistically significant thermal control factors and interactions affecting the viability of the cell and repeatability of the experiment. The levels of the four cryosurgically-relevant thermal control factors considered in this work are chosen to be thawing rate, 4.72 to 34.5 ℃/min; end temperature, -20 to -68 ℃; holding time, 0 to15 min; and cooling rate, 1.29 to 14.0 ℃/min, based on open literature and limit of available experimental facility. Analysis of variance on the experimental data is performed to determine the contribution of each thermal control factor and the optimal test condition for maximum cell injury and experimental repeatability. Results show that the holding time, end temperature, thawing rate-holding time interaction, and thawing rate (listed in the order of contribution) are the statistically significant thermal and interaction factors affecting the cell viability, and the cooling rate dominates the experimental repeatability of this study. The cell viability is found to decrease with the decrease in the thawing rate and end temperature and with the increase in the holding time and cooling rate; this observed trend is consistent with exiting experimental data of other types of cells and present cryoinjury mechanisms. The repeatability of the experiment increases with the decrease in the cooling rate. Within the ranges of thermal control factors studied in this work, the optimal test condition is found to be A2B1C2D2 (i.e. thawing rate, 4.72±0.22 ℃/min; end temperature, -68 ℃; holding time, 15 min; cooling rate, 1.29±0.01 ℃/min) for the maximum cell injury and experimental repeatability. From the verification experiment, the measured average viability under optimal test condition falls within the limits of the confidence interval (at 95% confidence level) around the estimated average viability calculated from the Taguchi experimental data. This indicates that in this work all important factors are included and the confounding is insignificant in the design of the L8(27) two-level orthogonal array of the Taguchi method.
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