## 3 Results and Discussion
This observation was slightly different from other studies, wherein fast signal decay was observed [1; 12] in samples stored at LT, but in reasonable agreement with earlier observations in which ESR signals, in general, showed considerable stability [13; 14]. The UV-induced signal (main singlet) from all the sample sets was found to have reduced its intensity immediately after AAT1 (data labeled as \"soon after AAT1\" in the plot) and then followed by signal growth. The behavior of the signal growth with time was also observed to be variable among different storage and location conditions and quite similar to that shown in Figure 4.0 While a larger increase in the signal intensity was seen in non-vacuum-stored AAT samples in comparison to the vacuum-stored, the AAT samples, in general, appeared to be sensitive to light. Thus, the most prominent way to keep the signal intensity moderately stable (or unchanged) was demonstrated by the vacuum storage at LT without light exposure. Furthermore, the intensity of the \"bulge\", which was also observed to be stable in vacuum  
Figure 4.1 Continuous monitoring of the temperature and humidity during UV exposure recorded from three different dual data channel loggers. Each exposure was set to a power-on time of 30 min with a power-off interval of 5 min. The average maximum recorded temperature was 50 \({}^{\circ}\)C, and the average minimum recorded humidity was 8%. stored samples, particularly at LT, instantly disappeared after AAT1 (spectral data not shown). The AAT also cut the chance of recurrence of the 'bulge' in all samples stored under different conditions (up to 7 days). This observation demonstrated that the application of AAT was able to sufficiently remove the signal contribution from heat-related effects (i.e., bulge) and reduce the intensity of the UV-induced signal (i.e., main singlet). Next, the X-ray irradiation of the samples was conducted 7 days after AAT1. The sensitivity to radiation of the AAT samples was observed to be invariant (exhibited a fairly constant dose-response) with the storage conditions (i.e., vacuum storage at RT, non-vacuum storage at RT, and vacuum storage at LT). The radiation sensitivity and fading behavior of the vacuum-stored samples at RT, in both with and without light exposure, were comparable to each other, and the same relationship was also observed for those in non-vacuum-stored. The dose-response of the vacuum-stored samples at RT was higher by a factor of 1.5-2 compared to non-vacuum-stored (also at RT), and about 3 times lower than that of vacuum-stored samples at LT. An interesting observation in this plot was the similarity between the initial dose-response to 20 Gy of the vacuum-stored samples at LT without light exposure in Experiment 2 (see Figure 7E) and the initial dose-response of the AAT samples (before storage) in Experiment 1 (see Figure 4A-D). The premise behind the disparity of the radiation sensitivity may be related to the regrowth behavior of the UV-induced signal under various storage conditions following AAT. For instance, it was reported that the UV-induced signal can still be observed following water treatment when stored inside a tightly closed polyethylene bag under RT and LT conditions [1], although a rigorous comparison between the vacuum and non-vacuum storage (or whether the type of vacuum bags also matter) may be difficult to assess and requires further work. Lastly, all five sample sets displayed a strong signal reduction following AAT2. The rate of change in the magnitude and stability of the signal was found to be higher in non-vacuum storage at RT with light exposure, suggesting that the light may have amplified the enhancement effect caused by the AAT. This observation was also consistent with the above results in Experiment 1, wherein the signal stability of the AAT samples depends strongly on storage conditions. As a result of these observations, the AA was confirmed to be sensitive to light, demonstrating a substantial increase in the ESR peak-to-peak intensity to the fingernail spectrum.