## 2 Materials and Methods
ESR measurements were performed at room temperature on an X-band spectrometer (JES-FA100, JEOL Ltd., Tokyo, Japan) operating at \(\sim\)9.441 GHz with an ES-UCX2 resonator using a 5-mm diameter sample tube. Parameters used for the spectra acquisition were: 1 mW microwave power; 0.4 mT modulation amplitude; 10 mT sweep width; 30 s sweep time; 0.03 s time constant; the number of scans was 10. The corresponding nominal values of the third and fourth line of the MgO:Mn\({}^{2+}\) reference sample at g = 2.033 and g = 1.981 were used for the g-factor adjustment. ESR measurements were conducted at different \begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline \multirow{2}{*}{**Experiment**} & \multicolumn{3}{c}{**Without Light Exposure**} & \multicolumn{3}{c}{**With Light Exposure**} \\  & \multicolumn{3}{c}{**(in Darkness)**} & \multicolumn{3}{c}{**(in Ambient Illumination)**} \\ \cline{2-7}  & \multicolumn{2}{c}{**Vacuum-Stored**} & \multicolumn{2}{c}{**Non-Vacuum-Stored**} & \multicolumn{2}{c}{**Vacuum-Stored**} & \multicolumn{2}{c}{**Non-Vacuum-Stored**} \\ \cline{2-7}  & **RT** & **LT** & **RT** & **LT** & **RT** & **LT** & **RT** & **LT** \\ \hline
1 & \(\bullet\) & \(\bullet\) & - & \(\bullet\) & \(\bullet\) & - & - & - \\ \hline
2 & \(\bullet\) & \(\bullet\) & \(\bullet\) & - & \(\bullet\) & - & \(\bullet\) & - \\ \hline \hline \end{tabular}  
Notes: \(\bullet\): used; \(\prec\) not used; RT: room temperature (20 \({}^{\circ}\)C); LT: low temperature (\(-\)20 \({}^{\circ}\)C).  
\end{table} 
Table 1: List of various experimental storage and location conditions used for the fingernail samples in Experiments 1 and 2. Figure 3: Schematic of the irradiation setup for the fingernail samples exposed to 20 Gy of X-rays. elapsed times from 0 (immediately) up to 7 (or 9) days after UV exposure, treatment, or irradiation procedure. Throughout this paper, all recorded spectra were normalized to their respective sample weight. The ESR spectra from the three AA-treated subset samples were averaged and subtracted from the water-treated (background) control sample. The resulting background-subtracted signal was displayed as a single spectrum or datum point in the plots. The reported error values were calculated as the standard deviation of the three AA-treated subsets of samples. The temperature and humidity during measurements were always monitored using a dual channel data logger (LR5001, Hioki, Nagano, Japan) with a built-in sensor (LR9504, Hioki, Nagano, Japan) and a communication adapter (LR5091, Hioki, Nagano, Japan). In the experiment with UV exposure, the samples were exposed for 30 min at room temperature using a portable UV light emitting device with a luminance intensity of 170 mW/cm\({}^{2}\) at 365 nm wavelength (Portable Cure 100, HLR100T-2, SEN LIGHTS Corporation, Osaka, Japan). Note that the portable UV light was situated at room temperature laboratory condition. The experimental procedures used in the present study were designed to investigate the effects of AA treatment (hereafter \"AAT\") (a non-toxic antioxidant) on the ESR signals of the irradiated (i.e., X-ray and UV irradiation) and unirradiated fingernails. Repeated treatments and irradiations were done to examine the behavior changes of the ESR peak-to-peak intensities in terms of signal stability and sensitivity to radiation. All procedures (except during irradiation) were conducted under subdued red light.