## 3 Results and Discussion  
Figure 3 shows the evolution of the ESR spectra obtained from (a) non-chemically and (b) chemically treated fingernail samples before and after irradiation with 20 Gy of \({}^{137}\)Cs \(\gamma\)-rays following storage in the vacuum chamber. All spectra were recorded soon after the corresponding chemical treatment or irradiation of the samples and continuously monitored for up to 7 days. Each spectrum is an average of 12 spectra from 4 sample collections (3 portions of chemically/non-chemically treated samples per collection). Solid lines correspond to the ESR signals measured after exposure to radiation,  
Figure 2: Experimental setup for the irradiation of the fingernail samples with the \(\gamma\)-ray irradiator (**left**) and the geometry of irradiated samples placed in between two \({}^{137}\)Cs \(\gamma\)-ray sources (**right**). while dotted lines are the background signal before irradiation (referred to as \"NT\(-\)BKG\". Dashed lines show the background signal after chemical treatment of the samples (referred to as \"T\(-\)BKG\"). As can be seen, the ESR signals of both non-chemically and chemically treated samples increased during the first day of storage in the vacuum chamber and continuously increased up to 7 days after \(\gamma\)-ray irradiation. This behavior was very similar to most of the irradiated vacuum-stored samples with water treatment [35; 36; 38]. It seemed, notwithstanding, that the increase rate in chemically treated samples (30% signal increase over the first 24 h after irradiation) was slower than those in the non-chemically treated samples (39%). Moreover, it was found that the non-zero, quasi-stable background signal substantially reduced its ESR intensity when subjected to DTT, compared to the non-chemically treated background signal (NT\(-\)BKG) demonstrated in Figure 3a. It should also be noted that the background signal with chemical treatment (T\(-\)BKG) was quite stable: there was no signal growth in its ESR intensity for 1 day after storage in the vacuum chamber at room temperature. Comparative plots on the evolution of ESR spectra observed in the fingernail samples exposed to 20 Gy of \({}^{137}\)Cs \(\gamma\)-rays, following storage in the freezer, are shown in Figure 4. Each of the spectra shown here is the mean of 12 spectra obtained from four sample collections (three portions of chemically/non-chemically treated samples per collection). It is worth mentioning that the chemically treated samples presented in Figure 4b were also kept inside the vacuum chamber for 24 h in between chemical treatment and irradiation. All notations used in Figure 4 are the same as those described in Figure 3.  
As seen in this figure, the freezer storage resulted in better stability of ESR signals for both chemically and non-chemically treated samples following \(\gamma\)-ray irradiation, in contrast with the vacuum-stored samples. The recorded ESR signals in freezer-stored non-chemically treated samples increased by about 15% after 1 day of exposure and further increased up to 25% after a week (Figure 4a). As with chemically treated samples, there was only about a 9% increase in the ESR intensity after 1 day and 17% after 7 days (Figure 4b). Furthermore, the use of DTT for chemical treatment prior to irradiation was found to have significantly reduced the intensity of the ESR spectra in irradiated fingernail samples (i.e., RIS). These observations are in accordance with previously reported work from [PERSON] et al. [26]. It was confirmed that the background signal from unirradiated freezer-stored samples with chemical treatment (T\(-\)BKG) also showed no significant increase within 24 h of storage time inside the vacuum chamber (Figure 4b), as seen with the vacuum-stored samples (Figure 3b).