The antioxidant activity of phytochemicals and of the methanolic extract of Lavandula stoechas was evaluated by β-carotene-linoleate bleaching, DPPH radical scavenging, ferric reducing/antioxidant power (FRAP). The obtained results were compared with antioxidant activities of synthetic antioxidants, such as BHT and BHA. The highest antioxidant activity of the extract was observed by DPPH radical scavenging assay, which was 84.45 ± 5.1% at 1 mg ml −1 . Rutin, rosmarinic acid, and caffeic acid were main phenolics in the extract. The total phenolic content of the methanolic extract of Lavandula stoechas was found to be 105.5 ± 2.7 mg gallic acid equivalent (GAE). Electron spin resonance (ESR) measurements were also performed on the samples. Free radicals were determined by ESR method. g value was found to be 2.0034 for the Lavandula stoechas; 2.0052 for quercetin.

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Poly(2-hydroxyethyl methacrylate)-co-poly(4-vinyl pyridine) and poly(HEMA)-co-poly-(4-VP) copolymers were synthesized by free radical polymerization. K2S2O8 was used as an initiator. Chain lengths of the copolymer was changed by varying the monomer/initiator ratio. These polymers have molarites of 2.6 and 2.1 respectively and are called COP2 and COP4. The samples were exposed to gamma rays at room temperature. After irradiation, the EPR spectra of COP2 and COP4 were recorded between 120 K and 450 K. From the temperature dependence of the line intensity, it was concluded that unpaired spin concentration in the irradiated samples has been changing with temperature. A theoretical study, presented in this report, was aimed to test success of the machine learning methods and to select the best learning method.

The polycrystals of 2,4 diaminotoluene were produced by slow evaporation of solvent. The polycrystalline samples were exposed to 60 Co gamma rays with dose rate of 0.950 kGy/h, at room temperature, for 12, 24, 48, and 72 hours. The electron paramagnetic resonance measurements were carried out on these samples in the temperature range between 298 K and 400 K. No electron paramagnetic resonance signal was observed in the samples irradiated for 12, 24, 48 hours. Two types of radicals were detected using ESR spectrometer in the sample irradiated for 72 h. These radiation damage centers were called RI and RII. The average values of g and the hyperfine coupling constant were calculated. This study also investigates the potential usage of machine learning methods and aims to test the success of these methods and to select the best method.

The free radicals and their concentration in resin materials may impact biocompatibility and polymerization properties of dental materials. The aim of this study was to determine whether there are free radicals and to obtain useful information about thermal stability of materials using electron spin resonance (ESR) spectroscopy, TGA (Thermogravimetry Analysis) and DTA (Differential Thermal Analysis) methods. Epoxy resin-based sealers AHPlus and MM-Seal samples, freshly mixed and set, were prepared to be analysed with ESR and thermal methods. The free radicals were found in dental materials. As radical concentration in AHPlus have changed very slowly, the concentration in MM-Seal have decreased dramatically. Also, MM-Seal was found to decompose in three steps with the increasing temperature, while decomposition of the AHPlus occurred in two steps.