Browsing by Author "Engin, Birol"

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Citation - WoS: 8
Citation - Scopus: 9
Esr Dosimetric Properties of Gamma Irradiated Different Origin Eyeglass Samples
(Pergamon-Elsevier Science Ltd, 2021) Karaaslan, Hulya; Engin, Birol
In the present research, mineral and organic origin eyeglasses (CR-39) were examined with respect to their potential application in the dosimetry of ionizing radiation by using electron spin resonance (ESR) technique. Before irradiation, organic and mineral origin eyeglasses did not exhibit any ESR signal. But they do produce radiation-induced ESR spectra after gamma irradiation. The variations of the radiation-induced resonance signals of organic and mineral origin eyeglasses with microwave power and modulation amplitude were investigated and the optimum spectrometer operating conditions were determined. The dose-response curves of the organic and mineral origin eyeglasses exposed to gamma radiations were found to be described well by a linear and single exponential saturation functions in the dose ranges of 0.1-10 and 0.05-10 kGy, respectively. For mineral eyeglasses this behavior was linear at lower doses (0.05-1 kGy). Despite the observed fading with time in the signal intensity, measurable ESR signals were obtained even 54 days after irradiation for organic origin eyeglass, while the corresponding value for the mineral eyeglass was 154 days. The study also showed that the thermal stability of the radiation-induced ESR signal of mineral eyeglass sample was higher than the signal of organic origin eyeglass.
Investigation of Free Radicals Generated on the Surface of Baked Rice Pudding Samples Using Electron Spin Resonance (ESR) Spectroscopy
(Springer Wien, 2025) Karaaslan, Hulya; Engin, Birol
Electron Spin Resonance (ESR) spectroscopy provides a powerful tool for investigating paramagnetic species generated during thermal treatment of organic matter. In this study, ESR was employed to examine heat-induced free radicals on the surface of baked rice pudding, a heterogeneous organic system containing carbohydrates that undergo thermally driven chemical transformations. Systematic measurements were performed to analyze the evolution of ESR signal intensity, peak-to-peak line width, and g-value as functions of heating temperature and duration. The results demonstrate that radical formation becomes significant above 200 degrees C, reaches a maximum at 350 degrees C, and decreases at higher temperatures. The g-values shift toward the free-electron value (g = 2.0023) with increasing temperature, reflecting changes in the electronic environment of the radicals. Kinetic analysis of time-dependent spectra yielded an activation energy of 12.8 kJ/mol for radical formation, consistent with values reported in other foods. Moreover, the radicals exhibited remarkable stability under ambient conditions, indicating persistent paramagnetic centers in the burnt surface layer. These findings highlight the applicability of ESR spectroscopy for characterizing thermally generated free radicals in heterogeneous organic systems. The study not only provides quantitative insight into the radical formation mechanisms but also demonstrates the use of a widely available food material as a model system for exploring spin dynamics under thermal treatment.