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Abstract: A differential scanning calorimeter (DSC) has been used to monitor the influence of high-energy Co60 gamma-irradiation on physical ageing in Se96Sn4 glass. It is observed that the relaxation process in the studied glass is slow after 1 and 3 years of natural storage, and can be highly accelerated by γ-irradiation. The glass transition temperature T g and the endothermic peak area, which is directly related to the relaxation enthalpy Δh, were found to exhibit a remarkable change after irradiation and also during an additional natural storage for 6 months and 1 year of the irradiated Se96Sn4 glass. T g value of γ-irradiated glass increases by 12K; meanwhile, that of additional 6-months- and 1-year-stored glass T g increases by 19 and 20K in comparison to its counterpart of 1-year-aged non-irradiated sample. The same trend is also observed for Δh, which becomes 2.33, 3.61 and 3.65 times that of the 1-year-aged non-irradiated case, respectively, for γ-irradiated, additional 6-months- and 1-year-stored glass. These indications reveal that γ-irradiation activates the relaxation of the glass towards a state thermodynamically close to the equilibrium super-cooled liquid state. [Copyright &y& Elsevier]

The main objective of this study is to identify the atmospheric 7 Be concentrations in 130 surface air samples collected from three stations located in Riyadh, Haql and Khafji cities in Saudi Arabia between November 2012 and April 2014. Monthly variations as well as seasonal patterns of 7 Be were studied using a medium-volume air sampler and a gamma spectroscopy system equipped with a high-purity germanium (HPGe) detector. 7 Be exhibited one maximum specific activity in summer and one minimum in winter with average monthly concentrations of 12.4 ± 0.9, 15.4 ± 1.2, and 18.0 ± 1.3 mBq m -3 in Riyadh, Haql and Khafji, respectively. Overall, the average 7 Be concentration in the three stations was 12.9 ± 1.0 mBq m -3 , whereas the maximum value of 29.5 mBq m -3 was registered in Khafji city in August 2013. Besides 7 Be, measurements indicate observations of 4 0  K, 137 Cs, 226 Ra radionuclides in surface air samples collected from the three stations. 4 0  K showed measurable concentrations, whereas the concentrations of 137 Cs and 226 Ra were only detected in a limited number of samples., (Copyright © 2020 Elsevier Ltd. All rights reserved.)