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    A Monte Carlo investigation of some important radiation parameters and tissue equivalency for photons below 1 keV in human tissues
    (IOP Publishing Ltd, 2022) Rafiei, Mustafa Mohammad; Parsaei, Sara; Kaur, Parminder; Singh, K. J.; Büyükyıldız, Mehmet; Kurudirek, Murat
    The attenuation coefficients are important input values in estimating not only the dose and exposure in radiotherapy and medical imaging, but also in the proper design of photon shields. While studies are widely available above 1 keV, the attenuation coefficients of human tissues for photon energies less than 1 keV have not been studied yet. In this study, the attenuation coefficients of water and some human tissues were estimated for low energy photons using the MCNP6.1 code in the energy region 0.1 keV-1 keV. Mass attenuation coefficients were estimated at photon energies of 100, 150, 200, 250, 300, 350, 400, 450, 500, 550, 600, 650, 700, 750, 800, 850, 900, 950 and 1000 eV for water and ten human tissues (Soft, Breast, Lung, Bone, Brain, Eye lens, Ovary, Skin, Thyroid and Prostate). Results were compared with those available in literature and a fairly good agreement has been obtained. These data were then used to calculate the mean free path, half value layer, tenth value layer, effective atomic number and specific gamma-ray constant (useful for calculation of dose rate) as well. Moreover, for comparison the effective atomic number of the water has been obtained using the results of this work and using the data available in NIST database from 0.1 to 1 keV. In addition, the human tissues were compared with some tissue equivalent materials in terms of effective atomic number and specific gamma-ray constant to study the tissue equivalency from the results, the muscle-equivalent liquid with sucrose has been found to be the best tissue equivalent material for soft tissue, eye lens and brain with relative difference below 4.1%.
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    Study of low-energy photon interactions below 1 keV for some biological molecules of human body
    (Springer Heidelberg, 2022) Mohammad Rafiei, Mustafa; Parsaei, Sara; Kaur, Parminder; Singh, K. J.; Buyukyildiz, Mehmet; Kurudirek, Murat
    In the present work, the authors have studied the radiation interactions at very low photon energies (below 1 keV) for some materials of biological importance, viz. water, glycerol, adenine, guanine, palmitic acid, myristic acid, valine, tryptophan, histidine, glucose and ribose. The parameters including mass attenuation coefficient, mean free path, half value layer, tenth value layer, effective atomic number, mass energy absorption coefficient, gamma constant and dose rate have been investigated in the energy range from 100 to 1000 eV. MCNP6.1 simulations have been employed in this study. Water was found to have higher values of mass attenuation coefficient and effective atomic number among the other materials, whereas palmitic acid possesses relatively lower values except for the energy region wherein abrupt changes occur near the K edge absorption energies. The values of mean free path, half value layer and tenth value layer were observed to be close to hair-like thickness or a thickness of few cell layers. Exposure to such low-energy photons can be very damaging to the skin cells and even the DNA. Such study will prove to be very useful for radiological applications.
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    TiB2 Thin Film Coated Glass and High Speed Steel (HSS) in Applications of Radiation Shielding Technology
    (Bursa Teknik Üniversitesi, 2020) Büyükyıldız, Mehmet; Turan, Ahmet; Tavşanoğlu, Tolga; Şakar, Erdem; Yücel, Onuralp; Kurudirek, Murat
    TiB2 (titanium diboride) is a transition metal boride with remarkable properties and, its thin-film coatings can be deposited on various substrates to develop the wear resistance properties of substrates. Radiation interaction properties of TiB2 coated glass and HSS are very significant as well for shielding applications and it has not been investigated so far. In this work, linear attenuation coefficient (µ), half-value layer (HVL), tenth-value layer (TVL) and mean free path (MFP) of TiB2 coated glass and HSS (AISI-M2) were measured using a 133Ba radioactive point source at energies 80.8, 276.4, 302.8, 356 and 383.8 keV. A comparison has been made with some radiation shielding concretes with respect to MFP. Energy absorption and exposure buildup factors (EABF and EBF) of composites were also calculated in the experimental energy region 50 – 500 keV. TiB2 coated glass and HSS were found to be better radiation shielding materials than the standard shielding concretes concluding that they can be further developed for radiation shielding applications.