abstract  introduction: recently uses of medium and high energy x-rays has been increased in iran and radiotherapy centers along with a variety of accelerators have been installed in some provinces. in the other hand there is no sufficient skill in designing and making radiotherapy treatment rooms. this study was conducted to evaluate the efficacy of different mixtures of barite concrete for sh...

in some special cases, rubber compounds with high amounts of unsaturated elastomer are recommended with organic sulfur donors instead of mineral sulfurs. in this condition, activated sulfur is produced in situ and curingprocess is facilitated without accelerators. organic sulfur donor compounds have low thermal stability and in the vulcanization temperature produce free and activated sulfurs. t...