background: megavoltage beams used in radiotherapy are contaminated with secondary electrons. different parts of linac head and air above patient act as a source of this contamination. this contamination can increase damage to skin and subcutaneous tissue during radiotherapy.  monte carlo simulation is an accurate method for dose calculation in medical dosimetry and has an important role in opt...

vast application of the antibiotic drugs in animals without due attention  to withdrawal times necessitates quality control of food stuff in terms of antibiotics' residues. antibiotic residues in food stuff cause bacterial resistance, allergic reactions, toxicity,  carcinogenic effects and change of natural micro flora of intestine in consumers. so, the aim of the present study is detectio...