1. Department of Physics; Acharya Nagarjuna University; Nagarjuna Nagar Guntur AP 522 510 India
2. Food Technology Division; Bhabha Atomic Research Centre; Trombay Mumbai 400 085 India
3. Department of Physics; KakaniVenkataRatnam College; Nandigama AP 521 185 India
4. Department of Physics; Andhra Loyola College; Vijayawada AP 520008 India