Add to ORKGI want to thank my research advisor Dr. L. Sunil Chandran for his guidance, perseverance and for the faith he has shown in me. It was in no way possible for me to write this thesis without his encouragement and support. All the work for this thesis was done under his guidance. It is an honour to mention that my parents and my brother made it possible, in every sense of the word, for me to be what I am today. Megha has also been very supportive. I would also like to thank Dr. Anita Das for her encouragement, for all the discussions we had and for bearing with all my thoughts throughout all the work done for this thesis. Manu helped in proofreading the thesis. I would like to thank the faculty and staff of CSA department for all the support a...