Gratitude is offered where it is due, and foremost is to my advisor Prof. Dr. Winfried Plass whose continued support and guidance in all the matters scientific put me in a position to present this work. Particular is the appreciation for his endless patience which helped me discover my own eccentricities. I feel overwhelmingly indebted to BBG and all the members of our family for their patience during my long stay abroad. That I took so long to return is my failing. That they still own me is their magnanimity. Greatly acknowledged are the contributions of my colleague Dr. Axel Buchholz towards my handling of matters of which I had little knowledge and no experience, i.e. living in Germany, understanding the vogonic poetry of German officialdom and moving from Siegen to Jena. Besides, his help in solving occasional computer hardware problems enabled my research work to run smoothly. Special thanks to my former Rumanian colleague Dr. Simona Nica for giving the semblance of social existence to what was a secluded life in Siegen. During her stay in AG Plass, she was always kind and helpful. The memorable conversations we had, covered a wide range of topics from latest scandals (from anywhere) to Schopenhauer. Particularly, her aversion towards agreeing on almost anything made the conversations much more enjoyable (and explosive).