These articles are substantially reproduced in this thesis: The main content of these is reproduced in Chapters 3, 4, 5, 6, respectively. However some of the material in the works, notably parts of the introductions to each of the articles, as well as corresponding preliminaries sections, have been moved to the introduction here in Chapter 1, as well as to the Preliminaries, Chapter 2. This has been done in part to avoid repetitions of literary backgroud and basic concepts, as well as to present a more unified, self-contained work.The author of the thesis has also jointly co-authored the following two other articles, which will nonetheless not make it into the thesis.