This thesis involves the study of a repulsive-attractive N-body problem, which is a subclass of a quasihomogeneous N-body problem [5]. The quasihomogeneous N-body problem is the study of N point masses moving in R3N, where the negative of the potential energy is of the form, X 1≤i<j≤N bmimjr−β ij + X 1≤i<j≤N amimjr−α ij . In the above equation, rij is the distance between the point mass mi and the point mass mj , and a, b, α > β > 0 are constants. The repulsive-attractive N-body problem is the case where a < 0 and b > 0. We start the ground work for the study of the repulsive-attractive N-body problem by defining the first integrals, collisions and pseudo-collisions and the collision set. By examining the potentials where a < 0 and b > 0, we see that the dominant force is repulsive. This means that the closer two point masses get the greater the force acting to separate them becomes. This property leads to the main result of the first chapter: there can be no collisions or pseudo-collisions for any repulsive-attractive system. In the next chapter we study central configurations of the system. Quasihomogeneous potentials will have different central configurations than homogeneous potentials [6], thus requiring the classification of two new subsets of central configurations. Loosely speaking, the set of central configurations that are not central configurations for any homogeneous potential are called extraneous. The set of configurations that are central configurations for both homogeneous potentials that make up the quasihomogeneous potential, are called simultaneous configurations. We also notice that every simultaneous central configuration will be non-extraneous, therefore the two subsets are disjoint. Next we show the existence of oscillating homothetic periodic orbits associated with non-extraneous configurations. Finally in this chapter, we investigate the polygon solutions for repulsive-attractive N-body problems [11]. In particular we show that the masses need no longer to be equal, for repulsive-attractive potentials. It will be shown that there exists a square configuration with m1 = m2 6= m3 = m4, that leads to a relative equilibrium. Therefore, for N = 4 the set of extraneous configurations is non-empty. The last chapter deals with the complete analysis of the generalized Lennard- Jones 2-body problem. The generalized Lennard-Jones problem is the subcase of the repulsive-attractive N-body problem, where a = −1, b = 2, and α = 2β. We proceed as in [13] by using diffeomorphic transforms to get an associated system thereby generating a picture of the global flow of the system. This gives us the complete flow for the generalized Lennard-Jones 2-body problem.

In this day and age of europeanisation and internationalisation of all aspects of society, including law, the topic of medieval maritime law has attracted increasing interest.  Regulating sea shipping, which is characterised by the connection between different ‘nations’, sea law is intrinsically international.  Or is it?  The existence of a common medieval maritime law has often been presumed, but is researched thoroughly for the first time in this study. By analysing the developing and spread of the written sea laws across Northern Europe and by comparing the contents of the different maritime regulations, as well as the legal practice in five Northern European towns (Lübeck in Northern Germany, Reval (Tallinn) in Estonia, Danzig (Gdansk) in Poland, Kampen in the Netherlands and Aberdeen in Scotland) by using the examples of shipwreck, jettison and ship collision, the author has aimed to determine whether it is accurate to speak of a common law of the sea in medieval Northern Europe on the level of the books of law, their contents and the practice of the law at the town courts. Research has proven that there was no uniformity on any of these levels, despite occasional similarities between the laws and the judgements passed by the courts.  There was no single law compilation available throughout Northern Europe at any time during the Middle Ages, there were no common regulations in the written laws and there was  no uniform legal practice in the towns of Northern Europe. The divergence between the five towns handled in this study could largely be explained by the different role each of the towns played on the European stage.

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Copies of author's previously published articles inserted / Bibliography : leaves 171-190 / v, 190 leaves : ill ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (Ph.D.)--University of Adelaide, Dept. of Physics and Mathematical Physics, 1991

Copies of three of the author's previously published articles inserted as appendix B. / Includes bibliographical references / 124 leaves : ill ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (Ph.D.)--University of Adelaide, Dept. of Physics and Mathematical Physics, 1993

List of author's previously published works included / Bibliography: leaves 165-177 / v, 177 leaves : ill ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (Ph.D.)--University of Adelaide, Dept. of Physics and Mathematical Physics, 1994

Thesis (Ph. D.)--University of Adelaide, Dept. of Physics and Mathematical Physics, 1993. / Copies of three of the author's previously published articles inserted as appendix B. Includes bibliographical references.

Thesis (Ph.D.)--Australian National University, 2006.

Thesis (Ph. D.)--Carleton University, 2003. / Includes bibliographical references (p. 262-286). Also available in electronic format on the Internet.

Thesis--Rijksuniversiteit te Leiden. / Summary also in Dutch. Includes bibliographies. Also issued in print.