At the completion of this work I take great pleasure in thanking and acknowledging the people who have supported me over the eight years of my university education, and in particular the last four years.
I could not have started down this path without the support and understanding of my family and my wife. Their encouragement has enabled me to pursue my goals with vigour. I hope that they can take as much pleasure from this finished work as I do.
I thank my PhD thesis supervisor, Dr David L. Jauncey of the Australia Telescope National Facility. His guidance and insight has helped shape this work into what it is, and his careful proof reading of draft papers and the final thesis manuscript was very much appreciated. I am also grateful for the input of my advisor, Dr Geoffrey V. Bicknell of the Mount Stromlo and Siding Spring Observatories
I would like to thank the members of the Astronomical Measurements Group at the Jet Propulsion Laboratory in Pasadena, led by Dr Robert A. Preston. A substantial fraction of my time over the last 4 years has been spent at JPL, working in the AMG, without a doubt providing the most productive and enjoyable periods of my thesis.
Many other people have been involved in the work presented here, without whom the final results could not have been achieved. I refer here to the numerous people who have staffed the SHEVE telescopes over the last four years, changing tapes, making equipment work, and dealing with the logistics of getting an ad hoc VLBI array up and running a few times per year with a great deal of success. These people are too many to thank individually but Dr John E. Reynolds and Dr Anastasios K. Tzioumis deserve special mention; they are the driving force behind much of what happens in the SHEVE operation.
Finally, this work was supported financially by an Australian Postgraduate Award. Financial support for travel was provided by the Mount Stromlo and Siding Spring Observatories, the Jet Propulsion Laboratory, the Australia Telescope National Facility student program, and the Department of Industry, Science, and Tourism. I am grateful for the generous financial support of the organisers of the workshop ``Jets from Stars and AGN'' held in Bad Honnef, Germany, in particular Dr Wolfgang Kundt. Generous financial support provided by Dr Phillip Hardee allowed me to attend the workshop on ``Energy Transport in Radio Galaxies and Quasars'' in Tuscaloosa, USA. An IAU grant allowed me to attend IAU 175, ``Extragalactic Radio Sources'', in Bologna, Italy. These conferences and workshops have provided invaluable opportunities for me to present some of the results of my work and learn from the wider international community.
This research has made use of the NASA/IPAC Extragalactic Database (NED) which is operated by the Jet Propulsion Laboratory, California Institute of Technology, under contract with the National Aeronautics and Space Administration. Part of this research was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under contract with the National Aeronautics and Space Administration.