Nanoclusters have special importance in nanotechnology because of their low dimensionality, which provides electronic, chemical, and magnetic properties that differ from those of the equivalent bulk materials. Suitably controllable self-assembly methods are required in order to incorporate nanoclusters into useful devices. The self-assembly method used in this study employs V-grooves as a template element for nanocluster device fabrication. The V-grooves are fabricated by optical lithography on SiO2/Si wafers and KOH wet etching. Bi clusters deposited on a V-groove form a self-assembled conducting wire. The clusters are produced using an inert gas aggregation source inside an ultra high vacuum compatible system. In order to characterise the assembly process, Bi clusters with different average sizes and velocities are deposited on V-grooves with different widths. The cluster bouncing was found to be the main process in forming the cluster wires. The bouncing angles were smaller than the incident angle, and they are dependent on the cluster size and velocity. For a certain bouncing angle, the wire width reflects the V-groove width because of the fixed bouncing angle. Nanocluster devices were fabricated by depositing the clusters on V-grooves with pre-formed Au/NiCr electrical contacts. The amount of the deposited material required to form an electrically conducting wire was found to be a function of the V-groove width and the wire length. The two point I(V) measurements in the voltage range between -1 and +1V showed linear characteristics for low resistance wires (kΩ), and non-linear characteristics for the high resistance ones (MΩ). The silicon substrate was used as a back gate. Applying a voltage to the gate was found to modify the electrical conduction of the cluster wire. The temperature dependence of the resistance of the nanocluster wires was studied in the temperature range of 4.2-473K, and all of the measured wires showed a negative temperature coefficient of resistance. These measurements allowed a detailed study of the conduction mechanisms through the cluster wires. The study showed that Bi clusters can be used for device fabrication. To size select the clusters prior to using them for the device fabrication, a high transmission mass filter is required. This transmission can be obtained using the von Issendorff and Palmer mass filter if it is operated using the optimum operation conditions. The mass filter consists of two pairs of parallel plates with horizontal openings in Plates 1 and 2, and it operates on the time of flight principle. During this project, the operation conditions of this mass filter were studied using both experiment and simulation. The study showed that the beam deflection angle is a critical factor in optimising the mass filter transmission efficiency. This angle is dependent on the accelerating voltage, ion mass, and the horizontal velocity of the ions. The optimum operation conditions for the mass filter were found and used to study the mass distribution of Pd ions produced by a magnetron sputtering source with variable cluster aggregation length.

Plants are continually exposed to a vast array of pathogens, and generally succeed in defending themselves. An important part of this process is the induction of defence gene products that hinder pathogen growth and delay or prevent disease development. The way in which plants do this is multi-factorial, and includes regulatory proteins known as transcription factors (TFs) which directly regulate the expression of defence-related genes. The expression and activity of these TFs can be differentially regulated by pathogen challenge, as well as following exposure to defence-related signalling molecules such as methyl jasmonate (MeJA). To identify TFs potentially involved in MeJA signalling and plant defence, the expression of all 1,534 putative Arabidopsis (Arabidopsis thaliana) TF genes identified in the genome (at the time) were screened by Real-Time Quantitative PCR (RT-Q-PCR) for altered transcript expression 6 h following either MeJA treatment or inoculation with the incompatible fungal pathogen Alternaria brassicicola. This primary screen identified 134 TF genes that showed a significant change in expression compared to mock-treated plants, and included many genes of previously unknown function belonging to APETALA2/Ethylene Response Factor (AP2/ERF), MYB, WRKY, and NAC TF gene families. Twenty-four of these TF genes were shown to be repressed or induced by MeJA, as well as repressed or induced by A. brassicicola (i.e. co-regulated). A high proportion of these co-regulated genes were members of either the AP2/ERF or WRKY TF gene families. Selected TF genes that showed significant differential regulation following MeJA exposure or A. brassicicola inoculation were profiled in a four-point timecourse over a 24 h period. It was found that the AP2/ERF TF genes identified in the primary screen were the most consistently and reproducibly regulated family of genes. The majority of these regulated TF genes belong to two distinct subclusters of AP2/ERFs in an amino acid based sequence similarity tree, implicating the B3 and B1a subclusters in MeJA signalling and A. brassicicola defence. One gene from each subcluster was chosen for further analysis, based on its consistent pattern of induction by MeJA and A. brassicicola as well as the compatible fungal pathogen Fusarium oxysporum. These two TFs were AtERF2 (B3 cluster) and AtERF4 (B1a cluster). Transgenic Arabidopsis plants were generated that stably overexpress the AtERF2 TF gene. Analysis of these plants revealed that this TF is a positive regulator of a subset of MeJA-responsive defence genes encoding the antimicrobial proteins PDF1.2 and CHIB. Additionally, AtERF2-overexpressing lines displayed increased resistance to the fungal pathogen F. oxysporum compared to wild-type plants, as well as enhanced sensitivity to the MeJA-inhibition of root elongation. In contrast to the positive regulation displayed by AtERF2, functional analysis of AtERF4 by both stable overexpression and insertional inactivation in Arabidopsis clearly demonstrated that AtERF4 acts as a negative regulator of the MeJAresponsive expression of PDF1.2. Furthermore, it was demonstrated that AtERF4 acts as a negative regulator of resistance to F. oxysporum and antagonizes the MeJAinhibition of root elongation. Overall, the work undertaken during this PhD has identified two conserved clusters of AP2/ERF TFs with members that display contrasting roles in the regulation of defence gene expression, along with resistance to F. oxysporum and root sensitivity to MeJA. These results suggest that plants co-ordinately express multiple repressor- and activator-type AP2/ERFs during pathogen challenge to modulate defence gene expression and hence the development of disease. By identifying and characterising selected members of the AP2/ERF TF family, this work has provided a greater understanding of the mechanisms of the plant defence response leading to disease resistance. In doing so, it has provided novel tools to assist in the development of pathogen-resistant plants for use by the agricultural industry.

Thesis (M.S.)--Auburn University, 2007. / Abstract. Includes bibliographic references (ℓ. 16-21, 50-51)

Thesis (Ph. D.)--University of Texas at Austin, 2006. / Vita. Includes bibliographical references.

Thesis (Ph. D.)--University of North Texas, Aug., 2007. / Title from title page display. Includes bibliographical references.

Zugl.: Karlsruhe, Univ., Diss., 2004

Thesis ( Ph.D.) -- McMaster University, 1998. / Includes bibliographical references (leaves 136-139). Also available via World Wide Web.

Thesis (LL. M.)--Judge Advocate General's School, United States Army, 1972. / "April 1972." Typescript. Includes bibliographical references. Also issued in microfiche.

Thesis (Ph.D.) -- McMaster University, 2005. / Supervisor: Dr. Sigal Balshine. Includes bibliographical references (p. 103-126)

Thesis (Ph.D.)--Australian National University, 2003.