No description available.

No description available.

<p>Dendrites are the primary sites of information input into neurons. Proper establishment and maintenance of dendritic structure is essential for the function of neural circuits. In response to certain stimuli, the shape of dendritic arbors may be refined and remodeled. Despite the importance of dendrite structural plasticity in health and disease, the molecular mechanisms governing this process are not well understood. One genetically tractable platform to study context-dependent remodeling is the Drosophila peripheral nervous system. A subset of sensory neurons, the class IV dendritic arborizing neurons, has been shown to prune and regrow dendrites during metamorphosis. My research has focused on the mechanism through which these neurons regenerate a morphologically distinct dendritic structure. A forward genetic protein trap screen was conducted to identify genes differentially expressed during metamorphosis compared to larval stages. I identified Cysteine proteinase-1 as a gene upregulated in class IV neurons during dendrite regeneration under control of ecdysone hormone. Neurons carrying mutations of Cysteine proteinase-1 were unable to target and elaborate secondary dendritic arbors, resulting in disrupted morphology. These data were found to phenocopy dendrite regeneration defects in neurons lacking the homeobox transcription factor cut. Furthermore, I present evidence that Cysteine proteinase-1 can regulate a truncated cut isoform with altered function. This research presents a novel insight into the molecular mechanisms of sensory neuron dendrite remodeling. New directions arising from this study include potential conservation of this mechanism across species, downstream effectors of identified genes, and characterization of other systems subject to context-dependent dendrite regeneration. Elucidating the processes regulating dendrite remodeling will provide useful insight into nervous system function in health and disease.</p> / Dissertation

Recently, stochastic geometry has been shown to be a very powerful tool to model, analyze, and design networks with random topologies such as wireless ad hoc and sensor networks as well as multi-tier cellular networks. In stochastic geometry analysis, point processes are used to model the positions and the channel access behaviors of the nodes. The thesis develops analytical frameworks to characterize the performance of large-scale wireless networks with random topologies. In particular, I use stochastic geometry tools to model, analyze, and design ad hoc networks, star-connected sensor networks, and infrastructure-based two-tier cellular networks. I have optimized the tradeoff between outage probability and spatial frequency reuse efficiency in carrier sensing-multiple-access based ad hoc networks. I have developed a novel spectrum efficient design paradigm for star-connected wireless sensor networks. For downlink transmission in cellular networks with cognitive femto access points (FAPs), I have quantified the performance gain imposed by cognition and developed a paradigm to optimize the spectrum sensing threshold for cognitive FAPs. Finally, I have developed a novel modeling paradigm for uplink transmission in cellular networks and obtained simple expressions for network performance metrics including the outage probability and average rate. Furthermore, I have revealed a transition point in the behavior of uplink transmission in cellular networks that depends on the relative values of the network parameters.

No description available.

No description available.

This thesis investigates advanced silicon devices fabricated using phosphorous ion implantation. The novel devices presented are the silicon quantum cellular automata cell and the few-donor device implanted with controlled numbers of phosphorous donors. In addition, the thesis presents novel measurements of a phosphorous implanted silicon double-dot device, a crucial building block of a quantum cellular automata cell. The devices were fabricated using standard lithographic techniques and, in the case of few-donor devices, a new method of controlled single ion implantation using on-chip detector electrodes. The positional accuracy of the implanted ions was achieved using a resist mask defined by electron beam lithography. A series of subsequent process steps has also been developed to repair the substrate implantation damage, define surface control gates, and to define single electron transistors used for readout via the detection of sub-electron charge transfer signals in the device. The device operations were achieved at mK-temperatures using various measurement techniques. In the case of quantum cellular automata cells, the device operation was demonstrated directly by switching the polarization of the cells from one logic state to another and detecting the corresponding change in the electrostatic environment using single-electron transistors. The control gate limits necessary for stable QCA cell operation were also determined, indirectly demonstrating QCA logic state switching. The double-dot device operation was demonstrated using SET detection in both linear and for the first time in non-linear regimes. In addition, source-drain conductance detection of charge states, simultaneous detection using single-electron transistors and source-drain conductance, and source-drain bias spectroscopy measurements of these systems were also achieved. In the case of few-donor implanted devices, isolated charge transfers were detected in both MOS and PIN based devices. The signals corresponded to between 0.01 and 0.05 of a single electron charge, induced on the islands of the SETs. The magnetic field dependence of the charge transfers detected in few-donor implanted devices was also investigated, along with basic phosphorous donor ionization experiments. The devices were also measured using SETs operated in rf mode, yielding consistent results. The work presented in this thesis is a step towards realizing a silicon charge-based quantum computer and other advanced single-electron devices based on phosphorous ion-implantation in silicon.

Thesis (D.Sc.) -- University of Adelaide, Dept. of Microbiology, 1976.

Thesis (Ph.D.) -- University of Adelaide, Dept. of Microbiology, 1974.

Thesis (Ph. D.)--Washington State University, August 2008. / Includes bibliographical references (p. 88-101).