Repeatedly retrieving information from memory can induce forgetting of related, un-retrieved information below baseline, an effect termed retrieval-induced forgetting (RIF; Anderson, Bjork & Bjork, 1994). The inhibitory account of RIF (e.g., Anderson, 2003) has received extensive support in the literature, especially through studies designed to empirically test inhibitory-based principles of RIF in adults. These principles include cue independence (RIF persists in the absence of the cue used during practice), interference/competition dependence (inhibition serves to resolve interference/competition between the cue and associated items during practice), strength independence (RIF is not strictly due to a target strengthening and competitor forgetting trade-off), retrieval-specificity (retrieval attempts are required to create the interference/ competition responsible for triggering inhibition), and output interference independence (RIF persists when output interference is controlled). However, competition-based explanations do not require an inhibitory component and can also account for many adult RIF findings. Very little RIF research has examined young children’s memory, whose immature memory systems might not be capable of demonstrating an inhibitory-driven effect. This dissertation filled this gap in the literature by thoroughly evaluating the inhibitory account of RIF in kindergartners (Ks). Two groups of Ks completed two RIF tasks that tested cue independence, competition/interference dependence, and strength independence in the first experiment, and retrieval-specificity, output interference independence, and strength-independence again in the second experiment. When a novel cue was used to test final memory (Experiment 1), and when a cue-free recognition test was used that controlled for output interference (Experiment 2), no RIF was found. These results, along with correlational evidence of strength dependence, favour a competition-based account of Ks’ RIF. Implications for inhibition theory and the potential development of RIF are discussed.

No description available.

ITC/USA 2005 Conference Proceedings / The Forty-First Annual International Telemetering Conference and Technical Exhibition / October 24-27, 2005 / Riviera Hotel & Convention Center, Las Vegas, Nevada / This paper presents the results of land-based SHF channel modeling experiments. Channel modeling data were collected at Edwards AFB, California at S-Band, X-Band and Ku-band. Frequency domain analysis techniques were used to evaluate candidate channel models. A graphical user interface (GUI) was developed to search for the optimum channel parameters. The model parameters corresponding to different frequencies were compared for multipath events captured at approximately the same locations. A general trend was observed where the magnitude of the first multipath reflection decreased as frequency increased and the delay remained relatively unchanged.

Cilia are small microtubule based structures found on the surface of almost all mammalian cells, enclosed in a highly specialised extension of the cell membrane. Components of several key developmental signalling pathways, in particular Hedgehog (Hh) signalling, are enriched in cilia and cells with mutations in cilia structure show aberrant signalling, suggesting cilia act as “antennae” to focus these signalling cascades. A spectrum of human diseases, termed ciliopathies, are caused by problems in cilia formation or cilia function, which display wide ranging phenotypes from embryonic lethality to retinal degeneration, polydactyly to cystic kidneys. Despite recent advances in the understanding of the essential roles cilia play in mammalian development, exactly how these complex structures are put together, how they carry out their diverse functions, and how they are regulated is not well understood. In this thesis, I describe a screen for genes involved in cilia formation and function. While optimising ciliogenesis and immunofluorescence protocols for the screen, the phenotypes of two ciliary mutant cell lines were analysed. Wdr35yet/yet and Dync2h1pol/pol mouse lines were identified in an ENU screen for genes involved in early development, and shown to have gross phenotypes similar to other ciliary mutants (Mill et al. 2011). Intraflagellar transport (IFT) is the active transport of proteins up and down the ciliary axoneme. Dync2h1 is a retrograde IFT motor component, whereas Wdr35 is part of the retrograde IFT-A complex. In this thesis, the cellular phenotypes of mouse embryonic fibroblasts derived from these mutants are described, showing that despite the fact both genes are thought to be involved in retrograde IFT, they show distinct ciliary phenotypes, suggesting novel roles for Wdr35 in mouse ciliogenesis. An siRNA screen was carried out in mouse fibroblasts to identify genes involved in (i) cilia formation, assayed by immunofluorescence for ciliary markers, and (ii) cilia function, assayed by activity of a Hh responsive luciferase transgene as an indirect readout of ciliary function. Although scalable, I initially screened a small test set of thirty-six putative cilia candidates, identified by cross species transcriptomic analysis. We identified several possible hits, many of which were in the ciliome database but also importantly, several genes with no known link to ciliogenesis. Repeats, correlation of phenotype to knockdown efficiencies and localisation studies validated two hits, Ccdc63 and Azi1. Ccdc63 is a novel coiled-coil gene with no previous link to ciliogenesis; the phenotype for this gene was analysed in real time using fluorescently tagged ciliary markers. A second hit, Azi1, was followed up in more detail. The reduction in ciliogenesis upon Azi1 knockdown was confirmed with separate siRNAs, and was rescued by overexpressing siRNA insensitive Azi1-GFP, confirming the phenotype is not due to off-target effects of the siRNAs. Azi1 gene trap mutant mice were generated and confirmed to be null mutations. Surprisingly, the mice survive, showing Azi1 is not essential for mammalian ciliogenesis. However, mutant males are infertile, with highly reduced sperm count and sperm abnormalities indicative of an arrest at Stage IX of spermiogenesis, when the flagellum, a highly specialised motile cilium, forms. The small number of sperm that do get to the epididymus are immotile. We suggest Azi1 is essential to in the formation of the sperm flagella and male fertility.

International Telemetering Conference Proceedings / November 04-07, 1991 / Riviera Hotel and Convention Center, Las Vegas, Nevada / This paper describes the design considerations and methodology applied to solve the practical problems posed in the creation of a high bit rate telemetry relay system and specifically the techniques implemented to enhance signal to noise performance under adverse operational conditions.

International Telemetering Conference Proceedings / October 23-26, 2000 / Town & Country Hotel and Conference Center, San Diego, California / Several test programs have reported degraded Global Positioning System (GPS) performance when L-band (1435-1535 MHz) telemetry is used while other test programs have had acceptable GPS performance with L-band telemetry. Most test programs seem to have minimal problems with S-band telemetry interfering with GPS performance if a bandpass filter is used between the GPS antenna and the low noise amplifier (LNA). This paper will present measured data on GPS performance with L- and S-band telemetry and explain what must be done to minimize interference to GPS. The paper will present both GPS signal-to-noise ratio (S/N) values as well as measured spectra from telemetry transmitters. System design guidelines for compatible operation will be presented.

published_or_final_version / abstract / Electrical and Electronic Engineering / Doctoral / Doctor of Philosophy

published_or_final_version / abstract / Electrical and Electronic Engineering / Doctoral / Doctor of Philosophy

This thesis investigates the improvements that can be made to Bayesian passive sonar tracking in the context of active-passive sonar data fusion. Performance improvements are achieved by exploiting the prior information available within a typical Bayesian data fusion framework. The algorithms developed are tested against both simulated data and data measured during the SEABAR 07 sea trial. Results show that the proposed approaches achieve improved detection, decreased estimation error, and the ability to track quiet targets in the presence of loud interferers. / text

In an interference network, multiple transmitters communicate with multiple receivers using the same communication channel. The capacity region of an interference network is defined as the set of data rates that can be simultaneously achieved by the users of the network. One of the most important example of an interference network is the wireless network, where the communication channel is the wireless channel. Wireless interference networks are known to be interference limited rather than noise limited since the interference power level at the receivers (caused by other user's transmissions) is much higher than the noise power level. Most wireless communication systems deployed today employ transmission strategies where the interfering signals are treated in the same manner as thermal noise. Such strategies are known to be suboptimal (in terms of achieving higher data rates), because the interfering signals generated by other transmitters have a structure to them that is very different from that of random thermal noise. Hence, there is a need to design transmission strategies that exploit this structure of the interfering signals to achieve higher data rates. However, determining optimal strategies for mitigating interference has been a long standing open problem. In fact, even for the simplest interference network with just two users, the capacity region is unknown. In this dissertation, we will investigate the capacity region of several models of interference channels. We will derive limits on achievable data rates and design effective transmission strategies that come close to achieving the limits. We will investigate two kinds of networks - "small" (usually characterized by two transmitters and two receivers) and "large" where the number of users is large. / text