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Defective alkanethiol monolayers were studied as a model system to understand the stress changes observed in microcantilever-based DNA hybridization experiments. An exponential relationship between defect density and surface stress was found by performing simultaneous electrochemical/stress-sensing experiments. Microcantilevers with a range of defective alkylthiol self assembled monolayers were prepared and stress change/electrochemical data were collected in perchlorate, chloride, and bromide-containing electrolytes. Defects were probed using a ferrocene-thiol labeling technique which provides quantitative measurement of defect area. Using defects and solutions containing charge transferring adsorbates is suggested as a method for enhancing the surface stress signals in cantilever sensor systems. The best response from this study was obtained in bromide, as its exponential function had the sharpest increase with defect density.

Photovoltaic (solar electric) technology has shown significant potential as a source of practical and sustainable energy; this study focuses on increasing the performance of photovoltaic systems through the use of improved control and power interfaces. The main objective is to find an effective control algorithm and topology that are optimally suited to extracting the maximum power possible from photovoltaic modules. The thesis consists of the following primary subjects: photovoltaic modelling, the topological study of photovoltaic interfaces, the regulation of photovoltaic voltage, and maximum power tracking. In photovoltaic power systems both photovoltaic modules and switching mode converters present non-linear and time-variant characteristics, resulting in a difficult control problem. This study applies in-depth modelling and analysis to quantify these inherent characteristics,s pecifically using successive linearization to create a simplified linear problem. Additionally, Youla Parameterisation is employed to design a stable control system for regulating the photovoltaic voltage. Finally, the thesis focuses on two critical aspects to improve the performance of maximum power point tracking. One improvement is to accurately locate the position of the maximum power point by using centred differentiation. The second is to reduce the oscillation around the steady-state maximum power point by controlling active perturbations. Adopting the method of steepest descent for maximum power point tracking, which delivers faster dynamic response and a smoother steady-state than the hill climbing method, enables these improvements. Comprehensive experimental evaluations have successfully illustrated the effectiveness of the proposed algorithms. Experimental evaluations show that the proposed control algorithm harvests about 1% more energy than the traditional method under the same evaluation platform and weather conditions without increasing the complexity of the hardware.

This research investigates the use of conducting polymer coatings on platinum (Pt) electrodes for use in neuroprostheses. Conducting polymers aim to provide an environment conducive to neurite outgrowth and attachment at the electrode sites, producing intimate contact between neural cells and stimulating electrodes. Conducting polymers were electropolymerised onto model Pt electrodes. Conventional polymers polypyrrole (PPy) and poly-3,4-ethylenedioxythiphene (PEDOT) doped with polystyrenesulfonate (PSS) and para-toluenesulfonate (pTS)were investigated. Improvement of material properties was assessed through the layering of polymers with multi-walled carbon nanotubes (MWNTs). The ability to incorporate cell attachment bioactivity into polymers was examined through the doping of PEDOT with anionic laminin peptides DCDPGYIGSR and DEDEDYFQRYLI. Finally, nerve growth factor (NGF), was entrapped in PEDOT during polymerisation and tested for neurite outgrowth bioactivity against the PC12 cell line. Each polymer modification was assessed for electrical performance over multiple reduction-oxidation cycles, conductivity and impedance spectroscopy, mechanical adherence and hardness, and biological response. Scanning electron microscopy was used to visualise film topography and x-ray photon spectroscopy was employed to examine chemical constitution of the polymers. For application of electrode coatings to neural prostheses, optimal bioactive conducting polymer PEDOT/pTS/NGF was deposited on electrode arrays intended for implantation. PC12s were used to assess the bioactivity of NGF functionalised PEDOT when electrode size was micronised. Flexibility of the design was tested by tailoring PEDOT bioactivity for the cloned retinal ganglion cell, RGC-5, differentiated via staurasporine. It was established that PEDOT films had superior electrical and cell growth characteristics, but only PPy was able to benefit from incorporation of MWNTs. Bioactive polymers were produced through inclusion of both laminin peptides and NGF, but the optimum film constitution was found to be PEDOT doped with pTS with NGF entrapped during electrodeposition. Application of this polymer to an implant device was confirmed through positive neurite outgrowth on vision prosthesis electrode arrays. The design was shown to be flexible when tailored for RGC-5s, with differentiation occurring on both PEDOT/pTS and PEDOT/DEDEDYFQRYLI. Conducting polymers demonstrate the potential to improve electrode-cell interactions. Future work will focus on the effect of electrical stimulation and design of bioactive polymers with improved cell attachment properties.

Formal methods are increasingly accepted for developing software systems, however their application to user-interface development is less common. In this thesis, we demonstrate the utility of formal object-oriented techniques for specifying, designing and implementing user-interfaces. The specification of a user-interface describes user-perceivable operations and information structures for an interactive system in an implementation-independent way. Operations of a user-interface specification define tasks. User-interfaces can be specified by a system of communicating agents where some agents are presented to users. An agent and its presentation together define an interactor. Defining the presentation of interactors is a design concern. Widgets are common re-usable interactors for which the presentation is usually well defined. Definitions of widgets may be stored in a library. We illustrate the characteristics of notations for interactor based specification using the Object-Z language and demonstrate using interactors from a widget library. Formal methods enable a "model-based" approach to be taken to the development of user-interface designs. A specification in terms of widgets is derivable from an abstract interactor-based specification. A corresponding user-interface design is usually easily identified from a widget-based specification. Interactor-based user-interface designs can be used to define an architecture for a corresponding system implementation. Derivation of a widget-based specification from an abstract specification corresponds to a task decomposition (i.e., the abstract and widget-based specifications enable the same tasks to be performed, although the operations involved differ). Task decomposition defines a compatibility relation between user-interface specifications. We give "specification patterns" to assist incrementally transforming an abstract user-interface specification to an equivalent specification in terms of widgets.

Thesis (Ph. D.)--University of Texas at Austin, 2007. / Vita. Includes bibliographical references.

Thesis (Ph. D.)--Virginia Polytechnic Institute and State University, 1990. / Vita. Abstract. Includes bibliographical references (leaves 89-94). Also available via the Internet.

Thesis (M.Sc.)--York University, 2005. Graduate Programme in Computer Science. / Typescript. Includes bibliographical references (leaves 123-127). Also available on the Internet. MODE OF ACCESS via web browser by entering the following URL: http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&res_dat=xri:pqdiss&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&rft_dat=xri:pqdiss:MR11829