An automatic implantable cardiac defibrillator (AICD) is a device that is implanted in the chest to constantly monitor and, if necessary, correct episodes of arrhythmia. While the longevity of the average AICD patient has increased to 10 years after implantation, only 5% of implants functioned for seven years, and this mismatch poses a significant and ever growing clinical and economic burden. Moreover, there are now efforts to “piggyback” devices on AICDs and BVPs for additional functionality, all of which require more power. An innovative approach towards generating power for AICDs is to harness the energy of the heart by embedding energy generators in AICD leads. The cardiovascular system as a source generator is appealing due to its ability to continuously deliver mechanical energy as long as the patient is alive. Herein a device incorporating nanostructured piezoelectrics was developed as a means to harvest the energy of heart. The generator system integrates inorganic piezoelectric nanomaterials, including aligned arrays of nanowires of crystalline zinc oxide (ZnO), with elastomeric substrates. The design combines several innovative structural configurations including a “wavy” flexible electrode and a layout where the nanowires are near or on the neutral mechanical plane. A wet synthetic strategy to reliably prepare piezoelectric ZnO nanostructures directly onto the devices was also developed and optimized to produce nanowires with high densities, large aspect ratios and high orientation. The elastomeric support permits direct integration within AICD leads and is small and flexible enough to not add resistance in systole. The flexible devices were integrated into a testbed mimicking the input a failing right ventricle and the results demonstrate progress towards energy harvesting from the cardiovascular system. A model was developed to gain insight as to how to structure the nanowire array within the latitude of the synthesis to boost the energy production. To further improve the output, the nanowires were passivated with dipolar molecules to change their resistivities and the barrier height of the Schottky contact. A novel low photon energy photoelectron spectroscopy tool was developed to measure the effects of the molecules on the individual nanowire properties. This concept of using nanostructured piezoelectrics as a means to convert the energy of the body may in the coming years represent a paradigm shift from battery dependant AICD modules to completely autonomous functional systems. / text

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Central to the practical use of nanoscale materials is the controlled growth in technologically meaningful quantities. Many of the proposed applications of the nanomaterials potentially require inexpensive production of the building blocks. Solution-based synthetic approach offers controllability, high throughput, and scalability, which make the process attractive for the potential scale-up. Growth kinetics could be readily influenced by chemical interactions between the precursor and the solvent. In order to fully utilize its benefits, it is therefore pivotal to understand the decomposition chemistry of the precursors used in the reactions. Supercritical fluids were used as solvent in which high temperature reactions could take place. Silicon nanowires with diameters of 20~30 nm was synthesized in supercritical fluids with metal nanocrystals as seeds for the nanowire growth. To unravel the effect of silicon precursors, several silicon precursors were reacted and the resulting products were investigated. The scalability of the system is discussed based on the experimental data. The nanowires were characterized with various characterization tools, including high-resolution transmission electron microscopy and electron energy loss spectroscopy. The crystallographic signatures were analyzed through the transmission electron microscopic study, and fundamental electrical and optical properties were probed by electron energy loss spectroscopy. Carbon nanotubes were prepared by reacting carbon-containing chemicals in supercritical fluids with organometallic compounds that form metal seed particles in-situ. A batch reaction, in which the temperature control was relatively poor, yielded a mixture of multiwall nanotubes and amorphous carbon nanofilaments with a low selectivity of nanotubes in the product. When reaction parameters were translated into a continuous flow-through reaction, nanotube selectivity as well as the throughput of the total product significantly improved. Magnetic properties of various metal nanocrystals were also studied. Colloidal synthesis enables the growth of FePt and MnPt3 nanocrystals with size uniformity. The as-synthesized nanocrystals, however, had compositionally disordered soft-magnetic phases. To obtain hard magnetic layered phase, the nanocrystals must be annealed at high temperatures, which led to sintering of the inorganic cores. To prevent sintering, the nanocrystals were encapsulated with silica layer prior to annealing. Interparticle magnetic interactions were also explored using particles with varying silica thickness. / text

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We present experimental studies based on all three methods by which the generation of squeezed light in semiconductors has thus far been demonstrated experimentally: Fourwave mixing, multi-photon absorption and direct generation at the source. Four-wave mixing was used to generate femtosecond-pulsed quadrature squeezed light by cross-phase modulation in single-crystal hexagonal CdSe at wavelengths between 1.42 and 1.55 μm. We measured 0.4 dB squeezing (1.1 dB is inferred at the crystal) using 100 fs pulses. The wavelength and the intensity dependence, as well as variations in the local oscillator configuration were investigated. At higher intensities squeezing was shown to deteriorate owing to competing nonlinear processes. We also characterised the nonlinear optical properties of CdSe in this wavelengths range using an interferometric autocorrelator. In addition, we studied the feasibility of extending this technique to AlGaAs waveguides. The key problems are addressed and solutions are proposed. In a different experiment we used an AlGaAs waveguide to demonstrate for the first time photon-number squeezing by multi-photon absorption. By tuning the pump energy through the half bandgap energy we could effectively select two- or three-photon absorption as the dominant mechanism. Squeezing by these two mechanisms could be clearly distinguished and was found to be in good agreement with longstanding theoretical predictions. We also established the generality of the effect, by demonstrating the same mechanism in organic semiconductors, where it led to the first ever observation of squeezed light in an organic material. Finally, we present our measurements of photon-number squeezing in high-efficiency double heterojunction AlGaAs light-emitting diodes. We measured squeezing of up to 2.0 dB. In addition, we observed quantum noise correlations when several of these devices were connected in series.

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The rheological, color, micro-structural, and electrical properties of surimi seafood gels were investigated. Various starches and protein additives at different ratios were evaluated with Alaska pollock surimi under ohmic heating at different heating rates to determine their functional properties and further to compare these properties with those of conventionally cooked gels. Native starches at low concentration were able to enhance rheological properties due to their gelatinization during heating. Pregelatinized starch decreased texture properties; however, it could suppress the undesirable appearance of the final product because its granules could absorb the surrounding water during chopping and perform a higher degree of retrogradation when cooling. A mixture of native and pregelatinized starches showed a positive trend at high concentration. The more starch added, the lower the L* and b* values of the gels. Protein additives improved textural properties, but negatively affected gel colors. Lower moisture content of the final products showed higher strength in texture, but lower lightness values. Gels cooked under ohmic heating with a slow heating rate mostly exhibited better texture properties than conventionally cooked gels. Electrical conductivities increased when temperature increased, resulting in a linear relationship. Electrical conductivity also significantly increased with moisture content, and slightly increased with applied frequency and voltage. There were some changes in the magnitude of electrical conductivity of surimi-starch paste when temperature increased, most obviously seen at a high concentration of native starch with slow ohmic heating. This indicated that starch gelatinization affected the electrical conductivity of surimi-starch paste while heating. / Graduation date: 2003

This thesis investigates the presence of multiple (quasi-TEM) modes in inverted embedded microstrip lines. It has already been shown that parasitic modes do exist in inverted embedded microstrips due to field leakage inside the dielectric substrate, especially for high dielectric constants (like Silicon). This thesis expands upon that work and characterizes those modes for a variety of geometrical dimensions. Chapter 1 focuses on the theory behind the different transmission line modes, which may be present in inverted embedded microstrips. Based on the structure of the inverted embedded microstrip, the conventional microstrip mode, the quasi-conventional microstrip mode, and the stripline mode are expected. Chapter 2 discusses in detail the techniques used to decompose the total probed field into the various modes present in the inverted embedded microstrip lines. Firstly, a short explanation of the finite-difference time-domain method, that is used for the simulation and modeling of inverted microstrips up to 50 GHz is provided. Next, a flowchart of the process involved in decomposing the modes is laid out. Lastly, the challenges of this approach are also highlighted to give an appreciation of the difficulty in obtaining accurate results. Chapter 3 shows the results (dispersion diagrams, values/percentage of the individual mode energies ) obtained after running time-domain simulations for a variety of geometrical dimensions. Chapter 4 concludes the thesis by explaining the results in terms of the transmission line theory presented in Chapter 1. Next, possible future work is mentioned.

Semiconducting properties and related defect disorder for well defined TiO2 single crystal were studies. Semiconducting properties have been determined using simultaneous measurements of two independent electrical properties, including electrical conductivity, ??, and thermoelectric power, S, at elevated temperatures (1073-1323 K) in the gas phase of controlled oxygen activity (10-10 Pa &lt p(O2) &lt 75 kPa). Measurements of s and S were conducted (i) in the gas/solid equilibrium and (ii) during equilibration. Oxygen vacancies have been identified as the predominant defects in TiO2 over a wide range of p(O2). Individual conductivity components related to electrons, electron holes and ions, were determined from the obtained ?? data. The effect of p(O2) on these individual components was considered in the form of a diagram. This work led to the discovery of the formation and diffusion of Ti vacancies. However, the obtained diffusion data indicate that, in the temperature ranges commonly used in studies of semiconducting properties (1000-1400K), the Ti vacancies concentration is quenched and may thus be assumed constant. In addition it was shown that Ti vacancies in appreciable concentrations form only during prolonged oxidation. It was determined that the discrepancies in the reported n-p transition point are related to the concentration and spectrum of impurities as well as the concentration of Ti vacancies. It has been shown that the n-p transition point in high-purity TiO2 is determined by the Ti vacancy concentration. A well defined chemical diffusion coefficient, Dchem, was determined using kinetic data obtained during equilibration. A complex relationship between p(O2) and Dchem was observed. These data showed a good agreement between the obtained diffusion data and defect disorder. Examination of the determined equilibration kinetics, led to the discovery of two kinetic regimes, the result of the transport of defects at different mobilities. The determined data are considered well defined due to the following reasons: 1. The studied specimen was of exceptionally high purity and free of grain boundaries (single crystal) 2. The specimen was studied in the gas phase of controlled and well defined oxygen activity which was continuously monitored. 3. Whenever the experimental data were measured in equilibrium, the gas/solid equilibrium has been verified experimentally. 4. A good agreement between the two, self-confirmatory, electrical properties, including ?? and S has been determined simultaneously and independently. The defect disorder model derived in the present work may be used for tailoring controlled semiconducting properties through the selection of annealing conditions involving the temperature and oxygen activity.