Over the past few decades, surface dielectric barrier discharge (SDBD) actuators have been studied extensively as aerodynamic flow control devices. There has been extensive research on producing SDBD plasmas through excitation by sinusoidal high voltage in low-speed flows, resulting in local acceleration of the flow through the electrohydrodynamic (EHD) effect. However, high-speed flow control using SDBD actuators has not been considered to the same extent. Control through thermal perturbations appears more promising than using EHD effects. SDBDs driven by nanosecond repetitively pulsed (NRP) discharges (NRP SDBDs) can produce rapid localized heating and have been used to produce better flow reattachment in high-speed flows. While surface actuators based on NRP DBDs appear promising for high-speed flow control, the physics underlying the plasma/flow coupling are not well understood and the actuators have yet to be fully characterized or optimized. In particular, methods for tailoring the plasma characteristics by varying the actuator’s electrical or geometrical characteristics have not been thoroughly explored.<div>In the current work, NRP SDBD actuators for control of high-speed flows are developed and characterized. As discussed previously, it is believed that the mechanism for high-speed flow control by these plasmas is thermal perturbations from rapid localized heating. Therefore, the goal is to design actuators that produce well-defined filamentary discharges which provide controlled local heating. The electrical parameters (pulse duration, PRF, and polarity) and electrode geometries are varied and the optimal configurations for producing such plasma filaments over a range of ambient pressures are identified. In particular, single and double sawtooth shaped electrodes are investigated since the enhanced electric field at the electrode tips may permit easier production of “strong” (i.e. higher temperature) filaments with well-defined spacing, even at low pressure. Time-resolved measurements of the gas temperature in the plasma will be obtained using optical emission spectroscopy (OES) to assess the thermal perturbations produced by the actuators. To the author’s knowledge, these will be the first such measurements of temperature perturbations induced by NRP SDBDs. The plasma structure and temperature measurements will be correlated with schlieren visualization of the shock waves and localized flow field induced by the discharges. Finally, the optimized actuators will be integrated into a high-speed flat plate boundary layer and preliminary assessment of the effect of the plasma on the boundary layer will be conducted.<br></div>

Mammalian odorant receptors (ORs) are Class I G-protein coupled receptors (GPCRs) located within the nasal epithelium. Odorant receptors interact with Galpha olfactory, a Galpha S type G-protein. Activated Galpha olfactory stimulates adenylate cyclase and the resulting increase in cAMP concentration opens cyclic nucleotide gated channels allowing Ca2+ to enter the cell. The increased Ca2+ then activates a Ca2+ activated Cl- channel which further depolarizes the cell. This depolarization initiates an action potential that reaches the axon of the olfactory sensory neuron located in the main olfactory bulb. Information from the main olfactory bulb is then transmitted to higher regions of the brain. Olfactory information is initially coded through the interaction of odorant molecules with hundreds of distinct ORs, but difficulty in exogenous expression of odorant receptors has delayed the identification of ligands for individual ORs. However, expression of mouse odorant receptors in Xenopus laevis oocytes allows for a systematic screening for potential ligands, as well as for efficient study of the structure-function relationship of the receptors and their ligands. My screening of odorant receptors using Xenopus oocytes included the coexpression of a signal transduction system and the use of robotic two-electrode voltage clamp electrophysiology. In this study, I investigated the structural basis for ligand recognition in mouse odorant receptors. First, I expanded the molecular receptor ranges of seven Class I odorant receptors. By use of a high throughput assay, I was able to expand upon current knowledge in the field for the mouse odorant receptors 23-1, 31-4, 32-11, 40-4, 42-1, 42-2 and 42-3. I then examined one receptor (MOR23-1) in more detail. I used the substituted cysteine accessibility method to identify residues within transmembrane domain five of this receptor that are accessible from the extracellular space. These residues may line the ligand binding site or the ligand access pathway. Conventional mutations of A205 caused little alteration in the molecular receptive range of the receptor, suggesting that this residue may not play a significant role in ligand interaction within the binding pocket. Mutagenesis of G111, a residue within transmembrane domain three caused significant shifts in the molecular receptive range of the receptor, but the location of this residue within the binding pocket could not be confirmed by the substituted cysteine method. Previous reports had suggested significant similarity between the molecular receptive ranges of the seven mouse odorant receptors that I used in my research. By expanding upon the known aliphatic ligands for each receptor identified new ligands for each receptor, I was able to show that the molecular receptive ranges of these receptors are in fact distinct. The experimental identification of residues located within the binding pocket on transmembrane five of mouse odorant receptor 23-1 provides an improved understanding of ligand recognition by this receptor class and will aid in better computer modeling of these receptors. This increased accuracy of the computer models of these basic Class I GPCRs may aid in future drug discoveries. Since GPCRs constitute a significant fraction of current drug targets, understanding the mechanism of ligand interactions with mouse odorant receptors may aid in the development of more efficacious compounds in the treatment of many common ailments.

Lithium ion battery systems are promising solutions to current energy storage needs due to their high operating voltage and capacity. Numerous efforts have been conducted to model these systems in order to aid the design process and avoid expensive and time consuming prototypical experiments. Of the numerous processes occurring in these systems, solid state transport in particular has drawn a large amount of attention from the research community, as it tends to be one of the rate limiting steps in lithium ion battery performance. Recent studies have additionally indicated that purposeful design of battery electrodes using 3D microstructures offers new freedoms in design, better use of available cell area, and increased battery performance. The following study is meant to serve as a first principles investigation into the behaviors of 3D electrode architectures by monitoring concentration and cycle behaviors under realistic operating conditions. This was accomplished using computational tools to model the solid state diffusion behavior in several generated electrode morphologies. Developed computational codes were used to generate targeted structures under prescribed conditions of particle shape, size, and overall morphology. The diffusion processes in these morphologies were simulated under conditions prescribed from literature. Primary results indicate that parameters usually employed to describe electrode geometry, such as volume to surface area ratio, cannot be solely relied upon to predict or characterize performance. Additionally, the interaction between particle shapes implies some design aspects that may be exploited to improve morphology behavior. Of major importance is the degree of particle isolation and overlap in 3D architectures, as these govern gradient development and lithium depletion within the electrode structures. The results of this study indicate that there are optimum levels of these parameters, and so purposeful design must make use of these behaviors.

No description available.

A system for extracellular neural interfacing that had the capability for stimulation and recording at multiple electrodes was presented. As the core of this system was a custom integrated circuit (IC) that contained low-noise amplifiers, stimulation buffers, and artifact-elimination circuitry. The artifact-elimination circuitry was necessary to prevent the activity of the stimulation buffers from interfering with the normal functioning of the low-noise amplifiers. The integrated circuits were fabricated in in a 0.35 micron CMOS process. We measured input-referred noise levels for the amplifiers as low as 3.50 microvolts (rms) in the in the bandwidth 30 Hz-3 kHz, corresponding to the frequency range of neural action potentials. The power consumption was 120 microwatts, corresponding to a noise-efficiency factor of 14.5. It was possible to resume recording signals within 2 ms of a stimulation, using the same electrode for both stimulation and recording. A filtering algorithm to remove the post-discharge artifact was also presented. The filtering was implemented using a field-programmable gate array (FPGA). The filtering algorithm itself consisted of blanking for the duration of the stimulation and artifact-elimination, followed by a wavelet de-noising. The wavelet de-noising split the signal into frequency ranges, discarded those ranges that did not correspond to neural signals, applied a threshold to the retained signals, and recombined the different frequency ranges into a single signal. The combination of the filtering with the artifact-elimination IC resulted in the capability for artifact-free recordings.

Microsystem and integrated circuitry components are mostly manufactured using semiconductor technologies. Fabrication using high strength metals, for demanding aerospace, mechanical, or biomedical applications, requires novel technologies which are different from those for silicon. A promising mass production method for micro/meso scale components is electrochemical micromachining. The complex system, however, requires high precision mechanical fixtures and sophisticated instrumentation for proper process control. This study presents an electrochemical micromachining system with a closed-loop feedback control programmed using a conditional binary logic approach. The closed-loop control is realized using electrical current as the dynamic feedback signal. The control system improves material removal rate by 250% through optimizing inter electrode gap and provides robust automation reducing machining variation by 88%. The new system evokes production of higher quality microcomponents. Workpiece damage is reduced by 97% and increased feature sharpness is observed.

Proposed research object aims to develop and implement the novel imaging technique to delineate tissue boundaries based on electrical impedance of tissues.

The aim of this research is to improve the understanding of the impact on the cochlear dynamics corresponding to surgical tools, processes and hearing implants such that these can be designed more appropriately in the future. The results suggest that enhanced performance of implants can be achieved by optimisation of the location with respect to the cochlea and have shown that robotic surgical tools used to enable precise, simplified processes can reduce harm and offer other benefits. With an ageing population, and where exposure to noise on daily basis is increased rather than industrial settings, at least two factors of age and noise, will contribute to a greater incidence of hearing loss in the population in the future. In the research a mathematical model of the passive cochlea was produced to increase understanding of the sensitivity and behaviour of the fluid, structure and pressure transients within the cochlea. The investigation has been complemented by an innovative experimental technique developed to evaluate the dynamics in the cochlear fluids while maintaining the integrity of the cochlear structure. This technique builds on the success of the state-of-the-art surgical robotic micro-drill. The micro-drill enables removal of bone tissue to prepare a consistent aperture onto the endosteal membrane within the cochlea. This is known as preparing a ‘Third window’. In this technique the motion of the exposed endosteal membrane is treated as the diaphragm element of a pressure transducer and is measured using a Micro- Scanning Laser Vibrometer operating through a microscope. There are two principal outcomes of the research: First, the approach has enabled disturbances in the cochlea to be contrasted for different surgical techniques, which it is expected to allude preferential methods in future surgery in otology. In particular it was shown that when using the robotic micro-drill to create a cochleostomy that the disturbance amplitude reduces to 1% of that experienced when using conventional drilling. Secondly, an empirically derived frequency map of the cochlea has been produced to understand how the location of implants affects maximum power transmission over the required frequency band. This has also shown the feasibility of exciting the cochlea at a third window in order to amplify cochlear response.

The anode material in a conventional design of solid oxide fuel cell (SOFC) operating above 1123 K is typically made from NiO/Zirconia. NiO/Zirconia anodes are known to perform well in hydrogen but exhibit difficulties when natural gas is used as a fuel. Natural gas is much cheaper than hydrogen and widely available but causes carbon deposition and deactivation of the NiO/Zirconia SOFC anode. One objective of this work was to prepare and characterize NiO/Zirconia anodes both as powders and as applied to extruded zirconia tubes. The problem of carbon deposition when NiO/Zirconia anodes operate in methane, the main component of natural gas, was investigated. Another aim was to address the problem of coking with an effort to moderate carbon deposition by using additives to the NiO/Zirconia anode. Temperature programmed reduction (TPR) was used to study the reaction characteristicso f NiO/Zirconia anodes.T he carbon depositedo n thesea nodesa fter methane decomposition and reforming was characterized using temperature programmed oxidation (TPO). The anodes were placed in a reactor (stainless-steel, alumina or zirconia) tube in a test assembly developed for an extruded tubular SOFC. The reactor inlet was connected to a flexible gas handling system and the exhaust to a continuously sampling mass spectrometer. This system also allowed simultaneous study of electrical and catalytic measurementsThe various conditions for methane reforming have been shown to influence the character of carbon deposited and the quantity deposited. Conditions such as anode calcination temperature, anode reduction regime, reforming temperature and reforming time have all been shown to influence the reactions occuring on the anode including carbon deposition, subsequently characterized by TPO. NiO/Zirconia powders have also been shown to behave differently from NiO/Zirconia anodes adhered to zirconia tubes. An alkali metal additive has been shown to moderate carbon deposition and improve cell performance. Small additions of Li, typically 1 mol %, to the Ni/Zirconia anode cause a decrease in carbon deposition after reforming at temperatures of 1123 K and 1173 K. The activation energy of surface carbon removed by oxygen is lowered by approximately 50 kJ mot' for the 1 mol % Li doped Ni/Zirconia anode compared to the undoped powder. Anodes doped with Li displayed greater cell performances. The improvements seen with these additives show that their use could offer a viable alternative to conventional anodes in current SOFC systems. Tubular solid oxide fuel cells have been tested in a custom built rig whereby electronic and catalytic measurements can be sampled simultaneously. This was used to monitor the influence of drawing current on the reactions occurring on the anode. The presence of alkali Li on the doped Ni anode surface has been shown to interfere with surface reactions under electrochemical load/steam reforming

Vagus nerve stimulation (VNS) is an approved therapy for patients suffering from refractory epilepsy. While VNS is currently an open loop system, making the system closed loop can improve the therapeutic efficacy. Electrical recording of peripheral nerve activity using a nerve cuff electrode is a potential long-term solution for implementing a closed-loop controlled VNS system. However, the clinical utility of this approach is significantly limited by various factors, such as poor signal-to-noise ratio (SNR) of the recorded electroneurogram (ENG). In this study, we investigated the effects of (1) modifying the electrode contact dimensions, (2) implementing an external shielding layer on the nerve cuff electrode and (3) exploring shielded bipolar nerve cuff designs on the recorded ENG. Findings from both computer simulations and animal experiments suggest that significant improvements in peripheral nerve recordings can be achieved.