The layered transition metal oxide composition series of Li1+xV1-xO2 was synthesized using the solid state synthesis technique. X-ray diffraction was used to determine the dependence of structure on composition and clearly indicated a structural anomaly at x = 0 caused by the unusual magnetic ordering on the triangular lattice of the V3+ layer. To prevent magnetic frustration V3+ cations undergo orbital ordering and subsequent periodic displacent to form “trimers”. The periodicity of this phenomena results in a superlattice structure that can be observed as a faint peak in XRD spectra. The relationship between composition, superlattice peak intensity and lattice parameters was clearly documented for the first time. Li/Li1+xV1-xO2 cells were made and tested. Recent literature has shown that the transformation to 1T Li2VO2 upon lithiation is dependant on a nonzero x (ideally x = 0.07 for maximum capacity) to make a small number of tetrahedrally coordinated Li sites accessible. These sites then act as a trigger for shearing into the 1T phase. The cells described within this work intercalated significant amounts of lithium at a higher potential than the to 1T transition, possibly signifying occupation of a large number of the tetrahedral sites. LiVO2 is known to undergo delithiation even in ambient conditons and this can lead to cationic disorder. Cationic disorder is an inhibitor of anion sheet shearing and this suggests that sample handling could be a cause of the observed electrochemical behaviour. The effects of air and water exposure were investigated.

The improvement of volumetric energy density remains a key area of research to opti-mize Li-ion batteries for applications such as extending the range of electric vehicles. There is still improvement to be made in the energy density in the positive elec-trode materials. The current thesis deals with determining the phase diagrams of the Li-Mn-Ni-O and Li-Co-Mn-O systems in order to better understand the structures and the electrochemistry of these materials. The phase diagrams were made through careful analysis of hundreds of X-ray di raction patterns taken of milligram-scale combinatorial samples. A number of bulk samples were also investigated. The Li-Mn-Ni-O system is of particular interest as avoiding cobalt lowers the cost of the material. However, this system is very complex: there are two large solid-solution regions separated by three two-phase regions as well as two three-phase regions. Comparing quenched and slow cooled samples shows that the system trans-form dramatically when cooled at rates typically used to make commercial materials. The consequences of these results are that much of the system must be avoided in order to guarantee that the materials remain single phase during cooling. This work should therefore impact signi cantly researchers working on composite electrodes. Two new structures were found. The first was Li-Ni-Mn oxide rocksalt structures with vacancies and ordering of manganese which were previously mistakenly identi ed as LixNi2xO2. The other new structure was a layered oxide with metal site vacancies allowing manganese to order on two superlattices. The electrochemistry of both these materials is presented here. Finally, the region where layered-layered composites form during cooling has been determined. These materials were long looked for along the composition line from Li2MnO3 to LiNi0.5Mn0.5O2 and the most significant consequence of the actual locations of the end-members is that one of the structures contains a high concentration of nickel on the lithium layer. Layered-layered nano-composites formed in this system are therefore not ideal positive electrode materials and it will be demonstrated that single-phase layered materials lead to better electrochemistry.

In this work, numerical and experimental methods are used to characterise the effects of convective transport in an anode-supported tubular solid oxide fuel cell (SOFC). To that end, a computational fluid dynamics (CFD) model is developed to compare a full transport model to one that assumes convection is negligible. Between these two approaches, the variations of mass, temperature, and electrochemical performance are compared. Preliminary findings show that convection serves to reduce the penetration of hydrogen into the anode, and becomes more important as the thickness of the anode increases. The importance of the permeability of SOFC electrodes on the characterization of convection is also investigated. Experiments performed on Ni-YSZ anodes reveal that permeability is a function of the cell operating conditions, and increases with increasing Knudsen number. An empirical Klinkenberg relation is validated and proposed to more accurately represent the permeability of electrodes in a CFD model. This is a departure from an assumption of constant permeability that is often seen in the literature. It is found that a varying permeability has significant effects on pressure variation in the cell, although according to the electrochemical model developed in this work, variation in permeability is only found to have minor effects on the predicted performance. Furthermore, it is revealed that an electrochemical model which makes the simplifying assumption of constant overpotential is in error when predicting current and temperature variation. In this work, this is found to predict an unrealistic spatial variation of the current. It is suggested that this approach be abandoned for the solution of a transport equation for potential which couples the anodic and cathodic currents. This will lead to a more realistic prediction of temperature and performance. / Thesis (Master, Mechanical and Materials Engineering) -- Queen's University, 2008-11-04 13:54:35.743

Purpose: Intravaginal probes used for recording electromyography (EMG) from the pelvic floor muscles (PFMs) likely record activity from nearby muscles (crosstalk), and move during functional tasks, causing motion artifact data contamination, threatening the validity of results obtained. This study investigated the test-retest reliability and validity of surface EMG recordings from the PFMs using a novel, theoretically superior electrode in comparison to a commercially available intravaginal probe, the FemiscanTM. Methods: Healthy subjects (n=20) performed tasks with each vaginal electrode in situ: i) PFM maximal voluntary contractions (MVC), ii) coughs, iii) unilateral hip adductor/external rotator contractions at 25%MVC, 50%MVC, and MVC while keeping the PFMs relaxed or maximally contracted, and iv) transversus abdominis contractions (TrA; recorded using fine-wires) at 25%MVC, 50%MVC, MVC. Analyses: i) Intraclass correlation coefficients (ICC), ii) t-tests of proportions (α=0.05), iii) repeated measures ANOVAs and Tukey’s post-hoc testing (α=0.05) and iv) cross-correlation functions between peaks of transversus abdominis and PFM activity were used to determine the between-trial and between-day reliability of each vaginal electrode, a difference in prevalence of motion artifact contamination between electrodes, and the presence of crosstalk from the hip and TrA, respectively. Results: Between-trial reliability of both vaginal electrodes was excellent (ICC(3,1)=0.943-0.974). Between-day reliability was less consistent (ICC(3,1)=0.788-0.924 and 0.648-0.715 for the FemiscanTM and novel electrode, respectively). No significant difference in the proportion of files contaminated with motion artifact using each electrode existed. At submaximal intensities of hip muscle contractions, the FemiscanTM recorded significantly higher EMG amplitudes compared to what it recorded when the hip was relaxed, whereas the novel electrode did not, indicating that the FemiscanTM recorded crosstalk from the hip musculature. Low cross-correlation coefficients (<0.90) and large time delays (≥ 0.5 milliseconds) between peaks of PFM and TrA activity indicated that neither vaginal electrode recorded crosstalk from the TrA. Conclusion: The novel electrode is a promising tool to record EMG from the PFMs, as it records less crosstalk from the hip musculature than current technology while maintaining a high degree of reliability when comparing results collected within the same session; however, this electrode should not be used to compare one’s muscle activity between days. / Thesis (Master, Rehabilitation Science) -- Queen's University, 2011-02-07 14:46:30.811

No description available.

<p>In this thesis, I present the electrochemical studies of three dendrimeric polypropylene imine (PPI) nanomaterials and their applications as a platform in the development of a novel label free DNA nanobiosensor based on electrochemical impedance spectroscopy. Cyclic voltammetry (CV), differentia pulse voltammetry (DPV), square wave voltammetry (SWV) and electrochemical impedance spectroscopy (EIS) techniques were used to study and model the electrochemical reactivities of the nanomaterials on glassy carbon electrode (GCE) as the working electrode.</p>

<p>Electrophysiological intracellular recordings from freely behaving animals can provide information and insights, which have been speculated or cannot be reached by traditional recordings from confined animals. Intracellular recordings can reveal a neuron's intrinsic properties and their communication with other neurons. Utilizing this technology in an awake and socially behaving brain can bring brain research one step further. </p><p>In this dissertation, a customized miniature electronics and microdrive assembly is introduced for intracellular recording from small behaving animals. This solution has realized in vivo intracellular recording from freely behaving zebra finches and mice. Also, a new carbon nanotube probe is presented as a surface scanning tip and a neural electrode. With the carbon nanotube probe, intracellular and extracellular neural signals were successfully recorded from mouse brains. Previously, carbon nanotubes have only been used as a coating material on a cell-culturing platform or on a metal based neural electrode. This probe is the first pure carbon nanotube neural electrode without an underlying platform or wire, and it is the first one that has achieved intracellular and extracellular recordings from vertebrate cortical neurons.</p> / Dissertation

Die vorliegende Arbeit befasst sich mit der Anwendbarkeit von transparenter Elektronik basierend auf oxidischen Halbleitern in Multielektrodenarrays zur Messung von neuronalen Signalen. Im ersten experimentellen Kapitel werden auf Zinkoxid basierende Bauelemente untersucht. Verschiedene Varianten von Feldeffekttransistoren (FETs) werden charakterisiert und ihre Eignung zur Detektion von Zellsignalen überprüft. Die Anwendbarkeit physikalischer Modelle zur Beschreibung von ZnO-basierten Metal-Halbleiter-FETs (MESFETs) wird behandelt. Weiterhin wird die Eignung von einfachen Inverterschaltungen zur Spannungsverstärkung diskutiert. Das zweite Kapitel thematisiert Rauschmessungen an unterschiedlichen ZnO-basierten Proben, darunter Dünnfilme, Mikronadeln, MESFETs und Inverter. Darauf aufbauend wird die Auswirkung des gemessenen Stromrauschens auf die Sensitivität der Bauelemente nachvollzogen und theoretisch modelliert. Im dritten Kapitel wird das Verhalten der Bauelemente im Kontakt mit Elektolyt beschrieben. Die Signalübertragung von Spannungsänderungen im Elektrolyt auf die Chipelektronik wird mit verschiedenen Messmethoden charakterisiert. Dabei kommt teilweise ein selbstgebauter Vorverstärker zum Einsatz, dessen Aufbau ebenfalls beschrieben wird. Die Stabilität der verwendeten Materialien in physiologischen Salzlösungen und ihre Biokompatibilität wird überprüft. Darüber hinaus werden FETs mit Elektrolytgate und Zinkzinnoxid-Kanal vorgestellt.

Automated and continuous processes are the future trends in downstream protein purification. A functionalized nanometer-scale membrane electrode system, mimicking the function of cell wall transporters, can selectively capture genetically modified proteins and subsequently pump them through the system under programmed voltage pulses. Numerical study of the two-step pulse pumping cycles coupled with experimental His-GFP releasing study reveals the optimal 14s/1s pumping/repel pulse pumping condition at 10 mM bulk imidazole concentration in the permeate side. A separation factor for GFP: BSA of 9.7 was achieved with observed GFP electrophoretic mobility of 3.1×10-6 cm2 s-1 V-1 at 10 mM bulk imidazole concentration and 14 s/1 s pumping/repel duration. The purification of His6-OleD Loki variant directly from crude E. coli extracts expression broth was demonstrated using the pulse pumping process, simplifying the separation process as well as reducing biopharmaceutical production costs. The enzymatic reactions showed that His6-OleD Loki was still active after purification. A nanoporous membrane/electrode system with directed flow carrying reagents to sequentially attached enzymes to mimic nature’s enzymes-complex system was demonstrated. The substrates residence time on the immobilized enzyme can be precisely controlled by changing the pumping rate and thereby prevent a secondary hydrolysis reaction. Immobilized enzyme showed long term storage longevity with activity half-life of 50 days at 4℃ and the ability to be regenerated. One-step immobilization and purification of His-tagged OleD Loki variant directly from expression broth, yielded 98% Uridine Diphosphate glycosylation and 80% 4-methylumbelliferone glycosylation conversion efficiency for the sequential reaction. A flow-through electroporation system, based on a novel membrane/electrode design, for the delivery of membrane-impermeant molecules into Model Leukocyte cells was demonstrated. The ability to apply low voltage between two short distance electrodes contributes to high cell viability. The flow-through system can be easily scaled-up by varying the micro-fluidic channel geometry and/or the applied voltage pulse frequency. More importantly, the system allows the electrophoretical pumping of molecules from the reservoir across the membrane/electrode system to the micro-fluidic channel for transfection, which reduces large amount of reagents used.

Lithium-ion batteries (LIBs) are the most commonly used type of rechargeable batteries with a global market estimated at $11 billion, which is predicted to grow to $60 billion by 2020. The global commercialization of Li-ion batteries is impeded by issues such as poor cycle life (5000 cycles achieved in some LIBs) in high energy and power density applications because of the rising internal resistance due to aging and safety concerns such as overcharge which ultimately leads to thermal runaway and explosions. A battery’s performance mainly depends on external factors such as electrode thickness and degree of compacting, and the type of conductive additive and electrolyte mixture used, and internal factors such as its internal temperature and state of charge. The performance suffers due to aging or erroneous mechanisms such as decomposition of the electrode or electrolyte material affecting the lifetime. In this thesis, an attempt is made to improve the lifetimes of the Li-ion batteries by incorporating suitable electrolyte additives, which were incorporated in the battery electrolyte to prevent overcharge. Also, several conductive electrode additives were incorporated as filler materials in an anode to explore the effects on its discharge capacities.