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Lower back injuries are an illness which plague our society. Although almost everyone will experience some form of lower back pain in his or her lifetime, it is a sickness that is poorly understood, calling for new and innovative research. Much of this back pain is attributed to mechanical factors. Hence, it is important to understand the mechanics of the spine and the mechanical effects of degenerative changes that may lead to back pain. The spine is a complex three-dimensional structure and it is therefore necessary to study its mechanics with in vitro tests that replicate physiological movements as closely as possible. Traditional spinal testing machines have been unable to simulate the kinematic behaviour of intervertebral joints as they have limited degrees of freedom and cannot produce dynamic motion. The first aim of this research was to commission a robotic testing facility to overcome the limitations of traditional testing machines. This facility incorporated a six degree-of-freedom (DOF) robot arm with a six DOF force transducer. Mechanical tests performed on this facility could simulate the dynamic three-dimensional kinematics of the lumbar spine. In addition, this research aimed to assess the existence of a region of laxity during spinal joint motion defined as the Neutral Zone, and to determine the effect of specific lesions introduced into the intervertebral disc. To investigate these aims, in vitro mechanical tests on spinal specimens were performed using the robotic testing facility. To ensure these tests produced experimental results that were indicative of the mechanics of the spine in life, the intervertebral disc height had to be representative of the disc height in life. A set of experiments was performed to determine a method for ensuring this. The post-mortem disc height change due to a period of time exposed to a moist environment, freezing, defrosting and application of a constant compressive load was documented in a group of sheep spines. Specimens that were frozen immediately upon removal from the body produced the most predictable results. These specimens required no preloading to ensure the disc height during mechanical testing was similar to that in life. In accordance with this result, specimens used in the ensuing mechanical tests were frozen immediately on removal from the body and stored frozen until required for testing. Tests performed on sheep spines with the robotic facility verified the existence of a Neutral Zone. A criterion was determined that defined the Neutral Zone as the region of spinal joint rotation where the gradient of the load/deformation curve is within +/-0.5 dNm/degree from zero. This definition was used to determine the extent of the Neutral Zone in spinal motion during different movements. A Neutral Zone of approximately four degrees was found in intact spinal motion segments during flexion/extension. Only spinal musculature can stabilise the spine in this region of rotation. The removal of the zygapophysial joints increased the Neutral Zone in flexion/extension by approximately two degrees and caused the appearance of a Neutral Zone in axial rotation of approximately one degree. This suggests that during these motions, the zygapophysial joints are the main passive stabilisers. The mechanical effects of intervertebral disc lesions were examined by experimentally introducing three types of tears (rim lesions, radial tears and concentric tears) into sheep intervertebral discs and comparing the mechanical response of the injured joint to the joint's response prior to the creation of the lesions. Radial tears and concentric tears had no effect on the maximum moments resisted by the intervertebral disc or the hysteresis of the joint's response to motion. An anterior rim lesion increased the Neutral Zone by approximately 1.5 degrees and reduced the maximum moment resisted by the intervertebral disc by approximately 20% during extension in L1/L2 specimens. Rim lesions were also found to reduce the maximum moment resisted by the intervertebral disc in lateral bending and axial rotation for all levels by approximately 15% and 25% respectively. Rim lesions did not affect the hysteresis of intervertebral disc motion. In summary, this research commissioned a robotic testing facility capable of simulating the dynamic, three-dimensional kinematics of the lumbar spine and provided a unique insight into the three-dimensional mechanics of intervertebral joints. Testing was performed on sheep joints, however the outcomes provide an insight into the mechanical response of the human spine. The Neutral Zone was shown to exist but only in flexion/extension. This implies that damage to the spinal muscles may produce an unstable structure during flexion/extension within this Neutral Zone. Rim lesions reduce the ability of the intervertebral disc to resist all modes of motion. This suggests that the presence of rim lesions will produce overloading of other spinal elements and instigate progressive degenerative changes.

Neutral molecular radicals have received increasing attention as building blocks for functional molecular materials owing to their intrinsic conductive and magnetic properties. However, for these systems to be technologically viable, the molecular framework must be capable of stabilizing the unpaired electron, but also enable a degree of control and modulation of the desired properties. To achieve these goals, the design of the radical template requires consideration of the intrinsic effects on the electronic structure and those from a supramolecular perspective. In that regard, thiazyl radicals are promising candidates, as their physical attributes can be tuned systematically for the application at hand. In the pursuit of tunable thiazyl frameworks, two thiatriazinyl radicals have been synthesized and functionalized with heteroaromatic substituents. The contrasting nature between the attached thienyl and pyridyl substituents was evident upon establishing the preparative routes towards the neutral radical, and further demonstrated when the radicals were characterized spectroscopically. Structural analysis has emphasized the ability for the heteroaromatic moieties to direct the assembly of molecules into different supramolecular arrangements, in addition to self-associating into tightly bound structures. While dimerization voids the spin properties of these radicals, the redox-versatile thiatriazinyls were designed to explore the physical properties originating from metal coordination. Using the more robust anionic precursor, a dinuclear dysprosium complex was isolated and structurally analyzed, where oxidation of the ligand occurred in the process. A mechanism towards the self-assembly of the complex has been proposed by NMR studies using the isostructural yttrium analogue, which has provided insights on the metal-ligand reactivity. Furthermore, single-molecule magnet behaviour was observed for the dysprosium complex following magnetic investigations. In contrast to thiatriazinyls, the resonance-stabilized pyridine-bridged bisthiadiazinyls can remain undimerized in the solid state. Three derivatives have been developed with thienyl attachments and vary by the atomic substitution at the basal carbon position (i.e., R = H, F, Cl). Solution measurements illustrated spin delocalization extending across the π-framework, while halogenation provided a handle to fine-tune the energies of frontier molecular orbitals. Moreover, the ability of the thienyl rings to engage in various interactions was manifested in the polymorphic behaviour for each derivative. The solid-state structures were analyzed from single-crystal X-ray diffraction and highlighted the range of supramolecular architectures afforded by these systems. Lastly, two crystallographic phases of a bisdithiazolyl derivative were isolated selectively, such that the low-temperature phase possess an unprecedented high-symmetry trigonal space group. The mix-matched sizes of the beltline substituents afforded a honeycomb arrangement of stacked radicals. Magnetic measurements depicted a transition to an antiferromagnetically ordered state below 8 K, from which a high-temperature series expansion function was developed to model the magnetic data. Analysis of the results suggest the presence of two equivalent spin-spiral sublattices spanning across the crystal lattice three-dimensionally.

RNA molecules interact by forming inter-molecular base pairs that compete with the intra-molecular base pairs of their secondary structures. Here we investigate the patterns of neutral mutations in RNAs whose function is the interaction with other RNAs, i.e., the co-folding with one or more other RNA molecules. We find that (1) the degree of neutrality is much smaller in interacting RNAs compared to RNAs that just have to coform to a single externally prescribed target structure, and (2) strengthening this contraint to the conservation of the co-folded structure with two or more partners essentially eliminates neutrality. It follows that RNAs whose function depends on the formation of a specific interaction complex with a target RNA molecule will evolve much more slowly than RNAs with a function depending only on their own structure.

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For an Electrical Vehicle, the power is delivered from the battery pack to the electric motor through the use of power converter. Many research projects have been conducted in improving the efficiency of traction inverters. Inverter topologies are categorized based on the number of voltage levels of the inverter output phase voltage. The conventional 2-level Voltage Source Inverter (VSI) is commonly used as a traction inverter due to its simple structure. Due to the recent trend in utilizing higher DClink voltage in traction motor drives to achieve a higher power rating, multi-level inverters are gaining attention to replace the conventional VSI in EV powertrain. Multi-level voltage source inverters (MLVSI) have been widely adopted in high-power converters and medium-voltage drives. There are four major categories of MLVSI: the Flying Capacitor (FC), Neutral Point Clamped (NPC), Cascaded and Hybrid. The power rating of the MLVSI increases with the increase of inverter levels, but the size, number of switching devices, cost and control difficulty also increases. Due to the above reasons, 3-level NPC can be a good solution for traction inverters. Due to the structure and control limitation, Diode Clamp NPC suffers from uneven loss distribution and neutral point voltage balancing issues. This issue can be resolved with Active Clamped NPC (ANPC). In this thesis, the design, simulation, prototyping and testing of a 70kw 3-level ANPC traction is introduced. / Thesis / Master of Science (MSc)

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The earth's ionosphere-thermosphere region is a coupled environment which is governed by interactions between the overlapping neutral constituents and ionospheric plasma. The mid-latitude thermosphere-ionosphere system is very complex owing to its sensitivity to both the polar and equatorial processes. The mid-latitudes is also a relatively unexplored and less understood region primarily due to the paucity of observing instruments that have traditionally been available. However, the past 9 years of mid-latitude expansion of the Super Dual Auroral Radar Network (SuperDARN) has provided new access to continuous large-scale observations of the sub-auroral ionosphere. On the other hand, the past 3 years of mid-latitude expansion of the North American Thermosphere Ionosphere Observation Network (NATION) Fabry-Perot interferometer array, has created a critical resource for measuring the thermospheric neutral winds. The overlap of these two observing networks in the mid-east North American sector has resulted in a strong ground-based large-scale platform for co-located study of mid-latitude thermosphere-ionosphere dynamics for the first time. The coupling between ions and neutrals is a very important process for controlling the thermospheric dynamics. Ion-neutral coupling at high latitudes has been studied in many previous papers, but there have been very few studies focused on the mid-latitude region. Hence, in this work we have studied the ion-neutral coupling mechanisms and timescales at mid-latitudes during disturbed geomagnetic conditions by using the co-located observations from the SuperDARN-NATION array. The study has focused on the main phase as well as the late recovery phase of a geomagnetic storm which occurred on October 2-3, 2013. Ion drag is known to drive the neutral circulation during the main phase of storm at auroral latitudes, while the neutral wind disturbance dynamo mechanism is known to generate ionospheric electric fields and currents during the recovery phase. By using the methods of ion-neutral momentum exchange theory and time lagged correlation analysis, we analyzed the timescales at which the ion-neutral coupling operates. The ions are observed to drive the neutral winds on a timescale of ~ 84 minutes in the storm main phase which is significantly faster than expected from the driving due to local ion-drag alone (~ 124 minutes). This suggests that along with ion-drag, other local and non-local storm-time influences like Joule heating are also playing an important part in driving the neutral winds. On the other hand, in the late recovery phase, the neutral winds are found to be strongly coupled with the ions and maintain the ion convection without any significant time delay which is consistent with effect of the 'disturbance dynamo' or 'neutral-flywheel' persisting well into the late recovery phase. The timescales and underlying physics understood through this work serve as an important contribution to our knowledge of ion-neutral coupling processes at the middle latitudes. Looking forward, the expansion of co-located SuperDARN-NATION coverage at mid-latitudes, and developments in the tools of large-scale visualization through FPI wind field mapping and SuperDARN convection maps, has created a very strong basis for using the results and analysis tools developed in this work for large-scale ion-neutral coupling characterization in future. / Master of Science

Neutral red (NR), a eurhodin dye, is often used for staining living cells, but we demonstrated for the first time that NR can also serve as a CO2 sensor, because of NR's unique pH dependent optical properties, which change with dissolved carbon dioxide (dCO2) concentrations. In the present study, the optical sensitivity of NR was quantified as a function of changes in absorption and emission spectra to dCO2 in a pH 7.3 buffer medium at eight different dCO2 concentrations. NR exhibited a response time of two minutes for equilibration under pure N2 to 100% CO2 with an ~200% percent change (%∆) in emission intensity and >400%∆ in absorbance, both with full reversibility. Important to its application to biological systems, NR exhibited zero sensitivity to dissolved oxygen, which has routinely caused interference with CO2 measurements. NR exhibited pH sensitive emission and excitation energies with dual excitation maxima at 455 nm and 540 nm, and a single emission maximum at 640 nm. The CO2 sensing properties of NR were benchmarked by a comparison to pyranine = 8-hydroxypyrene-1, 3,6-trisulfonic acid trisodium salt) = HPTS. Future studies will evaluate the feasibility of NR as an intracellular in vivo pCO2 sensor in aquatic organisms critically impacted by increasing global CO2 levels. Stabilization of a well-known green emission phosphor, Pt-POP = diplatinum(II) tetrakispyrophosphite, was carried out using various protocols including polymerization, encapsulation within a polymer matrix and by varying other parameters, such as the solvent, pH, and concentration of the phosphor. A slight modification to the novel microwaveassisted synthesis protocol that our group has pioneered vs conventional reflux heating has yielded stabilized Pt-POP with a simultaneous doubling of the synthetic yield obtained. Heating to 260 °C produced a different form of PtPOP (exhibiting red/663 nm instead of green/515 nm phosphorescence and red-shifted spin-forbidden excitation maximum of 556 nm instead of 450 nm in both the solid-state and solution). This finding gives rise to additional broadening of the technological applications of this phosphor in terms of sensing under variable temperature, gaseous environment, pH and solvent.

Neutral particles play an important role on the performance of tokamak plasmas. In this dissertation, the original TEP methodology has been extended to take into account linearly (DP_1) and quadratically (DP_2) anisotropic distributions of angular fluxes for calculations of transmission probabilities. Three approaches, subdivision of optically thick regions, expansion of collision sources and the diffusion approximation, have been developed and implemented to correct effects of the preferential probability of collided neutrals escaping back across the incident surface. Solving the diffusion equation via the finite element method has been shown to be the most computationally efficient and accurate for a broader range of D/l by comparisons with Monte Carlo simulations. The average neutral energy (ANE) approximation has been developed and implemented into the GTNEUT code. The average neutral energy approximation has been demonstrated to be more accurate than the original local ion temperature (LIT) approximation for optically thin regions. The simulations of the upgraded GTNEUT code excellently agree with the DEGAS predictions in DIII-D L-mode and H-mode discharges, and the results of both the codes are in a good agreement with the experimental measurements.