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One of the limiting factors for improved performance of the spark ignited internal combustion engine is the phenomenon of knock. The present investigation makes a survey of the available models for auto-ignition for introduction into an existing phenomenological combustion model. A mathematical model of knock, based on a degenerate branched chain mechanism for the prediction of autoignition delay time, was considered and introduced into the combustion model. Experiments were carried out on a single cylinder variable compression ratio engine to validate the model. The interaction of acoustic waves with unsteady combustion leading to unstable combustion and thus triggering knock is considered. This work examines the relationship between the variation in the power of the frequency component corresponding to the natural frequency of the combustion chamber, and the occurrence of knock. A model based on the relaxation oscillation phenomenon is developed to calculate the oscillating frequency of the flame front. This model was developed on the basis that the gas contents of the combustion chamber in an internal combustion engine can be considered as a 'lumped parameter' spring mass damper system. Analysis of the frequency spectrum of flame ionization data show a favourable comparison with the predictions from the model, thus, opening the possibility of future work on correlating the acoustic instability in the combustion chamber to knock in spark ignition engines.

The focus of this study was to determine the balance measures most sensitive and accurate in detecting balance deficits associated with functional ankle instability (FAI). Subjects consisted of those with a history of ankle sprains and resultant symptoms of giving way (N=17; Height=167.72±9.11 cm; Mass=67.81±12.29 kg; Age=23.35±3.62 yrs) and subjects without a history of ankle injuries (N=17; Height=168.16±8.32 cm; Mass=66.22±12.35 kg; Age=23.35±3.26 yrs). Data collection consisted of each subject performing static and dynamic balance tests. Static stability was assessed with force plate measures, the Balance Error Scoring System, foot lift test, and time-in-balance test. Dynamic stability was assessed with the Star Excursion Balance Test, side hop test, and figure-of-eight hop test. Significant receiver operating characteristic curves and therefore cutoff scores were found for the foot lift test (P=0.011; cutoff=4.84 foot lifts), time-in-balance test (P=0.020; cutoff=41.23 s), center-of-pressure velocity (P=0.026; cutoff=1.56 cm/s), anterior-posterior time-to-boundary standard deviation of the minima (P=0.054; cutoff=3.72 s), posteromedial reach direction of the Star Excursion Balance Test (P=0.039; cutoff=0.91 normalized to leg length) and side hop test (P=0.044; cutoff=12.88 s). The associated positive (≥2) and negative (≤0.05) likelihood ratios with each cutoff score indicated that changes in positive and negative posttest probabilities from the pretest probability of 50% were small, yet significant. Essentially, the significant change between pretest and posttest probabilities indicates that clinically relevant information was gained by conducting these balance measure because they quantified a high proportion of individuals with a positive test who have FAI and a low proportion of individuals with a negative test who have FAI. No significance was found for the Balance Error Scoring System (P=0.249), center-of-pressure area (P=0.547), anteromedial (P=0.134) and medial (P=0.125) reach directions of the Star Excursion Balance Test, and the figure-of-eight hop test (P=0.117). In conclusion, we found the foot lift test, time-in-balance test, center-of-pressure velocity, anterior-posterior time-to-boundary standard deviation of the minima, posteromedial reach direction of the Star Excursion Balance Test, and the side hop test to be sensitive and accurate balance measures for detecting balance deficits associated with FAI. We suggest utilizing these measures and their cutoff scores to evaluate balance deficits associated with FAI.

Rupture of the anterior cruciate ligament (ACL) is a major clinical problem, leading to instability of the knee joint. This is especially unfortunate, as ACL failure is most commonly encountered in sports, where it affects healthy, younger people who wish to pursue an active life-style. Due to the frequency and potential severity of injuries, a need still exists for information on the biomechanical properties of ligaments under loading conditions, which occur at the time of trauma. The aims of this study were to examine the effect of different loading conditions on the mechanical properties and the appearance of the ruptured ligaments when viewed by scanning electron microscopy. Examining the appearance of collagen fibres at these surfaces should help us understand more about what actually happens during and after the fracture process. This study represents a combination of the two fields of tissue mechanics and fracture morphology for understanding the failure of biological tissues. (Abstract shortened by UMI.)t.

The focus of this thesis is on electro-osmotically pumped flow of viscoelastic fluids through microchannels. Fluid transport in microscaled structures is typically laminar due to the low Reynolds numbers involved. However, it is known that viscoelastic polymeric liquids can display striking instabilities in low Reynolds number flows. The motion of polymer doped solutions electrically pumped through microchannels is studied at low Reynolds number. It is found that extensional instabilities can be excited in such microflows with standard electro-osmotic pumping (approximately mm/s flow rate regime), occurring at the viscoelastic instability threshold. The existence of these instabilities must inform design as microfluidic applications move beyond simple fluids towards using biological materials and other complex suspensions, many of which display elasticity. It is further found that discrete and persistent microgels are formed at sufficiently high current densities. Prior work has found up to orders of magnitude increase in mixing rates, however additional fluid deformation effects (notably shear) exist in other studies and high viscosity solvents are used. The flows here exclude shear, a ubiquitous feature in mechanically driven cavity flows, and low viscosity solvents typical in microfluidic applications are used. The device is also highly symmetric minimizing Lagrangian chaos deformation and mixing of fluids. It is demonstrated that viscoelastic instabilities reduce mixing relative to low viscosity polymer-free solutions. The decrease in mixing found is consistent with the understanding that viscoelastic flows progress towards Batchelor turbulence, and demonstrates that, in contrast to common expectations, viscoelastic flows are effectively diffusion limited. Electro-osmotic pumped devices are the ideal platform to study isolated viscoelasticity and elastic turbulence, where additional effects (such as shear, or Lagrangian deformation manipulations) can be introduced in a controlled manner allowing fundamental studies of viscoelasticity and mixing. Besides the viscoelastic experimental observations it is shown that (1) a recently discovered instability due to density fluctuation has an analogue in polymeric fluids corresponding to the viscoelastic instability threshold, (2) inspection of correlations in microparticle image velocimetry (micro-PIV) data in unstable polymer flows reveals the relaxation time of polymer solutions, and (3) poly(ether sulfone) polymer films can act as negative electron beam resist.

Abstract Lung cancer is one of the most common cancer death in Taiwan. The dead population of lung cancer are over five thousands per year. High mortality and bad prognosis displayed the severity of the lung cancer. RAPD (Random Amplified Polymorphic DNA), a simple technique for the detection of genomic instability, has been used in this research. We inquire into genetic variation in carcinogenesis, and find out genes association with NSCLC. Three or more than three DNA fragment patterns of normal and lung cancer samples exhibited by RAPD from the seven arbitrary were classified as genomic instability. Four out of seven arbitrary primers have been used for lung cancer RAPD analysis and three of them were newly designed in this investigation. Analysis of genomic instability with these seven random primers in twenty-seven NSCLC patients revealed that 81.48% of NSCLC exhibited genomic instability. The RAPD reproducibilities of primer 6 and primer 7 were the best among the seven primers used in this study. Therefore, the variable DNA fragments of primer 6 and primer 7 in RAPD analysis were subcloned and sequenced for the study of the possible mutated genes in NSCLC. Results showed that DNA gains or losses were found in chromosomes 2, 4, 6, 14 and 22. After bioinformatic searching and alignments with human Genebank, some oncogenes (such as RABL2B, c-fos, n-myc and mas1) and tumor suppressor gene (AR) were found located nearby the locus of these subclones. Genomic instability was investigated in relation with the clinical-pathological features such as age, stage, tumor size, metastasis, differential status, survival days and cancer types. Results, evaluated by the X2 test, were not significant except tumor stage.

Hypervelocity gouging occurs in high speed sliding systems such as rocket sled test tracks, light gas guns, and railguns. Gouging takes the form of teardrop-shaped craters on the rail surface, and usually only occurs above a threshold speed which is dependent on the slider and rail material properties. In this dissertation, the onset of gouging was studied from three perspectives: application of existing modeling techniques developed for gouging and related fields of research, performing new high-speed experiments using a medium-caliber railgun, and analyzing rail microstructural evolution during gouge onset. A previous gouging model based on shock mechanics was extended, while other models based on mechanisms such as Rayleigh waves, bending waves, and shear band formation were ruled out. An effective Reynolds number approach from explosive welding research was applied to gouging with encouraging results. Based on similarities between gouging, explosive welding, and Kelvin-Helmholtz waves, a linear instability analysis was also performed. A total of 22 railgun experiments were performed to explore different aspects of gouging. Through these experiments, the effect of new slider materials, thin aluminum coatings, and macroscopic rail indentations on the gouging of copper alloy rails were examined. Results using new materials matched the existing models well, though galling damage to copper rails was often as severe as gouging. Gouging was delayed using electroplated aluminum coatings as thin as 2 μm, though this is not necessarily a robust solution. Macroscopic indentations were found to have negligible effect on the threshold velocity for gouging onset, though the morphology of the gouges was strongly affected. Both galling and gouging craters were shown to initiate at existing defects. This applied to both microscopic and macroscopic features. A consistent microscopic feature observed prior to galling and gouging were deformation bands that resembled persistent slip bands on the rail surface. Another consistent feature was the transfer of slider material to the rail prior to galling and gouging. This suggests that gouging may not be triggered by micro-impact events, but by instabilities associated with high-speed thermoplastic shear. / text

Replication fork stalling is a source of potentially tumourigenic genomic instability. The RecQ family helicase, Rqh1, is critical for the prevention of replication fork collapse and the formation of potentially deleterious recombination intermediates following fork stalling. Previous work in our lab with Schizosaccharomyces pombe (fission yeast) has shown that rqh10/rqh10 diploids are inherently unstable and show rapid reversion to the haploid state. The current work exploits this characteristic of fission yeast rqh10 mutants in a screen for genes that normally promote replication associated genomic instability. The rqh10rad30 mutant strains employed in this work incorporate the checkpoint deficiency caused by a lack of Rad3, so as to exacerbate the genomically unstable nature of this model. The current work describes the lithium acetate transformation based random mutagenesis by non-homologous integration of the ura4+ selectable marker into the rqh10rad30 fission yeast strains. This random mutagenesis generated extensive (24,500 – 50,000) mutant libraries. The quality of the libraries was assessed by can1 mutant assay, confirming an adequately extensive mutagenesis for the proposed screen. The process to be employed in the screen would involve the crossing of the mutant libraries, with the hope of generating diploids that will have two mutant copies of the same gene. Some of these diploids would appear unusually stable, showing a normal sporulation phenotype. This would indicate the mutation of a gene that normally promotes genomic instability following replication fork stalling. The practicality of the proposed screen of a vast number of diploids was assessed and described in detail in the current work. A technique involving inverse PCR (IPCR) adopted from previous work to identify mutants of interest, was also investigated. The investigation of this technique, and the work of others, suggests that transformation using such selectable marker fragments results in most apparent transformants containing extrachromosomal ura4+ fragments. These fragments are thought to provide the predominant template for IPCR, rendering the process unsuccessful at identifying the mutation in the current screen. However, with the mutant libraries generated, and the screen procedure detailed, the stage is set to conduct the screen once a more appropriate mutation location technique is identified. / Thesis (Master, Pathology & Molecular Medicine) -- Queen's University, 2008-05-31 22:25:14.009

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