A Thesis submitted to The University of Arizona College of Medicine - Phoenix in partial fulfillment of the requirements for the Degree of Doctor of Medicine. / This investigation assessed the diagnostic accuracy of thin-slice (1mm) axial Magnetic Resonance Imaging (MRI) in the detection and classification of meniscal tears. Meniscal injuries are a common reason for knee pain and the use of MRI has become standard in their assessment. However, the classification of tears and not merely the detection of lesions has become increasingly important to surgeons in deciding between surgery and conservative management. There is a growing body of literature examining the utility of axial MR images in aiding radiologists to more accurately describe and classify morphological characteristics of meniscus tears. However, the thick- slice (4-5mm) axial sequences utilized at many institutions typically only produce 1-2 images on which the menisci can be visualized, which does not provide the required detail to accurately describe the morphological characteristics of meniscal lesions. This study adds to the growing body of literature examining the diagnostic capabilities of MRI with TSAi to accurately describe meniscal tear morphologies. Imaging reports from 107 patients with clinically suspected meniscus injuries who underwent MRI with thin-slice axial imaging were compared to arthroscopic findings using receiver operating characteris (ROC) analysis to assess the diagnostic accuracy of MRI with thin- slice axial imaging (TSAi). The sensitivity and specificity of MRI with TSAi for meniscal tear detection were found to be 91% and 37.5% respectively. Furthermore, MRI with TSAi was highly specific for bucket handle (98.5%) and root ligament tears (94.1%). The findings of our investigation indicate that MRI with TSAi may assist surgeons in determining the need for operative versus conservative management. MRI with TSAi may be particularly helpful in the case of root tears, which were not as readily identified with traditional MRI techniques and often require surgical intervention due to morbidity associated with unrepaired root tears.

Orientador :Carlos Amadeu Pallerosi / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia de Campinas / Made available in DSpace on 2018-07-13T23:14:02Z (GMT). No. of bitstreams: 1 Queiroz_JorgeLuizLima_M.pdf: 1353439 bytes, checksum: e5ea1efd218c892faa7fe521a4cf112f (MD5) Previous issue date: 1990 / Resumo: O desenvolvimento de atuadores de força cada vez mais sofisticados, surgem a cada momento, impulsionado pelas necessidades da industria moderna. As áreas da automática e da robótica necessitam de atuadores com grande força inicial e pequeno deslocamento, dentre os vários tipos com acionamento hidráulico ou pneumático. Construiu-se um dispositivo tensor capaz de gerar força axial pela expansão radial de um tubo elástico. Os experimentos mostraram que a pressão necessária para exercer uma dada força é muito menor que a correspondente a cilindros axiais. O dispositivo tensor é de baixíssimo custo, peso e facilidade de fabricação. Os protótipos foram analizados em um equipamento de teste especialmente projetado. Foram construídos gráficos que mostram as relações entre a força e o deslocamento áxil, em função da pressão interna. As características construtivas e suas aplicações práticas são apresentadas, bem como os modelos matemáticos e computacionais / Abstract: The development of even more sophisticated load actuator appears every day due to the necessities of the modern industry. The areas of automation and robotics require actuators of large initial force and small displacement with the various types of actuators with hydraulic or pneumatic command. In this work a tensor device of low cost and weight and of simple construction is proposed. The prototypes were analysed in a specially designed testing equipment. The relations between the force and axial displacement are presented as well as the mathematical and computational models / Mestrado / Mestre em Engenharia Mecânica

Background: The paediatric craniocervical junction has anatomical, physiological and biomechanical properties that make this region unique to that of the adult spine, vulnerable to injury, and contribute to the complexity of management. Traditionally, on-lay fusion with external Halo immobilisation has been used. Instrumented fusion offers intra-operative reduction and immediate stability. Methods: A retrospective review of a single surgeon’s prospectively maintained database was conducted for all cases of paediatric patients that had undergone a fusion involving the occipito-atlanto-axial region. Case notes were reviewed and a radiological analysis was done. Results: Sixteen patients were managed with on-lay fusion and external immobilisation and twentyseven patients were managed with internal fixation using screw-rod constructs. The fusion rates were 80% and 90.5% respectively. Allograft bone grafting was found to be a significant risk factor for non-union. Conclusion: The screws can be safely and predictably placed as confirmed on radiological follow-up with a high fusion rate and an acceptable complication rate. Uninstrumented onlay fusion with Halo immobilization remains an acceptable alternative. Allograft in the form of bone croutons or demineralised bone matrix is a significant risk factor for non-union and posterior iliac crest graft should be used preferentially.

Until recently, concrete flow in tremie-placed drilled shafts has been mischaracterized as rising uniformly with laitance formation occurring only at the top of the rising concrete in the shaft. In actuality, concrete first fills a portion of the reinforcement cage to a sufficient height to promote radial flow into the cover region. Depending on support fluid type, the radial flow can produce laitance-filled creases/channels projecting the reinforcing cage configuration to the side of shaft surface. The flow pattern (and creases) can affect filter cake thickness, cover quality and propensity for corrosion. This research examines 52 tremie-placed laboratory drilled shaft specimens constructed using bentonite, polymer or natural support fluid to identify correlations between support fluid type and laitance channel formation. The extent of the laitance channel effect was quantified with surface texture, corrosion potential, and strength distribution methods. A direct correlation between the use of bentonite support fluid and laitance channel formation was identified which showed a high propensity for corrosion and lower concrete strengths.

<p>Pressure gain combustion is beneficial for engine cycle efficiency, compactness, and less emissions. In this disseration, two classes of fluid expansions systems were developed to harness power from the high-speed flow delivered by the pressure gain combustor: a compact expansion system and an efficiency expansion system. In addition, a new class of pressure probes for expansion systems is developed.</p> <p>A numerical methodology is carried out to design and characterize these expansion devices and measurement systems via steady and unsteady Reynolds Averaged Navier stokes simulations. Firstly, the compact expansion system is achieved by developing a supersonic axial turbine. Performance of the supersonic axial turbine exposed to fluctuations from a nozzle downstream of a rotating detonation combustor is assessed with an increased level of complexity, including time-resolved stator, time-resolved rotor, and time-resolved turbine stage characterization. Power extraction, damping of fluctuations, and loss budgeting are evaluated. Unsteady heat transfer assessment is performed to investigate the convective heat flux distribution and decomposition. A performance map is constructed to explore the operating limit. Afterwards, the efficient expansion system is achieved by retrofitting an existing subsonic axial turbine. Without redesigning turbine airfoils, the stator endwall contour was modified to integrate the subsonic axial turbine to a diffuser and a rotating detonation combustor. Performance of the retrofitted subsonic axial turbine exposed to fluctuations form a diffuser is evaluated at several frequencies, amplitudes and inlet Mach numbers, with an increased level of model fidelity, including unsteady stator alone, unsteady turbine stage with a reduced model, full unsteady turbine stage assessment. Turbine efficiency, damping of oscillations, and loss budgeting are assessed. A multi-step optimization strategy is utilized to enhance turbine efficiency by improving the endwall contouring. A performance map is created to examine the operating range. Finally, a new type of pressure probes was developed and angular calibration was performed. A whisker-inspired design enabled the reduction of the vortex shedding effect.</p>

The use of collection systems for magnetic sorbents such as Magnetic Activated Carbon are discussed in order to gauge their efficacy in marine environments. Two collectors were built and tested, one which utilized a radial orientation of magnets and another with axially placed magnets. The two systems underwent a series of test with differing linear velocities and angular velocities. From the results, the axial system outperformed its radial counterpart, being most effective with a relatively high concentration of discs placed in series. The medium concentration, however, proved increasingly effective with higher velocities, meaning an optimization concentration exists for this design. The radial system was tested with high and low concentrations of small and large magnets, respectively. The larger magnets, although providing less concentration points in the alternating array, proved more effective for the collection of MAC. From these tests several new innovations were suggested, including belt tensioners, add on mechanisms, and a hybridized design in order to fully optimize the collection of MAC.

During mouse development, the primordia of the posterior body including the trunk and tail tissues of the embryo forms largely from a bipotential cell population that resides in the posterior growth zone in vertebrate embryos. This bipotential cell population contains neuromesodermal progenitors (NMP) which are found in the tail bud which replaces the primitive streak after gastrulation and contributes to axial elongation by the formation of both the spinal cord and paraxial mesoderm derivatives. The three vertebrate Cdx genes, Cdx1, Cdx2 and Cdx4, encode transcription factors that play important roles in axial elongation since the triple Cdx mutant embryos fail to generate any tissue posterior to the occipital primordia. A comparison of Cdx mutant phenotypes suggests that Cdx2 is the most important contributor to axial elongation since Cdx2 heterozygous mutants exhibit foreshortened tails and Cdx2 conditional mutants exhibit axial truncation and complete loss of tail bud structures. Cdx2 target genes, such as Wnt3a, Cyp26a1 and T, are also essential for axial elongation. Cdx1 null mutants are viable and exhibit homeosis of cervical and anterior thoracic vertebrae, while Cdx4 null mutants are phenotypically normal. In addition, it has been shown that simultaneous loss of multiple copies of Cdx alleles disrupts axial elongation more severely than each single mutation which suggests there is overlapping function among the Cdx family. The genetic network underlying regulation of axial elongation by the Cdx family is not fully understood due in part to this functional overlap. In this thesis, I employed a conditional Cre-loxP system to derive conditional mutants lacking all Cdx functions. Additionally, Pax2-GFP transgenic mice where GFP is expressed under the control of Pax2 locus were used to enrich tail bud NMP cells for RNA-seq and ChIP-seq analysis for Cdx2. Using this approach, I revealed new target genes and pathways that are regulated by Cdx members and likely involved in axial elongation.

In this dissertation, we utilize the discrete Fourier analysis on axially symmetric data generation and nonparametric estimation. We first represent the axially symmetric process as Fourier series on circles with the Fourier random coefficients expressed as circularlysymmetric complex random vectors. We develop an algorithm to generate the axially symmetric data that follow the given covariance function. Our simulation study demonstrates that our approach performs comparable with the classical approach using the given axially symmetric covariance function directly, while at the same time significantly reducing computational costs. For the second contribution of this dissertation, we apply the discrete Fourier transform to provide the nonparametric estimation on the covariance function of the above circularly-symmetric complex random vectors under gridded data structure. Our results show that these estimates has closely related to the simultaneous diagonalization of circulant matrices. The simulation study shows that our proposed estimates match well with their theoretical counterparts. Finally through the Fourier transform of the original gridded data, the covariance estimator of an axially symmetric process based on the method of moments can be represented as a quadratic form of transformed data that is associated with a rotation matrix.

During a ten-stage compressor rig test conducted at Wright-Patterson AFB, several instances of compressor surge were observed. While surge is known to occur in high-speed multi-stage compressors, very little transient data pertaining to such events exists in the open literature, exclusive of engine data. In an attempt to make more data of this type available to researchers, surge data from the ten-stage compressor test is presented and analyzed in this thesis. Graphical presentation and data analysis techniques are employed in an effort to characterize the surge behavior of this compressor. Furthermore, the predictions of a computer-based transient compressor model are compared to the data for study. In the course of reviewing the data included in this thesis, certain abnormalities were noted in the overall behavior of this compressor. During testing, several researchers found that the speed boundary between surge and rotating stall occurred between 80% and 81 % corrected design rotor speeds. 1hls boundary did not change when the compressor discharge volume was increased or decreased. This seemed to contradict accepted theory, which predicts a shift in the surge/rotating stall boundary with discharge volume changes. An investigation into the possible causes of this phenomenon was conducted as part of this thesis. Several theories were explored, including the possibility of excess volume communicating with the compressor during instability. Although the excess volume theory could not be proven, it remains the most likely cause of the usual surge/rotating stall boundary behavior. / Master of Science

Dynamic compression system response is a major concern in the operability of aircraft gas turbine engines. Computer models have been developed to predict compressor response to changing operating conditions. These models require a knowledge of the steady state operating characteristics as inputs, which limits the ability to use them as predicting tools. The full range of dynamic axial flow compressor operation spans forward and reversed flow conditions. A model for predicting the wide flow range characteristics of axial flow compressor stages has been developed and a parametric study of the effect of changing design variables on steady state performance has been conducted. This model was applied to a 3-stage, low speed compressor with very favorable results and to a 10-stage, high speed compressor with mixed results. Conclusions were made regarding the inception of stalling and the effects associated with operating a stage in a multistage environment. It was also concluded that there are operating points of an isolated compressor stage that are not attainable when that stage is operated in a multi-stage environment. A stage located in a multi-stage environment can also operate at points which cannot be reached when the stage is operated in isolation. / Master of Science