Theses and Dissertations at Montana State University (MSU)
Permanent URI for this collectionhttps://scholarworks.montana.edu/handle/1/733
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Item Superfluid hydrodynamics in neutron stars(Montana State University - Bozeman, College of Letters & Science, 1991) Mendell, Gregory AllenItem A study in quantum hydrodynamics(Montana State University - Bozeman, College of Letters & Science, 1960) Zook, Herbert A.Item Macroscopic observation of hydrodynamics and pseudomonas aeruginosa bioflim processes in a porous media reactor(Montana State University - Bozeman, College of Engineering, 1990) Abedeen, FeisalItem Fully-developed turbulent flow in smooth and rough-walled pipe(Montana State University - Bozeman, College of Engineering, 1969) Gow, John LeonardItem Hydrodynamic analysis of coupled plasmons(Montana State University - Bozeman, College of Letters & Science, 1970) Burdick, David LeoItem Combining hydrodynamic modeling with nonthermal test particle tracking to improve flare simulations(Montana State University - Bozeman, College of Letters & Science, 2009) Winter, Henry deGraffenried, III; Chairperson, Graduate Committee: Petrus MartensSolar flares remain a subject of intense study in the solar physics community. These huge releases of energy on the Sun have direct consequences for humans on Earth and in space. The processes that impart tremendous amounts of energy are not well understood. In order to test theoretical models of flare formation and evolution, state of the art, numerical codes must be created that can accurately simulate the wide range of electromagnetic radiation emitted by flares. A direct comparison of simulated radiation to increasingly detailed observations will allow scientists to test the validity of theoretical models. To accomplish this task, numerical codes were developed that can simulate both the thermal and nonthermal components of a flaring plasma, their interactions, and their emissions. The HYLOOP code combines a hydrodynamic equation solver with a nonthermal particle tracking code in order to simulate the thermal and nonthermal aspects of a flare. A solar flare was simulated using this new code with a static atmosphere and with a dynamic atmosphere, to illustrate the importance of considering hydrodynamic effects on nonthermal beam evolution. The importance of density gradients in the evolution of nonthermal electron beams was investigated by studying their effects in isolation. The importance of the initial pitch-angle cosine distribution to flare dynamics was investigated. Emission in XRT filters were calculated and analyzed to see if there were soft X-ray signatures that could give clues to the nonthermal particle distributions. Finally the HXR source motions that appeared in the simulations were compared to real observations of this phenomena.Item Relativistic accretion flows onto supermassive black holes : shock formation and iron fluorescent emission lines in active galactic nuclei(Montana State University - Bozeman, College of Letters & Science, 2005) Fukumura, Keigo; Chairperson, Graduate Committee: Sachiko TsurutaOne of the exciting discoveries from the recent X-ray spectroscopic studies of active galactic nuclei (AGNs) is the so called βrelativistically-broadened iron fluorescent emission lineγ often detected in the hard X-ray spectra. It is generally believed to originate from the inner part of the accretion disk surrounding a supermassive black hole (BH) at the center. Although we have begun to obtain some physical insight regarding such emission lines supported by theoretical models (e.g., disk-corona model), exactly how and where the observed fluorescence may take place is still disputable. Here, an X-ray data with XMM-Newton Observatory of a typical narrow-line Seyfert 1 galaxy, NGC 4051, is analyzed based on a partial covering model to consistently explain the observed time-resolved temporal/spectral variations. This model implies that the intrinsic emission varies significantly in the presence of the covering cloud. We often detect a hard X-ray continuum originating from a hot region close to the central engines of AGNs. As a promising X-ray source candidate, relativistic hydrodynamic (HD) shocks are investigated systematically and then extended to the magnetohydrodynamic (MHD) shocks, given the widely accepted suggestion that the presence of the magnetic fields could play an important role in the accreting flows. I show that both HD and MHD shocks can form in the vicinity of the BH, perhaps responsible for creating such a hightemperature region where hard X-rays are produced. Particularly in the MHD shocked plasma, the hydro/magneto-dominated states are found. Considering the effect of such magnetic fields in the accretion disk, I calculate nonstandard iron fluorescent line profiles in the presence of spiral density waves and find multiple sharp sub-peak structures in extremely skewed line profiles, which will be detectable with upcoming X-ray satellites such as Astro-E2 XRS for testing the model. This dissertation is the result of my own work and also includes some work done in collaboration. Parts of this dissertation have been either already published in or submitted to the Astrophysical Journal and presented at conferences, while some are still in progress.Item Pseudomonas aeruginosa biofilm structure, behavior and hydrodynamics(Montana State University - Bozeman, College of Letters & Science, 2004) Purevdorj, B.; Chairperson, Graduate Committee: William J. CostertonBiofilm formation by bacterial pathogens is an important factor in the progression and treatment of many infectious diseases. Biofilm structural development is a dynamic process dependent on many cellular and environmental parameters including Quorum Sensing (QS) and hydrodynamics. Since QS is dependent on a threshold autoinducer concentration, it was hypothesized that the flow dynamics in the bulk fluid surrounding the biofilm would play an important role in expression of QS and the genes that are under its control. In order to investigate the relative contribution of hydrodynamics and QS on biofilm development, biofilms were grown from wild type Pseudomonas aeruginosa PAO1 and the cell signaling lasI mutant PAO1-JP1 under laminar and turbulent flows. When morphology of the biofilms were quantified using Image Structure Analyzer (ISA) software, a multivariate analysis demonstrated that both QS and hydrodynamics influenced biofilm structure, suggesting that QS was not required for biofilm development but affected structural heterogeneity in biofilms. GFP reporter based gene expression analysis of QS regulated lasB (coding for elastase) expression during biofilm development in laminar flow further supported these results. Detachment has been recognized as another factor that may define structural morphology of biofilms. Under flow conditions hollow biofilm clusters were formed as a result of active detachment process, termed as "seeding dispersal". A differentiation of a "seeding" microcolony into an interior motile, swarming, phenotype and a non-motile surrounding, "wall phenotype" formed as a prelude to the dispersal process in which the interior cells swarmed out of the microcolony from local break out points and spread over the wall of the flow cell. A critical microcolony diameter of approximately 100 æm was required for differentiation suggesting that regulation was related to cell density and mass transfer conditions. It was found that rhamnolipid (rhlA-) biosurfactant was not required and QS system (PAO1-JP2) was shown to be important in this process, possibly by sensing nutrient limitation within the biofilm microcolonies. These results strengthen a current view of multi-cellularity and coordinated behavior in prokaryotes as well as a dynamic network of overlapping pathways and cellular mechanisms that act on biofilm development in a complex interrelated manner.Item Empirical velocity predictions at culvert inlets(Montana State University - Bozeman, College of Engineering, 2006) Patton, Jesse Earl; Chairperson, Graduate Committee: Joel CahoonThe velocity distribution at the entrance cross section of a culvert is typically diverse, reflecting the nuances of the bed material, debris and other hydraulic factors just upstream of the culvert. These diverse inlet velocity fields have been observed to perpetuate some distance into the culvert, impacting the ability of fish to travel upstream in the culvert barrel. It is important to be able to quantitatively describe the inlet velocity field, especially as this serves as a necessary boundary condition for three-dimensional modeling of fluid flow in culverts. While there are various theory-based models of velocity distributions in open channels, velocity distributions at culvert inlets tend to be chaotic and are not well represented by analytic methods. The goal of this project was to use field data collected at existing culverts to estimate the density at which velocity observations should be collected to adequately describe the nature of the velocity at the culvert inlet. Two methods of data analysis were utilized to determine the required density of velocity observations. The first approach randomly selected velocities to be used as predictors and did not stress the location of the predictors, but instead emphasized the number of velocity observations needed to describe the nature of the velocity at the culvert inlet. The second method employed the idea that the location of the predictors was more important than quantity of predictors used. Results indicate that the pattern of velocity measurements is important - that is, velocities should not be measured at randomly selected positions in the cross section, but should follow a geometric pattern where the measurement density increases in zones having larger velocities. Also, it appears that if one follows the rigorous implementation of the USGS method for measuring stream flow (often referred to as the velocity-area method in texts), velocity predictions can be extrapolated using the inverse-distance-squared technique to adequately describe the inlet velocity field. The implication of this research is that there are steps that can be followed to adequately describe the nature of the velocity at culvert inlet even through the velocity distributions are chaotic in these regions.Item Influence of pollutant loading rate on seasonal performance of model constructed wetlands(Montana State University - Bozeman, College of Engineering, 2007) Schultz, Rickey Lynn, Jr.; Chairperson, Graduate Committee: Otto Stein; Paul Hook (co-chair)Constructed wetlands (CW) are a viable alternative wastewater treatment technology for many wastewater types. However, recommended loading rates vary widely between regulatory agencies. A greenhouse experiment was carried out for approximately 19 months to study the effect of loading rate, plant species selection, temperature and season on pollutant removal in bench-scale constructed wetlands. The wetlands were operated in batch mode at batch lengths of 3, 6, and 9 days, corresponding to loading rates of 210, 105, and 70 kg COD/ha·d, respectively. Greenhouse temperature cycled from 4°C to 24°C. Treatments included plant species Carex utriculata, Schoenoplectus acutus and Typha latifolia and unplanted controls. Water and air temperature, redox potential, COD, SO4 2-, NH4 +, PO4 3- and pore volume were monitored throughout the study. Data from the current research is compared with a previous study performed under similar conditions, but with a 20 day batch length resulting in a loading rate of 32 kg COD/ha·d. Performance of all treatments and loading rates was compared on the basis of percent COD and SO4 2- removal, redox potential, and remaining NH4 + and PO4 3- concentration.