An investigation into the numerical prediction of boundary layer transition using the K.Y. Chien turbulence model

Assessments were made of the simulation capabilities of transition models developed at the University of Minnesota, as applied to the Launder-Sharma and Lam-Bremhorst two-equation turbulence models, and at The University of Texas at Austin, as applied to the K. Y. Chien two-equation turbulence model. A major shortcoming in the use of the basic K. Y. Chien turbulence model for low-Reynolds number flows was identified. The problem with the Chien model involved premature start of natural transition and a damped response as the simulation moved to fully turbulent flow at the end of transition. This is in contrast to the other two-equation turbulence models at comparable freestream turbulence conditions. The damping of the transition response of the Chien turbulence model leads to an inaccurate estimate of the start and end of transition for freestream turbulence levels greater than 1.0 percent and to difficulty in calculating proper model constants for the transition model

A sensitive genetic-based detection capability for Didymosphenia geminata

It is now well recognized that the increase in global transportation over the last two decades has brought with it an increased potential for the introduction of unwanted microorganisms (aquatic or terrestrial) that may have drastic effects on human and ecosystem health and agriculture. We have developed and validated a unique genetic fingerprinting tool for D. geminata. In concert, we developed field collection and preservation techniques specific for D. geminata along with genetic-based procedures that can now reliably detect D. geminate from a complex environmental community with a high degree of sensitivity. Recent work (Phase 2) has shown that the described methods will provide detection levels from <1 – 10,000 cells ml-1. We contend that the genetic based detection approaches used in this study offer great promise to meet the increasing demands to monitor the global threat from invasive micro-organisms

Enhanced detection of induced fluorescence from residual radioactive materials

Radiation detection is often is hampered by signal losses and noise. Conversion of decay particle energy to photons by scintillation, or induction of emissions from fluorescent materials by laser excitation, offers improved signal-to-noise ratios and the possibility of remote detection. This dissertation investigates the enhancement of induced fluorescence afforded by the application of scintillator-loaded polymer films to a radioactive material and of silanol ligand solutions to a fluorescent material; Prompt ultraviolet fluorescence from barium fluoride (BaF2)-loaded polymer films was induced by exposure to a 99Tc source and measured by scintillation counting. Scintillation photons suffer less attenuation in media than do the 99Tc beta particles and occur in a region of negligible solar background. Films with BaF2 loaded between 0 and 80% were drawn to thicknesses between 508 and 1270 mum. BaF2 crystals, from 0.25 and 5 mum diameter as determined by scanning electron microscopy (SEM), are significantly likely to scatter ultraviolet scintillations, thereby increasing the potential for photon absorption by EVA with a resulting decrease in detectable yield. Scintillation intensity was maximized in thin films (102 mum dry thickness) with high loading (80% by mass); Visible fluorescence from uranyl perchlorate solids contacted with Fe(III) or functionalized polyhedral oligomeric silsesquioxanes (POSSRTM ) is induced by light from a 414-nm pulsed laser, and the time-resolved intensities and lifetimes measured by intensified charge-coupled device (CCD) camera at 23 °C. Uranyl lifetimes were 4.08 +/- 0.02 mus for a 4.8 +/- 0.2 mM UO2(ClO4)2 (aq) solution and 225 +/- 2 mus for a 0.048 mumol UO2(ClO4) 2 solid. With 8.85 times molar excess Fe(III) added, dynamically quenched lifetimes were 3.73 +/- 0.03 micros for the 4.8 +/- 0.2 mM UO 2(ClO4)2 (aq) solution and 124 +/- 5 mus for the 0.048 mumol UO2(ClO4)2 solid. Fluorescence spectra of solids were red-shifted by 6 nm for each maximum due to increased hydrolysis of the uranyl ion; The effects of ligands in 4.2 times molar excess to UO2 2+ were determined by dissolution in buffered ethanol and deposition onto solid UO2(ClO4)2. Uranyl fluorescence intensity was quenched by both ligand solutions by more than ten fold. The lifetimes were reduced from tauo = 225 +/- 2 is to tau = 66 micros for TriSilanolEthyl POSSRTM SO1444 and to tau = 77 micros for TetraSilanolPhenyl POSSRTM SO1460Na, indicating increased shielding of uranyl from ethanol quenching by POSSRTM SO1460Na. The additional effects of Fe 3+ in 8.85 times molar excess to UO22+ were determined by deposition of these ligand solutions onto solids containing UO2(ClO4)2 and Fe(ClO4)3 . Fluorescence intensity was further quenched to by more than twenty five fold. Lifetimes of tau = 13 micros for POSSRTM SO1444 and tau = 46 micros for POSSRTM SO1460Na were measured; The feasibility of enhanced detection of surface radioactive materials using induced fluorescence measurements is demonstrated, and improved methods, including the use of nanoparticle scintillators, phosphate-based solutions, and ion imprinted polymers are recommended