Diffusion Of Magnetospheric Protons By Turbulent Drift Waves

Thesis (Ph.D.) University of Alaska Fairbanks, 197

Intermetallic phase selection in dilute Al-Fe-Si alloys

The DC casting of 1000 series AI-Fe-Si alloys often results in the formation of a defect known as the Fir Tree Zone (FI'Z) caused by variations in the type of binary AI-Fe eutectic intennetallic phase. These include AI3Fe, which is the equilibrium phase, and ~Fe, AImFe and AlxFe which are all common metastable phases found in DC cast ingots. Variation in the solidification conditions across a DC cast ingot.in particular, the cooling rate and local solidification velocity, bring about transitions from one intennetallic phase to another. The composition of the alloy, especially the presence of minor trace elements is also known to affect the transitions, but its effect has been less well studied. Equipment was constructed which reliably simulated DC casting conditions and enabled the FfZ to be reproduced. Experiments were conducted to examine the effect of the concentration of Fe, Si (and Fe:Si ratio) and of low levels «0.04 wt %) of Mg, Ti, Ti-B, V and Mn on the occurrence of phases causing the defect. Intennetallic phases extracted from the matrix by dissolution in hot butanol were identified by XRD. It was found that presence of Ti-B grain refmer had a large effect on the intennetallic phase selection, whilst the other trace element additions had lesser effects. In order to understand the way in which each element was affecting phase selection, experiments were conducted using DSC and a Bridgman furnace to isolate the variables of cooling rate and growth velocity respectively. A curve fitting technique was used to obtain values of eutectic nucleation onset temperature from DSC data where the primary aluminium and eutectic peaks overlapped. A technique was developed to extract intennetallic particles from DSC samples for examination in the TEM. It was found that the addition Ti-B grain refmer affected the phase selection by altering the nucleation temperature. The addition of Mg was found to stabilise the equilibrium phase by its affect on both growth temperature an nucleation temperature The effect of Ti was less clear in that it stabilised the equilibrium phase in the DSC experiments but tended to stabilise the metastable phase in the Bridgman experiments

Studies of Flows in Plasmas

Note a pdf document "DOE-flow-final-report' should be attached. If it somehow is not please notify Walter Gekelman ([email protected]) who will e mail it directl

Quantification of Urinary Mevalonic Acid as a Biomarker of HMG-CoA Reductase Activity by a Novel Translational LC-MS/MS Method

Background: Mevalonic acid (MVA), as a product of 3-hydroxy-3-methylglutaryl coenzyme A reductase, represents a potential multipurpose biomarker in health and disease. A translational urinary MVA quantification method was developed, validated and used to demonstrate the diurnal variation of urinary MVA excretion in rats and healthy children. Methods: Urinary MVA was converted to mevalonolactone at pH 2, extracted with ethyl acetate and quantified by reversed-phase liquid chromatography-tandem mass spectrometry. Results: The assay had a dynamic range of 0.0156-10 µg/ml with precision <15% CV, accuracy 85-115% and was transferred between laboratories. Urinary MVA excretion in rats and healthy children displayed a diurnal variation consistent with the known diurnal variation of hepatic 3-hydroxy-3-methylglutaryl coenzyme A reductase activity. Conclusion: Urinary MVA can be quantified accurately over a wide dynamic range by a validated translational and transferable method with biomarker capability

Marine-derived quorum-sensing inhibitory activities enhance the antibacterial efficacy of tobramycin against Pseudomonas aeruginosa.

Bacterial epiphytes isolated from marine eukaryotes were screened for the production of quorum sensing inhibitory compounds (QSIs). Marine isolate KS8, identified as a Pseudoalteromonas sp., was found to display strong quorum sensing inhibitory (QSI) activity against acyl homoserine lactone (AHL)-based reporter strains Chromobacterium violaceum ATCC 12472 and CV026. KS8 supernatant significantly reduced biofilm biomass during biofilm formation (-63%) and in pre-established, mature P. aeruginosa PAO1 biofilms (-33%). KS8 supernatant also caused a 0.97-log reduction (-89%) and a 2-log reduction (-99%) in PAO1 biofilm viable counts in the biofilm formation assay and the biofilm eradication assay respectively. The crude organic extract of KS8 had a minimum inhibitory concentration (MIC) of 2 mg/mL against PAO1 but no minimum bactericidal concentration (MBC) was observed over the concentration range tested (MBC > 16 mg/mL). Sub-MIC concentrations (1 mg/mL) of KS8 crude organic extract significantly reduced the quorum sensing (QS)-dependent production of both pyoverdin and pyocyanin in P. aeruginosa PAO1 without affecting growth. A combinatorial approach using tobramycin and the crude organic extract at 1 mg/mL against planktonic P. aeruginosa PAO1 was found to increase the efficacy of tobramycin ten-fold, decreasing the MIC from 0.75 to 0.075 µg/mL. These data support the validity of approaches combining conventional antibiotic therapy with non-antibiotic compounds to improve the efficacy of current treatments