Plasma Discharges in Gas Bubbles in Liquid Water: Breakdown Mechanisms and Resultant Chemistry.

The use of atmospheric pressure plasmas in gases and liquids for purification of liquids has been investigated by numerous researchers, and is highly attractive due to their strong potential as a disinfectant and sterilizer. However, the fundamental understanding of plasma production in liquid water is still limited. Advancements in the field will rely heavily on the development of innovative diagnostics. This dissertation investigates several aspects of electrical discharges in gas bubbles in water. Two primary experimental configurations are investigated: the first allows for single bubble breakdown analysis through the use of an acoustic trap. The second experiment investigates the resulting liquid phase chemistry that is driven by a dielectric barrier discharge in the bulk liquid. Breakdown mechanisms of attached and unattached gas bubbles in liquid water were investigated using the first device. The breakdown scaling relation between breakdown voltage, pressure and dimensions of the discharge was studied and a Paschen-like voltage dependence was discovered. High-speed photography suggests the phenomenon of electrical charging of a bubble due to a high voltage pulse, which can be significant enough to prevent breakdown from occurring. The resulting liquid-phase chemistry of the plasma-bubble system was also examined. Plasma parameters such as electron density, gas temperature, and molecular species production are found to have both a time-dependence and gas dependence. These dependencies afford effective control over plasma-driven decomposition. The effect of plasma-produced radicals on various wastewater simulants is studied. Various organic dyes, halogenated compounds, and algae water are decomposed and assessed. Toxicology studies with melanoma cells exposed to plasma-treated dye solutions are completed; treated dye solution were found to be non-toxic. Thirdly, the steam plasma system was developed to circumvent the acidification associated with gas-feed discharges. This steam plasma creates its own gas pocket via field emission. This steam plasma has strong decontamination properties, with continued decomposition of contaminants lasting beyond two weeks. Finally, a “two-dimensional bubble” was developed and demonstrated as a novel diagnostic device to study the gas-water interface, the reaction zone. This device is shown to provide convenient access to the reaction zone and decomposition of various wastewater simulants is investigated.PhDNuclear Engineering and Radiological SciencesUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/116739/1/sngucker_3.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/116739/2/sngucker_2.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/116739/3/sngucker_1.pd

Simulated Beam Extraction Performance Characterization of a 50-cm Ion Thruster Discharge

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/97099/1/AIAA2012-3795.pd

Guidelines for the use of flow cytometry and cell sorting in immunological studies

International audienceThe classical model of hematopoiesis established in the mouse postulates that lymphoid cells originate from a founder population of common lymphoid progenitors. Here, using a modeling approach in humanized mice, we showed that human lymphoid development stemmed from distinct populations of CD127(-) and CD127(+) early lymphoid progenitors (ELPs). Combining molecular analyses with in vitro and in vivo functional assays, we demonstrated that CD127(-) and CD127(+) ELPs emerged independently from lympho-mono-dendritic progenitors, responded differently to Notch1 signals, underwent divergent modes of lineage restriction, and displayed both common and specific differentiation potentials. Whereas CD127(-) ELPs comprised precursors of T cells, marginal zone B cells, and natural killer (NK) and innate lymphoid cells (ILCs), CD127(+) ELPs supported production of all NK cell, ILC, and B cell populations but lacked T potential. On the basis of these results, we propose a "two-family" model of human lymphoid development that differs from the prevailing model of hematopoiesis