Doctor of Philosophy

dissertationState and national policy makers for 150 years have promoted public access to higher education, supported through state tax funds and more recently through federal direct appropriations and tax expenditures. In the past 3 decades, state tax funding of higher education has declined, resulting in increased reliance on tuition and reduced college affordability, thereby raising barriers to access. There are also vast differences in how well states fund higher education, with some providing more generous tax funds and others steadily providing less. Higher education researchers have conducted ongoing inquiry regarding factors that may influence the level of state legislative support for higher education. These include institutional, political, economic, cultural, demographical, and fiscal factors. Several have pointed to what appears to be an inverse relationship between state funding of higher education and state funding of Medicaid. This study employs regression analyses of a 20-year, 50-state panel of data (1992-2011), considering the changes in budget share devoted to higher education, Medicaid, K-12 Public Education, and Corrections. During that 20-year period, higher education's share declined in 33 states, Medicaid's increased in 44 states, and 28 states experienced both a decrease in higher education's share and an increase in Medicaid's. Also considered were political party control of states, and changes in Gross State Product. The analysis tries to determine if increases in Medicaid's share is contributing to a decline in the share for higher education, and whether the share for each budget category explains state funding variations. A fixed effects regression model, taking into account both the differences within (across time) and between (across states), determined that 85% of the variation in the error term is due to the wide cross-sectional state differences. This calls into question much of the prior research that relied on ordinary least squares regression models, and did not account for what Zhu called "cross-unit heterogeneity." These findings indicate that additional research is needed, both quantitative (considering groupings of states rather than all 50 states), and interpretive case studies to elicit more insights and research questions that will yield more definitive answers about budgetary tradeoffs between higher education funding and other budgetary categories

Constricted high enthalpy arc heater design and performance data, including calculations for a 10 MW design First interim technical report

Performance prediction and design analysis of constricted coaxial-flow arc air heaters for materials testing and atmospheric entry simulatio

ESD Challenges for NASA Astronauts in Upcoming Missions

Electrostatic charging of insulators is well known to pose potential threats to electronic systems under terrestrial systems. We were asked to evaluate potential hazards associated with replacement of an electronics board in the vacuum of space during the upcoming Hubble Service Repair mission in September 2008. A device called a "tribot" was built to simulate triboelectric charging of several insulators that are capable of contact charging against astronaut's gloves and suit materials. Materials were evaluated as the extent of not only the magnitude of electric fields generated by the frictional action, but also any resulting discharge which would be a source of EMI. Experimental results are quite surprising and unexpected when compared with tests performed under ambient conditions under dry and humid air

Electrostatic Characterization of Lunar Dust Simulants

Lunar dust can jeopardize exploration activities due to its ability to cling to most surfaces. In this paper, we report on our measurements of the electrostatic properties of the lunar soil simulants. Methods have been developed to measure the volume resistivity, dielectric constant, chargeability, and charge decay of lunar soil. While the first two parameters have been measured in the past [Olhoeft 1974], the last two have never been measured directly on the lunar regolith or on any of the Apollo samples. Measurements of the electrical properties of the lunar samples are being performed in an attempt to answer important problems that must be solved for the development of an effective dust mitigation technology, namely, how much charge can accumulate on the dust and how long does the charge remain on surfaces. The measurements will help develop coatings that are compatible with the intrinsic electrostatic properties of the lunar regolith

Temporal control of Wnt signaling is required for habenular neuron diversity and brain asymmetry

Precise temporal coordination of signaling processes is pivotal for cellular differentiation during embryonic development. A vast number of secreted molecules are produced and released by cells and tissues, and travel in the extracellular space. Whether they induce a signaling pathway and instruct cell fate, however, depends on a complex network of regulatory mechanisms, which are often not well understood. The conserved bilateral left-right asymmetrically formed habenulae of the zebrafish are an excellent model for investigating how signaling control facilitates the generation of defined neuronal populations. Wnt signaling is required for habenular neuron type specification, asymmetry and axonal connectivity. The temporal regulation of this pathway and the players involved have, however, remained unclear. We find that tightly regulated temporal restriction of Wnt signaling activity in habenular precursor cells is crucial for the diversity and asymmetry of habenular neuron populations. We suggest a feedback mechanism whereby the tumor suppressor Wnt inhibitory factor Wif1 controls the Wnt dynamics in the environment of habenular precursor cells. This mechanism might be common to other cell types, including tumor cells

Relative Emergence of Weeds and Corn and Soybean

The success of integrated weed management relies on matching control strategies to the specific weed problem in a field. This requires information not only on what weed species and how many of these weeds are present in a field, but also knowledge of the distribution of the weeds throughout the field and the stage of development of these weeds. Weed control recommendations typically provide information on appropriate tillage methods and herbicide selection. The information concerning weed infestations used to base these recommendations typically is not of sufficient detail to optimize the efficiency of these strategies. Information on weed populations can be improved by increasing the time spent scouting fields. However, time restraints during the busy spring season restrict this opportunity. This problem could be alleviated with an improved understanding of the environmental influences on weed emergence and growth, therefore allowing us to predict when best to invest time in scouting. Armed with greater knowledge of weed development and populations, a person could determine the optimum time for tillage and crop planting to reduce weed populations, maximizing the effectiveness of mechanical weed control operations, and for timing of burndown and postemergence herbicide applications. Although there has been considerable research and modeling of weed emergence in recent years, little effort has been directed toward development of emergence information for persons involved in weed management. This paper provides information on how weed emergence timing influences weed management systems. Included are preliminary rankings of relative emergence for important weed species in the Midwest. The Leopold Center for Sustainable Agriculture is supporting efforts to develop more precise emergence indices that will be of greater benefit in aiding the development of more efficient weed management systems

Entropic phase separation of linked beads

We study theoretically a model system of a transient network of microemulsion droplets connected by telechelic polymers and explain recent experimental findings. Despite the absence of any specific interactions between either the droplets or polymer chains, we predict that as the number of polymers per drop is increased, the system undergoes a first order phase separation into a dense, highly connected phase, in equilibrium with dilute droplets, decorated by polymer loops. The phase transition is purely entropic and is driven by the interplay between the translational entropy of the drops and the configurational entropy of the polymer connections between them. Because it is dominated by entropic effects, the phase separation mechanism of the system is extremely robust and does not depend on the particlular physical realization of the network. The discussed model applies as well to other polymer linked particle aggregates, such as nano-particles connected with short DNA linkers

Particle Removal by Electrostatic and Dielectrophoretic Forces for Dust Control During Lunar Exploration Missions

Particle removal during lunar exploration activities is of prime importance for the success of robotic and human exploration of the moon. We report on our efforts to use electrostatic and dielectrophoretic forces to develop a dust removal technology that prevents the accumulation of dust on solar panels and removes dust adhering to those surfaces. Testing of several prototypes showed solar shield output above 90% of the initial potentials after dust clearing