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The presence of bubbles within liquid pools is ubiquitous in many natural and industrial settings. Plants and other living systems can release gas bubbles which detach and rise up through lakes and the ocean. Degassing also forms gas bubbles on solid surfaces inside the liquids, like that from champagne or poured soda drinks. The bubbles eventually rise to the pool surface, where they can bounce or pop into the air. The detailed dynamical interaction of the bubble and the free surface can be greatly affected by any impurities on their surface, which can affect the mobility of the free surface. In this dissertation, we use both experiments and numerical simulations to study these hydrodynamics. First, we study the rise and bouncing of bubbles or water droplets from the free surface inside a perfluorocarbon liquid. From all four different configurations of mobile/immobile interface pairs we show that the mobile interface always induces stronger bouncing but faster coalescence. The bouncing enhancement ratio between mobile and immobile interface is $1.8\pm0.1$ for bubbles and $1.5\pm0.1$ for water droplets, with the size range from $250 \, \mu m - 550 \, \mu m$ for bubble and $600 \, \mu m - 1200 \, \mu m$ for droplet. Then the top phase is replaced with a glass plate to eliminate the influence from other internal properties besides surface mobility. Since our numerical simulations perfectly reproduce the experiments, we extend our simulations to the free frontal collision of two equivalent droplets. The results not only support our previous conclusions but also predict another peculiar second-collision phenomenon under certain conditions. Then we replace the surrounding liquid with more practical ones of water and ethanol. In extra-pure water, we find that a millimeter-sized bubble has a mobile interface. We add arachidic acid on the top surface to further investigate bouncing from an immobile interface without changing the interfacial tension. The bouncing enhancement by mobile vs immobile interfaces is once again verified for the water-air interface. For millimeter-sized bubbles, as we increase the bubble size from $780 \, \mu m - 1550 \, \mu m$ the bouncing enhancement ratio decreases from 1.8 to 1.2. Finally, we look into the bubble shape and evolution of the liquid film profile during the bouncing from a top glass substrate, using interferometry and numerical simulations. We use 640 nm laser interferometry with a maximum thickness resolution of 120 nm. The center-of-mass trajectory and film profiles are measured for the first bounce of bubbles between 0.8 mm to 1.2 mm. Then we compare the 1.48 mm bubble impact on a no-slip top wall with the SRYL model prediction, where they shared the same dimple diameter but have a non-trivial deviation in dimple depth. Lastly, we simulate the frontal collision between two identical 1.45 mm bubbles, which have complex multi-dimple formations during the bouncing process.

<p> Several concepts have been developed recently in the intraurban mobility literature. Among them the concepts of aspirations, place utility and stress are of particular importance. Nevertheless, their definition appears to be not very clear.</p> <p> This paper aims to clarify them by employing concepts from the consumer choice theory as they are used in equilibrium models in Geography. With this purpose in mind the world of a specific equilibrium model is used. The distinction between the hypothetical world of this model and the real world is continuously emphasized.</p> <p> In order to clarify further the concepts mentioned above a particular example is given. In this example a Cobb-Douglas is used as a utility function.</p> / Thesis / Master of Arts (MA)

<p> A numerical method was developed to calculate the passing stress of pile-ups in a general internal stress field. This method was used to calculate the passing stress for a pile-up of like edge dislocations for a sinusoidal internal stress field, a simple tilt wall, and a Van der Merwe net of misfit dislocations. The passing stresses for single dislocation for these internal stress fields were also calculated.</p> <p> The Burgers vectors of a common set of misfit dislocations at the interface of Ni3Ge particles in a Ni matrix were determined. The surface slip lines of a directionally solidified sample of Ni-20% Ge alloy tested in compression were examined.</p> / Thesis / Master of Engineering (MEngr)

This dissertation consists of three essays examining the important role of job connections, references, and word of mouth information in labor markets. The first essay examines the importance of job connections for internal migrants. In this chapter, I develop a theoretical model where labor market networks provide labor market information with less noise than information obtained in the formal market. This model predicts lower initial wages and greater wage growth after migration for migrants without contacts. I then use data from the National Longitudinal Study of Youth (NLSY) to examine whether migrants who used social connections when finding their first job assimilate faster in the new region. Consistent with the theoretical model, I find that migrants who did not use social connections take longer to assimilate in the new region. The second essay models how screening workers through social networks impacts labor mobility in markets with adverse selection. When there is asymmetric information in labor markets, worker mobility is constrained by adverse selection in the market for experienced workers. However, if workers can acquire references through their social networks then they can move more easily between jobs. In this chapter I develop a simple labor market model in which workers can learn the productivity of other workers through social interaction. I show that networks increase wages and mobility of high-productivity experienced workers; however, networks discourage workers from accepting jobs outside their job-contact network, because of adverse selection. The third essay in this dissertation examines the importance of social networks in labor markets when work is produced jointly. Most employers cite poor attitude and poor fit with firm culture as their greatest problems in recruiting employees, rating these factors more important than skill. This is easily explained when the output of the firm requires that workers engage in work together. In this essay, I explain why it might be rational for firms to hire through social networks even when worker skill is observed perfectly, if these workers are better able to do joint work with the firm s existing employees. / Ph. D.

Critically ill patients can be prescribed bed rest as a therapeutic intervention. Immobility from bed rest can cause neuromuscular deconditioning and weakness. Preventing immobility by implementing mobilization activities may prevent these complications from occurring. Currently, mobility protocols are lacking. The purpose of this literature review is to analyze the evidence related to mobilizing patients in the Intensive Care Unit (ICU). In the future, a standard mobility protocol should be instituted for critically ill patients indicating when and how to begin mobilization. The efficacy of mobility protocols relies on an interdisciplinary team for positive outcomes to prevent complications of inactivity and promote patient safety. Future implementation of mobilization can decrease patients' lengths of stay and extensive rehabilitation from inactivity. Nursing education, practice and research should focus on interventions to prevent complications of immobility by identifying mobilization techniques, safety approaches and the use of protocols.

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The long-term mobility and availability of trace metals has been cited as a potential hazard by critics of EPA 503 rule governing the land application of biosolids. The purpose of this research was to investigate the long-term effects of biosolids application on trace metals distribution and mobility. A single application of aerobically digested biosolids was applied to 1.5 x 2.3 m confined plots of a Davidson clay loam (clayey, kaolinitic, thermic, Rhodic Paleudult) in 1984 at 0, 42, 84, 126, 168, and 210 Mg/ha. The highest biosolids application supplied 4.5, 760, 43, and 620 kg ha-1 of Cd, Cu, Ni, and Zn, respectively. Radish (Raphanus sativus L.), lettuce (Lactuca sativa Var longifolia) and barley (Hordeum vulgare) were planted at the site. Soils were sampled to a depth of 0.9 m and sectioned into 5 cm increments after separating the Ap horizon. Total (EPA 3050B), available (Mehlich-I), sequential extraction, and dispersible clay analyses were performed on samples from the control, 126 Mg/ha and 210 Mg/ha treatments. Extractable (0.005 DTPA, 0.01 M CaCl2, and Mehlich-1) Cd, Cu, Ni, and Zn were measured on 15 cm-depth samples from each plot. Simple linear regression between plant metal concentration and biosolids-added trace metals were computed to determine uptake coefficients (UC) of crops for each metal as outlined by USEPA Part 503 Rule. Results indicated that more than 80% of the applied Cu and Zn are still found in the topsoil where biosolids were incorporated with slight enrichment down to 0.3 m. Biosolids application increased the concentration of trace metals in all the extracted fractions, with a large proportion of Zn and Cd present in the available forms. The major portion of Cu, Zn and Ni was associated with the metal-oxides fraction. Biosolids treatments had no significant effect on the yield of the crops. Plant uptake of trace metals differed among crops. Plant tissue metal concentrations increased with biosolids rate but were within the normal range for these crops. Trace metals concentration in plants generally correlated well with their concentrations extracted with 0.005 M DTPA, 0.01 M CaCl2 and Mehlich-1. Mehlich-1 gave the highest correlation coefficients for Cu and Zn and, therefore, was the most reliable in predicting their availability and uptake by the crops grown. Availability of trace metals as measured by Mehlich-I, DTPA, and CaCl2 extraction were higher in amended plots as compared to the control and increased linearly in response to biosolids addition. Metal concentration in the plants exhibited a plateau response in most cases. Several linear increases were observed in some cases in 2003 when the soil pH decreased below 5.5. The uptake coefficients values generated for the different crops were in agreement with the values set by the Part 503 Rule. / Ph. D.

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