Thesis (Ph. D.)--Lehigh University, 2002. / Includes bibliographical references and vita.

Includes bibliographical references (p. 78-89).

The first study focused on the magnitude and rate of sorption of hydrophobic organic compounds by two, well-characterized soils. The composition of organic matter had a small effect on the magnitude of the organic carbon normalized equilibrium distribution coefficients. The sorbates sorbed more strongly to the humic-coated soil, most likely due to the organic matter's less polar nature as compared to the fulvic material. The molecular solute descriptor, ¹Xᵛ, performed slightly better than the empirical solute descriptor, K(ov), in evaluating equilibrium sorption coefficients. Thus, sorbate structure may have a secondary influence on the overall magnitude of equilibrium sorption. Sorbate structure exhibited a greater influence on sorption kinetics than on sorption equilibrium. Distinct differences in the magnitudes of mass transfer coefficients for the humic and fulvic soils were observed when relating them to the molecular solute descriptor, ¹Xᵛ. The differences in mass transfer coefficients were attributed to both sorbate structure and the quantity and morphology of soil organic matter. The intrasorbent diffusion coefficients were believed to be the same for both the humic and fulvic material. The second study focused on using a biodegradable solute to measure processes that affect in-situ biodegradation during well-controlled field and laboratory experiments. Specifically, this study investigated how residence time and scale influence the extent and rate of in-situ biodegradation of an organic solute undergoing transport. The transport of the biodegradable solute was compared to that of bromide and/or pentafluorobenzoic acid, which are conservative, non-degradable tracers. Laboratory experiments were conducted to simulate both the flow velocity and residence time conditions existent in the field. Mass recovery the biodegradable solute decreased as the residence time increased, ranging from 14 to 95 percent for the field sites. Mass recoveries in the laboratory experiments were approximately 30% to 40 % less than in the field experiments. The first-order biodegradation rate constants did not vary with residence time for either field site. In addition, the average rate constant value for both field sites was very similar (0.21 d⁻¹).

Thesis (PhD)--University of South Australia, 2004.

Thesis (PhD) -- University of South Australia, 1994

Specific ion effects on protein interfaces have been observed for many years, but yet comprehensive explanations regarding the mechanism by which ions interact with proteins and more general aqueous interfaces are still under investigation. Realistically, ion specificity on protein stability is due to numerous contributions and interactions between the solution and protein. However, the most important contribution is arguably the hydrophobic effect, specifically the change in free energy when water molecules are liberated from the interfacial region upon protein folding. In the work presented here, the effects of different ions on the critical micelle concentration (CMC) of 1, 2 –Hexanediol were examined to study salt effects on hydrophobicity by the means of fluorescence spectroscopy. Our results show that anions and cations do exhibit the specific effects on hydrophobic interactions. However, the origin of these specific ion effects different for cations and anions. Cation specific effects are caused by their ability to form cavities in solution, while anion specific effects arise from their ability to interact with the interface. These results are of interest to the researchers in the protein folding field, providing significant experimental hydrophobicity data necessary for theoretical biologists that are attempting to predict protein structures. / February 2015

Thesis (M.Sc.Eng.) PLEASE NOTE: Boston University Libraries did not receive an Authorization To Manage form for this thesis or dissertation. It is therefore not openly accessible, though it may be available by request. If you are the author or principal advisor of this work and would like to request open access for it, please contact us at open-help@bu.edu. Thank you. / A superhydrophobic surface combines chemical hydrophobicity with roughness. Due to the surface tension of water, the water cannot penetrate between the roughness elements, which remain filled with dissolved gas; the water surface thus remains suspended over the gas, creating shear free flow regions. In this study, we conducted experiments to study drag in flows over deformable superhydrophobic walls. Our superhydrophobic walls were fabricated by lithographically defining pores on 1-um-thick silicon nitride membranes; the membranes were then treated with silane to make them hydrophobic. For the flow experiments, we fabricated microchannels in which one wall was the porous and deformable superhydrophobic membrane and the other wall was a rigid hydrophilic surface. We measured the pressure drop and the flow rate in these microchannels; we simultaneously used white light interferometry to visualize the deformations of the superhydrophobic membrane. From both sets of measurements, we determined the relevant quantities, including the slip length at the liquid-solid interface. The results from these measurements suggest that the drag onthese deformable superhydrophobic walls is due to a complex interplay between wall deformation and shear-free flow; in most cases, it is not possible to directly observe the drag reduction due to the reduction in the solid-liquid interfacial area. / 2031-01-01

archives@tulane.edu / Solubility is the ability of a molecule to favorably interact with a solvent. While seemingly simple in application many phenomena arise from knife-edge like conditions between solubility and insolubility. Herein, three of these phenomena; co-non-solvency, the hydrophobic effect, and the direct and reverse Hofmeister effects are investigated in detail to parse out a mechanistic view of solubility in each case. The first phenomenon, co-non-solvency, is the insolubility of a thermo-responsive polymer and a mixture of two good cosolvents. Host-guest systems are used to probe small molecule interactions in the presence of cosolvents for co-non-solvent effects. The second phenomenon, the hydrophobic effect, is often colloquially described as “oil and water do not mix.” However, this is much more complex when diving into the energetic contributions. Host-guest systems are used to determine structural effects novel hosts and guests have on the hydrophobic effect in collaboration with the computational community. The third phenomenon, the Hofmeister effects, are explored through the fine tuning of solubility of lysozyme through the addition of sodium perchlorate in varying pHs. This is used to determine a mechanistic view of protein solubility in the presence of salts. / 1 / Nicholas Ernst

Cavity formation resulting from the water-entry of solid objects has been the subject of extensive research owing to its practical relevance in naval, military, industrial, sports and biological applications. The cavity formed by an impacting hydrophobic sphere normally seals at two places, one below (deep seal) and the other above the water surface (surface seal). For Froude numbers , the air flow into the resulting cavity is strong enough to suck the splash crown above the surface and disrupt the cavity dynamics before it deep seals. In this research work we eliminate surface seals by means of a novel practice of using cone splash-guards and examine the undisturbed transient cavity dynamics by impact of hydrophobic spheres for Froude numbers ranging . This enabled the measurement of extremely accurate pinch-off heights, pinch-off times, radial cavity collapse rates, and jet speeds in an extended range of Froude numbers compared to the previous work of Duclaux et al. (2007). Results in the extended regime were in remarkable agreement with the theoretical prediction of scaled pinch-off depth, and experimentally derived pinch-off time for . Furthermore, we investigated the influence of confinement on cavity formation by varying the cross-sectional area of the tank of liquid. In conjunction with surface seal elimination we observed the formation of multiple pinch-off points where a maximum of four deep seals were obtained in a sequential order for the Froude number range investigated. The presence of an elongated cavity beneath the first pinch-off point 5 resulted in evident "kinks" primarily related to the greatly diminished air pressure at the necking region caused by supersonic air flows (Gekle et al. 2010). Such flows passing through second pinch-offs were also found to choke the cavities beneath the first pinch- off depths causing radial expansion and hence disappearance of downward jets.

This thesis examines droplets striking water repelling surfaces as well as the movement of a soil based bacteria under various light and heat conditions. Droplet impact studies have shown that introducing a macroscopic feature to a water repelling surface can reduce the amount of time that droplet is in contact with the surface. By manipulating water droplets to impact different sized needles at varying speeds, we present how a needle can induce a similar reduction in the residence time of the droplet to more widely studied features. Results show the spreading and lift-off characteristics of the droplet are dependent on the impact speed as well as the size of macroscopic feature. A separate topic examines environmental motivators for mobility in a terrestrial cyanobacteria species called Microcoleus vaginatus. This cyanobacteria is indigenous to cold deserts, such as the Colorado Plateau or Mojave Desert in North America, and is essential to the health and preservation of the biological soil crust. These bacteria are the first organisms to grow in new soil, secreting a carbohydrate that acts as soil glue, thereby increasing soil adhesion. It has been shown that these bacteria will rise to the surface of the soil from their subsurface homes after rainfall, but it is unclear how they are able to make this journey. It is also unclear if other factors, such as nutrient levels or heat and light, affect their movement. Here we present an investigation of M. vaginatus’ response to light and heat in order to determine if these basic stimuli affect movement, thereby informing future restorative models.