Thesis (Ph. D.)--State University of New York at Binghamton, Chemistry Department. 2004. / Includes bibliographical references.

No description available.

The release of ionic solute from melting seasonal snow produces an influx of ion laden water into hydrologic systems at the start of spring snowmelt. The spatial and temporal variability of meltwater and solute release from melting snow was investigated at different spatial scales to assess the magnitude and variability of this process. Four laboratory experiments were performed where an 0.4 m³ volume of snow was placed in a plexiglass box and melted from above. NaCl and dye tracer experiments revealed contemporaneous areas of concentrated dye and dilute meltwater in flow fingers, indicating that meltwater in preferential flow paths is diluted by low concentration water from the top of the snowpack. Meltwater discharge and meltwater electrical conductivity were measured in snow lysimeters, and snow accumulation and electrical conductivity of samples from snowpits were measured over four snowmelt seasons at an alpine field site. Peak snow-water equivalent ranged from 0.57 to 2.92 m, and lysimeter discharges ranged from 20 to 205% of the mean flow; however mean lysimeter flow was representative of snow ablation observed in snow pits. The electrical conductivity in snowpit samples and lysimeter meltwater averaged 2-3 μS cm⁻¹. Peak meltwater electrical conductivity ranged from 6 to 14 times that of the bulk premelt snowpack. The highest conductivities were observed during the first few days following the onset of flow, and the lysimeters that began flowing earliest tended to have the highest conductivities at the onset of flow. A mathematical model for solute transport in snow was developed that includes the effects of mass transfer between mobile and immobile liquid phases, advection, hydrodynamic dispersion, and melt—freeze episodes. The ability of the model to accurately simulate solute movement and release depends on the validity of the assumption of one—dimensional flow and on the accuracy of modeling the snowpack energy balance. This model is preferable to the empirical models of solute elution currently in use for investigations of watershed hydrogeochemical response because it has the ability to respond directly to changes in snow accumulation or meteorlogical conditions.

Thesis (Ph. D - Hydrology and Water Resources) - University of Arizona. / Includes bibliographical references (leaves 206-216).

Thesis (M.S.)--Rochester Institute of Technology, 1990. / Typescript. "References": leaves 82-83.

Thesis (M. S.)--Chemical Engineering, Georgia Institute of Technology, 2009. / Committee Chair: Paul Kohl; Committee Member: Jiri Janata; Committee Member: Tom Fuller.

Thesis (Ph. D.)--University of Wisconsin--Madison, 1981. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 211-217).

Thesis (Ph. D.)--University of Iowa, 2007. / Supervisor: Claudio J. Margulis. Includes bibliographical references (leaves 236-242).

No description available.

Thesis (MSc)--Stellenbosch University, 2004 / ENGLISH ABSTRACT: In an ongoing study an empirical force field that can correctly model N,N'- dialkylimidazolium halide ionic liquids, the Imidazolium Ionic Liquid Force Field - IILFF, was developed based on experimental data obtained from the Cambridge Structural Database (CSD) and data calculated using Gaussian98. Different conformations of the isolated cations were optimised at the Hartree-Fock level using the 6-31G(d) basis set. Structural, vibrational and partial atomic charge data of the lowest energy conformation of each cation were taken as observables during optimisation of the force field parameters. Initial parameters of the IILFF were taken from existing force fields and were optimised using the above mentioned data. The IILFF was used to minimise isolated cations as well as crystals. These results were successfully tested against isolated cations minimised using Gaussian98 and the experimental crystals. Finally, the melting process of the 1,3-dimethylimidazolium chloride crystal was studied using an NPT ensemble starting from an ordered crystal cell and increasing the simulation temperature beyond the experimental melting temperature. The IILFF was then used to calculate the potential energy of the system. / AFRIKAANSE OPSOMMING: In 'n voortgaande studie om 'n empiriese kragveld te bou wat N,N' -dialkielimidasoliumhalied ioniese vloeistowwe korrek kan modelleer is die Imidasolium Ioniese Vloeistof Kragveld (nVK) ontwikkel. Die kragveld is ontwikkel gebasseer op eksperimentele data verkry uit die Cambridge Strukturele Databasis (CSD) asook uit data vanaf Gaussian98 berekeninge. Verskillende konformasies van die geïsoleerde katione is geoptimiseer deur middel van Hartree Fock 6-31G(d) berekeninge. Strukturele data, asook vibrasies en gedeeltelike atoom ladings van die laagste energie konformasie van elke katioon is gebruik as waarneembare veranderlikes vir die bepaling van die optimale kragveld parameters. Beginwaardes vir die nVK is geneem uit bestaande kragvelde en geoptimiseer met behulp van bogenoemde data. Die IIVK is gebruik om geïsoleerde katione asook kristalle te minimiseer. Die resultate is suksesvol getoets teen geïsoleerde katione wat met behulp van Gaussian98 geminimiseer is en eksperimenteel bepaalde kristalle. Laastens is die smeltproses van die 1,3-dimetielimidasolium chloried kristal bestudeer met behulp van 'n NPT ensemble. Daar is begin by 'n geordende kristal en die simulasie temperatuur is verhoog tot meer as die eksperimentele smeltpunt. Die IIVK is dan gebruik om die potensiële energie van die sisteem te bepaal.