Thesis (M.Sc.)--University of Alberta, 1997. / Submitted to the Faculty of Graduate Studies and Research in partial fulfilment of the requirements for the degree of Master of Science, Division of Neuroscience. Also available online.

Thesis (Ph. D.)--University of Texas at Austin, 2004. / Supervisors: Gang Yu and Stephen M. Gilbert. Vita. Includes bibliographical references. Also available from UMI.

Thesis (M.S.)--Villanova University, 2006. / Chemistry Dept. Includes bibliographical references.

Thesis (Ph. D.)--Ohio State University, 1987. / Includes vita. Includes bibliographical references (leaves 192-198). Available online via OhioLINK's ETD Center.

Thesis (Ph. D.)--Lehigh University, 2006. / Includes vita. Includes bibliographical references (leaves 117-125).

The goals of this project were to synthesize voltage-gated ion channels based upon previously studied pore-formers and to further explore the mechanism of ion transport with this type of pore-former. The syntheses of bis-macrocyclic bola-amphiphiles started with two different macrocycles prepared via a two-step cyclization from maleic anhydride by reaction with 1,8-octanediol alone or with triethyleneglycol. The macrocycles were then modified to a set of mono-adducts and bis-adducts by Michael addition of thiols (3-mercaptopropanol, 2-mercaptoacetic acid, or 3-mercaptopropionic acid). The mercaptopropanol adduct was converted to a mesylate and coupled with a carboxylate derivative to form a bis-macrocycle. Repetitious gel permeation chromatography gave a bis-macrocycle bearing only one head group, a carboxylate. The second head group was added via Michael addition to give a bis-macrocyclic bola-amphiphile which could have either the same head groups or different head groups. Two symmetrical transporters were synthesized via another route: two macrocycles reacted with 2-mercaptoethyl sulfide to generate a bis-macrocycle, and the same head group was then simultaneously added to both ends to give a symmetrical bola-amphiphile. Transporters with different combinations of head groups were synthesized to compare head group effects on cation transport properties, while different macrocycles were used in the backbone of transporter candidates to give two series of compounds for comparison of their behaviors. The second phase of this project investigated the transport properties of candidates using pH-stat titration. The pH-stat titration of bilayer vesicles allowed determination of dynamic transport properties: transport rate, apparent kinetic order and cation selectivity. Combined with information from planar bilayer experiments (done by D. Loock), it was found that an asymmetrical bis-macrocyclic bola-amphiphile with an acetate and a succinate head group behaves as voltage-gated ion channel in planar bilayers. An ion transport mechanism of the present system was proposed which involves the formation of active aggregates (probably dimers or oligomers). / Graduate

No description available.

This thesis presents observations from the Bosphorus (Strait of Istanbul), Turkey, made to study the effects of mixing, entrainment and frictionally induced shear on the dynamics of an exchange flow. The well known two-layer structure with an upper layer of brackish Black Sea water over an opposing undercurrent of salty Mediterranean water was observed. It is likely that the exchange was maximal as it seemed to be bounded by two hydraulic controls at the strait's ends; a sill control at the Black Sea was readily identifiable and the exchange also appeared to be controlled at the south exit toward the Sea of Marmara. The lower layer lost 15 to 20% of its volume to the upper layer because of upward mixing caused by interfacial shear and turbulence created at bends and lateral protuberances. The exchange was quasi-steady, except during a so-called Orkoz when strong winds caused a reversal of the upper layer flow. Between the controls the interface sloped steeply throughout the strait indicating that mass and momentum exchange between the layers and friction along the interface and sidewalls were important. The hydraulics of a single layer flow with entrainment is examined with a reduced gravity model. Expressions are derived for the local change of layer thickness and Froude number as function of the entrainment velocity. It is shown that entrainment, like friction, acts to force the flow toward criticality, although the layer thickness can increase if the Froude number is smaller than 1/2. For certain Froude numbers the effects of friction and entrainment on the layer thickness and the hydraulic state of the flow are found to be of comparable magnitude. A two-layer model with entrainment is developed. Predicted and observed interfacial slopes are found to be in reasonable agreement. The classical definition of hydraulic control assumes layers with uniform velocity so that further consideration is required if there is frictionally induced shear as observed in the Bosphorus. If a shear flow preserves the shape of its velocity profile, a standard formula suggests that hydraulic control is achieved when the depth-averaged flow speed is less than ( gh)1/2. On the other hand, shallow water waves have a speed relative to the mean flow of more than (gh)1/2, suggesting that information could propagate upstream. This apparent paradox is solved by showing that the internal stress required to maintain a constant velocity profile depends on flow derivatives, thus altering the wave speed without introducing damping. By contrast, an inviscid shear flow does not maintain the same profile shape, but is shown to exhibit hydraulic control when the depth-averaged speed equals the inviscid long wave speed. In the Bosphorus the similarity assumption was found to approximately hold indicating that hydraulic control could not be defined using classical inviscid theory. / Graduate

Developments in information and communication technology have opened up new possibilities for local tour operators. However, many small tour operators are faced with problems regarding the marketing of their products and services, especially problems relating to the choice of distribution channels. This study therefore undertakes a survey of the place and role of tour operators in the tourism industry, before investigating the different distribution channels available to tour operators as well as the factors that influence a tour operator’s choice of distribution channels. This is done by means of a literature study and a brief investigative questionnaire submitted to a number of small tour operators. The study concludes that the different situations pertaining to different small tour operators make it impossible to determine a set of distribution channels applicable to every tour operator. However, it identifies a number of considerations that individual tour operators can take into account to support their choice of distribution channels, taking cognisance of their unique situations. These include factors like the target market selected, positioning and the establishment of a trade mark, quality of service, specialisation, the nature of the destination and the background of the tourists, control over the marketing process, information and communication, cost-efficiency, and pragmatic considerations. / Prof. C.J. Jooste

Policy makers and financial institutions advocate the use of formal (regulated) remittance channels as the best way to harness remittances. In this research I study the benefits of formal and informal remittance channels from a Zimbabwean migrant’s perspective. The factors, particularly the Zimbabwean migrant’s demographics, adopted country and channel variables will influence the migrant’s choice of remittance channel. Categorical and numerical data that influence the choice of remittance channel used was collected from Zimbabwean migrants resident in South Africa, the United Kingdom and the United States. Categorical date was analysed using a log linear model - correspondence analysis which explores relationships between two or more dimensions. Numerical data was analysed using correlation analysis to examine linear associations and relationships between variables. The research is intended to create an understanding of what influences the migrant’s choice of remittance channels which could assist the policy makers (particularly in Zimbabwe and South Africa) understand how to best harness both remittance channels and improve the financial structures if they hope to increase the migration of remittances from informal to formal remittance channels.Copyright / Dissertation (MBA)--University of Pretoria, 2010. / Gordon Institute of Business Science (GIBS) / unrestricted