No description available.

No description available.

No description available.

No description available.

No description available.

This thesis examines the changes in the microstructure of clays and mudrocks due to the influence of the environment of deposition and subsequent compaction. A sedimentary model is proposed in which the development of fissility in shales and the formation of hydrocarbon source rocks are attributed to the chemical conditions at the time of deposition. The geotechnical properties of fresh sediments are considered and the ability of the depositional environment to affect these properties is assessed. From a SEM analysis of mudrocks it is shown that there is a correlation between microstructure and the conditions at the time of deposition. organic-rich shales formed in anoxic environments are characterized by a preferred orientation of microstructure. Mudrocks formed under oxic conditions show a random orientation. This characteristic fabric of shales results from the peptizing capability of certain organic compounds in the environment of deposition and is considered to be a contributing factor to the development of fissility. A laboratory simulation of the depositional environment is described. Test results show that pure clays sedimented with organic compounds in a marine environment exhibit an increased parallelism of particles compared with those without organic compounds. A mechanism is described whereby the organic compounds are adsorbed onto the clay particle surfaces and promote peptization. The fabric of sediments obtained under laboratory conditions is found to control the rate of consolidation. Clays with a preferred particle orientation have slower rates of water loss and this is suggested to be an important factor with respect to the formation of under-compacted mud rocks. Statistical methods applied to the analysis of directional data obtained from SEM micrographs are reviewed and a measure for the anisotropy index of mudrock microstructure is proposed.

Both centrally and systemically administered dopamine agonists and antagonists decrease ingestive behaviour. The aim of this thesis was to examine whether drugs acting at different receptor subtypes decreased intake in different ways. A microstructural analysis was used to examine dopaminergic drug effects on licking behaviour. A dopamine D3 receptor agonist, 7-OH-DPAT, a dopamine D2 receptor antagonist raclopride and a mixed dopamine D2/D3 agonist quinpirole were compared in this paradigm. These drugs reduced the number of licks by differentially decreasing parameters which are thought to reflect the palatability of the stimulus such as mean bout duration of licking and the initial rate of licking. Follow-up experiments were conducted to further examine the possibility that motor deficits were underlying decreases in licking parameters. The effects of raclopride and 7-OH-DPAT were compared to the effects of a dopamine Dl antagonist SCH- 23390 and were analysed using a brief contact licking test. Again, the behavioural expression of anorexia induced by these drugs seemed to rely on a differential decrease in mean bout duration. Results also revealed that the three drugs used differed in the extent to which they produced a motoric deficit Attempts to block the effects of 7-OH-DPAT on licking (wameters were made by using the putative D3 receptor antagonists PNU-99194A and amisulpride. In addition, the effects of these drugs alone on licking behaviour were examined PNU-99194A failed to block the effects of 7-OH-DPAT and was relatively ineffective in producing changes in licking behaviour when administered alone. Amisulpride blocked the effects of 7-OH-DPAT only at high doses and when injected alone produced an increase in intake through an increase in mean bout duration of licking. Results from Chapters 4,5 and 6 suggested that 7-OH-DPAT was having an effect on palatability. Therefore, Chapter 7 presents an experiment which examines the effect of 7-OH-DPAT on the licking behaviour of rats which encounter a devaluation of reward (successive negative contrast). 7-OH-DPAT reduced successive negative contrast leading to the proposal that D3 receptors may mediate relative as well as absolute reinforcer value. These results bear important implications for understanding the role of dopamine receptor subtypes in components of food reward and appetitive behaviour in general and may well have implications for the treatment of eating disorders.

No description available.

Thesis (PhD)--University of South Australia, 1997

Electron irradiation may be a useful method for treating inorganic cosmetic powders such as talc for undesirable microorganisms if it can be established that no loss of quality or efficacy results as a consequence of the technique. A commercial electron accelerator was used to prepare bulk samples by exposure to electron irradiation under different conditions. A morphological characterisation of the control talc was carried out using microscopy techniques and focused on the particle size, shape and surface features of individual particles. Asperity dimensions vs. Roughness values were compared. Assessment of the bulk properties of the powders as a function of absorbed dose showed no serious impact on the quality or efficacy of the powder for cosmetic applications. The particle size and the level of dust expelled during impact were maintained. Changes to the surface chemistry of the irradiated powders were apparent from an increase in pH and water retention with increasing dose. Improvements to the fragrance retention occurred for both irradiated powders tested. Importantly a satisfactory microorganism level was achieved with the lowest absorbed dose level tested i.e. 5 kGy. Analysis of the crystallography did not show the development of a new phase. Mechanical testing using a slip-peel tester found an increase in the stick-slip behaviour occurred for the powder exposed to the highest absorbed dose only. Atomic force microscopy (AFM) testing of the lift-off force showed an increase in adhesion with increasing dose. Surface roughness increased with dose, while no change in elastic properties was found using nanoindentation suggesting the differentiating factor is due to surface features. Microstructural analysis used the transmission electron microscope (TEM). Voids were observed, which decrease in size, yet increase in number with increasing voltage. Prior to void development a loss of crystalinity is seen using electron diffraction. Explorative data analysis using factor analysis and Independent Component Analysis was performed on the void development data to discover the controlling mechanisms. Two distinct normally distributed populations were identified, each driven by 2-3 critical mechanisms. The distinct behaviour differences of the mechanisms may be utilised for characterisation of more complex properties of crystal microstructures.