"April 2002" Includes bibliographical references (leaves 200-249)

"April 2002" / Includes bibliographical references (leaves 200-249) / xv, 249 leaves : ill., plates (some col.) ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (Ph.D.)--University of Adelaide, Dept. of Animal Science, 2003

"April 2002" / Includes bibliographical references (leaves 200-249) / xv, 249 leaves : ill., plates (some col.) ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (Ph.D.)--University of Adelaide, Dept. of Animal Science, 2003

Phenomenological models are presented which predicts transpiration rates (E) of individual leaves of Scaevola plumieri, an indigenous dune pioneer, and Ammophila arenaria, an exotic grass species introduced to stabilise mobile sand. In both cases E is predictably related to atmospheric vapour pressure deficit (VPD). VPD is calculated from measurements of ambient temperature and humidity, hence, where these two environmental variables are known, E can be calculated. Possible physiological reasons for the relationships of E to VPD in both species are discussed. Scaling from measurements of E at the leaf level to the canopy level is achieved by summing the leaf area of the canopy in question. E is predicted for the entire canopy leaf area by extrapolation to this larger leaf area. Predicted transpiration rates of individual shoot within the canopy were tested gravimetrically and shown to be accurate in the case of S. plumieri, but less so in the case of A. arenaria. Using this model, the amount of water used by a known area of sand dune is shown to be less than the rainfall input in the case of S. plumieri in wet and dry years. The water use of A. arenaria exceeds rainfall in the low-rainfall year of 1995, while in 1998 rainfall input is slightly higher than water extraction by the plants. Using a geographic information system (GIS), regional maps (surfaces) of transpiration were calculated from surfaces of mean monthly temperature and mean monthly relative humidity. Monthly surfaces of transpiration were subtracted from the monthly median rainfall to produce a surface of mean monthly water deficit. Areas of water surpluses along the coast correspond with the recorded distribution of both species in the seasons that the plants are most actively growing and reproducing. This suggests that unfavourable water availability during these two species growth periods limit their distributions along the coast. In addition to unfavourable water deficits, additional climatic variables that may be important in limiting the distribution of these two species were investigated using a discriminant function analysis.

M.Sc. / Since plants are stationary, their immune systems have adapted to their environments to enable them to overcome or respond appropriately to various environmental, physical and physiological stresses that they may encounter by developing complicated defense mechanisms. The plant defense response activates complex biochemical and structural changes in plant cells. Heat stress per se, appears to be a priority stress response in plants, and increased disease susceptibility may be a result of this response. In this study, altered gene expression levels mediated by a heat treatment in Arabidopsis thaliana seedlings were analyzed. Seedlings were exposed to a heat stress of 42C for 30 minutes, followed by a 2.5 hour recovery period at 25ºC. RNA that was isolated from the heat stress treated plants as well as control plants (untreated) was used to perform suppression subtractive hybridization (SSH) in order to obtain a forward and a reverse DNA library. The forward SSH library represented the genes that were up-regulated due to the heat shock and the reverse SSH library represented the down-regulated genes. Sequenced clones from these libraries were BLAST against the A. thaliana genome using the Genbank database and the Accession numbers retrieved were then used for Bioinformatics analysis to obtain functionality of the genes found. The bioinformatics tools used were TAIR tools, DAG graphs and FatiGO and genes were categorized into the biological processes, molecular functions and cellular components. The TAIR tools and FatiGO were then used to analyze microarray data obtained for a similar study, in order to compare the genes identified with SSH. The genes coding for photosystem IID, serine-type peptidase, phospholipase D α, a S-locus protein kinase, regulator of chromosome condensation (RCC1) and Glucose-6-phosphate translocator are prominently up-regulated whilst other genes encoding photosystem I, plastocyanin-like mavicyanin, carbohydrate trans-membrane transporter MSS1, zinc finger C3HC4 ring family protein, ubiquitin conjugating enzyme 35 (UBC35) and integral membrane family proteins are significantly down-regulated. The FatiGO results helped to assign functionality to the genes that were found. For the SSH forward library, the cellular protein metabolic pathway was the most highly expressed term (19.21%), whereas in the microarray data, the term „positive regulation of response to stimulus‟ and membrane disassembly had a 100% expression. The reverse SSH data (down-regulation) found phosphate metabolic process as the most highly expressed term with an expression of 44.36% ix and the microarray data (negative fold-change) found the term photorespiration to be the most highly expressed with 93.54% expression. These high levels of negative expression indicate the down-regulation of these processes in the cell during heat shock. From these results it can be assumed that at the onset of a heat stress, the plant‟s immediate response is to activate pathways of regulation as a response to the stimulus as a self-protection mechanism, and repress other pathways such as photorespiration in order to preserve its energy such as ATP. These findings suggest that the plant is well equipped to overcome stress in its environment by activation/repression of specific organelles and pathways in the system, in order to maintain its equilibrium. Studies such as these can prove to be helpful to solve the interesting question of how a plant overcomes various environmental stresses in order to prevent disease susceptibility.

No description available.

A glucose glycine liquid model system fortified with 24 ppm of iron as either ferrous sulfate, ferric orthophosphate or ferric orthophosphate + 110 ppm ascorbic acid was thermally processed as 240, 250 and 260°F for 3, 6, 9, 12 and 15 minutes. Levels of elemental, nonelemental, soluble, total ionic and ferrous iron were measured for the model systems at each processing parameter. Data from the iron profiles were evaluated for the effect of iron salt; ascorbic acid; glucose and glycine, and processing temperature and time on changes in the iron chemistry during processing. The ferrous sulfate model system resulted in significantly higher levels of soluble and ferrous iron. Soluble iron from the ferric orthophosphate model system increased significantly with the addition of ascorbic acid. The presence of glucose and glycine prevented formation of insoluble iron hydroxides during processing of the ferrous sulfate system, promoted solubilization and ionization of iron for the ferric orthophosphate system and restricted the enhancing effect of ascorbic acid on the ferric orthophosphate profile. The interaction of the iron salt with the model system was stimulated by the application of heat. The insignificant correlation between process lethality values and the iron profile for each iron salt indicated that changes in the iron profile were time and temperature dependent. Kinetic parameters were calculated for all three model systems. The ferric orthophosphate iron profile was less sensitive to temperature change than either of the other two model systems. Evaluation of samples at sequential time intervals during the processing treatment allowed for a better understanding of the reaction mechanisms that occurred during processing which brought about a change in the iron profile of each model system. / Master of Science

Call number: LD2668 .T4 1985 B55 / Master of Science

Thesis (M. Tech.) - Central University of Technology, Free State, 2010

The teeth are amongst the most resilient elements of the human skeleton and are thus often utilised in routine forensic investigation involving the identification of unknown remains. The teeth, however, also have other practical forensic applications. Teeth exposed to thermal stress have the potential to not only aid in identification but also in understanding the circumstances surrounding the fire. Previous investigations have drawn conclusions that if a fire flares up suddenly and intensively, the teeth burst and enamel is lost. If the blaze commences gently and burns slowly, then the first observable morphologic change is the colour. The teeth subsequently are difficult to handle, thus changes in teeth can indicate the history of exposure to thermal conditions. Children are twice as likely to become victims of house fire because of an inability to safely evacuate from areas of danger. The literature demonstrates, however, that research on the effects of incineration on teeth is mostly restricted to the permanent teeth. The apparent lack of knowledge on the effects of incineration on deciduous teeth thus necessitates further research in this area. This research project primarily aims at understanding the effect of extreme temperatures on deciduous teeth. It also aims to relate colour changes that occur post heating with fragility to aid in proper handling of samples in a forensic scenario and to determine the possibility of identifying incineration temperature based on tooth condition. The samples analysed composed of 90 deciduous teeth (45 molars and 45 anteriors) extracted as a part of clinical treatment were used for the study. The project involved exposing extracted deciduous teeth to temperatures ranging from 100°C to 1100°C for 30 minutes using a laboratory Gallenkamp oven. Unheated deciduous teeth were used as controls for the project. Post-incineration the teeth were then analysed under a stereomicroscope and SEM for morphological changes. A colorimetric analysis was also undertaken to evaluate the colour changes induced in the primary teeth due to the thermal stress. It was found that it was possible to identify the incineration temperature based on the tooth condition when the colour changes, stereomicroscopic findings and SEM images were utilised collectively. It was also concluded that the thermally induced changes observed in primary teeth occur at lower temperatures in comparison to the permanent teeth. It was also established that post-incineration deciduous teeth are fragile and show a tendency to fragment after minimal exposure to thermal stress as compared to the permanent teeth. Moreover enamel and dentin remained identifiable in primary teeth even after exposure to 1100°C for 30 minutes while cementum lost its structural morphology at 900°C.