Journal and Proceedings of The Royal Society of New South Wales
STUDENT THESES ABSTRACTS IN VOLS 118-132 (Part 3 of 5: VOLS 127-128)
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CONTENTS
(in chronological order of publication)
| 1984-1990 [v118 pts 1-2 to v122 pts 3-4] | |
| Go to Theses Abstracts Archive Part 1 | |
| 1990-1993 [v123 pts 1-2 to v126 pts 3-4] | |
| Go to Theses Abstracts Archive Part 2 | |
| 1994 [v127 pts 1-2] | |
| Pickering, Catherine M. | Reproductive Ecology of Five Species of Australian Alpine Ranuncu1us |
| Kaynak, Akif | A Study of Conducting Polyrrole Films in the Microwave Region |
| Baxter, Rohan A. | Representation Issues in Genetic Algorithm Function Optimization |
| Roberts, Maureen B. | The Diamond Path: A Study of Individuation in the Works of John Keats |
| Bills, Peter J. | Barotropic Depth-Averaged and Three-Dimensional Tidal Programs For Shallow Seas |
| Zhu, Jin | Tannin Toxicity Studies in Mice and Sheep |
| Parkinson, Murray L. | Multi-Frequency MF/Lower HF Ocean Radar Studies of Wind-Wave Transients |
| Woodward, Roslyn | 'It's so strange when you stay sick'; The Challenge of Chronic Fatigue Syndrome |
| 1994 [v127 pts 3-4] | |
| Aldrich-Wright, Janice Rae | Chiral Discrimination Processes in Some Metal Chelate Systems of Biological Interest |
| Fitzsimmons, Stuart | Movement Behaviour and Structure of Groups of juvenile MULLET, Mugil cephalus (Linnaeus) |
| Tan, William Kian Meng | Perinatal Hypoxic Encephalopathy: Pathogenesis and Pharmaceutical Intervention |
| Quinsey, Patricia M. | Intake of Organochlorines from the Breastmilk of Victorian Women |
| 1995 [v128 pts 1-2] | |
| Hurdal, Monica K. | Dipole Modelling for the Localization of Human Visual Evoked Scalp Potential Sources |
| Wang, Jinxian | Population Dynamics of Steinernema carpocapsae and Heterorhabditis bacteriophora in in vivo and in vitro culture |
| Mahony, Robert | Optimization Algorithms on Homogeneous Spaces: with Application in Linear Systems Theory |
| Scrivener, Andrew M. | Wood Digestion in Panesthia aribrata |
| Douglas, Andrea M. | The Development of Mutation Detection Techniques and their Application to Disease Diagnosis |
| Kidd, Susan E. | Development of Metal Chelates as Potential Probes of DNA Structure |
| 1995 [v128 pts 3-4] | |
| Cunningham, Elizabeth A. | Introductory Studies of Silica Fume released as a By-Product of Electrometallurgical Process |
| Long, John M. | Light Scattering Studies of Microstructure in YBa2Cu3O7-x Super-conductors |
| Mallinson, Samuel G. | Shock Wave/Boundary Layer Interaction at a Compression Corner in Hypervelocity Flows |
| Beavis, Sara G. | Geological Factors influencing erosion gullying in the Greenfell Gooloogong Area, Mid- western New South Wales |
| Lappas, P. | Parameters affecting S.I. Engine Knock |
| 1996-1997 [v129 pts 1-2 to v130 pts 3-4] | |
| Go to Theses Abstracts Archive Part 4 | |
| 1998-1999 [v131 pts 1-2 to v132 pts 3-4] | |
| Go to Theses Abstracts Archive Part 5 | |
Vol 126 parts 1-2, p. 89 [1993] |
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Doctoral Thesis Abstract: Some aspects of the pathogenicity and immunity of bovine leukemia virus infection in cattle and sheep.
Magtouf H. Gatei
A series of research studies on bovine leukemia virus (BLV) infection was designed to investigate viral infectivity, oncogenicity and immunological responses in cattle (natural host) and sheep (experimental model). The research also concentrated on the possibility of developing an efficient vaccine against this retroviral infection.
Specific monoclonal antibodies were used to identify lymphocytes bearing surface immunoglobulin, T he1per (BoT4), T cytotoxic (BoTS) cells and total T cell phenotypes over a four months observation period, The results showed that the numbers of B cells in BLV infected cattle with persistent lymphocytosis (PL) were significantly (P < 0.01) higher than those of BLV+PL- and BLV free cows. The percentages of bovine major histocompatibility determinants, BoT4 and BoTS T cells, were significantly reduced (P<0.01) in BLV+PL+ cows.
Serum concentrations of immunoglobulins IgG1, IgG2 and IgM over the same observation period were also studies. There was a significant decrease (P<0.0001) in the level of IgM in the sera of BLV+PL+ cattle compared to that in BLV+PL- and healthy cattle. There were no significant differences in Ig61 and Ig62 concentrations between the three cattle groups.
Intravenous inoculation of sheep was used to test the infectivity of blood and nasal and saliva secretions from BLV+PL+, BLV+PL- and BLV free cows. 1t was found that 200 to 20,000 lymphocytes from BKV+PL+ donors induced infection in recipient sheep within 3 - 8 weeks post infection (P.I.). The inoculation of blood from BLV+PL- donors did not induce seroconversion in recipient sheep over 24 weeks of the observation period. Inoculation of saliva and nasal secretions from all BLV infected donors failed to bring about SLV transmission. A significant but transient increase (P < 0.05) in the peripheral blood lymphocytes was observed in recipient
Twelve sheep were injected with phytohaemagglutinin cultured peripheral blood mononuclear cells from a naturally infected BLV+PL+ donor cow and their responses compared to 7 control sheep. The massive appearance of lymphoid cells in the blood of infected sheep indicated tumour development as confirmed histologically by peripheral lymph node (LN) biopsy performed at the time of lymphocyte proliferations. Nine out of 12 sheep (75%) died due to lymphosarcoma over a 10 - 22 months period. Gross tumours were usually found in the heart and mesenteric LNs of all leukemic sheep. Occasionally, the tumours were also detected in the abomasum, urinary tract and uterus. The liver, spleen, kidney and lung showed no solid tumours but were infi1trated with malignant lymphoblastic cells whether or not they showed gross involvement. A significant transient elevation of circulating lymphocytes in these sheep was also observed at 2 weeks after infection.
Synthetic overlapping peptides covering the entire sequence of the BLV gp51 antigen (Ag) were tested on peripheral blood mononuclear cells (PBMCs) from BLV infected and healthy cattle and sheep to determine the immunodominant T cell epitopes, The results provide evidence that residues corresponding to the sequences 61 - 70 and 131 - 14G amino acids of the gp51 Ag constitute the immunogenic sites of T4 (CD4) and T8 (CDS) epitopes respectively. The incorporation of these sites may be useful in the development of an efficient vaccine against BLV infection.
Vaccination of recipient sheep with vaccinia virus vectors expressing BLV envelope (env) gene (gp51 and gp30) or gp51 alone was carried out. The recipient sheep were subsequently challenged with 4 x 104 PBMCs from a BLV+PL+ donor cow. Vaccination with recombinants of BLV env gene induced high levels of T4 pro1iferation following booster vaccine inoculation. At two weeks after challenge, these sheep developed a slight increase in the gp51 antibody titres. Th
Vol 126 parts 1-2, pp.90-91 [1993] |
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Doctoral Thesis Abstract: Provenance, Diagenesis and Reservoir Characteristics of Sandstones of the Great Australian Basin Succession in NSW
Fuxiang He
The Middle Jurassic and lower Cretaceous sandstones of the Great Australian Basin (GAB) in NSW (i.e., Eromanga and Surat Basins) comprise two petrofacies: a fluvial quartzose petrofacies and a lacustrine to marginal-/shallow-marine volcanolithic petrofacies. Detrital mineralogy, chemical composition of detrital feldspars (AnAbOr%), detrital mode (QFL%) and regional petrofacies distribution of these sandstones indicate the existence of two major provenances: for the quartzose sandstones, a dominantly cratonic provenance consisting of plutonic/metamorphic basement rocks and/or older sedimentary successions flanking the GAB on the west and south; and for the volcanolithic petrofacies which are rich in andesitic VRFs, a mainly contemporary volcanic orogen located along the northeastern continental margin of Australia. A regionally developed stratigraphic alternation of these two petrofacies defines a recurrent petrologic cycle that manifests contemporary episodic tectonic activity of the volcanic orogen – craton couplet. The Early Cretaceous marine transgression in GAB also extended into the Lower Cretaceous Murray Infrabasin (MIB), but the lithic sandstones of MIB are rich in metamorphic rock-fragments reflecting local provenances different from those that sourced the GAB proper.
Diagenetic processes in the sandstones include physical compaction, clay infiltration (in some quartzose sandstones), dissolution/alteration of labile grains (e.g., VRPs, feldspars and mica) and cementation. In the volcanolithic sandstones, the diagenetic minerals comprise smectite, zeolite, kaolinite, carbonate and minor chlorite and illite; in the quartzose sandstones, the suite consists of kaolinite and quartz plus some carbonate and minor smectite and chlorite. Dissolution and cementation (and the occurrence of secondary porosity) in the volcanolithic sandstones are believed to be related to the acidic pore-fluids partly derived from diagenesis of the intercalated organic-rich mudrocks. The chemical diagenesis (and the development of secondary porosity) in the quartzose sandstones, which constitute some of the main aquifers in the Great Artesian System, results from the interaction between the meteoric pore-fluid and sandstone constituents.
In the lithic sandstones, core porosity ranges from 24.0% to 40.0% (with mean 35.0%), permeability from 1.8 to 4805.2 (md) (with mean 125.0 md); in the quartzose sandstones, these values are 16.3% to 34.2% (with mean 29.0%) and 1.3 - 18400.0 (md) (with mean 676.l md) respectively. Results of petrography, SEM and mercury intrusion porosimetry show that the volcanolithic sandstones contain mainly microporosity, and the quaztzose sandstones contain mainly primary and secondary intergranular porosity. The distribution patterns of porosity and permeability in the lithic and quartzose sandstones have good correlations with their respective depositional environments.
Parameters influencing sandstone porosity and permeability were examined using stepwise multiple regression. Porosity of the lithic sandstones (Q < 50.0 whole-rock%) is closely related to sediment age, content of detrital quartz (Q) and pore-fillings and burial depth (the multiple correlation coefficient r = 0.81); for the quartzose sandstones (Q > 50.0%), the parameters are burial depth, formation temperature and pore-fillings (r = 0.78); porosity of very quartzose sandstones (Q > 75.0%) is correlated closely with sediment age and grain-size (r = 0.85). Permeability of the lithic sandstones is related to pore-fillings, burial depth, detrital quartz and pore fluid chemistry (r = 0.66); for the quartzose sandstones, the parameters are grain-size, burial depth, formation temperature and sediment age (r = 0.75).
Factor analysis reveals the relationship among the petrological and petrophysical variables, and the relationships between these variables and the geological processes of source-rock weathering, sediment transportation and deposition, and diagenesis. Four factors have been established: Factor I is defined by grainsize, sorting, and pore-fluid chemistry; Factor II, defined by porosity and pexmeability and the content of matrix and detrital quartz; Factor III is defined by formation temperature, burial depth and sediment age; Factor IV is defined by the content of cements.
Based on the existing geological and geochemical evidence, there exists no petroleum source within the Eromanga Basin succession in NSW. In South Australia and Queensland, some of the Eromanga Basin hydrocarbon was likely generated in the Middle Jurassic Birkhead Formation and the Upper Jurassic - Lower Cretaceous Mura Member/Mooga Formation; but much of the Eromanga Basin hydrocarbon is likely to have been derived from the underlying Cooper Basin source rocks.
Vol 126 parts 1-2, p.87 [1993] |
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Doctoral Thesis Abstract. 19F NMR of Erythrocytes: 'Split Peak' Phenomenon, Membrane Potential and Membrane Transport
Arron S.L. Xu
An abstract from the thesis submitted to the University of Sydney for the degree of Doctor of Philosophy, December 1992.
Fluorinated solutes such ad difluorophosphate (DFP), monofluorophosphate (MFP), hexafluorophosphate (HFP) and trifluoroacetate (TFA) all showed well-resolved 19F NMR resonances when they were added to erythrocyte suspensions. The broader resonances from intracellular soutes was shifted to high frequency with respect to their extra cellular counterparts.
The 19F NMR chemical shifts of the above-mentioned compounds were shifted to high frequency in the presence of proteins. An increase in temperature also led to a shift of the 19F resonances to high frequency. Results from this work support the hypothesis that the disruption of hydrogen bonding between the fluorine atom and the solvent water atoms, by hydrated haemoglobin, is the principal physical basis for the 'split peak' phenomenon see with erythrocyte suspensions.
The well-resolved 19F NMR resonances of DPP enabled its transmembrane mass-distribution to be determined directly from an erythrocyte suspension. At transmembrane electrochemical equilibrium, the distribution of DFP was goverened by the membrane Donnan potential. The membrane potential measured using DFP was independent of the concentration of the probe molecule, and the haematocrit of the suspensions with a large range.
A novel adaption of a 19F NMR magnetisation-transfer technique was derived to measure the rapid membrane transport of DFP. The transport was shown to be mediated exclusively by band-3. The transport was temperature dependent; the 'break-point' temperature of the equilibrium efflux was -31oC. Under similar conditions, the ratios of the influx rates for solutes at a concentration of 20 mM were DFP:hypophosphite:F-:Cl- were 1.0:1.5:33.0:68.1.
The membrane-transport of TFA in human erythrocytes was significantly slower that DFP. By differentiating the inhibition brought about by a number of compounds, including stilbine disulfonates, α-cyano-4-hydroxycinnamate, p-chloromercuriphenylsulfonic acid, and N-ethylmaleimide, band-3 was found to be the dominant transporter of TFA uptake into human erythrocytes. A small fraction of the uptake was mediated by the monocarboxylate transporter. Under physiological conditions, transport via simple diffusion via the lipid of the membranes was negligible.
The 19F NMR spectrum showed well-separated quartets arising from beryllofluorides BeF2, BeF3- and BeF42-. This phenomenon facilitated the study of the multiple equilibria associated with the complexes in a solution. In erythrocyte suspensions, the 19F NMR spectra showed resonances from the intracelluar populations of the complexes shifted to higher frequencies relative to their extracellular counterparts. The erythrocyte membrane-transport of the complexes was completely inhibited by stilbene disulfonates; the results suggested that band-3 was the exclusive transporter for BeF42-, and intracellular BeF2 arose as the result of the redistribution of the various intracellular complexes via the multiple equilibria.
The 9Be NMR resonances of the complexes were, a quintet, a quartet and a triplet for BeF42-, BeF3- and BeF2, respectively, and they overlapped extensively. 9Bc NMR decoupling simplified the 19F NMR spectrum. The 19F magnetisation transfer among various complexes in either cis or trans compartments indicated interconversion among the different species in the cis compartment, and the transmembrane exchange occurred within sub-minute time scale.
Vol 126 parts 1-2, p.88 [1993] |
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Doctoral Thesis Abstract. Atlantis: a Tool for Language Definition and Interpreter Synthesis
Michael John Oudshoorn
A thesis submitted for the Degree of Doctor of Philosophy in the Department of Computer Science, University of Adelaide, 1992
Programming language semantics are usually defined informally in some form of technical natural language, or in a very mathematical manner with techniques such as the Vienna Definition Method (VDM) or denotational semantics. One diffculty which arises from serious attempts to define language semantics is that the resulting definition is generally suitable for a single limited kind of reader. For example, the more formal kind of definition may suit a compiler writer or a language designer, but will be less convenient for other potential classes of reader, such as programmers. The latter frequently make use of some completely separate description (e.g., an introductory text book on the language); not surprisingly, inconsistencies between these separate descriptions and the language definition are commonplace.
This thesis develops a technique for the definition of programming language semantics which is suitable for a wide range of potential readers, This technique employs an operational semantic model which is based on the algebraic specification of abstract data types; the semantic model manipulates multi-layer descriptions of language semantics and supports multiple passes in these descriptions.The semantic technique described in this thesis lends itself to the semi-automatic generation of an interpreter from the language definition, a fact which acts as an incentive to language designers to produce a formal definition of any new programming language, since the prototype implementation allows experimentation with new language features and their semantics. The system which generates an interpretive implementation from a language definition is called ATLANTIS, A Tool for LANguage definiTion and Interpreter Synthesis, and is also described in this thesis.
Vol 127 parts 1-2, p.61 [1994] |
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Doctoral Thesis Abstract: Reproductive Ecology of Five Species of Australian Alpine Ranunculus.
Catherine M. Pickering
Abstract of a Thesis Submitted for the Degree of Doctor of Philosophy at the Australian National University.
Current hypotheses in reproductive ecology were investigated using the Australian alpine perennial herbs Ranunculus muelleri, R. dissectifolius, R. graniticola, R. millanii, and R. niphophilus. Based on the results from these experiments, reproductive strategies are proposed that may also apply to other perennial herbs.
Direct limitation of seed set by pollen and resources was investigated by the experimental manipulation of pollen and resources in the field. Seed set was not limited by pollen in R. graniticola; was limited only at one time during the flowering season in R. millanii; was slightly limited by the amount of pollen transferred by pollinators in R. muelleri and R. niphophilus; and was significantly limited by pollen in R. dissectifolius. The addition of nutrients to plants had no effect on seed set in any of the species. Removal of all but a single flower from plants increased seed set on the remaining flower only in R. dissectifolius. Removal of half the leaves from a plant had no effect on total seed set in R. muelleri, R. dissectifotius, R. graniticola and R. niphophilus.
Seed production is direct1y proportional to plant size, as measured by leaf number, in R. muelleri, R. dissectifolius, R graniticola and R. niphophilus, with bigger plants producing more seed by producing more flowers. Plant size affected the flowering pattern of all five Ranunculus species, with plant size being correlated with the number of flowers produced which, in turn, was correlated with the duration of flowering of the plant and, in some species, the amount of synchrony with conspecifics. These correlations applied both within and among species.
Based on ovule estimates of plant gender, Ranunculus plants were phenotypically as well as morphologically hermaphrodite. However, seed estimates indicate that populations of R. muelleri, R. dissectifolius and R. millanii had irregularly bimodal distributions of gender with non-seeding and functionally bisexual plants; population of R. niphophilus had amodal distributions of gender with plants exhibiting a range of genders from nearly non-seeding to very female; and populations of R. graniticola were unimodal with plants being functionally as well as phenotypically hermaphrodite. Plant size was correlated with several aspects of gender in R. muelleri, R. dissectifolius, R. graniticola and R. niphophilus.
Flowering of Ranunculus species is restricted by snow cover early in the season, and appears to be restricted by drought later in the season, but the date of flowering did not affect the amount of seed produced by a plant nor seed set per flower. When the overlap in flowering among species was quantified using the novel measure, interspecific synchrony, only moderate levels of synchrony were found for most combinations of species, indicating that there was some temporal displacement of flowering among the five species. Moderate to high levels of seed set for interspecific crosses, compared with intraspecific crosses, were obtained for all combinations of crosses among the five species in the field. These high levels of interspecific compatibility indicate that the alpine Ranunculus species are likely to experience selection for temporal divergence of flowering which would reduce the loss of reproductive resources associated with the production of hybrid seed.
Vol 127 parts 1-2, p.62 [1994] |
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Doctoral Thesis Abstract: a Study of Conducting Polyrrole Films in the Microwave Region
Qif Kaynak
Abstract of a Thesis Submitted for the Degree of Doctor of Philosophy at the University of Technology, Sydney, 1994.
This thesis is a comprehensive characterisation of conducting polypyrrole films in the microwave frequency region. Microwave investigations presented in this thesis can be grouped under three interrelated sections, namely, i) transmission, reflection, absorption behaviour, ii) shielding effectiveness studies and iii) microwave dielectric properties. Reflection, transmission and absorption behaviour of polypyrrole films with dc conductivities ranging from 0.001 S/cm to 50 S/cm are presented. Results show that the electrical conductivity of the doped polypyrrole films have a significant effect on transmission, reflection and absorption of microwaves. Samples with low conductivity (low dopant concentration) exhibited high transmission whereas highly conducting films were reflective. Significant absorption of microwave radiation was only observed for samples of intermediate conductivity. Transmission and reflection experiments on polypyrrole films were simulated by using finite element methods. Solutions obtained by theoretical methods were in excellent agreement with the experimental results, confirming the dependability of the measurement methods used. The agreement between experiment and theory for 50 micron films provided confidence to extend the theoretical methods to include the effect of sample thickness on microwave reflection, transmission and absorption properties of films with a wide range of conductivities Having access to such data including the effect of dopant concentration, conductivity and sample thickness on microwave transmission, reflection and absorption, would be extremely valuable for the design of microwave devices and fundamental understanding of material properties.
The wide range of modulation of conductivity and dielectric properties of semiconducting and conducting polymers allows variation of reflectivity and absorption of electromagnetic waves not available with conventional materials Therefore a study on the shielding effectiveness of conducting polypyrrole assumes particular importance. A method of measuring plane-wave shielding effectiveness (SE) is presented. Shielding effectiveness as a function of conductivity and frequency (300 MHz-2 GHz) were studied. Shielding effectiveness of PPy films was found to increase with the increase in conductivity. SE measurements carried out on PPy samples aged in room temperature for a period of about 2 years revealed that shielding effectiveness degraded by 10 to 15 dB over the test frequency band. However highly doped films retained relatively high levels of shielding. A shielding effectiveness of above 40 dB was obtained with highly doped (O.1 M p-TS) conducting polypyrrole film over the frequency range 300 MHz to 2 GHz, making it attractive for consideration in shielding applications.
Microwave dielectric properties of the electrochemically synthesised polypyrrole with a wide range of doping levels are presented. Methods for determining the complex permittivity in the microwave regime are discussed. The variation of the complex permittivity as a function of polymer dopant concentration at room temperature using cavity perturbation methods at frequencies of 2.45 GHz and 10 GHz are presented. Measurements indicate that the real (ε') and imaginary (ε") parts of the dielectric constant increase in magnitude with increasing polymer doping level. Both ε' and ε" were small for lightly doped samples, but increased at higher dopant concentrations. Complex dielectric constant measurements were also performed on semi conducting polypyrrole films for the temperature range 90K-400K. The real part ε' of the complex dielectric constant increased slightly with increase of temperature whereas the imaginary part ε" increased significantly with temperature. Results were verified by using theoretical methods.
Vol 127 parts 1-2, p.63 [1994] |
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Masters Thesis Abstract: Representation Issues in Genetic Algorithm Function Optimization
Rohan A. Baxter
This work examines representation issues in the optimization of real parameter numerical functions using genetic algorithms. The optimization of these functions has applications in many areas. The genetic algorithm (GA) is a search technique that evaluates populations of candidate solutions using an objective function. It selects the better candidates for reproduction and so generates new candidate solutions for testing. The standard genetic algorithm and its relationship to other optimization methods is described. The method of representation of candidate solutions affects the optimization performance of genetic algorithms.
The desirable properties for experimental test function suites are discussed. De Jong's test suite has been widely used in previous work. These functions are shown to be hill-climbing easy. It is shown that simple hill-climbing algorithms are faster and more accurate than genetic algorithms on this test suite. Genetic algorithms are better suited to optimizing hill-climbing hard functions. A new test suite is introduced and its suitability assessed. It is proposed that the new suite is a more test-bed for genetic algorithm optimization performance, its functions are multi-modal and hill-climbing hard.
Genetic algorithms are then shown to efficiently optimize hill-climbing hard functions. The effects of different integer coding functions on the performance of the genetic algorithm optimization are investigated. The reflected Gray code is found to perform better than the other Gray codes analyzed on the old test suite. However the Binary code is found to do better on the new test suite. The balanced Gray code is implemented and its performance assessed. Three relevant code characteristics are identified as promoting genetic algorithm performance. An acyclic, near-Gray code is then presented with these characteristics. This insight into code characteristics suggests a new interpretation for some previous results by Caruana and Caldwell.
The relative performance of binary and real number coding representations is investigated, This is an area of some controversy as practitioners use real number coding because it works. However existing genetic algorithm theory suggests binary coding should do better. Contrary to some claims, binary codings are found to generally outperform real codings on the high dimensional multi-modal test functions when similar selection and reproduction operators are used. The experimental methodology employed and the significance of the results are discussed.
Vol 127 parts 1-2, p.64 [1994] |
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Doctoral Thesis Abstract: The diamond path: a study of individuation in the works of John Keats
Maureen B. Roberts
Romanticism as a particular phase in the evolution of Western consciousness is characterised by a creative reconnection to the collective unconscious as a key aspect of introverted thinking. Individuation as self-realisation involves, as does the Romantic imagination, the struggle to unify recreatively through the balance and synthesis of opposites. After a brief discussion of these ideas, this thesis examines the development of Keats' poetry in terms of a basic pattern of transformation in which an initially unified state of consciousness is divided, then re-collected as a "higher" unity through a process of maturation.
Two important uniting symbols - the diamond orb in Endymion and the square edged stone at the end of The Fall of Hyperion - form the two ends of a thread of development along which Keats' poetry is self-creative through its healing of the "dis-ease" of inner division to reform the unified self. This quest for unity is examined through several paradigms of individuation, all of which are harmonious with the basic principles of Romanticism and Jungian thought. These are, in order, the Neoplatonic quest for the One as Truth and Beauty, the alchemical synthesis of opposites to form the Philosophers' Stone, the Gnostic paradox of the "fortunate fall" into self-division, and the creative tension between the unified Apollonian self and the Dionysian self-divided sufferer who is in principle synonymous with Milton's Satan. Keats accordingly inverts the significance of the Miltonic Christian Fall by ascribing a positive potential to the Dionysian transitional state of paradox. Within this perspective Keats' philosophy of "Soul-making" expresses the Gnostic striving of the divine "spark" as the latent individuality of the self to ascend through the ambivalent space of individuation to conscious realisation.
Through the progressive integration of all these principles, Keats is seen to be an intuitively Gnostic and primarily introverted thinker whose quest for redeeming self-knowledge reflects his own maxim: "That which is creative must create itself."
Vol 127 parts 1-2, p.65 [1994] |
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Doctoral Thesis Abstract. Barotropic depth-averaged and three-dimensional tidal programs for shallow seas.
Peter J. Bills
This thesis reports the development and testing of three programs for computing tides in shallow seas and their particular application to Spencer Gulf, South Australia.
The first program solves the three-dimensional barotropic non-linear long-wave equations discretised using finite differences. The σ-transformation is used in the vertical with non-uniform depth-level spacing. The overall difference scheme is three-level in time and of leap-frog type for the computation of tidal elevations, and two-leve1 in time for velocity calculations. It uses explicit differencing in the horizontal direction and implicit differencing in the vertical. The second program solves the depth-averaged analogue of these equations. The third program is an adaptation of the depth-averaged program to include the modelling of the covering and uncovering of tidal flats.
All three programs are designed to handle general boundary configurations while using only four distinct element types. Appropriate forms of the discretised equations for a particular element configuration are automatically selected using the element type numbers in algebraic switches. The coding and accuracy of the differencing used is checked by comparing predicted results with analytical solutions for idealized basins. Wave propagation analyses of the difference formulations for linearized forms of the equations are also carried out.
Depth-averaged and three-dimensional models of Spencer Gulf are developed with the open boundary at the entrance to the Gulf. Height-specified and combined radiation/height-specified open boundary conditions are compared in the case of the depth-averaged model. Three formulations for bottom stress (depth-averaged model) and two forms for vertical eddy viscosity coefficient (three-dimensional model) are examined. The role of the horizontal eddy viscosity terms in introducing artificial friction is discussed. Both models are driven simultaneously by the four major tidal constituents O1, K1, M2 and S2. Comparisons of results using linear and non-linear equations are made in the depth-averaged case. Results clarify and extend the work from earlier numerical models of Spencer Gulf and predict new features of tidal flow near Wallaroo.
A modification of the method for incorporating the wetting and drying of tidal flats due to Flather and Heaps (1975) is presented and applied in a depth-averaged fine-grid model of Northern Spencer Gulf. It gives stable predictions over a 32 day simulation. Stability and accuracy are enhanced if a de Chèzy coefficient of quadratic friction is used. This suggests that a locally depth-dependent coefficient of quadratic friction is more suited to very shallow tidal modelling than a constant coefficient. An appraisal of the built-in filtering behaviour of some common finite difference formulations and their role ia suppressing grid-scale oscillations is presented.
The Northern Spencer Gulf tidal flat model numerically confirms the observation of a residual eddy south of Lowly Point. A complementary eddy is predicted to the north of Lowly Point. The model predicts that Ward Spit, a large sand bar to the east of Port Bonython, is uncovered only at low springs. This prediction is supported by annotation on an old map of the region. A mechanism for the creation and maintenance of Ward Spit is suggested based on a plot of residual vectors for depth-averaged velocity.
Reference:
Flather, R. A. and Heaps, N. S. (1975), Tidal computations for Morecambe Bay, Geophysical Journal. Royal Astronomical Society, 42, pp. 489 517.
Vol 127 parts 1-2, p.66 [1994] |
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Doctoral Thesis Abstract: Tannin Toxicity Studies in Mice and Sheep
Jin Zhu
Toxicities of tannic acid (TA), oak and yellow-wood (YW) tannins were studied in mice and sheep following oral or intraperitoneal (i.p.) administration. Oral dosing of mice with tannin extract from oak leaf or acorn produced severe periacinar liver necrosis without kidney damage when the tannin content was high - a relationship previously reported with YW. Oak leaves (Quercus robur and Q. acutissima) with a tannin content of 3.03 to 8.79% TA equivalent (TAE) did not produce toxicity when given to sheep by gavage daily for 4-18 days. However, Q. robur leaf with a tannin content of 13.92%TAE produced severe liver necrosis without renal injury in one sheep after 2 days dosing. These preliminary studies suggest that oak leaf in Australia is generally non-toxic unless the tannin content is high; and that the oak tannin is hepatotoxic rather than nephrotoxic.
Punicalagin, a hydrolysable tannin isolated from YW leaf, produced periacinar coagulative liver necrosis in mice but not kidney necrosis when given orally or i.p. The oral dose (>0.50 g/kg bw) required to produce toxicity was at least 20 times greater than the i.p. dose. The i.p. toxicity of punicalagin in sheep was similar to that in mice and, prior to necrosis, steatosis in the liver was a consistent finding but this was not found in sheep given YW leaf. Serial liver biopsies in sheep given YW leaf orally showed that the liver necrosis was initially midzonal before becoming periacinar. Terminalin, another tannin isolated from YW leaf produced renal tubular necrosis similar to that described in cattle following naturally occurring YW poisoning and liver necrosis similar to that produced by punicalagin in mice and sheep.
Liver necrosis was not observed histologically or detected biochemically in sheep dosed orally with TA, but transmission electron microscopy showed focal hepatocellular necrosis, steatosis and acicular crystal cleft formation, There were significant increases in blood methaemoglobin concentration (P<0.05) and decreases in blood pH (P<0.01) and oxyhaemoglobin concentration (P<0.05) by 32 h after dosing. When TA was given i.p. in sheep, liver necrosis similar to that seen in punicalagin intoxication was produced, together with metabolic acidosis and compensatory respiratory alkalosis, but not methaemoglobinaemia. Sheep given TA intra-abomasally developed liver, kidney and abomasal necrosis. Thus while TA is hepatotoxic when given parenterally to sheep, when given orally it does not produce renal or significant hepatic injury, but rather causes metabolic acidosis and methaemoglobinaemia.
In sheep intoxicated i.p. with punicalagin, terminalin or TA, or orally with YW leaf, or intra- abomasally with TA, plasma liver enzymes and bilirubin levels significantly (P<0.05) increased, while plasma glucose and total protein concentrations significantly (P<0.05) decreased. The decrease in plasma protein was considered to be due to tannin precipitation.
When TA was dosed intra-abomasally in sheep, TA and its metabolites (gallic acid, 4W-methyl gallic acid and ellagic acid) were found in the plasma. With oral dosing, gallic acid and pyrogallol were found in the plasma. Gallic acid gradually decreased in both urine and ruminal fluid, while pyrogallol increased and resulted in methaemoglobinaemia.
TA produced periacinar liver necrosis in mice dosed orally. Gallic acid, ellagic acid and pyrogallol did not produce hepatic or renal lesions, although pyrogallol caused death due to methaemoglobinaemia. Thus TA, rather than its metabolites, is responsible for liver necrosis in animals. When given orally to rummants, TA is metabolised to pyrogallol, which in turn produces methaemoglobinaemia.
In conclusion, this study showed that two tannins, punicalagin and terminalin, are the toxic principles in YW leaf; tannin metabolites, gallic acid, pyrogallol and ellagic acid, are not hepatotoxic or nephrotoxic; and TA, when given orally, produces liver necrosis in monogastric animals and methaemoglobinaemia in ruminants.
Vol 127 parts 1-2, pp.67-68 [1994] |
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Doctoral Thesis Abstract: Multi-Frequency MF/lower HF ocean radar studies of wind — wave transients.
Murray L. Parkinson
A Medium-Frequency (MF: 0.3-3 MHz)/lower High-Frequency (HF: 3-30 MHz) phased-antenna array on Bribie Island, Queensland, Australia, consists of a 1-km line of 10 transmitter antennae aligned east-west, and orthoganol to a 1-km line of 10 receiver antennae. The array is normally phased to produce a near-vertical radar beam, but for these studies it was converted to operate as a surface-wave radar used for coherent ocean-backscatter studies. This was accomplished by changing impedance-matching circuits at the base of transmitter antennae, thereby converting them from crossed-horizontal dipoles to top-loaded vertical dipoles which emit maximum radiation in the horizontal plane.
A new body of MACRO-11 machine control software was developed to direct the crossing of transmitter and receiver beams in the horizontal direction and steerable in azimuth. A computer model describing the effective radiation pattern formed by the array was also developed, and it was used to calculate the radiation pattern across an entire celestial hemisphere of any chosen radius.
Transmitting at frequencies 1.98, 3.84, and 5.80 MHz, the Bribie Island radar is sensitive to first order to sea waves of length 75.7, 39.0, and 25.8 m respectively (radio waves coherently backscatter form sea waves of half the radio wavelength). Similar experirnents to those reported here have usually been performed at the upper HF to very-high-frequency (VHF: 30-300 MHz) range. The experiments reported here were thus partly novel because of the use of lower frequencies with a large steerable array achieving a high angular resolution.
Complex time series of sea echoes recorded at frequency 3.84 MHz showed random modulations in amplitude and phase which were adequately explained by beats between Doppler-shifted echoes from the different portions of the radar footprints encompassing turbulent surface-current flows, An alternative explanation was the direct observation of random modulations in the sea-wave Fourier components.
Hundreds of sea-echo Doppler spectra recorded during four field studies were analysed to show the limited coherence of sea waves. Generally, sea waves were less coherent than a continuous tone, with coherence deteriorating for shorter waves, and possibly during shoaling. Because of the noise-like quality of the waves, it was shown that incoherent spectral averaging is the optimum procedure for revealing spectral information otherwise buried in noise.
Shallow water depths may have had another important effect on the observed sea-echo spectra. It was suggested that the first-order sea echoes were broadened because the phase speeds of gravity waves (and thus the Doppler shifts they produce) were modified by the bathymetry of radar footprints. Allowing for contributions by familiar broadening mechanisms, it was further suggested that the proportion of the footprints corresponding to various water depths may be inferred from the remaining Doppler broadening. A best-case error analysis showed that a MF surface-wave radar transmitting at frequency 0.5 MHz should remotely sense the bathymetry of the sea down to water depths of 145 m with >15% accuracy.
A new technique for deducing the time constant for evolution of the wind-wave peak in scalar sea spectra down the frequency range was developed – it involved a comparison between the observed growth rates of Bragg-peak amplitude (first-order sea echoes) and theoretical growth rates implied by established scalar sea spectrurn models. A time constant of 1.3 ± 0.4 h was estimated for U10=7 m s-1, an area of sea =19 km, and an integration time of 0.48 h, but the time constant values were controlled by the temporal resolution of the measurement process.
Because the radar-derived time constant was in good agreement with the accepted buoy-derived value, it was suggested that no dilemma is presented by the fact that VHF radars are known to track the observed sea-truth changes in wind direction to within minutes (as opposed to hours). This is because the short sea waves to which VHF radio waves are sensitive probably veer rapidly in azimuth (in the order of 0.1o s-1), and in general the time scale for veering of directional sea spectrum may depend upon the degree of wave spreading, as well as wave frequency.
The directional factor of sea spectra is an important oceanographic quantity which is infrequently measured by a limited number of techniques. I showed how the large phased-antenna array might be used to measure directional factors by inverting the observed first-order sea echoes measured simultaneously at many azimuths (and a number of ranges and frequencies) through rapid control of beam direction. This new measurernent technique was made possible by the advanced digital beam-steering and signal-processing capabilities of the Bribie Island radar. Preliminary observations demonstrated that, in principle, this new technique can be used to measure t,he directional factor automatically, including dominant sea direction and angular spread with high resolution (± 2o) in near real time, especially if the radar is relocated to a more favourable geographic site.
Other cursory studies presented here included the range sensitivity of the Bribie Island radar, an explanation of mysterious 'ground' echoes, and the results of initial searches for skywave-propagated sea echoes. It is advocated that the Bribie Island radar may operate in the sky-wave mode to remotely sense, for exarnple, sea-direction vortices associated with tropical cyclones off the coast of North Queensland, However, care will be required to ensure that ionospheric echoes are not confused with genuine sea echoes.
In summary, the work described in this thesis is clearly original, but it can only be considered a pilot study on the use of the Bribie Island radar for sea-scatter studies. This is because it is also apparent from the work presented within that HF measurements in compiex oceanographic environments are not straight forward. Many follow-through experiments with the deployment of in situ probes collocated with radar footprints will be necessary to obtain more convincing results confirming (or refuting) the present interpretations. Thus, this work contributes to scientific knowledge in the sense of posing new ideas and questions, rather than providing definitive answers.
Vol 127 parts 1-2, p.69 [1994] |
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Doctoral Thesis Abstract: 'It's so strange when you stay sick'. The challenge of chronic fatigue syndrome
Roslyn Woodward
Chronic Fatigue Syndrome (CFS) remains poorly understood, despite the recent definition of the syndrome by the United States Centers for Disease Control (Holmes et al, 1988), and the growing biomedical and public interest in it. This thesis explores the nature of the condition, its explanations, effects and management. It also highlights important concerns for people who have chronic conditions which medical science has yet to understand or recognise, and discusses doctors' dilemmas about appropriate care for such conditions.
The research relies principally on information gathered from interviews over a two year period with fifty people who have been given a diagnosis of CFS. The related issue of appropriate care is examined from the perspective of peop1e with CFS, but is complemented by the views of twenty doctors.
Drawing on the experiences of people with CFS, I present an account of the illness, beginning with a detailed description of the symptoms over time and their effects on people's lives, This natural history of the condition also reflects people's concerns about their problem. It shows how the erratic and sometimes peculiar symptoms brought feelings of uncertainty and estrangement, feelings that became increasingly pronounced as their health deteriorated.
The account then broadens from a description of the illness and its pervasive effects to encompass the impact of social and medical responses on people as they sought help and advice about their condition. Although viruses were triggers in people's initial deterioration into poor health, the development appears to have been influenced by the medical uncertainties about the condition, The decline into poorer health was moderated when people had understanding and a meaningful framework for interpreting the problems. Over time, two related contrasts emerged. There was a contrast between the long term health and sense of well being of those people whose doctors had been consistently respectful, and the majority of participants who received responses that they felt disregarded their symptoms. Secondly, there was a contrast between people's deteriorating health prior to diagnosis, and their health afterwards. As the majority of doctors in the study expressed reservations about the va1ue of providing people with a diagnosis for this condition, these findings about the changes associated with diagnosis have important implications for the management and care of this and other conditions which create uncertainty.
The study also suggests that individuals who have developed this illness have characteristics in common, They have been active, productive and conscientious people. Their style of coping with illness has been one of active denial and defiance, characterised by an early and often enduring determination to ignore symptoms and overcome difficulties. In combination with demanding life circumstances, this style of coping with illness and with medical doubt seems to be implicated in the onset and the development of the condition. Many individuals began to question this coping style only after they had a diagnosis. The changes that occurred in people's health over time seemed to be related to their ability to relinquish this coping style. On the basis of this finding, I argue that management of CFS rests on early identification of the problem and change in the individual's style of coping.
Vol 127 parts 3-4, p. 155-156 [1994] |
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Doctoral Thesis Abstract (Macquarie University): Chiral Discrimination Processes in Some Metal Chelate Systems of Biological Interest
Janice Rae Aldrich-Wright
This thesis reports on the design, synthesis and optical resolution of a set of chiral metal complexes which are intended to be of value for probing the comformational structures of DNA via intercalation. Optimisation of the molecular size of the parent diimine ligand was achieved by synthesis of several phen-based bidentate ligands, including the novel compound dpq, (dipyrido[6,7-d:2'3'-f]quinoxaline) and these bidentates then were incorporated into [M(diimine)n+, complexes. The effectiveness of the use of tetradentates as a means of overall shape control was investigated by synthesis of related [M(tetradendate)(diimine)n+ complexes.
The crystal structure of one of these complexes, cis-β-[(Ru(picenBz2)(o-pda)](PF6)2, was determined at room temperature. Crystal data: C34H38N6F12P2Ru is triclinic, space group P 1 (No.2), with a =10.129 b 10.338, c = 19.587 A, α = 104.42, β = 93.36, γ = 92.000 and Z= 2. The structure was refined by block matrix least squares methods to R = 0.075 for 3057 non-zero diffractometer data. Both PF6 groups were subject to disordering with respect to their fluorine atom positions, and these have been interpreted in terms of partial occupancies. The X-ray structure, including observed torsion angles and consequent calculated coupling constants, is consistent with the NMR analysis.
Classical and chromatographic means of optical resolution of the complex products were investigated, with the aim of developing not only a method which would separate enantiomers but which also could act as a preliminary screening technique for structural probes of DNA. Resolutions using antitnonyl(+)tartrate were successful for [M(diimine)3]n+ species when the diimine is phen or dpq. Racemic mixtures of [Ru(bipyMe2)2(phen)]2+ and [M(diimine)3]n+ were eluted on Sephadex with enantiomeric enrichment of the leading and trailing fractions. The diastereomers of [Ru(diimine)2(aa)]n+ complexes, where the diimine is bipy or phen and aa is trp, N-Methyl-S-trp, G, asp, were resolved using μbondapak HPLC columns, eluted with an ion pairing reagent.
Figure 1 A computer generated stereoview of α-[Ru(picenBz2)(dpq)]2+complex, with dpq occupying the intercalation site of six base-pair DNA model.
Chiral stationary phases were developed for HPLC applications although only one of these columns showed selectivity for the chiral metal complexes. A covalently-bound DNA stationary phase was developed and used to optically resolve [Ru(dpq)312+and [Ru(phen)3]2+, and confirmed that effective aromatic overlap does influence column retention times. Other immobilised-DNA stationary phases were examined, such as DNA-hydroxylapatite, cellulose-DNA column and DNA-paper. The DNA-paper proved to be an easy way of simultaneously comparing a number of metal complexes, and the Rf data correlated well with the aromatic area available for intercalation.
Computer modelling has been used extensively for the preparation of the illustrations throughout the thesis and, by adapting crystallographic data of analogous metal complexes, as a design aid in investigating the effects of structural variations on complementary fit and likely efficiency of DNA binding for the probe molecules developed (Fig 1).
Vol 127 parts 3-4, p. 157 [1994] |
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MSc Thesis Abstract:- Movement Behaviour and Structure of Groups of juvenile MULLET, Mugil cephalus (Linnaeus).
Stuart Fitzsimmons.
Movement behaviour and group structure of juvenile mullet, Mugil cephalus (Linnaeus), and obligate schooling species, was investigated for known focal individuals within small group sizes (blocks of two, three and four fish).
Plots of swimming patterns indicated two main types of movement behaviour – (a) inactive groups that covered short distances and executed few turns, and (b) active groups that covered larger distances and executed many turns. Mean swimming speeds (body lengths/sec) and mean turning frequencies (turns/sec) both declined significantly with increasing group size, with significant differences between blocks of similar sized groups being attributed to individual variation. However, within blocks the movement behaviour of individuals was generally highly coordinated. As the size of the group increased, behavioural convergence mediated by the monitoring of companions rapidly masked individual variation and led to the characteristic uniformity of such associations.
In conjunction with mean swimming speeds, separation angles (degrees) were used to categorize groups into congregations (< 0.2 BL/sec, nonpolarized >200), shoals (> 0.2 BL/sec, non-polarized >200), and schools (> 0.2 BL/sec, polarized < 200). Separation angles determined the level of polarization between individuals within groups, with polarization angles ranging from 00 (parallel orientation) to 900 (nonparallel orientation). Polarized groups of mullet were estimated to have separation angles of < 200 and non-polarized groups> 200. Although these cut-off limits were arbitrary, groups within each category generally.' displayed movement behaviours quantitatively different from one another.
Polarization of individuals' headings and synchrony of their movements were generally dependent upon mean swimming speeds, with schooling behaviour generally exhibited more often by faster moving groups. As mean swimming speed decreased, groups tended to exhibit more shoaling and congregating behaviour. Focal pairs of fish within faster moving groups (> 0.5 BL/sec) had significantly correlated swimming speeds and headings at lag of 0 - 1 seconds. As swimming speed decreased, lag time between correlated movements increased. In the slowest moving groups (< 0.2 BL/sec), speed and heading of focal fish were not significantly correlated for lags between -5 to +5 seconds.
Distances between focal pairs (body lengths), and positional bearing (degrees) only significantly effected co-ordination of swimming speeds or headings in a small number of groups. This could be attributed to the fact that group structure did not vary significantly between blocks of similar size or for each group.size. Mean interfish distance of the focal pairs varied from 0.49 to 2.1 body lengths (BL), regulated around a mean of ± 1 BL. The response fish in most instances swam at a mean position diagonally behind the focal fish, either to the left or right hand side.
A significant leader/follower relationship was observed in most groups, with the focal fish dominating the leadership for the duration of analysis. The duration of leadership did not significantly vary between groups of similar size or for each group size The duration of leadership of a single individual decreased significantly as mean swimming speeds, mean turning frequencies and separation angles increased, with group structure having no significant effect on duration of leadership.
Movement behaviour of group structure was analysed for four-fish groups within three treatments of varying physical attributes. In the tank with a structure present (clump of artificial weed), the focal pairs of individuals had mean swimming speeds significantly faster than those in the control tank and smaller tank. However, mean swimming speeds were not significantly different between groups within the smaller tank and the control tank. Groups within the smaller tank performed significantly more turns than control and structured tank groups, but mean distance travelled between turns was significantly lower. The separation angle of the focal pairs did not vary significantly between treatments or between blocks. In most blocks, mean separation angle of the focal pairs were lower compared to those of the overall group, which was attributed to the fish three and four having headings dissimilar to the focal fish. As for control groups, interfish distances and positional bearings did not significantly differ between treatments.
In summary, obligate schooling species, such as mullet, can exhibit consistent individual differences in behaviour which is considered to be the principal underlying source of variation between blocked pairs. Movement behaviour of individuals can be significantly influenced by the addition of only a single extra individual when group size is small. In nature, as small groups merge into larger associations, behavioural convergence becomes more broadlybased and the influence of particular individuals is less obvious. However. factors such as separation angle and group structure, interfish distance and positional bearing, were relatively fixed. Neither individual variation or group size had any significant effect on these parameters.
Vol 127 parts 3-4, p. 159 [1994] |
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DOCTORAL THESIS ABSTRACT: PERINATAL HYPOXIC-ISCHAEMIC ENCEPHALOPATHY: PATHOGENESIS and PHARMACOLOGICAL INTERVENTION.
William Kian Meng Tan
Perinatal hypoxic-ischaemic encephalopathy is associated with an increased risk of neurological deficits. Certain aspects of the pathogenesis of damage are still unclear. To address some of the hypotheses relating to the mechanisms of damage and recovery, chronically instrumented near-term fetal sheep were subjected to transient hypoxia-ischaemia; this procedure induces an encephalopathy showing characteristics similar to that seen in some asphyxiated term infants. Electrocorticographic (ECoG) activity was quantified with realtime spectral analysis. On-line cortical impedance was used to estimate changes in extracellular space that occur concomitantly with cytotoxic oedema and reflect cell membrane function. Histological outcome was assessed 72 hours after ischaemia.
It is not known whether postasphyxial seizures either extend damage or are an expression of existing damage. MK-801, an N~ receptor antagonist and potent anticonvulsant (0.3 mg/kg), suppressed the epileptiform activity, delayed the onset of secondary oedema and reduced neuronal damage. These results suggest that WDA mediated epileptiform activity that develops after a global hypoxic-ischaemic insult worsens neuronal outcome in the immature brain.
Hypoxia-ischaemia is associated with an increase in cerebral lactate levels and a decrease in tissue pH. It is not clear whether lactic acidosis worsens neuronal injury in the developing brain or is protective. Acutely induced lactic acidosis (fetal arterial lactate concentrations: 11.2 ± 1.0 mmol/1; pH:7.04 ± 0.06) superimposed on a 10- minute cerebral ischaemia delayed recovery of ECoG and accentuated hippocampal damage.
Treatment strategies against hypoxicischaemic injury in the perinatal period are limited. The effectiveness of GM1, a glycosphingolipid which is an endogenous component of plasma membrane, was evaluated. GM1 (30 mg/kg), started 2 hours before a severe insult, improved recovery of acute cortical oedema and ECoG activity and reduced neuronal loss without compromising arterial blood pressure or metabolic status.
Three 10-minute episodes of reversible cerebral ischaemia, repeated at 1 hour interval, can markedly sensitise the fetal brain to neuronal loss. The same dose of GM1 given immediately after the first insult counteracts this sensitisation and protects against subsequent insults through stabilisation of membrane function. These results demonstrate the potential of GM1 as a strategy to protect the CNS of distressed fetuses at risk of hypoxicischaemic injuries.
Vol 127 parts 3-4, p. 159 [1994] |
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Intake of organochlorines from the breastmilk of Victorian women.
PATRICIA M. QUINSEY
Organochlorines have been distributed throughout the environment. Many organochlorines are pesticides and some are industrial pollutants. Due to their high lipophilicity, toxicity in particular animal species and ability to bioaccumulate in animals, the use of these chemicals has been restricted. Mobilisation of fat tissue by weight loss or breastfeeding allows stored organochlorines to re-enter the blood stream. Excretion of organochlorines in breastmilk is a significant way for women to reduce their body burden. Unfortunately, in the process breastmilk can transfer organochlorines from mother to child.
The purpose of this project was to estimate infants' daily intake of organochlorines from breastmilk and to trace the elimination patterns of these compounds from the mothers.
Each infant was test-weighed over twenty-four hours to provide an accurate milk intake. The entire content from one breast was collected at the midmoming feed. Three collections occurred for each mother at intervals of a month. The lipophilic material was extracted from the milk and the organochlorines were separated by gel permeation chromatography. The organochlorine extract was analysed by selected ion monitoring on a gas chromatograph-mass spectrometer (GC-MS).
The lipid content of milk varies dramatically and this factor influences the concentration of organochlorines in breastmilk. The determination of the levels of organochlorines present on a milk~fat basis accounts for changes in lipid composition. The amount of milk an infant drinks daily varies from mother to mother. To determine reliable intakes of organochlorines it is essential to measure the amount of milk consumed by each infant.
Residues of p,p'-DDE, pp'-DDT, dieldrin, aldrin, α, β, γ, δ-HCH, HCB, oxychlordane, trans-nonachlor, heptachlor epoxide and PC13s were detected. There was widespread contamination of breastmilk with p,p'-DDT and its metabolite p,p'-DDE, HCB, PCBs, oxychlordane and HCHs, with p,p'-DDT and HCB being found in nearly all samples. A number of infants received daily intakes of p,p'-DDT, heptachlor epoxide, total chIordane, dieldrin and PCBs above the acceptable daily intakes (ADIs). Generally, the levels of organochlorines detected in the breastmilk represents no danger to the infant.
The main human source of organochlorines is probably foodstuffs, There was no significant difference between the concentrations of organochlorines found in breastmilk from the two regions studied. The use of termiticides in houses was not associated with the level of organochlorines found in breastmilk. Over the period of lactation a general downward trend in concentration of organochlorines was observed, with levels of p,p'-DDE decreasing significantly. The concentrations of p,p'-DDT and dieldrin in human milk have decreased in Victoria, whilst levels of HCB and PCBs have increased. The byproducts of some chlorinated industrial processes and the disposal of PCB-containing products are possibly increasing the environmental burden of these organochlorines.
Vol 128 parts 1-2, pp.36-38 [1995] |
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Master of Science (Mathematics) Thesis Abstract: Dipole Modelling for the Localization of Human Visual Evoked Scalp Potential Sources
Monica K. Hurdal
Thesis submitted for the Degree of Master of Science in the Department of Mathematics, University of Newcastle, 1994.
One of the major goals of electrophysiology is the determination of sources of electrical activity in the human brain. Visual stimuli elicit visual evoked scalp potentials (VEPs) which can be recorded non- invasively as electroencephalograms (EEGs) by using scalp electrodes. This electrical activity is generated by electrical sources in the brain. A model of the head structure is required as well as a model of a source of electrical activity. Using this type of model, the location of electrical sources can be estimated.
The use of electrophysiological techniques, such as the standard 10-20 system of electrode placement and the use of brain scans as a further aid to VEP research are described, as is the anatomy of the visual cortex. The visual field appears to have a retinotopic mapping onto the visual cortex which can be represented by a cruciform model where the visual field locations project onto the opposite hemisphere of the primary visual cortex and the upper and lower fields project onto the lower and upper parts of the visual cortex respectively.
In this thesis, the forward problem, which is the prediction of a potential distribution due to a given electrical source, is examined. Various head models are reviewed and a three shell model which represents the head as three concentric spheres is used. The source of electrical activity is assumed to be a dipole. The forward problem is solved with this model and implemented practically with computer programs. Modifications involving rotations are applied to the model in order to accomplish this. These programs calculate a potential distribution on the surface of the scalp when given a single neural source. The radii of the spheres representing the head and their conductivities are incorporated into the model and a dipole source is described by six parameters which determine the position and orientation of the source. Topography maps are used to display the electrical potential distributions.
Subsequently, the inverse problem, which is to determine a dipole source that is the best generator of a given potential distribution, is solved in the least squares sense. The same model is used as in the forward problem. As the calculation of the potential is nonlinear in three of the six parameters, various minimization search algorithms are discussed. A computational procedure which uses the Levenberg-Marquardt method for nonlinear least squares is implemented and determines the best dipole source by varying the six parameters associated with the dipole's position, orientation and strength. Predictions of the potentials at the electrode sites which are closest to tpe observed potentials in the least squares sense are-obtained. The dipole at this point is thought of as the source of the observed EEG activity.
When solving the inverse problem, the choice of electric potential reference site should not affect the location of the dipole source. A new method is presented which adds an additional parameter, a constant, to the model that is to be estimated along with the six dipole parameters. This method accounts for variations in the reference site of the observed potential data so an estimated dipole source is not affected by the reference site. Confidence intervals involving the model parameters are also calculated and help determine the validity of the dipole solution. Testing has revealed that quick convergence rates of the dipole salution, high signal to noise ratios in the EEG data, small confidence interval ranges for the estimated parameters, and similar observed and predicted results help to indicate the validity of a dipole solution.
The computer implementation of the inverse problem is then applied to visual evoked potential data obtained from two experiments. In this manner dipole source localization is applied to experimental findings as a data analysis technique. The first experiment uses a checkerboard pattern reversal stimulus and the second uses a pattern onset stimulus and data is analyzed for two subjects in both experiments. Both experiments also use magnetic resonance imaging (MRI) scans of the subjects' heads to determine if morphological diAerences between subjects contribute towards individual difFerences in the VEPs.
Results from the checkerboard pattern onset experiment using dipole source localization revealed that stimuli in the left visual field generated sources in the right hemisphere of the brain. The sources due to upper visual field stimuli localized lower in the visual cortex than did the sources which were caused by stimuli in the lower visual field. In addition, the sources due to the peak positive and negative latency in a cyclic waveform from the same stimulus condition were located in the same position but had opposite orientations, indicating a polarity reversal. These results conform to the cruciform model. However, as the stimulus moved from the upper visual field to the lower visual field, a polarity reversal was only seen in some of the stimulus conditions. As stimulus eccentricity increased, the dipole sources due to the upper visual field stimuli moved deeper into the cortica1 tissue, but this was more diAicult to see in the lower visual field sources.
Results from the pattern onset experiment did reveal a polarity reversal as the stimulus moved from upper to lower visual fields. It was expected that the first component would be striate related. Three peak components were observed, but no conclusions could be made about the origin of the source for the evoked potential response. There was a large variability in the VEPs between subjects. The MRI scans revealed large variability in the calcarine fissures between subjects as well. The dipole localization of the VEPs in conjunction with the MRI scans indicated that the large individual variability between subjects could be explained by anatomical difFerences in the occipital lobe rather than functional differences.
Thus, dipole source modelling for the localization of human visual evoked potential sources is examined in this thesis. Dipole analysis results of the two experiments in conjunction with magnetic resonance images and electrical potential topography maps help to indicate how anatomical differences in the brain may play a role in individual variability. These experiments demonstrate that dipole source localization has a practica1 place in analyzing visua1 evoked potential data. Dipole modelling is a useful and effective tool for the localization of human visual evoked potentials.
This research has been presented at two conferences which will have their proceedings published (Hurdal, McElwain and Finlay, 1995; Hurdal, McElwain and Finlay, in press) as well as a third conference (Hurdal, unpublished). A paper including the dipole source localization method is in submission for publication (Hurdal, McElwain and Finlay, in submission). A paper incorporating results from one of the visual evoked potential studies has been published (Chorlton, Hurdal, Fulham, Finlay and McElwain, 1994) and another VEP paper which uses dipole source localization is also in submission (Hurdal, Fulham, McElwain and Finlay, in submission).
References
Chorlton, M. C., Hurdal, M. K., Fulham, W. R., Finlay, D. C. and McElwain, D. L. S. (1994), Visual evoked potentials to small stimuli presented along a vertical meridian: Individual differences and dipole modelling, Australian Journal of Psychology 46, 87-94.
Hurdal, M. K. (unpublished), Using an equivalent dipole model to localize human brain electrical activity evoked by visual stimuli. Presented at the 1994 Australian and New Zealand Industrial and Applied Mathematics Conference.
Hurdal, M. K., McElwain, D. L. S. and Finlay, D. C. (1995), Dipole source localization of human visually evoked scalp potentials, pp. 192 – 193 in Liebert, B., Ward, P. B. and Michie, P., Biological Psychology, 39, Abstracts of papers presented at the Third Annual Conference of the Australian Society for Psychophysiology, 187 – 202. Presented at the 1993 Australasian Conference on Psychophysiology.
Hurdal, M. K., McElwain, D. L. S. and Finlay, D. C. (in submission), Dipole source localization: Confidence intervals and reference-free modelling, IEEE Transactions on Biomedical Engineering.
Hurdal, M. K., McElwain, D. L. S. and Finlay, D. C. (in press), Dipole source estimation: The localization of visually evoked potential sources, Brain Topography. Presented at the 1994 Pan Pacific Conference on Brain Electric Topography.
Hurdal, M. K., Fulham, W. R., McElwain, D. p. g. and Finlay, D. C. (in submission), Localization of brain activity associated with pattern reversal VEPs using the equivalent dipole technique. Electroencephalography and Clinical Neurophysiology.
Vol 128 parts 1-2, p.39 [1995] |
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Doctoral Thesis Abstract: Population dynamics of Steinernema carpocapsae and Heterorhabditis bacteriophora in in vivo and in vitro culture
Jinxian Wang
The population development of Heterorhabditis bacteriophora and Steinernema carpocapsae has been studied in larvae of the greater wax moth, Galleria mellonella, after being initiated from a single reproductive individual. The insect host was used to establish an optimal standard for fecundity with which to compare the fecundity obtained in in vitro culture,
Studies of the population dynamics of H. bacteriophora and S. carpocapsae in in vitro solid culture showed that inoculum size is important for optimising the final yields of infective juveniles, and the time in which these are achieved. The highest yield for H. bacteriophora was found with an inoculum of one million infective juveniles per flask which was ten fold the optirnal inoculum for S. carpocapsae. Studies on the populations of these nematodes derived from the extremes of high and low inocula (one or two infeetive juveniles to ten miHion infective juveniles per flask) also provided interesting infonnation on the population development of the nematodes, The significance of these findings for commercial mass production are discussed.
In liquid culture, varying inoculum sizes of S. carpocapsae was shown to have a greater effect on the population development and the final yields of infective juveniles than in solid culture, particularly with lower levels of inocula. Liquid culture required much larger inocula, and the nematodes did not reproduce when the inoculum was low. The effects of shear force from agitation for oxygenation in, and other factors involved with, in vitro monoxenic liquid culture are also discussed. The relationship between the populations of S. carpocapsae and its symbiotic bacteriu, Xenorhabdus nematophilus, was investigated and the symbiotic bacterium populations were shown to be influenced by the population development of the nematode.
The present study also demonstrated the separate effects of different levels of oxygen and carbon dioxide on the population development and final yields of S. carpocapsae. Lowering oxygen levels resulted in slower population development and reduced final yields of infective juveniles. Negligible or no increase of nematode populations was found with oxygen levels below 2%, In contrast, the higher the carbon dioxide levels, the lower the nematode yields, with yields in 10% CO2 being little more than half, and in 20% CO2 being only about one thirtieth, the yields in air. These findings have significant bearing on optimising yields of infective juveniles in the mass production of entomopathogenic nematodes.
Preliminary studies were made on the possibility that pheromones affect the formation and recovery of the infective juveniles of S. carpocapsae. Despite a variety of experiments with culture supernatant and solvent extracts of cultures, no positive results were achieved. Further investigations are needed to finally determine the existence and effect of such pheromones.
Vol 128 parts 1-2, p. [1995] |
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Optimization Algorithms on Homogeneous Spaces: with Applications in Linear Systems Theory.
Robert Mahony
Constrained optimization problems are commonplace in linear systems theory. In many cases the constraint set is a homogeneous space and the additional geometric insight provided by the Lie-group structure provides a framework in which to tackle the numerical optirnization task. The fundamental advantage of this approach is that algorithms designed and implemented using the geornetry of the homogeneous space explicitly preserve the constraint set.
In this thesis the numerical solution of a number of optimization problems constrained to homogeneous spaces are considered. The first example studied is the task of determining the eigenvalues of a symmetric matrix (or the singular values of an arbitxary matrix) by interpolating known gradient flow solutions using matrix exponentials. Next the related problem of determining principal components of a synmmetric matrix is discussed. A continuous-time gradient flow is derived that leads to a discrete exponential interpolation of the continuous-time flow which converges to the desired 1imit. A comparison to classical algorithms for the same task is given. The third example discussed, this time drawn from the field of linear systems theory, is the task of arbitrary pole placement using static feedback for a stzuctured class of linear systems.
The remainder of the thesis provides a review of the underlying theory relevant to the three examples considered and develops a mathematical framework in which the proposed numerical algorithms can be understood. This framework leads to a general form for a solution to any optimization problem on a homogeneous space. An important consequence of the theoretical review is that it develops the mathematical tools necessary to understand more sophisticated numerical algorithms. The thesis concludes by proposing a quadratically convergent numerical optimization method, based on the Newton-Raphson algorithm, which evolves explicitly on a Lie-group.
Keywords: Constrained optimization, Lie groups, Homogeneous spaces, Symmetric eigenvalue problem, Linear systems theory, Steepest ascent method, Newton-Raphson method.
Vol 128 parts 1-2, pp.41-42 [1995] |
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Doctoral Thesis Abstract: Wood Digestion in Panesthia cribrata
An abstract from the thesis submitted to the University of Sydney for the degree of Doctor of Philosophy, July 1994.
Andrew M. Scrivener
The Australian cockroach Panesthia cribrata lives in and feeds on rotting Eucalyptus spp. logs. All of the carbohydrates in the wood diet were digested by the cockroach to some extent; lignin was not digested. Carbohydrase activities in the gut were generally appropriate to the diet. Endo-β-1,4-glucanase (EC 3.2.1.4), β-glucosidase (EC 3.2.1.21), endo-β-1,4-xylanase (EC 3.2.1.8), α-amylase (EC 3,2,1.1), maltase (EC 3.2.1.20) and sucrase (EC 3.2.1.48) activities were similarly distributed in the gut, with more than 90% of each activity in the foregut and midgut.
The cellulase of P. cribrata is endogenous and consists of two major (EG1 and EG2) and at least four minor endo-β-1,4-glucanase components and one major (GD1) and one minor (GD2) β-glucosidase component. EG1 and EG2 were purified by molecular sieve and ion exchange chromatography and had molecular weights of 53,600 and 48,800, respectively. With carboxymethylcellulose (CMC) the Km, Vmax and kcat for EG1 were 9.4 mg/ml, 22.2 mg reducing sugar/min/mg protein and 20.0 s-1, respectively; corresponding values for EG2 were 6.8, 88.3 and 64.2. Values for Km, Vmax and kcat were also calculated for activity against cellotetraose and cellopentaose; neither EG1 or BG2 hydrolysed cellobiose or cellotriose. Relative activities of EG1 and EG2 against CMC and crystalline cellulose were 5200: 1 and 3500: 1, respectively. EG1 and EG2 constituted approximately 13% of the protein in the foregut and midgut contents. It is proposed that the inefficiency of EG1 and EG2 against crystalline cellulose is compensated for by their presence in large amounts in the gut. Four minor components (EG3 6) contributed between 4 and 10% of the gut endo-β-1,4-glucanase activity.
The β-glucosidase components GD I and GD2 were partially purified. Values for Km and Vmax with cellodextrins from cellobiose to cellopentaose and p-nitrophenyl-β-D-glucopyranoside were estimated for GD1 and GD2; neither component hydrolysed CMC or crystalline cellulose. GD1 was competitively inhibited by glucono-δ-1,5-lactone (Ki = 0.33 mM), but was not inhibited by glucose at physiological concentrations.
P. cribrata inhabit wood extensively degraded by fungi; the contribution of fungal cellulase to cellulose digestion in P. cribrata was investigated. Minor cockroach and fungal endo-β-1,4-glucanase components co-eluted on Bio-Gel A-0.5 m; minor P. cribrata components were shown to be endogenous as they were present in salivary gland and midgut epithelium extracts and extracts from cockroaches maintained on cellulose and starch. Fungal cellulase was not present in the gut, did not synergise with cockroach cellulase and did not contribute to cellulose digestion in P. cribrata. Fungi are not required to convert crystalline into amorphous cellulose as both were hydrolysed at similar rates by cockroach gut extracts. It is concluded that fungi soften the wood, facilitating burrowing by the cockroach.
Vol 128 parts 1-2, p. 43 [1995] |
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The Development of Mutation Detection Techniques And Their Application to Disease Diagnosis
A thesis submitted for the degree of Doctor of Philosophy in the Department of Forensic Medicine, Monash University, July 1994.
Andrea M. Douglas, B.Sc.(Hons.)
Advances in the polymerase chain reaction (PCR) have been responsible for much of the progress in human genetics that has taken place of late. The development of PCR has revolutionised the methods available for the detection of DNA mutations at the molecular level. The purpose of this research was to assess specific PCR mutation detection techniques, to test the efficiency of existing protocols, and improve upon these where necessary. In addition, to allow the ultimate analysis of mutation detection, a more practical sequencing protocol for PCR products than those currently avai1able was to be developed.
The cytochrome P450 IID6 enzyme is responsible for the metabolism of at least 25 drugs, resulting in two distinct phenotypes in the population, the extensive (EM) and poor (PM) metabolisers. The identification of the mutant alleles causing the PM phenotype allows the genetic testing of individuals via DNA based assays. This study tested the efficiency of existing PCR screening procedures in both clinical and forensic samples. Previously used PCR/RFLP based techniques were assessed with regard to the detection of the three major inactivating mutations in the CYP2D6 gene. These methods were found to be limiting, either because of the lack of controls for restriction enzyme digestion, or because of the need for multiple rounds of PCR. These detection methods were therefore modified to indude a site-specific PCR method which resulted in the analysis of all the mutations in a single PCR. This simpler PCR method was successful in accurately predicting phenotype in 88 % of individuals. When individuals were homozygous for two mutant alleles or two wild-type alleles present at either locus the accuracy was 96 %. Furthermore, when individuals were heterozygous for both of the CYP2D6(A) and (B) alleles it was discovered that phenotyping was more complex, requiring familial analyses.
A simple, multiplex method was also developed for the direct sequendng of PCR products, superior to previously described protocols. Sequencing reactions were performed directly on PCR products without the need for purification of the template by removal of residual deoxyribonucleoside triphosphates and primers. The coupling of a chemiluminescent detection system with the use of the same primers in the initial and sequencing PCRs allowed the sequencing of a number of PCR fragments on the one gel.
In the course of extending this direct sequencing protocol to PCR products greater than 1 kilobase, it was found that the sequencing procedure was more efficient if smaller PCR fragments were amplified and then multiplexed. In addition, during the process of optimising these larger PCR systems, it was demonstrated that degradation of PCR products occurs in the 94 oC denaturation step of the cycling. Thus, the denaturation time is now considered a variable that needs to be optimised with any new PCR system.
An analysis of the entire apolipoprotein AI gene resulting in the detection of previously unknown point mutations demonstrated the reliability of this sequencing method to search for point mutations in a defined region of DNA. Furthermore, the variation of gel loading of sequencing samples employed ia this study resulted in the detection of new mutations in a more efficient manner.
Vol 128 parts 1-2, p. 44 [1995] |
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Development of Metal Chelates as Potential Probes of DNA Structure
Susan E. Kidd
Abstract from the thesis submitted to Macquarie University for the degree of Doctor of Philosophy, March 1994.
A series of ruthenium(II) complexes containing the N4-tetradentate ligand N,N'-bis(2-picolyl)-1,2-diaminocyclohexane (picchxn) has been synthesised. The complex products showed a predisposition for the tetradentate to coordinate in a cis-β structural arrangement to the metal ion. Only in one case did the ligand coordinate to form a cis-α complex. With the isolation of Λ-β2-[Ru(RR-picchxn)-(dmso)Cl]Cl04.2H2O and Λ-β2-[Ru(RR-picchxn)-(dmso)Cl]Cl04.3.5H2O and their enantiomers (n is either 1 or 2) it is shown that the interaction of Ru(II) and picchxn is neither truly stereo- nor enantiospecific.
On reaction of the enantiomeric β2 forms with the amino acids (aa), S-alanine or S-tryptophan, the complexes Λ-(or Δ-)β-[Ru(RR-(or SS-)picchxnmi)(aa)]+ were formed. Here the coordinated tetradentate was found to undergo a photo-oxidative dehydrogenation reaction to form a monoimine (picchxnmi) with the amino acid not being oxidised, The isolation of Λ-β2-[Ru(RR-picchxnmi)(dmso)Cl]ClO4.0.5H2O suggested that this photo-oxidative reaction was not an isolated occurrence for the arnino acid complexes only.
All products were characterised by a combination of microanalysis, electronic absorption, nuclear magnetic resonance and circular dichroism spectroscopic methods.
Both enantiomeric forms of the β2 and βn species were observed to interact with calf-thymus DNA. The proposed interaction for these complexes is one of cova1ent binding which is found to be photoinduced. The amino acid complexes under photo-controlled conditions, are not labile and do not show any major form of interaction with calf-thymus DNA.
To further develop complexes to act as spectroscopic probes of nucleic acid structure via intercalation into DNA, the β2-dmso-Cl enantiomeric complexes wem reacted with a number of bidentate ligands based upon substituted 1,10-phenanthroline or o-phenylenediamine, During these reactions the picchxn ligand remained stereospecific in its coordination to the central metal ion. Again the tetradentate in these complexes was shown to be susceptible to photo-oxidative dehydrogenation to form the monoimine. One such complex, Λ-β-[Ru(RR-picchxnmi)(phen)](ClO4)2.phen.3.5H2O was found to cocrystallise with an unbound phen molecule, and containing both phens in a stacking arrangement. These non-labile bidentates prevented covalent binding of the Ru(picchxn)2+ moiety to DNA.
Intercalation of the phen based complexes was concluded if their visible absorption spectra showed a red shift and hypochromicity when combined with DNA in aqueous solution, The complexes containing phen, dip, dppz or dppzMe2 are proposed to behave in this manner. The metal complex with the most potential for use as a chiral probe of DNA is thought to be β-[Ru(picchxnmi)-(dip)2+, with its Λ enantiomer showing a 95% preference when interacting with calf-thymus DNA. Lower preferences were determined for the racemic diamine and monoimine phen species although again their Λ enantiomers are preferred.
Vol 128 parts 3-4, p. 141 [1995] |
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Introductory Studies of Silica Fume Released as a By-product of Electrometallurgical Processes
An abstract from the thesis submitted to the University of Tasmania for the degree of Master of Environmental Studies, awarded May 1994.
Elizabeth A. Cunningham
The introductory studies of silica fume re1eased as a by-product of electrometallurgical processes which have been undertaken in this thesis included, as the central theme, a consideration of the morphological characterization of the fume particles. Using a Transmission Electron Microscope the count median diameter (CMD) was calculated to be 340A with a geometric standard deviation (σg) of 1.86. The characterization was somewhat limited in scope, in that the morphological assessment included primary particle size only not aggregate size.
On the basis of the characterization of the silica fume as an ultrafine aerosol, predictions of possible patterns of deposition in the human respiratory system were attempted. The predictions were. based on the findings of a literature review of the deposition of particles in the respiratory system, and attempted to reflect patterns of deposition to be expected in the general community.
The literature on the effects of silica fume inhalation on both animal and human respiratory systems was reviewed and included the results of a minor survey conducted in southern Tasmania on some aspects of respiratory health in the population living in two geographical areas of Tasmania, one of which was situated in the vicinity of a silicon smelter. The review was undertaken to provide a basis for an examination of the previous and current TLV recommendations for industry by the ACGIH. The current problems with regard to the monitoring of silica fume are discussed as well as the need for future studies in the industry.
Vol 128 parts 3-4, p. 142 [1995] |
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Light Scattering Studies of Microstructure in YBa2Cu3O7-x Superconductors.
John M. Long.
Raman spectroscopy and optical microscopy have proven to be useful techniques for the characterisation of YBa2Cu3O7-x and other ceramic superconductors. As the primary electrical properties of bulk YBa2Cu3O7-x superconductors are dependent on microstructure of the materials, an investigation was carried out to apply Raman spectroscopy and optical microscopy to the analysis of microstructure in polycrystalline YBa2Cu3O7-x. The two techniques have not previously been used closely together for microstructural analysis of YBa2Cu3O7-x. It was found that the two methods work well together. Raman spectroscopy provides much detailed information on individual grains of particular samples, and optical microscopy provides more overall, general information concerning a whole sample surface. MicroRaman techniques were far superior to conventional Raman techniques when applied to the analysis of YBa2Cu3O7-x.
Micro-Raman spectroscopy analysis was directly correlated with optical microscopy observations. Sample colours as observed through crossed polarisers were calibrated and correlated with primary sample properties such as oxygen stoichiometry and orientation of YBa2Cu3O7-x grains. The presence and distribution of impurities was determined by both Raman spectroscopy and optical microscopy.
Refinenents of Raman analysis techniques were also developed. A Raman spectral peak near 335 wavenumbers (cm-1) was found to have a systematic variation in asymmetry as a function of oxygen stoichiometry, 7–x. This variation was calibrated against the position of another Raman peak near 500 cm-1 whose position is sensitive to 7–x. YBa2Cu3O7-x grains can have an orientation such that in a Raman experiment, the peak near 500 cm-1 is weakly detected (or not at all), but that near 335 cm-1 is easily detected, and the asymmetry of this peak may give a measure of 7–x, an essential parameter in the preparation of YBa2Cu3O7-x as a superconductor. Two previously published mathematical equations used to describe peak asymmetry were examined, and one was selected as more convenient for routine analysis of YBa2Cu3O7-x samples. A ratio between the intensity of the peak near 335 cm-1 and the sum of the intensities of two other peaks near 440 and 500 cm-1 was established to partly quantify grain orientation,
The partial substitution of dysprosium for yttrium in some YBa2Cu3O7-x samples was also detected by micro-Raman spectroscopy as part of their microstructural analysis.
The effect on the spectra of strong laser irradiation was also investigated. Heating caused by the incident laser beam produced one or two extra Raman peaks from crystal defects between 550 and 650 cm-1, depending on the orientation of the grain under examination and its initial oxygen stoichiometry, The results are more or less consistent with previously published results of similar heating experiments.
The experiments were carried out in the context of a larger research programme on microstructural and electrical properties of polycrystalline YBa2Cu3O7-x. Some of the samples from this programme were examined. Some correlations were found between the microstructural properties and previously determined electrical properties.
Vol 128 parts 3-4, p. 143 [1995] |
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Thesis Abstract: Shock Wave / Boundary Layer Interaction at a Compression Corner in Hypervelocity Flows.
Samuel George Mallinson
Hypervelocity flow over compression corners with both sharp and blunt leading edges is examined. In particular, the effects of real gas behaviour on the shock wave / boundary layer interaction at the corner are investigated. The flat plate flow, which is the datum case, is also considered in detail.
The problem was studied both experimentally and theoretically, Experiments were conducted in a free-piston driven shock tunnel with reservoir enthalpies and free-stream speeds ranging up to 19 MJ kg-1 and 5.5 km s-1, respectively. Measurements were made of the surface pressure and heat transfer. Some flow visualization data were also obtained. The experimental data were compared with several theories that are strictly valid for perfect gas flows. The local flat plate similarity method was also extended to include real gas effects and used to predict flat plate and compression corner flow for three idealized conditions of practical importance.
Real gas effects on the sharp leading edge flat plate flow appeared to be small. For the blunt leading edge flat plate flows, the pressure and heat transfer were greater than for the sharp leading edge flows. These differences seemed less pronounced at high enthalpy. It is thought this may be due to the smaller shock stand-off that occurs for real gas flows.
The separation and plateau pressures, the upstream influence, the peak heating near reattachment and the incipient separation angle are important characteristics of compression corner flow, With leading edge sharp, the high and low enthalpy data for these characteristics compared well with each other and also with theories strictly valid for perfect gas flows. With leading edge blunt, the plateau pressure appeared to increase and the upstream influence and the pressure & heat transfer on the ramp face were seen to decrease relative to the sharp leading edge flows. The plateau pressure and upstream inffluence at high and low enthalpy seemed to compare well with each other. There were some discrepancies between the peak heating data for high and low enthalpy, which was perhaps due to transition to turbulence on the ramp face.
From the experimental data, the real gas effects on flat plate and compression corner flow do not seem significant. It was, however, still of interest to examine real gas effects on shock wave/boundary layer interaction. To do this, the local flat plate similarity theory for laminar hypersonic flows was extended to include real gas effects. The gas chemistry was based on the ideal dissociating gas rnodel. It was shown that the boundary layer displacement thickness is reduced for a real gas by an amount that depends upon the energy lost to endothermic processes in the boundary layer, This suggests the extent of separation, which varies with the displacement thickness, would be reduced by real gas effects. The theory predicted the real gas effects on the pressure and heat transfer for flat plate flow to be small, For the compression corner, the theory indicated lower levels of pressure and higher levels of heat transfer on the ramp face. The latter is attributed to the reduced boundary layer thickness for the real gas.
Vol 128 parts 3-4, p. 144 [1995] |
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Geological factors influencing erosion gullying in the Grenfell-Gooloogong area, mid western New South Wales.
Sara G. Beavis
An abstract of a thesis submitted to the University of New South Wales for the Degree of Doctor of Philosophy, 1992.
The Thesis is concerned with understanding the geological influences on gully erosion. Although it is accepted that a factorial complex, comprising parent material, climate, topography, land-use and drainage basin area, defines the system, the roles of geology has been assessed by selecting sites where other variables are constant.
Extensive field surveys and laboratory analyses have formed the basis for describing quantitatively the influence of geological structure on gully pattern, orientation and density. Furthermore, field evidence has indicated that groundwater discharge, in association with major faults and/or highly fractured parent material, is of major importance in the location of gully systems.
The different parent materials, having varying mineralogy, texture, fabric and degree of weathering, influence the soil's physical, chemical and engineering properties. Mechanisms of erosion are a dynamic expression of soil properties. This relationship, although it cannot be quantified, explains the observed phenomenon of the same process producing dissimilar rates of linear extension.
The study of mechanisms led to the development of equipment to measure directly water throughflow at gully headcuts. Results strongty suggest that throughflow is the most significant process of water movement at gully headcuts, effecting detachment of material from the headcut face. It has been shown, further, that the configuration of throughflow hydrographs is influenced by the clay mineralogy of the soil.
Soil properties influence the incidence and severity of erosion gullying. Multiple regression analyses have been utilised to define statistically the relationship between soil properties and rates of erosion. It is clear from this research that the relationship is complex, and that the various geological/soil factors are interactive and do not operate in isolation. Significantly, it has been found that the interaction between, and the controlling set of, variables causing erosion, are unique according to parent rock associations.
Multiple regression analyses have quantified further the variability of controlling sets of factors. When hydrological parameters are held constant, over 90% of the variance in the rate of linear extension of gullies is accounted for by soil properties. Even taking the hydrological factors into account, soil properties account for over 50% of the variance.
Vol 128 parts 3-4, p. 145-146 [1995] |
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Parameters Affecting S.I. Engine Knock
Petros Lappas
Abstract from the thesis submitted to the University of Melbourne for the degree of Master of Engineering Science, August 1995.
A high speed, single cylinder spark ignition engine with an optically accessible combustion chamber, was used to study the influence of various engine parameters on knock tendency. The test engine resulted from major modifications made on an existing engine situated in the thermodynamics laboratory of the Mechanical Engineering departrnent at the University of Melbourne. Knock was assumed in this study to be initiated by the spark plug as the ignition source ("Spark Knock"). The parameters influencing knock that were examined were inlet air temperature, coolant temperature, engine speed and combustion chamber shape. An irnproved understaoding of engine factors affecting knock, should lead to methods for its reduction. Knock reduction is crucial in developing spark ignition engines with higher compression ratios that offer greater thermal efficiencies.
The spark advance required to initiate knock was found to increase with engine speed. The spark advance increase was approximately 10 degrees for each 200 r/min increase in engine speed over the range tested. This is because, the time for which the end-gas is exposed to extremes of pressure and temperature during combustion, reduces with engine speed and lessens the chance of knock unless the spark is further advanced.
To avoid engine damage, incipient knock was produced corresponding to sudden acceleration of the flame traversing the fuel-air charge in the combustion chamber, Thus, the knock tendencies of two combustion chambers were compared. The first combustion chamber contained a "swirl vane" (close to the inlet valve) whilst this vane was removed for the other chamber. Numerical results including pressure and crank angle data for various knocking conditions that were obtained from the swirl vane combustion chamber, were manipulated and compared with theoretical expectations. Data manipulation entailed visual screening of important points of the "raw" data, and numerical filtering. The data was then processed by a "reduction" program to convert the filtered data into an acceptable form with SI units.
Combustion duration (in ms), which is a direct indication of the time for which the end-gas is exposed to extremes of pressure and temperature, was evaluated with the aid of computer code developed by the author to determine important information including mass fraction burnt history. The code was based on a combustion model that assumes separated regions of burnt and unburnt gas in the combustion chamber, The flame shapes observed in combustion photographs taken confirms this assumption, thus validating the model used.
Despite the well known phenomenon that knock tendency increases with inlet air temperature, there was no relationship detected between inlet air temperature and knock advance. This is because of the errors associated with the determination of the knock advance due to a) necessary haste whilst increasing the spark timing (until knock is initiated) because of imminent cylinder overheating and b) the non-proportional alteration of spark advance due to eccentricity in the advance screw mechanism. For similar reasons, the expected increase in knock sensitivity with cylinder head coolant temperature was not detected.
Even though all tests had a similar degree of knock, higher NOx levels were recorded in tests with higher engine speed and inlet air temperature, because of the higher pressures and temperatures reached in these conditions.
The observations from the swirl vaned combustion chamber did not conflict with established theory on the causes of spark knock. Combined with concepts expanded by the author, this knock theory (which is intimately connected to autoignition theory) was applied to combustion photographs for both combustion chambers to predict which one was the least likely to knock. Computer code was written to demonstrate the insignificance of heat transfer relative to burn-rate. On the basis that autoignition is highly dependent on burn-rate and less so on end-gas heat transfer, the combustion chamber without the swirl charnber was predicted as the one least likely to knock.