Showing papers by "University of Wollongong published in 1990"

Thermoluminescence dating of a 50,000-year-old human occupation site in northern Australia

Abstract: THE oldest secure date for human occupation in Greater Australia is 40kyr from eastern Papua New Guinea1, whereas slightly younger dates have been reported from southern Australia2. We now report thermoluminescence (TL) dates that suggest the arrival of people between 50 and 60 kyr in northern Australia. TL dates were obtained from sandy footslope deposits at two former occupation sites that yielded a range of stone artefacts in their primary depositional setting. Artefacts terminated mid-way down one profile, which had a basal age of about 100 kyr. Confidence in the TL dates is given by their close correspondence with radiocarbon dates obtained from the upper occupation levels. These TL dates are not only the oldest yet proposed for Aboriginal occupation but also may mark the time of initial human arrival on the Australian continent.

The impact of sea-level rise on mangrove shorelines:

Abstract: There are extensive mangrove forests along the tropical shorelines of the world; they are particularly well developed in, though not exclusively restricted to, areas that are sheltered and muddy. Stratigraphic studies of the sediments underlying both the mangrove forests themselves and associated wetlands indicate that there have been considerable changes in the extent of these wetlands as a result of past sea-level fluctuations. Further changes in the area covered by mangroves are to expected if the sea rises at the rates anticipated as a result of the greenhouse effect. The exact response of a mangrove coastline will depend upon shoreline topography, sources of sediment, rates of sediment supply, and the rate of sealevel rise. The stratigraphy and chronology of Holocene deposits on mangrove shorelines allow reconstruction of the way that mangrove forests have responded

Low-frequency filtering and the processing of local-global stimuli.

Abstract: The role of low-spatial-frequency information in the processing of global stimuli made up of local elements was examined. After selective removal of low spatial frequencies two major changes occurred in the pattern of results. First, response times to global stimuli were significantly slower and the usual speed advantage of global over local processing was lost. Second, when processing local features the usual decrease in response speed when the local and global letters are not the same (consistency effect) was not obtained. These effects could not be explained by changes in error rate, by contrast variation resulting from the process of filtering, or by loss of visual sensitivity due to greater eccentricity of global images.

Gradient-based adaptive IIR notch filtering for frequency estimation

Abstract: The use of gradient-based algorithms with infinite impulse response (IIR) notch filtering for estimating sinusoids imbedded in noise is investigated. Two notch filter model structures are presented. The first is for applications where two signal sources with correlated noise components can be assessed. The second can be used in situations where only one composite signal source is available. Error surface analysis indicates that second-order modules are unimodal and result in guaranteed convergence. Higher-order modules are multimodal and require judicious choice of initial parameter estimates. Simulation results are included to demonstrate the performance characteristics of both filter structures. >

Attitudes towards corporate social responsibility and perceived importance of social responsibility information characteristics in a decision context

Abstract: This study addressed the questions of perceived importance of social responsibility information (SRI) characteristics in a decision context, as well as the attitudes of institutional investors toward social responsibility involvement. The results showed that SRI presently disclosed in company annual reports did not have any significant impact on institutional investors' decisions. However, if SRI were presented in quantified, financial form, and were focused on product improvement and fair business practices, such information would be perceived as more important for investment decisions. Attitudes toward corporate social responsibility also suggested that institutional investors were not totally opposed to company involvement in social activities.

Captives of Controversy: The Myth of the Neutral Social Researcher in Contemporary Scientific Controversies:

Abstract: According to both traditional positivist approaches and also to the sociology of scientific knowledge, social analysts should not themselves become involved in the controversies they are investigating. But the experiences of the authors in studying contemporary scientific controversies—specifically, over the Australian Animal Health Laboratory, fluoridation, and vitamin C and cancer—show that analysts, whatever their intentions, cannot avoid being drawn into the fray. The field of controversy studies needs to address the implications of this process for both theory and practice.

The extended korteweg-de vries equation and the resonant flow of a fluid over topography

Abstract: The extended Korteweg-de Vries equation which includes nonlinear and dispersive terms cubic in the wave amplitude is derived from the water-wave equations and the Lagrangian for the water-wave equations. For the special case in which only the higher-order nonlinear term is retained, the extended Korteweg-de Vries equation is transformed into the Korteweg-de Vries equation. Modulation equations for this equation are then derived from the modulation equations for the Korteweg-de Vries equation and the undular bore solution of the extended Korteweg-de Vries equation is found as a simple wave solution of these modulation equations. The modulation equations are also used to extend the solution for the resonant flow of a fluid over topography. This resonant flow occurs when, in the weakly nonlinear, long-wave limit, the basic flow speed is close to a linear long-wave phase speed for one of the long-wave modes. In addition to the effect of higher-order terms, the effect of boundary-layer viscosity is also considered. These solutions (with and without viscosity) are compared with recent experimental and numerical results.

Microatolls and recent sea level change on coral atolls

Abstract: MICROATOLLS are colonies of corals, commonly Porties, which are dead on top but living around their perimeter, and are found in intertidal environments on coral atolls. They can grow to several metres in diameter. Their upward growth is constrained by sea level through prolonged exposure at the lowest spring tides1,2, and their dead upper surfaces have been limited by past sea levels. They act as natural recorders of sea level, which is of particular significance for coral atolls thought to be susceptible to inundation and erosion if sea level rises in response to global warming. X-radiographs of vertical slices through microatolls from the Maldives and Cocos (Keeling) Islands (Indian Ocean) and Kiribati (Pacific Ocean) record sea-level fluctuations over the past few decades. There is a high degree of reproducibility between adjacent corals, although on Cocos we noted geographical variation in the pattern of change around the atoll. The majority of microatolls sampled on these atolls record a slight fall in sea level over the past ten years.

Frequency domain analysis of power system forced oscillations

Abstract: A frequency domain approach is used to analyse power system forced low frequency oscillations. The gain characteristics of a closed loop transfer function, Gd(s)= Δδ/ΔPd, which reflects the effect of disturbances on power angle oscillations, are shown to be crucial in identifying the frequency ranges in which amplified oscillatory disturbances can occur. It is shown that tuning power system stabilisers (PSS), based on eigenvalue analysis, lack the insight gained from the explicit evaluation of the Gd(s) gain response. The proposed approach identifies a risky situation which could not be detected on an eigenvalue pattern. For weakly connected systems, the inherent negative damping effects, along with the PSS derivative feedback action, result in a situation where a PSS, tuned to locate the eigenvalues corresponding to the natural mode ωn at well damped locations, can still cause a hazardous situation. While flattening the |Gd(jω)| peak at ωn, the derivative supplementary excitation feedback loops can create another peak which may match oscillatory tie-line disturbances, thereby causing amplified oscillations. The paper also proposes a dynamic gain reduction scheme which can overcome this situation by decoupling the negative damping effects while accentuating the stabilising effects of the PSS derivative feedback. It is shown that a considerable reduction in the tie-line mode oscillations can be achieved. Generalisation to multimachine networks is straightforward. An Appendix is included to describe a systematic derivation of a polynomial matrix that evaluates disturbance rejection/attenuation functions in a general multi-machine environment.

Thermoluminescence dating of late Quaternary dune sand, Manawatu/Horowhenua area, New Zealand: A comparison with 14C age determinations

Abstract: Samples of dune sand from two previously described sections in the southwestern North Island have been dated by the thermoluminescence method. At the first site, Koputaroa Phase dune sand immediately underlying Aokautere Ash ( = Oruanui Ash 14C dated at c. 22 590 yr B.P.) was dated at 24 200 ± 3700 yr. At the second site, Holocene dune sand was dated at 3000 ± 500 yr. Factors influencing the error limits of the thermoluminescence dates are discussed. The results confirm that coastal dunes were migrating inland during the last stadial of the Otira Glaciation and indicate that the thermoluminescence method could usefully be applied in the dating of upper Quaternary deposits in this region.

Cholera toxin B‐gold, a retrograde tracer that can be used in light and electron microscopic immunocytochemical studies

Abstract: The purpose of this study was to test whether a new retrograde tracer, the B subunit of cholera toxin conjugated to colloidal gold particles (CTB-gold), was taken up and transported by neurons in the central nervous system of the rat Retrograde transport of CTB-gold was assessed from axon terminals, from damaged nerve fibers, and from axons of passage For light microscopy, CTB-gold was visualized by silver intensification; for electron microscopy, sections were silver-intensified with or without subsequent gold toning Retrogradely transported CTB-gold was detected in neurons after survival times of 12 hours to 42 days and appeared as black punctate deposits in perikarya and proximal dendrites at the light microscope level Ultrastructurally, the deposits were usually associated with lysosomes Injections of CTB-gold into the caudal ventrolateral medulla or into the lateral horn of the spinal cord gave small well-defined injection sites and resulted in retrograde labelling in medullary neurons in the same locations as similarly placed injections of wheat germ agglutinin-horseradish peroxidase When injected into the superior cervical ganglion, CTB-gold was transported to nerve cell bodies in the spinal cord, but application of CTB-gold to the cut cervical sympathetic trunk did not label neurons in the spinal cord Injection of CTB-gold into the nodose ganglion retrogradely labelled neurons in the dorsal motor nucleus of the vagus and the nucleus ambiguus CTB-gold was not transported anterogradely from injections sites within the medulla Nerve fibers and cell bodies containing neuropeptides, monoamines, or neurotransmitter-synthesizing enzymes were readily immunostained after silver intensification of retrogradely transported CTB-gold Immunoreactivity for neuropeptides and enzymes was also demonstrated ultrastructurally after silver intensification and gold toning These results show that CTB-gold is retrogradely transported from nerve terminals and fibers of passage but not from damaged axons CTB-gold gives well-localized injection sites and persists in neurons for weeks Transported CTB-gold is easily visualized and its detection is compatible with light and electron microscopic immunocytochemistry These properties make CTB-gold a valuable tool for studying the connectivity and neurochemistry of pathways in the central nervous system

Biomechanical factors affecting performance in netball. Implications for improving performance and injury reduction.

Abstract: Despite netball having one of the largest number of participants of any team game within the Commonwealth there has been limited research conducted which biomechanically analysed skills of the game. However, information presented from biomechanical analyses of skills can provide coaches with the necessary theoretical basis to teach netball fundamentals to junior players. Biomechanical information can also be used to refine the existing techniques of experienced netball players so they may achieve optimal technical performance of game skills while minimising the potential for injury.

The kinetics of rugby union scrummaging.

Abstract: Two rugby union forward packs of differing ability levels were examined during scrummaging against an instrumented scrum machine. By systematically moving the front‐row of the scrum along the scrum machine, kinetic data on each front‐row forward could be obtained under all test conditions. Each forward pack was tested under the following scrummaging combinations: front‐row only; front‐row plus second‐row; full scrum minus side‐row, and full scrum. Data obtained from each scrum included the three orthogonal components of force at engagement and the sustained force applied by each front‐row player. An estimate of sub‐unit contributions was made by subtracting the total forward force on all three front‐row players from the total for the complete scrum. Results indicated the primary role of the second‐row appeared to be application of forward force. The back‐row ('number eight') forward did not substantially contribute any additional forward force, and added only slightly to the lateral and vertical ...

The foraging behaviour of a nectar feeding marsupial, Petaurus australis.

Abstract: The foraging behaviour of non-flying nectar feeding mammals has been examined rarely. The exudivorous yellow-bellied glider (Petaurus australis) was observed to feed extensively (70% of the total feeding observation time) on the nectar of all species of Eucalyptus present at a site in southeastern Australia. Gliders harvested nectar, and presumably pollen also, whenever eucalypt flowers were available and selected trees with 2–3 times as many flowers as that on trees randomly selected along a transect. The abundance of flowering trees varied temporally and, at times when few flowering trees were present, gliders chose trees with fewer flowers than at times when flowering trees were abundant. When flowering trees were superabundant or scarce, there was no relationship between the number of flowers in a tree and the duration of visits by gliders. However, at intermediate levels of abundance, the amount of time a glider spent in a tree was related to the number of flowers in a tree. Gliders devoted 90% of the time outside their dens to foraging and the above relationship is suggested to reflect two foraging options which maximize net energy gain for different abundances of flowering trees. Although gliders spent considerable lengths of time in individual trees feeding, initial deposition of cross pollen when gliders first arrive in a tree may be substantial and thus, may provide significant amounts of outcrossing for these eucalypts.

EHD Enhancement of Nucleate Boiling

Abstract: This paper describes: (a) an experimental investigation into the effect of an electric field applied to pool boiling of Freon (R114) on a finned tube and (b) a theoretical model of electrically enhanced nucleate boiling applicable to simple surfaces only. Experimental results have shown electrohydrodynamic (EHD) enhancement of heat transfer to be manifest in two ways: (1) elimination of boiling hysteresis, (2) augmentation of nulceate boiling heat transfer coefficients by up to an order of magnitude. These effects were also observed in electrically enhanced boiling of Freon/oil mixtures. A new analytical model is described whereby EHD nucleate boiling data from previous studies (employing simple apparatus comprising heated wires with concentric cylinder electrodes) have been correlated for the first time using the concept of an electrical influence number. This dimensionless parameter is based upon the relationship between applied electric field intensity and changes in bubble departure diameter at a heat transfer surface.

Calcium-induced opacification and proteolysis in the intact rat lens.

Abstract: When intact rat lenses were incubated in artificial aqueous humor in the presence of 1 mM calcium and a sulfhydryl reagent p-chloromercuriphenyl sulfonate (pCMPS) a visible annular opacity developed within 4 hours. Combined photographic and ion-sensitive microelectrode investigations of the lenses demonstrated that the subsequent linear increase in opacification was accompanied by an increase in internal free calcium. Opacities were not observed in lenses incubated in the absence of either pCMPS or calcium. Gel electrophoresis of the soluble and urea-soluble fractions from lenses exposed to 1 mM calcium for periods of up to 14 hours showed no evidence for crystallin degradation and only minor proteolysis of cytoskeletal proteins. When lenses were incubated under identical conditions, but with 5 mM calcium, the degree of opacification increased up to approximately 8 hours and then remained constant. A progressive loss in cytoskeletal proteins was observed which correlated with a further increase in free calcium such that by 14 hours of incubation, when the internal calcium approached 1 mM, most of the spectrin and vimentin present in the cortex of the lens had disappeared. An unidentified 110-kilodalton protein also disappeared from lenses incubated in 5 mM calcium. These results indicate that proteolysis by calcium-dependent enzymes such as calpain may play a significant role in cytoskeletal regulation and metabolism in the lens. A role for cytoskeleton/membrane/crystallin interaction in calcium-induced opacification is discussed.

Reluctance motor with strong rotor anisotropy

Abstract: A new rotor design for the synchronous reluctance motor is presented. It has something in common with the segmented and axially laminated rotors that have been developed in the past. The new rotor achieves strong anisotropy by interleaving magnetic iron lamination with nonmagnetic spacers of approximately equal thickness. It is shown that the magnetizing inductance is very much lower in the quadrature than the direct axis and that this rotor has the potential to develop more torque than earlier machines. Laboratory results are presented, and the machine is compared with an induction motor in the same frame. >

A friction effect in low-load hardness testing of copper and aluminium

Abstract: Vickers hardness tests were conducted on samples of copper and aluminium in a cold rolled or annealed condition to determine the apparent hardness variation in the load range 15 g to 20 kg. The variation was greatest for the soft specimens. Lubrication with an extreme-pressure lubricant was effective in reducing the hardness values to a virtually constant level for each metal. It is therefore reaffirmed that the hardness variation is attributable to friction and that strain hardening propensity is important in governing the magnitude of the variation. Comparison of these findings with data previously reported for similar tests on iron suggests that the phenomenon is probably an indentation size effect.

The Share Investment Decision Process and Information Use: An Exploratory Case Study

Abstract: This paper describes the use of accounting and other information in the share investment decision process of an institutional investor. The study was conducted within the context of an organisation's everyday working environment. The focus was on qualitative data and analysis of a case study rather than on quantitative data and general tendency analysis of a random sample. It is concluded that the significance of the annual report as an information source changes over the period of one year. It varies from serving as a primary information source to serving in a confirmatory role. Furthermore, the annual report also acts as a stimulus for identifying specific questions rather than merely as a source of information in response to prior questions.

Holocene emergence in the Cook Islands, South Pacific

Abstract: There is evidence of Holocene emergence on several of the Cook Islands. On Suwarrow Atoll there are extensive outcrops of emergent, but truncated, reef on the northern atoll rim, radiocarbon-dated 4680–4310 years B. P., overlain by younger cemented boulder conglomerates. On the northeast of the atoll there are fossil algal ridges indicating up to 1 m of emergence; the landwardmost has been dated 4220 years B. P., the intermediate one 3420 years B. P. and the present one 1250 years B. P. On Mitiaro, a makatea island in the Southern Cooks, there are emergent reefal deposits in the centre of the reef flat dated 5140–3620 years B. P. Similar thought poorly preserved deposits occur on Mauke, and an erosional bench and notch occurs on Atiu. Emergence on all islands appears synchronous with that reported on Mangaia, where a relative fall of sea level of at least 1.7 m in the last 3400 years has been reported. The evidence for emergence is broadly similar to that described from French Polynesia, though timing of emergence appears to differ.

Sea level and coral atolls: Late Holocene emergence in the Indian Ocean

Abstract: The Cocos (Keeling) Islands in the eastern Indian Ocean were visited by Charles Darwin, who described geomorphological evidence that he considered supported his subsidence theory of coral-reef development. However, several other accounts of the reef islands have questioned Darwin9s interpretation, and have suggested that a conglomerate platform that underlies most of the reef islands may indicate recent emergence of the atoll. Radiocarbon ages on corals from this conglomerate platform, reported here, indicate that it formed in the late Holocene. Fossil in situ microatolls above present upper coral growth limits, the elevation of associated beachrock, and the morphological similarity of the conglomerate platform to the present reef-flat deposits indicate a late Holocene sea level above the present relative to the atoll. The atoll has undergone at least 0.5 m of emergence since about 3000 yr B.P. This represents the first radiometrically dated evidence of Holocene emergence from islands in the eastern or central Indian Ocean.

Thermoluminescenge and Uranium‐Thorium chronologies of pleistocene coastal landforms of the Illawarra region, New South Wales

Abstract: SUMMARY TL determinations of the ages of aeolian sands and U/Th determinations of the ages of crusts on rock platforms in the Illawarra region, especially at Red Point, indicate that these techniques give considerable promise of a major advance in deciphering the Pleistocene coastal record in Australia. The methods of dating are outlined, and problems of laboratory and field interpretation are considered. The longstanding debate as to whether the +2 m level of platforms is modern or is a Pleistocene relict has been resolved for the Illawarra coast, where these platforms can be shown to have been formed during the Last Interglacial high stand of the sea. By inference, the +4 m level must be of at least the same age. The +6 to 7 m level was cut by about 300Ka and may be as old as Pliocene. Four aeolian units at Red Point reworked from nearby barrier beach complexes date from c. 25Ka, 45Ka, 125Ka, and 300 to >400Ka. Reconnaissance surveys and dating indicate that aeolian sands of similar ages occur elsewhere...

NMR identification of a partial helical conformation for bombesin in solution.

Abstract: The conformation of bombesin in trifluoroethanol/water mixtures has been studied using 1H-NMR spectroscopy. By a combination of two-dimensional 1H-NMR techniques and measurement of vicinal NH-α-CH spin-spin coupling constants, the secondary structure of the molecule has been determined. Bombesin adopts a helical structure in the region from Asn-6 to Met-14 with the remaining N-terminal portion existing as a more extended structure. The structure is very similar to that proposed from Fourier-transform infrared spectroscopic measurements for bombesin inserted into lipid bilayers [D. Erne & R. Schwyzer (1987) Biochemistry 26, 6316–6319]. The absence of a hydrogen bond between the sidechains of Trp-8 and His-12 is discussed in terms of the ionization state of His-12. Stabilisation of the helix results when His-12 is in the ionized state.

Similarity solutions for nonlinear diffusion — further exact solutions

Abstract: Although the nonlinear diffusion equation has been extensively studied and there exists substantial literature in many diverse areas of science and technology, the number of exact concentration profiles is nevertheless limited. In a recent article in this journal (Hill [1]) a brief review of known exact results is given, as well as an elementary integration procedure which appears to be a general device for obtaining integrals associated with similarity solutions. This paper extends the results given in [1] and for particular power law diffusivitiescm (such asm = −/12, −1, −/32 and −2) presents a number of new exact solutions obtained by fully integrating the ordinary differential equations derived in [1]. In addition new results are found for a general nonlinear diffusion equation which includes one-dimensional diffusion with an inhomogenouus and nonlinear diffusivitycmxmas well as symmetric nonlinear diffusion in cylinders and spheres. Moreover by a separate and ad-hoc procedure a new solution is obtained of the travelling wave type but with a variable wave speed. Some of the new exact solutions obtained for one-dimensional nonlinear diffusion with power law diffusivitiescmare illustrated graphically.