Showing papers by "University of Wollongong published in 1994"

Dietary fats, membrane phospholipids and obesity.

Abstract: Modifications in dietary fat profile have been shown to affect body weight gain and adiposity. This may occur through changes in the partitioning between oxidation and storage and/or alterations in membrane structure, which may in turn influence metabolic rate. All the dietary fat classes are substrates for the biosynthetic elongase and desaturase enzymes. Obesity is associated with increased delta 9 desaturase activity, reduced delta 5 desaturase activity and perhaps reduced delta 6 desaturase activity. Dietary lipid profile can affect the activity of each of these enzymes. A number of possible mechanisms linking dietary fat subtypes with development of obesity are discussed, including modification of sodium potassium pump activity and alterations in mitochondrial proton leakage.

Seasonal changes of the adrenocortical responses to stress in redpolls, Acanthis flammea, in Alaska

Abstract: Male and female redpolls (Acanthis flammea) showed marked increases in circulating corticosterone up to 1 hour after exposure to a common stress—capture, handling and restraint—indicating that their hypothalamo-pituitary-adrenal axis responded to acute stress in a manner similar to that of other vertebrates. We used this protocol as a measure of responsiveness of the adrenocortical cells to acute stress in general and for comparison with gender and across seasons. In both sexes the adrenocortical response to stress was reduced in January (at Fairbanks, 64°N) and maximal when birds were breeding in June at Toolik Lake (69°N). The elevation of circulating corticosterone following capture and handling in breeding males at Barrow (71°N) was significantly less than in breeding males at Toolik Lake. There were also considerable variations among individuals in the intensity of the adrenocortical responses, particularly in the maximum levels of corticosterone attained. This individual variation correlated significantly with fat score and/or body mass in both sexes only in breeding birds at Barrow. This difference may be explained by generally lower, and thus reduced variability in body fat and mass in birds sampled in the warmer climate of Toolik Lake. A similar trend was seen in non-breeding birds, but this was not significant. Additionally, in January, baseline cortisterone levels in males were correlated with body mass, although this relationship did not hold when both sexes were considered. Body mass and fat score in winter were similar to those of redpolls sampled at Barrow in June. These data suggest that redpolls may be able to adjust their responsiveness to acute stresses in relation to fat stores. Those with greater fat depots had reduced responsiveness to stress. © Wiley-Liss, Inc.

Evidence for restricted gene flow in the viviparous coral seriatopora hystrix on australia's great barrier reef.

Abstract: Viviparous, branching corals such as Seriatopora hystrix are expected to generate most recruits through asexual reproduction (fission or fragmentation) but are expected to use sexual reproduction to produce widely dispersed colonists. In this study, allozyme electrophoresis was used to test for variation in the relative contributions of sexual and asexual reproduction to recruitment and to assess the apparent scale of larval dispersal (gene flow) in the central Great Barrier Reef. Fifty-seven collections (within ≤ 25 m2 ) of fragments from sets of approximately 40 colonies were made (where possible) within each of five habitats on each of 12 reefs. These reefs, within the central region of the Great Barrier Reef, were separated by up to 90 km and included one inner-shelf continental island and groups of seven midshelf reefs and four outer-shelf reefs. Most collections contained a high level of multilocus genotypic diversity and hence showed little evidence of recruitment through fragmentation, although the majority of collections displayed large and consistent deficits of heterozygotes. Allele frequencies varied greatly among collections (FST = 0.43), and this variation was sufficient to explain two-thirds of observed deficiencies of heterozygotes via a Wahlund effect. A hierarchical assessment of FST values revealed that 45% of allelic variation occurred among reefs (FST = 0.20), and only 16% of variation within reefs was explained by variation among five major habitat types (FST = 0.05). A relatively small component of the total variation among samples was attributable to across-shelf variation among the groups of middle- and outer-shelf reefs (FST = 0.03); however, the outer-shelf reefs form a single UPGMA cluster separate from all but 4 of the other 43 collections. These data imply that widespread dispersal does occur but that the direction or magnitude of gene flow may be influenced by the along-shelf movement of major ocean currents and weather-dependent currents on or near reefs. Each reef, therefore, forms a partially isolated and highly subdivided population.

Flow transmission along an arid zone anastomosing river, cooper creek, australia

Abstract: Cooper Creek is characterized by an exceptionally wide floodplain and a complex system of anastomosing channels which together can accommodate a large range of highly variable flows. In consequence flood frequency curves are unusually steep. With minimal tributary contribution over the two study lengths - Currareva-Nappa Merrie (> 400 km) and Nappa Merrie-Innamincka (32 km) - downstream output is largely controlled by upstream input, so that similar flow regimes and hydrograph forms can be maintained despite transmission losses and the variable activation of channels. Input-output relationships defined in terms of total flow volume and peak discharge suggest that, above a threshold flow of about 25% duration, transmission losses exceed 75% on average over the Currareva-Nappa Merrie length. The large difference in absorption between primary channels on the one hand and subsidiary channels and the floodplain surface on the other means that transmission losses vary non-linearly with stage. They are relatively low when flow is confined to the primary channels, but increase at higher stages as lesser channels and the floodplain are activated. Early levels do not recur until flows of < 0.5% duration are attained when output/input ratios increase rapidly with discharge. The influences of seasonality and background flow on output discharge are small relative to that of input discharge. Despite the long river distance, peak flows at Currareva and Nappa Merrie are well correlated. However, over the shorter Nappa Merrie-Innamincka length with its more confined system of channels, correlations are better and transmission losses less. They vary from 60% just above the threshold discharge to

Using Path Transforms to Guide the Search for Findpath in 2D

Abstract: This article will present a new approach to the 2D findpath problem for robots that have three degrees of freedom of move ment (3 DOF) This approach is based on a new extension to distance transform planning called the path transform Path transforms have the desirable potential field property of taking into account clearance from obstacles without suffering the problem of local minima Because path transforms guide the search for a 3-DOF path where solution paths are likely to lie, the computational burden of the new approach is low compared with that in previously reported results The low computational burden is also due to efficient collision detection A new hier archical collision checking based on distance space bubbles is presented The new approach to findpath is guaranteed to find a solution path if it exists Computer simulation results of solving the findpath problem in nontrivial environments are presented

Virtual Reality in Education: Defining Researchable Issues

Abstract: Ever since technologies began offering something to learners and the process of learning, we have been besieged by proponents who claim wonderful advantages for each new technology, praising the superiority of each new form over its precursors. In this environment virtual reality (VR) might be seen as the latest white knight in the arsenal of educational technologies. In this paper, we have sought to reflect on what we want to achieve as educational outcomes and the efficacy of VR for the design of modern learning environments. We have also sought to link current beliefs about learning with the need to experience a world in which the pedagogical assumptions can be embedded into the objects, contexts and relationships from which the user might derive further complex concepts.

Measurements of trace gases emitted by Australian savanna fires during the 1990 dry season

Abstract: During 18–23 July 1990, 31 smoke samples were collected from an aircraft flying at low altitudes through the plumes of tropical savanna fires in the Northern Territory, Australia. The excess (above background) mixing ratios of 17 different trace gases including CO2, CO, CH4, several non-methane hydrocarbons (NMHC), CH3CHO, NO x (− NO + NO2), NH3, N2O, HCN and total unspeciated NMHC and sulphur were measured. Emissionratios relative to excess CO2 and CO, and emissionfactors relative to the fuel carbon, nitrogen or sulphur content are determined for each measured species. The emission ratios and factors determined here for carbon-based gases, NO x , and N2O are in good agreement with those reported from other biomass burning studies. The ammonia data represent the first such measurements from savanna fires, and indicate that NH3 emissions are more than half the strength of NO x emissions. The emissions of NO x , NH3, N2O and HCN together represent only 27% of the volatilised fuel N, and are primarily NO x (16%) and NH3 (9%). Similarly, only 56% of the volatilised fuel S is accounted for by our measurements of total unspeciated sulphur.

Experimental measurements of river‐bank erosion caused by boat‐generated waves on the gordon river, Tasmania

Abstract: Erosion of natural river banks by boat-generated waves is an increasingly serious problem on the navigable reaches of many rivers, particularly on the middle and estuarine reaches. An experiment designed to link bank erosion rates with easily measured wave characteristics, conducted on the scenic lower Gordon River in Tasmania, provides information useful for river management. Within a boat-generated wave train a number of characteristics were measured and most showed a high correlation with measured rates of bank retreat. Maximum wave height within the train is the simplest measure and is associated with a major threshold in erosive energy on unconsolidated sandy alluvium at wave heights of 30 to 35 cm. At maximum wave heights above 35 cm all but the most resistant bank sediments erode. Reducing maximum wave heights to < 30 cm by limiting boat speeds, and reducing the frequency of boat passages, caused a dramatic decline in bank erosion along the river.

Communication skills in accounting education: perceptions of academics, employers and graduate accountants

Abstract: Communication skills are central to intellectual interaction between the providers and the recipients of information. The importance of accounting starts with the gathering and processing of information and ends with the communication of processed information. This paper examines the communication skills which employers, academics and graduate accountants consider necessary to the newly graduated accountant. It also identifies and considers the differences in perception which occur between these groups and suggests solutions to the communication gap. This study confirms findings from previous research that new graduate accountants experience communication-related problems in early employment. In addition, it provides evidence that the Australian accounting curriculum has contributed to the development of communication skills. However, the paper highlights the need for the reconsideration of an emphasis on communication skills in the accounting curriculum, a role which arises from the very nature of accoun...

Effect of aerobic and strength training on pain tolerance, pain appraisal and mood of unfit males as a function of pain location

Abstract: The purpose of this study was to examine the effect of aerobic and strength conditioning on pain tolerance, pain appraisal and mood as a function of upper and lower limb pain location. Unfit males (n=48) were randomly assigned to one of four groups: aerobic training, strength training, combined aerobic and strength training, and a ‘no training’ (control) group. The fitness regimens consisted of exercising at least three times per week for 12 weeks. Pain tolerance and appraisal and mood were ascertained before the treatment (baseline), and after 6 and 12 weeks. Statistical analyses using MANOVA indicated that the presence of aerobic training increased upper limb pain tolerance but was also linked to a more severe pain appraisal compared with the absence of aerobic training. Aerobic work also improved vigour while decreasing fatigue, tension and depression. Strength training had no influence on pain tolerance and positive mood states, but increased depression. Lower limb pain tolerance was unaffected by the...

Landscape - a usefully ambiguous concept

Abstract: L'ambiguite du concept de paysage permet de reduire le fosse qui normalement existe entre plusieurs disciplines. Le fil qui lie geographie, archeologie et anthropologie autour du theme du paysage est la notion d'histoire. Le concept de paysage s'etend de la forme physique et des proprietes de la terre a l'utilisation humaine et aux conceptions de cette terre

Intergranular and intragranular critical currents in silver-sheathed Pb-Bi-Sr-Ca-Cu-O tapes.

Abstract: The role of the intergranular and intragranular critical current densities in silver-sheathed Pb-Bi-Sr-Ca-Cu-O tapes is investigated by means of magnetic-moment measurements in perpendicular field at different temperatures using a superconducting quantum interference device magnetometer. We find that low-field magnetic-moment loops are mainly caused by the intergranular (transport) critical current density ${\mathit{J}}_{\mathit{c}}^{\mathit{J}}$ but that in high fields the contribution from the intragranular critical current density ${\mathit{J}}_{\mathit{c}}^{\mathit{G}}$ becomes significant. The low-field data can be described well in terms of a critical-state model for a thin strip of a homogeneous type-II superconductor in a perpendicular field where ${\mathit{J}}_{\mathit{c}}^{\mathit{J}}$ flows over the entire tape. The high-field data require in addition a description in terms of a critical-state model for the grains where ${\mathit{J}}_{\mathit{c}}^{\mathit{G}}$ circulates in each grain. Strong mechanical bending of the tape causes ${\mathit{J}}_{\mathit{c}}^{\mathit{J}}$ to disappear while ${\mathit{J}}_{\mathit{c}}^{\mathit{G}}$ is unaffected. The experimental data reveal the hysteretic nature of ${\mathit{J}}_{\mathit{c}}^{\mathit{J}}$ which is caused by the trapping of flux in grains. In all the tapes measured, ${\mathit{J}}_{\mathit{c}}^{\mathit{J}}$ is found to be much smaller than ${\mathit{J}}_{\mathit{c}}^{\mathit{G}}$. Comparing the remanent ${\mathit{J}}_{\mathit{c}}^{\mathit{J}}$ with ${\mathit{J}}_{\mathit{c}}^{\mathit{G}}$ in different tapes, we find that strong pinning in grains does not imply a high remanent intergranular critical current density.

Solving linear diffusion equations with the dual reciprocity method in Laplace space

Abstract: The dual reciprocity method (DRM) is applied in the Laplace space to solve efficiently time-dependent diffusion problems. Since there is no discretation in time and there are no domain integrals involved in a calculation, the proposed approach seems to have provided considerable savings on computer operating costs and in data preparation, and thus leads to certain advantages over existing methods. Three numerical examples are presented, which demonstrate well the efficiency and accuracy of the new approach.

A structural analysis of external debt and economic growth: some evidence from selected countries in Asia and the Pacific

Abstract: In an attempt to resolve the existing controversy about the cause and effect relationship between external dept and economic slowdown, Granger causality tests are conducted with data on indebted developing countries of Asia and Pacific. The results of these tests indicate that the Bulow–Rogoff proposition that the external debts of developing countries are a symptom rather than a cause of economic slowdown is rejected. They also indicate that the Dornbush–Krugman proposition that external dept leads to economic slowdown is also rejected. Moreover, a feedback-type relationship is not rejected for two countries. In view of the mixed results, this paper also estimates the nexus of inter-relationship between public and private external dept accumulation, capital accumulation and production within a simultaneous equation system. The estimation results indicate that the full effects of the public and private external depts on GNP are small and of an opposite sign, whereas an increase in the GNP level raises sub...

The word-length effect in probed and serial recall

Abstract: The word-length effect in immediate serial recall has been explained as the possible consequence of rehearsal processes or of output processes. In the first experiment adult subjects heard lists of five long or short words while engaging in articulatory suppression during presentation. Full serial recall or probed recall for a single item followed the list either immediately or after a 5-second delay to encourage rehearsal. The word-length effect was not influenced by recall delay, but was much smaller in probed than in serial recall. Examination of the serial position curves suggested that this might be due to a recency component operating in probed recall. Experiment 2 confirmed a word-length-insensitive recency effect in probed recall and showed that this was resistant to an auditory suffix, unlike the small recency effect found in serial recall. Experiment 3 used visual presentation without concurrent articulation. Under these conditions there was no recency effect for either recall method, but the wo...

Nonlinearly balanced Boolean functions and their propagation characteristics

Abstract: Three of the most important criteria for cryptographically strong Boolean functions are the balancedness, the nonlinearity and the propagation criterion. This paper studies systematic methods for constructing Boolean functions satisfying some or all of the three criteria. We show that concatenating, splitting, modifying and multiplying sequences can yield balanced Boolean functions with a very high nonlinearity. In particular, we show that balanced Boolean functions obtained by modifying and multiplying sequences achieve a nonlinearity higher than that attainable by any previously known construction method. We also present methods for constructing highly nonlinear balanced Boolean functions satisfying the propagation criterion with respect to all but one or three vectors. A technique is developed to transform the vectors where the propagation criterion is not satisfied in such a way that the functions constructed satisfy the propagation criterion of high degree while preserving the balancedness and nonlinearity of the functions. The algebraic degrees of functions constructed are also discussed, together with examples illustrating the various constructions.

Method and apparatus for pulsed electrochemical detection using polymer electroactive electrodes

Abstract: In a first embodiment, a target analyte in solution is detected by exposing the solution to an electrode that includes a conducting electroactive polymer to which a periodic alternating voltage is coupled. Upon exposure to the analyte, an electrode characteristic is varied, which variation is detected by measuring electrode current as a function of time and as a function of the periodic alternating voltage. The alternating voltage waveform has an oxidizing time period and a reduction time period, which periods and waveform duty cycle may be controlled to enhance electrode sensitivity, selectivity, and to substantially eliminate electrode fouling and data hysteresis. In a second embodiment, a receptor is bound to the electrode, to which is coupled an alternating voltage waveform that permits a mating target substance to reversibly bind to the receptor such that measurement of electrode current provides a measure of such reversible binding. The second embodiment is especially useful for detecting antibodies, antigens, haptens, DNA, RNA, and enzymes. Either embodiment may be used for detection in flow-through electrochemical cells, flow injection analysis, liquid, and ion chromatography, as well as in capillary electrophoresis.

On constructions and nonlinearity of correlation immune functions

Abstract: A Boolean function is said to be correlation immune if its output leaks no information about its input values. Such functions have many applications in computer security practices including the construction of key stream generators from a set of shift registers. Finding methods for easy construction of correlation immune functions has been an active research area since the introduction of the notion by Siegenthaler. In this paper we study balanced correlation immune functions using the theory of Hadamard matrices. First we present a simple method for directly constructing balanced correlation immune functions of any order. Then we prove that our method generates exactly the same set of functions as that obtained using a method by Camion, Carlet, Charpin and Sendrier. Advantages of our method over Camion et al's include (1) it allows us to calculate the nonlinearity, which is a crucial criterion for cryptographically strong functions, of the functions obtained, and (2) it enables us to discuss the propagation characteristics of the functions. Two examples are given to illustrate our construction method. Finally, we investigate methods for obtaining new correlation immune functions from known correlation immune functions. These methods provide us with a new avenue towards understanding correlation immune functions.

Plunge pools and paleoprecipitation

Abstract: Sedimentary sequences in the form of ridges or terraces surrounding plunge pools at the base of waterfalls can provide records of past discharge and as a consequence an indirect measure of rainfall variations over many thousands of years. Waves generated by the waterfall deposit sands and pebbles as a beach at the perimeter of the plunge pool. As climatic conditions change, plunge pools expand and contract, leaving these beaches as relic sedimentary deposits. The first sedimentary sequence of this kind to be analyzed for records of Quaternary climate changes is in Kakadu National Park, Northern Territory, Australia. Temporally, this record correlates closely with other paleoclimate proxies on both the Australian and African continents as well as the Indian subcontinent. The stratigraphic data indicate that this part of northern Australia was much wetter during the early to mid-Holocene (∼10-5 ka) and also during the last glacial maximum (∼22-18 ka). These pluvial periods are attributed to a strengthening of the northwest monsoon despite a considerably lower sea level during the last glacial maximum.

The role of technology in sustainable development

Abstract: The inability of governments represented at the 1992 Earth Summit to reach a consensus on reducing either population growth or consumption, and the political need for the concept of sustainable development to accommodate economic growth, mean that the achievement of sustainable development will depend on our ability to reduce the environmental impact of resource use through technological change. This will require the redesign of our technological systems and not merely the application of technological fixes that are seldom satisfactory in the long term. Past attempts by the appropriate technology movement to affect such a redesign neglected the social dimensions of technological change. Modern advocates of sustainable development will similarly fail unless they recognize the need for fundamental social change and a shift in priorities. >