Showing papers by "University of Western Australia published in 1980"
TL;DR: In this article, the authors considered the problem of transient natural convection in a cavity of aspect ratio A [les ] 1 with differentially heated end walls and used scale analysis to show that a number of initial flow types are possible, collapsing ultimately onto two basic types of steady flow, determined by the relative value of the non-dimensional parameters describing the flow.
Abstract: The problem of transient natural convection in a cavity of aspect ratio A [les ] 1 with differentially heated end walls is considered. Scale analysis is used to show that a number of initial flow types are possible, collapsing ultimately onto two basic types of steady flow, determined by the relative value of the non-dimensional parameters describing the flow. A number of numerical solutions which encompass both flow types are obtained, and their relationship to the scale analysis is discussed.
532 citations
TL;DR: Stromatolites are the least controversial evidence of early life; they are organosedimentary structures resulting from the growth and metabolic activity of microorganisms as discussed by the authors, and the oldest well established occurrence was in the 2,900-3,000 Myr Pongola Supergroup of South Africa; five or six additional occurrences are known from the later Archean3.
Abstract: Stromatolites are the least controversial evidence of early life; they are organosedimentary structures resulting from the growth and metabolic activity of microorganisms1. Before this report, however, the oldest well established occurrence was in the 2,900–3,000 Myr Pongola Supergroup of South Africa2; five or six additional occurrences are known from the later Archean3. The only proposed example from older rocks is of a possibly stromatolitic microfabric from 3,500 Myr cherts in South Africa4; as yet that interpretation has not been supported by the discovery of macroscopic stromatolites. Here we describe stromatolites 3,400–3,500-Myr old from the Pilbara Block of Western Australia. These are the oldest firmly established biogenic deposits now known from the geological record.
419 citations
TL;DR: A method for the highly efficient desalting of 50–200 μl volumes of solution containing from 10 ng to 5 mg of protein has been developed and should be especially useful for the removal of unbound ligand from a rapidly dissociating ligand-binding protein complex.
289 citations
TL;DR: In this paper, the response of a lake to wind may be classified into four regimes with respect to thermocline deepening behavior, depending on the relative sizes of the parameters describing wind strength, basin size and stratification.
Abstract: An analysis of the time scales of processes relevant to wind mixing in lakes indicates that the response of a lake to wind may be classified into four regimes with respect to thermocline deepening behavior, depending on the relative sizes of the parameters describing wind strength, basin size and stratification. The dependence is described in terms of a mixed layer Richardson number and the aspect ratio of the mixed layer thickness to length. The classification is used to explain the diversity of phenomena reported in the literature for wind events in a number of different lakes and laboratory tanks which are either short enough or narrow enough for rotational effects to be unimportant. The classification is derived with reference to a two-layer, rectangular basin in the absence of Coriolis forces and surface heating. The classification is exended in a simple way to more realistic stratifications and basin shapes to predict the overall mixing features of a wind event. Response to wind varies from...
268 citations
TL;DR: This article found that older children were more likely to make sense of the questions through characteristics of the elements referred to, or through rules that might be expected to apply in the situations referred to; the younger children, on the other hand, made sense of questions by importing additional context.
Abstract: When five-and seven-year old children were presented with questions intended to be bizarre (in the sense that their meaning required clarification, or that further information beyond that provided was required for an answer), the children almost invariably gave replies. The older children were more likely to do so by making sense of the questions through characteristics of the elements referred to, or through rules that might be expected to apply in the situations referred to; the younger children were more likely to make sense of the questions by importing additional context. Older children were also more likely to indicate their uncertainty about the questions by qualifying their responses in some way.
190 citations
TL;DR: All species showed higher proportions of organic nitrogen as ureide and several-fold lower ratios of asparagine to glutamine in their xylem sap when relying on N(2) than when utilizing NO(3), and the biochemical significance of the above differences was discussed.
Abstract: Xylem sap composition was examined in nodulated and nonnodulated cowpea (Vigna unguiculata [L.] Walp.) plants receiving a range of levels of NO3 and in eight other ureide-forming legumes utilizing NO3 or N2 as sole source of nitrogen. A 15N dilution technique determined the proportions of plant nitrogen derived from N2 in the nodulated cowpeas fed NO3. Xylem sap composition of NO3-fed, nodulated cowpea varied predictably with the relative extents to which N2 and NO3 were being utilized. The ratios of asparagine to glutamine (N/N) and of NO3 to ureide (N/N) in xylem sap increased with increasing dependence on NO3 whereas per cent of xylem nitrogen as ureide and the ratio of ureide plus glutamine to asparagine plus NO3 (N/N) in xylem sap increased with increasing dependence on N2 fixation. The amounts of NO3 and ureides stored in leaflets, stems plus petioles, and roots of cowpea varied in a complex manner with level of NO3 and the presence or absence of N2 fixation. All species showed higher proportions of organic nitrogen as ureide and several-fold lower ratios of asparagine to glutamine in their xylem sap when relying on N2 than when utilizing NO3. In nodulated (minus nitrate) cowpea and mung bean (Vigna radiata [L.] Wilczek) the percentage of xylem nitrogen as ureide remained constant during growth but the ratio of asparagine to glutamine varied considerably. The biochemical significance of the above differences in xylem sap composition was discussed.
166 citations
TL;DR: There is apparently a relationship between the pattern of LH secretion after introducing the rams, and the ovulatory response that can be expected, according to radioimmunoassay of plasma samples.
152 citations
TL;DR: There is no evidence in their analyses or arguments to change the previous conclusion that interspecific competition has played a role in the adaptive radiation of Darwin's Finches, and some unsolved problems in biogeography are drawn attention.
Abstract: We conducted a field study of some of Darwin's Finches (Geospiza species) in order to assess the relative importance of interspecific competition and habitat features in determining the observed biogeographic, ecological and morphological characteristics of these species (Abbott et al., 1977). Strong et al. (1979) have criticized one of our methods and have reanalyzed a small portion of our data. They employed stochastic models to generate expected beak size differences between sympatric species, and then compared expected with observed differences. Finding a generally close correspondence between expected and observed differences, they concluded that random processes are sufficient to account for the observations, and that therefore there is no need to invoke deterministic processes such as competition as we had done. Strong et al. (1979) obtained the same results and drew the same conclusion from analyses of beak size differences among birds on the Tres Marias islands of Mexico and the Channel islands of California. Simberloff and his associates have also drawn the same conclusion from a series of other analyses performed in like manner (Connor and Simberloff, 1978; Simberloff, 1978). We take issue with the procedures Strong et al. (1979) have used in their analyses and with the way in which our statements and interpretations have been represented. We identify five problems in their analyses and five sources of confusion in the interpretation of results. We find no evidence in their analyses or arguments to change our previous conclusion that interspecific competition has played a role in the adaptive radiation of Darwin's Finches. Finally, we draw attention to some unsolved problems in biogeography, concerning principally the separation of potentially conflicting effects of different processes such as dispersal and competition.
144 citations
139 citations
TL;DR: The development and maturation of synapses in the molecular layer of the occipital cortex of rats at 15, 20, 28, 75 and 224 days postnatal were examined and quantitative ultrastructural techniques were employed, and it is postulated that negatively curved synaptic junctions may be non-functional.
129 citations
TL;DR: It was concluded that simulators represent a viable procedure given the skill to be assessed in the present research and the experience of the students.
Abstract: While the use of simulated patients for the assessement of medical students' skills is increasing there is little data on whether students perform differently vs real patients. The present study examined this issue using second-year medical students' ability to empathize with simulated and genuine patients. Forty second-year students each conducted two interviews which were audio-recorded and later rated by raters who had achieved a high degree of reliability using the 9-point accurate empathy scale (Truax, 1967). Ten students saw a genuine patient for each interview while ten students saw simulators on both occasions. Of the remaining twenty students, ten saw genuine patients at the first interview and simulated patients at the second session. This order was reversed for the remaining ten students. No significant differences were found in the levels of empathy between students' interaction with genuine or simulated patients. As the students were also unable to discriminate between the two groups of patients it was concluded that simulators represent a viable procedure given the skill to be assessed in the present research and the experience of the students.
TL;DR: In this paper, the problem of bounding the order of a permutation in terms of its degree in a group was studied and the best result for the case where the group is a primitiv e group was given.
Abstract: CHERYL E PRAEGE R AN JAD N SAXLThe proble omf bounding the order of a permutation grou G ipn terms of itsdegree n was one of the central problem of 19tsh century group theory (see [4]) Itis closely relate to thde 1860 Grand Prix proble of them Pari s Academy but it, shistory goe isn fact much further back (see eg an [3]d [10]), [1] The hear of thteproblem is of course the case where G a is primitiv e group The best result here is dueto A Bocher t [2] if: G is primitiv ane d A
TL;DR: The internal structure of one of the major batholiths, the Shaw batholith, resembles an Archean gneiss belt as mentioned in this paper, suggesting that deformation and metamorphism are not a direct consequence of the emplacement of granitic magmas.
Abstract: The Archean Pilbara block, Western Australia, is cited as a type example of a granite-greenstone terrane. New field evidence reveals that the internal structure of one of the major batholiths, the Shaw batholith, resembles an Archean gneiss belt. Greenstone intercalations within the gneiss belt can be traced into the surrounding greenstone sequence and were incorporated during subhorizontal thrusting and recumbent folding episodes. These early tectonic episodes preceded solid-state diapiric uprise of an overthickened crust. Granitic plutonism and partial melting of the sialic crust appear to have played an important role only in the later stages of the tectonic evolution of the Shaw batholith. Deformation and metamorphism are not a direct consequence of the emplacement of granitic magmas, contrary to the widely accepted magmatic model of batholith formation.
TL;DR: In this article, post-fire species changes were documented over a portion of the northern section of the jarrah forest of Western Australia from a series of sites of known age since last fire.
Abstract: Post-fire species changes were documented over a portion of the northern section of the jarrah forest of Western Australia from a series of sites of known age since last fire. Species richness and species diversity were observed to increase following fire for several years, followed by a gradual decline. Dominance-diversity curves indicated that maximum diversity occurred from 3 to 5 years following fire. The species composition of sites of different regions was more similar than sites of similar time since burn. The significance of the results to the programme of controlled burns is discussed.
TL;DR: Loss of neural sensitivity indicates loss of nonlinear behaviour in the mechanics which is undetectable shortly after death.
TL;DR: Scanning microscopy was used to examine guinea pig cochleas for structural damage immediately after exposure to a pure tone ranging from 96 to 129 dB SPL, finding that N1 threshold losses spread progressively to lower frequencies as exposure intensity increased.
TL;DR: In the last two decades, a number of hallowed theories, raised on a cushion of metaphysical speculation above the mundane historical evidence, have succumbed to attacks based on rigorous logic and source analysis as discussed by the authors.
Abstract: The last two decades have seen a welcome erosion of traditional dogmas of Alexander scholarship, and a number of hallowed theories, raised on a cushion of metaphysical speculation above the mundane historical evidence, have succumbed to attacks based on rigorous logic and source analysis. The brotherhood of man as a vision of Alexander is dead, as is (one hopes) the idea that all Alexander sources can be divided into sheep and goats, the one based on extracts from the archives and the other mere rhetorical fantasy. One notable theory, however, still flourishes and has indeed been described as one of the few certainties among Alexander's aims. This is the so-called policy of fusion. As so often, the idea and terminology go back to J. G. Droysen, who hailed Alexander's marriage to Rhoxane as a symbol of the fusion (Verschmelzung) of Europe and Asia, which (he claimed) the king recognised as the consequence of his victory. At Susa the fusion of east and west was complete and Alexander, as interpreted by Droysen, saw in that fusion the guarantee of the strength and stability of his empire. Once enunciated, Droysen's formulation passed down the mainstream of German historiography, to Kaerst, Wilcken, Berve and Schachermeyr, and has penetrated to almost all arteries of Alexander scholarship. Like the figure of Alexander himself the theory is flexible and capable of strange metamorphoses. In the hands of Tarn it developed into the idea of all subjects, Greek and barbarian, living together in unity and concord in a universal empire of peace. The polar opposite is an essay of Helmut Berve, written in the heady days before the Second World War, in which he claimed that Alexander, with commendable respect for Aryan supremacy, planned a blending of the Macedonian and Persian peoples, so that the two racially related (!) Herrenvolker would lord it over the rest of the world empire. On Berve's interpretation the policy had two stages. Alexander first recognised the merits of the Iranian peoples and placed them alongside the Macedonians in his court and army hierarchy. Next came the ‘Blutvermischung’, the integration of the two peoples by marriage.
TL;DR: The length of the extension zone (LEZ) of emerging wheat leaves varied with the stage of leaf development and between leaves with the length of The ratio LEZ/LES varied from 0·60 when the leaf tip emerged from the encircling sheath to 0·35 when the ligule emerged.
Abstract: Summary
The length of the extension zone (LEZ) of emerging wheat leaves varied with the stage of leaf development and between leaves with the length of the encircling sheath (LES). The ratio LEZ/LES varied from 0·60 when the leaf tip emerged from the encircling sheath to 0·35 when the ligule emerged. The relationship between LEZ/LES and an index of leaf development (DI), defined as the sheath length of the growing leaf relative to LES, was: LEZ/LES= 0·632 exp (-0.622.DI); (r= 0.91). 14C incorporation studies supported the measurement of extension zone location and length.
There appeared to be a small zone of non-expanding tissue, within the extension zone, around the ligule, but it was not a major discontinuity within the whole extension zone. The relative extension rate of the extension zone declined by only 50 % from leaf tip to ligule emergence whereas the relative extension rate of the whole leaf declined by 90 % over the same interval.
There was little variation in protein and carbohydrate concentrations around the upper limit of the extension zone in emerging leaves. For studies of leaf growth in wheat where it is not possible to measure LEZ, harvesting the lower 50 % of the enclosed part of an emerging leaf would adequately sample the extension zone.
TL;DR: In this article, Hindi-English bilinguals completed two blocks of trials where each trial involved presentation of a letter string requiring a lexical decision, and the results support the view that lexical representation in bilinguals is language-specific.
Abstract: Forty-eight Hindi-English bilinguals completed two blocks of trials where each trial involved presentation of a letter string requiring a lexical decision. In the first block subjects were exposed to 22 words and 11 non-words in either English or Hindi. In the second block the original words were repeated in either the same language or in the alternative language. In this block the old (repeated) words were mixed with 22 new words, and 22 non-words. Twelve subjects were included in each of the four groups given by the factorial combination of blocks and languages. Reaction time in the lexical decision task was facilitated when words were repeated in the same language (109 and 125 ms in the English-English and Hindi-Hindi groups respectively), but little or no facilitation was observed in the inter-lingual conditions (-22 and 23 ms in the Hindi-English and English-Hindi conditions respectively). The results support the view that lexical representation in bilinguals is language-specific.
TL;DR: Guinea pigs were exposed to a 10 kHz pure tone and damage to the cochlea was investigated immediately after exposure, or after a recovery period ranging from 18-25 days.
TL;DR: The effect of inoculation, with a VA mycorrhizal fungus on growth and phosphorus uptake of subterranean clover was examined using three phosphorus sources with different solubilities.
Abstract: SUMMARY
The effect of inoculation, with a VA mycorrhizal fungus on growth and phosphorus uptake of subterranean clover was examined using three phosphorus sources with different solubilities. Mycorrhizas markedly increased growth and phosphorus content of tops at intermediate rates of phosphorus application for all sources.
The effectiveness of phosphorus for plant growth for mycorrhizal plants relative to non-mycorrhizal plants was the same for a water soluble source (superphosphate) and two insoluble sources (C-grade Christmas Island rock phosphate and calcined Christmas Island rock phosphate). The effectiveness of phosphorus from each of the three sources for phosphorus uptake by mycorrhizal plants relative to non-mycorrhizal plants was also independent of the solubilities of the phosphorus sources applied.
At a given phosphorus concentration in tops, non-mycorrhizal subterranean clover produced more dry matter than mycorrhizal clover supplied with superphosphate. Mycorrhizal and non-mycorrhizal subterranean clover supplied with C grade rock phosphate had the same dry weight at a given phosphorus concentration in their tops.
VA mycorrhizas increased zinc but not calcium uptake by subterranean clover.
TL;DR: The principal nitrogenous solutes produced from N 2 -fixation and exported from the nodules of cowpea were allantoin and allantoic acid, and the following evidence suggests that these ureides were derived from purines.
TL;DR: Daily observation of ovarian activity in cycling ewes by laparoscopy shows that visual estimation of the age of corpora lutea must be primarily related to changes in their colour rather than toChanges in either their shape or size.
TL;DR: In this paper, model cation exchange curves are presented for an idealized kaolinite surface where the charge on the surface has its origin in cation substitution in the structure, and hence, is pH independent.
Abstract: Model cation-exchange curves are presented for an idealized kaolinite surface where the charge on the surface (1) has its origin in cation substitution in the structure, and hence, is pH independent; and (2) is produced by protonation/deprotonation reactions of oxide-like sites, and hence, depends on the acid and base strengths of the surface sites, as welt as the ionic strength. Two pH-independent situations are considered: one where the exchanging ions have no selectivity for the surface and are all in the diffuse layer; and one where selectivity exists for one ion and where that ion is partly in a Langmuir-Stern layer and partly in the diffuse layer. If one of the exchanging ions is a proton, the shape of the curves and their position on the pH scale depend on ionic strength and ionic selectivity. The model curves are compared with data for actual kaolinites. Under most conditions exchangeable AI is released from the structure, and the shape of the charging curves becomes similar to that of an oxide- like surface. However, if titration is carried out rapidly, or account is taken of the presence of AI, the proton binding curves are similar in shape to those expected for sites resulting from cation substitution in the structure of kaolinite, either near the surface or at the edge of the crystal.
TL;DR: Some mechanism that prevents inbreeding seems to be present in the grey-crowned babbler population, and eight of 20 loci tested were polymorphic, with an average proportion of heterozygous loci individual of 9.4%.
Abstract: The grey-crowned babbler, Pomastostomus temporalis, is a non-migratory species with delayed breeding and prolonged association of young with siblings and parents. Since these conditions are conducive to incestuous matings, we have studied allozymic variation in a population in southeastern Queensland, to evaluate the possibility of close inbreeding. Eight of 20 loci tested were polymorphic, with an average proportion of heterozygous loci individual of 9.4%. No deficiency of heterozygotes was found, indicating the absence of detectable inbreeding. Some mechanism that prevents inbreeding seems to be present.
TL;DR: It is suggested that non-avian pollinators, predatory insects, and characteristics of the breeding system may also have been important in the evolution of the observed flowering phenology and patterns of seed set.
Abstract: Flowering phenology and seed set characteristics of five species of Banksia were studied in relation to the nectarivorous birds which feed at their inflorescences. Within the Banksia woodland at the study site near Perth, the flowering seasons of the Banksia species were sequential and only slightly overlapping, providing a year-round nectar source. Although honeyeaters visited alt five species, seed set was very low in each case. Caging experiments indicated that, in B. attenuata at least, alternative pollinators may play a more important role in pollination than do nectar-feeding birds. It is suggested that non-avian pollinators, predatory insects, and characteristics of the breeding system may also have been important in the evolution of the observed flowering phenology and patterns of seed set.
TL;DR: In this article, the structural design problem is acknowledged to be commonly multi-criteria in nature and various bases for multicriteria optimization methodologies are outlined and a computationally viable method for generating Pareto optimal solutions is adopted for structural design problems where the criteria may be non-commensurable.
Abstract: The structural design problem is acknowledge to be commonly multi-criteria in nature. The various bases for multi-criteria optimization methodologies are outlined and a computationally viable method for generating Pareto optimal solutions is adopted for the structural design problem where the criteria may be non-commensurable. A numerical example on optimal truss design illustrating non-commensurable criteria is given.
TL;DR: It is concluded that the limb does not limit the number of survivors, and therefore the hypothesis that motoneurone numbers are determined by the need to eliminate ventral horn cells not connected with appropriate limb regions, or by factors operating within the central nervous system.
Abstract: The death of large numbers of young neurones is a striking feature in the developing nervous system. Many authors have postulated that the neurones are produced in excess of the numbers that their target tissues can support, forcing them to compete for survival1–3. Observations on developing limb motoneurones (ventral horn cells) in both frogs and chicks seem to support this hypothesis. Normally, one-half to three-quarters of ventral horn cells die as limb movements begin4,5, but some of these (up to 25% in chicks, 7% in frogs) can be rescued by the provision of supernumerary limb buds before motor axon outgrowth begins6–10. Conversely, amputation of the limb bud causes an increased death rate approaching 100% (refs 4,11). The crucial test of the hypothesis depends on its prediction that the limb should limit the number of surviving motoneurones, and here I have attempted to make the test. For this, both sides of the spinal cord were forced to project to a single hind limb bud well before the onset of ventral horn cell death. It was found that the combined total of surviving motoneurones (right plus left sides) projecting to the single limb exceeded the number that projects to one limb in normal animals by up to ∼100%. It is concluded that the limb does not limit the number of survivors, and therefore the hypothesis is refuted, at least for ventral horn cells. It now seems more likely that motoneurone numbers are determined either by the need to eliminate ventral horn cells not connected with appropriate limb regions, or by factors operating within the central nervous system.