scispace - formally typeset
Search or ask a question

Showing papers by "University of Sydney published in 1980"


Journal ArticleDOI
TL;DR: In this paper, a solution for the elastic stress intensity factors at the tip of a slightly curved or kinked two-dimensional crack is presented for the deviation of the crack surface from a straight line and is carried out by perturbation procedures analogous to those of Banichuk [1] and Goldstein and Salganik [2, 3].
Abstract: A solution is presented for the elastic stress intensity factors at the tip of a slightly curved or kinked two-dimensional crack. The solution is accurate to first order in the deviation of the crack surface from a straight line and is carried out by perturbation procedures analogous to those of Banichuk [1] and Goldstein and Salganik [2, 3]. Comparison with exact solutions for circular arc cracks and straight cracks with kinks indicates that the first order solution is numerically accurate for considerable deviations from straightness. The solution is applied to fromulate an equation for the path of crack growth, on the assumption that the path is characterized by pure Mode I conditions (i.e., K II=0) at the advancing tip. This method confirms the dependence of the stability, under Mode I loading, of a straight crack path on the sign of the non-singular stress term, representing tensile stress T acting parallel to the crack, in the Irwin-Williams expansion of the crack tip field. The straight path is shown to be stable under Mode I loading for T 0.

1,681 citations


Journal ArticleDOI
TL;DR: The conceptual clustering of numerous concepts from family therapy and other social science fields reveals two significant dimensions of family behaviour, cohesion and adaptability as discussed by the authors, i.e., family behavior, cohesion, and adaptivity.
Abstract: The conceptual clustering of numerous concepts from family therapy and other social science fields reveals 2 significant dimensions of family behaviour, cohesion and adaptability. These 2 dimension...

768 citations


Journal ArticleDOI
TL;DR: Within the range of annual survivorship rates of most lizard species, trade-offs between fecundity and survival are likely to be the main evolutionary determinants of optimal levels of “reproductive effort”.
Abstract: Many theoretical models of life-history evolution rely on the existence of trade-offs between current fecundity and probable future fecundity and survival. Such “costs” of reproduction have been demonstrated only rarely. Field and laboratory studies on six species of Australian scincid lizards show that gravid females are more vulnerable to predation than are non-gravid females, primarily because (i) they are physically burdened (running speeds are reduced by 20 to 30%), and (ii) they bask more often (in some species). However, food intake is not reduced in gravid animals. A review of published literature suggests that reproductive trade-offs are widespread among reptiles, but the nature of the reproductive “costs” may vary widely among related species. Within the range of annual survivorship rates of most lizard species, trade-offs between fecundity and survival are likely to be the main evolutionary determinants of optimal levels of “reproductive effort”. Trade-offs between fecundity and bodily growth are less likely to be significant.

634 citations


Journal ArticleDOI
TL;DR: A compact closed category is a symmetric monoidal one whose internal-horn [A, C] has the form CBA' as mentioned in this paper, and is defined as a monoidal category d with tensor product @ and unit object I with a single O-cell, the l-cells of B being the objects of ti with @ as their composition.

495 citations


Book ChapterDOI
01 Jan 1980
TL;DR: The immune response may be related to cancer chemotherapy in several ways, and chemotherapy and immunotherapy may be used together in the treatment of specific neoplasms.
Abstract: The immune response may be related to cancer chemotherapy in several ways. First, the patient with advanced cancer may have depressed immunological responsiveness prior to commencement of chemotherapy. Secondly, chemotherapy itself may markedly influence the immune response. Finally, chemotherapy and immunotherapy may be used together in the treatment of specific neoplasms. Before discussing these in detail, it is pertinent to review the immune response and the techniques by which it can be assessed.

457 citations


Journal Article
TL;DR: It is shown that requirements for the accurate modeling of engineering flows are best met by a new molecular model called the variable hard sphere, or VHS, model, and the necessary kinetic theory for the application of this model is presented.
Abstract: The computational and physical requirements for the successful application of the direct simulation Monte-Carlo method to typical engineering flows, as opposed to earlier applications to artificial test cases, are discussed. An outline is given of the changes that have occurred in the program structure as a result of both altered requirements and advances in computer technology. The accumulated experience from applications of the classical molecular models is reviewed. It is shown that requirements for the accurate modeling of engineering flows are best met by a new molecular model called the variable hard sphere, or VHS, model, The necessary kinetic theory for the application of this model is presented.

424 citations



Journal ArticleDOI
TL;DR: Experimental evidence indicates that the unstirred layers of solution bathing aquatic plant cells or organs represent a major factor limiting their rate of photosynthesis under natural conditions and may also limit membrane transport of HCO3− where this occurs.
Abstract: Summary We review and reassess experimental evidence which indicates that the unstirred layers of solution bathing aquatic plant cells or organs represent a major factor limiting their rate of photosynthesis under natural conditions. Unstirred layers may also limit membrane transport of HCO3− where this occurs. Some authors have suggested that aquatic plants carry out C4photosynthesis and cite in support measurements of discrimination between 13C and 12C. We propose that this discrimination can also be a manifestation of the presence of unstirred layers or membrane transport or both.

296 citations


Journal ArticleDOI
TL;DR: A generalization of the bounds obtained by Wiener and by Hashin and Shtrikman for complex dielectric constants is presented in this article, where the authors show how to derive the bounds for complex constants.
Abstract: A generalization of the bounds obtained by Wiener and by Hashin and Shtrikman is derived for complex dielectric constants.

276 citations


Journal ArticleDOI
TL;DR: Experimental manipulations at midtidal levels were used to test hypotheses about the effects of grazing by molluses and of physical factors during low tide on this pattern of algal community structure, and the role of grazing in the diversity and structure of intertidal algal communities.
Abstract: The cover of foliose algae is sparse to non-existent above a low-level algal zone on many shores in N.S.W., except in rock-pools. Above this algal zone, encrusting algae, mostly Hildenbrandia prototypus, occupy most of the primary substratum on sheltered shores. Experimental manipulations at midtidal levels were used to test hypotheses about the effects of grazing by molluses and of physical factors during low tide on this pattern of algal community structure. Fences and cages were used to exclude grazers: molluscs grazed under roofs and in open areas. Cages and roofs provided shade, and decreased the harshness of the environment during low tide: fences and open areas had the normal environmental regime. In the absence of grazers, rapid colonization of Ulva and slower colonization by other foliose algae occurred in all experimental areas. The rate of colonization by Ulva sporelings was initially retarded on existing encrusting algae, but after a few months, cover of Ulva equalled that on cleared rock. Most species of algae only grew to maturity inside cages, and remained as a turf of sporelings inside fences. No foliose algae grew to a visible size in open, grazed areas. Grazing thus prevents the establishment of foliose algae above their normal upper limit on the shore, but the effects of physical factors during low tide prevent the growth of algae which become established when grazers are removed. Physical factors thus limit the abundance of foliose algae at mid-tidal levels. The recolonization of cleared areas by Hildenbrandia was not affected by the presence of a turf of sporelings, nor by the shade cast by roofs, but was retarded in cages where mature algae formed a canopy. Even under such a canopy, Hildenbrandia eventually covered as much primary substratum as in open, grazed areas. This encrusting alga is able to escape from the effects of grazing by having a tough thallus, and by its vegetative growth which allows individual plants to cover a lot of substratum, and by the tendency for new individuals to start growing from small cracks and pits in the rock, which are apparently inaccessible to the grazers. Mature foliose algae are removed from the substratum by waves, and many individual plants died during periods of hot weather. Sporelings in a turf were eliminated, after experimental fences were removed, by the combined effects of macroalgal grazers, which invaded the areas, and microalgal grarers which ate the turt from the edges inwards. The results obtained here are discussed with respect to other studies on limits to distribution of intertidal macroalgae, and the role of grazing in the diversity and structure of intertidal algal communities. Some problems of these experimental treatments are also discussed.

276 citations


Journal ArticleDOI
G. M. Kelly1
TL;DR: In this paper it was shown that the reflexion exists and is given as the colimit of a simple transfinite sequence, if A is cocomplete and the Tk preserves either colimits or unions of suitably-long chains of subobjects.
Abstract: Many problems lead to the consideration of “algebras”, given by an object A of a category A together with “actions” TkA → A on A of one or more endofunctors of A, subjected to equational axioms. Such problems include those of free monads and free monoids, of cocompleteness in categories of monads and of monoids, of orthogonal subcategories (= generalized sheaf-categories), of categories of continuous functors, and so on; apart from problems involving the algebras for their own sake.Desirable properties of the category of algebras - existence of free ones, cocompleteness, existence of adjoints to algebraic functors - all follow if this category can be proved reflective in some well-behaved category: for which we choose a certain comma-category T/AWe show that the reflexion exists and is given as the colimit of a simple transfinite sequence, if A is cocomplete and the Tk preserve either colimits or unions of suitably-long chains of subobjects.The article draws heavily on the work of earlier authors, unifies and simplifies this, and extends it to new problems. Moreover the reflectivity in T/A is stronger than any earlier result, and will be applied in forthcoming articles, in an enriched version, to the study of categories with structure.

Journal ArticleDOI
01 Jun 1980
TL;DR: In this paper, an approximate theory of depletion stabilization and depletion flocculation is presented based upon the rotational isomeric state-Monte Carlo procedures for calculating the conformation of macromolecules between two particles and the Flory-Huggins theory of polymer solutions.
Abstract: An approximate theory of depletion stabilization and depletion flocculation (i.e., stabilization and flocculation of colloidal particles by polymers in free solution) is presented. This is based upon the rotational isomeric state-Monte Carlo procedures for calculating the conformation of macromolecules between two particles and the Flory-Huggins theory of polymer solutions. It is shown that reasonable agreement between theory and experiment can be achieved for the critical volume fractions of polymer required to induce both depletion flocculation and depletion stabilization. The presence of adsorbed or attached polymer at the interface may have a significant effect on the onset of both flocculation and stabilization; this is especially true if the molecular weight of the attached chains is comparable to or greater than that of the free polymer. The effects of the steric chains, however, are reduced if the free polymer is significantly higher in molecular weight. Free energy minimization procedures are then necessary to calculate the polymer distribution between the plates. The agreement obtained between theory and experiment suggests that the theory incorporates the dominant factors that control depletion flocculation and stabilization.

Journal ArticleDOI
TL;DR: Rat ventricular myosin contains two isoenzymes which can be separated by polyacrylamide gel electrophoresis in the presence of pyrophosphate buffers, and these phenotypes differ in their kinetic properties.

Journal ArticleDOI
TL;DR: It is concluded that the ventrolateral area is either the site of origin or an essential part of the central vasomotor pathway mediating the CIR and that this pathway projects dorsomedially before descending to the spinal cord.
Abstract: The ventrolateral medulla has been postulated to contain chemosensitive neurons. This study investigated the role of this region in the generation of the pressor response to cerebral ischemia (CIR) in anesthetized paralyzed artificially ventilated rabbits. A circumscribed and highly sensitive pressor area in the ventrolateral medullary reticular formation 2-4 mm rostral to the obex, separate from the well-known dorsal pressor area, was mapped by use of a stimulating electrode. Electrolytic destruction of this area resulted in a profound reduction in resting mean arterial pressure (MAP). After restoration of baseline MAP with norepinephrine infusion, the CIR was greatly reduced (by mean 70.2% of control), but pressor responses from the dorsal medulla were unaffected. In contrast, lesions of greater size placed in the ventrolateral medulla more caudally did not significantly alter resting MAP and only slightly reduced the CIR (by mean 17.0% of control). Vasomotor responses to stimulation of the ventrolateral pressor area were unaffected by caudal ventrolateral lesions, but greatly reduced by dorsomedial lesions in the same plane. It is concluded that the ventrolateral area is either the site of origin or an essential part of the central vasomotor pathway mediating the CIR and that this pathway projects dorsomedially before descending to the spinal cord.

Journal ArticleDOI
TL;DR: Although cuticular and epidermal penetration by the rust and death of the penetrated cell were similar in two cultivars, subsequent hyphal branching and growth was decreased and retention of trypan blue stain was increased in the resistant cultivar.
Abstract: Although cuticular and epidermal penetration by the rust and death of the penetrated cell were similar in two cultivars, subsequent hyphal branching and growth was decreased and retention of trypan blue stain was increased in the resistant cultivar. No uredinia formed in the resistant cultivar. Phytoalexin formation began earlier in the resistant cultivar and at a time when many cells had changed in their physiology as revealed by stain retention. A product of germinating urediniospores caused more rapid browning and phytoalexin formation in pods of the resistant cultivar.

Journal ArticleDOI
TL;DR: In this article, three primary types of Holocene embayment fill are recognized: open ocean, barrier estuary and drowned river valley, and an evolutionary model is proposed to account for their various stages of development.

Journal ArticleDOI
J. B. Moss1
TL;DR: In this article, a turbulent premixed flame in an LPG/air mixture issuing from a 50 mm diameter pipe was measured along a line at an angle of about 50° to the normal to the flame front.
Abstract: Measurements have been made in the turbulent premixed flame in an LPG/ air mixture issuing from a 50 mm diameter pipe. The flame was of the classical bunsen type with a half cone angle of 16° Measurements were made along a line at an angle of about 50° to the normal to the flame front. Concentration, or the progress variable c, was measured by the light scatter technique and velocity u by laser Doppler velocimetry. The correlation between u and c is found to be positive through much of the flame indicating a counter-gradient flux. The joint probability density function (pdf) of u and c is well modelled by essentially burnt and unburnt gas with only a small contribution of the partially reacted gas. The conditioned pdf' s for velocity in the unburnt and burnt gas show a considerable increase in both mean and variance for the burnt gas.

Journal ArticleDOI
TL;DR: Emission mechanisms for meter-λ solar radio bursts are reviewed in this article with emphasis on fundamental plasma emission. But the authors do not consider the effect of solar radiation on the radio bursts themselves.
Abstract: Emission mechanisms for meter-λ solar radio bursts are reviewed with emphasis on fundamental plasma emission.

Journal ArticleDOI
TL;DR: The behavior of the East Australian Current system is qualitatively different on either side of a line extending south-southeast of Sugarloaf Point (32°30°S).
Abstract: Oceanographic data from the last two decades show that the behavior of the East Australian Current system is qualitatively different on either side of a line extending south-southeast of Sugarloaf Point (32°30°S); to the north and east of the line, dynamic height contours and satellite buoy tracks are either open, or they consist of large eddies elongated in the north-south direction. South and west of the line, flow consists of relatively small, near-circular eddies. Just south of Sugarloaf Point, northward currents on the continental shelf appear to be common, suggesting entrainment toward a separation flow near Sugarloaf Point which may be topographically controlled. The oceanographic data suggest that the separation point is more closely defined in summer, when the current is strong, than in winter. Merchant ship, current atlas and continental shelf sediment data generally support this description of the East Australian Current. However, current atlas data collected between 1854 and 1938 sugg...

Journal ArticleDOI
TL;DR: X-ray microanalysis has confirmed, and measured, the phosphorus content of cytochemically-demonstrated polyphosphate granules in onion mycorrhizas, and fulfils the hypothesis that phosphorus is translocated in the fungus by means of the transport of polyph phosphate granules by cytoplasmic streaming.
Abstract: Summary X-ray microanalysis has confirmed, and measured, the phosphorus content (0·03 g cm-3) of cytochemically-demonstrated polyphosphate granules in onion mycorrhizas. The volume occupied by the granules measured from stereoscopic high-voltage electron micrographs of thick sections was 0·8 % of the fungal volume, and cytoplasmic streaming rates of the extra-matrical mycelium in soil measured in the light microscope were around 12·6 cm h-1. From these data a flux rate of about 2·7 × 10-8 mol P cm-2 s-1 has been calculated, which fulfils the hypothesis that phosphorus is translocated in the fungus by means of the transport of polyphosphate granules by cytoplasmic streaming.

Journal ArticleDOI
TL;DR: Evidence is provided to suggest that increases in population density in certain ecological zones have occurred due to changes in energy harnessing methods, and comparison between the population densities of the high density Australian hunter‐gatherers and some New Guinea shifting agriculturalists reveals only marginal differences, suggesting that comparable levels of energy harnessed have been achieved by different means.
Abstract: Population and technology have been seen as remaining relatively stable for the length of Australia's prehistory. This viewpoint is challenged and evidence is provided to suggest that increases in population density in certain ecological zones have occurred due to changes in energy harnessing methods. A case study from south‐western Victoria demonstrates that the high density hunter‐gatherer populations of the area lived a semi‐sedentary life, had a broad based subsistence economy supported by a specialized technology which included the construction of large‐scale water controls. The development of these high energy expenditure systems is discussed, and mechanisms promoting change within hunter‐gatherer economies are described. A comparison between the population densities of the high density Australian hunter‐gatherers and some New Guinea shifting agriculturalists reveals only marginal differences, suggesting that comparable levels of energy harnessing have been achieved by different means.

Book ChapterDOI
01 Jan 1980
TL;DR: The role of those who will not let their thought be dissipated in endless ramifications as mentioned in this paper is to discover, or to restate, simple and direct, yet profound and forceful, arguments which lead to important conclusions about major philosophical issues.
Abstract: Some philosophers in their work are led on to ever greater complexity; others seek simplicity and clarity of argument and vision. Each type of mind serves to check the shortcomings of the other. In our age philosophy is more professionalized than ever before, so as a result the first sort of mind is in the ascendant. All the more important, therefore, is the role of those who will not let their thought be dissipated in endless ramifications. Richard Taylor’s particular intellectual contribution has been to discover, or to restate, simple and direct, yet profound and forceful, arguments which lead to important conclusions about major philosophical issues. He has done this in a way which involves no sacrifice of contemporary standards of rigor and exactness.

Journal ArticleDOI
TL;DR: A model for Lara is proposed in which the acidification is attributed to active efflux of H+, and it is calculated that both the equilibrium concentration of CO2 and its rate of production outside the cell can be high enough to support the observed rates of C assimilation, without postulating transport of the species HCO3− or H2CO3.
Abstract: Although it is generally believed thatChara and some fresh-water angiosperms transport bicarbonate ions inwards across their plasma membranes, there has been no direct demonstration of such transport in these plants. The (indirect) arguments for their transporting HCO 3 − are arguments against the inward diffusion of CO2 at the observed rates. They rest on calculations of the equilibrium concentration of CO2 or of the maximum rate at which CO2 might be produced from HCO 3 − at the pH of the medium outside the cells. SinceChara acidifies the medium over about half the cell surface during C assimilation, these calculations have been based on questionable premises. We propose a model forChara in which the acidification is attributed to active efflux of H+, and we calculate that both the equilibrium concentration of CO2 and its rate of production outside the cell can be high enough to support the observed rates of C assimilation, without postulating transport of the species HCO 3 − or H2CO3. Calculations are presented also for alternative models in which there is membrane transport of HCO 3 − . The first includes symport of H+ with HCO 3 − , again dependent on active H+ efflux. In the second, there is active electrogenic transport of HCO 3 − . In this case the low pH in the medium outside the cell is caused by the dissociation of H2CO3 produced by hydration of CO2 which leaks from the cell cytoplasm. All three models are consistent with the observations to date, but the first is more economical of postulates. It can also explain the apparent transport of HCO 3 − by fresh-water angiosperms such asEgeria.

Journal ArticleDOI
TL;DR: The foraging behaviour of Australian honeyeaters is reviewed in terms of diet,Foraging selectivity, foraging flight mode, quality and quantity of nectar encountered per flower, flower densities encountered and effect of predation.
Abstract: The foraging behaviour of Australian honeyeaters is reviewed in terms of diet, foraging selectivity, foraging flight mode, quality and quantity of nectar encountered per flower, flower densities encountered and effect of predation. At the same time comparisons are made between honeyeaters and hummingbirds. These two groups of birds are superficially similar. Both feed on nectar and insects. Both tend to have long curved bills and tongues adapted for removal of nectar from flowers. Both tend to feed at long, red flowers. However, on close inspection, honeyeaters and hummingbirds are quite dissimilar. For example, many honeyeaters include fruit in their diets. Hummingbirds almost never eat fruit. Honeyeaters appear to be considerably less nectarivorous and more insectivorous than hummingbirds. Honeyeaters are, for the most part, larger than hummingbirds and they usually perch while feeding whereas hummingbirds usually hover. Honeyeaters but not hummingbirds often flock while feeding. Predation appears to be considerably more important for honeyeaters than for hummingbirds. Territorial defense of flowers seems common in hummingbirds but uncommon in honeyeaters. These differences are discussed in detail and explanations are offered for them wherever possible.

Journal ArticleDOI
15 Dec 1980-Cancer
TL;DR: In men and women matched by age, site, and thickness of primary lesions, women with very thick tumors still survived longer, and the association between decline in prognosis with increasing age and decline in proportion of thin lesions with increasingAge was much closer in men than women.
Abstract: Efforts were made to further explain female superiority in survival of 753 patients with clinical Stage I malignant melanoma. Two factors contributing to this female superiority in survival drew some of their prognostic value from the correlation with tumor thickness. (1) More than twice as many women as men had primary lesions located on the extremities, which were prognostically favorable anatomical sites in both men and women. In addition, women with extremity lesions had a more favorable prognosis than men with extremity lesions. This sex differential in survival for patients with extremity lesions was partly attributable to the fact that the extremity lesions of women were significantly thinner than those of men. (2) Significantly more women than men were under age 50; this age group of women had a significantly better prognosis than the corresponding age group of men. The sex differential in survival for patients under 50 years was partly attributable to the fact that the women's lesions were significantly thinner than those of men. There was only a slight sex differential in the survival of patients 50 years and over, a finding in consonance with the smaller difference in tumor thickness between these older men and women. The association between decline in prognosis with increasing age and decline in proportion of thin lesions with increasing age was much closer in men than women. In men and women matched by age, site, and thickness of primary lesions, women with very thick tumors still survived longer.


Journal ArticleDOI
TL;DR: The establishment of aOH− (or H+ permeable membrane at high pH suggests that the large fluxes of OH− ( or H+ which occur in the alkaline band in photosynthesizing cells are passive.
Abstract: Above a critical external pH (about 10.5), theChara membrane acquires new propertes. In this state the membrane potential is close to the equilibrium potentials for H+ and OH−, hyperpolarizing as external pH increases with a slope of −59 mV/pH unit. The membrane conductance increases by an average factor of 2.4 above the critical pH. These changes are explained by an increase in permeability to OH− (or H+). The establishment of a OH− (or H+ permeable membrane at high pH suggests that the large fluxes of OH− (or H+ which occur in the alkaline band in photosynthesizing cells are passive.

Journal ArticleDOI
15 Sep 1980
TL;DR: In this paper, a finite-field perturbation method is applied in calculating polarisabilities and polarisability gradients at the CI level for H 2 O, D 2 O and T 2 O at the SCF and CI levels, respectively.
Abstract: Finite-field perturbation methods are applied in calculating polarisabilities and polarisability gradients at the CI level for H 2 O, D 2 O, T 2 O, HDO, HTO and DTO. Dipole moments and dipole moment gradients are also calculated. The resulting Raman scattering activities and infrared absorption intensities are derived and compared with the SCF results in part V along with other theoretical and experimental values. Higher-order moments and polarisability tensor components are calculated for H 2 O at the SCF and CI levels and for CH 4 at the SCF level. The calculated values are compared with the results of other calculations as well as the currently available experimental values.

Journal ArticleDOI
TL;DR: The results described are consistent with the hypothesis that differential sperm and ovum transport in the human fallopian tube isthmus is at least partially determined by the presence or absence of estrogen-dependent luminal mucus.