Showing papers by "University of Melbourne published in 1978"
TL;DR: In this article, the classical electrochemistry of the electrical double layer appropriate to materials that operate as electrodes is shown to be a limiting description for non-electrode materials such as clays, inorganic oxides, insoluble salts, latex colloids and biosurfaces.
424 citations
TL;DR: In this article, the authors trace the development and study of phase transitions from late last century to the present day, with a brief historical sketch and a description of the statistical mechanics of phase transition.
Abstract: This article traces the development and study of phase transitions from late last century to the present day. We begin with a brief historical sketch and a description of the statistical mechanics of phase transitions. Particular attention is given to the modern era which began in 1944 with Onsager's celebrated solution of the two-dimensional Ising model. Points of development since Onsager, which are highlighted in this article, include the study of critical exponents, the scaling hypothesis, realisation of the universality of critical exponents and the recent renormalization group approach to critical phenomena. The basic idea of the renormalization group method, rather than the detailed application of the recipe to particular cases, is stressed and is discussed critically in some detail.
349 citations
TL;DR: Most patients did not achieve the desired amount of salt restriction and a stricter adherence to the diet might have caused further falls in blood-pressure, so salt restriction should be tried before drugs.
322 citations
TL;DR: This result suggests that there is a functional summation of responses of detecting elements at threshold over an area the size of which is reciprocally related to the spatial frequency.
266 citations
TL;DR: In this paper, change in sodium concentration of lateral ventricle CSF caused by intracarotid infusion of hypertonic solutions was measured in conscious sheep, and it was found that 1.6 m urea infusion produced the largest rise of CSF[Na] caused slow antidiuresis and inconsistent small water intake, whereas 2 m glucose, 2 M galactose or 0.15 m NaCl did not.
240 citations
TL;DR: Four fluorescent probes sensitive to the fluidity gradient of the lipid bilayer are described and used to study the phase transitions of dipalmitoyl phosphatidyl-choline.
228 citations
TL;DR: In association with a devastating earthquake in 1960, thousands of debris avalanches, landslides, and mudflows occurred in the Andes of south-central Chile as discussed by the authors, which have profoundly influenced the regional vegetation.
Abstract: In association with a devastating earthquake in 1960, thousands of debris avalanches, landslides, and mudflows occurred in the Andes of south-central Chile. Catastrophic mass movements associated with seismic activity have affected the Andes of south-central Chile several times in the past 400 years and have profoundly influenced the regional vegetation.
224 citations
TL;DR: In this article, the roll-up of an initially plane semi-infinite vortex sheet and the starting flow past an infinite wedge with separation at the wedge apex modelled by a growing vortex sheet are considered.
Abstract: Two problems involving the unsteady motion of two-dimensional vortex sheets are considered. The first is the roll-up of an initially plane semi-infinite vortex sheet while the second is the power-law starting flow past an infinite wedge with separation at the wedge apex modelled by a growing vortex sheet. In both cases well-known similarity solutions are used to transform the time-dependent problem for the sheet motion into an integro-differential equation. Finite-difference numerical solutions to these equations are obtained which give details of the large-scale structure of the rolled-up portion of the sheet. For the semi-infinite sheet good agreement with Kaden's asymptotic spiral solution is obtained. However, for the starting-flow problem distortions in the sheet shape and strength not predicted by the leading-order asymptotic solutions were found to be significant.
171 citations
TL;DR: In this paper, a new model is proposed in which grainboundary sliding (GBS) in a group of grains is accommodated by a grain emerging from the next layer of grains, giving the correct increase in surface area.
Abstract: Current models for obtaining large superplastic flow without change of grain size are two-dimensional; they therefore involve rearrangement of grains without increasing the surface area of the specimen as it deforms. A new model is proposed in which grainboundary sliding (GBS) in a group of grains is accommodated by a grain emerging from the next layer of grains, giving the correct increase in surface area. This also produces curved grain boundaries and there is some rotation of grains involving plastic flow in a zone along grain boundaries (the “mantle”) of predictable width. Grains do not have to be uniform and regular for the process. Characteristic configurations of marker lines are produced by the deformation. All these features are shown to have been observed in the literature. The model does not predict a threshold stress. It can be linked with a previous constitutive equation based on the climb and glide of dislocations in the grain mantles.
157 citations
TL;DR: This paper found that syntactic decisions are made during sentence production and showed that deep clauses are major planning units and that some planning for clauses occurs at the end of the preceding clause, indicating that syntax influences production and were discussed in relation to previous studies of pausing and speech disruption.
129 citations
TL;DR: The effects of clonidine on prejunctional α-adrenoceptors in guinea-pig atria and post-junctive α-ADRs in rabbit aorta were studied and compared.
Abstract: The effects of clonidine on prejunctional α-adrenoceptors in guinea-pig atria and postjunctional α-adrenoceptors in rabbit aorta were studied and compared.
1.
In isolated aortic strips, clonidine acted as a partial agonist on postjunctional α-adrenoceptors, causing smooth muscle contraction. There was no indirect component to the effect of clonidine. The contractile response to clondine was competitively antagonized by phentolamine. Clonidine competitively antagonized the contractile effect of noradrenaline.
2.
In isolated guinea-pig atria, the effect of clonidine on stimulation-induced release of transmitter noradrenaline was inversely dependent on the frequency of electrical stimulation. Using stimulation of 5 pulses (1 Hz for 5 s) and 20 pulses (2 Hz for 10 s), clonidine (10 μM) decreased release; using 50 pulses (2.5 Hz for 20 s) or 90 pulses (3 Hz for 30 s), release was unaffected; using 150 pulses (5 Hz for 30 s), release was enhanced.
3.
The inhibitory effect of clonidine on transmitter release in guinea-pig atria using 5 pulses (1 Hz for 5 s) was concentration-dependent.
4.
The enhancement of release in atria with clonidine (10 μM), using stimulation of 150 pulses (5 Hz for 30 s) was unaffected by cocaine (30 μM) but was reversed by phentolamine (3 μM).
5.
The results in guinea-pig atria are consistent with a partial agonistic effect of clonidine on prejunctional α-adrenoceptors; as an agonist clonidine is approximately 500 times more potent on these receptors than on postjunctional α-adrenoceptors in rabbit aorta.
TL;DR: In this article, isomerization and hydrogenolysis reactions of neopentane and neohexane were studied in the presence of excess hydrogen at 455 to 625 K in a flow reactor over various Pt/silica and Pt/Y-zeolite catalysts having dPt in the range 1 to 20 nm.
TL;DR: In this paper, a sample of Brazilian gem opal of this banded type has been found to contain a band in which there are spheres of two different sizes mixed together, which can be seen in section in electron micrographs of replicas of chips of this specimen.
Abstract: GEM OPALS consist of a regularly ordered array of silica spheres of uniform size1. Generally in any given gem stone the uniformity is maintained throughout the gem, although occasional samples contain bands in which the size varies from band to band. A sample of Brazilian gem opal of this banded type has now been found to contain a band in which there are spheres of two different sizes mixed together. Long-range ordering within this mixture has produced several different types of regular superstructures, which can be seen in section in electron micrographs of replicas of chips of this specimen (Fig. 1).
TL;DR: The factors important in prey selection by fish and the functional significance of vertical migration in both components of the zooplankton are discussed in the light of the changing patterns of fish predation.
Abstract: Diel changes in the composition of crustacean zooplankton and the diets of fish predators from an intertidal eelgrass flat were monitored concurrently. The zooplankton is characterized by two major components. The obligate zooplankters (holoplanktonic calanoid copepods and meroplanktonic decapod larvae) appear to exhibit vertical migration, being present in higher densities near the surface of the water column at night. The facultative zooplankton (amphipods and ostracods) are benthic during the day, but move up into the water column at night. Planktivorous midwaterdwelling fish consume calanoid copepods and decapod larvae during the day and cease feeding or switch their diet to amphipods at night. Benthic-dwelling fish consume some amphipods during both day and night. The factors important in prey selection by fish and the functional significance of vertical migration in both components of the zooplankton are discussed in the light of the changing patterns of fish predation.
TL;DR: In this article, the hydrogen and oxygen adsorption properties of ruthenium surfaces are characterized and shown to be analogous to those of other noble metals, including Pd, Rh, Ir, Pt and Au.
TL;DR: The dopamine content of the canine renal cortex is greater than can be attributed to its presence in noradrenergic axons only and by fluorescence histochemistry numerous catecholamine‐containing axons are seen to be associated with renal cortical arteries and arterioles.
Abstract: — The dopamine (DA) content of the canine renal cortex is greater than can be attributed to its presence in noradrenergic axons only. Most of the excess DA is in the outer part of the cortex. By fluorescence histochemistry numerous catecholamine-containing axons are seen to be associated with renal cortical arteries and arterioles. The fluorescence is abolished following treatment of animals with 6-hydroxydopamine or with reserpine, but is restored to some axons if reserpine is followed by systemic administration of 1-DOPA. This procedure does not restore fluorescence to atrial noradrenergic axons after reserpine-induced depletion. Pretreatment of animals with guanethidine abolishes axonal fluorescence and depletes tissue NA and DA from atrium, but in renal cortex the tissue DA level is little affected and some fluorescent axons remain. These results are discussed in the light of previous functional evidence for dopaminergic autonomic axons in the canine kidney.
TL;DR: In this article, a model of triopoly pricing in the world wheat market is presented, showing that if major exporters continue to be concerned with relative market-shares, the triopoly will reform, stocks will accumulate, and lower prices will prevail; however, prices will be more variable, and possibly higher, than before 1972/73.
Abstract: When the residual demand curve for wheat facing the United States and Canada shifts to the left, or when the exportable surplus of Australia is large, market-shares of these duopolists are reduced. Such circumstances lead to the formation of a market-share triopoly with Australia. The evidence for this proposition is examined and a model of triopoly pricing in the world wheat market is presented. If major exporters continue to be concerned with relative market-shares, the triopoly will reform, stocks will accumulate, and lower prices will prevail; however, prices will be more variable, and possibly higher, than before 1972/73.
TL;DR: A field study of the coexisting, nocturnally active small mammals Sminthopsis crassicaudata and Mus musculus showed that both species occupied nests during the day in groups of up to nine individuals, with nest-sharing common in winter but declined during the breeding period of spring and summer.
Abstract: A field study of the coexisting, nocturnally active small mammals Sminthopsis crassicaudata and Mus musculus showed that both species occupied nests during the day in groups of up to nine individuals. In S. crassicaudata , nest-sharing was common in winter (up to 70% of individuals), but it declined during the breeding period of spring and summer; in M. musculus , nest-sharing remained common throughout the year. Some (about 30%) nest-sharing was interspecific. Diurnal torpor occurred in both species during the colder months, but in fewer than 10% of the individuals observed. Nest-sharing in S. crassicaudata is interpreted as a behavioral energy-conserving device to counter seasonal depression of temperature and food supply; torpor appears to be used only when foraging conditions are particularly poor. A similar explanation may apply to M. musculus .
TL;DR: In this article, the authors reported that the expected narrow zone of coagulation at low salt (i.e. pH and salt concentration) expands into the usual broad coagulations zone at high salt, where the stabilizing effect of Li+ and K+ counter ions is attributed to a hydration barrier at the interface.
Abstract: Coagulation studies of amphoteric latex sols of various i.e.p. values in LiNO3, KNO3 and CsNO3 solutions are reported for a wide range of salt concentrations and pH. Three different techniques for the study of coagulation phenomena all indicate reversibility, in that sols coagulated by pH or salt are able to be redispersed. K+ and Li+ counter ions are able to stabilize these sols in the high salt concentration region. With NO3– and Cs+, the expected narrow zone of coagulation at low salt (i.e.p. coagulation) expands into the usual broad coagulation zone at high salt, where coagulation is observed at all pH values. The stabilizing effect of Li+ and K+ counter ions is attributed to a hydration barrier at the interface.
TL;DR: In the Heathcote greenstone belt of central Australia as mentioned in this paper, meta-andesites and metadacites have been interpreted as the crust of a marginal sea which developed by rifting of thin continental-type crust at the leading edge of a palaeo-Australian plate in the early Cambrian.
TL;DR: By applying small lateral oscillations to a glass tube from which smoke was issuing, perfectly periodic coflowing jets and wake structures were produced at Reynolds numbers of order 300-1000 as discussed by the authors.
Abstract: By applying small lateral oscillations to a glass tube from which smoke was issuing, perfectly periodic coflowing jets and wake structures were produced at Reynolds numbers of order 300-1000. These structures remained coherent over long streamwise distances and appeared to be perfectly frozen when viewed under stroboscopic light which was synchronized with the disturbing oscillation. By the use of strobing laser beams, longitudinal sections of the structures were photographed and an account of the geometry of these structures is reported.When the tube was unforced, similar structures occurred but they modulated in scale and frequency, and their orientation was random.A classification of structures is presented and examples are demonstrated in naturally occurring situations such as smoke from a cigarette, the wake behind a three-dimensional blunt body, and the high Reynolds number flow in a plume from a chimney. It is suggested that an examination of these structures may give some insight into the large-scale motion in fully turbulent flow.
01 Jan 1978
TL;DR: The evidence that CNPase is a true myelin component is presented herein and there is strong evidence that cholesterol ester hydrol enzyme is a myelin enzyme.
Abstract: 2′,3′-Cyclic nucleotide 3′-phosphodiesterase (CNPase, EC 3.1.4.37*) has been widely used for several years as a marker for the presence of myelin in the central nervous system, but no review is available on its application and limitation as a marker enzyme and there is no information on its role in myelin. This was the first enzyme to be unequivocally characterized as a myelin component; previously it had been thought that myelin was enzymatically inert (Adams et al., 1963). Several other enzymes have now been proposed as being myelin-associated (for references see Carnegie and Sims, 1977; Norton, 1977), but evidence of myelin association is incomplete for some of these, such as protein kinase (Carnegie et al., 1974; Miyamoto and Kakiuchi, 1974; Steck and Appel, 1974; Miyamoto, 1976) and phosphoprotein phosphatase (Miyamoto and Kakiuchi, 1975). In the case of nonspecific esterase (Keoppen et al., 1969; Frey et al., 1971; Rumsby et al., 1973; Mitzen et al., 1974) and arylamidase (Banik and Davison, 1969; Riekkinen and Clausen, 1970; Riekkinen and Rumsby, 1972; Mezei and Palmer, 1974) there is some controversy as to whether the enzymes are truly myelin-associated or are bound as an artifact of the preparation of myelin. There is strong evidence that cholesterol ester hydrolase is a myelin enzyme (Eto and Suzuki, 1973). The evidence that CNPase is a true myelin component is presented herein.
TL;DR: It was concluded that RuBPCase was being degraded more rapidly than the other proteins, since the proteinase exhibited maximum activity during the slowest period ofprotein loss (II), and was declining in activity while the rate of protein loss remained stable during the third and final period of total protein loss.
Abstract: In crude extracts from the primary leaf of wheat seedlings, Triticum aestivum L., cv. Olympic, maximum proteinase activity, as determined by measuring the rate of release of amino nitrogen from ribulose-bisphosphate carboxylase (RuBPCase), was found to be obtained only when EDTA and L-cysteine were included in the extraction buffer. Highest proteinase activity was obtained by grinding at pH 6.8, although the level of activity was similar in the pH range 5.6 to 8.0; this range also coincided with maximum extractability of protein. The lower amount of RuBPCase degrading proteinase extracted at low pH was not due to an effect of pH on enzyme stability. The optimum temperature of reaction was 50° C and reaction rates were linear for at least 120 min at this temperature. In the absence of substrate the proteinase was found to be very sensitive to temperatures above 30° C, with even short exposures causing rapid loss of activity. The relation between assay pH and RuBPCase degradation indicated that degradation was restricted to the acid proteinase group of enzymes, with a pH optimum of 4.8, and no detectable activity at a pH greater than 6.4. The levels of extractable RuBPCase proteinase exhibited a distinct diurnal variation, with activity increasing during the latter part of the light period and then declining once the lights were turned off. The effect of leaf age on the level of RuBPCase, RuBPCase proteinase and total soluble protein was investigated. Maximum RuBPCase activity occurred 9 days after sowing as did soluble protein. After the maximum level was obtained, the pattern of total soluble protein was shown to be characterised by three distinct periods of protein loss: I (day 9-13) 125 ng leaf(-1) day(-1); II (day 15-27) 11 ng leaf(-1) day(-1); III (day 29-49) 22 ng leaf(-1) day(-1). Comparison of the pattern of RuBPCase activity and total protein suggest that the loss of RuBPCase may be largely responsible for the high rate of protein loss during period I. Proteinase activity increased sharply during the period of most rapid loss of RuBPCase activity, and because the specific activity of RuBPCase also declined, we concluded that RuBPCase was being degraded more rapidly than the other proteins. Once the majority of the RuBPCase was lost, there did not appear to be a direct relation between RuBPCase proteinase activity and rate of total soluble protein loss, since the proteinase exhibited maximum activity during the slowest period of protein loss (II), and was declining in activity while the rate of protein loss remained stable during the third and final period of total protein loss.
TL;DR: It is proposed that the NEBs are receptors monitoring intrapulmonary PCO2 and so leading to modulation of activity in afferent nerve fibres (type containing agranular vesicles) and the presence of NEBs solely with an adrenergic (efferent) innervation poses a problem with this interpretation.
Abstract: Neuroepithelial bodies (NEB) were identified in the lung of Bufo marinus. The characteristics of the cells and their innervation were studied with electron and fluorescence microscopy before and after close vagosympathetic denervation. The bodies consist of low columnar cells which rest on the epithelial basal lamina. The majority of the cells do not reach the lumen of the lung (basal cells); the few which do (apical cells) are bordered by microvilli and possess a single cilium. The neuroepithelial cell cytoplasm contains a variety of organelles the most characteristic of which are dense cored vesicles. Microspectrofluorometry and electron microscopic cytochemistry indicate significant quantities of 5-hydroxytryptamine in these cells. The neuroepithelial bodies could be divided into three groups on the basis of their innervation: 1) About 60% of the NEBs are innervated solely by nerve fibres containing agranular vesicles which form reciprocal synapses; 2) about 20% are innervated solely by adrenergic nerve fibres which form distinct synaptic contacts; and 3) the remaining 20% are innervated by both types of nerve fibres. It is proposed that the NEBs are receptors monitoring intrapulmonary PCO
2 and so leading to modulation of activity in afferent nerve fibres (type containing agranular vesicles). The presence of NEBs solely with an adrenergic (efferent) innervation poses a problem with this interpretation.
TL;DR: In this article, the detection of lines in the gas phase EPR spectrum of the HO 2 radical at a frequency of 9 GHz is reported, and the measurements are combined with the data from the far infrared LMR spectrum and with the zero-field frequencies in the microwave spectrum and fitted to determine a very nearly complete set of ground state parameters.
TL;DR: The relaxin conformation is rigorously examined by a computer graphics system and it is found possible to accommodate the relaxin sequence within the insulin main-chain geometry.
Abstract: THE sequence of the ovarian peptide, relaxin, has recently been reported1,2 and the observation1 that it can be accommodated into the insulin fold has been discussed3,4. Only 11 residues, including the cystines, are common to insulin and relaxin (Fig. 1), but the probable identity of the cystine pairings and the preservation of the hydrophobic character of buried residues suggests some structural homology between the two hormones. The extent of sequence changes and the remote relationship between the corpus luteum and the pancreas, the respective sources of relaxin and insulin, makes homology of the two hormones most interesting. We have therefore rigorously examined the relaxin conformation by a computer graphics system and found it possible to accommodate the relaxin sequence within the insulin main-chain geometry.
TL;DR: Yohimbine and some of its isomers are relatively potent antagonists of 5HT on the rat isolated fundus preparation and their potency may be related to their ability to produce behavioral and cardiovascular effects in man and dogs.
TL;DR: A more intensive study of this population where samples have been taken from inside and outside the cellar during both vintage and non-vintage periods over two years found no relationship between the distributions of tolerance and of Adh phenotypes although tolerance can be directly related to the selective effect of alcohol in the adult environment.
Abstract: A DETAILED understanding of the balanced selective forces maintaining the alcohol dehydrogenase (Adh) polymorphism of Drosophila melanogaster will come about when the properties of the enzymatic products of the genotypes can be directly related to selective forces acting on the phenotypes. This approach has been discussed by Clarke1, but it was Gibson2 who first probed the Adh locus in this way when he successfully selected for a specific allele using high levels of ethanol. Enzyme activity of AdhF / AdhF, AdhF / Adhs and Adhs / Adhs genotypes on specific alcohol substrates can generally be related to differential survival and changes in gene frequency in population cages1–8. Briscoe, Robertson and Malpica3 showed a higher AdhF frequency in a Spanish wine cellar population than at a neighbouring site and explained this by the relative ethanol resistance of adult Adh phenotypes. In a study of an Australian winery population McKenzie and Parsons9 also observed differences in ethanol tolerance between the cellar and peripheral sections of the population but they found no correlation between tolerance and Adh frequencies. We now report a more intensive study of this population where samples have been taken from inside and outside the cellar during both vintage and non-vintage periods over two years. In this population a different adaptive system is operating. Unlike Briscoe et al., we found no relationship between the distributions of tolerance and of Adh phenotypes although tolerance can be directly related to the selective effect of alcohol in the adult environment.