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Showing papers by "University of Sydney published in 1974"


Journal ArticleDOI
TL;DR: In this paper, a theory of the flow of people along a channel which may be of variable width, or have a partial blockage in it is presented in kinetic form to facilitate comparison with observation.

383 citations


Journal ArticleDOI
TL;DR: Phytoplankton pigments at a coastal station off Sydney, Australia, were studied by cellulose thinlayer chromatography and determined the position of patches of copepods, diatoms, green algae and dinoflagellates in the water column by noting the presence of definitive pigments on the chromatograms.
Abstract: Phytoplankton pigments at a coastal station off Sydney, Australia, were studied by cellulose thinlayer chromatography. The chromatographic procedure distinguished chlorophylls a, b and c, chlorophyllide a, pheophytin a and pheophorbide a, and the major carotenoids carotene, astaxanthin, fucoxanthin, peridinin, diadinoxanthin and neoxanthin. Chlorophyllide a and pheophorbide a were the most significant chlorophyll-a degradation products in the water column, chlorophyllide a coming from chlorophyllase activity of senescent diatoms, and pheophorbide a from faecal pellets of copepods. Chlorophyll c occurred in every sample, even where there was no trace of chlorophyll a. Because of the greater chemical and biological stability of chlorophyll c compared to chlorophyll a, high chlorophyll c:a ratios result from a large proportion of senescent or detrital material in the samples. Determining the position of patches of copepods, diatoms, green algae and dinoflagellates in the water column was easily done by noting the presence of definitive pigments on the chromatograms.

268 citations


Journal ArticleDOI
TL;DR: The general conclusion from the model is that there is an effective limit to niche overlap in the real world, and that this limit is insensitive to the degree of environmental fluctuation, unless it be very severe, which seems in accord with an increasing body of field data.

215 citations


Journal ArticleDOI
TL;DR: It is shown that dispersal may increase the persistence time of a population by several orders of magnitude.
Abstract: The hypothesis that dispersal in a heterogeneous environment can be an important factor in population stability is examined. It is shown that dispersal may increase the persistence time of a population by several orders of magnitude.

181 citations


Journal ArticleDOI
TL;DR: This paper presents a technique which permits comparison of the amount of resource overlap observed in a given case with that expected for a group of similar species co-existing in the absence of competitive interactions, and can be evaluated the likelihood of competitive processes being important in the situation under study.
Abstract: When several species co-exist, the amount by which they overlap in their use of resources is a measure of their similarity to one another. As such, resource overlap does not measure the amount of competition among them. When the resources are not limiting to population growth, patterns of resource use may overlap to any degree. However, when the species are frequently in competition for their resources, natural selection will favor the separation of their requirements, and the amount of resource overlap will be reduced.This paper presents a technique which permits comparison of the amount of resource overlap observed in a given case with that expected for a group of similar species co-existing in the absence of competitive interactions. From this comparison can be evaluated the likelihood of competitive processes being important in the situation under study.

176 citations


Journal ArticleDOI
TL;DR: In this article, it was shown that the observed precursors to PKIKP can be explained by random variations of about one percent having a correlation distance of about 30 km in this layer.

173 citations


Journal ArticleDOI
TL;DR: The qualitative properties of the model can be understood within the framework of a more general mathematical model and it is shown that the type of dispersal pattern and the number of subpopulations may influence the persistence of a population without affecting the mean subpopulation size.
Abstract: In a previous paper (Roff, 1974) a simulation model was presented demonstrating the importance of dispersal in a spatially heterogeneous environment. In the present paper this model is analysed in detail. It is shown that the qualitative properties of the model can be understood within the framework of a more general mathematical model. The effect of dispersal in a heterogeneous environment is to reduce the variance in the environmental fluctuations. How the subpopulations are connected with respect to dispersers may be the primary factor in determining the change in population size with changes in environmental fluctuations. Both the type of dispersal pattern and the number of subpopulations may influence the persistence of a population without affecting the mean subpopulation size. Finally, it is noted that the “value” of a dispersal pattern changes with changes in parameter values and a shift from one parameter value to another may lead to a qualitative change in the type of dispersal pattern “favoured”.

139 citations


Journal ArticleDOI
TL;DR: Variations in the form and number of root canals are greater in the mesial roots and in some specimens the mesia root was divided into two and in the main variations show multiple canals with subdivisions and communications frequently with one common apical foramen.
Abstract: — Variations in the form and number of root canals are greater in the mesial roots and in some specimens the mesial root was divided into two. The main variations show multiple canals with subdivisions and communications frequently with one common apical foramen. Little difference was noted between root canals in young teeth and those in heavily worn mature teeth.

128 citations


Journal ArticleDOI
01 Jun 1974-Genetics
TL;DR: Genotypic frequencies were analysed for two years in a permanent population of the cladoceran crustacean, Daphnia magna, which was polymorphic for an esterase and for malate dehydrogenase, and non-random associations between genotypes at structural and regulatory loci showed temporal changes.
Abstract: In permanent habitats populations of the cyclical parthenogen, Daphnia magna, reproduce by continued parthenogenesis and are subject to only sporadic sexual recruitment. The genetic effects of this breeding system have been investigated by analyzing allozyme frequencies in thirteen populations of D. magna.—Genotypic frequencies at polymorphic loci characteristically deviated markedly from Hardy-Weinberg proportions and gametic phase imbalance between loci was frequent. Genotypic frequencies were subject to violent, selectively determined oscillations over short periods of time. These observations suggest that permanent populations of D. magna ordinarily consist of a limited number of highly structured genotypes. The adaptational advantages offered by such structuring may have been a major selective factor favoring the evolution of cyclical parthenogenesis.

127 citations


Journal ArticleDOI
TL;DR: Germinating seeds of lucerne, guar, carob and soybean initially depleted raffinose series oligosaccharides and then galactomannan, accompanied by a rapid increase and then a decrease in α-galactosidase levels.

125 citations


Journal ArticleDOI
TL;DR: Analysis of patterns of use of space as shown by the antecedent and subsequent histories of sites chosen by 43 new colonists, and sites vacated through the loss of 34 residents on the rubble patches suggests that the 3 species do not differ in their requirements for space on rubble patches, and that they are in competition for a short supply of such space.
Abstract: There exists on Heron Reef, at the southern end of the Great Barrier Reef, an 8-species guild of ecologically very similar, territorial, herbivorous reef fishes. All individuals of these species maintain territories on rubble substrata throughout juvenile and adult life. Territories are defended from all other guild members. Three rubble patches, each containing residents of 3 guild species: Pomacentrus apicalis, P. wardi, and Abudafduf lachrymatus, have been monitored for 12 to 18 months. This paper examines the patterns of use of space as shown by the antecedent and subsequent histories of sites chosen by 43 new colonists, and sites vacated through the loss of 34 residents on the rubble patches. In addition, variation through time is examined in the total amount of space held in territories on each rubble patch. The 3 species show similar preferences for space as colonists, although adult and juvenile colonists behave differently. Numbers of colonists detected on rubble patches are not proportional to the resident populations of the 3 species. Residents of the 3 species are equal in their abilities to enter spaces vacated through mortality, although they differ slightly in methods used to enter sites. They do not respond preferentially to sites previously occupied by any particular species. P. wardi shows a higher rate of mortality than the other species, and residents of this species are more often dislodged by new colonists. The total amount of space held on any rubble patch did not vary during the year from September, 1972 to October, 1973. The data are interpreted as supporting the hypothesis that the 3 species do not differ in their requirements for space on rubble patches, and that they are in competition for a short supply of such space. Differences exist in their strategies for obtaining and holding such space. These differences are important for explaining the continued presence of P. wardi on rubble patches. P. apicalis and a. lachrymatus are both specialists in holding territories on the upper reef slope. No differences have been detected in their requirements or competitive abilities. P. wardi is a fugitive species on the upper reef slope, coexisting because it maintains a refuge from competition by occupying some un-preferred sites off rubble patches.

Journal ArticleDOI
TL;DR: High dose of clonidine i.v. enhanced single aortic baroreceptor fibre discharge at a given MAP in anaesthetized animals, but there was no effect at low dose; at high dose these effects are reinforced by peripheralbaroreceptor resetting.

Journal ArticleDOI
TL;DR: In this article, a discussion of the relationship between the stresses in an ideal sphere and the reported behaviour of real particle aggregates is presented. And the strength of coagula and flocculated material is highly dependent on the size to which the aggregate has grown.

Journal ArticleDOI
TL;DR: The stabilizing effect observed depends on environmental variation and is not produced by diffusion alone, so the conclusions are fairly independent of the details of the model.


Journal ArticleDOI
TL;DR: A 61-year-old woman who had proximal muscle weakness since 38 years of age showed widespread muscle wasting, absent tendon reflexes, and electromyographic findings of a neuropathy, consistent with a generalized disorder of carnitine metabolism that may involve carnitines transport across cell membranes.
Abstract: A 61-year-old woman had proximal muscle weakness since 38 years of age. Eventually, her distal muscles became affected and she showed widespread muscle wasting, absent tendon reflexes, and electromyographic findings of a neuropathy. On biopsy, there was a lipid storage myopathy, lipid-containing vacuoles in leukocytes, and vacuoles in Schwann cells. The muscle carnitine level was abnormally low, but the serum carnitine level was normal. The findings are consistent with a generalized disorder of carnitine metabolism that may involve carnitine transport across cell membranes.

Journal ArticleDOI
TL;DR: The SEM permitted in situ observation of these deposits, which allowed the crystal structure and the organization of the crystalline deposits to be observed, and these deposits can be grouped into three major groups according to the organization and site of deposition of the crystals.
Abstract: The calcium carbonate deposits of Cyanophyte, Charophyte, Chlorophyte, Phaeophyte and Rhodophyte algae have been studied with the scanning electron microscope. The SEM permitted in situ observation of these deposits, which allowed the crystal structure and the organization of the crystalline deposits to be observed. The CaCO3 was deposited either as argonite or calcite. The CaCO3 depositing algae can be grouped into three major groups according to the organization and site of deposition of the crystals. The first group (Group A) exhibits extreme organization and the CaCO3 is deposited on an organic matrix within the cell. The deposits of algae of Group B are formed within the cell wall or mucilage and also show some organization. The deposits of algae of Group C are completely extracellular and exhibit no organization.

Journal ArticleDOI
TL;DR: Pregnant guinea-pigs exposed to an environmental temperature of 42·0–42·5 °C for 1 h on day 21 of gestation and their embryos were removed at periods from 45 min of heating to 48 h following exposure, indicating blocks to the cell generation cycle before prophase and in metaphase.
Abstract: Pregnant guinea-pigs were exposed to an environmental temperature of 42·0–42·5 °C for 1 h on day 21 of gestation. Their embryos were removed at periods from 45 min of heating to 48 h following exposure. Histological preparations of embryos showed clumping of nuclear chromatin and subsequent death of cells which were at about the stage of mitosis. Affected cells were particularly numerous in the central nervous system. Further mitotic activity was inhibited for 6–8 h. Squash preparations of the telencephalon at 1 h after heating showed an increase from 3 to 86 % in the number of mitotic cells showing damage in the form of nuclear clumping; this number fell progressively to 30% by 24 h after heating. The proportion of cells in various stages of mitosis changed considerably at 1–8 h after heating, but had returned to pre-heating values by 24 h. The proportion of cells in prophase fell markedly, while the proportion of metaphase cells was doubled at 4 h after heating, indicating blocks to the cell generation cycle before prophase and in metaphase.

Journal ArticleDOI
TL;DR: From the virtual absence of chiasmata in metaphase I stages of the haploids it is inferred that crossing over requires a more precise DNA alignment than is provided by synaptonemal complex formation alone.
Abstract: Normal synaptonemal complexes have been found in haploid barley meiotic prophase at stages equivalent to pachytene in diploids. Reconstructions of serially sectioned nuclei have shown that up to 60% of the haploid chromosomes may pair in either intra- or interchromosomal associations. The extent and nature of the synaptonemal complex formation suggest that the chromosome pairing is non-homologous. From the virtual absence of chiasmata in metaphase I stages of the haploids it is inferred that crossing over requires a more precise DNA alignment than is provided by synaptonemal complex formation alone.

Journal ArticleDOI
01 Dec 1974-Heredity
TL;DR: It is suggested that populations of Daphnia magna consist of a limited number of ecologically differentiated clones.
Abstract: Large changes in genotypic frequencies have been observed over a 2-year period in a population of Daphnia magna polymorphic for two alleles of malate dehydrogenase. These changes were not the result of migration or random drift. Genotypic differences in both parthogenetic and sexual egg production were observed. There was a strong correlation between the parthogenetic fecundities of the genotypes and their frequencies 1 month later. Sexual egg production was enhanced among low fitness genotypes. These observations strongly suggest that populations of Daphnia magna consist of a limited number of ecologically differentiated clones.

Journal ArticleDOI
TL;DR: It was concluded that keyboard design and ... every part of the upper limb which was a site of symptoms in operating was more often affected on the right side than the left, and part of limb affected was usually associated with some adverse operating posture of that region.
Abstract: A trial of physiotherapy for muscle incoordination and aching (occupational cramp and myalgia) in teleprinter operators revealed an association between these types of symptoms of operating difficulty and disadvantageous operating postures, which in turn were thought to be related to keyboard layout. The purpose of this paper is to analyse the relationship between posture and symptoms. Subjects of symptoms and unaffected operators were interviewed, tested in various ways, and observed in teleprinter operating. Adverse operating postures of arm and hand were, with the exception of two types of posture, more often right than left sided (when they were not bilateral) and commoner in subjects than controls. Every part of the upper limb which was a site of symptoms in operating was more often affected on the right side than the left (when not bilaterally affected). Part of limb affected was usually associated with some adverse operating posture of that region. It was concluded that keyboard design and ...

Journal ArticleDOI
TL;DR: The administration of δ9-THC significantly potentiated the anticonvulsant effectiveness of phenytoin against electroshock seizures and this effect was further potentiated by the concurrent administration of CBD.
Abstract: The anticonvulsant activity of orally administered δ9-tetrahydrocannabinol (δ9-THC), δ8-THC, cannabidiol (CBD) and cannabinol (CBN) was tested in mice utilizing electroshock and chemoshock methods. In doses tested δ9-THC afforded no protection to mice from chemoshock seizures and was effective against electroshock only in high doses (160–200 mg/kg). CBD and CBN (150–200 mg/kg) were without effect in both tests.

Journal ArticleDOI
TL;DR: The cardiac glycosides act on the failing heart to produce a marked inotropic effect, and for this purpose they are unrivaled by any synthetic or semisynthetic substitute.

Journal ArticleDOI
01 Jan 1974
TL;DR: In this article, the effects of the in-plane deformations on lateral buckling of determinate beams and cantilevers, beam columns, continuous beams, and portal frames are investigated.
Abstract: In the classical analysis of the flexural-torsional buckling of beams, beam columns and rigid-jointed plane frames, it is assumed that the major axis rigidity is very large, so that the small in-plane deformations can be neglected. The effects of the in-plane deformations on lateral buckling are investigated in this paper for determinate beams and cantilevers, beam columns, continuous beams, and portal frames. This is done by deriving more accurate governing differential equations, and by obtaining closed form or numerical solutions of these. The results obtained indicate that the classical critical loads or moments are generally conservative, except for the members which are highly restrained laterally. The sources of error in the classical analysis are also studied, and their effects are demonstrated. The results of experiments on small scale beams, which are in close agreement with the theoretical predictions, are reported.

Journal ArticleDOI
TL;DR: In this paper, the warping and distortion at the ends of members of doubly symmetric I-section are studied theoretically and experimentally, and the increases in the resistances to warping due to web stiffeners or by web stiffener or by additional webs are investigated.
Abstract: The warping and distortion at the ends of members of doubly symmetric I-section are studied theoretically and experimentally, and the increases in the resistances to warping and distortion caused by web stiffeners or by web stiffeners or by additional webs are investigated. Analytical expressions are given for the warping and distortion restraint stiffnesses of single members. The behavior of rigid angle joints between I-section members is then studied, and it is deduced that the warping and distortion at a joint are interdependent. A finite element model is proposed, and this is used to determine the effects of member length, joint angle, and stiffener arrangement on the restraint against end warping. Simple approximations are obtained for estimating the warping restraints, and these are shown to be conservative.

Journal ArticleDOI
TL;DR: With these wheat‐meat meal diets biotin concentrations of up to 120 μg/kg diet were associated with FLKS mortality but when the biotin concentration was raised to 145 μg/, growth was maximised and mortality due to FLKS eliminated and there was evidence that the concentration of biotin levels in breeder diets may affect the incidence of FLKS in their progeny.
Abstract: Synopsis Experiments were conducted with caged broilers using diets containing 79% wheat and 20% meat meal. In the first experiment an outbreak of fatty liver and kidney syndrome (FLKS) occurred. Mortality was prevented, and subsequent growth rate was improved, by a single oral dose of a mixture of water‐soluble vitamins. A similar but less concentrated mixture successfully controlled a field outbreak of FLKS and lowered overall mortality. In further experiments, it was shown that a deficiency of biotin was the main contributing factor in causing FLKS. With these wheat‐meat meal diets biotin concentrations of up to 120 μg/kg diet were associated with FLKS mortality but when the biotin concentration was raised to 145 μg/kg diet growth was maximised and mortality due to FLKS eliminated. There was also evidence that the concentration of biotin levels in breeder diets may affect the incidence of FLKS in their progeny.

Journal ArticleDOI
TL;DR: Two separate episodes of an encephalitis occurred in dogs after the administration of a few batches of a combined, live attenuated distemper/hepatitis virus vaccine, with the presence of nucleocapsid, indistinguishable from that seen indistemper infection.
Abstract: Two separate episodes of an encephalitis occurred in dogs after the administration of a few batches of a combined, live attenuated distemper/hepatitis virus vaccine. The lesions consisted of eosinophilic intranuclear and intracytoplasmic inclusions in large neurones, together with a nonsuppurative encephalitis and malacia of the ventral pontine gray matter. The presence of nucleocapsid, indistinguishable from that seen in distemper infection, indicates that a distemper or distemper-like virus was directly involved.

Journal ArticleDOI
TL;DR: In this paper, a waveguide method of providing a selective surface for solar energy applications is described, and some measurements of a vacuum-deposited mesh are given, and elementary theory indicates that ratios of solar absorptance to thermal emittance of 30:1 should be possible at temperatures of about 200°C.

Journal ArticleDOI
TL;DR: In this article, a solution to the problem of the consolidation of a clay layer resting on a rough rigid base and subject to general surface loading is given, evaluated for the particular cases of a uniformly loaded strip, circle and square for a variety of Poisson's ratio's.

Journal ArticleDOI
TL;DR: Intense interest in the importance of local itnmunity as a distinct part of the body's immune system has developed in the last decade but isolated reports in the older literature clearly established the concept of local as distinct from humoral immunity.
Abstract: Intense interest in the importance of local itnmunity as a distinct part of the body's immune system has developed in the last decade. However, isolated reports in the older literature clearly established the concept of local as distinct from humoral immunity. Work conducted early in this century quite convincingly demonstrated that oral administration of killed or living cultures of Shigella elicited specific intestinal resistance to infection, whereas systemic immunity was virtually absent (Davies 1922, Besredka 1927). The important studies of Burrows and his colleagues (Burrows et al. 1947, Burrows & Havens 1948) who worked with Vibrio cholerae in guinea pigs emphasized the separation of the local and humoral immune systems and demonstrated that resistance to oral challenge with living Vibrio cholerae organisms was correlated with levels of copro-antibody. Thus for the first time attention was drawn to the association between protection and the level of local antibody. Other studies on the genital tract and mammary gland also suggested that a separate local immune system existed in these tissues although the evidence, especially with regard to the mammary gland, was equivocal.