Showing papers by "University of Sydney published in 1983"

Computational Galerkin Methods

Abstract: For many of the examples given in chapter 1, acceptable accuracy, and often very high accuracy, could be achieved with less than five terms in the trial solution. The advent of computers has brought both a demand for solutions of high accuracy and an interest in problems that are inherently more complex than the simple examples given in section 1.2.

What is a law of nature

Abstract: Acknowledgements Part I. A Critique of the Regularity Theory: 1. Introductory 2. Critique of the regularity theory (1): the problem of accidental uniformities 3. Critique of the regularity theory (2) 4. Critique of the regularity theory (3) Part II. Laws of Nature as Relations Between Universals: 6. Laws of nature as relations between universals 7. Functional laws 8. Unsubstantiated laws 9. Probabilistic laws 10. Further considerations concerning the form of laws 11. Are the laws of nature necessary or contingent? Conclusions Index.

The Separation of Madagascar and Africa

Abstract: Identification of a sequence of east-west trending magnetic anomalies of Mesozoic age in the western Somali Basin helps define the position of Madagascar in the Gondwana reconstruction. The anomalies are symmetric about ancient ridge segments and are flanked to the north and south by the Jurassic magnetic quiet zone. The motion of Madagascar relative to Africa was from the north and began in the middle Jurassic, about the same time as the initial breakup of Gondwanaland. Sea-floor spreading ceased when Madagascar assumed its present position in the Early Cretaceous.

Experimental analyses of the structure and dynamics of mid-shore rocky intertidal communities in New South Wales.

Abstract: At mid-shore levels on rocky shores in New South Wales, grazing gastropods are the dominant species in sheltered areas. Where wave-exposure is great, barnacles occupy most of the space. At intermediate levels of waveexposure, there are mixtures of grazing gastropods and barnacles, and the patterns of occupancy of space, and structure of the community change from time to time. The major species found in these areas are the coronuloid barnacle Tesseropora rosea, the patellid limpet Cellana tramoserica, the smaller acmaeid limpet, Patelloida latistrigata, which is mostly confined amongst barnacles, and the predatory whelk Morula marginalba. The roles of each of these species in determining the structure and persistence of intertidal communities were investigated by experimental manipulations of the densities of each of these organisms. In most experiments, a range of densities of limpets and barnacles was used, rather than the simple removal of all of one species.

Some teratogenic properties of ethanol and acetaldehyde in C57BL/6J mice: implications for the study of the fetal alcohol syndrome

Abstract: To investigate the teratogenic effect of acute alcohol exposure, pregnant C57BL/6J mice were exposed to 25% ethanol (either two doses of 2.9g/kg or one dose 5.8g/kg) during the organogenic period either by intraperitoneal injections or by intubation. The incidence of malformations varied according to (1) the stage of embryonic development at the time of exposure, (2) the route of administration of the alcohol, and (3) the amount of alcohol given and the time period over which it was administered. Oral doses of alcohol were teratogenic although less so than the same dose given intraperitoneally, and two intraperitoneal doses four hours apart produced significantly more malformation than the same two doses six hours apart. The primary metabolite of alcohol, acetaldehyde, was also investigated for its teratogenicity. It was found that one or two doses of four percent acetaldehyde (0.32g/kg), administered intraperitoneally were teratogenic. A further attempt was made to raise blood acetaldehyde levels by exposing mice to disulfiram, an inhibitor of acetaldehyde dehydrogenase, prior to administration of alcohol. The disulfiram pretreatment did not increase the malformation rate. Treatment with alcohol on day 7 or 8 caused a variety of facial abnormalities, some of which were comparable to those seen in children with fetal alcohol syndrome. Exposure on day 9 or 10 resulted in limb defects. The results suggest that one or more episodes of heavy maternal drinking at critical periods in pregnancy may severely damage the embryo and may produce many features of the fetal alcohol syndrome.

Increased rates of genetic change in dairy cattle by embryo transfer and splitting

Abstract: Possibilities for increased rates of genetic change in dairy cattle through embryo transfer and embryo splitting are examined, using the multiple ovulation and embryo transfer systems previously proposed. These involve embryo transfer from 1-year-old females (juvenile scheme, generation interval 1·8 years) and from females after 1 lactation (adult scheme, generation interval 3·7 years), with use of males at similar ages. Though selection is less accurate than in conventional progeny testing, the annual rate of genetic improvement can be increased, and even doubled. If the number of transfers is restricted andm the inbreeding rate is limiting, the adult scheme for both sexes is preferred. A scheme with 1 024 transfers per year and 512 females milk-recorded per year will sustain a rate of genetic improvement some 30% above that possible by a conventional national progeny-testing programme. Because of the relatively small number of animals involved, it is argued that greater control over recording, breeding and selection should be possible, leading to a larger proportion of the possible genetic gains being realized in practice. Other advantages, and disadvantages of these systems, and their integration in dairy cattle improvement are discussed.

Tropical Territorial Damselfishses: Is Density Limited by Aggression or Recruitment?

Abstract: The spatial distributions of two common damselfishes, Potnacentrus wvardi and P. flavicauda, suggest that they compete for common resources within lagoons of the southern Great Barrier Reef. Both fishes are herbivores that defend territories on rocky substrata covered with shallow water, but are segregated by microhabitat. When young P. flavicauda recruit into the habitat where P. w'ardi are most numerous, they have lower persistence than counterparts on reefs where conspecifics predominate. Several experiments were done, using as replicates the large patch reefs populated by P. wiardi, to determine what effects territory-holding individuals have on the distribution and abundance of conspecifics, P. flatvicauda, and other grazing fishes. Total and selective removal of the numerically dominant P. wardi revealed that these reefs are mostly repopulated by larval fishes (recruitment), rather than by already recruited fishes (immigra- tion). P. wardi are the most frequent recruits. The removals also showed that resident P. wtnardi do not determine the numbers of nonspecific larvae invading their territories, and do not reduce their survival after recruitment (at least for 300-400 d). They do determine the growth of such juveniles. Despite this interaction, there was no evidence that either density or biomass is usually regulated in these populations. Both measures vary greatly among replicate reefs. The lack of numerical equilib- rium, within the study period, was caused by a patchy and limiting supply of larval recruits. Manipulations also showed that resident P. bxardi do not limit the recruitment or reduce the postrecruitment survival of P. flavicauda on large patch reefs. An unknown density-independent cause is implicated in the observed habitat segregation and in the failure of P. flavicauda to reach breeding size on such reefs. The removal of P. wardi produced different results for the fish grazers from other families, de- pending upon their feeding strategy. For example, solitary acanthurids concentrated their grazing activities on reefs with fewer damselfishes, but a schooling parrotfish did not. The outcomes of these perturbations support a nonequilibrial view of reef fish communities, rather than hypotheses that emphasize the importance of competition among populations usually at carrying capacity.

Length of larval life in twelve families of fishes at “One Tree Lagoon”, Great Barrier Reef, Australia

Abstract: The length of larval life in some coral reef fishes was estimated from the number of growth increments in the otoliths of newly settled fishes. We examined 210 individuals comprising 38 species and 5 unidentified taxa, and belonging to 12 families. During 2 successive austral summers (1976–1977 and 1978–1979), specimens were collected from the lagoon at One Tree Reef, Great Barrier Reef, Australia. By assuming that growth increments in otoliths are laid down on a regular daily cycle commencing near the time of hatching, we calculated typical ages ranging from 3 to 6 wk with a minimum of just over 2 wk and a maximum of 12 wk. The otoliths also contain distinctive microstructural features which can serve as approximate temporal markers for the change from the postlarval to juvenile life stage.

Physical Variability of Sandy Beaches

Abstract: This paper examines sandy beach types that exist in wave environments ranging from low ( 2.5m). Three basic beach types — reflective, intermediate and dissipative, composed of six beach states have been identified. Each beach state can be classified by its wave-sediment characteristics. In addition, the paper discusses the environmental conditions required to produce each beach state, and their associated morphology; surfzone circulation and dynamics; mode and scale of sediment exchange and erosion; and spatial and temporal variability.

Variation in leaf toughness and phenolic content among five species of Australian rain forest trees

Abstract: Several leaf characteristics, including toughness and total phenols and condensed tannins, were measured in Australian rain forest leaves of different ages and related to observed herbivory rates. In most cases, toughness and chemical toxicity increased as leaves aged, and corresponding insect grazing decreased. Herbivory losses ranged from 4.8% to 32.5% leaf area losses, and were more positively correlated with toughness than with phenolics. It is suggested that a suite of factors, including physical and chemical characteristics of leaves as well as spatial and temporal factors, interact to create variation in grazing intensities.

Light-harvesting processes in algae

Abstract: Publisher Summary The importance of algae, both as a contribution to the understanding of living things and in practical terms, hardly needs stressing today. Despite the previous emphasis on photosynthesis research in land plants there is now a large corpus of work on algae. This chapter intends to bring much of the dispersed literature together, so as to achieve an integrated framework from which conclusions can be drawn to further stimulate research. Organisms from the borderline of groups loosely called prokaryotes, plants, and animals have been discussed along with how the majority of algae are influenced by the light climate properties. The structure and function of the photosynthetic membrane have been described. Various kinds and levels of light harvesting available to algae are reviewed briefly. A more detailed analysis of some biochemical and biophysical aspects of light harvesting are also given. Light is essential to all photosynthetic autotrophs. But it is only to the extent that light is limiting to growth that light-harvesting strategies become important. It is therefore necessary to consider under what conditions light does become limiting for algal growth. Strategies of light harvesting are discussed in terms of general ecological, taxonomic, morphological, and cytological aspects. The chapter looks into photosynthetic pigments, reaction centre complexes, and pigment protein (light-harvesting) complexes with details of the principles of light harvesting in light of quantum chemistry and transfer of excitation energy, structure and function, distribution of excitation energy between the photosystems, and interaction of the light-harvesting apparatus with other photosynthetic processes.

Cutaneous factors related to the risk of malignant melanoma.

Abstract: In a case-control study, 287 women with malignant melanoma were compared with 574 age-matched controls. Red hair colour at age 5 years was associated with a tripling of risk [relative risk (RR) = 3.0], blonde hair with a 60% increase (RR = 1.6) and fair skin with a doubling (RR = 2.1). Women with melanoma also reported that they tended to burn (RR = 1.4) and to freckle (RR = 1.9) after exposure to sunlight. Since fair skin, red hair, and the tendency to burn or freckle after exposure to sunlight all cluster in the same individuals, the extent to which each of these factors had an independent influence on susceptibility to melanoma was investigated. Hair colour, especially red hair, proved to be the major determinant, followed by skin colour. The reporting of above average numbers of naevi on the body was as strong a predictor of melanoma as was red hair colour (RR = 3.4). A history of psoriasis was also more common in cases than controls (RR = 3.0) as was a history of vitiligo (RR = 1.8). A history of acne appeared to be protective (RR = 0.4) as did a history suggestive of chloasma (RR = 0.6) and premature greying of the hair (RR = 0.6). These relationships were irrespective of hair and skin colour.

Metal-tolerant bacterial populations from natural and metal-polluted soils

Abstract: The toxicity of several metals towards bacterial populations from natural and metal-polluted soils could be described either partially by a single exponential equation or completely by the sum of two exponential functions. Bacterial populations from both soils contained two subgroups, one of which could tolerate metals over a greater range of concentrations than the other. Most bacteria comprising the more mctal-tolerant subgroup were Gram-negative and were multiple drug resistant. Exceptions were organisms, tentatively identified as coryncforms, isolated on nickel-supplemented medium. It is suggested that, in general, Gram-negative bacteria arc more metal-tolerant than Gram-positivc organisms and, in soils containing comparatively low levels of metal pollution, may be able to function without the need for plasmid-mediated metal-tolerance.

Sudies on low metabolisable energy wheats for poultry using conventional and rapid assay procedures and the effects of processing

Abstract: 1. A significant proportion of wheat cultivars grown in New South Wales had low apparent metabolisable energy (AME) values (< 13.0 MJ/kg dry matter) for growing broilers when determined by the conventional total collection technique. 2. The low AME was due to a reduced starch digestibility and was not improved by grinding the wheat finely or by steam pelleting the diet. 3. Higher AME values were obtained when determinations were made with adult cockerels than with growing broilers when the conventional technique was used. 4. AME values determined using a rapid bioassay technique (Farrell, 1978) with growing broilers or adult cockerels were considerably higher than values determined using the conventional procedure with growing broilers. 5. Inter‐laboratory studies showed that the true metabolisable energy (TME) assay gave reproducible values for individual and blended wheat samples, but that these values were higher than AME values determined by the conventional procedure. Similar TME values were found wi...

Generating exact solutions of the two‐dimensional Burgers' equations

Abstract: Burgers’ equation is well suited to modelling fluid flows as it incorporates directly the interaction between the non-linear convection processes and the diffusive viscous processes. In one dimension the Cole-Hopf procedure transforms Burgers’ equation into the linear heat conduction equation. As a result many exact solutions of Burgers’ equation are available in the literature. Thus Burgers’ equation has often been used as a model equation for comparing the accuracy of different computational algorithms. This aspect of Burgers’ equation is reviewed by Fletcher.’ The two-dimensional Burgers’ equations

The transitive groups of degree up to eleven

Abstract: (1983). The transitive groups of degree up to eleven. Communications in Algebra: Vol. 11, No. 8, pp. 863-911.

Confirmatory Factor Analysis of Multitrait Multimethod Matrices.

Abstract: Campbell and Fiske (1959) argue that the demonstration of construct validity requires both convergent validity and discriminant validity; that is, multiple indicators of the same construct should be substantially correlated with each other, but less correlated with indicators of other constructs. They propose collecting measures of more than one trait, each of which is assessed by more than one method. Convergent validity is inferred from agreement between measures of the same trait assessed by different methods. Discriminant or divergent validity refers to the distinctiveness of the different traits, and is inferred from the relative lack of correlation between different traits. Support for these characteristics is based upon inspection or analysis of a multitrait-multimethod (MTMM) matrix. MTMM matrices have been analyzed by a variety of different procedures (Althauser & Heberlein, 1970; Alwin, 1974; Joreskog, 1974; Kavanagh, MacKinney, & Wolins, 1971; Kenny, 1979; Lomax & Algina, 1979; Schmitt, 1978; Schmitt, Coyle, & Saari, 1977; Werts & Linn, 1970). The most frequently employed procedures have been the original Campbell-Fiske criteria (Campbell & Fiske, 1959) and an ANOVA model (Kavanagh et al., 1971; Stanley, 1961). More recently, applications of confirmatory factor analysis have been applied to MTMM matrices, though the approach has been described under a variety of different labels: restricted factor analysis.(Boruch & Wolins, 1970), confirmatory factor analysis (Kenny, 1976; Werts, Jireskog, & Linn, 1972), path analysis (Schmitt, 1978; Schmitt et al., 1977), and exploratory factor analysis (Lomax & Algina, 1979). Most of the other procedures, though not necessarily described in terms of confirmatory factor analysis, do involve applications that are special cases of the more general approach described in this paper (see Alwin, 1974; Avison, 1978). This paper provides a pedagogical exposition of the confirmatory factor analysis of MTMM matrices, and compares this approach with the application of the CampbellFiske criteria and the ANOVA model. These analyses will be performed on the MTMM matrix presented in Table 1. Although the methodology and content relevance of the study are not emphasized here, these details are elaborated elsewhere (Marsh, 1982; Marsh & Overall, 1979). Briefly, university instructors in 329 college classes were asked to evaluate their own teaching effectiveness on the same nine-trait (35 items) instrument that was completed by their students. The definition and calculation of these nine traits are described in the earlier research (Marsh & Overall, 1979). The names of the trait factors of both teacher (A1, A2, etc.) and student (B,, B2, etc.) responses are presented in Table 1. Table 1 also includes correlations that are corrected for attenuation due to measurement error. These are indicated below the main diagonal of the entire 18 x 18

Reptilian viviparity in cold climates: testing the assumptions of an evolutionary hypothesis

Abstract: Viviparity (live-bearing) in reptiles often is interpreted as an adaptation to cold climates. This hypothesis relies on (i) body temperatures of gravid females being higher than soil (nest) temperatures; (ii) embryonic development being accelerated by this temperature difference; and (iii) survivorship of hatchlings being increased if eggs hatch before the advent of cold weather in autumn. I gathered data to test these assumptions, using eight species of scincid lizards in a high-elevation area of southeastern Australia.Due to behavioural thermoregulation, body temperatures of gravid lizards average ca. 7°C higher than soil (nest) temperatures. Oviparous female lizards retain eggs in utero for ca. 50% of development. Laboratory studies show that a temperature increase from 17°C (mean nest temperature) to 24°C (mean lizard temperature) reduces incubation periods of eggs by >40 days in heliothermic species, and <20 days in a thigmothermic species. In the field, soil temperatures drop to lethally low levels shortly after the usual time of hatching. Simple calculations show that without the acceleration of development caused by uterine retention, eggs could not hatch prior to the onset of these low temperatures in the field. These results support the major assumptions of the "cold climate hypothesis" for the evolution of reptilian viviparity.

Molecular size limit for movement in the symplast of the Elodea leaf

Abstract: A range of water-soluble fluorescent dyes and dye conjugates have been injected into cells in Elodea canadensis Michx. leaves. All compounds are unable to cross the plasmalemma between living cells and the external solution, are not degraded to other fluorescent compounds by tissue homogenates, and do not affect cytoplasmic streaming. Despite being unable to cross the plasmalemma, molecules up to 874 dalton pass from cell to cell, smaller molecules showing greater mobility. The conjugate of fluorescein isothiocyanate and leucyl-diglutamylleucine (874 dalton) appears to be close to the limit for movement: in only three out of 17 injections was any movement visible; this movement was only to adjacent cells and was close to the limit of detection. Dye molecules of 1678 dalton and larger did not pass from cell to cell. From the relationship between the size of the dye molecules, measured using molecular models, and their intercellular mobility, the equivalent pore diameter of the Elodea leaf plasmodesmata has been estimated to lie within the range 3.0–5.0 nm.

Correction for bias in visual transect censuses of coral reef fishes

Abstract: Transect techniques for censusing reef fishes, and the sources of bias inherent in them are considered. A technique, derived from aeraly survey methods, is demonstrated to correct a bias in density estimates due to the width of the transect being censused. This bias is sufficient on a transect 1 m wide to underestimate density by 11.1–26.7% for five species or species groups examined. The bias is still greater on wider transects. Because this bias varies in degree among species, comparisons among species should not be made using uncorrected transect data. Comments are made on other probable sources of bias in transect data, and on ways of minimising bias when making visual transect censuses.

Classification of Bacteroides nodosus by agglutination tests.

Abstract: One thousand two hundred and sixty seven isolates of Bacteroides nodosus from 292 sheep in 58 flocks were examined. Of these, 1260 could be classified by slide agglutination into 8 serogroups designated A to H. Up to 6 serogroups were detected in individual flocks, with up to 4 serogroups being detected in a single foot. Of the 292 sheep examined, 38 (13%) carried mixed serogroup infections. Determination of the range of serological types infecting a flock frequently required the examination of a number of isolates from each of a number of sheep. Cross-tube agglutination tests carried out on 44 isolates and their antiserums indicated that members of some serogroups could be divisible into subgroups or serotypes. These results suggested that 16 or more serotypes of B. nodosus might exist. The nature of the antigens responsible for both slide and tube agglutination reactions needs to be determined.

Subcortical projections to lateral geniculate and thalamic reticular nuclei in the hooded rat.

Abstract: Restricted injections either of horseradish peroxidase conjugated with wheat germ agglutinin, or of unconjugated horseradish peroxidase were made into hooded rats in order to distinguish subcortical sources of afferents to dorsal lateral geniculate nucleus from those to the adjacent visually responsive thalamic reticular nucleus, which modulates geniculate activity. Five “nonvisual” brainstem regions project to the dorsal lateral geniculate nucleus: mesencephalic reticular formation, dorsal raphe nucleus, periaqueductal gray matter, dorsal tegmental nucleus, and locus coeruleus. Projections are generally bilateral, but ipsilateral projections dominate. Of these regions, three also project ipsilaterally to the thalamic reticular nucleus: mesencephalic reticular formation, periaqueductal gray matter, and dorsal tegmental nucleus. Similar discrete injections of horseradish peroxidase into ventral lateral geniculate nucleus allowed a comparison of afferents to dorsal and ventral lateral geniculate nuclei. In addition to the five nonvisual brainstem regions which project to the dorsal division, the ventral lateral geniculate nucleus receives afferents from the perirubral reticular formation and the central gray matter at the thalamic level. The dorsal and ventral lateral geniculate nuclei receive substantially different afferents from subcortical visual centres. The dorsal division receives projections from superior colliculus, pretectum, and parabigeminal nucleus whereas the ventral division receives afferents from superior colliculus, additional pretectal nuclei, lateral terminal nucleus of the accessory optic system, and the contralateral ventral lateral geniculate nucleus.