Showing papers by "University of Melbourne published in 1986"

Thermal annealing of fission tracks in apatite: 1. A qualitative description

Abstract: Confined fission-track lengths have been used to study the degree of annealing of induced fission tracks in samples of a single fluorapatite crystal (Durango apatite), heated for various times (between 20 min. and 500 days) at temperatures between 95° and 400°C. In all annealed samples the mean confined track length is always less than that in unannealed control samples. As annealing progresses, the mean length is reduced and the length distribution broadens, slowly at first, and then more rapidly below a length reduction (ll0) of ∼ 0.65. In addition, the variation of track length with angle to the crystallographic c-axis becomes progressively more anisotropic. As the mean track length approaches zero, the only tracks left are aligned parallel to the c-acis. In heavily annealed samples (ll0 < 0.65) observation of individual tracks after sequential etching steps shows the presence of unetchable “gaps” in a small proportion of tracks. The existence of these gaps is borne out by annealing studies of heavy-ion tracks in apatite slices. These studies also show the anisotropy characteristic of annealing in apatite. The annealing of fission tracks in apatite appears to be characterised by two processes. For small degrees of annealing the dominant process brings about a progressive shrinking of the track from each end, with tracks perpendicular to the c-axis shortening more rapidly than those parallel to it. As annealing becomes more severe (ll0 < 0.65) the tracks begin to break up into discontinuous portions. Track length distributions in annealed apatites reflect the interplay of these processes. The effect of apatite composition on annealing has been studied using spontaneous tracks in apatites from a sample in which considerable geological annealing has occurred. Electron microprobe studies show that apatite grains rich in Cl are more resistant to annealing, while fluorapatite is more readily annealed.

Confined fission track lengths in apatite: a diagnostic tool for thermal history analysis

Abstract: Fission-track ages in apatite are generally accepted as giving a measure of the time over which a sample has been exposed to temperatures below approximately 100° C. A compilation of the lengths of confined fission tracks in a wide variety of apatites from different geological environments has shown that the distribution of confined track lengths can provide unique thermal history information in the temperature range below about 150° C over times of the order of 106 to 109 years. The distribution of confined lengths of freshly produced induced tracks is characterised by a narrow, symmetrical distribution with a mean length of around 16.3 μm and a standard deviation of the distribution of approximately 0.9 μm. In volcanic and related rocks which have cooled very rapidly, and never been reheated above about 50° C, the distribution is also narrow and symmetric, but with a shorter mean of 14.5 to 15 μm, and a standard deviation of the distribution of approximately 1.0 μm. In granitic basement terrains which are thought never to have been significantly disturbed thermally, since their original post-emplacement cooling, the distribution becomes negatively skewed, with a mean around 12 or 13 μm and a standard deviation between 1.2 and 2 μm.This distribution is thought to characterise slow continuous cooling from temperatures in excess of 120° C, to ambient surface temperatures. More complex thermal histories produce correspondingly complex distributions of confined tracks. The continuous production of tracks through time, coupled with the fact that the length of each track shrinks to a value characteristic of the maximum temperature it has experienced, gives a final length distribution which directly reflects the nature of the variation of temperature with time. Most distinctive of the myriad possible forms of the final distribution are the bimodal distributions, which give clear evidence of a two-stage history, including high and low temperature phases. The study of confined length distributions therefore offers invaluable evidence on the meaning of any fission-track age, and bears the potential of providing rigorous constraints on thermal history in the temperature regime below about 150° C. The results of this study strongly suggest that any apatite fission-track age determination should be supported by a confined track length distribution.

A theoretical and experimental study of wall turbulence

Abstract: In this paper the dimensional-analysis approach to wall turbulence of Perry & Abell (1977) has been extended in a number of directions. Further recent developments of the attached-eddy hypothesis of Townsend (1976) and the model of Perry & Chong (1982) are given, for example, the incorporation of a Kolmogoroff (1941) spectral region. These previous analyses were applicable only to the ‘wall region’ and are extended here to include the whole turbulent region of the flow. The dimensional-analysis approach and the detailed physical modelling are consistent with each other and with new experimental data presented here.

Cloning of cDNA for a stylar glycoprotein associated with expression of self-incompatibility in Nicotiana alata

Abstract: Self-incompatibility in flowering plants is controlled by the S gene. A complementary DNA clone encoding a style protein of Nicotiana alata which segregates with the S2 allele has now been sequenced. The S-allele-associated style components in different genotypes of N. alata and in Lycopersicon peruvianum, another self-incompatible species in the family Solanaceae, are homologous.

Abundant calcitonin receptors in isolated rat osteoclasts. Biochemical and autoradiographic characterization.

Abstract: Calcitonin receptors have been characterized for the first time in isolated osteoclasts. These receptors have been demonstrated by autoradiographic and biochemical methods, and the cells have also been shown to respond to calcitonin with a dose-dependent increase in cyclic AMP. The receptors in rat osteoclasts are specific and of high affinity (dissociation constant, Kd, 1 to 6 X 10(-10) M), and are present in greater numbers than in any cell previously studied (greater than 10(6) per cell). Chemical cross-linking of 125I-labeled salmon calcitonin to osteoclasts using disuccinimidyl suberate resulted in identification of a receptor component with a relative molecular weight of 80,000-90,000. By counting grains in autoradiographic experiments, we found that greater than 80% of specifically bound radioactivity was associated with multinucleate osteoclasts and the remainder was associated with mononuclear cells that are not osteoblasts, but that may be osteoclast precursors.

Parsing WH-constructions: Evidence for on-line gap location

Abstract: Two experiments investigate how people assign a grammatical meaning to WH-phrases in embedded questions. The first experiment replicates Crain and Fodor's (1985) finding that object NPs take longer to read in a WH-question than in a corresponding declarative sentence, suggesting that people expect not to find an object, presumably because they have associated the object semantic role with the WH-phrase. Experiment 1 also shows that there is no such difficulty at the subject NP, suggesting that the subject semantic role is not associated with the WH-phrase in the same way as the object role. Experiment 2 investigated whether people assign a semantic role to the WH-phrase which cannot be grammatically acceptable; the evidence suggests that people are not prone to make such mistakes.

Resonant flow of a stratified fluid over topography

Abstract: The flow of a stratified fluid over topography is considered in the long-wavelength weakly nonlinear limit for the case when the flow is near resonance; that is, the basic flow speed is close to a linear long-wave phase speed for one of the long-wave modes. It is shown that the amplitude of this mode is governed by a forced Korteweg-de Vries equation. This equation is discussed both analytically and numerically for a variety of different cases, covering subcritical and supercritical flow, resonant or non-resonant, and for localized forcing that has either the same, or opposite, polarity to the solitary waves that would exist in the absence of forcing. In many cases a significant upstream disturbance is generated which consists of a train of solitary waves. The usefulness of internal hydraulic theory in interpreting the results is also demonstrated.

On the thermo-tectonic evolution of northern England; evidence from fission track analysis

Abstract: The limited amount of fission track data previously available in Northern Britain has shown unexplained Cretaceous ages in the Southern Uplands and Lake District. Apatite fission track analysis has been applied to 23 samples from Caledonian intrusive bodies, to further investigate these ages. Fission track data of sphene has been carried out on seven samples and zircon in one sample.Apatite fission track ages vary from a maximum of 278 ± 12 Ma in the Cheviot Granite, down to ages of ∼ 60 Ma in the Carrock Fell region, with intermediate ages of ∼ 140 Ma in the Eskdale Granite and ∼ 80 Ma in the Shap Granite. This variation in fission track age is accompanied by changes in the distribution of confined fission track lengths. Samples with the youngest ages (∼ 60 Ma) have long, narrow distributions (mean length > 14 μm; standard deviation ∼ 1 μm) typical of samples which have had all pre-existing tracks erased by elevated temperatures, and subsequently cooled rapidly so that all tracks now observed have formed at low temperatures. As ages increased from 60 Ma, a component of shorter tracks becomes more dominant, representing tracks which have been shortened at elevated temperatures. Thus ages greater than 60 Ma are ‘apparent ages’, representing a partial overprint of a pre-existing track record, while the ∼ 60 Ma ages record a total resetting at this time.The heating responsible for the observed fission track annealing may be due to residence at temperatures in the range 70–125 °C over many tens of Ma, or to a short lived heat pulse perhaps associated with the Tertiary igneous province of the northwest. In either case, uplift and erosion on a scale of kilometres at ∼ 60 Ma ago is necessary to produce the observed pattern of fission track parameters. This uplift may be related in some way to basin inversions, also on a kilometre scale, known to have taken place at around the Late Cretaceous/Early Tertiary to the southeast (Cleveland, Sole Pit and Broad Fourteens Basins). No previous evidence of such uplift in Northern England has been reported, and the study reported here highlights the unique potential of apatite fission track analysis for the detection of mild thermo-tectonic events, often in areas where no other evidence exists.

Nutrient cycling and nitrogen mineralization in eucalypt forests of south-eastern Australia: II. Indices of nitrogen mineralization

Abstract: Nutrient pools in litter and soil and the major nutrient transfers and additions in rainfall, throughfall and litterfall were measured in eight mature, undisturbed eucalypt forests covering a range of species, climate, productivity and soil type. Litterfall is the major pathway for the return of N, P, Ca and usually Mg, to the soil. The forests covered almost the range of litterfall reported for eucalypt forests and, in conjunction with published data, litterfall was strongly related to climatic variables. Extractable P in the soil and P concentrations in litter and litterfall were significantly higher in two sub-alpine forests (Eucalyptus pauciflora andE. delegatensis) than in all other forests. In general, nutrient turnover, particularly N turnover, was related to the rate of organic matter turnover. Rates of organic matter turnover in these forests and in other studies of eucalypts were correlated with climatic conditions using the simple climatic scalar developed by Vitousek. Nitrogen turnover, especially that proportion cycling via leaf litterfall is primarily a function of organic matter turnover, but litter quality appears also to have an influence.

Glucose tolerance and insulin sensitivity in ponies and Standardbred horses

Abstract: Summary The existence of an innate insulin insensitivity in ponies was investigated and compared with the situation in larger breeds of horse. Ponies that were fat or had previously suffered laminitis were found to be far more intolerant to oral glucose loading (1 g/kg bodyweight [bwt]) than normal ponies or Standardbreds. These ponies also exhibited a far greater response in plasma insulin levels after glucose loading. Insulin response tests (0.4 iu/kg bwt insulin intravenously) showed only a minimal and very protracted response in both the fat and laminitic groups. The relevance of these findings in regulation of carbohydrate and lipid metabolism, and their role in the pathogenesis of hyperlipaemia, are discussed.

Use of Hepes buffer for microalgal culture media and fixation for electron microscopy

Abstract: N-2-hydroxyethylpiperazine-N-2′-ethanesulfonic acid (Hepes) has been tested as an alternative to tris-(hydroxymethyl)aminoethane (Tris) for hydrogen-ion buffering of algal cultures. Hepes satisfactorily buffered both freshwater and artificial seawater media and has been used successfully to grow 25 species of microalgae from five classes. Electron microscopic fixations of Tetraselmis striata Butcher (Prasinophyceae) and Amphidinium rhyncocephalum Anissimowa (Dinophyceae) buffered by Hepes have given far superior ultrastructural preservation than fixations buffered by Tris. The substitution of Hepes for Tris allows a defined seawater medium to be used as a fixative vehicle for the first time.

Negation and Control in Prolog

Abstract: We investigate ways of bringing PROLOG closer to the ideals of logic programming, by improving its facilities for negation and control. The forms of negation available in conventional PROLOG systems are implemented unsoundly, and can lead to incorrect solutions. We discuss several ways in which negation as failure can be implemented soundly. The main forms of negation considered are not, not-equals, if-then-else and all solutions predicates. The specification and implementation of all solutions predicates is examined in detail. Allowing quantifiers in negated calls is an extension which is easily implemented and we stress its desirability, for all forms of negation. We propose other enhancements to current implementations, to prevent the computation aborting or looping infinitely, and also outline a new technique for implementing negation by program transformation. Finally, we suggest what forms of negation should be implemented in future PROLOG systems. The poor control facilities of conventional PROLOG lead to infinite loops and inefficiency. More flexible computation rules can often overcome these problems. We first introduce control primitives for database and recursive predicates, then show how control information can be generated automatically, using these primitives. Automatically reordering subgoals in clauses is also considered. This allows programmers to concentrate more on the logic of a problem, making programming simpler. We give examples using several different styles of programming. The implications of automatic control for the design of control primitives is also discussed. Next, we re-examine the theoretical foundations of PROLOG systems with flexible computation rules. The SLD resolution model is extended, to correct a previous over-simplification. The extension also brings to light a much greater flexibility of computation rules, which has previously been overlooked. A rule which behaves like intelligent backtracking is given as an example. Finally, we take an overview of the many approaches to control in PROLOG. Some general principles for evaluating and classifying control rules are given. These show the deficiencies of current systems more clearly. We make suggestions for future implementations of PROLOG with extra control facilities.

Three distinct subpopulations of sheep T lymphocytes.

Abstract: Monoclonal antibodies reactive with distinct T lymphocyte subpopulations have been described in man, mouse and rat and structural analyses of these antigens have demonstrated a high degree of evolutionary conservation. This report describes the reactivity of three monoclonal antibodies (mAb), 19-19, alpha SBU-T4 and alpha SBU-T8, which define T cell subpopulations in the sheep. The mAb alpha SBU-T4 and alpha SBU-T8 define the sheep CD4 and CD8 molecules, respectively. These two antigens show similar tissue distributions, molecular weights and fluorescence-activated cell sorter profiles to human, mouse and rat CD4 and CD8 molecules. The mAb 19-19 is reactive with a subpopulation of T lymphocytes which displays a tissue distribution unlike that reported for a T cell subset in any other species. 19-19 stains 7% of efferent lymph lymphocytes, 15% of peripheral blood lymphocytes but only 1-3% of lymph node lymphocytes. Two-color immunofluorescence demonstrates that the 19-19+ T cell subset is SBU-T4- and SBU-T8-, and thus defines a third T cell subpopulation in sheep. Immunohistology on frozen lymph node tissue sections localizes 19-19 mAb-reactive cells to the subcapsular region of the lymph node and lymph node trabeculae. Only 1% of thymocytes are 19-19+ and these cells are located mainly in the medulla and often arranged as foci around blood vessels. The 19-19 mAb immunoprecipitates from sheep lymphocytes an antigen with an apparent molecular mass of 215 kDa under both reducing and nonreducing conditions. It is concluded that alpha SBU-T4 and alpha SBU-T8 recognize the sheep homologues of the human T4 and T8 antigens, respectively, whereas 19-19 recognizes an antigen (termed SBU-T19) which has not been reported in any other species.

What attracts attention when driving

Abstract: Twenty-five observers were asked to report what attracted their attention while driving along a 21·9 km route through a suburban district. A second group of equal size made similar reports in the laboratory while watching a movie film of the same route. The results obtained from the laboratory trial closely parallelled those obtained in the field and it is concluded that laboratory studies using a movie simulation provide a satisfactory means of studying the distribution of attention using a concurrent verbal report technique. It is noted that the absence of a driving task has no substantial effect on attentive behaviour suggesting that the visual information presented by the movie film is sufficient to generate attentive processes characterstic of driving. It is found that advertising attracts a good proportion of attention but in those sections of the route where there was little advertising attention was directed to an even greater extent to other objects not related to driving. It seems that some 30 t...

Replantation of teeth and antibiotic treatment.

Abstract: Administration of antibiotics is usually recommended when a traumatically avulsed tooth is replanted, in order to prevent bacterial contamination. In the present study, permanent lateral incisors of monkeys were extracted, allowed to dry for 1 h and then replanted. Some teeth had their pulp chambers opened labially and left open for 3 wk after replantation. The monkeys were treated with antibiotics (i.m.) either at the lime of replantation or 3 wk after replantation. In some monkeys, antibiotics were placed in the pulpal cavity. Comparisons were made of the effect of endodontic treatment on periodontal healing and root resorption. The monkeys were killed 8 wk after replantation. It was found that after systemic antibiotic treatment at the time of replantation there was no inflammatory root resorption. Also, endodontic treatment at the time of replantation prevented inflammatory root resorption. When systemic antibiotic treatment was instituted 3 wk after (he replantation, there was no reduction of the inflammatory root resorption as compared with teeth without antibiotic treatment. Application of antibiotics in the pulp 3 wk after replantation almost completely eliminated the inflammatory resorption. In all the treatment groups where administration of antibiotics or endodontic treatment had prevented, reduced or eliminated inflammatory root resorption, 30–45% of the root surface area was ankylotic 8 wk after replantation.

Antibiotic Production: a Possible Function for the Metapleural Glands of Ants (Hymenoptera: Formicidae)

Abstract: Secretions from the metapleural gland of the Australian ant Myrmecia nigriscapa Roger were bioassayed against the spores of soil fungi that commonly occur where this ant nests. Four of the seven fungal species were nonentomogenous: Cladosporium resinae (Lindau) DeVries, Colletotrichum gloeosporioides (Penz.) Sacc, Gliocladium roseum Bain, and Mucor plumbeus Bon. Three were entomogenous: Beauveria bassiana Bals. Vuill., Paecilomyces lilacinus (Thorn.) Samson, and Metarhizium brunneum Petch. Metapleural secretions significantly reduced germination of the spores of all fungal species except M. brunneum. In this species, experimental and control spores germinated at approximately equal rates, but the secretions significantly reduced subsequent hyphal growth. These data, together with previously published experiments that show suppression of mycelial growth in eight other soil fungi by metapleural secretions, are consistent with the hypothesis that the metapleural gland is a source of antibiotic. The other social Hymenoptera, the bees and wasps, protect their juvenile stages in antibiotic-impregnated brood cells. By contrast, ants appear to utilize antibiotic secretions from the metapleural gland.

Tooth Avulsion and Replantation--A Review

Abstract: The major causes of post-replantation tooth loss are inflammatory root resorption and root resorption associated with ankylosis. Recent studies have concentrated on delineating the cellular interactions in the pulp and periodontium in order to more fully understand the various factors affecting the prognoses of such teeth. The aim of this report is to discuss the nature of the pathology responsible for tooth loss following avulsion and to review recent replantation and attachment studies.

Further observations of elastic effects in tubular entry flows

Abstract: The current understanding of tubular entry flows for Newtonian fluids and the influence of elasticity on these flows in the absence of shear thinning and significant fluid inertia is reviewed. While tubular entry flow for Newtonian fluids both with and without fluid inertia is now a solved problem, no single worker has been able to predict any of the significant elastic effects observed for constant viscosity elastic liquids in such flows. New elastic flow phenomena are reported which complicate the problem even more. Two distinctly different flow patterns are observed in a four to one contraction for two constant viscosity elastic fluids with essentially the same characteristics times. Tubular entry flows of elastic liquids develop (with increasing λγ) in the same way only if the contraction ratio is high enough. At sufficiently low contraction ratio, a lip vortex (at the tube entrance) and a corner vortex (in the upstream tube corner) can both be present and interacting with the lip vortex dominating the flow when vortex enhancement and growth occurs. The entry flow problem for elastic liquids is far more complex than originally imagined and is indeed a challenge for numerical simulation and selection of constutitive equations.

Structural Analysis of Secreted Root Slime from Maize (Zea mays L.).

Abstract: Secreted slime isolated from the incubation medium of Zea mays roots maintained axenically contains fucose, arabinose, xylose, galactose, and glucose as the major monosaccharides. The slime preparation contains low levels (3% weight/weight [w/w]) of uronic acids. Methylation analysis reveals an extraordinarily diverse range of glycosyl residues. The fucosyl residues are primarily terminal (60%) and 3-linked (33%) with a relatively small proportion being 2-linked (6%). The methylation data are consistent with, but not proof of, the presence of a range of polymers including arabinogalactan-proteins (AGPs), xyloglucans, arabinoxylans, and glucans in the slime. The specific binding of the β-glucosyl Yariv reagent, a dye which binds and precipitates AGPs, to the slime preparation and to the outer periclinal epidermal cell wall surface in root sections, is further evidence for the presence of AGPs. Low levels of phenolic acids (approximately 0.17% w/w), in particular trans-ferulic acid, and protein (approximately 6% w/w) were also detected.