Showing papers by "Griffith University published in 1992"

Conceptions of Teaching Held by Academic Teachers.

Abstract: This study examines conceptions of teaching held by academic teachers in the fields of science and social science, in two universities: a distance university in the UK and a traditional one in Australia. A five level classification of conceptions of teaching is proposed. A process of arriving at this scheme is discussed and a formalised coding system is presented which helps to delimit, with greater confidence, the boundaries of each conception, and helps to order conceptions, to compare conceptions proposed by other researchers, and to place individuals within conceptions. The same coding system is then used to define the concepts of student-centered and teacher-centered approaches to teaching. There is a strong suggestion that teaching conceptions are context-dependent.

Recreation specialization reexamined: The case of vehicle‐based campers

Abstract: Measurement of recreation specialization has been limited to the observation and recording of behaviors associated with activities and has ignored, to a large extent, individual affective attachment to participation. This article reports on the development of a construct called recreation involvement, which includes measures of both prior participation history and affective attachment (enduring involvement). In recognition of the multidimensional nature of the construct, a cluster‐analysis procedure was used to differentiate four subgroups of vehicle‐based campers, each of which showed different recreation involvement profiles. Subsequently, evidence is presented to show that variation in the focus of recreation involvement, as demonstrated by the profiles, influenced attitudes of campers toward management strategies and character of facility provision in the study area.

Leaf-litter processing by invertebrates in a mangrove forest in Queensland

Abstract: The way leaf shredders handle and shred leaves under laboratory conditions and in the mangrove forest at Myora Springs, Queensland, Australia, was investigated during the period 1980 to 1984. Field observations on the behaviour of the crab Sesarma erythrodactyla during low tide revealed that this species spends most of its time foraging over mud. S. erythrodactyla eats mangrove leaves where they fall or drags them into burrows or hollow logs. Through their feeding activities, crabs (S. erythrodactyla, Metopograpsus frontalis, Helice leachii, Clistocoeloma merguiensis, Leptograpsus variegatus, Paragrapsus laevis, Ilyograpsus paludicula), isopods (Exospaeroma alata, Campaecopia sp.) amphipods (Orchestia sp., Melita sp.), and a capitellid polychaete (Capitellides sp.), break down whole mangrove leaves into small particles. The way in which a leaf is broken down by leaf-shredders influences the size and composition of the particulate organic matter (POM) in the environment. The POM egested by leaf-shredders varies from 32 to 1171 μm. POM in this size range occurs in the guts of 38 invertebrate species which feed on mud, suggesting that they depend on the plant detritus produced by leafshredders as a source of food. Leaf-shredders therefore constitute a primary link in the marine food web of mangrove forests.

Competitive exclusion, or species aggregation? : An aid in deciding.

Abstract: There is a long-standing dispute over whether the analysis of species co-occurrence data, typically on islands in an archipelago, can disclose the forces at work in structuring a community. Here we present and utilise three “scores” S, C and T. S gives the mean number of islands shared by a species pair in the presence/absence data under study. The scores C and T are based on the way that a pair of species occurs on a pair of islands. When each species occurs on a different island, this adds to the “checkerboard score” C; if they occupy the same island, this increases the “togetherness score” T.

Host specificity of arboreal and free‐living insect herbivores in rain forests

Abstract: Available information about the host specificity of arboreal and free-living insect herbivores in rain forests is scarce, but suggests that polyphagy may be more widespread than previously thought. The study of the arthropod fauna associated with an overstorey tree in Australia, Argyrodendron actinophyllum (Sterculiaceae), supports this contention. A conservative 11% of herbivore species foraging within this tree appear to be specialists, whereas this proportion decreases further to 3.0–4.5% when non-herbivore species are included. Argyrodendron actinophyllum presents several features which may promote a polyphagous strategy among herbivores. These observations are discussed in the wider context of ecological and evolutionary pressures shaping feeding strategies of insect herbivores in rain forests. These selection pressures include principally plant biochemistry, predation pressure of generalist predators, and structural diversity and environmental unpredictability of rainforest environments. The strength of association between herbivores and rainforest host-trees is likely to depend on three factors, acting at both the tree and rainforest community level: chemical traits of foliage (including chemical defences and nutrient levels), young foliage availability and enemy-free space. Given the complex interactions possible among these factors, rainforest host-trees may sustain herbivore faunas ranging from highly specialized to highly generalist. SUMMARY Argyrodendron actinophyllum presents several features which may promote a polyphagous strategy among herbivores: low nutrient levels and high fibre content, apparent scarcity of qualitative defences, relatively unpredictable availability of young foliage and low predation-pressure from arboreal ants in its foliage. This situation may be different for other rainforest tree species, depending on their biological features. Without speculating on the relative importance of each factor, these observations suggest that the strength of association between communities of insect herbivores and their rainforest host-trees may depend on the following factors, acting at both the component and compound rainforest-community level: chemical traits of foliage (including chemical defences and nutrient levels), young foliage availability (including factors related to plant phenology, plant abundance and plant growth strategy) and enemy-free space. These factors, which may be interrelated (i.e. amount and type of chemical defences related to nutrient availability, host phenology related to nutrient availability and searching behaviour of generalist predators/ parasitoids related to host phenology and apparency), may generate complex sets of combinations, which are likely to differ between rainforest component communities. In these conditions, rainforest host-trees may sustain herbivore faunas ranging from highly specialized to highly generalist. These considerations demonstrate a requirement for the study of arboreal insect communities associated with host-trees of dissimilar features growing in similar rain forest types, as well as in different rainforest environments.

Identification of the loci of the collagen-associated Ehrlich chromogen in type I collagen confirms its role as a trivalent cross-link

Abstract: Collagenous peptides containing the Ehrlich chromogen (EC) were selectively isolated from a tryptic digest of bovine tendon by coupling to a diazotized polyacrylamide support. The isolated p-phenol-azo-EC peptides were purified and characterized by amino acid and sequence analyses. EC occurred in stoichiometric amounts in trimeric cross-linked chains originating from the known cross-link regions of type-I collagen. The major locus of the EC was alpha 2(I)Hyl-933 x alpha 1(I)Lys(Hyl)-9N x alpha 2(I)Lys(Hyl)-5N but it was also shown to occur at the loci alpha 1(I)Hyl-87 x alpha 1(I)Lys(Hyl)-16C x alpha 1(I)Lys(Hyl)-16C and alpha 1(I)Hyl-930 x alpha 1(I)Lys(Hyl)-9N x alpha 2(I)Lys(Hyl)-5N. After sequence analyses of the C-terminal helical cross-link region alpha 2(I)928-963, corrections are presented for residues 927, 930, 932 and 933 of the bovine alpha 2(I) chain. The collagen-associated EC is postulated to be a trisubstituted pyrrole formed by the reaction of the aldehyde form of a telopeptidyl lysine residue with a bifunctional keto amino cross-link. It is also proposed that when the telopeptidyl lysine residue is hydroxylated the above reaction will result in pyridinoline formation.

Environmental Education: A Mismatch between Theory and Practice

Abstract: The lack of correlation between theory and practice of environmental education in Australian schools is investigated. The current form of environmental education does not develop a commitment to environmental conservation among students or give them the power to take action in resolving environmental problems.

Factors controlling ammonia loss from trash covered sugarcane fields fertilized with urea

Abstract: Ammonia losses following surface applications of urea to trash covered sugar cane fields were investigated in four climatic zones of tropical Queensland. Volatilization of ammonia and evaporation of water were determined by micrometeorological techniques. The results showed that the pattern, rate and extent of ammonia loss were controlled by the availability of water in the trash and its evaporation. Water added by dewfall, rainfall or condensation of evaporated soil moisture dissolved some of the urea and allowed it to be hydrolyzed to ammonia by the urease enzyme in the sugarcane residues; when the water evaporated, ammonia was lost to the atmosphere.

Interactions between the bovine milk fat globule membrane and skim milk components on heating whole milk

Abstract: Heating raw milk at 80 deg C for 2.5-20 min was found to result in compositional changes in the milk fat globule membrane (MFGM). The yield of protein material increased with duration of heating, due to incorporation of skim milk proteins, predominantly beta- lactoglobulin, into the membrane. Lipid components of the MFGM were also affected, with losses of triacylglycerols on heating.

An analysis of an ordinary differential equation model for a two-species predator-prey system with harvesting and stocking

Abstract: An analysis is presented for a model of a two-species predator-prey system where each species can be harvested or stocked. Using methods from bifurcation theory the qualitative nature of the steady-state solutions is examined. The effect of harvesting and stocking rates and the prey carrying capacity is examined in detail.

Incremental Evaluation of Datalog Queries

Abstract: We consider the problem of repeatedly evaluating the same (computationally expensive) query to a database that is being updated between successive query requests. In this situation, it should be possible to use the difference between successive database states and the answer to the query in one state to reduce the cost of evaluating the query in the next state. We call this process “incremental query evaluation.”

Involvement in Risk Recreation: A Comparison of Objective and Subjective Measures of Engagement

Abstract: The “Adventure Model” suggested a positive relationship between intrinsic motives and levels of engagement based on the self-reported level of experience of participants in risk recreation. This co...

Vigilance does not covary with group size in an island population of silvereyes (Zosterops lateralis)

Abstract: Numerous studies on different taxonomic groups have found that vigilance behavior is negatively correlated with group size, as predicted by several theoretical models. This follows the logical argument that each individual in a larger group can spend less time scanning for predators (and more time feeding), while the group as a whole maintains a high probability of detecting an approaching predator. We investigated the relationship between these variables in the population of silvereyes (Zosterops lateralis chlorocephala) on Heron Island, Great Barrier Reef. The study used procedures of field observation that controlled or measured other variables with which vigilance is often correlated: food density and quality, temperature, time of day, distance from cover, habitat obstructions, observer proximity, breeding status, age, sex, and dominance. There was no relationship between scanning behavior and group size under these conditions. There are several possible explanations, related to the silvereyes' biology, for this lack of covariation. An additional explanation is that Heron Island is a predator-free environment for this species, and covariation between group size and vigilance is not expected in the absence of predators.

Transmission electron microscopy and high-resolution transmission electron microscopy studies of the early stages in the degradation of yba2cu3o7-δ superconductor in water vapour

Abstract: The initial stages of water vapour attack of the high-temperature superconductor YBa2Cu3O7-δ have been studied by transmission electron microscopy (TEM). The planar defects both of thickness 0·2 nm and of thickness 0·4 nm reported previously have been observed. The defects are sometimes associated with preexisting sites of strain in the material, but such strain is certainly not required for their nucleation, since often they occur in initially perfect material. A model for the thinner defect has been developed, which fits well with the TEM observations, as well as with bond valence calculations and previous work on the degradation of YBa2Cu3O7-δ by water. The implications of the model for that degradation process are discussed.

Aluminium-fused bis-p-tert-butylcalix[4]arene: a double cone with two π-arene ⋯ H interactions for included methylene chloride

Abstract: Treatment of p-tert-butylcalix[4]arene 1 with [H3Al(NMe3)]2 results in trimetallation and deprotonation by the tertiary amine, yielding the bis(calix[4]arene), [{(1– H4)Al}2]2–[HNMe3]+2, 2, which has been isolated with included methylene chloride; distorted five-coordinate O-bound aluminium centres [Al–O 1.74(1)–2.35(1)A] fuse the slightly flattended cone calixarene units with the methylene chloride H-atoms residing over two opposite aromatic rings in each cone, C ⋯ ring centroid 3.54 A.

The arthropod community of an Australian rainforest tree: Abundance of component taxa, species richness and guild structure

Abstract: The arthropod community within the crowns of Argyrodendron actmophyllum (Sterculiaceae) in a subtropical rainforest near Brisbane, Australia, was investigated during a 2 year study using interception traps and restricted canopy fogging. The total arthropod density was 34 individuals m−2 of leaf area. Spiders, psyllids, thrips, psocids and chrysomelids were most abundant. The most diverse families included Curculionidae, Cicadellidae, Staphylin-idae, Cerambycidae, Theridiidae, and Chrysomelidae. The arboreal community of A. actinophyllum exhibited several features common to arthropod communities from temperate and tropical rainforest trees. Affinity with temperate trees was suggested by the relatively high densities of certain species, by high proportions (in terms of individuals) of sap-suckers and non-insect predators, and by a low proportion of ants. Affinity with tropical rainforest trees was expressed by high proportions of scavenging fauna, particularly wood-eaters and fungalfeeders.

Degradation of triglycerides by a pseudomonad isolated from milk: molecular analysis of a lipase-encoding gene and its expression in Escherichia coli.

Abstract: Psychrotrophic lipolytic bacteria represent a significant problem in the storage of refrigerated dairy products. A lipase-encoding gene has been cloned and characterized from a highly lipolytic strain of Pseudomonas. The nucleotide sequence of the gene predicts a polypeptide of M(r) 49,905, which was identified when the gene was expressed in Escherichia coli.

Changes in structure of the bovine milk fat globule membrane on heating whole milk.

Abstract: The effects of heat-induced interactions between milk fat globule membrane components and skim milk proteins in whole milk on the structure of the membrane were examined by isopycnic sucrose density gradient centrifugation and by using Triton X-100 as a membrane probe. Skim milk components were incorporated into all the lipoprotein fractions separated by density gradient centrifugation. High density complexes, higher in density than those found in the natural milk fat globule mcmbranc, were formed during the heat treatment. Losses of natural membrane polypeptides from the medium and low density lipoproteins were observed on heating. Heating whole milk also altered the rate of release of membrane components by detergent, with decreases in protein released and an increase in phospholipid constituents released. Studies on washed cream indicated that some of the changes in the membrane on heating whole milk occurred due to thc heat treatment alone, independent of the interactions with skim milk proteins. Reproduced with permission from Cambridge University Press.

Towards a theory of workplace learning

Abstract: This paper examines a range of theoretical issues associated with learning in natural settings, such as the workplace. It considers the need for enhancing theoretical approaches to learning vocational skills in workplaces, giving particular attention to the physical, social and psychological contributions provided in those settings. It is argued that every sort of setting has the capacity to provide physical, social and cultural contributions to learning. Consequently, any learning theory has to take account of settings, enculturation and the social contribution to the learning. However, given the goals of vocational education and the specific contributions of natural settings the development of a theory of learning in natural settings should be addressed outside of the existing theoretical frameworks to provide the primacy that these contributions deserve. It is postulated that such a theory will guide actions in the provision of vocational skill development in natural settings, such as workplaces. It ma...

Limiting Procedures for the Optical Phase Operator

Abstract: We examine some of the attempts to describe the phase of a single field mode by a quantum operator acting in the conventional infinite Hilbert space. These operators lead to bizarre properties such as non-random phases for the number states and experience consistency difficulties when used to obtain a phase probability density. Moreover, in these approaches operator functions of phase are not simply functions of a phase operator. We show that these peculiarities do not arise when the Hermitian optical phase operator is employed. In our opinion, the problems associated with the descriptions of phase in conventional infinite Hilbert space arise from the nature of the limiting process.

Influence of leaf traits on the spatial distribution of arboreal arthropods within an overstorey rainforest tree

Abstract: . 1 Several attributes of foliage were measured from the Australian rainforest tree Argyrodendron actinophyllum Edlin (Sterculiaceae). These were related to estimates of abundance per leaf area of the most common arthropod guilds and families sampled with restricted canopy fogging. 2 When all these arthropod groups were considered, much of the overall variance in arthropod spatial distribution could be attributed to leaf age characteristics, arthropod aggregation patterns, arthropod activity and distance to tree trunk. 3 The fraction of variance which could be specifically explained by foliage attributes such as nitrogen-, water- and fibre-content, specific leaf weight, and epiphyll load was small for most arthropod groups (usually <30%). However, an index of food quality explained a higher proportion of variance (50%) in the abundance of phloem-feeders. Leaf size and foliage compactness did not influence significantly the abundance of any arthropod group. 4 Most herbivores were more abundant on young foliage than on mature leaves. With the exception of Corylophidae and Chrysomelidae, which were more abundant in the lower and upper canopy respectively, arthropod stratification was not conspicuous within the inner core of tree crowns. 5 The results firstly emphasize the distribution of young foliage as a key factor affecting the abundance of many herbivores and, secondly, the importance of the local illumination regime for host leaf production and its indirect effects on the spatial distribution of arboreal arthropods.

Site-specific mutagenesis of Escherichia coli asparaginase II. None of the three histidine residues is required for catalysis.

Abstract: Site-specific mutagenesis was used to replace the three histidine residues of Escherichia coli asparaginase II (EcA2) with other amino acids. The following enzyme variants were studied: [H87A]EcA2, [H87L]EcA2, [H87K]EcA2, [H183L]EcA2 and [H197L]EcA2. None of the mutations substantially affected the Km for L-aspartic acid beta-hydroxamate or impaired aspartate binding. The relative activities towards L-Asn, L-Gln, and l-aspartic acid beta-hydroxamate were reduced to the same extent, with residual activities exceeding 10% of the wild-type values. These data do not support a number of previous reports suggesting that histidine residues are essential for catalysis. Spectroscopic characterization of the modified enzymes allowed the unequivocal assignment of the histidine resonances in 1H-NMR spectra of asparaginase II. A histidine signal previously shown to disappear upon aspartate binding is due to His183, not to the highly conserved His87. The fact that [H183L]EcA2 has normal activity but greatly reduced stability in the presence of urea suggests that His183 is important for the stabilization of the native asparaginase tetramer. 1H-NMR and fluorescence spectroscopy indicate that His87 is located in the interior of the protein, possibly adjacent to the active site.

Molecular analysis of an esterase-encoding gene from a lipolytic psychrotrophic pseudomonad.

Abstract: Summary: An esterase gene (estA) from a lipolytic psychrotroph (Pseudomonas sp. LS107d2), was cloned in Escherichia coli and its nucleotide sequence was determined, revealing an ORF encoding a polypeptide of 389 amino acid residues, with a molecular mass of 42276 Da. Labelling of plasmid-encoded proteins with [35S)methionine, using the maxicell procedure, gave a single polypeptide of molecular mass 42 kDa, consistent with that calculated from the ORF. Colonies of E. coli cells containing estA produced a clear halo when grown on solid media containing tributyrin; no clearance was produced when cells were grown on media containing triolein. Extracts of cells containing estA also hydrolysed water-soluble nitrophenol esters, but were unable to cleave water-insoluble substrates. The preference for water-soluble substrates indicates that the gene product is an esterase.