Showing papers by "University of Queensland published in 1995"

Direct Observation of Transfer of Angular Momentum to Absorptive Particles from a Laser Beam with a Phase Singularity

Abstract: Black or reflective particles can be trapped in the dark central minimum of a doughnut laser beam produced using a high efficiency computer generated hologram. Such beams carry angular momentum due to the helical wave-front structure associated with the central phase singularity even when linearly polarized. Trapped absorptive particles spin due to absorption of this angular momentum transferred from the singularity beam. The direction of spin can be reversed by changing the sign of the singularity.

Attention, Memory, and the “Noticing” Hypothesis

Abstract: Schmidt (1990) claimed that consciousness, in the sense of awareness of the form of input at the level of “noticing”, is necessary to subsequent second language acquisition (SLA). This claim runs counter to Krashen's (1981) dualsystem hypothesis that SLA largely results from an unconscious “acquisition” system, the contribution of the conscious “learning” system to SLA being limited and peripheral. Important to a theory of SLA that allows a central role to the act of noticing is a specification of the nature of the attentional mechanisms involved, and of their relationship to current models of the organization of memory. With this in mind the present paper reviews current research into the nature of attention and memory and proposes a model of the relationship between them during SLA that, it is argued, is complementary to Schmidt's noticing hypothesis and oppositional to the dual-system hypothesis of Krashen. In light of this model, I argue that differential performance on implicit and explicit learning and memory experiments is caused by differences in the consciously regulated processing demands of training tasks and not by the activation of consciously and unconsciously accessed systems. I also argue that the attentional demands of pedagogical tasks and individual differences in memory and attentional capacity both affect the extent of noticing, thereby directly influencing SLA.

The Sry-related gene Sox9 is expressed during chondrogenesis in mouse embryos

Abstract: Mutations in the human SRY-related gene, SOX9, located on chromosome 17, have recently been associated with the sex reversal and skeletal dysmorphology syndrome, campomelic dysplasia. In order to clarify the role of this gene in skeletal development, we have studied the expression of mouse Sox9 during embryogenesis. Sox9 is expressed predominantly in mesenchymal condensations throughout the embryo before and during the deposition of cartilage, consistent with a primary role in skeletal formation. Interspecific backcross mapping has localized mouse Sox9 to distal chromosome 11. The expression pattern and chromosomal location of Sox9 suggest that it may be the gene defective in the mouse skeletal mutant Tail-short, a potential animal model for campomelic dysplasia.

The theory of planned behaviour: the effects of perceived behavioural control and self-efficacy.

Abstract: The present study was undertaken to assess the utility of the theory of planned behaviour, using separate measures of the two variables that are considered to comprise the notion of perceived behavioural control, namely, beliefs concerning the controllability of the behaviour and efficacy expectancies. The study was concerned with the prediction of intentions to engage in regular exercise (for at least 20 minutes, three times a week for a fortnight) and actual exercise behaviour. A sample of 146 undergraduate subjects participated in the study. It was prospective in design; measures of attitudes, norms, intentions, perceived control and self-efficacy were obtained at the first wave of data collection, while actual behaviour was assessed two weeks later. The results of the study revealed support for the view that separate measures of self-efficacy and perceived behavioural control should be employed in the theory of planned behaviour. In the first instance, confirmatory factor analysis revealed that the two variables could be empirically distinguished. Second, the effects of perceived behavioural control and self-efficacy on behavioural intentions and actual behaviour differed. As predicted, efficacy expectancies influenced behavioural intentions, but not actual behaviour. In contrast, levels of perceived behavioural control had no effect on behavioural intentions, but emerged as a significant (positive) predictor of actual behaviour (there was also evidence that the effects of intentions on behaviour were moderated by the level of perceived behavioural control).

On the deep structure of information systems

Abstract: . The deep structure of an information system comprises those properties that manifest the meaning of the real‐world system the information system is intended to model. In this paper we describe three models we have developed of information systems' deep‐structure properties. The first, the representational model, proposes a set of constructs that enable the ontological expressiveness of grammars used to model information systems (such as the entity‐relationship model) to be evaluated. The second, the state‐tracking model, proposes four requirements that information systems must satisfy if they are to faithfully track the real‐world system they are intended to model. The third, the good‐decomposition model, proposes three necessary conditions that information systems must meet if they are to be well decomposed. The three models provide a theoretically based, structured way of evaluating grammars that are used to analyse, design and implement information systems and scripts that have been generated using these grammars to describe specific information systems.

Anatomical methods in cell death

Abstract: Publisher Summary This chapter describes methods for studying the morphology of cell death and the criteria used in identifying apoptosis and necrosis. Electron microscopy provides the most reliable method for recognizing the two processes; in many cases, however, they can be identified confidently using light microscopy alone. The recognition of apoptosis and necrosis is based primarily on the distinctive changes that take place within the affected cells. However, when these two processes occur in vivo, they also differ in their distribution and in the tissue reactions that are associated with them. These latter features may be of subsidiary use in identification. Thus, apoptosis involves scattered individual cells in a tissue, whereas necrosis involves groups of adjoining cells. Necrosis is accompanied by an acute inflammatory response with exudation of neutrophil leukocytes and monocytes; this event is characteristically absent in apoptosis. The light microscopic recognition of apoptosis depends on the detection of discrete well-preserved apoptotic bodies. Although convoluted budding cells are sometimes observed in smears, they are rarely seen in paraffin sections of immersion-fixed tissue.

Protein and energy utilization by ruminants at pasture.

Abstract: Low live weight gain of cattle in the wet season of tropical areas was identified as a major limitation to achieving annual growth rates from tropical pasture systems sufficient to meet new market specifications of young animals of high carcass weight Both protein and energy are limiting nutrients for growth Net transfer of feed protein to the intestines is often not complete, and losses occur with grasses and legumes when CP content exceeds 210 g of CP/kg of digestible OM This protein loss is important because a collation of experimental data indicated that cattle consuming low- and high-quality pasture and silage-based diets all responded to extra protein The response was less for the higher-quality forage The role of legumes in supplying this protein was investigated and, unless legumes can increase total DMI by at least 30%, they will not supply sufficient intestinal protein to increase live weight gain by about 300 g/d The problem with legumes and some grasses is the loss of protein from the rumen, and increasing energy supply to the rumen, either through improved digestibility or energy supplements, is a strategy that could be used to reduce this Strategies to increase the proportion of escape protein would be successful, but incorporation of lowly degradable protein fractions into legumes may be more difficult because of the level of expression of these protein fractions required for a significant live weight gain response Cattle entering the wet season usually exhibit compensatory growth and are exposed to high ambient temperatures and often to high humidity Intestinal protein above that stipulated in feeding standards may be beneficial in these circumstances, and more emphasis should be placed on the ability of legumes to supply protein postruminally At present the protein delivery capacity of agronomically competitive legumes seems to be inadequate for the higher growth rates required in production systems, and supplements of energy and protein will be needed to achieve these higher targets until new cultivars appear

Role-Conflict, Ambiguity, and Overload - a 21-Nation Study

Abstract: The extent of role conflict, role ambiguity, and role overload reported by middle managers from 21 nations was related to national scores on power distance, individualism, uncertainty avoidance, an...

A structural model of the dimensions of teacher stress

Abstract: A comprehensive survey of teacher stress, job satisfaction and career commitment among 710 full-time primary school teachers was undertaken by Borg, Riding & Falzon (1991) in the Mediterranean islands of Malta and Gozo. A principal components analysis of a 20-item sources of teacher stress inventory had suggested four distinct dimensions which were labelled: Pupil Misbehaviour, Time/Resource Difficulties, Professional Recognition Needs, and Poor Relationships, respectively. To check on the validity of the Borg et al. factor solution, the group of 710 teachers was randomly split into two separate samples. Exploratory factor analysis was carried out on the data from Sample 1 (N = 335), while Sample 2 (N = 375) provided the cross-validational data for a LISREL confirmatory factor analysis. Results supported the proposed dimensionality of the sources of teacher stress (measurement model), along with evidence of an additional teacher stress factor (Workload). Consequently, structural modelling of the 'causal relationships' between the various latent variables and self-reported stress was undertaken on the combined samples (N = 710). Although both non-recursive and recursive models incorporating Poor Colleague Relations as a mediating variable were tested for their goodness-of-fit, a simple regression model provided the most parsimonious fit to the empirical data, wherein Workload and Student Misbehaviour accounted for most of the variance in predicting teaching stress.

Deafness, Conversation and Theory of Mind

Abstract: The child's developing theory of the mind as an interconnected network of beliefs, desires and feelings that govern behaviour provides a cornerstone for social and intellectual life. Recent research has suggested that autistic children have difficulty acquiring such a theory. Although it is speculated that a specific neurological deficit may be responsible for autistic children's difficulties on false belief tasks devised to test a theory of mind, these may also be due to a lack of exposure to conversation about mental states. In this study we explored the development of a theory of mind in a group of 26 signing, prelingually-deaf Australian children of normal intelligence, aged 8-13 years. Results revealed that 65% of these deaf children failed a simple test of false belief which normal preschoolers, mentally retarded children, and other handicapped groups--apart from children with autism--routinely pass at a mental age of 4-5 years. No significant difference emerged between deaf children's performance and that of autistic children tested on the same task in previous research. We discuss the results in terms of a conversational account of the development of a theory of mind in deaf children, and the extent to which this account is applicable to children with autism.

Conservation and dynamics of microsatellite loci over 300 million years of marine turtle evolution.

Abstract: Microsatellite loci consisting of (CA)(n) repetitive arrays were obtained from three species of marine turtle, and primers were designed to test for polymorphism within species and the persistence of microsatellites across species. Homologous loci were found in each test of six marine species within two families (Cheloniidae and Dermochelyidae), as well as in a freshwater species (Emydidae, Trachemys, scripta), which indicates a conservation of flanking sequences spanning approximately 300 million years of divergent evolution. The persistence of homologous microsatellites across marine turtles was confirmed by direct sequencing of loci across species and by the discovery of polymorphism in 24 of 30 cross species tests. The conservation of flanking sequences could be due to a slow rate of base substitution in turtle nuclear DNA, as previously reported for mtDNA. In contrast, the presence of up to 25 alleles per locus per species indicates that the replication slippage events responsible for changes in allele length operate as in mammals. Comparisons of alleles among species revealed that alleles of the same length may not be homologous due to mutations within the flanking sequences. Levels of heterozygosity were consistently higher in species from which the primers were designed, which suggests problems with cross-species comparisons of variability. Within species, microsatellite variation between divergent populations was consistent with results from previous mtDNA studies indicating the usefulness of microsatellites for comparing male- versus female-mediated gene flow.

Optical Particle Trapping with Higher-order Doughnut Beams Produced Using High Efficiency Computer Generated Holograms

Abstract: Laser beams containing higher-order phase singularities can be produced with high efficiency computer generated holograms made with very simple equipment. Using such holograms in an optical tweezers experiment we have successfully trapped reflective and absorptive particles in the dark central spot of a focused charge 3 singularity beam. Angular momentum absorbed from the beam can set particles into rotation.

Markers for monitoring overtraining and recovery.

Abstract: Physiological and mood state parameters were monitored during a 6-month swimming season in an attempt to determine markers of overtraining and recovery. Fourteen elite male and female swimmers were tested early-, mid-, and late-season and shortly before and after major competition. Training details and subjective ratings of well-being were compiled by the athletes in daily logs. Three swimmers were classified as stale based upon performance deterioration and prolonged, high fatigue levels. Staleness scores were calculated for each athlete using performance change from early- to late-season and daily fatigue ratings for the season. Regression analysis revealed a battery of well-being ratings which predicted staleness scores, accounting for 76% of the variance. The late-season stress ratings and plasma catecholamine levels at rest predicted staleness scores, accounting for 85% of the variance. During tapering, well-being ratings predicted improvement in competitive performance, accounting for 72% of the variance of the improvement in race times from previous best times. It was concluded that self-reported ratings of well-being may provide an efficient means of monitoring both overtraining and recovery; plasma catecholamine levels at rest may provide an additional objective tool for diagnosis.

Distributed multimedia and QOS: a survey

Abstract: Quality of service (QOS) is increasingly important for all components within distributed multimedia systems, as this survey reveals. We discuss the QOS parameters found in communication protocols, operating systems, multimedia databases and file servers, as well as those directly affecting the human user. >

Parallel and Sequential Methods for Ordinary Differential Equations

Abstract: 1. Aspects of parallel computing 2. An introduction to sequential ODE methods 3. Order and stability - a general framework 4. Parallel linear algebra 5. Direct methods for ODEs 6 . Diverse approaches to parallelism 7. Waveform relaxation techniques 8. Discrete waveform methods 9. Implementation of waveform algorithms List of symbols References

Task Complexity and Second Language Narrative Discourse

Abstract: Researchers need to identify what differences second language tasks set at different levels of complexity make to measures of learner language, in order to provide a basis for pedagogic decisions about grading and sequencing such tasks. This study examined differences in the production of oral narrative discourse by 12 adult second language learners of English on narrative tasks that simulated the ability to describe events in the Here-and-Now versus the There-and-Then. Target-like use, propositional and syntactic complexity, lexical load, pausing, and utterance length were measured under the two conditions. A MANOVA showed significant differences between the two conditions. Separate ANOVAs for each measure showed a significant difference between the two conditions for measures of lexical load and an almost significant difference for measures of target-like use. The more complex There-and-Then condition elicited greater accuracy and a higher ratio of lexical to grammatical words. There was also a trend suggesting greater utterance length for narratives performed under the simpler Here-and-Now condition. These results support the claim that complex tasks elicit less fluent, but more accurate and complex production than do simpler tasks.

Strength and power assessment. Issues, controversies and challenges.

Abstract: Athletic strength and power refer to the forces or torques generated during sporting activity. Their assessment can be used for strength diagnosis or talent identification, to monitor the effects of training interventions and to estimate the relative significance of strength and power to particular athletic pursuits. However, strength and power assessment is a difficult task. Reasons for this include: the fledgling status of research within the area, our limited understanding of the mechanisms underpinning strength and power performance and development, and limitations associated with various forms of dynamometry. This article describes a frame work for the collection of data which may ultimately lead to recommendations for the assessment of strength and power in sporting contexts. Such a framework will be evolutionary and depends upon synergistic improvements in our understanding of: the physiological mechanisms underpinning strength and power development; the effect that various training regimens have upon the development of strength and power; and factors influencing the validity and reliability of dynamometry. Currently, isometric, isoinertial and isokinetic dynamometry are employed in assessment. Each form has its supporters and detractors. Basically, proponents and critics of isokinetic and isometric dynamometry emphasise their apparently high external and apparently low internal validity respectively. While the converse applies for isoinertial dynamometry. It appears that all 3 modalities can have acceptable reliability, however this should be established rather than assumed, as the reliability of each can be threatened by a number of considerations (e.g. instruction for isometric tasks, the impact of weight used during weighted jumping tasks, and the effects of gravity and feedback on isokinetic performance). While reliability is a seminal issue in assessment, it is not the only critical issue. Specifically, there has been little research into the correlation between strength and power measures and athletic performance. This work is central to the use of such indices in talent identification. To date, this work has generally been limited to heterogeneous rather than homogeneous groups. More work is required in this area. Furthermore, not all modes of assessment are sensitive or similarly sensitive to various training interventions. This suggests that these modalities are measuring different neuromuscular qualities. How these qualities relate to performance requires more work, and will determine the contexts in which various strength and power assessment modalities and protocols are used. Following are conclusions from the review: (i) it is unlikely that one assessment procedure can be used for a multitude of ends (e.g. talent identification and monitoring the effects of training); (ii) different levels of athlete ability within a given sport may require different assessment regimens; (iii) minor changes in procedure may alter the usefulness of a procedure and (iv) we must be prepared to question assumptions pervading the field which are based upon anecdotal evidence. There are limitations with, and should be delimitations in the use of the various protocols and forms of dynamometry.

An evidence based approach to individualising treatment

Abstract: To which groups of patients can the results of clinical trials be applied? This question is often inappropriately answered by reference to the trial entry criteria. Instead, the benefit and harm (adverse events, discomfort of treatment, etc) of treatment could be assessed separately for individual patients. Patients at greatest risk of a disease will have the greatest net benefit as benefit to patients usually increases with risk while harm remains comparatively fixed. To assess net benefit, the relative risks should come from (a meta-analysis of) randomised trials; the risk in individual patients should come from multivariate risk equations derived from cohort studies. However, before making firm conclusions, the assumptions of fixed adverse effects and constant reduction in relative risk need to be checked.

A redefinition of somatosensory areas in the lateral sulcus of macaque monkeys

Abstract: The present investigation was designed to determine the organization of somatosensory fields in the lateral sulcus of macaque monkeys using standard microelectrode recording techniques. Our results provide evidence for two complete representations of the body surface. We term these fields the second somatosensory area (SII) and the parietal ventral area (PV) because of their similarities in position, internal organization, and relationship to anterior parietal fields, as described for SII and PV in other mammals. Areas SII and PV are mirror-symmetrical representations of the body surface, sharing a common boundary at the representations of the digits of the hand and foot, lips, and mouth. These fields are located adjacent to the face representations of anterior parietal fields (areas 3b, 1, and 2), and are bounded ventrally and caudally by other regions of cortex in which neurons are responsive to somatic or multimodal stimulation. The finding of a double representation of the body surface in the region of cortex traditionally designated as SII may explain conflicting descriptions of SII organization in macaque monkeys. In addition, the present study raises some questions regarding the designation of serial processing pathways in Old World monkeys, by suggesting that fields may have been confused in studies demonstrating such pathways. We propose that SII and PV are components of a common plan of organization, and are present in many eutherian mammals.

Anisotropic wave propagation through finite‐difference grids

Abstract: An algorithm is presented to solve the elastic-wave equation by replacing the partial differentials with finite differences. It enables wave propagation to be simulated in three dimensions through generally anisotropic and heterogeneous models. The space derivatives are calculated using discrete convolution sums, while the time derivatives are replaced by a truncated Taylor expansion. A centered finite difference scheme in cartesian coordinates is used for the space derivatives leading to staggered grids. The use of finite difference approximations to the partial derivatives results in a frequency-dependent error in the group and phase velocities of waves. For anisotropic media, the use of staggered grids implies that some of the elements of the stress and strain tensors must be interpolated to calculate the Hook sum. This interpolation induces an additional error in the wave properties. The overall error depends on the precision of the derivative and interpolation operators, the anisotropic symmetry system, its orientation and the degree of anisotropy. The dispersion relation for the homogeneous case was derived for the proposed scheme. Since we use a general description of convolution sums to describe the finite difference operators, the numerical wave properties can be calculated for any space operator and an arbitrary homogeneous elastic model. In particular, phase and group velocities of the three wave types can be determined in any direction. We demonstrate that waves can be modeled accurately even through models with strong anisotropy when the operators are properly designed.

Factors influencing the occurrence of flow state in elite athletes

Abstract: Understanding factors which may influence the occurrence of flow in elaite athletes was the goal of the present investigation. Twenty-eight elite level athletes from seven sports were interviewed about the factors they perceived influenced their experience of flow state. Inductive content analyses of athletes' responses to questions about what facilitates, prevents, and disrupts flow, resulted in 10 dimensions that synthesized the 361 themes suggested by the athletes. These themes and dimensions provided insight into factors that may influence whether or not flow occurs in elite athletes. For example. some of the more salient factors influencing whether or not flow occurred included: preparation, both physical and mental; confidence; focus; how the performance felt and progressed; and optimal motivation and arousal level. This study also involved asking elite athletes about the perceived controllability of these factors, and of the state of flow itself. The majority of the athletes interviewed pe...