Intercepting a moving target: effects of temporal precision constraints and movement amplitude

The effects of temporal precision constraints and movement amplitude on performance of an interceptive aiming task were examined. Participants were required to strike a moving target object with a 'bat' by moving the bat along a straight path (constrained by a linear slide) perpendicular to the path of the target. Temporal precision constraints were defined in terms of the time period (or window) within which contact with the target was possible. Three time windows were used (approx. 35, 50 and 65 ms) and these were achieved either by manipulating the size of the bat (experiment 1a), the size of the target (experiment 1b) or the speed of the target (experiment 2). In all experiments, movement time (MT) increased in proportion to movement amplitude but was only affected by differences in the temporal precision constraint if this was achieved by variation in the target's speed. In this case the MT was approximately inversely proportional to target speed. Peak movement speed was affected by temporal accuracy constraints in all three experiments: participants reached higher speeds when the temporal precision required was greater. These results are discussed with reference to the speed-accuracy trade-off observed for temporally constrained aiming movements. It is suggested that the MT and speed of interceptive aiming movements may be understood as responses to the spatiotemporal constraints of the task.

Psychological science in Australia

This paper is a brief account of the Australian Strategic Review of the Psychology Discipline and its Research. Issues discussed include Australia's contribution to world research in psychological science, research funding, the age and qualifications of researchers, the social and economic benefits arising from the applications of research outcomes, multidisciplinary issues, the role of psychology in industry, links between the discipline and the profession of psychology, professional training, cross-cultural issues, and educational issues. Priorities for development of research and postgraduate training are identified, and include human factors and other areas related to technological change, clinical psychology with particular attention to health psychology, industrial and organizational psychology, and neuroscience and physiological psychology.

A study of the stability of subcycling algorithms in structural dynamics

Algorithms for explicit integration of structural dynamics problems with multiple time steps (subcycling) are investigated. Only one such algorithm, due to Smolinski and Sleith has proved to be stable in a classical sense. A simplified version of this algorithm that retains its stability is presented. However, as with the original version, it can be shown to sacrifice accuracy to achieve stability. Another algorithm in use is shown to be only statistically stable, in that a probability of stability can be assigned if appropriate time step limits are observed. This probability improves rapidly with the number of degrees of freedom in a finite element model. The stability problems are shown to be a property of the central difference method itself, which is modified to give the subcycling algorithm. A related problem is shown to arise when a constraint equation in time is introduced into a time-continuous space-time finite element model. (C) 1998 Elsevier Science S.A.

Australian doctors' beliefs and practice regarding Helicobacter pylori

Objective: To determine beliefs and behaviours of Australian doctors regarding Helicobacter pylori. Design: Anonymous reply-paid postal survey mailed in December 1995 and again in March 1996. Subjects: All members on the mailing lists of the Gastroenterological Society of Australia Endoscopy Section (n = 397) and the Australian Society of Infectious Diseases (n = 264; those without medical qualifications were asked not to reply), and 400 general practitioners (GPs) randomly selected from the Royal Australian College of General Practitioners. Main outcome measures: Differences between specialist groups in belief in a causative association between H. pylori and peptic disease and in use of eradication therapy and pre- and post-treatment testing for H. pylori. Results: 92.6% of doctors believed H. pylori causes duodenal ulcer, with GPs significantly less likely to believe than gastroenterologists (odds ratio [OR], 0.22; 95% confidence interval [CI], 0.00-0.81). In duodenal ulcer, 93.4% of doctors believed H. pylori eradication therapy should be given, but fewer (83.4%) claimed to give it always or mostly, with GPs less likely to report giving it than gastroenterologists (OR, 0.06; 95% CI, 0.02-0.19). For non-ulcer dyspepsia, gastrointestinal surgeons were more likely than gastroenterologists to believe in a causative link with H. pylori (OR, 5.6; 95% CI, 3.0-10.7) and in a need for eradication therapy (OR, 3.6; 95% CI, 1.7-7.7). Most doctors (79.3%) believed in confirming the presence of H. pylori before eradication therapy in duodenal ulcer. Only 51.6% believed post-eradication testing necessary (45.5%), yet 79.1% reported performing it. Conclusions: Significant differences exist between specialist groups in beliefs and self-reported behaviours regarding H. pylori.

Metabolic analysis of poly(3-hydroxybutyrate) production by recombinant Escherichia coli

Poly(3-hydroxybutyrate) (PHB) production by fermentation was examined under both restricted- and ample-oxygen supply conditions in a single fed-batch fermentation. Recombinant Escherichia coli transformed with the PHB production plasmid pSYL107 was grown to reach high cell density (227 g/l dry cell weight) with a high PHB content (78% of dry cell weight), using a glucose-based minimal medium. A simple flux model containing 12 fluxes was developed and applied to the fermentation data. A superior closure (95%) of the carbon mass balance was achieved. When the data were put into use, the results demonstrated a surprisingly large excretion of formate and lactate. Even though periods of severe oxygen limitation coincided with rapid acetate and lactate excretion, PHB productivity and carbon utilization efficiency were not significantly impaired. These results are very positive in reducing oxygen demand in an industrial PHA fermentation without sacrificing its PHA productivity, thereby reducing overall production costs.

Associations between rural background and where South Australian general practitioners work

Objective: To determine the association between rural background on practice location of general practitioners (GPs) (rural or urban). Design: Comparison of data from two postal surveys. Subjects: 268 rural and 236 urban GPs practising in South Australia. Main outcome measures: Association between practice location (rural or urban) and demographic characteristics, training, qualifications, and rural background. Results: Rural GPs were younger than urban GPs (mean age 47 versus 50 years, P<0,01) and more likely to be male (81% versus 67%, P=0.001), to be Australian-born (72% Versus 61%, P=0,01), to have a partner (95% versus 85%, P= 0.001), and to have children (94% Versus 85%, P=0.001). Similar proportions of rural and urban GPs were trained in Australia and were Fellows of the Royal Australian College of General Practitioners, but more rural GPs were vocationally registered (94% versus 84%, P=0,001). Rural GPs were more likely to have grown up in the country (37% versus 27%, P= 0,02), to have received primary (33% versus 19%, P=0,001) and secondary (25% versus 13%, P=0,001) education there, and to have a partner who grew up in the country (49% Versus 24%, P=0.001). In multivariate analysis, only primary education in the country (odds ratio [OR], 2.43; 95% CI, 1.09-5.56) and partner of rural background (OR, 3.14; 95% CI, 1.96-5.10) were independently associated with rural practice. Conclusion: Our findings support the policy of promoting entry to medical school of students with a rural background and provide an argument for policies that address the needs of partners and maintain quality primary and secondary education in the country.

The role of the church in developing the law: response to commentators

Three of the four commentators endorse our concerns about intervention by the Roman Catholic church as an omicus curiae in civil litigation, with few reservations. One commentary rejects our arguments in We deal first with the three commentaries that support our arguments; secondly, with the reservations and qualifications in those commentaries, and thirdly, with the commentary that totally rejects our arguments.

Heterogeneity, saving-investment dynamics and capital mobility in Latin America

The purpose of this paper is to analyze the dynamics of national saving-investment relationship in order to determine the degree of capital mobility in 12 Latin American countries. The analytically relevant correlation is the short-term one, defined as that between changes in saving and investment. Of special interest is the speed at which variables return to the long run equilibrium relationship, which is interpreted as being negatively related to the degree of capital mobility. The long run correlation, in turn, captures the coefficient implied by the solvency constraint. We find that heterogeneity and cross-section dependence completely change the estimation of the long run coefficient. Besides we obtain a more precise short run coefficient estimate compared to the existent estimates in the literature. There is evidence of an intermediate degree of capital mobility, and the coefficients are extremely stable over time.

A spectral clustering algorithm for manufacturing cell formation

A graph clustering algorithm constructs groups of closely related parts and machines separately. After they are matched for the least intercell moves, a refining process runs on the initial cell formation to decrease the number of intercell moves. A simple modification of this main approach can deal with some practical constraints, such as the popular constraint of bounding the maximum number of machines in a cell. Our approach makes a big improvement in the computational time. More importantly, improvement is seen in the number of intercell moves when the computational results were compared with best known solutions from the literature. (C) 2009 Elsevier Ltd. All rights reserved.

Stimulating dormancy release and emergence of annual ryegrass (Lolium rigidum) seeds using short-term hydrated storage in darkness

Experiments were performed to determine whether the dormancy release effect of hydrated storage in darkness (dark-stratification) is common amongst annual ryegrass populations and has the potential to occur under field conditions. Dormant seeds from all populations tested (22) became sensitive to light during dark-stratification, enabling them to germinate when subsequently exposed to light. Under controlled temperature (25/15degreesC), light (12-h photoperiod), and hydration (solidified agar-water) conditions, more seeds germinated by 28 days if the first 14 days were in darkness followed by exposure to light for 12 h per day than if they were exposed to light throughout or darkness throughout. Constraint over the conditions imposed during dark-stratification and germination was gradually reduced to investigate whether the dormancy release effect was diminished. Dark-stratification was effective in promoting germination when performed under natural diurnal temperatures, and burial in moist soil provided suitable conditions for dark-stratification to occur. The surface of moist soil, with natural diurnal temperatures and sunlight, was suitable for germination of dark-stratified seeds. Dark-stratification is a quick and effective means to enhance the sensitivity of dormant annual ryegrass seeds to light, enabling the majority of the population to germinate. However, large quantities of light are required to promote germination of dark-stratified seeds, so buried seeds must be moved to the soil surface to allow exposure to adequate light for germination.

Ultraviolet signals ultra-aggression in a lizard

Understanding the role of multiple colour signals during sexual signalling is a central theme in animal communication. We quantified the role of multiple colour signals (including ultraviolet, UV), measures of body size and testosterone levels in settling disputes between male rivals in an elaborately ornamented, African lizard, played out in a large 'tournament' in the wild. The hue and brightness (total reflectance) of the UV throat in Augrabies flat lizards, Platysaurus broadleyi, as well as body size, were consistent and strong predictors of 'fighting ability'. Males with high fighting ability were larger and displayed a UV throat with low total reflectance. In contrast, males with low fighting ability were smaller and had violet throats with broader spectral reflectance curves (higher total reflectance). As fighting ability is associated with alternative reproductive tactics in this system (territorial versus floater), we also examined the role of colour signals in predicting male reproductive tactic. Territorial males had UV throats with higher chroma but had poorer body condition than floater males, probably because of the energetic costs of maintaining a territory. Although testosterone was not a significant predictor of fighting ability or reproductive tactic, it was correlated with the hue of the UV throat, suggesting that testosterone may impose some constraint on signal expression. Lastly, we show that within the context of the natural signalling environment, UV-reflective throats constitute a conspicuous, effective signal that male Augrabies flat lizards use to advertise their status honestly to rivals. (c) 2006 The Association for the Study of Animal Behaviour. Published by Elsevier Ltd. All rights reserved.

Haptic information stabilizes and destabilizes coordination dynamics

Goal-directed, coordinated movements in humans emerge from a variety of constraints that range from 'high-level' cognitive strategies based oil perception of the task to 'low-level' neuromuscular-skeletal factors such as differential contributions to coordination from flexor and extensor muscles. There has been a tendency in the literature to dichotomize these sources of constraint, favouring one or the other rather than recognizing and understanding their mutual interplay. In this experiment, subjects were required to coordinate rhythmic flexion and extension movements with an auditory metronome, the rate of which was systematically increased. When subjects started in extension on the beat of the metronome, there was a small tendency to switch to flexion at higher rates, but not vice versa. When subjects: were asked to contact a physical stop, the location of which was either coincident with or counterphase to the auditor) stimulus, two effects occurred. When haptic contact was coincident with sound, coordination was stabilized for both flexion and extension. When haptic contact was counterphase to the metronome, coordination was actually destabilized, with transitions occurring from both extension to flexion on the beat and from flexion to extension on the beat. These results reveal the complementary nature of strategic and neuromuscular factors in sensorimotor coordination. They also suggest the presence of a multimodal neural integration process-which is parametrizable by rate and context - in which intentional movement, touch and sound are bound into a single, coherent unit.

Predictors of cheating behavior at a university: A lesson from the psychology of work

The present study investigated students' behavior across academic departments to establish how personality, demographic, educational, attitudinal, and climate (both psychological and departmental) predicted self-reported cheating behavior at a university, Participants were 107 students from a variety of academic disciplines, The results explain 50.5% of the variability in self-reported cheating behavior in terms of demographic (male, school education qualifications), departmental climate, and individual differences (Lie and Neuroticism scales), We concluded that an expanded theoretical perspective (utilizing a wide range of person and situation variables) explained more variability than would otherwise be explained from any single perspective, and that findings from the literature of integrity at work generalize to educational settings. Finally, we discuss the limitations and implications of this research.

Muslims and the Australian labour market, 1980-2001

The unemployment of Muslims in Australia was 28 and 25 per cent compared to the national total of around nine per cent in 1986 and 1996 respectively (Australian Bureau of Statistics). This article conceptually analyses the disadvantaged position of the Muslims in the Australian labour market from 1980 to 2001 within a framework of 'structural racism'. It studies the Muslims from three perspectives: first, a comparative study of the qualifications and unemployment of the Muslim labour force in relation to the dominant population. Secondly, it examines the extent of this disadvantaged position in comparison with other ethnic minorities within an historical context. Finally, the basis of structural racism is explored to demonstrate how the Muslims have become systematically victimized. The analysis concludes that Muslims are significantly disadvantaged in Australia on the basis of their ethnicity and religion.

Interaction of directional, neuromuscular and egocentric constraints on the stability of preferred bimanual coordination patterns

We investigated how the relative direction of limb movements in external space (iso- and non-isodirectionality), muscular constraints (the relative timing of homologous muscle activation) and the egocentric frame of reference (moving simultaneously toward/away the longitudinal axis of the body) contribute to the stability of coordinated movements. In the first experiment, we attempted to determine the respective stability of isodirectional and non-isodirectional movements in between-persons coordination. In a second experiment, we determined the effect of the relative direction in external space, and of muscular constraints, on pattern stability during a within-person bimanual coordination task. In the third experiment we dissociated the effects on pattern stability of the muscular constraints, relative direction and egocentric frame of reference. The results showed that (1) simultaneous activation of homologous muscles resulted in more stable performance than simultaneous activation of non-homologous muscles during within-subject coordination, and that (2) isodirectional movements were more stable than non-isodirectional movements during between-persons coordination, confirming the role of the relative direction of the moving limbs in the stability of bimanual coordination. Moreover, the egocentric constraint was to some extent found distinguishable from the effect of the relative direction of the moving limbs in external space, and from the effect of the relative timing of muscle activation. In summary, the present study showed that relative direction of the moving limbs in external space and muscular constraints may interact either to stabilize or destabilize coordination patterns. (C) 2003 Published by Elsevier B.V.