Complexity, age and motor competence effects on fine motor kinematics

Prehension is a fundamental skill usually performed as part of a complex action sequence in everyday tasks. Using an information processing framework, these studies examined the effects of task complexity, defined by the number of component movement elements (MEs), on performance of prehension tasks. Of interest was how motor control and organisation might be influenced by age and/or motor competence. Three studies and two longitudinal case studies examined kinematic characteristics of prehension tasks involving one-, two- and three-MEs: reach and grasp (low-complexity); reach, grasp and object placement (moderate-complexity); and reach, grasp and double placement of object (high-complexity). A pilot study established the suitability of tasks and procedures for children aged 5-, 8- and 11-years and showed that responses to task complexity and object size manipulations were sensitive to developmental changes, with increasing age associated with faster movements. Study 2 explored complexity and age effects further for children aged 6- and 11-years and adults. Increasing age was associated with shorter and less variable movement times (MTs) and proportional deceleration phases (%DTs) across all MEs. Task complexity had no effect on simple reaction time (SRT), suggesting that there may be little preprogramming of movements beyond the first ME. In addition, MT was longer and more on-line corrections were evident for the high- compared to the moderate-complexity task for ME1. Task complexity had a greater influence on movements in ME2 and ME3 than ME1. Adults, but not children, showed task specific adaptations in ME2. Study 3 examined performance of children with different levels of motor competence aged between 5- and 10-years. Increasing age was associated with shorter SRTs, and MTs for ME1 only. A decrease in motor competence was associated with greater difficulty in planning and controlling movements as indicated by longer SRTs, higher %DTs and more on-line corrections, especially in ME2. Task complexity affected movements in all MEs, with a greater influence on ME1 compared to Study 2. Findings also indicated that performance in MEs following prehension may be especially sensitive to motor competence effects on movement characteristics. Case studies for two children at risk of Developmental Coordination Disorder (DCD) revealed two different patterns of performance change over a 16-17 month period, highlighting the heterogeneous nature of DCD. Overall, findings highlighted age-related differences, and the role of motor competence, in the ability to adapt movements to task specific requirements. Results are useful in guiding movement education programmes for children with both age-appropriate and lower levels of motor competence.

Fine-scale adaptation in a clonal sea anemone

Local adaptation in response to fine-scale spatial heterogeneity is well documented in terrestrial ecosystems. In contrast, in marine environments local adaptation has rarely been documented or rigorously explored. This may reflect real or anticipated effects of genetic homogenization, resulting from widespread dispersal in the sea. However, evolutionary theory predicts that for the many benthic species with complex life histories that include both sexual and asexual phases, each parental habitat patch should become dominated by the fittest and most competitive clones. In this study we used genotypic mapping to show that within headlands, clones of the sea anemone Actinia tenebrosa show restricted distributions to specific habitats despite the potential for more widespread dispersal. On these same shores we used reciprocal transplant experiments that revealed strikingly better performance of clones within their natal rather than foreign habitats as judged by survivorship, asexual fecundity, and growth. These findings highlight the importance of selection for fine-scale environmental adaptation in marine taxa and imply that the genotypic structure of populations reflects extensive periods of interclonal competition and site-specific selection.

Processing and quality of cashmere tops for ultra-fine wool worsted blend fabrics

This study has focussed on three main areas. First, an evaluation of the physical attributes of cashmere tops available to commercial spinners; second, the influence of processing variables on the efficiency of producing cashmere tops from raw Australian cashmere; and third, the influence of design of cashmere ultrafine wool blends on the fibre curvature of tops. Testing the physical attributes of cashmere tops from traditional and new sources of supply, was followed by statistical analyses based on factors of origin, processor and other determinants. The analyses demonstrated important processor effects and also that cashmere from different origins shows commercially important variations in fibre attributes. It was possible to efficiently produce Australian cashmere tops with Hauteur, tenacity, extension, softness and residual guard hairs quality attributes equivalent to those observed in the best cashmere tops. The blending of cashmere with wool resulted in a reduction of the mean fibre curvature of the blend compared with the unblended wool. The present work demonstrated that the fibre curvature properties of blended low crimp ultrafine wool tops were closer to the properties of pure cashmere tops than were tops made from blended standard high crimp ultrafine wool. The attributes of textiles made from the relatively rare Australian low curvature cashmere could enhance the marketability of both Australian cashmere and low curvature wool.

Fine structure of shear bands formed during hot deformation of two austenitic steels

Shear bands formed during both cold and hot plastic deformation have been linked with several proposed mechanisms for the formation of ultrafine grains. The aim of the present work was to undertake a detailed investigation of the microstructural and crystallographic characteristics of the shear bands formed during hot deformation of a 22Cr-19Ni-3Mo (mass%) austenitic stainless steel and a Fe-30 mass%Ni based austenitic model alloy. These alloys were subjected to deformation in torsion and plane strain compression (PSC), respectively, at temperatures of 900°C and 950°C and strain rates of 0.7s_-1 and 10s_-1, respectively. Transmission electron microscopy and electron backscatter diffraction in conjunction with scanning electron microscopy were employed in the investigation. It has been observed that shear bands already started to form at moderate strains in a matrix of pre-existing microbands and were composed of fine, slightly elongated subgrains (fragments). These bands propagated along a similar macroscopic path and the subgrains, present within their substructure, were rotated relative to the surrounding matrix about axes approximately parallel to the sample radial and transverse directions for deformation in torsion and PSC, respectively. The subgrain boundaries were largely observed to be non-crystallographic, suggesting that the subgrains generally formed via multiple slip processes. Shear bands appeared to form through a co-operative nucleation of originally isolated subgrains that gradually interconnected with the others to form long, thin bands that subsequently thickened via the formation of new subgrains. The observed small dimensions of the subgrains present within shear bands and their large misorientations clearly indicate that these subgrains can serve as potent nucleation sites for the formation of ultrafine grain structures during both subsequent recrystallisation, as observed during the present PSC experiments, and phase transformation.

The effect of strain rate on the deformation mechanisms and the strain rate sensitivity of an ultra-fine-grained Al alloy

An ultra-fine-grained Al alloy was subjected to compression tests at different strain rates. The strain rate sensitivity of the flow stress was estimated. A strong effect of the baseline strain rate on the mechanisms of plastic deformation was found. It is suggested that a decrease of strain rate results in activation of micro shear banding due to grain boundary sliding. A connection between the strain rate, strain rate sensitivity, and the prevalent deformation mechanism was established.

Intersection and partition graphs

This thesis reviews previous work done on both general partition graphs and existential partition graphs, which are a generalised form of general partition graphs, and extends some of the results.

Processing of fine-grained aluminum foam by spark plasma sintering

Porous materials are now becoming attractive to researchers interested in both scientific and industrial applications due to their unique combinations of physical, mechanical, thermal, electrical and acoustic properties in conjunction with excellent energy absorption characteristics. Metallic foams allow efficient conversion of impact energy into deformation work, which has led to increasing applications in energy absorption devices. In particular, foams made of aluminum and its alloys are of special interest because they can be used as lightweight panels, for energy absorption in crash situations and sound or heat absorbing functions in the automotive industry with the aim to reduce weight to improve crashworthiness, safety and comfort.

Deformation mechanisms in an ultra-fine grained Al alloy

This work focuses on the deformation behavior of an ultra-fine grained Al-Mg-Si alloy processed by equal channel angular pressing over a wide range of temperatures and strain rates. The effect of temperature and strain rate on the homogeneity of plastic deformation, the evolution of microstructure, the strain rate sensitivity and the underlying deformation mechanisms are investigated. It is demonstrated that the localization of plastic deformation at the micro scale is triggered by grain boundary sliding due to grain boundary sliding due to grain boundary diffusion. The contributions of different deformation mechanisms during the plastic deformation of the material are discussed.

How fine the air

Collections of quiet and reflective images that seem to imply a narrative. Drummond explores the abandoned, the forgotten, the fleeting, the rundown andthe empty buildings, people or moments. Turning upside-down the conventional ideas of aesthetic value, Drummond finds beauty amidst rubbish, empty spaces and the ostensibly ugly or overlooked. These works involve an accumulation of evidence and signs of habitation and presense, the way we're living, ultimately creating some kind of rough portraiture.

Facilitating dynamic web service composition with fine-granularity context management

Context is an important factor for the success of dynamic service composition. Although many contextbased AI or workflow approaches have been proposed to support dynamic service composition, there is still an unaddressed issue of the support of fine-granularity context management. In this paper, we propose a granularity-based context model together with an approach to supporting the intelligent context-aware service composing problem. The corresponding case study is provided to show the validity of our approach.