209 research outputs found

    An investigation of handwriting legibility and pencil use tasks in healthy older adults

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    This project explores handwriting legibility and pencil use tasks in 120 healthy older Australian adults, aged 60 to 99 years. A cross sectional study design was used. The aim of these studies was to explore if handwriting legibility or pencil use performance deteriorated as people aged. This is important to help therapists determine if handwriting difficulties following stroke, or other medical conditions, are more likely a consequence of condition-related impairments or due to ‘normal ageing’. Tasks performed under standardised test conditions included writing copied and self-composed sentences, shopping lists, transcribing a telephone message and completing the ‘lines’ and ‘dots’ pencil use Motor Assessment Scale (MAS) subtests. Handwriting legibility was scored using the Modified Four Point Scale-version 2. The first study explored the distribution of handwriting legibility scores in healthy older adults, relationships between handwriting legibility, age and writing task and reliability of rating procedures. Results indicated that handwriting generally remained legible in older adults, regardless of increasing age. The second study explored the performance of older adults without stroke on the ‘lines’ and ‘dots’ tasks, the relationship between age and task performance, and the relationship between writing speed and performance on the ‘lines’ task. Results indicated that many older adults failed the ‘lines’ task and many over 90 years of age failed the ‘dots’ task. Results suggest that impaired handwriting legibility in older adults who have had a stroke (or other medical condition) is likely due to the effects of the medical condition (or the complexity of the task) rather than ‘normal ageing’. However, failure to pass the ‘lines’ and ‘dots’ tasks is likely related to a combination of age and individual skill level and not solely due to condition-related impairment. A revised method for rating performance on the ‘lines’ and ‘dots’ tasks is also proposed

    On the origin of high m magnetospheric waves

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    A survey of Advanced Rio-Imaging Experiment in Scandinavia data reveals evidence for a previously overlooked generation mechanism of high azimuthal wave number magnetospheric waves. Here we present observations of pulsating cosmic noise absorption with azimuthal wave numbers as high as 380, suggestive of precipitation modulation by magnetospheric waves. Dispersion relations of the small-scale precipitation pulsations are indicative of the proposed origin. Previous studies of magnetospheric waves, together with data from the Charge And Mass Magnetospheric Ion Composition Experiment (Magnetospheric Ion Composition Sensor) instrument aboard the Polar spacecraft, provide support for the theory

    Drift orbits and neoclassical transfort in the H-1NF heliac

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    This thesis is concerned with neoclassical transport in the H-1NF heliac, and contains an examination of drift-orbit geometries, a description of a neoclassical Monte Carlo transport code, and a description of a method to use that code to self-consistently calculate ambipolar radial electric fields. We set out to study the contributions to neoclassical transport in H-1NF, by first describing the topology and the abundance of collisionless, trapped particle orbits in the presence of radial electric fields. We give an overview of the trapped orbit geometries in H-1NF, and develop a method to numerically classify the trapped particle orbits. On average, the trapped particle fraction in H-1NF is 40%, with approximately 5%, 15%, and 20% of the orbits in the deeply trapped, helically trapped, and toroidally trapped states, respectively. A condensed version of this component of the thesis has been submitted to Nuclear Fusion. The orbit studies provide a background for the development of a neoclassical Monte Carlo transport code, MCMuPPeT (for Monte Carlo, Multi Processing Plasma Transport). Using the code, we compare several Monte Carlo transport diagnostics, taken from the literature. Confinement times and diffusion coefficients are calculated for plasma conditions which will be achievable in H-1NF after the National Facility upgrade. Since the electric field can dominate in the determination of the transport, we develop an iterative method to self-consistently calculate the ambipolar radial electric field, using the Monte Carlo code. The method is applied to the Argon plasma conditions observed in H-1NF, in the experimentally observed Improved Conhnement Mode (ICM). To help interpret the results, the ambipolar electric fields were calculated in the same conditions using a well-known analytic model which was geometrically-fitted to H-1NF for our purposes. Qualitative agreement was found between both of the neoclassical models and the experimental results; the electric fields predicted in the ICM conditions are typically twice as large as those predicted in the conditions before the transition. The two models were also used to look for the neoclassically predicted transition from negative to positive radial electric field. Positive radial electric fields were observed, at long mean free path, in Hydrogen plasma conditions which will be achievable in H-1NF after the National Facility upgrade. We have also developed methods to optimise the Monte Carlo code for both parallel and vector computing environments. Two Message Passing algorithms that we use to parallelise the MC code are presented in the appendix

    Generation and transport of a low energy intense ion beam

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    The paper describes experiments on the generation and transport of a low energy (70-120 keV), high intensity (10-30 A/cm(2)) microsecond duration H+ ion beam (IB) in vacuum and plasma. The IB was generated in a magnetically insulated diode (MID) with an applied radial B field and an active hydrogen-puff ion source. The annular IB, with an initial density of j(i)similar to10-20 A/cm(2) at the anode surface, was ballistically focused to a current density in the focal plane of 50-80 A/cm(2). The postcathode collimation and transport of the converging IB were provided by the combination of a "concave" toroidal magnetic lens followed by a straight transport solenoid section. With optimized MID parameters and magnetic fields in the lens/solenoid system, the overall efficiency of IB transport at the exit of the solenoid 1 m from the anode was similar to 50% with an IB current density of 20 A/cm(2). Two-dimensional computer simulations of post-MID IB transport supported the optimization of system parameters. (C) 2004 American Institute of Physics
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