VARIATION IN MOTION ANALYSIS OF SPRINT HURDLES: PART 1CO-ORDINATE DEVIATION IN 3-DIMENSIONAL RECONSTRUCTION

INTRODUCTION. An understanding of the different variation sources in experimental sport research is fundamental to technical analysis (Yeadon, 1994). Individual variable level variation in the event of sprint hurdles was presented by Salo el al. (1995). The aim of this study was to investigate the variation al the digitised co-ordinate level. METHODS Hurdle c1earances were videotaped with two genlocked cameras (50 Hz, at a 90 degree angle from the hurdle symmetrically on both sides of the lane). Two randomly selected trials (female and male) were digitised eight times by the same operator using APAS. The separate raw co-ordinates (u, v) of both camera views and the raw 30 co-ordinates (after OLT) 01 all digitised trials were transformed to Excel software. Standard deviation (SO) for the all 18 body landmarks were calculated separately for every single analysed field. The lowest SO of each condition and each co-ordinate direction (including diagonal combination) was selected as a base unit. All other SOs were standardised to these base units. RESULTS The mean SO of each landmark over all digitised fjelds in u-and v-directions ranged fram 2.3 to 8.7 (female) and from 2.6 to 7.1 (male) relative SO units. This variation resulted in SO of 0.017, 0.009, 0.016 and 0.025 m in X-, y-, z-and diagonal directions, respectively, for the female athlete as a maxirna mean of an individual landmark in the 30 re-construction. The respective SO values for the male trial were 0.017, 0.012, 0.018 and 0.027m. The maximum variation of an individual landmark in a single field of one view was 22.5 SO-units (female) and 30.0 SO-units (male). However, most of the landmarks had less than 4 SO-units variation in most of the analysed fields. DISCUSSION The lowest SO was selected for the base unit, as this presented the most accurate situation which an operator was able to reach in repeated digitising. Generally at an average level, the variation of raw 3D coordinates can be considered acceptable. However, there were c1early problematic situations, when landmarks gained up to 30 times more variation in a single field than the best situation. The influence of this huge variation on variables depends upon whether it appears at a critical moment. In this study, the largest variation occurred in an air phase around the highest point of the flight path. For the male athlete, the trailleg and the ipsilateral arm were obstructed by the trunk for the other camera view. This had only a slight eHect on the maximum height of the centre of mass (GM) (SO= 0.01 m). However, the distance of the GM peak to the hurdle varied significantly (SO= 0.11 m). Oue to lower trail leg path Ihe same problem did not occur for the female athlete (SO= 0.00 and 0.01 m, respectively). Based on this study, it is elear that large variation occurs in manual digitising at the co-ordinate level and this variation can have critica! and important effects for variable values. REFERENCES Salo, A., Grimshaw, P.N. & Viitasalo, J.T. (1995). The repeatabIlity of motion analysis and the reproducibility of athletes in sprint hurdles. In: XlIIISBS Symposium. Abstracts. Thunder Bay, Ontario, Canada. Yeadon, M.A., & Ghallis, J.H. (1994). The future of pertormance-related sports biomechanics research. Journal 01 Sports Sciences, 12, 3-32

Steady transcritical flow over an obstacle: Parametric map of solutions of the forced extended Korteweg-de Vries equation

Transcritical flow of a stratified fluid over an obstacle is often modeled by the forced Korteweg-de Vries equation, which describes a balance among weak nonlinearity, weak dispersion, and small forcing effects. However, in some special circumstances, it is necessary to add an additional cubic nonlinear term, so that the relevant model is the forced extended Korteweg-de Vries equation. Here we seek steady solutions with constant, but different amplitudes upstream and downstream of the forcing region. Our main interest is in the case when the forcing has negative polarity, which represents a hole. The effects of the width of the hole and the amplitude of the hole on these steady solutions are then investigated. © 2011 American Institute of Physics.published_or_final_versio

Soliton formation from a pulse passing the zero-dispersion point in a nonlinear Schr\"odinger equation

We consider in detail the self-trapping of a soliton from a wave pulse that passes from a defocussing region into a focussing one in a spatially inhomogeneous nonlinear waveguide, described by a nonlinear Schrodinger equation in which the dispersion coefficient changes its sign from normal to anomalous. The model has direct applications to dispersion-decreasing nonlinear optical fibers, and to natural waveguides for internal waves in the ocean. It is found that, depending on the (conserved) energy and (nonconserved) mass of the initial pulse, four qualitatively different outcomes of the pulse transformation are possible: decay into radiation; self-trapping into a single soliton; formation of a breather; and formation of a pair of counterpropagating solitons. A corresponding chart is drawn on a parametric plane, which demonstrates some unexpected features. In particular, it is found that any kind of soliton(s) (including the breather and counterpropagating pair) eventually decays into pure radiation with the increase of the energy, the initial mass being kept constant. It is also noteworthy that a virtually direct transition from a single soliton into a pair of symmetric counterpropagating ones seems possible. An explanation for these features is proposed. In two cases when analytical approximations apply, viz., a simple perturbation theory for broad initial pulses, or the variational approximation for narrow ones, comparison with the direct simulations shows reasonable agreement.Comment: 18 pages, 10 figures, 1 table. Phys. Rev. E, in pres

Transcritical flow of a stratified fluid: The forced extended Korteweg-de Vries model

Transcritical, or resonant, flow of a stratified fluid over an obstacle is studied using a forced extended Korteweg-de Vries model. This model is particularly relevant for a two-layer fluid when the layer depths are near critical, but can also be useful in other similar circumstances. Both quadratic and cubic nonlinearities are present and they are balanced by third-order dispersion. We consider both possible signs for the cubic nonlinear term but emphasize the less-studied case when the cubic nonlinear term and the dispersion term have the same-signed coefficients. In this case, our numerical computations show that two kinds of solitary waves are found in certain parameter regimes. One kind is similar to those of the well-known forced Korteweg-de Vries model and occurs when the cubic nonlinear term is rather small, while the other kind is irregularly generated waves of variable amplitude, which may continually interact. To explain this phenomenon, we develop a hydraulic theory in which the dispersion term in the model is omitted. This theory can predict the occurence of upstream and downstream undular bores, and these predictions are found to agree quite well with the numerical computations. © 2002 American Institute of Physics.published_or_final_versio

Developing clinical practice guidelines: target audiences, identifying topics for guidelines, guideline group composition and functioning and conflicts of interest

Clinical practice guidelines are one of the foundations of efforts to improve health care. In 1999, we authored a paper about methods to develop guidelines. Since it was published, the methods of guideline development have progressed both in terms of methods and necessary procedures and the context for guideline development has changed with the emergence of guideline clearing houses and large scale guideline production organisations (such as the UK National Institute for Health and Clinical Excellence). It therefore seems timely to, in a series of three articles, update and extend our earlier paper. In this first paper we discuss: the target audience(s) for guidelines and their use of guidelines; identifying topics for guidelines; guideline group composition (including consumer involvement) and the processes by which guideline groups function and the important procedural issue of managing conflicts of interest in guideline development

Heating up the cold bounce

Self-dual string cosmological models provide an effective example of bouncing solutions where a phase of accelerated contraction smoothly evolves into an epoch of decelerated Friedmann--Robertson--Walker expansion dominated by the dilaton. While the transition to the expanding regime occurs at sub-Planckian curvature scales, the Universe emerging after the bounce is cold, with sharply growing gauge coupling. However, since massless gauge bosons (as well as other massless fields) are super-adiabatically amplified, the energy density of the maximally amplified modes re-entering the horizon after the bounce can efficiently heat the Universe. As a consequence the gauge coupling reaches a constant value, which can still be perturbative.Comment: 28 pages, 13 figure

Noise induced oscillations in non-equilibrium steady state systems

We consider effect of stochastic sources upon self-organization process being initiated with creation of the limit cycle. General expressions obtained are applied to the stochastic Lorenz system to show that departure from equilibrium steady state can destroy the limit cycle at certain relation between characteristic scales of temporal variation of principle variables. Noise induced resonance related to the limit cycle is found to appear if the fastest variations displays a principle variable, which is coupled with two different degrees of freedom or more.Comment: 11 pages, 4 figures. Submitted to Physica Script

Evidence-based selection of theories for designing behaviour change interventions : using methods based on theoretical construct domains to understand clinicians' blood transfusion behaviour

Peer reviewedPostprin

Translating clinicians' beliefs into implementation interventions (TRACII) : a protocol for an intervention modeling experiment to change clinicians' intentions to implement evidence-based practice

Background: Biomedical research constantly produces new findings, but these are not routinely incorporated into health care practice. Currently, a range of interventions to promote the uptake of emerging evidence are available. While their effectiveness has been tested in pragmatic trials, these do not form a basis from which to generalise to routine care settings. Implementation research is the scientific study of methods to promote the uptake of research findings, and hence to reduce inappropriate care. As clinical practice is a form of human behaviour, theories of human behaviour that have proved to be useful in other settings offer a basis for developing a scientific rationale for the choice of interventions. Aims: The aims of this protocol are 1) to develop interventions to change beliefs that have already been identified as antecedents to antibiotic prescribing for sore throats, and 2) to experimentally evaluate these interventions to identify those that have the largest impact on behavioural intention and behavioural simulation. Design: The clinical focus for this work will be the management of uncomplicated sore throat in general practice. Symptoms of upper respiratory tract infections are common presenting features in primary care. They are frequently treated with antibiotics, and research evidence is clear that antibiotic treatment offers little or no benefit to otherwise healthy adult patients. Reducing antibiotic prescribing in the community by the "prudent" use of antibiotics is seen as one way to slow the rise in antibiotic resistance, and appears safe, at least in children. However, our understanding of how to do this is limited. Participants will be general medical practitioners. Two theory-based interventions will be designed to address the discriminant beliefs in the prescribing of antibiotics for sore throat, using empirically derived resources. The interventions will be evaluated in a 2 × 2 factorial randomised controlled trial delivered in a postal questionnaire survey. Two outcome measures will be assessed: behavioural intention and behavioural simulation.This study is funded by the European Commission Research Directorate as part of a multi-partner program: Research Based Education and Quality Improvement (ReBEQI): A Framework and tools to develop effective quality improvement programs in European healthcare. (Proposal No: QLRT-2001-00657)

GRIDKIT: Pluggable overlay networks for Grid computing

A `second generation' approach to the provision of Grid middleware is now emerging which is built on service-oriented architecture and web services standards and technologies. However, advanced Grid applications have significant demands that are not addressed by present-day web services platforms. As one prime example, current platforms do not support the rich diversity of communication `interaction types' that are demanded by advanced applications (e.g. publish-subscribe, media streaming, peer-to-peer interaction). In the paper we describe the Gridkit middleware which augments the basic service-oriented architecture to address this particular deficiency. We particularly focus on the communications infrastructure support required to support multiple interaction types in a unified, principled and extensible manner-which we present in terms of the novel concept of pluggable overlay networks