60,002 research outputs found
Head and trunk movement strategies in quiet stance : from the deficit of vestibular loss to the expertise of tightrope walkers via prosthetic feedback
No full textIs the head more locked to the trunk or stabilised in space during quite stance? Does prosthetic vestibular feedback have a positive impact on movement strategies and muscle synergies of those with vestibular loss? Does training in tandem stance lead to improved movement strategies and/or reweighting of sensory inputs? These questions have not been answered to date. This thesis attempted to answer these questions with appropriate, but new, techniques. The coordination of the head with respect to the trunk and pelvis during quiet, feet side by side, stance in normal and vestibular loss subjects was examined as well as the effect of prosthetic feedback on the strategies and synergies used by vestibular loss subjects. Changes in movement strategies and sensory feedback in tight-rope walkers with considerable training in tandem stance (one foot before the other), were also investigated.
Subjects performed the stance tasks under different sensory conditions: with eyes open or closed, and on either a firm or foam surface. Stance was either side by side stance or tandem stance. For one experiment, vibrotactile and auditory balance feedback of trunk sway was used in addition. Subject groups were bilateral vestibular loss (BVL) patients, trained tightrope walkers and age matched controls. Two further groups of young and elderly healthy subjects were used to characterise differences in head movements with aging. In all studies roll and pitch angular velocities were recorded with six body-worn gyroscopes; a set of two worn at the upper trunk, an identical set at the hips and another lighter set worn on a head band. In one study with BVL subjects, another of the lighter gyroscopes was strapped onto the lower leg. For the balance feedback study surface EMGs were recorded from pairs of antagonistic muscles at the lower leg, trunk and upper arm. Data from all experiments was analysed in both time and frequency domains. For the analysis of tandem stance an estimate of centre of mass movement was calculated as well as its time to reach a virtual stability boundary.
The results indicated that under most sensory conditions, two legged, feet side by side stance conditions, head sway at the head for both the roll and pitch direction is greater than at the upper trunk and the pelvis. For low and mid-frequencies (<0.3 Hz) the head is locked to the trunk i.e. there is a tendency for the head and trunk to move as one unit but the head movement is always more than expected from a pure inverted pendulum movement mode. For the BVL subjects the head on trunk locking is more rigid and characterized by higher resonant frequencies. Prosthetic feedback reduced pelvis sway angle displacements in BVL subjects to values of age-matched healthy controls for all stance tasks. Movement strategies in BVL subjects were reduced in amplitudes with feedback but otherwise not changed. Reduced amplitudes are achieved with improved antagonistic muscle synergies. As we observed with feet side by side stance, tandem stance is also multisegmental. Keeping balance while standing on a tightrope appears to require similar intersegmental movement strategies for the head, trunk and pelvis to those used with other, less difficult tandem stance tasks. The difference with respect to untrained normal subjects is that faster trunk movements are used by tightrope walkers as they explore the limits of the base of support. At the same time they reduce relative head and pelvis movements to those of the trunk via changed proprioceptive weightings
The effect of Core Stability Exercises (CSE) on trunk sagittal acceleration
No full textThis thesis was submitted for the degree of Doctor of Philosophy and awarded by Brunel University.Aims: The aim of this study was to investigate Core Stability Exercise (CSE) induced changes in trunk sagittal acceleration as a measure of performance in participants following an acute onset of non-specific low back pain (LBP). Methodology:
A Lumbar Motion Monitor (LMM) was used to measure trunk sagittal acceleration. The LMM was demonstrated to be reliable [Intra-Class Correlation (ICC) for average sagittal acceleration (0.96, 95% CI 0.90-0.98) and peak sagittal acceleration (0.89, 95% CI 0.75-0.96) with a 95% limit of agreement for the repeated measure of between -100.64 and +59.84 Deg/s2 ]. Pain was measured using the Visual Analogue Scale (VAS) and disability was measured with the Roland Morris Disability Questionnaire (RMDQ). Results:
Differences in mean trunk sagittal acceleration between control and experimental groups at time points were assessed using a regression analysis (ratio of geometric means [95%CI]) and demonstrated to be not statistically significant (3 weeks (20%) 1.2 [0.9 to 1.6], p=0.2; 6 weeks (10%) 1.1 [0.8 to 1.5], p=0.7; 3 months (20%) 1.2 [0.8 to 1.9], p=0.9). Similarly, differences in mean pain score (3 weeks (30%) 1.3 [0.8-2.2], p= 0.3); 6 weeks (20%) 1.2 [0.7-2.0], p=0.6; 3 months (0%) 1.0 [0.5-1.9], p=1.0) and difference in mean disability score (6 weeks (0%) 1.0 [0.7-1.5], p= 1.0, 3 months (30%) 1.3 [0.8-1.9], p= 0.3) between groups were also not statistically significant. Conclusions: This work does not infer that CSE are definitively effective in reducing pain, improving subjective disability and improving trunk performance after an onset acute of non-specific LBP. However, there is a suggestion of clinical importance and a possible mechanism by which they may work. Further investigation into this mechanism may provide future effective management strategies for intervention of acute non-specific low back pain with optimistic cost implications for healthcare delivery in general and Physiotherapy in particular
Early postoperative interventional ASD-closure for severe atrial right to left shunt in a neonate with common arterial trunk
No full textAlthough closure of an atrial septal defect (ASD II) with an occluding device in the first year of life is not a routine procedure, it is a feasible treatment, even in neonates. Case reports on the off-label use of Amplatzer devices have been repeatedly published, but there are no reports on using the Amplatzer Duct Occluder (ADO) to close an atrial septal defect in a neonate. We report on a successful catheter closure of an ASD II with ADO in a severely cyanotic neonate, seven days after surgical repair of common arterial trunk. Due to progressive cyanosis and clinical signs of right ventricular failure, which developed after common arterial trunk repair, the neonate underwent cardiac catheterization. Diastolic filling impairment of the right ventricle (right ventricle hypertrophy, pulmonary regurgitation, and residual right ventricle outflow tract obstruction) was thought to be the cause of impaired right ventricle diastolic filling, resulting in the right-to-left shunt at the atrial level. Under transesophageal echocardiographic guidance, ADO was delivered through a 5 French sheath into the atrial septal defect. Amplatzer duct occluder closed the defect and proved to be stable in position after disconnection. During the procedure, the child was stable and then transferred to the intensive care unit with significantly improved oxygen saturation. This is the first report on placing a duct occluder in the atrial septal position, which is a novel procedure for-small neonates
A Dynamic Subfilter-scale Stress Model for Large Eddy Simulations Based on Physical Flow Scales
No full textWe propose a new definition of the length scale in an eddy-viscosity model for large-eddy simulations (LES). This formulation extends and generalizes a previous proposal [Piomelli, Rouhi and Geurts, Proc. ETMM10, 2014], in which the LES length scale was expressed in terms of the integral length-scale of turbulence determined by the flow characteristics and explicitly decoupled from the simulation grid; this approach was named Integral Length-Scale Approximation (ILSA). As in the original ILSA, the model coefficient was determined by the user, and required to maintain a desired contribution of the unresolved, subfilter scales (SFS) to the global transport. We propose a local formulation (local ILSA) in which the model coefficient is local in space, allowing a precise control over SFS activity as a function of location. This new formulation preserves the properties of the global model; application to channel flow and backward-facing step verifies its features and accuracy
Large-eddy simulation of a separated flow with a sub-filter scale model based on the integral length-scale
No full textA new sub-filter scale model for large-eddy simulations, which uses a length-scale proportional to the integral scale of the turbulence instead of the grid resolution to parametrize the modelled stresses, will be assessed in the prediction of the flow of a boundary-layer over a rough surface, which includes separation and reattachment
Trunk Control and Lesion Locations According to Alberta Stroke Program Early CT Score in Acute Stroke: A Cross-Sectional Study
No full textBackground: Stroke is a leading cause of disability in elderly people. Lesion location and size, and trunk control early after stroke have been found predictive of functional outcome. Trunk control is an important aspect of postural control, and commonly found to be impaired. A hemispheric difference in the regulation of postural control has been suggested, but limited knowledge of a relationship between specific lesions and trunk control exists. Objective: To explore the relationship between middle cerebral artery (MCA) lesion locations and trunk control post stroke, and compare trunk control between patients with lesions in single and multiple locations, and between left and right hemispheres. Methods: A cross-sectional design was used. Patients were recruited from a hospital stroke unit. Assessment tools: Trunk Impairment Scale–modified Norwegian version and Alberta Stroke Program Early CT Score (ASPECTS). Statistics: Descriptive, Independent t-test, Mann-Whitney’s U-test, Chi-Square test. Results:109 patients with first time middle cerebral artery lesions were included, 71 with multiple and 38 with single ASPECT locations. Trunk control was poorer in multiple (median 8.0) than in single (median 11.0) lesion locations, P=0.011. The most common single lesion locationswereM5 (50%) and internal capsule (18.4%). M5 is situated in the anterior parts of the MCA territory and hypothesized to represent sensory and motor areas of the cortex. Patients with lesions of M5 locations in the right hemisphere achieved poorer scores on trunk control than patients with left sided locations, P=0.030. Conclusions: The results indicate that patients with lesions in multiple ASPECT locations have poorer trunk control than patients with single locations, and that trunk control is poorer after single right M5 lesions as compared to left. We recommend therapists to have specific attention towards trunk control in rehabilitation of patients with MCA lesions and especially with a right M5 location early post stroke
Dynamic routing in circuit-switched non-hierarchical networks
No full textThis thesis studies dynamic routing in circuit-switched non-hierarchical networks based on learning automata algorithms. The application of a mathematical model for a linear reward penalty algorithm is explained. Theoretical results for this scheme verified by simulations shows the accuracy of the model. Using simulation and analysis, learning automata algorithms are compared to several other strategies on different networks. The implemented test networks may be classified into two groups. The first group are designed for fixed routing and in such networks fixed routing performs better than any dynamic routing scheme. It will be shown that dynamic routing strategies perform as well as fixed routing when trunk reservation is employed. The second group of networks are designed for dynamic routing and trunk reservation deteriorates the performance. Comparison of different routing algorithms on small networks designed to force dynamic routing demonstrates the superiority of automata under both normal and failure conditions. The thesis also considers the instability problem in non-hierarchical circuit-switched networks when dynamic routing is implemented. It is shown that trunk reservation prevents instability and increases the carried load at overloads. Finally a set of experiments are performed on large networks with realistic capacity and traffic matrices. Simulation and analytic results show that dynamic routing outperforms fixed routing and trunk reservation deteriorates the performance at low values of overload. At high overloads, optimization of trunk reservation is necessary for this class of networks. Comparison results show the improved performance with automata schemes under both normal and abnormal traffic conditions. The thesis concludes with a discussion of proposed further work including expected developments in Integrated Service Digital Networks
Near Wall PIV-Measurements on the Windward Slope of a Hill
No full textThe turbulent flow over periodic hills was measured near to the wall, using planar Particle-Image-Velocimetry (PIV) at high spatial resolution. Our focus is on the near wall turbulence structure on the windward slope of the hill. For large-eddy simulation (LES) we suspect that, if this was not predicted accurately, it affects the prediction of the velocity profiles over the hill crest which in turn will affect the recirculation length downstream of the hill. Regarding the time averaged velocities, we were able to resolve the linear viscous region of the boundary layer. The velocity distribution and also the Reynolds stress does not comply with the law of the wall as it is valid for a turbulent boundary layer at equilibrium
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