Diss. (sammanfattning) Uppsala : Sveriges lantbruksuniversitet, 2006. / Härtill 4 uppsatser.

Thesis (PhD) - Swinburne University of Technology, 2007. / Doctor of Philosophy, Swinburne University of Technology - 2007. Typescript. Bibliography: p. 209-229.

Diss. Stockholm : Handelshögskolan i Stockholm, 2010.

Pursuit behaviours are vital in predator-prey interactions and in courtship for many flying animals. Existing research on target-directed flight behaviours in insects, birds and bats has aimed at identifying simple geometric rules describing the pursuit-flight trajectories. However, these geometric rules are only part of the picture as they only consider the outcome of the commanded changes in flight kinematics, and not the underlying guidance laws (dynamics) which generate these commands. To intercept a target, a pursuer implements a guidance law using sensory feedback to determine the required change in flight velocity, and the resulting kinematics determines the flight geometry. Most of the research until recently has examined insect flight systems, as the ethics of working with birds of prey are more complex and measuring their wide-ranging flight trajectories is difficult. Studies of predator-prey pursuit in birds have only described the geometrical rules for target interception, therefore overlooking the guidance laws which implement them. Therefore the aim of this thesis is to complete the picture by identifying the guidance laws used by birds of prey as they pursue and intercept targets both in the air and on the ground. I used onboard cameras and GPS to study attack flights in peregrine falcons (Falco peregrinus), and high-speed ground photogrammetry for attacks in Harris' hawks (Parabuteo unicinctus), to show that two different raptor species effectively implement the same guidance law of pure proportional navigation for intercepting manouevring and non-manouevring prey-targets. Proportional navigation is a feedback law whereby the bird's line-of-sight rate is fed back, in order to command a turn-rate in proportion to the change in line-of-sight rate, with a constant of proportionality N. Harris' hawks were found to use this guidance law in its simplest case with an N of approximately 1. This amounts to a pure pursuit course, meaning the bird maintains a heading angle of zero at all times (its velocity vector points at the target). Peregrine falcons were found to use a variety of values of N resulting in a quicker path to interception. A remarkable feature of most bird of prey eyes is that they possess two regions of high visual acuity - the shallow and deep foveae. The deep fovea is optimised for long-range vision, and is directed at approximately 45° to the side of the head. It has been proposed that the head is held in line with the body for streamlining, while the body is turned in flight to fixate the image of the prey on the deep fovea, resulting in a curved trajectory. My results contradict this theory, as falcons were seen to use saccadic head movements to maintain the image of the prey in their field of view whilst flying along curved trajectories - suggesting a different visual strategy. I provide the first quantitative analysis of how birds are able to guide their flight for successful prey capture. Not only does this provide new insights into animal behaviour and evolution, but this research has many applications in engineering, where there is a wide and growing interest in vision-based approaches to guidance and control in both civil and military spheres.

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Introduction Globally stroke remains the leading cause of adult disability. An aging population and a reduction in stroke case fatality has led to an increasing number of people living with stroke i.e. stroke survivors. The ability to perform important day-to-day activities, such as walking and housework, is frequently impaired in stroke survivors. Therefore, it has become essential to address the long-term needs of stroke survivors, prompting focussed research on life after stroke. A reduction in physical fitness after stroke may contribute to stroke related disability. It is possible to improve physical fitness by regular, structured physical activity. Improving physical fitness after stroke and increasing physical activity are aspects of life after stroke that are increasingly being researched. Although the evidence base for the benefits of physical fitness training is growing, research has indicated that benefits gained are not always maintained at follow-up. To facilitate the uptake and maintenance of physical activity after stroke, it is essential to understand why many stroke survivors do not undertake regular physical activity. Understanding this difficult concept will enable the tailoring of behaviour change interventions to promote and maintain physical activity after stroke. However, there has been limited work in developing theory driven behaviour change interventions to increase physical activity in stroke survivors. Therefore, the aim of this thesis was to develop and test a behaviour change intervention to increase physical activity after stroke. Methods In order to address the above aim, six interlinking studies were conducted within the development and feasibility stages of the MRC framework for the development of complex interventions. A systematic review (study one) examined barriers and facilitators to physical activity perceived by stroke survivors. This study showed a lack of literature in this area, and that the already published studies had limited generalisability to the UK stroke population. Therefore, it was deemed appropriate to conduct a qualitative study (study two) to examine the perceived barriers and facilitators to physical activity in the local stroke population. Both studies one and two highlighted the influence of self-efficacy towards increasing physical activity. As part of earlier work conducted prior to this PhD, there was previously unanalysed data on perceived barriers and facilitators to physical activity after stroke. These quantitative data encompassed specific questions exploring self-efficacy and intention to physical activity post stroke. In light of the evidence it was deemed necessary to analyse these data (study three). It was envisaged that the behaviour change intervention would incorporate a feedback device, so participants could clearly see how much daily physical activity they were undertaking. An opportunity arose to collaborate with a team at Newcastle University who had developed an accelerometer that incorporated an immediate feedback screen. Therefore, a device validation study was conducted as study four. Results from studies one to four were combined, with the use of the Theoretical Domains Framework, and the behaviour change intervention was developed. Two uncontrolled pilot studies (studies five and six) were conducted to determine the feasibility and acceptability of the behaviour change intervention to the stroke population. Results The systematic review included six articles, providing data on 174 stroke survivors. Commonly reported barriers were environmental factors, health concerns and stroke impairments. Commonly reported facilitators were social support and the need to be able to perform daily tasks. Qualitative interviews were conducted with 13 stroke survivors, at which point data saturation was reached. The most commonly reported TDF domains were ‘beliefs about capabilities’, ‘environmental context and resources’ and ‘social influence’. The quantitative study provided data from 50 stroke survivors. Intention and self-efficacy were high, with self-efficacy graded as either 4 or 5 (highly confident) on a five-point scale by [34 (68%)] participants, whilst 42 (84%) participants “strongly agreed” or “agreed” that they intended to increase their walking after their stroke. Ten participants were recruited to validate the new accelerometer. Mean time since stroke was 29 days (SD =27.9 days). The 10 participants walked a mean distance of 245 meters (SD=129m) and their mean walking speed was 0.79ms-1 (SD=0.34ms-1). The Culture Lab were unable to develop the accelerometer in the necessary time frame and therefore no accelerometer was available for trialling the behaviour change intervention. Therefore, pedometers were used to record step count during the behaviour change intervention. A total of four participants took part in the 12 week behaviour change intervention, over two study periods. All participants managed to increase their step counts during this time. The studies had problems both with recruitment and retention of participants. These issues have been discussed. Conclusions This work has enhanced the understanding of the barriers and facilitators perceived by stroke survivors to increase physical activity. This work has allowed the development of a theoretically driven, complex behaviour change intervention that was successfully trialled with a small group of stroke survivors. Areas of further research have been discussed.

Questions revolving around the possibility and justifiability of reductive analyses of the concept 'not', lie at the heart of many of the problems in the philosophical interpretation of not-descriptions. In this thesis, I wish to show, by discussing various problems in the logic of not-descriptions, that, and why, reductive analyses must be unsatisfactory.

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