Studies on photoionisation

Imperial Users onl

Image and Performance, Agency and Ideology: Human Figurative Representation in Anglo-Saxon Funerary Art, AD 400 – 750

This thesis investigates the topic of human imagery and hybrid human imagery rendered on metalwork of early Anglo-Saxon date recovered within eastern England. It presents the first definitive catalogue of its kind in this region and timeframe. Taking inspiration from recent transitions in thinking on early Anglo-Saxon art, the major topics of consideration include: a) the interrelationship between image, object and the user, b) the changing portrayal of human representation and the social implications of such developments and c) the emergence of new bodily gestures in representational art. These key themes might provide an understanding of how and why human imagery changed as it did, how and by whom it was deployed in life and death and the role this type of imagery performed in the construction and presentation of social identity

Comparison of fructose and glucose ingestion before and during endurance cycling to exhaustion

The aim of this study was to compare the effect of pre-exercise and exercise ingestion of fructose and glucose during prolonged cycling exercise. The primary purpose was to determine if ingesting fructose before and during exercise was as beneficial or more beneficial than glucose ingestion. Seventeen trained subjects performed a control cycle to exhaustion. At least one week later, each subject performed a second ride to exhaustion ingesting either fructose or glucose before and during exercise. Blood was drawn before and at timed intervals during exercise to determine blood glucose, lactate and free fatty acid (FFA) levels for all three conditions (control, fructose, glucose). Gas measurements (Beckman Metabolic Measurement Cart) were taken at approximately 10 minute intervals, to ensure each subject was cycling at 75% VO2 max. and to determine respiratory exchange ratio (RER). Exercise time to exhaustion for the control group was significantly less (see document) than either the fructose (p < .02) or glucose (p < .001) group, but the fructose and glucose groups were not significantly different from each other. Blood glucose levels in the fructose group remained more stable than the glucose group and actually increased throughout the exercise test to exhaustion. Prior to the onset of exercise, the blood lactate level of the control group was significantly (see document) lower than either the fructose (p < .002) or the glucose (p < .01) group. The fructose and glucose groups did not show any significant differences in blood lactate over time. There were no significant differences in blood FFA between the treatment groups during the exercise test to exhaustion, but the control group FFA level was significantly (see document) higher than that of the fructose group (p <.02) prior to the onset of exercise. All three groups demonstrated gradual declines in RER throughout the exercise test to exhaustion. In this study it was established that fructose and glucose are of equal value in prolonging exercise time to exhaustion in endurance cycling performance. Ingesting fructose before and during exercise allowed for a more constant supply of glucose to be available to the working muscles than glucose ingestion. The more stable blood glucose levels with fructose ingestion may be beneficial in reducing perceived exhaustion, increasing mental alertness and postponing the athletes' perception of 'hitting the wall’, thereby allowing for an enhancement in exercise performance

Application of nonlinear control theory in weapon guidance and control

This thesis considers the application of nonlinear control theory in two subjects pertinent to weapon applications. Initially, Section 2 considers the development of a simple nonlinear autopilot for a Laser Guided Bomb (LGB). Later a nonlinear autopilot design is developed using a Pulse-Width Modulated (PWM) controller derived from the method developed by Bemelli-Zazzera et al4. This is applied to an LGB utilising a “bang-bang” actuator, enabling the control surfaces to achieve a pseudo-proportional response. The PWM design stems from an equivalent Pulse Amplitude Modulated controller, which required a design technique to be developed for a linear autopilot and, in addition, simulation of an electro-mechanical actuator. Simulation demonstrated that the PWM controller can achieve the desired response but the design must incorporate actuator dynamics. Section 3 considers the use of nonlinear control theory to examine the nonlinear intercept equations using a Proportional Navigation (PN) guidance law. Using a simple heuristic example, PN is introduced and vector algebra used to develop a simple model of the intercept. The model is then used to illustrate the importance of the kinematic gain. Using the method pioneered by Ha et al16, Lyapunov theory is used to demonstrate that PN is a robust guidance law. Although generally derived assuming the target maintains rectilinear flight, Lyapunov theory is used to demonstrate interception is always possible provided the pursuer has sufficient manoeuvre advantage over the target. Noting that many missiles incorporate a 1 directional warhead, Lyapunov theory is used to design a time-varying rate bias that controls the direction of approach to the target. Simulation demonstrates that the guidance requirements are indeed achieved by this law but additional effort is required by the control system. In Section 3 it is demonstrated that the PN guidance law will always ensure an intercept, i.e. it does not by itself generate miss-distance. In the final part of Section 3, using adjoint software designed by Zarchan42, it is demonstrated that miss-distance develops in practical systems as the result of sub-system dynamicsMPhi

The causes of falls: views of older people with sight impairment

Background Sight impairment increases with age and, compared with the general older population, older people with sight impairment are more likely to fall. There is a growing body of evidence on the views and perceptions of older people about falls, but little is published on the views of older people with sight impairment. Objective To explore what older people with sight impairment believe to be the causes of falls. Design A qualitative design was used, incorporating focus groups and interviews in which participants discussed falls and falls prevention. Framework analysis was employed to identify themes arising from participants' discussions of the causes of falls. Setting and participants Fifty-four community dwelling men and women with sight impairment, aged 65 and over, were recruited from across Greater Manchester, UK. Results Five types of factors were identified that were believed to cause falls: (i) health issues and changes in balance caused by ageing; (ii) cognitive and behavioural factors; (iii) the impact of sight impairment on getting around the home; (iv) the impact of sight impairment on negotiating the environment away from home; and (v) unexplained falls. Discussion and conclusions Older people with sight impairment reported many researched risk factors previously identified by older people without sight impairment but also described many perceived risks unique to people with sight impairment. There are few interventions to prevent falls aimed at older people with sight impairment, and the results of this study allow further tailoring of such interventions based on views of older people with sight impairment

Eligibility screening older research participants using remote cognitive assessment—experiences and reflections from a primary care randomised controlled trial

Background The COVID-19 pandemic forced many research teams to adjust the way they conduct studies, including moving to remote delivery of some or all of their recruitment and data collection processes. The Montreal Cognitive Assessment (MoCA) is widely used in research and is available in multiple formats for different groups and assessment settings. Here, we reflect on our experiences of administering the MoCA Blind/Telephone as part of the initial telephone eligibility check for participation in a randomised controlled trial with community-dwelling older people with frailty. Main body In response to COVID-19, a number of changes were made to the trial’s screening and recruitment procedures, to minimise the amount of time the researchers would spend in the participants’ homes when recruitment began in May 2021. One of the changes was for the researchers to conduct a cognitive assessment for eligibility during an initial telephone call, rather than during the subsequent home visit for consent and baseline data collection. We found that in comparison with conducting the assessment in-person, telephone administration caused uncertainty for the researchers about whether participants were struggling to answer questions due to cognition or hearing impairment. Some participants experienced practical difficulties when combining holding a telephone and completing one of the assessment items. It was hard for the researchers to judge the emotional impact that undertaking the assessment was having on the older people on the telephone, without visual warning signs of fatigue or mood. We discuss the potential impact of these issues on trial recruitment and participant engagement, and the feasibility of videoconferencing as an alternative method of conducting the MoCA. Conclusion The MoCA is a useful tool when cognitive impairment is part of screening and data collection and it is helpful to have the option to use the test remotely. However, as we have found, telephone testing is not always straightforward. Researchers should weigh up the pros and cons for each individual study, especially those involving older adults. If choosing remote methods, consider the practicality of using videoconferencing and think about the possible impact of telephone assessment on the relationship with the (potential) research participants. Trial registration Personalised care planning for older people with frailty ISRCTN16123291 28/08/2020

Catalytic CO Oxidation on Nanoscale Pt Facets: Effect of Inter-Facet CO Diffusion on Bifurcation and Fluctuation Behavior

We present lattice-gas modeling of the steady-state behavior in CO oxidation on the facets of nanoscale metal clusters, with coupling via inter-facet CO diffusion. The model incorporates the key aspects of reaction process, such as rapid CO mobility within each facet, and strong nearest-neighbor repulsion between adsorbed O. The former justifies our use a "hybrid" simulation approach treating the CO coverage as a mean-field parameter. For an isolated facet, there is one bistable region where the system can exist in either a reactive state (with high oxygen coverage) or a (nearly CO-poisoned) inactive state. Diffusion between two facets is shown to induce complex multistability in the steady states of the system. The bifurcation diagram exhibits two regions with bistabilities due to the difference between adsorption properties of the facets. We explore the role of enhanced fluctuations in the proximity of a cusp bifurcation point associated with one facet in producing transitions between stable states on that facet, as well as their influence on fluctuations on the other facet. The results are expected to shed more light on the reaction kinetics for supported catalysts.Comment: 22 pages, RevTeX, to appear in Phys. Rev. E, 6 figures (eps format) are available at http://www.physik.tu-muenchen.de/~natali

Oxygen-covered tungsten crystal shape: time effects, equilibrium, surface energy and the edge-rounding temperature

The equilibrium crystal shape (ECS) of oxygen-covered tungsten micricrystal is studied as a function of temperature. The specially designed ultrafast crystal quenching setup with the cooling rate of 6000 K/s allows to draw conclusions about ECS at high temperatures. The edge-rounding transition is shown to occur between 1300 K and 1430 K. The ratio of surface free energies $\gamma(111)/\gamma(211)$ is determined as a function of temperature.Comment: 8 pages, 10 figures, submitted for publicatio