2,340 research outputs found

    Stability of a liquid thread and stability and nonlinear evolution of multi-layer fluid flow

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    This thesis is concerned with stability and existence of waves in interfacial and free surface problems. Considered is the curtain coating problem, with specific emphasis on trilayer and bilayer flows, and the breakup of a viscous thread with a solid core. Experiments on curtain coating and sheet breakup are mostly conducted by industry and as such are hidden in patents or kept secret by companies trying to gain an edge in a competitive market. Experiments on curtain breakup concentrating on the effect that surfactants have upon the stability and the effect of differing fluid properties are discussed. It is shown that multiple layers of different fluid are more stable when reducing the flow rate of the lowest layer. Single and multi-layer fluid flow down an inclined plane is studied with the emphasis on the effect of an insoluble surfactant. Bilayer and trilayer flow down an inclined plane is considered. The main point of interest here is the existence of multiple unstable modes for a single set of parameters. A long wave model describing the multi-layer flow is discussed. Time-dependent solutions to this model system lead to the discovery of travelling wave solutions present in the dynamics. The travelling wave solutions are further investigated through Fourier analysis leading to the discovery of branches of solutions emerging from wavenumbers for which the flow is neutrally stable. The normal mode stability of annular Stokes flow of a viscous thread with a solid core is discussed which extends work done for negligible viscosity and small wavenumbers

    No Picnic: 3 Commando Brigade in the South Atlantic: 1982

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    A comparative study on the clinical decision making processes of nurse practitioners versus medical doctors using scenarios within a secondary care environment

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    Subjects This study was conducted from May 2012 to January 2013.Aim To investigate the decision-making skills of secondary care nurse practitioners compared to those of medical doctors.Background A literature review was conducted, searching for articles published from 1990 to 2012. The review found that nurse practitioners are key to the modernisation of the National Health Service. Studies have shown that compared to doctors, nurse practitioners can be efficient and cost-effective in consultations.Design Qualitative research design. Methods The information processing theory and think-aloud approach were used to understand the cognitive processes of 10 participants (5 doctors and 5 nurse practitioners). One nurse practitioner was paired with one doctor from the same speciality, and they were compared using a structured scenario-based interview. To ensure that all critical and relevant cues were covered by the individual participating in the scenario, a reference model was used to measure the degree of successful diagnosis, management and treatment.Results The data were processed for 5 months, from July to November 2012. The two groups of practitioners differed in the number of cue acquisitions obtained in the scenarios. In our study, nurse practitioners took three minutes longer to complete the scenarios. Conclusion This study suggests that nurse practitioner consultations are comparable to those of medical doctors within a secondary care environment in terms of correct diagnoses and therapeutic treatments. The information processing theory highlighted that both groups of professionals had similar models for decision-making processes.NH

    Hydroecological impacts of climate change modelled for a lowland UK wetland

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    Conservation management of wetlands often rests on modifying hydrological functions to establish or maintain desired flora and fauna. Hence the ability to predict the impacts of climate change is highly beneficial. Here, the physically based, distributed model MIKE SHE was used to simulate hydrology for the Lambourn Observatory at Boxford, UK. This comprises a 10 ha lowland riparian wetland protected for conservation, where the degree of variability in the peat, gravel and chalk geology has clouded hydrological understanding. Notably, a weathered layer on the chalk aquifer surface seals it from overlying deposits, yet is highly spatially heterogeneous. Long-term monitoring yielded observations of groundwater and surface water levels for model calibration and validation. Simulated results were consistent with observed data and reproduced the effects of seasonal fluctuations and in-channel macrophyte growth. The adjacent river and subsidiary channel were found to act as head boundaries, exerting a general control on water levels across the site. Discrete areas of groundwater upwellings caused raised water levels at distinct locations within the wetland. These were concurrent to regions where the weathered chalk layer is absent. To assess impacts of climate change, outputs from the UK Climate Projections 2009 ensemble of global climate models for the 2080s are used to obtain monthly percentage changes in climate variables. Changes in groundwater levels were taken from a regional model of the Chalk aquifer. Values of precipitation and evapotranspiration were seen to increase, whilst groundwater levels decreased, resulting in the greater dominance of precipitation. The discrete areas of groundwater upwelling were seen to diminish or disappear. Simulated water levels were linked to specific requirements of wetland plants using water table depth zone diagrams. Increasing depth of winter and summer groundwater levels leads to a loss of Glyceria maxima and Phragmites australis, principal habitat for the endangered Vertigo moulinsiana. Further, the reduced influx of base-rich groundwater and increased dominance of high pH rain-fed waters alters the acidity of the soil. This leads to changes in species composition, with potential reductions in Carex paniculata, Caltha palustris and Typha latifolia

    Therapeutic alliance in parent-focussed interventions for youth depression

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    The aim of this thesis was to investigate the role of therapeutic alliance in group-based parent-focussed interventions for youth depression. Results suggested that while therapist alliance ratings are likely not clinically important in parent-focussed interventions for youth depression, alliance plays an essential role in parents benefitting therapeutically from parent-focussed interventions
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