Vacuum technology and space simulation

Manual on vacuum technology and space simulatio

On the Path-Integral Derivation of the Anomaly for the Hermitian Equivalent of the Complex PTPT-Symmetric Quartic Hamiltonian

It can be shown using operator techniques that the non-Hermitian $PT$-symmetric quantum mechanical Hamiltonian with a "wrong-sign" quartic potential $-gx^4$ is equivalent to a Hermitian Hamiltonian with a positive quartic potential together with a linear term. A naive derivation of the same result in the path-integral approach misses this linear term. In a recent paper by Bender et al. it was pointed out that this term was in the nature of a parity anomaly and a more careful, discretized treatment of the path integral appeared to reproduce it successfully. However, on re-examination of this derivation we find that a yet more careful treatment is necessary, keeping terms that were ignored in that paper. An alternative, much simpler derivation is given using the additional potential that has been shown to appear whenever a change of variables to curvilinear coordinates is made in a functional integral.Comment: LaTeX, 12 pages, no figure

The Only Eye Study (OnES): a qualitative study of surgeon experiences of only eye surgery and recommendations for patient safety

OBJECTIVE: Performing surgery on patients with only one seeing-eye, where complications may result in catastrophic vision loss, presents unique challenges for the ophthalmic care team. There is currently no evidence regarding how surgeons augment their care when treating only eye patients and no guidelines for how these patients should be managed in hospital eye services. This study aimed to explore ophthalmic surgeons' experiences of only eye surgery and perceptions of current practice. DESIGN AND PARTICIPANTS: Ten ophthalmic surgeons were asked to relate their experiences and views on performing only eye surgery in indepth, semistructured interviews. Interviews were audio-recorded and transcribed. Qualitative data were subjected to thematic analysis to identify key themes. SETTING: Hospital eye service. RESULTS: Five key themes emerged relating to surgeons' experiences and perceptions of only eye surgery: (1) differences in approach to consent, (2) strategies for risk reduction, (3) unmet training needs, (4) value of surgical mentor and (5) emotional impact of unsuccessful outcomes. Recommendations for improving the surgical journey for both the patient and the surgeon related primarily to better recognition and understanding of the complexities inherent with only eye surgery. CONCLUSIONS: Outcomes of only eye surgery may be improved through a number of methods, including development of purpose-designed training fellowships, adoption of stress-reducing strategies and enhancement of available support services. The findings identify emerging themes unique to only eye surgery and the need for guidelines on the provision of care for these high-stakes surgical patients

The non-linear transient behavior of second, third and fourth order phase-locked loops

Non-linear transient behavior of second, third, and fourth order phase-locked loop

Seeing is believing: an interpretative phenomenological analysis of the experiences of the ‘spiritual but not religious’ in Britain

A majority of the British population now consider themselves not religious, but many of these individuals still have some beliefs they consider spiritual. This study explores the connections between the beliefs and practices of five British participants who identified as ‘spiritual but not religious’ (SBNR). Semi-structured interviews with each participant were analyzed inductively using interpretative phenomenological analysis (IPA). This analysis developed seven sub-themes that were organized into two superordinate themes: ‘Experiencing Transcendence’ and ‘Constructing a Personal Spirituality’. The participants’ spirituality was an important part of their identities and lives. They pragmatically and eclectically drew on a wide range of spiritual tools and resources to enrich their lives. In a complex world where they considered traditional sources of religious or spiritual authority untrustworthy, the participants developed their own answers to existential questions that resonated with their own experiences of the world. Both their personal experiences and sociocultural influences were important in shaping and sustaining the participants’ worldviews and practices. These idiosyncratic ways that individuals made sense of their experiences show why it is important the research tools used to study worldview dynamics are sensitive to a wide range of factors and the iterative interactions between them

‘I believe in something; I don’t know what it is’: an exploration of five British Hindus’ worldviews using interpretative phenomenological analysis

Previous research has suggested individuals can draw on resources from a diverserange of existential cultures when constructing their personal worldviews. However, the ways individuals’ beliefs and worldviews are acquired and develop is still onlypartially understood. This study investigates these processes of worldview dynamicsby exploring the beliefs and practices of five British Hindus. Semi-structured interviews with each participant were inductively analyzed using interpretative phenomenological analysis (IPA). This analysis developed six sub-themes which formed two superordinate themes: ‘Everybody has their own way’ and ‘Focusing on this world’. The analysis shows the complexity of many individuals’ worldviews and demonstrates how individuals can live in a hinterland between religiosity and non-religiosity. For these participants, existential beliefs were idiosyncratic and deeply personal. They rejected some aspects of their cultural heritage while retaining others. The participants were comfortable with uncertainty about such matters and were highly tolerant of divergent beliefs. Understanding how these participants made sense of their world increases our understanding of both worldview dynamics and the forms that secularity can take in modern Britain. This shows why more nuanced understandings of ‘belief’ are necessary to explore the complexity of people’s lived experiences

Quantum field dynamics of the slow rollover in the linear delta expansion

We show how the linear delta expansion, as applied to the slow-roll transition in quantum mechanics, can be recast in the closed time-path formalism. This results in simpler, explicit expressions than were obtained in the Schr\"odinger formulation and allows for a straightforward generalization to higher dimensions. Motivated by the success of the method in the quantum-mechanical problem, where it has been shown to give more accurate results for longer than existing alternatives, we apply the linear delta expansion to four-dimensional field theory. At small times all methods agree. At later times, the first-order linear delta expansion is consistently higher that Hartree-Fock, but does not show any sign of a turnover. A turnover emerges in second-order of the method, but the value of $$at the turnover is larger that that given by the Hartree-Fock approximation. Based on this calculation, and our experience in the corresponding quantum-mechanical problem, we believe that the Hartree-Fock approximation does indeed underestimate the value of$$ at the turnover. In subsequent applications of the method we hope to implement the calculation in the context of an expanding universe, following the line of earlier calculations by Boyanovsky {\sl et al.}, who used the Hartree-Fock and large-N methods. It seems clear, however, that the method will become unreliable as the system enters the reheating stage.Comment: 17 pages, 9 figures, revised version with extra section 4.2 including second order calculatio

Using a fuzzy inference system to control a pumped storage hydro plant

The paper discusses the development of a fuzzy inference system (FIS) based governor control for a pumped storage hydroelectric plant. The First Hydro Company's plant at Dinorwig in North Wales is the largest of its kind in Europe and is mainly used for frequency control of the UK electrical grid. In previous investigations, a detailed model of the plant was developed using MATLAB(R)/SIMULINK(R) and this is now being used to compare FIS governor operation with the proportional-integral-derivative (PID) controller currently used. The paper describes the development of an FIS governor, and shows that its response to a step increase in load is superior to the PID under certain conditions of load. The paper proceeds to discuss the implications of these results in view of the possible practical application of an FIS governor at the Dinorwig plant