Showing papers by "University of Exeter published in 1996"
TL;DR: Three broad categories of naturalistic sampling are described: convenience, judgement and theoretical models, which are illustrated with practical examples from the author's own research.
Abstract: The probability sampling techniques used for quantitative studies are rarely appropriate when conducting qualitative research. This article considers and explains the differences between the two approaches and describes three broad categories of naturalistic sampling: convenience, judgement and theoretical models. The principles are illustrated with practical examples from the author's own research.
5,299 citations
TL;DR: In this paper, a theoretical model was developed for predicting the elastic constants of honeycombs based on the deformation of the honeycomb cells by flexure, stretching and hinging, which can be used to derive expressions for the tensile moduli, shear moduli and Poisson's ratios.
804 citations
TL;DR: There is a need to increase the understanding of this enigmatic molecule since it could be involved in a wide range of important functions from antioxidant defence and photosynthesis to growth regulation.
794 citations
TL;DR: (1996).
Abstract: (1996). Dynamic Programming and Optimal Control. Volume 1. Journal of the Operational Research Society: Vol. 47, No. 6, pp. 833-834.
747 citations
TL;DR: Methods for exploring spatial variation in disease risk, spatial and space-time clustering, and the raised incidence of disease around suspected point sources of pollution are examined.
Abstract: This paper reviews a number of methods for the exploration and modelling of spatial point patterns with particular reference to geographical epidemiology (the geographical incidence of disease). Such methods go well beyond the conventional ‘nearest-neighbour’ and ‘quadrat’ analyses which have little to offer in an epidemiological context because they fail to allow for spatial variation in population density. Correction for this is essential if the aim is to assess the evidence for ‘clustering’ of cases of disease. We examine methods for exploring spatial variation in disease risk, spatial and space-time clustering, and we consider methods for modelling the raised incidence of disease around suspected point sources of pollution. All methods are illustrated by reference to recent case studies including child cancer incidence, Burkitt’s lymphoma, cancer of the larynx and childhood asthma. An Appendix considers a range of possible software environments within which to apply these methods. The links to modern geographical information systems are discussed.
743 citations
TL;DR: The role of the key informant technique as a qualitative research method is considered and the potential contribution of the approach to health care research is examined.
Abstract: Background and objective This article considers the role of the key informant technique as a qualitative research method and examines the potential contribution of the approach to health care research. Method The principles underlying the technique and the advantages and disadvantages are considered, illustrated with examples from a range of social science studies. Results and conclusion An example of the author's own use of key informants in a study of the professional relationship between general practitioners and specialists is described.
665 citations
TL;DR: Biological-motion displays, which convey no information while static, are able to give a rich description of the subject matter, including the ability to judge emotional state, but this ability is disrupted when the image is inverted.
Abstract: It is well known that biological motion, as produced by point-light displays on a human body, gives a good representation of the represented body-eg its gender and the nature of the task which it is engaged in. The question is whether it is possible to judge the emotional state of a human body from motion information alone. An ability to make this kind of judgment may imply that people are able to perceive emotion from patterns of movement without having to compute the detailed shape first. Subjects were shown brief video clips of two trained dancers (one male, one female). The dancers were aiming to convey the following emotions: fear, anger, grief, joy, surprise, and disgust. The video clips portrayed fully lit scenes and point-light scenes, with thirteen small points of light attached to the body of each dancer. Half the stimuli were presented the right way up, while half were inverted. The subjects' task was to judge which emotion was being portrayed. Full-body clips gave good recognition of emotionality (88% correct), but the results for upright biological-motion displays were also significantly above chance (63% correct). Inversion of the display reduced biological-motion (but not full-body) performance to close to chance but still significantly above chance. A space-time analysis of the motion of the points of light was carried out, and was related to the discriminability of the different emotions. Biological-motion displays, which convey no information while static, are able to give a rich description of the subject matter, including the ability to judge emotional state. This ability is disrupted when the image is inverted.
644 citations
20 May 1996
TL;DR: It is informally shown that the quantum inspired genetic algorithm performs better than the classical counterpart for a small domain.
Abstract: A novel evolutionary computing method-quantum inspired genetic algorithms-is introduced, where concepts and principles of quantum mechanics are used to inform and inspire more efficient evolutionary computing methods. The basic terminology of quantum mechanics is introduced before a comparison is made between a classical genetic algorithm and a quantum inspired method for the travelling salesperson problem. It is informally shown that the quantum inspired genetic algorithm performs better than the classical counterpart for a small domain. The paper concludes with some speculative comments concerning the relationship between quantum inspired genetic algorithms and various complexity classes.
601 citations
TL;DR: An analytic model is presented to describe the existence of photonic energy gaps in the propagation of surface plasmon polaritons on corrugated surfaces, designed to give direct access to expressions for the electromagnetic field and surface charge distributions associated with modes at the band edges thus allowing their physical character to be easily appreciated.
Abstract: We present an analytic model to describe the existence of photonic energy gaps in the propagation of surface plasmon polaritons on corrugated surfaces. We concentrate on elucidating the physical origin of the band gap, and accordingly we place strong emphasis on the physical reasoning and assumptions that we use. Our model is designed to give direct access to expressions for the electromagnetic field and surface charge distributions associated with modes at the band edges, thus allowing their physical character to be easily appreciated. Having established why a band gap occurs we then find expressions for the central position and width of the gap. We compare the results of our model for the gap width with those already in the literature, and find excellent agreement. Our results for the central position of the gap, notably the prediction that it should fall as the corrugation amplitude rises, contradicts one prediction made in the literature. We also reexamine the comparisons made in the literature between experiment and theory for the gap width, and find them inadequate because the theories have been compared to inappropriate experimental data. Consequently we present our own recent experimental data, enabling us to validate our theoretical results, in particular confirming our prediction that the central position of the gap falls as the corrugation amplitude is increased. The limitations of our model are discussed, as well as possible extensions and areas for future research.
527 citations
TL;DR: In this article, the adsorption of the fallout radionuclides 137 Cs and 210 Pb by individual size fractions in soils and their specific surface area was derived from laboratory experiments and empirical observations of natural soils and sediments.
515 citations
TL;DR: The authors argued that most of the facts characterising small-scale businesses, including high failure rates, reliance on bank credit rather than equity finance, relatively low interest rate margins, and credit rationing, can be explained by a tendency for those who are excessively optimistic to dominate new entrants.
Abstract: This paper argues that most of the facts characterising small-scale businesses, including high failure rates, reliance on bank credit rather than equity finance, relatively low interest rate margins, and credit rationing, can be explained by a tendency for those who are excessively optimistic to dominate new entrants. Drawing on findings in psychology, we model entrants as relatively naive optimisers. Banks on the other hand are viewed as well informed and efficient processors of information. 'The over-weening conceit which the greater part of men have of their own abilities, is an ancient evil remarked by the philosophers and moralists of all ages. Their absurd presumption in their own good fortune, has been less taken notice of. It is, however, if possible still more universal. There is no man living who, when in tolerable health and spirits, has not some share of it. The chance of gain is by every man more or less overvalued, and the chance of loss is by most men under-valued, and scarce by any man, who is in tolerable health and spirits, valued more than it is worth.'
TL;DR: It was discovered that there was a strong relationship between musical achievement and the amount of formal practice undertaken, and strong support to the theory that formal effortful practice is a principal determinant of musical achievement.
Abstract: A sample of 257 young people aged between eight and 18 who had undertaken individual instrumental tuition were interviewed in depth about their performing history from the start of playing. A subset of 94 of these individuals also kept a practice diary for a 42-week period. The data collected allowed estimates to be calculated of the amount of time devoted to various types of practice and other activities. The sample was selected in order to encompass a wide range of levels of musical achievement, from pupils at a highly selective specialist music school through to individuals who had abandoned instrumental study after less than a year of formal instruction. Data about formal examination successes confirmed the very wide range of achievement in the sample. It was discovered that there was a strong relationship between musical achievement and the amount of formal practice undertaken. Weaker relationships were discovered between achievement and amount of informal playing. There was no evidence that high achievers were able to gain a given level of examination success on less practice than low achievers. High achievers tended to be more consistent in their pattern of practice from week to week, and tended to concentrate technical practice in the mornings. These data lend strong support to the theory that formal effortful practice is a principal determinant of musical achievement. © The British Pschological Society.
01 Mar 1996
TL;DR: An algorithm for iterative learning control is proposed based on an optimisation principle used by other authors to derive gradient-type algorithms and has potential benefits which include realisation in terms of Riccati feedback and feedforward components.
Abstract: An algorithm for iterative learning control is proposed based on an optimisation principle used by other authors to derive gradient-type algorithms. The new algorithm is a descent algorithm and has potential benefits which include realisation in terms of Riccati feedback and feedforward components. This realisation also has the advantage of implicitly ensuring automatic step-size selection and hence guaranteeing convergence without the need for empirical choice of parameters. The algorithm achieves a geometric rate of convergence for invertible plants. One important feature of the proposed algorithm is the dependence of the speed of convergence on weight parameters appearing in the norms of the signals chosen for the optimisation problem.
TL;DR: In this paper, a 15kD secreted protein with characteristics that establish it as a class I hydrophobin was identified, which is necessary for infection-related development of Magnaporthe grisea on rice leaves and for full pathogenicity toward susceptible rice cultivars.
Abstract: The rice blast fungus expresses a pathogenicity gene, MPG1, during appressorium formation, disease symptom development, and conidiation. The MPG1 gene sequence predicts a small protein belonging to a family of fungal proteins designated hydrophobins. Using random ascospore analysis and genetic complementation, we showed that MPG1 is necessary for infection-related development of Magnaporthe grisea on rice leaves and for full pathogenicity toward susceptible rice cultivars. The protein product of MPG1 appears to interact with hydrophobic surfaces, where it may act as a developmental sensor for appressorium formation. Ultrastructural studies revealed that MPG1 directs formation of a rodlet layer on conidia composed of interwoven ~5-nm rodlets, which contributes to their surface hydrophobicity. Using combined genetic and biochemical approaches, we identified a 15-kD secreted protein with characteristics that establish it as a class I hydrophobin. The protein is able to form detergent-insoluble high molecular mass complexes, is soluble in trifluoroacetic acid, and exhibits mobility shifts after treatment with performic acid. The production of this protein is directed by MPG1.
Book•
18 Apr 1996TL;DR: In this article, a note on weights, measures, money and boundaries is given for the agricultural revolution in the sixteenth century and a review of the literature on agricultural revolution reconsidered is given.
Abstract: Preface A note on weights, measures, money and boundaries 1. The agricultural revolution 2. Farming in the sixteenth century 3. Agricultural output and productivity, 1500-1850 4. Institutional changes, 1500-1850 5. The agricultural revolution reconsidered Guide to further reading Bibliography.
TL;DR: In this paper, a detailed account of a violent confrontation between students and police during a demonstration held in November 1988 -the so-called "Battle of Westminster" is described. But the analysis is limited to the students involved in the conflict, how the conflict spread and upon the psychological consequences of involvement.
Abstract: This paper aims to extend the social identity approach to crowd behaviour (Reicher, 1984, 1987) in order to understand how crowd events, and crowd conflict in particular, develop over time. The analysis derives from a detailed account of a violent confrontation between students and police during a demonstration held in November 1988 - the so-called 'Battle of Westminster'. It focuses on how students came to be involved in the conflict, how the conflict spread and upon the psychological consequences of involvement. This analysis is used to develop general hypotheses concerning the initiation and development of collective conflict. It is concluded that, while the social identity model is of use in understanding these phenomena, it is necessary to recognize how social categories are constructed and reconstructed in the dynamics of intergroup interaction.
TL;DR: In this paper, the first observation of a full photonic band gap for surface modes was made, where it was shown that propagation is prohibited in all directions for modes with energies between 1.91 and 2.00 eV.
Abstract: We report the first observation of a full photonic band gap for surface modes. An experimental study has been made of the propagation of surface plasmon polaritons on a silver surface that is textured with a hexagonal array of dots with a periodicity of 300 nm. We find that propagation is prohibited in all directions for modes with energies between 1.91 and 2.00 eV.
TL;DR: This article investigated the role of the rural idyll in maintaining rural gender relations and found that women's attitudes towards and experiences of two key elements of the idyll; the family and the community.
TL;DR: In this article, a model of tax evasion is investigated in which a social custom utility is derived when taxes are paid honestly and there is a conformity payoff from adhering to the standard pattern of social behaviour.
TL;DR: The authors investigated the extent to which the supply of collateral affects business formation in the UK and found that a 10% rise in the value of unreleased net housing equity increased the number of new VAT registrations by some 5%.
Abstract: This paper investigated the extent to which the supply of collateral affects business formation in the UK. Bank loans are typically secured on the entrepreneur’s house. Using a variety of data and formulations, evidence is found that a 10% rise in the value of unreleased net housing equity increased the number of new VAT registrations by some 5%. Since we find that businesses formed in response to increases in the value of housing assets seem to be of at least average quality as measured by survival chances, there appears to be a large pool of untapped entrepreneurial talent.
TL;DR: An algorithm for iterative learning control is developed on the basis of an optimization principle which has been used previously to derive gradient-type algorithms and has numerous benefits which include realization in terms of Riccati feedback and feedforward components.
Abstract: An algorithm for iterative learning control is developed on the basis of an optimization principle which has been used previously to derive gradient-type algorithms. The new algorithm has numerous benefits which include realization in terms of Riccati feedback and feedforward components. This realization also has the advantage of implicitly ensuring automatic step size selection and hence guaranteeing convergence without the need for empirical choice of parameters. The algorithm is expressed as a very general norm optimization problem in a Hilbert space setting and hence, in principle, can be used for both continuous and discrete time systems. A basic relationship with almost singular optimal control is outlined. The theoretical results are illustrated by simulation studies which highlight the dependence of the speed of convergence on parameters chosen to represent the norm of the signals appearing in the optimization problem.
TL;DR: It is demonstrated that focus groups enhance the validity of existing questionnaires by highlighting those concerns held by users and providers that would otherwise have been neglected.
Abstract: Most mental health researchers rely upon quantitative methods of data collection Whilst such methods are commonly seen as reliable, qualitative methods are often seen as more valid Despite the value of qualitative methods of data collection, however, many researchers denigrate their use Qualitative research is often viewed as lacking in scientific rigour This paper explores the use of the focus group as a qualitative instrument to enhance the validity of existing questionnaires for mental health service users and providers Between July and August 1995 four focus groups were conducted in Exeter and Taunton among service users (with severe or long-term mental health problems) and providers (community psychiatric nurses, social workers and occupational therapists) It is demonstrated that focus groups enhance the validity of existing questionnaires by highlighting those concerns held by users and providers that would otherwise have been neglected
TL;DR: In this paper, the authors consider the way in which specific narrative forms can be utilized to explore the reflexive relationships between the body and self over time in ways that fuse the personal and the societal.
Abstract: This article considers the way in which specific narrative forms can be utilized to explore the reflexive relationships between the body and self over time in ways that fuse the personal and the societal. It does so by providing moments from my own narrative of self that focus upon an interrupted body project and its impact upon my relationship to past, present, and future selves. In the telling, Iattempt to engage the reader by communicating the subjectivity of such moments in a provocative, disruptive, fragmented, and emotionally charged manner. My own narrative, its performative element, and its gendered nature are then considered in relation to the inevitable fragility of self-narratives in contemporary society. Finally, I discuss issues of access to specific narratives within a political economy of developmental opportunities, and the implications of this differential resourcing for who, and what, people can become.
Book•
01 May 1996TL;DR: Menon et al. as discussed by the authors compared the United States experience and evidence on audit committees and monitoring with the position in the United Kingdom (UK), where there has been a steady growth in the number of major companies voluntarily forming audit committees over the last 15 years.
Abstract: Menon and Williams indicate that many United States (US) over-the-counter (OTC) firms which form audit committees appear not to rely on them (cf. Menon, K., Williams, J.D. 1994. Journal of Accounting and Public Policy, 13(2), 121–139). Reliance on audit committees appears to depend upon board composition, while audit committee activity is associated with firm size. In this paper, we compare the US experience and evidence on audit committees and monitoring with the position in the United Kingdom (UK), where there has been a steady growth in the number of major companies voluntarily forming audit committees over the last 15 years (Collier, P.A. 1996. Accounting, Business and Financial History 6(2), 121–140). We contend that the dataset is best analyzed using the Heckman procedure (cf. Heckman, J.A. 1979. Econometrica 47(1), 153–161) which captures the two stages of the decision on audit committee activity. Our results show little support from the UK data for the findings of Menon and Williams (cf. Menon and Williams, 1994. Journal of Accounting and Public Policy 13(2), 121–139). However, consistent with their agency theoretic perspective of monitoring, we found that high quality (Big Six) auditors, and to some degree leverage have a positive relationship with audit committee activity. Contrary to an agency theoretic expectation, we found that audit committee activity is reduced in firms that combine the role of chairman and chief executive. On the basis of this result we explored the impact of insiders (executive directors) and found that their presence on an audit committee had a significant negative impact on audit committee activity. This result suggests that the emphasis placed by the US Securities and Exchange Commission (SEC) (Staff Report on Corporate Accountability, US Government Printing Office, Washington, DC, 1980, p. 491) and the Cadbury Committee (Committee on the Financial Aspects of Corporate Governance. 1992. Report of the Committee on the Financial Aspects of Corporate Governance. Gee, London) on the independence of audit committee members may be well founded. The reduction in audit committee activity that arises from the combination of the role of chairman and chief executive officer, and the presence of insiders on the audit committee, has important policy implications. Indeed, in the UK, both practices are the subject of recommendations in the Hampel Committee report Hampel Committee 1998. Committee on Corporate Governance. Gee, London.
TL;DR: In nondiabetic MODY3 subjects insulin secretion demonstrates a diminished ability to respond when blood glucose exceeds 8 mmol/l, and β-cell dysfunction is present before the onset of overt hyperglycemia in this form of MODY.
Abstract: One form of maturity-onset diabetes of the young (MODY) results from mutations in a gene, designated MODY3, located on chromosome 12 in band q24. The present study was undertaken to define the interactions between glucose and insulin secretion rate (ISR) in subjects with mutations in MODY3. Of the 13 MODY3 subjects, six subjects with normal fasting glucose and glycosylated hemoglobin and seven overtly diabetic subjects were studied as were six nondiabetic control subjects. Each subject received graded intravenous glucose infusions on two occasions separated by a 42-h continuous intravenous glucose infusion designed to prime the beta-cell to secrete more insulin in response to glucose. ISRs were derived by deconvolution of peripheral C-peptide levels. Basal glucose levels were higher and insulin levels were lower in MODY3 subjects with diabetes compared with nondiabetic subjects or with normal healthy control subjects. In response to the graded glucose infusion, ISRs were significantly lower in the diabetic subjects over a broad range of glucose concentrations. ISRs in the nondiabetic MODY3 subjects were not significantly different from those of the control subjects at plasma glucose levels <8 mmol/l. As glucose rose above this level, however, the increase in insulin secretion in these subjects was significantly reduced. Administration of glucose by intravenous infusion for 42 h resulted in a significant increase in the amount of insulin secreted over the 5-9 mmol/l glucose concentration range in the control subjects and nondiabetic MODY3 subjects (by 38 and 35%, respectively), but no significant change was observed in the diabetic MODY3 subjects. In conclusion, in nondiabetic MODY3 subjects insulin secretion demonstrates a diminished ability to respond when blood glucose exceeds 8 mmol/l. The priming effect of glucose on insulin secretion is preserved. Thus, beta-cell dysfunction is present before the onset of overt hyperglycemia in this form of MODY. The defect in insulin secretion in the nondiabetic MODY3 subjects differs from that reported previously in nondiabetic MODY1 or mildly diabetic MODY2 subjects.
TL;DR: Ab initio cluster methods are used to investigate vacancy-impurity complexes in diamond and assign the 1.682 eV, twelve-line optical band to a vacancy-Si complex which has a very unusual, possibly unusual, structure.
Abstract: Ab initio cluster methods are used to investigate vacancy-impurity complexes in diamond. We assign the 1.682 eV, twelve-line optical band to a vacancy-Si complex which has a very unusual, possibly unique structure with a Si atom at the center of a split vacancy. The method also successfully accounts for the 1.945, 2.156, and 2.985 eV optical transitions in trigonal vacancy-N defects and estimates of radiative lifetimes are given.
TL;DR: The approach taken in this paper is to organize the inevitable errors so as to minimize their impact in the context of a multiversion system, i.e., the system functionality is reproduced in multiple versions, which together will constitute the neural-net system.
Abstract: In this paper we address the problem of constructing reliable neural-net implementations, given the assumption that any particular implementation will not be totally correct. The approach taken in this paper is to organize the inevitable errors so as to minimize their impact in the context of a multiversion system, i.e., the system functionality is reproduced in multiple versions, which together will constitute the neural-net system. The unique characteristics of neural computing are exploited in order to engineer reliable systems in the form of diverse, multiversion systems that are used together with a "decision strategy" (such as majority vote). Theoretical notions of "methodological diversity" contributing to the improvement of system performance are implemented and tested. An important aspect of the engineering of an optimal system is to overproduce the components and then choose an optimal subset. Three general techniques for choosing final system components are implemented and evaluated. Several different approaches to the effective engineering of complex multiversion systems designs are realized and evaluated to determine overall reliability as well as reliability of the overall system in comparison to the lesser reliability of component substructures.
TL;DR: This paper examined the way in which different speakers may construe both the context and the categories involved in a single event through an analysis of Margaret Thatcher's and Neil Kinnock's leadership speeches to their respective party conferences during the British miners' strike of 1984-5.
Abstract: This paper examines the way in which different speakers may construe both the context and the categories involved in a single event. This is achieved through an analysis of Margaret Thatcher's and Neil Kinnock's leadership speeches to their respective party conferences during the British miners' strike of 1984–5. The analysis shows that both speakers construe the nature of the event such that their party is representative of an ingroup which encompasses almost the entire population and such that their policies are consonant with the definition of the ingroup identity. Thus their category constructions mirror the ways in which the respective leaders seek to mobilize the electorate during the strike. This analysis is used for two purposes: firstly, to argue for an integration of self-categorization theory with rhetorical/discursive psychologies and hence for further research into the ways in which self-categories may be contested in argument rather than determined by cognitive computations; secondly, to argue for further research into how political rhetoric may affect mass action through the ways in which collectivities are defined.
TL;DR: In this article, the role of parents in the development of musical ability was investigated and it was found that the most successful children had parents who were the most highly involved in lessons and practice in the earliest stages of learning.
Abstract: Interviews were conducted with 257 children and their parents; all of the children had studied a musical instrument but differed in the extent of their mastery. The purpose of the study was to investigate the role of parents in the development of musical ability. It was discovered that the most successful children had parents who were the most highly involved in lessons and practice in the earliest stages of learning. These successful music learners often had parents who were involved with music themselves. Parental involvement in music typically took the form of listening to music rather than performing it, and tended to increase over the child's learning period. The children who failed to continue with lessons had parents who were, on average, less interested in music and who did not change their own degree of involvement with music over their child's learning period. Overall, the most musically able children had the highest levels of parental support.
TL;DR: In this paper, the past and likely future trends in water temperature from different parts of the world are collated and the potential causes of trends in the thermal regimes of streams and rivers are many, but the existing database of water temperature information is inadequate to provide a global perspective on changes during the recent, even more remote, past.
Abstract: Information on past and likely future trends in water temperature from different parts of the world is collated. The potential causes of trends in the thermal regimes of streams and rivers are many, but the existing database of water temperature information is inadequate to provide a global perspective on changes during the recent, let alone the more remote, past. Data from Europe suggest that warming of up to ca. 1°C in mean river temperatures has occurred during the 20th century, but that this trend has not been continuous, is distorted by extreme hydrological events, is not correlated with simple hydrometeorological factors and has been influenced by a variety of human activities. Predictive studies indicate that an accelerated rise in stream and river temperatures will occur during the next century as a consequence of global warming. However, forecasts must be tentative because future climatic conditions are uncertain and interactions between climate, hydrological and vegetation changes are complex.