Showing papers by "University of Sheffield published in 1996"

Beyond the divide between cognition and discourse: using interpretative phenomenological analysis in health psychology

Abstract: This paper introduces interpretative phenomenological analysis (PA) and discusses the particular contribution it can make to health psychology. This is contextualized within current debates, particularly in social psychology, between social cognition and discourse analysis and the significance for health psychology of such debates is considered. The paper outlines the theoretical roots of PA in phenomenology and symbolic interactionism and argues the case for a role for PA within health psychology. Discussion then focuses on one area in the health field, the patient's conception of chronic illness and research in medical sociology from a similar methodological and epistemological orientation to PA is introduced. The paper concludes with an illustration of PA from the author's own work on the patient's perception of renal dialysis.

Regulation of light harvesting in green plants

Abstract: When plants are exposed to light intensities in excess of those that can be utilized in photosynthetic electron transport, nonphotochemical dissipation of excitation energy is induced as a mechanism for photoprotection of photosystem II. The features of this process are reviewed, particularly with respect to the molecular mechanisms involved. It is shown how the dynamic properties of the proteins and pigments of the chlorophyll a/b light-harvesting complexes of photosystem II first enable the level of excitation energy to be sensed via the thylakoid proton gradient and subsequently allow excess energy to be dissipated as heat by formation of a nonphotochemical quencher. The nature of this quencher is discussed, together with a consideration of how the variation in capacity for energy dissipation depends on specific features of the composition of the light-harvesting system. Finally, the prospects for future progress in understanding the regulation of light harvesting are assessed.

Analysis of a micro-electric generator for microsystems

Abstract: Supplying power to remote microsystems that have no physical connection to the outside world is difficult, and using batteries is not always appropriate. A solution is offered by the device proposed in this paper, which generates electricity from mechanical energy when embedded in a vibrating medium. This microgenerator has dimensions of around 5 mm × 5 mm × 1 mm. Analysis predicts that the power produced is proportional to the cube of the frequency of vibration, and that to maximize power generation the mass deflection should be as large as possible. Power generation of 1 μW at 70 Hz and 0.1 mW at 330 Hz are predicted for a typical device, assuming a deflection of 50 μm.

Appetite-suppressant drugs and the risk of primary pulmonary hypertension. International Primary Pulmonary Hypertension Study Group

Abstract: Background Recently in France, primary pulmonary hypertension developed in a cluster of patients exposed to derivatives of fenfluramine in appetite suppressants (anorexic agents), which are used for weight control. We investigated the potential role of anorexic agents and other suspected risk factors for primary pulmonary hypertension. Methods In a case–control study, we assessed 95 patients with primary pulmonary hypertension from 35 centers in France, Belgium, the United Kingdom, and the Netherlands and 355 controls recruited from general practices and matched to the patients' sex and age. Results The use of anorexic drugs (mainly derivatives of fenfluramine) was associated with an increased risk of primary pulmonary hypertension (odds ratio with any anorexic-drug use, 6.3; 95 percent confidence interval, 3.0 to 13.2). For the use of anorexic agents in the preceding year, the odds ratio was 10.1 (95 percent confidence interval, 3.4 to 29.9). When anorexic drugs were used for a total of more than three m...

Is job satisfaction U-shaped in age?

Abstract: It is generally believed that job satisfaction increases linearly with age. However, there are persuasive arguments, and some empirical evidence, that the relationship is Ushaped, declining from a moderate level in the early years of employment and then increasing steadily up to retirement. This paper investigates that relationship, using survey responses from a large sample of British employees. For overall job satisfaction, satisfaction with pay, and satisfaction with the work itself, a strongly significant U-shape is observed. Ordered probit techniques, which take account of the ordinality of satisfaction data, are used to analyse the relationship between these forms of satisfaction and a large set of individual and job characteristics. Despite the inclusion of 80 control variables, significant coefficients persist for the age and age-squared variables (the latter representing the non-linear component). The paper thus provides strong evidence for a U-shaped relationship between age and job satisfaction. Furthermore, it is shown that a similar age pattern occurs for employees' context-free mental health, suggesting that both job satisfaction and context-free mental health are affected by non-job factors of life-stage and personal circumstances. The importance of changes in expectations with increasing age is emphasized. There have been many investigations into the relationship between age and different forms of job satisfaction. Significant variations across age are commonly found, with older employees tending to report higher satisfaction than younger ones (e.g. Doering, Rhodes & Schuster, 1983; Glenn, Taylor & Weaver, 1977; Warr, 1992), Observed age differences in overall job satisfaction are greater than those associated with gender, education, ethnic background or income (Clark, 1993;. Weaver, 1980). However, two questions remain unanswered. First, given that there is a positive relationship between age and job satisfaction, is it simply linear or does it contain a nonlinear component? And, second, what underlying variables can account for the pattern of job satisfaction differences between age groups?

Free histidine as a metal chelator in plants that accumulate nickel

Abstract: A NUMBER of terrestrial plants accumulate large quantities of metals such as zinc, manganese, nickel, cobalt and copper in their shoots1. The largest group of these so-called 'metal hyperaccumulators' is found in the genus Alyssum, in which nickel concentrations can reach 3% of leaf dry biomass2,3. Apart from their intrinsic interest, plants exhibiting this trait could be of value in the decontamination of metal-polluted soils4–6. However, the biochemical basis of the capacity for metal accumulation has not been elucidated. Here we report that exposing hyperaccumu-lator species of Alyssum to nickel elicits a large and proportional increase in the levels of free histidine, which is shown to be coordinated with nickel in vivo. Moreover, supplying histidine to a non-accumulating species greatly increases both its nickel tolerance and capacity for nickel transport to the shoot, indicating that enhanced production of histidine is responsible for the nickel hyperaccumulation phenotype in Alyssum.

The Soil Seed Banks of North West Europe: Methodology, Density and Longevity

Abstract: Preface 1 Seed banks: coverage, criteria and classification 2 Principal features of the data 3 Methods for the study of seed banks 4 Description and guide to the interpretation of the database 5 The database 6 Data sources and references cited in the text

Seed banks and seed dispersal: important topics in restoration ecology

Abstract: Restoration ecology deals with the scientific and ecological background of nature management practices aiming at the re-establishment of plant species which have disappeared. As we focus on semi-natural landscapes, these disappearances can be caused by intensification of agricultural practices or cessation of human interference. Nature management practices attempt to re-establish the often species-rich original plant communities by the removal of nutrients (sod cutting, hay-making, grazing) after eutrophication (Schiefer 1984; Bobbink & Willems 1991; Oomes 1992; Bakker & OUT 1995), rewetting after severe drainage (Grootjans & Van Diggelen 1995; Koerselman & Verhoeven 1995), scrub and woodland removal (clear cutting, grazing) after bush encroachment (Willems 1988; Poschlod & Jordan 1992). The re-appearance of plant species may depend on their persistence in the soil seed bank as a ‘memory’ of the original plant community. If the species has been lost from the persistent soil seed bank, it has to be transported to the site of re-appearance by some vector, e.g. wind, water, animals, man, and incorporated into the fresh seed bank. The site of re-appearance after emerging either from the old seed bank or from the fresh seed bank has to be proven to be a safe site from the point of view of abiotic and biotic conditions (Harper 1977). Without the presence or arrival of seeds no re-appearance in the established vegetation will be possible. For this reason we focus on seed bank dynamics and seed dispersal in restoration ecology. We will present (i) a review of current methods of seed bank analysis including estimations of longevity and density, and (ii) the state of the art on methods and results of seed dispersal.

Anabranching rivers: their cause, character and classification

Abstract: Anabranching rivers consist of multiple channels separated by vegetated semi-permanent alluvial islands excised from existing floodplain or formed by within-channel or deltaic accretion. These rivers occupy a wide range of environments from low to high energy, however, their existence has never been adequately explained. They occur concurrently with other types of channel pattern, although specific requirements include a flood-dominated flow regime and banks that are resistant to erosion, with some systems characterized by mechanisms to block or constrict channels, thereby triggering avulsion. The fundamental advantage of an anabranching river is that, by constructing a semi-permanent system of multiple channels, it can concentrate stream flow and maximize bed-sediment transport (work per unit area of the bed) under conditions where there is little or no opportunity to increase gradient. On the basis of stream energy, sediment size and morphological characteristics, six types of anabranching river are recognized; types 1–3 are lower energy and types 4–6 are higher energy systems. Type 1 are cohesive sediment rivers (commonly termed anastomosing) with low w/d ratio channels that exhibit little or no lateral migration. They are divisible into three subtypes based on vegetative and sedimentary environment. Type 2 are sand-dominated, island-forming rivers, and type 3 are mixed-load laterally active meandering rivers. Type 4 are sand-dominated, ridge-forming rivers characterized by long, parallel, channel-dividing ridges. Type 5 are gravel-dominated, laterally active systems that interface between meandering and braiding in mountainous regions. Type 6 are gravel-dominated, stable systems that occur as non-migrating channels in small, relatively steep basins. Anabranching rivers represent a relatively uncommon but widespread and distinctive group that, because of particular sedimentary, energy-gradient and other hydraulic conditions, operate most effectively as a system of multiple channels separated by vegetated floodplain islands or alluvial ridges.

Budget Processes and Commitment to Fiscal Discipline

Abstract: This paper develops a political-economy model of the budget process focusing on the common pool problem of the public budget. We show that the externality arising from the fact that public spending tends to be targeted at individual groups in society while the tax burden is widely dispersed creates a bias towards excessive expenditures and debt. This bias can be reduced by introducing elements of centralization in the budget process, that is, institutional structures that strengthen a comprehensive view of the budget over the particularistic view of the spending ministers and the members of parliament. Using examples from EC countries, we show how budget processes lack or possess such elements. We then present empirical evidence supporting the claim that centralizing elements reduce the deficit bias. The last section concludes with models for reform of the budget process.

On Combining Artificial Neural Nets

Abstract: This paper reviews research on combining artificial neural nets, and provides an overview of, and an introduction to, the papers contained in this special issue, and its companion (Connection Science, 9, 1). Two main approaches, ensemble-based, and modular, are identified and considered. An ensemble, or committee, is made up of a set of nets, each of which is a general function approximator. The members of the ensemble are combined in order to obtain better generalization performance than would be achieved by any of the individual nets. The main issues considered here under the heading of ensemble-based approaches are a how to combine the outputs of the ensemble members, b how to create candidate ensemble members and c which methods lead to the most effective ensembles? Under the heading of modular approaches, we begin by considering a divide-and-conquer approach by which a function is automatically decomposed into a number of subfunctions which are treated by specialist modules. Other modular approaches ...

The demands—control model of job strain: A more specific test

Abstract: Karasek (1979) proposed that job demands and decision latitude interact to cause psychological strain. Main effects of these job variables on strain have been often found, but the predicted interaction between them has been less consistently demonstrated. We argue that this lack of support results from inadequate specification and operationalization of the independent variables. In particular, most empirical tests of the interaction have been based on a general measure of decision latitude which encompasses a wide range of job properties including control, task variety and learning opportunities. Yet, theoretically, it is control which is the crucial factor. In this study we used more focused measures of demands and control, with a sample of 1451 manufacturing employees, and found clear evidence of the predicted interaction effect. Parallel analyses using a measure of decision latitude rather than of job control did not show an equivalent effect. It is recommended that greater attention be paid to congruence between theory and measurement.

A fast method of molecular shape comparison: A simple application of a Gaussian description of molecular shape

Abstract: A Gaussian description of molecular shape is used to compare the shapes of two molecules by analytically optimizing their volume intersection. The method is applied to predict the relative orientation of ligand series binding to the proteins, thrombin, HIV protease, and thermolysin. The method is also used to quantify the degree of chirality of asymmetric molecules and to investigate the chirality of biphenyl and the amino acids. The shape comparison method uses the newly described shape multipoles that can also be used to describe the inherent shape of molecules. Some results of calculated shape quadrupoles are given for the ligands used in this work. © 1996 by John Wiley & Sons, Inc.

Paternity in eusocial Hymenoptera

Abstract: Variation in paternity frequency in colonies of eusocial insects has profound effects on the relatedness among offspring and on the genetic diversity of colonies. Data on queen \`mating-frequency' in eusocial Hymenoptera vary in both quality and the phase of the \`mating' process they address. Some are observational studies of the range or maximum number of copulations; others are derived from estimates of the number of sperm in males and queens; others use genetic techniques to determine the paternity of different males among female offspring. Only the latter data can be used to calculate relatedness among offspring females. Previous reviews drew attention to these problems, but their results have established the impression that high paternity frequencies are common, largely because multiple copulations are frequently observed. For ants, we show that: (i) the range of observed copulations overestimates effective paternity frequency; and (ii) the mean effective paternity frequency in 19 species, for which accurate data based on allozyme analysis of mother - offspring combinations are available, is only 1.16 (range 1-1.48). Over one third of these species have queens in which only one male contributes to paternity. Data from 34 species, which include less detailed genetic studies and four species studied using sperm counts, give similar results. Only two species, both Atta leaf cutter ants and both studied using data on sperm stored in queen spermathecas, appear to have effective insemination frequencies above two. Data on bees and wasps show a similar trend. We conclude that reliably documented high paternity or insemination frequencies (> 2) are currently restricted to one phylogenetically isolated and highly eusocial taxon each in ants, eusocial bees and wasps (Atta, Apis and Vespula, respectively). This pattern justifies the working hypothesis that multiple mating, by lowering the relatedness between female offspring and thereby the benefits of reproductive helping behaviour, has not been a general constraint for the evolution of eusociality in the Hymenoptera. Using reliable data on paternity frequency and insemination, we re-analyse two factors that it has been suggested correlate with mating frequency: colony population and number of egg-laying queens per colony. We find the following. 1. There is a significant positive correlation between paternity/insemination frequency and colony size for monogynous ants, but not for polygynous ants. This result seems to support the `sperm limitation' hypothesis, that queens which need to be highly fecund copulate multiply to store sufficient sperm. We note, however, that the same trend is expected when large and/or long-lived colonies profit more from having genetically diverse offspring. 2. There is no significant negative correlation between paternity/insemination frequency and number of queens per colony. However, when the analysis is restricted to species with large colonies and no intranidal mating, the correlation between paternity frequency and queen number becomes marginally significant. Several previous reviews have addressed the possible adaptive significance of multiple paternity. In contrast, and in keeping with the data that show single paternity to be frequent, we discuss selective reasons for single or low paternity. We compare the relative effects of multiple paternity and multiple maternity on genetic diversity within colonies and show that they are not equivalent, and we also discuss directions for future research on paternity issues in social insects.

Towards a holistic model of professional competence

Abstract: Describes a model of professional competence which attempts to bring together a number of apparently disparate views of competence, including the “outcomes” approach, a key feature of UK National Vocational Qualifications, and the “reflective practitioner” approach, suggested by Schon and now well recognized within professional education programmes.

Oral white lesions with special reference to precancerous and tobacco- related lesions: conclusions of an international symposium held in Uppsala, Sweden, May 18-21 1994. International Collaborative Group on Oral White Lesions.

Abstract: An international group of epidemiologists, clinicians and pathologists with a special interest in oral white lesions and their precancerous significance has reviewed earlier work on this topic and identified some of the problems associated with previous definitions, descriptions and classifications. Modifications to these definitions, descriptions and classifications have been proposed, accompanied by explanations of the reasons for identifying the need for changes to be made. Leukoplakia may be a provisional or definitive diagnosis dependent upon the circumstances of oral examination and the availability of other information. Guidelines are provided to assist in the application of the definitions of oral leukoplakia and illustrations depict the homogeneous and non-homogeneous clinical variants. Consideration is also given to the importance of a red component in a white lesion, or a lesion that is entirely red (erythroplakia). A new clinical staging procedure for oral leukoplakia is also proposed.

The role of practice in the development of performing musicians

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.

On the Performance Assessment and Comparison of Stochastic Multiobjective Optimizers

Abstract: This work proposes a quantitative, non-parametric interpretation of statistical performance of stochastic multiobjective optimizers, including, but not limited to, genetic algorithms. It is shown that, according to this interpretation, typical performance can be defined in terms analogous to the notion of median for ordinal data, as can other measures analogous to other quantiles.

Methods of automatic term recognition : a review

Abstract: Following the growing interest in "corpus-based" approaches to computational linguistics, a number of studies have recently appeared on the topic of automatic term recognition or extraction. Because a successful term-recognition method has to be based on proper insights into the nature of terms, studies of automatic term recognition not only contribute to the applications of computational linguistics but also to the theoretical foundation of terminology. Many studies on automatic term recognition treat interesting aspects of terms, but most of them are not well founded and described.This paper tries to give an overview of the principles and methods of automatic term recognition. For that purpose, two major trends are examined, i.e., studies in automatic recognition of significant elements for indexing mainly carried out in information-retrieval circles and current research in automatic term recognition in the field of computational linguistics.

Species-range-size distributions: patterns, mechanisms and implications

Abstract: Species-range-size distributions have received remarkably little attention in contrast to species-abundance distributions. However, recognition of the importance of regional scale phenomena for local assemblage structure, and the emergence of 'macroecology', have begun to change this situation. A growing number of studies suggests that these distributions are, in general, approximately lognormal, although interpretation is complicated by a variety of factors. Assuming the distribution pattern to be real, it can be viewed in terms of evolutionary and ecological determinants of species occurrences, although their relative significance remains unclear. The form of the distribution has a variety of important consequences, particularly for inventories of faunas and floras and for conservation.

Angels and Devils: Moral Landscapes of Childhood

Abstract: What it means to be a child varies over space and time. Historically, the dominant Western construction of childhood has oscillated between representing children as the bearers of original sin—devi...

Applications of electro-rheological fluids in vibration control: a survey

Abstract: Electro-rheological (ER) fluids are now regarded as one of the most versatile of the materials available for building smart structures and machines. In principle, ER fluids promise an elegant means of providing continuously variable forces for the control of mechanical vibrations. In practice, the development of industrial devices has been hampered by the unavailability of suitable ER fluids. Prompted by recent advances in ER fluid development this paper provides a comprehensive survey of ER devices for vibration control. The key modes of operation are identified and progress towards a unified approach to visualizing the macroscopic behaviour is summarized before presenting a comprehensive survey which includes contributions to the identification of ER fluid dynamics and the application of feedback control. The discussion of results includes some thoughts on future trends.