Showing papers by "University of York published in 1998"

Grounded Theory Methodology: The Pressing Need for a Coherent Logic of Justification

Abstract: The originators of the grounded theory approach to qualitative research now disagree on certain procedural aspects of the methodology, while agreeing on others, and dispute its epistemological implications. In this article it is argued that the rift can be traced to a conflict over the logic of justification of the approach. Strauss and Corbin endorse Dewey's instrumentalism, including its prizing of the experimental method, and introduce a form of hypothetico-deductivism into the grounded theory method. Alternatively, although subscribing tacitly to the experimental method, Glaser does not tie it in with instrumentalism, and insists that grounded theory properly involves only the inductive phase of inquiry. It is argued that both instrumentalism and induction are inadequate as rationales for the grounded theory method. A new logic of justification, termed methodological hermeneutics and derived from Margolis's reconciliation of realism and relativism, has been developed by the author. When applied to the...

Nutritional Interactions in Insect-Microbial Symbioses: Aphids and Their Symbiotic Bacteria Buchnera

Abstract: Most aphids possess intracellular bacteria of the genus Buchnera. The bacteria are transmitted vertically via the aphid ovary, and the association is obligate for both partners: Bacteria-free aphids grow poorly and produce few or no offspring, and Buchnera are both unknown apart from aphids and apparently unculturable. The symbiosis has a nutritional basis. Specifically, bacterial provisioning of essential amino acids has been demonstrated. Nitrogen recycling, however, is not quantitatively important to the nutrition of aphid species studied, and there is strong evidence against bacterial involvement in the lipid and sterol nutrition of aphids. Buchnera have been implicated in various non-nutritional functions. Of these, just one has strong experimental support: promotion of aphid transmission of circulative viruses. It is argued that strong parallels may exist between the nutritional interactions (including the underlying mechanisms) in the aphid-Buchnera association and other insect symbioses with intracellular microorganisms.

Variations in population health status: results from a United Kingdom national questionnaire survey.

Abstract: Objective: To measure the health of a representative sample of the population of the United Kingdom by using the EuroQoL EQ-5D questionnaire. Design: Stratified random sample representative of the general population aged 18 and over and living in the community. Setting: United Kingdom. Subjects: 3395 people resident in the United Kingdom. Main outcome measures: Average values for mobility, self care, usual activities, pain or discomfort, and anxiety or depression. Results: One in three respondents reported problems with pain or discomfort. There were differences in the perception of health according to the respondent9s age, social class, education, housing tenure, economic position, and smoking behaviour. Conclusions: The EQ-5D questionnaire is a practical way of measuring the health of a population and of detecting differences in subgroups of the population. Key messages Measurement of health outcome requires the observation of states of health Patients9 involvement in recording and assessing their own state of health is a major element in the process of evaluating the impact of health care The EuroQoL EQ-5D questionnaire highlights variations in states of health which are consistent with previously published results High degrees of pain are reported in the general population. A category for pain is absent and thus undetected in the survey of disability by the Office of Population Censuses and Surveys

Qualitative Methods in Social Work Research: Challenges and Rewards

Abstract: Introduction The Researcher as Instrument Getting Started Choosing a Topic and Designing the Study Ethical Issues in Qualitative Research Entering the Field and Sampling Strategies Data Collection Data Management and Analysis Rigor and Relevance in Qualitative Research Telling the Story Writing Up the Qualitative Study Multimethod Research The Synergy of Combining Qualitative and Quantitative Methods Epilogue Qualitative Methods in Social Work Education: Toward Developing an Infrastructure

Ploughing up the wood-wide web?

Abstract: Key species groups that affect major ecological processes are vital components of community diversity Many such key groups are found in the soil, including the mycorrhizal fungi that may connect plants into a functional “wood-wide web”1 Arbuscular mycorrhizal associations are formed by fungi of the order Glomales with 90% of land plant families, and many arbuscular mycorrhizal fungi are thought to have a broad host range2 Here we show that, despite this broad host range, the diversity of arbuscular mycorrhizal fungi is strikingly low in arable sites compared with a woodland

Language-impaired preschoolers: a follow-up into adolescence.

Abstract: This paper reports a longitudinal follow-up of 71 adolescents with a preschool history of speech-language impairment, originally studied by Bishop and Edmundson (1987). These children had been subd...

An introduction to markov modelling for economic evaluation

Abstract: Markov models are often employed to represent stochastic processes, that is, random processes that evolve over time. In a healthcare context, Markov models are particularly suited to modelling chronic disease. In this article, we describe the use of Markov models for economic evaluation of healthcare interventions. The intuitive way in which Markov models can handle both costs and outcomes make them a powerful tool for economic evaluation modelling. The time component of Markov models can offer advantages of standard decision tree models, particularly with respect to discounting. This paper gives a comprehensive description of Markov modelling for economic evaluation, including a discussion of the assumptions on which the type of model is based, most notably the memoryless quality of Markov models often termed the ‘Markovian assumption’. A hypothetical example of a drug intervention to slow the progression of a chronic disease is employed to demonstrate the modelling technique and the possible methods of analysing Markov models are explored. Analysts should be aware of the limitations of Markov models, particularly the Markovian assumption, although the adept modeller will often find ways around this problem.

Coming Out in the Age of the Internet: Identity “Demarginalization” Through Virtual Group Participation

Abstract: Internet newsgroups allow individuals to interact with others in a relatively anonymous fashion and thereby provide individuals with concealable stigmatized identities a place to belong not otherwise available. Thus, membership in these groups should become an important part of identity. Study 1 fou

Neural responses to facial and vocal expressions of fear and disgust

Abstract: Neuropsychological studies report more impaired responses to facial expressions of fear than disgust in people with amygdala lesions, and vice versa in people with Huntington's disease. Experiments using functional magnetic resonance imaging (fMRI) have confirmed the role of the amygdala in the response to fearful faces and have implicated the anterior insula in the response to facial expressions of disgust. We used fMRI to extend these studies to the perception of fear and disgust from both facial and vocal expressions. Consistent with neuropsychological findings, both types of fearful stimuli activated the amygdala. Facial expressions of disgust activated the anterior insula and the caudate-putamen; vocal expressions of disgust did not significantly activate either of these regions. All four types of stimuli activated the superior temporal gyrus. Our findings therefore (i) support the differential localization of the neural substrates of fear and disgust; (ii) confirm the involvement of the amygdala in the emotion of fear, whether evoked by facial or vocal expressions; (iii) confirm the involvement of the anterior insula and the striatum in reactions to facial expressions of disgust; and (iv) suggest a possible general role for the perception of emotional expressions for the superior temporal gyrus.

Local scale control for edge detection and blur estimation

Abstract: We show that knowledge of sensor properties and operator norms can be exploited to define a unique, locally computable minimum reliable scale for local estimation at each point in the image. This method for local scale control is applied to the problem of detecting and localizing edges in images with shallow depth of field and shadows. We show that edges spanning a broad range of blur scales and contrasts can be recovered accurately by a single system with no input parameters other than the second moment of the sensor noise. A natural dividend of this approach is a measure of the thickness of contours which can be used to estimate focal and penumbral blur. Local scale control is shown to be important for the estimation of blur in complex images, where the potential for interference between nearby edges of very different blur scale requires that estimates be made at the minimum reliable scale.

Authority, autonomy, and parent–adolescent conflict and cohesion: A study of adolescents from Mexican, Chinese, Filipino, and European backgrounds.

Abstract: This study examined whether parent-child conflict and cohesion during adolescence vary among families characterized as having different cultural traditions regarding parental authority and individual autonomy Approximately 1,000 American adolescents from immigrant and native-born families with Mexican, Chinese, Filipino, and European backgrounds reported on their beliefs, expectations, and relationships with parents; longitudinal data were available for approximately 350 of these youths Despite holding different beliefs about parental authority and individual autonomy, adolescents from all generations and cultural backgrounds reported similar levels of conflict and cohesion with their parents Discussion focuses on the relative importance of cultural beliefs and social settings in shaping the nature of parent-child relationships during adolescence

Considering the Vignette Technique and its Application to a Study of Drug Injecting and HIV Risk and Safer Behaviour

Abstract: Vignettes are stories generated from a range of sources including previous research findings. They make reference to important factors in the study of perceptions, beliefs and attitudes. Vignettes have primarily been used by psychologists in North America and used in quantitative surveys but more recently they have been used in a small number of qualitative studies. Drawing from a range of studies in the social sciences this paper considers the value of vignettes together with the difficulties associated with the technique. It introduces the technique in a study that explores drug injectors’ perceptions of human immunodeficiency virus (HIV) risk and safer behaviour inside and outside the prison system.

Analytical formulation for the shielding effectiveness of enclosures with apertures

Abstract: An analytical formulation has been developed for the shielding effectiveness of a rectangular enclosure with an aperture. Both the magnetic and electric shielding may be calculated as a function of frequency, enclosure dimensions, aperture dimensions and position within the enclosure. Theoretical values of shielding effectiveness are in good agreement with measurements. The theory has been extended to account for circular apertures, multiple apertures, and the effect of the enclosure contents.

Locally accessible conformations of proteins: Multiple molecular dynamics simulations of crambin

Abstract: Multiple molecular dynamics (MD) simulations of crambin with different initial atomic velocities are used to sample conformations in the vicinity of the native structure. Individual trajectories of length up to 5 ns sample only a fraction of the conformational distribution generated by ten independent 120 ps trajectories at 300 K. The backbone atom conformational space distribution is analyzed using principal components analysis (PCA). Four different major conformational regions are found. In general, a trajectory samples only one region and few transitions between the regions are observed. Consequently, the averages of structural and dynamic properties over the ten trajectories differ significantly from those obtained from individual trajectories. The nature of the conformational sampling has important consequences for the utilization of MD simulations for a wide range of problems, such as comparisons with X-ray or NMR data. The overall average structure is significantly closer to the X-ray structure than any of the individual trajectory average structures. The high frequency (less than 10 ps) atomic fluctuations from the ten trajectories tend to be similar, but the lower frequency (100 ps) motions are different. To improve conformational sampling in molecular dynamics simulations of proteins, as in nucleic acids, multiple trajectories with different initial conditions should be used rather than a single long trajectory.

How much of the relation between population mortality and unequal distribution of income is a statistical artefact

Abstract: The absolute income hypothesis—that holding other factors constant, the higher an individual's income the better is their health—is supported by a considerable body of evidence.1 2 3 However, according to the more recent relative income hypothesis, an individual's health is also affected by the distribution of income within society. Someone with a given income would have worse health if he or she lived in a society with greater inequality of income than in a society in which income is more equally distributed.4 Several recent papers examining the relation between population mortality and income inequality seem to support the relative income hypothesis.5 6 7 8 9 10 11 They suggest that greater inequality is associated with higher population mortality and that this relation persists even when account is taken of the average income of the population. However, some scepticism has been expressed about the relative income hypothesis.12 To quote one of the papers cited above, the “mechanisms underlying the association between income distribution and mortality are poorly understood.”7 There may be a very simple explanation for some, or all, of the reported associations between inequality of income and population health used to support the relative income hypothesis. They may be, at least partly, a statistical artefact caused by using population data rather than individual data. A positive correlation between population mortality and income inequality can arise at aggregate level even if inequality has no effect on the individual risk of mortality. Thus, we do not need the relative income hypothesis to explain the observed associations between population health and income inequality—the absolute income hypothesis will serve. The absolute income explanation can be illustrated with the help of the figure (the mathematical argument is presented in the Appendix 1). In this, the individual risk of mortality depends …

Mechanisms of Na+ Uptake by Plant Cells

Abstract: Soil salinity affects vast areas of land globally, with a particularly high impact in some agricultural intensively used soils due to irrigation practice. A diverse range of plants is able to thrive on saline soils but all major crop species are intolerant to salt. Identification of pathways for Na + transport across plant cell membranes has been highlighted as comprising a key gap in our understanding of salt tolerance in plants. During the last few years there have, however, been remarkable advances in this area as Na + permeable ion channels in plant cells have been characterized. This review summarizes the present knowledge regarding Na + transport pathways across plant membranes. In particular, data on selectivity, conductance, abundance and regulation of the major cation uptake channel types have been collected and this information has been integrated into a simple model in order to address the following questions: (i) how much Na + enters the cell through an ensemble of different channel types in saline conditions? (ii) what is the relative contribution of each channel type to the total Na + inward current? (iii) how does modulation of the activity of the different channel types affect the ability of the plasma membrane to discriminate between K + and Na + ? The model calculations underline the importance of voltage-independent non-selective cation channels in Na + -uptake and suggest that future research in the field of salt tolerance in plants should include studies on the regulation of this channel type.

Symmetric functional differential equations and neural networks with memory

Abstract: We establish an analytic local Hopf bifurcation theorem and a topological global Hopf bifurcation theorem to detect the existence and to describe the spatial-temporal pattern, the asymptotic form and the global continuation of bifurcations of periodic wave solutions for functional differential equations in the presence of symmetry. We apply these general results to obtain the coexistence of multiple large-amplitude wave solutions for the delayed Hopfield-Cohen-Grossberg model of neural networks with a symmetric circulant connection matrix.

Checks of model adequacy for univariate time series models and their application to econometric relationships

Abstract: Tests derived from time series analysis play an important role in many empirical studies. These tests are frequently applied to the residuals obtained by fitting an econometric model using some standard estimator. We focus attention here on tests developed for univariate time series models. Various approaches to testing the adequacy of such models are discussed and compared. The validity and sefulness of applying these tests to econometric residuals are then examined and some Monte Carlo evidence is reported.

Finding out about filling-in: a guide to perceptual completion for visual science and the philosophy of perception.

Abstract: In visual science the term filling-in is used in different ways, which often leads to confusion. This target article presents a taxonomy of perceptual completion phenomena to organize and clarify theoretical and empirical discussion. Examples of boundary completion (illusory contours) and featural completion (color, brightness, motion, texture, and depth) are examined, and single-cell studies relevant to filling-in are reviewed and assessed. Filling-in issues must be understood in relation to theoretical issues about neural-perceptual isomorphism and linking propositions. Six main conclusions are drawn: (1) visual filling-in comprises a multitude of different perceptual completion phenomena; (2) certain forms of visual completion seem to involve spatially propagating neural activity (neural filling-in) and so, contrary to Dennett's (1991; 1992) recent discussion of filling-in, cannot be described as results of the brain's "ignoring an absence" or "jumping to a conclusion"; (3) in certain cases perceptual completion seems to have measurable effects that depend on neural signals representing a presence rather than ignoring an absence; (4) neural filling-in does not imply either "analytic isomorphism" or "Cartesian materialism," and thus the notion of the bridge locus--a particular neural stage that forms the immediate substrate of perceptual experience--is problematic and should be abandoned; (5) to reject the representational conception of vision in favor of an "enactive" or "animate" conception reduces the importance of filling-in as a theoretical category in the explanation of vision; and (6) the evaluation of perceptual content should not be determined by "subpersonal" considerations about internal processing, but rather by considerations about the task of vision at the level of the animal or person interacting with the world.

Changes in Auxin Response from Mutations in an AUX/IAA Gene

Abstract: Transcription of the AUX/IAA family of genes is rapidly induced by the plant hormone auxin, but evidence that AUX/IAA genes mediate further responses to auxin has been elusive. Changes in diverse auxin responses result from mutations in the Arabidopsis AXR3 gene. AXR3 was shown to be a member of the AUX/IAA family, providing direct evidence that AUX/IAA genes are central in auxin signaling. Molecular characterization of axr3 gain-of-function and loss-of-function mutations established the functional importance of domains conserved among AUX/IAA proteins.

Climatic influences on human body size and proportions: Ecological adaptations and secular trends

Abstract: This study reevaluates the long-standing observation that human morphology varies with climate. Data on body mass, the body mass index [BMI; mass (kg)/stature (m)2], the surface area/body mass ratio, and relative sitting height (RSH; sitting height/stature) were obtained for 223 male samples and 195 female samples derived from studies published since D.F. Roberts' landmark paper “Body weight, race, and climate” in 1953 (Am. J. Phys. Anthropol. 11:533–558). Current analyses indicate that body mass varies inversely with mean annual temperature in males (r = −0.27, P < 0.001) and females (r = −0.28, P < 0.001), as does the BMI (males: r = −0.22, P = 0.001; females: r = −0.30, P < 0.001). The surface area/body mass ratio is positively correlated with temperature in both sexes (males: r = 0.29, P < 0.001; females: r = 0.34, P < 0.001), whereas the relationship between RSH and temperature is negative (males: r = −0.37, P < 0.001; females: r = −0.46, P < 0.001). These results are consistent with previous work showing that humans follow the ecological rules of Bergmann and Allen. However, the slope of the best-fit regressions between measures of body mass (i.e., mass, BMI, and surface area/mass) and temperature are more modest than those presented by Roberts. These differences appear to be attributable to secular trends in mass, particularly among tropical populations. Body mass and the BMI have increased over the last 40 years, whereas the surface area/body mass ratio has decreased. These findings indicate that, although climatic factors continue to be significant correlates of world-wide variation in human body size and morphology, differential changes in nutrition among tropical, developing world populations have moderated their influence. Am J Phys Anthropol 106:483–503, 1998. © 1998 Wiley-Liss, Inc.

Figures of speech: Figurative expressions and the management of topic transition in conversation

Abstract: In conversation, speakers occasionally use figurative expressions such as “had a good innings,” “take with a pinch of salt,” or “come to the end of her tether.” This article investigates where in conversation such expressions are used, in terms of their sequential distribution. One clear distributional pattern is found: Figurative expressions occur regularly in topic transition sequences, and specifically in the turn where a topic is summarized, thereby initiating the closing of a topic. The paper discusses some of the distinctive features of the topic termination/transition sequences with which figurative closings are associated, particularly participants’ orientation to their moving to new topics. Finally, the interactional use of figurative expressions is considered in the context of instances where their use fails to secure topical closure, manifesting some conflict (disaffiliation, etc.) between the participants. (Figurative expressions, idioms, conversation, topic)* One feature of conversation that contributes to its colloquial character is that, from time to time, speakers use certain forms of idiomatic expressions which may be regarded as figures of speech. The following fragment from a telephone conversation illustrates this kind of linguistic object, the use of which we shall examine in this article.

Lay perspectives: advantages for health research

Abstract: Although involvement of the consumer is increasingly being advocated in health related research, it is not welcome universally. Furthermore, the underlying rationale is rarely made explicit. Policy makers, health care professionals, and researchers need to be clear about the benefits and ways of including lay perspectives and the criteria for evaluating these. Examples of lay involvement in setting research agendas,1 2 3 4 methodological debate,5 and specific projects4 6 4 are accumulating, but little clear evidence about the benefits and costs of different ways of incorporating lay input into health services research is available. We outline two basic reasons for incorporating lay perspectives into research and discuss some common objections. A framework is offered to help clarify the dimensions of lay involvement in health research. We use the term “lay” to mean people who are neither health care professionals nor health services researchers, but who may have specialised knowledge related to health. This includes patients, the general public, and consumer advocates. The current interest in incorporating lay perspectives into health services research reflects broad social and political trends and developments in health care that have involved some breaching of the boundaries between medical professionals and others. The assumptions that the “experts”–doctors and biomedical researchers—are the best judges of what research is needed and should be exempt from democratic accountability are questioned. In addition, theoretical and empirical work on the philosophy and sociology of science has shown that the culture and values of those involved can influence research and the knowledge derived from it.8 The relevance of much research that has been driven by narrow professional and academic interests is increasingly being questioned.9 10 ![][1] #### Summary points Including lay people in health services research has been mandated politically and could improve the quality and impact of research Patients and … [1]: /embed/graphic-1.gif

Predisposing Gene for Early-Onset Prostate Cancer, Localized on Chromosome 1q42.2-43

Abstract: Summary There is genetic predisposition associated with ⩾10% of all cancer of the prostate (CaP). By means of a genomewide search on a selection of 47 French and German families, parametric and nonparametric linkage (NPL) analysis allowed identification of a locus, on chromosome 1q42.2-43, carrying a putative predisposing gene for CaP (PCaP). The primary localization was confirmed with several markers, by use of three different genetic models. We obtained a maximum two-point LOD score of 2.7 with marker D1S2785. Multipoint parametric and NPL analysis yielded maximum HLOD and NPL scores of 2.2 and 3.1, respectively, with an associated P value of .001. Homogeneity analysis with multipoint LOD scores gave an estimate of the proportion of families with linkage to this locus of 50%, with a likelihood ratio of 157/1 in favor of heterogeneity. Furthermore, the 9/47 families with early-onset CaP at age P = .001.

Resilience in natural and socioeconomic systems

Abstract: We, as a society, find ourselves confronted with a spectrum of potentially catastrophic and irreversible environmental problems, for which conventional approaches will not suffice in providing solutions. These problems are characterized, above all, by their unpredictability. This means that surprise is to be expected, and that sudden qualitative shifts in dynamics present serious problems for management. In general, it is difficult to detect strong signals of change early enough to motivate effective solutions, or even to develop scientific consensus on a time scale rapid enough to allow effective solution. Furthermore, such signals, even when detected, are likely to be displaced in space or sector from the source, so that the motivation for action is small. Conventional market mechanisms thus will be inadequate to address these challenges.

Invariance in automatic influences of memory : toward a user's guide for the process-dissociation procedure

Abstract: Three experiments investigated assumptions of the process-dissociation procedure for separating consciously controlled and automatic influences of memory. Conditions that encouraged direct retrieval revealed process dissociations. Manipulating attention during study or manipulating study time affected recollection but left automatic influences of memory relatively invariant. However, paradoxical dissociations were found when conditions encouraged use of a generate-recognize strategy, violating assumptions underlying the estimation procedure. Use of subjective reports to gain estimates produced parallel results. Easily observed correlations are shown to be not useful for testing assumptions underlying the process-dissociation procedure. A multinomial model produced results that agree with those from the process-dissociation approach.