Showing papers by "University of Exeter published in 1990"
TL;DR: It is found that the proposed simulated annealing algorithm provides better solutions than repeated iterative improvement algorithm, for a fixed total computational time.
305 citations
TL;DR: In this paper, the authors evaluated organizational performance as a function of perceived self-efficacy, task complexity, assigned and self-set goals, and analytic strategies in managerial decision-making in a stimulated organization.
298 citations
TL;DR: It is shown that terrestrial hosts have, on average, fewer component species than aquatic hosts, and the data refute the time hypothesis, which would predict that fishes as the oldest lifestyle should have the richest helminth communities.
Abstract: We examine patterns of community richness among intestinal parasitic helminth communities in fishes, herptiles, birds and mammals with respect to the comparative number of component species in a host population. We show that terrestrial hosts have, on average, fewer component species than aquatic hosts. We also show that the mean number of component species in aquatic hosts increases from fishes through herptiles to birds before declining slightly in mammals. For terrestrial hosts, the mean number of component species increases from herptiles, through birds, reaching a maximum in mammals. We conclude that: (i) habitat of the host is more important in determining community richness than is host phylogeny; (ii) the phenomenon of ‘host capture’ may be largely responsible for increased species richness in some host groups; (iii) aquatic birds harbour the richest intestinal helminth communities; and (iv) as we interpret them, our data refute the time hypothesis, which would predict that fishes as the oldest lifestyle should have the richest helminth communities.
289 citations
TL;DR: The identification of a mutant with only one phosphate uptake system provides further evidence that ‘normal’ uptake of ions occurs via two distinct transport systems.
Abstract: SUMMARY
The mechanism of phosphate and arsenate uptake was investigated in arsenate-tolerant and non-tolerant genotypes of Holcus lanatus L. It appeared that arsenate and phosphate were taken up by the roots by the same uptake system in both genotypes, although the uptake system had a much greater affinity for phosphate than arsenate. In non-tolerant plants the uptake of both anions was much greater than for tolerant plants at low phosphate and arsenate concentrations. High-affinity uptake appeared to be absent in the tolerant plants for both arsenate and phosphate. The absence of this high-affinity uptake is discussed in terms of arsenate tolerance in this species. The identification of a mutant with only one phosphate uptake system provides further evidence that ‘normal’ uptake of ions occurs via two distinct transport systems. The theoretical and ecological implications of this altered phosphate uptake mechanism are considered.
265 citations
TL;DR: The caesium-137 technique for investigating rates and patterns of soil loss has now been successfully applied in a wide range of environments as discussed by the authors, but some uncertainty still surrounds the ability of the technique to provide quantitative estimates of rates of erosion.
Abstract: The caesium-137 technique for investigating rates and patterns of soil loss has now been successfully applied in a wide range of environments. However, some uncertainty still surrounds the ability of the technique to provide quantitative estimates of rates of erosion. The wide range of calibration relationships that have been employed by individual workers to derive erosion rates from estimates of the amount of 137Cs (caesium-137) lost from the soil profile, emphasize the uncertainty involved. Existing calibration procedures, involving both empirical relationships and theoretical models and accounting procedures are reviewed and their limitations and inconsistencies are identified. Further research is required in this important area, if the clear potential of the caesium-137 technique is to be fully realized.
264 citations
TL;DR: British children have surprisingly low levels of habitual physical activity, and many children seldom undertake the volume of physical activity believed to benefit the cardiopulmonary system.
Abstract: OBJECTIVE--To examine the patterns of physical activity among British schoolchildren aged 11 to 16 and to assess whether the children experience the intensity and duration of physical activity that are believed to stress the cardiopulmonary system appropriately. DESIGN--Cross sectional study of a sample of children drawn from a larger survey of coronary risk factors in children. Continuous monitoring of heart rate for 12 hour periods on three school days and one Saturday. SETTING--Two communities in Devon. SUBJECTS--266 Children (163 girls, 103 boys) aged 11 to 16 randomly selected from a sample of 707 children. MAIN OUTCOME MEASURES--Percentage of time and number of sustained periods in which heart rate was greater than 139 beats/min. Anthropometric measures and external assessment of sexual maturity with Tanner9s indices. RESULTS--The boys had heart rates greater than 139 beats/min for a significantly higher percentage of time than the girls (p less than 0.01) during the weekday (6.2% v 4.3%) and the Saturday (5.6% v 2.6%). The boys had significantly more five and 10 minute periods with heart rates greater than 139 beats/min than the girls during the Saturday and weekdays and more 20 minute periods during the weekdays. 84 Girls and 37 boys had no 10 minute period with a heart rate greater than 139 beats/min during the three weekdays and 112 girls and 65 boys had no such 10 minute period during the Saturday. No significant relation was detected in either sex between the amount or habitual physical activity (heart rate) and skinfold thickness or maturity group. CONCLUSIONS--British children have surprisingly low levels of habitual physical activity, and many children seldom undertake the volume of physical activity believed to benefit the cardiopulmonary system. Boys are more active than girls. The pubertal stage of development or body fatness, or both, do not seem to be sensitive indicators of physical activity in either girls or boys.
264 citations
TL;DR: The trend is towards models that take account of coping resources and individual competence, and towards an understanding of how ordinary families deal with specific crises that arise.
Abstract: Recent years have seen a tremendous growth and reconceptualization in approaches to understanding the impact of chronic disease on children and their families. The traditional deficit-centred model is slowly being replaced. The trend is towards models that take account of coping resources and individual competence. The emphasis is away from identifying psychopathology within families, and towards an understanding of how ordinary families deal with specific crises that arise
259 citations
TL;DR: In this article, the potential for using the radionuclide caesium-137 as an environmental tracer to indicate sources of soil erosion in the Chinese Loess Plateau is introduced.
Abstract: The potential for using the radionuclide caesium-137 as an environmental tracer to indicate sources of soil erosion in the Chinese Loess Plateau is introduced. The caesium-137 contents of soil profiles have been used to estimate soil erosion losses from different topographic and land use conditions at Lishi, Shanxi Province, and Luochuan, Shaanxi Province. At uncultivated sites the caesium-137 has accumulated in the upper soil profile, whilst it has been mixed within the plough layer of cultivated soils. Eroded soils contain relatively less caesium-137, and simple calibration techniques are applied to quantify soil loss. Preliminary results suggest that caesium-137 may be of considerable value in assembling data on the rates and spatial distribution of soil loss and in identifying the source areas of eroded sediment.
246 citations
TL;DR: In this article, the authors analyze six recent studies dealing with the measurement of international harmonization of financial reporting and propose an alternative methodology for measuring harmonization suggested, and discuss the issues and problems relating to the definition and operationalization of terms, sources of data, statistical methods and causation.
Abstract: This paper analyses six recent studies dealing with the measurement of international harmonization of financial reporting. Methodological issues and problems relating to the definition and operationalization of terms, sources of data, statistical methods and causation are discussed, and an alternative methodology for measuring harmonization suggested.
240 citations
TL;DR: In this article, improved correlations are described to correlate data on diffusivities D and the related energies of activation, and solubilities S and related heats of solution of gases in polymers.
228 citations
TL;DR: Results confirm Granrud's (1987) findings that size constancy is present at birth, and suggest that the real size had been perceived as constant across the familiarization trials.
TL;DR: Two exploratory studies examining the acquisition, development and maintenance of gambling behaviour involving adolescent fruit machine gamblers were carried out and factors which directly relate to the cognitive biases (notably erroneous beliefs about skill) during gambling activity are discussed.
Abstract: A number of recent studies have shown there may be a strong cognitive bias in explaining persistent gambling. Theories that have been put forward include the illusion of control, “cognitive regret,” biased evaluations and the “psychology of the near miss.” Two exploratory studies examining the acquisition, development and maintenance of gambling behaviour involving adolescent fruit machine gamblers were carried out. Those factors which directly relate to the cognitive biases (notably erroneous beliefs about skill) during gambling activity are discussed with reference to the above cognitive influences.
TL;DR: Most bryophytes, including species of well-illuminated habitats, function in effect as shade plants, with low chlorophyll a/b ratios, and become light-saturated at relatively low irradiance.
TL;DR: For instance, this article found that infants respond to a stimulus consisting of two object pieces with a gap where the occluding block had been but did not respond to the continuous rod.
Abstract: In experiments described by Kellman and Spelke (1983) and Kellman, Spelke, and Short (1986) , 4-month-old infants were habituated to a stimulus (usually a rod) which moved behind a central occluder, so that only the top and bottom of the rod was visible. Subsequently, the infants increased responding to a stimulus consisting of two object pieces with a gap where the occluding block had been but did not respond to a continuous rod, suggesting that during the habituation trials, they had been perceiving a connected object, that is, they were “filling in” the unseen portion. The present article describes five experiments which were designed to see if perception of object unity is present at birth. In Experiments 1, 2, and 5, moving, occluded displays were shown to newborn infants. In Experiment 1, the familiarized stimulus was an outline square which underwent translatory motion behind a stationary occluder, and in Experiments 2 and 5, the familiarized stimulus was a rod which moved back and forth behind a stationary occluder. In all three experiments, the newborns subsequently gave a strong preference for a continuous, rather than a broken, stimulus. Experiments 3 and 4 showed, respectively, that newborns perceive both moving and stationary parts of a moving, occluded display, and that the preferences found in Experiments 1, 2, and 5 are best interpreted as novelty, rather than familiarity, preferences. In striking contrast to the above, in Experiment 5, 4-month-old infants, tested under the same conditions as the newborn infants, gave a strong novelty preference for two object pieces rather than a continuous stimulus, a finding which replicates the results of Kellman et al. (1986) . These findings argue against the view that infants begin life with a knowledge of the unity and coherence of objects and suggest that infants' understanding of objects changes in the early months of life. Unlike 4-month-olds, newborns appear to perceive only that which is immediately visible, and they seem to be unable to make perceptual inferences from visual input.
TL;DR: In this paper, the authors reported the use of large supercomputer resources to perform the first ab initio calculations on the polarisability and magnetisability of C 60 and its smaller analogue C 20 2+.
TL;DR: In this article, the effects of decision frame and opportunity on tax evasion behavior in the context of a business management task that required subjects to file simulated tax returns were examined in six different countries.
TL;DR: Results of cluster analysis show that the different plant organs and tissues examined can be separated on the basis of their endophytic fungi and that characteristic communities of the three Alnus species can be recognized.
TL;DR: In the U.K., the major commercial gambling activity in adolescents is the playing of slot machines (commonly known as “fruit machines”) as mentioned in this paper, and the negative effects of fruit machine addiction have been reported by various helping organizations (e.g. Gamblers Anonymous) and the national press, including allegations of attempted murder, suicide and prostitution as well as a wider incidence of petty crime.
Abstract: In the U.K., the major commercial gambling activity in adolescents is the playing of slot machines (commonly known as “fruit machines”). Over the past few years, the negative effects of “fruit machine addiction” have been reported by various helping organizations (e.g. Gamblers Anonymous) and the national press, including allegations of attempted murder, suicide and prostitution as well as a wider incidence of petty crime. Fifty adolescent fruit machine players from a ‘user population’ participated in a face-to-face interview and questionnaire study examining factors in the acquisition, development and maintenance of gambling behaviour. Nine adolescent males were deemed to be pathological gamblers as measured by the American Psychiatric Association DSM-III-R diagnostic criteria, and a number of serious consequences were reported including gambling debts, truancy and stealing.
TL;DR: In this paper, the effects of anisotropic compliant wall compliance on the Tollmien-Schlichting waves and the two previously identified wall modes, namely travelling-wave flutter and divergence, were investigated.
Abstract: A fairly simple theoretical model of an anisotropic compliant wall has been developed. It has been used to undertake a comprehensive numerical study of boundary-layer stability over such walls. The study is based on linearized theory, makes the usual quasi-parallel-flow approximation, uses the Blasius profile as the basic undisturbed flow and assumes two-dimensional disturbances. An investigation is carried out of the effects of anisotropic wall compliance on the Tollmien–Schlichting waves and the two previously identified wall modes, namely travelling-wave flutter and divergence. In addition global convergence techniques are used to search for other possible instabilities.An asymptotic theory, valid for high Reynolds numbers, is also presented. This can provide accurate estimates of the eigenvalues. It is applicable to a much wider class of compliant walls than the relatively simple model used for the numerical study. An important use of the asymptotic theory is to help identify and elucidate the various energy-exchange mechanisms responsible for stabilization or destabilization of the instabilities. A reduction in the production of disturbance energy by the Reynolds shear stress is the main reason for the favourable effect of anisotropic wall compliance on instability growth. Other energy-exchange mechanisms, which have been found to make a significant contribution, include energy transfer from the disturbance to the mean flow due to the interaction of the fluctuating shear stress and the displaced mean flow, and the work done by the perturbations in wall pressure and shear stress.It is found that anisotropic wall compliance confers very considerable advantage with respect to reduction in instability growth rate and transition delay. Using a fairly conservative criterion an almost ten-fold rise in transitional Reynolds number is predicted for anisotropic walls having the appropriate properties. Anisotropic wall compliance makes travelling-wave flutter much more sensitive to viscous effects and has a considerable stabilizing influence. The application of global convergence methods has led to the discovery of an anomalous spatially growing eigenmode which, according to conventional interpretation, would represent an instability. Further study of an appropriate initial-value problem has revealed that the new eigenmode is probably not an instability and that, for compliant walls, complex wavenumbers with positive real and negative imaginary parts do not necessarily correspond to an instability.
TL;DR: A measure of the large-wave-vector limits of the spin-wave and magnetic-exciton dispersion relations and the surprisingly strong magnetic field dependences of the measured energies are caused by the disorder present in the system.
Abstract: Measurements of activated conductivity for well-resolved Landau levels at filling factors v=1, 2, and 3 reveal a large exchange contribution to the energy gap, both at v=1 and 3 (the familiar exchange-enhanced g factor) and for the first time demonstrate a similar contribution at v=2. These results provide a measure of the large-wave-vector limits of the spin-wave and magnetic-exciton dispersion relations. The surprisingly strong magnetic field dependences of the measured energies are caused by the disorder present in the system.
TL;DR: In this paper, the authors used a grating to provide the necessary extra momentum to accelerate the plasmon-polaritons at a metal-air boundary, and obtained a p-s conversion of up to 66% for silver-coated gratings of appropriate depth.
Abstract: Surface plasmon-polaritons may be excited by photons at a metal-air boundary if a grating is used to provide the necessary extra momentum. Rotation of the grating so that the grooves are no longer perpendicular to the plane of incidence reduces the coupling efficiency while at the same time producing some s-polarised radiation in the reflected beam. When the grooves are at 45° to the plane of incidence maximum p-s conversion is obtained. Conversion efficiencies of up to 66% have been recorded for silver-coated gratings of appropriate depth. By scanning the angle of incidence and using a crossed polariser on the detector a strong resonance peak is observed. The application of this phenomenon to optical sensing is considered.
TL;DR: The Golombok Rust Inventory of Marital State (GRIMS) as discussed by the authors is a companion questionnaire to the GRISS, and concentrates on aspects other than the sexual in a dyadic relationship between two adults living together.
Abstract: Research in marital therapy has been disadvantaged by the lack of a good, short and recent psychometric questionnaire to objectively assess the state of a marriage for research, demographic and clinical purposes. The Golombok Rust Inventory of Marital State (GRIMS) is a companion questionnaire to the Golombok Rust Inventory of Sexual Satisfaction (GRISS), and concentrates on aspects other than the sexual in a dyadic relationship between two adults living together. It is a 28 item psychometrically constructed inventory designed to produce a single scale along which changes in a marriage may develop as marital therapy progresses. It has been shown to be valid for this purpose, and to have a good reliability.
TL;DR: In this article, the authors focus on the experiences and concerns of a range of physical education teachers at different stages in their careers and the manner in which they respond to perceptions of marginality.
Abstract: In Western cultures subjects defined as practical have had consistent difficulty in gaining acceptance within the curriculum. These subjects have been marginalised and accorded low status, which has influenced their positioning in relation to other subjects in terms of the allocation of power, resources and funding in schools. For those who choose to teach such subjects the construction of a career is highly problematic. Utilising the life‐history method this paper focuses upon the experiences and concerns of a range of physical education (PE) teachers at different stages in their careers and the manner in which they respond to perceptions of marginality. A strong classroom orientation is seen to be held on entry into teaching, which informs the dominant response of strategic compliance that reduces the capacity of these teachers to challenge and transform the structures that constrain them. The role of initial teacher education programmes in reproducing this process is discussed and it is sugges...
TL;DR: One-dimensional reductions of the self-dual Yang-Mills equations yield various classical systems depending on the choice of the Lie algebra associated with the selfdual fields as mentioned in this paper.
Abstract: One-dimensional reductions of the self-dual Yang-Mills equations yield various classical systems depending on the choice of the Lie algebra associated with the self-dual fields. Included are the Euler-Arnold equations for rigid bodies in n dimensions, the Kovalevskaya top, and a generalization of the Nahm equation which is related to a classical third-order differential equation possessing a movable natural boundary in the complex plane.
TL;DR: Endophytic fungi of the xylem and bark of Quercus robur and Salix fragilis have been compared to detect interspecific and tissue-specific differences in the communities, revealing a homogeneous distribution of colonization within the samples.
TL;DR: A preliminary study of eight adolescents addicted to playing and gambling on coin-in-the-slot machines (more commonly known as ‘fruit machines’) finds that adolescent gambling is more widespread than is generally recognized, and in some cases may even be pathological.
Abstract: Although most sources treat gambling as an adult phenomenon, adolescent gambling is more widespread than is generally recognized, and in some cases may even be pathological. This paper outlines a preliminary study of eight adolescents addicted to playing and gambling on coin-in-the-slot machines (more commonly known as 'fruit machines'). Factors involved in the onset of fruit machine playing are examined along with their alternative gambling activities and associated problems. The role of 'skill' and 'excitement' components in persistent playing are also discussed.
TL;DR: Analysis of the response rates to individual slides showed that, compared with prereversal training, only the feature that had been subjected to reversal contingencies showed a reversed correlation with response rate, and the remaining features showed the same correlation withresponse rate as they had before reversal training.
Abstract: Eight pigeons were trained to discriminate between sets of color photographs of natural scenes. The scenes differed along five two-valued dimensions (site, weather, camera distance, camera orientation, and camera height), and all combinations of the feature values were used. One value of each dimension was designated as positive, and slides containing three or more positive feature values were members of the positive stimulus set. Thus, each feature had an equal, low, correlation with reinforcement, and all features had zero correlations with each other. Seven of the 8 pigeons learned this discrimination, and their responding came under the control of all five features. Within the positive and negative stimulus sets, response rates were higher to stimuli that contained more positive feature values. Once discrimination had been achieved, reversal training was given using a subset of the slides. In this subset, only a single feature was correlated with reinforcement. All pigeons learned this reversal successfully and generalized it to additional photographs with the same feature content. After reversal, the original reinforcement contingencies were reinstated, and training was continued using all the slides except those that had been used in reversal. Reversal generalized to these slides to some extent. Analysis of the response rates to individual slides showed that, compared with prereversal training, only the feature that had been subjected to reversal contingencies showed a reversed correlation with response rate. The remaining features showed the same correlation with response rate as they had before reversal training. Thus, reversal on some members of a category following category discrimination training led to generalization to stimuli within the category that were not involved in the reversal, but not to features that were not reversed. It is therefore inappropriate to refer to the pigeons as learning a concept.
TL;DR: The steroidal glycoalkaloid solamargine caused significant disruption of phosphatidylcholine/cholesterol liposomes at a concentration > 50 μM whereas the normally co-occurring glycoalkeroid solasonine was ineffective at up to 150 μM and in combination, the two compounds produced a marked synergism.
TL;DR: The proportion of endogenous N 2 O production was lower in casts than soils indicating the more complete reduction of nitrogen oxides to N 2 under anaerobic conditions.
Abstract: Laboratory incubations were carried out. with and without acetylene, of earthworm casts and soil cores collected in permanent pastures with different fertilizer and drainage regimes. Nitrous oxide production (+ C 2 H 2 ) was consistently higher from casts than soil material from all sites. In the undrained, unfertilized plot the mean rate of N 2 O production from casts was nearly 5 times higher than from the soil. Moisture content was correlated with denitrification for casts but not for soils although both materials were near to saturation throughout the 8 week study. The proportion of endogenous N 2 O production (−C 2 H 2 ) was lower in casts than soils indicating the more complete reduction of nitrogen oxides to N 2 under anaerobic conditions. Earthworm casts constitute important microsites for denitrification and contribue to the spatial heterogeneity of these gaseous-N fluxes.
TL;DR: Two cases of carcinoma of the minor salivary glands are presented in which most cells had clear cytoplasm, and it is considered intra‐oral clear cell carcinoma to be a distinct tumour of low malignant potential.
Abstract: Two cases of carcinoma of the minor salivary glands are presented in which most cells had clear cytoplasm. Both patients had clinical histories in excess of 10 years and, in the one case with adequate follow-up, no recurrence had occurred after a further 11 years. Both tumours were locally invasive. The clear cells contained small amounts of glycogen, but no intracytoplasmic mucin. Immunohistochemical and ultrastructural studies showed epithelial features, with no evidence of myoepithelial differentiation. These tumours were very similar to the small number of previously reported cases, which were all considered to be low-grade carcinomas. Amongst the differential diagnoses, the most important is metastatic clear cell carcinoma of the kidney and this can only be confidently excluded clinically or by the use of imaging techniques. In summary, we consider intraoral clear cell carcinoma to be a distinct tumour of low malignant potential.