Showing papers by "University of Exeter published in 1983"
TL;DR: In this paper, the limitations of the sediment delivery ratio concept by considering the problems of temporal and spatial lumping and its blackbox nature are reviewed, and the significance of recent concern for the role of sediments in the transport of nutrients and contaminants to sediment delivery studies is introduced.
1,286 citations
TL;DR: The growth of Gortler vortices in boundary layers on concave walls is investigated in this article, and it is shown that the concept of a unique neutral curve so familiar in hydrodynamic-stability theory is not tenable in the gortler problem except for asymptotically small wavelengths.
Abstract: The Growth of Gortler vortices in boundary layers on concave walls is investigated. It is shown that for vortices of wavelength comparable to the boundary-layer thickness the appropriate linear stability equations cannot be reduced to ordinary differential equations. The partial differential equations governing the linear stability of the flow are solved numerically, and neutral stability is defined by the condition that a dimensionless energy function associated with the flow should have a maximum or minimum when plotted as a function of the downstream variable X. The position of neutral stability is found to depend on how and where the boundary layer is perturbed, so that the concept of a unique neutral curve so familiar in hydrodynamic-stability theory is not tenable in the Gortler problem, except for asymptotically small wavelengths. The results obtained are compared with previous parallel-flow theories and the small-wavelength asymptotic results of Hall (1982a, b), which are found to be reasonably accurate even for moderate values of the wavelength. The parallel-flow theories of the growth of Gortler vortices are found to be irrelevant except for the small-wavelength limit. The main deficiency of the parallel-flow theories is shown to arise from the inability of any ordinary differential approximation to the full partial differential stability equations to describe adequately the decay of the vortex at the edge of the boundary layer. This deficiency becomes intensified as the wavelength of the vortices increases and is the cause of the wide spread of the neutral curves predicted by parallel-flow theories. It is found that for a wall of constant radius of curvature a given vortex imposed on the flow can grow for at most a finite range of values of X. This result is entirely consistent with, and is explicable by the asymptotic results of, Hall (1982a).
367 citations
TL;DR: In this paper, the authors advocate the use of grounded theory as a way of handling the problem of non-standard data generated by qualitative social research, which makes analysis problematic. The approach is illustrated, in the context of organizational research, by three cases of grounded theoretical analyses: (a) a study of face-to-face interaction in a hospital between nurses and patients' relatives; (b) a field-study based on the complex organizational interrelationships associated with small batch production manufacturing; and (c) a documentary-based analysis of the organizational pre-conditions
Abstract: Qualitative social research generates large amounts of non-standard data which make analysis problematic. This discussion advocates the use of grounded theory as a way of handling these problems. The approach is illustrated, in the context of organizational research, by three cases of grounded theoretical analyses: (a) a study of face-to-face interaction in a hospital between nurses and patients’ relatives; (b) a field-study based on the complex organizational interrelationships associated with small batch production manufacturing; and (c) a documentary-based analysis of the organizational pre-conditions of large-scale accidents. The discussion of the cases stresses the manner in which the qualitative data collected were manipulated in order to give them theoretical shape.
290 citations
TL;DR: The effects of different grazing intensities of the millipede Glomeris marginata on a variety of forest organic substrates show that the animals amplified existing patterns of nutrient release.
Abstract: Decomposing oak litter was incubated in laboratory microcosms and the effects of adding a variety of soil animals upon nitrogen and cation release were monitored. Various groups of macrofauna caused a marked increase in ammonium release with smaller increases in calcium, potassium and sodium leaching. Microfauna also had significant but much less marked effects upon nitrogen and cation release. The effects of different grazing intensities of the millipede Glomeris marginata on a variety of forest organic substrates show that the animals amplified existing patterns of nutrient release.
152 citations
TL;DR: Results suggest that reproductive isolation between two populations of Mimulus guttatus could evolve as a direct result of adaptive differentiation in sympatry.
Abstract: A genetic system producing postmating reproductive isolation between two populations of Mimulus guttatus is described. In one population, Copperopolis, there is a single gene tightly linked to, or pleiotropic to, the gene for copper tolerance. In the other, Cerig-y-drudion, a limited number of genes are involved. The genes interact in a complementary manner to produce F1 inviability. These results suggest that reproductive isolation could evolve as a direct result of adaptive differentiation in sympatry.
142 citations
TL;DR: The results indicate that copper tolerance in this organism has evolved in a manner analogous to other adaptations such as mimicry, industrial melanism and pesticide resistance, and suggest that physiological models of metal tolerance involving many biochemical and physiological changes may need revision.
Abstract: Evidence is presented that copper tolerance in the yellow monkey flower, Mimulus guttatus is determined primarily by a single major gene. Selfed progenies of segregating T × T families produce families which are all T, segregating or all NT in a 1:2:1 ratio. Segregating T × NT crosses produce approximately 1:1 ratios. Significant heterogeneity between families within classes suggests that there are genetic modifiers also segregating, though some of the heterogeneity may be due to environmental factors. These results indicate that copper tolerance in this organism has evolved in a manner analogous to other adaptations such as mimicry, industrial melanism and pesticide resistance. The results also suggest that physiological models of metal tolerance involving many biochemical and physiological changes may need revision.
127 citations
TL;DR: In this article, the authors highlight the problems associated with interpreting data on the resistivity of thin thin films and point out that extreme care must be taken in analysing data and a thorough study should be made of the morphology of the films from which data are taken.
119 citations
TL;DR: For instance, this article found that if they had to send a cheque as a gift, they would spend more than twice as much on it as on the other kinds of presents.
114 citations
TL;DR: It is concluded that non-interactive models of insular colonization, with constant immigration and extinction rates, are of limited applicability to pond colonization in temperate areas.
Abstract: SUMMARY. 1. The rate and nature of colonization of ball-clay ponds by aquatic macrophytes and macroinvertebrates were studied by comparing communities present in a scries of ten ponds of similar dimensions, but of different ages, ranging from 6 months to 15 years.
2. Multivariate analyses of the biotic data distinguished between‘neutral’and‘acid’ponds; further analyses concentrated on the former type.
3. Initial colonization of neutral ponds was rapid with a predictable sequence of species arrival, probably reflecting short dispersal distances. Variations in macroinvertebrate invasion times were related to dispersal strategy and ability. As the pond aged, successional changes, linked with macrophyte colonization, produced a shift in dominance from algivores and predators towards epiphyton grazers and detritivores. Some evidence of succession of species within invertebrate orders was found.
4. Low pH affected colonization principally by preventing the establishment of acid-intolerant immigrant species, but also by retarding succession.
5. It is concluded that non-interactive models of insular colonization, with constant immigration and extinction rates, are of limited applicability to pond colonization in temperate areas.
100 citations
TL;DR: In this paper, the authors of these tests claim in the manuals that their sets of factors are definitive or embracing of the most variance, but in reality a small and well validated set of factors can be extracted from these tests.
85 citations
TL;DR: Reproductive cycles are described for subtidal and intertidal populations of the, starfish Asterias rubens L. and for a subtidal population of the starfish Marthasterias glacialis L. on the south-west coast of Britain.
Abstract: Reproductive cycles are described for subtidal and intertidal populations of the, starfish Asterias rubens L. and for a subtidal population of the starfish Marthasterias glacialis L. on the south-west coast of Britain. Intertidal A. rubens had a clearly defined reproductive cycle with spring-early summer spawning. Pyloric caecum indices were inversely related to gonad indices. Subtidal A. rubens had lower gonad indices and less seasonal variation in the pyloric caecum indices. Gonad indices of M. glacialis suggest few animals in the population studied were breeding, but it is likely that this species also spawns in summer.Plankton samples and larval rearing studies suggest a planktotrophic pelagic life of approximately 90 days for A. rubens. Field observations and laboratory experiments show larvae settle on a wide range of substrata. Recruitment to an intertidal population of A. rubens at Hollicombe Reef occurred in July 1980 and September 1981. Growth of juvenile starfish was followed for 17 months. Juvenile starfish feed carnivorously at the completion of metamorphosis. Early growth is rapid; however, there is a reduction in the growth rate during winter months. Feeding and growth of juvenile A. rubens is compared with published data on juvenile starfish of other species.
TL;DR: In this paper, the authors investigated the behavior of water sorbed by charcoals and in zeolites and found that the motion of protons is more liquid-like in the higher water content material, and that the mean activation energies for H + translation increase markedly relative to those around ambient temperature.
TL;DR: In spite of major changes in obstetric practice and in the maternal population, the same factors were shown to be highly significant and the magnitude of the associations had changed little.
TL;DR: In this article, a modification of Trinervitermes mounds by Cubitermes resulted in a 2-fold increase in available P, whereas organic C remained the same and N increased by 1.4-6.0 times.
Abstract: Soil-feeding termites ingest humified, organic-rich soil. The soil faeces are used for nest construction and mounds of two species of Cubitermes contained more soil, clay, exchangeable Ca and Mg, available P, total N and organic C than adjacent topsoil. Available P increased by 1.4–6.0 times. Mounds of a plant-debris feeding termite, Trinervitermes , contained significantly more of these fractions, with the exception of available P, than adjacent topsoil. The modification of Trinervitermes mounds by Cubitermes resulted in a 2-fold increase in available P, whereas organic C remained the same and N increased by 1.5-times. The relatively large increase in available P resulting from soil feeding termites could be attributed to the high pH regime in their hind-guts.
TL;DR: The morphology, histology and ultrastructure of the mesenteric and proctodaeal components of the mixed segment are described in detail, together with the disposition of the associated gut musculature, the patterns of peristalsis and the streaming movements of soil particles in the gut lumen.
Abstract: The morphology, histology and ultrastructure of the mesenteric and proctodaeal components of the mixed segment are described in detail, together with the disposition of the associated gut musculature, the patterns of peristalsis and the streaming movements of soil particles in the gut lumen. The mesenteric epithelium is characterized by very extensive basal infoldings which are associated with a large population of mitochondria, but evidence of significant protein synthesis and secretion is lacking. It is proposed that this tissue is a transporting epithelium whose major function is the secretion of a copious, K+ -rich fluid into the intestinal lumen to irrigate the hindgut (proctodaeum) and that alkaline hydrolysis of humic fractions by this fluid is an essential component of digestion.
Malpighian tubules are present, but do not participate in fluid excretion. Since the hind-guts of soil-feeding termites are exceptionally voluminous and elongated and the major symbiotic micro-organisms occupy fixed positions by virtue of their attachment to the lining cuticle, it is argued that flushing is necessary to sustain microbial activity and for the recovery of end-products by the host. A survey of the protodaeal epithelium suggests that the anterior colon (P4a) is the most likely site of fluid reabsorption and that the wall of the hindgut anterior to this site is impermeable. The greater degree of ultrastructural differentiation of the mixed segment of Cubitermes severus and its more complete morphological separation from the midgut suggests that this species is a more advanced soil-feeder than Procubitermes aburiensis.
TL;DR: In the immediate aftermath of the Glorious Revolution, there appeared an anonymous pamphlet, Political aphorisms, which purported to instruct its readers in "true maxims of government" as discussed by the authors.
Abstract: In the immediate aftermath of the Glorious Revolution, there appeared an anonymous pamphlet, Political aphorisms, which purported to instruct its readers in ‘true maxims of government’. The identity of the author of this bold doctrinal claim is not known, and while it would be useful to have this knowledge, it is not, for reasons which will become clear, the most crucial element of the story. What is important is the historical significance of the role played by Political aphorisms as part of the process by which the ‘revolution principles’ of 1689 gained widespread acceptance in eighteenth-century England. In this essay, we offer one concrete illustration of the complex process by which political ideas are transmitted from one generation to another; and, we shall argue, the example provides a case study of the conscious effort to formulate an ideological defence of specific political principles and practices in order to preserve the historical meaning of a partisan perspective.
TL;DR: In this paper, the authors used the results of calculations of the electronic properties of two types of defect (the soliton and its vacancy complex) given in an accompanying paper to explain the electrical and mobility properties of dislocations in silicon in terms of solitons associated with strongly reconstructed partials.
Abstract: The experimental evidence for an explanation of the electrical and mobility properties of dislocations in silicon in terms of solitons (i.e. antiphase defocts) associated with strongly reconstructed partials is presented. This paper uses the results of calculations of the electronic properties of two types of defect (the soliton and its vacancy complex) given in an accompanying paper. We suggest that the absence of spin centres in high-temperature-deformed silicon can be interpreted through the soliton being a negative-U Anderson centre. We support this hypothesis with theoretical arguments. These solitons form obvious nucleation points for double kinks and a theory of dislocation velocity is given, starting from this premiss. The expression for the dislocation velocity is formally identical to that of Hirth and Lothe, its doping dependence is the same as that of Hirsch’s theory and the calculated effective donor and accoptor levels are in good agreement with observation. © 1983 Taylor & Francis Group, LLC.
TL;DR: In this paper, the authors classified estuaries into three categories: stratified, partially mixed, and well mixed, based on the degree of mixing of freshwater and seawater, and used the presence of size sorting with small mean size, diversity range, and proportion of exotic individuals for the recognition of tidal effects in ancient estuarine deposits.
TL;DR: The results presented in this article are believed to be the first of their kind with an on-line location system mapping the stimulated zone during injection and have been an essential tool in understanding the geothermal reservoir performance.
Abstract: One of the most promising techniques for monitoring the effects of hydraulic stimulation or fracturing is the use of the induced microseismicity to define the shape and orientation of the stimulated regions. The results presented in this work are believed to be the first of their kind with an on-line location system mapping the stimulated zone during injection. The stimulation was undertaken as part of an investigation into the generation of hot dry rock geothermal reservoirs and consisted of a 3.5-million gal injection at flow rates as high as 40 bbl/min. Many thousands of microseismic events were produced, located, and presented as maps to enable the interpretation to proceed during the operation. These results represent a considerable step forward in the state of the art of monitoring hydraulic stimulation and have been an essential tool in understanding the geothermal reservoir performance. 28 references.
TL;DR: In this paper, the authors describe the process for the evaporation of He atoms from the surface of liquid 4He, which is a particularly simple quantum process: a phonon inthe liquid with energy ħω > EB, the binding energy, propagates to the free surface where it is either reflected or gives all its energy to an atom on the surface.
Abstract: We report here the process for the evaporation of He atoms from the surface of liquid 4He. It is a particularly simple quantum process: a phonon inthe liquid with energy ħω > EB, the binding energy, propagates to the free surface where it is either reflected or gives all its energy to an atom on the surface. This energy is used to overcome the binding forces and the balance, ħω − EB, is carried away by the atom as kinetic energy.
TL;DR: Aero-aquatic Hyphomycetes showed the greatest percentage survival, and only species of Saprolegniales with oospores survived anaerobic conditions.
Abstract: Aero-aquatic Hyphomycetes were tested for their ability to survive on beech leaf disks under anaerobic conditions for periods of up to 12 months. Helicodendron triglitziense, H. conglomeration and H. giganteum showed 100% survival, while H. luteo-album and H. hyalinum showed reduced survival. Survival of aero-aquatic Hyphomycetes, Ingoldian aquatic Hyphomycetes and members of the Saprolegniales was also compared on hemp seeds under anaerobic conditions. Aero-aquatic Hyphomycetes showed the greatest percentage survival. Articulospora tetracladia, Achlya colorata (isolate lacking oospores) and Dictyuchus sterilis failed to survive even 3 months. No significant difference was found in the survival of Tricladium splendens from a stagnant drainage ditch and from a fast-flowing river. Only species of Saprolegniales with oospores survived anaerobic conditions.
TL;DR: In this article, measurements of thalli of Rhizocarpon geographicum on the recent moraines of the Glacier de Valsorey and their surroundings are considered in relation to thallus growth rates and colonization following glacial recession Photographs taken in 1975 and 1979 show that up to c 35 cm diam the relation of maximum growth-rate to thalli size is approximated by a growth curve of the kind derived by Aplin and Hill, rising asymptotically towards a constant rate of radial growth.
Abstract: Measurements of thalli of Rhizocarpon geographicum on the recent moraines of the Glacier de Valsorey and their surroundings are considered in relation to thallus growth rates and colonization following glacial recession Photographs taken in 1975 and 1979 show that up to c 35 cm diam the relation of maximum growth-rate to thallus size is approximated by a growth curve of the kind derived by Aplin and Hill, rising asymptotically towards a constant rate of radial growth (here c 05 mm year−1) Growth-rates of many individual thalli fall well below the maximum Parameters of the fitted growth curves are used to construct curves of thallus radius against time Taken in conjunction with the field measurements these suggest two main phases of colonization, one from about 1880 to 1910, and one from about 1930 onwards Some general considerations relating to lichenometry and lichen growth curves are discussed
TL;DR: In this paper, a dynamic model for the pattern of ice flow during the Wolstonian glaciation of eastern England is outlined, where the central mechanism comprises North Sea ice crossing the northern Lincolnshire Wolds, in force, to occupy central and northwest Lincolnshire and the lower Trent valley before being replaced and deflected southwest and south by the more powerful Vale of York ice.
TL;DR: In this paper, the vegetational context and age of Flandrian estuarine deposits have been determined at Waterside, near the mouth of the present estuary, and correlated with the Main Postglacial Shoreline elsewhere in eastern Scotland.
Abstract: Relict Flandrian estuarine deposits in the Ythan valley are confined to an area in the lower valley around the present estuary. They rest upon a discontinuous layer of peat over an irregular surface of sand and gravel, and consist for the most part of a grey silty clay, or carse deposit, which forms terraces or small areas of carseland. At the seaward end of the estuary the grey silty clay contains a layer of grey, micaceous, silty fine sand, which tapers into the basal peat, whilst in places the surface of the grey silty clay is covered by peat and/or blown sand. The vegetational context and age of these deposits have been determined at Waterside, near the mouth of the present estuary. Here, the grey silty clay accumulated as the result of a marine transgression which began in the early Flandrian, and culminated between about 6189·95 and some time prior to 4000·80 radiocarbon years B.P. The carseland surface produced by this phase of accumulation is the highest Flandrian estuarine surface in the valley, at about 4·5 m O.D., and is correlated with the Main Postglacial Shoreline elsewhere in eastern Scotland. Withdrawal of the sea from this level may have been interrupted by the formation of a lower carseland surface before present levels were reached, though this is far from certain. The grey, micaceous, silty fine sand layer is dated at approximately 6850·140 radiocarbon years B.P., and is correlated with similar layers that may have been deposited following a storm surge. The paper concludes with some considerations on the age and distribution of the Main Postglacial Shoreline in eastern Scotland.
TL;DR: Children were asked to define 'being healthy' and what they must do to remain healthy and assigned a central role to diet in maintaining good health.
Abstract: 20 children at each of 4 age-levels (6, 8, 9 and 11 years) were interviewed about their knowledge of health and illness. Children were asked to define 'being healthy' and what they must do to remain healthy. Knowledge of diseases and their prevention was poor. Children assigned a central role to diet in maintaining good health. The results are discussed in relation to possible ways of improving health education to school-children.
TL;DR: It is suggested that the habituation effects and the subsequent novelty preferences found in the experiments are most reasonably interpreted as a function of memory formation, and evidence is presented for the storage of visual experience from birth.
Abstract: There is some controversy concerning the youngest age at which an infant will habituate to a visual stimulus or will prefer a novel to a familiar pattern. One suggestion has been that apparently successful reports of habituation and dishabituation in the newborn baby are attributable to retinal adaptation. This interpretation was tested in two experiments. In both experiments monocular conditions of viewing were used: newborns were habituated with one eye as the ‘seeing’ eye, and posthabituation novelty preferences investigated with the other eye. Significant preferences were found both for a novel colour (experiment 1) and for a novel shape (experiment 2), which implies that a retinal-adaptation model can be ruled out. It is suggested that the habituation effects and the subsequent novelty preferences found in the experiments are most reasonably interpreted as a function of memory formation, and evidence is presented for the storage of visual experience from birth. The results also demonstrate some form ...
TL;DR: Hybrids between bream and roach, Ahrumis brama and Rutilus rutilus, occur in the lower reaches of the River Exe and were positively identified by their meristic features and shape of the pharyngeal bone.
Abstract: Hybrids between bream, Ahrumis brama, and roach, Rutilus rutilus. occur in the lower reaches of the River Exe and were positively identified by their meristic features and shape of the pharyngeal bone. The growth of bream and hybrids was determined by backcalculation from scales. Annual checks were laid down in early June. The mean length for age of female bream was significantly larger than that of males for fish 6 years of age and older. This divergence in growth rate was associated with the sexual maturation of the fish. Data for the sexes were combined and compared with the growth rate of hybrids and roach from the same region. Hybrid growth was similar to that ofbream for the first 6 years of life but was intermediate between that of the two parent species in the older age groups. Some hybrids with developing gonads were found. A change in the diet of bream from planktonic feeding to a benthophagic habit with age was noted. Detritus, substrate and chironomid larvae formed the bulk of the diet of hybrids.
TL;DR: In this paper, a program of over-coring rock stress measurement was conducted at South Crofty mine, Camborne, at a depth of 790 m in the Carmenellis granite to obtain information required for the Camborne School of Mines (CSM) hot dry rock (HDR) Geothermal Energy Research Programme at Rosemanowes quary in Cornwall, U.K. The measurements were undertaken to obtain an independent confirmation of stress magnitudes measured by hydraulic fracturing at the quarry and an indication of stress directions.
TL;DR: The results indicated that the alternate forms of the Multidimensional Health Locus of Control scale could be considered parallel, but a sex difference appeared in the factor structure of the test such that the male sample yielded only two factors while the female sample yielded the three scale factors as expected.
Abstract: The validity of the alternate forms of the Multidimensional Health Locus of Control scale and the underlying dimensionality of the three test scales were investigated using 70 male and 77 female British university students. A classical item analysis, principal component and image component factor analysis were undertaken. The results indicated that the alternate forms could be considered parallel. However, a sex difference appeared in the factor structure of the test such that the male sample yielded only two factors while the female sample yielded the three scale factors as expected.