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  • Articles  (20)
  • 1995-1999  (20)
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  • Articles  (20)
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  • 1
    ISSN: 1440-1703
    Keywords: Drepanotermes tamminensis ; harvesting rate ; Isoptera ; nutrient dynamics ; simulation model ; termites
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A series of papers have been published which describe the influence of vegetation and soil type on the Western Australian wheatbelt termite,Drepanotermes tamminensis (Hill), and also on its litter harvesting levels and contribution to the soil nutrient budget. This paper integrates these findings by means of a computer simulation model. The model consists of three modules which respectively describe the dynamics of litter on the ground, the dynamics of litter within termite mounds and how these in turn influence nutrient loads within the habitat. The outputs of the model suggest that this litter harvesting termite plays an important role in the nutrient dynamics of the area and it provides an estimate of the unmeasured variable, litter consumed in mounds by termites, which is consistent with measurements for other termite species with similar feeding habits.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Agroforestry systems 45 (1999), S. 365-394 
    ISSN: 1572-9680
    Keywords: agricultural mimics ; ecosystem function ; eucalypt woodland ; kwongan
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract In this article we assess the potential for developing mimics in situations where detailed data on the ecophysiology and ecosystem function of the native ecosystem are not available. We examine two ecosystems in south western Australia, and draw together available information on these. We discuss woodlands dominated by Eucalyptus salmonophloia, which formerly covered much of the valley bottom land in the Western Australian wheatbelt, and kwongan or heath which occurs on sandplain soils at the top of the landscape. From both of these we derive possible mimics which utilise aspects of the native vegetation which we hypothesise contributed to ecosystem function and resilience, but which still allow the production of a harvestable agricultural product. We conclude that situations for which we have adequate ecological knowledge from which to develop sound mimics are likely to be rare. We hence have to be prepared to make best-bet estimates and use these to develop experimental mimic systems.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Agroforestry systems 45 (1999), S. 7-9 
    ISSN: 1572-9680
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Agroforestry systems 45 (1999), S. 425-438 
    ISSN: 1572-9680
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Agroforestry systems 45 (1999), S. 43-55 
    ISSN: 1572-9680
    Keywords: design of agricultural mimics ; ecosystem function ; non-equilibrium ; prediction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The science of ecology is undergoing many important shifts in emphasis and perspective which have important implications for its role in designing sustainable farming systems. In particular, a shift has occurred from the equilibrium paradigm to one which recognises the dynamic, non-equilibrium nature of ecosystems. Allied to this is the recognition that ecosystems can occur in any one of a number of alternative stable states, depending on the disturbance and management history. An increased emphasis on spatial patchiness in ecosystems has also emerged as appropriate tools have emerged to analyse spatial mosaics. These features have led to a recognition that considerable uncertainty is associated with the outcome of any particular ecosystem modification; hence predictive capacity is also low. Recent considerations of the interrelation between biodiversity and ecosystem function have also explored the questions of how many species need to be in a system to fulfil certain functions and confer resilience. We identify a set of steps that are required for the development of an agricultural system based on mimicking natural ecosystems. Central to this is identifying (1) the functions which are currently suboptimal in the agricultural system, and (2) the species which have key functional roles in the natural system, and then reaching decisions as to the array of species needed to confer system function and resilience.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Chichester : Wiley-Blackwell
    Communications in Numerical Methods in Engineering 14 (1998), S. 409-418 
    ISSN: 1069-8299
    Keywords: adaptive refinement procedure ; nearly incompressible problems ; error estimation ; Engineering ; Numerical Methods and Modeling
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: A numerical study is carried out employing some selected 2D elements and an automatic adaptive refinement procedure for the solution of a problem involving a nearly incompressible material. For a material with Poisson's ratio close to 0·5, it is found that both hybrid elements and high-order Lagrangian triangles can be used to provide a reliable solution. Furthermore, the rate of convergence of the elements is not affected by the high value of Poisson's ratio, and a near-optimal convergence rate is achieved in all the numerical tests run. © 1998 John Wiley & Sons, Ltd.
    Additional Material: 9 Ill.
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  • 7
    ISSN: 1573-6865
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary There is compelling evidence that the epithelial cell lineages of the gastrointestinal tract are derived from a common stem cell precursor, but the details of the subsequent cellular hierarchies remain uncertain. In this context, it is important to know the arrangement of cell proliferation that gives rise to the final cell populations. In rodents, a number of studies have been performed examining the possible proliferative capacity of endocrine cells, but a wide range of technical problems makes interpretation of these data difficult. Continuous labelling studies suggest that there is potential for proliferation in endocrine cells but flash labelling studies have not been conclusive. In man there are no data on this issue. We have taken advantage of the ability to perform double immunostaining for operational markers of proliferation (Ki67 antigen) and endocrine cell phenotype (chromogranin expression). We demonstrate that there are no double-labelled cells in the normal stomach, small intestine or colon of fetal, neonatal or adult humans. Moreover, no double-labelled cells are found in pathological states associated with endocrine cell hyperplasia (gastritis, ulcerative colitis). These data indicate that the normal endocrine cells of the human gut have no proliferative capacity and that, in this cell lineage, population expansion precedes differentiation.
    Type of Medium: Electronic Resource
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  • 8
    ISSN: 1573-6865
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary There is compelling evidence that the epithelial cell lineages of the gastrointestinal tract are derived from a common stem cell precursor, but the details of the subsequent cellular hierarchies remain uncertain. In this context, it is important to know the arrangement of cell proliferation that gives rise to the final cell populations. In rodents, a number of studies have been performed examining the possible proliferative capacity of endocrine cells, but a wide range of technical problems makes interpretation of these data difficult. Continuous labelling studies suggest that there is potential for proliferation in endocrine cells but flash labelling studies have not been conclusive. In man there are no data on this issue. We have taken advantage of the ability to perform double immunostaining for operational markers of proliferation (Ki67 antigen) and endocrine cell phenotype (chromogranin expression). We demonstrate that there are no double-labelled cells in the normal stomach, small intestine or colon of fetal, neonatal or adult humans. Moreover, no double-labelled cells are found in pathological states associated with endocrine cell hyperplasia (gastritis, ulcerative colitis). These data indicate that the normal endocrine cells of the human gut have no proliferative capacity and that, in this cell lineage, population expansion precedes differentiation.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 41 (1998), S. 777-777 
    ISSN: 0029-5981
    Keywords: Engineering ; Numerical Methods and Modeling
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: No Abstract
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 40 (1997), S. 3601-3638 
    ISSN: 0029-5981
    Keywords: automatic adaptive refinement ; shell analysis ; assumed strain element ; error estimations ; Engineering ; Numerical Methods and Modeling
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: An automatic adaptive refinement procedure for the analysis of shell structures using the nine-node degenerated solid shell element is suggested. The basic adaptive refinement principle and the effects of singularities and boundary layers on the convergence rate of the nine-node element used are discussed. A new stress recovery procedure based on the patch convective co-ordinate system concept is developed for the construction of a continuous smoothed stress field over the shell domains. The stress recovery procedure is easy to implement, requires a modest computational effort and needs only local patch information. It can be applied to shells with non-uniform thickness as well as to multi-layered shell structures. The smoothed recovered stress obtained is then used with the Zienkiewicz and Zhu error estimator for a posteriori error estimation during the adaptive refinement analysis. Numerical results which are in good agreement with theoretical predictions are obtained and they indicate that the current adaptive refinement procedure can eliminate the effect of singularities inside the problem domains so that a near-optimal convergence rate is achieved in all the numerical examples. This also indicates that the stress recovery procedure can produce an accurate stress field and as a result the error estimator can reflect the error distribution of the finite element solution. Even though in the current study only one type of element is used in the analysis, the whole adaptive refinement scheme can be readily applied to any other types of degenerated solid element. © 1997 John Wiley & Sons, Ltd.
    Additional Material: 24 Ill.
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