Showing papers by "University of East Anglia published in 1987"

Seasonal temperatures in Britain during the past 22,000 years, reconstructed using beetle remains

Abstract: Seasonal and mean annual temperatures can be reconstructed from radiocarbon-dated beetle remains to yield a synthesis of the palaeoclimatic history of Britain over the last 22,000 years. The reconstructions agree well with independent evidence from periglacial features and provide a detailed picture of the glacial to interglacial transition 14,500–9,000 years ago.

Speciation by reinforcement

Abstract: Speciation has a central place in evolution, linking genetic processes within populations to the generation of biological diversity. The formation of new species must involve the evolution of barriers to gene flow within existing species, but how these barriers arise remains a problem. In the case of prezygotic isolation it is possible that natural selection directly favours characters that decrease gene flow. Where two populations have diverged to such an extent that they produce unfit hybrids, individuals will leave more offspring if they mate within their own population. Characters increasing assortive mating will be favoured until eventually two species may result. This is the widely accepted model of speciation by reinforcement. However, recent studies suggest serious limitations on the efficacy of reinforcing selection and a lack of well-substantiated examples.

Term graph rewriting

Abstract: Graph rewriting (also called reduction) as defined in Wadsworth [1971] was introduced in order to be able to give a more efficient implementation of functional programming languages in the form of lambda calculus or term rewrite systems: identical subterms are shared using pointers.

Precipitation Fluctuations over Northern Hemisphere Land Areas Since the Mid-19th Century.

Abstract: An extensive array of measurements extending back to the mid-19th century was used to investigate large-scale changes in precipitation over Northern Hemisphere land areas. Significant increases in mid-latitude precipitation and concurrent decreases in low-latitude precipitation have occurred over the last 30 to 40 years. Although these large-scale trends are consistent with general circulation model projections of precipitation changes associated with doubled concentrations of atmospheric carbon dioxide, they should be viewed as defining large-scale natural climatic variability. Additional work to refine regional variations and address potential network inhomogeneitics is needed. This study attempts to show secular precipitation fluctuations over hemispheric and continental-scale areas of the Northern Hemisphere.

Testing for Regret and Disappointment in Choice Under Uncertainty

Abstract: Much of the experimental evidence concerning violations of von Neumann-Morgenstern expected utility theory has been collected fr om experiments designed with conventional theory in mind and does not provide direct tests of alternative models such as regret theory and disappointment theory. This paper reports and discusses recent evidence produced by an exp erimentspe cifically designed to test for the impacts of regret and disappointment, and to indicate their relative importance. Copyright 1987 by Royal Economic Society.

Thermal expansion of sea water associated with global warming

Abstract: The relationship between greenhouse-gas forcing, global mean temperature change and sea-level rise due to thermal expansion of the oceans is investigated using upwelling–diffusion and pure diffusion models. The sensitivities of sea-level to short-timescale forcing and deep-water formation rate changes are examined. The greenhouse-gas-induced thermal expansion contribution to sea-level rise between 1880 and 1985 is estimated at 2–5 cm. Projections are made to the year 2025 for different forcing scenarios. For the period 1985–2025 the estimate of greenhouse-gas-induced warming is 0.6–1.0 °C. The concomitant oceanic thermal expansion would raise sea level by 4–8 cm.

A handbook of Fourier theorems

Abstract: Preface 1. Introduction 2. Lebesque integration 3. Some useful theorems 4. Convergence of sequences of functions 5. Local averages and convolution kernels 6. Some general remarks on Fourier transformation 7. Fourier theorems for good functions 8. Fourier theorems in Lp 9. Fourier theorems for functions outside Lp 10. Miscellaneous theorems 11. Power spectra and Wiener's theorems 12. Generalized functions 13. Fourier transformation of generalized function I 14. Fourier transformation of generalized function II 15. Fourier series 16. Generalized Fourier series Bibliography Index.

A framework for assessing mathematical creativity in school children

Abstract: In spite of the neglect of the study of creativity specifically within the subject of school mathematics, the notion of creativity is apparently considered by many mathematical educators to be relevant and important in terms of children doing mathematics. Some of the research and literature associated with creativity in school mathematics, mainly from English speaking countries, is reviewed. Particular attention is given to attempts to assess creative ability in school mathematics. Two key aspects emerge: the ability to overcome fixations in mathematical problem-solving, and the ability for divergent production within mathematical situations. It is proposed that these might form the basis for a framework for fostering and rewarding mathematical creativity in schoolchildren.

Unconfined Ice-Shelf Flow

Abstract: The spreading of an unconfined ice shelf in two horizontal directions involves the variation of the two horizontal velocity components and the thickness in both directions. Exploiting the slow variation of physical quantities in both horizontal directions compared to vertical variation allows simple solution of the vertical momentum balance and the derivation of plane stress equilibrium equations for integrals of the horizontal stresses through the thickness, together with integrated traction conditions on a front contour defining the boundary of smooth flow. This contour, however, is not prescribed, but is part of the solution. Equilibrium of the region between this smooth contour and the sea margin determines the integrated front tractions in terms of the sea water pressure provided that restrictions on stresses in the margin region can be made. The resulting two-dimensional system of integropartial differential equations on the unknown domain is a complex problem.

Effects of terrestrial isopods on the decomposition of woodland leaf litter.

Abstract: The indirect contribution terrestrial isopods make to decomposition processes by stimulating microbial activites has been quantified in laboratory experiments. The extent to which microbial metabolism is enhanced as a result of the passage of Betula pendula leaf litter through the alimentary system of isopods was measured for both freshly fallen and decayed leaves. Faeces derived from 1 g freshly fallen litter lost 75 mg g-1 D.W. more than did intact leaves, as a result of enhanced microbial metabolism. Faeces derived from 1 g of previously decayed leaves, which were shown to be the preferred food of isopods, lost only 17.5 mg g-1 D.W. more than intact decaying leaves. The isopod's direct contribution to soil metabolism was calculated to be 151 mg and 138 mg g-1 litter ingested when fed on freshly fallen and decayed leaves respectively. It is concluded that the physical and chemical changes in the leaf substrate which result from fragmentation and digestion by isopods do not necessarily accelerate the subsequent decomposition of the litter very significantly. Fungal propagule density was 3.2x and 3.6x higher in faeces derived from freshly fallen and decayed leaves respectively than in the intact litter. Numbers of viable bacteria were correspondingly 126x and 34x higher in faeces than in the freshly fallen and the decayed leaves. Levels of microbial inhibitors were lower in the faeces than in the leaves but levels of free amino acids stayed higher for longer in the faeces than they did in intact litter. In the field the physical removal of litter by the soil macrofauna from surface to deeper and moister microsites may be the most important indirect contribution that they make to decomposition processes.

Polyhedral subdivision methods for free-form surfaces

Abstract: One of the central issues in computer-aided geometric design is the representation of free-form surfaces which are needed for many purposes in engineering and science. Several limitations are imposed on most available surface systems: the rectangularity of the network describing a surface and the manipulation of surfaces without regard to the volume enclosed are examples. Polyhedral subdivision methods suggest themselves as a solution to these problems. Their use, however, is not widespread for several reasons such as the lack of boundary control, and interpolation and interrogation capabilities.In this paper the original work on subdivision methods is extended to overcome these problems. Two methods are described, one for controlling the boundary curves of such surfaces, and another for interpolating points on irregular networks. A general surface/surface intersection algorithm is also provided: seven decisions need to be made in order to specify a particular implementation. The algorithm is also suitable for intersecting other classes of surfaces amongst which are the popular Bezier and B-spline surfaces.

Ecological studies at Lough Hyne

Abstract: Publisher Summary This chapter reviews on how the distribution of marine organisms in a limited coastal area is determined, how they react with each other and with their inanimate environment, and how their numbers are controlled. The chapter involves the assessment of physical and chemical conditions of the environment, observations of distribution and abundance of plants and animals, field experiments in which it interfere either with the inanimate environment or with its occupants, observations of behavior, and experiments in the laboratory. The chapter starts with a brief description of the topography of Lough Ine, and with some comments on those geological characteristics which throw light on the origin of the Lough or determine the present features of the shore. It proceeds to the hydrographical features - the water currents set up by the tides and the physical and chemical conditions of the water, and the distribution of sediment. It then describes the distribution of some important and conspicuous inhabitants of the rocky shores, relating their distribution to current, wave action, exposure to air, and other inanimate conditions, and biotic factors such as predation. Systematic problems and problems of natural selection arose incidentally during the course of the work.

Global optimization algorithms for a cad workstation

Abstract: This paper describes two new versions of the controlled random search procedure for global optimization (CRS). Designed primarily to suit the user of a CAD workstation, these algorithms can also be used effectively in other contexts. The first, known as CRS3, speeds the final convergence of the optimization by combining a local optimization algorithm with the global search procedure. The second, called CCRS, is a concurrent version of CRS3. This algorithm is intended to drive an optimizing accelerator, based on a concurrent processing architecture, which can be attached to a workstation to achieve a significant increase in speed. The results are given of comparative trials which involve both unconstrained and constrained optimization.

The early twentieth century Arctic high — fact or fiction?

Abstract: Reconstructions of monthly mean sea-level grid-point pressure from station pressure data over the Arctic region using an objective technique have revealed two serious errors in the gridded data. First, all gridded data (from the U.S. Historical Weather Map series) for the Arctic Ocean area away from the North Atlantic sector appears to be between 4 and 6 mb too high before about 1931. The semi-permanent Arctic high produced in the early historical map series was the result of a lack of basic station data, and the belief amongst many North American meteorologists of the 1920s and 1930s of the existence of a polar or glacial anticyclone. The second error affects only north-western North America for the years 1899–1909. Here pressure is again too high compared with reconstructed data. The cause of this error is not immediately apparent, but is probably the result of an erroneous correction to sea level for stations in the region. Both errors seriously affect the homogeneity of the gridded Arctic series. The objective scheme used to reveal the errors, can also be used to derive correction factors for the gridded data prior to 1931.

Global surface-temperature responses to major volcanic eruptions

Abstract: The impacts of pollution resulting from large explosive volcanic eruptions on the atmospheric heat budget and planetary albedo are not in doubt1,2. However, the effects of volcanic aerosols on the surface climate are less clear and still controversial3,4. In a previous study5 it was shown that significant surface cooling occurs over the landmasses of the Northern Hemisphere in the first few months after a major eruption in that hemisphere. Here we extend that work using new surface-air temperature compilations based on land and marine data6 for both the Northern and Southern Hemispheres. Our results indicate that major Northern Hemisphere eruptions have an immediate effect on the Northern Hemisphere average surface temperature but little or no effect on the Southern Hemisphere average. Southern Hemisphere eruptions affect both Southern and Northern Hemisphere temperatures after a lag of between six months and a year.

Educational theory, practical philosophy and action research

Abstract: (1987). Educational theory, practical philosophy and action research. British Journal of Educational Studies: Vol. 35, No. 2, pp. 149-169.

Determination of the glass-forming concentration range in binary alloys from a semiempirical theory: Application to Zr-based alloys

Abstract: A semiempirical theory is presented to calculate free-energy diagrams of glass-forming alloys. The theory is based on the enthalpy of formation of the solid solution expressed as a sum of two contributions: (a) a chemical contribution due to electronic redistribution in forming the alloy, and (b) an elastic contribution arising from the difference in size between solute and solvent atoms. The enthalpy of formation of the amorphous phase has only the chemical contribution. The theory is used to successfully describe the glass-forming concentration range of some Zr-based alloys, which have been experimentally analyzed by several distinct techniques.

On the analysis of competition at the level of the individual plant.

Abstract: The extent to which some measure of local crowding can account for the performance of individual plants is examined with reference to populations of two species of annual plant. Only a relatively small proportion of the variation in individual plant yield could be accounted for by measures of local crowding. These included the number of close neighbours, an estimate of the area available to each plant and competitive pressure. A multiple regression that took account of both emergence time and local crowding increased the proportion of variance that could be accounted for up to 50%. Computer simulations of the growth of indivudual plants in monoculture were then caried out in order to determine whether the unexplained variation resulted from fundamental flaws in the models or from unaccounted for sources of variation in the field. The results from the simulations again indicated that only a relatively low proportion of the variation in individual plant yield could be accounted for by emergence time and local density, even though these were known to be the only variables present. These findings are discussed in relation to the relative importance of one-sided and two-sided competition, and the complex cross-correlations that occur between individuals in plant populations. These two factors will make it very difficult for field workers to determine accurately what factors determine individual plant yield and in particular to predict the effects of local crowding on the performance of individual plants.

Measurements of dimethyl sulphide in frontal regions

Abstract: In June 1984 measurements of dimethyl sulphide (DMS) were made along surface transects and on vertical profiles across the shelf break and tidal fronts to the southwest of the British Isles. Surface concentrations were in the range 44–780 ng DMS-S 1 −1 . Much of this variability is ascribed to the species composition of the phytoplankton, with localized populations of Phaeocystis and, probably, coccolithophores being important sources of DMS. The implications of these results are discussed in relation to sampling strategies required to estimate the flux of volatile organic sulphur compounds from the sea to the atmosphere for shelf ecosystems.

Male spermatophore investment increases female fecundity in a grasshopper.

Abstract: were uniform for all migrants, whereas our model allowed violation of both constraints. We now return to the erroneous intuition that motivated this study. Our analysis showed that, at equilibrium, allele frequencies in the two subpopulations are equal. Given this fact, we can understand why gene flow between subpopulations does not alter the equilibrium sex ratio. When the allele frequencies in the subpopulations are equal, gene frequencies in the immigrant pollen are identical to those in the resident pollen. The immigrant pollen increases the size of the resident pollen pool but not its composition. Since it does not alter the composition, it can have no effect on gene-frequency change in that population, regardless of how strong or weak, or how asymmetric the pollen flow. This observation thus provides a partial explanation for our finding that gene flow does not affect the equilibrium. It does, however, leave unanswered the question of why allele frequencies in the two populations must be the same at an equilibrium. Although we have not been successful at reaching a full intuitive understanding of the result, the analysis does show that whatever evolutionary forces may be generated by migration, they do not affect the equilibrium sex ratio. Fisher's result ofa primary sex ratio of liz still holds.

Spreading structure of the Troodos ophiolite, Cyprus: Some paleomagnetic constraints

Abstract: It has been suggested that grabens on the northern flank of the Troodos ophiolite formed by listric faulting in an oceanic environment and represent axial valleys fossilized by ridge-jumping This paleomagnetic survey of the Solea graben was carried out to constrain the structural interpretation An analysis was devised which restores both the dikes sampled to vertical and the primary remanent magnetizations to a previously derived, structurally corrected, remanent magnetization direction Typically, two solutions for the original dike orientation and the pole and angle of net rotation are obtained for each dike sampled These solutions can be separated if a locally consistent original dike strike is assumed Reasons are discussed for the selection of the solution that gives an original northwesterly dike strike Results are consistent with a graben: rotations are up to 78° at the sites studied Rotation vectors are subhorizontal and subparallel to the original dike strike, suggestive of an axial process for the development of the structure However, on the basis of field observations, an alternative mode of origin is proposed, invoking ephemeral extreme upper crustal extension by listric faulting on the west flank of an intermediate- to fast-spreading axis, the grabens being formed by antithetic faulting

Logical framework approach to the monitoring and evaluation of agricultural and rural development projects

Abstract: This paper provides a brief and accessible statement of the basic structure of the Logical Framework Approach. It is hoped that this will encourage further use of the approach which, although time-consuming, provides not only sound guidance on the structuring of a monitoring and evaluation system but also helps to emphasise the role of planners and managers in specifying the intermediate and final objectives of the programme and project concerned.

Identification of the ligand-exchange process in the alkaline transition of horse heart cytochrome c.

Abstract: Magnetic-circular-dichroism (m.c.d.) spectra over the wavelength range 300-2000 nm at room temperature and at 4.2K of horse heart cytochrome c are reported at a series of pH values between 7.8 and 11.0, encompassing the alkaline transition. The effect of glassing agents on the e.p.r. spectrum at various pH values is also reported. Comparison of these results with spectra obtained for the n-butylamine adduct of soybean leghaemoglobin support the hypothesis that lysine is the sixth ligand in the alkaline form of horse heart cytochrome c. The m.c.d. and e.p.r. spectra of horse heart cytochrome c in the presence of 1-methylimidazole have also been examined. These studies strongly suggest that histidine-18, the proximal ligand of the haem, is the ionizing group that triggers the alkaline transition. Low-temperature m.c.d. and e.p.r. spectra are also reported for Pseudomonas aeruginosa cytochrome c551. It is shown that no ligand exchange takes place at the haem in this species over the pH range 6.0-11.3.