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Showing papers by "University of East Anglia published in 1984"


Journal ArticleDOI
TL;DR: In this article, the authors derived formulas for the correlation coefficient between the average of a finite number of time series and the population average, where the subsample signal strength (SSS) and expressed population signal (EPS) were derived.
Abstract: In a number of areas of applied climatology, time series are either averaged to enhance a common underlying signal or combined to produce area averages. How well, then, does the average of a finite number (N) of time series represent the population average, and how well will a subset of series represent the N-series average? We have answered these questions by deriving formulas for 1) the correlation coefficient between the average of N time series and the average of n such series (where n is an arbitrary subset of N) and 2) the correlation between the N-series average and the population. We refer to these mean correlations as the subsample signal strength (SSS) and the expressed population signal (EPS). They may be expressed in terms of the mean inter-series correlation coefficient r as SSS ≡ (Rn,N)2 ≈ n(1 + (N − 1)r)/ N(1 + (N − 1)r), EPS ≡ RN)2 ≈ Nr/1 + (N − 1)r.Similar formulas are given relating these mean correlations to the fractional common variance which arises as a parameter in a...

2,949 citations


Journal ArticleDOI
01 Apr 1984
TL;DR: In this article, the authors examined the role of large particles in the removal of fine particles by shear-controlled coagulation and concluded that the flat size distributions are quasi-stationary results of shear control.
Abstract: Work of the last 10 years has demonstrated that oceanic particle size distribution by volume tends to be flat at mid-water depths (equivalent to a cumulative particle number distribution with a slope of −3) and is peaked in nepheloid layers with active resuspension and in surface waters with active biological production. The observed loss of fine peaks from the suspensions to yield flat distributions requires aggregation of the material, as the fines settle slowly. Mechanisms leading to particle collision are examined; for interactions between particles of similar size, Brownian motion dominates below 1.5 to 8 μm. However, if large particles (such as ‘marine snow’) are present at realistic concentrations, they become important in the removal of fine particles by shear-controlled coagulation. The coagulation times calculated for shear are too long for steady state to be presumed while the size distributions evolve under the influence of coagulation mechanisms. Therefore suggestions that the flat size distributions are quasi-stationary results of shear-controlled coagulation are rejected, and the notion that there is sub-equal production of particles at different points in the spectrum is favoured. Such production and the subsequent scavenging of small particles by large settling ones confers great importance on components of biological origin in both providing elements of the total size spectrum and determining the distribution and sedimentation of others of lithogenic origin. In surface waters, filtration rates by zooplankton indicate that aggregation rates of particles above submicron sizes are biologically determined.

699 citations


Journal ArticleDOI
TL;DR: In this article, the authors propose the Political Economy of Accounting (PEA) framework to understand and evaluate the functions of accounting within the context of the economic, social and political environment in which it operates.
Abstract: Existing research on the choice of accounting methods for corporate reports emphasizes private interests. In particular, shareholders' interests predominate in studies of the effects of accounting information on individual users. Attempts at assessing the social value of accounting reports, using the approach of marginal economics to information or the analysis of economic consequences also exhibit, in their execution, a pronounced shareholder orientation. This paper suggests that an alternative approach, the Political Economy of Accounting, may be fruitful. This approach seeks to understand and evaluate the functions of accounting within the context of the economic, social and political environment in which it operates. Research within this framework is identified as having normative, descriptive and critical qualities, and the paper concludes with some illustrations of potential research areas.

648 citations


Journal ArticleDOI
01 Jan 1984
TL;DR: In this article, the authors present an algorithm for fitting subsets of Bilinear models to time series data, based on the Kronecker matrix product (KMP) and Markovian representation.
Abstract: 1 Introduction to Stationary time Series and Spectral Analysis.- 1.1 Some basic Definitions.- 1.2 Spectral Densities and Spectral Representations.- 1.3 Higher Order Spectra (Polyspectra).- 1.4 Bispectral Density Functions.- 1.5 Standard Linear Models - their spectra and bispectra.- 1.6 State Space Representation of Linear Time Series Models.- 1.7 Bispectra and Linear Processes.- 1.8 Invertibility of Time Series Models.- 2 The Estimation of Spectral and Bispectral Density Functions.- 2.1 Introduction.- 2.2 Estimation of the Spectral Density Function.- 2.3 Estimation of the Bispectral Density Function.- 2.4 Optimum Bispectral Window.- 2.5 Comparison of Bispectral Lag Windows.- 2.6 Bispectral Density Function of BL(1,0,1,1) Model.- 3 Practical Bispectral Analysis.- 3.1 The Choice of Truncation Point (M).- 3.2 Comparison of Parametric and Non-Parameteric Bispectral Estimates.- 3.3 Bispectral Analysis of some Time Series Data.- 3.4 Some Nonlinear Phenomena.- 4 Tests for Linearity and Gaussianity of Stationary time Series.- 4.1 General Introduction.- 4.2 Spectrum and Bispectrum of Linear Processes.- 4.3 Test for Symmetry and Linearity.- 4.4 Test for Linearity.- 4.5 Choice of Parameters.- 4.6 Numerical Illustrations.- 4.7 Applications to Real Time Series.- 5 Bilinear time Series Models.- 5.1 Non-Linear Representations in terms of independent random variables.- 5.2 Bilinear Time Series Models.- 5.3 Volterra Series Expansion of YBL(p) Models.- 5.4 Expressions for Covariances and Conditions for Stationarity.- 5.5 Invertibility of the VBL(p) Model.- 5.6 Conditions for Stationarity of the Diagonal Bilinear Model, DBL(?).- 5.7 Conditions for Stationarity of the Lower Triangular Bilinear Model, LTBL (?,?).- 5.8 Estimation of the Parameters of Bilinear Models.- 5.9 Determination of the Order of Bilinear Models.- 5.10 Numerical Illustrations.- 5.11 Sampling Properties of Parameter Estimations for the BL(1,0,1,1) Model.- 6 Estimation and Prediction for Subset Bilinear time Series Models with Applications.- 6.1 Introduction.- 6.2 An Algorithm for Fitting Subset Bilinear Models.- 6.3 Estimation of the Parameters of SBL(k?,m).- 6.4 Residuals.- 6.5 Fitting Subset Bilinear Models to Time Series Data.- 7 Markovian Representation and Existence Theorems for Bilinear time Series Models.- 7.1 Markovian Representations.- 7.2 Existence of the Bilinear Model BL(p,0,p,1).- Appendix A On the Kronecker Matrix Product.- Appendix B Linear Least Squares Solutions by Householder Transformations.- Appendix C Fitting the Best AR Model.- Appendix D Time Series Data.- Listing of Programs.- Program 1.- Program 2.- Program 3.- Program 4.- References.- Author Index.

574 citations


Journal ArticleDOI
TL;DR: In two linked, shallow, freshwater basins, phytoplankton densities in summer were very different as discussed by the authors, with a large stand of water lilies and the adjacent open water was clear with chlorophyll a concentrations generally 100 pg*literl.
Abstract: In two linked, shallow, freshwater basins, phytoplankton densities in summer were very different. Hudsons Bay supported a large stand of water lilies, and the adjacent open water was clear with chlorophyll a concentrations generally 100 pg*literl. Hudsons Bay water, in bioassays, could support great phytoplankton growth in summer and did so in spring and fall. The period of clear water coincided with the presence of the lily stand. Zooplankton populations were of rotifers and small-bodied Cladocera in Hoveton Great Broad, but mostly of Cladocera, including large-bodied individuals of plantassociated species, in Hudsons Bay. Zooplanktivorous fish were present and there was evidence of feeding by them in both basins. Coexistence with fish of the large, apparently efficiently grazing Cladocera in Hudsons Bay depended on provision of daytime refuges for the Cladocera among the lilies, and grazing was greatest in the adjacent open water at night. Grazing control was helped by a hydrological regime which favored small and rapidly growing phytoplankters, rather than inedible colonial forms with slow growth. Weed-associated grazers may be important in maintaining the dominance of aquatic plants in shallow lakes which would otherwise more rapidly become dominated by phytoplankton as nutrient loading increased.

546 citations


Book
01 Jan 1984
TL;DR: A tapestry in space and time, change, meaning and acts of identity, the discourse of social life, and communication: words and world.
Abstract: Acknowledgements 1. Linguistics and sociolinguistics 2. A tapestry in space and time 3. Language varieties: processes and problems 4. Discovering the structure in variation 5. Rhoticity 6. At the intersection of social factors 7. Change, meaning and acts of identity 8. The discourse of social life 9. Communication: words and world 10. Action and critique 11. Language and social explanation Further reading References Index.

461 citations


Journal ArticleDOI
01 May 1984-Nature
TL;DR: In this paper, the authors describe a region of the world ocean where a fast deep mean flow is augmented (or reversed) by intense intermittent currents, which occurs about 5 km below the Gulf Stream or its rings.
Abstract: Fast currents, high concentrations of suspended sediment and grooved mud beds are associated with erosion in frequent abyssal storms where a fast deep mean flow is augmented (or reversed) by intense intermittent currents. This occurs about 5 km below the Gulf Stream or its rings. The waning phase of a storm results in development of bedforms and rapid deposition of a mud blanket. Several other regions of the world ocean display evidence of abyssal storm activity.

308 citations


Journal ArticleDOI
TL;DR: The fourth-rank tensors that embody the elastic or other properties of crystalline anisotropic substances can be partitioned into a number of sets in order that each shall acknowledge the symmetry of one or more of the crystal classes and moreover make up a closed linear associative algebra of hypercomplex numbers for the purpose of calculating the sums, products and inverses of its constituent tensors, to which end coordinate invariant expressions of the tensors are adopted.
Abstract: The fourth-rank tensors that embody the elastic or other properties of crystalline anisotropic substances can be partitioned into a number of sets in order that each shall acknowledge the symmetry of one or more of the crystal classes and moreover shall make up a closed linear associative algebra of hypercomplex numbers for the purpose of calculating the sums, products and inverses of its constituent tensors, to which end coordinate invariant expressions of the tensors are adopted. The calculations are simplified immensely, and ensuing physical analyses are well prepared for, once the structure of every algebra is unravelled completely in terms of a number of separate subalgebras isomorphic to familiar algebras such as the binary one of the complex numbers, the quaternary one of the 2x2 matrices and the octonary one of the complex quaternions. The fourth-rank tensors do not seem to have been submitted previously to the present algebraic point of view, and nor do those of any other rank: a parallel, but less intricate, development can be provided for the second-rank ones.

237 citations


Journal ArticleDOI
TL;DR: In this article, the spatial patterns of precipitation variability over the United Kingdom were examined for the period 1861-1970 using principal components analysis, and significant inhomogeneities in the Nicholas and Glasspoole England and Wales precipitation series at 1915 and 1957 were detected and quantified.
Abstract: The spatial patterns of precipitation variability over the United Kingdom are examined for the period 1861–1970 using principal components analysis. Most of the variance (around 50 per cent) is explained by the first component, which is characterized by uniform variability over the whole region. Higher-order components isolate differential variability between different regions. The first four components are essentially the same for all months, all seasons and the annual total, highlighting the intra-annual constancy of inter-regional variability and pointing to strong geographical and topographical control. A subdivision of the analysis period into two halves produces no change in the component patterns, but changes in the variance explained by the first component imply that summer precipitation has become less spatially variable since 1915. On the basis of the principal components analysis the England and Wales region is divided into five coherent subregions. A regression technique is developed to produce a homogeneous area-average precipitation series for England and Wales using the longest site precipitation records available and maintaining even spatial coverage. The method used allows changes in the reliability of the area-average due to changes in the density of station coverage to be quantified. An empirical relationship between the standard error of estimate of area-averaged precipitation and the number of recording sites is derived. Significant inhomogeneities in the Nicholas and Glasspoole England and Wales precipitation series at 1915 and 1957 are detected and quantified. The Nicholas and Glasspoole series as a whole is found to underestimate precipitation amounts noticeably in the late eighteenth and early nineteenth centuries.

225 citations


Journal ArticleDOI
TL;DR: Evidence is presented which suggests that this is due to inhomogeneity in the vesicle population and inositol trisphosphate -induced Ca2+ release can also be demonstrated, under appropriate experimental conditions, in a more purified microsomal fraction essentially free of mitochondria.

166 citations


Journal ArticleDOI
TL;DR: In this article, a model for the evolution of bulk melt waters can be constructed by assuming that rock mineral weathering and solute acquisition are controlled by carbonate equilibria.
Abstract: Chemical models for the evolution of bulk melt waters can be constructed by assuming that rock mineral weathering and solute acquisition are controlled by carbonate equilibria. Different open- and closed- system models are defined by variations in the rates of weathering relative to the rate of hydrogen-ion supply by the dissolution and dissociation of CO2, and can be recognized by characteristic pH and ∑+ relationships. The observed and inferred compositions of englacial and subglacial melt suggest that mixing is unlikely to be conservative and that closed-system conditions result where post-mixing weathering reactions occur. The final composition of bulk melt waters is determined by the mixing ratio between englacial and subglacial melt, the extent of post-mixing evolution, and opportunity for mixing with ground waters or re-equilibration with the atmosphere.

Journal ArticleDOI
TL;DR: In this article, a new reconstruction of the climate and sea-ice record for Iceland from medieval times to A.D. 1780 is presented, based on all available documentary sources.
Abstract: A new reconstruction of the climate and sea-ice record for Iceland from medieval times to A.D. 1780 is presented, based on all available documentary sources. The importance of careful historical analysis to separate reliable from unreliable material is stressed, and these reconstructions are the first to have been produced using only reliable data. The major previous works on the subject (those of Thoroddsen, Koch, and Bergþorsson1), which all include unreliable material, are discussed. Prior to A.D. 1600 the data are not considered to be full enough to permit a quantitative interpretation. For the period A.D. 1601 to 1780 decadal temperature and sea-ice indices are given.

Journal ArticleDOI
TL;DR: This result establishes that there is electrical coupling between islet cells and suggests that the space constant of the coupling ratio within the islet tissue is of the order of a few β-cell diameters.
Abstract: Two microelectrodes have been used to measure membrane potentials simultaneously in pairs of mouse pancreatic islet cells. In the presence of glucose at concentrations between 5.6 and 22.2 mM, injection of current i into cell 1 caused a membrane potential change in this cell, V1, and, provided the second microelectrode was less than 35 micron away, in a second impaled cell 2, V2. This result establishes that there is electrical coupling between islet cells and suggests that the space constant of the coupling ratio within the islet tissue is of the order of a few beta-cell diameters. The current-membrane potential curves i-V1 and i-V2 are very similar. By exchange of the roles of the microelectrodes, no evidence of rectification of the current through the intercellular pathways was found. Removal of glucose caused a rapid decrease in the coupling ratio V2/V1. In steady-state conditions, the coupling ratio increases with the concentration of glucose in the range from 0 up to 22 mM. Values of the equivalent resistance of the junctional and nonjunctional membranes have been estimated and found to change with the concentration of glucose. Externally applied mitochondrial blockers induced a moderate increase in the junctional resistance possibly mediated by an increase in intracellular Ca2+.

Journal ArticleDOI
TL;DR: In general, the greater the mean relative growth rate (MRGR) of apterous morphs of Rhopalosiphum padi (L.), the greater their fecundity.
Abstract: Aphid size, although generally a good indicator of fecundity is not a good indicator of aphid performance over a wide range of conditions In general, the greater the mean relative growth rate (MRGR) of apterous morphs of Rhopalosiphum padi (L), the greater their fecundity Intrinsic rate of increase (rm) is even more closely correlated with mean relative growth rate than fecundity Once these criteria are quantified for a morph of a particular species of aphid over a range of conditions the morphs intrinsic rate of increase on a particular host can be estimated by a quick measure of its mean relative growth rate RESUME Croissance des pucerons et taux de multiplication La taille des pucerons, bien que consideree generalement comme un bon indice de la fecondite, n'est pas un bon indice pour leurs performances dans une grande gamme de conditions En general, plus le taux moyen de croissance relative est eleve chez les types apteres de Rhopalosiphum padi, plus leur fecondite est importante Le taux intrinseque de croissance (rm) est encore plus etroitement lie au taux moyen de croissance relative que la fecondite Une fois que ces criteres ont ete quantifies pour un type d'une espece donnee de puceron dans une gamme de conditions, les taux intrinseques de croissance des differents types sur un hote particulier peuvent ětre estimes par une mesure rapide de leur taux moyen de croissance relative

Journal ArticleDOI
01 Oct 1984-Nature
TL;DR: In this article, the authors used continuous monthly surface air temperature for the Northern Hemisphere land masses to resolve the month-by-month development and decay of the initial climatic impact of major explosive volcanic eruptions.
Abstract: Major explosive volcanic eruptions inject ash and gas into the upper atmosphere, producing aerosol layers which can affect the global energy balance and climate1. Empirical studies have shown that major eruptions can produce a decrease in surface air temperature of up to a few tenths of a degree Celsius over the Northern Hemisphere land masses and that the effects may last for 2 or 3 yr (refs 2–4). This temperature decrease has been simulated by numerical models using realistic estimates of the nature of the aerosol cloud1. Previous empirical studies of volcanic effects have examined fluctuations in monthly, seasonal or annual climate data, but generally only at a frequency of one observation per year. This has rendered determination of the timing of the onset of effects during the first year impossible. Using continuous monthly surface air temperature for the Northern Hemisphere land masses, we resolve the month-by-month development and decay of the initial climatic impact. In the case of Northern Hemisphere eruptions, abrupt cooling occurs during the first two to three months, which is more rapid than previously assumed.

Journal ArticleDOI
TL;DR: In this paper, the analysis of the time-averaged geomagnetic field is extended back to 200Ma, and the results indicate that a small axial quadrupole of the same sign as the axial dipole may have persisted throughout the Cenozoic.
Abstract: Summary. The analysis of the time-averaged geomagnetic field is extended back to 200Ma. Palaeomagnetic poles from the major plates have been carefully selected from recent compilations of reliable results for each region. These were returned, with their corresponding sampling sites, to their locations at the estimated dates of magnetization, in a fixed-hotspots framework. The corrected results were then grouped into 20Ma windows at intervals of 10Ma representing the past 100Ma, and 40Ma windows at 30Ma intervals for the more sparse 100–200Ma data. Global means and Fisher statistics were calculated for each window having included the axial quadrupole in the calculation. The value of this coefficient which gave the maximum value for the Fisher precision parameter (tightest grouping of poles) was taken as representative of each interval. The results indicate that a small axial quadrupole of the same sign as the axial dipole may have persisted throughout the Cenozoic. This is equivalent to a northward offset axial dipole field (far-sided effect). During the late Cretaceous, this component appears to have changed sign with respect to the dipole. Negative values seem to have obtained throughout the Cretaceous long normal polarity interval, corresponding to a southward offset dipole (near-sided effect). The data distribution is inadequate for the resolution of the quadrupole at earlier times, and zero values cannot be discounted. Little relative motion is implied between the hotspots and the geomagnetic axis for the past 90 Ma, the global mean polar path curving around the predicted fixed-hotspots pole at a distance of typically 5° latitude with little sign of rapid Tertiary polar wander as implied by studies of Pacific data alone. Between 100 and 200 Ma, however, there is a clear difference between the two reference frames, amounting to 17–19° in the Jurassic. This may reflect motion of the mantle relative to the geomagnetic axis, but may also include errors due to inaccurate determination of hotspot tracks and inter-hotspot motion.

Journal ArticleDOI
07 Apr 1984-Nature
TL;DR: In this article, the authors reported on the reconstruction of July-August surface air temperature for Edinburgh, Scotland, for the period AD 1721-1975 using maximum latewood density and ring-width data from pine trees in the Scottish Highlands.
Abstract: The use of wood density measurements in dendroclimatology is a relatively recent development1 There have been few attempts to use these data in climate reconstruction or to test the result rigorously We now report on the reconstruction of July–August surface air temperature for Edinburgh, Scotland, for the period AD 1721–1975 using maximum latewood density and ring-width data from pine trees in the Scottish Highlands In a series of tests, it is shown that the relationship between the climate and tree-ring variables is statistically significant and stable with time, confirming the power of dendroclimatic reconstruction even in a moist region such as the British Isles

Book ChapterDOI
01 Jan 1984
TL;DR: In organ culture studies of the bovine lens, a marked decrease in protein synthesis and net leakage of proteins was associated more strongly with an increase in calcium than with a increase in sodium, and the stability of the lens protein gel thus seems to depend on maintaining a low internal level of calcium ions.
Abstract: Calcium has long been known to play a role in cataract formation but techniques have only recently become available for investigating the physiological mechanisms Previous studies showed that lens membrane permeability alters when the external calcium concentration falls below 1 mM, so it was interesting that values for human aqueous from cataract patients ranged from 045 to 20 mM The mean value for the aqueous was one half that for the plasma The calcium concentration in cataractous lenses ranged from 01 to 64 mM and lenses with a high calcium concentration also had a high sodium content In lenses with near normal sodium content the highest calcium concentrations were associated with highly localized opacities, while nuclear cataracts had a low calcium content The relationship between calcium and transparency was investigated in a rat lens system using ion-sensitive microelectrodes The distribution of free calcium in the lens varied with age and was correlated with a change in the sensitivity of the lens to cold cataract and a change in lens birefringence The highest free calcium levels were obtained from lenses incubated in 10 mM-calcium in the absence of glucose and these lenses showed most light scattering Ion-sensitive microelectrode techniques applied to human lenses yielded calcium levels of 01 microM-2 mM In lenses with dense, highly localized opacities the calcium distribution was not uniform and was highest in regions that scattered most light The movement of calcium through individual membrane channels was investigated using patch clamp techniques Three types of ionic channels have been identified in the lens The smallest appears to be a calcium channel; the larger current fluctuations are associated with sodium and potassium movements In organ culture studies of the bovine lens, a marked decrease in protein synthesis and net leakage of proteins was associated more strongly with an increase in calcium than with an increase in sodium The stability of the lens protein gel thus seems to depend on maintaining a low internal level of calcium ions

Journal ArticleDOI
TL;DR: In this article, a 3-year study of moorhens defending linear territories along ditches in a grazing marsh habitat was conducted, and the authors found that the relative difference in resource holding potential between an owner and its two neighbours provided the best correlation with territory size.

Journal ArticleDOI
TL;DR: It was concluded that plant structure is an important factor in determining the quality of a habitat for coccinellids.
Abstract: | 1. To determine the effect of plant structure on the searching efficiency of Coccinella septempunctata L. larvae, their functional response on pea and bean plants was compared. 2. The attack coefficient a was lower on pea than on bean plants. 3. This was not due to a difference in the coincidence of prey distribution and predator searching effort, but was due to larvae falling off the smooth leaves of pea plants significantly more frequently than off bean plants. 4. It was concluded that plant structure is an important factor in determining the quality of a habitat for coccinellids.

Journal ArticleDOI
TL;DR: In this article, the results of multiple regression analyses showed that strength loss was most closely related to temperature in summer, when the model accounted for only 38% of the variation, and to stream pH in autumn and winter.
Abstract: SUMMARY. 1. Ceilulolytic decomposition, measured by loss of tensile strength in strips of cellulose test cloth, was estimated in thirty-four stream sites in experiments in summer, autumn and winter. 2. The results of multiple regression analyses showed that strength loss was most closely related to temperature in summer, when the model accounted for only 38% of the variation, and to stream pH in autumn and winter, when the models accounted for 52% and 75% of the variation, respectively. 3. The relationship between decomposition rate and the structure of invertebrate communities in streams of dissimilar pH is discussed. We argue that a very rapid rate of decomposition of coarse particulate organic matter may profit consumers of fine particulate organic matter at the expense of coarse particle shredders.

Journal ArticleDOI
TL;DR: The authors resume du role de l'heterogeneite structurale, des couplages magnetiques dipolaires, de la structure moleculaire et du mouvement moleculaires dans la determination des spectres RMN du proton and des proprietes de relaxation de solides heterogenes tels que les polymeres semicristallins.
Abstract: Bref resume du role de l'heterogeneite structurale, des couplages magnetiques dipolaires, de la structure moleculaire et du mouvement moleculaire dans la determination des spectres RMN du proton et des proprietes de relaxation de solides heterogenes tels que les polymeres semicristallins. Mesures de la relaxation spin-reseau du proton en labo et en referentiel tournant pour du polyethylene cristallise en solution et au fondu, du polypropene isotactique recuit et trempe et du polybutene-1 isotactique

Journal ArticleDOI
TL;DR: The roles that competition and predation play indetermining the structure and richness of stream invertebrate communi-ties are discussed and evidence that density compensation occurs, niche width decreases and niche overlap declines as speciesrichness increases is discussed.
Abstract: ALAN G. HILDREW, COLIN R. TOWNSEND* and JEANETTE FRANCISSchool of Biological Sciences. Queen Mary College. London, and*School of Biological Sciences, University of East Anglia. NorwichSUMMARY. I. The results of a survey of thirty-four stream sites, differingin pH and invertebrate species richness, indicated that the pool of locallyavailable, suitably adapted species was smaller in the acid streams. Thisplays a part in determining the general pattern of lower species richness atmore acid sites.2. Diversity of feeding categories increased with species richness,indicating that a greater range of food resources was available in the lessacid, more species-rich communities.3. The pattern of predation varied with pH and species richness. Thenumbers of large insect predators were lower in the less acid, morespecies-rich communities and this was correlated with the presence of fish.4. A detailed study of the guild of detritivorous stoneflies in four streamsdiffering in species richness provided evidence that density compensationoccurs, niche width decreases and niche overlap declines as speciesrichness increases,5. We discuss the roles that competition and predation play indetermining the structure and richness of stream invertebrate communi-ties.

Journal ArticleDOI
TL;DR: The data support the view that, within an islet, most but not necessarily all cells are electrically synchronized, and that the coupling can be modulated by natural and pharmacological secretagogues.
Abstract: beta-Cells in microdissected islets of Langerhans produce rhythmical bursts of electrical activity. This was monitored with two micro-electrodes simultaneously and the frequency and phase (collectively referred to as synchrony) of the two signals was investigated. At any instant two impaled cells produced bursts of the same frequency even when separated by up to 400 micron. When the electrode tips were separated by less than about 20 micron and current injection showed the cells to be ionically coupled the two signals were in phase and had almost identical shape. The phase relations between cells further apart were variable, the leading cell usually being located deeper within the islet than the other impaled cell. Increasing the glucose concentration increased electrical activity, reduced any phase lags and made the shape of the bursts more similar. There was less lag between the responses from two cells when the glucose concentration was suddenly reduced, than when it was suddenly increased. Qualitatively similar observations were made in glibenclamide-treated mice, a treatment previously shown to increase dye coupling between islet cells. However, the response to increasing glucose concentrations showed less phase lag; likewise the phase lag between bursts was reduced. Furthermore the response to current injected into one cell could be detected at much larger distances (up to 80 micron) than in control islets. This suggests that electrical coupling of beta-cells was improved in sulphonylurea-treated mice. Electron microscopy of both control and glibenclamide-treated mouse islets fixed at the end of each electrophysiological experiment showed the region impaled by the electrodes to be well preserved and, whenever the electrodes penetrated at least 20 micron into the islet, to contain a large proportion of beta-cells. The data support the view that, within an islet, most but not necessarily all cells are electrically synchronized, and that the coupling can be modulated by natural and pharmacological secretagogues.

Journal ArticleDOI
TL;DR: In this paper, the spatial characteristics of the annual and seasonal temperature variations are described using principal components analysis of the station anomaly data, and the first two principal components are similar PC1-winter is also similar to the winter pattern for linen trend found by van Loon and Williams for 1956-73.
Abstract: Antarctic temperature variations for 1957°82 have been objectively analyzed by gridding monthly data, from 16 stations, onto a 5° latitude by 10° longitude grid, from 65 to 90°S. These gridded data were used to calculate monthly values of the spatial mean temperature south of 65°S. The uncertainty in the area average is estimated to be 0.22°C for the annual values prior to 1970. After 1970 there is an additional uncertainty of about 0.10−0.16°C due to the cessation of Byrd station. The annual mean and summer areas averages show significant linear warming trends amounting to 0.74 and 0.77°C respectively. Spatial characteristics of the annual and seasonal temperature variations are described using principal components analysis of the station anomaly data. The first two principal components of the annual and winter data are similar PC1-winter is also similar to the winter pattern for linen trend found by van Loon and Williams for 1956–73. The warming trend associated with this pattern ceased in the ...

Journal ArticleDOI
TL;DR: In this paper, the deformation-dependent part of the internal energy is considered as a symmetric function of the principal stretches rather than depending only on their product, as in the original development.
Abstract: In the first part of the paper, consisting of Sections 2 and 3, physical grounds are adduced for weakening the concept of strictly entropic elasticity as applied to elastomeric materials. The resulting notion of modified entropic elasticity is shown to provide an alternative formulation of a model of rubberlike thermoelasticity proposed by C hadwick (1974). In the second part (Sections 4 and 5) Chadwick's model is generalized by allowing the deformation-dependent part of the internal energy to be a symmetric function of the principal stretches rather than depending only on their product, as in the original development. Consistently with the molecular theory of polymer networks, and with experimental findings, the extended model predicts that the deviatoric stress is not entirely entropic in origin, but arises in part from changes of internal energy. The energetic fraction of the retractive force in an extended cylinder is calculated and discussed in some detail and the paper concludes with a correlation of theoretical results with measurements on specimens of a lightly cross-linked natural rubber.

Journal ArticleDOI
TL;DR: Polarization reversal (PR) is the term given to the turning point in the spatial pattern of growth and development in a nation when continuing relative concentration ceases and urban deconcentration or spatial decentralization commences.
Abstract: Polarization reversal (PR) is the term given to the turning point in the spatial pattern of growth and development in a nation when continuing relative concentration ceases and urban deconcentration or spatial decentralization commences. The focus of this paper is on those LDCs with fast growth rates of population which are reaching a transitional stage in their pattern of economic development as well as a change in direction of their spatial development. The paper briefly discusses why a PR turning point may be anticipated as the economy of a nation grows and the urban system develops. It then examines possible indices of PR and of alternative definitions, arriving at a new and narrower definition of PR. This definition and the earlier measures are then considered in the context of Sao Paulo, which underwent increasing polarization of urban population from 1950-1970, but experienced a PR turning in the 1970s. This may be the first documented example of PR in an LDC.

Journal ArticleDOI
TL;DR: In this article, electron energy loss spectroscopy was used to measure the vibrational spectra of acetylene chemisorbed on Cu(111), Ni(110), and Pd(110) at low temperature.

Journal ArticleDOI
01 Apr 1984-Tellus B
TL;DR: In this article, the average values from the existing literature data for themolecular diffusivities of the gases were found to vary with the diffusivity raised to the power 0.57.
Abstract: The air-water transfer velocities for H,, He and Xe have been measured simultaneously inlaboratory-tank experiments. Using average values from the existing literature data for themolecular diffusivities of the gases, the transfer velocities are found to vary with the diffusivityraised to the power 0.57. This exponent is in reasonable agreement with the findings from otherlaboratories, as well as field studies, provided average diffusivities are used consistently.Although interpretation is limited by uncertainties in presently available diffusion coefficients, theresults may be interpreted as supportive of both the surface-renewal and boundary-layer modelsof air-water gas exchange, but they provide little evidence for the appropriateness of the filmmodel. DOI: 10.1111/j.1600-0889.1984.tb00231.x

Journal ArticleDOI
TL;DR: The data indicate that the osmotic stresses induced in the lenses of diabetic and non-diabetic patients are different, and the diabetic lenses were also distributed in the middle range when nuclear colour was graded on a scale from I to V, while normal lenses were normally distributed at either end of the scale.